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EXHIBIT 80
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Original article
the geologic of talc
Using setting
deposits as an indicator of
amphibole asbestos content
· · · Gent
Bradley S. Van Gosen Heather A. Lowers Stephen J. Sutley Carol A.
impacts on the human respiratory system, have been the
Abstract Thisstudy examined commercial talc focus of considerable research and contentious debate for
deposits in the U.S. and their amphibole-asbestos at least 30 years (Goodwin 1974; Occupational and Safety
content. The study found that the talc-forming and Health Administration 1992). Talc-asbestos issues
environment directly influenced the amphibole and have drawn renewed attention, such as news reports in
amphibole-asbestos content of the talc deposit. 2000 contending that the fibrous talc used to add strength
Large talc districts in the U.S. have mined to the best-selling brands of children's crayons contained
hydrothermal replaced dolostone.
tales that amphibole asbestos (Beard and others 2001). To investi-
Hydrothermal talcs, created by siliceous fluids gate the extent and character of amphibole minerals in
heated by magmas at depth, consistently lack talc deposits, a group at the U.S. Geological Survey
amphiboles as accessory minerals. In contrast, (USGS) is examining the relationships between amphi-
mineable talc deposits that formed by contact or boles and talc in U.S. deposits. This study, involving field
regional metamorphismconsistently contain examinations and sampling, laboratory analyses, and an
amphiboles, locally as asbestiform varieties. extensive literature review, has revealed that a consistent
Examples of contact metamorphic deposits occur in occurs within large (commercial) and small
relationship
Death Valley, California; these talc-tremolite U.S talc deposits-that is, the primary talc-forming
deposits accessory amphibole-asbestos.
contain Talc environment directly controlled the ultimate amphibole
bodies formed by regional metamorphism always content of the talc deposit.
contain amphiboles, which display a variety of Talc deposits are the products of metasomatism caused by
compositions and habits, including asbestiform. regional metamorphism, contact metamorphism, or
Some industrial mineral deposits are under scrutiny hydrothermal processes (meteoric fluids or brines heated
as potential sources of accessory asbestos minerals. by distant or buried
intrusions). Two of these talc-forming
Recognizing consistent relations between the talc- mechanisms-contact metamorphism and hydrothermal
forming environment and amphibole-asbestos processes-are well represented by large, historically
content may be used in prioritizing remediation or mined deposits in the Death Valley region of southern
monitoring of abandoned and active talc mines. California. Results of field and laboratory studies on these
Death Valley deposits, described herein, reflect the con-
Keywords Talc · Amphibole-asbestos · Geologic
sistent associations of amphibole-rich talc deposits with
· Hydrothermal · Metamorphic · USA
setting contact metamorphism versus amphibole-poor talc with
hydrothermal processes.
A number of U.S. talc deposits of commercial size (under
past or present economic conditions) were formed by
metasomatic processes driven by regional metamorphism;
Introduction these large bodies consistently contain talc intergrown
with amphiboles, such as tremolite and (or) anthophyllite.
The presence of amphibole asbestos as minor accessory Debate over the asbestos mineral content (major versus
minerals in some talc deposits, and its potential health trace amounts) within these talc-amphibole deposits is the
result of differing interpretations of the predominant habit
(asbestiform versus non-asbestiform) of the amphibole
I Received:26 September2003 / Accepted:24 November 2003 particles.The complicating factors that face analysts
ª
examining this type of talc ore material are discussed.
r r 2004
B. 5. Van Gosen(C 3) H. A. Lowers· 5. 1 Sutley C. A. Gent
U.S.GeologicalSurvey,DenverFederalCenter,M.S.905, ASheSt0S
Box 25046,Denver,CO80225,USA
Email:bvangose@usgs.gov
Tel.:+1-303-2361566 Asbestos is a commercial-industrial term with a long his-
"Asbestos"
Fax:+1-303-2361425 tory, and is not a mineralogical definition. in the
920 EnvironmentalGeology(2004)45:920-939 DOl 10.1007/s00254-003-0955-2
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latter half of the 20th century became widely used in regu- mineral fibers intergrown with the vermiculite deposits
parti-
latory language to refer to well developed, long, thin mined and milled near the town from 1923 to 1990 (U.S.
cles (fibers or fibrils) and fiber bundles of specific mineral Senate Committee on Environment and Public Works
compositions, which have fulfilled particular industrial 2000; Dearwent and others 2000). The California Division
applications. In the U.S., asbestos is most commonly of Mines and Geology has mapped outcrops of ultramafic
defined as the asbestiform
variety of 6 naturally occurring rocks in California to indicate country rocks with the
hydrated silicate
minerals; these include chrysotile, the potential to host chrysotile and actinolite-series asbestos
asbestiform member of the serpentine group, and five (Churchill and Hill 2000). Other examples of occupational
minerals of the amphibole group: the asbestiform varieties and environmental exposures to asbestos are described in
of (1) riebeckite (commercially called crocidolite), (2) Nolan and others (2001).
cummingtonite-grunerite (commercially called amosite), The history and study of naturally occurring asbestos, its
(3) anthophyllite (anthophyllite asbestos), (4) actinolite associated health impacts, and the multiple, complex
(actinolite asbestos), and (5) tremolite (tremolite asbestos) issues that revolve around asbestos are discussed in
(Occupational Safety and Health Administration 1992). The Campbell and others (1977), Ross (1981), Zoltai (1981),
qualities of asbestos that make it useful and desirable for Levadie (1984), Skinner and others (1988), Mossman and
commercial use are its high tensile strength, flexibility, Occupational Adminis-
and others (1990), Safety and Health
its resistance to heat, chemicals, and electricity. tration (1992), Guthrie and Mossman (1993), Nolan and
The inherent properties of asbestos-fibers that are dura- others (2001), and Virta (2001, 2002). Current federal
ble, long, and thin-appear to contribute to the toxicity of regulations are provided in the Code of Federal Regula-
these mineral particles when lodged inside the human tions (CFR), including regulations on occupational expo-
respiratory system (Stanton and others 1981; Wylie and sures to asbestos excepting construction and ship-related
others 1993). Occupational exposures to asbestos have work (CFR 29, part 1910.1001); CFR regulations are
been linked to asbestosis (scarring of the lungs, "pulmo- updated as needed on July 1.
