Mr STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES ECONOMIC GEOLOGY OF THE BISHOP TUNGSTEN DISTRICT CALIFORNIA SPECIAL REPORT 47 1956 uiV iV CALIFORNIA JUL 17 1957 LIBRARY DIVISION OF MINES FERRY BUILDING, SAN FRANCISCO SPECIAL REPORTS ISSUED BY THE DIVISION OF MINES l-A. Sierra Blanca limestone in Santa Barbara County, Cali- fornia, by George W. Walker. 1950. 5 pp., 1 pi. Price 250 1-B. The Calera limestone, San Mateo and Santa Clara Counties, California, by George W. Walker. 1950. 8 pp., 1 pi., 6 figs. Price 25tf. 2. Geology of part of the Delta-Mendota Canal near Tracy, California, by Parry Reiche. 1950. 12 pp., 5 figs. Price 25 0. 3. Commercial "black granite" of Diego County, California, by Richard A. Hoppin and L. A. Norman, Jr. 1950. 19 pp., 18 figs. Price 250. 4. Geology of the San Dieguito pyrophyllite area, San Diego County, California, by Richard H. Jahns and John F. Lance. 1950. 32 pp., 2 pis., 21 figs. Price 50 0. 5. Geology of the Jurupa Mountains, San Bernardino and Riverside Counties, California, by Edward M. MacKevett. 1951. 14 pp., 1 pi., 14 figs. Price 250. 6. Geology of Bitterwater Creek area, Kern County, Califor- nia, by Henry H. Heikkila and George M. MacLeod. 1951. 21 pp., 2 pis., 15 figs. Price 350. 7-A. Gem- and lithium-bearing pegmatites of the Pala district, San Diego County, California, by Richard H. Jahns and Lauren A. Wright. 1951. 72 pp., 13 pis., 35 figs. Price $2.50. 7-B. Economic geology of the Rincon pegmatites, San Diego County, California, by John B. Hanley. 1951. 24 pp., 1 pi., 5 figs. Price 350. 8. Talc deposits of steatite grade, Inyo County, California, by Ben M. Page. 1951. 35 pp., 11 pis., 25 figs. Price 850. 9. Type Moreno formation and overlying Eocene strata on the west side of the San Joaquin Valley, Fresno and Merced Counties, California, by Max B. Payne. 1951. 29 pp., 5 pis., 11 figs. Price 600. 10-A. 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Photogcologic interpretation using photogrammetric dip cal- culations, by D. H. Elliott. 1952. 21 pp., 9 figs. Price 500. 16. Geology of the Shasta King mine, Shasta County, Califor- nia, by A. R. Kinkel, Jr., and Wayne E. Hall. 1951. 11 pp., 3 pis., 4 figs. Price 500. 17. Suggestions for exploration at New Almaden quicksilver mine, California, by Edgar H. Bailey. 1952. 4 pp., 1 pi. Price 250. 18. Geology of the Whittier-La Habra area, Los Angeles County, California, by Charles J. Kundert. 1952. 22 pp., 3 pis., 19 figs. Price 500. 19. Geology and ceramic properties of the lone formation, Buena Vista area, Amador County, California, by Joseph A. Pask and Mort D. Turner. 1952. 39 pp., 4 pis., 24 figs. Price 750. 20. Geology of the Superior talc area, Death Valley, California, by Lauren A. Wright. 1952. 22 pp., 1 pi., 15 figs. Price 500. 21. Geology of Burruel Ridge, northwestern Santa Ana Moun- tains, California, by James F. Richmond. 1952. 1 pi., 11 lij;s. Price 500. 22. Geology of Las Trampas Ridge, Berkeley Hills, California, by Cornelius K. Ham. 1952. 26 pp., 2 pis., 20 figs. Price 750. 23. Exploratory wells drilled outside of oil and gas fields in California to December 31, 1950, by Gordon B. Oakeshott, Lewis T. Braun, Charles W. Jennings, and Ruth Wells. 1952. 77 pp., 1 pi., map. Price, map and report, $1.25; map alone, $1. 24. Geology of the Lebec quadrangle, California, by John C. CroweU. 1952. 23 pp., 2 pis., 10 figs. Price 750. 25. Rocks and structure of the Quartz Spring area, northern Panamint Range, California, by James F. McAllister. 1952. 38 pp., 3 pis., 13 figs. Price 750. 26. Geology of the southern Ridge Basin, Los Angeles County, California, by Peter Dehlinger. 1952. 11 pp., 1 pi., 7 figs. Price 500. 27. Alkali-aggregate reaction in California concrete aggregates, by Richard Merriam. 1953. 10 pp., 12 figs. Price 350. 28. Geology of the Mammoth mine, Shasta County, California, by A. R. Kinkel, Jr., and Wayne E. Hall. 1952. 15 pp., 9 pis., 5 figs. Price 750. 29. Geology and ore deposits of the Afterthought mine, Shasta County, California, by John P. Albers. 1953. 18 pp., 6 pis., 9 figs. Price 750. 30. Geology of the southern part of the Quail quadrangle, Cali- fornia, by Charles W. Jennings. 1953. 18 pp., 2 pis., 16 figs. Price 750. 31. Geology of the Johnston Grade area, San Bernardino County, California, by Robert Barton Guillou. 1953. 18 pp., 1 pi., 19 figs. Price 750. 32. Geological investigations of strontium deposits in southern California, by Cordell Durrell. 1953. 48 pp., 9 pis., 12 figs. Price $1.25. 33. Geology of the Griffith Park area, Los Angeles County, California, by George J. Neuerberg. 1953. 29 pp., 1 pi., 15 figs. Price 500. 34. Geology of the Santa Rosa lead mine, Inyo County, Cali- fornia, by Edward M. Mackevett. 1953. 9 pp., 2 pis., 3 figs. Price 500. 35. Tungsten deposits of Madera, Fresno, and Tulare Counties, California, by Konrad B. Krauskopf. 1953. 83 pp., 4 pis., 52 figs. Price $1.25. 36. Geology of the Palen Mountains gypsum deposit, Riverside County, California, by Richard A. Hoppin. 1954. 25 pp., 1 pi., 32 figs., frontis. Price 750. 37. Rosamond uranium prospect, Kern County, California, by George W. Walker. 1953. 8 pp., 5 figs. Price 250. 38. Geology of the Silver Lake talc deposits, San Bernardino County, California, by Lauren A. Wright. 1954. 30 pp., 4 pis., 18 figs. Price $1.00. 39. Barite deposits near Barstow, San Bernardino County, California, by Cordell Durrell. 1954. 8 pp., 4 pis., 1 fig. Price 500. 40. Geology of the Calaveritas quadrangle, Calaveras County, California, by Lorin D. Clark. 1954. 23 pp., 1 pi., 7 figs. Price $1.75. 41. Geology of the Angels Camp and Sonora quadrangles, Calaveras and Tuolumne Counties, California, by John H. Eric, Arvid A. Stromquist, and C. Melvin Swinney. 1954. 55 pp., 4 pis., 21 figs. Price $3.75. 42. Geology of mineral deposits in the Ubehebe Peak quadran- gle, Inyo County, California, by James F. McAllister. 1955. 64 pp., 3 pis., 26 figs. Price $2.00. 43. Geology of a portion of the Elsinore fault zone, California, by John F. Mann, Jr. 1955. 22 pp., 2 pis., 5 figs. Price 750. 44. Bibliography of marine geology and oceanography, Califor- nia coast, by Richard D. Terry. 1955. 131 pp., 2 figs. Price 750. 45. Exploratory wells drilled outside of oil and gas fields in California to December 31, 1953, by Charles W. Jennings and Earl W. Hart. 1956. 104 pp., 2 figs., map. Price $1.50. 46. Geology of the Huntington Lake area, Fresno County, California, by Warren B. Hamilton. 1956. Price 750. STATE OF CALIFORNIA GOODWIN I. KNIGHT, Governor DEPARTMENT OF NATURAL RESOURCES DeWITT NELSON. Director DIVISION OF MINES FERRY BUILDING. SAN FRANCISCO 11 OLAF P. JENKINS. Chief SAN FRANCISCO SPECIAL REPORT 47 AUGUST 1956 ECONOMIC GEOLOGY OF THE BISHOP TUNGSTEN DISTRICT CALIFORNIA By PAUL C. BATEMAN U. S. Geological Survey. Menlo Park. California With a Section on the PINE CREEK MINE By PAUL C. BATEMAN and LAWSON A. WRIGHT U. S. Geological Survey, Menlo Park, California U. S. Vanadium Company, Bishop, California Price $4.00 Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/economicgeologyo47bate ECONOMIC GEOLOGY OF THE BISHOP TUNGSTEN DISTRICT, CALIFORNIA * By Paul C. Bateman OUTLINE OF REPORT Page Abstract 5 Introduction 5 Biography Geologic formations Principal features Sedimentary rocks of the White Mountains Metamorphic rocks of the Sierra Nevada Quartz diorite and hornblende gabbro Granitic rocks Volcanic rocks Alluvial deposits Mineral deposits Mining history Contact-metamorphic tungsten deposits Rocks Internal organization of the deposits Geologic environment of the deposits Leached outcrops and secondary enrichment Grade of ores . — Outlook for the district Suggestions for prospecting Tungsten mines and prospects The Pine Creek pendant Pine Creek mine, by Paul C. Bateman and Lawson A. Wright Adamson mine Brownstune mine Tungstar mine Hanging Valley mine Lakeview mine Lambert mine Round Valley Peak prospect (Adamson prospect) Occurrence northwest of Pine Creek Federal housing project Blue Grouse prospect Moore prospect (Sunnyboy mine) Mountain Basin prospect The Bishop Creek pendant Schober mine — — Merrill prospect Lindner prospect (Oomph claims) Brackett prospects Peterson prospects Waterfall prospect Stevens prospect East end of North Lake Green Lake area Chocolate Peak area Tungsten Hills Round Valley septum Round Valley (Big Shot) mine Western Tungsten mine Tungsten Hill (Little Shot) mine Deej) Canyon (Tungsten City) area Little Sister mine Jackrabbit mine Tungsten Blue (Shamrock) mine Tungsten Peak prospect Aeroplane (Mesa Tungsten) mine Lookout prospect (Tiptop claims) White Caps mine Hilltop prospect Van Loon prospects Sierra front southwest of Bishop Rossi mine Chipmunk mine (Pickup claims) Yaney mine Brown prospect (L. and L. claims) Early-Morhardt prospect West of Keough Hot Springs 1 Publication authorized by the Director, U. S. Geological Survey. 7 9 9 9 9 11 11 12 13 13 14 15 15 17 19 20 20 20 21 22 22 22 34 35 36 37 37 38 39 39 39 39 39 40 40 41 41 41 42 43 43 43 43 43 44 44 44 45 46 46 47 47 47 48 48 74 74 74 74 75 75 75 76 77 77 77 Page Shannon Canyon area 77 Marble Tungsten mine 77 Buckshot prospect 78 Prospects in the Middle fork of Shannon Canyon 78 Scattered prospects in the Sierra Nevada 79 Rattlesnake prospect 79 McVan claim 79 Bakoch prospect 79 Prospects south of Taboose Creek 79 Tungsten in the White Mountains 79 Mohawk Shaft area 80 R. and R. claims 80 Metalliferous vein deposits 80 Gold 80 Cardinal mine 80 Poleta mine 80 Fish Springs Hill 81 Cleveland mine 82 Commetti mine 82 Antimony 82 Bishop Antimony mine 82 Cobalt 83 Bishop Silver-Cobalt prospect 83 Nonmetallic deposits 83 Barite 83 Gunter Canyon barite mine 83 Talc 83 Blue Star mine 83 Mt. Tom talc prospect 84 Pumice 84 Rhyolite tuff 85 Expansible rhyolite (perlite) 85 Feldspar and clay 86 Limestone and marble 86 Granite 86 Gravel and sand 86 References cited 87 Illustrations Page Plate 1. Economic map of the Mt. Tom quadrangle In pocket 2. Economic geologic map of the Bishop quad- rangle In pocket 3. Economic geologic map of the Big Pine quad- rangle In pocket 4. Economic geologic map of the northeastern one-third of the Mt. Goddard quadrangle.. In pocket 5. Block diagram of the Pine Creek mine In pocket 6. Geologic maps and sections of the lower area of the Adamson mine In pocket 7. Maps and sections showing the underground geology of the Tungstar mine In pocket 8. Geologic maps and sections of the Round Val- ley mine In pocket 9. Geologic maps and section of the Western Tungsten mine In pocket 10. Geologic maps and sections of the Little Sister mine In pocket 11. Geologic maps and sections of the Tungsten Blue (Shamrock) mine In pocket 12. Geologic maps and section of the Aeroplane mine In pocket 13. Geologic maps and sections of the Chipmunk mine In pocket 14. Geologic maps and seetyms of the Marble Tungsten mine In pocket (3) Special Report 47 Page Figure 1. Map showing: location of the Bishop district 49 2. Magnetic profiles in the Deep Canyon area, Tung- sten Hills 50 .'{. Block diagram of the South ore body, Pine Creek mine, showing the tungsten and molybdenum ore shoots 51 4. Sectional diagram of the Main ore body, Pine Creek mine, showing the tungsten and molybdenum ore shoots 52 5. Sectional diagram of the North ore body, Pine Creek mine, showing the tungsten ore shoots 53 G. Geologic map and section of the Loop ore body, Pine Creek mine, showing the tungsten ore shoots 54 7. Geologic map of the Brownstone mine 55 8. Geologic map of the upper adit in the Hanging Val- ley mine 56 9. Geologic maps and section of the Lakeview mine.. 57 10. Geologic maps of the Lambert mine 58 11. Geologic maps and section of the Schober mine 59 12. Geologic maps of the Lindner prospect (Oomph claims) — 60 13. Geologic map of the Coyote Lake prospect (Black Monster claim) 61 14. Geologic sketch map of the Munsinger prospect 62 15. Geologic sketch map of the Little Egypt prospect.^ 62 16. Geologic map of the Chocolate Peak area 63 17. Underground geology in the upper workings of the Tungsten Hill (Little Shot) mine 64 18. Geologic maps of the Jackrabbit mine 65 19. Geologic maps of the underground workings in the White Caps mine before stoping 66 20. Geologic maps of the Rossi mine 67 Page 21. Geologic maps of the adit levels in the Yaney mine before glory hole was made 68 22. Geologic maps of the Bakoch prospect 69 23. Composite map of the main workings in the Cardinal gold mine 70 24. Map and section showing the underground geology of the Poleta gold mine 71 25. Geologic map of Fish Springs hill 72 26. Geologic map of the adit level in the Bishop Anti- mony mine 73 27. Geologic map of the rhyolite hill south of Big Pine 73 Photo 1. Aerial photograph of west side of Pine Creek pendant at Pine Creek mine 25 2. Aerial photograph looking down Morgan Creek into Pine Creek 26 3. Outcrop of ore body at Brownstone mine 27 4. Site of buildings at portal of Tungstar mine, burned in 1946 27 5. Headframe of shaft at Lakeview mine 28 6. Round Valley mine 28 7. Tungsten Blue (Shamrock) mine 28 8. Open pit at Tungsten Blue (Shamrock) mine 28 9. Opencut at Rossi mine 28 10. Glory hole at Yaney mine 29 11. Pumice pit of Insulating Aggregates Co 29 12. Lacustrine pumice bed in Insulating Aggregates Co. pit 30 13. Southeast side of rhyolite hill 6 miles south of Big Pine 30 14. "Perlite" at working face in Fish Springs quarry 30 Economic Geology of Bishop Tungsten District ABSTRACT This report is a presentation of the economic results of a geo- logic study of the Bishop district, a highly productive tungsten- hearing region in eastern California. The area studied comprises about 800 square miles, two-thirds of which is in the eastern Sierra Nevada. Also included in the area is the north end of Owens Valley, Round Valley, the south part of a plateau that is called Volcanic Tableland, and a 15-mile span along the west side of the White Mountains. Maps showing the economic geology of the district, especially designed for use in mining and prospecting, have been prepared using as base maps the Mt. Tom, Bishop, Big Pine, and northeast one-third of the Mt. Goddard 15-minute quad- rangle maps of the U. S. Geological Survey. The Sierra Nevada, in the mapped area, is made up largely of granitic rocks ranging in composition from granite to granodi- orite ; but masses of metamorphic rocks and dark-colored horn- blende gabbro, diorite, and quartz diorite are distributed through the granitic terrane as roof pendants, elongate and generally dis- continuous screens or septa that lie between different kinds of granitic rocks, and small inclusions. Owens Valley and Round Valley are underlain chiefly by alluvial deposits, including valley fill, fan deposits, lake deposits, and terrace gravels. Basaltic flows and cinder cones are found along the west side of Owens Valley, being especially common south of Big Pine and west of Bishop. In the northern part of the mapped area, the north end of Owens Valley terminates against the Volcanic Tableland, the surface of which is composed of rhyolite tuff. The White Mountains on the east side of Owens Valley are composed chiefly of highly de- formed fossiliferous sedimentary rocks of Early Cambrian age and by unfossiliferous sedimentary rocks of Early Cambrian or Late Precambrian age. The value of the tungsten mined from the district is far greater than that of all other mineral commodities (not including water), and the mines seem capable of yielding at least as much tungsten as has already been produced. Although the district has been heavily prospected, it is possible that new discoveries will be made that will materially increase the ultimate production. The tungsten yield to the end of 1953 is estimated to be in the order of 1,300,000 short-ton units (a short-ton unit is 20 pounds) of WOa. Of this, more than 1,000.000 units of WOa, plus notable amounts of molybdenum and copper, was produced from the Pine Creek mine of the U. S. Vanadium Co., one of the most productive tungsten mines in the United States. In addition to tungsten, the district has yielded an estimated 2,000 tons of copper (chiefly from the Pine Creek tungsten mine and the Cardinal gold mine), 6,000,000 pounds of molybdenum (from the Pine Creek mine), 100,000 ounces of gold, 100,000 tons of pumice, and 20,000 tons of ex- pansible rhyolite (perlite). None of the gold mines have been operated since World War II, but between 1048 and 10. r >3 the pro- duction of pumice was at a steady rate, and the production of ex- pansible rhyolite increased markedly. Other mineral commodities that have been mined include silver, antimony, barite, talc, sand and gravel, granite, marble, and rhyolite tuff. The tungsten deposits, with a few exceptions, are tactite (con- tact metamorphic) deposits and commonly occur in the marginal parts of masses of marble, adjacent to intrusive granitic rock. Most of the productive deposits are in the Pine Creek pendant or in the Tungsten Hills, but a few mines and many prospects are in the Bishop Creek pendant and in other areas of metamorphic rock. The distribution of tungsten deposits suggests that the composi- tion of the granitic rock is a significant factor in the localization of the tungsten deposits. Of 54 deposits described in this report, 47 are associated with the 3 youngest and lightest colored of the granitic intrusive rocks ; included among the 47 are all of the de- posits with significant production. The 3 light-colored granitic rocks are shown collectively on the economic geologic quadrangle maps as "granite," and 5 other darker lined granitic intrusive rocks are shown as "granodiorite." Many of the better exposed tungsten deposits can be shown to be related to features that acted as traps for ore-bearing solutions. Broadly these traps are of two kinds (1) irregularities in the intrusive contact, and (2) favorable structures and beds in the host metamorphic rocks. The classification of traps is further sub- divided and related to the size, grade, and configurations of the deposits. INTRODUCTION Purpose and Scope of the Report. This report pre sents the economic results of a geologic study of the Bishop district, a highly productive tungsten-bearing area in east-central California (fig. 1). The Bishop dis- trict has never been a legally organized mining district and its boundaries are vague; local usage is variable and provides little basis for clear definition of the dis- trict boundaries. In this report, entirely for convenience, the Bishop district is considered to be coincident with the area studied and mapped geologically; and the terms "Bishop district" and "mapped area" are used interchangeably. The mapped area, comprising about 800 square miles, is shown on the Mt. Tom, Bishop, Big Pine, and northeastern one-third of the Mt, Goddard 15- minute quadrangle maps of the U. S. Geological Survey. (Pis. 1, 2, 3, and 4.) All of the economic mineral deposits in the mapped area were studied, but inasmuch as the value of the tungsten that has been mined far exceeds that of all the other mineral commodities (except water), the greater part of the report deals with the tungsten deposits. Studies of several of the tungsten deposits, made by members of the U. S. Geological Survey between 1939 and 1945 as part of the wartime strategic minerals pro- gram of that Survey, served as the nucleus from which the present study grew. Maps of these deposits were brought up to date, and deposits not previously mapped were examined and the ones that seemed likely to yield significant data were mapped. Field work was carried on during the summers of 1945 to 1950, inclusive, and a few weeks were spent in the field during the summers of 1951 and 1952. This report is directed to those interested in mining and prospecting; both the maps and the text are re- stricted as much as possible to features that seem to have direct bearing on the discovery and exploitation of the mineral deposits. To spare the person interested mainly in the discovery and exploitation of mineral deposits the necessity of thumbing through pages of geo- logic material of little obvious significance to mining and prospecting other geologic data have been either much compressed or, where possible, eliminated entirely. The report is divided into two main parts. The first and shorter part includes a general description of the geology of the district, with emphasis on those aspects that pertain to the mineral deposits. The second part deals with the ore deposits and with the mines by which they are developed. In the first part, rock units and structures shown on the accompanying quadrangle maps of the economic, geology are briefly described. In order to make the maps more valuable in prospecting, the relationship of each unit represented on the map to mineral exploration is summarized in the map explana- tions. In the second part of the report, the individual mineral deposits are described, with maps and other illustrations of the better-developed and more-productive deposits. Preceding the descriptions of the tungsten de- posits, which are more fully described than other kinds of deposits, is a general discussion of their common geological associations and of their internal structure. Special Report 47 Following the descriptions of tungsten deposits are de- scriptions of several vein deposits of gold, silver, anti- mony, cobalt, and barite. Pumice, with a fairly steady production, and expansible rhyolite (perlite), which is being recovered in the region in increasing amounts, are more fully described than most other nonmetallic de- posits. Deposits of marble, talc, clay and feldspar, and sand and gravel are described briefly. Principal Economic Results. The results of the study pertain chiefly to the tungsten deposits for which the region is best known. The more obvious results are em- bodied in the quadrangle maps showing the economic geology of the region and in the detailed maps and descriptions of the mineral deposits. These data are useful in prospecting in the region and in the explora- tion and development of the deposits described, but they are even more valuable as the material upon which to base broad concepts relating to the distribution, geo- logic relationships, and structure of the mineral deposits. Concepts relating to the geologic environment and internal structure of the tungsten deposits are developed, and a procedure for more efficient prospecting in this and contiguous areas is suggested. Inasmuch as the tungsten deposits, with a few exceptions, are tactite (contact-metamorphic) deposits, they occur most com- monly in the marginal parts of masses of marble and less commonly in other calcareous rocks, at or near con- tacts with intrusive granitic rock. Thus, the presence of marble or other calcareous rock and granitic rock ordi- narily is a requisite for tactite tungsten deposits. The distribution of the tungsten deposits in the mapped region suggests further that the kind of granitic rock present also is significant in the localization of tungsten deposits. Of 54 deposits described in this report, 47 are associated with the 3 youngest and lightest colored of the granitic intrusives, which are represented collec- tively on the accompanying quadrangle maps .showing economic geology as "granite." This statistic also sug- gests that the very existence of the district itself may be related to the presence of these "granites," but ex- tensive geologic mapping in contiguous areas to obtain information as to the broader distribution of both the calcareous and the intrusive rocks is required before this suggestion can be regarded as more than a tentative hypothesis. Many of the more extensively developed and conse- quently better-exposed tungsten deposits can be shown to be related to features that appear to have acted as traps for ore-bearing solutions. Broadly these traps are of two kinds: (1) irregularities in the intrusive contact and (2) favorable structures and beds in the host metamorphic rocks. The classification of traps can be further subdivided and related to size, grade, and con- figuration of the deposits. Recognition of the structural relationships of a deposit can aid in planning mine development by making it possible to predict the be- havior of the deposit laterally or in depth. Although more than 50 tungsten deposits have been found in the Bishop region, the area has not been pros- pected so exhaustively as to preclude the possibility of finding additional deposits. A procedure for prospecting in this region that seems likely to yield maximum bene- fits for minimum effort is to examine first the areas underlain by metamorphic rock, and especially areas un- derlain by calcareous metamorphic rock, paying partic- ular attention to the parts at or near contacts with gra- nitic intrusive rock. Although the light-colored rock shown as "granite" on the quadrangle maps appears to be more favorable than other instrusive rocks, it would be unwise to neglect contacts with somewhat darker "granodiorite. " Next, the areas mapped as amphibolite, quartz diorite, and hornblende gabbro, which in many places enclose abundant small metamorphic inclusions, should be searched for inclusions with tactite. Finally, the contacts between adjacent granitic intrusive masses should be searched for small masses of metamorphic rock with tactite. Individual granitic intrusives are not distin- guished on the economic geologic maps, being grouped into the two general classes of "granite" and "grano- diorite"; but the contacts between the individual intru- sives are shown. Along these contacts only a few of the larger masses of metamorphic rock could be delineated, and along some of them masses too small to be shown on the maps also are present. Within the granitic intru- sives a few small masses of metamorphic rock, in addi- tion to those shown on the maps, may be found ; but indiscriminate prospecting of the areas underlain by gra- nitic rocks will be found far less rewarding than pros- pecting the contacts between granitic intrusives. These procedures for prospecting are equally applicable in adjacent parts of the Sierra Nevada where accurate geologic base maps are not available. Geologic mapping in such areas would permit more efficient prospecting, as the favorable areas outlined in mapping could be ex- amined in detail, and time would not have to be spent in the random examination of geologically unfavorable ground. Previous Work. Several papers published before the end of the 19th century dealt with specific features in the Bishop area, but it was not until 1905, when J. E. Spurr published the results of a geologic reconnaissance of Nevada south of the 40th parallel and adjacent por- tions of California (Spurr, 1905), that the Bishop dis- trict was described in a geologic report. Spurr 's report includes a map on which a threefold distinction is made in the Bishop district between granular or coarse por- phyritic igneous rock in the Sierra Nevada, strata of Cambrian age in the White Mountains, and strata of Pleistocene age in Owens Valley. The following year a paper by W. T. Lee (1906) on the ground-water re- sources of Owens Valley was issued in which are in- cluded descriptions of the surficial deposits and an interpretation of the structure of Owens Valley. In 1912 and 1913 Adolph Knopf (1918) made a geologic recon- naissance of the Inyo Range and eastern slope of the southern Sierra Nevada, which covered the south half of the area described in the present report. About 20 years later, during the 1930 's, a series of structural studies of the metamorphic and intrusive rocks of the crest and eastern slope of the Sierra Nevada was made by Evans B. Mayo. The report resulting from these studies that deals most fully with the Bishop district is one called "Deformation in the interval Mt. Lyell-Mt. Whitney" (1941). Also during the 1930 's, C. M. Gilbert studied the volcanic region north of Bishop, including the Vol- canic Tableland in the north-central part of the Bishop region (Gilbert, 1938 and 1941). Economic Geology op Bishop Tunosten District Although several papers describing tungsten deposits within the Bishop region have been issued, no compre- hensive report that deals exclusively with the tungsten deposits in the Bishop region has hitherto been pub- lished. The earliest geologic report on the tungsten de- posits was by Adolph Knopf (1917), who visited the deposits of the Tungsten Hills in 1916 when the deposits discovered in the preceding 3 years were being brought into production. Shortly afterward, in the summer of 1918, Esper S. Larsen, Jr. also examined the deposits in the Tungsten Hills as well as the Pine Creek mine in Pine Creek Canyon. His report (Hess and Larsen, 1921) includes sketch maps of the Little Sister, Round Valley, and Pine Creek mines. The next geologic study of a tungsten deposit was not until 1934, when Randolph Chapman studied the contact metamorphism along the north side of the Round Valley septum, at the Round Valley mine (Chapman, 1937). With the outbreak of World War II in 1939, the Geological Survey intensified its investigations of the strategic minerals of the United States, and in 1941 Dwight M. Lemmon published two preliminary papers on tungsten-bearing districts within the area covered bv the present report. One deals with the deposits in the Tungsten Hills (1941a, Bull. 922Q), and the other deals with deposits in higher parts of the Sierra Nevada near Bishop (1941b, Bull. 931E). Two preliminary publications based on the present study have been issued ; one report is on the Pine Creek and Adamson mines (Bateman, 1945), and the other is on the tungsten deposits in the Tungsten Hills (Bate- man, Erickson, and Proctor, 1950). Much of the data contained in these papers has been incorporated in the present report. In addition to these reports on the tungsten deposits, which are based on detailed field examinations, brief descriptions of many mines in the district are included in reports of county or commodity surveys by the Cali- fornia Division of Mines, in "Mineral Resources of the the United States," and in "Minerals Yearbook." Paul Kerr's noteworthy memoir "Tungsten Mineraliza- tion in the United States" contains not only brief de- scriptions of most of the tungsten deposits in the Bishop district but also a theoretical discussion of the means by which tungsten is introduced into masses of metamorphic rocks such as the Pine Creek pendant (1946, pp. 17-18, 142-147). Acknowledgments. This report on the Bishop tung- sten district is a result of a cooperative project between the U. S. Geological Survey and the California State Division of Mines. Study of the mines was largely made possible through the fine cooperation extended to the writer, both by individuals and by the mining companies. Among the company mine staffs that have extended as- sistance are the U. S. Vanadium Co., the Tungstar cor- poration, and Panaminas, Inc. I am especially indebted to Mr. Lawson Wright of the mine staff of the U. S. Vanadium Co., who has joined me in the preparation of the part of the report dealing with the Pine Creek mine. The following individuals have aided materially by sup- plving information or assistance : H. 0. Johansen of the El Diablo Mining Co., Victor Krai, Gerald Hartley. Howard Stephens, Mike Millovitch, A. II. "Salty" Peter- sen, B. W. Van Vorhis, J. E. Morhardt, Gale Green, Joseph Smith, Robert Symons, J. F. Brackett, and E. E. Ives. Others too numerous to mention also contributed information that has been incorporated in this report. The writer was aided in the field by the following members, or former members, of the Geological Survey, most of whom assisted me for one summer field season : M. P. Erickson, strategic mineral studies (1943), P. D. Proctor (1946), M. W. Ellis (1947), J. W. Reid (1947), R. M. Campbell (1948), M. P. Carman (1948), E. 1). Jackson (1949), L. D. Clark (1949), R, P. dohnson (1950), R. L. Parker (1950), II. S. Imholz (1950), E. M. MacKevett (1951), and Dallas Peck (1952). During the preparation of this report, the writer profited from dis- cussions with colleagues on the Geological Survey about many of the problems relating to tungsten deposits. GEOGRAPHY Location and Accessibility. The mapped region, with an area of about 800 square miles, lies between 37° 00' and 37° 30' north latitude and 118° 15' and 118° 45' west longitude. It includes part of the crest and east slope of the Sierra Nevada, extends eastward across the Moor of Owens Valley, and embraces an elongate strip along the lower slopes of the White Mountains. The area is largely in northern Inyo County, but includes 70 square miles in southern Mono County and 49 square miles in Fresno County. The region, a lightly populated country midway be- tween Los Angeles, Calif., and Reno, New, is accessible from Los Angeles by U. S. Highway 6, and from Reno by U. S. Highway 395. Highway 6 also extends north- east through Nevada. A Greyhound bus route between Los Angeles and Reno provides the only regularly sched- uled passenger service into the area. Access from the Central Valley of California is difficult — the closest high- ways across the Sierra Nevada, through Tioga and So- nora passes, are closed by snow during the winter. A narrow-gauge railway operated by the Southern Pacific Co. runs from Laws south to Keeler — a distance of 67 miles — with a transfer point at Owenyo, 54 miles south of Laws, to a standard-gauge branch from the main Southern Pacific lines. Neither the branch line nor the narrow gauge provides passenger service. The narrow- gauge line formerly was part of the Carson and Colorado line and extended north into Nevada ; but service to the north was discontinued some years ago, and north of Laws the rails have been removed. Motor freight service into the area is supplied by the Southern Pacific Co. and by Western Truck Lines. Three towns lie within the mapped area, Bishop, Big Pine, and Laws; a fourth center of population is along Pine Creek, where the IT. S. Vanadium Co. maintains housing for its workers at Rovana and Seheelite. Bishop is the largest town in Owens Valley, having a popula- tion of about 3.000. Formerly it was a center for agri- culture and cattle raising; but with the acquisition of a large part of the arable land in Owens Valley by the city of Los Angeles in the 1920's and 1930's, to protect its water supply, the importance of these pursuits has diminished. Concomitant with the decreasing importance of agriculture has been a notable increase in tourist trade, and Bishop is now primarily a tourist center. Surfact FeaUires. The area studied is one of great relief, with altitudes ranging from less than 4.000 feet 8 Special Report 47 on the floor of Owens Valley to more than 14,000 feet along the Sierra Nevada erest. The Owens Valley, a deep north-northwest-trending trough more than 70 miles lon miles long that extends from the vicinity of Chocolate Peak to Bishop Pass. The gneiss consists predominantly of quartzo- feldspathic material separated by thin, discontinuous dark layers composed of biotite and hornblende. Metavolcanic Hocks. The largest mass of metavol- canic rock, in the south end of the Pine Creek pendant, contains both mafic and felsic metavolcanic rocks. Small bodies of mafic metavolcanic rock are also found in other parts of the region, but felsic metavolcanic rock was mapped only in the Pine Creek pendant. The mafic rocks are chiefly of andesitic composition. They are fine grained, generally equigranular but locally porphyritic, and commonly slightly schistose. Locally, they contain amygdules composed of quartz and hornblende, and one layer exposed intermittently along the bottom of the canyon of Horton Creek in the vicinity of Horton Lake is a volcanic breccia. The breccia consists of angular, stretched-out, volcanic fragments ranging in length from less than an inch to as much as several feet, embedded in a fine tuffaceous matrix. Felsic metavolcanic rocks of rhyolitic composition are confined to a belt on the west side of Mt. Tom between the Tungstar and Hanging Valley mines. The rock is fine to medium grained, and is porphyritic. Quartz phenocrysts predominate in tuffaceous rock, and plagio- clase predominates in dikes. Metasedimentary rocks locally are intercalated in both the mafic and felsic metavolcanic rocks. Common sedi- mentary rocks interstratified with the metavolcanic rocks are marble, eale-hornfels, and quartzite. The Hanging Valley mine is in one such layer of marble. Quartz Diorite and Hornblende Gabbro Under the designation of quartz diorite and horn- blende gabbro of Mesozoic age are included all of the coarse-grained, dark-colored igneous or igneous-appear- ing rocks, as well as a few small masses of finer grained amphibolite of probable metamorphic origin. Thus the group comprises rocks of diverse mineral content and fabric, and probably also of different origins. Distinc- tion between the different kinds of dark-colored rocks is difficult and, in places, unsatisfactory. All of them contain plagioclase feldspar and hornblende, and lighter colored varieties commonly contain quartz, microcline, and biotite as well. Of the coarse-grained rocks, the darker colored ones are hornblende gabbro, and the lighter colored ones are diorite or quartz diorite. Several masses of hybrid quartz diorite contain significant amounts of material that appear to have been introduced from bordering lighter colored granitic rocks. Both the hornblende gabbro and quartz diorite are characterized by hetero- geneity of fabric and by variations within short dis- tances, even within a hand specimen, in the relative proportions of the constituent minerals, although in some places the fabric is fairly constant over wide areas. The fabric ranges from equigranular to seriate or por- phyritic— locally, large poikilitie crystals of hornblende enclose smaller crystals of the other mineral constituents. Some exposures exhibit extreme irregularity in the dis- tribution of the light and dark minerals. Banding, present in some outcrops, consists of alternating light- colored layers composed mainly