STATE OF CALIFORNIA EARL WARREN. Governor DEPARTMENT OF NATURAL RESOURCES WARREN T. HANNUM, Director DIVISION OF MINES Ferry Building, San Francisco 1 1 OLAF P. JENKINS. Chief AN FRANCISCO SPECIAL REPORT 8 AUGUST 1951 TALC DEPOSITS OF STEATITE GRADE INYO COUNTY, CALIFORNIA By BEN M. PAGE Prepared in Cooperation with the United States Geological Survey Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/talcdepositsofst08page TALC DEPOSITS OF STEATITE GRADE, INYO COUNTY, CALIFORNIA f By Ben M. Pace * OUTLINE OF REPORT Page __ 3 Illustrations — Continued \BSTRACT INTRODUCTION 5 Acknowledgments (5 Location 6 Topography and accessibility 6 Climate, water, and timber }EOLOGY 7 Llthology 7 Geologic structure 9 Comparative features of individual deposits 9 Physical characteristics 9 Origin 12 Size and shape of ore bodies 13 Reserves 13 MIXES AND PROSPECTS 13 Talc City mine 13 Alliance mine and Irish lease 20 Alliance mine 21 Irish lease 22 White Mountain talc mine 23 Florence mine 27 Trinity talc mine 29 East End mine and Bob Cat claims 29 Frisco talc mine 30 Victory talc mine 30 Viking talc mine 31 White Swan talc mine 31 Lakeview talc mine 31 Blue Stone talc mine 32 Willow Creek talc mine 32 White Eagle talc mine 33 Eleanor talc claim 35 BIBLIOGRAPHY 3", Illustrations Plate 1. Surface geology of the Talc City mine, Inyo County In pocket 2. Geology of B, C, I), and Intermediate levels, Talc City mine In pocket 3. Vertical sections, Talc City mine In pocket 4. Surface geology of the Alliance talc mine and Irish lease, Inyo County In pocket 5. Geologic plans and section of underground workings, Alliance talc mine, Inyo County__ In pocket 6. Surface geology of the White Mountain talc mine, Inyo County In pocket 7. Geologic cross-sections, White Mountain mine, Inyo County In pocket 8. Geologic map of adits, White Mountain mine In pocket 9. Geologic map of the South Deposit, Florence tale mine, Inyo County In pocket 10. Surface and underground geology of the Frisco talc mine, Inyo County In pocket 11. Geologic map of the White Eagle mine, Inyo County In pocket Page Figure 1. Photo of ceramic insulators made of steatite^. 4 2. Photo of ceramic articles made of steatite 5 3. Index map of steatite deposits 7 4. Photo of Tale City mine 9 5. Geologic map of Talc City mine area 10 6. Photomicrograph of massive dolomite, Talc City mine 11 Figure i. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 2"). Page t Published by permission of the Director, U. S. Geological Sur- vey. Manuscript submitted for publication January 1951. * Geologist, U. S. Geological Survey. Photomicrograph of slightly altered silica rock, Frisco mine ]■_> Photomicrograph of high-grade steatite from Talc City mine i;j Geologic maps and section, East Side work- ings, Talc City mine 17 Geology of miscellaneous adits, Talc City mine 19 Diagram of parts of West and Central ore bodies, Talc City mine 20 Photomicrograph of silica rock from Alliance mine o () Photomicrograph of silica rock from Alliance mine 21 Photomicrograph of steatite from Alliance mine oj Cross-section of the Irish lease 23 Photo of White Mountain mine 24 Photomicrograph of silica rock. White Moun- tain mine 25 Photomicrograph of silica rock. White Moun- tain mine 26 Map and cross-section of Main adit, South Deposit, Florence mine 28 Cross-section, Viking talc mine 31 Cross-section, White Swan mine 32 Cross-section, Willow Creek mine 33 Geologic section at main quarry, White Eagle mine 34 Photomicrograph of talcose granitic rock, White Eagle mine 34 Sketch section, Eleanor talc mine 35 ABSTRACT Steatite is exceptionally pure talc suitable for the manufacture of high-frequency radio insulators and for other exacting uses. It was a critical mineral during World War II. At the beginning of the war there was a single major domestic source, the Talc City mine, Inyo County, California. During the war talc from several other mines in California, Nevada, New Mexico, and Montana was utilized as steatite. California continues to lead in the production of domestic steatite. All known steatite deposits in the State are in Inyo County. Talc of near-steatite quality occurs in other California counties, but has not proved acceptable to manufacturers of high frequency insulators. At the end of 1942 the known steatite reserves of Inyo County were estimated to be only 8(i,7(M) tons and the rate of production was computed to be equivalent to about 15,(MK) tons annually. Produc- tion slackened somewhat, and exploration and development since 1942 have revealed substantial tonnages of steatite which tend to maintain known reserves. The supply of Inyo County steatite is seriously limited, however. Many of the Inyo County steatite deposits are geologically similar in some respects. Limestone is the most prevalent original rock. Massive dolomite of hydrotbermal origin has replaced the lime- stone in areas measuring hundreds or thousands of feet in breadth. Unaltered remnants of limestone occur as "islands" in the tracts of massive dolomite. Silica rock resembling quartzite also forms islands in some of the massive dolomite. The talc deposits are com- monly ragged, elongated, steeply-dipping bodies in massive dolomite or silica rock. They are of hydrotbermal origin and are generally localized at lithologic contacts along which some differential move- ment has occurred, but some are localized by faults or minor shears within a single rock type. There are various host rocks. Steatite ore bodies have been formed by the replacement of massive dolomite at Talc City. East End. Victory, Trinity, and White Swan mines ; steatite ore bodies have resulted from the replace meiit of silica rock at Alliance, Irish, Frisco, Viking, and White (3 Special Report 8 Talc Deposits op Steatite Grade, Inyo County fountain mines; steatite has replaced limestone at the Blue Stone nd Willow Creek mines; tale of near-steatite quality has replaced ranite at the White Eagle mine. Therefore, the steatizing solutions re not strictly selective in their action, although they show a prefer- nce for certain host rocks. INTRODUCTION "Steatite" in a mineralogical sense means soapstone •r massive talc, but in present-day industry the word has . different connotation. In commercial usage and in this eport, steatite means exceptionally pure talc l suitable i for use as the principal ingredient in certain ceramic jodies. Because these bodies are widely employed for ligh-frequency insulators in radios and other military ind civilian equipment 2 (see fig. 1), steatite was included n the list of critical minerals during World War II. Although steatite has never been adequately defined, t is generally understood to mean certain varieties of ale containing less than 1.5 percent CaO, less than 1.5 percent Feo03, and minute amounts only of other chemi- 'al and mineral impurities. The commercial designation steatite is also dependent upon favorable firing proper- ties, and satisfactory electrical and physical character- istics of the final product. 3 Commercial acceptance is generally contingent, moreover, upon adequate supplies i)f uniform material, as the dies of the manufacturer are designed for raw material of constant shrinkage prop- erties. Lava-grade block talc is a variety of steatite dis- tinguished by its suitability for machining. It must be free of flaws and must not crack during firing. Formerly, lava-grade block talc was the only type of steatite used for insulators. Now, however, it is employed only in rela- tively small quantities for spacers in radar vaccuum tubes and for other specialized purposes. Since the discovery in the early 1920 's that pulverized talc could be used for making insulators, most steatite has been ground before firing. It is mixed with a binder, and pressed or extruded into the required shapes. Because of these technical ad- vances, the definition of steatite does not stipulate blocky characteristics. During World War II emphasis was placed upon the importance of steatite in the manufacture of radio insulators, and consumption of the raw material was re- stricted to such purposes. However, steatite is equal, or superior, to ordinary talcs for many less exacting uses. Therefore, it has been used during peacetime in the manu- facture of high-quality paper, cosmetics, insulating cores for electric stoves, gas burner tips, and many other items. The consumption of steatite for certain nonessential pur- poses constitutes a problem in conservation. Foreign countries, including France, Italy, and Manchuria, provided much of the steatite-grade talc used in the United States prior to World War I, when Cali- fornia became an important producer. During the years 'A good discussion of talc in general, with references, will be found in Engel, A. E. J., Talc and ground soapstone in Industrial minerals and rocks : Am. Inst. Min. Met. Eng., pp. 1018-1(141, 1949. 2 Anon., Talc: Ceramic Industry, vol. 32, pp. 38-40, 1949. This gives other references on the ceramic uses of talc. 3 A Conservation Order of the War Production Board (M-239, March 28, 1944, as amended, p. 1) imperfectly defines steatite as follows: " 'steatite talc' means naturally occurring magnesium silicate both crude and beneficated, suitable for use in the manufacture of electrical insulators and containing not to exceed one and one-half percent (1J%) lime (CaO), not to exceed one and one-half percent xcept at the properties which are over 5,000 feet above ;ea level. Juniper and pifion, but no large trees, grow in iome of the higher areas. Figure 3. Index map showing location of California steatite and near-steatite deposits on record in 1942. All are in Inyo County. Inset gives location of area in outline map of state. GEOLOGY A reconnaissance of the Inyo Range is described by Knopf and Kirk, 9 and the reader is referred to their paper for a general discussion of part of the area. How- ever, the talc deposits are not mentioned by Knopf and Kirk, and the major deposits including those of the Talc City mine (see fig. 5) lie to the southeast of the terrain covered in the reconnaissance. Most of the steatite deposits are associated with three kinds of rock : limestone, silica rock, and massive dolo- mite. The limestone, Paleozoic ( ?) in age, is the principal original rock. The "silica rock" of this report is a quartzite-like material ; it may be recrystallized sandstone, or it may be a product of hydrothermal alteration. The massive dolomite is definitely an alteration product de- rived mainly from limestone. The typical areal distribution of the three characteris- tic rocks is as follows (see fig. 5) : The limestone occurs " Knopf, Adolph, A geologic reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, California ; with a section by Kirk, Edwin, The stratigraphv of the Inyo Range: U. S. Geol. Survey, Prof. Paper 110, 130 pp., 1918. chiefly as extensive tracts, within which arc large areas of massive dolomite. The massive dolomite areas contain "islands" of unaltered limestone, islands of silica rock, and talc deposits. The massive dolomite is the most preva- lent rock in the immediate vicinity of the mines. The majority of the steatite deposits are lenses or irregular masses in dolomite or silica rock. Much of the steatite is along contacts between two rock types, but some is localized by fractures within a single rock unit. Exceptions to the above generalities include deposits in which massive dolomite is lacking, or in which silica rock is absent. Some steatite is associated with various rocks that are not present at the more typical deposits. Granitic rocks are exposed within half a mile to 2 miles of most of the steatite mines, and one deposit of un- certain quality is largely within a granitic host rock. Lithology The rocks of the Inyo County steatite areas are un- correlated units which show some resemblances from mine to mine. The stratigraphy is not yet understood ; the age of the sedimentary formations is not known, some of the rocks are secondary products, and other rocks (e.g., the silica rock) may or may not have a stratigraphic posi- tion. For these reasons, it is impossible at present to give a columnar section for the various talc deposits. The lithologic features that are possessed in common are de- scribed here, and local characteristics and additional rock varieties will be treated in the descriptions of individual mines. Limestone. The oldest rocks in the immediate vicin- ity of the steatite mines are limestone. The age is probably Paleozoic, but positive evidence is lacking. Undoubtedly more than one formation is represented ; however, the strata have not been assigned to formational units. Expanses of limestone, extending partly around the periphery of the principal mine areas, form the back- ground of most of the talc deposits (see fig. 5). Limestone also occurs as remnants within the mine areas, where much of it has been altered to massive dolomite. The sev- eral lithologic varieties may be grouped into two main types. The most prevalent type of limestone, exemplified at the Talc City mine, is a well-stratified gray rock with subordinate thin white layers a fraction of an inch thick. Locally it is slightly fissile, but is not highly jointed. Dur- ing weathering it develops smooth outcrop surfaces. This rock is easily scratched by steel, and effervesces vigor- ously in cold, dilute hydrochloric acid. A few layers con- tain poorly-defined crinoid (?) fragments, and others contain minute bits of carbonized plant remains. A second, less plentiful, type of limestone is dense, relatively hard, siliceous, and contains dolomitic beds. This variety is black, weathering to a pale-gray or tan- gray color, and it commonly contains flint or siliceous streaks with coarser texture than flint. It is distinctly stratified in beds :] inches to '1 feet thick, but is not thinly laminated or platy except where altered. It is scratched less easily than pure limestone, and efferveces less readily in cold, dilute hydrochloric acid. The "stratified dolomite and limestone" of the Talc City mine and the "flinty dolomitic limestone" of the White Mountain mine are examples of this type of rock. Special Report 8 Silica Rock. A silica rock, consisting of quartz and closely resembling quartzite, is prominent in most of the Inyo County steatite areas. It forms strong, massive out- crops. The silica rock is unstratified, and contains no fossils. It is gray where fresh, but in many places it weathers dark brown. The brown color is helpful in dis- tinguishing the rock from the massive dolomite which commonly surrounds it. The silica rock cannot be scratched by steel, and when it is struck by a hammer sparks sometimes are produced. The silica rock generally occurs in isolated, discon- tinuous patches of peculiar shapes, within areas of mas- sive dolomite (fig. 5). Lack of areal continuity and lack of systematic structural arrangement are the most puz- zling features of the rock. Two hypotheses regarding the silica rock are as fol- lows : (1) At one time it may have been sandstone, which has since been partly recrystallized. If so, it should prop- erly be termed quartzite. Or (2) it may be a product of hydrothermal alteration of dolomite. The first hypothesis is supported by the fact that ordinary quartzites do occur in the Inyo Range; an im- portant example is the Eureka quartzite (Ordovician), which serves as a marker bed in the range. 