Anthophyllite asbestos in North Carolina

              CI
3:77
C 2 North Carolina
Department of Conservation and Development
Robert L. Stallings, Jr., Director
Division of Mineral Resources
Jasper L. Stuckey, State Geologist
Bulletin 77
Anthophyllite Asbestos
in North Carolina
by
Stephen G. Conrad, William F. Wilson, Eldon P. Allen
Division of Mineral Resources
and
Thomas J. Wright
North Carolina State Minerals Research Laboratory
Raleigh
1963
North Carolina
Department of Conservation and Development
Robert L. Stallings, Jr., Director
Division of Mineral Resources
Jasper L. Stuckey, State Geologist
Bulletin 77
Anthophyllite Asbestos
in North Carolina
by
Stephen G. Conrad, William F. Wilson, Eldon P. Allen
Division of Mineral Resources
and
Thomas J. Wright
North Carolina State Minerals Research Laboratory
Raleigh
1963
MEMBERS OF THE BOARD
OF CONSERVATION AND DEVELOPMENT
Hargrove Bowles, Jr., Chairman Greensboro
Dr. Mott P. Blair, Vice Chairman Siler City
John M. Akers Gastonia
Robert E. Bryan , Goldsboro
Mrs. B. F. Bullard Raleigh
Daniel D. Cameron Wilmington
Mrs. Fred Y. Campbell Waynesville
Dr. John Dees Burgaw
William P. Elliott, Sr. Marion
E. Hervey Evans, Jr. Laurinburg
E. R. Evans Ahoskie
Andrew Gennett Asheville
Luther W. Gurkin, Jr. Plymouth
Woody R. Hampton Sylva
Charles E. Hayworth High Point
Gordon C. Hunter Roxboro
Roger P. Kavanagh, Jr. __ Greensboro
R. Walker Martin Raleigh
Carl G. McCraw Charlotte
Lorimer W. Midgett Elizabeth City
Ernest E. Parker, Jr. Southport
R. A. Pool Clinton
Eric W. Rodgers Scotland Neck
Robert W. Scott Haw River
James A. Singleton, Jr. __ Red Springs
J. Bernard Stein Fayetteville
Paul H. Thompson Fayetteville
Charles B. Wade, Jr. Winston-Salem
ll
LETTER OF TRANSMITTAL
Raleigh, North Carolina
September 25, 1963
To His Excellency, HONORABLE TERRY SANFORD
Governor of North Carolina
Sir:
I have the honor to submit herewith manuscript for publication as
Bulletin 77, "Anthophyllite Asbestos in North Carolina", by Stephen G.
Conrad, William F. Wilson, Eldon P. Allen and Thomas J. Wright.
This report contains the results of a detailed investigation of geology
and mineral dressing characteristics of the anthophyllite asbestos de-posits
in North Carolina and should be of value to those interested in
the economic development of these deposits.
Respectfully submitted,
Robert L. Stallings, Jr.
Director
CONTENTS
Page
Abstract 1
Introduction 1
Location and distribution 1
Purpose of investigation .
. 1
Previous work 3
Present investigation 3
Acknowledgments 4
Geography 4
Climate 4
Topography 4
Accessibility 5
Regional geology 5
Rock types 5
Structure and metamorphism 6
Peridotites and related ultramafic rocks 7
Distribution 7
Character and relations 7
Petrography 8
Dunite 8
Saxonite (harzburgite) 8
Pyroxenite 9
Enstatolite 9
Websterite 9
Soapstone 10
Alteration of peridotite 10
Serpentinization 10
Steatitization 11
Amphibolization 12
Chloritization 12
Origin 12
Age 13
Asbestos deposits 14
Mineralogy and geologic occurrence 14
Crysotile 14
Amphibole asbestos 14
Tremolite 14
Actinolite 15
Crocidolite 15
Amosite 15
Anthophyllite 15
Uses 15
Character and classification of North Carolina deposits 17
General statement 17
Cross-fiber veins 17
Slip-fiber veins 17
Mass-fiber deposits 17
Peripheral zones 18
Anthophyllite-enstatite bodies 18
Origin of anthophyllite asbestos 19
History of mining and production 20
Mining methods 21
Reserves 21
Description of mines and prospects 21
Spruce Pine area 21
Avery County 21
Burleson mine 21
Frank mine 22
Other prospects 22
Page
Mitchell County 22
J. H. Pannell prospect 22
Soapstone Branch prospect 22
Other prospects 24
Yancey County 24
Blue Rock mine 24
Newdale mine ' 25
J. C. Woody mine 26
Sam Grindstaff mine 26
Gas Thomas prospect 27
C. W. Allen prospect 27
Other prospects 27
Lake Toxaway area 27
Transylvania County 29
Kilpatrick mine 29
Oakland mine 29
Walnut Cove Creek mine 30
Miller mine 30
Jennings No. 1 mine 31
Socrates prospect 32
Other prospects 32
Jackson County 32
Asbestos mine 32
Rattlesnake prospect 34
Brockton mine 35
Bad Creek prospect 35
Jennings No. 2 mine 36
Round Mountain mine 36
Coldsides Mountain mine 36
Harris prospect 37
Glenville-Norton area 37
Bryson-Manus mines 37
Henderson mine 40
Alders mine 40
Holden mine 40
Other mines and prospects 40
Macon County 40
Higdon mine 40
Peterman mine 42
Commissioner Creek prospect 42
Caldwell County 42
Johns River mine 42
Evaluation and Beneficiation 45
Introduction 45
Dry processing 45
Sample 1855A 45
Sample 1855B 45
Sample 1856 45
Sample 1857A 45
Sample 1857B 45
Sample 1858 49
Sample 1859 49
Sample 1872A 49
Sample 1872B 49
Comparison of the plus 28 mesh fiber products 49
Acid leaching and wet processing 50
Conclusions 50
References cited 60
ILLUSTRATIONS
Page
Figure 1. Geographic distribution of ultramafic bodies in
western North Carolina 2
2. Properties of asbestos fibers 16
3. Map showing location of asbestos mines in
Yancey County, North Carolina 23
4. Map showing location of asbestos mines in the
Brush Creek area, Yancey County, North Carolina 28
5. Map showing location of asbestos mines in the
Sapphire Valley area, North Carolina 33
6. Map showing location of asbestos mines in Chattooga
Ridge area, Jackson County, North Carolina 38
7. Map showing location of asbestos mines in the
Glenville-Norton area 39
8. Map showing location of peridotites in Ellijay
Creek area, Macon County 41
9. Map showing location of Johns River asbestos prospect,
Caldwell County, North Carolina 43
10. Flowsheet for treatment of asbestos ore 46
11. Flowsheet for low grade, short-fiber ore 50
Table 1. Distribution and composition of products from
dry process 47
2. Distribution and composition of products from
dry process 47
3. Distribution and composition of products from
dry process 48
4. Properties of plus 28 mesh aspirated fiber 48
5. Cleaning re-treatment of aspirated fiber 1857A
Screen analysis of + 28 mesh fiber 1858 49
6. Comparison of chemical and mineralogical content
of talc and anthophyllite concentrates 49
Plate 1. Photomicrographs of typical anthophyllite asbestos
ores and related rocks 53
2. Photomicrographs of typical anthophyllite asbestos
ores and related rocks 55
3. Photomicrographs of typical anthophyllite asbestos
ores and related rocks 57
4. Geology of the Newdale asbestos mine, Yancey County,
North Carolina in pocket
5. Geologic cross-sections of the Newdale asbestos mine,
Yancey County, North Carolina in pocket
6. Geology of the Blue Rock asbestos mine, Yancey
County, North Carolina in pocket
7. Photographs of typical ore samples; and contact
relationships at the Newdale and Blue Rock mines,
Yancey County, North Carolina 59
Vll
Anthophyllite Asbestos in North Carolina
by
Stephen G. Conrad, William F. Wilson and Eldon P. Allen
ABSTRACT
Asbestos deposits in North Carolina are associated with a group of basic magnesian rocks com-monly
referred to as peridotites. These rocks range from dunite to soapstone in composition, and are
part of a discontinuous belt of ultramafic igneous rocks that traverse the eastern part of North America
from east-central Alabama to western Newfoundland. In North Carolina the peridotite belt lies chiefly
west of the Blue Ridge in the mountainous section of the State. However, a few isolated bodies occur in
the Piedmont section of Burke, Caldwell, Polk, Wilkes and Wake counties.
Although various types and quantities of asbestiform minerals can be found in practically all of
the individual peridotite bodies throughout the area, the most important commercial deposits occur as
anthophyllite asbestos associated with altered bodies in the Toxaway area of Jackson and Transylvania
counties and in the Spruce Pine area of Yancey and Avery counties.
Based on the arrangement of the fibers in respect to the wall rock and to each other, three types of
anthophyllite asbestos ore are recognized. These types are referred to as cross-fiber veins, slip-fiber
veins and mass-fiber deposits. Cross-and slip-fiber veins are the most common and are present to some
extent in ultramafic bodies that range in composition from relatively unaltered dunite to soapstone. The
mass-fiber deposits are divided into peripheral zones associated with partly to thoroughly altered bodies,
and small, oval shaped bodies composed mostly of anthophyllite and enstatite.
Past production from North Carolina has been mostly from mass-fiber deposits of the peripheral
zone type. However, mass-fiber deposits of the anthophyllite-enstatite variety appear to have consider-able
potential.
The North Carolina State Minerals Research Laboratory determined the physical and chemical
properties of nine selected ores and investigated methods of separating the major mineral components
by dry and wet benefication processes.
INTRODUCTION
Location and Distribution
The asbestos deposits in North Carolina are
associated with a group of basic magnesian rocks,
commonly referred to as peridotites. These per-idotites
are part of a discontinuous belt that tra-verses
the eastern part of North America from
east-central Alabama to western Newfoundland,
a distance of more than 2,000 miles. In North
Carolina the peridotite belt lies chiefly west of the
Blue Ridge in the mountainous section of the
state ; however, a few isolated bodies occur in the
Piedmont section in Burke, Caldwell, Wilkes and
Wake counties.
Although various types and quantities of asbes-tos
can be found in most of the individual per-idotite
bodies throughout the area, practically all
of the commercial deposits of asbestos occur in
highly altered bodies in the Lake Toxaway area of
Jackson and Transylvania counties and in the
Spruce Pine area of Yancey and Avery counties.
The accompanying map (Figure 1) of a portion
of western North Carolina shows the distribution
of the main belt of peridotites and related ultra-mafic
rocks. Owing to the fact that most of the
peridotites are lenticular or oval masses, usually
less than 300 or 400 feet in length, it was neces-sary
to exaggerate their dimensions on the map in
order for them to be distinct.
Purpose of Investigation
North Carolina has been a small, but consistent
producer of anthophyllite asbestos for many years.
Although the peridotite bodies with which the
asbestos is associated have been studied at various
~ a to
VI
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2E
<3g
times for other economic minerals, such as olivine,
vermiculite, chromite, and corundum, there have
been no systematic studies of asbestos.
Asbestos is a highly important industrial min-eral
for which there are practically no substitutes.
In view of the fact that the demand for asbestos
should continue to increase for some years to come
and that research is developing new uses for all
varieties of asbestos, an appraisal of North Caro-lina's
anthophyllite asbestos resources seems de-sirable
at this time.
It is the purpose of this report to present as
complete an appraisal as possible of the antho-phyllite
asbestos resources of the State. A com-bination
of several factors indicate that the pros-pects
appear very favorable for developing an im-portant
asbestos producing industry in the State
within the next few years. It is hoped that this
report will contribute materially to the develop-ment
of such an industry.
Previous Work
Owing to the fact that an unusual number of
economic minerals are associated with them, the
peridotites have been of interest for well over
100 years. Because of its value as a natural abra-sive,
next to diamond in hardness, and as a gem
stone, corundum was the first mineral of the peri-dotites
to draw attention. The first reference to
corundum in North Carolina appeared in an ar-ticle
in the American Journal of Science by John
Dickson in 1821. Kerr (1875, pp. 129-130, 293,
298-299) briefly describes the "chrysolyte (dun-yte)
" ledges and the associated minerals serpen-tine,
asbestos, chromite and corundum. Included
in this same volume (Appendix D, pp. 91-97) is a
more detailed discussion of corundum and its
associated rocks by C. D. Smith.
The first systematic study of the peridotites in
western North Carolina was by Lewis (1896).
This was a preliminary report on corundum and
the basic magnesian rocks based on field studies
during 1893 and 1894. This study was expanded
and continued for several more years and in 1905
Pratt and Lewis published a comprehensive re-port
on the geology, petrology and mineralogy of
the belt of corundum-bearing rocks in western
North Carolina. This report is considered to be
somewhat of a classic in geologic literature and
has served as the bases of much subsequent work.
It was a valuable aid in the present study and
greatly facilitated the fieldwork.
After the introduction of artificial abrasives
about 1900, the importance of corundum was
greatly reduced and corundum mining in North
Carolina ceased about 1906. Subsequently, the
peridotites received very little attention until the
Tennessee Valley Authority began its study of
regional products during the middle and late
1930's. Several reports dealing with economic
minerals associated with the peridotites resulted
from studies conducted by the Tennessee Valley
Authority in cooperation with the North Carolina
Division of Mineral Resources. The first of these
was by Hunter (1941) on the fosterite olivine de-posits.
Others were by Hunter, Murdock and Mac-
Carthy (1942) on the chromite deposits and by
Murdock and Hunter (1946) on the vermiculite
deposits. During World War II the U.S. Geologi-cal
Survey and the U.S. Bureau of Mines investi-gated
several of the abandoned corundum mines
in Clay, Macon and Jackson counties as a possible
domestic source of corundum. The results of these
studies were reported by Ballard (1947a, 1947b)
and Hadley (1949).