of feldspar, and dark- colored layers that contain abundant hornblende. In a few places orbicular structures are developed. Amphibolite grades, in places, into hornblende gabbro or quartz diorite, and these rocks grade into each other, making delineation on the maps of the different kinds of rocks unduly time consuming in comparison with the value of such distinction. Furthermore, much of the quartz diorite is in (dose association with, and appears to grade into, mafic metavolcanic rock. Distinction of quartz diorite from metavolcanic rock, nevertheless, was possible in most places because of the coarser granularity of the quartz diorite and because of subtle differences in the fabric of the two rocks. All of the dark-colored rocks, but especially amphib- olite and hornblende gabbro, contain in many places abundant metamorphic inclusions. Among these inclu- sions calcareous rocks generally are well represented, and provide possible sites for tungsten deposits. Most of the tungsten deposits in the Deep Canyon area of the Tungsten Hills, for example, are in small metamorphic inclusions in hornblende gabbro. Granitic Rocks All the granitic rocks of Mesozoic age, with the excep- tion of the darker colored quartz diorite and hornblende gabbro just described, are grouped on the economic geologic maps into "granodiorite" and "granite." The intrusive rocks included under "granite" are slightly younger, a little lighter colored, and somewhat less calcic than those included under "granodiorite," but other- wise the rocks are similar and belong to the same general sequence of intrusion. Individual granitic bodies generally meet masses of metamorphic rock or other bodies of granitic rock along sharply defined planes, but at a few places the marginal rock has been brecciated and penetrated by dikes. The rock within a single intrusive body commonly has a somewhat similar appearance throughout the body and can be distinguished from the rock in other contiguous intrusive bodies. Rock of similar appearance, however, commonly is repeated in other bodies not. in direct con- tact with the intrusive. Some, but by no means all, contacts between individual granitic bodies are occupied by thin, discontinuous septa of metamorphic rock, only the largest of which are rep- resented on the maps. Because metamorphic masses too small to be shown on the maps but large enough to con- tain tungsten deposits of minable size occur along some 12 Special Report 47 contacts, the contacts between the individual intrusive bodies are shown on the maps, even though the adjacent bodies may be represented by the same pattern as "granite" or " granodiorite. " Small inclusions of meta- morphic rock generally are sparse in the central parts of individual intrusives, but in some are more abundant in the marginal parts. Granite. The rocks designated as "granite" on the economic geology maps include the three youngest and lightest colored intrusives, with which most of the tungsten deposits are associated. Technically, one is an orthoelase-albite granite and the other two are quartz monzonites. Granodiorite. The rocks represented as "granodio- rite" are similar to the "granite," but are darker col- ored and more calcic; and their emplacement preceded slightly that of intrusives designated as "granite." Although in the mapped region few tungsten deposits have been found along the contacts of the intrusives of granodiorite, tungsten deposits are found in other parts of the Sierra Nevada in association with granodiorite (Krauskopf, 1953). Volcanic Rocks Volcanic rocks of Cenozoic age are widespread at lower altitudes, and a few masses are found in higher parts of the Sierra Nevada. Rocks of both basaltic and rhyolitic composition are represented. The most extensive mass of volcanic rock is in the Volcanic Tableland, which is underlain by the rhyolitic Bishop tuff of Gilbert (1938). With the exception of a small dome 7 miles south of Big Pine, this is the only mass of rhyolitic rock exposed in the mapped region. Basalt is more widespread, although the aggregate volume of all the exposed basalt is far less than that of the rhyolitic tuff in the Volcanic Tableland. Basalt. Slightly eroded basalt flows and cinder cones of Pleistocene age are found south of Big Pine in the alluvial slope at the base of the Sierra Nevada ; and dikes, necks, and eroded flows are found west and south- west of Bishop on the lower slopes of the Sierra Nevada and adjacent alluviated areas. A few dikes and necks crop out at higher altitudes in the Sierra Nevada, and locally abundant boulders of basalt in glacial moraine indicate that basalt formerly was more widespread at higher altitudes. Although the flows and cinder cones south of Big Pine appear to be younger than most masses of basalt found elsewhere in the area — indeed, several ages of basalt may be represented — all the basalt is of about the same mineral composition. Typically it con- sists of large olivine phenocrysts and more numerous but less conspicuous augite phenocrysts in a fine-grained matrix of phagioclase, augite, and magnetite. Fresh rock from the flows and intrusive masses is dark gray to black, whereas basaltic cinders are grayish red to mod- erate red, making them easy to distinguish from basaltic lava, even from a distance. Crater Mountain, the most extensive mass of basalt, is made up almost entirely of scoriaceous lava, although reddish cinders are present in the composite vent. Red Mountain, a few miles farther to the south, is a well-preserved cinder cone, but a mod- erately extensive flow issues from near the base of the cone. Rhyolite. The most extensive mass of ryholite is the Bishop tuff of Gilbert (1938, p. 1829-1862), which makes up the Volcanic Tableland. The only other rhyolitic mass in the mapped area, in a small hill 7 miles south of Big Pine, currently is being exploited as expansible "per- lite." The Bishop tuff of Pleistocene age has been described in some detail by Gilbert. He concluded that it is a "welded tuff," and that it originated in nuees ardentes, or "flows" of intensely hot, discrete, fragments of vis- cous magma lubricated by gases emitted from the frag- ments. The welding was accomplished by melting to- gether of the fragments by heat contained within the mass itself. The tuff is composed of several layers that differ from one another in color, density, degree of consolidation, and texture ; but regardless of these varients the con- stituents of the tuff are about the same everywhere it has been examined. Scattered at random through a ma- trix of fine vitric tuff are fragments of pumice, discrete crystals of quartz and sanidine, rounded pellets of ob- sidian, and, less commonly, accidental fragments of gra- nitic or metamorphic rock or of basalt. Crystals of quartz and sanidine also occur as phenocrysts in the pumice fragments. For commercial use the tuff can be subdivided into hard ' ' consolidated tuff, ' ' which comprises most of the formation, and unconsolidated "pumiceous tuff." Un- consolidated "pumiceous tuff" within the mapped area is essentially confined to a thick layer that is present at the base of the formation in exposures along the south and southwest margins of the Volcanic Tableland. In the cliff along the south edge of the Volcanic Table- land, the unconsolidated pumiceous layer that forms the lower part of the Bishop tuff is about 200 feet thick and of pale-pink color. It rests comformably and with sharp contact on a layer of white pumice ; at the top it grades upward through a baked zone about 15 feet thick into the overlying consolidated tuff. Typically, the layer con- sists of rounded pumice fragments as much as several inches in average diameter in an unconsolidated ashy matrix. Locally, larger pumice fragments have accumu- lated at the base of the formation in heaps as much as 10 feet high. One interesting variation in the pumiceous layer is found along the east edge of the Volcanic Table- land where the rock adjacent to a tongue of consolidated tuff has a bright-pink color. The greatest exposed thickness of consolidated tuff, in the Owens River and Rock Creek gorges, is at least 500 feet. To the south and southeast the consolidated tuff thins, and in the cliff along the south edge of the Vol- canic Tableland only about 50 feet of consolidated tuff overlies the 200 feet of unconsolidated pumiceous tuff. In the Owens River gorge the tuff is composed of sev- eral layers that range in color from white through pink to varying intensities of gray and red purple, and which differ from one another in density, degree of consolida- tion, and texture. From a distance the individual layers appear to be in sharp contact with one another, but on closer examination most contacts are difficult to deter- mine within a few feet. Presumably the layers represent separate impulses of material that poured out at inter- vals so closely spaced that the whole mass cooled together. The degree of consolidation of the tuff varies both laterally and with respect to vertical position. Laterally, the comparatively dense, welded rock exposed in Rock Economic Geology of Bishop Tungsten District 13 Creek and Owens River gorges grades to softer, less- consolidated rock in the vicinity of Fish Slough in the southeast part of the Volcanic Tableland. Gilbert (1938, p. 1829-1862) has demonstrated that the tuff exposed in the walls of Rock Creek and Owens River gorges is progressively more dense and compacted with depth, and that the contained pumice fragments are more flattened. A low, rounded rhyolite dome 7 miles south of Big Pine is currently being exploited for expansible perlite. The dome is a mile long, has a maximum width near the middle of half a mile, and rises about 200 feet above the alluvial slope from the Sierra Nevada. The rocks are all glassy, but several lithologically distinct units in con- centric arrangement are recognizable. Gentle dips of the flow banding in the marginal parts of the dome and steep or vertical dips in the interior indicate that the structure in cross section is fan shaped. The dome is described in more detail under the heading "Expansible rhyolite (perlite)." Alluvial Deposits Among the widespread alluvial deposits shown on the quadrangle maps are moraines, lacustrine deposits, and terrace deposits of Pleistocene age; fan deposits ranging from Pleistocene to Recent age ; and talus, stream gravel, soil, and valley alluvium of Recent age. Although most of these surficial deposits have no commercial value, some have been put to economic use. The value of soil needs no comment, nor does the equally obvious utilization of stream gravel and fan deposits for sand and gravel. Material suitable for sand and gravel is widespread, and the pits from which it has been mined are located pri- marily with reference to economic rather than geologic factors. More deserving of treatment is a pumice layer that is interbedded in the upper part of a series of Pleisto- cene sands and gravels. The demand for pumice has increased in recent years, and that trend promises to continue. The geologic aspects of the pumice are both interesting and significant to its exploitation. Ptimice Layer. A conspicuous layer of white pumice, the locus of several pits, is the uppermost layer of a series of alluvial deposits of Pleistocene age. The pumice layer conformably underlies the lower unconsolidated layer of the Bishop tuff all along the south and east sides of the Volcanic Tableland. The pumice layer also crops out intermittently in the alluvial deposits that flank the west side of the White Mountains and has been intersected in borings as much as 600 feet beneath the floor of Owens Valley. In the north part of the mapped area the maximum observed thickness of the pumice bed is about 20 feet, and it thins southward. It has not been found south of the highway from Big Pine to Deep Spring Valley, but- it is exposed intermittently for many miles north of the mapped area. The obviously erratic distribution of the pumice in the alluvial slope is partly the result of dis- continuous preservation and partly of faulting; some exposures of pumice are in up-faulted or up-tilted blocks. Individual pumice particles are angular, and range in size from fine dust to 2 inches in average diameter. The pumice fragments are unaltered, firm, and per- fectly white— well suited for light-weight aggregate. Fragments of foreign material are rare. Although the pumice fragments are tightly packed, they are not cemented. The most striking feature of the pumice bed, con- spicuous in many outcrops, is gradational increase up- ward in the average size of the pumice fragments. Ordinarily, beds in which the size of the fragments increases upward are considered to be upside-down, but regional relationships leave no doubt that the pumice layer is right side up. The angularity of the fragments precludes transporta- tion of the pumice in any way except through the air, but within this limitation two hypotheses merit consider- ation as providing an explanation for the inverse size gradation of the fragments. The hypothesis that best explains all of the observed feature's is that the pumice was ejected from a vent in which the explosive force was increasing, and that the pumice fell on dry land. Coarser material was blown higher and carried farther as the explosive force in the vent waxed, so that away from the immediate vicinity of the vent progressively coarser material accumulated. The alternate hypothesis, and one that formerly was favored by the writer, is that pumice of random size blown into the air fell into a body of standing water. All of the pumice fragments would have floated for a period, but the smaller ones would have become saturated and sunk first, followed by progressively larger ones. The workability of this mechanism was established by dumping some of the pum- ice into a beaker and observing that the smaller pumice fragments do settle first and are followed by progres- sively larger ones. This hypothesis is attractive because it does not entail the special circumstance of increasing explosive force in the vent, but nevertheless, it fails to explain the distribution of accidental fragments of meta- morphic and granitic rock in the pumice which also arc size graded from small in the lower part of the pumice to larger in the upper part. MINERAL DEPOSITS The Bishop region is most notable in mineral pro- duction for its tungsten deposits, but quartz veins have yielded gold and silver, and nonmetallic deposits have yielded pumice, perlite, barite, talc, building stone, ce- ramic materials, gravel, and limestone. The yield from the tungsten mines to the end of 1953 is estimated at approximately 1,300,000 short-ton units of W0 8 .* Of this, the Pine Creek mine accounts for more than 1,000,- 000 units, and, in addition, has yielded more than 3,000 short tons of molybdenum and 2,000 short tons of cop- per as byproducts. Incomplete data in the files of the U. S. Bureau of Mines record a yield from the quartz veins in the mapped area of 70,548 ounces of gold and about 16,000 ounces of silver, plus 274,567 pounds of copper and a little lead recovered in smelting. Evaluation of the data suggests that the total production from quartz veins may amount to 100,000 ounces of gold and about 40,000 ounces of silver. Production data are not available for most nonmetal- lic minerals, but records of perlite production arc avail- able and the production of pumice can be estimated * The tungsten content of ore and of concentrate is usually given in units of WOa regardless of the actual form of the tuiiRsl. unit is 1 percent of a ton. Thus, a short-ton unit (the unit of this report) is 20 pounds of contained \V(in. 14 Special Report 47 roughly. The yield of perlite sinee it was first mined in 1949 and 1952 amounts to almost 20,000 tons. Pro- duction records of pumice are not available, but a rough calculation, based on the sizes of the pits from which it has been mined, suggests a total production of about 100,000 tons. The dollar value of the yield of these commodities cannot be compared directly, because these values are not known, but a rough comparison can be made by calculating the value of the total yield of each com- modity at 1954 prices. Thus, the tungsten yield would be valued at $88,000,000; the gold, silver, and copper yield from quartz veins about $3,600,000 ; and the pum- ice and perlite yield at $400,000 to $450,000. Present trends suggest that tungsten will continue to be the most valuable mineral commodity for many years, but that the production of perlite and pumice will increase. Although the amount of perlite that has been mined is small, the volume has increased each year, and in view of an expanding market and the very large reserve the rate of production is expected to increase materially. None of the quartz veins was worked in 1953, and only a change in the price of gold or in the economic outlook will bring about renewed mining of these deposits. Mining History Records of mining in the vicinity of Bishop prior to 1890 are scanty, but undoubtedly prospecting and mining were carried on by the earliest settlers. Tungsten was not mined until 1916; before then gold was the chief metal mined. The following excerpts from The Story of Inyo, by W. A. Chalfant (1933), pioneer pub- lisher and author, give a clue to the early mining ac- tivity: "Owensville [a town near the present site of Laws that existed for a few years after 1863] looked to mines in the White Mountains for its upbuilding. The Golden Wedge mine, many years later still bearing that name and included in a group known as the South- ern Belle, was the first find ... A reduction plant was built on Swansea Flat (Fish Slough) by an Owensville company . . . One of the companies operating in the White Mountains bore the name of the San Francisco. A 'town,' called Graham City, after D. S. Graham, the superintendent, was started 'at the foot of Keyes Dis- trict, opposite Bishop Creek Valley,' says a letter of the time. No other identification is obtainable, though its prospects were supposed to be so promising that a corre- spondent of the Alta [San Francisco Alta California] wrote: 'Should the mines (and of this there appears to be no doubt) turn out all right, this town will rival Aurora or Virginia Citv itself for population.' " (Chal- fant, 1933, p. 211-213)/ "... Poleta provided the mining excitement of 1881. Prospecting had gone on in the White Mountains east of Bishop from the earliest coming of white settlers, with such results that more than one ambitious 'city' had been staked out, only to be forgotten. In all probability some of the claims which changed hands for thousands during the days of Poleta were on the same ground that made Keyes District the hope of prospectors in the middle '60's." (Chalfant, 1933, p. 294). In 1870 and again in 1888 Mr. W. A. Goodyear trav- eled through Owens Valley examining the geology and ore deposits. His observations are included in the 8th annual report of the State Mineralogist (1888, p. 224- 309). From his notes of 1870 Mr. Goodyear writes (p. 281), "Owensville. Another utterly deserted village, consisting of the ruins of some twenty or twenty-five houses, more or less. The houses were built of the mate- rial of the volcanic table land to the north [the Bishop tuff of Gilbert (1938)], which is soft, and cuts easily; and the village is said to have been built by a mining excitement, though I saw no mines, nor any ores, and only a very few little prospecting holes in the mountains to the east." In describing his travels of 1888, Mr. Good- year writes (p. 234), "But at Fish Spring Arrastras, a little to the north of Red Mountain, and a little southeast of the highest and most prominent volcanic cone in the region ... a small granite hill sticks its head up through the volcanic matter [Fish Spring Hill]. And in this hill they have found one or two small veins of rich gold- bearing quartz filled with sulphurets. Mr. Jas. McCarthy is working some of these ores in arrastras, the tailings from which he concentrates in sluice boxes, so as to save the pyrites for shipment and treatment elsewhere, as these sulphurets are said to be very rich in gold. ' ' In 1892, the Poleta mine and the mines in Fish Springs Hill were in operation and were worked intermittently until 1941. The Cardinal mine, on Bishop Creek, by far the largest producer of gold in the Bishop District, was operated from 1911 to 1922 and from 1934 to 1940. Dur- ing the depression years of the 1930 's, the activity in gold mining was intensified, and a great many deposits were worked. With the coming of World War II gold mining ceased and in 1953 no gold mine in the Bishop District had been reopened. An event of the greatest significance to mining as well as to the economy of the northern Owens Valley region occurred in August 1913 on the Jackrabbit claim in the Tungsten Hills, when tungsten ore was found in place. Knopf (1917, p. 231) relates the circumstances of the discovery as follows : ' ' The discovery was the result of careful prospecting, though it was eventually hastened by chance. Three partners, who were mining placer gold in Deep Canyon, found that the concentrates they ob- tained were difficult to clean because a heavy white min- eral persistently accumulated in considerable amount with the gold. The troublesome material proved to be scheelite ; and when the identity and value were known, search was soon begun to find it in bedrock. After all the quartz float in the area adjoining Deep Canyon, so it is reported, had been broken open in vain during the course of a year and a half, the scheelite was finally found in its rock matrix by J. G. Powning, who while out hunting recognized the long-sought mineral in an outcrop of garnet rock on which he had just shot a rabbit, an adventitious circumstance to which the dis- covery claim owes its name." Early in 1916, when the price of tungsten rose to unprecedented heights, mining was begun in the Deep Canyon area. The first mining was on the Aeroplane claims, and shortly thereafter the Little Sister mine was in operation. The town site of "Tungsten City" was laid out in Deep Canyon, below the mines. In the following year mining was begun at Nobles Camp (Round Valley mine) and at the Pine Creek mine, and exploratory work was carried out at the Chipmunk prospect, the Mineral Dome prospect (Rossi mine), the McVan claims, and the Buckshot prospect. Economic Geology of Bishop Tungsten District 15 With the end of World War I, the tungsten market collapsed, forcing the tungsten mines to close. Between 1920 and 1023, no production of tungsten is reported in the United States. Some work was done at the Pine Creek mine in 1024, and in the following deeade most of the mines wore operated at one time or another. In the middle 1930 's, harbingers of a new war, which pushed he price of tungsten upward, and introduction of the iltraviolet light as a means of prospecting resulted in die reopening of many mines and a wave of prospecting. By 1941, all of the known deposits in the Bishop district, >xcept the Yaney mine which was found to contain tung- sten in early 1948, had been discovered. Peak production for the district was reached during World War II, when the price and sale of tungsten con- ■ent rates was fixed by Federal law; but at the end of he war Government contracts to purchase tungsten con- entrates were cancelled and the price declined, once igain forcing curtailment or abandonment of many tperations. Following the outbreak of hostilities in Korea the federal Government in 1951 established a domestic pur- thase program. This program provides for the purchase >f tungsten concentrates at $63.00 per unit until 1,000,000 units of WO a have been bought or until July 1958, whichever occurs first. With this stabilization >f the market, production has increased, though in 1953 t was well below the peak production of World War II. Sand, gravel, granite, marble, and rhyolite tuff have >een mined intermittently since the time of the earliest vhite settlers. The Bishop tuff was used for building dock in Owensville in 1863, and was locally a popular milding material until the 1930 's when cement, blocks \ - ith pumice aggregate proved to be cheaper and easier o use. Pumice for aggregate and for use in plaster has teen mined more or less constantly since then. Barite vas mined from the Gunter Canyon barite mine in 1928 ;nd 1929, but the deposit was idle from 1930 to 1953. Talc was last mined at the Blue Star tale mine in 1945. The newest nonmetallic mineral commodity is expansible hyolite (perlite), which has been mined from a rhyolite till south of Big Pine only since 1949. Contact- Metamorphic Tungsten Deposits The tungsten deposits in the Bishop district, with one r two exceptions, are contact-metamorphic or tactite leposits. Such deposits generally are conceived to have ormed at high temperatures by the interaction of lime- ;ich sedimentary or metamorphic rock with hot solutions hat emanated from intrusive magma. Seheelite, the only aluable tungsten-bearing mineral, is contained locally ii dark-colored lime-silicate rock called tactite that was ormed from the lime-rich rocks as part of the contact ■tamorphism. Tactite generally is in the margins of lasses of lime-rich rock adjacent to intrusive igneous ock. Most masses of tactite arc accompanied by a periph- ral zone of light-colored lime-silicate minerals in the ontiguous calcareous rocks. In addition, in many deposits hin quartz veins and thicker silicified zones, accom- lanied in places by valuable sulfides, locally penetrate he tactite and the adjacent igneous rock. Although the contact metamorphic tungsten deposits ommonly are called tactite deposits, that appelative by o means signifies that all tactite contains commercial amounts of seheelite. On the contrary, many tactite masses contain no seheelite; where 1 seheelite is present it usually is restricted to certain zones within the tactite. although in a few places seheelite is disseminated throughout a tactite mass. Tactite masses that contain scheelite-bearing zones of a grade that is commercially exploitable are called ore bodies; the scheelite-bearing zones themselves are called ore shoots. Rocks In the contact metamorphism of lime-rich rocks by heat and solutions derived from intrusive magma, three new kinds of rock can be formed: (1) tactite, (2) light- colored calc-silicate rock, and (3) quartzose rock. Under optimum conditions, all three rocks can develop along a given segment of contact between igneous and calcareous sedimentary or metamorphic rocks, but commonly tactite masses are unaccompanied or are accompanied by only one of the other new rocks. Tactite and peripheral light- colored calc-silicate rock are thought to form contempo- raneously, and after thermal metamorphism that changes impure limey rocks to calc-hornfels. The quartzose rocks form somewhat later, though in the same general period of mineralization. Tactite. The term "tactite" was introduced by F. L. Hess (1919, p. 377-378) and defined by him as "a rock of more or less complex mineralogy formed by the con- tact metamorphism of limestone, dolomite or other soluble rocks into which foreign matter from the in- truding magma has been introduced by hot solutions or gases. It does not include the enclosing zone of tremolite, wollastonite, and calcite." The term "tactite" is now deeply entrenched in the United States, both in the liter- ature and in local usage, in connection with tungsten de- posits. A synonymous term, in the opinion of the writer, is the older and more widely known term "skarn," which was originally used to describe similar assemblages of silicate minerals associated with Swedish iron ores. Garnetite is a partial equivalent of tactite, corresponding to those assemblages of dark silicate minerals in which garnet predominates. Although no mineral by definition is essential to tactite, the tactite of the Bishop district consists chiefly of light-brown to reddish-brown garnet of the grossu- larite-andradite series, grayish-green pyroxene of the diopside-hedenbergite series, olive-green epidote, and quartz; these minerals occur together in various combi- nations and proportions. Less abundant and usually with more local distribution are colorless fluorite, pale-olive idocrase, green-to-black amphibole, and white-to-yellow- ish-gray or pale-olive seheelite. In addition to these more typical minerals, many tactite masses contain subordi- nate amounts of calcite and such light-colored calc- silicate minerals as wollastonite, diopside, grossularite garnet, zoisito, and feldspars. However, if these minerals predominate, the rock is not, properly speaking, tactite. Sulfides and oxides, though genetically related to the silicified rocks, locally are disseminated in tactite. In the Pine Creek and adjacent mines along the west side of the Pine Creek pendant molybdenite, chalcopyrite, and bomite are the most common sulfides; sphalerite, galena, and magnetite are found locally in other parts of the district. l(j Special Report 47 In the Bishop district scheelite occurs in many differ- cut kinds of taetite; hence no definite statement relating scheelite to certain varieties can be made. Nevertheless, certain kinds of taetite do seem to contain scheelite more commonly and in greater abundance than others. Per- haps the most generally applicable statement that can be made is that darker colored taetite is a commoner host tor scheelite than lighter colored taetite. A reasonable explanation for this association is that dark-colored tae- tite commonly is formed from relatively pure marble and that consequently its formation involved the intro- duction of the maximum amounts of silica, iron, and other substances (including tungsten) from the igneous magma. Most lighter colored taetite, on the other hand, formed from impure calcareous rock with the addition of smaller amounts of material. The scheelite in dark-colored taetite generally is dis- seminated through the taetite in rounded grains that range from "pin points" to half an inch or more in diameter. On the other hand, much of the scheelite in lighter colored taetite is localized in layers that origin- ally were comparatively lime rich or in fractures. Schee- lite crystals in fractures commonly are tabular rather than equidimensional ; and where an appreciable amount of the scheelite contained in a taetite mass is confined to fractures, care must be exercised in making visual esti- mates not to over estimate the scheelite content. An illustrative example of the distribution of scheelite in a lighter colored variety of taetite is found in the Western mine; there, much of the scheelite lies along joint sur- faces in paper-thin crystals as much as an inch across, and most of the rest is confined to garnet-rich layers in the taetite. Among the dark-colored varieties of taetite that are hosts to scheelite, one composed essentially of reddish- brown garnet and gray-green pyroxene is the commonest; in the Pine Creek, Rrownstone, and Adamson mines this rock appears to be the sole host for scheelite. Other varie- ties of taetite also are common, however. In several de- posits garnet-rich taetite, generally with minor amphi- bole or pyroxene, is the host rock in tungsten-bearing zones. In the Shamrock and Lakeview mines a rock com- posed chiefly of epidote is the host rock for scheelite, and in the Lakeview nunc garnet-rich taetite is barren. Most seheelite-bearing taetite contains little quartz, but in a few places seheelite-bearing taetite contains 10 percent or more of quartz. The ore at the Schober mine, which was notably rich, consisted chiefly of quartz, pyrrhotite, and scheelite, with minor garnet, epidote, and calcite. Some of the richest ore in the Tungstar mine was com- posed principally of scheelite and feldspar (oligoclase), a rock that hardly conforms to the definition of taetite. Although no single mineral is a constant associate of scheelite, fluorile where present generally is confined to zones that contain scheelite. On the other hand, rock that contains idocrase rarely contains scheelite. In the formation of taetite a large amount of material must be added from the intrusive magma, and a volu- metrically equal amount of material must be expelled. For example, taetite composed of 3 parts of garnet with ISO percent of the andradite molecule and 1 part of py- roxene with 70 percent of the hedenber<;ite molecule — a common rock in the ore bodies in the Pine Creek mine — consists by weight, in round figures, of 124 percent cal- cium, IS percent silicon, 9 percent iron, 6 percent alu- minum. 1 percent magnesium, and 42 percent oxygen. I: the taetite were formed from pure calcite marble, all o: this material except the calcium and oxygen must hav< been derived from the intrusive magma. In places, how ever, crystals of pale diopside scattered through tht marble suggests that the magnesium also was containec in the marble. Some silicon and aluminum may also havi been derived from the marble; but most of the silicon iron, and aluminum must have been introduced from th< magma. The sequence of formation of the minerals in tactin is not completely understood, but some general relation ships can be pointed out. Dirty marble appears to havi been converted partly or wholly to light-colored silicati minerals before material from the ore solution was intra dueed. Hence, light-colored minerals in taetite, such ai plagioclase, pale diopside, and wollastonite, were formec very early. The earliest minerals formed by the reaction o: marble with the ore solution appear to be pyroxene am garnet ; in taetite composed chiefly of pyroxene and gar net, at least part of the scheelite appears to have formec contemporaneously with these two minerals. Quartz aiu olive-green epidote appear to have been formed later epidote by replacement, and quartz by replacement or by fracture filling. The scheelite in taetite composed chiefhj of epidote may have been introduced at the time of form at ion of epidote but more likely was derived from tht replaced rocks. In any event, in places where the tung sten ore is composed chiefly of epidote, the scheelite vvai redistributed. Quartz is a late-formed mineral and is dis seminated in or penetrates the taetite as veinlets. Ii places, the quartz contains large euhedral crystals o garnet, epidote, or scheelite, which probably formed fron material picked up by the quartz during its introduction Light-Colored Calc-Silicatc Rock. The distinction be tween light-colored ealc-silicate rock formed contempora neously with taetite, and calc-hornfels formed somewha earlier is difficult inasmuch as the mineral content of tin two rocks may be identical. The areal distribution of < zone of silicate rock is the chief clue to its classification If the silicate rock forms a zone peripheral to the tactiti in the contiguous marble, it is ordinarily considered t( have formed contemporaneously with the taetite and t< be the rock here called light-colored, calc-silicate rock The only mine in the Bishop district where a zone o: light -colored, calc-silicate rock can be clearly distiri guished is the Pine Creek mine. In this zone, which i: several hundred feet wide at the surface, the marble i: bleached and recrystallized to a coarse white aggregate of calcite and silicate minerals. The commonest silicati minerals are white to pale green diopside and white t< very light gray wollastonite ; but white-to-pink zoisite white feldspar, pale pink grossularite garnet, and whiti or very pale green tremolite are common. Idocrase, per haps, is more characteristic of light-colored, calc-silieata rock than of taetite, though it occurs in both. The inner contact of the light-colored calc-silicate zoni with taetite is sharp in most places, but the abundance of silicate minerals decreases with distance from the con tact. It is not clear in the Pine Creek mine how mucl material (other than calcium) was introduced from solu tions that emanated from the intrusive magma, and hov much was contained as impurities in the original rock It is thought, however, that material from both source is present. Economic Geology op Bishop Tungsten District Quartzose Rods. Quartz has been introduced into many taetite bodies, and into the adjacent granitic rock, pither as sharp-walled veins or as thicker silicified zones with gradational walls. The main loci for quartzose rocks are contacts between taetite and granitic rock, hut in places quartzose rocks are completely enclosed in taetite or in granitic rock. The sharp-walled veins fill fractures, and many of the silicified zones replace sheared rock. Tims the quartzose rocks clearly were formed after the consolidation of the adjacent granitic rock and after the taetite. Quartz veins ordinarily are clean and contain no rem- nants of the host rock, but relicts of the host rock are common in silicified zones. In granitic rock the dark minerals rarely survive even moderate silicification and the common relicts is feldspar. In taetite, pyroxene or ?pidote are the common relict minerals found with quartz in silicified zones ; garnet is less stable than either of these minerals in the presence of quartz, and where rpiartz has been introduced, garnet generally has been converted to pyroxene. Quartz-pyroxene rock is common in the Pine Creek mine. In the Bishop district the quartzose rocks rarely con- tain scheelite, but locally groups of large, well-formed, commonly euhedral crystals are found. On the other hand, the quartzose rocks are closely (and presumably genetically) associated with the sulfide minerals. In the Pine Creek mine molybdenite, chalcopyrite, and bornite are associated with quartz, and in other deposits sphal- erite and galena are found with quartz. It is true that locally sulfides are disseminated in fine grains through taetite and that in places thin sulfide veinlets with little or no quartz cut taetite, but generally sulfide-bearing quartzose rock can be found in the vicinity. Internal Organization of the Deposits The distribution of scheelite in taetite is often spoken of as "spotty," a truism that cannot be denied. Never- theless, some sort of order, though commonly crude, has been found to exist in most deposits that are sufficiently well exposed to show the relationships of the deposit in three dimensions. The internal organization of taetite deposits, and especially consideration of the distribution and configuration of ore shoots, can be considered most effectively if the deposits are subdivided into two broad classes: (1) deposits in the margins of pendants and larger septa, and (2) deposits in small metamorphic inclusions. Deposits in the Margins of Pendants and Larger Septa of Metamorphic Rock. Taetite bodies in the margins of larger metamorphic masses exhibit great diversity in their size, shape, internal structure, and scheelite con- tent. Taetite does not occur along all contacts between marble and intrusive rock and is notably irregular in thickness and scheelite content where it does occur. In places, only a thin selvage of taetite a few inches thick is present; in others great masses 100 feet or more thick occur. Some taetite masses are tabular, some are tube- like or chimneylike, and some exhibit bizarre shapes. Some lie along the intrusive contact, whereas others extend outward from it along beds or fractures in the metamorphic rocks. The taetite bodies dip and rake in various directions and angles, and some are too irregular for description in these terms. 