10 Some steatite deposits of the region are clearly associated with ordinary quartzite, as at the Blue Stone mine (fig. 3). Possibly the silica rock of most of the steatite deposits is also quartzite. This possibility is favored by the texture of some, but not all. of the silica rock; locally the quartz grains are well- rounded, as in many sandstones. The main objections to the theory that the silica rock is quartzite are occasioned by the distribution. The rock must have been a stratiform sedimentary formation at one time, if it is quartzite, but obviously it is no longer strati- form in its typical occurrences. The separate patches of silica rock cannot be explained as the result of erosion of a formerly continuous stratum, because the distribu- tion is as erratic at depth as it is on the surface of the ground. The field relations cannot be interpreted purely as a result of faulting, as the requisite faults for such a theory do not exist. If the silica rock actually represents former sandstone beds, there are two possible explana- tions for its present lack of stratiform continuity: (1) parts of the sandstone may have disappeared by con- version into dolomite; (2) the sand of the original sand- stone beds may have been gathered into separate masses by some process which produced the present scattered discontinuous bodies of silica rock surrounded by un- broken dolomite. According to this view, the gathering-up of the sand, forming isolated masses, was accomplished before the dolomitization of the bordering rocks, as the massive dolomite shows no corresponding deformation. The hypothesis of hydrothermal origin readily ex- plains the field relations of the silica rock. According to this hypothesis, hot waters rose upward through the dolomite and altered it to silica rock. This occurred only where fractures, temperature, pressure, or chemical con- ditions were appropriate; therefore, the silica rock was produced not as a continuous mass, but as a number of separate bodies. The hydrothermal interpretation is fa- vored by the lack of bedding in the silica rock, and by the virtual absence of minerals other than quartz; there are "' Merriam, Charles W., oral communication. practically no grains of feldspar on ferromagnesian min- erals. The texture of some of the rock is in accord with the hydrothermal hypothesis, as some specimens show irregularly shaped grains closely fitted together along intricate boundaries. This is inconclusive evidence, how- ever. Silica rock is second only to massive dolomite as a host rock for steatite. Steatite-bearing silica rock gen erally occurs as "islands" in massive dolomite. This is the relationship at the Alliance mine, for example. However, some of the talc at the White Mountain mine is in silica rock that is 50 to 100 feet outside the dolomite area. Massive Dolomite. Limestone has been altered to massive dolomite in the immediate proximity of the talc deposits. The color of the dolomite ranges from white to gray to black, probably because carbonaceous material in vary- ing amounts is retained from the original limestone. Out- crops of massive dolomite are extensive and prominent, and commonly have harsh, hackly surfaces. The rock surfaces are criss-crossed by small grooves which look as though they had been made by the dull edge of a knife. The grooves are spaced approximately ^ to 1 inch apart, and are caused by the solution of thin calcite seams that occupy joints in the dolomite. The massive dolomite is devoid of bedding, unlike the limestone of the district, and it contains no remnants of fossils. It is tougher and harder than the limestone, but may be scratched by steel. The dolomite must be scratched or pulverized before it will effervesce in cold, dilute hydrochloric acid ; however, the numerous calcite seams effervesce more readily and may be misleading. The massive dolomite varies in grain size. In many specimens the grains are barely discernible with a hand lens. In other specimens, they are easily seen by the naked eye, and the rock is best described as a dolomitic marble. The field relations of the massive dolomite point to a hydrothermal derivation from limestone. The dolomite areas are partly bordered by unaltered limestone, and the limestone beds locally terminate against the dolomite rather abruptly. The relationships cannot be explained by faulting, as the limestone is not separated from the dolomite by gouge, breccia, slickensided surfaces, or other evidence of faults. In places the dolomite has invaded limestone in tongues and cross-cutting bands, obliterat- ing the bedding. Within the dolomite areas, islandlike remnants of unaltered limestone are found. The dolo- mitized zones are unrelated to topography, open fissures, or indications of weathering ; therefore, they cannot be ascribed to the action of meteoric waters. Massive dolomite is pre-eminent as a host rock for steatite. Most of the deposits are in, or adjacent to, mas- sive dolomite. This is illustrated by 12 of the 15 steatite properties examined in Inyo County. Some of the ore bodies are completely enveloped by dolomite, as at the Trinity mine, but some are within islandlike patches of other rock isolated within the massive dolomite ; the steatite-bearing "islands" consist of silica rock, stratified dolomite, or limestone. A few deposits are just outside the periphery of dolomitized areas. Other Rocks. Slate and thin-bedded sandstone, in minor amounts, are associated with the limestone of the Irish lease (fig. 3), and a small thickness of hornfels occurs southwest of the Talc City mine (fig. 5). Talc Deposits of Steatite Grade, Inyo County Figure 4. View of Talc City mine from the southeast. OH — west glory hole ; HF — headframe of main shaft ; BA — B level adit. Granitic igneous rocks are exposed in the vicinity of some of the talc deposits. Megascopically they appear to range from granite to granodiorite or quartz monzonite. Some of the granitic areas near the talc mines are located as follows : one is between Keeler and Darwin, just south of the Talc City mine ; another is on the east side of the Inyo Range just north of the White Mountain talc mine ; and a very large granitic area, shown by Knopf u be- tween Independence and Saline Valley, extends to the White Eagle and Willow Creek talc mines near the north end of Saline Valley (fig. 3). The relations between the plutonic rocks and the other petrologic units are only partly understood, but Paleozoic ( ?) limestone and hornfels are intruded in some places (fig. 5). The granitic rocks of the Inyo Range are probably outlying extensions of the plutonic complex of the Sierra Nevada. If this is so, their age is probably late Jurassic or early Cretaceous. Dike rocks ranging from basalt or diabase to light- colored felsite occur near the Frisco, Talc City, and White Mountain mines. The dikes cut across Paleozoic ( ?) lime- stone and the granitic rocks, and small altered dikes have been found in the massive dolomite. Geologic Structure Folds. The unaltered rocks (chiefly limestone) in the vicinity of the steatite mines are generally folded. For example, north of the Talc City mine there is a pair of tightly compressed synclines, south of the mine there are several isoclinal folds, and to the east and west of the mine the beds dip from 50° to 90° (fig. 5). The rocks of some of the steatite areas show no fold axes, but nevertheless dip moderately to steeply, and probably represent the limbs of former folds. Some folds in limestone have been practically obliter- ated by dolomitization, the massive dolomite retaining only a few remnants of stratified limestone. The orienta- tion of the unreplaced strata indicates the probable pre- dolomite structure ; this is illustrated at the Talc City mine. The major folding in the region occurred before the emplacement of the granitic intrusions, according to Knopf, 12 and is probably late Jurassic in age. It preceded, and may have facilitated, the dolomitization. 11 Knopf, Adolph, A geologic reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, California: U. S. Geol. Survey Prof. Paper 110. pi. II, 1918. a Knopf, Adolph, A geological reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, California: t - . S. Geol. Survey Prof. Paper 110, p. 9, 1918. Faults. Faults of several ages have been observed and inferred. They may be classified as: (1 i pre-dolomit*, (2) post-dolomite and pre-steatite, (3) post-steatite. Pre-dolomite faults are not positively established, but are indicated by incomplete evidence. For example, at the Talc City mine early faulting is suggested by the apparent repetition of lithologic units that occur as unal- tered remnants surrounded by massive dolomite. No fault is visible, but perhaps dolomitization obliterated it, leav- ing unaltered parts of the hanging-wall block and the footwall block isolated in the expanse of dolomite. Any faults which existed prior to the hydrot hernial action doubtless facilitated dolomitization. Post-dolomite and pre-steatite faults are important, as they are occupied and bordered by talc in some places. They are probably faults of small to moderate displace- ment (1 to 100 feet?) for the most part, except at the White Mountain mine, where the displacement may have been several hundred feet. Post-steatite faulting on a minor scale is shown by the sheared condition of most of the talc. This sheared condition in many places resulted from renewed move- ment on pre-steatite faults. An exceptional post-steatite fault of great displacement (thousands of feet?) forms one boundary of the productive steatite area at the White Mountain mine, but most of the other mine areas have not been so strongly affected by post-steatite movements. Structural Relations of Ore Deposits. 13 Structural controls are visible or may be surmised in many steatite deposits. Contacts between rock units have favored the development of some ore bodies, as at the Talc City mine, where much of the steatite occurs along the boundaries between massive dolomite and stratified dolomite or lime- stone. At the Alliance mine the main ore body is at the juncture between massive dolomite and silica rock. The contacts between lithologic units were probably incipi- ent planes of weakness before the talc was deposited. Minor differential movement in the rocks was concentrated at the contacts of adjoining lithologic units. Faults are likewise effective as structural controls. Some of the steatite at the White Mountain mine occurs along a fault between dolomitic limestone and silica rock. Some minor deposits of the Talc City area are wholly en- closed in massive dolomite, which appears to have been sheared or faulted on a small scale prior to the deposition of the talc. In some localities, such as the Victory mine, no struc- tural control of the ore bodies is apparent. Comparative Features of Individual Deposits The following table indicates some of the similarities and differences between the various steatite deposits de- scribed in this report. One or two near-steatite deposits are included. Physical Characteristics It is generally impossible to distinguish steatite from other grades of talc at sight, but most steatite has certain common fractures. It is often possible to judge by the outward appearance whether or not a material merits thorough testing. For final identification, a talc suspected of being steatite must be laboratory tested; analyses i^The term "ore", which in a strict sense applies to metallic deposits, is used loosely in this report to designate talc of steatite quality In this paper "ore deposit" or "ore body" means a mlnable mass of steatite This usage, although debatable, is well established in the steatite mines. 10 Special Report 8 / 5 ■6 + **- + D = 2 t I* I I 8=6 it |\| ."| tDcsj -^ J *0 ~?'J l*sc. hiuon inm 3H«* iH HLnJ-fuQfiJff- + < < Q. < s UJ i < o WflHMffl + + X Lu THLn7£»S^ + + LU j JlH~U~ll!r + + o h- ll 1 Z < LrlHuV + + JuiUu + + UJ X i°. co t— > if + + Ll > •- / + + o O t? + + + + + + o o _i o UJ o o o 1o o -' IMI f '">* „ , . , , ,. ., , Al . These figures are, of course, inaccurate. Thev are ex- of calcium carbonate and carbon dioxide ; and the steati- tremely conservative, and merely denote the order of ma- ration ot the silica rock involved the removal of some nitude of the rese rves. If the total of 86,700 tons had bee~n silica to make room for the added constituents. Perhaps correct, and if the rate of mining early in 1943 had been the hot waters obtained their content of magnesia and maintained, Inyo County steatite would have been ex- sihca at various depths from dolomite and silica rock hausted in 1948. Fortunately, although some deposits respectively, and redistributed these ingredients. The were worke d out during the war, the discovery of new ore vigor of steatizing solutions is illustrated at the White bodies and the f urt her development of old ones tended to Eagle mine, where granite and other host rocks have been maintain the reserves in much the same wav that known altered to talc. 1 ' Evidently the solutions were not strictly domestic petroleum resources were maintained during the selective, although they generally did show a preference past seV eral decades. However, steatite reserves are with- for certain rock types such as massive dolomite and silica 0U f doubt seriouslv limited rock. New or continued hydrothermal activity produced MINES and prospects disseminated pyrite in some of the talc bodies, which are therefore not of steatite quality. More shearing also took . . c .' ne place, and affected steatite and non-steatite talc in nearly v /he ™lc Cl $ mine } s 19 miles by road southeast of all the deposits Keeler and 6 miles northwest of Darwin, Inyo County, California, in a group of hills near the south end of the Size and Shape of Ore Bodies i nvo Range (figs. 3 and 5). Although the area is over The individual steatite deposits studied in Inyo 5,000 feet in altitude, it is arid and provides neither tim- County by the Geological Survey are very small to mod- ber nor water for mining. There is no city at Talc City, erate in size, .containing a few hundred to a few thousand despite the implication of the name. The mine was studied tons, and are not nearly as large as many talc deposits of by the writer during a period of about 7 weeks in 1942. non-steatite quality. At the White Mountain mine a Literature concerning the Tale City mine is very 10-year output of about 7,000 tons came from more than meager, although several brief references by Ladoo, 18 half a dozen separate ore bodies. The largest proved Sampson, 19 Tucker, 20 Waring and Huguenin, 21 and others steatite deposits in California are at the Talc City mine, appear in various books and journals. In the existing ar- where about 135,000 tons came mainly from two ore tides there is little more than a paragraph or two con- bodies not depleted by the end of 1942. cerning the geology. In contrast to the above, some of the non-steatite talc History and Production. The mine was first oper- of California occurs in deposits that contain from half a ated briefly about 1917 or 1918 under the name of million to more than a million tons. Simonds talc mine. In 1918 it was purchased from the In general, most of the steatite ore bodies are elon- ^Udoo, R . B .. Talc and soapstone: u. s. Bur. Mines Bull. 213, gated lenses Or pods, as much a.S 600 feet in length and pp. 111-117. 1923. Gives geological notes and flow sheet of mill. The rn j , • ,1 • 1 t i i -l it L . 1, ■ , mining company is referred to as the Inyo Tali Company. 50 teet in thickness. In detail they are highly irregular, ^Sampson, E., U. s. Geological Survey, Mineral Resources for with rao-opfl outlines fraverl ends offshoots aiul locally 1920, part II, pp. 203-204, 1923. Describes the talc and its technology, wnn rag^eu outlines, rrd\eu entis, onsnoois, anu locaiij ^Tucker, w. B., California Div. .Mines Rept. it. pp. 300-301, gradational boundaries. Some steatite deposits contain 1920-21. Gives geological notes. Refers to mine as Simonds Talc mine. _ -lii e i-i • • 11 1 i 1 Tucker, W. B., California Div. Mines Rept 22, pp. 523-524, 1926, many residual lumps of the original host rock, and grade Two paragraphs on geology and development. into cou ntry rock full of talc seams and stringers. This u ^^\ ) ^\f^^^^^S{^^S n t^ ttanam D ' V ' * Mi " es RePt " Wright, L. A., White Eagle talc deposit: an example of steat- '■" Waring,' C. A., and Huguenin, E., California Div. .Mines Repl ization of granite: (abst) Geol. Soc. America Bull., vol. 59, p. 1385, 15, pp 126-127, 1919. Report includes a reconnaissance geologic map 1948. of Inyo County. 