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California Division of Mines and Geology 

Ferry Building, San Francisco, CA 94111 



This volume, "Mineral Resources of California", is Port I of a larger 
work. Mineral and Wafer Resources of California. It was prepared by 
members of the staffs of the U.S. Geological Survey, the U.S. Bureau 
of Mines, and the California Division of Mines and Geology, at the 
request of Senator Thomas H. Kuchel. It is issued by the California 
Division of Mines and Geology as number 191 in the Bulletin series. 

Part II, a companion volume dealing with water, is not distributed 
by the Divison of Mines and Geology. 


Edmund G. Brown, Governor 


Hugo Fisher, Adminisfrafor 

DeWitt Nelson, Director 




Ian Campbell, Sfote Geologisf 

Price $2.00 

Author Index— Mineral Resources of California 


Adams, J. W. 

Rare Earths 350 

Addicott, W. O. 

See under RepenninR, C. A. 
Albers, J. P. 

Geomorphic Provinces 35 

Mineral Resources — Introduction 77 

Topographic and Geologic Maps-_ 21 

Topography 23 

Alfors, J. T. 

Cobalt ^^ 139 

Allison, Jil. C. 

See under Peterson, G. L. 
Aune, Q. A. 

Antimony 81 

Arsenic 85 

Bismuth 102 

Bailey, E. H. 

See under Davis, F. F. 
Bateman, P. C. 

Geology of the Sierra Nevada _ 54 

Bowen, O. E. 

Limestone, Dolomite, and Lime 

Products 221 

Broderick, G. N. 

See under Kinkel, Arthur R., Jr. 
Burnett, J. L., and Weiler, C. T. 

Shale, Expansible 37-1 

Butler, A. P. 

See under Walker, G. W. 
Campbell, Ian 

Tlie Mineral Industry of California 11 
Chesterman, C. W. 

Fluorspar 1G5 

Pumice, Pumicite, Perlite, and A^ol- 

canic Cinders 33G 

Clark, W. B. 

Gold 179 

Platinum Group Metals _ __ 332 

Cleveland, G. B. 

Aluminum 71t 

Diatomite 151 

Davis, F. F., and Bailey, E. H. 

Mercury 247 

Davis, F. F., and Hewett, D. F. 

Manganese _ __ 243 

Dibblee, T. W., Jr. 

Geology of the Transverse Ranges 6 
Dil)blee, T. W., Jr., and Hewett, D. F. 

Geology of the Mojave Desert Re- 
gion __ G2 

Durrell. Cordell 

Quartz Crystal 344 

Strontium 408 

Edgerton, C. D., Jr. 

Carbon Dioxide 119 

Natural Gas Liquids 209 

lOspenshade, G. H. 

Kyanite, Andalusite, and Related 

Minerals 212 

lOvans, J. R. 

Thorium 420 

Fischer, R. P. 

Vanadium _ 439 

Gastil, R. G. 

See under Peterson, G. L. 
Gay, T. E. 

See under Macdonald, G. A. 
Goldman, H. B. 

Sand and Gravel ^ 301 

Sands, Specialty _ 369 

Stone, Crushed and Broken 392 

Stone, Dimension 400 

Gower, H. D. 

Phosphate 328 

Gray, C. H., Jr. 

Tin 422 

Gross, E. B. 

Beryllium 99 

Gem Stones 169 

Hamilton, W. B. 

Geology of the Salton Trough 73 

Herz, Norman 

Titanium 426 

Hewett, D. F. 

See under Davis, F. F. 

See under Dibblee, T. AV,, Jr. 
Hotz, P. E. 

Nickel 279 

Irwin, W. P. 

Geology of the Klamath Moun- 
tains 40 

Also see under Smith, G. I. 
Jennings, C. "W. 

Peat 288 

Jones, D. L. 

See under Repenning, C. A. 
Kelley, F. R. 

Clay 126 

King, P. B. 

Geologic History of California 27 

King, R. U. 

Molybdenum 262 

Kinkel, A. Robert, and Kinkel, 
Arthur R., Jr. 

Copper 141 

Kinkel, Arthur R., Jr., and 
Broderick, G. N. 

Sulfur 410 

Landis, E. R. 

Coal 134 

Lemmon, D. M. 

Garnet 168 

Tungsten 429 

Lesure, F. G. 

Feldspar 158 

Mica (Muscovite, biotite, and ver- 

miculite) 254 

Macdonald, G. A., and Gay, T. E. 

Geology of the Southern Cascade 
Range, Modoc Plateau, and 
Great Basin Areas in North- 
eastern California 43 

McNitt, J. R. 

See under White, D. E. 
Moore, Lyman 

Iron 199 

Morton, P. K. 

f^admium 113 

Zinc 444 

Oakeshott, G. B. 

Geology of the California Coast 

Ranges 36 

Graphite 186 

Padan, J. W. 

Offshore Resources (ICxclusive of 

Petroleum) 280 

I'arker, R. L. 

Niobium and Tantalum 284 

Peterson, G. L.. Gastil, R. G., and 
Allison, E. C. 

Geology of the Peninsular Ranges 70 
Repenning, C. A., Jones, D. L., and 
Addicott, W. O. 

Geology of the Great Valley 48 

Rice, S. J. 

A.sbestos 80 

Calcite, Optical Grade 114 

Ross, D. C. 

Quartzite and Quartz 340 

Also see under Stewart, J. H. 
Schambeck, F. J. 

See under Smith, M. B. 
Smith, A. R. 

Magnesium Compounds 235 



Smith, a. ]. 

Bromine HI 

Calcium Chloride 117 

Iodine 19S 

Potash 334 

Salt 356 

Sodium Carbonate 3S5 

Sodium Sulfate 389 

Smith, G. I., and Irwin, W. P. 

I^ithium 233 

Smith, M. B. 

Asphalt and Bituminous Rock 92 

Smith, M. B., and Schambeck, F. J. 

Petroleum and Natural Gas 291 

Smith, AV. C. 

Borax and other Boron Compounds 104 

Staler, H. K. 

Silver 381 

Stewart, J. H., and Ross, D. C. 

Geolog-y of the Great Basin South 

of the 39th Parallel 59 

Stewart, U. M. 

Lead ._ 210 

Stinson, M. C. 

Minor Metals 258 

Zirconium and Hafnium 448 

Thayer, T. P. 

Chromite 120 

Troxel, B. W. 

Wollastonite 441 

Walker, G. W., and Butler, A. P. 

Uranium 43G 

Weber, F. H., Jr. 

Barite 9 4 

Weiler, C. T. 

See under Burnett, J. T>. 
White, D. E., and McXitt, J. ll. 

Geothermal Knergy 174 

WithinKton, C. F. 

Gypsum and Anhydrite ISS 

Wright, L. A. 

Pyrophyllite 342 

Talc and Soapstone 414 












Senator Thomas H. Kuchel 






Printed for the use of the Committee on Interior and Inisular Affairs 

67-164 WASHINGTON : 1966 


On November 13, 1964, I requested the Secretary of the Interior 
to determine if a comprehensive summary report on the mineral and 
water resources of California could be prej^ared for the use of citizens, 
professional personnel, and government, civic, and industrial leaders 
interested in mining, water, and industrial development. 

This report-, prepared in response to my request by members of the 
U.S. Geological Survey, the U.S. Bureau of Reclamation, the U.S. 
Bureau of Mines, the California Division of Mines and Geology, and 
the California Department of Water Resources, with the cooperation 
of other individuals, is a thorough, detailed, and comprehensive work 
which I am sure will be of great value to all interested in the mineral 
and water resources of the State of California. 

I wish to express my thanks and appreciation to Secretary of the 
Interior Udall and to those in his Department, to the State of Cali- 
fornia agencies, and to all the individuals who contributed their efforts 
in compiling this very valuable and comprehensive report. 

Thomas H. Kuchel, 

U.S. Senator. 


Department of the Interior, 
Washington, D.C., March 26, 1966. 
Hon. Thomas H. Kuchel, 
U.S. Senator, Washington, D.C. 

Dear Senator Kuchel : We are pleased to transmit herewith part I 
of a summary report on the mineral and water resources of California 
which has been prepared in response to your request of November 13, 
1964, Part I is a summary report on the mineral resources. It has 
been prepared by the Geological Survey in collaboration Avith the 
California Division of Mines and Geology and the Bureau of Mines. 

This report covers all mineral commodities known to exist in poten- 
tially significant amounts in California. Because of the comprehen- 
siveness of the report, the discussion of each commodity is necessarily 
brief. The distribution and availability of the coimnodities are por- 
trayed graphically in numerous maps, charts, and diagrams. It is 
hoped that the report will provide the needed data and in a form 
that meets with your approval. 

A summary report, on the water resources of California, which you 
also requested, is nearing completion. It is being prepared as a com- 
panion volume to the report on minerals and will comprise Part II of 
the report. The manuscript for Part II will be transmitted to you 
as promptly as possible. 
Smcerely yours, 

Stewart L. ITdall, 
Secretary of the Interior. 



Part I. Mineral Resources 













(By J. P. Albers, U.S. Geological Survey, Menlo Park, Calif.) 

This report describes in siunmaiy form the mineral resources of 
California and includes a brief description of the geology. The use, 
mamier of occurrence, distribution, and outlook for all known mineral 
commodities in the State are discussed, and, where available, statistics 
on the production of the commodities are summarized. 

It is the purpose of this report to present an objective appraisal of 
California's mineral resources, based on information presently avail- 
able. The treatment of each commodity is necessarily brief, but those 
who wish to make deeper inquiry will "find the list of references after 
each article useful. 

The term "resources" as used in this report applies to materials in the 
ground that are known to be minable, and to materials that are not 
minable at present but which may come into such demand as to become 
minable in the future. "Reserves" are materials that may or may not 
be completely explored but may be quantitatively estimated and are 
considered to be economically exploitable at the time of the estimate. 
Reserves fluctuate because they are dependent on economic conditions, 
technologic factors, and available information. A low-reserve figure 
does not necessarily mean that the resource is near exhaustion. It may 
indicate that exploration is lacking or that a depressed market has 
lowered the value of the commodity to the point where the material can 
no longer be considered economically exploitable. "Ore" is mineral 
material that may be mined at a profit. 

The subject material and outline and the selection of authors of 
articles was worked out jointly by staff members of the U.S. Geological 
Survey and the California Division of Mines and Geology ; the ma- 
jority of the articles in this part were written by members of the U.S. 
Geological Survey, the California Division of Mines and Geology, and 
the U.S. Bureau of Mines, but three articles were written by university 
staif members who have special knowledge of the topic discussed ; one 
author, now employed by a private firm, w^as until recently with the 
U.S. Bureau of Mines. The organization w4th which an author is 
affiliated is shown with his name under the title of each article. 

John P. Albers, of the Geological Survey, w^th the editorial and 
coordination assis'tance of Richard M. Stewart, of the California Divi- 
sion of Mines and Geology, assembled and edited the report. 



The mineral industry of California 11 

Topographic and geologic maps 21 

Topography 23 

Geologic history of California 27 

Geomorphic provinces 35 

Geology of California Coast Ranges 36 

Geology of the Klamath Mountains 40 

Geology of the southern Cascade Range, Modoc Plateau, and Great 

Basin areas in northeastern California 43 

Southern Cascade Range 43 

Modoc Plateau 46 

Great Basin 47 

Geology of the Great Valley 48 

Geology of the Sierra Nevada 54 

Geology of the Great Basin south of the 39th parallel 59 

Geology of the Mojave Desert region 62 

Geology of the Transverse Ranges 66 

Geology of the Peninsular Ranges 70 

Geology of the Salton Trough 73 

Mineral resources 77 

Introduction 77 

Aluminum 79 

Antimony SI 

Arsenic 85 

Asbestos 86 

Asphalt and bituminous rock 92 

Barite 94 

Beryllium 99 

Bismuth 102 

Borax and other boron compounds 104 

Bromine HI 

Cadmium 113 

Calcite, optical grade 114 

Calcium chloride 117 

Carbon dioxide 119 

Chromite 120 

Clay 126 

Coal 134 

Cobalt 139 

Copper^ 141 

Diatomite 151 

Feldspar 158 

Fluorspar 165 

Garnet 168 

Gem stones 169 

Geothermal energy i 174 

Gold 179 

Graphite 186 

Gypsum and anhydrite 188 

Iodine 198 

Iron 199 

Kyanite, andalusite, and related minerals ^ — 212 

Lead 216 

Limestone, dolomite, and lime products 221 



Jlineral resources — Continued. Pa^e 

Lithium 233 

Magnesium compounds 235 

Manganese 243 

Mercury 247 

Mica (muscovite, biotite, and vermiculite) 254 

Minor metals 258 

Cesium and rubidium 259 

Gallium 259 

Germanium 259 

Indium 260 

Rhenium 260 

Selenium 261 

Thallium 261 

Molybdenum 262 

Natural gas liquids 269 

Nickel 279 

Niobium and tantalum 284 

Offshore resources exclusive of petroleum 286 

Peat 288 

Petroleum and natural gas 291 

Introduction 291 

United States rank as world producer of oil 295 

California's rank in United States production 295 

Geologic occurrence 295 

Economic factors affecting exploration 298 

History of discovery and development 302 

Discovery by prospecting near seepages, 1865-1907 302 

Discovery primarily by the use of geology, 1908-1935 303 

Discovery by the use of geology and reflection seismometry, 

1936 to present 304 

Natural gas 308 

Oil and gas provinces in California 311 

Los Angeles sedimentary basin 311 

Ventura sedimentary basin 313 

San Joaquin sedimentary basin 315 

Sacramento sedimentary basin 316 

Santa Maria sedimentary basin 317 

Salinas-Cuyama sedimentary basin 318 

Santa Cruz and Eel River sedimentary basins 319 

Offshore 319 

History of discovery and development offshore 321 

Resources 322 

Proved reserves 322 

Potential resources 325 

Onshore 325 

Offshore 326 

Selected references 327 

Phosphate 328 

Platinum group metals 332 

Potash 334 

Pumice, pumicite, perlite, and volcanic cinders 336 

Pyrophyllite 342 

Quartz crystal 344 

Quartzite and quartz 346 

Rare earths 350 

Salt 356 

Sand and gravel 361 

• Sands, specialty 369' 

Shale, expansible 374'' 

Silver 381 

Sodium carbonate 385 

Sodium sulfate 389 

Stone, crushed and broken 392 

Stone, dimension 400 


Mineral resources — Continued. P»so 

Strontium 408 

Sulfur 410 

Talc and soapstone 414 

Thorium 420 

Tin 422 

Titanium 426 

Tungsten 429 

Uranium 436 

Vanadium 439 

WoUastonite 441 

Zinc 444 

Zirconium and hafnium 448 


Plate 1. Geologic map of California facing 450 


1. Mineral production in California, 1900-1964 15 

2. Rehef map of California, showing geomorphic province boundaries 24 

3. Generalized stratigraphic correlation chart for California facing — 36 

4. Index map of Great Valley locating selected paleogeograpbic features. 51 

5. Trends in U.S. production and imports of antimony 82 

6. Antimony in California 84 

7. Principal asbestos deposits in California 90 

8. Asphalt and bituminous rock in California 93 

9. Baiite in California 96 

10. Beryllium in California 101 

11. Bismuth in California 103 

12. Boron in California 106 

13. Calcite (optical grade) in California 115 

14. Production of chromite in California since 1885 in relation to total 

United States production and consumption, world production, and 

domestic price 121 

15. Chromite districts and principal deposits in California 123 

16. Clays produced in California 132 

17. Coal in California 137 

18. Cobalt in California 140 

19. Copper production in California 1862-1964 143 

20. California copper production by decades, 1862-1964, showing produc- 

tion of major districts 144 

21. Principal copper localities in California by size categories based on 

production plus metal remaining in the deposits 146 

22. Regional distribution of diatomaceous earth in California 154 

23. Feldspar in California 162 

24. Fluorspar in California 166 

25. Selected gem stone localities in California — 172 

26. Thermal springs of California, showing localities that have been drilled 

for geothermal energy 176 

27. California's gold production 182 

28. Gold-bearing areas in California 184 

29. Production of gypsum in California, 1945-64 189 

30. Gypsum and anhydrite in California 191 

31. Iron ore in California 205 

32. Principal kyanite and andalusite deposits in California 215 

33. Lead deposits in Inyo County 219 

34. Principal limestone and dolomite districts in California _- 227 

35. Map showing locations of plants producing magnesium compounds in 

California, some areas with commercial grade dolomite, and selected 

magnesite deposits — 236 

36. Domestic production of magnesia from ores and brines in the United 

States, 1947-63 242 

37. Principal manganese mines in California 246 

38. Mercury districts in California 252 

39. Mica in California 257 


Figure Page 

40. Molybdenum in California 267 

41. Geographic distribution of natural gas liquids production in California. 270 

42. Production of natural gas liquids in California, 1911-64 271 

43. Production of natural gas liquids in California, by Counties, 1960-64. _ 273 

44. Nickel in California 281 

45. Niobium and tantalum in pegmatites in California 285 

46. Peat in California 290 

47. California oil fields 293 

48. California gas fields and principal productive sedimentary basins 294 

49. California oil and gas production in principal sedimentary basins, 

according to geologic age of i ocks 299 

50. Average price of California crude oil and natural gas 300 

51. Imports of crude oil and natural gas into California 300 

52. Oil disc very record for California by individual years 304 

53. Exploratory wells for oil and gas in California 307 

54. California crude oil production 308 

55. Southern and central California oil and gas fields facing 308 

56. Northern California dry gas fields 310 

57. California gas production 311 

58. California offshore oil production 323 

59. Offshore oil and dry gas production in Ventura sedimentary basin, Cali- 

fornia 323 

60. Estimated proved reserves of crude oil and natural gas in California, on 

January 1 of each year 325 

61. Phosphate in California 331 

62. Locations where platinum has been recovered in California 333 

63. Pumice, pumicite, perlite, and volcanic cinder deposits in California.- 341 

64. Pyrophyllite operations in California 343 

65. Quartz crystal deposits in California 346 

66. Rare-earths in California ^ 353 

67. Salt deposits In California 357 

68. California and U.S. sand and gravel production, 1920-64 364 

69. Major sand and gravel deposits in California 368 

70. Specialty sand deposits in California 373 

71. Annual production of expanded shale aggregate in California 376 

72. Expansible shale in California 377 

73. Silver in California 382 

74. Location of sodium carbonate producers in California 387 

75. Sodium sulfate deposits in California 390 

76. Principal crushed and broken stone quarries in California 395 

77. California dimension stone production, 1887-1963 401 

78. Principal sources of dimension stone in California 402 

79. Strontium in California 409 

80. Sulfur in California 411 

81. Talc mines in California 418 

82. Titanium deposits in California and types of ore 427 

83. Tungsten in California 434 

84. Uranium in California 437 

85. Vanadium in California 440 

86. Wollastonite in California 443 

87. Principal zinc mines in California and types of ore 446 

88. California placer deposits containing above average zircon concen- 

trations 450 


1. Mineral commodities in which California ranked first in production in 

1963 11 

2. Mineral commodities in which California has ranked in the top three 

States in production at various times in recent years 11 

3. Mineral production in California, 1963 and 1964 79 

4. Properties of asbestos minerals 87 

5. Asbestos production in California, 1887-1964 89 

6. Barite deposits of California 97 


Table Pago 

7. World production and United States consumption of beryllium in 

short tons 100 

8. Beryllium deposits in California 100 

9. Principal boron compounds and minerals of California 105 

10. Analyses of waters containing high concentrations of calcium chloride. _ 117 

11. Percentage of carbon dioxide in natural gas from representative Cali- 

fornia fields. 120 

12. U.S. and California clay production, 1963 130 

13. Classification of coals by rank 136 

14. Range of analyses of representative California coals, as received basis.. 138 

15. Copper production in California, 1862-1964 145 

16. Principal copper localities in California 147 

17. Principal formations containing diatomaceous earth in California 155 

18. Reported feldspar deposits in California 163 

19. Areas explored by drilling for geothermal energy in California, with 

pertinent data 177 

20. Production of electricity in kilowatt hours. The Geysers Power Plant, 

Pacific Gas and Electric Co., Sonoma County, California 178 

21. Distribution of calcium sulfate in California 190 

22. Iron ore districts, mines, deposits, and prospects in California 202 

23. United States production of kyanite and synthetic muUite, and imports 

and exports of kyanite (short tons) 213 

24. California consumption of limestone and dolomite during 1964 221 

25. Plants producing synthetic magnesia, other magnesium compounds, 

and calcined dolomite in California, 1964 237 

26. Salient statistics on magnesite, magnesia, and dead-burned dolomite.. 239 

27. Mica and vermiculite occurrences in California 256 

28. Molybdenum deposits in California 264 

29. Production of natural gas liquids in California, 1911-64 271 

30. Production of natural gas liquids in California, by counties, 1954-64 — 272 

31. Operating natural gasoline and cycle plants as of January 1, 1964 275 

32. Comparative values of California's total mineral production and natural 

gas liquids, 1954-64 278 

33. Price per gallon and total value of natural gas liquids, by type, 1954-64. 279 

34. Estimated proved recoverable reserves of natural gas liquids in Cali- 

fornia and in the United States, December 31, 1964 279 

35. Oil and gas production and reserve data for six leading producing 

States 296 

36. Giant oil fields in California ^- 306 

37. Summary of the features of pumice, pumicite, perlite, and volcanic 

cinder deposits of California 339 

38. Rare-earth mineral occurrences in California 352 

39. Estimated production capacity, sea water-evaporation plants in Cali- 

fornia 356 

40. Salt deposits with record of production in California 359 

41. Principal sand and gravel producing areas (exclusive of specialty sand 

operations) 366 

42. Specialty sand deposits in California 372 

43. Silver in California (From U.S. Geological Survey Mineral Investiga- 

tions MR-34) 383 

44. Chemical analyses of brines 388 

45. Sodium sulfate deposits in California 391 

46. Principal crushed and broken stone quarries in California 393 

47. Pyrite and pyrrhotite production from which sulfur was recovered 412 

48. Shipments of tungsten ore and concentrates from California mines 

1906-1957, in short tons of 60 percent WO3 432 

49. Tungsten mines or districts in California with combined production 

and reserves exceeding 10 tons tungsten 435 

67-164 O— 66— pt. I- 


(By Ian Campbell, Chief, California Division of Mines and Geology, 

San Francisco, Calif.) 

In 1965, 117 years after John Marshall's historic discovery of gold 
at Sutter's mill, the California legislature enacted a bill (SB 265) de- 
signating native gold as the official "State Mineral." In the same bill, 
the legislature designated serpentine as the official "State Rock." The 
one designation may be somewhat overdue; the other is assuredly 
timely. For in 1852, only four years after Marshall's discovery, Cali- 
fornia's gold production reached a total of more than $81,000,000 (at 
the current price of gold, this would be almost $140,000,000), a figure 
never since equaled. In that year serpentine was virtually unnoticed — 
except as "hungry rock," i.e., known to be barren of gold and therefore 
something to be shunned by prospectors. 

In 1964, however, California's gold production had dropped to less 
than $2,500,000 — the lowest figure since 1848. Serpentine (in the form 
of chrysotile asbestos), which until very recently California had never 
produced in amomits of more than a few hundreds of tons annually, 
had increased in value from less than $25,000 in 1960 to nearly $4,500,- 
000 in 1964, with promise of further increases over the next many years. 
Wittingly or not, the legislature, in calling attention to gold and ser- 
pentine, had most appropriately commemorated nearly four genera- 
tions of mining history and economics. 

In 1962, California became the "first state" (in population). Yet 
she had already achieved more "firsts" in mineral production than had 
any other state. In 1963, she stood first among the states in annual 
production of : 

Table 1 

[In thousands] 

Asbestos $1,547 

Boron 54,981 

Cement 147.656 

Diatomite C) 

Mercury 2,575 

Pumice $2,017 

Rare earths C) 

Sand and gravel 128, 178 

Talc 1, 427 

Tungsten C) 

1 Figures are confidential. 

And California, in addition to these current "firsts," has been at 
various times in recent years among the top three States in the pro- 
duction of: 

Table 2 


Lithium salts 


Calcium chloride 

Refractory and caustic 

Sodium carbonate 



Sodium sulfate 


Natural gas liquids 




Sulfur ore 







Iron ore 




Only three States surpass California in the value of their total 
production of fuels; a few exceed California in the total value of 
metallic minerals; a very few are ahead in the total of industrial 
minerals. But no State comes even close to California in averaged 
rank with respect to all three of the components of the minerals in- 
dustry. Nor does any other State approach California in the num- 
ber (80) and diversity of commercial mineral products. What has 
led to this preeminence? The answers lie in the history and in the 
geology of the State. 

Inadequate as the early records are, there is no doubt but that 
metals, nonmetals, and fuels had all been produced in California, in 
small amounts, long before the coming of the Forty-niners. Yet it 
was not until 1849 that mining became significant in the history or 
the economy of the State. From that date, thenceforward for many 
^-^ears, mining (and this meant essentially gold mining) was a domi- 
nant factor. The "California gold rush," precipitated by Marshall's 
1848 discovery, represented a mass movement of people and a redi- 
rection of the hitherto well-established pastoral economy that, even 
in the hindsight of history, is difficult fully to appraise or appreciate. 
Thus the Californian of the mid-twentieth century complains, or 
boasts, or stands in awe (as the case may be) of "the population ex- 
plosion" that saw the State's population, between 1948 and 1960, in- 
crease by a factor of about 57 ])ercent. He has forgotten (or never 
knew) that between 1848 and 1860 the State's population expanded 
from 14,000 to 380,000— an increase of 2700 percent ! It was gold that 
brought about that phenomenal growth, and it was gold that, for many 
years, principally sustained the State's burgeoning economy. Gold 
constituted new wealth, provided new capital in lavish amoimts, and 
made possible new investments which in turn exDanded and diversified 
the economy. If California's annual productioji of gold today seems 
minuscule by comparison with the production of grapes, or cotton, 
or airj^lanes, or motion pictures, California should never forget the 
legacy she owes to her gold which, in a ven^ real sense, made possible 
the State's present preeminence and her affluent economy. 

In retrosi^ect, it is a remarkable circunxstance that such an army of 
gold seekers as constituted the Forty-niners and their immediate fol- 
lowers, most of them wholly unsuited to, and inexperienced in, mining 
practice, should have been so successful. Although it would be im- 
possible to document, it would probably be a fair statement to say 
that in so short a time no mining venture, before or since, has at- 
tracted so large a number of people ; and that of these so few had had 
any previous mining experience. Yet their suc^ess^whatever may 
have been the ups and downs in the fortunes of individuals — is at- 
tested by the more than half a billion dollars of gold produced in 
just the first decade after the discovery. And this success — whatever 
it may have owed to the perseverance and ingenuity of amateurs 
turned miners — was largely conditioned by the favorable geology. 
Nowhere, before or since, lias so much gold been laid out, almost ready 
to hand, by nature. Here is not the pla<^e to detail the metallogenic 
and geomorphic events that conspired to spread these riches along 
the foothills of the Sierra Nevada and elsewhere in the State. Suffice 
it to say that the values in the first, easily discovered and easily 


worked placers, provided the capital and the modicum of exerience 
necessary to develop the more difficult, but often more rewarding 
"hicrh bench gravels" and so on to the "drift mines" and, eventually, 
the great "hydraulic mines," the gold dredges and the lode mines 
Avhich, with the pittances now being added by the recent innovation 
of "skin-diving for gold," have brought the State's total production 
of gold to the impressive figure of more than 2i/<{ billion dollars. The 
bulk of this, be it remembered, was produced when the price of gold 
was only $20.67 an ounce, and when a dollar was worth many times 
what it is today. 

If the favorable-to-mining character of California's geology had 
first been demonstrated in the distribution of j>lacer gold in a region 
where it was relatively easy to win, and where life was relatively 
easy to sustain, it was further demonstrated in the distribution of 
mercury, which for many years was second only to gold in the State's 
mineral production. Nowhere else in the world have imj^ortant de- 
posits of mercury existed withm easy access of inajor deposits of 
gold. Yet the fact is that the New Almaden mine, the largest pro- 
ducer of mercury in North America, had been discovered in 1845 and 
lay less than 100 miles from the gold of the Mother Lode! Nor 
was the New Idria, se^-ond in total production to the New Almaden, 
much farther away. These convenient and relatively economical 
sources of quicksilver made for ready application of the amalgama- 
tion process, then the most efficient method for extraction of free gold 
from gangue, and thereby further enhanced the mining economy of 
the State. 

If the early ^old seekers were largely amateure when they arrived 
at the "gold diggins," they of necessity soon became professionals. 
California's isolation from the manufacturing centers of the eastern 
seaboard not only called for development of ingenuity and imiovation 
in local mining enterprise, but led also to local foundries, local machine 
sJiops, and to adaptations to local needs — many of which contributed 
to widespread improvements in mining and milling methods. The 
first major transportation of water in the State (still an item of utmost 
concern to California) came about in order to supply the huge hy- 
draulic mines, themselves a major mining development of the time. 
Philip Diedesheimer, at Georgetown, California, in 1859, perfected 
square-set timbering, later to prove so important on the Comstock 
lode. Stamp mills, of a size and efficiency never before dreamed of, 
became realities. Years later (in 1918) another California develop- 
ment, tlie Gould Furnace with its greatly increased efficiency, proved 
a boon to mercury mining in the State and throughout the world. 
Nor should it be forgotten that the Cottrell Filter, a significant step 
in making mineral processing compatible with agriculture and even 
with urbanization was initially a California development. 

Nevertheless, despite discoveries of new deposits, new developments 
in mining practice, and greater experience on the part of the miners, 
the inexorable economics of a non-renewable resource (increasing costs 
of operation and/or exhaustion of the mines) inevitably became felt 
in the gold-mining industry of the State. In addition, three other 
widely spaced events contributed to what currently amounts almost to 
the demise of this industry. The first (in 1880) was the "Sawyer 


decision" making illegal any mining activity which dumped excessive 
amounts of silt into streams, with consequent harmful effects on fishing 
and agriculture. Next there came, in 1941, the somewhat misnomered 
"gold mine closing act" (L-208), an order issued by the War Produc- 
tion Board primarily as a means of furthering needed war industries, 
but which nevertheless did effect the closing of most gold mines. And 
the third factor has been the postwar continuing rise in the costs of 
labor and materials which has essentially squeezed — against the pegged 
price of gold of $35 an ounce — ^the remaining life out of such mines 
as were able to resume production following World War II. 

Because gold has constituted such a large proportion of California's 
output of metallic minerals, the very significant production of other 
metallic minerals has not always been fully appreciated. Mercury has 
already been mentioned as antedating gold and as being currently, and 
for many years past, one of the "California firsts," both in total and in 
amiual rank of production. As early as the 1850's, prospectors, 
whether disappointed in their gold mmes or otherwise seeking diversi- 
fication, discovered and developed deposits of silver, copper, lead, and 
zinc. Beginning about 1870, California was for some years the lead- 
ing producer of chromite in the country, and was even exporting to 
England. This industry incidentally underwent spectacular revival 
in the State, under the impetus of greatly increased prices, during the 
two world wars, contributing significantly to supplies of this strategic 
metal. Manganese and tungsten mining have likewise been highly 
responsive to war demands and price increases. Lacking war-time 
bonuses and post-war subsidies, manganese is no longer being mined 
in the State; tungsten — by virtue of the tremendous developments at 
the Pine Creek deposit in the eastern Sierra Nevada — still is bemg 
produced, along with significant amounts of by-product molybdenum. 

One war-torn development, among the metal mines, has grown and 
is continuing to grow : mining of iron ore. Until the onset of World 
War II, California was virtually without an iron and steel industry. 
Mineral economists, although aware of deposits of iron ore within the 
State, had tended to discount the deposits as "too erratic" and, since 
the State lacked any local sources of coal and coke, many predicted 
that there would never be an iron and steel industry in the State. They 
had not fully foreseen the impetus of war demands, and the needs of 
the post-war expanding population. Currently, iron ore is being pro- 
duced not only in amounts sufficient to supply the fully integrated 
Fontana plant of the Kaiser Steel Co., but also in significant amounts 
for export to Japan. 

Important as all of these metallic minerals have been, and are, they 
constitute today only a very minor part of California's mineral in- 
dustry. Almost unheralded, the industrial minerals ("nonmetals") 
long since overtook the metals in terms of value in the State's econo- 
my (figure 1). The figures stand today at more than $500,000,000 
annually for the industrial minerals, versus slightly less than $60,000,- 
000 for the metals. And the trend of the industrial minerals has been 
steeply upward for over twenty years. 


$ 1 .300 


$998. 152.000 

503.917.000 ;■ 
1964) ^ 

$256,000,000 /^ 


;>v:'all.metaj.s^— ^ 

/ $58. 441.000, 

"/•>7$55,000. 000 
/$2, 486.000^ 

;-.. (1964),r:r> 
^'r;'~ — GOLD 

-] 1 ^ 

1900 1910 192 1930 1940 1950 1960-64 

FiGUBE 1. Mineral production in California, 1900-64, 











2 00 









As far back as the late 1850's, a San Francisco physician, Dr. Jolin 
A. Veatch, was spending his summers traversing the t^tate in horse and 
buggy, looking for sources of borax, then in demand chiefly for its 
medicinal virtues. His discovei-y of borax crystals in the muds of 
Borax Lake, and the subsequent story of borax in California consti- 
tutes one of the more fascinatincr records of nonmetallic mining his- 
tory. It IS a story of how the geography of the industi-y shifted from 
the lake muds in Lake County, to the "salt marshes" of southeastern 
California and Nevada, to Death Valley and to Calico, and eventually 
to Searles Lake and the Kramer district ; of how the geology and 
mineralogy shifted from borax to ulexite, to colemanite, to kernite, 
and now to brines and to borax again (with colemanite once more 
looming over the horizon) ; and of how^ prices have dropped (vis-a-vis 
the Consumer Price Index) and of how demand and production have 
increased — to the point where boron and boron compounds have for 
many years exceeded in value the State's gold production and have 
constituted the State's principal export mineral, contributing signifi- 
cantly to the "favorable balance of trade" enjoyed by the State's 

If the history of California borax mining provides contrasts with 
gold, other industrial minerals provide additional contrasts — with 
both gold and borax. This is particularly true of the constniction 
materials, especially rock, sand and gravel. These are commodities 
that, unlike gold and borax and many other minerals, depend for their 
demand on density of population more than upon special qualities and 
rarity of occurrence. And these are commodities which, because of 
their bulk, seldom enter significantly into interstate — much less inter- 
national — commerce. They are therefore relatively imnimie to the 
effects of changing tariifs, subsidies, import quotas, and international 
cartels, and to this extent provide a less fluctuating and a sounder ele- 
ment in the mineral economy. Yet sand and gravel, except such as was 
mined incidental to the recovery of gold, did not even figure in the 
early records of the State's mineral production. Today, with an an- 
nual output of nearly 113,000,000 tons, valued at nearly $130,000,000, 
sand and gravel is the State's leading mineral industry in terms of 
volume, and shares with cement the top place in value among the 
State's "hard minerals." 

Nevertheless, the industrial minerals are not without their problems. 
If the sand and gravel industry is dependent on population growth, 
the spread of population is rapidly threatening to become a deterrent 
to the industry, in that "suburbia" is already in competition with the 
needs of the industiy for the acreage that constitutes its "ore." Like 
any other mineral, suitable deposits of sand and gravel are severely 
limited in their occurrences by the facts of geology. And deposits are 
further limited by the facts of economics: bulk materials cannot be 
moved long distances without incurring prohibitive cost. Yet, in a 
number of instances, the sand and gravel industry is being "zoned out 
of its own holdings" through the spread of urbanization and the lack 
of imderstanding, on the part of the public, of the geology and eco- 
nomics of the situation. Without an understanding, "suburbia" will 
soon be in the position of denying to itself (except at greatly increased 


costs) the very materials on which its own g^o^vth (homes, streets, 
schools, public buildings, etc.) depends. The problem — be it noted— 
is basically a man-made problem and offers hope, therefore, that man 
will eventually resolve it. 

Is oil a mineral ; is natural gas a mineral ? Even to suggest that these 
are minerals would raise the hackles of some semantically inclined 
mineralogists; but to suggest that they are not will assuredly raise the 
hacldes of every mining and petroleum engineer and economic geol- 
ogist. Although the definition may be "largely of academic interest," 
the practical fact is that petroleum and related products constitute 
mineral resources as truly as do gold and silver and borax and asbestos. 
Principles of exploration and extraction and processing, and even of 
marketing, may differ in details but in broad fundamentals of geology 
and of economics they are the same. Certainly, therefore, any intro- 
ductory discussion of the State's mineral industry must call attention 
to the "black gold" Avhich for many years has been its premier mineral 
resource. Inasmuch, however, as there is extensive discussion of this 
most important industry in a following chapter, only certain salient 
features will here be mentioned. 

Although oil seeps and tar sands were known to the Indians and 
were very locally exploited during the Spanish regime, significant 
commercial production of oil did not get under way in California until 
1876, with the initial development of the Newhall field. This was at 
a time (further evidence that the gods continued to smile on Cali- 
fornia ! ) when the production of the "yellow metal" had declined dras- 
tically from the flush years of the 185d's and 1860's (see fig. 27) . As a 
result the growth of the "black gold" industry came at a particularly 
opportune time for the State's economy. Subsequent production rec- 
ords (see fig. 54) have placed California second only to Texas in total 
production of oil, and have clearly placed oil as the State's No. 1 min- 
eral resource. It is of interest, too, to note that the banner year for 
gold came in 1852 ; the banner year for oil, 105 years later, in 1957. 
From this, one might perhaps predict that significant amounts of oil 
will still be produced in the State 100 years from now, just as gold is 
still a multi-million dollar industry more than 100 years after Mar- 
shall's discovery. That decline in petroleum production has set in, 
is shown by the charts, but that the decline is recently being arrested 
is also shown. This comes about through important new discoveries — 
particularly of gas fields; through improved secondary recovery 
methods (primary recovery, even with modern methods, still leaves 
50 to 75 percent of the oil "in the ground) ; and through adjudication 
of jurisdictions which now^ permit development of off-shore oil poten- 
tial, in particular of the East Wilmington field, destined to be one of 
the country's great oil fields. 

All of California's oil and gas occurrences are directly related to 
her complex geology which — ^because of the complexity — ^^has called for 
exceptionally sophisticated (and expensive) geological and geophysi- 
cal approaches to the problems of discovery and exploitation. For the 
same reason, successful solutions have been exceptionally rewarding. 
Thus the yield of the average California oil well is anticipated to be 
more than three times that of the average well in the United States, 


and in some fields as many as 10 separate zones, over depth intervals of 
more than 6,000 feet, have been commercially developed. Small won- 
der, then, that the California petroleum industry has long enlisted 
exceptionally able management, exploration and engineering teams in 
order successfully to develop this major mineral resource. 

Production records for the major components of California's min- 
eral industry have been given in figure 1. To what extent can growth 
lines justifiably be extended into the future? Projections are no more 
than predictions, but prediction can in this case be based on the facts 
of geology and history. California has been peculiarly blessed with 
a complex geology, doubtless in part the result of the "unease" of the 
crust, described in the chapter on Geologic History of California. The 
distinctive geology has in turn provided an unequalled diversity of 
minerals, many in notable concentrations. The chapter headings in the 
Table of Contents of this volume document the great diversity of use- 
ful mineral products enjoyed by the State — a most favorable factor in 
her economy. Mineral-wise, California is far from the "one-crop" 
State she once was in the hey-day of gold mining. Moreover, a greater 
number of different minerals (over 700 distinct species) are known to 
occur in California, and more minerals (45) not as yet known any- 
w^here else in the world, occur in California than in any other state. 
And, mining history in California has built a tradition of exploration 
and innovation — a recent example being the successful harnessing of 
geothermal power at The Geysers — ^the first, and still the only such 
development in North America. 

With the combination of men and minerals to be found in the State, 
the future of the mineral industry should indeed be bright. But there 
are many who, with considerable justification, view it with misgivings. 
These stem from a recognition of two trends. One of these is the 
growing conflict over land use. As mining turns more and more to 
open pit, and to larger and larger operations, more acreage is involved, 
and more public pressure develops to insist on other uses for such 
acreage, whether for recreation, for urbanization, for "wilderness," 
or just '"''anything but mining !" The other trend is towards lesser in- 
volvement of fewer people in the mineral industries. This results 
partly from changes within the industry whereby smaller operations, 
involving in the aggregate many men, are giving way to larger oper- 
ations involving huge capital outlays and often fewer men. (For ex- 
ample, to install the new Redding operation of the Calaveras Cement 
Co. — a relatively small operation, as some cement plants go — required 
some $16,000,000 in capital outlay. On a weekend, when the mine is 
shut down, the largely automated mill, which has an annual capacity 
of 1,500,000 barrels, can operate with only five men ! And the con- 
version a few years ago of the underground mine of the U.S. Borax 
and Chemical Corp. at Kramer to an open-pit operation, and instal- 
lation of a new" mill, required an initial capital investment of around 
$20,000,000. Yet the number of miners and millmen has decreased 
at the same time that output was being increased.) The increasing 
number of mergers, and the absorption of small companies by larger 
in the petroleum industry is further testimony to the changes that are 
going on. The net effect of these trends — greatly amplified by popula- 
tion growth, per se — is that, whereas 100 years ago almost every Cali- 


fornian had some familiarity, and many were directly involved, with 
the mineral industry, today scarcely one in a thousand has any con- 
cept of how dependent he is, at virtually every turn of his everyday 
life, on the products of mines and oil wells. Far less does he have any 
concept of mineral industry operations, economics, or geology. It is 
these people who now frame the laws under which the industry must 
operate. It has been well said that government — Federal, State, and 
local — "calls the turns" on the fortunes of the mineral industry as 
never before. California has most favorable geology; she has the 
mineral resources; she has the wherewithal for maintaining a minerals 
industry second to none. Will her citizens prove sufficiently know- 
ledgeable to meet the challenge? That is the question that now looms 
largest in California's unfolding mining history. 


(By J. P. Albers, U.S. Geological Survey, Menlo Park, Calif.) 

Topographic maps show the surface features of a region, including 
mountains, valleys, rivers, lakes, and man-made features. Such maps 
are essential to the comprehensive development of the natural re- 
sources of the State and are extremely useful to engineers, geologists, 
administrators, conservationists, foresters, economists, planners, 
farmers, and many others. 

Topographic maps are prepared at different scales, depending on 
the map's purpose. Larger-scale maps show more details than small- 
scale maps. The standard topographic map scales of the U.S. Geologi- 
cal Survey are 1 : 24,000 and 1 : 62,500. A topographic quadrangle 
map at scale 1:24,000 (1 inch =2,000 feet) covers a rectan^ilar area 
measuring 7i/^ minutes of latitude by 71^ minutes of longitude, and 
a map at 1: 62,500 scale (approximately 1 inch=l mile) covers a rec- 
tangular area measuring 15 minutes of latitude by 16 minutes of longi- 
tude. Topographic maps of much larger areas at scales of 1 : 250,000, 
1 : 500,000, and 1 : 1,000,000 are commonly prepared by compilation 
processes from the 7i/2-minute and 15-minute topographic maps. 

A map showing the topography of California has been published 
by the U.S. Geological Survey (1953) at a scale of 1:500,000, and 
maps prepared by the Army Map Service covering 2° of longitude 
by 1° of latitude at a scale of 1 : 250,000 are also available for the 
entire State. Fifteen-minute quadrangle maps are available for nearly 
the entire State, and 7%-minute quadrangle maps cover much of the 
western part of the State. Any of these maps may be purchased by 
mail from the U.S. Geological Survey, Denver, Colorado, or over the 
counter at Los Angeles, Menlo Park, and San Francisco, California. 

Geologic maps show the distribution of rock units at the surface of 
the earth. Such maps are fundamental for the intelligent exploration, 
development, and appraisal of mineral and water resources of a region, 
and they are being used increasingly in planning and engineering 
urban development and highway construction. The geology is gen- 
erally plotted on topographic base maps, and consequently geologic 
maps are usually published at the same scale as the topographic base. 
Most geologic mapping is done at scales of 1 : 24,000 or 1 : 62,500 but 
larger scales (1: 12,000 and larger) are becoming increasingly wide- 
spread, particularly for pointing out geologic conditions and hazards 
that need to be evaluated in areas of mushrooming urban development. 
Large-scale maps are also commonly employed in the evaluation of 
highly mineralized areas, but other scales are also employed, depend- 
ing on the purpose. 

A geologic map of California is being prepared by the California 
Division of Mines and Geology on topographic base maps at 1 : 250,000 



scale. Of the 27 sheets required to cover the State, 21 had been 
pubhshed at the end of 1965. Much of the geology on these sheets is 
necessarily based on reconnaissance geologic mapping as less than 
25 percent of the State has been mapped at scales considered adequate 
for most purposes. Plate 1 of this report is a geologic map at scale 
1 : 2,500,000 compiled from the 1 : 250,000-scale sheets. It therefore 
portrays the geology only in a very generalized form. 


(By J. P. Albers, U.S. Geological Survey, Menlo Park, Calif.) 

California's landscape, embracing 158,297 square miles, is, like its 
geology, extremely varied. Viewed overall, the dominant topographic 
features of the State are the Great Valley (also known as the Central 
Valley), the Sien-a Nevada, and the Coastal mountains (fig. 2). The 
Great Valley is a vast elliptical bowl 400 miles long by about 50 miles 
wide whose floor stands a few tens to a few hundred feet in altitude. 
It is boimded on the east by the mighty Sierra Nevada with its south- 
westward extension the Tehachapi Mountains, on the northeast by 
the rugged Cascade Mountains, and on the west by the Coastal moun- 
tains, including the Klamath Mountains and California Coast Ranges. 
The northern part of the Great Valley is drained by the southward- 
flowing Sacramiento River system and the southern part is drained by 
the northward-flowing San Joaquin River system. About 30 miles 
west of the city of Stockton, the two drainage systems converge, and 
the waters find their way to the ocean through the only exit from the 
mountain-rimmed valley via San Francisco Bay and the Golden Gate. 

Lofty mountain peaks that tower above precipitous gorges and 
canyons characterize the contour of the Sierra Nevada. The highest 
peaks, including Mount Wliitney (14,495 feet) are in the southern 
part of the 385-mile-long range, and the altitude of the range crest in 
general declines toward the north, where the altitude of the highest 
peaks is less than 8,500 feet. The Sierra Nevada is a gigantic fault 
block about 80 miles wide tilted westward, and the gentle western 
slope is traversed by about a dozen major streams that flow into the 
Sacramento and San Joaquin Rivers in the Great Valley. Many of 
these westward-flowing streams occupy deep valleys — some as much 
as half a mile deep. By far the most rugged and spectacular valley is 
"The Incomparable Valley'" — Yosemite — carved largely by ice many 
thousands of years ago and through which now flows the Merced River. 
The east side of the Sierra Nevada through much of its length drops 
precipitously into Owens Valley. In the vicinity of Momit Wliitney 
the relief measures nearly 2 miles in a horizontal distance of only 
6 miles. 

North of the Great Valley and north of the Sierra Nevada the land- 
scape is dominated by two volcanic mountains, Lassen Peak (10,457 
feet) , and towering Mount Shasta (14,162 feet) . East of these peaks 
is the Modoc Plateau with an average altitude of about 5,000 feet but 
above which numerous volcanic cones rise as much as 2,000 feet. In 
the extreme northeast comer of the State, the rugged Warner Moun- 
tains, culminating in Eagle Peak (9,883 feet), tower nearly a mile 
above the general level of the Plateau. 

Northwest of the Great Valley is an area of complex rugged topog- 
raphy known as the Klamath Mountains. The highest peaks — Mount 




Eddy, and Thompson Peak— ascend to about 9,000 feet, and the prni- 
cipal rivere— the Khimath and Trinity— have cut deep twistnig gorges. 
In contrast to" the Khimath Mountains, the California Coast Kanges, 
extending for nearly 600 miles south-southeast from the Oregon 
border, and lying between the Great Valley and the ocean, are mark- 
edly linear in character. They consist of numerous, often mdistnict, 
ridges from 2,000 to 7,500 feet high separated by the valleys of such 
rivers as the Eel, Mad, Russian, and Salinas, as well as smaller 

. {' A-i^ 

FiGUBE 2. Relief map of California, showing geomorphic province boundaries. 


South and southeast of the Sierra Nevada, and extending to the 
California border at the Colorado Eiver is a great expanse of desert 
terrain characterized by short rugged mountain ranges, immense sandy 
valleys, and dried lake bottoms. Most of this area is known as the 
Mojave Desert, but the extreme sovithem part of the area is referred 
to as the Colorado Desert (Salton Trough geomorphic province). A 
feature peculiar to the region is that most of the rivers dry up in 
the valleys by evaporation. The Salton Sea in the southern part of 
the desert region is about 250 feet below sea level and the highest 
peaks in the region rise to nearly 7,500 feet. 

The region north of the Mojave Desert and east of the Sierra 
Nevada is also desert, made up of extremely rugged, linear ranges 
that attain altitudes of more than 14,000 feet. The highest peak is 
White Mountain Peak (14,242 feet) near the Nevada border. Other 
prominent topographic features of this region, which is part of the 
Great Basin geomorphic province, are Owens Valley and Death 
Valley; the lat'ter includes the lowest point on the North American 
Continent at 282 feet below sea level. This lowest point is only 80 
miles from Mount "V^Hiitney, the highest point in the conterminous 
United States. 

West of the Mojave Desert and south of the Great Valley and Coast 
Ranges a group of linear ranges trends generally west, across the 
northwestward grain of topography that typifies much of the rest of 
the State. These ranges, of which Santa Rosa and Santa Cruz Islands 
are a seaward extension, attain maximum altitudes of about 10,000 
feet m the San Gabriel Mountains just north of Los Angeles. The 
metropolitan area of Los Angeles is built on a broad coastal valley 
that stands in general only a few^ tens of feet above sea level. Hence, 
the relief in the immediate vicinity is nearly 2 miles. Southeast of 
the valley in which Los Angeles is situated a group of northwest- 
trending ranges extends southward into Baja California and is known 
collectively as the Peninsular Ranges. The highest peak in these 
ranges (San Jacinto) rises to 10,831 feet but the general altitude of 
the range crests is variable and in general much lower. 

67-164 O — 6i6— pt. I- 


(By P. B. King, U.S. Geological Survey, Menlo Park, Calif.) 

To the earth scientist, California is a region of surpassing interest, 
as it is a virtual laboratory of geology in the making. Scientists and 
non-scientists alike are aware of its frequent earthquakes, some of 
destructive intensity. These are manifestations of the region's uneasy 
crust; the geologist finds even more eloquent manifestations of such 
unease in the great faults that interlace the State, along which the 
rocks have been shifted even in modern time, and in the steep up- 
ending of some of the very youngest stratified rocks. 

California's crustal unease is related to its coastal position; the 
State is, in fact, but one segment of a zone of unease that extends 
nearly around the Pacific Ocean border, into South America in one 
direction, and through Alaska, Japan, and Indonesia, in the other, 
whose bolder manifestations are its many erupting volcanoes and 
destructive earthquakes. California is the daughter of the North 
American continent and the Pacific Ocean basin; according to one 
plausible hypothesis it was once a part of the ocean basin, and since has 
been built up by earth forces to become part of the continent. 

Mostly, we know California's geologic history during the last 230 
million years (during Mesozoic and Cenozoic times). The record of 
earlier times is known only in places ; elsewhere it has been obliterated 
by the crowded events of later times. 


The record of earlier events is most plentiful nearest the continental 
interior — in the desert ranges east of the Sierra Navada and in south- 
eastern California (the Great Basin and Mojave Desert of the map). 
Here, the oldest rocks that emerge are a basement complex of Pre- 
cambrian granites and gneisses that has yielded isotopic ages of 1,000 
million to 1,300 million years. (Some granites and gneisses of about 
the same age also occur nearer the coast in the highly faulted Trans- 
verse Ranges north of Los Ang eles and San Ber nardino, but their re- 
lations to the surrounding rocks are not as"clear.) In the desert 
ranges this basement is followed in places by sedimentary strata of 
younger Precambrian age, and is covered even more widely by Paleo- 
zoic strata (formed between 600 million and 230 millions years ago) ; 
in some areas the Latter total 10,000 or 20,000 feet in thickness. For 
the most part, these strata are the products of sedimentation in shallow, 
quiet seas which spread from time to time over the edges of the conti- 
nent. Many of the strata are limestone, containing fossils of shelly 
marine organisms; some strata are quartz sandstone and mudstone, de- 
rived from the waste of the continental interior. 

Paleozoic strata are preserved farther west, in the Sierra Nevada 
and Klamath Mountains, but in smaller fragments that are greatly 



interrupted by younger rocks. Here limestone is very subordinate, 
and most of the strata are mudstone and coarser, poorly washed, dirty 
sediments (graywackes), interrupted in places by lava flows, some of 
which contain a pillow structure which indicates that they were 
erupted under water. In this western area we have seemingly entered 
another Paleozoic world — one not truly a part of the continent, but 
rather, a world along the border of the Pacific Ocean. 


In the Sierra Nevada and Klamath Mountains these Paleozoic strata 
are succeeded by others of Triassic and Jurassic age (formed between 
230 and 135 million years ago), which are so similar to them that they 
are difficult to distinguish except for occasional happy discoveries 
of diagnostic fossils. Evidentlv the world of the Pacific Ocean border 
still persisted here in these times — with its muddy and dirty sediments 
and its eruption of submarine lavas. 

But mighty events were in the making, which reached a climax 
late in Jurassic time. In the Sierra Nevada we find that all the 
strata — Paleozoic, Triassic, and Jurassic — have been turned steeply on 
end, and have been so changed by heat and pressure that they are now 
honifels, slate, or even crystalline schist. They have, further, been 
invaded, distended, or broken off by granitic rocks, which ascended 
into them from deeper levels in the crust. In the western foothills of 
the Sierra Nevada the granitic rocks form small dispersed bodies, but 
in the higher parts of the present range to the east they coalesce into 
a vast, nearly continuous body, known as the "Sierra Nevada batho- 
lith." Emplacement of the granitic rocks occurred during and after 
the upending of the strata in which they are embedded; isotopic de- 
terminations indicate that emplacement extended through a period of 
nearly 100 million years, or from early in the Jurassic until late in 
the Cretaceous, but the greatest volumes were emplaced mainly dur- 
ing Late Jurassic and Early Cretaceous times. 

Similar granitic rocks, enclosing small to large remnants of the 
earlier strata, occur in the higher mountains throughout the length of 
California — the Klamath Mountains, the Sierra Nevada, the Trans- 
verse Ranges, and the Peninsular Ranges (from which they continue 
southward into Baja California). An outlier of such rocks occurs 
nearer the Pacific in a long strip in the Coast Ranges south of San 
Francisco Bay ; these rocks front the coast in the northern Santa Lucia 
Range, and project at sea in the Farallon Islands. 

These mighty events — upending of the strata, emplacement of 
granitic rocks, and the rest — produced mountain ranges which are 
the first in California for which there is good documentation. The 
events have been called the "Nevadan orogeny." By this orogeny, a 
belt of considerable width was subtracted from the Pacific Ocean bor- 
der and was added to the North American continent. 

During and after the orogeny, in Late Jurassic and Cretaceous time 
(140 to 70 million years ago), sedimentation continued along the ocean 
border, west of the newly formed mountain ranges. Remnants of these 
younger sediments lap up on the edge of the deformed rocks of the 
Sierra Nevada, as thougli toward a shoreline. Farther west, along the 
west side of the Great Valley, they attain a thickness of 20,000 to 30,000 


feet and have been called tlie Knoxville, Paskenta, Horsetown, and 
Chico Formations. These are a vast sequence of dominantly muddy 
sedimentary rocks, with frequent thin sandy intercalations, that con- 
tain shelly fossils in many places. Probably they were laid down on a 
shelf at the edsre of the continent. 

A significant feature of these Upper Jurassic and Cretaceous sedi- 
mentary rocks is the nature of their feldspar content. Mineral ogical 
studies indicate that they contain grains of potassium feldspar, and 
that these grains are rather sparse in the lower beds but become very 
abundant in the higher beds, where they dominate over all other kinds 
of feldspar. Potassium feldspar is characteristic of coarse granitic 
rocks like those in the Sierra Nevada and elsewhere in the Nevadan 
orogenic belt, and the increasing abundance of its grains in the higher 
strata indicates that as time went on the granitic rocks of this orogenic 
belt were being more and more penetrated and worn down by erosion. 

Within the Coast Ranges west of the Great Valley, however, the 
place of these shelf sediments is taken by a more enigmatic sequence, 
the Franciscan Formation. The Franciscan contains fewer fossils, but 
^\^hat fossils have been found indicate that it was laid down at nearly 
the same time as the shelf sediments to the east. The Franciscan is a 
mass of great but unknown thickness, pervasively sheared and dis- 
turbed, composed of mudstone and coarser dirty sedimentary rocks 
(graywackes), pillow lavas, bedded chert, glaucophane schist, and 
rare limestone lenses. Seemingly it was deposited in much deeper 
water than the shelf sediments previously described, and farther out 
from the Pacific Ocean shoreline. 


The stage was now set for the evolution of California into its pres- 
ent form, which was accomplished during Cenozoic time, or during 
the last 70 million years. 

Seerra Nevada 

During the early part of this time the site of the Sierra Nevada had 
been worn down to low hills and ridges, representing the stumps 
of the mountains that were produced during the Nevadan orogeny. 
Streams with gentle gradients drained westward across it, heading 
somewhere east of the present crest. Their ancient chamiels are still 
preserved in places on the hilltops of the Sierra Nevada, filled with 
water- worn gravels — the "auriferous gravels" so eagerly sought by 
the 49'ers and their successors. During Miocene time (25 to 12 million 
years ago) the northern half of the range was also buried by sheets 
of lava and volcanic debris, related to the volcanism in the Cascade 
Range to the north (see below) . 

The present Sierra Nevada occupies only part of the area of the 
earlier Nevadan mountains, which had extended the length of Cali- 
fornia and beyond to the north, south, and east. The part which forms 
the present range was blocked out after ^Miocene time (perhaps begin- 
ning 12 million years ago) . Then, the block was broken from the land 
to the east along great faults; its eastern side was raised along the 
faults to form the present range crest, and the western slope was tilted 
toward the Great Valley (which is, in fact, the depressed and buried 
western part of the block). This uplift was progressive and was ac- 


complished during several stages. It was virtually completed by the 
end of Pliocene time (about 3 million years ago), although some fault- 
ing and uplift continued during succeeding Quaternary time. 

Northeastern California 

The northe-astern corner of California is quite different ivoni the 
remainder of the State, as it is built almost wholly of young volcanic 
rocks ; it is one edge of an extensive volcanic region that extends far 
northward and northeastward across Oregon, Washington, and Idaho. 

Here, especially during Miocene and Pliocene time, lava flows and 
sheets of fragmental volcanic debris spread widely over the land as a 
result of eruptions from fissures and volcanic vents. These rocks range 
in composition from basalt through andesite to rhyolite. The eruptive 
material accumulated to great thickness; in the Warner Range in the 
northeasternmost part of the State at least 7,500 feet of the accumula- 
tions have been raised to view by faulting, with their base not visible. 
Farther west, the volcanic accumulations have built up the Cascade 
Range that extends with increasing height into Oregon. 

Volcanic activity continued into late Cenozoic time. In the western 
part of the volcanic area, two great volcanic cones that dominate the 
landscape of northern California — Mount Shasta (altitude 14,162 
feet) and Mount Lassen (altitude 10,457 feet) — were formed veiy late 
in geologic time. The lofty cone of Shasta, covered most of the year 
by snow and supporting a few permanent glaciers, seems now to be 
inactive, but the lesser cone, Lassen, underwent a minor eruption in 
1915 — the only volcano south of Alaska that has erupted during mod- 
em times within the continental United States. Surrounding these 
larger cones are myriads of smaller cones and craters which, as on 
their surrounding lava flows and other volcanic products, vegetation 
has scarcely regained its foothold — all testifying the relative recency 
of volcanic activity in this part of California. 

Coastal Mountains 

During the evolution of the present Sierra Nevada and Cascade 
Range in Cenozoic time many more and varied events were transpir- 
ing on the sites of the coastal momitains to the west — the Coast Ranges 
north and south of San Francisco Bay, the Transverse Ranges, and the 
Peninsular Ranges. 

An outstanding feature of these ranges is the high-angle faults that 
traverse them, which have had a large but uncertain influence on tlieir 
evolution. The largest and most famous of these faults is the San 
Andreas, which extends nearly the length of California, from Punt a 
Arena north of San Francisco, 620 miles southeastward, almost to if 
not across the Mexican border. But branching from or parallelmg 
the San Andreas are other faults of nearly equal magnitude, and they 
are crossed in the region of the Transverse Ranges by other high-angle 
and low-angle faults of east- west trend. 

Nearly everything about these high-angle faults has been hotly 
debated by geologists — the time of their inception, their subsequent 
history, and the magnitude and nature of the movements among them. 


Most of the streams which cross the San Andreas fault turn to the 
right at the fauU line for a few hundred or a thousand feet before 
resuming their normal course, giving eloquent testimony of a lateral 
shift of the geography on the two sides by these amounts during the 
last 25,000 years or so ; similar shifts of a few feet occurred on the San 
Andreas fault during the San Francisco earthquake of 1906. Can 
movements of the same kind be projected farther into the past? 

The Te mblor Range we st j>f B akersfield, bordering the San Andreas 
fault on the east, is tormecT chiefly of Miocene marine strata (25 mil- 
lion to 12 million years old), which contain masses of shattered blocks 
of granitic and metamorphic rocks that taper to the east — evidently 
landslide debris derived from highlands west of the fault. Yet just 
west of [he faii U, in the latitude of the Temblor Range the surface is 
now formed only of non-marine Miocene strata. The highlands from 
which the landslides came have disappeared, and there is a strong sus- 
picion that they have been shifted from their Miocene location by 
lateral movement along the San Andreas fault; a possible source of 
the landslide material is in highlands of granitic and metamorphic 
rocks on the west side of the fault which are now 60 to 80 miles to the 
f northwest. 

This, and similar lines of evidence, suggest the existence of the San 
Andreas and other faults at least during the last 25 million years. 
But still greater anomalies exist in the Jurassic and Cretjiceous_gra- 
nitic and stratified rocks, which are commonly quite unlike on the 
opposite sides of the faults. For a long distance south of San Fran- 
cisco, for example, the older rocks east of the San Andreas fault are 
Franciscan Formation, and those west of it are granitic and meta- 
morphic. Also, distinctive granitic and metamorphic rocks west of 
the San Andreas fault in the longitude of Los Angeles are very much 
like those east of the fault near the Salton Sea, 130 miles to the south- 
east. The full meaning of these anomalies remains to be explained, 
but they imply not only the existence of high-angle faults before Mio- 
cene time, but of very great movements along them, whether lateral 
or otherwise. 

If lateral shifts in the position of the blocks enclosed by the high-an- 
gle faults lias been as extensive and as long-persistent as has been sug- 
gested, there is a large factor of uncertainty in any attempt to recon- 
struct the succession of geogi-aphies of California during Cenozoic 

Almost as striking as the high- angle faulting in the coastal moun- 
tains is the strong folding and tilting of their strata — not only of the 
earlier Jurassic and Cretaceous strata, but also of those which formed 
during Cenozoic time, including even some of the yoimgest. The rela- 
tion (or lack of it) between this tilting and folding and the high- 
angle faulting remains one of the vexing problems of California 

The record of tilting and folding in the coastal mountains of Cali- 
fornia during Cenozoic time is unusually well documented, because it 
went on hand in hand wnth sedimentation. Thus, strata which were 
folded at some time are likely to have been eroded, and their eroded 
surface to be overlain unconformably by younger strata — the strata 
both below and above the unconfonnity (that is, the strata which 


were laid down before and after the folding) being datable by means 
of their contained fossils. 

The stratigraphic sequences in the coastal mountains of California 
contain many such unconformities, indicating that folding occurred at 
many times. Moreover, the magnitude, or even the existence of the 
unconformities varies greatly from place to place, indicating that each 
folding was essentially a local event. A record so complex is difficult 
to generalize into any climaxes or widespread orogeny, but it seeins 
possible that there were several gross times of orogeny, or genuine 
formation of mountains, as we shall see. 

The results of these movements are suggested by the reconstructions 
of the geography, in the form of paleogeographic maps, wliich have 
been made of the coastal area of California for various stages of Ceno- 
zoic time. These reconstructions indicate that parts of the area were 
at various depths beneath the sea and received marine deposits, that 
other parts were low plains or basins along the coast that received 
non-marine deposits, and that still other parts were hills or moun- 
tain ridges that were undergoing erosion. Many of these ridges proj- 
ected as islands or peninsulas, surrounded or nearl)^ so by the sea. 
The geography of all the coastal area through Cenezoic time was thus 
much like that which still persists in southern California — with the 
otfshore Channel Islands surrounded by shallow to deep marine waters, 
and the mountain-girt plains or basins onshore, such as the Los An- 
geles and Ventura basins. 

The reconst met ions of the geograjihy during the Cenozoic show 
great variations through time (which incidentally implies the ephem- 
eral nature of the seemingly immutable present geography of south- 
ern California). Seas waxed and waned in extent, mountain ranges 
cam« up only to disappear — all presumably in response to succe^ive 
pulses of folding, and possibly also to movements along the high- 
angle faults. 

The deposits laid down on the sites of the present coastal mountains 
are largely of clastic nature. Marine deposits that were principally 
mud and sand in varying proportions, are now distinctive formations 
of shale and sandstone. Gravelly beds occur near some of the former 
shorelines, and dominate altogether in some of the non-marine areas 
farther inland. Some deposits contain volcanic debris and interbedded 
lava flows, especially those of Miocene age. Among the non-clastic 
deposits, limestone is either lacking altogether or is very subordinate; 
much more important are the diatom-bearing siliceous shales, altered 
in part to chert, whose white, thin-bedded outcrops are a characteristic 
feature of the Coast Range landscape. They are typified by the 
Miocene Monterey Shale. 

The Cretaceous and older deposits of the coastal mountains seem 
nearly everywhere to be unconformable beneath the Cenozoic deposits, 
as though an important orogeny occurred before the latter were laid 
down. In some areas, to be sure, the Cretaceous is succeeded by Pale- 
ocene. Eocene, and younger strata, and any intervening break is little 
apparent. Elsewhere, howeA'er, much younger Cenozoic strata lie on 
the deeply eroded surface of the Cretaceous and older rocks, as a result 
of movements near the end of Cretaceous time and later. North and 
south of San Francisco Bay and west of the San Andreas fault, Mio- 


cene strata have been deposited directly over Cretaceous granites of 
deep-seated origin. One can picture these granites as having been 
forced up into mountain ridges late in Cretaceous or early in Cenozoic 
time, and the ridges not worn down to low gi'ound again until the 

Miocene time (25 million to 12 million years ago) marked a great 
spreading of the seas and their deposits over the site of thg^ coasta l 
mountains, and eastward across the Great Valley towardTThe SierFa 
Nevada, where the marine deposits pass into deposits laid down on the 
land. But a succession of movements in the later part of Miocene time 
produced much folding and faulting of the Miocene and older strata, 
and raised many areas into lands or even mountains — all adding up to 
a general time of orogeny. 

After this orogeny, marine incursions in the area of the coastal moun- 
tains never equalled their former extent. DuringXlkiiieufi-aiid Quater- 
nary time (the last 12 million years), sedimentation was confined to 
smaller, generally mountain-girt areas — embayments along the coast 
which received marine deposits, and basins farther inland which 
received non-marine deposits; for part of the time, however, seas also 
extended over much of the San Joaquin Valley. Notably among the 
coastal embayments are the Los^Ajlgeles and Ventura basins, which 
received as much as 177000 feet of the younger Cenozoic marine de- 
posits. Tliese basins subsided very rapidly early in Pliocene time and 
were covered to great depth by marine water; thereafter, they gradu- 
ally filled with sediments, whose contained Foraminifera indicate that 
they were laid down in progessively shallower water, until filling of 
the basins was completed. 

During later Cenozoic time, as earlier, sedimentation was inter- 
rupted from time to time and place to place by folding and faulting. 
Important movements occurred in places during the Pliocene, but the 
last climax of movement was during the middle of the Pleistocene, one 
or two million years ago; this has been called the "Coast Range" or 
"Pasadenan orogeny." It is well displayed in the Palos Verdes Hills 
southwest of Los Angeles, where older Pleistocene marine deposits 
liave been up-ended and folded to the same extent as the strata beneath, 
and their eroded surfaces overlain by later Pleistocene marine terrace 
deposits wliich have been uplifted from beneath the sea, but are other- 
wise only gently tilted. 

Manifestations of this orogeny also occur in the Ventura basin, and 
at many other places farther north, but its effects were variable — in 
some places producing steep folding of the older Pleistocene strata, 
in others vertical uplift of mountain areas with little accompanying 
folding, and in still others little or no disturbance between the older 
and younger Pleistocene deposits. Nevertheless, this orogeny, com- 
bined with the times of defonnation which preceded it, has made the 
coastal mountains of California essentially what they are today. Sub- 
sequent modifications have been minor, although, as we have seen, 
California is still an uneasy land. 

A final feature of coastal California deserves mention, as an indica- 
tion of the fluctuating relations betAveen sea and land. All along the 
coast one can observe terraces on the mountain slopes, rising step-like 
from the sea. The lowest terraces, a few hundred feet or less above 


the present sea, are well preserved and are covered by deposits con- 
taining marine shells ; clearly, these are old shoreline or beach deposits, 
now raised above the water. The higher terraces, some more than a 
thousand feet above the water, are progressively more and more 
eroded and destroyed the higher one ascends, yet many of these pre- 
serve marine deposits also. 

Modt^rn oceanographic surveys offshore have produced the addi- 
tional interesting fact that much of the sea bottom sloping away from 
the land is terraced also. Former shorelines thus exist, not only 
above present sea level, but at least 400 feet beneath it. Sea level 
along the California coast has thus not only fluctuated downward, 
but upward. 

Great fluctuations in sea level with respect to the land along the 
Calif orina coast are thus indicated. However, at least a part of these 
fluctuations were not caused by actual crustal movement ; the locking 
up of ocean water in the great continental glaciers during the Pleis- 
tocene ice ages, and tlie subsequent melting of the glaciers, produced 
worldwide variations in sea level amounting to hundreds of feet, both 
below and above present sea level. Nevertheless, the higher marine 
terraces along the California coast could not easily have been produced 
in this manner, and these at least imply that various parts of the 
coast have been greatly uplifted at very late periods in geologic time. 


(By J. P. Albers, U.S. Geological Survey, Menlo Park, Calif.) 

Because of the size of Califoniia and _its extremely varied and 
complex geology, it is desirable to divide the State into eleven physical 
or geomorphic provinces and describe the geology of each of these 
separately. Each province is characterized by rather similar land 
forms or combinations of land forms throughout its area, and by a 
geologic record that contrasts with that of neighboring provinces, 
especiall}^ in the later part of its geologic history. Certain kinds of 
mineral deposits tend to occur within particular geomorphic provinces. 

The eleven geomorphic provinces into which California is divided 
are (fig. 2) : (1) Coa^t Riuiges — a system of noi*thwest-t rending lon- 
gitudinal mount a in ranges made up of Mesozoic and Cenozoic rocks, 
controlled by. faulting and folding; (2) Klamath Momitains — a group 
of complex rugged momitains made of Paleozoic and Mesozoic rocks 
intruded by gi-anitic and ultramafic rocks, and characterized by ir- 
regular drainage; (3) Southern Cascade Mountains — a chain of vol- 
canic mountains most prominent of which are Mount Shasta and Las- 
sen Peak ; (4) Modoc Plateau — a plateau-like surface built of volcanic 
rocks, bomided indefinitely on the west by the Cascade Mountains and 
on the east by the Great Basin ; (5) Sierra Nevada — a great westward- 
tilted fault block made mainly of granitic rocks, subordinate Paleozoic 
and Mesozoic sedimentary and volcanic rocks, numerous inclusions and 
pendants of metamorphic rocks, and elongate bodies of ultramafic 
rocks; (6) Great Valley (also known as the Central Valley) — an el- 
liptical plain bounded by mountains on all sides and underlain by 
Mesozoic and Cenozoic rocks; (7) Great Basin — northwest-trending 
fault-block mountains made of Precambrian to Cenozoic rocks, and 
broad intervening alluvial-filled valleys and playas with no drainage 
to the sea; (8) Transverse Ranges — west-trending ranges made of 
Precambrian to Cenozoic rocks; (9) Mojave Desert — area wedged be- 
tween San Andreas and Garlock faults and consisting of isolated 
northwest-trending mountain ranges made of Precambrian to Cenozoic 
rocks ; well over 50 percent of the terrain is broad intermontane val- 
leys with playas and interior drainage; (10) Salton Trough — a low- 
lying desert basin filled with alluvial deposits; the Salton Sea is a 
promment feature; (11) Peninsular Ranges — northwest-trending 
ranges made chiefly of Mesozoic granitic and metamorphic rocks. 

The geology of the individual provinces is described on subsequent 
pages, following a resume of the geologic history of the State. The 
correlation chart (fig. 3) gives in generalized form the sequence 
and age of formations in the individual provinces and the approximate 
correlation of units between provinces. The authors of the individual 
province descriptions are responsible for the stratigraphic column 
given for their province. The stratigraphic nomenclature and age 



assignments used in this report, are derived from many published 
sources and do not necessarily follow the usage of the U.S. Geological 


(G. B. Oakeshott, California Division of Mines and Geology, San Francisco, 


The Coast Ranges province includes a series of north-northwest- 
trending mountain ranges and intermontane valleys bounded on the 
east by the Great Valley and on the west by the Pacific Ocean. A 
narrow segment of the province extends northward into coastal 
Oregon. The boundary between the northern Coast Ranges (north of 
San Francisco Bay) and the Klamath Mountains province is the South 
Fork Mountain fault zone. The south end of the southern Coast 
Ranges (south of San Francisco Bay) is marked by the abrupt change 
to east-west topographic and structural trends of the Transverse 
Ranges in Santa Barbara and Ventura Counties. 

The Coast Ranges mclude numerous rugged, individual mountain 
ranges which extend in elevation from sea level to maximum heights 
of 6,000 to 7,000 feet; they are separated by short, narrow, inter- 
montane valleys. 

Geology of the province is extremely complex. Each of the ranges 
has had a more or less independent and individual history, although 
major episodes in that history link the Coast Ranges into a province 
which is geologically and physiogr^phically distinctive. 

The Precambrian history of the Coast Ranges is unknown as no 
rocks of that age have been recognized. Neither are there any rock 
formations of known Paleozoic or Triassic age, although it is quite 
likely that the Sur Series represents part of this time, perhaps late 

Great thicknesses of Upper Jurassic to Recent sedimentary, vol- 
canic, and plutonic rocks reveal a complex history of deposition on the 
continental shelves and in deep, narrow marine troughs. Intermittent 
volcanism, plutonic intrusion, and orogenic activity were inter- 
spersed throughout this time. The last major orogeny, which de- 
veloped the present "Coast Ranges province," occurred during late 
Pliocene to mid-Pleistocene time. Late Jurassic orogeny and granitic 
intrusion affected the Coast Range region to some extent as it did the 
Transverse Ranges, Sierra Nevada, Klamath Mountains, and much of 
the rest of California. Similarly, mid-to-Late Cretaceous mountain 
building took place, accompanied by the greatest and most widespread 
granitic invasions of California's history. Intermittent and local 
crustal disturbances occurred throughout the Tertiary, culminating 
in the Pliocene and Pleistocene Coast Range orogeny. This involved 
the most profound deformation in the history of the Coast Ranges. 

Basement rocks of the Coast Ranges consist of two groups: (1) 
Upper Jurassic to Upper Cretaceous rocks of the Franciscan Forma- 
tion that were deposited in deep offshore troughs, or eugeosynclines, 
and (2) the Upper Paleozoic ( ? ) gneisses and schists of the Sur Series 
intruded by Upper Jurassic ( ? ) and Upper Cretaceous granitic rocks. 
Older rocks have not been found beneath either of these major groups. 









T109 t> 

FiouRE 3. Generalized atratigraphic correlation chart for California. 



The Sur Series consists of gneisses, schists, and marble — formed from 
thick sedimentary and volcanic formations that were affected by high- 
grade metamorphism. They crop out most extensively in the Santa 
Lucia and Santa Cruz Mountains. Rocks of the Sur Series, and the 
granitic rocks that intrude them, yield extremely valuable crushed 
and broken stone, and limestone for the manufacture of cement. The 
Sur Series is also a major source of dolomite. 

The Franciscan Formation consists of at least 20,000 feet of gray- 
^yacke, dark shale, metavolcanic rocks, chert, minor limestone, and 
metamorphic rocks of the blue-schist and green-schist facies. The 
Franciscan is intruded by peridotite and serpentine, which perhaps 
also constitute the material of the upper mantle on which the Fran- 
ciscan was deposited. These masses of ultramafic rock in places con- 
tain deposits of chromite, and are also the parent rocks of the nickel- 
bearing laterites. These rocks are also the source of extensive asbestos 
deposits being mined in San Benito and adjacent Fresno counties. 
The Franciscan Formation supplies crushed and broken stone and 
riprap, and has been a major source of manganese in the past. Fran- 
ciscan rocks are found in all parts of the Coast Ranges except in the 
20- to 40-mile-wide strip between the San Andreas and Nacimiento 
fault zones. 

A major group of rocks with an aggregate thickness on the order 
of 30,000 feet represents all epochs from Late Jurassic to Late Cretace- 
ous time. These unmetamorphosed shelf-facies rocks — sandstone, 
shale, siltstone, and minor conglomerate and limestone — lie on the Sur 
Series and Franciscan Formation and are also contemporaneous (at 
least, in part) with the Franciscan Formation and the granitic rocks. 
The thickest, most continuous sections of the shelf-facies sedimentary 
rocks dip under the Great Valley from the east flanks of the Diablo and 
Mendocino Ranges. Lower and Upper Cretaceous rocks are predomi- 
nantly dark sandstone (graywacke) and arkose (granitic sandstone) 
Avith minor shale and conglomerate. They contain larger proportions 
of K-feldspar grains than does the Franciscan. 

Cenozoic formations comprise a great variety of sedimentary and 
volcanic rocks but all are apparently of shallow marine (shelf and 
slope) and continental origin. Rapid lateral changes in facies and 
thicknesses reflect intermittent localized folding, faulting, and volcan- 
ism. Those changes are most marked at the margins of the basins 
and ranges. Paleocene marine sedimentary rocks are quite similar to 
those in Upper Cretaceous formations, but are not as thick or as wide- 
spread. Progressively more restricted seaways from Paleocene to late 
Eocene time limited the deposition of Eocene sands, muds, and clays 
to narrow basins in the area of the Coast Ranges. 

From late Eocene to middle Miocene time, seaways in the Coast 
Range region were severely restricted and climates became markedly 
seasonal and locally semi-arid. Conglomerate, sandstone, shale, and 
mudstone of these epochs include shallow-marine materials and exten- 
sively distributed, and locally thick continental red beds. Oligocene 
formations crop out only in the southern Coast Range; probably the 
northern Coast Range area was above sea level during Oligocene time. 
In the Santa Cruz, Santa Lucia, and Diablo Ranges, shallow-water 
marine sandstone, shale, some conglomerate, and local tuff beds repre- 


The Sur Series consists of gneisses, schists, and marble — formed from 
thick sedimentary and volcanic formations that were affected by high- 
grade metamorphism. They crop out most extensively in the Santa 
Lucia and Santa Cruz Mountains. Rocks of the Sur Series, and the 
granitic rocks that intrude them, yield extremely valuable crushed 
and broken stone, and limestone for the manufacture of cement. The 
Sur Series is also a major source of dolomite. 

The Franciscan Formation consists of at least 20,000 feet of gray- 
wacke, dark shale, metavolcanic rocks, chert, minor limestone, and 
metamorphic rocks of the blue-schist and green-schist facies. The 
Franciscan is intruded by peridotite and serpentine, which perhaps 
also constitute the material of the upper mantle on which the Fran- 
ciscan was deposited. These masses of ultramafic rock in places con- 
tain deposits of chromite, and are also the parent rocks of the nickel- 
bearing laterites. These rocks are also the source of extensive asbestos 
deposits being mined in San Benito and adjacent Fresno counties. 
The Franciscan Formation supplies crushed and broken stone and 
riprap, and has been a major source of manganese in the past. Fran- 
ciscan rocks are found in all parts of the Coast Ranges except in the 
20- to 40-mile-wide strip between the San Andreas and Nacimiento 
fault zones. 

A major group of rocks with an aggregate thickness on the order 
of 30,000 feet represents all epochs from Late Jurassic to Late Cretace- 
ous time. These unmetamorphosed shelf-facies rocks — sandstone, 
shale, siltstone, and minor conglomerate and limestone — lie on the Sur 
Series and Franciscan Formation and are also contemporaneous (at 
least, in part) with the Franciscan Formation and the granitic rocks. 
The thickest, most continuous sections of the shelf-facies sedimentary 
rocks dip under the Great Valley from the east flanks of the Diablo and 
Mendocino Ranges. Lower and Upper Cretaceous rocks are predomi- 
nantly dark sandstone (graywacke) and arkose (granitic sandstone) 
with minor shale and conglomerate. They contain larger proportions 
of K-f eldspar grains than does the Franciscan. 

Cenozoic formations comprise a great variety of sedimentary and 
volcanic rocks but all are apparently of shallow marine (shelf and 
slope) and continental origin. Rapid lateral changes in facies and 
thicknesses reflect intermittent localized folding, faulting, and volcan- 
jsm. Those changes are most marked at the margins of the basins 
and ranges. Paleocene marine sedimentary rocks are quite similar to 
those in Upper Cretaceous formations, but are not as thick or as -wide- 
spread. Progressively more restricted seaways from Paleocene to late 
Eocene time limited the deposition of Eocene sands, muds, and clays 
to narrow basins in the area of the Coast Ranges. 

From late Eocene to middle Miocene time, seaways in the Coast 
Range region were severely restricted and climates became markedly 
seasonal and locally semi-arid. Conglomerate, sandstone, shale, and 
mudstone of these epochs include shallow-marine materials and exten- 
sively distributed, and locally thick continental red beds. Oligocene 
formations crop out only in the southern Coast Range: probably the 
northern Coast Range area was above sea level during Oligocene time. 
In the Santa Cruz, Santa Lucia, and Diablo Ranges, shallow-water 
marine sandstone, shale, some conglomerate, and local tuff beds repre- 


sent deposits in rather restricted embayments and channels. South- 
ward from the San Francisco Bay area, the Oligocene strata become 
more continental and in the southern end of the Coast Ranges are 
entirely land-laid. 

Lower and middle Miocene formations consist of marine, shelf-f acies 
sandstone, conglomerate, shale, and mudstone which were deposited in 
rather narrow basins extensively in the southern Coast Ranges and in 
a narrow trough as far north as the central Mendocino Range in the 
northern Coast Ranges. Middle Miocene seas were more widespread 
than those of the early Miocene. Great volumes of volcanic materials 
were extruded during middle Miocene time — tuff, breccia, agglomerate, 
rhyolitic to andesitic flows, and plugs. 

Shallow seas reached a maximum extent in early late Miocene time. 
The most widespread Tertiary formation is the Monterey Formation 
of middle to late Miocene age which is found throughout the Coast 
Ranges as far north as Point Arena. All common lithologic types 
are represented, but most characteristic are siliceous shale, chert, and 
diatomaceous shale. The Miocene Epoch closed with deposition of 
coarser sandy marine sedimentary f acies, such as the San Pablo, Santa 
Margarita, and Sisquoc Fonnations in more restricted basins between 
the rising Coast Ranges. 

In Pliocene time, sands, muds, and some tuff were deposited in nar- 
row, shallow marine embayments throughout the Coast Ranges as far 
north as the Eureka Basin. Most of the formations appear too diin, 
or were not deposited, in the anticlinal-crest areas, reflecting uplift 
and folding of many of the individual Coast Ranges. Late Pliocene 
and early Pleistocene time were marked by very restricted and thin 
local marine beds in narrow basins, and a remarkably widespread and 
locally thick series of conglomerate and gravel. Floods of gravel and 
coarse sand deposited in the chaimels, deltas, and floodplains of 
streams almost covered the site of the southern Coast Ranges and ex- 
tended locally along the margms of the northern Coast Ranges. Vol- 
canism was locally important, but did not compare with the great 
middle Miocene volcanic epoch. Late Quaternary formations include 
some coastal marine terrace deposits, bay muds, and beach sands, but 
most are flat-lying alluvium and local lake deposits. 

Formations of Tertiary age are the principal source and reservoir 
rocks for petroleum and natural gas. Most of the petroleum products 
have come from the southern Coast Ranges. Principal production 
is from Miocene and Pliocene formations in the Santa Maria, Cuyama, 
and Salinas basins, and from the eastern flanks of the Diablo and 
Temblor ranges. Upper Miocene and lower Pliocene marine sedi- 
mentary rocks provide nearly all of California's diatomite. Quat- 
ernary deposits are supplying most of the State's needs for sand and 
gravel. Salt (sodium chloride) , bromine, and magnesimn compounds 
are now obtained in large quantities from the waters of San Fran- 
cisco Bay and the Pacific Ocean at Moss Landing. 

Three great north-northwest-trending fault zones dominate the 
structural pattern of the Coast Ranges. The most westerly of these 
is the Nacimiento-Sur fault zone which separates the western coastal 
block of Franciscan basement rocks from the granitic block east of 
that fault zone. This fault is probably essentially normal, with per- 


haps some strike-slip in a right lateral sense, but in its northerly 
projection extends into the Siir Thrust zone. No earthquakes of his- 
toric record seem to have originated in the Nacimiento-Sur fault zone. 

The great San Andreas fault, striking obliquely across the Coast 
Ranges and Coast Range structures from the coast at Point Arena to 
the Tehachapi Mountains 400 miles southeast is California's best- 
known structural feature. South of the Tehachapi Mountains, the 
fault zone extends along the east side of the Salton Sea. It extends 
northward, offshore, probably at least as far as the Mendocino Escarp- 
ment. Like the Nacimiento fault zone, the San Andreas separates 
Franciscan basement on the east from the granitic basement. Move- 
ments on tlie San Andreas fault during the Quaternary have been 
right slip and normal; older displacements, probably beginning in 
Late Jurassic time, which formed the Franciscan-granitic rock contact, 
were perhaps predominantly vertical. Geologists are strongly divided 
on this latter point, however; some maintain that there has been a 
cumulative right slip of several hundred miles. The San Andreas 
fault dips very steeply east and is essentially straight in strike except 
at its southerly end and where it turns eastward as it enters the Trans- 
verse Ranges province. Prominent branches of the San Andreas fault - 
are the Pilarcitos, Hay ward, and Calaveras faults in the San Francisco 
Bay area. The Pilarcitos is an older, inactive fault, but the others 
have been the sources of a great many of California's earthquakes. 

A third great fault zone, possibly related to the Nacimiento and San 
Andreas in origin, is the South Fork Mountain fault which separates 
the Franciscan block on the west from the Mesozoic granitic (and 
older crystalline rock) block on the east. This great fault zone con- 
stitutes the geologic and structural boundary between the Coast 
Ranges and the Klamath Mountains provinces. The major contact 
between Sierran granitic "basement" and Franciscan Formation of 
the Coast Ranges, which lies buried beneath sediments of the west side 
of the Great Valley, may be a southward continuation of the South 
Fork Mountain fault. This is an old, inactive fault. 

Apparently of major importance in the structural picture are 
elongate masses of peridotite and the serpentine derived from it; they 
are essentially sill-like bodies which seem to have intruded rocks as 
young as Late Cretaceous in age. Because of the extreme mobility 
of serpentine, such bodies are almost eveiywhere in fault contact with 
other rock formations and are most commonly aligned along fault 
zones. They commonly appear as "cold intrusions" faulted against 
later rocks. Together with rocks of the Franciscan Formation, they 
form a series of diapiric structures or piercements along the anticlinal 
crest of the Diablo Range. 

Folding of the Coast Ranges, like the accompanying faulting, has 
been complex, and individual fold axes can seldom be traced more 
than a few miles. Axial trends are generally parallel to the major 
faults and thus tend to strike a little more westerly than the trend of 
the Coast Ranges as a whole. Very little is known of structures within 
the complex Sur Series and of how these rocks responded to the forces 
which built the Coast Ranges. History of deformation within the 
Franciscan Formation is also little known because of the complex 
lithology, the discontinuity of individual lithologic units, and the 


massive character of the gray wacke which comprises such a large part 
of the Franciscan. General heterogeneity of structure within the 
Franciscan Formation is in striking contrast to the more open folding 
of the shelf-and-slope sedimentary facies of approximately equivalent 
ages. Major faults in the Coast Ranges are much more continuous 
than the folded structures. Fold axes do not commonly continue from 
one range into the next. 

The Coast Ranges are flanked on the east by many thousands of 
feet of Upper Jurassic, Cretaceous, and Cenozoic shelf- facies sedi- 
mentary rocks which dip homoclinally toward the Great Valley from 
the north end of the Sacramento Valley to the south end of the Diablo 
Range. This thick group of shelf- facies rocks is separated from the 
heterogeneously structured, eugeosynclinal Franciscan rocks on the 
west by a major fault zone marked by sill-like bodies of serpentine. 

The Coast Ranges were formed essentially by contemporaneous 
folding, faulting, and uplift, probably beginning in Late Jurassic 
time, and occurring again and again with increasing intensity to culmi- 
nate in the mid-Pleistocene. Local uplift and depression, fault move- 
ments, and mild folding have continued to the present. 

Selected Refebences 

Bailey, E. H., Irwin, W. P., and Jones, D. L., 1965, Franciscan and related rocks, 
and their significance in the geology of western California : California Div. 
Mines and Geology Bull. 183, 177 p. 

Bowen, O. E., Editor, 1962, Geologic guide to the gas and oil fields of northern 
California : California Div. Mines and Geology, Bull. 181, 412 p. 

California Division Mines, 1951, Geologic guidebook of the San Francisco Bay 
counties — history, landscape, geology, fossils, minerals, industry, and routes 
to travel ; Bull. 154, 392 p. 

California Division Mines and Geology, Geologic map of California, scale 
1 : 250,000; sheets covering parts of Coast Ranges include Weed (1964), Red- 
ding (1962), Ukiah (1960), Santa Rosa (1963), San Francisco (1961), San 
Jose (in preparation 1965), Santa Cruz (1959), Fresno (in preparation 1965). 
San Luis Obispo (1959), Bakersfield (1965), Santa Maria (1959), and Los 
Angeles (in preparation 1965). 

California Division Oil and Gas, 1962. California oil and gas fields — maps and 
data sheets: Part I, San Joaquin-Sacramento valleys and northern coastal 
regions, p. 1-493; Part II, Los Angele.s-Ventura basins and central coastal 
regions, p. 495-913. 

Hinds, N. E. A., 1952, Evolution of the California landscape: California Div. 
Mines Bull. 158, p. 157-181. 

Oakeshott. G. B., Editor, 1959, San Francisco earthquakes of March 1957 : Cali- 
fornia Div. Mines Spec. Rept. 57, 127 p. 

Taliaferro, N. L., 1943, Geologic history and structure of the central Coast Ranges 
of California : California Div. Mines Bull. 118, p. 119-163. 


(By W. P. Irwin, U.S. Geological Survey, Menlo Park, Calif.) 

The Klamath Mountains are made up of rocks that for the most part- 
are older and more highly defonned than those of surrounding prov- 
inces. These older rocks, some of which are metamorphosed, are sedi- 
mentaiy and volcanic in origin. Their principal deformation was dur- 
ing the Nevadan (Jurassic) orogeny, during which they were intruded 
by ultramafic and granitic rocks. These rocks, including the intni- 


sives, form a complex foundation, or subjacent terrane, on which 
younger less deformed sedimentary and volcanic rocks are deposited. 
The subjacent terrane of the Klamath Mountains is comparable to that 
of the Sierra Nevada, and the two doubtless join beneath a cover of 
superjacent rocks at the northeni end of the Great Valley (pi. 1) . 

The sedimentary subjacent rocks are chiefly slaty shales, sandstones, 
and conglomerate, but locally include discontinuous lenses of limestone 
and thin-bedded chert. Volcanic rocks, most of which are basaltic or 
andesitic, but some of which are rhyolitic, occur at irregular intervals 
throughout the stratigraphic section of subjacent rocks. Tlie most 
complete succession of subjacent strata is in the eastern part of the 
Klamath Mountains, where the stratigraphic section is 40,000 to 50,000 
feet thick and ranges from Late Ordovician to Middle Jurassic in age 
(fig. 3). The economically most important of these are the Balaklala 
Rhyolite (Devonian) and Bully Hill Rhyolite (Triassic) for their 
copper deposits, the Bragdon Formation (Mississippian) for its gold- 
bearing quartz veins, and the McCloud Limestone (Permian) quarried 
for the manufacture of cement. In the western Klamaths, where the 
geology is more complex and not as thoroughly studied, the strata 
range from Devonian ( ? ) to Late Jurassic in age. These are separated 
from the better known strata in the eastern Klamaths by an arcuate 
belt of metamorphic rocks that is concave to the east (pi. 1). The 
metamorphic belt includes homblendic and micaceous schists that were 
formed from volcanic and sedimentary rocks during the Carboniferous 
or earlier. 

The subjacent strata were deposited mainly in the ocean along the 
border of the ancient continent ; perhaps some of the volcanics formed 
small islands and the limestones formed shallow reefs. This general 
environment of deposition likely existed essentially until the Nevadan 
orogeny, although there are gaps in the stratigraphic record as well as 
evidence of tectonic activity earlier, but perhaps less intense than the 
Nevadan. During the Nevadan orogeny, the thick, orderly succession 
of strata were folded, faulted, and intruded by ultramafic and granitic 
rocks. This orogeny culminated in the Late Jurassic with regional 
emergence of the subjacent terrane above sea level. 

The overall structure of the subjacent terrane, which presmnably 
developed chiefly during the Nevadan orogeny, is not clearly known. 
Most of the principal folds and faults trend parallel to the arcuate 
lithic belts, as do many linear ultramafic bodies and certain of the 
granitic intrusives (pi. 1). The arcuate pattern is intei-preted to re- 
sult from westward thrusting along low-angle faults; ultramafic rock 
has been intruded along some of the thrust faults. The ultramafic 
rocks are important as a source of chrome ore. 

With emergence of the Klamath Mountains, near the close of the 
Jurassic, great quantities of debris were shed from the newly made 
land into the bordering seas. Erosion proceeded so vigorously that, 
by the Early Cretaceous, the cover was stripped from the once deeply 
buried Nevadan batholithic rocks. The detritus from the eroded cover 
was deposited as a thick section of strata m the bordering seas on the 
upturned edges of the deformed subjacent strata and on the eroded 
batholithic rocks. 

Deposition of the marine superjacent strata continued during most 
of the Cretaceous as the land area shrank owing to erosion and slow 

67-164 o— «e^-pt. I- — -4 


submergence. Near the end of the Cretaceous, the Klamath reg:ion 
again rose above sea level, and although it is clear that the Cretaceous 
superjacent deposits once covered much of the Klamath region, only a 
few small patches now remain to be seen. The end of the Cretaceous 
marked the last significant marine invasion of the Klamath region. 

During the Tertiary, the Klamath Mountains province continued to 
undergo erosion and was the source of detritus for marine and conti- 
nental strata now exposed around much of its perimeter in Oregon and 
along its eastern side in California. Within the province, the Tertiary 
is represented chiefly by the continental Weaverville Formation of 
probable Oligocene age (fig. 3). The Weaverville Formation crops 
out in several structurally controlled, northeast-trending patches in the 
southern part of the province, and lies un conformably on Cre- 
taceous and older rocks. It consists of beds of locally derived sand- 
stone, mudstone, conglomerate, tuff, and lignite that probably were de- 
posited on flood plains and in swampy lakes. In the extreme western 
part of the province a few small, thin patches of essentially horizontal 
beds of friable detrital rocks are found on the crests of ridges. These 
rocks, called the Wimer Beds, contain marine fossils of late Miocene 

The crests of the ridges, on which the remnants of the Wimer Beds 
are found, are similar in altitude to the crests of other ridges nearby. 
This accordance of crestlines led to the idea that many of these broad- 
topped ridges are remnants of an ancient land surface of low relief, 
named the Klamath peneplain. Crestlines equated with this hypo- 
thetical erosion surface are widespread in the Klamath Mountains and 
increase in altitude from about 2,500 feet in central Del Norte County 
to more than 6,000 feet in southern Trinity County. A succeeding 
cycle of erosion, the Sherwood stage, destroyed much of the so-called 
Klamath peneplain and developed broad land surfaces at lower alti- 
tudes between the remnants. The Sherwood surface has in turn been 
dissected deeply by modern streams, giving rise to a second set of ac- 
cordant ridges. 

Volcanic rocks that range from basalt to rhyolite in composition 
erupted extensively along the eastern edge of the Klamath Mountains 
during the Cenozoic Era. They are the principal rocks of the Cas- 
cades province and are prominent in the northern part of the Great 
Valley. Within the limits of the Klamath Mountains these volcanic 
rocks occur as thin erosional outliers that at some places have over- 
lapped the boundary between the subjacent terrane and the Cretaceous 
superjacent rocks. The oldest of these is the Tuscan Formation of 
Pliocene age, which consists of clastic volcanic rocks interlayered with 
sands and gravels. 

Weakly consolidated Pleistocene gravels of the Eed Bluff Formation 
are widespread in the northern part of the Great Valley and lap onto 
the southeastern edge of the Klamath Mountains. Within the Klam- 
ath Mountains, sands and gravels are found on terraces at many levels 
along the courses of the major streams, and some of the higher of these 
may be equivalents of the Red Bluff Formation. Many of these ter- 
race deposits, as well as the sands and gravels in the present drainage 
channels, have been an important source of placer gold. 


Selected References 

Albers, J. P., and Robertson, J. F., 1961, Geology and ore deposits of Blast Shasta 

copper-zinc district, Shasta County, California : U.S. Geol. Survey Prof. Paper 

338, 107 p. 
Davis, G. A., and Lipman, P. W., 1962, Revised structural sequence of pre- 

Cretaceous metamorphic rocks in the southern Klamath Mountains, California : 

Geol. Soc. America Bull., v. 73, no. 12, p. 1547-1552. 
Diller, J. S., 1906, Description of the Redding quadrangle [California] : U.S. Geol. 

Survey Atlas, Folio 138, 14 p. 
Irwin, W. P., 1960, Geologic reconnaissance of the northern Coast Ranges and 

Klamath Mountains, Clalifomia : California Div. Mines Bull. 179, 80 p. 
, 1964, Late Mesozoic orogenies in the ultramafic belts of northwestern 

California and souithwestern Oregon: U.S. Geol. Survey Prof. Paper 501-O, 

p. C1^9. 
Kinkel, A. R., Jr., Hall, W. E., and Albers, J. P., 1956, Grcology and base-metal 

dei)osits of West Shasta copper-zinc district, Shasta County, California : U.S. 

Geol. Survey Prof. Paper 285, 156 p. 
Sanborn, A. F., 1960, Geology and paleontology of the Big Bend quadrangle, 

Shasta County, Oalifomia : California Div. Mines Spec. Rept. 63, 26 p. 
Wells, F. G., Walker, G. W., and Merriam, C. M., 1959, Upper OrdoviCian( ?) and 

Upper Silurian formations of the northern Klamath Mountains, California : 

Geol. Soc. America Bull., v. 70, no. 5, p. 645-649. 


(By G. A. Macdonald, U.S. Geological Survey, Hawaii Institute of Geophysics, 
Honolulu, Hawaii ; and T. E. Gay, Jr., California Division of Mines and 
Geology, San Francisco, Calif. ) 

The Cascade Range, Modoc Plateau, and Great Basin geomorpliic 
provinces in northeastern California are discussed together in this sec- 
tion because their general lithologic and structural continuities are 
more notable than their dissimilarities. 

Southern Cascade Range 

The Cascade Range is a volcanic mountain range that extends south- 
ward into California from Oregon and Washington. In Oregon and 
northernmost California, the oldest rocks of the range — the Western 
Cascade series— are Miocene in age and rest on marine and nonmarine 
sedimentary rocks of Eocene and Oligocene age. The Western Cascade 
rocks consists of lava flows of basaltic, andesitic, and dacitic composi- 
tion, with intercalated pyroclastic rocks, some of which are rhyolitic. 
They are characterized by a general alteration of ferromagnesian mm- 
erals to chlorite and related minerals, which gives a slight greenish 
coloration to the rocks. Tlie alteration is probably the result of a 
general permeation by hydrothermal solutions near the end of the 
Miocene Epoch, when the rocks were somewhat uplifted by mountain- 
building movements. In Oregon, the rocks were invaded by small 
Tertiary granitoid intrusions which brought some deposition of metal- 
lic ores. In California, however, these intrusions are not exposed, and 
no economic metallization has yet been found in the Western Cascade 
rocks of this State. 

As their name implies, the Western Cascade rocks are exposed in a 
north-south belt along the w^esteni side of the Cascade Range. In 
California, this belt is about 5 to 15 miles wide and extends about 50 


miles south of the Oregon border. The southernmost exposures of the 
rocks are just southwest of the toAvn of Mount Shasta. 

After the Western Cascade rocks were eroded for an interval in late 
Miocene to early Pliocene time, volcanic activity resumed in the early 
Pliocene. A new series of rocks, the High Cascade series, was erupted 
to form a ridge overlapping and parallel to the Western Cascade series 
but slightly farther east — a belt about 30 to 40 miles wide and 150 miles 
long in California. 

The High Cascade rocks range from basalt to rhyolite, with py- 
roxene andesite predominating. The High Cascade volcanism resulted 
in an extension of the Cascade Range some 80 miles southeast of the 
Western Cascade belt, beyond Mount Lassen, to Lake Almanor. At 
the soutlieast end of the Higli Cascade belt, its lavas overlap the 
metamorphic and granitic rocks of the Sierra Nevada along an irregu- 
lar line that runs in general southwestward from near Susanville past 
Lake Almanor toward Oroville. The oldest of the Pliocene High Cas- 
cade rocks in California are near the southeast end of the raiige. Li 
the region just southwest of Lassen National Park, High Cascade 
andesite flows are overlain by the late Pliocene Tuscan Formation. 
The latter consists largely of volcanic breccias deposited as mudflows, 
grading westward into volcanic conglomerates and sandstones, and 
spreading far southward over the western edge of the Sierra Nevada. 
Interbedded with the Tuscan breccias near their base is the rhyodacitic 
Nomlaki Tuff Member, formed by incandescent flows of volcanic ash 
that were still so hot when they came to rest that the particles of glass 
became welded together in the middle and lower parts of the layer. 

In the area east of Redding, Cascade lavas are absent beneath the 
Tuscan Formation, which there rests directly on sedimentary rocks of 
Eocene and Late Cretaceous age. The Eocene rocks consist of con- 
glomerate and sandstone of the nonmarine Montgomery Creek Forma- 
tion, containing fossil leaves, petrified wood, and some beds of low- 
grade coal. The Late Cretaceous rocks are sandstones and shales, 
which elsewhere contain some petroleum, but so far none has been 
found in this area. 

Tlie early High Cascade lavas were very fluid basalt and basaltic 
andesite that erupted quietly, with very little explosion. They erupted 
from fissures and built a broad ridge of overlapping, low shield vol- 
canoes and lava flows. As time passed, some of the erupting lava 
became more silicic, and the amount of explosive activity increased. 
Big composite cones of interbedded andesitic lava flows and pyroclastic 
debris were built along the cres't of the ridge, with associated domes 
and flows of dacite, and, toward its southern end, rhyolite. The big 
cones included Mount Shasta; Burney Mountain; Crater (Magee) 
Peak; a mountain known as Mount Tehama, or Brokeoff Volcano, 
that once occupied the vicinity of the present Lassen Peak; and an- 
other that once stood just to the southwest, in the area of Mineral. 
On the flanks of the latter, huge flows of rhyolite lava and ash were 
erupted, and probably as a result of the draining of this magma from 
beneath, the top of the mountain collapsed to form a caldera like the 
well-known caldera of Crater Lake in Oregon. The summit of 
Brokeoff Volcano also caved in to form a caldera, within which con- 
tinued volcanism built a series of dacite domes, including Lassen Peak. 


Just nortli of the great dome of Lassen Peak a row of similar domes, 
the Chaos Crags, grew in very recent time. Explosions at their base 
undermined the north edge of the domes, which collapsed in a series 
of avalanches to form the Chaos Jumbles. About the same time a flow 
of incandescent ash swept down the valley of Manzanita Creek from 
the northwest side of Lassen Peak. The last of the avalanches and 
the ash flows occurred only about 200 years ago. Mount Lassen erupted 
most recently during the summers of 1914-1917, with a small flow of 
lava at the summit ot the dome, and mudflows and a glowing avalanche 
to the northeast, down the valleys of Lost and Hat Creeks. 

Momit Shasta, the largest of the Cascade Range volcanoes, rises 
10,000 feet above its base and has a volume of about 80 cubic miles. 
The main cone consists at the base largely of flows of basaltic andesite, 
and in its upper part predominantly of flows of pyroxene andesite with 
a smaller proportion of dacite. Pyroclastic materials and mudflow 
deposits are spai^se. After the main cone had formed, a north-south 
fissure across it controlled the emplacement of a later series of donies, 
cinder cones, and associated lava flows, ranging from basalt to dacite. 
During late Pleistocene time, flows of basaltic andesite extended more 
than 40 miles southward along the Sacramento River Canyon from 
Everitt Hill, a small shield volcano on the southwest flank of Mount 
Shasta. At Shasta Springs a large volume of water issues from the 
base of these flows. Also in the waning stages of the volcano, an east- 
west fissure on its western flank resulted in the lateral cone of Shastina, 
and the dome of Black Butte at the western base of the moimtain. 
Postglacial lava flows from vents below Shastina, and two small domes 
that grew in the crater of Shastina, escaped erosion by the glaciers that 
covered most of Mount SKasta and Shastina during the Pleistocene 

The latest eruptions of Shasta, possibly as recent as 1786, formed a 
blanket of pumice and cinder over the top of the mountain. A small 
acid hot spring still exists at the edge of the snowfield that fills the 
summit crater. Although there is no sign that they are imminent, 
future eruptions of Shasta, Lassen, and other Cascade volcanoes, are 
not only possible, but probable. 

The Medicine Lake Highland, some 35 miles east of Mount Shasta, 
is generally regarded as an outlier of the Cascade Range. The region 
is underlain by the Oligocene to Miocene Cedarville Series and the 
Pliocene Warner Basalt, both of which are widespread in the Modoc 
Plateau, to the east. The building of the Highland was preceded, in 
early Pliocene time, by eruption of flows and domes of rhyolite and 
rhyolitic obsidian and a flow of incandescent ash, and farther w^est by 
the building of a series of cones of massive basalt flows. Then, in 
late Pliocene and early Pleistocene time, a shield volcano 20 miles 
across was formed, of pyroxene andesite. After reaching a height of 
about 2,500 feet, the top of the shield collapsed to form a caldera 6 
miles long, -4 miles wide, and 500 feet deep. Lava rising along the cir- 
cular fractures that bomided the caldera formed flows that poured into 
it, building cones that eventually overtopped its rim and sent new 
flows down the outside of the shield. The resulting eight small vol- 
canoes completely hide the caldera boundaries, forming between them 
the basin that holds Medicine Lake. Later Pliocene and Pleistocene 


eruptions of andesite, dacite, and rhyolite built broad ridges north 
and south of the laJie basin, including the perlitic rhyolite mass of 
Mount Hoffmann, flows of glassy dacite just north of Medicine Lake 
and on the south side of Mount Hoffman, and finally — about 1700 
years ago — the obsidian masses of Little Glass Momitain and Glass 
Moimtain. Transition of the Medicine Lake Highland to the Modoc 
Plateau is marked by Recent basalt flows and cinder cones of types 
widespread in the Plateau, on the flanks of the Highland. 