nary interstitial fibrosis"), lung cancer, and malignant
mesothelioma (tumor development within the pleural
membrane perito-
lining the chest cavity and (or) in the
neum lining the abdominal and pelvic walls and their vis-
EXpl0itable talc deposits
cera) (Skinner and others 1988; Mossman and others 1990;
Guthrie and Mossman 1993; Nolan and others 2001). His- and amphiboles
torically, chrysotile has accounted for more than 90% of the
world'sasbestos production, and presently over 99% of the Talc is a hydrous silicate with an idealized composition of
world production
(Ross and Virta 2001; Virta 2001, 2002). Mg3Si40m(OH)2, but can contain major amounts of Fe,
Whereas mining, processing, and use of chrysotile has been minor Al and F, and trace Mn, Ti, Cr, Ni, Ca, Na, and K
much more common, several studies suggest that amphi- (Evans and Guggenheim 1988; Greenwood 1998). Signifi-
bole asbestos, even when occurring as a minor accessory in cant talc deposits occur in the U.S. in the Appalachians,
chrysotile deposits, may be the primary cause of meso- from Vermont to Alabama, in the West in Montana,
thelioma in asbestos-related occupations (Ross 1981, 1984, California, Nevada, Washington, Idaho, and New Mexico
2001; Mossman and others 1990; Browne and Wagner 2001; (Piniazkiewicz and others 1994). Large deposits also occur
Gibbs 2001; Langer 2001; Pooley 2001a, 2001b). As noted by in Texas, and small soapstone mines once operated in
Mossman and others (1990, p. 296): "The persistence of Arkansas, but economic deposits are otherwise lacking
amphiboles in human lungs may be attributed to their between the Appalachians and the Rocky Mountains.
increased ability to penetrate the peripheral lung, lack of Commercial talc deposits have replaced two general rock
clearance, or durability". Wagner and others (1960) types: (1) Dolostone (dolomite or dolomitic marble), which
described the high rates of malignant mesothelioma in were selectively replaced by reactions with large volumes of
workers and nearby residents of crocidolite (asbestiform heated waters carrying silica in solution, mobilized by
riebeckite) mines in the Cape Province of South Africa. magmatic or metamorphic mechanisms. The dolostone-
Following publication of that study in 1960, mesothelioma hosted replacement deposits range from cm-thick pods to
became increasingly recognized as an occupational risk in the 29-m-thick talc body at the Treasure Chest mine near
the mining, milling, and handling of rocks that contain Dillon, Montana (Berg 1979). Today and in the past, the
amphibole asbestos and their by-products. largest talc producing districts in the U.S. exploited talc
In recent years, there has been a renewed focus upon the deposits replacing dolostone, and to a lesser extent, mag-
hazards related to inhalation of amphibole asbestos; in nesite. (2) The second common talc hosts are ultramafic
particular, exposures due to the mining and processing of rocks, mainly dunites and peridotites, altered by metaso-
some amphibole-bearing industrial mineral deposits, as matism through contact or regional metamorphism. Mag-
well as environmental exposures to amphibole-rich nesium silicates in these rocks reacted with SiOrsaturated
bedrock, such as road cuts and excavations that expose aqueous pore fluids during metamorphism to form nearly
asbestos-bearing rock (Browne and Wagner 2001). For monomineralogic bodies of talc adjacent to zoned
example, unusually high incidences of asbestos-related sequences of talc-carbonate-, calcic amphibole-chlorite-,
mortality and respiratory disease in the small town of and chlorite-dominant zones in addition to complexly
Libby, Montana, have been attributed to amphibole mixed zones (described by Sanford 1982). These deposits
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form rinds on the ultramafic bodies or nearly replace them; randomly selected talcose rock at each particular sample
they are typically tabular or lenticular talc bodies that can spot. The samples are intended to represent the talcose
reach 100 m in thickness and extend more than 300 m in material mined
at each site, collected mainly from mines
length. Large deposits of this type are mined in Vermont, that are inactive and abandoned, excepting those samples
and smaller deposits have been mined in other eastern collected from an active open pit of the Yellowstone mine,
states, California, and Texas. The ultramafic-hosted southwest Montana.
deposits have been equally important sources of pure talc Dust coating the inside of the plastic sampling bag was
and darker talc (soapstone), the dark talcose bodies owing examined using a JEOL 5800-LV scanning electron
their coloration to amphibole, serpentine, and chlorite microscope (SEM), equipped with an Oxford ISIS energy-
impurities (Piniazkiewicz and others 1994). dispersive system (EDS) with ultra-thin window detector.
The host rock composition and process of formation The EDS provided semi-quantitative chemical data that
determines the qualities
of talc, which in turn affects the was reduced using the Oxford ISIS standardless software
industrial of a particular
applications deposit. The grain with the ZAF correction procedure selected. Analyses were
size and shape, color, and purity of talc influence its uses performed on single, isolated structures, not on fibers that
(Piniazkiewicz and others 1994). In addition, the talc- The operating condi-
lay across other mineral particles.
forming mechanism-hydrothermal processes, contact tions of the instrument were 15 kV, 0.5-3 nA (cup), and
metamorphism, or regional metamorphism-directly approximately 30% dead time. These conditions would
influenced the ultimate amphibole content of the talc ore excite an analysis volume of ~2 µm.
body, described below through examples. Within a single The matrix corrections used do not account for particle
mineral deposit, such as some talc ore bodies, amphibole geometry. However, Small and Armstrong (2000) demon-
crystals may range in habit from blocky to prismatic to strated that at 10-15 kV (utilized geometry-
by this study)
acicular to asbestiform. In describing amphibole asbestos, induced errors in the analyses of particles can be relatively
Wylie (2000, p. 56) notes that: "Amphibole-asbestos fibrils small. One of the amphibole-rich study samples was
µm"
range in width from about 1 to 0.01 and "individual analyzed by EDS and by electron probe microanalysis with
fibrils and bundles of fibrils may attain lengths of wavelength dispersive spectroscopy (WDS) to evaluate the
hundreds to thousands of times their widths". accuracy of the EDS measurements. Table 1 shows the
comparison of analytical resultsby EDS and WDS. The
amphibole nomenclature used in this study follows the
recommendations of Leake and others (1997).