17 In most places scheelite is disseminated in commercial amounts only through part of the taetite, although in a lew places all of a mass of taetite contains scheelite in commercial amounts. The distribution of scheelite within taetite is almost as varied as the distribution of taetite itself, but commonly the shapes of the commercial schee- lite-bearing zones (ore shoots) reflect in ;t modified way the configuration of the enclosing taetite mass. Most ore shoots have sharp boundaries and do not grade through broad zones of submarginal ore to barren taetite, but in a few places such gradations do exist. In spite of the great diversity in the size, shape, and internal structure of tactile masses, or more correctly because of it, it is possible to relate the configuration of most deposits to certain geologic factors that appear to have controlled their localization. Many taetite bodies are the product of more than one factor, but in most deposits one factor dominated the others. The factors that controlled the localization of deposits are (1) ir- regularities in the intrusive contact, (2) favorable beds, and (3) fractures in the host metamorphic rock. Irregularities in the intrusive contact have localized several taetite masses, including some with productive ore bodies. In general, contacts along which the beds are concordant are more regular than contacts where the beds are discordant. Sills tend to penetrate into the open ends of the beds at discordant contacts. Some tae- tite masses lie beneath dikes or benchlike projections in the intrusive contact, whereas others are in reentrants in the contact in which no closure of intrusive rock over the top of the taetite can be seen or reasonably inferred. Examples of taetite masses beneath intrusive rock are the North ore body in the Pine Creek mine (fig. 5), the Northwest ore body in the Adamson mine (pi. 6), and smaller masses of taetite in the Marble Tungsten mine (pi. 14). At each place the marble just beneath the in- trusive rock has been replaced by taetite. In depth most of the taetite gives way to marble, and taetite continues downward with diminishing thickness only along the intrusive contact. The richest concentrations of scheelite are in the upper parts of the taetite masses, just beneath the overlying intrusive rock; the grade falls with depth. Although a limit to the depth to which minable ore ex- tends is inherent in the -structure, that depth may com- pare favorably with the vertical extent of other ore bodies controlled by factors that theoretically place no limit on the depth. Taetite bodies localized in reentrants in the igneous contact in which the intrusive rock does not close over the deposit also are represented. The most notable ex- ample is the South ore body of the Pine Creek mine (fig. :5), which extends about 1,000 feet down a plunging trough associated with an S-shaped bend in the intrusive contact. At the surface all of the calcareous rocks em- braced in the reentrant are replaced by taetite that contained scheelite in commercial amounts; but in depth the taetite occupies only the trough and one side of the reentrant, and scheelite is restricted to a narrow zone in one side of the tactile adjacent to the intrusive. Several other much smaller outcrops of taetite with marginal amounts of scheelite are in reentrants bounded on three sides by intrusive rock, but none of them has been extensively explored underground. Among these are the Little Egypt (tig. 15) and Coyote Creek prospects in the Bishop Creek pendant and the Tungsten Peak prospect 18 Special Report 47 in the Tungsten Hills. Each of these taetite masses occu- pies a small segmenl of an otherwise regular contact along which only a thin selvage of tactile has been devel- oped. The extent in depth of these bodies is limited theoretically by the extent of the irregularity, and recent exploration of the deeper parts of the South ore body in the Pine Creek mine indicates that the bottom termina- tion of the ore body coincides with the lower limit of the trough in which it is localized. The limitation of taetite to lime-rich rocks and the preferential development of taetite and of tungsten ore shoots in cleaner marble rather than in silicated marble or calc-horufels are the commonest examples of strati- graphic control. As might be expected, the best examples of stratigraphic control of the configuration of taetite deposits and of tungsten ore shoots are in places where the lime-rich rock is composed of layers with obviously different amounts of impurities and where the beds are discordant with the contact. The Round Valley mine (pi. 8) provides such an example. The prevailing rock in the Round Valley pendant in the vicinity of the Round Valley mine is somewhat shaly marble, whereas to the west it is schist and to the east it is partly garnetized calc-hornfels. Thus, it would appear that the ore body was formed in shaly marble in preference to other rocks with little or no free ealcite. Within the ore body, the scheelite-bearing ore shoots are closely restricted to beds that appear to have been somewhat cleaner than most. The strike and dip of the ore shoots is determined by the strike and dip of the beds, and the rake is determined by the intersection of the beds with the igneous contact. The maximum depth to which the ore body and its con- tained ore shoots might extend is set by the lower limit of the metamorphic host rock. In some places stratigraphic control over the configu- ration of an ore body is indicated even though no ob- vious chemical or physical difference is evident between the beds that are mineralized and those that are unmin- eralized. For example, the east boundary of the Main ore body in the Pine Creek mine (fig. 4) coincides in most places with a stratigraphic horizon. Nevertheless, marble in extensions of the mineralized beds appears very similar to marble in the beds just outside of the ore zone, although it is possible that unrecognized slight sys- tematic chemical or physical differences do exist. The possible influence of premineral fracturing in the min- eralized beds, likewise, cannot be evaluated. Premineral fractures in the host rock are thought to have been contributory factors in the localization of most taetite deposits and to have been the dominant control in some. In only a few places can direct evidence be found that relates premineral fracturing to the distribu- tion of taetite or of tungsten ore, because the formation of taetite tends to destroy preexisting structures. The usually expectable function of premineral fractures would he to supply the permeability required for the initial introduction of the ore-forming solutions, but some fractures also could limit the movement of solu- tions. Either regional stresses or stresses arising from the intrusion of magma could produce fracturing along con- tacts between unlike rocks. Certainly, intrusive contacts must have been subject to severe strain during the solidification of the contiguous intrusive. Control of the distribution of taetite by a fracture i, 1 most apparent in the Pinnacle ore body of the Pin : Creek mine and in the Hanging Valley mine. The Pin h nacle ore body (pi. 5) extends outward from the intru \< sive contact across the bedding in the host marble- i Although the outcrop of the ore body is too steep fo ; careful examination of the wall rocks for evidences offset strata, localization along a fracture seems the onl; possible explanation for the orientation of the ore body In the Hanging Valley mine (fig. 8) the ore is in rhom bohedral shoots with very small horizontal dimension and much greater vertical dimensions. The shoots an bounded on the sides by steep east-trending beds aiu north-trending fractures. Unlike the fracture at the Pin nacle ore body, which presumably provided a channel fo; the egress of ore-forming solutions, the fractures heri 1 appear to have acted as dams to confine the solutions. 1 similar relationship is found in the Western mine when scheelite-bearing parts of the taetite at several place: meet barren taetite at a fracture surface. Nevertheless, ii the Western mine much of the scheelite lies along frac tures. Among the ore bodies that may have been localized, ai least in part, by fracturing, but for which the evidenc< is inconclusive, is the Main ore body of the Pine Creel* mine (fig. 4). The fact that this ore body through strike length of 400 to 600 feet and through an explorec vertical distance of more than 2,000 feet, occupies the same sequence of beds, strongly suggests stratigraphic control. Yet the beds in which the ore body is localized dc not seem to be materially different from adjacent beds that have not been mineralized. Furthermore, these same beds must be in juxtaposition with the same intrusive rock at many places along the 2i-mile span of barren in- trusive contact south of the mine area. Visible fractures in the ore body clearly guided late silica-rich solutions that deposited quartz and sulfides. If the deposition ol quartz involved reaction with the wall rock to the same extent as the formation of taetite, the evidence of such fracturing would be obscured and much or all of it lost entirely. Conceivably similar channels provided means of entry for the slightly earlier solutions that brought in silica, iron, tungsten, and other substances required to form taetite. Deposits in Small Inclusions of Metamorphic Rock] It would be erroneous to equate small inclusions with small tungsten deposits. Most inclusions, though small, in terms of the features that can be shown on a regional map, are sufficiently large to contain extensive tungsten ore bodies. In the Bishop district, the yield from the Tungstar mine, which is in a small inclusion, is exceeded only by that of the Pine Creek mine. Notable yields have also come from the Schober, Rossi, Little Sister, and Aeroplane mines, and lesser yields from the White Caps and Jackrabbit mines, all of which are in small inclu- sions. The number of commercial tungsten deposits in inclusions suggests that inclusions are especially favor- able to the formation of deposits. The term "inclusion" implies that not only is the body enclosed in igneous rock in outcrop, but also that it is underlain and before erosion was overlain by igneous rock. The bottoms of the inclusions at the Jack- rabbit and Tungsten Blue mines have been determined in mining, and the inclusion at the White Caps mine is Economic Geology of Bishop Tungsten District 1!) known to lie beneath a capping of quartz monzonite. Furthermore, at the Tungsten Blue, Schober, and Tung- star mines the inclusions broadened downward for a short distance from very small outcrops, suggesting that the inclusions were completely capped by igneous rock at a level not much higher than the present erosion surface. Although an ore body can occupy an entire inclusion, and apparently does at the Tungsten Blue mine, most inclusions contain nonscheelite-bearing rocks, including barren tactite. All of the stratigraphic and structural relationships described in connection with deposits in the margins of larger metamorphic masses can also apply to deposits in small inclusions. Nevertheless, in most deposits the capping of igneous rock overshadows other relationships. The deposits are closely allied with deposits along continuous contacts that lie beneath benchlike projections of intrusive rock. The most sig- nificant characteristic of deposits in inclusions is that the amount of scheelite contained in tactite generally diminishes with depth ; a correlative characteristic is that tactite is less abundant in depth, giving way down- ward to light-colored calc-silicate rock and to marble. Downward decrease in the tungsten content of the tac- tite is readily demonstrable in the Tungstar, Schober, Little Sister, and Aeroplane mines. In the Tungstar mine, tungsten persists in commercial amounts to the deepest mine levels, but the grade falls progressively from about 5.0 percent of WO s in the outcrop to about 1.0 percent in the deepest workings. In the Schober, Little Sister, and Aeroplane mines, the tactite in the deepest levels contains little or no scheelite, although at each deposit commercial ore was mined in glory holes from the outcrops of the same tactite bodies. Downward change of tactite to light-colored calc-silicate rock takes place in the Little Sister mine. In that deposit the tactite exposed at the surface southwest of the main glory hole is replaced on the haulage level by light-colored calc- silicate rock. In the deeper parts of the Tungstar mine, residual lenses of marble were encountered in the ore body though none were found in the upper parts. The greater abundance of tactite, as well as of scheelite within the tactite in the upper part of inclusions, sug- gests that mineralizing solutions from the igneous magma were trapped beneath an already solidified crust of granitic rock over the top of the inclusion. If the foregoing generalizations are correct, two infer- ences can be made regarding exploration for new de- posits in inclusions. (1) Inclusions of marble and light- colored calc-silicate rock, though they may be the roots of inclusions that contained tactite and possibly tungsten ore bodies in their upper eroded parts, are not likely to contain ore bodies in their deeper parts. (2) If a means were found to locate buried metamorphic inclusions, only the upper parts would need to be tested to determine whether or not they contain tungsten ore bodies. Excep- tions to these generalizations can, of course, readily be visualized, but the data in hand suggest that they are not common. Geologic Environment of the Deposits The universal requisite for the presence of a tungsten- bearing tactite deposit is the juxtaposition of calcareous and granitic rock; in the few places where no granitic rock is exposed in the vicinity of a tactite deposit, it is inferred to he present at no great depth. In the Bishop district the distribution pattern suggests that most of the deposits are in an even more restricted environment. With few exceptions the host rock is relatively clean calcareous marble, and the accompanying granitic rock generally is the lighter colored rock designated as "gran- ite" on the quadrangle maps. Comjmsition of the Calcareous Host Rock. In the Bishop district most of the contact-metamorphic tungsten deposits are in tactite that formed from nearly pure marble, and only a few are in tactite that formed from impure marly, siliceous, or dolomitic calcareous rock. Furthermore, the tactite formed from impure calcareous rocks commonly is lighter colored than tactite formed from almost pure limestone and contains little or no scheelite. The major part of the parent rock of the tactite at all of the productive deposits, everywhere that the parent rock can be determined, was almost pure marble, with the possible exception of the Round Valley mine in the Round Valley septum. The calcareous rock exposed in the vicinity of the Round Valley mine generally is some- what impure, but it is less impure than the calcareous beds in most other parts of the Round Valley septum. It is true that several prospects in the Bishop Creek pendant, notably the Lindner, Munsinger, Waterfall, and Stevens prospects, are in less extensive masses of tactite that were formed from calc-hornfels. A simple yet reasonable explanation for this prefer- ence of tactite for cleaner marble is found in the mineral changes that accompanied a period of thermal metamor- phism known to have preceded slightly the formation of tactite. In this metamorphism, clean limestone was simply recrystallized to marble with no loss in either the solubility or the chemical reactivity of the rock, whereas impure calcareous rock was converted partly or completely, depending on the composition, to compara- tively insoluble and inert calc-hornfels. Of the two rocks, the marble was far more susceptible to reaction with later tactite-forming solutions. Composition of the Adjacent Igneous Rock. Classic theory on the genesis of ore deposits genetically relates contact-metamorphic deposits to igneous rocks and pro- poses that the metal content is a function of the composi- tion of the associated igneous rock. In conscious or un- conscious recognition of this concept, a question often posed by prospectors is this: "Is the distribution, size, or grade of contact-metamorphic tungsten deposits re- lated to the composition of the associated igneous rock?" For the Bishop district the answer to the first part is "yes," and to the second and third parts, "probably yes." The tungsten deposits in the mapped area are found in contact with most of the granitic rocks as well as with the smaller masses of dark-colored quartz diorite and hornblende gabbro. Simple tabulation reveals that of 54 deposits in the Sierra Nevada, 39 are in tactite that is in direct contact with rock designated on the quad- rangle maps as "granite," 5 are in tactite in contact with "granodiorite," and 10 are in small metamorphic inclusions that are enclosed in quartz diorite or horn- blende gabbro. These statistics seem to indicate that in the mapped area the "granite" is favorable to the local- ization of tungsten-bearing tactite and that the "grano- diorite" is unfavorable, but that quartz diorite and 20 Special Report 47 hornblende gabbro, in view of the limited outcrop area of these rocks, are the most favorable. Nevertheless, many experienced mining geologists would object strongly, on theoretical "rounds, to interpreting the data to signify genetic relationship between the tungsten deposits and quartz diorite or hornblende gabbro — an objection that finds some support in field relationships. The masses of quartz diorite and hornblende gabbro are small as com- pared with granitic rock, so that in outcrops granitic rock is never far from the enclosed tungsten deposits and in depth may be even closer. Furthermore, in the hornblende gabbro mass east of Shreves Camp (Andrews Camp) on the south fork of Bishop Creek, which con- tains many metamorphic inclusions, the only ones in which notable amounts of scheelite-bearing tactite has been found are in the eastern margin adjacent to a mass of granitic rock. The impact of this relationship is some- what reduced, however, by the random distribution of deposits in the quartz diorite and hornblende gabbro of the well-prospected Deep Canyon area of the Tungsten Hills. If the tabulation of deposits enclosed in quartz diorite and hornblende gabbro is revised to show the closest granitic rock, it is found that all of them are associated with rock shown on the quadrangle maps as "granite." With this revision 49 deposits are associated with "granite" and only 5 with "granodiorite. " An equally impressive statistic is that all 23 of the deposits that have yielded sufficient tungsten to be classed as produc- tive are associated with "granite." These data, even without the readjustment for the de- posits enclosed in quartz diorite and hornblende gabbro, strongly support the view that in the mapped area the "granite" is especially favorable to the formation of tungsten-bearing tactite deposits. The data further sug- gest that the district may owe its existence to the pres- ence of the rocks designated as "granite," but wide- spread geologic mapping in adjacent areas of both the metamorphic and the granitic rocks is required before this suggestion can be regarded as more than a hypoth- esis. A recently published paper by Krauskopf (1953) records many deposits in the western part of the Sierra Nevada that are associated with granodiorite. Leached Outcrops and Secondary Enrichment Leaching of tungsten from the outcrops of ore bodies and its secondary enrichment in depth are controversial subjects. Gannett (1919) has shown that the preferential leaching of tungsten from outcrops by sulfate-bearing waters is theoretically possible ; but almost no reliable information in support of either leaching or secondary enrichment of tungsten has been published, and differ- ences of opinion on these subjects are not likely to be resolved until much more observational data are avail- able. In the Bishop district the geologically recent, deep dissection of most parts of the region is not conducive to a ground-water circulation that favors surface leaching or secondary enrichment in depth, and the tactite in most outcrops is little altered. Only in the Yaney mine docs the disposition of minerals provide a basis for postu- lating secondary enrichment. This mine is unique in the district in that the chief tungsten mineral is ferberite in pyramidal crystals that are pseudomorphs after scheelite. These crystals are embedded in a matrix of jarosite, opal, and quartz, which also contain tungsten in un- known but probably colloidal form. A small amount of scheelite also is present, and tungstite has been identi- fied. The average grade of the ore is about 2.0 percent WO.{. The setting and the residual beds of tactite and calc-hornfels suggest that the deposit is an altered tactite deposit. Several factors suggest that the deposit has been secondarily enriched in the process of its alteration from tactite: (1) the high grade of the deposit, which is higher than that of most tactite deposits, (2) the fact that scheelite in tactite deposits is rarely euhedral, sug- gesting that the ferberite crystals do not occur as pseu- domorphs after original scheelite crystals in tactite, and (3) the colloidal (?) tungsten that certainly has been moved at least a short distance. Grade of Ores The average grade of ore mined in the district is about 0.5 percent of WOn, but substantial amounts of ore with as much as 2.0 percent of WO3 has been mined from the Tungstar, Schober, and Yaney mines. The lowest grade of ore that has been profitably exploited exclu- sively for tungsten, from the Shamrock mine in the Tungsten Hills, contained about 0.4 percent of WO3. Prom time to time ore with even less tungsten, but with recoverable copper and molybdenum, has been profitably treated at the Pine Creek mill. Factors favorable to the profitable exploitation of lower-grade ores are low alti- tude of the deposit, large volume of ore mined daily, reliable and inexpensive transportation, and an ore body of sufficient size and of such configuration as to favor cheaper methods of mining. In most deposits the ore shoots have fairly sharp walls and do not grade through a zone of submarginal ore into barren or nearly barren tactite. Common practice in mining is to examine each face under ultraviolet light before blasting. In this way the ore mined is kept at a profitable grade, and low-grade or barren tactite is left in pillars or discarded as waste. Hand sorting under ultraviolet light has not been employed widely, although from time to time a few tons of ore are sorted from tactite in which the scheelite distribution is notably sporadic. In most deposits the grade of the ore within an ore shoot is even, but this is not true of all ore shoots. In deposits with both high-grade and low-grade ore, the ore is commonly mixed to maintain an average grade. In this way lower-grade ore can be mined than would otherwise be possible. Outlook for the District On the assumptions that the economics of tungsten mining does not change materially and that no major new discovery is made, the district appears to be at about half life; approximately as much ore will be produced after January 1, 1954, as was produced before. Although it is true that some formerly productive deposits are exhausted, and that others contain only submarginal ore, large reserves of ore remain in the known deposits. Un- doubtedly, new discoveries will be made in the district as a result of prospecting, but they will be fewer than in the past and will entail increasing geologic and engi- neering assistance. As in the past, most new discoveries will probably be relatively small, but it is possible that a major new discovery will be made and extend materially the life of the district. Economic Geology of Bishop Tungsten District 21 Suggestions for Prospecting Because the tungsten in the mapped area is in contact- metamorphie deposits, prospecting should be confined as closely as possible to the examination of the contacts of lime-rich metamorphic rocks with intrusive rock. On the map four kinds of metamorphic rock — marble, cale- hornfels, hornfels and schist, and metavolcanic rocks — and three kinds of intrusive rock — "granite," "grano- diorite, " and quartz diorite and hornblende gabbro — are delineated. In prospecting, the masses of marble merit first attention, because most of the known deposits in the district are in marble host rock and because, on theo- retical grounds, marble is more favorable than any other kind of metamorphic rock to the formation of tungsten- bearing tactite deposits. A few tungsten deposits in the district are formed in calc-hornfels, and these rocks, as well as intercalated beds or lenses of marble too thin to be shown separately on the maps, should be prospected after the masses of marble. The masses of hornfels and schist and of metavolcanic rock are of interest, because locally these rocks also contain thin beds of marble or calc-hornfels. Although most of the deposits that have been found are associated with "granite" rather than "gran- odiorite," and the "granite" therefore is postulated to be more favorable to tungsten deposits, nevertheless, the data are not so convincing as to warrant limiting pros- pecting to areas underlain by "granite." On the con- trary, places that otherwise seem favorable for prospect- ing should not be overlooked because the local intrusive is "granodiorite" rather than "granite." The masses of quartz diorite and hornblende gabbro are of special in- terest, not because they have any genetic relationship with the tungsten deposits, but because many of them are crowded with small inclusions of metamorphic rock. The darker hued rocks with abundant hornblende seem to contain more lime-rich inclusions than the lighter hued mafic rocks. Small masses of metamorphic rock also occur as septa along the contacts between intrusive masses. Only the larger septa could be shown on the quadrangle maps, but the traces of the contacts between the intrusives are shown to serve as guides for further examination of these contacts. Prospecting along these contacts is far more likely to result in finding tungsten ore bodies than blind searching through the granitic terrane. An efficient procedure for prospecting in the mapped area is first to examine the larger bodies of metamorphic rocks shown on the quadrangle maps, especially the lime-rich ones, paying particular attention to the parts at or near contacts with intrusive rock. Next, the areas mapped as quartz diorite and hornblende gabbro, espe- cially the darker hued ones, should be searched for tactite in metamorphic inclusions including those too small to be represented on the quadrangle maps. Finally, the contacts between intrusive bodies can be searched for tactite in small screens of metamorphic rock. Efficient prospecting involves a combination of day- time and nighttime activity. The most generally accepted procedure is to search for bodies of tactite during the daytime, and then for scheelite at night with an ultra- violet light. The talus below intrusive contacts can be examined for scheelite at night under ultraviolet light or in the daytime by panning. Examination of the talus is especially helpful where the slopes are too steep to prospect readily ou foot or where an intrusive contact is concealed by talus or slope wash. Panning the gravels in stream channels can also be helpful, but is less valu- able in prospecting for tungsten than for gold because scheelite is easily shattered and ordinarily is not found very far from its source. Once a body of scheelite-bearing tactite is located, it should be sampled to establish the average grade. High- grade samples of "hot spots" are misleading and have no bearing on the average grade of the deposit, Samples should be taken impartially in the daytime. Before sampling, however, it is desirable to mark off the bound- aries of the scheelite-bearing rock at night under ultra- violet light, dividing it into zones that appear to be of about the same grade. The grade of the rock in the outcrop can then be determined by taking a suitable number of chip or channel samples across each zone. The outline of the scheelite-bearing rock, the boundaries of the grade zones, and the positions of the samples • should be plotted on a map, preferably one with accu- rately measured distances. Magnetometer Test. An especially tantalizing field for finding new tungsten ore bodies is in small meta- morphic inclusions that do not crop out at the surface. Abundant inclusions are exposed at the surface in some masses of quartz diorite or hornblende gabbro ; and un- doubtedly others are buried in nearby parts of the intrusive rock, some perhaps only a few feet beneath the surface. A fair percentage of these inclusions con- tain tactite deposits in their upper parts. Inasmuch as the surface geology gives no clue to the precise positions of buried metamorphic inclusions, it is natural to turn to geophysics for help. One geophysical method that seemed to have some chance of success in locating these bodies is based on the measurement of the magnetic polarization of the rocks. To determine the applicability of this method, tests were made with a vertical-intensity magnetometer over known inclusions composed chiefly of tactite. Unfortunately, these tests indicate that the mag- netic properties of the tactite masses tested are not sufficiently different from those of the enclosing intru- sive rocks to be useful in delineating buried tactite inclusions. The tests were made by Gordon Bath and C. H. Sandberg of the IT. S. Geological Survey. The following is their description of the tests and their interpretation and appraisal of the results: "The magnetic polarization of a rock is a function of the content of magnetic minerals, chiefly magnetite. In places, the magnetic polarization of two rocks is sufficiently different to delineate an inclusion of one of the rocks in the other, and, under ideal circumstances, to indicate something of its position, depth, and mag- netite content. To investigate the possibility that meta- morphic inclusions made up preponderantly of tactite can be distinguished by their magnetic properties from the enclosing intrusive rock, measurements with a ver- tical-intensity magnetometer were taken over remnants of tactite masses at the Jackrabbit, Tungsten Blue (Shamrock), and White Caps mines in the Deep Canyon area of the Tungsten Hills. Essentially, the tests con- sisted of measuring the vertical magnetic intensity along traverses that extended from the intrusive rock into or across tactite inclusions. At the Jackrabbit and Tungsten 22 Special Report 47 Blue mines tactite inclusions crop out at the surface, but at the White Caps mine the tactite body lies beneath a capping of quartz monzonite. In fig. 2 the positions of the traverses arc plotted on abbreviated geologic maps of the deposits, together with profiles showing the mag- netic variation along each traverse. "Most of the profiles suggest that the magnetic polari- zation of tactite generally is a little different from that of the enclosing intrusive rocks, but the difference is too small to be used in the delineation of concealed inclu- sions. In general, the magnetic values of tactite are lower than those of quartz diorite and hornblende gabbro and higher than those of (piartz monzonite, but local variations caused by dikes, discarded pieces of iron, topographic irregularities, and irregularities in the distribution of magnetite within the rocks are far greater than the average differences between tactite and the intrusive rocks." Tungsten Mines and Prospects Inasmuch as the tungsten deposits are of contact- metamorphic origin, they are confined to the masses of metamorphic rock. Most of the deposits occur together in groups, but a few are isolated. The largest numbers of deposits, including most of the productive ones, are in the Pine Creek and Bishop Creek pendants, and in the Deep Canyon (Tungsten City) area and Round Valley septum of the Tungsten Hills. Several deposits also are associated with a belt of metamorphic rocks along the east-trending segments of the Sierra Nevada front south- west of Bishop and in Shannon Canyon. The Pine Creek Pendant The Pine Creek pendant (pi. 1) is a lens of metamor- phic rock almost 7 miles long and as much as a mile wide. From the northeast face of Basin Mountain the pendant extends northward across Horton Creek, Mt. Tom, and Pine Creek, to the south end of Wheeler Crest. Outcrop altitudes range through more than 6,000 feet — from a low point of about 7,400 feet on the floor of Pine Creek canyon to a high point of 13,652 feet on the summit of Mt. Tom. The pendant is bounded by granite and quartz monzonite everywhere except at the north end where it is truncated abruptly by- dark-colored hornblende gabbro. Both north and south of the pendant, along the same trend, are found small septa and inclusions of metamorphic rock. The northern two-thirds of the pendant, north of the summit of Mt. Tom, is relatively simple, both litho- logically and structurally. In this sector the pendant consists mainly of biotite-quartz hornfels, which is flanked for 3f miles on the west side by marble. North of Pine Creek the beds strike about N. 20° W., concordant with the long axis of the pendant, and dip steeply. South of Pine Creek the strike swings to the southeast, then to the east. A clearly defined tight symmetrical syncline, thought to be the major structural feature of the north part of the pendant, is exposed in the biotite-quartz hornfels in Pine Creek Canyon. The greatest width of the marble in the west side of the pendant is about 1,800 feet ; at the north end it pinches gradually to about 200 feet. In the widest part, the marble encloses three lenses of biotite-quartz hornfels. Isolated blocks of marble such as are found near the Cable Lakes, at the Lambert mine on the ridge south of Elderberry Canyon, and at the Moore prospect on the north side of Horton Creek Canyon possibly are dislocated remnants of this marble. The southern third of the pendant is totally unlike the northern part of the pendant, consisting chiefly of metavolcanic rocks that are intricately penetrated by quartz monzonite, quartz diorite, and hornblende gabbro. The most common metavolcanic rock is dark-colored meta-andesite, but north of the Hanging Valley mine light-colored metarhyolite locally predominates. The metarhyolite generally is free of metamorphosed sedi- mentary rocks, but intercalated in the meta-andesite are layers of schist, biotite-quartz hornfels, calc-hornfels, and marble. The metavolcanic rocks are structurally dis- cordant with the rocks in the northern part of the pendant and in most places are separated from them by an irregular band of quartz diorite that passes through the crest of Mt. Tom. On the southwest side of Mt. Tom the flow layers in the metavolcanic rocks generally strike eastward, but farther east the strike swings to the south. Dips are somewhat variable but are generally steep. Pine Creek Mine* The Pine Creek mine of the U. S. Vanadium Co. is in the largest known tungsten deposit in the region and one of the most productive tungsten deposits in the United States. The ore bodies crop out along the east wall of a cirque at the head of Morgan Creek, a southward-flowing tributary to Pine Creek (photo 1). They are on the west side and near the north end of the Pine Creek pendant, along the contact between the extensive belt of marble that occupies the west side of the pendant and quartz monzonite. The deposit com- prises five ore bodies, called from south to north (1) the South ore body, (2) the Main ore body (formerly called the North ore body), (3) the Pinnacle ore body, (4) the North ore body (formerly called the level E ore bodies), and (5) the Loop ore body (pi. 5). Almost all the ore mined has been extracted from the Main, South, and North ore bodies, although some came from a pit in the outcrop of the Loop ore body; neither the Loop nor the Pinnacle ore bodies has been developed underground. The altitudes of the outcrop range from about 11,200 feet to more than 11,900 feet ; the lowest working in the mine, the Zero adit, is at an altitude of 9,430 feet. In spite of the high altitude of the mine, it is readily accessible by road. The mill and main offices, at the head of lower Pine Creek, at an altitude