Modoc Plateau 

The Modoc Plateau is a highland region capped by vast late Tertiary 
and Quaternary basalt plains and numerous volcanic shield cones that 
largely overlap older basin-range structures. These structures are 
typified by fault-block mountains of Tertiary volcanic rock, wnth inter- 
vening basin-like grabens that commonly contain sedimentary rocks 
deposited in large Pliocene and Quaternary lakes that had resulted 
from interruption of the drainage by faulting or volcanism. To the 
east and southeast the Modoc Plateau merges w^ith the Great Basin, 
across an arbitrary boundary. The Warner Range, which borders the 
Modoc Plateau on the east, is generally regarded as a part, of the Great 
Basin, but its rocks and general structure are continuous with those of 
the Modoc region. On the west, the border of the Modoc Plateau with 
the Cascade Range is also indefinite; the faulting characteristic of the 
Modoc region extends into the edge of the Cascade Range, and some 
types of rocks arci conunon to both provinces. 

The oldest rocks of the Modoc region are a series of interbedded lava 
flows, pyroolastic rocks, and lake deposits forming some of the block- 
faulted ranges, and generally tilted at an angle greater than 20°. 
Through similar lithology and structiu'al relationships, they are cor- 
related with the Cedarville Series, which is best exposed in the Warner 
Range, w^here it ranges in age from late Oligocene to late Miocene. 
The Cedarville Series is mainly andestitic, but ranges from basalt to 
rhyolite. Several small gold, copper, and mercury deposits have been 
fomid in rocks associated with it. 

Rocks of Pliocene age include both volcanic and lake deposits. The 
latter include the Alturas Formation, which occupies the basin west of 
the Wanier Range in the vicinity of Alturas, and similar rocks in the 
basin of Lake Britton and the valley of Willow Creek west of Tulelake. 
The lake sediments are tuffaceous siltstones and ashy sandstones — the 
latter commonly ranging to current- bedded, water-laid tuffs — and 
thick, extensive deposits of diatomite with variable ash content. The 
Pliocene volcanic rocks include basalt and andesite lava flows and mud 
flows, and dacitic to rhyolitic pyroclastic rocks. Southwest and west 
of Alturas, the Alturas Formation is locally associated with beds of 
pumiceous welded tuff, fonmed by incandescent flows of ash ; the tuff 
has been quarried to a minor extent for buildmg stone. Similar but 
less- welded Pliocene ash-flow deposits are also present in the momitains 
between Canby and Adin, where they are interbedded with lava flows 
and mud-flow deposits, as well as stream- and lake-deposited sediments. 

The older Pliocene rocks, like those of Miocene age, are found in 
block-faulted mountain ranges. Later volcanic rocks, also tentatively 
assigned to the Pliocene, are much less faulted and retain to a much 


greater degree their original constructional land forms. These include 
a series of small shield volcanoes between Honey Lake and the Madeline 

Throughout much of the Modoc Plateau region the basins between 
the fault-block ranges were flooded by wide-spreading, very fluid flows 
of basalt, erupted mostly from fissure vents, that formed flat plain 
surfaces rather than volcanic cones. These "plateau" basalts have 
generally been i-eferred to as "Warner Basalt," but because of uncer- 
tainty of the correlation with the basalt farther northeast, the basalt 
in the region just north of Lassen National Park has been called the 
Burney Basalt. At the north edge of Lake Britton, pillow lavas at 
the base of the Warner Basalt are intermingled with Pliocene diato- 
maceous lake sediments, and are almost surely of Pliocene age; but 
near Lassen Park the Burney Basalt overlaps folded and eroded 
andesites that cannot be older than latest Pliocene, and it is therefore 
milikely that the basalt is older than earliest Pleistocene. In the 
Modoc Plateau region as a whole, the rocks called Warner Basalt 
probably range from late Pliocene to Pleistocene in age. 

Younger than the Warner Basalt is a series of lower Pleistocene to 
Recent basalt flows and associated cinder cones ; small shield volcanoes, 
many of them capped with cinder cones; and lake beds. The lake 
sediments resemble those of Pliocene age. Tlie shield volcanoes are 
mostly basalt, but partly andesite. Chemically, mineralogically, and 
texturally, many of these flow basalts resemble the Warner Basalt. 
Many of them are of pahoehoe type, like most of the Warner flows, 
and in places contain many lava tubes such as those of the Lava Beds 
National Monument and Hat Creek Valley, where the lavas are 
probably less than 2000 years old. 

Other very recent flows are of the aa or block lava type. These in- 
clude the Callahan and Burnt Lava flows on the flanks of the Medicine 
Lake Highland, and the quartz basalt flows at Cinder Cone in the 
northeastern part of Lassen National Park, which last erupted in 1851. 

The faults of the Modoc region trend in a northwesterly to north- 
erly direction. The Likely fault is believed to have had appreciable 
right-lateral movement, but most of the faults are normal, with pri- 
marily vertical displacement. The normal faulting reached a maxi- 
mum near the end of the Miocene, but has continued into Recent time. 
Occasional earthquakes suggest that some of the faults, such as that 
along the east side of Hat Creek Valley, are still active. 

Large volumes of water issue from the Warner and later basalts 
at several places, including Big Spring, near Old Station on Hat 
Creek ; Rising River, farther north in the same valley ; the springs at 
Burney Falls and along Burney Creek just above the falls; and those 
at the headwaters of Fall River. The latter, with a flow of about 900 
million gallons daily, are among the largest springs in the United 

Great Basin 

Two minor projections of the Great Basin province — the Warner 
Range-Surprise Valley area, and Honey Lake Valley — adjoin the 
Modoc Plateau and the Sierra Nevada provinces in northeastern Cali- 
fornia. Their dominant northeast-trending block-faulted structure 


is characteristic of the Great Basin province, but their rocks are re- 
lated to adjacent provinces rather than to those of the Great Basin. 
The Warner Range is uplifted at least 5,500 feet vertically, west of 
the Surprise Valley normal fault, and consists mainly of andesitic 
to basaltic flows and pyroclastic rocks of the Oligocene to Miocene 
Cedarville series. Flows of Pliocene to Pleistocene "Warner Basalt" 
cover the gentler sloping south^vest flank of the range, and w^th the 
coalescing Miocene and Pliocene shield volcanoes that form its south- 
ern end, are transitional from the Great Basin to the Modoc Plateau. 
Toward the Oregon border, the range has a steeper, faulted western 
front, lapped with Quaternary gravels that probably represent accel- 
erated erosion and transport in glacial times. Intrusive masses of post- 
Cedarville rhyolitic rocks in the northern part of the range include 
the gold veins of the High Grade district, the quicksilver showings 
along the Goose Lake front of the range, and notable deposits of 
obsidian and perlite. 

Surprise Valley, the near- desiccated site of Pleistocene Lake Sur- 
prise — contemporary of Lake Lahontan, wiiich was only 35 miles to the 
south — is a graben east of the spectacular Surprise Valley fault scarp. 
Numerous hot springs and the eruption of a mud volcano in 1955 sug- 
gest recency of fault movement and continued connection with under- 
lying thermal zones. 

Honey Lake Valley is a graben wedged between the northern end 
of the Sierra Nevada granitic mountains, and the southern end of the 
Modoc Plateau volcanic terrane. Spectacular faults form the Sierra 
front and bound the Fort Sage Mountains block at the southeast end 
of the Valley. Steeply tilted and folded Tertiary lake sediments at 
the southeast end of Honey Lake are almost concealed by Recent lake 
and alluvial cover. Tufa-building hot springs along the northeast 
edge of the valley, some with traces of quicksilver, suggest hidden ex- 
tensions of province-bounding faults. 


(By C. A. Bepenning, D. L. Jones, and W. O. Addicott, U.S. Geological Survey, 

Menlo Park, Calif. ) 

The Great Valley of California is an elongate northwest-trending 
structural trough formed by the westward tilting of the Sierra Nevada 
block against the eastern flank of the Coast Ranges. In general, sed- 
iments deposited in this trough dip uniformly westward away from 
the Sierra Nevada except in a belt along the southern and western 
sides of the Great Valley where deposition was greatest and where 
deposits generally dip to the east. Tlie Coast Ranges have not devel- 
oped in as structurally uniform a way as has the Sierra Nevada and 
the western limit of the Great Valley depositional basin was poorly 
defined in pre-Tertiary time. In early Tertiary time, however, evolu- 
tion of the Coast Ranges progressed to the point where the western 
limits of the Great Valley depositional basin were in large part co- 
incident with those of the modern geomorphic province. 

In this great trench the accumulation of sediments may locally have 
reached a thickness of 6 miles in the San Joaquin Valley and 10 miles 


in the Sacramento Valley. Most of the deposits in the Sacramento 
Valley are composed of Upper Jurassic and Cretaceous sandstone and 
siltstone of marine origin. The deposits in tlj£LSaiL JoaquinJValley by 
contrast, are_largeIyJlce_taceojLS_|indJCerfciary marine sandstone, silt- 
stone, and claystone with an increasing proportion of continental 
deposits in younger strata. The consequent fticies variations in the 
Tertiary deposits of the San Joaquin Valley have led to a complex 
stratigraphic nomenclature and have provided a wide variety of 
stratigraphic traps for the accumulation of petroleum. 

Pre-Tertiary Rocks 

Clastic upper Mesozoic rocks, ranging in age from Late Jurassic to 
Late Cretaceous, form an enonnously thick wedge that thickens from 
a few hundred f eeft on the east to over 40,000 feet on the west. The 
rocks on the eastern side are dominantly shallow Avater marine, with 
perhaps some minor brackish water or nonmarine beds present, and 
on the western side are dominantly deep water, marine turbidites. Tlie 
present western margin of these rocks is a major fault marked by 
extensive intrusion of serpentine that separates the structurally simple, 
eastward-dipping rocks of the Great Valley from the structurally 
complex and partly metamorphosed upper Mesozoic rocks of the Coast 

Upper Jurassic rocks are thickest along the western edge of the 
Sacramento Valley where they comprise about 15,000 feet of 
dominantly dark gray fine- to coarse-grained clastic sediments. 
Marine volcanic rocks are locally present in the lower part of the 

In the San Joaqum Valley, Upper Jurassic rocks are much thinner 
than in the Sacramento Valley, and range in thickness from a few 
hundred feet to perhaps several thousand feet. The dominant rock 
type is bluish-gray siltstone and shale with fossiliferous, light gray- 
weathering limestone concretions. 

Lower Cretaceous rocks are thickest and most widespread on the 
western side of the Sacramento Valley where they comprise 15 to 20 
thousand feet of alternating thick units of mudstone, sandstone, and 
conglomerate. Facies changes along strike are common, and there 
is complex intertonguing and lensing-out of sandstone and conglom- 
erate beds. 

In the San Joaquin Valley, a very thm sequence of lowermost 
Cretaceous rocks apparently rests conformably on Upper Jurassic 
rocks, and this, in turn, is overlain directly in many places by thick 
Upper Cretaceous rocks. In a few places, beds of late Early Cretace- 
ous (Albian) age crop out, but their distribution and relationship are 
poorly understood. Apparently much of the San Joaquin Valley 
region either received little or no sediment during most of Early 
Cretaceous time, or the rocks were removed by erosion prior to deposi- 
tion of Upper Cretaceous beds. 

Upper Cretaceous rocks are widespread on both the east and west 
sides of the Great Valley and consist of alternating thick units of 
sandstone, mudstone, and locally thick conglomerate lenses. In the 
southern and central part of the western Sacramento Valley, each 


sandstone and mudstone imit has received a formational name as 
shown on the correlation chart, but these units become unreco^izable 
to the north. On the east side of the Sacramento Valley, a few thou- 
sand feet of fossiliferous sandstone, shale, and conglomerate are ex- 
posed in the valleys of the major rivers. Near Chico these deposits 
have been named the Chico Formation. 

Uppermost Cretaceous rocks which occur only in the subsurface in 
the southern and central parts of the Sacramento Valley contain large 
reserves of gas. The principal Cretaceous producing horizons are the 
Forbes Formation, Kione Formation or Sand, and Starkey Sand. 

Upper Cretaceous rocks of the San Joaquin Valley are generally 
subdivided into the P anoche Gro up or Formation and the overlying 
Moreno Formation or shale. The Panoche Group comprises over 
20,000 feet of alternating thick units of shale, sandstone, and conglom- 
erate that exhibit rapid f acies changes along strike. 

The Moreno Formation consists of about 3,000 feet of purple and 
maroon claystone with minor beds of sandstone and white porcellan- 
ite. Organic remains, mainly fish scales, foraminifera, and diatomite, 
are common, as is pyrite in the subsurface and gypsimi at the surface. 
Deposition probably took place in a restricted basin with stagnant 
conditions near the bottom. The uppermost part of the Moreno 
Formation is of earliest Tertiary age. 

Significant natural gas production from sandstone reservoirs in the 
Panoche and Moreno is developed in several fields in the northern 
part of the San Joaquin Valley, principally in the vicinity of Stockton. 

Tertiary Rocks 

In contrast to pre- Tertiary deposition, Tertiary deposition took 
place in more limited basins which more nearly approximate the 
modern boundaries of the province. Three structural developments 
restricted the Tertiary depositional basins: evolution of the Coast 
Ranges progressively limited the westward continuity of depositional 
basins with the Pacific; proportionately greater westward tiltmg of 
the southern part of the Sierra Nevada block accentuated basining 
in the San Joaquin Valley area so that marine basins gradually with- 
drew southward from the Sacramento Valley ; and a prominent arch, 
the Stockton arch, united the Sierra Nevada with the Coast. Ranges 
and disintegrated the continuity of the marine depositional basins 
within the Great Valley province (fig. 4) . 

Paleocene and early Eocene marine deposits were formed in the 
southern part of the Sacramento Valley. This sequence includes the 
Martinez and Meganos Fonnations, important gas producing units. 
The overlying Capay Formation is a widespread transgressive unit 
that unconformably oversteps lower Tertiary and Upper Cretaceous 
rocks towards the north and the east in the subsurface. These for- 
mations are composed of dark gray, green, and brown siltstone, sand- 
stone, and conglomerate with locally abundant glauconite. Scattered 
continental deposits of probable Paleocene or Eocene age occur in 
the northern end and along the eastern side of the Sacramento Valley. 

Two unusual subsurface features of early Eocene age are the Prince- 
ton and Meganos Gorges of the central and southern parts of the 




Tertiary and Quaternary 
I sedimentary rocks 

I Pre-Tertiary rocks and 
iTertiary volcanic rocks 


Figure 4. Index map of Great Valley locating selected palegeograpMc features. 

Sacramento Valley. These south- to southwest-trending submarine 
erosional channels and their sedimentary fill are important in the en- 
trapment of gas in west -dipping Cretaceous and lower Tertiary 

Marine early Tertiary shale and minor sandstone included in the 
Lodo Formation were deposited in a basin lying between the Stock- 
ton arch and Bakersfield. One of several prominent Paleocene to 
middle Eocene sandstone units along the western side of the basin, 
the Tesla Formation, may have been deposited in a strait that crossed 
the western end of the Stockton arch and united the Paleocene to 
middle Eocene basins on either side. Part of the early Tertiary con- 
tinental deposits along the east side of the San Joaquin Valley may be 
equivalent in age to the Lodo. 


A widespread unconformity separates early Eocene from late Eo- 
cene rocks south of the Stockton arch. On this erosion surface the 
Domengine Sandstone and the Kreyenhagen Shale were deposited. 
North of the arch a relatively thin blanket of sandstone, the lone 
Formation, covers the east side of the south half of the Sacramento 
Valley. Thick late Eocene deposits consisting of interbedded shale 
and sandstone (Domengine?, Nortonville, and Markley Formations) 
are present only in the southwestern part of the valley. Late Eocene 
deposits are missing on the Stockton arch. In tJ^e Sa n Jo aquin Val- 
ley the late Eocene marine basin extended southward to deposit the 
thick Tejon Formation at the foot of the San Emigdio Mountains. 
Continental sediments of apparent late Eocene age were deposited 
along the foot of the Sierra Nevada. 

Oligocene deposits were formed in essentially the same basms as the 
late Eocene deposits. North of the Stockton arch a pronounced period 
of erosion followed late Eocene deposition. In the southern part of 
the Sacramento Valley a prominent south- to southwest-trending sub- 
marine channel of latei Eocene to Oligocene age, the Markley Gorge, 
was eroded into lower Tertiary strata and subsequently filled with 
marine sand and siltstone. South of the arch, however. Eocene to 
Oligocene deposition appears to have been continuous. Oligocene 
sediments are donnnantly shale and are often jncludedjgith the under- 
lying Kreyenhagen ^Kale. In tKe^outhem part of the San Joaquin 
Valley, however, sandstone, partly of continental origin, is a prominent 
part of the Oligocene section. 

In early Miocene time no marine deposits were formed north of the 
Stockton arch. South of the arch lower Miocene marine deposits in 
the south half of the San Joaquin Valley consist of sandstones and 
sandy shales including the Temblor Formation and the Vedder Sand. 
Continental formations border these marine deposits on the south and 
the southeast. A fairly thick sheet of continental deposits interfingers 
with the marine section in the central part of the San Joaquin basin 
and extends northward across the Stockton arch into the Sacramento 
Valley. Extensive rhyolitic tuffs and other volcanic materials are 
present in the continental lower and middle Miocene deposits of the 
Sacramento Valley. 

In middle Miocene time the areas of deposition remained essentially 
the same but less marine sandstone was formed. Sand content in- 
creased again during the late Miocene as the basin shoaled and the 
shoreline began retreating towards the west. The Santa Margarita 
Sandstone of the eastern part of the marine basin was overlain by 
nonmarine Miocene- and Pliocene deposits including the Chanac For- 
mation. To the west, in the deeper part of the basin from Coalinga 
to the southern end of the valley, dominantly fine-grained diato- 
maceous, cherty and siliceous sediments were deposited. Discontinuous 
offshore sandstones in the southern part of the basin, such as the 
Stevens Sand, form many oil-producing stratigraphic traps. 

North of the Stockton arch, the sea gradually transgressed east- 
ward from the San Pablo basin west of the Great Valley and by late 
Miocene time extended into, the western part of the Sacramento Valley. 

During the late Miocene and the Pliocene volcanic sediments being 
deposited in the southeastern quarter of the Sacramento Valley 


changed composition from rhyolitic (Valley Springs Formation) to 
andesitic (Mehrten Formation). The change from rhyolitic to ande- 
sitic debris is also found in the marine conglomerates of the San Pablo 
Group near the southwestern edge of the Sacramento Valley. 

Tectonic activity in the Great Valley at the beginning of Pliocene 
time resulted in erosion in many areas, particularly along the western 
edge of the San Joaquin Valley. Many of the oil fields in this area 
produce either from structural traps caused by the early Pliocene 
warping or from truncated Miocene reservoir beds sealed by Pliocene 
deposits. With few exceptions, the present boundaries of the Great 
Valley were developed during the early Pliocene orogeny, and Pliocene 
deposition, largely continental, took place in all parts of the valley. 

Pliocfiiie-4iLarine deposition in the Great Valley was restricted to 
the south half of the San Joaquin Valley. In the western part of the 
area shallow water conglomerate, sandstone, and sandy shale of the 
Jacalitos, Etchegoin, and San Joaquin Formations were deposited. 
The basal Pliocene units unconformably overlie the upturned edges 
of older rocks along the western and southern margins of the valley. 
As Pliocene deposition continued the sea gradually retreated and 
the thick wedge of continental deposits of the southeastern part of the 
valley spread basinward. The nonmarine Chanac and Kern River 
Forrnations of the southeastern San Joaquin Valley are continuous 
Avith Pliocene continental deposits that cross the Stockton arch and 
extend throughout the Sacramento Valley. 

Pleistocene Eocks 

Deposition in most parts of the Great Valley was continuous from 
Pliocene to Pleistocene time. In the area of marine Pliocene deposi- 
tion fresh-water lakes were formed at about the beginning of Pleis- 
tocene time due to disintegration of the seaway between the Great 
Valley and the Pacific by rising blocks of the Coast Ranges. Lacus- 
trine sandy shale and sandstone of the Tulare Formation unconform- 
ably overlie marine Pliocene rocks along the west side of the Valley. 
These grade marginally into continental deposits. 


During the later Mesozoic the Great Valley was the site of deposi- 
tion of a great wedge of marine sedimentary rocks that reached 
thicknesses of more than -1:0,000 feet along the west side. As deposition 
continued the locus of maximum sedimentation gradually was dis- 
placed southward from the northern part of the Great Valley to the 
extreme south end by latest Tertiary time. Widespread Mesozoic 
deposits of Late Cretaceous age gave way to much restricted deposi- 
tional basins in the early Tertiary when the Great Valley became 
separated by the cross- valley Stockton arch. Tertiary marine deposi- 
tion in the southern part of the Sacramento Valley north of the 
Stockton arch continued into the Oligocene after which the seas re- 
treated to the San Pablo Basin, a small marginal basin to the south- 
west. The initial locus of marine Tertiary deposition in the San 
Joaquin Valley was centrally located adjacent to the Vallecitos Straits, 
a persistent Paleocene to middle Miocene connection to the sea. Begin- 
ning in late Eocene time, the locus of deposition shifted toward the 


south end of the Valley and an additional marine connection opened 
along the southwest side of the Valley. Upper Eocene and later 
sedimentary deposits were localized in sub-basms created by a cross- 
valley submarine ridge, the Bakersfield arch. Marine deposition ceased 
at the close of the Pliocene. 

Selected References 

Payne, M. B., 1960, Type Panoche, Panoche Hills, Fresno County, California : 

Soe. Ek?on. Paleontologists and Mineralogists, Pacific Section, Guidebook 1960 

Spring Field Trip, 12 p. 
Reed, R. D., 1933, Geology of California : Tulsa, Oklahoma, Am. Assoc. Petroleum 

Geologists, 355 p. 
Repenning, C. A., 1960, Geologic summary of the central valley of California with 

reference to the disposal of liquid radioactive waste : U.S. Geol. Survey Trace 

Elements Invest. Rept. 769, 69 p. 
Safonov, Anatole, 1962, The challenge of the Sacramento Valley, California : 

in Bowen, O. E., Jr., ed.. Geologic guide to the gas and oil fields of northern 

California : California Div. Mines Bull. 181, p. 74-97. 
Woodring, W. P., Stewart, Ralph, and Richards, R. W., ItKlO, Geology of the 

Kettleman Hills oil fields, California : U.S. Geol. Survey Prof. Paper 195, 170 p. 


(By P. C. Bateman, U.S. Geological Survey, Menlo Park, Calif.) 

The Sierra Nevada is a strongly asymmetric mountain range — it has 
a long gentle western slope and a short steep eastern escarpment that 
culminates in its highest peaks. It is 50 to 80 miles wide and iiuis west 
of north through eastern California for more than 400 miles- — from 
the Mojave Desert on the south to the Cascade Range and Modoc 
Plateau on the north. Mount Wliitney, in the southeastern part of the 
range, attains a height of 14,495 feet and is the highest point in the 
conterminous 48 States. The "High Sierra,-' a spectacular span of the 
crest, which extends north from Mount Whitney for about a hundred 
miles, is characterized by a procession of 13,000- and 14,000-foot peaks. 

The Sierra Nevada is a tremendous physical barrier and a highly 
effective trap for capturing moisture from air moving eastward from 
the Pacific. Warm moist air from the ocean is forced upward into 
colder regions ; and because cool air can hold less moisture than warm 
air, precipitation across the Sierra Nevada is heavy. The small pre- 
cipitation in the arid Great Basin to the east, in the rain shadow of the 
Sierra Nevada, is evidence of the effectiveness of the Sierra Nevada as 
a trap for moisture. 

General Geologic Relations 

The Sierra Nevada is a huge block of the earth's crust that has 
broken free on the east along the Sierra Nevada fault system and been 
tilted westward. It is overlapped on the west by sedimentary rocks 
of the Great Valley and on the north by volcanic sheets extending 
south from the Cascade Range. Volcanic sheets cap large areas in the 
north part of the range. 

Most of the south half of the Sierra Nevada and the east half of the 
north part is composed of plutonic (chiefly granitic) rocks of Mesozoic 
age. These rocks constitute the Sierra Nevada batholith, which is part 


of a belt of plutonic rocks that runs southward into Baja California 
and northward into western Nevada, Idaho, and British Columbia. 
In the north half of the range the batholith is flanked on the west by 
the western metamorphic belt, a terrane of strongly deformed and 
metamorphosed sedimentary and volcanic rocks of Paleozoic and 
Mesozoic age. J^The famed Mother Lodt passes through the heart of 
the western metamorphic belt. Farther south, scattered remnants of 
metamorphic rock are found within the batholith, especially in the 
western foothills and along the crest in the east -central Sierra Nevada. 
Sedimentary strata of Paleozoic and late Precambrian age predomi- 
nate east of the Sierra Nevada in the Wliite and Inyo Mountains. 

Paleozoic and Mesozoic Stratified Rocks 

The Paleozoic strata in the metamorphic remnants of the eastern 
Sierra Nevada are chiefly metamorphosed sandstone, shale, and lime- 
stone, whereas those in the western part of the range contain abundant 
volcanic rocks and sedimentary rocks that were derived from volcanic 
rocks. The materials in the eastern strata were derived chiefly from 
the erosion of older terranes and accumulated in shallow seas where 
limestone reefs flourished (miogeosynclinal environment) ; on the other 
hand, much of the materials in the western strata were derived from 
volcanic outpourings and accumulated to great thickness in deeper 
parts of the ocean (eugeosynclinal environment). 

The most complete section of Paleozoic rocks in the eastern Sierra 
Nevada is in the Mount Morrison roof pendant, where more than 
30,000 feet of strata of Ordovician to Permian ( ? ) age are exposed. 
Tliere the oldest rocks, chiefly slate and chert, are overlain by sandy 
limestone and calcareous sandstone; these strata are overlain, in turn, 
by thin-bedded hornfels that was derived from siltstone, mudstone, 
and shale. 

In the western metamorphic belt, most of the Paleozoic strata have 
been referred to the Calaveras Formation, which contains sparse fossils 
of Permian age in its upper part, but which is very thick and for the 
most part unfossiliferous. However, strata of Mississippian and 
Silurian ( ?) ages are present in the Taylorsville area, at the north end 
of the belt. In the southern part of the western metamorphic belt, the 
most extensive Paleozoic rocks are carbonaceous phyllite and schist 
with thinly interbedded chert, but lenses of mafic volcanic rocks and 
carbonate are widespread and locally attain thicknesses of several 
thousand feet. In the northern part, mafic volcanic rocks, slate, and 
sandstone constitute about equal parts of the Paleozoic section. 

Strata of Mesozoic age crop out in several northwest -trending belts 
that parallel the long axis of the Sierra Nevada. In the eastern part 
of the range, a belt of metamorphic remnants that contains Mesozoic 
strata extends for more than 150 miles. The rocks in this belt are 
chiefly volcanic rocks of intermediate composition and graywacke- 
type sandstone derived chiefly from volcanic rocks. These rocks 
weather gray and contrast strongly with nearby strata of Paleozoic 
age which weather reddish brown. The thickest section of Mesozoic 
strata is exposed in the Ritter Range roof pendant and is about 30,000 
feet thick. Early Jurassic fossils have been collected from a locality 
about 10,000 feet above the base of this section. 


In the western metamorphic belt, the Paleozoic strata are flanked 
by Mesozoic strata on the west and, in the north part, also on the east. 
In additi6n, at least part of the strata in a g:ronp of roof pendants that 
extends for about 65 miles southeast through the heart of the batholith 
from lat ';}T° N. is of Mesozoic age. 

These strata of the western metamorphic belt have yielded both 
Triassic and Jurassic fossils, but Triassic strata are of small extent 
and m.ost of the strata are Upper Jurassic. The Upper Jurassic rocks 
include sequences of slate, graywacke, conoflomerate, and volcanic 
rocks. These rocks commonly are interbedded and in places inter- 
tongue with volcanic rocks. 

The Paleozoic and Mesozoic strata of the Sierra Nevada have been 
complexly folded and faulted, and steep or vertical beds, cleavage, and 
lineations, including fold axes, are common. A predominance of op- 
posing, inward-facing top directions in the strata on the two sides of 
the range define a complex faulted synclinorium, the axial part of 
which is occupied by the granitic rocks of the batholith. The axis of 
the synclinorium trends about N. 40° W. in the central part of the 
range but trends northward in the northern part. 

The eastern limit of the synclinorium is marked by a belt of Pre- 
cambrian and Cambrian rocks that extends from the White Mountains 
southeastward into the Death Valley region. The western limit pre- 
sumably lies beneath the Cretaceous and Tertiary strata of the Great 
Valley. The range-front faults that bound Owens Valley and the east 
side of the Sierra Nevada strike obliquely across the major structures 
in the Paleozoic and Mesozoic strata. In the White and Inyo Moun- 
tains and in many remnants within the Sierra Nevada batholith the 
strata are strongly folded and faulted, causing many repetitions of 
formations, but in the Mount Morrison and Ritter Eange pendants of 
the eastern Sierra Nevada the gross structure is homoclinal, and tops 
of beds face west across more than 50,000 feet of vertical or steeply 
dipping strata ranging from Ordovician to Jurassic in age. 

In the western metamorphic belt the gross distribution of strata 
resulting from the development of the synclinorium has been reversed 
by movement along steeply dipping fault zones of large displacement, 
and the Paleozoic strata lie between two belts of Mesozoic strata. The 
internal structure of the individual fault blocks is, in general, homo- 
clinal, and most tops are to the east; beds dip eastward steeper than 
60°. The homoclinal structure is interrupted in parts of the belt by 
both isoclinal and open folds, but even in such places the older strata 
of a fault block generally are exposed near its west side and the 
younger strata near its east side. 

The Sierra Nevada lies within the mobile belt of the western Cordil- 
lera and represents part of the extended deformation within that re- 
gion. The steep dips of thick stratigraphic sequences Avithin the 
Sierra Nevada indicate that the amplitude of the synclinorium was 
very great and that the sialic upper crust was depressed deeply into 
the region of the lower crust or mantle. This circumstance and the 
localization of the granitic rocks in the axial region of the syncli- 
norium suggests that the magmas that rose from depth and crystal- 
lized to granitic rock were formed by partial fusion of sialic rocks 
that had been depressed into regions of high temperature. 


The Batholith 

The batliolith is composed chiefly of quartz-bearing granitic rocks 
ranging in composition from quartz diorite to alaskite, but includes 
scattered smaller masses of darker and older plutonic rocks as well as 
renuiants of Paleozoic and Mesozoic metamorphic rocks. In gen- 
eral, granodiorite and quartz diorite predominate in the western Sierra 
Nevada and quartz monzonite in the eastern Sierra Nevada, but some 
felsic plutons are f omid in the west and some mafic ones in the east. 

Tlie granitic rocks are in discrete masses or plutons that are in sharp 
contrast with one another or are separated by thin septa of meta- 
morphic or mafic igneous rocks or by late aplitic dikes. Individual 
plutons range in area from less than a square mile to several hundred 
square miles — the limits of many large plutons have not been deline- 
ated. On the whole, the batholith appears to consist of a few large 
plutons and a great many smaller ones. All of the larger and some 
of the smaller plutons are elongate in a northwesterly direction, paral- 
lel with the long direction of the batholith, but many of the smaller 
ones are elongate in other directions or are irregularly shaped or 
roimded. \^ 

Isotopic dates of minerals by the potassium-argon method and of 
whole rocks by the rubidium-strontium method suggest at least three 
age groups of granitic rocks. In the eastern Sierra Nevada several 
granodiorites are at least 180 million years old (Late Triassic or Early 
Jurassic) ; in the western Sierra Nevada the plutons appear to be 140 
to 150 million years old; and along and just west of the crest the 
plutons appear to be 80 to 90 million years old (early Late Cretaceous) . 

The batholith is almost devoid of mineral deposits except for con- 
tact-metasomatic deposits of tungsten. Nevertheless, the batholith is 
generally thought to be the source of the many deposits of gold, copper, 
lead, zinc, and silver peripheral to it. Major tungsten deposits occur 
in the eastern Sierra Nevada where Paleozoic carbonate rocks are in 
contact with silicic intrusives, and in the western Sierra Nevada in a 
migmatite zone in granodiorite. Rich deposits of gold, copper, chrome, 
limestone, and building stone are present in the western metamorphic 

During the Early Cretaceous the Sierra Nevada was part of a nar- 
row north-trending highland that lay between the Pacific region and 
the Rocky Moimtain geosyncline. The enormous quantities of ma- 
terial that were deposited in those areas suggest deep erosion of the 
Sierra Nevada region, amounting to several miles, between the em- 
placement of the Late Jurassic and the early Late Cretaceous plutons. 
The amomit of material eroded from the Sierra Nevada since the end 
of the Cretaceous has been much less — perhaps only a mile or two on 
the average. Thus it seems probable that the present level of exposure 
is much deeper into the Jurassic intrusives than into the Cretaceous 
intrusives. ^v 

Uplift and Sculpturing of the Sierra Nevada 

The sedimentary deposits in the Great Valley were deposited across 
the downslope continuation of the tilted Sierra Nevada block. Dur- 
ing the Tertiaiy, a deep basin formed in the southern part of the Great 
Valley while only a shallow basin formed in the north part, suggesting 

67-164 0^«6— pt. I 5 




much greater tilting and uplift of the southern than of the northern 
Sierra Nevada. A deep Cretaceous basin in the north part of the Great 
Valley suggests precisely opposite conditions during the Cretaceous — 
that is, greater tilting and uplift of the northern Sierra Nevada. 

The volumes of sedimentary rocks that have collected in the Great 
Valley during different epochs indicate that the rate of sedimentation 
increased progressively during the Tertiary. This suggests, in turn, 
that the a^^erage rate of uplift of the Sierra Nevada also increased 
progressively during the Tertiary although there is evidence to indi- 
cate that tilting and uplift occurred at irregular intervals. The de- 
tails of uplift have been studied from records of erosion surfaces, from 
the profiles of ancient and modern streams, and from the sedimentary 
histoi-y in the Great Valley. The minimum ages of landforms have 
been determined from animal and plant remains collected from sedi- 
mentary deposits that rest on the landforms and by potassium-argon 
dating of volcanic rocks. 

During the first part of the Tertiarj' the Sierra Nevada was a broad, 
gently sloping upland. Gold-bearing gravels were deposited in broad 
graded streams during the Eocene and Oligocene. In late Miocene 
time extensive bodies of rhyolite tuff and associated gravel (Valley 
Springs Formation) were deposited across the old landscape of the 
northern Sierra Nevada. Somewhat later, during the Pliocene, ande- 
sitic mudflows together with conglomerate and sandstone (Mehrten 
Formation) buried the northern Sierra Nevada under a volcanic 
blanket that ranged from 1,500 feet thick at the west foot of the range 
to more than 4,000 feet along the crest. These eruptions buried the 
old drainages, and new drainages were then developed upon the con- 
structional surface of the volcanic rocks. Apparently, the southern 
Sierra NevacDt was not affected by widespread volcanism, although 
volcanic outpourings took place locally. 

During the later part of the Tertiary, sporadic westward tilting 
resulted in rhe uplift of erosion surfaces to different levels. Tlie most 
recent major uplift occurred after volcanic rocks, with a potassium- 
argon age of about 3 million years, were erupted, and as a result streams 
were entrenched in narrow, steep-sided can3'ons. 

During the early stages of uplift, the southern Sierra Nevada was 
the west flank of a broad arch that extended across the region east 
of the Sierra Nevada to Death Valley, and it seems likely that some 
such structure also existed for the northern Sierra Nevada. As the 
curvature of the arch increased, faults began to form and eventually 
the crest and east flank of the arch broke up to form Owens Valley 
and the basins and ranges eastward to Death Valley. 

During the Pleistocene, after the crest of the Sierra Nevada had 
been uplifted to near its present height, glaciers formed and swept 
down canyons both to the east and to the west. These glaciers sharj)- 
ened peaks, rounded canyons to U -shapes, and formed myriad other 
forms that add so much to the interest and beauty of the Sierran 

The last uplifts and glaciations took place so recently that we cannot 
say they are of the past. Continued earth movements are indicated 
by earthquakes and minor seismic activity along the east side and 
near the south end of the range and by geodetic measurements. Only 


a slight increase in average winter precipitation, especially if accom- 
panied by lowering of the average summer temperature, would initiate 
a new epoch of glaciation. 

Selbxjted references 

Bateman, P. C, Clark, L. D., Huber, N. K., Moore, J. G., and Rinehart, C. D., 

1963, The Sierra Nevada batholith — a synthesis of recent work across the 

central part : U.S. Geo!. Survey Prof. Paper 414-D, p. D1-D46. 
Clark, L. D., 1965, Stratigraphy and structure of part of the western Sierra 

Nevada metamorphic belt: U.S. Geol. Survey Prof. Paper 410, 70 p. 
Durrell, Cordell, 1940, Metamorphism in the southern Sierra Nevada northeast 

of Visalia, California : California Univ. Dept. Geol. Sci. Bull., v. 25, p. 1-118. 
Ferguson, H. G., and Gannett, R. W., 1932, Gold quartz veins of the Alleghany 

district, California : U.S. Geol. Sur\^ey Prof. Paper 172, 139 p. 
Johnston, W. D., 1940, The gold quartz veins of Grass Valley, California : U.S. 

Geol. Survey Prof. Paper 194, 101 p. 
Knopf, Adolph, 1918, A geological reconnaissance of the Inyo Range and eastern 

slope of the southern Sierra Nevada, with a section on the stratigraphy of 

the Inyo Range, by Edwin Kirk: U.S. Geol. Survey Prof. Paper 110, 130 pi 
, 1929, The Mother Lode system of California: U.S. Geol. Survey Prof. 

Paper 157, 88 p. 
Lindgren, Waldemar, 1911, The Tertiary gravels of the Sierra Nevada : U.S. Geol. 

Survey Prof. Paper 73, 226 p. 
Lindgren, Waldemar, Turner, H. W., and Ransome, F. L., (individually and 

coauthors), 1894-1900, "The Gold Belt folios": U.S. Geol. Survey Atlas, Folios 

3, 5, 11, 17, 18, 29, 31, 37, 41, 43, 51, 63. 66. 
Macdonald, G. A., 1941, Geology of the western Sierra Nevada between the Kings 

and San Joaquin Rivers, California : California Univ. Dept. Geol. Sci. Bull., 

V. 26, no. 2, p. 215-286. 
Matthes. F. E., 1930, Geologic history of the Yosemite Valley : U.S. Geol. Survey 

Prof. Paper 160, 137 p. 
Muir. John, 1879, Studies in the Sierra: Overland, v. 12, p. 393-403, 489-500; 

V. 13, p. 67-69, 174-l&i, 393-401, 530^40; v. 14, p. 64-73. ^ 
, 1880, Ajicient glaciers of the Sierra, California : Californian, v. 2, p. 



(By J. H. Stewart and D. C. Ross, U.S. Geological Survey, Menlo Park, Calif.) 

The Great Basin in California south of the 39th parallel is a tri- 
angular-shaped area lying east of the Sierra Nevada, north of the 
Mojave Desert, and west of the continuation of the Great Basin into 
Nevada. The region consists of high mountain blocks trending gen- 
erally north-northwest separated by deep basins. The contrast in 
elevation between the mountains and basins is great. The lowest part 
of Death Valley is 282 feet below sea level, the lowest point on the 
North American continent, and the Panamint Range west, of Death 
Valley rises to over 11,000 feet. Owens Valley, a promment trough 
along the western side of the region, lies generally about 4,000 feet 
above sea level, and the AVhite-Inyo Mountains on the east and the 
Sierra Nevada on the west both rise to over 14,000 feet. 

The decipherable geologic history of the region has been long and 
complex. The preserved record indicates long periods of marine 
deposition, shorter periods of orogeny (mountain building) and gra- 
nitic intrusion, and both ancient and fairly recent volcanic activity. 
Inasmuch as the Great Basin geology of California is so closely related 
to that of Nevada, readers are also referred to the geologic summary 
(p. 11-39) in the report on the mineral and water resources of Nevada 
(Nevada Bureau of Mines Bull. 65, 1964) . 


The ranges of the Great Basin are characterized by complex struc- 
ture — tight folds, high-angle faults, and low-angle thrust faults are 
common. Vertical movement on the numerous high- angle faults has 
been a major factor in outlining the basins and ranges, which give 
the region its desolate scenic beauty. Major high-angle faults essen- 
tially bound the region on the west (Sierra Nevada frontal fault) and 
on the south (Garlock fault) . Other major high-angle faults lie along 
one or both sides of Panamint Valley, Saline Valley, and Owens Val- 
ley, and along Death Valley. In addition to vertical movement, the 
Death Valley-Furnace Creek fault system may have as much as 50 
miles of right-lateral offset. A major low-angle thrust fault system 
is found in the southern Death Valley area (Amargosa thrust), and 
an as yet unnamed thrust, segments of which have been identified in 
the Inyo, Last Chance, and Saline Ranges, may have moved late Pre- 
cambrian and Cambrian strata more than 20 miles over upper Paleo- 
zoic rocks. 

The tectonic forces that cracked the earth's crust in these tremen- 
dous movements are still being felt. In 1872 one of the largest historic 
earthquakes in the United States shook Owens Valley; the zone of 
visible faults associated with this earthquake extends for more than 
100 miles along the valley. 

The oldest rocks exposed in this part of the Great Basin consist 
largely of gneiss, schist, and granitic rock that crop out mostly in the 
ranges around Death Valley and locally elsewhere in the southernmost 
part of the region. On the basis of radiometric ages of zircon (Lan- 
phere and others, 1963), these rocks are about 1,800 m.y. old. These 
rocks were probably originally clastic sediments which were later in- 
volved in orpgenic movements, metamorphosed, and intruded by 
granitic rocks. They form the basement of the thick section of upper 
Precambrian, Paleozoic, and Mesozoic sedimentary rocks. 

During late Precambrian time a marine trough developed in the 
region and many thousands of feet of sediment were deposited. The 
oldest of these deposits belongs to the Pahrump Series which consists 
of phyllitic siltstone, quartzite, conglomerate, limestone, and dolomite, 
and is as thick .as 7,000 feet. These strata were intruded by diabase 
during the Precambrian, and talc deposits formed near the contacts 
of the diabase and carbonate rocks. Locally, uplifts occurred within 
the basin of deposition during and immediately after the time the 
Pahrump Series being deposited. 

Following deposition of the Pahrump Series, a clastic section com- 
posed dominantly of marine sand and silt was laid down during the 
remainder of the late Precambrian and during the Early Cambrian. 
This section is over 10,000 feet thick. These strat.a were derived from 
source areas to the east and southeast, of the region and were deposited 
in a northeast-trending trough that deepened to the west. The basal 
formation of this section, the Noonday Dolomite, contains large de- 
posits of lead, silver, and zinc. 

Above the clastic section of late Precambrian and Early Cambrian 
age is a section of marine carbonate rocks ranging in age from Middle 
Cambrian to Devonian. These strata are locally about 12,000 feet 
thick. In Nevada, strat.a of this age are divided into three assem- 
blages, an eastern carbonate assemblage of nearshore to offshore, shal- 


low- water deposits; a transitional assemblage of offshore, mostly 
shallow- wat-er deposits of shale, limestone, and chert; and a western 
siliceous and volcanic assemblage of offshore, mostly deep-water de- 
posits (Roberts, in Nevada Bur. Mines Bull. 65, 1964, p. 22-25) . The 
deposits of this age in California are mostly part of the eastern car- 
bonate assemblage, although some deposits in the Inyo Mountains 
probably belong to the transitional assemblage. Deposits in the Si- 
erra Nevada west of the Great Basin definitely belong to the transi- 
tional assemblage. 

During the Mississippian a mountain chain rose in about the same 
area as the present southern Sierra Nevada, and coarse detrital ma- 
terial derived from this highland was deposited in the southern Great 
Basin. This mountain chain extended into central Nevada where the 
orogenic event that produced the chain is referred to as the Antler 
orogeny (Roberts and others, 1958). The mountain building in 
Nevada was accompanied by large-scale thrusting of lower Paleozoic 
strata to the east. Thrusting of this age, however, has not been recog- 
nized in the southern Great Basin in California, but a mid-Paleozoic 
unconformity in the Inyo Mountains may reflect the marginal effects 
of this orogeny. The amount of coarse detrital material derived from 
the Antler orogenic belt decreases rapidly during the Mississippian. 
Later in the Mississippian and also in the Pennsylvanian, fine silt and 
minor amounts of carbonate were deposited in the western part of the 
Great Basin in California. Deposits of these periods become more 
limy to the east and are dominantly carbonate rock near the California- 
Nevada state line. The Mississippian and Pennsylvanian strata are 
over 6,000 feet thick in the Great Basin in California. 

Coarse detrital material was again introduced into the basin during 
the Permian, apparently from a source area to the west in the site of 
the present Sierra Nevada. This orogenic event is i-eferred to as the 
Sonoma orogeny in Nevada (Silberling and Roberts, 1962) . Deposits 
of Permian age are about 3,000 feet thick. 

At the start of the Triassic, fine marine muds were deposited in a 
north-south trough in the Great Basin in California. The highlands 
that existed in the site of the Sierra Nevada during Permian time 
apparently sank below the sea before Triassic time, as the Triassic 
strata do not contain coarse debris that would indicate the presence of 
a highland. The marine Triassic deposits, which are about 2,000 feet 
thick, are overlain by at least 7,000 feet of volcanic rocks of Triassic 
and Jurassic age. 

During the Jurassic and Cretaceous in the Great Basin in Cali- 
fornia, orogenic movements took place and great granitic batholiths 
were emplaced. Most of the stiiictural features in the region, except 
for Cenozoic liigh-angle faulting, were probably produced during 
these periods. The dates of emplacement of the granitic bodies is 
established on the basis of radiometric K-Ar dating. The contacts 
of these granitic rocks with Paleozoic limestone and dolomite are the 
site of many tungsten, talc, and silver-lead-zinc deposits. Gold-silver- 
quartz veins are probably also related to this period of granitic 

During the Tertiary, thick continental deposits were laid down in 
local basins and volcanic activity was widespread. The thickest 


Tertiary sedimentary sections are in the Death Valley region, and 
some of these strata contain deposits of borate minerals. Volcanic 
activity was prominent a short distance east of Death Valley (the 
Greenwater Volcanics) and also along^ the western side of the Great 
Basin in California. Large caldera-like features (volcano-tectonic 
structures) fonned in Long Valley and at Mono Lake. These volcanic 
centers were the source for thick deposits of ash-fall and ash-flow 
tuffs, and lava flows. At the Mono Craters volcanic center, among the 
latest formed features are domes of obsidian within shallow craters in 
pumice. The last volcanic event in much of the Great Basin in 
California was the extrusion of basalt and the formation of cinder 
cones. Ubehebe Crater, an explosion vent in basaltic rocks in the 
northern part of Death Valley, and the many cones in the Coso 
Moimtains, are examples of this episode. 

In the latter part of the Tertiary, the physiographic features — the 
basins and ranges — began to take the shape we see today. High-angle 
faulting was dominant, outlining momitain blocks and defining the de- 
pressed basin areas. This basin-range faulting is still continuing — as 
late as the 1950's, tens of feet of vertical movement along such faults 
resulted in strong earthquakes in the Great Basin in neighboring 

The increased precipitation that accompanied Pleistocene glaciation 
developed a system of large lakes in the Great Basin. Lake Manly, 
one of the better known lakes, filled Death Valley to a depth of about 
600 feet. The return of the arid conditions we know today dried out 
these lakes to form the saline lakes and barren playas so characteristic 
of this region. Borates, potassium and sodium compounds, lithium, 
phosphate, and bromine are recovered commercially at Searles Lake 
and Owens Lake from these lake deposits and their associated brines. 
During the latest history of the region, and continuing today, erosion 
of the mountain ranges and deposition of the debris has formed con- 
spicuous alluvial fans along the flanks of the ranges. 

Selected Rb:ferences 

Lanphere, M. A., Wasserburg, G. J. F., and Albee, A. L., 1963, Redistribution 
of strontium and rubidium isotopes during metamorphisni, World Beater Com- 
plex. Panamint Range. California, in Isotopic and Cosmic Chemistry : Am- 
sterdam, North-Holland PubUshing Co., p. 269-^20. 

Nevada Bureau of Mines, 1964, Mineral and water resources of Nevada, pre- 
pared by the U.S. Geological Survey and the Nevada Bureau of Mines: U.S. 
Senate Doc, Nevada Bur. Mines Bull. 65, 314 p. 

Roberts, R. J., Hotz, P. E., Gilluly, James, and Ferguson, H. G., 1958, Paleozoic 
rocks of north-central Nevada : Am. Assoc. Petroleum Geologists Bull., v. 42, 
no. 12, p. 2,813-2,857. 

Silberling, N. J., and Roberts, R. .!., 1962. Pre-Tertiary stratigraphy and structure 
of northwestern Nevada : Geol. Soc. America Spec. Paper 72. 52 p. 


(By T. W. Dibblee, .Jr., and D. F. Hewett, U.S. Geological Survey, Menlo 

Park, Calif.) 

The Mojave Desert is an area of low mountain ranges that separate 
many undrained alluviated basins or valleys. In the western part 
these have no definite pattern, but in the central and eastern parts 


many of them trend northwest and north. Relief increases eastward 
as altitudes of the alluviated valleys decrease from 4,000 feet at the 
western margins of the desert to near sea level at the Colorado River. 

The rocks of the Mojave Desert province are separable into two 
major divisions, (a) pre-Cenozoic rocks, and (b) Cenozoic sedimen- 
tary and volcanic rocks. The pre-Cenozoic rocks are composed of (1) 
metamorphic and old sedimentary rocks, and (2) igneous rocks. 

The metamorphic rocks are gneisses and schists of known and prob- 
able Precambrian age. They were recrystallized at great depth from 
rocks that were mostly sedimentary and which formed enormously 
thick sections. The gneisses are coarsely crystalline banded rocks 
composed mostly of quartz, feldspar, and biotite mica. They are ex- 
posed east and south of Baker, near Barstow and Randsburg, and near 
the southwestern border of the Mojave Desert. In a few places the 
gneisses contain deposits of rare-earth and radioactive minerals. The 
schists are foliated micaceous rocks. They are exposed only near 
Randsburg and in the Orocopia and Chocolate Mountains in the south- 
ern part of the desert. 

Old sedimentary rocks, mapped as the Pahrump Series of late Pre- 
cambrian age, are found in only two areas in the extreme northeastern 
part of the Mojave Desert; one in the Silurian Hills north of Baker 
and the other farther east in the Kingston Mountains. This unit 
rests unconformably on gneiss, is many thousands of feet thick, and 
consists mostly of quartzite, shale or hornfels, and dolomite. 

The Precambrian rocks are overlain unconformably by a great 
thickness of old marine sedimentary strata of Paleozoic age, divided 
into formations as shown on the columnar section (fig. 3). They are 
most extensive in the northeastern Mojave Desert near the Nevada 
state line, notably in the Kingston, Ivanpah, and Providence Moun- 
tains. The lower half of this stratigraphic section is of Cambrian 
age; in the Kingston and Ivanpah Mountains this section is mostly 
quartzite and shale (the basal unit, the Noonday Dolomite, has re- 
cently been assigned to the Precambrian). In the Providence Moun- 
tains the basal part of the Cambrian section is quartzite, the remainder 
is mostly limestone and dolomite. The rest of the Paleozoic (Devon- 
ian to Permian) section in these areas is mostly limestone and dolo- 
mite. Remnants of similar rocks of known and probable Paleozoic 
age engulfed in granitic intrusive rocks occur in many other parts of 
the desert, notably in the mountains southwest of Needles, in areas 
southeast of Twentynine Palms, in areas near Victorville, and in the 
Tehachapi Mountains west of Mojave. 

Two nonmarine sedimentan' formations of Triassic and Jurassic 
ages have been mapped in several places near the Nevada state line. 
Marine formations of these ages were recognized at one place near 
Baker, and possibly at another near Barstow. The thick section of 
slate (pre-Cenozoic rocks of unknown age) in the southeastern Mojave 
Desert near Blythe may be of this age. 

The pre-Cenozoic igneous rocks are of two types, metavolcanic and 
plutonic. The metavolcanic (and hypabyssal) rocks are mostly ande- 
sitic porphyry of Mesozoic age that f omi a complex of extrusive and 
shallow intrusive masses and dike swarms in the central Mojave 


The pliitonic igneous rocks are coarsely ciystalline and were em- 
placed at great depth. Most are granitic, are widespread, and make 
up the major part of the pre-Cenozoic rocks of the Mojave Desert. 
The oldest of these are granitic rocks (quartz monzonite) exposed in 
the northeastern part (Hewett, 1956), and anorthosite and syenite in 
the Orocopia Mountains east of Salton Sea (Crowell and Walker, 
1962) . All are of Precambrian age and intrude gneiss. Gray granitic 
rock (quartz monzonite) of Jurassic ( ?) age is A^-idespread in the east- 
central Moj a ve Desert, Gray to black diorites and gabbros of Mesozoic 
age crop out locally in many parts of the desert. All these Mesozoic 
plutonic rocks are intrusive into the metamorphic and old sedimentary 
rocks. Nearly all the above-mentioned i)re-Cenozoic rocks are in- 
truded by gray-white granitic rock (q[uartz monzonite to granite) of 
Cretaceous age that is very extensive in almost all parts of this prov- 
ince, especially in the western and central parts. 

Metallic mineral deposits containing sulfides of iron, copper, lead, 
zinc, and silver, and commonly containing disseminated gold and 
silver, form veins in pre-Cenozoic rocks in many parts of the desert 
region. Most are found in metamorphic and old sedimentai-y rocks 
near intrusive contacts with granitic rocks; many occur in the granitic 
rocks. Tungsten ores occur under similar conditions. Other deposits 
containing these minerals except tungsten are found in fault or shear 
zones in these rocks. Deposits of iron ores are found in old sedimen- 
tary rocks along or near contacts with the intrusive granitic rocks of 
Jurassic(?) age. In the southwestern Mojave Desert, limestone is 
being quarried extensively for industrial uses, mainly for cement 

The Cenozoic sedimentary and volcanic rocks lie uncomformably 
upon the pre-Cenozoic rocks which were deeply eroded during Cre- 
taceous time. Those of early Tertiary age are sedimentary and are 
known in only one area strictly within the jDrovince, namely in the 
Orocopia Mountains east of Salton Sea where about 2,500 feet of ma- 
rine sandstone (Maniobra Fonnation of Crowell and Susuki, 1959) of 
Eocene age are exposed. 

Elsewhere on the Mojave Desert the Tertiary volcanic and sedi- 
mentary rocks are nonmarine, of middle and late Tertiary age, and 
are widespread. The most extensive Tertiary unit is an assemblage, 
as thick as 10,000 feet, of volcanic lava flows, breccias, tuffs, and some 
sedimentary rocks, of probable Oligocene to early Miocene age. It is 
exposed in many areas in all but the southwestern part of the prov- 
ince. The volcanic rocks, which range from rhyolite through andesite 
to basalt, were erupted from groups of vents and fissures, later filled 
with volcanic plugs, in many areas within these parts. Near Mojave 
in the western Mojave Desert, this assemblage was named the Gem 
Hill Formation of the Tropico Group ; in areas north of Barstow, as 
the Pickhandle Formation. Elsewhere it is not named. Ores of gold 
and silver, some very rich, were mined from veins in the volcanic 
plugs associated with this unit, notably near Mojave, Randsburg, 
Barstow, and Ludlow. These plugs contain veins of barite near 
Barstow and Ludlow and manganese ore near Ludlow. The volcanic 
rocks also contain perlite, pumicite, and tufi", of commercial grades. 

The above-described volcanic and sedimentary unit is overlain, in 


places imconformably, by a predominantly sedimentary unit as thick 
as 5,000 feet of middle Miocene to early Pliocene age. In tlie \yestern 
Mojave Desert it is known as the Barstow Formation near Barstow; 
Punchbowl Formation at Cajon Pass; and Fiss Fanglomerate near 
Kosamond. At the west end of the Mojave Desert this unit grades 
westward into marine beds. Commercial minerals in this unit include 
the world's largest deposit of borate minerals that are being mined 
from lake-bed shale near the base of this unit at Boron. Similar lake- 
bed shales of this unit contain deposits of borate and strontiimi min- 
erals and of absorptive tuff or bentonite, near Barstow, Yermo, and 

Stratigraphic sections of middle and late Pliocene age are exposed 
in the northern part of the province, notably west of Mojave and east 
of Randsburg. In the Eandsburg area the section includes andesite 
flows and tuffs associated with andesitic intrusions. In other parts 
of the province much of the dissected alluvial sediments may be of 
this age. 

Deposits of Quaternary age that fill the desert valleys are mainly 
alluvial sediments, some lake-bed clays, and dune sand. In a few 
places they include local basalt flows and cinder cones. The cinder 
cones are composed of basaltic pumice which is quarried for industrial 
uses. The clays of Bristol Lake near Amboy in the central Mojave 
Desert contain enormous deposits of salt with calcium chloride which 
are being quarried for industrial uses. 

The pre-Cenozoic metamorphic and old sedimentary rocks of the 
Mojave Desert province are complexly folded, faulted, and intruded 
by plutonic igneous rocks. These igneous rocks, mostly granitic, 
which extend southeastw^ard from the Sierra Nevada province, 
assimilated most, of the pre-exisiting rocks. All this happened during 
the Mesozoic Era. 

The Tertiary stratified rocks which rest on the deeply eroded surface 
of the pre-Cenozoic rocks are themselves tilted, faulted, and deformed 
into folds mth axes that trend mostly west to northwest. They were 
deformed during late Tertiary and early Quaternary time. In many 
places Quaternary alluvial sedunents and basalt flows are slightly 
deformed in the same manner. 

The Mojave Desert Region is in large part bounded geologically on 
the southwest by the San Andreas fault and on the northwest by the 
Garlock fault, or physiographically by mountain ranges uplifted along 
these master faults. Both are vertical, active faults along w^hich move- 
ment was mainly horizontal ; the area southwest of the San Andreas 
fault has moved northwest, and that, northwest, of the Garlock fault 
has moved southwest, relative to the wedge-shaped block that forms 
the major part of the Mojave Desert province. The southwest half of 
the Mojave block itself is broken by a number of vertical faults parallel 
to the San Andreas fault. Along many of these faults the terrain has 
slipped horizontally as on the San Andreas. South of the Garlock 
fault, and north of Salton Sea, the Mojave block is broken by some 
vertical faults that trend east, along which the terrain has slipped in 
part, horizontally ns on the Garlock fault. All or most of these faults 
within the Mojave block involve Quartemary formations and are 
therefore active. The Garlock fault becomes a southw^est-dipping 


thrust fault at its east end as it curves southeastAvard around the 
Avawatz Mountains. 

The structural pattern of the eastern part of the Mojave Desert 
province differs from that of the western and central parts and is more 
like that of the Basin and Range province to the north. In this part 
the old sedimentary rocks are compressed into folds vnih axes that 
trend mostly north ; some are broken by low-dipping thrust faults that 
are themselves folded. Most of this deformation occurred before or 
during the invasion of the Mesozoic granitic rocks, but some of the 
thrust faults involve lower Pliocene formations. Some of these show 
no topographic expression and therefore have long been inactive. 

Selejcted References 

Bassett, A. M., and Kupfer, D. H., 1964, A geologic reconnaissance of the south- 
eastern Mojave Desert, California : California Div. Mines and Geology Spec. 
Rept. 83, 43 p. 

Bowen, O. E., Jr., 1954, Geology and mineral resources of the Barstow quadrangle, 
California : California Div. Mines Bull. 165, 208 p. 

Crowell, J. C, and Susuki, Takeo, 1959, Eocene stratigraphy and paleontology, 
Oricopia Mountains, southeastern California : Geol. Soc. America Bull., v. 70, 
no. 5, p. 581-592. 

Crowell, J. C, and Walker, J. W. R., 1962, Anorthosite and related rocks along 
the San Andreas fault, southern California : California Univ. Geol. Sci. Pub.. 
V. 40, no. 4, p. 219-288. 

Gardner, D. L., 1941, Geology of the Newberry and Ord Mountains. San Bernar- 
dino County, California : California Jour. Mines and Geology, v. 36, no. 3, 
p. 257-304. 

Hewett, D. F., 1954a, General geology of the Mojave Desert region, California, 
in Geology of southern California : California Div. Mines Bull. 170, chap. II, 
contr. 1, p. 5-20. 

, 1954b, A fault map of the Mojave Desert region, in Geology of southern 

California: California Div. Mines Bull. 170, chap. IV, contr. 2, p. 15-18. 

1956, Geology and mineral resources of the Ivanpah quadrangle, Cali- 

fornia and Nevada : U.S. Geol. Survey Prof. Paper 275, 172 p. 

Hulin, C. D., 1925, Geology and ore deposits of the Randsburg quadrangle of 
California : California Bur. Mines Bull. 95, p. 1-148. 

Simpson, E. C, 1934, Geology and mineral deposits of the Elizabeth Lake quad- 
rangle, California : California Jour. Mines and Geology, v. .30, p. 371^15. 


(By T. W. Dibblee, Jr.. U.S. Geological Survey, Menlo Park, Calif.) 

The Transverse Range region is one of eastward-trending mountain 
ranges and valleys. It is so named because this trend is transverse to 
the generally northwesterly trending features of southern California. 

The lowlands of the San Bernardino and Los Angeles plains of the 
eastern part of this region rise abruptly northward to the San Bernar- 
dino and San Gabriel Mountains, respectively, two of the most rugged 
and highest ranges in southern California. Westward the San Gabriel 
Mountains split into two mountain chains, including the Santa Ynez 
Range on the north and the Santa Susana Range on the south, sep- 
arated by the Santa Clara River Valley. Westward from Los Angeles 
stretch the Santa Monica Mountains, and their westward projection 
into the sea is formed by the four channel islands, north of which lies 
the Santa Barbara channel. 


The rock units of the Transverse Kange region may be divided into 
two main groups, (a) crystalline basement complex of met amorphic 
and plutonic rocks, and (b) sedimentary and volcanic rocks. 

The basement complex, exposed mostly in the eastern part of the 
province, is composed of hard crystalline metamorphic rocks and plu- 
tonic igneous rocks. It forms the old terrane upon which the sedimen- 
tary and volcanic rocks were deposited. The metamorphic rocks ciy- 
stallized at great depth from rocks of mostly sedimentary origin. The 
plutonic igneous rocks intruded the metamorphic rocks also at great 
depth in the form of molten magmas that crystallized into coarse- 
grained, mostly granitic, rocks. 

The metamorphic rocks of this complex are described below, from 
supposedly oldest to youngest, together with their economic aspects. 
(1) Gneiss, Precambrian ( ? ) . This rock is coarsely crystalline, lay- 
ered ; formed by severe metamorphism probably from rocks that were 
mostly sedimentary. The gneiss is exposed mainly in the San Ber- 
nardino and San Gabriel Mountains. In some areas it contains layers 
of coarse, white marble. In a few places the gneiss contains small 
deposits of graphite and (or) radioactive minerals. The marble has 
been quarried for roofing aggregate. (2) Pelona Schist, Precam- 
brian ( ? ) . This is a highly foliated micaceous rock, recrystallized from 
mostly sedimentary rocks. It is exposed in the San Gabriel and San 
Bernardino Mountains. In places it contains a little soapstone (stea- 
tite) and manganese ore. The schist is quarried for use as slab rock. 
(3) Metasedimentary rocks. Paleozoic. These rocks are exposed mostly 
in the San Bernardino Mountains where they rest unconformably on 
gneiss, and consist of the Saragossa Quartzite overlain by the Furnace 
Limestone. Gold was mined from shear zones in both these forma- 
tions. The Furnace Limestone is quarried for industrial uses, includ- 
ing cement manufacture. (4) Santa Monica Slate, pre-Cenozoic 
(Triassic ( ? ) and Jurassic) . This rock, crystallized from shale, is ex- 
posed only in the Santa Monica Mountains. It has been quarried for 
slab rock. (5) Unnamed schist, pre-Cenozoic. This fine-grained fol- 
iated rock crops out only on Santa Craz Island. 

The plutonic igneous rocks of the basement complex include anorth- 
osite and syenite, Precambrian, exposed only in the western San Gab- 
riel Mountains and which contain small deposits of titaniferous iron 
ore; small masses of quartz diorite, diorite, and gabbro, Mesozoic or 
older; and large masses of granitic rocks, mostly quartz monzonite, 
late Mesozoic. 

The sedimentary and volcanic rocks rest unconformably on the base- 
ment complex in the eastern part of the province. They underlie al- 
most all the western part where they form an assemblage as thick as 
40,000 feet. The stratigraphic formations that make up this assem- 
blage are as shown on the columnar section (fig. 3) . 

Formations of late Mesozoic age are marine sandstone, shale, and 
conglomerate, as in the Coast Kange province. They include the 
Franciscan Formation, thickness unknown, Espada Formation, at 
least 7,000 feet thick, and Jalama Formation, about 3,500 feet thick, 
all in the Santa Ynez Range, and "Chico" sandstone as thick as 3,000 
feet in the Santa Susana Range. The Franciscan Formation contains 
mafic volcanic flows and serpentine intrusions, in addition to sandstone. 


shale, and conglomerate, and is the host formation for deposits of 

The foniiations of Paleooene and Eocene age also are nearly all 
marine sandstone, shale, and some conglomerate. The total thickness 
is 8,000 feet or more. They are overlam by the mostly Oligocene 
Sespe Formation comjx>sed of about 3,000 feet of nonmarine sedi- 
ments. In the western Santa Ynez Range the Sespe grades laterally 
Avestward into the marine Alegria Formation. All of these forma- 
tions contain oil-producing sands. At the east end of Santa Clara 
River Valley, the equivalent of the Sespe, or the Vasquez Fonnation, 
contams volcanic flows, also small deposits of borate minerals at one 

The lower Miocene section, about 2,000 feet thick, is marine and 
consists of the Rincon Shale Avith Vaqueros Sandstone at the base. 
This sandstone is an important petroleum, producer along the Santa 
Barbara coastal area. In the Santa Monica Momitains and eastward 
this section consists of sandstone and shale of the Topaiiga Formation. 

The marine middle Miocene to lower Pliocene section ranges from 
2,000 to 7,000 feet thick. The basal part locally is com^wsed of vol- 
canic flows that are thickest in the Santa Monica Mountains and 
Channel Islands. The rest of the section is mostly siliceous and 
diatomaceous shale of the Monterey (or Modelo), Puente, and Sisquoc 
Fonnations, which locally contain sandstone. Diatomite is quarried 
from the Monterey Shale and Sisquoc Formation in the western Santa 
Ynez Mountains near Lompoc. In Ventura County, sandstones in 
the Monterey (or Modelo) Shale produce large amounts of petroleum. 
On the north side of the San Gabriel Momitains the section is composed 
of the nonmarine Mint Canyon and Pmichbowl Formations. 

The Pliocene section miderlies the Santa Clara River Valley and 
Santa Barbara Channel where it consists of some 15,000 feet of marine 
sandstone and shale of the Pico Formation. This formation is the 
largest producer of petroleum in the province. Eastward the Pico 
thins and in part grades laterally into the noimiarine Saugus For- 
mation. The Pico Fonnation is overlain by about 2,000 feet of marine 
Pleistocene sands of the Mudpit Shale and Santa Barbara Fonnation. 
These grade laterally eastward into the nonmarine Saugus Formation. 

The basement complex of the Transverse Range province, as in ad- 
jacent provinces, is complex structurally as well as in rock distribu- 
tion. It is composed of severely folded metamorT)hic rocks, complexly 
intruded by the various plutonic igneous rocks. 

This province has no delinite geologic bomidaries, but it is in large 
part bomided on the north and south by major east-trending faults. 
It is partly bomided by the southeast -trending San Andreas fault but 
this and the San Gabriel fault to the southwest also transect it 

Movement on the highly active San Andreas fault is horizontal. 
The northeast block has shifted southeastward relative to the southwest 
block, but simultaneously tliese blocks have been pushing against each 
other with terrific force. As a result of this force the terrane of base- 
ment complex that forms the San Bernardino Mountains was squeeze<:l 
up like a wedge between the San Andreas fault and thrust faults to 
the northeast. Similarly, the terrane of basement complex that fonns 


the San Gabriel Mountains and those to the northwest was squeezed 
up between the San Andreas and the San Gabriel faults, but the 
western part of this block was downwarped to form the Ridge basin, 
which is filled with Tertiary sedimentary rocks. As a result of these 
movements, the basement complex of all these ranges is severely 
shattered, and the overlying Tertiary stratified rocks are severely 
compressed into folds with east-trending axes. 

The enormously thick stratigraphic section of mostly marine forma- 
tions of Cretaceous and Cenozoic ages that underlies the western part 
of the Transverse Range province accumulated in a great crustal 
downwarp, or trough, that geologists call the Ventura basin. It was 
submerged during Cretaceous and most of Cenozoic time when it 
subsided continuously until more than 40,000 feet of sediments accumu- 
lated in it. The axis of this trough followed the area now occupied 
by the Santa Clara River Valley and westward into the Santa Barbara 
Channel, which is the still-submerged part of this downwarp. 

The strata along the flanks or margins of the Ventura basin have 
been squeezed up by tremendous compressive forces to form the west- 
ern Transverse Ranges. On the north flank, the Santa Ynez-Topatopa 
Range was formed mainly by uplift and southward tilt of the strata 
along the Santa Ynez fault at the north base of this range, and in part 
by arching and thrust faulting of these strata. On the south flank, 
the Channel Islands and Santa Monica Mountains were formed 
largely by uplift and arching of the strata along a zone of east- 
trending faults. Farther north on this flank the Santa Susana 
Range was formed by arching of the strata, partly on two thrust faults. 
Within or adjacent to these major upheavals, the strata are com- 
pressed into numerous folds of east-trending axes. Many of these 
folds near the axial part of the Ventura basin have entrapped the 
petroleum and gas of this basin to form the oil fields of this province. 

In summary it may be said that the physiographic features of the 
Transverse Range province are the effect of an enormous amount of 
north-south crustal shortening that resulted from tremendous com- 
pressive forces. Part of tliis shortening is between the marginal 
Santa Ynez Fault and the zone of faults through or adjacent to the 
Channel Islands and Santa Monica Mountains. These are steep faults 
transverse to the great San Andreas fault. Movements on these are 
in part horizontal, in which the terrane north of the Santa Ynez fault 
has been pushed westward, and the submerged terrane south of the 
Channel Islands-Santa Monica fault has been pushed eastward, rela- 
tive to tlie intervening transverse block. 

Selected References 

Bailey, T. L., and Jahns, R. H., 1954, Geology of the Transverse Range province, 
southern California, in Geology of southern California : California Div. Mines 
Bull. 170, chap. II, eontr. 6, p. 83-106. 

Crowell, J. C, 1954, Strike-slip displacement of the San Gabriel fault, southern 
Califoniia, in Geology of southern California : California Div. Mines Bull. 170. 
chap. IV, contr. 6, p. 49-52. 

Dibblee, T. W., Jr., 1950, Geology of southwestern Santa Barbara County, Cali- 
fornia : California Div. Mines Bull. 1.50, 95 p. 

Hoots, H. W., 1931, Geology of the eastern part of the Santa Monica Mountains, 
Los Ajigeles County, California : U.S. Geol. Survey Prof. Paper 165-C, p. 83-134. 

.lahns, R. H., 1940, Stratigraphy of the eastern Ventura basin, California, with a 


description of a new lower Miocene mammalian fauna from the Tick Canyon 
Formation : Carnegie Inst. Washington Pub. 514. p. 14.5-194. 

-. 1954, (ed), Geology of southern California: California Div. Mines Bull. 

170, map sheets nos. 3, 4, 5, 6, 7, 8, 9, 10, 20, 25, 26, 27, 28, 29, 30, and 31 (sep- 
arate author for each sheet) . 
Kew, W. S. W., 1924, Geology and oil resources of a part of Los Angeles and 

Ventura Counties, California : U.S. Geol. Survey Bull. 753, 202 p. 
Noble, L. F., 1954, The San Andreas fault zone from Soledad Pass to Cajon Pass, 

California, in Geology of southern California : California Div. Mines Bull, 

170, chap. IV, contr. 5, p. 37-48. 
Oakeshott, G. B., 1958, Geology and mineral deposits of the San Fernando 

quadrangle, Los Angeles County, California : California Div. Mines Bull. 172, 

139 p. 


(By G. L. Peterson, R. G. Gastil, and E. C. Allison, Department of Geology, 
San Diego State College, San Diego, Calif.) 

The Peninsular Ranges, bounded on the east by the Gulf of Cali- 
fornia and Salton Trough and on the north by the Transverse Ranges, 
constitute a distinctive physiographic and geologic province. Baja 
(Lower) California, Mexico, the 800-mile-long peninsula tliat sep- 
arates the eastern Pacific from the Gulf of California, constitutes the 
bulk of the province, but only that relatively small portion north of 
the international border is discussed here. 

In general aspect, the province most closely i-esembles the Sierra 
Nevada province and has had a somewhat similar geologic history. 
Apparently the development of the province began with a thick 
accumulation of predominantly marine sedimentary and volcanic 
rocks. Ages of these oldest rocks are as yet poorly documented, but 
late Paleozoic and early Mesozoic fossils have been reported, and 
Jurassic fossils are locally present in the western part of the province. 
Following this accumulation, in mid-Cretaceous time, the province 
underwent a pronounced episode of mountain building. The thick 
accumulation of sedimentary and volcanic rocks was complexly meta- 
morphosed and invaded by igneous intrusions. These intrusive rocks, 
the Southern Calif ornia batholith, now constitute the dominant terrain 
of the province. A period of erosion followed the mountain-building 
episode, and during Late Cretaceous and Cenozoic time, sedimentary 
and subordinate volcanic rocks were deposited upon the eroded surface 
of the batholithic and pre-batholithic rocks. These post-batholithic 
rocks occur principally along the western and northern margins of the 
province. Thus, in terms of geologic history, rocks of the province can 
be subdivided into three general units: 1) pre-batholithic rocks, 
2) the Southern California batholith, and 3) post-batholithic rocks. 
Each of these gross rock units and its economic significance is outlined 
below. Cenozoic faulting and changes of sea level relative to land 
level added distinctive topographic features which are discussed on a 
later page. 

Pre-batholithic Rocks 

Pre-batholithic rocks occur principally in the highlands or centrally 
located part of the province. They occur on the western flank of the 
batholith and as remnants in numerous areas within the batholith. 
These metamorphic rocks are further divisible into two broadly differ- 
ing types. The first and probably oldest type is more common in the 


central and eastern parts of the province. In general, this group of 
rocks is a highly metamorphosed assemblage of schists, amphibolites, 
(^uartzites, gneisses, and crystalline limestones. Evidence for the age 
of this complex is scanty, but most investigators regard it as late Paleo- 
zoic and early Mesozoic. (^rushed and broken stone, dimension stone, 
and crystalline limestone (used in the manufacture of cement) are 
important economic commodities. Other economic deposits derived 
from these rocks are also associated with the batholithic rocks and are 
discussed below. 

A second assemblage of pre-batholithic rocks occurs on the western 
side of the province, ajid principally occupies a narrow belt extending 
down the coast from the Santa Ana Mountains to San Diego. In con- 
trast to the first, tliis belt of rocks consists of the mildly metamorphosed 
slates and argillites of the Bedford Canyon Formation and a thick 
succession of volcanic and related rocks designated the Santiago Peak 
Volcanics. Offsliore, on Santa Catalina Island, there is a small ex- 
posure resembling tlie Franciscan Formation, a unit more character- 
istic of the Coast Ranges. The entire Avesteni belt of metamorphic 
rocks is apparently of Jurassic and Early Cretaceous age, as is indi- 
cated by several recent fossil discoveries. Crushed stone, decorative 
building stone, and pyrophyllite (used i:)rincipally as an insecticide 
base) are apparently the only commodities now being obtained from 
this belt of rocks. 

The structural details of tlie pre-batholithic rocks are highly com- 
plex, but individual rock units have a predominant northwesterly trend 
and are generally inclined steeply to the southwest or northeast. This 
persistent grain is disrupted in many areas, however, by igneous intru- 
sions associated with the batholith. 

Batholithic Rocks 

The Southern California batholith constitutes the backbone and 
dominant portion of the province, extending from near Los Angeles 
southeastward approximately 1,000 miles to the southern extremity of 
Baja California. Average widtli of outcrop in southern California is 
approximately 70 miles. The }:)atholith is by no means a single homo- 
geneous rock unit, but a complex series of intrusions and related meta- 
morphic rocks. Various investigators have described, mapped, and 
named numerous smaller rock divisions within the batholith. These 
smaller divisions range widely in rock type including gabbros, tonal- 
ites, granodiorites, and granites. Radiometric age determinations date 
the filial consolidation of the batholith at 00 to 100 million years ago, in 
mid-Cretaceous time. 

A variety of mineral resources are associated with the ])atholithic 
and pre-batholithic rocks. Ores of copper, gold, molybdenum, nickel, 
silver, and tmigsten have been mined sporadically. Tlie deposits are 
mostly low grade, however, and mining activity was greatest during 
times of exceptional demand, such as during the world wars. Far 
more important in recent years has been the production of crushed 
and broken stone and dimension stone. Of the latter, several varieties 
such as "black granite" (gabbro) and "gray granite" (quartz diorite 
or granodiorite) are quarried at several localities and marketed for 
industrial purposes and as decorative building or monument stone. 


Numerous pegmatite dikes cut across the earlier igneous and meta- 
morphic rocks of the batholithic complex. The gem- and lithium mica- 
bearing pegmatites of Kiverside and San Diego Counties are particu- 
larly well known. These deposits have yielded numerous minerals 
including pink and green tourmaline, garnet, quartz crystals, lepido- 
lite, beryl, spodumene, topaz, and feldspar. These dikes have consti- 
tuted one of the most important sources of gem and lithium minerals 
in the United States. 

Post-Batholithic Rocks 

Sedimentary and subordinate volcanic rocks deposited on the eroded 
surface of the batholithic and pre-batholithic rocks are confined princi- 
pally to the coastal area of the province. In this report they are 
further subdivided into two areas of outcrop for purpose of descrip- 
tion. The first, and southernmost area consists of a narrow strip ex- 
tending from Oceanside south to the International border. Post- 
batholithic rocks of this area are almost entirely sedimentary and 
consist of poorly consolidated, richly fossiliferous, and generally flat- 
lying units of sandstone, shale, and conglomerate. Formations in- 
clude, in ascending order, Rosario (Cretaceous), La Jolla and Poway 
(Eocene), San Diego (Pliocene), and Sweitzer, Lindavista, and Bay 
Point (Pleistocene) . IVIaterials used chiefly in the construction indus- 
try (sand and gravel, clay, expansible shale, and specialty sands) are 
extracted from these miits and constitute some of the most important 
economic commodities of San Diego County at the present time. In 
the past, minor amounts of placer gold have been obtained from some 
of the Eocene gravels of this area. 

North of Oceanside, the width of area covered by post -batholithic 
rocks increases markedly and extends inland to the vicinity of Pomona 
and northward to the Transverse Ranges. In this area, the Los An- 
geles basin, sedimentary rock units are both more numerous and 
individually thicker, and are more deformed than farther south. Ap- 
parently this area was persistently do^vn warped and occupied by the 
sea throughout much of Cenozoic time, and tectonically was more 
comparable to the Transverse Ranges than to the remainder of the 
Peninsular Ranges. As with the post -batholithic rocks to the south, 
materials used in the construction industries are important economic 
commodities, but in contrast, the Los Angeles basin is also well known 
as one of the most important petroleum provinces on the western shore 
of North America. 

Post-batholithic volcanic rocks occur as minor units in the Los 
Angeles basin, in areas south of Elsinore, and near Jacumba. Volcanic 
rocks also occur on Santa Catalina Island and constitute the dominant 
rock type of San Clemente Island. Economic significance of these 
volcanic rocks is negligible at present. 

Structure and Topography 

Structurally, the province appears to be an uplifted and westward- 
tilted block. The eastern flank is the highest and most rugged part, 
with altitudes gradually decreasing toward the ocean. Cutting across 
this large-scale pattern are numerous, large, northwest-trending faults. 


These faults subdivide the province into several subparallel blocks 
AVhich are topographically expressed as northwest-trending ranges and 
interv^ening valleys. The largest faults j)arallel the San Andreas fault 
system and are probably closely related. A much smaller northeast- 
trending set of faults appears to be associated with the major set. Ap- 
parently the faults were active throughout much of Cenozoic time. 
Activity to the present is indicated by recent warping and displace- 
ments, by liot springs along the fault traces, and by seismic unrest in 
the vicinity of many of the larger faults. 

Distinctive topographic features of the coastal part of the province 
include numerous bench-like surfaces developed w^hen the sea was at 
higher levels. These marine terraces are abundant in certain tectoni- 
cally active areas, such as near Palos Verdes. In other areas only three 
main terraces have been developed. Many of the coastal cities of 
southern California such as San Diego, Del Mar, and Oceanside are 
located largely on these terraces. 

Selected References 

Allison, E. C, 1964, Geology of areas bordering Gulf of California, in van Andel, 

T. H., and Shore, G. G., Jr., eds.. Marine geology of the Gulf of California : Am. 

Assoc. Petroleum Geologists Mem. 3, p. 3-29. 
Beal, C. H., 1948, Reconnaissance of the geology and oil possibilities of Baja 

California, Mexico : Geol. Soc. America Mem. 31, 138 p. 
Bushee, Jonathan, Holden, John, Geyer, Barbara, and Gastil, Gordon, 1963, Lead- 
alpha dates for some basement rocks of southwestern California : Geol. Soc. 

America Bull., v. 74, no. 6, p. 803-806. 
Gray, C. H. Jr., 1961, Geology of the Corona south quadrangle and the Santa Ana 

Narrows area ; Riverside, Orange and San Bernardino Counties, California : 

California Div. Mines Bull. 178, p. 1-58. 
Hanna, M. A., 1926, Geology of the La JoUa quadrangle, California : California 

Univ, Dept. Geol. Sci. Bull., v. 16, no. 7, p. 187-246. 
Hudson, F. S., 1922, Geology of the Cuyamaca region of California, with special 

reference to the origin of the nickeliferous pvrrhotite: California Univ., Dept. 

Geol. Sci. Bull., v. 13, no. 6, p. 175-152. 
Jahns, R. H., ed., 1954, Geology of southern California : California Div. Mines 

Bull. 170, 878 p. 
Larsen, E. S., Jr., 1948, Batholith and associated rocks of Corona, Elsinore, and 

San Luis Rey quadrangles, southern California : Geol. Soc. America Bull., 

V. 57, no. 3, p. 233-260. 
Merriam, R. H., 1946, Igneous and metamorphic rocks of the southwestern part 

of the Ramona quadrangle, San Diego County, California : Geol. Soc. America 

Bull., v. 57, no. 3, p. 233-260. 
Miller, W. J., 1946, Crystalline rocks of southern California : Geol. Soc. America 

Bull., V. 57, no. 5, p. 457-542. 
Silberling. N. J.. Schoellhamer, J. E., Gray, C. H., Jr., and Imlay, R. W., 1961, 

Upper Jurassic fossils from Bedford Canyon Formation, southern California : 

Am. Assoc. Petroleum Geologists Bull., v. 45, no. 10, p. 1,746-1,748. 
Weber, F. H., Jr.. 1963, Geology and mineral resources of San Diego County, 

California : California Div. Mines and Geology County Rept. 3, 309 p. 


(By W. B. Hamilton, U.S. Geological Survey, Denver, Colo.) 

The Salton Trough is a desert- basin extending northwestward into 
southern California from the Gulf of California. The trough is 
bounded by mountains of Precambrian, Paleozoic, Mesozoic, and Ter- 
tiary rocks, but is itself mostly a plain of low relief floored bj^ surficial 
deposits. A region 85 miles long and up to 30 miles wide, which is 

67-164 O — ^66 — pt. I 6 


most of the surface of the trough, is below sea level, dammed from 
the Gulf by the delta of the Colorado River. The fluctuatino; surface 
of the 30-mile-long Salton Sea is more than 200 feet below sea level. 

The Salton Troujjh is filled by late Cenozoic sediments whose maxi- 
mum tliickness, about 21,000 feet, is just south of tlie Mexican border 
(Biehler and others, 1964). The stratigraphy of the valley fill, as 
exposed in the deformed areas about the basin and as known from 
well records, was described by Dibblee (1954). The sediments repre- 
sent continuous deposition from late( Miocene time to the present 
and, except for the marine Imperial Formation low in the section, are 
continental clastic strata. Fanglomerates, alluvial sands and silts, 
and lacustrine silts and clays, interfinger complexly and have been 
given various formation names by Dibblee (Borrego, Brawley, Cane- 
brake, Mecca, Ocotillo, Palm Spring, Split Mountain). The lacus- 
trine Borrego Fonnation contains thin strata of thenardite (sodium 
sulfate) east of Salton Sea. Large deposits of gypsum occur just be- 
low the Imperial Formation in Fish Creek Mountain west of El Centro. 
Silicic and intermediate volcanic rocks are present locally in the upper 
Cenozoic section. 

Pre-Cenozoic crystalline rocks are exposed throughout the moun- 
tains that border the trough and similar rocks presumably underlie the 
Cenozoic sedhnents that fill it, but are exposed in the trough only in 
several low uplifts along strike-slip faults. In the Mecca Hills, north 
of the Salton Sea, anorthosite and gneiss of Precambrian age and 
schist of probable Paleozoic age underlie Pliocene and Quaternary 
sandstone and fanglomerate (Crowell, 1962, p. 26-29). Jurassic 
(about 155 million years old) quartz diorite forms Superstition Moun- 
tain, northwest of El Centro (Bushee and others, 1963). Undated 
granitic and metamorphic rocks crop out in a small mass at the Mexi- 
can border near the east edge of the trough (Strand, 1962) . 

Five small extrusive rhyolite domes of Quaternary age protrude 
throu.q-li the sediments of the trougli at the southeast end of the Salton 
Sea (Kelley and Soske, 1936). The northeast line of the domes is 
crossed by a northwest-trending line of hot springs, mud pots, and 
mud volcanoes ("N^Hiite, 1955). Carbon dioxide at high pressure and 
temperature is plentiful here in shallow subsurface reservoirs and is 
produced commercially where it is found with a low Avater content 
(White, 1955) . A mile-deep well drilled nearby for geothermal power 
encountered very hot (about 600° F) brine containing about 33 percent 
by weifflit of sodium, calcium, and potassium chlorides, and in addi- 
tion lithium, barium, lead, silver, copper, and other metals in amounts 
far higher than those known elsewhere in subsurface brines (White 
and others, 1963). Commercial use of the brine and its geothermal 
heat is to be expected once waste-disposal problems are solved. 

The present Salton Sea has been maintained bv irrigation water 
since it fonned in 1905-1906 when the Colorado Eiver broke into the 
Salton Trough during floods. A higher stand of the Salton Sea, end- 
ing only a few centuries ago, left wave-cut shorelines, lacustrine shells, 
and locally travertine, about the basin to an altitude generally a little 
above present sea level (e.g., Dibblee, 1954, pi. 2) . 

Wind-blown sand fomis deposits throughout much of the Salton 
Trough. By far the largest are the Sand Hills, a belt ahout 5 miles 


wide of dunes trendintj northwestward for 40 miles from the Mexican 
border in the eastern part of the trough. 

The Salton Trough is the northern extension of the structural de- 
pression of the Gulf of California. Continental crust, lacking beneath 
the deep southern part of the Gulf, thickens gradually northward 
along the northern part ; it is about 20 miles thick at the International 
border, and 25 miles thick at the north end of the Salton Trough 
(Biehler and others, 1964). The structure of the Salton Trough is 
dominated by the several right-lateral strike-slip faults of the San 
Andreas system — San Jacinto, Imperial, San Andreas proper, etc, — 
which trend obliquely into it from the northwest. The faults present 
an en echelon array, stepping to the right; individual faults strike 
more westerly than does the fault system as a whole, or than does the 
gulf depression into which the system trends. Right-lateral surface 
offsets within the Salton Trough occurred during earthquakes of 1857 
(San Andreas fault; the offset sector was mostly northwest of the 
trough, but probably extended into it), 1934 (San Jacinto fault, in 
Mexico; Biehler and others, 1964), and 1940 (Imperial fault). De- 
formation of the region is continuing at a very rapid rate, and the 
southwest margin of the trough moved several feet northwestward, 
relative to the northeast margin, Avithin the short period 1941-1954, 
without further surface faulting (Whitten, 1956, fig. 3). Future se- 
vere earthquakes accompanying surface faulting are to be expected. 

Previous late Quaternary right-lateral offsets along the San An- 
dreas fault in the trough are indicated by displaced drainage lines and 
by the tight, locally isoclinal folds with steeply plunging axes of Pleis- 
tocene and alluvial sediments adjacent to the fault. Total Cenozoic 
displacement has been enormous: distinctive middle Eocene strata are 
displaced 180 miles along it, from the Orocopia Mountains at the 
northeast edge of the Salton Trough to the Tejon region (Crowell, 
1962) ; displacement of mid-Cretaceous granitic rocks has been 300 
miles (c.f. Hill and Dibblee, 1953). The Gulf of California appar- 
ently opened as the Peninsula of Baja California pulled obliquely 
away from the mainland during Cenozoic time, and the Salton Trough 
probably formed by tensional thinning of the continental crust accom- 
panying this motion (Hamilton, 1961) . 

The folding and minor faulting, like the major strike-slip faulting, 
demonstrate clockwise torsion within the trough throughout late Ceno- 
zoic time (Dibblee, 1954, p. 28). The primary right-lateral faults 
trend northwestward. Minor left-lateral faults trend northeastward, 
and probably represent adjustments between blocks dragged by the 
major faults. Folds in the Cenozoic sediments trend mostly eastward 
and are en echelon, along or near both the major and minor fault zones. 

Selected References 

Biehler, Shawn, Kovach, R. L., and Allen, C. R., 1964, Geophysical framework 
of northern end of Gulf of California structural province : Am. Assoc. Petro- 
leum Geologists Mem. 3, p. 126-143. 

Bushee, Jonathan, Holden, John, Geyer, Barhara, and Gastil, Gordon. 1963, 
Lead-alpha dates from some basement roclcs of southwestern California : 
Geol. Soc. America Bull., v. 74, no. 6. p. 803-806. 

Crowell, J. C, 1962. Displacement along the San Andreas fault. California : 
Geol. Soc. America Spec. Paper 71, 61 p. 


Dibblee, T. W., Jr., 1954, Geology of the Imperial Valley region, California, [Pt. 

2] in Chap. 2 of Jahns, R. H., ed.. Geology of southern California : California 

Div. Mines Bull. 170, p. 21-28. 
Hamilton, Warren, 1961, Origin of the Gulf of California : Geol. Soc. America 

Bull., V. 72, no. 9, p. 1,307-1,318. 
Hill, M. L., and Dibblee, T. W., Jr., 1953, San Andreas, Garlock, and Big Pine 

faults, California : Geol. Soc. America Bull., v. 64, no. 4, p. 443-4.58. 
Kelley, V. C, and Soske, J. L., 1936, Origin of the Salton volcanic domes, Salton 

Sea, California : Jour. Geology, v. 44, no. 4, p. 496-509. 
Strand, R. G., 1962, Geologic map of California, San Diego-El Centro sheet: 

California Div. Mines and Geology, scale 1 : 250,000. 
White, D. E., 1955, Violent mud-\^olcano eruption of Lake City Hot Springs, 

northeastern California : Geol. Soc. America Bull., v. 66, no. 9, p. 1,109-1,130. 
White. D. E., Anderson, E. T., and Grubbs, D. K., 1963, Geotherraal brine well— 

mile-deep drill hole may tap ore-bearing magmatic water and rocks under- 
going metamorphism : Science, v. 139, no. 3,558, p. 919-922. 
AVhitten, C. A.. 1956, Crustal movement in California and Nevada : Am. Geophys. 

Union Trans., v. 37, no. 4, p. 393-398. 



(By J. P. Albers, U.S. Geological Survey, Menlo Park. Calif.) 

The economic value of a mineral resource is determined by the cost 
of mining and processing, cost of marketing, including transportation 
to market, and by the demand for the commodity. Costs and demand 
vary with fluctuations in local or national economy, advances in the 
technological fields of exploration and exploitation, and increases in 
requirements by industry and the expanding population. A resource 
that cannot be developed profitably today may become the basis for a 
profitable enterprise in the future because of these constantly changing 
sociologic, technologic, and economic factors. 

A distinctive characteristic of mineral economics is that once a min- 
eral resource is exhausted it cannot be replaced. This creates problems 
both in concepts of conservation and execution of resource develop- 
ment. For this reason, efficient development, intelligent use, and con- 
tinuing search for new or substitute mineral resources are of impor- 
tance to economic growth. Advances in the techniques of exploration 
and processing of mineral resources have been successful in meeting 
the most fundamental needs of the nation's economy to date. How- 
ever, with depletion of high-grade deposits, it will become necessary 
to locate and develop deposits that are lower grade, particularly those 
that give promise of yielding more than one mineral commodity, others 
that are deeply buried, and still others that are farther from estab- 
lished markets. 

The accumulation of a mineral or rock to form an economic deposit 
is the result of one or more specific geologic processes, and therefore 
each type of mineral resource is limited in distribution to certain geo- 
logic environments. Thus, the occurrence of many individual mineral 
commodities in California is more or less restricted to specific geologic- 
geomorphic provinces. Deposits of many metals, particularly base 
and precious metals, are concentrated in dej^osits by aqueous solutions 
emanating from large deep-seated bodies of magma. Deposits of this 
origin commonly occur as veins that fill fractures in the host rock, or 
occur as a metasomatic replacement of the host rock. The primary 
deposits of gold, copper, silver, tungsten, and molybdenum in the 
Sierra Nevada region originated as emanations of solutions from the 
more silicic, lighter-colored f acies of granitic rocks of the Sierra Ne- 
vada batholith. However, it is important to note that these metallifer- 
ous deposits are restricted to the sedimentary and volcanic rocks that 
were invaded by the batholith, and that the batholith itself is barren. 
Similar conditions prevail in the Klamath Mountains where deposits 
of base and precious metals are found in rocks invaded by granitic 
plutons, and in the Mojave Desert and Great Basin where iron, rare- 
earths, and base-metal deposits are found principally as a replacement 



of carbonate rocks near igneous contacts. Such commodities as talc, 
pyrophyllite, kyanite, and andalusite, are also closely related to igne- 
ous rocks, being the product of the metamorphism of invaded country 
rock by the heat and emanations from the igneous intrusion. 

Other mineral comLmodities found in close association with deep- 
seated igneous rocks include mica, feldspar, gemstones, chromite, as- 
bestos, and nickel. Tliese are commonly in the igneous rocks them- 
selves rather than in the invaded country rock. Mica, feldspar, beryl, 
and many gemstones are most commonly extracted from pegmatites, 
irregular dike-like bodies of very coarsely crystalline igneous rock in- 
truded into igneous rock of finer grain size. However, mica and feld- 
spar also are extremely abundant in many ordinary' igneous and meta- 
rnorphic rocks and in some localities are produced commercially from 
the bulk mining of these rocks. Chromite, asbestos, and nickel are 
associated with dark mafic and ultramafic igneous rocks — the first two 
commodities with peridotite and serpentinite, and the latter with 
peridotite, serpentinite, and gabbro. Chromite crystallized contem- 
]^oraneously with the ultramafic rock, and deposits of this mineral 
formed by a process called magmatic segregation. Asbestos occurs as 
small vein-like fracture fillings mostly in ultram.afic rock that have 
been serpentinized, and nickel is present in sulfide minerals and also 
indigenously in very small amounts in ultramafic rocks. 

Mercuiy deposits are found chiefly in regions of extensive Cenozoic 
volcanic and tectonic activity. The most important deposits in Cali- 
fornia, however, are found hi silica-carbonate rock, a hydrothermal 
alteration of serpentine found mainly in the Franciscan Formation of 
the Coast Ranges. Nevertheless, cinnabar, which replaces the silica- 
carbonate rock, is thought to be a product of volcanic activity. In 
places in California, the mercury mineral cimiabar is being deposited 
around presently active hot springs. 

Mineral fuels such as petroleum, natural gas, peat, and asphalt, are 
products of organic decay and recomposition in a sedimentary envi- 
romnent, and these resources are therefore in sedimentary rocks. In 
California, mineral fuels are best preserved in thick sedimentary de- 
posits of late Mesozoic and Tertiary age found in the San Joaquin, Los 
Angeles, and other sedimentary basins. Diatomaceous earth results 
from accumulation of the siliceous shells of microscopic plants in either 
a marine or continental sedimentary environment; commonl}^ it is in 
sedimentary deposits that are in close association with volcanic rocks. 
Hence de]X)sits of diatomaceous earth occur not only in upper Meso- 
zoic and Tertiary sedimentary^ terranes such as the southern Coast 
Ranges but also in volcanic terranes such as the Modoc Plateau. 

Some of California's most important mineral commodities are the 
saline minerals — boron and borax, bromine, calcium chloride, potash, 
salt, sodium carbonate, and sodium sulfate. Deposits of these com- 
modities were formed in two large saline lakes that developed during 
late Cenozoic time mainly in closed basins in the Great Basin province. 
They are the product of evaporation of waters richly charged with 
mineral constituents. Gypsum and anhydrite are more widely dis- 
tributed but somewhat less soluble products of evaporation that formed 
in many marine and continental basins in the State. 

The "purpose of this generalized and incomplete review of Cali- 
fornia's mineral resources is to demonstrate how the occurrence of 
individual resources or groups of resources is restricted to certain 



geologic environments within the State. A more detailed summarj^ of 
the resources on a commodity-by-commodity basis is given in the 
succeeding pages. 

California's production of the various mineral commodities during 
1963 and 1964, the latest years for which figures are available, is given 
in table 3. 

Table 3. — Mineral production, in California,^ 1963 and. 196^^ 



Barite (crude) 

Boron minerals 

Calcite (optical grade) pounds.. 

Cements . 376-pound barrels,. 

Clays 3 

Copper (recoverable content of ores, etc.) 

Feldspar long tons. 

Geni stones 

Gold (recoverable content of ores, etc.). -.troy ounces.. 


Lead (recoverable content of ores, etc.) 


Magnesian compounds from sea water and bitterns 

(partly estimated) MgO equivalent.. 

Mercury 76-pound flasks.. 

Mica, scrap 

Natural gas million cubic feet.. 

Natural gas liquids: 

Natural gasoline and cycle products 

thousand gallons.. 

Lp gases do 


Petroleum (crude) thousand 42-gallon barrels.. 

Pumice, pumicite and volcanic cinder 

Salt (common) 

Sand and gravel 

Silver (recoverable content of ores, etc. )--troy ounces.. 

Stone « 

Sulfur ore long tons.. 

Talc, pyrophyllite, and .soapstone. 


Zinc (recoverable content of ores, etc.)... 

Value of items that cannot be disclosed: Bromine, cal- 
cium chloride, carbon dioxide, masonry cement (1963), 
clays (ball and fuller's earth) 1964, coal (lignite), dia- 
torhite, iodine, iron ore, lithium minerals, molyb- 
denum, perlite, platinum-group metals, potassium 
salts, rare-earth metals, sodium carbonate, sodium 
sulfate, steam (natural), tin, tungsten concentrate, 
uranium, and values indicated by footnote '. 



Short tons 


19, 591 


700, 183 


46, 278, 000 

3, 395, 000 


75, 516 


86, 867 

756, 000 



82, 397 

13, 592 


646, 486 

715, 303 

393, 503 

39, 873 

300, 908 

460, 000 

1, 716, 000 

112, 185. 000 

157, 000 

37, 977, 000 


120, 452 






54, 981 

147, 656 








189, 420 

54, 188 

17, 329 


746, 232 



128, 178 


58, 253 





90, 366 



Short tons 


55, 041 




47, 204, 000 

3, 651, 000 


102, 264 


71, 026 



577, 000 

94, 739 
10, 291 


664. 051 

720, 373 

352, 614 

35, 391 

300, 009 

443, 000 

1, 525. 000 


172, 000 

45, 805, 000 


132, 601 




$4, 419 


60, 871 


149, 933 








198, 551 

54, 088 

15, 893 


729, 022 


129, 333 









' Production as measured by mine shipments, sales, or marketable production (including consumption 
by producers) . 
- Excludes masonry cement included with "Value of items that cannot be disclosed." 
3 Incomplete figure. Ball clay and fuller's earth included with items that cannot be disclosed. 

* Withheld to avoid disclosing company confidential data. 

* Weight not recorded. 
» Includes slate. 

Source: U.S. Bureau of Mines. 


(By G. B. Cleveland, California Division of Mines and Geology, Los Angeles, 


Aluminum, the second most abundant metal in the earth's crust, is 
found in nearly all rocks. Only under special geologic conditions, 
however, does it occur in large high-grade deposits that can be eco- 
nomically worked as a source of the metal. At present, the only im- 


portant ore of aluminum is bauxite. The principal domestic deposits 
of bauxite are in Arkansas, Georo-ia, Alabama, .and Mississippi. These 
contain less than one percent of the world's reserves, and many cannot 
compete either in quality or price with foreign imports. In 1963, the 
domestic deposits supplied only about 12 percent (1,525,000 long tons) 
of the bauxite consumed in the United States. The balance ^.fibout 
11,318,000 long tons) was drawn principally from the Caribbean 
islands of Jamaica, Haiti, and the Dominican Eepublic, and from 
the Guianas. The IJnited States ranks first in the production of pri- 
mary aluminum metal, supplying about 2,313,000 tons of the world 
total of about 6,095,000 tons in'l963. 

Aluminum has an extremely wide variety of uses. Most of them 
are in products where light weight or resistance to corrosion are im- 
portant — military equipment, industrial, farm and residential building 
materials, automobiles, home appliances, and materials and containers 
It is also used in industrial chemicals, and electrical wire. 

Bauxite is a colloidal mixture composed of various proportions of 
the minerals gibbsite (A1(0II)3) and the dimorphic forms boehmite 
and diaspore, both (AIO(OH)). Common impurities are rutile, 
siliceous minerals such as kaolinite and quartz, as well .as the iron 
oxides — limonite, hematite, and goethite — and the carbonate minerals 
calcite, magnesite, and siderite. Bauxite is gray, cream, yellow, dark 
red, or earthy brown, is normally pisolitic or oolitic and generally has 
a mottled appearance. Bauxite is a residual product formed by the 
deep weathering of aluminous rocks under tropical conditions, and 
is commonly a constituent of lateritic soils. All domestic deposits are 
Eocene in age. 

The known occurrences of bauxite in California are limited to small 
deposits which are associated with fire clay. None of these deposits 
has proved large enough to haA'e been developed as a commercial source 
of aluminmn; nor has this metal been recovered from any raw mate- 
rial mined in California. However, other alumina-rich deposits, prin- 
cipally the large anorthosite bodies in the southern part of the State 
and the alumina-rich clays, constitute potential resources that may 
eventually yield aluminum on a commercial basis. 

The only large anorthosite bodies known in California are exposed 
in the western San Gabriel Mountains of southern California and have 
a combined outcrop area of about 50 square miles. The San Gabriei 
Mountain anorthosite is composed of calcic andesine (97 percent) 
with small amounts of apatite and zircon. 

Although California contains no known deposits of clay that com- 
pare in alumina content with the high-alumina (40 percent and above) 
or diasporic clays (50 j^ercent or more alumina), some of the State's 
fire clay can be classified as alumina-rich clay. The alumina-rich fire 
clays from California deposits range from about 30 to 40 percent 
alumina. These deposits are in the Eocene lone Fonnation which 
occurs alone: the western foothills of the Sierra Nevada, the Paleocene 
Silverado Formation exposed in the Alberhill-Corona area of River- 
side Countv, and in the Eocene Tesla Formation in eastern Alameda 
County. These clav beds vary in their alumina content, and the higher 
grade material would have to be selectively mined. 

Aluminum has been produced experimentally or on a small-scale 
commercial basis from anorthosite, high-alumina clays, alunite, neph- 
eline syenite, leucite, andalusite, and aluminous shales. When bauxite 


reserves become depleted, one or more of these materials may be de- 
veloped on an economic basis. 

Selected References 

Allen, V. T., 1929. The lone Formation of California : California Univ., Dept. 
Geol. Sci. Bull., v. 18, no. 14, p. 347-448. 

Cleveland, G. B., 1957, Almninuni. in Mineral commodities of California : Cali- 
fornia Div. Mines Bull. 176. p. 29-33. 

, 1957. Clay, in Mineral commodities of California : California Div. Mines 

Bull. 176, p. 131-152. 

Dietrich, W. F., 1928. Clay resources and the ceramic industry of California: 
Oalifoniia Div. .Alines Bull. 99, 383 p. 

Higgs, D. v.. 1954. Anorthosite and related rocks of the western San Gabriel 
Mountains, southern California : California Univ. Pub. Geol. Sci., v. 30, no. 3, 
p. 171-222. 

Lundquist, R. V., 1963, Recovery of alumina from anorthosite, San Gabriel Moun- 
tains, California, using lime soda sinter process : U.S. Bur. Mines Kept. Inv. 

Oake.shott, G. B., 1958, Geology of the San Fernando quadrangle, Los Angeles 
County, California : California Div. Mines Bull. 172. 147 p. 

Stamper, J. W., 1964. Aluminum: U.S. Bur. Mines Minerals Yearbook 1963, p. 

U.S. Bureau of Mines. 1953, Materials survey, bauxite : U.S. Bur. Mines, 13 
chapters (loose leaf), various pagings. 

Williams, L. R., 1965. Alumina and bauxite, in Mineral facts and problems : U.S. 
Bur. Mines Bull. 630. 


(By Q. A. Aune. California Division of Mines and Geology, Redding, Calif.) 

Antimony is a brittle, silver-white metal with a melting point of 
630.5 °C. Antimony metal has the property of expanding when cooled 
and of hardening certain other metals when alloyed Avith them. The 
effect of antimony in lead alloys is to add stiffness and physical 
strength, to resist chemical action, and to make sharp, accurate cast- 
ings. In nonmetallic compounds, it may be used as an opacifying 
agent or as a pigment. Certain antimonial compounds have fire- 
extinguishing characteristics which account for the bulk of antimony 
consumption during wartime. The nearly complete dependence of the 
United States on foreign su])ply as shown in figure 5, and the diversity 
of its major uses earn antimony's classification as a strategic mineral. 

A substantial portion of metallic antimony produced in the United 
States is secondary antimony reclaimed from scrap metal (fig. 5). In 
recent years, production of antimonial lead has consumed roughly 
18,000 tons of antimony annually, over two-thirds of this from sec- 
ondary antimony, and most of it used in auto batteries. Production 
of bearing metal, cable covering, sheet and pipe, solder, and type metal 
has also relied heavily on secondary antimony. 

Antimony deposits may be classified in two types. The mineralogi- 
cally simple type consists dominantly of antimony minerals in a sili- 
ceous gangue, commonly with a little pyrite and in places small 
quantities of other metal sulfides. The original antimony mineral is 
stibnite (antimony sulfide) or, rarely, native antimony. Where ex- 
posed to oxidation, the original minerals are converted to antimony 
oxide. Although most of the world's production is from deposits of 
the simple type, most of the antimony mined in the United States is, 
for economic reasons, from deposits of the complex type : ores mined 
primarily for lead, gold, silver, quicksilver, zinc, or tungsten, with 
antimony as a by-product. 






























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Most of the antimony deposits of California, as shown on figure 6, 
are of the simple type — small ore bodies that commonly show struc- 
tures characteristic of epithermal deposits — fissure fillings, irregular 
disseminations in vugs or "pockets" and breccia, and haphazard frac- 
ture control. 

