GIFT OF kV i I I V ADVERTISEMENT. [Monograph XIII. J The publications of the United States Geological Survey are issued iu accordance with the statute approved March 3, 1879, which declares that "The publications of the Geological Survey shall consist of the annual report of operations, geo- logical and economic maps illustrating the resources and classification of the lands, and reports upon general and economic geology and paleontology. The annual report of operation.-! of the Geological Survey shall accompany the annual report of the Secretary of the Interior. All special memoirs and reports of said Survey shall be issued in uniform c[U-ii'to series if deemed necessary by the Director, but otherwise in ordinary octavos. Three thousand copies of each shall bo published for scientific exchanges ;iinl for sale at the price of publication; and all literary and cartographic materials received iu exchange shall be the property of the United States and form aipart of the library of the organization : And th money resulting from the sale of such publications shall be covered into the Treasury of the Unite, I Slates." On July 7, 188i, the following joint, resolution, referring to all Government publications, was passed by Congress: "That whenever any document or report shall lie ordered printed by Congress, there shall l>e printed, inadditiou to the number in each case stated, the 'usual number' (1,900) of copies for binding iind distribution among those entitled to receive them." Except iu those casesin which an extra number of any publication has been supplied to the Sur vey by special resolution of Cougress or has been ordered by the Secretary of the Interior, this oliice has no copies for gratuitous distribution. ANNUAL REPORTS. I. First Annual Report of the United States Geological Survey, by Clarence King. 1880. . 7!) pp. 1 map. A preliminary report describing plan of organization and publications. II. Second Annual Report of the United States Geological Survey, 188Sf-'81, by J. W. Powell. 1882. 8 C . Iv, 588 pp. b'l pi. 1 map. III. Third Annual Report of the United Stales Geological Survey, 1881-'82, by J. W. Powell 1883. 8. xviii, 5(>4 pp. (i7 pi. and maps. IV. Fourth Annual Report of the United States Geological Survey, 1882-'83, by J. W. Powell. 1884. 8. xxxii, 471! pp. 85 pi. and maps. V. Fifth Annual Report of the United States Geological Survey, 1883-'84, by J. W. Powell. 1385. 8. xxxvi, 4(51) pp. 58 pi. and mans. VI. Sixth Annual Report of the United States Geological Survey, 1884-'85, by J. W. Powell. l - '86. 8. xxix, 570 p[>. <>5 pi. and maps. VII. Seventh Annual Report of the United States Geological Survey, 1883-'8G, by J. W. Powell. 1888. 8. xx, 65tj pp. ~2 pi. and maps. The Eighth and Ninth Annual Reports are in press. MONOGRAPHS. Monograph I is not yet, published. II. Tertiary History of the Grand Canon District, with atlas, by Clarence E. Duttoii, Capt. , U. S. A. 1882. 4. xiv, 264 pp. 42 pi. and atlas of 24 sheets folio. Price f 10.12. III. Geology of the Comstork Lode, and the Washoe District, with atlas, by George F. Becker. 1*-<2. 4. xv, 4*J pp. 7 pi. and atlas of 21 sheets folio. Price $11. IV. Comstock Mining and Miners, by Kliot Lord. H83. 4. xiv, 451 pp. 3 pi. Price $1.51). V. The Copper-Hearing Rocks of Lake, Superior, by Roland Duer Irving. 1883. 4. xvi, 4ti4 pp. 151. 29 pi. Price fl.8f>. VI. Contributions to the- Knowledge of the Older Meso/,oic Flora of Virginia, by William Morris Fontaine. 1883. 4. xi, 144 pp. 54 1. 54 pi. Price $1.05. VII. Silver-Lead Deposits of Eureka, Nevada, by Joseph Story Curtis. 1881. 4. xiii, 200 pp. 10 pi. Price |1. ,'(). VIII. Paleontology of the Eureka District, by Churles Doolittlo Walcott. 18S1. I '. xiii,2'.H pp. 241, 24 pi. Price $1.10. I I [ ADVERTISEMENT. X. Brachiopoda and La mcl I i branchial a of the Kan tan Clay is and Oreonsaud Marls of New Jersey, >ert P. Whitiield. 1885. 4. xx, 338 pp. 3". pi. 1 in;i]>. Trice SI. 15. C. Dinocerata. A Monograph of :in Extinct Order of Gigantic Mammals, by Othuiel Charles IX by Kobert X. Dinocerata. A Monograj Marsh. l->-(;. 4. xviii, 243pp. 561. 50 pi. Price $2.70. XI. Geological History of Lake Lahontan, a Quaternary Lake, of Northwestern Nevada, by Israel Cook Russell. 1S85. 4. xiv, 288 pp. 40 pi. and maps. Price. .*!. 75. XII. Geology and Mining Industry of Leadvillo, Colorado, with atlas, by Samuel franklin Em- uions. 1S8G. 4. xxix, 770 pp. 45 pi. and atlas of 35 sheets folio. Price $>8.40. XIII. Geologv of tht) Quicksilver Deposits of the' Pacific Slope, with atlas, by George F. Becker. 1888. 4. xix, 486 pp. 7 pi. and atlas of 14 sheets folio. Price JJ2.00. XIV. Fossil Fishes and Fossil Plants of the Triassie Rocks of New Jersey and the Connecticut Valley, by John S. Newberry. .1888. 4. xiv, 152 pp. 26 pi. Price $1.00. In preparation: XV. Younger Mesozoie Flora of Virginia, by William M. Fontaine. XVI. Paleozoic Fishes of North America, by J. S. Newbcrry. XVII. Description of New Fossil Plants from the Dakota Group, by Leo ].csi|iiereux. Gasteropoda of the New Jersey Cretaceous and Eocene Marls, by K. P. Whitfield. Geology of the Eureka Mining District, Nevada, with atlas, by Arnold Hague. Lake Bonneville, by G. K. Gilbert. Sanropoda, by O. C. Marsh. Stegosauria, by O. C. Marsh. Brontotheridto, by p. C. Marsh. The Penokee-Gogebic Iron- Bearing Series of North Wisconsin and Michigan, by Roland D. Irving. Report on the Denver Coal Basin, by S. F. Emmons. Report on Silver Clitf and Ten-Mile Mining District, Colorado, by S. F. Einmous. Flora of the Dakota Group, by J. S. Nowberry. The Glacial Lake Agassiz, by Warren Uphani. Geology of the Potomac Formation in Virginia, by W. M. Fontaine. BULLETINS. Each of the Bulletins contains but one paper and is complete in itself. They art 1 , however, num- bered iu a continuous scries, and may bo bound in volumes of convenient size. To facilitate this, each Bulletin has two paginations, one proper to itself and another which belongs to it as part of I be volume. 1. On Hyperstheno-Andesite and on Triclinic Pyroxene in Augitic Rocks, by Whitman Cross, with a Geological Sketch of Buffalo Peaks, Colorado, by S. F. Euimons. 1883. 8 1 -'. 42pp. 2 pi. Price in cents. 2. Gold and Silver Conversion Tables, giving the coining values of troy ounces of line metal, etc., computed, by Albert Williams, jr. 1883. 8. 8pp. Price 5 cents. 3. On the Fossil Faunas of the Upper Devonian along the meridian of 7(i "30', from Tompkins County, N. Y., to Bradford County, Pa., by Henry S. Williams. 1884. 8. 3G pp. Price 5 cents. 4. On Mesozoic Fossils, by Charles A. White. 1884. 8. 36 pp. Dpi. Price f> ccnls. 5. A Dictionary of Altitudes in the United States, compiled by Henry Gannett. 1884. 8''. 325pp. Price 20 cents. 6. Elevations in the Dominion of Canada, by J. VV. Spencer. 1884. 8. 43 pp. Price 5 cents. 7. Mapotcca Geologica Americana. A Catalogue of Geological Maps of America (North and South), 17f>2-1881, in geographic and chronologic order, by Jules Marcou and John Belkuap Marcou. 1884. 8. 184 pp. Price 10 cents. 8. On Secondary Enlargements of Mineral Fragments in Certain Rocks, by R. D. Irving and C. R. Van Hise. 1884. 8. 56 pp. 6 pi. Price 10 cents. 9. A Report of work done in the Washington Laboratory dnrmg the liscal year 1883-'84. F. W. Clarke, chief chemist; T. M. Chatard, assistant chemist. 1884. 8. 40pp. Price 5 cents. 111. On the Cambrian Faunas of North America. Preliminary studies, by Charles Doolittle Wal- cott. 1884. 8. 74, pp. 10 pi. Price 5 cents. 11. On the Quaternary and Recent Mollusca of the Great Basin ; with Descriptions of New Forms, b\ M. Ellsworth Call.- Introduced by a sketch of the Quaternary Lakes of the Great Basin, bv G. K. Gilbert. 1881. 8. Gli pp. 6 pi. Price 5 cents. 12. A Cr.vstallographic Study of the Thijiolite f Lake Lahontan, by Edward S. Duna. 1884. 8. 31 pp. 3 pi. Price 5 cents. 13. Boundaries of the United States and of the several Slates and Territories, with a Historical Sketch of the Territorial Changes, by Henry Gannett. IS-C>. H '. 135 pp. Price 10 cents. 14. The, Electrical and Magnetic Properties of the Iron-Carburets, by Carl Barns and Vincent Slronhal. 1885. tf. 238pp. Price 15 cents. !.">. On the SJeMi/oic and CYnozoic Paleontology of California, by Charles A. White. 1885. 8. 33 pp. Price 5 cents. Hi. On the Higher Devonian Faunas of Ontario County, New York, by John M. Clarke. 1885. 8~. ,-li pp. :< pi. Price :"> cents. 17. On the Development of Cr.x slalli/.al ion in the Igneous Rocks of Washoe, Nevada, with Notes on the Geology of (lie District, by Arnold Hague and Joseph P. Iddings. 18*5. 8. 44 pp. Price 5 cents. ADVERTISEMENT. Ill 18. On Marine Eocene, Fresh-water Miocene, and other Fossil Molhisca of Western North America, by Charles A. White. 1885. 8. 20pp. 3 pi. Price 5 cents. 19. Notes on the Stratigraphy of California, by GeorgoF. Becker. 1885. 8. 28pp. Price5cents. 20. Contributions to too Mineralogy oC tint Rooky Mountains, !>y Wliitman Cross and W. F. Hi lie- brand. H85. 8. 114 pi>. 1 pi. Price' 10 cents. 21. The Lignites <>t 'the (treat Sioux Reservation. A Report on the Region hot. ween the Grand and Morean Rivera, Dakota, by Bailey Willis. 188.'). 8. 1C pp. , r >pl. Priee 5 rents. 2-1. On New Cretaceous Fossils from California, liy Charles A. White. 13S5. 8. 35pp. 5 pi. Price r> ceuts. 23. Observations on the .Junction bstween the Eastern Sandstone and the Kewet,naw Sjries oa Keweeuaw Point, Lake Superior, by 11. D. Irving and T. C. Chamberlin. 18i r >. 8. 121 pp. 17 pi. Price l.'i cents. 24. List of Marino Mollnsca, comprising the Quaternary fossils and recent forms from American Localities between Cape HaUeras and Capo Roqne, including the Bermudas, by William llealey Dall. 1*35. 8. :i:!G pp. Price 25 cents. 25. The Present Technical Condition of the Steel Industry of the United States, liv Phineas Barnos. 1835. 8. 85 pp. 1'rico 10 cents. 20. Copper Smelting, by Henry M. Howe. 1885. 8. 107pp. Price 10 cents. 27. Report of work done in the Division of Chemistry and Physics, mainly during the fiscal year 1884-'85. 1886. 8. 80 pp. Price 10 cents. 28. The Gabbros and Associated Hornblende Rocks occurring in the Neighborhood of Baltimore, Md., by George lluntington Williams. 1886. 8. 78pp. 4 pi. Price 10 cents. 29. On the Fresh-water In vertebrates of the North American Jurassic, by Charles A. White. 183.5. 8. 41 pp. 4 pi. Price 5 cents. 30. Second Contribution to the Studies on the Cambrian Faunas of North America, by Charles Doolittle Walcott. 1*80. 8 e . 309 pp. 3:5 pi. Price 25 cents. 31. Systematic Review of our Present Knowledge of Fossil Insects, including Myriapods and Arachnids, by Samuel llnbbard Scudder. 1830. 8. 128 pp. Price 15 cents. 32. Lists and Analyses of the Mineral Springs of the United States; a Preliminary Study, bv Albert C. Pealo. 1880. 8. 235pp. Price 20 cents. 33. Notes on the Geology of Northern California, by J.S.Dillor. 1830. 8. 23pp. Price 5 cents. 34. On the relation of the Laramie Molluscan Fauna to that of the succeed ing Fresh- water Eocene and other groups, by Charles A. White. 188U. 8. 54pp. 5 pi. Price 10 cents. :!f>. Physical Properties of the Iron-Carburets, by Carl Barns and Vincent Stronhal. 1883. 8. Gv! pp. Price 10 cents. 36. SiibsidenceofFiueSolidParticlesiiiLiquiils, byCarl Barus. 188>i. 8. 58pp. Price lOceuts. 37. Types of the Laramie Flora, by Lester F. Ward. 1887. 8 J . 354pp. 57 pi. Price 25 ceuts. 3*. Peridoti to of Elliott County, Kentucky, by. I. S. Diller. 1887. 8. 31pp. 1 pi. Price 5 cents. 31). The Upper Beaches and Deltas of the Glacial Lake Agassiz, by Warren Upham. 1887. 8. 84 pp. 1 pi. Price 10 cents. 40. Changes in River Courses in Washington Territory duo to Glaciation, by Bailey Willis. 1837. 8. 10pp. 4 pi. Price 5 cents. 41. On the Fossil Faunas of the Upper Devonian the Gonesee Section, New York, by Henry S. Williams. 18*7. 8. 121 np. 4 pi. Price 15 cents. 42. Report of work done in the Division of Chemistry and Physics, mainly during the fiscal year 1 .V80. F. W. Clarke, chief chemist. 1887. 8. 152pp. 1 pi.' 'Price 15 cents. 4:!. Tertiary and Cretaceous Strata of the Tnscaloosa, Tomhigbeo, and Alabama Rivers, by Eugene A. Smith and Lawrence C. Johnson. 1*37. 8. 180 pp. 21 pi. Price 15 cents. 44. Bibliography of North American Geology for 183!'), by Nelson II. Darton. 1887. 8. 35 pp. Price 5 cents. 45. The Present Condition of Knowledge of the Geology of Texas, by Robert T. Hill. 1887. 8. 94 pp. Price 10 cents. 46. Nature and Origin of Deposits of Phosphate of Lime, by R. A. F. Ponrose, jr., with an Intro- duction by N. S. Slialcr. 1*83. 8. 143 pp. Price 15 ceuts. 47. Analyses of Waters of the Yellowstone National Park, with an Account of the Methodiof Analysis employed, by Frank Austin Gooch and James Edward Whit lield. 1338. 8. 84pp. Price 10 cents. 48. On the Form and Position of the Sea Level, by Robert Simpson Woodward. 1833. 8. 88 pp. Price ID cents. Numbers 1 to ('< of the Bulletins form Volume I; Numbers 7 to 14, Volume II; Numbers 15 to 23, Volume III; Numbers 24 to 30, Volume IV; Numbers 3L to :!;!, Volume V: Numbers :17 to 41, Volume VI; Numbers 42 to 40, Volume VII. Volume VIII is not yet complete. In press: 49. On the 1 Latitudes ami Longitudes of Certain Points in Missouri, Kansas, and New Mexico, by R. S. Woodward. 50. Formulas and Tables to facilitate the construction and use of Maps, by R. S. Woodward. 51. Invertebrate Fossils from California, Oregon, Washington Territory, and Alaska, by C. A. White. 52. On the Snbaerial Decay of Rocks and the Origin of the Red Color of Certain Formations, by Israel C. Russell. 53. Geology of the Island of Nantncket, by N. S. Shaler. IV ADVERTISEMENT. In preparation : Notes on the Geology of Southwestern Kansas, by Robert Hay. On the Glacial Boundary, by G. F. Wright. The Gabbros and Associated Rocks in Delaware, by F. D. Chester. Fossil Woods and Lignites of the Potomac Formation, by F. H. Kno\vltou. Mineralogy of the Pacific Coast, by W. II. Melville and Waldera&r Lindgreu. Report of work done iu the Division of Chemistry and Physics, mainly during the fiscal year 1836-'87. A Report on the Thermo Electrical Measurement an 1 High Temperatures, by Carl Barns. The Greenstone Schist, Areas of the Mcnoininee an;l .\I.in|iii'tti' R 'gions of Michigan, by George H. Williams; with an introduction by R. D. Irving. Bibliography of the Paleozoic Crustacea, by A. W. Vogdes. The Viscosity of Solids, by Carl Barns. Author-Catalogue of Contributions to North American ({oology, by N. II. Darton. On a Group of Volcanic Rocks from thoTewan Mountains, New Mexico, and on the occurrence of Primary Quartz in certain Basalts, by J. P. Iddings. On the relation-! of Ihe Traps of the Jura-Trias of New Jersey, bv N. H. Darton. Altitudes between Lake Superior and the Rocky Mountains, by Warren Upham. Mesoxoic Fossils in the Permian of Texas, by C. A. White. STATISTICAL PAPERS. Mineral Resourcei of the United States [1832], by Albert Williams, jr. 188:?. 8. xvii, 813 pp. Price r>0 cents. Mineral Resources of the United States, 1333 ami 1834, by Albert Williams, jr. 1885. 8. xiv, lolii pp. Price <>0 cents. Mineral Resources of the United States, 1835. Division of Mining Statistics and Technology. l*8.i. 8 J . vii, r.7i> pp. Price 40 cents. Mineral Resource! of the Unite:! States, 183.5, by D.ivid T. Diy. 1337. 8. viii, 81.! pp. Pri.-o ' 50 cents. Mineral Resources of the United States, 1837, by David T. Day. 1833. 8. vii, 832 pp. Price f>0 cents. In preparation : Mineral Resources of the United States, 1888, by David T. Day. The money received from the sale of these publications is deposited in the Treasury, and tin- Secretary of that Department declines to receive bank checks, drafts, or postage stamps ; all remit- tances, therefore, must be by POSTAL NOTE or MONEY ORDER, made payable to the Librarian of the U. S. Geological Survey, or in CURRENCY for the exact amount. Correspondence relating to the pub- lications of the Survey should be addressed To THE DIRECTOR OF THE UNITED STATES GEOLOGICAL SURVEY, WASHINGTON, D. C. WASHINGTON, D. C., March 15, 1889. ADVERTISEMENT. LIBRARY CATALOGUE SLIPS. United States. Ilcpartmmt of the interior. ( U. S. geological survey). Department of the interior | | Monographs | of the | United States geological survey | Volnmo XIII | [Seal of the tlepart- inent] | Washington | government printing office | 1888 Second till,': United States geological survey | J. W. Powell, director | | Geology | of the | quicksilver deposits | of the | Pa- ' cilic slope | with an atlas | liy | George F. Becker | [Vignette] | Washington | governme, it printing office | 1888 4. six, 480 pp. 7 )il. am\ folio atlas of 14 pi. Becker (George Ferdinand). United Srat.es geological survey | J. W. Powell, director | | Geology ! ofthe ! (juioksilverdeposita | of the | Pacific slope | with an atlas | l,y | George F. Becker | [Vignette] | Washinglon | government printing office | 1888 4. six, 48(5 pp. 7 pi. anil fi.lio atlas of 14 pi. [UsiTF.i> STATUS. Department of the interior. (U. S. geological eurvey) Monograph XIII|. United States geological survey | J. \V. Powell, director | | . Geology | ofthe | qnickgilverdepoaita | of the | Pacific slope | with K, an atlas | l.y | (J.-orge F. Bec.ker | [Vignette] | Washinijton | goveruinent. printing office | 18S8 J| 40. xi\-, 4xii|,p. 7 pi. anil folio atlas of 14 pi. (UNITED STATUS. Department of the interior. (U. S. geological Monograph XIII]. UFI7BESITT U. S. GEOLOGICAL SURVEY MONOGRAPH XHI, PL. 1. SKETCHMAP SHOWING DISTRIBUTION OF QUICKSILVER MINES IN CALIFORNIA friucipal Surveys Other deposits referred to Minor Surveys . o Traces oi'ore SteamboaT Spring 124 123' f n-ii I' Becker, Geolo^isl in charge. DEPARTMENT OF THE INTERIOR MONOGRAPHS OF THE UNITED STATES GEOLOGICAL SURVEY VOLUME XIII WASHINGTON GOVERNMENT PRINTING OFFICE 1888 tnUVEKSITY t s* UNITED STATES GEOLOGICAL SURVEY J. W. POWELL, IIRECTOR GEOLOGY OK THE QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE WITH AN ATLAS BY UNIVERSITY GEORGB T. BECKER \\ WASHINGTON GOVERNMENT PRINTING OFFICE 1888 LETTER OE TRANSMITTAL DEPARTMENT OP THE INTERIOR, U. S. GEOLOGICAL SURVEY, CALIFORNIA DIVISION OF GEOLOGY, Washington, D. C., July 19, 1887. ./ SIR: I have the honor to transmit herewith a report on the geology of the quicksilver deposits of the Pacific slope, prepared in accordance with your instructions. Very respectfully, your obedient servant, GEORGE F. BECKER, Geologist -in Charge. Hon. J. W. POWELL, Director U. S. Geological Survey. ' OT THR ^ [TJHIVZRSITY) CONTENTS. Page. LETTER OKTUAXSMITTAI, v PREFACE- xm 111: IKK OUTLINE OK KESl'I.TS XV CHAPTER I. Statistics and history 1 II. Notes on foreign occurrences of quicksilver 14 III. The sedimentary rocks 56 IV. The massive rocks 140 V. Struc'. ural and historical geology of tbe quicksilver belt 176 (Appendix to Chapter V, remarks on the genus Aucella, by Dr. C. A. White) 226 VI. Descriptive geology of the Clear Lake region 233 VII. Descriptive geology of Sulphur Bank 251 VIII. Descriptive geology of the Knoxville district 271 IX. Descriptive geology of the New Idria district 291 X. Descriptive geology of the New Almadou district 310 XI. Descriptive geology of the Steamboat Springs district 331 XII. Descriptive geology of the Oathill, Great Western, and Great Eastern districts 354 XIII. Other deposits of the Pacific slope 365 XIV, Discussion of the ore deposits 387 XV. On the solution and precipitation of cinnabar and other ores 419 XVI. The origin of the ore 438 XVII. Summary of results 451 INDEX , .". 477 VII ILLUSTRATIONS. Page. PLATE I. Distribution of quicksilver mines in California Frontispiece II. Distribution of quicksilver deposits throughout the world 15 III. European and other foreign forms of Aucella 231 IV. American forms of ducella 232 V. Geological map of Oathill 354 VI. Geological map of the Great Western district 358 VII. Map of the Great Eastern district 362 Fio. 1. Zoisite microlites 78 2. Authigenetic augite in altered sandstone 88 3. Authigenetic hornblende in altered sandstone 89 4. Clastic quartz partially converted to serpentine 123 5. Ruptures produced by compression of strata 236 6. Dendritic sinter on the shore of Borax Lake 206 7. Partly metamorphosed anticlinal 276 8. Sandstone undergoing serpentinization 277 9. Serpentine forming from sandstone 278 10. Diagrammatic vertical cross-section of the Reding ton mine 289 11. Contact between metamorphic rocks and Chico beds 296 12. Sketch of New Idria ore bodies 303 13. Fissures of the New Alniaden district 329 14. Vertical cross-section of the Napa Consolidated mine 357 15. Vertical cross section of the Great Western mine 360 16. Vertical longitudinal section of the Great Western mine 361 17. Vertical cross-section of the Great Eastern mine 364 18. Geological sketch map of the Mayacmas Range 369 19. Linked veins , 410 20. Simple fissure vein and chambered vein 411 IX LIST OF ATLAS SHEETS. SHKKT I. Title. II. Contents. III. Geological map of the Clear Lake district. IV. (Zoological map of the Sulphur Bank district. < Topographical map of the region of Clear Lake. ( Geological map of the Kuoxville district. VI. Geological map of the New Idria district. VII. Geological map of the New Almadeu district. VIII. Ore bodies of the New Almaden shown beneath the topography. IX. Map of the workings of the New- Almaden mine. X. Vertical cross-section of the New Almaden mine on a broken line nearly north and south. XI. Two north and south sections of the New Almadeu mine. XII. Kast and west section of the New Almaden mine. XIII. Plan of clays, New Almaden mine. XIV. Geological map of the Steamboat Springs district. XI TJFIVE1 7 PREFACE. The field work of the investigations recorded in this volume occupied nearly the whole of three seasons, beginning' in 1883. All the mines might have been examined and the maps colored in a much shorter time, but it was found soon after the examinations were begun that they could not be completed satisfactorily without also solving some important general prob- lems affecting the whole region, and much of the time spent was devoted to these questions. The examinations of the Knoxville and New Idria districts furnished me with strong paleontological and structural grounds for believing that an important and previously undetermined non-conformity existed in the Coast Ranges. On my application, Dr. C. A. White devoted one season to examining my collections of fossils and their field occurrence with me. He indorsed my conclusions in all respects. The paleontological statements of this report are all on his authority, excepting where otherwise accredited. It was found that the quicksilver districts of California afforded a re- markable opportunity for the investigation of the metamorphism of Meso- zoic rocks and that it was highly desirable to determine what connection, if any, existed between the formation of ore deposits and this metamorphism. The investigation occupied much time and was most laborious. It was known before these investigations were undertaken that the deposition of cinnabar was probably still taking place at Sulphur Bank and Steamboat Springs. It was of course necessary to make an effort to dis- cover whether such was really the case, and, if so, under what conditions the solution and precipitation of cinnabar and the accompanying minerals occurred. The problems presented by this inquiry were far from being simple or readily solved. Dr. W. H. Melville has had charge of my laboratory throughout the period covered by these investigations. He has made all the analyses re- XIII xiv PREFACE. corded in this report, as well as a large part of the experiments. A portion of his time has been occupied in investigations which are not recorded here, but which I hope to publish soon. His work has been very difficult, but entirely satisfactory to me. Mr. H. W. Turner has assisted me in all the field work, and Chapter XII is written from his notes. His accuracy and powers of observation have been very valuable to me. Mr. Waldemar Lindgren joined me only in time for the last season's field work. His assistance in the microscopical lithology has been very efficient and important. I could not without aid have accom- plished in a reasonable time so trying an investigation as that of the meta- morphic rocks of the Coast Ranges. For myself, I may say that I have studied with care in the field every portion of the areas surveyed in detail ; I spent months at the micro- scope and made many important chemical experiments on the solubility of ores. It has been my endeavor to do justice to all sides of a very fine sub- ject and to draw only legitimate conclusions from the facts observed by my assistants and myself. I approached the problems mentioned above entirely without preconceived ideas of the solutions to be reached, and have expressed my conclusions as to the geology of California or of other regions without regard to the opinions of others; but, while entertaining some confidence in the correctness of my results for the region surveyed, I do not even incline to the hypothesis that all crystalline sedimentary rocks have a history similar to that of those which I have described or that ore deposits are all formed in a similar way. The superintendents of the mines examined have afforded me every facility, often at inconvenience to themselves, and I have much to thank them for. Mr. Louis Janin has supplied me with many valuable notes gathered in his large experience as a mining expert. Mr. Frank Reade, who assisted me in examining the Comstock lode, was surveyor of the New Almaden mine during the period covered by the present investigation, and he prepared for me the excellent plans and sections of that mine. In addition to those who took part in the present investigation I am indebted to numerous previous observers, to whom I have endeavored to assign due credit in the proper places. PREFACE. xv Readers will perhaps notice the absence of illustrations of magnified thin sections in this volume. After having presented in a former report illustrations of tins kind which are generally acknowledged to be unsur- passed by any yet published, I have come to the conclusion that the lessons which they teach do not repay their cost in time and money. I have thought it best to make each chapter in this volume as far as possible independent of the rest. In doing so I am sure that I meet the wishes of many readers who will care to consult only certain portions of the book. This plan, however, involves some repetition, which may prove wearisome to continuous readers. I crave their indulgence in this resped; for the sake of the larger class. Personally, I should prefer never to re- state a fact or an opinion. After the manuscript of this report was substantially completed I was authorized to visit the great Almaden mine in Spain and the Tuscan deposits. Such a visit was almost essential to the purposes of the investigation ; for the results which I had reached from study of the American deposits differed in important respects from the conclusions of some geologists respecting the great Spanish deposit If they were right, it became necessary to warn American miners that cinnabar might be looked for under very different conditions from those described in this volume. If the greatest quicksilver deposit of the world proved similar in its mode of occurrence to those of California, the conclusions drawn from the latter would ' gain greatly in strength. I had the satisfaction of finding that the deposit of Almaden showed an association with eruptive phenomena, a structure, and a mineral association similar to those which are typical of the Pacific slope. Such statements as that the Almaden ore bodies are not veins-, that the cinnabar is free from other sulphides, that it is accompanied by no gangue minerals, that it was deposited with the inclosing rocks, that it is deposited by sub- stitution for sandstone, and that there is no evidence of a connection between the deposition and eruptive phenomena these allegations are, in my judg- ment, erroneous. The Tuscan deposits, too, I found similar to some in Cali- fornia. Only a few notes concerning my studies of these mines are included in this volume. I exuect to write more fully of them hereafter. JULY, 1887. BRIEF OUTLINE OF RESULTS. Quicksilver appears to be rather more than three times as abundant in nature as silver. The quicksilver produced in the world from 1850 to 1885, inclusive, weighed 1.74 times as much as the silver produced, but the value of the silver \vas about 1G.4 times that of the quicksilver. The great quick- silver-producing localities of 'the world have been Almaden in Spain, Idi'ia in Austria, Huancavelica in Peru, California, and the province of Kwei-Chau in China. No statistics are known to exist of the Chinese product. The total known products of the other regions take rank in the order in which they are named above, but of late years Peru has produced uothiug and from 1850 to 1885 California yielded about half the total product. The production of Italy is more important than it is usually assumed to be. In 1886 the yield was 7,478 flasks. The production of California, which was nearly 80,000 flasks in 1677, was only about 30,000 in 1886. A chain of quicksilver deposits of very greatly varying commercial importance almost girdles the world. Beginning in Spain, these deposits are distributed along the great chain, including the Alps, Caucasus, and Himalayas to China ; thence through Japan along the eastern edge of the Asiatic conti- nent to the Arctic circle, Beginning again in Alaska, the deposits follow the western Cordilleras down to Chili. Brief descriptions of the more important or more interesting of these deposits are given in Chapter II and serve as an introduction to the discussions of the deposits of the Pacific slope. The sedimentary rocks of the Coast Ranges of California are almost all composed of granitic detritus. A portion of those havo been subjected to very intense metamorphisin and have been con- verted into thoroughly crystalline rocks, in part schistose. These rocks are of Cretaceous age and are grouped as pseudodiabasc, pseudodiorite, glaucophane-schists, phthanites, and serpentine. Very elaborate field studios, microscopical examinations, and chemical analyses of these rocks are given in Chapter III, which is mainly devoted to the investigation of their origin and the processes by which they have become reerystalline. The conclusion reached is that dynamical action, together with warm waters carrying imigncsian salts and silica in solution, effected the metamorphi? a at the epoch of an exceedingly violent upheaval. This chapter also includes an investigation of concretions in sandstone, which are referred to the action of organic matter, and an analysis of the conditions under which decomposition xvill produce rounded nodules, like pebbles. The massive rocks of the quicksilver areas include granite, ancient porphyries, andesites, rhyolite, and basalt, A new group of andesites is discussed, for which the name anperites is suggested. It is shown that these rocks are of variable mi neralogical composition, even in the same eruptions, while all of I hem share a trachytic habitus. The name, is simply a latinized equivalent of trachyte. Very remarkable andcsitic and basaltic glasses occur near Clear Lake in areas of unusual size. These glasses are extremely aeid, but rontain als>. -i very high percentage of alkalis, and it is because of this peculiar chemical composition (hat they have failed to crystallize, not because they have cooled more rapidly or under less pressure than the accompanying crystalline rocks. An attempt is also made to show that the original crust of the earth was granitic and reasons are given for believing that the MON XIII II XVII xvni BRIEF OUTLINE OF RESULTS. primeval rock is exposed in California. The lavas burst through the granite, and the conclusion is reached that they cannot possibly consist of reinelted sediments. The historical and structural geology of the quicksilver belt is discussed in Chapter V. It is shown that the metamorphosed rocks pass over into early Crctaoeous beds containing a very charac- teristic fossil of the genus Aucclla. Soon after the era in which this mollusk lived the Neornmian occurred the great upheaval which induced the metamorphism. The next strata in point of ago com- prise a hitherto undetected group of the middle Cretaceous called the Wallala beds. They were laid down uncouformably on the already metamorphosed Neocomian. At the very end of the Cretaceous the Chico series were deposited for the most part on the metamorphic rocks and unconformably with them. Following the Chico are the Tejon beds, which are here regarded as Eocene; but there was continuity of life and of sedimentation from the Chico to rheTeJon, or fiom the Cretaceous to the Ter- tiary a state of things detected nowhere else in the northern hemisphere. Upou the T^jou lie the Miocene rocks with no notable non-conformity. The close of the Miocene was marked by an impor- tant upheaval, which was recognized by earlier observers. The volcanic period seems to have begun nearly at this time. The end of the Pliocene was also marked by disturbances, and most of the asper- ites seem to have been erupted at this epoch. The ore deposits stand in close relation to the volcanic phenomena and are probably nearly or quite all Post-Pliocene. The gold belt of California contains -4i, t >. 4'.i7, anil vol. 7. Hs. PRINCIPAL DISTRICTS COMPARED. and is certainly far from being exhausted ; on the contrary, in the metliod of exploitation followed, large pillars of ore are left as reserves. The con- tents of these reserves would be sufficient to yield the usual product for very many years to come, but no autlionUiUve statement of the total amount of metal contained in them has been made. The total recorded yield is nearly four million flasks. The deposits of Idria wore discovered, according to some authorities, in 1490; according to others, in 1497. Since 1580 they have been worked by government officials for public account. The mines and reduction works are extremely well managed, and the greatest additions which have been made to the technology and geology of quicksilver have come from this establishment. The mine is worked at a large profit, and in 1880 the director, that eminent mining geologist, the late M. V. Lipold, stated with evident and justifiable pride that the average clear profit to the state for the preceding sixty -five years had been 3(55,000 florins 1 per annum. The profit in 1874 lacked but a few thousand of 2,000,000 florins, and in only three of the sixty-five years was there a deficit. As at Ahnaden, the deposit grows stronger in depth, and in 1880 the reserves were known to contain no less than 30,142,000 kilograms, or 873.504 flasks of 75 Spanish pounds. The total known product up to January, 188(5, is over a million and a half of flasks; but no data were preserved for some forty years during the term which had elapsed since work began. The product of Idria lias been about three-eighths of that of Almaden. In northern Italy, at no great distance from Idria, are several deposits, of which the principal is the Vallalta. There is also a series of mines in Tuscany stretching along the western coast of Italy. Some of the de- posits arc of considerable commercial importance. The product is given I iv Mr. A. d'Achiardi as follows, in kilograms: Tuscan IIUIH-M . 1800. 3, 500 30,256 1870. if., (mil 31,192 1878. 3,080 1879. 129, COO 2,464 1880. nr>, 94D 1 Austrian paper money. A florin, silver, is $d.-l- J 7-'. The value of paper fluctuate)*. At 15 eeuts the above yearly profit would be sit',1, >:>(). 6 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. This table serves to show how the quicksilver mining industry has been transferred from Vallalta to Tuscany. The sum of the products here given for five years is 13,087 flasks, Spanish standard, or an average of 2, 01 7 flasks a year. From 1850 to 18GO ihe average was probably con- siderably lower. Since 1880 it has been greater. 1 The ore deposits of Huancavelica, in Peru, were discovered soon after the invention of the amalgamation process. There are over forty deposits in the district, but the principal mine was the Santa Barbara. This mine was sometimes worked by the state and was sometimes leased to private parties on condition that the metal obtained should be made over to the state at a fixed price. Stealing, however, was prevalent to such an extent that merchants flocked to Huancavelica with no inconsiderable sums of money to buy from miners and foremen the metal which it was their duty to turn into the treasury. The technical management seems to have been as bad as the business administration of this property, and there can be little doubt that skillful and honest work would have secured a far larger total output, With all disadvantages, the Santa Barbara mine alone yielded to the state about as much quicksilver as has thus far been produced in California. Of the mines of Kwei-Chau, in China, very little is known. Baron von Richthofen, however, a most excellent judge, believed this district to be the richest quicksilver region in the world. Table of products.. I have thought it worth while to bring the figures repre- senting the known production of the more important quicksilver regions together for comparison in the following table. The figures for Almaden are taken from a memoir by Mr. II. Kuss 2 and data furnished by Mr. J. B. Randol. 3 In Mr. Kuss's table of product for 1800 to 1875, there is a misprint amounting' to 1,000,000 kilograms. Mr. Randol's data prove that the total for this period given by Mr. Kuss is correct and that the misprint is between 1 soo and 1850. The product of Almaden for 1 885 was 47,021. flasks. The 1 According to data furnished to me l>y the superintendents of the Siele and the Cornachitio mines (the only oues at work, so far as I can ascertain, in Tuscany), the average product for the five years 1881 to 1885 was 5,789 flasks. The product for ls-if, was 7,478 ilastks. 'Anuales den mini's, vol. 13, 1878, p. 150. 'Mineral Resources IT. S. 1883 and 1884, p. 492. PRODUCTION. 7 data for Idria up to January 1, 1880, are from an official publication. 1 The amount of quicksilver definitely known to have been produced in the six- teenth century is 2,934,000 kilograms. "At the beginning of the seven- teenth century the production rose, aml r beginning with 1612, the product was for some years 1,680 metrical centals annually. During the later years the average yearly product was 1,120 centals." I shall assume that this latter and smaller output extended over seventy years. This assumption, in combination with the figures just given, leads to the total product prior to 1800 which appears in the table. The production of Idria from 1800 onwards is from exact official figures. 2 The data for Huancavelica are taken from Mr. M. E. de Rivero's memoir on the district. 3 The data from 1571 to 1790 are for the Santa Barbara mine alone, from which the state received 1,040,469 quintals 30 pounds 15 ounces dur- ing this period. The known product subsequent to 1790 includes other mines as well as the Santa Barbara. Product of the principal dint rifts, in Spanish flasks of 75 Spanish pounds or 34.507 kilo- gramg. First record. Up to 1700. l~UOto 1800. 1800(01850. 1 .-'Mi to 1880. Total to Jan., 1886. Year. 1564 517 084 1 22] 477 1 091 975 1 135 576 3 965 812 Idria 1B28 S99 861 608 743 349 99g 301 549 1 552 379 1571 881 867 543 64 9 75 604 1 501 113 1850 1 429 346 1,799,412 2, 373, 862 1,408,905 2, 806, 471 8, 448, 650 Discovery of California deposits. In the last century Mexico was almost entirely dependent upon Spain and Peru for the quicksilver needed for the amalga- mation process. As this process was indigenous to Mexico and was also a national industry peculiarly suited to her resources, it was felt to be specially 1 Das k. k. Quecksilberwerk xu Idri.i in Krain, 1881. 4 In tins memoir already referred to, Lipold gives the product of the mine from 1800 to the end of 1879 at 78,430 metrical centners, which is ^27,43-2 flasks. The present director, Mr. Job. Novak, has been good enough to supply me with the following figures, in flasks: 1880. 1881. 1882. 1883. 1884. 1885. 1886. Product of Idria 10 510 11 333 11 65 D Memoria sobre ul rico mineral de azoguo do Ituaucavelica, Lima, 1848. UNIVERSITY 8 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. desirable that quicksilver mines should be developed on her own soil. Accordingly, as far back as 1783, quicksilver mining was made the subject of special legislation. A quicksilver fund was established out of the public revenues for the purpose of promoting the discovery and development of quicksilver mines. On every hundred weight of the metal produced a bounty was paid, and a large sum was offered to those who should succeed in pro- ducing a specified quantity annually. 1 Not only are there many skillful miners and prospectors in Mexico, but so universal is the interest in the subject that a knowledge of ores has become almost instinctive among Mexicans. It would be supposed that, when their natural acuteness in mineralogy was sharpened by the promised rewards, some of the many cinnabar deposits of California would have been discovered within a few years after the promulgation of the edicts of 1783; but this did not happen for more than sixty years. It has been asserted that the California Indians knew of the cinnabar of New Almaden and used it for paint long before the Spanish-American immigrants became acquainted with it. The evidence on this point seems to be quite inconclusive, and it is not impossible that the incident is bor- rowed from the history of Peru, where, as all historians are agreed, the subjects of the Incas were familiar with the use of vermilion. The same story has been related within a few years of Nevada Indians. It is hard to say whether it is more probable that the aborigines repeated the same series of discoveries in personal adornment at these three points or that the whites have forced the same characteristic anecdote into service a number of times, with changes of names and dates. It has also been assorted that the Spanish Californians excavated cinnabar at New Almaden and used it to paint the mission church at Santa Clara. The occurrence was certainly known as early as 1824, when Antonio Sufiol and Luis Chaboya erected a mill on a neighboring stream and endeavored to extract silver from the cinnabar. A second attempt of the same kind was made in 1835. Late in 1845 Andreas Castillero, a Mexican officer who was on a journey to Slitter's Fort, passed through Santa Clara. The mysterious ore was shown to him, and he is 1 The notes on tlto history of tin; discovery of quicksilver in California urr derived from the testi- mony in the case of The I 'mini States ''< s '- Andreas Cast! Hero, disci dod by I lie Snin'eine Court, December term, ISfri. (Black's S. C. R., vol. 2.) DISCOVERY OF NEW ALMADEN. 9 said to have visited the mines. He shortly afterwards returned, and what occurred, according to the testimony of Jacob P. Leese, is so curious and interesting- as to be worth ([noting: About the latter part of November, ofHrst of December, 1845, I went into the mission of Santa Clara to dine with Padre Real, of the mission. Mr. C.istillero was there. Our general conversation through dinner was about this mine and of experi- ments which Castillero had beeu trying to find out what the mineral was. He made a remark and said he thought he knew what it was. If it was what he supposed it was he had made his fortune. We were anxious to know what it was. He got up from the table and ordered the servant to pulverize a portion of this ore. After it was pulverized he ordered the servant to bring in a hollow tile full of lighted coals. He took some of the powdered ore and threw it on the coals. After it got perfectly hot lie took a tumbler of water and sprinkled it ou the coals with his lingers. He then emptied the tumbler and put it over the coals upside down ; then took the tum- bler off and went to the light to look at it; then made the remark that it was what he supposed it was "quicksilver." He showed all who were there the tumbler, and we found that it was frosted with minute globules of metal, which Castillero collected witli his linger and said it was quicksilver. He then said to-morrow he would test it thoroughly and find out what it was worth. He considered it very rich on account of the weight of the ore, and if it proved as rich as the quicksilver mines in Spain, that the Mexican government had ottered to any one for the discovery of such a mine in the Republic of Mexico one hundred thousand dollars. Like so many Mexican practices, this test has a very quaint and medi- eval character, but it was nevertheless founded upon correct principles and was calculated to afford a demonstration of the presence of quicksilver without the use of reagents which were, perhaps, inaccessible to Castillero. Ity the use of glowing coals and water he effected a steam-roasting of the ore, which was sure to liberate metallic mercury if cinnabar was present, and the cold wet tumbler acted as an efficient closed condenser. The test was, in fact, equivalent to the ordinary blow-pipe test in a closed tube, the action of alkaline reducing agents being replaced by that of steam. Castillero laid claim to the property as a mine containing silver, gold, and quicksilver. He either had difficulty in thinking of a mine contain- ing no precious metals or thought it expedient to make his claim sufficiently broad. There was nothing unnatural in the association, for the three metals are found together at almost innumerable points in America and Europe. In the opinion of the Supreme Court of the United States, indeed, this as- sociation constitutes an inconsistency which tended strongly to impair the validity of the entire claim, but judicial geology is well known to belong 10 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. to a special school. Work was begun almost immediately under Castil- lero's direction, gun-barrels being used ;is retorts. These insignificant reduction works have now grown to very imposing dimensions, but the ijiiantity of ore in sight is no longer so satisfactory. The other deposits of California have been found in part by systematic prospecting and in part by accident. The Redington mine was discovered in making excavations for a highway. The Sulphur Bank, as its name im- plies, was worked for sulphur for some time before the presence of the un- derlying cinnabar was suspected. The very high prices which quicksilver brought in 1X74 and 1X75 greatly stimulated production and the discovery of deposits. None of those found grows richer as depth from the surface increases, but most of them are very imperfectly developed, and, as will be shown in subsequent chapters, this feature depends upon peculiarities of the systems of fissures connected with the ore deposits, not upon characteristics of cinnabar. It is by no means impossible that great deposits of cinnabar, comparable with those of Idria, if not with those of Almaden, still exist in California. None such, however, is now known and the amount of ore in sight is not great. production in California. The following table of production of the mines of California has been compiled from year to year by Mr. J. B. Randol and is well known to those interested in the subject. PRODUCT OF CALIFORNIA. 11 Production of quid-nil rcr on the Pacific Slope, in flasks o/"7>i pounds avoirdupois. Years. J < d ^ r New I.lrin. | te .9 1 Sulphur Bauk. | J - . Great "West- iiu. Pope Valley. l| a-o S , Q M o HI ^ 4 I 5 1850 . 7 ~-.\ = ( } rt ' fW <* 1851 '^7 779 1 P. 1 tJ a a 1H52 in 901 2 a g_C 18J3 'VI -1^ ! r a il lh.-,l .- " I- " ij il 1855 29 U" *"5 3! *a 185G 7 138 1 = 1857 28 04 ?-i t jrl ?1 1858 r> 7111 I-oi.2-, - = = ^ > || 1859 1,294 .'. " i. 11 |a I860 7 Otil ~i| si 2 18CI 34 429 If! ^3 A 1802 39 671 a o 444 *'t ^g 1863 32 803 ' III 852 P"-" 1864 42 489 = SS 1 914 c-a 800 00 " m 1865 .... 47 194 5 %. 1 ~ 3 545 || 2 1806 35 150 6 55 2 '54 c~ S3 1867 24, 461 11 4:i 7,862 >5 .- *a 1868 25, 628 1" VI) 8,686 U 1 122 E 1869 16, 898 ]o :Mr> S, 018 |4 1 580 1 fe * 1870 14, 423 9 KXK 4, 516 || 1,220 1871 18,568 8 180 2 128 !* 1 970 "2 a 1872 is r,7i 8 171 3 046 p. ] 830 IBS S a S 1873 11,042 3,294 340 1 955 ?S 1874 9,084 6 911 6,678 573 1 1 12' 1 645 1 743 |S.? 1875 13, 648 8 432 7,513 5 372 3 342 3 3M 1 940 1 927 533 1876 20 549 7 <>7o 9 183 8 367 7 381 4 32 1877 23 906 6 316 9 399 10 993 6 241 1878 15, 852 5,138 6,686 9,465 9,072 4 963 1 075 3 049 1 534 1879 "0 514 4 4"5 4 S16 9 249 15 540 6 333 1 3 OI > 1880 . 23 465 3 "09 2 139 10 706 6 67 n 6 442 27 r i 1881 26, 060 2 775 2 194 11 152 5 228 6 241 5 55 1882 28 070 1,953 2 171 ;"j Oil 1 138 5 179 6 812 28,00* i i;i'.; I,SM 2,612 84 3,869 5 90 1684 20, OlO 1, 025 881 890 1,179 3,292 4 307 1885 21 400 1 144 J 385 1 296 35 3 469 1886 18,000 1,406 409 1,449 1 949 5 247 Total ... 853,259 ' 126, 099 97, 637 77 138 55 910 56 761 18 097 45 216 1 Including .Ktn;i. 12 QUICKSILVER DEPOSITS OF TEE PACIFIC SLOPE. Production of quicksilver on the Pacific Slope, in flasks o/7Gi pound* a STenrs. Oceanic. Oakland. California. Great East- ern. Snnderland. Cloverdale. Abbott. Manhattan. Various mines.' Total yearly production of Califor- nia mines. S t 7,723 8 27, 778 a 4, 099 20, 000 OO OQJ I ::n, 1104 . 3 e5K 33, 000 .5 2, SO'.' 30, 000 1 2X, 1:0-1 S3 5,239 31, 000 > 11.7CIC 13,000 2~ 2,939 lll.OOi 2 S 571 35, 00. It 1, 8*5 42, OC( o-S > 6, K7G 40, 5J 1864 S ^ 2,280 47, 48i 2,201 53, 00( 5 I 2, 621 46, 55( 1867 11 3, 1K4 47, 00( > c B ns 47, 72* a 33,81 C rt 30, 07' 840 81,881 1 31 6-> 1873 p. 3, 'J7fi 27, 041 '.'7, 75( 1875 412 0) |M 3,747 so, -:,( 1876 2,358 2,160 9f5 387 1,570 1.0J8 1,436 976 2,585 75, 07< 1877 2, 575 1,385 1,516 505 735 1,291 830 439 1,234 79, 39t 1878 1 679 1 (J'5 1 610 1 366 472 116 158 C3, K( 779 1 110 1 455 18 101 73,68- 166 422 1 *>79 59,92 1881 1 065 208 376 60, F5 1882 2 124 211 52, 73 1883 1 609 lul 40, 72 1884 332 7 31,91 1886 89) 32, 07 1886 735 780 29,98 Total 7 391 6 831 5 653 11, 775 2, 777 2,661 2, -Hi 1,415 64, 353 1,451,37 1 'The column of various mines includes the product of the Buckeye, Mt. Jiirkxiiti, Huron, Ite.lla Union, American, Porter, Wall Street, Rattlesnake, Kentuck, and other mines. This column includes, iu 1882, 50 flasks produced in Oregon. GEOGRAPHICAL POSITION. 13 Geographical position of mines. The following list will enable the reader to find some of the mines mentioned in the preceding table, as well as others to be referred to later, on the sketch-map of California (PI. I) and to appreciate approximately the geographical position of others: Distribution of quicksilver mines. (Mines marked M are iu the Mayacmas district.) Abbott, Colusa county. Altooua, Trinity count}'. American (M), Lake county. Bacon (M), Lake county. Bella Union, Napa county. Buckeye, Colusa county. California (Reed), Yolo county. Cerro Bonito, Fresno county. C'lovcnlalc (M), Sonoma county. Euriquita, Santa Clara county. Guadalupe, Santa Clara county. (Ircat Eastern, Sonoma county. Great Eastern (M), Lake county. Great Western (M), Lake county. Kentucky (M), Sonoma county. Little Panocbe, Fresno county. Los Prietos, Santa Barbara county. Manhattan, Napa county. Man/anita, Colusa county. Mt. Jackson, Sonoma county. Napa Consolidated, Napa county. New Aluiaden, Santa Clara county. New Idria, Fresno county. Oakland (M), Sonoma county. Oceanic, San Luis Obispo county. Ocean View, San Luis Obispo county. Picacbo, San Benito county. Pope Valley, Napa county. Rattlesnake (M), Sonoma county. Redington, Napa county. Reed (same as California), Yolo county. San Juan Bautista, Santa Clara county. St. John, Solano county. Stayton, San Benito county. Steamboat Springs, Ormsby county, Nev. Sunderland. San Luis Obispo county. Wall street (M), Lake county. Other interesting statistical information with reference to quicksilver may be found in the Mineral Resources issued bv the U. S. Geological f O Survey. CHAPTER II. NOTES ON FOREIGN OCCURRENCES OF QUICKSILVER, There are few districts besides those of the Pacific Slope in which mer- curial ores are met with in such abundance as to be of great commercial importance. The Almaden mines, in Spain, take the first rank, and those of Idria, in southern Austria, have yielded and will continue to yield a con- siderable product. Several thousand flasks a year are also extracted from the Tuscan mines. China now produces little quicksilver, though she for- merly exported it, besides supplying the home demand. This is not due to the exhaustion of the mines, and there seems to be good reason to suppose that the deposits of Kwei-Chau are of great extent and value. Peru has yielded very large quantities of quicksilver in former times, but the mines are in part exhausted and in part have been ruined by bad mining. While the number of highly productive localities is small, the localities in which ores occur are very numerous, and many of these have been of temporary or local importance. The geological interest attaching to a locality is not dependent upon the amount of metal which it has furnished to the markets of the world, but upon the relations between cause and effect which the occurrence serves to elucidate, and a brief review of the deposits known to exist away from the Pacific Slope will form the fittest introduction to the subject of this memoir. It will appear in the subsequent chapters that nearly every mineral association and mode of occurrence known to exist elsewhere is repeated in California and Nevada, so that the mercurial deposits of the Pacific Slope admirably represent those of the world so far as they are known. I have made no systematic endeavor to exhaust geological literature with reference to foreign occurrences of mercurial ores, though it is certain that no very important deposits have escaped me. I have sought to compile 14 IT. S . GEOLOGICAL SUKVEY. 180' ISO' IMP' 130 I2O 110 100' 90' 80' ' 60' SO* 4O* 3O" SO DISTRIBUTION OF Q TH HOI' OHO I Districts which are or have bi-rn pi-odnctivc llislrii-l MONOGRAPH XIII, PL. II. II,- jo- go' 'iO So' 60 10' flu 90* 100' 110* J0 130' 1W 1*0* 160' : K s i L.V.K R D T: POST r i^ s ;THE: WOULD which OIT has been clrU-cledO C ouucrtin^' lines OftO.K Becker, Geologist in charsfe. 01 UNIVERSITY NORTH AMERICAN LOCALITIES. 15 notes on comparatively little-known deposits rather than on those which have been most frequently described, and I have altogether omitted a con- siderable number of unimportant occurrences in Germany and Austria, de- scriptions of which are readily accessibte-in standard works on mining geology. Two reviews of the quicksilver deposits of the world have been of great use to me. These are by Mr. A. Noggerath 1 and Prof. A. d'Achiardi 2 respectively. The sketch-map of the world (PI. II) accompanying this chapter will be of some assistance in following the text, but its principal purpose is to illus- trate the larger features of the distribution of cinnabar. NORTH AMERICA. Away from the Pacific Slope the United States possesses no known deposits of cinnabar. There is, indeed, a settlement named Cinnabar near the Yellowstone Park, but I am informed that no mercuric sulphide has been found there. A telluride of mercury, coloradoite, is found with tel- lurides of gold and silver and with free gold in some of the mines of Boulder county, Colo , but only in small quantities. 3 In notices of the distribu- tion of quicksilver the statement has often been made that cinnabar is found in Connecticut in river sands. I have not found a citation of tlie original O authority for this statement. Prof. J. D. Dana writes me that he knows of no such occurrence, and it is safe to assume that no discovery of cinnabar could have been made near the home of this famous mineralogist without coming to his knowledge. Towards the beginning of the century cinnabar was reported at nu- merous points iu the Eastern States; it was even said to be very abundant in the beach sands of the Great Lakes. Had these assertions been correct they certainly would have been confirmed. Gold amalgam has been found at Plymouth, Vt,, and the native copper of one of the mines at Lake Su- perior is said by M. Ilautefeuille to contain a little mercury. 4 r. fur HITJJ-, IIiittc.ii- mill Salinenwesen im preuss. Staate, vol. 10, 18(W, p. :irfti. 1 1 ntrlalli lin-o mineral! e miuiciv, vol. 1, 183:i, p. 100. 'Kiimioiis ami Kcckcr : Statistics and Technology of tbe Precious Metals, Tenth Census Repts. U. S., vol. 1:5, p. iii;. 4 Geological Survey of Canada, Otology of Canada, 1803, p. 518. 16 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Nova scotia. In the auriferous region of Nova Scotia cinnabar and native quicksilver are said to have been found at .Gay's River and globules of the metal were washed from a soft slate at Waverley. 1 There is certainly nothing improbable in these reports, for cinnabar and mercury occur in many of the gold fields of the world. same Domingo. Mr. W. S Courtney 2 quotes "an English writer about the close of the last century" as stating that there is "mercury at the head of the river Yaque." Mercury is also enumerated among the minerals of Hayti by Mr. J. D. Champlin, jr. 3 In Mr. Gabb's memoir on Santo Do- mingo I find no mention of this metal. Mexico. Ores of quicksilver occur at a great number of localities in Mexico, the number of deposits being estimated by Prof. A. del Castillo at not less than fifty. He is also of the opinion that the country is capable of yielding annually the 2,000,000 or 2,500,000 pounds necessary for home consumption. 4 Most of the mines appear to be unsatisfactory, however, for in 1882 but one quicksilver mine was in operation. 5 Quicksilver ores occur in the following States of Mexico, arranged as nearly as may be in the order of their latitude : Chihuahua, Durango, Zacatecas, San Luis Potosi, Guanajuato, Queretaro, Hidalgo, Jalisco, Mex- ico, Morelos, Guerrero, Oaxuca. Those of Guadalcanal 1 , in the State of San Luis Potosi, and of Huitzuco, in the State of Guerrero, are the most im- portant. 6 According to Mr. D. de Cortazar 7 quicksilver ores in Mexico occur in primary, transition, secondary, and tertiary strata, but are found every- where near eruptive rocks. Humboldt describes one deposit as forming a vein of considerable width and length "in veritable pitchstone porphyry." The walls of this vein were impregnated to some extent, so that traces of cinnabar and metallic 1 II. How: Mineralogy of Nova Scotia, Hi! 1 .*, p 61. "The Gold Fields of St. Domingo, 1800, p. 119. 3 Eucyc. Brit., 9th c.d., article Hu.vti. 4 A note communicated to tin- Mining and Scientific Press, San Francisco, January 1G, 1875. I re-, gret not having liccn able to obtain a rojiy of this author's work, Momoria sohru las minus de azogue de America, 1872. 6 On the authority of Mr. Lorenzo Castro : Eucyc. Brit., article Mexico. 6 S. Ramirez: Uiqtiuza iniucni de. Mexico, p. 91. 'Repts. Phila. luternat. Exh. 1876 to Parliament, vol. 3, London, 1S78, p. 389. MEXICAN LOCALITIES. 17 mercury were observed in the porphyry at considerable distances from the vein. 1 At Durasno, between Tierra Nueva and San Luis de la Paz, in the State of Guanajuato, he inspected a cinnabar deposit forming a layer 2 rest- ing on porphyry. The cinnabar deposits in the mining district of Guadalcazar were dis- covered in 1840. Though they are numerous they appear to be of no great value, for in 1874 they were not yielding enough quicksilver to sup- ply the demand in the state in which they lie. 3 This district forms the subject of a paper by Mr. Ramirez, 4 from which the following notes are taken. The country rock of the district is chiefly limestone, with a few intercalated beds of shale. The rock is compact and usually of a bluish- gray tint. No fossils are known to occur in it, nor does it stand in such relations to other strata as to render a stratigraphical determination of its age practicable. It is supposed, however, to be Cretaceous both by Mr. Ramirez and by Mr. V. d'Aoust. 5 The region also contains granites and porphyries; the latter inclose deposits of silver ores, but the quicksilver ores are confined to the limestone in the district in which this metal has been exploited. According to Noggerath, however, cinnabar with pyrite and galena is also found in granite in this region. Ores of quicksilver occur at numerous points along a belt nearly forty miles in length (sixty kilometers), which extends to the northwest of Guadalcazar. The deposits occur mainly as layers in the limestone, but 'Essai politique sur le royaume de la Nouvelle Espagne, p. 585. The vein is called the San Juan de la Chica. It traverses the mountain of the Calzoues and extends to Chichimlara. I have not been" able to find these localities on the maps. 2 I shall use this word to translate the term man to, which does not seem to correspond to any ex- pression recognized in English or German mining technology and seems also to bear a somewhat vari- able meaning among Spanish-American miners. Humboldt (ibid., p. 584) defines manto as " une couche horizontale," but hori/.ontality is certainly not a necessary attribute of inantos as the term is used by Spanish-American mining geologists. Rivero, in describing the deposits of Huancavelica, re- peatedly uses the expression manto 6 capa, and capa is the term employed for a stratum of sediment- ary rock. According to F. A. Moesta (Ueber das Vork. ;ler Chlor-, Rrom- nnd lodvorbindnngen, p. 25), the Chilian miners use this word to describe any layer or sheet of mineral, irrespective of origin, so that strata of sedimentary rock and veins crossing strata, as well as dikes, may all be called mantos. Rivero, however, makes a sharp distinction between veins and raantos, and both he and the Mexican geologists seem to mo to understand by manto either an ore-bearing stratum or a deposit resembling a stratum, such as a bed-vein, irrespective of the question whether or not the ore deposition has accom- panied sedimentation. No doubt the term is much more loosely used by miners. 3 Castillo, loc. cit. 4 Anales del ministerio do fomento, Mexico, vol. 3, 1877, p. 339. "Comptes rendus Aead. sci., Paris, vol. 83, 1876, p. 289. MON XIII 2 18 QUICKSILVER DEPOSITS OF THE PACIFIC! SLOPE. irregular networks of veins, or stockworks, are also found. The limestone forming the immediate walls of the layers differs from that which is more remote from the deposits, the rock at the contact tending to assume a blackish color and a compact granular structure. The deposits are ordi- narily separated from the country rock by a deposit of gypsum. 1 The chief ore is cinnabar, often hepatic and sometimes accompanied by the seleno-sulphide guadalcazarite, first described by Mr. del Castillo from this locality. Calcite and fluorspar are the gangue minerals. Native sulphur occurs with the ore in the principal vein of the district, the Trinidad. This appears to me to suggest the recency of the deposit and its deposition from hot sulphur springs; for most native sulphur is certainly formed by the decomposition of hydrogen sulphide in contact with air. Mr. Ramirez sup- poses the sulphur formed by sublimation; but I do not find in his descrip- tion any evidence of the former prevalence of very high temperatures, and the presence of calcite and fluorspar indicates deposition from solutions. The deposits of Huitzuco, about fifty miles north of Tixtla, in the State of Guerrero, were discovered in March, 1874. The geology and the deposits of mercury, silver, lead, and other metals of this state have been described by Mr. T. L. Laguerenne. 2 Granite seems to underlie the coun- try. Upon it rest metamorphic rocks, including serpentine and eruptive masses. In the neighborhood of Huitzuco the rocks are metamorphic slates and limestones which have been much disturbed. The cinnabar deposits are mainly pockets of various dimensions and layers, but veins also exist. The deposit of Tepozonalco is a vein (veta) between slate and limestone, both rocks being metamorphosed and disturbed. The ore is argentiferous and is distributed through the entire vein matter. The ordinary ore of the district is livingstonite, a sulphide of antimony containing mercury. Cin- nabar is said also to form pseudomorphs after stibnite. 3 Prof. F. Sandberger has given a very interesting account of specimens of ore sent to him from Huitzuco by Mr. F. Velten. They represent a series from fresh stibnite to pseudomorphs of cinnabar after stibnite, containing only 1 1 suppose this mineral to result from the reaction of iron sulphate, produced by the oxidation ot pyrite, on the limrstnnr walls. 2 AnaIes del ministerio do fumento, Mexico, vol. 7, 1882, p. 605. 'Vi-lten and Lehnianii: Siljuin^shrr. k. liaj-cr. Akad. Wi.su., vol. >, Munich, 1HIJ7, p. yO'.i, cited by d'Achiardi, SOUTH AMERICAN LOCALITIES. 19 traces of antimony. The first step is an oxidation of stibnite to stibiconite, accompanied by a more or less complete impregnation with black, amorphous metacinnabarite. The transformation of the whole mass to cinnabar follows. The change from black to red sulphidels~considered as due to the probable solubility of mercuric sulphide in calcium sulphide. Quartz and gypsum are the gangue minerals. 1 At Chilapa also, near Tixtla, cinnabar occurs in a well defined vein in metamorphic slate. Quartz and iron oxides constitute the gangue, and the vein matter incloses fragments of country rock. In places the quartz is stained with copper. Cinnabar impregnates the entire width of the vein. At San Onofre mercurial ores occur under conditions similar to those at Guadalcazar; near San Felipe are veins of cinnabar in porphyry; near Guanajuato deposits of cinnabar and mercuric iodide occur in Tertiary clays and conglomerates ; at Loma de Encinal veins of cinnabar exist in decomposed porphyry; and rich mercurial deposits are said to occur at Maltrata, In 1876 Mr. Geo. T. Walker, reporting in manuscript on the Guanacevi district, in the State of Durango, calls attention to the fact that, in the La Colcrada silver mine, ores containing cinnabar occur close to the hanging wall of the vein. This occurrence has a parallel in this country near Belmont, Nev. Guatemala. According to Noggerath, a specimen of cinnabar from Gua- temala, accompanied by barite, exists in Berlin. I have met with no other mention of quicksilver ores in Central America. SOUTH AMERICA. Colombia. Mr. R. R. Hawkins, of my staff, found native quicksilver disseminated in globules in a clay soil near the town of Graces, on the Isth- mus of Panama. He also found float cinnabar near the Magdalena river, in the State of Tolima. " Near Choco," probably the bay of that name, " gold amalgam and platinum are found together." 2 Humboldt mentions cinnabar as occurring in the province of Antioqu'ia, in the valley of the Santa Rosa, to the east of the river Cuaca, and also between the towns, Ibague and Carthago. 