Study methodS Samples for x-ray diffraction (XRD) analyses were pul-
verized and mechanically split. The minerals identified by
Samples of talc ore material were collected at several mine XRD in the samples were categorized as major, minor, and
"Major"
sites, which are described below. Each sample was trace mineral constituents of the analyzed split.
collected as a composite, containing at least 30 pieces of minerals are estimated to comprise >25 wt% of the
Table 1 and single unpolished grains, and (2) electron probe microanalysis
Comparison of the analyses of tremolite particles in one tremolite- with wavelength dispersive spectroscopy (WDS) on polished grains.
rich specimen from the Death Valley region, as measured by two Data are expressed in cation proportions, which were calculated by
techniques: (1) energy dispersive x-ray analysis (EDS) on polished stoichiometry using 23 oxygen atoms
Mount Particle Analysis K Na Ca Mn Fe Mg Ti Al Si
type L xW method
(µm)
Polished 203×I06 WDS 0.01 0.06 1.88 0.01 0.04 4.93 bdl 0.03 7.99
EDS bdi bdi 1.7 bd) 0.1 4.9 bd! bdl 8.I
Polished 362×226 WDS 0.01 0.06 1.88 0.01 0.05 4.94 bdl 0.03 7.97
EDS bdl bdl 1.7 bdi bd! 5.0 bd1 bdl 8.1
Polished 620×228 WDS 0.01 0.06 1.87 0.02 0.06 4.90 bd! 0.03 8.00
EDS bdl bdl 1.7 bdl 0.1 5.0 bdl bdl 8.1
Polished 241×28.8 WDS 0.01 0.05 1.88 0.02 0.06 4.94 bdl 0.03 7.99
EDS bdl bd1 1.8 bdl bdl 4.9 bdl bd1 8.1
Polished 140×14.3 W DS 0.01 0.05 1.85 0.02 0.06 4.93 bdl 0.04 8.00
EDS bdl bdl 1.8 bdi 0.1 5.0 bdl bd! 8.1
Loose 225×170 EDS bd! bdl 1.8 bdl 0.1 4.9 bdl bd! 8.1
Loose 445×l66 EDS bd! bd! 1.8 bd! 0.1 4.8 bd1 bdi 8.1
Loose 104×27.1 EDS bdl bdl 1.7 bdl 0.1 5.0 bdt bdl 8.1
Loose 20.2×3.4 EDS bd! bdl 1.7 bdl 0.1 5.1 bd! 0.1 8.0
Loose 18.5×0.9 EDS bdl bdi 1.8 0.1 0.1 5.2 bdl bdl 7.9
Loose 5.8×0.8 EDS bdl bdl 1.7 0.1 0.2 5.1 bdl 0.1 7.9
Loose 6.7×l.1 EDS . bd! bdl 1.9 bd! 0.1 5.3 bdl bdl 7.8
Loose 3.9×l.5 EDS bdl bdl 1.8 bdl bdi 5.0 bdi 0.1 8.0
Loose 13.4x1.0 EDS bdl bdl 1.8 0.1 0.1 5.1 bdl 0.2 7.9
bdl, below the detection limit of the analytical technique
922 EnvironmentalGeology(2004)45:920-939
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"minor"
sample, minerals form 5-25 wt% of the sample, Talc City district, California
"trace"
and minerals form <5 wt% of the sample. These The historical significance of the Talc City mining district
estimates were based on the experience of the XRD oper- in California from World War I through the 1940s is well
ator with his instrumentation and its data output. The documented by Page (1951). The district is in the Talc City
pulverized splits examined by this study provide snapshots Hills about 47 km southeast of Lone Pine, California. Page
of the mineralogy ·and variability in the talcose ores. visited and sampled the district pro-
during its peak of
However, quantitative estimates of the talc or amphibole duction in the mid 1940s; the reader is referred to his
content should not be interpreted from the XRD results report (Page 1951) for descriptions of the district's geol-
shown in this report. ogy, talc deposits, and mines. Gay and Wright (1954)
The XRD techniquecan identify the amphibole minerals completed a geologic map of the Talc City area.
within a sample as members of the tremolite-actinolite- The talc deposits of the Talc City district are thick lenses
ferroactinolite series, but is not able to determine the and irregular masses hosted mainly by dolomite. To a
specific amphibole species. It is also not possible to posi- much lesser extent talc bodies occur in "silica rock",
tively distinguish between tremolite and the sodic-calcic named by Page (1951) for an unstratified, massive rock
amphiboles winchite and richterite by XRD. composed mostly of interlocking quartz; it resembles
quartzite in outcrop. Limestone is also nearby. Bedded
dolomite is altered to massive dolomite adjacent to the talc
deposits; both are often closely associated with silica rock.
The silica rock is discontinuous at the mine sites, forming
Amphibole-poor talc deposits
isolated lenses surrounded by massive dolomite. Silica
formed by hydrothermal processes rock appears to be partially replaced by talc at some of the
deposits. Petrographic examination of the silica rock
Geologic environments that host reveals microscopic patches of talc in interstitial areas
hydrothermal talc deposits between grains (Page 1951).
quartz
"hydrothermal"
The term is commonly used in a general Granitic bodies crop out from about 0.8 to 3.2 km distance
sense to describe the actions and products of hot fluids, from the mines. The granitic rocks locally have been
often, but not always, implying an association with igneous
hydrothermally altered, suggesting they were affected by
processes. In this discussion, hydrothermal talc refers to the talc-forming hydrothermal event(s) and were not the
deposits thought to be the products of fluids heated by a of fluids. Dikes
source ranging in composition from basalt
distant magma usually at depth. For example, in
source, to diorite crop out near the Talc City and Frisco
to felsite
the Talc City district, California, no evidence of contact or mines (Page 1951). These dikes are also hydrothermally
regional metamorphism is apparent in the host or country altered and interpreted to predate the talc alteration (Page
rocks; the source of the heat that drove the talc-forming 1951). A magmatic source of hydrothermal fluids is not
process is not obvious, and has been attributed to buried obvious within the district. If buried, it may be best viewed
or distant igneous intrusions. Heat sources for the south- methods.