14 Special Report 8 California Talc Company by the Inyo Tale Company, which about 1922 became the Sierra Talc Company, the present owner of the mine and the largest producer of steatite in the nation. This concern has offices at 5509 Randolph Street, Los Angeles, and mills at Keeler and Los Angeles. Messrs. Franklin Booth, P. II. Booth, W. H. Booth, and Otis Booth have served as executive officers of the company, which is now owned by Mrs. Dorothy P. Dodds and Mr. Otis Booth. From 1918 to 1942, Mr. W. A. Reid was mine superintendent at Talc City ; since 1942, Mr. James McNeil has held this position. During the first few years of operation, the mine pro- vided raw material for insulating cores of Hotpoint stoves. The cores were turned out of block talc, which was then fired. It was later found that ground talc could be used for the same products, preventing great waste, and all the ore is now ground. Much talc from this mine has been sold to the paper, rubber, and cosmetic industries. However, manufacturers of electrical insulators for radio and other equipment began to draw upon the Talc City production about 1936, and by 1942 virtually the entire output was used in high-grade electrical ceramics. The mine is the largest producer of steatite in the United States, and prior to World War II it was almost the sole domestic source of radio ceramic steatite. The Talc City mine is said to have yielded 130,000 tons by early 1942. In 1941 the year's output was 5,800 tons, before the advent of the war-time steatite crisis. This crisis developed in mid-1942 and strained the ca- pacity of the 20-year old mine to the limit. The Talc City mine produced approximately 70 percent to 80 percent of the nation's wartime steatite supply, an accomplish- ment which was only made possible by the adoption of more modern mining and engineering methods. Mine Workings. The surface of the ground at the Talc City mine is characterized by large waste dumps (fig. 4), and by several subsidences where enormous gap- ing cracks furrow the surface of the ground. Underground prospecting and development have been carried out exclusively by driving new workings, with no geologic mapping (prior to 1942) and with no core drilling. Geologic studies are now difficult because most of the older drifts and crosscuts are inaccessible. Glory holes have been used during the past. The two largest are the "West" and the "Central"; in addition, there are the "Evening Star" and the "Ridge" glory holes (see pi. 1). These were tapped by several adits. More recent stoping and drifting at deeper levels beneath the glory holes has caused caving, and at present large portions of the ground surface and old underground work- ings are subsiding. In the upper parts of the caved ground a good deal of country rock has become mingled with the remnants of talc. Since the days when talc was removed from glory holes through shallow adits, a maze of deeper drifts and cross-cuts has evolved, amounting to several miles of exca- vation. Not all of these workings are now accessible, but some are shown on the accompanying maps. There are two inclined shafts (pi. 1 ). One is on the west side of the principal hill, and the other on the east side. The west shaft starts at the A level and leads successively to the B level (63 feet lower than the collar), the 100-foot level, the C level (148 feet below the collar), and the D level (about 255 feet lower than the collar of the shaft). The shaft continues downward about 50 feet below the D level. The D level includes extensive workings, which were largely obstructed by caved talc and country rock at the time of the writer's field work (1942). According to Mr. Henry Mulryan, the D level was reopened and was yield- ing a substantial tonnage of steatite in 1946. Various inter- mediate levels (pi. 2) are not reached from the main shaft directly, but are connected by winzes or raises with the levels enumerated. In addition to the shaft, the nearby B level adit allows access to the workings (pis. 1 and 2). The eastside shaft was abandoned for some time and was reopened in 1942. Drifts branch from it at depths of 58 feet and 94 feet below the collar. The east side work- ings are now connected with the main workings, but were separate in 1942. In addition to the principal shafts and workings, about a dozen miscellaneous adits and shafts are con- nected imperfectly or not at all with the rest of the mine. Operation. The operational history of the mine may be divided into tw T o unequal parts, the first of which pre- vailed until the middle of 1942. The second part had just begun at the end of the writer's field work. Before 1942, glory holes and underground caving involved great waste and danger. Occasionally ore was removed by simply taking out a section of lagging in a drift, allowing the adjacent broken talc to slide out onto the floor. More generally, the ore bodies were partly sur- rounded by workings driven in substantial country rock that was less likely to collapse; slanting chutes (raises) were then constructed into the nearby talc. The ore usually "mined itself" after the stopes reached an appreciable size, particularly after the ground had been disturbed by mining at deeper levels. During a period of months material was drawn from the chutes until broken country rock predominated over the talc fragments, or until dolomite "boulders" repeatedly clogged the chutes, halting the mining at that particular place. Premature stoping of ore near the D and C levels caused settling and shattering of overlying ore, and the partial collapse of drifts and stopes, many of which were not yet worked out. Afterwards, the talc remaining above the D and C levels was approached with difficulty. Since the middle of 1942, during the later operations, an effort has been nade to avoid caving. In the east side workings, square sets have been used, and the ore has been systematically removed. The talc is trammed by hand from the stopes to buckets in the shafts. At the surface the ore is carefully hand-sorted, to eliminate visible calcite, dolomite, iron oxide, and excessively dark talc. The bulk of the lump talc is of steatite grade ; the screenings, however, are higher in lime and are not used for steatite. The steatite is sent by truck 19 miles to the company 's mill at Keeler, on a spur of the Southern Pacific Railroad. There the talc is ground in a Raymond mill with a whizzer air separator on top, then it passes through a cyclone. Tests for lime con- tent, color, and fineness are made frequently during each mill run. The product, which is minus 200-mesh, is sacked for shipment, representative samples being retained for reference. All shipments of Talc City steatite are now ground talc, which is nearly pure white regardless of the color of the ore. Most of the product is sent by rail to manufacturers in the eastern states. Talc Deposits op Steatite Grade, Tnyo County 15 General Geology. The general geologic setting of the Talc City mine is shown on the sketch map (fig. 5), and the areal geology at the mine is shown in greater detail in plate 1. The talc occurs as irregular, elongated bodies in an area of massive dolomite. The dolomite is almost sur- rounded by Paleozoic (?) limestone from which it was derived by hydrothermal alteration. Within the area of massive dolomite there are remnants of unaltered lime- stone, remnants of sedimentary stratified dolomite, and peculiar "islands" of a silica rock that resembles quart- zite. A large mass of granitic rock that has intruded the limestone extends to within 3,000 feet of the mine. Limestone (Paleozoic?) a'most encircles the mine at a distance, and small patches of it are present near the workings (fig. 5 and pi. 1). Most of this limestone is gray, with a few thin white layers. A stratified dolomite and limestone, different from that described above, occurs near the talc deposits (pi. 1). Its stratigraphic relationships are unknown, as it is prin- cipally found as isolated patches surrounded by massive dolomite. There is a marked difference between the charac- ter of the rock underground and the character on the sur- face. Surface exposures are distinguished by a tan to gray, smooth "buckskin" appearance, and by streaks and blebs of rusty, siliceous material that jut out in relief. Micro- scopic examination of the stratified dolomite and lime- stone collected from outcrops shows a sprinkling of coarse silt and fine sand, largely quartz, in a fine-grained car- bonate matrix. Underground, the rock resembles shaly limestone and effervesces freely in cold, dilute acid. It is much softer, more fissile, and much less dolomitic than where exposed in surface outcrops. Probably these differ- ences are caused by hydrothermal alteration near the ore bodies ; most of the underground exposures of the strati- fied dolomite and limestone are in the immediate vicinity of the talc. Many of the workings within this type of rock have ragged, splintery, somewhat unstable backs and walls. A silica rock closely resembling quartzite forms prominent outcrops at the Talc City mine. It characteris- tically occurs as isolated, discontinuous patches of peculiar shapes within massive dolomite (pi. 1), and its strati- graphic relationships are unknown. Massive dolomite, utterly different from the strati- fied dolomite and limestone, is the predominant rock at the Talc City mine, and envelops or borders the talc deposits. It is a product of hydrothermal alteration, and was chiefly derived from limestone ; it forms a tract 2,000 to 3,000 feet wide, and interrupts the expanse of gray limestone that constitutes the neighboring terrain (fig. 5). Within the area of massive dolomite are a few patches of unaltered gray limestone, tan stratified dolomite and limestone, and silica rock. The massive dolomite is devoid of stratification, has harsh, hackly outcrop surfaces, and ranges in color from pale gray to gray black. The single specimen tested by the writer was iron-free. The rock consists of subhedral to anhedral dolomite grains which, in most samples are 0.015 to 0.05 millimeter in diameter (fig. 6). The texture is coarser in the northeastern parts of the B level and C level of the mine, and these coarser facies are best described as dolomitic marble. Diabase occurs in three or four very small dikes within the mine area. The dikes are from 2 inches to 2 feet thick, and are quite irregular, having filled branch- ing joints in the massive dolomite. The word "diabase" is loosely applied here, as the original texture and min- erals can only be surmised. Most of the rock is altered to a soft, fine-grained, dark-green material that disinte- grates like shale in the open air. The best-exposed dike may be seen at the mouth of the A-level adit; near the main hoist house. This dike shows a relict flow structure and amygdules of quartz and calcite. The chief mineral is matted, fine chlorite, with talc and some kaolinite ( ?). There is a sprinkling of microscopic pyrite and limonite specks, and a few minute grains of sphene. Outcrops of granitic rock (granodiorite?) are within 3,000 feet of the Talc City mine (fig. 5). This rock is exposed over a large area ; it is cut by many basalt dikes. The granitic rock is bordered by hornfels in places, but elsewhere it has intruded limestone of the type that is found at the Talc City mine. Geologic Structure. Folds, and perhaps a major fault, existed at the site of the Talc City deposits before the hydrothermal alteration of the rocks took place, but these structures have largely been effaced by dolomitiza- tion. The limestone that partly encircles the mine is strongly folded ; the steeply dipping strata strike toward the mine, but are obliterated at the edge of the dolomitized area. Within the area of massive dolomite, the isolated patches of gray limestone and tan stratified dolomite are unaltered remnants of formerly continuous formations. The strata composing these remnants follow two trends (pi. 1). In the southern part of the mine area the strike of the remnants varies only a few degrees from north, but in the northern part the strike is west-northwest. The elongated talc bodies reflect imperfectly the strike of the neighboring stratified remnants, hence the talc also shows two dominant trends. These two trends were probably inherited from the strike of beds on two limbs of a fold, or on two sides of a fault. The existence of a pre-dolomitization fault is also suggested by the repetition of lithologic units at the West ore body and the Central ore body (pi. 1). The arrange- ment and lithology of silica rock and stratified dolomite and limestone is almost identical in these two parallel ore bodies. Perhaps faulting of an inclined series of strata brought two formations into position side by side ; dolo- mitization then obliterated the fault and engulfed all but the present remnants of the original formations. Post-dolomitization faults of small to moderate dis- placement are present. Faulting has produced conspicu- ous effects within and along most of the larger talc bodies. Much of the talc was formed by replacement of wall rock along faults and subsequent mechanical movements have largely been concentrated in the ore bodies which are physically very weak, rather than in the strong country rock. Consequently countless, interlacing slickensided surfaces within some of the talc masses give the illusion that slippage has amounted to thousands of feet. The movements that produced such pronounced effects in the talc yielded a few small, inconspicuous shears only in the massive dolomite. Most of the shears in dolomite are marked by an inch or two of gouge and breccia; some are bordered by silicified and sparsely pyri- tized zones. Some show solution effects of ground water, which has utilized them as channels, making some of the fissures as wide as 3 feet. 16 Special Report 8 Some shears in the dolomite are not parallel with the ore bodies. Most of these are of little importance and are not traceable for more than 100 feet, but a possible exception is a fault ( ?) called the "Watercourse" which is said to terminate the Central ore body. The under- ground workings at the ' ' Watercourse ' ' were inaccessible at the time of the mapping. Breccia zones poorly defined in comparison with the distinct shears, were noticed in the massive dolomite in a few places near the mine. They are mostly recemented with calcite. Some of them are linear, and others have no geometrical form, but none of them show fault surfaces. Large-scale phenomena of a different sort occur a quarter of a mile south of the mine, and also half a mile east of it. Here breccia in zones over 150 feet wide resembles a coarse mosaic, in which well-separated fragments of gray dolomite are bound together by white calcite. There are no distinct borders or fault surfaces along the zones. The Talc. The Talc City ore is fine-grained, with no megascopic flakes, needles, or fibers. Some of it is highly sheared and slickensided, but some is less dis- turbed and is moderately massive when first opened up in the mine ; upon exposure,- incipient cracks open up and often produce a crude, irregular platy structure. The talc is softer than the fingernail but is quite brittle. Thin edges are translucent. Pale gray green, with or without a tinge of tan, is the typical color of the best steatite but some of the talc is dark gray and some is dark brown. The darkest varieties are said to contain more iron and alumina than the light-colored material, and most of them are not steatite. Megascopic impurities in some of the talc include limonite cubes that range from pin-point size to one- eighth inch, veinlets and coarse chunks of calcite, and inclusions of dolomite or partly altered limestone country rock. Talc containing these substances is sorted out. More commonplace but less serious are thin stains of iron oxide, which do not contribute appreciable amounts of iron unless very abundant. Some thin dendritic films of man- ganese dioxide are also found, but these are not harmful. The run-of-mine ore is of steatite quality, and some of the select material is exceptionally pure. The follow- ing analyses, kindly furnished by the Sierra Talc Co., are representative of the quality being shipped as steatite : Loss SiO, MgO AW, CaO Fe,Oj Alkalis on ign. Sierramie #1 __ 50.61 30.01 1.65 0.84 0.92 0.26 5.04 Sierra Hi-Grade #1 __ 60.56 30.19 1.46 0.80 0.00 0.22 5.68 The accompanying photomicrograph (fig. 8) shows one mineral impurity only, a minute crystal of sphene. Other specimens of the talc show sparse microscopic specks of sphene, leucoxene, and an unknown mineral that occurs in extremely small equant grains of low relief. The steatite is essentially an aggregate of microscopic matted talc flakes, shreds, and stubby slivers, the last mainly showing a length-to-width ratio of 2 :1 or 3 :1. Most of the grains are only 0.005 to 0.025 millimeter long, and most are anhedral to subhedral. There is no obvious preferred orientation of the bulk of the tiniest flakes, but the larger grains exhibit one or two directions of imper- fect parallelism. Some of the largest flakes and shreds (about 0.5 millimeter long) occur at random, but others form continuous, ill-defined, crooked streaks with the talc crystals oblique to the borders of the streaks. A few of the larger shreds are in splotches with a subradiating arrangement. The writer has not seen any relict textures inherited from earlier minerals. Many non-steatite talcs show remnants of tremolite, but the Talc City ore does not. Occurrence. The geologic relationships of the talc are illustrated in the accompanying maps and sections, figures 9 and 10, plates 1-3. Without exception the talc is associated with the massive dolomite. Some talc is in or next to the residual islands of sedimentary rock sur- rounded by dolomite, but some is in the massive dolomite itself. Most or all the talc of steatite grade has been derived from massive dolomite. More specific ore controls include the following : (1) Contacts between massive dolomite and stratified dolomite or limestone, (2) shears, and to some extent joints, within the massive dolomite, and (3) contacts involving the silica rock. Significant quantities of talc are found in places where only one of these three features is present, but all three ore controls are evident along parts of the large Central ore body. The talc deposits are elongated, narrow, ragged, and irregular in plan and cross section. In a general way they dip steeply toward the southwest. Some have definite hanging walls or footwalls with polished and grooved surfaces, and with thick talc gouge. "False walls" are commonplace where the ore has been sheared and slicken- sided internally. Some talc masses have no distinct hang- ing wall or footwall; some have not even a moderately regular boundary, and in some masses, the contact with the country rock is gradational. Most of the ore bodies contain at least a few "boulders" (rounded inclusions) of dolomite. Some large offshoots containing hundreds of tons of talc extend from the main bodies at unpredictable inter- vals. In contrast to the large offshoots, thin stringers of talc branch from the main talc masses, following joints; they rarely widen out into another ore body. On the other hand, stringers of talc within well-defined shears in a few places do lead to ore bodies. Even locally barren shears may serve as a possible guide to talc. One such shear, which is barren on the east side of the main ridge, may be followed to the Evening Star ore bodv on the west side of the hill. The occurrence of talc along contacts between mas- sive dolomite and stratified dolomite and limestone re- quires special mention. The talc frequently grades into country rock on the side towards the stratified material. As a rule there is an intermediate zone of "semi-talc," which may be scratched with the fingernail but which effervesces in acid, evidently being an intergrowth of talc and calcite. Within certain layers of this partly altered rock, true talc occurs in intermittent lenses a few inches in length. The talc in and near the stratified country rock is commonly dark brown and has stains of iron oxide, but the talk adjacent to the massive dolomite country rock is generally light-colored ore, is practically free of iron, and is of steatite quality. Principal Ore Bodies. Although there are perhaps a score of talc deposits at Talc City, most of the produc tion has come from three or four. Most of the others are quite small. In this report the westernmost large deposit (see map, pi. 1) is called the West ore body, the next one Talc Deposits of Steatite Grade, Inyo County 17 VERTICAL SECTION THROUGH SHAFT El. collar 996.7 ft. -'\ 94- FOOT LEVEL \ \ \ \ > 1 \ £"' \ nvl i El. collar 996.7ft Gently inclined raise, approx. 