1 Sit/uugsber. k. bayer. Akart. Wiss., Munich, July 3, 1875. Noggerath, loc. cit. 20 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Ecuador. Near the town of Azogue (Spanish for quicksilver) cinnabar occurs in veins in the more ancient sandstones. Between this point and Cuenca, at which quicksilver has also been mined, fragments of cinnabar are found with gold in gravels. Deposits similar to those of Azogue are worked within the city of Loja. 1 Peru. Of late years Peru has yielded no considerable quantities of quicksilver, though it was formerly one of the great quicksilver-producing countries of the world. The most northerly deposit is that of Clionta, 2 in the western Andes, close to the frontier of Ecuador. Mr. BugdolP de- scribes the deposit as a bed in early Paleozoic rocks. It is composed of clay, sand, pyrite, and cinnabar. The ore impregnates the sandstone foot- wall to some extent. In the direction of the strike the ore is replaced by pyrite. Veins of lead ore cross the cinnabar deposit nearly at right angles. In the Santa Apolonia Mountains, near Cajamarca, globules of quick- silver occur in trachyte. Specimens were exhibited at Paris in 1878 in the fine collection of Mr. A. Raimondi. 4 Humboldt notes the appearance of quicksilver at Vuldivui, " in the province of Pataz." There is now no such province, and I presume the locality to be near the town of that name. The same geologist states that cinnabar is found at the Baths of Jesus, to the southeast of Guacarachuco (probably another form of the name Huacrachuco). These baths are no 1 H. A. Webster: Encyc. Brit., article Ecuador. * The deposits mentioned in Peru being somewhat nurue'roiis, the following table may be convenient to readers. The latitudes are only approximate: Localities. Provinces. Latitude. Chonta 1 Cajamarca Pataz Libertad Huacrachuco. Caraz Santa Huaraz Cerro de Pasco Tauli Huancavelica Ayaviri 14 40 3 Zeitschr. fiir Berg-, Hiitten- uitd Salinenwesi'ii im prc.iias. Staatr, vol. 10, 1802, p. 3'J1. , p. 1231. 32 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. carrying cinnabar exists in slates supposed to be Silurian in the Sierra de Montenegro, which is the eastern end of the great Sierra Nevada. Cin- nabar and silver amalgam, containing G per cent, of quicksilver, perhaps kongsbergite, occur near Culvas de Vera, in the province of Almeria. Copper and lead ores occur in the same neighborhood. At Aquilas, on the boundary between Murcia and Almeria, quicksilver ore was found and a furnace was started, but is not now in operation. Near the famous lead- mining town of Linares, in the province of Jaen, cinnabar occurs along the partings between strata. Cinnabar occurs at La Creu, in the province of Valencia. I have had an opportunity of examining a series of specimens from this locality in the museum of the Technical High School of Aachen. The country rock is sandstone. The gangue minerals are quartz and carbonates, with which the cinnabar is intimately mingled. Pyrite is also abundant. The ores occur in veinlets in the rock, and some of the cavities have not been com- pletely filled. The absolute impregnation is slight. Cinnabar is also found, according to Noggerath, in the province of Teruel, in a cupriferous quartz vein, and the same sulphide has been recog- nized in the provinces of Castellon and Alicante, on the east coast of Spain. Finally it occurs, according to the same authority, in western Spain, in the province of Badajos. The Almaden district is close to the boundary of Ciudad Real and Badajos, and a small part of it lies in the latter province. Excepting at this point I could learn of no occurrence in Badajos. France. No important quicksilver deposit has ever been opened in France, though during the last century quicksilver ores were mined at Menildot, in the department of Manche, in northeastern France. This mine had a considerable production from 1730 to 1742. 1 A mine is said to have been worked recently at Prunieres, in the department of Isere, somewhat over twenty miles from Grenoble. This statement, however, is erroneous. Mr. II. Kuss, of the French mining service, who is stationed at Grenoble, writes me that, from 1850 to 1854, explorations were made at this locality, but without success. The principal vein carried small quan- tities of blende, calamine, tetrahedrite, and galena, and the vein matter was 1 Burat : G6o\. appl., vol. 2, p. i:;i>. FEENCH LOCALITIES. 33 sometimes stained bright red with finely-disseminated cinnabar, particularly in the neighborhood of calamine. The gangue was calcite and the inclosing rock was dolomitic limestone of the Lias. The veins were very irregular and before long disappeared altogether. The proportion of cinnabar was always very small and no metal was produced. At Chalanches, in the same department, it is found with sulphides of lead and zinc in veins, in- closed by crystalline schists which contain traces of platinum. At Alle- mond, also in Isere, cinnabar, native quicksilver, and silver amalgam occur in a vein. In central France, at Peyrat, in the department of Haute- Vienne, native quicksilver is found in a decomposed granite. In and near the Cevennes Mountains, also in southern France, native quicksilver occurs (e. g., near Montpellier) in Tertiary or Quarternary beds. This locality was discovered in 1760. The regions in which quicksilver has been found in France also con- tain other metals, as is not unusual in other countries. In Manche, blende, calamine, and galena are found; in Haute-Vienne, lead, antimony, and tin; in Isere, lead, silver, and gold; in Hdrault and Aveyron, tetrahedrite and galena. 1 On the island of Corsica cinnabar is said to occur in a state of great purity in the Balagna, in the territory of the commune Occhia and can- ton of Belgodere. 2 The Balagna is a district lying east of Calvi, on the north coast of Corsica, and its port is lie Rousse. Interesting deposits of cinnabar are found on Cape Corso, the northern promontory of the island. It is found with stibnite in granite (pegmatite), serpentine, euphotide, schists, and serpentiniferous limestone. With stibnite it forms crusts of a few cen- timeters in thickness occupying fissures in the rocks. The gangue, when there is any, is quartzose. Pyrite, a little blende, and native sulphur are found in some veins, and arsenic lias been detected. Mr. Hollande states that the fissures have been filled through the action of hot springs. 3 itaiy. Cinnabar is widely distributed in Italy and Sicily, though most of the occurrences are of very small importance. The northern part of the Venetian state is contiguous to Carniola, in which lies the Idria mine. 1 Burat: G6ol. appl., vol. 2. 2 Noggerath, loc. cit. 3 D. Hollamle: Bull. Soc gdologique France, 1675-1876, vol. 4, Paris, 1876, p. 31. JION XIII 3 34 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Both the Austrian and Italian portions of this region show many deposits of cinnabar, of which not a few have been exploited to some extent. The most famous of the Italian mines in this region is the Vallalta, near Agordo. 1 The deposit occurs at and near the contact between a mass of quartz porphyry and sedimentary rocks of Triassic age, consisting of sandstones, shales, graphitic slate, limestone, and a certain conglomerate. The deposit is irregular in width, but follows the porphyry and ends in strike with this eruptive rock. The cinnabar is found as impregnations in the porphyry and in the sandstone and as stringers in the shales, but the great mass of it is in the conglomerate, which does not seero to be found except in the deposit The matrix of the conglomerate is commonly tal-_ cose, and embedded in it are rounded pieces of gypsum, calcite, quartz, limestone, and porphyry. Small grains and stringers of cinnabar are scat- tered through the rock. The ordinary material of the deposit contains only two-tenths to 1 per cent, of quicksilver, but the impregnation of cinna- bar increases in some places to such an extent that the greater part of the ground-mass is ore, inclosing fragments of gypsum, calcite, and quartz, as well as foils of magnesian mica. Professor vom Rath estimated the metal- lic contents in such a case, from the specific gravity of the mass, at no less than 24 per cent. The deposit is intersected by numerous veins of cinna- bar, accompanied by seams of gypsum. The only sulphide accompany- ing the ore is pyrite, crystals of which are often embedded in the cinnabar. At the contact between the ore body and the graphitic slate metallic quick- silver was found. Professor vom Rath expresses no opinion as to the ori- gin of this deposit, but in the light of what is now knoM n of the occur- rence of quicksilver I should suppose that the ore had reached its position along a fissure at or near the contact between the porphyry and the adja- cent rocks. The so-called conglomerate would seem, from its constituents, to be more strictly a breccia formed by movements prior to the deposition of ore. The precipitation of gypsum and cinnabar must have been in part simultaneous, since some of the gypsum is reddened by admixture of ore. The occurrence of native quicksilver in contact with graphitic rock (and, so far as reported, there only) is suggestive of reduction. The copper depos- ilird liy (i. VOID Path: Zeitsclir. Driitscli. gcol. Gesell., vol. Hi, ti4, p. 121. ITALIAN LOCALITIES. 35 its near Agordo are in the same series of rocks and at no great distance. The production of the Venetian mines has never been large and of late years has become. insignificant. Some data are given in Chapter I. Traces of cinnabar are found in Loinbardy in quartzite, but the quantity is nowhere considerable. 1 In Tuscany numerous deposits of quicksilver occur in a belt about one hundred and twenty-five miles in length, running parallel to the west coast and at an average distance of about twenty miles from the ocean. The southern end of this series of deposits is at Mt. Amiata. The Levigli- ani mine, near Serravezza, at the northern end of the belt, was known as early as 1163. The cinnabar is accompanied by guadalcazarite, siderite, and pyrite in a quartz gangue and occurs in steatitic schists in small irregular veins. The chief mines of this belt are at its southern extremity. Amiata is. a great trachytic mass resting upon rocks which are Post- Jurassic and probably Eocene. They are for the most part calcareous. All around the edge of the lava and in the Eocene rocks occur quicksilver deposits, many of which have been exploited. Mr. B. Lotti also found cinnabar in the trachyte itself, near its edge, showing that the deposits are later than the eruption. The principal mine is the Siele, about five kilometers from Selvena. This, as described by d'Achiardi, is sunk on a stratum of marl many meters in thickness, which is impregnated with cinnabar. Stringers of calcite, spotted with cinnabar, are frequent in this deposit. The same author gives geolog- ical notes on several Italian mines not mentioned here. Cinnabar occurs at La Tolfa, not far from Civita Vecchia, associated with fluor-spar and blende. Xoggerath writes : "At Vesuvius the occurrence of quicksilver is very doubtful. Fr. Hoffmann, in his history of geognosy, speaking of the products of Vesuvius, says that among the metallic substances Dolomieu mentions also quicksilver and stibnite, but they have never since been found, as Breislack explicitly states ; hence an error seems to have been made here." On referring to Hoffmann's history- it does not appear to me that he intends to ascribe to Dolomieu the assertion that at Vesuvius he found quicksilver. 1 A. d'Achiardi, loc. cit. ^Geschichte der Gcognosie imd Schilderuug der vulkaniscLcn ErscbeiuuDgen, Berlin, ls'38, p. 477. 36 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. I think Hoffmann means to deny the opinion held by Dolomieu that quick- silver and stibnite are volcanic emanations. Dolomieu, in his treatise on volcanic products, 1 does classify these minerals as products of sublimation, but I have been unable to find any passage in his writings in which he men- tions having observed them at Vesuvius. In his Voyage aux iles de Lipari I find no allusion to the subject. It may be, ho wever, that in some of his less known writings he gives the facts upon which his opinion was based. Noggerath, writing in 1862, makes the comment that one may assent to Hoffmann's view of the matter the more readily because, thus far, quicksil- ver has nowhere been found in volcanic rocks, but since 1862 cinnabar and quicksilver have been often found in volcanic rocks, and cinnabar and stib- nite have frequently been discovered together. Prof. E. de Chancourtois, in his lectures at the-ficole des Mines, has been in the habit of showing specimens of cinnabar and realgar which he found at Pozzuoli, near Naples, at the opening of the principal fumarole, and which had been deposited from the jet of aqueous and sulphurous gases. 2 Cinnabar as a product of volcanic action thus exists near Mt. Vesuvius, if not upon it. Noggerath records six localities in Sicily in which traces of cinnabar have been found, but without any details as to occurrence or association. One of the localities, Paterno, ten miles northwest of Catania, is at the base of Mt. JEtna. It would be very interesting to know what relation this oc- currence bears to the lavas and hot springs which must exist not far from it. I have been unable to learn anything further about it. Germany. The quicksilver deposits of Rhenish Bavaria have lost all the commercial importance they once possessed, but not their geological interest. They have been very fully described by Prof. H. von Dechen 3 and a digest appears in von Cotta's Ore Deposits. It is therefore un- necessary to dwell upon them here. The deposits formed veins in rocks of Carboniferous age, and to some extent impregnations in sandstones. They were accompanied by a melaphyre (probably diabase), and ore was sometimes found in spots and cracks in this rock, but a connection between 1 Journal de physique, do chiuiie, d'histoire uaturelle et des arts, Jean Claude LainetLerie, vol. 1, 1794, p. 102. -Holland: Bull. Soc. uiineralogique, vol. 1, 1878, p. 99. 3 Archiv fiir Mineral., Karstcu, vol. 22, 1848. PALATINATE MINES. 37 its eruption and the genesis of ore was not established. The cinnabar was accompanied by pyrite, copper ores, and lead and silver minerals, but these were for the most part rare. The gangue was composed of calcite, quartz, chalcedony, and heavy spar, and bituminous matter was not infrequent. They were richest at the top and gave out in depth. It is an interesting fact that cinnabar occurred in these mines as a fossilizing mineral, having replaced organic remains, for this seems to prove that organic matter may precipitate cinnabar from solutions. Metacinnabarite seems to have occurred in these mines, for von Dechen 1 twice mentions among the ores Quecksilber-Mohr, though without any remark. This name is the German equivalent of 2Elliiops mineralis and means amorphous, black, mercuric sulphide, produced by grinding together metallic quicksilver and sulphur. It seems impossible that this geologist should have applied this designation without ascertaining the chemical character of the compound and very strange that he should have made no comment on the novelty of the mineral. Analyses and descriptions of this mineral, as it occurred at the Redington mine, were first published by Dr. G. E. Moore in 1870. It is curious that the Neues Jahrbuch, in reporting von Dechen's monograph, quoted his conclusions almost word for word, but omitted Quecksilber-Mohr from the list of ores. No other quicksilver mines, so far as I am aware, have been worked in Germany, though cinnabar and quicksilver have been detected at nu- merous points and a little of the metal has been secured in the course of the treatment of ores of other metals. The occurrences have so often been described that no detailed notice is necessary, but a few instances may be cited. In Bavaria, near Neustadt, cinnabar was found in masses of quartz inclosed in granite. In Saxony, near Lossnitz, it has been recognized in quartz inclosed in crystalline schists. In the Harz Mountains cinnabar occurs at numerous points. The Rammelsberg mine (iron and copper pyrites and galena) contains a small quantity of mercury. At Tilkerode and Clausthal tiemanite and mercurial clausthalite (lead selenide) are found. Cinnabar has been found in veins crossing early Paleozoic rocks, with heavy spar and siderite, in the Hiilfe Gottes mine. At Kreuznach and 1 Archiv fur Mineral., Karstcn, pp. 430 OT UNIVERSITY 38 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPK. other points in Prussia cinnabar occurs in veins traversing eruptive and .sedimentary rocks. These cases would lead one to suppose that cinnabar occurs in much the same manner as other metallic sulphides. Austria. TJic deposits of Idria were discovered during the closing .years of the fifteenth century. After a number of vicissitudes they passed into the hands of the state and have been worked by the government for public account ever since the year 1580. The geology of these mines is of great interest, for not only has it been studied with the closest attention by highly competent geologists daily for many years, but the occurrences are such as to throw much light upon the nature of the deposit and the method of genesis. Mr. M. V. Lipold, as a member of the Austrian Geological Surve}", examined and mapped the country surrounding the mines in 1856. In 1SH7 he took charge of the mines, and in 1874 published a memoir on the geology of the deposits and of the surrounding region. 1 In 1880 he wrote another paper upon the ore deposits. 2 From these memoirs the information given below is chiefly de- rived. In 1878 Mr. Lipold was good enough to accompany me through the mines under his charge. My stay was far too short to enable me to add any original observations to those which the director -had made ; but, since his conclusions appear from the literature not even yet to find entire accept- ance, I may state that, to me, the presence of a fissure system such as Mr. Lipold described, and the direct dependence of the distribution of ore upon this fissure system, seemed proved beyond question. The region surrounding Idria is composed of Carboniferous, Triassic, and later rocks, which have been subjected to great disturbances. Of these the chief is a compressive strain, the axis of which has a northwest and southeast direction. This strain is manifested in part as a fold and partly also by a dislocation. The faulting has taken place chiefly upon a single northwest and southeast fissure, which, however, as is so usual, is accom- panied by other fractures parallel to it. In the course of the faulting move- ment a portion of the Carboniferous beds have been driven over the Triassic strata, thus inverting the natural order. This fact formerly caused the age 1 Jahrbuch k. k. geol. Reichsaustalt, Wien, vol. 24, 1874, p. 425. . "Das k. k. Quecksillierwerk zn Idria, 1881. IDRIA. 39 of the strata in which the ores are found to be greatly exaggerated, but sub- sequently inversion of the strata was proved both by structural evidence and by the discovery of satisfactory fossils. The principal fissure on which dislocation took place can be traced on the surface. It is also exposed in the mines, where the crushing and crum- pling of the Triassic beds which it traverses are plainly visible. The attend- ant parallel fissures are likewise exposed by the workings. The Triassic strata belong to various subdivisions of the Alpine Trias (Werfen, Gutten- . stein, Wengen, and Ikonca groups). Lithologically they consist of schists, sandstones, and more or less dolomitic limestones; in short, of all the chief varieties of sedimentary rocks. All of these stratigraphical divisions and all of the lithological varieties of rock carry more or less ore in the neigh- borhood of the fissures, while none of the rocks carry ore outside of the region of disturbance. Furthermore, the deposits lie along the fissures, hav- ing the same strike and dip as these. There is thus abundant evidence that the ore deposition and the fissure system are directly related. The form of the deposits differs greatly in various parts of the ore-bear- ing region: To the southeast the fissures cut across the beds and the ore forms true and unmistakable veins filled with wall-rock, cinnabar, and gangue minerals. In the northern part of the mine the fissure for some distance follows the planes of bedding of the Triassic rocks and the ore is inter- posed between the beds somewhat as if it were a stratum. The cinnabar is found, however, not only between strata and impregnating strata, but in the cracks penetrating the sedimentary beds, showing that the deposition fol- lowed the disturbance and that the coincidence of the fissure and the planes of bedding was due only to the fact that these, when nearly vertical, were surfaces of least resistance. In short, this is a bed vein, that is, a vein which happens to coincide in direction with the stratification. In the same part of the mine a portion of the lower Triassic limestones and dolomites have been crushed, and the deposit assumes the form of an irregular reticulated deposit or stockwork. Where the rock is sandy or porous, impregnations are found. The mineralogical character of the ore is extremely simple. Cinnabar is the prevailing mineral, of course. Native quicksilver is found in small 40 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. quantities, especially at contacts with the Carboniferous beds. Pyrite is tolerably abundant, sometimes associated with metallic mercury. No other metalliferous mineral occurs. The usual gangue minerals are quartz, cal- cite, and dolomite, and they have been deposited simultaneously with the cinnabar. Idrialite occurs in shapeless masses and is especially associated with hepatic cinnabar. In one region a small quantity of fluor-spar has been detected with cinnabar and dolomite. Mr. Lipold regarded the asso-' elation of minerals and the manner of their occurrence as conclusively proving that the ore had been deposited from fluid solutions, a conclusion which appears to me entirely justifiable. This mine, unlike others in southern Austria and northern Italy, grows richer as its depth increases, and the known reserves in 1880 were sufficient to maintain the production at the current rate for over seventy years. There are noteworthy analogies between this mine and that of Almaden. In the latter the ore occasionally crosses strata, though usually following the stratification. In both, reticulated deposits are found, though at Idria the reticulated mass is irregular in outline, while at Almaden it is tabular. Pyrite is the only foreign metallic mineral abundant in either deposit. In both a part of the deposits follow the stratification and in both there is evidence of disturbance preceding ore deposition. Impreg- nations occur in sandstone in each mine. Both deposits grow stronger as the depth increases. Thus, while the general impression produced by the two chief mines of cinnabar is different, the difference is one rather of de- gree in the development of particular features than of fundamental char- acter. Cinnabar is also found at many points in Carniola, Styria, Carin- tliia, Salzburg, and the Tyrol. At a number of these localities small quan- tities of quicksilver have been produced, but none is commercially im- portant. The mode of occurrence, so far as known to me, is in each case similar to that of other deposits more or less fully described in this review. In Bohemia cinnabar, quicksilver, and calomel are found with iron deposits. At Horowitz the quantities obtained were so considerable that from time to time a few hundred-weight of quicksilver were produced as an incident to the production of hematite. The latter forms a bed in Silurian schists, while the cinnabar, accompanied by heavy spar and pyrite, is found LOCALITIES IN EASTERN EUROPE. 41 in cracks in the schists at right angles to the bedding. 1 In specimens which I have examined calc-spar also is present The reader may be reminded that at Mieres, also, bodies of iron ore are found with cinnabar. Hi-ngary. Though mercurial tetralred-rite is not unknown elsewhere, it seems particularly characteristic of Hungary, and it is well known to metallurgists that small quantities of quicksilver have been obtained for a very long time as an incident to the roasting of copper ores in the Hun- garian Erzgebirge. In this region mercurial gray copper ore, pyrite, cin- nabar, and amalgam occur in veins inclosed by crystalline schists and gabbro, usually with quartz and heavy spar as gangue minerals. Ores of antimony, lead, and iron are also found with those of quicksilver. One variety of the mercurial tetrahedrite contains no less than 16.7 per cent, of quicksilver. Cinnabar and quicksilver also exist at many points in Transylvania, though not in deposits of much commercial value. Very interesting is a vein in the Carpathians, between Transylvania and Bakowina, at Thihuthal, which occurs at the contact between a dike of lava and much-altered argil- laceous schist. The vein is sixteen inches thick and is filled with calcite, dolomite, and country rock. This vein matter contains streaks and bunches of cinnabar. Small quantities of galena and zincblende are also found in it. 2 servia. An important deposit of cinnabar was discovered in Mt. Avala, near Belgrade, in 1883, or, more properly speaking, rediscovered, since the Romans seem to have opened a mine upon it. This deposit has formed the subject of an important study by Prof. A. von Groddeck. 3 Ore has been found at six points near Mt. Avala. These localities do not form a straight line, but are distributed over a triangular space. The country rock is serpentine, believed to be an alteration product of an enstatite- olivine rock. The ore is mainly cinnabar, but native quicksilver and a little calomel are found. Pyrite and rnillerite, finely disseminated, accompany the cinnabar, and in a single locality galena also occurs. The gangue 1 Von Gotta : Erzlagerstatteu, part 2, p. 204. "Ibid., part 2, p. 269. The average annual product of quicksilver in Hungary from 1864 to 1883, twenty years, is said to have been 26.C5 metric tons, or 772 flasks, Spanish standard (Mineral Resources U. S. 1885, p. 293). "Zeitschr. filr Berg-, Hiltten- und Salinen \vesen im preuss. Staato, vol. 33. 42 QUICKSILVER DEPOSITS OF TJTE PACIFIC SLOPE. minerals are chalcedony, quartz, calcite, dolomite, barite, and iron oxides. Chrome iron is disseminated in the serpentine and the gangue. The ore is found in seams and stringers of quartz and heavy spar, which intersect the vein matter in all directions, and also in impregnations. Prof, von Groddeck regards the deposits as intimately related to a fissure system and of a vein-like character, but infers from the micro-structure of the ore that it has in part replaced serpentine. In a series of specimens from Avala, shown to me by Professor Arzruni in Aachen, this replacement is not ap- parent. Messrs, de Prado, Monasterio, Kuss, and others consider a portion of the ore of Almaden to have been substituted for sandstone or quartzite, and Mr. Lipold believed that ore had replaced a part of the Idrian schist (Lagerschiefer). One would expect, in all these cases, to find descriptions of rounded kernels of rock inclosed by more and more angular envelopes of ore, the outermost bounded by irregular fissure surfaces, for this struct- ure is usually associated with pseudomorphism. I do not find such de- scriptions nor have I seen any _such occurrences in California, where cinnabar is often met with in contact with serpentine, sandstone, and schist. Neither have I seen anything of the kind at Almaden, at Idria, or at the Tuscan mines. Turkey in Europe Mr. W. Fischbach l examined workable deposits of cin- nabar and native quicksilver in the neighborhood of Prisren, in Albania. This place I take to be identical with Prisrend or Perserin, eighty miles east-northeast of Scutari and about four miles from the river Driu. He also reports occurrences at Crescevo, in Bosnia. There is a town Kreshevo, perhaps equivalent to Crescevo, near Serajevo, in Bosnia. Mr. A. Conrad 2 examined deposits in the Inatch Mountains, near Serajevo. They are in- closed in schists and limestones and are nearly vertical, sometimes forming veins and sometimes beds. The vein matter consists of country rock, cal- cite, and dolomite. The cinnabar inclosed in the vein matter is accompa- nied by pyrite, blende, and, it would appear, by traces of gold. Some of the deposits are several meters in thickness and, Mr. Conrad believes, could be exploited with profit if operations should be intelligently conducted. 'Berg- uml hiittenm. Zeitung, vol. 32, 1873, p. 109. "Revue de gfiol., vol. 5, 186. r >-'6C>, p. 115. LOCALITIES IN EUROPE AND AFRICA. 43 Mr. Fisclibach also mentions that a concession has been granted for mining native quicksilver at the Dardanelles. Russia. Besides some points in the Ural Mountains, which will be mentioned under the head of Siberia, a discovery of cinnabar was made by Mr. Minenkoff in southern European Russia in 1879. The locality is west of the Azof railway, between the stations Nikitoffka and Gavriloffka, and seems to be about eighteen miles southwesterly from the town of Bachmut. The deposits consist of a stratum of sandstone overlain by clay slate. The ore-bearing stratum is in part impregnated with cinnabar. It is also trav- ersed by many cracks, in which well-developed crystals of cinnabar are found. The rocks underlying the principal stratum are likewise fissured, and the cracks in it also are sometimes filled with cinnabar. According to Professor Tschermak galena is intimately mingled with the cinnabar. 1 All the rocks belong to the Carboniferous. The deposit is said to be rich, and exploitation on a commercial scale was commenced in 1886, as Professor Arzruni informs me. There are ancient superficial mine workings on the metalliferous beds. 2 AFEICA. Algeria. Within a few years there was a mine called the Ras-el-Ma worked fifteen miles southeast of Philippeville, province of Constantine. Mr. Tissot states that this deposit occurred in the nummulitic limestone (Eocene) immediately at the contact with argillo-talcose schists. In his opinion the metalliferous emanations were derived from the latter rock. This mine was patented in 1861 and abandoned in 187C. He also mentions a very regular mercuriferous vein at Taghit, in the valley of the Oued-Abdi. It occurs in the lower Cretaceous. 3 Mr. A. Heckmanns informs me that in the province of Algiers, near Palestro, at a locality called Douar Guer- rouma, there are typical veins in upper Cretaceous limestone which carry decomposed blende and lead ores. These ores contain silver and quick- silver, the latter sometimes to the extent of 3i per cent. The quicksilver is not recovered at present. 1 Tschermaks mineral. Mittheil., vol. 7, 1685, p. 93. - M. Iliriakoff: Geol. Fiireuingens Stockholm Forhamll., vol. 8, No. 6, 1836. "Texte explicatif de la carte gdologique de Constantine, pp. 59 and 05. Also, Notice g6ol. et min., D<5p. de Constantine, Exp. univ. de Paris, 1878, pp. 22 and 23. 44 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. In 1876 the Bey of Tunis exhibited a collection of ores illustrative of the resources of his dominions. The chief mineral products of Tunis in- clude lead and mercury. 1 ASIA. southwestern Asia. Near Smyrna Mr. Fischbach (loc. cit.) found a rich vein of cinnabar accompanied by antimony ore. This is the only record of quicksilver in Asia Minor in my possession. Ibn Mohelhel, an Arabian author of the ninth century, reported quicksilver as occurring in the western portion of Zendjan, in Persia, General A. Houtum Schindler, of the Persian army, found cinnabar and native quicksilver in the district indicated by Mohelhel. 2 Cinnabar occurs with gold in alluvial washings. Furthermore, cinnabar and native quicksilver are found inconsiderable abundance in the basalt of the district, which also carries realgar. Sulphur, too, is plentiful and lead and silver are mined near by. This locality would appear to be a solfataric one, not dissimilar to those of California. In Afghanistan Captain Hutton 3 reports that quicksilver is mined at latitude 31 18', longitude 62 18' 30". Globules of the metal are also said to occur in a cellular lava at Aden. 3 Siberia. Cinnabar is found in various secondary deposits in the gold- mining districts of the Ural Mountains; for example, near the Beresowsk smelting works, near Miask, and near Bogoslowsk. At the last locality pieces of cinnabar weighing a pound and a half have been found, but the original deposits of ore have never been detected in this region. 4 In the auriferous sands of Olem-Trawiansk cinnabar occurs in large pieces, an examination of which is said to justify the conclusion that the original deposits were quartz veins. 5 It is hard to see how such fragments can justify any positive conclusion as to the form of the deposits, but it is something to know the nature of the gangue. Professor Arzruni informs me that to the south of the district in which Miask is situated no cinnabar has been found, while to the north it occurs in rolled fragments in most of the gold placers. Cinnabar also occurs at the Ildekansk quicksilver mine, in the district 1 J. M. Safford: R?pt Phila. Intermit. Kxh. 1870 to Parliament, vol. 3, London, 1878, p. 481. 2 Jahrbuch k. k. geol. Reichsaustalt, Wicn, vol. 31, 1881, p. 183. 3 V. Ball: Economic Geology of India, p. 170. N. von Kokscharow: Matcrialen zur Mineral. Russlaiuls, vol. 6, 1870, p. 'jri!!. C. Zincken: Jterg- niul Iiiitti-nm. /citnng, vol. :), 1880, p. :IGO. THE SIBERIAN MIXE. 45 of Nertschinsk, in eastern Siberia, near the borders of Manchuria. The ore, which has only been found in small quantities, forms little veins and bunches in yellowish-gray limestone, the gangue being calcite and quartz. It is said that this deposit was discovered as far back as 1759, but was worked only to a depth of thirteen meters. In 1 797 the mine was reopened and eleven pounds of quicksilver were obtained. In 1834, exploration in the neighborhood disclosing nothing more, it was decided to abandon the mine. In 1837 a four-inch vein was found in the hanging, but, although it was decided to work the mine, nothing was done. In 1853 prospecting was resumed, but only traces of ore were found. It has not been worked since. 1 A specimen of the ore from this mine was exhibited in Philadelphia by the School of Mines of St. Petersburg. Some travelers in later years have regarded the existence of a quick- silver mine in Nertschinsk as altogether mythical. 2 It certainly existed, but the above data show how small an affair it was. No other mine so insignificant has probably ever been so famous. Endless fables have been circulated as to the inhuman confinement of prisoners in the poisonous atmosphere of this mine. It is highly improbable that more than half a dozen miners were ever at work in it at one time, while mercurial poison- ing in quicksilver mines occurs only where native quicksilver is abundant, a very rare case excepting at Almaden. They are ordinarily as healthful as any other subterranean excavations. Native quicksilver is not mentioned as having been observed at Ildekansk. The Nertschinsk district also pro- duced gold, tin, silver, and lead. The country seems chiefly composed of granite and crystalline schists. Cinnabar has also been said to occur in Kamtschatka. 3 I do not know the exact locality, nor have I been able to discover on whose authority the statement was made. Mr. George Kennan informs me that while he was at Anadyrsk, on the Anadyr River, in 1867, the natives (Chukchis) assured him that native quicksilver occurs in the neighborhood. As a proof of their statements they brought him something like 100 grammes of the 1 Von Kokscharow (loc cit.) and A. Oserskij : Abriss der Geologic, dor Mineralreichthiimcr und dcs Horgbaues von Transbaikalien, St. Petersburg, 1867. '' Dr. Henry Lansdell (Through Siberia, 18812) could learn of no quicksilver miuo at Nertschiusk and cited other authorities to the same effect. 3 Noggerath, loc. cit. 46 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. metal in a glove. Mr. Kennan considers it almost impossible that this quicksilver can have been obtained by the natives from Europeans, either by design or by accident, arid believes that it represents an actual occur- rence. He was not shown any cinnabar. china. Mr. R. Pumpelly discovered in Chinese literature records of the occurrence of quicksilver in ten of the eighteen provinces. 1 The only province certainly known to contain important deposits is Kwei-Chau. Of this locality Baron F. von Richthofen writes as follows: 2 Quicksilver has been from of old the chief commercial product of Kwei-Chau. At the beginning of the present century it was still among the regular articles of export from Canton. Then it failed and became an article of import, rising gradually in quantity until it reached the figure of over 10,000 piculs [a picul being 133J pounds] in 1831 and 1832. Suddenly the Chinese no longer required the foreign quicksilver, and from 1838 commenced again to. export it. This state lasted until about 1849. Since then it has become again a regular article of import, but the quantity required is much less than in former years, and is about 3,000 or 4,000 piculs annually. These alternate flood and ebb tides were probably caused by the periodical disturbances in Kwei-Chau. When the last one commenced, in 1848, the mines were abandoned, and they have not been reopened since. [The minister of the Chinese Empire to the United States informs me that of late years mining has been resumed.] The places where the quicksilver occurs appear to be limited to a well-defined belt which extends through the whole province from southwest to northeast [over 300 miles]. One of the principal mining districts, and the only one in regard to which I was able to get some information, was Kai-Chau (in Kwei-Yang-Fn). The mines there were scattered over an area of 10 li diameter [about 3 miles] * * * I was una- ble to get a clear idea regarding the mode of occurrence of the ore, but it is said to exist in considerable quantity and to have been difficult to mine only on account of the presence of much water. * * * The mines have the advantage of being near Wang-Ping-Chau ; the metal can therefore conveniently and cheaply be shipped to Hang-Kow [a treaty port]. * * * The number of places at which quicksilver is found and was mined is so great as to make it not improbable that in respect to the quantity of this metal awaiting extraction Kwei-Chau is far ahead of any other known quicksilver-producing country on the globe. In many places cinnabar is brought to the surface in plowing the fields. Since Baron von Richthofen is a mining geologist of the first rank and was familiar with the quicksilver deposits of Austria and California, his opinion as to the resources of China is entitled to great weight, Kwei-Chau, 1 Geological Researches in China etc. The provinces are Shen-Si, Kan-Sn,' Shan-Tung, Ngan-IIwui, Sze-Chuen, Hu-Nan, Kwei-Chau, Cheh-Kiang, Kwang-Tiing, Kwang-Si. Letter VII to the Shanghai Board of Trade, 187-2, p. 81. Prof. J. D. Whitney has been kind enough to furnish mo with a copy of that portion of this rare publication bearing on the province of Kwei-Chau. CHINA AND JAP at the time of his visit, had been in a state of chronic disorder since 1848 ; indeed, the number of unburied corpses made the country extremely un- healthful. Realgar and orpiment are exported from Kwei-Chau, and many other metallic ores are said to exist therer The neighboring- province of Yun-Nan is the auriferous district of China. According to d'Achiardi, fine natural crystals of cinnabar have reached Europe from Yun-Nan. Thibet. Thibet lies close to Yun-Nan and is often mentioned as a locality in which cinnabar occurs. I have not met with a citation of authority for this statement and do not 'know the exact locality. corea. Mr. Pumpclly (loc. cit.) ascertained from Chinese records that Corea contained cinnabar deposits. Mr. Ernest Oppert 1 states that the province of Hoang-Hai contains deposits of quicksilver, tin, and lead. The geology of Corea has very recently been investigated by Dr. C. Gottsche. 2 He found the province of Hwang- Haido (equivalent to Hoang-Hai) princi- pally occupied by crystalline schists, through which older and younger eruptive rocks have burst. He notes the presence of hot springs in this province. Other portions of Corea, under similar geological conditions, are auriferous. japan. At Shizu, in the neighborhood of Sendai, province of Rikuzen, very thin veins of cinnabar occur in a whitish volcanic rock. 3 It would be interesting to know whether this is a rhyolite or a solfatarically decomposed eruptive rock of a more basic type. A quicksilver mine has been worked near Ainoura, on the peninsula of Hirado, in Matsiira Kori of Nagasaki Ken. The former superintendent, Mr. Gower, reports that the exploitation was stopped in consequence of a discouraging accident to the reducing plant. The ore consists in part of impregnations in sandstone and in part fills small fissures and seams. The country rock belongs to the Coal Measures. 4 British India. It is said that quicksilver mines formerly existed in Cey- lon, near Colombo, and that the" Dutch exported quicksilver from them to Europe. 5 In the Andaman Islands, also, it is said, quicksilver used to ' Voyages to Corea, 1830, p. 171. Sitzungsberichte dcr Berliuer Akademie, vol. 36, 1886. * J. G. H. Godfrey: Quart. Jour. Geol. Soc. London, vol. 34, 1878, p. 555. H. S. Mnnroe: Trans. Am. last. Min. Eng., vol. 5, 1876-'77, p. 29'J. s J. F. Dickson: Encyc. Tint., 9th edition, article Ceylon. 48 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. be obtained. The rocks here are similar to those of California near San Francisco. Traces of native mercury are reported from Madras. Dutch India. In Borneo cinnabar has long been known to exist. At the gold diggings of Sarawak small rolled fragments of cinnabar are found, and the antimony ores, of which the district yields large quantities, also contain some mercury. By systematic prospecting, original deposits of cin- nabar were found about 1867. The chief deposit is at a hill known as Tagora. The rock consists of partially metamorphosed, interbedded shales and sandstones. The ore is found in the slate and more rarely in the sand- stone. It is a very irregular deposit, but includes vein-like developments. Calcite, heavy spar, and pyrite accompany the ore. At Gading, a few miles west of Tagora, stibnite and cinnabar occur together. Cinnabar was first mined in 1868. The product in 1872 was 1,733 flasks; in 1873, 1,505 flasks. 1 In 1880 the value of the quicksilver produced in Sarawak was #G6,300. 2 Mr. S. B. J. Skertchly, formerly or the Geological Survey of Great Britain, informs me that he has examined alluvial deposits from the interior of north Borneo containing gold and cinnabar. On the island of Sumatra, in the southern part of the Pedang highlands, in the neighborhood of Sibelaboe, fine particles of cinnabar accompanied by magnetic iron occur in crystal- line schists, but not in quantities sufficiently large to warrant mining oper- ations. 3 Quicksilver is also reported from the island of Java at Samarang. 4 Spanish India Unimportant quantities of quicksilver ores are reported to occur in the Philippine Islands. 5 Australia Rev. W. B. Clarke, who has so greatly contributed to the elucidation of the mining geology of Australia, wrote as follows in 1875:" Some years since, I reported on the occurrence of mercury in this colony, but my expectation of the discovery of a lode of cinnabar has been disappointed. The cin- 'A. H. Everett: Notes on the Distribution of the Useful Minerals in Sarawak, not dated, but seemingly written in 1874. * Mining Journal, London, 1882, p. 415. This value corresponded, at the London prices for 1880, to about 2,000 flasks. a R. D. M. Verbeek : Beschr. Sumatra's Westkust, 1883, p. 5G2. 4 D'Achiardi, loc. cit. 6 This note is derived at second hand from J. Roth : Geologische Beschafl'enLcit der Philippinen. 'Mines and Mineral Statistics of New South Wales, etc., Sydney, 1875, p, 201. AUSTRALASIAN LOCALITIES. 49 nabar occurs 011 the Cudgegoug in drift lumps and pebbles, and is pr.obably the result of springs, as in California. In New Zealand, and in the neighborhood of the Clarke River, north Queensland, the same ore occurs in a similar way. About this date work was in progress on a quicksilver mine on the Cudgegong, 1 but in 1876 the official reports pass it over in silence. In 1878 specimens of cinnabar and quicksilver were exhibited in Paris, 2 but no information was afforded concerning the character of the deposits. Cinnabar has been mined at the Wilkinson mine in Kilkivan, fifty miles from Maryborough, Queensland. 3 According to the prospectus of a mining company a few tons of quicksilver were extracted in Kilkivan in 1885. Cinnabar is said to exist in West Australia also. 4 Mr. Noggerath reports small quantities of crystalline cinnabar in a gold vein in Bendigo County, Victoria. This very interesting occurrence is not mentioned by Mr. William Nicholas in his catalogue of localities of minerals which occur in Victoria, 5 nor by Mr. R. B. Smyth in his Mines and Mineral Statistics of Victoria. The observation has probably never before been published in English. The same author mentions gold amalgam at German Reef, on the Tarrangower. New Zealand. As long ago as 18GG it was known that quicksilver occurs a few miles southeast of Omapere Lake, near the Bay of Islands. In 1870 Mr. F. W. Ilutton 7 visited the locality, where there are numerous springs, hot and cold. He found two warm sulphur springs accompanied by mercurial deposits. The sandstone was impregnated with native mer- cury and cinnabar. He also detected an open vein a quarter to a half inch in width in the sandstone, lined with a black ore of mercury, accom- panied by sulphur and globules of quicksilver. He ascertained that this black ore was a sulphide containing some iron. Mr. Hutton thus nearly anticipated Dr. G. E. Moore's discovery of metacinnabarite. This ore is now known to occur at several mines in California, at Huitzuco in Mexico, 1 Annual Report of the Department of Mines, New South Wales, 1875, Sydney, 187G, p. 31. 2 Repts. of the U. S. Commissioners Paris Univ. Exp., 1&78, vol. 4, p. 246. 3 D. do Corhtzar, loc. cit. *R. Acton: Eucyc. Brit., !Hh edition, article Australia s Geol. Survey Victoria, Kept. Prog., 1876, p. 280. "Prepared for the Victorian exhibition, 1872. 'Trans. New Zeal. Institute, vol. 3, 1870, p. 253. MON XIII 4 50 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. and in Rhenish Bavaria, as well as in New Zealand. A greasy hydrocar- bon accompanied the deposit described by Mr. Ilutton. Dr. J. Hector 1 gives an interesting account of an occurrence at Ohaeawai, on the south side of Omapere Lake, and therefore near Mr. Hutton's locality. Hot springs and steam escape from the terminal end of a scoriaceous stream of lava, which has emanated from conical hills on the south side of the lake. These springs deposit a brown "sandstone" in laminated beds. This inco- herent, granular, silici&us sinter includes fragments- of the surrounding vegetation. It also contains thin layers of cinnabar-sand and globules of metallic mercury. No great amount of the ore exists in the sinter, how- ever, and its interest is purely scientific. Prof. A. Liversidge 2 reports rolled fragments of cinnabar from Waipori, and native quicksilver, with copper and sulphur, from Tokomairiro. CONCLUSIONS. Incomplete as are most of the foregoing notes on deposits of quick- silver ores, they seem to point to some conclusions which are not likely to be much modified by more detailed descriptions. Age of the inclosing rocks. From the crystalline schists, presumably of Archaean age, to Quaternary beds, strata of all the larger groups of geo- logical formations are known to carry cinnabar. The mere age of the in- closing rocks cannot, therefore, be a controlling factor in the distribution of mercurial ores. More deposits are found in Pre-Tertiary rocks than in those of Tertiary or Post-Tertiary age, a fact susceptible of very simple explana- tion Cinnabar deposits are also found in granite and in eruptive rocks, including Post-Tertiary basalts. Lithoiogicai character of inclosing rocks. Cinnabar occurs in conglomerates, sand- stones, limestones, and shales, or in all the great lithological subdivisions of unaltered strata. It occurs also in quartzites, slates, serpentines, and crystalline schists, as well as in basic and acidic volcanic rocks. Thus the lithological character of the inclosing rock does not determine the deposition of the ore. If there is any rock for which cinnabar seems to 1 Eept. Geol. Explorations, 1874-1876, p. 5. 2 Trans. New Zeal. Institute, vol. 10, 1877, p. 502. DISTRIBUTION OF CINNABAR. 51 exhibit a partiality it is sandstone, but rich deposits are common in lime- stone, shale or slate, and serpentine, and are not unknown in other rocks. No definite relation between the lithological character of the inclosing rocks and the richness of deposits is apparent from the descriptions. Relations to lines of disturbance Comparison of tllC sketcll-Diap (PL II) with any physical chart of the globe shows that the quicksilver deposits bear a most intimate relation to lines of disturbance. The great mountain chain of Eurasia includes the Pyrenees, the Alps, and the Himalayas. This, which might conveniently be called the Alpimalayan chain, breaks up into divergent ranges at each end, or in Spain and China. The larger part of the known occurrences of Eurasia are distributed along the Alpima- layan chain, and their frequency is very nearly proportionate to our knowl- edge of the regions in which they occur. There is little reason to doubt that, when Kurdistan, Afghanistan, and Thibet are better known, quicksil- A r er localities as yet undiscovered will be found. At the western end of the chain the quicksilver deposits, like the ranges, scatter. This appears also to be the case in China, since, according to Mr. R. Pumpelly, cinnabar oc- curs in ten out of the eighteen provinces of China; but I have not thought the information sufficiently definite to justify me in entering the localities on the map. The chief localities not immediately in the Alpimalayan chain are those on the western coast of Italy. These deposits form a line which may manifestly be regarded as a mere offshoot from the great belt of disturbance. The outlying range of the Ural Mountains is marked by a few traces of cinnabar. The famous deposit of eastern Siberia seems quite isolated. The occurrences of Kanitschatka and Japan lie along a line of disturbance marked by a series of active and extinct volcanoes, and the deposits of the East Indian islands are associated with similar evidences of dynamic action. The American deposits from Alaska to Chili lie near the coast, along the western ranges of the Cordillera system, and the line in which they oc- cur is marked from one end to the other by manifold evidences of profound disturbance. The Brazilian deposits, like that of Nertschinsk, are in mount- ainous, metalliferous regions, but seem only remotely connected with the 52 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. main line of mountains; and a similar statement is true of the traces of cin- nabar found in Santo Domingo and in Nova Scotia. The deposits of Australia, such as they are, lie along the principal mountain range of that continent, and those of New Zealand, like those of the East Indies, are accompanied by evidences of disturbance marked by volcanoes. Relations to volcanic phenomena. In a few cases tli 6 deposition of cinnabar has been observed at the vents of volcanic emanations, viz, at Pozzuoli in Italy, near Lake Omapere in New Zealand, and 'at localities on the Pacific Slope. There are other cases in which cinnabar is immediately associated with hot springs and sulphur deposits in such a way as to sug- gest the former existence of hot sulphur springs of volcanic origin. Such are the deposits of Guadalcazar in Mexico, the Baths of Jesus in Peru, and those of Persia. Hot springs exist close to the great deposit of Huancave- lica, but whether they contain sulphur I do not know. Cinnabar and na- tive quicksilver are found in eruptive rocks a part of which are recent, in melaphyre in Rhenish Bavaria, quartz porphyry at Vallalta, trachyte at Mt. Amiata, trachyte or basalt in Transylvania, basalt in Persia, pitchstone por- phyry in Mexico, trachyte in Peru, and, I may add, in andesite and basalt in California. As has already been pointed out, cinnabar also occurs along belts marked by the presence of volcanoes, active or extinct. This is espe- cially notable in Italy, in western Asia, New Zealand, and throughout the entire American series of deposits from Alaska to Chili. Mineral association. The most common metallic mineral associated with cin- nabar is pyrite, and this sulphide is perhaps never entirely absent, though it is not mentioned in some of the descriptions. It is so common, however, that were it absent in any deposit mention would probably be made of the fact. Traces of copper sulphides perhaps come next in frequency, but ar- senical and antimonial compounds are found abundantly in some deposits. The quantity of arsenic at Huancavelica seriously interfered with the work- ing of the ore, and livingstonite is an important ore in Mexico. The ore of Mieres is like that of Huancavelica. Mr. de Chancourtois found realgar with quicksilver at Pozzuoli ; Dolomieu is said to have found cinnabar and stibnite on Mt. Vesuvius, but there is some doubt whether this geologist made such ASSOCIATED ROCKS AND ORES. 53 a statement. Antimony accompanies cinnabar in Corsica and at Smyrna; realgar and cinnabar are found together in Persia. Realgar is one of the exports of the quicksilver region of China. Gold is intimately associated with quicksilver and cinnabar at a great number of points, sometimes in veins, but oftener in gravels. There is no deposit of great importance, however, from which both metals can be profitably extracted. Ores of copper and zinc are not seldom found with cinnabar ; lead and silver ores are more rare; but, as in the case of gold, it is seldom that valuable de- posits of any of these metals carry important quantities of quicksilver or that valuable deposits of cinnabar contain important quantities of the other metals. It is nevertheless interesting to observe that, with the exception of tin, all the chief metallic ores are sometimes deposited together with cinna- bar. The gangue minerals accompanying cinnabar are nearly always either silica, often in part of hydrous varieties, or carbonates in which calcite pre- dominates. As Mr. d'Achiardi remarks, the character of the gangue seems largely determined by the nature of the adjacent rock. Baryte and fluor- spar are not infrequent and bituminous matter is found in a very large pro- portion of quicksilver mines. Form or the deposits. Except in the case of gravels, I know of no case in which it is clear that cinnabar has been deposited simultaneously with the other material of stratified rocks. It is true that observers have not infre- quently asserted of cinnabar deposits that they were coeval with the inclos- ing rocks, but the only ground for this opinion which I have seen given is conformability between deposits of ore and the surrounding strata. This is by no means adequate to establish the point in question. In most cases it seems certain that the deposition of ore was subsequent to some disturb- ance of the country rock. In these cases the ore is deposited in interstitial spaces, and possibly also to some extent by substitution for rocks or other minerals. There is no doubt that true veins of cinnabar occui', sometimes cutting sedimentary rocks and sometimes following the stratification. Re- ticulated masses and impregnations are also common. It is often supposed that the characteristic forms of cinnabar deposits are not to be brought under any of these categories ; but I cannot see sufficient evidence in the literature to prove this supposition. Selvages and comb structure are often 54 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. absent, and sometimes the walls of vein-like deposits are not well defined. But veins of ideal structure, such as those vipon which the diagrams of text- books are founded, are not common in all regions, even in gold, silver, or copper deposits. Small veins in hard, coherent rock often assume this sim- ple form, but large veins in volcanic or partially metamorphosed rocks are often indistinctly bounded and are very complex in structure. In many parts of the Comstock lode, for example, there is no definite hanging wall, and the bonanzas of that great vein are masses of brecciated rock filled in with ore. So, too, the gold veins of California are in great part bed veins, a fact due to the nearly vertical position of the strata before the deposition of ore, and they are often somewhat indistinctly defined. In short, the char- acter of the fissure which a vein fills must depend on the physical properties of the rock, and clean-cut open fissures can be formed only in appropriate material. In many cases a fracture will produce a belt of crushed country rock, instead of an open crack, and the ore deposited in the interstitial space will depart to a corresponding degree from an ideal vein. Where the strata of a region have a nearly vertical position prior to the formation of veins, bed veins must prevail. When ore is deposited in contact with porous rocks, such as many sandstones, impregnation must take place. The chief differ- ence between an impregnation in sandstone and the injection of a breccia is that in the former case the interstitial space is due to the original structure of the rock, instead of being brought about by dynamic action accompany- ing the formation of the main fissure. Impregnations of other ores, as well as those of mercury, are not uncommon. Mr. Lipold showed conclusively that the deposit of Idria consists of simple veins, reticulated masses, and impregnations. Evidence is given above which tends to show that the deposit of Almaden is similar, except that the reticulated masses are tabular and vein-like and that bed veins greatly predominate over those which cut the beds. Ilumboldt's descrip tion of Huancavelica shows that similar conditions there prevail. At Yal- lalta, also, stringers of ore pierce the shales, the porphyry is impregnated, and the main mass of the ore seems to be a somewhat tabular or vein-like stockwork. In. short, all the better -known deposits are referable to the three forms of deposits described by Mr. Lipold, and I know of no sufficient SOURCE OP THE ORE. 55 evidence to justify the belief that cinnabar occurs on a large scale as deposits coeval with the inclosing- rocks. Cinnabar is not known to exist as cave-fillings. Several geologists think that cinnabar has been to some extent substituted for sandstone, shale, or serpentine ; but, while this may be true to some extent, this process does not seem to have been sufficiently rapid to impress upon the deposits the peculiar character seen in some lead mines. The hypothesis of the substitution of cinnabar appears to me thus far to lack sufficient proof. Genesis and source of the ore. The mineral associations in which cinnabar is found seem to show conclusively that it has been deposited from solutions. A very large part of the known deposits of cinnabar are extremely similar in character, a fact which seems indicative of a similar origin. It is cer- tain that some of the deposits are due to precipitation from hot volcanic springs and it may fairly be inferred that many of them were formed in this manner. The diversity of the country rocks in which the deposits occur is evidence that only a part of them can have derived their metallic contents from their own wall rocks; the remainder must owe their cinnabar to some source between the point at which the waters acquired their heat and the surface. Between the depth at which volcanic foci. He and the surface of the earth there must be substances of world-wide distribution which frequently contain mercury in some form as an original ingredient. These substances are probably massive rocks, and the only known rock of correspondingly wide distribution is granite. I now pass to the geology of the cinnabar deposits of the Pacific Slope. After describing them I shall return to the subjects mentioned in these conclusions. T7HI7ERSIT7 CHAPTER III. THE SEDIMENTARY ROOKS. General character. The Coast Ranges of California present a truly remarka- ble opportunity for the investigation of some of the most important phe- nomena embraced under the general term of metamorphism. To give a clear ideaof the unusual advantages afforded by this area it is necessary to anticipate s.ome of the results reached. Field examinations were made for this memoir at numerous points from above Clear Lake to the region of New Idria, thus partially covering a belt of the Coast Ranges about 230 miles in length. Throughout this whole region there is structural and lithologieal evidence that granite of very uniform character underlies the entire country. Ex- cepting the belt of schists along the coast from Santa Cruz southward, it is estimated that 90 per cent, of all the rocks of this region are sandstones, altered or unaltered. These sandstones are also extremely uniform in char- acter, and wherever they are inconsiderably modified the slides prepared from them show that they are directly or indirectly derived from the gran- ite, or, in other words, that they are arcose. Of this material of known origin a portion has been highly altered. The alteration processes to which it has been subjected are identical from one end of the region to the other and innumerable transitions are presented. It is difficult to estimate the areas occupied by the metamorphic rocks of the Coast Ranges, because the occurrences are extremely irregular. A moderate estimate of the exposures between Clear Lake and New Idria, which consist of holocrystalline meta- morphic rocks, sandstones in which reerystallization lias made considerable progress, phthanites, and serpentine, is 3,000 square miles. Large areas, covered by late Cretaceous and Tertiary strata, are also known to be un- derlain by metamorphics, and this series extends far to the north and to the FACILITIES FOR STUDY OF METAMORPHISM. 57 south of the limits indicated without substantial change in character. The study is thus not one of merely local recrystallization, but of regional meta- morphism, which is not of uniform intensity and is therefore the better fitted for investigation. The age of the altered beds is known, from direct paleontological evi- dence at a number of localities, to be Neocomian, and there is no evidence that any considerable quantity of older rocks is included within the area. The epoch of the metamorphism is also clearly proved to be in the earlier portion of the Cretaceous period, and probably about the close of the Neo- comian. The most interesting alteration processes to which the sandstones have been subjected are closely similar to those which characterize metamorphic areas elsewhere, consisting chiefly in the metasomatic 1 recrystallization of sediments to holocrystalline feldspathic rocks carrying ferromagnesian sili- cates and in the formation of vast quantities of serpentine. At the same time these rocks present peculiarities distinguishing them from many highly altered rocks in other regions. The metamorphism accompanied or followed an upheaval of unusual violence. In tin's uplift the granite must have been shattered as well as the overlying strata. The metamorphism was chemically of such a character as to necessitate the supposition that solutions rising to the surface from the shattered granite beneath co-operated in the process. Thus the origin of the sedimentary rocks, their mineralogical character in an unaltered state, their age, the approximate epoch at which they were metamorphosed, and the general character of the conditions of metamor- phism are all known, while the exposures illustrating the comparatively few more important problems involved are numberless. I am not aware that metamorphism has ever been studied under conditions so favorable for elucidation. It is unnecessary to say that the material is far from ex- hausted by a single investigation. Much remains to be done, especially from a chemical point of view ; indeed, the chemical details of the greater part of the transformations are still unknown. 1 Jiy metasomatism I uadi-i'stand iiml desire to express a change . &9o; and A. A. J alien : On tlm geological action of ihr hunins ;u-i(ls, Proc. Am. Assoc. Ailv. Sci., vol. 2$, 1879, JIM. 311-410. CONCRETIONS IN SANDSTONES. 