of 7,900 feet, are reached from Bishop by driving 10 miles north on U. S. Highway 395, then 8 miles west on a surfaced road that follows Pine Creek. From the mill a private dirt road extends in steep switchbacks along the east wall of the canyon of Morgan Creek to the portals of the under- ground workings and to pits in the outcrop. From the mill it is 2\ miles to the portal of the Zero adit, presently the main haulage level, and 5 to 7 miles to the portals of higher adit levels (not in use) and to open pits in the outcrops of the ore bodies. A preliminary report on the Pine Creek and adjoin- ing Adamson mine was published in 1945 (Bateman, 1945). The detailed maps and descriptions contained in this preliminary report are not repeated here, but most of the geologic concepts then tentatively advanced have been reevaluated and incorporated here in revised form. * By Paul C. Bateman and Lawson A. Wright, Chief Engineer, Pine Creek Mine, U. S. Vanadium Company, Bishop, California. : ■ Economic Geology of Bishop Tungsten District 23 The mine is entered through adits and is developed from them by means of raises, levels, and snblevels. The main adits are level C, level A, and the Zero adit, at alti- tudes of 11,215, 10,1)40, and 9,430 feet respectively. Levels A and C interseet the Main, South, and North ore bodies, whereas the Zero adit intersects only the Main >re body, where it is called the 1,500 level. At the north nd of the mine a less extensive adit, level E at an alti- tude of 11,380 feet, is limited to the North ore body. In 1954 the Zero adit served as the main haulage level ; the ipper parts of the deposit, where all the other adits are oeated, had not been Avorked since 1949. The mine can be thought of as consisting of two parts: (1) the part above level A, locally called the "old nine," and (2) the deeper part between level A and he Zero adit. The "old mine" is considered to be essen- ially exhausted, although it seems probable that with 'hanging conditions exploitation of the contact above evel A sometime will be renewed, if only on a small scale and by lessees. All of the ore now being mined is from the Main ore body between 1,500 level (Zero adit) uul level A. The outcrops of all the ore bodies except the Pinnacle >re body have been exploited by means of open pits, the argest of which is in the South ore body. Pits in the ^lain and North ore bodies, though smaller, have been he source of significant volumes of ore. Level workings n the block between level A and the surface totaled ibont 24,000 feet ; but owing to subsequent stoping, only he main adits are essentially intact. The Main ore body vas developed underground between level C and the urface by means of 4 snblevels, and between levels A aid C by means of 6 snblevels. The South ore body was leveloped by levels A and C and by 3 intermediate evels. The North ore bodies were penetrated by levels V, C, and E and by several snblevels and raises. The upper part of the ground between level A and the ,500 level (Zero adit level) has been prospected by neans of a 250-foot internal shaft and by a crosscut rom the bottom of the shaft ; and the lower part has >een developed from the 1,500 level by means of aises and level workings. At the end of 1953, however, iauch of the block of ground between level A and the ,500 level had not been explored. The Pine Creek deposit was discovered sometime prior o 1916 by M. B. Sherwin, a mineral surveyor who lo- ated it for a presumed content of silver-lead ore, but the :>cation was allowed to lapse. In 1916, the deposit was eloeated by Sproule and Vaughn, and Sproule hand- icked some high-grade molybdenum ore from the out- rop (Hess, 1916, p. 778). The first mining for tungsten as by the Pine Creek Tungsten Company in 1918 and 919, but owing to the slump in the tungsten market at lie end of World War I mining was suspended in 1919. n 1924, the Tungsten Products Co. reopened the mine nd constructed a 125-ton mill on the shore of the small- st and most easterly of the Morgan Lakes, about a mile sutlieast of the Sontli ore body. Access to the mine at lat time was by means of an abandoned road from the orth alonp: Rock Creek and through Morgan Pass. The ■ngsten Products Co. continued to operate during 1925 nd part of 1926. Between 1927 and 1936, the mine was ile except for a brief period in 1933 when it was oper- ted bv Herbert Sillinger. The mine was purchased by the U. S. Vanadium Co. in 1936. Between 1937 and 1939 the U. S. Vanadium Co., after thorough sampling of the outcrop, extended level A north along the intrusive contact into the Main ore body. In the same period the existing private road and aerial tramline were constructed from the floor of Pine Creek Canyon to the mine. A mill was built first on the site of the earlier mill; but after experimental testing in a pilot, plant that still stands at the company settlement of Scheelite, the present mill was erected. All the ore mined prior to 1948 was from above level A, but in 1943 the Zero adit was started with its portal 7,000 feet south of the outcrop of the Main ore body and 1,500 feet lower than level A (photo 2). The upper part of the intervening block of ground had been scantily ex- plored by means of the internal shaft sunk 250 feet beneath level A in the Main ore body, the crosscut from the bottom of the internal shaft, and by diamond-drill borings from the crosscut, the two deepest of which inter- sected the Main ore body 550 and 700 feet below level A. Thus the deepest penetration of the contact was a full 800 feet above the level of the Zero adit. The adit was completed in 1948, but only after overcoming severe diffi- culties resulting from the heavy flow of ground water from solution cavities in the marble and from fractures in the quartz monzonite. The completion of the Zero adit coincided closely with the depletion of ore reserves in the upper part of the mine; and in early 1949, following a fire that destroyed several installations at the portal of level A, including the loading tower of the aerial tram and the building that housed the primary crusher, under- ground w r ork above level A was suspended, although from time to time ore is trucked from the surface pits. Since the completion of the Zero adit all exploration and mining has been in the Main ore body above the 1,500 .level. Total production * from the Pine Creek mine to the end of 1953 amounts to 1,057,498 units of W0 3 , 6,130,- 559 pounds of molybdenum and 1,967.97 tons of cop- per. In addition, 670 ounces of gold was recovered from the sulfides in smelting. Most of this production was made by the U. S. Vanadium Co.; the total prior production amounted to only a little more than 18,000 units of WOg with no reported recovery of cop- per, molybdenum, or gold, except the small amount of molybdenite that was hand sorted by J. H. Sproule in 1916. The rate of production by the U. S. Vanadium Co. increased from 975 units of WO3 in 1937, when develop- ment work was being pushed at the expense of produc- tion, to 142,951 units in 1942, when the maximum rate was achieved. Production since then has been steady but at a lower rate, except for short periods during 1945 and 1947 when the mine was temporarily shut down. Pro- duction for 1953 amounted to 84,171 units of WO,. The mine contains both tungsten and molybdenum ill well-defined shoots. All of the ore bodies contain tung- sten ore shoots, whereas molybdenum ore shoots have been found only in the upper parts of the South and .Main ore bodies. The configuration of the shoots were determined by assays; cutoff grades of 0.4 percent of \VO :i and 0.4 percent Moftj were assumed. The assay data indicate that the tungsten ore shoots contain an Data supplied by the I". S Vanadium Co s i 1 1 1 1 Publish) 'I w itii permls- 24 Special Report 47 average of about 0.7 percent of W0 3 , with the grade of different shoots ranging from 0.6 to 1.0 percent. The molybdenum shoots in the upper part of the Main ore body contained an average of about 1.0 percent of M0S2, plus substantial amounts of copper; no data are available of the grade of the molybdenum ore that was mined from the South ore body. The assay data also in- dicate that both the tungsten and molybdenum shoots have fairly sharp boundaries and are not bordered by large tonnages of marginal -grade ore. The tactite out- side of the tungsten ore shoots contains an average of 0.24 percent of WO3, and the tungsten ore shoots not coextensive' with molybdenum shoots contain about 0.2 percent of MoS-j. The grade of the ore in place reflects only in a general way the grade of the ore that is delivered to the mill, f 11 the upper part of the Main ore body the tungsten and molybdenum shoots were about 25 percent coextensive, so that in mining, the ore of each metal diluted the ore of the other. Tn the 3-year period, 1942 to 1944 inclusive, when exploitation of the upper part of the mine, above level A, was at its peak, the mill heads averaged about 0.45 percent W0 3 , 0.20 MoS 2 , and 0.12 CuO. In com- parison, between 1949 and the end of 1953, when all the ore milled was extracted from the Main ore body above the 1,500 level, the mill heads contained 0.52 percent of W0 3) but only minor amounts of molybdenum and neg- ligible amounts of copper. Although a few small blocks of ore have been mined in the past from shrinkage stopes, all of the ore mined in 1953 was from blasthole stopes. Mining from blasthole stopes has been found to be the cheapest, easiest, and most convenient method of ore extraction. The following statistics for the last half of 1952 and all of 1953 give a measure of the economy that has been achieved by the use of blasthole stopes: ore mined, 197,000 tons; total feet drilled, 102,200; feet drilled per man shift, 49.5; feet drilled per bit, 35; tons mined per man shift, 96.2; pounds of powder (60 percent) to break one ton, 0.27. Because the ore shoots are essentially vertical and in fresh, unaltered rock that stands well, no timbering is required and the stopes are left open. Some stopes are as much as 60 feet wide and several hundred feet long. Wide stopes (20 to 60 feet wide) are prepared some- what differently than narrow ones (less than '20 feet wide). In preparing a wide stope sublevels are driven along one wall of the proposed stope at vertical intervals of 40 feet, and at one end a continuous slot is cut across the ore. This slot is made by driving a 6-foot by 10-foot slot-raise to connect the sublevels and by driving slot- crosscuts from the slot-raise at each sublevel to the limits of the ore. Parallel vertical downholes, on 3- to 4-foot centers, arc drilled from the slot-crosscuts and are blasted 1o the slot-raise. The ore is then prepared for blasting by drilling rings of drill holes across the ore from the sublevels. These rings, spaced 5 feet apart, encompass cither 90° or 180° of arc. In 1953, AB holes (1| inch di- ameter) were drilled, with 14 feet of burden at the ends of the holes. The rings are blasted in pairs with milli- second delays, starting at the slot and retreating to a manway raise. Narrow stopes (less than 20 feet wide) are prepared by driving sublevels along the wall of the proposed stope at vertical intervals of 50 feet. Then the sublevels are widened to the limits of the ore, a practice locally called undercutting. A slot is then cut across the ore at one end of the proposed stope in the same way as in wider stopes. However, instead of drilling rings of holes as in wider stopes, rows of vertical holes on 7-foot centers are drilled across the ore body. These rows are blasted in pairs, starting at the slot. The broken ore is pulled through scram drifts (slusher drifts) and dropped into 10-ton differential cars that are hauled in 8-ear trains by 13-ton General Electric trolley locomotive. At the portal the ore in the cars is dumped by a rotary tipple into a surge bin that feeds a 36 by 48-inch jaw crusher. From the crusher a 3-inch product is carried by means of a belt conveyor into a 1,000-ton storage bin. The ore from this bin is them moved to the mill in 2|-ton buckets over a 2,000-foot aerial tram. The Pine Creek mill, one of the largest and most effi- cient plants for the treatment of tungsten ores in the world, incorporates flotation, gravity, and chemical proc- esses. The products include both natural and artificial scheelite, molybdenite, molybdenum trioxide, and a flo- tation concentrate of copper sulfides. Treatment of the ore as it is received from the aerial tram begins with secondary crushing in a gyratory crusher, and that product is fed into ball mills. From the ball mills the crushed ore passes through classifiers with return circuits for oversize particles into a process of bulk sulfide flotation, and then into one of scheelite flotation. Some powellite (CaMo0 4 ) is floated with the scheelite. The bulk sulfide flotation concentrate is re- ground and molybdenite floated from the copper sulfides. The molybdenite is shipped directly to the market and' the copper concentrate to a smelter. Both the scheelite flotation concentrate and the flota- tion tailings go over a series of concentrating tables, in separate circuits, to recover coarse scheelite. The result- ing high-grade table concentrate is either shipped for use in the manufacture of alloys in which the 2 to 3 percent of molybdenum contained in the scheelite is not harmful, or it is reground for further purification in the chemical plant. After the deletion of coarse scheelite on the tables, the scheelite flotation concentrate goes into the chemical- treatment plant in order to separate the remaining tungsten from molybdenum and to recover high-grade, marketable products of both metals. Briefly this is done by (1) converting the tungsten and molybdenum into soluble tungstate anl molybdate by pressure digestion with a suitable chemical; (2) precipitating molybdenum trisulfide and filtering it off ; (3) precipitating tungsten as calcium tungstate (artificial scheelite). Before ship- ment, the molybdenum trisulfide is roasted to molybde- num trioxide, and the calcium tungstate is nodulated The deposit lies along a 3,000-foot segment of the eon tact between quartz monzonite and the marble that flanks the west side of the north part of the Pine Creek pendant The mine area is near the north end and on the wesi side of the marble, along a span where the outcrops of the marble are narrowest. At the north end of th< mine property the width of the marble is about 200 feet southward the width increases gradually to about 50( feet at the north end of the South ore body where, owing Economic Geology op Bishop Tungsten District U -a o Special Report 47 u N o.f x. X o a, > U s Economic Geology of Bishop Tungsten District •J7 I'hoto 3. Outcrop of ore body at Brownstone mine. Tactite (dark) is between quartz monzonite on right and marble on left. Gently dipping aplite and pegmatite dikes cut all the other rocks. Compare with Figure 7 (Cliff section). Photo 4. Site of buildings at portal of Tungstar mine, burned in 1040. Hanging Valley mine in middle distance. •js Special Rki-ort 47 Photo •">. Headframe of shaft at Lakeview mine. Photo 7. Tungsten Blue (Shamrock) mine. Photo S. Open pit at Tungsten P.lue (Shamrock) mine. Plio'io (J. Hound Valley mine. Contact between granite on left ami tactite, cnlc-hornfels, and marble on right is shown by dashed line. Economic Geology of Bishop Tungsten District 29 -IT [ "*£ i^>"* *•***"-" •"* *?i<^ Photo 10. Glory hole at Yaney mine I m&L Photo 11. Pumice pit of Insulating Aggregates Co. This pit has not been worked for several years as is shown by the low shrubs on the floor of the pit. Only lacustrine pumice in lower half of face is utilized ; upper hall is lower pumiceous layer of Bishop tufl of Gilbert (1938). Floor of pit is on lacustrine sandstone. :u) Special Report 47 \ V Photo 12. Close view of lacustrine pumice bed in Insulating Aggregates Co. pit. Photo 13. Southeast side of rhyolite hill 6 miles south of Big Pine. Cliff-forming member at base is gray vitrophyre. Dark slopes above arc thinly iuterlayered gray vitrophyre and obisidian. Sum- mil and upper slopes are perlite. Photo by Charles Chesterman. i.'kt' i l'lroro 14. Perlite at working face in Fish Springs quarry. Phott by Charles Chesterman. Economic Geology of Bishop Tungsten District •n to a step in the intrusive contact, the width of the marble increases abruptly to about 1,000 feet. Tactite is present along most of the 3,000-fool span of contact in the mine area; but ore bodies, which arc thicker masses of taetite that contain within them rich shoots of tungsten and molybdenum occupy, in the ag- gregate, about 1,000 feet, or one-third of the outcrop length. Between the ore bodies the tactite is either too thin or too low grade to be exploitable. Of the five ore bodies that have been found, all but the Pinnacle ore body are in the margins of the marble adjacent to quartz monzonite ; the Pinnacle ore body is entirely enclosed in marble. In the mine area, the trace of the intrusive contact, except for minor variations, is remarkably straight even though it transgresses the bedding in the marble at a small angle. In most places, both the beds and the con- tact are essentially vertical, causing vertical sections to appear concordant, but locally, in the proximity of the north ore body, the beds dip east at high angles away from the contact. All the components of a typical contaet-metamorphic tungsten deposit are developed ; these consist of tactite, light-colored cale-silicate rock, and quartzose rock. The tactite varies in thickness from a few inches along some segments of the contact between ore bodies, to 100 feet or more in the upper part of the South ore body. The most abundant minerals in the tactite are grayish-green or black pyroxene and reddish-brown garnet. Quartz and calcite are common, with idocrase and epidote less com- mon. Scheelite generally is present in finely disseminated grains that fluoresce white to yellow, indicating a mod- erate content of the powellite molecule (CaMo() 4 ). Scheelite is most abundant in rock that is composed chiefly of green or black pyroxene and dark reddish- brown garnet but with only a little quartz. Siliceous tactite or tactite composed of paler silicate minerals generally contains little scheelite. In the mine area the marble for an average distance of 200 feet from the quartz monzonite is bleached and contains light-colored silicate minerals in varying amounts. Some beds contain more silicate minerals than [others, owing to more abundant impurities in the orig- , final limy sediment. Common silicate minerals are wol- Ijla.stonite, colorless or pale-green diopside, feldspar, Midocrase, and pale-pink garnet. Locally, the silicate min- jierals make up all or most of the rock, but more com- monly the rock consists of coarse calcite crystals with Knterstitial silicate minerals. Quartz-rich layers parallel ito the stratification in the marble are derived from orig- (inal sedimentary layers rich in quartz. The quartzose rocks delineated on the illustrations in- lelude two kinds of rock: (1) lenticular zones of silicified (quartz monzonite and tactite, and (2) dikes and sills of quartz-feldspar rock. Although of different origins, these /rocks were difficult to distinguish from each other in ■napping, especially as many of the quartz-feldspar dikes Rare partly silicified. The silicified zones are most common (along the intrusive contact, however ; whereas the quartz- ■ feldspar rocks are commonest at some distance from the [intrusive contact in the taetite or in the adjacent marble. Neither of these rocks ordinarily contains scheelite; but the silicified rocks in places contain molybdenite, chal- bdpyrite, and bornite. The silicified zones consist chiefly of quartz but con- tain remnants of minerals from the enclosing quartz monzonite or tactite. .Most silicified zones grade into the wall rock, but some have sharp boundaries. The walls commonly are somewhat shattered, suggesting that the quartz was introduced along shear zones. Accom- panying the silicified zones are veinlets of quartz rang- ing in thickness from less than an inch to a foot or more. Difficulty arises in the classification of tactite that contains large quantities of quartz, either evenly dis- tributed through the rock or in a network of veinlets. On the illustrations such rock is included under "tactite with little or no scheelite," although the data in hand suggest that in most places quartz has been added to originally quartz-poor tactite. Some, but not all, of the quartz veinlets and silicified zones are accompanied by the valuable molybdenum and copper sulfides — molybdenite, chalcopyrite, and bornite. Some masses of molybdenite from veins weighed as much as 1;") pounds, and euhedral crystals an inch or more across are common. In addition to their occurrence in quartz veins, the sulfides also are locally disseminated in taetite, usually in quartz-rich parts that contain little or no scheelite. These disseminated sulfides are com- monly in grains about the size of a pin head. The latest (piartz veinlets, cutting all the other contact rocks, gen- erally are barren of sulfides. The quartz monzonite southwest of the deposit is pene- trated by numerous aplitic and pegmatitie dikes, the offshoots of a granite mass that lies south of Pine Pake. These dikes generally strike eastward and dip 20° to 30° S., into their parent mass. The dikes are most abun- dant along Pine Creek canyon and farther south, but a few extend into the mine area. Most of those that reach the pendant penetrate through the taetite but die out in the marginal parts of the marble in thin-branching dikelets. Kerr (1946, p. 17-19) su^ested that these dikes, together with other mafic and felsic dikes on the east side of the pendant, are the source of the tungsten- bearing solutions. Geometrical relations where the dikes cut tactite indicate, however, that the dikes were em- placed through dilation of their walls and that at the time of their emplacement all the contact rocks, includ- ing not only tactite but also the silicified rocks, the last constituents of the contact zone to be formed, were already in existence. The fabric of the tactite furnishes no support for postulating late introduction of scheelite into the tactite; scheelite appears to be contemporaneous with garnet and pyroxene. A few grains of molybdenite have been found locally in some of the dikes near the contact zone, but field relationships indicate that the molybdenite was picked up by the magma of the dike. The relationship of the dikes to the tactite is especially well illustrated at the Brownslone mine (photo 3). Underground postmineral fractures are conspicuous because of the alteration of their walls to thick clayey gouge by ground water. Many of the factures are parallel with a regional system of near-vertical joints that is prominently developed in the quartz monzonite. The measurable displacement on most fractures is small, generally less than 1 foot ; but on a few it is as much ;is Hi feet. .Movements of much greater magnitude are ruled out by the absence of offsets in the e;ist contact of the marble with biotite-quartz hornf'els It has been 32 Special Report 47 suggested thai the Main and the South ore bodies are offset portions of a single ore body, but detailed map- ping proves that this suggestion is an impossibility. The fractures provide openings for the storage of large amounts of water; and when the Zero adit was driven, the whole area was drained. The water in some fractures was under pressure of as much as 150 pounds per square inch when first encountered in borings. The maximum flow of water in the Zero adit during its ad- vance was about 2,000 gallons per minute; although the rate is greatly reduced, water is still flowing from some fractures. Solution cavities are prominent in the Main and South ore bodies in the ground above Level A; but in driving the Zero adit only one solution eavity was eneountered, about 3,000 feet from the portal. The cavities are de- veloped in marble, most commonly adjacent to tactite. Individual cavities range from a few inches to as much as several feet in width and extend as much as 200 feet along the strike. Most of the cavities are filled Avith granitic sand and coarser fragments of granite, marble, and contact rock. The detritus-filled eavities locally are called "sand streaks." Stratification in the detritus is usually steep but ranges from horizontal to vertical. The dips are undoubtedly initial, and steep ones probably resulted from deposition in narrow crevices simul- taneously with solution of the marble. Within the detrital fillings are slickensided surfaces caused by slight slippage along minor fractures. Most of the ore bodies are well enough developed so that their configuration, geologic relationships, and in- ternal structure can be established. Each of the ore bodies is different from the others in one or more aspects, and most provide examples with which other less-devel- oped ore bodies can be compared. All of the ore bodies contain zones with scheelite in commercial amounts, which constitute the tungsten ore shoots, and the upper parts of the Main and South ore bodies also contain shoots of molybdenum and copper ore. Sulfides of molybdenum and copper are locally dis- seminated in small amounts in the contact rocks outside of the molybdenum-copper shoots, and some molybdenum and copper are recovered in milling tungsten ore. The configurations of the ore shoots are fixed by assay data, especially in the Main ore body where the data are more than adequate for interpreting the distribution and con- figuration of the ore shoots. Much of the upper part of the South ore body was mined before the U. S. Vanadium Co. purchased the mine, and assay data from the out- crop and higher levels, unfortunately, are lacking. The tungsten shoots closely coincide with quartz-poor tactite composed chiefly of grayish-green to black pyroxene and reddish brown garnet. The molybdenum-copper shoots, on the other hand, occur locally in both tactite and the quartz-rich rocks, although they are more closely associ- ated with the latter. The tungsten ore shoots generally are regular in shape and lie parallel to the enclosing mass of tactite. They comprise between a third and half of all of the rock represented on the illustrations as tactite. Most of the tungsten shoots are surprisingly continuous in view of the reportedly sporadic distribution of scheelite in tac- tile masses. The tungsten shoots in the Main ore body can be identified from level to level through several hundred feet ; many are sufficiently large and persistent, botl laterally and in depth, to be stoped individually. The molybdenum-copper ore shoots, as compared witl the tungsten ore shoots, are more limited in their dis tribution, and have less sharply defined boundaries. Mos of the molybdenum is contained in molybdenite, but sonn is in powellite (CaMo0 4 ), an alteration product o molybdenite, and in scheelite. In computing the molyb denum content of the ore, all of the molybdenum is cal eulated as MoS 2 . The copper is contained in chalcopyrib and bornite, although in a few places incrustations oJ green and blue chrysocolla and green malachite art found on fracture surfaces. All of the copper is calcu lated as CuO. The South ore body is on the w T est side of a north! facing, wedge-shaped, marble salient that is formed bj a step in the intrusive contact at the south end of tin mine area (pi. 5). On the surface, quartz monzonite envelopes the north end of this salient, and on the east side a tongue penetrates south into the marble for about 100 feet. Between the surface and level A the crest of this tongue plunges south at about 30° ; consequently in depth the tongue of quartz monzonite penetrates in- creasingly farther to the south into the marble. The marble salient dips nearly vertical, but rakes about 60° to the south. The ore body occupies the point and part of the west side of the salient, and like the salient dips vertically and rakes about 60° to the south. The outcrop of the South ore body was more extensive than that of any of the other ore bodies in the mine, but the ore body thinned downward and its total bulk is far less than that of the Main ore body. On the surface it was more than 300 feet long and 150 feet wide, but it was less than 100 feet wide on level C and not more than 50 feet wide on level A. The length on level A is about the same as on the surface. A single diamond-drill boring from level A, which intersected the ore body 600 feet below level A, indicates further thinning to 15 feet. The ore body has not been identified on the 1,500 level, and the geologic relationships indicate that both the marble salient and the ore-body bottom well above the 1,500 level. The ore body appears to have contained between the surface and level A a single tungsten ore shoot (with an average grade of at least 0.75 percent of WO :! ), which in plan become shorter and narrower in depth (fig. 3). No assay data are available from the outcrop of the ore body, but the extent of the open pit suggests that except for a core of quartzose rock that pinched out downward just below the floor of the pit the entire ore body con- tained scheelite in sufficient abundance to be mined. Assays from level C indicate that all of the tactite except a small zone in the northern tip contained minable amounts of scheelite, but assays on level A indicate that only the south and narrower half of the ore body con- tained scheelite in minable amounts. Molybdenum in amounts of 0.4 percent or more of MoS L . was restricted to the upper part of the ore body. Inspection of the open pit reveals notable amounts of molybdenite in the walls, both in veinlets and in siliceous parts of the tactite. On level C, ore with significant amounts of molybdenum was present in only two small areas, and on level A no significant concentrations of molybdenite are indicated. Economic Geology of Bishop Tungsten District 33 It seems reasonable to assume that the sharp reentrant in the granite contact was the dominant control over the localization of the ore body, but it fails to explain the upward thickening of the ore body and the greater abundance of both scheelite and molybdenite nearer the surface. A possible explanation for these features is that the ore at the surface, before erosion, lay just beneath a granite bench or protrusion. The possibility of the existence of such a cap is suggested by analogy with the Main ore body where a similar core of quartzose rock with abundant sulfides of copper and molybdenum seems to be related to an overhang in the intrusive contact. The Main ore body, the largest and most productive ore body in the mine, crops out about 300 feet north- east of the South ore body. The ore body averages about 300 feet in length and 75 feet in width, but the width ranges from 30 to almost 200 feet and the length from 350 to GOO feet. In depth, the ore body has been ex- plored from the outcrop, at an average altitude of Slightly above 11,600 feet, downward to the 1,500 level, at 9,430 feet— a vertical distance of almost 2,200 feet (fig. 4). The plan dimensions of the outcrop are exception- ally small — 350 feet long and with an average width of about 50 feet. The maximum plan dimensions, just above the 1,500 level, are GOO feet long and almost 200 feet wide near the middle. Although irregularities in the configuration of the ore body are readily apparent, in a broader view the ore body is remarkably regular. It strikes about N. 20° W. and dips and rakes vertically, generally concordant with both the intrusive contact and with the bedding in the enclosing marble. The only significant exception to the concordance of the ore body, the intrusive contact, and the bedding is at the south end of the ore body where both the bedding and the ore body diverge in strike from the contact. At most places the ends of the ore body finger out into marble, and marble lenses also are found within the ore body. The quartz monzonite contact is irregular in most places, and locally lar sec. 15, T. 7 S., R. 30 E., at an altitude of about 12,000 feet. Largely because the ore mined was high grade, averaging about 2.0 percent of WO :i , the mine ranks second in total production among the mines of the Pine Creek pendant, being exceeded only by the much more productive Pine Creek mine. The best means of access to the mine is the jeep road to the Hanging Valley mine; a fork leading to the Tungstar mine branches from the Hanging Valley mine road at the crest of the high southeast-facing escarpment on the northwest side of Horton Creek canyon. The mine can also be reached on foot or horseback from Pine Creek canyon by means of a 7-mile trail that follows Gable Creek for about 3 miles, then switchbacks up the west slope of Mt. Tom. The Tungstar deposit was discovered in 1937 by Bill Wasso and Gerard Crawford, and acquired by the Tung- star Corp. in 1938. It was brought into production in 1939 after the erection of a mill and a 2.6-mile aerial tram. The mill was in Pine Creek canyon at 7,400 alti- tude near the junction of Gable Creek with Pine Creek. Mining operations were carried on from November 1939 to October 1946, when the mine installations and upper tram terminal burned. During this interval first the mill, then the aerial tram were replaced. Tn 1951, the mill and office buildings were destroyed by snowslides. The deposit consists of two ore bodies, the Greene ore body and the Stevens ore body. Both bodies are in meta- morphic inclusions in an irregular dikelike mass of quartz diorite that separates biotite-quartz schist on the north from a scries of metavolcanic rocks on the south. Almost all the production has come from the Greene ore body; the Stevens ore body, which crops out a few hundred feel south and uphill from the Greene ore body, has sup- plied little ore. The Greene ore body is in a carrot-shaped inclusion with a vertical extent of more than 300 feet and a maxi- mum outcrop dimension of only about 100 feet (pi. 7). The ore body was originally developed by means of h glory hole, an adit level (A level) that intersected the ore body 65 feet beneath the lowest outcrop, an interme- diate level between A level and the glory hole, and sev- eral raises and sublevels. An inclined winze was later sunk from A level to a depth of 180 feet, and levels were extended into the ore body at 70, 100, 130, and 180 feet vertically beneath the winze collar. Subsequently, a two- compartment vertical shaft was sunk to a depth of 280 feet beneath A level, and connections were made with the existing levels ; in addition, a new level was extended into the ore body from the bottom of the shaft. Company records show that a 320-foot level was developed at the bottom of a winze sunk from the 280 level, but the level was not inspected by the writer ; and consequently a map of the level is not included on plate 7. Accurate sur- veys were never made of either the 320-foot level or of the borings. The ore above A level was mined by the glory-hole system and the open-stope method. Mining in open stopes proved unworkable for extracting the ore beneath A level when a stope above the 100 level caved, resulting in the loss of both the level and the stope. As a conse- quence, practically all the block between A level and the 280 level was mined by square setting and back filling. The ore above the 180 level was hoisted through the winze, but the ore beneath the 180 level was trans- ferred through the shaft. The Greene ore body is a tabular tactite mass that dips steeply to the west (pi. 7). It occupies almost all of the metamorphic inclusion, but barren hornfels is present on A level, and unmineralized lenses of marble are found on the 280 level. The longest axis of the ore body is nearly vertical ; the next longest is in a northly direc- tion. The south part of the ore body is thickest on all the levels. On A level the thinner northern part is sepa- rated from the thicker southern part by quartz diorite, possibly through faulting, but on the deeper levels the ore body thins gradually to the north. Company maps of the surface and upper mine workings show a diorite core in the south-central part of the ore body, which extends downward from the surface for about 65 feet. According to Lemmon (1941b, p. 93), the outcrop was 100 feet long and 20 to 40 feet wide. On A level it was 70 feet long and averaged 20 feet wide. Downward, the long horizontal dimension increased to a maximum of 175 feet on the 130 level, then diminished to less than 100 feet on the 180 level. The 280 level was briefly ex- amined in 1946, before the mine installations burned, but the geology was not mapped. Nevertheless, it was evident that the plan dimensions of the ore body on the 280 level were less than on the 180 level. The borings from the 320 level intersected tactite only near their collars ; the cores are largely of dark-colored quartz diorite. Fractures filled with clay gouge, which are prominent in the upper part of the mine, are thought to be faults of small displacement. The tactite of the ore body consists largely of garnet and epidote, but includes quartz, pyrite, sphene, apatite, oligoclase, and potash feldspar. In the upper parts of the mine the pyrite is oxidized, but in the lower levels it is only slightly altered. The scheelite, with blue-white fluorescence, commonly is present in coarse crystals, Economic Geology op Bishop Tungsten District 37 sonic of which arc several inches in average diameter. In deeper parts of the mine some of the best ore was a coarse-grained aggregate of oligoclase, potash feldspar, pyrite, and scheelite. Decrease in the WO3 content of the mill heads during the life of the mine suggests that the scheelite content of the ore body diminished with depth. The grade of the mill heads diminished from 2.6 percent WO3 for the first 17,000 tons mined in 1939 and 1940 (Lenhart, 1941, p. 67-71) to about 2.0 percent in 1943, then to little more than 1.0 percent in 1946. The weighted