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C/ 3:80 6.£ Norih ouroiina Stare Library Raleigh North Carolina jyj e Q, Department of Conservation and Development Dan E. Stewart, Director Doc. Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 Digitized by the Internet Archive in 2013 http://archive.org/details/pyrophyllitedepo1967stuc North Carolina Department of Conservation and Development Dan E. Stewart, Director Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 MEMBERS OF THE BOARD OF CONSERVATION AND DEVELOPMENT James W. York, Chairman Raleigh R. Patrick Spangler, First Vice Chairman Shelby William P. Saunders, Second Vice Chairman Southern Pines John M. Akers Gastonia John K. Barrow, Jr. Ahoskie J. 0. Bishop Rocky Mount David Blanton Marion Harry D. Blomberg Asheville Robert E. Bryan Goldsboro William B. Carter Washington Arthur G. Corpening, Jr. . High Point Moncie L. Daniels, Jr. Manteo Koy E. Dawkins Monroe Dr. J. A. Gill Elizabeth City John Harden . Greensboro Gilliam K. Horton Wilmington Dr. Henry W. Jordan Cedar Falls Petro Kulynych Wilkesboro William H. Maynard Lenoir W. H. McDonald Tryon Jack Pait Lumberton John A. Parris, Jr. Sylva Oscar J. Sikes, Jr. Albemarle T. Max Watson Spindale 11 LETTER OF TRANSMITTAL Raleigh, North Carolina March 1, 1967 To His Excellency, HONORABLE DAN K. MOORE Governor of North Carolina Sir: I have the honor to submit herewith manuscript for publication as Bulletin 80, "Pyrophyllite Deposits in North Carolina," by Jasper L. Stuckey. This report contains detailed information on the occurrence, distri-bution and geology of pyrophyllite in North Carolina and should prove to be of considerable value to those interested in the mining and processing of this valuable mineral resource. Respectfully submitted, DAN E. STEWART Director m CONTENTS Page Abstract 1 Introduction 1 Previous work 1 Geology of the Carolina Slate belt 4 General statement 4 Distribution and character of the rocks 4 Felsic volcanic rocks 5 Mafic volcanic rocks 6 Bedded argillites (volcanic slate) 6 Igneous intrusive rocks 7 Environment of deposition 7 Structural features 7 Age of the rocks 8 Geology of the pyrophyllite deposits 9 Introduction 9 Distribution 10 Geologic relations 11 Form and structure 11 Mineralogy of the deposits 12 Pyrophyllite 12 Quartz 12 Sericite 12 Chloritoid 12 Pyrite 13 Chlorite 13 Feldspar 13 Iron oxides 13 High alumina minerals 13 Petrography 13 Origin of the pyrophyllite deposits 14 Earlier theories 14 Analyses of rocks 16 Origin of North Carolina pyrophyllite 18 Source of mineralizing solutions 18 Conditions of pyrophyllite formation 19 Reserves 19 Mining methods 20 Processing 21 Uses of pyrophyllite 21 Mines and prospects 23 Granville County 23 Daniels Mountain 23 Bowlings Mountain 23 IV Long Mountain 24 Robbins prospect No. 1 24 Jones prospect 24 R. E. Hilton property 24 E. C. Hilton property 24 Robins-Uzzell property 25 Robbins prospect No. 2 25 Orange County 25 Murray prospect 25 Hillsborough mine 25 Teer prospects 25 Alamance County 27 Snow Camp mine 27 Major Hill prospects • 27 Chatham County 28 Hinshaw prospect 28 Randolph County 28 Staley deposit 28 Pilot Mountain prospects 28 Moore County 29 McConnell prospect 29 Jackson prospect 30 Bates mine 30 Phillips mine 30 Womble mine . .31 Reaves mine 31 Jones prospect 33 Currie prospect 33 Ruff prospect 33 Hallison prospect 33 Standard Mineral Company 33 Tucker and Williams pits 35 Sanders prospect . .35 Montgomery County 36 Ammons mine 36 North State property 1 36 North State property 2 36 Cotton Stone Mountain 37 Standard Mineral Company 37 References cited 37 ILLUSTRATIONS Facing Page Plate 1. Pyrophyllite deposits in North Carolina 23 2. Piedmont Minerals Company 26 A. Mill B. Open pit mine 3. Glendon Pyrophyllite Company 32 A. Mill B. Open pit mine (Reaves) 4. Standard Mineral Company 34 A. Mill B. Open pit mine VI Pyrophyllite Deposits of North Carolina By Jasper L. Stuckey ABSTRACT All the known occurrences of pyrophyllite in North Carolina are found in Granville, Orange, Alamance, Chatham, Randolph, Moore and Montgomery counties where they are associated with vol-canic- sedimentary rocks of the Carolina Slate Belt. These rocks consist of lava flows interbedded with beds of ash, tuff, breccia and shale or slate that vary in composition from rhyolitic, or acid, to andesitic, or basic, and fall into three natural groups : Felsic Volcanics, Mafic Volcanics, and Bedded Argillites (Volcanic Slate). They have been folded, faulted and metamorphosed to the extent that they contain a well defined cleavage that strikes northeast and dips, in general, to the northwest. The pyrophyllite deposits which are irregular, oval or lens-like in form occur in acid volcanic rocks that vary from rhyolite to dacite in composition. The field, microscopic and chemical evidence indicates that the pyrophyllite bodies were formed by metasomatic replacement of the host rocks through the agency of hydrothermal solutions under conditions of intermediate temperature and pressure. Pyrophyllite has a variety of uses chief of which are in paints, rubber goods, roofing materials, ceramic products and insecticides. Reserves, while not large, are ample for several years. INTRODUCTION The pyrophyllite deposits of North Carolina are associated with volcanic-sedimentary rocks of the Carolina Slate Belt. Volcanic-sedimentary and similar rocks form a belt or zone along the east-ern border of the Piedmont Plateau and parts of the Coastal Plain all the way from the vicinity of Petersburg and Farmville, Virginia, southwest across North Carolina, South Carolina and into Georgia, as far as the southern part of Baldwin County south of Milledgeville—a total distance of over 400 miles. In North Carolina the zone occupied by volcanic-sedimentary rocks is known as the Carolina Slate Belt. It is in this belt that the pyrophyllite deposits of the state are found. The western border of the Carolina Slate Belt lies a few miles east of Charlotte, Lexington and Thomasville, crosses Guilford County southeast of Greensboro and continues northeast across the northwest corner of Alamance and Orange coun-ties and the center of Person County to the Vir-ginia line. The eastern limits of this belt are marked, by the cover of Coastal Plain sediments. PREVIOUS WORK Due to the presence of a wide variety of min-erals in them, the rocks of the Carolina Slate Belt have been of interest for approximately 150 years. These rocks, because of their complex character and well developed cleavage, were called slates by a number of investigators over a period of 70 years before their true nature began to be recognized. The first published report on that part of the slate belt in which pyrophyllite deposits are known to occur was a descriptive list of rocks and minerals from North Carolina by Denison Olmsted (1822). In this list he de-scribed novaculite, slate, hornstone, whetstone and talc and soapstone from several counties in-cluding Orange and Chatham. He stated that the talc and soapstone were extensively used for building and ornamental purposes and added that Indian utensils of the same materials were com-mon. In 1823, Olmsted was appointed by the Board of Agriculture to make a geological survey of the State. In his first report (1825) he called atten-tion to the "Great Slate Formation which passes quite across the State from northeast to south-west covering more or less of the counties of Person, Orange, Chatham, Montgomery —." The presence of talc and soapstone was noted in Orange, Chatham and other counties together with beds of porphyry in the eastern part of the formation and bands of breccia consisting of rolled pebbles interbedded in a ferruginous green-stone in different places. Ebenezer Emmons (1856), one of the most competent geologists of his time, considered the Carolina Slate Belt rocks to be among the oldest in the country and placed them in his Taconic system which he divided into an upper and lower member. The upper member consisted of clay slates, chloritic sandstones, cherty beds and brec-ciated conglomerate. The lbwer member consisted of talcose slates, white and brown quartzites and conglomerate. He did not recognize the presence of volcanic rocks in what is now known as the Carolina Slate Belt. In his lower unit, Emmons found what he considered to be fossils and named them Paleotrochis major and Paleotrochis minor. Diller (1899) recognized these as spherulites in rhyolite. Emmons described in some detail the phyro-phyllite deposits near Glendon, Moore County, then known as Hancock's Mill and classed the talcose slates, or those containing the pyrophyl-lite, as the basal member or oldest rocks of his Taconic system. He further pointed out that pyro-phyllite occurred in the same position in Mont-gomery County. Prior to this time the pyrophyllite had been considered as soapstone, but Emmons tested it before the blowpipe and found it to contain alumi-num and classed it as agalmatolite. He gave the physical properties of this mineral together with its uses and the methods of mining near Han-cock's Mill. Brush (1862) analyzed some of the material from Hancock's Mill, Moore County and showed it to be pyrophyllite. Kerr (1875) placed the rocks of the slate belt in the Huronian, which in his classification is a division of the Archean and considered them to be sedimentary. He mentioned talc and soapstone from Orange and Chatham counties but added nothing to the description already published by Emmons. Kerr and Hanna (1893) in "Ores of North Carolina," described some old gold mines in the Deep River region and stated: "It is worthwhile to add that part of what passes for talc is pyro-phyllite and even hydromicaceous." Williams (1894) recognized for the first time the occurrence of ancient acid volcanic rocks in the slate belt. He studied a small area in Chatham County and applied for the first time modern petrographic methods to the study of these rocks. He described this area in part as follows : "Here are to be seen admirable exposures of volcanic flows and breccias with finer tuff deposits which have been sheared into slates by dynamic agen-cies." He classed the slate belt rocks as Precam-brian in age. Nitze and Hanna (1896) first used the name Carolina Slate Belt for the rocks Olmsted (1825) had designated the "Great Slate Formation." They recognized the occurrence of volcanic rocks in the slate belt and suggested that there had been more than one volcanic outbreak and during at least one period of inactivity slates had been deposited. They did not mention pyrophyllite but described in some detail the Bell, Burns and Cagle gold mines, all of which are in the pyro-phyllite area along Deep River in Moore County and pointed out that there had been much silicifi-cation at all of these and some propylitic altera-tion at the Bell mine in particular. Pratt (1900) described the pyrophyllite de-posits near Glendon and showed by chemical analysis that the mineral is true pyrophyllite. He described the pyrophyllite deposits as follows: "They are associated with the slates of this region but are not in direct contact with them, being usually separated by bands of siliceous and iron breccia which are probably 100 to 150 feet thick. These bands contain more or less pyrophyllite and they merge into a stratum of pyrophyllite schists." He offered no suggestion as to the origin of either the slates, breccia or pyrophyllite. Weed and Watson (1906) in a report on "The Virgilina Copper District," concluded that the rocks of that area were Precambrian volcanics, chiefly an original andesite that had been greatly altered by pressure and chemical metamorphism. Laney (1910) presented a report on the "Gold Hill Mining District of North Carolina," in which he stated: "The rocks here included under the general term slates while having many local vari-ations seem clearly to represent a great sedi-mentary series of shales with which are inter-bedded volcanic flows, breccias and tuffs. In their fresh and massive condition the slates are dense, bluish rocks which show in many places well defined bedding planes and laminations. The vol-canic flows, breccias and tuffs which are inter-bedded with the slates apparently represent two kinds of lava, a rhyolitic and an andesitic type." Pogue (1910) presented a report on the "Cid Mining District of Davidson County," in which he described the rocks of that area as follows: "Wide bands of sedimentary, slate-like rock, com-posed of varying admixtures of volcanic ash and land waste have the greatest areal extents. Inter-calated with these occur strips and lenses of acid and basic volcanic rocks, represented by fine and coarse-grained volcanic ejecta and old lava flows." Laney (1917) in a report on the Virgilina dis-trict classed the rocks in the area studied as volcanic-sedimentary and stated: "Under this group are placed both the acid and basic flows and tuffs and the water laid tuffs and slates." Stuckey (1928) presented a report on the Deep River region of Moore County in which he di-vided the rocks of the Carolina Slate Belt in that area into slates, acid tuffs, rhyolites, volcanic breccias and andesite flows and tuffs. He noted that the schistosity dipped to the northwest and interpreted the structure as a closely compressed synclinorium with axes of the folds parallel to the strike of the formations. In addition, he pointed out that metamorphism is not uniform through-out the area. Bowman (1954) studied the structure of the Carolina Slate Belt near Albemarle, North Caro-lina, and recognized sedimentary rocks, volcanic tuffs and flows, and mafic intrusives in the area. He interpreted the structure as a series of undu-lating open folds. Conley (1959); Stromquist and Conley, 1959; and Conley (1962 b) divided the rocks in the Albemarle and Denton 15-minute quadrangles into (1) a lower volcanic sequence consisting largely of felsic tuffs that have been folded into an anticline plunging to the southwest, (2) a volcanic-sedimentary sequence consisting of a lower argillite unit, an intermediate tuffaceous argillite unit and an upper graywacke unit which have been folded into a syncline also plunging to the southwest and (3) an upper volcanic sequence consisting of mafic and felsic volcanic rocks which unconformably overlie the first two sequences. According to Conley (1962 a), "In Moore County only the lower and middle units appear to be present; however, some rhyolite in the area might belong to the upper unit. The exact strati-graphic relationships of some of the rocks in the county are in doubt because of the gradational nature of the contacts, a condition further com-plicated by intense folding and faulting and lack of outcrops." Conley and Bain (1965) suggested that the rocks of the Carolina Slate Belt in North Carolina can be divided into natural, mappable rock units. They proposed and named a set of rock units or formations into which these rocks might be divided, gave their areal extent and described their structure and lithology. From oldest to youngest these proposed formations are: Morrow Mountain rhyolite Badin greenstone Tater Top Group Unconformity Yadkin graywacke McManus formation Tillery formation Efland formation Uwharrie formation Albemarle Group The Uwharrie formation is composed chiefly of subaerially deposited felsic pyroclastic rocks. These are felsic tuffs consisting of interbedded lithic, lithic-crystal and devitrified vitric-crystal tuffs, welded flow tuffs and rhyolite. The Efland formation is a water-laid sequence consisting of andesitic tuffs with interbedded greenstones, conglomerates, graywackes and flows. The Albemarle Group is a water-laid sequence of pyroclastics and sediments which is divided into the Tillery formation, the McManus forma-tion and the Yadkin graywacke. The Tillery formation is composed in part of finely laminated argillite exhibiting graded bed-ding and in part of andesitic tuff and greenstone. The McManus formation is predominantly a felsic tuffaceous argillite formerly known as the Monroe slate. The Yadkin graywacke is a dark-green gray-wacke sandstone containing interbeds of mafic tuffaceous argillite, mafic lithic-crystal tuff and felsic lithic tuff. The older rocks are in part unconformably overlain by subaerially deposited pyroclastics and flows known as the Tater Top Group. From base to top the group is composed of basaltic tuffs and flows overlain by rhyolite flows. The Tater Top Group is divided into the Badin greenstone and Morrow Mountain rhyolite. The Badin greenstone is composed of lithic crystal tuffs and a basal unit of flows and flow tuffs of andesitic composition. The Morrow Mountain rhyolite consists of dark-gray to black porphyritic rhyolite contain-ing prominent flow banding. Conley and Bain described the Troy anticli-norium, with a northeast-southwest trend, as the major structural feature of the Carolina Slate belt. West and southwest of the Troy anticlinori-a um, northeast trending open folded synclines and anticlines predominate. East of the Troy anticli-norium the rocks are more intensely folded. They are compressed into northeast trending asym-metric folds whose axial planes usually dip steeply to the northwest. In many places, argil-lite has been converted into slate and phyllite. They considered the age of Carolina Slate Belt rocks to be early Paleozoic. GEOLOGY OF THE CAROLINA SLATE BELT GENERAL STATEMENT In North Carolina rocks of the Carolina Slate Belt actually form two belts that are separated by sedimentary rocks of the Durham, Deep River and Wadesboro Triassic basins and by the Roles-ville granite pluton and associated gneisses and schists. The first and most important of these and the one Olmsted (1825) first called the "Great Slate Formation" and Nitze and Hanna (1896) first called the Carolina Slate Belt lies to the west of the belt of Triassic rocks and varies in width from 20 to 60 miles. It is widest between Sanford and Lexington and narrows to the north and south. It crosses the central part of the State in a northeast-southwest direction from Anson and Union counties on the southwest to Granville, Person and Vance counties on the northeast and underlies all or parts of Anson, Union, Mecklen-burg, Cabarrus, Stanly, Montgomery, Moore, Chatham, Randolph, Davidson, Rowan, Guilford, Alamance, Orange, Durham, Person, Granville and Vance counties. This belt contains all the known pyrophyllite deposits in North Carolina and will be considered in detail below. The second belt in which Kerr (1875) first recognized metavolcanic rocks lies to the east of the belts of Triassic, igneous and metamorphic rocks. It begins in Anson County on the south, varies greatly in width and regularity and con-tinues in a northeast direction to Northampton County on the north. It is exposed at the surface in all or parts of Anson, Richmond, Moore, Har-nett, Lee, Wake, Johnston, Wayne, Wilson, Frank-lin, Nash, Halifax and Northampton counties. The eastern limits of this belt are unknown due to the cover of Coastal Plain sediments. A deep well in Camden County about 8 miles north of Elizabeth City, the county seat of Pasquotank County, penetrated rocks that are apparently of the Carolina Slate Belt. Two deep wells—one a few miles southeast of Kelly, Bladen County and the other 4 miles south of Atkinson, Pender Coun-ty— both penetrated Carolina Slate Belt rocks. West of a line from Elizabeth City to Atkinson, of the few wells that reached basement, some penetrated granite, some penetrated gneiss and schist and a few penetrated rocks of the Carolina Slate Belt. It is possible that if the crystalline floor be-neath Coastal Plains sediments was exposed, the types and percentages of rocks in this floor would not differ greatly from those found west of Coastal Plain sediments in Harnett, Johnston, Wake, Wilson, Franklin, Nash, Vance, Warren, Halifax and Northampton counties, where gneisses and schists, granites and rocks of the Carolina Slate Belt occur in about equal amounts. Pyrophyllite has not been found in this eastern zone of Carolina Slate Belt rocks and they are not considered further in this report. DISTRIBUTION AND CHARACTER OF THE ROCKS The rocks of the Carolina Slate Belt, west of the Durham, Deep River, and Wadesboro Triassic basins, consist of lava flows interbedded with beds of ash, tuff, breccia and shale or slate. All of these except the flows contain much nonvol-canic material in the form of mud, clay, silt, sand and conglomerate. (Also present is much non-descript material, some of which may be vol-canic, which for the lack of a better term has been designated land waste) . The flows, breccias, tuffs and ash beds and beds of shale or slate are all interbedded and in general do not appear to occupy definite stratigraphic positions in the series. The flows vary from rhyolite through andesite to basalt. The rhyolites and andesites vary from fine grained to coarsely porphyritic whereas the basalts are often amygdaloidal. The breccias vary from rhyolitic to andesitic in com-position and in fragment size from one-half inch to nearly a foot in diameter. The fragments of the breccias are in turn fragmental, apparently pyroclastic in origin. Some of the fragments in the breccias are sharply angular, although many are rounded, indicating transportation and de-position. The tuffs, while containing both acid and basic materials, are in general of an acid composition and composed of fragments less than half an inch in diameter. These fragments which vary from angular to rounded are often embedded in much fine-grained material apparently of non-volcanic origin. Beginning in the vicinity of the Randolph- Chatham county line, 15 to 20 miles south of Siler City, and continuing northeast through Siler City to the northern part of Orange County and the southeastern part of Person County are a number of beds of quartz conglomerate varying in width from a few inches to as much as 250 feet and of unknown length. The quartz pebbles in this conglomerate are generally less than an inch in diameter, well rounded and embedded in silt and sand, further indicating sedimentary processes. The shales and slates, which are generally well bedded, are composed of fine-grained volcanic materials (and much land waste) in the form of clay, silt and fine sand. Finally, much of the fine-grained materials in the breccias, tuffs and por-tions of the shales and slates strongly resemble metasiltstone and metagraywacke of some of the metagraywacke rocks in other areas, further indi-cating sedimentary processes. A wide variety of rocks are present in the Carolina Slate Belt and various attempts have been made to divide them into units or forma-tions. Conley (1959) and Stromquist and Conley (1959) proposed a three fold division of the rocks of the Albemarle and Denton 15-minute quadrangles, while Conley and Bain (1965) pro-posed a set of nomenclature for the rock-strati-graphic units and their areal extent in the Caro-lina Slate Belt. Since these proposals are not well known and generally accepted and since the rocks of the Carolina Slate Belt fall into three natural divisions, it appears that these three natural divi-sions are to be preferred in this discussion. These three divisions are Felsic volcanic rocks, Mafic volcanic rocks and Bedded argillites (volcanic slate). FELSIC VOLCANIC ROCKS Felsic. volcanic rocks occupy about half of the Carolina Slate Belt in the central part of the State and are the predominating rocks in the eastern part of the Piedmont Plateau. In this area they occupy much of the Carolina Slate Belt west of the Durham and Deep River Triassic basins and northeast of Anson, Union and Stanly counties. The felsic volcanic rocks consist largely of ma-terials of volcanic flow or fragmental origin. The flows are essentially rhyolite, while the frag-mental materials vary from rhyolitic to dacitic in composition. The fragmental rocks consist of breccias and coarse and fine tuffs, with coarse and fine tuffs making up the greater portion of the occurrences. Lenses of mafic volcanics and bedded slate of limited extent are also present. The fragmental rocks consist of fine and coarse tuffs and breccias. The coarse tuffs predominate and contain the fine tuffs and breccias as inter-bedded bands and lenses. The fragments compos-ing these rocks are angular to well rounded and vary in size from nearly a foot to a fraction of an inch in diameter. The fine tuff occurs interbedded with both the slate and coarse tuff and grades into each of them. It has no wide areal extent but occurs as narrow bands and lenses in the coarse tuffs. Microscopically the fine tuff shows a crypto-crystalline ground mass with fragments of quartz and feldspar (orthoclase, albite, oligoclase) as well as secondary minerals epidote, clinozoisite, chlorite and calcite. Iron oxides are sparingly present. Some sections show small rock frag-ments containing original flow structure while others exhibit a parallel arrangement of the par-ticles due to metamorphism. The coarse tuff varies from a massive to a highly schistose type of rock, that in places has been so slightly changed as to show some of its original characters. There is every gradation to a fine tuff on one hand and to a breccia on the other. The freshly broken rock proves to be made up of quartz and feldspar grains and rock frag-ments of less than one-half an inch in diameter set in a bluish or greenish-gray groundmass, the whole often resembling an arkose. In thin section the coarse tuff shows fragmental phenocrysts of quartz, orthoclase and acid plagio-clase with fragments of different kinds of rocks, some of which show definite flow structure, all embedded in a fine-grained groundmass. Kao-linite, epidote and calcite form secondary prod-ucts. Biotite and muscovite are rare. Grains of hematite and limonite as well as small particles of titanite and apatite are found in most sections. Flows of rhyolite occur as narrow bands and lenses in the tuff into which they appear to grade at places. This apparent gradation is possibly due to the fact that some material classed as silicified fine tuff may be partially devitrified rhyolite. The rhyolite is dense and indistinctly porphyritic, with a dark gray to bluish color, and in fresh fracture shows a greasy luster. Flow lines have developed in numerous places and are best seen on weathered surfaces, while amygdaloidal structure may be found in a number of outcrops. In thin section the rhyolite shows phenocrysts of plagioclase (chiefly oligoclase) orthoclase and quartz, named in the order of relative abundance. Kaolinite, epidote and chlorite have developed commonly from the weathering of the feldspars, and calcite is frequently found along fractures in the rocks. Acid volcanic breccia includes all felsic rocks that exhibit a fragmental character sufficiently well defined to attract attention in the hand speci-men, and in which the fragments are over one-half inch in diameter. The size of the fragments (observed) varies from one-half inch to several inches in diameter. These rocks consist partly of brecciated tuff and partly of brecciated rhyolite. When freshly broken the breccia often shows a greenish or mottled-gray color, produced by vari-ous colored fragments in a finer groundmass. In places the breccia has been strongly sheared and it nearly always shows some mashing and schis-tosity, but on the whole is more massive than the finer tuff rocks. Thin sections show little difference from the regular coarse tuffs. The fragments are chiefly of tuffaceous or rhyolitic character with occa-sional slate fragments. Phenocrysts of quartz, orthoclase and plagioclase (chiefly oligoclase) are abundant. The fragments of the brecciated rhyo-lite phase show a flow structure. In all phases of the breccia the groundmass is altered and kao-linized. Grains of iron oxide chiefly hematite are present, while the secondary minerals epidote and calcite and secondary quartz are plentiful. MAFIC VOLCANIC ROCKS Mafic volcanic rocks are scattered throughout the northern two thirds of the Carolina Slate Belt, but are most abundant along the western side. The rocks of this unit consist of volcanic fragmental and flow materials. The fragmental materials are chiefly normal tuffs and breccias of andesitic composition, while the flows vary from andesite to basalt. The tuffs are generally andesitic in composi-tion. In places they are fine grained and lack the fragmental appearance. In such areas, one of which may be seen along U.S. Highway 64, for a mile west of Haw River in Chatham County, the rock strongly resembles a graywacke. The tuffs contain much epidote and often have a greenish color. Other colors vary from dark gray to nearly black. In addition to epidote, plagioclase, quartz and secondary calcite, iron oxides are present. The mafic fragmental rocks are not as strongly metamorphosed as the felsic fragmental rocks, but contain a cleavage that strikes northeast and dips northwest in the southern part of the area and to the southeast in the northern part. The mafic breccia is distinctly more basic than the felsic breccias and appears to be mainly ande-sitic in composition. It consists chiefly of brec-ciated tuffs and flows, but ranges all the way from a fine and highly mashed tuff to a massive coarse breccia with fragments up to several inches in diameter. It varies from a dark gray through a chlorite and epidote green color. In thin section this rock appears more uniform than in the hand specimen. Fragmental materials embedded in a feldspathic groundmass make up most of the rock. The following minerals are present: orthoclase, plagioclase (oligoclase and andesine) chlorite, epidote, zoisite, clinozoisite, quartz, calcite, iron oxides, kaolinite and sericite. The andesite and basalt occur as bands and lenses interbedded with the fragmentals. The andesite is dark green in color, usually massive or fine grained, but occasionally coarsely por-phyritic. A coarse porphyritic variety, with horn-blende crystals up to two inches long occurs in western Randolph County. The basalt is dark to nearly black and often amygdaloidal. Both the andesite and the basalt are characterized by the lack of a well defined cleavage. The minerals pres-ent include epidote, plagioclase, quartz, secondary calcite and iron oxides. Epidote is the most abun-dant mineral present, giving the rock its green color. The name greenstone is often used for this rock. BEDDED ARGILLITES (VOLCANIC SLATE) Bedded argillites (volcanic slate) commonly referred to as slate, bedded slate, or volcanic slate, occur in the southern part of the Carolina Slate Belt and extend as far north as the central part of Davidson and Randolph counties. A few small areas occur on the east side of the belt in Montgomery, Moore and Chatham counties. There are, also, some small areas east of the Jonesboro fault in Anson and Richmond counties. The bedded argillites (volcanic slate) consist chiefly of dark colored or bluish shales or slates, which are usually massive and thick bedded. How-ever, the beds occasionally show very finely marked bedding planes. Contacts between the slates and tuffs are usually gradational and often a single hand specimen will show gradation from a bedded slate to a fine-grained tuff. In