67 Some of these acids also combine with silica to silico-azo-lmniic acids. According to Mr. P. Thenard, acids of this series form spontaneously in the soil from humic acid, the ammonia of rain water, the nitrogen of the air, and the silica contained in the soil. Modus operands. It is clear that a fragment of undecom posed organic mat- ter embedded in a porous sandstone may decompose under the action of percolating surface waters and that under favorable conditions it may yield humic acid which will attack the magnetite, always present in greater or smaller quantity. With the silica of the rock silico-azo-humic acid may also be produced. Were large quantities of organic matter present to- gether with much water the result might be a mere bleaching of the sand- stone; but, if small quantities of the solutions of the humic compounds only are formed, they will be drawn into the surrounding sandstone by capillary action and a more or less nearly spherical mass will be impregnated with them. This mass may, perhaps, increase in size until the organic matter is exhausted. The humic compounds are very unstable, and a globular mass, such as is supposed above, would soon decompose into carbonic acid, water, etc. There would then remain a spheroidal mass of carbonates and silicates of the bases which had been dissolved at an earlier stage. The latter being formed at low temperatures would not improbably be hydrous. Calcium phosphate is soluble in solutions of carbonic acid, and one would therefore expect to find the phosphorus of the organic substance also diffused through the mass. The hypothesis of a decomposing organic nucleus thus appears to account in a rational manner for all the observed facts. summary of evidence. The fossils occasionally met with in sandstone con- cretions are so rare as only to suggest that these masses may have been indurated through the indirect action of organic matter. The presence of phosphoric acid in notable quantities in the. matrix of concretions which contain no fossils greatly strengthens the hypothesis that organic matter once existed in these masses, but has since disappeared. When it is found that the chemical character of the matrix of these concretions is also such as would result from the decomposition of organic matter by processes of which the main features are well known, the weight of the concurrent evidence is 68 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. very great. It is clear that the formation of concretions is due to the pres- ence of small masses of some foreign substance in the sandstone. Were this substance composed of any other elements than carbon, hydrogen, nitrogen, and phosphorus, such elements would almost inevitably appear as y:omponents of the concretion. It thus appears to me nearly certain that he concretions are due to the action of decomposition-products arising rom organic matter. It is evident that the formation of concretions by means of organic matter, as sketched above, is a result which will take place only under some- what special conditions. If sufficient organic matter exists in a rock, indu- ration of the entire mass may occur. If the huinic components are washed through the rock without being allowed to decompose, the rock will be bleached. Both of these last cases are considered by Professor Julien in the paper referred to above, but he does not particularly discuss the subject of concretions NODULES RESULTING FROM EXTERNAL ATTACK. cases to be discussed. Besides the concretions discussed above, rounded nod- ules are found in many decomposing rocks. In the present memoir such occurrences will be noted in the basalts of the Sulphur Bank mine and in the partially serpentinized rocks, especially near Knoxville, Napa County. They are also well known to occur in some decomposed granites and in an- desites, those for instance near the Comstock lode. The principles on which they are formed are extremely simple, but, so far as I know, they have never been stated, and a lack of knowledge of them has often led to erroneous assumptions of a mysterious ball structure in the rocks which favors such decomposition. As will be seen below, pebbles in brooks and on beaches, as well as grains of sand, are rounded in a manner closely analogous. Deduction of relations. Suppose a sphere of any homogeneous substance, into which liquids can penetrate a small but finite distance, and let this dis- tance be assumed as the unit of length. Then, if r is the radius of the sphere, the volume of the solid which can be permeated by a liquid acting on the exterior is a spherical shell, the content of which is : V = J it >' 3 -* n (r-l) s = j n (3r ! NODULES. 69 The surface of the sphere is, say, S=:4 ir r 2 and The surface of the material exposed to the action of the fluid per unit of volume of the shell acted upon, orS/V, may readily be seen from this equation to diminish rapidly as the radius of the sphere increases. 1 For example, if the radius is unity, or just equal to the depth to which the solid is permeable, S/V = 3; if r=2, S/ V = 1.7 ; if r =4, S/V=1.3, and if the radius is infinite or if the attacked surface is flat, S/'Vz=l. Suppose a unit of volume of a thoroughly porous, solid substance in any given shape and exposed to the action of a solvent liquid: the liquid will become partially saturated near the surface of the solid and will act less vigorously upon the underlying portions. It is clear, therefore, that, if the body is given the shape of a slender rod and is acted upon by the fluid from one end only, it will dissolve less rapidly than it would if the same mass were formed into a thin sheet and were attacked over the whole of ''one surface of this sheet. It is easy to see that the rate at which solution will take place in this case is nearly proportional to the surface exposed to jlie action of the fluid. Hence it is sufficiently accurate for the present purpose to assume that the rate at which a spherical mass will be attacked by a corrosive fluid will be proportional to the surface exposed per unit of volume of the permeable shell, or to S/V. This function (and therefore, also, the rate at which so- lution will take place), as has been shown above, varies in a certain inverse ratio to the radius of the sphere. 2 If, therefore, any comparatively dense, irregular body is acted upon by solvent or decomposing solutions, the portions the radii of curvature 1 The portion of the sphere which is not reached hy the fluid is essentially a positive quantity, and 4 when / becomes less than unity,- n (>' I) 3 disappears from the value of S/V, which thus becomes 9 equal to 3/r. This is a hyperbola, asymptotic to both axes, and S/V is in Unite- fon - = 0. At the point at which = 1 this hyperbola passes over into the curve of the third degree given in the text. The hyperbola would be asymptotic to S/V = 0, while the higher curve is asymptotic to S/V = 1. 2 This conclusion is not affected by the uncertainty which exists as to the exact function represent- ing the rate of solution in terms of S/V ; for it is clear that in any ease this function and S/V must vary directly, and that both of tlicin, therefore, vary invcrsrlj as the radius of curvature. 70 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPK. of which are equal to or less than the distance to which the fluid can per- meate will yield very rapidly, while those of less abrupt curvature will he more slowly decomposed or dissolved. There will thus he a constant tend- ency to diminish the curvature of the more salient portions and, if the mass is not too thin, to reduce it to a sphere. cases. Two special cases need consideration: If the action of the fluid were strictly confined to the surface or if the mass were absolutely imper- meable, the radius of curvature would always be infinite compared with the distance to which a fluid could penetrate, and, if solution took place, the mass would always retain an angular form, the surfaces of which would be parallel to those which it originally presented. On the other hand, if the fluid could permeate to the center of the body, all portions would be attacked at once and it would disintegrate almost .simultaneously through- out its mass. Nearly every American has daily opportunities for observing the rela- tions here reduced to exact terms. Clear, solid ice is practically imperme- able by water, and an angular fragment of such ice in a glass of water becomes only slightly rounded, while the surfaces at all stages of the melting process are nearly parallel to the original ones. On the other hand, a bit of ice which is clouded with small air bubbles is permeable by water to the depth of these bubbles, and consequently the edges and cor- ners of an angular mass of such ice are quickly rounded. Again, a lump of cane sugar is very porous and fluids permeate to its center. It there- fore disintegrates under the action of a solvent fluid almost without pre- liminary rounding of the edges and corners. Application to decomposing rocks. The behavior of rocks to dissolving or decom- posing agencies is similar. There do not seem to be any rocks, excepting perhaps some obsidians, which are permeable only to an insensible distance by fluids ; but there are many rocks so dense that fluids penetrate them with great difficulty and very slowly. In such cases the corrosive reagents which waters contain are neutralized by the time the solutions have pene- trated to a very small depth, and corrosive action is limited to this thin outer layer As decomposition is completed in the outer layer, active reagents will of course permeate farther and farther into the rock. The geometrical 71 results will clearly be those discussed above. An angular mass of such a rock will yield to the decomposing agencies directly as S/\ r , or in an inverse ratio to its radius of curvature, and, if the mass is homogeneous, it will gradually be reduced to the spherical- form. It thus becomes evident that angular blocks of basalt attacked by sulphuric acid or other corrosive fluids tend to the spherical form, not because of any variation in the internal structure, but, on the contrary, because they are substantially homogeneous. The rocks which do not weather or decompose to rounded masses are the more permeable class. Thus, in the Washoe district dense andesites and basalts tend to the spherical form, Avhile tufaceous masses and porous rocks decompose Avith tolerable uniformity throughout. In terms of the mathe- matical discussion for the latter, r < 1. Just so along the quicksilver belt: dense rocks undergoing serpentinization show rounded nodules of unaltered or slightly altered material, while more permeable masses are gradually changed to serpentine throughout. It may not be amiss to note that the depth to which a rock will be at- tacked by any decomposing fluid depends somewhat upon the nature of the fluid. If the reaction between the liquid and the solid is a rapid one the liquid will become substantially saturated comparatively near the surface, while, if the reaction is feeble and slow, the fluid Avill penetrate to a greater depth before losing its corrosive power. Complex cases sometimes result from the co existence of various reactions, each leading to a particular kind of decomposition. Application to pebbles. It is evident that the principles applied in the fore- going discussion are not limited to the action of fluids. Any disintegrating agency acting uniformly on the surface of an angular body or acting suc- cessively on all points of its surface Avill be governed by similar laws. Consider a fragment of rock in a stream bed or on a beach. It suffers frequent impacts from other bodies of similar average size and composition. Each of these impacts disintegrates the mass at the small surface of contact to a certain average depth, and these impacts are repeated in indefinite number on all portions of its surface. The result must be the same as if the rock fragment were subjected to a disintegrating action simultaneously at all points of its surface, and, just as in the case of a solvent fluid, the 72 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. mass must tend to a spherical form, provided tha,t it is of uniform composi- tion. If the body is permeable to different depths in different directions or if it offers more resistance to abrasion in one direction than it does in others, the surfaces which offer the least resistance will evidently be most rapidly attacked. Hence, pebbles of sedimentary rocks, which do not in general possess equal coherence in all directions, will not tend to a spherical form, but to one more or less approaching a spheroid or even an ellipsoid. It appears from the literature of geology that rounded masses resulting from the decomposition of comparatively impermeable rocks have not infrequently been mistaken for water-worn pebbles. When one considers that in both cases the approach to the spherical form is due to similar causes this does not e'.em so strange as it otherwise might. CEYSTALLINE METAMOKPHIC ROCKS. Groups of metamorphic rocks. The metamorphosed rocks of the Coast .Ranges may be divided into serpentine and a more or less crystalline series. The latter, indeed, usually contain some serpentine ; but serperitinization is evi- dently in part a secondary process and will be discussed, together with the massive serpentines, in a succeeding section. The division of the crystal- line series which appears best to satisfy both their microscopical charac- ter and their field occurrence is as follows : (1) Partially metamorphosed sandstones, in which, although a process of recrystallization has begun, the clastic structure as seen under the microscope is not obliterated, though more or less obscured. These rocks will be referred to hereafter, for the sake of brevity, as altered sandstones. (2) Granular metamorphics, in which thorough metasomatic recrystallization of the sandstones has transformed the mass into a granular, holocrystalline aggregate which, in its most com- plex development, consists of augite, amphibole, feldspar, zoisite, and quartz, with accessory minerals. This class cannot be sharply separated from the first or from the following, but it forms a natural group, one or several of the constituents of which may be suppressed, forming different varieties within the group. (3) Glaucophane schist of an origin similar to that of the granular rocks, usually carrying mica, quartz, and other minerals. GROUPS OF METAMOKPI1IO ROCKS. 73 (4) Phthanites or schistose rocks which have been subjected to a process of silicification. There is seldom any doubt about the rnacroscopical determination of the third and fourth of these groups ; in-a, large proportion of cases also, the granular rocks can readily be distinguished from the altered sandstones with the naked eye or the loupe, but this is by no means always possible. Many rocks which to the naked eye appear to be merely considerably altered but perfectly recognizable sandstones turn out, upon microscopical examination, to be holocrystalline and to have lost entirely the character- istic clastic structure. The granular rocks are separable, under the microscope, into several varieties, according to their mineralogical composition ; but it is seldom possible to distinguish these varieties macroscopically. In dealing with eruptive rocks the eye soon accustoms itself to the perception of very minute differences of appearance which represent or are associated with microscopical peculiarities. The metamorphic rocks are physically and chemically much more heterogeneous than eruptives, and it is only in extreme cases that the habitus is characteristic of the precise mineralogical composition. As will appear in the sequel, the altered sandstones and the granular rocks form a series which is in reality unbroken. The processes of altera- tion can be studied in rocks retaining as clearly as possible evidences of their clastic character. The same processes can be traced through series in which the clastic elements gradually disappear and in the extreme members of which a holocrystalline mass of authigenetic minerals is presented. In the altered sandstones various transformations begin simultaneously, and, according to the physical and chemical conditions under which the meta- morphism occurred, one or other of these changes may predominate in the fully altered rock. In this way types are produced so distinct that were these alone submitted to examination little analogy would be perceived between them ; but they are, in fact, connected with one another, as well as with the unaltered sedimentary rpcks, by very gradual transitions. In describing the various types more or less repetition is unavoidable. For the sake of brevity it seems expedient to begin the discussion of the 74 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. rocks by noting the minerals which result from the metamorphic processes one by one, leaving for subsequent discussion the various combinations in which they occur. Biotite. When foils of biotite are compressed into zigzag outlines by the pressure of adjacent clastic grains the mineral is evidently allothigenetic. In some other cases there is a lack of decisive proof as to the origin of the biotite, but there are also occurrences which can only be interpreted as au- thigenetic. The authigenetic biotite scales are sharper in outline than the allothigenetic foils, and are usually of a light, clear, chestnut-brown color. In cross-section they are often seen to be undulous, but do not form broken lines like clastic foils. They are frequently embedded in recrystallizing feldspar grains. The quantity of this mica detected is small, and it seems probable that when formed it readily passes over into white mica by epi- genesis. In one glaucophaue schist from New Idria there is a great abun- dance of fine, nearly uniaxial biotite. Muscovite. The epigenetic formation of white mica from biotrteand from feldspar has long been recognized. In the recrystallizing sandstones of the Coast Ranges white mica is rather rare as an indubitably allothigenetic com- ponent, but is very common as an alteration product of brown mica. It also appears to form in the cementing mass of fine detritus and deposits between the clastic grains of sandstones; but, while the occurrences and the analogies are such as to warrant an opinion that such foils of white mica are authi- genetic or epigenetic on authigenetic biotite, it can hardly be demonstrated that this material is not allothigenetic. In the more altered rocks it is seen forming in disintegrating feldspar grains and it is an important constituent of the glaucophane schists. Where it can be separated in foils it is found that the angle of the optical axes is large. Augite. Though a careful watch has been kept for rhombic pyroxene, none has thus far been detected in any of the nietamorphic rocks. In the rocks which retain an unmistakably clastic structure augite is rare, a fact which appears to be due to the tendency of the mineral to decomposition when the structure of the rock in which it exists is sufficiently open to permit of the free percolation of solutions. There are a few examples, however, which leave no doubt as to the fact of the formation of augite in sandstones COMPONENT MES'EKALS. 75 undergoing the process of metasomatic recrystal-lization, and which thus form a link between typical sandstones and the more highly altered rocks in which the clastic origin is not evident on mere inspection. In these rocks minute bacillar augitcs make their appearance irt newly formed aggregates limited by the outlines of the original clastic grains. There is clearly a tendency to parallelism and to grouping of these augite crystallites, and the evidence points irresistibly to the conclusion that under favorable circumstances large solid crystals of augite form by the union of these smaller masses. In a considerable number of instances these microlites are actually united in close groups bounded by crystallographic outlines. The usual occurrence of gar- net in metamorphic rocks indicates an entirely similar process of aggrega- tion. It is quite impossible to ascribe any but an authigenetic origin to these characteristic occurrences of augite in newly formed aggregates arising from the alteration of clastic grains, nor is such a formation surprising, since the artificial reproduction of augite by the action of heated water under pressure upon appropriate mineral mixtures is a well known phenomenon. A fine example of a partially formed augite crystal in an altered sandstone is shown in Fig. 2, page 88. In the more fully crystallized metamorphic rocks augite is often very abundant. It is of lighter tint under the microscope than the ordinary bamboo-colored augites of eruptive rocks, is monochroitic, and extinguishes at high angles. It readily passes over into uralite, chlorite, epidote, and ser- pentine. The uralite often has a bluish tint approaching that of glaucophane. There is a marked tendency in the larger augite crystals to the development of the orthopinacoidal cleavage, and in a few of the rocks the pyroxene is well developed diallage. Hornblende This mineral occurs in the recrystallized and recrystallizing rocks in two forms. Brown hornblende forms much in the same way as augite and is observed sometimes in the same slides with it. Groups of hornblende microlites also show common crystallographic outlines; a case of this kind is shown in Fig. 3, page 89. Either minute chemical differences or certain physical conditions seem to regulate the preponderance of the one mineral over the other, so that the fully recrystallized rocks are divisible with some sharpness into horriblendic 76 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. and augitic groups. No clear indication has been detected that the mode of occurrence differs for the two classes. This may nevertheless ba the case, for the amphibolic and pyroxenic rocks are macroscopically indis- tinguishable, excepting in a few cases, and differences in occurrence would thus readily escape detection. At present it seems more likely that the controlling factor is an unknown and certainly very slight difference of chemical composition. Observation has shown me that it is absolutely necessary in some eruptive rocks to resort to a chemical explanation of the replacement of one of these minerals by the other without affecting the probability, in another class of instances, that the same replacement is due to differences of physical condition. 1 Green hornblende is also very abundant. Much of this is certainly uralitic and some of it appears probably due to the alteration of brown hornblende. There are also cases in which the green hornblende, so far as can be judged, is a direct product of metasomatic action, but none in which every other explanation is excluded. There are further instances which suggest the existence of a brown nralite, btit these cases are believed to be better explained by envelopment. The authigenetic hornblendes are readily distinguished from allothi- genetic fragments, the latter being commonly of a dark, dirty-green color and much more pleochroitic than the newly formed mineral. The outline of clastic fragments is usually characteristic. In extreme cases there is some difficulty in distinguishing green hornblende from chlorite, but where the particles are not excessively minute the oblique extinction of the former is generally perceptible. oiaucophane. This is a prominent component of the micaceous schists 2 and occurs also in the more composite granular rocks and in the amphibo- lite. Cross-sections frequently show the amphibolic outline and cleavage. The pleochroism and absorption are strong. The pleochroic colors are a, brownish yellow to colorless; 1)> violet; c, ultramarine blue. The absorp- 1 For some curious evidence bearing on this point, ECC my Geology of the Comstock Lodo ami ihe Washoe District, Mon. U. S. Gcol. Survey No. 3, p. GO. 'According to Mr. H. G. Hanks, glaucophane was detected by Mr. Micbel-L<5vy, in 1878, in speci- mens of micaceous schist from the Wall Street quicksilver mine, Lake County, exhibited at the Paris exposition in 1878. (Fourth Annual Report of the State Mineralogist of California, 1883-'84, p. 182.) COMPONENT MINERALS. 77 tion is e> i> a. The angle of extinction is that of amphibole, but the interference colors are of lower order. The specific gravity is 3.10 to 3.11,' but the mineral is visually so intimately associated with others as to make a perfect separation difficult. The genetic relations of the glaucophane are not entirely clear. In the greater number of cases it is closely associated with ordinary actinolite, and there appear to be unquestionable transitions between the two. Thus, one portion of an area of entirely undecomposed amphibole of uniform orientation is often bright blue, another green, and these pronounced tints shade off into each other by imperceptible gradations. Had only these oc- currences been observed, the conclusion would have been almost inevita- ble that the two varieties of amphibole had been produced simultaneously and by the same methods. There are other cases, however, in which nar- row streaks of the blue mineral appear along the junction of actinolite crystals, which suggest the possibility of epigenesis of glaucophane upon actinolite. I am inclined to consider this suggestion misleading, however, because fibration and sensible difference of orientation would almost inev- itably result from such a process. zoiskc. Much the most interesting mineral yet detected in the rocks undergoing metasomatic recrystallization is zoisite, which as an important rock-forming mineral has hitherto been observed only in the saussuritic crystalline schists and gabbros. In the rocks of the Coast Ranges this mineral is one of the first indications of recrystallization; it is found in slides of every group of the recry stall! zed rocks and is often present in large quantities, especially in the schists. The zoisite presents no good cleavage, but traces of fissility parallel to the main axis are sometimes visible. The prisms are usually jointed and terminal faces are often distinct. Measurements of the projection of the interfacial angle between the brachydome and brachypinacoid agree with the real value of this angle as well as could be expected. Square cross-sec- tions are not uncommon and often only a single corner appears to be trun- cated. This irregular development of faces in the vertical zone is charac- teristic of zoisite. 2 "Liideeko found the spccilie gravity of glaueophane, from Syra, 3.101 (Kotli: All#. mid cliein. Gool p. 21). -' Pann's System of Mineralogy, p. 2DO. 78 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The color of the zoisite, as seen by the naked eye, varies from gray to deep green. In the former case it is of course colorless in thin section, and this is usually the case in the augitic and hornblendic rocks, though a faint greenish yellow may sometimes be observed. In the glaucophane rocks the color is usually deeper, and the pleochroism h then distinct in thin section, c being yellowish green to light grass green and a and l> almost colorless. The absorption is hardly perceptible. The pleochroism increases with the thickness of the section. The axes of elasticity, when their position can be determined, are always strictly parallel to the vertical crystallographic axis and to the pinacoidal faces. The angle of the optical axes is large and the plane of the axes is parallel to one of the pinacoidal faces. The colors of interference usually range between a bluish gray and a pale yellow, but are occasionally more vivid. The intensity of the colors often seems to vary considerably with the state of aggregation. Zoisite occurs in the phthanites as well as in the other metamorphic rocks, biit usually in much longer needles than in the other metamorphic rocks. Fig. 1 shows both types of crystals, between which there are plenty of intermediate forms. Tic;. 1. 7-oiaite ivicroliles, a, 6, ami c, from a glaucophane rock, No. 31, Sulphur ISii'.k. a and I arc magnified 175 diameters; c, ICG diameters ; d is from minute quartz veins in phlbanite (Xo. 51, Mt. Diablo) and in magnified ISj diameters. For the purpose of checking the microscopical determination of this mineral, two separations and analyses were made. Though great care was taken in the separation and purification, the character of the rocks showed that only approximate results were to' bo expected. No. 98, Sul- ZOISITE. 70 phur Bank, which will be described on a future page, consists mainly of glaucophane and zoisite; but fine needles of the former penetrate the latter. The purest lot of zoisite had a specific gravity of 3.21, which is less than that of unmixed zoisite, but greater than that of glaucophane. Its compo- sition was found to be as follows: Water at above 10'J, H-0 5.25 Silica, SiO- 39.80 Titanic acid, TiO-' Trace Aluraiua, AW 22.72 Ferric oxide, Fe-O :> 4. 85 Ferrous oxide, FeO 1.49 Manganous oxide, MuO 0. 26 Lime, CaO 17.55 Magnesia, MgO ' 3.89 Soda, Na*O 4.09 Potassa, K 2 O 0.12 Total 100.02 The atomic ratio H 2 : R" : Pc vi : Si is represented by 2.62 : 4.54 : 6.82 : 12. This clearly does not correspond to pure zoisite, of which the ratio is 1 : 4 : 9 : 12, and the question arises whether it may represent any other lime-alumina silicate. A glance at the minerals of similar composition, the density of which lies between 2.90 and 3.50, shows that the choice is small, and in fact, among known minerals, is limited to zoisite and prehnite. The specimen analyzed was more acid than zoisite, but more basic than prehnite. Considering that the maximum density of prehnite is 2.95 and that the known impurity of the specimen is acid, the tendency is all to the suppo- sition that the mineral is zoisite. If one supposes the admixture to bo simply a bisilicate of a protoxide base and that this impurity contained about one-fourth of the silica, the above atomic ratio reduces almost ex- actly to 3 : 4 : 9 : 12. It is true that glaucophane is an aluminous amphi- bole and that if sesquioxides are subtracted from the analysis the ratio 4:9:12 cannot be exactly preserved; but the rock also contains quartz and the atomic ratio of zoisite is known to vary to some extent. The figures discussed, in connection with the known impurities, are thus suffi- cient to show that the mineral is not prehnite and is far more closely allied to zoisite than to any other known mineral. There is an excess of water 80 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. shown by the analysis, which seems to have arisen from imperfect desic- cation. A second separation was undertaken with No. 219, Sulphur Bank, a rock composed chiefly of greenish zoisite and actinolite, the former em- bedded in the latter. It was impossible wholly to separate the two minerals and the purest sample had a specific gravity of no less than 3.37, show- ing that much actinolite remained. The analysis gave the following results : Loss above 100, H 2 O 1.119 Silica, SiO 2 39.196 Phosphoric acid, P 2 O S Trace Titanic acid (rutile), TiO- 1.169 Alumina, APO 3 22.760 Ferric oxide, Fe s O 3 6.487 Ferrous oxide, FeO 1. 783 Nickel oxide, NiO Trace Manganous oxide, MnO 0.090 Lime, CaO 22.023 Magnesia, MgO 1. 643 Soda, Na 2 O 3.382 Potassa, K 2 O 0.575 Total 100.227 This analysis gives the atomic ratio H 2 : R" : R vi : Si = 0.57 : 4.56 : 7.22 : 12. Here, also, if the admixed silicate has a protoxide base and if it contains about one-sixth of the silica, the ratio is reduced to one resem- bling that of zoisite, viz, : 4 : 9 : 12. In this case there is too little water instead of too much, but in performing the analysis the sample was accidentally dried at somewhat above 100. Although zoisite is extremely abundant in the metamorphic rocks of California, there were no specimens which seemed so well adapted to a separation as the two discussed above. The manner in which the compo- nents of these rocks are intergrown renders separations almost impracti- cable. Impure as the materials analyzed were, however, the results show that the substance in question was really a zoisite. Under different conditions zoisite possesses a considerable similarity to other minerals. Especially when granular, it might at first sight be confounded with epidote ; but it is distinguished by its color, its mono- ZOISITE. 81 chroism or slight dichroism, by the colors of interference, and, when seen in cross-section, by the angle of extinction. The more highly colored zoisite in prisms bears a superficial resemblance to augite, which needs: only to be pointed out to avoid confusion. The mineral in the form of small prisms and needles may readily be confounded with apatite. The latter, however, does not give the yellow interference tints of zoisite and seldom shows .the liglnVgreen tint in natural light which is frequent in zoisite. The index of refraction of zoisite seems to be higher than that of apatite, so that its crystals stand out in relief from the slide sim- ilarly to those of zircon, though not to the same extent. Cross-sections of zoisite are also usually square, and by careful use of the micrometer screw zoisite prisms may usually be seen to be fluted or furrowed in the direction of the principal axis, while apatite prisms display, so far as I know, no such irregularity of surface. The distinction between these min- erals can be drawn by one or more of these means in almost all cases, but the discrimination requires watchfulness. Microlites of zoisite sometimes present an appearance somewhat resembling that of a rhombic pyroxene, but hypersthene is as a rule strongly dichroitic, while enstatite is usually fibrous and seldom if ever forms crystals. Prehnite is a mineral which might readily be confounded with zoisite, from which it is distinguished by specific gravity and by behavior to acids. These are not very satisfactory distinctions, because it is hardly practicable to test every slide with acids or to obtain the specific gravity of the mineral in every specimen. A con- siderable number of such tests have been made, however, and in no case did either test indicate the presence of prehnite, nor has prehnite been detected macroscopically. /oisite in the recrystallizing sandstones not only forms in aggregates of recrystallizing minerals, but also results from the attack of quartz grains. Well developed crystals of zoisite, with somewhat rounded terminal faces, may often be seen growing into quartz grains from the outside almost exactly as they might develop iu a limpid fluid. It must of course be sup- posed in such cases that there is a space between the ingrowing crystal and the surrounding quartz which admits of the penetration of fluids, though under the microscope no such opening is visible. If there is one, the para- MON XIII- 82 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. sitic crystal must enlarge in diameter as well as in length, and such appears to be the fact, for the longer crystals are as a rule also the larger ones. Zoisite is unknown in eruptive rocks, except as an epigenetic constitu- ent In the Coast Ranges the relations of the zoisite to the disintegrating clastic elements of the altered sandstones are such SANDSTONES. In various specimens of altered sandstone one or other process of transformation may be lacking or insensible, but in a number of cases a single slide furnishes an almost complete epitome of the entire series. I do not think it possible to convey to the reader a better idea of the metamorphism of the sandstones than by describing a few typical in- stances. Examples. A good example of an altered sandstone is afforded by a rock from near Knoxville. 2 Macroscopically it is a dark-green, fine-grained sandstone, evidently somewhat altered. Seen under the microscope with a low power it appears to be a typical sandstone, with only insignificant changes. With a No. 4 Hartnack it is seen to contain numerous unaltered blende. The statements applicable to the viridite of the hornblende from Franoke's point of view are true also of the chloritic material derived from angite and which, as we have seen, so often fills feldspathic sections, for these two substances, so imperfectly determined from a chemical point of view, present fundamental analogies in composition. We have been led to regard the epidote inclosed in feld- sparsections not as psendomorphic after feldspar, but as a result of the transformation of chloritic matter. There are, furthermore, numerous instances of this transformation." 'Zeitschr. fiir Krys. uud Mineral., Oroth, vol. (>, p. 321. 8 No. 8, Coast Eauge collection, bed of Jericho Creek. 88 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. grains of granitic quartz and feldspars, but it also becomes apparent that a great proportion of the allothigenetic minerals have been converted into aggregates of new minerals. Especially important is the presence in this slide of unquestionably authigenetic augite and hornblende. Augite occurs in several places under circumstances which place its authigenetic character beyond doubt. Of these the best is illustrated in the accompa- nying Fig. 2. It is a slightly greenish prism with terminal faces forming angles on the right and left sides, respectively, of l'2b and 128, and an angle of extinction of about 30. It occurs in a crystalline aggregate fill- ing the position of a clastic grain of which the outlines are traceable. The portion not occupied by the augite is composed of macrocrystalline feld- spar and quartz. There are also films of serpentine among the grains. The upper right-hand corner of the augite is changed to uralite. FIG. 2. Authigenetic angitc in altoml sandstone, No. 8, Coast Ranges. A, augite; w, nralite; /, mioiocrystallino feld- spar; 7, quartz grain ; , serpentine. Magnified 11? diameters. Authigenetic hornblende of light-brown color is also present, and the best example appears in the following Fig. 3. It is surrounded on two sicles by microcrystalline, authigenetic feldspar and lies against a clastic orthoclase grain. As appears from the cut, a large part of the outline is as sharp as possible. The unabraded corners, the color and character of the mineral, and the association all forbid its being regarded as allothigenetic. On the left side are a number of hornblende microlites in parallel position, apparently representing the incomplete portion of the crystal. ALTERED SANDSTONES. 89 Various other phenomena can be studied in this slide: Zoisite, in prisms and granular masses, is developing in some of the clastic grains; triclinic feldspar, in grains and in polysynthetic microlites, is forming in others; and the resolution of quartz as well as oT feldspar can be observed. White mica is forming authigeneticallv, and perhaps also apatite. Decomposition has also set in and the slide contains some serpentine. These phenomena are better observed, however, in other cases. Fir,. H. Authigenetic hornblende in altered sandstone, No. 8, Coast Ranges, a, clastic quartz; b, clastic feldspar; c, authi^euetH'. hornblende; . 093 Soda, NaK) 4.597 Potassa, K'O 0. 1!)9 Total 100.482 The atomic ratio deduced from this analysis is H 2 : R" : fi vl : Si 0.162 : 1.116 : 0.935 : 3.272. No. 11, Knoxville, appears microscopically a green, much-altered sandstone, intersected by numerous minute veins of white mineral. Under the microscope it is found to be a holocrystalline pseudodiabase consider- ably decomposed. The feldspars are in part granular, but chiefly lath- shaped crystals from O.l mm to 0.4 mm in length. They are mostly clouded by very small interpositions. The greater part show polysynthetic structure, and the highest angles of extinction found were from 16 to 18 on each side of the twinning plane. The fine grain of the rock and the presence of much epigenetic chlorite make separation difficult. It was found, how- ever, that the last precipitate fell at a density of 2.63, and there is there- fore little orthoclase, if any, in the rock. The feldspar must be chiefly, if not wholly, oligoclase. The veins in this slide are filled for the most part with beautiful prismatic crystals of plagioclase mixed witli calcite. The augite occurs as imperfect prismatic crystals and grains, either included in the feldspars or between the crystals of the latter. Its color is very faint ; it is not dichroitio and gives characteristic extinctions. The large amount of chlo- PSEUDODIABASE. 99 rite appears due to the decomposition of the augite. Zoisite is not very abundant in this slide, but is present in characteristic prisms. Ilmenite and leucoxene are frequent. Xo. 36, Sulphur Bank, is a dark-green, fine-grained, crystalline rock, in which feldspars and bisilicates can be seen with the naked eye. Under the microscope all the feldspars appear to be twinned and those which are favorably placed for examination give angles of extinction appropriate to oligoclase. The slide contains a little quartz. The pyroxene is mostly in the form of small grains, but there are some larger crystals giving the angle of extinction of augite. The mineral is almost colorless. The slide also contains one hornblende prism. Titanic iron and unquestionable tran- sitions from this to titanite are common. This slide shows notable secondary changes. Uralitization, which is so common in the pseudodiabases, is here entirely absent) The augite de- composes directly into serpentine and chlorite, both of which are abundant. A complete analysis of this rock was made. The composition is ex- tremely similar to that of No. 21, Coast Ranges, given above: Loss at 100, H-O 0.389 Loss above 100, H-O 2.965 Silica, SiO- 51.278 Phosphoric acid, P 2 O S 0.131 Titanic acid, TiO 2 1.330 Alumina, A1 2 3 15.048 Ferric oxide, Fc-O 3 2.415 Ferrous oxide, FeO 8.014 Nickel oxide, NiO 0.098 Manganous oxide, MnO 0.251 Lime, CaO 7.079 Magnesia, MgO C. 069 Soda, Na a O 4.433 Potassa, K-O 0. 123 Total 99.623 The atomic ratio deduced from this is H 2 : 11" : S vi : Si = 0.373 : 0.931 : 0.974 : 3.419. PSKUDODIORITE. The pseudodiabase passes by transition into gabbroitic modifications on the one hand and into pseudodiorite on the other. There is no general 100 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. and characteristic distinction between pseudodiorite and pseudodiabase, as seen under the microscope, excepting the character of the bisilicate, and it is only when the bisUicate is unusually abundant that the two rocks can be told apart without the microscope. An interesting pseudodiorite is No. 179, Knoxville. This is a fine- grained, crystalline, dark-green rock, in which amphibole is visible macro - scopically. Under the microscope it is seen that the rock is a porphyry, containing large grains of hornblende 5:i a fine-grained, colorless grouncl- imass. When well exposed this groundmass shows a faint net- work of green- ish lines, which, judging from the form of the net, represents the outlines of the original clastic structure. Cracks also intersect the groundmass, and these often radiate from the porphyritic hornblendes in a very peculiar manner, as if the hornblendes had expanded forcibly while forming. The groundmass is very fine-grained, the individuals ranging from 0.01 mm down- wards. Polysynthetic microlites were not detected, but the material precisely resembles that in another rock from the same district (No. 105, Knoxville), which was isolated and found to have a specific gravity of 2.64, to contain 59.14 per cent, of silica, and to correspond qualitatively to andesine in composition. The hornblende is of a brownish-green color and forms grains reach- ing half a millimeter in length. In the hornblendes are small shreds and patches of glaucophane. In other pseudodiorites (for example, No. 183, Knoxville), there is more glaucophane and single crystals of amphibole may be seen, blue at one end, green at the other, and of intermediate tints in the middle. The glaucophanic pseudodiorites form a link between the granular, crystalline rocks and the glaucophane schists. This slide shows ilmenite and leucoxene, but no zoisite was detected. There runs through the slide a vein which is filled with chlorite and a colorless mineral of un- certain character. The hornblende in the pseudodiorites is sometimes so abundant as to form much the greater part of the rock, which may then be considered as an amphibolite. One of the best examples of this kind is No. 56, Knox- ville. It is composed almost exclusively of long, slender, greenish crystals GABBROS. 101 of actinolite in nearly parallel arrangement, giving the mass a schistose character. The microscope shows a little white mica, chlorite, and serpen- tine in the rock. Included in the actinolite are also grains of titanite, brown, somewhat pleochroitic prisms of rutile, nnd small zircons. Long, thin, dark inclusions, arranged parallel to the cleavage of the amphibole, are perhaps also rutile. The following analysis shows the composition of this rock: Loss at 100, H-O 0.008 Loss above 100, H-'O .'. 0.910 Silica, SiO 2 50. 4;i7 Alumina, Al'O" 8.183 Chromic oxide, Cr ! O' 0.480 Ferric oxide, Fe-O 1 1.059 Ferrous oxide, FeO 6. 285 Manganous oxide, MnO 0.213 Lime, CaO 11.550 Magnesia, MgO 17.628 Soda, Na-O 2.982 Potassa, K-O 0.503 Total 100.304 The atomic ratio deducible from this analysis is H 2 : H" : R vl : Sir: 0100 : l.f>73 : 0.539 : 3.362. GABBROITIC PSKUDODIABASK. While a tendency to the development of the clinopinacoidal cleavage of the pyroxenes of the pseudodiabase has been already noted, character- istic diallage is somewhat rare. One occurrence is known on Bagley Creek, at Mt. Diablo, the great mass of which is composed of zoisite-pseudodiabase and phthariites. It is a dark-green rock, composed of granules of from one to two millimeters in diameter. Fresh feldspar and the grayish-green, al- most metallic luster of the diallage cleavage surfaces are visible with the naked eye. Under the microscope the diallage is monochroitic, nearly colorless, and carries inclusions in the direction of the best cleavage. The slide con- tains a little uralitic hornblende. In a few places a decomposition-product, similar in appearance to the ferruginous cement of the sandstones, appears to have formed from the diallage. The feldspars are clear and give extinc- tions jis high as 30 on each side of the twinning plane, indicating the pres- ence of labradorite. 102 QUICKSILVER DEPOSITS OF THE I'ACIFIC SLOPK. The hand specimens of this rock do not greatly resemble eruptive masses and the nature of the occurrence clearly indicates their metamorphic character, but the slide is indistinguishable from thin sections of eruptive gabbros. There appears to be no reason to consider the above-described rock as anything more than a variety of the pseudodiabase. A similar rock is found at the Great Western, and at New Almaden a gabbro occurs as pebbles, apparently derived from the mountains to the south. GLAUCOPIIAXE SCHISTS. character. Accompanying the granular, holocrystalline metamorphics, in much smaller quantities than these, are somewhat schistose rocks, which are sometimes evidently micaceous and sometimes appear to the naked eye chloritic. All of these are found to carry glaucophane, iisually accompa- nied by zoisite and mica. Some of them are macroscopically indistinguish- able from specimens from Syra. They are so related structurally to the granular rocks as to show them to be members of the same series, and, as has been shown, glaucophane and zoisite both occur in the granular rocks. It is worthy of note that the plagioclase of the granular rocks and the glau- . cophane of the schists each imply the presence of sodium in the solutions, by which metasomatosis of the sandstone series was effected. The zoisites also, at least in part, contain alkalis. Though glancophane rocks are not infrequent in the Coast Ranges they usually occur only in small patches, and it is seldom possible to trace them to their unaltered form. At Mt. Diablo, however, they certainly pass over into slightly altered shales, and there is also evidence elsewhere that the schistose structure is an original feature, not a result of metamorphism. The predominant cleavage in these schists is marked by a prevailing similarity of direction of the glaucophane prisms and mica foils, although by no means all of the crystals of either mineral are similarly placed. The structure and association of minerals will best be described by examples. Examples. No. 31, Sulphur Bank, is a schistose, gneiss-like rock, in which layers of greenish mica, in small foils, traverse a fine-grained, reddish or greenish gray, granular mass. Bluish-gray grains of glauco- (iLAlJCOIMfANU H01I1ST. 103 phane are also macroscopically visible. Under the microscope a great portion of the rock is seen to be made up of interlocking grains of quartz and nnstriated feldspar. In the Thoulet solution a considerable amount of feldspathic material floats at .'5.59, and this-gives a strong potash reaction, showing that the material is at least in part orthoclase. Higher specific gravities and chemical tests show that plagioclase is also present. The slide contains a number of large glaucophane crystals, some of them, which arc cut across the principal axis, exhibiting the characteristic amphibole prism and cleavage. The optical properties are as described on a previous page. There are few microlites of glaucophane. Embedded in the mass of feldspar and quartz are numerous green hexagonal foils, which give the optical reactions of mica and are soluble with difficulty in hot sulphuric acid. The mineral is probably a biotite. White ' mica is also present. The scales of this mineral cannot well be separated, but in a similar rock (No. 117, Coast Ranges) white mica is present in foils of considerable size, which can be separated. They show a large angle between the optical axes, and are therefore probably muscovite. Zoisite is abun- dant in No. 31, in well developed, pointed prisms with terminal faces. It is greenish and slightly dichroitic, which is unusual. The slide contains a few garnets and much titanite. Some well developed rhombs of the latter min- eral include ilmenite grains. Apatites, zircons, and a little chlorite con- nected with the biotite were observed. In the groundmass are groups of long, colorless, radiating fibers, which appear to extinguish light in the direction of the main axis and when densely massed give very vivid inter- ference colors. These properties correspond to fibrolite, and, did these needles occur in a true gneiss, instead of in a Cretaceous, metamorphic rock, no hesitation would be felt in identifying them as such. Under the cir- cumstances and in the absence of opportunity for determining their specific gravity, it is not safe to pronounce on their composition. No. 147 corresponds in some particulars to the rock just described; brilliant, brown biotite, however, with characteristic interference figure, replaces the muscovite, and a small portion of the feldspar shows striations. The glaucophane is in all respects similar. Apatite is present, but zoisite could not bo identified with cnrtaintv. 104 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. No. 98, Sulphur Bank, is a greenish-gray, schistose rock, consisting chiefly of glaucophane and zoisite. The latter occurs in imperfect prismatic crystals, with a maximum length of from O.l mm to 0.2 mm . The prisms show longitudinal furrows. The zoisite is distinct!} 7 dichroitic and has a faint olive-green tint when the prisms are parallel to the principal section of the nicols. Sections perpendicular to the main axis are square, often with one truncated corner. The extinctions are normal and the colors of interference' are gray to yellow in the prisms, but more vivid in granular aggregates. The angle of the optical axes appears to be large. Glaucophane, in needles and long, imperfect, nearly parallel prisms, gives the rock its cleavage. Quaiiz, albite, muscovite, and titanite arc present. The rock was reduced to a grain of one-third of a millimeter, and sep- arated by the Thoulet method with the following result: Specific gravity of solution. 3.22 3.21 3.10 3.03 2. 04 2.56 2.C8 diameter if] recipit;ito. Small quantities of opacito and titanite. Tolerably pure zoisite, which was repeatedly purified. For anal\ KM, j*ce p. 71). No precipitate. Glaucopliane suspended. Glaucophane, with some zoisite and muscovite. Nearly pure quartz. A small quantity of feldspar, probably albite. A very few grains of a colorless, indeterminable imru'r. 1. A complete analysis of the rock gave the following result: Loss at 1CO, H-O 0.000 Loss above 100, II-O 3.842 Silica, SiO 3 49.680 Phosphoric acid, P 2 5 0.206 Titanic ocid, TiO- 1.305 Alumina, AW 13.603 Ferric oxide, Fc 5 O 3 1. 8C2 Ferrous oxide, FcO 8.606 Manganoiis oxide, MuO 0.038 Lime, CaO 10. 9G? Magnesia, MgO 6. 203 Soda, Na'O 3.091 Potassa, K=O 0. 11U Total W.584 DECOMPOSITION OF THE ROOKS. 105 Tho atomic ratio dedueible from this analysis is IP : R" : S VI : Si = 0.427 : 1.04-1 : 0.868 : 3.312. DECOMPOSITION OF THK CRYSTALLINK ROCKS. character. All the crystalline rocks iu'Q often found in a more or less J advanced stage of decomposition. Besides serpentinization, which will be treated in a separate section of this chapter, there have been other processes lit work, particularly the epigenetio formation of uralite, chlorite, and nac- rite. Though it is difficult to make out the precise relation of these trans- formations to serpentinization, reasons are given elsewhere for believing them to belong substantially to a different period from the serpentinization. The conversion of augite to uralite is common in the augitic metamor- phics and ordinarily presents no peculiarity. As has already been men- tioned, however, brown hornblende and augite are in one case so associated as to suggest epigenesis, though it is believed that the phenomenon is really one of envelopment. Chlorite forms directly from brown hornblende, ural- ite, augite, and garnet. It is also not infrequently found in needles in feld- spar in such a way as to suggest the supposition that it may be a result of the attack of feldspar by solutions. Epidote is found much less abundantly than it often is in eruptive rocks. Its relations to chlorite are referred to under the description of epidote. In a single pseudodiabase from New Almaden somewhat irregular, six-sided scales, showing 1 radial striation and remaining sensibly dark between crossed nicols, occur in the feldspars and are supposed to be nacrite. Less well developed flakes of a similar sub- stance are common in other rocks, but no considerable quantity of anything corresponding to the descriptions of kaolin has been detected. Iron oxides, carbonates, and leucoxene (probably titanite) are abundant. 1'IITHANITKS. character Associated with the sandstones of every group in the Coast Ranges is more or less shale, which, however, seldom forms any large por- tion of the exposures. Some of these shales do not effervesce with acid, and analysis shows that these contain extremely little lime or magnesia ; others are composed to a large extent of carbonates. The shales of the 106 QUICKSILVER DEPOSITS OF TIIK PACIFIC SLOPE. Knoxville group are sometimes unaltered, but more frequently silicified to chert-like masses of green, brown, red, or black colors, intersected by in- numerable veins of silica. These highly altered shales, when very thin- bedded, break into parallelopipedic fragments, but where the beds reach a thickness of half an inch or more there is a decided tendency to conchoidal fracture. The green varieties are infusible before the blow-pipe, while the brown specimens are more or less fusible. The only essential difference appears to be in the state of oxidation of the iron, which is partially solu- ble in the reddish rocks. The most convenient name for these rocks is phthanite, introduced by Haiiy to designate quartzose, argillaceous rocks with a compactly schistose structure. This term has sometimes been em- ployed in a more special sense to denote siliceous beds intercalated in lime- stone, but this limitation will not be adopted here. 1 PhthanJtes occur in all the metamorphic districts of the Coast Ranges, and, though the quantitative proportion which they bear to the other rocks is not great, the marked contrast between them and the surrounding masses gives them prominence. Geologically it is impossible to dissociate the phthanites from the altered sandstones, holocrystalline, metamorphic rocks, and serpentine. All of these rocks, with transitional varieties, are found together and are often mingled in the confused masses of rubble which have sometimes resulted from intense dynamical action. The metamorphic character of the phthanites is manifest both from their structure and from the transitions which exist, for example, at Venado Peak, New Idria into ordinary shales. Under the microscope, also, the most highly indurated specimens are found to contain fossils The peculiar habitus of the phthanites appears to arise from the fact that the shales have offered great resistance to serpentinizatibn, although they have not wholly escaped this alteration, while they were admirably adapted both to silicification and to the display of a net-work of quartz veins. The mass of the phthanites as seen under the microscope consists mainly of fine-grained, crystalline silica, occasionally accompanied by a 1 Compare Mr. Renard's Recherches lithologiques snrles ]>litl)aiiit<\s du ciilciiirn r;irl>oiiil7>n> do Be]. gi. Ifil. VARIETIES OF SERPENTINE. 109 talline 'substances, but that colors are usually apparent in laminated and fibrous varieties. According to Professor Rosenbusch 1 the distribution of color in polarized light varies with the structure, here in patches, there sinuous or in parallel streaks. Especially where the structure is fibrous and chrysotile-like the change of colors, though not strong, is unmistakable. Where the structure permits of optical examination the substance is found to polarize light more or less strongly and to be biaxial, with a highly varia- ble angle between the optical axes. Messrs. Fouque and Michel-Levy 9 pro- nounce serpentine a colloid mineral without any proper action on polarized light, although eminently susceptible of presenting the optical phenomena due to pressure. Thus, in very thin sections the colors of polarization affect very pale, bluish tints and the greater part of the substance does not react between crossed nicols; but in thick slabs, on the contrary, the colors are often vivid and brilliant. On the other hand, foliaceous varieties of the mineral have been described in a number of very important investigations of the serpentinoid rocks which agree with Professor Rosenbusch's descrip- tion. Rocks of this class were investigated b}' Mr. von Drasche and later by Messrs. Weigand, 3 Becke, 4 and Hussak, 5 all of whom found them mainly composed of foliaceous, distinctly polarizing, serpentine varieties, such as bastite, picrosmine, and metaxite. Mr. Hussak has described this material minutely and referred it to antigorite. According to this authority it has considerable pleochroism, is biaxial, and shows blue-gray tints be- tween crossed nicols. The analysis is that of a somewhat ferruginous ser- pentine. Mr. F. Eichstiidt, 8 in discussing the antigoritic serpentines of northern Sweden, says that the foliaceous mineral always extinguishes light when the cleavage plane coincides with a principal plane of the nicols, but that when the cleavage plan is horizontal the mineral remains dark between crossed nicols. It does not dichroise sensibly. The interference colors are often quite vivid, especially in the coarser, foliaceous varieties, but are fre- quently feeble and then change from black to grayish blue. 1 Phys. der Mineral., p. 372. -Miu. uiic., p. 441. 3 Tscherniaks mineral. Mittheil., vol. 3, 1875, p. 183. 4 Ibid., vol. 1, 1878, p. 459. "Ibid., vol. 5, 1883, p. 61. "Grol. Fiireuingens Stockholm ForhftUtD., vol. 7, 1^4, \>, 358. 110 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. No serpentine which remains dark between crossed nicols is found in the slides from the Coast Kanges, and excellent cleavage pieces mounted in balsam give biaxial interference figures and show that the bisectrix and the plane of the optical axes are perpendicular to the cleavage. The angle of the optical axes in the cases thus examined is not very small. In cross- section the extinction always takes place exactly parallel to the traces of the cleavage. The colors of polarization vary greatly. They are sometimes confined to different shades of gray; often, however, portions of slides in which gray is the prevalent color show dull, yellow tints, and in rather exceptional cases reddish tints are visible. This variation is frequent in slides of irre- proachable thinness and uniformity and does not depend on a mere differ- ence in the thickness of the rock section. In grinding slides, however, it is found, as would be supposed, that thick masses give more brilliant colors than thin ones. The serpentine usually shows the merest trace of dichroism, but occasionally a very perceptible change of color may be observed. Only one case is known (No. 21, New Almaden) where a remarkably vivid -green serpentine is strongly dichroitic and might readily be confounded with chlorite unless examined between crossed nicols. A particularly pure-look- ing, light-green, marmolitic serpentine (No. 110, New Idria) was selected for investigation. A complete analysis was made, with the following re- sult : Silica, SiO 2 41.540 Magnesia, MgO 40.420 Water, IPO 14.175 Alumina, AK) 1 2.480 Ferrous oxMe, FeO 1.370 Nickel oxide, NiO 0.040 100. 025 In pure serpentine 40.42 per cent, of magnesia corresponds to 41.52 per cent, of silica. It appears, therefore, that this mineral is in fact a serpentine comparatively free from impurities and certainly containing no talc. A slide was also cut across the lines of structure at a point where the specimen appeared extremely uniform. When reduced to the proper thinness it was found that the material was far from homogeneous. A por- TKSTS OF SERPENTINE. Ill tion as seen under the microscope appeared absolutely colorless by trans- mitted light, while the remainder was of yellowish and brownish tints, in spots almost opaque, although by reflected light this portion retained the pale apple-green color of the hand specimen. The more highly colored portions of the slide appear to be clouded by the presence of extremely tnicrocrystalline particles, perhaps ferric oxide; but these particles can hardly have any direct connection with the more brilliant colors of polari- zation, for the portions containing them, when in proper relation to the nicols, extinguish light almost as completely as the others. The entire slide has a banded structure, occasioned by the arrange- ment of fibers, which is similar in character to that most usual in the ser- pentine of the Coast Ranges, though more simple. The colorless portion between crossed nicols varies from black to light gray, and the brilliancy of the tints increases with the coloration, being yellow in certain positions where the mass is lightly colored and red where the color in natural light is more intense. Precisely the same relation was observed in slides from other localities and of all degrees of impurity. For comparison two serpentines from Sulphur Bank (Nos. 786 and 78e) were analyzed. The former is a nearly black, impure-looking mass, through which are distributed foils similar to those of bastite, excepting that they lack the metallic luster. Under the microscope it was found to contain, besides much opacite, serpentine polarizing in yellow tints, though the preponderating mineral shows gray interference colors. No. 78e is a light-green mineral from the same locality as that last mentioned, but much purer in appearance. Dark serpentine. Light serpentine. Water H 2 13 81 14 16 Silica SiO 2 39 64 41 86 Alumina APO 3 ] 30 69 Chromic oxide Cr'-'O 3 29 24 7 76 4 15 Nickel oxide KiO 33 0. 12 20 37 13 38 63 100. 38 99.93 112 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. Both specimens are evidently essentially serpentine and the principal difference is in the amount of ferrous oxide. While the comparison of these analyses with the slides of the specimens from which they were made might seem sufficient to test the relations of the chemical and optical properties, it was considered best to pursue the subject somewhat further, because minute quantities of minerals other than serpen- tine might escape detection in the analysis. It seemed especially desirable to establish the absence of talc and chlorite from the substances regardea as serpentine under the microscope. Talc, indeed, could not escape detec- tion in flakes or grains of sufficient size to be submitted to optical examina- tion, but it seemed possible that intimate mixtures of talc and serpentine might be present, since talc is known to occur pseudomorphically after most of the minerals which have been shown to be converted into serpentine and after many more besides. Chlorite, on the other hand, shows a considerable range of optical properties and bears some resemblance to serpentine. A series of simple microchemical tests was therefore made upon the slides and specimens. Serpentine is readily attacked by warm sulphuric or chlorhydric acid, while talc is decomposed by neither and chlorite is not sensibly at- tacked by chlorhydric acid. It was shown by the application of these tests that the more vividly polarizing serpentine did not differ in chemical behav- ior from that which gives only gray tints between crossed nicols and that the serpentine in the altered sandstones behaves exactly like the massive serpentine. The optical discrimination between chlorite and serpentine was fully confirmed, and no trace of an admixture of talc in the serpentine could be detected. 1 'A more detailed account of these tests may possibly bo of interest to some readers, since the pub- lished statements as to the behavior of these minerals are in part not quite consistent and are in somt> cases incomplete. The marmolitic serpentine of which an analysis has been given was found to be slowly but completely decomposed by both chlorhydric and sulphuric acids when hot, a colloid mass remaining. A slide of a serpentine from near Kuoxville, which showed great variation in the colors of polarization, was uncovered, and a portion which gave brilliant tints was cut oft' and after washing in alcohol was heated with adrop of sulphuric acid. The serpentine was completely decomposed, and on partial evaporation prisms of magnesium sulphate, extinguishing light at about 1G, and later hexag- onal uniaxial scales were formed, as described by Professor Haushofer (Mik. Reaetionen, p. 90). No other salts were formed. To tost the serpentine of the sandstones, specimen No. 57, Clear Lake, wns selected, because it contains a very remarkable pseudomorph.to be described hereafter. A portion of the slide was selected containing a quartz surrounded by supposed serpentine, from which distinct, tooth-like projections penetrated the quartz. A perforated cover was placed over this spot and the balsam washed away with alcohol. A minute drop of chlorhydric acid was added and the slide heated IDENTITY OF THE SERPENTINE. 