30 ft. above drift of upper end Dolomite PfdfH Stratified dolomite, limestone T40 Contact (Dashed where approximately located) $50 Fault or Shear showing dip (Dashed where approximately located) Strike and dip of beds ■^30 Variable dip a Shaft at surface K Shaft going above and below levels m Bottom of shaft Foot of raise or winze Head of raise or winze 50 ioo Feet Figukb 9. Geologic maps and section, Kast Sid., workings, Talc I ity min< 18 Special Report 8 to the east is called the Central ore body, and the deposit at the East Side shaft is the East Side - ore body. A few hundred feet north of these is the Evening Star ore body. The West and Central ore bodies show a remarkable similarity in trend and geology, as indicated on the map. It might be supposed that they represent a single original deposit faulted into two segments, but this is not so. The country rock may have been repeated by faulting, but if it was, the faulting occurred before the talc was formed. The conjectured fault must' have been a pre-dolomitiza- tion structure, as no vestige of such a feature in the mas- sive dolomite is now exposed. The West and Central ore bodies have yielded the larger part of the Talc City output. Widespread caving has made it impossible to trace all the former outlines of the ore accurately, but Mr. W. A. Reid obligingly added his recollections to the writer's piecemeal restoration. In- tact remnants of talc still afford a good deal of first hand information. The West ore body is said to have been exploited first, and was once considered worked out. It was mined largely by means of three glory holes. On the surface the talc comprised an elongated zone 550 feet long, between massive dolomite and stratified dolomite and limestone. Patches of silica rock of the hanging wall terminate at a shallow depth (pi. 3), probably having been altered to massive dolomite ; the ore body also terminates at a rela- tively shallow depth at the localities explored to date. Only two downward prolongations of the ore were en- countered at the B level. One of these was part of a wide bulge, and it had various offshoots. The bulkiest portion of the West ore body at the B level is said to have measured 40 by 60 feet in plan, but in many other places the width was only 5 or 10 feet. It is quite probable that additional undiscovered prongs of ore extend to depth south of the present B-level workings, but that region has not been explored. The writer believes that downward "roots" of the West ore body occur like the roots of a tooth. The south end of the ore body has moderately regular walls near the surface and dips steeply westward ; the irregular, wide north end apparently was steeply inclined toward the west also. Although most of the northern portion is worked out, part of the southern half of this ore body was being mined above the A level at the close of 1942. The Central ore body (pis. 1-3 and fig. 11) is more persistent at depth than the West body, but is otherwise similar. Although the heart of the deposit has been mined, this body is not worked out, and its ultimate depth is not known with certainty. The Central ore body extends at least from the surface to the workings below the D level, a vertical distance of almost 400 feet. According to re- ports, a crosscut 50 feet below the D level disclosed steatite ore ; here again it is very likely that downward extensions occur discontinuously along the strike, and some of these probably reach below the present workings. On the sur- face this talc-bearing zone is 680 feet in length, but some parts are so narrow they cannot be mined. The southern part of the Central ore body lies between massive dolo- mite (the footwall), and stratified dolomite and limestone (the hanging wall). These relations prevail from the ground surface to the I) level. The northern part of the Central ore body lacks a stratified hanging-wall formation --' Not to he confused with the Bast End talc mine less than a mile away. at the surface and at the B level, but the stratified dolo- mite and limestone are present at the C level. The mass of stratified rock adjacent to the ore evidently plunges north- ward, so it extends much farther north within the mine than it does on the surface. Therefore it is possible that the talc deposit itself will have a greater length under- ground than on the surface. The northern part of the ore body, as now exposed, consists of a shear zone incompletely occupied by talc that in places is only a few inches thick, but which swells out locally to 5 or 10 feet. This northern part of the Central ore body is nearly vertical at the sur- face, but dips to the west at depth (pi. 3) ; it was being re-explored on the C level in 1942. The southern half of the Central ore body is thick in places, a width of about 40 feet being reported at one crosscut that is now caved. Large, irregular, intricate offshoots of talc occur in the massive dolomite footwall, and some of these can be mined. The East Side ore body may possibly be a branch or a faulted segment of the Central talc deposit. The "water- course" (open fault?) which is said to terminate the Central body, lies between the two deposits in the mine. However, on the surface of the ground no evidence sup- ports the faulting hypothesis. The East Side ore body is inconspicuous at the ground surface. Underground exposures show that it is an ill- defined, elongated lens with many inclusions of country rock (fig. 9). It dips 42°-62° SW, is 2 to 15 feet thick, and in late 1942 was developed for more than 180 feet along the strike and 100 feet down the dip. The stratified rocks of the hanging wall contain thin streaks of talc, making the west boundary of the ore rather vague. The footwall boundary is even less distinct, as talc containing dolomite inclusions grades into dolomite with interlacing talc stringers. The fourth ore body has been mined at the Evening Star glory holes (pis. 1 and 3) . The talc that was first pro- duced from this ore body was not considered entirely satisfactory for steatite, and about half of it was rejected because of limonite cubes and stains. However, after 1942 acceptable steatite was mined from the deposit. As in the occurrences described above, the Evening Star ore body is bordered by massive dolomite on one side, and by strati- fied dolomite and limestone on the other side. Silica rock is present also. The talc-bearing zone is not as linear in plan as the other three ore bodies except at the west end, which is a steep shear containing only a foot or so of talc. The eastern end of the Evening Star ore body is in part a bulge on the same shear, but the major mass of talc is a stubby branch. The ore body was formerly said to extend downward as a funnel to a depth of only 40 feet below the surface, but this has been disproved by exploration since 1942. Mr. Henry Mulryan states that a wide con- tinuation of the deposit has been found at depth. At the surface, the ore ends toward the east against an almost unbroken barrier of massive dolomite, but, juding from the West ore body, the subsurface extent of the Evening Star deposit will prove to be quite different from the extent on the surface. Probable Downward Continuation of Ore Bodies. Because the neighboring limestone in the vicinity of the Talc City mine may be an ancestral rock without which the talc might not have developed, the former downward extent of the limestone is of importance. The remnants of limestone all dip steeply and have very little curvature, Talc Deposits op Steatite Grade, Inyo County 19 25 TRUE NORTH ^ kIS 3 » o m o r - o w a -< CD > r s o ^ g oto S Zi O -< m o o ^- *— m CD m m o m a (S) s U) ro 3 > o CO - 20 Special Report 8 indicating that the limestone once extended downward a great distance: the massive dolomite derived from it is probably likewise vertically persistent, comprising a great volume of rock suitable for the formation of talc. If the granitic rock exposed to the south extends beneath the Talc City mine at depth, the upper surface of the underlying granite may be one of the limits of the talc- bearing zone, but its general position at present can be inferred only. The massive dolomite is not noticeably coarser at the C level than at the H level, offering no indi- cation that an igneous intrusion is very close. Similar negative evidence is afforded by the lack of lime-silicate minerals in the massive dolomite. Pyrite, and limonite pseudomorphs after pyrite, are numerous in some of the deepest ore now exposed, but they are equally prominent in some of the talc at the surface of the ground. Finally, relatively few dikes are found in the mine, but dikes are plentiful near the granite contact half a mile south of Talc City. These conditions seemingly indicate that the upper surface of the granite has not been closely ap- proached by the mine workings. The foregoing facts do not demonstrate that talc will extend downward indefinitely, for temperature and pres- sure conditions and other factors undoubtedly played an essential part in the control of ore formation. However, it is likely that ore occurs at least a hundred feet, and probably several hundred feet, below the present work- ings. E X PLANATION Ore body ot surface Ore body ot B level Ore body ot C level Feet approximate ,->.-> Figure 11. Generalized diagram of parts i>f the West ore body and Central ore body. Talc- City mine, showing variation In shape with depth. Composite map based on Incomplete data. 1 !» 4 2. •^«r Figure 12. Photomicrograph of silica rock from the Alliance ] mine showing sand ( ?) grains of quartz with later rims of chlorite. , Incipient mylonitization is indicated. The braided black streak bisecting the picture is a micro-shear zone, consisting of coherent I pulverized matter. This rock is the host rock for talc in the Alliance mine. Uncrossed nicols. Alliance Mine and Irish Lease The Alliance mine and Irish lease are on adjoining claims slightly more than half a mile north of the Talc City mine, and 6 or 7 miles northwest of the city of Dar- win. They are about 5,300 feet above sea level, and are i reached by road from Lone Pine and Keeler. Lauren A. Wright and the author studied these properties during a period of 4 days in December 1942. The Rocks of the Area. The areal distribution of the rocks is shown in figure 12. Limestone, dark gray and i distinctly stratified, occurs in the south part of the map area. Poorly preserved crinoid fragments were found in some places. Outcrops are gray to buff, and are numerous ! but not very prominent. Most of the limestone underlies sandstone and slate, described below, but some is also] found above the slate. Sandstone, thin-bedded and in part shaly and red-' dish, overlies the main mass of limestone in at least one place on the Irish lease. Tt is only 5 or 10 feet thick, and is included with the slate on the geologic map. Slate, mainly dark gray or greenish gray, overlies ( the thin sandstone member along the southern border of | the map area. Slate or other argillaceous material prob-j ably once existed in other places at the site of the Alli- ance mine, as some of the profoundly altered rocks in and near the workings are dark and rich in alumina. One 1 such altered rock, although granulated almost beyond recognition, appears to have been a silty argillite ; it is [ exposed near the footwall of the talc deposit near the! Palmers' new shaft. Massive dolomite is the most abundant rock in the' northern part of the map area. For the most part it is: devoid of bedding and is everywhere barren of fossils. I It is fine to medium in grain size, compact, and tough. Outcrops are plentiful; they vary from pale gray to buff and gray black, and exhibit harsh surfaces with tiny j projections and depressions. The massive dolomite is a hydrothermal alteration or replacement of limestone.) Near the talc some of the dolomite lias been changed to soft, white, non-talcose substance. Talc Deposits of Steatite Grade, Inyo County •21 Silica rock forms the central part of tlie mine area and is topographically the most prominent material, appearing in numerous bold outcrops which weather brown. Its contacts with dolomite are very sharp in many places. Probably the silica rock is a quartzite, as locally indicated by rounded to subangular "rains of moderately uniform size (fig. 12), but some specimens contain closely fitting quartz grains with mutually embayed boundaries (fig. 13). Interesting alteration products in the silica rock are associated with the Alliance talc deposit. Initial petro- graphic study points to the silica rock as the original material in most places. The quartz was sheared (fi»-. 12) and mylonitized in places, and was then hydrothermally altered. The resulting rock is much darker than the un- affected silica rock, and in fact bears scarcely any mega- scopic resemblance to it. The altered rock is dark gray, in some places tinged with dull green, and may be scratched with steel. In it are residual quartz grains, which commonly predominate over the other constituents, but are somewhat masked by them. Some of the quartz grains are "frayed", having been partly chloritized. Chlorite aggregates encircle these frayed grains, and fine chlorite mosaics are also localized in rounded areas. The finest constituents of the rock bave not been determined, and the composition of the wispy, black, mylonitic streaks is unknown. A further, or perhaps parallel, alteration of the silica rock has produced most of the talc at the Alliance mine. Figure 13. Photomicrograph of silica rock from the mine, showing incipient development of talc, which has the quartz grain-s.-Crossed nicols. Geologic Structure. The most important structural relations are those of the central mass of silica rock, which is apparently bordered by faults both on the south and on the northwest, as explained below. Talc occurs along both of these fractures. The Alliance mine is on the north- west fault, whereas the Irish lease is on the south fault, South of the silica rock, the limestone and slate dip northward against the main mass of silica rock (fig. 15). Therefore a fault exists along the discordant contact, unless the silica rock is an alteration product of the lime- . 1 m m Figure 14. Photomicrograph of steatite from the Alliance mine. The only mineral shown is talc, but tun or three other minerals occur in minute quantities elsewhere in the specimen. Uncrossed nicols. stone and slate strata which run into it. The fault, if such it is, was formed prior to the hydrothermal activity that produced talc along the border of the silica rock, and is now completely healed. The northwest edge of the silica rock is bordered by soft altered rocks and by talc, beyond which is massive dolomite. The soft altered rocks have developed along an east-northeast shear, and some renewed displacement has occurred. Slickensided surfaces are widely distributed in the altered rocks, but the most persistent plane of move- ment is that which forms the hanging wall of the principal talc zone; this fault surface dips gently northwest, away from the silica rock, and passes beneath the massive dolo- mite. Elsewhere, the bonier of the silica rock is not a fault contact, although many portions are relatively straight and decidedly discordant with respect to the strike of the nearest stratified rocks. No gouge, breccia, slickensides, or shears are present ; the silica rock and adjacent massive dolomite are not separated by so much as a single crack in many places. The outline of the silica mass is well exposed, and its shape shows that faulting or at least post-altera- tion faulting cannot account for the strange shape and distribution of the silica rock. Alliance Mine Ownership and History. Mrs. Edith Lockharl and George Koest of Darwin, California, are the owners of the Alliance mine, but lessees have carried on all operations. The Sierra Talc Company worked the deposit in 1939; subsequently M. C. Williams has been the lessee. Mr. Williams operated the mine in 1940-41, then sub-leased it to the T. S. Diatom Company in 1941-42, and to the Pal- mer Development Company in 1!I42. The latter company achieved the largest share of the total production, which is estimated to have been slightly over 4. .">(>() tons by the end of 1<)42. Probably at least hall' of this tonnage was sold for radio ceramic steatite. Mini Workings ami Opt ration. The surface work- ings are shown in plate 4. The large open pit undoubtedly was the site of earliest operation. In pari the pit was worked as a glory bole, tapped by shallow adits. 