composi-tion the bedded argillites vary from felsic tuffa-ceous argillite to mafic tuffaceous argillite inter-mixed with varying amounts of weathered material and land waste. Much of the slate is massive and jointed showing little effects of meta-morphism while in other places it has been strongly metamorphosed and shows a well defined slaty cleavage. The cleavage or schistosity does not in most places correspond to the bedding planes of the rock. In places, especially near igneous intrusives and mineralized zones, the slate is often highly silicified and resembles chert. IGNEOUS INTRUSIVE ROCKS The Carolina Slate Belt is bordered on the west by an igneous complex composed of gabbro, diorite and granite and intruded at many places, particularly in the northern half by granitic-type rocks. These igneous intrusives apparently vary from late Ordovician to early Permian in age. ENVIRONMENT OF DEPOSITION The occurrence of volcanic-sedimentary rocks along the western edge of the Coastal Plain and eastern edge of the Piedmont Plateau, in a long narrow belt that extends from southeastern Vir-ginia to central Georgia, with a length of more than 400 miles and width up to 120 miles, sug-gests deposition under geosynclinal conditions. As indicated above, these rocks consist of a great volcanic-sedimentary series varying from felsic to mafic in composition and composed of lava flows, beds of breccia, coarse tuff, fine tuff and ash, and feeds of shale or slate now designated as bedded slates or argillites. The lava flows and the coarse angular tuff and breccias could have been formed on land or under water. Conclusive evi-dence for one as opposed to the other is lacking. Many of the tuffs and breccias consist largely of subangular to rounded fragments that were cer-tainly reworked and deposited in water. The bedded slates and argillites were definitely water laid. Their composition, both chemical and physi-cal, and their texture indicate that they were not transported great distances. Finally, the presence of varying amounts of nonvolcanic materials or land waste in the form of mud, clay, silt, sand and at places rounded quartz pebbles up to an inch in diameter indicate that varying amounts of materials were brought into the area from ad-jacent land masses. There seems to be little doubt that the rocks of the Carolina Slate Belt were formed in a eugeo-syncline. The volcanic materials in this geosyn-cline came largely from beneath the surface by volcanic eruptions, while the nonvolcanic sedi-ments came from narrow belts of uplift that were present in or adjacent to the trough. The thickness of these rocks is variable but un-known. It appears possible, however, that in cen-tral North Carolina, west of the Durham, Deep River and Wadesboro Triassic basins, the vol-canic- sedimentary series may have a thickness up to 20,000 or 30,000 feet. The period of volcanic-activity during which this great series of volcanic-sedimentary rocks were being formed must have continued through a very long time, perhaps hundreds of thousands or even millions of years. During this time, there were innumerable alter-nations between quiet upwelling of lava, explo-sive activity piling up great amounts of tuff, breccia and ash and periods of comparative quiet accompanied by weathering, erosion and deposi-tion of the bedded deposits. Between successive outbursts the magma probably underwent some degree of differentiation so as to give rise to more acid rocks at one time and more basic at another. Such changes were not great for at no time did the products depart far from the general type which was a relative acid magma rich in soda. STRUCTURAL FEATURES The chief structural features of the rocks of the Carolina Slate Belt are cleavage planes, joints, folds and faults. The first of these to be of interest was the cleavage planes. Olmsted (1825) designated these rocks as the Great Slate Formation because of the well developed, slate-like cleavage which he observed over most of the area. In general, rocks of the Carolina Slate Belt south of U.S. Highway 70 from Durham to Greensboro have a well defined cleavage that strikes northeast and dips steeply to the north-west. North of this line the cleavage continues to strike northeast but much of the dip is to the southeast and at a lower angle than that which dips to the northwest. No explanation for this change in dip is readily available. The metamorphism which produced the cleav-age was not as intense as was originally thought and also varied widely from place to place. At places, metamorphism was so severe that the cleavage has become schistosity and the rocks are essentially schists. At other places, the cleavage apparently grades into jointing. As a result, the massive rocks are highly jointed and contain poorly developed cleavage planes. Recent work has revealed that folding is better developed than was formerly thought. It is now established that the rocks are in general well folded into a series of anticlines and synclines. The largest and most important fold is the Troy anticlinorium which trends in a northeast-south-west direction and whose axis lies a short dis-tance west of Troy. West and southwest of the Troy anticlinorium, northeast-trending open fold-ed synclines and anticlines predominate. The most important of these is the New London syn-cline. East, southeast, and northeast of the Troy anticlinorium the intensity of the folding in-creases. The rocks are tightly compressed into northeast-trending, asymmetric folds whose axial planes usually dip steeply to the northwest. The bedded argillites (volcanic slate) seem to have consolidated readily and folded like normal sediments while the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. This is indicated by the mashed and sheared condition of practically all the tuffs while in numerous cases more or less well preserved bedding planes in the slates indi-cate definite folding. Numerous insignificant faults occur in nearly all parts of the Carolina Slate Belt. These in gen-eral never amount to more than a few feet and are doubtless only the adjustments due to the folding of the rocks and are not of any great structural importance. However, along the east-ern border of the belt where the Carolina Slate Belt rocks have been compressed into northeast-trending asymmetric folds whose axial planes dip steeply to the northwest, thrust faults are present. The abundance and importance of these faults in relation to the overall structure of the Carolina Slate Belt are not yet fully established, but recent geologic mapping has revealed the presence of such faults in Moore and Orange counties. AGE OF THE ROCKS Emmons (1856), the first worker to date the rocks of the Carolina Slate Belt, considered them to be mainly slates and quartzites of sedimentary origin as shown by the presence of rounded peb-bles. He divided these rocks into a lower and upper series and placed them in his Taconic system which was early Paleozoic in age. He con-sidered the talcose slates of the lower series to have essentially the same composition as the underlying primary series and stated: "The tal-cose slates may be regarded as the bottom rocks, the oldest sediments which can be recognized, and in which, probably, no organic remains will be found." Later Emmons found near Troy, Montgomery County, two or three species of fossils in the lower series of the Taconic system. These fossils, which belonged to the class of zoophites, the low-est organisms of the animal kingdom, were found through about 1000 feet of rock and occurred from a few in number to abundant. The fossils were considered to be corals of a lenticular form that varied in size from a small pea to two inches in diameter. At first, Emmons considered the difference between the small and the larger forms to be the result of age but later decided that they were specific and named the small form Paleotrochis minor and the large form Paleotrochis major. These forms were of interest to Emmons main-ly in showing that lower Taconic rocks were fos-siliferous rather than in actually dating the rocks. Paleotrochis major and Paleotrochis minor were later identified as spherulites in rhyolite and not fossils, Diller (1899). Kerr (1875) classed the rocks of the Carolina Slate Belt as Huronian in age, which in his classi-fication is a division of the Archean. Williams (1894) classed them as Precambrian in age. Wat-son and Powell (1911) on the basis of fossils, considered the Arvonia slates of the Piedmont of Virginia to be Ordovician in age. Laney (1917) on the basis of the work by Watson and Powell, classed the volcanic-sedimentary rocks of the Virgilina district of the Carolina Slate Belt as Ordovician in age. In recent years the trend has been to place the age of these rocks as early Paleozoic, probably Ordovician. According to the U.S. Geological Sur-vey, Professional Paper 450A, Research 1962, "Lead-alpha measurements by T. W. Stern on zircon collected by A. A. Stromquist and A. M. White from felsic crystal tuffs in the Volcanic Slate belt of the central North Carolina piedmont have confirmed a previously inferred Ordovician age for these unfossiliferous rocks." White, et. al. (1963) gave the details on the collection and evaluation of two samples of zircon from the Albemarle quadrangle and stated: ". . . the indi-cated age for each is Ordovician according to Holmes time scale (Holmes, 1959, p. 204) ." Recently, St. Jean (1964) reported the first authentic discovery of fossils in the Carolina Slate Belt of North Carolina. The discovery con-sisted of two abraded and moderately distorted thoraxes and pygidia of a new trilobite species. The specimens were collected from a piece of stream rubble in Island Creek at Stanly County Road 1115. The type rock in which the fossils occurred is present in outcrops upstream. St. Jean classed the specimens as a new species ques-tionably assigned to the Middle Cambrian genus Paradoxides and stated: "Although the generic assignment is questionable, the morphologic char-acters of the two specimens indicate an age no younger than Middle Cambrian and no older than the age of the oldest known Early Cambrian tri-lobites." "The specimens are significant because they represent the first authentic fossil material from the Piedmont south of Virginia and provide paleontological documentation of the age and marine nature of a lithologic unit in the area. Micropygous Cambrian trilobites are more com-mon in eugeosynclinal belts, which part is in keeping with the paleogeographic and lithologic setting." Granites of post-Ordovician but Paleozoic age and diabase dikes of Triassic age both intrude the Carolina Slate Belt rocks. The granites apparently furnished the solutions that produced the pyro-phyllite and associated minerals, and are con-sidered further below. The diabase dikes have no relations to the pyrophyllite deposits and are not discussed further. GEOLOGY OF THE PYROPHYLLITE DEPOSITS INTRODUCTION Just when pyrophyllite was first discovered in North Carolina is not known. Olmsted (1822) in a report entitled, "Descriptive Catalogue of Rocks and Minerals Collected in North Carolina" listed talc and soapstone from several counties includ-ing Chatham and Orange and stated that fhey were extensively used for building and orna-mental purposes, and added that Indian utensils of the same materials were common. In 1825 he called attention to the "Great Slate Formation" which passes across the State from northeast to southwest and again noted the presence of talc and soapstone in Chatham and Orange counties. Since no talc and soapstone are known to occur in rocks of the Carolina Slate Belt and since pyrophyllite is found at a number of localities in the belt it is quite probable that the deposits mentioned by Olmsted were pyrophyllite. Emmons (1856) described a material which was locally known as soapstone at Hancock's Mill, (Now Glendon) Moore County and near Troy, Montgomery as follows : "A rock, which occurs in extensive beds, and known in the localities where it is found as a soapstone, can by no means be placed properly with the magnesium minerals. It is white, slaty, or compact translucent, and has the common soapy feel of soapstone, and resem-bles it so closely to the eye and feel that it would pass in any market for this rock. It has, how-ever, a finer texture, and is somewhat harder; but it may be scratched by the nail, so that it ranks with softest of minerals: it scratches talc, and is not itself scratched by it; it is infusible before the blowpipe, and with nitrate of cobalt gives an intensely blue color, proving thereby the presence of alumina in place of magnesia." He classed the mineral as agalmatolite, the figure stone of the Chinese, and described the methods used in quarrying it at Hancock's Mill. Brush (1862) analyzed some of the material from Hancock's Mill, Moore County and showed it to be pyrophyllite. Pratt (1900) described the deposits and pub-lished further analyses of the pyrophyllite. He stated that : "While the talc deposits of Cherokee and Swain counties are pockety in nature and of limited depth, the pyrophyllite formation is con-tinuous and of considerable, though of unknown depth." Pratt described the pyrophyllite as follows: "While possessing many of the physical proper-ties of talc and often being mistaken for it, the pyrophyllite is quite different in its chemical com-position, and is a distant mineral species. Al-though this mineral probably cannot be put to all the uses of talc, it can be used for the larger number of them, and those for which the talc is used in the greatest quantity. Some of this might be of such quality that it could be cut into pencils, but the most of this mineral would only be of value when ground. It is soft with a greasy feel and pearly luster, and has a foliated structure. The color varies from green, greenish and yel-lowish- white to almost white; but when air-dried they all become nearly white. Very little compact pyrophyllite has been observed that would be suitable for carving, as is used in China, although considerable of this has been used in the manu-facture of slate pencils." Pratt presented three chemical analyses of pyrophyllite from Moore County that were very close to the theoretical composition of that min-eral. He, also, pointed out that the deposits had been worked almost continuously since the Civil War. Hafer (1913) noted that the pyrophyllite did not differ greatly from the sericite found in the old gold mines of the slate belt and may have originated in the same manner. He, also, called attention to the masses of pyrite-bearing quartz that are often found associated with the pyro-phyllite deposits. Stuckey (1928) presented the first detailed re-port of the pyrophyllite deposits of North Caro-lina. He described their distribution, geological setting, form or shape, mineralogy, origin and possible continuation with depth. He classed the deposits as hydrothermal in origin and thought that they might continue to considerable depths. DISTRIBUTION Pyrophyllite occurrences are known along the eastern half of the Carolina Slate Belt from the vicinity of Wadesville in the southwestern part of Montgomery County northeastward to the northern part of Granville County near the Vir-ginia line. These occurrences may consist of a single deposit or they may contain several pros-pects or deposits. In Montgomery County pyrophyllite is known to occur near Wadesville ; on Cotton Stone Moun-tain, 3.5 miles north of Troy; just east of State Road 1312 near Abner; and northeast of Asbury in the northeastern corner of the county. Consid-erable prospecting has been done near Wadesville and the area appears promising for mining. Limited prospecting has been done on Cotton Stone Mountain but no mining has been carried out. Limited prospecting and some mining have been carried out on the deposit near Abner but the property is currently idle. One deposit north-east of Asbury appears to have been worked out, but another is promising for future development. In Moore County, pyrophyllite is found ap-proximately four miles southwest of Spies near the point where Cotton Creek enters Cabin Creek ; near Robbins; and in a zone several miles long that lies along Deep River north of Glendon. The Robbins area contains the only underground mine, which is the largest pyrophyllite mine in the State, and several open pit prospects. The Glendon zone contains three active open cut mines and a number of prospects. Pyrophyllite is known to occur in Randolph County in the vicinity of Pilot Mountain about 8 miles southeast of Asheboro, just north of State Highway 902, and near Staley in the northeastern part of the county. In the Pilot Mountain area there are four prospects, one of which has been explored and considerable iron-stained pyrophyl-lite is reported to be present. No mining has been carried out in this area. The deposit near Staley, which at one time contained the second largest mine in the State, has been worked out and aban-doned. The only known pyrophyllite area in Chatham County is located near the Chatham-Alamance county line on the Hinshaw property. This prop-erty is about 2 miles east of State Road 1004 and a short distance north of State Road 1343. Pyro-phyllite crops out at three places in the area, one of which has been prospected to a limited extent. No mining is being carried out in the area. Pyrophyllite is known to occur at two localities near Snow Camp in southern Alamance County. On Pine Mountain southeast of Snow Camp is a major open pit mine from which pyrophyllite has been mined for more than 20 years. About 2 miles east of Snow Camp there are several pyro-phyllite exposures on a prominent hill known as Major Hill. Major Hill lies south of State Road 1005 and between State Roads 2356 and 2351. The outcrops in Major Hill are promising and prospecting is currently underway. In Orange County pyrophyllite is known to occur in the vicinity of Teer in the southwestern part of the county; near Hillsborough; and on the Murray estate about 6 miles northeast of of Hillsborough. In the vicinity of Teer, prospect-ing has been carried out at three or more places 10 and limited mining was done at one time. This area has been abandoned at least temporarily. South and southwest of Hillsborough are three prominent hills which trend northeast and parallel the major geologic structure of the area. The northern most of these hills contains a major open cut pyrophyllite mine that is an important pro-ducer of pyrophyllite, andalusite, sericite and silica. The deposit in the Murray property north-east of Hillsborough lies south of State Road 1538 and west of State Road 1548. Considerable pro-specting has been carried out on this property, but no mining has been done. In Granville County, pyrophyllite deposits are found on Bowlings Mountain northwest of Stem ; at several places on Long Mountain which lies to the northwest of Bowlings Mountain; and on Daniels Mountain about 9 miles north of Oxford. On Bowlings Mountain, which is located about three miles slightly northwest of Stem, prospect-ing and some mining have exposed a major pyro-phyllite deposit. To the northwest of Bowlings Mountain is a northeast trending series of irregu-lar hills that occupy an area a mile or more in width and some 4 miles long, known as Long Mountain. Prospecting and some exploration have demonstrated the presence of pyrophyllite at sev-eral places on Long Mountain, but no mining has been done. About 9 miles north of Oxford and 1.5 miles northeast of State Highway 96 and east of Mountain Creek is Daniels Mountain on which pyrophyllite is known to occur. No prospecting or mining has been done on this mountain. GEOLOGIC RELATIONS All the pyrophyllite deposits of North Carolina occur in acid volcanic rocks, chiefly in medium to fine-grained tuffs and to a less extent in an acid volcanic breccia. They are not found at any place in a basic andesitic type of rock or asso-ciated with a typical water-laid slate. At the Phillips, Womble and Reaves mines, which are found in the Deep River pyrophyllite zone north of Glendon, Moore County, the footwall side of the pyrophyllite bodies is an acid volcanic breccia. Next to the footwall is a highly mineralized pyro-phyllite zone that grades into a fine-grained acid tuff. At places the pyrophyllite grades into and replaces parts of the brecciated footwall. Where the band of volcanic breccia is absent from the footwall side of the deposits, in this zone, the pyrophyllite bodies are much nearer the slate than where the breccia is present, but they are never found in normal slate. On the hanging wall side the pyrophyllite grades into medium to fine-grained acid tuff. The geologic distribution of the pyrophyllite deposits is probably controlled in part by the composition of the rocks and in part by rock structures. As indicated above (page 8), the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. As a result, the acid tuffs and breccias developed shear zones along which the pyrophyl-lite mineralization was later concentrated. A few shear zones, particularly those along Deep River near Glendon and near Robbins (both in Moore County) were developed along major thrust faults. However, the great majority of the pyro-phyllite deposits are found in shear zones that do not show any evidence of containing faults. FORM AND STRUCTURE A prominent feature of the pyrophyllite bodies is their irregular, oval, or lens-like form. This structure is observed along the strike and also vertically to the depths reached in mining. In nearly every deposit that has been developed enough to show the true structure, bodies and lenses of pyrophyllite are found along with lenses of tuffaceous rocks that exhibit various stages of alteration. Most pyrophyllite deposits occur as narrow bands or zones aligned with the cleavage strike and dip of the country rock. They range in size from those measured in inches up to 500 feet wide and 1500 to 2000 feet long. The strike of the cleavage in both the country rock and the pyrophyllite bodies is northeast-southwest, while the dip is steeply to the northwest. In most cases the larger mineralized zones con-sist of a very siliceous footwall, a well developed mineralized zone and a highly siliceous and seri-citic hanging wall. Where these conditions exist contacts between the mineralized zone and the footwall and the hanging wall are gradational. Contacts between the footwall and country rock and the hanging wall and country rocks are, also, gradational. When the siliceous footwall and the sericitic hanging wall are absent, as they fre-quently are, contacts between the mineralized zones and the country rocks are gradational. Excellent examples of the siliceous footwall may be seen at the Bowlings Mountain deposit, 11 Granville County, at the Hillsborough deposit, Orange County, at the Staley deposit, Randolph County, and at the mine of the Standard Mineral Company, Moore County. In general, it consists of a light blue-gray to white, fine-grained to medium-grained rock having the general appear-ance of quartzite. Selected samples from the more massive portions of this rock consist almost en-tirely of silica. The rock has been fractured con-siderably at places and contains varying amounts of sericite and pyrophyllite. When fresh, the rock is hard and dense and breaks with a conchoidal fracture. When weathered, it breaks down to a sandy friable material that is usually white, but is often stained various shades of yellow and red by iron oxide. The siliceous footwall ranges from less than 5 to more than 50 feet in thickness and in many cases extends the entire length of the deposit. When it occurs as a massive unit, it often crops out as bold ledges near the crest of the hill as at the Staley and Hillsborough deposits. However, as at the mine of the Standard Mineral Company near Robbins, Moore County, it may not crop out at all. From the footwall mineralization increases inward to rich zones and lenses of pyrophyllite and then decreases towards a schistose and seri-citized hanging wall. MINERALOGY OF THE DEPOSITS The minerals most commonly observed in the pyrophyllite deposits in the apparent order of their abundance are pyrophyllite, quartz, sericite, chloritoid, pyrite, chlorite, feldspar, iron oxides, zircon, titanite, zeolites and apatite. Of these, only the first eight are present in important amounts or related to the development of the pyrophyllite. The other minerals are present in small amounts to the extent they might occur as accessory constituents of an igneous rock or as products of regional metamorphism or weather-ing. In addition, small amounts of fluorite have been found with quartz veins intruding the fault zone at the Phillips mine. Also, varying amounts of the high-alumina minerals andalusite, dia-spore, kyanite and topaz have been found in sev-eral pyrophyllite mines and prospects. The posi-tion of these high-alumina minerals in the mineral sequence of the pyrophyllite deposits is not clear and they are discussed below. Pyrophyllite Pyrophyllite is a hydrous aluminum silicate with the general formula H2Al2Si40i2. It crystal-lizes in the orthorhombic system, but good crys-tals are rare. It commonly occurs as (1) foliated, (2) granular and (3) radial or stellate masses. The color varies from nearly black through yel-lowish white, green, and apple green to pure white. It has a specific gravity of about 2.8 to 2.9, and a hardness less than the finger nail. It has a pearly luster, a greasy feel and commonly occurs as masses, lenses and pockets associated with quartz, sericite and chloritoid. The pyrophyllite in the deposits near Glendon and Robbins, Moore County, consists almost entirely of the foliated variety. That in the other major deposits consists largely of massive granular and radial fibrous forms with occasional small amounts of the foli-ated variety. Quartz Quartz is an oxide of silicon with the general formula Si02 . It crystallizes in the hexagonal system, and good crystal specimens are common. Quartz is colorless when pure, has a conchoidal fracture, a viterous luster, a hardness of 7 and a specific gravity of 2.65. It is abundant through-out the deposits everywhere except in the very purest pyrophyllite and occurs (1) as large masses of cherty or milky appearance, (2) as clear veins and stringers in the deposits and along the walls, and (3) as small masses and nodules in the altered or only partly altered rock. Sericite Sericite is a fine-grained variety of mica, usual-ly muscovite, occurring in small scales and having the composition (H,K)AlSi04 . It crystallizes in the monoclinic system, has a basal cleavage, a hardness of 2-2.25, a specific gravity of 2.76-3 and a vitreous luster. The color varies from color-less through gray, pale green, and violet to rose-red. Sericite is often concentrated as bands or zones along the hanging wall of the pyrophyllite bodies and to a lesser extent along the footwall. It is, also, present as finely divided scales and flakes and as zones through good pyrophyllite. Chloritoid Chloritoid probably crystallizes in the triclinic system but rarely occurs in distinct tabular crys- 12 tals. It often occurs in the form of sheaves or rosettes. The general formula is H2 (Fe,Mg) Al2Si07 . It has a basal cleavage, a pearly luster, a hardness of 6.5 and a specific gravity of 3.52- 3.57. The color varies from dark gray through greenish black to grayish black. Chloritoid is found in varying amounts in all the pyrophyllite deposits but is most abundant in those along Deep River north of Glendon, Moore County where an acid iron breccia forms part of the footwall. Pyrite Pyrite has the formula FeS2 , crystallizes in the isometric system and often occurs as good crys-tals. It has a conchoidal fracture, a hardness of 6-6.5, a specific gravity of 4.95-5.10, a metallic luster and a brass-yellow color. It is present in small amounts associated with the silicified tuff along the walls of the pyrophyllite bodies and in the lenses of silicified country rock included in the deposits. Chlorite Chlorite, probably clinochlore, has the formula H8Mg5Al2Si3 18 , crystallizes in the monoclinic sys-tem and usually occurs as flakes or scales. It has a hardness of 2-2.5, a specific gravity of 2.65-2.78, a pearly luster, and a grass-green to olive color. Chlorite occurs rather commonly in the impure portions of the pyrophyllite bodies and in the altered wall rocks. Feldspars Feldspars, orthoclase (KAlSi3 8 ), albite (NaAlSi3 8 ), and in one case andesine, a mixture of albite (NaAlSi3 8 ) and anorthite (CaAl2Si2 9 ), were found in small amounts in the less silicified portions of the wall rock of the pyrophyllite bodies. Orthoclase and albite are more abundant due to the fact that they are com-mon constituents of the rhyolitic and dacitic rocks in which the pyrophyllite was formed. Iron Oxides Iron oxides, chiefly hematite Fe2 3 and magne-tite Fe3 4 , occur in small amounts in each pyro-phyllite deposit studied, but most abundantly in the footwall of the mines along Deep River north of Glendon, Moore County, where an acid iron breccia is present. High Alumina Minerals One or more of the high-alumina minerals an-dalusite (Al2Si05 ), diaspore (A12 3H20), kyanite (Al2Si05 ) and topaz (AlF) 2Si04 , are present in varying amounts in most of the pyrophyllite de-posits except those in Moore County, and Conley (1962a) reported collecting a specimen from the fault zone in the Phillips mine that contained pyrophyllite, diaspore, topaz and fluorite. The occurrence of high-alumina minerals in the pyrophyllite deposits is quite irregular, with the greatest concentrations near the footwall and lesser amounts along the hanging wall and asso-ciated with lenses of only partly altered country rock included in the deposits. Andalusite is abun-dant in the Hillsborough deposits. In the deposit on Bowlings Mountain, Granville County, there is considerable topaz as well as small amounts of andalusite and kyanite. Some blocks of topaz are in the pyrophyllite deposits today and represent material that was not replaced or destroyed dur-ing pyrophyllite formation. PETROGRAPHY A careful study of a number of thin sections cut from specimens collected at the various mines and quarries shows that the pyrophyllite deposits have been formed in volcanic tuffs and to some extent in a volcanic breccia that varied from dacitic to rhyolitic in composition. Sections from specimens of tuff and breccia col-lected along the walls of the pyrophyllite bodies and from partly altered country rock included in them show that the minerals of the pyrophyllite bodies were formed in the order of quartz, pyrite, chloritoid, sericite, and pyrophyllite; and that these minerals have definite relations to each other and to the feldspars and iron oxides in the country rock. The first change was a marked silicification of the enclosing rocks accompanied by a rapid de-crease in their normal mineral content. The feld-spars, rock fragments, and fine-grained ground-mass of the rocks were readily replaced by quartz to the extent that the altered rocks became masses of cherty and milky quartz. At the Womble and Phillips mines north of Glendon, Moore County and at the Staley mine 