It should be pointed out that the above men-tioned
publications represent only the most sig-nificant
work done on the peridotites of North
Carolina. As the peridotite belt traverses prac-tically
the entire length of eastern North America,
there is a vast amount of literature available that
has been prepared by other state surveys, the
federal survey, the Canadian survey and individ-ual
workers. However, as this report is concerned
only with the asbestos deposits in North Carolina,
it is beyond its scope to review all of the literature
on asbestos and the peridotites.
Present Investigation
The present geologic study of anthophyllite as-bestos
deposits was begun in the spring of 1960.
The purpose of the study was to gather as much
information as possible on the distribution, char-acter,
origin and potential reserves of asbestos in
North Carolina.
As the individual peridotite bodies number in
the hundreds, it was possible to visit only a limited
number of deposits in the time alloted to the
project. However, an attempt was made to locate
and examine all of the deposits that had been
worked for asbestos plus as many of the other
peridotites as possible. Particular attention was
given to the deposits currently being mined and
to those that were mined in recent years. Detailed
geologic maps were made of three selected deposits
and geologic sketch maps were made of numerous
others.
Samples considered to be representative of the
different types of ore and associated rocks were
collected from most of the deposits examined.
Some 50 thin-sections were prepared from these
samples for petrographic analyses.
An important phase of this project was the
mineral dressing studies conducted by the North
Carolina State College Minerals Research Labora-tory.
Thomas J. Wright, Mineral Dressing Engi-neer,
carried out these studies, the results of which
are discussed in detail in the latter part of this
report.
Acknowledgments
This report was authorized by and conducted
under the direction of Dr. Jasper L. Stuckey,
State Geologist, who also furnished much back-ground
material and spent several days in the
field with the writers when the project was initi-ated.
Many persons have made important contribu-tions
to this investigation. Particularly helpful
were Mr. Fred A. Mett, President, and Mr. Frank
Burleson, Mine Foreman, of the Powhatan Mining
Company. Both were very generous with their
time in locating abandoned asbestos workings,
and gave freely of their extensive knowledge of
asbestos gained through many years of explora-tion
and mining of asbestos in North Carolina,
Georgia and South Carolina. Mr. Joseph H. Kettle-strings,
President, and Mr. Joe Sherertz, Mine
Superintendent, of the Blue Rock Mining Corpora-tion
of Illinois were also most helpful and coopera-tive.
Mr. Louis Dendy, Highlands, acted as guide
on several occasions and his familiarity with the
peridotites in Macon, Jackson and Transylvania
counties save the writers much time and effort in
locating many of the peridotites in those counties.
Local residents and land owners of the various
areas visited were most helpful in supplying back-ground
material and directions and their coopera-tion
is gratefully acknowledged.
Mr. William T. McDaniel, Chief Engineer,
North Carolina State College Minerals Research
Laboratory, made many helpful suggestions as to
how the work of the Division of Mineral Resources
and that of the Minerals Research Laboratory
could best be coordinated. He also spent several
days in the field with the writers collecting bulk
samples for laboratory analyses. His cooperation
and advice and that of the other personnel at the
Minerals Research Laboratory has added much
to this report.
GEOGRAPHY
Climate
The main area of the peridotite belt is coinci-dent
with the mountain section of the State, and
therefore falls within a distinct climatic zone. The
high elevations of the mountains have a two-fold
influence on the climate in this section of the
State. First, is a general reduction in temperature
and secondly, is an increase in rainfall. This re-duction
in temperature results in pleasant sum-mer
weather, but conversely it also means that the
mountain section generally experiences the coldest
temperature in the State during the winter
months. The mean annual temperature for the
area is about 54 degrees, but varies between the
extremes of 45 and 58 degrees.
Rainfall in the mountain region varies more
than in any other section of the State. The largest
amounts occur in the southern part of Transyl-vania,
Jackson, Macon and Clay counties and
along the southeastern crest of the Blue Ridge.
This section of the mountains receives more rain-fall
than anywhere else east of the Rockies. In a
small area in the vicinity of Highlands, Macon
County, annual rainfall is up to 80 inches. The
driest part of the State is also in the mountain
section. A small area between Asheville and Mar-shall
receives slightly less than 40 inches of rain
annually.
This significant rainfall variation is attributed
to the fact that the high rainfall areas in the
southern and eastern sides of the mountains re-ceive
their principal rainbearing winds from the
east and south. The moisture-laden winds coming
up over the mountains from the east or south, re-lease
most of the possible rain over the upslope,
and descend to lower elevations as relatively dry
winds.
Topography
Except for a relatively few isolated ultramafic
bodies which occur in the Piedmont division, the
peridotite belt lies entirely within the Mountain
division of the Appalachian province. This pro-vince
is made up of many minor ranges and, un-der
various names, extends in a southwest to
northeast direction from central Alabama to New
York. However, western North Carolina is the
culminating region of the Appalachian Mountains
and contains the greatest masses, the highest ele-vations
and the most rugged topography in the
Mountain division.
In North Carolina the eastern border of the
Mountain division is marked by the Blue Ridge
Mountains, which rise rather abruptly some 1500
to 2000 feet above the Piedmont. The average ele-vations
of the Blue Ridge ranges between 3000
and 4000 feet, but a few points approach 6000 feet
in elevation. The western boundary is marked by
the Unaka and Great Smoky Mountains which
have elevations ranging from 3000 to 6000 feet.
Between these two bordering chains lies the pla-teau
region of western North Carolina.
The plateau region is divided by a number of
cross ridges into several smaller plateaus or
basins. These cross ridges run more or less per-pendicular
to the bordering mountain chains in
much the same manner as rungs on a ladder. The
most prominent ridge is the Black Mountains,
which consist of a single ridge that extends some
15 miles from where it leaves the Blue Ridge and
contains a dozen peaks which exceed 6000 feet in
elevation. One of these, Mount Mitchell, has an
altitude of 6,684 feet and is the highest mountain
east of the Mississippi River. Other cross ridges,
from northeast to southwest, are the Pisgah
Mountains, New Found Mountains, Balsam Moun-tains,
Cowee Mountains, Nantahala Mountains
and the Valley River Mountains.
The mountain section is about 200 miles long
and varies from 15 to 50 miles in width. Its total
area is about 6000 square miles. The crest of the
Blue Ridge marks the Eastern Continental Divide.
Streams flowing to the west eventually drain into
the Gulf of Mexico, while those flowing east drain
into the Atlantic Ocean.
Accessibility
Although the mountain section contains the
most rugged topography in the State, the area is
made readily accessible by a network of state and
federal highways. Major highways that traverse
the area are U.S. Highways 19, 23, 25, 64, 70,
221, 321 and 421. In addition, Interstate High-ways
26 and 40 will also eventually traverse the
area. Each county contains numerous State main-tained
secondary paved and unpaved all-weather
roads that make even the most remote areas rea-sonably
accessible. The entire mountain section is
covered with a maze of old wagon and logging
roads. Many of these can be traveled without too
much difficulty by jeep or other 4-wheel drive
vehicles.
Asheville is the rail center of the area. The
Southern Railway System operates lines from
Asheville southwest through Murphy into Geor-gia,
northwest through Marshall into Tennessee,
southeast through Tryon into South Carolina, and
east through Marion to points east and north. The
Clinchfield Railroad serves the northeast section
of the area. Its main line runs from Marion,
through Spruce Pine and on northwestward into
Johnson City, Tennessee.
In addition to highway and rail transportation,
Asheville is serviced by daily flights of Piedmont,
United and Delta Airlines.
REGIONAL GEOLOGY
Rock Types
The main belt of ultramafic rocks in North
Carolina lies in the Blue Ridge province and is
associated with a vast complex of Precambrian
metamorphic and plutonic rocks (King, 1955).
The metamorphic rocks consist mainly on silice-ous,
micaceous gneisses and schists interlayered
with hornblende gneisses and schists. Keith (1903,
1904, 1905, 1907a, 1907b) referred to these rock
types as Carolina gneiss and Roan gneiss, respec-tively.
The Carolina type rocks vary considerably in
composition and include muscovite-biotite gneiss,
biotite gneiss and schist, mica schist, quartz-mica
schist, quartzite, and garnet-and kyanite-mica
gneiss and schist. The mica gneisses contain abun-dant
orthoclase and plagioclase feldspars and var-ious
proportions of muscovite, quartz, garnet and
other accessory minerals. With a decrease in the
feldspars, and an increase in quartz and the micas,
the gneisses grade into mica schist, some of which
contain practically no feldspar (Olsen, 1944, p.
17). Many of the Carolina type gneisses and
schists apparently were originally sedimentary
beds ; however, some show relict volcanic struc-tures,
and others may have been intrusive igneous
rocks.
Hornblende, or Roan type rocks, are interlay-ered
with the micaceous rocks in various propor-tions.
In some areas, notably the Spruce Pine dis-trict
of Mitchell, Yancey and Avery counties,
large areas are underlain almost entirely by horn-blende
rocks. The two most abundant types of
hornblende rocks are hornblende schist and horn-blende
gneiss. The schistose rocks are composed
almost entirely of needle-like crystals of horn-blende
and minor amounts of quartz and feldspar.
The gneissic rocks are composed mostly of horn-blende,
plagioclase feldspar and quartz. In many
cases, the hornblende is segregated into thin
layers that are separated by thicker layers com-posed
mainly of quartz and feldspar. Many of the
Roan type gneisses and schists probably origi-nated
either as intrusive rocks, or volcanic flows
of intermediate to basic composition. However,
much of it is thought to have been impure cal-careous
sedimentary deposits interbedded with
the originally sandy and shaly beds of the Caro-lina
type rocks.
Large areas in the Blue Ridge (see Geologic
Map of North Carolina, 1958) are underlain by
rocks mapped by Keith (1903, 1904, 1905, 1907)
as Cranberry granite and Henderson granite.
These rocks are highly metamorphosed and con-sidered
by recent workers (Eckelmann and Kulp,
1956) to be sedimentary in origin and strati-graphically
equivalent. The Cranberry is pre-dominantly
a layered gneiss; however, it varies
considerably in composition and contains num-erous
granite layers and layers of mica schist and
amphibolite. The Henderson is a relatively uni-form
gneiss containing abundant eye-shaped feld-spar
crystals, some up to an inch long, that give
it a distinctive appearance.
Granitic rocks intrude the metamorphic com-plex
in several parts of the region. Southwest of
Asheville, in Transylvania, Jackson and Macon
counties, occur large areas of Whiteside granite
(Keith, 1907). It is predominently a light grey to
white, equigranular, massive granite that con-tains
numerous inclusions of the surrounding
gneisses and schists, and many associated pegma-tites.
Large masses of a coarse-grained pegmatitic
granite, commonly referred to as alaskite, occur
in the vicinity of Spruce Pine, Mitchell County.
Associated with the alaskite are numerous pegma-tites
which are found near the margins of the
alaskite bodies and in the surrounding gneisses
and schists. Other masses of granite rocks occur
in Swain, Haywood and Madison counties, west of
the main belt of ultramafic rocks.
Interrupting the metamorphic and plutonic
rocks at several places in the Blue Ridge province,
are areas of relatively low-grade metamorphosed
sedimentary rocks of Cambrian (?) age. All of
these areas are complex structural features and
are referred to as the Murphy belt (Keith, 1907;
Van Horn, 1950), the Hot Springs window (Oriel,
1950) , the Grandfather Mountain window (Keith,
1903; Bryant and Reed, 1960), and the Brevard
belt (Keith, 1905).
The metamorphic and plutonic complex is bor-dered
on the west and northwest by the Ocoee
series, which is an extremely thick sequence of
clastic sedimentary rocks of Late Precambrian
age (King et. al., 1958). These rocks underlie a
large area in westernmost North Carolina and
form the Great Smoky Mountains. However, they
are west of and devoid of any ultramafic igneous
rocks.
Structure and Metamorphism
Except for a relatively few mafic intrusive
rocks of Triassic age, the rocks of the Blue Ridge
province have been subjected to several successive
episodes of deformation and metamorphism. The
resulting structural and metamorphic features
are thus complex and only generally understood
in many areas of the region.
All of the metamorphic rocks of the region are
generally strongly folded, and have a well devel-oped
foliation that is usually parallel to the com-positional
layering in the gneisses and schists.
This foliation, or cleavage, in most cases com-pletely
obscures the primary structures and has
a regional northeast strike and dips to the south-east
at moderate to steep angles.
The degree of regional metamorphism varies
considerably within the area. Metamorphic grade
ranges from relatively low-grade gneisses and
schist to middle-and high-grade staurolite and
kyanite schist. Detail geologic studies in the
Spruce Pine district (Brobst, 1962) and Grand-father
Mountain area (Bryant and Reed, 1962)
and radiometric age determinations (Long, Kulp
and Ecklemann, 1959 ; Tilton and others, 1959
;
Kulp and Eckelmann, 1961) reveal the rocks in
these areas have been subjected to two, and pos-sible
four, periods of metamorphism.
Clearly recorded metamorphic episodes have
been established for the Precambrian (1000 to
1100 million years ago) and the middle Paleozoic
(350 million years ago) . A possible early Paleozoic
regional metamorphism (450 million years ago)
and an episode of low grade regional metamor-phism
during late Paleozoic time have been sug-gested
on the basis of a few radiometric dates and
other geologic evidence; however, these periods
are as yet only tentative (Bryant, 1962, p. 20-23).
6
PERIDOTITES AND
RELATED ULTRAMAFIC ROCKS
The peridotites in North Carolina were de-scribed
in great detail by Pratt and Lewis (1905)
.
However, that publication has been out of print
and unavailable for general use for a number of
years. It is beyond the scope of this report to
discuss the geology of the peridotites in great
detail. However, the asbestos deposits are directly
related to the peridotites, and it is necessary to
have some knowledge of the peridotites before
the asbestos deposits can be understood. There-fore,
a general discussion of the periodotites is
included for the benefit of those readers not
familiar with the geology of these rocks.