22 Special Report 8 An inclined shaft near the glory hole extends to a depth of 70 feet, and two levels connect with it (pi. 5), one at 45 feet and one at 70 feet. Most of the 45-foot level is now inaccessible. The workings at the 70-foot level com- prise about 450 feet of drifts and crosscuts. Prom these there are several raises and large, gently dipping stopes that have been supported in places by square sets but which more generally have been allowed to cave. Rem- nants of an inclined winze may be discerned on the 70- foot level (pi. 5). This winze is said to have been sunk 40 feet in ore. The talc, in 1942, was sorted at the mine into two grades "black" and "white," and sent by truck to Keeler. Here the dark variety was shipped by rail for milling, but the light was bought and milled at Keeler by the Sierra Talc Company. The light-colored talc was used in electrical ceramics, but the dark talc was used for other ceramics and for fillers. The Ore Zone. There is no single all-inclusive mass of talc at the Alliance mine, but if semi-talcose rocks are included there is a principal ore-bearing zone (pi. 5). This ore zone has formed along a system of shears ; it lies between the main body of silica rock and the adjacent expanse of massive dolomite, and it dips gently northwest beneath the dolomite. The soft hydrothermal products in the ore zone form a belt about 30 feet thick, and include dark-gray chloritic substances derived partly from silica rock and partly from slate or argillite, light-colored, softened, semi-talcose silica rock, and nearly pure talc. The talc has few distinct boundaries. It appears and disappears by gradation within the altered zone. Unlike the talc of the Talc City mine, it has been formed as a replacement of the silica rock. Well-defined masses or lenses of talc can rarely be found, as there is a general erratic blending of talc and semi-talc. However, shapeless masses of talc large enough to permit mining are en- countered commonly. The one distinct boundary of the talc-bearing zone is its fault contact with the massive dolo- mite of the hanging wall. Nature of the Talc. There are two varieties of ore, the light-colored and the dark. The light-colored talc varies from white to gray, and is frequently mottled ; the dark talc is dark gray to black. Both types are some- what blocky, but are cut in all directions by many in- cipient cracks. There is no schistose, platy, flaky, or fibrous texture visible to the naked eye. The grain size is very fine (fig. 14), most of the talc particles being 0.005 to 0.02 millmeter long. Numerous pseudo-spherulitic clusters of subradiating grains are about 0.04 millimeter long. These are not shown in the photograph. Some of the clusters are elongated and some are composite, and in places they almost touch one another. The only min- erals other than talc noted by the writer were a few small grains of sphene, a trace of leucoxene, and extremely small equant specks of low relief. The talc is translucent on the thinnest edges only. Color is of no assistance in distinguishing the ore from associated semi-talcose rocks, and about the only simple criteria are "soapy feel" and softness of the talc, in com- parison with the adjacent materials. The light-colored talc, which probably constitutes 30 percent to 50 percent of the ore in the Alliance mine, is steatite used for radio electric ceramics. It has been analyzed by the Bureau of Mines, which very kindly pro vided the results below : U.S.G.S. No. 30 — Alliance mine. From stope on 70-foot level Collected by Page, .5/1/42. About 100 lbs. of light-colored ore CaO, 0.13% ; Fe 2 O a , 0.80%. Color fired 2,300° F, light cream some specks. 2% impurities. The dark talc probably has not been used for radk electric purposes. It is said to be relatively high ir alumina, and may therefore contain pyrophyllite or chlor- ite. The Bureau of Mines supplied the laboratory result* shown below, but evidently made no test for alumina. U.S.G.S. No. 68 — Alliance mine. Collected by Wright anc Page from ore pile ; about 20 lbs. CaO, 0.16% ; Fe 2 O a , 0.74% , Color fired 2,300° F, light cream. Mineral impurities, verj : low ; abrasion, soft. These interesting results show that the calcium and iron content of the dark talc is essentially the same as that of the light-colored talc, and that this dark ore burns light. The dark talc may be steatite even though it is nol marketed as such. The Alliance ore is more chunky and less brittle thar, that of the other nearby mines, and would appear to be more suitable for lava-grade block talc. The Geologi cal Survey submitted block specimens to M. Kirchbergei & Co., Inc., for machining and firing tests. The Survey's samples and Kirchberger's results are shown in Table 2 Irish Lease This property, immediately adjacent to the Alliance mine, is owned (as of 1942) by Mrs. Eva Irish, 929 Soutl Detroit Street, Los Angeles, California. When visited bj the writer it was operated by a lessee, W. J. Quacken bush of Darwin, California. Development at the claims has all been recent, appar ently, and on a very small scale ; the entire productior has amounted to only a few hundred tons. As showr in plate 4, there are four shafts, three of which are scarcely more than deep pits (8 feet, 17 feet, and IS feet deep, respectively). The fourth shaft, very close tc the others, was more than 35 feet deep in May 1942, and was connected with short drifts which are shown ir part in figure 15. Occurrence and Nature of the Ore. All workings lie along or near the contact between silica rock and slate (pi. 4, fig. 15), where a zone of alteration includes dis- continuous masses of talc. The slate dips at an angle ol 50°-60° into the silica rock with a discordance of aboul 20° between the two, and it is likely that a fault existed here prior to the formation of the talc. The talc, more or less enveloped in partly softened rock, occurs in irregular streaks, blebs, and masses thai are generally distributed in an elongated zone, but whicl individually are not all parallel with the zone. The talc bearing ground is at least 35 by 250 feet in plan, but onh a small portion is actually talc. Most or all of the tal< originated from the alteration of silica rock. The ore is fine-grained, soft, and blocky ; it is more opaque and more nearly pure white than the Alliance product. The Bureau of Mines has kindly made an analysis which is as follows : U.S.G.S. No. 67— Irish lease. Collected by B. M. Page fron loading chute (weight about 20 lbs.). CaO, 0.16%; FeO 1.16% color fired 2,300° F, buff; mineral impurities, verji low, abrasion, soft. Talc Deposits op Steatite Grade, Inyo County Table 2 Weigh t in pounds No. Where collected AIM Sierra Talc Co. mill at Keeler 3£ All-2 Sierra Talc Co. mill at Keeler 9i All-3 100-level 4| All-4 Carlson raise in mine 7| Original color Mottled gray Black Dark gray Dark gray Fit ittti text* Satisfactory Satisfactory Satisfactory Satisfactory Iron ii.ntli Low Low Low Medium Machine- ability G I Good ( rOOd Good 23 Conclusion Best * Fair Good Xo value * This sample was the best of 22 samples tested from steatite-producing mines. Thus the ore appears to be well within steatite limits in all characteristics for which it was tested. The actual use of the talc, however, is unknown to the writer. NW 8 SE M ot tolc olong-^V drifl pmche plone of' sei E XPLANATION £31 Tolc-oDserved Tolc-probable Altered silica rock Contoct t Dashed where approximately located) Figure 15. Cross-section B-B' of the California. Irish lease, Inyo County, White Mountain Talc Mine 23 The White Mountain mine was studied by L. A. Wright and B. M. Page during 5 weeks in August and September 1942. The mine is within and adjacent to an unnamed can- yon on the east side of the Inyo Range, Inyo County, California (fig. 3). It is reached by road via Lone Pine and Keeler, the latter village being only 8 or 9 miles away by direct line, but 35 or 40 miles by road. More than half the road is unpaved and a part is very steep. The altitude of the area (between 6,000 and 7,000 feet) is such that surface operations are hampered by snow in the winter. Above the mine are spectacular limestone cliffs near the crest of the Inyo Range (fig. 16). The area is in the belt of juniper and pinon, which were formerly used for tim- bering the mine workings. The White Mountain mine has a scanty water supply, which is piped a mile or two from a high spring above the camp. 13 This section has been compiled from a report by Lauren A. Wright and Ben M. Page. It is said that the White Mountain talc was known to Indians and that some was sold by them to the old and famous Cerro Gordo mine for use as a refractory. In 1914 Roy C. Troeger of Los Angeles, California, claimed the deposit, which was named the Cerro Gordo Xoapstone. Mr. Troeger was still the owner of the mine in 1942, but had never operated it. It was virtually unde- veloped until some time in the 1930 's when it was leased by the Sierra Talc Company, which came into ownership of the Florence and Mae West properties nearby. Mining of the White Mountain talc was found to be unprofitable to the company, so the lease was given up after about 5 years. Ownership of the Florence and Mae West was retained, but no subsequent work on those two properties has been done directly by the company. William Bonham of Line Pine succeeded the Sierra Talc Company as operator of the White Mountain mine, which he has leased since 1938 from Roy Troeger. Under this arrangement the mine has become one of the few pro- ducers of steatite in the United States. Brief notes concerning the White Mountain mine have been published by Tucker and Sampson. 24 Mine Workings and Operation. There is no inte- grated system of workings at the White Mountain mine ; instead about 40 adits, many of which were begun for prospecting purposes, are scattered over an area of 30 acres. Most of the adits show at least traces of talc, but few have exposed minable bodies. The one place where interconnected workings once existed is in the central part of the mine, where the Sierra Talc Company drove a tun- nel and worked one or two additional levels. The portals of this tunnel are labeled 8 and 16 on the accompanying map, plate 6. (AH such numbers are arbitrary designa- tions by the writer.) The Sierra Talc Company mined from the glory hole above the aforementioned tunnel, and from a small glory hole near adit no. 2. Most of their production came from the larger glory hole. The company also drove part of adit no. 36 and sank a 30-foot shaft, now caved and obliter- ated, near adit no. 24. As they were unable to apply large- scale methods of mining, the company abandoned the operation. Nearly all of the subsequent workings have been made by William Bonham. Mr. Bonham discovered a steatite ore body just be- neath the ground surface and just above the old tunnel driven by his predecessors. The removal of this ore left "the Big Room" (see pi. 6). Since the exploitation of "the Big Room," mining and prospecting have some- times consisted of "gophering" by a crew of four to eight men. Hand drilling is preferred, most of the rock being soft or well fractured. When ore is found it is usually -'♦Tucker, W. B., and Sampson, R. J., California Div. Mines Kept. 34, pp. 492-495,' 1938. 24 Special Report 8 taken out by wheelbarrow or by mine cars and dumped directly into a truck, which takes it about 40 miles to the Sierra Talc Company's mill at Keeler. Selective blast- ing and shoveling are employed, but no hand sorting is done. During the time of the writer's investigation a small amount of ore was mined from adits numbered 11, 28, and 2!) on plate 6. No ore was blocked out ahead of mining. Production. The Sierra Talc Company produced less than 100 tons a month from the White Mountain mine and probably reached a total of 2,000 to 5,000 tons. Under the present system, about 200 tons a month is being shipped and it is thought that Mr. Bonham has produced altogether 3,000 to 6,000 tons. This would make the out- put of the White Mountain mine between 4,000 and 10,000 tons, during a period of approximately 10 years up to the end of 1942. Despite the difficulties of its operation, the mine was one of the two producers of steatite in the United States at the opening of World War II, and it still holds an important place in the industry. By agreement, the Sierra Talc Company has the exclusive privilege of buying the talc. Rock Units. The rocks at the White Mountain mine represent a thick sedimentary section that has been faulted and subjected to igneous intrusion and hydrothermal alteration. Certain stratigraphic relationships are there- fore indistinct. The sedimentary rocks contain no recog- nizable fossils, but a Paleozoic age is assumed from the presence of crinoids, corals, and brachiopods in nearby formations of similar lithology. Alteration near the talc- bearing zone has locally converted some rock varieties to white, pulverent materials, and in some cases the original rock cannot be determined. Figckb Hi. Part of the White Mountain mine. Camera facing- south- west. Photo l/.i/ L. A. Wriylit. 1 ) Banded Limestone. A white and light gray- banded and stratified limestone that occurs in isolated masses within a massive dolomite is assumed to be the oldest of the rocks near the mines. It is exposed in the southwest corner of the White Mountain area, is separated from the other sedimentary units by a fault, and bears no relation to the talc bodies. It is the only non-inagnesian limestone in the vicinity and undoubtedly represents tht relatively unaltered portions of a rock now largely dolo mitized. Local distortions occur within the limestone, bui cannot be recognized in the surrounding dolomite. 2) Flinty Dolomitic Limestone. A gray to black fine-grained flinty dolomitic limestone is the oldest rock east of the above-mentioned fault, within the mine area. The flint occurs in varying abundance as thin, discontinu- ous, irregular layers which are generally the main indica- tions of bedding. The upper portion of the limestone is in places characterized by well-defined bedding planes and by the absence of flint. This is shown in the workings of, the White Mountain mine north of the main canyon. Hydrothermal processes related to or contempora- neous with those producing the talc have altered parts of the flinty dolomitic limestone in the immediate neighbor- hood of the ore bodies. The two most common products of this wall-rock alteration are: (1) a gray, soft, micaceous rock superficially resembling shale, and (2) white, fibrous aggregates of tremolite and other silicates. Flint, where present, has remained unchanged in both types of altera- tion. 3) Sandy Dolomite. A gray sandy dolomite that weathers to a buff color occurs stratigraphically higher than the flinty dolomitic limestone at the White Mountain mine. An uncomformable relationship is possibly indi- cated by a locally exposed angular discordance and angu- lar flinty dolomitic limestone blocks within the sandy dolomite at one place. The sand occurs as well-rounded grains in layers which are in places cross-bedded. These layers, although difficult to recognize on fresh surfaces, are brought into prominent relief by weathering. 4) Silica Rock. A white to light-gray, massive silica rock occurs at several horizons in and above the upper portion of the flinty dolomitic limestone, and commonly separates the limestone from the overlying rocks. The silica rock is composed essentially of quartz, is generally associated with the most highly altered rocks, and is found near most of the talc occurrences at the White Mountain mine. These relations, together with its discontinuous distribution, would seemingly indicate a hydrothermal origin. The same inference may be drawn from the "jig- saw" texture of some specimens (fig. 17). However, a sedimentary origin is suggested by possible bedding planes, and by the rounded grains of quartz in some speci- mens. 5) Massive Dolomite. A massive, coarsely crystal- line, white, light-buff or gray dolomite occurs at the White Mountain mine ; it is coarser and somewhat paler than that at Talc City. All such dolomite has been mapped as a single unit although probably several sedimentary rock types have been dolomitized. (Iradational contacts exist between the massive dolomite and both the sandy dolomite and banded limestone. A large portion of White Mountain talc occurs in a zone near the contact of the massive dolomite with the ; adjacent rocks. 