3 13 miles west of Staley, Randolph County, the silici-fication was accompanied or immediately followed by the development of pyrite, as this mineral is found in the silicified wall rocks of the mines and in included masses of silicified country rock but not in good pyrophyllite. Chloritoid is found in varying amounts at all the prophyllite prospects and mines but is more abundant at some including the Womble and Phillips mines north of Glendon, Moore County and the Murray prospect 5 miles northeast of Hillsborough, Orange County and the Staley mine 3 miles west of Staley, Randolph County. At the Womble and Phillips mines it is apparently re-lated to an acid iron breccia which contains con-siderable magnetite and hematite and forms the football of these deposits. The chloritoid at the Murray prospect and the Staley mine seems to be related to bands and zones of greenstone in the wall rocks of the bodies near the pyrophyllite. The chloritoid was not observed replacing the iron oxides but the marked increase and close association of chloritoid with the iron oxides at every point where the latter are present suggests a close genetic relation between the two. The chloritoid was developed along with or soon after the silicification of the tuff and in thin sections is seen to have partly replaced the quartz. Sericite is often concentrated as bands or zones along the hanging wall of the pyrophyllite bodies and to a lesser extent along the footwall. It is also present as finely divided flakes and scales and as zones through good pyrophyllite. Thin sec-tions cut from silicified and partly prophyllitized masses from the various pyrophyllite deposits show sericite associated with pyrophyllite and having about the same relations to the quartz. The cherty or flinty masses of quartz in the pyro-phyllite bodies are cracked and shattered and partly replaced by sericite. The microscope shows pyrophyllite to be the last mineral formed. In every case silicification preceded the development of pyrophyllite. The feldspars diminish with silicification so that feldspar and pyrophyllite are seldom found in the same section. Where pyrophyllite is found in sections with chloritoid, it occurs in every crack and opening in the sheaves and bundles of chloritoid as a replacement of the chloritoid. Prac-tically all specimens except those from the purest pyrophyllite, contain some quartz, the amount of the latter depending upon the purity of the speci-men in terms of pyrophyllite. In sections from such specimens the pyrophyllite is replacing the quartz. Sections from the masses of cherty or milky quartz associated with pyrophyllite show both sericite and pyrophyllite replacing the quartz with sericite apparently earlier than the pyro-phyllite. The position of the minerals andalusite, diaspore, kyanite and topaz in the sequence is not clear, but they appear to have been formed before or early in the pyrophyllitization process as they have been replaced partially by sericite and pyro-phyllite. ORIGIN OF THE PYROPHYLLITE DEPOSITS In considering the origin of the pyrophyllite deposits, it has been necessary to take into ac-count their shape and distribution, their relations to the enclosing rocks, their mineralogical com-position, the relations of the associated minerals to each other, and the relations of the pyrophyl-lite to the associated minerals and the enclosing rocks. Over the years, ideas as to the origin of pyrophyllite have changed and future develop-ment of the deposits may disclose new informa-tion that may require new explanations. This is especially true since the deposits are associated with metamorphic rocks and ideas on the origin of metamorphic rocks and their contained miner-als are in a state of change. EARLIER THEORIES Before discussing the origin of North Carolina pyrophyllite, reference should be made to the views expressed by other writers on the origin of this mineral and the chloritoid and sericite asso-ciated with it. Emmons (1856) considered pyrophyllite (agal-matolite) as a sedimentary rock near the base of his Taconic system. Levy and Lacroix (1888) stated that pyrophyllite occurs in metamorphic rocks while Dana (1909) classed it as a mineral formed at the base of schists or as a mineral of the crystalline schists and Paleozoic metamor-phics. Clapp (1914) described pyrophyllite deposits on the west side of Vancouver Island, British Columbia. Both alunite and pyrophyllite occur in andesite, dacite and associated pyroclastic rocks. This series and in particular its fragmental parts, has been metasomatically altered to quartz-sericite- chlorite rocks, quartz-sericite rocks, 14 quartz-pyrophyllite rocks and quartz-alunite rocks. Clapp concluded that most of the minerali-zation was caused by hot sulphuric acid solutions of volcanic origin which were active during the accumulation of the pyroclastic rocks, and as a result of relatively shallow depths and low pres-sures. He postulated little change in the bulk composition of the original volcanic rocks and interpreted most of the new minerals as having been developed from feldspars. In general, how-ever, the quartz-pyrophyllite rocks show a net gain in alumina, a loss of potash and either a loss or a gain in silica. Buddington (1916) and Vhay (1937) have described in detail the pyrophyllite deposits in the Conception Bay Region of Newfoundland. These deposits occur in a thick series of Pre-cambrian rhyolite and basalt flows which contain interlayered breccias, tuffs and some waterlaid materials. These volcanic rocks were altered re-gionally with the development of abundant chlo-rite and silica. Locally, some of the rocks were pyrophyllitized, some pinitized and some silici-fied. Some of the pyrophyllite concentrations are found in rhyolite breccias and conglomerates, but most are limited to the rhyolite flows. The pyro-phyllite itself forms single, well defined veins, as well as series of inter-connecting veins, lenses and pockets. The development of the pyrophyllite evidently involved the introduction of large amounts of alumina, the replacement of alkalies by hydroxyl, and the removal of silica, both that occurring as free quartz and that in the other minerals. Much of the pyrophyllitized rock may once have been a relatively homogeneous glass. Buddington (1916) concluded that these de-posits were formed by the metasomatic replace-ment of previously silicified rhyolites by thermal waters under conditions involving dynamic stress and intermediate temperatures and pressures. The solutions evidently moved along fault or shear zones, and the deposits have a marked schistosity. Vhay (1937) concluded that the individual flakes of pyrophyllite have a random orientation and that the schistosity of the deposits represent an inherited feature preserved by differential re-placement along schistose structures already established. The pyrophyllite deposits in the San Dieguito area of San Diego County, California, have been described in detail by Jahns and Lance (1950). These deposits were formed by the alteration of volcanic flows, breccias and tuffs that ranged in composition from andesite to rhyolite. Jahns and Lance (1950) described the origin of these deposits as follows : "The mode of occur-rence of the San Dieguito pyrophyllite, particu-larly its distribution with respect to fractures and shear zones in the host volcanic rocks, indi-cates that it was formed by replacement of these rocks. Its development was accompanied by intro-duction of Si02 , A12 3 and probably OH. The phyrophyllite bearing rocks, including those of highest grade, contain fresh pyrite and other sul-fide minerals at depths in excess of 20 feet in most parts of the area. Both pyrophyllite and sulfides appear to be hypogene, and are plainly earlier than the widespread iron oxides, man-ganese oxides and clay minerals of supergene origin. "Under the microscope both pyrophyllite and quartz replace feldspars and other original min-erals of the volcanic rocks, and in many places the two replacing minerals are of the same gen-eral age. As pointed out by Bastin and others, (1931) aggregate, rather than sequential replace-ment, is characteristic of hypogene processes. Zonal distribution of replacing minerals with respect to remnants of earlier minerals, a feature so common in supergene replacement, is con-spiciously absent from the pyrophyllite-bearing rocks. Moreover, the replacement is not particu-larly selective; the pyrophyllite, although first attacking parts of the groundmass in the volcanic rocks is generally distributed throughout the phenocrysts and groundmass minerals." They conclude : "The metamorphism of the vol-canic rocks in the San Dieguito area, and the subsequent introduction of silica and pyrophyl-lite almost certainly took place during late Trias-sic or Cretaceous time. A considerable thickness of volcanic rocks was removed by erosion prior to deposition of the latest Cretaceous sediments in the region, so that it is impossible to establish a maximum depth at which the pyrophyllite de-posits were formed. At no place is the total thick-ness of the Santiago Peak volcanics known, but it may well have amounted to several thousand feet. On the basis of the general geologic relations and the indirect evidence from laboratory investiga-tions, it seems likely that the San Dieguito pyro-phyllite deposits were formed hydrothermally under conditions of intermediate temperatures 15 and pressures. This is in accord with conclusions reached by Buddington (1916) for somewhat similar deposits in the Conception Bay region of Newfoundland, and by Stuckey (1925) for the deposits in the Deep River region of North Caro-lina. In contrast, the deposits on Vancouver Is-land, British Columbia, appear to have been formed under near surface conditions." Based on a study of samples collected from various pyrophyllite deposits of North Carolina, Zen (1961) tended to disregard the effect of hydrothermal replacement solutions on the forma-tion of the pyrophyllite bodies. He considered the presence of the three phase mineral assemblage of the ternary system A12 3 — H2 —Si02 to indicate that water acted as a fixed component. He further noted, however, that to say water acted as a fixed component did not completely imply the absence of a free solution phase (hy-drothermal solutions). Such a phase could have existed, but certainly did not circulate freely through the system destroying the buffering mineral assemblages. Conley (1962a) concluded: "The bulk chemical composition of the pyrophyllite deposits is essen-tially the same as that of the country rock. All of the chemical elements present in the pyrophyl-lite deposits are present in the country rock, with the exception of fluorine, copper and gold. These elements are associated with quartz veins and silicified zones and were obviously brought in from an outside source. The pyrophyllite deposits could have formed in place with either addition or substraction of chemical elements if the ele-ments were properly segregated and recrystallized into new minerals." LeChatelier (1887) determined the tempera-ture at which pyrophyllite loses its water and found two points of marked loss, one at 700° and the other at 850° C. Stuckey (1924) made a com-parative dehydration test of pyrophyllite and sericite and found that sericite lost its water much faster than pyrophyllite at lower temperatures and at 750° C was practically dehydrated while the pyrophyllite held about 1 percent of its water which was finally lost at approximately 900° C. Rogers (1916) classed sericite as a typically low temperature mineral associated with the last stages of hydrothermal alteration while Lindgren (1919) classed it as a mineral common to hydro-thermal alterations at shallow and intermediate depths and pointed out that in acid rocks of the rhyolitic type silicification and sericitization are common near the surface, but did not agree with Rogers that sericite is a late mineral. While much has been published regarding the nature of chloritoid there is little definite infor-mation on its genesis. Clark (1920) stated that chloritoid is formed in schists where much iron and water are present, and that it is intermediate between the micas and chlorite and may alter into either. Manasse (1910) described a schist of sericite, quartz, rutile, tourmaline, chlorite and epidote from the Alps of Italy, closely associated with and occurring on both sides of a marble, in which chloritoid is abundant. Niggli (1912) in a study of the chloritoid and ottrelite groups of the Swiss Alps decided that the two minerals are identical. He pointed out that chloritoid is abundantly developed in schists that were originally high in clay content and thought that its formation was directly due to pressure and relatively independent of tempera-ture. He gave a diagram showing that regardless of temperature, chloritoid is formed with an in-crease in pressure and conversely it drops out when the pressure diminishes. ANALYSES OF ROCKS In Table 1, on page 17, there are a number of chemical analyses of rocks and minerals from the Carolina Slate Belt of North Carolina and for comparison, several analyses of similar rocks from other regions. Number 1 is a rhyolite from Flat Swamp Mountain in the Carolina Slate Belt of Davidson County, North Carolina, while Num-ber 2 is a devitrified rhyolite from South Moun-tain, Pennsylvania. Number 3 is an average of 115 analyses of rhyodacite and rhyodacite-obsidian obtained from widespread areas. Num-ber 4 is dacite from Kemp Mountain in the Carolina Slate Belt of Davidson County, North Carolina. Number 5, is dacite tuff, 1 mile south-east of Monteith Bay, Vancouver Island, while Number 6, is the same type of rock a short dis-tance away that has been silicified and altered to a cherty quartz-sericite rock. Numbers 7, 8, 9 and 10, represent commercial pyrophyllite from 4 mines in North Carolina. Analyses Number 1 through 5, Table 1, page 17, represent normal or average rhyolite and dacite rock types, and as is to be expected the bulk com-position of these analyses is remarkably uniform. Si02 varies from 66.27 to 74.67 percent, A12 3 16 from 10.78 to 15.39 percent, CaO from 0.34 to 3.68 percent, Na2 from 3.40 to 5.46 percent, K2 from 1.74 to 3.01 percent, and H2 from a trace to 0.68 percent. Analyses number 7 through 10, represent average commercial pyrophyllite, and as might be expected the bulk composition of these analyses is remarkably uniform. Si02 varies from 57.58 to 64.68 percent, A12 3 from 28.34 to 33.31 percent, CaO from a trace to 0.72 percent, Na2 from 0.06 to 0.38 percent, K2 from a trace to 3.90 percent, and H2 from 5.40 to 5.86 per-cent. This change in bulk composition from rhyolite and dacite to pyrophyllite was brought about by silicification of the rhyolite and dacite to a cherty quartz rock as shown in analysis number 6, fol-lowed by replacement to pyrophyllite. As silicifi-cation advanced there was a decrease in alumina and alkalies and an increase in silica. Replace-ment by pyrophyllite, in some cases, preceded or accompanied by sericite, resulted in a decrease in silica and an increase in alumina, potash increas-ing with the sericite content, while water in-creased from about 1 percent to an average of 5.59 percent. The conditions indicated by the above analyses may be observed at many of the pyrophyllite de-posits in the area. Beginning in walls of unaltered rhyolitic or dacitic tuff there is a gradual transi-tion through silicification, sericitization and pyro-phyllitization to lenses and masses of practically pure pyrophyllite in the interior of the bodies. As a result, the mineral bodies contain walls of silicified country rock that on the interior por-tions have been more or less sericitized and par-tially to completely pyrophyllitized. Table 1. Analysis of Rhyolite, Dacite and Pyrophyllite 1 2 3 4 5 6 7 8 9 10 Si02 74.67 73.62 66.27 72.33 73.22 87.80 64.53 57.58 64.68 64.54 A12 3 10.78 12.22 15.39 14.56 13.46 9.08 29.40 33.31 28.34 28.88 Fe2 3 1.25 2.08 2.14 0.15 2.33 0.40 0.33 0.60 0.45 FeO 2.11 2.23 2.22 0.96 nd 0.67 nd nd nd MgO trace 0.26 1.57 0.91 0.42 trace trace trace trace CaO 1.47 0.34 3.68 2.55 1.50 trace trace 0.72 0.36 Na2 5.31 3.57 4.13 3.40 5.46 0.62 0.28 0.06 0.38 0.12 K2 2.68 2.57 3.01 2.82 1.74 1.70 trace 3.90 0.01 0.18 H2 0.59 0.68 0.30 0.62 1.04 5.86 5.56 5.54 5.40 C02 1.30 Ignition 0.40 Total 100.16 99.09 99.26 99.24 99.71 100.04 100.33 100.74 100.27 99.33 1. Rhyolite from Flat Swamp Mountain, North Carolina, Pogue (1910) p. 54 2. Devitrified rhyolite from South Mountain, Pennsylvania, Williams (1892) p. 494 3. Average of 115 analyses of rhyodacite and rhyodacite-obsidian, Nockolds (1954) p. 1014 4. Dacite from Kemp Mountain, Davidson County, North Carolina, Pogue (1910) p. 57 5. Dacite tuff 1 mile southeast of Monteith Bay, Clapp (1914) p. 120 6. Silicified dacite tuff (cherty quartz-sericite rock) Monteith Claim, Clapp (1914) p. 120 7. Pyrophyllite from Rogers Creek Mining Company's mine, Pratt (1900), p. 26 8. Pyrophyllite from Standard Mineral Company's mine, Stuckey (1928), p. 36 9. Pyrophyllite from Womble mine, Stuckey (1928) p. 36 10. Pyrophyllite from Gerhard Bros., Staley, North Carolina, Stuckey (1928) p. 36 17 ORIGIN OF NORTH CAROLINA PYROPHYLLITE The field, microscopic and chemical evidence indicates that the pyrophyllite deposits in North Carolina have been formed through the metaso-matic replacement of acid tuffs and breccias of both rhyolitic and dacitic composition. The de-velopment of pyrophyllite was accompanied by the introduction of Si02 , A12 3 and water. The quartz, pyrite, chloritoid, sericite and pyrophyl-lite in the mineralized bodies are apparently of hypogene origin. Evidences that the deposits have been formed by replacement are as follows : (1) Gradational contacts between pure pyrophyllite and the unaltered country rocks. (2) The preservation of structures of the primary rocks in the mineralized rocks, such as bedding planes of the finer tuffs, and fragmental outlines of the coarser tuffs and breccias. (3) The presence of masses and lenses of practically pure or only partly altered country rock, appar-ently unattached and completely surrounded in the mineral bodies. (4) The introduction of some elements and the removal of others. (5) The lack of any noticeable change in the volume of the original rocks during the mineralization processes. (6) The massive and homogeneous structure of the py-rophyllite. The following sequence of events is deduced : (1) The metamorphism of the volcanic fragmental and flow rocks in which the mineral bodies were later formed. (2) The silicification of the volcanic fragmental and flow rocks by metasomatic processes as is indicated by the presence of original structures of the vol-canics in the silicified materials, and by the pres-ence of entirely surrounded fragments of only partly silicified volcanic rocks in the quartz areas. (3) The development of pyrite in the silicified areas, accompanying or immediately following the silci-fication of the volcanics. (4) The development of chloritoid to some extent in all the pyrophyllite bodies and in abundance in parts of these deposits that are near iron rich forma-tions. (5) The development of sericite by the replacement of the previously silicified volcanic fragmental and flow rocks. (6) The development of pyrophyllite by replacement of the previously silicified and mineralized tuffs and breccias, closely associated with or immediately following the formation of the sericite. SOURCE OF MINERALIZING SOLUTIONS The pyrophyllite forming solutions were evi-dently of hypogene origin, but their source is not so easily demonstrated. The only intrusive igneous rocks that are exposed near any pyrophyllite de-posits in the area are diabase dikes, which are clearly later than the pyrophyllite mineralization. While none of them are known to be exposed in or near a pyrophyllite deposit there are a great many granite type intrusive rocks exposed at widely scattered localities in the pyrophyllite area. During the latter half of the nineteenth cen-tury there were a number of active gold and cop-per mines throughout the Carolina Slate Belt that were important enough to receive considerable attention in reports of the North Carolina Geolog-ical Survey between 1856 and 1917. Nitze and Hanna (1896) pointed out that the gold and cop-per deposits throughout the Carolina Slate Belt are very similar and that much silicification had accompanied the formation of the ores. They at-tributed this mineralization to hot carbonated, alkaline waters of deep seated origin. Laney (1910) found much silicification associated with the ore bodies (gold and copper) at Gold Hill, and concluded that the mineralization had been produced by hot solutions given off from a granite that had been intruded into the volcanics in the immediate vicinity of the ore bodies. Pogue (1910) found practically the same conditions in the Cid district of Davidson County, except that there were no known intrusive igneous rocks to have furnished the solutions. He concluded, how-ever, that there were large igneous masses in-truded into the rocks of the district from below, but that these rocks did not reach the surface. If Nitze and Hanna are correct in their state-ments that the gold and copper mines of the en-tire slate belt are in general alike, and if Pogue is correct in assuming a large intrusive magma below the Cid district that belonged to a period when large amounts of igneous rocks were in-truded into the Piedmont Plateau and brought near the surface, it seems that the same condi-tions must have existed in the pyrophyllite re-gion and that the gold ores of the various mines were formed by hot solutions from igneous mag-mas below. There is a close relation between the pyrophyllite deposits and the metalliferous de-posits at a number of places. One that may be used as a type example is the mine of the Stand-ard Mineral Company near Robbins, Moore Coun-ty, where the pyrophyllite schist grades directly into the silicified tuff at the old Cagle gold mine. This seems to indicate that the same source that 18 furnished the hot solutions to deposit the gold and copper ores in the slate belt also furnished the hot solutions to produce the pyrophyllite bodies. CONDITIONS OF PYROPHYLLITE FORMATION Different investigators have indicated that py-rophyllite may form under conditions varying from high temperature and pressure to low tem-perature and pressure such as exist near the surface. The information available on the origin of chloritoid. seems to indicate that it forms at fairly high temperatures and according to Niggli (1912) is directly dependent upon fairly high pressure. Graton (1906) classed the gold-quartz veins of the Southern appalachians as high temperature in origin, while Laney (1910) and Pogue (1910) both indicated that the gold and copper ores of the Gold Hill and Cid districts were formed under conditions of temperature and pressure varying from high to intermediate. That the pyrophyllite bodies were formed by hot solutions given off from the same source and acting at about the same time is indicated by the close association of the pyrophyllite bodies with the old gold mines, especially the Cagle gold mine near Robbins, Moore County and at the Brewer gold mine (Powers, 1893) in South Carolina. Hafer (1913) noted the presence of copper bearing pyrite in the mine of the Southern Talc Company at Glen-don, Moore County. It is possible that at the pyrophyllite deposits there was a gradual change from high tempera-ture and pressure to low temperature and pres-sure of hydrothermal alteration near the surface during the period of activity of the hot solutions. The writer, however, agrees with Buddington (1916) and Jahns and Lance (1950) and believes that the pyrophyllite deposits of the Carolina Slate Belt in North Carolina were formed under conditions of intermediate temperature and pres-sure. While considering the source of the solutions and the conditions under which the pyrophyllite was formed the problem of a line of entrance for rising solutions should not be overlooked. As has been stated above, the pyrophyllite de-posits occur as elongate bodies or lenses several times as long as they are wide. In at least four localities, near Robbins, Moore County, along Deep River north of Glendon in Moore County, near Hillsborough in Orange County, and north of Stem in Granville County, the pyrophyllite bodies occur as a long zone of lenses from 50 feet to 500 feet wide and from 250 feet to 2000 feet long that can be traced for considerable distances along strike. The mineral bodies are all found in acid tuffaceous rocks and in some cases, particu-larly along Deep River north of Glendon in Moore County, on the limbs of anticlines (as they were worked out and mapped in the field). It seems unreasonable for a special type of vol-canic tuff to have been formed as long narrow bands so widely separated while at all other points there were such wide variations in the material. The conclusion, therefore, is that there was either faulting or some lines of weakness developed along which the solutions entered to form the mineral deposits. Recently, Conley (1962 a) has shown that the pyrophyllite deposits along Deep River, north of Glendon, and those southwest of Robbins in Moore County, were formed along fault zones. There has not been enough detailed mapping carried out to determine the true conditions at the other de-posits in the slate belt. Stuckey (1928) pointed out that the pyrophyllite bodies were formed by the replacement of acid tuffs and breccias of both dacitic and rhyolitic composition and that the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. It is logical to assume, therefore, that all the pyrophyllite bodies were formed along lines of weakness, either fault zones or shear zones. RESERVES Sufficient evidence is not available to determine accurately the reserves of pyrophyllite in North Carolina, but there is sufficient information to establish the presence of fairly dependable indi-cated reserves. Of some 15 known occurrences of pyrophyllite in North Carolina only 5 or 6 have been developed enough to indicate important re-serves of mineable pyrophyllite. These major deposits occur near Robbins and Glendon, Moore County, near Snow Camp, Alamance County, near Hillsborough, Orange County and near Stem, Granville County. All of these deposits, with two exceptions occur along prominent hills or ridges. The Glendon deposits occur in gently undulating topography, while that near Robbins occurs in a relatively flat area covered largely by a thin veneer of Coastal Plain sand. 19 To-date, with one exception, all the pyrophyl-lite mining in the State has been carried out largely from shallow pits and open cuts that have seldom reached a depth greater than 50 or 75 feet. The one exception to these conditions is at the mine of the Standard Mineral Company at Robbins, Moore County, where a shaft 650 feet deep and drifts and stopes are being used. In none of these pits, open cuts, or mines has there been any major change in the pyrophyllite or associated minerals with depth. Even though pyrophyllite should not be found in commercial amounts to depths of over 200 feet, there is enough available to that depth, in the more promising deposits, to support an important industry for many years under efficient mining, milling and concentration practices. The processes of milling have been such that everything that went into the mill had to be pure enough to make a good finished product. It is only recently that any attempt has been made to use separating and concentrating machinery in the removal of grit and other impurities. This has meant that a large amount of material which con-tained 50 percent or more of pyrophyllite has been going on the dumps as waste. If the methods of milling could be improved to the point where all material containing as much as 40 to 50 per-cent pyrophyllite could be utilized, it would prac-tically double the available amount on the basis of milling practices formerly carried out. Pratt (1900) pointed out that the pyrophyllite is continuous and of considerable, though un-known depth. Hafer (1913) suggested that pyro-phyllite should be found to the same depths that the gold mines of the area have reached, and in-dicated that gold had been mined to a depth of 500 feet. This statement seems very reasonable when it is realized that there is a close relation in the distribution of the gold and pyrophyllite mines, and also a strong possibility that the solu-tions forming both come from the same source. Stuckey (1928) stated: "Taking into consider-ation the mineralogy and origin of the deposits, the source of the solutions and the relations in the distribution of the gold and pyrophyllite de-posits, it seems reasonable to expect pyrophyllite in commercial amounts to a minimum depth of 500 feet. This statement does not mean that every pyrophyllite deposit can be developed into a mine at that depth. It does mean, however, that all indications point to a depth of that magnitude for the larger bodies which really show promise at the surface." The results obtained in exploring for pyrophyl-lite over the intervening years have borne out this statement. Some small prospects have been explored that did not prove continuous with depth, but drill holes more than 500 feet deep have failed to reach the limits of the major de-posits. The pyrophyllite deposits occur as irregular lenses 50 to 500 feet wide and 500 to 1500 or more feet long. The bodies of workable pyrophyllite usually occur near the center of the deposits and vary in width from a few feet to more than 100 feet. Pyrophyllite has a specific gravity of 2.8 to 2.9 and weighs 175 pounds per cubic foot. Each 100 feet of length and depth of a pyrophyllite body 100 feet wide should yield 50,000 tons allow-ing for a 60 percent recovery. Using these figures and assuming recovery to a depth of 400 to 500 feet, a reserve of some 10 to 12 million tons of pyrophyllite is indicated in North Carolina. During the past 15 years it has been frequently stated that all the really promising pyrophyllite deposits in North Carolina had been discovered and were controlled by three or four major min-ing companies. Recently, detailed prospecting by two major companies has resulted in the discovery of promising occurrences of pyrophyllite in three new areas. These deposits have not been explored and detailed information on them is not available. These discoveries are interesting, however, as indicating that undiscovered bodies of pyrophyl-lite are still available in North Carolina to those willing to do the necessary prospecting to find them. MINING METHODS The first reference to pyrophyllite mining in North Carolina was by Emmons (1856, p. 217) who stated: "Large quantities have been ground the last year in Chatham County for the New York market." He, also stated (p. 53) "The rock does not split readily with gunpowder; when quarried in this mode, as at Hancock's, it breaks out in illshapen shattered masses. Hence it should be cut out with a sharp pick or an edged instru-ment of suitable form." At first prospecting and mining were carried out by pits, shallow