by geophysical
west Montana talc event(s) are speculated to be sills that Page (1951) proposed a model for talc formation in the
intruded an overlying Proterozoic basin, heating and Talc City area that involved the following events:
circulating basin brines towards underlying Archean
talc" 1. The area was originally covered by mostly limestone,
marbles. Thus, "hydrothermal refers to talc ore
with lesser mterbeds of dolomite, shale, and sandstone;
bodies that are not directly associated with regional
2. Hydrothermal fluids rich in Mg rose through and
metamorphism and are not found directly against an
fractured the overlying limestones and altered them
igneous intrusion.
into massive
dolomite, perhaps also converting
The large, amphibole-poor, hydrothermal talc deposits of
sandstones to the "silica rock";
southwest Montana, Talc City, California, and west Texas,
3. A second event of fracturing accompanied another
as examples, may represent the products of saline, sili-
influx of hydrothermal waters enriched in S1 and Mg,
ceous fluids mobilized by basin-scale or localized mag-
which replaced massive dolomite with large talc
matic activity. This genetic association is supported by the
deposits and replaced sihca rock with talc lenses. Page
recent fluid-inclusion study by Gammons and Matt (2002)
of the hydrothermal tale deposit currently excavated at the (1951) suggested the talc formed by the addition of
silica and water to dolomite, and the addition of silica,
Yellowstone mine, southwest Montana, which
indicated
the presence of highly saline fluids during the talc for- water, and Mg to silica rock. This general reaction,
shown below, is commonly invoked to explam the
mation. They proposed that "high heat flow, enhanced by
replacement of dolomite by talc:
injection of thick sills into the (Proterozoic) sedimentary
pile, forced connate brines out of the bottom of the
Basin and into the underlying or adjacent 3 dolomite + 4Si02%) + 1H2O = 1 talc +3 calcite +3CO2
(Proterozoic)
Precambrian basement, where they caused retrograde
metamorphism and formation of economic talc and Abundant and shearing of country rocks in the
deposits" fracturing
chlorite (replacing dolomitic marble and quar- district suggest that fracture systems controlled and aided
tzo-feldspathic gneiss, respectively) (Gammons and Matt fluid flow and talc formation. Page's interpretations
2002, p. 44). are based on field relationships. However, by general
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appearances, the talc deposits and associated rocks of the southwest Montana talc bodies are lenticular and elongate,
Talc City district do not display features typical of regional and in most places, talc lenses are parallel to the lithologic
metamorphic processes, such as prominent foliation or layering of the marble. However, talc bodies cut across
compression structures. layering at the Yellowstone mine (Cerino 2002).
The study sampled talc ore from pits or dumps at five sites The origin of the southwest Montana talc deposits is not
in the Talc City district (Tables 2 and 3). No evidence of completely understood, but recent work has reaffirmed
amphibole minerals was found in ore samples from this earlier observations that the talc bodies appear to have
district based on x-ray diffraction (Table 2) and SEM-EDS formed during the Precambrian because they are restricted
analyses of the samples. Platy talc is mixed with small to Archean dolomitic marbles and do not replace overlying
amounts of calcite, clinochlore, dolomite, quartz, kaolinite, Cambrian dolomites. This observation was supported by a
vermiculite (uncertain identification) and K-feldspar (lis- published age of 1.36 Ga by the ®Ar/39Ar method for
ted left to right in decreasing abundance). A friable white muscovite intergrown with talc in the Ruby Range (Brady
layer interlayered with the talc ore body at the Frisco mine and others 2003). A recent fluid inclusion study of the
consists of mostly quartz with accessory plagioclase, Yellowstone mine deposits (Gammons and Matt 2002,
muscovite, dolomite, talc, and kaolinite. Thus, none of the p. 44) determined that "the fluids responsible for talc
descriptions of Page (1951), nor the results of our sam- formation were saline brines (roughly 7x saltier than
pling and mineralogical analyses, indicate the presence of modern seawater), and were enriched in CaCl2". They
amphiboles in the talc deposits of the Talc City district. calculated burial depths during talc formation of more
than 3 km at formation temperatures of 190 to 250 °C.
Their model for talc formation at the Yellowstone mine
Yellowstone mine, southwest Montana site involves saline fluids that descended along growth
The Yellowstone talc mine is on the northeast flank of the faults in an overlying Proterozoic basin that may have
Gravelly Range near Ennis, Montana. This enormous talc existed above the Archean dolomitic marbles at about
(greater than 5.5 million short tons of known
body reserves) 1.36 Ga; they suggested the saline fluids were either sup-
is the largest known in southwestern Montana, a region that plied by connate brines in the basin sediments or by
contains a total of 57 talc mines, talc prospects, and known seawater. Their model, as well as earlier models
overlying
talc occurrences (Berg 1979; Van Gosen and others 1998)· in southwest Montana
for talc formation (Olson 1976;
The Yellowstone mine is the largest talc-producer in the Anderson and others 1990; Brady and others 2003), invoke
U.S., and two other large talc mines, the Regal and Treasure
very large water to rock ratios to form these deposits,
State mines, currently operate farther to the west in the Ruby through the general reaction:
Range. All three mines are open-pit operations.
All of the economically important talc deposits in the Ruby 3 dolomite + 4Si04,q) + 4H20 = 1 talc + 3Ca2+ + 6HCO3
and Gravelly Range region of southwest Montana replaced
dolomitic marbles of Archean age. In much smaller Anderson and others (1990) suggested that water to rock
amounts, talc also replaced magnesite, quartz, tremolite, ratios of more than 600 are required by this reaction to
serpentine, and calcite, which are accessory constituents of carry sufficient silica in solution and flush most of the
the host marble (Berg 1979). Talc occurrences range from calcite out of the system.