The Stayton district in San Benito and Merced Counties is the larg- 
est antimony mining district in California, although production has 
been small, limited to perhaps 500 tons of antimony metal, none since 
World War II. Antimon}^ occurs as stringers and cavity fillings of 
tarnished stibnite which are localized in numerous north-northwest- 
trending fault zones in Tertiary basalts and tuffs. In late 1949 and 
throughout 1950, the Cordero Mining Co. of Palo Alto and the U.S. 
Bureau of Mines prospected the Quien Sabe mine, a principal deposit 
of this district, and revealed a moderate tonnage of ore averaging 
three percent antimony. 

The Wildrose Canyon deposit in the Panamint Range, Inyo County, 
has been the principal past producer in California. Antimony oxides 
and stibnite occur in blanket -type breccia deposits in schists, and as 
fissure fillings in quartz veins. 

At the Transportation (Old Dependable) deposit, near the base of 
the Panamint Range a few miles east of the Wildrose Canyon deposit, 
stibnite and antimony oxides occur in small, scattered masses in shale 
overlying limestone. Other deposits in Inyo County occur at the Hill- 
top, Rocket, and Darwin mines on the west slope of the Argus Range, 
and the Bishop mine on the east slope of the Sierra Nevada near 

A number of deposits have been worked for antimony in Kern 
County. Most of these deposits consist of stibnite and quartz in veins 
along shear zones in granodiorite or quartz diorite. The largest de- 
posit of this type is the San Emigdio (Antimony Peak) deposit in 
southeastern Kern County. Calcite, pyrite, and antimony oxides are 
also present. The deposit was mined intermittently from 1882 to 1892, 
during World War I, and most recently in 1940-1941. 

Deposits at Antimony Flat, eastern Kern County, consist of small 
nodules and clusters of radiating stibnite blades disseminated along 
poorly exposed steeply dipping quartz veins in granodiorite. Stib- 
nite occurs in quartz veins in silicified andesitic rock at the Mammoth 
Eureka mine 17 miles east of Caliente in east-central Kern County; 
this mine was the source of an undetermined quantity of antimony ore 
during World War I. At the Tom Moore mine, aggregates of bladed 
and massive stibnite and native antimony occupy a quartz vein in a 
shear zone in metamorphic rocks. At the Jenette-Grant mine, stib- 
nite occurs with quartz along a limestone-schist contact. 

In the Atolia district, near the west border of San Bernardino 
County, stibnite is locally present in subordinate proportions in veins 
in quartz monzonite. Mineralogy is complex. Chalcedony, quartz, 
scheelite, and carbonates of calcium, iron, and magnesium are princi- 
pal minerals, with cinnabar also locally present. At the Desert Anti- 
mony (Wade) deposit in the Mountain Pass area, eastern San Bernar- 
dino County, quartz-stibnite-barite-calcite veins occur in granitic 


Total inferred California reserves of antimony metal from ore esti- 
mated to contain greater than one percent antimony, assuming such 
"ore" could be economically worked, would be on the order of only 15 
to 20 thousand tons, a small amount compared to America's annual 




























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needs, and most of this tonnage is in the Stayton district. Many of 
the deposits are largely "high-graded" or worked out. Any large 
tonnage developments probably must come from new deposits. Such 
new deposits, if present, would seem most likely to occur in areas 
favorable to epithermal deposition. Such areas are most likely to 
occur ill the Great Basin provmce and the eastern margin of the Sierra 
Nevada. Somewhat lesser possibilities are in the central Coast Range 
and eastern Klamath Mountain areas. 

Selected eefebences 

Bailey, B. H., and Myers, W. B., 1M2, Quicksilver and antimony deposits of the 
Stayton district, California : U.S. Geol. Survey Bull. 931-Q, p. 405-434. 

, 1949, Quicksilver and antimony deposits of the Stayton district, Califor- 
nia : California Div. Mines Bull. 147, p. 37-56. 

Goldman, H. B., 1957, Antimony, in Mineral commodities of California : Califor- 
nia Div. Mines Bull. 176, p. 35-44. 

Jermain, G. D., and Ricker, Spangler, 1949, Investigations of Antimony Peak. 
Kern County, California : U.S. Bur. Mines Rept. Inv. 4505. 

Lesemann, R. H., 1965, The changing pace and pattern in the business of min- 
ing — antimony : Eng. Min. Jour., New York, v. 166, no. 2, p. 129-131. 

Moulds, D. E., 19&4, Antimony, in U.S. Bur. Mines Minerals Yearbook 1963, v. I, 
p. 235-244. 

Norman, L. A., Jr., and Stewart, R M, 1951, Mineral resources of Inyo County : 
California Jour. Mines and Geology, v. 47, no. 1, p. 28-29, 36-37. 

Troxel, B. W., and Morton, P. K., 1962, Mines and mineral resources of Kern 
County, California : California Div. Mines and Geology County Rept. 1, p. 

U.S. Bureau of Mines, 1965, Antimony, in Mineral facts aiid problems: U.S. Bur 
Mines Bull. 630, preprint, 10 p. 

White, D. E., 1940, Antimony deposits of the Wildrose Canyon area, Inyo Countv, 
California : U.S. Geol. Survey BuU. 922-K, p. 307-325. 

White, D. E., 1962, Antimony in the United States : U.S. Geol. Survey Mineral Inv. 
Resources Map MR-20. 

Wiebelt, F. J., 1956, Quien Sabe antimony mine, San Benito County, OaUfomia : 
U.S. Bur. Mines Rept. Inv. 5192. 

Wright, L. A., Stewart, R. M., Gay, T. E., and Hazenbush, G.C., 1953, Mines and 
mineral deposits of San Bernardino County, California : California Jour. Mines 
and Geology, v. 49, nos. 1-2, p. 59-60. 


(By Q. A. Aune, California Division of Mines and Geology, Redding, Calif.) 

Arsenic is produced as a by-product of copper and lead smelting 
and in the recovery of gold and silver. It is recovered only in the 
form of arsenious oxide (white arsenic), as no metallic arsenic has 
been produced in the United States since about 1950. The United 
States ranked as a major producer and consumer of arsenical products 
in 1964. Other im])ortant producing countries in the free world in- 
clude Sweden, Mexico, and France. No domestic ores are mined ex- 
clusively for arsenic. The first recorded production of white arsenic 
in the United States was in 1901. Arsenic is used for manufacturing 
calcium and lead areenate insecticides and herbicides, in chemicals 
for wood preservation, and is added to lead shot and glass. A small 
amount is used in the recently developed solid state masers and 

The most common occurring arsenic-bearing minerals are the sul- 
fides arsenopyrite, realgar, and orpiment. Arsenopyrite is commonly 
associated in hypothermal vein deposits with the ores of tin, nickel, 
cobalt, silver, and gold, and with pyrite, chalcopyrite, galena, and 


sphalerite in mesothermal deposits. Realgar and orpiment occur in 
epithermal deposits with the ores of silver and antimony and in de- 
posits formed by sublimation from hot springs. 

In the early 1920's, California deposits were mined principally for 
their arsenic content at Grass Valley, Nevada County ; at the Contact 
mine in Kem County; and at the Black Momitain prospect in San 
Diego Coimty. 

Arsenic, principally in the mineral arsenopyrite, has a widespread 
occurrence in the ore deposits of California, but at present is of doubt- 
ful commercial interest in any California deposit. It is especially 
abundant in the arsenopyrite-bearing silver ores of the Randsburg 
district in Kern and San Bernardino Counties, and in the arseno- 
pyrite-bearing gold ores of the Alleghany district in Sierra County 
and the Mother Lode of the Sierra Nevada. Arsenopyrite and sulf- 
arsenides are also present in the base-metal ores of the Mojave Desert, 
the Sierra Nevada foothills, and the Shasta mining district. 

Since 1924, large quantities of byproduct arsenic available for im- 
port from Mexico have held prices down. More recently many uses 
of arsenic as a toxic agent have fallen off with the advent of organic 
compounds such as DDT. These competitive conditions have rendered 
California arsenic mining unprofitable, and the closing of nonferrous 
metal mines, from which arsenic might be recovered as a by-product, 
has terniinated production in the State. 

Sbxected References 

California Agricultural Exi>eriment Station, 1954, Herbicidal properties of arsenic 

trioxide : Calif. Agr. Expt. Sta. Bull. 7.39, 28 p. 
Goodwin, J. G., 1957, Arsenic, in Mineral commodities of California : California 

Div. Mines Bull. 176, p. 45-48. 
McMahon, A. D., 1964, Arsenic, in U.S. Bur. Mines 1963 Minerals Yearbook, v. I, 

p. 24.5-249. 
Sayre, R. H., 1924, Arsenical ore deposits in the United States : Eng. Min. Jour., 

V. 118, p. 929-932. 
U.S. Bureau of Mines, 1965, Arsenic, in Mineral facts and problems: U.S. Bur. 

Mines Bull. 680, preprint, 6 p. 


(By S. J. Rice, California Division of Mines and Geology, San Francisco, Calif.) 
Uses and Economic Importance 

Asbestos is one of the few important nonmetallic minerals that is 
largely imported from foreign sources. Of the 790,000 tons of asbestos 
used in the United States in 1964, only about 100,000 tons were pro- 
duced from domestic deposits. Most of the remainder was imported 
from Canada. 

Certain grades of asbestos are indispensable to the construction and 
transportation industries, and all grades occupy important places in 
the general industrial economy. Most of the important uses of asbes- 
tos are based on the fact that it has physical characteristics similar 
to those of organic fibers, yet it is both noncombustible and non- 
corrosive. These physical properties are summarized in table 4. As 
used in the manufacture of numerous products, asbestos acts as a 
reinforcing agent or as a friction or insulation material. The princi- 
pal use is in the manufacture of asbestos-cement products such as pipe. 












































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shingles, wallboard, and corrugated sheets. Large quantities also are 
used in the manufacture of vinyl and asphalt floor tiles, friction 
materials such as clutch facings and brake bands, insulation materials, 
and gaskets. Small amounts of the spinning grades of strong-fiber 
varieties are woven into asbestos fabrics for various special uses. 

Mineralogy and Geologic Occurrences 

The word asbestos is not a mineral name, but a term applied to 
several naturally fibrous minerals that are used primarily because of 
their fibrous characteristics. These minerals include chrysotile, cro- 
cidolite, amosite, anthophyllite, and tremolite. 


Chrysotile is the most important asbestos mineral, accounting for 
more than 90 percent of the world's asbestos production. Chrysotile 
fibers of good quality are silky, highly flexible, and have a tensile 
strength somewhat greater than that of silk. 

Chrysotile occurs only in seri:)entine, a fine-grained rock composed 
almost entirely of hydrous magnesium silicate minerals similar to 
chrysotile in composition. Almost all masses of serpentine contain 
chrysotile, most commonly in cross-fiber veins that rarely are more 
than half an inch thick. In places, however, the fibers lie along faults 
or shear planes and are not so apparent. Only rarely is chrysotile 
sufficiently abundant in the rock to constitute an asbestos ore body. 
Most of the chrysotile fibers in any deposit are very short (less than 
one-sixteenth of an inch long), and clean extraction of the asbestos 
requii-es complicated and expensive milling equipment, so a large vol- 
ume of fiber-rich rock is required for a commercially valuable ore 

About 40 percent of the world production of chi-ysotile comes from 
cross-fiber deposits in a relatively small district in the province of 
Quebec, Canada. The discovery of these rich deposits in 1877 laid 
the foundation of the modem asbestos industry. Substantial amounts 
of chrysotile are produced from similar deposits in the U.S.S.R. and 

Amphibole asbestos 

Amphibole asbestos is a general term for all varieties other than 
chrysotile. These are all members of an exceedingly common group 
of rock-forming silicate minerals characterized by perfect prismatic 
cleavage. Only a few of the amphibole minerals, principally those 
that are aluminum-poor, become sufficiently fibrous to be used as as- 
bestos. In approximate order of economic importance, these are 
crocidolite, amosite, anthophyllite, and tremolite. 

The principal source of crocidolite — blue asbestos — is the Union of 
South Africa, but lesser quantities are produced in Australia and 
Bolivia. Commercial deposits of this variety have not been found in 
California. Amosite, a yellowish-gray, long-fiber variety, is produced 
in Africa, and has not been found else wliere. Both of these varieties 
oc^ur as cross-fiber veins in metamorphosed sedimentary rocks rich in 
silica and iron, and both have strong fibers. 

Most anthophyllite asbestos occurs in massive deposits derived by 
metamorphism of peridotite. The fibers have no preferred orienta- 
tion, but are arranged in bundles of varying sizes oriented at random. 



Deposits of this type are mined in Finland and North Carolina. In 
(California, long-fiber anthophyllite occurs as veins along; faults in ser- 
pentine; the fibers are oriented roughly parallel to the walls of the 
veins. The latter mode of occurrence is characteristic also of tremo- 
lite asbestos deposits in the State, and, in this environment, the two 
varieties cannot easily be differentiated. The fibers of both are white 
and very weak. 

History of Development or California Asbestos Deposits 

Although asbestos has been mined sporadically in California since 
1887, a full-fledged asbestos industry did not emerge in the State until 
1960. This dramatic emergence is demonstrated by the production 
figures, table 5. Prior to" 1960, only 9,049 tons, valued at $331,454 
had been produced, whereas production during the interval 1960-1964 
was 87,782 tons, valued at $6,412,764. Much of the earlier production 
was of amphibole asbestos, long-fiber tremolite and anthophyllite, 
mined and hand sorted from small deposits. It was sold primarily 
for use as filter fiber. Current production is entirely chrysotile. 

Table 5. — Ashestos produotiwi in California, 1887-19S4 















$1, 175 



$2, 867 



















1890 ..- 







15, 000 






10, 225 


1 37 













]■ 131 







1920 ._ 


} 165 

12, 100 






19, 275 










} 224 

16, 779 
















21, 401 







\ 25 


1956 _. 


} 858 








} ^^ 




} 2, 695 

84, 050 







} 219 




J 7,280 

125, 115 








321, 719 





\ 309 



19, 591 

1, 546, 890 












Note.— Where necessary in order to conceal output of individual producers, production figures are com- 
bined to cover a 2- or 3-year period. During years omitted there was no recorded production. 

During and immediately after World War I, when asbestos prices 
were high, attempts were made to develop chrysotile deposits in Cali- 
fornia, particularly those near Copperopolis, Calaveras County, and 
Washington, Nevada County. These operations failed, largely because 
there was only a very limited market for asbestos on the Pacific Coast 
at that time. Transportation rates made fiber from this area non- 
competitive on the eastern market with that from Quebec. 

The recent surge of develoiDment of California deposits was stimu- 
lated by the post-World War II population and industrial boom on 
the West Coast. Several new plants that manufacture asbestos prod- 
ucts were constructed in California, and older ones were enlarged. 
The principal asbestos products manufactured here utilize the shorter 
grades of chrysotile that can be produced in abundance in California. 

67-164 0—66— pt. I 7 



This growing demand resulted in extensive exploration of deposits in 
Calaveras, Fresno, and San Benito Counties in 1959 and 1960, and 
by 1964 four asbestos mills had been constructed to process ores from 
these deposits. 

Occurrences In California 

Serpentine, the principal host rock for asbestos deposits, is abundant 
in California, and asbestos has been found at numerous localities in 
the State (fig. 7). Most of the deposits that have been worked have 
been described by AViebelt and Smith (1959), but only four areas 
contain deposits of chrysotile asbestos that are presently being mined. 

Gopperojyolis area 

The first chrysotile asbestos deposit worked in California is located 
7 miles southeast of Copperopolis, Calaveras County (Kice, 1963). 
This deposit is similar to those in Quebec in that the chrysotile occurs 
as stockworks of cross-fiber veins in massive serpent inized peridotite. 


Amph i bole asbest os 

^ Deposit worked 
in 1965 
Chrysotile asbestos 

1. Copperopolis 
Co a linga 

SALTON \ -<V33- 

f^s«.i"«" _N, — ' 

^- — ■■'■ 



FiouEE 7. Principal asbestos deposits in California. 


Width of the veins is highly variable, from less than one-thirty- 
second of an inch to about an inch, but only a small percentage of 
them will yield fibers more than one-fourth inch long. The ore body 
apparently occupies the crest of an anticline in a large sill of serpentine. 
Although several unsuccessful attempts were made to develop this 
deposit in the early 1900's, not until 1959 was it thoroughly explored 
by trenching and core drilling. This work indicated an elliptical- 
shaped ore body, some 1,800 feet long and 375 feet in average width. 
Sufficient tonnage was proved — more than 20,000,000 tons of ore con- 
taining about 61^2 percent asbestos — to indicate a commercial deposit 
(Merritt, 1962, p. 58). In 1962, a mill was constructed at the deposit 
capable of processing 2,500 tons of ore per day and of recovering any 
grade of milled fiber. The mine is now operated by Pacific Asbestos 

Napa area 

A deposit of cross-fiber chrysotile asbestos in sheared serpentine, 
about 18 miles northeast of Napa, was the site of a small asbestos 
operation during World War II and during the middle 1950's. The 
veins are narrow, ordinarily yielding fibers less than one-sixteenth of 
an inch long, so that only the shorter fiber grades can be recovered 
from the rock. 

A 40-ton mill installed on the property in the early 1940's was inad- 
equate for modem operations, so it was replaced in 1959 by a new mill 
having a capacity to process about 125 tons of ore per day. It is 
operated by Asbestos Bonding Co. 

Goalinga area 

A large serpentine mass in the southern Coast Ranges, some 20 
miles northwest of Coalinga, Fresno County, constitutes one of the 
largest asbestos deposits in the world. The bulk of this mass, alto- 
gether some 14 miles long and 4 miles wide, has been highly sheared 
and much of the serpentine recrystallized to flaky, matted chrysotile 
along the closely spaced shear planes (Rice, 1963). Cross-fiber veins 
are rare in this deposit, and the recoverable fiber is all short, but the 
chrysotile content is very high, exceeding 50 percent in places. Fiber 
produced from this deposit has attributes that promise an interesting 
future for the district. Among these, Coalinga fiber is superior to 
Canadian short fiber in whiteness and in its ability to absorb hydro- 
carbons (Munro and Reim, 1962) . 

The commercial asbestos potential of this enormous deposit, which 
probably contains more than 100 million tons of ore, was not recog- 
nized by the industry until 1959, when Union Carbide Nuclear Co. 
l)egan filing mineral claims in the area, then largely open Federal 
land. Other companies soon were attracted to the area, and by 1965, 
three mills having an aggregate productive capacity of about 50,000 
tons of fiber per year were in operation. Companies active there in 
1965 were Coalinga Asbestos Co., Atlas Corp., and Union Carbide 
Nuclear Co. 

Recent discoveries and commercial development of California as- 
bestos deposits indicate that the potential for new discoveries in the 


State is high. The total outcrop area of serpentine in the Coast 
Ranges, Sierra Nevada, and Klamath Mountains is on the order of 
2,000 square miles, and significant portions of this have not been 
prospected for asbestos. It seems probable that more discoveries will 
be made of Coalinga-type deposits in the southern Coast Ranges. 
Also, many interesting chrysotile prospects in the serpentine masses 
in Shasta, Trinity, and Siskiyou Counties (Wiebelt and Smith, 1959) 
suggest that this relatively remote area is a promising one. 

Selected References 

Badollet, M. S., 1951, Asbestos, a mineral of unparalleled properties : Canadian 

Inst. Min. and Met., Tran. v. 54, pp. 151-160. 
Bowles, Oliver, 1955, The asbestos industry : U.S. Bur. Mines Bull. 552. 
Merritt, P. C, 1962, California asbestos goes to market : Min. Eng., v. 14, no. 9, 

pp. 57-60. 
Messell, M. J., 1947, Examination and valuation of chrysotile asbestos deposits 

occurring in massive serpentine : Am. Inst. Mining Metall. Engineers Trans., 

V. 173, pp. 79-84. 
Munro, R. C, and Reim, K. M., 1962, Coalinga — newcomer to the asbestos in- 
dustry : Min. Eng., v. 14, no. 9, pp. 60-62. 
Rice, S. J., 1957, Asbestos, in Mineral commodities of California : California 

Div. Mines Bull. 176, pp. 49-58. 
, 1963, California asbestos industry : California Div. Mines and Geology, 

Min. Inf. Service, v. 16, no. 9, pp. 1-7. 
Sinclair, W. E., 1955, Asbestos, its origin, production, and utilization : Min. 

Pub.. Ltd., Salisbury House, London, 512 p. 
Wiebelt, F. J., and Smith, M. C, 1959, A reconnaissance of asbestos deposits 

in the serpentine belt of northern California : U.S. Bur. Mines Inf. Circ. 7860, 

52 p. 


(By M. B. Smith, U.S. Geological Survey, Los Angeles, Calif.) 

The primary use of native asphalt and bituminous rock in Califor- 
nia in the past has been for road-paving material. However, crude 
oil has been recovered from these rocks at several localities. These 
latter operations were not commercially successful, but it seems likely 
that the future use of bituminous rock will be for its oil content. 

Asphalt (brea) in California occurs at the surface where it is usu- 
ally mixed with soil, and in vein-like fracture fillmgs in rocks. Some 
veins are nearly pure asphalt. Bituminous roclis, mainly sandstones 
or finer grained rocks impregnated with viscous asphaltic material, 
crop out at the surface in many places, and in some places they extend 
to depths of seA'eral hundred feet where they contain less viscous fluid 
and will yield oil to wells. 

Nearly all the deposits in the State are in sedimentary rocks of Mio- 
cene to Recent age in the California Coast Ranges, Transverse Ranges, 
and Peninsular Ranges provinces (fig. 8). Most of the deposits are 
at the surface near the margins of the sedimentary basins. They also 
occur in the basins where some rocks are near the surface as a result of 
folding or faulting, or where oil has migrated along faults. 

The present production of bituminous sandstone in the United 
•States is very small, only 1,800 tons valued at $15,000 in 1963. 
Past production in California has been about 1.5 million tons of bi- 
tuminous sandstone with a value of $4.75 million, 219,000 tons of 
asphalt with a value of $2 million, and 24,500 barrels of crude oil 
with a value of $100,000. 




Pr i nc i pa I occurrences 

1 . Edna 

2 . Casma I i a 

3 . S is qu oc 

4 . Grac i osa Ridge 

5 . Santa Cr uz 

6 . McKi 1 1 r ick 

7 . Point Arena 

8. La Br ea Creek 

Minor occurrences 
9 . Ca r p i n te r ia 
10. Rancho La Brea 

Figure 8. Asphalt and bituminous rock in California. 

The production of native asphalt ceased long ago. The production 
of bituminous sandstone reached a peak in 1910, but then decreased 
rapidly as petroleum asphalt from refineries captured the market for 
road paving material. It was discontinued in 1949, and the only 
operation since that time has been the quarrying of a bituminous 
rock which is then burned to obtain lightweight concrete aggregate 
and pozzolan. Crude oil has not been recovered from such deposits 
since 1959. 

The resources of oil recoverable by known methods from bituminous 
rocks in California are believed to be large. Estimated reserves are 
about 300 million barrels that could be recovered from only those 
deposits that have been quite well examined and worked in places. 


However, this oil can not be recovered at a cost now competitive with 
crude oils from wells. As the recovery of this oil by quarrying or 
mining would require moving about 400 million tons of rock, it seems 
that some method of recovering the oil from the rocks in the ground 
offers the best prospect. 

Also it has been estimated (Duncan, D.C., written communication) 
that 1 billion barrels of oil-equivalent could be -recovered from the 
higher grade bituminous shale of late Miocene and Pliocene age in 
the State, and that as much as 70 billion barrels of oil-equivalent 
is present in widespread Miocene shales (Rubel, 1955). 

Selected References 

Adams, E. W., and Beatty, W. B., 1962, Bituminous rocks in California : Cali- 
fornia Div. Mines and Geology. Mineral Information Service, v. 13, no. 4, 
p. 1-9. 

Ball Associates, Ltd., 1965, Surface and shallow oil-impregnated rocks and shal- 
low oil fields in the United States : Oklahoma City, Okla., Interstate Oil Com- 
pact Commission, 375 p. 

Eldridge, G. H.. 1901. The asphalt and bituminous rock deposits of the United 
States: U.S. Geol. Survey 22d Ann. Kept., p. 209-452. 

Gore, F. D., 1924, Oil shale in Santa Barbara County, California : Am. Assoc. 
Petroleum Geologists Bull., v. 8, no. 4, p. 450-472. 

Holmes, C. X.. Page, B. M., and Duncan, D. C, 1951, Bituminous sandstone de- 
posits of Point Arena. INIendocino County, California : U.S. Geol. Survey Oil 
and Gas Inv. Map OM 125. 

Jennings. C. W., 1957, Asphalt and bituminous rock, in Mineral commodities of 
California : California Div. Mines Bull. 176, p. 59-70. 

Page, B. M.. Williams, M. D.. Henrickson, E. L., and others, 1944, Geol(^y of the 
bituminous sandstone deposits near Edna, San Luis Obispo, California: U.S. 
Geol. Survey Oil and Gas Inv. Prelim. Map 16. 

Page. B. M.. Henrickson, E. L., Williams. M.D., and Moran, T. G., 194.5, Asphalt 
and bituminous sandstone deposits of part of the McKittrick district, Kern 
County, California : U.S. Geol. Suney Oil and Gas Inv. Prelim. Map 35. 

Page. B. M.. Williams, M. D., Henrickson, E. L.. and others. 1945. Bituminous 
sandstone deposits near Santa Cruz, Santa Cruz County, California : U.S. 
Geol. Survey Oil and Gas Inv. Prelim. Map 27. 

Rubel, A. C, 1955. Shale oil as a future energy resource : Mines Mag., Oct. 1955. 
p. 72-76. 

U.S. Department of the Intei-ior, Energy policy staff. 1963, Supplies, costs, and 
uses of the fossil fuels : U.S. Dept. Interior, 34 p., tables. 

Williams, M. D., and Holmes, C. N., 1945, Geology of oil-impregnatetl diatomace- 
ous rocks near Casmalia. Santa Barbara County. California : U.S. Geol. Survey 
Oil and Gas Inv. Prelim. Map 34. 


CBy F. H. Weber, Jr., California Division of Mines and Geology, Los Angles, 


Barite, naturally occurring barium sulfate, is the heaviest of the 
)ionmetallic industrial minerals ; its specific graA-ity is 4.6. It is used 
principally as a weighting agent in oil and gas well drilling fluids, and 
to manufacture barium cliemicals; lesser amounts are used in paints, 
rubber, and glass, as high-density aggregate in concrete for nuclear 
shielding, and for other purposes. The United States is the leading 
world producer, importer, and consumer of crude barite, with a con- 
sumption in 1963 of 1,400,000 tons, valued at about $14,000,000. Of 
this amount, 824,000 tons, valued at $9,447,000 was mined domestically. 


principall;^ in Missouri, Arkansas, Georgia, and Nevada, with smaller 
quantities in California and several other states. 

The total recorded output of barite mined in California, from 1910 
to 1963, is 735,000 tons, with a value of $5,440,000. The annual con- 
sumption of the crude mineral from 1959 to 1963 by California indus- 
tiy fluctuated between 100,000 and 130,000 tons, but only about 5,000 to 
15,000 tons were mined annually in the State. Most of the crude 
Ijarite rock consumed in California is mined in Nevada, where de- 
posits are numerous and commonly large and relatively high iii grade; 
they yield barite rock of at least 4.2 in specific gravity, the minimum 
weight suitable when crushed and gromid, for use in drillmg fluids. 
Thus the resultant low cost of the crude mineral compensates for the 
relatively high transportation cost to California processing facilities. 
Crude barite for use ni drilling fluids is processed in California prin- 
cipally/- by Baroid Division of National Lead Co., Macco Corp., Calada 
Materials Co., Industrial Minerals and Chemical Co., and Yuba Min- 
erals and Milling, Inc. ; barium chemicals are manufactured by FMC 
Corp. The value per short ton of crude barite delivered to these 
facilities, ranges from about $13 or $14 to about $22 or $23 per ton, 
the value generally being higher in southern California. Fluctua- 
tions in the amount of barite consumed in the State generally reflect 
the activity in drilliiig, with less activity in mid-1965 reflected in lesser 
tonnages of barite being consumed. 

Though California furnishes only a small proportion of the crude 
barite rock that it consumes, the State contains more than 150 known 
barite localities, including 7 deposits that have yielded more than 
15,000 tons, and about 15 deposits which have yielded from 100 to 
10,000 tons as shown on fig. 9 and on table 6. Deposits mined since 
1960 that have yielded at least several hundred tons are the Ninemile 
Canyon (1961-1963) and Bald Mountain (1963-1965) in the Sierra 
Nevada; the Glidden Co. (1962-1964) and Alwood (1962) in the 
Klamath Mountains; the Gunter Canyon (1962-1965) in the White 
Mountains; and the Leviatlian (1961) and Silver Bow (1961) in the 
Calico Mountains. 

Slightly more than 90 percent of the total barite mined in California 
has come from 5 deposits that are part of a crude belt which extends 
at least from the southern to the northern Sierra Nevada; and may 
extend, interrupted by the Cascade Mountains, into the Klamath 
Mountains. The deposits occur in metamorphic rocks of the Cala- 
veras Formation and similar units. Of these 5 deposits, 2 lie in the 
southern part (El Portal, Ninemile Canyon) and 3 in the northern 
part (Almanor, Democrat, Spanish). The deposits of the southern 
part, consist of long, steeply dipping vein-like bodies of quartz-barite 
rock which averages about 3,9 to 4.1 in specific gravity. These bodies 
occur within north- to northwest-trending linear zones which are at 
least 3 miles in length, but commonly are offset by minor faults; in- 
dividual fault segments of the barite bodies are at least 3,000 feet in 
length, and range in thickness from 1 to 40 feet and perhaps average 
3 to 8 feet. Nearly all barite rock mined has been upgraded by jigging 
(Ninemile Canyon, Bald INIountain) or by a combination of jigging 
and sink-float (El Portal, mined from 1910 to 1948, and the source of 
almost 60 percent of the total barite mined in California) . The most 



124- 123. J22. J21 

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Prospect: or known output less 
than 100 tons ol crude barite 

Output 100 to 10,000 tons 

Output more than 10,000 tons 

Pr ocess i ng facilities 

a . Bar Id , Ma reed 

b . Ca lada , Harbor City 

c. FMC, Modesto 

d. Industrial Minerals, Florin 
e . Mace 0, Rosamond 

I . Yuba , Suiter City 


* 1 8 \ 



<>..]:rr::- ' TF y-,V 



1 n F • 

+ \^ -j- ) SAN DIE"" 

119° 118° 


,SALTON \ -=,33° 

m° "^" 

Figured. Barite in California ( numbers refer to table 6 ) . 

recently developed deposit is the Bald Moimtain; this deposit and the 
Devils Gulch together probably contain at least several hundreds of 
thousands of tons of barite rock to a depth of 50 feet or less. Deposits 
in the northern part of the belt consist of dark-gray barite, from 3 
to 10 feet thick, which is interlayered with phyllite and related rocks; 
the three productive deposits now are mostly worked out at the surface. 
Projections of linear zones within this belt, utilizing known geology, 
would make excellent targets for future prospecting. 

In recent years, the Glidden Co. deposit, on Girard Ridge in the 
Klamath Mountains, has been the principal State source of barite rock 
of greater than 4.2 specific gravity. This deposit consists chiefly of 
dark-gray barite from 3 to 10 feet thick which is interlayered with 


Tabic 6. — Barite deposits of California 
[Numbera refer to localities shown in fig. 9] 

I. Afterthought and others (including Hirz Mount. Greenwood, Exposed Treas- 

ure, Bidwell, Ranch) (a). 

2. Almanor (includes Cameron, Syntheticlron Color mines) (e). 

3. Alwood (a). 

4. Austin (e). 

5. Bald Mountain (two properties : Baro, Palonia) (b). 

6. Buckhorn (b). 

7. Calico Mountains and vicinity deposits (include Barium Queen, Big Medicine, 

Burcham-Waterloo, La Mountain, Lead Mountain, Leviathan, Mount 
General, Penny, Silver Bow, Silverado, Waterman) (b, d) . 

8. Callahan Ranch lead-barite (e). 

9. Camp Nelson (a). 

10. Chickencoop Canyon barite-witherite-sanbornite (a). 

II. Clavey River (e). 

12. Death Valley region (Bradbury Well, Miller Spring, Greenwater, Warm 

Spring Canyon (a). 

13. Democrat (c). 

14. Devils GiUch (EgenhoflE) (b, c). 

15. El Portal (b, c). 

16. Fremont Peak (Gabilan Peak) (a). 

17. Glidden Company (Loftus) (C). 

18. Hansen and others (including Ludlow Belle) (b). 

19. Indian Valley (Dawn) silver-barite (d). 

20. Kingston (e). 

21. Labrea Canyon (c). 

22. Liscom Hill (a). 

23. Mountain Pass (Molybdenum Corp. of America) rare-earth minerals (d). 

24. Ninemile Canyon (Paso Barvta ; includes Barite King mine) (b, c) . 

25. Noble (e). 

26. Ord Mountain copper-gold (d). 

27. Palo Verde (includes Palo Verde, White Swan properties) managanese- 

barite (a). 

28. Pine Hill gold (d). 

29. Pipeline Canyon (a). 

30. Red Hill mercury (a). 

31. Ritter Ranch (a). 

32. Sacramento Mountains barite-fluorite, etc., deposits (a). 

33. San Dimas (a). 

34. Sands (a). 

35. Spanish (c). 

36. Topaz (a). 

37. White Mountains deposits (including Gunter Canyon, White Mountains, 

Bitch, Starr, Last Chance, and Smith) (c). 


(a) Relatively small deposits, large tonnages of barite rock not apparent at 

surface. Potential seems limited. 

(b) Large or possible large tonnages of lower grade rock of less than 4.2 specific 

gravity, as indicated in text. 

(c) Small to large tonnages of rock may exist beneath present surface workings. 

Largely mined out at surface. 
\ d ) Barite might be recovered as a by-product. 
(e) Potential undetermined. 

gently dipping, mildly metamorphosed siltstone and shale of Devonian 
age. The barite occurs stratigraphically at an interval of about 15 
to perhaps several hundred feet beneath several large, adjacent bodies 
of limestone. This limestone occurs in a north-northeast-trending 
belt 11 miles long which should be prospected for additional barite. 
The Calico Mountains and vicinity, on the Mojave Desert, is the 
site of a famous old silver district which was active mainly from 1882 


to 1896. Barite occurs principally as an important gangue mineral in 
noi+hwest-trending silver-bearing veins which consist mostly of jas- 
per. Barite seems to be most abundant in the northwest part of the 
Calico district itself, and at the AVaterman and Lead Mountain mines. 
The most important barite recovery oi>eration has been at the former 
Le\'iathan silver mine, where the mineral was recovered from 1957 to 
1961 by air separation from nx^k of about 3.5 in specific gravity. 
Barite once was recovered briefly from the tailings of the Waterman 
mine ; and small tonnages of barite of 4.0 to •4.2 grade have been shipped 
from the Silver Bow and other properties. Recently active prospects 
include the Penny and Big Medicine, which may contain large ton- 
nages of low-gi'ade rock. Deposits similar to the Calico Mountain 
deposits are the Hansen and others, which lie to the east. 

At Mountain Pass, on the Mojave Desert,, the Molybdenum Corp. of 
America recovers rare-earth minerals from large carbonate bodies 
which consist also of 20 to 25 percent barite ; barite might be recovered 
as a by-product at the recently ex])anded operation. The Gunter Can- 
yon and other deposits in the White Mountains consist of generally 
thin veins of connnonly high grade barite. Also of possible significance 
is the Labrea Canyon deposit, mined out at the surface, but possibly 
containing additional white barite bodies below the surface. A re- 
cently located deposit is the Buckhorn, in the eastern Sierra Nevada, 
which consists principally of two adjacent, north-northwest -trending, 
irregular zones which are about 150 feet long and 35 to 75 feet wide; 
the zones consist of white, granular barite which is very thinly inter- 
layered with silicified mudstone ("chert"). Small quantities of white 
barite occur ii\ the Afterthought and several similar deposits in the 
Klamath Mountains, and in the Palo Verde deposit on the Mojave 
Desert. Additional deposits that have been prospected in recent years 
are the Sands, Kingston, and Topaz. 

The greatest potential resources of barite in California consist of the 
larger, lower grade deposits which mostly today cannot compete with 
rock shipped into California from Nev^ada. A factor that might lead 
to greater exploitation of these deposits is the use, in recent years, of 
some lower grade barite for drilling; one company, for example, 
markets a product of 4.0 specific gravity. In addition, greater amounts 
might be produced competitively by beneficiation, or as a by-product, 
especially if tlie higher grade Nevada deposits become depleted. 

Selected References 

Brobst, D. A.. 19.58, Barite resources of the United States: U.S. Geol. Survey 

Bull. 1072-B. p. 67-130. 
Brobst, D. A., and Ward, F. N., 1965, A turbidimetric test for barium and its 

geolog-ic application in Arkansas : Econ. Geology, v. 60, no. 5. p. 1020-1040. 
Drake. H. J.. 1964, Barite, from Minerals Yearbook 1964: U.S. Bur. Mines, pre- 
print, 12 p. 
Horton, R. C, 1963, An inventory of barite occurrences in Nevada : Nevada Bur. 

Mines Rept. 4. IS p. 
Kundert, C. J., 19.57, Barite, in Mineral commodities of California : California 

Div. Mines Bull. 176, p. 71-74. 
Lewis, R. W., 1965, Barium, a chapter from Mineral facts and problems 1965 ed. : 

U.S. Bur. Mines Bull. 030, preprint, 9 p. 
Tyler, P. M., 1945, Barium minerals, in Taggert, A. F., Handbook of mineral 

dressing — ores and industrial minerals : New York, John Wiley and Sons, 

Inc., p. 3-06 to 3-09. 
Weber, F. H., Jr., 1963, Barite in California : California Div. Mines and Geology 

Min. Inf. Serv., v. 16, no. 10, p. 1-10. 



(By E. B. Gross, California Division of Mines and Geology, San Francisco, Calif.) 

Beryllium is one of the less common lightweight metals which has 
become a more significant connnodity as new uses for it have devel- 
oped. Since 1945, beryllium and beryllium oxide have been fabricated 
into rods used in nuclear reactors to moderate the speed of fission 
neutrons and to control tlie reflection of neutrons to the reactor core. 
It has been used also in neutron gen^^rators as a neutron source. 

Metallurgical uses of beryllium consume most of the metal pro- 
duced. Small amounts of beiyllium added to steel increase its tensile 
strength. However, its ability to add strength and hardness to soft 
and ductile metals such as copper, aluminum, and magnesium in- 
creases its usefulness in alloys of the lighter metals. More than half 
of the total beryllium is used in a beryllium-copper alloy which is 
hard, resistant to fatigue, and non-magnetic. Uses for this alloy in- 
clude springs, special tools, and other non-magnetic devices. A light- 
weight beryllium-aluminum alloy has found limited applications in 
air-frames and structures of aircraft and missiles and for guidance 
mechanisms. Beryllium oxide has been used in refractory materials, 
where its high electrical resistivity and melting point of 4,658°F is 

Increasing uses for beryllium have necessitated more intense ex- 
ploration for source materials. Research equipment such as beryl- 
lometers (neutron activation detectors) and a fluorescent method for 
detecting small amounts of beryllimn in rocks have evolved. In 1964, 
beryllium ores were processed only in Pennsylvania and Ohio. 

The primary occurrence of beryllium is within pegmatite dikes asso- 
ciated with granitic and syenitic intrusive bodies; deposits have been 
found in quartz-rich veins associated with fluorite and in veins within 
quartz monzonite. Lately, the most promising source of ore has been 
the disseminations of beryllium-bearing minerals in granites and 
rhyolitic tuffs. Beryllium-rich tactites contain helvite or beryllium 
dispersed w^ithin the contact minerals of the replacement deposit. Al- 
luvial occurrences, derived from primary intrusive igneous rocks, have 
been the source of only limited production. Beryllium has been found 
in about 43 minerals, of which only three contam sufficient beiyllium 
to be of interest as source materials. Beryl (BeaAlaSieOis) is the 
principal ore mineral and is obtained chiefly from zoned granitic peg- 
matite bodies, most commonly within the inner zones. Because of this 
sparse distribution, conventional mining and concentration processes 
are not followed, and most of the ore has to be concentrated by hand- 
cobbing. Recently deposits of lower grade containing the beryllium 
mmerals phenacite (Be2Si04) and bertrandite (Be4Si207(OH)2*) have 
been found disseminated in rhyolitic tuffs. 

The element, beryllium, was discovered by the French chemist Louis 
Vaugelin, in 1797. An appreciable amount of beryllium was produced 
by F, Wohler of Germany in 1828. In 1916, the first ingot of beryl- 
lium metal was obtained in the United States, but interest in uses of 
beryllium did not develop until 1926, when it was alloyed with copper. 
The beryllium industry grew from this and similar metallurgical uses. 



Production of beryllium ore in the United States has declined since 
1957 (see table 7) . In 1963, only one ton of ore was produced follow- 
ing the removal of government price support. World production m 
1957 was 11,300 short tons of 11 percent BeO, compared to about 6,500 
tons in 1964. Brazil yielded most of the foreign production. In the 
United States, 14 states produced beryllium ore, but no deposits in 
California have been exploited. 

Table 7. — World production and U.S. consumption of beryllium 

[In short tons] 
















1957 — 










1962 — 


1963 .- — 




1 Estimated. 

Beryl has been found in many pegmatites in California, primarily 
in the Peninsular Ranges of San Diego and Riverside Counties (see fig. 
10). Two beryllium discoveries include one near Lone Pine, Inyo 
County, in the Great Basin province and the other in pegmatites near 
Jacumba, San Diego County (Weber, 1962). No commercial pro- 
duction has come from either of these deposits. A list of beryllium- 
bearing deposits, chiefly containing beryl, are given by county in table 
8. Other rare beryllium-bearing minerals are mentioned in the table. 

Table 8. — Beryllium deposits in California 

No. on 
fig. 10 

Pegmatite deposits 



Near Academy. 

Fresno - 




East of Lone Pine 

Mount Lowe area 

Thompson Gem mine, Mount Thompson 

Fano mine, Coahuila Mountains 

Near Hemet- - 

Jensen quarry, near Riverside 

Mears, base of Box Spring Mountain 

Southern Pacific silica quarry, near Nuevo 

Aguange Mountain, near Oak Grove 

Katrina deposit, near Pala (helvite, phenacite, 

bertrandite) . 
Himalaya and Esmeralda mines, Mesa Grande — 

Mac mine, near Rincon (helvite) 

Mines near Ramona (hambergite) 

Crystal mines, near Jacumba 

Near Jamestown .-. — 


Los Angeles. 






San DiegO- 


West of Lone Pine (mineral not identified). 




CaUfomia Division of 
Mines Bulletin 173. 






Beryl |iu m prospec t 

■-■9 '-V -T- - 
H I5,i 


Figure 10. Beryllium in California (numbers refer to table 8). 

Future appraisal of beryllium deposits in California will depend on 
improved exploration techniques, applying new research instruments 
for detecting large, low-grade disseminated deposits. Large tonnages 
of low-grade beryllium ore perhaps may be present in some of the 
Mojave Desert and Great Basin provinces of California, analogous 
to the deposits already delineated in Utah, Colorado, and Nevada. 
However, exploitation of these low-grade deposits will be delayed 
until adequate processing procedures are resolved. Only minor quanti- 
ties of beryl have been obtained from contact metamorphicf rocks and 
alluvial deposits. 


Selected Refebences 

Eilertsen, D. E., 1962, Beryllium : California Div. Mines and Geology, Min. Inf. 

Service, v. 15, no. 2, p. 12-18. 
Griffitts, W. R., Larrabee, D. M., and Norton, J. J., 1962, Beryllium in the United 

States : U.S. Geol. Survey Mineral Inv. Resources Map MR-35. 
Murdoch., Joseph, and Webb, R. W., 1956, Minerals of California : California Div. 

Mines Bull. 173, p. 74-76, 249. 
U.S. Bureau of Mines, 1965, Commodity data siunmaries, p. 14-15. 
Warner, L. A., Holser, W. J., Wilmarth, V. R., and Cameron, E. H., 1959, Occur- 
rence of nonpegmatite beryllium in the United States : U.S. G^ol. Survey Prof. 

Paper 318, p. 198. 
Weber, F. H., Jr., 1962, A beryl discovery in southeastern San Diego County, 

California : California Div. Mines and Geology, Min. Inf. Service, v. 15, no. 

2, p. 8-11. 
Wright, L. A., 1957, Beryllium, in Mineral commodities of California : California 

Div. Mines and Geology Bull. 176, p. 75-78. 


(By Q. A. Aune, California Division of Mines and Geol(^y, Redding, Calif.) 

Bismuth is a brittle, silver- white metal with a reddish hue, and has 
a low melting point of 271.3°C. Its principal uses depend on its 
ability to impart, desirable qualities of f usability, castability, and ma- 
chinability to a wide variety of industrial alloys; and on its value as 
an ingredient in pharmaceutical compounds, salts, and mixtures used 
for indigestion remedies, antacids, bum and wound dressings, anti- 
syphilitics, dusting powder, and cosmetics. 

Bismuth is obtained mainly as a by-product in the metallurgical 
treatment of silver, lead, zinc, copper, gold, tungsten, tin, and molyb- 
denum ores. Native bismuth, bismuthenite, and a number of other 
bismuth-bearing minerals are commonly found in stringers and pockets 
in hydrothermal veins with the above ores. Bismuth minerals also 
occur in contact metamorphic deposits and in pegmatites. 

Twenty tons of bismuth ore were mined at the Lost Hoi'se mine. 
Riverside Comity, in 1909 ; concentrates containing up to 14 percent 
bismuth were obtamed from the Garnet Dike tungsten mine, Fresno 
Comity, but no attempt was made to recover bismuth from the con- 

Bismuth occurrences are relatively widespread, as shown in figure 
11. The paucity of recorded California production is not an indica- 
tion of the lack of production, but signifies that the source of the bis- 
muth was not reported. The by-proMduct relationship of bismuth to 
other metals coupled with the small domestic supply places a major 
reliance on foreign sources and marketing of bismuth material. 

Native bismuth and several oxidized bismuth minerals have been 
reported with, arsenopyrite and gold in quartz veins at the Big Blue 
group of mines in Kern Comity. The Darwin and other mines of 
the Darwin district, Inyo County, contain bismuth in association with 
lead-silver-zinc-tungsten ores. Mineralization is in replacement and 
vein deposits in limestone and calc-silicate rocks. Bismuth is asso- 
ciated with gold-copper vein deposits between Tertiary monzonite 
and rhyolite at the Bagdad-Giase mine, San Bernardino County ; it 
also occurs in the form of a bismuth sulfide associated with copper 






- — „^ Relatively important deposit 
S ! Single deposits or clusters of 

deposits that have produced bis- 
muth: or depos it s that contain 
-. at least 0.027o bismuth in ores or 
^<: \.\^'''concent rates : or deposits reported 
"f^- I to contain fairly abundant bismuth 
mine r a Is . 

Re ported occurrences 

Single deposit or clusters of 
depos it s that contain bismuth 
minerals : or depos it s from which 
si^lected samples of ores or con- 
c^Wtrates contain at least 0.02% 
b i smuth . 

After Coope r (1 962 ) 


Figure 11. Bisnuith in California. 

minerals in a quartz vein that cuts a foliated micaceous quartzite at 
the Lost Horse mine in the Pinon Mountain district, Riverside County. 
At the Garnet Dike tunfrsten mine, a contact metamorphic deposit 
in Fresno County, bismuthinite occurs with scheelite in a tactite zone 
having the form of a vertical chimney with a maximum diameter of 
about 60 feet. Bismuth occurs in association with tungsten-molyb- 
denum-copper ores in tactite near a quartz monzonite contact at the 
Pine Creek mine, Inyo County. Oxidized bismuth minerals occur 
with garnet, epidote, clinozoisite, and other contact metamorphic 
minerals in a highly metamorphosed limestone at the United Tmigsten 
copper mine in San Bernardino County. Native bismuth, bismuth- 


inite and bismutite occur with tourmaline, lepidolite, and other peg- 
matite minerals in the gem mines at Pala, Rincon, and Jacumba, San 
Diego County. 

There are numerous other bismuth occurrences in California that 
are unappraised or are regarded as having no potential importance 
as sources of the metal. Since between 80 and 90 percent of the annual 
total TTnited States consumption (roughly 1,000 tons) is in the 
northern and eastern United States, California ore has little market- 
ing advantage over foreign ores. 

Selected REFiatENCES 

Anonymous, 196-5, The changing pace and pattern in the business of mining: 
New York:, Eng. and Mining Jour., v. 166, no. 2, p. 138-139. 

Chesterman, C. W., 1957, Bismuth, in Mineral commodities of California : Cali- 
fornia Div. Mines Bull. 176, p. 79-81. 

Cooper, J. R.. 1982, Bismuth in the United States: U.S. Geol. Survey Mineral 
Inv. Resources Map MR-22. 

Logan, C. A., Braun, L. T., and Vernon, J. W., 1951, Mines and mineral resources 
of Fresno Countyi California : California Jour. Mines and Geology, v. 47, 
no. 3, p. 485-522. 

Moulds, D. B., 1964, Bismuth, in U.S. Bur. Mines 1963 Minerals Yearbook: 
U.S. Bur. Mines, v. 1, p. 311-315. 

Prout, J. W., Jr., 1940, Geology of the Big Blue group of mines, Kernville, Cali- 
fornia : California Jour. Mines and Geology, v. 36, no. 4, p. 413. 

Tucker, W. B., and Sampson, R. J., 1929, Riverside County : California Div. 
Mines, Mining in California, 25th Rept. State Mineralogist, v. 25, no. 4, p. 483. 

U.S. Bur. of Mines, 1965. Bismuth, in Mineral facts and problems : preprint, 
U.S. Bur. Mines Bull. 630, 8 p. 


(By W. C. Smith, U.S. Geological Survey, Menlo Park, Calif.) 

About 100 years ago California became the first domestic producer 
of borax, and about 40 years ago it became the largest supplier of boron 
raw materials to the world market (Ver Planck, 1956 and 1957; W. C. 
Smith, 1960 and 1962). California's share of world production has 
been 90 i^ercent in many years, and probably will be nearly as large in 
the future, although Turkey has been increasing its production and 
Argentina and Chile have large deposits that are potentially more 
productive than they have been in the past. California's leadership 
of the world's borax industry has been based upon large-scale, eco- 
iiomical operations at two major boron deposits, Searles Lake and 
Kramer, each established in the late 1920's and repeatedly expanded 
as consumption required. The known reserves in these two major 
deposits and in potentially workable colemanite deposits are estimated 
to be large enough to sustain California's production at recent rates 
for the next hundred years. 

In the following description of use, production, and geologic occur- 
rence of borax and other boron compounds, it will be convenient to refer 
by name to the principal compounds and boron minerals of California, 
so tliese are listed on table 9, with chemical composition and boron 
content. Borax is chemically the same, whether mineral, industrial 
compound, or tlie familiar household pharmaceutical. 


Table 9. — Principal bormi compounds and minerals of California 


Chemical composition 

Boron content (calcu- 
lated weight percent) 



Chemical compounds: 







Anhydrous borax -- - 



Boric acid . . . . 




Borax - 












Colemanite -- 



Uses of Boron Compounds 

The use of boron comix>unds has increased over the years, and this 
trend is expected to continue. Among the scores of industrial, agri- 
cultural, and consumer uses, the largest is that of borax in glass and 
glazes. About a fourth of production goes into glass, notably fiber- 
glass, heat-resistant glass, and optical glass. The many uses in the 
chemical and allied industries are summarized by Johnstone and 
Johnstone (1961), and recent research in boron compounds is reviewed 
each year in the Minerals Yearbook of the V.S. Bureau of Mines 
(Miller, 1964; Stipp and Schreck, 1963, etc.). 


Borax mining began in 1864. In the five-year period 1959 to 1963, 
inclusive, California's production of borax and other boron compounds 
was equivalent to 331,941 tons of B2O3 per year, with a value near 
$49,000,000 per year (Miller, 1964). Boron "is exceeded in value of 
products only by oil, gas, and construction materials. Figures for 
production combine all products and are in terms of equivalent tons of 
B0O3. Most of the raw material is processed in elaborate plants at the 
deposits, and the principal bulk commodities shipped are refined borax, 
anhydrous borax, and boric acid. The California producers ship only 
minor tonnages of crushed or otherwise partly treated borate minerals. 
A trend toward higher values per ton should be recognized; among the 
reasons for it are the increase in shipments of anliydrous forms (to 
save on freight costs) and the increase in numl>er of refined boron com- 
pounds prepared at the primary plants. 

California supplies essentially all the boron products consumed in 
the United States, although small quantities of special boron-bearing 
materials are imported. About half the production is exported. Dis- 
tribution abroad is mainly to the highly developed industrial areas 
of the free world. For other regions, accurate statistics are not avail- 
able, but we believe that only the U.S.S.R. and China are producing 
and that their output is less than that of the free world (Sokoloff, 

Geologic Occurrence 

In California, the principal boron deposits are in the Mojave Desert 
and adjacent parts of the Great Basin in the eastern and southeastern 

671-164 O — 6&— pt. I 8 



O O 


Br ine 

2. Owens Lake 

3 . Sear les Lake 

Coleman i te 
Ca I ico 

Four Corners 
Frazier Mtn. 
Furnace Creek group 

8. Lang 

9. Shoshone-Gerst ley 


Minor deposits 

10. Amargosa 

1 1 . Borax Lake 

12. Eagle 

13- Harmony 

14- Koehn Lake 
J5. Sa line Va I lev 

Figure 12. Boron in California. 

pai-ts of the State (fig. 12) . Boron is not known to occur in nature as 
the element. And here, as elsewhere, the boron is in solution in water 
or combined witli other elements in hydrated sodium and calcium 
borate minerals, among- which the best known is borax (see table 9). 
All the deposits in California are geologically young (Cenozoic) and 
of continental origin. They are classed as evaporites, with the de- 
posits of common salt, sodium carbonate, and sodium sulfate that orig- 
inate as saline residues where surface water dries up in arid inland 
basins. Evaporation is almost the whole story of origin for many of 
these salines, with the important qualification that during the crucial 
final stages when minerals come out of solution the dominant process — 
sometimes the only process that can be identified later from the exist- 
ing mineral assemblage — may be temperature change (for borax, cool- 
ing) , or chemical reaction as waters mix, or replacement of susceptible 
minerals. Equally important for the origin of boron deposits in arid 
basins is location within one of the world's Cenozoic volcanic-tectonic 


belts, where waters contain significantly more boron than average. 
Many California and western Nevada waters are boron-bearing, pre- 
siunably because of some fundamental relationship to the well-lmown 
belt that follows the Pacific Ocean margin. Where this volcanic- 
tectonic belt passes through areas long dominated by inland basins and 
arid climate, as in western South America between latitudes 15° and 
30° S. as well as in California, the accimiulated salines include mujor 
borate deposits. 

Searles Lake brine 

At Searles Lake borax is recovered from brine that also yields potash, 
sodium carbonate, and several minor coproducts. Two large chemical 
plants, operated by American Potash & Chemical Corp. and Stauffer 
Chemical Co., treat brines pumped from groups of shallow wells that 
penetrate saturated layers of crystalline saline minerals in a section 
of lake beds underlying the Searles Lake play a (Teeple, 1929) . Halite 
of the uppermost saline layer is exposed in the center of the playa, 
where it forms a hard salt pan 10 or 12 square miles in area. The 
layers containing the commercially valuable brines also underlie the 
mud flats that encircle the central salt, so their total extent is about 
40 square miles. In the stratigraphic section, the productive saline 
layers are in two zones, separated by a "parting mud" that is 12 or 14 
feet thick, and underlain by a "bottom mud." The upper saline zone 
generally is 70 to 80 feet thick, the lower zone 30 to 40 feet. In these 
zones, it is estimated, about 40 percent of the volume is brine. The 
subsurface layers of saline minerals are more or less coarsely crystal- 
lized and have a porous, vuggy structure, so they yield brines freely. 
The brine stands essentially at the surface of the playa, the brine level 
evidently being maintained there by subsurface flow. 

Reserves at Searles Lake have been estimated as adequate for 50 
years production (Dyer, 1950), and an estimate in these terms is more 
appropriate than separate figures for tonnage and grade of the several 
coproducts, all of which must be produced and marketed. 

As the lake beds of this saline deposit lie where they accumulated, 
evidence of their origin is obtainable not only from study of the 
stratigraphy and mineralogy of the sediments but also from study of 
the topography of the basin and the region. The slopes above the 
playa are marked with many ancient shorelines, the highest at 640 
feet above the salt flat at a position fixed by tlie altitude of an overflow 
channel leading eastward to Panamint Valley. These show that the 
basin has contained a succession of lakes. Regional surveys have 
shown that the lakes received water mostly from the west, and mainly 
from a long section of the eastern slope of the Sierra Nevada that 
drains via the Owens River into Owens Lake (Gale, 1915). In cool 
moist periods of the past, Owens Lake would overflow and the runoff 
would go through China Lake into Searles Lake and, at maximum 
flow, beyond. In the commercially drilled sediments of Searles Lake, 
then, one major climatic swing from cool-moist to warm-dry is repre- 
sented by the bottom mud and lower saline zone, another by the parting- 
mud and upper saline zone (Flint and Gale, 1958; Smith, G. I., 1962; 
Smith and Haines, 1964) . 

The quantities of chemicals concentrated in Searles Lake required 
evaporation of enormous amounts of Owens River water, which pre- 
sumably had a composition alx)ut the same in the Pleistocene as it is 
now (339 ppm total dissolved solids and 1 ppm boron; Clarke, 1924). 


Chemical analyses of Owens River water show that the principal 
source of its boron is a g-roup of thermal springs in the headwaters 
region, nearly 150 miles from Searles Lake. The Searles Lake brines 
contain about .34.5 percent total dissolved solids, including 0.35 percent, 
boron (commonly reported as l.() or 1.7 percent of NaoBiO:; see 
analyses in table 44). The "solid" minerals of the saline layers were 
also once in solution; they are halite, trona, hanksite, and several less 
abundant sodium chloride, sulfate and carbonate minerals. Addi- 
tional chemical precipitate is in tlie main mud layers and the thin mud 
layers within the saline zones; they contain much calcium carbonate 
in gaylussite, aragonite, calcite, and dolomite (Smith and Haines, 
1964). Boron is distributed through the section. In addition to the 
boron in brine, the deposit contains crystalline borax, the amount 
ranging from a few crystals in the bottom mud and at several other 
horizons to a borax lens 5 feet thick in the upper salt. 

Kramer horax deposit 

At Kramer, bedded borax interlayered witli shale and siltstone is 
mined from a large open pit and processed in an adjacent refinery by 
the U.S. Borax »)i Chemical Corp. (Barnard and Kistler, 1965). The 
lake beds that contain the borax have no known outcrops — the ore was 
found by drilling — and they lie at depths of 150 to 1,000 feet, beneath 
younger beds recently found to be middle Miocene in age (R. H. Ted- 
ford, written conmiunication, 1965). The ore contains, on average, 
nearly 25 percent BoO.f. It is as much as 200 feet thick and extends 
under about 500 acres. Reserves are estimated to be about 100 million 
tons. Even at recent high rates of extraction, this is about 100 years' 

The lithology and mineralogy of the Kramer ore body require 
classing the borax as a lake deposit, and as an evaporite only in a 
qualified sense. The associated sediments lack structural features 
attributable to desiccation, and the array of saline minerals that typi- 
cally result from extensive evaporation is absent. The shale and 
siltstone beds are thin and banded, and, like the occasional layers of 
tuffaceous sandstone, they persist laterally with uniform thickness and 
composition. Along beds, the initial borax content seems to vary 
little, but in vertical section, the ore ranges from lean to rich, some 
layers being shale containing scattered borax crystals and others 
nearly solid borax enclosing scattered lumps of shale, with gradations 
between. Apparently the 200-foot section of borax and accompany- 
ing sediments accumulated in a quiet, continuous lake in which condi- 
tions varied from time to time, but only in a narrow range. That the 
precipitation of borax probably was caused by cooling seems likely, 
and overflow to carrv awav other saline components seems required 
(Gale, 1946; Bowser, 1964). 

Among other borate minerals at Kramer, colemanite and kernite 
occur in quantity. Colemanite was the first borate found in the 
district (1913) and, with associated ulexite, was the first borate mined 
(1924 to 1927). Colemanite occurs in a thin zone which is above the 
borax ore body, and which also underlies a much larger area, about a 
mile by 4 miles in extent (Gale, 1946). Kernite, which was mined 
for several years after 1927 but is not processed in the present opera- 
tions, extensively replaces borax in the deeper parts of the ore body 
(Christ and Garrels, 1959: Schaller, 1929). 


(Jolemanite deposit h 

Colemanite and ulexite are produced in the Death Valley region, 
where the U.S. Borax & Chemical Corp. oj^erates one mine near 
Shoshone and one in Corkscrew Canyon, and the Keni Comity Land 
Co. operates one mine in Furnace Creek wash. A few hmidred tons 
l^er year of the calcium-bearing borates are shipped as crushed mineral 
for special uses. Other colemanite deposits, now idle but mined be- 
tween 1900 and 1927, are near Death Valley, m the Calico Mountains 
of the Mojave Desert, and at Lang in Los Angeles County, and Frazier 
Mountain in the northwest corner of Ventura County (Noble, 1916; 
Foshag, 1921 ; Grale 1914b) . One major deposit, discovered by drilling 
done for the Geological Survey duruig 1957 but not opened for min- 
ing, lies subsurface about 8 miles east of Kramer (Benda, Erd, and 
Smith, 1960). This deposit, estimated to contain between 15 and 
40 million tons, averages about 14 percent B2O3 (Griswold, 1959). 
Borate-bearing horizons in the Death Valley area, if drilled, probably 
would be found to contain a comparable tonnage and grade (California 
Div. Mines and Geology, 1963). The colemanite deposits offer a 
substantial resource for the future. 

The colemanite deix)sits are in lake beds of Tertiaiy age. The de- 
posits along Furnace Creek, studied by McAllister (1964), are typical. 
The largest deposits are in the lower part of the (Pliocene) Furnace 
Creek Formation, and are lenses or groups of lenses enclosed in cal- 
careous mudstone, sandstone, conglomerate and calcareous chipstone. 
The section also contains gj'psiferous beds, some limestone, and in- 
trusive basalt in sheets and fragmental masses. Calling the ore "cole- 
manite," as customaiy, is misleading, because ulexite and probertite 
are major constituents, each occurring as minable masses of one mineral 
and also intimately mixed with other borates. Colemanite, in many 
places if not everywhere in these deposits, is a replacement mineral. 
Most conspicuously, it replaces ulexite, but it also replaces limestone, 
forming cross-cutting masses and veins. The ulexite is a dense, mas- 
sive variety, unlike the "cottonball" ulexite of recent playa deposits, 
and apparently recrystallized. Probertite may also be a replacement 
of ulexite ; it is of lower water content. Mining has exposed a zonal 
structure in some of the ore, in which colemanite is nearest the sur- 
face or envelops ulexite, and probertite is deepest, within ulexite. 
The lenticular form of the deposits and their spread along the outcrop 
of the lower part of the Furnace Creek Formation suggests accumula- 
tion from place to place in an extensive lake, or in a group of shallow 
intermittent lakes in an extensive basin. The evidence that the lake 
waters were persistently^ calcareous suggests that water containing 
sodimn borate entered locally, and that ulexite was precipitated where 
waters mixed. 

Mhwr deposits 

California has several minor deposits which contain no reserves 
of significance but do present features of historic and scientific in- 
terest. The first borax mined in the United States (1864-1868) was 
dug from the bottom mud of Borax Lake, Lake County ( Vonsen and 
Hanna, 1936) . Tlie occurrence of coarse borax crystals grown in bot- 
tom mud suggests some similarity to the Kramer deposit; also, the 


precipitation of trona, halite, northupite, and gaylussite in a year 
when tlie hike desiccated (1934) suggests simihirity to Searles Lake. 
The hike has a small drainage basin, within which there are springs 
that presumably supplied borax-bearing water like that of much- 
studied springs at Sulphur Bank, 9 miles to the west, which contain 
720 ppm of boron ( White, 1957) . 

From 1874 to 1907 borax was produced from "marsh" deposits in 
Death Valley, Saline Valley (Gale, 1914a), Koehn Lake, and at the 
margin of Searles Lake. Such deposits are salt crusts, or efflorescences, 
accumulated on top of the muddy surfaces of wet playas. Both borax 
and ulexite occur in this environment, accompanied by sodium car- 
bonate, sulfate, and chloride saline minerals. The Death Valley floor 
obviously receives boron weathered from outcrops of the colemanite 
deposits in the adjacent hills. This relationship points to the conclu- 
sion that similar solution, transport, and redeposition has been occur- 
ring in southeastern California at least since the middle Miocene, with 
changes in the pattern of basins and ranges causing boron to move 
from one sedimentary section to a new one. 

Summary of Boron Resources 

Searles Lake and Kramer, the major sources, have reserves large 
enough to sustain production at recent rates for 50 to 100 years. 
Colemanite deposits, noAv little worked, contain additional large re- 
sources potentially workable under favorable economic conditions. 
Geologic studies indicate that the borate deposits of California occur 
in sections of arid-basin sediments that range in age from Miocene to 
Recent. Past drilling lias demonstrated that the major borate de- 
posits lie concealed beneath alluvial deposits that cover extensive areas 
in the southeastern part of the State, and it is probable that future 
drilling will discover additional deposits. 

Selected References 

Barnard. R. M., and Kistler, R. B., 1965, Stratigraphic and structural evolution 

of the Kramer sodium borate ore body, Boron, California [abs.] : Northern 

Ohio Geol. Soc, Symposium on Salt, 2d, Cleveland. 
Benda, W. K., Erd, R. C, and Smith, W. C, 1960, Core logs from five test holes 

near Kramer, California : U.S. Geol. Survey Bull. 1(>45-F, p. 319-393. 
Bowser, C. J., 1965, Geochemistry and petrology of the sodium borates in the 

nonmarine evaporite environment [abs.] : Dissert. Abs., v. 25, no. 12, pt. 1, 

p. 7199. 
California Division of Mines and Geology, 1963, California mineral production, 

1962 : California Div. Mines and Geology, INIineral Inf. Serv., v. 16, no. 1, p. 8-9. 
Christ, C. L., and Garrels. R. M.. 1959, Relations among sodium borate hydrates 

at the Kramer deposit. Boron, California : Am. .Tour. Sci., v. 257, no. 7, p. 516- 

Clarke, F. W., 1924, The data of geochemistry, 5th ed. : U.S. Geol. Survey Bull. 

770, 841 p. 
Dub, G. D., 1947. Owens Lake — source of sodium minerals: Am. Inst. Mining 

Metall. Eng. Tech. Pub. No. 2235. Mining Technology, v. 11. no. 5, 13 p. 
Dyer, B. W.. 1950. Searles Lake development: Colorado School Mines Quart., 

V. 45, no. 4B, p. 39-44. 
Flint. R. F., and Gale. W. A., 19.58. Stratigraphy and radiocarbon dates at Searles 

Lake, California : Am. .Jour. Sci., v. 256, no. 10. p. 089-714. 
Foshag, W. F.. 1921, The origin of the colemanite deposits of California : Econ. 

Geology, v. 16, no. 3, p. 199-214. 
Gale. H. S., 1914a, Salt, borax and potash in Saline Valley, Inyo County, Cali- 
fornia : U.S. Geol. Survey Bull. 540-N, p. 416-421. 


— — , 1914b, Borate deix)sits in Ventura County California : U.S. Geol. Survey 
Bull. 540-0, p. 434-456. 

-, 1915. Salines in the Owens, Searles, and Panamint basins, southeastern 

California : U.S. Geol. Survey Bull. 580, p. 251-323. 

-, 1946, Geology of the Kramer borate district, Kern County, California : 

California Jour. Mines and Geology, v. 42, no. 4, p. 325-378. 
Griswold, W. T., 1959, Colemanite as an important source of borates : Am. Inst. 

Mining Metall. Engineers Preprint No. 59H20. 
Johnstone, S. J., and Johnstone, M. G.. 1961, Minerals for the chemical and 

allied industries, 2d ed. : New York, John Wiley & Sons, Inc., 788 p. 
McAllister, J. F., 1964, Preliminary geologic map of the Furnace Creek borate 

area. Death Valley, California : U.S. Geol. Survey open-file map, April 3, 1964, 

scale 1 : 24,000. 
Miller, W. C, 1964, Boron in Metals and Minerals (except fuels) : U.S. Bur. Mines 

Mineral Yearbook 1963, v. 1, p. 317-325. 
Noble, L. F., 1926, Note on a colemanite deposit near Shoshone, California, with 

a sketch of the geology of a part of Amargosa Valley : U.S. Geol. Survey Bull. 

785, p. 63-75. 
Schaller, W. T., 1929, Borate minerals from the Kramer district, Mojave Desert, 

California : U.S. Geol. Survey Prof. Paper 158-1, 173 p. 
Smith, G. I., 1962, Subsurface stratigraphy of late Quaternary deposits, Searles 

Lake, California : a summary : U.S. Geol. Survey Prof. Paper 450-C, art. 82, 

p. C65-C69. 
Smith, G. I., and Haines, D. V., 1964, Character and distribution of nonclastic 

minerals in the Searles Lake evaporite deposit, California : U.S. Geol. Survey 

Bull. 1181-P. p. P1-P58. 
Smith, W. C, 1960, Borax and borates, in Industrial Minerals and Rocks : New 

York, Am. Inst. Mining Metall., and Petroleum Engineers, 3d ed., p. 103-118. 
, 1962, Borates in the United States, exclusive of Ala.ska and Hawaii : U.S. 

Geol. Survey Mineral Inv. Resource Map MR-14. 
Sokoloff, V. P., 1964, The mineral industry of the U.S.S.R. : U.S. Bur. Mines. 

Minerals Yearbook 1963, v. 4, p. 749-778. 
Stipp, H. E., and Schreck, V. R., 1963, Boron in Metals and Minerals (except 

fuels) : U.S. Bur. Mines Minerals Yearbook 1962, v. 1, p. 327-343. 
Teeple, J. E., 1929, The industrial development of Searles Lake brine : New York, 

Chemical Catalog Co. 
Ver Planck, AV. E., 1956, History of borax production in the United States : 

California Jour. Mines and Geology, v. 52, p. 273-291. 
, 1957, Boron to Mineral commodities of California : California Div. Mines 

Bull. 176, p. 87-94. 
Vonsen, Magnus, and Hanna, G. D., 1936, Borax Lake, California : California 

Jour. Mines and Geology, v. 32, p. 99-108. 
White, D. E.. 1957. Magmatic. connate, and metamorphic waters : Geol. Soc. 

America Bull., v. 68, no. 12, pt. 1. p. 1659-1682. 


(By G. I. Smith, U.S. Geological Survey, Menlo Park, Calif.) 

Most of the bromine produced in the United States comes from 
plants in Texas and Micliigan whicli extract it from sea water and 
well brines. Production also comes from oil-well brines in Arkansas, 
and from two plants in California. One of these California plants 
utilizes sea-water bitterns left over from the solar evaporation of 
salt, and the other uses saline brines pumped from Searles Lake. 

Bromine is used most extensively m additive compounds for gas- 
oline. Smaller quantities are used in the manufacture of fireretarding 
and fireproofing materials, fire extinguishers, fumigating mixtures, 
sanitizing additi^^es for swimming-pool water, bleaches, photographic 
emulsions, laboratory reagents, and medicinal and pharmaceutical 
preparations (Miller, 1964). 


Production of bromine in the United States began in the mid-1800's. 
Output was somewhat limited because of competition with the Stass- 
furt deposits in Germany, but at the time of World War I, domestic 
production rose to 1.7 million pounds per year. By 1929, the wide- 
spread use of bromine in gasoline antiknock compounds resulted in 
an increase of domestic production to about 6.5 million pounds per 
year, and by 1939, production had risen to 37.9 million pounds. Dur- 
ing World War II, national production rose to 102.1 million pounds. 
By 1963, domestic annual output had reached 203.3 million pounds, 
and was valued at $48.5 million (Keiser, 1960) . 

Production of bromine in California began in 1926 when plants were 
built at Chula Vista and San Mateo to extract bromine from the bit- 
terns produced during solar salt evaporation along the edges of San 
Diego and San Francisco Bays. The San Mateo plant closed about 
1930, and the Chula Vista plant closed in 1945. In 1931, a new plant 
was constructed at Newark, on the southeast shore of San Francisco 
Bay, by the California Chemical Corp. ; it is now operated by the In- 
organic Chemical Division of the FMC Corp. and uses bittern pro- 
duced by the Leslie Salt Co. The bittern contains 0.175 percent bro- 
mine, and the bromine is recovered during the first step of a process 
that also produces magnesia. Since 1940, bromine has also been ex- 
tracted from Searles Lake by the American Potash & Chemical Corp. 
In that operation, bromine, along with several other products, is ex- 
tracted from a complex brine that contains about 0.085 percent bro- 
mine. Current production data from these California plants are not 
published, but in 1957, their combined output was estimated to be about 
2 million pounds of bromine and bromine compounds a year, which 
would have been a little over 1 percent of the Nation's total (Ver 
Planck, 1957). 

In May 1965, bromine was selling for 221^ cents per pound in tank- 
car lots; other bromine-bearing chemicals were higher priced (quoted 
by the Oil, Paint, and Drug Reporter, May 31, 1965). With prices 
in this range, transportation costs are not a large part of the total 
price, and producers in most parts of the country and world are able 
to compete for available markets. 

Future resources of bromine are essentially unlimited because of 
the use of sea water as one of the raw materials. California's pro- 
duction, however, comes from plants that extract bromine from brines 
that may someday become unavailable. The resources in Searles Lake 
are presumably large, but bromine production will cease if extraction 
of the several other components becomes unprofitable. The plant 
using bitterns at Newark is de))endent upon the continued production 
of salt, and, as noted in the chapter on Salt, that industry is jeopar- 
dized by the population expansion which tends to encourage the con- 
version of evaporating pond areas into real estate or other types of 


Selected References 

Keiser, H. D., 1960, Minor industrial minerals, in Industrial minerals and rocks : 
Am. Inst. Mining Metall. Petroleum Engineers, p. 605-621. 

Miller, W. C, 1964, Bromine : U.S. Bur. Mines, Minerals Yearbook, 1963, v. 1, p. 

Stipp, H. E., 1960, Bromine, m Mineral facts and problems, 1960: U.S. Bur. 
Mines Bull. 585, p. 149-154. 

Ver Planck, AY. E., 1957, Bromine in Mineral Commodities of California : Cali- 
fornia Div. Mines Bull. 176, p. 95. 



(By P. K. Morton, California Division of Mines and Geology, Los Angeles, Calif.) 

Only in comparatively recent years has cadmimn been recognized 
as an important metal to man. During the first 60 years after its 
discovei-y in 1817 by F. Strohmeyer, little use was found for the 
metal. Most of the important use-development of the metal came 
after 1919 with the advent of an electroplating process developed by 
M. J. Udy. 

The primary uses of cadmium are listed below in the approximate 
order of consumption : 

1. Plating — 55 to 60 percent. Cadmium is used as a corrosion- 
resistant coating on a wide variety of iron and steel products by 
electroplating, hot dip, spray, or vacumn plating methods. 

2. Cadmium sulfide, sulfoselenide, and lithopone — 15 percent. 
Utilized as yellow, orange, and red pigments. 

3. Other cadmium compounds — 15 to 20 percent. This cate- 
gory includes stearate for vinyl plastics, phosphors for television 
tubes, and nitrate for nickel-cadmium batteries. 

4. Low melting point fusible alloys such as solders, automatic 
fire-sprinkler systems, etc. 

A small but important use of cadmium is in cadmium sulfide crystals 
which are used in the aerospace industry for solar energy conversion, 
in radiation detection devices, and photosensitive elements. 

The only known primary sources of cadmiimi are zinc ores, and zinc- 
bearing lead and copper ores. Greenockite (cadmium sulfide) is the 
principal ore mineral of cadmium, but it rarely occurs except in close 
association with sphalerite, a zinc sulfide. Most of the cadmium re- 
covered, however, does not occur as greenockite but as a constituent 
of zinc minerals — principally sphalerite. Sphalerite has been shown 
to contain as much as 4.5 percent cadmium (Rankama and Sahama, 
1950, p. 708). Zinc concentrates processed in the United States con- 
tain an average of from 0.1 to 1.4 percent cadmium (Schroeder, 1965, 
p. 4). California zinc concentrates have yielded an average of 0.22 
to 0.28 percent cadmium (Goodwin, 1964, p. 97) . 

World production in 1919 was about 200,000 pounds; in 1963 it was 
26,300,000 pounds. United States production rose from 131,000 
pounds in 1919 to 503,000 pounds in 1925, and increased rapidly to an 
average annual production of about 10 million pounds for the five- 
year period from 1959 through 1963. Shipments by United States 
producers in 1963 totaled 10,124,000 pounds valued at $21,880,000. 

Total California production figures are not available, but during 
the five-year period ending in 1963 the estimated California cadmium 
production was about 5,600 pounds. In terms of the United States 
production during the same period this amounts to about 0.01 percent. 

The close association of cadmium to zinc results in the unfortunate 
circumstance wherein cadmium reserves and production are a function 
of zinc reserves and production. In California, cadmium is found in 
the lead-zinc ores of the Great Basin province in Inyo and San Ber- 
nardino Counties; the copper-zinc ores of the foothill belt in the west- 
ern Sierra foothills; and tlie Shasta County copper-zinc district. 

(The reader is referred to the zinc section of this volume for further 
discussion of these areas.) 


Selected References 

Goodwill, J. G.. 1957. Cadmium, in Mineral commodities of California : Califor- 
nia Div. Mines and Geology Bull. 176, p. 97-98. 
Hanipel, C. A. 1954, Rare metals handbook : New York, Reinhold Pub. Co., p. 

Johnstone, S. J., and Johnstone, M. G.. 19G1, Minerals for the chemical and 

allied industries : New York, John Wiley and Sons., Inc., p. 103-110. 
Mentch, R. L., and Lansche, A. M., 195S, Cadmium, a materials survey: U.S. 

Bur. Mines Inf. Circ. 7881. 43 p. 
Pendergast, R. A., 1965, Cadmium, market guide, in Eng. and Mining Jour. 

Metal and Mineral Markets, May 31, 1965 : New York, McGraw-Hill Pub. Co., 

p. 5-19. 
Rankama, Kalervo, and Sahama, Th. G., 1960, Geochemistry : Univ. Chicago 

Press, p. 708-714. 
Schroeder, H. J., 1964, Cadmium, in Minerals Yearbook, 1963: U.S. Bur. Mines, 

p. 333-a40. 
, 1965, Cadmium. /» Mineral facts and problems: U.S. Bur. Mines Bull. 

630, 9 p. 
U.S. Bur. Mines, 1965, Cadmium, /;(■ Commodity data summaries, p. 22-23. 


(By S. J. Rice, California Division of Mines and Geology, San Francisco, Calif.) 
Use and Economic Importance 

Transparent and nnflawed calcite (Iceland spar) is made into polar- 
izing prisms for use in several types of optical instruments. These 
prisms yield very high quality polarized light for such instruments 
as polarizing microscopes, metalographs, saccharimeters, dichroscopes, 
photometers, colorimeters, and polariscopes. Although the unit price 
is high, calcite suitable for these purposes is rare, and only a few hun- 
dred pounds at most are used annually. Artificial materials such as 
polaroid have been used increasingly as a substitute for calcite polariz- 
ing prisms since World War II, but expanding demand for research- 
quality instruments should guarantee a ready market for optical-grade 
calcite, which is superior to known substitutes for some uses. 

Calcite suitable for optical purposes must be transparent, water- 
clear, and free from microscopic inclusions, cleavage cracks, or twin- 
ning. It must also occur in masses large enough to yield crystals or 
cleavage rhombohedra at least about one cubic inch in volume. In 
any deposit, the percentage of optical-grade material recoverable is 
very low compared to the amount of clear calcite present. 

Mineralogy and Geological Occurrence 

Calcite (CaCOs) is one of the most common minerals, but only 
rarely does it occur in the form of the large transparent crystals called 
Iceland spar. It is characterized by highly perfect rhombohedral 
cleavage and a hardness of 3, and it effervesces vigorously in dilute 
hydrochloric acid. Its value as an optical material is based on its 
strong double refraction. This is a property whereby light passing 
through a cleavage rhomb is resolved into two separate rays that are 
polarized at right angles to each other, and which are refracted at 
different angles. The latter phenomenon can be demonstrated by 
placing a cleavage fragment of clear calcite over a dot on a piece of 
paper and observing that two dots appear. 



Iceland spar is found lining cavities within discontinuous calcite 
veins and pockets that rarely can be traced laterally or downward for 
more than a few tens of feet. Although calcite veins occur in many 
kinds of rocks, most of the productive deposits in the world are en- 
closed in volcanic locks, and appear to have formed during the last 
stages of volcanism. Since the late 1930's most of the domestic re- 
quirements for Iceland spar have been supplied from such deposits in 
the states of Sonora and Chihuahua, Mexico (King, 1946 and 1947; 
Fries, 1948). Domestic production has been largely from California, 
Montana, and New Mexico. 

Occurrences in California 

Iceland spar has been mined at three localities in California (see fig. 
13). The only one being worked in 1965 is on the western side of 
Momit Baldwin, near the head of Convict Creek in Mono Coimty. The 


Figure 13. Oalcite (optical grade) in California. 


deposits here occur as numerous lenses or huge druses in marble (Mayo, 
1934) . The druses are ellipsoidal to irregular in shape, up to about 
40 feet in length, and bordered by very coarsely crystalline white cal- 
cite. They are lined with large crystals, some up to several cubic feet 
in volume, of clear calcite from wiiich the optical -grade material is ob- 
tained. Sand and clay fills most of the cavities found, and large crys- 
tals that have fallen from the roofs of the cavities are found embedded 
in this fill. Optical-grade calcite was discovered in this area prior to 
1934, but systematic exploitation was first undertaken bv the U.S. 
Calcite Co. in 1963. 

An Iceland spar deposit in Modoc County, about 10 miles south of 
Cedarville, was mined intermittently in the period 1920-1925 (Hughes, 
1931), but has since been idle. The calcite occurs in veins as much as 
three feet thick that are in andesite. Individual crystals recovered 
from this deposit were relatively small, up to about 12 ounces. About 
1,000 ounces of Iceland spar were sold from this deposit in 1920-1921, 
probably the mine's most active period. 

During World War II, Iceland spar was produced from deposits 
on the east side of the Santa Rosa Mountains in San Diego County 
and used to manufacture optical ring gunsights (Weber, 1963). Here 
the crystals occur with common calcite and gypsum as veins which 
filled joints in conglomerate, the largest deposits being at the intersec- 
tions of joints. The calcite crystals are unusual in that they are thin 
and tabular, being flattened perpendicular to the c axis. Those mined 
were as much as 18 inches in diameter and 3 inches thick, but as 
trimmed to useable plates they averaged between 2 and 3 inches in 
diameter and 14 fo % inches thick. Some 6,000 pounds of Iceland 
spar were shipped from this deposit from late 1942 to early 1944, but 
not all of it was useable (Wright, 1957) . 

The wide geographic distribution of known deposits in California, 
as well as the diversity of geological environments in which they are 
found, suggest that possibilities are good for finding additional de- 
posits in the State. Present marketing conditions, and those of the 
foreseeable future, appear to be good for this commodity. 

Selected References 

Fries, Carl. .Jr.. 1948, Optical calcite deposits of the Republic of Mexico: U.S. 

Geol. Siin-ey Bull. 954-D, 179 p. 
Gwinn, G. R.. 1945. Mining optical calcite : Min. Cong. Jour., v. 31. no. 5, p. 67-72. 
Hughes, H. H., 1941, Iceland spar and optical fluorite: U.S. Bur. Mines Inf. Circ. 

6468R, 19 p. 
King, C. R., 1946, How a sudden demand for optical calcite was met : Eng. Mining 

.Jour., V. 147, no. 5, p. 80-81. 
, 1947, Finding and mining optical calcite crystals : Eng. Mining Jour., v. 

148, no. 6, p. 94-96. 
Mayo, E. B., 1934, Geology and mineral deposits of Laurel and Convict Basins, 

southwestern Mono Countv. California : California Jour. Mines and Geology, 

V. 30, no. 1, p. 84-85. 
Newman, E. W.. 1945. Methods of prospecting and mining optical calcite in 

Montana : Am. Inst. Mining Metall. Engineers, Mining Technol., v. 9, no. 6, 

10 p. 
Weber, F. H., Jr.. 1963. Mines and mineral resources of San Diego County, 

California : California Div. Mines and Geology, County Rept. 3, p. .52-.54. 
Wright, L. A., 1957, Calcite. optical grade, in Mineral commodities of California : 

California Div. Mines Bull. 176, p. 99-100. 




(By G. I. Smith, U.S. Geological Survey, Menlo Park, Calif.) 

About a third of the calcium chloride used in the United States is a 
by-product of the Solvay sodium carbonate process. The other two- 
thirds comes from natural brines. Of this, Michigan produces 95 
percent; California, 4 percent; and West Virginia, 1 percent (Babcock, 

The natural brines from which calcium chloride is produced are 
generally neutral to slightly acid, and are high in calcium, sodium, 
and chloride, but low in carbonate and sulfate as shown in table 10. 
The brines used for calcium chloride production in Michigan (table 
10, analysis 8) and West Virginia come from wells sunk into Paleozoic 
formations. California production comes entirely from late Qua- 
ternary deposits in Bristol Lake. 

Table 10. — Analysis of waters containing high concentrations of calcium chloride 

[Analyses in parts per million; n.d., not determined or not reported] 













Total dissolved sol 
ids (percent) 



43, 000 


57, 370 


172, 900 










17, 190 


46, 070 


104, 600 












22, 600 


44, 760 







Sea area 


14, 400 

18, 400 

61, 200 






Sea geo- 


40, 000 











ca. 5-6 



Oil field 

















Oil field 















source of 














1. Durrell, 1953, p. 13, analysis II; brine from drainage canal in salt body. Analysis by W. W. Brannock. 

2. Durrell, 1953, p. 13; analysis I; brine from shallow well. Analysis by W. W. Brannock. 

3. Gale, H. S., and Hicks, W. B., 1920. Brine from depth of 36 feet. Analysis by Smith, Emery & Co. 

4. Recalculated to actual concentrations from data of Coleman, 1929, quoted by Ver Planck, 1957. Well 
on Mullet Island. 

5. White, D. E. (1965). Analysis by J. D. Hem and others. 

6. White, Hem, and Waring, 1963, table 13, analysis 1. Analysis by D. O. Watson. 

7. White, Hem, and Waring, 1963, table 13, analysis 2. 

8. White, Hem, and Waring, 1963, table 13, analysis 8. 

Bristol Lake lies in the east-central part of the Mojave Desert 
province (see fig. 67, chapter on Salt). The fill beneath the floor of 
this closed depression consists of more than a thousand feet of salt 
and clay (Bassett and others, 1959), but the brines abnormally rich 
in calcium chloride (table 10, analysis 2) are restricted to the top 32 
feet (Gale, 1951, p. 10). Cadiz Lake, in an adjacent basin, contains 
a similar but less rich calcium chloride brine (table 10, analysis 3). 
Similar brines have also been found in springs and in a geothermal 
well in the Imperial Valley of California (table 10, analyses 4 
and 5). 


Geologic explanations for the origin of Bristol Lake brine are not 
satisfactory. The brine's characteristics are quite different from those 
in most dry lakes, though somewhat similar to those obtained from 
some oil fields. Examples of such brines are found in a few Cali- 
fornia fields (table 10, analyses 6 and 7) , but better and more common 
examples are found in oil field brines of other states that come from 
older rocks. 

Consumers of calcium chloride in the United States mostly utilize 
the tendencies of its solid form to absorb water .and its solutions to 
freeze at low temperatures. About 30 percent of the solid calcium 
chloride produced is used for deicing road surfaces, 25 percent is for 
dust control, 13 percent is for inhibiting the loss of moisture in con- 
crete during setting and curing, and 5 percent is for refrigeration. 
The rest is used chiefly for freezeproofing bulk shipments of frag- 
mental materials, for dustproofing mines and roads, and for dehumidi- 
fying. Because of the high density of calcium chloride solutions, it 
is .also used in oil-well drilling and as a ballast for tractor tires ( Ver 
Planck, 1957 ; Reiser, 1960 ; Babcock, 1964) . 

The properties of calcium chloride are uncommon, and for many 
years the material was regarded as nearly worthless. Over the last 
20 years or so, however, consumers have discovered many new uses, 
and established uses have become widespread. For example, in 1962, 
production of natural and synthetic calcium chloride in the United 
States was 672,000 tons, double the amount produced 10 years earlier 
(Reiser, 1960 ; Babcock, 1964) . 

In the period 1959-1963, annual production of 75-percent-equivalent 
calcium chloride from natural sources averaged about 437,000 tons; 
this was valued at $8.32 million, or about $19 per ton. California 
production in 1953 was about 16,000 tons (Ver Planck, 1957), and the 
State's 1963 share in national production from natural sources shows 
that this tonnage has remained about the same. 

Most of the product marketed in California is used for the treatment 
of ore and seaweed and by the concrete industry, but smaller quan- 
tities .are used for dust control, refrigeration, drying operations, and 
oil-well drilling (Ver Planck, 1957). California markets have not 
grown as fast as those in the rest of the country because they do not 
include populous areas affected by winter driving problems. 

Producers of calcium chloride from the brines of Bristol Lake are 
the National Chloride Co. of America and the Leslie Salt Co. (for- 
merly the California Salt Co.). Both companies concentrate the 
natural brines (table 10, analysis 2) by solar evaporation until most of 
the salt is precipitated and the more soluble calcium chloride is con- 
centrated in the solution. Mucli of the brine is sold in that form ; the 
rest is sold to the Hill Bros. Chemical Co., located nearby, where it is 
converted to solid flake form (Ver Planck, 1957) . 

Future production and consumption of calcium chloride are likely 
to increase rapidly because ucav uses are being consistently developed. 
Natural resources are large. Although not all of it could be recovered 
economically, the total amount of calcium chloride in Bristol Lake is 
estimated to be enough to last hundreds of years at present production 
rates. Additional sources of calcium chloride in California might lie 
in Cadiz Lake, in the geothermal brines of the Salton Sea area, and in 
oil field brines. 


Selected References 

Babcock, CO., 1964, Calcium and calcium compounds : U.S. Bur. Mines Minerals 

Yearbook, 1963, v. 1, p. 311-346. 
Bassett, A. M., Kupfer, D. H., and Barstow, F. C. 1959, Core logs from Bristol, 

Cadiz, and Danby Drv Lakes, San Bernardino County. California : U.S. Geol. 

Survey Bull. 1(>45-D, p. 97-138. 
Durrell, Cordell, 1953, Geological investigations of strontium deposits in southern 

California : California Div. Mines Spec. Kept. 32, 48 p. 
Gale, H. S., 1951, Geology of the saline deposits, Bristol Dry Lake, San Bernardino 

Countv, California : California Div. Mines Si)ec. Kept. 13, 21 p. 
Gale, H.' S., and Hicks, W. B.. 1920, Potash in 1917: U.S. Geol. Survey Mineral 

Resources, 1917, pt. 2, p. 397-481. 
Reiser, H. D.. 1960. Minor industrial minerals, in Industrial minerals and rocks: 

New York, Am. Mining Metall. Petroleum Engineers, p. 605-621. 
Ver Planck, W. E., 1957, Calcium chloride : California Div. Mines Bull. 176, p. 

White, D. E., 1965, Saline waters of sedimentary rocks: Am. Assoc. Petroleum 

Geologists Mem. 4. 
White, D. E., Hem, J. D., and Waring, G. A., 1963, Chemical composition of sub- 
surface waters, in Data of geochemistry : U.S. Geol. Survey Prof. Paper 440-F, 

67 p. 


(By C D. Edgerton, Jr., U.S. Bureau of Mines, Pittsburgh, Pa.) 

Carbon dioxide is a colorless, odorless, nonflammable, heavier-than- 
air gas commonly found in association with natural gas in subsurface 
reservoirs. The concentration of carbon dioxide here may range from 
a fraction of 1 percent to nearly 100 percent. It is also fomid m many 
volcanic gases, in mineral springs, and in emissions from other phe- 
nomena related to geothermal activity. Carbon dioxide occurs in the 
earth's atmosphere in concentrations of less than 1 percent. 

Carbon dioxide can be readily liquified and solidified. In the latter 
state it is known as dry ice, and is an excellent refrigerant. In the 
solid state, its temperature is minus 109° F. It passes from the solid 
to the gaseous state without going through a liquid phase. 

Industry uses carbon dioxide principally in the manufacture of 
carbonated soft beverages and as a refrigerant. It also is used in the 
preservation of food and other products that would deteriorate if 
exposed to air, in fire extinguishers, and as an explosive. 

In California, carbon dioxide formerly was produced commercially 
from three fields, one in Imperial County and two in Mendocino 
County. These fields, however, have not produced for several years. 
In 1965, the State's only production of naturally occurring carbon 
dioxide came from a plant near Taft, in Kern County, operated by 
Tidewater Oil Co. which extracted the product from natural gas 
from nearby oil fields. Tidewater sold the carbon dioxide to aircraft 
companies for use in freezing rivets, and to bottlers of carbonated 
beverages. Another plant in the same area, operated by Standard 
Oil Co. of California, extracted carbon dioxide from natural gas, 
but the product was not marketed. The latter plant was operated to 
upgrade the natural gas by removing the carbon dioxide in order 
that the natural gas would meet pipeline specifications. 

Although the State's production of naturally occurring carbon 
dioxide is, at present, limited to the above, various analyses by the 
Bureau of Mines indicate the presence of carbon dioxide in the natural 



gas from a number of the State's fields. Table II gives the percentage 
of natural gas from representative California fields. 

Table 11. — Percentage of carbon dioxide in natural gas from representative 

California fields 



of carbon 


Ten Section 

Santa Maria 




West Los Angeles 
Midway Sunset. - 


Kem River 


Santa Barbara 




Los Angeles.. - 









Only a small percentage of the carbon dioxide produced in Califor- 
nia comes from natural sources. Most of it is produced by calcining 
limestone, during the fermentation of alcohol, and as a by-product of 
other industrial processes. 

Selecsted References 

Burrell, G. A., 1911, Analyses of natural gas from the southern California oil 
fields, Chapter in Allen, I. C, and Jacobs, W. A., Physical and chemical prop- 
erties of the petroleums of the San Joaquin Valley, California : U.S. Bur. 
Mines Bull. 19, p. 47-56. 

Girdler Corporation, Gas Process Division, 1942, The effective separation of 
hydrogen sulfide and carbon dioxide from gases and liquids ; the girbotol 
process : Louisville, Ky., 40 p. 

Goldman, H. B., 1957, Carbon dioxide, in Wright, L. A., ed., Mineral commodities 
of California : California Div. Mines and Geology Bull. 176, p. 105-112. 

Gregory, L. B., and Scharmann, W. G., 1937, Carbon dioxide scrubbing by amine 
solutions : Indus, and Eng. Chemistry, v. 29, p. 514^519. 

Kidde (Walter) and Company, Inc., Aviation Division, 1941, Magic bottles; 
the story of compressed gases in aviation, 20 p. 

Mason, J. W., and Dodge, B. F., 1936, Equilibrium absorption of carbon dioxide 
by solutions of the ethanolamines : Am. Inst. Chem. Eng. Trans., v. 1, p. 27-47. 

Miller, R. D., and Norrell, G. P., 1964, Analyses of natural gases of the United 
States, 1961 : U.S. Bur. Mines Inf. Circ. 8221, 148 p. 

Quinn, E. L., and Jones, C. L., 1936, Carbon dioxide : Am. Chem. Soc. Mon. Ser. 
No. 72, 294 p. 


(By T. P. Thayer, U.S. Geological Survey, Washington, D.C.) 

Chromite, as the only economic source of chromium, is an essential 
commodity for modern industry, and over the last 10 years the United 
States has used about 1,200,000 long tons of it annually. About 60 
percent of the total is reduced to ferrochromium and used metallurgi- 
cally in steel alloys for strength and resistance to corrosion, and ap- 
proximately 28 percent is used in high-temperature furnace linings, 
especially in the steel industry. The chemical industry consumes the 
remaining 12 percent to make dichromate as a basis for dyes, tanning, 
and chromium plating. Although magnesite can be substituted for 
much of the chromite in refractories, there are no satisfactory substi- 
tutes for chromiimi in the metallurgical and chemical industries. 

The United States has depended on imported chromite since about 
1880 (see fig. 14), and even when imports were interrupted by war 



1910 1920 

1930 1940 1950 1960 

Figure 14. — Production of chromite in California since 1885 in relation to total 
United States production and consumption, world production, and domestic 
price. Note increase in proportion of concentrates in the United States as a 
whole, and decreasing peaks in California production during the last three 
war periods despite successively higher prices (most data from U.S. Bureau 
of Mines Minerals Yearbooks) . 

has been unable to obtain as much as half of its needs from domestic 
deposits. Total domestic production of 1.9 million long tons is equiv- 
alent to about 18 months consumption at recent rates, and Califor- 
nia's production of 543,000 long tons would last about 5i/^ months. 
Between about 1875 and 1940, before development of large deposits 
in Montana, California was the principal domestic source of chromite. 

67-164 o — 6&-^t. I- 


Chromium ores are mixtures of the mineral chromite with gangue 
minerals, mostly serpentine and magnetite, in various proportions. 
The chromite contains all the chromium in the ore, but in addition 
contains variable amount of iron oxide, MgO, and AI2O3 as essential 
constituents. The chromium content of an ore depends, then, on two 
factors: the ratio of chromite to gangue and the composition of the 
chromite mineral. Ores that contain too much gangue can be raised 
to usable grade by grinding the ore and separating the chromite from 
the gangue by several physical processes, but if the chromite itself 
is too low in chromium, commercial grade cannot be attained. Most 
California chromite is of the metallurgical type, for which conven- 
tional specifications require 48 percent CrsOa, a Cr :Fe ratio of 3 :1, 
and Si02 not more tlian about 5 percent; lower grade ores can be 
used metallurgically, however, with some loss in efficiency. Before 
1940, most ore mined was high enough in grade to ship as lumpy ore 
directly or after sorting by hand, but since then most mine-run ores 
have been concentrated. Although the High Plateau mine in Del 
Norte County has yielded relatively large amounts of lumpy ore 
averaging more than 48 percent CraOs with Cr :Fe ratio exceeding 3 :1, 
it is exceptional. Shipments from California between 1950 and 1958 
were mostly concentrates which averaged 43 to 44 percent CrjOs with 
Cr:Fe between 2.6:1 and 2.7:1. 

The chromite deposits in California are of two types: irregular 
lenticular to tabular bodies of the podiform type (Thayer, 1964) that 
occur only in peridotite and serpentinite, and placer or sand deposits. 
Beach sands south of Crescent City are known to contain chromite, 
but have not been fully explored; they are not believed to be large 
(Wells and others, 1946, p. 74) . 

The known podiform deposits in California range in size from a 
few pounds to about 135,000 long tons of ore, the size of the ore body 
that was mined out at the Grey Eagle mine in Glenn County. Many 
deposits are of massive ore, with sharp boundaries, but the larger ones 
are of disseminated ore and commonly grade into barren rock. The 
ore bodies occur individually or in clusters distributed more or less at 
random in the peridotite or serpentinite. Most deposits have been 
found by surface exposures or by drilling and mining in the vicinity 
of exposed ore bodies. In a few places, as in the San Luis Obispo 
district (Walker and Griggs, 1953, p. 50), ore bodies are alined along 
shear zones. Despite much research, however, no economic method 
has been devised as yet for finding the numerous chromite deposits that 
must lie just below the ground surface in many parts of the world. 

The principal chromite districts of the State (fig. 15) are in the 
Klamath Mountains, in the northern Sierra Nevada, and in the 
southern Coast Ranges. Two relatively small areas, Del Norte County 
and the San Luis Obispo district, have yielded 215,600 long tons of 
chromite, nearly 40 percent of the recorded State total, and the 13 
largest mines produced 244,700 tons, slightly more than 45 percent 
of the State total. Several hundred small mines and prospects are 
known. The random distribution of deposits is emphasized by pro- 
duction of 10 percent of the State total from two essentially isolated 
mines (see fig. 15), the Grey Eagle in Glenn County (Rynearson 
and Wells, 1944), and the Butler Estate in western Fresno County 
(Matthews, 1961). 







- I 


V \ n "Ti 

\ V:-^^rfmJ CASCADE 

■\ A :)^ 


Qi rict L Jo — - . 








Limit of chronite producing area, 
dashad nhe r a i nde finite 
• 3 

Mine or deposit whose production plus remaining 
resources is equivalent to 10,000 tons or more 
of shipping ore and concentrates 

Mine or deposit whose production plus remaining 
resources is equivalent to 2,000 to 10,000 tons 
of shipping ore and concentrates 

Key to principal nines, deposits, or 
closely grouped deposits 

1 . H igh Pla teau aina 

2 . French Hill ulna 

+ ,V. 

Seiad CreeK (Mountain View) deposit 
5 . Little Cast le Creek nine 
X 6. Noble Electric Steel group (IO deposits) 

'X 118° 



riposa/ y 

/> r s 

Bishop 'v 




Z. \ r— ' V^ V 

'-FRESNffU^ , S 

•\pENlTpiL\ -7 ^_vi.\ ^'^ 

sMONTEREY^l^rX M f TlW>*RE ^ '.I 

— 37° 

I N Y O ^ \ 

7. Grey Eagle line (^""^ 

8. Lambert aine 

9. Dobbas aina , 
10. Pillikin a in a (6 daposils) 
1 1 . But lar Estate aina 

12. Castro aina (10 deposits) 

13. Tr inidad-Morcross group 














iimferiaC~~-~v^ ! 
SALTON ) '-=,33° 

Figure 15. Chromite districts and principal deposits in California. 

The record of chromite production in California since World War 
I (fig. 14) clearly shows the impact of declining reserves and in- 
creased difficulties in mining. Although many deposits and districts 
were then relatively inaccessible, 143,700 long tons was shipped from 
the State in the 3 years 1916-1918; the peak year was 1918 when 
63,145 tons was produced. In 3 years during World War II (1942- 
1944) 124,347 tons was produced, wdth a maximum of 54,420 tons in 
1943; but during the Korean War it took 5 years (1953-1957) to 
produce 124,342 tons with 31,162 tons as the annual peak. In 1918 
the price or ore exceeded $45 for only a short time; in terms of 



1954 dollars, peak realized prices during the three periods 1916-1918, 
1942-1944, and 1953-1957 averaged $60, $65 to $75, and $80 to $90, 
respectively. During the last two periods, moreover, a market was 
assured by Government purchase programs (U.S. Commerce Dept., 
1962, p. 82) ; this was not the case during World War I. During 
World War I most of the ore was of the lumpy type desired by 
industry, and required only hand sorting. The outstanding chromite 
mine during World War II was the Grey Eagle, where the Rustless 
Mining Co. obtained 30,806 tons of concentrates averaging 46 percent 
CraOs and a Cr : Fe ratio of 2.67 : 1 from ore averaging 13 percent 
CraOg,' 33 tons of rock was mined for every ton of concentrates ob- 
tained (Dow and Thayer, 1946, p. 9). Comparisons of the sizes of 
open pits with production from San Luis Obispo district during the 
chromite purchase program of the 1950''s indicates comparable ratios 
of waste rock to concentrates. The average price of about $90 per 
long ton received for ore averaging 42 to 43 percent CrgOs and a 
Cr : Fe ratio of 2.6 to 2.7 : 1 was equivalent, quality considered, to 
twice the highest world prices in 1956 and 1957, and 3 or 4 times 
the world price in the first half of 1965. When the Government 
purchase program ended May 30, 1958, California shipments were 
at a, rate of about 35,000 tons a year. 

The chromite resources of California were estimated by the U.S. 
Geological Survey ^ as equivalent to 100,000 long tons of CrjOs in the 
ground or about 210,000 tons of standard metallurgical-grade ore, as of 
1956. No overall figures are available on ore reserves when mining 
stopped in 1958, but it is unlikely that they equalled a year of produc- 
tion. Because of the long-term uncertainty of the Government sub- 
sidy, ore was mined as fast as it was found ; future mining will, there- 
fore, depend on discoveries. The only known moderately large 
chromite deposits are in El Dorado, Siskiyou, and Tehama Counties. 
Low-grade disseminated deposits, largely in the Pillikin and Dobbas 
mines, in El Dorado County, were estimated (Cater and others, 1951, 
p. 108) to contain about 600,000 tons of rock averaging 5 percent 
CraOa; concentrates, however, average only about 43 percent CroOa 
with Cr : Fe ratio of 1.3 to 2.3 : 1 (Cater and others, 1951, p. 137) . "in 
Siskiyou County some 275,000 tons of disseminated ore is known, most 
of it in the Seiad Creek (Mountain View) deposit; although the total 
CroOs content is equivalent to nearly 40,000 tons of 48 percent concen- 
trates, milling tests have not achieved satisfactory recoveries (Engel 
and others, 1956, p. 6) . Deposits in the vicinity of North Elder Creek, 
Tehama County, were estimated in 1943 (Rynearson, 1943, p. 204) to 
contain the equivalent of 24,000 tons of standard ore, but all of Tehama 
County shipped only 3,350 tons in the period 1952-1958. 

The California potential for production of usable chromite might be 
summarized by applying a factor of 75 or 80 percent to the tonnages 
given in the following statement of the Materials Advisory Board 
( 1959, p. 44) regarding the United States : 

Although many miners may disagree, the Government purchase programs 
for chromite during World War II and from 1951-1958 give a reliable measure 

1 Estimate by T. P. Thayer, Department of the Interior Information Service, press 
release, June 5, 1957. 


of the production potential of the pod deposits. The production record of high- 
grade ores from the pod deposits may be summarized as follows : 


Base price (in 1954 

Annual production of 

ores and concentrates 

(+ 45 percent CrjOa 

in thousands of long 


1942-44 . . 


13 6-25 7 


12 8-29 

This shows that a base price 32 percent higher and major improvements in 
mining technology managed to increase production of high-grade ore by only 
10 percent. The depletion of reserves is illustrated by the San Luis Obispo 
district in California, where plans were being made late in 1957 to handle 80 
tons of rock for every ton of concentrates from an operation expected to pro- 
duce about 10,000 tons of concentrates. Although a higher base price might 
increase production of the +45 percent ores above the 20,000 tons annually for a 
very few years, progressive depletion is inevitable. Lowering specifications 
below the last purchase program cutoff (42% CraOa, Cr: Fe ratio of 2: 1) might 
double the tonnage, but with high-silica concentrates. 

In conclusion, neither the history of chromite mining nor known 
chromite reserves indicate that California could provide more than 
a small part of our national requirements for chromium. Over the 
long term the United States and the free world have little choice but 
to depend increasingly on major sources of supply in Southern Rho- 
desia, the Republic of South Africa, Turkey, and the Philippines. 
Furthermore, the outlook for developing large sources of chromite in 
the Western Hemisphere is not encouraging. 

Selected References 

California Division of Mines, 1946-1965, Geological investigations of chromite in 
California : California Div. Mines Bull. 134, published by chapters as follows : 
Part I. Klamath Mountains 

Chap. I. Del Norte County, by F. G. Wells, F. W. Cater, Jr., and G. A. 