Distribution
As previously stated, the peridotites and re-lated
ultramafic rocks in North Carolina are part
of a discontinuous belt that traverses the eastern
part of North America for a distance of more
than 2000 miles. In North Carolina the main belt
of peridotites lies west of the Blue Ridge and east
of the Great Smoky and Unaka Mountains. A
number of isolated bodies occur east of the Blue
Ridge in several of the Piedmont counties.
The peridotite belt enters North Carolina from
Georgia in the southwestern counties of Clay,
Macon and Jackson. It is at its greatest width
in this area and extends from Shooting Creek on
the west to Brevard on the east. It continues in a
northeast direction through parts of Transylvania,
Haywood, Buncombe, Madison, Yancey, Mitchell,
Avery, Watauga, Ashe and Alleghany counties.
In the southwestern counties the peridotite bodies
are scattered over an area nearly 40 miles wide.
However, from north of Waynesville to the vicin-ity
of Burnsville the peridotites are confined to
a single narrow belt. In Yancey County the bodies
again become more widely distributed and the
belt is wider than elsewhere north of the French
Broad River. In Alleghany County, the peridotites
pass into Virginia, where they continue north-eastward
for some distance.
Character and relations
Although the peridotites are quite extensive in
western North Carolina the actual area they cover
is comparatively small. With a few exceptions,
the average area of outcrop covers only a few
acres and in many cases less than an acre. The
peridotite body at Buck Creek, Clay County, is
one of the largest single bodies in the Appalachian
region. It covers a little more than 300 acres, or
about one-half a square mile (Hadley, 1949, p.
109).
The Webster-Balsam area in Jackson County
contains the largest peridotite mass in the State.
A number of disconnected outcrops form an elipti-cal
shaped body that is commonly referred to as
the Webster ring-dike. It has a major axis which
is about six miles long and is alined northeast-southwest,
and a minor axis about three and one-half
miles long alined northwest-southeast. The
largest single body exposed in the ring-dike is the
Webster peridotite, which is a crescent shaped
body 2.75 miles in length and up to 1800 feet in
width. It is exposed from a short distance north
of the town of Webster, southward to a point 0.75
mile south of the Tuckaseigee River, and then
nearly due east for 1 mile.
Other large peridotite bodies in the Webster
ring-dike are the Balsam Gap deposit, the Dark
Ridge deposit, the Addie deposit and the Cane
Creek deposit. Most of the commercial olivine pro-duction
in North Carolina has come from several
of the peridotite bodies in the Webster ring-dike.
Most of the peridotites are lens shaped bodies
in which the major axis is two to three times as
long as the minor axis. The major axis is usually
alined more or less parallel to the regional schis-tosity,
but crosscutting bodies are not uncommon.
In a few instances, such as the Webster peridotite,
part of the body is alined parallel to the schis-tosity
and part of it cuts across the schistosity.
Although most of the peridotites are lens shaped
or elliptical in outline, some masses are nearly
uniform in width on outcrop and can be traced
along strike for relatively long distances. Others
are more radical in outline, having finger-like, or
curved and irregular apophyses which branch off
of the main mass and cut into the country rock.
On outcrop, the peridotites exhibit unique char-acteristics
and are easily distinguished from the
surrounding gneisses and schists. They are mas-sive
and more resistant to weathering than rocks
with a well developed schistosity. Consequently,
the larger peridotite bodies often form prominent
knobs and peaks when they occur on or near the
crests of hills or mountains, and moderate cliffs
or spurs when on the slopes. The contact between
the peridotite and adjacent rock is always sharp
and characterized by a zone of schistose talc,
vermiculite and chlorite. This zone ranges from
a few inches to several feet wide, is always present
and is clearly of secondary origin.
Those peridotites composed mostly of olivine
(dunite) always form a barren, rocky surface
that is covered with a thin, poor soil that is con-spicuously
lacking in vegetation. This lack of
vegetation is in sharp contrast to the surrounding
thick growth of vegetation which usually grows
in the soil derived from the gneisses and schists.
The peridotite protrudes above the surface as
rounded, solution-pitted, boulder-like outcrops
and ledges. The outcrops have a characteristic
dull-brown or rusty color, which is the result of
the weathering of olivine.
Petrography
Peridotite is a general term used for essentially
nonfeldspathic plutonic rocks consisting mainly of
olivine, but which may contain varying amounts
of other mafic minerals such as amphiboles,
pyroxenes, and in some cases mica. The peridotites
in North Carolina vary considerably in minera-logical
composition, both within individual de-posits
and from one deposit to another. By detail
petrographic analysis it is possible to identify
numerous individual rock types that occur in the
peridotites. However, many of these types are
compositional variations that are not perceptible
in hand specimens or on outcrop. For all practical
field purposes, the ultramafic rocks can generally
be classed as dunite, saxonite, pyroxinite or soap-stone.
The following is a brief description of these
major rock types
:
Dunite: Dunite is the most important variety
of peridotite in North Carolina. It is composed
almost entirely of olivine, but contains a small
percentage of a few primary accessory minerals
such as chromite and enstatite.
Olivine is a magnesium iron orthosilicate,
(Mg,Fe) 2 Si04 . However, the ratio of Mg:Fe
varies considerably. Thus the composition of
olivine can range from forsterite (Mg2Si04 ) at
one end of the series to fayalite (Fe2Si04 ) at the
other. Previous work by Hunter (1941, p. 13) in-dicates
that the average composition of the un-altered
olivine deposits in North Carolina is about
90 percent forsterite and 10 percent fayalite.
The largest bodies of peridotite are dunite
masses, some of which are composed of 90 per-cent,
or more, olivine and slightly serpentinized
olivine. Some of these dunite bodies, such as the
Buck Creek deposit, and those in the Webster
ring-dike, crop out over relatively large areas,
extend to unknown depths and contain unlimited
amounts of minable olivine.
In most of the dunite bodies the fresh olivine
is pale green, yellowish-green or gray-green in
color. It is predominantly fine to medium grained
and granular. The individual grains rarely occur
in distinct crystal form, but are usually irregular
in outline and fit together perfectly without in-terstitial
spaces or cementing material. This lack
of cementing material and the granular texture
combine to produce a friable, sandy rock upon
weathering.
The dunites contain a wide variety of primary
and secondary accessory minerals. Chromite is
the most common primary mineral and is char-acteristic
of all the peridotites throughout the
region. It occurs as small to medium, well-devel-oped
octahedral crystals that are disseminated
throughout the dunite, or as small lenses and thin
veins of massive chromite surrounded by olivine.
In most cases the chromite constitutes less than
one precent of the bulk of the rock, but in some
places it makes up as much as 25 percent of the
dunite (Hunter, 1941, p. 28). Sporadic attempts
have been made to mine chromite at several of
the dunite bodies in North Carolina, but none of
these attempts have resulted in successful mines.
In addition to chromite, other primary accessory
minerals often associated with the dunites include
enstatite and picotite.
Olivine is quite susceptible to alteration and
weathering, and these processes have produced a
number of secondary minerals which are com-monly
associated with the dunites and all of the
peridotites in general. Serpentine, talc, vermicu-lite,
chlorite and anthophyllite are present, with-out
exception, in varying amounts in the dunites.
Other minerals often found associated with the
dunites include magnetite, actinolite, phlogopite,
garnierite, magnesite, corundum, spinel, picro-lite,
limonite, chalcedony, sepiolite (?), and oc-casionally
tourmaline.
Saxonite (harzburgite) : Saxonite, like dunite,
is composed mostly of olivine and the usual acces-sory
minerals, but in addition contains significant
amounts of the orthorhombic pyroxenes, enstatite
and bronzite. The enstatite and bronzite occur as
well developed, lath shaped crystals that are dis-seminated
through the olivine. Usually, the pyro-xene
crystals are much larger than the olivine
grains. Crystals up to one-half inch long are com-mon,
and crystals an inch or more in length are
frequently present. In many cases, the enstatite
and bronzite have been partly to completely al-tered
to talc.
8
Occasionally an individual peridotite body is
composed principally of saxonite. More often, how-ever,
saxonite forms part of a larger dunite body,
being in contact with or completely surrounded
by the dunite.
Pyroxenite: As the name implies, rocks of this
type are composed essentially of pyroxene. Two
types of pyroxenite are found in closest connec-tion
with the peridotites of the area, enstatolite
and websterite.
Enstatolite : This rock is composed mostly, and
in some cases almost exclusively, of the orthor-hombic
pyroxene, enstatite. Although it is not
nearly as common as the peridotites, enstatolite
is found throughout the region. In some places it
forms a minor part of a larger peridotite mass
as at Corundum Hill, Macon County, and at the
Sapphire mine in Jackson County. More often, as
at other localities in the Toxaway area and in
Yancey and Avery counties, it forms separate
rock masses of varying size.
The enstatite usually occurs as large, bladed.
interlocking crystals of gray to bluish-gray color
that are oriented in all directions in respect
to each other. Individual crystals as much as six
inches long and one and a half inches wide are not
uncommon. In most cases, the enstatite has under-gone
variable degrees of alteration, but the origi-nal
character of the mineral is still easily dis-cernible.
The alteration products consist almost
entirely of fibrous anthophyllite and talc along with
minor amounts of chlorite. The talc occurs around
the edges and along the cleavage cracks of the
enstatite crystals and also as disseminated and
variously oriented flakes and foliae. Chlorite is
often closely associated with the talc. The antho-phyllite
usually takes the form of the original
enstatite crystal with the fibers oriented parallel
to the long direction of the enstatite. It is also
present as lath shaped crystals that penetrate the
enstatite in all directions. In some deposits, the
replacement of enstatite by fibrous anthophyllite
and talc is practically 100 percent complete;
whereas, in others unaltered enstatite is present
in amounts in excess of 50 percent.
The enstatite crystals enclose irregular masses
and individual grains of olivine and numerous
grains of magnetite and chromite. Olivine is us-ually
present in amounts of less than 10 percent.
Minor amounts of magnesite are present as ir-regular
masses enclosed in, or around the edges,
of the enstatite.
Without exception, the enstatolite bodies are
considerably smaller than even the moderate size
dunite bodies. The largest enstatolite bodies do
not exceed 300 or 400 feet in their longest dimen-sion,
and most of them are more on the order of
100 to 200 feet in length. Quite frequently several
small, but separate enstatolite bodies will occur in
close proximity to each other.
Observations made at abandoned corundum
workings and from more recent asbestos mining
operations, clearly demonstrate that the enstato-lite
bodies are isolated, pod-like and eliptical
shaped masses that do not extend to any great
depths. In general, the long dimension of the
enstatolite bodies conform to the regional schis-tosity
of the country rocks. However, in a few
instances it appears that the major axis is in-clined
at a steep angle to the horizontal and the
body is actually oriented in a vertical or near
vertical position.
The enstatolite bodies are completely enclosed
in an envelope of schistose talc, chlorite and ver-miculite
that ranges from a few inches to over two
feet in thickness. In some places, the enclosing
envelope is composed entirely of unusually large,
foliated crystals of emerald green chlorite. The
contact between the chlorite and adjacent enstato-lite
is quite sharp. The contact between the enclos-ing
envelope and adjacent country rock is also
sharp and is frequently marked by slickensides.
The areas in which individual enstatolite bodies
are most common are coincident with areas of acid
igneous intrusive rocks. Namely, the Toxaway
area of Jackson and Transylvania counties, in
which occur large masses of the Whiteside granite
and associated pegmatites, and the Spruce Pine
pegmatite district of Mitchell, Yancey and Avery
counties. Although no pegmatites have been ob-served
that directly cut an enstatolite body, num-erous
examples can be cited in which pegmatites
are in contact with, or very closely associated
with enstatolite. In fact, this relationship was
observed at all the enstatolite bodies examined
during this investigation. It is particularly promi-nent
at those deposits where mining operations
have exposed the contact zone between the enstato-lite
and surrounding country rock.
Websterite : This rock type is very restricted in
its occurrence and is, therefore, somewhat unique.
It was first described and named by Williams
(1891) from specimens collected a short distance
southeast from the town of Webster, Jackson
9
County. Here, the websterite forms a distinct
elongated mass that is completely surrounded by
dunite. It has a maximum outcrop width of about
500 feet and can be traced northwestward along
the strike of the dunite for about one mile (Pratt
and Lewis, 1905, p. 95) . It is also found associated
with dunite about 3 miles east of Webster on Cane
Creek, one mile north of its confluence with the
Tuckaseigee River. Soil derived from websterite
supports a moderate growth of vegetation which
is in sharp contrast to the relatively barren dunite
and the websterite is therefore easily distin-guished
in the field.
Websterite is composed of the monoclinic pyro-xene
diopside and the bronzite variety of the or-thorhombic
pyroxene enstatite. The minerals are
present as an equigranular aggregate in which
the diopside usually prevails over the enstatite.
Large anhedral crystals of both pyroxenes are
disseminated throughout the mass of the rock. It
closely resembles the dunite with which it is as-sociated,
but it has a brighter green color than
the dunite and is much less altered.
Soapstone: Soapstone is a general term applied
to massive, impure talc-rich rocks derived from
peridotites and pyroxenites. It is a combination
of several minerals and its composition is there-fore
quite variable. The chief constitutents usually
include talc, amphibole and chlorite. In some cases,
soapstone forms a minor part of a larger peridotite
body, or it may occur as a separate mass. It is
common throughout the length of the peridotite
belt in North Carolina, but appears to be more
plentiful toward the northeast end of the belt. In
Ashe and Alleghany counties, a number of rela-tively
large ultramafic bodies appear to be com-posed
entirely of soapstone.