113 Talc occurs abundantly in the metamorphic areas of the gold belt, and the Survey collections contain fine specimens from that region. Ac- cording to Mi-. H. G. Hanks it is also found at two or three localities in the Coast Ranges. Nothing would be less_ surprising than the discovery in the Coast Ranges of serpentines containing flakes of talc such as are de- scribed by Hussak, but this combination is not as yet known to occur The analyses also exclude deweylite and the minerals allied to it. It still rein? ins possible that some hitherto unrecognized mineral closely allied to serpentine enters into the serpentinoid mass, but the gradation of prop- erties is so complete that this seems improbable. The variations in the col- ors of polarization possibly correspond to the replacement of a greater or smaller portion of magnesium by iron, accompanying which there is likely to be a change in the angle of the optical axis. This angle is known to vary greatly in serpentines. The higher color in natural light of the por- tions which polarize most vividly may be due to the presence of ferric oxide as an impurity. The association of a partial replacement of mag- nesium by iron and a separation of a little iron oxide would not be unnatural. The mineral described as antigorite by Mr. Eichstadt corresponds in most respects to that described by Mr. Hussak and others and to the ser- nearly to the point at which balsam softens. It was soon found that the serpentine was attacked. Fresh portions of acid were added from time to time, and at last it appeared that most of the serpen- tine was decomposed, leaving a colloidal mass. Some portions in immediate contact with the quartz grain at points where indentation had been observed appeared to be entirely converted into gelati- nous silica. The portions which were only partially decomposed almost ceased to give interference colors. At the edge of the acid drop upon the cover there formed prisms supposed to be magnesium chloride, giving angles of extinction of over 30. The solution was washed off, evaporated on a second glass, and sulphuric acid added. Prisms giving a low angle of extinction formed on partial evapora- tion. On evaporating until fumes of sulphuric anhydride were given off, the hexagonal scales ap- peared, and on standing a few moments under the microscope these uniaxial crystals deliquesced. The substance under examination was thus certainly a magnesium silicate, and not a talcose mixture. No other crystals made their appearance. To test the behavior of chlorite a pseudodiabase (No. CGft, Sulphur Banl<) was selected and a port ion, exposed through a perforated cover, was treated witliehlorhydric acid exactly as the serpentine had been. There was no evidence under the microscope of any attack, even al'ier repeating the treatment, several times. On boiling powder from the same specimen in chlorhydric iicid it was found that the chlorite was decomposed when the acid was strong, but not when it was dilute. Both magnesia and alumina went into solution. It is probable therefore, but not certain, that this chlorite is the prochlorite of Dana. The highly dichroitic serpentine (from No. 21, New Al- maclen) was similarly tested. It dissolved in warm, dilute chlorhydric acid in the thin section and when the pulverized rock was boiled in strong acid magnesia, but no sensible quantity of alumina was dissolved. MON XIII 8 114 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. pentines of the Coast Ranges. The Swedish serpentine, however, is stated to be sensibly uniaxial, which, as EichstJidt remarks, perhaps means only that the angle of divergence of the optical axis in this case is extremely small. It seems doubtful whether the isotropic mineral referred to by Messrs. Fouqu^ and Michel-LeVy can lie the same as that of the Coast Ranges, Microstructure of the serpentine. Of tll6 HUiny Varieties of SerpeiltillO wllicll have received separate' mineralogical names several are recognizable mac- roscopically in the Coast Ranges. The most ordinary is the massive green mineral of different shades usually intersected by highly polished, curved surfaces. Such rock is often traversed by narrow veins of white or light-green, fibrous chrysolite. Marmolitic modifications are also abundant In many of the serpentines dark, rounded scales are frequent, and these often show in some lights a metallic luster answering to bastite or schiller- spar in part. Under the microscope there are found to be great differences in the structure and arrangement of the groups of fibers or scales of which the serpentine is built up. These are sometimes felted, but more often united in bundles of approximately similar orientation. In the latter form they answer to the descriptions of antigorite. Not infrequently groups of scales are seen under the microscope, forming masses of considerable size, in which the orientation is substantially uniform, and in sections cut obliquely to the predominant cleavage of these masses a fine, yellow, metallic luster is some- times observable once in every complete revolution. It is uncertain to what this luster is due. These masses are of course the so-called bastite scales. There are, however, many other aggregates similar in all respects excepting that they show no metallic luster. The groups of parallel foils are sometimes separated from the surrounding mass by sharp lines, which in no case present crystallographic outlines, but often the demarkation is not sharp. The mineral of which the antigoritic, chrysolitic, and bastitic aggre- gates are built up appears to be essentially the same, and in no way differ- ent from that of the felted aggregates. It corresponds well to the descrip- tions of antigorite, but answers equally well in all essential particulars to STEUCTURE OF SERPENTINE. other biaxial varieties. To give separate mineralogical names to mere vari- ations in the arrangement of the foils of a foliaceous mineral seems an un- necessary complication of terminology, nor can I see why the presence of a peculiar luster in the so-called bastite~slfould entitle it to a separate name. Lustrous labradorites are not regarded as of a different mineralogical spe- cies from labradorites not possessing this interesting peculiarity. It thus appears sufficient to classify the mineral characterizing the serpentinoid rocks of the Coast Ranges as a distinctly biaxial serpentine. This sepa- rates it from the colloid mineral of Messrs. Fouque' and Michel-Ldvy and from the possibly uniaxial antigorite of Mr. Eichstadt. The necessity of a division of serpentine into more than these three mineralogical varieties seems to me doubtful. Of more interest and importance than this minute classification of va- rieties is the structure resulting from the grouping of adjacent microscopic aggregates. Two types of such structure are known, one in serpentine, produced by the decomposition of olivine and representing the net-work of cracks of the parent mineral, usually emphasized by the presence of more or less opaque matter. The other, called grate structure, was first studied by Mr. von Drasche in Alpine serpentines, which he showed to be derived from augitic and amphibolic rocks. In serpentines of this class the foliated or fibrous mineral is arranged in narrow, somewhat sharply limited bands, which are nearly straight, though often discontinuous, and cross one another at high angles. The interstitial spaces are filled with less regularly dis- posed material. Mr. F. Becke observed the same structure in some of the Grecian serpentines. Mr. Eichstadt has shown that in some of the Swe- dish serpentines olivine decomposes into serpentine, exhibiting this grate- structure, which consequently does not necessarily represent cleavages in a parent mineral. It appears to me probable that it is at least in part con- nected with a change of volume attending the decomposition of the min- erals from which the serpentine is derived. There can be little doubt, how- ever, that in some cases the position of the grate-bars has been influenced by cleavages in the original mineral. In the serpentines of the Coast Ranges the olivinitic net-structure has not been detected, nor has any olivine been found either in the serpentine or 116 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. in the rocks with which it is geognostically associated. Basalt, it is true, is common in some districts where serpentine abounds, but this basalt appears to be Post-Tertiary, while the serpentinization took place early in the Cre- taceous. At New Almaden also pebbles of an olivinitic gabbro have been found, which probably come from -the neighborhood of Mt. Bache. This rock does not occur in place at New Almaden and is very fresh, the olivines showing the merest traces of serpentine. Macroscopically it strongly re- sembles the gabbros from Mt. Diablo and the Great Western, which contain no olivine. It is not impossible that some of the serpentine of the Coast Ranges may have been derived from an olivinitic rock like this, but if so the quantity thus formed must be inconsiderable compared with the rest, since no trace of it has been detected elsewhere. The greater part of all the serpentine shows more or less perfectly developed grate-structure. In polarized light the bars usually give higher colors of interference than the interstitial matter, but this relation is some- times reversed. With low powers a single bar often appears to extinguish light simultaneously all over, but when more magnified the extinction is seen to be undulous and to correspond to the composite nature of the bars, which are made up of foils or fibers in nearly parallel positions. The inter- stitial matter often gives very faint and undulous colors of interference, but has not been found isotropic. The more regular grate-structure passes over by gradations into a less symmetrical disposition, and felted fibrous masses are not uncommon in which irregular patches show slight differences of tint both in polarized and in natural light. In the altered sandstones many substances are of course included, and in some cases it might be questioned whether these rocks should be classed as serpentines with very abundant inclusions or as sandstones carrying" much serpentine. So, too, a part of the granular metamorphics contain a very large amount of serpentine. In the purer serpentines residual grains are not abundant, but augite may sometimes be observed with cleavages parallel to the grate-bars. These isolated augite grains show appropriate oblique extinction and characteristic colors of polarization Chromic iron is a common inclusion in the purer serpentines, but by no means invariably present. It is of a deep, dull-brown color, transparent, monochroitic, iso- DERIVATION OF SERPENTINE. 117 tropic, and when separated gives a strong chromium reaction. Numerous deposits of chromic iron intimately associated with serpentine are known in the Coast Ranges. Magnetite is almost always present. The origin of serpentine. Nocxtended hisforical account of the views held of the origin of serpentine is necessary here. The present investigation is not founded on any similar inquiry, nor do I suppose that all serpentines in other regions have had an origin similar to that of the serpentine of the Coast Ranges. A few historical notes, however, may serve to refresh the reader's memory. The occurrence of serpentine in dikes led to its classification as an eruptive rock by the earlier geologists, Avho were unaware of its composi- tion, and even long after it was known to be a hydrated mineral there are frequent references to it in the literature, unaccompanied by any qualifi- cation or explanation, in which it is classified as igneous. The close and frequent connection between gabbro and serpentine led L. von Buch, in 1810, to suppose that serpentine was a dense or cryptocrystalline form of that rock. This suggestion is interesting as showing how long the relation- ship of the rocks has been recognized. Direct eruption of the serpentines has also been maintained, in a modified form, by more recent Italian geolo- gists, who suppose outbursts from the depths of the earth of a hydrated, magnesian mud which consolidated to serpentine. In 1857 Dr. T. Sterry Hunt showed that when a mixture of magnesium carbonate and free silica is heated in a solution of alkaline carbonate a hvdrous, magnesian silicate is formed and the alkaline carbonate is re- generated. He soon afterwards came to the conclusion that this process, though locally important, would not explain the greater part of the occur- rences. In 1860 he proposed as an explanation of the massive serpentines the reaction between the soluble silicates of lime and alkalis from decaying rocks and the magnesian salts of natural waters. Dr. Hunt admits, however, that serpentines are also formed by epigenesis, at least from olivine and enstatite. 1 Dr. Hunt's view, while not generally accepted, has earnest advocates, and some geologists who reject this theory for a majority of cases believe it to be the true explanation of some occurrences. 1 Geol. History of Serpentines, 1883, 117 ; Origin of Crystalline Rocks, 1834, 105. 118 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The theory of the origin of serpentine most usually entertained is that it results from the alteration of other minerals. There is much variation of opinion, however, as to what minerals may yield serpentine. Breithaupt is said to have been the first to detect the pseudomorphosis of serpentine after hornblende (1831) and to infer the derivative character of serpentine rocks. Later, serpentine was found pseudomorphic after a long list of min- erals. Olivine, brucite, hornblende, augite, diallage, chondrodite, calcite, staurolite, dolomite, spinel, chromite, mica, and garnet are mentioned by Prof. J. Roth. Prof. J. D. Dana has personally identified the greater part of this list from a New York locality arid also found pseudomorphs after apatite. 1 Bischof, Professor vom Rath, and others have shown that the conversion of feldspars to serpentine is probable, and, at the congress of Bologna, Professor Szab6, as reported by Mr. Lotti, stated this as his opin- ion; but I am not aware that full proof of this change has ever been- offered. That it occurs in the rocks of the Coast Ranges, however, seems beyond doubt. In 1866 Professor Sandberger 2 and in 1867 Professor Tschermak 3 studied the transformation of olivine rocks to serpentine, though neither of them asserted that olivine, which had long been known to yield serpentine, was the sole source whence serpentine was derived. "The occurrence of em- bedded pyrrhotite," Professor Sandberger says, "may be said to be almost characteristic of the serpentines which have been derived from hornblende rocks, and the same mineral occurs in serpentines which are derived from diabases." Professor Tschermak, though stating that the masses known as serpentine and schiller-spar rocks, which he had had an opportunity of ex- amining, all contained olivine as a principal constituent, also remarks that diallage and bronzite grains are often converted into schiller-spar in these rocks. For some time afterwards, however, there was a strong tendency to ascribe almost all serpentine to the alteration of olivine, which was found to be more widely distributed and mere frequent than had previously been suspected. Thus, in 1873 Professor Rosenbusch wrote: "It appears to be 1 Am. Jour. Sci., 3d series, vol. 8, 1874, p. 380. "Neues Jahrbuch fur Mineral., 18fifi, p. 385; ibid., 1807, p. 171. 3 Ibid., 1868, p. 88. DERIVATION OF SERPENTINE. 119 more and more confirmed by the investigations, particularly the microscop- ical ones, hitherto made, that only the alteration first described by Sand- berger from olivine rocks to serpentine occurs in nature." This supposition, still maintained by some, was soon found too narrow to include the observed facts, and in 1877 the same distinguished lithologist acknowledged that ser- pentines or serpentinoid rocks are often formed from pyroxene and amphi- bole. In view of the earlier literature of the subject it seems indeed most improbable that the serpentines should have a single origin. The evi- dence of actual pseudomorphism in many cases was sharply questioned by Scheerer as early as 1846 and later by Mr. Delesse and Dr. Hunt, and no doubt some cases of erroneous determination were detected. Many in- stances, however, stood the test of these challenges. All the more important cases have also been reobserved since 1867, and at present the number of occurrences of serpentine shown by microscopic research to be derived from rocks containing olivine as a subordinate constituent only or not at all is on the increase. According to the law of thermochemistry, in any mixture of substances capable of reacting upon one another the resulting compound will be that whose formation is attended by the most rapid evolution of heat. 1 Any given mineral will therefore be produced not in general under a single set of conditions, but under any combination of the whole range of conditions in which the formation of any other compound would be attended by a slower liberation of heat. The wider the range of these conditions the commoner will be the mineral, and, since conditions are never exactly repeated, the assertion that a mineral is common is nearly equivalent to the statement that its formation is attended by the most rapid evolution of heat under diverse sets of conditions. Thus, to take one of many examples, there are Imt few ferruginous compounds which in weathering or in roasting do not yield hydrous or anhydrous ferric oxide ; or, in other words, whether the temperature be low or high, the formation of ferric oxide from almost num- berless compounds of iron involves the liberation of heat more rapidly than any other change. That serpentine occurs at all is sufficient evidence that its formation is attended by the liberation of heat under certain conditions. 1 See my IIIIVHT, A m-\v law ( i licriiioi'lii-mistry : Am. Join-. Si-i., M serie*, vol. 31,1886, p. WO. 120 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. That it is common leads to the belief that these conditions are not narrowly restricted, and this is confirms;! by the fact that it forms in the olivines of decomposing basalts and also in limestone beds. It is no more surprising that serpentine should form from many and different minerals or under dif- ferent circumstances than that ferric oxide should do the same. Bischof held a similar opinion, calling attention to the fact that serpen- tine is among the last products of alteration and that in it the series of processes of mineral formation and alteration have nearly reached the limit of possibility. Indeed few geological chemists would be inclined to dispute a proposition of this kind. Dr. Hunt, for instance, who points out the anal- ogy between the modes of occurrence of serpentine and pinite, says of the latter that its constancy of composition and wide distribution show it to be a compound readily formed and of great stability. Such being its character, he continues, it might be expected to occur as a frequent product of the aqueous changes of other and less stable silicates, and "its frequent occur- rence as an epigenic product is one of the many examples to be met with in the mineral kingdom of the law of the ' survival of the fittest.'" That the same statement applies to serpentine is manifestly true. It would seem to follow that the origin of serpentine in each naturally defined geological area requires independent investigation and that the results obtained in one such area are not necessarily applicable to others. It will be seen in the following pages that the observations are not recon- cilable either with the supposition that the serpentines of the Coast Ranges are derivable from a single mineral or that they are unaltered sediments. They seem to be in this region the most stable compound which could result under a certain set of physical conditions from the mutual reaction of siliceous and magnesian substances. structural evidence as to origin. Serpentine is found throughout the metamor- phic areas of the Coast Ranges in very irregular patches, both near quick- silver deposits and at long distances from the mines. In some metamorphic regions for example in the immediate neighborhood of Clear Lake it is found only in small quantities, while at Knoxville and at New Idria large areas are almost exclusively composed of more or less pure serpentine. 1 Origin of the Crystalline Rocks, 1884, p. 53. MODE OF OCCURRENCE OF SERPENTINE. 121 Near the Golden Gate, at Mt. Diablo, and in many other localities it is very abundant. In fact, though the quantitative relations of the various meta- morphic rocks vary greatly in different neighborhoods along the quicksilver belt, all varieties are to be found in almost every district. Serpentine is commonly, but riot always, intimately associated with pseudodiabase. These rocks stand in such relations to the unaltered sandstones in very numerous cases that no geologist carefully examining the localities could fail to con- clude that they are modifications of the sandstone. . This was substantially the conclusion at which Professor Whitney arrived. Knoxville affords ad- mirable opportunities for studying this connection. Highly inclined strata strike into serpentine areas in such a manner as wholly to preclude the sup- position that the serpentine represents an earlier mass ; one side of an an- ticlinal fold is serpentinizcd, while the other is unaltered and carries excellent fossils, and there are clear cases of transition through altered sandstones. Mt. Diablo affords equally favorable opportunities for determining the age and relations of the serpentine. In many other localities the relations of the serpentine to unaltered rocks are evident, although it is seldom that the age of these unaltered rocks can be immediately determined. The reason for assigning them all to the Neocomian will be given in Chapter V. Field observation makes it clear that in most cases the transformation to serpentine began along cracks in sandstone or in rocks resulting from the alteration of sandstone and worked toward the centers of the frag- ments thus separated from one another. Where this process is incomplete, partially rounded nuclei of rock retaining the sandstone habitus are to be seen, divided by a net- work of serpentine. Such exposures remind one of the appearance presented under the microscope by olivines in process of con- version into serpentine. Sometimes, but not often, the serpentine assumes a radial form, the fibers being normal to the surface of the nucleus. Pro- fessor Whitney observed such an instance at Newldria; I found some very beautiful ones at Knoxville. Two cuts illustrating such occurrences will be given in the description of the Knoxville district. It is not possible from a mere field examination to determine whether the serpentine results directly from the action of solutions upon sandstone or whether the sedimentary rock first becomes crystalline and is subsequently UNIVERSITY 122 QUICKSILVER DEPOSITS OP THE PAOIFIC SLOPE. serpentinized. The observer would incline to the belief that both methods were followed, but the conclusion would not be certain, because many rocks which are really holocrystalline appear to the eye to be mere sand- stones somewhat modified. It will be seen in the sequel that both proc- esses can be traced microscopically. The serpentinoid rocks invariably show evidence of violent dynamic action. Traces of stratification are often visible, but can never be followed more than a few feet, and single cropping? frequently exhibit remnants of stratification in all sorts of contradictory directions. There is usually little evidence of plication ; as a rule, the rock was reduced to a confused mass of rubble prior to serpentinization. The blocks indeed were often some yards long, but even these were generally divided by numerous cracks. Microscopical evidence of derivation. Willie it is not possible tO follow ill tll6 field the transitions of the components of the altered rocks, the indications of field observation were found to be borne out by microscopical and chem- ical examination. It can be shown, as I think beyond dispute, that all of the principal minerals of sandstones and granular, metamorphic rocks are converted into serpentine, and the inference with regard to some of the less important Ones is also strong. After the investigations of the last fifteen years, together with the earlier macroscopical examinations, it will surprise no one to hear that in the granular, metamorphic rocks of the Coast Ranges augite and hornblende are found passing into serpentine. The attack takes place along the surfaces and cracks, exactly as in uraliti- zation and chloritization, while the resulting mineral has all the distinctive characteristics described in the preceding pages. Sometimes partial pseu- domorphs may be observed in which a kernel of the bisilicate is embedded in a mass of serpentine, surrounded by an outline characteristic of the par- ent mineral. This, however, is rare, apparently because well developed crystals of augite and hornblende are also rare. Though Bischof, vom Rath, and others have shown that the conver- sion of feldspar to serpentine was probable, I am not aware that it has ever been conclusively proved. In the altered sandstones and the granular metamorphics of the Coast Ranges, however, it seems beyond doubt that this alteration lias taken place. In very numerous cases grains of feldspar PSEUDOMORPHIC SERPENTINE. 123 remain embedded in serpentine, and these grains show outlines differing essentially from those of deformed crystals or clastic fragments, but resem- bling in all respects corroded masses. Cracks in such feldspars are also filled with serpentine, and it is manifest "Tinder the microscope that feld- spathic material lias been removed from the walls of these cracks, so that they woiild no longer fit were they brought together. This evidence is of exactly the kind commonly accepted as proving the attack of other min- erals. In one instance the phenomena are still more conclusive. In a slide from Sulphur Bank (specimen No. 107), a feldspar shows such a crack much widened, and, from the serpentine mass occupying it, sharp, elongated teeth of serpentine bite into the clear feldspar. It is impossible to explain such a case otherwise than as an actual conversion of the feldspathic material under the action of corrosive solvents. The serpentine is characteristic and unmistakable. The feldspar is unstriated, but probably triclinic. Other sat- isfactory occurrences show that both plagioclase and orthoclase are converted into serpentine. FIG. 4. Clastic quartz partially converted to serpentine, which penetrates from the ontsicle in needles. The specks within the quartz are fluid in.-luaions and the straight prism is a small apatite. Magnified 5,'i diameters. That quartz is sometimes converted into talc is well known In the altered sandstones of the Coast Ranges it is converted into serpentine. This is shown, exactly as in the case of feldspar, by the presence, in patches of serpentine, of irregular grains of quartz with corroded surfaces A very beautiful case of the conversion of quartz to serpentine occurs in altered sandstone from Clear Lake (specimen No. 57), and is illustrated in Fig. 4. A clastic quartz grain of characteristic form, full of fluid inclu- sions, containing an embedded apatite microlite, and behaving as usual in polarized light, has been attacked from the outside. The exterior of the 124 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. original mass is now entirely occupied by felted fibers of serpentine, and long, slender microlites pierce the quartz grain toward its center like pins in a cushion. That there might be no doubt as to the correct interpreta- tion of this important case another quartz was selected in the same slide, which showed the same phenomena, though less beautifully. This was tested by chemical methods, as described on page 112, and the green min- eral was proved to be a silicate of magnesium, attackable by chlorhydric acid. The serpentine which was chemically tested in this second case was absolutely indistinguishable in color, texture, or behavior in polarized light from that surrounding the quartz shown in the figure, and the distance of the two occurrences from each other was only about 3 nim . The long mi- crolites which pierce the quartz are of the same color as the strip of ser- pentine occupying the periphery of the section. Their optical properties capnot be well observed, because they are embedded in the brilliantly polarizing quartz, but there appears no reason to suppose that they differ chemically from the serpentine at their bases. Even if they belonged to another mineral species, however, the structure is such as to show that they must be regarded as an intermediate product between quartz and the sur- rounding serpentine, which would make little difference from a geological point of view. Apatite is found in process of conversion to serpentine in specimen No. 107, Sulphur Bank, one of the specimens in which the presence of autlii- genetic apatite was proved by chemical as well as by optical means. The apatite crystals embedded in serpentine in this slide are seen to be cor- roded and the indentations are occupied by serpentine. As already men- tioned, Professor Dana has observed pseudomorphs of serpentine after apatite. There are also a number of cases in which chlorite appears to be altered to serpentine. Thus in specimen No. 261, Sulphur Bank, a chlorit~ ized pseudodiabase, areas of chlorite are intersected by cracks, along the walls of which serpentine is disposed in such a way as to lead to the belief that the latter mineral is epigenetic ; but, as in the case of the conversion to epidote, the fibrous character of the chlorite somewhat weakens the evi- dence obtainable from observation. Bischof regarded the serpentinization rSEUBOMORPHIC SERPENTINE. 125 of chlorite as probable. 1 Mica and garnet have been observed elswhere undergoing conversion to serpentine.. The mica foils are so small and pos- sess such irregular outlines in most of the rocks of the Coast Ranges where serpentinization can be traced that this -change, though probable, cannot be definitely asserted. Garnet is seen in the few slides which show it in process of conversion to chlorite; but a change to serpentine has not been distinctly traced in the Coast Ranges. Zoisite, as it occurs in these rocks, is not well suited to exhibit pseudomorphic alteration. It appears in smaller quantity in the rocks containing much serpentine, however, than in those containing little. The prevalence of this mineral in the saussuritic gabbros of Europe, the intimate relations between these rocks and the serpentines, and the absence of observations on the presence of zoisite in massive ser- pentines, either in the Coast Ranges or elsewhere, point towards the prob- ability of a serpentinization. Olivine has not once been detected in the rocks associated with serpentine in the Coast Ranges or in the serpentines themselves, and olivine cannot have contributed in an appreciable degree to the formation of these serpentines, important as is the part which this min- eral plays in some other serpentinoid areas. The chemical changes indicated by the observations described above on the alteration of bisilicates, feldspar, quartz, and apatite to serpentine are very strange, and the results may possibly fail to be accepted by some because of their strangeness. It is a truism, however, that observation almost always outstrips scientific theories, or that these are commonly framed to embrace- the results of observation, while the changes indicated here are not more perplexing than many other reactions once were, for which reasonable explanations have been discovered. Mineral chemistry is full of puzzles, some of them so familiar that their chemical difficulties are hardly appreciated. That a number of different minerals should all be re- placed by serpentine under certain appropriate conditions is in itself not more remarkable than that from a single solution an equal number of min- erals should be precipitated almost or quite simultaneously; yet in the study of veins such cases occur so frequently that they attract no attention. 1 Lehrbuch chem. und phys. Geol., vol. 2, 1864, p. 7*'.). 126 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. It has doubtless happened in times past that observers have attempted to cut the gordian knot of metamorphism by assuming such replacements as seemed convenient. This method of dealing with the subject is as super- ficial as a flat denial of all conceivable methods of genesis, excepting one, of a certain product. General course of serpentinization Having Stated in detail tll6 character of the evidence as to the serpentinization of the mineral constituents of the sand- stones and the granular metamorphic rocks, it only remains to indicate the course of the transformation as a whole. In the sandstones which have merely weathered, but which have not been subjected to even incipient recrystallization, or, in other words, in the sandstones of later age than the Neocomian, serpentine has not been detected with certainty, though it has been carefully sought, while chlorite is common. I know of no reason, however, why small quantities of serpentine should not hereafter be found in these rocks. There is abundant evidence that serpentinization was not widespread or important in the later rocks, but this does not exclude local or partial repetition at later dates of the conditions which induced serpen- tinization at the close of the Neocomian. One of the important results of this investigation is that the slightly recrystallized, older sandstones were subject to serpentinization as well as those which had undergone complete transformation. In these rocks, of course the more permeable aggregates yielded most readily to attack and were first affected by the change. In such cases the phenomena of recrystallization and serpentinization may be studied side by side, and it is rarely the case that some small patches and streaks of serpentine are not observable in these sandstones. At a further stage the interstitial space between the remains of the clastic grains is almost wholly filled with ser- pentine, which then attacks these nuclei, as has been described, though, as might be expected, the process is irregular, so that one portion of a slide is often more serpentinized than others. The quartz appears to yield more slowly to serpentinization than the feldspar, and this more slowly than the fine-grained cement. The extent of surface exposed is of course an im- portant factor. As the amount of the serpentine increases, traces of grate- structure make their appearance; but, though this fact is easily established, DECOMPOSED SERPENTINE. 127 the material at hand does not afford the means of following in detail the history of the grate structure. In the pseudodiabase and pseudodiorite it is naturally the bisilicates. which first show traces of the serpentimzation process, and for these min- erals the history is exactly parallel to that of direct chloritization. The ferromagnesian silicates yield to this process much more easily than the feldspar and the quartz, which behave as in the slightly altered sandstones. This fact leads to the belief that the greater part of the massive serpentine has resulted from pseudodiabase and pseudodiorite, a view supported by structural considerations; for, since both recrystallization and serpentiniza- tion are dependent on a fissure system, serpentinization in slightly altered sandstones appears to mean that during this process the solutions diverged from their old channels or that, where in the first stage solutions permeated to but a slight extent, they penetrated abundantly at the later period. This would probably be less common than a similar distribution of solutions at each of the two periods. Decomposition of serpentine. In nearly all the serpentine localities it is evident that this rock is subject to tolerably rapid decomposition under the action of the atmosphere. The subject has been studied in Bohemia by Mr. A. Schrauf, 1 with whose results the observations made in the Coast Ranges O agree. Where the serpentine is directly exposed to the action of the atmos- phere, it is often bleached and converted to a porous mass, which is nearly pure silica, containing very little magnesia or iron. Where serpentine has been subjected to solfataric action in the immediate neighborhood of ore bodies, the bases have often been removed and silica has replaced nearly or quite all of the original mass. While this is a common change near ore bodies, such replacements have also occurred to a small extent at long dis- tances from known occurrences of ore, and it may be that this process has gone on to some extent at different periods. Since by far the greater part of the silicified serpentine bears such a relation to the ore bodies as to lead to the conclusion that the process was attendant on that by which the ore was produced, it will be discussed hereafter in that connection. 1 Zeitschr. fiir Krys. und Miu., Grotb, vol. 6, p. 321. 128 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Serpentine is also converted into carbonates of lime and magnesia in the Coast Ranges, and the process can be followed in detail in some cases. No. 223, Knoxville, is a grayish-green serpentine full of minute veins, the material of which does not effervesce with cold, dilute chlorhydric acid. Under the microscope these veins are seen to be composed of carbonates often exhibiting cleavage. On removing the cover it was found that a portion of the carbonates dissolved slowly in cold acid, while a portion remained unattacked. Dolomite and magnesite are thus probably both present. No attempt was made to determine the quantity of magnesia in these carbonates. It is manifest from this slide that the substance of the serpentine lias actually been replaced, for the masses between the veins are rounded and would no longer fit together were the veins removed. The result is a net- structure similar to that observed when olivine is decomposed to serpentine. METAMORPHIC ROCKS OF UNCERTAIN AGE. Gavilan Range and Steamboat rocks. In the foregoing pag6S tllOSe metaillOrpllic rocks only have been considered which are actually known to be of Knox- ville age or which there are good grounds for referring to that epoch. In the course of this investigation metamorphic rocks of uncertain age have been encountered at two localities. One of these is in the Gavilan Range, where an extraordinarily, crystalline limestone is associated with granite and gneissoid rocks. The occurrence is so different from the remainder of the altered rocks of the Coast Ranges examined that it could not be referred to the same series without much more investigation than it has been prac- ticable to devote to it. I suspect it to be of far greater age than the rest of the exposures. Under the microscope the gneissoid rock is found to be of the Archaean gneiss type. It is chiefly composed of quartz, orthoclasc, plagioclase, and biotite. There is a decided tendency to granophyric structure, and veins and clusters of fibrolite are abundant. This rock con- tains no zoisite. At Steamboat Springs the sedimentary rocks are greatly disturbed and in part highly metamorphosed. They seem to belong to the series re- garded as Jura- Trias by the geologists of the fortieth parallel, and are certainly older than the Tertiary. The area examined is too small to PKOOF OF METAMORPHISM. make any investigation of the metamorphism very profitable. The sides show that a portion of these rocks are thoroughly recrystallized and that in mineral composition and in structure they strongly resemble the metamor- phosed rocks of the Knoxville group irrthe Coast Ranges. There is at present nothing improbable in the supposition that they Avere actually metamorphosed at the same time The study of these rocks will be re- sumed in connection with the geology of the gold belt of California. CONDITIONS ATTENDING THE METAMORPHISM. In the foregoing pages the unaltered and the metamorphosed rocks of the Coast Ranges have been described from a lithological point of view. It remains to consider the metamorphic process as a whole in its geological and chemico-physical relations. Proofs of metamorphism The division of opinion as to the origin of many of the crystalline rocks is such that it is not superfluous to insist upon the proofs of the derivative character of the holocrystalline rocks and of the serpentine of the Coast Ranges. It appears that at least one mineral of nearly universal distribution in the granular and schistose rocks and in the phthanites is especially significant in this respect, and that a sound argu- ment may be based upon its occurrence independently of other evidence. Zoisite seems to be characteristically the result of secondary processes which have taken place at no very high temperature. It has never been observed as an original constituent of eruptive rocks, which could hardly be the case if it were at all common. This merely negative evidence is sup- ported by that afforded by its composition, which includes basic hydrogen, while no such compounds, so far as I know, have ever been proved to form original constituents of eruptive masses, and, judging from what is known of eruptions, it is difficult to conceive that they should so occur. 1 On the ; Zoisite is usually referred to the epidote group, of which only ullauite is kuowii to occur in erupt- ive rocks. The composition of ullauite, however, is somewhat uncertain, since, according to Professor Rammelsberg, it has the oxygen ratio of garnet rather than of ephlote, while there appear to be both hydrous and anhydrous varieties. According to Prof. J. D. Dana, the hydrous allanites are properly altered forms of the species. There can be little doubt that the unaltered allauites of eruptive rocks are anhydrous. Messrs. Fouque and Michel-Levy regard xoisite as a scapolite, for which I know of no ground ex- cepting that its centesimal composition is the same as that of meionite. The scapolit.es also are known only as the result, of secondary or metamorphiu action. 3ION XI II 9 130 QUICKSILVEK DEPOSITS OF THE PACIFIC SLOPE. other hand, zoisite has been abundantly proved by Hunt, Cathrein, and others to be peculiarly characteristic of rocks which, whether regarded as decomposed eruptives, as metamorphic, or as original crystalline sediments, indicate the formation of this mineral at moderate temperatures. Taking all these circumstances into consideration, it appears that scarcely a single mineral species could have been selected which would afford a better criterion of the prevalence, at the epoch of its formation, of temperatures decidedly below a red heat, and probably much below. Zoisite might conceivably occur in two ways, and it is not improbable that it actually does so occur. If found, among mere decomposition-products, replacing primary minerals pseudomorphically as aggregates, it would seem to prove that the rock in which it occurred had simply been decomposed under physical conditions appropriate to the formation of zoisite But, if zoisite is found embedded in clear, continuous masses of minerals which can be shown to be authigenetic, it would seem to afford conclusive evi- dence that these minerals have been formed at moderate temperatures. This latter mode is characteristic of a great portion of the rocks of the Coast Ranges and very often in cases where from the mere inspection of slides it might readily be supposed that the material under examination was eruptive. While zoisite appears to form an admirable indication of the metamor- phic character of the holocrystalline rocks of California, it must not be sup- posed that their determination as altered sediments is dependent on the identification of zoisite. Before the mineral character of the constituent which proved to be zoisite was known, there was abundant evidence, both from field examination and from microscopical study, that the rocks in question were metamorphic, and the conclusions would remain substantially as here presented if it should be proved that zoisite is a common, original constituent of the most typical eruptive diabases and diorites. The present investigation may properly be regarded as proving, quite independently of its chemical constitution or of its occurrence in whatever class of rocks else- where, the wide distribution in metamorphic rocks of zoisite both as an authigenetic. constituent and as one of the first of these constituents in the order of development. PKOOF OF METAMOEPHISM. 131 The stratigraphical relations of the holocrystalline and serpentinoid rocks to unaltered beds, in part fossiliferous, at a great number of localities are such as absolutely to preclude the supposition that these masses are either older sedimentary rocks or that they are intrusive. The field rela- tions of the holocrystalline rocks and of the serpentine to the sandstones, as well as their microscopical character, are such as equally to preclude the supposition that they represent local or regional precipitations of crystalline sediments of the same age as the fossiliferous rocks. I feel almost justified in stating that at the Post-Neocomian epoch of metarnorphism the rocks of the Coast Ranges between Clear Lake and New Idria contained no intrusive masses and that no eruptions accompanied this upheaval. It is true that in a few cases isolated specimens of the crystal- line, metamorphic rocks simulate the microscopic appearance of eruptive masses to an extraordinary degree, but these occurrences when examined on the spot prove to pass over into manifestly metamorphic material. Two or three such pseudoeruptive rocks were discovered in the collections from the Sulphur Bank and, after the microscopical work recorded in this chapter was completed, these localities were revisited. In none of them was there the slightest structural evidence of eruptivity ; in all it was manifest that the suspected rock passed over into ordinary, unmistakably metamorphic beds within a few feet and in every direction. By no means the whole country between Clear Lake and New Idria has been investigated, but so many localities have been examined with care and so many reconnaissances have been made into the intervening regions that it would be very strange if any considerable quantity of eruptive rock occupying the position indi- cated had escaped detection. For, though a particular variety of lava may sometimes be confined to very narrow limits, as is the case with the rhyolite of New Almaden, eruptive phenomena, once initiated, usually and perhaps invariably extend over wide areas Epoch of metamorphism As will be shown in a subsequent chapter, the age of all the fossiliferous rocks associated with the metamorphics is Neocomian Some of the most important areas of metamorphic rocks are certainly of this age, and reasons will appear hereafter for supposing that no consider- able portion of the metamorphic series was deposited at an earlier date. 132 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The epoch of the uplift lies between the end of the period in which the Knoxville and Mariposa beds were deposited and the beginning of that in which the unmetamorphosed Wallala series was laid down, or, according to the paleontological determinations, between the Neocomian and a middle' Cretaceous period resembling the Gossau. Unless the violent dislocation which took place between these periods was preceded by a gentle uplift of the country above water and of this no evidence is known the folding and crushing which form so prominent a feature of the Coast Ranges must have taken place at the close of the Neocomian. That the metamorphism cannot have preceded the uplift is certain, from the fact that the confused mass of rubble resulting from dynamic action -has often been recemented by the metamorphic processes. The association of the evidences of dynamic action with the alteration is such as to make it clear that the metamorphism was to a great extent dependent on the crushing of the rock. There is no evidence that any considerable time elapsed between the crushing and the ensuing chemical changes; but, since the rocks now exposed were then buried at a considerable depth, such an interval might have elapsed without leaving recognizable traces. On the other hand, it appears certain that the metamorphism was effected under different physical conditions from those now prevalent, because, as has been pointed out, the process of decomposition now progressing is inconsistent with the process of recrystallization. It is most natural to suppose the dif- ference to have been one of temperature. That a higher temperature pre- vailed in the rocks at the time of the upheaval is also certain ; for the crushing of the rocks was of the utmost intensity and indicates the dissipa- tion, or conversion into heat, of an enormous energy. There is therefore strong reason to suppose that the metamorphism followed immediately upon the upheaval. Former depth of the present exposures. In comparing the metamorphic Cretaceous rocks of the Coast Ranges with the older crystalline schists, particularly as described by Dr. Lehmann, one point of difference is especially striking. In the older rocks fractures are comparatively rare, and it also appears altogether probable that at a sufficient depth below the surface solids must flow rather than undergo comminution. Hence the intense plication of CONDITIONS OF METAMOKPHISM. 133 such rocks, in which even crystals of feldspar are bent at sharp angles instead of breaking, indicates that they have been subjected to mechanical forces of great intensity while under immense pressure or when buried at a great depth. In the Coast Ranges, on-the other hand, the metamorphic rocks have been crushed to an astonishing degree. This is especially observable in the phthanites, which are often intersected by so fine a net- work of minute fissures, now filled with quartz veins, that a portion of the net is visible only under the microscope. Plication of strata is indeed extremely frequent ; but, at least in a great proportion of cases, this has not been accomplished to any great extent by flexure of the rock mass. It was attended by the formation of innumerable cracks, which have gaped more or less and thus permitted readjustment without great displacement of the fragments. The fragments having been recemented in their new posi- tion, the strata became once more coherent. Often also the rocks have been crushed to a mere, confused mass of rubble, in which the original stratigraphical relations are entirely obscured. These relations appear to demonstrate not only the expenditure of enormous energy, but also that the Cretaceous rocks at the time they were metamorphosed were not buried at great depths, perhaps not more than two or three thousand feet below the surface. This being granted, it may readily be understood that, even if the character of the rocks and of the metamorphism in the Archaean were exactly similar to that of the Cretaceous strata of the Coast Ranges, the latter would inevitably be less uniformly altered, while at least the quantitative relations of the products of alteration in these mountains would probably differ from those characteristic of similar masses altered under a far greater and far more uniform pressure. Dynamic conditions. The Post-Neocomiaii uplift was accompanied by in- tense compression in a northeast and southwest direction. The strata of the Coast Ranges were partly plicated and partly crushed, while on the gold belt they were driven into a nearly vertical position. Both areas appear to have been and still to be underlain by granite at no very great depth. What the bed rock in the great valley of California may be is not definitely known, but there seems no reason to suppose that it is not granite there also. It is impossible to suppose any force which would 134 QFJCKSILVER DEPOSITS OF THE PACIFIC SLOPK. crumple the overlying strata by horizontal translation over the granitic surface while the granite remained undisturbed, and it therefore inevitably follows that the granite must have been fissured and crushed or deformed, or, more probably, crushed in the higher portions and plastically molded in the deeper regions. The granite, like the sedimentary rocks, must have been heated by the conversion of sensible motion into molecular motion. Nearly all rocks are permeable by water, and in eveiy region there is a system of percolating, subterranean currents. There must have been such systems in the sedimentary and massive rocks of California before the great upheaval, and this system must have been as thoroughly dis- turbed at the uplift as were the rocks themselves. Old vents were closed, porous beds compressed, and the fractures caused by the convulsion cer- tainly afforded new paths of weak resistance. The waters were warmed by the heated rocks, and consequently became more powerful solvents, and cannot but have attacked many of the minerals with which they were in contact. So far all the circumstances appear simple and certain, and it may be added that, since the uplift as a whole bears the character of a violent com- pression, the interstitial space was probably greatly diminished and the heated mineralized waters were driven toward the surface When one at- tempts to pursue the subject further and to reason upon the special char- acter of the mineral waters, or the particular temperature, or the ensuing reactions, observation appears to be the only guide. A priori it is clear only that very considerable modifications in the character of the sedi- mentary rocks must be expected and that as the action diminished a series of transformations might occur. So far as can be known, there is nothing unreasonable in the supposition either that the solutions may have been basic at some points and acid at others or that at the same points they may have been basic at some stages of metamorphism and acid at others. chemical indications. The pseudodiabase and psendodiorite are much more basic than the sandstones, as is also the serpentine, while the phthanites are more acid than the shales from which they are derived. Serpentin- ization and silicification have often gone on in the same rock mass, and the evidence from many widely separated localities appears to indicate that CHEMICAL INDICATIONS. 135 silicification followed serpentinization, while it is certain that serpentiniza- tion postdated the formation of the holocrystalline metamorphics. The serpentinoid rocks, like the phthanites, are sometimes intersected by quartz veins, but the conversion of serpentine 4nto opal has taken place only locally and is for the most part referable, not to the Fost-Neocomian epoch of metamorphism, but to the volcanic period of ore generation. A difficulty must always arise in discussing- metamorphic rocks, from the inevitable lack of positive knowledge as to the composition of the sedi- ments prior to metamorphism. It is indeed one of the advantages which the Coast Ranges afford for the study of metamorphism that the origin of the sediments is known and that the composition of the unaltered strata as a whole is uniform. No geologist needs to be told, however, that this uni- formity cannot extend to hand specimens. It is impossible to say that any particular sample of pseudodiabase or serpentine once had the composition of a second sample representing unaltered sandstone, and it is consequently also impossible to ascertain the exact quantity and quality of the changes which have been wrought in it by the action of mineral solutions. It fol- lows, however, from the study of the relations of many metamorphosed masses to the iinaltered or slightly altered rocks surrounding them, that the pseudodiabase, pseudodiorite, and serpentine are as a whole derived from sandstones of average character. The fresh sandstones carry magnesia, but not in great quantities, for the allothigenetic, ferromagnesian silicates form a small part of the mass, while the matrix is sometimes nearly pure calcium carbonate and never appears to contain considerable quantities of magnesia. The observations cannot be reconciled without supposing that very large quantities of mag- nesia have been supplied in solution from extraneous sources, though the precise quantity cannot be determined in any given case. One and only one evident source for this supply of magnesia exists, viz, the ferromag- nesian silicates of the underlying granite. The wide horizontal extension of the granite is well established. Its depth is entirely unknown, but must be very great, since it is nowhere cut through. An inexhaustible supply of magnesia was thus at hand, as well as heated waters, with a probable upward tendency at the period of metamorphism, but under what precise 136 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. conditions magnesia passed into solution is not known, nor even what salt of magnesia was dissolved. The structural evidence, however, strongly favors the supposition that the silica of the sandstones reacted directly upon magnesian solutions. Were it otherwise, the sandstones might have been impregnated with hydrous and anhydrous, ferromagnesian silicates, but the quartz grains could not have been attacked, as they certainly are in the altered sandstones, while in the recrystallized rocks they have alto- gether disappeared. The experimental researches of Dr. Hunt and of Mr. Daubre'e indi- cate the kind of reaction which must be supposed to have gone on in the rocks of the Coast Ranges. As has already been stated, Dr. Hunt found that when alkaline carbonates in solution are heated with silica and mag- nesium carbonate an alkaline silicate is formed which reacts upon the magnesium carbonate, yielding an insoluble magnesium silicate and regen- erating the alkaline silicate. So, also, Mr. Daubre'e discovered that water heated at a high pressure in glass with kaolin results in the formation of zeolites, feldspar, pyroxene, and quartz. In such experiments the tem- perature and pressure must of course be reduced below the boiling point before any satisfactory examination of the results can be made. Conse- quently, it is not at present possible to say under what special conditions of temperature and pressure each mineral was formed. The heated waters in the granite and the overlying strata of the Coast Ranges must have contained carbonic acid in solution. It is not inconsistent with any known facts to suppose that these waters attacked the granite at great depths, dis- solving alkalis, magnesium, and iron, with perhaps a certain amount of silica; nor is there anything to forbid the supposition that at lower press- ures, and perhaps also at lower temperatures, such solutions brought in contact with calcareous sandstone would form feldspars, pyroxene, amphi- bole, and serpentine. In the experiments solution and precipitation were confined to the same locality, while in the Coast Ranges solution went on at great depths and precipitation at more moderate ones; but nothing is as yet known which makes it necessary to suppose that the conditions of tem- perature and pressure or the general character of the* reactions in the Coast Ranges differed essentially from those in the experimental investiga- SIMCIFH1ATIOST. 1.37 tions referred to. It would b3 easy, but hardly profitable, to speculate further on this subject, to which I hope to contribute by experiment on a future occasion. The basic solutions rising from the granite converted the acid sand- stones into more basic compounds: feldspars, ferromagnesian bisilicates, serpentine, etc. The solutions thus became more acid, and it can hardly be doubted that after producing their full effect upon the sedimentary rocks the waters contained free silica in solution. It is an interesting and impor- tant question what became of this silica, which was certainly in part ex- tracted from the sandstones. It is absolutely certain from the principle of maximum dissipativity that any solution will deposit its contents or change its chemical character at the very first opportunity or at the first moment when heat can be set free by any chemical or physical alteration. Hence, in general, mineral solutions permeating rock masses can only in very ex- treme cases traverse long distances without substantial change. The silica dissolved by the waters which effected the metarnorphism of the rocks of the Coast Ranges must consequently have redeposited this material as near the place where it was dissolved as possible. There appear to be only two possibilities in the case: either the silicification which is so prominent in the Coast Ranges was due to these siliceous waters or the solutions pene- trated to the surface of the region as it then existed and there precipitated so much of their load as could be thrown down under diminished tempera- ture and pressure. My own preconceptions would incline me to the former of these hypotheses, which involves a speedy precipitation and makes a portion of the process of metamorphism independent of material derived from extraneous sources. This may bo the true theory, but I have not been able to gather any information confirmatory of it. Throughout the field work efforts have been made to determine the relative age of the proc- esses of metamorphism, and in each area it has appeared that silicification was probably a later phenomenon than serpentinization, which, again, cer- tainly followed the recrystallization of the sedimentary rocks. Thus ser- pentinoid rocks are often intersected by quartz veins, while such veins partially converted into serpentine or showing infiltrated serpentine have nowhere been detected. Massive serpentines, it is true, are seldom pene- 138 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. trated by quartz veins excepting in the mines, but this rock is too soft and tough to be readily fissured. While serpentinization and silicification are usually so associated as to lead to the belief that the latter followed the former, it is anything but improbable that exposures may hereafter be discovered from which it will appear that at least in some cases silica was thrown down very near areas of serpentinization and simultaneously with the progress of the latter process. To sum up the results in a few words, it appears reasonably certain that the conversion of sandstones and shales to holocrystalline rocks took place at the period of the Post-Neocomian upheaval at temperatures some- what above those now prevalent, at considerable but not at enormous pressure, and at the expense of basic solutions rising from the underlying shattered granite; further, that serpentinization of holocrystalline, metamor- phic rocks and slightly altered sandstones took place at somewhat lower temperatures, also at the expense of rising solutions. It is probable, but not absolutely certain, that the regional silicification was subsequent to ser- pentinization and mainly produced in a similar manner. The formation of ore deposits was not contemporaneous with the metamorphism. Impregna- tion of the rocks with calcite and gypsum went on at ordinary temperatures and is still in progress. Chloritization was effected at least mainly at ordi- nary temperatures. In no. case which has been examined are the holo- crystalline rocks of the metamorphic series injected eruptives or original sediments, nor are any of the serpentines studied original sediments. No considerable portion of the serpentines can have been derived from olivine and in no case has any occurrence of serpentine been traced to an olivinitic rock. Comparison between Neocomian metamorphics and the Archaean. \\ hetllCl" tll6 Al'cllSBan rocks are metamorphosed sediments or crystalline precipitates or of igneous origin is a question upon which eminent authorities differ, and one upon which neither evidence nor argument will be offered here. It is a matter of interest, however, to compare the altered strata of the Knoxville group with the crystalline Pre-Paleozoic rocks, since they appear to have much in com- mon. That there is no slight similarity between the metamorphic rocks of the Coast Ranges and the strata of Archaean areas is evident from the fact COMPARISON WITH THE ARCILEAN. 139 that more than one well known geologist has believed that he recognized as Archaean, areas now known to be Neocomian. The metamorphism of the Coast Ranges may fairly be considered, at least in part, as regional, since most of the rocks of the Knoxville group are considerably altered and there are areas of many hundred square miles now exposed in which no patches of unchanged or very slightly modified rocks are known to exist. Nothing like the uniformity often prevalent in Archaean areas, however, is to bo found in the Coast Ranges. On the other hand, though the general appear- ance of many of the Knoxville rocks differs widely from that of correspond- ing Archaean masses, there is much similarity in detail. Recrystallization is very prevalent in the California metamorphics and a crystalline development is characteristic of the Archrean. Muscovite rocks are frequent in the Coast Ranges, while biotite, though rare, is certainly one of the authigenetic min- erals in the California metamorphic area. Plagioclase, augite, and horn- blende are also abundantly developed. Mineral combinations similar to those of diabase, gabbro, and diorite are common both in the Coast Ranges and in many Archaean areas. Gneissoid rocks carrying albite and orthoclase, though not predominant in the Coast Ranges, are found there, and the mixt- ure of zoisite and plagioclase, called saussurite, is frequent in both series, as are also the accessory minerals ilmenite, titanite, rutile, apatite, and chromic iron Finally, serpentine is even more common in the Coast Ranges than in most Archaean areas. Of the more important features of the Arcluean series none appears to be entirely absent among the metasomatically recrystallized rocks of the quicksilver belt which have thus far been investigated, but the quantitative relations of the various minerals and rocks in the two series are widely different. A slight difference in the chemical composition of the sed- iments of the Coast Ranges, or of the solutions by the help of which their recrystallization has been effected, or of the pressure under which the reac- tions took place would have considerably changed the quantitative relations of the minerals formed. A greater depth from the surface would manifestly also have promoted uniformity. Whatever, then, is the real origin of the Archaean series, it appears certain that rocks indistinguishable from them might have been produced under conditions not greatly dissimilar to those which prevailed in the Coast Ranges at the close of the Neocomian. CHAPTER IV. THE MASSIVE ROCKS. General character of the massive rocks. Tll6 litliology of tllG Pacific slope received so much attention of late years that it is unnecessary and would be undesirable to treat the eruptive rocks of this area as if they were undescribed. The region is indeed vast; but it is also one in which the character of the rocks is remarkably persistent. In the following pages, therefore, only the more peculiar features of the massive rocks encountered in the present investigation will be enlarged upon. These are granite, older porphyries, andesites of several varieties, rhyolite, and basalt. PRK-TEBTIARY ERUPTIVES. Distribution of the granite. As. has been stated in the preceding chapter, granite appears to underlie the sedimentary rocks of the Coast Ranges and of the Sierra Nevada. According to Professor Whitney, a large portion of the mountain system from Fort Tejon southward is composed of granite. There are also large exposures of it in Shasta and Trinity Counties. In the region between Clear Lake and New Idria it is found in the Gavilan Range, occupies considerable areas near Monterey, forms the Farallone Islands, and appears at Point Reyes and other localities in the neighborhood. Near the town of Gnadala, on the coast, in Mendocino County, large masses of conglomerate are formed of granite bowlders cemented by granitic detritus. In the interior of the Coast Ranges north of San Francisco it has not been met with in place to the south of the Trinity Mountains, but probably occurs in some of the chaparral-covered hills, since a very large part of the pebbles in Cache Creek are granite. 