Rynearson, 1946, p. 1-76. 
Chap. II. Siskiyou County, by F. G. Wells and F. W. Cater, Jr., 1950, 

p. 77-127. 
Chap. III. Shasta, Tehama, Trinity, and Humboldt Counties, by F. G. 
Wells and H. E. Hawkes, 1966. 
Part II. Coast Ranges 

Chap. I. Northern Coast Ranges, by D. H. Dow and T. P. Thayer, 1946, 

p. 1-38. 
Chap. II. Southern Coast Ranges, by G. W. Walker and A. B. Griggs, 
1953, p. 39-88. 
Part III. Sierra Nevada 

Chap. I. Tuolumne and Mariposa Counties, by F. W. Cater, Jr., 1948, 

p. 1-32. 
Chap. II. Calaveras and Amador Counties, by F. W. Cater, Jr., 1948, 

p. 33-60. 
Chap. III. Tulare and eastern Fresno Counties, by G. A. Rynearson, 

1948, p. 61-104. 
Chap. IV. El Dorado County, by F. W. Cater, G. A. Rynearson, and 

D. H. Dow, 1951, p. 105-167. 
Chap. V. Northern Sierra Nevada (Placer, Nevada, Sierra, Yuba, Butte, 
and Plumas Counties) by G. A. Rynearson, 1953, p. 169-323. 
Engel, A. L., Shedd, E. S., and Morrice, E., 1956, Concentration tests on California 

chromite ores : U.S. Bur. Mines Rept. Inv. 5172, 10 p. 
Jenkins, O. P., 1942, Economic mineral map of California, No. 3 — Chromite: 
California Div. Mines map vpith text. 


Materials Advisory Board, 1959, Report of the panel on chromium, in Report 

of the Committee on Refractory Metals : Natl. Acad. Sci. Natl. Research 

Council, Rept. MAB-154-M1, v. 2, p. 25-47. 
Matthews, R. A., 1961, Geology of the Butler Estate chromite mine, southwestern 

Fresno County, California : California Div. Mines Spec. Rept. 71. 
Rynearson, G. A., and Wells. F. G., 1944, Geology of the Grey Eagle and some 

nearby chromite deposits in Glenn County, California : U.S. Geol. Survey 

Bull. 945-A, p. 1-22. 
Thayer, T. P., 19G4, Principal features and origin of podiform chromite de- 
posits, and some observations on the Guleman-Soridag district, Turkey : Econ. 

Geology, v. 59, p. 1497-1524. 
U.S. Bur. Mines Minerals Yearbook for various years. 
U.S. Commerce Dept., 1962, Materials Survey, Chromium : Business and Defense 

Sen- ices Adm., 96 p. 
Wells, F. G., Page, L. R., and James, H. L., 3940, Chromite deposits of the 

Pilliken area, Eldorado County, California: U.S. Geol. Survey Bull. 922-0, 

p. 417-460. 
Wells, F. G., Smith, C. T., Rynearson, G. A., and Liverm'ore, J. S., 1949, Chromite 

deposits near Seiad and McGuffy Creeks, Siskiyou County, California : U.S. 

Geol. Survey Bull. 948-B, p. 19-62. 


(By F. R. Kelley, California Division of Mines and Geology, San Francisco, 


The term "clay" is a broad one, and has been used to include many 
diverse materials. In general, it "implies a natural, earthy, fine- 
grained material which develops plasticity when mixed with a limited 
amount of water" (Grim, 1953). The term commonly is used both in 
referring to a definite group of silicate minerals, and as a rock term 
to indicate detrital rocks of the smallest grain size (less than about 
four microns) , regardless of the composition of the particles. Grim 
distinguishes between "clay minerals" and "clay materials", and the 
latter is a useful term under which many of our industrial clays 
would fall. 

Wet mud can be molded and shaped, and will dry to a hard mass 
that will have considerable strength, as long as it is not again sub- 
jected to moisture. Developing plasticity in a clay by the addition 
of water is a reversible process, which can be repeated at will. But 
if the clay body is subjected to prolonged and intense heating its char- 
acter is changed, and it becomes hard and immune to further attack 
by moisture. These are the characteristics of clay which account for 
much of its usefulness. 

The clay minerals characteristically are hydrous alimiinum silicates, 
with other elements such as magnesiimi, iron, potassium, sodium, and 
calcium in some of them. Most of them are "layer-silicates", with 
sheet-like lattice structures resembling the micas. Based on chemical 
composition .and crystalline structure, three main groups are dif- 
ferentiated, as follows : 

kaolinite group 

montmorillonite group 

hydrous mica or illite group 
Various other minerals, such as attapulgite, sepiolite and the mixed- 
layer clays have clay-like properties, but do not fit into the three 
groups mentioned. 

mineral and water resources of california 127 


Because clays have been utilized for so many purposes over ,a long 
period and are such a diverse group of materials, many other classi- 
fications have been used in their description. Geologically, clays may 
be classified on the basis of their origin as residual, i.e., formed in 
place, and sedimentary, i.e., transported from their place of origin. 
The terms high-alumina clay and ferruginous clay refer to chemical 
composition; refractory clay and semiplastic clay refer to physical 
properties; brick clay and bleachmg clay refer to use. No single 
classification will serve all purposes. 

For gathering statistical information, the U.S. Bureau of Mines 
employs a classiiication based on industrial use, as follows: 

kaolin or china clay 

ball clay 

fire clay, including stoneware clay 


fuller's earth 

miscellaneous clay 
Much information is cataloged imder this classification, and it .affords 
a convenient standard. 

Kaolin or china clay 

These clays are composed largely of kaolinite, but may have much 
quartz, mica, feldspar, or other material from the parent rock still 
present. Wliite kaolins are used in whiteware bodies and other high- 
grade ceramic uses, and as fillers and coating materials in papermak- 
ing. Kaolins also are used as fillers in rubber .and linoleum, and in 
various chemical, medicinal, and cosmetic applications. 

Ball clay 

The important characteristic of the ball clays is their high plasticity 
and bonding power. They are composed largely of poorly crystalline 
kaolinite and are very fine grained. They are used in blending with 
other clays to enhance their workability in manufacturing ceramic 
products such as sanitary ware, wall tile, and the like. 

Fire and stoTieioare clay 

These are made up primarily of kaolinite-group minerals, but vary 
widely in composition. Their most important property is refractori- 
ness (high resistance to heat), and they are subdivided into several 
classes on the basis of a test known as the pyrometric cone equivalent. 
Clays above cone 19 (P.C.E. 19, about 1,520°C or 2,T68°F) on this 
scale are regarded as fire clays. They are further designated as low 
duty, ranging from 19 to 28 ; medium duty, from 29 to 30 ; high duty, 
from 31 to 32 ; and super duty 33 (about 1,745 °C or 3,173°F) or above. 
Fire clays vary widely in plasticity, and the fired color may vai-y from 
near-white to red. They are used in a variety of ceramic products, 
ranging from common brick to art pottery, sewer pipe, and orna- 
mental tile. Some of the best grades go into refractory brick for use 
in the steel industry. Some low-grade fire clay is used in the manu- 
facture of stoneware. 



The term "bentonite" is a rock name, originally applied to a highly 
swelling clay material in Wyoming and other Rocky Mountain states. 
This clay is derived from the alteration of volcanic ash and is com- 
posed principally of montmorillonite. Many bentonites are non- 
swelling, and it has been established that only montmorillonites hold- 
ing sodium as an exchangeable ion will swell conspicuously, but if this 
ion is replaced by calcium, the material loses its swelling properties. 

The bentonites are the most reactive of the clays, and are useful as 
plasticizers, absorbents, binders, pelletizers, filtration and clarification 
aids, ion exchange media, reservoir sealers, and drilling muds. 

Fuller's earth 

Fuller's earth is a nonswelling bentonitic material also composed 
principally of montmorillonite. It is a highly absorptive clay, and 
owes its usefulness to its ability to absorb various organic molecules 
in the purification of mineral and vegetable oils, and a variety of other 

Miscellaneous clay, including shale 

This group takes in a variety of clay materials, including the low- 
grade alluvial clays, shales, many soil materials, and any argillaceous 
material that does not fit into one of the other groups. Natural clay 
materials are usually mixtures, and the less pure clays of any of the 
groups may be classified as miscellaneous clays. Any of the clay min- 
erals may be present, plus other detrital minerals, including quartz, 
mica, the feldspars and others, as well as rock fragments and organic 
matter. The miscellanous clays have a variety of uses. For specific 
purposes, they are upgraded by blending with higher quality clays to 
develop certain properties. Large quantities of miscellaneous clays 
go into the manufacture of heavy clay products, such as coimnon brick, 
structural tile, and sewer pipe. For this purpose, the clay must de- 
velop some plasticity but must not shrink excessively, and must fire to a 
suitable color and strong texture at reasonably low temperatures. 
Organic matter in a clay material may cause bloating, and large 
amounts of bloating clays are used in the manufacture of expanded 
shale lightweight aggregate. Large tonnages of common clays of 
suitable bulk composition go into the production of portland cement, as 
a source of alumina and silica. Smaller amounts are used as fillers for 
various purposes, rotary drilling muds, and a variety of other uses. 

Geologic Ocgubrence of Clays 

The clay materials are secondary, forming as alteration products 
of pre-existing rock materials by weathering processes or hydrother- 
mal alteration, or in some cases by diagenetic processes. The more 
soluble constituents of the original rocte are leached out, leaving be- 
hind the relatively stable aluminum silicates which are refomied as 
clay minerals. If the alkalis and alkaline earths are not completely 
removed, the clay minerals formed may be montmorillonites or illites. 
Kaolinite appears to represent a more advanced stage of clay forma- 
tion. Under severe chemical weathering, the kaolinite itself may break 
down, leaving only a residue of aluminum and iron oxides, such as in 
the lateritic soils of the tropics. 


Clay deposits may be residual or transported, according to their 
relationship with neighboring rock bodies. Residual clays are formed 
when chemical weathering alters the surface rocks to appreciable 
depths. Such weathering is most active under warm, moist climatic 
conditions, and if removal of the weathered residues by mechanical 
erosion is slow, a weathered zone of considerable depth may be 

If the clay, once formed, is removed and transported elsewhere, it 
may be laid down as a sedimentary clay deposit. These are usually 
interbedded with other sediments, but the clays tend to stay in suspen- 
sion until finally they settle out in sheltered basins of relatively quiet 
water. Sedimentary clays commonly are associated with lignite, de- 
rived from the thick vegetation of marshy areas bordering the basins. 

In California, the fire clays of the lone and Alberhill areas are sedi- 
mentary clays associated with white sands and lignite. Warm, moist, 
semitropical climates prevailed in these areas during parts of the 
Paleocene and Eocene Epochs, and mantles of residual clay were devel- 
oped on the alumina-rich bedrock of the low-lying land areas. Much 
material was eroded from these residual zones, and deposited in 
lagoons, swamps, and along the shallow margins of the adjacent seas 
to form these sedimentary clay deposits. 

Hydrothermal clays are formed when hot, chemically active waters 
rise through fissures and leach the soluble constituents out of the sur- 
rounding rocks, leaving a residue of kaolinized wallrock. The altered 
zone will be of limited lateral extent and will grade outward into fresh 
rock, but it may extend to considerable depth. 

Bentonite deposits appear to have formed by the alteration of vol- 
canic ash beds. Volcanic glass is unstable, and the transformation to 
montmorillonite takes place as carbonate- and acid-rich groundwater 
percolates through the fine-grained mass. Similar changes occur 
during the diagenesis of many sediments, as the action of ground water 
causes the formation of authigenic clay minerals within the sedimen- 
tary material. 

History or Discovery and Development 

As the early gold seekers spread through central California, they 
also foimd other mineral materials of potential value, including coal 
and clay, but the beginnings of clay mining are not well documented. 
At first, the recovery of useful clays was incidental to early coal-mining 
operations, which were carried on at several localities, including Mount 
Diablo, Corral Hollow and Carbondale, in the lone area. One of the 
earliest potteries in the State was at Antioch, using clay from the 
Black Diamond Coal mine. 

At Corral Hollow, coal mining had started by 1858, and high-grade 
clays of the district became the basis for a thriving clay industry which 
operated until 1912, when it was discontinued due to high mining costs. 
The Dosch pit north of lone was opened up in 1864 and is the oldest 
continuously operating clay pit in the State. In 1865, the clays of the 
lone district were mentioned in the reports of the State Geological 
Survey. The Gladding, McBean mine and plant at Lincoln began 
operations in 1875 and has operated continuously since that date. In 



southern California, coal mining at Alberhill dates from 1882, and clay 
production from 1895. 

In the early days of the State, destructive fires had resulted in a de- 
mand for bricks, and local brickyards were established in many of the 
towns throughout the State. In the last few decades, as transporta- 
tion improved, many of these small operations became uneconomic and 
have passed out of existence ; now, most of the brick manufacturing is 
done near the larger population centers. 

The demand for a variety of clays and clay products continues, and 
clay production in California is at an all-time high. 

California Clay Production 

Clay materials are common and widespread, and are utilized in 
many countries of the world, but no overall, world-wide production 
figures are available. During 1963, the United States produced over 
50 million tons of clay of all types, valued at about $181 million (see 
table 12). In general, clay production is largest in the more indus- 
trialized nations. Considering kaolin and china clay production 
alone, the United States is the source of about 36 percent of the world 
production of over 8,757,000 tons, followed by the United Kingdom 

Table 12. — U.S. and California clay production, 1963 


and china 


Ball clay 

Fire clay 




U.S. production (tons) 

U.S. production (dollar value; 
California production (tons).. 
California production (dollar 


California percent of U.S. 


California rank among States 

(dollar value) 

Price per ton (average U.S.).. 

3, 163, 573 

59, 770, 274 

18, 941 

297, 989 


3 5(?) 

547, 668 




8, 390, 174 

39, 557, 870 

531, 390 

1, 920, 589 



1, 584, 516 

18, 536, 229 


2 282, 928 

2 1.7 

$11. 70 

481. 817 
11, 210, 618 



3d, 031, 254 

44, 257, 364 

2, 800, 900 

5, 165, 419 



' Unapportioned. 
valued at $363,910. 
2 1962. 

3 Georgia 1st. 
* Tennessee 1st. 
5 Ohio 1st. 
« Wyoming 1st. 
' Florida 1st. 

Combined production of ball clay and fuller's earth for California was 29,608 tons , 

In 1963, California's production of all clays totalled 3,395,281 tons, 
valued at $8,030,830, and based on dollar value, it ranked fifth among 

the states, as follows : 

Percent of total value U.S. production 

Georgia 30.0 

Pennsylvania 8. 1 

Ohio 7.7 

Wyoming 6. 3 

California 4.4 

Of California's mineral commodities in 1963, clay was ninth in dollar 
value at 0.5 percent of the total, or if mineral fuels are excluded it 
ranked sixth, at 1.6 percent, behind cement, sand and gravel, stone, 


boron and lime. Production of clay was reported by 65 companies, 
from about 100 properties, in 34 different counties. About one-quarter 
of this production was fire clay, and nearly two-thirds Avas miscella- 
neous clay, of which 41 percent went into portland cement, 29 percent 
into expanded shale aggregate, and 30 percent into heavy clay products 
and other uses. 

California Deposits 

Fire clay deposits 

Fire clays of good quality have been mined in several districts in 
California (see fig. 16) . Along the western foothill belt of the Sierra 
Nevada, the sedimentary formations of the Great Valley overlap on 
the gently sloping Mesozoic bedrock surface. In many places, the 
oldest rocks of the Great Valley sedimentary sequence are light-colored 
sandstones and clays of Eocene age, known as the lone Formation. 
These sediments are well exposed over a 2 by 12 mile area near lone, 
in Amador County, where they are made up of clayey sandstones, 
clays, siliceous gravels, conglomerates and lignite, of variable tliick- 
ness and lithology. The clays are kaolinitic, and occur in lenses up 
to 30 feet thick. The formation dips gently westward and is overlain 
by tuffaceous sediments of Miocene age. The fire clays of this district 
have been used in refractories and heavy clay products for many years, 
and recently high-grade clays and glass sand have been recovered 
from the clayey sandstones. 

Elsewhere along the foothill belt, to the northwest and southeast, 
there are occasional exposures of the lone Formation, as at Lincoln, 
in Placer County, a major source of fire clays for 90 years. Other 
localities include Michigan Bar, Folsom, Valley Springs, Knight's 
Ferry, and Cooperstown, where some of the recent production has 
been ball clay, usable as a blending material in the manufacture of 
wall tile and other products. 

The lone beds dip into the synclinal trough of the G;reat Valley, 
and, west of the valley, beds of comparable age and lithology are 
exposed at several places. At Tesla, in Alameda County, coal and 
clay were mined from these beds for many years, but the beds dip 
steeply, and large-scale open-pit mining is not possible. For this 
reason, mining operations were stopped many years ago, although 
some of the clays were of excellent quality. 

In southern California, a major zone of high-grade fire clays occurs 
in western Riverside County, from the Alberhill area northwest to 
Corona, and around the northern end of the Santa Ana Mountains into 
Orange County. During Paleocene time, the Mesozoic crystalline bed- 
rock of the area was deeply weathered, with the development of 
residual clays, and some of these were removed and deposited with 
Paleocene beds of the Silverado Formation. Sandy beds are inter- 
stratified with the sedimentary clays, and in many places the Silverado 
is overlain by several feet of Quaternary conglomerate. 

Alberhill and the Corona area have been major sources of clays for 
refractories and heavy clay products for many years. In the Clay- 
mount area west of Corona, mining of highly refractory clays began 
in 1925. A new major clay deposit was opened up south of Corona 
in 1954. 




Kao I in or china clay 


Ba 1 1 clay 


Fire clay 

Ben ton j te 

Ful ler's earth 
M Jscel laneous clay 

MOJAVE -p^s- 

FiGtTBE 16. Clays produced in California. 

In southern Orange County, near El Toro, small amounts of high- 
grade kaolins are recovered by washing a clay -sand mixture from the 
Silverado Formation. 

Bentonitic clay deposits 

Many deposits of bentonitic clay material are scattered over the 
southern part of California. They occur in rocks of various ages, 
but the majority are Tertiary. 

South of Owens Lake, near Olancha, is an important source of non- 
swelling bentonite. This clay is derived from a tuff, altered by hydro- 
thermal solutions, and occurs as a low-dipping bed about 16 feet thick, 
beneath a layer of basalt. It is classed as a fuller's earth, and is used 
as a filtering and decolorizing agent. 

In San Benito County, bentonitic beds occur near the base of the 
Kreyenhagen Shale, exposed in the steeply dipping south flank of the 


Vallecitos syncline. This material has been used as a reservoir and. 
canal sealer, and some has been used as an insecticide carrier. 

Near Hector, in San Bernardino County, a unique swelling ben- 
tonitic material is mined. It is high in magnesia, low in silica, and has 
a small lithium content, and is derived from an altered basic tuff or 
flow in a lake bed sequence. It resembles Wyoming bentonite in its 
swelling properties, and has been extensively used in rotary drilling 
mud. After beneficiation, some is used in pharmaceuticals and bever- 
age clarification. 

Bentonite is being mined at several other localities, including Death 
Valley Junction, Tecopa, Brawley, and Vidal. 

Other deposits 

Clay deposits in the Hart area, eastern San Bernardino County, 
have been mined for more than 40 years. These clays were formed by 
hydrothermal alteration of Tertiary rhyolites. Some of them are 
classed as kaolins and others as ball clays, and they are used in pottery, 
sanitary ware, and wall tile. 

In southeastern Mono County, high-grade kaolin is produced from 
a deposit near Casa Diablo. This clay is a hydrothermally altered 
tuff, occurring in a horizontal deposit up to 25 feet in thickness. 
Some of this clay is sold as a filler in papermaking. 

Common clay deposits 

Common clays are abundant in California, and large tonnages of 
alluvial clays and shales are mined annually near population centers, 
for use in heavy clay products such as building brick. Often the 
common clays are blended with others to make higher grade ceramic 
products. Large quantities are also used in making portland cement 
and expanded shale aggregate. Nearly every county in the State 
has produced common clay in the past. 

Resource Potential and Future Prospects 

No detailed information on California's clay reserve and potential 
resources is available, and only rather broad estimates can be made. 
Each of the several types of clay is a separate entity, and, furthermore, 
the use of a given clay material may depend more on relatively obscure 
and subtle physical properties than on its general classification; so 
there w^ould be many special cases to consider in any detailed estimate. 

Kaolin. — California's resources are small, and large amounts are 
brought in from outside sources. There is some chance for discovery 
of new deposits, but perhaps the best means to improve the California 
position is research to find new ways of using some of the lower 
grade kaolinitic clays. 

Ball clay. — This follows the pattern of kaolinite, with small Cali- 
fornia production and large imports brought in from Kentucky and 
Tennessee. However, there appear to be moderate resources of ball 
clay available and, as time goes on, the local material should find wider 
acceptance and use as additional testing on its properties is done. 

Fire clay. — Reserves appear to be satisfactory, except for the most 
refractory grades of fire clay. Additional fire clay can probably be 
found by drilling programs, based on careful studies of sedimentary 
trends. The State's known small deposits of super-duty refractory 


clay have been depleted, and this clay is now imported. Careful 
exploration and drilling might find new small deposits of super-duty 
clay, but probably far short of enough to meet needs. 

Bentonite and fuller's earth. — Intensive prospecting and testing 
probably would bring to light more deposits of usable bentonite of 
many diverse types. However, the outlook appears to be unfavorable 
for finding large resources of Wyoming- type swelling bentonite. 

Common clay. — Large resources appear to be available. However, 
urbanization around the population centers will restrict the use of 
some deposits, and recovery operations will be forced further away as 
the cities expand. 

Selected References 

Carlson, D. W., and Clark, W. B., 1954, Mines and mineral resources of Amador 
County, California : California Jour. Mines and (Jeology, v. 50, no. 1, p. 149-285. 

Cleveland, G. B., 1957, Clay, in Mineral commodities of California : California 
Div. Mines Bull. 176, p. 131-152. 

Cooper, J. D., 1963, Clays: U.S. Bur. Mines Minerals Yearbook, 1963, v. I, 
p. 393-418. 

, 1965, Clays, in Mineral facts and problems, 1965 ed. : U.S. Bur. Mines 

Bull. 630, preprint, 14 p. 

Dietrich, W. F., 1928, The clay resources and the ceramic industry of California : 
California Div. Mines Bull. 99, 383 p. 

Gray, C. H., Jr., 1961, Mines and mineral deposits of the Corona South quad- 
rangle : California Div. Mines Bull. 178, p. 59-120. 

Grim, R. E., 1953, Clay mineralogy : New York, McGraw-Hill Book Co., Inc., 
384 p. 

, 1962, Applied clay mineralogy : New York, McGraw-Hill Book Co., Inc., 

422 p. 

Klinefelter, T. A., and Hamlin, H. P., 1957, Syllabus of clay testing : U.S. Bur. 
Mines Bull. 565, 67 p. 

U.S. Bur. Mines, 1965, Commodity data summaries. Clays, p. 32-33. 


( By E. R. Landis, U.S. Geological Survey, Denver, Colo. ) 

Of the total energy' consumed in the United States in 1963, 22 per- 
cent was furnished by coal. Only oil, with 41 percent, and gas, with 
33 percent, outpaced coal (U.S. Bureau of Mines, 1964a, p. 50). Over 
half of the coal produced in 1963 in the United States was burned to 
generate electricity, almost 19 percent was used to produce coke, about 
24 percent was used industrially, and about 6 percent went for retail 
deliveries (U.S. Bureau of Mines, 1964a, fig. 14) . Only a very small 
amount of coal is mined in California but 1,690,000 tons were shipped 
into the State from Utah and New Mexico in 1963 to make coke for 
smelting steel and for other industrial uses (U.S. Bureau of Mines, 

Coal is an organic sedimentary rock composed of metamorphosed 
plant material admixed with a subordinate amount of inorganic con- 
stituents. The plant material may have accumulated at its growing 
site or may have been transported by water and wind to its deposi- 
tional site. Peat is excluded by definition because it is not metamor- 
phosed, but it is the material from which coal is derived. Coal 
results when peat is buried and progressive changes in physical 
and chemical properties take place, mainly related to time and 
weight of overlying sediments. In places the changes are speeded 


by pressure from structural deformation or heat from igneous intru- 
sive rocks. The progressive metamorphism increases the carbon con- 
tent and heat vakie while decreasing the moisture and volatile matter 
contents. Coals are classed by rank, according to the degree of meta- 
morphism, from lignitic to subbituminous, bituminous, and anthracitic, 
and the rank is generally an index to the usability and value of the 
coal (table 13). Anthracitic coal is largely used for domestic and 
other space heating, but some is blended with bituminous coal to make 
coke. Bituminous and subbituminous coal range widely in properties 
but in general the higher rank coal is likely to be used for special pur- 
poses, such as making metallurgical coke, and the lower rank coal is 
likely to be used solely for heat energy, as in steam-electric utility 
plants. Lignitic coal is largely used as a source of heat energy but 
carbon, industrial gases, humic acid compounds with a great variety of 
uses, and montan wax are also derived from lignite. 

Coal deposits range in shape from thin beds of wide extent, to thick 
nearly equidimensional bodies. As with other stratified rocks, the 
shape and attitude of coal beds are affected by the deforming forces, 
folding, faulting, and igneous intrusion. For profitable development 
under present-day conditions with a high degree of mechanization, 
coal beds mined underground should be 3i/^ feet or more thick with a 
small range in thickness, flat-lying, not broken by faults, and at depths 
of less than 1,000 feet. In surface, or strip, mining the additional 
important factors are thickness and character of the material over- 
lying the coal bed — the coal should be less than 100 feet below the sur- 
face and the overburden should be easily removable. 

In 1963, the United States mined 16 percent of the world coal out- 
put, about 477 million tons, and ranked third in production behind 
the U.S.S.R. with 584 million tons and Germany (East and West) 
with 559 million tons (U.S. Bureau of Mines, 1964a, p. 168-170). 
First recorded production of coal in California was in 1855, and the 
annual coal production exceeded 100,000 tons during most years be- 
tween 1867 and 1903 (Jennings, 1957, p. 153). The coal was used for 
steam generation by the railroads and steamships, and for industrial 
and domestic heating. Oil and gas began to displace coal as a heat 
source shortly after 1900 and by 1914 annual coal production was a 
few thousand tons. In recent years the amount of coal produced an- 
nually in California has probably been a few thousand tons, almost 
all of which is used as a raw material from which montan wax and a 
few by-products are derived. Montan wax is used in shoe polishes, 
floor waxes, electrical insulation, leather dressings, inks, carbon paper, 
protective coatings and waterproofing compounds, greases, phono- 
graph records, rubber, investment castings, and many other allied 
products (Jennings, 1957, p. 162). Almost all of the coal imported 
into California is carbonized to make coke and by-product chemicals. 
Only 37,000 tons of the total 1,690,000 tons that were shipped from 
Utah and New Mexico went to retail deliveries and other uses (U.S. 
Bureau of Mines, 1964b) . 

Small, scattered deposits of coal are reportedly present in 43 counties 
of the State but have been mined or intensively prospected at less 
than a dozen localities in 11 counties (Jennings, 1957, p. 153) (fig. 17) . 





, , 
































T— ( 














. I 



es a 




40 to *o *r. CO CO 

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Dx; S ® S "^ 

03 -^ H © ^-^ 
(B-g a> q 0) 

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"''amounts of coal have been mined 

^-— A---r \^i. Areas in which significant 

Other areas mentioned in text 

^TEHAMA ""t:^ /^, ,.„. ''^,; 

yr '°' X 

i,ENN)Bt\rrX'^-,p:;^„rtj Coal reported (Jennings. 1957. 
Qi \ /X'.-^'::i^Ji: fig.1: and U.S. Bureau 

of Mines. 1947. fig 2) 

Figure 17. Coal in California. 

The following brief discussion is derived largely from Jennings (1957) 
and the U.S. Bureau of Mines ( 1947) . 

High- volatile bituminous coal is present in the Temblor ( ?) Forma- 
tion of early and middle Miocene age in the Stone Canyon district of 
southeastern Monterey County, and some bituminous coal occurs in 
rocks of Eocene age in southern San Benito County. The bitumi- 
nous coal in the Stone Canyon district may be of the variety known 
as cannel coal, which characteristically has as much or more volatile 
matter as carbon and is noncoking (U.S. Bureau of Mines, 1947, p. 4) . 
Subbitmninous coal and lignite occur in the Montgomery Creek Forma- 
tion in Shasta County, in the Te^la Formation in Alameda County, 
and in the Domengine Formation in Contra Costa County. These 
three rock units are all Eocene in age and are probably partially or 

67-164 O — 66— pt. I- 




completely equivalent to each other. Subbituminous coal is also pres- 
ent in the Temblor Formation of Miocene age in Mendocino County 
and in rocks of Eocene age in Siskiyou County. Lignitic coal occurs 
in rocks of Early Cretaceous age, and in the Weaverville Formation 
of Oligocene (?) age in Trinity County; in the Silverado Formation 
of Paleocene age in Riverside and Orange Counties, though the avail- 
able incomplete analysis suggests that some or all of this coal may be 
subbituminous ; and in the lone Formation of Eocene age in Amador 

The coal beds of California do not range widely in age, and the 
differences in rank are due largely to differences in amount of struc- 
tural deformation that the deposits have undergone. The coal-bearing 
rocks in the Coast Ranges have been folded and faulted and the coal 
has commonly been metamorphosed to higher ranks than the coal in the 
foothills of the Sierra Nevada and in the Peninsular Ranges where the 
strata dip gently or are horizontal (Jennings, 1957, p. 153) (table 14) . 

Table 14. — Range of 

analyses of representative California coals, as-received basis 

Sample source 


Rank (table 13) 











value (B.t.u. 

per pound) 

Stone Canyon,' 

Monterey County. 
Mount Diablo,' 

Contra Costa 

Corral Hollow,' 

Alameda County. 
Alberhill,3 River- 




High volatile B 



Lignite A * or 
ous C. 

Lignite A 

4. 4- 8. 

17. 6-18. 

40. 3-45. 8 

44. 8-50. 

39. 2-41. 1 

30. 9-31. 3 

30. 3-36. 

23. 3-26. 4 

13. 2-15. 7 

7. 5-15. 9 

16. 4-18. 

7. 6-15. 2 

4. 1-4. 6 

2. 9-3. 1 

11, 420-12, 130 

2 8, 110 

side County. 

lone, Amador ' 

1. 0-1. 3 

5, 640- 6, 060 

1 U.S. Bureau of Mines (1947). 

2 Only 1 calorific value reported. 

3 Jennings (1957) . 

* Reported to be lignite; but may be subbituminous. 

Significant quantities of coal have been mined in only five areas — 
Mount Diablo in Contra Costa County, Corral Hollow in Alameda 
County, Stone Canyon in Monterey County, Alberhill in Riverside 
County, and lone in Amador County (fig. 17). Total recorded pro- 
duction to date is about 5,310,000 tons, of which about 3,500,000 tons 
was mined in the Mount Diablo district between 1855 and 1902 (Jen- 
nings, 1957, p. 153). Of the remainder, at least 350,000 tons were 
mined in the Corral Hollow district between 1897 and 1902 (Jennings, 
1957, p. 157). 

According to Karp (1949, p. 341), the known coal resources of Cali- 
fornia are estimated to be more than 100 million tons, of which 
Averitt 1961, p. 85) estimates about 50 percent is lignitic coal, 40 
percent subbituminous, and 10 percent bituminous. The general 
assumption that for every ton of coal actually produced another ton 
has been lost in mining or is unrecoverable is probably valid for areas 
such as California where precise information is unavailable. 


Selected References 

American Society for Testing Materials, 1964, Proposed revised tentative specifi- 
cations for classification of coals by rank (ASTM Designation: D388-T). 

Averitt, Paul, 1961, Coal reserves of the United States— A progress report, Jan- 
uary 1, 1960: U.S. Geol. Survey Bull. 1136. 

Jennings, C W., 1957, Coal, in Mineral commodities of California : California 
Div. Mines Bull. 176, p. 153-164. 

Karp, S. E., 1949, California coal : Compass, v. 26, p. 341-344. 

U.S. Bureau of Mines, 1947, Analyses of Arizona, California, Idaho, Nevada, and 
Oregon coals : U.S. Bur. Mines Tech. Pai>er 696. 

U.S. Bureau of Mines, 1964a, Mineral Yearbook, 1963, v. 2, Fuels, p. 49-174. 

, 1964b, Bituminous coal and lignite distribution. Quarterly, March 1964. 


(By J. T. Alfors, California Division of Mines and Geology, San Francisco, 


Cobalt compounds have long been used to give a beautiful blue color 
to pottery and to glass. This ancient use still pei"sists, but the re- 
markable ability of cobalt metal to impart great strength to alloys 
at high temperatures, and magnetic qualities to certain alloys, has led 
to increased use of cobalt in the past 20 years. Recently, other refrac- 
tive metals have partially replaced cobalt for high-temperature super- 
alloys and the amount of cobalt used for permanent -magnet alloys 
also has declined on account of substitutes (U.S. Bureau of Mines, 
1965, p. 39). 

The domestic consumption of cobalt in 1963 was 10.5 million pounds, 
7 percent less than 1962. The major uses of cobalt were for high- 
temperature, high-strength alloys (23 percent) and for permanent- 
magnet alloys (22 percent). Uses in steel (12 percent) and other 
products brought the total consimiption of metallic cobalt to 75 per- 
cent. Nonmetallic (exclusive of salts and driers) consumption, 
mainly m pigments and as ground-coat frit, was 13 percent of the 
total. Sales and driers account for 12 percent of the domestic con- 
sumption (Ware, 1964, p. 2-3) . 

Cobalt is generally recovered as a by-product of copper or nickel 
ores. Some cobalt is obtained during the processing of iron, gold, 
lead, and silver ores. Other metals associated with cobalt include 
zinc, manganese, uranium, platinum, and chromium (Vhay, 1952, p. 
VI-5, 6; Centre dTnformation du Cobalt, 1960. p. 8-29). 

The important primary ore minerals of cobalt are skutterudite 
((Co,Ni,Fe)As3), carrollite (C00CUS4), limiaeite (C03S4), and co- 
baltite (CoAsS). The principal cobalt minerals in the oxidized zone 
of mineralization are asbolite (a cobalt-bearing mixture of hydrous 
manganese and iron oxides), heterogenite (a hydrous oxide of cobalt 
and copper), sphaerocobaltite (C0CO3), and eiythrite (Co3(As04)2" 
8H2O) (Bilbrey, 1960, p. 216; Centre dTnformation du Cobalt, 1960, 
p. 8-10). 

Cobalt deposits commonly are associated with mafic or ultramafic 
igneous rocks as magmatic segregations of sulfides or as vein or re- 
placement deposits formed by hydrothermal activity. Cobalt-bearing 
vein deposits are less commonly associated with granitic rocks. Cobalt 
is concentrated to economic grade in some lateritic soils developed on 



serpentinized peridotite and other ultramafic rocks. A good summary 
of the geology of a large nmnber of cobalt deposits is given by Vhay 

The Centre d'Information du Cobalt (1960, p. 1-7) has summarized 
the history of cobalt since its use in ancient Persia and Egypt. From 
the 16th century until 1874, cobalt was produced chiefly in Norway, 
Sweden, Saxony, and Hungary. The lateritic cobalt ores from New- 
Caledonia were the main source of cobalt from 1874 until 1904 and 
thereafter the silver-cobalt-arsenic veins of Ontario, Canada, provided 
virtually all of the world's supply. Extraction of cobalt from the 
copper ore deposits of Katanga, Belgian Congo (now Republic of the 
Congo) began in 1924 and since 1940 Union Miniere du Haut-Katanga 
has been the largest producer of cobalt in the world. Other major 
cobalt producers are Canada, Morocco, and Northern Rhodesia. 

^ s 1 s K 1 1 y o\u 

\M(ib^tvi,TAfl'Ns/\ "T" 

S^"5H OmoJoc ! 

Eurvk^ "^ \ "i 



— •^ 

PULMAS ^^ ao- 

-ft LAKE -.l 'i Vi) V ■,»<<>> _• : 
VSONOMAV^N^lL'. _ >,^,„\ ^- ^alpine' ^ 

1 . Ma r J ohn pros pec t 

2. Ju I ian-Cuyamaca area 


SANTA S'T fT ^ .-^ ^ y ~ 


iNTEREY '1 \ V ; TiVaRF ^ A 

. " tin; ■*— \ BakemfuW 

- l^ omspo 

% X- 



*'+' r ^'**'-"f^H-'^. Jl/__ y SAN BERNARDINO •;^ 


150 Milts 

^"^N^V^^^T^r A DESERT j 

■^\ — 





Figure 18. Cobalt in California. 


The Betlilehem CornAvall Corp, has recovered cobalt from pyrite 
associated with the Coriuvall, Pennsylvania, magnetite ore since 1940, 
and in 1963 was the only domestic producer mining cobalt (Ware, 
1964, p. 1 ) . From 1952 to 1959, the Calera Mining Co. produced cobalt 
from the Blackbird district of Idaho. The National Lead Co. re- 
covered cobalt at Frederickstown, Missouri, from 1955 to 1961. 

Minor occurrences of cobalt -bearing minerals liave been reported 
from numerous localities in California (Murdoch and Webb, 1956, 
p. 52, 60-61, 76, 123, 146, 260-262, 301 ; 1960, p. 11, 13-14, 19), but there 
has been no commercial production of cobalt in the State. A few tons 
of cobalt ore were mined at the Mar John property (fig. 18) in 
Calaveras County in 1924 but were not marketed (Chesterman, 1956, 
p. 165). A list of California occurrences of cobalt is given by Vhay 
(1952, p. VI-38, VI-39, VI-54) but most of them are very small 
deposits. Any future production of cobalt in California would un- 
doubtedly be as a by-product in the mining of copper, nickel, or iron 
ore. The areas with most potential are the copper deposits of the 
Foothill Copper Belt of the Sierra Nevada and the Friday nickel 
deposit, Julian-Cuyamaca area, San Diego County. 

SELECTEa) Refesiences 

Bilbrey, J. H., Jr., 1960, Cobalt, in Mineral facts and problems, Anniversary 
Edition : U.S. Bureau of Mines Bull. 585, p. 213-224. 

Centre d'Information du Cobalt in collaboration with the staff of Battelle 
Memorial Institute, 1960, Cobalt monograph : Centre d'Information dti Cobalt. 
Brussels, Belgium. 

Chesterman, C. W., 1956, Cobalt, fn Mineral commodities of California : Cali- 
fornia Div. Mines Bull. 176, p. 165-168. 

Murdoch, Joseph, and Webb, R. W., 1956, Minerals of California : California 
Div. Mines Bull. 173, 452 p. 

, 1960, Supplement to minerals of California for 1955 through 1957 : Cali- 
fornia Div. Mines Bull. 173, suppl., 64 p. 

U.S. Bureau of Mines, 1965, Commodity data summaries. 

Vhay, J. S., 1952, Cobalt Resources, m Materials survey — cobalt: National Secu- 
rity Resources Board, 148 p. 

Ware, G. C, 1964, Cobalt, Minerals Yearbook, 1963, U.S. Bureau of Mines, 


(By A. Robert Kinkel, U.S. Bureali of Mines, San Francisco, Calif., and Arthur 
R. Kinkel, Jr., U.S. Geological Survey, Washington, D.C.) 

Copper is one of the most versatile and widely used metals. Its 
superior electrical conductivity and alloying characteristics are re- 
sponsible for its importance in the industrial economy. About half of 
all copper consumed is for electrical applications and about 40 percent 
is used for alloy manufacture, largely brass. The automotive industry 
uses 30 to 40 pounds per vehicle and accounts for about 9 percent of 
the copper consumed in the United States. In addition to its role in 
copper-base alloys (brass and bronze), copper is an important con- 
stituent of a large number of alloys having a metal other than copper 
as the principal component (McMahon, 1965). 

The world is adequately endowed with sources of copper. New 
discoveries and extensions of mines in many copper provinces of the 
world during the 1950's greatly increased the known world copper 


resources. In addition to the primary sources of copper metal, a large 
reserve of secondar^^ copper (scrap) has been accumulated and is con- 
tinually being augmented. The collection and processing of this scrap 
into secondary metal constitutes an important segment of the copper 
industry in all major consuming countries. 

Since World War II there has been considerable change in copper 
mining technique. In 1939, when the average copper ore mined con- 
tained 1.29 percent copper, 59 percent of the copper output came from 
open-pit mines. In 1963, when the average ore mined contained 0.74 
percent copper, 81 percent of the ore was from open-pit mines. The 
trend is toward very' large, but low-grade deposits that can be mined 
by highly mechanized methods, and thus at low cost. Most California 
copper deposits have been medium sized to small deposits that require 
underground mining, and thus are less favorable for mining miless 
the grade of the ore is high. 

California's copper production has been an important economic 
asset in the past, although it was moderate by national standards. 
California accounted for over 15 percent of the national total, from 
1862 to 1866, and for over 5 percent in 1867-1868, 1901 and 1909. 
During years of peak copper production (1909, 1916, and 1924), the 
State accounted for about 3 percent of the national total. During 
1906-1918 the value of the State's copper output exceeded $10 million 
annually (see fig. 19). 

The principal copper deposits of California occur in five areas. 
These are: 1) the counties of the northern Coast Ranges; 2) Shasta 
County; 3) Pliunas County; 4) the Foothill copper belt, which ex- 
tends from Butte Comity south to Fresno County ; and 5) the southern 
counties of Inyo, San Bernardino, San Diego, and Imperial. By 
far the largest part of the copper produced in California has been 
from massive pyrite-type ores. Silver and gold are the major by- 
products of California copper ores. Sulfur and iron from pyritic 
copper ores could be produced if economic conditions were favorable. 

History and Production 

The mining history of California began with the discover}' of gold 
in 1848, although copper had been produced previously from a few 
small deposits in Los Angeles County. Exploration following the 
discovery of gold resulted in the discovery of many base-metal de- 
posits, and copper production began in Calaveras Coimty in 1862, and 
soon after in Amador County. Mines of Calaveras County eventu- 
ally became the largest producers in the 250-mile- long Foothill copper 
belt. Production from this belt virtually ceased during 1868-1881, 
for the gold and silver content of the surface-enriched ores decreased 
on reaching the primaiy sulfide zone and would no longer support the 
cost of shipping the ore to smelters in Wales. Durmg the early 1880's 
production was revived in the Foothill belt for a short, period, and 
between 1902 and 1960 there was almost continual, although small, 
production from one or more mines along the belt. Foothill belt pro- 
duction was 4,700 tons of copper in 1917, a level not approached in 
later years (see fig. 20). 

Copper was discovered in Plumas County shortly after production 
began in the Foothill belt and small amounts were produced inter- 
























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O o . 



JC «^ o 




to CO 








Shas t a 
Coun ty 

PI umas 




. L-^ 1 , 





03 ' 

oo > > 

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CD r~ 

O oo GO 

CD Oi O 

CD _ _ 











o '— 
03 (Ji 









FiGUEE 20. California copper production by decades, 1862-1964, showing produc- 
tion of major districts. 

mittently from 1865 to 1869. The first significant production began 
in 1914, and by 1925 output reached 13,500 tons of copper. Copper 
mining virtually ceased in Plumas County after 1941 when the Walker 
mine (No. 21, fig. 21) was closed. 

The East and West Shasta districts (Nos. 10 and 11) did not begin 
copper production until about 1894 but by 1896 were the principal 
source of copper. A peak production of 25,000 tons was attained in 
1909. Mines of the East and West Shasta districts produced a total 
of slightly over 10,000 tons annually between 1906 and 1918 from local 
smelters. With the exception of the period 1924-1929 and a short 
period during World War II, production rates have not since been 

Copper production in other areas of the State has been relatively 
small. Minor copper was produced in the northern Coast Ranges (in 
Del Norte, Humboldt, Siskiyou, and Trinity Counties) in the 1860's 
and 1870's, but reached significant proportions from Siskiyou and 
Trinity Counties from 1915 and 1930 and again in Siskiyou County 
from 1943 to 1945. Small tonnages were produced perioclically from 
central and southern Coast Range counties. Pyrite mines in Alameda 
County (No. 60) have a reported output of 284,000 tons of copper- 
bearing pyrite from 1901 to 1925 ; this ore was mined mainly for sulfur 



but it probably contained about 4,000 tons of copper, part of which 
was recovered. 

The bulk of the copper in California was produced during 1891-1930 
as shown in table 15 and figure 20. The significance of Shasta, Plumas, 
and the Foothill belt counties production is tliown on figure 20 and 
table 15. 

Table 15. — Copper production in California, 1862-1964 



Short tons 

of dollars 

1862-90 . 






1891-1930 - - 




1961-64 - - 




210, 100 



Short tons 

Percent of 
State total 

Shasta . 


162, 700 







Foothill belt counties.. . . ._ 


Northern Coast Ranee counties - 


others - - -- 




Since the mid-1950's the bulk of the copper produced has been 
obtained as a by-product in processing tungsten ore at the Pine Creek 
mine (No. 62), Inyo County and from numerous polymetallic mines 
in Inyo and San Bernardino Counties. The principal localities are 
listed in table 16. 

Shasta District 

The East and West Shasta districts account for about 53 percent of 
the copper produced in California. Nine mines produced copper in 
the West Shasta district and three in the East Shasta district. In 
both districts the large copper- and zinc-bearing massive pyrite de- 
posits contain minor gold and silver. Ore bodies in the West Shasta 
district are generally large flat-lying lenses essentially concordant 
with bedding in felsic volcanic flows and pyroclastic rocks of Devonian 
age (Kinkel, Hall and Albers, 1956). Ore bodies in the East Shasta 
district are smaller, steeply dipping, and are lenticular to vein-like 
or tabular (Albers and Eobertson, 1961). They are also essentially 
concordant with foliation and generally with bedding in felsic vol- 
canic flows and pyroclastic rocks of Triassic age. In both areas the ores 
are in the uppermost parts of thick piles of submarine volcanic rocks 
which are overlain by argillic marine sediments. The rocks in both 
areas are moderately folded and metamorphosed, and locally they are 
strongly sheared. 

Ore in the West Shasta area is mainly massive pyrite that contains 
several percent copper in parts of the ore but less than half of one 
percent copper in other parts. Some of the ore was mined mainly for 



its sulfur content. Zinc is erratically distributed, but some of the ore 
contains more than 10 percent zinc. The ores generally have a zinc : 
copper ratio of about 2:1, but most of the zinc was not recovered. 
Cadmium occurs in appreciable quantities but was not recovered. 
Insoluble material, mainly quartz and sericite, ranges from 3 to 5 per- 
cent in most of the ore. Ore in the East Shasta district is also a massive 
pyritic zinc-copper ore that contains minor gold, silver, galena., and 
tetrahedrite, and has a gangue of barite, quartz, sericite, and anhydrite. 
Ore bodies of the East Shasta district are generally smaller than those 
of the West Shasta district but are of higher grade. 


S hor t tons of c oppe ; 

50 to 1 .000 
1 ,000 to 50. COO 
50.000 to 100.000 
Over 100.000 

FiGUKE 21. Principal copper localities in California by size categories based on 
production plus metal remaining in the deposits (numbers refer to table 16). 



Table 16. — Principal copper localities in California 


Del Norte. 
Siskiyou. . 



Plumas.. - 




El Dorado 










San Bernardino 

San Diego. 



District or mine 

Wimer District. 
French Hill District. 
Gray Eagle Mine. 
Blue Ledge Mine. 
Klamath River District. 
Scott River District. 

Copper BluS Mine. 
Horse Mountain District. 
West Shasta District. 
East Shasta District. 
French Gulch District. 
Redding District. 
MinersviOe District. 
New River District. 
Mad River District. 
Island Mountain Mine. 
Tom Head District. 
Colyear Springs District. 
Lights Creek District. 
Genesee District. 
Red Rock District. 
Saw Pit Flat District. 
Inskip District. 
Big Bend Mine. 
Meadow Lake District. 
Foothill Belt, Boss-San Juan Mine. 
FoothiU Belt, Mineral Hill Group. 
Foothill Belt, Spenceville Mine. 
Foothill Belt, Dairy Farm Mine. 
Foothill Belt, VaUey View Mine. 
Foothill Belt, El Dorado Copper Mine. 
FoothiU Belt, LUyama Mine. 
Foothill Belt, Funnybug Mine. 
Foothill Belt, Noonday Mine. 
Foothill Belt, Cosumnes Copper Mine. 
Foothill Belt, Big Canyon Mine. 
Foothill Belt, Copper Hill Mine. 
Foothill Belt, lone Copper Mine. 
Foothill Belt, Newton Miae. 
Foothill Belt, Penn Mine. 
Foothill Belt, Nassau Mine. 
Foothill Belt, Quail HiO Mine. 
Foothill Belt, CopperopoUs Group. 
Foothill Belt, Napoleon, Collier Mines. 
Foothill Belt, Oak Hill Mine. 
Foothill Belt, Salambo Mine. 
Foothill Belt, La Victoria Mine. 
Foothill Belt, Blue Moon Mine. 
Foothill Belt, Pocahontas. 
Foothill Belt, Green Mountain Group. 
Foothill Belt, Buchanan Mine. 
Foothill Belt, Jesse Belle, Daulton Mines. 
Foothill Belt, Krohn Mine. 
Minarets District. 
Foothill Belt, Painter Mine. 
Foothill Belt, Fresno Copper Mine. 
Foothill Belt, Copper King Mine. 
Camp Wishon District. 
Ahna, Leona Mines. 
Lundy District. 
Pine Creek Mine. 
Loretto Mine. 
Clark Mountains District. 
Ivanpah Mountains District. 
Providence District. 
Signal District. 
Needles District. 
Whipple Mountains District. 
Turtle Mountains District. 
Buckeye District. 
Fry Mountains District. 
Ord Mountain District. 
Ramona District. 
Julian District. 
Ogilby District. 


Lights Creek and GsTiesee districts 

Plumas County contains three major deposits and numerous small 
deposits. At the Engels and the Superior mines in Lights Creek 
district (No. 20) the ore occurs as steeply dipping replacement veins 
and stockworks in granitic rock. Sulfides are mainly bornite and 
chalcocite (Anderson, 1931). At the Walker mine in the Genesee 
district the ore occurs as seams, stockworks, and disseminations of 
chalcopyrite, chalcocite, and pyrrhotite in schistose rocks (Knopf, 
1935). The Engels and Superior mines were closed in 1930 and the 
Walker mine in 1941. 

Foothill copper helt 

The Foothill copper belt extends along the west flank of the Sierra 
Nevada batholith. At least 40 copper-zinc mines have been operated 
along this narrow 250-mile-long belt but only a few have produced 
large amounts of copper and zinc. The Foothill belt contains folded 
and metamorphosed sedimentary and volcanic rocks of Paleozoic and 
Jurassic age (Heyl, 1948). Along the ore zone the rocks are inter- 
bedded felsic and mafic volcanics and related pyroclastic rocks and 
intrusives, and marine shales that are in part altered to slate. The 
degree of metamorphism is variable but generally increases toward 
the south along the belt. Most ore bodies appear to be in the upper 
part of a thick, partly submarine, volcanic pile, the Amador Group 
of Middle and Late Jurassic age, which is overlain by the Mariposa 
Slate of Late Jurassic age. 

In the Foothill copper belt the ores are massive sulfide made up 
mainly of pyrite; they contain chalcopyrite and sphalerite and 
small amounts of gold and silver. The sparse gangue minerals are 
quartz, barite, sericite, and chlorite. Ore occurs as steeply dipping 
lenticular or tabular bodies in siliceous, sericitic, and pyritic zones, 
and ore bodies are peneconcordant with both schistosity and bedding. 
In the southern part of the belt where the metamorphism is of hi^gher 
grade along the ore zone as in Madera and Fresno Counties, pyrrhotite 
is more common and in places exceeds pyrite in abundance. Some 
deposits contain minor galena, tetrahedrite, bornite, and cobalt. At 
the Jesse Belle mine (No. 53) in Madera County part of the ore 
contained up to 0.3 percent cobalt. 

The Penn mine (No. 41) is the largest copper-zinc deposit in the 
Foothill belt. Individual ore lenses at this mine have a steep pitch- 
length of as much as 1,000 feet, a breadth from 100 to 400 feet, and a 
thickness of as much as 30 feet. This mine has produced about 40,000 
tons of copper and over 6,000 tons of zinc. Zinc exceeds copper in 
the ore but was not recovered during most of the period of operation 
(Heyl, Cox, and Eric, 1948) . 

The eastern part of the Foothill belt (locally known as the East 
belt) contains many small but rich vein and replacement deposits of 
bornite and chalcocite in metamorphic and igneous rocks, generally 
in a quartz gangue. 

Other districts 

The southernmost copper districts are in Inyo, San Bernardino, San 
Diego, and Imperial Counties, which lie within the Basin and Range 


province. This province is characterized by a thick accumulation of 
Paleozoic carbonate rocks with interbedded slates and quartzites; these 
are block faulted. The mineral deposits occur as veins and replace- 
ment deposits of complex lead-zinc-copper ores in carbonate rocks. In 
the western and southern parts of the area, intrusive and metamorphic 
rocks become increasingly connnon with little change in the mineraliza- 
tion apart from increasing gold content in the western deposits and 
copper in the southern deposits. 

Several copper deposits in the noithern Coast Kanges have been im- 
portant producers in the past. Deposits occur largely as vein, replace- 
ment, and disseminated deposits in folded and faulted sedimentary 
rocks and in felsic and mafic volcanic rocks. Chalcopyrite, chalcocite, 
or bornite, with variable amounts of sphalerite, are the common min- 
erals. The deposit of massive cupriferous pyrite at Island Mountain 
(No. 17), Trinity County, lias been one of the largest producers of 
copper m the area ( Averill, 1941) . Native copper is reported in small 
amounts throughout the Coast Ranges. The only significant sulfide 
producers in the southern part of the Coast Ranges have been the Alma 
and Leona deposits of copper-bearing massive pyrite in Alameda 
County (Davis, 1950). 

Reserves and Potential Resources 

A numbei of inactive copper deposits in California are known to 
contain sufficient ore to support moderate production rates for several 
years. These resources are small by national standards, and many 
deposits would be difficult to mine under present economic conditions 
liecause of the cost of mine rehabilitation, transportation, and other 
factors. The resource potential of copper in California lies in undis- 
covered ore bodies in a number of areas that are favorable for ex- 
ploration with modern techniques. 

Known or reasonably assured copper resources are mainly in five 
areas. These are: 1) Shasta County; 2) Foothill copper belt; 3) Plu- 
mas County; 4) northern Coast Ranges; and 5) Minarets district. 
The known copper resources of California total about 470,000 tons of 

Practically all of the copper mined in California has come from 
deposits that were exposed at the surface. There are geologic reasons 
for believing that undiscovered ore bodies should be present in a num- 
ber of areas, and based on past production, these should be of sufficiently 
high grade to warrant mining. Ore bodies in two of the most produc- 
tive' areas, the Shasta district and the Foothill belt, are not marked by 
broad alteration halos or other features that give surface clues to the 
presence of ore that may exist a short distance beneath the surface. 
Exploration for subsurface ore bodies can be limited to certain zones 
or horizons by geologic study that will give information on the 
processes of ore deposition, but this must be followed by the geo- 
physical and geochemical techniques that have been developed so 
rapidly in the past decade but have not yet been applied in most of 
these areas. Past production and geology of the Shasta, Foothill, and 
other promising areas suggest that many copper ore bodies wiU still 
be discovered in California. 


Technical and Marketing Problems 

Almost all of California's copper has come from underground 
mines. Those in the Shasta area are in rocks that generally allow 
open unsupported stopes, but some support of the walls is generally 
required in the steep ore bodies in schistose rock along the Foothill 
belt. Principal deterrents to mining are the generally small size of 
the ore bodies except for a few in the West Shasta district, the fine 
grinding required by many of the massive pyritic ores, and high 
transportation costs to smelter's. Discovery of adequate reserves would 
encourage the establishment of centrally located mills, although anti- 
pollution requirements discourage local smelting. 

Many treatment and marketing problems are encountered by pros- 
pective copper producers in California. Although California is a 
major consumer of copper products, the market for rolled, shaped, or 
alloyed products is now supplied by imports or from secondary sources. 
The nearest copper smelters treating non-company ores and concen- 
trates are at Tacoma (Washington), Anaconda (Montana), Hayden, 
Superior, and Douglas (Arizona). The freight rates to any of these 
plants from California deposits are prohibitive for all but the higher 
grade ores. 

An increasingly serious problem confronting all mining enterprises 
is the reluctance of State and Federal agencies to look favorably on 
any enterprise which might impair the esthetic value of possible 
recreational and scenic areas. Antipollution legislation will continue 
to be important economically in California mining. These factors 
all increase the cost of mining, but none would be prohibitive if re- 
serves of adequate size and grade could be found. 

Selected References 

Albers, J. P., and Robertson, J. F., 1961, Geology and ore deposits of the East 

Shasta copper-zinc district, Shasta County, California: U.S. Geol. Survey Prof. 

Paper 338, 107 p. 
Anderson, C. A., 1931, The geology of the Engels and Superior mines, Plumas 

Gounty, California (with a note on the ore deposits of the Superior mine) : 

California Univ. Dept. Geol. Sci. Bull., v. 20, no. 8, p. 293-330. 
Averill, C. V., 1941, Mineral resources of Trinity County : California Jour. Mines 

and Geology ,v. 37, no. 1, p. 23-24. 
Davis, F. F., 1950, Mines and mineral resources of Alameda County : California 

Jour. Mines and Geology, v. 46, no. 2, p. 279-348. 
Heyl, G. R., 1948, Foothill copper-zinc belt of the Sierra Nevada, California, in 

Copper in California : California Div. Mines Bull. 144, p. 11-29. 
Heyl, G. R., Cox, M. W., and Eric, J. H., 1948, Penn zinc-copper mine. Calaveras 

County, California, in Copper in California: California Div. Mines Bull. 

144, p. 61-84. 
Jenkins, O. P., and others, 1948, Copper in California : California Div. Mines 

Bull. 144, 429 p. 
Knopf, Adolph, 1935, The Plumas County copper belt, California. Copper re- 
sources of the world : "Washington, 16th Internat. Geol. Cong., v. 1. p. 241-245. 
Kinkel, A. R., Jr., Hall. W. E., and Albers, J. P., 1956, Geology and base metal 

deposits of the West Shasta copper-zinc district, Shasta Coimty, California : 

U.S. Geol. Survey Prof. Paper 285, 156 p. 
McMahiOn, A. D., 1965, Copper, a materials survey: U.S. Bur. Mines Inf. Circ. 

8, 225, 340 p. 
Southern Pacific Company, 1964, Minerals for industry, v. 2-3, 449 p. 
U.S. Bureau of Mines, 1910-1931, Mineral resources, copper and state chapters : 

U.S. Bur. Mines. 
, 1932-1964, Minerals Yearbook, state chapters. 



(By G. B. Cleveland, California Division of Mines and Geology, Los Angeles, 

Calif. ) 

Diatomite (Kieselgiilir) is the commercial name for a unique sedi- 
mentary rock called diatomaceous earth. This rock consists almost 
wholly of fine-grained particles of an inert form of silica, similar 
chemically to the mineral opal. The particles range in size generally 
from a few to a few hundred microns; each particle is essentially flat, 
commonly perforated, and all the particles are loosely packed to yield 
a highly porous and permeable material. This combination of prop- 
erties makes diatomite an efficient medium for the rapid filtration of 
industrial solutions. Filtration lias been the principal use of diato- 
mite, and, in 1965, this use accounted for about half of the United 
States production; about one- fourth was consumed as fillers, one- 
twentieth for lieat and sound insulation, and the balance distributed 
among some of the three hundred known uses, such as absorbents, 
lightweight aggregate, pozzolan, abrasives, pesticide carriers, and 


Diatomaceous earth is an accumulation of fossils. The fossils are 
mainly of diatoms, a class of minute plants that live in water; unlike 
most terrestrial plants, they are simple, one-celled form of largely 
floating (plankton) organisms. The shape and ornamentation of 
the diatom shell (frustule), which is the most diverse imaginable, 
is the main basis for separating the many thousands of species knowm. 
Being aquatic, diatoms occur in waters throughout the world, but 
their remains accumulate as diatomaceous earth only in ocean or lake 
basins where ecologic conditions support enormous numbers of indi- 
viduals. Cool, clear, well-lighted water promotes the growth of 
diatoms, but more important is a constant source of chemical nutrients 
to replenish those; taken out of solution during the growth of the 
diatom community. 

The principal lacustrine deposits of the State all lie in volcanic 
terranes, and the common association of volcanic ash with diato- 
maceous earth in both marine and lacustrine strata is well estab- 
lished. Volcanic processes appear to play a significant part in the 
formation of diatomaceous earth, and this relationship can best be 
demonstrated for deposits of lacustrine origin and near-shore deposits 
of marine origin. During volcanic episodes, established drainage 
systems commonly are dammed by lava flows, and new basins may be 
created atop the flows themselves ; these may ultimately fill with water 
and form lakes. Lakes, being infinitely smaller systems than oceans, 
are much more sensitive to slight chemical and physical changes. 
Chemical nutrients essential to diatom growth are not readily sup- 
plied to streams feeding lake watei*s during normal weathering and 
erosion. However, solutions, and emanations accompanying vol- 
canism, and ranging widely in chemical composition and concentra- 
tion, may be introcluced into lake waters, enriching them in those 
elements necessary for diatom growth. Chief among these elements 
is silica which the diatom uses in building its shell. Silica is presumed 
to be supplied both by silica-rich hydrotheraial solutions and by the 
chemical oreakdown of volcanic ash. Ash deposited directly into a 
lake breaks down chemically and provides a ready source of silica, 


while a long-term supply is derived from subaerially deposited ash, 
which is carried by streams into the lake basin during subsequent 
erosion of adjacent highlands. Among the several other elements 
required by diatoms, the concentration of nitrogen and phosphorus is 
considered a limiting factor in diatom growth because of the relative 
paucity of these elements in lake and ocean water. 

Recent work has shown that the volcanic environment is not a req- 
uisite for the fonnation of thick marine diatomaceous sediments. 
Studies indicate that, in the Gulf of California, the concentration of 
silica, and presumably other nutrients, is replenished periodically and 
diatoms flourish. The subsequently formed sediments are of purity 
comparable to those of California's principal commercial diatomite 
deposits. The nature of diatomaceous earth formed in a marine en- 
vironment differs somewhat from that formed in a lacustrine environ- 
ment. Generally, each habitat supports a diatom flora indigenous to 
it, and relatively few diatoms flourish in both marine and lacustrine 
waters. Moreover, marine deposits generally comprise a wider vari- 
ety of species. An individual deposit of either marine or lacustrine 
origin may have an advantage over the other type in certain com- 
mercial applications, but suitable material from both kinds of deposits 
has been successfully processed for all the principal uses. Generally, 
the marine deposits have proven to be a more abundant and versatile 
source of material for a wider range of applications than have those 
of lacustrine origin. 

Diatomaceous earth is light colored, generally gray to white, but 
commonly ivory, pale pink, pale green, yellowish-brown, or dark 
brown. Diatomaceous earth, being composed principally of opaline- 
like silica (Si02*nH20), is a relatively inert rock soluble only in 
strong acids or alkalies. Commonly clay and volcanic ash are main 
impurities, with some silica sand, calcium or magnesium carbonates, 
and iron oxides or iron carbonates present. The pH ranges from about 
4.5 to 8. The natural moisture content is generally high, rangmg 
commonly above 50 percent in commercial deposits. The specific 
gravity of opal ranges from 1.8 to .25. However, because of the poros- 
ity of the individual diatom shell and the degree of compaction, the 
apparent specific gravity of dry unconsolidated diatomaceous earth 
ranges from 0.12 to 0.25, and dry consolidated material has a specific 
gravity of about 0.4. The porosity of commercial diatomaceous earth 
ranges from 75 to 85 percent. The combined water (about 6 percent) 
is driven off between 500° and 800°C and the melting point is reached 
between 1,400° and 1,600°C; however, earths containing certain impu- 
rities may melt well below 1,400°C. Specifications for commercial 
diatomite (largely filter use) emphasize particle-size distribution and 
species of diatoms (shapes and sizes), as well as density and physical 
state, with chemical purity generally a secondary consideration. 

History of Development 

The commercial value of diatomite was not recognized until the 
late 1880's, when a small amount was mined from the deposits at 
Lompoc for building stone; in 1889, production records show that 
39 tons of diatomite were mined from deposits near Calistoga in 
Napa County. During the early 1900's, only a few hundred tons 


were mined annually in California, but the material was being tested 
for several uses, such as heat insulation and refining of beet sugar. 
The latter use bacame the foundation of the modern diatomite in- 
dustry, and filter application has been a prime consideration in the 
evaluation of any diatomaceous earth deposit planned for large scale 
exploitation. The Lompoc deposits were being actively developed 
at the turn of the century, and, beginning in 1904, the deposits in 
Monterey County were developed. At the time of World War I, 
California's annual production had reached about 13,000 tons. 

The diatomite industry developed rapidly after World War I, 
from an important statewide industry to one of national and even 
international significance. The Johns-Manville Corp. gained control 
of a large part of the Lompoc deposits in 1928, and, in 1930, the 
Dicalite Co. opened the extensive deposits in the Palos Verdes Hills 
in Los Angeles County. The industry was consolidated by a few 
large corporations during the 1940's, and, with the stimulus of World 
War II and industrial expansion since then, a steady rise in both 
tonnage and average price has been recorded. The Dicalite Co. ac- 
quired deposits neai- Lompoc in 1942, and in 1944, the company was 
purchased by the Great Lakes Carbon Corp. Mining of diatomite 
in Monterey County ceased in 1942 after nearly $500,000 worth of 
material had been produced. The Palos Verdes Hills deposits were 
alDandoned in 1958, when the Great Lakes Carbon Corp. centered 
all of its production at Lompoc. The Lompoc area since has retained 
and re-enforced its position as the main world source of diatomite. 

Production Factors 

For over 50 years, the United States has been pre-eminent among 
the countries of the world in the mining and processing of diatomite, 
and California yields about 80 percent of the approximately 500,000 
tons mined annually in the United States. About one-quarter of this 
tonnage is exported to over 60 countries. Exports go mainly to 
Europe, but important markets are in the Orient, Australia, and Latin 
America. Diatomaceous earth deposits occur throughout the world, 
but only the largest, best suited and best situated deposits can compete 
in the world market. In recent years this market has expanded and 
undeveloped deposits near the European, Asian and Latin American 
consuming centers have taken on new significance. Deposits have 
been developed or new plants built in France, Mexico, and Yugoslavia, 
and some interest has been shown in developing deposits in Iceland. 
Established sources in Brazil, Denmark, France, Gennany, Italy, and 
elsewhere are all contributing a larger share as well. Most significant 
is the development of the Kussian diatomite industry which is esti- 
mated to yield nearly 350,000 tons annually, making it second only 
to the United States. 

The United States is the largest consumer of diatomite, and Cali- 
fornia supplies the major part of this market, with the balance coming 
from domestic sources, mainly from deposits in Nevada. California 
production during the last several years has maintained a steady in- 
crease in volume and dollar value to meet the increasing demand 
through industrial growth of both the United States and foreign 
countries. The value of diatomite production places this commodity 
among the most important industrial minerals mined in the State. 

67-164 O— 66^pt. I 11 



The annual value in recent years has equaled, that of the combined 
annual values of clay, gold, gypsum, mercury, pumice, and talc. A 
significant demand exists for diatomite in the manufacturing and 
agricultural industries of California, but the principal markets lie in 
central and eastern United States. Although the State possesses 
large and varied resources, several thousand tons of mainly filler grade 
material is brought annually into California from deposits in adjacent 

Occurrences in California 

Although diatomaceous strata are accumulating in modem basins, 
the principal commercial sources of diatomite are from ancient de- 
posits. In California, the oldest marine formation known to contain 

. _... 

I \ j TRINITY ( 

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Regi ons 
1 . Coasta I 

2 . Great Val ley 

3. Modoc Plateau 

4. Chann e I Islands 

5. Desert 

Commerci a I depos i ts 

+ ^ 




us- Minor 

TUOHMNE "';^ONO\ -|- 38* 



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Figure 22. Regional distribution of diatomaceous earth in California. 



diatomaceous earth is the Moreno Formation of Late Cretaceous and 
Paleocene age, and the earliest diatom-bearing lacustrine strata are 
those in the upper part (Miocene) of the Cedarville Series, The 
thickest and purest commercial deposits known in the State were 
formed during late Miocene and early Pliocene times. 

At various times since the Cretaceous Period, diatomaceous earth 
contributed a significant part of the stratigraphic record in California, 
and, although much of the older deposits have been chemically altered 
to dense cherty rocks and great volumes of material have been eroded 
away, California still possesses widespread resources (table 17), As 
shown on figm'e 22, these occur in five geographic regions: Coastal, 
Great Valley, Modoc Plateau, Channel Islands, and Desert, and minor 
occurrences are sparsely scattered elsewhere (fig, 22) . 

Table 17, — Principal formations containing diatomaceous earth in California 

Geologic age 

Formation i and distribution (shown on fig. 22) 



Lacustrine 2 



Unnamed strata in local basins 

eastern Siskiyou County and 

western Modoc County. 
Unnamed strata in Mono basin. 

Long Valley basin (Mono 

County) and Owens basin(*) 

and Indian Wells Valley basin 

(Inyo County). 
Unnamed strata in Knight's Ferry 

area western Tuolumne County; 

may be upper Phocene(*). 
Unnamed strata in southwestern 

sart of Imperial County; may 

be Recent. 
Mohawk Lake Beds (may be 

Pliocene in part). 
Cache Formation (Pliocene or 

Alturas . . 





Unnamed strata at Point Reyes 

western Marin County. 
Unnamed strata in south-central 

Monterey County. 
Purisima - 







Sonoma Volcanics(*) 


Coso (Pliocene or Pleistocene) 

Upper part, Cedarville series 

Unnamed strata in Long Valley 
area eastern Lassen County 
(probably upper Pliocene or 
Pleistocene) . 




Sisquoc (Miocene and Pliocene) 

Monterey (**) 



Modelo .. 

Maricopa (of former usage) 

Salinas (of former usage) 


Pismo (Miocene and Pliocene) 

Round Mountain 

Unnamed strata on San Clemente 

Unnamed strata on Santa Cata- 

Una Island (*). 
Santa Marearita(?) . ... 

Reef Ridge 


Kreyenhagen (Eocene and Oligo- 
cene) (*). 

Markley (Member of Kreyen- 




Upper Creta- 




' Known commercial deposits: major sources (**); minor sources (*). Some formations listed are equiva- 
lents of each other, notably the Monterey Formation and its local designations; some formation names 
are no longer in use but appear in the Uterature. 

2 Numerous diatomaceous earth deposits of the lacustrine type occur throughout the Modoc Plateau 
Region (3). These deposits have not been studied and no geologic age or formation assignment has been 
made; they probably range in age from Miocene to Recent. 


Coastal region 

The coastal counties, from Lake southward to Orange, form a broad 
belt from which nearly all of the diatomite has been produced in Cali- 
fornia. The marine Sisquoc and Monterey Formations have yielded 
b}^ far the greatest tonnages, with minor production from the lacus- 
trine part of the Sonoma Yolcanics. The principal deposits occur 
near Lompoc, in Santa Barbara County ; at Bradley and Monterey, in 
Monterey County; and on the Palos Verdes Peninsula in Los Angeles 
County. Other diatomite deposits occur south of Morro Bay in San 
Luis Obispo County; on the north and south slopes of the Santa 
Monica Mountains and in the Puente Hills, in Ventura and Los An- 
geles Counties ; near Santa Ana and San Juan Capistrano in Orange 
County ; and in southern Napa and Sonoma Comities. 

The Lompoc deposits are believed to be the largest source of diato- 
mite currently being exploited in the world. The diatomite occurs as 
gently folded strata in isolated patches in the northern hills of the 
western Santa Ynez Mountains south of Lompoc, and in the Purisima, 
Casmalia, and Solomon Hills, north of Lompoc. In these areas the 
diatomaceous earth is in the upper part of the Monterey Formation 
and lower part of the Sisquoc Formation, and is many hundreds of feet 
thick. However, most of this contains too much clay and other im- 
purities for industrial use. Only certain selected strata a few feet or 
few tens of feet thick that meet commercial specifications are quarried 
for industrial use. The aggregate thickness of the commercial diato- 
mite may be several hundred feet. 

The two principal companies operating in this area, the Johns- 
Manville Products Corp., which with its predecessors pioneered the 
development of the Lompoc deposits, and the Dicalite Division of 
Great Lakes Carbon Corp., mine from several extensive quarries in the 
hills south of Lompoc. On the north side of the Lompoc Valley, Dia- 
tomic Chemical Co. mines and processes diatomite, mainly for absorb- 
ents. North of the Lompoc Valley, in the Casmalia Hills bituminous 
diatomaceous shale is mined for lightweight aggregate and pozzolan 
by the Airox Co. This material is calcined by simple burning, utiliz- 
ing the natural oil in the rock as a fuel. Numerous other deposits of 
possible commercial grade occur in the Lompoc area but these have 
been mined only intermittently. The Basalt Rock Co., Inc. in recent 
years has mined diatomite from the Sonoma Volcanics of Pliocene 
age in southern Napa Comity. 

Great Valley region 

Thick sequences of diatomaceous earth, that range in age from Late 
Cretaceous through late Miocene occur along the western edge of the 
San Joaquin Valley, from the ]Mount Diablo area in Contra Costa 
County southeastward into Kern County. The main deposits are in 
the Moreno Formation of Late Cretaceous and Paleocene age, 
Kreyenhagen Formation of Eocene and Oligocene age and the prob- 
able northern extensions of the Kreyenhagen, the Markley Member. 
Other sources several hundred feet thick are in the Monterey and Reef 
Ridge Formations of Miocene age. These diatomaceous strata com- 
monly extend for several miles along the west margin of the valley and 
dip gently to steeply east. Locally, the material is light colored and 


nearly pure, but, for the most part, is pale tan to brown and consid- 
erably contaminated with clay. Exploitation of these sources has 
been attempted at various times, but no sustained oi>erations have 
developed nor has any signiticant volume of material been mined. 

Across the valley in the vicinity of Knight's Ferry in southwestern 
Tuolumne County, occurs a relatively pure, nearly white deposit of 
diatomite of lacustrine origin, of Pliocene or Pleistocene age. The 
diatomite layer is at least 15 feet thick. The Pacific Clay Products 
Co. has mined several thousand tons from this deposit in recent years. 

Modoc Pl-ateau 

Numerous deposits of diatomac^ous earth are scattered throughout 
the volcanic terrane of northeastern California. These were formed 
during part of the long volcamc history of this region, which began 
in early Tertiary time and has continued to the Recent. Contrary to 
general belief, the deposits in this region are not all capped by volcanic 
flows ; most of them are exposed at the surface or lie below a thin sedi- 
mentary cover; only some of the better known deposits are intercalated 
with flows. The diatomaceous earth beds range from a few feet to 
a few hundred feet thick, and some deposits occur over tens of square 
miles. The material commonly is brilliant white and relatively pure, 
but many deposits are considerably contaminated with volcanic ash. 

The evolution of the diatom flora in the various lake basins of this 
region bears on the nature of the deposits and on the possible commer- 
cial suitability of the material. The earliest known deposits are of 
Miocene age and are comprised commonly of only one species of 
diatom, Melosira gromalata. This is a thick-walled form that is not 
suitable for filter or many other uses. Subsequently, however, vari- 
ous species of diatoms invaded local basins in this region, and the 
corresponding deposits comprise a more diverse flora. The early 
Pliocene and Pleistocene deposits may have many tens of species rep- 
resented, and this material is better suited for many industrial 

Some of the better known deposits are near Alturas, in Modoc Coun- 
ty ; along Willow Creek near Dorris, in Siskiyou County ; around the 
shores of Lake Britton, and along Hat Creek in Shasta County. Nu- 
merous other localities are known, and many more probable occurrences 
are suggested by geologic maps. The Modoc Plateau region offers the 
best place for locating new sources of diatomite in California. 

Channel Islands region 

The rocks of the eight Channel Islands are for the most part similar 
to those of the adjacent coastal area, and diatomaceous earth is known 
to occur on Santa Catalina, San Clemente, Santa Cruz, and Santa Rosa 
Islands. Marine(?) diatomaceous earth occurs with upper Miocene 
andesite east of Isthmus Cove on Santa Catalina Island; unnamed 
marine strata of middle Miocene age, in part diatomaceous earth, occur 
south of Wilson Cove and at other places on San Clemente Island; 
diatomaceous shales of the Monterey Formation are exposed on Santa 
Rosa and Santa Cruz Islands. Minor production has been recorded 
from the deposit on Santa Catalina Island. 

Desert region 

In the eastern desert of California diatomaceous earth was deposited 
in lakes along an integrated drainage system during Pleistocene time, 


and in a similar but less known system during Pliocene time. The 
diatomaceous earth layers in this region are generally less than 10 
feet thick; the material is off-white in color, and nearly all of the 
deposits are contaminated with volcanic ash. Diatomaceous earth is 
known to occur in several of the Pleistocene basins, of which the prin- 
cipal sources are in Long Valley, Mono County ; Owens Valley, from 
which minor production has been recorded ; and Indian Wells Valley, 
Inyo County. Diatomaceous earth of Pliocene age is intercalated 
with lacustrine rocks in the Coso Range, Inyo County. 

Acknowled gmcnt . — Dr. Paul W. Leppla and Earnest L. Neu of the Great Lakes 
Carbon Corp. kindly provided information and reviewed the manuscript. 

Selected References 

Bramlett, M. N., 1946, The Monterey Formation of California and the origin of 

its siliceous rocks: U.S. Geol. Survey Prof. Paper 212, 57 p. 
Burnett, J. L., and Jennings, C. W., 1962, Geologic map of California, Chico 

sheet : California Div. Mines and Geology, scale 1 : 250,000. 
Calvert, S. E., 1964, The accumulation of diatomaceous silica in the sediments of 

the Gulf of California [abs.] : Los Angeles, Soc. Econ. Paleontologists and 

Mineralogists Ann. Mtg. 
Cleveland, G. B., 1958, Poverty Hills diatomaceous earth deposit, Inyo County. 

California : California Jour. Mines and Geology, v. 54, no. 3, p. 305-316. 
, 1961, Economic geology of the Long Valley diatomaceous earth deposit. 

Mono County, California : California Div. ]Mines and Geology, map sheet 1. 
Dibblee, T. W., Jr.. 1950, Geology of southwestern Santa Barbara County, Cali- 
fornia — Point Arguello, Lomix)C, Point Conception, Los Olivos, and Gaviota 

quadrangles : California Div. Mines Bull. 150, 95 p. 
Gay, T. E., and Aune, Q. A., 1958, Geologic map of California, Alturas sheet ; 

California Div. Mines, scale 1 : 250,000. 
Hanna, G. D., 1927, Cretaceous diatoms from California : California Acad. 

Sci., Occ. Papers 13, 48 p. 
Hart, E. W., 19 , Diatomite, in Mines and mineral resources of Monterey County : 

California Div. Mines and Geology County Rept. (in press). 
Lohman, K. E., 1960, The ubiquitous diatom — A brief survey of the present 

state of knowledge: Am. Jour. Sci., v. 258-A (Bradley Volume), p. 180^191. 
Lydon, P. A., Gay, T. E., and Jennings, C. W., 1960, Geologic map of California, 

Westwood sheet : California Div. Mines, scale 1 : 250,000. 
Oakeshott, G. B., 1957, Diatomite, in Mineral commodities of California : 

California Div. Mines Bull. 176, p. 183-193. 
Olmsted, F. H., 1958, Geologic reconnaissance of San Clemente Island, Califor- 
nia : U.S. Geol. Survey Bull. 1071-B, 68 p. 
Schoellhamer, J. E., and Kinney, D. M., 1953, Geology of a part of Tumey and 

Panoche Hills, Fresno County, California : U.S. Geol. Survey Oil and Gas 

Inv. Map OM-128. 
Woodring, W. P., and Bramlette, M. N., 1950, Geology and paleontology of the 

Santa Maria district, California : U.S. Geol. Survey Prof. Paper 222, 185 i\ 
Woodring, W. P. Bramlette, M. N., and Kew, W. S. W., ]946, Geology and paleon- 
tology of Palos Verdes Hills, California : U.S. Geol. Survey Prof. Paper 207. 

145 p. 


(By F. G. Lesure, U.S. Geological Survey, Washington, D.C.) 

Feldspar has been produced in California nearly continuously since 
prospecting was first reported in 11)09 in Monterey and San Diego 
Counties. More than 70 deposits in 11 counties have been mined or 
prospected, but production from most of these has been small. Total 
production from 1910 through 1963 is probably greater than 600,000 


long tons of feldspar worth a little more than $4,000,000. From 1909 
to 1951 most of the production came from coarse-grained feldspathic 
pegmatites and amounted to nearly 170,000 tons. Yearly production 
ranged from less than 1,000 tons in 1910 and 1911 to nearly 15,000 tons 
in 1928 (Sampson and Tucker, 1931, p. 407; U.S. Bureau of Mines 
Minerals Yearbooks). In 1952 the Del Monte Properties Co. began 
recovering feldspar by flotation methods from beach sand in Monterey 
County. Soon after this the Owens-Illinois Glass Co. also began pro- 
ducing feldspar from an adjacent deposit. Because of this increased 
production from beach sands California has ranked second after North 
Carolina in feldspar production since 1957. 


Feldspar is the general name for a group of aluminum silicate min- 
erals that contain varying amounts of potassimn, sodium, or calcium. 
The feldspars are important rock-fonning minerals and constitute 
nearly 60 percent of many igneous rocks. The principal potassium 
feldspare are orthoclase and microcline which have the same chemical 
composition (KAISisOs) but different cryst^al form. The sodiimi- 
calcium feldspars, called plagioclase, form a complete series of min- 
erals that range in all proportions from pure NaAlSiaOg (albite) to 
pure CaALSiaOs (anorthite) . Natural orthoclase and microcline gen- 
erally contain 10 to 24 percent NaAlSiaOg and plagioclase generally 
contains 5 to 15 percent KAlSisOs- Intergrowths of orthoclase or 
microcline with albite are called perthite, a common pegmatite min- 
eral. The potassium feldspars and the more soda-rich forms of plagio- 
clase are the types generally mined, but calcium-rich feldspar has been 
mined from anorthosite bodies in Los Angeles County (Gay and 
Hoffman, 1954, p. 666). 

Geologic Occtjrrence 

Commercial deposits of feldspar are found in pegmatites, granites 
and related igneous rocks, and beach sands. 

Pegmatites are generally light-colored coarsely crystalline igneous 
rocks, found as lenticular or tabular bodies in metamorphic rocks or 
associated with large granitic intrusions. Individual mineral grains 
range in length from an inch or less to many feet. Feldspar, quartz, 
and mica are the most common minerals present, but many rare and 
unusual minerals are found in some deposits. In many pegmatites 
the minerals are more or less evenly distributed throughout, but in 
others the minerals are segregated into certain layers or parts of the 
body called zones. In some pegmatites these zones can be selectively 
mined to recover the desired minerals by hand sorting and are, there- 
fore, important economically. Until recently most of the feldspar pro- 
duced in the United States was perthite which is commonly concen- 
trated as very large crystals in certain zones in pegmatite bodies. 

Granite and related igneous rocks are composed of one or two kinds 
of alkalic feldspar and quartz and minor amounts of various other 
minerals, mainly muscovite, biotite, hornblende, or rarely pyroxene. 
Deposits range from small masses measured in feet to very large masses 
measured in miles. Grain size ranges from less than one-fourth inch 


to an inch or more. Today, deposits of granite that contain only small 
amounts of ferro-magnesian minerals are mined in bulk and a mixture 
of potassium and sodnnn feldspar is recovered by milling and flotation. 
Beach sands and alluvial deposits rich in feldspar are composed of 
loose sand grains generally less than one-fourth inch in diameter. 
Few deposits are rich enough to be worked and only the deposits of 
Pacific Grove, Monterey County, California, have been worked 

In 1963 about 57 percent of the feldspar used in the United States 
was from flotation concentrates, IT percent was from hand sorting, and 
16 percent was from feldspar-ricli sand (Cooper, 1964, p. 496). In 
1957 these figures were 42, 46, and 12 percent, respectively. 

Economics and Uses 

The average price of crude feldspar was $10.06 per long ton in 
1963 and $9.51 in 1960 (Cooi^er, 1964, p. 495). The average price of 
ground feldspar was $12.28 per short ton in 1963 and $13.40 in 1960. 
From 1956 to 1963 about 55 percent of the feldspar sold in the United 
States was used in glass, 30 percent in pottery, 5 percent in enamel, 
and 10 percent in other ceramic uses, scouring soaps, and abrasives. 
Feldspar is used in glass and ceramics as a flux and to impart strength, 
toughness, and durability to the end product (Castle and Gillson, 1960, 
p. 360) . The glass industry buys feldspar or one of its substitutes as 
total units of alumina (AI2O3) plus potash (K2O) plus soda (NaaO). 
The iron content must be no more than 0.05 percent FcsOa for most 
glass grade feldspar, but amber glass may contain up to 0.50 percent. 
Potassium feldspar is generally preferred in the ceramic industry. 

The United States is self -sufficient in feldspar production capacity. 
There is an mcreasing shortage of high-grade potassium feldspar but 
there is an mcrease in use of lower grade and finer grained materials 
through milling and flotation. For the past 70 yeai^ the United States 
has been the leading producer and user of feldspar; production in 
the last few years has averaged 520,000 long tons a year or about one- 
third world production (Wells, 1965). The largest production comes 
from North Carolina, California, and Comiecticut. Other important 
producing states include Colorado, Georgia, Maine, New Hampshire, 
South Dakota, and Virginia. Much of the high-grade potassium 
feldspar used in California has come from Kingman, Arizona. 

In recent years various materials have been used in the glass and 
ceramic industries as substitutes for feldspar. Chief among these are 
nepheline syenite, aplite, talc, pyrophyllite, and blast furnace slag (de 
Polo, 1960, p. 286). Most nepheline syenites contain too much iron 
oxide for use in glass, but a deposit in Ontario, Canada, that is low 
in iron is mined extensively. Talc has largely replaced feldspar in 
wall tile manufacture in California (Wright, 1957, p. 199) . 

Occurrences in California 

Pegmatites containmg deposits of feldspar are widely distributed 
m the southern part of California (Jahns, 1954, p. 42) but only the 
famous gem-bearing pegmatites of San Diego County have been 


studied in detail (Jahns and Wright, 1951; Hanley, 1951). Feldspar 
deposits are particularly abundant in the Peninsular Range provmce, 
parts of the southern Sierra Nevada, and the Transverse Ranges as 
shown on fig. 23 and listed in table 18. 

More scattered occurrences are also found in the Great Basin and 
Mojave Desert provinces. Larger masses of fuier grained, feldspar- 
rich igneous rock which might be sources of flotation feldspar are 
present but have not been prospected. 

The known deposits or occurrences are listed in table 18 (p. 163). 
Most of these are described briefly by Sampson and Tucker ( 1931) , and 
the larger deposits are described in more detail by Wright (1957) and 
Weber (1963, p. 72-82) . The largest production in the past few years 
has come from the dune sands of Pacific Grove, Monterey County, in 
an area about 6 miles long and 1 mile wide. The sands are composed of 
53 percent quartz, 46 percent feldspar, and less than 1 percent other 
minerals. The largest pegmatite deposit is the Pacific mine, San 
Diego County, which produced 87,000 tons of feldspar from 1921 to 
1943. The only pegmatite deposit worked extensively in recent years, 
however, is the White Butte deposit of San Bernardino County, 
mined by Gladding McBean and Co., 1940-1960. 

Another type of feldspar occurrence that might become important 
has been recently described by Sheppard and Gude (1965), who have 
found that potash feldspar is the major constituent in a fine-grained 
friable tuff, 1.5 to 4 feet thick, in the Barstow Formation of Miocene 
age in the central part of the Mud Hills, 10 miles north of Barstow, 
San Bernardino County. The tuff underlies an area about 1.5 miles 
long and 14 ^^^il^ wide. The material is composed of 87 to 94 percent 
potash feldspar, a few percent analcime and quartz, and trace amounts 
of other minerals. Iron content ranges from 0.1 to 1.76 percent Fe203. 
Although no tests have yet been made, the material may be a potential 
source of potash feldspar for ceramics and glass. 

Future Outlook 

An increasing market for feldspar in California will develop with 
the continued growth of local glass and pottery industries. The State 
has abundant resources of feldspar in zoned pegmatites, feldspar- 
rich granitic rocks, and beach sands, but the feldspar-rich sands of 
the Pacific Grove area are the principal reserves at this time. The 
chief merit of zoned pegmatites lies in the benefits of selective small- 
scale mining confined to a single zone to take full advantage of the 
enrichment of that zone. Small capital investments by individuals 
or partnerships are required to enter pegmatite mining. Although 
most operations are for one mineral, such as feldspar, it is possible to 
obtain several products, that is, feldspar, quartz, and mica. Recent 
studies have increased the general knowledge of the occurrence, origin, 
and economic importance of pegmatite deposits (Cameron and others, 
1949; Jahns, 1955), and studies made during World War II have 
helped improve techniques of prospecting and exploration (Norton 
and Page, 1956). Renewal of pegmatite mining is hindered by the 
low cost of the commodity, the smallness of most known deposits, and 
the lack of custom mills where small operators can sell crude ore 



— •^'»2° 


123' 122- 121. 120- 

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, 5, ^ s I s K 1 1 ■! o\ij/ — >J Yj 

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'TUOLUMNE :.\mon6\ 












.-•MARIPOSy' vJSk 

^^ X J / "■-^- — ^.. 

/6 1^ SAN 

>\mer«^i^--- A.**" r" 









T _ A 



^ 122° 

Production and reserves 
> 50.000 tons 

Production and reserves 

1. 000 to 50.000 tons 


Prospect or occurrence 

^ jKINllS^ 

' jKlNl.^; 

K i 




SAN ■ 

" ! IIIQ ^— \ Bt»krn.tiftl(t 

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rs '^^ 


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I O^J A V E 


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, , r ^— ,'nv'' SAN BERNARDINO "26 •• 

^BARBARA I ■■1>,,_\^S ANOEU-'.S' ^ V 




Figuke23. Feldspar in California (numbers refer to table 18) 

(Wright 1957, p. 199). Recovery of feldspar from granitic rocks is 
not feasible in California -as long as feldspar-rich sands like those at 
Pacific Grove are available. The recent discovery of potash feldspar 
in tuff warrants further investigation. 

Table 18. — Reported feldspar deposits in California 


No. on 
fig. 23 


















Nebicite, Sierra White - 


Unnamed occurrence 

Harrison Stock Farm 

Bardin... ..1 

Jens, Johnson Bros 

Pacific Grove 

Britton Ranch 

Carter, Goodale 

Honora Realty Co., Yokohl Valley 

White King - 

Nine Mile Canyon - 

Pegmatite occurrences.. 


U nnamed occurrence 

White Butte _ 

Unnamed occurrences '_ 


Unnamed occurrences 

Clement and Blackburn 

McKnight Cornishstone 

Unnamed occurrence _ 

White Rock.__ _....._ 

Silica Mining & Products 

Cal ipro ducts , Duncan _ 


Chicago-Pacific, Gates Chemical Co., 
Lambert's Poultry Grits, Stanley Alu- 
mina Silicate, Vail. 

Keystone and Lucky Jim 


Albert Ranch, Brown Ranch, La Borde, 
Morgan Ranch, Patterson Ranch, River- 
side Portland Cement, TuUy, Weir Ranch 
Ensley-Spaulding, K. and K. Ranch, 

Perris Mining Co 


Last Chance 



Coahuila Brave 

Pala district. Spar King 

Lookout, Pearson 


Rincon district 

Bear, Langer 

Mesa Grande district. Powers group. 

Black Canyon 


Hoover, McGinty Mountain 

Spanish Bayonet 

Laguna Junction, White Rose 

Toms Dream 

Buckthorn, Crestline, Gem Spar, Elder 

Pacific mine 



Marden, Walker, Ward and Williams, 

White Butte. 
Dos Cabezas, Moore, Overlook 

EUiot, Red Desert 

Superstition Mountains 

Cargo Muchacho Mountains 

Sampson and Tucker, 1931, pp. 419-420. 
Norman and Stewart, 1951, pp. 99-100. 
Logan and others, 1951, p. 502. 

Sampson and Tucker, 1931, p. 415. 
Sampson and Tucker, 1931, p. 420. 
Wright, 1957, p. 197; Sampson and Tucker, 1931, 

p. 420. 
Messner, 1954, pp. 5-8. 
Sampson and Tucker, 1931, p. 432. 


Tucker and Sampson, 1938, p. 483. 
Wright, 1957, p. 197. 
Dibblee and Chesterman, 1953, p. 32. 
Troxel and Morton, 1962, p. 266. 
Spurck, 1964, p. 75. 

Wright and others, 1953, p. 165; Wright, 1957, p. 197. 
Oesterling and Spurck, 1964, p. 172. 
Sampson and Tucker, 1931, p. 426. 
Spurck, 1964, p. 75. 
Sampson and Tucker, 1931, p. 426. 
Wright and others, 1953, p. 144. 
Oesterling and Spurck, 1964, p. 172. 
Sampson and Tucker, 1931, p. 445. 
Gay and Hoffman, 1954, p. 666. 
Gay and Hoflman, 1954, pp. 525, 665. 
Gay and Hoffman, 1954, p. 665. 
Gay and Hoffman, 1954, pp. 525, 665-666. 

Sampson and Tucker, 1931, p. 426. 
Sampson and Tucker, 131, p. 425. 
Sampson and Tucker, 1931, pp. 420-426. 

Sampson and Tucker, 1931, pp. 422-424. 

Sampson and Tucker, 1931, pp. 424-425. 
Sampson and Tucker, 1931, p. 421. 
Sampson and Tucker, 1931, p. 423. 


Sampson and Tucker, 1931, p. 422. 
Jahns and Wright, 1951, p. 51; Tucker and Reed, 

1939 p. 37 
Tucker and Reed, 1931, pp. 31, 37. 
Weber, 1963, p. 79. 
Hanley, 1951. 
Weber, 1963, pp. 79, 81. 
Weber, 1963, pp. 82-87. 
Weber, 1963, p. 79. 
Sampson and Tucker, 1931, p. 430. 
Weber, 1963, pp. 75, 80. 
Everhart, 1951, p. 114. 
Weber, 1953, p. 80; Sampson and Tucker, 1931, p. 

Weber, 1963, p. 83. 

Weber, 1963, p. 79; Wright, 1957, p. 197. 
Wright, 1957, pp. 196-198; Weber, 1963, pp. 76-78. 
Sampson and Tucker, 1931, p. 431. 
Weber, 1963, p. 84. 
Weber, 1963, pp. 81, 83, 217. 

Sampson and Tucker, 1931, pp. 428-430; Tucker and 

Reed, 1939, p. 11. 
Weber, 1963, p. 80; Sampson and Tucker, 1942, 

Sampson and Tucker, 1942, p. 134. 
Henshaw, 1942, p. 159. 


Seleoteid References 

Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, L. R., 1949, Internal 

structure of granitic pegmatites : Econ. Geology Mon. 2, 115 p. 
Castle, J. E., and Gillson, J. L., 1960, Feldspar, nepheline syenite, and aplite, in 

Industrial minerals and rocks, 3d ed. : Am. Inst. Mining Metall. and Petroleum 

Engineers, New York, p. 339-362. 
Cooper, J. D., 1964, Feldspar, nepheline syenite, and aplite: U.S. Bur. Mines 

Minerals Yearbook 1962, v. 1, p. 495-503. 
de Polo, Taber, 1960, Feldspar, in Mineral facts and problems : U.S. Bur. Mines 

Bull. 585, p. 283-289. 
Dibblee, T. W., Jr., and Chesterman, C. W., 1953, Geology of the Breckenridge 

Mountain quadrangle, California : California Div. Mines Bull. 168, 56 p. 
Everhart, D. L., 1951, Geology of the Cuyamaca Peak quadrangle, San Diego 

County, California, in Oi"ystalline rocks of southwestern California : California 

Div. Mines Bull. 159, p. 51-115. 
Gay, T. E., Jr., and Hoffman, S. R., 1954, Mines and mineral deposits of Los 

Angeles County, California : California Jour. Mines and Geology, v. 50, nos. 

3-4, p. 467-709. 
Hanley, J. B., 1951, Economic geology of the Rincon pegmatites, San Diego 

County, California : California Div. Mines Spec. Rept. 7-B, 24 p. 
Henshaw, P. C, 1942, Geology and mineral deposits of the Cargo Muchacho 

Moimtains, Imperial County, California : California Jour. Mines and Geology, 

V. 38, no. 2, p. 147-196. 
Jahns, R. H., 1954, Pegmatites of southern California, [Pt.] 5 in Chap. 7 of Jahns, 

R. H., ed.. Geology of southern California : California Div. Mines Bull. 170, 

p. 37-50. 
, 1955, The study of pegmatites, in Pt. 2 of Bateman, A. M., ed., Econ. 

Geology 50th Ann. Volume, pt. 2, p. 1,025-1,130. 
Jahns, R. H., and Wright, L. A., 1951, Gem- and lithium-bearing pegmatites of 

the Pala district, San Diego County, California : California Div. Mines Spec. 

Rept. 7-A, 72 p. 
Logan, C. A., Braun, L. T., and Vernon, J. W., 1951, Mines and mineral resources 

of Fresno County, California : California Jour. Mines and Geology, v. 47, no. 3, 

p. 485-552. 
Messner, W. E., 1954, Flotation of Del Monte sand: California Div. Mines, 

Mineral Inf. Service, v. 7, no. 7, p. 5-8. 
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. 
Norton, J. J., and Page, L. R., 1956, Methods used to determine grade and 

reserves of pegmatites : Mining Eng., v. 8, no. 4, p. 401-414. 
Oesterling, W. A., and Spurck, W. H., 1964, Eastern Mojave and Colorado Deserts, 

in Southern Pacific Company, Minerals for industry, southern California, Sum- 
mary of Geological Survey of 1955-1961, v. 3, San Francisco, p. 99-242. 
Sampson, R. J., and Tucker, W.B., 1931, Feldspar, silica, andalusite and kyanite 

deposits of California; California Jour. Mines and Geology, v. 27, no. 3, p. 

Sheppard, R. A., and Gude, A. J., 3d., 1965, Potash feldspar of possible economic 

value in the Barstow Formation, San Bernardino County, California : U.S. 

Geol. Survey Circ. 500, 7 p. 
Spurck, W. H., 1964 Western Mojave Desert, in Southern Pacific Company, Mm- 

erals for industry, southern California, Summary of Geological Survey of 

1955-1961, V. 3, San Francisco, p. 37-97. 
Troxel, B. W., and Morton, P. K., 1962, Mines and mineral resources of Kern 

County, California : California Div. Mines and Geology County Rept. 1, 370 p. 
Tucker, W. B., and Reed, C. H., 1939, Mineral resources of San Diego County, 

California : California Jour. Mines and Geology, v. 35, no. 1, p. 8-55. 
Tucker, W. B., and Sampson, R. J., 1938, Mineral resources of Inyo County: 

California Jour. Mines and Geology, v. 34, no. 4, p. 368-500. 
Weber, F. H., Jr., 1963, Geology and mineral resources of San Diego County, 

California : California Div. Mines and Geology County Rept. 3, 309 p. 
Wells, J. R., 1965, Feldspar, in Mineral facts and problems, 1965 ed. : U.S. Bur. 

Mines Bull. 630, preprint, 7 p. 
Wright, L. A., 1957, Feldspar, in Wright, L.A., ed.. Mineral commodities of Cali- 
fornia : California Div. Mines Bull. 176, p. 195-200. 
Wright, L. A., Stewart, R. M., Gay, T. E., Jr., and Hazenbush, G. C, 1953, Mines 

and mineral deposits of San Bernardino County, California : California Jour. 

Mines and Geology, v. 49, nos. 1-2, p. 49-260. 



(By C. W. Chesterman, California Division of Mines and Geology, 

San Francisco, Calif.) 

Fluorspar is a term applied to a mineral aggregate which is com- 
posed principally of fiuorite and which contains sufficient fluorine to 
be useful in the chemical, metallurgical, and ceramic industries. 

Fiuorite (CaFg) is the only fluorine-bearing mineral of economic 
importance. When pure, it contains 48,7 percent fluorine and 51.3 
percent calcium. Fiuorite has a hardness of 4 on the Mohs' scale, 
compared with 3 for calcite and 7 for quartz, and a specific gravity of 
3.00 to 3.25. It has three perfect cleavages and occurs in many colors 
ranging through dark purple, blue and yellow to white and colorless. 
On the basis of these physical properties, fiuorite can readily be dis- 
tinguished from calcite and quartz with which it is commonly asso- 

The principal use of fluorspar is in the production of hydrofluoric 
acid. An exceedingly pure grade of finely ground (80 to 100 mesh) 
fluorspar, normally containing a minimum of 97 percent CaF2, is com- 
bined with sulfuric acid to form hydrofluoric acid. Hydrofluoric acid 
is used in the production of plastics, fungicides and pesticides, refriger- 
ants, high octane gasoline, and in the manufacture of artificial cryolite 
and aluminum fiuoride which are used in the production of aluminum. 

The metallurgical use of fluorspar in steel production, once the most 
important, is now second in importance. Metallurgical-grade fluor- 
spar should contain at least 85 percent CaF2, and materials analyzing 
below that value are subject to penalties. 

Third in consumption of fluorspar is the ceramic industry, which 
uses finely ground fluorspar in the manufacture of opalescent, opaque 
and colored glasses, earthenware glazes, and opacified enamels. Ce- 
ramic-grade fluorspar must contain at least 85 percent CaFg, less than 
4 percent SiOs, and less than 0.14 percent FejOa. 

Most fluorspar of commercial interest occurs in veins and irregular 
bodies enclosed in sedimentary, metamorphic, or igneous rocks. They 
are replacement deposits and cavity fillings, and have a fiuorite con- 
tent generally ranging from 50 to 95 percent. Fiuorite also occurs 
as a gangue mineral associated with copper, lead and silver ores. 

Agricola (1546, p. 109) was the first to use the name fiuorite because 
the mineral became fluid when heated to high temperatures. The 
fact that fiuorite has low viscosity and the ability to form eutectics 
when in the molten state led to an early use of the mineral in many 
metallurgical processes, especially in steel manufacture. 

The United States production of fluorspar in 1963 was 586,000 
short tons, approximately 80 percent of the domestic consumption. 
Production of fluorspar in the United States has decreased in recent 
years due to competition of foreign imports, especially those from 
Mexico, and has resulted in the closing down of many domestic mines. 
Production of fluorspar in California to date has been less than 1,000 
short tons, and is unable to keep pace with the demands of industry. 

There are many occurrences of fluorspar in California, but those 
deposits from which small quantities have been produced are in Inyo, 
Riverside, and San Bernardino Counties (fig. 24). 




1. Warm Spring Canyon 

2 . Pa 1 en Mount a ins 

3. Little Maria Mountains 

4 . Cave Canyon 

'v 5. Orocopia Mountains 
1 N Y O XS \ 



Figure 24. Fluorspar in California. 

At a deposit en the north slope of Warm Springs Canyon,- Panamint 
Range, Inyo County, fluorspar occurs in veins from 1 foot to 10 feet 
thick that cut Precambrian granite gneiss (Crosby and Hoffman, 
1951, p. 632) The CaFo content of representative samples ranges from 
29 to 65 percent. A small quantity of fluorspar was produced from 
one of the veins; the property has been idle since the 1940's. The 
Palen Momitains, eastern Riverside Comity, contain many veins 
of fluorspar. At one locality near the north end of this range, a 
fluorspar-bearing vein, 5 feet in thickness occurs in monzonite. The 
vein consists of green, white, and purple fluorite in a matrix of mala- 
chite, azurite, calcite, and quartz. A deposit on the east slope of the 


Little Maria Mountains, about 14 miles south of Rice, Riverside 
County, contains several fluorspar-bearing veins from 18 inches to 3 
feet in thickness, and as much as 40 feet in length. These veins occur 
in quartzite and schist. An analysis representative of 130 tons which 
was shipped from the deposit in 1944, showed 87 percent CaFz, 4 per- 
cent Si02, 0.47 percent CaO, 2.25 percent AI2O3, and 0.15 percent 


The largest number of known fluorspar deposits in California is 
in San Bernardino County, but only one area has been p)roductive. 
In the Cave Canyon district near Afton, fluorspar is associated with 
fine-grained andesitic rocks which occur as intrusive bodies and flows. 
The volcanic rocks are fractured and form breccias which, in places, 
contain much coarse crystalline fluorspar. The fluorspar-bearing 
zones of brecciated andesite are irregular and range from 1 foot to 
50 feet in thickness. They are traceable for nearly 2,000 feet on the 
surface. Some fluorspar occurs in veins that range from a few inches 
to 4 feet in thickness. The richer parts of the fluorspar-bearing zones 
locally contain 10 to 40 percent fluorite, but such concentrations are 
small. Both silica and calcite are present, but metallic sulfides are 
lacking. Analysis of representative samples shows a range of 35 to 
86 percent CaFa, 8 to 44 percent SiOg, and 2 to 29 percent CaCOs 
( Burchard, 1933, p. 373-374 ) . 

In 1955, fluorspar was discovered in the Orocopia Mountains, a 
few miles south of Shaver Summit, eastern Riverside Coimty. Here, 
several veins of fluorspar, ranging from a few inches to six feet in 
width, occur in shear and breccia zones in coarse-grained Mesozoic 
quartz monzonite. The veins are parallel and pinch and swell along 
their strike. The largest vein has been prospected intermittently 
along a strike length of 500 feet. Mine-run fluorspar contains over 
91 percent CaFg , and a hand-picked sample was found to contain 
97.83 percent CaF,. The fluorspar meets all specifications for metal- 
lurgical uses, and a small shipment was made early in the spring of 
1955 to the Kaiser Co. at Fontana, California, for use in steel manu- 
facture. The prospect has been inactive since 1956. 

The potential for a substantial fluorspar production in California 
is certainly not indicated by its total production in the State. Al- 
though there are numerous occurrences of fluorspar in California, 
they appear to be in small deposits of several thousand tons or less. 
However, the potential for new discoveries is good, especially in areas 
where there has been limited production and where prospecting and 
exploitation have been on a limited basis only. 

The copper- and fluorite-bearing siliceous veins in the carbonate 
rocks of the Tin Mountain area, Inyo County, the fluorite veins in the 
granitic and metamorphic rocks of the Orocopia and Palen Mountains, 
Riverside County, and the fluorite-sericite replacement veins in the 
Goodsprings (Cambrian to Devonian?) Dolomite in Clark Mountain, 
San Bernardino County, are worthy of further prospecting and ex- 

Selected References 

Agricola. Georg, 1546, De Natura Fossilium : Translated from First Latin Edi- 
tion of 1546 by M. C. and J. A. Bandy : Geol. Soc. America Spec. Paper 63, 1955. 

Burchard, E. F., 1933, Fluorspar deposits in western United States: Am. Inst. 
Mining Metall. Engineers Trans., v. 109, p. 373-374 and 395. 


Chesterman, C. W., 1957, Fluorspar in mineral commodities of California : Cali- 
fornia Div. Mines Bull. 176, p. 201-204. 

Crosby, J. W., and Hoffman, S. R., 1951, Fluorspar in California : California 
Jour. Mines and Geology, v. 47, no. 4, p. 619-638. 

McAllister, J. F., 1952, Rocks and structure of the Quartz Spring area, northern 
Panamint Range, California : California Div. Mines Spec. Rept. 25, p. 36. 


(By D. M. Lemmon, U.S. Geological Survey, Menlo Park, Calif.) 