average of assays of the ore intersected in the borings from the 320 level shows a further decrease to 0.73 percent WO3. Ex- amination of the ore body under ultraviolet light, made at intervals of 1 to 2 years, support the interpretation that the grade of the ore decreased with depth. The decrease of grade with depth is similar to relations be- tween grade and depth in deposits in the Deep Canyon area of the Tungsten Hills, where the deposits are also in metamorphic inclusions. Also, as in the Deep Canyon mines, the occurrence of unaltered marble on the 280 level of the Tungstar mine suggests less-intense additive metamorphism. The Stevens ore body is suggestive of the roots of an inclusion, which may have contained rich ore in its eroded upper parts. It consists largely of marble that is penetrated by anastomosing scheelite-bearing silicate bands. The scheelite content of the ore body as a whole is too low for profitable exploitation, but that of the silicate bands is high. Attempts at selective mining of the silicate material have not been successful because sig- nificant amounts of unmincralized marble were present in the ore, and in milling it breaks down to slime, which interferes with the gravity concentration of the scheelite. The ore body is underlain at a shallow depth by quartz diorite ; B level passes beneath it in quartz diorite, and a raise through the center of the ore body is in quartz diorite to within a few feet of the surface. Hanging Valley Mine. The Hanging Valley mine (fig. 8) is on the west flank of a high talus-filled valley about a mile southwest of the Tungstar mine. It is in the NWi Sec. 22, T. 7 S., R. 30 E., at an altitude of about 11,740 feet. The mine is reached by means of a road fol- lowing Horton Creek to Horton Lake ; then by a narrow steep jeep road that switchbacks spectacnlarly up the 2,000-foot high escarpment north of the lake. Because of heavy snows, access by road is ordinarily possible only during the summer and fall months. The Hanging Valley deposit was located in 1939 by Mike Millovitch and Pete Jono; but because of the in- accessibility of the deposit development has been slow. Construction of the mine road was expensive and con- sumed several years' time. In 1950, the Hanging Valley Mining Corp. merged with the Tungstar Corp. to form the Tungstar-Hanging Valley Mining Co. Although the production has been small, continued exploration and development may lead to greater production. The aver- age grade of ore mined has been in excess of 1.0 per- cent W0 3 . The Hanging Valley deposit crops out through talus at only one place, but regional relationships indicate that it is along or very near to a northwest-trending contact between quartz monzonite on the southwest and metamorphic rocks of the Pine Creek pendant on the northeast. It is developed by means of two adil levels separated vertically 115 feet, and by several raises, a 45-fool winze, and several small stopes. Only the upper adit is shown on figure 8; the lower adit was driven in 1952 and reached the ore zone after the writer examined the deposit. The ore is in a zone of metamorphic rocks consisting of tactite, hornfels, and marble, which is penetrated ir- regularly by quartz monzonite. Masses of rock that are impregnated with abundant pyrite are exposed at two places in the upper adit. Bedding is obscure at most places, but where it is discernible, it strikes westward and dips vertically or steeply south. Near-vertical, north-trending fractures of unknown, but probably small, displacement cut the beds. Quartz monzonite exposed in the faces of the two longest forks of the upper adit may be part of the main quartz monzonite mass on the southwest, but neither exposure has been penetrated far enough to demonstrate that it is not a dike. Other exposures of quartz monzonite are appar- ently parts of dikelike masses. The ore is discontinuous in plan ; eight separate small shoots are distinguishable in the upper adit. Explora- tion through raises, winzes, and by diamond drilling demonstrates that, in contrast with their limited extent horizontally, the ore shoots are vertically persistent. One shoot has been explored in a raise to 40 feet above the upper adit level, and another has been followed in a winze to 45 feet beneath the level. Furthermore, ore intersected in diamond-drill borings at depths as much as 90 feet beneath the upper adit level seem to represent extensions of ore shoots exposed on the level. Some of the ore shoots are obviously confined beneath east-trend- ing, near-vertical beds and north-trending, near-vertical fractures; but others show no apparent relationship to either bedding or fractures. Flat or gently dipping fractures are said to coincide with abrupt changes in the scheelite content of the ore. Lakevinr Mine. The Lakeview mine is in the Cable Lakes area near the head of Gable Creek, a tributary to Pine Creek, at an altitude of about 10,600 feet. It is near the north boundary of see. 21, T. 7 S., R. 30 E., about 1 mile N. 70° W. from the Hanging Valley mine and 11 miles S. 75° W. from the Tungstar mine. The mine is reached from the paved road in Pine Creek canyon by means of 3 miles of trail that follows Gable Creek. The deposit, which contains a single small, high- grade ore shoot, was found in 1940 by P. W. Carpenter; the owners in 1954 were George Brown and K. C. Irons of Bishop. The deposit was worked intermittently from 1940 to 1943, and hand-sorted ore (probably about 60 tons) was packed out on mules. In 1953 George Brown moved a small mill onto the property and treated ore from the dumps. Mine workings include a small opencut, a 47-foot shaft, about 100 feet of level workings from the bottom of the shaft, and two raises from the shaft level, one of which connects with the opencut (fig. !> and photo 5). The mine is in the south end of a thin layer of marble and tactite that averages 60 feet in outcrop width and can be traced from the mine about 1,600 feel in a northwesterly direction. The northwestern 1,000 feet of the layer lies between schist on the southwest and quartz 38 Special Report 47 diorite on the northeast, but farther southeast quartz monzonite crops out in places on both sides. Although taetite is developed in the layer at several places, ore has been found only about 150 feet from the south- east end. In the mine area the marble strikes about N. 30° W. and is nearly vertical. In outcrop, about half of the marble is altered to taetite; in addition, small lenses of .-neissic amphibolite and pyroxene hornfels are devel- oped in the west margin of the marble. Quartz monzo- nite, locally with abundant schist fragments, lies on both sides of the marble and taetite, except at the south end of the east side where a wedge of schist intervenes be- tween marble and quartz monzonite. Two kinds of taetite occur, nearly barren taetite that consists chiefly of dark reddish-brown garnet, and schee- lite-bearing taetite that consists chiefly of olive-green epidote with small amounts of quartz, amphibole, and calcite. The scheelite crystals generally are one-eighth to one-quarter of an inch across, and locally crystals occur as much as 2 inches across and with well-developed crystal faces. Garnet taetite is more abundant than the scheelite-bearing epidote taetite and occurs in two masses, one in either side of the marble layer. Scheelite- bearing epidote taetite, on the other hand, is limited to a single ore shoot— 60 feet long and averaging 10 feet in outcrop width, which is enclosed in garnet taetite and marble. In depth, the ore shoot diminishes in size, as is shown on the vertical projection of the ore shoot in fig. 9. The scheelite content of the ore also decreases downward from several percent of W0 3 at the surface to probablv less than a percent in the epidote taetite exposed oii the shaft level. Presumably the ore shoot extends only a few feet beneath the shaft level. The geology of the mine area supplies no clue to guide exploration for other concealed ore shoots, although it is not improbable that other shoots exist at depth. Else- where along the 1,600-foot-long layer of marble and taetite no commercial ore has been found; and inasmuch as it has been examined by several prospectors, it seems unlikely that further surface prospecting will result in the discovery of another ore body. Lambert Mine. The Lambert tungsten mine is about 7,000 feet N. 25° E. from the summit of Mt. Tom, on the east side of a cirque at the head of Elderberry Can- yon at an altitude of slightly more than 10,800 feet. A dirt road that joins the paved road along Pine Creek near Rovana leads to the mouth of Elderberry Canyon ; from the end of the road a trail follows Elderberry Creek (J miles to the mine. The deposit was found by Stanley Lambert of Bishop in 1940. In 1941 the property was leased to Kenneth G. Irons and Associates, who in 1942 and 1943 mined a few hundred tons of high-grade ore from a single ore body and prospected the intrusive con- tacts in the vicinity of the mine. The mine was idle from 1944 to 1954. The ore was packed by mules to the mouth of Elderberry Canyon, where it was stockpiled for later transfer to a mill by truck. The mine is in the northwest end of a diamond-shaped mass of metamorphic rock that is bounded on all sides by quartz monzonite. From the mine, which is low on the south wall of the cirque at the head of Elderberry Canyon, the metamorphic mass extends southeastward about 2.000 feet, across the crest of a ridge almost to the bottom of the next canyon south of Elderberry Can- yon. The greatest width of outcrop of the mass is along the crest of the ridge, and it thins both to the north- west and to the southeast toward the canyon bottoms. This outcrop pattern may be interpreted to indicate that the mass pinches downward and that it does not ex- tend much below the level of the ends, but the outcrop pattern may be explained equally well by assuming other configurations for the mass. The most abundant rock in the metamorphic mass is gray or white marble, which contains a few silicated layers, but on the west side a 200- to 300-foot-wide belt of biotite-quartz hornfels extends north from the ridge crest to the bottom of Elderberry Canyon, and on the east side quartzite and calc-hornfels are present along the ridge crest. The beds, except locally near the margins 1 of the mass, strike northward and dip steeply or ver- tically. The ore body (now exhausted) was on the north con- tact of the marble, about 250 feet east of the biotite-quartz hornfels in the west side of the metamorphic mass. In the mine area both the bedding in the marble and the intrusive contact are irregular, but they are concordant in a general way ; the average strike is easterly and most recorded dips are 30° to 60° to the south. The ore body, a gently curved lense of taetite 6.") feet long and 8 to 10 feet wide near the center, pinched out downward less than 30 feet beneath the outcrop (fig. 10). The average grade of the ore mined was about 2.0 percent of WOs, but the ore body was richer in the central part and leaner at the ends. Much of the ore was crushed by post- mineral faulting along the contact, but the faulting does not seem to have had any significant effect on the distri- bution of either taetite or of scheelite within taetite. The ore body was mined in an opencut, but the intru- sive contact in the immediate vicinity of the ore body was further explored by means of three short adits : a 20-foot crosscut through the east end of the ore body, a 40-foot drift driven east along the intrusive contact from the face of the opencut, and a 50-foot drift, 20 feet lower than the opencut, driven eastward under the ore body from a prospect opencut. In the 50-foot drift the thick- ness of the taetite is only about 2 feet and is separated from the quartz monzonite by a zone of altered talcose rock. The intrusive contact west of the ore body to the biotite-quartz hornfels is talus covered, but four small masses of nearly barren taetite crop out through the talus. This part of the contact has been explored under- ground by means of an adit that was driven about 140 feet east from a portal 200 feet west and about 100 feet below the outcrop of the ore body. In this adit only a few very small bodies of nearly barren taetite were pene- trated. Along this span the contact is irregular and in most places is faulted. Much of the marble adjacent to the contact is altered to talc. East of the ore body the intrusive contact extends 1,200 feet to the crest of the ridge. The 600 feet adjacent to the ore body is covered by talus, but the eastern 600 feet is opened by more than a dozen small prospect pits. The taetite exposed ranges from 6 to 10 feet in width. Scheelite is visible in most outcrops, but no bodies of minable grade or size were found. The contact south and east of the ridge crest also was examined during the course of the mining in 1942 and Economic Geology of Bishop Tungsten District 39 1943 without finding minable ore bodies, although ex- tensive masses of taetite at the southeast tip of the meta- morphic block were sampled. The analyses of the samples showed that the seheelite content of the taetite exposed there is too low for profitable exploitation. Round Valley Peak Prospect (Adamson Prospect). The Hound Valley Peak prospect is on the east side of Wheeler Crest in a notch between Round Valley Peak and an unnamed peak to the east. The average altitude is about 11,200 feet. Neither a road nor a trail leads to the deposit ; but it can be reached fairly readily on horse- back or on foot from Rock Creek Lake, 31 airline miles to the west, or from a jeep trail that follows the morainal ridge along the east side of Rock Creek Canyon. The jeep trail terminates at some small lakes on the east fork of Rock Creek, only about 2 miles from the property ; but the region has been designated as a "Wilderness area" by the U. S. Forest Service and the road is not open to the public. The deposit was discovered in 1939 by D. B. Adamson of Bishop, who located three claims, but it has been ex- plored by only a few shallow prospect pits. Taetite crops out locally along the east and southeast sides of the screen of metamorphic rocks that extends northeast from the Pine Creek pendant, Biotite-quartz hornfels is the dom- inant rock in most parts of the screen, but a 4,000-foot span in the prospect area is chiefly marble. The most extensive exposure of taetite, near the middle of the east contact of the marble, is about 300 feet long and 50 feet wide. About 1,000 feet to the south another mass about 150 feet long crops out. Both out- crops contain sparsely disseminated seheelite, probably in amounts too smali for profitable exploitation, espe- cially in view of the inaccessibility of the deposit and the relatively short season during which mining could be carried on. In the span between the two taetite masses, tongues of quartz monzonite penetrate deeply into the marble; enough of the contact is exposed through talus to demonstrate that it is not paralleled by large bodies of taetite like those exposed. North of the northern taetite mass the east contact is concealed by talus and slope wash, but taetite crops out intermittently. Most of the exposed taetite, however, contains little seheelite. Occurrence Northwest of Pine Creek Federal Housing Project. A mass of taetite with some seheelite, found in the course of the geologic mapping, is about 2 airline miles northwest of the Federal housing project in Pine I 'reek Canyon at an altitude of about 10,000 feet. The taetite is an inclusion in the north margin of a mass af hornblende «abbro. Chips were found to contain seheelite, but the taetite mass was not examined in the field under ultraviolet light. The occurrence can be reached on foot by following the alluvial-filled canyon on the north side of Pine Creek half a mile north of the housing project. From he head of the alluviated part of the canyon, follow the nain drainage, which lower in the canyon is on the west side of the alluvial fill. The occurrence is 1 mile north- west from the head of the alluvium about 1,000 feel southwest of the bottom of the drainage. The hornblende jabbro in which the taetite is enclosed is darker hued ;han the quartz monzonite and quartz diorite in the dcinity, and near the taetite is orbicular with individual orbicles of hornblende and feldspar averaging about an inch in diameter. Blu( (! nuts, Prospect. The Blue Grouse prospect, owned by Fred Austin of Bishop, is in the bottom of Pine Creek canyon about a quarter of a mile above the U. S. Vanadium Co. tungsten mill. In the vicinity of the prospect a wedge of quartzite lies between the marble in the west side of the pendant and the quartz monzonite west of the pendant. Lenticular and discontinuous bodies of taetite are present along the contact between the marble and quartzite, generally adjacent to dikes or apophyses of granitic rock. The taetite bodies have been explored by short adits and prospect pits. Although locally high-grade ore is exposed over small areas, the average seheelite content in the taetite outcrops ap- pears low. The most extensive body, about 150 feet long and 10 to 15 feet wide, is exposed in the bottom of the canyon. The taetite in the body is somewhat lighter in color than the most common variety in the nearby Pine Creek or Brownstone mines, and consists of quartz, fluorite, epidote, pale-green diopsidic pyroxene, ealeite, pink garnet, seheelite, and sphene. Other smaller taetite bodies present in the north wall of the canyon are de- veloped along coarse-grained pegmatitic dikes like those that have broken and dislocated the ore body at the Brownstone mine. Moore Prospect (Sunnyboy Mine). A prospect on the southeast flank of Mt. Tom in the NWi sec. 24, T. 7 S., R, 30 E., is held by R. W. Moore of Bishop. The claims are along the crest of a southeast-trending spur at an altitude of about 10,400 feet. The only production was in 1943 when a test sample of less than 100 tons was shipped to the Red Hill Mill near Bishop. A jeep or tractor trail that branches north from the Hanging Valley road where it enters Horton canyon leads about li miles to the prospect. The prospect is in an irregular but apparently exten- sive body of taetite in the southwest part of an elongate north-trending mass of marble. The outcrop of the marble is about 1,000 feet long and 200 feet wide. It forms a craggy butte with nearly vertical sides that rises abruptly above the general level of the spur. The marble is bordered on the north and northeast sides by quartz monzonite, on the southeast side by gneissic quartz diorite, and at the south end and southwest sides by talus, which is probably underlain by quartz diorite or quartz monzonite. The south part of the marble is cut by aplitic dikes, some as much as 100 feet thick, which presumably are offshoots from the quartz monzonite. Much of the taetite is localized along the aplitic dikes, but some at the base of the butte may be related to the concealed contact of the marble with quartz diorite or quartz monzonite. The taetite in the base of the cliff is readily accessible, but that higher in the butte can be examined only by climbing the butte, aided by a ladder and by ropes fastened to the rock walls. Most of the taetite exposed contains no seheelite, but locally it eon- tains moderate amounts; no ore shoots large enough or rich enough to support a sustained mining operation have been found. Mountain Basin Prospect. A small body of scheelite- bearing taetite that was discovered in 1942 by Thomas Ill Special Report 47 Soinor and Pete Jono is exposed on the north wall of the prominent cirque in the west side of Basin Mountain, at an altitude of 10,600 feet. It is in the SK 1 , sec. 2(5, T. 7 S., R. .'iO E., and is reached most easily by walking about 1! miles south along the east face of Basin Mountain from the dirt road to the Hanging Valley mine, leaving the road where it crosses the moraine at the entrance to the deep canyon occupied by Ilorton Creek. The tactite is along the upper contact of a tabular mass of marble that is enclosed in quartz monzonite. The outcrop of the marble is about 200 feet long and 50 feet wide. The beds and upper contact strike northward and dip 30° to the west. The tactite is about 20 feet long and averages 2 feet in thickness where it is exposed in the cirque wall. It has been explored underground by means of a 15-foot adit. Under ultraviolet light the tactite appears to contain substantial amounts of schee- lite, possibly as much as 1.0 percent. It has not been extensively developed because of its small size and the lack of a road. The Bishop Creek Pendant The Bishop Creek pendant underlies about 20 square miles — lf> square miles in the northeast corner of the Mt. Goddard quadrangle, about 2 square miles in the southeast corner of the Mt. Tom quadrangle, and less than 1 square mile each in the northwest corner of the Big Pine quadrangle and southwest corner of the Bishop quadrangle. If smaller outlying masses are included, the area is increased by 2 or 3 square miles. In shape, the pendant is very irregular, being embayed and intricately penetrated by all the bordering intrusive rocks. The heart and least deformed part of the pendant is along Coyote Ridge on the east side of the south fork of Bishop Creek; from the heart of the pendant 2 large somewhat more deformed lobes extend northwest across Table Mountain and northeast across Lookout Mountain. Altitudes in the pendant area range from 8,600 feet at the Cardinal gold mine, where a narrow projection from the pendant crosses the main fork of Bishop Creek, to more than 12,000 feet at the Hunchback, 1 mile northeast of Green Lake; but unlike the Pine Creek pendant, which occupies extremely rugged terrain, much of the area of the Bishop Creek pendant is gently rolling uplands partly covered by soil and fluvioglacial deposits. The west part of the pendant is cut, by the canyon of the South Fork of Bishop Creek, and the east part, along the escarpment between Coyote Ridge and Coyote Valley, is dissected by a chain of cirque basins. The western part of the pendant is readily accessible by the surfaced roads along the Middle and South Forks of Bishop Creek, but the eastern part can be reached in a vehicle only by a private access road built by A. II. (Salty) Petersen to claims he holds in the northeast part of the pendant. This road, which runs southwest from Bishop, is too steep and the road bed too loosely packed for travel in an ordinary passenger car. A num- ber of branch roads from Petersen's road have been built by prospectors and stockmen to various parts of the pendant area. The pendant consists largely of biotite-quartz hornfels, quartz-feldspar hornfels, calc-hornfels, andalusite horn- fels, metachert. and marble. These rocks are distributed in mappable units composed of one or more rock types They were thrown into a series of north-trending fold during an orogenic period that preceded the intrusions and were further deformed during the emplacement o the intrusions. In addition to deformation by folding the metamorphic rocks are cut by faults, some of whicl have minimum displacements of thousands of feet. The pendant contains not only several tungsten mines and prospects in tactite, but also a gold deposit ii micaceous quartzite at the Cardinal mine. Most of the tungsten deposits are along contacts between marble oi calc-hornfels and granitic rocks, but the Schober mine and Merrill prospect are in small metamorphic inclusions in the marginal part of a mass of hornblende gabbro near quartz monzonite. The Schober mine is the only deposit in the pendant that has been operated profitably but some others offer hope for successful operation, and new discoveries may be made. Schober Mine. The Schober mine, near the center of sec. 23, T. 8 S., R. 31 E., at an altitude of 10,000 feet, is on the east side of the South Fork of Bishop Creek. In 1942 and 11)43, when the mine was in operation, it was accessible from the Circle S ranch on the surfaced road that follows the South Fork of Bishop Creek, by means of a 3-1-mile private dirt road, but the dirt road was washed out in 1946. The mine can also be reached via Coyote Flat by a steep, winding, dirt road. The deposit was discovered in late 1940 by Harold Schober and sold in 1941 to the El Diablo Mining Co. This company built the road from the South Fork of Bishop Creek to the mine and trucked ore from the deposit to its mill near Bishop. The mining operation was very profitable. In 1943 the ore body was exhausted, and, after exploration at depth failed to reveal addi- tional ore, the mine was shut down. The mine workings consist of a pit 85 feet wide and 100 feet long measured across the rim, and 15 to 40 feet deep ; 115 feet of level workings into the walls of the pit ; an inclined shaft sunk to a depth of 140 feet be- neath the floor of the pit; 150 feet of level workings on the 68-foot level of the shaft ; and 70 feet of miscella- neous short crosscuts and raises. In addition trenches with an aggregate length of about 680 feet have been bulldozed on the surface north and east of the pit (fig. ID. The mine is in an inclusion composed of tactite and hornfels in the eastern margin of a mass of hornblende gabbro. The outcrop of the hornblende gabbro is ellip- tical, with an average diameter of about 1 mile. The hornblende gabbro is entirely surrounded by quartz monzonite ; the contact between these rocks is about 150 feet east of the pit. In the vicinity of the deposit the soil mantle is thick, and the inclusion cropped out in a single exposure only a few feet in diameter. The exposures of the contact be- tween the metamorphic rocks and hornblende gabbro in the walls of the pit are steep, but on the west side of the inclusion the metamorphic rock clearly dips under the hornblende gabbro. By analogy with the deposits in small inclusions in the Deep Canyon area of the Tung- sten Hills, it is assumed that before erosion the inclusion was overlain by hornblende gabbro only a short distance above the outcrop. Economic Geology OP BlSHOP Tungsten District 41 Scheelite ore of minable grade was found only in the upper part of the inclusion; the floor of the pit coincides approximately with the lower limit of the ore. Typical tactite contained very little scheelite; and the ore was coarsely crystalline rock that consisted chiefly of pyrrho- tite. scheelite, and quartz, with a little garnet, epidote, and calcite. Classes of scheelite as much as 6 inches across were found during the course of the mining operation. The pyrrhotite was oxidized to limonite to a depth of tbout 20 feet with no significant change in the scheelite ontent of the oxidized ore, such as might have resulted from extensive leaching or secondary enrichment. The operators report, however, finding a few specimens of tungstite (WO3), a mineral considered to be of sec- ondary origin, in a single spot in the gossan. The average grade of the ore milled was about 2.0 percent of WO3. Some low-grade, fine-grained ore is exposed in the workings beneath the pit, but the grade is probably too low for profitable exploitation. On the 68-foot level, the scheelite mineralization is confined to a single bed in a zone that is cut by numerous cross faults of small dis- placement. Other exposures of tactite are present in the bulldozer trenches, but none of the tactite contains scheelite. Merrill Prospect. The Merrill prospect, near the lorth boundary of sec. 2(i. T. S S., R. 32 E., is about 3,000 feet S. 20 W. from the Schober mine and about 200 feet higher. A dirt road leads from the Schober mine to the Merrill prospect. Boulders of high-grade ore were found in the detritus covering the steep hill slope at the prospect, but ore was lot found in place. A short adit passes through slope wash and hornblende gabbro without encountering tactite. The locale of the prospect is very similar to that of the Schober mine; it is in the marginal part of the same mass of hornblende gabbro close to quartz monzo- lite. Although it is possible that all the ore is in float, additional exploration is desirable before the prospect is abandoned. Lindner Prospect (Oomph Claims). The Oomph laims, held bv Ed and Charles Lindner, are in the XE j sec. 2, T. 9 S., R. 31 E., at an altitude of 10,800 feet. They are on the west edge of the rolling upland that con- stitutes Coyote Ridge, and overlook the canyon of the South Fork of Bishop Creek on the west. The tungsten prospect on the claims can be reached by trail from the surfaced road along the South Fork of Bishop Creek, yv by a dirt road that was extended westward in 1952 the prospect from the private road to Coyote Flat. Only about 30 tons of ore had been shipped from the prospect to the end of 1953. The workings in 1954 con- isted of eight small pits and a 75-foot adit. The prospect is along an east-trending, steeply dipping •ontact between thin-bedded calc-hornfels on the north md granodiorite on the south (fig. 12). The beds in the •alc-hornfels strike about X. 30° W., almost perpendicu- ar to the intrusive contact and dip steeply. The calc- lornfels is in the core of a tight anticline and is overlain ;tratigraphically by a thick unit of micaceous quartzite, which crops out both to the southwest and northeast. \plitic dikes and sills penetrate the calc-hornfels. Tactite masses are developed at widely spaced inter- nals in the calc-hornfels adjacent to the granodiorite •ontact. The tactite masses extend from the intrusive contact into the calc-hornfels along bedding planes for distances of as much as 20 feet, pinching with distance from the contact. Between the tactite masses, only a dis- continuous selvage of tactite a few inches thick is de- veloped in the calc-hornfels contiguous with the grano- diorite. Specimens of fresh tactite are notably rich in quartz, and also contain lesser amounts of pyroxene, epidote. amphibole, and garnet. .Much of the tactite is scheelite bearing, and most of the scheelite-bearing tactite also is limonitic, indicating the former presence of sulfides. One mass of tactite grades outward from the intrusive contact into a gossanlike, limonite-quartz rock that ap- pears to be a fissure filling. The scheelite-bearing parts of the tactite appear under ultraviolet light to contain 0.5 to 1.0 percent of WO3. Undoubtedly small pods of ore will be mined from the deposit from time to time, but it seems unlikely that more than a few tons of ore can be developed for mining at any one time without inordinate expense. Bracket! Prospects. Two claims, the Black Monster (Coyote Lake prospect) and the Snow Queen, were lo- cated in 1941 by J. F. Brackett, Robert Brackett, Bill Skinner, and Maynard Rossi. The claims, which are in the east half of sec. 36, T. 8 S., R. 31 E., are accessible by roads that branch from the Coyote Flat road. Both claims cover tactite bodies that were prospected in the summers of 1942 and 1943, but which have not been explored since then. In 194:5, J. P. Brackett started con- struction of a gravity mill on the east shore of Coyote Lake, but it was never completed. A few tons of ore was hauled to the Jones mill, south of Benton, which then was operated as a custom mill. On the Black Monster claim tactite is exposed on the northwest side of Coyote Lake at an altitude of about 10,500 feet. The tactite crops out discontinuously through glacial debris for 430 feet alon^ a northerly trending line (fig. 13). The strike of the exposed beds is parallel to the line of outcrops, indicating that the tactite is in the form of a bed. Biotite-quartz hornfels is exposed in three outcrops on the west side of the tactite, but because the eastern limit of the tactite is not exposed, one can state only that the minimum thickness of the tactite is at least 20 feet. Both the tactite and the schist and hornfels are penetrated by quartz monzonite. Workings include a 15-foot shaft sunk in the north part of the tactite, a 12-foot shaft sunk in the south part, and a number of bulldozer trenches, most of which are in glacial till and do not expose bedrock. Tactite with minable amounts of scheelite has been found only in the north end of the series of outcrops and in the south shaft; only sparsely scattered crystals are present in other exposures of tactile on the claim. Ore with about 0.5 percent of WO3 is exposed in the 15-foot shaft and in an outcrop about 70 feet farther north, near the north edge of the ma]) area, but the intervening covered span has not been prospected to establish con- tinuity between the two exposures (see fig. 13). A small prospect pit about 40 feet south of the 15-foot shaft pene- trates only barren tactite. In the south pari of the tactile, scheelite in commercial amounts was found in the 12-foot shaft where it was confined to a small lens about a foot thick parallel with the bedding. The lens has been mined out but is reported to have contained several percent of 42 Special Report 47 WO,. Specimens of the ore contain scheelite crystals as much as half an inch across. Most of the crystals are equidimensional, but some thin, tabular crystals lie along joint planes. The prospect on the Snow Queen claim is about half a mile south of the Black Monster prospect and 500 feet higher, at an altitude slightly above 11,000 feet. It is on the upper slope of the escarpment that bounds Coyote Ridge on the east. The prospect is in an L-shaped mass of tactite that lies on the northeast and northwest sides of a rectangular inclusion of marble in quartz monzomte. Tactite also crops out in a thick band on the southeast side of the marble, but it contains only traces of scheelite. In the core of the marble, where the beds are least disturbed, they strike north to about N. 25° W. and dip 45 E3. ; but in' the north part, in the vicinity of the pros- pect, the beds, though somewhat contorted, generally strike north or northeastward and dip eastward. The longer leg of the L-shaped tactite mass, on the northeast side of the marble, is in direct contact with quartz mon- zonite, whereas the shorter leg on the northwest side is separated from quartz monzonite by a thin layer of schist. The shorter leg of the tactite mass is obviously concord- ant with the bedding and the longer leg discordant, but the dip of the longer leg is not known — it may dip steeply to the east. The apparent anomaly of the shorter leg on the northwest side of the contact being concordant with north- or northwest-striking beds is the result of the intersect ion of the bedding with a steep hillside. The only part of the tactite that contains noteworthy amounts of scheelite is a 60-foot span that extends south- east along the longer discordant leg from the join of the two legs^The tactite in this span, with an average out- crop width of about 3 feet, appears under ultraviolet light to contain about 0.5 percent of W0 3 . This span has been prospected only by means of two shallow cuts, one at the juncture of the legs, and one about 40 feet to the southeast. The tactite in the southeasterly cut con- tains scheelite in bands parallel with the bedding in the marble but discordant with the tactite body. A sample from this cut, taken by the owners, assayed 2.1 percent W0 3 , according to J. F. Brackett. Petersen Prospects. A. II. (Salty) Petersen holds sev- eral claims in the northeast part of the Bishop Creek pendant. He built the access road to Coyote Flat with forks to all his claims and constructed a gravity mill in the W. .', sec. 16, T. 8 S., R. 32 E., on the west side of Coyote Creek. The mill has been used to test and to treat small lots of ore from the prospects. The Munsinger prospect is in the NW| sec. 17, T. 8 S.. R. 32 E., at an altitude of 9,800 feet. The prospect is along a northwest-trending contact between quartz mon- zonite on the northeast and ealc-hornfels on the south- west. The contact is nearly vertical, and the beds in the calc-hornfels dip 35° toward the southwest, away from the contact (fig. 14). The contact has been explored in an openent and in a short adit whose portal is about 150 feet north of the openent and 40 feet lower. Thin tactile has replaced the ealc-hornfels along the contact, and it extends outward and downward from the contact along favorable beds for distances of as much as 12 feel from the contact. The geologic relationships are the same in both the adit and in the openent, except that in the openent a larger part of the calcareous rock is converted to tactite. Scheelite is disseminated irregu larly through the tactite. The Hilltop prospect is half a mile west of the Munsinger prospect in the NE> sec. 18, T. 8 S., R. 32 E The prospect is at the point of a marble salient int( quartz monzonite. From the prospect the contact trends south in one direction and west in the other. Darl* garnet-pyroxene tactite with sparsely disseminatec scheelite is exposed to a depth of about 6 feet in ar openent. A short distance south of the opencut the beds strike northward and dip vertically, but locally the sur- face is soil covered. The Little Egypt prospect is in the west-central pari of sec. 7, T. 8 S., R. 32 E., at an altitude of about 9,75C feet. The prospect is on the crest of a ridge between twci forks of Coyote Creek. The area to the north and below the prospect is covered by an extensive basalt flow that is readily visible from the Bishop Creek road. The pros- pect is in a small salient that is the northernmost tip bl the eastern part of the Bishop Creek pendant. The salient is almost isolated from the main pendant ; quartz monzonite lies on three sides and on the fourth only a narrow neck of tactite connects the salient with the rest of the pendant (fig. 15). Tactite crops out over an area of about 3,000 square feet. All of the marble in the salient is converted to quartz-pyroxene tactite, in striking contrast with the slight silication of the marble in contact with quartz monzonite in nearby areas. The tactite contains unevenly distributed scheelite ; in places it appears to contain enough to be of minable grade, and in others it is