Alteration of Peridotite
In their present state, the peridotites and re-lated
ultramafic rocks represents a variety of dis-tinct
but related rock types. However, it is gen-erally
believed that all of the peridotites, when
first formed, were either dunite or saxonite of a
very similar and uniform mineralogical and
chemical composition. Since their formation, these
rocks have been involved in one or more episodes
of regional metamorphism and subjected to hydro-thermal
solutions emanating from granite and
pegmatite intrusions. These processes have differ-entially
altered the original character of the ultra-mafic
rocks and have produced the variety of rock
types now present.
Four processes of alteration and the resulting
products are clearly discernible in the North Caro-lina
peridotites. These processes are (1) serpen-tinization,
(2) steatitization, (3) amphibolization
and (4) chloritization.
All of these processes occur more or less to-gether
throughout the length of the peridotite
belt. However, one mode of alteration usually
predominates over the others and thus some sec-tions
of the belt are characterized by the abun-dance
of certain alteration products such as ser-pentine,
talc, amphibole, etc. The processes of
serpentinization and steatitization are the most
widespread and are in fact present to some degree
in all of the peridotites. Amphibolization and
chloritization are more local in their development.
These modes of alteration of the peridotites,
particularly serpentinization and steatitization,
have been the subject of considerable research
and much controversy for many years. It was be-yond
the purpose of this study to make a separate
investigation of the alteration processes as they
apply to the North Carolina peridotites. There-fore,
only a brief discussion of the processes, as
described in previous literature, and their pos-sible
application to the North Carolina peridotites
is included here.
Serpentinization: Serpentinization is defined as
that process of alteration in which ferromagnesian
minerals, or rocks, are converted to serpentine
minerals. This process is best exemplified in the
dunites and saxonites where the olivine has been
partly to completely altered to serpentine.
In the dunites and saxonites the formation of
serpentine always begins along the periphery of
the olivine grains and progresses toward the cen-ter.
Under the microscope, all stages of develop-ment
can be observed. In some cases the serpen-tinization
has been so complete that only a small
remnant or skeleton of the original olivine crystal
remains.
Although all of the dunites exhibit some ser-pentinization
the degree of alteration varies from
one deposit to another. Many of the larger dunite
masses contain a core of relatively unaltered,
granular olivine which is more or less concentri-cally
surrounded by more throughly serpentinized
olivine. This type of zoning is common among the
dunites throughout the peridotite belt.
The process by which serpentinization of ultra-mafic
igneous rocks takes place has long been a
controversial subject. However, recent theories
generally subscribe to one or more of the follow-
10
ing modes of origin: (1) autometamorphism-alteration
of peridotite and dunite by a late
stage portion of the ultramafic magma while it is
in the process of crystallization; (2) direct pre-cipitation
of serpentine from a hydrous peridotite
magma; (3) alteration of dunite and peridotite
by hydrothermal solutions, generally presumed to
come from granites younger than the peridotites
;
and (4) serpentinization during tectonic trans-port,
with water supplied from the enclosing
rocks. At one time, serpentinization of dunite and
peridotite was considered to be a surface phe-nomenon
due to weathering processes. However,
it is now well established that serpentinization is
a deep-seated reaction and that weathering proc-esses
are responsible for the formation of only
negligible amounts of serpentine.
Recent experimental work on the system
MgO-SiO, -H2 by Bowen and Tuttle (1949) has
added greatly to the understanding of the ultra-mafic
complexes and the process of serpentiniza-tion.
Their work has, to a certain extent, elimi-nated
some of the former conflicting theories of
serpentinization. Based on their experimental
data, Bowen and Tuttle (1949, p. 453) conclude
that, ". . . our results seem to exclude the possi-bility
of the intrusion at comparatively low tem-peratures
of a magma of serpentine composition
which crystallizes, wholly or in part, directly to
serpentine. Many geologists believe that the field
data indicate such an origin for serpentine. The
more modern and systematically developed form
of the hypothesis (Hess, 1938) postulate that
there is early separation of olivine and pyroxene,
but that they are transformed by their own highly
aqueous mother liquor, an autoserpentinization.
Other geologists believe field facts point to the
formation of serpentine through introduction of
solutions into a rock already completely crystal-lized
to anhydrous minerals (olivine or olivine
and pyroxene). This interputation is in better
accord with our experimental results".
In the hypothesis advocated by Bowen and
Tuttle, they submit that under certain conditions
of crustal deformation a mass of dunite or perido-tite
may become mobilized. During its tectonic
transport it is intruded into an aqueous environ-ment
and acquires water (serpentinizing solu-tions)
from the surrounding wet rocks. Under
favorable temperature and pressure conditions,
serpentinization of the peridotite proceeds simul-taneously
with its transport and emplacement.
The conditions of tectonic transport probably
facilitate serpentinization because of granulation
and fracturing which make the material more
readily accessible to water. Because of its physical
properties, the serpentine, thus formed, in turn,
makes the mass more mobile and continued de-formation
and intrusion is greatly facilitated.
Based on field relationships of the dunites and
peridotites noted during this investigation and
those observed by previous workers, it appears
that the tectonic transport hypothesis, as de-scribed
by Bowen and Tuttle (1949, pp. 439-460),
most satisfactorily accounts for the major serpen-tinization
of the North Carolina peridotites. As
pointed out by Bowen and Tuttle (1949, p. 456)
if a dunite or peridotite mass was subjected to
this action, a mass that is peripherally serpen-tinized
but the central part of which is not ser-pentinized
would be an expected result. As pre-viously
noted, this type of zoning is quite common
in North Carolina peridotites. Also, the lack of
significant contact metamorphic effects in the
adjacent country rock, a relationship that has
been noted by a number of previous workers, is
accounted for in the Bowen and Tuttle hypothesis
by the fact that their experimental data suggests
that the ultramafic rocks were at comparatively
low temperature at the time of emplacement.
Although it appears that the majority of the
serpentinization that has affected the North Caro-lina
peridotites took place during tectonic trans-port
and before final emplacement, it is very un-likely
that this is the only mode of serpentiniza-tion
that has acted on the peridotites. Subsequent
periods of metamorphism and granite intrusions
have undoubtedly been responsible for the develop-ment
of some serpentine, particularly along in-ternal
faults and shear planes (Hunter, 1941, p.
36).
Sleatitization : Steatitization is that mode of
alteration of the ultramafic rocks which results in
the formation of talc. The process is considered by
most recent workers to be later than serpentiniza-tion
and that the alteration to talc was effected
by hydrothermal solutions.
Talc is a common constitutent of all the ultra-mafic
rocks in North Carolina and it is derived
from the alteration of olivine, pyroxenes and
amphiboles. In the dunites it occurs as large dis-seminated
pseudormorphs after enstatite and as
microscopic envelopes around the edges of the
olivine grains. In the saxonites and enstatolites,
talc frequently replaces enstatite and anthophyl-
11
lite. Talc may develop as scales along the cleavage
cracks of the enstatite and gradually replace it,
forming a pseudormorph. More often, however, it
forms irregularly distributed and oriented scales
in the enstatite, which develop in size until the
original mineral is replaced. In the case of the
alteration of anthophyllite to talc, the talc usually
develops parallel to the cleavage cracks.
In many cases, steatitization has proceeded to
the point where the ultramafic body is more or
less a talcose rock, or soapstone. In some of these
soapstone bodies, thin layers of pure, apple-green,
foliated talc have developed along what appear to
be local shear planes.
A very common occurrence of talc is with ver-miculite
and chlorite in the thin border zone of
schistose rocks that usually envelops the ultra-mafic
bodies. Talc is not always present in this
zone because in some instances the envelope is
composed entirely of chlorite. However, talc and
vermiculite usually occur together.
From a recent detailed petrographic and geo-chemical
study of some selected talc-bearing ultra-mafic
rocks in Vermont, Chidester (1962, p. 94)
concluded that "steatitization took place contem-poraneously
with and at essentially the same tem-perature
as regional metamorphism, without
notable changes in temperature during the steati-tization
process". Chidester (1962, p. 128) further
suggests that the steatitizing solutions were of
a simple nature, consisting mainly of C02 , H2
and Si that were derived from rocks of sedimen-tary
parentage during progressive metamor-phism.
That the solutions effecting steatitization
were independent of a magmatic source is con-trary
to the view held by most previous workers
who considered the steatitizing solutions to be hot
igneous solutions derived from nearby or under-lying
acid igneous rocks.
As described by Chidester (1962), some of the
characteristics of the Vermont talc-bearing ultra-mafic
rocks have similar counterparts in many
of the North Carolina ultramafic bodies. However,
whether or not steatitization in the North Caro-lina
ultramafic rocks can be attributed to similar
processes as those that effected the Vermont ul-tramafics
can be determined only by much more
detailed study.
Amphibolization : The development of amphi-bole
is very common in the ultramafic rocks in
North Carolina. In the dunites minute needle-like
crystals of amphibole (usually anthophyllite) oc-cur
disseminated throughout the mass. The
needles are usually straight, oriented in all direc-tions,
and penetrate several individual olivine
grains. An increase of the amphibole needles in
both size and number ultimately leads to the local
development of zones composed almost entirely of
crossed and interlocking amphibole minerals.
Anthophyllite also occurs in the dunites as narrow
veins that cut through the body in all directions.
The alteration to amphibole is particularly evi-dent
in the enstatolites. Where enstatite is present
in the rocks, the needles of amphibole may pene-trate
the enstatite in all directions, or develop
parallel to the long dimension of the enstatite
crystals. In either case, this type of alteration has
evidently resulted in the formation of some of the
mass-fiber asbestos deposits.
The alteration of olivine to anthophyllite in-volves
the loss of magnesium and iron or the ad-dition
of silicia, whereas the alteration of enstatite
to anthophyllite is a physical transformation as
the two minerals have essentially the same chemi-cal
composition. Amphibolization is a late stage
process that took place after the individual peri-dotite
bodies were emplaced in their present rela-tive
positions and after any crushing or granula-tion
effects. This is demonstrated by the fact that
the amphibole crystals are oriented in all direc-tions
with respect to each other and, except for
cross fracturing, are not disturbed.
Chloritization : Chlorite is present in the ultra-mafic
rocks as dissiminated flakes and foliae, as
narrow veins that penetrate the rocks in all
directions, and as a peripheral zone that practi-cally
always borders the peridotites.
The alteration of olivine or enstatite to chlorite
involves the addition of significant amounts of
alumnia and water plus the loss of magnesium and
iron in the case of olivine and the loss of silica
in the case of enstatite. Dunite usually contains a
small amount of alumnia, but not enough to per-mit
the alteration of more than an insignificant
part of the rock to chlorite. Thus it is evident
that solutions originating from without must have
been responsible for supplying the necessary
alumina and water and removing or redepositing
the excess magnesium and iron.
Origin
The ultramafic rocks have been of interest for
many years and have been investigated by many
able geologists. However, many questions remain
to be answered concerning the source and manner
of formation of peridotite, dunite and pyroxenite,
12
their mode of intrusion, and the manner and cause
of alteration.
Prior to 1900 there was considerable contro-versy
among contemporary workers as to whether
or not the dunites were of sedimentary or igneous
origin (Pratt and Lewis, 1905, p. 125-137). How-ever,
by the turn of the century, the igneous char-acters
of the dunites had been well established
and generally accepted. After an igneous origin
for the ultramafics had been established, most
workers regarded dunite and peridotite as'the
products of direct consolidation from a magma of
their own composition.
Bowen (1915, p. 79-80) first pointed out that
dunite, consisting almost entirely of olivine with
no significant amounts of other minerals to give
the mutual fluxing effects that ordinarily prevails
in mineral assemblages, could exist in the com-pletely
liquid state only above the very high
temperature at which olivine melts (1800° C.)
The lack of evidence that these rocks ever existed
at such very high temperature led Bowen to con-clude
that dunite was never liquid as such, but
was formed by accumulation of early olivine cry-stals
from a complex magma. Later, Bowen (1917,
p. 237) suggested, "that when the mass of olivine
crystals thus accumulated was subjected to the
appropriate forces it might be intruded into other
rocks as a solid or substantially solid mass with
little, if any, liquid to lubricate its flow".
Contrary to Bowen's hypothesis, Hess (1938)
suggested that peridotites in narrow belts asso-ciated
with strongly deformed zones of the earth's
crust (alpine type peridotites) were derived
from a highly aqueous ultramafic liquid approxi-mating
serpentine in composition. He further
suggested that such magmas were generated by
differential fusion of the peridotite substatum un-der
local impact of a very greatly thickened seg-ment
of the overlying granitic crust where it was
down folded at the onset of orogeny. The high
concentration of water was assumed to lower the
temperature of crystallization enough, at least in
some instances, so that serpentine crystallized
directly from the magma.
Bowen and Tuttle (1949, p. 439-460) studied
the system MgO-Si02-H2 in the laboratory at
temperatures up to 1000° C. and pressures as
great as 40,000 lb in2
. The results of their investi-gation
indicate that peridotite magma could exist
only at temperatures well above 1000° C. even if
the water content was 10 percent or more. Con-sequently,
they conclude (1949, p. 455) that "the
possibility of the formation of dunites, serpen-tines,
and peridotites from such supposed magma
intruded at low temperatures is definitely ex-cluded".
The low-temperature (probably not more
and possibly less than 500° C.) metamorphic ef-fects
evident of the contacts of most ultramafic
bodies appear, therefore, to require these rocks to
have been intruded in a crystalline state.
Based on their experimental results and estab-lished
field relationships, Bowen and Tuttle (1949,
p. 455-456) suggests that under certain condi-tions
of crustal deformation dunitic and related
material can be intruded in a completely crystal-line
state into accessible levels of the earth. They
picture the mass as a slowly advancing crystalline
peridotite which is being deformed and granulated
during transport. As it moves into the zone of wet
rocks it absorbs water from them, especially
peripherally, and so becomes partially serpen-tinized.