shafts, drifts and open cuts. As demands for larger quantities increased and off color material became salable, open cuts — 20 made possible by information from diamond drill-ing and by modern earth-moving machinery have furnished most of the production. The largest, and only modern underground pyrophyllite mine in North Carolina, is operated near Robbins, Moore County, through a 650 foot shaft, drifts and stopes. PROCESSING The processing of pyrophyllite has changed slowly through the years as demands and uses for the mineral have increased and changed. Prior to about 1855 it was used only locally—for stove linings, fireplaces, chimneys, mantels and grave-stones— and was cut and shaped to fit the par-ticular need. The production of pyrophyllite crayons was started about 1880 and continued until about 1920. Ground pyrophyllite was first produced in 1855, (Emmons 1856, p. 217) . From 1855 to 1913 grinding was carried out, first at Hancock's Mill and later at Glenn's Mill, both located on Deep River near the present village of Glendon, Moore County. The grinding stock was carefully selected, air dried, and crushed. It was then crushed by hand, ground with millstones and passed through bolting cloth. In 1902 the first mill constructed exclusively for grinding pyrophyllite was built near a deposit along Deep River, north of Glendon. This was followed in 1904 by a second mill on another de-posit about a mile away. Both mills were alike in that the grinding stock was air dried and crushed. In one mill the crushed material was passed through a hammer mill, ground with mill-stones, fed into a ball mill, ground 8 hours and screened. In the other mill, the crushed material was ground with millstones, the fines removed by air, and the coarse material fed into a ball mill, ground, and screened. Both of these mills were abandoned by the end of 1921. Before 1918, all the known pyrophyllite de-posits of any importance were located along the north side of Deep River, in the general vicinity of Glendon, Moore County. In that year, what later proved to be the largest known pyrophyllite deposit in the state was discovered about 2 miles southwest of Robbins, Moore County, when wagon wheels brought up a fine white material that proved to be pyrophyllite. The first modern grind-ing plant was built on this property about 1921. The process first used consisted of crushing, grinding in a hammer mill and screening. The hammer mill did not prove satisfactory for grind-ing, and after some modifications, the process was abandoned. A new process was installed, con-sisting of crushing and grinding in a roller mill, and screening. As the ceramic market for pyro-phyllite has become more important, conical peb-ble mills for fine grinding have been installed in this and other plants in the State. At the present time three companies—the Standard Mineral Company at Robbins, the Gen-eral Minerals Company at Glendon, and the Piedmont Mineral Company at Hillsborough are mining and processing pyrophyllite for market. A fourth company, the North State Pyrophyllite Company at Greensboro is mining pyrophyllite and producing a variety of pyrophyllite refrac-tories but is not selling pyrophyllite as such. None of these companies is carrying out benefi-ciation or true mineral dressing on crude pyro-phyllite. By selective mining, blending, grinding and screening, a wide variety of grades, stand-ardized both as to grain size and chemical com-position, is being produced for fillers and specialty products and for use in ceramic bodies and re-fractories. In the processes used to-date, only pyrophyllite pure enough to make a salable finished product has been used. As a result, much good material containing 40 to 60 percent pyrophyllite has been discarded. In view of the somewhat limited re-serves and increasing demands, too much good material is being left in the ground or thrown on the dumps. However, as demands have increased, improved methods of grinding and screening have reclaimed much material formerly discarded. Re-search on the removal of iron, free silica and other impurities has been carried out. As a result, larger tonnages of pyrophyllite of higher quality than that now being produced should be made available to industry as demands increase. USES OF PYROPHYLLITE Pyrophyllite has a wide range of uses which are dependent largely upon the remarkable physi-cal properties of the mineral. Most of these uses are similar to those of talc, to the extent that the two minerals are often used interchangeably. Py-rophyllite is a hydrous aluminum silicate with the formula H2Al2Si40i2. It occurs in several common habits, the best known, perhaps, being the rosette-like aggregates of radially disposed fibers and elongate flattened crystals. A flaky or foliated 21 variety with a slaty cleavage is common along the north side of Deep River and near Robbins in Moore County. A third variety consists of masses of grains and fibers that lack orientation or layering. In some of the finer-grained occur-rences, the pyrophyllite individuals are rosette-like in detail although this is rarely apparent to the unaided eye. While the chemical formula of theoretically pure pyrophyllite is rather simple, most commer-cial pyrophyllite contains varying small quanti-ties of the elements, iron, calcium, magnesium, sodium, potash and titanium. The chemical com-position can be useful in predicting the behavior of pyrophyllite where very exact controls are required in the manufacture of certain products. In ceramic bodies, for example, such properties as color, shrinkage and absorption of tile bodies can be predicted in terms of the raw pyrophyllite used in them. The nature and uses of several types of pyro-phyllite from North Carolina have been effec-tively summarized in a booklet published by the R. T. Vanderbilt Company (1943) of New York. For further details on the properties of pyro-phyllite the reader should consult Grunner (1934), Hendricks (1938), and Ross and Hend-ricks (1945). Prior to about 1855, pyrophyllite was used locally for tombstones, and such stones, still well preserved, may be seen in two or more cemeteries near Glendon. Emmons (1856) described it as an excellent substitute for soapstone in stove linings, fireplaces, chimneys and mantles. He stated that it was not suitable for paint as it became translu-cent when mixed with oil, but described it as a filler that helped retain the perfume in soap and added that large quantities were ground for the New York market in 1855. He described it as suitable for anti-friction powder and use in cos-metics and quoted Dr. Jackson to the effect that it would make a very refractory material for stoneware and crucibles. At present, pyrophyllite is used chiefly in the manufacture of insecticides, rubber, paint, ceram-ics, refractories, plastics, and roofing paper. It has a number of minor uses for products including cosmetics, wallboard, rope and string, special plaster, textile products, paper, linoleum and oil-cloth, and several types of soap. The best pro-duction figures available indicate that about one half of the current annual production goes into insecticides, rubber and paint, one third into ceramics and refractories and the remainder into plastic, roofing paper, linoleum, cosmetics and a host of minor uses. According to Jahns and Lance (1950) : "A large part of the domestic production of pyrophyl-lite is incorporated into paints and particularly non-reflecting and other special types in which flake pigments of light color are desired. High oil absorption of ground pyrophyllite and its free-dom from grit also are desirable properties for paint use. Ground material is employed as a filler in rubber goods, certain roofing and flooring ma-terials, special plasters, plastics, insecticides, tex-tile products, paper, linoleum and oilcloth, rope and string, several types of soap and in some fertilizers. It serves as a "loader" in paper and textile fabrics, where its whiteness and resistance to the effects of fire and weather are particularly desirable. This resistance also partly accounts for its use in roofing papers and other asbestos and asphalt goods. Its corrosion resistance makes it an especially satisfactory filler in battery cases. There are indications that it also may serve effec-tively as a low noise filler in phonograph records. "With a low bulk density and slight acidity in ground form, high absorptive characteristics, and superior qualities as a flake-form dusting agent, pyrophyllite is an excellent carrier for such active insecticides as DDT, nicotine, pyrethrum and rotenone. The flakiness of the mineral leads to desirable adhesion on leaves and other parts of dusted plants, and its softness and freedom from grittiness when finely ground make for reduction of wear on nozzles and other parts of mechanical insecticide dispensers. "Pyrophyllite of great purity and whiteness has been used as a base for cosmetics and toilet prep-arations, but the total amount is not large. The lubricating properties of the mineral underlie its use in some greases, in tires and other rubber goods, on machine-driven box nails, and in vari-ous kinds of dies. On the other hand, it also is employed as a fine, "soft" abrasive in the scour-ing and polishing of certain foodstuffs, as well as some painted or lacquered surfaces. It serves as a high-quality packing and insulating material, as a constituent of adhesive, corrosion-resistant covering compounds, and as an absorbent for oil substances in a wide variety of products. It, also, can be processed for use in crayons and pencils. 22 "As a constituent of ceramic bodies, pyrophyl-lite is being more and more widely used. It is a good substitute for feldspar and quartz in wall-tile bodies, as it decreases their shrinkage and their crazing by thermal shock or moisture ex-pansion. It also is employed as a source of alumi-num in enamels, and as a raw material for semi-vitreous dinnerware and some types of refrac-tories." Uniformity of grain size and mineral content is becoming important for all uses. For ceramics, whiteware, and wall tile, where the size of the finished product must be controlled accurately, pyrophyllite is one of the best materials available provided it is perfectly uniform in grain size and composition. For use in special refractories, such as car tops for tunnel kilns, monolithic furnace lining and furnace lining requiring rapid tem-perature changes, pyrophyllite makes an excel-lent body that is shock-resistant. MINES AND PROSPECTS Beginning on the northeast in Granville Coun-ty, near the Virginia line, and continuing in a southwesterly direction to the southwestern part of Montgomery County is an irregular zone, along the eastern part of the Carolina Slate Belt, that contains all the known occurrences of pyrophyl-lite in North Carolina. Prospects, outcrops and/or mines are known to occur in Granville, Orange, Alamance, Chatham, Randolph, Moore and Mont-gomery counties. GRANVILLE COUNTY Daniels Mountain Pyrophyllite bodies occur in three localities in Granville County. One of these is on Daniels Mountain, a prominent ridge that rises nearly 200 feet above the surrounding countryside. Daniels Mountain is located approximately 9 miles slightly northwest of Oxford, about 1.5 miles east of North Carolina Highway 96 and just south of Mountain Creek. The area is un-derlain with acid volcanic rocks. Small amounts of pyrophyllite occur on the north end of this ridge. No prospecting had been done at the time the writer visited the ridge. Espenshade and Pot-ter (1960) described Daniels Mountain as fol-lows : "Another deposit of pyrophyllite occurs on a prominent ridge rising nearly 200 feet above the surrounding countryside, about 14 miles northeast of Bowlings Mountain deposit, 9 miles northwest of Oxford, and about l 1/^ miles east of North Carolina Highway 96. Float and low outcrops of dense siliceous rock are abundant for about three-quarters of a mile along the ridge. Chloritoid occurs in some rock, disseminated hematite and magnetite are also present. Blocks of massive pyrophyllite, 1 to 2 feet long, are dis-tributed along a distance of 600 to 700 feet at the north end of the ridge. Other aluminous min-erals have not been discovered." Bowlings Mountain A major pyrophyllite deposit is present on Bowlings Mountain, a prominent hill that is lo-cated about 3 miles northwest of Stem and 10 miles southwest of Oxford, Granville County. The hill rises to an elevation of about 700 feet above sea level (approximately 200 feet above the sur-rounding countryside), has a trend of about N 15° E and conforms to the pattern of a series of rather pronounced ridges to the northwest. The pyrophyllite deposit which lies along the crest and northeastern slope of the mountain is ap-proximately 500 feet wide and more than 1500 feet long. The strike is N 15° E and the apparent dip is 70° to 80° to the northwest, paralleling the strike and dip of the country rock. Prospecting was first carried out on the south-west end of the ridge and near the western slope, about the turn of the century, when a pit known as the Harris prospect was opened. This pit which was 15 to 20 feet long, 6 feet wide and 6 to 10 feet deep was opened on an outcrop of radiating or needle-like crystals of iron-stained pyrophyl-lite. About 1940 a shaft was sunk to a depth of approximately 80 feet near these old pits. The phyrophyllite found in this shaft did not differ materially from that found in the surface pits and the work was abandoned. About 1949 or 1950, Carolina Pyrophyllite Company began exploration and development work here, consisting of pitting and trenching followed by drilling, during the course of which a large tonnage of pyrophyllite was discovered. Following this exploration work, 2 opencuts were developed from which considerable pyrophyllite was mined and shipped by truck to a grinding plant at Staley, some 80 miles to the southwest, before that mill was closed in 1960. 23 On the southeast or footwall side of the deposit is a medium-grained, dense, quartzitic rock con-taining pyrite that seems to represent the foot-wall of the deposit. Northwestward from the quartzitic rock mineralization is quite apparent. Massive and crystalline pyrophyllite occurs in very fine-grained schistose zones in sericite schist. Tough, white, granular rock containing coarse-grained andalusite, quartz, and pyrophyllite is present in parts of the deposit. Massive topaz identical in appearance with the dense topaz from the Brewer mine in South Carolina is abundant as float adjacent to the quartzitic footwall. Here, it is found concentrated in a series of rather poorly defined zones covering an area more than 100 feet long and 200 feet wide. Individual pieces range from less than one-fourth inch to 3 feet in diameter. Outcrops in the area are rare, but, in recent road cuts along the northern end of the mountain, topaz is exposed as a series of narrow, irregular veinlike masses in sericite schist. It also occurs as stringers a few inches thick in phyrophyllite in the southernmost open cut. The topaz occurs as boulders in the quartzitic rock, filling cracks and fractures, as small knotty masses disseminated throughout the rock and as large massive pieces which in some cases appear to grade into the host rock. The andalusite and topaz, older than the pyrophyllite, appear to re-place the country rock and in turn are replaced by pyrophyllite. Long Mountain About a mile or two to the northwest of Bowl-ings Mountain is a zone of irregular hills from 1 to 1.5 miles wide and 4 to 5 miles long that is known as Long Mountain. This ridge trends about north 20 degrees east and lies partly to the north and partly to the south of State Road 1139. The highest point on Long Mountain is a knob north of State Road 1139 and along the western side of the ridge that is known as High Rock Mountain. It rises to an elevation of some 150 to 200 feet above the surrounding country-side and 700 feet above sea level. Pyrophyllite outcrops of varying size and promise, some of which have been prospected and some of which have not, are widely scattered throughout Long Mountain. Robbins Prospect 1 On the Robbins property, in the vicinity of High Rock Mountain is an area about 1000 feet wide and 2000 feet long on which radiating pyro-phyllite, associated with quartz veins, is common but not abundant. No prospecting has been done in this general area and the potential for commer-cial deposits of pyrophyllite is unknown. Most of the pyrophyllite visible is badly iron stained. Jones Prospect To the east of the Robbins tract and about 1500 feet north of State Road 1139, some 4 or 5 pros-pect trenches that varied in length from 150 to 300 feet and up to 8 or 10 feet deep were opened on the Jones land some 8 or 10 years ago. Details of this prospecting are not available but indica-tions for pyrophyllite are good. The country rock is a medium to fine-grained felsic volcanic tuff that has a cleavage which strikes north 20 to 30 degrees east and dips steeply to the northwest. Both foliated and radiating pyrophyllite, some of which is iron stained, is farily common. R. E. Hilton Property Adjoining the Jones land on the east is the land of R. E. Hilton on which there is a zone varying from 250 to 500 feet wide and about 1000 feet long that contains promising outcrops of pyro-phyllite. No prospecting has been done on this property but bold outcrops of good pyrophyllite make it appear promising. E. C. Hilton Property Along the east side of Long Mountain and south of State Road 1139 there are two interest-ing areas of pyrophyllite on the land of E. C. Hilton. The first of these, which is about 1500 feet south of State Road 1139 and near a recent sawmill site, consists of about three acres on which bold outcrops of pyrophyllite mixed with similar outcrops of felsic volcanic rocks are abun-dant. No prospecting has been done here but the outcrops indicate the possible presence of im-portant amounts of good pyrophyllite. The other area is on a prominent hill about 1500 feet farther southeast and beyond a small stream. Surface exposures of pyrophyllite are not extensive but some interesting outcrops of radiating crystals may be seen. Considerable prospecting in the form of drilling, the results of which are not known, was carried out here about 8 or 10 years ago. The country rock at both of these prospects is a medi-um to fine-grained, felsic volcanic tuff. 24 Robbins-Uzzell Property About 1500 feet south of State Road 1139 and to the southeast of High Rock Mountain is an unnamed ridge that ranges between 500 and 600 feet above sea level. This ridge which begins near the head of an east flowing stream continues in a south 20 degrees west direction to and beyond Dickens Creek a distance of 1.5 to 2 miles. The northeast end of this ridge is a part of the Rob-bins tract while the southwest end is a part of the Uzzell land. No prospecting has been done on this ridge but outcrops of excellent pyrophyllite remarkably free of iron stain make it promising as a source of pyrophyllite. Robbins Prospect 2 Just east of Knap of Reeds Creek and a short distance south of State Road 1139 is a power transmission line tower. Beginning near this tower and extending to the southwest for a dis-tance of 800 to 1000 feet is a pyrophyllite body that is 300 to 400 feet wide. The cleavage in this mineral body strikes about north 35 to 40 degrees east and dips steeply to the northwest. The rocks surrounding this deposit consist of medium- to fine-grained acid volcanic materials. The north-west 150 to 200 feet of the deposit consists largely of good quality pyrophyllite that varies from mas-sive to foliated. The southeast or footwall portion to a width of 75 or 100 feet appears to be in part sericite. This is a promising deposit that could contain considerable high-grade pyrophyllite. ORANGE COUNTY Murray Prospect Pyrophyllite deposits occur in three localities in Orange County. One of these known as the Mur-ray property is located on a ridge about 5 miles northeast of Hillsborough near the intersection of State Roads 1538 and 1548. State Road 1538 passes just to the north of the property while State Road 1548 lies just to the east. Here along a ridge in an area of medium to fine-grained acid volcanic rocks are old prospect pits up to 30 feet long by 10 feet wide and 6 feet deep. Most of the pits are about 10 feet long by 4 feet wide and 6 feet deep. The pits are scattered over an area 75 to 100 feet wide and 500 feet long. Pyrophyllite of the foliated or schistose variety is present on the dumps and in the sides of the pits as well as in an occasional outcrop. Chloritoid is abundant in the walls of some of the pits, especially near narrow bands of greenstone in the felsic volcanics. This area probably contains pyrophyllite of value. Hillsborough Mine Immediately south of Hillsborough are three prominent hills which trend northeast and paral-lel the major geologic structure of the area. From northeast to southwest these hills are often desig-nated Hill No. 1, Hill No. 2 and Hill No. 3. Al-though the three hills appear to be much alike in many ways, the developed mineralization is limited to Hill No. 1, the northeastern most of the three. Here, prospecting was started in 1952 by the North State Pyrophyllite Company fol-lowed by mining a few years later. The zone of mineralization as exposed by the open cut mining operations is some 1500 feet long and from 100 to 250 feet wide. It strikes approximately N. 50° E. and dips from 60 to 80 degrees to the northwest. The mineral body has a footwall of dense siliceous rock that forms the crest of the hill or ridge and a hanging wall of sericite schist. The chief min-erals in the deposit in the order of decreasing abundance are silica, massive and crystalline or radiating pyrophyllite, sericite, andalusite and topaz. Minor amounts of diaspore have been re-ported. Andalusite is abundantly disseminated throughout the deposit and seems to be consider-ably more abundant than pyrophyllite in much of the deposit. It is light blue, greenish blue or gray in color, has a pronounced blocky appearance, and occurs as small fragments about one-fourth inch in diameter, disseminated sparingly to abundant throughout the quartzose rock. Topaz occurs spar-ingly in the deposit, apparently being limited largely to disseminated grains and masses in the fractured quartzose footwall rock. Recent field work indicates that to the south-west mineralization similar to that on Hill No. 1, now being worked by Piedmont Minerals Com-pany, may be present in workable amounts on the northwest side of Hill No. 2 and in a prominent knob on the northwest side and near the north-east end of Hill No. 3. Teer Prospects In the southwestern part of Orange County, approximately 10 miles southwest of Hillsbor- 25 A. Mill B. Open Pit Mine Plate 2. Piedmont Minerals Company 26 ough, and in the general vicinity of Teer, there are a number of pyrophyllite outcrops, at least three of which have been prospected. On the north end of Mitchell Mountain and about one-half mile southwest of Teer, North State Pyrophyllite Com-pany carried out prospecting and produced a small amount of pyrophyllite. A pit 100 feet long, 30 feet wide at the top and 15 feet deep was exca-vated. The strike of the cleavage is N. 55° E. and the dip is 75 degrees to the northwest. The amount of good grade pyrophyllite was too low for economic mining and the prospect was ban-doned. About 3 miles almost due north of Teer and between State Road 1117 and Cane Creek, on the farm of Salina Sykes is a small prospect pit that contains minor amounts of radiating pyro-phyllite. No production was made and the pit is now abandoned. About one mile almost due north of Teer and between State Roads 1115 and 1116, considerable prospecting and some mining for pyrophyllite was carried out on the land of Clarence Bradshaw by the Carolina Pyrophyllite Company, between 1958 and 1961. A pit 200 feet long by 100 feet wide at the top and about 80 feet deep was exca-vated. The pyrophyllite content of the rock was originally 24 percent. The cleavage of the rock strikes about N. 55° E. and dips 75 degrees to the northwest. ALAMANCE COUNTY Snow Camp Mine The Snow Camp pyrophyllite deposit being worked by the North State Pyrophyllite Com-pany, is located on Pine Mountain about 3.5 miles southeast of Snow Camp. Prospecting was started in 1935 and over the intervening years the de-posit has been a major producer of massive pyro-phyllite. The pyrophyllite is shipped by truck to the company's plant at Pomona, North Carolina where it is used in the manufacture of firebrick, brick-kiln furniture and other refractory prod-ucts. The deposit is a lenticular body of massive pyrophyllite and fine-grained quartz about 35 feet long and 250 feet wide. Open pit mining had developed walls nearly 100 feet high in the east and south sides of the pit until parts of them were removed for safety reasons in 1965. A rib of high-silica rock is present near the center of the deposit. This rib has been quite heavily mineral-ized in places and parts of it have been mined out. Coarse-grained andalusite was reported to have been found in a zone several feet wide in the northern part of the deposit, but it did not seem to be very abundant. This deposit still appears to contain a large reserve of high-grade pyrophyl-lite. Major Hill Prospects About 2 miles east of Snow Camp there are several pyrophyllite outcrops on a prominent hill, known locally as Major Hill. Major Hill lies south of State Road 1005, between State Roads 2356 and 2351, and north of State Road 2348. This hill is somewhat irregular in shape, but slightly elon-gate in a direction a little north of east. Two small exposures of pyrophyllite are to be seen in old prospect pits near the west end of the hill, but they do not appear to be of commercial size. Beginning about midway of the hill from west to east and along the southern slope some 250 feet from the crest is a zone of pyrophyllite about 1000 feet long and 50 to 100 feet wide that ap-pears from outcrops to contain a considerable ton-nage of high-grade massive pyrophyllite. Due to wooded conditions and lack of outcrops the geolog-ical setting could not be satisfactorily determined. It appears, however, that the pyrophyllite is in an area of medium- to fine-grained tuffaceous rocks of volcanic origin and acid composition. This deposit is on land belonging to the North Carolina National Guard. Immediately to the east of the deposit on the National Guard land is a deposit 100 to 150 feet wide and 350 to 500 feet long on lands of the Holliday estate. This deposit contains both pyro-phyllite and sericite which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the northwest. This deposit appears to contain a con-siderable tonnage of minable material. To the northeast of this deposit and near the east end of Major Hill is another deposit of promise on the Holliday estate. The outcrop is irregular in shape but appears to be 150 to 300 feet wide and 400 to 500 feet long. Pyrophyllite and sericite, both of which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the northwest, are present in varying amounts in this deposit. To the south and southeast of the above de-scribed deposits is another deposit on the south-east tip of Major Hill and on lands of the Holliday estate. This deposit is 150 to 250 feet wMe and 27 400 to 500 feet long. It contains both pyrophyllite and sericite which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the north-west. Because the above described three deposits, on the Holliday estate are all in wooded areas and rock outcrops are not too abundant it was not possible to establish completely the geological setting. It appears, however, that all three are in areas of medium- to fine-grained tuffaceous rocks of volcanic origin and acid composition. In the spring and summer of 1966 these deposits were under option to and being prospected by the North State Pyrophyllite Company. On the Richardson land, a short distance north-east of Major Hill and just west of State Road 2351, is an interesting occurrence of pyrophyllite. The outcrop area which is elongated in a north-east direction appears to be about 100 feet wide and 350 to 500 feet long. Both massive and radiat-ing pyrophyllite are present. About 2 miles east of Snow Camp and a short distance north of State Road 1005, the Carolina Pyrophyllite Company is quarrying sericite on a small ridge on a hill adjacent to the Foust lands. The sericite is being shipped by truck to Glendon where it is ground and blended with pyrophyllite. Open pit mining indicates a large tonnage of rock which may extend into the Foust lands to the north. CHATHAM COUNTY Hinshaw Prospect The only known pyrophyllite deposits in Chat-ham County are on the farm of Don Hinshaw in the northwestern corner of the county. This prop-erty is about 2 miles east of State Road 1004 and a short distance north of State Road 1343. It can be reached by leaving State Road 1004 at State Road 1343 about 2.5 miles south of the Chatham- Alamance line. Follow State Road 1343 about 1.5 miles northeast to the Hinshaw farm. The out-crops are in a wooded area a short distance north of the Hinshaw home. Here, some years ago, Carolina Pyrophyllite Company opened a pit some 10 feet wide, 15 feet deep and 25 to 40 feet long. Near this pit, pyrophyllite is scattered through rocks over a distance of 100 feet long and 25 to 50 feet wide. To the northeast are other outcrops that look promising. Enough pyrophyllite out-crops are present in the area to indicate that it is worth prospecting. RANDOLPH COUNTY Pyrophyllite is known to occur in Randolph County in two areas. One of these is in the north-eastern corner of the county about 3.5 miles west of Staley. The other is on the southern slopes of Pilot Mountain just north of State Highway 902 and about 8 miles east of Asheboro. Staley Deposit The Staley deposit, now worked out, was at one time the second largest pyrophyllite mine in the State. The main part of the deposit lay along the crest and northwest side of a rather steep hill as a lenticular body 100 to 200 feet wide and 350 feet long. The cleavage strike was approximately N. 50° E. and the dip was 60 to 70 degrees to the northwest. When abandoned the open cut was about 180 feet wide, 300 feet long and 250 feet deep. The hanging wall of the deposit consisted of a volcanic ash largely altered to a sericite schist. A central zone
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Title | Pyrophyllite deposits in North Carolina |
Creator |
Stuckey, Jasper L. (Jasper Leonidas), 1891-1979. |
Contributor | North Carolina. Division of Mineral Resources. |
Date | 1967 |
Subjects |
Pyrophyllite--North Carolina Geology--North Carolina |
Place |
North Carolina, United States |
Time Period |
(1954-1971) Civil Rights era (1945-1989) Post War/Cold War period |
Description | Bibliography: p. 37-38; |
Publisher | s.n. |
Agency-Current |
North Carolina Department of Environmental Quality |
Rights | State Document see http://digital.ncdcr.gov/u?/p249901coll22,63754 |
Physical Characteristics | vi, 38 p. : ill., map ; 28 cm. 1 folded map in pocket. |