nearly barren. The Coyote Creek prospect, in the NEj; see. 30, T. 8 S., R, 32 E., at an altitude of about 9,800 feet, is on the north side of Coyote Creek. The deposit is in a salient of tactite along a northwest-trending contact between granodiorite on the east and marble, with interbeds of calc-hornfels, on the west. The beds in the marble are discordant with the contact, striking on the average a few degrees north of east and dipping nearly vertically. The salient of tactite and calc-hornfels is about 20 feet wide and extends about 150 feet beyond the general trace of the contact into the granodiorite. It is exposed on the southeast-facing nose of a wedge of granodiorite. It has been explored by means of three small surface cuts and by an adit that passes through only a small amount of barren tactite before entering granodiorite. In the outcrop an ore zone 4 feet wide and containing about 2.0 percent of WO3 was exposed for about 60 feet along the strike. Most of this ore has been mined. The ex- posures in the adit directly beneath this ore zone arc mostly of granodiorite, indicating that the tactite is cut 1 off by granodiorite at a very shallow depth. Quartz seams in the center of the tactite contained appreciable 1 amounts of argentiferous galena; microscopic and X-ray studies indicate that the galena contains inclusions of; bismuth and of schapbachite ( ?) (AgBiS 2 ). North from the prospect for almost a mile, marble and calc-hornfels are in contact with granodiorite, but the contact itself is covered by alluvium. At one place about 300 feet north of the main prospect the contact wasj uncovered in an opencut, but only a thin selvage of tactite with a little scheelite was found — the rock also contained some argentite. South along the contact calc- Economic Geology op Bishop Ti ngsten District 43 hornfels with a few thin interbeds of marble replaces the marble. In this direction also the eontacl is partly covered by alluvium, but a few scheelite showings have been prospected in shallow pits. A north-trending contact between quartz monzonite and marble at the southeastern base of Lookout Mt. lias been prospected by means of a group of trenches and small opencnts. The prospect is in the X\V] see. 19, T. 8 S., R. 32 E., at an altitude of about 10,700 Eeet. Both the contact and marble beds strike north, but the contact is nearly vertical whereas the marble dips 50 W. The tactite along the contact is irregular and generally thin, with tactite extending outward and downward alon»' favorable beds. The scheelite content is low. Waterfall Prospect. The Waterfall prospect is on the west side of the South Fork of Bishop Creek a little more than a mile south of the Circle S ranch. The pros- pect is at an altitude of about 8,750 feet, approximately 7.") feet higher than Bishop Creek at the closest point. In the summer of 1951 the property was held by Ralph Adams, Richard Riley, and Bart Van Vorhees, who em- ployed two men at the deposit. Some ore is reported to have been nulled, but the production is small. In the vicinity of the deposit the strata consist of ealc-hornfels and quartzite with thinner interbeds of marble. The beds strike X. to X. 10° W. and dip 50° to 80° W. To the west the strata are obscured by glacial debris and to the east they are concealed by valley fill. Selvages of tactite ranging from 6 to 30 inches in thick- ness are developed in the margins of a bed of light-gray marble. The tactite consists chiefly of light-brown garnet and quartz with lesser amounts of chlorite and scheelite. The tactite on the east side of the marble appears to contain the most scheelite. On the surface, where it is exposed for about 130 feet along the strike, the tactite averages about 2 feet in thickness. Underground it has been explored by means of a 30-foot crosscut and a 28-foot raise from the end of the crosscut. Examination under ultraviolet light indicates that the best ore is at the surface; in the raise the scheelite content of the ore diminishes downward. Minute pyrife crystals are locally disseminated through the ealc-hornfels east of the marble; a few small lenses of massive sulfides, consisting mostly of pyrrhotite, with minor pyrite, ehalcopyrite, and bornite occur also. Tactite is developed locally in ealc-hornfels adjacent to quartzite 1,200 feet S. 75° E. from the Waterfall pros- pect, on the east side of the valley. The tactite locally contains scattered crystals of scheelite, but no minable ore is exposed. A small cut has been made in one of the better showings. Stevens Prospect. Howard Stevens of Bishop has found several small masses of high-grade ore in the tains alonjr the northwest base of Table Mountain in sec. 20, T. 8 S., R. 31 E. lie also has uncovered a few small lenses of scheelite-bearinj-- tactite in the ealc-hornfels beneath the talus, but none of sufficient size to be mined have yet been found. In 1953 the general area was being further prospected. East End of North Lake. A small lens of tactite that locally contains a little scheelite was found in 1950 at the east end of North Lake in the SEj sec. 19, T. 8 S., R. 31 E. The occurrence was not visited by the writer. but it probably is in ealc-hornfels like those on the west side of Table .Mountain. Green Lake Area. Small masses of tactite cropping out over a lew square feci are found at several places north and northeast of Green Lake, and a few of them have been prospected by means of small pits. Some of the tactite is in limestone and ealc-hornfels, ad- jacent to granite sills and dikes, but on The Hunchback several masses of tactite and marble are enclosed in dio- rite. Locally the tactite contains scheelite, but generally in amounts insufficient for successful exploitation. Chocolate Peak Area The Chocolate Peak metamorphic area, in the SE cor- ner of sec. 23 and the XE corner of sec. 26, T. 9 S.. R, 31 E., is separated from the main mass of the Bishop Creek pendant by more than a mile of granitic rock. The metamorphic area contains a few lenticular tactite masses that have been prospected for scheelite, but the area is better known for the occurrence of cobalt. Choco- late Peak is reached from South Lake, at the end of the road alon» the South Pork of Bishop Creek, by following the trail to Bishop Pass and Kings Canyon National Park for about 2 miles. The principal claims in the Chocolate Peak area have been held for several years by the Bishop Silver-Cobalt Mines Co. Mr. Jack O'Brien, president of the company, lived on the property until his death in 1953. The accompanying map of the Chocolate Peak area (fig. 16) and much of the following description is based on an unpublished report by Mr. .1. S. Vhay of the Geo- logical Survey, who studied the area and the deposits in 1942. In Chocolate Peak a wide variety of complexly de- formed metamorphic rocks underlie an area of a little less than 1 square mile. On the accompanying map, the metamorphic rocks are divided into four "roups, (1 ) tac- tite, (2) quartzite and hornfels, including minor mica schist and thin interbeds of marble, (3) marble, includ- ing interbeds and small masses composed partly of wol- lastonite, diopside, or epidote, and (4) gneiss. The metamorphic rocks have been intruded by dikes of aplite, alaskite, pegmatite, and diorite, and by granitic rocks that are identical with the bordering plutonic intrusives. On the north and east sides the Chocolate Peak rocks are bounded by several kinds of granitic rock; on the south and west they are bounded by gneiss that extends in an elongate mass out of the map area to Bishop Pass, about 3 miles to the north, before being terminated by granitic rock. The distribution of the metamorphic rocks in Choco- late Leak is complex, and the structure is complicated. In most exposures the beds dip steeply and in many places are vertical. Folds are evident in the outcrops, and faults are indicated both by the outcrop pattern of the rocks and by physiographic evidence. On the east side of Lone Lake the contact between gneiss on the west and marble and hornfels on the east is almost certainly a fault. Tungsten Occurrences. Lenses of garnet-epidote tac- tite occur within the gneiss, especially on the south side of Chocolate Leak. Tactile also is present in small masses north of Chocolate Peak, along the trail from South Lake. Some of the tactite masses have been prospected for scheelite by means of shallow pits and opencuts, but 44 Special Report 47 none of the masses appears under ultraviolet light to contain sufficient scheelite for profitable exploitation. Tungsten Hills Iii the Tungsten Hills mining for tungsten has been confined almost entirely to two areas, the Deep Canyon (Tungsten City) area in the southeast part of the hills, and the Round Valley septum in the northwest part of the hills. The geologic associations and internal structure of the deposits in the two areas are quite different. Round Valley Septum The Hound Valley septum, 8 miles west of Bishop in the northwestern part of the Tungsten Hills, is a mass of metamorphic rocks about a mile long in an easterly direction and less than half a mile wide (pi. 1). It lies between granite on the north and quartz monzonite on the south and is one of a number of metamorphic septa along an intrusive contact that can be traced southeast across the Tungsten Hills, then south from Bishop along the range front for several miles. Most of the septum is composed of calcareous rocks that were derived from shaly limestone, including shaly marble, calc-hornfels, and garnet-diopside rock; but the western third is largely schist with a few interbeds of calc-hornfels and tactite, and the east end is chiefly quartzite and schist. The contact on the west side of the calcareous rocks with the schist is stratigraphie, but the contact on the east side with quartzite and schist is a north-trending fault. In the east end of the septum, a thin band of marble lies along the north edge of the chist and quartzite adjacent to granite, and extends for several hundred feet in a prong southeast between the quartz monzonite and granite. Although locally the beds are highly contorted, the main structural relations appear simple. Except for the extreme east end of the septum, where the structure is locally complicated, the beds generally strike northward across the long axis of the septum and dip to the west. Unless the beds are overturned, the schists in the west part of the septum lie stratigraphically above the calcar- eous rocks in the central part. Tungsten mineralization appears to have been confined to the northern contact of the septum with granite ; the southern contact with quartz monzonite has been repeat- edly prospected without finding any scheelite. Three mines in the septum have been operated, the Round Valley mine in the central part, the Western mine at the west end, and the Little Shot mine at the east end. Round Valley (Big Shot) Mine. The Round Valley mine is one of the oldest and next to the Little Sister mine the most productive deposit in the Tungsten Hills. Although most of the production was made in 1917 and 1918, since 1928 it has been operated intermittently by several companies and shows promise of substantial future production. To the end of 1945, 19,000 units of WOa was recovered. In 1918, the oidy year for which complete production figures are available, 9,500 units of WO3 was recovered from .'52,000 tons of ore mined, a yield of 0.:{ percent; but the tails contained close to 0.2 percent WO3 (Bateman, Erickson, and Proctor, 1950, p. 39). In 1948 and 1949, the Otis A. Kittle Mining and Exploration Co. developed and mined an ore shoot in the west end of the mine, but operations were sus- pended in 1949 when the price for tungsten fell below $20.00 per unit. Between 1951 and 1954, the mine has been leased by the Pinnacle Mining Co. from the owners, Al Stevens, Howard Stevens, and associates of Bishop ; and emphasis has been on exploration and development with little ore other than that from development work- ings being mined. The deposit, in the SE] sec. 34, T. 6 S., R. 31 E., is in the northwest part of the Tungsten Hills along the north side of the Round Valley septum. The accompany- ing maps and sections (pi. 8) cover the western part of the mine property, which contains most of the produc- tive ore bodies. Only a small amount of ore has been mined from the eastern part of the property, and no mine work has been done since Lemmon examined the mine in 1940. Persons interested in the eastern part of the prop- erty should consult Lemmon 's report (1941a, pp. 512- 513). Workings in the western part of the property include a main glory hole, several smaller glory holes and pits, two adit levels, a 78-foot inclined-shaft level, a level from the bottom of the inclined shaft, and an inclined winze from the west end of the shaft level (photo 6). A crosscut driven in 1948 provides the inclined-shaft level with a portal at the surface. The inclined winze at the west end of the inclined-shaft level has been deepened since the preparation of the accompanying maps and sec- tions; about 175 feet beneath the inclined-shaft level another level has been extended east about 80 feet, where a second winze has been sunk. In the mine area the septum is composed chiefly of impure marble, tactite, and calc-hornfels. Because much of the tactite and calc-hornfels are thinly interlayered with each other, they are included in a single unit on the maps and sections, except for layers of scheelite- bearing tactite, which are shown separately. The marble is in sharp contact with the tactite and calc-hornfels, which occur together in a zone bounded on one side by granite and on the other by marble. Within the silicate zone, tactite predominates near the granite and calc- hornfels near the marble, but they interfinger complexly and on both large and small scales. The zone of tactite and calc-hornfels is 150 feet wide at the west end of the area mapped, and it narrows east- ward to only a few feet at the east end. Some beds are replaced farther from the granite than others by tactite and calc-hornfels, and the contact between the marble and silicate rocks therefore is irregular. Although the contact between the silicated rock and marble commonly is sharp, euhedral garnet crystals locally are developed in some limestone beds beyond the limit of the silicate rock. Near the contact the beds generally strike north- ward and dip west, intersecting the contact at a wide angle. In general, the beds are steepest in the east part of the mapped area and to the west dip more gently. In the vicinity of the glory hole the granite contact dips to the south about 50°. Many fractures are evident near the granite contact, and in places the contact is sheared. Two steeply dipping faults south of the granite contact and striking parallel to it are the most persistent frac- tures in the mine area. Numerous other less continuous faults and fractures were mapped in the glory holes and in the underground workings. Economic Geology op Bishop Tungsten District 45 Much of the tactite and eale-hornfels in the main glory hole are coated with a yellow-green substance that has been identified as nonfronite (hydrous iron silicate). In the main glory hole and in the pits west of the glory hole the rock within 20 feet of the granite contact also is stained with iron oxides. These stains are derived from the weathering of pyrite contained in narrow quartz stringers locally present in the tactite and calc-hornfels. The quartz stringers contain no scheelite but do contain epidote and a black mineral that has been tentatively identified as a manganese oxide. Although the zone of tactite and calc-hornfels lies along the granite contact, the principal ore shoots are parallel with the bedding. Scheelite occurs all along the granite contact but is too irregularly distributed for profitable mining. In the bedded ore shoots the amount of scheelite is generally constant for distances of as much as 100 feet from the contact, then the amount diminishes rather abruptly. Several bedded ore shoots have been explored, the most extensive of winch, for convenience, have been given names on the accompanying maps and sections. The ore shoot that supplied most of the ore mined prior to 11)48 is the Glory hole shoot. It is about 20 feet thick and contains scheelite in exploitable amounts as much as 100 feet from the granite contact, measured along the strike of the mineralized bed. It is developed by means of the large glory hole, the inclined-shaft level, and numerous raises and small stopes between the glory hole and the inclined-shaft level. This ore shoot is essentially mined out above the inclined-shaft level except for pillars be- tween the glory hole and the inclined-shaft level. The ore shoot has been explored beneath the inclined-shaft level only by means of a short crosscut from the bottom of a shallow winze (about 20 feet deep) sunk from the shaft level. The ore left in pillars above the inclined- shaft level appears locally to contain as much as 1.0 percent of WO;!, but the scheelite is not evenly distrib- uted and the average is probably about 0.5 percent. The exposures on the inclined-shaft level and in the crosscut from the winze sunk from the shaft level appear to con- tain somewhat less scheelite, but inasmuch as the schee- lite distribution within ore shoots commonly is erratic, it would be unwise to conclude that the downward pro- jection of the ore shoot is too low grade for mining. On the contrary, the ore shoot merits thorough testing in depth. A mineralized zone east of the glory hole, called the East ore shoot on the maps and section has been explored by means of the adit east of the main glory hole, the east- ernmost glory hole in the mapped area, and the <>lory-hole level. It is mineralized across an average width of 30 to 40 feet, but appears under ultraviolet light to contain only 0.2 to 0.3 percent of W0 3 . The distribution of scheelite is irregular ; most of it is in narrow streaks localized in seams parallel to the bedding and along crosscutting fractures. About 65 feet west of the Glory hole ore shoot on the inclined-shaft level is the Middle ore shoot. This shoot has been mined above the inclined-shaft level from small stopes. Presumably this shoot also is the one that has been explored in depth in the winze sunk from the level that was driven east from the bottom of the winze from the inclined-shaft level. The shoot appears to average about 20 feet in thickness. On the inclined-shaft level it docs not appear to contain sufficient scheelite for prof- itable exploitation, but in the deep winze and in the level at the collar of the deep winze, it is estimated to contain at least 0.5 percent of WO ;) across the full width and along an exposed strike length of about 50 feet. The inclined winze at the west end of the inclined- shaft level is sunk in the Winze ore shoot, which, except for the Glory hole ore shoot, has been the most produc- tive in the deposit. In 1948 and 194!) the Otis A. Kittle Mining and Exploration Co. sank the winze to 150 feet with the bottom SO feet below the inclined-shaft level. About 6,000 tons of ore was mined from a stope north of the winze, between the winze and the granite contact. The ore mined contained about 0.7 percent of WO3. Subsequently, in 1951 and 1952, the Pinnacle Mining Co. deepened the winze probably about another 100 feet. Some ore was mined by enlarging the winze, but no regular stopes were made. In the vicinity of the stope mined by the Otis A. Kittle Mining and Exploration Co., the ore shoot terminates on the south against a steep east-trending fault, pvob- ably one of the two persistent faults mapped on the surface. On the north side of the fault the beds are bent around near the fault and locally strike X. 60 to 70° W. and dip 40 SW. The pattern of distortion in the rocks adjacent to the fault suggests that the south side of the fault is downthrown. Insufficient exploration has been carried on to determine the magnitude of the fault or to find the offset segment of the ore shoot, if one exists. By analogy with the same or similar faults ex- posed in the glory hole, the displacement on the fault is measurable in tens of feet and the fault is postmineral, and an offset segment of the ore shoot exists. Western Tungsten Mine. The Western Tungsten mine, in the SW] see. 34, T. (i S.. R. 31 E., is at the western end of the Round Valley pendant, 2,000 feet west of the Round Valley nunc. It is the property of J. P. Birchim and Bert Shively. In 1937 to 1938 it' was operated by the Pacific Tungsten Co.; in 1940. by the Western Tungsten Co.; and in 1943, by the Tungsten Reduction Co. The mill was dismantled in 1944. and for the following 10 years the nunc was idle. The mine workings include two opencuts, several prospect pits and trenches, a small glory hole used primarily for a transfer chute, and a haulage adit (pi. 9). The total production, judging from the amount of ore removed from the mine workings, has amounted to about 10,000 tons of ore, which is reliably reported to have contained 0.4 to ().■") percent WO3. In the vicinity of the deposit the pendant is composed of several nearly vertical, elongate bodies of tactite in- terstratified with schist and hornfels. It is not clear whether the tactite bodies are parts of a single, isocli- nally folded and cross-faulted bed, or whether several beds are represented. The curved ends of some of the bodies surest that they are terminated by northwest-striking, premineral faults. The contact between the metamorphic rocks and .-.. None of the ore shoots is identi- fiable on the adit level; the only ore exposed in the adit is about 50 feet from the portal where scheelite is in the tactite adjacent to an apophysis of quartz diorite. Tungsten Bliu (Shamrock) Mine. The Tungsten Blue mine lias been the most productive deposit developed since World War I in the Tungsten Hills. The mine, in ■is Special Report 47 the NW! Sec. 12, T. 7 S., R. 31 E., is about 3,700 feet \. 10° E. from the Little Sister mine and about 1,400 feet north of the -Jackrabbit mine. The total production to the end of 1945 was 38,400 tons, from which 10,460 units of W();i was recovered, a yield of 0.27 percent. In 1!)40 and 1941, the Bishop Tungsten Co. mined about 35,000 t«ms, and in 1943 and 1944 the El Diablo Mining Co. produced the small additional tonnage (Bateman, Erickson, and Proctor, 1950, p. 36). The deposit also was worked by Don Buergner in 1951 when ore was shipped to the U. S. Vanadium Co. mill in Pine Creek, but the production records for this are not available. Except for a small tonnage of ore that might be mined in the walls of the glory hole, commercial ore appears to be exhausted. In 1950 the workings consisted of a glory hole, under- ground stopes, a 300-foot haulage adit with a connecting raise to a grizzly level and the glory hole, and an upper adit that lies mainly in the northeast wall of the glory hob'. In the operations in 1951 the glory hole was en- larged into a pit with the consequent destruction of the underground stopes, the grizzly level, and part of the upper adit (photos 7 and 8). The accompanying maps and sections show the deposit as it was before the en- largement of the glory hole in 1951 (pi. 4). The ore body comprises the whole of a tactite inclu- sion in hornblende gabbro. The tactite is made up chiefly of epidote and quartz with minor amounts of garnet, fibrous pale blue-green amphibole, opal, magnetite and hematite, sphene, and scheelite. Examination of the tactite under ultraviolet light shows that scheelite is disseminated throughout the tactite, but that it is more abundant along fractures. Adjacent to the tactite, the hornblende gabbro commonly is epidotized; the epidoti- zation extends farthest along fractures. Generally the contact between epidotized gabbro and tactite is grada- tional, and the precise position of the contact is difficult or even impossible to determine, but locally it is sharp. Some of the tactite along such contacts may well have been formed from gabbro rather than from a calcareous sediment. The extent of the deposit seems to be established within close limits. The south, the west, and part of the north sides are vertical where they are exposed in the glory hole ; but exposures in the grizzly level and in the upper adit, both of which have been removed in mining, indicate that hornblende gabbro dips from the northeast under the deposit at about 40°. Exposures in the upper wall on the south side of the glory hole also indicate that before mining the deposit was partly capped by epidotized gabbro, and this is substantiated by the observations of the original locator of the deposit, Mr. Nick Pappas, and others. Tungsten Peak Prospect. The Tungsten Peak pros- pect, owned by Nick Pappas, is about half a mile north of the Tungsten Blue mine, in the SW] Sec. 1, T. 7 S., K. 31 E. The prospect is in a small detached block of tactite entirely surrounded by quartz monzonite, and is adjacent to a moderately extensive block of metamorphic rock that also is enclosed in quartz monzonite and granite. On the northwest side it is separated only a few feel from the larger mass of metamorphic rock. The tactite exposed in the outcrop and in a shallow shaft, the only working, does not contain sufficient scheelite to be of commercial grade. Aeroplane (Mesa Tungsten) Mine. The Aeroplane mine, in the NW| Sec. 13, T. 7 S., R. 31 E., is about half a mile southeast of the Little Sister mine on the ridge between Deep Canyon and McGee Creek. It is reached from the south by an access road that branches north from the road to the Buttermilk Country. Most of the production was made during World War I, when it was operated by the Standard Tungsten Co. In 1940, it was operated as the Moonlight mine, and in 1942, 1943, and 1944 as the Mesa Tungsten mine. Between 1951 and 1953, a high-grade pod of ore in the old workings was profitably mined by Lee Early and J. E. Morhardt. The production to the end of 1945 amounted to 51,000 tons from which 16,000 units of W0 3 was recovered. The average grade of all the ore mined was probably between 0.4 and 0.5 percent W0 3 . In 1918, the Standard Tungsten Co. produced 12,544 units of W0 3 from 44,000 tons of ore, a yield of 0.285 percent WO ;t . In April, 1944, the yield was not more than 0.2 percent, for only 4 to 5 units was recovered from 25 tons of ore mined daily. The recovery, however, was only about 50 percent, for a composite sample of the tailings contained 0.21 percent W0 3 (Bateman, Erickson, and Proctor, 1950, p. 35). The workings consist of a glory hole 150 feet long, 30 feet wide, and at least 100 feet deep ; a haulage level driven 415 feet southeast beneath the glory hole and connected with it by means of a raise ; an opencut and an irregularly enlarged 40-foot inclined shaft on the east side of the glory hole ; a 260-foot adit several hundred feet north of the glory hole ; and a number of shorter adits and prospect pits. The mine is in a small crescent-shaped block of meta- morphic rock that lies between quartz diorite on the north and west and a stock of aplitic granite on the east (pi. 12). Quartz monzonite is in contact with the meta- morphic rocks at the two ends of the crescent. Dikes of all the intrusive rocks penetrate the metamorphic rocks. The metamorphic rocks include coarsely crystalline white marble, light-gray calc-hornfels, quartzite, and two varieties of tactite. One variety, consisting chiefly of reddish-brown garnet and bright-green epidote, eon- tains virtually all the scheelite. Part of this rock also contains abundant quartz in which coarse euhedral crys- tals of sphalerite occur locally. The other variety of tactite, which is more widespread, consists chiefly of pale-green idocrase and less-abundant pink garnet. In the vicinity of the glory hole, where the beds strike northward and dip nearly vertically, two ore bodies have been discovered, one on either side of a 20-foot- thick bed of calc-hornfels. The east ore body, which is opened by the glory hole, has yielded most of the ore. Very little scheelite can be seen in the rock that remains in and around the glory hole, and the downward exten- sion of the ore zone at the adit level contains only sparse scheelite. The general relationships of the rocks and of the Avorkings indicate that the ore body was tabular and probably only a few feet thick, oriented parallel with the bedding. Scheelite in lesser amounts probably was disseminated in the wall rocks. The ore body on the west side of the calc-hornfels, developed by means of an opencut and an irregularly enlarged inclined shaft, is about 10 feet thick and does Economic Geology of Bishop Tungsten District 49 II9°I5 38°00 37°30 37°00' II9°I5 II8°45' II8°I5 Figure 1. Map showing Hie location of the Bishop district. 50 Special Report 47 Area underlain chiefly by hornblende gabbro SURFACE MAP TUNGSTEN BLUE SHAMROCK MINE »- 17° Uj/i: o'Qr "T/O Anomaly caused by an east-trending aplite dike Magnetic data by Gordon Both and C H Sandberg 1954 Geology is shown at adit level. Traverses are on surface where rock is quartz monzon- ite and no tactite crops out. ADIT LEVEL WHITE CAPS MINE EXPLANATION Area underlain chiefly by hornblende gabbro SURFACE MAP JACKRABBIT MINE Soil cover and slope wash Quartz monzonite qd Quartz diorite 9b Hornblende gabbro egb Epidotized gabbro Magnetic profile Values gammas relotive to arbitrary datum. Line of traverse Also datum for magnetic profile. Figure 2. Magnetic profiles in the Deep Canyon area. Tungsten Hills. Economic Geology of Bishop Tungsten District f»] EXPLANATION Molybdenum ore shoots (Cut-oft 04% M0S2) Tungsten ore shoots (Cut-off 0.4% W0 3 ) Toctite with little or no scheelite m Quorlz monionite Note No assay dato from pit is available Outline of tungsten ore shoot is inferred Much of 'he loctite also contomed rich molybdenum ore, but the data ore not adequate to show the distribution of molybdenum Geology by Pool C Botei and Low 1954 Figure :i. Block diagram of the South ore body, Pine Creek mine, showing the tungsten and molybdenum ore shoots. 52 Special Report 47 EXPLANATION Talus on surface, and detritus in solution cavities Molybdenum ore (cut-off grade ■0.47oMoS 2 ) Tungsten ore (cut-off grade-0.4%W0 3 ) Tactite containing little or no scheelite L. Quartzose rocks ncludes quartzose tactite, silicified quartz monzonite, rock composed largely of quartz vein lets, and dikes and sills of quartz-feldspar rock Marble (silicated in part) Quartz monzonite (includes small masses of quartz diorite) Geology by Pout C Botemon ond Lawson A Wright (1954) FIGURE 4. Sectional diagram of the Main ore body, Pine Creek mine, showing the tungsten and molybdenum ore shoots. Economic Geolooy of Bishop Tungsten District 53 EXPLANATION Talus Tungsten ore shoots (Cut-off 0,4% W0 3 ) Toctlte containing little or no scheelite Quartzose rock (silcified quartz monzonite and siliceous tactile) Quartz monzonite f I **> \»„^ll- Quartz diorite Marble (silicated in part) Geology by Paul C. Botemon and Lowson A Wright (1954) Scale in feet Figure ">. Sectional diagram of the North ore body. Pine ('reek mine, showing the tungsten ore shoots. 54 Special Rkport 47 N 38 500 SURFACE MAP EXPLANATION — 1— .q m Quartz monzonite and granite Tactite EI t Tactite containing sc he elite nn Marble, partly si I icated Contact SECTION A-A" A' 11,900 11,800 -11,700 90 Fault, showing dip Pit outline Geology by L.A.Wright 1951 1_ 100 ' SCALE 200 FEET Figure <;. Geologic map uml section of the Loop ore body, Pine Creek mine, showing the tungsten ore shoots. Economic' Geology of Bishop Tungsten Distric COMPOSITE MAP OF MINE WORKINGS UPPER STOPE LOWER STOPE ADIT LEVEL UPPER TRAM TERMINAL Dump SKETCH OF CLIFF FACE LONGITUDINAL SECTION A - A* .)., EXPLANATION Tactile W/a Marble •' Jop 1 \'\ and pegmat \ qm, Quartz monzomte Contact, showing dip Doshed where approxim- ately located or restored. Foot of raise or winze Head of" raise or winze Boundary of mine workings Doshed where projected or restored Note. Mopped by brunton ond tope method Dimensions and orientation of illustration are approximate Mopped by Paul C Botemon, September 1947, and D. C. Ross ond C D Rmehart, September 1953 Figure 7. Geologic map of the Rrown stone mine. ;>i; Special Report 47 EXPLANATION 45 Scheelite-bearing tactite Tactite and light colored calc silicate rock s • Pyrite-bearing rock Marble -_--hf- Contact, showing dip Dashed where approximately located. -til — Fault, showing dip Dashed where approximately located. *~90 Vertical fault o Foot of raise Dark colored hornfels % + qm + + + Quartz monzonite CD Top of winze □ Ore chute Paul Bateman, July 1948 Logging along adit 50 100 ZlEEE 150 SCALE 200 FEET Figure 8. Geologic map of the upper adit in the Hanging Valley mine. Economic Geology of Bishop Tungsten District 57 \ + qm(migmatized) -f + SHAFT LEVEL Powder house ■ -Raise 3~shaft level EXPLANATION tal Tolus and glacial till tactite containing scheelite (epidote toctite) Tactite containing littte or no scheelite (garnet toctite) am + + Quartz monzonite \ amph : Amphibolite ^m Marble (includes minor amounts of lime-silicate rock :hf-_-_ Hornfels Contact. Dashed where approximately located. Strike and dip of beds SURFACE MAP VERTICAL PROJECTION OF ORE SHOOT Plane of projection is N25°W Mapped by P. C. Bateman and E M. MacKevett July 1951 90 Strike of vertical beds czz Opencut or trench E Roise or shaft at surface EO Bottom of shaft i£_ 100 150 Feet ® Foot of raise Figure it. Geologic maps and section of the Lakeview mine. 58 Special Report 47 < _i o. X K 10 -V % \- ' Z3 o H IBi * >- (J 9) El o> WW + _5 c o u o + c WW 5 + o \\\\^ + o o <= o O ■o -o a> o> "5 o" « t) fl, 10 ■o S°o a> a o dip. ately cone o § o. Cl a. E > ' -o ,"° c - <» » -D $ o „> c O sz a. $ 0) I (/) o jr T3 <-" * W w _ 1 *- H <= O — v» = Q. O G c o *• H4jon anji Economic Geology of Bishop Tungsten District 59 EXPLANATION Soil cover ond slope wash Toctite Quartz-sulfide rock ond gossan Toctite, quortz-sulfide rock, and gossan contoining scheelite Hornblende gabbro hf Hornfels Contoct, showing dip Doshed where inferred Fault, showing dip Dashed where approximately located Strike and dip of beds Rim of prospect pit, bulldozer trench, or glory hole Bottom of glory hole H Shaft at surfoce H Inclined workings Chevrons point down Bottom of shoft Mopped by, DM Lemmon ond Paul C. Batemon August 1943 Slope wash C MAP ADIT IN EAST SIDE OF GLORY HOLE 68' LEVEL SECTION A-A' Contour interval 5 feet Datum is approximately sea level Figure 11. Geologic maps and section <>f the Scliober mine. (SO Special Report 47 "'"^_ GEOLOGIC MAP 2"wide fissure ( narrow brown, soft ore beds cut off by fissure) I v2 wide zone (obove waist level) of soft brown ore along contact, zone narrows to 8' to south (probably related to 5' zone on south face) 2" pegmatite vein, scottered scheelite in vein EXPLANATION ol Slope wash iron-stamed gossantike matenol Tactite, with little or no scheelite 5 horizontal zone, approximately l' high lamps from contoct to face (soft, brown ore) Toctite with scheelite Cole -hornfels All soft, brown ore, somewhat poorer in foce UNDERGROUND WORKINGS L'CgVd /\H Gronodionte ICC J Dior i te 80 120 Feet Contact, showing dip Dashed where approximately located. Fault, showing dip Strike and dip of beds £? Opencut /!#;■ Dump Projeclion of underground workings Mapped by DC Ross ond CD Rinehort July 1954 Contour interval 10 feet Dotum approximate meon seo level FIGURE 12. Geologic maps of the Lindner prospect (Oomph claims), Economic Geology of Bishop Ti ngsten District 61 50 EXPLANATION Glacial till and soil cover Tactite containing little or no scheelite Tactite with scheelite Hornfels + + + + qm + + + + Quartz monzonite Contact dashed where approximately located. Strike and dip of beds "90 Strike of vertical beds Rim of pit or open cut s Shaft - Dump 100 I5C Scale in feet Contour interval 5 fee' Datum is opproximotely sea level Mapped by; Paul C. Bateman and Max P Enkson August 1943 4 Figure 13. Geologic map of the Coyote Lake pfospecl i Black Monster claim). 