veinlets and pods centimeters thick up to huge masses, Regardless of the source of the hydrothermal fluids or the
such as the thick talc body at the Yellowstone mine, which circulation mechanism, the end result at the Yellowstone
is at least 30 m thick (bottom not yet found). Most of the mine site is large bodies of mainly massive talc with light
Table 2
Mineral abundances in samples Site name, Latitude, Minerals identified
of hydrothermal talc ore col. sample number longitude by x-ray diffraction
lected from abandoned talc
mines in the Talc City district Major Minor Trace
near Lone Pine, California. The
latitude and longitude values
Preview
FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 EXHIBIT 80 FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 Original article the geologic of talc Using setting deposits as an indicator of amphibole asbestos content · · · Gent Bradley S. Van Gosen Heather A. Lowers Stephen J. Sutley Carol A. impacts on the human respiratory system, have been the Abstract Thisstudy examined commercial talc focus of considerable research and contentious debate for deposits in the U.S. and their amphibole-asbestos at least 30 years (Goodwin 1974; Occupational and Safety content. The study found that the talc-forming and Health Administration 1992). Talc-asbestos issues environment directly influenced the amphibole and have drawn renewed attention, such as news reports in amphibole-asbestos content of the talc deposit. 2000 contending that the fibrous talc used to add strength Large talc districts in the U.S. have mined to the best-selling brands of children's crayons contained hydrothermal replaced dolostone. tales that amphibole asbestos (Beard and others 2001). To investi- Hydrothermal talcs, created by siliceous fluids gate the extent and character of amphibole minerals in heated by magmas at depth, consistently lack talc deposits, a group at the U.S. Geological Survey amphiboles as accessory minerals. In contrast, (USGS) is examining the relationships between amphi- mineable talc deposits that formed by contact or boles and talc in U.S. deposits. This study, involving field regional metamorphismconsistently contain examinations and sampling, laboratory analyses, and an amphiboles, locally as asbestiform varieties. extensive literature review, has revealed that a consistent Examples of contact metamorphic deposits occur in occurs within large (commercial) and small relationship Death Valley, California; these talc-tremolite U.S talc deposits-that is, the primary talc-forming deposits accessory amphibole-asbestos. contain Talc environment directly controlled the ultimate amphibole bodies formed by regional metamorphism always content of the talc deposit. contain amphiboles, which display a variety of Talc deposits are the products of metasomatism caused by compositions and habits, including asbestiform. regional metamorphism, contact metamorphism, or Some industrial mineral deposits are under scrutiny hydrothermal processes (meteoric fluids or brines heated as potential sources of accessory asbestos minerals. by distant or buried intrusions). Two of these talc-forming Recognizing consistent relations between the talc- mechanisms-contact metamorphism and hydrothermal forming environment and amphibole-asbestos processes-are well represented by large, historically content may be used in prioritizing remediation or mined deposits in the Death Valley region of southern monitoring of abandoned and active talc mines. California. Results of field and laboratory studies on these Death Valley deposits, described herein, reflect the con- Keywords Talc · Amphibole-asbestos · Geologic sistent associations of amphibole-rich talc deposits with · Hydrothermal · Metamorphic · USA setting contact metamorphism versus amphibole-poor talc with hydrothermal processes. A number of U.S. talc deposits of commercial size (under past or present economic conditions) were formed by metasomatic processes driven by regional metamorphism; Introduction these large bodies consistently contain talc intergrown with amphiboles, such as tremolite and (or) anthophyllite. The presence of amphibole asbestos as minor accessory Debate over the asbestos mineral content (major versus minerals in some talc deposits, and its potential health trace amounts) within these talc-amphibole deposits is the result of differing interpretations of the predominant habit (asbestiform versus non-asbestiform) of the amphibole I Received:26 September2003 / Accepted:24 November 2003 particles.The complicating factors that face analysts ª examining this type of talc ore material are discussed. r r 2004 B. 5. Van Gosen(C 3) H. A. Lowers· 5. 1 Sutley C. A. Gent U.S.GeologicalSurvey,DenverFederalCenter,M.S.905, ASheSt0S Box 25046,Denver,CO80225,USA Email:bvangose@usgs.gov Tel.:+1-303-2361566 Asbestos is a commercial-industrial term with a long his- "Asbestos" Fax:+1-303-2361425 tory, and is not a mineralogical definition. in the 920 EnvironmentalGeology(2004)45:920-939 DOl 10.1007/s00254-003-0955-2 FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 Original artide latter half of the 20th century became widely used in regu- mineral fibers intergrown with the vermiculite deposits parti- latory language to refer to well developed, long, thin mined and milled near the town from 1923 to 1990 (U.S. cles (fibers or fibrils) and fiber bundles of specific mineral Senate Committee on Environment and Public Works compositions, which have fulfilled particular industrial 2000; Dearwent and others 2000). The California Division applications. In the U.S., asbestos is most commonly of Mines and Geology has mapped outcrops of ultramafic defined as the asbestiform variety of 6 naturally occurring rocks in California to indicate country rocks with the hydrated silicate minerals; these include chrysotile, the potential to host chrysotile and actinolite-series asbestos asbestiform member of the serpentine group, and five (Churchill and Hill 2000). Other examples of occupational minerals of the amphibole group: the asbestiform varieties and environmental exposures to asbestos are described in of (1) riebeckite (commercially called crocidolite), (2) Nolan and others (2001). cummingtonite-grunerite (commercially called amosite), The history and study of naturally occurring asbestos, its (3) anthophyllite (anthophyllite asbestos), (4) actinolite associated health impacts, and the multiple, complex (actinolite asbestos), and (5) tremolite (tremolite asbestos) issues that revolve around asbestos are discussed in (Occupational Safety and Health Administration 1992). The Campbell and others (1977), Ross (1981), Zoltai (1981), qualities of asbestos that make it useful and desirable for Levadie (1984), Skinner and others (1988), Mossman and commercial use are