Collection | North Carolina State Documents Collection. State Library of North Carolina |
Type | text |
Language | English |
Format | Bulletins |
Digital Characteristics-A | 3105 KB; 49 p. |
Series | Bulletin (North Carolina. Division of Mineral Resources) ; no. 80. |
Serial Title | North Carolina Geological Survey bulletin |
Digital Collection | North Carolina Digital State Documents Collection |
Digital Format | application/pdf |
Audience | All |
Pres File Name-M | pubs_geology_pyrophyllitedeposits1967.pdf |
Pres Local File Path-M | \Preservation_content\StatePubs\pubs_geology\images_master\ |
Full Text | C/ 3:80 6.£ Norih ouroiina Stare Library Raleigh North Carolina jyj e Q, Department of Conservation and Development Dan E. Stewart, Director Doc. Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 Digitized by the Internet Archive in 2013 http://archive.org/details/pyrophyllitedepo1967stuc North Carolina Department of Conservation and Development Dan E. Stewart, Director Division of Mineral Resources Stephen G. Conrad, State Geologist Bulletin 80 Pyrophyllite Deposits in North Carolina by Jasper L. Stuckey Raleigh 1967 MEMBERS OF THE BOARD OF CONSERVATION AND DEVELOPMENT James W. York, Chairman Raleigh R. Patrick Spangler, First Vice Chairman Shelby William P. Saunders, Second Vice Chairman Southern Pines John M. Akers Gastonia John K. Barrow, Jr. Ahoskie J. 0. Bishop Rocky Mount David Blanton Marion Harry D. Blomberg Asheville Robert E. Bryan Goldsboro William B. Carter Washington Arthur G. Corpening, Jr. . High Point Moncie L. Daniels, Jr. Manteo Koy E. Dawkins Monroe Dr. J. A. Gill Elizabeth City John Harden . Greensboro Gilliam K. Horton Wilmington Dr. Henry W. Jordan Cedar Falls Petro Kulynych Wilkesboro William H. Maynard Lenoir W. H. McDonald Tryon Jack Pait Lumberton John A. Parris, Jr. Sylva Oscar J. Sikes, Jr. Albemarle T. Max Watson Spindale 11 LETTER OF TRANSMITTAL Raleigh, North Carolina March 1, 1967 To His Excellency, HONORABLE DAN K. MOORE Governor of North Carolina Sir: I have the honor to submit herewith manuscript for publication as Bulletin 80, "Pyrophyllite Deposits in North Carolina," by Jasper L. Stuckey. This report contains detailed information on the occurrence, distri-bution and geology of pyrophyllite in North Carolina and should prove to be of considerable value to those interested in the mining and processing of this valuable mineral resource. Respectfully submitted, DAN E. STEWART Director m CONTENTS Page Abstract 1 Introduction 1 Previous work 1 Geology of the Carolina Slate belt 4 General statement 4 Distribution and character of the rocks 4 Felsic volcanic rocks 5 Mafic volcanic rocks 6 Bedded argillites (volcanic slate) 6 Igneous intrusive rocks 7 Environment of deposition 7 Structural features 7 Age of the rocks 8 Geology of the pyrophyllite deposits 9 Introduction 9 Distribution 10 Geologic relations 11 Form and structure 11 Mineralogy of the deposits 12 Pyrophyllite 12 Quartz 12 Sericite 12 Chloritoid 12 Pyrite 13 Chlorite 13 Feldspar 13 Iron oxides 13 High alumina minerals 13 Petrography 13 Origin of the pyrophyllite deposits 14 Earlier theories 14 Analyses of rocks 16 Origin of North Carolina pyrophyllite 18 Source of mineralizing solutions 18 Conditions of pyrophyllite formation 19 Reserves 19 Mining methods 20 Processing 21 Uses of pyrophyllite 21 Mines and prospects 23 Granville County 23 Daniels Mountain 23 Bowlings Mountain 23 IV Long Mountain 24 Robbins prospect No. 1 24 Jones prospect 24 R. E. Hilton property 24 E. C. Hilton property 24 Robins-Uzzell property 25 Robbins prospect No. 2 25 Orange County 25 Murray prospect 25 Hillsborough mine 25 Teer prospects 25 Alamance County 27 Snow Camp mine 27 Major Hill prospects • 27 Chatham County 28 Hinshaw prospect 28 Randolph County 28 Staley deposit 28 Pilot Mountain prospects 28 Moore County 29 McConnell prospect 29 Jackson prospect 30 Bates mine 30 Phillips mine 30 Womble mine . .31 Reaves mine 31 Jones prospect 33 Currie prospect 33 Ruff prospect 33 Hallison prospect 33 Standard Mineral Company 33 Tucker and Williams pits 35 Sanders prospect . .35 Montgomery County 36 Ammons mine 36 North State property 1 36 North State property 2 36 Cotton Stone Mountain 37 Standard Mineral Company 37 References cited 37 ILLUSTRATIONS Facing Page Plate 1. Pyrophyllite deposits in North Carolina 23 2. Piedmont Minerals Company 26 A. Mill B. Open pit mine 3. Glendon Pyrophyllite Company 32 A. Mill B. Open pit mine (Reaves) 4. Standard Mineral Company 34 A. Mill B. Open pit mine VI Pyrophyllite Deposits of North Carolina By Jasper L. Stuckey ABSTRACT All the known occurrences of pyrophyllite in North Carolina are found in Granville, Orange, Alamance, Chatham, Randolph, Moore and Montgomery counties where they are associated with vol-canic- sedimentary rocks of the Carolina Slate Belt. These rocks consist of lava flows interbedded with beds of ash, tuff, breccia and shale or slate that vary in composition from rhyolitic, or acid, to andesitic, or basic, and fall into three natural groups : Felsic Volcanics, Mafic Volcanics, and Bedded Argillites (Volcanic Slate). They have been folded, faulted and metamorphosed to the extent that they contain a well defined cleavage that strikes northeast and dips, in general, to the northwest. The pyrophyllite deposits which are irregular, oval or lens-like in form occur in acid volcanic rocks that vary from rhyolite to dacite in composition. The field, microscopic and chemical evidence indicates that the pyrophyllite bodies were formed by metasomatic replacement of the host rocks through the agency of hydrothermal solutions under conditions of intermediate temperature and pressure. Pyrophyllite has a variety of uses chief of which are in paints, rubber goods, roofing materials, ceramic products and insecticides. Reserves, while not large, are ample for several years. INTRODUCTION The pyrophyllite deposits of North Carolina are associated with volcanic-sedimentary rocks of the Carolina Slate Belt. Volcanic-sedimentary and similar rocks form a belt or zone along the east-ern border of the Piedmont Plateau and parts of the Coastal Plain all the way from the vicinity of Petersburg and Farmville, Virginia, southwest across North Carolina, South Carolina and into Georgia, as far as the southern part of Baldwin County south of Milledgeville—a total distance of over 400 miles. In North Carolina the zone occupied by volcanic-sedimentary rocks is known as the Carolina Slate Belt. It is in this belt that the pyrophyllite deposits of the state are found. The western border of the Carolina Slate Belt lies a few miles east of Charlotte, Lexington and Thomasville, crosses Guilford County southeast of Greensboro and continues northeast across the northwest corner of Alamance and Orange coun-ties and the center of Person County to the Vir-ginia line. The eastern limits of this belt are marked, by the cover of Coastal Plain sediments. PREVIOUS WORK Due to the presence of a wide variety of min-erals in them, the rocks of the Carolina Slate Belt have been of interest for approximately 150 years. These rocks, because of their complex character and well developed cleavage, were called slates by a number of investigators over a period of 70 years before their true nature began to be recognized. The first published report on that part of the slate belt in which pyrophyllite deposits are known to occur was a descriptive list of rocks and minerals from North Carolina by Denison Olmsted (1822). In this list he de-scribed novaculite, slate, hornstone, whetstone and talc and soapstone from several counties in-cluding Orange and Chatham. He stated that the talc and soapstone were extensively used for building and ornamental purposes and added that Indian utensils of the same materials were com-mon. In 1823, Olmsted was appointed by the Board of Agriculture to make a geological survey of the State. In his first report (1825) he called atten-tion to the "Great Slate Formation which passes quite across the State from northeast to south-west covering more or less of the counties of Person, Orange, Chatham, Montgomery —." The presence of talc and soapstone was noted in Orange, Chatham and other counties together with beds of porphyry in the eastern part of the formation and bands of breccia consisting of rolled pebbles interbedded in a ferruginous green-stone in different places. Ebenezer Emmons (1856), one of the most competent geologists of his time, considered the Carolina Slate Belt rocks to be among the oldest in the country and placed them in his Taconic system which he divided into an upper and lower member. The upper member consisted of clay slates, chloritic sandstones, cherty beds and brec-ciated conglomerate. The lbwer member consisted of talcose slates, white and brown quartzites and conglomerate. He did not recognize the presence of volcanic rocks in what is now known as the Carolina Slate Belt. In his lower unit, Emmons found what he considered to be fossils and named them Paleotrochis major and Paleotrochis minor. Diller (1899) recognized these as spherulites in rhyolite. Emmons described in some detail the phyro-phyllite deposits near Glendon, Moore County, then known as Hancock's Mill and classed the talcose slates, or those containing the pyrophyl-lite, as the basal member or oldest rocks of his Taconic system. He further pointed out that pyro-phyllite occurred in the same position in Mont-gomery County. Prior to this time the pyrophyllite had been considered as soapstone, but Emmons tested it before the blowpipe and found it to contain alumi-num and classed it as agalmatolite. He gave the physical properties of this mineral together with its uses and the methods of mining near Han-cock's Mill. Brush (1862) analyzed some of the material from Hancock's Mill, Moore County and showed it to be pyrophyllite. Kerr (1875) placed the rocks of the slate belt in the Huronian, which in his classification is a division of the Archean and considered them to be sedimentary. He mentioned talc and soapstone from Orange and Chatham counties but added nothing to the description already published by Emmons. Kerr and Hanna (1893) in "Ores of North Carolina," described some old gold mines in the Deep River region and stated: "It is worthwhile to add that part of what passes for talc is pyro-phyllite and even hydromicaceous." Williams (1894) recognized for the first time the occurrence of ancient acid volcanic rocks in the slate belt. He studied a small area in Chatham County and applied for the first time modern petrographic methods to the study of these rocks. He described this area in part as follows : "Here are to be seen admirable exposures of volcanic flows and breccias with finer tuff deposits which have been sheared into slates by dynamic agen-cies." He classed the slate belt rocks as Precam-brian in age. Nitze and Hanna (1896) first used the name Carolina Slate Belt for the rocks Olmsted (1825) had designated the "Great Slate Formation." They recognized the occurrence of volcanic rocks in the slate belt and suggested that there had been more than one volcanic outbreak and during at least one period of inactivity slates had been deposited. They did not mention pyrophyllite but described in some detail the Bell, Burns and Cagle gold mines, all of which are in the pyro-phyllite area along Deep River in Moore County and pointed out that there had been much silicifi-cation at all of these and some propylitic altera-tion at the Bell mine in particular. Pratt (1900) described the pyrophyllite de-posits near Glendon and showed by chemical analysis that the mineral is true pyrophyllite. He described the pyrophyllite deposits as follows: "They are associated with the slates of this region but are not in direct contact with them, being usually separated by bands of siliceous and iron breccia which are probably 100 to 150 feet thick. These bands contain more or less pyrophyllite and they merge into a stratum of pyrophyllite schists." He offered no suggestion as to the origin of either the slates, breccia or pyrophyllite. Weed and Watson (1906) in a report on "The Virgilina Copper District," concluded that the rocks of that area were Precambrian volcanics, chiefly an original andesite that had been greatly altered by pressure and chemical metamorphism. Laney (1910) presented a report on the "Gold Hill Mining District of North Carolina," in which he stated: "The rocks here included under the general term slates while having many local vari-ations seem clearly to represent a great sedi-mentary series of shales with which are inter-bedded volcanic flows, breccias and tuffs. In their fresh and massive condition the slates are dense, bluish rocks which show in many places well defined bedding planes and laminations. The vol-canic flows, breccias and tuffs which are inter-bedded with the slates apparently represent two kinds of lava, a rhyolitic and an andesitic type." Pogue (1910) presented a report on the "Cid Mining District of Davidson County," in which he described the rocks of that area as follows: "Wide bands of sedimentary, slate-like rock, com-posed of varying admixtures of volcanic ash and land waste have the greatest areal extents. Inter-calated with these occur strips and lenses of acid and basic volcanic rocks, represented by fine and coarse-grained volcanic ejecta and old lava flows." Laney (1917) in a report on the Virgilina dis-trict classed the rocks in the area studied as volcanic-sedimentary and stated: "Under this group are placed both the acid and basic flows and tuffs and the water laid tuffs and slates." Stuckey (1928) presented a report on the Deep River region of Moore County in which he di-vided the rocks of the Carolina Slate Belt in that area into slates, acid tuffs, rhyolites, volcanic breccias and andesite flows and tuffs. He noted that the schistosity dipped to the northwest and interpreted the structure as a closely compressed synclinorium with axes of the folds parallel to the strike of the formations. In addition, he pointed out that metamorphism is not uniform through-out the area. Bowman (1954) studied the structure of the Carolina Slate Belt near Albemarle, North Caro-lina, and recognized sedimentary rocks, volcanic tuffs and flows, and mafic intrusives in the area. He interpreted the structure as a series of undu-lating open folds. Conley (1959); Stromquist and Conley, 1959; and Conley (1962 b) divided the rocks in the Albemarle and Denton 15-minute quadrangles into (1) a lower volcanic sequence consisting largely of felsic tuffs that have been folded into an anticline plunging to the southwest, (2) a volcanic-sedimentary sequence consisting of a lower argillite unit, an intermediate tuffaceous argillite unit and an upper graywacke unit which have been folded into a syncline also plunging to the southwest and (3) an upper volcanic sequence consisting of mafic and felsic volcanic rocks which unconformably overlie the first two sequences. According to Conley (1962 a), "In Moore County only the lower and middle units appear to be present; however, some rhyolite in the area might belong to the upper unit. The exact strati-graphic relationships of some of the rocks in the county are in doubt because of the gradational nature of the contacts, a condition further com-plicated by intense folding and faulting and lack of outcrops." Conley and Bain (1965) suggested that the rocks of the Carolina Slate Belt in North Carolina can be divided into natural, mappable rock units. They proposed and named a set of rock units or formations into which these rocks might be divided, gave their areal extent and described their structure and lithology. From oldest to youngest these proposed formations are: Morrow Mountain rhyolite Badin greenstone Tater Top Group Unconformity Yadkin graywacke McManus formation Tillery formation Efland formation Uwharrie formation Albemarle Group The Uwharrie formation is composed chiefly of subaerially deposited felsic pyroclastic rocks. These are felsic tuffs consisting of interbedded lithic, lithic-crystal and devitrified vitric-crystal tuffs, welded flow tuffs and rhyolite. The Efland formation is a water-laid sequence consisting of andesitic tuffs with interbedded greenstones, conglomerates, graywackes and flows. The Albemarle Group is a water-laid sequence of pyroclastics and sediments which is divided into the Tillery formation, the McManus forma-tion and the Yadkin graywacke. The Tillery formation is composed in part of finely laminated argillite exhibiting graded bed-ding and in part of andesitic tuff and greenstone. The McManus formation is predominantly a felsic tuffaceous argillite formerly known as the Monroe slate. The Yadkin graywacke is a dark-green gray-wacke sandstone containing interbeds of mafic tuffaceous argillite, mafic lithic-crystal tuff and felsic lithic tuff. The older rocks are in part unconformably overlain by subaerially deposited pyroclastics and flows known as the Tater Top Group. From base to top the group is composed of basaltic tuffs and flows overlain by rhyolite flows. The Tater Top Group is divided into the Badin greenstone and Morrow Mountain rhyolite. The Badin greenstone is composed of lithic crystal tuffs and a basal unit of flows and flow tuffs of andesitic composition. The Morrow Mountain rhyolite consists of dark-gray to black porphyritic rhyolite contain-ing prominent flow banding. Conley and Bain described the Troy anticli-norium, with a northeast-southwest trend, as the major structural feature of the Carolina Slate belt. West and southwest of the Troy anticlinori-a um, northeast trending open folded synclines and anticlines predominate. East of the Troy anticli-norium the rocks are more intensely folded. They are compressed into northeast trending asym-metric folds whose axial planes usually dip steeply to the northwest. In many places, argil-lite has been converted into slate and phyllite. They considered the age of Carolina Slate Belt rocks to be early Paleozoic. GEOLOGY OF THE CAROLINA SLATE BELT GENERAL STATEMENT In North Carolina rocks of the Carolina Slate Belt actually form two belts that are separated by sedimentary rocks of the Durham, Deep River and Wadesboro Triassic basins and by the Roles-ville granite pluton and associated gneisses and schists. The first and most important of these and the one Olmsted (1825) first called the "Great Slate Formation" and Nitze and Hanna (1896) first called the Carolina Slate Belt lies to the west of the belt of Triassic rocks and varies in width from 20 to 60 miles. It is widest between Sanford and Lexington and narrows to the north and south. It crosses the central part of the State in a northeast-southwest direction from Anson and Union counties on the southwest to Granville, Person and Vance counties on the northeast and underlies all or parts of Anson, Union, Mecklen-burg, Cabarrus, Stanly, Montgomery, Moore, Chatham, Randolph, Davidson, Rowan, Guilford, Alamance, Orange, Durham, Person, Granville and Vance counties. This belt contains all the known pyrophyllite deposits in North Carolina and will be considered in detail below. The second belt in which Kerr (1875) first recognized metavolcanic rocks lies to the east of the belts of Triassic, igneous and metamorphic rocks. It begins in Anson County on the south, varies greatly in width and regularity and con-tinues in a northeast direction to Northampton County on the north. It is exposed at the surface in all or parts of Anson, Richmond, Moore, Har-nett, Lee, Wake, Johnston, Wayne, Wilson, Frank-lin, Nash, Halifax and Northampton counties. The eastern limits of this belt are unknown due to the cover of Coastal Plain sediments. A deep well in Camden County about 8 miles north of Elizabeth City, the county seat of Pasquotank County, penetrated rocks that are apparently of the Carolina Slate Belt. Two deep wells—one a few miles southeast of Kelly, Bladen County and the other 4 miles south of Atkinson, Pender Coun-ty— both penetrated Carolina Slate Belt rocks. West of a line from Elizabeth City to Atkinson, of the few wells that reached basement, some penetrated granite, some penetrated gneiss and schist and a few penetrated rocks of the Carolina Slate Belt. It is possible that if the crystalline floor be-neath Coastal Plains sediments was exposed, the types and percentages of rocks in this floor would not differ greatly from those found west of Coastal Plain sediments in Harnett, Johnston, Wake, Wilson, Franklin, Nash, Vance, Warren, Halifax and Northampton counties, where gneisses and schists, granites and rocks of the Carolina Slate Belt occur in about equal amounts. Pyrophyllite has not been found in this eastern zone of Carolina Slate Belt rocks and they are not considered further in this report. DISTRIBUTION AND CHARACTER OF THE ROCKS The rocks of the Carolina Slate Belt, west of the Durham, Deep River, and Wadesboro Triassic basins, consist of lava flows interbedded with beds of ash, tuff, breccia and shale or slate. All of these except the flows contain much nonvol-canic material in the form of mud, clay, silt, sand and conglomerate. (Also present is much non-descript material, some of which may be vol-canic, which for the lack of a better term has been designated land waste) . The flows, breccias, tuffs and ash beds and beds of shale or slate are all interbedded and in general do not appear to occupy definite stratigraphic positions in the series. The flows vary from rhyolite through andesite to basalt. The rhyolites and andesites vary from fine grained to coarsely porphyritic whereas the basalts are often amygdaloidal. The breccias vary from rhyolitic to andesitic in com-position and in fragment size from one-half inch to nearly a foot in diameter. The fragments of the breccias are in turn fragmental, apparently pyroclastic in origin. Some of the fragments in the breccias are sharply angular, although many are rounded, indicating transportation and de-position. The tuffs, while containing both acid and basic materials, are in general of an acid composition and composed of fragments less than half an inch in diameter. These fragments which vary from angular to rounded are often embedded in much fine-grained material apparently of non-volcanic origin. Beginning in the vicinity of the Randolph- Chatham county line, 15 to 20 miles south of Siler City, and continuing northeast through Siler City to the northern part of Orange County and the southeastern part of Person County are a number of beds of quartz conglomerate varying in width from a few inches to as much as 250 feet and of unknown length. The quartz pebbles in this conglomerate are generally less than an inch in diameter, well rounded and embedded in silt and sand, further indicating sedimentary processes. The shales and slates, which are generally well bedded, are composed of fine-grained volcanic materials (and much land waste) in the form of clay, silt and fine sand. Finally, much of the fine-grained materials in the breccias, tuffs and por-tions of the shales and slates strongly resemble metasiltstone and metagraywacke of some of the metagraywacke rocks in other areas, further indi-cating sedimentary processes. A wide variety of rocks are present in the Carolina Slate Belt and various attempts have been made to divide them into units or forma-tions. Conley (1959) and Stromquist and Conley (1959) proposed a three fold division of the rocks of the Albemarle and Denton 15-minute quadrangles, while Conley and Bain (1965) pro-posed a set of nomenclature for the rock-strati-graphic units and their areal extent in the Caro-lina Slate Belt. Since these proposals are not well known and generally accepted and since the rocks of the Carolina Slate Belt fall into three natural divisions, it appears that these three natural divi-sions are to be preferred in this discussion. These three divisions are Felsic volcanic rocks, Mafic volcanic rocks and Bedded argillites (volcanic slate). FELSIC VOLCANIC ROCKS Felsic. volcanic rocks occupy about half of the Carolina Slate Belt in the central part of the State and are the predominating rocks in the eastern part of the Piedmont Plateau. In this area they occupy much of the Carolina Slate Belt west of the Durham and Deep River Triassic basins and northeast of Anson, Union and Stanly counties. The felsic volcanic rocks consist largely of ma-terials of volcanic flow or fragmental origin. The flows are essentially rhyolite, while the frag-mental materials vary from rhyolitic to dacitic in composition. The fragmental rocks consist of breccias and coarse and fine tuffs, with coarse and fine tuffs making up the greater portion of the occurrences. Lenses of mafic volcanics and bedded slate of limited extent are also present. The fragmental rocks consist of fine and coarse tuffs and breccias. The coarse tuffs predominate and contain the fine tuffs and breccias as inter-bedded bands and lenses. The fragments compos-ing these rocks are angular to well rounded and vary in size from nearly a foot to a fraction of an inch in diameter. The fine tuff occurs interbedded with both the slate and coarse tuff and grades into each of them. It has no wide areal extent but occurs as narrow bands and lenses in the coarse tuffs. Microscopically the fine tuff shows a crypto-crystalline ground mass with fragments of quartz and feldspar (orthoclase, albite, oligoclase) as well as secondary minerals epidote, clinozoisite, chlorite and calcite. Iron oxides are sparingly present. Some sections show small rock frag-ments containing original flow structure while others exhibit a parallel arrangement of the par-ticles due to metamorphism. The coarse tuff varies from a massive to a highly schistose type of rock, that in places has been so slightly changed as to show some of its original characters. There is every gradation to a fine tuff on one hand and to a breccia on the other. The freshly broken rock proves to be made up of quartz and feldspar grains and rock frag-ments of less than one-half an inch in diameter set in a bluish or greenish-gray groundmass, the whole often resembling an arkose. In thin section the coarse tuff shows fragmental phenocrysts of quartz, orthoclase and acid plagio-clase with fragments of different kinds of rocks, some of which show definite flow structure, all embedded in a fine-grained groundmass. Kao-linite, epidote and calcite form secondary prod-ucts. Biotite and muscovite are rare. Grains of hematite and limonite as well as small particles of titanite and apatite are found in most sections. Flows of rhyolite occur as narrow bands and lenses in the tuff into which they appear to grade at places. This apparent gradation is possibly due to the fact that some material classed as silicified fine tuff may be partially devitrified rhyolite. The rhyolite is dense and indistinctly porphyritic, with a dark gray to bluish color, and in fresh fracture shows a greasy luster. Flow lines have developed in numerous places and are best seen on weathered surfaces, while amygdaloidal structure may be found in a number of outcrops. In thin section the rhyolite shows phenocrysts of plagioclase (chiefly oligoclase) orthoclase and quartz, named in the order of relative abundance. Kaolinite, epidote and chlorite have developed commonly from the weathering of the feldspars, and calcite is frequently found along fractures in the rocks. Acid volcanic breccia includes all felsic rocks that exhibit a fragmental character sufficiently well defined to attract attention in the hand speci-men, and in which the fragments are over one-half inch in diameter. The size of the fragments (observed) varies from one-half inch to several inches in diameter. These rocks consist partly of brecciated tuff and partly of brecciated rhyolite. When freshly broken the breccia often shows a greenish or mottled-gray color, produced by vari-ous colored fragments in a finer groundmass. In places the breccia has been strongly sheared and it nearly always shows some mashing and schis-tosity, but on the whole is more massive than the finer tuff rocks. Thin sections show little difference from the regular coarse tuffs. The fragments are chiefly of tuffaceous or rhyolitic character with occa-sional slate fragments. Phenocrysts of quartz, orthoclase and plagioclase (chiefly oligoclase) are abundant. The fragments of the brecciated rhyo-lite phase show a flow structure. In all phases of the breccia the groundmass is altered and kao-linized. Grains of iron oxide chiefly hematite are present, while the secondary minerals epidote and calcite and secondary quartz are plentiful. MAFIC VOLCANIC ROCKS Mafic volcanic rocks are scattered throughout the northern two thirds of the Carolina Slate Belt, but are most abundant along the western side. The rocks of this unit consist of volcanic fragmental and flow materials. The fragmental materials are chiefly normal tuffs and breccias of andesitic composition, while the flows vary from andesite to basalt. The tuffs are generally andesitic in composi-tion. In places they are fine grained and lack the fragmental appearance. In such areas, one of which may be seen along U.S. Highway 64, for a mile west of Haw River in Chatham County, the rock strongly resembles a graywacke. The tuffs contain much epidote and often have a greenish color. Other colors vary from dark gray to nearly black. In addition to epidote, plagioclase, quartz and secondary calcite, iron oxides are present. The mafic fragmental rocks are not as strongly metamorphosed as the felsic fragmental rocks, but contain a cleavage that strikes northeast and dips northwest in the southern part of the area and to the southeast in the northern part. The mafic breccia is distinctly more basic than the felsic breccias and appears to be mainly ande-sitic in composition. It consists chiefly of brec-ciated tuffs and flows, but ranges all the way from a fine and highly mashed tuff to a massive coarse breccia with fragments up to several inches in diameter. It varies from a dark gray through a chlorite and epidote green color. In thin section this rock appears more uniform than in the hand specimen. Fragmental materials embedded in a feldspathic groundmass make up most of the rock. The following minerals are present: orthoclase, plagioclase (oligoclase and andesine) chlorite, epidote, zoisite, clinozoisite, quartz, calcite, iron oxides, kaolinite and sericite. The andesite and basalt occur as bands and lenses interbedded with the fragmentals. The andesite is dark green in color, usually massive or fine grained, but occasionally coarsely por-phyritic. A coarse porphyritic variety, with horn-blende crystals up to two inches long occurs in western Randolph County. The basalt is dark to nearly black and often amygdaloidal. Both the andesite and the basalt are characterized by the lack of a well defined cleavage. The minerals pres-ent include epidote, plagioclase, quartz, secondary calcite and iron oxides. Epidote is the most abun-dant mineral present, giving the rock its green color. The name greenstone is often used for this rock. BEDDED ARGILLITES (VOLCANIC SLATE) Bedded argillites (volcanic slate) commonly referred to as slate, bedded slate, or volcanic slate, occur in the southern part of the Carolina Slate Belt and extend as far north