62 Spfxial Report 47 0) -•— c o _ lO c o E > : r \° : x,^§^ d> 1^7 * ^7 //#\^- CD tt) 0) u. c> in O O Ql .O o 1\\1' o £/ r o 0) * X A o Ml § o o *\ 1*1 ° o- ° o \ / Z < 3C1H1 OE X sJ SJ JS Oj S P gW » <* X> rH o- ►3 o C o fa 0) o 3f1«l Economic Geology of Bishop Tungsten District 63 + 1= S n .1* 1I» T? F i r ; t ! t 64 Special Report 47 UPPER ADIT LEVEL ^•Xj^Ore shoot SHAFT LEVEL Elevation at collar of shaft 5640' ± COMPOSITE MAP EXPLANATION /// / / Iron-stained calc-silicate rock and tactite A Marble \f\/ i,/ Granite X \ \ \ X N >::e J \ \v\y"\ '07 / / ' t / / / / Contact, approximately located ~ T 70 Strike and dip of beds B Shaft at surface Kl Shaft going obove and below levels 12 Bottom of shaft SECTION A-A' Mapped by P. C. Bateman, 1944, and E. M. MacKevetf and B. Sheehan, March 1952 40 I i i i L 40 80 Feet Figure 17. Underground geology in the upper workings of the Tunssten Hill (Little Shot) mine. Economic Geology of Bishop Tungsten District 65 ADIT LEVEL EXPLANATION Soil cover and slope wash Quartz dionte Hornblende gabbro, and epidotized gabbro Tactite with scheelite Contact (Dashed where not accurately locoted) Mine workings projected on surface mop Kl Foot of raise M P Enckson November 1943 Strike and dip of beds n Rim of glory hole or trench Dump in plan SURFACE MAP Contour interval 10 feet Datum approximate mean sea lew Figure 18. Geologic maps of the Jackrabbit mine. 66 Special Report 47 o Economic Geology of Bishop Tungsten District 67 m§jpf + SURFACE 65-FOOT LEVEL PROFILE THROUGH SHAFT 90-FOOT LEVEL Mopped by Pool C Botemon ond Dollos Peck, July 1947 and August 1952 XPL«N ATION Soil cover and slope wash Quartz Toctite containing little or no scheeiite Toctite containing scheeiite v& Hornfels ond schist mm Granite Contact, showing dip Doshedwhereinterred. Fault, showing dip dashed where approx- imately locoted Fault breccio Strike and dip of beds 50 150 =1 — 200 feet i Sloped obo ve lev el Shaft going below obove level and SI Bottom of shaft H Foot of ro ise Heod of w inze □ Ore chu te Contour interval 10 feet Datum mean sea level Figure 20. Geologic maps of the Rossi mine. 68 Special Report 47 UPPER ADIT EX PL AN ATION _f!L_ Altered rock (ore) To c t i t e M l Calc-hornfels vo Contact, showing dip Dashed where approximately located Strike and dip of beds Foot of roise or winze Head of raise or winze Project outline of upper adit and connecting raise Geology by PC. Bateman, October 1948 LOWER ADIT 50 I , i i i L_ 100 150 Feet + Figure 21. Geologic maps of the adit levels in the Yaney mine before glory hole was made. Economic Geology op Bishop Tungsten Distkkt (in + T) 3 / S o / j= o * v £ S - \\\ o X 'o a ?; 3 1 \V ^ I = ,§ O O 3 o O a. O- O o o o 70 Special Report 47 a o fs a « s Economic Geology of Bishop Tungsten District 71 Approximate trace of intersection of vein with foult zone Portal of ad E'ev 5480' EXPLANATION Foult, showing dip Dashed where approximately located. Vertical foult Strike and dip of beds Strike and dip of joints Shown on section. Explored extent of vein Workings in plane of vein. Development workings Inclined workings Chevrons point down at 4 foot intervals. Foot of raise or winze Head of roise or winze Stope Mopped by E M MocKevett, August 1951 COMPOSITE MAP OF WORKINGS Ootum oppronmoie sea level SECTION A-A Figure 24. Map and section showing the underground geology of the Poleta gold mine. 72 Special Report 47 EXPLANATION Alluvial-fon deposits t- ^. Basalt Diorite dikes Porphyry dikes Quartz monzonite Contact (Dashed where approximately located) U "dT so Fault, showing dip (Dashed where approximately located. U, upthrown side; D, downthrown side.) Gold-quartz vein Strike and dip of quartz vein or stringer it 5 Mopped by Paul C. Bateman, 1950 SCALE IN FEET Datum mean seo level Contour interval 40 feet Figure 25. Geologic map of Fish Springs hill. Economic Geology of Bishop Tungsten District 7:: 64' to surfoce Mapped by Paul Dean Proctor, March 1946 EXPLANATION Quartz veir .locally containing itlbniu Unbroken Breccio =--^_ Gouge, showing strike of minor pervasive slip planes Quortzite, schist ond hornfels Prominent slip planes showing dip GEOLOGIC MAP OF THE ADIT LEVEL IN THE BISHOP ANTIMONY MINE 50 100 150 200 Feet Vtrticol slip plane IX Shaft going above and below level SI Bottom of shaft Foot of raise Figure 26. Geologic map of the adit level in the Bishop antimony mine. EXPLANATION Alluviol-fon deposit Light-gray pumiceous rhyolite (perlite) m Gray vitophyre andobsidion thinly interlayered 1000 2000 3000 SCALE IN FEET Dotum meon seo level Contour interval 40 feet Figure 27. Geologic map of the rhyolite hill south of Big Pine. Gray vitrophyre Strike and dip of flow banding Horizontal flow banding Vertical foliation Geology by Poul C Botemon(l95l) 74 Special Report 47 not appear to be more than 40 to 50 feet long, although poor exposures permit direct observation of only a few feet along the strike. The ore body is cut off downward by quartz diorite before reaching the haulage level. The ore remaining appears under ultraviolet light to contain only a few tenths of one percent of WO3. A third small mineralized zone several hundred feet farther north has been worked in a stope above the North adit. This zone, like the ore bodies in the glory hole and inclined shaft, is tabular parallel to the bed- ding and is adjacent to calc-hornfels, but here the beds strike X. 60° E. and dip 45° KE. The ore zone crops out about 80 feet above the adit level, at the head of a raise from the stope, but it cannot be traced on the surface along the strike. In the walls of the stope the ore zone is about 4 feet thick and has been mined along the strike for abont 40 feet. Downward it is cut off by quartz diorite and only a small root reaches to the adit level. The scheelite content of the rock exposed in the walls of the stope is greater than that in the exposure in the adit, but in both places it appears too low for profitable mining. Occurrences of scheelite have been found in several of the shorter adits and prospect pits on the property, but no ore bodies have been developed. Lookout Prospect (Tiptop Claims). An extensive mass of tactile caps the hill 1,500 feet N. 25° E. from the Aeroplane mine along the boundary between sec. 12, T. 7 S., R. 31 E., and sec. 7, T. 7 S., R. 32 E. The trace of the lower contact of the tactite with qnartz monzonite on the surface suggests that it is horizontal. At the Lookout prospect several prospect pits and short adits have been dug into the tactite adjacent to the qnartz monzonite contact, but no ore bodies have been found. Near the contact the tactite contains scheelite in amounts that, according to Lemmon (1941a. p. 509), might aver- age 0.1 percent WO3. White Caps Mine. The White Caps mine, in the SE^ sec. 13, T. 7 S., R 31 E., is on the west side of McGee Creek, about 2,000 feet southeast of the Aero- plane mine. It is accessible from the road to the Butter- milk Country by means of a short branch road to the north. The deposit was discovered in 1940 by E. C. Castle and "Cap" Aubrey of Bishop, who still owned the property in 1953. The mine development consists essentially of a stope 100 feet long, 25 feet high, and from 5 to 20 feet wide. This stope was made between an adit level and a shaft level whose floor was only 16 feet beneath that of the adit level (see fig. 19). Approxi- mately 2,500 tons of ore mined from the stope in 1943 and 1944 by Aaron J. Smith, then operator of the Red Hill mill, is reliably reported to have contained 0.45 percent of W0 3 (Bateman, Erickson, and Proctor, 1950. P- 37). The original location was made on a small nearly barren outcrop of tactite entirely surrounded by quartz monzonite in the west bank of McGee Creek. Exploration on the adit level demonstrated that this unpromising showing is one end of a more extensive mass of tactite concealed beneath quartz monzonite and that a tungsten <>ic shoot existed within the tactite. The tactite has an average width of at least 20 feet and extends beneath quartz monzonite in a westerlv direction from the out- crop more than 100 feet. Several raises in the hack of the stope that pass upward within a few feet into qnartz monzonite define the upward limit of the tactite mass; but the bottom of the tactite mass was not reached in the floor of the stope. The floor of the stope is close to the water table, below which mining costs would have been increased substantially; consequently, the ground beneath the stope has not been explored. Bedding faintly visible in the tactite is vertical and strikes parallel to the stope and to the longer horizontal axis of the tactite mass. The tactite seems likely to continue vertically downward with the bedding for some distance beneath the stope. A single ore shoot, 80 feet long and averaging 10 feet in width, has been developed. Thirty feet from the mine portal the shoot is 20 feet thick and nnder nltraviolet light appears to contain about 1 percent of W0 3 . In the west part of the shoot the thickness and grade decrease, and the tactite in the face of the stope contains almost no scheelite. By analogy with other deposits that lie beneath a capping of igneous rock, the scheelite content probably diminishes in depth. Any future production probably will come from the downward extension of the ore shoot, but lack of any exploration beneath the stope makes it impossible to pre- dict the depth to which the ore will extend. Drifting from the barren west end of the tactite conceivably could result in the finding of a second ore shoot deeper in the hill. Hilltop Prospect. The Hilltop prospect, in the "WJ sec. 8, T. 7 S., R. 32 E., is on the northeast side of a ridge on the east side of the Tungsten Hills; it is almost isolated from the main mass of the hills. The deposit consists of two tactite inclusions in hornblende to 1(> feet wide. The longer dimension trends N. 80° \V., parallel to the strike of the bedding. Both bedding and walls are vertical. The tactite has been explored to a depth of 20 feet in an opencut. Scheelite is distributed irregularly through the tactite. The average content of WO3 is probably less than 0.5 percent, although locally bunches of ore are higher in and again in 1953 and 1954, and by George Kerr in 1950 and 1951. Between 1942 and early 1945 about 4,000 units was recovered in a small gravity 7S Special Report 41 mill that was just outside the mine portal, and in the last half of 1045 and in 1946 an additional 500 units was recovered. The ore mined since 1949 has been shipped to the 1 T . S. Vanadium Co. Tine Creek mill where 2,220 units of \VO : . was recovered in 1950 and 1951 and 1,190 units in 1953 and 1954.* Taetite is limited, at least in outcrop, to the south contact of a mass of coarsely crystalline white marble that is bounded by granite and quartz monzonite (pi. 14). Interbeds of calc-hornt'els occur within the marble. Ill outcrop the marble mass is more than 500 feet long in an easterly direction and has a maximum width of about 350 feet. It is intruded by dikes and irregular masses of quartz monzonite and by a pegmatite dike. The general structure may be an open syncline that plunges steeply to the north, but the details are complex. In the eastern part the beds generally strike about N. 65° E. and dip 75° to 80° NW., and in the western part they appear to strike generally northwestward with steep dips, but with many irregularities. The marble is cut into several sep- arate blocks by quartz monzonite. Different lithology and discordant attitudes in the bedding of the different blocks indicate dislocation and rotation. Two nearly parallel faults about 40 feet apart strike N. 10° W. across the marble. The more easterly fault is vertical, whereas the more westerly one dips steeply west. Measurement of offset segments of a flat pegmatite dike and of an interbed of eale-hornfels indicates that the block between the faults is a horst. The east side of the east fault is downthrown about 40 feet, and the west side of the west fault appears to be downthrown about 50 feet. Two masses of taetite 160 feet apart crop out along the south contact of the marble. Both masses appear to dip steeply north under the marble. The contact of the marble with quartz monzonite between the two taetite masses is concealed by alluvium, but because taetite is resistant to eroson and usually crops out prominently, it seems likely that little taetite exists along the concealed segment. Most other exposed contacts between marble and quartz monzonite are occupied only by a thin sel- vage of wollastonite. Typical taetite consists chiefly of red-brown garnet, but with lesser amounts of amphibole, quartz, calcite, and magnetite. Epidote is present in large, sporadically distributed crystals. Scheelite is rather evenly dissemi- nated through the taetite in tiny pinpoint sized grains, but appears to be somewhat more abundant in parts nearer the marble. The ore milled contained about 0.45 percent of WOs on the average, but because the scheelite is in such fine grains only about 60 percent was recovered. The east outcrop of taetite has been mined above the adit level in a glory hole. This body of ore is cut off just above adit level by a dike of quartz monzonite that enters the nietamorphic rocks flatly, but which sends offshoots downward along the beds. Crescent-shaped taetite bodies underlie the quartz monzonite dike — the ends extend downward along either the main quartz monzonite contact or along contacts with the sill-like off- shoots from tin' dike. Along the main contact, taetite continues downward to the shaft level but thins in depth. * Published with permission of the owners. The odd shapes of the bodies arc shown in the sectioi (pl. 14). Both the adit and the shaft level are driven along tl contact into tin 1 zone beneath the west taetite outcro The adit level lies beneath the flat dike except at tl west end, where it follows a barren contact bet wee marble and quartz monzonite. On the adit level gocj ore is found down the dip from the west taetite outcro Further exploration of the south contact appears dJ sirable, but the absence of ore on most other contac ' does not favor their exploration. A water tabic a fe feet below the shaft level is a deterrent to deeper e ploration or development, but additional lateral explor tion of the south contact of the marble by extending tlj levels toward the west could result in the discovery additional minable ore. The pendant must end a sho distance east of the shaft, and exploration in that dire tion would be difficult because the deepest workings a at about the same elevation as the canyon bottom. Buckshot Prospect. The Buckshot prospect is at tl! eastern base of the Sierra Nevada, half a mile north the mouth of Shannon Canyon. The prospect, in a lc knob that projects through the slope wash, is in the S^j sec. 20, T. 8 S., R. 33 E., at an altitude of about 4,7( feet. It is reached from an abandoned segment of U. Highways 6 and 395 that joins the maintained highws at Keough Hot Springs. About 1] miles south of th 1 junction a dirt road extends west 1} miles up the slo] of the fan of Shannon Canyon to the deposit. The knob, which consists chiefly of coarsely crystallh white marble in steeply dipping beds, is at the nor end of a mass of dark-colored diorite that extends t ward the southwest along the north side of Shamu Canyon. Taetite is developed along the north conta of the marble with the diorite. The taetite consists chief of epidote, amphibole, calcite, and quartz, with less amounts of chlorite, pyroxene, garnet, magnetite, spher apatite, rare pyrite, and sparse, sporadically distribute scheelite. The diorite adjacent to the taetite is high' epidotized, and locally the contact between taetite ai diorite is occupied by epidote-bearing quartz that co tains sporadic crystals of scheelite. The taetite has been prospected by means of a sms opencut and several small prospect pits, all many yea old. According to Knopf, who examined the deposit June 1916 (Knopf, 1917, p. 249), extremely rich ore w| then exposed in places; presumably it was mined out about that time; none of the remaining taetite conta! scheelite in minable amounts. Prospects in the Middle Pork of Shannon Canym Several prospects along the Middle Pork of Shan™ Canyon are reached by a continuation of the access ro; to the Marble Tungsten mine. The lowest deposit is abo three-quarters of a mile west of the Marble Tungsl mine, and the highest is about a mile west. The lowest prospect, in the SE' t sec. 31, T. 8 X., R. E., at an altitude of 7,000 feet, is on the north side the canyon. The prospect is in taetite that constitut the western end of a lenslike inclusion in granite. Mc of the inclusion is made up of siliceous hornfels. Ti outcrop of the taetite is about 80 feet in length, and varies irregularly in width. The taetite consists chiei of garnet, epidote, calcite, and quartz with subordina magnetite, chlorite, pyroxene, epidote, and seheelii Economic GliOLOGY OP BlSIIOP TUNGSTEN DISTRICT 7!) Associated with the tactile is light-colored silicate rock that appears to consist chiefly of pale garnet and wollas- tonite. The outcrop has been prospected by means of small opencuts, and in 1952 an adit was being driven in jjgranite to intersect the taetite at depth. Farther west in the canyon and 500 feet higher, in the SEj sec. 36, T. 8 S., R. 32 E., and the XWJ sec. 6, J I|T. 9 S., R. 33 E., other bodies of garnet-rich taetite are bund. These taetite bodies, locally with associated calc- jhornfels, are either in or along the margins of an irregu- larly shaped mass of diorite. Although there is no record f! of any production, a few tons of ore appear to have been "trucked from a taetite body exposed in the door of the tycanyon. Scattered Prospects in the Sierra Nevada Rattlesnake Prospect. The Rattlesnake prospect is on 'the lower northeast slope of Mt. Tom, in the SW] sec. 31, T. 6 S., R. 31 E., at an altitude of about 6,000 feet. In 1051 the prospect was held by Lee Early of Bishop i and associates. The rocks in the vicinity of the prospect include a wide variety of metasedimentary rocks, with \ marble and calc-hornfels predominant. These rocks crop I out over a rectangular area of about a quarter of a square mile. On the west and south they are bounded by piartz monzonite, and on the northeast, along the range Front, by alluvial-fan deposits. Dikes of quartz monzonite ind aplite penetrate the metasedimentary rocks and small bodies of diorite are found locally along the quartz nonzonite contact. In general, the metasedimentary rocks strike northward and dip 50° to 75° W., but locally :hey are highly contorted. The prospect is on the south side of a sharp draw that •nts across the metasedimentary rocks. Prospecting since he end of "World War II lias been by means of bull- lozer; but an adit, caved at the portal, has been driven nto one mass of taetite. Bulldozer trenches, which total ibout 600 feet in length, expose several taetite bodies. The largest, a body about 6 feet thick and traceable for ibout 50 feet, lies adjacent to a dike of (piartz mon- lonitc. It is cut off on the southeast end by a fault that trikes X. 50° to 70° W. and dips to the south. The other Mid of the taetite is overlapped by slope wash. Smaller actite bodies, generally less than 2 feet thick and lot traceable more than 30 feet, lie along bedding planes (vithin the marble. Scheelite is sparsely disseminated hrough the taetite. McYati Claim. The McVan claim, examined by vnopf in 1916 (1917, p. 248), has not been worked for [ great many years and was inspected only very briefly luring the present investigation. The claim is on the onth side of Rawson Creek about 1:', ! miles from the anyon month. It is in the SE] see. 2, T. 8 S., R. 32 E., t an altitude of about 6,000 feet. Small masses of diorite re found scattered through the granite country rock in lie vicinity of the claim. According to Knopf, small in- lusions of metamorphosed limestone, most of which are lot more than a few cubic yards in volume, are found in he heart of the diorite masses. Taetite. consisting of arnet and epidote with a little quartz and scheelite, is evelopod locally in the limestone. Bakoch !'ros/>< <-t . The Bakoch prospeel is in a knob hat projects through the moraines between Big Pine and Baker creeks. It is in the SW| sec. 26, T. <) S., R. 33 E., at an altitude of about 5,400 feet. It is accessible by means of a dirt road that branches west from the paved road along Big Pine Creek about 5 miles south- west of Big Pine. The property, which consists of five claims, was Id- eated in 1940 or 1!M1 by Nick Bakoch and John Som- merville of Big Pine. In 1941, it was leased to Tom Vignich and Ralph Hunger of Big Pine, who subleased it in 1943 and 1!)44 to the now defunct Twin Pines Tungsten Co. In 1044, a few hundred tons of ore was mined and treated in a mill that was constructed in Big Pine, but the operation proved unprofitable. The prop* erty was idle from 1944 to 11(53. The mine workings consist of a 120-foot adit, a 95-foot raise to the surface from near the face of the adit, and a U'\v prospect pits. Taetite with sparse sporadically distributed scheelite is developed along a contact between marble on the north and (piartz monzonite on the south, which, in general, strikes N. 70° W. and dips steeply north. The taetite ranges from 5 to 40 feet in thickness and crops out in- termittently along the strike for about 500 feet (fi<^. 22). The marble beds strike north to northwestward and dip 50° to 60° E., intersecting the taetite at a moderately large angle. The south side of the taetite near the east end is in fault contact with micaceous quartzite, which separates it from the (piartz monzonite. Farther west, marble and micaceous quartzite lie between the taetite and (piartz monzonite; but at the west end of the series of outcrops the most extensive mass of micaceous quartz- ite lies north of the taetite, and the taetite is in direct contact with (piartz monzonite. In the outcrop of the taetite, scheelite is present in commercial amounts only in two small areas, and in the underground workings only a few widely scattered grains of scheelite could be found with an ultraviolet light. One scheelite-bearing area in the outcrop, just west of the adit portal, is about 2.") feet long, 4 feet wide, and is estimated to contain about 0.5 percent of \VO : , ; the other, 150 feet west of the adit portal in a shallow pit about 5 feet square, appears to contain 1.0 to '_'.() percent of WO3. Inasmuch as neither of the zones con- tinues downward to the adit, the amount of ore in each appears to be small. Prospects South of Taboose Creek. At the base of the Sierra Nevada in sections 11 and 12, T. 11 S„ R. 33 E., and extending south of the mapped area into sections 13 and 14, are several tungsten prospects. The prospects are in low, rounded hills in which marble, calc-hornfels, taetite, and (piartz monzonite project through the slope wash. The taetite masses appear to be extensive, but most of them contain no scheelite. The outcrops thai contain scheelite are not sufficiently high grade for profitable mining and have been explored only by means of small opencuts and prospect pits. Tungsten in the White Mountains Scheelite-bearing (piartz veins and taetite deposits have been found at several places in the White Moun- tains, but most of the deposits found have been disap- point in":, either because of small size or low grade Within the mapped area scheelite has been reported only in the vicinity of the .Mohawk shaft (a working that was sunk for gold), but just east of the mapped 80 Special Report 47 area in the Redding Canyon drainage a taetite deposit was worked in 1952. Both localities are adjacent to masses of intrusive quartz monzonite. Mohawk Shaft Ana. The rock in the dump at the collar of the Mohawk shaft, near the south boundary of sec. 24, T. 5 S., R. 34 E., contains scheelite in sparse amounts. Traces of scheelite are also found in streaks a few inches long in the hornfels southeast of the shaft for a distance of some hundreds of feet. If the gold vein penetrated by the Mohawk shaft were to be worked for "old, the possibility of recovering scheelite as a by- product should be investigated. R. and R. Claims. A tungsten deposit on the R. and R. claims, in the White Mountains on the south side of Redding Canyon, is about a quarter of a mile east of the mapped area"; but because the deposit is comparatively close to Bishop a brief description is included. The de- posit is on the south boundary of the RE] sec. f), T. 7 8., R, 34 E., at an altitude of 6,800 feet. Two claims, located in 1951 by Reese and Robbins, were leased in late 1951 by Don Biiergner and Ralph Adams. After constructing the access road to the deposit from the road in the bottom of Redding Canyon, work on the deposit was started in January 1952. During 1952 several thousand tons of ore was mined and trucked to the Pine Creek mill of the U. S. Vanadium Co. for treatment, but in 1953 the deposit was idle. Mining was in an opencut with the use of a power shovel. The area was prospected in the late 1800's for gold, and probably also for copper, and several of the old prospect adits are near the tungsten deposit. Taetite is developed locally, adjacent to a stock of porphyritic quartz monzonite, in gently dipping limestone with in- terbeddcd shale of the Silver Peak group. Little or no taetite has been developed along contiguous parts of the same contact. The taetite fingers out into the marble, but some tongues extend as much as a hundred feet or more from the quartz monzonite. The taetite consists chiefly of rock made up largely of garnet, and of rock that consists of calcite, epidote, garnet, and pyroxene. Fine yellowish-fluorescent grains of scheelite are dis- seminated through these rocks. Pyrrhotite-quartz rock, locally with chalcopyrite, is present in some parts of the mass but contains no scheelite. Pink zoisite (thulite) also is common in parts of the deposit. Metalliferous Vein Deposits Because the main emphasis of the study of the Bishop district has been on the tungsten deposits, most of the Other metalliferous deposits were examined only in a perfunctory manner. Except for one antimony deposit (the Bishop Antimony mine) and one cobalt occurrence (the Bishop Silver-Cobalt prospect), all of the metal- liferous vein deposits in the district were worked for gold and silver. A thorough study of the gold mines would have consumed a large amount of time, probably without producing commensurate results, because none of them has been operated since World War II and during the period of field work many were caved or otherwise inaccessible. Descriptions of both the Bishop Antimony mine and the Bishop Silver-Cobalt prospect, as well as of several of the more productive gold mines, arc included in the following pages, although much of the data is based on reports by others rather than < the observations of the writer. Incomplete data in the files of the IT. S. Bureau Mines record a yield from gold mines in the district quartz veins of 70,548 ounces of gold, about 16,0( ounces of silver, 274,569 pounds of copper, and 3,41 pounds of lead. Evaluation of the records suggests th the actual production of gold may be in the order <| 100,000 ounces, with proportionately larger amounts f cross faults that strike N. 70° to 80° E. and dip 55° 5. The northwest segment of the vein is displaced on hese faults 150 feet to the northeast relative to the southeast segment. The southeast segment of the ore aody dips 65° NE., whereas the northwest segment is ertical. According to Tucker and Sampson (1938, p. 389) four principal ore shoots were mined, which ranged n length from 20 to 300 feet, and in width from 6 to 16 feet. Poleta Mine. The Poleta mine, which is owned by C. H. Olds and A. F. Beauregard of Bishop, is in the Y\ nite Mountains, in the NWi sec. 8, T. 7 S., R, 34 E., at in altitude of 5,800 feet. The road along Poleta Canyon leads to the mine. The mine is one of the oldest in the Bishop district. According to Chalfant (1933, p. 294): Poleta provided the mining excitement of 1881. . . . [n all probability, some of the claims which changed hands for thousands during the days of Poleta were on the same ground that made Keyes District the hope of prospectors in the middle '60 's. " The mine was operated in the late 1930 's by II. A. Van Loon of Bishop but has been idle since 1941. The production since 1900 amounts to more than 2,000 ounces of gold and 800 ounces of silver, and the total production may be about twice these amounts. According to Tucker and Sampson (1938, p. 415), a segment of the vein, exposed in the deeper part Df the mine, with a thickness of 8 inches, contained about |35.00 per ton in gold. The deposit is in a quartz-sulfide vein that lies within a bedding-plane gouge zone in thin-bedded limestone of t'ne Silver Peak group. The setting is a structurally com- plex zone on the southwest side of an anticlinal nose that plunges steeply to the south. Near the mine the beds are folded and faulted, and locally a secondary cleavage is developed. Nevertheless, the exposures in the mine indicate that locally the strata are in good order. The main workings are a 400-foot adit and a 600-fool incline winze sunk down the dip of the vein (tig. 24). The collar of the winze is 150 feet from the portal of the adit. From the winze, levels have been driven along the vein, with stopes between the levels. A vertical shaft or raise connects one of the stopes above the adit level witli the surface. In the mine the beds strike northeastward and dip 20° to 50° NW. The vein, localized along a bedding plane, is in the hanging wall of a zone of highly altered gouge that ranges up to 6 feet thick. The explored part of the vein has the form of a shallow trough that plunges gently to the north. The vein pinches and swells, ranging in thickness from 2 inches to 2.1 feet. To the northeast and east it pinches out, and on the west it is cut off by a highly brecciated fault zone that strikes northeast- ward and dips 35° to 45° NW. The intersection of the fault and vein trends northward. At the adit portal and on the 200-foot level, where the fault zone is best ex- posed, it is about 20 feet thick. Mullion structures and slickensides in the walls of the gouge in which the vein is localized indicate that tin 1 latest movement was down the dip, with the hanging wall moving upward. No criteria bearing on the movement of the breccia zone that cuts off the vein on the west were recognized. In the deeper part of the mine the vein consists chiefly of quartz, calcite, and auriferous pyrite, with a little chalcopyrite, but in the upper levels the sulfides are altered to limonite that carries free gold. Much of the limonite is in pseudomorphs after pyrite. Sericite is present locally along fractures. Fish Springs Hill The gold-bearing quartz veins in Fish Springs Hill were worked prior to 1890 and intermittently up to World War II. Fish Springs II ill is at the south end of the Crater Mountain basalt field and is bordered by lava on all sides except the southeast. Along the south- east side, alluvial-fan deposits are deposited against the margins of the hill. The hill, roughly triangular in shape, is cut through by a wind gap near the south end. The highest point is at an altitude of 5,460 feet, and the area in which the gold veins are concentrated is 400 to 600 feet lower. The hill consists chiefly of granodiorite. An albite porphyry dike somewhat more than 100 feet wide in outcrop runs southeast through the south half of the hill; and several thin, steeply dipping diorite dikes cut northeast through the north part of the hill, and north- west through the south part. Most of the gold-quartz veins are within a limited area on the southwest slope of the hill, north of the wind gap; but the Coimnetti mine, one of the chief producers, is south of the wind gap. The slopes of the lull are covered by a thick mantle of slope wash, and at the surface the veins are exposed only in prospect pits and at the portals of adits. Most of the pits and adit portals are partly buried by slope wash, and some portals are caved. Only the main adits in the Cleveland mine are in good condition. N'o attempt was made to map the underground workings, hut a geologic map of the sur- face was prepared showing the trace of the outcrops of 82 Special Report 47 the main veins (fig:. 25). Because of the limited exposures il was not possible to map the outcrops of the large num- ber of smaller veins. At most outcrops the strike and the dip of the vein were recorded and plotted; doubtless some of the outcrops shown by strike and dip symbols are on the same vein. Most of the veins strike somewhat north of west and dip 20° to 50° to the north, but several, including some of the most productive ones, lie on the walls of the diorite dikes and dip steeply. In the northernmost ex- posures a few veins dip to the south. The mineralogy of all the veins is similar. Sulfides are disseminated in the veins, and in places masses composed of pyrite and chalcopyrite are found. The pyrite is partly altered to limonite, which contains free gold. Much of the ore was run through arrastras located on Birch Creek, but some ore rich in sulfides was hand sorted for shipment to a smelter. The area is now divided into two properties, the Cleve- land mine area, including most of the mines north of the wind gap, and the Commetti mine south of the wind gap. In times past, however, a number of independent mines were operated in the hill and some of their names are preserved in the names of the veins; Cleveland, United, Commetti, and Gold Bug are among those. The names "Magnet," "Tombstone," "Queen," and "Tip Top," listed in an early report of the State mineralogist, undoubtedly are older names for some of the same veins. The following brief descriptions of the Cleveland and Commetti mines are largely summaries of data contained in the 17th, 22nd, and 34th reports of the State min- eralogist (Tucker, 1921, p. 279-280; Tucker. 1920, p. 4(57-468; Tucker and Sampson, 1938, p. 292-293). Cleveland Mine. The Cleveland mine is owned by Mr. E. E. Ives, who lives on Birch Creek a mile south of Fish Springs Hill, probably on the site of the arrastras of early days. The total recorded production * from 1893 to 1949 is 2,677 ounces of gold, 2,000 ounces of silver, and 1,55] pounds of copper. The workings on the Cleve- land property consist chiefly of about 50 adits as much as 800 feet in length on 10 or 12 different veins. The chief veins are the Cleveland vein, the Cleveland blanket, and the Gold fin"' vein. The Cleveland vein is on the north wall of a diorite dike that strikes X. 75° W. and dips 80° S. Three adits have been driven west into the vein. The lowest and middle (Cleveland) adits are each 640 feet long and are separated vertically 93 feet. The highest adit (Tip Top), 120 feet long, is 168 feet higher than the middle adit. The vein is also intersected by the Browder adit, which was driven north along a gently dipping vein. The Cleveland blanket dips 20° to 40° to the north and on the south terminates against the Cleveland vein. In thickness it ranges from a few inches to 2 feet or more. It has been developed through an adit driven at the same elevation as the Cleveland adit and which meets the Cleveland adit near the faces of both levels. The Gold Bug vein, southwest of the Cleveland vein, dips 15° to 40° to the north and has been developed through three adits, the lowest driven 200 feet, the mid- dle (>()() feet, and the highesl MO feet. Ore mined from this vein is said to have contained abundant sulfides. * Published with permission of owner. Commetti Mine. Two parallel quartz veins are pres ent on the walls of a 15-foot thick diorite dike in th Commetti mine. The dike and veins strike N. 80° W. am dip 85° S. The veins are as thick as 4 feet but connnonl; contain centers of "porphyry " (probably altered grano diorite), with quartz 12 to 18 inches thick on each sid of the porphyry. Most of the development has been ii the south vein, but some development workings am stopes are in the north vein. Recorded production from 1889 to 1941 is 1,566 ounces of gold and 1,41! ounces of silver, plus about 400 pounds of copper. Three adits have been driven west in the south o hanging-wall vein, and deeper levels have been drivei from a winze sunk 260 feet from the lowest adit. Thi upper adit is 300 feet long, the intermediate adit 80( feet long (also reported 536 feet long), and the lowes' adit 450 feet long. The intermediate adit is 100 fee above the lowest adit. In this adit three ore shoots wen developed, each about 75 feet long and about 150 fee apart. The first shoot was intersected 100 feet west o: the portal. The shoot was stoped to the surface and t< about 60 feet below the level. The sale of the ore fron these stopes is reported to have yielded $100,000.00. At 440 feet from the portal of the lowest adit a winz< was sunk 260 feet. From the winze a level at 110 fee- was driven west 385 feet, at 155 feet a level was drivei west 70 feet at 210 feet a level was driven west 270 feet and at 256 feet a level was driven east. The drift at 21( feet is in the north or footwall vein. Two winzes, on* inclined and one vertical and each about 50 feet deep were sunk below the 256 level. It is reported that 21 tons of ore valued at $30.00 per ton was shipped fron these winzes. Sorted ore from the 256 level shipped to < smelter is reported to have yielded $70.00 per ton. Antimony Bishop Antimony Mine. The Bishop Antimony mini is 1 mile west of the Rossi mine in low hills that projed from the Sierra front into valley alluvium. The deposil is in the southeast corner of sec. 23, T. 7 S., R, 32 E. about 3^ miles southwest of Bishop. The deposit was operated in the early part of World War TT, and twe 10-ton lots of antimony ore were shipped. The ore was concentrated in a small gravity mill on the property The deposit has not been worked since 1943, and the mill has been utilized intermittently for the concentra- tion of scheelite from tungsten ores. In 1953, ore from the Round Valley mine was being treated in the mill. Stibnite and oxidized antimony minerals occur in the gouge of a vertical, east-trending range-front fault (fig 26). The mineralized zone has been explored by means of a vertical two-compartment shaft, an adit level ap- proximately 500 feet long that connects with the main shaft 64 feet beneath the shaft collar, a second shaft that extends from the adit level 44 feet to the surface and a lower level developed from the main shaft. In 1946 the lower level was filled with water and therefore inaccessible. A raise above the adit level near the main shaft connects with some small stopes above the level. The fault zone ranges from a few feet to 10 feet or more in width, but it is mineralized only locally. The stibnite is commonly localized in late slips that cut across the fault gouge. Subsidiary slips in the wall-rock schist, that are parallel with the main fault, also are t Published with permission of owner. Economic Geology op Bishop Tungsten District 83 Eneralized locally. The stibnite occurs as small stringers anging from a fraction of an inch to <> inches in width md from a few inches to several feet in length. In places he stibnite is associated with quartz or pyrite. iobalt Bishop Silver-Cobalt Prospect. Cobalt minerals have teen identified in the Chocolate Peak area, on claims of he Bishop Silver-Cobalt Mines Co. Sulfides (chiefly >yrite or pyrrhotite) in small amounts are disseminated trough much of the metamorphic mass of Chocolate Yak and, upon oxidation to limonite, stain the rocks Blow or brown; but the only authenticated occur- ence of cobalt is on the west side of Chocolate Peak, bout •")()() feet east of Long Lake (fig. l(i). The tonnage f mineralized rock at this locality appears to be too mall and the content of cobalt, copper, and nickel too ttle for profitable exploitation, but the occurrence is of iterest because it suggests that minable deposits may et be found in the Sierra Nevada. The following description of the cobalt occurrence is ased on work done by J. S. Vhay (written communica- 1011 ) of the Geological Survey. The outcrop of the lineralized zone is from 6 to 18 feet wide and can be raced X. 65° W. about 200 feet, but the southeast 100 ?et contains only pyrite ; thus, the segment that con- lins cobalt is only about 100 feet long. The mineralized j>ne cuts a variety of metamorphic rocks, including ealc- ornfels, siliceous hornfels, quartzite, and quartzose •hist, all of which are iron stained. The zone is partly licified and contains pyrrhotite, chalcopyrite, and ihalerite, plus lesser amounts of cobaltite and arsenopy- te, and a little pyrite. Locally, gossan with green cop- er stain and erythrite (cobalt bloom — hydrous cobalt rsenate) is present as a result of oxidation of the llfides. The sulfides are in disseminations in silicified X'k and in narrow richer streaks that range from 6 to 1 inches in width. Samples from some of the narrow reaks of sulfide in the outcrop contained as much as 88 percent of cobalt, but the rock across a mining idth contains less than 0.10 percent. An adit has been driven 14(i feet toward the outcrop the mineralized zone, chiefly in marble that contains few silicated layers, but the adit does not appear to ive been driven far enough to cut the full width of le mineralized zone. Only a few thin stringers are ex- jsed in the adit, most of which strike about X. 15° W:, though a .'Much-thick veinlet in the face of the adit Irikes X. 4.')