This partial serpentinization greatly in-creases
the mobility of the mass and facilitates
further intrusion.
The hypothesis advocated by Bowen and Tuttle
on the origin and subsequent serpentinization of
dunites, peridotites and related ultramafic rocks
is the most compatible with the facts as known to
date, and is generally accepted as a working hypo-thesis
by most geologists.
Assuming that all of the ultramafic bodies
were at one stage in their development composed
largely of crystalline olivine with minor amounts
of pyroxene, it is difficult to account for all of the
variations now present in the North Carolina ul-tramafic
rocks only by the Bowen and Tuttle
hypothesis. Since their emplacement, the ultra-mafics
have been subjected to one or more periods
of regional metamorphism and in many instances
emanations from granitic intrusions. The effects
of these processes on the ultramafics have not been
studied in the light of modern petrographic and
geochemical methods, and the exact nature of the
changes involved is not understood at this time.
However, many of the local variations in degree
of alteration and the local development of antho-phyllite,
vermiculite, chlorite, talc and corundum
are the result of subsequent metamorphism and/or
granitic intrusive activity.
Age
A definite age for the ultramafic rocks has not
been established, but certain relationships have
been noted which serve to restrict their age. First,
they are intrusive only into the gneisses and
13
schists that Keith (1903) mapped as Carolina
gneiss and Roan gneiss, and which have been
established by radiometric age determinations to
be Precambrian in age. Also, at a number of places
mica pegmatite and alaskite are intrusive into
the ultramafic rocks. In the Spruce Pine district,
these pegmatites have been dated radiometrically
at 350 million years (Kulp and Eckelmann, 1962).
Thus, the ultramafics are younger than the
gneisses and schists but older than the pegmatites.
Keith (1903) considered the ultramafics to be
"Archean" (Precambrian) in age, but Pratt and
Lewis (1905, p. 159) classed them as Paleozoic
in age. Recent detailed geologic mapping in the
Spruce Pine district and the Grandfather Moun-tain
area still leaves the question of the age of the
ultramafics unanswered. Brobst (1962) classed
them as Precambrian (?) whereas, Bryant (1962)
classed them as Middle or Lower Paleozoic (?).
The fact that many bodies of ultramafic rock oc-cur
near, but nowhere intrude rocks of the Ocoee
series (Upper Precambrian) seems to be, in the
writers' opinion, a point in favor of a Precam-brian
age for the ultramafic rocks in North Caro-lina.
ASBESTOS DEPOSITS
Mineralogy and Geologic Occurrence
Asbestos is a commercial term applied to sev-eral
naturally fibrous minerals that are used pri-marily
because of their fibrous character and other
qualities such as resistance to heat and acid.
Chrysotile is the most important commercial va-riety
and constitutes about 95 percent of the total
world production. Other varieties of asbestos in-clude
tremolite, actinolite, crocidolite, amosite and
anthophyllite. All of these minerals vary in chemi-cal
and physical properties and have different
modes of occurrence.
Chrysotile: Chrysotile (H4Mg3 Si2 9 ) is a
fibrous form of the mineral serpentine. It occurs
most commonly as cross fiber veins that range
from a fraction of an inch to over six inches in
width. Fibers of good quality are silky, highly
flexible and have a high tensile strength. Almost
all of the commercially valuable deposits occur as
cross-cutting, discontinuous veins in massive ser-pentine
bodies that have been derived from the
alteration of peridotite. A relatively small district
in the province of Quebec, Canada, contains
numerous rich chrysotile asbestos deposits. These
deposits are associated with a northeast-trending
belt of serpentinized peridotite bodies. Approxi-mately
one-half of the worlds annual production
of asbestos comes from this district.
Chrysotile also occurs in thin alteration zones
in dolomite or dolomitic limestone along contacts
with basic igneous intrusive rocks. In places,
chrysotile of excellent quality is found in this en-vironment.
However, the ore zones are usually
rather narrow and only those deposits of unusual
fiber length can be profitably mined.
Deposits of this type occur at several places in
Arizona and have supplied most of the domestic
production of long fiber chrysotile (Stewart,
1955).
Chrysotile asbestos is reported to occur at sev-eral
places in North Carolina in association with
the ultramafic rocks. Several of these localities
were examined during this investigation, but the
presence of chrysotile could not be confirmed. If
chrysotile is associated with any of the ultramafic
rocks in North Carolina, it occurs in very minor
amounts and is very likely of no commercial sig-nificance.
Amphibole asbestos: All varieties of asbestos
other than chrysotile belong to the amphibole
group of minerals and are collectively referred
to as amphibole asbestos. The amphiboles are a
complex series of silicate minerals that are char-acterized
by perfect prismatic cleavage with
angles of 50° and 124° between the cleavage
planes. The only amphibole minerals that occur
in asbestiform masses are tremolite, actinolite,
crocidolite, amosite and anthophyllite.
All of the asbestiform amphiboles contain iron
and with the exception of crocidolite contain mag-nesium.
Anthophyllite is distinguished from trem-olite
and actinolite by the absence of calcium, and
crocidolite from the other asbestiform amphiboles
by the presence of a notable amount of sodium.
Chemically, tremolite and actinolite are very
closely related. The replacement of one element by
another is a prevalent characteristic of the amphi-bole
asbestos minerals. This variation in composi-tion
results in corresponding changes in their
physical properties and causes somewhat erratic
and unpredictable physical characteristics in some
amphibole asbestos ores from different localities
(Bowles, 1955, p. 3)
.
Tremolite: Tremolite (Ca2Mg5Si8 22(0H2 ) is
one of the most common varieties of amphibole
asbestos. It usually consists of gray to white silky
14
fibers that are sometimes as much as a foot or
more in length. The fibers are coarser and much
weaker than chrysotile, but fibers of considerable
strength and flexibility are occasionally found.
Tremolite asbestos occurs most commonly as slip-fiber
veins in shear zones. It is found in a variety
of host rocks, but most of the commercial deposits
occur in ultramafic rocks derived from dunite and
peridotite.
Tremolite is commonly present in the ultramafic
rocks in North Carolina, occurring most often as
long slender needles that penetrate the other
minerals in all directions. However, it has not
been found in commercial quantities in North
Carolina.
Actinolite: Actinolite (Ca2 (Mg,Fe) 5 (Si4Ou) 2
OHo) is similar to tremolite, but contains iron in
place of some of the magnesium. Actinolite asbes-tos
is commonly green or grayish green and the
fibers are quite weak and brittle. It is similar to
tremolite in occurrence and is of very little value
as a commercial asbestos.
Actinolite, like tremolite, is widespread in the
ultramafic rocks in North Carolina, but there are
no known localities where this type of amphibole
asbestos occurs in significant quantities.
Crocidolite: Crocidolite (Na6Fe1oSi 1c04o(OH) 2 )
is the fibrous form of the amphibole riebeckite. It
is a beautiful, highly fibrous mineral that has a
very silky luster and a dull lavender color. It is
commonly referred to as blue asbestos. Its fibers
are flexible and stronger than chrysotile, but
somewhat coarser. The principal source of cro-cidolite
asbestos is the Union of South Africa.
There, it occurs as thin, cross-fiber veins in iron-rich
sedimentary rocks (Bowles, 1955, p. 37).
Smaller amounts are produced in Australia and
Bolivia. There are no known commercial deposits
of crocidolite in the United States.
Amosite: Amosite (FeMg) 7 Si8 22 (OH) 2 ) is
a fibrous modification of the monoclinic amphi-bole
grunerite. It may contain as much as 40 per-cent
iron oxide and has been classed as a high-iron
anthophyllite. However, it is monoclinic in
crystallization and, therefore, not a true antho-phyllite
(Bowles, 1955, p. 2). It is white to
yellowish-gray in color and consists of long, fairly
strong fibers. Amosite is mined only in South
Africa and occurs in isolated cross-fiber veins in
the same host rock as crocidolite asbestos.
Anthophyllite: Anthophyllite asbestos (Mg7 Si8
22 (OH) 2 ) is the fibrous form of the orthorhom-bic
amphibole anthophyllite. The fibers are char-acteristically
short, only slightly flexible and have
a low tensile strength. Unweathered anthophyl-lite
is greenish-gray to gray, but upon weathering
the fibers become brownish-white. Most commer-cial
anthophyllite asbestos occurs as mass-fiber
deposits associated with altered dunites and re-lated
ultramafic rocks. It also occurs in cross-fiber
veins and slip-fiber veins. Anthophyllite asbestos
has been mined in a number of countries through-out
the world. However, the principal domestic
sources are found in Georgia and North Carolina.
Uses
Asbestos is a unique mineral, and because of its
fibrous character and resistance to heat and chemi-cals
it has many specialized uses for which there
are no satisfactory substitutes. On the basis of
use, asbestos falls into two principal classes, spin-ning
and nonspinning fiber. Only the longer fibers
of chrysotile and crocidolite qualify as spinning
fiber. Nonspinning fiber comprises the shorter
grades of chrysotile and crocidolite and both the
long and short fiber grades of amosite, anthophyl-lite
and other amphibole varieties.
Spinning fibers posses the necessary strength
and flexibility that allows them to be spun, in
much the same manner as cotton and wool, into
textile products such as cloth, yarn, tape, etc. The
asbestos fabrics are used extensively for lagging
cloth, brakeband linings, clutch facings, safety
clothing, packing, gaskets and numerous other
products in which heat insulating, fireproofing
and heat resistant properties are required.
Nonspinning asbestos fibers of both the chryso-tile
and amphibole variety are used in hundreds
of products in numerous industries. Large quan-tities
of the shorter grades of asbestos are used
in all types of fireproofing and heat insulating
products in the building trade. A few of the most
common uses include roofing shingles, pipe cover-ing,
wallboard, millboard, water and sewer pipes,
and wall and floor tiles.
Anthophyllite asbestos has a low tensile
strength and is therefore, not used in products in
which the fiber must impart strength to the
product. However, it is superior to all other varie-ties
of asbestos in resistance to heat and acid and
is well suited for numerous products in which
these properties are of prime importance.
The main uses of anthophyllite are for chemical
filters; in plastic cement to cover boilers, pipes
15
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16
and furnaces ; as a filler in rubber, battery boxes
and molded electronic insulation products; for
welding rod coatings; and as an admixture in
cement and plastic flooring, accoustical and other
wall plasters, and stucco (Bowles, 1955, p. 14).
Character and Classification
of North Carolina Deposits
General Statement: Various types and quanti-ties
of asbestiform minerals are associated with
the ultramafic rocks in North Carolina. Chrysotile
asbestos is reported to occur at several places.
However, some of these localities were examined
during this investigation but the presence of
chrysotile could not be confirmed. If chrysotile is
associated with any of the ultramafic rocks in
North Carolina, it occurs in very minor amounts
and is very likely of no commercial significance.
Tremolite and actinolite are also very commonly
associated with the ultramafic rocks, but they oc-cur
in very limited amounts and most often are
not in a fiberous form.
Anthophyllite is the only asbestiform mineral
found in North Carolina that occurs in sufficient
quantity and quality to be considered an asbestos
ore. Based on the arrangement of the fibers in
respect to the wall rock and to each other, three
types of anthophyllite asbestos are recognized.
These types are referred to as cross-fiber veins,
slip-fiber veins and mass-fiber deposits. The mass-fiber
deposits are further divided into peripheral
zones and oval shaped bodies composed mostly of
anthophyllite and enstatite.
Cross-fiber veins: Cross-fiber anthophyllite oc-curs
in veins, with the fibers arranged parallel
to each other and perpendicular to the walls of
the vein. Although not the most productive in
terms of tonnage, cross-fiber anthophyllite is by
far the most common mode of occurrence for
asbestos in North Carolina. The veins are present
in rocks that range from dunite to soapstone in
composition and are present throughout the length
of the ultramafic belt.
The veins range from a fraction of an inch up
to 8 or 10 inches wide, but are most often between
1 and 3 inches wide. They cut through the enclos-ing
rock in all directions, and it is not uncommon
for one vein to intersect another, usually at near
right angles. Many cross-fiber veins are composed
of practically pure anthophyllite asbestos. This is
particularly true of the veins associated with
dunite. In the more altered ultramafic rocks, talc
is commonly associated with the anthophyllite and
in some instances talc has almost completely re-placed
the anthophyllite.
The contact between the' vein material and en-closing
rock is usually quite sharp. In many cases,
differential movement between the vein material
and the enclosing rock has distorted the orienta-tion
of the fibers. Where differential movement
has taken place, the fibers in the outer portion of
the vein have been sheared and rearranged so
that they are more or less parallel to the vein
walls. The fibers in the interior of the vein may
be distorted or slightly curved, but remain es-sentially
perpendicular to the vein walls.
At least four attempts have been made in the
past to mine cross-fiber vein deposits. In each case
the ore was evidently of excellent quality, but the
limited quantity present in any one deposit pre-cluded
any extensive or long range mining opera-tion.
Slip-fiber veins: Slip-fiber asbestos also occurs
in veins, but in this case the fibers are arranged
approximately parallel to the enclosing walls. As
there are all gradations in orientation of fibers
between cross-fiber and slip-fiber, it is generally
concluded that cross-fiber is converted to slip-fiber
by differential movement of the wall rock
with respect to the vein material. Except for the
orientation of the fibers with respect to the wall
rock, slip-fiber anthophyllite asbestos is similar to
cross-fiber in character and mode of occurrence.
However, slip-fiber asbestos is not nearly as com-mon
in the North Carolina ultramafic rocks as is
cross-fiber asbestos.
One of the most interesting features of the slip-fiber
veins are the unusually large pieces of pure
anthophyllite asbestos that are associated with
them. Pieces 1 to 2 feet in length and up to 4
inches in diameter are not uncommon, and some
pieces up to 3 feet in length and 6 inches in
diameter have been found.