as the central part of Davidson and Randolph counties. A few small areas occur on the east side of the belt in Montgomery, Moore and Chatham counties. There are, also, some small areas east of the Jonesboro fault in Anson and Richmond counties. The bedded argillites (volcanic slate) consist chiefly of dark colored or bluish shales or slates, which are usually massive and thick bedded. How-ever, the beds occasionally show very finely marked bedding planes. Contacts between the slates and tuffs are usually gradational and often a single hand specimen will show gradation from a bedded slate to a fine-grained tuff. In composi-tion the bedded argillites vary from felsic tuffa-ceous argillite to mafic tuffaceous argillite inter-mixed with varying amounts of weathered material and land waste. Much of the slate is massive and jointed showing little effects of meta-morphism while in other places it has been strongly metamorphosed and shows a well defined slaty cleavage. The cleavage or schistosity does not in most places correspond to the bedding planes of the rock. In places, especially near igneous intrusives and mineralized zones, the slate is often highly silicified and resembles chert. IGNEOUS INTRUSIVE ROCKS The Carolina Slate Belt is bordered on the west by an igneous complex composed of gabbro, diorite and granite and intruded at many places, particularly in the northern half by granitic-type rocks. These igneous intrusives apparently vary from late Ordovician to early Permian in age. ENVIRONMENT OF DEPOSITION The occurrence of volcanic-sedimentary rocks along the western edge of the Coastal Plain and eastern edge of the Piedmont Plateau, in a long narrow belt that extends from southeastern Vir-ginia to central Georgia, with a length of more than 400 miles and width up to 120 miles, sug-gests deposition under geosynclinal conditions. As indicated above, these rocks consist of a great volcanic-sedimentary series varying from felsic to mafic in composition and composed of lava flows, beds of breccia, coarse tuff, fine tuff and ash, and feeds of shale or slate now designated as bedded slates or argillites. The lava flows and the coarse angular tuff and breccias could have been formed on land or under water. Conclusive evi-dence for one as opposed to the other is lacking. Many of the tuffs and breccias consist largely of subangular to rounded fragments that were cer-tainly reworked and deposited in water. The bedded slates and argillites were definitely water laid. Their composition, both chemical and physi-cal, and their texture indicate that they were not transported great distances. Finally, the presence of varying amounts of nonvolcanic materials or land waste in the form of mud, clay, silt, sand and at places rounded quartz pebbles up to an inch in diameter indicate that varying amounts of materials were brought into the area from ad-jacent land masses. There seems to be little doubt that the rocks of the Carolina Slate Belt were formed in a eugeo-syncline. The volcanic materials in this geosyn-cline came largely from beneath the surface by volcanic eruptions, while the nonvolcanic sedi-ments came from narrow belts of uplift that were present in or adjacent to the trough. The thickness of these rocks is variable but un-known. It appears possible, however, that in cen-tral North Carolina, west of the Durham, Deep River and Wadesboro Triassic basins, the vol-canic- sedimentary series may have a thickness up to 20,000 or 30,000 feet. The period of volcanic-activity during which this great series of volcanic-sedimentary rocks were being formed must have continued through a very long time, perhaps hundreds of thousands or even millions of years. During this time, there were innumerable alter-nations between quiet upwelling of lava, explo-sive activity piling up great amounts of tuff, breccia and ash and periods of comparative quiet accompanied by weathering, erosion and deposi-tion of the bedded deposits. Between successive outbursts the magma probably underwent some degree of differentiation so as to give rise to more acid rocks at one time and more basic at another. Such changes were not great for at no time did the products depart far from the general type which was a relative acid magma rich in soda. STRUCTURAL FEATURES The chief structural features of the rocks of the Carolina Slate Belt are cleavage planes, joints, folds and faults. The first of these to be of interest was the cleavage planes. Olmsted (1825) designated these rocks as the Great Slate Formation because of the well developed, slate-like cleavage which he observed over most of the area. In general, rocks of the Carolina Slate Belt south of U.S. Highway 70 from Durham to Greensboro have a well defined cleavage that strikes northeast and dips steeply to the north-west. North of this line the cleavage continues to strike northeast but much of the dip is to the southeast and at a lower angle than that which dips to the northwest. No explanation for this change in dip is readily available. The metamorphism which produced the cleav-age was not as intense as was originally thought and also varied widely from place to place. At places, metamorphism was so severe that the cleavage has become schistosity and the rocks are essentially schists. At other places, the cleavage apparently grades into jointing. As a result, the massive rocks are highly jointed and contain poorly developed cleavage planes. Recent work has revealed that folding is better developed than was formerly thought. It is now established that the rocks are in general well folded into a series of anticlines and synclines. The largest and most important fold is the Troy anticlinorium which trends in a northeast-south-west direction and whose axis lies a short dis-tance west of Troy. West and southwest of the Troy anticlinorium, northeast-trending open fold-ed synclines and anticlines predominate. The most important of these is the New London syn-cline. East, southeast, and northeast of the Troy anticlinorium the intensity of the folding in-creases. The rocks are tightly compressed into northeast-trending, asymmetric folds whose axial planes usually dip steeply to the northwest. The bedded argillites (volcanic slate) seem to have consolidated readily and folded like normal sediments while the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. This is indicated by the mashed and sheared condition of practically all the tuffs while in numerous cases more or less well preserved bedding planes in the slates indi-cate definite folding. Numerous insignificant faults occur in nearly all parts of the Carolina Slate Belt. These in gen-eral never amount to more than a few feet and are doubtless only the adjustments due to the folding of the rocks and are not of any great structural importance. However, along the east-ern border of the belt where the Carolina Slate Belt rocks have been compressed into northeast-trending asymmetric folds whose axial planes dip steeply to the northwest, thrust faults are present. The abundance and importance of these faults in relation to the overall structure of the Carolina Slate Belt are not yet fully established, but recent geologic mapping has revealed the presence of such faults in Moore and Orange counties. AGE OF THE ROCKS Emmons (1856), the first worker to date the rocks of the Carolina Slate Belt, considered them to be mainly slates and quartzites of sedimentary origin as shown by the presence of rounded peb-bles. He divided these rocks into a lower and upper series and placed them in his Taconic system which was early Paleozoic in age. He con-sidered the talcose slates of the lower series to have essentially the same composition as the underlying primary series and stated: "The tal-cose slates may be regarded as the bottom rocks, the oldest sediments which can be recognized, and in which, probably, no organic remains will be found." Later Emmons found near Troy, Montgomery County, two or three species of fossils in the lower series of the Taconic system. These fossils, which belonged to the class of zoophites, the low-est organisms of the animal kingdom, were found through about 1000 feet of rock and occurred from a few in number to abundant. The fossils were considered to be corals of a lenticular form that varied in size from a small pea to two inches in diameter. At first, Emmons considered the difference between the small and the larger forms to be the result of age but later decided that they were specific and named the small form Paleotrochis minor and the large form Paleotrochis major. These forms were of interest to Emmons main-ly in showing that lower Taconic rocks were fos-siliferous rather than in actually dating the rocks. Paleotrochis major and Paleotrochis minor were later identified as spherulites in rhyolite and not fossils, Diller (1899). Kerr (1875) classed the rocks of the Carolina Slate Belt as Huronian in age, which in his classi-fication is a division of the Archean. Williams (1894) classed them as Precambrian in age. Wat-son and Powell (1911) on the basis of fossils, considered the Arvonia slates of the Piedmont of Virginia to be Ordovician in age. Laney (1917) on the basis of the work by Watson and Powell, classed the volcanic-sedimentary rocks of the Virgilina district of the Carolina Slate Belt as Ordovician in age. In recent years the trend has been to place the age of these rocks as early Paleozoic, probably Ordovician. According to the U.S. Geological Sur-vey, Professional Paper 450A, Research 1962, "Lead-alpha measurements by T. W. Stern on zircon collected by A. A. Stromquist and A. M. White from felsic crystal tuffs in the Volcanic Slate belt of the central North Carolina piedmont have confirmed a previously inferred Ordovician age for these unfossiliferous rocks." White, et. al. (1963) gave the details on the collection and evaluation of two samples of zircon from the Albemarle quadrangle and stated: ". . . the indi-cated age for each is Ordovician according to Holmes time scale (Holmes, 1959, p. 204) ." Recently, St. Jean (1964) reported the first authentic discovery of fossils in the Carolina Slate Belt of North Carolina. The discovery con-sisted of two abraded and moderately distorted thoraxes and pygidia of a new trilobite species. The specimens were collected from a piece of stream rubble in Island Creek at Stanly County Road 1115. The type rock in which the fossils occurred is present in outcrops upstream. St. Jean classed the specimens as a new species ques-tionably assigned to the Middle Cambrian genus Paradoxides and stated: "Although the generic assignment is questionable, the morphologic char-acters of the two specimens indicate an age no younger than Middle Cambrian and no older than the age of the oldest known Early Cambrian tri-lobites." "The specimens are significant because they represent the first authentic fossil material from the Piedmont south of Virginia and provide paleontological documentation of the age and marine nature of a lithologic unit in the area. Micropygous Cambrian trilobites are more com-mon in eugeosynclinal belts, which part is in keeping with the paleogeographic and lithologic setting." Granites of post-Ordovician but Paleozoic age and diabase dikes of Triassic age both intrude the Carolina Slate Belt rocks. The granites apparently furnished the solutions that produced the pyro-phyllite and associated minerals, and are con-sidered further below. The diabase dikes have no relations to the pyrophyllite deposits and are not discussed further. GEOLOGY OF THE PYROPHYLLITE DEPOSITS INTRODUCTION Just when pyrophyllite was first discovered in North Carolina is not known. Olmsted (1822) in a report entitled, "Descriptive Catalogue of Rocks and Minerals Collected in North Carolina" listed talc and soapstone from several counties includ-ing Chatham and Orange and stated that fhey were extensively used for building and orna-mental purposes, and added that Indian utensils of the same materials were common. In 1825 he called attention to the "Great Slate Formation" which passes across the State from northeast to southwest and again noted the presence of talc and soapstone in Chatham and Orange counties. Since no talc and soapstone are known to occur in rocks of the Carolina Slate Belt and since pyrophyllite is found at a number of localities in the belt it is quite probable that the deposits mentioned by Olmsted were pyrophyllite. Emmons (1856) described a material which was locally known as soapstone at Hancock's Mill, (Now Glendon) Moore County and near Troy, Montgomery as follows : "A rock, which occurs in extensive beds, and known in the localities where it is found as a soapstone, can by no means be placed properly with the magnesium minerals. It is white, slaty, or compact translucent, and has the common soapy feel of soapstone, and resem-bles it so closely to the eye and feel that it would pass in any market for this rock. It has, how-ever, a finer texture, and is somewhat harder; but it may be scratched by the nail, so that it ranks with softest of minerals: it scratches talc, and is not itself scratched by it; it is infusible before the blowpipe, and with nitrate of cobalt gives an intensely blue color, proving thereby the presence of alumina in place of magnesia." He classed the mineral as agalmatolite, the figure stone of the Chinese, and described the methods used in quarrying it at Hancock's Mill. Brush (1862) analyzed some of the material from Hancock's Mill, Moore County and showed it to be pyrophyllite. Pratt (1900) described the deposits and pub-lished further analyses of the pyrophyllite. He stated that : "While the talc deposits of Cherokee and Swain counties are pockety in nature and of limited depth, the pyrophyllite formation is con-tinuous and of considerable, though of unknown depth." Pratt described the pyrophyllite as follows: "While possessing many of the physical proper-ties of talc and often being mistaken for it, the pyrophyllite is quite different in its chemical com-position, and is a distant mineral species. Al-though this mineral probably cannot be put to all the uses of talc, it can be used for the larger number of them, and those for which the talc is used in the greatest quantity. Some of this might be of such quality that it could be cut into pencils, but the most of this mineral would only be of value when ground. It is soft with a greasy feel and pearly luster, and has a foliated structure. The color varies from green, greenish and yel-lowish- white to almost white; but when air-dried they all become nearly white. Very little compact pyrophyllite has been observed that would be suitable for carving, as is used in China, although considerable of this has been used in the manu-facture of slate pencils." Pratt presented three chemical analyses of pyrophyllite from Moore County that were very close to the theoretical composition of that min-eral. He, also, pointed out that the deposits had been worked almost continuously since the Civil War. Hafer (1913) noted that the pyrophyllite did not differ greatly from the sericite found in the old gold mines of the slate belt and may have originated in the same manner. He, also, called attention to the masses of pyrite-bearing quartz that are often found associated with the pyro-phyllite deposits. Stuckey (1928) presented the first detailed re-port of the pyrophyllite deposits of North Caro-lina. He described their distribution, geological setting, form or shape, mineralogy, origin and possible continuation with depth. He classed the deposits as hydrothermal in origin and thought that they might continue to considerable depths. DISTRIBUTION Pyrophyllite occurrences are known along the eastern half of the Carolina Slate Belt from the vicinity of Wadesville in the southwestern part of Montgomery County northeastward to the northern part of Granville County near the Vir-ginia line. These occurrences may consist of a single deposit or they may contain several pros-pects or deposits. In Montgomery County pyrophyllite is known to occur near Wadesville ; on Cotton Stone Moun-tain, 3.5 miles north of Troy; just east of State Road 1312 near Abner; and northeast of Asbury in the northeastern corner of the county. Consid-erable prospecting has been done near Wadesville and the area appears promising for mining. Limited prospecting has been done on Cotton Stone Mountain but no mining has been carried out. Limited prospecting and some mining have been carried out on the deposit near Abner but the property is currently idle. One deposit north-east of Asbury appears to have been worked out, but another is promising for future development. In Moore County, pyrophyllite is found ap-proximately four miles southwest of Spies near the point where Cotton Creek enters Cabin Creek ; near Robbins; and in a zone several miles long that lies along Deep River north of Glendon. The Robbins area contains the only underground mine, which is the largest pyrophyllite mine in the State, and several open pit prospects. The Glendon zone contains three active open cut mines and a number of prospects. Pyrophyllite is known to occur in Randolph County in the vicinity of Pilot Mountain about 8 miles southeast of Asheboro, just north of State Highway 902, and near Staley in the northeastern part of the county. In the Pilot Mountain area there are four prospects, one of which has been explored and considerable iron-stained pyrophyl-lite is reported to be present. No mining has been carried out in this area. The deposit near Staley, which at one time contained the second largest mine in the State, has been worked out and aban-doned. The only known pyrophyllite area in Chatham County is located near the Chatham-Alamance county line on the Hinshaw property. This prop-erty is about 2 miles east of State Road 1004 and a short distance north of State Road 1343. Pyro-phyllite crops out at three places in the area, one of which has been prospected to a limited extent. No mining is being carried out in the area. Pyrophyllite is known to occur at two localities near Snow Camp in southern Alamance County. On Pine Mountain southeast of Snow Camp is a major open pit mine from which pyrophyllite has been mined for more than 20 years. About 2 miles east of Snow Camp there are several pyro-phyllite exposures on a prominent hill known as Major Hill. Major Hill lies south of State Road 1005 and between State Roads 2356 and 2351. The outcrops in Major Hill are promising and prospecting is currently underway. In Orange County pyrophyllite is known to occur in the vicinity of Teer in the southwestern part of the county; near Hillsborough; and on the Murray estate about 6 miles northeast of of Hillsborough. In the vicinity of Teer, prospect-ing has been carried out at three or more places 10 and limited mining was done at one time. This area has been abandoned at least temporarily. South and southwest of Hillsborough are three prominent hills which trend northeast and parallel the major geologic structure of the area. The northern most of these hills contains a major open cut pyrophyllite mine that is an important pro-ducer of pyrophyllite, andalusite, sericite and silica. The deposit in the Murray property north-east of Hillsborough lies south of State Road 1538 and west of State Road 1548. Considerable pro-specting has been carried out on this property, but no mining has been done. In Granville County, pyrophyllite deposits are found on Bowlings Mountain northwest of Stem ; at several places on Long Mountain which lies to the northwest of Bowlings Mountain; and on Daniels Mountain about 9 miles north of Oxford. On Bowlings Mountain, which is located about three miles slightly northwest of Stem, prospect-ing and some mining have exposed a major pyro-phyllite deposit. To the northwest of Bowlings Mountain is a northeast trending series of irregu-lar hills that occupy an area a mile or more in width and some 4 miles long, known as Long Mountain. Prospecting and some exploration have demonstrated the presence of pyrophyllite at sev-eral places on Long Mountain, but no mining has been done. About 9 miles north of Oxford and 1.5 miles northeast of State Highway 96 and east of Mountain Creek is Daniels Mountain on which pyrophyllite is known to occur. No prospecting or mining has been done on this mountain. GEOLOGIC RELATIONS All the pyrophyllite deposits of North Carolina occur in acid volcanic rocks, chiefly in medium to fine-grained tuffs and to a less extent in an acid volcanic breccia. They are not found at any place in a basic andesitic type of rock or asso-ciated with a typical water-laid slate. At the Phillips, Womble and Reaves mines, which are found in the Deep River pyrophyllite zone north of Glendon, Moore County, the footwall side of the pyrophyllite bodies is an acid volcanic breccia. Next to the footwall is a highly mineralized pyro-phyllite zone that grades into a fine-grained acid tuff. At places the pyrophyllite grades into and replaces parts of the brecciated footwall. Where the band of volcanic breccia is absent from the footwall side of the deposits, in this zone, the pyrophyllite bodies are much nearer the slate than where the breccia is present, but they are never found in normal slate. On the hanging wall side the pyrophyllite grades into medium to fine-grained acid tuff. The geologic distribution of the pyrophyllite deposits is probably controlled in part by the composition of the rocks and in part by rock structures. As indicated above (page 8), the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. As a result, the acid tuffs and breccias developed shear zones along which the pyrophyl-lite mineralization was later concentrated. A few shear zones, particularly those along Deep River near Glendon and near Robbins (both in Moore County) were developed along major thrust faults. However, the great majority of the pyro-phyllite deposits are found in shear zones that do not show any evidence of containing faults. FORM AND STRUCTURE A prominent feature of the pyrophyllite bodies is their irregular, oval, or lens-like form. This structure is observed along the strike and also vertically to the depths reached in mining. In nearly every deposit that has been developed enough to show the true structure, bodies and lenses of pyrophyllite are found along with lenses of tuffaceous rocks that exhibit various stages of alteration. Most pyrophyllite deposits occur as narrow bands or zones aligned with the cleavage strike and dip of the country rock. They range in size from those measured in inches up to 500 feet wide and 1500 to 2000 feet long. The strike of the cleavage in both the country rock and the pyrophyllite bodies is northeast-southwest, while the dip is steeply to the northwest. In most cases the larger mineralized zones con-sist of a very siliceous footwall, a well developed mineralized zone and a highly siliceous and seri-citic hanging wall. Where these conditions exist contacts between the mineralized zone and the footwall and the hanging wall are gradational. Contacts between the footwall and country rock and the hanging wall and country rocks are, also, gradational. When the siliceous footwall and the sericitic hanging wall are absent, as they fre-quently are, contacts between the mineralized zones and the country rocks are gradational. Excellent examples of the siliceous footwall may be seen at the Bowlings Mountain deposit, 11 Granville County, at the Hillsborough deposit, Orange County, at the Staley deposit, Randolph County, and at the mine of the Standard Mineral Company, Moore County. In general, it consists of a light blue-gray to white, fine-grained to medium-grained rock having the general appear-ance of quartzite. Selected samples from the more massive portions of this rock consist almost en-tirely of silica. The rock has been fractured con-siderably at places and contains varying amounts of sericite and pyrophyllite. When fresh, the rock is hard and dense and breaks with a conchoidal fracture. When weathered, it breaks down to a sandy friable material that is usually white, but is often stained various shades of yellow and red by iron oxide. The siliceous footwall ranges from less than 5 to more than 50 feet in thickness and in many cases extends the entire length of the deposit. When it occurs as a massive unit, it often crops out as bold ledges near the crest of the hill as at the Staley and Hillsborough deposits. However, as at the mine of the Standard Mineral Company near Robbins, Moore County, it may not crop out at all. From the footwall mineralization increases inward to rich zones and lenses of pyrophyllite and then decreases towards a schistose and seri-citized hanging wall. MINERALOGY OF THE DEPOSITS The minerals most commonly observed in the pyrophyllite deposits in the apparent order of their abundance are pyrophyllite, quartz, sericite, chloritoid, pyrite, chlorite, feldspar, iron oxides, zircon, titanite, zeolites and apatite. Of these, only the first eight are present in important amounts or related to the development of the pyrophyllite. The other minerals are present in small amounts to the extent they might occur as accessory constituents of an igneous rock or as products of regional metamorphism or weather-ing. In addition, small amounts of fluorite have been found with quartz veins intruding the fault zone at the Phillips mine. Also, varying amounts of the high-alumina minerals andalusite, dia-spore, kyanite and topaz have been found in sev-eral pyrophyllite mines and prospects. The posi-tion of these high-alumina minerals in the mineral sequence of the pyrophyllite deposits is not clear and they are discussed below. Pyrophyllite Pyrophyllite is a hydrous aluminum silicate with the general formula H2Al2Si40i2. It crystal-lizes in the orthorhombic system, but good crys-tals are rare. It commonly occurs as (1) foliated, (2) granular and (3) radial or stellate masses. The color varies from nearly black through yel-lowish white, green, and apple green to pure white. It has a specific gravity of about 2.8 to 2.9, and a hardness less than the finger nail. It has a pearly luster, a greasy feel and commonly occurs as masses, lenses and pockets associated with quartz, sericite and chloritoid. The pyrophyllite in the deposits near Glendon and Robbins, Moore County, consists almost entirely of the foliated variety. That in the other major deposits consists largely of massive granular and radial fibrous forms with occasional small amounts of the foli-ated variety. Quartz Quartz is an oxide of silicon with the general formula Si02 . It crystallizes in the hexagonal system, and good crystal specimens are common. Quartz is colorless when pure, has a conchoidal fracture, a viterous luster, a hardness of 7 and a specific gravity of 2.65. It is abundant through-out the deposits everywhere except in the very purest pyrophyllite and occurs (1) as large masses of cherty or milky appearance, (2) as clear veins and stringers in the deposits and along the walls, and (3) as small masses and nodules in the altered or only partly altered rock. Sericite Sericite is a fine-grained variety of mica, usual-ly muscovite, occurring in small scales and having the composition (H,K)AlSi04 . It crystallizes in the monoclinic system, has a basal cleavage, a hardness of 2-2.25, a specific gravity of 2.76-3 and a vitreous luster. The color varies from color-less through gray, pale green, and violet to rose-red. Sericite is often concentrated as bands or zones along the hanging wall of the pyrophyllite bodies and to a lesser extent along the footwall. It is, also, present as finely divided scales and flakes and as zones through good pyrophyllite. Chloritoid Chloritoid probably crystallizes in the triclinic system but rarely occurs in distinct tabular crys- 12 tals. It often occurs in the form of sheaves or rosettes. The general formula is H2 (Fe,Mg) Al2Si07 . It has a basal cleavage, a pearly luster, a hardness of 6.5 and a specific gravity of 3.52- 3.57. The color varies from dark gray through greenish black to grayish black. Chloritoid is found in varying amounts in all the pyrophyllite deposits but is most abundant in those along Deep River north of Glendon, Moore County where an acid iron breccia forms part of the footwall. Pyrite Pyrite has the formula FeS2 , crystallizes in the isometric system and often occurs as good crys-tals. It has a conchoidal fracture, a hardness of 6-6.5, a specific gravity of 4.95-5.10, a metallic luster and a brass-yellow color. It is present in small amounts associated with the silicified tuff along the walls of the pyrophyllite bodies and in the lenses of silicified country rock included in the deposits. Chlorite Chlorite, probably clinochlore, has the formula H8Mg5Al2Si3 18 , crystallizes in the monoclinic sys-tem and usually occurs as flakes or scales. It has a hardness of 2-2.5, a specific gravity of 2.65-2.78, a pearly luster, and a grass-green to olive color. Chlorite occurs rather commonly in the impure portions of the pyrophyllite bodies and in the altered wall rocks. Feldspars Feldspars, orthoclase (KAlSi3 8 ), albite (NaAlSi3 8 ), and in one case andesine, a mixture of albite (NaAlSi3 8 ) and anorthite (CaAl2Si2 9 ), were found in small amounts in the less silicified portions of the wall rock of the pyrophyllite bodies. Orthoclase and albite are more abundant due to the fact that they are com-mon constituents of the rhyolitic and dacitic rocks in which the pyrophyllite was formed. Iron Oxides Iron oxides, chiefly hematite Fe2 3 and magne-tite Fe3 4 , occur in small amounts in each pyro-phyllite deposit studied, but most abundantly in the footwall of the mines along Deep River north of Glendon, Moore County, where an acid iron breccia is present. High Alumina Minerals One or more of the high-alumina minerals an-dalusite (Al2Si05 ), diaspore (A12 3H20), kyanite (Al2Si05 ) and topaz (AlF) 2Si04 , are present in varying amounts in most of the pyrophyllite de-posits except those in Moore County, and Conley (1962a) reported collecting a specimen from the fault zone in the Phillips mine that contained pyrophyllite, diaspore, topaz and fluorite. The occurrence of high-alumina minerals in the pyrophyllite deposits is quite irregular, with the greatest concentrations near the footwall and lesser amounts along the hanging wall and asso-ciated with lenses of only partly altered country rock included in the deposits. Andalusite is abun-dant in the Hillsborough deposits. In the deposit on Bowlings Mountain, Granville County, there is considerable topaz as well as small amounts of andalusite and kyanite. Some blocks of topaz are in the pyrophyllite deposits today and represent material that was not replaced or destroyed dur-ing pyrophyllite formation. PETROGRAPHY A careful study of a number of thin sections cut from specimens collected at the various mines and quarries shows that the pyrophyllite deposits have been formed in volcanic tuffs and to some extent in a volcanic breccia that varied from dacitic to rhyolitic in composition. Sections from specimens of tuff and breccia col-lected along the walls of the pyrophyllite bodies and from partly altered country rock included in them show that the minerals of the