140 GRANITE. 141 The arcose character of the sandstones of the Coast Ranges has been described. In the Sierra Nevada granite is abundant, even in the foot-hills. The higher Sierra, where not masked by lavas, consists chiefly of this rock. From the main Sierra range the granite~extends to Steamboat Springs and Washoe Lake. Here it disappears under the eruptive rocks of the Virginia Range, but reappears on the eastern side of this range near the southern end of the Comstock lode. The lithological character of the granites examined, from the Washoe district to the Farallone Islands, does not greatly vary, the chief difference being in the proportion of hornblende present. Some of the granite from the neighborhood of the Comstock carries little or no hornblende, while at Washoe Lake hornblende is particularly abundant. A moderate amount of hornblende occurs in the granite of Steamboat Springs and on the west- erly slope of the main Sierra. The Rocklin granite, from the western base of the range, is also hornblendic. In the central Coast Ranges hornblende is not abundant in the granite, only a portion of the specimens showing this mineral and none a very large amount. At the Comstock and at Steamboat Springs, as well as on the eastern slope of the Sierra, the granite immediately underlies strata at least as old as the Mesozoie. In the Coast Ranges, also, Neocomian beds rest upon it. No distinctly intrusive granite of Mesozoic or Tertiary age has been rec- ognized in the present investigation. That such exists, as asserted by Pro- fessor Whitney, I by no means deny; but there is at least some ground for supposing that the main part of the rock is Archrean. Granite O f steamboat springs. This is a rather coarse-grained, gray rock, the grains averaging 1.5'" : " to 2 mm in diameter. Plainly visible are quartz, feld- spar (in part triclinic), dark-green hornblende, and black mica. Under the microscope are seen quartz, oligoclase, orthoclase, dark-bro\vn, uniaxial biotite, dirty-green hornblende, and accessory minerals. These last are apatite, titanite, zircon, magnetite, chlorite, epidote, and ferric oxide. The quartzes are in large part composite grains and of course contain fluid in- clusions. The feldspars show in many cases undulous extinction and very often also zonal structure. The crystals of primary consolidation are bet- ter distinguished from those of secondary consolidation than is usual in 142 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. granites. Of these the first are long prisms of oligoclase (with appropriate extinctions), more or less irregular prisms of hornblende (often with good hexagonal cross-sections), and irregular foils of biotite. The minerals of secondary consolidation are quartz and orthoclase, with perhaps a portion of tli3 oligoclase. This division is only approximate, however, for grains of quartz are embedded in well developed hornblende prisms of first con- solidation. The plagioclase in some of these specimens is much more striking under the microscope than the orthoclase, and this fact might lead an ob- server to doubt which mineral predominated. In cases of this kind there is really no means of determining by microscopical examination the rela- tive quantities present, for, since the areas of the grains cut by the slide vary with the form and position t)f the grains as well as with their cubic contents, the most careful study of the areas exposed, or even of the areas of each grain, will lead to no definite result unless the difference in quan- tity is very great. To test the matter 42 grams of such a specimen were reduced to a grain of 0.5 mm , which, in consideration of the coarseness of the rock, was considered sufficiently fine, and separated by the Thoulet method. The separation seemed very successful, there being a very small loss from dust. The following is the result: Per cent. (1) At specific gravity 2.77, ferromagnesian silicates.... 17 (2) At specific gravity 2.67, impure feldspar 5 (3) At specific gravity 2.64, feldspar 12 (4) At specific gravity 2.62, quartz 34 (5) At specific gravity 2. CO, feldspar, with some quartz 9 (6) At specific gravity 2.58, feldspar 12 (7) At specific gravity 2.5G, feldspar 5 (8) At specific gravity 2.54, feldspar 6 The only triclinic feldspar detected under the microscope was oligo- clase, and the feldspar heavier than quartz was undoubtedly of this species. As appears from the table, about 17 per cent, of this mineral fell before the quartz. At first sight it would appear that orthoclase predominated greatly in the rock, since the larger part of the feldspar is lighter than quartz. It is a suspicious circumstance, however, that the range of densities is so great, and mixtures are to be suspected. Chemical tests of (5), (6), (7), and (8) UFIVSRSIT7 GRANITE. X&'.JT"' 0.012 This is evidently a plagioclase rock and must be considered a por- phyritic diorite. PORPHYRIES. 145 Had the porphyries found in the Chico conglomerate been ejected after the Post-Neocomian upheaval they would almost certainly have been de- tected in the extensive exposures examined at and to the south of Ne\v Idria. The porphyry at this point is therefore probably of nearly the same age as the similar rock found associated in the Knoxville conglomerates with granite pebbles and with fossils characteristic of the Knoxville series. The eruption of this porphyry must antedate a part of the Knoxville period, and the negative evidence is that it preceded the entire group of strata in which the fragments occur. Like the porphyry found in the granite at Steamboat Springs it is not improbably little younger than the granite. Diabase from steamboat springs. Among the greatly disturbed, partially meta- morphosed, highly inclined, sedimentary rocks of Steamboat Springs, which are overlain by andesites and basalts, occur some conglomerates. In these were found dark pebbles of a crystalline rock strikingly resembling the material which forms the east wall of the Comstock lode in Virginia City. Under the microscope these pebbles proved to be plagioclase-pyroxene porphyries with a crystalline groundmass. The pyroxenes are entirely decomposed, but the chlorite and other decomposition products retain the characteristic forms of augite or hypersthene. To which of these minerals the original substance belonged cannot therefore be told. This rock is microscopically as well as macroscopically indistinguishable from the por- phyritic diabase of the Comstock. The beds in which the pebbles occur are at least as old as the Mesozoic. 1 LAVAS. volcanic rocks of steamboat springs. The andesites and basalts of Steamboat Springs form a most interesting series both in themselves and because they throw some additional light upon the important occurrences near the Com- stock lode, which is only six miles from the Springs in a straight line and 1 1 have already drawn attention to the rocks of Steamboat Springs iu a paper entitled " Washoe rocks" : Bull. California Acad. Sci. No. G, 1836, p. 'Jll; see, also, my paper On the texture of massive rocks: Am. Jour. Sci., :id series, vol. 33, 1837, p. 50; and Bull. U. S. Geol. Survey No. 17, On the Develop- ment of Crystallization in the Igneous Rocks of Washoe, Nevada, with Notes on the Geology of tho District, by Messrs. Hague and Iddings. MON XIII 10 146 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. lies on the opposite flank of the same range. A portion of this series also possesses a close analogy to some of the andesites of the Coast Ranges. A detailed account of the occurrence of these rocks will be given in the descriptive geology of the locality. Here it is sufficient to state that the latest eruption is normal basalt and the earliest a normal, dense hornblende- andesite, while between the two comes a series of pyroxenic eruptions which form a natural group. All of this group have the rough fracture and porous texture which a few years ago would have led to its being called trachyte. 1 The exposures, as is so usual in the Great Basin, are admirable, a large proportion of the entire neighborhood being bare rock. Andesites of steamboat springs. The predominant variety of the older horn- blende-andesite of Steamboat Springs is a grayish-blue, dense, fine-grained, thin-bedded rock, with a few porphyritic feldspars of small size. It is entirely similar to one variety of the earlier hornblende-andesite of the Washoe district. Intermingled with this rock in the eastern portion of the mass are patches of coarser-grained and more porphyritic modifications. The relations of these patches to the' fine-grained material were studied with great care, and no evidence was found that they were separate erup- tions ; on the contrary, it was clear at several points that they represented merely local modifications of structure. These coarser-grained rocks are in- distinguishable from the prevalent older hornblende-andesite of the Washoe district. In the western area of the earlier hornblende-andesite the fine- grained, fissile rock is also abundant, but here it is associated with consid- erable, masses of wkat is plainly glassy rock. Transitions were distinctly traced here also. Under the microscope no very definite lines can be drawn between these older rocks. Thus, No. 313 is a gray rock showing many porphyritic, black hornblendes Under the microscope this specimen is found to be composed of brownish-green hornblendes with heavy, black borders (many 'Previous to my examination of the Comstock, the United States geologists and Professor Zirkel regarded the later hornblcnde-audesite of Washoe and many similar occurrences elsewhere as trachyte. I showed that the Washoe rock contained no sanidine and stated that, from a cursory examination of the trachyte slides of the fortieth parallel collection, there was " much reason to believe that trachyte occurs less often than had been supposed in the Ore it B:isin area" (Second Ann. Rept. U. S. Geol. Sur- vey, 1880-'31, p. :!()(); Geology of the, Comstock Lode, Mon. U. S. Geol. Survey No. 3, p. 374). A year later Messrs. Hague and I Idhigs announced that tliero were no trachytes in the collections 01 the fortieth parallel from th .-. (ire.it I5.isin (Thir.l Ann. Rrpt.U. S. Geol. Survey, 18rfl-'32, p. 12). ANDESITES. 147 of which have entirely replaced the amphibole), a very little pyroxene, and a moderate number of porphyritic plagioclases embedded in a fine-grained, holocrystalline groundmass of magnetite and feldspar, a portion of the latter being granular and a portion microlitic. In No. 25a, a light-gray rock with small porphyritic hornblendes, the amphibole is entirely replaced by black border, the porphyritic feldspars are small and few in number, and the gronndmass is a more uniform, fine-grained material. No 18 is a specimen of the prevalent fine-grained variety and presents under the microscope no considerable difference from No. 25, excepting that the hornblendes are smaller. The glassy variety of this rock shows under the microscope small brown hornblendes with heavy black borders, an occasional pyroxene, a few small porphyritic feldspars, and a groundmass consisting of feldspathic microlites and magnetite embedded in a glass base. Fluidal structure is common. The younger andesites of Steamboat Springs are all of the trachytic type, gray or reddish or yellowish rocks, rough and soft. Though these rocks stand in such close relations that I shall venture to propose a single name to embrace them all, they are divisible into three groups. In one large area the rock is extremely uniform and is essentially a pyroxene- andesite containing abundant augite and hypersthene. 'A few very minute, black-bordered hornblendes are usually visible under the micz-oscope, but they certainly do not form 1 per cent, of the entire quantity of bisilicates. This rock contains no mica. Large porphyritic plagioclases, which appear to be andesine, are embedded with the bisilicates in a groundmass of feldspar microlites and magnetite. A second pretty well defined variety is a hornblendic rock in general appearance similar to the first variety. It always contains more or less pyroxene. It also often contains mica. This last mineral seems to be entirely absent in some croppings and even over small areas. A few flakes only occur in other masses, while in others still it is fairly abundant, and in one area brown mica with a variable angle be- tween the optical axes forms a large part of the rock. This rock appears to be substantially identical with that which I called later hornblende-andesite in the Washoe district, where also mica is present in variable quantities and is sometimes absent. Messrs. Hague and Iddings prefer to rename 148 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. this rock hornblende-mica-andesite, a term which would be misleading* as applied to Steamboat Springs, where later hornblende -andesite is certainly appropriate, since five well defined dikes of it cut the earlier hornblende- andesite. A portion of these dikes show mica ; the others, none. The greater part of this rock is holocrystalline, but some croppings contain glass, sometimes in imperfect spherolitic forms. In two cases hornblendes with concentric, double, black borders were noticed. More interesting than either of these varieties of the younger -ande- sites is the third, which, for lack of a better name, I will call provisionally transition andesite. This variety occurs in a number of areas shown on the western portion of the map, some of which are small, isolated, and excel- lently exposed. They are as trachyticin texture as the associated varieties and are frequently laminated, the sheets being half an inch to an inch in thickness and not very sharply divided from one another. The andesites of Clear Lake show the same structure. The transition andesites are of exceedingly variable composition, even in the smaller areas. Some speci- mens are almost purely pyroxenic; others, at a distance of only a few feet, carry much more hornblende than pyroxene. Sometimes mica is present, but oftener absent, though it has been found in all of the principal areas. In one area olivine also has been detected in several specimens. One of these comes from a portion of the rock which appears to lie beneath the remainder and is much denser than usual, but other olivinitic specimens are of the ordinary trachytic type. The younger andesites are comparatively recent, though older than the basalt. They show few signs of erosion and cap a large part of the Vir- ginia Range near Steamboat Springs. They also form the Flufaker Buttes, between Steamboat and Reno, where, too, micaceous and non-micaceous rocks are found in company. The younger andesites are nearly contem- poraneous. The highly micaceous, later hornblende-andesite overlies and appears to have followed the less micaceous portion of the same variety. The relative ages of the pyroxenic and hornblendic varieties are not abso- lutely certain. On the map will be found a dike of later hornblende-andesite, which should cut pyroxene-andesite were it younger than the latter. It is not thus shown, but it is not impossible that it may do so, for at the points ANDESITES. 149 where it should be exposed the ground is so covered with bowlders of the pyroxene-andesite, which have rolled down from the adjoining hill, that the croppings may have been concealed. Repeated and careful search was made for them in vain. The transition-andesite, though, like the others, certainly younger than the earlier hornblende-andesite, does not stand in structural relation to the other varieties. That it is very nearly of the same age seems certain. In the Washoe district the micaceous rocks suc- ceeded the pyroxene rocks of Mt. Kate, 1 but are connected with them by transitions. On the other hand, Mr. Lindgren found that near Bodie pyrox- ene outflows succeeded micaceous ones. It would be a very easy matter so to arrange the slides of the older and younger andesites of Steamboat that they would seem to form a con- tinuous series, and a tolerable argument might thus be offered for regarding the rocks as substantiallv one. It would be more difficult to treat the hand . 01). 150 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. would unquestionably have been classified as trachytes by nearly every American geologist a few years since. They are nearly all soft, rough, light-colored rocks, possessing great similarity in external appearance and in their mode of occurrence. This similarity cannot be regarded as acci- dental, for the series of younger andesites found at Steamboat is repeated at Mt. Shasta, which I visited for the purpose of instituting a comparison, and in part also near Clear Lake, while the area regarded as trachyte by all field observers . at Washoe previous to my study of that district em- braces highly pyroxenic, non-micaceous rocks as well as micaceous, horn- blendic andesite. If the macroscopical resemblance and the intimate asso- ciation of these rocks be not accidental, it must be due to common features in their origin or history, and they may therefore properly be regarded as forming a natural group, recognized by earlier observers, though wrongly named. They are all more or less pyroxenic rocks, which may contain both mica and hornblende or one of these minerals or neither. Horn- blende occurs in this series over large areas without associated mica, and mica (near Clear Lake) in large areas without associated hornblende. The members of this series are connected by transitions wherever I have studied them. There is certainly a marked distinction between this series and the older hornblende-andesite, both at Steamboat and at Washoe, as there is also at the latter locality between it and the earlier dense pyroxene-ande- site. Near Clear Lake also the earlier pyroxene-andesite is distinct. The causes of these differences are not as yet known. I do not believe that they depend simply upon the rate of cooling or upon the pressure under which the rock has cooled. As has been mentioned, a portion of the older hornblende-andesite of Steamboat is glassy, while directly associated with the glass is ordinary, dense, older andesite. That a glassy magma cooled slowly under considerable pressure will crystallize appears almost certain, and it is to be inferred that the earlier andesite at this locality has not been very deeply eroded. Consequently dense andesites may consolidate near the surface. On the other hand, there are many exposures of the younger andesites at depths of hundreds of feet, and in the Sutro tunnel at a depth of some 2,000 feet below what must be supposed to have been the surface of the rock at the period of eruption. Such exposures are indeed ASPE RITES. 151 holocrystalline, but tliey retain their trachytic character in spite of having cooled at great depths. I incline to the supposition that, owing to chemical differences in the material of secondary consolidation, a greater change of volume has accompanied this final process-in the more recent series than in the earlier one and that the cracked feldspars and the smaller cohesion of the trachyte-like rock are due to this change of volume. Bulk analyses of the younger andesites indicate a slightly more acid composition, but it would be a matter of great difficulty to separate the crystals of primary and secondary consolidation for analysis. Means of deciding this question may, however, be devised. Should the series of younger andesites discussed above, together with the transitional varieties, prove common on the Pacific slope and, as a rule, distinct from the earlier and denser rocks, these plagioclase rocks might conveniently be termed asperitc*, 1 at least for field purposes, in reference to their trachytic character. If these relations, traced by me at four impor- tant localities and suggested by hasty inspection at other points, are gen- eral, it will only be necessary to substitute the term asperite for trachyte on many of the earlier geological maps of the western United States to represent the facts from a modern point of view. Even if the term asperite does not obtain a permanent place in lithological nomenclature, it cannot be amiss to consider its expediency. The nomenclature of lithology is and must always remain more or less arbitrary. That classification is the best which takes account of the greatest number of natural relations; but no classification can embrace them all. To my mind it is an advantage that the term asperite expresses structural as well as mineralogical distinc- tions, for, though a purely mineralogical classification of rocks is extremely simple, it ignores many of their properties which are of the utmost interest and importance. . That the ultimate classification will be purely mineralog- ical appears to me in the highest degree improbable, nor can I believe that it will be founded solely upon microscopical peculiarities. 2 1 From asper, rough, the Latin equivalent of T/iax_v~. 'C. W. Giimbcl (Sitzungsbcr.k.bayer. Akad. Wiss., Munich, vol. 2, 1681, pp. 305-36?) suggested ten- tatively that the audesitio rocks of South and Central America might be divided iuto two types, one trachytic, the other basaltic iu habitus. I was not aware of this suggestion when the text was writ- ten. Giimbel's material was meager. In his specimens of trachytic habitus, corresponding to my as- periteg, bo found no mica. The specimen* of basaltic habitus which ho examined iiirlu>lr 2 Ferric oxide Fe"0* 1 410 064 4 45G '7.02 110 71 12 Nickel oxidn, NiO 411 1 551 4 Oil 7 72 1 ^60 8 838 13 61 Soda "NTa ? O 8 090 3 047 5 98 Potassa K-O 4 515 1 507 89 Chlorine Cl .. 1'9 Loss at 100 Il'O f 614 Loss above 100 H 2 O J 0. 428 ( 13 J 1.06 Total (less 0.027 O 0.110 Cl. in I) JOO. 085 99 9"8 100 13 1 A small amount of iron in the ferric state was not di'termineil, because unnecessary for the purpose for which the analysis was originally made. Atomic ratio of I, H- : Si : R" : R"=0. 047 : 5. 027 : 0. 506 : 0. 474. Atomic ratio of II, H- : Si : fi' 1 : R"=0. 082 : 3. 825 : 0. 937 : 0. 887. Atomic ratio of III, H- : Si : fi" : U"=H. 118 : 3. 444 : 0. 669 : 1. 376. The difference in composition between the glass and the nearly holo- crystalline basalts is extremely similar to that pointed out between the crys- talline and glassy forms of andesite. There is nearly three times as much alkali in the glass as in the olivinitic basalt from Burns Valley, and only one-fifth as much lime and magnesia. It is a curious fact that if 10 per cent, of lime were added to this obsidian it would closely approximate in composition to some kinds of window-glass. Analogous occurrences. The association of coiiiparati velv acid glasses with neutral or basic lavas is not unknown. In the trachyte of Mt. Amiata, in Tuscany, Professor vom Rath found small grains of a substance which had foiriVSRSITY 160 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. been taken for quartz, but which on separation and analysis proved to be glass. 1 The inclosing rock contained 67.06 per cent, of silica, while the fol- lowing analysis shows the composition of the glass : Specific grav ity 2. 351-2. :>out the time at which this monograph was transmitted, a very elaborate study of the Amiata rocks was published by Mr. J. Francis Williams in the Xeues Jahrbuch fiir Mineral., V. Beilage-Band, 1887, p. 381. He regards the whole mountain as a single massive which is typically developed as trachyte toward the center, but tends sometimes to an andesitic and sometimes to a rhyolitic composition at the edge. The rock is all more or less glassy. A very pure glass from Fosso del Diluvio gave: Sp.gr., 2.346; SiO 2 , 73.57; CaO, 0.99; MgO, 0.26; Na 2 O,3.0l>; K-O, 5.74. An analysisof typical trachyte from the Poggio Traburzolo gave: Sp. gr., 2.562 ; SiO 2 , 64.76; CaO, 3.24; MgO, 1.74; Na-O, 2.67; K-O, 5.49. As in the case of the Clear Lake andesite and basalt, the glass is more acid than the rock, and the proportion which the alkalis bear to the earths is much greater in the amorphous material. Here also tin? glass was prevented from crystallizing by peculiarities of composition, not of the physical condi- tions to which it was subjected. 3 Neues Jahrbnch fiir Mineral., 18(51), p. 3C>; ibid.. 1ST.:, p. :>?. BASALTIC GLASS. 161 These analyses are directly comparable with those of the basalt and basaltic obsidian and with the andesite and andesitic obsidian from Clear Lake, and the character of the differences is manifestly the same. In each case the glass is comparatively very rich~in alkalis and silica and contains only a little lime or magnesia. inferences. In the rocks from Amiata and the Rossberg only small blebs or streaks of acid glass are found. At Clear Lake, on the other hand, im- mense quantities of glass, covering large areas, accompany crystallized rocks in such a manner as to leave no doubt of their direct connection. The nature of the cases is the same, but the size of the masses is very different, and I am not aware that any instance has ever been studied in which areas of glass which must be measured by the square mile are thus connected with crystallized rocks of a different chemical composition. It is plain from these occurrences that associated masses of very different chemical composi- tion and of great volume sometimes form portions of the same eruptions. They pass over into one another by transitions, but, whether they never have been more thoroughly mingled than they now are or whether, having been intimately mingled, they have separated by eliquation, it is perhaps impossible to decide at present. The conditions show that they were in contact in a fluid state and that the passage from the crystalline to the amorphous rocks is a gradual one. It is manifest that, in the case of these comparatively recent and super- ficial rocks, the crystallization has been governed by the chemical compo- sition, for the glassy and crystalline masses, while of different composition, have been subjected to physical conditions which were nearly identical. It cannot be doubted that there are many cases in which the differences in structure of massive rocks are referable to chemical variations which are perhaps numerically small. Even in the lavas it is not an infrequent thing to find rounded masses which differ greatly in rnineralogical composition from the surrounding mass, and yet these have been subjected to ex- actly the same physical conditions as the material in which they are em- bedded. Even, therefore, if no chemical difference known to be significant could be discovered, it would inevitably follow that such a difference nev- ertheless existed, for variations in texture must be due to variations either MON XIII 11 162 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. in composition or in the physical conditions to which the several masses have been subjected. A few tenths of 1 per cent, of carbon in iron changes its fusibility and texture enormously and trifling quantities of silica or alumina cause immense variation in the fusibility of the normal bisilicate, iron blast-furnace slag. It is well known that when furnace men desire a slag which fuses less readily than this they do not dare to add either alumina or silica, because either raises the melting point so rapidly. Lavas, which are natural slags, must be affected in a similar way bv these or by other substances, such as titanium. Granitoid and porphyritic texture. While tll6 obsIdiailS of Clear Lake aild of the Rossberg have evidently remained amorphous because of their peculiar chemical composition, it by no means follows that had they been cooled sufficiently slowly they might not have crystallized. On the contrary, the- ory and experiment alike point to the supposition that vitreous substances will always crystallize if they have sufficient opportunity. This is gener- ally admitted. It is often supposed to be merely an extension of the acknowledged tendency to crystallization to maintain that, if glassy magma is only cooled slowly enough, the result will be a mass which is not merely holocrystal- line, but of granitic structure The difference between typical granular texture and porphyritic text- ure, however, is a very different matter from the distinction between holo- crystalline and glassy structure, a fact which appears to have escaped the attention of many lithologists. The conclusion to be drawn from granular structure is that various minerals crystallized simultaneously, while the larger mineral constituents of porphyries have evidently crystallized in advance of the groundmass surrounding them. If a substantially homogeneous fluid cools very slowly indeed, the tendency will be for some of the resulting compounds to crystallize in ad- vance of others, and therefore to attain a considerable size and good crvs- tallographic development. This follows both from theory and experiments familiar to every chemist. If the cooling of such flifid is continued at a very slow rate, the interstices must fill with other crystals the growth of which will be interfered with by mutual opposition and the obstruction of EOCK STRUCTURE. 163 the earlier crystals, and the final result will in general be a porphyry. Only in the limiting and just supposable case that the formation of the various final mineral ingredients of a rock liberates heat at exactly the same rate can they all crystallize simultaneously from a substantially fluid mass and produce a granular structure. This inference is strengthened by observa- tions on typical porphyries. It is acknowledged that the larger crystals of good porphyries antedate eruption and have been formed at the enormous pressures which must prevail at the sources of eruption. Had such rocks never been ejected and had they cooled in place at an almost infinitesimal rate, it seems to me that only porphyries could have resulted from the process. On the other hand, if a heterogeneous but more or less intimately mingled mass is acted upon by chemically active solutions, the reaction yielding heat most rapidly will vary from point to point with the composi- tion. In such a magma a granular structure would naturally result. These are the conditions attending metamorphism, and highly metamorphic rocks are typically granular. Eruptive granular rocks (or those which most geol- ogists believe to be eruptive) frequently, if not always, exhibit the best of evidence that they are by no means of uniform composition, and have there- fore never been thoroughly or substantially fluid. Portions of such rocks a few inches apart present differences in structure and mineralogical com- position much more marked than those observed in lavas. The differences can be due only to physical or chemical causes, and. since so closely ad- joining portions of rocks must have been subjected to the same pressure and must have cooled at the same rate, the only possible conclusion is that the composition changes. These variations are so great and so abrupt as to indicate that the original magma was not substantially fluid, a conclu- sion long ago reached by Scheerer. A lack of fluidity and of homogeneity thus characterizes magmas which yield granular rocks. This partial fusion cannot be in general the result of pressure, for, while it is certain that some magmas would yield porphyries if cooled at depths of many miles below the surface, granular rocks of analogous composition are known in many cases to overlie sedimentary material later than the Archrean, and cannot have been subjected to pressures so great as those under which the magmas of the corresponding porphyries were substantially fluid. 164 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. conclusions It will readily be seen to be a consequence of the above facts that granular rocks having precisely the same composition as porphy- ries cannot have been so highly heated as the latter and that granular rocks as a group, unless they differ from the porphyries in chemical com- position far more than has hitherto been suspected, cannot have been subjected to temperatures on the whole so intense. Differences in texture are in a great proportion of cases certainly due to differences in composi- tion, and, even if one were to find a continuous column of rock porphy- ritic at the upper end and gradually passing over into a granitoid mass at the lower end, the occurrence would not prove that the difference in text- ure was due to difference in pressure and rate of cooling, unless the com- position were also proved to be identical (an impossibility) or it could be shown that the granular rock had once been a real fluid and not merely a half-fused mass full of solid particles of various kinds. Such instances as the lavas of Clear Lake, the mingled granular and porphyritic diorites of the Comstock, and many exposures of granite show that the homogeneity of any single body of massive rock cannot be taken for granted and that differences of composition lead to differences of texture almost certainly greater than those resulting from the weight and slow conduction of thou- sands of feet of rock. 1 ORIGIN OF THE MASSIVE ROCKS. importance of the subject. Granite underlies the Coast Ranges and the Si- erra Nevada, and much of the surface of these ranges is flooded with lava. The question of the origin of these rocks is of great importance to a thor- ough discussion of the ore deposits, for it is from the granite or the lava that the ore is most likely to have been derived. The genesis of the re- 1 1 have discussed this subject more fully iu a paper on The texture of massive rocks: Am. Jour. Sci., '3d series, vol. 3:5, 1887, p. 50. Prof. A. Lagorio has published a very valuable memoir on the nat- ure of glass base and on the process of crystallization in eruptive rocks (Tschermaks mineral. Mii- thcil., vol. 8, 1887, p. 421). This paper reached me after the transmission of this volume. The author carefully considers both the chemical and physical influences affecting the tundeucy to crystallization. He points out the high alkali contents of the glasses and reaches the conclusion that potassium silicates are the last to solidify. He refers granitoid structure to the sudden consolidation under pressure of supersaturated solutions of several salts. This does not seem to me a satisfactory explanation. Simul- taneous supersaturation of a solution of several silicates seems to me improbable, as docs also their simultaneous precipitation from supersaturated solution. ORIGIN OP MASSIVE KOCKS. 165 agents in which the ore was dissolved previous to its deposition was also, beyond a doubt, closely connected with the origin of the massive rocks. Hypothesis of sedimentary origin. As is well known, many geologists suppose not only granite, but all eruptive rocks, to be products of the more or less complete fusion of the sedimentary strata. On this supposition there would be more or less organic matter or carbon distributed throughout all rocks, and this material would exercise a most important influence on sub- terranean chemical reactions. While the writers referred to maintain that the massive rocks, without exception, have passed through the sedimentary state, all are agreed that the material of which they are composed must have originally formed a portion of the primeval massive crust of the globe. Most of them are of the opinion that these primeval rocks are so deeply buried beneath their own accumulated waste as to be totally inac- cessible and that we know nothing of their character. The opinion here sketched in its leading features is an old one, and, though a large number of leading geologists dissent from it, it has found many able defenders. These seem to me to have overlooked some objections and to have general- ized too broadly from certain analogies. It is difficult to understand how on a globe continually .affected by upheaval and subsidence the rocks un- derlying the sedimentary material can ever be entirely buried. It is equally difficult to imagine any means by which the primeval rocks can have been reduced to a clastic state at the enormous depth called for by the hypothesis, a deptli of at least twenty miles from the surface. Primeval conditions. Geologists and physicists are substantially agreed that the earth was once an intensely heated, plastic or fluid spheroid. This I will assume to be true. When water began to condense on the cooling globe there were of course no sediments. Even as they first solidified the rocks cannot have been absolutely level, so that some portions of the surface were more exposed than others. For the sake of simplicity in rea- soning, one may first consider what would have happened after the first oceans formed, had there been no such thing as upheaval and subsid- ence. It is clear that all the more elevated portions of the original surface .of the globe would have beeu cut down by erosive processes and that the entire globe would have been eventually covered by a shallow ocean, the 166 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. bottom of which would have been in general a sedimented area. In certain localities one may suppose that oceanic currents might have cut through this stratum of sediment and eroded the underlying primeval rocks to some extent, but it is certain that action of this description would soon find a limit, and that thereafter no sensible mechanical action would be exerted on the primeval rocks. Consequently, the quantity of sediment could never increase perceptibly beyond a certain fixed and very moderate limit. Effect of upheavrj^. If upheaval were now supposed to be introduced into terrestrial economy, portions of the universal sedimented area would be raised into continents and would undergo erosion. The stratum of sedi- ment having been removed, the primeval rock would again be exposed and its degradation would increase the total amount of sedimentary material. If upheaval were confined to certain areas and were a continuous process, while corresponding subsidence took place in other and distinct areas, primeval rocks would continue to be exposed in continental regions, at least for a very long time. If upheaval and subsidence were to alter- nate in the same areas, but if in certain regions the upheavals were on the whole somewhat in excess of the subsidences, primeval rocks would appear at the surface of these areas from time to time and the total quantity of sediment on the globe would at these times receive accessions. Upheavals and subsidences could alternate and balance one another on each portion of the globe only if the influences tending to produce these movements were everywhere exactly balanced. The mere fact that the poles receive less heat than the equatorial regions establishes a difference of physical conditions on various portions of the earth, which certainly in- fluences erosion and cannot but affect changes of level. However complex and remote the connection may be between upheaval and evaporation, some relation certainly subsists between them, and it is not possible that on a globe like ours there should not be a tendency to a greater prevalence of uplifts in some regions than in others. Bearing of Dana's continental theory It is deal* that, if ProfeSSOl* 1 hum's tllCOry of the permanence of continental areas is correct, it substantiates the con- clusion drawn above, that there are areas in which the tendency to upheaval on the whole exceeds the tendency to subsidence. There is much evidence UPHEAVALS. 167 in favor of Professor Dana's theory, though some geologists do not accept it. If tills theory were absolutely disproved, it would still be impossible to suppose that upheaval and subsidence everywhere exactly balance each other in the long run. If continents once existed where the great oceans now lie, a perfect history of the earth would show that there were conti- nents in some parts of the world through larger portions of geological time than in other recrions. In regions where the total erosion has exceeded the o o total sedimentation, the original crust must almost certainly be exposed. Bearing of principle of hydrostatic equilibrium Nothing ill geology is IBOrC CCl'taill than that the earth is very nearly in a condition of hydrostatic equilibrium, 1 and it is the maintenance of this equilibrium which necessitates upheaval and subsidence. This is perfectly evident if the interior of the earth is fluid. It is also true if the earth is solid to the center and as rigid as steel or glass; for a mass as large as the earth of either of these substances could not maintain a shape diverging considerably from a form of fluid equilibri- um for any length of time. Even masses of metal of a few tons (e. g., metallic mirrors for astronomical purposes) undergo deformations by their own weight. So also will a slab of marble supported at its extremities, and, in short, the flow of solids in general is a well recognized fact. 2 Now, if the earth is a solid, highly viscous mass, as Thomson and Darwin have concluded, the effect of the subsidence of, say, a sedimented oceanic area must be felt to the center of the earth, and the earth from the center to the surface must partake in an upheaval. If, on the other hand,, the globe con- sists of a solid shell, which is growing thicker,^arid a fluid ball upon which the shell floats, the effect of the subsidence of a given area must be to depress the fluid magma underlying this area and to raise some other column of the fluid under eroded regions. Even in this case, then, at least the superficial portion of the fluid ball partakes in the movement attending upheaval and subsidence. 1 l.abbage, I believe, was the first to point out this now familiar fact. 1 In discussing the nuestion of the solidity of the earth, geologists seem sometimes to forget that timi' outers into the conception of viscosity. The earth may be as rigid as steel with reference to forces which rapidly change thoir directions like those exerted by the sun and moon, but as plastic as putty tu much smaller stresses acting continuously through long periods of time in a single direction. The rigidity of the earth claimed for it by physicists is not inconsistent with the flexure of strata. So a stick of sealing-wax may be slowly contorted by its own weight, but a smart blow will break it like glass. 168 QUICKSILVER DEPOSITS OF THE PACIFIC! SLOPE. consequent effects of upheaval. Granting, as one inevitably must, that there are areas over which there is a tendency to the prevalence of upheavals over subsidences, the layer of a supposed fluid interior of the globe which con- gealed to-day on the under surface of the crust in such areas must rise gradually or intermittently and will be exposed to the air at some remote future period. Or if the globe is a viscous solid, the plastic mass beneath the lowest sediments in areas of predominant upheaval must be rising to- ward the sui-face. In either case it would appear from the above that the exposure at the surface of the earth of material upon which no ray of light has ever fallen since the outer layer of the earth congealed must be of daily occurrence. Logical consequences of sedimentary hypothesis TllC Supposition that all the material now exposed to view has passed through the sedimentary condition seems to be conceivable only in one way. It implies the hypothesis that upheaval and subsidence are substantially superficial phenomena, in which the inte- rior of the earth has no part. It supposes that the sediments which subside, off a coast perhaps, afterwards flow laterally and again ascend to the sur- face at some other point, perhaps in a fluid or plastic state, as lava or granite. This is a condition of things which cannot always have existed. The pri- meval massive rocks must evidently have been exposed until the entire quantity of material which has ever been brought into the form of sedi- ment was eroded from their surfaces, and, during that period, the interior of the earth must have partaken in the movements of upheaval and subsi- dence. The greater the quantity of matter which is assumed to have been at some time sedimentary, the longer must the exposure of primeval mass- ive rocks have continued and the more difficult does it become to under- stand how the interior can ever have ceased to be affected by upheaval and subsidence. The geologists who take this view are compelled to assume an enormous thickness for sedimentary material, and they must consequently also suppose that primitive rocks have been exposed during an enormous period. The fact appears to be, however, that the supposed failure of the earth's interior, say beneath a mean depth of twenty miles, to partake in the movements of upheaval and subsidence is totally inexplicable on mechanical principles. Some geologists have hotly assailed physicists for EEOSION. 1 69 maintaining that no great part of the earth can be fluid. The hypothesis that only a superficial layer of the globe is affected by upheaval and subsi- dence appears to me to imply that beneath this thin shell the earth is not the highly viscous solid of Sir William Thomson, but a body of absolute, ideal, and impossible rigidity, for only then could it fail to share in the def- ormation of the surface. The problem viewed as one of erosion. Tll6 aVCl'age tllicklieSS of tll6 Sedimentary rocks is in my opinion often greatly exaggerated. It is true that if the greatest thicknesses of the formations are added they form an enormous total ; but we all know that sediments are thickest near shore lines and dis- appear altogether at a distance from the shore. According to those author- ities who maintain that even the igneous rocks are fused sediments, of course the later sedimentary rocks are composed of the same material which en- tered into earlier strata. That this is to a large extent the case is evident. Clearly, however, it must also have been the case to some extent from the date of the first upheaval after oceans formed on the surface of the globe. As time went on the exposed areas of the primitive rocks must have de- creased while a larger and larger proportion of freshly formed rocks was produced at the expense of the older beds. After a certain time the addi- tions to the total amount of detrital material in a given period, say one thousand years, would be very small, and from that time onward the quan- tity of detrital material would remain nearly constant. Now, if one supposes the average thickness of sedimentary rocks at some past epoch to have been only one mile, it is evident that only a minute proportion of any land area similar to the present continents, or even of much bolder configuration than these, could be occupied by exposed primeval rocks. 1 If an average thick- ness of one mile of sedimentary material would reduce the area of primitive rocks to a very small one, how is it possible to account for the formation of twenty times this quantity of detritus ? I do not think it can be done. character of the process of degradation. The hypothesis that this almost incredible quantity of detrital material exists, as applied by advocates of the sedi- mentary origin of massive rocks, involves the assumption that degradation 1 Gaiinctt's fsl imato of the mean elevation of the United States, excluding Alaska, is 2,000 feet, say half a, mile. LoipoHU's estimate for Europe is '297 meters, or 975 feet, say a sixth of a mile. 170 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. of primitive rocks came to a complete close. The last exposed primitive rocks must have subsided and have been buried under sediments formed from pre-existing strata, and this subsidence must have exceeded in amount the sum of all the upheavals to which they have since been subjected- This seems to me a very artificial hypothesis, quite out of harmony with those theories which have been found to accord best with other geological facts. It is seldom that we find in nature abruptly arrested processes, such as this is supposed to be, excepting where these are reversible, which this is 'not. It is more natural to suppose that the area of primitive rocks diminished progressively without ever being completely or irrevocably buried. Thus, in the second million of years after oceans came into ex- istence, one may imagine half as much fresh detritus to have formed as in the first million years; in the third such period half as much as in the second, and so on to the present day. Had this been the actual case, the total amount of sediment at the end of an infinite time would differ infi- nitely little from twice the quantity of sedimentary material at the end of the first million years, and infinitesimal areas of primeval rocks would still remain exposed even after the process had continued for an infinite time. In using this numerical illustration I do riot of course intend to imply that the particular numbers selected are in themselves probable. The length of the successive periods, in each of which the total quantity of fresh detritus derived from the primeval massive rocks was half that sim- ilarly produced in the preceding period, may have varied regularly or irregularly. But I do maintain that neither theory nor observation affords any ground for the hypothesis that, during some one period in the earth's history, the entire area of primeval rocks was obliterated, never to reappear If I am right in doing so, it is improbable that the primeval rocks have been or ever will be entirely concealed from view at all points on the earth's surface during any considerable time. In other words, contemplation of the process of erosion leads to the same result as was reached by consid- ering the mechanism of upheaval. Relations of granite. The observations which are usually cited in support of the sedimentary origin of lavas depend upon the relation of granites to other rocks. That granites are sometimes so connected with crystalline schists PRIMEVAL ROCKS. 171 as to lead to the belief that they pass over into one another is certain. It is also maintained by many geologists (erroneously, as I believe) that cases occur in which a series of transitions exists from granite to glassy lavas. If both these propositions were correct, it would follow that a transformation of sediments into lavas would be possible under certain conditions, but it would not follow that this is the usual history of lavas or even that it is the history of a single lava. Neither does it follow that because some granites are metamorphosed sediments all granites are of this class. Possible character of primeval rocks. TllC oldest Sedimentary 1'Ocks COmpOSO the Archaean wholly or in part. These rocks are also much more uniform in composition than later stratified rocks. They must have been derived in great part from the primeval rocks, which therefore possessed the same mean composition as the schists. This composition is substantially iden- tical with that of granite. Hence, a rock chemically similar to granite formed the primeval surface. This rock must also have formed at high temperatures, very slowly, and under great pressure. It must inevitably have been chiefly crystalline, and all analogy and experiment lead to the belief that it can have contained no glass. It must have been a holocrys- talline porphyry or a granular rock. The atmosphere previous to the solidification of the surface of the globe must have contained at least as much water as the ocean now holds, as well as most of the carbon now present in limestones, coal beds, etc. The pressure of this atmosphere must have been at least three or four thousand pounds per square inch and the boiling point of water must have been correspondingly high. When, or soon after, the temperature at the surface sank to the critical point of water (580 C., Mendelejeff), and therefore while the surface was still red-hot, water must have condensed upon it. Judging from what is known experiment- ally of igneo-aqueous fusion, conditions more favorable to this process could not be imagined. Now there is much reason to suppose that granite has been produced by igneo-aqueous fusion. It is therefore in the highest degree probable that the terrestrial surface when the earth first ceased to glow was granite, very probably accompanied to some extent by allied plagio clastic rocks. It is far from impossible that portions of it may have had a gneissoid structure. 172 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. The foregoing paragraph contains no novel statement. Scrope, 1 in 1825; MacCulloch, 2 in 1831; and Elie de Beaumont, 3 in 1847, all maintained that the primeval rock from which the strata are derived must have been granitic. In 1859 Mr. Daubree 4 entered more fully into the physical theory of the formation of the primitive rocks. Taking as a basis Humboldt's estimate of the mean depth of the ocean (3,500 meters), he calculated that the barometric pressure of the sea water alone in the form of vapor would amount to almost exactly two hundred and fifty atmospheres, or say 3,700 pounds per square inch. Later estimates of the area and depth of the sea diminish this figure somewhat, but only to the extent of about a hundred pounds."' When the temperature of the earth was too high to permit of the condensation of water, this pressure wns farther augmented by other vapors and gases. The purely igneous rocks formed prior to the condensation of any water, as Daubree infers, must have been changed by the action of the water first precipitated at very high temperatures and pressures into a mass of crystallized minerals, exactly as in his own experiments in sealed tubes crystals were developed from amorphous materials. Inquiring whether the earliest aqueous precipitation corresponds to the period of the formation of granite, he replies that we cannot affirm this in an absolute manner, but may presume it. This presumption of Mr. Daubree, previously indicated by others on less satisfactory grounds, seems to me to gain greatly in force by the reasons which I have adduced above. My argument shows it utterly improbable that the rocks which antedate the formation of consid- erable seas should even now be everywhere concealed, while it is well known that the lowest visible rocks the world over are granitic. In 1879, again, Mr. R. Mallet speculated upon the character of the earliest seas. He 1 Considerations ou Volcanoes Leading to tlio Establishment of a New Theory of the Earth, quoted by Dr. Hunt, Origiu of Crystalline Rocks, sec. 17. * System of Geology, vol. 2, p. 88. "That very granite," he adds, "may be visible; but we can- not as yet distinguish it from the many successive ones which have acted in the elevation of the strata." 3 Bull. Soc. g. syuth. stir le me'tain : Ann. des mines, 5th series, vol. Ifi, p. 471. 15 Dr. Kriimmel's revision of the question of the total quantity of water in the ocean (extract from a note to the Gottiugen Academy, Nature, vol. 19, 1879, p. 348) leads to about 3,584 pounds per square inch. 6 Quart. Jour. Geol. Soc. London, vol. 36, 1880, p. 112. PEIMEVAL ROCKS. 173 deduced the conditions as Daubrt'e had done and pointed out the "bearing of the critical point of water. But the chief application which he makes of the results is in the endeavor to account for the great quantity of detrital mate- rial in existence. He points out that the^degradation of elevations would be more rapidly effected by heated waters than by cold ones, and infers, as I understand him, that hot waters would also ultimately yield a greater quan- tity of detritus than cold waters. The latter of these propositions does not appear to me to follow from the former or from Mr. Mallet's arguments. It would seem to me certain that the maximum accumulation of clastic material would be more rapidly approached were the water hot, but that this maximum would be a similar quantity whether the water were hot or cold. It is perhaps unnecessary to point out that if the purely igneous super- ficial layer ot fhe earth's mass was converted into a crystalline rock resem- bling granite at enormous pressures and at temperatures approximating to 500 C. the quantity of water in the fluid state which was instrumental in the transformation must have been comparatively small, for the great press- ure was due to the fact that most of the water formed a gaseous constituent of the atmosphere. This accords with the views of Scheerer and subsequent investigators, that no great quantity of water is needed to render aqueo- igneous fusion possible. Sedimentation must, therefore, at this period have been an extremely subordinate phenomenon. 1 There is thus every reason to suppose that the original massive rocks were granitic in composition and in texture. The fact that eruptive gran- ites were ejected in later times only shows that at certain depths beneath the surface the conditions of heat, pressure, and moisture which once pre- vailed upon the surface were repeated. That detritus from the original granite under great pressure and at high temperature may also sometimes be metamorphosed into a material similar to the original granite is cer- ' As the temperature sank still further and oceans began to accumulate, the water must have heen highly charged with mineral matter. It is to this later period that Dr. Hunt, who accepts Dau- brcVs exposition of the action of the earliest condensed water, ascribes the formation of the Arclm-an whists as chemical precipitates. In the text I am Lot concerned with the formation of the crystalline schists, but I wish to state that it appears to me impossible to suppose no crystalline precipitates to have been deposited. I do not doubt that such were formed in a manner nearly or quite identical with that which Dr. Hunt maintains. As appears in a preceding chapter, however, I cannot agree with this brilliant thinker in ascribing nearly all crystalline stratified rocks to this process, nor can I believe that anything like the entire Archiean has been thus produced. 174 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. tainly not surprising. Neither of these facts even tends to prove that the primeval rocks were not granitic or that they are now nowhere exposed. How primeval granite is to be discriminated in all cases and with certainty from that which was erupted in subsequent geological ages or from highly metamorphosed rocks is another question, to which a definite answer cannot yet be given. At present general evidence only is attainable. California granit. Granite underlies the greater part of the State of Cali- fornia. This granite must be exposed to very different depths. The Sierra has been undergoing erosion ever since the early Paleozoic, and on the lower portions of its eastern flanks are metamorphosed strata not younger than the early Mesozoic. At the McCloud River the Carboniferous also appears to rest on granite. The granite of the Coast Ranges has been covered by sediments a large part of the time which has elapsed since the Paleozoic and has been far less exposed to erosion than that of the Sierra; yet granites from the various localities are almost indistinguishable. Though there may be granites within this area of different origins and ages, I ran see no reason to suppose that the great underlying mass is not substantially one It is probably continuous with the granitic areas of Idaho and Arizona and is too extensive to be regarded as an eruption or a series of eruptions. Were it metamorphic, evidences of the fact would probably be frequent, whereas, so far as is known, there are very few localities in the State that suggest this derivation. While both metamorphic and eruptive granites will probably be found, the main mass must be at least as old as the Archrean, and, while I do not assert positively that it is primitive granite, this appears to me far more probable than any other hypothesis. As was pointed out above, the formation of more or less gneissoid rock probably accompanied that of the primeval granite and the presence of such material in a granitic area does not prove that it is not primeval. 1 California lavas. The lavas have unquestionably come up through the granite and are of infragranitic origin. There is no direct evidence what- 'A portion of tlie primeval crystalline rocks, though perhaps a small one, was probably plagio- clastic. It would be difficult otherwise to account for the quantity of soda in t.h>' clastic rocks. If Professor l.a^orio is correct, as he seems to me to be, in asserting iliat sodium silicates separate from magmas morn readily than potassium compounds, it, would seem that oitlmclaso should have predom- inated in the outer crust of the earth, or in the primeval grauitie rocks, and that plagioclase should have predominated in the iiifragranitic rocks, or in the lavas. This, of course, accords with observation. UNIVERSITY CALIFORNIA GRANITE. ever that the material of which they are composed has ever yet been de- posited from water, and, on the contrary, there are weighty reasons for supposing that they have ascended through primeval rocks. The absence of hydrocarbons in a part of volcanic emanations is also, as Bunsen showed, a very strong argument against the supposition that any organic matter (or any sedimentary rocks of later date than the origin of life) exists at the sources of volcanic activity. An argument in favor of the sedimentary origin of lavas is often drawn fro:n the supposed great variations in the composition of these rocks. This seems at first sight to be justified by the literature of lithology, but those who have specially occupied themselves with that branch of geology are well aware that the uniformity of eruptive porphyries is astonishing and that typical rocks are the rule the world over. In geological reports hundreds of square miles of a normal lava will be described in a paragraph, while a few square yards of some abnormal, highly exceptional variety of the rock will require pages of description and discussion. The literature of the subject is thus apt to convey a false im- pression. conclusions. The arguments presented as to the origin of the massive rocks of California may be briefly summarized. If the mechanism of up- heaval and subsidence is considered, it seems impossible that rocks from beneath the accumulation of clastic material should not often be brought to the surface. If the mechanism of erosion is considered, i t appears most improbable that, through degradation in any combination with subsidence, the entire area of primeval rocks should ever disappear for any length of time. The deepest-seated rocks known are granitic. If the conditions attending the earliest precipitation of water on the earth's surface be consid- ered, these conditions seem to be those known experimentally to favor the production of crystalline minerals and which are believed on good grounds to be those attending the formation of granite. The evidence in California is all in favor of the hypothesis that the main mass of the underlying granite is primeval, or that it antedates the formation of extensive oceans, and that it is free from organic matter. The lavas come from beneath the granite and are, a fortiori, thoroughly Azoic. CHAPTER V. STRUCTURAL AND HISTORICAL GEOLOGY OF THE QUICKSILVER BELT. 1 General results. No attempt has been made in the present investigation thoroughly to elaborate the general geology of the entire area in which the quicksilver deposits occur, but, in addition to what has been made known by other geologists on this subject, it was found indispensable for a proper discussion of the quicksilver deposits further to _elucidate some of the more important structural and historical relations of the rocks inclosing- them. Such facts bearing upon the general geology of these ore deposits as are now known will be presented in this chapter in chronological ar- rangement Their bearing will perhaps be clearer if the reader is at once put in possession of some of the main conclusions reached, which are as follows : The Coast Ranges experienced a great upheaval (the first traced) probably about the close of the Neocomian, this being the same disturb- 1 Messrs. Antisell, Blake, and New berry contributed valuable papers, containing information on the geology of the Coast Ranges, to the Pacific Railroad reports. Under Professor Whitney, Messrs. Brewer, Gabb, King, and others'studied this area. Their results are to be found in the well know n publications of the California survey. Mr. Jules Marcou has also written on the subject, especially in the Bulletin of the French Geological Society, vol. 2, 1883, p. 407, and the. Proceedings of the California Academy of Sciences contain numerous pertinent papers. I have endeavored to make such use of this material as seemed advisable. Dr. C. A. White has co-operated with me in the study of the general geology of the region, his standpoint being that of the paleontologist. The importance of some of the results reached led us to publish a part of them in. advance of this memoir. The papers in -which these were announced are: On the Mesozoic and Ceuozoic Paleontology of California, by C. A. White (Bull. U. S. Geol. Survey No. 13); On New Cretaceous Fossils from California, by C. A. White (Bull. U. S. Geol. Survey No. &2), and Notes on the Stratigraphy of California, by G. F. Becker (Bull. U. S. Geol. Survey No. 19). I have also used facts and arguments adduced by me in a paper entitled "The relations of the mineral belts of the Pacific Slope to the great upheavals" (Am. Jour. Sei., lid scries, vol. 28, 1884, p. 209) and iu Statistics and Technology of the Precious Metals, by S. F. Einmous arid G. F. Becker, Tenth Census Repts. U. S., vol. 13, Chapter I. The present chapter also contains much that is new. 176 FORMATIONS IN CALIFORNIA. 177 ance which .added an important portion of the auriferous slates to the Sierra Nevada. The Coast Ranges belong to the same mountain system as the Sierra Nevada. The upheaval mentioned was accompanied or fol- lowed by intense metamorphism, the only event of the kind known to have occurred in the history of the Coast Ranges. A great non-conformity exists between the metamorphic rocks and the overlying late Cretaceous strata. The Tojon formation is shown to be Eocene, as it was regarded by Conrad, and it is here shown to be absolutely continuous with the Upper Cretaceous The ore deposits have an intimate structural connec- tion with the system of fissures along which the upheaval of the ranges took place. So, also, has the distribution of volcanic rocks, the earliest of which probably date from the Pliocene. The ore deposits appear to be contemporaneous with and later than the eruptions and have a more or less intimate chemical relation to them. Formations found in California. The reader may perhaps be glad to be reminded of the formations which have hitherto been recognized in California It is' not absolutely certain that the Archrean occurs in this State, but, as I pointed out some years .since, the unquestionable occurrence of the Ar- chaean in Arizona, together with the similarity of the rocks of southeastern California to those of the adjoining territory, makes it highly probable that San Bernardino County is largely Archaean. 