its high tensile strength, flexibility, Occupational Adminis- and others (1990), Safety and Health its resistance to heat, chemicals, and electricity. tration (1992), Guthrie and Mossman (1993), Nolan and The inherent properties of asbestos-fibers that are dura- others (2001), and Virta (2001, 2002). Current federal ble, long, and thin-appear to contribute to the toxicity of regulations are provided in the Code of Federal Regula- these mineral particles when lodged inside the human tions (CFR), including regulations on occupational expo- respiratory system (Stanton and others 1981; Wylie and sures to asbestos excepting construction and ship-related others 1993). Occupational exposures to asbestos have work (CFR 29, part 1910.1001); CFR regulations are been linked to asbestosis (scarring of the lungs, "pulmo- updated as needed on July 1. nary interstitial fibrosis"), lung cancer, and malignant mesothelioma (tumor development within the pleural membrane perito- lining the chest cavity and (or) in the neum lining the abdominal and pelvic walls and their vis- EXpl0itable talc deposits cera) (Skinner and others 1988; Mossman and others 1990; Guthrie and Mossman 1993; Nolan and others 2001). His- and amphiboles torically, chrysotile has accounted for more than 90% of the world'sasbestos production, and presently over 99% of the Talc is a hydrous silicate with an idealized composition of world production (Ross and Virta 2001; Virta 2001, 2002). Mg3Si40m(OH)2, but can contain major amounts of Fe, Whereas mining, processing, and use of chrysotile has been minor Al and F, and trace Mn, Ti, Cr, Ni, Ca, Na, and K much more common, several studies suggest that amphi- (Evans and Guggenheim 1988; Greenwood 1998). Signifi- bole asbestos, even when occurring as a minor accessory in cant talc deposits occur in the U.S. in the Appalachians, chrysotile deposits, may be the primary cause of meso- from Vermont to Alabama, in the West in Montana, thelioma in asbestos-related occupations (Ross 1981, 1984, California, Nevada, Washington, Idaho, and New Mexico 2001; Mossman and others 1990; Browne and Wagner 2001; (Piniazkiewicz and others 1994). Large deposits also occur Gibbs 2001; Langer 2001; Pooley 2001a, 2001b). As noted by in Texas, and small soapstone mines once operated in Mossman and others (1990, p. 296): "The persistence of Arkansas, but economic deposits are otherwise lacking amphiboles in human lungs may be attributed to their between the Appalachians and the Rocky Mountains. increased ability to penetrate the peripheral lung, lack of Commercial talc deposits have replaced two general rock clearance, or durability". Wagner and others (1960) types: (1) Dolostone (dolomite or dolomitic marble), which described the high rates of malignant mesothelioma in were selectively replaced by reactions with large volumes of workers and nearby residents of crocidolite (asbestiform heated waters carrying silica in solution, mobilized by riebeckite) mines in the Cape Province of South Africa. magmatic or metamorphic mechanisms. The dolostone- Following publication of that study in 1960, mesothelioma hosted replacement deposits range from cm-thick pods to became increasingly recognized as an occupational risk in the 29-m-thick talc body at the Treasure Chest mine near the mining, milling, and handling of rocks that contain Dillon, Montana (Berg 1979). Today and in the past, the amphibole asbestos and their by-products. largest talc producing districts in the U.S. exploited talc In recent years, there has been a renewed focus upon the deposits replacing dolostone, and to a lesser extent, mag- hazards related to inhalation of amphibole asbestos; in nesite. (2) The second common talc hosts are ultramafic particular, exposures due to the mining and processing of rocks, mainly dunites and peridotites, altered by metaso- some amphibole-bearing industrial mineral deposits, as matism through contact or regional metamorphism. Mag- well as environmental exposures to amphibole-rich nesium silicates in these rocks reacted with SiOrsaturated bedrock, such as road cuts and excavations that expose aqueous pore fluids during metamorphism to form nearly asbestos-bearing rock (Browne and Wagner 2001). For monomineralogic bodies of talc adjacent to zoned example, unusually high incidences of asbestos-related sequences of talc-carbonate-, calcic amphibole-chlorite-, mortality and respiratory disease in the small town of and chlorite-dominant zones in addition to complexly Libby, Montana, have been attributed to amphibole mixed zones (described by Sanford 1982). These deposits EnvironmentalGeology(2004)4S:920-939 921 FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 Original artide form rinds on the ultramafic bodies or nearly replace them; randomly selected talcose rock at each particular sample they are typically tabular or lenticular talc bodies that can spot. The samples are intended to represent the talcose reach 100 m in thickness and extend more than 300 m in material mined at each site, collected mainly from mines length. Large deposits of this type are mined in Vermont, that are inactive and abandoned, excepting those samples and smaller deposits have been mined in other eastern collected from an active open pit of the Yellowstone mine, states, California, and Texas. The ultramafic-hosted southwest Montana. deposits have been equally important sources of pure talc Dust coating the inside of the plastic sampling bag was and darker talc (soapstone), the dark talcose bodies owing examined using a JEOL 5800-LV scanning electron their coloration to amphibole, serpentine, and chlorite microscope (SEM), equipped with an Oxford ISIS energy- impurities (Piniazkiewicz and others 1994). dispersive system (EDS) with ultra-thin window detector. The host rock composition and process of formation The EDS provided semi-quantitative chemical data that determines the qualities of talc, which in turn affects the was reduced using the Oxford ISIS standardless software industrial of a particular applications deposit. The grain with the ZAF correction procedure selected. Analyses were size and shape, color, and purity of talc influence its uses performed on single, isolated structures, not on fibers that (Piniazkiewicz and others 1994). In addition, the talc- The operating condi- lay across other mineral particles. forming mechanism-hydrothermal processes, contact tions of the instrument were 15 kV, 0.5-3 nA (cup), and metamorphism, or regional metamorphism-directly approximately 30% dead time. These conditions would influenced the ultimate amphibole content of the talc ore excite an analysis volume of ~2 µm. body, described below through examples. Within a single The matrix corrections used do not account for particle mineral deposit, such as some talc ore