pyrophyllite bodies were formed in the order of quartz, pyrite, chloritoid, sericite, and pyrophyllite; and that these minerals have definite relations to each other and to the feldspars and iron oxides in the country rock. The first change was a marked silicification of the enclosing rocks accompanied by a rapid de-crease in their normal mineral content. The feld-spars, rock fragments, and fine-grained ground-mass of the rocks were readily replaced by quartz to the extent that the altered rocks became masses of cherty and milky quartz. At the Womble and Phillips mines north of Glendon, Moore County and at the Staley mine 3 13 miles west of Staley, Randolph County, the silici-fication was accompanied or immediately followed by the development of pyrite, as this mineral is found in the silicified wall rocks of the mines and in included masses of silicified country rock but not in good pyrophyllite. Chloritoid is found in varying amounts at all the prophyllite prospects and mines but is more abundant at some including the Womble and Phillips mines north of Glendon, Moore County and the Murray prospect 5 miles northeast of Hillsborough, Orange County and the Staley mine 3 miles west of Staley, Randolph County. At the Womble and Phillips mines it is apparently re-lated to an acid iron breccia which contains con-siderable magnetite and hematite and forms the football of these deposits. The chloritoid at the Murray prospect and the Staley mine seems to be related to bands and zones of greenstone in the wall rocks of the bodies near the pyrophyllite. The chloritoid was not observed replacing the iron oxides but the marked increase and close association of chloritoid with the iron oxides at every point where the latter are present suggests a close genetic relation between the two. The chloritoid was developed along with or soon after the silicification of the tuff and in thin sections is seen to have partly replaced the quartz. Sericite is often concentrated as bands or zones along the hanging wall of the pyrophyllite bodies and to a lesser extent along the footwall. It is also present as finely divided flakes and scales and as zones through good pyrophyllite. Thin sec-tions cut from silicified and partly prophyllitized masses from the various pyrophyllite deposits show sericite associated with pyrophyllite and having about the same relations to the quartz. The cherty or flinty masses of quartz in the pyro-phyllite bodies are cracked and shattered and partly replaced by sericite. The microscope shows pyrophyllite to be the last mineral formed. In every case silicification preceded the development of pyrophyllite. The feldspars diminish with silicification so that feldspar and pyrophyllite are seldom found in the same section. Where pyrophyllite is found in sections with chloritoid, it occurs in every crack and opening in the sheaves and bundles of chloritoid as a replacement of the chloritoid. Prac-tically all specimens except those from the purest pyrophyllite, contain some quartz, the amount of the latter depending upon the purity of the speci-men in terms of pyrophyllite. In sections from such specimens the pyrophyllite is replacing the quartz. Sections from the masses of cherty or milky quartz associated with pyrophyllite show both sericite and pyrophyllite replacing the quartz with sericite apparently earlier than the pyro-phyllite. The position of the minerals andalusite, diaspore, kyanite and topaz in the sequence is not clear, but they appear to have been formed before or early in the pyrophyllitization process as they have been replaced partially by sericite and pyro-phyllite. ORIGIN OF THE PYROPHYLLITE DEPOSITS In considering the origin of the pyrophyllite deposits, it has been necessary to take into ac-count their shape and distribution, their relations to the enclosing rocks, their mineralogical com-position, the relations of the associated minerals to each other, and the relations of the pyrophyl-lite to the associated minerals and the enclosing rocks. Over the years, ideas as to the origin of pyrophyllite have changed and future develop-ment of the deposits may disclose new informa-tion that may require new explanations. This is especially true since the deposits are associated with metamorphic rocks and ideas on the origin of metamorphic rocks and their contained miner-als are in a state of change. EARLIER THEORIES Before discussing the origin of North Carolina pyrophyllite, reference should be made to the views expressed by other writers on the origin of this mineral and the chloritoid and sericite asso-ciated with it. Emmons (1856) considered pyrophyllite (agal-matolite) as a sedimentary rock near the base of his Taconic system. Levy and Lacroix (1888) stated that pyrophyllite occurs in metamorphic rocks while Dana (1909) classed it as a mineral formed at the base of schists or as a mineral of the crystalline schists and Paleozoic metamor-phics. Clapp (1914) described pyrophyllite deposits on the west side of Vancouver Island, British Columbia. Both alunite and pyrophyllite occur in andesite, dacite and associated pyroclastic rocks. This series and in particular its fragmental parts, has been metasomatically altered to quartz-sericite- chlorite rocks, quartz-sericite rocks, 14 quartz-pyrophyllite rocks and quartz-alunite rocks. Clapp concluded that most of the minerali-zation was caused by hot sulphuric acid solutions of volcanic origin which were active during the accumulation of the pyroclastic rocks, and as a result of relatively shallow depths and low pres-sures. He postulated little change in the bulk composition of the original volcanic rocks and interpreted most of the new minerals as having been developed from feldspars. In general, how-ever, the quartz-pyrophyllite rocks show a net gain in alumina, a loss of potash and either a loss or a gain in silica. Buddington (1916) and Vhay (1937) have described in detail the pyrophyllite deposits in the Conception Bay Region of Newfoundland. These deposits occur in a thick series of Pre-cambrian rhyolite and basalt flows which contain interlayered breccias, tuffs and some waterlaid materials. These volcanic rocks were altered re-gionally with the development of abundant chlo-rite and silica. Locally, some of the rocks were pyrophyllitized, some pinitized and some silici-fied. Some of the pyrophyllite concentrations are found in rhyolite breccias and conglomerates, but most are limited to the rhyolite flows. The pyro-phyllite itself forms single, well defined veins, as well as series of inter-connecting veins, lenses and pockets. The development of the pyrophyllite evidently involved the introduction of large amounts of alumina, the replacement of alkalies by hydroxyl, and the removal of silica, both that occurring as free quartz and that in the other minerals. Much of the pyrophyllitized rock may once have been a relatively homogeneous glass. Buddington (1916) concluded that these de-posits were formed by the metasomatic replace-ment of previously silicified rhyolites by thermal waters under conditions involving dynamic stress and intermediate temperatures and pressures. The solutions evidently moved along fault or shear zones, and the deposits have a marked schistosity. Vhay (1937) concluded that the individual flakes of pyrophyllite have a random orientation and that the schistosity of the deposits represent an inherited feature preserved by differential re-placement along schistose structures already established. The pyrophyllite deposits in the San Dieguito area of San Diego County, California, have been described in detail by Jahns and Lance (1950). These deposits were formed by the alteration of volcanic flows, breccias and tuffs that ranged in composition from andesite to rhyolite. Jahns and Lance (1950) described the origin of these deposits as follows : "The mode of occur-rence of the San Dieguito pyrophyllite, particu-larly its distribution with respect to fractures and shear zones in the host volcanic rocks, indi-cates that it was formed by replacement of these rocks. Its development was accompanied by intro-duction of Si02 , A12 3 and probably OH. The phyrophyllite bearing rocks, including those of highest grade, contain fresh pyrite and other sul-fide minerals at depths in excess of 20 feet in most parts of the area. Both pyrophyllite and sulfides appear to be hypogene, and are plainly earlier than the widespread iron oxides, man-ganese oxides and clay minerals of supergene origin. "Under the microscope both pyrophyllite and quartz replace feldspars and other original min-erals of the volcanic rocks, and in many places the two replacing minerals are of the same gen-eral age. As pointed out by Bastin and others, (1931) aggregate, rather than sequential replace-ment, is characteristic of hypogene processes. Zonal distribution of replacing minerals with respect to remnants of earlier minerals, a feature so common in supergene replacement, is con-spiciously absent from the pyrophyllite-bearing rocks. Moreover, the replacement is not particu-larly selective; the pyrophyllite, although first attacking parts of the groundmass in the volcanic rocks is generally distributed throughout the phenocrysts and groundmass minerals." They conclude : "The metamorphism of the vol-canic rocks in the San Dieguito area, and the subsequent introduction of silica and pyrophyl-lite almost certainly took place during late Trias-sic or Cretaceous time. A considerable thickness of volcanic rocks was removed by erosion prior to deposition of the latest Cretaceous sediments in the region, so that it is impossible to establish a maximum depth at which the pyrophyllite de-posits were formed. At no place is the total thick-ness of the Santiago Peak volcanics known, but it may well have amounted to several thousand feet. On the basis of the general geologic relations and the indirect evidence from laboratory investiga-tions, it seems likely that the San Dieguito pyro-phyllite deposits were formed hydrothermally under conditions of intermediate temperatures 15 and pressures. This is in accord with conclusions reached by Buddington (1916) for somewhat similar deposits in the Conception Bay region of Newfoundland, and by Stuckey (1925) for the deposits in the Deep River region of North Caro-lina. In contrast, the deposits on Vancouver Is-land, British Columbia, appear to have been formed under near surface conditions." Based on a study of samples collected from various pyrophyllite deposits of North Carolina, Zen (1961) tended to disregard the effect of hydrothermal replacement solutions on the forma-tion of the pyrophyllite bodies. He considered the presence of the three phase mineral assemblage of the ternary system A12 3 — H2 —Si02 to indicate that water acted as a fixed component. He further noted, however, that to say water acted as a fixed component did not completely imply the absence of a free solution phase (hy-drothermal solutions). Such a phase could have existed, but certainly did not circulate freely through the system destroying the buffering mineral assemblages. Conley (1962a) concluded: "The bulk chemical composition of the pyrophyllite deposits is essen-tially the same as that of the country rock. All of the chemical elements present in the pyrophyl-lite deposits are present in the country rock, with the exception of fluorine, copper and gold. These elements are associated with quartz veins and silicified zones and were obviously brought in from an outside source. The pyrophyllite deposits could have formed in place with either addition or substraction of chemical elements if the ele-ments were properly segregated and recrystallized into new minerals." LeChatelier (1887) determined the tempera-ture at which pyrophyllite loses its water and found two points of marked loss, one at 700° and the other at 850° C. Stuckey (1924) made a com-parative dehydration test of pyrophyllite and sericite and found that sericite lost its water much faster than pyrophyllite at lower temperatures and at 750° C was practically dehydrated while the pyrophyllite held about 1 percent of its water which was finally lost at approximately 900° C. Rogers (1916) classed sericite as a typically low temperature mineral associated with the last stages of hydrothermal alteration while Lindgren (1919) classed it as a mineral common to hydro-thermal alterations at shallow and intermediate depths and pointed out that in acid rocks of the rhyolitic type silicification and sericitization are common near the surface, but did not agree with Rogers that sericite is a late mineral. While much has been published regarding the nature of chloritoid there is little definite infor-mation on its genesis. Clark (1920) stated that chloritoid is formed in schists where much iron and water are present, and that it is intermediate between the micas and chlorite and may alter into either. Manasse (1910) described a schist of sericite, quartz, rutile, tourmaline, chlorite and epidote from the Alps of Italy, closely associated with and occurring on both sides of a marble, in which chloritoid is abundant. Niggli (1912) in a study of the chloritoid and ottrelite groups of the Swiss Alps decided that the two minerals are identical. He pointed out that chloritoid is abundantly developed in schists that were originally high in clay content and thought that its formation was directly due to pressure and relatively independent of tempera-ture. He gave a diagram showing that regardless of temperature, chloritoid is formed with an in-crease in pressure and conversely it drops out when the pressure diminishes. ANALYSES OF ROCKS In Table 1, on page 17, there are a number of chemical analyses of rocks and minerals from the Carolina Slate Belt of North Carolina and for comparison, several analyses of similar rocks from other regions. Number 1 is a rhyolite from Flat Swamp Mountain in the Carolina Slate Belt of Davidson County, North Carolina, while Num-ber 2 is a devitrified rhyolite from South Moun-tain, Pennsylvania. Number 3 is an average of 115 analyses of rhyodacite and rhyodacite-obsidian obtained from widespread areas. Num-ber 4 is dacite from Kemp Mountain in the Carolina Slate Belt of Davidson County, North Carolina. Number 5, is dacite tuff, 1 mile south-east of Monteith Bay, Vancouver Island, while Number 6, is the same type of rock a short dis-tance away that has been silicified and altered to a cherty quartz-sericite rock. Numbers 7, 8, 9 and 10, represent commercial pyrophyllite from 4 mines in North Carolina. Analyses Number 1 through 5, Table 1, page 17, represent normal or average rhyolite and dacite rock types, and as is to be expected the bulk com-position of these analyses is remarkably uniform. Si02 varies from 66.27 to 74.67 percent, A12 3 16 from 10.78 to 15.39 percent, CaO from 0.34 to 3.68 percent, Na2 from 3.40 to 5.46 percent, K2 from 1.74 to 3.01 percent, and H2 from a trace to 0.68 percent. Analyses number 7 through 10, represent average commercial pyrophyllite, and as might be expected the bulk composition of these analyses is remarkably uniform. Si02 varies from 57.58 to 64.68 percent, A12 3 from 28.34 to 33.31 percent, CaO from a trace to 0.72 percent, Na2 from 0.06 to 0.38 percent, K2 from a trace to 3.90 percent, and H2 from 5.40 to 5.86 per-cent. This change in bulk composition from rhyolite and dacite to pyrophyllite was brought about by silicification of the rhyolite and dacite to a cherty quartz rock as shown in analysis number 6, fol-lowed by replacement to pyrophyllite. As silicifi-cation advanced there was a decrease in alumina and alkalies and an increase in silica. Replace-ment by pyrophyllite, in some cases, preceded or accompanied by sericite, resulted in a decrease in silica and an increase in alumina, potash increas-ing with the sericite content, while water in-creased from about 1 percent to an average of 5.59 percent. The conditions indicated by the above analyses may be observed at many of the pyrophyllite de-posits in the area. Beginning in walls of unaltered rhyolitic or dacitic tuff there is a gradual transi-tion through silicification, sericitization and pyro-phyllitization to lenses and masses of practically pure pyrophyllite in the interior of the bodies. As a result, the mineral bodies contain walls of silicified country rock that on the interior por-tions have been more or less sericitized and par-tially to completely pyrophyllitized. Table 1. Analysis of Rhyolite, Dacite and Pyrophyllite 1 2 3 4 5 6 7 8 9 10 Si02 74.67 73.62 66.27 72.33 73.22 87.80 64.53 57.58 64.68 64.54 A12 3 10.78 12.22 15.39 14.56 13.46 9.08 29.40 33.31 28.34 28.88 Fe2 3 1.25 2.08 2.14 0.15 2.33 0.40 0.33 0.60 0.45 FeO 2.11 2.23 2.22 0.96 nd 0.67 nd nd nd MgO trace 0.26 1.57 0.91 0.42 trace trace trace trace CaO 1.47 0.34 3.68 2.55 1.50 trace trace 0.72 0.36 Na2 5.31 3.57 4.13 3.40 5.46 0.62 0.28 0.06 0.38 0.12 K2 2.68 2.57 3.01 2.82 1.74 1.70 trace 3.90 0.01 0.18 H2 0.59 0.68 0.30 0.62 1.04 5.86 5.56 5.54 5.40 C02 1.30 Ignition 0.40 Total 100.16 99.09 99.26 99.24 99.71 100.04 100.33 100.74 100.27 99.33 1. Rhyolite from Flat Swamp Mountain, North Carolina, Pogue (1910) p. 54 2. Devitrified rhyolite from South Mountain, Pennsylvania, Williams (1892) p. 494 3. Average of 115 analyses of rhyodacite and rhyodacite-obsidian, Nockolds (1954) p. 1014 4. Dacite from Kemp Mountain, Davidson County, North Carolina, Pogue (1910) p. 57 5. Dacite tuff 1 mile southeast of Monteith Bay, Clapp (1914) p. 120 6. Silicified dacite tuff (cherty quartz-sericite rock) Monteith Claim, Clapp (1914) p. 120 7. Pyrophyllite from Rogers Creek Mining Company's mine, Pratt (1900), p. 26 8. Pyrophyllite from Standard Mineral Company's mine, Stuckey (1928), p. 36 9. Pyrophyllite from Womble mine, Stuckey (1928) p. 36 10. Pyrophyllite from Gerhard Bros., Staley, North Carolina, Stuckey (1928) p. 36 17 ORIGIN OF NORTH CAROLINA PYROPHYLLITE The field, microscopic and chemical evidence indicates that the pyrophyllite deposits in North Carolina have been formed through the metaso-matic replacement of acid tuffs and breccias of both rhyolitic and dacitic composition. The de-velopment of pyrophyllite was accompanied by the introduction of Si02 , A12 3 and water. The quartz, pyrite, chloritoid, sericite and pyrophyl-lite in the mineralized bodies are apparently of hypogene origin. Evidences that the deposits have been formed by replacement are as follows : (1) Gradational contacts between pure pyrophyllite and the unaltered country rocks. (2) The preservation of structures of the primary rocks in the mineralized rocks, such as bedding planes of the finer tuffs, and fragmental outlines of the coarser tuffs and breccias. (3) The presence of masses and lenses of practically pure or only partly altered country rock, appar-ently unattached and completely surrounded in the mineral bodies. (4) The introduction of some elements and the removal of others. (5) The lack of any noticeable change in the volume of the original rocks during the mineralization processes. (6) The massive and homogeneous structure of the py-rophyllite. The following sequence of events is deduced : (1) The metamorphism of the volcanic fragmental and flow rocks in which the mineral bodies were later formed. (2) The silicification of the volcanic fragmental and flow rocks by metasomatic processes as is indicated by the presence of original structures of the vol-canics in the silicified materials, and by the pres-ence of entirely surrounded fragments of only partly silicified volcanic rocks in the quartz areas. (3) The development of pyrite in the silicified areas, accompanying or immediately following the silci-fication of the volcanics. (4) The development of chloritoid to some extent in all the pyrophyllite bodies and in abundance in parts of these deposits that are near iron rich forma-tions. (5) The development of sericite by the replacement of the previously silicified volcanic fragmental and flow rocks. (6) The development of pyrophyllite by replacement of the previously silicified and mineralized tuffs and breccias, closely associated with or immediately following the formation of the sericite. SOURCE OF MINERALIZING SOLUTIONS The pyrophyllite forming solutions were evi-dently of hypogene origin, but their source is not so easily demonstrated. The only intrusive igneous rocks that are exposed near any pyrophyllite de-posits in the area are diabase dikes, which are clearly later than the pyrophyllite mineralization. While none of them are known to be exposed in or near a pyrophyllite deposit there are a great many granite type intrusive rocks exposed at widely scattered localities in the pyrophyllite area. During the latter half of the nineteenth cen-tury there were a number of active gold and cop-per mines throughout the Carolina Slate Belt that were important enough to receive considerable attention in reports of the North Carolina Geolog-ical Survey between 1856 and 1917. Nitze and Hanna (1896) pointed out that the gold and cop-per deposits throughout the Carolina Slate Belt are very similar and that much silicification had accompanied the formation of the ores. They at-tributed this mineralization to hot carbonated, alkaline waters of deep seated origin. Laney (1910) found much silicification associated with the ore bodies (gold and copper) at Gold Hill, and concluded that the mineralization had been produced by hot solutions given off from a granite that had been intruded into the volcanics in the immediate vicinity of the ore bodies. Pogue (1910) found practically the same conditions in the Cid district of Davidson County, except that there were no known intrusive igneous rocks to have furnished the solutions. He concluded, how-ever, that there were large igneous masses in-truded into the rocks of the district from below, but that these rocks did not reach the surface. If Nitze and Hanna are correct in their state-ments that the gold and copper mines of the en-tire slate belt are in general alike, and if Pogue is correct in assuming a large intrusive magma below the Cid district that belonged to a period when large amounts of igneous rocks were in-truded into the Piedmont Plateau and brought near the surface, it seems that the same condi-tions must have existed in the pyrophyllite re-gion and that the gold ores of the various mines were formed by hot solutions from igneous mag-mas below. There is a close relation between the pyrophyllite deposits and the metalliferous de-posits at a number of places. One that may be used as a type example is the mine of the Stand-ard Mineral Company near Robbins, Moore Coun-ty, where the pyrophyllite schist grades directly into the silicified tuff at the old Cagle gold mine. This seems to indicate that the same source that 18 furnished the hot solutions to deposit the gold and copper ores in the slate belt also furnished the hot solutions to produce the pyrophyllite bodies. CONDITIONS OF PYROPHYLLITE FORMATION Different investigators have indicated that py-rophyllite may form under conditions varying from high temperature and pressure to low tem-perature and pressure such as exist near the surface. The information available on the origin of chloritoid. seems to indicate that it forms at fairly high temperatures and according to Niggli (1912) is directly dependent upon fairly high pressure. Graton (1906) classed the gold-quartz veins of the Southern appalachians as high temperature in origin, while Laney (1910) and Pogue (1910) both indicated that the gold and copper ores of the Gold Hill and Cid districts were formed under conditions of temperature and pressure varying from high to intermediate. That the pyrophyllite bodies were formed by hot solutions given off from the same source and acting at about the same time is indicated by the close association of the pyrophyllite bodies with the old gold mines, especially the Cagle gold mine near Robbins, Moore County and at the Brewer gold mine (Powers, 1893) in South Carolina. Hafer (1913) noted the presence of copper bearing pyrite in the mine of the Southern Talc Company at Glen-don, Moore County. It is possible that at the pyrophyllite deposits there was a gradual change from high tempera-ture and pressure to low temperature and pres-sure of hydrothermal alteration near the surface during the period of activity of the hot solutions. The writer, however, agrees with Buddington (1916) and Jahns and Lance (1950) and believes that the pyrophyllite deposits of the Carolina Slate Belt in North Carolina were formed under conditions of intermediate temperature and pres-sure. While considering the source of the solutions and the conditions under which the pyrophyllite was formed the problem of a line of entrance for rising solutions should not be overlooked. As has been stated above, the pyrophyllite de-posits occur as elongate bodies or lenses several times as long as they are wide. In at least four localities, near Robbins, Moore County, along Deep River north of Glendon in Moore County, near Hillsborough in Orange County, and north of Stem in Granville County, the pyrophyllite bodies occur as a long zone of lenses from 50 feet to 500 feet wide and from 250 feet to 2000 feet long that can be traced for considerable distances along strike. The mineral bodies are all found in acid tuffaceous rocks and in some cases, particu-larly along Deep River north of Glendon in Moore County, on the limbs of anticlines (as they were worked out and mapped in the field). It seems unreasonable for a special type of vol-canic tuff to have been formed as long narrow bands so widely separated while at all other points there were such wide variations in the material. The conclusion, therefore, is that there was either faulting or some lines of weakness developed along which the solutions entered to form the mineral deposits. Recently, Conley (1962 a) has shown that the pyrophyllite deposits along Deep River, north of Glendon, and those southwest of Robbins in Moore County, were formed along fault zones. There has not been enough detailed mapping carried out to determine the true conditions at the other de-posits in the slate belt. Stuckey (1928) pointed out that the pyrophyllite bodies were formed by the replacement of acid tuffs and breccias of both dacitic and rhyolitic composition and that the tuffs and breccias remained in a state of open texture and tended to mash and shear instead of folding. It is logical to assume, therefore, that all the pyrophyllite bodies were formed along lines of weakness, either fault zones or shear zones. RESERVES Sufficient evidence is not available to determine accurately the reserves of pyrophyllite in North Carolina, but there is sufficient information to establish the presence of fairly dependable indi-cated reserves. Of some 15 known occurrences of pyrophyllite in North Carolina only 5 or 6 have been developed enough to indicate important re-serves of mineable pyrophyllite. These major deposits occur near Robbins and Glendon, Moore County, near Snow Camp, Alamance County, near Hillsborough, Orange County and near Stem, Granville County. All of these deposits, with two exceptions occur along prominent hills or ridges. The Glendon deposits occur in gently undulating topography, while that near Robbins occurs in a relatively flat area covered largely by a thin veneer of Coastal Plain sand. 19 To-date, with one exception, all the pyrophyl-lite mining in the State has been carried out largely from shallow pits and open cuts that have seldom reached a depth greater than 50 or 75 feet. The one exception to these conditions is at the mine of the Standard Mineral Company at Robbins, Moore County, where a shaft 650 feet deep and drifts and stopes are being used. In none of these pits, open cuts, or mines has there been any major change in the pyrophyllite or associated minerals with depth. Even though pyrophyllite should not be found in commercial amounts to depths of over 200 feet, there is enough available to that depth, in the more promising deposits, to support an important industry for many years under efficient mining, milling and concentration practices. The processes of milling have been such that everything that went into the mill had to be pure enough to make a good finished product. It is only recently that any attempt has been made to use separating and concentrating machinery in the removal of grit and other impurities. This has meant that a large amount of material which con-tained 50 percent or more of pyrophyllite has been going on the dumps as waste. If the methods of milling could be improved to the point where all material containing as much as 40 to 50 per-cent pyrophyllite could be utilized, it would prac-tically double the available amount on the basis of milling practices formerly carried out. Pratt (1900) pointed out that the pyrophyllite is continuous and of considerable, though un-known depth. Hafer (1913) suggested that pyro-phyllite should be found to the same depths that the gold mines of the area have reached, and in-dicated that gold had been mined to a depth of 500 feet. This statement seems very reasonable when it is realized that there is a close relation in the distribution of the gold and pyrophyllite mines, and also a strong possibility that the solu-tions forming both come from the same source. Stuckey (1928) stated: "Taking into consider-ation the mineralogy and origin of the deposits, the source of the solutions and the relations in the distribution of the gold and pyrophyllite de-posits, it seems reasonable to expect pyrophyllite in commercial amounts to a minimum depth of 500 feet. This statement does not mean that every pyrophyllite deposit can be developed into a mine at that depth. It does mean, however, that all indications point to a depth of that magnitude for the larger bodies which really show promise at the surface." The results obtained in exploring for pyrophyl-lite over the intervening years have borne out this statement. Some small prospects have been explored that did not prove continuous with depth, but drill holes more than 500 feet deep have failed to reach the limits of the major de-posits. The pyrophyllite deposits occur as irregular lenses 50 to 500 feet wide and 500 to 1500 or more feet long. The bodies of workable pyrophyllite usually occur near the center of the deposits and vary in width from a few feet to more than 100 feet. Pyrophyllite has a specific gravity of 2.8 to 2.9 and weighs 175 pounds per cubic foot. Each 100 feet of length and depth of a pyrophyllite body 100 feet wide should yield 50,000 tons allow-ing for a 60 percent recovery. Using these figures and assuming recovery to a depth of 400 to 500 feet, a reserve of some 10 to 12 million tons of pyrophyllite is indicated in North Carolina. During the past 15 years it has been frequently stated that all the really promising pyrophyllite deposits in North Carolina had been discovered and were controlled by three or four major min-ing companies. Recently, detailed prospecting by two major companies has resulted in the discovery of promising occurrences of pyrophyllite in three new areas. These deposits have not been explored and detailed information on them is not available. These discoveries are interesting, however, as