Garnet constitutes a mineral group of six main gradational species 
that are closely related, having the same isometric crystal habit and 
the same general formula but composed of different combinations of 
the silicates of magnesium, aluminum, iron, calcium, manganese, 
chromium, and rarely titanium. They are hard (range from 6.5 to 
7.5), tough, moderately heavy (sp. gr. 3.5 to 4.2), and without cleav- 
age but with a sharp fracture. 

The principal commercial use is in coated abrasives, formed by 
cementing closely sized grains to paper or cloth. Garnet-coated papers 
and cloth are used primarily in woodworking but also in finishing 
leather, hard rubber, plastics, felt, and the softer metals. Garnet is 
used extensively in finely sized loose grains to grind glass and lenses ; 
a sludge of 25 micron garnet and water was used in an intermediate 
finishing operation in grinding the main mirror of the 120- inch tele- 
scope at Lick Observatory, Mount Hamilton, Calif. (Hill, 1959). 
Garnet is also used in sizes between 17 and 45 mesh for sandblasting 
because it is tougher and heavier than the commonly used silica sand, 
making it a more efficient impact abrasive, and it can be reused. 

Garnet is found in many geologic environments and is geographi- 
cally widespread. Two species are of principal commercial use: (1) 
almandite, Fe3Al2( 8104)3, which occurs in schists and gneisses, and 
(2) andradite, CasFeo (8104)3, found in contact metamorphosed lime- 
stone altered to skarn (tactite), in schist, in serpentine, and in some 
igneous rocks. The chemical compositions given are for pure end 
members, seldom found, for most natural garnets are mixtures and 
are named on the basis of the dominant type. 

Since World War II, ganiet output in the United 8tates has ranged 
from 6,578 short tons in 1949 to 14,626 tons in 1963, valued at $1,412,- 
000. The principal production in 1963, as in many years past, was 
almandite pyrope (Levm, 1960) from a small area in the Adirondack 
Mountains of New York. The remainder of the output came from 
alluvial deposits in Idaho and was used principally for sandblasting 
(Ambrose, 1964) . 

The relatively small United States demand for garnet concentrates 
is amply met by these two states. New York also exports to foreign 
markets ; its product is superior in the world market as well as in the 
United States ( Vogel, 1960) . 

Garnet is widely known in California (Troxel, 1957), especially as 
a gangue mineral in contact metamorphic tungsten deposits. Most of 
the tungsten ores must be finely ground to recover the scheelite, leav- 
ing the garnet in too fine a state to be useful as an impact abrasive. 
However, some tailings from ores treated in World War I in the 
Tungsten Hills west of Bishop, California, were fairly coarsely ground 


to pcass 8 to 14 mesh. Some garnet concentrates were derived from 
these tailings in 1938-40 and marketed for impact abrasives at a price 
of $18 a ton. Small amounts were produced intermittently through 
1955, the last year of recorded output, and several thousand tons were 
shipped in 1954-55 (Calif. Mining Jour., 1954, v. 23, no. 11, p. 16). 

Despite widespread distribution of garnet in California, the outlook 
for production is poor. Although the abrasive quality of the garnet 
in many deposits is unknown, most garnet produced would be too fine 
grained for impact abrasives, and garnet for other uses cannot be 
produced competitively unless markets are large enough to warrant 
expensive processing plants to treat deposits less favorably endowed 
than those of New York. 

Selected References 

Ambrose, P. M., 1964, Abrasives, in Minerals Yearbook 1963 : U.S. Bur. Mines 
Bull., V. 1, p. 191. 

Hill, C. H., Sr., 1959, Grinding the Lick Observatory mirror : Grinding and Finish- 
ing, V. 5, no. 3, p. 26-27. 

Levin, S. B., 1960, Genesis of some Adirondack garnet deposits : Geol. Soc. America 
Bull., v. 61, p. 519-565. 

Troxel, B. W., 1957, Abrasives, in Mineral commodities of California : California 
Div. Mines Bull. 176, p. 23-25. 

Yogel, H. H., 1960, Garnet, in Ladoo, R. B., Abrasives, in Industrial Minerals 
and Rocks, 3d ed. : Am. Inst. Mining Metall. and Petroleum Engineers Trans., 
p. 9-13. 


(By E. B. Gross, California Division of Mines and Geology, San Francisco, 


Gem materials, both precious and semiprecious, include minerals 
and organic substances that are used for personal adornment, orna- 
mental objects, and decorative and special industrial purposes. In- 
dustrial gem materials include inferior grades of diamonds and other 
hard stones which are used for instrument bearings, and cutting tools 
and abrasives. Synthetic gems with compositions identical with natu- 
ral gems are being used in increasing quantities in the industrial ap- 
plications as substitutes for natural gem materials. Synthetic sap- 
phires are used in needle valves, lasers, dielectric wafers, and optical 
instruments. Imitation gem materials which attempt to resemble 
natural or synthetic stones are not considered gem stone commodities. 
Of 135 different substances that have been used for ornamental pur- 
poses, only about 60 mineral species have most of the attributes to 
qualify as gem stones. 

A gem material, to be classified as such, must have certain physical 
and chemical properties, namely : resistance to abrasion, transparency, 
usually high refractivity to light, hardness (preferably 7.5 or greater, 
Mohs' scale), lack of strong parting or cleavage, and absence of in- 
ternal and external flaws. Besides the above characteristics, a gem 
stone must have, above all, beauty of form and color, and be rare. An 
other essential factor for many gem stones is the quality of adapt- 
ability to faceting and polishing. 

Only certain minerals — diamond, corundum (ruby and sapphire), 
chrysoberyl (alexandrite), and beryl (emerald) satisfy most of the 
above characteristics and are customarily considered precious gems. 

67-164 O — 66 — pt. I 12 


Semiprecious inorganic gem stones and organic gem materials (jet, 
amber, and pearl) comprise the bulk of the gem materials. The 
semiprecious gems do not have all the essential attributes of precious 
gems, yet many are desired for personal adornment. Most semi- 
precious gem stones are silicates which include andalusite, benitoite, 
beryl (aquamarine, morganite) golden cordierite (iolite), diopside, 
enstatite, epidote, feldspar, garnet, idocrase, jadeite, lazurite (lapis 
lazuli), nephrite, olivine (peridote), phenacite, rhodonite, scapolite, 
sodalite, sj^hene, spodumene (kmizite), topaz, tourmaline, zircon, and 
zoisite (thulite). Some colored varieties of quartz, such as amethyst, 
rose, citrme, aventurine and rock crystal, are classed as semiprecious 
stones. A few oxides, such as hematite and spinel, and phosphates, 
such as lazulite and turquoise, may be classed as semiprecious, although 
the phosphates generally are soft. Obsidian, although not strictly a 
gem stone, is of commercial importance in California. 

Many of the semiprecious stones are polished in rounded form, 
cabochon, or cut into rectangular or square shapes with few facets 
because of their low refractivity. Gems may be given special treat- 
ment, such as heat or X-ray ludiations, usually to improve the color ; 
the color change may be permanent or temporary depending on method 
of treatment. 

Most gem stones are faceted or polished to increase their beauty 
and value. The various cuts mclude brilliant, baguette, marquise, 
pear shape, step, emerald, and lens cut. The truly precious gems, 
after cutting and polishing, bring very high retail prices depending 
on quality and number of carats (one carat=0.2 grams). Because 
of high duties applied to cut gems, however, most importers ship gems 
in the natural state to the United States ; these subsequently are faceted 
in New York or Los Angeles. Also, gems are cut in England, north- 
ern European countries, India, and Burma. In 1963, the retail value 
of a one-carat diamond ranged from $575 to $1,650. Emeralds have 
the same range of values, because of their rarety. Alexandrites are 
about $400 per carat, while rubies and sapphires vai-y considerably in 
price, depending upon color, adaptability to faceting and polishing, 
and absence of flaws. Their range is between $200 to $800 per carat, 
with ruby commanding the higher price. Semiprecious stones and 
organic gems bring much lower prices, in the range of $5 to $100 
per carat. 

The sales of synthetic gems have not affected those of natural stones, 
except for special industrial uses. These include synthetic diamonds, 
corimdum, and spinel. Synthetic rutile (titania) and (fabulite), a 
strontium titanium oxide, have beauty because of their extreme re- 
fractivity, more brilliance than diamonds, but they lack durability. 
In recent years, emerald has been made in large ciystals synthetically 
by the Chatham process in San Francisco. The synthetic emeralds 
also command higli prices. 

The geologic occurrences of gem stones is varied. Many of the most 
valued gems are primary constituents of igneous rocks. Ultramafic 
rocks occurring in plugs or dikes contain diamonds disseminated 
irregularly throughout the rock. Other gems found in mafic rocks 
are sapphire and ruby, enstatite, olivine, and garnets (pyrope and 
uvarovite) . More acidic igneous rocks contain notably garnet, sphene, 


I'utile, topaz, and zircon. Alkaline igneous rocks occasionally contain 
gem quality garnet, corundum, zircon, and rutile. Pegmatite dikes as- 
sociated with granitic and syenitic igneous bodies include the greatest 
variety of gem stones. They have yielded beryl, chrysoberyl, dan- 
burite, cordierite, sphene, tourmaline, spodumene, topaz, lazulite, 
apatite, and zircon. Many of the best formed gems have been ob- 
tained from miarolitic cavities in pegmatites. The world's best known 
and most productive gem-bearing pegmatites are in Minas Geraes 
province of Brazil. Most emeralds have come from pegmatites in 
Columbia, and sapphires and rubies from deposits in India and Ceylon. 

Metamorphic rocks have produced gem andalusite, lazurite, and 
spinels, ancl contact deposits have yielded apatite, cordierite, corun- 
dum, axinite, idocrase, epidote, and garnet. Nephrite and jadeite 
have formed by hydrothermal processes at the contact of igneous 
rocks with serpentine. Hydrothermal vein deposits have been the 
source for datolite, and various types of quartz (such as amethyst, 
rock crystal, jasper, agate, and citrine), also benitoite, opal, fluorite, 
and topaz. Many of the above minerals are found in gem-bearing 
placers, some of which are richer than the primary deposits. Most 
gem minerals are chemically inert, resistant to abrasion, and thus be- 
come concentrated in residual soils and in heavy stream and beach 

The value of United States production of gem stones has increased 
from $1.2 million in 1960 to $1.4 million in 1964, a small value com- 
pared to imports of $192.5 million in 1960 and $265 million in 1964. 
Nearly 88 percent of the total imports are diamonds, chiefly from 
Africa. Consumption of gems in the United States far exceeds its 

More than 60 gem minerals, mostly semiprecious, are produced com- 
mercially from domestic sources. At present, California and Oregon 
rank first in semiprecious gem stone mining in the United States, each 
producing about 14 percent of the total. For the last few years, the 
semiprecious gems mined in California included jade, obsidian, tour- 
maline, turquoise, jasper, opal, and various minor mineral specimens 
which in value amounted to $200,000 annually. 

The earliest gem collecting in California was by Indians who ob- 
tained tourmaline and turquoise from Riverside and San Diego Coun- 
ties. The first recorded discovery was made by Henry Hamilton in 
1872 at Thomas Momitain in Eiverside County (Wright, 1957) . Tour- 
maline float was noted from a pegmatite dike. In 1892, tourmaline 
was f omid in the Pala district followed by a very rich tounnaline-bear- 
ing pegmatite discovery m 1898 at Mesa Grande. Commercial gem 
mining in California was most active in a pegmatite zone, about 25 
miles long. This comprised three major districts: Pala, at the north- 
west end, Rincon, and Mesa Grande, near the southeast end, all within 
the Peninsular Ranges in San Diego and Riverside Counties (see fig. 
25). Most intensive mining in Mesa Grande area was during 1900- 
1910 and in the Pala area during 1903-1914 (Wright, 1957) . Although 
tourmaline was the chief commodity, other gems such as spodumene 
(kunzite) and gem quality beryl were mined. Incomplete production 
statistics for the three areas indicate a total value of $319,200 for Pala, 
$2,000 for Rincon, and $814,000 for Mesa Grande. 



'^•'" 123- 122= 121- 120- 

"^'TBZ^V-T- ' \ 1^ r ^ r -L "2- EXPLANATION 

^*»?( •^ ) I 11 ' ^ ("'° I GEM STONE MODE OF OCCUItRENCE 

\\5: ; S I s K ifv o\ L' v/SN' \^5 ^' AS"^*"" -----petrified wood, concretions 

nK-h.AMATJ^P<\r--^ 9^"°T™ ' 3. Ben.toite ,ei„ 

I \ jT ^ --• lL ■ { > \ *■ siUcified serpentine 

( IM fAKJ-NIT A ^K r7^7\ 'n 1 — i^""i 5. Corundum vein 

^l._A \M«)U-|S^TA5<NS/ \ I ^\Z141- 6. D..™o„d detrit.l deposits 

Euivkaj^^ \ \ / ou Lt. I I ^ \. '■ Garnet tactite, vein, pegmatite 

/7 1 \l TRINITY "^ /-^ l\^''%. I rT" 

/ 1 \ y ^M J CAsCAbE \ <^ I 9- Jxieite, 

( ^ \ /^ /^"^^ '"t _.^ [,_. \ -y^ : Nephrite - -hvdrot herma 1 replacement, 

I S l\. «;^'"' " V^O u N Va I N6,_j^^^>4ll veins 

\^ , j w^si \ ^*^ .^ ^^ v\^^ ■ 10. Lapis Lazuli-- -metamorphosed limestone 

40'-XL {} r^'^^"*MA^i2^/^ ■■=%,; 11. Obsidian lavaflo.s 

\q'%-. q*' \ -'(•5 Tfl " 12- Opal vein, petrified wood 

\-a'\ \ \ V \S^ ^. % '3. Rhodonite vein 

]■("%. ' AenV /■ BIT&E ,"V' SIERRa~\1 '*' Spodumene pegmatite 

/ \^ ^: j r Q\; \^/ I _tt'~^ * '5* Top'* volcanic rock, pegmatite 

( •^ 0\ 4-.V---ja|4, \,^<5^''3^NEVADa1 ■• '6- Tourmaline pegmatite 

, V O / itiW A*''^r? ^..^^ ' '■• 17.,,'Du-quoise vein 

124- \ ^j^""- ft '!r^'^V^"^''-Q >'■ -t-39° *• Pala district 

\ y . l'^ tSacrarrbcui D# c •'Or •/• C. MesaGrande district 

~^^H.Cy%->\\' 1^\K /TUOLUMNE ■AmU^OV -\~^&' 

VoNTEREV^^^y ,^^^4^0\ -V 12^3,. 

V^LUis Ab-"-""^. \ Yi^\^ ., *«16 ""^l^" 

( -^ "-K KERN \^ • • _ "\ 

r^*''"^H-~--\Z- ^' ifsAN berna'r'dino \ 

? Itg^RBARAj^VxALOSANGELESJ ,'^ • 1 * Y 

^^"-^^^^^XlJl^^^rr^ ^ DESERT y 

34-+ ^ o ^..^■••^^^^^•^^^ ^-^^^'^^v.^--^ r 

121- • ^^V>\°2fVX^'' ° ' ? 

50 100 150 MILES ^X */^ ^ \. X^ / 

' ^ ' ^ V'^^'^^A'^^^ \ 

33"+ 4- \ + I^^'^'^'^'^CtrooghW 

120° 119° 118° f«suiDK<p> .TVJ-- r 


FiGUBE 25. Selected gemstone localities in California. 

Gem minerals have been recovered also from scattered pegmatites 
in Coahuila, Red, and Thomas Mountains in Riverside County. Other 
districts in San Diego Comity have included Ramona, Julian, and 
Aguanga Mountains. Since 1925, most of the mines in the above dis- 
tricts have been idle on a full-time commercial basis, but mterest of 
mineral collectors has remained high, so that part-time operators have 
screened dumps and midertaken sporadic mining in recent years. 

Other gem operations Avithin the State have been minor. Prior to 
1920, an estimated 500 diamonds have been recovered from placer min- 
ing for gold in the westeni foothills of the Sierra Nevada (Murdoch 
and Webb, 1956) . Few of the diamonds exceeded 2 carats. Benitoite 
(BaTiSiaOo), a mineral found in blue crystals, occurs only m San 
Benito County, California, and was actively mined from 1907-1909. 


Since then, few crystals of gem quality have been found. Chrysoprase, 
a green variety of chalcedony, was found in 1878 near Visalia, Tulare 
County. Other occurrences of chrysoprase in veins were developed in 
Tulare County and were exploited between 1878 and 1911. Massive 
idocrase ( calif ornite) was mined near Happy Camp, Siskiyou County, 
from 1900 to 1911. Since then, mineral collectors have obtained small 
quantities from the deposits. Jadeite and nephrite have been mined 
sporadically in many small deposits since 1930 m the Coast Ranges, 
chiefly in Monterey, Marin, Mendocino, San Benito, and San Luis 
Obispo Counties (Crippen, 1951; Yoder and Chesterman, 1951; and 
Chesterman, 1951 ) . More recently, 1963, nephrite-j ade has been found 
m Mariposa County. All occurrences are in veins, lenses, or pods asso- 
ciated with serpentine. 

Gem quartz crystal occurrences are known in Amador, Inyo, Lake, 
Mariposa, and Tulare Counties. Only two turquoise deposits have 
been developed, these for a brief time (1903-1909) in San Bernardino 
County. Miscellaneous gem materials such as obsidian, agate, jasper, 
rhodonite, opal, and other materials useful for lapidary work have 
been collected in recent years, but large-scale mining of gem stones has 
been inactive for years. 

California will contmue to rank high among the States in production 
of semiprecious gem stones. However, most new discoveries will be 
found by mmeral collector and prospectors. Possible sources include 
pegmatites from both the Penmsular Ranges and from scattered dikes 
along the western foothills of the Sierra Nevada. Contact meta- 
morphic bodies of the SieiTas might yield gem quality epidote, garnet, 
sphene, and spinel. Nephrite-j ade, some of good cutting and polish- 
ing quality has been found in Mariposa County. Other deposits might 
be exposed under similar geologic conditions elsewhere in the State. 
Jade (jadeite and nephrite) potential is still promising in the Sierra 
Nevada and Coast Ranges, where serpentine is abmidant. Desert 
areas of southeastern California are possible locations for new agate 
and turquoise occurrences. 

Selected References 

Chesterman, C. W., 1951, Nephrite in Marin County, California : California Div. 
Mines, Spec. Rept. lOB, p. 1-11. 

Crippen, R. A., 1951, Nephrite jade and associated rocks of the Cape San Martin 
Region, Monterey County, California : California Div. Mines Spec. Rept. 
lOA, p. 1-14. 

Hanley, J. B., 1951, Economic geology of the Rincon pegmatites, San Diego 
County, California : California Div. Mines Spec. Rept. 7B, p. 1-24. 

Jahns, R. H., and Wright, L. A., 1951, Gem and lithium-bearing pegmatites of 
the Pala District, San Diego County, California : California Div. Mines Spec. 
Rept. 7A, p. 1-71. 

Jahns, R. H., 1960, Gem stones and allied materials, in Industrial Minerals 
and Rocks : Am. Inst. Mining Metall. Engineers, p. 383--441. 

Kunz, G. F., 1905, Gems, jewelers' materials, and ornamental stones of Cali- 
fornia : California Mining Bur., Bull. 37, p. 1-171. 

Murdock, J. and "Webb, R. W., 1956, in Minerals of California. California Div. 
Mines, Bull. 173, p. 452. 

Schlegel, D. M., 1957, Gem stones of the United States : U.S. Geol. Survey Bull. 
1042G, p. 203-251. 

U.S. Bureau of Mines, 1965, Commodity data summaries, p. 56-57. 

Wright, L. A., 1957, Gem stones, in Mineral commodities of California : Cali- 
fornia Div. Mines Bull. 176, p. 205-214. 

Yoder, H. S., and Chesterman, C. W., 1951, Jadeite of San Benito County, Cali- 
fornia : CalifjOrnia Div. Mines Spec. Rept. IOC, p. 1-8. 



(By D. E. White, U.S. Geological Survey, Menlo Park, Calif., and J. R. McNitt, 
California Division of Mines and Geology, San Francisco, Calif. ) 


Geothermal energy, or the natural heat of the earth, is useful in 
generating electricity and for space heating. Total world utilization 
of geothermal energy is roughly equivalent to 1 million kw, which is 
small in comparison to the major sources of energy. The first steam 
well for power w^as drilled in Larderello, Italy, in 1904; present Italian 
production capacity is about 350,000 kw. No major interest was 
shown by other countries until the 1950's when New Zealand first 
demonstrated that very hot water tapped at depth (rather than 
steam) can yield steam of adequate quality and quantity to be com- 
mercially attractive. As the hot w^ater flows into and up the well and 
pressure decreases, some water flashes into steam and both water and 
steam erupt to the surface like a continuously erupting geyser. Pro- 
duction capacity in New Zealand in 1965 is 182,000 kw. 

The Geysers steam field in California, the only commercially pro- 
ductive area in the United States (1965), first attracted interest in the 
1920's; exploration proved that natural steam without liquid water 
could be produced from wells drilled a few hundred feet deep. The 
steam was similar in temperature and pressure to that of Larderello, 
but the commercial climate was not then sufficiently favorable. In 
1955 exploration was again undertaken, eventually resulting in suc- 
cessful generation of power by 1960 ; a second-stage unit was installed 
in 1962 and construction of a third stage is underway in 1965; wdien 
completed, total capacity will be 51,000 kw. Actual production of 
power by year is shown in table 20. 

Within the United States, California leads all other states in areas 
explored (15 of total of about 30; see table 19). In addition to The 
Geysers, two other very promising areas in California are the Salton 
Sea and Casa Diablo. 

Engineering aspects of geothermal energy are summarized by 
Smith (1964) and economic aspects by Kaufman (1964). The pro- 
ceedings of the Ignited Nations Conference on New Sources of Energy, 
Rome, 1961 (see citation for Smith, 1964) contains a large variety 
of papers on general principles and individual areas of the world. 

Geologic Occurrence 

The earth is a tremendous reservoir of thermal energy, most of 
which is too deeply buried or too diffuse to consider as recoverable 
energy. In general, temperatures increase with depth: the average 
is approximately 1° C. per 160 feet of depth or 1° F. per 100 feet. 
Commercial geothermal areas occur where the rate of temperature 
increase is at least 2 times the "normal" rate, and 5 to 10 times 
"normal" averaged over hundreds or several thousands of feet in depth 
is much more favorable. Two important factors determine the eco- 
nomic potential of a geothermal area: temperature, and an adequate 
supply of water or steam. Except in very porous rocks, most of the 
energy of a geothermal reservoir is stored in the solid rocks rather 


than in water or steam in the pore spaces, as commonly supposed 
("\Vliite, 1965) . The supply of water or steam must be large enough, 
eitlier within the reserv^oir, or by access of water from outside the reser- 
voir, to maintain a necessary rate of production for some minimum 
time (large enough and long enough to pay a profit for the 
investment) . 

Geot hernial reservoirs can be classified into two types: (a) those 
with permeable extensions to the surface, permitting escape of thermal 
fluids as hot springs and fumaroles; and (b) deep insulated reser- 
voirs with capping rocks of low permeability and little or no surface 
expression. Gradations exist between extremes of the two types. 

Keservoirs related to hot springs are characterized by high near- 
surface permeabilities, at least locally on faults and fractures, per- 
mitting water, steam, and contained heat to escape. Many hot sprmgs 
discharge heat at rates of ten to hundreds of times the "normal" 
heat flow of the earth for equal areas. The Upper (Old Faithful) 
Geyser Basin of Yellowstone Park is a familiar example. Its esti- 
mated heat flow from 1 sq. mi. is about 600 times that of an equal 
area of "normal'' crust of the earth (White, 1965). Temperatures 
near the surface are very high because of the upward transfer of 
enormous quantities of heat in the escaping water and steam — about 
90 x 10*^ cal per sec. One important consequence of a convection 
svstem of circulating fluids, with vigorous leakage of heat, is that 
tne lower part of the system is cooled by inflowing cooler water; 
temperatures deep in the system are therefore cooler than would 
otherwise exist. 

Deep reservoirs with little or no surface expression require a perme- 
able reservoir rock overlain by impermeable rock such as shale that 
provides insulation and also inhibits convection loss of fluids and heat. 
At Larderello, Italy, exploration was first focused near feeble nat- 
ural springs, which were leakages from the system. Other reservoirs 
have since been found with no surface expression other than high 
rates of temperature increase with depth. The Salton Sea geothermal 
area in California is an example of a deep insulated reservoir with 
very meager natural leakage. 

Most geothermal systems are dominated by liquid water, coimnonly 
much above 100° C (212° F) because of the high existing pressures. 
In such systems, steam can form by boiling near the surface, as the 
hot water rises and pressure decreases sufficiently. In a very few 
explored systems (Larderello and nearby areas of Italy and The Gey- 
sers, California), the heat supply is so high and the rate of flow of 
fluids through the system so low that the available water is converted to 
steam, even where pressures exceed 300 pounds per square inch. Ex- 
perience is showing that these dry steam systems are rare and that 
extensive utilization of geothermal energy must depend largely upon 
steam that can be "flashed" from hot waiter with release of pressure. 

Occurrences in California 

The known hot spring areas of California are shown in figure 26 
(modified from Stearns, Stearns, and Waring, 1937, plate 15). 

Fifteen areas have been explored for geothermal energy (table 19 
and figure 26). Three areas of particular interest are described 
briefly below : 






1 Explored for geothermal encrgv 
T Numbers keyed to table 

80 C t o boi 1 ing 

20 to 80 °C 

tENN / BL-ftTE y siggRj^ 

Qi I / "i I ^^'^ ;. 

.-^•U: \ V0L0\-i-A'EL DORa'dO,- N^.. 







TUOLUMNE 1\i»(Jno\ -|- 3 


t'^X ..,0^^ 

/..__ „ , 





»NT*C • >\MERe<9 

sAfi-A ^- 

'1 xV'-FRESNCf 

\pENITCf|\-7 ,y\ 

— X 

Bishop 'v 



> ^\. 

I N Y O ^ \ 







N/IOJA-VE -|^\35° 




150 MILES 







-\- ) SAN DIEGCf 

118° ?*s«i<T)i»e" 

»*SU< Bi' 



JSAUTON \ -=,33° 




Modified from Stearns, Stearns, 
and waring, 1937, plate 15 

FIGURE 26. Thermal springs of California, showing localities that have been 
drilled for geothermal energy (numbers refer to table 19) . 

The Geysei-s, Sonoma Coimty, California (McNitt, 1963), and re- 
lated areas (table 19) occur along a five-mile length of a northwest- 
trending and steeply dipping fault zone. Three areas are being 
developed, including The Geysers, Sulphur Bank, one mile to the 
Avest, and The Little Geysers, four miles to the southeast. Upper 
Tertiar}' volcanic rocks lie to the south and east of The Geysers, and 
the Clear Lake volcanic field of Quaternary age is less than 20 miles 
to the northeast . However, the geothermal zone is underlain by almost 
impermeable sandstone, basalt, and serpentinite of the Jurassic and 
Cretaceous Franciscan Formation. 






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Dry steam is obtained by drilling wells into the fault zone. The 
wells range from several hundred to 5,000 feet deep. Static wellhead 
pressures range from 100 to 500 pounds per square inch and seem to 
reflect the hydrostatic pressure and thickness of a groundwater cover 
overlying the steam (McNitt, 1963). Measured flow rates from in- 
dividual wells range from 15,000 Ib/hr at 78 psi to 184,000 Ib/hr at 
120 psi. The heat content of the steam averagas about 1,200 Btu per 
pound (670 cal per gm). Power production since 1960 is listed in 
table 20. 

Table 20. — Production of electricity in kilowatt-hours. The Geysers Poicer Plant, 
Pacific Gas & Electric Co., Sonoma County, California (excluding station uses; 
data from A. W. Bruce, Pacific Gas d Electric Co.. 1965) 

Year: Production 

1960 33, 576, 944 

1961 94, 019, 840 

1962 100. 461, 120 

1963 167, 9.52, 960 

19&4 203, 790, 080 

In the Salton Sea area, very saline brine was discovered in reservoir 
rocks below a capping of fine-grained sediments. Details of tempera- 
tures and production capacity have not been released for publication. 
Temperatures of 270°C to 370°C are indicated near 5,000 feet (White, 
1965). The exploration wells have all produced at rates that are 
qualitatively impressive; they are distributed through an area at least 
6 miles long and 2 miles wide adjacent to Salton Sea. Published geo- 
physical data (summarized in McNitt, 1963, fig. 14) suggest that an 
almost equal area extends out under the sea. 

The brine has a salinity of about 30 percent, consisting dominantly 
of sodium, calcium, and chloride but with very high contents of potas- 
sium, iron, manganese, zinc, lead, copper, silver, and other rare 
elements. Economic interest is focused about equally on the energy 
and potassium contents of the brine. Other by-products of value, 
such as lithium, silver, and other metals, may also be recoverable. 

The Casa Diablo area is in the large structural depression of Jjong 
Valley, which may be related to extensive volcanic activity during the 
past million years (McNitt, 1963; Wliite, 1965). Porous and perme- 
able volcanic tuffs and breccias are probably interstratified at depth 
with lava flows; in some respects this area is comparable to Wairakei, 
New Zealand. Ten wells have been drilled in less than 2 square miles, 
and most of these have produced satisfactorily. 

Problems That Threaten Broad Utilization 

The presence of reservoirs sufficiently high in temperature and in 
supply of natural fluids must first be proved by exploration. Hot 
water areas are likely to be the most abundant but rapidly cooled water 
may deposit either CaCOs or Si02 in wells and treatment plant ; other 
chemical substances, such as boron, arsenic, and salts may constitute 
effluent problems that require treatment or subsurface disposal. In 
addition, geothermal exploration is not adequately covered by existing 
state and federal laws; unsympathetic treatment can easily discourage 
the development of a promising new natural resource. 


Appraisal of Regions 

The appraisal of a region must be based on rates of temperature in- 
crease that are likely to occur with depth, and the probability of 
finding adequate reservoir rocks that will yield natural fluids to 
wells in required quantities. We have adequate temperature -depth 
data only from sedimentary basins that have been explored for oil 
and gas. Most of these are characterized by nearly "normal" rates 
of increase rather than the abnormally high rates demanded for geo- 
thermal energy. The Salt on Trough (fig. 26) is one outstanding 
exception, and moderately high temperatures have also been reported 
locally in the Transverse Ranges and the Great Valley. 

In other regions of the state, data on geothermal gradients and con- 
ducted heat flow are very inadequate. We can hypothesize that ther- 
mal springs are abundant where heat flow is high and permeable struc- 
tures permit water to circulate deeply. Other regions may lack ther- 
mal springs because their average heat flow is too low. A combination 
of these factors probably explains the scarcity of thermal springs in 
the Sierra Nevada, the Klamath Mountains, and most of the Cali- 
fornia Coast Ranges. 

The required heat sources are most likely to occur in regions of 
Pliocene and Quaternaiy volcanism. The clusters of thermal springs 
associated with Quaternary volcanic extrusions near Mono Lake, 
Mount Lassen, Modoc County, Lake County, southern Inyo Comity, 
and Salton Sea attest to the importance of volcanism in supplying 
abnormally high rates of heat flow. 

The most favorable regions in California are the Salton Trough, 
the California segments of the Modoc Plateau and Great Basin; and 
local parts of the California Coast Ranges and the Southern Cascade 

Selected References 

Kaufman, Alvin, 1964, Economic appraisal of geothermal i)Ower: Mining Eng., 
Sept. 1964. p. 62-66. 

McNitt, J. R., 1963, Exploration and development of geothermal power in Cali- 
fornia : California Div. Mines and Geology, Spec. Rept. 75, 45 p. 

Smith, J. H., 1964, Harnessing of geothermal energy and geothermal electricity 
production : United Nations Conf. New Sources Energy, Rome, 1961, Proc., 
v. 3, p. 3-59. 

Stearns, N. D., Stearns, H. T., and Waring, G. A., 1937, Thermal springs in the 
Unitetl States: U.S. Geol. Survey Water-Supply Paper 679-B. 206 p. 

White, D. E., 1955, Violent mud-volcano eruption of Lake C>tv hot springs, 
northeastern California : Geol. Soc. America Bull., v. 66, p. 1109-1130. 

, 1965, Geothermal energy : U.S. Geol. Survey Oirc. 5ly. 

White, D. E. and Roberson, C. E., 1962, Sulphur Bank, a major hot-spring quick- 
silver deposit, in Petrologic Studies — A Volume in honor of A. F. Buddington : 
Geol. Soc. America, p. 397-428. 


(By W. B. Clark, California Division of Mines and Geology, Sacramento, Calif). 

Of the various properties that, give gold an outstanding place in 
the world of metals, the most important are resistance to cori'osion, 
reflectivity, malleability, and high specific gravity. Man has used 
gold as a medium of exchange and in ornaments and the arts since 


prehistoric times. The principal use at present continues to be in 
monetary systems or in coinage. Federal controls closely regulate 
the ownership and distribution of gold, except for gold in the natural 
state. Although it is illegal to possess gold coins other than as curios 
in the United States, they are minted and circulate freely in a number 
of other countries. Considerable amounts are used in jewelry and 
the decorative arts, including watch cases, rings, gold leaf, gilding, 
gold plating and decorative finishes on ceramics and other materials. 
The growth of these uses has paralleled the growth in population 
and gross national product. Substantial amounts are used in dentistry 
and lesser amounts in the chemical industry and glass making. The 
development of new scientific devices and instrumentation has been 
reflected in increasing uses of gold. 

To many persons, gold is California's best-known metal. It was 
the principal attraction to the early-day pioneers and stimulated the 
State's growth for many years. 

In California, the principal primary deposits are mesothermal gold- 
quartz veins that are associated with the intrusion of granitic bodies 
and occur either in slates, schists, and greenstones that have been 
intruded by the granitic bodies, or in the granitic rocks themselves. 
The veins range from a fraction of an inch to tens of feet in thickness; 
many deposits consist of a series of parallel of branching quartz 
stringers separated by slabs of country rock. 

In a typical deposit, the gold occurs as microscopic grains, plates, 
or threads in the quartz and is commonly associated with varying 
amounts of pyrite and small amounts of other sulfides; gold associated 
with tellurides has been found, the most notable occuiTences being 
at Carson Hill. The extent of the ore shoots varies greatly. Many 
extend to depths of only a few hundred feet; in others, such as the 
veins at Grass Valley or in the Mother Lode, the deposits extend to 
inclined depths of 5,000 to 10,000 feet. 

Massive or vein-like replacement deposits of pyrite that contain cop- 
per and zinc also contain some gold and silver. Also, the iron oxide- 
rich gossans that cap such deposits have yielded substantial amounts of 
gold. The most important deposits have been in the Shasta and Sierra 
Nevada Foothill copper-zinc belts and the Plumas County copper 
belt. Gold is a constituent of lead-zinc and lead-silver replacement 
deposits in the Great Basin. It is a minor constituent of contact 
metamorphic tungsten and copper ores in the Sierra Nevada and of a 
few mercury deposits in the Coast Ranges. 

A number of important epithermal gold deposits are found in Cali- 
fornia, the most productiA^e being the Bodie, Mojave, and Rand dis- 
tricts. These deposits consist of gold-bearing zones of alteration and 
silicification in igneous or metamorphic rocks. The ore commonly 
consists of silicified breccia containing fine free gold and disseminated 
sulfides. The zones of alteration often are extensive and usually have 
a bleached appearance. In a few deposits, the gold is associated with 

Because of its high specific gravity and resistance to weathering, 
gold is easily concentrated in placer deposits; vast amounts have been 
recovered from California's placers. All of the streams that flow 
through the gold-bearing regions have been productive. The gold 


particles are flat or rounded and range from microscopic size "flour 
gold" to nuggets 100 or more ounces in weight. Many large nuggets 
have been found in California, especially in Alleghany, Columbia, 
Downieville, Magalia, and Sierra City districts. The gold particles 
are everywhere associated with black sands composed of magnetite and 
smaller amounts of ilmenite, chromite, zircon, garnet, pyrite, and in 
some places platinum. 

The placer deposits in California range from early Tertiary to 
Recent in age. The Recent placers are in and adjacent to the present 
streams; the older gravels are on terraces adjacent to the present 
channels or high on the interstream ridges. The extensive older 
Tertiary channels in the northern and central Sierra Nevada have 
been preserved by a thick cover of volcanic rock. They are charac- 
terized by abundant quartz pebbles and cobbles and in places by coarse 
nuggets.* There are dry desert placers in several areas in southeastern 
California. In these deposits, small rounded grains of gold are found 
in loose sand. Gold, usually in very fine grains, has been recovered 
from placers on some of the beaches along the coast. 

Gold was first recovered in California some time between 1775 and 
1780 on the lower Colorado River. These early operations were on a 
small scale and lasted only a few years. They extended west and north 
into the Cargo Muchacho and Picacho districts. Later in the 1820's, 
1830's, and 1840's, placer gold was recovered near San Diego and in 
the San Gabriel Mountains. None of these early operations had much 
significance in the development of the State. On Januaiy 24, 1848, 
James W. Marshall made his historic discovery at Sutter's Mill at 
Colma on the American River. Soon afterward, the gold rush was in 
full sway as thousands of gold seekers poured into California. Gold 
also was discovered in the Trinity River by Pearson B. Reading in 
1848. In a few short years, most of the State had been explored, and 
many areas had been permanently settled. California's gold rush had 
a profound influence on the entire western United States and many 
parts of the world. 

The flush production of the first few years of the gold rush was 
from rich and virgin surface placers. In 1851, the State's output 
attained an all-time high of almost 4 million ounces valued at 81.2 
million dollars. As the rich surface placers declined in the middle 
and late 1850's, river mining and then hydraulic mining became the 
chief gold sources. 

As a result of hydraulic mining, which was first done in 1852 near 
Nevada City, Nevada County and at Yankee Jim's in Placer County, 
large quantities of evacuated material w^as allowed to flow into the 
rivers, and was alleged to cause flooding and silting of farmlands 
downstream. This eventually led to litigation between farmers and 
the hydraulic miners. In a famous court case in 1884 (Woodruff vs. 
North Bloomfield Gravel Mining Co. (16 Fed. Rep. 25)), Judge 
Lorenzo Sawyer issued an injunction prohibiting the dumping of 
debris into the Sacramento and San Joaquin Rivers and their trib- 
utaries. Injunctions against other mines followed. A few mines 
constructed tailings dams or reservoirs and continued to operate for a 
few years. For a short time, drift mining of buried gravel channels 
partly made up for the loss of placer gold production from hydraulic 



In 1876, rich ^old-bearino; deposits Avere discovered at Bodie in 
Mono County. The rush to tliat district continued until about 1888. 
In 1893, the discovery of "cold in Goler Gulch in the El Paso Moun- 
tains in eastern Kern County led to the discovery and the resulting 
rush to the nearby Band district. Other productive southern Cali- 
fornia districts of the 1890's and early lOOO's were the Cargo Muchaco, 
Stedman, Picacho, and Mojave districts. 

During these years, great improvements were made in mining and 
milling methods and equipment which enabled many more lode de- 
posits, especially larger but low-grade ores, to be profitably mined. 
The first successful bucket-line dredge was started on the Feather 
River near Oroville in 1898. Gold dredging soon became a major 
industry that has continued for more than 65 years. 

The general prosperity, that began during World War I and con- 
tinued through the 1920's, witli accompanying high costs, caused a 
significant decrease in gold production in California. In 1930, out- 
put started to rise because of the depression and resulting low operat- 
ing costs. This rise was accelerated in 1934 when the price of gold 
was increased from $20.67 to $35 per fine ounce. Many mines were 
reopened, and there was much exploration which resulted in significant 
discoveries. Thousands of miners were employed in the quartz mines 
at Grass Valley, Nevada City, Alleghany, Jackson, Jamestown, Sutter 
Creek, and Mojave. There were many active bucket-line dredges, 
and dragline dredges became important gold sources. In 1940, gold 
production amounted to 1,455,000 fine ounces valued at nearly $51 
million, the highest figures since the gold rush. Most of the major 
events are graphically recorded in figure 27. 

J81 .2 MILL ION 











850 1860 1870 1880 1890 

1900 1910 1920 1930 1940 1950 1960 1964 1970 

Figure 27. California's gold production. 


World War II caused a precipitous drop in gold production. War 
Production Board Limitation Order L-208 was issued in 1942 and 
caused the gold mines to be shut down. Order L-208 was lifted in 
1945. Some of the dredges resumed operations, and some of the 
major lode mines in Grass Valley, Alleghany, and Sutter Creek were 
reopened. Gold production increased slightly for 4 yeai*s. However, 
in 1950, production resmned its decline because of rising costs and 
d.epletion of dredging ground. This trend was accelerated by the 
Korean War. The last large mine on the Mother Lode shut down in 
1953. Tlie large mines at Grass Valley shut down in 1956, ending a 
major industiy that had lasted 106 years. The last dredge in the 
Folsom district was shut down in 1962, ending more than 60 years of 
operations. The mines at Alleghany, the last active quartz-mining 
district, have recently curtailed operations or shut down, and the 
dredges at Hammonton, the last major dredging field have gradually 
curtailed operations. 

Since 1848, California has yielded more than 106 million fine ounces 
of gold, valued at 2.42 billion dollars. These figures are far greater 
than those for any other State and represent about 35 percent of the 
total United States production. In 1964, California's gold produc- 
tion amounted to Yl,028 fine ounces valued at $2,485,980 which placed 
it fifth among the States in output. Much of this production came 
from the three active bucket-line dredges in the Hammonton district 
of Yuba County. Some gold was produced from a few small lode 
mines in the Sierra Nevada and Klamath Mountains. In addition, 
gold was produced from small-scale placer-mining operations, in- 
cluding a few dragline dredges, prospectors, skin divers, and "snipers." 
Some gold was recovered as a byproduct in sand and gravel plants 
along the east margin of the Great Valley and from tungsten and lead- 
zinc mines in eastern and southeastern California. 

Most of California's gold production has come from five geomorphic 
provinces: The Sierra Nevada, which has been by far the most pro- 
ductive, Klamath Mountains, Great Valley, Great Basin, and Mojave 
Desert. Lesser amomits liave been recovered in the Transverse 
Ranges, Peninsular Ranges, and Modoc Plateau, and small amounts 
in the Coast Ranges. The distribution of gold-bearing areas is shown 
in figure 28. 

The Sierra Nevada, the dominant mountain range in California, has 
been the source of the bulk of the State's gold output and contains the 
largest number of and most productive gold districts. Most of the 
primary deposits are associated with intrusions of the granitic rocks 
of the great Sierran batholith. The gold-bearing veins occur for the 
most part in the belt of metamorphic rocks that extends along the 
western slope of the northern half of the range, along the western 
foothills, and in granitic stocks that are branches of the main batholith. 

In the northern part of the range lie such rich and famous districts 
as the Alleghany, Sierra City, Nevada City, and Grass Valley. The 
Mother Lode belt lies to the southeast extending from El Dorado to 
Mariposa County. It is a system of linked or en echelon gold-quartz 
veins and mineralized schist and greenstone that extends from George- 
town and Greenwood southeast to Mariposa, a distance of 120 miles. 

The placer deposits of the western Sierra Nevada have yielded vast 
quantities of gold; some estimates have placed it to be more than 40 






Go Id -bear ing area 
Lode gold d istr ict 

Placer gold district 

Dradiing field 


Figure 28. Gold-bearing areas in California. 

percent of the State's total output. They are divisible into the older 
or Tertiary deposits which are on the interstream ridges, and Quater- 
nary or younger deposits that are found in and adjacent to the present 
streams. The Tertiary deposits have been mined chiefly by hydraul- 
icking and drift mining and the Quaternary deposits by dredging and 
various small-scale placer methods. The gold in the dredge fields 
along the east margin of the Valley was derived from the Sierra 
Nevada while that from the northern end of the Valley was derived 
from the Klamath Mountains. 

The Klamath Mountains have been the second most productive area. 


Here, the largest sources of gold have been the placer deposits of the 
Klamath-Trinity-Salmon River system and tributaries to the upper 
Sacramento River. Not only has gold been recovered from the present 
stream channels but also from adjacent older terrace and bench gravel 
deposits. Lode-gold deposits are found throughout the province, but 
the most productive have been the French Gulch, Liberty, and Harri- 
son Gulch districts. The gold-quartz veins occur in slate and schist 
and often are associated with dioritic dikes. Large amounts of by- 
product gold have been recovered from the massive sulfide deposits 
of the East and West Shasta copper-zinc districts. 

The Great Basin and Mojave Desert provinces of eastern and south- 
eastern California have been significant sources of gold. The Bodie 
district has been the largest source of gold in the Great Basin, while 
the Rand, Mojave, Stedman, and Cargo Muchacho district contain the 
most productive mines in the ]\Iojave Desert. Moderate amounts of 
gold have been mined in the Transverse Ranges, the principal sources 
having been the Acton and San Gabriel districts. Moderate amounts 
also have been recovered in the Cuyamaca, Julian, and Pinacate dis- 
tricts in the Peninsular Ranges and from the Hayden Hill district in 
the Modoc Plateau. Gold occurs in a number of places in the Coast 
Ranges including the Frazier Mountain district which sometimes is 
classified as being in the Transverse Ranges. Gold occurs in beaches 
along the ocean usually in very small amounts. 

Resource Potential 

At the present time, the outlook for gold mining in California is 
poor. The few active commercial mining operations are gradually 
shutting down. There is very little possibility of a revival of gold 
mining under present economic conditions. A small rise in the price 
of gold would probably result in an increase in exploration and devel- 
opment in some of the more isolated "high-grade'" or pocket mining 
districts. However, it seems doubtful if there would be much effect in 
the large minmg districts, because of the great expense in recondi- 
tioning the mines, because many of the workable deposits have been 
largely depleted, and because in many districts land values have so 
greatly increased in recent years as to preclude their use in mining 
again. Another factor in the mountainous regions in California is 
the inundation or the plans to inundate many important mines and 
gold-bearing areas by reservoirs. A major change in economic condi- 
tions with a resulting large decrease in costs would undoubtedly stimu- 
late gold mining in California as it did during the depression of the 
1930's. A large rise in the price of gold would also stimulate the 
industry in California. 

The largest undeveloped gold-bearing deposits in California are: 

(1) the deeply buried Tertiary channel gravels in the Sierra Nevada; 

(2) unmined terrace deposits in parts of the Klamath-Trinity River 
system ; (3) low-grade gravel deposits adjacent to the dredging fields; 
(4) gravels too deep to be mined by existing equipment in the Great 
Valley; (5) deep but undeveloped veins in the major lode-gold dis- 
tricts; and (6) large bodies of mineralized schist and greenstone in 
certain districts. In addition, there are extensive zones of alteration 

107-164 O — 66 — pt. I 13 


in certain districts that are known to contain gold values, but which 
have not been systematically examined. Most of the above deposits 
are too low in grade to be mined commercially under the present 
economic conditions. Tlie deeply buried channel gravels and the deep 
veins would have to be mined by expensive underground methods. The 
large bodies of mineralized schist and greenstone and the wide zones of 
alteration could possibly eventually be mined by open-pit and low unit- 
cost methods. 

Selected References 

Averill, O. V., and others, 1946, Placer mining for gold in California : California 

Div. Mines Bull. 135, 377 p. 
Clark, W. B.. 1957, Gold, in Mineral Commodities of California : California Div. 

Mines Bull. 176, p. 215-226. 
Clark, W. B., in preparation. Gold districts of California : California Div. Mines 

and Geol. Bull. 
Ferguson, H. G., and Gannett, R. W., 1932, Gold-quartz veins of the Alleghany 

district, California : U.S. Geol. Survey Prof. Paper 172, 139 p. 
Gardner, D. L., 1954, Gold and silver mining districts in the Mojave desert region 

of southern California : California Div. Mines Bull. 170. chap. 8, no. 6, p. 51-58. 
Haley, C. S., 1923, Gold placers of California : California Mining Bur. Bull. 92, 

167 p. 
Hanks, H. G., 1882, Placer, hydraulic, and drift mining : California Mining Bur. 

Rept. 2, p. 28-192. 
Hill, J. M., 1929, Historical summary of gold, silver, copper, lead, and zinc 

produced in California : U.S. Bur. Mines Econ. Paper 3, 22 p. 
Hulin, C. D.. 1925, Geology and ore deposits of the Randsburg quadrangle : 

California Mining Bur. Bull. 95, 152 p. 
Jenkins, O. P., and others, 1948, Geolc^c guidebook along Highway 49 — Sierran 

gold ibelt — The Mother Lode Country : California Div. Mines Bull. 141, 164 p. 
Johnston, W. D., Jr.. 1940, The gold-quartz veins at Grass Valley, California : 

U.S. Geol. Survey Prof. Paper 194, 101 p. 
Joslin, G. A., 1945, Gold, in Economic Mineral Resources and Production of 

California : California Div. Mines Bull. 130, p. 122-151. 
Knopf, Adolph, 1929, The Mother Lode system of California : U.S. Geol. Survey 

Prof. Paper 157, 88 p. 
Lindgren, Waldeiaar, 1911. The Tertiary gravels of the Sierra Nevada : U.S. 

Geol. Survey Prof. Paper 73, 226 p. 
Logan, C. A., 1935. Mother Lode gold belt of California : California Div. Mines 

Bull. 108, 240 p. 
Yale, C. G., 1896. Total production of gold in California since 1848 by years 

according to different authorities : California Mining Bur. Rept. 13, p. 64-65. 


(By G. B. Oakeshott, California Division of Mines and Geology, San Francisco, 


The mineral graphite is a crystalline form of pure carbon and is 
characterized by softness, perfect basal cleavage, and a greasy feel. 
A commercial distinction made between "amorphous" and "crystalline" 
graphite is based solely on relative grain size ; the "amorphous" variety 
is the finer grained. The grades and specifications of graphite used 
in industry are complex and involved. Particles of crystalline flake 
graphite may be as large as 8-mesh ; particles of artificial graphite in 
collodial dispersions may be only 5 millionths of an inch in diameter. 

The most useful properties of graphite are its resistance to chemical 
action and the action of molten metals, its infusibility (graphite does 
not melt, but sublimes at about 6500°F), opacity, softness, and perfect 


A larger tonnage of graphite is used in the United States for foundry 
facings (41 percent of the amorphous graphite used in 1963) than for 
any other purpose. Consumption of natural graphite in the United 
States, by use, in approximate order of decreasing amounts, is in 
foundry facings, steel-making, lubricants, refractories, crucibles, filler 
for dry batteries, and "lead" pencils. 

Presently (1965), natural crucible flake graphite is on the critical 
list and is eligible for government financial assistance up to 50 percent 
of exploration costs. 

Much grapliite has been formed by the metamorphism of carbona- 
ceous sediments, including coal, with resultant crystallization of the 
carbon. However, some is associated with intrusive igneous rocks 
and with pegmatites; the mineral is also a constituent of meteorites. 
Graphite in California, all of the amorphous variety, occurs in schists 
and gneisses, most, if not all, of which are of sedimentary origin. 

From 1865 to 1935, graphite was produced intermittently in Cali- 
fornia, but no production has been recorded since. A 50-ton concen- 
tration mill was constructed at the Kagel deposit, Los Angeles County, 
and produced small-flake graphite between 1918 and 1928. The total 
yield of California graphite is estimated to have been about 1,500 tons, 
valued at $137,000. The low quality of the graphite, low-grade ore, 
the small tonnage of griiphite consumed, and ample world supply are 
the principal causes of the lack of production from California for the 
past 30 years. 

World production of natural graphite in 1963 was 730,000 tons. 
The largest producing country was Korea (North and South) ; fol- 
lowed in order by Austria, U.S.S.R., China, and the Malagasy Repub- 
lic. Statistics for the United States are concealed, so as not to reveal 
the production of any one company, as Southwestern Graphite Co. at 
Burnet, Texas, has long been the comitry's only producer (Drake, 
1964). United States' consumption of graphite in 1963 was 47,000 
tons, valued at $6,111,000 (Drake, 1964) . 

A third of the counties of California, chiefly in the Sierra Nevada, 
Klamath Mountains, Coast Ranges, and Transverse Ranges, contain 
graphite schists which have been prospected, but the small production 
has come almost entirely from Los Angeles, Tuolumne, Mendocino, 
and Sonoma Counties. 

Several deposits in Los Angeles County were discussed by Beverly 
(1934). Deposits in the Placerita Formation (Paleozoic?), upper 
Kagel Canyon, and several in Pacoima Canyon and vicinity in the 
western San Gabriel Mountains of Los Angeles County were described 
by Oakeshott (1937; 1958). The crude graphite-bearing rock con- 
tains 7 to 15 percent graphite in flakes less than 0.25 mm in diameter. 

Although graphite is Avidely distributed in pre-Cretaceous meta- 
morphic rocks throughout California, owners of graphite deposits in 
the State have had difficulty in meeting competition provided by the 
higher quality imported material. No change in this situation is 

Selected References 

Beverly, Burt, Jr., 1984, Graphite deposits in Los Angeles County, California : 

Econ. Geology, v. 29, no. 4, p. 346-355. 
Drake, H. T., 1964, Graphite, in Minerals Yearbook: 1963, U.S. Bur. Mines, 

p. 578-581. 


Oakeshott, G. B., 1937, Geology and mineral deposits of the western San Gabriel 
Moiuitains, Los Angeles County : California Div. Mines Rept. 33, p. 245-248. 

, 1957, Graphite, in Mineral commodities of California : California Div. 

Mines Bull. 176, p. 227-229. 

-, 1958, Geology and mineral deposits of San Fernando quadrangle, Los 

Angeles County, California : California Div. Mines Bull. 172, p. 15, 51, 107, 
109, 112. 


(By C. F. Withington, U.S. Geological Survey, Washington, D.C.) 

The calcium sulfate minerals gypsum and anhydrite occur in beds 
formed by preciptation from saline waters, generally in partly 
isolated arms of the sea. Gypsum is hydrous calcium sulfate 
(CaSOi'SHsO), generally white or light gray; impurities may color 
it dark gray, black, pink, green, or yellow. The most common form 
is massive rock gypsum, a compact aggregate of small crystals occur- 
ring in beds as much as 100 feet thick. Alabaster is a compact, very 
fine-grained variety of gypsum. Gypsite is an impure, earthy mixture 
of gypsum (rarely more than TO percent), sand, silt, and clay formed 
near the surface in deposits that are seldom more than 15 feet thick 
and a few acres in extent. Gypsite is generally gray mottled with 
white, buff, or cream; iron may color it pink or red. Other gypsum 
varieties include satin spar and selenite. 

Anhydrite, calcium sulfate (CaS04), is slightly heavier and harder 
than gypsum. It is gray, bluish gray, or white; impurities may color 
it red, pink, gray, or black. Anhydrite may occur as isolated crystals 
or lenses within a gypsum deposit, it generally replaces gypsum at 

Gypsum ic the more useful of the two minerals ; most gypsmn is cal- 
cined to be used as plaster, principally in the manufacture of wallboard 
and other prefabricated gypsum products. Uncalcined or raw gyp- 
sum is used as a retarder for portland cement and as a soil conditioner. 
Gypsite. is used extensively as a soil conditioner. Anliydrite is used 
primarily as a soil conditioner and to a lesser extent as a retarder for 
Portland cement. 

Since 1960 California has led the United States in the production 
of gypsum. From 1880, when the first gypsum was produced in the 
State at Pomt Sal (Santa Barbara County), through 1964, an esti- 
mated 27 million short tons of gypsum was produced. In 1964, pro- 
duction was 1,893,000 tons, of which about a million tons was gypsite. 
Nearly three-quarters of the gypsite was produced in Kern County 
for use as a soil conditioner for the potato and cotton crops in the San 
Joaquin Valley (Davis and others, 1963, p. 174) . The annual produc- 
tion of gypsum and gypsite since 1945 is given in figure 29. Contrary 
to the national trend, the average price per ton of gypsmn in Cali- 
fornia dropped between 1945 and 1964, due largely to the increased 
use of the less expensive gypsite. Resources of gypsite are sufficient 
to supply the State for many years; those of gypsmn are not great 
and within a few years most of the gypsmn used in the State will be 
imported. Imports of gypsum into California from Mexico and Ne- 
vada in 1963 amounted to more than 600,000 tons. 


Price Per Ton 













- 3.000 

- 2.400 


1 .200 

- 600 

Figure 29. Production of gypsum in California, 1945-64. 



Occurrences in California 

Gypsum and gypsite occur mainly in the southern part of the State. 
In addition to the deposits listed in table 21, gypsum was manufac- 
tured as a by-product of magnesium derived from sea water in A'la- 
meda County and as a by-product of phosphoric acid in Fresno and 
San Joaquin Counties. The gypsum and gypsite deposits are here 
described by county ; their distribution is shown on figure 30. 

Table 21. — Distribution of calcmnv sulfate in California 


Type of deposit 


Fresno. . 
Imperial - 



Kings -- 

Los Angeles. 




San Benito 

San Bernardino.- 

San Diego (described with Imperial 

San Joaquin 

San Luis Obispo 

Santa Barbara 










do— . 






Selenite veins 






Pliocene (?). 

Miocene {?). 

Recent or Pleistocene. 


Recent and OUgocene or Miocene 


Late Cretaceous. 

Permian (?). 


Pliocene and Pleistocene (?). 

Tertiary, Permian (?). 



Pliocene to Pleistocene, Recent. 

Miocene to Pliocene. 


Miocene and Pliocene (?) . 

Fresno County 

Gypsite occurs in several small deposits in the northwestern corner 
of the county, including those in the Panoche Hills (No. 1) (see fig. 
30), and in Tumey Gulch (No. 2) (Ver Planck, 1952, p. 49-51). In 
1959, a plant was constructed near Mendota to process the gypsite from 
the Panoche Hills, which averages 40 percent or more gypsum; the 
overburden contains as much as 18 percent CaS04-2H20 (Kock Prod- 
ucts, 1959a, p. 58). The Little Panoche Valley deposit (No. 3) has 
yielded some gypsite guaranteed to average 70 percent gypsum, but no 
production has been reported since about 1953. Other gypsite deposits 
include: Monocline Eidge (No. 4), Oil Fields (No. 5), and those at 
Coalinga (No. 6). 

Invperial and San Diego Counties 

The gypsum deposits in Imperial County, the most extensive in the 
State, are in the western part of the county, extending westward into 
San Diego County. 

Gypsum occurs on the northwest side of the Fish Creek Mountains 
and on the northeastern edge of the Vallecito Mountains, Avhere it con- 
formably overlies poorly consolidated gray sandstones and conglom- 
erates of the Split Mountain Formation of which it is a part (Ver 
Planck, 1952, p. 30). Overlying the gypsum are the marine shales 
of the Imperial Formation. 

The best exposures of gypsum are in the open pit of the United 
States Gypsum Co. at the north end of the Fish Creek Mountains 
(No. 7). Here it is white to light-gray, massive, fine- to medium- 





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Gypsum occurrence or group 
of occurrences 

Gypsum mine or group ol nrnes 
(active 1957-63) 

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Gyps ite pit or group of pits 
(act ive t957-63) 



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Figure 30. Gypsum and anhydrite in California (numbers refer to deposits named 

in text). 

grained rock gypsum, in beds that range from about 5 to 100 feet in 
thickness ; the thicker sections of gypsum appear to liave been concen- 
trated along the crests of minor folds where it has been squeezed from 
the flanks. 

In the open pit, gyp.sum is found to a depth of 50 feet; below, it is 
mixed with lenses and thin stringers of anhydrite that gradually in- 
crease in thickness and quantity until the entire mass becomes anhy- 
dritic. The anhydrite is very fine to fine grained, bluish ^ray to white, 
becoming pink at the base, and includes traces of halite and other 
soluble sodium salts. 


The original extent of the basin in which the gypsum was deposited 
is unknown, as the gypsum is now in isohited erosional remnants 
scattered over an area about 4 miles long and 2i/2 miles wide. The 
largest deposit, a mass about 2 miles long and half a mile wide, is 
being developed by the U.S. Gypsum Co. near the north end of the 
exposures. In the Vallecito Mountains nortlnvest of the Fish Creek 
Mountains (No. 8) , are other exposed deposits reported to be sufficient 
to supply a gypsum plant "* * * for 100 years" (Rock Products, 
1959b, p. 50). 

About 1 mile north of the open pit of the U.S. Gypsum Co. and 
separated from it by Fish Creek (No. 9) is an isolated outcrop of 
gypsum (Durrell, 1953, p. 5-7), thin bedded and dark at the base, 
grading upward to lighter and more massive rock. 

A small gypsum deposit from which a limited amount of agricul- 
tural gypsum has been produced is on the extreme eastern side of 
the Fish Creek Mountains (No. 10). Other deposits include those 
in the Coyote Mountains (Nos. 11 and 12) , 

Inyo County 

Southeast of Tecopa at China Ranch in the Death Valley region 
(No. 13), gypsum occurs in tilted lake beds of Pliocene(?) age (Ver 
Planck, 1952, p. 38-39). The gypsum beds range from 6 inches to 
3 feet in thickness separated by thin laminations of shale. The 
gypsum is compact, white to light gray. Deposits at Black Mountain 
(No. 14), Copper Canyon (No. 15), and Furnace Creek (No, 16) are 
probably of early Pliocene age. They resemble the deposit at China 
Lake, where some mining was done in 1916 and 1917. 

Kern County 

Kern County is the largest producer of gypsite in the United States. 
In 1962 nearly three-quarters of all the gypsite produced in California, 
about 855,000 tons, came from this county (Davis and others, 1963, 
p. 202). The largest deposits are in the Lost Hills (No. 17), a low 
northwest-trending range about 25 miles west of Wasco. The gypsite 
occurs as flat-lying lenses, as much as 20 feet thick, of white, earthy, 
soft, and powdery material overlain by 3 to 10 feet of sandy soil. 

The major producer in the Lost Hills is H. M. Holloway, Inc., of 
Wasco, California. In mining operations, drilling to determine the 
extent of the deposit is followed by removal of overburden by scraper, 
after which the gypsum is picked up by a mobile milling unit, which 
screens the material and piles it into windrows. The materials, as much 
as 3,000 tons daily, is sold by the truck load for soil conditioner in 
three grades, 60, 65, and 70 percent gypsum. 

Gypsite also occurs in the vicinity of McKittrick in the western part 
of the county (No. 18), where it was formed in shallow basins by re- 
sidual Aveathering of gypsiferous beds in the Monterey Shale and the 
Tulare Formation (Ver Planck, 1952, p. 53). It is white on the sur- 
face and gray at depth. Gypsite has been produced here intermittently 
since 1900. In 1955, the Superior Gypsum Co. of Bakersfield opened 
a deposit in the Bitterwater Creek area in the Temblor Range (No. 19) 
(Rock Products, 1955, p. 102). Gypsite is also produced near Mari- 
copa (No. 20) and Taft (No. 21) . 

Other gypsite deposits are: at Kern Lake (No. 22), Koehn Lake 
(No. 23), McClure Valley (No. 24) (Hess, 1920, p. 64-65) ; Blackwells 


Comer (No. 25) (Ver Planck, 1952, p. 123) ; Cottomvood Creek (No. 
26), 16 miles east of Bakersfield (Hess, 1920, p. 70-71) ; Buena Vista 
Lake, (No. 27) (Hess, 1920, p. 73) ; and Pioneer (No. 28) (Hess, 1920, 
p. 70). 

Gypsum occurs in Cuddy Canyon (No. 29) as thin lenses, inter- 
bedded with sandstone (Ver Planck, 1952, p. 39^0) . 

Kings County 

Deposits of gypsite of playa lake origin are in the Avenal Gap and 
Kettleman Hills area, southeast of Avenal. Those at Avenal Gap (No. 
30) , average about 6 feet thick. The upper 2 feet consist of hard gray 
silt with streaks and blebs of finely divided gypsum, the lower 4 feet of 
fine-grained soft yellowish- white gypsite mixed with sand (Ver 
Planck, 1952, p. 56-57). The deposits in the Kettleman Hills (No. 
31) , similar to those at Avenal Gap, are being worked by the McPhaill 
Gypsum Co. of Visalia. 

Los Angeles County 

Gypsite occurs at Palmdale (No. 32), derived from the gypsiferous 
shales of the Escondido Formation. The deposits are exploited ex- 
tensively from 1892 to about 1915 (Ver Planck, 1952, p. 57). 

At Mint Canyon (No. 33), a gypsiferous zone as much as 15 feet 
thick occurs in the Vasquez Formation. The gypsum is gray to brown, 
in thin beds interbedded with coarse, angular, greenish sandstone. 

Hess (1920, p. 75) reported the production of gypsite in 1904 and 
1905 in Charley (Charles) Canyon (No. 34). 

Merced Gov/nty 

Gypsite was being produced in 1952 from the western foothills of 
Merced County. The deposits are close to the surface and range from 
6 inches to 6 feet iij; thickness (Davis and Carlson, 1952, p. 227-228). 
This material, guaranteed to contain 30 percent gypsum (California 
Bureau of Chemistry, 1954, p. 185), is produced by the Agricultural 
Minerals and Fertilizer Co. of Los Banos, in the Ortigalita Creek area 
(No. 35). 

Another deposit occurs along the Los Banos Creek (No. 36) (Ver 
Planck, 1952, p. 125). 

Orange Cou/nty 

W\ni^ fine-grained gypsum occurs in Gypsum Canyon on the west/- 
ern slope of the Santa Ana Range (No. 37) (Hess, 1920, p. 77), in a 
bed 8 to 10 feet thick that contains dolomite inclusions. Apparently 
the gypsum-bearing rocks have been folded and gypsum thickened 
locally by plastic flowage. A similar deposit of unknown extent has 
been reported from Sycamore Canyon (No. 38) (Ver Planck, 1952, 
p. 125). 

Riverside County 

In Riverside County gypsum occurs in the Little Maria, Maria, 
Palen, and Riverside Mountains, and gypsite occurs in the foothills of 
the Santa Ana Mountains near Corona. Only in the Little Maria 
Mountains has there been extensive production. 

The gypsum in the Little Maria Mountains is in an east-trending 
belt 21/^ miles long to 1 and 2 miles wide that crosses the middle of the 


mountains. Gypsum is interbedded with shale, limestone, and gypsi- 
ferous schists of the Maria Formation of "post-Cambrian" ao^e (Miller, 
1944, p. 25) , and can tentatively be correlated with the gypsum-bearing 
Kaibab Limestone of Permian age in southern Nevada and northwest- 
ern Arizona. 

Most of the gypsum on the western side of the mountains is asso- 
ciated with buff limestone; minor amounts have been found with 
schists. The sequences of gypsum-bearing rock are as much as 150 
feet thick and are poorly exposed ; the surface is marked by a light- 
gray soil. The gypsum is interbedded with green schist, quartzite, and 
limestone, and generally is in masses too impure to exploit. 

Coarse-grained white gypsum that averages about 93 percent pure 
is exposed in the southern part of the mountains (No. 39). This 
deposit was worked by open-pit methods by the Utah Construction Co. 
from 1947 to 1950. The gypsum is in beds that range from 3 to 60 
feet in thickness and are associated with green schist. The beds strike 
N. 25° E. and have an average dip of 60° NW. Light-blue massive 
anhydrite was exposed in the workimrs. 

The gypsum in the eastern end of the belt has been extensively ex- 
ploited west of the town of Midland by the U.S. Gypsum Co. Two 
of the six beds of gypsum present are thick enough to be considered 
economic ; the remaining beds are thin discontinuous lenses. Gypsum 
crops out on the north edge of the belt (No. 40), and on the south 
edge of the belt ( No. 41 ) . 

The individual gypsum beds are faulted and folded into minor 
flexures ; gypsum is thickest in the crests of the anticlines as the result 
of plastic flowage from the flanks during folding. 

Dense anhydrite, white to light blue gray, is found at depths of 
30 to 100 feet below the surface. Near the anhydrite gypsum is 
snow white and purer than at other places, suggesting that the waters 
which liydrated the anhydrite also introduced some impurities. 
Naturally-calcined anhydrite, formed by heat generated by move- 
ment along faults in gypsum, occurs as white powdery gouge 2 to 4 
feet wide. 

The U.S. Gypsum Co. has been mining gypsum from these deposits 
by open-pit and underground methods since 1925; at present only 
open-pit methods are used- The material is blasted, loaded bv shovel 
into tmcks for transport about 2% miles to the mill at Midland, where 
it is crushed, ground in raymond mills, and calcined. The plant 
produces plaster, lath, and wallboard. The capacity of the open pit 
and mill is about 750 tons a day. 

Gypsum occurs about 3% miles east of Midland, on the west slope 
of tiie Maria Mountains (No. 42). The gypsum, in two beds sepa- 
rated by limestone in a bluff 300 to 500 feet high, is probably equivalent 
to that in the Little Maria Mountains (Tucker and Sampson, 1945, 
p. 170-172). Some development work has been done, but no gypsum 
has been produced. In 1957 this deposit was owned by the U.S. 
Gypsum Co. 

Gypsum in three isolated masses in an east-trending belt about 3 
miles long and from % to li/^ miles wide occurs at the north end 
of the Palen Mountains (No. 43 ) . Massive beds of white, fine-grained 
gypsum are highly faulted and folded (Hoppin, 1954, p. 9). 


Gypsum occurs on the east side of the Riverside Mountains in the 
northeast corner of the county, south of Vidal (No- 44) in the Colorado 
River Indian Reservation. Deposits inchide the Parkford and the 
Riverside gypsum deposits, both owned by the Indian Tribal Council. 
The age of the gypsum is unknown, but is probably equivalent to the 
Kaibab Limestone of Permian age. The gypsum in the Parkford 
deposit, is massive, white, and interbedded with limestone (Tucker 
and Sampson, 1945, p. 170). The individual beds, which crop out 
in four north-trending hogbacks, are as much as 50 feet thick, and 
dip 30° to 60° W. Some development work has been done, but no 
production reported. Gypsite in beds as much as 10 feet thick occurs 
below the outcrop. 

The Riverside deposit is similar. The gypsum in beds alternating 
with limestone, has an aggregate thickness of 70 feet and is traceable 
along the outcrop for about 1,000 feet. Samples from this deposit 
are reported to average 98 percent gypsum (Tucker and Sampson, 
1945, p. 170). 

South of Corona, in the extreme western edge of the coimty, gyp- 
site occurs in the foothills of the Santa Ana Mountains, in a belt S^ 
miles long (No. 45) (Gray, 1961, p. 82-86). The gypsite is in Haga- 
dor. Gypsum (Main Street) , and Eagle Canyons. The material assays 
only 15 to 38 percent gypsum. 

San Benito County 

Gypsum has been reported in Bitterwater Valley (No. 46) , 10 miles 
northeast of King City. The gypsum is in the Paso Robles Formation 
in lenses 3 to 7 feet thick and as much as 900 feet wide. It is associ- 
ated with beds of siltstone and light -gray sandstone (Ver Planck, 
1952, p. 40) . Some gypsum has been produced for agricultural use, 
but since 1949 tlie deposits have not been worked. 

The Tully deposit (No. 47), on the eastern side of Bitterwater Val- 
ley consists of beds and masses of gray to white gypsum mixed with 
clay. A similar deposit from which some gj^psite was produced around 
1906 is fomid just west of Hernandez (No. 48) (California State Min- 
ing Bureau, 1906, p. 286-287). 

A deposit of gypsite of unknown geologic setting Avas reported by 
Ver Planck (1952, p. 127) at Silver Creek (No. 49). 

San Bemardino County 

At the south end of Death Valley in the Avawatz Mountains gyp- 
sum is associated with salt and celestite in deformed Tertiary lacus- 
trine beds. These beds are exposed in a northwest-trending belt about 
10 miles long and 1 to 2 miles wide in the foothills on the north side of 
the mountains (No. 50). Ver Planck (1952, p. 45-46) has described 
the gypsum in five areas here. 

Bristol Playa Lake covers an area of about 35 square miles (No. 51) . 
Gypsum is present Avithin the playa both as dunes and as irregular beds 
and isolated selenite crystals and plates as much as an inch long mostly 
along the northwest border of the lake (Hess, 1920, p. 81-82). This 
deposit was worked by open-pit methods from 1906 to 1924 (Ver 
Planck, 1952, p. 47) and the gypsimi was shipped to a plaster mill at 
the rail head at Amboy. 

Danby Playa Lake (No. 52) , 14 miles long and 1 to 4 miles wide, has 
deposits similar to those of Bristol Lake. Selenite crystals associated 


with clay and silt make up as much as one-third of the lake sediments, 
and are concentrated along the northeast margins of the lake. Knobs 
of selenite crystals mixed with clay stand as much as 10 feet above 
the lake surface. 

Gypsum occurs in the Clark Mountains in the northeast corner of 
the comity near the Nevada State line (Ver Planck, 1952, p. 2-1-27) 
(No. 53). White, sugary gypsum, in rocks that can be correlated 
with the Kaibab Limestone of Permian age in Nevada, occurs in 4 or 
5 beds or series of beds which crop out for about 2 miles along a dry 
wash. These beds range from a few feet to as much as 50 feet in 
thickness, strike N. 40° W., and dip about 50° SW. 

The Red Canyon deposit (No. 54), is on the west-central part of 
the Shadow Mountains about 12 miles north of Baker (Wright and 
others, 1953). Gypsum is in lay ere a few inches thick in yellow 
siltstone of Tertiary age. The largest exposed body is a 6-foot 
sequence of thin beds of gypsum exposed for about 70 feet along strike. 
Some prospecting has been done. 

The Owl Hole Spring deposit (No. 55) is similar to the Avawatz 
Mountain deposit (Ver Planck, 1952, p. 39). Thin beds of gypsum 
and gypsiferous shale occur in Pliocene(?) lake beds which strike 
east and dip north. 

Deposits of unknown extent are reported from Field (No. 56) and 
the Calico Mountains (No. 57) (Ver Planck, 1952, p. 128). The latter 
was apparently worked briefly in 1916. 

San Joaquin Goimiy 

Selenite in veins near Vemalis (No. 58) has been reported by 
Ver Planck (1952, p. 129). These occurrences are of mineralogic 
interest only. 

San Luis Ohispo County 

Gypsite occurs in the Carrizo Plain (No. 59) in rocks of the 
McKittrick Group of former usage (Jacalitos to Tulare interval) 
along the margins of playa lakes. The deposits are essentially 
elongate lenses, the largest about 1,500 feet long and as much as 4 feet 
thick, of limy tan, sandy or earthy gypsite associated with fine-grained 
gravels or gray silt. Deposits several miles east of Simmler (No. 60) 
are Avorked by the Superior Gypsum Co. of Bakersfield, which pro- 
duces material guaranteed to <*ontain at least 70 percent gypsum 
(California Bureau of Chemistry, 1954, p. 187) . 

Other deposits include: 1) tan limy gypsite at Shandon (No. 61) 
(Ver Planck, 1952, p. 58-59), in a lens about 500 yards long and 200 
yards wide on the mai-gin of a playa lake from which some mining 
has been reported, and 2) lenticular masses of gypsum along Alamo 
Creek (No. 62) and Arroyo Grande Creek (No. 63).. 

Santa. Barbara Coimty 

Gypsum at Point Sal (No. 64) occurred as nodules and veins in 
shale of Miocene age. This deposit, mined from about 1880 to 1889, 
was the fii-st important source of gypsum in the State (Ver Planck, 
1962, p. 67). 

Deposits in the Caliente Formation of Miocene to Pliocene age (Ver 
Planck, 1952, p. 41) crop out in a northeast-trending belt about 7 miles 


long on the northeastern edge of the county in Cuyama Valley (No. 65) 
and extend to Ventura County. The beds consist of interbedded dark- 
brown shale, sandstone, and thin lenticular gypsum as much as 10 
feet thick. The gypsum is white and alabaster in texture and contains 
green shale laminae and lenses. In 1960, agricultural gypsite was 
produced from a small deposit one-half mile south of Ventucopa; the 
deposit is now exhausted. 

Shasta County 

Gypsum and anhydrite occur as large bunches or masses as gangue 
minerals in the deeper levels in the Bully Hill and Rising Star copper- 
zinc mines (No. 66), (Graton, 1910, p. 100, 103). Masses of gypsum 
are commonly banded by inclusions of thin parallel films of sericitic 
and chloritic material. Included in the calcium sulfate minerals are 
finely disseminated crystals of pyrite. Graton believed that the anhy- 
drite was introduced by ore-bearing solutions and later altered to 

Ventura Ommty 

Gypsum has been produced in Quatal Canyon, from 10- to 30-foot- 
thick beds in the Santa Margarita Formation, which crops out at 
irregular intervals for a distance of 7 miles in a northwest-trending 
belt. On the northern edge of the belt (No. 67), on the north side of 
Quatal Canyon, the Monolith Portland Cement Co. has produced 
gypsum for cement retarder. Other deposits occur north and south 
of Quatal Canyon (Ver Planck, 1952, p. 35). 

At the south end of the belt of gypsum-bearing rocks, in Burges 
Canyon, gypsum lenses as much as 10 feet thick are associated with 
green shale. Extremely fine grained alabaster, notably at French 
Point (No. 68), has been used locally for art objects. 

Other gypsum deposits were reported from Ojai Valley (No. 69) ; 
on the east flank of South Mountain, 4 miles south of Santa Paula, 
(No. 70) ; and 4 miles south of Fillmore (No. 71) from which some 
production was reported (Hess, 1920, p. 85). 

Selected References 

California Bureau Chemistry, 1954, Fertilizing materials : California Dept. Agr. 

Spec. Pub. 255, 216 p. [1955]. 
California State Mining Bureau, 1906, The structural and industrial minerals 

of California : California Mining Bur. Bull. 38, 412 p. 
Davis, F. F., and Carlson, D. W., 1952, Mines and mineral resources of Merced 

County [California] : California Jour. Mines and Geology, v. 48, p. 207-251. 
Davis, L. E., Edgerton, C. D., Ashizawa, R. Y., and Giorgetti, L., 1963, The 

mineral industry of California : U.S. Bur. Mines Minerals Yearbook 1962, v. 

3, p. 159-225. 
Durrell, Cordell, 1953, Geological investigations of strontium deposits in southern 

California : California Div. Mines Spec. Rept. 32, 48 p. 
Graton, L. C, 1910, The occurrence of copper in Shasta County, California : 

U.S. Geol. Survey Bull. 430, p. 71-111. 
Gray, C. H., Jr., 1961, Mines and mineral deposits of the Corona South quad- 
rangle. Riverside and Orange Counties, California : California Div. Mines 

Bull. 178, p. 59-120. 
Hess, F. L., 1920, California, in Gypsum deposits of the United States: U.S. 

Geol. Survey Bull. 697, p. 58-86. 
Hoppin, R. A., 1954, Geology of the Palen Mountains gypsum deposit. Riverside 

County, California : California Div. Mines Spec. Rept. 36, 25 p. 


Miller, W. J., 1944, Geology of Palm Spring-Blythe Strip, Riverside County, 
California : California Jour. Mines and Geology, v. 40, p. 11-72. 

Rock Products, 1955, Gypsum plant in full scale operation : Rock Products, v. 
58, no. 10, p. 102. 

, 1959a, New plants dot industries horizon : Rock Products, v. 62, no. 11, 

p. 58. 

-, 1959b, National Gypsum dedicates Waukegan plant, plans others : Rock 

Products, V. 62. no. 11, p. 50. 
Sharp, R. P., 1935, Geology of Ravenna quadrangle, California [abs.] : Pan- 
American Geologist, V. 63, no. 4, p. 314 ; Geol. Soc. America Proc. 1935, p. 336 

Tucker, W. B., and Sampson, R. J., 1945, Mineral resources of Riverside County 

[California] : California Jour. Mines and Geology, v. 41, no. 3, p. 121-182. 
Ver Planck, W. E., Jr., 1952, Gypsum in California : California Div. Mines Bull. 

163, 151 p. 
Wright, L. A., Stewart, R. M., Gay. T. E., Jr., and Hazenbush, G. C, 1953, Mines 

and mineral deposits of San Bernardino County, California : California Jour. 

Mines and Geology, v. 49, nos. 1-2, p. 49-259 [plus 192 p. tabulated list of 

mines and mineral deposits in San Bernardino County]. 


(By G. I. Smith, U.S. Geological Survey, Menlo Park, Calif.) 

Iodine is produced in the United States from well brines. Plants 
operated by the Dow Chemical Co. in Michigan and California furnish 
the entire domestic output, and this satisfies a large part of United 
States requirements (Miller, 1964; Stipp, 1960). 

Most iodine is first produced in crude form (at least 99 percent 
pure), but before use is either resublimed to a purer elemental form 
or converted to potassium iodide or other inorganic or organic com- 
pounds. Its uses are many. Iodine and its salts are used as antiseptics 
and for other medical purposes, as additives to food for both humans 
and animals, as components of photographic emulsions, and for sani- 
tation, metal production, and other specialized chemical uses. The 
isotope iodine-131 is used as a tracer for industrial and research pur- 
poses. Consumption of iodine in the United States has increased 
steadily ; in 1963 it was 8 percent higher than in 1962, and more than 
twice that of 1953. The current price of crude iodine in kegs is $1.18 
per pound (Miller, 1964). 

In the early 18()0's, iodine was produced in Europe from seaweeds ; 
these plants concentrate iodine from sea water, and, after treatment, 
some seaweed residues contain as much as 1.8 percent iodine. In the 
late 1860's, production of iodine as a by-product of the Chilean nitrate 
industry began, and that source dominated world supply for over a 
half a century. In 1928, production from brines began in Louisiana^ 
and by 1932, production from California brines became the major 
domestic source. Similar sources were developed at about the same 
time in Kussia, Germany, France, and England (Reiser, 1960; Ver 
Planck, 1957 ; Stipp, 1960 ; Miller, 1964) . 

Iodine production in California started in 1932 at a plant at Long 
Beach operated by the General Salt Co. Shortly thereafter, a plant 
operated by the Deepwater Chemical Co., Ltd., was started at Comp- 
ton, and the Dow Chemical Co. started extraction operations at Seal 
Beach, Venice, and Inglewood. All use brines that accompany the oil 
pumped to the surface in oil wells. Several fields produce brines con- 


tainin^ abnormal quantities of iodine, but only those at Dominguez, 
Playa del Rey, Inglewood, Seal Beach, and Long Beach contain recov- 
erable amounts. These brines average 2i/2 to 3 percent total solids and 
contain an average of about 50 ppm iodine (Ver Planck, 1957). Only 
the Dow Chemical Co. plant at Seal Beach is still in operation, and 
production is currently being transferred from that plant to Michigan 
(Miller, 1964). 
No other economic sources of iodine are known in California. 

Shh^ected References 

Keiser, H. D., 1960, Minor industrial minerals, in Industrial minerals and rocks : 
New York. Am. Inst. Mining Metall. Petroleum Engineers, p. 605-621. 

Miller, W. C, 1964, Iodine: U.S. Bur. Mines, Minerals Yearbook, 1963, v. 1, 
p. 595-599. 

Stipp, H. E., 1960, Iodine, in Mineral facts and problems : U.S. Bur. Mines Bull. 
585 p. 473—479. 

Ver Planck, W. E., 1957, Iodine : California Div. Mines Bull. 176, p. 241-243. 


(By Lyman Moore, U.S. Bureau of Mines, San Francisco, Calif.) 
Importance and Use 

Iron ore is the basic raw material for iron and steel, the foundation 
of industrialized civilization; in tonnage, over 90 percent of all metal 
consumed in the United States is iron or steel. 

Iron in a relatively pure state, such as wrought iron, is a tough 
malleable inexpensive metal. Sfeel is a mixture (alloy) of iron and 
carbon. The term alloy steel is used to describe mixtures of steel and 
other elements such as tungsten, nickel, vanadium, and many others. 
By varying the carbon content, heat treatment, and forming methods, 
steels can be made having a wide range of physical properties. Prop- 
erties range from those of low carbon steel with moderate yield 
strengths and the ductility required to allow cheap mass production 
by pressing and stamping, to spring steels having high yield strengths. 
Engineering, tool, razor, stainless, and other specialized steels possess 
extreme strength, hardness, toughness, resistance to corrosion and 
heat softening, and other desirable properties. The relatively low 
price of steel, along with its versatility, makes it the indispensible 
metal in our economy. The principal users in the United States, in 
decreasing order of importance are: 1) automotive, 19 percent of the 
total consumption; 2) construction, 17 percent; 3) containers, 8 per- 
cent; 4) oil and gas industry, 7 percent; 5) industrial machinery, 
6 percent; 6) rail transport, 6 percent; 7) electrical machinery, 3 
percent; 8) appliances, 3 percent; and 9) agricultural, 2 percent. 

Geologic Occurrence 

Iron is an abundant metal, comprising about 5 percent of the earth's 
crust. Iron ore deposits are widely distributed throughout the world, 
and are estimated to contain over 70,000 million tons of iron ore. 
Under present economic conditions, only ore bodies located conveni- 
ently to steel markets and sources of coking coal or deposits either of 


iiniisual size and orade or particularly adapted to low-cost produc- 
tion can be utilized. 

A variety of geologic processes have formed the iron concentra- 
tions whicli supply the world's industry. The most prominent, known 
as the Lahe. Superior ty])e, occurs in northern Minnesota, Wisconsin, 
and Michigan, and in Labrador, Venezuela, Brazil, Russia, South 
Africa, India, Australia, and China. These deposits were formed in 
Precambrian time through the selective leaching of meteoric waters 
of thick sedimentary iron formation called taconites. Taconites con- 
sist of banded or irregularly intermingled chert and ferric oxide. 
Technologic advancements have made it profitable to utilize portions 
of the iron formation itself. 

Sedimentary iron ores, although generally low grade, have been 
of great past importance, partly because of their frequent geographical 
proximity to coal measures. However, recent reductions in world 
iron ore prices, brought about by improved mining and processing 
methods and cheaper transportation, have reduced production from 
these deposits. The most important sedimentary iron ore districts 
have been Birmingham, Ala.; Lorraine, France; Luxembourg; and 
Yorkshire, England. The ores oc^'ur in well-defined sedimentary beds 
and have a wide regional extent. In some locations the beds are as 
thick as 40 feet, but they rarely exceed 12 feet. Hematite, limonite, 
or siderite may be the predominant iron mineral and the ores usually 
have an oolitic structure. 

Kirimrr-type deposits, mainly magnetite with considerable apatite, 
occur in northern Sweden. They conunonly are tabular and were 
fonned by processes of fractional crystallization and injection sim- 
ilar to those that result in the intrusion of igneous dikes. 

Contact metamorphic deposits are common throughout the world 
and many examples are known in the western United States, includ- 
ing California. These deposits are formed at high temperatures in 
limestone or dolomite beds at their contact with intrusive rocks. 
Magnetite is the principal iron mineral and a gangue of garnet and 
other lime and magnesium silicates is characteristic. Contact deposits 
are not formed in chemically inert rocks and in these the mineralizing 
solutions proceed some distance from the source and deposition takes 
place as the solutions cool. These deposits are referred to as hydro- 
ihermal and are a type of deep-seated vein deposit. Replaceinent 
deposits are formed in limestone or other rocks. 

History and Production 

Tlie first iron works in the United States was built near Jamestown. 
Va., in 1620 and the first steel was made in 1728 at Hartford, Conn. 
Modern United States steel numufacture began with the first pour 
of Bessemer steel in 1864, followed by the first open-hearth steel in 
1868. The 1860 census reported United States production of 3.2 mil- 
lion long tons of iron ore, slightly less than 1 million short tons of 
pig iron, and only 11,838 short tons of steel. By 1900, United States 
production was 27.5 million long tons of iron ore, 13.8 million short 
tons of pig iron (34 percent of world output). In 1963, production 
was 73.6 million long tons of iron ore, 71.8 million short tons of pig 
iron (23 percent of world output), and 75.6 million short tons of 


finished steel (26 percent of world output). The United States has 
been the world's largest producer of iron and steel since 1897. 

Only small quantities of iron ore were produced in California be- 
fore World "War II, Foundries and rolling mills have been active 
in the State since the pioneer period and the first open hearth was 
built in 1884. The steel furnaces were charged with scrap and im- 
ported pig iron; the rolling and finishing mills used imported ingots 
and coils as well as ingots cast locally. No blast furnaces were in 
operation. Production of pig iron in California was hampered by a 
lack of coking coal, which had to be shipped in from tlic Rocky Moun- 
tain or Appalachian fields; by the small size of the market, which 
prevented the use of more efficient large-sized furnaces; and by low 
shipping rates, as ballast for steel imports. 

California's primary iron and steel production has grown rapidly 
since Kaiser Steel Corp. built a blast furnace in 1942 at Fontana. Al- 
though there is still only the one primary plant in the State, pig-iron 
capacity has been increased from about 400,000 short, tons in 1942 to 
almost 2 million tons in 1960. This capacity is still only a little over 
2 percent of United States capacity whereas California has 10 percent 
of the nation's population. Thus, continued growth of the industry 
within the State seems probable. 

Present blast furnace capacity requires about 3.2 million long tons 
of iron ore containing 60 percent Fe. An export market for iron ore 
with Japanese steelmakers has developed since 1950 and contracts in 
force in 1964 provide for the shipment of 1 million long tons per year 
from mines within the State. Other California uses of iron ore are 
as lump in open-hearth steelmaking, as an ingredient in low-heat port- 
land cement, as heavy aggregate for ballast and nuclear shielding, as 
a pigment, as a fluxing agent, and miscellaneous uses. These other uses 
require about 200,000 long tons of iron ore per year. 

Iron ore production statistics for California have not been published 
since 1956. It is believed that in recent years blast furnaces have been 
operating at near capacity and that iron ore has been exported at 
somewhat above published contract levels. Thus, overall production 
is about 4.4 million long tons of 60 percent iron ore per year. This is 
about 3 percent of the United States total and places California sixth 
among the producing states. 

Occurrences in California 

The important iron occurrences in California are shown on figure 
31 and basic information concerning each deposit is given in table 22. 

Geographically, California's iron deposits are concentrated in the 
Mojave Desert province in western San Bernardino and Riverside 
Counties. About 99 percent of the State's production has come from 
this area. The area contains over 90 percent of the State's known 
resources. All of the Moiave deposits are of igneous origin and differ 
mainly in the kind of wall rock present and its consequent effect upon 
the type of deposit formed. Contact metamorphic deposits, the area's 
most prominent type, are formed at high temperatures in limestone 
or dolomite at their contact with intrusive rock. The Eagle Moun 
tain and Lava Bed deposits are of this type. They are characterized 
by magnetite replacement and a gangue of contact silicates such as 

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Figure 31. Iron ore in California (numbers refer to table 22). 

garnet, epidote, and pyroxene. Other deposits, such as the Vulcan, 
show similar structural relationships but rock alteration processes 
were less intense. Some deposits are of the hydrothermal replacement 
and vein-filling type. An example is the Iron Age, where magnetite 
occurs as veins in granite some distance from any apparent source of 
ore-depositing solutions. 

Other iron-ore deposits occur in the Sierra Nevada province, par- 
ticularly in Western Madera County. The Minarets is the most im- 
portant and is a hydrothermal replacement in dacite. Western Shasta 
County, in the Klamath Mountain province, contains contact meta- 
morphic magnetite deposits. A small sedimentary limonite deposit 


occurs in San Luis Obispo County and some production has come from 
beach sands in Santa Cruz County. The State's most prominent iron- 
ore deposits are described below. 

Eagle Mountain district 

Most of California's iron-ore production has come from the Eao;le 
Mountain district (No. 68, fif^. 31) in Riverside County, 60 miles east 
of Indio. Deposits occur throuo:hout a belt that extends 7 miles east- 
west and has a width of about 1 mile. Past production has been 
mostly from larg-e ore bodies at the eastern end of the belt. Kaiser 
Steel Corp. is the only producer and owns most of the district's mineral 
rights. Most of the blast furnace feed for Kaiser's Fontana steel mill, 
plus the ore needed to satisfy a 1 million-ton-per-year export contract 
is obtained from the Ea^^le Mountain mine. 

The mineralized area is underlain by a series of quartzites and dolo- 
mites which have been folded into a broad anticline that locally is 
closely folded and faulted. Large elongate bodies of quartz mon- 
zonite have intruded the sediments with the development of calcium 
magnesium silicates in the dolomite and with heavy iron mineraliza- 
tion, particularly in two dolomite beds. The ore deposits are roughly 
tabular in shape conforming to the distribution of the dolomite. Indi- 
vidual ore bodies extend for as much as 3,000 feet along the strike 
and have been developed to a depth of 1,000 feet on a dip of 45°. The 
ore width being mined consists of a footwall ore bed 40 to 140 feet in 
width and a hanging-wall ore bed 30 to 300 feet in width. The two 
beds are separated by 200 to 300 feet of barren quartzite. 

The primary ore is magnetite but throughout a thick zone of oxida- 
tion it has been partially weathered to liematite. The ore ranges from 
40 to 50 percent Fe and is beneficiated before use. Sulfur, the only 
contaminant, is low enough in the oxidized ore to permit use without 
further treatment. In the primary ore, sulfur content is reduced by 
sintering or pelletizing. 

Kaiser Steel Corp. has estimated that 108,675,000 long tons of ore 
containing 45.2 percent Fe can be mined profitably at 1965 prices from 
the present open pit. No estimate has been published of resources in 
the remainder of the district. 

Lava Bed dv^trict 

The Lava Bed district, 30 miles northeast of Lucerne Valley, has 
produced over 50,000 long tons of direct shipping iron ore from the 
Bessemer, Morris Lode, and Ebony properties. Extensive explora- 
tion has been done on the Bessemer, Morris Lode, and Cat-Man-Ord 

Bessemer. — Production from this property (No. 52, fig. 31) totaled 
28,000 tons from 1945 to 1951. The Bessemer deposit consists of 
replacements of magnetite in dolomite along an irregular contact with 
granite. The mineralized dolomite occurs as remnants, now engulfed 
in granite, or as points of dolomite surrounded on three sides by the 
intrusive. The largest ore body covers an area of about 50,000 square 
feet and has been mined by open pit. In the deposit medium-width 
veins of high-grade ore are interspersed with barren or selectively 
replaced beds of dolomite. Fourteen small ore bodies crop out in the 
area and additional bodies were found under nearby alluvium by mag- 


iietite prospecting and drilling (Wright, 1953, p. 86-100). The de- 
posit was estimated to contain 1.8 million tons of ;^0 to 65 percent Fe 
ore of which 240,000 tons contained between 60 and 65 percent Fe 
(Calif. Div. Mines Bnll. 129). 

Morris Lode.—T\\^ Morris Lode (No. 54, fig. 31) produced 17,500 
tons in 1949-1950 for use in cement manufacture and a few thousand 
tons of lump ore in 1957. The mineralized area is underlain by 
dolomitic limestone intruded by granitic rocks. Large skarn areas 
were formed in the dolomite along the granite contact. Two types 
of ore occurrences are present: (1) Small irregular bodies of high- 
grade ore are found along the dolomite-granite contact, often coni- 
pletely replacing small inclusions of dolomite, and (2) a large deposit 
of medium- and low-grade ore is found in a skarn zone adjacent to 
the contact. In 1944-1945, a magnetic anomaly 1,000 feet wide and 
1,500 feet long was delineated. Subsequent drilling revealed an ore 
body with an area of about 10 acres. Eight drill holes intersected 
from 120 to 921 feet of iron ore with an average grade of 37.32 
percent Fe. Two holes drilled in a zone of lower magnetic intensity 
surrounding this area intersected from 100 to 400 feet of material 
with more than 15 percent Fe ( Wiebelt, 1947) . 

Magnetite is the predominant ore mineral but some primary he- 
matite is found at depth and somewhat earthy secondary hematite 
and limonite occur near the surface. The ore has about 2 percent 
sulfur in the form of pyrite, but phosphorus and other impurities 
are low. 

Baxter' district 

The Baxter district is about 16 miles west of Baker, and immediately 
north of the Mojave River. Although no production figures have 
been published the Cave Canyon mine has had moderate production, 
and small production has come from the Cronese and Cave Mountain 
properties. Shipments were made from 1934 to 1957. The iron ore 
was used almost entirely in the manufacture of low-heat portland 

Cave Canyon mine. — The area containing this deposit (No. 37, fig. 
31 ) is underlain by Precambrian gneiss and quartzite, by a later Pre- 
cambrian limestone, and by Tertiary sandstone and f anglomerate. In- 
trusive into the Precambrian rocks is a diorite porphyry to which 
the iron mineralization is related. The ore area is intensely brecciated 
by faulting and folding. The iron ore occurs as a replacement of 
the Precambrian rocks and the pi-evalence of remnants of unreplaced 
limestone in the ore zone indicates that this rock was most susceptible 
to mineralization. In places, quartzite also is mineralized and grades 
into ore. The iron was deposited as magnetite but has been oxidized 
to about one-half hematite. Some gypsum is present. 

Reserves were estimated in 1944 as 4,105,000 long tons, of which 
only 1,350,000 long tons was recoverable at 1944 prices. Because 
of the intense brecciation, much dilution of the ore is inevitable during 
mining, and beneficiation would be required to make a high-grade 

Providence district 

The Providence district is on the west slope of the Providence Moun- 
tains in San Bernardino County about 9 miles southeast of Kelso. 


All of the district's production has come from the Vulcan mine (No. 
43, fig. 31), which provided the primary source of iron ore for the 
Fontana steel plant during World War II. It produced 2,643,000 
long tons in the period from 1942 when the mine was opened, to 
1947 when demand Avas shifted to the Eagle Mountain mine. Sub- 
sequent production has consisted only of moderate quantities of lump 
ore and ore for use in low-heat portland cement manufacture. 

The Vulcan area is imderlain by marine sedimentary rocks ranging 
in age from Cambrian to Jurassic which were intruded by quartz 
monzonite in Jurassic time and which were later intruded and partly 
covered by Tertiary rhyolite. The iron-ore deposit occurs as a mush- 
room-shaped replacement in marbleized Cambrian limestone adjacent 
to quartz monzonite whose contact with the limestone and ore is a 
fault plane. x4.t the surface the ore body was 700 feet long and 325 
feet wide, but at depth the deposit decreased in horizontal cross section 
and became pipe shaped. The ore has been intersected to a depth of 
900 feet in drill holes. Hard, dark magnetite is the primary ore 
mineral. A small amount of hematite, which decreases at depth, is 
present. Sulfur, occurring in pyrite, is prominent in the primary ore 
and is the only impurity of consequence. Weathering removed the 
sulfur from the upper 50 feet of the deposit. 

The property was estimated in 1944 to contain 5,680,000 long tons 
of plus 50 percent Fe in the main ore body and additional ore in the 
south ore body. After consideration of ore mined subsequent to 1944 
and after including the south ore body, reserves are estimated at 
5,520,000 long tons. 

Silver Lake district 

The Silver Lake district is in San Bernardino County, about 13 
miles northwest of Baker. All of the production has come from the 
Iron Mountain property which contains most of the district's re- 
sources. The adjoining Iron King is a small deposit similar in 
character to the Iron Mountain. 

Iron Maunfam rnin-e. — Moderate quantities of ore were shipped by 
Kaiser Steel Corp. to its Fontana plant from this property (No. 29, 
fig. 31) during 1953 and from 1962 to 1964. The district was explored 
by the U.S. Geological Survey in 1943 and 1944, and in 1944, the U.S. 
Bureau of Mines drilled 12 holes on the property. 

The ore-bearing formation is an extensive breccia over 200 feet 
thick consisting predominately of broken limestone but containing 
lenses composed of fragments of igneous and contact-metamorphic 
rocks and of iron ore. Individual lenses are chiefly of one type of 
rock. The breccia is underlain by sandstone and conglomerate and in 
the mine area is overlain only by alluvium. A few hundred feet south 
of the iron-ore deposits the sediments are in fault contact with 
andesite that has l)een intruded by quartz monzonite. However, no 
igneous rocks are known to intrude the sedimentary series containing 
the iron-ore breccia. 

Iron occurs as lenses of both solid massive magnetite and of breccia 
ore. In addition to iron oxide, the latter ore contains fragments of 
contact-metamorphic rock and partly replaced limestone. The ore 
lenses are conformable to the limestone breccia and dip at angles of 
20 to 35° with the long dimension of the oreshoots extending down 


the dip. Magnetite is the predominant iron ore mineral; a small 
amount of secondary hematite also is present. The ore is low in sulfur 
and phosphorus. Opinions differ as to the origin of the deposit ; some 
geologists consider it a contact-metamorphic deposit that has been 
shattered by faulting; others consider it to be a product of coarse 
weathering of a now completely eroded iron-ore deposit ; and it is not 
unreasonable to consider it a hj^drothermal deposit derived from the 
quartz monzonite or from an unexposed igneous source. 

Ore resen^es as established by Bureau of Mines drilling in 1944 
were 6,175,000 long tons of material containing 54 percent Fe. 

Kingston district 

The Kingston district (No. 27, fig. 31) is in northeastern San Ber- 
nardino County, 20 miles east of Tecopa. All of the ore, except for 
some small prospects, occurs in the Beck deposit in a single geologic 
horizon. The substantial size of the deposit was proven in 1924 when 
14 holes were diamond drilled. However, only small quantities have 
been mined and shipped for test work, chiefly because of high trans- 
portation costs. 

Magnetite occurs as the replacement of a 100-foot-thick white crys- 
talline limestone bed in a Precambrian series of quartzite, dolomite, and 
limestone. A thick sill of amphibolite of uncertain age occurs imme- 
diately below the limestone. Along the limestone-amphibolite contact, 
iron ore replacements occur in the footwall of the limestone bed. In 
places the iron mineralization occurs across the full thickness of the 
limestone and extends into the igneous rock. The deposits dip steeply 
and are cut off at a depth of several hundred feet by a nearly horizontal 
post-ore tlirust fault. The iron-ore deposits are thought to have been 
formed by hydrothermal processes from solutions emanating from a 
large body of quartz monzonite of Tertiary age that occurs south of 
the deposits. 

Iron mineralization occurs for over 1 mile along the limestone- 
amphibolite contact and two main ore bodies are present. The west- 
ern deposit is 1,100 feet long, has a maximum width of 140 feet, and 
has been intercepted by drilling at 600 feet below the outcrop. The 
eastern ore body is 1.100 feet long, 30 to 60 feet wide, and was inter- 
cepted by drilling 250 feet below the outcrop. A split and a smaller 
oreshoot 200 feet farther east are also considered part of the eastern 
ore body. Massive magnetite and hematite make up the bulk of the 
deposit, but the ore carries inclusions of quartz and calcite and patches 
of unreplaced limestone and dolomite as well as various silicates of 
iron, calcium, and magnesium. Pyrite is common and the sulfur con- 
tent of the ore is about 0.40 percent ; phosphorus is low. 

No recent estimate of ore reserves is available. In U.S. Geological 
Surve}' Bulletin 871, published in 1936, reserves were estimated at 12 
million long tons. The average grade of the ore is about 56 percent 

Dale district 

The Dale district is in San Bernardino County, 25 miles east of 
Twentynine Palms. Production to the end of 1963 was about 273,000 
long tons of lump ore and concentrate. Except for several hundred 
tons, production has come from the Iron Age mine and almost all of 


the district's reserves are in the downward extension of the Iron Age 

Iron Age mine. — The property (No. 60, fig. 31) was patented in 
1902, but only about 11,000 tons was produced before 1956. A con- 
centrating plant was installed in 1956. 

The ore occurs in numerous steeply dipping, parallel replacement 
veins in porphyritic granite. The largest oreshoot is 15 to 100 feet 
wide and about 400 feet long. The other veins are much narrower. 
Persistence of the mineralization in depth has been established by 
drilling. The deposit is of the hydrothermal type. Dense magnetite, 
which has been oxidized to hematite near the surface, constitutes the 
bulk of the ore body. The ore is high grade, with very low sulfur, 
phosphorus, and other impurities. 

Minarets deposit 

The Minarets deposit (No. 13, fig. 31) is 69 miles northeast of Fresno 
in western Madera County, an alpine area inaccessible to motor ve- 
hicles. It has been known since the 1860's but its isolated location has 
discouraged exploration. The deposit was tested in 1944 and 1945 
with surface sampling and two diamond drill holes. 

The mineralized area is underlain by a slightly metamorphosed 
sequence of dacite and andesite flows which are the host for the iron 
deposition. Granite crops out nearby but it is clearly older than the 
mineralization, which is apparently derived from a deeply buried 
source. The main ore body is an elongated lens composed of somewhat 
irregular layers of magnetite, or magnetite and actinolite, which are 
completely enclosed within the volcanic series and seemingly have 
replaced it. The magnetite is distributed throughout the ore body as 
a series of sheets in which the proportions of magnetite and actinolite 
vary gradationally. The sheets or layers are roughly parallel to the 
trend of the ore body. The area of good-grade ore, in which the host 
rock is mainly replaced by magnetite and actinolite, is surrounded by 
an irregular zone in which the magnetite content grades from ore to 
waste. The iron values consist mainly of magnetite with a gangue of 
actinolite and minor feldspar and chlorite. Phosphorus ranges from 
0.30 percent to 0.80 percent. The ore contains no other contaminants. 

An ore body 1,500 feet long and 15 to 175 feet wide is exposed on the 
surface. It was cut at depths of 250 and 300 feet by two drill holes. 
In 1944 the deposit was estimated to contain 5 million tons of indicated 
and inferred ore with a grade of 60 percent Fe and 2 million tons of 
material containing 25 percent Fe. Bureau of Mines sampling and 
drilling indicated that the deposit was of lower grade but that the 
ore tonnage was larger (Severy, 1946) . 

Shasta and California deposit 

The iron-bearing area (No. 2, fig. 31) is on the east side of Shasta 
Reservoir in Shasta County, about 12 air miles north of Redding. Iron 
ore has been produced intermittently since 1892 Avhen it was used as a 
smelter flux. About 15,000 tons was mined from 1907 to 1918 for use 
in a nearby electric smelting plant and from 1942 to 1945 about 300,000 
tons was sold for use as ship ballast. During 1944 the Bureau of 
Mines drilled and sampled tlie deposit and made beneficiation tests. 

Iron-ore deposits occur in an irregular contact-metamorphic zone 
2,000 feet long and 300 to 1,000 feet wide formed in the Permian 
McCloud Limestone along its contact with intrusive quartz diorite. 


The contact zone contains large proportions of garnet and epidote 
along with small or localized occurrences of pyroxene, clilorite, and 
serpentine. Irregular masses and pods of magnetite are intercalated 
within the skarn and additional magnetite is disseminated throughout 
the skarn. Individual pods range in size from a few tons to 25,000 
tons or more. Two areas, one about 250 feet in diameter, and the other 
100 feet in diameter, contain concentrations of large magnetite masses 
and have an overall grade of about 40 percent Fe. Both of these areas 
have been proven to a depth of over 500 feet by drilling. These areas 
have been mined selectively. The ore contains magnetite with varying 
proportions of garnet, epidote, and other contact minerals, 0.17 percent 
sulfur, and minor phosphorus, and other impurities. 

The Shasta and California iron-ore deposits were estimated in 1945 
to contain 4,680,000 long tons of ore with an average grade of 37.82 
percent Fe, above a depth of 500 feet. 

Resource Potential 

Known iron ore deposits in California were inventoried by the U.S. 
Bureau of Mines in 1964. These deposits were estimated to contain a 
total of 972 million long tons of ore with an average grade of 42 per- 
cent Fe. Approximately one-half of this ore was classed as proven or 
indicated and one-half was inferred on the basis of geomagnetic or 
other information. It was further estimated — after considering the 
stripping required or the mining difficulty expected, the anticipated 
beneficiation expense, and transportation costs — that the following 
quantities of 65 percent Fe pellets could be made from this material 
at the indicated price levels with delivery in Los Angeles or San 
Francisco : 

Amount of 65 percent Fe pellets producible (cumulative totals) 
Price : Long tons 

$15.00 271, 000, 000 

$20.00 430, 000, 000 

$25.00 571, 000, 000 

In preparing these estimates, the Bureau of Mines engineers assumed 
neighboring deposits could be combined and operated as a unit to se- 
cure lower operating costs and that processing losses could be limited 
to 10 percent. 