Slip-fiber asbestos has accounted for only a very
small percentage of the total asbestos mined. Most
of it has been recovered incidental to mining for
cress-fiber and mass-fiber ore.
Mass-fiber deposits: Mass-fiber ore differs from
cross- and slip-fiber ore in that it does not occur
in veins, but forms the body of the rock. The
fibers are arranged in bundles of varying size that
are oriented in all directions in respect to each
other. Also, in some mass-fiber deposits the antho-phyllite
is arranged in distinct, cone shaped or
radial structures.
17
Two distinct types of mass-fiber ore are asso-ciated
with the ultramafic rocks in North Caro-lina.
Based on their mode of occurrence these two
types of ore are classed as (1) peripheral zones,
and (2) individual ultramafic bodies composed
mostly of anthophyllite and enstatite.
Peripheral zones: It has been previously
pointed out that the ultramafic rocks are char-acteristically
enclosed by a relatively thin zone of
schistose talc, chlorite and vermiculite. This zone
ranges from a few inches to several feet wide and
pinches and swells around the ultramafic body.
Usually one mineral prevails over the others. In
some cases the zone is composed almost entirely of
talc, and in others either vermiculite or chlorite
predominates. Mass-fiber anthophyllite asbestos
is often associated with this peripheral zone of
alteration.
Although a peripheral zone of schistose rock is
characteristic of all the ultramafic rocks, the
presence of a well developed zone of mass-fiber
asbestos is much less common. In a few instances,
a peripheral zone of mass-fiber asbestos is asso-ciated
with dunite. However, most of the deposits
which have been mined for asbestos are associated
with the smaller and more thoroughly altered
bodies of peridotite and enstatolite. Where present,
the zone of mass-fiber asbestos usually lies adja-cent
to the mass of the ultramafic body and is
separated from the country rock by a thin layer of
schistose talc and/or vermiculite. The contact be-tween
the asbestos zone and the outside layer of
schistose rock is usually relatively sharp and uni-form.
The contact between the asbestos and the
mass of the ultramafic body is also sharp, but at
times quite irregular. The width of the asbestos
zone ranges from a few inches up to as much as
6 to 8 feet. However, the average width is from 1
to 2 feet. Some of the peripheral zones of asbestos
are very uniform in width, although it is not un-usual
for a relatively wide zone to narrow rapidly,
both along strike and at depth.
The mass-fiber asbestos associated with the
peripheral zone varies in color from grayish white
to various shades of mottled buff and light-brown.
Ore that lies on and near the surface is usually
badly stained by iron oxide and quite soft. The
deeper ore is more compact, but the fibers can be
easily separated by hand. Much of the mass-fiber
ore is very coarsely crystalline material composed
of interlocking bundles of fibers that are as much
as 2 to 3 inches in length. Other mass-fiber ore is
less coarsely crystalline and in some deposits the
fibers are arranged in distinct radial form.
The peripheral zones of mass-fiber ore are com-posed
predominantly of asbestos. Anthophyllite
usually makes up more than 85 percent of the
rock and talc is the only other mineral present in
significant amounts. Trace amounts of chlorite,
magnesite and magnetite are usually present.
Because of the high percentage of asbestos
present in the mass-fiber deposits, the high ratio
of ore recovery to total amount of rock mined,
and the relatively simple mining methods em-ployed,
most of the past production of North Caro-lina
asbestos has come from peripheral zone mass-fiber
deposits.
Anthophyllite-enstatite bodies: Many of the
ultramafic bodies occur as small, pod shaped
masses that are composed predominantly of vary-ing
percentages of enstatite, anthophyllite and
talc. These rocks were described by Lewis (1896,
p. 25) and referred to as enstatite rock. Later,
Pratt and Lewis (1905, p. 30) proposed the term
enstatolite for these rocks and they have since
been referred to by that name. Although Lewis
(1896, p. 26) and Pratt and Lewis (1905, p. 30)
described enstatolite as being composed essential-ly
and almost exclusively of enstatite and talc
derived from the alteration of enstatite, many
of the rock masses previously referred to as en-statolite
contain equal or greater amounts of an-thophyllite
and talc than enstatite. In these cases
the term enstatolite is somewhat misleading. How-ever,
as most of the anthophyllite and talc present
in these rocks was evidently derived from the
alteration of original enstatite, the term is re-tained
in this report in reference to some of the
mass-fiber anthophyllite bodies.
As previously stated in the section of this report
dealing with petrography, the enstatite usually
occurs as large, bladed, interlocking crystals that
are oriented in all directions in respect to each
other. In some deposits, in excess of 50 percent
of the rock is composed of relatively unaltered
enstatite. However, quite frequently the enstatite
has undergone considerable alteration. In such
cases, the alteration products consist almost en-tirely
of anthophyllite and talc along with minor
amounts of chlorite. It is these more thoroughly
altered enstatolite bodies that contain significant
amounts of mass-fiber anthophyllite asbestos. The
degree of alteration of the individual enstatolite
bodies varies considerably within a single mass
and from one deposit to another. Consequently,
the percentage of anthophyllite present is also
18
quite variable. In some deposits, the replacement
of enstatite by fibrous anthophyllite and talc is
practically 100 percent complete; whereas, in
others anthophyllite is present in amounts of 20
percent or less.
The mass-fiber ore associated with enstatolite
bodies occurs in two distinct forms. The most com-mon
variety is that in which the anthophyllite
fibers have developed parallel to the long direc-tion
of the enstatite crystals and assumed the
form of the original rock mass. The asbestos oc-curs
in broad, flat interlocking bundles of fibers
that are oriented in all directions in respect to
each other. One of the most striking features of
this type of ore are the unusually large crystals
(secondary after enstatite) of fibrous anthophyl-lite
present in some of the deposits. Interlocking
crystals up to 6 inches long and 1 to 2 inches wide
are common and occasionally crystals that ap-proach
1 foot in length are present. However, the
average length is between 1 and 3 inches. Fresh,
unweathered ore in bluish gray to gray in color,
massive and quite tough. The fibrous character of
the fresh ore is not readily apparent, but the ends
of the variously oriented crystals become fibrous
when struck with a hammer or otherwise broken.
Less common but equally distinct is the variety
of mass-fiber ore in which the fibers occur as a
mass of interlocking cones. The fibers radiate
from a common center and vary from a 14 inch
up to about 1 inch in length. In some cases, the
apex of an individual cone is as much as 14 inch
higher than the perimeter, and in others the cones
are almost flat. Individual, well shaped cones are
not common because of mutual interference dur-ing
development, but the tendency toward radial
and cone structure is quite evident in all of the
ore.
The ore varies from light, bluish gray to yellow-ish
gray in color and is massive, compact and
quite tough. The fibers are generally short and
splintery. Talc is the most commonly associated
mineral and is developed parallel to the asbestos
fibers and fills the spaces around and between the
cones.
Origin of anthophyllite asbestos: In discussing
the origin of the North Carolina anthophyllite
asbestos deposits, two aspects of the problem have
to be considered. First, is the origin of the amphi-bole
mineral (anthophyllite), and second is the
development of the fibrous or asbestos form.
In the case of the origin of the amphibole min-eral,
it may be stated that anthophyllite is not
the result of original crystallization, but has
developed from secondary processes. The altera-tion
of dunite to anthophyllite is quite common,
and in thin sections olivine can be seen in all
stages of alteration to anthophyllite. Some sec-tions
show only a few slender needles of antho-phyllite
that are scattered throughout the ground-mass
of olivine. The needles are usually straight,
show no preferred orientation and a single crys-tal
often penetrates several olivine grains. At the
other extreme, some sections are composed almost
entirely of crossed and interlocking anthophyllite
crystals with only small remnants of the original
olivine grains left. Thus, it is apparent that dun-ite
and perdiotite may alter to mass-fiber asbestos.
As previously noted, many of the dunites ex-hibit
a definite zoning. This zoning is character-ized
by a core of nearly pure olivine which shows
little, if any, effects of serpentinization. The core
is surrounded by a zone of serpentinized olivine
which in turn is surrounded by an outside zone
composed principally of amphibole minerals. An-thophyllite
is the predominant amphibole but
minor amounts of tremolite and actinolite are also
present. This type of amphibolization has evident-ly
resulted in the development of the peripheral
zone type of mass-fiber asbestos.
The alteration of a pyroxene mineral to an
analogous amphibole is a common alteration and
is generally indicative of metamorphic or other
geologic processes which produce unstable physi-cal
conditions. The alteration of pyroxene (en-statite)
to amphibole (anthophyllite) is well ex-emplified
in the enstatolites. This process can be
observed in all stages of development, and it is
quite obvious that the mass-fiber asbestos deposits
associated with enstatolite have resulted from
the alteration of enstatite to anthophyllite.
Cross- and slip-fiber veins of anthophyllite as-bestos
are also unquestionably of secondary ori-gin,
but they do not reveal any evidence of having
been derived directly from some other mineral
as is the case in the mass-fiber varieties. The veins
were evidently developed in pre-existing frac-tures
by solutions moving through the ultramafic
rocks. Many of the cross-fiber veins are from 2
to 6 inches wide and it is very improbable that
veins of this width represent open fissures. Most
likely, the fissures were minute fractures in the
rocks and the cross-fiber veins were formed at
the expense of the wall rock by the action of the
solutions on the wall rock. Subsequent minor re-adjustments
in the rock mass caused the local
formation of slip-fiber veins.
The exact nature of the formation of the frac-
19
tures along which the solutions moved is un-known.
They probably are the result of adjust-ment
to strain, or slight changes in volume,
brought about during one or more periods of
regional metamorphism and/or igneous intrusion
after the ultramafics were implaced in their
present position.
From the foregoing, it is obvious that the an-thpohyllite
asbestos deposits are the end result
of perhaps diverse, and certainly complex, geol-ogic
processes. Enough detail information is not
available at this time to make anything more
than general statements concerning the origin of
these deposits. However, field relationships and
limited laboratory work substantiate the fact that
anthophyllite was not an original mineral consti-tuent
of the ultramanc rocks, but was formed by
secondary processes. The ultramanc rocks in
North Carolina have been subjected to one or
more periods of regional metamorphism and, in
many instances, to igneous activity. It is not
clear which of these processes are more closely
related to the development of anthophyllite. The
fact that anthophyllite is present in various forms
in rocks that range from dunite to soapstone in
composition, and is present throughout the entire
length of the peridotite belt, seems to indicate a
metamorphic origin. On the other hand, the in-timate
relationship between some of the asbestos
deposits and pegmatite dikes, quartz veins, corun-dum,
chlorite, vermiculite and tourmaline, offer
strong evidence that hydrothermal solutions were
responsible for the development of anthophyllite.
This suggests that all of the anthophyllite cannot
be attributed to any one process, but is the result
of a combination of factors that involve both met-amorphism
and hydrothermal solutions.
The development of the fibrous or asbestos form
of anthophyllite seems to be largely a physical
phenomenon directly related to weathering. This
relationship has been noted by many previous
workers at asbestos deposits throughout the
world. Hopkins (1914, p. 106) further suggests
that the fibrous form of amphibole is mainly the
result of inherent abnormal development of pris-matic
cleavage, but becomes more pronounced on
weathering.
That a direct relationship exists between de-gree
of fiberization and extent of weathering is
also quite apparent in the asbestos deposits in
North Carolina. This is particularly true in the
peripheral zone mass-fiber deposits and the an-thophyllite-
enstatite mass-fiber deposits. In fact,
it is common practice to allow ore mined from
some of these mass-fiber deposits to remain in a
stockpile exposed to the elements for a year or
more. This is reported to soften the ore consider-ably,
which results in easier milling and increased
fiber length recovery.
History of Mining and Production: Between
1870 and about 1900, North Carolina was a
leading producer of domestic corundum. During
this period, mining operations were carried on at
a number of the ultramafic bodies and numerous
others were prospected for corundum. Asbestos
was noted at practically all of these mines and
prospects, but little attention was paid to it by
the corundum miners. The first recorded attempt
to mine asbestos in North Carolina was about
1901. A serpentine deposit near North Wilkesboro
on the land of J. B. Church was worked by means
of an open cut 100 feet long and 1 to 35 feet deep.
The asbestos was reported to be of the chrysotile
variety and occurred in veins that varied from *4
to 2 inches in width (Pratt, 1902, p. 98). This
operation lasted only a short time and no pro-duction
was recorded.
From about 1910 until about 1925 considerable
prospecting for amphibole asbestos was carried
out in Ashe, Avery, Caldwell, Jackson, Macon,
Mitchell, Avery and Yancey counties, and a num-ber
of favorable prospects were located. How-ever,
the only production recorded for this period
was in 1919 when North Carolina ranked third
nationally in the production of asbestos. All of
this production came from one producer, N. C.
McFalls, Cane River, Yancey County, and con-sisted
entirely of anthophyllite asbestos (Drane
and Stuckey, 1925, p. 34).
In 1925, the National Asbestos Company built
a plant at Minneapolis, Avery County, to process
anthophyllite asbestos ore from the Frank de-posit,
located 2.5 miles south of Minneapolis on
the North Toe River. This mine and mill operated
on a small scale until the late 1930's and both
have been inactive since that time. Another plant
was built at Norton, Macon County, at about the
same time as the one at Minneapolis. However, if
it ever processed any ore it was only a very limit-ed
amount.
Between 1930 and 1947 a number of mining
companies and individuals mined small to moder-ate
amounts of anthophyllite asbestos from de-posits
in Avery, Yancey, Mitchell, Jackson and
Macon counties. From 1941 to 1945, W. T. Hippey
mined several thousand tons of ore from the Hip-pey
mine near Micaville, Yancey County. About
20
1941 the Industrial Minerals Corporation began
mining at the Blue Rock mine a few miles south
of Micaville, Yancey County, and for several years
produced relatively large tonnages of high grade
mass-fiber anthophyllite asbestos which was pro-cessed
at the company's mill at Spruce Pine. The
Blue Rock mine was later controlled by the Min-ing
and Milling Corporation of America and pro-duction
was reported for 1953 and 1954. The mine
has been worked intermittently for the past sev-eral
years by the Blue Rock Mining Corporation
of Illinois.