indicating that undiscovered bodies of pyrophyl-lite are still available in North Carolina to those willing to do the necessary prospecting to find them. MINING METHODS The first reference to pyrophyllite mining in North Carolina was by Emmons (1856, p. 217) who stated: "Large quantities have been ground the last year in Chatham County for the New York market." He, also stated (p. 53) "The rock does not split readily with gunpowder; when quarried in this mode, as at Hancock's, it breaks out in illshapen shattered masses. Hence it should be cut out with a sharp pick or an edged instru-ment of suitable form." At first prospecting and mining were carried out by pits, shallow shafts, drifts and open cuts. As demands for larger quantities increased and off color material became salable, open cuts — 20 made possible by information from diamond drill-ing and by modern earth-moving machinery have furnished most of the production. The largest, and only modern underground pyrophyllite mine in North Carolina, is operated near Robbins, Moore County, through a 650 foot shaft, drifts and stopes. PROCESSING The processing of pyrophyllite has changed slowly through the years as demands and uses for the mineral have increased and changed. Prior to about 1855 it was used only locally—for stove linings, fireplaces, chimneys, mantels and grave-stones— and was cut and shaped to fit the par-ticular need. The production of pyrophyllite crayons was started about 1880 and continued until about 1920. Ground pyrophyllite was first produced in 1855, (Emmons 1856, p. 217) . From 1855 to 1913 grinding was carried out, first at Hancock's Mill and later at Glenn's Mill, both located on Deep River near the present village of Glendon, Moore County. The grinding stock was carefully selected, air dried, and crushed. It was then crushed by hand, ground with millstones and passed through bolting cloth. In 1902 the first mill constructed exclusively for grinding pyrophyllite was built near a deposit along Deep River, north of Glendon. This was followed in 1904 by a second mill on another de-posit about a mile away. Both mills were alike in that the grinding stock was air dried and crushed. In one mill the crushed material was passed through a hammer mill, ground with mill-stones, fed into a ball mill, ground 8 hours and screened. In the other mill, the crushed material was ground with millstones, the fines removed by air, and the coarse material fed into a ball mill, ground, and screened. Both of these mills were abandoned by the end of 1921. Before 1918, all the known pyrophyllite de-posits of any importance were located along the north side of Deep River, in the general vicinity of Glendon, Moore County. In that year, what later proved to be the largest known pyrophyllite deposit in the state was discovered about 2 miles southwest of Robbins, Moore County, when wagon wheels brought up a fine white material that proved to be pyrophyllite. The first modern grind-ing plant was built on this property about 1921. The process first used consisted of crushing, grinding in a hammer mill and screening. The hammer mill did not prove satisfactory for grind-ing, and after some modifications, the process was abandoned. A new process was installed, con-sisting of crushing and grinding in a roller mill, and screening. As the ceramic market for pyro-phyllite has become more important, conical peb-ble mills for fine grinding have been installed in this and other plants in the State. At the present time three companies—the Standard Mineral Company at Robbins, the Gen-eral Minerals Company at Glendon, and the Piedmont Mineral Company at Hillsborough are mining and processing pyrophyllite for market. A fourth company, the North State Pyrophyllite Company at Greensboro is mining pyrophyllite and producing a variety of pyrophyllite refrac-tories but is not selling pyrophyllite as such. None of these companies is carrying out benefi-ciation or true mineral dressing on crude pyro-phyllite. By selective mining, blending, grinding and screening, a wide variety of grades, stand-ardized both as to grain size and chemical com-position, is being produced for fillers and specialty products and for use in ceramic bodies and re-fractories. In the processes used to-date, only pyrophyllite pure enough to make a salable finished product has been used. As a result, much good material containing 40 to 60 percent pyrophyllite has been discarded. In view of the somewhat limited re-serves and increasing demands, too much good material is being left in the ground or thrown on the dumps. However, as demands have increased, improved methods of grinding and screening have reclaimed much material formerly discarded. Re-search on the removal of iron, free silica and other impurities has been carried out. As a result, larger tonnages of pyrophyllite of higher quality than that now being produced should be made available to industry as demands increase. USES OF PYROPHYLLITE Pyrophyllite has a wide range of uses which are dependent largely upon the remarkable physi-cal properties of the mineral. Most of these uses are similar to those of talc, to the extent that the two minerals are often used interchangeably. Py-rophyllite is a hydrous aluminum silicate with the formula H2Al2Si40i2. It occurs in several common habits, the best known, perhaps, being the rosette-like aggregates of radially disposed fibers and elongate flattened crystals. A flaky or foliated 21 variety with a slaty cleavage is common along the north side of Deep River and near Robbins in Moore County. A third variety consists of masses of grains and fibers that lack orientation or layering. In some of the finer-grained occur-rences, the pyrophyllite individuals are rosette-like in detail although this is rarely apparent to the unaided eye. While the chemical formula of theoretically pure pyrophyllite is rather simple, most commer-cial pyrophyllite contains varying small quanti-ties of the elements, iron, calcium, magnesium, sodium, potash and titanium. The chemical com-position can be useful in predicting the behavior of pyrophyllite where very exact controls are required in the manufacture of certain products. In ceramic bodies, for example, such properties as color, shrinkage and absorption of tile bodies can be predicted in terms of the raw pyrophyllite used in them. The nature and uses of several types of pyro-phyllite from North Carolina have been effec-tively summarized in a booklet published by the R. T. Vanderbilt Company (1943) of New York. For further details on the properties of pyro-phyllite the reader should consult Grunner (1934), Hendricks (1938), and Ross and Hend-ricks (1945). Prior to about 1855, pyrophyllite was used locally for tombstones, and such stones, still well preserved, may be seen in two or more cemeteries near Glendon. Emmons (1856) described it as an excellent substitute for soapstone in stove linings, fireplaces, chimneys and mantles. He stated that it was not suitable for paint as it became translu-cent when mixed with oil, but described it as a filler that helped retain the perfume in soap and added that large quantities were ground for the New York market in 1855. He described it as suitable for anti-friction powder and use in cos-metics and quoted Dr. Jackson to the effect that it would make a very refractory material for stoneware and crucibles. At present, pyrophyllite is used chiefly in the manufacture of insecticides, rubber, paint, ceram-ics, refractories, plastics, and roofing paper. It has a number of minor uses for products including cosmetics, wallboard, rope and string, special plaster, textile products, paper, linoleum and oil-cloth, and several types of soap. The best pro-duction figures available indicate that about one half of the current annual production goes into insecticides, rubber and paint, one third into ceramics and refractories and the remainder into plastic, roofing paper, linoleum, cosmetics and a host of minor uses. According to Jahns and Lance (1950) : "A large part of the domestic production of pyrophyl-lite is incorporated into paints and particularly non-reflecting and other special types in which flake pigments of light color are desired. High oil absorption of ground pyrophyllite and its free-dom from grit also are desirable properties for paint use. Ground material is employed as a filler in rubber goods, certain roofing and flooring ma-terials, special plasters, plastics, insecticides, tex-tile products, paper, linoleum and oilcloth, rope and string, several types of soap and in some fertilizers. It serves as a "loader" in paper and textile fabrics, where its whiteness and resistance to the effects of fire and weather are particularly desirable. This resistance also partly accounts for its use in roofing papers and other asbestos and asphalt goods. Its corrosion resistance makes it an especially satisfactory filler in battery cases. There are indications that it also may serve effec-tively as a low noise filler in phonograph records. "With a low bulk density and slight acidity in ground form, high absorptive characteristics, and superior qualities as a flake-form dusting agent, pyrophyllite is an excellent carrier for such active insecticides as DDT, nicotine, pyrethrum and rotenone. The flakiness of the mineral leads to desirable adhesion on leaves and other parts of dusted plants, and its softness and freedom from grittiness when finely ground make for reduction of wear on nozzles and other parts of mechanical insecticide dispensers. "Pyrophyllite of great purity and whiteness has been used as a base for cosmetics and toilet prep-arations, but the total amount is not large. The lubricating properties of the mineral underlie its use in some greases, in tires and other rubber goods, on machine-driven box nails, and in vari-ous kinds of dies. On the other hand, it also is employed as a fine, "soft" abrasive in the scour-ing and polishing of certain foodstuffs, as well as some painted or lacquered surfaces. It serves as a high-quality packing and insulating material, as a constituent of adhesive, corrosion-resistant covering compounds, and as an absorbent for oil substances in a wide variety of products. It, also, can be processed for use in crayons and pencils. 22 "As a constituent of ceramic bodies, pyrophyl-lite is being more and more widely used. It is a good substitute for feldspar and quartz in wall-tile bodies, as it decreases their shrinkage and their crazing by thermal shock or moisture ex-pansion. It also is employed as a source of alumi-num in enamels, and as a raw material for semi-vitreous dinnerware and some types of refrac-tories." Uniformity of grain size and mineral content is becoming important for all uses. For ceramics, whiteware, and wall tile, where the size of the finished product must be controlled accurately, pyrophyllite is one of the best materials available provided it is perfectly uniform in grain size and composition. For use in special refractories, such as car tops for tunnel kilns, monolithic furnace lining and furnace lining requiring rapid tem-perature changes, pyrophyllite makes an excel-lent body that is shock-resistant. MINES AND PROSPECTS Beginning on the northeast in Granville Coun-ty, near the Virginia line, and continuing in a southwesterly direction to the southwestern part of Montgomery County is an irregular zone, along the eastern part of the Carolina Slate Belt, that contains all the known occurrences of pyrophyl-lite in North Carolina. Prospects, outcrops and/or mines are known to occur in Granville, Orange, Alamance, Chatham, Randolph, Moore and Mont-gomery counties. GRANVILLE COUNTY Daniels Mountain Pyrophyllite bodies occur in three localities in Granville County. One of these is on Daniels Mountain, a prominent ridge that rises nearly 200 feet above the surrounding countryside. Daniels Mountain is located approximately 9 miles slightly northwest of Oxford, about 1.5 miles east of North Carolina Highway 96 and just south of Mountain Creek. The area is un-derlain with acid volcanic rocks. Small amounts of pyrophyllite occur on the north end of this ridge. No prospecting had been done at the time the writer visited the ridge. Espenshade and Pot-ter (1960) described Daniels Mountain as fol-lows : "Another deposit of pyrophyllite occurs on a prominent ridge rising nearly 200 feet above the surrounding countryside, about 14 miles northeast of Bowlings Mountain deposit, 9 miles northwest of Oxford, and about l 1/^ miles east of North Carolina Highway 96. Float and low outcrops of dense siliceous rock are abundant for about three-quarters of a mile along the ridge. Chloritoid occurs in some rock, disseminated hematite and magnetite are also present. Blocks of massive pyrophyllite, 1 to 2 feet long, are dis-tributed along a distance of 600 to 700 feet at the north end of the ridge. Other aluminous min-erals have not been discovered." Bowlings Mountain A major pyrophyllite deposit is present on Bowlings Mountain, a prominent hill that is lo-cated about 3 miles northwest of Stem and 10 miles southwest of Oxford, Granville County. The hill rises to an elevation of about 700 feet above sea level (approximately 200 feet above the sur-rounding countryside), has a trend of about N 15° E and conforms to the pattern of a series of rather pronounced ridges to the northwest. The pyrophyllite deposit which lies along the crest and northeastern slope of the mountain is ap-proximately 500 feet wide and more than 1500 feet long. The strike is N 15° E and the apparent dip is 70° to 80° to the northwest, paralleling the strike and dip of the country rock. Prospecting was first carried out on the south-west end of the ridge and near the western slope, about the turn of the century, when a pit known as the Harris prospect was opened. This pit which was 15 to 20 feet long, 6 feet wide and 6 to 10 feet deep was opened on an outcrop of radiating or needle-like crystals of iron-stained pyrophyl-lite. About 1940 a shaft was sunk to a depth of approximately 80 feet near these old pits. The phyrophyllite found in this shaft did not differ materially from that found in the surface pits and the work was abandoned. About 1949 or 1950, Carolina Pyrophyllite Company began exploration and development work here, consisting of pitting and trenching followed by drilling, during the course of which a large tonnage of pyrophyllite was discovered. Following this exploration work, 2 opencuts were developed from which considerable pyrophyllite was mined and shipped by truck to a grinding plant at Staley, some 80 miles to the southwest, before that mill was closed in 1960. 23 On the southeast or footwall side of the deposit is a medium-grained, dense, quartzitic rock con-taining pyrite that seems to represent the foot-wall of the deposit. Northwestward from the quartzitic rock mineralization is quite apparent. Massive and crystalline pyrophyllite occurs in very fine-grained schistose zones in sericite schist. Tough, white, granular rock containing coarse-grained andalusite, quartz, and pyrophyllite is present in parts of the deposit. Massive topaz identical in appearance with the dense topaz from the Brewer mine in South Carolina is abundant as float adjacent to the quartzitic footwall. Here, it is found concentrated in a series of rather poorly defined zones covering an area more than 100 feet long and 200 feet wide. Individual pieces range from less than one-fourth inch to 3 feet in diameter. Outcrops in the area are rare, but, in recent road cuts along the northern end of the mountain, topaz is exposed as a series of narrow, irregular veinlike masses in sericite schist. It also occurs as stringers a few inches thick in phyrophyllite in the southernmost open cut. The topaz occurs as boulders in the quartzitic rock, filling cracks and fractures, as small knotty masses disseminated throughout the rock and as large massive pieces which in some cases appear to grade into the host rock. The andalusite and topaz, older than the pyrophyllite, appear to re-place the country rock and in turn are replaced by pyrophyllite. Long Mountain About a mile or two to the northwest of Bowl-ings Mountain is a zone of irregular hills from 1 to 1.5 miles wide and 4 to 5 miles long that is known as Long Mountain. This ridge trends about north 20 degrees east and lies partly to the north and partly to the south of State Road 1139. The highest point on Long Mountain is a knob north of State Road 1139 and along the western side of the ridge that is known as High Rock Mountain. It rises to an elevation of some 150 to 200 feet above the surrounding country-side and 700 feet above sea level. Pyrophyllite outcrops of varying size and promise, some of which have been prospected and some of which have not, are widely scattered throughout Long Mountain. Robbins Prospect 1 On the Robbins property, in the vicinity of High Rock Mountain is an area about 1000 feet wide and 2000 feet long on which radiating pyro-phyllite, associated with quartz veins, is common but not abundant. No prospecting has been done in this general area and the potential for commer-cial deposits of pyrophyllite is unknown. Most of the pyrophyllite visible is badly iron stained. Jones Prospect To the east of the Robbins tract and about 1500 feet north of State Road 1139, some 4 or 5 pros-pect trenches that varied in length from 150 to 300 feet and up to 8 or 10 feet deep were opened on the Jones land some 8 or 10 years ago. Details of this prospecting are not available but indica-tions for pyrophyllite are good. The country rock is a medium to fine-grained felsic volcanic tuff that has a cleavage which strikes north 20 to 30 degrees east and dips steeply to the northwest. Both foliated and radiating pyrophyllite, some of which is iron stained, is farily common. R. E. Hilton Property Adjoining the Jones land on the east is the land of R. E. Hilton on which there is a zone varying from 250 to 500 feet wide and about 1000 feet long that contains promising outcrops of pyro-phyllite. No prospecting has been done on this property but bold outcrops of good pyrophyllite make it appear promising. E. C. Hilton Property Along the east side of Long Mountain and south of State Road 1139 there are two interest-ing areas of pyrophyllite on the land of E. C. Hilton. The first of these, which is about 1500 feet south of State Road 1139 and near a recent sawmill site, consists of about three acres on which bold outcrops of pyrophyllite mixed with similar outcrops of felsic volcanic rocks are abun-dant. No prospecting has been done here but the outcrops indicate the possible presence of im-portant amounts of good pyrophyllite. The other area is on a prominent hill about 1500 feet farther southeast and beyond a small stream. Surface exposures of pyrophyllite are not extensive but some interesting outcrops of radiating crystals may be seen. Considerable prospecting in the form of drilling, the results of which are not known, was carried out here about 8 or 10 years ago. The country rock at both of these prospects is a medi-um to fine-grained, felsic volcanic tuff. 24 Robbins-Uzzell Property About 1500 feet south of State Road 1139 and to the southeast of High Rock Mountain is an unnamed ridge that ranges between 500 and 600 feet above sea level. This ridge which begins near the head of an east flowing stream continues in a south 20 degrees west direction to and beyond Dickens Creek a distance of 1.5 to 2 miles. The northeast end of this ridge is a part of the Rob-bins tract while the southwest end is a part of the Uzzell land. No prospecting has been done on this ridge but outcrops of excellent pyrophyllite remarkably free of iron stain make it promising as a source of pyrophyllite. Robbins Prospect 2 Just east of Knap of Reeds Creek and a short distance south of State Road 1139 is a power transmission line tower. Beginning near this tower and extending to the southwest for a dis-tance of 800 to 1000 feet is a pyrophyllite body that is 300 to 400 feet wide. The cleavage in this mineral body strikes about north 35 to 40 degrees east and dips steeply to the northwest. The rocks surrounding this deposit consist of medium- to fine-grained acid volcanic materials. The north-west 150 to 200 feet of the deposit consists largely of good quality pyrophyllite that varies from mas-sive to foliated. The southeast or footwall portion to a width of 75 or 100 feet appears to be in part sericite. This is a promising deposit that could contain considerable high-grade pyrophyllite. ORANGE COUNTY Murray Prospect Pyrophyllite deposits occur in three localities in Orange County. One of these known as the Mur-ray property is located on a ridge about 5 miles northeast of Hillsborough near the intersection of State Roads 1538 and 1548. State Road 1538 passes just to the north of the property while State Road 1548 lies just to the east. Here along a ridge in an area of medium to fine-grained acid volcanic rocks are old prospect pits up to 30 feet long by 10 feet wide and 6 feet deep. Most of the pits are about 10 feet long by 4 feet wide and 6 feet deep. The pits are scattered over an area 75 to 100 feet wide and 500 feet long. Pyrophyllite of the foliated or schistose variety is present on the dumps and in the sides of the pits as well as in an occasional outcrop. Chloritoid is abundant in the walls of some of the pits, especially near narrow bands of greenstone in the felsic volcanics. This area probably contains pyrophyllite of value. Hillsborough Mine Immediately south of Hillsborough are three prominent hills which trend northeast and paral-lel the major geologic structure of the area. From northeast to southwest these hills are often desig-nated Hill No. 1, Hill No. 2 and Hill No. 3. Al-though the three hills appear to be much alike in many ways, the developed mineralization is limited to Hill No. 1, the northeastern most of the three. Here, prospecting was started in 1952 by the North State Pyrophyllite Company fol-lowed by mining a few years later. The zone of mineralization as exposed by the open cut mining operations is some 1500 feet long and from 100 to 250 feet wide. It strikes approximately N. 50° E. and dips from 60 to 80 degrees to the northwest. The mineral body has a footwall of dense siliceous rock that forms the crest of the hill or ridge and a hanging wall of sericite schist. The chief min-erals in the deposit in the order of decreasing abundance are silica, massive and crystalline or radiating pyrophyllite, sericite, andalusite and topaz. Minor amounts of diaspore have been re-ported. Andalusite is abundantly disseminated throughout the deposit and seems to be consider-ably more abundant than pyrophyllite in much of the deposit. It is light blue, greenish blue or gray in color, has a pronounced blocky appearance, and occurs as small fragments about one-fourth inch in diameter, disseminated sparingly to abundant throughout the quartzose rock. Topaz occurs spar-ingly in the deposit, apparently being limited largely to disseminated grains and masses in the fractured quartzose footwall rock. Recent field work indicates that to the south-west mineralization similar to that on Hill No. 1, now being worked by Piedmont Minerals Com-pany, may be present in workable amounts on the northwest side of Hill No. 2 and in a prominent knob on the northwest side and near the north-east end of Hill No. 3. Teer Prospects In the southwestern part of Orange County, approximately 10 miles southwest of Hillsbor- 25 A. Mill B. Open Pit Mine Plate 2. Piedmont Minerals Company 26 ough, and in the general vicinity of Teer, there are a number of pyrophyllite outcrops, at least three of which have been prospected. On the north end of Mitchell Mountain and about one-half mile southwest of Teer, North State Pyrophyllite Com-pany carried out prospecting and produced a small amount of pyrophyllite. A pit 100 feet long, 30 feet wide at the top and 15 feet deep was exca-vated. The strike of the cleavage is N. 55° E. and the dip is 75 degrees to the northwest. The amount of good grade pyrophyllite was too low for economic mining and the prospect was ban-doned. About 3 miles almost due north of Teer and between State Road 1117 and Cane Creek, on the farm of Salina Sykes is a small prospect pit that contains minor amounts of radiating pyro-phyllite. No production was made and the pit is now abandoned. About one mile almost due north of Teer and between State Roads 1115 and 1116, considerable prospecting and some mining for pyrophyllite was carried out on the land of Clarence Bradshaw by the Carolina Pyrophyllite Company, between 1958 and 1961. A pit 200 feet long by 100 feet wide at the top and about 80 feet deep was exca-vated. The pyrophyllite content of the rock was originally 24 percent. The cleavage of the rock strikes about N. 55° E. and dips 75 degrees to the northwest. ALAMANCE COUNTY Snow Camp Mine The Snow Camp pyrophyllite deposit being worked by the North State Pyrophyllite Com-pany, is located on Pine Mountain about 3.5 miles southeast of Snow Camp. Prospecting was started in 1935 and over the intervening years the de-posit has been a major producer of massive pyro-phyllite. The pyrophyllite is shipped by truck to the company's plant at Pomona, North Carolina where it is used in the manufacture of firebrick, brick-kiln furniture and other refractory prod-ucts. The deposit is a lenticular body of massive pyrophyllite and fine-grained quartz about 35 feet long and 250 feet wide. Open pit mining had developed walls nearly 100 feet high in the east and south sides of the pit until parts of them were removed for safety reasons in 1965. A rib of high-silica rock is present near the center of the deposit. This rib has been quite heavily mineral-ized in places and parts of it have been mined out. Coarse-grained andalusite was reported to have been found in a zone several feet wide in the northern part of the deposit, but it did not seem to be very abundant. This deposit still appears to contain a large reserve of high-grade pyrophyl-lite. Major Hill Prospects About 2 miles east of Snow Camp there are several pyrophyllite outcrops on a prominent hill, known locally as Major Hill. Major Hill lies south of State Road 1005, between State Roads 2356 and 2351, and north of State Road 2348. This hill is somewhat irregular in shape, but slightly elon-gate in a direction a little north of east. Two small exposures of pyrophyllite are to be seen in old prospect pits near the west end of the hill, but they do not appear to be of commercial size. Beginning about midway of the hill from west to east and along the southern slope some 250 feet from the crest is a zone of pyrophyllite about 1000 feet long and 50 to 100 feet wide that ap-pears from outcrops to contain a considerable ton-nage of high-grade massive pyrophyllite. Due to wooded conditions and lack of outcrops the geolog-ical setting could not be satisfactorily determined. It appears, however, that the pyrophyllite is in an area of medium- to fine-grained tuffaceous rocks of volcanic origin and acid composition. This deposit is on land belonging to the North Carolina National Guard. Immediately to the east of the deposit on the National Guard land is a deposit 100 to 150 feet wide and 350 to 500 feet long on lands of the Holliday estate. This deposit contains both pyro-phyllite and sericite which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the northwest. This deposit appears to contain a con-siderable tonnage of minable material. To the northeast of this deposit and near the east end of Major Hill is another deposit of promise on the Holliday estate. The outcrop is irregular in shape but appears to be 150 to 300 feet wide and 400 to 500 feet long. Pyrophyllite and sericite, both of which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the northwest, are present in varying amounts in this deposit. To the south and southeast of the above de-scribed deposits is another deposit on the south-east tip of Major Hill and on lands of the Holliday estate. This deposit is 150 to 250 feet wMe and 27 400 to 500 feet long. It contains both pyrophyllite and sericite which have a cleavage that strikes N. 50° to 60° E. and dips steeply to the north-west. Because the above described three deposits, on the Holliday estate are all in wooded areas and rock outcrops are not too abundant it was not possible to establish completely the geological setting. It appears, however, that all three are in areas of medium- to fine-grained tuffaceous rocks of volcanic origin and acid composition. In the spring and summer of 1966 these deposits were under option to and being prospected by the North State Pyrophyllite Company. On the Richardson land, a short distance north-east of Major Hill and just west of State Road 2351, is an interesting occurrence of pyrophyllite. The outcrop area which is elongated in a north-east direction appears to be about 100 feet wide and 350 to 500 feet long. Both massive and radiat-ing pyrophyllite are present. About 2 miles east of Snow Camp and a short distance north of State Road 1005, the Carolina Pyrophyllite Company is quarrying sericite on a small ridge on a hill adjacent to the Foust lands. The sericite is being shipped by truck to Glendon where it is ground and blended with pyrophyllite. Open pit mining indicates a large tonnage of rock which may extend into the Foust lands to the north. CHATHAM COUNTY Hinshaw Prospect The only known pyrophyllite deposits in Chat-ham County are on the farm of Don Hinshaw in the northwestern corner of the county. This prop-erty is about 2 miles east of State Road 1004 and a short distance north of State Road 1343. It can be reached by leaving State Road 1004 at State Road 1343 about 2.5 miles south of the Chatham- Alamance line. Follow State Road 1343 about 1.5 miles northeast to the Hinshaw farm. The out-crops are in a wooded area a short distance north of the Hinshaw home. Here, some years ago, Carolina Pyrophyllite Company opened a pit some 10 feet wide, 15 feet deep and 25 to 40 feet long. Near this pit, pyrophyllite is scattered through rocks over a distance of 100 feet long and 25 to 50 feet wide. To the northeast are other outcrops that look promising. Enough pyrophyllite out-crops are present in the area to indicate that it is worth prospecting. RANDOLPH COUNTY Pyrophyllite is known to occur in Randolph County in two areas. One of these is in the north-eastern corner of the county about 3.5 miles west of Staley. The other is on the southern slopes of Pilot Mountain just north of State Highway 902 and about 8 miles east of Asheboro. Staley Deposit The Staley deposit, now worked out, was at one time the second largest pyrophyllite mine in the State. The main part of the deposit lay along the crest and northwest side of a rather steep hill as a lenticular body 100 to 200 feet wide and 350 feet long. The cleavage strike was approximately N. 50° E. and the dip was 60 to 70 degrees to the northwest. When abandoned the open cut was about 180 feet wide, 300 feet long and 250 feet deep. The hanging wall of the deposit consisted of a volcanic ash largely altered to a sericite schist. A central zone |
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