bodies, amphibole geometry. However, Small and Armstrong (2000) demon- crystals may range in habit from blocky to prismatic to strated that at 10-15 kV (utilized geometry- by this study) acicular to asbestiform. In describing amphibole asbestos, induced errors in the analyses of particles can be relatively Wylie (2000, p. 56) notes that: "Amphibole-asbestos fibrils small. One of the amphibole-rich study samples was µm" range in width from about 1 to 0.01 and "individual analyzed by EDS and by electron probe microanalysis with fibrils and bundles of fibrils may attain lengths of wavelength dispersive spectroscopy (WDS) to evaluate the hundreds to thousands of times their widths". accuracy of the EDS measurements. Table 1 shows the comparison of analytical resultsby EDS and WDS. The amphibole nomenclature used in this study follows the recommendations of Leake and others (1997). Study methodS Samples for x-ray diffraction (XRD) analyses were pul- verized and mechanically split. The minerals identified by Samples of talc ore material were collected at several mine XRD in the samples were categorized as major, minor, and "Major" sites, which are described below. Each sample was trace mineral constituents of the analyzed split. collected as a composite, containing at least 30 pieces of minerals are estimated to comprise >25 wt% of the Table 1 and single unpolished grains, and (2) electron probe microanalysis Comparison of the analyses of tremolite particles in one tremolite- with wavelength dispersive spectroscopy (WDS) on polished grains. rich specimen from the Death Valley region, as measured by two Data are expressed in cation proportions, which were calculated by techniques: (1) energy dispersive x-ray analysis (EDS) on polished stoichiometry using 23 oxygen atoms Mount Particle Analysis K Na Ca Mn Fe Mg Ti Al Si type L xW method (µm) Polished 203×I06 WDS 0.01 0.06 1.88 0.01 0.04 4.93 bdl 0.03 7.99 EDS bdi bdi 1.7 bd) 0.1 4.9 bd! bdl 8.I Polished 362×226 WDS 0.01 0.06 1.88 0.01 0.05 4.94 bdl 0.03 7.97 EDS bdl bdl 1.7 bdi bd! 5.0 bd1 bdl 8.1 Polished 620×228 WDS 0.01 0.06 1.87 0.02 0.06 4.90 bd! 0.03 8.00 EDS bdl bdl 1.7 bdl 0.1 5.0 bdl bdl 8.1 Polished 241×28.8 WDS 0.01 0.05 1.88 0.02 0.06 4.94 bdl 0.03 7.99 EDS bdl bd1 1.8 bdl bdl 4.9 bdl bd1 8.1 Polished 140×14.3 W DS 0.01 0.05 1.85 0.02 0.06 4.93 bdl 0.04 8.00 EDS bdl bdl 1.8 bdi 0.1 5.0 bdl bd! 8.1 Loose 225×170 EDS bd! bdl 1.8 bdl 0.1 4.9 bdl bd! 8.1 Loose 445×l66 EDS bd! bd! 1.8 bd! 0.1 4.8 bd1 bdi 8.1 Loose 104×27.1 EDS bdl bdl 1.7 bdl 0.1 5.0 bdt bdl 8.1 Loose 20.2×3.4 EDS bd! bdl 1.7 bdl 0.1 5.1 bd! 0.1 8.0 Loose 18.5×0.9 EDS bdl bdi 1.8 0.1 0.1 5.2 bdl bdl 7.9 Loose 5.8×0.8 EDS bdl bdl 1.7 0.1 0.2 5.1 bdl 0.1 7.9 Loose 6.7×l.1 EDS . bd! bdl 1.9 bd! 0.1 5.3 bdl bdl 7.8 Loose 3.9×l.5 EDS bdl bdl 1.8 bdl bdi 5.0 bdi 0.1 8.0 Loose 13.4x1.0 EDS bdl bdl 1.8 0.1 0.1 5.1 bdl 0.2 7.9 bdl, below the detection limit of the analytical technique 922 EnvironmentalGeology(2004)45:920-939 FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 Original article "minor" sample, minerals form 5-25 wt% of the sample, Talc City district, California "trace" and minerals form <5 wt% of the sample. These The historical significance of the Talc City mining district estimates were based on the experience of the XRD oper- in California from World War I through the 1940s is well ator with his instrumentation and its data output. The documented by Page (1951). The district is in the Talc City pulverized splits examined by this study provide snapshots Hills about 47 km southeast of Lone Pine, California. Page of the mineralogy ·and variability in the talcose ores. visited and sampled the district pro- during its peak of However, quantitative estimates of the talc or amphibole duction in the mid 1940s; the reader is referred to his content should not be interpreted from the XRD results report (Page 1951) for descriptions of the district's geol- shown in this report. ogy, talc deposits, and mines. Gay and Wright (1954) The XRD techniquecan identify the amphibole minerals completed a geologic map of the Talc City area. within a sample as members of the tremolite-actinolite- The talc deposits of the Talc City district are thick lenses ferroactinolite series, but is not able to determine the and irregular masses hosted mainly by dolomite. To a specific amphibole species. It is also not possible to posi- much lesser extent talc bodies occur in "silica rock", tively distinguish between tremolite and the sodic-calcic named by Page (1951) for an unstratified, massive rock amphiboles winchite and richterite by XRD. composed mostly of interlocking quartz; it resembles quartzite in outcrop. Limestone is also nearby. Bedded dolomite is altered to massive dolomite adjacent to the talc deposits; both are often closely associated with silica rock. The silica rock is discontinuous at the mine sites, forming Amphibole-poor talc deposits isolated lenses surrounded by massive dolomite. Silica formed by hydrothermal processes rock appears to be partially replaced by talc at some of the deposits. Petrographic examination of the silica rock Geologic environments that host reveals microscopic patches of talc in interstitial areas hydrothermal talc deposits between grains (Page 1951). quartz "hydrothermal" The term is commonly used in a general Granitic bodies crop out from about 0.8 to 3.2 km distance sense to describe the actions and products of hot fluids, from the mines. The granitic rocks locally have been often, but not always, implying an association with igneous hydrothermally altered, suggesting they were affected by processes. In this discussion, hydrothermal talc refers to the talc-forming hydrothermal event(s) and were not the deposits thought to be the products of fluids heated by a of fluids. Dikes source ranging in composition from basalt distant magma usually at depth. For example, in source, to diorite crop out near the Talc City and Frisco to felsite the Talc City district, California, no evidence of contact or mines (Page 1951). These dikes are also hydrothermally regional metamorphism is apparent in the host or country altered and interpreted to predate the talc alteration (Page rocks; the source of the heat that drove the talc-forming 1951). A magmatic source of hydrothermal fluids is not process is not obvious, and has been attributed to buried obvious within the district. If buried, it may be best viewed or distant igneous intrusions. Heat sources for the south- methods. by geophysical west Montana talc event(s) are speculated to be sills that Page (1951) proposed a model for talc formation in the intruded an overlying Proterozoic basin, heating and Talc City area that involved the following events: circulating basin brines towards underlying Archean talc" 1. The area was