° W. Nonmetallic Deposits Xonmetallic deposits that have been mined in the strict include barite, talc, pumice, rhyolite tuff', ex- msible rhyolite (perlite), feldspar and clay, marble, anite, and sand and gravel. In 1953, only pumice, ex- msiblc rhyolite (perlite), and sand and gravel were ■ed. Pumice has been mined at a fairly steady rate ice 1945, and expansible rhyolite (perlite) has been ined at a steadily increasing rate since it was first arketed in 1949. The production of sand and gravel for local use, and the amount mined annually is riable. trite (hotter Canyon Barite Mine. The Gunter Canyon rite mine, on claims held by Mr. Joseph Smith of Laws, is in the canyon of Gunter (reek at an altitude of about 6,200 feet, about 5 miles northeast of Laws and half a mile south of the boundary between Inyo and .Mono Counties. A road to the deposit joins I'. S. High- way (i two miles north of Laws. Barite veins 2 to S feet thick are exposed in the lower walls of the canyon in an area where a small mass of Campito sandstone is exposed in the core of an anticline. The barite veins have been explored and developed by means of an inclined shaft (said by Mr. Smith to be 200 feet deep), five short adits with small stopes at vein intersections, an opencut about 30 feet across, and several prospect pits and trenches. According to Tucker and Sampson (1938, p. 4S1 ) a considerable tonnage was shipped from the de- posit in 1928 and 1!)2!>. Outcrops of barite are distributed in a north-trending zone about 400 feet long. Individual veins, however, cut across the trend of the zone, striking northwest to west- northwest and dipping 50° to !»() XE, roughly parallel with a prominent cleavage. The veins are not traceable on the surface for distances much greater than 50 feet. Most vein exposures are from 1 foot to 3 feet thick, but locally, at intersections with north- or east-trending gouge-filled faults, thicknesses reach as much as 8 feet. In a few places faults offset the veins a few feet, but most of the movement on faults was premineral. The barite is dense, fine "rained, and light gray to white. Tucker and Sampson (PK58, p. 481) report that it carries 94 percent of barium sulfate and has a specific gravity of 4.2. The centers of the veins are structureless, but near the margins the barite is banded parallel with the vein walls. Locally, the barite interfingers irregularly with the wall rock, suggesting that the veins were de- veloped, at least in part, by replacement of the wall rocks. In mapping the geology of the part of the White Mountains within the Bishop district, barite float was observed at a number of other places, most abundantly on the north side of the second canyon north of Poleta Canyon, in the unsurveyed ground north of sections 5 and 6, T. 7 S., R. 34 E. Prospecting in this area may result in the discovery of exploitable barite veins. Talc Talc has been mined in the Bishop region only at the Blue Star mine in the canyon of Big Pine Creek, but an occurrence on the lower east slope of Mt. Tom was pros- pected shortly after the end of World War II. Higher on the east face of Mt. Tom in the lower adit of the Lambert tungsten mine, a thin irregularly developed selvage of talc is present along a contact between tactite and marble, but no effort was made to exploit it. Blue Star Mine. The Blue Star talc mine is in the SE1 sec. 31, T. !) S., P. 33 E., at an altitude of 8,300 feet. It is on the south wall of the canyon of Pig Pine Creek, about 1,100 feet above the canyon bottom. A dirt road that branches south from the surfaced road along Pig Pine Creek leads to the base of the canyon wall directly below the deposit. From the end of the road a trail leads to the deposit. Both talc and marble have been produced, tale as recently as 1945 and marble as recently as 111 Is. The mine was idle in 1953. The marble is not suitable for building stone, and most of it probably was crushed for 84 Special Report 47 use as roofing granules. When the mine was in opera- tion, a 1,200-foot gravity surface tram was used to lower rock from the deposit to a eompartmented bin at the end of the road. From the bin the talc and marble were trucked to the Blue Star grinding plant at Zurich. .Marble was quarried from the surface, but most of the talc was mined underground. The portal to the access adit is caved, but according to Tucker and Sampson (1938, p. 492) the development workings consisted of an adit driven 200 feet in a southeasterly direction, and a southwest-trending drift 120 feet long that branches from the adit 140 feet from the portal. In mining, a square-set system was required because of the weakness of the rock in the talc-bearing zones. At the deposit a mass of dark-colored amphibolite with a central core of marble is enclosed in granitic rocks. The texture of the amphibolite as seen in a microscope indicates that the amphibolite was derived from basalt. The amphibolite occupies a position along an east-trend- ing contact between granite on the north and quartz monzonite on the south. Other masses of marble, calc- hornfels, amphibolite, and diorite are found at intervals along the contact west of the Blue Star mine for about 2 miles, but none of them has been demonstrated to con- tain tale in minable amounts. The marble outcrop is about 100 feet wide and 500 feet long, and the enclosing amphibolite outcrop is about 800 feet wide and 1,200 feet long, but because both the marble and amphibolite are concealed by slope wash at their south ends, the exact dimensions are not known. The marble is white and coarsely crystalline and con- sists largely of calcite but contains scattered grains of diopside and brucite. In the outcrop small masses of talc are present in the amphibolite along the south contact of the marble. These masses are generally only a few feet across and grade into the amphibolite. According to Tucker and Sampson (1938, p. 492), the masses mined were all small; one of the largest was 15 feet wide, 70 feet long, and 45 feet high. Much of the talc is in crystal aggregates that pseudomorph other minerals. Crystalline aggregates with a radiating structure 3 or 4 inches across are com- mon, and many masses are 6 inches or more across. These forms are pseudomorpbs after hornblende or ac- tinolite, demonstrating, together with the gradational relationships of the talc, that the talc was formed from the amphibolite. The alteration could readily have taken place by means of hydrothermal solutions that brought in water and carried away lime and possibly alumina. Mt. Tom Talc Prospect. A body of talcose hornfels on the lower east slope of Mt. Tom, in the SW^ sec. 6, T. 7 S., R. 31 E., at an altitude of 7,400 feet, has been prospected by means of a few small pits. A 6-mile access road from Round Valley to the prospect was built near the end of World War 1 1, but it has not been maintained and the last mile was not passable in 1952. The prospect is in the south end of an inclusion of calc hornfels enclosed in quartz monzonite. The tale ex- posed is irregularly developed through the hornfels, and none appears to he in bodies large enough or pure enough for profitable exploitation. Pumice The mapped region includes the south half of a belt of pumice deposits. In the mapped area, the deposits are confined to the margins of the Volcanic Tableland an to the alluvial slope that flanks the White Mountains o the west side. With the single exception of the Van Loo "fines" pit, all of the pits are in outcrops of a layer white pumice of Pleistocene age. This layer is compose almost entirely of tightly packed, angular, unaltere pumice fragments as much as 2 inches in average diam* ter, with sufficient strength for use as lightweight a< gregate. In the north part of the mapped area, the layt of white pumice is 12 to 20 feet thick with an averaj^ thickness of about 18 feet; it thins southward and he not been identified south of Zurich. The pumice layer is exposed oidy locally where faultin and warping, in conjunction with erosion, have brougb the layer to view. The most continuous exposures are i the cliff along the south margin of the Volcanic Table 1 land and in the edges of the terraces along the east mav gin of the Volcanic Tableland. In both places the pumic layer is flat or gently dipping and underlies the lowe 1 unconsolidated pumiceous layer of the Bishop tuf 1 Smaller, less-continuous outcrops in the alluvial slop 1 along the White Mountain front are in a tilted or ur lifted block bounded by faults. In the margins of th Volcanic Tableland the pumice rests on unconsolidate' sandy sediments and is overlain by the lower uncoil 1 solidated pumiceous layer of the Bishop tuff of Gilber (1938) ; along the White Mountain front the pumic layer is generally interstratified in alluvial detritus, al though in places it rests directly on eroded Lower Cam : brian strata. The outcrops of pumice that have been exploited ar those that have little or no overburden and can be minei in open pits. Lack of exploitation of the extensive out crops in the cliff along the south side of the Volcani 1 Tableland, presumably is the result of the thick over burden of Bishop tuff of Gilbert (1938). The deposit along the east margin of the Volcanic Tableland, wher' the overburden is much thinner and can be stripper away with a bulldozer, are the most extensively devel oped in the mapped area (photos 11 and 12). Most of the pits have been operated only intermit' tently, and only the Van Loon "fines" pit and the pit: of the Insulating Aggregates Co. along the east side o! the Volcanic Tableland have been operated with somij degree of continuity in the past few years. The outcrop; on the property of the Insulating Aggregates Co. havt! been worked for a great many years, and pits are strung out along the contact for about 2,000 feet. Older pit:' lie both north and south of those now being worked Because the amount of overburden thickens toward the Volcanic Tableland, it has been most economic to mint along the outcrop, stripping as little overburden as pos sible. Most of the material mined from these pits is sole in Los Angeles, chiefly as a material for acoustical plas; ter. The material is mined with power shovels, anc 1 crushed and sized in a dry mill near the pits befort 1 shipment. Unlike the other pits in the mapped region, the Var Loon "fines" pit is in the lower unconsolidated pumi ceous layer of the Bishop tuff. This layer consists of fine tuff that contains sporadically distributed rounded: pumice fragments. The pumice fragments are generally somewhat larger but much weaker than those in th| Economic Geology of Bishop Tungsten District 85 jumice layer. Because of their weakness the pumice frag- nents are valueless, but the tuffaceous material is re- tovered for use in the place of sand in the manufacture f pumice bricks and wall sections. These "fines" are lauled to a plant owned by II. A. Van Loon in the outhern outskirts of Bishop. Aggregate for the bricks nd wall sections is trucked from a pit 15 miles north f Bishop. The exploitable reserve in the layer of angular pum- ice is comparatively small if the pumice can be mined ommercially only in open pits. Such reserves are argely confined to areas contiguous with the outcrops. )n the other hand, if because of an improved market or letter mining methods the pumice can be mined under- ground, the exploitable reserve is vastly greater. All or .lmost all of the Volcanic Tableland in the mapped area, nd part of the alluvial slope along the west side of he White Mountains is underlain at depth by the pum- ce layer. In the Volcanic Tableland, several square ailes contiguous to the outcrops can safely be said to be inderlain by the pumice layer. The only geologic factors hat might complicate mining are the many small faults hat cut the Volcanic Tableland, and the possibility that lownfaulted or downwarped parts of the pumice layer nay be below the water table. In the span along the Vhite Mountain the difficulties are apt to prove more evere. The faults along this span are more numerous, nd many are of greater magnitude than those that cut he Volcanic Tableland. Whereas in the Volcanic Table- and it is possible to predict from the displacement of he surface the "magnitude and direction of the move- ient on faults, expensive borings would be required long the White Mountain front to ascertain the depth, ttitude, and extent of the faulted segments of the lumice layer. Reserves of pumiceous tuff in the lower unconsoli- ated layer of the Bishop tuff of Gilbert (1938), ex- loited only in the Van Loon "fines" pit, are virtually ■limited. An area of several square miles west of Pish Hough is underlain by the tuff at the surface, and it xtends to depths of 100 feet or more. On the property f the Insulating Aggregates Co., the choice can be made etween pale-yellow or orange tuff and light-red tuff. hyolite Tuff For many years, beginning in the days of the early ettlers in Owens Valley, the Bishop tuff of Gilbert 1938) was used as a building stone, and buildings con- tructed of tuff still stand, especially north of Laws, [ore recently, concrete blocks with pumice aggregate ave taken the place of the natural blocks, and the tuff 5 no longer quarried. Two old quarries in tuff are in the lapped area, one on the west side of Round Valley long U. S. Highway 395, in the S. \ sec. 23, T. 6 S., R. 1 E., and the other 4 miles north of Bishop in the S. \ be. 14, T. 6 S., R. 32 E. xpansible Rhyolite (Perlite) Expansible rhyolite or "perlite" makes up a large art of the rhyolite hill 7 miles south of Big Bine. 'his hill, in sections 24 and 25, T. 10 S., R. 33 E., nd in sections 19 and 30, T. 10 S., R. 34 E .. is bout a mile long and has a maximum width near ie middle of about half a mile. It is elongate in an easterly direction and rises about 200 feet above the alluvial apron that extends out from the Sierra Nevada front (photo 13). Ownership of the hill is divided between two groups. The west end, called the Brooke perlite deposit, is owned by Mr. Douglas Robinson and associates; and the east end. called the Fish Springs perlite deposit, is owned by Mr. Morris Albertoli. A quarry is on each property, but the only active operation in 1953 was the Fish Springs quarry on the southeast side of the hill, which was leased by the United States Mining Co. (Soloman Gindoff and Groveland Monteperte). The perlite is mined by means of a power shovel and is crushed and screened in a plant at the base of the hill below the quarry (photo 14). The Brooke perlite deposit was oper- ated in 1950 and 1951 when the deposit was leased to the American Perlite Co. (Art Detloff and J. J. Thomas). At that time a plant for crushing and screening the perlite was at the west end of the hill near the quarry, but it has been dismantled. The geology of the hill was studied some vears ago by Evans B. Mayo (1944, p. 599-620), before the rhyolite was found to be expansible and of commercial value. Mayo's report includes detailed descriptions of the rocks and structures. The present more limited discussion deals only with features essential to an understanding of the broad structure of the hill. The hill is thought to be, technically, an extrusive dome with attendant short flows. The distribution of the component rocks and the attitudes of the flow band- ing suggest that the rhyolite mass is shaped like an asymmetric mushroom, with the stem (vent) approxi- mately beneath the high point in the east end of the hill. From the vent, viscous rhyolite flowed in all direc- tions, but more flowed east down the alluvial slope than in other directions, thus producing the elongation of the hill. In the central and north parts of the hill the flow layers generally are steep, whereas at the south end and along the southeast side, the flow layers are flat or gently dipping. The steep dips in the central part of the hill probably are the result of buckling during flowage; contortions of the flow layers are conspicuous along the north margin of the hill. Three kinds of rock are distinguished on the accom- panying map of the hill (fig. 27) : (1) dense, gray vitro- phyre (glassy lava with a few crystals), (2) thinly in- terlayered, black glassy obsidian and gray to buff vitro- phyre, and (3) light-gray pumiceous rhyolite (expansi- ble rhyolite). The overall relationships indicate that the rocks were extruded separately in this order. In most places the rocks are readily distinguishable and are in sharp contact with one another. Pumiceous rhyolite occupies the central part of the hill and is flanked con- centrically first by an obsidian-bearing layer, then by gray vitrophyre. Locally, on the northeast side of the hill, a second obsidian-bearing layer is intercalated in the gray vitrophyre. In the western part of the hill the obsidian-bearing layer is missing between the pumiceous rhyolite and gray vitrophyre. Pumiceous rhyolite is the only rock that is known to be expansible, although parts of the gray vitrophyre also may be expansible. At the surface the pumiceous rhyolite is highly brecciated. but in the Brooke quarry it is less pumiceous and more coherenl than most places. 86 Special Report 47 Structurally, the most interesting of the rock units is the one composed of thinly interlayered obsidian and gray vitrophyre. The obsidian-bearing units crop out only locally, but their presence is clearly marked in most places by dark-gray soil that contains abundant obsidian pellets. In most exposures the obsidian bands have been stretched out into thin discontinuous lenses, and, locally, where the rock is most strongly contorted, the obsidian is in rounded pellets that are separated from one another by gray vitrophyre. ' At the Fish Springs quarry, where the flow layers generally are flat, gray vitrophyre appears as the lowest layer and is overlain by an obsidian-bearing layer, with pumiceous rhyolite at the top. Although the various rock units locally are conformable with one another, in some places the pumiceous rhyolite bears crosscutting relationships to the rocks in the outer margins of the hill. Especially significant in this regard are dikes of pumi- ceous rhyolite that cut both the gray vitrophyre and the obsidian-bearing layers. In the east part of the hill the pumiceous rhyolite appears to rest on the upper obsidian-bearing layer, which is thought to be a gently dipping flow. However, in the west end of the hill, where the west and south- west margins of the pumiceous rhyolite are concealed by alluvial fan material, the lower limit of the pumi- ceous rhyolite is not exposed. The pumiceous rhyolite above the obsidian-bearing layer in the east part of the hill and above the general level of the fan in the west part comprises in the order of 25,000,000 cubic yards of material. Some additional pumiceous rhyolite may under- lie the west end of the hill below the level of the fan, but the data in hand give no suggestion of the amount. Feldspar and Clay Material from a fine-grained granophyric dike that cuts through quartz monzonite in the foothills north- west of Big Pine has been used as filler in the manu- facture of storage batteries and has been tested for use in the manufacture of ceramics. The dike trends about N. 25° E. and dips about 70° W. and can be traced from the range front southwest for about 3 miles. It varies in thickness from 10 feet to 30 feet; in places it consists of two or more parallel dikes. The dike is cut by several north-trending faults, most of which dis- place the dike only slightly. Two faults, however, each offset the outcrop of the dike about 400 feet ; at each faidt the more westerly segment is offset to the north. The dike is partly altered, in most places, to a claylike material, but where fresh consists of a microscopic inter- growth of quartz and orthoclase, with some albite. A few crystals of quartz and orthoclase are large enough to be seen with a hand lens, but most of the material is so finely intergrown that the mineral content is difficult to determine, even with a microscope. The dike has been opened at two places, at the front of the range and 1 \ miles to the south. The working at the range front, called the Nebecite Feldspar-Kaolin deposit, is owned by Stuart Bedell and J. W. Newman of Big Pine. It is 'in the S| sec. 2, T. 9 S., R. 33 E. Workings consist of an opencut and a 25-foot adit. The dike here is highly altered, especially on the hanging- wall side. According to Norman and Stewart (1951, p. 99), 1,000 tons of material has been mined for use as filler. The other working, known as the Sierra White feld spar deposit (Big Pine kaolin deposit), is in the NW; sec. 14, T. 9 S., R. 33 E. It is owned by Huntley Indus trial Minerals, Inc., of Bishop. The property is reachec from the road along Baker Creek by a 2-mile access roac that branches north from the Baker Creek road near it! end. The workings consist of three opencuts, two clos< together and the third 1,500 feet farther to the north The largest cut is about 125 feet in length and has i working face more than 50 feet high ; the other cuts are somewhat smaller. According to Norman and Stewan (1951, p. 99), 4,000 tons of rock had been produced tc February 1950, and operations were continuing at th< rate of 300 to 450 tons per month, but operations wen suspended in 1951. The material mined was sold for us*, as filler in the manufacture of battery boxes. No other dikes precisely like this one were identified in the mapped area, but an albite porphyry dike thai crops out in Fish Springs Hill may be genetically re- lated. The alteration of the dike appears to be a weathering phenomenon because it is the least altered where it has been eroded the most deeply. Limestone and Marble Limestone and marble for roofing granules and allied uses has been shipped from four places in the area: from quarries on the north side of Big Pine Creek in the NJ sec. 34, T. 9 S., R. 33 E. ; from the Blue Star talc mine on the south side of Big Pine Creek; from the Marble Tungsten mine in Shannon Canyon ; and from a quarry at the base of the White Mountains in sec. 23, T. 5 S., R. 33 E. No data are available about the operation at the quarry in the White Mountains, but it must have been carried on many years ago. Marble was shipped from several of the other quarries for several years following the end of World War II, but no rock has been shipped since 1948. Granite An old granite quarry is in the east side of the Tung- sten Hills just north of the Deep Canyon road, near the , boundary line between sees. 6 and 7, T. 7 S., R. 32 E. The quarry is in medium-grained rock, much finer grained than the common Sierra Nevada granite. The rock has a dark cast and is very fresh. The purpose for which the rock was quarried was not determined. Gravel and Sand Gravel suitable for aggregate in concrete or for road beds is present in almost all of the fans and stream beds built by streams flowing out of the Sierra Nevada, and the locations of most gravel pits have been selected for economic rather than geologic reasons. Nevertheless, cer- tain simple geologic concepts are usually considered, though not consciously, in the selection of a site for a gravel pit. The two important considerations that in- volve geologic concepts are the kind of material and the size of the material in the raw gravel. The fans and stream channels of the Sierra Nevada generally are granitic, whereas the fans along the front of the White Mts. consist largely of metamorphic material, commonly with a somewhat limy matrix. The average size of the material in a fan generally increases toward the head. Along the Bishop Creek road, for example, the particles making up the Bishop Creek Economic Geology of Bishop Tungsten District 87 'an can be seen to increase progressively in size toward ;he head of the fan. At Bishop, which is at the lower dge of the fan, most of the particles are sand and clay ;ize ; west from Bishop the fan material grades through jravelly sands to sandy gravels ; and above Oteys Sierra tillage to the head of the fan the material is coarse and )Ouldery. A large fan usually includes coarser material han a small fan. The material in the heads of the small ! ans at the north base of the Tungsten Hills is fine nough for road material and contains only a few large )oulders, most of which have rolled off the adjacent lopes. Similar-sized material from a large fan would be bund only at a considerable distance below the head of he fan. The locations of the principal gravel and sand pits re shown on the economic geologic maps. Most of them ire in the vicinity of Bishop. A pit in the lower part f the Pine Creek fan on the west side of Round Valley, n the southeast corner of sec. 17, T. 6 S., R. 31 E., erved as a source for gravel in the construction of tun- els and power plants in the Owens River Gorge by the )epartment of Water and Power of the City of Los Angeles. Pits in the NW£ sec. 36, T. 6 S., R. 31 E., be- ang to the California Division of Highways and supply oad gravel. North of Bishop, in the south half of see. 9, T. 6 S., R. 32 E., is a pit from which the Bishop ngineering and Construction Co. produces sand and ravels. Southwest of Bishop in the E^ sec. 14, T. 7 S., 32 E., is an old pit that serves as the town dump, mailer pits are found about 1 mile farther to the outheast in the center of sec. 24. South of Big Pine ust west of Fish Springs a pit has been dug in the de of a basalt cinder cone. REFERENCES CITED Bateman, P. C, 1945, Pine Creek and Adamson tungsten mines, ayo Countv, California : California Jour. Mines and Geology, v. 1, p. 231-249. Bateman, P. C, Erickson, M. P.. and Proctor, P. C, 1950, eology and tungsten deposits of the Tungsten Hills, Inyo County, alif. : California Jour, of Mines and Geology, v. 46, no. 1, p. 7-42. Chalfant, W. A., 1933, The story of Inyo : Citizens Print Shop. ic, Los Angeles. Chapman, R. W., 1937, The contact-metamorphic deposit of ound Valley, Calif.: Jour. Geology, v. 45, no. 8, p. 859-871. Gannett, R. W., 1919, Experiments relating to the enrichment tungsten ores : Econ. Geology, v. 14, no. 1, p. 68-78. Gilbert, C. M., 1938, Welded tuff in eastern California: Geol. oc. America Bull., v. 49, p. 1829-1S62. Gilbert, C. M., 1941, Late Tertiary geology southeast Mono Lake, Calif.: Geol. Soc. America Bull., v. 52, p. TSI-SKl. Goodyear, W. A.. 1888, Inyo County: Calif. Min. Bur. Kept 8 p. 224-309. Hess, F. L., 1916, Tungsten: in U. S. Geological Survey, Min- eral resources of the United States in 1916, p. 77S. Hess, F. L., 1919. Tactite, the product of contact metamorphism : Am. Jour. Sci., 4th ser., v. 48, p. 377-378. Hess, F. L., and Larsen, E. S., 1921, Contact-metamorphic tung- sten deposits of the United States: I'. S. Geol. Survey Bull 725 p. 245-309. Kerr, P. F., 1946, Tungsten mineralization in the United States: Geol. Soc. America, Mem. 15, 241 p. Knopf, Adolph, 1917, Tungsten deposits of northwestern Inyo County, Calif.: U. S. Geol. Survey Bull. 640, p. 229-249. Knopf, Adolph, 1918. A geologic reconnaissance of the Inyo Range and eastern slope of the southern Sierra Nevada : V. S. Geol. Survey Prof. Paper 110, 130 p. Krauskopf, K. B., 1953, Tungsten deposits of Madera, Fresno, and Tulare Counties, California: California Div. Mines, Special rept. 35. Lee, W. T., 1906, Geology and water resources of Owens Valley, Calif. : U. S. Geol. Survey Water-Supply Paper 181, 28 p. Lemmon, D. M., 1941a, Tungsten deposits in the Tungsten Hills, Inyo County, Calif.: U. S. Geol. Survey Bull. 922Q, p. 497-514. Lemmon, D. M., 1941b, Tungsten deposits in the Sierra Nevada near Bishop, Calif.: U. S. Geol. Survey Bull. 931E, p. 79-104. Lenhart, W. B., 1941, Milling scheelite at Tungstar mine: Min. Cong. Jour., v. 27, no. 4, p. 67-71. Maxon, J. V., 1935, Pre-Cambrie stratigraphy of the Inyo Range : Geol. Soc. America, Proc. for 1934. p. 314. Mayo, E. B., 1941, Deformation in the interval Mt. Lyell-Mt. Whitney, Calif. : Geol. Soc. America Bull., v. 52, p. 1001-1084. Mayo, E. B., 1944, Ryolite near Big Pine, Calif. : Geol. Soc. America, Bull., v. 55, p. 599-620. Mineral resources of the United States, Chapters on tungsten : U. S. Geological Survey 1906-1923, U. S. Bureau of Mines 1924- 1931. Minerals Yearbook, Chapters on tungsten : U. S. Bureau of Mines 1932-1954. Norman, L. A., Jr.. and Stewart, R. M., 1951, Mines and mineral resources of Inyo County : California Jour. Mines and Geology, v. 47, no. 1, p. 17-223. Spurr, J. E., 1905, Descriptive geology of Nevada south of the fortieth parallel and adjacent portions of California: U. S. Geol. Survey Bull. 208, 229 p. Tucker, W. B., 1921. Inyo Countv: California Min. Bur. Rept. 17, p. 273-305. Tucker, W. B., 1926, Inyo County : California Min. Bur Rept. 22, p. 453-530. Tucker, W. B., and Sampson, R. J., 1938, Mineral resources of Inyo County: California Jour. Mines and Geology, vol. 34, p. 368-500. Walcott, C. D., 1895, Lower Cambrian rocks in eastern Cali- fornia: Am. Jour. Sci., 3rd ser., v. 49, p. 141-144. Walcott, C. D., 1908, Cambrian sections of the Cordilleran area: Smithsonian Misc. Coll., v. 53, p. 185-1S8. 3806 4-56 3M printed in CALIFORNIA STATE PUNTING OFFICE EXPLANATION J? Alluvial deposit.* Include* tall,., Ml. 'an OtpoaiU , BIIIM aond. l„,n„ g.aTtL,. and lair ttdin Unl,nal./n,..ndand„a,,l /«- rood.. Odd nfirup and »"r/nnng malfnnl N^. ' : f 4: . - ■■'-' ; ' V 'V'~ s" yjf f*& U„l^ t IP? i f « '■-•. " fl-tr..." nil, and fines art used m place of -and in making Mil- 'U ■ ■..„^,/. U...-1 (.. :,... I ;■!.,.; ■ ■(,-, .'„,,,. i ;..,„..■. ■■r.,;,„ i .-.:t l.l.f »„ ,,hi, ■„ strength required for concrete nonrepair I'rt* an polishing material a Pumice layer Bed is as much an SO fit! thick ntar north boundary of mapped area bat thin* I- thr ,».,,th. fom,,,,;-,! .it hunt, .i.i U nI.i- 'ragmen!, that are suitnb .... In,hl„,„,bl ...,..;..,,„<, I I'l: li-'i "Urir.f in ".fill I'larcs. Chief It* or, t.,t I,., 1,1. .,.-,. ,1,1 a.,.,,,.,.,1, ,., eemenl l-i-'k.:. and in ar..„ Ural pin t" ■A (t«ll Ms., o/i CjMwnu towdimlc I II ECONOMIC AND GEOLOGIC MAP OF THE MT. TOM QUADRANGLE, CALIFORNIA I By Psiul C. Bntcman § SCALE I 62500 CONTOUR INTERVAL 40 FEET Geology surveyed in 1950 , gfd Granitic rocks 'Granite," gf, includes S rocks, 1 granite and t quart; momoniles, «-ith which most of the knou-n lung, ten deposits '!'■■ a-aanal'd. ".,in, -.l;iiula,il nu-1,11 ' i:ai-',li. .-.,le-h..r„'eh. and Mi.; ,fl.l.,,d,ai.„la,„ -ik >,;„. of these inclusion* an <■■■■ mall la -h..:, „„ the map. In thr Deep > a,,u„„ Metavolcanic rocks Chiefly dark-colored meladacite with intercalated beds and tenses of marble, eatr-h.,„frl.; neb,,!, and quarlziU. hut h .ratty include,' Itihl-colorcd mtta- thyohte. hit, realm,, I '-,!■■ and lenn ..{ marble are the host for sehethle- btarina lacliu f granitic rock u-ith marble intercalated in cirtc-hornfelx should be cart fully prospected far Unai-U-n art bodies. Includes biotite-quarh hornftls, qwtrU-Jtld por hamfel,. andalwnlt homfels, schist, metachert, gncits, and other nanrnlrare.nti m/lasedimentary rocks. May also contain bed' and tenia at marhh- l.„i small U, be -howii. Contacts of the granitic rock with iioncalcareous 'aek.~ are not fatarahle far tungsten •iepastts. but contacts u ilh intercalated wnrbl. b,,l or. tarorable. ZenmZd f^'om qZ'l^ciiisor masses'. ' SYMBOLS Contact Dashed where approximately located. Strike and dip ot beds il flow bands in melavolcanic rock I 'V ■ ' ■ ■ ■ ■ ■ ■ ECONOMIC AND GEOLOGIC MAp ()| ,. T1I| . HIsnol , QUADRANGLE CALIFORNIA ; l' h Bv Paul C. Batcmnn £ \ 12 i ;>e/vi , SB**"****" 1 * Geology sutvejri »> 19^0 Strike and dip of beds or flow bands i Wi tungsten ••■ * n i OIVISION OF MINES wiW^ifOW* STATE OF CALI FORNIA \\ OLAF P. JENKINS, Chief g^V*. * DEPARTMENT OF NATURAL RESOURCES JNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY e us*""" rf 1 so**?!**"*" >fc>°' «$^ # •** ,^»; ITT- 'tf*. Alluvia] deposits facilities valley fill, fan deposits, dune sand, terraci Malcrtnk for .■■anil unit ijruvel (or contrite, and n imniur r< <■ oHsocia(«d. , ■■ iih vhith ■i tungsten deposits a includes antral darker colored, mare calcic inlrusiees with which only a few small noncommercial tungsten deposits are associated. Then intrusttcs range from quart: momomte to granodioritc. Although the data in hand suggest that "granite" it a more favorable associate of tungsten deposits than "granodioritc," the data are not conclusive, and certainly do not warrant recommending that prospecting be restricted to "granite" areas. The con- tacts between individual intrusiee masses are shown, even where both rocks are represented by the name color and pattern, because they are occupied in many placet by discontinuous strips of metasedimentary rocks, including marble, many of which arc too small to show on the map. Prospecting of these contacts for slivers of marble and for tunai'lai o-e bodies will be found far more rewarding than indiscriminate searching for small inclusions within the granitic masse*. Some intrusive ma.'se-i runtnin inclusions in their margin.'', hot moil a', clean in thnr central parts. Quartz diorite and hornblende gabbro Includes hornblende gabbro, dioritc, quartz dinritr, and amphiludite. All of these rock.? nrr dark minted tit- mmpared nith the jr„,,i!i'- r...-l : . ,<„ m . ,.f the roek-s, e.-.p.nnllii the tlo'k' I -me- 'hornblende nahhto , a.aUnn ahnndant inclusions of marble, ealc-homfeh, and other metasedimentary rocks. Some of these inclusion* are tor, small I; slum- on the map At the Srhnher mine on the east -,de of th. Smith Fork ,,( Hishop ''reek calcareous inclu- sions in dark colored masses of hornblende gabbro have been exploited for the tungsten deposits they contain. -hornfels, schist, and 33 VV.. o | i%^t:. 1 N Marble ly marble farmed from clean limestone, hit locally include:: i of noncatcartous or impure calcareous material. Contacts :■ and granitic rocks are especially favorable for tungsten r is locally developed along these contacts. Include:, hi otitc-quarlt hotnfels, quartz-feldspar hornfels, andalusitc hornfels, schist, metachert, gnnt.'-. and other noncaleare.ois m-tas,dimentary rocks. May also contain beds and lenses of marble fi»> small to be m ,/uarl: wins or masses, and cobalt is known to occur in silicified rock at one place in the Chocolate I'eak 60>- Strike and dip of beds Strike and dip of foliation 4? Mine X Pros pee I W i tungsten M«( gold ECONOMIC AND GEOLOGIC MAP OF THE MT. GODDARD QUADRANGLE, CALIFORNIA By Haul C. Bateman SCALE I Geology surveyed in 1950 CONTOUR INTERVAL 40 FED _l_ EXPLANATION Doshed where inferred. Strike of vertical beds Diamond drill hole Dashed where projected. Underground workings projected Geology by Paul C Baterr and M PEnckson, 1944; Paul C.eotemon, 1953 PLATE 6. GEOLOGIC MAPS AND SECTIONS OF THE LOWER AREA OF THE ADAMSON MINE. O 100 20^0 390 4q0 feel STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES k T 1 _^--^£j Sh i ■'■ ^^ >^ ^- -^-i ^^^- i; section e-e' SECTION A-A 1 SURFACE MAP + mm GEOLOGIC MAPS AND SECTIONS ROUND VALLEY MINE INYO COUNTY P C BATEMAN ANO M P ERICKSON rS44 (SO 200 FEET STATE OF CALIFORNIA EPARTMENT OF NATURAL RESOURCES EXPLAIN AT ION SECTION A-A' SECTION B-B' GEOLOGIC MAPS AND SECTIONS OF THE LITTLE SISTER MINE INYO COUNTY, CALIFORNIA EXPLANATION '2jl'±Jt.\±1 Granite Joined g OuaHj n HAULAGE ADIT SURFACE MAP Dump in plai r SECTION B-B' SECTION A-A GEOLOGIC MAPS AND SECTIONS OF THE TUNGSTEN BLUE SHAMROCK MINE INYO COUNTY, CALIFORNIA HAULAGE ADIT - ,-__-~x--- ~^---j?0Mi:' SECTION A-A' GEOLOGIC MAPS AND SECTIONS OF THE AEROPLANE MINE INYO COUNTY, CALIFORNIA .cinN OF MINES ^JTjFNKIN S, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Special Report 47 Plate 13 SOUTH ADIT Mopped by Max P Er.cksi June 1944 A 6100- + + + \ + WM/f-f + qm + ■JfXjK'A-t- -■ + + YimQt +q F* 6050'- JwJlf-+ + f ///*'+ + + Hv + + + 6000'- + + / ) s H^\ + ^^ 6100'- + + M^ ° + + + +\. -F'n^, + + + t 4, m + , + + + ' r + + +; f + + ,. 6050'- + + J Hj^' 5 "''"" ' + + ;» j ' t»'5»V '1£.' 4M q+m 6000'- + SECTION A-A SECTION B- EXPLANATION Soil cover i * 1 ictite containing Tactile containing scheellte 0^7^ Hornlels W$ii orite dikes kiiH Gronite + + + + qm + + + + Que rtz moruon J^^&l Hornblende gobbrc Contact, showing dip Dashed where opprox- imately located Foult, showing dip Dashed where approx- imately located Vertical foult Strike ond dip of I Strike of vertical beds r\ B Shoft ot surfa 150 200 feet 4= GEOLOGIC MAPS AND SECTIONS OF THE CHIPMUNK TUNGSTEN MINE Special Beporl 47 EXPLANATION SI jaH S GEOLOGIC MAP GEOLOGIC SECTIONS SHAFT LEVEL Snatl GEOLOGIC MAPS AND SECTIONS OF THE MARBLE TUNGSTEN MINE