The present poste<l price for California iron pellets delivered in 
Japanese steel centers is $16.25 per long ton of 64 percent grade. Con- 
tracts i^rovide for delivery of 1.8 million tons per year from 1966 until 
1974. This is equivalent to a price of $12.35 at Los Angeles or San 
Francisco and well under the $15.00 price used in the above estimate. 

As exploitation of deposits progresses, it is likely that total resource 
figures will be expanded considerably. 

Iron ore resists erosion and iron oxides have distinctive colors and 
are high in specific gravity, so surface accumulations are easily recog- 
nized. In addition, magnetite, a major iron mineral, is the easiest of 
all minerals to find by geophysical prospecting methods. For these 
reasons, it is probable that a greater proportion of the nation's iron 
occurrences have been discovered than is the case for other commodi- 
ties. Nearly all of California's known surface deposits were described 
in reports dated prior to 1915. During the 1950's, private industry 
undertook extensive airborne geomagnetic prospecting throughout the 


State's iron districts, spurred by the rapid o^rowth of demand for steel 
on the Pacific Coast. Tliis exploration, while it failed to find any new 
districts, resulted in the discovery of many additional ore bodies in 
previously known areas and indicated that large resources of iron ore 
were present in California. 

Additional g;eoma2:netic surveys will find new ore bodies, but the 
rate of future discoveries is certain to be much lower than in the past. 
Obviously, the most promising- areas for exploration are in the Mojave 
Desert and Klamath Mountains regions where previously examined 
districts will be surveyed for deep-lying ore bodies and areas between 
districts will be prospected for completely buried deposits. 

Selected References 

California Division of Mines, 1{>48, Iron resources of California : California Div. 

Mines Bull. 129, 265 p. 
, 1957, Mineral commodities of California : California Jour. Mines and 

Geology Bull. 176, 736 p. 
Carlson. D. W., and Clark. W. B.. 1954, Mines and mineral resources of Amador 

County, California : California Jour. Mines and Geology, v. 50, no. 1, p. 200-201. 
Franke, H. A., 1935, Mines and mineral resources of San Luis Obispo County. 

California : California Jour. Mines and Geology, v. 31, no. 4, p. 423-425. 
Harder. E. C. 1909, Some iron ores of western and central California : U.S. Geol. 

Survey Bull. 430, p. 225-227. 
Hubbard, H. G., 1943. Mines and mineral resources of Santa Cruz County, 

California : California Jour. Mines and Geology, v. 39, no. 1, p. 35-36. 42-43. 
, 1950, Mines and mineral resources of Madera County, California : Cali- 
fornia Jour. Mines and Geology, v. 46, no. 4, p. 458. 
Norman, L. A., Jr., and Stewart, R. R., 1951, Mines and mineral resources of 

Inyo County, California : California Jour. Mines and Geology, v. 47. no. 1, 

p. 54. 
Saul, R. B., Gray, C H., and Evans, J. R., (19 ), Mines and mineral resources 

of Riverside County, California: California Jour. Mines and Geology. (In 

Severy, C. L., 1M6, Exploration of the Minarets Iron Deposit, Madera County. 

California : U.S. Bur. Mines Rept. Inv. 3,985. 12 p. 
, 1948, Mining methods at the Yulcan iron mine, San Bernardino County, 

California : U.S. Bur. Mines Inf. Circ. 7.437. 11 p. 
Shattuck, .7. R. and Ricker, Spangler, 1948, Shasta and California iron-ore 

deposits, Shasta County California : U.S. Bur. Mines Rept. Inv. 4,272. 11 p. 
Wiebelt, F. J.. 1947, Bessemer iron project, San Bernardino County. California : 

U.S. Bur. Mines Rept. Inv. 4,066, 13 p. 
. 1948. Iron Mountain deposits, San Bernardino County, California : 

U.S. Bur. Mines Rept. Inv. 4,236, 11 p. 
Wright, L. A.. 1953, Mines and mineral deposits of San Bernardino County, 

California : California Jour. Mines and Geology, v. 49, nos. 1 and 2, p. 86-100. 


(By G. H. Espenshade, U.S. Geological Survey, Washington, D.C.) 

Industrl\l Use 

Kyanite and andalusite are aluminum silicate minerals that were 
once mined in California for the manufacture of refractory materials 
with high-alumina content. Related minerals of similar composi- 
tion — sillimanite, dumortierite, and topaz — can be used for the same 
purposes and are also known to occur in California, but have not been 
mined here. These minerals are commonly known as the sillimanite 
group (also as the kyanite group), and are used to manufacture re- 



fractory materials that will withstand high temperatures and abrupt 
temperature changes such as occur in metallurgical and glass fur- 
naces and certain tyi^s of kilns and boilers. "V^Hien heated to high 
temperatures these minerals all convert to the compound mullite 
(3 AI2O3.2 Si02) and silica; refractories made from these materials 
are commonly known as mullite refractories. Mullite can also be made 
using other high-alumina materials, such as diaspore clay, bauxite, 
and alumina, provided the content of iron and other impurities is low; 
this type of mullite is known in the industry as synthetic mullite. 

History and Production 

The sillimanite group of minerals came into use for the manufacture 
of mullite-bearing materials in the 1920's and consumption of these 
materials has grown steadily ever since. United States demand was 
largely supplied for many years by lump kyanite imported from India, 
and later from Kenya. Kyanite, andalusite, dumortierite, and topaz 
have been produced domestically from mines in California, Georgia, 
Nevada, New Mexico, North Carolina, South Carolina, and Virginia 
(Klinefelter and Cooper, 1961 ; Espenshade, 1962). Production from 
the California mines (the White Mountain andalusite mine, Mono 
County, and the Ogilby kyanite mine. Imperial County) ceased about 
1945. United States production from 1950 to 1962 consisted of kyanite 
concentrates from mines in South Carolina (Henry Knob deposit) 
and Virginia (Baker Mountain and Willis Mountain deposits). In 
1962 production of kj^anite concentrates was started from a mine at 
Graves Mountain, Georgia. Current United States production comes 
entirely from these four kyanite mines in Georgia, South Carolina, and 

Over the years the supply pattern has gradually changed from 
mainly foreign sources of material to predominantly domestic sources 
at the present time. Another very significant change in the industry 
has been the development of large-scale production of synthetic mullite. 
The United States is now no longer dependent upon imported kyanite. 
Kleinfelter and Cooper (1961, p. 30) state: "If imports were to be cut 
off completely, the United States could become self-sufficient within a 
few months by accelerating the production of synthetic mullite." 
Free world production of kyanite minterals in 1963 was about 170,000 
short tons, which came mostly from the Eepublic of South Africa, 
India, the United States, and Australia, in order of production (Var- 
ley, 1965 ) . The changing pattern of the domestic industry since World 
War II is indicated in table 23. 

Table 23. — United State.'< production of kyanite and synthetic mullite, and 
imports and exports of kyanite {short tons) 




Kyanite production (estimated) ' 
Synthetic mullite production 2--. 

Kyanite imports ' 

Kyanite exports 2_ 











I Varley (1965, p. 104). 

^ Klinefelter and Cooper (1961, p. 32-33) and U.S. Bureau of Mines Minerals Yearbooks. 

214 mineral and water resources of california 

Geologic Occurrence 

Kyanite, andalusite, and sillimanite all have the same chemical 
composition (ALSiOs, consisting of 62.9 percent alumina and 37.1 
percent silica), but have different crystal structure. They typically 
occur in metamorphic rocks, but also in some quartz veins and pegma- 
tites, and in some river and beach placers. Many deposits of these 
minerals are evidently metamorphosed aluminous sediments, but in 
some quartzose deposits hydrothermal processes seem to have been 
active. Although the AlaSiOs minerals are very common in some 
metamorphic rocks, they are rarely abundant enough or sufficiently 
free of impurities (attached or included grains of other minerals) 
for the deposits to be of economic value. They are generally most 
abundant in quartzose metamorphic or altered rock, where they are 
associated mainly with quartz, and in some places with other aluminum 
silicates, and may constitute 20 to 40 percent of the rock; massive 
segregations of the ALSiOs minerals may occur locally. These quartz- 
ose deposits have been the most productive deposits in all parts of 
the world. The ALSiO^ minerals are probably more widespread in 
micaceous schist, gneiss, and hornfels, but rarely make up more than 
about 15 percent of such rocks. Dumortierite (about 65 percent 
alumina and 30 percent silica, plus boron) and topaz (about 55 percent 
alumina and 33 percent silica, plus flourine) are not nearlj^ so common 
as the AlzSiOs minerals; they may occur in quartzose masses and 
quartz schist with other aluminous minerals, in quartz veins, and in 

Occurrences in California 

All of the kyanite group of minerals have been found in California, 
but in minable quantities at only two places : kyanite in a deposit near 
Ogilby, Imperial County, and andalusite at the White Mountain 
deposit. Mono County (fig. 32). Both deposits were mined during 
the same period, from the 1920's to about 1945, and yielded a total 
production of about 36,000 tons of aluminum silicate rock, according 
to Wright (1957). 

At the Ogilby deposit, kyanite occurs with quartz in very large 
masses associated with quartzite and quartz-muscovite schist (Samp- 
son and Tucker, 1931; Henshaw, 1942; and Wright, 1967). The 
quartz-kyanite rock occurs discontinuously over a distance of about 
a mile and has a maximum thickness of about 400 feet. Most of this 
rock contains more than 15 percent kyanite; the mined rock is said to 
have averaged 35 percent kyanite or iDetter. Only a small part of the 
quartz-kyanite rock was mined ; bodies of similar but unmined quartz- 
kyanite rocks are said to occur in the area (Wright, 1957). About 
21,000 tons of ore was mined from several quarries; kyanite was sepa- 
rated from decrepitated quartz by screening to give two products, one 
with 50 percent kyanite and 50 percent silica, and the other with 70 
percent kyanite and 30 percent silica (McLenegan, 1956). The Vitre- 
frax Corp. of Los Angeles operated the Ogilby mine until 1946 ; the 
Aluminum Silicates Co. of Los Angeles acquired the property in 1949 
(McLenegan, 1956) , and is said to have recently leased the property to 
Western InrUistrial Minerals Co. which may resume mining operations. 

At the Wliite Mountain deposit. Mono Comity, andalusite and 
diaspore occur in irregular veins and masses within a zone several 





Wh i te Mounta ins 
Q_jinda I us i te depos i t 

^ 116* «... . 

Ogi Iby 

kyan i te 

de pos i t 

Figure 32. Principal kyanite and andalusite deposits in California. 

miles long and less than a mile wide in quartzite and quartz-sericite 
schist associated with nietaporiDliyry and quartz monzonite (Jeffery 
and Woodliouse, 1931 ; Lemmon, 1937 ; and Wright, 1957) . The main 
mine working yielded about 20,000 tons of hand -cobbed ore that con- 
tained 53 percent or more andalusite. Because of very rugged ter- 
rain, this material had to be carried by mule back for 31/^ miles to a 
truck depot. The mine was operated by Champion Sillimanite, Inc., 
and the ore shipped to the parent company. Champion Porcelain Co., 
Detroit, where it was mixed with clays, dumortierite from Nevada, 
or alumina for the manufacture of porcelain and spark-plug cores. 

Mmerals of the kyanite group occur in minor to moderate amounts 
at numerous other localities in California. All the localities known 
prior to 1958 are listed by Murdoch and Webb (1956 ; 1960) , who note 
that andalusite is known to occur in 14 counties, kyanite and sillimanite 


in 7 counties each, topaz in 6 counties, and dumortierite in 4 counties. 
The AlaSiOs minerals occur most abundantly in metamorphic rocks, 
particularly in roof pendants of hornfels and schist in the Sierra 
Nevada srranitic batholith. 



Probably the only deposits of the kyanite group of minerals known 
in California that can be considered as resources are the White Moun- 
tain andalusite deposit and the Ogilby kyanite deposit. Wright 
(1957) states that they have remained idle "largely because no ready 
market exists for the kyanite and because most of the known bodies of 
higher grade and easily recovered andalusite had been removed." 
McLenegan (1956) concluded that there is a potential market for these 
minerals in California and Nevada of about 10,000 tons annually, 
and that this demand could rise to 40,000 tons if adequate local sources 
were found. As Wright (1957) indicates, revival of the kyanite- 
andalusite mining industry in California will require the development 
of local markets, discovery of sufficient high-quality ores, and the 
ability to compete with synthetic mullite, as well as with kyanite pro- 
duced from the southeastern states. 

Selected References 

Espenshade, G. H., 1962, Pyrophyllite, kyanite and related minerals in the United 
States (exclusive of Alaska and Hawaii) : U.S. Geol. Survey Mineral Inv. Map 

Henshaw, P. C, 1942, Geology and mineral resources of the Cargo Muchacho 
Mountains, Imperial County, California : California Div. Mines Rept. 38, 
p. 147-196. 

Jeffery, J. A., and Woodhouse, C. D., 1931, A note on a deposit of andalusite 
in Mono County, California ; its occurrence and technical importance : Cali- 
fornia Div. Mines Rept. 27, p. 459-464. 

Klinefelter, T. A., and Cooper, J. D., 1961, Kyanite, a materials survey ; U.S. 
Bur. Mines Inf. Circ. 8040, 55 p. 

Lemmon, D. M., 1937, Geology of the andalusite deposit in the northern Inyo 
Range, California : Stanford Univ., impublished Ph.D. thesis. 

McLenegan, J. D., 19.%, Refractories consumption and high alumina mineral 
resources in California and Nevada : U.S. Bur. Mines Rept. Inv. 5183, 16 p. 

Murdoch, Joseph, and Webb, R. W., 1956, Minerals of California : California 
Div. Mines Bull. 173, 452 p. 

, 1960, Minerals of California for 1955 through 1957 : California Div. Mines 

Bull. 173, supp., 64 p. 

Sampson, R. J., and Tucker, W. B., 1931. Feldspar, silica, andalusite, and kyanite 
deposits of California : California Div. Mines Rept. 27, p. 450-458. 

Varley, E. R., 1965, Sillimanite : Over.seas Geological Surveys (London), 165 p. 

Wright, L. A., 1957, Kyanite, andalusite, and related minerals, in Mineral com- 
modities of California: California Div. Mines Bull. 176, p. 275-280. 


(By R. M. Stewart. California Division of Mines and Geology, San 

Francisco, Calif.) 


Lead probably was one of the first metals to be won from its ores 
by smelting. The properties of lead that make it most useful are its 
softness and workability, high specific gravity, extreme resistance 


to corrosion, and a combination of low-melting point aiid high-boiling 
point. Estimates of lead usage in the United States indicate that 10 
percent is used primarily because of its specific gravity; 30 percent 
because of its softness, malleability and resistance to corrosion; 25 
percent because of its alloying properties; and 33 percent because of 
the properties of its chemical compounds (Perry, 1945, p. 66-67). 
About three-fourths of the lead used is in a metallic form, alone or 
alloyed. Although lead has a very wide variety of uses, about 54 
percent was absorbed during 1963 by the two principal uses, storage 
batteries, and gasoline antiknock additives. Pigments, chemicals, 
cable sheathing, and construction materials constitute other major uses 
of lead. Lead has the highest secondary recovery factor of the com- 
mon metals; about 60 percent of the lead in use ultimately will be 
recovered as scrap. 


The primary mineral galena (PbS) is the chief ore mineral of lead 
throughout the world, but the secondary minerals, anglesite (PbS04) 
and cerussite (PbCOs) also are significant ore minerals in the oxidized 
zone of some deposits. Other significant, although less abundant, 
minerals in the oxidized zone of lead deposits are : those of the pyro- 
morphite series (Pb5(P04As04)3Cl) ; linarite, a basic sulfate of lead 
and copper; plumbojarosite (PbFe6(OHi2(S04)4) ; and wulfenite 
(PbMo04). Silver and zinc minerals commonly are associated with 
lead minerals in California as well as throughout the world. (See sec- 
tions on silver and zinc in this report.) Primary lead-zinc deposits in 
California typically occur as cavity fillings or replacement bodies, and 
most occur in Paleozoic carbonate rocks. Most lead-zinc deposits 
clearly are associated wtih intrusive igneous rocks. 

In the oxidized zone, galena alters to anglesite which in turn alters 
to cerussite. Anglesite and cerussite are relatively insoluble, and lead 
ore is the most resistant of all base metal ores to further chemical al- 
teration. Enrichment can take place in the oxidized zone, however, 
by leaching of sulfur, zinc, and iron and possibly other constituents 
from the ore. All of the lead deposits in California have been oxidized, 
but primary sulfide minerals are present, in minor to major propor- 
tions, in all of them. 


The first lead mined in California probably was that produced from 
the southern part of the Panamint Range prior to 1859 by Mormons, 
and early developments were prompted by the silver content of the 
lead ores. The Cerro Gordo district, which ranks second after Darwin 
as a source of lead in California, was discovered prior to 1866, possibly 
as early at 1862. Production started in the Tecopa district at the 
Gunsight mine in 1865 ; and the first of the highly productive mines 
in the Darwin district was discovered in 1874. Although discoveries 
in other districts were being made during this same general period, 
or followed closely, none was to equal any of these three in importance. 

The principal mines in the Darwin district yielded ore valued at 
about $3,000,000 prior to 1900; $4,000,000 between 1900 and 1945, 
Avhen the Anaconda Copper Mining Co. purchased the principal 
mines; and $18,000,000 between 1945 and 1953 (Carlisle, and others, 

67-164 O— '616— pt. I 15 


p. 44) . Following a mid-year drop in lead and zinc prices in 1957. 
Anaconda suspended operations at Darwin and at the Shoshone mines 
in the Tecopa district. 

The Cerro Gordo district is credited with ore valued at $17,000,000 ; 
the Cerro Gordo mine has a total output valued at $15,000,000, and 
although it was worked intermittently until the late 1940's, has not 
been a significant source of lead since 1877. 

Prior to 1947, all the mines in the Shoshone group had yielded about 
250,000 tons of ore that had a gross value of about $5,000,000. More 
than half of this was produced by the Tecopa Consolidated Mining 
Co. during the period 1912-1928. As stated by Carlisle (1954, p. 46), 
operations by the Anaconda Co. since 1947 resulted in the production 
of more than 160,000 tons of ore that contained about 40,000,000 
pounds of lead, 6,000,000 pounds of zinc, 870,000 ounces of silver, and 
15,600 ounces of gold. The operations were suspended late in 1952, 
were resumed in 1956, but terminated during 1957. 

Lead production in California has been affected most by the national 
and international situation and the resultant price structures, not 
only for lead but for the other base metals and for silver as well. Un- 
doubtedly, the production of lead in the future will be similarly 


In terms of total production, the United States has, since 1893, 
been the world's chief source of lead, and, since 1900, has been the 
chief user of the world's lead. Since 1940, however, the United States 
has been forced to rely upon imports for a large part of the lead re- 
quired by its expanding industrial complex. Since 1960, mines in 
the United States have produced less than 10 percent of the world's 
total and have supplied only about 23 percent of the total lead used 
domestically. Recently discovered deposits in Missouri are now being 
developed and may soon reverse this trend. 

Deposits in California have yielded a total of about 495 million 
pounds of lead from 1877 through 1964. This output represents only 
about eight-tenths of one percent of the total mine production of 
lead in the United States for the same period. During the decade 
ending with 1964, the annual production of lead in California ranged 
from a low of 103 tons in 1961 to a high of 9,296 tons in 1956. The 
1964 production of 1,546 tons was the highest since 1957, when pro- 
duction reached 3,458 tons. Mines in Inyo County have been the 
source of about 93 percent of the State's total. 

Occurrences in California 

Most of the lead produced in California has been obtained from 
three districts in Inyo County shown on fisrure 33. These are: the 
Cerro Gordo district, about 13 miles east of Lone Pine and near the 
crest of the Inyo Range ; the Darwin district, about 35 miles southeast 
of Lone Pine; and the Tecopa district, at the southern end of the 
Nopah Range in the southeastern corner of Inyo County. 

The host rocks for the ore bodies in the Cerro Gordo district are 
limestone, marble, and quartzite beds of Devonian age. The Devonian 
and overlying Carboniferous rocks have been intruded by two small 
stocks of monzonite porphyry and by dikes of monzonite porphyry, 



1. Cerro Gordo Mine and district 

2. DarHin Mines and district 

3. Defense Mine. Modoc District 

4. Lippincott Mine 

5. Santa Rosa Mine 

6. Shoshone Mines, Tecopa district 

7. Ubehebe Mines 

Other mines and prospects 

See section on copper^ silver 
and zinc for distribution of 
other lead-bearing deposits 
in the St ate 

Figure 33. Lead deposits in Inyo County. 

diabase, and quartz-diorite porphyry, in that order (Carlisle and 
others, 1954, p. 43). The ore bodies, all nearly vertical, south-plung- 
ing, chimney-like bodies, were distributed, according to Knopf (1918, 
p. 113), through a north- to northwest-trending zone 1,500 feet long 
and several hundred feet wide. The ore minerals are argentiferous 
galena, cerussite, anglesite, smithsonite, sphalerite, tetrahedrite, and 
pyrite. Much of the zinc in the lead-rich deposits was removed by 
meteoric water and formed secondary deposits. 

The ore bodies of the Darwin district occur in Pennsylvania lime- 
stone which is folded about northeasterly to northwesterly axes. 
One of the major structural features influencing mineralization was 
a northwest-plunging anticline, the axis of which lies near the crest 
of the Darwin Hills. The limestone has been silicated in a wide zone 
peripheral to a quartz diorite stock that was intruded mainly along 
the core of this anticline and for an exposed distance of about 5 miles. 
Mineralization is contact metasomatic ranging to mesothermal (Hall 
and MacKevett, 1962, p. 69), related to the quartz diorite, and has been 
guided by igneous contacts, bedding planes, and cross fractures. "In 
order of importance, the orebodies are: (1) bedded replacements that 
commonly are more or less localized along anticlinal flexures and lie 
near but not in contact with the intrusive sills; (2) irregular replace- 


ments of (he silicated limestone along fissures; and (3) fissure filling:s" 
(Carlisle and others, 1954, p. 45) . 

The major primary sulfides are artjentiferous galena and sphalerite. 
Minor to very minor proportions of pyrite, chalcopyrite, tetrahedrite, 
bornite, chalcocite, and covellite are present. Extensive but irregular 
oxidation has produced ceiiissite, anglesite, plumbojarosite., sooty 
argentite, and cerargyrite. Leaching of zinc, sulfur, and some iron 
has been important in the residual enricliment of the oxidized ore 
(Davis and Peterson, 1949, p. 138) . 

Nearly all the lead ore from the Tecopa district has been produced 
from several mines that were consolidated as the Anaconda Copper 
Co.'s Shoshone mines. The host rock for all the ore bodies is the 
Noonday Dolomite of late Precambrian age which lies unconformably 
upon Precambrian metamorphic and sedimentai'y rocks and is over- 
lain by Lower Cambrian sedimentary rocks. The largest ore bodies 
appear to have formed at junctions of the northwest-trending Sho- 
shone fault with cross fractures and faults (Carlisle, and others, 1954, 
p. 46). Most of the ore in each of the deposits is highly oxidized. 
Cerussite and anglesite are predominant, and are associated with iron 
oxides, smithsonite, calamine, linarite, and caledonite. Residual 
galena, pyrite, and sphalerite are present in minor proportions. 

The Santa Rosa mine at the southern end of the Inyo Range, and 
several mines, notably the Defense, Minietta, and the Modoc, in the 
northern end of the Argus Range (the Modoc district) in Inyo County 
have been important sources of lead. 

Most of the rest of the lead that has been mined in California has 
been a by-product of the copper-zinc and gold mines of the Klamath 
Mountains and Sierran foothill areas (see sections on copper, gold, 
and zinc). Other areas that have yielded relatively small quantities 
of lead ore include the Clark Mountain district in northeastern San 
Bernardino County, a small district on the west slope of the Santa 
Ana Mountains in Orange County, and the northern Panamint Range 
in InyoCoimty. 


It is doubtful that the deposits that have yielded most of California's 
lead in this century are exhausted. The cessation of operations at 
the larger mines, such as Darwin, probably was due more to an un- 
favorable price stnicture for the metallic concentrates than to lack 
of ore of a grade that in prior operations had been economically suc- 
cessful. Tlie districts that have been the source of major proportions 
of the California production undoubtedly will, again, be the sites of 
further exploration when the price structure for lead (perhaps with 
a boost from copper, silver, or zinc) becomes favorable. In the long 
view, this situation is inevitable. 

Selected References 

Bishop, O. M., 1960, Lead, in Mineral facts and problems : U.S. Bur. Mines Bull. 
585, p. 429-444. 

Carlisle, Donald, and others, 1954, Base metal and iron deix)sits of s,outhern 
California. [Pt.] 5 iu Chap. 8 of Jahns. R. H., ed.. Geology of southern Cali- 
fornia : California Div. ]Mines Bull. 170, p. 41-49. 

Goodwin, J. G., 1957, Lead and zinc in California : California Jour. Mines and 
Geology, v. 53, p. 353-724. 

Hall, W. E., and MacKevett, E. M., Jr., 1962, Geology and ore deposits of the 
Darwin quadrangle Inyo County, California : U.S. Geol. Survey Prof. Paper 
368, 87 p. 


Knopf, Adolph, 1918, A geologic reconnaissance of the Inyo Range and the 

eastern slope of the southern Sierra Xavada, California : U.S. Geol. Survey 

Prof. Paper 110, 106-118. 
MacKevett, E. M., Jr., 1953, Geology of the Santa Rosa lead mine, Inyo County, 

California : California Div. Mines Spec. Rept. 34, 9 p. 
Moulds, D. E., 1964, Lead, in U.S. Bur. Mines Minerals Year book, 1963: U.S. 

Bur. Mines, p. 701-735. 
Norman, L. A., Jr., and Stewart, R. M., 1951, Mines and mineral resources 

of Inyo County : California Jour. Mines and Geology, v. 47. p. 59-68, 80-81. 
Perry, R. A., 1945, The lead industry: Min. Metall., p. 66-67, (Feb.). 
Stewart, R. M., 1957, Lead, in Mineral commodities of California: California 

Div. Mines Bull. 176, p. 281-292. 
U.S. Bureau of Mines, 1965, Lead, in Commodity data summaries, p. 80-81. 


(By O. E. Bowen, California Division of Mines and Geology, San Francisco, Calif. ) 

Importance or Calcareous Materials in California 

California, the most highly populated state in the union and also 
among the fastest growing in population, is fortunate to have vast 
resources of carbonate rocks to supply its expanding industries. Her 
cement industry alone, largest in the United States and probably in 
the world, for an equivalent political unit, consumes about 13,000,000 
tons of limestone and fossil seashells each year. In excess of 4,500,000 
tons of carbonate rocks are consumed annually by a great number 
of other industries, led by : aggregates for the construction industry, 
magnesian and high-calcium lime manufacturing, limestone and dolo- 
mite for steel manufacturing, roofing granules for the construction 
hidustry, limestone for sugar refining and limestone for glass manu- 
facturing, as shown in table 24. The value of carbonate rocks to the 
State's economy is immense, as it occurs widely distributed and is 
available at a relatively low cost compared to other raw materials. 

Table 24. — California consumption of limestone and dolomite during 1964 ^ 


1. Cement (from limestone, siliceous limestone, oyster shells) 12,750,000 

2. Aggregates — including concrete aggregate, road base, etc. (from 

limestone, magnesian limestone, dolomite) 2,000,000 

3. Magnesian lime (from dolomite, magnesian limestone) 500,000 

4. Steel flux (from limestone) 450,000 

5. Roofing granules (from limestone and dolomite) 4.50,000 

6. Sugar refining (from high-calcium limestone) 285,000 

7. White fillers (from high-calciimi limestone ; includes whiting, 

paper fillers, asphalt tile, linoleum, etc.) 210,000 

8. Glass (from high-calcium limestone) 200,000 

9. High-calciiim lime (from high-calcium limestone) 200,000 

10. Agriculture (from limestone and oyster shells ; includes fertilizer 

fillers, mineral foods, soil amendments) 135,000 

11. Poultry grit (from limestone, oyster shells) 105,000 

12. Riprap (limestone, magnesian limestone) 100,000 

13. Dimension stone (limestone, magnesian limestone, dolomite) 70,000 

14. Terrazzo chips 40,000 

15. Asphalt filler (limestone, magnesian limestone) 12,000' 

16. Miscellaneous (chemicals, concrete pipe, stucco, oil well drill- 

ing, etc.) 150, 000 

Total 17, 607, 000 

1 Tonnajres are estimated and include commercial and noncommercial items as well as 
imports. Data adapted in part from the U.S. Bureau of Mines, U.S. Census Bureau, and 
sources in industry. 


Limestone is one of the few raw materials that are absohitely basic 
in modern industry and necessary to our present civilization. In addi- 
tion to its major use in the manufacture of portland cement, it is the 
source of lime, for which there are over 7,000 uses. Most of these uses 
depend oji the caustic properties of calcium oxide or calcium-mag- 
nesium oxide produced by calcination of limestone or dolomitic lime- 
stone. In some of these uses, it serves to combine with and remove 
unwanted materials from a desired product as in the manufacturing 
of steel, and the refining of sugar and petroleum. Many of its uses 
are almost as old as recorded history, and because it is economical it 
has been widely employed. 

Origin, Accumulation, and Characteristics of Limestone and 


Limestone occurs in nature in many degrees of purity. Calcium is 
the principal metallic alkaline element which gives limestone the char- 
acteristics which make it a fundamental raw material. Magnesium 
is another metallic alkaline element present in all dolomites and in 
some limestones. For some industrial uses, magnesium is an important 
desirable constituent; for others, it is a harmful impurity. Alumi- 
nous, siliceous- and iron-bearing impurities may be critically dele- 
terious in some chemical processes and beneficial in others — as in the 
manufacture of portland cement. Sulfur and phosphorus may be 
present only in trace amounts if the limestone or dolomite is to be 
used in steel manufacturing. For glass manufacturing, the iron con- 
tent must be extremely low. Limestone, fossil seashells, magnesian 
limestone, and dolomite are at present the only carbonate raw" mate- 
rials that are economically feasible to mine in California at the present 

Calcite (CaCOg) is the predominating mineral in limestone. Dolo- 
mite ( CaCOs.MgCOs) is the principal mineral in rock dolomite. Arag- 
onite (also CaCOs) is the chief mineral secreted by organisms and 
found in seashells, but it is metastable and in time changes to calcite. 
In common industrial usage, a carbonate rock containing 95 percent 
or more of CaCOs is termed high-calcium limestone; one containing 
between 5 and 10 percent MgO is called magnesian or dolomitic lime- 
stone; one containing between 10 and 15 percent is limy dolomite; and 
one between 15 and 21.6 percent MgO is called dolomite. The terms 
"high calcium" and "chemical grade" are used more or less syn- 
onymously. In California, however, open-market availability of 
high-grade limestones is such that any producer who expects to com- 
pete in selling limestone or dolomite on the open market has to produce 
a rock having more than 97 percent CaCOa, if he expects to sell it as 
"high-calcium" or "chemical-grade" limestone, or it must contain 
20 percent or more ]\IgO to compete as dolomite. 

Many aquatic plants and animals, secrete calcium carbonate or a 
mixture of calcium and magnesium carbonates for protective and sup- 
porting parts. As many of these organisms are colonial or at least 
gregarious in habit, their remains may accumulate and be preserved 
in large concentrations. Micro-organisms also may contribute in- 
directly to the chemical precipitation of carbonate minerals by up- 


setting the equilibrium of the aqueous system, by catalytic activity, and 
so on. Changes in temperature and composition of ocean and lake 
waters also may result in direct chemical precipitation of carbonate 
minerals. Organisms appear to play the predominating role in lime- 
stone formation, mechanical concentration of carbonate detritus plays 
an important secondary role in limestone formation, and chemical 
precipitation appears to play a lesser role. A few large deposits of 
limestone have accumulated by direct chemical precipitation from 
vents of warm mineral springs. Dolomite apparently forms chiefly 
by replacement of pre-existing limestone masses, predominantly by 
diagenetic replacement on the sea floor, but also by mobilization of 
magnesian agueous solutions during the granitic emplacement phase 
of fold-mountain building. 

A great majority of California limestone and dolomite deposits 
occur in metamorphosed or partly metamorphosed marine sedimentary 
rock sequences. Most commonly, they are interbedded with non- 
carbonat© sedimentaiy rocks and make up only a small part of the 
stratigi'aphic section in which they occur. In a few remotely situated 
parts of the State, i.e., southern Inyo and northern San Bernardino 
Counties, carbonate rocks do form the bulk of some sedimentary sec- 
tions and reach thicknesses of more than 10,000 feet. In contrast to 
many other limestone and dolomite-producing states, California de- 
posits tend to occur in steeply dipping, structurally complex, lenticular 
bodies of small areal extent rather than in flat -lying or gently dipping 
formations of large areal extent. Consequently, prospecting for lime- 
stone in California is more complex than in most other states. 

Probably the most common deleterious ingredient fomid in lime- 
stone and dolomite is silica (SiOo) in the fonn of chalcedony or chert. 
It occurs disseminated or in the form of streaks, nodules, or beds. 
Quartz and feldspar sand grains as well as rock detritus are abundant 
in parts of some California limestone and dolomite formations. These 
impurities may be disseminated through limestone matrix or concen- 
trated as partings and beds. Clay in the form of illite or kaolinite is a 
conmion minor constituent of limestones and dolomites. In some for- 
mations it is present in large amounts, so that the limestone grades 
into shaly limestone or into marl in some parts of a formation. Such 
rocks may be valuable sources of material for portland cement manu- 
facture, but, for most other purposes, clay is a harmful ingredient in 
both limestone and dolomite. 

Another widely distributed impurity in California carbonate rocks 
is organic matter in the form of hydrocarbons or gas, hydrogen sul- 
fide being the commonest gas. In strongly metamorphosed carbonate 
rocks, where recrystallization has been widespread, solid organic mat- 
ter generally has been convei-ted to graphite, and the evolved gas has 
been trapped in pores, minute fractures, and along cleavages in the 
rock. In ciystalline limestone valued for its light color, graphite is 
hannful because it smears badly during grinding and discolors the 
ground product. A large amount of organic matter can be deleterious 
in chemical processes where it commonly causes scmnming of a 

Other constituents that may be troublesome in carbonate rocks are 
pyrite, chlorite, glauconite, and collophane, but with the possible 
exception of pyrite, none of these is common in California deposits. 


Invasion of a limestone by granitic intrusive rocks may result in intro- 
duction, by replacement, of pyrite and other metallic sulfide minerals. 

History of Utilization of Carbonate Rocks in California 

The use of lime-bearing materials in California dates back to the 
building of the Spanish missions, where witewash and lime mortars 
were widely used in small quantities. Abalone shells, pismo clams, and 
other shells obtained on the beaches were probably the first materials 
burned into lime. Later, accumulations of fossil shells were found 
and finally it was discovered that the crystalline limestones, so widely 
distributed throughout California, could be used. Not until the gold 
rush days of the early 1850's did lime become important to the con- 
struction industry in California, but from then on hundreds of lime 
kilns sprang up all over California. This rising demand was directly 
related to the hazardous fires which repeatedly swept through towns 
made of frame buildings. Field stone or brick buildings laid up in 
mnd or in lime mortar became the standard type of construction 
throughout the gold country, and many of these remain in use today. 
A great deal of lime was imported from Europe to supply demand 
during the early part of the gold rush period. 

Both marble and limestone were used as structural materials in 
buildings as early as 1850. The marble-cutting business, once substan- 
tial in California, has almost disappeared, because high labor costs 
make California marble noncompetitive with marbles from Italy, 
Georgia, and elsewhere. Limestone has been used as railroad ballast, 
road metal, and the like from gold rush days, and as concrete aggre- 
gate since the turn of the century. 

The lime manufacturing business probably had its heyday between 
1880 and 1900 — in relation to its importance to the then current 
economy, if not in actual tonnage produced. Vast banks of lime kilns 
were constructed in the Santa Cruz Mountains, Santa Lucia Range, 
Sierran foothills, Tehachapi Mountains, and the southwestern Mo- 
jave Desert. Many of the lime companies were as important for their 
day as the portland cement companies now are — in relation to the 
rest of the economy. 

Although Portland cement was invented in England as early as 1824, 
it was not used to any great extent in California until the late 1850's 
and 1860's. The first cement used here was imported from Europe. 
Even then its use did not greatly supplant lime mortars nor did con- 
crete become serious competition to masonry construction until about 
the turn of the century. This was partly due to primitive methods of 
making and handling cement which resulted in non-uniformity of the 
product. Also, it was difficult to keep dampness from deteriorating 
the stored cement. 

Cement manufacturing in California dates from 1860, when a 
hydraulic cement (a type manufactured at considerably lower tem- 
peratures than Portland cement) was placed on the San Francisco 
market. Apparently, limestone from beds in the Martinez FoiTuation 
(Paleocene) and from Pleistocene fossil seashells were blended with 
clay as the raw materials for this venture. The first cement approach- 
ing a true portland cement was made at Santa Cruz in a brick kiln 
about 1877 from crystalline limestone and clay. Another early plant 


that produced portland-type cement was built on the Jamul Eanch 
in southern San Diego County in 1891. The California Portland 
Cement Co. built a plant at Slover Mountain near Colton in 1895 that, 
although enlarged and rebuilt several times, has been in continuous 
operation through the present day. 

Since the early 1900's, cement plants have been the largest consumers 
of limestone in California, but numerous other industrial users of 
limestone have been equally important to the economy of California, 
even though the quantity of material they consume is smaller. The 
many chemical industries which consume limestone, for its lime con- 
tent, for the carbon dioxide that can be evolved, or both, seem to have 
developed principally since 1900. Many had their beginnings through 
the impetus of World War I. 'Limestone was quarried for steel flux 
and copper refining flux as early as the 1880's, possibly as early as 
1860. The use of limestone in sugar refining dates back at least to 
1870 when E. H. Dyer built the first successful refinery at Alvarado, 
Alameda County. The glass industry^, another major consumer 
of California limestone, was initiated by the Illinois Pacific Coast 
Glass Co. at San Francisco about 1897 and by the San Francisco 
Glassworks (1890-1898). 

Dolomite probably was first used in California as marble building 
stone, particularly around Sonora and Columbia in the gold country. 
Dolomite marble dimension stone was produced commercially in Inyo 
County about 1888 and may have been produced in the Sonora-Colum- 
bia area of Tuolumne County in the 1870's and 1880's. Production 
of dolomite in California was intermittent and not large up to 1942. 
Except for durable material used as crushed stone, the commonest use 
for dolomite up to 1942 was as a basic flux in the manufacture of steel. 
In 1942, the Henry J. Kaiser interests initiated the use of calcined 
dolomite and seawater in the manufacture of magnesia for use in the 
production of magnesium metal, and in 1945 began to produce mag- 
nesia refractories. Within a decade, the other California producers of 
magnesia altered their processes to use dolomite. These firms are by 
far the greatest consumers of dolomite in California. Prior to the 
advent of the use of dolomite in manufacture of magnesia, it had been 
made by interaction of lime with sea water. Interaction of calcined 
dolomite with sea water gives a substantially larger yield of magnesia. 

Occurrence of Limestone and Dolomite in California 

Most of the limestone and dolomite deposits in California occur in 
strongly deformed and metamorphosed marine sedimentary rocks. 
Most commonly they are of Paleozoic age although there are some of 
Precambrian, Mesozoic, and Cenozoic ages. Unmetamorphosed Ter- 
tiary algal limestones of good grade are found in the Eocene Sierra 
Blanca Formation of Santa Barbara County, and the Paleocene Mar- 
tinez Formation of the Santa Monica Mountains. 01igocene( ?) and 
Miocene shell limestone of the Vaqueros Formation is extensively 
quarried in San Luis Obispo County. Quaternary seashell deposits 
have been exploited at San Francisco, Newport, and San Diego Bays. 
Recent marl of caliche tyi>e has been quarried in a small way in Fresno 
and San Diego Counties. Chalk, an earthy foraminiferal limestone, 
is unknown in California. 


The principal areas where carbonate rocks are abundant and rea- 
sonably near to markets and to transportation facilities are: (1) the 
Klamath Mountains of Shasta and Siskiyou Counties, particularly the 
southeast part adjacent to Redding; (2) the foothill belt of the Sierra 
Nevada from Placer to Tulare Comity; (3) the Santa Cruz, Gabilan, 
and Santa Lucia Mountains of the central Coastal Ranges; (4) the 
Tehachapi Mountains and adjacent southernmost Sierra Nevada; (5) 
the Argus and Panamint Ranges of Inyo County ; (6) the Victorville- 
Oro Grande-Adelanto vicinity of the southwestern Mojave Desert; 
(7) the northern San Bernardino Mountains adjacent to Lucerne 
Valley; (8) the Mescal, New York, and Providence Mountains of 
eastern San Bernardino County; (9) the northern part of the San 
Jacinto Mountains including the Palm Springs-Lake Hemet and 
Beaumont-San Jacinto areas; (10) the Big and Little Maria Moun- 
tains of eastern Riverside County; and (11) the Coyote Mountains 
of Imperial County, largest potential source for the San Diego market- 
ing area. 

Four formations have yielded industrial limestone in Shasta and 
Siskiyou Counties: the Hosselkus Limestone (Triassic), the Kennett 
Formation (Devonian) ; the McCloud Limestone (Permian) ; and the 
Gazelle Formation (Silurian). The Hosselkus Limestone extends 
south into the northern Sierra Nevada, but the others are confined 
largely to the Klamath Mountains. The Kennett and Hosselkus for- 
mations yield limestone that is predominantly blue-gray to black; the 
McCloud yields predominantly dove-gray rock. The Hosselkus 
Limestone has been metamorphosed very little and is fine grained; 
rock from the other three formations commonly is recrystallized and 
ranges from fine grained to medium grained. None of these forma- 
tions has yielded white rock of high-calcium grade. Limestone, prob- 
ably of Paleozoic age and of medium to course grain and blue-gray to 
white hues, exist in the relatively inaccessible interior of the Klamath 
Mountains, notably in the subrange known as the Marble Mountains. 
Among the four formations, the McCloud Limestone probably con- 
tains the largest resources, but in the most accessible parts both mag- 
nesia and silica tend to be widely and sporadically distributed. The 
Hosselkus Limestone contains more uniform rock. Limestone has 
been quarried from the McCloud Limestone, near Redding, from the 
Kennett Formation on Backbone Creek (a tributary to the McCloud 
River), from the Hosselkus Limestone near Ingot, and from the 
Gazelle Formation near Gazelle. 

Several deposits of Hosselkus Limestone of potential economic 
importance are in and adjacent to the Genessee Valley of Plumas 
County, near the Western Pacific Railroad. They have not yet re- 
ceived much attention because of the availability of more accessible 
materials. The same is true of several deposits on the Feather and 
Yuba Rivers of the northern Sierra Nevada. 

In the west-central Sierra Nevada, most industrial limestone and 
dolomite deposits are in discontinuous series of simple lenticular 
masses in other metamorphic rocks or as pendants in granitic rock. 
Less commonly, they occur in masses having complicated outlines be- 
cause of severe folding. A few of the limestone deposits have yielded 
fossils ranging, at various localities, from Mississippian to Permian, 
but fossil e^^dellce is very sparsely distributed. A few small bodies 








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Figure 34. Principal limestone and dolomite districts in California. 

occur ill Jurassic rocks. The principal districts in the west-central 
belt that are producing commercial limestone or dolomite are the Cool- 
Cave Valley and Diamond Springs-Shingle Springs areas of El 
Dorado County; the Volcano district of Amador County; the San 
Andreas district of Calaveras County; and the Standard-Sonora- 
Columbia district of Tuolumne and Calaveras Counties. 

The crystalline limestones of the west-central Sierran foothill belt 
are associated with slate, metachert, phyllite, mica schist and green- 
stone of the upper Paleozoic Calaveras Formation. The largest 
masses occur east of the Mother Lode belt, but these are medium to 
coarse grained and commonly are mixtures of limestone and dolomite 


SO that careful sampling and selective mining is often necessary. Rock 
colors most commonly are blue-gray or white or variations of these. 
Dolomite generally is white to off-white. A succession of relatiAely 
small lenses (most not over a quarter of a mile long by 300 feet or less 
thick) containing predominantly fine-grained, dense dove-gray to 
blue-gray limestone is found in a narrow belt in the foothill area west 
of the Mother Lode, from Placer County south to western Calaveras 
County. On the whole, these lenses have been less intensely meta- 
morphosed than deposits east of the Mother Lode, and limestone from 
them holds its lump form much better during calcination. However, 
only a few are large enough and of sufficiently high purity to be either 
active or potential sources of industrial limestone. 

Many of the central Sierran limestone masses are too magnesian to 
be useful for purposes other than magnesian lime, although there are 
a few nearly pure calcitic and dolomitic masses from which com- 
mercial rock may be obtained without selective mining. The Stand- 
ard-Sonora-Columbia district contains the largest, continuously ex- 
posed masses of carbonate rock in the Sierra Nevada, rocks of this 
kind underlying many square miles. However, replacement masses 
and smaller patches of dolomite of very irregular shape make selection 
of quarry sites difficult in this district. 

In the southern Sierra Nevada, faulting along both east and west 
margins of the range has resulted in greater elevation of the granitic 
core and greater removal of the metasedimentary cover by erosion. 
Consequently, there are notably fewer limestone deposits there than 
in other parts of the province, and these are more remotely situated 
from transportation systems and markets. Deposits in Tulare County 
along the Kaweah and Tule River drainages (Three Rivers and 
Porterville districts) are being developed in a small way as well as 
those clustered south of Lake Isabella in Kern Countv. 

Very fcAv reasonably accessible limestone deposits exist m the north- 
ern Coast Ranges, and the market is limited because of the small 
population. In the central Coast Ranges, large roof-pendants of 
crystalline limestone and dolomite are found in the Santa Cruz, 
Gabilan and Santa Lucia Mountains and in the Sierra de Salinas. 
Carbonate rocks of these complexes, of probable Paleozoic age, com- 
monly are coarse grained, and white and blue-gray colors predominate. 
Both high-grade limestones and high-grade dolomite occur in deposits 
large enough for major exploitation (masses aggregating tens to hun- 
dreds of millions of tons) ; deposits of the northern Gabilan Range 
and southern Santa Cruz Range supply much of the current demand 
in the San Francisco Bay area. Nearly all of the dolomite currently 
used in northern California is quarried from deposits in the northern 
Gabilan Range. Dense, fine-grained limestones found in the Fran- 
ciscan Formation of Jurassic and Cretaceous a^e also supply notable 
tonnages to San Francisco Bay industries, particularly to the cement 
plant at Permanente, Santa Clara County. Quaternary oyster shells 
dredged from San Francisco Bay supply one cement plant at Redwood 
City, San Mateo County. 

The immense resources of coarse-grained, white crystalline lime- 
stone of the Pico Blanco district constitute virtiially the only unde- 
veloped major deposits of high-grade limestone close to tidewater 
anywhere on the California, Oregon, and Washington coasts. They 


are close to State Highway 1, 25 miles southeast of Monterey and 
only 3 airline miles from the Pacific Ocean. Lack of close railroad 
facilities and access roads has hindered their development thus far. 
Tertiary unmetamorphosed limestones of considerable present eco- 
nomic importance, and even greater future significance as the popu- 
lation increases, are sparsely distributed in the southern Coast Kanges 
of San Luis Obispo, Santa Barbara and Ventura Counties. Beds 
of shell limestone in the 01igocene(?) and lower Miocene Vaqueros 
Formation are quarried at Lime Mountain west of San Miguel for 
use in sugar refineries of Salinas Valley. Deposits of algal limestone 
in the P^ocene Sierra Blanca Formation can supply good quality, 
dense limestone to industries in Santa Barbara and Ventura Counties 
should the demand rise. 

Extensive deposits of carbonate rocks in the Tehachapi Mountains 
between Mojave and Frazier Mountain support two cement plants, one 
at Mojave and one at Monolith. Other industries to be based on 
these deposits are in the planning stages. The carbonate rocks occur 
as pendants more or less encased in granitic rocks, either alone or 
interbedded with mica schist and quartzite in sequences referred 
to either the Bean Canyon Formation or the Kernville Series. These 
rock groups are probably of late Paleozoic and/or early Mesozoic 
age, although fossils have not been found in them. The rocks are 
commonly coarse grained and colors range from white to blue-gray. 
Masses of dense, fine-grained rock are unknown in this area. Lime- 
stone, dolomite, and magnesian limestones are all present within the 
district. Some very pure, very white, very coarse-grained limestones 
exist west of Cantil at the headwaters of the Back Canyon drainage. 
Potentially exploitable deposits of both limestone and dolomite occur 
in Neenach quadrangle east of Lebec, and large deposits of cement- 
grade rock are distributed through the district. Granitic intrusions 
are common within many of the limestone bodies, and silica and 
silicate minerals introduced by contact metamorphism are also a com- 
mon problem in the district. 

The chemical plants located at Searles Lake, Inyo County, to- 
gether with the rail facilities that serve them, create a favorable eco- 
nomic environment that allows the extensive limestone deposits (Car- 
boniferous?) of the Argus Eange to be exploited. Carbonate rock 
deposits across Panamint Valley in the Panamint Range may ulti- 
mately be brought into production. Both high-grade dolomite and 
limestone are foimd there. Light-gray colors prevail, and both lime- 
stones and dolomites are medium to fine grained. 

Extensive de}x)sits of fine-grained white dolomite are being mined 
imderground near Keeler in the Owens Valley of Inyo County for 
use as terrazzo chips and white .aggregate for the Los Angeles market- 
ing complex. Immense reserves of dolomite exist there, and lime- 
stone deposits can be developed farther to the east. The dolomite is 
in the Ely Springs and Hidden Valley Dolomites of Ordovician to 
Devonian age, whereas the best limestone is in the Lost Burro Forma- 
tion of Middle and Late Devonian age. 

In the Victorville-Oro Grande district of southwestern San Ber- 
nardino County, limestone, dolomite, and dolomitic limestone are all 
found in commercial quantities. 

Tliese may occur singly or together in a given deposit and in places 
are interbedded with other metasediments such as mica schist, quartz- 


ite, and homfels. The carbonate rocks are in the Carboniferous (?) 
Oro Grande Formation and also in the conglomerate member of the 
Permian Fairview Valley Fonnation. A majority of the carbonate 
masses of the district consist of strongly metamorphosed, coarsely 
crystalline rock, but there .are a few bodies of weakly metamorphosed, 
dense, fine-grained rock of notable size at Sparkhule Hill and Black 
Mountain. Limestone ranges from pure white to nearly black, but 
white and gray or variegated combinations of the two colors are com- 
monest. The Victorville-Oro Grande district ranks among the largest 
limestone producers in the State, but only a little dolomite and dolo- 
mitic limestone has been marketed thus far from the district because 
of small demand. Granitic intrusions and introduction of silicate 
minerals along granitic contacts are the principal problems in 

There are immense resources of limestone and magnesian limestone 
in the northern part of the San Bernardino Mountains of San Ber- 
nardino County in the Furnace Limestone. This is at least partly 
equivalent in age and lithology to the Oro Grande Formation of the 
nearby Victorville-Ore Grande district. In general, these rocks are 
strongly metamorphosed and coarsely crystalline, but there are some 
patches of finer-grained, dense, more weakly metamorphosed rock. 
^Vliite and blue-gray hues prevail, and select wliite rock is in demand 
for white filler and roofing granules. White rock has been quarried 
intermittently in the Cushenbury district for many years, and there 
is a cement plant near the mouth of Cushenbury Canyon. 

Extensive deposits of white, coarsely crystalline limestone rind 
cream-colored dolomite occur in the Little and Big Maria Mountains 
of eastern Riverside County near the railhead at Midland, particularly 
a few miles northwest of Midland. The relatively long distince from 
the Los Angeles marketing area and unfavorable freight rates have 
limited production thus far, but it is likely that they will be activated 
in the near future. The limestone and dolomite occur in strongly 
deformed, intensely metamorphosed crystalline complexes of Paleo- 
zoic or Precambrian age. INIany of the limestone deposits are of verv 
high purity. Tlie dolomites have too high an iron content for some 
uses, but otherwise some deposits are of good grade. 

In the Riverside-Colton district pendants of limestone of Paleozoic 
or Triassic age have supplied cement plants and numerous users of in- 
dustrial limestone since 1895. Enormous tonnages of limestone have 
been quarried at Slover Mountain near Colton and at Crestmore near 
Riverside. The cement plant at Colton has been in continuous opera- 
tion since 1895. Plants at Crestmore and Colton have just been re- 
built, indicating that reserves are far from depleted. White, and 
blue-gray colors prevail and the rock is coarsely crystalline. Both 
cement-grade and high-purity limestones are present. Properties in 
the district are owned almost exclusively by the two operating cement 
companies. Several large, undeveloped deposits occur in the San 
Jacinto and Santa Rosa Alountains of Riverside County within the 
area enclosed by a line connecting Beaumont, San Jacinto, Hemet, and 
Palm Springs, particularly northeast of Lake Hemet. Limited water 
supply and competing land use plans have hindered development of 
these favorably located deposits. 


A series of pendants and structural blocks containing crystalline 
limestone deposits are along the San Andreas fault zone in the vi- 
cinity of Wrightwood in the northeastern San Gabriel Mountains. 
As these deposits are near the Los Angeles marketing complex, sev- 
eral have intermittently produced industrial limestone. Few if any 
of them are sufficiently large to support a cement operation. The 
limestone ranges from white to blue-gray and is generally coarse 

The rapid growth of the San Diego metropolitan area has greatly 
increased the market potential for limestone, cement, and lime prod- 
ucts. Large deposits found in the Coyote Mountains of western Im- 
perial County or rock imported from Baja California below Todos 
Santos Bay ultimately will have to supply this increased demand, 
although smaller deposits exist in the Dos Cabezas, Jacumba, and 
Verruga vicinities of eastern San Diego County. There are no large 
deposits in either San Diego or adjacent Orange Counties. In the 
Coyote Mountains, very large resources of blue-gray to white, mediiun- 
to coarse-crystalline limestone and some dolomite occur in a crystal- 
line complex of late Paleozoic or early Mesozoic age. Overlapping 
this crystalline core are discontinuous masses of shell-bearing lime- 
stone up to 50 feet thick of Miocene age. These are of two sorts, 
one a compact, pinkish-cream-colored limestone (by far the most 
abundant), and a friable, dark-colored shell limestone or coquina 
which occurs in lenticular beds less than 20 feet thick. Both types 
are low in magnesia and could serve as supplemental sources of 
cement-grade limestone if the much larger crystalline limestone de- 
posits are brought into production. Some of the latter are a little 
high in magnesium for cement, but large bodies suitable for cement 
are present, notably in the vicinity of Carrizo Mountain. 

The Mescal, New York, and Providence Moimtains are adjacent 
mountain ranges in eastern San Bernardino County reasonably close 
to the Union Pacific Kailroad that contain very large resources of 
limestone and dolomite. These have been exploited in only a small 
way, because water supply, living conditions, distance from markets 
and rail-freight rates have been unfavorable. They are likely to be 
more extensively developed in the near future. The carbonate rocks 
range from white through dove-gray to dark blue-gray. Both fine- 
grained, dense rocks and medium- to coarse-crystalline varieties are 
found in the district. Limestones of industrial grade occur in the 
Triassic Moenkopi Formation, the Yellowpine and Bullion Members 
of the Mississippian Monte Cristo Limestone, the Crystal Pass Mem- 
ber of the Devonian Sultan Limestone, and even in some parts of the 
Cambrian to Devonian ( ?) Goodsprings Dolomite. Potentially usable 
dolomite occurs in Goodsprings Dolomite, the Ordovician Ely Springs 
Dolomite, the Ironside Dolomite Member of the Devonian Sultan 
Limestone and in the Cambrian Bonanza King Dolomite. 

Limestone and Dolomite Resource Potential 

California's resources of limestone, dolomite, and cement materials 
are very large in most grades of rock for most use categories and are 
more than adequate for the foreseeable future. The carbonate rock 
commodities are low-priced, and, as transportation costs form a sig- 


nificant part of total cost to the user, adjacency to markets is of prime 
importance. The areas of coastal or tidewater industries, for example, 
are very poorly supplied, and demand there may ultimately be satis- 
fied by imports because water- frei^rht rates are cheap. The search for 
higher valued deposits of very high purity, or deposits of very white 
or attractively colored rock continue — particularly for deposits well 
located with respect to potential consumers. At the present time, most 
producing deposits lie within 150 miles of marketing centers and a 
majority are within 75 miles of such centere. As the better-grade 
deposits close to market are depleted, it will be necessary to go farther 
from market or else to go more intensively into beneficiation of low- 
grade deposits situated close to markets. Competition and conflicting 
uses for land also tend to drive quarry and mine based industries 
farther and farther from markets. 

Because of remoteness, lack of water, or poor living conditions at 
some southern California deposits, some classes of carbonate rock for 
southern California markets are supplied from Nevada. Improved 
transportation and freight handling or adjustment in current rail- 
freight rates could change this situation. The burgeoning population, 
with its resultant expanding manufacturing and construction indus- 
tries, offer business opportunities unmatched elsewhere. 

Carbonate Rock Districts of Particular Major Future 


The San Diego marketing area ultimately will have to be supplied 
from the Coyote and Fish Creek Mountains of Imperial County, as this 
is the closest district containing major resources. Smaller deposits 
such as those at Dos Cabezas, Jacumba, and Montezuma Valley may 
be developed for local needs. Deposits south of Punta Banda, Baja 
California, could provide imports into the San Diego area. 

The notable resources of white crystalline limestone in the Little 
and Big Maria Mountains of eastern Riverside County may soon be 
developed, particularly if favorable rail-freight rates are established. 
Deposits in the San Jacinto and Santa Rosa Mountains of Riverside 
County are large and of fairly good quality. 

Deposits in the Mescal, Ivanpah, New York, and Providence Moun- 
tains, all of which are reasonably close to a railroad, are of near- 
future interest. Also, those in the Tehachapi Mountains and southern- 
most Sierra Nevada between Mojave and Frazier Mountain are of 
future interest. 

With the opening up of the interior of Santa Barbara and Ventura 
Counties, the extensive high-grade limestone deposits in the Eocene 
Sierra Blanca Formation ultimately will be utilized. Lack of good 
access roads has limited their development thus far, and the popula- 
tion and market situation is just reaching a favorable stage to attract 
new industries. 

Development of deep-water port facilities and an industrial complex 
around Moss Landing on Monterey Bay probably will result in devel- 
opment of the immense, high-grade, white crystalline limestone de- 
posits at Pico Blanco, Monterey County. These are the only large 
deposits of high-grade limestone close to tidewater on the Pacific Coast 
of California, Oregon, and "Washington. 


Selected References 

Blanks, R. F., and Kennedy, H. L., 1955, The technology of cement and concrete: 
New York, John Wiley and Sons, 414 p. 

Bogure, R. H., 1955, The chemistry of portland cement : New York, Reinhold Pub. 
Corp., 2d ed., 798 p. 

Bowen, O. E., 1957, Limestone, dolomite, and lime products, in Mineral commodi- 
ties of California : California Div. Mines Bull. 176, p. 293-306. 

Bowen, O. E., and others, in press. Limestone, dolomite and iwrtland cement in 
California : California Div. Mines and Geology Bull. 

Bowles, Oliver, 1952, The lime industry : U.S. Bur. Mines Inf. Circ. 7,651, 43 p. 

, 1956, Limestone and dolomite : U.S. Bur. Mines Inf. Circ. 7,738, 29 p. 

Clausen, C. F., 1960, Cement materials, //; Industrial minerals and rocks : New 
York, Am. Inst. Mining Metall., and Petroleum Engineers, p. 203-231. 

Gillson, J. L., and others, 1960, The carbonate rocks, in Industrial minerals and 
rocks : New York, Am. Inst. Mining Metall., and Petroleum Engineers, p. 132- 

Ham, W. E., and others, 1962, Classification of carbonate rocks : Am. Assoc. Pe- 
troleum Geologists Mem. 1, 272 p. 

Johnson, J.H., (compiler), 1952, Studies of organic limestones and limestone- 
building organisms : Colorado School Mines Quart., v. 47, no. 2, 94 p. 

Johnson, J. H., 1954, An introduction to the study of rock-building algae and algal 
limestones : Colorado School Mines Quart., v. 49, no. 2, 117 p. 

Key, W. W., 1960, Chalk and whiting, in Industrial minerals and rocks: New 
York. Am. Inst. Mining Metall., and Petroleum Engineers, p. 233-242. 

Kirk, R. E., 1952, Lime and limestone, in Encyclopedia of Chemical Technology : 
New York, Intrascience Encyclopedia Inc., v. 8, p. 346-381. 

Lamar, J. E., 1961, Uses of limestone and dolomite: Illinois State Geol. Survey 
Circ. 321, 38 p. 

Logan, C. A., 1947, Limestone in California : California Jour. Mines and Geology, 
V. 47, no. 3, p. 175-351. 


(By G. I. Smith and W. P. Irwin, U.S. Geological Survey, Menlo Park, Calif.) 

Most of the lithium obtained in California comes from saline brine 
in Searles Lake, one of the chief sources of the world's lithium, 
although known mainly for its other extractable components (see 
chapter on Sodium carbonate) . Much larger production of lithimn 
concentrate has come from pegmatite deposits in North Carolina; 
smaller quantities of pegmatite material come from the Black Hills 
in South Dakota. Other states from which lithium has been obtained 
are Arizona, New Mexico, Colorado, Wyoming, Massachusetts, New 
Hampshire, and Maine. 

Lithium has many uses. Major quantities are used in lithium 
greases, ceramics and glass, welding and brazing, and air conditioning. 
Large quantities have also been purchased by the Atomic Energy 
Commission whose interests probably include both the neutron absorp- 
tion capacity of the lithium-6 isotope, and the high-energy potential 
of the nuclear reaction l)etween lithium-6 and deuterium. Smaller 
quantities of lithium are used in production of batteries, pharmaceu- 
ticals, alloys, and as a catalyst. Future uses may include lithium as 
a heat-exchange mediiun in thermonuclear reactoi's, as a catalyst for 
new processes, and in new alloys. The lithium-6 isotope forms about 
7.5 percent of the lithium in natural deposits, and, if it becomes widely 
used for shielding and as a reactant in nuclear power plants, large 
quantities of tjie more abundant lithium-7 isotope might be left over 
for other uses (Schreck, 1960; Kesler, 1960; Eilertsen, 1964). 

67-164 O— 66— pt. I 16 


Minable lithium deposits are known on every continent. Of those 
being mined today, all except the deposit in California are pegmatites. 
Published data suggest that in 1963 the largest production outside the 
United States was in Khodesia, but large quantities also came from 
other African nations, Australia, and Canada. Unreported amounts 
w^ere produced in South America, and production from one or more 
Conunmiist nations is likely (Eilertsen, 1964) . 

In 1954 the United States produced about 38,000 tons of lithium 
minerals and compounds containing almost 2,500 tons of lithium oxide. 
This was valued at $3,126,000 (Schreck, 1961). At about the same 
time, the American Potash & Chemical Corp. at Searles Lake was 
estimated to have an annual production capacity of lithium carbonate 
equivalent to 200 to 300 tons of lithium oxide, or about 10 percent of 
national production (Ver Planck, 1957). Production figures for the 
years after 1954 have not been published. 

The production of lithium from the concentrated brines of Searles 
Lake started in 1938. The complex process used yields dilithium 
sodium phosphate along Avith six other products, then converts it to 
lithium carbonate for shipment. The brines, which average about 
0.015 percent lithium oxide, are pumped from the upper of two saline 
layers that were deposited during late Quaternary time (see section 
on Sodium carbonate). Lithium minerals, however, have not been 
found. Although the total production of lithium from this deposit 
will actually be determined largely by the reserves and future prices 
of its co-products, the lithium in it constitutes a sizable percentage of 
the United States indicated reserves (Norton and Schlegel, 1955; 

Prior to the recoverv of lithium from the brines of Searles Lake, 
California production of lithium-bearing minerals was from pegma- 
tites of the Pala district in northern San Diego County. The total 
reported production of lithium minerals mined from these pegma- 
tites is 23,480 short tons, valued at 432,800, for the period 1900-1928. 
Nearly all of this production was from the Stewart mine. The prin- 
cipal lithium-bearing mineral of the Pala district is the lithium-rich 
mica lepidolite, followed in order of importance by spodumene and 
amblygonite. The lithium deposits of the Pala district are chiefly 
zoned pegmatites; the spodumene generally occurs in the core and 
intermediate zones, and the minable concentrations of lepidolite mostly 
occur as a replacement of the primary pegmatite minerals along the 
lower parts of the spodumene-rich zones (Jahns and Wright, 1951). 

Additional sources of lithium in California appear to be few. Ab- 
normal concentrations occur in clays in the Mojave Desert. One, near 
Hector, contains a little over 1 percent lithium oxide (Foshag and 
Woodford, 1936; Ames, Sand, and Goldich, 1958) : another, northeast 
of Amboy, contains 0.50 percent (Foshag and Woodford, 1936) ; still 
another, near Boron, is reported to contain 0.5 to 1.0 percent (Kesler, 
1960). These percentages are close to those required for profitable 
operations from pegmatites (Norton and Schlegel, 1955), but the 
deposits are not currently considered economic sources of lithium. 
Brines from geothermal wells in the Salton Sea area contain about 
0.065 percent lithium oxide (White, 1965), but whether such com- 
ponents as lithium can be extracted will not be determined until sev- 
eral complex engineering problems have ])een solved. 


In two other western States, however, steps are beino; taken to ex- 
tract lithium from brines in amounts wliich may have major impact 
on all facets of the industry. A dry lake at Silver Peak, Nevada, is 
being: developed by the Foote Mineral Co. as a source of lithium; the 
subsurface brines are reported to be 6 to 7 times richer in lithium than 
other known source brines (P^n^. Mining Jour., 1965; Wall Street 
Jour., 1965). An option on brines from Great Salt Lake, Utah, has 
been taken by Lithium Corp. of America for future extraction of 
lithium chloride plus other products (P^ilertsen, 1964). 

Selected References 

Ames, L. L., Jr., Sand, L. B., and Goldich, S. S., 1958, A contribution on the 

Hector, California, bentonite deposit : Econ. Geology, v. 53, no. 1, p. 22-37. 
Eilertsen, D. E., 1964. Litliium : U.S. Bur. Mines, Minerals Yearbook, 1963, v. 1, 

p. 751-755. 
Engineering and Mining Journal, 1965, Foote Mineral Co., in Nevada : Eng. 

Mining Jour., v. 166, no. 4, p. 148. 
Foshag, W. F., and Woodford, A. O., 1936, Bentonitie magnesium clay mineral 

from California : Am. Mineralogist, v. 21, no. 4, p. 238-244. 
Jahns, R. H., and Wright, L. A., 1951, Gem- and lithium-bearing pegmatites of 

the Pala district. San Diego County, California : California Div. Mines Spec. 

Rept. 7A, 72 p. 
Kesler, T. L., 1960, Lithium raw materials, in Industrial minerals and rocks : 

New York, Am. Inst. Mining Metall. Petroleum Engineers, p. 521-531. 
Norton. J. J., and Schlegel, D. M., 1955, Lithium resources of North America: 

U.S. Geol. Survey Bull. 1027-G, p. 325-350. 
Schreck, A. E., 1960. Lithium, in Mineral facts and problems: U.S. Bur. Mines 

Bull. 585, p. 473-479. 

, 1961, Lithium, a materials survey : U.S. Bur. Mines Inf. Circ. 8053, 81 p. 

Ver Planck, W. E., 1957, Tiithium and lithiimi compounds : California Div. Mines 

Bull. 176, p. 307-312. 
Wall Street Journal, 1965, Foote mineral preparing brine .source of lithium : 

Wall Street Jour., May 10, p. 5. 
White, D. E., 1965, Saline waters of sedimentary rocks : Am. Assoc. Petroleum 

Geologists Mem. 4. p. 342-366. 


(By A. R. Smith, California Division of Mines and Geology, San Francisco, 


Three plants in California Droduce macnesium comoounds from 
sea water and sea water bittern by treatment wdth calcined dolomite 
(Ver Planck, 1957). Plants at Newark, Alameda County, and Moss 
Landing, Monterey County produce magnesia refractories and spe- 
cialty magnesias. Magnesium compounds of high purity for phar- 
maceutical and other chemical uses are manufactured in South San 
Francisco. A fourth operation in Chula Vista, San Diego County 
produces magnesium chloride from bittern without the use of dolomite. 

The most miportant commercial magnesium compounds produced 
in California are : the hydroxide, oxide, chloride, carbonate, trisilicate, 
and sulfate. The production of magnesium oxide from sea water is 
essentially one of reacting calcined dolomitic lime (combination of 
calcium and magnesium oxides) with sea w^ater to form magnesium 
hydroxide; the magnesia comes from both the calcined dolomite and 
sea water in about equal amounts. This magnesium hydroxide is 
then fired in rotary kilns to form magnesia that ranges from 65 to 98 
percent MgO. 



111 California, magnesium hydroxide also is the raw material for 
manufacturing basic magnesium carbonate which elsewhere is made 
from dolomite. Magnesium chloride is obtained at the Chula Vista 
plant, San Diego County by evaporating, with heat, bittern from an 
adjoining salt plant — discarding the precipitate and concentrating the 
liquor. To produce the trisilicate, sulflate, and other magnesium com- 
pomids, caustic calcined magnesia is used in chemical combination 
with the necessary acid radical. These are, for the most part, specially 
processed to meet rigorous physical and chemical standards. Loca- 
tion of the plants is shown on figure 35, and products are listed in 
table 25. 



Fibrtboard Papsr Product! Corp. |. 

Philadelphia Quartz Co. of Calif. 
Food Machinery and Chanical Corp.. 

NtHBrii plant 
Food Hachinary and Chaaiical Corp.. 

Chula Vista plant 

0. Kaisar AluBinu* and ChcBical Corp., 

Hots Landing oparalion 

1. Marina Magnaiiuv Products Division. 

■trek and Co. . Inc. 


I. Bald Cagia Mine 

7. Cadar Mountain 

3. Frasno 

4. Gray Eagia Mine 

5. Harhar Mina 

6. Ha Ml 

7. Hiion Rartch 
6. Kings 
9- flad Mounta in Mina 

I 0. Rad S I Ida dapos it 

1 1 . Saapson Mi na 

12. Snovf laha and Blanco Mines 

13. Success area 

14. Sull ivan 

15. lestern Mme 
IB. Ihite Rock Hint 


Hollister dotonita quarry. Food 
Machinery and Chasical Corp. 

Natividad dolonila quarry. Raiser 
AluffinuH and Cheancal Corp. 

Kae lar - independence area. Inyo County 

Sen Bernardino Mountains 

S lar ran f ooth 1 1 I dapos i li 

Victory 1 1 le-Or Brande deposits 

Figure 35. Map showing locations of plants producing magnesium compoimds 
in California, some areas with commercial grade dolomite, and selected mag- 
nesite deposits. 




















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The chemical and physical properties of the tAvo general classes 
of magnesium oxides are largely defined by the temperature of cal- 
cination : 

a. Dead-humed magnesia (refractory grade) is produced by burn- 
ing magnesite or magnesium hydroxide above 1,450° C. The result- 
ing magnesium oxide granules are chemically inert, (with less than 
2 percent carbon dioxide) and contain various proportions of iron 
oxide, silica, alumina, and lime, either as impurities in the raw ma- 
terial or as additives. "Periclase"', of which most refractorj- brick 
is presently made, is a dense crystalline magnesia containing over 90 
percent MgO, with chromite and silica as the principal additives. It 
is made by firing this mixture to extreme temperatures, 1,760° C or 
greater, depending on the type of bond desired for the brick. Natural 
magnesia is the mineral periclase. 

b. Gmistic-calc'med magnesia is produced by calcining magnesium 
hydroxide at temperatures of at least 1,200° C or to such degree that it 
contains less than 10 percent ignition loss (carbon dioxide and water), 
and slakes in water or air. It may contain 90 to 98 percent MgO : 
iron oxide, silica, alumina, and lime are undesirable impurities. 

Eefractory magnesia is consumed mainly by the steel industry to 
line open-hearth steel furnaces, either directly as grains or in refrac- 
tory bricks and mortars. Other major uses of magnesia refractories 
are in copper and lead smelters, in rotary kiln applications of the 
Portland cement industry, and the magnesia calcining plants them- 
selves. The use of dead-burned magnesia is increasing at a rate 
greater than the growth in use of metals, since magnesia refractories 
have increasingly supplanted other refractories in the metal-makmg 
industry. In 1930, the total apparent consumption of dead-burned 
magnesia by all industries was equivalent to about 4.16 pomids per 
ton of steel. By 1945, the figure had increased to 6.5 and in 1963 was 
about 14 pounds per ton of steel produced in the United States. 

The largest single market for caustic-calcined magnesia is in mag- 
nesium oxj'Chloride and oxysulfate cements, which are used mainly 
for fireproof, resilient flooring. The cement is prepared by mixing 
a solution of magnesium chloride or sulfate with ground, caustic- 
calcined magnesia. Other major uses for caustic-calcined magnesia 
are in the paper pulp, rayon, fertilizer, insulation, and chemical in- 
dustries. The other specially prepared magnesium compounds made 
in California are used to manufacture a variety of products. The 
rubber industry uses magnesium oxide in various synthetics (hypalon, 
neoprene, butyl) ; magnesium oxide, carbonate, hydroxide, and trisil- 
icate are primary ingredients in antacid preparations. 

Magnesium metal is used as a structural metal, an alloying con- 
stituent for other metals, and as a reducing agent to produce titanium, 
zirconium, hafnium, uranium, and beryllium. Since 1956, the metal- 
lurgical uses for primary magnesium have exceeded the structural 
uses, and in 1964 amounted to about 62 percent of the total use 
figure. Magnesium as an aluminum alloy accounts for two-thirds of 
this metallurgical classification. Since 1945, primary magnesium has 
not been produced in California. Magnesium production is shown on 
table 26. 



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Magnesium, the eighth most abundant element in the earth's crust, 
averages 2.09 percent in igneous rocks and about 4.77 percent, in lime- 
stones. Magnesium is the second most abundant metal after sodium 
in sea water, which contains the equivalent of 0.21 percent MgO as 
a chloride or sulfate. The most important magnesium-bearing min- 
erals are dolomite (Ca.,Mg) (CO3), magnesite (MgCOa) and brucite 
(Mg(OH)2. With the exception of a few hundred tons of imported 
brucite (used in the manufacture of epsom salt), sea water and dolo- 
mite are the only raw materials presently used in California's mag- 
nesia industry. Magnesite is mined at Chewelah, Washington, and 
Gabbs, Nevada (also the source of some brucite) ; elsewhere, olivine 
(MgFe)2Si04, foi-sterite (MgoSi04), and serpentine (H4Mg3Si209) 
have minor uses as refractories, and as a source of magnesium 

Prior to World War I, magnesite was not regularly produced in the 
United States; the needs for industry were met by imports, largely 
from Austria and Hungary. The first recorded production in Cali- 
fornia, and possibly in the United States, was from Cedar Momitain, 
Alameda County in 1886. However, the amount mined was small, and 
annual magnesite production in the United States (centered entirely in 
California) did not reach 10,000 tons until 1910. The first commer- 
cial production of magnesium compounds from sea water was obtained 
in 1928 at South San Francisco. The present operation is still on the 
original site and, since 1951, has been the Marine Magnesium Products 
Division of Merck & Co. 

The volume of magnesite mined in California between 1910 and 
1945 followed the fortunes of two world wars, until it finally suc- 
cumbed to dolomite and sea water as a source. xVnnual production of 
magnesite, used mainly for refractory purposes, rose to more than 200 
thousand tons by 1917, most of which came from C^ilifornia. Produc- 
tion dropped to a low in 1938, and rose slightly in 1941 to only 50 
thousand tons in California during the start-up period of the mag- 
nesia plant built by Westvaco Chlorine Products Corp. at Newark. 
The mining of magnesite, henceforth, declined steadily in California, 
with the increasingly efficient manufacture of magnesia from dolo- 
mite and sea water, until the Western mine stopped regular produc- 
tion in 1945. 

Calcined dolomite was initially used by Marine Products, followed 
by Kaiser in 1942, and was substituted for oyster shells as the precipi- 
tating agent in 1947 at the Newark operation. Since then, the use of 
dolomite has increased concurrently with that of magnesia. In 1964, 
the manufacture of magnesia used about 500,000 tons of California 

Dolomite, which now accounts for approximately one-half of the 
magnesia produced in California is generally restricted in occurrence. 
The dolomite used at Newark and Moss Landing is mined from sep- 
arate quarries in the Gabilan Range between Salinas and Hollister. 
These deposits consist of large roof pendants of crystalline dolomite 
(with some limestone) in Paleozoic(?) complexes. (Eefer to the 
section on "Limestone, dolomite, and lime products" for description 
of dolomite resources in California.) 

Magnesite has three major tyj^es of occurrence : (1) as large crystal- 
line bodies in dolomite, (2) within shear zones and veins, and as 


replacement-like bodies in serpentine, and (3) tis sedimentary del>osit^s 
associated Avitli playa lake beds. The larger magnesite dej^osits of 
the world, including those of Chewelah, Washington, and Gabbs, 
Nevada, and those in Austria and Manchuria, are of the dolomite 
replai^cment type. The magnesite of these deposits is crystalline, as 
constrasted with the cryptocrystalline or "amorphous*' variety, char- 
acteristic of deposits associated with serj)ent.ine and with lake 

Most of the magnesite deposits in California are aas<jc.iated with ser- 
pentine and (K'cur in the (^alifoniia Coast Ranges and in the western 
foothills of the Sierra Nevada. Many of the deposits and mines have 
been discussed l>riefly by l^-adley (1925, p. 41-140), and othei-s by 
Hess (1908) , and Gale ( 1914) . The Red Mountain magnesite district, 
on the border of Santa Clara and Stanislaus Counties, is a typical 
replacement deposit which has l)een studed in detail by Bodenlos 

Certain terrestrial brines are important sources of magnesium chem- 
icals. The l)est known are the magnesium -calcium chloride brines 
of Michigan, Ohio and West Virginia. In California, the brine of 
Bristol Lake, San Bernardino County belongs to this claas; but mag- 
nesium compounds are not recovered from it. 

The manufacturing process is fundamentally alike in the large 
operations of Food Machinery and Chemical Corp., Kaiser, and Marine 
Magnesium. Sea water is treated with a regulated amount of slaked 
dolomite or lime to precipitate the soluble bicarbonates as calcium car- 
bonate. At the Food Machinery and Cliemical Corp. plant, which 
uses concentrated salt water bittern, the sulfate must Hrst be removed 
by combining the bittern with calcium chloride. Then, the calcium 
carbonate is removed by thickening and the '"purified" sea water is 
combined with either dry or slaked calcined dolomite. The resulting 
magnesium hydroxide is washed witli fresh water to remove calcium 
chloride and thickened in a counter-current system to concentrate the 
sluri*y of magnesium hydroxide. The thickened magnesium hydrox- 
ide is filtered and fed into kilns for conversion to caustic-calcined 
or dead-burned magnesia. 

Synthetic magnesia (produced from sources other than brucite, 
magnesite, or magnesium silicate ores) supplies an increasing portion 
of the total domestic supply of both dead-burned and caustic-calcined 
magnesia. In 1947, synthetic magnesia accounted for about '^0 per- 
cent of the usage; by 195G, it increased to 5t) percent: and in 1968 the 
figure was 74 percent. Production from well brines, tlolomite, and/or 
raw sea water, and sea water bittern in 1963 accounted for about 48 
percent of the caustic-calcined magnesia sold or used, and for aboul 
79 percent of the refractory magnesia sold or used by producers in the 
United States. Because the economically useful supply of natural 
magnesite and brucite is exhaustible, the long-term trend will continue 
to favor production of synthetic magnesia. 

California's 1963 production of synthetic magnesia produced en- 
tirely from dolomite and sea water, accounted for about 18 percent of 
the total United States production of refractory and caustic-calcined 
magnesia from all sources (see fig. 36) . 

(California's production increased from 1950 to 1961 but has fallen 
off slightly since then (see table 26). This growth is mainly attribu- 













dol omi te , sea water 
and br ines 

From magnesJte, brucite, and 
minor magnesium silicate ores 










Figure 36. Domestic production of magnesia from ores and brines in the United 
States, 1947-63 (U.S. Bureau of Mines Minerals Yearbook, 1956 and 1963 

table to the increasing volume of refractory magnesia, with the ratio 
of caustic-calcined to refractory magnesia (produced in California) 
ranging from a low of 0.04 in 1950 through 0.26 (1955) ; 0.15 (1960) ; 
to 0.29 in 1963. Future production will probably reflect the general 
increasing demand for basic refractories and the use of various mag- 
nesium compounds with our expanding population. 

The resources of dolomite in southern California are great, especial- 
ly along the north part of the San Bernardino Mountains and in the 
Victorville area. In northern California, however, the known com- 
mercial dolomite deposits are presently in use except for the much 
less accessible Sierran foothill dolomite. The enormous amount of 
dolomite rock in the eastern Mojave Desert is, at present, quite re- 

A source of magnesia could result from combining the dolomite re- 
sources of San Bernardino County with sea water. Presently, Kaiser's 
Steel plant at Fontana and various portland cement plants are the 
prime users of magnesia in southern California. Should the market 
for magnesium compounds improve considerably with additional heavy 
industry, this potential may some day be realized. 

Selected References 

Bain, G. W., 1924, Types of magnesite deposits and their origin : Econ. Geology, 

y. 19, p. 412-433. 
Bradley, W. W., 1925, Magnesite in California : California State Min. Bur. Bull. 

79, 147 p. 
Bodenlos, A. J., 1950, Geology of the Red Mountain magnesite district, Santa 

Clara and Stanislaus Counties, California : California Jour. Mines and Geology, 

V. 46, p. 223-278. 


Bowen, O. E., Jr., 195i, Geology and mineral resources of Barstow quadrangle, 
San Bernardino County, California : California Div. Mines Bull. 165, p. 170- 

California State Mining Bureau, 1906, magnesite, in Structural and industrial 
minerals of California : California State Min. Bur. Bull. 38, p. 327-334. 

Comstock, H. B., 1963, Magnesium and magnesium compounds — A materials 
survey : U.S. Bur. Mines Inf. Cire. 8,201. 

Davis, R. E., 1957, Magnesium resources of the United States — A geologic sum- 
mary and annotated bibliography to 1953: U.S. Geol. Survey Bull. 1,019-E, 
p. 373-515. 

Gale, H. S., 1912, Late developments of magnesite deposits in California and 
Nevada : U.S. Geol. Survey Bull. 540, p. 483-520. 

Hess, F. L., 1908, The magnesite deposits of California : U.S. Geol. Survey Bull. 
355, 67 p. 

Ladoo, R. B., and Myers, W. M., 1951, Nonmetallie minerals: New York, Mc- 
Graw-Hill Book Co., 2d ed., p. 296-311. 

Manning, P. D. V., 1943, Magnesium — its sources, methods of reduction, and 
commercial applications : Min. and Met., v. 24, no. 440, p. 346-348. 

Perry, J. B., and Kirwan, G. M., 1942, The Bald Eagle magnesite mine, Cali- 
fornia : Am. Inst. Mining Metall. Engineers Trans., v. 148, p. 35-50. 

Pit and Quarry, 1931 (Nov. 18), California rotary-kiln lime plant uses oyster 
shells as raw material : Pit and Quarry, v. 23, no. 4, p. 22-24, 43. 

Rubey, W. W., and Callaghan, Eugene, 1936, Magnesite and brucite, in Hewett, 
D. F., and others, Mineral resources of the region around Boulder Dam : U.S. 
Geol. Survey BuU. 871, p. 114^144. 

Seaton, M. Y., 1942, Production and properties of the commercial magnesias : Am. 
Inst. Mining Metall. Engineers Trans., v. 148, p. 11-31. 

Traufifer, W. E., 1938 (May), Lime, gypsum, and magnesite produced from sea 
water and shells at new plant in California : Pit and Quarry, v. 30, no. 11, p. 

Ver Planck, W. E., 1957, Magnesium and magnesium compounds, in Mineral com- 
modities of California : California Div. Mines and Geology Bull. 176, p. 313-323. 

Vitaliano, C. J., 1950, Needles magnetite deposit, San Bernardino County, Cali- 
fornia : California Jour. Mines and Geology, v. 46, p. 357-372. 

Wicken, O. M., 1960, Magnesite and related minerals, in industrial minerals and 
rocks : Am. Inst. Mining Metall, and Petroleum Engineers, p. 533-544. 


(By F. F. Davis, California Division of Mines and Geology, San Francisco, Calif., 
and D. F. Hewett, U.S. Geological Survey, Menlo Park, Calif.) 

Manganese plays an extremely important role in the metallurgical 
technology of the modern steel age. It is used for pig iron and in a 
series of ferrous alloys used in steel-making. The principal alloys 
are ferromanganese, spiegeleisen, silico-manganese, and silicospiegel. 
Manganese from these alloys serves to remove free oxygen and sulfur 
in the melt, increases the strength and hardness of steel, and imparts 
a mobility which permits the steel to be rolled and forged more easily. 
Elemental manganese metal, 99.9 percent pure, is now produced elec- 
trolytically from an acid solution of oxide ores. The high purity of 
this product makes it especially useful for making stainless steel, 
alloy steels, and manganese alloys of the non-ferrous metals copper, 
zinc, aluminum, magnesium, nickel, tin, and lead. The chemical in- 
dustry is an important but relatively small consumer of manganese 
ore for such products as dry cell batteries, paints, varnishes, ceramics, 
chemicals, and miscellaneous items. About 96 percent of manganese 
used in the United States is consumed in the metal industries, 2i/| per- 
cent is used in dry cell batteries and the rest is used in a variety of 
chemical industries. 


Although the United States is the principal consumer of manganese 
ores, consuming some 1,840,000 tons in 1963, its deposits of high- 
grade metallurgical ores, containing over 40 percent manganese, are 
extremely small, and domestic production rarely has exceeded 10 per- 
cent of consumption. In 1963, domestic production was only 10,622 
short tons and general imports were 2,093,473 short tons. 

Although magmatic solutions are the primary source of manganese, 
usually the primary manganese minerals are not concentrated suf- 
ficiently to form ore (Jenkins and others, 1943). Most of the large 
ore deposits throughout the world, liowever, are associated with sedi- 
mentary rocks ; in others, minerals are principally oxides of secondary 
origin. Some of the hydrothermal and sedimentary deposits have 
been altered to manganese silicates. Because the silicates do not 
constitute ore, only the oxidized portions of the metamorphic deposits 
are mined. 

The Indians found and utilized manganese deposits in eastern and 
southeastern California as a source of face paint in prehistoric times. 
Gold seekers were probably the first white men to note manganese 
minerals in California, since a deposit near Sonora in the heart of the 
gold country was reported in 1857. The first production came from 
San Francisco Bay area where 200 short tons of manganese-bearing 
rock was mined from Red Rock Island in 1866. 

The Ladd mine in San Joaquin County was discovered in 1867 and 
produced ore regularly on a small scale until 1903. Production from 
California mines was negligible until World War I. Between 1915 
and 1921 inclusive, about 75,000 short tons of ore were produced. 
During this periocl more than 300 new manganese prospects were 
opened, and about one-third of them produced ore, much of it below 
peace-time specifications (Jenkins, 1943). Mining activity centered 
in the Coast Ranges, where the principal producing mines were the 
Ladd, Buckeye, and Thomas. Two mines, the Braito and the Mount 
Hough, at the north end of the Sierra Nevada, and mines in the 
Arlington and Paymaster districts in the desert of southeastern Cali- 
fornia also contributed substantially to the total production. 

Mine production again became sporadic between 1922 and 1940, 
but increased in 1941, as submarine warfare reduced foreign supply. 
In 1943, a dry concentrating plant was built near Patterson to process 
ore from the Buckeye mine for use in dry cell batteries. Several new 
deposits, sucli as the Blue Jay and the Trout Creek, were discovered in 
Trinity County and were the sources of high-grade, direct shipping 
ore. The Kaiser Steel Plant, erected at Fontana in 1943, provided an 
additional outlet for southeastern California, so that production in- 
creased from the manganese deposits in San Bernardino County and 
the Arlington and Langdon districts of Riverside County. The price 
of manganese ore declined after World War II, and only a token 
production of ore was reported from 1946 to 1951. 

During the Korean War period battery-grade ore was produced and 
milled at the Ladd mine from 1951 until the end of 1954 and in 1952 
the LT.S. Government established strategic mineral stockpiles in Ari- 
zona and New Mexico to encourage the production of low-grade (15 
to 40 percent Mn) domestic manganese ore. Important contributors 
to this program were the Pioneer (Whedon) mine. Imperial County; 


Blackjack mine, Riverside County; and the Big Reef and Logan 
mines, San Bernardino County. Concentrators were established at 
Poe's siding to serve the mines in central San Bernardino County; at 
Inca and Tasco siding to treat low-grade ores from the Arlington 
district, Rivereide County ; and at Ripley to treat ore from Imperial 
County. This program ended in 1959, and all California manganese 
mines closed. 

Except in wartime, there is little inducement for the capital invest- 
ment necessary to develop the large, low-grade deposits known in the 
United States. During 1954 when the government was accumulating 
a stockpile of this strategic mineral material, shipments of manganese 
ore from all domestic mines reached 206,128 short tons. 

California manganese mines yielded an all-time }>eak production 
of 37,747 short tons valued at $1,543,949 in 1954. This output in- 
cluded ores ranging from 15 to 50 percent manganese. A token pro- 
duction of ore (battery grade) was made in 1962 and none in 1963. 
Total production from Califronia deposits between 1866 and 1964 was 
320,205 short tons valued at $12,784,533. 

Occurrences in California 

The California deposits as shown in figure 37, lie chiefly in four 
geologic provinces within which they are concentrated in several rock 
or formation units : 

1. Most of the unmetamorphosed deposits of sedimentary origin lie 
in the Coast Ranges in a belt that extends from Humboldt to Santa 
Barbara Counties. The deposits occur in chert of the Franciscan 
Formation (Jurassic and Cretaceous) which is widely exposed. The 
explored ore bodies are lenses of carbonate which range in width from 
3 to 8 feet and extend several hundred feet along the outcrop. 

The rocks of the Franciscan Formation commonly are folded and 
faulted so that the ore zones now dip steeply. The primary minerals 
are manganese carbonate and manganiferous opal, which weather to 
high-grade "black oxide"' ore. Oxidation extends to depths of as 
much as 200 feet below the surface. It is believed that the silica and 
manganese were discharged by submarine springs or volcanos into 
ocean basins of restricted circulation, where they formed chert and 
managanese sediments (Jenkins, and others, 1943). Principal mines 
are the Ladd, Buckeye, Foster Mountain, Thomas Mountain, and 
Blue Jay. 

2. Metamorphosed sedimentary manganese deposits are widespread 
throughout the Sierra Xevada and are chiefly in rocks of the Calaveras 
Formation (Upper Paleozoic) and Amador Group (Jurassic). The 
depth of oxidation is generally very shallow, and most of the deposits 
are currently of little economic importance. Representative mines 
are the Braito and Mount Hough in Plumas County. 

3. In the Klamath Mountains of northern California, the manganese 
host rocks are both metamorphic and metasedimentary, ranging from 
Paleozoic to Jurassic in age. The depth of oxidation in these bedded 
deposits is shallow, and little ore has been produced. 

4. At numerous localities in the Mojave Desert region of south- 
eastern California, hypogene veins of manganese oxides with calcite 



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Figure 37. Principal manganese mines in California. 

and barite have formed in fissures that cut fanglomerate and volcanic 
rocks of Tertiary age, and older quartz porphyry. Most of the deposits 
consist of brecciated rocks cemented, impregnated, and partly replaced 
by manganese oxide, principally a hard oxide similar to psilomelane. 
The average manganese content of the deposits mined is from 15 to 
30 percent. The hard oxide can be hand-sorted in some places to give 
a product containing 40 to 45 percent of manganese (Jenkins, 1943). 
Principal mines are the Whedon (Pioneer), Blackjack, New Deal, 
Langdon, Logan and Big Reef. 

Recent work shows that manganese oxides also occur (a) in traver- 
tine aprons near hot springs, either uniformly distributed through 


the calcium carbonate or as layers of manganese oxide alternating 
with layers of calcium carbonate; and (b) as layers in stratified sedi- 
mentary rocks. The best evidence for a genetic relationship between^ 
hypogene veins and stratified deposits is based on the presence in the 
stratified deposits of minor metals such as tungsten, and on the areal 
distribution of the deposits (Hewett and others, 1963) . 

The total manganese ore produced in California from 1866 to 1964 
inclusive, is about equal to 16 percent of the current (1965) annual 
consumption in the United States. Most of the ore produced from 
1869 to 1954 came from sedimentary deposits in the Coast Ranges. 
During the decade 1954-1964, practically all the ore produced has 
come from the hypogene vein deposits of southeastern California. 

Even though much is known about the number and distribution of 
the manganese deposits in California, there is little information about 
the ore reserves. No bodies of high-grade shipping ore or bodies of 
moderate grade concentrating ore which can be mined and sold at 
competitive prices are known. Some deposits in the Coast Ranges and 
in the desert provinces could no doubt produce small quantities of ore 
at premium prices, but the size of these deposits is undetermined. 
Additional prospecting during periods of high prices probably will 
disclose a number of new small deposits in these provinces. 

Because many California deposits contain siliceous manganese 

minerals, some long-range potential for these refractory materials may 

exist if a satisfactory process can be developed for the recovery of the 

manganese. No data are available on the size and extent of the 

siliceous deposits. 

Selected Refekences 

Davis, F. F., 1957, Manganese, in mineral commodities of California : California 

Div. Mines and Geology Bull. 176, p. 325-339. 
De Huff, G. L., 1960, Mineral facts and problems, manganese : U.S. Bur. Mines 

Bull. 585, p. 493-510. 
Hewett, D. F., and Pardee, J. T., 1933. Manganese in western hydrothermal ore 

deposits, in Ore deposits of the Western States (Lindgren volume) : Am. 

Inst. Mining and Metall. Engineers, p. 488-491. 
Hewett, D. F., and Fleischer, M., 1960, Deposits of manganese oxides; Econ. 

Geology, v. 55, no. 1, p. 1-55. 
Hewett, D. F., Chesterman, C. W., and Troxel, B. W., 1961, Tephroite in Cali- 
fornia manganese deposits : Econ. Geology, v. 56, no. 1, p. 39--59. 
Hewett, D. F., Fleischer, M., and Conklin, N., 1963, Deposits of manganese 

oxides, supplement : Econ. Geology, v. 58, no. 1, p. 1-51. 
Jenkins, O. P., and others. 1943. Manganese in California : California Div. 

Mines Bull. 125, p. 1-385. 
Trask, P. D., 1950. Geologic description of the manganese deposits of California : 

California Div. Mines Bull. 152, p. 1-378. 


(By F. F. Davis, California Division of Mines and Geology, San Francisco, 
Calif., and E. H. Bailey, U.S. Geological Survey, Menlo Park, Calif.) 

Mercury, the silver-colored liquid metal commonly known as quick- 
silver, possesses physical and chemical properties which make it ex- 
tremely valuable for many industrial uses, in most of which no 
suitable substitutes are known. California is, and has been, the 
source of most of the mercury produced in the United States. Some 
of the properties of mercury and the industrial uses that result from 


these properties are listed below, and the proportion of the total 
domestic consumption used in each category during the past 5 years 
is shown in parentheses : 

1. High electrical conducti\dty : switches, relay tubes, rectifiers, 
oscillators, batteries, lamps, signs, and other electrical devices 
(22 percent), 

2. High specific gravity and uniform rate of expansion: in- 
dustrial and control instruments such as weight ometers, pres- 
sure gauges, analytical apparatus, flow meters, pendulums, pumps, 
gyrocompasses, clutches, barometers, thermometers, and heat- 
control devices (16 percent) . 

3. Amalgamation with other metals and fluidity : mercury elec- 
trolytic cells used in the production of chlorine and caustic soda 
(11 percent). 

4. Poisonous character of its compounds: seed disinfectants, 
turf fungicides, and plant germicides (5 percent) ; mold and mil- 
dew inhibitors and anti-fouling paints (8 percent) ; mercury salts 
and pharmaceuticals (5 percent) . 

5. Combinations of physical and chemical properties : hundreds 
of other uses, such as dental inlays and castings, power production, 
munitions industry, in the plup and paper industry, in the re- 
covery of gold, in general laboratories, and in atomic energy 
applications (33 percent) , 

Since satisfactory substitutes are generally unavailable, mercury 
has been considered an essential commodity both for civilian and mili- 
tary purposes, and it is generally included in lists of strategic materials 
during times of national emergency. 

*— Annual world production in the 1955-1964 period averaged about 
235,000 flasks, and the United States economy required each year about 
60,000 flasks, or about one-fourth of the world supply. Although the 
United States has in the last hundred years produced nearly as much 
mercury as it has used, the domestic production in the recent 10-year 
period has been only 48 percent of consumption and in 1964 amounted 
to only 21 percent. For the past 50 years the gap between supply and 
demand in the United States has been bridged by imports from Spain, 
Italy, Mexico, and Yugoslavia, where mercury can be recovered some- 
what more cheaply than at most domestic mines. As Spain and Italy 
have dominated world supplies in the past, they have been able to 
control the price of mercury simply by oversupplying or withholding 
stocks from the market, often to the detriment of domestic producers. 
In wartime, however, foreign sources are less accessible, and domestic 
mercury mines have been temporarily stimulated by price increases; 
concurrently foreign stocks accumulate, and, with the cessation of 
hostilities, the large quantity of mercury that becomes available has 
resulted in greatly depressed prices. This has lead to wider price 
fluctuations for mercury than for most other commodities and has 
given the mercury mining industry the reputation of being one of high 

Beginning in early 1964, a new and more liealthy trend in the mer- 
cury mining industry was initiated when the pric€ began to rise as a 
result of normal peace-time demand exceeding the world's production. 
The upward trend in price began from a level of about $225 a flask 
and continued into mid-1965, when it exceeded $700 a flask. This 


drastic increase generated a renewed interest in mercury mining and 
started a scramble to lease properties and put them into production. 
However, no immediate <^reat increase in production can be expected, 
because most of the California mines were inoperative prior to the 
price increase and must not only be rehabilitated but must also find 
new ore to exploit. ^ 

Cinnabar, HgS, the bright-red stable form of mercury sulfide, is 
the principal mercury ore mineral. Metacinnabar, HgS, the black 
sulfide of mercury, and silvery metallic mercury are found in the ore 
of some mines, but only in a few are they importiant ore minerals. 
Other very rare mercury minerals occasionally found in California 
are calomel, HgCl; eglestonite, HgCl204; and montroydite, HgO. 
Mercury ores contain few other metallic minerals. Pyrite or marcasite 
is generally present in small amounts, and stibnite, though commonly 
absent, is abundant in a few deposits. The principal gangue minerals 
are quartz, opal, chalcedony, calcite, dolomite, and magnesite. Liquid 
or solid hydrocarbons are present in minor amounts in many deposits. 
None of these minerals normally is abundant enough in California 
mines to require special treatment in ore extraction, but pyrite or stib- 
nite, if very abundant, can introduce difficulties. 

Mercury deposits are found chiefly in regions of extensive Tertiary 
or Quaternary volcanic and tectonic activity. The deposits are 
classed as epithermal, being fonned by the deposition of ore minerals 
from aqueous solutions at relatively low temperatures and a,t shallow 
depths. Their close association with hot springs is shown by the 
presence of cinnabar at Coso Hot Springs in Inyo County, The Gey- 
sers in Sonoma County, the Sulphur Bank mine in Lake County, and 
at Amadee Springs in Lassen Coimty, in all of which cinnabar is 
either being deposited or was very recently deposited. However, in 
most districts the mercury was deposited during an earlier period, the 
hot springs have ceased flowing, and any surficial spring deposits that 
were once present have been removed by erosion leaving the mercury- 
bearmg roots of the spring systems. 

Mercury ore bodies commonly are small, irregular, and more errati- 
cally distributed than are the ore bodies of other minerals. Cinnabar, 
perhaps with some metacinnabar or native mercury, fills fractures and 
voids or has replaced the host rock. Many ore bodies have been formed 
by the concentration of primary minerals in openings in porous or 
broken rocks, especially where they are overlain by relatively imper- 
vious rocks. Others that are equally as large and rich are the result of 
replacement of silica-carbonate rock, which is a hard brittle rock 
formed by the hydrothermal alteration of serpentine to a mixture of 
quartz or opal and a carbonate that is generally magnesite. 

More than 50 percent of the larger mercury deposits in California 
occur in this silica-carbonate rock, with the cinnabar in some deposits 
replacing the rock and in others just filling fractures. The silica- 
carbonate rock is associated with so many deposits it is commonly 
called "quicksilver rock," but it is much more widespread than the ore 
and is not very useful as a guide in prospecting. Other mercury de- 
posits in California occur in highly deformed sedimentary rocks of 
the Franciscan Formation, of Jurassic and Cretaceous age, with which 
the serpentine and silica-carbonate rock are associated. Still others 

6r-l©4 O — 66^pt. I 17 


occur ill the less deformed sedimentary rocks of the Knoxville, Pas- 
kenta, Chico, and Panoche Formations of simihir ao;e. Tertiary sedi- 
mentary and volcanic rocks locally contain major deposits in Cali- 
fornia, as do also Quaternary volcanic rocks. Even a few small Recent 
placer deposits have been successfully exploited. 

The history of the discovery and development of these deposits is as 
long and fully as colorful as the saga of California gold mining. In 
prehistoric time, cinnabar was used as a source of paint for war and 
tribal ceremonials by the California Indians, and they are known to 
have mined it at the site of the New Almaden mine, as well as elsewhere 
in the State, long before civilization reached California. The New 
Almaden deposit was rediscovered by white men in 1824, began pro- 
ducing in 1846, reached its peak in 1865 when nearly 50,000 flasks 
were recovered, and has been in production, though at a declining rate, 
almost ever since then. It is the oldest metal mine in California, and 
the first mercury deposit discovered in North America. In 1853 the 
deposit of the New Idria mine in San Benito County was discovered. 
It, too, has been mined almost continuously since its discovery, and, 
in 1965, was the most productive mercury deposit in the United States. 

As the demand for mercury for amalgamation increased following 
the gold rush of the 1850's, exploration for mercury expanded north- 
ward in the Coast Ranges, and soon important new discoveries were 
made at Knoxville, Oat Hill, and Aetna Springs in Napa County ; at 
Sulphur Bank and near Wilbur Springs in Lake County ; and in the 
Mayacmas district of Lake and Sonoma Counties. During the 1860's, 
hydraulic mining for gold on a grand scale, and the discovery of 
the Comstock lode in Nevada, led to still greater demand for mercury, 
and exploration southward from New Almaden led to the discovery 
of new mercury deposits in Santa Barbara and San Luis Obispo 
Counties. Many of the mines reached their peak of production in 
the mid-1870's, which were also peak years for the State as a whole. 
The Sawyer decision of 1884 adversely affected the hydraulic mines 
and curtailed the need for mercury. As a result, mercury production 
declined almost continuously for the next 37 years and many mines 
closed. All the major deposits were discovered by 1895, although 
a rich short-lived open-pit mine was developed in the Emerald Lake 
district of San Mateo County in 1955, and a rich new ore body was 
found at the Buena Vista mine in San Luis Obispo County in 1957. 

Since 1914, mercury production has been encouraged by five sepa- 
rate stimuli : the strategic demands of World War I, the industrial 
expansion of the late 1920's, the demands of World War II, the 
Korean War and Governmental aids of the late 1950's, and the indus- 
trial demands of 1964-1965. During each of these periods, the in- 
creased price led to renewed activity that resulted in an increase in pro- 
duction, but this came largely from deposits that had been known for 
many years. If history is repeated, we may expect many of the Cali- 
fornia mines now regarded as "worked out" to be successfully 

The worldwide unit of trade in mercury is the flask — a cast iron 
or steel cylinder about 5 inches in diameter and 12 inches long con- 
taining 76 pounds of liquid mercury. Total world production 
amounts to about 20 million flasks, and United States production is a 
little less than 314 million flasks. Deposits in California have yielded 


about 85 percent of the domestic production, or about 2% million 
flasks valued at about $200 million. This value is exceeded among 
metallic mineral producers in California only by the value of the 
output of gold and copper mines- 

Occurrences in California 

The highly productive mercury deposits of California lie in a belt 
extending through the California Coast Ranges from central Lake 
Coimty southward to Santa Barbara County. It contains the Na- 
tion's eight most productive mines, dominated by the ^reat New Ai- 
maden mine with a production record of over one million flasks, and 
the New Indria mine, which has yielded more than half a million 
flasks. Also included are about a hundred other productive mercury 
mines, many prospects, and the major mercury reserves of the United 
States. These are clustered in 21 districts, shown on figure 38, most 
of which contain one, or at most two, prominent deposits and numerous 
smaller ones, though an exception is provided by the Mayacmas dis- 
trict, in Napa, Sonoma, and Lake Counties, which contains several 
major deposits. 

One of the State's principal mercury mines, the Altoona in north- 
eastern Trinity County, is in the Klamath Mountains province. An- 
other less productive mine, the Walibu, is in the Tehachapi district at 
the southern end of the Sierra Nevada province. Relatively small 
amounts of mercury also have been obtained from outside the Coast 
Ranges province in the Patrick Creek and Beaver Creek districts in 
the Klamath Mountains, the Coso district in the Great Basin province 
of southwestern Inyo County, and the Tustin district of Orange 
County in the Peninsular Ranges province. 

The New Almaden mine, a few miles south of San Jose in Santa 
Clara County, is the most productive mercury mine in North America 
and provides a good example of ores in silica-carbonate rock. The 
mine area is miderlain mostly by ^rayw.acke, shale, and greenstone 
(altered mafic lavas) of the Franciscan Formation, and serpentine. 
The dominant structure is a northwest-trending anticline whose south- 
west limb has been highly sheared. Two major sills of serpentine 
appear to have been intruded up the north limb, to have converged 
near the crest, and to have continued down the southern flank. The 
serpentine was hydrothermally altered, particularly along its margins, 
to silica-carbonate rock. Cinnabar, the principal ore mineral, was 
introduced along a series of narrow northeast-trending fractures and 
replaced the silica-carbonate rock bordering them to form unusually 
rich ore bodies. The most productive ore bodies were formed along 
the margins of the two altered serpentine sills, and the largest was 200 
feet wide, 15 feet thick, and extended 1,500 feet on the dip. Cobbed 
ore mined during the first 15 years of recorded production averaged 
more than 20 percent mercury, and the ore produced during the entire 
productive history of the mine averaged only a little less than four 
percent. The workings at the New Almaden mine reach a point 2,450 
feet below the surface, making it the deepest mercury mine in the 
world, but almost half of the ore was removed .above the 800-foot 

The New Idria mine, in San Benito County, ranks second in pro- 
duction among mercury operations of North America and in 1965 





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Figure 38. Mercury districts in California. 

was the leading producer. It provides an example of a major producer 
having ore bodies in rocks otner than silica-carbonate or Franciscan 
sedimentary rock, though both are present in the area. The major 
structure in the New Idria district consists of a pluglike mass of 
serpentine and Franciscan graywacke pushed up through shale and 
sandstone of the Panoche Formation (Upper Cretaceous) and Terti- 
ary sedimentary rocks. The margins of the plug are steep faults which 
dip away from the central core, except in the New Idria mine area, 
where the contact dips inward to form the New Idria thrust fault. 
Beneath the New Idria thrust fault, the upper shales of the Panoche 
are crumpled and overturned; in some places highly broken Fran- 
ciscan sandstone and, in other places, serpentine lie above the fault. 