originally covered by mostly limestone, marbles. Thus, "hydrothermal refers to talc ore with lesser mterbeds of dolomite, shale, and sandstone; bodies that are not directly associated with regional 2. Hydrothermal fluids rich in Mg rose through and metamorphism and are not found directly against an fractured the overlying limestones and altered them igneous intrusion. into massive dolomite, perhaps also converting The large, amphibole-poor, hydrothermal talc deposits of sandstones to the "silica rock"; southwest Montana, Talc City, California, and west Texas, 3. A second event of fracturing accompanied another as examples, may represent the products of saline, sili- influx of hydrothermal waters enriched in S1 and Mg, ceous fluids mobilized by basin-scale or localized mag- which replaced massive dolomite with large talc matic activity. This genetic association is supported by the deposits and replaced sihca rock with talc lenses. Page recent fluid-inclusion study by Gammons and Matt (2002) of the hydrothermal tale deposit currently excavated at the (1951) suggested the talc formed by the addition of silica and water to dolomite, and the addition of silica, Yellowstone mine, southwest Montana, which indicated the presence of highly saline fluids during the talc for- water, and Mg to silica rock. This general reaction, shown below, is commonly invoked to explam the mation. They proposed that "high heat flow, enhanced by replacement of dolomite by talc: injection of thick sills into the (Proterozoic) sedimentary pile, forced connate brines out of the bottom of the Basin and into the underlying or adjacent 3 dolomite + 4Si02%) + 1H2O = 1 talc +3 calcite +3CO2 (Proterozoic) Precambrian basement, where they caused retrograde metamorphism and formation of economic talc and Abundant and shearing of country rocks in the deposits" fracturing chlorite (replacing dolomitic marble and quar- district suggest that fracture systems controlled and aided tzo-feldspathic gneiss, respectively) (Gammons and Matt fluid flow and talc formation. Page's interpretations 2002, p. 44). are based on field relationships. However, by general EnvironmentalGeology(2004)45:920-939 923 FILED: ERIE COUNTY CLERK 03/17/2023 08:48 PM INDEX NO. 815818/2020 NYSCEF DOC. NO. 289 RECEIVED NYSCEF: 03/17/2023 Original artide appearances, the talc deposits and associated rocks of the southwest Montana talc bodies are lenticular and elongate, Talc City district do not display features typical of regional and in most places, talc lenses are parallel to the lithologic metamorphic processes, such as prominent foliation or layering of the marble. However, talc bodies cut across compression structures. layering at the Yellowstone mine (Cerino 2002). The study sampled talc ore from pits or dumps at five sites The origin of the southwest Montana talc deposits is not in the Talc City district (Tables 2 and 3). No evidence of completely understood, but recent work has reaffirmed amphibole minerals was found in ore samples from this earlier observations that the talc bodies appear to have district based on x-ray diffraction (Table 2) and SEM-EDS formed during the Precambrian because they are restricted analyses of the samples. Platy talc is mixed with small to Archean dolomitic marbles and do not replace overlying amounts of calcite, clinochlore, dolomite, quartz, kaolinite, Cambrian dolomites. This observation was supported by a vermiculite (uncertain identification) and K-feldspar (lis- published age of 1.36 Ga by the ®Ar/39Ar method for ted left to right in decreasing abundance). A friable white muscovite intergrown with talc in the Ruby Range (Brady layer interlayered with the talc ore body at the Frisco mine and others 2003). A recent fluid inclusion study of the consists of mostly quartz with accessory plagioclase, Yellowstone mine deposits (Gammons and Matt 2002, muscovite, dolomite, talc, and kaolinite. Thus, none of the p. 44) determined that "the fluids responsible for talc descriptions of Page (1951), nor the results of our sam- formation were saline brines (roughly 7x saltier than pling and mineralogical analyses, indicate the presence of modern seawater), and were enriched in CaCl2". They amphiboles in the talc deposits of the Talc City district. calculated burial depths during talc formation of more than 3 km at formation temperatures of 190 to 250 °C. Their model for talc formation at the Yellowstone mine Yellowstone mine, southwest Montana site involves saline fluids that descended along growth The Yellowstone talc mine is on the northeast flank of the faults in an overlying Proterozoic basin that may have Gravelly Range near Ennis, Montana. This enormous talc existed above the Archean dolomitic marbles at about (greater than 5.5 million short tons of known body reserves) 1.36 Ga; they suggested the saline fluids were either sup- is the largest known in southwestern Montana, a region that plied by connate brines in the basin sediments or by contains a total of 57 talc mines, talc prospects, and known seawater. Their model, as well as earlier models overlying talc occurrences (Berg 1979; Van Gosen and others 1998)· in southwest Montana for talc formation (Olson 1976; The Yellowstone mine is the largest talc-producer in the Anderson and others 1990; Brady and others 2003), invoke U.S., and two other large talc mines, the Regal and Treasure very large water to rock ratios to form these deposits, State mines, currently operate farther to the west in the Ruby through the general reaction: Range. All three mines are open-pit operations. All of the economically important talc deposits in the Ruby 3 dolomite + 4Si04,q) + 4H20 = 1 talc + 3Ca2+ + 6HCO3 and Gravelly Range region of southwest Montana replaced dolomitic marbles of Archean age. In much smaller Anderson and others (1990) suggested that water to rock amounts, talc also replaced magnesite, quartz, tremolite, ratios of more than 600 are required by this reaction to serpentine, and calcite, which are accessory constituents of carry sufficient silica in solution and flush most of the the host marble (Berg 1979). Talc occurrences range from calcite out of the system. veinlets and pods centimeters thick up to huge masses, Regardless of the source of the hydrothermal fluids or the such as the thick talc body at the Yellowstone mine, which circulation mechanism, the end result at the Yellowstone is at least 30 m thick (bottom not yet found). Most of the mine site is large bodies of mainly massive talc with light Table 2 Mineral abundances in samples Site name, Latitude, Minerals identified of hydrothermal talc ore col. sample number longitude by x-ray diffraction lected from abandoned talc mines in the Talc City district Major Minor Trace near Lone Pine, California. The latitude and longitude values