1 If so, this formation may enter into the composition of the southern Sierra. The geologists of the fortieth parallel exploration also found the Archaean in central Nevada in its normal relation to the Paleozoic and determined areas close up to the California line in this latitude as Archajan. Their investigations did not extend into California, but they showed that during the Paleozoic a conti- nental area existed west of longitude 117 30', latitude 40, and it appears certain that this area must have embraced at least a portion of the great Sierra, which is thus probably composed to a considerable extent of Ar- cliEean schists. The Carboniferous was first recognized by Dr. Trask in 1834'-' on the McCloud River. Professor Whitney's party found it near 1 Tenth Census Kepts. U. S., vol. 13, p. 47. a Report on the Geology of the Coast Mountains etc., by Dr. John B. Trask, Senate [of California] Doc, No. 1.4, 1835, p. 50. MON XIII 12 178 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Pence's* ranch, in Butto County, and inferred from similarity of position and lithological character that other rocks on the western flank of the Sierra may also be of this age. No Carboniferous fossils are known to occur in the Coast Ranges. Fossiliferous beds were found by Professor Whitney's party at Genes- see Valley, in Plumas County, which Mr. Meek determined as Triassic. The material upon which this determination rests appears, however, to be somewhat meager and unsatisfactory. A similar fauna has been found at a few points in Nevada, 1 but not elsewhere in California. Near the south- ern end of the gold belt of California fossils were found on the Mariposa estate in 1 864 3 They were figured and described by Meek. 3 The mosi important shell he determined as AuceUa Erringtonii, the specific name being given in honor of a resident who drew attention to the occurrence of the fossil. Meek observes : 4 As tbis genus is, so far as kuown, entirely confined to the Jurassic rocks, while an Amw&ium like shell from the same slates is closely allied to a Jurassic species, and the genus Belemnites is not generally regarded as dating back beyond the commence ment of the Jurassic period, I can scarcely entertain a doubt that these gold-bearing slates really belong to that epoch, and probably to some of its lower members, at whic^i horizon most of the known European species of AuceUa are said to occur. The same species of Amelia was found by Professor Whitney's party, after the publication of Meek's determination, at a number of localities on the gold belt, and ammonites were also discovered. It will be observed that Meek laid the chief weight in his determination of the age of these beds on the occurrence of AuceUa. Previous to the discovery of the fossil fauna of the Mariposa estate fossils had been found at many points on the Coast Ranges and along the foot-hills of the Sierra, which were described by Mr. Gabb as Cretaceous. 5 Many more were added later, and Mr. Gabb ultimately divided the Creta- ceous of California into the Shasta, Chico, Martinez, and Tejon groups, the last being the highest. 'King: U. S. Geol. Kxpl. 40th Parallel, vol. 1, Systematic Geology. "The houor of the first discovery of these fossils was somewhat warmly contested. See Whitney's Auriferous Gravels aud Proc. California Acad. Nat. Sci.; also, Mr. Clarence King's Mountaineering in l he Sierras. 3 Geol. Survey California, Geology, vol. 1, p. 477. nin. P.il.ooutolo^y, vol. I, GABB'S DIVISIONS. 179 The following paragraphs, copied from Professor Whitney's preface to Greol. Survey California, Palaeontology, vol. 2, pages xiii and xiv, give a concise account of these formations in accordance with Mr. Gabb's later views and as they were finally adopted by the State survey: (1) TheTi'jon group, the most modern member, the Division B of Paleontology, Vol. I, is peculiar to California. It is found most extensively developed in the vicinity of Fort Tejon and about Martinez. From the latter locality it forms an almost con- tinuous belt in tbe Coast Ranges to Marsh's, 15 miles east of Monte Diablo, where it sinks under the San Jonquin plain. It was also discovered by the different members of the survey at various points on the eastern face of the same range as far south as New Idria, and, in the summer of 1S6G, by Mr. Gabb, in Mendocino County, near Hound Valley, the latter locality being the most northern point at which it is as yet known. It is the only coal-producing formation in California. This group contains a large and highly characteristic series of fossils, the larger part peculiar to itself, while a considerable percentage is found extending below into the next group, and several species still further down into the Chico group. Mr. Gabb considers it as the probable equivalent of the Maestricht beds of Europe. (2) The Martinez group is proposed provisionally, to include a series of beds ot' small geographical extent found at Martinez and on the northern flank of Monte Diablo. It may eventually prove to be worthy of ranking only as a subdivision of the Chico group. (3) The Chico group is one of the most extensive and important members of the Pacific Coast Cretaceous. Its exact relations with the formation in Europe have not yet been fully determined, though it is on the horizon of either the Upper or Lower Chalk, and may probably prove to be the equivalent of both. It is extensively represented in Shasta and Butte Counties and in the foot-hills of the Sierra Nevada as far south as Folsorn, occurring also on the eastern face of the Coast Ranges bordering the Sacra- mento Valley at Martinez, and again in Oristimba Canon, in Stanislaus County. It includes all of the known Cretaceous of Oregon and of the extreme northern portion of California, and is the coal-bearing formation of Vancouver's Island. (4) The Sh ista group is a provisional name, proposed to include a series of beds of different ages, but which, from our imperfect knowledge of the subject, cannot yet be separated; it includes all below the Chico group. It contains fossils, seemingly representing ages from the Gault to the Neocomian inclusive, and is found principally in the mountains west and northwest of the Sacramento Valley. Two or three of its characteristic fossils have been found in the vicinity of Monte Diablo, and one of the same species has been sent from Washington Territory, east of Puget Sound. Few or none of its fossils are known to extend upwards into the Chico group. 1 To these I have added another series of Cretaceous strata lying above the Shasta, and, according to the paleontological evidence, below the 1 Mr. Gabb's work on tlio fossils of California is mainly contained in Geol. Survey California, Pa- lieotitology, vols. 1 and >; but the following papers may be referred to for other discussions which relate to his work in that State: Am. Jonr. Conchol., vol. 2, pp. 87-92; ibid., vol. 5, pp. 5-18; Am. Jour. Sci..2d sorirs, vol. 11, 1-W, pp. 220-339 ; Proc. California Acad. Nat. Sci., vol. 3, pp. 301-306; ibid., vol. .'., pp. 7-8. 180 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Chico. This will be called the Wallala series. Above the Tejou is found unquestionable Miocene, and resting unconforinably upon the Miocene the Pliocene is met with in a few localities. To the Pliocene also belong the fresh-water beds of Cache Lake, which will be described later in this chap- ter. Between these last eras occurred an important upheaval recognized by Professor Whitney, and to which ho ascribed the formation of the Coast Ranges, while a great uplift of the Sierra and of the Basin ranges lie attributed, in accordance with the evidence before him, to a Post-Juras- sic upheaval. Nomenclature here adopted. To facilitate reference to the various groups of strata Dr. White and I have agreed to give local names to several of the California occurrences. The fossiliferous beds of the Mariposa estate will be known as the Mariposa beds; the groups especially characterized by the presence of Aucella in the Coast Ranges will be referred to as the Knoxville series, because they are typically developed and have been spe- cially studied in the neighborhood of the mining town of that name; the rocks from which Messrs. Gabb and Whitney obtained a large fauna, con- sidered by them as probably equivalent to the Gault, will ba called the Horsetown beds; and a series which occurs along the coast north of the Russian River will be denominated the Wallala beds. Meek's Jurassic on the western slope of tin Sierra Nevada is thus equivalent to the Mariposa beds. The Shasta group of Messrs. Gabb and Whitney is here divided into two series, recognized by them as distinct, the Knoxvillo and tho Horsetown. The designations Chico and Tejon are retained, but the latter is considered Eocene. The Martinez is regarded as a portion of the Chico series. G.-anite. As has been shown in the preceding chapters, there is much evidence that granite underlies the entire quicksilver belt, and indeed the whole of central California. South of San Francisco it is frequently exposed in positions where erosion has been greatest, viz, along the axial lines of ranges and at the sea-coast; it is also exposed at a few points somewhat north of San Francisco, on the coast; and the Farallone Islands, 20 miles off the Golden Gate, are granite. To the north of the Bay of San Francisco, away from the coast, granite is not known to occur in AX01KNT HOCKS. 181 place for about one hundred and twenty-five miles, but this is probably for want of exploration, since in some parts of Cache Creek, for example, granite predominates among the stream pebbles. 1 According to Professor Whitney 2 the highest portions of the T-rinity or Shasta Mountains are granite. The "Wallala beds, too, though far from any known outcrop of granite, are in large part granitic conglomerates and the sandstones of the entire quicksilver belt are arcose. I have nowhere met granites along the quicksilver belt which appeared to me to be intrusive. Gaviian limestone In the Gavilaii Range, some sixty miles south of the Bay of San Francisco, the lowest sedimentary formation encountered is in part limestone, which at the points examined is extraordinarily crystalline, oftentimes consisting of a loosely adherent mass of imperfect calcite crys- tals. Associated with it are rocks of the Archaean gneiss type. This occurrence has been very little investigated and nothing further is known of its age. It is possible that it is a member of the Knoxville series much more metamorphosed than usual, but it appears to me more probable that it is a remnant of some older formation which has perhaps under- gone repeated metamorphism. For the purposes of this memoir an exact determination of its character is not important. Before passing to a general characterization of the Knoxville beds, which will be found to be the most important and most interesting in the State of California, it seems best to present the somewhat complex evi- dence obtained as to the distribution and affiliations of this series; indeed, it appears hardly practicable to describe it without discussing its chemical and structural relations, unless the results which I have reached as to these are taken for granted. Metamorphism in the Coast Ranges. Tlll'OUgllOUt tllC Coast RaUgCS of California there occur large, irregular areas in a somewhat peculiar condition of meta- morphism, which has been discussed in a preceding chapter. Its prominent macroscopical characteristics are the predominance of recrystallization, ser- pentinization, and silicification. 1 A very large part of the country in this nciorluMl is covered with thickets (chaparral) which are practically impenetrable. s Geol. Survey California, Geology, vol. 1, p. l!j:i. 182 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The dynamical action which accompanied or preceded this metamor- phisrn was of a very violent character, so that in the greater proportion of cases it is a manifest impossibility to construct sections of the metamorphic areas, no stratum being 1 continuous for more than a few feet, Sharp con- tortion and plication are also common, but where they occur it is usually apparent that the flexures have been accomplished not in the main by plas- tic deformation, but by comminution of the entire mass, the residual frag- ments often averaging less than a quarter of an inch in diameter. In the accompanying distortion these particles have retained approximately their original relative positions and have subsequently been recemented, chiefly by silica. The minute, polyhedral rock fragments, however, have under- gone no visible distortion. These occurrences coincide in a remarkable manner with the results of Mr. Daubree's experiments on the fracture of various substances by torsion and pressure. 1 As is shown in Chapter III, this probably indicates that, at the time of upheaval, these strata were buried at a depth of not more than a few thousand feet below the surface The most striking instances of such fracturing are met with among thin-bedded rocks, either sandstones or sandy shales, and such are remark- ably frequent in this series ; indeed, they might be said to bo characteristic of it. 2 They are occasionally met with in other formations, and it would be strange indeed if the conditions favorable to thin bedding had prevailed along the Coast Ranges only during a single era. As a rule, however, the rocks which vest upon the metamorphic series are thick-bedded, rather coarse and uniform sandstones. Besides this series of metamorphic rocks there are others of different age in the Coast Ranges to which the term metamorphic might not improp- erly be applied. These will be described a little later. Age of the principal m2tamorphic rocks. With the possible CXCCptlOU of tllC limO- stone mentioned above, this metamorphic series is stratigraphically the lowest in the Coast Ranges and appears to rest upon the granite. It forms the crests of many mountain ranges and occupies the whole surface in some of the more mountainous regions. Detailed studies of the structure show 1 Bull. Soc. ge'ologique France, 3d series, vol. 7, 1878-79, p. 108. -The peculiarity of those thin-bedded, plicated, metamorphic rocks was observed by Professor Whitney. AGE OF THE METAMOKI'IIICS. 183 that as a rule the hills of metamorphic rock are synclinal, 1 and consequently they must have undergone great erosion. The elevations of later age do not exhibit this peculiarity. Rocks of the metamorphic series often- pass over into unaltered beds in the Coast Ranges under such circumstances as to leave no doubt that they are of the same age ; but unfortunately the unchanged strata seldom con- tain determinable fossils and only a small number of occurrences is known in which the age can be satisfactorily established by direct evidence. In addition to these cases, however, there is a considerable amount of tolera- bly satisfactory indirect evidence available, when all the circumstances are taken into consideration. The neighborhood of Knoxville affords an ex- cellent opportunity for the study of the metamorphic rocks. The section across the north fork of Davis Creek, a little north of the Reed mine, a short distance from Knoxville, shows that the ravine occupies an eroded anticli- nal, of which the western portion is highly metamorphic, while the eastern consists in part of highly fossiliferous strata containing Aucella of two varieties, with other molluscan remains characteristic of the horizon which in this memoir is called the Knoxville series. The geological map of the district shows that the strike of the unaltered strata throughout is tolerably constant, but that areas of metamorphic and unaltered rocks, the latter nearly all containing a few fossils, are interspersed in the most irregular manner. While the passage from metamorphosed to fresh rock is usually rather sudden, there are also clear cases of transition. The. whole structure and the stratigraphical relations are such as to preclude every hypothesis except one, viz, that the metamorphic rock is an alteration product of the same beds which contain Aucella and the accompanying fossils. Close to the Manzanita gold and quicksilver mine on Sulphur Creek, in Colusa County, the metamorphic rocks contain impressions of Aucella I'/orJiii, and close by are beds of limestone full of Rhynckohetta Wliilneyi? The metamorphic rocks of this region are serpentinized and silicified, and 'Also observed by Professor Whitney : The Auriferous Gravels, Mom. Mus. Comp. Zool. Harvard Coll., vol. 0, No. 1, 1880, chai>. 1. 2 These specimens were determine.l by direct comparison with spscimeu.s iu the collection of the State survey. The figure given in Oool. Survey California, Palirontolojjy, vol. 2, PI. XXXIV, is incorrect in important particulars. 184 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. the thin-bedded strata show the characteristic contortions accompanied by a fine net-work of veins of silica. At Mt. Diablo, too, there is abundant proof of the Knoxville age of the metamorphio rock. Professor Whitney, writing before Mr. W. M. Gabb had made his final divisions of the California Cretaceous, mentions the occurrences at Mt. Diablo as conclusive of the Cretaceous age of the metamorphic rocks, but without enumerating the .associated fossils. From an examination of the fossil localities in Mr. Gabb's work, however, it appears certain that these were Aucella etc. An examination which Dr. White and I undertook for the purpose shows that in Bagley Creek, about a mile from the summit, Aucella occurs abundantly close to the edge of the metamorphosed area indeed, in partially meta- morphosed strata conformable with those extremely altered and in struct- ural relations to them which very clearly indicated the same age. Mr. Tur- ner subsequently found a series of beds, some of which had escaped trans- formation and contained Aucella, though inclosed on botli sides by highly metamorphic strata. At .ZEtna Springs, in Napa County, near the ^Etna and Napa consolidated quicksilver mines, Aucella also occurs in the same un- mistakable relation to the metamorphic rocks. In the examinations described in this volume, Aucella has been detected in immediate connection witli the metamorphic beds near the St. John's mine, Solano Coiinty, and in the Santa Lucia Range, near San Luis Obispo. Mr. Gabb further mentions an Aucella locality below the New Almaden mines. I have not succeeded in finding Ancdla in this region, which, however, in the neighborhood of the area sur- veyed, shows only metamorphic rocks exactly similar to those of Mt. Diablo and Knoxville, Miocene rocks lying unconformably upon the metamorphics and volcanics. It appears substantially certain therefore that the Aucella- bearing beds which Mr. Gabb detected must have belonged to the meta- morphic series. The age of the metamorphic rocks is thus determined at a considerable number of points scattered along the Coast Ranges for a dis- tance of 300 miles, or nearly three-quarters of the entire length of the Coast Range system of mountains. Alcatraz Island, close to San Francisco, consists of metamorphic sandstone and shales not distinguishable from those of San Francisco -or of Mt. Diablo. Here Major Elliot discovered an Inoccramus not known to occur elsewhere, considered by Mr. Gabb and Dr. White as TEUTIA1MES. 185 establishing the Cretaceous age of these rocks, though indecisive of the portion of this formation to which they should be referred. The above comprise all the instances definitely known in which the age of the silicified and serpentinized metamorphic rocks is-4i*ectly determinable by paleonto- logical evidence. Mr. Gabb also found Aucdla along Puta Creek, Lake County. This stream runs through a region chiefly occupied by highly metamorphosed rocks, and, were the exact locality known, it would probably furnish another instance of transition. Besides the rocks referred to above, the Coast Ranges include others which have been subjected to more or less complete alteration. Thus, along the shore of Carmelo Bay, Miocene schists have been locally changed to a cindery mass, as if by the action of heat ; but these rocks bear no resemblance to the serpentinized and silicified material just described. More or less complete induration is common, even in the most recent rocks of the coast, and oxidation and impregnations with calcite and gypsum occur abundantly in rocks of all ages. In the Arroyo de la Penitencia, above Alum Rock, near San Jose, there is also an area of altered Miocene sandstones referred to by Professor Whitney. 1 The rock here is much indurated and is full of veins of calcite. No objection can be made to its description as metamorphic by Professor Whitney ; but it is not serpentin- ized and silicified and does not partake of the characteristics so strongly marked in the highly metamorphosed rocks of the Knoxville group. On the other hand, there are plenty of rocks of this group no more altered than the Miocene of the Arroyo de la Penitencia and some areas still less modi- fied. The Tertiary of the Arroyo has been subjected to influences seem- ingly identical with those which have affected portions of the Knoxville beds, but not to those which have produced in the older strata the charac- teristic serpentinization and silicification. Professor Whitney also refers twice 2 to altered beds in the San Fran- cisquito Pass, which, indeed, is to the south of the Coast Ranges as usually defined. In the first reference he states that "this belt of metamorpliic is referred by us to the Cretaceous formation from general analogy rather 1 Geol. Survey California, Geology, vol. 1, p. 51. Ibid., p. 1'Jo; The Auriforous Gravels: Mein. Mus. Comp. Zool. Harvard Coll., vol. f>, No. 1, 1880i . IP. 186 QUICKSILVER DEPOSITS OF THE PACIFIC SLOl'K. than from .any direct evidence of fossils:' In the second reference they are mentioned as " Miocene rocks turned up on edge and in places so much meta- morphosed as to be converted into mica-slate." No statement of the means of determination of the age of these beds accompanies this remark, which, however, occurs in a brief summary of the geology of the Coast Ranges. Whatever the evidence may be upon which the change of reference was made it can have little bearing upon the age of the metamorphics in the central Coast Ranges, nor is serpentinization referred to as forming a part of the phenomena. So far as is known, therefore, no beds in the Coast .Ranges of California younger than the Knoxville group have experienced the peculiar magnesian and siliceous metamorphism so characteristic of these ranges. This fact raises a presumption that the metamorphism was effected prior to the depo- sition of the rock resting upon the metamorphic series, and this presumption is confirmed by examination of the conglomerates of the later rocks. There rest upon the metamorphic series at different localities Wallala beds, which Dr. White regards as middle Cretaceous; Chico beds, representing the very close of the Cretaceous; and Miocene strata. The fossils of the Wallala series were found in a conglomerate consisting largely of serpentine pebbles, accompanied by siliceous, metamorphic rocks exactly similar to those accom- panying the serpentine in the altered rocks of the Knoxville series. At New Idria there is a bed of conglomerate associated with Chico fossils near an extensive metamorphic area. The pebbles are mainly siliceous, as, indeed, is usually the case in conglomerates derived from the metamorphic rock, for the simple reason that serpentine is both easily decomposed and easily abraded. Careful search, however, revealed pebbles in this conglomerate which consisted in part of serpentine, a result confirmed by microscopical examination. The Miocene, too, for instance at Ne\v Almaden, contains abundant pebbles manifestly derived from the surrounding metamorphic rock. No fossils older than the Knoxville group are known to occur in the Coast Ranges and no known fact suggests the existence of older rocks, excepting the character of the limestone and gneisscid rocks of the Gavilan Range already mentioned, for the habitus of the peculiar metamorphic rocks under discussion is remarkably uniform. KKAS OF METAMOKM'IUSM. 187 Similarity of lithological and physical character may, I think, be given too much weight in geological diagnosis. I cannot conceive, for example, that any degree of similarity between the rocks of California and those of Switzerland should properly -he- considered as even tending to prove the age of either. 1 I go further, and refuse to regard the metamor- phism of the rocks of liutte County as necessarily contemporaneous with that of the strata of Napa County, in spite of external similarity. On the other hand, within properly limited areas, observations show that the same fauna is associated with similar rocks; while, if it were impracticable to draw any conclusions as to age except where the rock is fossiliferous or where absolute continuity with fossiliferous localities uninterrupted by faults could be proved, geological mapping would be impossible. In Cali- fornia great use can be made of resemblances. Thus the Tejon strata of New Idria are mostly heavy-bedded sandstones of a peculiarly light color, which there distinguishes them from the tawny Chico sandstones. Both are fossiliferous there, as also near Mt. Diablo, where, at a distance of 125 miles from New Idria, they preserve the same external characteristics. Similarly, the Knoxville beds of Knoxville and Mt. Diablo are externally indistinguishable, and in their typical development, even when unaltered, very different from most of the later rocks. Strata older than the Knoxville period may nevertheless be included in the metamorphie series and may have undergone upheaval and meta- morphism at the same date. There is also a possibility that older rocks not only exist, but were metamorphosed before the deposition of the Knoxville, so that the metamorphie areas in contact with the Wallala beds on the coast and with the Chico strata at New Idria may conceivably be earlier than the Knoxville. Even this hypothesis, which, in the absence of any evi- dence tending to establish it, seems rather strained, would have no effect on the principal conclusions drawn in this chapter, unless it could also be 1 The resemblance between the Miocene sandstones and the Molasse of Switzerland was advanced by Mr. Jules Marcou floe, cit.) as an evidence of the Tertiary age of the California rocks. That the resemblance exists I can testify from observation. To me it indicates only that the California Miocene and the Molasse were both deposited near the shore of land areas largely composed of Archaean rocks. Mr. Marcou attributes to ignorance of lithology my failure to appreciate it as au indication of age, and he regrets that " a competent person has not been selected for the study of the Tertiaries of Califor- nia" (American Geological Classilication and Nomenclature, 1888, p. 52). I am very sorry that my work produces so bad au impression on Ibis veteran geologist. 188 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. maintained that the violent upheaval and metainorphism which followed the Knoxvillo left the supposed older areas undisturbed. This would con- flict with all analogy. The foregoing facts and the necessary inferences from them appear to justify the statement that the silicified and serpentinized metamorphic rocks of the Coast Ranges include a portion of the Knoxville beds, and do not include any portion either of the Chico or of the Wallala series, while if there were pre-Knoxville rocks within the metamorphic areas they must have undergone at least a fresh disturbance at the time when the Knoxville beds were broken up and metamorphosed. Non conformity between the Knoxville beds and the Chico. Had tllC pl'OOf of tlllS nOll- conformity been a simple matter, it could not have escaped the attention of some one of the able geologists who have worked in the Coast Ranges. The difficulty is in part due to the rarity of fossils in the older groups over a great portion of the area in question, which often leaves the observer without absolute proof of the age of the rocks about him; but complexity of structure is the main obstacle. Few geological phenomena are more striking than a non-conformity where the overlying strata are nearly hori- zontal, the underlying rocks greatly inclined, and the exposure tolerable. This combination is rare in the Coast Ranges, and no such case is known where the Shasta and Chico beds meet. The Post-Miocene uplift traced by Professor Whitney has folded, faulted, and broken the later Cretaceous and the Tertiary rocks, as well as the earlier strata upon which these were unconformably deposited; so that it is usually far from easy to make out the effects due to the earlier and later disturbances, respectively, and still more difficult to prove that no explanation except that of a non-conformity beneath the Chico will account for the facts. I believe that the structural evidence to be presented clearly establishes this non-conformity, but the proof, though convincing, is less abundant than could be wished. The evidence will first be presented from a purely structural point of view and will then be re-enforced by an independent, paleontological argument. In the neighborhood of the New Idria mine the metamorphic rocks have been greatly disturbed, while the Chico strata, though tilted at a high angle, are remarkably regular. Owing to the steepness of the contact, how- NON-CONFORMITY BELOW THE CHICO. 189 ever, no exposures showing both series together could be found from which thoroughly satisfactory inferences could be drawn as to the relations of the underlying and overlying rocks. I therefore resorted to a study of the exposures of each separately, for which the region offers unusual facilities. It was found possible to follow single strata of the Chico uninterruptedly for the greater part of a mile, and, by the aid of lithological peculiarities, combined with topographical indications and the strikes observed at the exposures, to recover the croppings with substantial certainty after passing intervals covered with detritus. The contact with the metamorphic rocks was also laid down and numerous dips were observed in the metamorphic area. In order to eliminate the disturbing influence of the irregularities of the topography, the croppings of each of these continuous strata and the contact of the metamorphic were reduced to their intersections with normal planes cutting the surfaces respectively at the mean elevation of their ex- posures. The results showed that adjoining Chico strata are parallel and thrown into extremely gentle undulations, while the metamorphic area is merely a shattered mass The contact has approximately the same general direction as the Chico beds, but does not entirely coincide with their strike. It is a rough line, but not rougher than one which would represent the ver- tical section of an ordinary sea-bottom near the coast. The dip of the Chico strata decreases as the distance from the contact increases. Either this structure represents a non-conformity or else the metamor- phism and accompanying disturbances occurred after the deposition of the Chico beds, but ended sharply at a certain line. It might at first sight seem impossible that an area several miles in width should be crumpled and broken quite as thoroughly as a representative area of the Archaean along the east- ern coast, the rocks being also for the most part converted into serpentine and chert, and that, nevertheless, both mechanical and chemical action should cease abruptly at a given line. Yet instances, of which the above might pass for a description, actually occur and are perhaps more frequent in the Coast Ranges than elsewhere. All geologists who have visited this region are aware of the very irregular distribution of the metamorphic areas, and it has already been pointed out that the metamorphic rocks pass over into unaltered or very slightly altered Knoxville beds suddenly, though 190 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. under circumstances which preclude the supposition that the adjoining- areas represent different formations. There are, however, significant differences between these occurrences and the conditions at New Idria. The limits of metamorphism in areas consisting of Knoxville beds, however sharp they may be, are exceedingly irregular, the outline being substantially inde- pendent of stratification, cutting strata more often than following them and presenting all sorts of convolutions; there are almost invariably also out- lying areas of metamorphic rock and included masses of unaltered rock; furthermore, at least here and there, distinct transitions occur between un- altered and metamorphic rock. At New Idria, on the other hand, a section of the contact normal to the surface extends over at least several miles (as far as it was followed) in a tolerably persistent general direction. There are no outlying patches of metamorphic rocks; the included masses of comparatively unaltered rock seem wholly different from the Chico strata above them, and, though there is a considerable alteration of a portion of the overlying mass, this alteration is not of the same character as the mag- nesian and siliceous metamorphism of the underlying rock; nor could I find any distinct, case of transition. Finally, as has already been men- tioned, in the Chico conglomerates a part of the pebbles entirely resemble the silicified or jaspery portions of the present metamorphic area, while a few are both rnacroscopically and microscopically indistinguishable from the serpentinized rocks of Knoxville age Some further evidence of the relation of the two series was found a few miles to the southeast of New Idria, where' a branch of Cantua Creek cuts through a portion of the range. Here the heavy-bedded, tawny Chico sandstones, lying at an angle of about 30, cap the hills which are inter- sected by the brook, while in the bed of the stream the thin-bedded, met- amorphic strata stand vertically. No actual contact, however, could be found, the interval being covered with detritus. There seems no reasonable explanation of the structure at and near New Idria, except on the theory of a non-conformity. Though the evi- dence may seem less satisfactory than that which would be presented by -an ideal exposure, it is derived from the correlation of the structural evidence along the contact for miles, and in tin's respect is superior to any but that NON-CONFORMITY BELOW THE CHIGO. 191 furnished by the very best local exposures of unconformable contacts; for every geologist must have observed cases where unconformable exposures are closelv simulated by local faults Could it be proved that the under- lying mass is of greater age than the Knoxville, the evidence would never- theless indicate a non-conformity between the Chico and the Knoxville, unless it could be shown that the convulsion which has so marvelously crushed the Knoxville beds, at least from Clear Lake to the neighborhood of New Almaden and again at San Luis Obispo, was unfelt at New Idria, which it would be difficult to do, in view of the fact that the comparatively gentle Post-Miocene upheaval certainly extended throughout the Coast lianges of California and Oregon. Mt. Diablo and the surrounding country consist of a core of metamor- phic rock inclosed nearly or quite quaquaversally by rocks of Chico and Tertiary age. The core is highly contorted and for the most part is in an extremely metamorphosed condition, though here and there it is compara- tively fresh and in some cases contains Aucella and associated fossils. The overlying Chico, Tejon, and Miocene strata are tilted, but otherwise com- paratively undisturbed. Over wide areas these three series seem to be per- fectly conformable, nor have I seen any case on the Pacific Coast where there seems any ground for suspecting a non-conformity within these limits. Mr. Turner spent several days in this region, collecting fossils from various beds and searching for some exposure in which the relations of the Knox- ville beds and the Chico could be well made out. The result was negative, no exposure being detected from which a non-conformity could be conclu- sively established. On the other hand, the structure is much more easily accounted for by supposing a non-conformity to exist than by assuming conformity. The upturned edges of the more recent strata form long, smooth curves, enveloping the plicated and metamorphosed core, and no- where was there any metamorphism in the strata identified as Chico. On the coast in Sonoma County, about two miles below Ft. Ross, there is a sharp contact between the Wallala beds and the metamorphic, serpen tinized rock which extends from this point to below the Russian River, if not to the Golden Gate. Passing back into the hills, the Wallala beds are found capping the iir^t range of elevations opposite portions of the shore, which TJHIVBRSITY 192 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. are composed of the metamorphic rockg. I believe no one could examine this locality without being convinced that the Wallala beds rest unconform- ably upon the metamorphic, nor could any one pass inland from the mouth of the Russian River to Knoxville without feeling' sure that the metamorphic is uniform in character and substantially continuous, though occasionally masked by eruptive rocks and possibly by a few patches of unaltered strata. There is, furthermore, much indirect structural evidence that a non- conformity must exist between the Knoxville beds and the Chico. Some- where between the end of the Knoxville and the beginning of the Miocene there was a great upheaval, accompanied by siliceous and magnesian metamorphism and followed by enormous erosion, for at many points the unaltered Miocene clearly rests unconformably upon the metamorphic rocks. This I have observed on San Bartolo Creek and in the valley of the San Benito, to which the other is tributary, and there is evidence of similar relations at Mt. Diablo and at New Almaden. Professor Whitney found the Miocene resting uncornformably upon the metamorphic between the Guada- lupe mine and Forbes's mill, and also near McCartysville, 1 as well as north of the Golden Gate, 2 for instance, near Tomales, 3 while, in speaking of the neighborhood of Suscol, he says: 4 " It is probable that the most extensive disturbances of the Cretaceous, as also the larger portion of the metamorphic action upon it, had taken place before the Tertiary marine and volcanic beds were deposited." If this non-conformity doas not occur between the Knoxville and the Chico, it must be sought between the Chico and the Tejon or between the Tejon and the Miocene. The stratigraphical relations at New Idria and at Mt. Diablo show that there was continuity of sedimentation from the Chico to the Tejon and the organic remains prove that there was continuity of life. The great non-conformity cannot, therefore, have been between these groups. Between the Tejon and the Miocene there is at least no general non-conformity. 5 Near New Idria and at Mt. Diablo, for example, the Mio- 1 Geol. Survey California, Geology, vol. 1, p. 69. 2 Ibid., p. 79. 1 Il.id., p. 83. Ibid., p. 103. "Professor whitiir.v (Am-. Grav., p. 'JG) writes: "Tlie Miocenftndt4ieCretaceoBeeoi everywhere to be couformable with eacll other." The Crelaeecus hero rcf.tml to in of course the Tojon. Mr. .7. NON-CONFOKMITY BELOW THE CI1ICO. 193 cene seems as strictly conformable with the Tejon as is this with the Chico. So, too, along the flank of the Sierra Nevada, both Chico and Miocene re- main almost perfectly horizontal. Had there bjen a great upheaval, accom- panied by intense metamorphism, between the Tejon and the Miocene, it seems impossible that no Chico or Tcjon strata should have been found metamorphosed. This indirect evidence alone would seem sufficient to establish the fact of a non-conformity between the close of the Knoxville and the beginning of the Chico. Add to this the direct evidence at New Idria and Ft. Ross, and the conclusion appears irresistible, irrespective of the paleontologies! argu- ment, which, again, of itself would have sufficed to lead to the same result. The paleontological argument for a non -conformity between the Knox- ville series and those which are found succeeding it may be very briefly .stated. Dr. White regards the fauna of the Knoxville group as lower Neo- comian, or at any rate as not later than this. The Chico, in his opinion, rep- resents the very latest portion of the Cretaceous formation. The exposures at Mt. Diablo, for example, show that there, at least, no deposits now inter- vene between the Knoxville and the Chico. Hence, the Knoxville beds at this locality must have been above water in the interval. If this interval had been a short one, the facts could be explained on the assumption of a mere, gentle oscillation of sea-level relatively to the land, and the non-con- formity might be one of erosion, or, in other words, would not necessarily imply a movement of great structural importance. But the Knoxville beds must either have been above water during the entire interval preceding the Chico or during a sufficient part of it to allow of the removal by erosion of any strata deposited subsequent to the close of the Knoxville. If one supposes denudation to be as rapid as se
  • les in the conglomerates of the \Vallala and the Chico groups show that metainorphic rocks existed near them when these beds were deposited, and these pebbles entirely resemble rocks known to be of Knoxville age. If they are really of this age, the metamorphisin and upheaval of the Knoxville beds must have preceded the Wallala period and there must be an unconformity. Again, the strati- graphical relations of the Wallala beds on the coast and of the Chico beds at New Idria to the adjoining metamorphic areas seem inexplicable except- ing on the theory of a non-conformity. Furthermore, a great non-con- formity certainly exists somewhere between the Knoxville beds and the Miocene. None such is found between the Miocene and the Tejon or be- tween the Tejon and the Chico. Hence the non-conformity must be be- tween the Chico and the Knoxville. Finally, the fossils prove that an im- mense time elapsed between the end of the Knoxville and the beginning of the Chico, while the Chico is now found in contact with the Knoxville at various points. This could not be the case unless an upheaval had inter- vened. Identity of the Mariposa and Knoxville beds. TllC gold belt of California, aS llitliei'tO traced out by miners and geologists, is an area of peculiar form. From Mari- posa County to Nevada City, in Nevada County, a distance of about one hundred and fifty miles, the belt is a strip of country nearly parallel to the crest of the Sierra and about thirty miles in width. Northward from Nevada City it rapidly widens, becoming at the same time less well defined. To the north it is finally terminated by extensive lava fields, while toward the northwest the country gradually loses its auriferous character as the coast is approached. Within the gold-bearing region three fossiliferous areas are known to exist. From the McCloud River to Pence's ranch extends a belt of highly indu- rated limestone containing Carboniferous fossils. In Genesee Valley the State survey found fossils regarded as Triassic and Jurassic. Both of these localities are far removed from the narrow strip of country lying along the foot-hills from Mariposa to Nevada, which is often known as the gold belt 196 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. proper. The fossiliferous Mariposa beds already mentioned occur near the southerly end of this narrow portion of the auriferous area. Previous to the discovery of fossils on the Mariposa estate in the series which I shall call the Mariposa beds, Professor Whitney and his associates had collected in the Coast Ranges Belemnites, a shell determined as Inoce- ramus Piochii, and some others, from the strata which I have entitled the Knoxville beds. Mr. Gabb described them as Cretaceous forms. 1 Some years after Mr. Meek had referred the Mariposa beds to the Jurassic Mr. Gabb redescribed Inoceramus Piochii as Aucella Piochii, 2 a change of genus which I understand to be unquestionably correct. This correction appeared to me at the very beginning of this investigation of great importance to the stratigraphy of the State, for through it the fauna of a large part of the known rocks supposed to belong to the Shasta group of the Cretaceous ac- quired the strongest resemblance to the fauna of the Mariposa County Ju- rassic. Indeed there seemed scarcely room left for a distinction; if Aucella is distinctively Jurassic, the Aucella-'beaiing beds of the Coast Ranges must be members of that system, while if these Aucella beds are Cretaceous Au-, cella is not a distinctively Jurassic genus, even in the State of California, and Mr. Meek's principal reason for assigning the Mariposa beds to the Ju- rassic is shorn of its validity. Dr. White afterwards fully confirmed this view, and after examination of Meek's types, together with new and better specimens which we collected, he is unable to draw any specific distinc- tion between the Aucella of the Mariposa beds and that of the Knoxville beds. Professor Whitney states that, while the Mesozoic age of the Mariposa beds is proved by their fossils, the Pre-Cretaceous age of these strata is dem- onstrated by their stratigraphical relations. Professor Whitney has indeed shown that Cretaceous strata rest unconformably" upon the upturned -edges of the auriferous slates along the foot-hills of the Sierra at several points ; 1 Geol. Survey California, Palaeontology, vol. 1. 2 Ibid., vol.2. 3 1 am perfectly satisfied of the existence of this non-conformity, though the localities where the Chico bods have been found resting ou the upturned edges of the auriferous slates are not near those in which Mesozoic fossils have been found in the older rocks. The Chico beds, where they occur along the foot-hills, have suffered little if at all from the Post-Miocene uplift in the Coast Ranges nii'l are nearly horizontal. The Mariposa beds are almost vertical. AGE OP THE MAEIPOSA BEDS. 197 but I find no record of any such bed so low as the Knoxville group. 1 All the fossils recorded in this position are Chico. This does not, indeed, pre- clude a possibility 'that the Mariposabeds are Jurassic and the Aucella beds of the Coast Ranges Cretaceous, for the former might have been above water during the Shasta epoch ; but, were Cretaceous strata containing the .so-called Aucella Piochii to be found resting in a nearly horizontal position upon the Mariposa beds, it would prove not only that the genus had per- sisted from Jurassic into Cretaceous times, but that in essentially the same locality the genus was represented immediately after a great and widespread upheaval by a species nearly or quite indistinguishable from one which had inhabited it prior to this convulsion and the attendant metamorphism. Zo- ologists would think such a survival very strange if it could be proved and highly improbable unless the proof were ample. On the other hand, if the Mariposa beds are considered as equivalent to the Knoxville beds of the Coast Ranges, the non-conformity between the Chico beds and those of Mariposa is the same which lias been traced in the .preceding pages as existing in the Coast Ranges; and, even if the species of AiiccUa found in the respective beds were different, the upheaval and meta- morphism of the two series, still referable to nearly the same period, would be presumptively simultaneous. The lithological resemblance of the rocks of the Mariposa estate to those of many portions of the metamorphic rocks of Knoxville age is very strong. There is a similar prevalence of thin-bedded strata, while silicifica- tion and serpentinization are equally the predominant characteristics. Pli- cation and fracture are less noticeable than in the Coast Ranges. One geologist has maintained that the fossiliferous rocks of this locality do not form an integral portion of the auriferous series. Neither Dr. White nor I was able to see any ground for th'.s assertion. The fossiliferous rocks are metamorphic, like the entire series; they have the same dip and strike and they are unquestionably auriferous, gold quartz veins occurring between the fossil-bearing strata and not simply near them. In short, we could see no way of separating the strata containing shells from the 1 The shull from Tuscan Springs recorded as Inoceramtis Piochii (Geal. Survey California, Geology, vol. 1, p. 207) is redet.ermiued :is a Mi/ til an in il>id., vol. a, p. 191. 198 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. remainder of the immense thickness of similar and apparently conformable slates. 1 The Knoxvilleand Mariposa series. TllOUgll the beds of tll6 KllOXville cllld Mtll'L- posa groups, which on the structural and paleontological grounds already stated are considered as of the same age, appear to have a very wide distri- bution in California, particularly along the two great mineral belts of the State, they have been found fossiliferous at only a comparatively small number of localities in Lake, Colusa, Yolo, Napa, Solano, Contra Costa, Santa Clara, San Luis Obispo, and Mariposa Counties. Owing to the ex- tremely disturbed and highly metamorphosed condition of the greater part of the series, all of these localities are of very restricted area. The areas covered by unaltered or very slightly altered rocks apparently of the same age are considerably larger, yet even these are small and seem to represent mere patches which by accidents of structure have escaped the general and very intense metamorphism. The features presented by the rocks of these series as a whole are somewhat unusual among beds so recent, and their general facies has led some able and experienced geologists to suspect. for them a far greater antiquity than is warranted by the detailed evidence. Though in some of the fossil localities shells are extremely abundant, sometimes making up a large portion of particular strata, the number of species found is small, and of the short list which can be enumerated many are so imperfect as to make their identification doubtful or hopeless.- The following Avere published by Mr. Gabb: Belemnites impressus Gabb. Liocium jmnHutuni Gabb. Pahcatractus crassus Gabb. Modiola major Gabb. Csrdiera mitraformis Gabb. AitecUa Piochii Gabb. Airesiug lira-tits Gabb. Rhynchonella \Vhitiieiji Gabb. RingineUa polita Gabb. Pecten complexicosta Gabb. ' Mr. J. Marcou stated that these schists "sont sonvent ties ropproch& des veines iiiotallit'ercs, sans toutefois jamais en renfermer" (Bull. Soc. ge\>logi<|iio Franco, 18s:!, ]>. 410). Ho now accepts without ohjection my statement that gold quartz veins occur !>ressus, has been regarded as certain. The fact that the Bclenwites, as a rule, do not present salient, or even satisfactory, features by which to determine specific differ- ences, detracts somewhat from the certainty of the last identification. Dr. White's opinion that Amelia, Erringtonii and A. Piochii Gabb are specifically identical has been formed after he had had better advantages for investigating the subject than seem to have been enjoyed by any other person who has written upon the paleontology of California. lie has not only examined the original types of those two forms, but hundreds of other specimens of A. Piocl/ii from Gabb's original locality, as well as from other places. Furthermore, we made a personal visit to the locality on the Mari posa estate where the type specimens of A. En-'nuitnmi were obtained, and collected better specimens of it from the auriferous slates there and in the immediate neighborhood than had before been known. We also obtained from the same slates fragments of an ammonite, some impressions of a shell apparently the Pholadomya orlicuhita of Gabb, others that represent a species of the Pectinida) (perhaps the Amusxium inn'i/nn of Meek), and still others which are undeterminable. On adding to these the fielcnmitcs pa- clficus of Gabb, the fauna of the auriferous slates of the Mariposa estate amounts to at least five species of mollusks. It is true that only the Aucella has been satisfactorily identified as occurring in both the auriferous slates 2 1 Geol. Survey California, Paleontology, vol. 2, pp. 20D-254. 1 Some of the specimens found in the auriferous slates of tho Mariposa estate show more or less distinct, radiating lines, anil tin- saino peculiarity has been observed among examples from the Knox- villo beds, as wall as among Russian and Alaskan examples. FAUNA OF THE KNOXVILLE SERIES. 201 and the Shasta group, but there is nothing in the character of the other four species of mollusks from the auriferous slates which would render in- consistent their reference to the age of the Knoxville beds. The specimens of Aucclla and otFei r auriferous slate species just re- ferred to were obtained by us from the rocks in place, those found near the left bank of the Merced Uiver, Mariposa County, Gal., about a quar- ter of a mile below Benton's mills, being especially satisfactory as regards both their position in the strata and their condition of preservation. Here the strata have an almost vertical dip and they are plainly an integral part of the great auriferous slate series. A part of our collection, as well as some of those which were collected by King, Gabb, and Miss Erring- ton, were obtained from within a few feet of the famous great quartz vein which traverses the Mariposa estate and which is inclosed in the aurifer- ous slates. \Ve did not obtain any Belemnites from the auriferous slates, as King and Gabb did, nor has Dr. White seen Gabb's B. pacificus, obtained from tliis formation, but not figured. From the description it is supposed to be identical with I>. nuterittitix White, 1 obtained by Mr. Dall from Alaska and found associated with an AurcUa regarded as of the same species as A. Errnii/ton'ii and J. Mncliii. That the Mariposa beds and the Knoxville beds are of the same age is considered as proved by the identity of Aucclla Piochii and A. Erringtonii, supported by the general character of the other fossils which the strata of both respectively bear. It is true that this is the only specific identifica- tion that has been made; but the species in question is one of extraordinarily wide geographical range and it is also one of great constancy and exclu- siveness as regards its distinguishing characteristics. Certain of the species which characterize the strata of the Shasta group in California have been recognized among the collections which have been reported by different persons from Washington Territory and British Columbia, as well as from Alaska and the Aleutian Islands. But none of the species of that group has been found in any North American strata to the eastward of the Pacific Coast region, if we except Greenland. While 1 See Bull. U. S. Geol. Survey No. 4, p. 13, PI. VI. 202 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. it is probable that the Horsetown beds of California are represented in those northern localities which have been referred to, it is more especially the equivalent of the fauna of the Knoxville beds that has been recognized as existing there. This recognition is mainly through the identification, among the collections which have been made there, of the AuceUa, which so strongly characterizes the Knoxville division of the Shasta group in California. Specimens regarded as specifically identical with the form which Mr. Gabb published under the name of AuceUa Ploclni have been presented to the Survey by Prof. Thomas Condon, which he collected at Puget Sound, Washington Territory. These specimens were in bowlders, but they nevertheless indicate the existence of an otherwise unknown locality to the north of Oregon. Mr. Whiteaves refers to the same species as being abundant at Tatlayoco Lake and other places in British Columbia,' and Professor Eichwald, Dr. P. Fischer, and Dr. White have published forms from different parts of Alaska which the last regards as specifically identical with it. Among the fossils collected in Alaska by Peter Doroschin, Eichwald 2 recognized all the forms of Amelia which Keyserling had published as occurring in Russia, namely, A. 'concentrica Fischer, A. mosqucnsis von Buch, A.pallasii, and A. crasslcollis Keyserling. The last two he considered as only varieties of A. concentrica. Dr. Fischer recognized only one species among Pinart's Alaskan collections, 3 which he referred to A. concentrica. Dr. White also recognized only one species among the collections brought from Alaska by Mr. Dall. Although the specimens were numerous and presented quite a wide variation of form, he regarded them all as repre- senting a variety of AuceUa concentrica. 4 Mr. Whiteaves (loc. cit.) recog- nized only one species among the collections from British Columbia, and this he referred to Amelia mosqucnsis. In the Knoxville beds of California there are two recognizable varieties of AttccUa, which are connected more or less closely by intermediate forms, 1 See Trans. Koyal Soc. Canada, sec. 4, 18-32, p. 84. 2 SeoGeoguo8t.-paIaeout. Bemerkmigen iiberdio Halliinscl Mangmulilak inul (lit- alcut iscln-n Inscln, 1871, pp. 185-187, PI. XVII. 3 See Voyage a la c6te nord-onest do I'Aiuc'rique, par M. Alph.-L. Piuart, pp. 33-30, PI. A. 4 Sen Bull. U. S. Geol. Survey No. 4, pp. 13, 14, PI. VI. AUCELLA. 203 but are decidedly different in extreme examples. It is usually the case also that one variety will be found to prevail in certain layers of rock, some- times almost exclusively, and the other variety in other layers. Adult examples of one of these varieties are large, robust, and often inflated. These approach the typical forms of A. concentrica more nearly than the others. Those of tlie other variety are smaller, more slender, and have a more delicate appearance. They seem to correspond more nearly with the type of A. mosqucnsis. Still, after examining numerous examples from Alaska, British America, Washington Territory, and California, besides some Russian examples of A. concentrica and A. mosquensis, believed to be authentic, in the collections of the Smithsonian Institution, Dr. White is of the opinion that all of them represent only one species. Indeed, he is disposed to regard as at most only varieties of one species all the forms which have from various authors received the names Aucella concentrica, A. )it*t//u'iisis, A. pallasii, A. crassicollis, A. Fiochii, and A. Erringtonii. However, it will be convenient, when discussing the Aucetta-bear'mg strata of California, to retain the names A. concentrica and A. mosquensis to indi- cate the more robust and the more elongate forms, respectively, as they occur in that State. Before dismissing this reference to Aucella, it is well to note how wide i-i the geographical distribution of the variable form which has been known under the various names which have just been mentioned. This shell was first known in various parts of Russia and subsequently upon the eastern coast of the Caspian Sea, 1 in northern Siberia, 2 on the island of Spitzbergen, 3 on Kuliii Island (off the east coast of Greenland), 4 and in Alaska, British Columbia, Washington Territory, and southward to central California, as mentioned on previous pages. Although it is so variable in certain of its features, so constant is it in its general characteristics and so distinct from related forms that paleontologists are now generally agreed as to its identity in all the widely separated localities which have just been indicated. 'See Kiclnvald's Geognost.-palaeont. Hiiiiierknngru fiber die. llalbinsel Mangisrliliik uticl die alentischen Inseln, 1871, p. 53. See MicldendorlV's 1,'eise in dc'ii aussei-si.e.ii Nordeu and Ostcn Siliri ..ins, vol. 1, parl 1, p. 255. : 'See Lindstroin : Oin Trias- och Jurafur.stRning.tr Iran Spetsbergen, Kongl. svensk. Vot.-Akad. TTandl.. vol. (i. No. (i, 1.-C7, p. 14. 1 See F. Tonlu, Die zweite dcutsclio Nordpolarfahrt, vol. 2, Ib74, pp. 497-505; also Quart. Jonr. Cicol. Sor. London, vol. I) I, 1*7',, p. 5CiO. 204 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. The age of the Aucetta-be&ring beds, whether in California or else- where, is not fully determined, apparently on account of the equivocal char- acter of the faunas associated with this fossil. Both Eichwald and Whiteaves contend that all the strata which bear Aucclla conccntrica and A. mosquensis are certainly of Neocomian age. On the other hand, Keyserling, Trautschold, D'Orbigny, and others as confi- dently assert that they are of Jurassic age and many paleontologists have hitherto regarded Aucclla as an exclusively Jurassic genus. Even so late as the year 1881 Mr. A. Pavlow, a member of the official geological com- mission of Russia, placed in the Jurassic series the well known strata which in eastern and other parts of Russia besur Aucella conccntrica, as the earlier Russian geologists also did. 1 Dr. White thinks it not impossible that Aucclla occurs in the Jurassic in some regions and in the Neocomian in others, just as a number of Lower Carboniferous species of Europe are found in the Upper Carboniferous of North America and as certain species are known to pass from the Devonian to the Carboniferous. lie inclines, however, to the opinion that the Cali- fornia occurrences are referable to the Lower Neocomian, which, as has been seen, is substantially the result at which Gabb arrived for the group here called the Knoxville series. As has been seen, the age of the metamorphic series of the Coast Ranges (which is that most usually associated with the quicksilver deposits), the age of a highly important portion of the auriferous slates of California, and consequently also the structural relations of the Coast Ranges and Sierra Nevada depend almost entirely upon two closely allied species, or- on two varieties of a single species, of Aucclla. The very great importance which this fossil thus acquires is much increased by the fact that it occurs along the Pacific Coast at various points up to Alaska, a distance of about two thousand miles, and again at very widely separated points in Europe. In the hope that it may lead to a more extended knowledge of the distribution of this peculiar and important fossil, I have induced Dr. White to prepare a description, with illustrations, of Aucclla, which appears as an appendix to 1 his chapter. 1 Sec Bull. Soc. gdologique Franco, M series, vol. 12, 1884, pp. 6S6-G9G. UORSETOWN BEDS. 205 The Horsetown beds. The Ilorsetown beds, as it seems convenient to call tlie group which occurs near Cottonwood Creek, Shasta County, are con- fined to that locality, so far as known, and their stratigraphies! relation to the Knoxville series is undetermined. The solution is very probably to be found in the eastern Coast Ranges in Tehama County, but this region is not known to have been geologically explored and it probably will not be ex- amined until a special study of the Coast Ranges as a whole is undertaken. The Horsetown beds are somewhat altered, but at the points visited by Dr. White and myself they do not show the characteristic serpentinization and silicification of the metamorphosed Knoxville beds. It cannot by any means be asserted definitely, however, that they were not involved in the upheaval and metamorphisin which took place after the Knoxville and be- fore the Wallala period, because much of the Knoxville series is also little altered. On the other hand, the Horsetown beds rest unconformably upon the auriferous slates of that region, which are of uncertain age, though ap- parently continuous with the Carboniferous of Pence's ranch. Professor Whitney detected this non-conformity, though expressing the result in some- what guarded terms. 1 The mining operations which have since been pros- ecuted have so exposed the rocks as to leave no room for any possible difference of opinion. The slates upon which the Horsetown beds lie are somewhat peculiar and differ physically from those of the Mariposa beds, showing a very thin cleavage and an unusual, silver-gray luster. They give to the eye an impression of great geological age. The fauna of the Horse- town beds includes the whole of Gabb's Shasta group, excepting the species already enumerated as belonging to the Knoxville. Mr. Gabb and Dr. White agree in considering the affinities of these fossils to be with those of the Gault, and therefore decidedly later than the Knoxville series. Though the Ilorsetown beds lie not far from the general line of the quick- silver belt, they are not known to occur anywhere in close connection with the ore deposits. The cascade Range. It is hardly possible to contemplate the close relation shown to subsist between the eastern and western ranges of central Cali- fornia without inquiring what connection, if any, exists between them 1 Geol. Survey California, Geology, vol. 1, p. 321. QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. and those north and south of the great valley of the State. Dr. White and I therefore visited Oregon and made several trips into the mountains of the Cascade Range from Roseburg. The sedimentary rocks appear to be underlain by granite, for, though we did not meet with this rock in place, it constitutes a large proportion of the stream pebbles. It is stated on the excellent authority of Rev. Thomas Condon to occur in place somewhat to the northward of this point. In a great number of localities we found upturned, crumpled, silicifiecl, and metamorphosed rocks exactly similar to those of Mt. Diablo, but our search for Aucella was not rewarded. Upon the metamorphic rocks lie uncon- formably somewhat tilted, unaltered sandstones. These are certainty Mio- cene, for, though we found no fossils ourselves, Dr. White examined ex- tensive collections of Miocene shells in entirely similar rock made by Rev. Thomas Condon, who gave us full information as to their occurrence in precisely similar positions, but somewhat north of Roseburg. Overlying the sandstones are large areas of volcanic rocks. 1 In the section made by the Columbia River no metamorphic rock or granite appears, but at least the southern portion of the range has a foun- dation similar to that of the California Coast Ranges, and, as I think, prob- ably of the same age. This cannot be stated as a certainty until AuceUa has been found in the Cascades; but, considering that this fossil certainly occurs near Puget Sound and that the lithological character and geological association of the metamorphic rocks at Roseburg are indistinguishable from those of known Neocomian localities in the Coast Ranges, no grave doubt remains. Chico beds, however, occur in central Oregon, and on this ground the Blue Mountains have been regarded as the northerly continuation of the Sierra. 