6) Dikes and Sills. Igneous rocks composing dikes and sills appear to be of two or more kinds. The central dike (pi. 6) is an intensely altered rhyolite or andesite with remnants of hornblende needles, vague outlines of feldspar phenocrysts, and specks of pyrite and limonite. Talc Deposits of Steatite Grade, Inyo County ■>:. Pine chlorite occurs fairly abundantly in the dike. The rock is »Tay at depth, but near the surface the character- istic color is rusty and mottled. Some of the sills in the area are probably basic ande- site in composition, consisting 1 of plentiful altered feld- spar phenocrysts and indeterminate groundmass minerals, with pyroxene converted to chlorite. These sills are green- ish in color. 7) Mantle. A mantle covers large portions of the area. In some places it is simply thick soil, in others it is landslide, mudflow, or ta'us material. It consists in some places of a single rock type, most commonly massive dolo- mite or silica rock, large boulders of which often appear to be nearly in place. In such places, however, the under- lying rock is not invariably the same type as that which predominates in the mantle. The mantle has an observed maximum thickness of 15 feet where it is cut by the mine workings, but it is probably thicker elsewhere. Talc deposits, undiscovered as yet, may be complete'y covered by the mantle. Geologic Structure. Most of the structural fea- tures are shown on the map (pi. 6) and on the geologic cross sections (pi. 7). The White Mountain mine lies within a zone of north- west-trending faults which vary in size and continuity. These faults have, as associated structures, innumerable small, discontinuous shears with non-uniform and very diverse attitudes. Folding is secondary in importance and is partly the result of drag along the larger fault planes. Several of the faults are of sufficient size to be recognized on the surface although their traces are partly obscured by alluvium and mantle. The three most important of these have been designated as (1) the western fault, (2) the eastern fault, and (3) the central fault zone. The western fault, which is the largest and appar- ently the most structurally significant of the three, tra- verses the southwest corner of the area and can be traced to the northwest for more than a mile. Future mapping may show that it is a Bas!n and Range type of fault. It is characterized by a zone of dolomitic breccia and elon- gated dolomite blocks; this zone, within the area, averages 80 feet in thickness and separates massive dolomite with its associated banded limestone on the southwest from similar dolomite and talcose silica rock on the northeast. The fault has a nearly vertical dip where it is exposed underground. The talc bodies are limited to the area northeast of the fault and similarly the banded limestone occurs only to the southwest of the breccia zone. Post-talc movement truncating the ore-bearing zone is inferred, as no hydrothermal effects are localized along the fault. The eastern fault, which also probably is of regional importance, crosses the northeast corner of the area. Mantle, however, covers a portion of its northwest exten- sion. Where best exposed south of the main canyon, the eastern fault is a brecciated zone averaging 20 feet in width. It is bordered on the northeast by massive dolo- mite and on the southwest by flinty dolomitic limestone. The fault dips gently westward in exposures near the main canyon, and steepens southeast of the canyon. A small andesite dike closely parallels the trace of the fault for a distance north of the canyon, and suggests the presence of an ancestral fault prior to the igneous intru- sion. No talc bodies have been localized along the fault. however, and it is probable that its more recent move- ment occurred after the emplacement of talc. The central fault zone, which is partly occupied by a dike, traverses the central portion of the area. It inter- sects two of the main talcose areas and in places contains talc. Recurrent movement has sheared and intimately fractured the dike, and has apparently caused masses to be separated from the main body. Underground exposures indicate a great local variance in the direction of strike and degree of dip of the dike and associated faults. Drag along the northeastern boundary of the dike has com- monly produced parallel anticlinal folding in the flinty dolomitic limestone and indicates a relative upward move- ment of the rock on the northeast side. One fault of the central zone is known to the miners as the "Black Wall" (see section B-B', pi. 7). It closely parallels the southwestern border of the dike in the vicin- ity of the glory hole. It is locally well exposed both on the surface and underground but cannot be extended with certainty for a great distance in either direction. Wher- ever recognized, the "Black Wall" consists of a zone of gouge and breccia of varying width, separating black flinty dolomitic limestone from light-colored silica rock. Talc occurs not only as crushed material within the faulted zone but also as discontinuous bodies within each wall rock. The fault changes in attitude from a northwest strike and a vertical dip in its southernmost exposure to an east strike and a gentle southward dip where last seen to the west. Whether the "Black Wall" fault existed as a struc- tural feature which localized the talc, or whether it de- veloped because a talcose contact zone offered the easiest relief to stresses is not certain. Obviously some movement has taken place since the formation of the talc. If the fault antedates the talc, the "Black Wall" may be ex- pected to extend southeastward with a reasonable degree of persistence beneath the mantle and at the same time retain its talcose nature. If the fault is younger than the talc, however, it would probably change its direction of strike to conform with the talcose border of the silica rock, or would distribute itself into a number of small barren shears. Figure 17. Photomicrograph of silica rock. White Mountain mine. The principal mineral is quartz, in interlocking urain-. show - ins incipient rims of talc. Crossed nlcols. 26 Special Report 8 The Talc. The White Mountain talc occurs as sev- eral varieties, which may be grouped into three main categories according to color as follows: (1) light-colored talc, (2) moderately dark talc, and (8) "black" talc. (1) The light-colored talc is white to gray white to tan, the last tint being common near the surface of the ground. Most of the light-colored talc is fine-grained, and except where sheared it lacks foliated or platy structure and breaks into irregular lumps. In places the texture is coarse enough to impart a very fine sugary appearance. The light-colored talc is softer than the fingernail but harder than some other talcs, and is less brittle than the Talc City material, which it approaches chemically. An analysis furnished by the Sierra Talc Company is as follows : Percent SiO. 01.40 A1»0 : , 1.57 VvA), .!M) CaO .40 Percent MgO 31.21 Xa,<) and K 2 .19 Loss on ignition 5.09 100.76 Iron Machine- Con- oxide ability elusion Good No value This composition, together with other favorable charac- teristics, places the tale among the best grades of steatite. This high-grade talc is derived not from the dolomite, but from silica rock. This is graphically indicated in figures 17 and 18, which illustrate the steatization of silica rock. Because of this origin, the main impurity found in the talc is quartz, rather than carbonates or tremolite which occur in many types of talc. The chunky and relatively tough nature of certain varieties of the ore, together with the favorable composi- tion, make some of it suitable for lava-grade block talc. The Geological Survey submitted block samples to M. Kirchberger & Co., Inc., for testing. The results are as follows : Where Wt. in No. collected lbs. Firing test WM-1 Mill at Keeler 4J Satisfactory High WM-2 Mill at Keeler — 4J Unsatisfactory Medium Good No value WM-3 Mill at Keeler 17i Satisfactory Medium Good Good WM-4 Mill at Keeler — 5 Satisfactory Medium Good Fair WM-5 Mill at Keeler 9 Satisfactory Low Good Good Although the foregoing data are not all favorable, the results are better than those obtained from most other California talc. No megascopic defects were noticed in the unsatisfactory samples prior to firing, but further experience might enable one better to evaluate the mate- rial before actual testing. (2) The darker talc is a neutral gray, but otherwise resembles the light-colored talc superficially. When ground it yields a white powder. This type of talc was formerly not accepted for radio ceramics, but in 1942 some of it was included in shipments of steatite. A sample (U.S.6.S. no. 41) was sent to the Bureau of Mines for analysis and was found to contain only 0.07 percent CaO and 0.58 percent Fe 2 0a. ('■]) The "black" talc is dark gray, but underground it appears to be black. When ground it yields a grayish- white powder. It is more brittle and more thoroughly fractured than the other two types, commonly occurring £ ¥ 0. 5 mm t Figure 18. Photomicrograph of silica rock partly altered to talc, White Mountain mine. The large grains are quartz, with frayed and embayed edges because of partial replacement by talc, which is the fine interstitial material. Crossed nicols. in fragments an inch or two in length. It is always asso- ciated with dark dolomitic limestone and is believed to have retained the pigment of the limestone. Very little importance has been attached to this talc, partly because it is not abundant, but some has found its way into stea- tite shipments. A sample (U.S.G.S. no. 40) was sent to the Bureau of Mines for analysis ; the CaO content was 0.88 percent, and the Fe 2 3 was 1.06 percent, so these two impurities fall within the range permissible in stea- tite. There are also small quantities of decidedly green "talc" in and along some of the dikes and sills. It prob- ably consists chiefly of chlorite, but this opinion is based upon a cursory examination. All the varieties of talc merge into country rock to some extent ; for instance, there are all gradations be- tween silica rock and pure white talc. Some of the inter- mediate materials ("semi-talc") are difficult to distin- guish from pure talc. Inclusions of partly altered country rock are numerous in the ore bodies, and some talcose fragments or nodules are found to have siliceous or cal- careous cores. The thorough fracturing of most ore bodies makes it impossible to sort out all of the talc fragments from the intermingled impure material. Localization. The distribution of the talc is graph- ically shown on the accompanying surface map (pi. 6), cross sections (pi. 7), and underground maps (pi. 8). It is obvious that there is no single large ore body, but in- stead an unknown number of small ones. The ore controls include: (1) contacts between va- rious rock types, (2) faults and fractures, and (3) favor- able rocks, to some extent. The first might be regarded as a special case of the second, since some movement has occurred along practically all contacts in the area. In general, the contacts are more important than shears and faults within a single formation. Talc at the White Mountain mine is not restricted to any particular rock type, but the individual kinds of talc are thus restricted. Unimportant "green tale" (chlorite?) occurs in or along dikes and sills, "black" talc is found Talc Deposits of Steatite Grade, Inyo County 27 in dark dolomitic limestone, and white talc of steatite jrade is generally associated witli the silica rock or massive lolomite. For this reason a silica hanging wall is favorable. There appear to he certain areal restrictions in the listribution of the talc of this mine. Xo tale was found west of the western fault or north of the contact where the massive dolomite begins along the northern edge of the map area (pi. 6). In fact, only small stringers of tale iave been found anywhere in the massive dolomite that partly encircles the productive area, and this dolomite might be classed as unproductive except for the fact that a mile away it contains some of the talc bodies at the Flor- ence mine. No talc was observed in otherwise unaltered rocks. There is invariably other evidence of hydrothermal activ- ity besides the presence of talc. The hard black, unaltered portions of the flinty dolomitic limestone are barren, but (this same formation in some places has been altered to i paler material containing talc. The silica rock also is •ommonly altered, friable, and pulverent where talc is 'ound. Principal Ore Zones. The geologic map (pi. 6) shows hat in the broadest sense there are two talc-bearing areas it the mine. The first is a lar»e islandlike mass that >ccupies the center of the terrain shown in plate 6 ; it •onsists essentially of flinty dolomitic limestone, and it is /irtually surrounded by massive dolomite. This is the nain producing area. The second, to the northeast, is a small counterpart of the first ; it consists of the same flinty lolomitie limestone, and is partially surrounded by the aassive dolomite. The following descriptions apply to the arjier of the two areas. The ore so far discovered in the main producing area >ccurs in two 0 :! , and therefore cannot be considered steatite and is not sold as such. However, this single analysis does not condemn the whole deposit, which has not been systematically tested. Some of the talc from deposits on the north side of the canyon is said to be of higher quality, the CaO con- tent ranging from 1.26 percent to 3.0 percent. 27 The Sierra Talc Company has kindly provided an analysis of such material, which shows only 1.14 percent CaO, 1.26 percent Fe ? 3 , and 1.72 percent A],() :i . Therefore, some of the talc is presumably of steatite grade. However, it is used in cosmetics and nonradioelectric ceramics. Trinity Talc Mine The Trinity mine is between Keeler and Darwin, about 1 mile southwest of the Talc City mine. In the past it has been known as the Pacific Coast Talc mine 28 and as the Angelus Talcs. Formerly owned by the Pacific Coast Talc Company, it has been acquired by the Sierra Talc Company of Los Angeles. During the last decade or two it was a major producer. The following data were ob- tained by the writer during a cursory examination May 1, 1942, at which time the mine was idle although still partly equipped. The geological setting is similar to that of the Talc City mine. All the talc observed is in the massive dolo- mite that extends uninterrupted to Talc City, and as at the Talc City mine, there is at least one mass of silica rock within the dolomite area. Perhaps the silica rock is the "igneous intrusive" mentioned by Tucker and Samp- son. 29 The talc observed at the Trinity does not occur along contacts, however ; it apparently was formed by the alteration of massive dolomite only. The ore bodies are lenses that lie in several attitudes, and which were prob- ably localized by minor fractures. One lens must have been at least 40 feet long and 25 feet thick, judging by the size of the main excavation. The talc seems physically identical with that of Talc City, being pale green, fine- grained, and rather massive. It is believed to have about the same composition, and officials of the Sierra Talc Company affirm that it is of steatite grade. The workings consist of several adits, a glory hole, a gently inclined shaft perhaps 100 feet long, a vertical shaft more than 50 feet deep, and several drifts, cross- cuts, and stopes. Only small remnants of talc are now visible. Un- doubtedly undiscovered ore bodies exist, but their dis- closure is not likely without the drilling of prospect holes. An area that might be explored is just south of the in- clined shaft at the dolomite-silica rock contact. A more careful study of the Trinity mine should be undertaken to determine its potentialities. East End Mine and Bob Cat Claims The East End mine is an inactive and largely worked- out property less than a mile northeast of the Talc City mine, about 6 miles northwest of Darwin. The East End deposit is reached by a road from the Lone Pine-Death Valley highway, and was examined by Lauren A. Wright and the writer December 8, 1942. It was operated by the Sierra Talc Company some years ago, and called by them the East End. It has subsequently been relocated as part of the Bob Cat claims by R. II. Bagley. 27 Mulrvan, Henry, oral communication. •"Tucker, W. B., and Sampson, R. J., California Dlv. Mines Rept. 34, pp. 492-495, 1938. 