The ore bodies occur chiefly in altered and indurated Panoche rocks 
beneath the thrust fault, and irregularities in the plane of the fault 
have closely controlled zones of deposition. Cinnabar fills open spaces, 
forming veins and stockworks, and rich ore formed where the fractur- 
ing was most intensive. Some ore also occurs in the altered Franciscan 
rocks and in silica-carbonate rock. Known ore extends in places 
through a vertical range of more than 1,400 feet and a horizontal 
span of about ten miles. One ore body was 300 feet long, 25 to 150 
feet thick, and extended through a depth of 800 feet. This ore shoot 
occupied a steep inverted trough at the intersection of the New Idria 
thrust fault with a tear fault. 

The other mines of the Coast Ranges are too numerous to be dis- 
cussed individually here, but reports on essentially all of them have 
been published (see references at the end of this article). Although 
formed under similar geologic conditions, the deposits show marked 
differences in the character, size, grade, and distribution of the ore 
bodies largely because of the diversity of rocks in which they formed. 

The relatively few mercury mines in California that are outside of 
the Coast Ranges province are even less similar. The only large one 
is the Altoona mine in the Klamath Mountains, which has yielded 
about 35,000 flasks. Tlie mine is in porphyritic diorite and serpentine, 
both of which are intensely altered and replaced by quartz and car- 
bonate. Tliree major faults traverse the area, and cinnabar and some 
native mercury form irregular ore bodies in and near the fault gouge. 
Ore shoots average 5 feet in width, extend along the strike 
100 to 300 feet, and down the dip for as much as 300 feet. The av- 
erage grade has been about 1 percent mercury. 

The Walibu (Cuddeback) mine, 10 miles northwest of Tehachapi in 
Kern County, exploits the southernmost of several small mercury oc- 
currences in the Sierra Nevada province. Here, mercury ore occurs 
in a rhyolite dike which has intruded the granitic rocks of the Sierra 
Nevada batholith. Cinnabar encrusts fracture walls, fills small brec- 
cia veins, and is disseminated as minute crystals through the more 
altered rhyolite. 

Farther east, in the Great Basin Province, small amomits of mercury 
have been obtained from Recent hot-spring deposits in the Coso dis- 
trict of southwestern Inyo County. Tliese mercury deposits consist of 
small irregular cinnabar veins in silicified and kaolinized tuff and 
granite. Near Tustin, Orange County, cinnabar and native mercury 
are associated with small veins of barite in country rock of Tertiary 

One may expect that California will continue to provide most of the 
mercury recovered in the United States. Although known and indi- 
cated reserves are only sufficient to sustain production for a few 
years, the history of the industry indicates that with the price of 
mercury high enough to stimulate exploration, as it was in mid-1965, 
new ore bodies will be sought and discovered. Although most of these 
will be satellitic to known deposits, new exploration techniques in- 
volving geochemical sampling, or the use of the recently developed 
mercury detectors may be able to locate wholly new areas with suffi- 
cient mercury concentration to be minable at the high prices likely to 
prevail in the years to come. 


Selected References 

Bailey, E. H., 1962, Mercury in tlie United States: U.S. Geol. Survey Mineral 
Inv. Res. Map MR 30. 

Bailey, E. H., and E>verliart, D. L., 1964, Geology and quicksilver deposits of the 
New Almaden district : U.S. Geol. Survey Prof. Paper 360, 206 p. 

Bailey, E. H.. and Smith, R. M., 1964, Mercury — its occurrence and economic 
trends: U.S. Geol. Survey, Circ. 496, p. 1-11. 

Davis, Fenelon F., 1957, Mercury, in Mineral commodities of California : Cali- 
fornia Div. Mines and Geo. Bull. 176, p. 341-356. 

Eckel, E. B., and Myers, W. B., 1946, Quicksilver deposit.s of the New Idria dis- 
trict, San Benito and Fresno Counties, California : California Div. Mines 
Rept. 42, p. 81-124. 

Linn, R. K.. and Deitrich, W. F.. 1961, Mining and fumacing mercury ore at 
the New Idria mine, San Benito County, California : U.S. Bur. Mines Inf. 
Circ. 8,033, p. 6-13. 

Pennington, J. W., 1959, Mercury — a materials survey : U.S. Bui-. Mines Inf. 
Circ. 7,941, p. 11-27. 

U.S. Bureau of Mines, 1965, Mercury potential of the United States : U.S. Bur. 
Mines Inf. Circ. 8,252, p. 1-376. 

Yates, R. G., and Hilpert, L. S., 1946, Quicksilver deposits of eastern Mayacmas 
district. Lake and Napa Counties, California : California Div. Mines Rept. 42, 
p. 231-286. 

(Muscovite, biotite, and vermiculite) 

(By F. G. Lesure, U.S. Geological Survey, Washington, D.O.) 

Moderate amounts of muscovite and small amounts of biotite and 
vermiculite have been mined in California since 1902. Most of the 
muscovite has come from six deposits (nos. 7, 11, 12, 15, 19, and 24, 
table 27), the biotite from one (no. 6, table 27), and the vermiculite 
from one (no. 22, table 27) . The total production of muscovite, 1902- 
1951, is valued at more than $198,574. 

The principal mica minerals are muscovite (white mica), biotite 
(black mica), and phlogopite (amber mica). All have a perfect 
basal cleavage and form crystals that can be split into thin sheets 
having various degrees of transparency, toughness, flexibility, and 
elasticity. The micas are common minerals, but only muscovite is 
mined extensively in the United States. Vermiculite is a micaceous 
mineral derived mainly from the chemical alteration of biotite and 

Two types of mica are sold : (1) sheet mica which must be relatively 
flat, free from most defects, and be large enough so that it can be 
cut in pieces 1 square inch or larger; and (2) scrap mica which is all 
mica that does not meet sheet mica specifications ; it is generally ground 
to a powder. Small sheets of untrimmed mica of poorer quality that 
can be punched or trimmed into disks 1 inch or larger in diameter are 
classified as punch mica and are included in the general term sheet 
mica. Sheet muscovite is an important insulating material in the 
electronic and electrical industries. Built-up mica made from very 
thin sheets, and reconstituted mica made from scrap can be substituted 
for larger sheet mica for some uses. The principal uses of scrap 
mica are in the roofing, wall paper, rubber, paint, and other industries. 

Vermiculite has little value in its natural form but when expanded 
by heat it forms a low density product with excellent thermal and 


acoustic insulation properties. It is used as a light-weight aggregate 
in concrete and plaster, as an extender or filler in paper, plastics, and 
paint, as a packing material, and as a soil conditioner. 

Sheet-quality muscovite is obtained from large crystals scattered 
throughout unzoned pegmatites or concentrated in certain units of 
zoned pegmatites. The value of sheet mica depends on the color, size, 
structure, and quality of the natural crj^stals. Details of the prepara- 
tion and classification of mica and trade practices of the industry are 
too elaborate to discuss here. The best published reference is by C. M. 
Rajgarhia (1951), whose knowledge of the subject was based on a 
lifetime of experience in the sheet mica business in India, which sup- 
plies most of the world's mica. Excellent references written in the 
United States are by Skow (1962), Montague (1960), Jahns and 
Lancaster ( 1950) , and Wierum and others ( 1938) . 

The discontinuous nature of most mica concentrations, the great 
range of quality of material, the expense of mining, and the large 
amount of hand labor needed for preparation generally limit sheet 
mica mining to periods of very high prices. Since the end of the 
Government purchasing program in June 1962, little sheet mica has 
been mined in the United States. Most of the sheet muscovite used 
in the United States comes from India and Brazil and the sheet and 
scrap phlogopite comes from Canada and the Malagasy Republic. 
Most of the recent domestic production of sheet mica has come from 
North Carolina, New Hampshire, and South Dakota. Only a few 
hundred pounds of poorer quality sheet mica have been produced in 
California, mostly from the Mount Alamo deposit, Ventura County. 
No deposits of high-quality sheet mica are known to occur in the State. 
Large quantities of fabricated sheet mica for electronic equipment 
are shipped into 'California from eastern manufacturers. 

Many pegmatite deposits contain only scrap mica, and a large 
amount of scrap is produced during the mining, trimming, and fabri- 
cating of sheet mica. Scrap mica is also recovered from muscovite 
and biotite schists and as a byproduct from the mining of feldspar and 
clay. Such scrap mica is generally referred to as flake mica. Most 
of the mica mined in the Ignited States is scrap mica and all the 
resources and most of the production of mica in California has been 
scrap quality. Scrap mica mined outside the State was ground by the 
Sunshine Mica Co. in Los Angeles County in 1963 (Davis, 1964, p. 
204) . A new mill in Mariposa County will process mica schist using a 
modification of a method for mica recovery developed by the U.S. 
Bureau of Mines (Browning and Bennett, 1965) . 

California has several plants that expand vermiculite ores shipped 
into the State. California Zonolite Co. operates plants in Sacramento 
and Los Angeles Counties using ore from Montana, and La Habra 
Products, Inc. operates a plant in Orange County using South African 
ore (Davis, 1964, p. 185) . No vermiculite has been mined in the State 
in recent years. 

The selling price of mica can range from only a few cents per pound 
for punch or scrap to many dollars a pound for large sheets of the 
best quality. In 1958 the price schedule under the U.S. Government 
purchase program for sheet mica of superior quality (termed "good, 
stained or better") ranged from $17.70 per pound for the smallest 



sizes to $70 per pound for the large sizes. Prices in 1958 for India 
mica of similar quality ranged from $2.50 to $37 per pound (Montague, 
1960, table 8) . In 1965 prices for sheet mica as quoted in the Engine- 
ering and Mining Journal Metals and Markets ranged from $0.07 
a pound for sheets II/2 inches across to $8.00 a pound for sheets 8 
inches or more across. Scrap mica is valued at the mine at $20 to 
$30 per short ton. Most of the buyers of mica are in the eastern 
United States. Prices for vermiculite ore, short ton, f.o.b. Montana, 
are listed by Engineering and Mining Journal Metals and Markets as 
$9.50 to $18.00, and South African ore, crude, c.i.f. Atlantic ports, 
$27.85 to $38.50. 

Occurrences in Californta 

Mica-bearing rocks are widespread in California. Mica schist is 
found in parts of the Klamath Mountains, the Sierra Nevada, and the 
mountain ranges and deserts of the southern part of the State. In 
general, the mica schists that are mined are parts of extensive areas 
of metamorphic rock and are available in large tonnages. Pegma- 
tites containing muscovite are also widespread but are neither large 
nor abundant. Sheet muscovite is rare or sparse in the pegmatites of 
the Sierra Nevada, Great Basin, Mojave Desert, and Transverse 
Ranges, and none is known in the pegmatites of the Peninsular Ranges 
(Jahns, 1954, p. 48). Scrap muscovite is common in the pegmatites 
of the Great Basin and rare to sparse in the pegmatites of the Sierra 
Nevada, Mojave Desert, Transverse Ranges, and Peninsular Ranges 
(Jahns, 1954, p. 48) . The known mica deposits are listed in table 27 
and the locations shown in figure 39. The most important deposit is 
the Micatalc mine of Imperial County which has produced, since 
1929, several tens of thousands of tons of flake mica from mica schist 
(Wright, 1957, p. 359). 

Table 27. — Mica and vermiculite occurrences in California 

No. on 
fig. 39 




Tlnname'l OfMirrenw 

Oesterling and Spurck, 1964b, p. 184. 


.. do. 

Tischler, 1964, p. 70. 



Wright, 1957, p. 359. 


Brushy Canyon 

Bowen and Gray, 1957, p. 212-213. 


Ruth Hill 

Logan and others, 1951, p. 511. 


Pacific Grove 

Wright, 1957, p. 359. 


Death Valley Mica 

Norman and Stewart, 1951, p. 103. 


Silver Lady Prospect 

(L. A. Wright, written communication, 1965). 


Lucky Betty -- - . - 

Tucker and Sampson, 1931, p. 377-379. 


Unnamed prospect 

Oesterling and Spurck, 1964a, p. 179. 





Hodge -.- . - 

Bowen, 1954, p. 151-152. 



Bowen, 1954, p. 152-153. 


Marshall and Davis 


Bowen, 1954, p. 153-154. 
Bowen, 1954, p. 154-158. 


Snow White - .--.-. 

Bowen, 1954, p. 158. 
Oesterling and Spurck, 1962a, p. 179. 


Unnamed occurrence. 


Unnamed prospect -- 


Nora-Evalyn. _- -^- _ _ _ 

Gay and Hoffman, 1954, p. 676. 


Apex, Dorothy Ann, and Mica 1 

Independent American Mining Co 

Mount Alamo 

Sterrett, 1923, p. 48. 


Unnamed occurrence 


Circle Group. .- 

Oesterling and Spurck, 1964a, p. 179. 
Weber, 1963, p. 79. 
W'eber, 1963, p. 280-282. 


Mica Gem 

Weber, 1963, p. 193. 



Henshaw, 1942, p. 195. 




Muscov i te in pegma t i te 

Muse ov i te in schist 

B i ot i te from sand 


V e r mic u li te 

FiGiTRE 30. Mica in California (numbers refer to table 27) . 

Selected References 

Bowen, O. E., Jr. 1954. Geology and mineral deposits of Barstow quadrangle, 
San Bernardino County, California : California Div. Mines Bull. 165, 208 p. 

Bowen, O. E., Jr., and Gray, C. H. Jr., 1957. Mines and mineral deposits of Mari- 
posa County, California : California Jour. Mines and Geology, v. 53, p. 35-343. 

Browning, J. S., and Bennett, P. E., 1965, Flotation of California mica ore : U.S. 
Bur. Mines Kept. Inv. RI-6668, 7 p. 

Davis, L. E., 1964, The mineral industry of California in U.S. Bur. Mines Min- 
erals Yearbook 1963, v. 3, Area Repts., p. 159-223. 

Gay, E. E., Jr., and Hoffman, S. R., 1954, Mines and mineral deposits of Los 
Angeles County, California : California Jour. Mines and Geology, v. 50, nos. 
3-4, p. 467-709. 

Henshaw, P. C, 1942, Geology and mineral deposits of the Cargo Muchacho Moun- 
tains, Imperial County, California : California Jour. Mines and Geology, v. 
38, no. 2, p. 147-196. 

Jahns, R. H., and Lanscaster, F. W., 1950, Physical characteristics of commercial 
sheet muscovite in the southeastern United States : U.S. Geol. Survey Prof. 
Paper 225, 110 p. 


Jahns, R. H., 1964. Pegmatites of southern California in Jahns, R. H., ed., Geol- 
ogy of southern California, Chap. VII, Mineralogy and petrology ; California 

Div. Mines Bull. 170, p. 37-^50. 
Logan, C. A., Braun, L. T., and Vernon, J. W., 1951, Mines and mineral resources 

of Fresno County, California : California Jour. Mines and Geology, v. 47, no. 

3, p. 485-552. 
Montague, S. A., 1960, Mica, in Industrial minerals and rocks, 3d, ed. : Am. Inst. 

Mining Metall. Petroleum Engineers, p. 551-566. 
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. 
Oesterling, W. A., and Spurck, W. H., 19Ma, Eastern Mojave and Colorado deserts, 

in Southern Pacific Company, Minerals for industry, Southern California, 

summary of geological survey of 1955-1961, Volume III : San Francisco, p. 

Oesterling, W. A., and Spurck, W. H., 1964b, Klamath Mountains and Cascade 

Range, in Southern Pacific Company, Minerals for industry. Northern Cali- 
fornia, summary of geological survey of 1955-1961, Volume II : San Francisco, 

p. 85-207. 
Rajgarhia, Chand Mull, 1951, Mining, processing, and uses of Indian mica : New 

York, McGraw-Hill Book Co., Inc., 388 p. 
Sampson, R. J., and Tucker, W. B., 1942, Mineral resources of Imperial County : 

California Jour. Mines and Geology, v. 38, no. 2, p. 105-145. 
Skow, M. L., 1962, Mica, a materials survey: U.S. Bur. Mines Inf. Circ. IC-8,125, 

240 p. 
Sterrett, D. B., 1923, Mica deposits of the United States : U.S. Geol. Survey Bull. 

740, 342 p. 
Tischler, M. S., 1964, Northern Sierra Nevada, in Southern Pacific Company. 

Minerals for industry, Northern California, s'lunmary of geological survey of 

1955-1961, Volume II : San Francisco, p. 9-83. 
Tucker, W. B., and Sampson, R. J., 1931, San Bernardino County: California 

Jour. Mines and Geology, v. 27, p. 262-401. 
Weber, F. H., Jr., 1963, Geology and mineral resources of San Diego County, 

California : California Div. Mines County Rept. 3, 309 p. 
Wierum, H. F., and others, 1938, The mica industry: U.S. Tariff Comm. Rept. 

130, 2d. ser., 155 p. 
Wright, L. A., 1950, Mica, in Mineral commodities of California : California 

Div. Mines Bull. 156, p. 184-186. 
, 1957, Mica, iii Wright, L. A., ed.. Mineral commodities of California : 

California Div. Mines Bull. 176, p. 357-362. 


(By M. C. Stinson, California Division of Mines and Geology, San Francisco, 


"Minor metals" is a term that is loosely applied to a group of metals 
each of which is uncommon and used in much smaller amounts than 
the common base metals. Of the 8 minor metals described herein, 
6 are recovered from residues collected in the smelting and refining 
of sulfide ores. Gallium, germanium, indium, and thallium are re- 
covered from zmc residues; selenium is recovered from copper resi- 
dues; and rhenium is recovered from molybdenum residues. Cesium 
and rubidium are recovered from pegmatite minerals. 

Each of these metals probably has been obtained from ores mined 
in California, but no data are available on their distribution or re- 
covery by the custom smelters. Flue dusts and other residues from 
American Smelting and Refining Company's smelters at Selby, Cali- 
fornia, as well as from other western smelters, are treated at the Globe 
Smelter in Denver where some of the minor metals are recovered and 


Cesium and Rubidium 

Cesium and rubidium are similar in occurrence, properties, and uses. 
Both are soft, silver-white metals, liquid at near room temperature, 
and react with oxygen and water. Because of their sensitivity to 
light, cesium and rubidium have been employed in photography, tele- 
vision, photomultiplier tubes, and scintillation counters. Recently, 
interest has been shown toward the use of cesium in ionic propulsion 
and thermionic power conversion. 

Pollucite (hydrous cesium aluminum silicate) , which occurs only as 
a rare constituent of pegmatites, is the principal source of cesium and 
rubidium; it contains as much as 36 percent cesium oxide and about 
three percent rubidium oxide. Cesium and rubidium also are found in 
the pegmatite minerals lepidolite (lithia mica), beryl (beryllium 
aluminum silicate) and rhodizite (complex borate of beryllium, alumi- 
num, and alkalies), as well as in carnallite (hydrous potassium mag- 
nesium chloride) which normally occurs in some saline deposits. 
Pollucite has been reported in the pegmatites of San Diego County, 
but these occurrences have not been of commercial importance. 

Cesium and rubidium were discovered by spectroscopic means about 
1860 by Bunsen and Kirchkotf . 

Production data on cesium and rubidium and their compounds are 
not available for publication. 


The uses of gallium are limited mainly because of its scarcity, high 
cost of extraction and purification, and its corrosive nature. The wide 
temperature range through which gallium remains a liquid makes it 
of use in high-temperature thermometers and in special use alloys. 
Gallium arsenide is being studied for application in high-frequency 
transistors, in tunnel diodes, and especially in the field of lasers. 

Gallium is as plentiful as lead in the earth's crust, but is much more 
Avidely dispersed. Gallium is a gray metal which is liquid at or near 
room temperatures. Because of its chemical similarity to aluminum, 
gallium is concentrated in clay-rich soils and clay minerals, particu- 
larly in those derived from bauxite. It is also concentrated by some 
plants, and, therefore, exists in certain coal deposits. Gallium was 
discovered by Lech and Bojsbaudian by spectroscopic means in 1875. 

Gallium is obtained commercially by the treatment of residues from 
aluminum and zinc smelting and refining. The gallium content of 
zinc ores from California is not known to the writer, nor has the 
gallium content of California coals and clays been investigated. In 
recent years, the demand for gallium has been very small, and pro- 
duction has not been reported. 


Germanium, a metalloid, is of value principally because it is a 
semi-conductor. This property has led to its use in the electronic 
industry, first as diode crystal rectifiers, and later in germanium tri- 
odes or transistors. 

Germanium occurs as a minor constituent in the sulfides of zinc, cop- 
per, and silver, and in trace amounts in coal deposits. Virtually all 
of the germanium produced in the United States is recovered during 


the treatment of zinc ores from the Tri-State district. The ger- 
manium is extracted from dust collected in electrostatic precipitators 
at the zinc smelter. 

Germanium was first identified and named by C, Winkler about 
1886. The use and production of germanium increased rapidly with 
the invention of the transistor. The estimated United States produc- 
tion of germanium in 1964 is 20,000 pounds. The XTnited States pro- 
duction of germanium has dropped steadily in the past few years, 
because increased manufacturing efficiency and smaller devices have 
resulted in lower demand for the material. Germanium has not been 
recovered from California zinc ores. 


Indium is a soft gray metal resembling tin. It is softer than lead, 
is extremely plastic, and is stable in air. Deformation can be re- 
peated almost indefinitely without causing the metal to become work 
hardened. Indium has a viscosity that changes very slightly over a 
wide temperature range. The metal has important lubricating prop- 
erties and alloys readily with other metals. 

Because of its mechanical and chemical properties, indium has a 
wide variety of uses and a great potential for new uses. One of the 
principal uses of indium is in sleeve-type bearings to promote resist- 
ance to corrosion and wear. It is also used in electronic devices in a 
variety of ways. 

Indium is not an essential constituent of any of the known minerals 
but is widely dispersed in the earth's crust. It is found in propor- 
tions of as much as one percent in iron-rich sphalerite, in tin ores, and 
in tmigsten ores. It also occurs in pegmatites and has been reported 
in alunite, manganotantalite, phlogopite, pyrrhotite, rhodonite, 
samarskite, and siderite. 

Indium w'as discovered by F. Reich and T. Richter by spectroscopic 
means in 1863. 

Most of the domestic production of indium is obtained from the 
chemical treatment of flue dust and other residues from lead and zinc 
smelters. The American Smelting and Refining Co. at Perth Amboy, 
New Jersey, is the only domestic producer of indium. 


Rhenium is a dense silver white metal with a high-melting point 
(3,440° C) . Rhenium has limited use in industry, principally because 
of its scarcity and high cost. The principal use of rhenium is in high- 
temperature alloys of tungsten and molybdenum. These rhenium al- 
loys liave exceptionally good high-temperature strength properties 
and sufficient ductility to be work-formed at room temperature. Other 
uses are in electronic devices, electrical contacts, thermocouples, and 

Although no minerals are known to contain rhenium as an essential 
element, it is widely dispersed in the earth's crust. It is concentrated 
in molybdenite in proportions of as much as 0.30 percent and in a num- 
ber of rare-earth minerals in proportions up to 0.001 percent. Rhen- 
ium is commercially extracted from flue dust residue collected in the 
roasting of byproduct molybdenite concentrates from copper ore mined 
in Arizona. 


Rhenium was first discovered in 1925 by W. Noddack and I. Tache 
by chemically treating columbite. 

Production data for rheniimi are not available. There is no pub- 
lished data on the rhenium content of California molybdenite. 


Selenimn is a gray crystalline solid with a semimetallic luster. It 
is a semi-metal found with, and related to sulfur and tellurium. 
Selenium has a wide variety of uses which would be more numerous 
if sufficient supplies were available. Probably the most important use 
of selenium is in the electronic .industry where, owing to its semicon- 
ductivity, it is of ^reat value as a rectifying medium. Other uses are 
in the manufacturing of glass, rubber, steel, and industrial chemicals. 
Selenimn was first used in the glass and ceramic industry as a de- 
colorizer. The consumption of selenium has increased rapidly since 
the invention of semiconductor, devices. 

Selenium is found in native sulfur and occurs in the forms of selen- 
ides of lead, mercury, silver, copper, and zinc. Selenium is present 
in many base metial ores in small proportions. 

In 1817, J. J. Berzelius obtained a red to brown precipitate from a 
sulfuric acid plant. From this precipitate he obtained a new element 
which he called selenium. 

The United States produced about 900 thousand pounds of selenium 
in 1964. This amount is about one-third of the world production of 

Some selenium was recovered until 1961, by Anaconda Co. from 
the processing of sulfur mined at the Leviathan sulfur mine in Alpine 
County. No other data are available on selenium recovered from Cali- 
fornia ores. 


Thallium is a soft bluish-white metal that alloys readily with most 
other metals but not with copper, aluminum, manganese, nickel, zinc, 
or selenium. The principal use for thallium is in insect and rodent 
poisons. Thallium has a significant use in electronics, low-melting 
alloys, and in glass. 

Thallium occurs in minute quantities in the sulfides of the coimtnon 
metals. Three thallium minerals are known : crookesite (copper thal- 
lium silver selenide), lorandite (thallium arsenic sulfide), and hutch- 
insonite (complex thallium-bearing arsenide) ; but they have not been 
found in commercial quantities. 

Thallium was discovered in 1861 by W. Cookes by spectroscopic 

Commercial thallium is produced in the United States from flue 
dusts and other residues that are recovered as byproducts of the roast- 
ing of lead and zinc ores. There are no production figures available. 

Selected References 

Goodwin, J. Grant, 1957, Minor metals, iti Mineral commodities of California: 

California Div. Mines Bull. 176, p. 363-366. 
Sargent, J. C, 1956, Mineral facts and problems : U.S. Bur. Mines Bull. 556, 1,042 

p. (cesium, p. 169-172; gallium, p. 291-2M ; germanium, p. 309-313; indium, p. 

359-364; rhenium, p. 745-749; rubidium, p. 751-754; selenium, p. 777-782; 

thallium, p. 871-875). 
U.S. Bureau of Mines, 1965, Commodity data summaries, cesium and rubidium, 

germanium, rhenium, and selenium : p. 28-29, 58-59, 124-125, 132-133. 



(By R. U. King, U.S. Geological Survey, Denver, Colo.) 

Molybdenum is a vitally important metal in our modern ferrous 
metals industry. About 85 percent of the molybdenum produced do- 
mestically is used as an alloying element in the manufacture of high- 
temperature alloy steels, stainless steel, castings, and special steel 
products. When alloyed witli iron and steel it improves the properties 
of hardness, toughness, and resistance to corrosion. Molybdenum 
also is used in the manufacture of chemicals, pigments, catalysts, 
lubricants, and agricultural products. New uses currently being de- 
veloped in the nuclear power field and in the missile and aerospace 
industries promise a continued increase in demand for this versatile 

Molybdenum is widely but sparsely distributed in the rocks of the 
earth's crust. It is found in trace amounts in most igneous and 
sedimentary rocks, in ocean water, in soils, and in plant and animal 
tissues. The average content of the earth's crust has been estimated 
to be about 0.00025 percent (2.5 parts per million). It is not found 
in its pure or native state but only in combination Avith other non- 
metallic elements such as sulfur and oxygen, and metallic elements 
such as iron, calcium, tungsten, and lead. About a dozen minerals 
are known to contain molybdenum as an essential element, but of these, 
only two: molybdenite (molybdenum disulfide, M0S2) and wulfenite 
(lead molybdate, PbMoOi) have been the source of most of the molyb- 
denum produced to date. Other molybdenum minerals which are of 
more than i>assing interest, either for their molybdenum content or 
their geologic significance, as the demand for this metal continues to 
rise include ferrimolybdite (yellow hydrous ferric molybdate) ; powel- 
lite (calciimi molybdate), which commonly occui'S with tungsten, 
jordisite (black, pow^dery molybdenum sulfide) . and ilsemannite (blue, 
water soluble molybdenum oxysulfate). Several rarer minerals of 
doubtful significance contain molybdenum combined with one or more 
of the following elements: bismuth, copper, magnesimn, vanadium, 
cobalt, and uranium. 

Deposits or concentrations of molybdenum minerals of economic 
significance are foimd chiefly in igneous rocks of granitic composition 
and in rocks of sedimentary origin closely related to granitic rocks, 
but also are known to occur in sandstone and lignite. In some deposits 
molybdenite is spai^sely distributed through rather large masses of 
fractured and altered rock ; these are known as disseminated deposits. 
Molybdenite may be the sole or chief economic mineral, such as at 
Climax, Colorado, and Questa, New Mexico, or it may be a minor 
metal associated with copper sulfides as in the large "porphyry" copper 
de^^osits of the southwest. Most of the world's production of molyb- 
denum comes from the disseminated type of dej^osit. Probably the 
most common type of molybdenum cle|X)sits are quartz veins, in which 
molybdenite is associated with minerals containing copper, tungsten, 
bismuth, lead, and zinc. Pegmatite bodies are a common host for 
unusually coarse crystals of molybdenite. Much of the early pro- 
duction of molybdenite came from vein and pegmatite deposits. 

Deposits of molybdenite often associated with scheelite, powellite, 
bismuthinite, or copper sulfides occur in zones of silicated limestone. 


or in tactile bodies near contacts with intrusive granitic rocks ; they 
are known as contact metamorphic deposits and are the source of 
molybdenum in California. 

In the United States today, the grade of the ore in large deposits (at 
least several million tons) mined primarily for the molybdenum con- 
tent, ranges from 0.2 to 0.5 percent M0S2, but molybdenum also may be 
profitably extracted as a byproduct or coproduct from certain copner, 
tmigsten, and uranimn oi'© bodies in which tha molybdenmn content 
is not greater than a few hundredths of one percent. Vein deposits, 
pegmatites, and many contact metamorphic deposits because of their 
limited size have meager economic j)otential except in those deposits 
where molybdenite content is at least several percent. 

Molybdenum is marketed either in the form of molybdenite con- 
centrates (at $1.55 per pound of contained molybdenum, 95 percent 
M0S2) or as roasted concentrate (molybdenum trioxide). Concen- 
trates, however, are not readily marketable in small or individual lots, 
a limiting factor to the economic potential of small deposits. 

Although the element molybdenum was identified in the latter part 
of the 18th century, its use for many years was restricted largely to 
chemicals and dyes. It was not until the early part of the present 
century that its potential value was recognized and wide applications 
for its use Avere developed. Intensive search for domestic sources of 
the metal followed, resulting in the discovery of vein deposits of wul- 
fenite and molybdenite in Arizona, and New Mexico, and of the large 
disseminated molybdenum and copper-molybdenum porphyry deposits 
of the southwestern states. - 

Commercial production of molybdenum began in the United States 
just before the turn of the century, and was small and intermittent 
until 1914. Since 1914, domestic production of molybdenum has in- 
creased each year with few exceptions, exceeding 500 short tons for 
the first time in 1925, and growing to a current annual rate of over 
33,000 short tons. The United States ranks first in world production 
of this valuable metal, accounting for about 70 percent of the total. 
About one-third of our domestic production is exported to some 30 
nations around the world. 

Mining of molybdenum in California is reported as early as the 
year 1894, from a disseminated molybdenite deposit near Ramona, San 
Diego County. Small quantities of molybdenum concentrates were 
produced from several properties between 1914 and 1918, and a small 
production is reported from a vein deposit between 1932 and 1935. 
From about 1937 through 1953 more than 6 million pounds of molyb- 
denum were produced from contact metamorphic tungsten deposits 
at the Pine Creek mine, Inyo County (Bateman, 1956, p. 23). Over 
the years California has ranked from 4th to 6th in U.S. production of 
molybdenum due solely to the consistent yield from the Pine Creek 

Occurrences in California 

California's molybdenum deposits are widespread, being reported 
from more than 80 localities in 24 counties. Of these, ten have yielded 
significant quantities of molybdenum, and one, the Pine Creek mine, 
is being successfully exploited today. Forty-four deposits or groups 
of deposits are briefly described in table 28, and their locations are 
shown on figure 40. 



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Figure 40. Moly.bdenum in California ( numbers refer to table 28) . 

Most of the known molybdenum deposits of California are in the 
Sierra Nevada province. They include the very productive deposits 
of the Pine Creek mine (no. 19, figure 40), which contain the largest 
molybdenum reserves in the State. According to Bateman (1956) 
the ore bodies are in a pendant of metamorphic rocks enclosed in gran- 
ite and quartz monzonite of the Sierra Nevada batholith. Both molyb- 
denum and tungsten occur in distinct shoots along the contact of a 
belt of marble on the west side of the pendant and quartz monzonite. 
The molybdenum ore shoots are subordinate to the tungsten shoots 
and are mostly confined to the upper parts of the deposit. Ore miner- 
als are scheelite and molybdenite with substantial amounts of copper. 
Some of the molybdenum shoots contained an average of about 1 per- 
cent M0S2. Although data are not available on which to calculate 
reserves, they can be fairly estimated to be large and adequate for 


continued production of molybdenum as a co-product with tungsten 
for many years. A number of other contact metamorphic deposits are 
known in which molybdenite is associated with scheelite, powellite, 
and copper sulfides, in skarn, tactite, or marble, but they are too small 
and their molybdenum content is too low to be of economic significance. 

Vein deposits of molybdenum also occur over the length of the 
Sierra Nevada province, but only two, the Mohawk (No. 4) and the 
Blue Speck (No. 15) have yielded any molybdenum of consequence. 
In these deposits, molybdenite occurs alone or with pyrite and chal- 
copyrite in quartz veins. 

Molybdenite is weakly disseminated in granodiorite at the Kaweah 
molybdenum property (No. 22) and at the Golden group (No. 28) in 
the southern part of the Sierra Nevada province. Although ore-grade 
material has been reported in these deposits, the average molybdenum 
content is too low for economic exploitation under present conditions. 

The southern Cascades and Klamath Mountains provinces contain 
only a few molybdenum deposits. Small shipments of sorted ore have 
been made from high-grade ore zones at the Boulder Creek mine (No. 
2) . The molybdenite is disseminated in an aplite dike, and is reported 
to average about 1 percent. 

Molybdenite occurs in a few vein deposits and in a disseminated 
deposit in the granitic rocks in the western part of the Great Basin 
province, and wulfenite is present in the upper parts of lead-zinc veins 
in porphyritic and metamorphic rocks in the Mojave Desert province. 
A little molybdenimi has been produced from the quartz-molybdenite 
vein deposits at the Lucky Boy Prospect (No. 29) and from the wul- 
f enite-bearing deposits at the Imperial Property ( No. 32 ) . 

Molybdenum deposits in the Coast Ranges and Transverse Ranges 
provinces consist of quartz veins in granitic rocks that contain small 
amounts of molybdenite. They have not been productive of molybde- 

Small amounts of molybdenum have been produced from two dis- 
seminated deposits in the western part of the Peninsular Ranges 
province in the veiy southern part of the State. The deposits are in 
a belt of aplitic rocks that trends northwestward from the Mexican 
border and include the Campo (No. 43) and Bour (No. 40) mines. 
The molybdenum content of these deposits is too low to be economically 
mined under present conditions. 

Potential sources of molybdenum in California are most likely to 
be found in disseminated deposits in aplitic rocks in the Peninsular 
Ranges and in the southern part of the Sierra Nevada, but the pos- 
sibility of finding high-grade bodies in some of the contact meta- 
morphic deposits in the central and northern parts of the Sierra 
Nevada should not be overlooked. 

Selected References 

Averill, C. V., 1939, Mineral resources of Shasta County : California Jour. Mines 
and Geology, v. 35, no. 2, p. 108-191. 

Bateman. P. C, 1956, Economic geology of the Bishop tungsten district, Cali- 
fornia : California Div. Mines Spec. Kept. 47, 87 p. 

Calkins, F. C, 1917, Molybdenite near Ramona, San Diego County, California : 
U.S. Geol. Survey Bull. 640-D. p. 73-76. 


Hess, F. L., 1908, Some molybdenite deposits of Maine, Utah, and California: 

U.S. Geol. Survey Bull. 340-D, p. 231-240. 
Horton, F. W., 1916, Molybdenum : Its ores and their concentration : U.S. Bur. 

Mines Bull. Ill, 128 p. 
Kirkemo, Harold, Anderson, C. A., and Creasey, S. C, 1965, Examinations of 

molybdenum deposits in the conterminous United States, 1942-1960 : U.S. 

Geol. Survey Bull. 1,182-E, 90 p. 
Krauskopf, K. B., 1953, Tvmgsten deposits of Madera, Fresno, and iTulare Coun- 
ties, California : California Div. Mines Spec. Rept. 35, 83 p. 
MacKevett, E. M., Jr., 1960, Geology and ore deposit's of the Kern River uranium 

area, California : U.S. Geol. Survey Bull. 1,087-F, p. 169-219. 
Pabst, A., 1954, Brannerite from California : Am. Mineralogist, v. 39, nos. 1-2, 

p. 109-117. 
Robertson, J. F., and Tatlock, D. B., 1965, Consumnes Copper mine, in Kirkemo, 

H., and others : Examinations of molybdenum deposits in the conterminous 

United States, 1942-1960: U.S. Geol. Survey Bull. 1,182-E, p. 35-36. 
Sampson, R. J., 1937, Mineral resource of Los Angeles County : California .Jour. 

Mines and Geology, v. 33, no. 3, p. 173-260. 
Stager, H. K., 1965a, White Horse and Bay Horse claims, in Kirkemo, Harold. 

and others, examinations of molybdenum deposits in the conterminous United 

States, 1942-1960 : U.S. Geol. Survey Bull. 1,182-E, p. 33-35. 
Stager, H. K., 1965b, September group claims, in Kirkemo, Harold, and others. 

Examination of molybdenum deposits in the conterminous United States, 1942- 

1960 : U.S. Geol. Survey Bull. 1,182-E, p. 40-41. 
Tucker, W. B., and Reed, C. H., 1939, Mineral resources of San Diego Counlty : 

California Jour. Mines and Geology, v. 35, no. 1, p. 8-55. 
, 1939, Mineral resources of San Diego County : California Jour. Mines and 

Geology, v. 34, no. 4, p. 368-500. 
Turner, H. W., 1898, Notes on rocks and minerals from California : Am. Jour. 

Sci., V. 5, p. 421^28. 
Walker, G. W., Lovering, T. G., and Stephens, H. G., 1956, Radioactive deposits 

in California : California Dept. Nat. Res. Div. Mines Spec. Rept. 49, 38 p. 
Weber, F. H., Jr., 1963, Geology and mineral resources of San Diego County, 

California : California Div. Mines and Geology, County Rept. 3, 309 p. 


(By C. D. Edgerton, Jr., U.S. Bureau of Mines, Pittsburgh, Pa.) 

Natural gas liquids are those hydrocarbon mixtures contained in 
natural gas in a subsurface reservoir, and which are recoverable as 
liquids by condensation, adsorption, absorption, compression, or re- 
frigeration. They include natural gasoline, condensate, or distillate 
(cycle products) and liquefied petroleum gases, commonly called LP- 
gases or more simply LPG. 

The types of natural gas liquids differ from each other in chemical 
composition and physical properties. Natural gasoline and conden- 
sate contain principally N-pentane and heavier hydrocarbons of the 
paraffin series. The boiling point of N-pentane under normal atmos- 
pheric pressure is 96.9° F. LP-gases include propane, N-butane, and 
iso-butane, with boiling points of minus 43.7° F, plus 31.1° F, and 
plus 10.9° F, respectively. Thus, LP-gases, which are nearly always 
in the gaseous state, vaporize in any ambient air temperature greater 
than 31.1° F. 

Natural gas liquids are found in association with natural gas al- 
though not all natural gas contains enough liquids to permit their 
economical extraction. Therefore, the geographic distribution of nat- 



ural gas liquids is less than that of natural gas. Natural gas in as- 
sociation with crude petroleum in a subsurface reservoir, and con- 
taining economic quantities of natural gas liquids, is termed oilwell 
gas, wet gas, or casinghead gas. Natural gas from reservoirs in which 
there is little or no accumulation of crude petroleum, and which thus 
contains no appreciable quantities of natural gas liquids, is called dry 


In California, natural gas liquids production comes entirely from 
eight contiguous counties situated in the southern part of the San 
Joaquin Valley, the southern coastal area, and the Los Angeles basin 
(fig. 41). The five largest counties, by rank, of natural gas liquids 
production, are Kern, Los Angeles, Ventura, Santa Barbara, and 
Orange. Fresno, Kings, and San Luis Obispo Counties produce 
relatively small quantities of natural gas liquids. 

FiGUEE 41. Area producing natural gas liquids (lined pattern). 



Table 29. — Production of natural gas liquids in California, 1911-64 

[Thousand gallons per year] 

1911 210 

1912 1,050 

1913 3,486 

1914 7, 770 

1915 12, 852 

1916 17,178 

1917 28, 812 

1918 32,256 

1919 40,404 

1920 48,216 

1921 58, 212 

1922 67,116 

1923 173, 334 

1924 232,554 

1925 303, 198 

1926 389,382 

1927 498, 036 

1928 584,094 

1929 840, 336 

1930 829, 710 

19Cn 680,358 

1932 551,376 

1933 499,968 

1934 507.612 

1935 544, 404 

1936 611, 898 

1937 641,508 

1938 690, 396 

1939— _: 640, 542 

1940 635, 124 

1941 659, 778 

1942 633,318 

1943 693,336 

1944 771,288 

1945 891, 744 

1946 910, 518 




064, 112 
115, 058 
140, 468 
189, 776 
240, 386 
266, 048 
307, 922 
319, 346 
290, 551 
287, 134 
234, 121 
196, 037 
230, 589 
187, 645 
108, 806 
072, 987 

Source : U.S. Bureau of Mines. 

Table 29 gives the total annual production of natural gas liquids in 
California from 1911 through 1964; figure 42 presents these data 

The peak year for natural gas liquids production was 1954, when 
more than 1.3 billion gallons was produced. From 1955-1964 pro- 
duction trended downward and in 1964 was 1.06 billion gallons, about 
81 percent of the 1954 figure. 

t1 .400.000 

1911 15 20 25 30 35 40 45 50 55 60 65 

Figure 42. Production of natural gas liquids in California, 1911-64. 


























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Table 30 gives the total yearly production of natural gas liquids in 
California, by counties, from 1954 through 1964. Data for the five 
major producing counties are shown on figure 43. Since 1954, only 
Santa Barbara County has shown steady growth in natural gas liquids 
production largely from development of offshore oilfields. 


350.000 - 




Los Ange les 


Ve n t u r a 




Santa Barbara 




'961 1962 1963 1984 

Figure 43. Production of natural gas liquids in California, by counties, 1960-M. 


As of January 1, 1964, there were 66 natural gasoline and cycle 
plants in California with a total capacity of 4,688,000 gallons of natural 
gas liquids per day. The average operating plant capacity was 71,000 
gallons per day. By comparison, there were 623 plants in the United 
States with a total capacity of 66 million gallons per day and an 
average operating plant capacity of 106,000 gallons per day. 

In California, 20 companies operate natural gas liquids plants. 
(This figure does not include the U.S. Naval Reserve mothball plant 
at Elk Hills.) 

Companies with natural gas liquids production capacities greater 
than 250,000 gallons per day are : 

per (lay 

Standard Oil Co. of California 677, 000 

Shell Oil Co 622,000 

Palomaeo 590, 000 

Union Oil Co. of California 449, 000 

Richfield Oil Corp 434,000 

Tidewater Oil Co 347,000 

Socony Mobil Oil Co., Inc 307, 000 

Texaco, Inc 251, 000 

Table 31 gives the companies that operate natural gas liquids plants, 
and plant capacities and locations. 


Natural gas liquids are extracted from natural gas at plants that 
are almost always located in the fields which produce the gas. The 
liquids are shipped from the field to refineries or dealers, by pipeline 
or truck, and the processed gas, devoid of most of its liquids content, 
is either reinjected into subsurface reservoirs to maintain reservoir 
pressure, or for secondary recovery operations, utilized for fuel in the 
field, or transported by pipeline to markets. In some areas of the 
United States, 60 percent or more oilwell gas is vented to the at- 
mosphere. In California, less than 1 percent of oilwell gas is vented. 
Thus, the conservation of this natural resource in California ap- 
proaches the maximum. 

There are four basic plant designs for the extraction of liquids from 
natural gas: (1) absorption, (2) adsorption, (3) compression, and 
(4) refrigeration. 

The absorption process is by far the most commonly utilized in both 
California and the United States. Plants representing about 90 per- 
cent of the total gas processing capacity make use of the absorption 
method, either by itself or in combination with refrigeration or com- 
pression methods. The .absorption process utilizes a solvent oil which 
flows in an absorbing tower countercurrent to the wet natural gas 
stream coming from the field. In so doing, the solvent oil strips the 
natural gas of its liquids. 

The rich solvent oil then goes into a distillation unit where the 
natural gas liquids are vaporized, leaving the solvent oil lean again 
for recycling to the absorbing tower. The gases then are condensed 
and usuall}^ refined further in a rectifying system before leaving the 
plant for the refinery. 





























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The adsorption process utilizes a solid adsorbing .agent instead of 
a solvent oil in a minimmn of two towers. In one tower the wet 
natural gas is introduced, where the entrained liquids are adsorbed 
(taken up on the surface) by the adsorbing agent. "VVlien the latter 
has accumulated .all the liquids it can hold, the wet natural gas stream 
is diverted to the other tower. The natural gas liquids on the surface 
of the adsorption agent in the first tower are then driven off by the 
application of heat, and are condensed and recovered. The adsorp- 
tion agent is thus regenerated for the next cycle. By usmg .a mini- 
mum of two towers, a continuous operation is effected. Adsorption 
plants account for about 10 percent of United States and less than 
2 percent of California processing capacity. 

A compression plant separates the natural gas liquids by com- 
pressing the incoming wet gas and then allowing it to expand. In 
so doing, the entrained liquids are cooled below their dew points, and 
thus separate out and are recovered. Often several cycles of com- 
pression followed by expansion are necessary to effect the practical 
ultimate in liquids separation. 

A refrigeration plant, like a compression plant, operates on the 
principle of cooling the natural gas liquids below their dew points so 
they will condense and separate from the natural gas. However, in 
this plant design, the liquids are cooled by circulating refrigerants 
rather than expansion following compression. 

A number of j)lants employ a combination of two or more of the 
above ])rocesses such as absorption-refrigeration, refrigeration-com- 
pression, and absorption-compression. Natural gas liquids extraction 
plants are individually designed using such parameters as total 
liquids content of the natural gas to be processed, composition of the 
liquids component, reservoir pressure, and local economics. 

By far the largest nmnber of plants in California, as in the United 
States, utilize the absorption design, followed by combination refrig- 
eration, compression, and adsorption designs. 


Most of the natural gas liquids produced in California, and espe- 
cially the natural gasolines, are shipped to petroleum refineries (com- 
monly by pipeline, but occasionally by tank truck) where they usually 
are catalytically reformed and blended to produce high-octane gaso- 
lines. LP-gases are sold, either by companies specializing in their 
sale and distribution, or by refineries, for residential, commercial, and 
industral fuel, as fuel for internal combustion engines, or as petro- 
chemical plant feedstocks where they are used in the manufacture of a 
multiplicity of chemicals including synthetic rubber. Some LP-gases 
are used in the secondary recovery of crude petrol emn by injecting 
them as a "slug" prior to injecting water or natural gas. Small quan- 
tities of natural gas liquids are used as solvents and in portable heating 
and lighting equipment such as camp stoves and lanterns, blow torches, 
and weed-burning units. 



Consumption of natural gas liquids in California during 1963 
for various purposes is given below : 

Use : gallons 

Residential and commercial fuel 233, 962 

Chemical plant feedstock ' 116, 902 

Petroleum refinery fuel M9, 476 

Exports 36,582 

Industrial fuel 36, 090 

Internal combustion engine fuel 33, 799 

Synthetic rubber manufacture ^24,066 

Secondary recovery of petroleum ^ 9, 072 

Utility gas 26, 4M 

Miscellaneous 3, 245 

Total 569,688 

1 Estimated. 

Source : U.S. Bureau of Mines. 

Value and Prices 

The relative value of natural gas liquids compared with the total 
value of all mineral commodities produced in California has shown an 
overall decline since 1954. In 1951, natural gas liquids accounted 
for nearly 8 percent of the total mineral revenue, but by 1961 this 
figure had dropped to less than 5 percent. The total value of natural 
gas liquids also declined during this period from $111.6 million to $70 

These declines reflected not only the decreasing output of natural gas 
liquids, but also an overall erosion of prices throughout the 10-year 
period. The average price of natural gasoline and cycle products 
dropped from 9.7 cents per gallon in 1954 to 7.5 cents per gallon in 
1964; that of LP-gases went from 5.6 cents to 4.5 cents per gallon. 

The values of California mineral production and natural gas liquids, 
from 1954 through 1964, are shown in table 32. 

Table 32. — Comparative values of California's total mineral production and 

natural gas liquids, 195Jf-6J!f 


Total value of all 
mineral production 

Total value of all 
natural gas liquids 

Percent of total 

mineral value 

represented by 

natural gas liquids 


Thousand dollars 
1, 430, 000 
1, 458, 000 
1, 555, 000 
1, 651, 000 
1, 424, 000 
1, 402, 000 
1, 561, 000 

Thousand dollars 
111, 555 
108, 382 
105, 947 
101, 776 

87, 163 




73, 754 

71, 517 





1956.- . 
















1964 . -- . 


The price per gallon and total value of natural gas liquids, by type, 
from 1954 to 1964, are shown in table 33. 


Table 33. — Price per gallon and total value of natural gas liquids, iy type, 1954-64 

Natural gasoline and cycle products 



Price per gallon 

Total value 
(thousand dollars) 

Price per gallon 

Total value 
(thousand dollars) 



89, 293 
89, 003 
84, 615 
68, 485 
68. 023 
62, 496 
57, 645 
54, 460 
54, 188 


22, 262 
19, 379 
21 332 

1955. - . 



20, 421 
18, 678 
21 260 




21 482 


21 805 


19, 294 
17, 329 
15, 893 




Table 34 gives reserves for California and the rest of United States 
as estimated by the American Gas Association Committee on Natural 
Gas Reserves. 

Table 34. — Estimated proi'cd rccovcraMc reserves of natural gas liquids in 
California and in the United. States, Dec. 31, 1964 ^ 

[Thousands of 42-gallon barrels] 


ated with oil 

wth oil 

in oil 


California, including offshore 

United States, exf^luding California 

4, 782, 088 

80, 513 
984, 535 

182, 706 
1. 707, 015 

7, 473, 668 

Total _ . 

4, 791, 833 

1, 065. 048 

1, 889, 751 

7, 746, 632 

' Includes condensate, natural gasoline, and liquefied petroleum gas. 

Selected References 

American Gas Association, American Petroleum Institute, and Canadian Petro- 
leum Association, Dec. 31, 1964, Reports on proved reserves of crude oil, 
natural gas liquids, and natural gas in the United States and Canada, 33 p. 

American Geological Institute, 1957, Glossary of geology and related sciences, 
p. 195. 

Hart, Earl W.. 1957, Natural gas liquids, in Mineral Commodities of California : 
California Div. Mines and Geology Bull. 176, p. 385-390. 

Oil and Gas .Journal, Mar. 29, 1964, Gas-processing number, v. 63, no. 13, p. 59-61, 
84-85, 98-100, 105, 108-109, 113-118, 120-123, 125-133. 

U.S. Bureau of Mines, 1960, Bull. 585, p. 601-602. 

, Minerals Yearbook, 1963 ed., v. II, p. 361-388 ; v. Ill, p. 170-171. 

, Jan. 1, 1964, Natural gas-processing plants in the United States : Mineral 

Industry Survey, 16 p. 

, Jan. 1, 1964, Petroleum refineries, natural gasoline plants, and cycle 

plants in District Five, 5 p. 

-, Aug. 3, 1964, Shipments of liquified petroleum gases and ethane in 1963 : 

Mineral Industry Survey, 12 p. 


(By P. E. Hotz, U.S. Geological Survey, Menlo Park, Calif.) 

Nickel, a hard, silvery white metal, has, besides its use in coinage, a 
multitude of industrial uses as an alloy with other metals. The prin- 
cipal consumption is in the production of ferrous alloys, but it also 


is combined with other metals, especially copper and chromium. To a 
lesser extent, uncombined metallic nickel is used for electroplating, in 
certain kinds of storage batteries, and in powder form it has many 
applications in the chemical and electronic industries. With each year, 
continuing research finds new uses for nickel, primarily as an alloy. 

The United States production of nickel in 1963 was about 4 percent 
of the free world production of 271,000 tons, while the consumption by 
this country was 125,000 tons or slightly more than 46 percent of the 
free world output. Most of the United States imports of nickel are 
from Canadian sulfide deposits; some, smelted from Canadian ores, 
comes from Norway; and a small amount derived from New Cale- 
donia nickel silicate ores is imported from France. The output from 
Cuban laterite deposits, formerly developed and mined by United 
States companies, now goes to the U.S.S.R. and Czechoslovakia in the 
form of concentrates ( Ware, 1964). The entire domestic mine output 
of nickel is from a lateritic deposit at Nickel Mountain, near Riddle, 
Oregon, owned by the Hanna Mining Co. There is no recorded pro- 
duction from California. 

The useful deposits of nickel ores are of two main types: (1) sulfide 
deposits, and (2) laterites. Both types have representatives in 

In the sulfide deposits pentlandite (Fe,Ni)9Ss, and pyrrhotite, an 
iron sulfide wdiich is commonly nickel if erous due to inclusions of 
pentlandite, are the principal nickel-bearing minerals. Minor quan- 
tities of other nickel minerals, including violarite, Ni2FeS4, and siege- 
nite (Co,Ni)3S4, and millerite, NiS, may also be present. The sulfide 
deposits are associated wdth mafic intrusive igneous rocks such as 
gabbro and peridotite, and occur in large disseminated bodies and small 
to moderate-size massive sulfide bodies. The mineralization is closely 
related to deep-seated magmatic processes which were responsible for 
the emplacement of the igneous intrusions into the surrounding county 

Lateritic deposits can be subdivided into two closely related types : 
(1) nickel silicate laterites of low iron content, and (2) ferruginous 
nickeliferous laterites. In nickel silicate ores the nickel-bearing min- 
erals are green hydrous nickel-magnesium silicates with rather widely 
variable nickel content, which are commonly referred to under the 
general name garnierite. The ferruginous nickeliferous laterites are 
surficial blankets of reddish-brown soil of variable, complex min- 
eralogy in which there is no specific, discernible nickel mineral. The 
nickel, invariably accompanied by smaller amounts of cobalt, is in- 
timately combined in an unidentified way with hydratecl iron com- 
pounds, clays, and serpentine minerals in the soil. The nickel silicate 
and ferruginous nickeliferous laterites are everyw^here underlain by 
bodies of ultramafic rock, commonly peridotite or serpentinite, from 
which the nickeliferous deposits have been formed by extensive weath- 
ering. Hence this type of deposit is referred to as secondary. Most 
peridotite and its altered equivalent, serpentinite, contains between 
0.1 and 0.3 percent nickel and about .01 percent cobalt, which occur 
as minor chemical constituents in one or more of the magnesium-iron 
silicate minerals of the parent rock. Under the influence of natural 
weathering processes, the rock-forming minerals are decomposed and 



the more soluble compounds, principally magnesia and silica, are 
carried away by downward percolating rainwater, while the less mobile 
constituents, including hydrous iron oxide, nickel, and cobalt are 
concentrated in a residual blanket. Under some circumstances some 
nickel is dissolved, removed, and redeposited with silica to form a 
boxwork of microcrystalline quartz and garnierite below the soil zone, 
above a substratum of partially weathered peridotite or serpentinite 
(Hotz, 1964). 

Sulfide Deposits 

A sulfide deposit occurs in the Julian-Cuyamaca area of San Diego 
County near the town of Julian, in the eastern part of the Peninsular 
Ranges province (fig. 44). The Friday mine (Creasey, 1946), which 
was probably discovered in the 188{)'s, has been intennittently ex- 
plored and developed by underground workings and diamond drilling. 


Ferruginous nickeli ferous 
lateri tes 

1. Pine Flat Mtn. 

2. Gasquet 

3. Rattlesnake Mtn. 

4. Little Red Mtn, 

5. Dunsmuir 

Siliceous laterites 

6. Pilliken 

7. Valley Springs 

8. Venice Hills and 
Deep Creek 

Nickel sulfide 

.MON<i\ 4-38- 9. Old Ironsides 
\ 10. Friday 


Figure 44. Nickel in California. 
©7-164 O— 6i6-^t. I 1& 


There is no recorded production ; however, the size of the underground 
workings indicates tluit several lumdred tons of ore luwe been mined. 
The deposit is a partly oxidized sulfide replacement of gabbro adjacent 
to a schist inclusion, (^reasey (1946, p. 27) estimated the indicated 
reserves to be approximately 5,000 tons averaging approximately 2.5 
to 3 percent nickel, from 0.5 to 1.0 percent copper, and as much as 0.15 
percent cobalt. Subsequent exjjloration under a DMEA contract con- 
firmed these estimates and showed that approximately three-fourths 
of the deposit is predominantly oxidized ore. Several other occur- 
rences of gossan (masses of oxidized sulfides) containing from 0.01 
to 1.45 percent nickel (Creasey, 1946, p. 27-28) are known in the 
Julian-Cuyamaca area, which suggest the presence of other nickel 
sulfide bodies, but limited exploration has not revealed any important 
deposits. Creasey (1946, p. 19-22) reports as much as 3 percent pyr- 
rhotite in the gabbro body, suggesting that the rock may contain small 
amounts of nickel, but no analyses of the rock for nickel have been 

Exploration under a DMEA contract of a small nickel- and copper- 
bearing gossan at the Old Ironsides mine, approximately 9 miles 
north-northeast of Ramona, San Diego County (Peninsular province) 
revealed a small shallow deposit averaging about 0.35 percent nickel. 

Lateritic Deposits 

The principal lateritic nickel de|X)sits in California occur in the 
northwestern part of the State, chiefly in Del Norte County and in 
southern Siskiyou County (Klamath Mountains province) ; deposits 
are also known in northern Mendocino County (California Coast 
Ranges). Some eroded remnants of de]3osits in the western Sierra 
Nevada province have been reported by Rice (1957, p. 396). 

The deposits in northwestern California are accumulations of later- 
itic soil resting on peridotite. They occupy nearly flat-lying to gently 
sloping areas on broad ridge crests, in saddles, and on benches on the 
sides of ridges in a thoroughly dissected and deeply eroded rugged 
mountainous terrain. The individual deposits are scattered, discon- 
tinuous areas that range from less than 100 acres to about 300 acres. 
Thickness of the blankets vary widely and are only approximately 
known, but range from as little as 10 to 15 feet to as much as 80 to 90 
feet. Characteristically, the deposits in northwestern California are 
blankets of reddish-brown soil at the surface grading downward 1 to 
3 feet below the surface to ocherous soil, which passes more or less 
gradationally downward into bedrock. Except for an occasional 
veinlet or film of garnierite coating joint surfaces, no nickel minerals 
have been recognized. In places isolated, residual blocks or boulders 
of leached, barren silica boxworks are scattered on the surface of the 
lateritic blankets, and chips of microcrystalline quartz occur in the 
soil and occasionally as veinlets near the base of the soil zone. 

Several deposits are known in Del Norte County wiiere lateritic soil 
has accumulated on a large pluton of peridotite and serpentine. The 
best known deposits, which have been explored by drilling by private 
companies and the U.S. Bureau of Mines (Benson, 1963), are at Pine 
Flat and Diamond Flat on Pine Flat Mountain about 20 miles north- 
east of Crescent City, near the California-Oregon boundary. Several 
others, some of which have been tested by private companies, are 


known near Gasquet, a town on Smith Eiver approximately 18 miles 
east of Crescent City. Some small patches of lateritic soil are also 
known along a long, narrow north-south ridge of ultramafic rock 
south of Gasquet, known as Rattlesnake Mountain. A few other 
isolated deposits only a few acres in extent are also known in this 
general region. 

One deposit is known in northern Mendocino County at Little Red 
Mountain, approximately 2.5 miles east of Leggett. The deposit 
occurs on the southern part of an isolated ultramafic body in the 
northern Coast Range province, and has been explored by a private 

In southern Siskiyou County a small lateritic deposit occupies the 
nose of a ridge in the Saci'amento River Canyon north of the mouth 
of Little Castle Creek, approximately 2 miles south of Dunsmuir. 
No active exploration of this deposit has been undertaken. 

Reconnaissance sampling and data from Bureau of Mines explora- 
tion (Benson, 1963) show that the thicknesses of the lateritic blankets 
vary widely and are only approximately known, but they are esti- 
mated to be less than 50 feet thick and probably, on the average, sel- 
dom more than 25 to 330 feet. The average nickel content ranges 
from 0.5 to 0.8 percent nickel, 0.01 to 0.1 percent cobalt, and the iron 
content is less than 20 percent. 

Several lateritic remnants on serpentinite are known in the western 
Sierra Nevada province (Rice, 1957, p. 396). They consist mostly of 
cappings of dense silica box work grading into jasperlike silicified 
serpentinite. Some garnierite fills cavaties in the boxwork and occurs 
as veinlets in the serpentinite. The cappings are more than 100 feet 
thick in places but the rocks are leached and the average nickel content 
is less than 0.5 percent. Siliceous laterite remnants are exposed at 
the Pilliken chromite mine in El Dorado County; a few miles east 
of Valley Springs in Calaveras County ; and in the Venice Hills and 
Deer Creek areas of Tulare County. The only known exploration of 
the western Sierra lateritic deposits through 1956 (Rice, 1957, p. 396) 
was in a small area in the eastern part of the Venice Hills. 

Resource Potential 

The resources of nickel are only imperfectly known. Reserves of 
nickel-bearing sulfide ores are very meager, probably amounting to 
less than a few thousand tons. There may be on the order of 25 million 
tons of nickeliferous laterites in nortliAvestern California which aver- 
age 0.8 percent nickel or less, distributed among several widely scat- 
tered deposits. It seems unlikely that these resources will be com- 
mercially exploited in the foreseeable future, because of their low grade 
and dispersal among several relatively small deposits. Unlike the 
Nickel Mountain deposit in Oregon they do not have bodies of high- 
grade nickel silicate with which to increase the average nickel content 
of the ore. 

Selected References 

Benson. W. T., 1963, Pine Flat and Diamond Flat nickel-bearing laterite deposits, 
Del Norte County, California : U.S. Bur. Mines Kept. Inv. 6,206, 19 p. 

Creasey, S. C, 1946, Geology and nickel mineralization of the Julian-Cuyamaca 
area, San Diego County, California : California Jour. Mines and Geology, v. 
42, no. 1, p. 15-29. 


Hotz, P. E., 1964, Nickeliferous laterites in southwestern Oregon and north- 
western California : Ecou. Geology, v. 59, no. 3, p. 355-396. 

Rice, S. J., 1957, Nickel, iu Mineral commodities of California : California Div. 
Mines Bull. 170, p. 391-399. 

Ware, G. C, 1964, Nickel : U.S. Bur. Mines, Minerals Yearbook, 1963, p. 843-857. 


(By R. L. I'arker, U.S. Geological Survey, Washington, D.C.) 

The rare metals, niobium and tantalum, have become increasingly 
important in modern technology and are required in certain electronic, 
nuclear, chemical, and high-temperature metallurgical applications. 
Both metals are used for A'acuum tube elements, su])er conductors, cor- 
rosive-resistant vessels, and laboratory ware, and as constituents in 
high-temperature alloys and austenitic stainless steel. Niobium is spe- 
cially used for cladding nuclear fuels, Avhereas tantalum is used for 
capacitors, rectifiers, and surgical implants and as a catalyst in the 
manufacture of butadiene rubber (Miller, 1959; Barton, 1962). 

Although the United States is the world's largest consumer of 
niobimn and tantalum, it is a small producer and relies on foreign 
sources for its ore supply. Critical shortages of these metals resulted 
in government allocation controls during World War II and the 
Korean War, and a strategic stockpile of niobium-tantalum raw ma- 
terials is now mamtained by the Government. During the last 10 
years imports of niobium-tantalum concentrates have ranged from 
an alltime high of 11,520,262 pounds in 1955 to a low of 3,591,530 
pounds in 1958. In 1963, 6,853,971 pounds of niobium-tantalum con- 
centrates were imported. Domestic production reached a peak of 428,- 
347 pounds of concentrates in 1958, most of which came from Idaho 
placers. This production, however, amounted to only about one-tenth 
of that year's domestic consumption. No domestic production has 
been recorded since 1959 (U.S. Bur. Mines Minerals Yearbooks, 1955- 

Niobium and tantakmi commonly occur together in the same min- 
erals. These minerals also commonly contain subordinate amounts 
of titanium, iron, manganese, rare earths, uranium, thorium, and other 
metals. Important ore minerals are columbite-tantalite. (Fe, Mn) 
(Nb, Ta)oOc; pyrochlore, NaCaNboOr.F; microlite, (Na,' Ca).Tao06 
(0,OH,F); euxenite, (Y,Ca,Ce,U,Th) (Nb,Ta,Ti)oOG; fergusonite 
(Y,Ca,U,Th) (Nb,Ta)04; and samarskite, (Fe,Y,U)2(Nb,Ti,Ta),0r. 

Niobium-tantalum minerals are found in granitic rocks and peg- 
matites, in alkalic rock complexes and associated carbonatites, and in 
placers derived from these rocks. Some granite massifs contain dis- 
seminated columbite-tantalite, euxenite, or other niobiiun-tantalum- 
bearing minerals as primary rock constituents, and in some places 
weathering and fluvial processes have concentrated these minerals into 
commercial deposits. Granite pegmatites are well known for their 
concentrations of rare minerals, including minerals of niobium and 
tantalum, but the erratic distribution and limited tomiage of these 
minerals in pegmatites commonly exclude pegmatites as an important 
source of supply. Even so, pegmatites are the principal source of the 
world's tantalum. 

Large low-grade deposits of niobium occur in alkalic rock complexes 
and related carbonatites in many parts of the world. Some multi- 



million ton deposits are known in central Africa, southeastern Canada, 
Norway, and Brazil, and at least five alkalic complexes with carbona- 
tites have been found in the United States. Niobium is contained in 
the mineral pyroclilore, which commonly is disseminated in the 
carbonatite. Alany such deposits are under extensive development and 
are expected to be the principal source of niobium in future years. 

Commercial deposits of niobiiun and tantalum have not been found 
in California, although an undisclosed — but presumably very small — 
amount of tantalum was produced from San Diego County in 1920 
(Weber, 1963, p. 41, 68). Niobium-tantalum minerals have been re- 
ported from widely scattered pegmatites in the State (see fig. 45), but 
many of the reported occurrences are poorly documented. So far as 
known, all of the niobium-tantalum minerals reported are present only 
as minor accessoiy constituents in the pegmatites and are not regarded 
as potential sources of niobium and tantalum. 


Niobium and tantalum in pegmat 
1 . Pegma t i t e near Milton 
Kern River uranium area 

3. Piute Mountains near Weldon 

4. Fano mine: Pegma t i f e -sec, 16, 
T. 7 S., R. 2 E.; An i t a mine 

5. Box Spring Moun tain 
6. Southern Pacific Silica Quarry 

7. Pomona Tile Quarry 

8. Pegma t i t e . Cady Moun ta 

9. Little Three mine 
1 0. R i nc on district 

,t. Pa la district 
2. Moun tain Lily mine 
13. Chihuahua Valley near Oakgrove 
14. Southwest slope of Lawson PeaK 
\1 5. Me s a Grande 

.MONO\ -I- 38* 


Figure 45. Niobium and tantalum in pegmatites in California. 


A carbonatite body associated with alkalic rocks at Mountain Pass, 
San Bernardino Ck)iinty contains one of the world's largest deposits 
of rare-earth minerals, although only traces of niobium have been 
fomid in the deposit (see p. 351, Kare-earth chapter, this volume) . The 
occurrence of carbonatite and alkalic rocks in this region, however, 
opens the possibility of finding similar and perhaps niobium-bearing 
rocks through future geologic study. 

Selected References 

Barton, W. R., 1962, Columbium and tantalum, a materials survey: U.S. Bur, 

Mines Inf. Circ. 8,120, 109 p. 
Hanley, J. B., 1951, Economic geology of the Rincon pegmatites, San Diego 

County, California : California Div. Mines Spec. Rept. 7-B. 24 p. 
Hewett, D. P., and Glass. J. J., 195.3, Two uranium-bearing pegmatite bodies in 

San Bernardino County, California : Am. Mineralogist, v. 38, p. 1.040-1,050. 
Irelan, William, Jr., 1890, Ninth annual report of the State Mineralogist: 

California Miu. Bur. Rept. 9, 352 p. 
Jahns, R. H., and Wright, L. A., 1951, Gem and lithium-bearing pegmatites of 
the Pala district, San Diego County, California : California Div. Mines 
Spec. Rept. 7-A, 72 p. 
Kunz, G. F., 1905, Gems, jeweler's materials, and ornamental stones of Cali- 
fornia : California Div. Mines Bull. 37, 171 p. 
MacKevett, E. M., Jr., 1960, Geology and ore deposits of the Kern River 

uranium area, California : U.S. Geol. Survey Bull. 1,087-F, p. 169-222. 
Miller, G. L., 1959, Tantalum and niobum : New York, Academic Press, Inc., 

767 p. 
Murdoch, Joseph, 1951. Notes on California minerals : nuevite-samarskite ; trona, 

and hanksite; gaylussite: Am. Mineralogist, v. 36, p. 3.58-361. 
Murdoch, Joseph, and Webb, R. W., 1956, Minerals of California : California Div. 

Mines Bull. 173, 4.52 p. 
1960, Minerals of California, Supplement for 1955-1957 : California Div. 

Mines Bull. 173, supp. no. 1, 64 p. 

1964, Minerals of California, Supplement for 1958-1961 : California Div. 

Mines Bull. 173, supp. no. 2, 28 p. 
Rogers, A. F., 1910, Minerals from the i)egmatite veins of Rincon, San Diego 

County, California : Colimibia Univ., School of Mines Quart., v. 31, p. 208- 

Schaller, W. T., 1911, Bismuth ochers from San Diego County, California: Am. 

Chem. Soc. Journ., v. 33, p. 162-166. 
1916, Cassiterite in Sail Diego County, California : U.S. Geol. Survey 

Bull. 620. p. 351-354. 
Schrader, F. C, Stone, R. W. and Sanford, S.. 1917, Useful minerals of the 

United States : U.S. Geol. Survey Bull. 624, 412 p. 
Weber, F. H., Jr.. 1963, Geology and mineral resources of San Diego County, 

California : California Div. Mines and Geology, County Rept. no. 3, 309 p. 


(By J. W. Padan,^ Ocean Resources, Inc., La Jolla, Calif.) 

One has only to read the popular press to gain an idea that mammoth 
rich accumulations of sea-floor minerals exist to enrich anyone with 
imagination enough to tool up for exploitation. In reality, the much- 
heralded day of large scale mining of marine minerals must be pre- 
ceded by years of detailed geologic exploration. 

"Wliat are the facts ? First, sea-floor minerals do exist. Second, in a 
few areas of the world, including California, they are being mined. 

1 Formerly with U.S. Bureau of Mines, Tiburon, Calif. 


Third, most of the mineral occurrences have crept into print on the 
basis of a solitary sample. Many of the "vast sea floor mineral de- 
posits" have been delineated on the basis of only 3 or 4 samples. Al- 
though they may fire our imaginations, to a statistician, these data 
are almost meaningless. 

This era of promotional literature has served a purpose — consider- 
able interest has been provoked in industrial, academic, and govern- 
mental circles. All eyes are on the next offshore move. 

What is the situation with respect to California's offshore minerals? 
The immediate industrial interest here, as elsewhere, is focused upon 
the near-shore area. Sand and gravel is being mined from several on- 
shore beach deposits. As coastal metropolitan areas expand and en- 
croach on much-needed deposits of inshore sand and gravel, offshore 
sources are certain to be sought both for construction purposes and for 
the restoration of storm-eroded beaches. Sea shells are clredged from 
San Francisco Bay as a source of lime for the manufacture of cement. 
Sand and silt are dredged for fill material in several coastal areas. 
Salt, bromine, and magnesium are recovered from sea water in many 
areas of the world, including California. As the saline water con- 
version program gains momentum, additional elements and compounds 
no doubt will be economically recovered as byproducts. Heavy min- 
erals, or black sands, will become exploration targets, especially off- 
shore from the mouths of rivers that have coursed through mineralized 
zones. Monterey, Drake's, and Half Moon Bays all have aroused some 
industrial interest for this reason. Ancient drainage patterns may 
offer further clues to offshore targets of heavy minerals. The heavy 
minerals of present economic interest are tin, gold, and iron ore (these 
three all are being mined offshore somewhere in the world), titanium 
ores, platinum, gem stones (diamonds are being mined off the African 
Coast; specimens of jade have been recovered by skin-divers off Cali- 
fornia) , and tungsten ores. 

Of all the minerals on the continental shelf, the one that perhaps 
will be exploited first is phosphorite, an essential fertilizer material. 
The concentrations of phosphorite appear to be widespread ; samples 
have been recovered from more than 250 locations, from Baja Cali- 
fornia to San Francisco. An attempt to mine one deposit was aban- 
doned, reportedly because of the presence of unexploded naval pro- 
jectiles on the sea-floor at the site. Considering the economic potential 
of this material, if it truly exists in the great tonnages that are indi- 
cated, the sampling to date has been rather modest. Samples of barite 
nodules and glauconite have been recovered from the shelf, but their 
presence in economic concentrations has not been proved, and their 
exploitation appears to be far in the future. 

California's continental shelf is narrow. In fact, some of the 
occurrences of the above-mentioned minerals actually are on the con- 
tinental slope. However, the opportunity to "widen" her shelf was 
presented to California last year when the Fourth Convention of the 
1958 Geneva Conference on The Law of The Sea became international 
law. The shelf now is defined as, ". . . the seabed and subsoil of the 
submarine areas adjacent to the coast but outside the area of the 
territorial sea, to a depth of 200 meters or, beyond that limit, to 
where depth of the superjacent waters admits of the exploitation of 


the natural resources of the said areas . . .". Thus, mining of the 
deep water nodules containing manganese, nickel, cobalt, and copper 
will legally extend the continental shelves of many coastal nations. 
The nodules have been sampled fairly well and appear to be present 
in quantity, but the deposit selected for initial exploitation will cer- 
tainly have to be sampled in considerably more detail. Once the 
extent and market value are determined with reasonable confidence, 
then there will be reason to solve the mining technology problems 
that may remain. Deep ocean red clays someday may become a 
source of alumina, and calcareous and siliceous oozes may find use 
as construction materials. 

Assessing the marine minerals in perspective, w^e can see that an 
expanded marine mineral industry in California depends upon an 
evaluation of "what is down there." Only an exploration program 
can supply the answers. The California-based federal program 
originally was conceived to fill this gap. However, Congress has re- 
oriented the program and the next move appears to be up to industry. 

Selected References 

Department of the Interior and Related Agencies Appropriations Bill, 1965: 
U.S. House of Representatives Committee on Appropriations, Rept. No. 1237, 
p. 12. 

Four Conventions and an Optional Protocol Formulatecl at the United Nations 
Conference on the Law of the Sea : Message from the President of the United 
States, The White House, Sept. 9, 1959, 80 p. 

Mero, J. L., 1965, The Mineral resources of the sea : New York, Elsevier Pub- 
lishing Co., 312 p. 


(By C. W. Jennings, California Division of Mines and Geology, San Francisco, 



The principal use of peat in the United States is as a soil conditioner. 
Peat contains a large percentage of fibrous and porous organic matter 
(humus) wliich improves the physical structure of the soil and pro- 
motes plant development when used in large enough quantities. Peat 
mixed with heavy clay soils makes them more granular, less plastic, 
and consequently more permeable to water, air, roots, and micro-orga- 
nisms. In sandy soils, peat helps bind the soil particles, retards exces- 
sive percolation, and makes the soils more retentive of moisture and 
nutrients. Contrary to popular belief, peat is not a fertilizer, and 
the nitrogen that it contains is not readily given up as a plant food 
like the "soluble nitrogen"' of artificial fertilizer. However, peat does 
contain soluble humic acid and is desirable for preparing soil for 
plants that prefer an acid condition, sucli as rhododendrons, azaleas, 
camellias, and gardenias. Peat commonly is mixed with sand and 
loam soil in the preparation of potting mixtures or media for the ger- 
mination of se«ds. 

The second largest market of peat in this country is as an ingredient 
or filler in mixed fertilizers in which it acts as a carrier for the primary 
nutrients — nitrogen, phosphoric oxide, and potash — not as an agent 


for supplying plant food. Well-decomposed peat dried and ground is 
ordinarily used for this purpose. 

Because of its moisture-absorbing qualities, fibrous peat sometimes 
is used as a litter material for bedding livestock, and its deodorizing 
capacity makes it useful in stable and poultry yards. Nurserymen, 
gardeners, and others use peat as a packing material for plants, fruit, 
vegetables, eggs, fish bait, and fragile materials, and as a medium for 
growing mushrooms and earthworms. Other uses of peat include fil- 
tering agents, dye stuffs, tanning substances, and as ^ibsorbent in surgi- 
cal dressings, but the quantities so used are small. 

In several European countries, peat is used as a fuel, but is is not so 
used in the United States because of ample supplies of superior fuels 
with much higher calorific values. 

Geologic Occurrence 

Peat is an accumulation of partly decomposed and disintegrated 
vegetal matter, representing the first stage in the transition of plants to 
coal. It forms in undrained depressions, plains, or river deltas that 
contain environments favorable to luxuriant growth of peat-forming 
plants. The plants range from woody shrubs and trees of swamps, to 
mosses, sedges, reeds, and grasses of marshes. Poor drainage is essen- 
tial in the formation of peat, because standing water largely excludes 
oxygen and prevents complete decay, thus enabling the carbonaceous 
matter to be preserved. 

The type of vegetation that accumulates determines the type of 
peat that is formed. The most valuable commercial peat is formed 
from aquatic mosses. Other commercial grades of peat include reed 
or sedge peat, and peat humus, which is a soil high in organic matter. 
Mosi of the peat deposits in California are classified as reed-sedge peat 
or peat hunms. A high-grade peat moss, however, is recovered from 
a single bog in Modoc County in northern California. 


"World production of peat in 1963 was estimated at 170 million short 
tons of which 60 percent was used for agricultural purposes and 40 
l^ercent for industrial fuel. The U.S.S.R. is the leading producer 
with 95 percent of the world output. The United States production 
is relatively small and represents less than 1 percent of the world total. 

The demand for agricultural peat in the United States has steadily 
increased in recent years, and, in 1963, the production reached nearly 
600,000 tons — more than double the production of 10 years ago. In 
addition, 261,000 tons of peat were imported, principally from Canada. 
Wliereas the domestic production of peat has been increasing from 
year to year, the quantity of imported peat has remained relatively 
constant. The principal peat producing states in the United States 
are Michigan, Indiana, Pennsylvania, California, and Washington; 
together these states account for three-fourths of the nation's output. 

In 1963, California ranked fourth among the states in the amount of 
peat produced and second in the value of sales. The average value 
per ton of peat in California was $11.29. The demand for peat in this 



State has risen phenomenally in the past 10 years. The value of peat 
sold in 1963 was $450,000 — more than (5 times the value ])roduced in 
1953. All of the peat produced in this State, as far as is known, was 
used for soil improvement. 

California Occurrences and Reserves 

Four widely scattered peat deposits are being worked in Oalifomia 
as shown on figure 46. These range from a peat moss operation near 
Likely, Modoc County, in the northeastern part of the State, to a reed- 
sedge type peat bog in a sag pond along the San Andreas fault near 
Banning, in southern California. The largest peat reserves are situ- 




124' 123- 122 

-n ) I \\ 



^{ S I S K |(y 0\u/-^ -^ \ > I 



Active peat plant 

Pea t bog (gene r a I area) 




41 = 

- 0-' ■ 

* ' I TRINITY > 


^ ^ ,J~. <f ENN / BU*-E v.- SIERRA 

^' ^-V--^) L4*5^^nevada]-.. 

-r» \ y 1 yolo\-^.A/ei. dorado.' N 
„ y ;■ \\ ^Sacrai*nto ■'Or 



1. John J. Harris, Peat Moss 
L i ke ly , Mod oc Co. 

2 . Vita Peat Inc. , 

Bethel Is.. Contra Costa Co. 

3. P. J. Ganbetta Delta Dredging, 
Brentaood . Cont ra Costa Co. 

4. Round Valley Peat bogs 

5. Scot t Va I ley pea t bog 

6 . la tsonv i I le pea t 

7 . Sail nas R i ve r pea t 

8. San Anton i o Va I ley Peat 

9. Ch i no pea t bog 

ID. McCe I Ian & Sons Peat. 

Huntington Beach, Orange Co. 
It. San Luis Rey peat bog 

38--K"'-e..l>Jfe^«^^ '"^^ / 



y- TUOLUMNE '";^\moNO\ -|- 38 

SJ'.c CLARA C \/ ^ 

37° — \>J 


. saJ?^.'' 





'"i \\ ^FRESNd^ 

x^ENITOl \ "7 .y\ 

SAN ! * 

-0 '■• \ 

C LUIS "-.X B.k»ni(«W 

35'-(- (y^AprX- J^;^ ^\y^ 








150 MILES 


+ \ + 

~\-\ — 

DESERT "'■> 


1 Y~34" 



\rr^* ^-^ 






SALTON \ '^33° 

,Su.Di«» [V_ I 




Figure 46. Peat in California. 


ated in the Sacramento-San Joaquin Delta area, where peat and peaty 
muck deposits cover an estimated 400 square miles. Two operators are 
dredging reed-sedge peat from Frank's Tract in this area. A small 
tonnage of i)e'at humus is being extracted from a deposit near Hunting- 
ton Beach, in Orange Comity. 

Peat has been mined from San Diego, Santa Cruz, and San Ber- 
nardino Counties, and U.S. Soil Survey maps show peat and peaty 
muck occurring in Round Valley, Inyo County; near the mouth of 
Salinas River, Monterey County: along San Antonio River and south 
of the mouth of Santa Maria River, Santa Barbara County; and in 
various sites in Siskiyou and Humboldt Counties (U.S. Department 
of Agriculture, 1919-19M). 

Reserves of peat in California have been estimated by the U.S. 
Geological Survey (U.S. Geol. Survey Circ. 293, 1953, p. 38) to be 72 
million short, tons (air-dried basis) . The peat reserves of the United 
States have been estimated at approximately 14 billion short tons. 


The outlook for the California peat industry is favorable and pro- 
duction is expected to increase. As the population of the State grows 
and more homes are built, more peat will be in demand by homeowners, 
landscape gardeners, and nurseries. Peat deposits in California have 
not been thoroughly studied for economic development; however, the 
location of many small deposits are shown on U.S. Department of Agri- 
culture soil maps. Possibly a number of these deposits could be 

Selected References 

Averitt, Paul, Berryhill, L. R., and Taylor, D. A., 1953, Coal resources of the 

United States : U.S. Geol. Survey Cir. 293, p. 38. 
Jennings, C. W., 1957, Peat, in Mineral commodities of California : California 

Divri;rines:BuTin76, p: 403^^8. ' ' 

Sheridan, E. T., 1965, Peat, in Mineral facts and problems : U.S. Bur. Mines Bull. 

U.S. Department of Agriculture in cooperation with University of California 

Agricultural Experiment Station, Soil Survey Reports. (The following Soil 

Survey Reports delineate peat deposits : Bishop area, 1928 ; Salinas area, 1925 ; 

Santa Ynez area, 1927 ; Santa Maria area, 1919 ; Shasta Valley area, 1923 ; 

Eureka area, 1925; Alturas area, 1931 : jacramento- San .Tongu'i r)pH-a arpa, 

1941 ; Santa Cruz area, 1944.) 


(By M. B. Smith and F. J. Schambeck, U.S. Geological Survey, 
Los Angeles, Calif. ) 


Oil is used primarily to produce energy for power or heat, and for 
lubrication. More than 2,300 separate products are made by the pe- 
troleum industry, some of the principal products being gasoline ; lubri- 
cants ; residual and distillate fuel oils ; jet fuel ; raw materials for the 
petrochemical, rubber, and fertilizer industries; and asphalt. 


Most of the crude oil produced in California is of napthenic base 
(often called asphaltic base). The crude oil is transported from the 
oil fields by pipe lines, ocean tankers, or tank trucks to the 34 refineries 
in the State, most of which are near Los Angeles and San Francisco. 
These refineries have a capacity of about 1,350,000 barrels per day. 

Natural gas is used primarily for space heating and for fuel, but 
some is used as a chemical raw material. Most gas in California 
occurs in two ways : (1) as "wet gas" in oil sands or closely associated 
with oil in an overlying gas cap, or (2) as "dry gas" in separate 
zones in oil fields or in gas fields not associated with oil. Wet gas 
commonly contains valuable constituents which are removed at proc- 
essing plants to obtain natural-gas liquids before the residue gas is 
used. Dry gas usually does not contain enough of these constituents 
to make the processing economically profitable, so after removing 
impurities and blending w^ith other gas to increase the heading value 
if necessary, it is distributed by pipe line and used. Slightly more 
than one-third of the gas produced along with oil in California is 
reinjected under pressure into the oil reservoirs for the purpose of 
restoring or maintaining the reservoir pressure and thereby increas- 
ing the recovery of oil. Most of this gas will be produced again at 
some later date. At present, less than 1 percent of the gas accompany- 
ing oil production is wasted by being allowed to escape into the 
air, and even this wastage generally occurs during testing operations. 

The production of oil and gas in California is extremely important 
to the economy of the State as it provides a local source of supply 
for a large part of the energy recfuirements of the large and rapidly 
growing industry and population. The production, refining, and 
distribution of petroleum utilizes a capital investment of $6.9 billion 
in facilities and equipment and furnishes employment to some 106,000 
persons. Oil producers pay an estimated $140 million annually as 
royalties to owners of interests in the production, and some $30 million 
annually for rentals on some 5.5 million acres of nonproductive land 
held under oil and gas leases. Taxes paid to state and local govern- 
ments (exclusive of those paid by gas utilities) are estimated at $620 
million for 1964. There are 69 plants in the growing petrochemical 
industry employing 45,000 persons with a $325 million payroll. Oil 
accounts for 79 percent of all tonnage through California harbors. 

The 1964 output of California's 42,000 producing oil wells and 900 
producing gas wells in some 350 fields (figs. 47, 48, 55, 56) was 299 mil- 
lion 42-gallon barrels of oil and 675 billion cubic fee (net) of gas with 
a value at the wells of about $940 million. Tliis amounted to 60 percent 
of the value of the entire mineral production in California for the year. 
The production %vas obtained from depths as shallow as 200 feet to as 
deep as 13,000 feet. The productive area totals about 425,000 acres, or 
less than 14 of 1 percent of the area of the State. The only substantial 
shut-in production is about 100,000 barrels per day from one zone in 
the Elk Hills field in Naval Petroleum Reserve No. 1. However, the 
daily yield from many large flowing wells is controlled and is less than 
their potential. 

The production of crude oil declined nearly continuously from the 
peak of 1 million barrels per day in 1953 to 8i3,000 barrels per day in 
1962. Since that year production has increased to 860,000 barrels daily 



4° 123° 122' 121" 

Uh A ^/, A -r}f^^^ O M o dIo ; 
Kb.AIVIAT>^ jCn O 5 1 


Outline of principal productive 
sedinantary basins 


TRINITV z-,,-^, 

r ?. J^ T^^JW "'W >■ SIERRA 


Oil f iaid 




p LAKE ; I -V Ws,) \\! Av: <^ _^.; : 

v\._/'\.vol2!1>;X J^'ri. dora'dq,- N;^. 


\sonoma<^naA' -t^. 







'H-l'Cr*^* ' 't^\ , TUOLUMNE 1^\moNO\ +38° 

Francisci>t-^ \'/.J — ' 

SANTA ss^ f-f \i .-^^ y ■ 


Bibhop "v 




<^.. -^^ 

'> \ 

C \\ ' N Y O <5, \. 

TAi.ARE ^ A -VK \ 






I I I 

^j^,^^ DESERT '■-> 

3-'iSS^'S^^^^X ' 1'' 


LOS ^GELES-K3--'^i,_'l'_- 




Figure 47. California oilfields. 

by mid-1965, and may increase to 1,000,000 barrels per day in the next 
few years. It has been estimated that the need for crude oil in Cali- 
fornia will increase about 3.8 percent annually through the year 2000. 

The gravity of California crude oil ranges from 6° to 60° API, but 
347,800 barrels per day, or 42 percent of the State's production in 
January 1965, was heavy crude below 20° API gravity. The price 
received by the producer at the well depends largely on the gravity. 
It ranges from $1.07 to $3.42 per barrel at present and averages about 

Along with the oil, the State's wells produce about 2.9 million barrels 
of water per day which must be disposed of according to the require- 





122'' 121' 


( S I S K ||y o\u/ — J Q, 
i W-K A K» A -^i W\"^ O M O Jo C 

4,.^ \Mdt^(b^TA/NSn^ 

> ...11 i ^< 


Outline of principal productive 
stdiMntary basins 



TRINITY' /"^^ ■ "YSSEJiX i 

.-^aCiJ CASCAf>E \ <\ I 

eSf^'J^li^e y, SIERRA 

Large gas f ie Id 
Saa I I gas f le Id 





.^ "><i^' 

SANTA CRU2-«S SANTA S^ rX \\ / ^ ^ i \ .Biri»t. V 

\SON0MA(^ N 


IOn6\ —^ 38° 





'> \ 

' jK^^^ 

I. '\ > N Y O ^ \ 






MOJAVE -|--^35° 






150 MILES 



, , I . %^^ CSALTON ) -=.33° 

+ \ + I ^^'^ "'"'° CtroughW 

119° 118° M{,s»>D"«° _^aV---^- r 


FiouKE 48. California gasfields and principal productive sedimentary basins. 

ments of the State AVater Pollution Control Board. Both the pro- 
duction and disposal of water increase the cost of producing oil. 

Forty-six pools or fields in the State are today partially or fully 
unitized, the first unit having been formed at the Kettleman North 
Dome field in 1931. Nineteen pools or fields, although not unitized, 
are operated essentially as units. 

The State Oil and Gas Supervisor, Division of Oil and Gas, is 
charged with the responsibility of carrying out the provision of State 
laws for the conservation of oil and gas. Among other things, these 
laws provide for supervision of operations so as to prevent, as far as 
possible, damage to underground oil and gas deposits from infiltrating 
water, and the loss of oil and gas; these laws also prohibit the un- 
reasonable waste of gas. The Division also supplies oil and gas field 
maps, publishes detailed descriptions of most fields in the State, and 
provides statistics on production. 


The Conservation Committee of California Oil Producers recom- 
mends schedules for production from 75 pools, based on determinations 
by engineering studies of what is considered the Maximum Efficient 
Rate (MER) of production. The Committee also provides production 

The California Division of Mines and Geology, the U.S. Geological 
Survey, and the American Association of Petroleum Geologists have 
published many maps and articles concerning the geology and occur- 
rence of oil in the State. The last also provides exploration statis- 
tics. On Federal lands the Conservation Division of the U.S. Geo- 
logical Survey supervises drilling and producing operations and deter- 
mines and collects the royalty. 

Information used in this chapter concerning the petroleum industry, 
the geology, and the occurrence of oil in the State has appeared m 
published reports too numerous to list; it is gratefully acknowledged. 
A selected list of references is included with this report. 

United States Rank as World Producer of Oil 

The demand for petroleum products in the United States in 1964 
was 11.3 million barrels daily. This demand was met largely by 
domestic production of 7,664,000 barrels of crude oil and gas con- 
densate, by the production of 1,147,000 barrels of natural gasoline and 
other liquid petroleum products, and by imports of 2,260,000 barrels 
of crude oil and products. Only 202,000 barrels per day of products 
and crude oil was exported. 

For many years until the mid-1940's, the United States produced 
approximately two-thirds of the oil in the world. In recent years, 
however, imports of crude oil and refined products into the United 
States have increased while exports have decreased, so that imports 
have exceeded exports since about 1948. In 1964, the United States 
produced about 33 percent of the free world's production, and about 
27 percent of the entire world's production which has been estimated 
at 28.1 million barrels daily. 

California's Rank in United States Production 

California was the major oil producing state from 1903-1914 and 
1923-1926. It was second to Texas until 1958 when Louisiana ex- 
ceeded California, mainly because of the development of large pro- 
duction in southern Louisiana, including offshore. California now 
ranks third in both current crude oil production and reserves (table 

Geologic Occurrence 

Commercial quantities of oil and gas occur imder pressure in the 
interconnected pores of reservoir rocks in pools or fields. All oil 
miderground contains some dissolved gas, so when oil is mentioned 
the contained gas is included also. The interconnected pores between 
the grains of sand or conglomerate comprise the space which holds 
most of the oil in California as in many other oil regions. It is esti- 
mated that 98 percent of the oil in the State occurs in rocks of those 
types. In addition, weathering, solution, chemical changes, and frac- 
turing also create porosity, and some oil is produced in California from 























































































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fractured cherts, fractured shales, fractured sandstones, and from 
weathered and fractured basement rocks beneath the sedimentary 

The pore spaces in most sedimentary rocks more than a short dis- 
tance beneath the surface were filled with water at some time in their 
history, so in oil reservoirs they generally contain what is called inter- 
stitial water as well as oil. 

For commercial production to be obtained, the reservoir rock must 
also be permeable as well as ix)rous. Permeability is the measure of 
the ease with which fluids move through the interconnected pore 

The original pressure in most California reservoirs is roughly 
equivalent to that which would be exerted by a vertical column of 
water extending nearly to the surface, but it exceeds that pressure in 
some fields. 

"Wlien the drill penetrates the reservoir rock and any drilling fluid 
in the hole is partially or completely removed, the reservoir energy 
causes the oil to move into the hole. The gas expands, the fluid moves 
toward the surface, and oil may flow from the well (a "gusher" if the 
flow is large and uncontrolled). If the fluid does not reach the sur- 
face, it is removed by pumping or by other mechanical means. The 
gas-free oil in stock tanks at the surface occupies less volmne than it 
did underground because the compressed gas dissolved in the oil in the 
reservoir escapes from the oil as the pressure is reduced from that in 
the reservoir to that in the tank. 

How the oil and gas were formed, how they move (oil and gas are 
migratory fluids), and how they accmnulate at the places where they 
are now found — the origin, migration, and accumulation — is still the 
subject of much scientific speculation, although a great deal is now 
known about cliaracteristics of the traps in which they have accumu- 
lated, as a result of studies of thousands of oil fields. It is now widely 
accepted that commercial petroleum is derived from the organic re- 
mains of plants and animals that were deposited in a low-oxygen, 
reducing environments in marine sediments, principally fine-grained 
muds, but also in sediments deposited in brackish to fresh w^ater (Hed- 
berg, 1964). The chief sources of oil and gas in California are be- 
lieved to be the thick organic shales (consolidated muds) so wide- 
spread in marine sedimentary rocks primarily of Tertiary age, but also 
of Cretaceous age (Hoots, 1943). 

It is believed that oil, along with water, escapes from the muds as 
they are compacted, and moves into coarser sediments through which 
it moves laterally into the traps in which it now occurs. Vertical 
migration, possibly along faults, may account for the present location 
of some of the oil at shallow depths in some California fields (Hoots, 

Regardless of the processes involved, oil usually moves toward 
higher elevations because these are areas of lower pressure, and be- 
cause oil is lighter than water. It accumulates in traps which may be 
classified as structural, stratigraphic, and combination (strati-struc- 
tural). A trap involves a porous reservoir rock, an overlying im- 
permeable cap rock, and a barrier in the reservoir which prevents 
further updip or lateral movement of the fluids. In traps that con- 
tain free gas, oil, and water, the fluids are arranged in approximately 

67-1164 O— 66— pt. I 20 


horizontal layers — gas being the lightest, at the top, then oil, and 
then water. The water almost always moves slowly into areas in 
which the pressure has been reduced by removal of the oil, and this 
movement may assist in recovering more of the oil in the reservoir. 

Levorsen (1954) defines a structural trap as one whose upper 
boundary has been made concave, as viewed from below, usually by 
folding or faulting or both, of the reservoir rock ; a stratigraphic trap 
as one in which the chief trap-making element is some variation in 
the stratigraphy or lithology of the reservoir rock; and a combination 
trap as one in which both causes are in approximately equal propor- 
tions. Most stratigraphic traps in California involve some element 
of structure. Commonly, multiple productive sands separated by 
impermeable shales are present in structural traps in California, an 
obvious favorable circumstance for additional accumulations. 

Environments favorable for a source of oil are not necessarily favor- 
able for the development of reservoirs, so oil occurrence depends in 
part on a favorable relationship of the two. Normally, either without 
the other does not result in a commercial oil occurrence (Weeks, 1958). 

Hedberg (1964) stated that California is in one of the two principal 
belts of oil occurrence in the world. In the United States, the north- 
south belt also includes the major oil field areas of the Rocky Moun- 
tains, the Mid-Continent, and the Gulf Coast regions. 

California is also in a mobile belt bordering the Pacific. Traps in 
which oil and gas may accumulate are commonly smaller but more 
numerous in such regions than in more geologically stable regions. 

The petroliferous provinces of the world, including California, are 
in sedimentary basins — geologically depressed areas in which great 
thicknesses of sedimentary rocks that were deposited in the interior 
of the basin thin toward the edges. 

In California, most of the oil is obtained from marine sands and 
conglomerates of Miocene and Pliocene ages (fig. 49) . Lesser amounts 
come from sands and conglomerates of Eocene, Oligocene, and Pleisto- 
cene ages and from fractured rocks of Miocene age; still smaller 
amounts come from sands of Late Cretaceous and Paleocene ages, and 
from fractured and weathered basement rocks of pre-Tertiary age. 
Gas is produced along with the oil from rocks of the previously men- 
tioned ages, but most of the dry gas is obtained from rocks of Late 
Cretaceous, Paleocene, Eocene, and Pliocene ages. The surface evi- 
dence of many geologic structures, both anticlines and faults, has re- 
sulted from the mid-Pleistocene deformation. Many fields are located 
on prominent hills or ridges which approximate the location and 
shape of the anticlinal structure of these hills or ridges because the 
anticlinal hills rose more rapidly than streams could erode and level 

Economic Factors Affecting Exploration 

The principal economic factors affecting exploration (including the 
drilling of exploratory wells) for oil and gas are, of course, the price 
(fig. 50), market demand, and accessibility to markets for the raw 
material at the time and in the foreseeable future in a free economy — 
in other w^ords how much of the production, if found, can be sold and 
at what price. 







Z 3 

« a 

*- — 









Pie istocene 


PI i ocena 














01 igocene 


• ? 






Pa leocene 



• # 




• * 

pre-Tert iary 
basement rocks 
age uncertain 





Oi I product ion, large 

Qi I product ion, sma 1 1 
to moderate 

Gas production, large 

Gas product ion, sma 1 1 
to moderate 

Figure 49. California oil and gas production in principal sedimentary basins, 

according to geologic age of rocks. 

Commonly, exploration has decreased in times of economic stress, 
lower prices, or an over-supply of oil, notably during the years of the 
great depression in the early thirties when exploration virtually 
ceased. Even in the thirties, however, the application of new explora- 
tory tools such as the reflection seismograph was instrumental in caus- 
ing farsighted organizations to search for prospects and to acquire 
rights to lands. 

Following the development of large flowing production in the twen- 
ties, principally from the Long Beach and Santa Fe Springs fields in 
1929, voluntary curtailment of production was generally accepted and 
has continued to some extent to the present, except for regulation of 
production by the Federal government from 1933 to 1935. 

Prior to World "War II, and occasionally since then, production of 
crude oil in California was greater than the demand, and large quan- 
tities of crude and products were sold on the world's markets, often 
at depressed prices. Since World War II, however, the local demand 
for both oil and gas has increased greatly as a result of industrial 
and population growth, and in recent years production in California 
has been insufficient to meet the local demand. Large and increasing 
amounts of gas have been brought into the State since 1947 through 
gas transmission lines from Texas, New Mexico, and Canada, and 



since 1951 large and constantlj^ increasing amounts of crude oil and 
petroleum products have been imported from other states and foreign 
sources (fig. 51). Among the consequences of this change in supply 
and demand are a relative stabilization in the price for crude oil but 
an increase in the price for gas. This latter increase has provided an 
incentive for expanded exploration for gas in the Sacramento sedi- 
mentary basin. 

,. Natural gas^ 

















oi ay 

Figure 50. Average price of California crude oil and natural gas. 



ources: Gas 

-Conservat ion 



of Cal if . 

oi 1 

/^\ ' / 

producers : 

Oi 1, U.S. 

Bur . 

y* ^<^^^ 

Mines and 














• / 
\ • * / 









• 1 1 

1 f 

1 1 1 

1 1 1 

1 1 1 

1 1 1 









FiGUKE 51. Imports of crude oil and natural gas into California. 


Perhaps the most remarkable feature of the California oil-produc- 
ing industry is the small size of the productive area that has produced, 
and still contains, so much oil (Hoots, 1943). About 13.25 billion 
barrels of oil has been produced prior to 1965 from approximately 
330,000 acres of productive land, or y^ of 1 percent (1/333) of the area 
of ithe State. The average recoveiy of 40,000 barrels per acre to date, 
and the estimate that this will increase to more than 53,000 by produc- 
tion from the presently known fields, is extremely high in comparison 
to other large areas in the United States. Several fields in the Los 
Angeles and Ventura basins have produced more than 100,000 barrels 
per acre, and the Long Beach field has yielded aJbout 500,000 barrels 
per acre. The yield of the average well in California during its pro- 
ductive life is expected to be 260,000 barrels, 3.5 times the average of 
wells in the rest of the United States. These large recoveries provide 
an incentive for exploration, and large rewards often result from a 

Political considerations and Federal, State, and local laws and ordi- 
nances, also affect exploration. Eestrictive provisions such as pro- 
hibitions against drilling within cities, or uncertain titles to offshore 
lands, at least delay exploration. Notable examples of the first were 
restrictions against drilling in Los Angeles and in Long Beach. After 
the restriction against drilling in Los Angeles was removed in 1950 
exploration was intensified and several large fields have been dis- 
covered. The restriction agamst drilling at Long Beach, because of 
the fear of subsidence, was partially the cause of the delay in devel- 
oping the huge East Wilmmgton field. An example of the second 
type is the more than 10-year delay in the leasing of a large part of the 
favorably regarded submerged lands offshore from southern Califor- 
nia, because the Supreme Court did not decide the ownershij) of the 
mineral rights in these lands, whether State or Federal, until early 
1956. Even though it was possible to explore these submerged lands 
by geophysical methods and, with certain restrictions, to drill wells 
for geologic information, it had not been possible to complete the 
exploration by testing wells to determine their productive capacity. 

Urbanization and the consequent increase in land values has locally 
retarded exploration and was a factor in the abandonment of the larg- 
est parts of some fields, notably the Los Angeles and Salt Lake fields 
in the Los Angeles basin. Exploration by ordinary seismic methods 
in urban areas is made almost impossible by ordinances and fear of 
large claims for alleged damages. Exploratory wells must often be 
directionally drilled from drill sites which may be costly and some- 
times difficult to obtain. 

Prior to about 1910, most wells in California were drilled with cable 
tools, equipment not well adapted for drilling to depths greater than 
in the old shallow fields in the relatively unconsolidated rocks in the 
oil regions in the State. The introduction of rotary tools soon per- 
mitted deeper exploratory wells, and discoveries were made at greater 

The drilling of exploratory wells has been greatly aided since the 
1920's by many improvements in the quality of equipment and in the 
technique of drilling. The principal improvements in technique are 
the ability to obtain cores of the rocks, to control the quality of the 


drilling fluid, and to evaluate the fluid-yielding capacity of the rocks 
without installing casing in the hole. Evaluation may be made by 
numerous devices which are lowered by cables, or by testers which 
permit the obtaining of samples of the fluids in tlie rocks and the ap- 
proximate determination of the volume of production that may be 
expected. The ability to survey holes, which was pioneered by Alex- 
ander Anderson at Long Beach, and the ability to drill directionally to 
predetermined locations are of great assistance. Directional drilling 
has aided exploration because wells can be drilled beneath built-up 
areas, beneath closed areas, beneath mountainous land in which access 
roads would be very costly, and from land to favorable locations be- 
neath the ocean. Hydraulic fracturing has been used to create per- 
meability in the reservoir rocks, and in at least one local area has 
resulted in a discovery. 

History of Discovery and Development 

That California is a petroliferous region was indicated as early as 
1542 when Cabrillo landed near Carpinteria in Santa Barbara County 
and found oil which had drifted from seeps beneath the ocean onto 
the beaches. In 1769, the Portola expedition found Indians using tar 
from the Eancho La Brea tar pits near Los Angeles. Portola used 
this tar as fuel for camp fires. Heizer (1943) mentions that explorers 
in 1775 reported that Indians used tarry material (chapapote) from 
springs near San Luis Obispo for caulking boats, and the Yokut 
Indians used oil from seepages in the San Joaquin Valley. 

In the 1800's, many seepages of oil and of ^as, and other near-surface 
indications such as gas in water wells or railroad tunnels, were found 
in the provinces on land which are now productive. Oil odors, oil 
slicks, and floating tar are evident on the water off the coast, and seeps 
off Redondo Beach and west of San Miguel Island are shown on maps 
by the U.S. Coast and Geodetic Survey. Many other evidences of 
these oil seeps have been observed on the water off southern California, 
tar and globules of oil have been observed in samples of the shelf 
sediments, and tar mounds on the ocean floor near Santa Barbara 
beneath 90 feet of water have been i)hotographed by Vernon and 
Slater (1963). 

Seepages are important because they indicate the presence of a 
source rock. Nearby all of the early fields within the oil provinces 
in the world have been found by drilling near seepages, but after 
the early stages most fields have been found following geological and 
geophysical studies. However, even in recent years many fields have 
been found by random drilling. 

Discovery hy prosjjecting near seepages, 1865-1907 

Many of the early wells in search of oil in California were drilled 
near seepages in the central and northern parts of the State. The 
first oil produced in California amounted to a few barrels from 
shallow wells on the Mattole River in Humboldt County. It was 
shipped to San Francisco in 1865. Several small producing wells 
were drilled near Ojai in the Ventura basin, including one said to 
be capable of producing 15 to 20 barrels ]>er day in 1866, but there 
M-as no market for the oil. The first truly commercial well in the 


State (Pico 4) was completed by the California Star Oil Works Co. 
ne^r Newhall in 1876, It produced 30 ban-els per day from a depth 
of 300 feet, and later made 150 barrels per day after it was deepened 
to 600 feet. The first California pipeline was laid in 1879 to carry 
this oil to the first California refineiy near Xewhall. 

Several fields were discovered in the latter 1800's, some of the present 
major oil companies were organized, and the first tankship was put 
into use. The fii'st large well was completed in 1892 by the Union 
Oil Co. near Santa Paula, and the JjOS Angeles field was discovered 
in 1892 by E. L. Doheny. The Ix>s Angeles field was the site of the 
first town-lot drilling in the State, and it soon became the State's 
largest producer. Thirty-two fields and some 2.5 billion barrels of 
oil were found in California during this period (Hoots, 1954). 

Some spectacular gushere — spectacular because they flowed out of 
control — were drilled. The famous Lakeview No. 1 gusher in tlie 
Midway-Sunset field flowed 'out control for li/^ years in 1910-1911 
from a depth of 2,225 feet. It produced as much as 68,000 barrels 
per day, and made a total of about 8.25 million barrels before sand 
entered the hole and choked off the flow. This is said to be the largest 
well in the United States. Large flows came from other wells, such 
as 12,000 barrels per day from a well in the Orcutt field near Santa 
Maria, and 10,000 to 20,000 barrels per day from early wells in the 
Midway-Smiset field. A well drilled in ]Midway-Smiset by the Lake- 
view Oil Co. is said to have flowed as much as 50,000 barrels per day. 
Other spectacular wells were those that blew out and caught fire. 
Many wells capable of large production have been completed in more 
recent years, but they are brought in under control ancl .are produced 
at only a fraction of their potential. 