The most consistent and largest producer of
anthophyllite asbestos in North Carolina is the
Powhatan Mining Company of Baltimore, Mary-land.
This company has mined asbestos in North
Carolina more or less continuously since 1918
(Fred A. Mett, personal communication). Pro-duction
has consisted mainly of the peripheral
zone type of high-grade, mass-fiber ore. Deposits
that have yielded from considerably less than a
hundred to several thousand tons of ore have been
prospected and mined in practically all of the
counties in which the peridotites occur. Mines that
have recently or are currently being mined by this
company, include the Kilpatrick mine, Transyl-vania
County; the Asbestos and Brockton mines,
Jackson County; and the Newdale mine, Yancey
County. In the past, all of the ore has been shipped
to the company's processing plant at Baltimore,
Maryland.
Mining Methods : Because of the size, shape and
occurrence of the deposits, all of the asbestos in
North Carolina has been mined by relatively sim-ple
open cut methods. In many instances, the
ore was recovered entirely by hand labor using
picks, shovels and wheelbarrows. More recent
mining operations utilize bulldozers, front-end
loaders, draglines and pneumatic drilling equip-ment.
Most of the ore mined to date has been the
peripheral zone type of mass-fiber asbestos. Pits
developed in this type of ore follow the contact
zone between the ultramafic body and the coun-try
rock and are therefore irregular in shape. Ore
near the surface that has been exposed to weather-ing
is quite soft and can be readily dug with a
pick or dragline. As the pit is deepened the ore
becomes fresh, massive rock that has to be brok-en
by explosives. When this becomes necessary
the drilling is done with pneumatic hand drills
and dynamite is used to charge the holes. The
mass-fiber ore is not hard, but is exceedingly
tough and blasting is not very effective except
when a good bench is present. Secondary breakage
is often necessary and this is usually done with
sledge hammers or dynamite.
Open pit mines developed in the peripheral zone
deposits are limited in depth. As the pit is deep-ened
the peripheral zone begins to dip underneath
the ultramafic body and timbering becomes nec-essary
in order to keep the pit open. Also, the
schistose contact zone is quite unstable which
makes hazardous working conditions. Therefore,
the development of the pit is usually limited to
the depth at which a dragline can effectively
operate.
The hard or mass-fiber ore associated with the
enstatolite bodies is mined by standard bench
type quarry methods. This type of ore differs from
the others in that much if not all of the body can
be utilized as ore and the mining does not have to
be as selective. This allows larger amounts of ore
to be mined by more efficient methods.
Reserves: Although accurate records are not
available to substantiate the claim, it is conser-vatively
estimated that total past production of
high grade, anthophyllite asbestos is at least
100,000 tons. Owing to the nature of the deposits
it would be virtually impossible to make a reason-able
estimate of the total reserves of anthophyl-lite
asbestos in North Carolina. However, based
on observations made during this investigation, it
appears that there is a minimum of 100,000 tons
of asbestos in sight. This includes only the hard
mass-fiber ore associated with the enstatolite.
Reserves of peripheral zone mass-fiber ore and
cross- and slip-fiber ore are unknown.
DESCRIPTION OF
MINES AND PROSPECTS
SPRUCE PINE AREA
The Spruce Pine area lies in the northeastern
section of the Blue Ridge Province in North Caro-lina
and includes parts of Avery, Mitchell and
Yancey counties. Numerous bodies of ultramafic
rocks are known to occur in the area and many
of them have been prospected and mined for as-bestos.
Mass-fiber anthophyllite asbestos is cur-rently
being mined from the Blue Rock mine and
the Newdale mine, both of which are located in
Yancey County.
Avery County
Burleson mine: This mine is located 1200 feet
21
west of SR (State Road) 1117, 2.5 miles south-west
of Newland and 0.6 mile north of Mt. Pleas-ant
church. It is on the east side of a south flowing
tributary to Hughes Creek.
This ultramafic body consists of two isolated
outcrops of enstatolite. The larger body crops out
directly behind the Burleson house and is the one
in which the mine was developed. The other out-crop
is located about 75 feet northwest of the
larger outcrop and is an oval shaped body that is
about 15 feet wide and 30 feet long that stands
about 10 feet above the surrounding ground level.
A traverse around both outcrops failed to reveal
any contact relationships and the true dimensions
of the body are unknown. However, it appears
that the body is about 100 feet long and 50 to 75
feet wide, the long dimension lying in a northwest-southeast
direction. Outcrops are poor, but the
adjacent country rock appears to be predominant-ly
hornblende gneiss, and garnetiferous-muscovite
gneiss that strikes N 20° E and dips 80° SE.
Both outcrops of enstatolite are well exposed
and are composed predominantly of large inter-locking
crystals of anthophyllite and enstatite.
Talc is also present in significant amounts. As
exposed in the face of the quarry, layering is a
distinct feature. The individual layers range from
less than two feet up to 5 feet in thickness and
have an apparent dip of 15° northeast. The body
is cut by numerous veins of cross-fiber anthophyl-lite
that vary from a fraction of an inch up to
two inches wide. Most of the veins are oriented
perpendicular to the layering.
This mine was worked by the Powhatan Mining
Company about 1958 and a small, but undeter-mined
amount of mass-fiber asbestos was recov-ered.
Also, a small amount of slip-fiber asbestos
was mined from a small pit at the southeast end
of the body. The mine workings consist of a verti-cal
face about 15 feet high and 30 to 40 feet wide.
The best grade ore is reported to have been recov-ered
from the northeast side of the face.
Frank mine: A large dunite body occurs just
south of Frank, about 2.5 miles south of Minnea-polis
and 4.3 miles southwest of Newland. The
North Toe River flows adjacent to and across part
of the formation. The dunite body is about 1400
feet long and averages about 400 feet in width,
the long dimension lying in an east-west direction.
It is well exposed in two barren hills on the south
side of the river. The larger and western-most hill
rises over 300 feet above river level.
Slip- and cross-fiber anthophyllite asbestos
which occurs in the contact zone and in many of
the interior faults (Hunter, 1941, p. 43) was pro-duced
intermittently for several years from this
deposit. The deposit has not been worked for
asbestos during the past 20 years, but according
to Bryson (1928, p. 27) the mining was done
chiefly by the open pit method although two small
tunnels were sent into the hillside to determine
the depth of the ore. The asbestos ore was hand
picked at .the mine and hauled by truck to a small
processing plant at Minneapolis. At the plant,
which had a daily capacity of 30 tons, the ore
was crushed, fiberized and screened.
Other prospects: Other small ultramafic bodies
that have been prospected for anthophyllite asbes-tos
are located on the south side of Hawshore
Mountain and on the northeast side of Big Elk
mountain south of Hughes.
Mitchell County
J. H. Pannell prospect: A small peridotite body
occurs on the south side of SR 1199, about 1 mile
southeast of Bakersville. The deposit crops out
on the nose of a low hill south of White Oak Creek
and within 50 feet of the road.
Hunter (1941, p. 57) reported the presence of
chrysotile asbestos as occurring in this deposit as
seams up to 6 inches thick and as individual fibers
and clusters of fibers penetrating individual oli-vine
grains. Several specimens of a finely fibrous
anthophyllite asbestos associated with serpentine
were collected during this investigation, but the
presence of chrysotile asbestos could not be con-firmed.
Soapstone Branch prospect: This deposit is lo-cated
on the west slope of Cane Creek Mountain,
1200 feet northwest of Rube Green Top at the
headwaters of Soapstone Branch. It is about 2
miles northeast of Hawk, Mitchell County and
2.5 miles northwest of Plumtree, Avery County.
It is situated in a very inaccessible area and can
be reached only on foot.
Although this deposit has not been prospected
and its value as an asbestos prospect is unknown,
it is of interest because of the relationship of the
various rock types exposed. The peridotite body is
about 400 feet long and 100 feet wide, the long
dimension lies in a north-south direction. It stands
up in prominent, massive outcrops above the
surrounding rocks and two pinnacle shaped out-crops
at the north end of the body are about 30
feet high. The south end of the body is composed
22
Figure 3
Scale
0.5 2 Miles
2
ULTRAMAFIC BODIES
MICAV1LLE 7.5' QUAD-MAP
SHOWING LOCATION OF
ASBESTOS MINES IN YANCEY CO., NC.
N
Figure 3. Map showing location of asbestos mines in Yancey
County, North Carolina. 23
mainly of talcose soapstone that is deeply weath-ered
and pitted. In the middle section, the body
consists essentially of serpentinized olivine.
At the north end of the body, along the west
and northwest side, three alteration zones are
distinctly displayed. The outermost zone is be-tween
2 and 3 feet wide and consists of coarse-grained
chlorite enterlayered with anthophyllite
and talc. The middle zone varies in width, but does
not exceed about 5 feet and is composed mostly of
amphibole minerals. The outer plus or minus 1
foot of this zone contains extremely large radial
shaped masses of anthophyllite and long-bladed
crystals of tremolite and/or actinolite. Also, con-siderable
amounts of talc are present. The inner-most
zone is composed mainly of anthophyllite
and talc. The anthophyllite occurs in radial and
cone shaped masses which are up to an inch in
diameter. Talc occurs dissiminated throughout the
anthophyllite as blade like crystals and masses.
This zone varies in width from a few feet up to
15 feet and can be traced for about 100 feet along
the west side of the body. All three of these zones
are very distinct and appear to be in a sharp
contact.
The interior of the body adjacent to the altera-tion
zones is composed of layered, serpentinized
dunite that contains small chromite crystals dis-siminated
throughout the mass. Also present are
numerous veinlets of cross-fiber asbestos which
cut the dunite at various angles.
On the east side, the dunite is in contact with
hornblende gneiss that strikes about due north
and dips 65° east. The contact on the west side
of the dunite is covered by slump material but
is also believed to be hornblende gneiss. Quartz-biotite
gneiss is also present in the immediate
area of the dunite, and a large concordant pegma-tite
dike crops out in the south bank of the branch
a few hundred feet south of the dunite body.
Other prospects: Two peridotite bodies occur
about 1.5 miles south of Spruce Pine just east of
Grassy Creek. One body is located about 300 feet
east of the bridge over Grassy Creek on the north
side of Carters Ridge Road (SR 1117). A few
outcrops are present in the road bank, but the
main mass of the body lies north of the road and
is present as disconnected boulder like outcrops
that can be traced through the woods to near the
crest of a prominent hill.
The other peridotite body is located about 500
feet south of SR 1117 directly behind a bowling
alley that faces State Highway 26. An abandoned
kaolin mine is located at the east end of this body.
A road which leads to this mine cuts across the
middle of the peridotite body.
The composition of these two bodies show con-siderable
variation. The bulk composition of the
most southern body appears to be dunite although
there is considerable alteration present along the
southeast end of the body in the vicinity of kaolin
mine. Selected samples collected from the body on
the north side of SR 1117 are composed of inter-locking
crystals of anthophyllite and tremolite.
Microscopic examination revealed the bulk of the
section to be composed of finely fibrous and acicu-lar
anthophyllite and tremolite crystals arranged
in an interlocking, subparallel schistose pattern.
Remnants of massive olivine grains and fine gran-ules
of magnetite are present throughout the
section. Talc is concentrated in the finely fibrous
anthophyllite.
The high percentage of anthophyllite present
in some of the outcrops present on the north side
of SR 1117 indicate that this body may have po-tential
as a mass-fiber deposit. However, the
proximity of the deposit to the highway and
several new homes may preclude any mining
operations.
Yancey County
Blue Rock mine: The Blue Rock mine is located
on the west side of the South Toe River about 2
miles southeast of Micaville. It can be reached by
travelling south on SR 1152, for 1.5 miles to the
Blue Rock Church. Turn west onto a private farm
road directly across from the church and follow
this road for 0.5 mile to the river. A low water
bridge makes the mine accessible by automobile
or truck except during periods of high water.
This mine has been worked intermittently since
1941 by several different mining companies and
has yielded a large tonnage of high grade, mass-fiber
asbestos. It is presently being operated from
time to time by the Blue Rock Mining Corpora-tion
of Illinois.
Most of the original rock mass has been re-moved
by mining operations and only a small
portion of the body remains in place. It is re-ported
that prior to mining, the deposit was a
large, massive outcrop that stood 25 to 30 feet
above the surrounding ground level. Present
workings show that the body is 100 feet long and
40 wide at its maximum width. It is eliptical or
pod shaped and its long dimension lies about N
10° E. The dip of the northwest and southeast
24
contacts indicate that the body is oval shaped in
vertical section and that it does not extend in
depth more than about 20 feet below the present
level of the quarry floor (subsequent exploratory
drilling has confirmed that is the case).
The ore body is located on the south slope of
a steep hill and has been developed into the face
of the hill. The present mine is an open pit quarry
that is horseshoe shaped in outline with the south
end open. The quarry walls are 20 to 30 feet high
and consist of 5 to 10 feet of undisturbed ore rock.
Waste material from the mine has been disposed
of at the south end of the quarry and a large
dump has been formed.
One of the most interesting features of this
deposit is the chlorite zone which completely en-velops
the body, except at the south end where
it has been removed by mining. The zone is from
1 to 2.5 feet wide and is composed of extremely
coarse-grained, emerald-green chlorite. It is par-ticularly
well exposed along the north and north-west
sides of the body. The outside of the zone is
in sharp contact with a reddish-brown saprolite.