28 Op. cit., p. 493. 30 Special Report 8 The main deposit contains pale-green, crudely foli- ated, fine-grained tale. It occurs as a lens between massive dolomite and a pray, platy limestone from which the dolo- mite was derived. This lens, largely mined out, is pene- trated by a 60-foot inclined shaft with an adit meeting the shaft at the 30-foot level. Between this adit level and a drift at the bottom of the shaft, the talc has been stoped for a lateral distance of more than 100 feet, the stopes being 5 to 15 feet wide. Most remnants of talc around the margins of the stopes are very thin, from a fraction of an inch to 2 feet in thickness. Prom the 60-foot level an inclined winze 35 feet loop follows the same ore body, which is \ foot to 5 feet thick. At the bottom of the winze a 70-foot drift blocks out part of the body below the 60- foot level, but in this drift the tale is thin and pinches to 1 foot at both ends of the drift. Within 100 feet of the main deposit, to the west and southwest, a cut reveals a talcose zone in a residual patch of stratified dolomite and limestone that is surrounded by massive dolomite. This talc, which is not an extension of the main body, is mainly very dark and hopelessly intercalated with country rock. Nearby, a 20-foot shaft exposes discontinuous talc 1 foot to 4 feet thick. On the other side of the main deposit, 100 to 200 feet to the northeast, there are two pits about 70 feet apart. One pit shows 6 feet of probable steatite and the other shows 4 feet of similar talc, but nearly continuous expo- sures of dolomite lie between the two pits. Thus, it is unlikely that a large talc body extends from one pit to the other. Still farther north of the main East End workings, the Bob Cat claims include a 20-foot shaft and two pits in separate ( ?) talc bodies 1 foot to 5 feet thick, in mas- sive dolomite with remnants of original stratified sedi- ments. No samples were taken, but the proximity of the Talc City mine together with superficial resemblance of the ore and identical occurrence suggest that the talc is of steatite grade. Frisco Talc Mine The Frisco mine was examined by Lauren A. Wright and the author. The geology was mapped mainly by Wright during two days in December 1942. The property is not more than a mile southwest of the Talc City mine ; it is 6 miles northwest of Darwin, and may be reached by good roads from Darwin or from Lone Pine and Keeler. On the Frisco no. 2 claim, a 65-foot shaft and short drift were made in 1942 by the Sierra Talc Company of Los Angeles. The shaft is between two sets of old pros- pects and workings made by the same company some years ago, but the old developments will not be fully treated in this report. The old operations produced "green talc" (chlorite, apparently) said to contain more than 20 per- cent alumina. After a number of years of inactivity, ex- ploration was resumed in 1942, and the recent shaft revealed talc of steatite grade. In July 1942, 100 tons of steatite was shipped from the Frisco. The next month only 22 tons was produced, and altogether the small mine had not yielded more than 300 tons of steatite by the end of 1942. The rocks are identical with those of the Talc City mine. Their distribution is shown in plate 10. Limestone, well stratified, appears in two neighbor- ing, strangely shaped patches. The limestone dips steeply westward, and the grayish strata project somewhat above the ground like thick shingles on n\^'. Massive dolomite is the most prevalent rock.. Its rela- tionship to the stratified limestone shows clearly that it has been altered from the limestone by hydrothermal solu- tions. The dolomite is pale gray to nearly black, free of fossils and stratification, and forms numerous rough- surfaced outcrops. Dikes of pale felsite (rhyolite?) are found near the mine. One dike is just west of the shaft, and others lie to the east beyond the map area. Being hydrothermallv altered, the felsite does not crop out well. Much of it has been altered to chlorite ( ?). Silica rock which resembles quartzite (fig. 7) occurs underground in the shaft and drift made in 1942. The steatite talc is associated with this silica rock and has been derived from it. The main masses of limestone, the felsite dike, and the strip of silica rock all converge toward a common point east of the 1942 shaft. As shown in pi. 10, the talc is near a felsite dike and close to the edge of the limestone area, but shows greatest affinity for the dolomite and a steeply dipping strip of silica rock. The talc body appears to be somewhat lenticular in shape. In the shaft it is interrupted by numerous in- clusions of siliceous rock, and it is probably likewise interrupted along the strike. The ore is pale, blocky, fine- grained, and soft. It is of steatite quality, as shown by its acceptance by the steatite industry. The talc extends down the shaft 50 feet, but further downward prolongation is rather doubtful (pi. 10). Lateral development may be encouraging, however, and if so, the downward explora- tion may be resumed later. On the surface, intermittent talc showings extend more than 100 feet along the strike and the width of the ore body is about 10 feet. Massive green chlorite (?) occurs abundantly as a replacement of parts of the felsite dikes at the Frisco mine. The chlorite (?), which was once produced as "green talc," was not being mined in 1942. About 1946 the mining of the green material was resumed, and the mineral is now sold under the name "Sierralite" for use in cordierite ceramic bodies. It is said to have the follow- ing composition 30 : Percent Percent SiO. 36.24 CaO 1.47 Fe,.0 3 1.19 Ign. loss (HaO)_ 12.19 ALO3 23.56 CO, 0.S6 MgO 23.39 Moisture 0.18 Alkalis 0.35 99.43 Victory Talc Mine The small Victory mine was examined by Lauren A. Wright and the author in December 1942, when mine de- velopment was in progress. The property is 7i miles north- west of Darwin and 15 miles southeast of Keeler, from which it is reached by dirt road. The owners are Mrs. Edith Lockhart and George Koest of Darwin, California, but the lessees and operators are A. C. Palmer and Ray- mond Palmer of Lone Pine. Two men were working on the premises in December 1942. 3,1 Analysis kindly furnished by Mr. Henry Mulryan. Talc Deposits of Steatite Grade, Inyo County 31 The talc is only 3 to 5 feet wide on the surface of the feet of tale; 15 feet farther east, a pit exposes 2 to 3 feet of tale in stringers. The rocks are similar to those at other talc mines in this region. Light-gray to black massive dolomite pre- dominates, but within it is an intermittent, apparently steeply dipping strip of silica rock that resembles .piartz- ite. The talc occurs sporadically and irregularly along this siliceous material (see accompanying cross section, fi<>-. 20), and probably was derived from it. The talc is white, opaque, blocky, and soft. It has some superficial orange-red stains (which are commonplace in the district) and a few limonite cubes. No sample was taken, but nearly all the talc in the district is of steatite grade except where obvious impurities are too abundant. White Swan Talc Mine The White Swan nunc or prospect is perhaps a mile west of the Viking property and is easily reached by road from the Lone Pine-Keeler-Death Valley highway. It is 15 miles southeast of Keeler and 11 miles northwest of Darwin. The writer was there for only a few hours in April 1942. The owner is Mrs. Edna M. Towers, 316 West Im- perial Highway, Los Angeles. The former lessee was a Mr. Wilcox, but no one worked the mine during 1942. Development includes two shafts less than 30 feet deep, partly in talc, and two or three adits less than 50 feet long in separate talc showings. The main working, however, is a branching adit shown in figure 21. One branch is over 400 feet long and mostly barren, while the other is about 50 feet and was chiefly in ore. The short branch was expanded into a stope which must have yielded 400 tons of talc. Total production cannot have exceeded 700 tons. The country rock and ore are superficially identical with those at Talc City. The country rock is massive gray dolomite, and the talc is fine-grained, blocky, and pale green. The ore occurs in frayed lenses and streaks, which dip steeply. The largest lens (see fig. 21) is visible for 125 feet along the strike but is only 1 foot to 5 feet thick. It has been mined up and down the dip about 30 to 40 feet. The continuation of the workable portion may be down- ward and to the west. The talc has been localized by minor fractures rather than by contacts between rock types ; it is chiefly bounded by dolomite, although some silica rock was noted nearby. Lakeview Talc Mine The Lakeview mine is idle, having seemingly been worked out. It is 2\ miles north-northwest of Keeler, near the foot of the Inyo Range but about 4,400 feet above sea level. The loading bin is reached by road from Lone Pine or Keeler, and the mine itself is 100 yards or so above the road on a steep hillside. A. C. Palmer and Raymond Palmer of Lone Pine were the operators of the property during its chief activ- ity, and probably produced between 1,000 and 3,000 tons of talc. The following data were collected by L. A. Wright and the writer in December 1942. 32 Special Report 8 Talc stope to i^BQ surface ^ Broken line = Y ^^\ ^j^level 22 ft above 15- ft/ winze 6- ft Dolomite 62 Foult or sheor, showing dip pen cut S Head of raise or winze too Feet Figure 21. Cross-section, White Swan tale mine. A vertical shaft 30 to 50 feet deep connects with one visible level at the bottom. From this level there are two principal stopes that almost reach the surface. They are close together, steep, and en echelon ; one is about 25 feet long and the other is 45 feet. Both stopes are 3 to 10 feet wide and 2 to 40 feet high. The floors are concealed, but at one end of the pair of stopes the ore pinches out and the other end is very near the surface of the ground, owing to the steepness of the hillside. One stope is in a steep lens of talc between quartzite and stratified gray dolomite or limestone. Dark talc occurs near the latter, and white talc near the quartzite. The other stope is along a steeply dipping talcose sliver of dolomite or limestone that is enclosed in a diabase dike. The diabase itself is not talcose. The ore remnants appear to be of high quality, and are probably steatite, but they were not sampled by the Survey. Blue Stone Talc Mine The Blue Stone mine is small, inactive, unequipped, ami perhaps largely worked out, but the remaining talc is probably of steatite quality. The property is on the side of a canyon on the west side of the Inyo Range, 10 eel ;he miles from Independence, and is reached by dirt road via Mazurka Canyon (see Mt. Whitney quadrangle). The railroad at Kearsarge is 9 miles away by road. Walter Sorenson of Lone Pine, California, is the owner, and W. H. Huntley of Bigpine was a recent lesseel Mr. Huntley accompanied Lauren A. Wright and th writer during a 3-hour examination of the mine Nove ber 30, 1942. Talc was noticed here by Goodyear 31 in the 1880 's. The predominant rock is thick-bedded, dark-gray Devonian (?) limestone containing discontinuous thin streaks of flint. The strata dip steeply but uniformly westward. Interbedded with the limestone is a quartzite member possibly 20 to 60 feet thick, which forms the foot- wall of the main ore body. The talc occurs within the limestone, from which it was derived. The main ore body is nearly mined out, its site being outlined by a steep lenticular stope that measures about 40 by 40 by 10 feet along its principal axes. The stope, which yielded the entire 800-ton output of the mine, con- nects directly with the surface of the ground. From the lower end of the stope, a chute leads to an adit about 50 feet below. This adit, which was driven in from the moun- tainside, is 100 to 200 feet long, and although it passes beneath the ore body and follows the controlling lime- stone-quartzite contact, it does not intersect any ore. The downward limit of the stoped body is thus quite definite, and the longitudinal limits are implied by the fact that the ore pinches to 12 or 18 inches at each end of the stope. Other intermittent talc showings 1 foot to 2 feet wide occur on the surface north of the main deposit, but are not visibly connected with it. About a third of a mile south of the main ore body, talc as much as 2 feet in width is exposed for 50 feet, partly in two small adits. This talc is bounded by flinty limestone, with no quart- zite, but is not far off strike from the main body. There are other small, discontinuous showings of talc. The ore at the Blue Stone is mainly mottled gray, soft, blocky, massive talc. The Bureau of Mines kindly reported as follows on a sample : I'.S.G.S. Xo. 6") — Blue Stone mine. Collected by Wright and Page, 11/.SO/4L' (about 15 lbs.). CaO. 0.10%; Fe s 3 , 0.42%; color fired 2300° F, white; mineral impurities, very low; abrasion, soft ; Tuscaloosa laboratory rating, O.K. The material is probably of steatite grade. Willow Creek Talc Mine This mine, although small, has reportedly yielded talc of steatite grade. It is now apparently worked out, having produced a probable total of about 1,000 tons, mostly within a year's time. Lauren A. Wright and the writer gathered the following data during May 1942, near the termination of mine operations. The deposit is on the steep south side of the valley of Willow Creek, which runs through the east flank of the Inyo Range and empties into the north end of Saline Valley. The Willow Creek mine is reached from Bigpine by a poor dirt road, the same one which leads to the White Eagle mine. The approximate longitude and latitude are: 117° 56' 15" west, and 36° 50' 40" north (see Ballarat quadrangle). The owner is Emil Carlson of Bigpine, Cali- fornia. Almost all the development and mining have been done by a lessee, G. P. Rogers of Bigpine. 3i Goodyear, W. A., California Div. Mines Rept. 8, p. 268, 18S8. Talc Deposits of Steatite Grade, Txyo County 33 The geology is unusual in that the mine appears to be in a landslide or an incipient landslide. There are large topographic benches farther up the mountainside, and the mine workings are in a highly fractured, extremely un- table rock mass with many gaping cracks. The most preva- lent rock is granite. Within it are pendants of white lime- stone, and along the edge of one pendant a lens of talc occurs, as shown in the accompanying figure 22, which indicates the outline of the ore prior to mining. The talc in us( have been at least 20 feet thick at its widest part, but it narrows rapidly along the strike. It lies transversely across a ridge and does not appear at lower levels in the [ravines on cither side of the ridge. The outlines of the talc ond limestone are shown as they were prior to mining. Glory hole \y ft r,V4tc ^ yt ..\l^^.~-i^ J ..Cj-n.„ ■ ■■■: ■■v.-:,-.y \ S \ \ '\ vel NW EXPLANATION MsM Talc *m Granite ssa Limestone Contact (dashed where approximately located) i i i i i ■ i i i 50 ioo Feet LA. Wright and B.M Poge,l942 Figure 22. Cross-section, Willow Creek talc mine. The deposit was mined mainly from two adits which tapped a glory hole. The ground was initially thoroughly fractured by natural movement down the steep mountain- side, and it was further disturbed by the mining. The lower adit was kept open with great difficulty and consid- erable danger and expense. The talc is gray-white, fine-grained, and bloeky, out- wardly resembling the associated limestone. Officials of the Sierra Talc Company, which purchased the ore, say that it is of steatite grade. 32 There is probably additional talc somewhere on the mountainside above, if the Willow Creek deposit is actually in a landslide, but unfortunately the slope is partly covered by other slides. White Eagle Talc Mine Geologically, the White Eagle mine is of interest be- cause much of the talc has been derived from the alteration of granite. It is doubtful, however, that the talc is of steatite quality. At the outset of World War II, the newly developed White Eagle mine was considered to be a potential source of steatite. Subsequently, either because of difficulties in sorting out impurities, or because of variability in the quality of the deposit, a controversy arose as to the utility of the talc. A leading radioceramics manufacturer tenta- tively approved the material, but later condemned a car- load shipment. Some large samples have given unsatis- factory analyses, while some small samples appear to be of steatite quality. If the talc of the White Eagle mine can be used for steatite, it represents a large reserve. Lauren A. Wright and the author studied the mine during May, 1942. The origin of the talc has recently been discussed by Wright. 