Discoi^ery frimarily hy the use of geology^ 1908-35 

Beginning about 1900, geologic mapping of rocks at the surface 
began to be used in a small way in the search for oil, but it was not 
until 1908 that this method resulted in the discovery of several fields 
(Hoots, 1954) . Early studies of the geology by personnel of the Cali- 
fornia State Mining Bureau (now California Division of Mines and 
GeologjO^ the U.S. Geological Survey, the universities, and by mem- 
bers of the oil industry greatly increased the knowledge of the geo- 
logic conditions favorable for accumulation, and thus aided explora- 
tion (fig. 52). 

The use of surface geologic mapping, and the interpretation of 
surface topography, in order to find anticlinal folds and fault traps, 
Avas accompanied by a gradual increase in geological interpretation of 
information obtained during drilling — known as subsurface geology. 
These came to be accepted as exploration tools by the oil industry. 
Random wildcat drilling continued to supplement the search for oil, 
but it was usually conducted along production-trend lines, on some 
supposed favorable topographic expression, or because of a showing in 
a nearby well. Fifty-three fields and about 7.6 billion barrels of oil 
were found in California during this period 1908-1935 (Hoots, 1954). 
Improved drilling techniques were partially responsible for some of 
these discoveries, as wells could now be drilled to depths greater than 
early wells on the same structure — for example, in the Kettleman 
North Dome field. Many of the large fields in the productive basins 



1,500,000,000 1 



100.000,000 : 

Hoots, 1954 

FiGUBE 52. Oil discovery record for California by individual years. 

were discovered during this period, includino; the large Long Beach, 
Santa Fe Springs, Huntington Beach, and Wilmington fields. The 
latter was discovered by a small edge well in 1932 ; at the time it was 
assumed to be only an extension of the Torrance field. 

Discovery by the lose of geology and reflection seismovietry^ 1936 to 

Since about 1936, exploration prior to drilling has been carried on 
mainly by the use of geolog}^ (surface and subsurface) and by the 
use of geophysical methods, principally the reflection seismograph. 
Geophysical methods which measure certain physical properties of 
rocks that are related to potential traps in reser\'oir rocks were first 
used in California in 1924. The methods used in the early stages did 
not result in the discoveries of new oil and gas fields, although they 
did contribute to the knowledge of the general geological structure of 
the oil-productive basins. 

The reflection seismograph, however, has proved to be successful in 
finding traps favorable for the accumulation of oil and gas in Cali- 
fornia, It also supplies data that is useful for subsurface geologic 
studies. No method has been found except the drill that can locate 
commercial amomits of oil directly. A small gas field (Paloma) was 
discovered in 1934 in the San Joaquin basin a result of reflection 
seismograph suiweys, and this was followed in 1936 by the significant 
discovery of the Ten Section oil field in the central part of the San 
Joaquin basin, also as a result of seismic maping. The latter discovery 
not only demonstrated that anticlinal folds concealed beneath the thick 
alluvial fill of the San Joaquin basin could be found by the reflection 
seismograph, but also that thick Miocene sands provide adequate 


reservoir rocks beneath the valley floor. The prolific main part of the 
Wilmington field was discovered in 1936 as a result of reflection seis- 
mograph surveys. 

The importance of stratigraphic traps had been emphasized by the 
discovery of the huge East Texas field in 1930, and the applicability of 
this new phase of geologic exploration to California was apparent. 
The search for traps of this kind resulted in the discovei-y of the Santa 
Maria Valley field in the Santa Maria basin in 1934, in the finding of 
the prolific East Coalinga Eocene field in the San Joaquin basin in 
1938, and later in the discovery of other fields in stratigraphic traps. 

The firsit major discoveries in a previously nonproductive sedi- 
mentai-y basin since the days of prospecting near seepages were made 
in 1947-1949 when the San Ardo, Russell Ranch, and South Cuyama 
fields were found in the Salinas-Cuyama basin. Stratigraphic think- 
ing played a large part in the discoveiy of these fields. Three small 
fields — Oil Creek, La Honda, and South La Honda — were discovered 
in the period 1953-1959 in the Santa Cruz (La Honda) basin, largely 
as the result of surface and subsurface geologic studies. Beginning in 
the late 1800's, several small doubtfully commercial wells had been 
drilled in this basin, but the discoveries in the 1950's first established 
commercial production. 

About 3.2 billion barrels of oil was found in California in the period 
1936-1952 (Hoots, 1954). The estimated amount of oil discovered 
annually from 1908 to 1952 and the methods of exploration which 
accounted for these discoveries is shown in figure 52 after Hoots 
( 1954) . This figure emphasizes the fact that the annual discovery rate 
has fluctuated widely, to a large extent due to the application of new 
methods or concepts of exploration. It is somewhat misleading, as 
all the oil in any one field is allocated to the year of first discovery 
of the field. This figure does, however, bring out the poor discovery 
record during the depression from 1929 to 1935 and the World War II 
period from 1940 to 1947. In recent years, the geological and geo- 
physical methods employed in exploration have become so intermingled 
that it is futile to attempt to separate the methods that have led to 
many discoveries. However, most exploratory wells in California's 
highly explored onshore regions have been located by subsurface 
geological studies, assisted by some geophysical information where 
wells are sparse. 

According to Hoots (1954), about 13.3 billion barrels of oil had 
been found in the State to the end of 1952. If this estimate is used, 
it appears that about 4.1 billion barrels was found during the period 
1953-1964, as production to the end of 1964 plus proved reserves at 
that time totaled 17.4 billion barrels. 

Figure 53 shows the total number of exploratory wells drilled 
annually in the State for oil and gas in the period 1942-1964. It also 
show^s the percentage of these wells that were successful in finding oil 
or gas, and the percentage of success in terms of footage. 

Development drilling — the drilling of proved locations Avithin known 
fields — has been sporadic since the early days of the oil industry in 
California. This sporadic drilling is due mainly to : (1) the develop- 
ment of new fields following discovery, (2) the price and demand for 



the crude of the quality that can be expected, (3) lease requirements, 
and (4) the operator's desire to maintain or increase his production. 
An average of about 2,000 development wells were drilled annually 
during the 4-year period 1961-1964. 

As in other oil-producing regions, a large part of the production 
comes from the "giant" fields — those fields which are expected to pro- 
duce more than 100 million barrels. There are 40 of these fields in 
California (table 36). These fields produce nearly three-fourths of 
California's oil and contain more than 80 percent of the estimated 
proved reserves. 

Table 36. — Grant ^ oilfields in California 

[Reserves from Oil and Gas Journal, v. 63, no. 4, Jan. 25, 1965, p. 155; others from Conservation 

Committee of California Oil Producers] 

Basin and field 



in 1964 

Number of 
wells produc- 
ing in 1964 


in 1964 



tive produc- 
tion to 
Jan. 1, 1965 



crude oil 

reserves as of 

Jan. 1, 1965 



Los Angeles sedimentary basin: 
Wilmineton . 


43, 977 

19, 669 

14, 797 

12, 507 









31, 533 
10, 568 


50, 675 

27, 724 

26, 813 


22, 791 















27, 379 
19, 513 


1, 125 
























35, 259 





10, 147 
8, 512 



1, 013, 488 
730, 628 
247, 966 
299, 510 
843, 301 
207, 245 
236, 953 
587, 995 
145, 178 
164, 714 
87, 693 
176, 036 


106, 705 


101, 723 

947, 890 
408, 523 
393, 479 
524, 291 
109, 401 

91, 417 
124. 270 
271, 471 

94, 027 

440, 395 
105, 937 

96, 634 
149, 464 

88, 449 
105, 100 
112, 566 

108, 167 
127, 118 

144, 989 
175, 628 

586, 422 

Huntington Beach 

150, 284 



Brea-Olinda - 


Long Beach - 


Coyote West 



27, 957 

Seal Beach . 

28, 190 

Santa Fe Springs. - 

26, 929 



Torrance . . 

25, 232 

Coyote East 


MontebellJ .- 


Ventura sedimentary basin: 

120, 956 

South Mountain 





San Joaquin sedimentary basin: 


Coalinea East Extension 

K!ern River 

56, 091 

Coalinea - 


Buena Vista 


Belridee South 

27, 412 

Cymric .. 

25, 152 

Coles Levee North .. 

35, 715 

Elk Hills 

1, 031, 108 

Lost Hills 

■ 10, 546 


20, 570 

Kettleman North Dome 

Kern Front — 


34, 624 
16, 082 

Mount Poso 

26, 932 


86, 362 

Rio Bravo 

29, 992 


13, 260 

Santa Maria sedimentary basin: 
Cat Canyon West 




Santa Maria Vallev 


Sahnas-Cuyama sedimentary 
San Ardo 

97, 205 

Cuyama South 

108, 332 

Total, 40 fields 

601, 529 


220, 145 


3, 382, 051 

' One hundred million barrels or more of recoverable oil. 











1 1 


1 1 1 1 1 








1 1 


1 i 


11 III 









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In 1964, 42,000 producing oil wells in the State yielded 817,395 
barrels per day, or an average of 20 barrels per well daily (fig, 54). 
However, production increased toward the end of the year and reached 
830 thousand barrels per day in December. 

In recent years, most large flowing wells are allowed to produce at 
only a part of their potential daily production in order to conserve 
reservoir energy, to increase the efficiency of production, and to in- 
crease the amount of oil that can ultimately be recovered from the 

Unitization or some form of cooperative agreement is very desirable 
for efficient production, for conservation, and for maximum ultimate 
recovery, especially in California with its diversified land interests. 
Unitization or such agreements are necessary for secondary recovery 
operations. More than 65 units or agreements are now in effect in the 
State, and several more are being formed. 

Natural Gas 

Gas, like oil, is believed to originate from organic material deposited 
principally in marine sediments, but why only gas is found in some 
large regions such as large parts of the Sacramento Valley is unknown. 
It seems probable that only gas was originally generated in such re- 
gions (Hedberg, 1964) . It has been suggested that gas rather than oil 
may originate due to differences in the organic source material or in the 
depositional or post-depositional environment. 

Gas produced with water from shallow wells was furnished to 
Stockton in the 1850's. Later, in the early 1900's, many California 









^ in 

(O CO 

en a> 

Less than 10,000 
barre Is da i ly 1861 - 


FiGUBE 54. California crude oil production. 












cities were supplied from gas zones in oil fields. Considerable gas 
lias been produced from these dry gas zones in oil fields since 1909 
when a gas zone was discovered in the Buena Vista field (fig. 55) in 
the San Joaquin basin. A prolific gas zone was discovered in the 
nearby Elk Hills field in 1919 and it is said that one well in that field 
produced more gas than any other single well in the country prior to 

The first dry gas field of importance was discovered at Buttonwillow 
(fig. 55) in the San Joaquin basin in 1927, but this discovery was soon 
overshadowed by the completion of wells producing large amounts 
of wet gas from the gas cap at the Kettleman North Dome field. In 
1933, the first high-pressure gas well in the Sacramento basin (fig. 48) 
was completed adjoining Sutter (Marysville) Buttes. A few addi- 
tional rather small dry gas fields were found prior to 1936, but the 
first two large dry gas fields, McDonald Island and Rio Vista (fig. 56), 
were discovered in the Sacramento basin in that year. The latter has 
produced 2.25 trillion cubic feet of gas, more than one-half of the 
State's dry gas production. It is by far California's largest gas field. 

Many dry gas fields have beeii found in the Sacramento basin (figs. 
48, 56) since 1936. Exploration there increased in the late thirties, 
was interrupted by World War II, and has been aggressively pursued 
since then, encouraged by the increasing price for gas (fig. 50), which 
is now about $0.30 per tiiousand cubic feet at the well. Four dry gas 
fields (fig. 55) have been found offshore in the Ventura basin in recent 
years. Another new offshore oil field in that basin yields dry gas from 
one sand. 

Large amounts of wet gas accompanying the production of oil were 
wasted in the early 1900's, especially from the town-lot fields of Hunt- 
ington Beach, Long Beach, and Santa Fe Springs (fig. 55) in the 
Los Angeles basin- Also, large amounts of wet gas were wasted from 
the Ventura and Kettleman North Dome fields. Wells in those fields 
flowed at large rates, and the amount of gas produced along with the 
oil was far in excess of available outlets. At that time the price of gas 
was low, and the present State laws which j^rohibit the unreasonable 
waste of gas were not passed until 1929. Beginning in the 1930's, the 
amount wasted decreased to 5 to 10 percent. The wastage now is less 
than 1 percent of the wet gas and practically none of the dry gas. 

Since 1947, when gas was first imported into California, the demand 
has exceeded the amount produced in the State. Increasing amounts 
have been brought in from Texas and New Mexico, and later from 
Canada (fig. 51), so that now 64 percent of the gas consumed here 
comes from outside the State. 

Gas production and the number of gas wells have increased rapidly 
in recent years (fig. 57), and 896 billion cubic feet was produced in 
California in 1964. About two-thirds was wet gas accompanying oil. 
However, more than one-third of the gas from oil wells was returned 
to the sands to increase the recovery of oil, so that the net withdrawal 
of wet gas in 1964 was 384 billion cubic feet. Per barrel of oil, wet 
gas production was 2,020 cubic feet gross and 1,280 cubic feet net. Dry 
gas production in 1964 was 291 billion cubic feet from 898 producing 
wells. The average heating value of this dry gas is approximately 
1,000 Btu per cubic foot. 

-i-— I- 

-^ -. 

W ' 


cities were supplied from fjas zones in oil fields. Considerable gas 
lias been produced from these dry <^as zones in oil fields since 1909 
when a gas zone was discovered in tiie Buena Vista field (fig. 55) in 
the San Joacjuin basin. A prolific gas zone was discovered in the 
nearby Elk Ilills field in 1919 and it is said that one well in that field 
produced more gas than anv othci- sinirle well in the country prior to 

Tlie first dry gas field of importance was discovered at- Buttonwillow 
(fig. 55) in *^he San Joacpiin basin in 19i>7, but this discovery was soon 
overshadowed t)y tlie completion of wells i)roducing large amounts 
of wet gas from the gas cap at the Kettleman North Dome field. In 
193'>, the lirst high-pressure gas well in the Sacramento basin (fig. 48) 
was completed adjoining Sutter (Marysville) Buttes. A few addi- 
tional ratlicr small dry gas fields wei-e found ])ri()r to 19J56, but the 
first two large dry gas fields, AfcDonald Island and Rio Vista (fig. 50), 
were discovered in the Sacramento basin in that year. The latter has 
])roduced 2.25 trillion cubic feet of gas, more than one-half of the 
State's dry gas production. It is by far California's largest gas field. 

Many dry gas fields have Ix^en found iri the Sacramento basin (figs. 
48, 56)' since 1936. Exploration there increased in the late thirties, 
was interrupted by "World "War II, and has been aggressively pursued 
since then, encouraged by tlie increasing jirice for gas (fig. 50), which 
is now about $0..'50 i)ei' tiiousand cubic feet at the well. Four dry gas 
fields (fig. 55) have lieen found offshore in the Ventura basin in recent 
yeai-s. Anothei- new offshore oil field in that basin yields dry gas from 
one sand. 

Large amounts of wet gas accompanying the production of oil were 
wasted in the early 1900*s, especially from the town-lot fields of Hunt- 
ington Beach, Long Beach, and Santa Fe Springs (fig. 55) in the 
Los Angeles basin- Also, large amounts of wet gas were wasted from 
the Ventura and Kettleman Xorth Dome fields. "Wells in those fields 
flowed at large rates, and the amount of gas ])roduced along with the 
oil was far in excess of available outlets. At that time the price of gas 
was low, and the present State laws which jirohibit the unreasonable 
waste of gas were not passed until 1929. Beginning in the 1930's, the 
amount wasted decreased to 5 to 10 percent. The wastage now is less 
than 1 percent of the wet gas and jiractically none of the dry gas. 

Since 1947, when gas was first im])orted into California, the demand 
has exceeded the amount i)roducP(l in the State. Increasing amounts 
have been brought in from Texas and New Mexico, and later from 
Canada (fig. 51), so that now 64 percent of the gas consmned here 
comes from outside the State. 

Gas production and the number of gas wells have increased rapidly 
in recent years (fig. 57), and 896 billion cubic feet was produced in 
California in 1964. About two-thirds was wet gas accompanying oil. 
However, more than one-third of the gas from oil wells was returned 
to the sands to increase the recovery of oil, so that the net withdrawal 
of wet gas in 1964 was 384 billion cubic feet. Per barrel of oil, wet 
gas production was 2,020 cubic feet gross and 1,280 cubic feet net. Dry 
gas production in 1964 was 291 billion cubic feet from 898 producing 
wells. The average heating value of this dry gas is approximately 
1,000 Btu per cubic foot. 


Figure 56. Northern California dry gas fields. 














FIGURE 57. California gas production. 

The oil fields in the San Joaquin and Los Angeles basins are the 
largest producers of wet gas, with lesser amounts from the Ventura, 
Salinas-Cuyama, and Santa Maria basins. About 80 percent of the 
dry gas produced in 1964 came from fields in northern California (fig. 
56), and nearly all these fields are in the Sacramento basin. Lesser 
amounts were produced in the offshore part of the Ventura basin (13 
percent), the San Joaquin basin (6 percent), the Eel basin (1 per- 
cent) , and a few other minor areas. 

Oil and Gas Provinces in California 

There are eight principal productive sedimentary basins (figs. 47, 
48) in the State which derive their names from the valleys or districts 
in which they occur. The major oil-producing basins and their per- 
centage of California's 1964 production are the San Joaquin (41), Los 
Angeles (34), Ventura (15), Salinas-Cuyama (6.3), and Santa Maria 
(3.4). The major dry-gas producing basin is the Sacramento which 
yields about 80 percent of the State's production. The Sacramento, 
Santa Cruz, and a few other small basins yield less than 1 percent of 
the State's oil, and the Eel River basin yields less than 1 percent of 
the dry gas. These eight basins, the outlines of which are slightly 
modified from those shown by Vlissides and Quirin (1964), have an 
area of about 31,000 square miles, about 19 percent of the area of the 

Los Angeles sedimentary hasin 

The Los Angeles sedimentary basin (figs. 47, 48) extends along the 
coast about 70 miles and inland as much as 40 miles. It has an area 


of about 1,450 square miles. This basin is the principal part of a more 
extensive structural depression which extends westward an uncertain 
distance beneath the ocean. 

The most distinctive geologic characteristics of the basin is the large 
concealed structural relief and the structural and stratigraphic com- 
plexity (Yerkes and others, 1965). Three principal west-north- 
westward-trending structural blocks are separated by the steep New- 
port-Inglewood and Whittier fault zones. The former probably 
separates genetically distinct groups of basement rocks on which the 
sedimentary rocks were deposited. 

Deformation, chiefly that beginning in Miocene time and culminat- 
ing in mid-Pleistocene time, formed anticlines and faults in the sedi- 
mentary rocks. These generally trend northwestward except in the 
northern part of the area where the structural trend is more nearly 
west. Deformation has continued to modern times as shown by earth- 
quakes, warping of Recent rocks, and subsidence in some areas and 
uplift in others. A nearly unique combination of geologic factors and 
timing of events seems to account for the prolific oil production from 
the basin (Barbat, 1958). 

At least 31,000 feet of sedimentary rocks are present above the base- 
ment floor in the deepest part of the central synclinal trough, about 
10 miles southeast of the center of Los Angeles (McCulloh, 1960). 
Edwards (1951) estimated that the volume of sedimentary rocks in 
the basin is about 2,250 cubic miles, and Barbat (1958) estimated that 
the volume of basinal sedimentary rocks within the drainage area of 
the oil fields is some 1,600 cubic miles. Even if the foi-mer vohune is 
used because it seems to be more comparable to estimates of the volume 
in other basins, the recovery per cubic mile of sedimentary rocks al- 
ready slightly exceeds the phenomenal amount of 2.33 million barrels. 

Most of the known fields are structural accumulations on anticlines 
or in fault traps, although some production of minor importance is 
obtained from stratigraphic traps. The more important fields occur 
along seven general productive trends which follow structural trends. 
The most publicly noticed fields are those that lie on anticlinal struc- 
tures along the Newport -Inglewood fault zone — Huntington Beach, 
Seal Beach, Long Beach, Domiquez, Inglewood, and Cheviot Hills. 

Most of the oil has been obtained from sands and conglomerates. 
More than one-half has come from the Repetto (?) Formation of early 
Pliocene age, and slightly less than one-half from rocks of late Miocene 
age (fig. 49). Relatively minor amounts are obtained from rocks of 
late Pliocene, middle Miocene, and pre-middle Miocene ages. 

Surface evidence — seepages, geology, and topography — supple- 
mented by subsurface studies led to the discovery^ of most of the fields 
in the basin prior to 1936. In that year, the prolific production in the 
Wilmington field was discovered as a result of seismic work. Since 
1953, advanced geological exploration techniques, core-hole drilling, 
and sparse seismic work have resulted in the discovery of seven new 
fields and several new pools in known fields. 

The Los Angeles sedimentary basin has been intensively explored. 
If the deep central part of the basin, where very few deep wells have 
been drilled is excluded, the density of exploratory wells is over 11 per 
square mile. 


Some 56 fields (fig. 55) in the basin have produced 5.33 billion 
barrels of oil to January 1, 1965 from 47,500 acres, or a recover}^ of 
about 112,000 barrels per acre. Long Beach, an outstanding field, has 
produced 843 million barrels from only 1,695 acres, or a recovery of 
500,000 barrels per acre. Several deA'elopments in recent years have 
greatly increased the production and reserves in the basin : 

1. The removal of restrictions which prohibited drilling within the 
cities of Los Angeles and Long Beach has resulted in intensified ex- 
ploration and in the discovery of several new fields and new pools in 
known fields in Los Angeles, and in the leasing of the huge East Wil- 
mington field at Long Beach. New fields and new pools in Los Angeles 
were producing more than 20,000 barrels of oil and 70 million cubic 
feet of gas daily in early 1965, and it is estimated that some 100 to 150 
million barrels of oil has been found since 1953. Also, it is estimated 
that production from the largely offshore East Wilmington field will 
be from 150 to 200 tliousand barrels daily by 1968, and that the field 
will eventually yield 1.2 to 1.5 billion barrels. 

2. Water is being injected into the oil reservoirs in several fields, 
especially in tlie Wilmington field where about 565,000 barrels of water 
is injected daily. The injection in the Wilmington field has nearly 
stopped subsidence of tlie land surface which had reached a maximum 
of about 27 feet, and is believed to have increased the daily oil produc- 
tion approximately 53,000 barrels. The field now produces about 
95,000 barrels per day, and it has been estimated that it would have 
declined to 42,000 barrels per day without water injection. The esti- 
mate of recoverable oil from the field has been increased about 400 
million barrels, of which some 218 million barrels is expected to come 
from the tidelands area of the field. 

Striking features of the production in this basin are: (a) prolific 
production from the relatively small sedimentary basin, and the small 
areal extent of some of the prolific fields; (b) the thick oil zones — a 
zone includes several sands separated by thin beds of shale; (c) the 
fact that the vertical thickness (oil columns) of the oil zones often 
greatly exceeds the "closure"' of the anticline — Long Beach, for ex- 
ample, has 2,200 feet of oil sand in six oil zones with a total thickness 
of 5,200 feet, although the estimated "closure" is only 1,600 feet; (d) 
subsidence of the surface along the ocean front in the Wilmington 
field; (e) subsurface damage to several hundred wells at Wilmington 
as the result of earth movements notably from 1947-1951. The move- 
ment in 1951 occurred at the time of an earthquake with an intensity 
of V on the Modified Mercalli Intensity scale; (f) oil wells in citrus 
and avocado groves and in business and high-class residential districts, 
often requiring development by directional drilling from sound- 
proofed derricks, and production from landscaped "islands"; (g) the 
close spacing of wells in areas of town-lot drilling; (h) the rows of 
pumping units a few feet apart along the ocean front, notably at 
Huntington Beach. Wells drilled from these surface locations were 
directionally drilled to properly spaced locations beneath the ocean; 
(i) the drilling and production platforms and islands a few miles off- 
shore and the large refineries close to the oil fields and the ocean. 

Ventura sedimentafry basin 

The Ventura sedimentary basin (figs. 47, 48) is an elongated east- 
ward-trending basin at least 130 miles long and 20 to 40 miles wide 

67-164 a— 66e- pt. I 21 


with an area of about 3,600 square miles. About 1,500 square miles of 
the eastern part of the basin, including the Soledad subbasin at the 
east end and a strip along the northwestern part of the basin, is on 
land ; the rest of the western part is submerged beneath as much as 
2,000 feet of water. 

Structurally, the basin is a regional syncline on which numerous 
eastward-trending folds have been superimposed, and which is broken 
by numerous large thrusts and reverse faults. Some faults dip south- 
ward, others north^vard. The central part of tlie basin lias been sub- 
jected to north-south compression with the result that most of the 
structural features trend westward in contrast to the northwestward 
structural trend in most of the other oil regions of the State. Many of 
the principal valleys retlect their synclinal structure, and many of the 
hills or mountains reflects their anticlinal structure. 

Sedimentary rocks about 58,000 feet thick were deposited in the 
basin and rest on a granitic and schist basement. Included in the 
sedimentary rocks are 13,000 to 15,000 feet of marine Pliocene rocks 
in the vicinity of Ventura, perhaps the greatest thickness of these rocks 
in the world. Eand (1951) estimated that some 17,000 cubic miles 
of sedimentary and volcanic rocks are present in the basin. If it be 
assumed that about 40 percent of this volume is on the land part of 
the basin from which production to January 1, 1965 has been about 
1.4 billion barrels, then about 206,000 barrels have been produced 
per cubic mile of sedimentary rocks in that part of the basin. 

Production is obtained from rocks of several different ages (fig. 
49), but most of the oil comes from Pliocene and Miocene marine 
sands and from nonmarine sands of Oligocene age. Lesser amounts 
are produced from Cretaceous, Pal eocene. Eocene, and Pleistocene 
sands, and from fractured rocks of Miocene age. 

Most of the 78 fields in the basin (fig. 55) are structural accumula- 
tions on faulted anticlines, but accumulations in fault or stratigraphic 
traps are common. In recent years, prospecting along thrusts and 
reverse faults has resulted in the discovery of several concealed anti- 
clinal and fault accumulations beneath these faults. 

The outstanding field in the basin is the Ventura field, wdiich has 
produced 694 million barrels to January 1, 1965. It is 7 miles long 
and about 1 mile wide, and is on the structurally highest part of the 
16-mile-long, severely faulted, Ventura anticline. The recovery from 
the 3,470 productive acres has been about 200,000 barrels per acre. 
Gas from shallow wells in the field was supplied to Ventura as early 
as 1903. 

Striking features of the production in this basin are: (a) thick 
Pliocene reservoirs in the Ventura field where there is a maximum of 
about 7,500 feet of oil-bearing Pliocene strata, excluding repetition 
by faulting; (b) the location of several fields in the rugged moun- 
tainous regions overlooking the Santa Clara River valley; (c) ac- 
cumulation of oil in the colorful nonmarine red beds of the Sespe 
Formation of late Eocene to early Miocene age; (d) higher-than- 
normal pressures in the Ventura field, especially in the deeper zones 
where pressures at a depth of 9,200 feet were 8,300 pounds per square 
inch, or about double that due to a column of water extending to the 
surface; and (e) the development of moderate production in one 



field in the basin by the unusual methods, for California, of drilling 
with air and artificial fracturing of the reservoir rocks in order to in 
crease the permeability. 

San Joaquin sedimentary basin 

Two large productive sedimentary basins — the San Joaquin and the 
Sacramento — occur in the Great Valley (figs. 47, 48) and include the 
valleys of those names and parts of the adjoining foothills. The 
Stockton arch separates these two basins about 60 miles east of San 
Francisco, and structurally unites the Diablo uplift on the west with 
the Sierra Nevada block on the east. On this broad arch. Cretaceous 
rocks are only about 3,500 -feet beneath the surface. 

The San Joaquin .sedimentary basin (figs. 47, 48) trends northwest- 
ward for 250 miles with a width of 50 to 60 miles. It has an area of 
about 11,350 square miles. The maximum thickness of the sedimentary 
rocks in the basin exceeds 30,000 feet, and the volume of those rocks 
has been estimated at about 31,000 cubic miles (Kilkenny, 1951). As 
the 105 fields (fig. 55) in the basin liave produced 5.5 billion barrels 
to January 1, 1965, the production has been about 180,000 barrels per 
cubic mile of sedimentary rocks, but that amount would be much 
larger, perhaps doubled, if only the volume of the rocks in the oil- 
productive southern part of the basin Avere used. 

Structurally, the basin is an asymmetric syncline, the axis of which 
lies near the west side of the San Joaquin Valley. According to 
Repenning (1960), tlie structural basin was formed by the westward 
tilting of the Sierra block against the eastern flank of the Coast 
Ranges. The basin floor slopes gently westward to its deepest part. 
East of the syncline, tension faults and gentle folds predominate; 
west of the syncline closer to tlie San Andreas fault, the strata are 
more steeply tilted and are broken by faults many of which are reverse 
faults resulting from compression. 

The Bakersfield arcli trends southwestward across the valley near 
the city of that name, and separates the San Joaquin basin into sub- 
basins. North of tlie arch the structural trend is northwestward; to 
the south the trend is more nearly westward. Near the southern bor- 
der of the basin, southward-dipping faults along which the upper 
block has moved northward and asymmetric folds such as Wheeler 
Ridge, in which the north flank dips more steeply than the south flank, 
suggest stresses from the south. 

Prominent anticlines in tlie Diablo and Temblor Ranges west of the 
San Joaquin Valley trend southeastward into the valley, and many 
are marked by prominent topographic features such as Kettleman 
Hills and Elk Hills on which large oil fields have been developed. 

The oil fields are concentrated in the southern part of the basin 
which contains a large thickness of organic shales of Tertiary age. 
These shales contain abundant remains of very small (microscopic) 
plants and animals. Several gas fields, and gas sands in oil fields, 
occur in the southern part, of the basin, but only gas fields have been 
found between Fresno and Stockton. 

Oil has accumulated in many varieties of traps, but much is in 
stratigraphic traps associated with some element of structure. How- 
ever, there are many structural accumulations on anticlines, and fault 


traps are more important than in other California basins, especially 
along the east side of the valley. 

Commercial accumulations occur in both marine and nonmarine 
rocks and are widely distributed through 10 to 15 thousand feet of 
strata ranging in age from Cretaceous to Pleistocene (fig. 49) . Some 
production on the east side of the valley is obtained from pre-Cre- 
taceous schist where it is overlain by oil-bearing sediments. About 
90 percent of the production has come from rocks of Miocene and 
later age (Simonson, 1958) including a large amount from nonmarine 

The Miocene, Pliocene, and Pleistocene rocks thin from south to 
north and become largely nonmarine in the north and east parts of 
the basin. The greatest thickness of sedimentary rocks is near the 
southern end where they are more than 6 miles thick. Cretaceous 
rocks, on the other hand, thin southward from the Stockton arch and 
are absent in the southern end of the valley. 

Striking features of the production in this basin are: (a) the great 
concentration of oil fields in the southern part of the valley; (b) the 
low^ API gravity of much of the oil near the margins of the basin; 
(c) the long-continued drilling of new wells in old fields; (d) the 
continual discoveries of new fields and extensions of old fields in the 
highly explored Rakersfield-Taft-Coalmga area in the southern part 
of the valley; (e) the large number of steam-injection secondary re- 
covery operations; and (f) the presence of Naval Petroleum Reserves 
No. 1 (Elk Hills) and No. 2 (Buena Vista Hills). The former is 
maintained as a billion-barrel reserve by the Navy, and only a relatively 
small amount of oil is produced for protection of the reservoirs; the 
latter is not maintained as a reserve, but is actively produced. 

Sacramento sedimentary basin 

The Sacramento sedimentai^ basin (figs. 47, 48) extends north- 
northwestward from the Stockton arch for 200 miles and is about 
50 miles wide, except at the southern end where it widens to 70 miles. 
It also may be divided into sub-basins. Rocks ranging in age from 
Late Jurassic to Pleistocene are present in this basin, but the Miocene 
and Pliocene rocks which yield prolific production in the southern 
part of the Great Valley are thin and nonmarine, and yield only 
minor amounts of gas. 

Sedimentary rocks cover an area of 11,350 square miles (Hobson, 
1951), but in this report the area of the basin is considered to be 
9,200 square miles. The sedimentary rocks probably have a maximum 
thickness beneath the valley of more than 35,000 feet, and the volume 
of Lower Cretaceous to Pliocene sedimentary rocks was estimated to 
be 44,000 cubic miles by Hobson (1951). The fields (fig. 56) in the 
basin have produced about 3.5 trillion cubic feet of gas to January 1, 
1965, or some 80 million cubic feet of gas per cubic mile of sedimen- 
tary rocks. 

Nearly all the production from the basin has been dry gas, al- 
though some condensate is produced from a few fields. Recently, 
moderate oil production has been found in sands of Paleocene and Late 
Cretaceous ages in one field and a small amount of oil has been pro- 
duced from a sand of Late Creataceous age in another field. Gas is 


obtained mostly from sands of Eocene, Paleocene, and Late Cretaceous 
ages, but some comes from younger Tertiary rocks (fig. 49). 

Structurally, the basin is an asymmetric syncline the axis of which 
is near the west side of the valley. The basement floor slopes gently 
westward from the Sierra Nevada into the deepest parts of the basin. 
Steeply dipping Jurassic and Cretaceous sedimentary rocks along the 
west border are separated from older basement rocks farther west 
by faulting. 

Sutter (Marysville) Buttes, a unique feature in the sedimentary 
basins of California, rises 2,000 feet above the lowlands in the central 
part of the valley, and is an eroded volcanic plug. Magma rising 
to the surface arched and tilted the adjoining Creataceous and Eocene 
rocks. The first commercial gas discovery in the basin was made 
in 1933 close to the igneous plug, and there are now many gas fields 
north, south, and west of the Buttes. A second unique feature in 
the basin is the presence in the subsurface of sediment-filled channels 
or gorges of pre-existing streams. Gas is found in stratigraphic 
traps in these gorges. 

Striking features of the production in the Sacramento basin are: 
(a) gas, rather than oil, production, perhaps because the source 
material, or the environment in which the rocks were deposited, 
differed from those in the oil-productive basins; (b) the large amount 
of gas produced from Cretaceous sands in contrast to the small amount 
of oil from rocks of that age in other California basins; (c) the much 
greater distance between wells than in the oil-productive areas be- 
cause gas travels farther and more freely through the reservoir 
sands; (d) the accumulations near the igneous plug of Sutter Buttes; 
and (e) the abnormally high reservoir pressures in many Cretaceous 

Although many seeps of high API gravity oil on the west side of the 
Sacramento Valley have long been known and some wells drilled near 
these seeps yielded a few barrels of oil, it was not until 1960 that a 
possible commercial amount of crude oil was found in one gas well. 
Early in 1963, the second and most important discovery of oil in the 
basin was made unexpectedly during the development of the Brent- 
wood field where only gas had been found previously. Oil production 
from these two fields to January 1, 1965, has been 1.6 million barrels, 
nearly all from the Brentwood field. 

Santa Maria sedimentary hasin 

The Santa Maria sedimentary basin (figs. 47, 48) which includes 
several sub-basins extends about 40 miles along the coast, as much as 
25 miles inland, and an uncertain distance offshore. The area of the 
onshore part is slightly less than 1,000 square miles. The maximum 
thickness of Tertiary and Pleistocene rocks in the basin is believed to 
be about 16,000 feet, and the onshore part of the basin possibly con- 
tains some 1,100 cubic miles of unaltered sedimentary rocks above the 
Jurassic basement (Hobson and Lupton, 1951) . 

Production of oil from the basin to January 1, 1965, has been 
approximately 500 million barrels, or a recovery of about 450,000 
barrels per cubic mile of sedimentary rocks. 

The major structural features have a general west -northwestward 
trend, and the last period of deformation was so geologically recent 


that the topography generally reflects the structure of the rocks — the 
major valleys are synclinal, and the hills are anticlinal. The Santa 
Maria Valley is an asymetric syncline, the axis of which is close to, or 
beneath, the anticlinal folds of the Casmalia and Solomon Hills which 
border the valley on the south. 

Production is obtained from the hard, brittle fractured cherts and 
shales in the Miocene Monterey Shale, from fractured sandstones of 
Miocene age, from fractured sandstones of the Jurassic Knoxville 
Formation, and from several sands of Miocene and Pliocene ages. 
Also, a few barrels of oil are produced from a sand that may be of 
Oligocene age. In contrast to the production from sands and con- 
glomerates in other regions in California, Regan and Hughes (1949) 
estimated that 77 percent of the production from the basin prior to 
1947 had come from fractured rocks, nearly all of Miocene age, and 
that only 23 percent had come from sands. The percentage from sands 
has probably increased since that time. 

Most of the 16 fields -(fig. 55) in the basin are structural accumula- 
tions on anticlines, but some are stratigraphic accumulations, for in- 
stance, the Santa Maria Valley field. This field, w^iich was discovered 
in 1934, was the first major stratigraphic trap accumulation discovered 
in California after the search for that type of trap began in the State. 
Oil accumulated in the Monterey Shale, which overlaps the basement 
rocks and is truncated updip by younger rocks. The latter, in turn, 
rest on the basement farther north. "Closure"' of 3,000 feet at the 
top of the Miocene sequence distinguishes this field from any other 
in California. 

Striking features of the production in this basin are: (a) the gen- 
erally low API gravity of the oil; (b) the location of several fields on 
high hills overlooking the Santa Maria Valley; (c) the loss of drilling 
fluid while penetrating the fractured reservoir rocks often being an 
indication of high permeability and, usually, of large initial produc- 
tion; and (d) the first large California gusher in the Orcutt field 
in 1904 flowed 12,000 barrels per day for several months, and pro- 
duced some 3 million barrels of oil during its flow^ing life. 

Salinas -Cuyama sedimentary basin 

The Salinas-Cuyama sedimentary basin (figs. 47, 48) is an elon- 
gated northwestward-trending basin between the much-publicized San 
Andreas fault zone on the northeast and the Nacimiento fault zone on 
the southwest. This basin is approximately 160 miles long and as 
much as 28 miles wide, and includes the Cuyama and Salinas Valleys 
and some of the intervening mountainous areas. The area of the basin 
is about 3,100 square miles, and it contains approximately 3,500 cubic 
miles of Miocene and younger rocks (Schwade and others, 1958) . The 
Tertiary rocks, or older sedimentary rocks which underlie those rocks 
in places, rest on a granitic basement in a large region called Salinia 
(by Reed (1933). The maximum thickness of sedimentary rocks in 
the basin probably exceeds 15,000 feet, but the depth to the granitic 
basement is much shallower in large parts of the basin. The 14 fields 
in the basin have produced approximately 380 million barrels of oil 
to January 1, 1965, or about 110,000 barrels per cubic mile of sedimen- 
tary rocks of Miocene or younger age. 

The three large fields (fig. 55) — San Ardo, South Cuyama, and 
Russell Ranch — in the basin greatly overshadow the several minor 


fields. The first field is on a broad, fiat anticline overlying a basement 
high; the latter two fields are accumulations on faulted anticlines. 
Nearly all of the oil is in sand reservoirs. 

Striking features are: (a) the many dry holes that were drilled 
prior to the discoveries in the late 1940's; (b) the more than 350 
exploratory tests drilled since the three major discoveries, finding only 
a few relatively small fields; (c) the many closed structures that are 
barren probably because they were formed in late geologic time after 
migration of the oil; (d) the very large accumulation of low API 
gravity oil in the San Ardo field — the only major field in the Salinas 
Valley part of the basin ; and (e) the tilted water table underlying the 
oil in the San Ardo field. . 

Santa Cruz and Eel River sedimentary hasins 

The Santa Cruz sedimentary basin (figs. 47, 48), which is along the 
coast about 25 miles south of San Francisco, has an onshore area of 
about 260 square miles. Small oil production is obtained at present 
from two fields in tlie basin from rocks of Eocene and Miocene ages 
(fig. 40). An old field which is not now producing yielded a few 
thousand barrels of oil from Pliocene rocks. 

The Eel River sedimentary basin (figs. 47, 48), which borders the 
coast in the northwestern part of California, has an onshore area of 
about 575 square miles. Two dry gas fields which yield gas from 
Pliocene rocks (fig. 49) have been found in the basin. Eleven pro- 
ducing wells in the Tompkins Hill field produced an average of about 
5 million cubic feet of gas daily in 1964. Only a small amount of gas 
has been produced from tlie Table Bluff field. No production has 
been reported from a possible third gas field, Grizzly Bluff. 


Seaward from the coastline of California a submerged region of 
more than 27,000 square miles is known as the continental shelf. The 
continental shelf is usually defined as that part of the ocean lying be- 
tAveen the low-water line and the sharp change in inclination of the 
sea bottom that marks the beginning of the continental slope (the shelf 
edge). Geologically, this abrupt change in inclination, rather than 
the present shoreline, marks the true edge of the continents (Trum- 
bull, 1958) . For convenience, the 100-fathom (600-foot) line is useful 
for an approximation of the shelf edge in most regions. On plate 1 
of this report the 500-foot contour line may be used as an 

North of Point Conception, the continental shelf off California is 
comparatively narrow, generally less than 10 miles and sometimes less 
than 1 mile wide. West of San Francisco, however, it widens to 
about 30 miles. 

South of Point Conception, the region between the mainland and 
the continental slope is broad and extends as much as 160 miles sea- 
ward. It is complex, with islands, flat-topped banks some of which 
are only slightly submerged, and about 14 closed basins (closed depres- 
sions deeper than the surrounding area). Because of this complexity 
this region has been called the continental borderland by Shepard 
and Emery (1941) to distinguish it from typical continental shelves 
in most other areas of the world. Its area is more than 19,000 square 


miles, and it is covered by Avater Avitli an averaoe depth of about 
3,500 feet and a maximum deptli in one locality of nearly 7,000 feet. 

The 1958 Ignited Nations Conference on the Law of the Sea provides 
that the sovereign rights of a nation to the subsoil off its coasts extend 
to where the sea is 656 feet deep and, beyond that limit, as much 
farther as it can exploit the resources of the undersea area. 

Early in 1065, the Supreme Court of the United States decided that 
the boundary of the State of California would be measured by a line 3 
geographic (3.45 statute) miles from the low-tide line of the mainland 
shore, and by lines a like distance around each island. As a conse- 
quence, the State of California or its grantees owns the mineral re- 
sources on slightly more than 5,000 square statute miles within the 
3-mile limit, as measured on 1961-62 maps. This area will likely be 
modified by the Supreme Court's decision which included Monterey 
Bay in the State. The United States owns, or can exploit, the mineral 
resources on the more than 22,000 square statute miles more than 
3 miles from the mainland or the islands. 

Public information concerning the geologic conditions offshore is 
very limited, especially north of Point Conception. Inferences may be 
made from geologic maps of the mainland and the islands. Perhaps 
the most important inference concerning oil and gas is that five of the 
onshore productive sedimentary basins (figs. 47. 48) doubtless extend 
offshore. There are sparse published records on the ages of the rocks 
from which oil production is now obtained offshore, and on the depths 
of some of the exploratory wells. In addition, published reports by 
Emery (1960), and by Bromery, Emery, and Balsley (1960) contain 
considerable geological and geophysical information on the continental 
borderland south of Point Conception, the best known area off the 
California coast. The following brief descriptions is taken from these 

Structurally, the borderland consists of many blocks of rouglily 
equal size. Emery suggests that these blocks are crossed by seven 
long primary faults most of which trend northwestward, and that 
many shorter features which may be faults or folds trend more west- 
ward between the primary faults. The anticlinal structure of some of 
the islands and of the sea bottom in places is known or inferred. The 
anticlinal structures on which several of the productive onshore oil 
fields are located extend beneath the ocean, and production is also 
obtained offshore on these features. Most of the fields off the coast 
from near Santa Barbara to Point (Conception are on a westward 
trend of faulted anticlines. 

The area of the closed basins and other deep flat areas in the border- 
land is about 9,000 square miles. Most of the basins are oriented 
parallel to the structural trend of the Peninsular Ranges on land, 
but the most northerly one which is believed to be the submerged 
extension of the Ventura basin is oriented parallel to the Transverse 
Ranges. These basins are closely related in form and probable origin 
to the land basins. Both are probably controlled by the regional 

The most widely distributed rocks on the sea floor in the border- 
land are of Miocene age, but the ocean bottom in the basins is largely 
covered with Pliocene and younger sedimentary rocks and micon- 


solidated sediments. It can be inferred that Miocene, and possibly 
older sedimentary rocks, are also present at depth in some or all of 
the basins. The present nearshore fields in the borderland produce 
oil from rocks of Pliocene, Miocene, and Oligocene ages. Early 
Tertiary and Cretaceous rocks crop out on some of the islands. 

The thickness of sedimentary rocks in the borderland is believed 
to be about 4,500 feet in one basin, and about 10,000 feet in another. 
Tliicker sedimentary rocks are doubtless present in parts of the bor- 
derland as the deepest offshore Avell, about three-fourths of a mile from 
the coast southeast of Santa Barbara, was drilled to a depth of ap- 
proximately 16,000 feet. 

North of Point Conception, thick sedimentary rocks are obviously 
present at places on the continental shelf but there is very little 
public information about the geology of this region. Outside of the 
3-mile line at least one exploratory well was drilled to a depth of 
approximately 10,400 feet, and several other wells have been drilled 
to depths of 7,000 to 8,000 feet. It can probably be assumed that 
sedimentary rocks were penetrated for most of these depths. The 
presence of thick sedimentary rocks west of the granitic Farallon 
Islands off San Francisco has been inferred by Thompson and Talwani 

Very large amounts of money have been spent by the oil industry 
in exploring for and developing oil and gas off the coast. Baldwm 
(1965) estimated that approximately $310 million was spent from 1949 
to early 1965 off the Pacific Coast for exploration, for acquiring leases, 
and for platforms prior to the drilling of development wells. Prob- 
ably about $270 million of this has been spent off California including 
$172 million for; State leases, $12.8 million for Federal leases, $25 
million for seismic geophysical lines, $35 million for the drilling and 
coring of some 2,650 holes, and $25 million for platforms and islands. 
The industry has also spent very large amounts of money for drilling 
development wells that produce oil from beneath the ocean, and for 
other costs incident to producing operations. 

History of discovery and development offshore 

The old Summerland field in the Ventura basin was the first field in 
California in which oil was produced from beneath the ocean. The 
field was discovered onshore prior to 1894, and in 1896 the first shallow 
wells beneath the water were drilled from wharfs, some of which 
extended a quarter of a mile from shore. A 1902 map shows 187 
productive offshore wells, and others may have been drilled later. 
The wharfs and wells have been destroyed by storms or torn down. 
About one-third million barrels of oil were produced offshore. 

Since 1929, many oil and gas leases for submerged lands within the 
3-mile limit have been issued by the State or its grantees. From 1927- 
1956, eight oil fields (fig. 55) in the Los Angeles and Ventura basins 
were extended beneath the ocean by directional drilling from land. 

The first discovery of a new field beneath the ocean, which at the 
time did not seem to be connected with an onshore field, was made in 
1948 at the Belmont offshore field in the Los Angeles sedimentary 
basin (fig. 55). Further development of the field did not start until 
1954, when a man-made island was constructed 8,300 feet from shore. 


Six additional producing oil fields and four producing dry gas fields 
have been discovered oiTshore in recent years. 

Leases on 516 square miles of Federal submerged land outside of the 
3-mile limit north of Point Conception were issued in 1963. Several 
exploratory wells, some of which were in about 600 feet of water, have 
been drilled on these lands recently, but no discoveries were reported 
to August 1965. No leases have been issued on Federal submerged 
lands south of Point Conception, but exploratory w^ells as deep as 
8,000 feet were drilled on these lands prior to 1965. 

Cumulative production to Januaiy 1, 1965, from about 2,000 off- 
shore wells was 778.1 million barrels of oil, 79 billion cubic feet of dry 
gas, and more than 57 billion cubic feet of wet gas. Statistics for wet 
gas are incomplete. The value of this oil, using the current average 
price of $2.4:7 per barrel, was about $1.75 billion. 

The eight oil fields that are extensions of onshore fields have pro- 
duced 95 percent of the offshore oil, mostly from the submerged parts 
of the Wilmington and Huntington Beach fields (fig. 55) in the Los 
Angeles sedimentary basin. The seven oil fields that have been dis- 
covered offshore are more recent fields. They have produced 38 million 
barrels, or only 5 percent of the total. 

In 1964, the offshore fields produced 40.5 millions barrels (fig. 58) 
at an average daily rate of 110,700 barrels, or slightly more than 
one-eighth of California's production. Offshore oil and gas production 
has increased rapidly in recent years (figs. 58, 59). Three of the off- 
shore fields are small, and each yielded less than 100 barrels per day 
in 1964. The production of dry gas in 1964, all of it in the submerged 
part of the Ventura sedimentary basin, was 35.6 billion cubic feet 
(fig. 59) , or about 100 million cubic feet daily. 

On January 1, 1965, oil and gas were being produced in 14 offshore 
oil fields and 4 offshore diy gas fields. One of the 14 oil fields now 
yields only a small amount of oil, but produces a moderate amount of 
dry gas. A small amount of oil was obtained prior to 1959 from the 
offshore part of one additional field. All these fields are in the sub- 
merged extensions of the Los Angeles and Ventura sedimentary basins. 
All are on submerged lands leased from the State or its grantees. 


The oil and gas resources of California may be divided into proved 
reserves and potential resources. 

Proved reserves 

Proved reserves are defined by the American Petroleum Institute as 
"the amount of oil in knoion petroleum deposits recoverable under ex- 
isting economic and operating conditions,"' or as sometimes stated by 
others, the recoverable reserves whose location and extent have been 
proved and measured by drilling. 

Generally, the published estimates of reser^^es as so defined are 
probably on the conservative side. Among the reasons for this are: 

1. Revisions and additions to reserves are commonly made for new' 
fields as they are developed, and it is seldom that the amount of re- 
coverable oil in a new field can be quantitatively estimated with rea- 



Of f shore Los Ange les 

sedimentary basin 

6 fields in 1 964 

-^••'Offshore Ventura sedimentary basin/ 
■ 8 f ie Ids in l 964 /• 

1935 1940 1945 1950 1955 1960 1964 

FiGUBE 58. California offshore oil production. 



i 9 


«, 8 


S 7 



§ 6 

d 5 
^ 4 

o ^ 

^ 3 


o 1 

8 f ie Ids 
in 1964 

Sources :Conse rva t i on Committee of 
Ca li f orn ia oil producers 

5 fields 
in 1964 

^ ■ 



— z 

H Z 
O < 


</) CD 


tr — 

° :^ 

1928 1930 







1965 <^ 

Figure .59. Offshore oil and dry gas production in Ventura sedimentary basin, 



sonable accuracy early in the life of the field. Several new fields in 
California are now in the early stages of development. 

2. Secondary recovery methods, some of which verge on well-stimu- 
lation methods, are being applied in more than 300 pools in some 
100 fields in the State. Because of the recency of the use of some of 
the thennal methods which are reported to have increased pixjduc- 
tion about 30,000 barrels per day, it is impossible to estimate how 
much additional oil may be recovered. It is quite certain, however, 
that additions of this kind are not included with the statistics on 
proved reserves in most inst-ances. Although it was estimated in 
1962 that about 29 percent of the oil found in the United States to 
that time would be recovered b}^ primary methods, it is believed that 
the primaiy recovery in California Avill on the average be somewhat 
less than 25 percent. In many California fields which produce viscous 
heavy (under 20° API gravity) oil, it is believed that the recovery 
by primary methods may be only about 10 percent. It is quite cer- 
tain that secondary' recoveiy methods will considerably increase the 
recovery from California fields. Statements have been made by repre- 
sentatives of the oil industry that the use of secondary recovery meth- 
ods will increase California reserves by more than 1 billion barrels. 

3. Xew techniques of Avell logging, testing, and completion some- 
times result in increased reserves in existing fields. 

4. The large East Wilmington field, partly onshore but mostly off- 
shore, is estimated to contain at least 1.2 billion barrels of recover- 
able oil. The field is known and has been approximately outlined, 
but development was not begun until the middle of 1965. Published 
reserves include 500 million barrels for this field. 

The proved reserves of crude oil in the United States as of Jan- 
uary 1, 1965, have been variously estimated at 35.1 billion barrels 
b}^ the Oil and Gas Journal and at 31 billion barrels by the Amer- 
ican Petroleum Institute. The proved resen-es of crude oil in Cali- 
fornia are estimated at -1.1 billion barrels (fig. 60, table 35), about 
1-t times the 1964 production, or 13.3 percent of the United States 
reserves according to the American Petroleum Institute. 

The estimated proved resen'es of crude oil in California declined 
from a high of 3.9 billion barels on January 1, 1954, to 3.6 billion 
barrels on January' 1, 1964. This declining trend was reversed in 
1964 when reserves increased 526 million barrels to 4.1 billion bar- 
rels, the largest ever estimated, due largely to the assignment of 500 
million barrels to the East Wilmington field. 

Several features of these reserves of crude oil are of imiwrtance. 

1. Although the proved reserves of California are 14 times the 
annual production, a much longer period than 14 years will be required 
to bring the oil to the surface. Several fields more than 50 years old 
are still producing large amounts of oil. 

2. Xearly all the proved reserves are in five sedimentary' basins in 
the southwestern part of the State, mainly in the San Joaquin basin 
(2.2 billion barrels) and the Los Angeles basin (1.25 billion barrels). 

3. More than 80 percent of the proved reserves in California are in 
the "giant" fields — those which are expected to yield more than 100 
million barrels of oil. There are 40 of these fields in California, at 
present, the last one having been discovered in 1949. However, recent 







••• Natura I gas ..•* 

Crude oil 

Sources: Gas, Calif. Div. Oil and 
Gas; Crude oil, Calif. Div. Mines 
and Geology Bui 1 . 118. 1 926-40 
American Petroleum Institute 1941-63 

I I I I I I I I I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I I I I 


5 « 

4 ^ 

3 - 




^ 1926 1930 1935 1940 1945 1950 1955 1960 1965 


Figure 60. Estimated proved reserves of crude oil and natural gas in California, 

on January 1 of each year. 

discoveries near Los Angeles and McKittrick may approach the 
"giant" class, if initially isolated discoveries prove to be single fields. 

4. The two fields with the largest proved reserves are Elk Hills in 
the San Joaquin basin fiT)m which only a small amoimt of oil is pro- 
duced at present because it is in Naval Petroleum Reserve No. 1, and 
the Wilmington field in the Los Angeles basin. To these might be 
added the largest known, but undeveloped, reserve of at least 1.2 bil- 
lion barrels in the East Wilmington field. 

Tlie proved reserves of natural-gas liquids in California on January 
1, 1965, were estimated at 270.8 million barrels (table 35). 

Tlie estimated proved reserves of natural gas in the United States on 
January 1, 1965, were 290 trillion cubic feet according to the Oil and 
Gas Journal. The reserves in California (fig. 60) on that date were 
10.2 trillion cubic feet according to estimates by the California Divi- 
sion of Oil and Gas, or about 15 times the annual net withdrawals (pro- 
duction less amount reinjected). The reserves in the State have in- 
creased about 1.5 trillion cubic feet since the middle 1950's. 

Approximately 60 percent of the gas reserves in California are wet, 
or oil-well gas. The largest reserves of wet gas are in the San Joaquin 
sedimentary basin, followed by the Los Angeles and Ventura basins. 
By far the largest resen^es of dry gas are in the Sacramento basin, 
followed by the Ventura and San Joaquin basins. 

Potential resources 

Onshore. — Conjectures concerning the potential resources onshore 
in California suggest that they are large. It is generally believed that 
the most favorable localities for new discoveries are in areas of proved 
oil generation within the principal productive sedimentary basins 
( figs. 47, 48 ) . Also favorable are some smaller sedimentary basins and 
other areas underlain by sedimentary rocks; minor amounts of oil and 
gas have been produced in several localities outside of the principal 
basins, especially in the California Coast Ranges. 

The complex geologic structure and statigraphy in California forms 
innumerable traps in which oil and gas may have accumulated. Prac- 
tically all the obvious traps in the principal basins were tested by the 


drill long ago, but very many obscure traps have been found in the 
past and certainly many more exist. Obscure traps are very difficult 
to find, but the discoveries in recent years show that they can be found 
in the already highly explored areas of California by creative think- 
ing in exploration. With some exceptions, for example in the Salinas- 
Cuyama sedimentary basin, it may be said that any trap in the princi- 
pal productive basins has a good chance of yielding oil or gas. 

Parts of the principal productive basins are relatively untested. 
Many additional concealed stratigraphic traps may be present, espe- 
cially on the flanks of known anticlinal structures and on the deeply 
buried flanks of the deepest parts of the basins. Not all of the known 
structural traps have been completely tested by drilling through all 
possible reservior rocks at adequately spaced locations. The area 
of the principal productive sedimentary basins is about 20 million 
acres, of which about 475,000 acres have yielded oil or gas. Approxi- 
mately 5.5 million acres of unproductive land in the State are under 
lease for oil and gas; a large part of this leased land is within the 
principal productive basins. 

The 13.25 billion barrels of oil already produced in California plus 
the 4.1 billion barrels of proved reserves of recoverable oil totals 17.4 
billion barrels. If it is assumed that this is 25 percent of the oil 
originally in place, about 52 billion barrels of oil will not be recovered 
by the primary methods of production. Some of this remaining oil 
is being recovered now by the use of secondary recovery methods. 

The Interstate Oil Compact Commission and several individuals 
(Supplies, costs, and uses of the fossil fuels. Energy Policy Staff, 
U.S. Department of the Interior, 1962) have made some estimates of 
the petroleum resources of California in addition to the proved re- 
serves of 4.5 billion barrels. These estimates include (a) 1 billion 
barrels of oil that can be expected to be recovered by established sec- 
ondary recovery operations, (b) 4.1 billion barrels that may be re- 
covered as a result of changed economic conditions or improved tech- 
nology, and (c) 1.3 billion barrels that could be recovered from known 
reserves of presently nonfluid oil in bituminous rocks or shale at a 
cost that is not now competitive with oil from wells. 

In eastern California, the Salton Trough, the Mojave Desert, the 
Great Basin, and the Modoc Plateau provinces (fig. 47) do not yield 
oil at present, and except in the Salton Trough, few wells have been 
drilled. Only one surface evidence of oil seems to be a verified seep, 
but petroliferous rocks are known in Nevada to the east, and oil seeps 
have been reported south of the border in Mexico. The southeastern 
part of the Great Basin province in California contains thick Paleo- 
zoic and Mesozoic marine sedimentary rocks which may be worth 
testing for oil and gas. 

Onlv a few very small showinas of o-as have been found in some 20 
exploratory wells in the major sedimentary basm m the Imperial 
Valley region of the Salton Trough province. Marine sedimentary 
rocks that crop out in the hills west of the valley have not been found 
to depths of more than 12,000 feet in the central part of the valley, 
but may be present at even greater depths. 

Offsiiore. — The potential resources of oil and gas off the coast of 
California, not only within the boundaries of the State but also on 
Federal lands outside the 3-mile line, are believed to be large. More 


than 6 years ago, it was estimated that fields on the mainland within 
8 miles of the coast would ultimately jdeld about 3.9 billion barrels 
of oil. Also, it was suggested that, if the offshore geologic province 
is similar to the onshore province, a like amount might ultimately be 
obtained from the offshore area inside the .3-mile line within the 
boundaries of California. It was pointed out that 50 percent of the 
prolific Los Angeles and Ventura sedimentary basins are believed to 
lie offshore, and that the Santa Maria basin extends offshore. The 
Santa Cruz and Eel River basins also probably extend offshore (figs. 

The amount of oil estimated to be recovered from the onshore fields 
can probably be increased tDjii)proximately 4.2 billion barrels largely 
because of the increased estimates for the "Wilmington field. Nearly 
0.8 billion barrels of oil has been produced offshore to 1965, so accord- 
ing to these estimates some 3.4 billion barrels may be produced off- 
shore from within the 3-mile line in the future. Probably 1.5 billion 
barrels of that amount can be expected from presently known fields, 
including East Wilmington. The remaining 1.9 billion barrels may 
represent an allowable amount for the potential offshore resources of 
other areas inside the 3-mile line within the State's boundaries on 
the basis of the foregoing estimates. 

Selected References 

Bailey, T. L., and Jahns. R. H.. 1954, Geology of the Transverse Range province, 
southern California [Pt.] 6 in Chap. 2 of Jahns, R. H., ed.. Geology of southern 
California : California Div. Mines Bull. 170, p. 83-106. 

Baldwin, T. A., 196.J, Pacific offshore exploration 1949--196.5: Am. Assoc. Petro- 
leum Geologists, Soc. Econ. Geologists, and Soc. Econ. Paleontologists and 
Mineralogists, Pacific Sec, 40th .Joint Ann. Metg., Bakersfield, California, 
April 1-2, 196.J. 

Barbat, W. F., 1958, The Los Angeles Basin area, California, in Habitat of oil, a 
symix)Sium : Tulsa, Okla., Am. Assoc. Petroleum Geologists, p. 62-77. 

Bauer, R. M.. and Dodge, J. F.. 1943, Natural gas fields of California : California 
Div. Mines Bull. 118. pt. 1, p. 33-36. 

Bowen, O. E., .Jr., ed., and others, 1962, Geologic guide to the gas and oil fields of 
northern California : California Div. Mines and Geology Bull. 181, 412 p. 

Bromery, R. W., Emery, K. O.. and Balsley, J. R., Jr., 1960, Reconnaissance air- 
borne magnetometer survey off southern California : U.S. Geol. Survey Geophys. 
Inv. Map GP-211. 

Edwards, E. C, 1951, Los Angeles region : Am. Assoc. Petroleum Geologists Bull., 
v. 35, no. 2, p. 241-248. 

Emery, K. O., 1960, The sea off southern California — a modern habitat of 
I>etroleum : New York, John Wiley and Sons, 306 p. 

Hart, E. W.. 1957, Natural gas, in Mineral commodities of California : California 
Div. Mines Bull. 176, p. 373-384. 

Hedberg, H. D., 1964, Geologic aspects of the origin of petroleum : Am. Assoc. 
Petroleum Geologists Bull., v. 48, no. 11, p. 1,75.5-1,803. 

Heizer, R. F., 1943, Aboriginal use of bitumen by the California Indians : Cali- 
fornia Div. Mines Bull. 118, pt. 1, chap. 3, p. 74. 

Hobson, H. D., 1951, Sacramento Valley : Am. Assoc. Petroleum Geologists Bull., 
V. 35, no. 2, p. 209-214. 

Hobson, H. D., and Lupton, B. C, 1951. Santa Maria province: Am. Assoc. Pe- 
troleum Geologists Bull., v. 35. no. 2, p. 224-230. 

Hoots, H. W., 1943, Origin, migration, and accumulation of oil in California : 
California Div. Mines Bull. 118, pt. 2. chap. 7, p. 2.52-276. 

Hoots, H. W., and Bear, T. L., 1954, History of oil exploration and discovery in 
California, [Pt.] 1. in chap. 9 of Jahns, R. H., ed.. Geology of southern Cali- 
fornia : California Div. Mines Bull. 170, p. 5-9. 

Hoots, H. W., Bear, T. L,.. and Kleinpell, W. D., 19.54, Geological summary of the 
San Joaquin Valley, California, [Pt.] 8, in chap. 2, of Jahns, R. H., ed.. Geology 
of southern California : California Div. Mines Bull. 170, p. 113-129. 


Jahns, R. H., 1954, Geology of the Peninsular Range province, southern California 

and Baja California [Mexico], [Pt.] 3, in Chap. 2 of Jahns, R. H., ed. Geology 

of southern California : California Div. Mines Bull. 170, p. 29-52. 
Jennings, C. W., 1957, Petroleum, in Mineral commodities of California : Cali- 
fornia Uiv. Mines Bull. 176, p. 409-424. 
Kilkenny, J. E., 1951, San Joaquin Valley : Am. Assoc. Petroleum Geologists Bull. 

35, no. 2, p. 215-218. 
Levorsen, A. I., 1954, Geology of i>etroleum : San Francisco, W. H. Freeman and 

Co., 703 p. 
McCuUoh, T. H., 1957, Simple Bouguer gravity and generalized geologic map 

of the northwestern part of the Los Angeles Basin, California : U.S. Geol. 

Survey Geophys. Inv. Map GP-149. 
, 1960, Gravity variations and the geology of the Los Angeles Basin of 

California : U.S. Geol. Survey Prof. Paper 400-B, p. 320-328. 
Rand, W. W., 1951, Ventura Basin : Am. Assoc. Petroleum Geologists Bull., v. 

35, no. 2, p. 231-240. 
Reed, R. D., 1933, Geology of California : Tulsa, Okla., Am Assoc. Petroleum 

Geologists, 355 p. 
Regan, L. J., and Hughes, A. W., 1949, Fractured reservoirs of Santa Maria 

district, California : Am. Assoc. Petroleum Geologists Bull., v. 33, no. 1, p. 

Repenning, C. A., 1960, Geological summary of the Central Valley of California, 

with reference to the disposal of liquid waste : U.S. Geol. Survey open-file 

Schwade, I. T., 1958, Geologic environment of Cuyama Valley oil fields, California, 

in Habitat of oil, a symposium : Tulsa. Okla., Am. Assoc. Petroleum Geologists, 

p. 78-98. 
Shepard, F. P., and Emery, K. O., 1941, Submarine topography off the California 

coast — canyons and tectonic interpretation : Geol. Soc. America Spec. Paper 

31, 171 p. 
Simonson, R. R., 1958, Oil in the San Joaquin Valley, California, in Habitat of 

oil — a symposium : Tulsa, Okla.. Am. Assoc. Petroleum Geologists, p. 99-112. 
Thompson, G. A., and Talwani, Manik. 1964, Geology of the crust and mantle, 

western United States : Science, v. 146, no. 3,651, p. 1,539^1,549. 
Trumbull, James, 1958, Continents and ocean basins and their relation to conti- 
nental shelves and continental slopes, [Pt.] 1, of An introduction to the geology 

and mineral resources of the continental shelves of the Americas : U.S. Geol. 

Survey Bull. 1,067, p. 1-26. 
U.S. Dept. Interior, Energy policy staff, 1963, Supplies, costs, and uses of the 

fossil fuels : U.S. Dept. Interior. 34 p., tables. 
Vernon, J. W., and Slater, R. A., 196:3. Submarine tar mounds, Santa Barbara 

County. California : Am. Assoc. Petroleum Geologists Bull., v. 47. no. 8. p. 

Vlissides, S. D., and Quirin, B. A.. 1964. Oil and gas fields of the United States : 

U.S. Geol. Sun-ey, map. 
Weeks. L. G.. 1958, Habitat of oil and some factors that control it, in Habitat of 

oil, a symposium : Tulsa. Okla., Am. Assoc. Petroleum Geologists, p. 1-61. 
Woodford, A. O., Schoellhamer. J. E.. Vedder. J. G.. and Yerkes, R. F.. [Pt.] 5. in 

chap. 2 of Jahns, R. H.. ed.. Geology of southern California : California Div. 

Mines Bull. 170, p. 65-81. 
Woodring, W. P.. and Bramlette, ^NI. N., 1950. Geology and paleontology of the 

Santa Maria district. California : U.S. Geol. Survey Prof. Paper 222. 185, p., 

Yerkes, R. F., McCulloh, T. H., Schoellhamer, J. E., and Vedder, J. G., 1965 

Geology of the Los Angeles basin : U.S. Geol. Survey Prof. Paper 420-A, 57 p. 


(By H. D. Gower. U.S. Geological Survey, Menlo Park. Calif.) 

Phosphate rock is the principal industrial source of phosphorous, an 
element essential in sustaining all life. Plants extract phosphorous 
from the soil, and animals in turn obtain phosphorous by consuming 
plants. Extensively farmed soil soon becomes depleted and unproduc- 


five iinloss addit ional phosplioroiis is added. Man has used pliosphatic 
material for fertilizer for iikhv than '2,000 years, hut it was not until 
the middle of the 19th century that he learned to produce fertilizers 
from phosphate rock, l^efore then bones, fish, and guano Avere the 
main sources of phosj)liate fertilizer. Today most phosphate ferti- 
lizers are nuule from phosphate rock. About 70 percent of the world's 
production of phosphate rock is used for the production of fertilizer. 
Phos[)horous has many other uses in industry. A few of the more 
important uses are in tlie nuuiufacture of deterg-ents and soaps, animal 
feed supi^lements, baking powders, metallurgical alloys, water soften- 
ing agents, petroleum refining agents and additives, drugs, and mili- 
tary devices (including incendiaiy bombs and smoke screens). 

In 196;> the world production of phosphate rock was slightly over 50 
million tons (Lewis, 1904). The I'nited States accounted for 39 per- 
cent of the world's total production. Florida produced 74 percent of 
the United States total, followed by the Western States (Idaho, Mon- 
tana, Utah, and "Wyoming) with 14 percent, and Tennessee and Arkan- 
sas with 1'2 perceiu. Sixty percent of United States production in 
1963 was used in agriculture, 19 percent in the chemical industry, and 
21 percent was exported (most of this was also used in agriculture) 
(I^wis, 1964). No phosphate rock has been produced in California. 

Phosphate is i)i'ecipitated under certain marine environments and 
nearly all of the woi-ld's important deposits of phosphate rock occur 
in rocks of marine origin. Several times during the Miocene Epoch 
conditions were such that phosphate was i)recij)itated over much of the 
southwestern part of Ualifornia. Although phosphate rock was 
deposited over a wide area oidy in certain places were conditions 
suitable for the accumulation of concentrations of phosphate of 
sufficient amounts to l)e of j^otential economic value. After the plios- 
phatic strata were formed they were buried and compacted imder thick 
accumulations of younger sediments and later deformed by folding 
and faulting. Subseciuent erosion removed the pliosphatic strata from 
many areas, and only i)art of the original pliosphatic strata remains. 

The principal phosphate mineral of marine phosphate rocks is a 
variety of apatite called carbonate-fluorapatite. In California it 
occurs as light-gray to dark-brown pellets (0.1 to 2.0 mm in diameter), 
nodules (more than 2 mm in diameter), and laminae of very finely 
divided i)hosphate. Most California phosphate rock is thin bedded 
and closely associated with siliceous shale and bentonite. 

Phosphate content is usually expressed as percent phosphorous 
pentoxide (PoO,-,) or less commonly as percent BPL (bone phosphate 
of lime) which is tricalcium phosphate, Ca.j(P04)2. One percent 
P-Or, equals 2.18 percent BPL. In the western phosphate field high- 
grade rock must contain a minimum of 31 percent P2O5, and low-grade 
rock must contain at least 16 percent PsO.-, (Service and Popoff, 1964). 
Very little is yet known about the California phosphate deposits, but 
all of the known deposits appear to be below the minimum standards 
for low-grade rock in the western phosphate field. However, close 
proximity to markets and possible ease of beneficiation may allow 
production from lower grade deposits in California. The only de- 
tailed chemical analyses of pliosphatic sections in California that are 
currently available are for one measured section in the central part of 

67-164 0—66 — pt. I 22 


the Indian Creek deposit of San Luis Obispo County. At that local- 
ity, about 50 feet of strata average nearly 4% percent P2O5 and the 
main 21-foot-thick j^hosphatic section averages about 6i/^ percent 
P2O5. The thickness and concentration of phosphate varies from 
place to place and in other parts of the area the phosphate may be 
greater or less than at the section analyzed. 

Occurrences in California 

The occurrence of phosphate in sedimentary rocks in California 
has been known for several decades, but it was not until about 1960 that 
its potential economic value was actively explored. By mid- 1965 four 
deposits of potential economic value had been examined in consider- 
able detail by commercial interests; these, as shown on figure 61, are the 
Chico-Martinez Creek deposit of Kern County, the Indian Creek de- 
posit of San Luis Obispo County, the Cuyama Valley Deposit of 
Santa Barbara County, and the Pine Mountain deposit of Ventura 
County. None of these deposits have yet been proven to be of com- 
mercial grade, but exploration work is continuing on the latter three 
deposits. There has also been some interest in the occurrence of 
low-fluorine nonmarine phosphate near Hyampom in Trinity County. 

Phosphate has been reported over a wide area of California (Gow^er 
and Madsen, 1964) , but most of the occurrences are concentrated in the 
southern Coast Ranges, western Transverse Ranges, and southwestern 
Great Valley (fig. 61). Nearly all of these occurrences are in rocks 
of Miocene age. Most occurrences shown on figure 61 are small and 
of no economic importance. However, they are important in pointing 
out areas for future prospecting, for the thickness and grade of phos- 
phatic sections can vary greatly over a short distance. A slightly 
phosphatic horizon in one area may grade laterally into a significant 
phosphate deposit only 2 or 3 miles away. 

Hyamj)oin 'prosfect 

Low-fluorine nonmarine phosphate rock interbedded with siliceous 
and tuffaceous shales of the Oligocene (?) Weaverville Formation 
(Lydon, 1964) has been prospected by L. D. Cartwright near Hyam- 
pom in Trinity County. Because of the low fluorine content, this 
material could be readily used in animal feed supplements and in 
lime and ammonium fertilizer. Veiy little exploration work hasl)een 
done on this occurrence, but it is questionable that it contains enough 
phosphatic rock to be of economic significance. 

Indian Creek frospect 

Phosphate rocks in the upper part of the Monterey Formation in 
the Indian Creek area, about 10 miles east of Creston in San Luis 
Obispo County, have been extensively prospected by Nicol Industrial 
Mineral Corp. The prospect is still under study. The pliosphate 
rocks occurs in thin pellet beds interbedded with siliceous shale and 
bentonite. Phosphate occurs throughout about 70 feet of section, but 
the main phosphatic zone is about 21 feet thick. 

Ghico-Martmez Creek frospect 

Pelletal phosphate rock in the lower part of the Temblor Forma- 
tion in the vicinity Chico-Martinez Creek in Kern County was pros- 







123' 122' 12r 120- 

^ s I s K ij V o\t;/^ Y) 
Kh.AMApTl iC' ^ 


V s s eV- 

CASCAbE N. <y^ 

lo-Ji^.J, rA^^"''"* >iypu'MA< X',1 

SC> '^ ■ \ — ^ I •, w 

\y"'i> V I~^ V^- ^ ^ 

' ^ «?_^ J~. <f'^''JL(| ""'T'^' ><' SIF.RRA 

-C'fe( J- \ .=A, \,{<^>i'^yNE^v;uAy••. 

VsonomaC sjL". ^'(I'iiA"-^ .yjAi.piNt/., 



phosphate prospect 

1 . Hyampom 

2 . Ind ian Creek 

3 . Ch ico-Mar t inez Creek 

4. Cuyama Va I ley 

5. pine Mountain 

phosphate occurrence 




V 118' 

.mon6\ -1—38° 

SANTA if^ r'y 

(lakaV V ^j 

'•+ \ 

^ ^\ ■^KRESN(JO^ , >\ INYOXb \ 



I ^'^X*"^^ O 

■■■' - BARBARA V4H 




M O J A V E -|- --^i- 


\^LnS ANCELESi \, 

^^li&^TT-^ ~^ DESERT > 

o.!^.- ^•^TVvr^^^-v 


+ \ + 





Figure 61. Phosphate in California. 

pected by Nicol Industrial Mineral Corp. The phosphate-bearing 
strata were exposed and studied in five trenches. Phosphate is con- 
centrated in three major zones ranging from about 30 to 65 feet m 
thickness. The deposit was not considered economic under current 
conditions and was abandoned. 

Cuyama Y alley frosfect 

Pelletal phosphate rock in the upper part of the Santa Margarita 
Formation on the south side of the Cuyama Valley near NeAv Cuyama 
is currently being examined by Nicol Industrial Corp. under a Feder- 
al phosphate prospecting permit. The phosphate zone has been ex- 
posed in 8 trenches. Where best developed the main phosphate zone is 
about 100 feet thick. 


Pine Mountain prospect 

Pelletal pliospluite rock in the upper part of the Santa Margarita 
F'orniation south of Fine Mountain in Ventura County is currently 
being studied by United States Gypsum Co. under a Federal phos- 
phate prospecting permit. The phosphate section has been exposed in 
o trenches. Where best developed the main phosphate zone is about 
100 feet thick. 

The pelletal phosphate rock of middle and late Miocene age appears 
to otl'er the most promise for economic deposits of phosphate rock in 
California. Pelletal phosphate strata in the Santa Margarita Forma- 
tion of late Miocene and early Pliocene ( ?) age extending in a south- 
east-trending belt through eastern San Luis Obispo, eastern Santa 
Barbara, and Ventura Counties looks particularly promising. The 
Monterey Formation of middle and late Miocene age in Monterey and 
San Luis Obispo Counties also holds promise of containing commer- 
cial deposits of pelletal phosphate. The pelletal phosphate horizons in 
the lower part (lower Miocene) of the Temblor Formation along the 
southeast border of the Coast Eanges and southwest border of the 
Great Valley also deserves further attention. The nodular and lami- 
nar finely divided phosphatic shales of Miocene age in Santa Barbara, 
Ventura, and western Los Angeles Counties are in places more than 
200 feet thick and, although of low grade, contain a great amount of 
phosphate. If an effective means of beneficiating these shales could 
be developed, they could offer significant phosphate resources, 

SELECTBa) Refeeences 

Gower, H. D., and Madsen, B. M., 1964, The occurrence of phosphate rock in 
California : U.S. Geol. Survey Prof. Paper 501-D, p. D79-D85. 

Lewis, R. AV., 1964, Phosphate rock : U.S. Bur. Mines Minerals Yearbook 1963, v. 
1, p. 877-898. 

Lydon, P. A., 1964, Unusual phosphatic rock: California Div. Mines and Geol- 
ogy Mineral Inf. Service, v. 17, no. 5, p. 65-74. 

Service, A. L., and Popoff, C. C. 1964, An evaluation of the western phosphate 
industry and its resources: U.S. Bur. Mines Rept. Inv. 6,485, 86 p. 


(By W. B. Clark, California Division of Mines and Geology, Sacramento, Calif.) 

The platinum group of metals includes platinum, palladium, irid- 
ium, osmium, rhodium, and iiithenium. Platinum is the most abun- 
dant and most important member of this group. All of these metals 
are essential in modern industry and are among the strategic and 
critical materials held in the national stockpile. L^nited States pro- 
duction of platinum metals is small; most is imported from foreign 

Although platinum is the most important member of the group, 
each of the metals has important industrial uses, and each metal ex- 
cept palladium commands a price much higher than gold. In May 
1965, the average prices per troy ounce were as follows: iridium, $92; 
osmium, $250; palladium, $33; platinum, $98; rhodium, $183; and 
ruthenium, $58. The uses of platinum and its alloys are based on: 
their resistance to corrosion, heat, and oxidation; electrical conductiv- 
ity; and superior catalytic properties. The major uses are: (1) cata- 
lysts in the production of high-octane gasoline and various chemicals 



such as sulfuric acid; and (2) alloys for jewelry, dentistry, and elec- 
trical apparatus. Platinum is used in laboratory apparatus and ware, 
in equipment used in the manufacture of glass and synthetic fibres, and 
in certain delicate sensing instruments. Palladium has uses similar 
to platinum, as well as in electrical contacts and in nonmagnetic 
watches. Tlie other platinum metals are used principally to improve 
the hardness and other properties of platinum and palladium. Os- 
mium and ruthenium are used in hard alloys for phonograph needles, 
fountain pen tips, and fine machine bearings. 

In California the platinum-group metals have been found only in 
stream placers, chiefly in the Sierra Nevada and Klamath Mountains 
(fig. 62). Thus far, no primary platinum-bearing deposits have been 



— U4: 


1 . Butte Creek 

2 . Callahan 

3 . Coma nc he 

4 . C ot t onwood 

5. Crescent City 

6. F I s om 
7 . Hammont on 

8 . Hayfork 

9. Jenny L i nd 
4- 41 " I 0. J unc t i on City 
' 1 1 . La Gran ge 

Lew I s t on 

Michigan Ba r 

Mt ne r s V I I le 


Or ov I I I e 

Plat I na 

Sa I mon River 

Se iad 

Smith River 

S ne I I I n g 

Trinity Center 


SAUTON \ ^i3' 


Figure 62. Locations where platinum has been recovered in California. 


found ill the State. Platinum alloyed with the other metals of the 
group occurs as small flakes, rounded grains, and irregular lumps in 
the placer deposits associated with gold and other heavy minerals at 
or near bedrock. The amount of platinum present in placer deposits 
in California is small; the average often is one ounce or less per 
100,000 cubic yards of gravel. 

Platinum and allied metals have been recoA'ered in California as a 
by-produot of placer gold mining since the days of the gold rush. 
The output of the State since 1850 is estimated to be about 28,000 
ounces. The most productive periods were from around 1910 to the 
early 1920's, when the annual output averaged more than 500 ounc^, 
and from the middle 1930's to the early 1940's, when production ranged 
from TOO to more than 1,000 ounces annually. An all-time high of 
1,358 ounces was produced in 1940. Some platinum is produced by 
the three gold dredges in the Hammonton district in Yuba County. 

World production of the platinum-group metals in 1963 amounted 
to about 1,530,000 ounces. Russia was the source of approximately 
800,000 ounces; Canada, 340,000 ounces; and South Africa, about 300,- 
000 ounces. Other sources included the United States with a produc- 
tion of 49,000 ounces and Columbia, which yielded 28,000 ounces. 

During the early days of mining in the State, most of the platinum 
was recovered from hydraulic mines. Later nearly all of it was re- 
covered by gold dredges. In the Klamath Mountains, the dredge 
fields were in the Klamath-Trinity RiA^er system or in tributaries of 
the upper Sacramento River. The hydraulic mines are on terrace 
gravel deposits adjacent to these rivers. In the Sierra Nevada, the 
hydraulic mines are located chiefly on Tertiary channel gravel deposits 
(see also section on Gold). Very small amounts of platinum have 
been recovered from beach placers in Del Norte and Humboldt 

Because all of the platinum metals in California are produced as a 
by-product of placer gold mining, the output of these metals will con- 
tinue to decrease as gold dredgmg declines. 


(By G. I. Smith, U.S. Geological Survey, Menlo Park. Calif.) 

Potash is a term that means potassium oxide, but it is used widely 
to denote several other potassium salts as well. It is an essential 
ingredient of fertilizers, and about 94 percent of the potash delivered 
to points within the United States is destined for agricultural use. 
The bulk of this went to States east of the Mississippi River ; less than 
1 percent of this amount went to California. The 6 percent of na- 
tional production destined for chemical or industrial uses was also 
mostly delivered to eastern states; about 5 percent of that fraction 
went to California. In 1963, production of all potassium salts in the 
United States Avas about 4,867,000 short tons which were equivalent 
to about 2,865,000 short tons of potassium oxide. Their value was esti- 
mated to be Jibout $109,000,000, or an average of about $22.40 a ton 
for all potassium salts, equivalent to $38.00 a ton of potassium oxide 
(Lewis, 1964). 

Potash production in the United States was started in the early 
1600's. A marketable product was made from wood ashes (thus the 


name, pot-ash), and by 1635, appreciable quantities were being ex- 
])orted. Around 1860, potash was found essential to plant growth, 
and, in 1862, the Stassfurt deposits m Gennany began significant pro- 
duction. Those deposits dominated the world supply until shortly 
after 1900 when minable deposits were found in Alsace (then in Ger- 
many, later in France) and in Spain. 

Just prior to World War I, the United States started intensive 
exploration for domestic sources of potash to replace the threatened 
p]uropean suplies. One of the areas studied intensively was Searles 
Lake, California, which in 1916 became a major domestic source. At 
the close of World War I, at least 127 other plants were also producing 
potash in the United States, but only, the one at Searles Lake survived 
the postwar decrease in price. -In 1925, potash was discovered in the 
Carlsbad district of New Mexico, and in 1931 production started. The 
large deposits in Saskatchewan, Canada, were discovered in 1943, and 
production started in 1958 (Ruhlman, 1960a, 1960b). 

At present, production from the LTnited States supplies about 24 
percent of the world total. Other major producing areas of today 
lie in West Germany, East Germany, France, Spain, U.S.S.R., and 
Israel-Jordan. These supply most of the markets of Europe, Africa, 
and west Asia. East Asia, Australia, and New Zealand, though, 
import large quantities of potash salts from the United States. In 
1963, U.S. exports of potash materials to all countries was 722,000 
tons, almost half of which went to Japan. During the same period, 
the United States imported 1,041,000 tons of potash materials, over 
half of which came from Canada (Lewns, 1964). 

About 92 percent of United States production comes from the late 
Paleozoic marine deposits in New Mexico. Other production comes 
from midergi'ound late Paleozoic marine deposits and late Quarter- 
naiy brine deposits in Utah, and from a late Quaternary brine deposit 
in California. Some by-product potash material is marketed from 
Michigan and Maryland (Lewis, 1964). A possible new source of 
potash consists of recently discovered deposits in eastern Arizona 
(Chem. Eng. News, 1963; Pierce and Gerrard, 1965). 

The only producing deposit in California is Searles Lake. This de- 
posit, described in more detail in the chapter on Sodium carbonate, lies 
in a closed depression in the southwestern part of the Great Basin of 
California. It consists of several saline layers that are permeated with 
brines containing the equivalent of between 3 and 5 percent potassium 
chloride (table 44, section on Sodium carbonate). Potassium com- 
pounds, along with six other products, are extracted from these brines 
by means of a complex process at the plant of the American Potash & 
Chemical Corp. In 1951, that plant's annual capacity was reported to 
be equivalent to 150,000 tons of potassium oxide, and in 1958, it was re- 
ported to be 170,000 tons (Ryan, 1951 ; Ruhlman, 1960b) ; these capac- 
ities are equal to about 6 percent of national production. 

Speculation has existed about the possibility of extracting potash 
from the geothermal brines in the Salton Sea area of California. In 
1963, five companies were actively exploring the area, primarily as a 
source of geothermal power. However, the hot brine contains up to 
25,000 ppm potassium (analysis 5, table 10, section on Calcium chlo- 
ride) , and one company has announced plans to experiment with the 
extraction of potasium salts from it (Lewis, 1964; Chem. Eng. News, 


1965). Production from this source, however, must await successful 
development of first the geothennal power and then the mineral re- 
sources, both of which involve solutions to complex engineering 

In the near future, potash production in California will probably re- 
main about the same. Production from the Searles Lake deposit is not 
likely to change greatly, and in terms of its share in the national 
market, might decrease. This is partly because the production of 
potash from this deposit must remain coordinated with the demand for 
its coproducts, and partly because increased potash production in other 
areas will tend to increase the supply available to California and other 
nearby markets. The significant production from other areas consists 
of the producing deposits in New Mexico which will continue to domi- 
nate the domestic supply for many years, the more recently developed 
deposits in Utah which may increase production in the future, the area 
being explored for potash in Arizona which may someday provide ad- 
ditional supplies, and the enormous deposits in Saskatchewan which 
may reasonably be expected to develop rapidly into a major source for 
the Western Hemisphere. 

Selected References 

Chemical and Engineering News, 1963, Interest developing in Arizona iwtash 

lands : Chem. Eng. News, Dec. 30, p. 18. 
— ■ ■, 1965, Morton Salt buys Simonize ; unveils finances : Chem. Eng. News, 

May 3, p. 23. 
Lewis, R. W., 1964, Potash : U. S. Bur. Mines, Mineral Yearbook, 1963, v. 1, p. 

Pierce, H. W., and Gerrard, T. A., 1965, Evaporite deposits of the Permian Hol- 

brook basin, Arizona [abs.] : Northern Ohio Geol. So. Symposium on Salt, 2d, 

Cleveland, 1965, program, p. 3. 
Ryan, J. E., 1951, Industrial salts; production at Searles Lake: Mining Eng., 

V. 3, no. 5, p. 447-452. 
Ruhlman, E. R., 1960a, Potash, in Industrial minerals and rocks : New York, Am. 

Inst. Mining Metall. Petroleum Engineers, p. 669-680. 
— ; 1960b, Potassium compounds, in Mineral facts and problems: U.S. Bur. 

Mines Bull. 585, p. 651-658. 


(By C. W. Chesterman, California Division of Mines and Geology, San Francisco, 


Pumice, pumicite, and volcanic cinders are products of explosive 
volcanic activity. Pumice is a very cellular, pale-gray to white vol- 
canic glass that occurs in fragments greater than one-eighth inch in 
diameter and in masses as much as 10 feet across. Pumicite, also known 
as volcanic ash, consists of finely divided angular glass particles, less 
than one-eight inch in diameter. The distinction between pumice and 
pumicite is one of particle size rather than structure or composition. 

Perlite, strictly defined, is a glassy volcanic rock characterized by an 
"onion skin" fracture, and which breaks into minute spherical frag- 
ments. Perlite, as well as many other siliceous volcanic glasses, will, 
when subjected to rapid controlled heating, expand into a Avhite, frothy 
material that resembles pumice. In an industrial sense, all expansible 
volcanic glasses may be referred to as perlite. 

''\/'olcanic cinders (scoria) resemble furnace clinkers and consist of 
small crystals of plagioclase and pyroxene enclosed in a mesh of still 


smaller crystals of these minerals and subordinate dark-colored vol- 
canic glass. 

Pumice is used principally as aggregate in the production of light- 
weight concrete, and as an abrasive. Although some pumicite is used 
as a pozzolan in the production of concrete and as an abrasive, its 
principal usage is as a pesticide carrier for agricultural sprays. 

About 40 percent of the perlite produced and expanded in the United 
States is used as aggregate in plaster. Other uses for expanded 
perlite include concrete aggregate, foundry sand, filter aid, filler, wall- 
board, and soil conditioning. 

Volcanic cinders find their greatest use in highway and railroad 
building. Minor, yet substantial, amounts of volcanic cinders are used 
as aggregate in concrete building blocks, monolithic concrete construc- 
tion, stucco, roofing granules, decorative stone in gardens, and as a con- 
ditioner of soils. 

^~ Pumice, pumicite, perlite, and volcanic cinders commonly occur to- 
gether and exist in California in regions underlain by Tertiary and 
Quaternary volcanic rocks. Pumice rarely forms seperate rock masses 
and is generally the major constituent of tuff and tuff-breccia. Massive 
pumice, however, can be found as tops of flows and domes of obsidian. 
Pumicite generally occurs as layers interbedded with fine-grained 

Since most of the pumice and pumicite mined in California is ob- 
tained from tuffs, tuff-breccias, and pumice breccias, their deposits 
may be classified, on the basis of their mode of deposition and origin 
as follows: (1) subaerial deposits — those deposited on dry land, (2) 
subaqueous deposits — those deposited in standing water, (3) Nuee 
ardentes deposits — lack bedding and show wide range in grain size, 
and (4) reworked deposits — show graded bedding, cross-bedding, and 
rounded fragments. 

The bulk of the pumice and pumicite produced in California has 
been from subaqueous and subaerial types of deposits. Deposits of 
subaerial pumice range in thickness from a few feet to 50 feet, and 
have an aerial extent of several square miles; subaqueous deposits 
range in thickness from a few feet to 30 feet, and are of considerable 
aerial extent. 

olcanic cinders are mined from cinder cones which formed around 
central openings or along fractures during explosive volcanic activity. 
Cinder cones are, in general, nearly circular in plan, range from a few 
hundred feet to several thousand feet in diameter, and are as much as 
I 500 feet high. The cones are stratified and consist largely of frag- 
\ ments that range from a fraction of an inch to several inches in 

Although perlite has many modes of occurrence, most commercial 
production has come from flows associated with thick accumulations 
of tuffs and lava flows, and from domes. In many places, flows of 
perlite-bearing rock are so recent that they are nearly flat-lying, but 
locally they are deformed. Individual flows of perlite range in thick- 
ness from a few feet to several tens of feet, and may be traced along 
their outcrop length for thousands of feet. Perlite domes range in 
size from several hundred feet to more than a mile in diameter, and 
frequently extend as much as several hundred feet above their base. 

The early known uses of pumice and pumicite date back to the days 


of the Roman Empire when pumicite was mixed with burned lime 
and used in the construction of the Pantheon and harbor installations 
on the Tiber. Many buildings in Belgium and France were built of 
pumice concrete during the 19th century. Ground pumice has been 
used as an abrasive for many years in the United States. Although 
only a limited amount of pumice was used as concrete aggregate 
prior to 1930, by the mid-1930's the demand for lightweight aggre- 
gate materials for military and domestic consumption had increased 
substantially, and consequently the production of pumice increased 

It has been known since about 1886 that perlite would expand, 
when properly heated, into a white, lightweight material. During 
the 1930's and early in the 1940's, research was conducted on the ex- 
pansion of perlite, and by 1945 a new industry was established and a 
new product— popped or expanded perlite — was introduced to the 
construction world. A wide variety of furnaces were designed, rang- 
ing from inclined stationary and rotary to vertical stationary. In 
each case, the purpose was to produce a consistently lightweight 
material (8 to 10 pounds per cubic foot) with a minimum of fines. 

The early use of volcanic cinders, undoubtedly, dates back several 
hundred years, but accurate records concerning where and when they 
were first used are scarce. The mining of volcanic cindei's in Cali- 
fornia was started about 1916 on a small scale, and the early uses were 
for concrete aggregate and as track ballast in railroad construction. 

The United States ranks third among the nations in the production 
of pumice, pumicite, and volcanic cinders, and first in the production 
of crude perlite. 

The annual production of pumice and pumicite in California has 
increased markedly from about 50 tons in 1909 to about 160,000 tons 
in 1964, as compared with tlie total United States production of over 
1,000,000 tons. California's peak production of pumice and pumicite 

isjipproximately 260,000 tons, attained in 1951. 

California ranks first in the Ignited States in the production of 
(volcanic cinders, and was the source of about 300,000 tons in 1964 as 
compared to a total United States production of about 1,600,000 tons. 

^rude perlite processed in the United States is mined from deposits 
in New Mexico, California, Arizona, Nevada, Colorado, I^tah, and 
Idaho. New Mexico produces approximately 75 percent of the total 
United States production, and (California is among the other impor- 
tant producing states. 

In 1964, there were 14 perlite expanding plants operating in Cali- 
fornia. Eleven of these plants are located in southern California and 
provide a wide range of expanded perlite products to consumers in 
this part of the State. There is one plant at Fresno and two in the 
San Francisco Bay area, at Antioch and Sausalito. 

Most of the pumice and pumicite deposits in California are in areas 
underlain in part by Tertiary and Quaternary volcanic rocks. Al- 
tliough considerable pumice and pumicite have been produced from 
tuffs of late Pliocene age, the bulk of California's output of these 
materials, as well as volcanic cinders, has come from tuffs and tuff- 
breccias of Pleistocene and Recent age. - » 

The distribution of the principal deposits, deposits from which 
there has been commercial production, or deposits which warrant fur- 
ther consideration are shown in table 37 and figure 63. 



Table 37. — Summary of the features of pumice, pumicite, perlite, and volcanic 

cinder deposits of California 


Name of deposit 


Thompson .. 



U.S. Pumice and Supply 
Co., Inc. 


Skoria Star Brick Co 

Pumice Stone mines 



Pumice and pumi- 

Volcanic cinders 



Great Northern Railroad. 


Porcupine Pit 




Long Haul Claims 

Volcanic cinders 

Sanford Cinders. 


Poison Lake Cinders 



Bowen Cinder 

William Silva . 


Volcanic cinders... 
Pumice. _____ . 

Basalt Rock Co. pumice 

Cinder Products 


Volcanic Ash Pit 



Sierra Placerite Corp 

Pumice and pumi- 

Bed Rock piimicite 


U.S. Pumice and Supply 
Co., Inc. 

.__- do -. 



Van Loon "Fine" west 






Pumice for aggregate purposes is mined from 

extensive layer, 10 to 40 feet thick, of loosely 

consolidated tuff-breccia. 
Pumice for aggregate purposes is mined from 

extensive layer, 3 to 6 feet thick, of loosely 

consolidated tufT-breccia. 
Pumiceous obsidian is quarried from top of 

Glass Mountain and used in the production 

of scouring bricks. 
Pumiceous obsidian is quarried from top of 

Glass Mountain and used in the production 

of scouring bricks. 
Pumice occurs as loosely consolidated tuff 

covering the ground and ranging in thickness 

from a few inches to 10 feet. 
Pumicite and pumice were mined from an 

extensive layer of white tuff which ranges in 

thickness from a few feet to 20 feet, and used 

as sand in cattle cars. 
Volcanic cinders mined from a cinder cone and 

used as ballast in railroad construction and 

Volcanic cinders produced from East Sand 

Butte, an extinct cinder cone. Material used 

principally as railroad ballast and bank 

Volcanic cinders produced from cone at Porcu- 
pine Port, Siskiyou County. Material used 

in railroad construction. 
Volcanic cinders produced from extinct cinder 

cone 1 mile east of Hotlum. Cinders used as 

aggregate for making building blocks. 
Pumice is mined for aggregate purposes from 

extensive tuff-breccia layer that ranges in 

thickness from 5 to 10 feet. 
Red and black volcanic cinders are quarried 

from eroded cinder cone and used as concrete 

Dark red and black volcanic cinders are quarried 

from cinder cone and used as concrete aggre- 
Pumice mined from 20-foot-thick layer of tuff 

and used as concrete aggregate. 
Pumice for aggregate purposes was produced 

from massive tuff of unknown thickness. 
Red volcanic cinders are quarried from eroded 

cinder cone and used as concrete aggregate. 
Coarsely vesiculated obsidian is quarried for use 

as aggregate in plaster and concrete. 
Sand from coarsely vesiculated obsidian is 

mined from extensive deposit and used as fill 

and in construction. 
Firm consolidated, yellowish- to buff-colored 

rhyolite tufl is quarried and sold as flagstone, 

ashlar strips, garden stone, and used in the 

making of terrazzo. 
Beds of grayish-white pumicite of variable 

thickness are interbedded with beds of silt 

and tuflaceous sand. Some pumicite produced 

and sold under trade name of "Lassenite". 
Vesiculated obsidian is quarried from tops of 

volcanic domes and used in the manufacture 

of scouring bricks. 
White pumice for aggregate purposes is mined 

from a 20-foot pumice bed. 
Pale pink pumice was mined from several 

quarries and used as aggregate for making 

building blocks. 
Several pumice beds with aggregate thickness 

of 30 feet were mined by benches and the 

pumice used as aggregate for making building 

Layer of pumice 20 feet thick, containing pink 

to white pujnice fragments, is mined and the 

pumice used as aggregate. 



Table 37. — Summary of the features of pumice, pumicitc, perlite, and volcanic 
cinder deposits of California — Continued 

No. on 
fig. 63 


Name of deposit 



.... do 

Van Loon "Fine" 

Pale pinkish pumice for aggregate purposes is 




Insulating Aggregates, Inc. 

Ray Gill and Donna 

Inyo Pumice Corp 

Lucky Lager^ ... 

mined from an extensive layer of unknown 

thickness and used in making building blocks 

and precast slabs. 
Extensive layer of grayish-white pumice is 

mined by open cut and the materia is ground 

and made into plaster aggregate. 
Extensive layers of pumice are being mined for 


_._. do.. ---- 

aggregate pumice. 
Creamy-white pumice has been mined for ag- 



gregate purposes from a layer of tuff about 30 
feet thick. 
Creamy-white pumice has been produced from 





Calsiico Corp _ 

a tuff bed of unknown thickness and used as 
aggregate in the manufacture of building 
Purr.''*" for aggregate and abrasive uses is being 


Cudahy Packing Co., 

Shoshone volcanic ash 

Redlite Aggregates 


produced from a bed of pumice lapilli tuff 
about 20 feet thick. 

White, fine-grained pumicite was mined from a 
9-foot bed in the Ricardo Formation (Plio- 

Flat-lying layer of grayish-white pumicite, 


Volcanic cinders... 




Volcanic cinders. . . 
.. do 

about 12 feet thick interbedded with lacus- 
trine sediments has been mined intermit- 
tently and the pumicite used in the manufac- 
ture of scouring soaps and cleansing com- 

Volcanic cinders produced from Red Cinder 
Mountain, cinder cone, for aggregate pur- 

Volcanic cinders for aggregate, roofing granules, 



and agricultural purposes. 
Pumice for aggregate and abrasive uses is being 


Su perlite. 

obtained from a thick tuff layer interstrati- 
fied with other tuffs that rest upon deeply 
eroded granite. 
Pumice for aggregate uses mined from tufl 


Mount Pisgah 

lavers associated with sands and gravels. 
Volcanic cinders used for aggregate. 


Dish Hill 

Pinto Cinders... .__ 

Cima Cinders 

Volcanic cinders for aggregate and roofing 

Volcanic cinders Quarried from cinder cone and 






Pumicite.. -. 



used as concrete aggregate, stucco, and soil 




Pumice and Pumicite 
Mining Co. 

California Industrial 
Minerals Co. 

Perlite Aggregates ... 

Pumice for aggregate purposes is produced from 
a laver of tuffaceous sandstone which has a 
maximum thickness of 30 feet. 

Buff-colored pumicite is produced from a 20-foot 
bed of p-imicite and used as insecticide carrier, 
in scouring soaps, manufacture of cement, 
and polishing agent. 

Medium-gray, dense perlite has been quarried 


Anadel Farm.. __ 

from an extensive flow that ranges in thick- 
ness from a few feet to 100 feet, and overlain 
by tuff. 

Medium-gray, dense perlite has been quarried 
from an extensive flow that ranges in thick- 
ness from 25 to 50 feet, and overlain in part 
by basalt flow. 

Extensive area underlain by a glassy flow com- 
posed of perlite and obsidian. 

Liglit-gray perlite is quarried from an elon- 





Cougar Butte.. .. 


Fish Springs . 


Glassy Rock 

gated dome of pumiceous perlite that meas- 
ures H mile wide and 1 mile in length. 
Medium-gray, dense perlite has been quarried 
from an extensive, gently southward-dipping 
flow that ranges in thickness from a few feet 
to 50 feet, and interbedded with tufl and 
tuffaceous sediments. 




Figure 63. Pumice, pumicite, perlite, and volcanic cinder deposits in California 

( numbers refer to table 37 ) . 

Resources potential of pumice, pumicite, perlite, and volcanic cind- 
ers is extremely great in California. No attemj)t is made to indicate 
reserves of these materials, because many of the deposits have never 
been examined carefully, and, as in the case for perlite, any reserve 
data would be meaningless unless such factors as uniformity and a 
definition of acceptable quality are known. 

Selected References 

Chesterman, C. W. 19.57, Pumice, pumicite, perlite, and volcanic cinders, in 

Mineral commodities of California : California Div. Mines Bull. 176, p. 433-448. 
Chesterman, C. W.. and Schmidt, F. S. 1956, Pumice, pumicite, and volcanic 

cinders in California : California Div. Mines Bull. 174, 119 p. 
Wright, L. A., Stewart, R. M., Gay, T. E., Jr., and Hazenbush, G. C, 1953, Mines 

and mineral resources of San Bernardino County, California : California Jour. 

Mines and Geology, v. 49, nos. 1 and 2, p. 185-190. 



(By L. A. Wright, Department of Geology and Geophysics, The Pemisylvania 
State University. University Park, Pa.) 

Use and Economic Importance 

Pyrophyllite (Al2Si40io(OH)2), like the mineral talc, is vei-j^ soft, 
micaceous in habit, soapy to the touch, and chemically inert. It is 
thus difficult to distinguish from talc. As industrial mmerals, they 
share most of the same uses and are competitive for the same markets. 
If sufficiently \vhite in the ground state and free of impurities, pyro- 
phyllite is useful as a paint extender. "Wliite-firing pyrophyllite is 
employed in the manufacture of ceramic products and of wall tile in 
particular. Pyrophyllite that grinds relatively dark is extensively 
marketed as an insecticide carrier and as a filler in various products, 
including asphalt and rubber (Chappell, 1960, p. 84-85). In 1963 an 
estimated 20,000 tons of pyrophyllite -was mined in California and was 
marketed mainly within the State. About 25 percent of this output 
was used in paints and ceramics. As most of the pyrophyllite that has 
been mined in California has proved too dark in color for these uses, 
it has been marketed principally as an insecticide carrier and filler. 

Geologic Occuerence 

Concentrations of pyrophyllite that are large enough to be of com- 
mercial interest occur in terranes of metamorphic rocks. Most of them 
can be shown to represent alterations of silicic volcanic rocks. The 
pyrophyllite of commerce consists of a schistose rock composed of 
a fine-grained mineral aggregate in which the mineral pyrophyllite 
is the most abundant constituent, but which commonly also contains 
abundant quartz and sericite. This rock occurs in tabular to highly 
irregular deposits. The most productive of the domestic sources of 
pyrophyllite are in North Carolina where bodies as much as 1,500 
feet long and 150 feet wide have been developed. Most of these 
deposits are lenticular in plan and appear to be best developed where 
the enclosing volcanic rocks have been thoroughly sheared. 

History of Discov'ery and Developihent 

The formal mining of pyrophyllite in California began in the early 
1940's with the opening of the Pioneer deposit near San Dieguito, 
west-central San Diego County (Jahns and Lance, 1950). This de- 
posit was most actively worked in the middle and late 1940's. It 
and several nearby deposits have been intermittently operated in re- 
cent years. 

The most productive pyrophyllite deposits in California are along 
the lower part of the west face of the White Mountains of Mono 



County (Wright, 1956, p. 455). These were opened in the mid-1940's 
and have been ahnost continuously worked since then, first at the 
Pacific mine and, in recent years, at the Colton mine. 

A third pyrophyllite-bearing area in California lies 12 miles north- 
east of Victorville in San Bernardino County. There the Victorite 
deposit (Wright and others, 1953, p. 243-244; Bowen, 1954, p. 158- 
160) , has been worked intermittently beginning about 1950. 

The only domestic sources of pyrophyllite are in North Carolina 
and California. In recent years the two states have yielded about 
150,000 tons annually. The output of North Carolina is several times 
that of California. 

Geologic Occukrenck in California 

The pyrophyllite deposits near San Diguito, San Diego County, 
and those near Victorville, San Bernardino County (figure 64), occur 
in volcanic rocks of Mesozoic age and are alterations of them. The 
bodies of pyrophyllite-bearing rocks are lenticular in shape. The 
mineable bodies are characteristically a feAv feet to a few tens of feet 
wide and as much as a few hundred feet in length. They form parts 
of much larger masses composed mostly of partially pyrophyllitized 
rock of no present commercial value. 


I . Pac 1 1 ic Mine 

2. Colton Mine 

3 . Victorite Mine 

4. Pioneer Mine 

Figure 64. Pyrophyllite operations in California. 


The deposits in the Wliite Mountains occur in a belt of highly meta- 
morphosed volcanic and sedimentary rocks of pre-Cretaceous age. 
These deposits are bordered by mica schist and quartzite and commonly 
contain highly quartzose layers of waste rock. The deposit at the 
Pacific mine appears to be the largest of the pyrophyllite bodies dis- 
covered to date in California. It is about 200 feet wide at the main 
quarry and appears to extend laterally for 1,000 or more feet. The 
commercial pyrophyllite is a friable schistose rock most of which is 
stained various shades of red, yellow or orange. Some of it is white 
or nearly so and is mined selectively. The Colton mine is about 2 miles 
south of the Pacific mine and in the same pyrophyllite-bearing belt. 
It has yielded relatively white pyrophyllite from a deposit that is 
about 100 feet in maximum exposed thickness and at least several 
hundred feet long. 

Resource Potential 

Meaningful estimates of the pyrophyllite resources in California are 
as yet unavailable because the deposits of the "WHiite Mountains and 
those near Victorville remain to be studied in detail. The three areas 
already noted contain many millions of tons of rock that is sufficiently 
rich in pyrophyllite to be of commercial interes