2 But shore lines and lines of structure, though intimately associated, do not always coincide. A depression of only 30 feet to-day would put Sacramento, Stockton, and an immense area of the Great Valley under water, while a depression of 400 feet would convert the Great Valley into 1 In answer to an inquiry, Prof. Joseph Le Conte states that, his remarks concerning the lower por- tion of the Cascade Range in Am. Jour. Sci., 3d series, vol. 7, p. 177, were not from personal ohserva- tion. He there suggested that the Cascades were a continuation of the Sierra. 1 U. 8. Geol. Expl. 40th Parallel, Systematic Geology, vol. 1, p. 4f>si. UNIVERSITY THE CASCADE a gulf, extending from Tulare Lake to above the town of Red Bluff. There is, indeed, abundant reason to suppose the Great Valley did form such a sheet of water within the recent period, for the marsh lands bordering on the lower Sacramento and San Joaquin llivers seem mere continuations of the mud flats of the Bay of San Francisco exposed at low tide, and the relations of the alluvial plains to the neighboring hills are indicative of the same conditions, while the character of some of the terraces on the sea- coast demonstrates that the sea-level not long ago was at least over 200 feet higher, relatively to the land, than it is now. 1 There would be nothing strange, therefore, in the discovery of brack- ish-water shells or even salt-water remains in the alluvium of the Great Valley, but this would not indicate that the Coast Ranges were non-existent at the time when such mollusks were alive. So, also, the Gulf of California now extends some one hundred and fifty miles to the eastward of the true coast line, or the western limit of Lower California. The fact that Chico fossils are found in central Oregon only proves, therefore, that tlie Cas- cades must have been broken through at one or more points during this period, and not that this range is more recent than the Chico. Southern continuation of the Coast Ranges. Tll6 main Structural Continuation of the united Coast Ranges and Sierra Nevada to the southward appears to be the peninsula of Lower California. Mr. Gabb, 2 who visited this region, stated that it is possible to trace an uninterrupted granite ridge from the San Gabriel Mountains, north of Los Angeles, through Los Angeles, San 1 Prof. George Davidson has traced from Lower California to Alaska the terraces which line the wi-stfni coast (1'roc. California Acad. Nat. Sci., vol. 5, p. DO). So great is the regularity of the surfaces of some of these terraces that he feels compelled to deny that they have been cut by wave action. He considers it probable that ice was the agent. My own opportunities for examining these terraces have been very limited, but in the region between Ft. Ross and Gualala I have studied them with some care. Their topography appeared to me indistinguishable from that of the beaches exposed at low water, and iit two points I detected Pholas borings on the terraces at a distance of several miles from one another. One of these points was by estimation 150 feet and the other 250 feet above sea-level. However the terraces of this region were formed, therefore, they have been at sea-level within a period which has been insufficient to obliterate extremely superficial markings in a very soft sandstone. Neither in this region or at Santa Cruz nor on the Farallone Islands was I able to see the necessity for attributing the excavation of the terraces to any other agency than that of the waves. That there are such terraces for which wave action may seem an inadequate explanation I do not of course deny; yet, if the level of the coast were to remain absolutely constant for a very long period, it appears to me that hard rocks and soft must eventually be cut away to a very nearly uniform depth. Mr. Goodyear (ibid., vol. 4, p. 295) has called attention to evidences of oscillation in the level of the coast of Oregon. 2 Geol. Survey California, Geology, vol. 2, appendix, p. 137. 208 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Bernardino, and San Diego Counties, into Lower California and along the peninsula to within a few miles of the old mission of Santa Gertrudis, while, from the exposure through denudation at Santa Gertrudis and again near Loreto, it is probable that between the mission and Cape San Lucas the granite nowhere lies at a greater depth than 1,000 feet. Dr. White has pointed out that fossils of the Atlantic Cretaceous fauna, which is entirely distinct from the fauna of the Pacific Cretaceous, are found on the western side of the Sierra Madre of Mexico, thus showing that Lower California was during the Cretaceous the dividing isthmus between the oceans and confirming Gabb's view. . Though the probabilities are thus strongly in favor of the theory that the Cascades and the mountains of Lower California are the main struct- ural continuations of the united Sierra and Coast Ranges, it by no means follows that these ranges form an isolated system or that these continua- tions of the California mountains are the only ones. On the contrary, there is much evidence that the Sierra is inseparable from the basin sys- tem, which appears to continue through Arizona and to unite with the Rocky Mountain system. Too little is known of northern Mexico and the territory of the United States immediately adjoining it lo justify any extended speculation on this subject, Pre-Cretaceous upheavals and metamorphism. TwO important ai'OaS of SCrpeiltillized and silicified, metamorphic rocks have been shown in the foregoing pages to be of the same age, probably Neocomian, and it has been established that these series were upheaved and metamorphosed prior to the deposition of the Wallala beds, regarded by Dr. White as Turonian. But there are other metamorphic rocks in California deposited long before the Neocomian. Thus the Carboniferous limestones on the McCloud River are ciystalline and the metamorphic shales near Pence's ranch, in Butte County, are at least in part Carboniferous. They bear considerable similarity to those of the Mariposa group, and, furthermore, they are nearly vertical and strike in nearly the same direction as those of the gold belt proper. The cniestion therefore at once arises whether their upheaval and metamorphism are ascribable to the same period as the uplift and alteration of the Mariposa and Knoxville beds. PERSISTENCE OF THE SIERRA NEVADA. 209 It is hoped that work now being done on the gold belt may afford a definite answer to this and other questions. In the absence of distinct evidence, however, the probabilities appear to be against the supposition that all the metamorphism which can be traced in this State is referable to a single period. It may be asserted with some confidence, as a result of all the geologi- cal work done from the Rocky Mountains to the Pacific, that there has been throughout geological time a definite tendency in the structural development of this area. The geologists of the fortieth parallel exploration showed that a fault began upon the west flank of the Wahsatch in the Archean, the same fault which Mr. Gilbert has traced as still in progress. The last- named geologist and Prof. Joseph Le Conte have also detected a similar fracture on the east side of the southern portion of the Sierra. The eastern portion of the Great Basin was lifted above the surface of the ocean after the close of the Carboniferous, the western portion of the same area fol- lowed before the Cretaceous, and at one or both of these epochs the coun- try was laterally compressed, an action no doubt closely connected with the progress of the great faults. About the time of the Neocomian Cal- ifornia experienced an east and west compression, and again at the close of the Miocene an uplift threw the horizontal strata of the coast into north and south folds. From the Wahsatch to the Pacific Coast there thus appears to have been a recurrent, if not a constant, tendency to lateral compression in substantially one and the same direction and to an increase of the land area west of the Wahsatch. This repetition of movements in a similar direction has tended to ob- scure the time relations of geological phenomena, particularly along the great Sierra Range, which has probably been one of the most persistent topographical features of the continent. Dr. White points out that an ex- traordinary difference has existed between the marine fauna of the Pacific Coast and that of the waters east of the Sierra from a time prior to the Cretaceous onward, and hence that a land barrier must throughout have occupied substantially the position of the Sierra Nevada, which must there- fore have experienced repeated upheavals to compensate for constant ero- sion. There are also said to be some paleontological grounds for sup- MON xi n 14 210 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. posing 1 at least a partial separation of these areas daring 1 the Carboniferous. This supposition is in entire accord not only with the structural anal- ogies of the region, but with the detailed observations of Mr. Clarence King 1 and his colleagues, who were led to infer the existence of a conti- nental area during the Paleozoic west of longitude 117 30', in latitude 40. Such a range as the Sierra, though partaking in the general compression and movement of the whole country, must offer a tremendous resistance, and, at any one of the active periods during which the physical conditions permitted contortion of strata along the western flank of the Sierra, these must have been driven against the barrier until they could yield no more. Thus if a pile of cloths were compressed from their edges (as in Hall's famous experiment) with enormous energy, they would be forced into plications so sharp that the dip at any point would be nearly vertical It seems to follow that at different upheavals (some of them perhaps as yet untraced) strata to the west of the great Sierra may have been driven into the nearly vertical position of the gold slates, their original stratigraphical relations thus becoming completely obscured. I do not consider it certain, therefore, or even probable, that the Carboniferous slates near Pence's ranch first assumed their present position subsequently to the Knoxville period. It may be that they have stood nearly as now ever since the Car- boniferous of Utah was raised above water, while the slates of Horsetown, of the age of which nothing is known, may possibly owe their vertical dip to still earlier convulsions. The Carboniferous slates of Pence's ranch are serpentinoid, and, though distinctions between them and the metamorphosed Knoxville beds might perhaps be drawn, the rocks are very similar. But, just as it seems to me that successive upheavals may have produced similar effects upon the arrangement of strata, I think the association of a certain uplift with a par- ticular series of chemical changes tends to show that analogous dynamical conditions might lead to molecular changes of the same kind. It seems therefore not at all impossible that both upheaval and metamorphism at Pence's ranch were in the main- earlier phenomena than those traced in the Coast Ranges. If so, their effect must have been felt throughout a great por- U. P. (!<"'. Kxi'l. 40th Parallel, vol. 1, Systematic Geology, p. 534. THE COAST L'AXGES AND THE SJEKKA. 211 _ tion of California, though the results in the Coast Ranges may have long since been obliterated. On the other hand, the post-Knoxville disturbance must have been felt at Pence's ranch, though its effects may have been trifling as compared with those of earlier convulsions. The Coast Ranges members of the western Cordillera system. As hag already bcCll Stated, I am unable to see any reason for dissenting from Professor Whitney's opinion that the fossiliferous beds of Mariposa form an integral portion of the modern Sierra Nevada range. It seems simply impossible that they should have assumed their present vertical position with a strike parallel to the crest and that they should have been profoundly modified by chem- ical action, except under conditions of disturbance amply sufficient to bring abovit essential modifications of the whole range. That there were at the time, or at least had been, mountains in nearly the same position does not impair the claim of this addition to be considered as much a part of the modern Sierra as any older portion. If the conclusions thus far stated be accepted, it follows at once that subsequently to the close of the Knoxville, but long before the beginning of the Chico, both the Sierra and the Coast Ranges experienced an upheaval. This was in all proba- bility not the first along the line of the Sierra and very possibly did not actually originate the Coast Ranges, but for the latter it is the first dis- tinctly traceable movement. It is conceivable that within the limits of time indicated two upheavals should have taken place, one affecting only the Sierra, the other only the Coast Ranges; but the probability of this alternative will scarcely be seriously maintained. The earlier determina- ble portion of the Coast Ranges must therefore be considered as due to the same disturbance which added the gold belt proper to the Sierra Nevada. There is much probability that a portion at least of the Cascade Range was elevated and metamorphosed at the same time. The relationship thus established is brought out more clearly by a comparison of the history of the ranges so far as it can be traced. Both the Sierra Nevada and the Coast Ranges were above water and underwent erosion during the interval between the Knoxville and the Chico epochs. Both ranges also sank just before the beginning of the Chico, admitting the ocean over a great part of the Coast Ranges and over 212 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE considerable areas at the base of the Sierra. Both appear to have risen partially and gently before the Tejon, particularly toward the north; at least the rocks of this epoch, so far as is known, are confined to the southern ex- tremity of the Sierra and to the Coast Ranges south of Martinez. A slow subsidence would appear to have taken place before the Miocene, rocks of this age extending along the Sierra far to the north of the Tcjon localities, while in the Coast Ranges they lie directly upon the metamorphic at a great number of points, clearly indicating a lower general level than dur- ing the preceding epoch. During the Pliocene very little of either range was below water. Not only was an important uplift of the Sierra Nevada contempora- neous with the first known upheaval of the Coast Range, but, even with the imperfect information at command, it is clear that the successive fluct- uations of level of the country since the close of this disturbance have affected these ranges substantially in the same manner, and I cannot but conclude that the new facts brought forward necessitate the reference of the Sierra Nevada and the Coast Ranges to a single mountain system. The Coast Ranges are, and probably always have been, of less altitude than the great Sierra, and they have consequently been more extensively immersed, just as would be the case if both were now to sink any given number of thousand feet. Between the Miocene and Pliocene periods the Coast Ranges also suffered disturbances in which at least the western base of the Sierra has not shared perceptibly. The Sierra, too, has undergone some faulting in which neither the Coast Ranges nor the basin ranges are known to have shared, but these differences do not appear to me sufficient to counterbalance the important coincidences in the history of the ranges. Date of upheaval and metamorphism. Tlld'C SCCmS eVCl'}' rOaSOIl tO SUppOSG that the upheaval of the Knoxville and Mariposa beds was substantially con- temporaneous with their metamorphism, but the exact period at which these phenomena took place is uncertain. That it was prior to the deposi- tion of the Wallala beds, and therefore before the Turonian, is indubitable. It must be left to future investigation to determine whether the uplift pre- ceded the G-ault. This, however, is more probable than the alternative hypothesis, for tho limited occurrence of the Hor.setown beds seems to indi- WALL A LA BEDS. 213 cate that an uplift, though possibly a gentle one, occurred between the Neoconiian and the Gault; so that, if it should prove that the Horsetown beds were involved in the inetamorphisin, there were probably two distinct uplifts between the Knoxville and the WaTlala, and of these the later must have been much the more violent. This appears less likely than that a single great movement took place at the close of the period characterized by the presence of Aacella and prior to the Gault. The waiiaia series. Along the coast in Sonoma and Mendocino Counties, from a little below Ft. Ross to beyond the town of Gualala or Wallala, 1 occurs a series of beds of very considerable thickness, standing at a high angle and mainly composed of thick-bedded, soft, tawny sandstones ex- ternally similar to those of the Chico group as it is found at New Idria and elsewhere. This series also includes large masses of conglomerate, the pebbles of which are chiefly granite and metamorphic rocks. That these beds lie unconformably upon the metamorphic has already been stated. The Wallala beds are for the most part extremely barren in fossils and no considerable number in any tolerable state of preservation were found excepting at a point on the shore about a mile above the town of Gualala At other points to the southward, however, fragments of Ino- ceramus, easily recognizable by the peculiar structure of the shell, and a few other imperfect fossils were found, so that there could be no doubt as to the faunal continuity of the beds, even had the exposure been less satisfac- tory. The National Museum has also received from Mr. C. R. Orcutt, of San Diego, a few fossils from Todos Santos Bay, in Lower California, a part of which Dr. White has determined as identical with those from Mendocino county. He has described the following: Goraliiochama Orcutti (geu. et sp. nov.). Trochus curyostomus, n. sp. . Nerita f. 1 The name of thin town and of the river which thcnvempties iuto the Pacific is variously spelled Gualula, Guadala, Wallialla, and Wallala. It is of Indian origin, aud the first form is an attempt to convert it into Spanish. The third form is evidently due to the resemblance of the sound to a famous mythological name. The Coast and Geodetic Survey, after careful consideration, have chosen the last spelling, which will no doubt eventually bo adopted on maps of the Coast. 214 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. Cerithiunt Pillinyi. u. sp. Cerithhtm totium sanctorum, n. sp. Solarium irallalense, n. sp. The collection from Mendocino County included the first and the last of these and also imperfect specimens of an Inoceraunis about a foot in length, Ostrea, Pcden, and Turritdla. Dr. White believes this fauna to indicate the middle Cretaceous and in some respects it reminds him of the Gossau. 1 The Wallala beds have never been recognized except at these two points, which are 600 miles apart. The northern locality was manifestly close to the shore of the ocean of that time, and the locality in Lower California appears to have been similar. It thus seems probable that the western shore of California was approximately in its present position during the Turonian epoch. The chico-T jon series. This group of rocks occurs for the most part on the slopes of the great valley of California, the western side of the Coast Ranges being covered with Wallala beds or Miocene strata where the meta- morphic series is not exposed. The prevalent rock variety is sandstone of medium grain and usually very soft. 3 The lower portion of the series is generally ferruginous and of a tawny hue, and spheroidal concretions, though met in later sandstones, also are particularly abundant in the Chico. The origin of these concretions is discussed in Chapter III. The upper part of the series is commonly characterized by an extremely light color, approaching pure white. The series also includes shales, though these are subordinate, and a very little limestone is met with in some localities, though not forming continuous strata. Along the Coast Ranges the Chico-Tojon series is, so far as I know, always perceptibly inclined and usually at a considerable angle, but in some of the localities on the west flank of the Sierra Nevada, as at Chico, the beds are very nearly horizontal. Traces only of cinnabar are known to occur in these rocks and no case of metamorphism similar to that which prevails in the rocks of the Knoxville group has been observed, though induration and a greater or less impreg- nation with calcite and gypsum are not uncommon. 1 Bull. U. S. Geol. Survey No. 22. 2 The branches of bushes growing close to erpppings of these saml.itonns often wear grooves into the rock which are sometimes as much as three inches in depth. OHIOO-TfiJON SERIES. 215 Ne\v Idria affords a fine exposure of these rocks, which at this point appear to be not less than 10,000 feet in thickness. The beds are tilted at angles reaching 45 and are so little concealed by soil that a continuous stratum may often be followed for a considerable distance. There is no indication at this point of any break in the continuity of deposition of the sandstones, which carry a sufficient number of fossils to show that both the Chico and the Tejon are represented. At Mt. Diablo, too, these formations appear exactly conformable, and, so far as is known, this is the case wher- ever they are found together. The difference in color is the only physical peculiarity by means of which a division can be made. Near the Vallecitos Canon, a few miles northwest of New Idria, and therefore close to the locality known as Griswold's in the reports of the State survey, the Tejon and Miocene occur near to each other and both are fossiliferous. This region appeared to me well adapted to test the question whether or not there existed between the Tejon and Miocene any fossiliferous strata or any barren strata which might represent an interme- diate age, for Messrs. Whitney and Gabb, regarding the Tejon as Creta- ceous and Eocene fossils as absent, believed that there were unfossiliferous beds in the position which the Eocene should have occupied. Mere col- lections of fossils would scarcely be adequate to determine this point, and at my request Dr. White examined this locality with the special purpose of determining the presence or absence of an intermediate fauna. He found the Miocene and Tejon 'conformable here, as they usually are elsewhere, and traced the fossiliferous Tejon beds so close to the fossiliferous Miocene beds as to leave no room for an intermediate series. The age of the Chico-Tejon series has been much discussed. Conrad first determined fossils from the Tejon which were collected by Prof. W. P. Blake near Ft, Tejon. 1 Of these specimens Conrad wrote: "The Eocene period is unequivocally represented by the beautifully perfect shells from the Canada de las Uvas." Either through a misunderstanding or a difference of opinion these arc referred to in the reports of the State survey as a "few imperfect fossils." 2 Conrad repeatedly reasserted, but never retracted, his 1 Pacific Railroad Reports, vol. f>, p. HI- 1 . i Mul. Survey California, Geology, vol. 1, p. 191. 216 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. view. 1 Gabb 2 vigorously maintained the Cretaceous age of the Ti'jon in his contributions to the State geological reports and elsewhere Prof. J. I). Dana considers the Tejon as probably Lower Eocene and gives a list of the Tcjon genera to show the Tertiary character of the fauna. 3 Prof. Jules Mnrcou asserts the Tertiary character of both the Chico and the Ti'jon on paleontologies! and apparently on lithological grounds. 4 Prof. Angelo Heil- prin, who has charge of Gabb's types, has ably reviewed the Tejon ques- tion and pronounces emphatically for its Eocene age 6 Finally, l)r White has examined many of the principal localities in the field and the collec- tions made by my party, as well as Gabb's types. His conclusion, as al- ready stated, is that the Chico is distinctly Cretaceous and the Tejon dis- tinctly Eocene, but that the two form an unbroken series with a gradual faunal change. At the time of the principal controversy on the subject of the age of the Tejon the doctrine of evolution had not permeated science. It is now generally accepted that transitions must exist between the faunal groups or the geological periods which have received distinct names, and that the divisions actually adopted were determined by the local conditions of those regions in which geology was first studied. Twenty years ago the influ- ence- of earlier views was still very strong, cases of transition were accepted with reluctance, and few doubted that any series of beds exhibiting internal evidence of continuity of life and sedimentation must be referred to a sin- gle one of the standard series of formations, however remote the occurrence might be from the typical localities of western Europe. This feeling was par- ticularly strong with reference to the Cretaceous and the Tertiary, between which, as everyone knows, there is a peculiarly sharp break, both in p]u- rope and in the eastern United States. It was not unnatural therefore that Gabb should deny with as much emphasis as italics are capable of giving that the case in hand was one of transition or that Conrad should resort 'Am. Jour. Conchol., vol. 1, 1865, p. 362; ibid., vol. 2, 180C, p, 97; Aui. Jour. Sci., 2d series, vol. 44, 1867, p. 376. 2 Am. Jour. Conchol., vol. 2, 1866, p. 87; Am. Jour. Sci., 2d scries, vol. 44, 1867, p. 226; Proc. California Acail. Nat. Sci., vol. 3, 1868, p. 301. The last is the most elaborate. 'Manual of Geology, pp. 457, 458, 491, 508. 'Rept, Chief Eng. U. S. A., 1876, p. 387; Bull. Soc. gdologique France, vol. 2, 1883, p. 407. 6 Proc. Phila. Acad. Sci., 1882, p. 195; Contributions to the Tertiary Geology and Paleontology of the United States, 1884, p. 102. CIIICO-TKJUN SERIES. 217 to the hypothesis of fossils washed out of earlier beds and redeposited in younger strata to account for the commingling of Cretaceous and Tertiary types in the Chico-Tejon series. In correcting their opinions Dr. White and I have simply taken advantage ofJlie advances which geological sci- ence has made since their day. Dr. White sums up the evidence as follows: ! The Maestricht, Faxoe, and other beds of Europe, although they are intermediate between the Upper Chalk and the Eocene, are too closely related by specific and ge- neric forms to the Chalk to be regarded as separate from the Cretaceous proper. Their fiiunnl relations to the Eocene are also too remote to allow of their being regarded as in any proper sense transitional between the Cretaceous and Tertiary. In Xew Zea- land, however, it appears probable from the reports of the government geological sur- veys that there is in those great islands a true transition from the Cretaceous to the Tertiary similar to that which occurs in California. 1 think the evidence which has been adduced to show the Eocene age of the upper or Tejon portion of the Chico-Tejon series is as conclusive as any evidence of that kind can be. Xow, if we apply the paleontological standard for indicating the age of formations which is generally accepted by geologists, we necessarily refer the fossils of the lower or Chico portion of that series to the Cretaceous. The question then arises, to what portion of the full Cretaceous series, as it is recognized in other parts of the world, is the Chico group really equivalent? If the Tejou group is Eocene, it is plain that the Chico group represents the upper portion of the Cretaceous, and it necessarily represents the very latest portion of that period. My opinion, therefore, is that it is, at least in part, later than any formation that has yet been referred to the Cretaceous period either in Europe or in America, and that it practically fills the gap which is indicated by * * * Sir Charles Lyell. 2 An examination of the figures and descriptions of the fossils which Mr. Gabbhas referred to the Chico group, together with his catalogue of California Cretaceous fos- sils, 3 shows that while a considerable portion of them, especially the Cephalopoda, are of types which indicate their Cretaceous age. a large part of them are of genera which are known to range from the early Cretaceous to the present time, and some of them belong to genera which are generally accepted as not older than the Tertiary. There- fore there, appears to be no inherent reason why this Chico fauna, even as it is repre- sented by Mr. Gabb, should not be regarded as belonging to the very latest portion of the Cretaceous period. The fact that oue or two Mesozoic types of cephalopoda pass up from these strata into those of the Tejon portion does not necessarily prove that the latter ought also to he referred to the Cretaceous, any more than the discovery of Am- monites in the Carboniferous of Texas and of India ought to require us to refer those strata to the Mesozoic, 1 Bull. U. S. Geol. Survey No. 15, pp. 16, 17. 2 See Lyell's Elements of Geology, 1871, p. 281. ' See Geol. Survey California, Paleontology, vols. 1 and 2, for the figures and descriptions, and vol. 2, pp. '309-254, for the catalogue. 218 QIH'KSILVEK DEPOSITS OF THE PACIFIC SLOPE. The intimate relation to each other of all the strata of this great Chico-Tejou se- ries, as shown by the mixed character of its fossils, is very perplexing when that con- dition is considered in relation to the established taxonomy of the formations, but it is very suggestive when considered with reference to a search after the complete sequence of geological events. Indeed, such a condition of things is what one ought to expect to find somewhere; but hitherto no other part of the world, if we except New Zea- land, has furnished so strikingan example of the intimate connection of two geological ages, or at least of such connection between the Cretaceous and the Tertiary. The Miocene. No sensible non-conformity is known to exist between the Tejon and the Miocene, yet the distribution of these two formations appears to indicate a change of level at or near the period which separates them, for the Miocene frequently rests upon the metamorphic rocks without the intervention of other beds During the Tejon these areas of metamor- phic rock must have been land and the subsidence must have been a gradual one. It may have been more rapid in some localities than in others, however, and it thus appears not unlikely that an appreciable lack of conformity may yet be detected at some point or points between the Tejon and the Miocene. 1 The Miocene occurs on both sides of the Coast Ranges and on the lower western flank of the Sierra. It is also abundant in western Oregon, but is not well represented, if it exists at all, in northern California. It is composed in large part of sandstones somewhat irregular in texture and color and usually distinct from the earlier rocks. A great area, however, is mostly occupied by extremely fine-grained schists. These are associated with bitumen in the lower counties and extend up the coast to Santa Cruz and beyond. They are unusually barren of fossils, while the sandstones often contain almost incredible quantities of shells. The San Benito Valley is very remarkable in this respect. The Post-Miocene upheaval. Tll6 PlioCClie of tllC CoaSt KailgCS is of VCiy limited extent and lies, as Professor Whitney showed, unconformably upon the Miocene, which is itself greatly disturbed. The combination of these facts shows that a great uplift took place between the two. As has been stated already, it is often far from easy to distinguish in detail the effects of this upheaval from those of the Post-Neocomian disturbance, audit may be added that still later uplifts further confuse the structure of the Coast 1 Since this memoir was transmitted Mr. J. Marcnn states that he has observed such a want of con- formity as is mentioned in a former foot-note. THE MIOCENE. 219 Ranges. In certain localities, however, as at New Idria, Mt. Diablo, and the Blue Range on Cache Creek, northeast of Knoxville, these effects can be somewhat satisfactorily compared, and it then appears that the Tertiary upheaval, important as it was, was far less violent than that which took place near the beginning of the Cretaceous. The extraordinary crushing so conspicuous in the Knoxville beds, and in which an almost inconceivable amount of energy must have been expended, is not observable in the dis- turbed strata of later age, which, as a rule, though inclined, form large adherent masses with gentle curves interrupted only at long intervals by faults. The beds from the Wallala to the Miocene are sometimes nearly vertical, but more generally lie at an angle of less than 45. Along the western base of the great Sierra the effect of the Post-Miocene upheaval of the stratified rocks is, so far as I know, scarcely perceptible. It does not follow that it produced no effect in this region; on the contrary, the absence of known Pliocene beds from the Sierra foot-hills seems to show that the range was raised considerably at this epoch, though the energy of this movement was insufficient to produce considerable flexure in the beds. At the eastern side of the range, on the other hand, the fresh-water Truckee Miocene beds were thrown into bold folds, their dip reaching 30. l The same upheaval was felt thoughout western Oregon, where it had the same comparatively gentle character as in the Coast Ranges. pliocene and Post-piiocene strata Pliocene beds, in part of marine origin, were shown by Professor Whitney to exist at a number of points in the Coast Ranges. None of these is included in the areas surveyed in connection with this memoir. An interesting fresh-water series, however, occurs to the east of Clear Lake, 2 about the north fork of Cache Creek. The beds belonging to it are entitled Cache Lake beds on the map of the region accompanying this volume. They are composed of gravel, sand, and calcareous beds, partially indurated in spots, probably by the action of humus acids. 3 These beds appear to have a great thickness when meas- ured perpendicularly to the dip, which varies from 10 to 40, and the up- 1 King: Op. cit., p. 405. -This occurrence is referred to by Professor Whitney, who discovered no fossils iu it (Auriferous Gravels, p. 23). 3 See page 04. 220 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE.. turned edges are much eroded. They contain abundant but imperfect plant remains. Shells are rare, but were found at four localities. These are only partially fossilized, but the larger ones are compressed and broken by the weight of the superincumbent strata or by the movement accompany- ing their uplift, Most of these were found in light-colored, calcareous, soft, and excessively fine-grained material, manifestly a lake deposit. The character of the deposits and the fact that the area occupied by them is continuous with a portion of Clear Lake led me to infer that Cache Lake might be regarded as representing Clear Lake at a more or less distant period. The recent lake deposits seem at some points to rest immediately upon those of Cache Lake, and I was unable to see any distinction between the fossil Anodonta and a species which is now abundant in Clear Lake These facts seemed to indicate that, in spite of very considerable upheaval, there existed a continuity of sedimentation and of life from the Cache Lake epoch to the present The shells were referred to Mr. R. E. C. Stearns, who fully confirmed my views from a paleontological standpoint, as the following abstract of his report will show: The most conspicuous form among the fossils is Anodonta Nuttalliana Lea, of the winged or connate variety, described by that author as A. ivalilamatensis. The numerous examples of this shell collected in the Cache Lake beds vary in no respect from living specimens readily obtain- able in the present lake. The living specimens from Clear Lake are also characteristic and remarkable for the extreme development of the dorsal wing. The prominence of this feature Mr. Stearns has observed to coin- cide with areas subject to periods of drought and severe freshet, It cer- tainly appears from the deposits of Cache Lake that there must have been great periodical variations in the quantity of sediments emptied into it, In Mr. Stearns's opinion this shell implies that the character of the streams emptying into Cache Lake was not markedly different from that of the pres- ent streams of the same area. The specimens range from an inch (adoles- cent) to over three and a half inches in breadth. Another shell represented by numerous specimens from the Cache Lake beds is Valvata virens Tryon. This species was originally described FEESH-WATER PLIOCENE. 221 from living specimens from the modern Clear Lake. A third abundant species is Bythinella intermedia Try on. This shell is not known to exist in Clear Lake, but has a wide distribution on the Pacific slope. The fauna of Clear Lake, however, has not been systematically investigated, and Mr. Stearns thinks it by no means improbable that B. intermedia still exists there. A single specimen, certainly belonging to the genus Pisidium, and probably to the species abdituin Hald., is not perfect enough for specific identification. There are several similarly imperfect specimens of Helisoma / ammon Gould and an imperfect Pliysa, which is either P. gyrina or P. lietcrostropha. All these are living forms. The age of these beds cannot of course be satisfactorily determined from fresh-water shells. The most careful watch was kept for vertebrate remains, but only a few fragmentary bones were discovered. These were referred to Prof. 0. C. Marsh, who reports finding among them the fragments of a pelvis, apparently of a horse; the lower portion of a scapula, which he thinks belonged to a camel; and the head of a large femur, probably of an elephant or a mastodon. These imperfect fossils, he concludes, suggest a very late Pliocene age for the beds in which they occur. The continuity of life between Cache Lake and Clear Lake, with the continuity of sedimen- tation mentioned above, appears to preclude the supposition that the beds are older than the latter part of the Pliocene. Professor Marsh's report seems to show conclusively that they are not recent, and that they must therefore represent the close of the Pliocene. This determination is of great impor- tance ; for it fixes with accuracy the age of the asperites of Clear Lake and, in conjunction with other facts, determines approximately the age of the asperites of Mt. Shasta. Distribution and age of the lavas. The region about Steamboat Springs, Nev., includes the Washoe district, the eruptive rocks of which have been more extensively discussed than those of any other locality on this hemisphere. In the chapter on the massive rocks it will be seen that my studies of the rocks of Steamboat Springs and of the Washoe district have led me to the conclusion that the younger andesites form a natural group of trachyte like rocks, which I have called asperites. This same group is widely distrib- uted in California. It forms a large and apparently the chief portion of 222 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. the material of Mt. Shasta and the country surrounding it. Between this region and Clear Lake the country is practically unknown. At Clear Lake asperites form the bulk of the andesitic eruptions. Andesitic areas also extend almost uninterruptedly in a southwesterly direction along the Ma- yacnias Range, including Mt. St. Helena, to the neighborhood of Vallejo, on San Pablo Bay, which is practically the northern end of the Bay of San Francisco. Most of this andesite belongs in the asperite group. Andesites reappear at Mt. Diablo and to the eastward of Tres Finos. Comparatively small amounts of older dense andesites occur at Clear Lake and in the Ma- yacmas Range. Rhyolite in the areas under discussion has been found only at New Almaden, but basalt is widely distributed. It occurs at Steamboat Springs and at Washoe and is abundant near Mt. Shasta and at Clear Lake In the ranges to the southward of Clear Lake basalt appears to be more widely distributed than andesite, occurring at Knoxville, in Sonoma County at the Mt. Fisgah quarry, at Mt. Diablo, and to the south of the Bay of San Francisco as far at least as the Panoche Valley. The volume of the basaltic eruptions is much inferior to that of the andesites. No eruptive rocks of the Pre-Tertiary age are known to be intercalated in the Knoxville or Chico-TYjon series or to have broken through them. The only earlier eruptions encountered are represented by pebbles in the Knoxville and Chico conglomerates, and these are believed to have cut the granite before the deposition of the Knoxville beds. Excepting these pebbles, the earliest eruption known is pyroxene-andesite, which preceded the Cache Lake period. Had this eruption antedated the Miocene, pebbles of the lava would almost certainly have been found in the Chico-Tc'jon series of Lower Lake. It may have accompanied the Post-Miocene up- heaval or it may have followed this uplift after an interval. I think it probable that the eruption took place at the time of the orographical change which dammed bade the waters of Cache Lake, probably early in the Plio- cene or just before it. Another outbreak took place at the close of the Cache Lake period after an interval long enough to permit of the deposition of at least a thousand feet of fresh-water strata. This eruption, represented by the asperites of Mt. Konocti, accompanied an orographical change which shifted the waters of Cache Lake to the present Clear Lake, and the lava LAVAS. 223 now rests in places upon the older fresh-water strata. The beds immediately below the undesite contain a few fossil remains which, as shown above, correspond to the close of the Pliocene. The Pliocene beds near Mt. Diablo also contain andesite pebbles. ~lrf addition to the relations of the andesites to the sedimentary rocks at Clear Lake and Mt. Diablo, there is some other evidence bearing upon their age. The asperites of Steamboat Springs and of Washoe show by the forms of their flows, by the slight traces of erosion, and the abundance of glassy modifications that . they are comparatively recent. A comparison of the form of Mt. Shasta with that of a theoretically perfect volcanic cone shows that it is indeed considerably eroded, yet not so much so as to obscure its derivation from a form closely resembling that deduced from theory. This is also true of Mt, Konocti, on Clear Lake. The forms of these cones, as well as the character of the material of which they are composed, thus show that they, too, are comparatively recent. Furthermore, the amount of de- parture of these cones from the theoretical form is about the same for each, and so, too, are the other evidences of erosion. Hence they are approxi- mately of the same age. From the relations of the asperite at Clear Lake to the strata, this age is known to be that of the end of the Pliocene, and Mt. Shasta, consequently, also dates from about the beginning of the Qua- ternary. I know of nothing tending to prove that the asperites of Washoe and Steamboat are either much older or much younger than the similar rocks of the Coast Ranges. Of the age of the rhyolite of New Almaden as compared with the other lavas nothing is known. It is clear, however, that it postdates the Post-Miocene uplift, for, while the Miocene of New Almaden is much dis- turbed, the rhyolite dike intersects the disturbed Miocene and has itself not been affected. The basalts are still younger than the andesites. The eruptions near Clear Lake are evidently referable to a somewhat extended period, but per- fect volcanic craters remain. There are also said to be among the Indians of the region traditions of eruptions. In northern California there is good reason for believing that there has been a small basaltic eruption within forty years. 224 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. There thus seem sufficient grounds for asserting that a more or less continuous, but very irregular, volcanic belt stretches along the trend of the Coast Ranges from Clear Lake 1 at least to the neighborhood of New Idria, and that the eruptions, beginning in the Pliocene, extended into the recent period The andesites preceded the basalts and may perhaps be consid- ered as confined to the Pliocene, if indeed this period can be sharply de- fined. There is considerable reason for believing that the andesitic eruptions of the volcanic belt of the Coast Ranges are of pretty nearly the same age as the main portion of the similar rocks of Steamboat and Mt. Shasta, and that there is no great difference in age between the basalts of Steamboat and those of the Coast Ranges. I by no means assert, however, that the suc- cessive phases of volcanic activity were absolutely contemporaneous over the whole coast. No uplift which the Coast Ranges have experienced compares in vio- lence with that of the Post-Neocomian epoch, and consequently, whether the initiation of volcanic action is referable to the very important Post- Miocene upheaval or not, it is a notable fact that volcanic activity did not accompany the most profound disturbance of the Pacific Coast. The meta- morphism of the rocks at the period of the Post-Neocomian upheaval, on the other hand, seems reasonably ascribable to the co-operation of the heat thus engendered. During the enormous period which elapsed from the close of the Neo- comian to the close of the Miocene the erosion was extremely great, yet no eruptions took place. But at the close of the Miocene great masses of soft sandstones were elevated, which under similar meteorological conditions would be eroded much more rapidly than the harder rocks of the meta- morphic series. The conditions in the Coast Ranges do not, therefore, ex- clude the hypothesis that the relief of pressure due to the rapid erosion of these soft rocks brought about the fusion of the lavas. It is manifest that the eruptions took place substantially along old belts of uplift lines of weakness which are certainly not younger than the Post-Neocomian upheaval, and, as I have pointed out on a preceding page, 1 Professor Whitney's par-lies met with uo volcanic rocks in the (.'oast Kan^cs iimpcr northward from Clear Lake. ORE DEPOSITS. 225 are probably far older The distribution of volcanic rocks in the belt where they occur, however, is very irregular, corresponding to the irregu- larity of the entire chain of mountains called the Coast Ranges. A close connection exists between the structural and historical geology of the quicksilver belt and deposits of cinnabar, as will appear in subse- quent chapters. Here it is sufficient to say that ore deposition has taken place only since the earlier volcanic eruptions and seems in all cases to have been brought about by heated solutions of volcanic origin. Cinna- bar occurs in almost every variety of the rocks found in the Coast Ranges, and the age and origin of the inclosing rocks do not seem to have affected the deposition of ore in any way. MON XIII 15 APPENDIX TO CHAPTER V. REMARKS ON THE GENUS AUCELLA, WITH ESPECIAL REF- ERENCE TO ITS OCCURRENCE IN CALIFORNIA. BY CHABLES A. WHITE. The fossil shells of the genus Aucella, although presenting no features which especially attract the attention of the ordinary observer, have come to possess uuusual interest in certain fields of paleoutological and geological inquiry. This is mainly due to the constancy of the distinguishing characteristics of the genus, its wide geographical distribution, its restricted range in geological time, and the contro- versy which has arisen as to the particular geological epoch which it represents. During the progress of his work, the results of which are recorded in this volume, these shells have become of especial interest to Dr. Becker because of their preva- lence in certain of the strata with which he has had to deal. I have therefore, in compliance with his request, prepared the following remarks upon the genus, its geo- graphical distribution, probable range in geological time, and the variation of the forms which have been referred to it under various specific names. It is well known to paleontologists that at least a large part of the different genera which have been proposed for the Aviculida 1 , the family to which Aucclln be- longs, are not so clearly definable and distinguishable from one another as could be desired, and also that the forms which have been ranged as species under those gen- era respectively are often found to be so exceedingly variable that it is difficult to decide whether they ought to be treated as species or only as varieties. While the features which distinguish Aucella as a genus are not so conspicuous as those which characterize many other molluscan genera, they have been found to be very constant in all the specimens yet known, even in cases of the most extreme variation in size and shape of the shell. Consequently this genus has not been found to merge into related generic forms by a modification of its distinguishing features, as have some of the other recognized genera of the Aviculida?, and we may speak of Aucella as a genus with much more definiteness than we are able to do concerning any of the species which have been recognized under it. The feature which more than any other distinguishes this genus being the short and peculiarly infolded anterior ear, the embedding of the shells in the stony matrix 226 REMARKS ON THE GENUS AUCELLA. 227 in which they are usually found obscures that feature in a large majority of the speci- mens which are collected. These shells iu their general shape so much resemble small examples of Inoceramus that they have been frequently referred to that genus by authors and collectors when their distinguishing generic features have been obscured as before mentioned ; but when their full characteristics are visible tLey are of course found to be without the transversely grooved hinge area and prismatic shell structure which characterize Inoceramus. The genus AuceUa Las been recognized in certain of the Mesozoic rocks of both the northern and southern hemispheres, but its remains' have been found far more abun- dantly in the former than iu the latter part of the world, and they seem to be usually more prevalent in high northern latitudes than farther south. Indeed, so far as I am aware, this genus has been recognized at only two localities in the southern hem- isphere, one being upon the northern island of New Zealand 1 and the other in the prov- ince of Sergipe, iu Brazil. 2 In both these cases the recognition of the genus has not been so complete and satisfactory as could be desired, because of the imperfection of the only specimens discovered. Still, there seems to be no reason to doubt the correct- ness of its identification in either case. In the former case the specimens studied by Professor vou Zittel seem to have been few as well as imperfect and iu the latter case only two or three imperfect examples were discovered. Therefore the following re- marks will refer mainly to those forms which have been obtained from the rocks of the northern hemisphere and referred to Aucclla under various specific names. The geographical distribution of Aucella in the northern hemisphere is circurnpolar, extending far to the eastward in certain regions, and it has been found at numerous localities and in great numbers. Its known north and south range iu the northern hemisphere is from far within the Arctic Circle to about latitude 45 in western Asia, to southern India, and nearly to latitude 35 in North America. It was first known in the vicinity of Moscow, 3 when it was referred to the genera Inoccramus and ATytilus, and afterward in Petschora Land, 4 when Keyserling proposed the generic name by which it is now known. Subsequently it was discovered upon the eastern shore of the Caspian Sea. 5 in northern Siberia, 6 upon Nova Zembla, 7 Spitsbergen" and Kuhn 9 Islands (the latter lying near the east coast of Greenland), in southern India, as already mentioned, 10 'Karl A. Zittel: Reise Museu narional ilo KID di' Jam-in), vol. 7, p. 50, PI. Ill, Figs. 11, 12, and 13. ' 3 Fischer DoWaldln- ini : Oryetographie dn gouvi-rm-munt de Mosuou, p. 177, PI. XIX, Fig. 5. and PI. XX, Figs. 1, >, and I!. 4 \. Ki'ysrrling: WUsenschaftliche liuohachtnngmi anfciner Keiso in das Potsuhora-Laiul, pp. 297- 301, PI. XVI, Figs. 1-17. s E. Eichwald: Geognoet.-palaeODt. ISi-inerkungen iibfr die Hulliinsi-1 Mangistihlak nnd die aleut- ixclnMi Inst-ln, p. 53, PI. VI, Figs. 10 and 11. ' Middi-ndorn": Ili-isc in di-n iiiisscrsten \orden nnd Oslen Sihcrirns, vol. 1, \o. 1, p. 255. S. A. TiilllMM-g: Hihang till kongl. svensk. Vet.-Akad. Hand]., v.ii. li, pp. 1-2-1, PI. II, Figs. 9-18. G. Lindsf riini: Oin trias- och Jnrafdrsteningar fran Spetsborgon, Kungl. svensk. Vet.-Akad. Haudl., vol. (i, No. (i, p. M, PI. Ill, Figs. I! and I. v F. Toula: Die zwi-id- dcutache Nordpolarfahrt, vol. 2, pp. 497-505; also, Feikleu and de Ranee: Quart. Jour. Ci-ol. Sor. London, vol. 34, 1876, p. 56. 10 F. Stoliczka: Pal. ludica, vol. 3, p. 404, PI. XXIII. 228 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. in Alaska, 1 British America, 2 and iu various parts of California. 3 In the, latter region the first-discovered examples were referred to the genera Inoceramm and Lima, re- spectively, and their relation to the Aucellax of the eastern hemisphere was not then suspected. Shells of this genus have been found at various other localities and have been referred to by various authors in their publications, but the foregoing references are sufficient to indicate the wide geographical and the interesting circutnpohir range of the genus. While the distinguishing generic features of the shells which have been found at all these widely separated localities in the northern hemisphere are constant, the range of variation in subordinate features, especially size and shape, is so great that no less than nine specific and several varietal names have been proposed by different authors who have studied them. Tue figures on the accompanying plates have been prepared to show the extremes of the variations which have been observed and to illustrate the principal forms respectively which have been selected as types of the proposed species. If only those forms to which the respective specific names have been applied had ever been known, the real specific identity of each might not have been questioned. For- tunately, however, Aucella having been a gregarious inolhisk, great numbers of speci- mens have usually been found wherever any have been discovered, except at the New Zealand, Brazilian, and Indian localities. Consequently, so large a number of inter- mediate varietal forms have been found that I do not hesitate to express the opinion that none of the proposed species can be clearly diagnosed from the others, nor to treat as a specific unit all the forms referred to, with perhaps the exception of the Indian, Brazilian, and New Zealand examples. It frequently happens that all or the greater part of the specimens found com- mingled in any given layer agree closely with some one of the recognized specific forms ; and it is also true that two or three of those forms aiv often found commingled in one and the same layer. It thus often happens that a collection of these shells made at one locality or in one neighborhood is found to contain representatives of more than one, and sometimes of the greater part, of the forms which have been recognized as species by different authors. These representative forms have usually been selected by authors lor reference and illustration, while little mention has been made of the intermediate forms. That the foregoing statement is correct appears from the pub- lications of the various authors referred to, and it also accords with my own obser- vations upon the collections that have been made in North America. In view of the facts just stated, the conclusion seems to be necessary that all the forms of Aucella which have yet been discovered, especially those of the northern hem- isphere, have so close a genetic relationship with one another as to hardly exceed the 1 E. Eichwalil: Geognost.-palaeont. Boiuerkuugcn liber die Halbinsel Mangischhik mill die aleut- ischeu Inseln, pp. 185-187, PI. XVII, Figs. 1-17; P. Fischer: Voyage alac6tonord-ouestdt< I'Ame'rique, par M. Alph. Pinart, pp. 33, PI. A, Figs. 4 and 5; C. A. White: Hull. U. S. Geol. Survey No. 4, pp. 10- 14, PI. VI, Figs. 2-12. ' 2 J. F. Whiteaves: Proc. Trans. Royal Soc. Canada, vol. 1, 1883, p. 84. 3 W. M. Gubb: Geol. Survey California, Paleontology, vol. 1, 18(!4, p. 187, PI XXV, Fig. 173; ibid., vol. 2, 1868, p. 194, PI. XXXI, Fig. 92; Proc. California Acad. Nat. Sci., vol. 3, 1885, p. 173; F. B. Meek: Geol. Survey California, Geology, vol. 1, 1865, p. 479, PI. I, Figs. 1-5; C. A. White: Hull. U. S. Geol. Survey No. 15; G. F. Becker: Bull, U. S. Geol. Survey No, 19. REMARKS ON THE GENUS AUCELLA. 229 limits which may be reasonably assumed as those of a single species. Professor von Zittel recognized the close relationship of the New Zealand form with A. concentrica, 1 found the Brazilian form to differ from the latter in hardly a greater degree, and Stoliczka's Indian species is evidently closely like certain varieties of A. concentrica. It may be, therefore, that we ought to regard- this relationship as extending to the Aiicellas of the southern hemisphere and possibly also to the Indian form, although the latter comes from strata which we seem bound to regard as of considerably later age than the others. Admitting this close genetic relationship of all the known forms of Aucella, it is necessary to further conclude that they have beeu dispersed from some geographical center. The only published reference to such dispersion that has come to my notice is a brief suggestion by Mr. A. Pavlow that in Russia they were derived from the north, 1 but this does not fully meet the broader question of circumpolar and still more extensive distribution. Having been dispersed from a single geographical center, the strata which bear the remains of the original colony are necessarily older than those which bear the re-' in lins of the colonies which were last established before the extinction of the genus to the extent of the time which was occupied by the dispersion and colonization. If, therefore, the dispersion was primarily from the north, the northern Aucella-benriug strata are necessarily older than the more southerly ones, and, if subsequent dispersion was from the eastern to the western hemisphere, the eastern strata referred to are neces- sarily older than the western. I think our present knowledgeof this subject is too meager to warrant any definite statement as to the directions in which dispersion has occurred: but the geographical distribution of this assumed single species is so extremely wide and its climatic range has been so very great that the time required for its dispersion may easily have extended from the closing epoch of the Jurassic into the Neocomian epoch of the < 'retaceous, and there are apparently good reasons for believing that such was really the case. The genus Aucella has beeu regarded by the majority of authors who have written upon it as diagnostic of the Jurassic age of the strata which bear it; but certain authors whose opinions are worthy of consideration are equally confident that all such strata should be. regarded as of Neocomian age. Professor vou Zittel refers his A. plictitit from Xew Zealand to the "Jura or Lower Cretaceous." The form described by me (op. cit.) from the province of Sergipe, Brazil, under the name of A. Irazilien is, is from strata that I have referred to the Xeocomian and there seems to be no possible reason to question the Cretaceous age of the Indian species described by Stoliczka. It is Profosor Eichwald more especially who has contended for the Neocomian age of the .1 Ht-illit -bearing strata of Europe and northern Asia, and he also makes the same claim for those of Alaska. Mr. Whiteaves (op. cit.) is equally confident of the Cre- taceous age of the Ana //((bearing strata of British Columbia. In California, although a part of the strata which bear A ncr.Ua have been referred to the Jurassic, those which bi-ar these shells most abundantly have been referred by all the geologists who have studied them to the Shasta group of the Cretaceous series, and there seems to be no good reason to doubt the correctness of that reference. 1 Bull. Soc. golngii[iie France, :iil series, vol. 12, 1S84, pp. GS4, p. 187, PI. 25, Figs. 173, 174. 2 Proc. California Acad. Nat. Sci., vol. 3, 1868, p. 173. 3 Geol. Survey California, Paleontology, vol. 2, ItW, p. 191, PI. 32, Fig. 92, a, l>, c. 'Geol. Survey California, Geology, vol. 1, 1865, pp. 479, 480, PI. I, Figs. 1,2,3, 4, and 5. ' ]>cr Jura, p. 501, PI. f.7. Fig. 2, and p. 582, PI. 73, Fig. 47. "Pal. Imlica, vol. 3, index, p. 513. THU UNI7ERSIT7 U. a. GEOLOGICAL SURVEY MONOGRAPH XIII PL -III 1 EUROPEAN AND OTHER FOREIGN FORMS OF AUCELLA. REMARKS ON THE GENUS AUCELLA. 231 sphere, with perhaps the exceptiou of the species from southern ludia. If that view is to be accepted without qualification, some one only of the various names which have been proposed must be selected to designate that widely variable species. A common custom among naturalists in such cases is to take the specific name first used or pro- posed by the author of the genus, which is finally recognized as the true one. But I do not think the judgment of subsequent naturalists who have availed themselves of con- stantly increasing knowledge should always be hampered by rigid rules of this kind I have therefore selected the specific name concentrica to be used in ordinary cases, because the form to which that name is applied appears to have been the first one dis- covered and also because it is more generally prevalent than the one to which Keyserling gave the name pallasii, although he placed the latter name first under the genus Aucclla. But in referring now to the various forms here illustrated I shall use the names which the different authors have applied to them. The figures on PI. Ill are mostly copies of those which represent the different forms that have been recognized in Europe, together with those fcorn southern India, New Zealand, and Brazil. Those upon PI. IV represent North American forms, a part of them being copies of figures previously published and a part having been prepared for this occasion. PLATE III. FIG. 1. A copy of Keyset-ling's figure of Amelia concentrica, from Reise in das Petschora-Land, PI. XVI, Fig. 16. FIGS. 2 and 3. Copies of Keyserling's figures (loe. cit., Figs. 13 and 14), representing A. concentrica var. sublturis. FIGS. 4 and 5. Copies of Keyserling's figures of A. crassicollis (loc. cit., Figs. 9 and 11). FIGS. 6, 7, and 8. Copies of Tullberg's figures of A. mosijuensis, from Nova Zembla (Biliaug till kongl. svensk. Vet. Akad. Handl., vol. 6, PI. II, Figs. 10, 17, and 18). These figures are regarded by Tullberg as representing the form which Koyserling gave as the type of A. mosqitensis. Keyserliug fig- ured only the right valve of one example, and, as the left valve was not illustrated, several anlhors be- sides myself have hitherto regarded A. mosquensls as having a more elongate form. Specimens having the beak of the left valve so short and so slightly prominent as is shown by Tullberg's figures have not often been observed in North American strata. FIG. 9. A copy of one of Keyserliug's original figures of his A. pallaiii (loc. cit., Fig. 4). The ra- diating linos shown ou this figure are often, but not always, observable on this form. They are some- times observable on the other forms, but are more often absent. FIGS. 10 and 11. Opposite views of a specimen in the U. S. National Museum from the vicinity of Moscow. It appears to belong to the form A. pallasii. FIGS. 12 ami 13. Opposite views of another example from near Moscow, presented to Dr. Becker by Professor Holzapfel. It may perhaps be regarded as a variety of A. pallasii, although some authors would probably regard it as quite as near to A. moK<]iifiifin. This uncertainty of specific recognition l>y different authors is of itself an indication of the instability of all the forms which have been des- ignated as species. FIGS. 14, 15, and 1C. Copies of Professor von Zittel's figures of his A. plicata from New Zealand (Reise der osterreichischon Fregatte Novara, Geol. Theil, vol. 1, part 2, Paleont., p. 32, PJ. VIII, Figs. 4, a, b, c). FIGS. 17 and 18. Copies of original figures of A. Iraziliensit White (Contribuicoes a Palaeontologia do Brazil, Archives Mnseu nac. do Rio de Janeiro, vol. 7). The narrow, rough seam along the middle of the figure is a mineral vein, and not a natural feature of the shell. I'n.s. 19 and 20. Copies of Stoliczka's figures of his A. parva (Pal. Indica, vol. 3, PI. XXXIII, Figs. 2a and 3). PLATE IV. FIGS. 1 and 2. Copies of Gabb's original figures of his Inoceramut [Aucella] Piochii (Geol. Survey, California, Paheontology, vol. 1, PI. XXV, Figs. 173 and 174). 232 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. FIGS. :i, 4, and 5. Copies of Gabb's subsequent figures of Aucrlla 1'iocliii (Gcol. Survey California, Paleontology, vol. 2, PI. XXXII, Figs. 92, 92), it is rloar that the upper surface of the anticlinals will tend to crack open and also that a similar tendency will exist in the lower surface of the synclinals. If metamorphism is then induced by rising waters holding mineral matter in solution, such as silicic acid, the compressed under surface of the anti- clinal will offer a resistance to percolation, while the fractured under sur- CHICO-TEJON SEEIES. 237 face of the synclinals will afford paths of least resistance. Metamorphism thus induced will therefore affect the synclinals more than the anticlinals, and, if erosion follows, not only will tlie relief and the fractured surface of the anticlinals tend to their degradation, but the resistance of the synclinals will be increased by the silicih'cation and cementation of the mass. It is quite conceivable that the combined effect of plication and metamorphism as here imagined should be such as to result in a much more regular mod- eling of the surface by erosion than would have been induced had either plication or metainorphisin alone influenced the course of degradation. 