The inside of the zone is in sharp contact with a
zone of coarse-grained, nonfibrous anthophyllite
rock which forms the walls of the quarry. In a
few places the anthophyllite rock has separated
from the chlorite zone along the contact and it
is quite evident that there is no gradation be-tween
the two rock types. Ore from the Blue Rock
mine is of the mass-fiber variety and is character-ized
by a radial, cone-like arrangement of the as-bestos
fibers. It varies from light bluish grey to
greenish gray in color and is composed mostly of
anthophyllite and talc.
In thin section the cone-like structures are re-vealed
to be composed of finely acicular and fibr-ous
anthophyllite and felted talc. Some of the
acicular anthophyllite has been altered to talc,
particularly along cross fractures and cleavage
planes. However, the alteration to talc is more
advanced in the finely fibrous anthophyllite. Skele-tal
magnetite is sparcely scattered through the
rock and usually has chlorite associated with it;
however, chlorite most often occurs as isolated
flakes. Anhedral magnesite occasionally occurs
with the felted talc and finely fibrous anthophyl-lite.
The average composition of two samples con-sidered
to be typical ore is as follows : anthophyl-lite
65 percent; talc, 27 percent; olivine, trace;
chlorite, 6 percent; serpentine, trace; magnesite,
trace; others (mostly magnetite), 2 percent.
The asbestos body is surrounded by a wide zone
of reddish-brown saprolite which appears to be
unusually high in iron. The saprolite zone grades
into fine- to coarse-grained, quartz-muscovite
schist that contains numerous stringers and pods
of pegmatite. The schist strikes northeast and
dips at a moderate to steep angle to the southeast
and seems to be the predominant country rock,
although interlayers of hornblende gneiss are also
present. A large alaskite body corps out in the
northwest bank of the river and extends to within
120 feet of the south end of the asbestos body.
Also, a large quartz vein is present 20 feet north
of the asbestos body, and outcrops of another
small ultramafic body are present 200 feet north-west.
Newdale mine: The Newdale mine is located 0.5
mile north of the South Toe River and U.S. High-way
19E, 1.1 miles northeast of Micaville. It can
be reached by travelling on State Highway 80 for
1 mile north of its intersection with U.S. Highway
19E. At this point turn west onto SR 1304, and
follow this road for about 1 mile to the mine.
The Newdale mine is currently being developed
by the Powhatan Mining Company and small
amounts of mass-fiber ore have been produced in-termittently
during the past 4 years.
The ore body is a massive, oval shaped body of
anthophyllite-enstatite rock that crops out on the
crest of a long, narrow ridge. It is roughly circu-lar
in outline and averages about 100 feet in
diameter. The body forms a single, barren out-crop
that stands up as much as 70 feet above the
surrounding ground level. Most of the mining to
date has been around the edges of the body, main-ly
on the northeast and southwest sides.
The ore rock is composed predominantly of
large, interlocking crystals of enstatite that ex-hibit
an advanced stage of alteration to antho-phyllite.
The individual blade shaped crystals
range from a fraction of inch up to 3 or more
inches in length. On a fresh surface the rock is
greenish gray to bluish gray in color and small
talc flakes distributed throughout give it a silvery
luster.
In thin sections of the ore it is quite apparent
that anthophyllite and talc have replaced much
of the original enstatite. Some sections contain
excellent examples of enstatite crystals that have
been completely replaced by anthophyllite and
talc. Enstatite occurs as large, highly altered
blades. Finely fibrous bundles of anthophyllite are
developed along cleavage cracks parallel to the
long dimension of the enstatite. Acicular and
25
fibrous anthophyllite occurs interstitially as well
as in random orientations that penetrate the
blades in all directions.
There is considerable variation in mineral com-position
within the deposit. Anthophyllite, olivine
and chlorite appear to be most abundant in the
northern portion of the deposit whereas talc and
enstatite are more abundant in the southern por-tion.
An average mineral composition as determined
from six thin sections representing both stockpile
and in-place ore is as follows: anthophyllite, 45
percent; enstatite, 15 percent; talc, 20 percent;
olivine, 6 percent; chlorite, 7 percent; serpentine,
5 percent; others (magnetite and chromite), 2
percent.
Where it has not been removed by mining
operations, a narrow schistose zone of talc, chlor-ite
and vermiculite is present between the antho-phyllite-
enstatite rock and the country rock. The
schistose zone varies from a few inches to several
feet in width and an exposure in an open cut
trench on the west side of the deposit exhibits
numerous slickensides. The schistose zone is also
well exposed in an abandoned adit that drifts part
way under the deposit from the southeast side.
The country rock that surrounds the ore body
is a deeply weathered, coarse-grained quartz-muscovite
schist that is thoroughly stained by
iron oxide to a deep reddish-brown color. It con-tains
numerous pods and stringers of pegmatite
that are predominantly concordant to the local
foliation, but a few are discordant. Adjacent to
the ore body the foliation of the schist parallels
the outline of the body ; however, away from the
ore body the foliation of the schist strikes about N
55° E and dips about 65° SE. Minor amounts of
hornblende gneiss are interlayered with the schist.
Numerous large pegmatites are in the general
vicinity of the ore body. Extensive scrap mica
workings are located about 700 feet southwest
and several abandoned sheet mica mines are lo-cated
within a few thousand feet north of the
body. Also, a large dunite body is located about
0.8 mile southeast of the asbestos mine between
State Highway 80 and Mine Branch.
J. C. Woody mine: The Woody mine is located
on the southeast side of a northeast flowing tribu-tary
to Rose Creek, about 0.5 mile south of Pleas-ant
Grove Church. The mine can be reached by
travelling on SR 1308 for 6.5 miles north of Mica-ville
to Pleasant Grove Church. Turn southwest
onto SR 1317 and travel about 0.75 mile to a farm
read that turns south off of SR 1317 and leads
to the Woody house. The mine is located 500 feet
east of the house.
This ultramafic body is composed mostly of rela-tively
unaltered dunite. The body is about 500
feet long, 200 feet wide and forms a prominent
hill southeast of the creek. The asbestos ore is the
peripheral zone mass-fiber variety and occurs in
a zone about 2 feet wide that lies between the
dunite and an alteration zone composed of talc,
chlorite and vermiculite.
The ore is massive, coarse grained and varies
from cream to tan in color. It is composed of in-terlocking
blades of asbestos fibers that contain
small, isolated patches of fine grained, dark gray
and black minerals. In thin section the ore is com-posed
predominantly of acicular to finely fibrous
anthophyllite. Concentrations of chlorite flakes in
the anthophyllite produce the larger dark gray
patches seen megascopically. A few small, dark
gray to black patches are caused by clusters of
magnetite granules. The anthophyllite fibers aver-age
about 6 mm. in length, but fibers that range
up to 12 mm. in length are not uncommon. Mineral
composition of a selected sample of ore is as fol-lows:
anthophyllite, 88 percent; chlorite, 10 per-cent;
others (mostly magnetite and limonite), 2
percent.
The percent mine workings consist of a small
open pit trench developed in the contact zone on
the north side of body adjacent to the creek. The
workings have not been extensively developed and
because of the heavy growth of vegetation along
the contact zone it is difficult to make a reliable
estimate on tonnage of ore present. However, it
appears that a fairly large tonnage of mass-fiber
ore is present in this deposit.
The predominant country rock is mica gneiss
that strikes N 45° E and dips about 60° SE. At
the southeast end, the body is in contact with a
large pegmatite that has been mined for kaolin
and mica. It is reported that several years ago a
small amount of vermiculite was mined from the
contact zone adjacent to the pegmatite.
Sam Grindstaff mine: The Grindstaff mine is
located en the northeast slope of Chestnut Moun-tain,
1000 feet southeast of Thunderstruck Knob.
It can be reached by travelling on SR 1308 for
5.6 miles north of Micaville to SR 1312. Turn
west on to SR 1312 and travel 0.2 mile to the in-tersection
with SR 1319. Turn northwest onto SR
1319 and followed this road 0.4 mile to its termi-nation.
The mine is located about 1000 feet north-
26
west of the end of SR 1319 and can be reached on
foot by following an abandoned logging road.
This ultramafic body is predominantly dunite
and is about 300 feet long and 150 feet wide. It
underlies the south slope of a prominent hill and
forms numerous boulder-like dun colored out-crops.
The mine workings are located at the north
end of the deposit and consist of a shallow open
cut trench that is up to 10 feet wide and about 75
feet long. The long dimension of the trench lies
in a northeast-southwest direction and dips at a
moderate angle to the northwest. Several smaller
prospect pits and trenches are located in the
immediate vicinity. The main trench appears to
be located along an interior fault or shear plane.
The asbestos occurs as a series of cross-fiber
veins that range from Y> inch to 5 inches in width.
It appears to be relatively free of impurities and
of good quality; however, the quantity of ore is
limited. An unknown amount of asbestos was re-covered
from this mine a number of years ago,
but it has not been worked for at least the past
ten years.
An exposure on the northwest side of the body
reveals that the dunite is in direct contact with
hornblende gneiss that strikes N 60° W and dips
80° NE. The usual talc-chlorite-vermiculite alter-ation
zone is absent at the contact, but a small
pegmatite stringer that is offset about 1 foot indi-cates
some faulting along the contact.
Cas Thomas prospect: A small body of enstato-lite
occurs on the Cas Thomas farm about 5.5
miles airline north of Micaville. The deposit can
be reached by travelling on SR 1308 for 7.6 miles
north of Micaville to SR 1315. Turn northeast
onto SR 1315 and follow this road for 1.2 miles
to the Thomas farm. The deposit is located about
1000 feet southeast of the Thomas house near the
North Toe River.
The deposit consists of a few boulder like out-crops
of enstatolite that occur near a small tribu-tary
stream. The area is covered with a thick
mantle of soil and heavy growth of vegetation and
the true dimensions of the body could not be
determined. However, it appears that the deposit
is less than 100 feet long. The deposit was pros-pected
for asbestos some years ago, but no ore
was produced. However, the deposit may have
potential as a source of mass-fiber asbestos of
the anthophyllite-enstatite variety.
C. W. Allen prospect: An abandoned asbestos
mine is located on the C. W. Allen property, 4.5
miles airline southwest of Burnsville. The de-posit
can be reached by travelling on U.S. High-way
19 E for 5.6 miles west of Burnsville to the
intersection with SR 1136. Turn south onto SR
1136 (Banks Creek Road) and follow this road
for 1.7 miles. Outcrops of dunite are exposed in a
roadcut on the south side of the road 150 feet
southwest of Allen Cemetery.
Relatively unaltered, dark-gray to green dunite
is exposed for about 80 feet along the roadcut. It
is in contact with hornblende gneiss on the south-east
side and quartz-muscovite gneiss on the
northwest side. The gneisses strike N 15 °E and
have a moderate dip to the southeast. The dunite
body can be traced southwest across an open pas-ture
for about 500 feet where it is well exposed
in the abandoned asbestos workings. In the im-mediate
vicinity of the mine area the dunite ex-hibits
various degrees of alteration. Some hand
specimens collected from the dump show relict
grains of olivine that are completely altered to
serpentine.
Very little asbestos can be seen in place, but
pieces picked from the mine dump indicate that
the asbestos ore was the cross-fiber vein variety.
Veins up to 3 inches in width are present and the
asbestos is stained a light yellowish brown by iron
oxide. The only impurities noted were a few flakes
of chlorite in the outer portion of the vein.
The mine is evidently the one referred to as the
Cane River mine that was worked in 1919 by
Mr. N. C. McFalls. No production records are
available, but from the size of mine workings, it
appears that only a few tons of asbestos were
recovered.
Other prospects: There are a number of other
ultramafic bodies scattered throughout Yancey
County. Time did not permit the exact location
and examination of many of these deposits and
their potential as asbestos prospects is unknown.
The general location of some of these deposits are
shown on the accompanying maps.
LAKE TOXAWAY AREA
Beginning in southern Jackson County near the
South Carolina state line, and continuing north-east
into western Transylvania County, an area
approximately 15 miles long and 5 miles wide con-tains
between 30 and 40 bodies of ultramafic
rocks. Lake Toxaway is about the geographic cen-ter
of this area.
All of the ultramafic bodies in this area are
small and are characterized by an advanced stage
27
Figure 4
0.5
Scale
1 Mile
Micaville
7.5 Minute-Quad
N
I
MAP SHOWING LOCATION OF ASBESTOS MINES IN
THE BRUSH CREEK AREA, YANCEY CO., N. C.
28
Figure 4. Map showing location of asbestos mines in the
Brush Creek area, Yancey County, North Carolina.
of alteration. Large tonnages of mass-fiber asbes-tos
of the peripheral zone type have been mined
from some of the deposits and the area also con-tains
large reserves of mass-fiber asbestos of the
anthophyllite-enstatite variety.
Transylvania County
Kilpatrick mine: The Kilpatrick mine is located
about 5.8 miles airline northwest of Rosman and
3 miles airline northeast of the post office at
Lake Toxaway. It can be reached by travelling on
State Highway 281 for 5.2 miles north of its inter-section
with U.S. 64 to SR 1309. Turn east onto
SR 1309 and travel 1.2 miles to a farm road on
the north side of SR 1309. The mine is located at
the end of this road about 500 feet north of the
farm house.
This mine was worked intermittently for several
years by the Powhatan Mining Company and
yielded a large tonnage of high grade anthophyl-lite
asbestos. It was abandoned in 1962 and the
mine workings have been back filled and leveled.
The ultramafic body at this locality appears to
be a dunite that has undergone considerable al-teration.
Outcrops of the main mass are poor and
those present are deeply weathered to an orange-brown
clay that contains numerous small flakes
of talc and asbestos fibers. The body lies on the
slope of a small hill and is covered with soil and
dump material from the mine and the exact
dimensions of the body could not be determined.
However, it appears to be between 200 and 300
feet long and about 100 feet wide. Outcrops of
ultramafic rocks of about