33 The White Eagle mine is on the very steep eastern slope of the Inyo Range overlooking Saline Valley, Inyo County, Calif., 1 mile south of Willow Creek. The work- ings are about 3,600 feet in elevation, the ore bin at the bottom of the aerial tram is approximately 2.500 feet, and the main camp (near the mouth of Willow Creek) is at an elevation of around 2,300 feet above sea level. Soil and vegetation are scanty along the arid eastern side of the Inyo Range. The camp is reached by a circuitous route from the Owens Valley highway. Automobiles must enter Saline Valley at the north end, following the Bigpine-Waucoba Canyon road. The road is partly steep, rough, tortuous, and generally unsatisfactory. Prom the foot of the moun- tain the mine is accessible only by a trail about half a mile in length. History, Operation, and Production. Mr. Elmer Oaks of Bigpine is the discoverer of the talc deposit. The property was not exploited until 1941 when it was leased to Mr. Wright Huntley of Bigpine. The mine was bought by the Sierra Talc Company in 194.5, but it is still leased to Mr. Huntley. Initial development of the property included the driving of three short adits one of which is in talc through- out. At the site of the latter adit, an open cut was made. Talc is mined from this cut, which has been enlarged and benched. After being hand-sorted, the talc is taken to the foot of the mountain by means of a 2,000-foot jig-back aerial tram. During the first year of production (1941-42) the mine was inactive a good part of the time. An effort was being made to produce talc of steatite grade, but sorting of the ore was difficult and only partly successful. About 1,570 tons of talc was produced in 1941, beginning in August of that year, but only 700 tons was shipped in the first 5 months of 1942. Altogether, 2,270 tons had been 3 - Booth, Otis, oral communication. "Wright, L. A.. White Eagle talc deposit: an example of stea- tization of granite: (abst) Geol. Soc. America Bull., vol. a9, l>. 138a, 1948. :u Sl'KCIAI. lkKl'OKT S 3620 3600 - 3580 - 3560 - 3540 J •SW A + ^\ ^*— + +N—-— Crest of • -~N + +\ minor ridge '. + +9' +\y + +\ t +\ + +\ * +\ o es E XPLANATION tc Gro Bench Vi-i Do \ '•■■• \ Foce of cu \ Tol V *° Adit, projected" fc Tolc + r+r + nite rock with DUS inclusions >: . /VV i dt>l omitic morble t JS Track yy~~^ 1 + X / dol^ + + \ i ' i '■ - gr + \ NN £ B M Poge 1942 FEET line of section KlIil'KK - .logii ■tiim Hi main (jujirry, VVhitK ICsigh> mini produced up to the time of this investigation. The talc is trucked 187 miles to the Sierra Talc Company mill at Keelcr. The Rocks and Geologic Structure. The east slope of the Inyo Range is an eroded fault scarp, steep and almost devoid of soil. The rocks near the base of the slope are sheared and crushed, but the mine itself is farther removed from the marginal fault which bounds the range, and considerable continuity was observed in the various rock units. The steepness of the escarpment has caused some landsliding, however, even at the site of the talc, deposit. The area] geology is shown on the accompanying map, plate 11. Silica rock occurs as an elongated body. It probably is quartzite and displays faint stratification, /unlike the silica rock of the Talc City mine. Possibly it has been altered to dolomite in places, as its thickness varies con- siderably where it is bordered on both sides by dolomitic marble. Dolomitic marble is one of the oldest rocks at the mine. It is light, warm brown on weathered surfaces, but where freshly broken it is white to gray. Much of the dolomitic marble is sufficiently coarse that the cleavage surfaces of the constituent crystals are readily visible at a casual glance. Granitic material (probably granite or quartz mon- zonite) has invaded and partly engulfed the silica rock and dolomitic marble. The granite is moderately dark gray, and contains both biotite and hornblende ; the grains arc small to medium in size. Numerous included slivers and blocks of dark schists and some basic igneous rocks are present within the granitic mass. In general the rock units occur in roughly parallel bands, as seen in plan, but there is much local irregularity, the granitic rock is moderately discordant in its relations with the other rocks. The dolomitic marble appears in iso- lated patches as well as in continuous bands. The silica rock varies in width and terminates abruptly at both ends. The talc body likewise is not tabular nor lenticular in form. These irregularities in the areal pattern of the rocks are Ihe result of igneous intrusion and hydrothermal al tcral ion rather than folding, fault ing, or other mechanics deformation. Despite the lack of uniformity in detail, all of tin mappable units strike nearly north-south, and in genera diji westward. Only one fault, a minor one, is shown on the map However, the footwall of the northern portion of the tak is a distinct plane which is either a joint or a shear plane On the whole, joints are notably abundant in this area. The Talc. Landslide and talus material locally cover the talc, and prior to the excavation of the open cut, it appeared that there were two main deposits rather than! a single large body. In plan the talc body is "I/' shaped, consisting of two contiguous segments of unequal thickness that are at right angles (see pi. 11), and which dip more or less Inward one another. The lengths of the segments are re- spectively about 250 and 200 feel. The corresponding map widths are 88 and !'"> feet, but these figures do not repre- sent the true thicknesses. Taking into account the dip of the talc, the slope of the ground surface, and the irregu- larity of the granite contact, the thickness of one branch of the talc body is locally 138 feet (fig. 23) and that of the other branch is locally 4(J feet. The talc grades into dolomitic marble, granite, and silica rock, and was almost certainly formed by hydro- thermal alteration of all three. It contains partly replaced inclusions of the three rock types. These inclusions are numerous and are one of the most troublesome features of the deposit. They range from less than 1 inch to more than 5 feet in diameter, and commonly resemble rounded nodules of talc. The talc composing the exterior of the nodules grades into a core of granitic rock, dolomite, or silica rock as the case may be, granitic cores probably pre- dominating. Skill is required in sorting out these inclu- sions, which are usually not broken open during mining and which therefore exhibit only the talcose exterior. Their volume is of some importance but has not been accurately ascertained. Inspection of the quarry face sug- gests that they constitute between 5 percent and 20 percent Figure 24. Photomicrograph of partly talcose granite rock, White Eagle mine. The rock shown is aboul half feldspar and half tale. Crossed nicols. Talc Deposits of Steatite Grade, Inyo County 35 »f the deposit, but the impurities may be even more abun- exposures of country nick definitely limit the ore bodv in hint in the southern part of the talc body. Thin sections thai direction. The thickness of the deposit, including >!' partly altered rock show the transition from granitic some "semi-talc", is about 15 feet. The vertical dimension rock to talc (fig. 24). is still unknown. The talc is gray white to greenish white and is fine- The country rock is mainly gray dolomite and dolo- prrained and structureless for the most part. It is soft but mitic marble, stratified in places. Within this material brittle and is so thoroughly fractured that it breaks into there is a band of silica rock that is either quartzit ■ a rather small pieces, increasing the difficulty of sorting it hydrothermal product. The talc occurs along the under by hand. In a few places the talc unmistakably exhibits a side of the siliceous rock, as shown in the accompanying relict igneous texture inherited from the original granitic sketch, figure 25. The ore is white next to the light silica rock. rock and dark next to the blue-gray dolomite, l'ossiblv An analysis kindly provided by the Sierra Talc Com- microscopic graphite was retained during hydrothermal pany fulfills commonly accepted steatite specifications, as alteration of the dolomite. It is said that the dark color follows: vanishes during firing. 34 Pe _r™ nt Percent The ore is massive, blocky, soft, semi-opaque, fine- Si ° a r,!, - 7(! S0:| ° 03 grained, and scarcely stained even at the surface of the Al*Oa 8.30 Na-O 0.I8 ground. The Bureau of Mines kindly gave the following Fe^Os 1.10 KaO 0.14 information based upon our two samples : CaO 0.30 Loss on ignition. 2.38 T.S.C.S. Xo. 63— Eleanor claim. White talc, collected from MgO 27.81 ndit by Wright and Page, 11/29/42 (about 10 lbs. 1 ; CaO, T ,. .-, , , , . „ . 0.08%; VeAh, 0.95%; color fired 2,300° F, buff ; mineral Individual samples such as the foregoing do not rep- impurities, very low; abrasion, soft. •resent the bulk of the deposit, which is variable. Some U.S.G.S. Xo. 04 — Eleanor claim. Dark talc, collected from large samples show more than 2 percent FeoO.-j and an • 1,lit hv Wright and Page, 11/29/42 (about 10 lbs.); CaO, appreciable content of feldspar. ££* ; Fes ° 3 ' 073% ; color Hml 2 ' 300 ° F ' cream; abrasion ' : " Mulryan, Henry, oral communication. EXPLANATION tc White talc Mottled gray and blue-block talc Silica rock Dolomite Contoct (Dashed where approximately located) Figure 25. Sketch section, Eleanor talc claim. Eleanor Talc Claim The recently discovered Eleanor talc claim overlooks Saline Valley from a point several hundred feet up on the eastern escarpment of the Inyo Range. It is less than a mile south of the White Eagle deposit and is approached by the same road, but the final ascent from the foot of the mountain is by trail. The approximate longitude and lati- tude are 117° 55' west and 36° 49' 30" north, juding from the Ballarat quadrangle map. G. P. Rogers of Bigpine and Frank Henderson are the owners. In November 1942, Lauren A. Wright and the writer gathered the data of this summary. At the time there were several small cuts and a 30-foot adit. The orebody is exposed along the surface for about 150 feet (slope distance) . The adit is near the south end of the deposit. About 100 feet south of the adit continuous BIBLIOGRAPHY Anon. (Page, B. M., and Wright, L. A.), Talc in the Ganim mine, Shasta County, California: U.S. Geol. Survey Strategic Min- erals Investigation, Prelim. Maps, 194."',. Anon., Talc: Ceramic Industry, vol. 32, pp. 38-40, 193!). Dana, E. S., The svstem of mineralogy of James Dwight Dana, 0th ed., pp. 678-680, 1904. Diller, J. S., Mineral Resources for 1913, I'.S. Geol. Survey, pp. 153, 155, 157-160, 1914. Engel, E. A. J., Talc and ground soapstone, in Industrial minerals and rocks: Am. Inst. Min. Met. Eng., pp. 1018-1041, 1949. Goodyear, W. A., California Div. Mines Rept. 8, p. 207, 1888. Klinefelter, T. A., Speil S., and Gottlieb S., Survey of the suitability of domestic talcs for high-frequency insulators: I'.S. Bur. Mines Rept. Inv. 3S04, 1945. Knopf, Adolph, A geologic reconnaissance of the Inyo Range and the eastern slope of the Sierra Nevada, California, with a sec- tion by Kirk, Edwin, The stratigraphy of the Inyo Range : U.S. Geol. Survey Prof. Paper 110, 1918. Ladoo, R. B., Talc and soapstone: U.S. Bur. Mines Bull. 213, pp. 111-117, 1923. Sampson, E., Mineral Resources for 1920, Part II. I'.S. deed. Survey, pp. 203-204, 1923. Sampson, E., Mineral Resources for 1922, U.S. Geol. Survey, pp. 81-83, 1923. Tucker, W. B., California Div. Mines Rept. 17, pp. 300-301, 1920-21. Tucker, W. B., California Div. Mines Rept. 22. pp. 523-524, 1926. Tucker, W. B., and Sampson, R. J., California Div. Mines Rept. 34, pp. 492-495, 1938. Waring, C. A., and Huguenin, E., California Div. Mines Rept. 15, pp. 126-127, 1919. Wright, L. A.. White Eagle talc deposit : an example of stent izal inn of granite: (abst.) Geol. Soc. America Bull., vol. 59, p. 1385, 1948. Wright, L. A.. California talcs: Min. Eng.. vol. Is7. no. 1. pp. 122-128, 1950; also, Trans. Am. Min. Met. Eng., vol. IK", pp. 122-128, 1950. 42682 4-51 2M printed m California state printing office DIVISION OF MINES OLAF P JENKINS. CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY SPECIAL REPORT 6 PLATE I EXPLANATION sdl Stratified dolomite ond limestone; ton to block NOTE As nearly as possible, talc bodies ore shown os they were prior to mining. Most out at the surface before map was mode Geology by B. M Page, Morch 1942 Topography by B M Page and M Erickson SURFACE GEOLOGY OF THE TALC CITY MINE, INYO COUNTY, CALIFORNIA IO0 50 Contour interval 20 feet Elevations referred to cottar of main shaft, which is IOOO. OO feet (assumed) + EXPLANATION GEOLOGY OF THE C LEVEL, TALC CITY MINE GEOLOGY OF INTERMEDIATE LEVELS, TALC CITY MINE GEOLOGY OF THE B LEVEL, TALC CITY MINE ology by 8 M Peg* GEOLOGY OF A PART OF THE D LEVEL, TALC CITY MINE GEOLOGY OF B, C, D AND INTERMEDIATE LEVELS, TALC CITY MINE STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT Of THE INTERIOR GEOLOGICAL SURVEY SPECIAL REPORT 6 PLATE 3 /.' ;.,' rZ' Limonit; cub.s I VERTICAL SECTION ALONG LINE B-B', TALC CITY MINE CENTRAL ORE BODY crest of moln rldje VERTICAL SECTION ALONG LINE C-C', TALC CITY MINE VERTICAL SECTION ALONG LINE D-D',TALC CITY MINE EXPLANATION WEST OREBODY Slrollflad dol VERTICAL SECTION ALONG LINE A-A', TALC CITY MINE VERTICAL SECTIONS, TALC CITY MINE EXPLANATION Altered dolomite Altered slate and silica rock Massive dolomite Contact, showing dip (Dashed where approximately located} Fault or shear, showing dip (Dashed where approximately located) S<~€0 Strike and dip of beds X,o Strike of vertical beds E B Vertical shaft -A3 Pit or open cut Dump Underground workings (Not all shown) -f SURFACE GEOLOGY OF THE ALLIANCE TALC MINE AND IRISH LEASE, INYO COUNTY, CALIFORNIA < iS ir a a a a U \$ '- h- - o Ul UJ 2 (J) ^ Q o ^ 1 < < h- O) 2 Ul < o _l z Q. < _J O _1 O < O _l o UJ CD BY 8 M PAGE ANO L A WRIGHT SEPTEMBER 1942 SURFACE GEOLOGY OF THE WHITE MOUNTAIN TALC MINE, INYO COUNTY, CALIFORNIA 1 DIVISION OF MINES OLAF P JENKINS. CHIEF SW A STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES WEST FAULT UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY -I- T7V3F a A13 + EAST FAULT vim CENTRAL FAULT AND DIKE SECTION A— A' SOUTHWEST HALF ROAD TO KEELER SECTION A — A' NORTHEAST HALF NE A' SPECIAL REPORT 8 PLATE 7 EXPLANATION Mantle — thick soil , talu ez Talc, semi- talc and intermingled material •J < \l < Dike, sill , rhyolite or ande Massive dolomite Silica rock Flinty, dolomitic limestone Sanded limestone '1LL1I approximately located) No 16 Adit Level Enfronce to glory hole ■f Fault or shear (Doshed *here approximately located) GEOLOGIC CROSS SECTIONS WHITE MOUNTAIN MINE INYO COUNTY, CALIFORNIA 200 250 FEET SECTION B — B SECTION C-C DIVISION OF MINES OLAF P. JENKINS, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY SPECIAL REPORT 8 PLATE 8 ADIT NO. 29 EXPLANATION ADIT NO 13 ADIT NO.8 a 59€3 + ADIT NO. 20 ADIT NO. 18 Tolc. semi-talc and intermingled material Dike, rhyolite or andesite Mossive dolomite Silica rock Flinty, dolomitic limestone Contact, showing dip (Dashed where indefinite) , Fault, showing dip (Dashed where approximately lacoled U, upthrown side. Q.downthrown side) Fault with variable dip Fault zone or shear zone Axis of anticline Strike and dip of beds Generalized strike of contorted beds ^X> Underground workings Ore chute Head of raise or winze IS Foot of roise or winze ADIT NO. 36 ADIT NO. 2 GEOLOGY BY LA WRIGHT AND 6 M PAGE. 1942 GEOLOGIC MAP OF ADITS, WHITE MOUNTAIN MINE Montie-soii,toius, etc I °°< I ESS Tolc I- Wl Contoct, shewing dip iOasnea nrfwra appro* Conceoled contact Fault or shear, showing dip imotely to cot BO") , Concealed toutl or shea Strike and dip of beds Underground workings ,1 di. Flinly, dotomitlc limestone Sandy dolomite w- Generalized strike and dip of beds Verlicol shaft Trench or open cut By L A.Wright and B.MPoge 1942 GEOLOGIC MAP OF THE SOUTH DEPOSIT FLORENCE TALC MINE, INYO COUNTY, CALIFORNIA Contour interval 20 feet Initio! elevation assumed to be 5500 feet of A A DIVISION OF MINES OLAF P. JENKINS, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY SPECIAL REPORT 8 PLATE 10 + ~SlOo EXPLANATION Talc and included matter Felsite, largely altered to chlorite Silica rocK Massive dolomite Wl Limestone- stratified Contact, showing dip (Dashed where approximately located) Fault or shear, showing dip (Dashed where approximately located) Strike and dip of beds H B Shaft at surface e m Bottom of shaft c? Open cut Underground workings Track and dump By L A. Wright and B M Page December 1942 SURFACE AND UNDERGROUND GEOLOGY OF THE FRISCO TALC MINE INYO COUNTY, CALIFORNIA Contour interval 10 feet Datum is assumed mean sea level I DIVISION OF MINES OLAF P. JENKINS. CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY SPECIAL REPORT 8 PLATE II EX PL A N ATION Talus ond landslide material Talc and semi-talc Granitic rocks with various inclusions Dolomitic morble Contact, showing dip (Dashed where opproximotely located) (Dashed where approximately located) Strike ond dip of beds Trench + Limit of quarry GEOLOGIC MAP OF THE WHITE EAGLE MINE INYO COUNTY, CALIFORNIA BY L. A. WRIGHT AND B.M.PAGE 1942 Bin chute + 300 FEET =3 Contour interval 20 feet Initial elevation assumed to be 3600 feet at A A