1 The chico-Tejon series. Toward the southern end of the map the Chico-Tejoii scries appears. It consists chiefly of soft sandstones of a tawny hue where exposed to oxidizing influences, but bluish in color below the water-line, as is usual with sediments containing a small amount of iron. This series, though tilted and disturbed, is not crushed or plicated like the older strata to the north. It also includes conglomerates full of metamorphic pebbles, in some cases showing an unusually brilliant polish. These pebbles are highly siliceous and on this account do not at first sight appear to resemble the extensively developed metamorphic series. In cases of this kind, how- ever, it is necessary to remember that even feldspathic rocks are rapidly disintegrated in moving water and that quartz is almost the only mineral which will long retain the form of pebbles. Concretions are common in these rocks, occasionally with fossil nuclei, but usually without any dis- tinguishable nucleus. They sometimes weather more and sometimes less rapidly than the rock in which they are embedded and are often composed of concentric shells. Some argillaceous deposits and a little limestone occur in this formation. The Chico-Tejon series of this region is fos- siliferous, though organic remains are by no means generally distributed through it. Mr. Gabb collected a considerable number of fossils here, and so also did my party. The Chico-Tejon series does not come in contact with the metamorphic rocks in such a way as to demonstrate a non-conformity, alluvium arid lava intervening on the surface ; but the sudden change in lithological character and the comparatively trifling disturbance of the unmetamorphosed rocks 1 See Daua, Manual of Geology, p. 750. OF USIYERSIT7 238 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. are sufficient to suggest a non- conformity. When this relation lias been shown to exist elsewhere it is manifest that it affords a satisfactory explana- tion of the facts at Clear Lake. No Miocene strata have been detected with certainty in this part of the country. It is possible that such were deposited and have since been completely removed by erosion ; but this appears to me very unlikely. Remnants of them would almost inevitably have been preserved, if not elsewhere, at least beneath the fresh-water Pliocene. I believe it much more probable that a gradual rise of this region took place in the early Tertiary, such as has occurred in recent times throughout the State, and that during the Miocene this was a land area. No violent uplift can have intervened between the Tejon (Eocene) and the Miocene, however; for, wherever the two come in contact, as is frequently the case to the south, they almost always appear entirely conformable. First andesitic eruption. After the deposition of the Cliico-T ejon rocks the first geological event traced was the eruption of Chalk Mountain. This was probably coeval with the ejection of some of the rock near Thurston Lake. These lavas are dense. pyroxene-andesites, which have been described in Chapter IV. Chalk Mountain lies upon the north fork of Cache Creek, about half a mile above the highest point of the creek shown on the map. It is a small conical hill, from a part of which the heavy bases have been extracted by sulphur springs, still feebly flowing. Portions of the mass are fresh, however. Chalk Mountain rests upon crumpled, metamorphic strata, which were deeply eroded before the ejection of the rock. The outflow of this rock certainly preceded the Cache Lake period, for the lake beds are found upon its sides, and fragments, either from Chalk Mountain or from other unknown masses of precisely similar Hthological character, are abundant throughout all the lake beds shown on the map. Chalk Mountain may have somewhat antedated Cache Lake, but there is as yet nothing to indicate an interval, and it seems more probable that its eruption accompanied the orographical changes which in the Pliocene, and probably early in that period, dammed back the waters of the region. cache Lake beds. That Cache Lake occupied an extensive area is certain. It extends to the east an unknown distance, and how great a proportion PLIOCENE DEPOSITS. 239 of it is included in the map has not been ascertained. These beds consist, first, of conglomerates, carrying pebbles of metamorphic rock identical with that which underlies them, and of pyroxene-andesite which cannot be discriminated from that of Chalk Mountain; secondly, of s..ind beds; and, thirdly, of argillaceous and calcareous deposits. For the most part the strata are but little compacted and may be reduced to powder in the hand; but there are frequently nodular masses which are consolidated to firm rock. Some of the bluffs of conglomerate for example, those in Grizzly Canon are stud- ded with such nodules, distributed somewhat uniformly over the surface. Elsewhere single strata of sand or clay are petrified, and occasionally, as on Perkins's Creek, considerable areas of sandstone fully solidified are met with. The impression conveyed by the prevalent distribution of the more extended and irregular, hardened masses is that they represent, the local action of cold, calcareous or siliceous waters upon the surrounding rock, an action which, if sufficiently prolonged, would result in the complete pet- rifaction of the whole system of beds. A similar effect of mineral springs on recent deposits may be seen at several points in the district, particularly along Sweet Hollow Creek. The isolated nodules cannot be produced in this way and, like those in the Chico of New Idria, they are probably due to the decomposition of organic matter, as explained in Chapter III. The Cache Lake beds have been subjected to comparatively little dis- turbance. They are tilted at angles varying from 10 to about 40, but the inclination seldom changes rapidly, and there is very rarely anything which can be regarded as contortion. Within the area of the map, too, no faulting was traced, though more or less important disturbances of this nature occur near Chalk Mountain and on the north fork of Cache Creek, east of the map limit. The thickness indicated by measuring the strata perpen- dicularly to the planes of stratification is very great some thousands of feet. I confess myself unable either to comprehend this or to ignore its significance. There i.s certainly no confusion between these beds and others of marine origin, since fresh-water shells were found in them at widely separated horizons; but the accumulation of several thousand feet of sediment in any lake except one of vast dimensions seems an impossi- bility. A careful search was made for faults without finding any. The 240 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. probabilities, however, seem to me in favor of tlie supposition that these really exist, but thus far have escaped detection. Even on this assumption I believe it impossible to reduce the estimate of the thickness of this deposit below 1,000 feet. cache Lak= fossils. The argillaceous strata of the Cache Lake period are full of organic remains, but unfortunately these are chiefly vegetable. Shells were detected in only four localities: on the Grizzly Canon road near the top of the divide between Burns's Valley and the north fork of Cache Creek; at an exposure on the hillside about a quarter of a mile north of this point; close to the mouth of Indian Creek; and in an exposure on Cache Creek a quarter of a mile below its intersection with the road from Lower Lake to Sulphur Bank. Of these the first and second are much the richest. They show a series of mollusks, the most important of which are identical with those now abundant in Clear Lake, while all of them survive on the Pacific slope, and not improbably in Clear Lake itself. They have been enumerated and discussed in Chapter V. According to Mr. Stearns, who is unquestionable authority on this subject, they show that the physi- cal conditions prevailing in Cache Lake were not markedly different from those of the present Clear Lake. The peculiarities of form of one of the shells, the ordinary Anodon of Clear Lake, are also such as to show that in spite of the difference of position and notwithstanding the very great oro- graphical modification which the country has undergone, there has been an absolute continuity of life from the Cache Lake period to the present time. No doubt mollusks, and particularly locomotory species like this AnotJon, are able to survive tolerably vigorous disturbances, but the facts show that from a faunal point of view the elevation of these lake beds was not cata- strophic. In spite of careful search vertebrate remains were found in only two localities. These points are a small side ravine leading into Grizzly Canon from the north and a vineyard near Lower Lake. other characteristics. As might be expected from the character of the Cache Lake deposits, they are extensively eroded. In many cases the resulting forms are strongly suggestive of those of the Bad Lands of Wyoming, showing fantastic pinnacles, pillars, and gorges. This is especially notice- able north of Chalk Mountain and in Cub Gulch. In most portions of the PLIOCENE DEPOSITS. 241 area the erosion lias been largely controlled by the stratification, and the resulting hills show straight slopes on one side parallel to the stratification and abrupt declivities on the other where the strata have been broken through. As seen from the Grizzly Canon road about two miles south of the north fork of Cache creek, a succession of such hills might be taken for a series of monoclinal uplifts. Near the stream the Cache Lake strata have also been extensively terraced. But, while the erosion of these beds has been considerable, when their prevalent earthy character and exposed position are taken into consideration it is clear that, geologically speaking, they must be comparatively recent, since otherwise they would long ago have been washed entirely away. On and near the north fork of Cache Creek the lake beds are covered unconformably by a deposit of gravel usually 50 feet or less in thickness. This is somewhat obscurely stratified, unconsolidated, and has been tilted, though less than the underlying lake beds. It presents no strata in which there would be any hope of finding fossils and its origin is not certain. It may possibly represent the very last stages of Cache Lake, or, as seems to me more probable, the earliest river deposits after the close of the Cache Lake epoch. The lake beds can best be studied in the eastern corner of the area mapped, for in the volcanic areas near Lower Lake the strata have been considerably altered. Especially is this the case near the andesite, which lies upon the Cache Lake beds conformably and has produced a decidedly metamorphic influence upon them. Tin's consists in depositions of calca- reous matter, silica, and ferric hydrates, apparently through the action of hot springs or of water heated by contact with the volcanic rock, rather than by the direct influence of the heat of the lava. Similar results are noticeable where the basalt has come in contact with the lake beds; for ex- ample, near the lime kilns, northeast of Burns Valley. The metamorphosed lake deposits yield a red soil full of white masses of calcareous rock, which is said to be extremely fertile. Relation of cache Lake to clear Lake. As may be seen from the map, Cache Lake overlapped the area at present occupied by Clear Lake, while, as Ir.is been pointed out, the identity of the shells in the two find other circumstances MON xm 1G 242 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. show that their history must have been continuous. The later andesite, represented by Mt Konocti, overlies the latest Cache Lake strata and also underlies the Clear Lake sediments. It is impossible to avoid the conclu- sion that the erupt ion of this rock accompanied the obliteration of Cache Lake and the orographical changes which confined the waters to their pres- ent bed. The vertebrate remains in the vineyard near Lower Lake thus fix the geological date at which the Cache Lake period terminated and also the date of the eruption of the asperites of Mt. Konocti. As was noted in Chapter V, the vertebrate fossils are Pliocene, while the amount of erosion and the relations to the modern lake beds show that they are Upper Plio- cene. The date of the eruptions is thus fixed at about the close of the Pliocene epoch. Later andcsitic eruption. The later andesite is most prominently represented by Konocti (or Uncle Sam) Mountain, but the same rock covers a large area to the southeast and a considerable tract to the northeast of the more southerly branch of the lake. It is described from a microscopical point of view in Chapter IV. The prevalent variety of the rock is a coarse- grained porphyry, sometimes dark and sometimes rather light colored. One of its marked features is the frequency of laminated structure. 1 The laminae are usually half an inch or more in thickness and not very sharply divided from one another. Weathered surfaces of such rock are corrugated, and at a little distance the rock might be thought sedimentary rather than volcanic. Where heavy masses are cut through, columnar structure is sometimes seen. It rs particularly fine near Little Borax Lake. Between Konocti and Thurston Lake there are also vast quantities of obsidian and pumice, the former covering almost continuously a large tract, through which the road from Kelseyville to Lower Lake passes. On this line it is about four miles in width and it is said to extend a still greater distance to the southwest. The best locality for the study of these forms is on Thurston Creek, between one and two miles northwest of Thurston Lake. Here the obsidian and pumice are inter.bedded with the porphyritic ande- 1 In Geol. Survey California, Geology, vol. 1, p. 96, Professor Whituey states that, as seen from the opposite side of the lake, Uncle Sara appears to be made up of a closely folded, synclinal mass, prob- ably of somewhat inctaiiiorphic Cretaceous sandstones. This impression he certainly received from the exposed cd^f.s of these flows. In Auriferous Gravels, p, 23, this mountain is correctly mentioned Dfi volcanic. ASPEKITB. 243 site, all being intermingled, often with the accompaniment of transitional forms. In some cases nodules of obsidian are immediately inclosed in con- centric layers of pumice and vesicular obsidian, while in other instances angular fragments of obsidian are directly embedded in structureless pumice. In this locality the stream has cut through solid obsidian, leaving sheer walls ten or more feet in height. Elsewhere in the district this glass is rarely found exposed in place, owing to its tendency to break up into small fragments which cover the surface. The andesitic obsidian is usually dis- tinguishable with ease from basaltic glass by its higher and more resinous luster and its greater opacity. The andesitic origin of this glass is demon- strated by its manner of occurrence. The microscopic character agrees with this reference. About three miles from Kelsey ville, on the Lower Lake road, and again a little northwest of Thurston Lake, stratified, andesitic tufa is found The former occurrence is very considerable and of course indicates the presence of water during the eruption, though Cache Lake beds have not been rec- ognized in the neighborhood. The presence of ponds or lakes near volca- noes is of course a usual phenomenon, due to the damming back of streams by ejecta or to more or less important orographical changes. Age of the younger andesite Excepting tll6 bed of Clear Lake, the whole region has been undergoing erosion ever since the andesitic eruption, and the surfaces of the flanks and peaks of Konocti show that the degradation has been considerable. There is no recognizable trace of a crater on the peak; on the contrary, the bedded flows of rock near the summit are shown in cross section. Sufficient time has elapsed since the eruption to permit considerable decomposition in exposed masses of rock. The sum- mit, however, is more exposed to degradation than the general surface of the country, which has been little lowered in recent times, the underlying metamorphic Cretaceous and Pliocene rocks, where they have been pro- tected by the andesite, not lying perceptibly above the ordinary level. The main area of andesite southwest of the lake probably overlies metamorphic hills, for ajtered Cretaceous strata appear under the volcanic rock at the ex- tremity of Elgin Point (" Snake Rocks") and at Bailey Point. 'The pres- ent topography of the country between Konocti and Thurstou Lake is 244 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. scarcely intelligible except upon the supposition that its principal features are due in great measure to those of the original lava surface ; for it presents a series of elongated basins either without apparent outlets or with only very narrow, sharply cut outlets, and these depressions either contain permanent lakes, like Thurston, or winter pools, like some others in the neighborhood, or present flat surfaces of fine soil, evidently the result of the silting up of lakes. These areas of sedimentation, flanked as they are by massive ridges of lava, cannot be due to erosive agencies, and there is nothing whatever to indicate that they are due to orographical changes postdating the andesite eruptions. Thurston Lake. Thurston Lake is a peculiar body of water, surrounded on three sides by heavy masses of andesite, with high and steep slopes. On the fourth side, toward the northwest, the lake bottom rises at a very slight angle and merges into an elongated valley of considerable length. The addition of a few feet of water would double the length of the lake in this direction, while adding almost imperceptibly to its extent elsewhere. The water marks show that the height of water varies about eleven or twelve feet. In spite of its lack of any visible outlet, this lake is fresh and abounds in animal life, some of the fish being apparently of the same species as those of Clear Lake. Its fluctuation is also sensibly the same as that of Clear Lake, and, as nearly as can be estimated without a special survey (a task which the dense brush would render very expensive), its level is the same. The only probable explanation of these facts would seem to be that there is an underground passage between the lakes a supposition in which there is no inherent improbability, since channels such as that supposed frequently exist in volcanic masses, especially within a moderate distance of their original surfaces. Little Borax Lake. As has been seen, there is much structural evidence to show that the andesitic rock of Konocti Mountain is not recent, but that it is geologically of late origin. The surroundings of Little Borax Lake, how- ever, seem to indicate a local activity long postdating the andesitic erup tion. This little saline body of water lies in a crater-like depression at the foot of the mountain, a portion of the walls being very abrupt and evidently representing fractured surfaces, while the basin itself contains very little MINES IN ANDKSITE. 245 detritus. Were it a crater anything like so old as the mass of the mountain, an outlet would almost certainly have been cut through the low swell of land separating it from Clear Lake on the east and much material must have fallen into the basin from the perpendicular cliffs of columnar andesite to the south. On the other hand, there seems to have been no outflow of lava, either andesitic or basaltic, from this basin. There is, moreover, evi- dence that Elgin Point has been considerably raised in very recent times, and it appears probable that the basin of Little Borax Lake was formed by an explosive outburst, which was nearly or quite contemporaneous with the basalt eruptions to the southeast. A partial renewal of volcanic activity on the old line of eruption at a period of volcanic disturbances in the im- mediate neighborhood is certainly nothing to be wondered at. The origin of the borax in this lake is no doubt entirely similar to that of the borax in the other and more important lake near Sulphur Bank, which will be dis- cussed in the next chapter. There are now no hot springs flowing into it, though there are warm springs associated with the andesite at several other points. Quicksilver deposits in andesite. At two localities on the southern side of Mt. Konocti cinnabar has been found. One of these is close to the base and was known as the Bowers mine. It is abandoned, and all that could be made out from the accessible workings was that the associated andesite is quartzose and is bleached by solfataric action. The Uncle Sam mine is high up on the flank of the mountain. It, too, is in dacite, much decomposed, as if by the action of heated waters or gases. A considerable quantity of ore was formerly extracted at this point and sold to the Sulphur Bank Company, but statistics were not obtainable. It is possible that the dacite eruptions were later than the mass of the mountain and that the solfataric action accompanying the outflows of this rock induced the deposition of ore, but no conclusion on this subject was reached. It is certainly remarkable that the only dacite occurrences known in the district are thus associated with the only quicksilver deposits known among the andesites. Basaltic eruptions. The eruptions of basalt of the Clear Lake region were greatly inferior in volume to those of andesite, oven more so than would 246 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. appear from an inspection of the map, for, owing to the greater fluidity of the lava, the basalt fields are of less depth than the andesitic masses. While, too, some general orographical changes appear to have accompanied the emission of basalt, as was almost inevitable, these were far smaller in amount than those which closed the Pliocene epoch. The basalt of the region under discussion is a fairly typical rock, pre- senting the usual structural peculiarities and mineralogical composition on the whole, though the distribution of olivine is irregular. In some occur- rences this mineral forms a large percentage of the whole mass, while in others considerable search with the lens, or even with the microscope, must be made to detect it. Very interesting glassy forms of basalt occur near Borax Lake, of which farther mention will be made in the next chapter. It does not appear that all the basalt was emitted at the same time, or even approximately so, for the evidences of erosion on some of the areas are very perceptible, while on others there has been no considerable degradation. On the whole, the basalt must be considered as decidedly recent, for only on that supposition can its state of preservation be accounted for. Thus, McPike crater is a rounded mass, unfurrowed by rivulets, at the top of which is an extremely regular, basin-like crater about nine hundred feet / o in diameter and fifty to one hundred feet deep, presenting a surface entirely covered with lapilli. That this basin contains no water is probably due to the porosity of the sides, which seem to be composed of lapilli. The walls are unbroken and vegetation has only begun to find root between the peb- bles. The only sign of age is the fact that the surfaces of the lapilli are reddened with ferric oxide. On the hills directly north of McPike crater the surface is covered with lapilli, which almost entirely conceal the under- lying metamorphic rocks. These pebbles could not possibly have been transported to their present position by water, which, on the contrary, must eventually sweep them down into the valley. In fact, they appear to have fallen as they lie during an eruption, since which there has not been suffi- cient rainfall to remove them. The north and south craters at Sulphur Bank are similarly fresh, excepting that in each case one side of the crater is broken down; but there is no evidence that this is a result of erosion, for there is no stream bed or dry wash leading into them. Close to the BASALT. Sulphur Bank, on Indian Island, on Red Hill, and west oFTIbwer Lake contorted masses of lava remain on the surface, where they chilled after oozing from vents or from cracks in the lava streams. It is also indicative of the lateness of the basalt eruptions that fragments of the rock are usually to be found only in the immediate neighborhood of the main areas. There does not seem to have been time enough since the eruptions to effect any general or even widespread distribution of pebbles. At Sulphur Bank it is also said that the Indians have traditions of eruptions. While this fact might have little significance were any portion of California now the seat of volcanic activity, it seems not without weight when it is remembered that the nearest volcano now active is very far away. At all events, it seems to me by no means impossible that the latest eruption may have occurred within a thousand years or even less. The relations of the basalt areas to the general structure of the under- lying metamorphic rocks are not easily studied, for lack of exposures. I have endeavored to make out the fissure system which no doubt connected the various vents of the basaltic eruptions, but have failed to reach any sat- isfactory conclusion. There are but two places in the district where basalt tables occur. Of these one is at the extreme eastern end of the McPike area, where the lava appears to have followed the bed of the north fork of Cache Creek and to have been subsequently undermined by the stream. The rock has fallen off in columns, leaving perpendicular walls. The other bluffs are com- prised in the area northeast of Red Hill, and, like all similar occurrences, are a result of undermining. In both cases I can but suppose that the lava represents much earlier eruptions than those which left the unimpaired cra- ters nearer the Sulphur Bank, though they are both Post-Pliocene, resting unconformably upon the uplifted Cache Lake beds. ciear Lake. Both the topography and an examination of the soils show that Clear Lake formerly occupied a considerably greater area than it now does. The flat land about Sulphur Bank once formed a portion of the lake bottom, and Avould again do so were the lake to rise 50 or 70 feet. A much smaller rise would flood the valley now in part occupied by Borax Lake, the surface of which is but a few inches above the level of the lake. 248 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. This valley must once have been much deeper than now and in part have silted up. Burns Valley, an area near the town of Lower Lake, the whole of Big Valley, and portions of the country about Upper Lake, as well as many small flats along the lake shore, .are clearly also covered with recent lake deposits. The causes which might have produced this shrinkage of the surface of the lake are erosion of the outlet or orographical changes, or both. Had the lake bed only been tilted to the southeast, the tendency would have been to expose the bottom to a considerable depth at the west end, but not near Lower Lake. Orographical changes alone are consequently insuffi- cient to explain the exposure of the meadows. Cache Creek, just beyond the limits of the map, passes through a narrow gorge of Cretaceous sand- stone, and the mere erosion of this barrier would produce the effect under discussion, but there is some evidence to show that orograplncal causes have influenced the grade of Cache Creek and consequently its capacity for eroding its bed. On the north fork of Cache Creek the banks are ex- tensively terraced and four or five flood plains are distinctly visible. This appears to mean a tilting of the country to the 'eastward, though probably to the extent of only a very few inches to the mile. Such a widespread secular change would increase the velocity of Cache Creek, as well as of its northern fork, and accelerate the erosion of the sandstone gorge near its source. Were the circumstances more favorable, such a change, if it really took place, might be detected on the banks of the lake, which would also be terraced. Two causes seem to have stood in the way of such a modification of the shore. The first of these is the resistance offered by the sandstone of the gorge, which would yield but slowly to an increased velocity of a current carrying little sand in suspension. It is well known that the erosive power of lake water is slight because it is so free from sand, and the erosion of the gorge would probably be still slower than it is were it not for the fact that Herndon Creek flows into Cache Creek between the lake -and the gorge. The second influence tending to prevent the for- mation of terraces is the tule belt. A strip of these reeds, from a few feet to a few yards in width, grows almost everywhere along the lake shore, CHANCES OF SURFACE. 249 separated from the beach by a few feet of open water. Even when the lake is in a state of very considerable agitation scarcely a ripple reaches the shore thus protected, and not only is the erosion of the banks in great measure prevented, but sedimentation is favored, so that in some places the shore appears to be growing into the lake by the accumulation of tule roots and sediment. On the whole, therefore, the lowering of the lake level in comparatively recent times is not improbably the result of the ero- sion of the bed of Cache Creek, assisted by a very gradual and gentle tilt- ing of the whole region toward the east or southeast. Certain limited orographical changes have unquestionably taken place about the lake in very recent times. At the end of Elgin Point is a steep bank, consisting of uncompacted strata of material precisely similar to that found on the old lake bottom areas at the Sulphur Bank, in Big Valley, and below the high-water mark of the lake. It consists of mud, in which pebbles of metamorphic rock and of later andesite are abundant. In the lower strata of this bank, which is about one hundred and fifty feet high, scoriaceous forms of andesite occur, which are no longer to be met with on the surface in the neighborhood. The southern side is a curved slope parallel to the planes of stratification and essentially unsculptured by wa- ter, and the bank would seem to represent an uplift of about the same date as the finely preserved craters near ' Sulphur Bank. If the hypothesis suggested with regard to the formation of the basin occupied by Little Borax Lake be correct, this uplift was probably its concomitant. These recent strata rest in part upon metamorphic rocks and in part upon the andesite which constitutes the main mass of Elgin Point. A very similar bank of the same date, but less well exposed for study, occupies the south side of the entrance to Upper Lake. It is the inevitable fate of lakes to be filled with sediments to a dead level, but, as the evidence seemed to be that the sediments of Clear Lake are not of great thickness, it appeared to me desirable to examine the to- pography of the bottom. Several hundred soundings were made for this purpose, the results of which are shown in the subaqueous contours on the map of the lake. From these it appears that the water is deepest near the narrows, as would be the case if the lake occupied valleys of erosion 250 QUICKSILVER DEPOSITS OF THE PAOIFIO SLOPE. between ranges which had attained essentially their present configuration prior to the formation of this sheet of water. The map, in accordance with the rules of the U. S. Land Office, shows the outline of the lake at high water. The subaqueous contours are referred as nearly as may be to the same level, or 10 feet above the lowest point which the lake has reached in ten years. This point was noted by Capt. R. S. Floyd, who has kept a full record of the level of the lake referred to throughout this period. The lake occasionally rises a little, more than 10 feet above low-water mark, but not enough to make any important differ- ence. CHAPTER VII. DESCRIPTIVE GEOLOGY OF SULPHUR BANK. [Atlas Sheet IV.] sedentary rocks of ths district. The results of a general study of the region of Clear Lake, undertaken for the purpose of throwing light upon the his- tory and geological relations of Sulphur Bank, have been presented in the preceding chapter. The area delineated in the detailed map of Sulphur Bank includes few formations. The underlying rock everywhere belongs to the Knoxville series (Neocomian), representing the opening of the Cre- taceous period. This rock was intensely crushed and irregularly metamor- phosed not long after its deposition, but neither the quicksilver deposits of this locality nor those of any other included in this memoir were formed at the epoch of metamorphistn. All the varieties of metamorphic rocks described in Chapter III occur in this small area, from almost unaltered sandstones up to material so highly recrystallized as closely to resemble an eruptive porphyry. Serpentine is also found in very small quantities on the ridge north of Borax Lake. It appears again near the end of Sunken Point, shown on Atlas Sheet III. The little spot of serpentine near Borax Lake might be shown on the- detailed map by a separate color, but the met- amorphism is so irregular in intensity that it would be quite impossible to delineate areas of pseudodiabase, pseudodiorite, and glaucophane schist. No eruptive rocks are interbedded in the metamorphic series at Sulphur Bank. This was established by careful observation in the field prior to the microscopical examinations. The latter showed that some specimens, so far as their microscopic character is concerned, might possibly be either ex- S51 252 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. treme members of the crystalline metamorphic series or true eruptive rocks. The region was revisited for the purpose of verifying the structural relations of these occurrences. The questionable rocks were then found to be sur- rounded by and to pass over into indubitable metamorphic material in such a way as to preclude any separation of them. The Sulphur Bank map shows no Chico-Tejon beds or Pliocene fresh- water strata and no andesite. Here, as elsewhere on Clear Lake, it is manifest that the level of the present sheet of water has sunk within no very long period, leaving fertile meadows. The composition, as well as the topographical relations of these meadows, shows that they are drained portions of the lake bed, for they are full of roots of the tule, which grows only near the water's edge and preferably in shallow water. Close to the basalt and in beds continuous with those which underlie the lava these roots are sometimes found petrified. Basalt. The only volcanic rocks on this map are basaltic, but their character and mode of occurrence are rather unusual and therefore interest- ing. They are in part olivinitic and in part free from olivine, but their microstructure is the same in both cases. In the area south of Borax Lake, just beyond the limits of the map, ordinary olivinitic basalt occurs. It adjoins a large field chiefly composed of obsidian and pumice, but contain- ing also rocks which, while manifestly in part glassy, have a thoroughly ba- saltic appearance. It is impossible to separate these occurrences in the field, and the more they are studied the more certain it appears that all this ma- terial is substantially from a single eruption. This is confirmed by micro- scopic examination, although the glass is an acid one, containing over 75 per cent, of silica (see pp. 158-162). The glass is usually of a gray color and is transparent even in masses a quarter of an inch or more in thickness. Between it and the pumice there is every conceivable gradation. The glassy forms sometimes include small fragments of crystalline basalt. This area is the only one in which this obsidian appears to be in place, yet the dissemination of chips of the same glass a square inch or less in area is something astonishing. In the immediate neighborhood of the obsidian field these chips are so plentiful that it is difficult to draw its outline with any accuracy. They gradually grow less abundant, but are still to be BASALTIC GLASS. 253 found beyond the crests of the hills surrounding the locality. Similar chips are occasionally met with all over the district; but this is in part due to human agency, for a spearhead of this glass was found miles away. Most such chips, however, are quite isolated and show no marks of artifice. Ex- plosions attending the eruption may account for the greater part of the frag- ments near the obsidian field ; how the more distant ones were transported I cannot guess Another feature of the basalt of this district, somewhat unusual in California, but not unknown in other portions of the State, is the formation of regular crater-cones. Dense basalts, when in a state of fusion, are prob- ably too fluid to build cones. Those at Sulphur Bank are composed of extremely porous basalt, much of it in the condition of lapilli. Each of them is broken through on one side, apparently by lava streams, not by water. The lapilli are more or less oxidized, but have accumulated no considerable quantity of soil and are not concealed by the scant herbaceous vegetation, though trees, particularly conifers, have taken root among them. Contorted forms of lava, too, are abundant at some of the croppings and everything points to a very recent date of eruption. General description of the bank The Sulphur Bank is an area exhibiting most manifest indications of solfataric action. It is not practicable to outline the exact area of decomposition, which, however, is substantially coincident with the southein half of the small basalt area in which it lies, including ' o all the more elevated portions of this area. The ore-bearing ground takes in a narrow strip of the sedimentary area to the south. The surface indica- tions of solfatarism consist in complete decomposition of a large portion of the basalt to a white, pulverulent mass, sulphur deposits, and hot mineral springs holding gases in solution. The locality was first worked for sulphur. At a distance of a few yards below the surface, however, cinnabar was found occurring with the sulphur, and lower still cinnabar was found in large quantities. The property has been worked for the most part by open cuts, with little regard to system. Jts appearance is very peculiar. The glare of white decomposition-products, the labyrinth of deep, open pits and trenches, and the acrid dust and evil smells of the locality produce a strong impression on the observer; but even to the geologist it is an interesting 254 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. rather than an agreeable one. Work in these cuts is so trying that few white miners have ever accepted employment in them a second day and almost all the labor is performed by Chinamen. origin of the basalt To my mind there is little question that the basalt of the Sulphur Bank was erupted on the spot. In the comparatively little decomposed portions of the area contorted forms and cindery masses of the lava still exist. This shows that it has experienced but little erosion. The two craters shown on the map are also extremely recent, as has been pointed out in the preceding chapter. Between the craters is a lava stream of very evident character ; but the lava is not continuous from the craters to the bank, the highest portion of which is over 50 feet above the level of the ground at the points of discontinuity. Had the basalt of the Sul- phur Bank come from the volcanoes, its original surface must have been lower than that of any point in the lava stream connecting the localities, and, if they were once thus connected, at least 50 feet of the rock has since been eroded. There is no ravine crossing the track of the flow to produce a local effect of this kind, and the surface indications entirely preclude the supposition that there has been any general degradation approaching such an amount since the basalt was extruded, or, indeed, any sensible amount of degradation. I look upon the hot springs as of volcanic origin and as a later phe- nomenon than the ejection of the basalt. There appears to be nothing to warrant the hypothesis that these springs were in action before the basalt eruption. On the contrary, the basalt lies upon recent lake deposits, some- times filled with tule roots, and a part of these are within the influence of the solfataric action, as is shown by their petrifaction. Had these springs existed for an indefinite time before the basalt was ejected the tule roots could not have grown. 1 Deposition of sulphur. The composition of the waters from different portions of the Sulphur Bank varies considerably, but that a large portion of them carry hydrosulphuric acid is evident from the smell. The formation of sulphur and sulphuric acid from hydrosulphuric acid by oxidation is one of 'These silicilieil roots of the tule (Scirpus Jaemtris) bear a strong resemblance to f'aitJiniles, and my specimens, in the absence of sufficiently full information, have been described and figured by Mr. Leo Lesquereux as a uew species of that geous (Proc. U. S. Nat Mil.-)., 1887, ji. :i(i). SULP11UK AT SULPHUR BANK. 255 the most familiar facts of chemical geology and of experimental chemistry. The relations of the two processes are readily seen from a therrao-chemical standpoint, for the reaction H 2 S + 40 = H-S0 4 liberates "207,500 calories and H 2 S+ 0-IFO + S liberates 59,100 calories. Hence if oxygen is present in excess, as it is at the surface of sulphur springs and in porous sinters partially saturated with solutions of hydro- sulphuric acid, this will simply be oxidized to sulphuric acid. But if oxy- gen is deficient, as it must be a short distance from the surface, a single atom of oxygen by combining with JfPS to 4H 2 SO' would produce only 50,375 calories, or 8,725 less than it sets free according to the second of the above reactions. Assuming, therefore, that the two reactions are ac- complished in nearly the same time, sulphuric acid will be formed at the surface of such a region as the Sulphur Bank and free sulphur below the surface. This is in correspondence with observations at sulphur springs the world over and with laboratory experiments. When sulphides of the alka- lis are present the reactions are more complex, but sulphur is also separated while hyposulphites are formed. There is thus nothing strange or novel in the occurrence of sulphur under the conditions present at Sulphur Bank. A portion of the sulphur occurring at the Sulphur Bank is formed by a slightly different reaction. Both on the surface and in the mine sulphurous acid may be smelt, and early in 1887 the odor of this gas was suffocatingly strong, even at some distance from the Hermann shaft. The sulphurous acid undoubtedly comes up with the other volcanic emanations, though per- haps not in direct contact with the hydrogen sulphide. Hydrogen sulphide and sulphur dioxide decompose mutually, forming water and sulphur. As a consequence, the timbers of the building above the shaft were coated with incrustations of sulphur crystals in February, 1887, and, at the Fiedler shaft as well, sulphur crystals had deposited in smaller quantity by the same method. sulphuric acid and its effects. The sulphuric acid formed at or close to the sur- face percolates downward to some extent and is eventually neutralized by free bases and by salts of feebler acids. The neutralization of the acid is chief! v effected bv the sodium carbonate broughtjw^EttejrJfcat waters and 256 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. aided by the ammonia. The basalt is attacked by the acid waters and no doubt by the sulphuric acid they contain. It is true that labradorite and augite are but little acted upon by acids in laboratory experiments, but this basalt has been exposed to the action of hot sulphuric acid for hundreds of years at least. Its resistance is also considerable, many kernels of fresh rock remaining in the decomposed envelopes. concentric decomposition. It is clear from numerous exposures that, after the basalt solidified at the Sulphur Bank, it was divided by cracks, marking in many cases a distinct though imperfect columnar structure. As usual, also, there were cross-fissures in the vertical columns. These cracks formed the passages by which the waters reached the surface and by which the acid formed at the surface became diffused. The solid masses of basalt sepa- rated by cracks from surrounding blocks were attacked from the outside by the acid waters. As decomposition progressed successive shells were formed, which grow more and more spherical as the centers are approached. This has been attributed to "ball structure" in the rock, but it appears to me unnecessary to assume any such predisposing cause, of which there is no other evidence in the structure of this lava either macroscopically or microscopically. It is shown in an earlier portion of this work (page G8) that this conformation is the natural result of the action of a corrosive fluid on a slightly porous, tolerably homogeneous material in .blocks which approximate to regular polyhedrons in form. The concentric shells which are so well developed here are themselves the results of the decomposition process and are not, in my opinion, pre-existing envelopes the presence of which has controlled the course of decomposition. Decomposed basalts showing this structure so strikingly do not occur, to my knowledge, else- where in California, though such are found in other parts of the world. An instance from Great Britain similar to that of Sulphur Bank is illus- trated by Dr. Geikie. 1 The ultimate residue, when the attack is complete, is almost pure silica. The depth to which the basalt has been decomposed by the acid waters varies in different exposures, and perhaps averages 20 feet. The limit is usually very sharply defined, and it may be considered certain that this 1 Text Book of Geology, 1st eil., Fig. 8(i. OCCURRENCE OF CINNABAR. 257 represents the permanent level of the alkaline waters prior to the beginning of mining operations. occurrence of cinnabar The mode of occurrence of cinnabar at the Sulphur Bank is interesting and significant. It does not occur in sensible quanti- ties at or close to the surface, but is found to a considerable extent mixed with sulphur in the lower portion of the zone of oxidation. The principal deposits are below this level. They are found in the more or less decom- posed basalt, in the underlying recent lake bottom, and in the Knoxville shales and sandstones. The cinnabar is associated chiefly with silica, in *> , part crystalline and in part amorphous. In the lava it appears as small seams, which commonly follow either the original cracks between the blocks or the concentric surfaces of the decomposed masses. In the lake deposits below the basalt the cinnabar is found as impregnations or irregular seams. In the workings from the Hermann shaft the ore occurs exactly as it does in most of the quicksilver mines of California, more or less completely fill- ing interstices in shattered rock masses. Sometimes ore of this kind has been found which was simply a brecciated mass of rock cemented by cin- nab*ar. The cinnabar in these cases has crystallized on the rock fragments, exactly as quartz often does, and frequently leaves hollow inclosed spaces. 1 To a small extent the more porous sandstones have been impregnated with ore. Besides quartz, iron pyrites and marcasite frequently appear in the gangue, calcite is not uncommonly also present, and small quantities of bitumen are often found. It is a fact of great interest that Dr. Melville has found small quantities of both gold and copper in the marcasite accom- panying the cinnabar. The inferences to be drawn from the mode of oc- currence of the cinnabar at this locality are not unimportant. The intimate association of the ore with sulphur, opal, quartz, pyrite, and to a smaller extent with calcite, is amply sufficient to show that it has been deposited from water. This would also be clear if the cinnabar were not accom- panied by and mixed with minerals which can have formed only in the wet way. The vuggs lined with cinnabar and the relations of the veinlets of ore to the fissure system of the rocks are of a character to convince any 1 See an illustration of such a specimeu iu Le Conte ami Rising's paper on this locality (Am. Jour. Sci., 3:1 scries, vol. 24, 1882, p. '.)). MON XIII 17 258 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. practiced observer that the deposition has taken place from solution, and not from vapor. The occurrence also limits the possibilities as to the origin of the ore. The formation of sulphur is still going on, and so also must be the decomposition of the basalt and the deposition of pasty hy- drous silica. The association of cinnabar with the sulphur and its deposi- tion along the concentric partings of the decomposed basalt blocks close to the fresh nuclei show that cinnabar is either now being deposited or that its deposition has ceased only very recently and must have gone on while the conditions were almost precisely those now existing. The copiously flowing springs which existed here before mining opera- tions began and the sulphur deposition show that the waters rising toward the surface come from a considerable depth. This must have been the case during the entire period of sulphur deposition. The ore cannot have leached downward from the basalt into the underlying rocks, nor can a trace of quicksilver be detected in the undecomposed basalt. Neither can the quicksilver have been derived from the layer of recent lake deposits un- derlying the basalt. This layer is thin, at least in places, and lies hundreds of feet above some occurrences of the ore. The original source of the quick- silver must then have been either in the Knoxville beds, chiefly sandstone, or below them. This sandstone is proved by microscopic examination to be arcose, or granitic detritus, and abundant evidence has been given in preceding chapters to show that granite underlies the Coast Ranges. The source of the quicksilver is consequently either granitic detritus or granite or it lies below the granite. Further than this the facts at this one locality do not justify conclusions as to the origin of the ore. soifatanc springs. A very remarkable feature of this mine is the abundance of hot springs, frequently carrying gases. These gases are often ammoni- acal and many of them carry sulphureted hydrogen. Others again have a nauseous smell which plainly indicates an organic origin. An analysis of gas from the Hermann shaft gave Carbon dioxide, CO 2 89.34 Hydrogen sulphide, H 2 S 0.23 Marsh gas, CH< 7.94 Nitrogen, N 2.49 Total.. 100.00 HOI WATER AT SULPHUR BANK. 259 On the southwest drift of the fifth level hot water and vapor are expelled from cracks with some force and with a noise resembling that of escaping steam. The quantity of steam condensed to a visible vapor, however, is not very great, and the thermometer stows only 80 C. (176 F.). The escaping gases smell of ammonia. This is the hottest water met with, though other springs show over 70 C. 1 composition of the waurs. It being clear that the cinnabar has come to the surface in solution under conditions little if at all different from those now prevailing, the composition of the waters becomes a matter of special in- terest. The following analyses show the composition of the contents of 1,000 cubic centimeters of hot water from two of the shafts in their prob- able combinations: Hermann shaft. Parrott shaft. Silica SiO* ... 03715 Ferrous carbonate, FoCO 3 00008 Calcium sulphate, CaSO 4 0^340 Calcium carbonate, CaCO 3 0350 05055 01890 Sodic carbonate Na 2 CO s 1 94675 Ammonium carbonate (H 4 N) 2 C0 3 00664 00 k> 8 Borax, XaB*O 7 1 87840 Sodic sulphate, Na 2 SO* Sodium chloride, NaCl 1 10^70 Potassium chloride, KCI k Fixed organic matter 00500 00760 Hydrogen sulphide H 2 S Carbon dioxide, CO 2 , 26^41 Total weight, grams .' 5 3G815 The simple instead of the acid carbonate of sodium is assumed in these analyses because the acid salt is at least in part dissociated in hot solutions. The sulphydric acid was combined to some extent as a soluble sulphide, but with what base it was united was not ascertained. Not a trace of mercury could be detected in solution, though, as will be. seen in Chapters XI and XV, waters very similar to these are certainly capable of dissolving cinnabar. Nature of the mercurifcrous solutions. 111 the hope of obtaining fui'tllCr light OU this subject Dr. Melville visited Sulphur Bank with chemical appliances 1 1 am not aware that mining operations have ever been carried on before where the inflowing water had so high a temperature as 176 F. The highest temperature which I observed in the Corn- stock was 170 F. 260 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. early in 1887. The most favorable opportunity for investigating the water at that time was presented at the Fiedler shaft, which communicates below ground with the Hermann shaft. Both had then been abandoned and water escaped from the top of the former into the lake. Its temperature was 128 F. (53J C.) and it was in a constant state of agitation from the es- cape of carbon dioxide and hydrogen sulphide. Large quantities of water were collected in new wooden pails and filtered hot. The filtrate on evap- oration and analysis showed all the substances recorded in the above anal- yses, and, in addition, alumina, manganese, cobalt, phosphoric acid, hypo- sulphurous acid, and some organic matter resembling humic or crenic acid. Repeated experiments showed not a trace of mercury, though the filtered water left small quantities of mercuric sulphide on the filter. This water under these physical conditions would thus appear to be incapable of dissolving cinnabar ; for otherwise the suspended sulphide must have been accompanied by the same substance in solution. This in- solubility is probably ascribable to the ammonia present; for in laboratory experiments we have found that different ammonia compounds precipitate mercuric sulphide from analogous solutions. It is not impossible that at pressures above one atmosphere ammonia compounds lack this precipitating power, and if the waters of Sulphur Bank were always amvuoniacal, as they have certainly been for the last twenty years, this hypothesis would account for the fact that no cinnabar whatever appeared at the surface of the Sul- phur Bank, the ore being met with only at a depth of several yards. It would also account for the mercuric sulphide in suspension in the water. The ores of the open cuts of the bank were also submitted to a care- ful examination, in order to ascertain the correspondence between their composition and that of the material dissolved in the waters. In immediate contact with the cinnabar all of the bases detected in the water were found, but neither chlorine nor boracic acid. A sufficient reason for the absence of these acids appears to be the solubility of the chlorides and the borates, which have never been found in any of the quicksilver mines beneath the surface, though at Knoxville and at Steamboat Springs borax exists in the waters, and it was very probably also present during the time of ore depo- sition at other mercuriferous localities. That the ores of Sulphur Bank have been in contact with solutions of chlorides and borates is very cer- DEPOSITS FROM HOT WATER. 261 tain, for the water of the mine carries a large amount of them, and, in the underground workings near ore, I collected efflorescences largely consisting of them, as was proved by analysis. Indeed, analyses of the salts crystal- lized out on the walls of the drifts showed all of the bases and acids de- tected in the water or the ore, excepting hyposulphurous acid, gold, and nickel. As cobalt was present in two cases, nickel might doubtless have been detected in traces. Hyposulphurous acid I suppose to result only from the oxidation of alkaline sulphides and gold is present only in very minute quantities in the marcasite. The waters as they reach the surface are far from being saturated solutions of borax or of alkaline chlorides, and there is no reason to assume any tendency for the metallic bases detected to decompose sodium chloride. On the other hand, sulphates of the alkaline earths are comparatively insoluble and might be deposited with the ore. Sulphuric acid has, moreover, constantly formed at the surface, diffusing downward to a greater or less extent. It is very likely that a large part of the sulphates now present in the ores of the surface workings have formed since the ground was broken, for the excavations have interfered with the flow of the water to the lake. It is plain from the foregoing that the waters are capable of depositing exactly such mineral mixtures as the ores represent, with the very impor- tant exception of the cinnabar. The conclusion that the ores have been de- posited from similar waters is inevitable. At the time of deposition either some slight variation in composition possibly the absence of ammonia enabled these waters to hold cinnabar in solution at ordinary pressures or they are now capable of dissolving cinnabar under somewhat different physical conditions, as was suggested above. Precipitation of the ore. The hypothesis that these waters under other physi- cal conditions would dissolve cinnabar finds some support from observa- tions of the circumstances attending the deposition of the ore. Cinnabar was found in the workings of the Hermann shaft several hundred feet below the surface, and in the open workings the richer portion of the ore occurs in part beneath the basalt and in part in its lower portion. Above the richer bodies comes a mixture of sulphur and cinnabar and at the original sur- face no mercuric sulphide whatever was found. These facts can hardly be 262 QUICKSILVER DEPOSITS OF TUB PACIFIC SLOPE. accounted for by supposing that the ore was precipitated by the sulphuric acid forming at the surface. The rock is attacked by acid to a depth of only about twenty feet, and the richer ores are found at lower levels, where no evidence of the presence of unneutralized acid occurs and where the composi- tion of the ore is substantially similar to that in the deep workings. If the ore had been precipitated by acidification of the solutions, it would be mainly found in the upper part of the bank or along the under surface of the layer of basalt which has been bleached by acid. This is not the case, and hence, while acidification of the solutions would undoubtedly have thrown the quicksilver down, other causes of precipitation must have been at work, and indeed must have been the chief ones. The fact that sulphuric acid forms at the surface is also insufficient to account for the absence of cinna- bar from the surface, for at Steamboat Springs, where acid forms in the same way as at Sulphur Bank, cinnabar did reach the surface. The forma- tion of sulphuric acid from hydrogen sulphide is not a rapid process, and in springs from which there is a considerable flow of water neutralization by the acid thus formed could take place only to a very short distance from the sur- face. The resulting distribution of ore would also be extremely irregular. There is indeed no proof that the main period of deposition of ore at Sulphur Bank was contemporaneous with the chief deposition of sulphur and the formation of sulphuric acid. One might rather suppose that when the deposition of ore was progressing most actively the upward flow of solutions and the emission of gases were too vigorous to permit the per- meation of the upper part of the bank by atmospheric oxygen. Little sulphur or sulphuric acid would then form, and only at the surface. As the activity of the springs diminished the permeation of oxygen would increase, and the sulphuric acid slowly formed at the surface would have an opportunity to diffuse through the rock. The sulphur beds may thus not improbably be in the main of later origin than the ore. While acidification is insufficient to account for the precipitation of the ore, diminution of pressure and of temperature must certainly have taken place as the solutions rose to the surface. So far as is known, too, these causes may be sufficient to explain the observed effect, but dilution with waters percolating from the lake or from springs may have contributed to the result. SULPHUR BANK MINE. 263 There is no trace of substitution of ore for the rock in any part of the mine. It is true that ore is sometimes found in the crevices of concentric layers of decomposed basalt, but it is evident that these crevices have first formed through decomposition and that the cavities have subsequently been partially filled with ore, as any other openings would have be 311. In true substitution, the solution of the substance of the rock is a condition of the deposition of ore and the interchange takes place molecule by molecule. It appears from the above that no absolute evidence of the deposition of ore at the present time has been reached, but that the precipitation of cinnabar, under some pressure, in the lower portion of the ore-bearing ground, is not improbably still in progress. 1 Professors Le Conte and Rising have also expressed the opinion that ore deposition has not ceased. The min3._The surface mine at Sulphur Bank is a labyrinth of excavations in and below the decomposed layer of basalt, In a few spots the workings have passed through the basalt, and lake beds, carrying cinnabar in greater or less quantity, were found below it. Between the Hermann shaft and the air shaft shown on the map an important ore body was followed down for several hundred feet. This body had been worked out before my examination and only the lowest portion of it was accessible. The small amount of ore re- maining consisted, as has already been stated, of partially metamorphosed sandstones and shales of the Knoxville group, carrying small stringers of cinnabar, quartz, and pyrite. The top of the ore body is said to have been in lake beds similar to exposures made near by during my visit, but I was not able to get satisfactory information as to the depth from the surface of the contact between the pebble-bearing lake deposits and the brecciated, metamorphic sandstones and shales. This, however, is not a matter of great consequence. The underground mine consists of a shaft 417 feet deep, with seven short levels. The rock is everywhere of the Knoxville group and sandstone predominates ; it is much disturbed and is full of slickensides, but the prev- alent dip is to the southeast. No second ore body of importance has been discovered, though traces of cinnabar are common. Excepting for the solfataric springs the underground mine at Sulphur Bank resembles the other principal quicksilver mines of California. The 'For a confirmation of this deduction, see the addendum to this chapter (p. 269). 264 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. same rocks are met in other mines and the gangue minerals and the relations of these substances to the vein rock are those most usual in California. This fact is an important one, for it proves that deposits indistinguishable from those found in the Redington, New Almaden, and other mines may be formed i n the same manner as those at Sulphur Bank, by precipitation from hot springs of volcanic origin. Partly, perhaps, on account of the degree to which the hot water and foul gases interfere with mining operations the prospecting of this property has been neglected, and there is an insufficient opportunity to study the structural relations of the ore and the fissures. I can, however, see no reason to suppose that the deposit is exhausted. A drift should be run through the ground which shows solfataric action beneath the surface mine at a depth of at least 200 feet, and from this gallery at least one cross-cut should be driven, so that the hopeful ground would be completely inter- sected in two directions. It would probably be found that these drifts would meet one or more dikes of basalt, the direction of which would mark the main fissure system ; but for some hundreds of feet from the surface the structure and- the disposition of ore are probably very irregular, and a sys- tem of straight drifts and cross-cuts would be the only thorough method of exploration. The abandoned mines on Mt. Konocti appear to have had an origin entirely similar to that of the Sulphur Bank. Their chief interest is due to the fact that they occur in andesitic lavas, thus adding to the list of differ- ent rocks in which cinnabar in some quantity is found and increasing the probability that all the cinnabar is derived from a single source. Little Sulphur Bank and Borax Lake. A few lllllldred feet tO the Cast of tllC UHld flat of Borax Lake, and just at the edge of the obsidian area, is the so-called Little Sulphur Bank. Here slight excavations only have been made. These show a considerable quantity of impure sulphur, and I was positively in- formed that traces of cinnabar had been found, though not enough to encourage further exploration. No water flowed from this locality during my visit, but the ground was moist and hot in spots. It is possible that during some seasons hot water may still find its way to the surface and drain into Borax Lake. Everything thus indicates that the locality is properly BORAX LAKE. 265 named and that there is here a repetition on a small scale of the phenomena of the larger Sulphur Bank. Borax Lake is a small and shallow sheet of water of variable area. Professor Whitney was informed that in 1 861 it dried up entirely. The examinations of the region described in the last chapter make it clear that the nearly flat area in which this pond is situated was formerly covered by the waters of Clear Lake. Although Borax Lake receives the drainage of the surrounding hills, it is still but little elevated above the larger body of water From this it is separated by a low ridge mainly and perhaps wholly com- posed of the obsidian and pumice described upon a preceding page. The b'oracic character of the lake was first detected by Dr. J. A. Veatch 1 in 185G. Later large quantities of borax crystals were extracted from the mud and borings were made in the bottom with a view to renewing the sup- ply, but in vain. Professor Whitney very properly regarded this lake as an evidence of former volcanic activity; but, to make sure that the borax was not leached out of the surrounding declivities by rain and merely con- centrated here, I had careful tests made of large quantities of the meta- morphic rock and obsidian. They showed no borax. The water of Borax Lake was analyzed by Dr. Melville, and the composition of one liter was found to be as follows: Grams. Silica, SiO 2 0.0109 Alumina, Al-O 3 0.0029 Ferrous carbonate, FeCO 3 0.0056 Manganous carbonate, MnCO 3 0.0018 Calcic carbonate, CaCO 3 0.0233 Magnesium carbonate, MgCO J 0.9448 Soclic carbonate, Na-CO 3 29.1671 Calcic phosphate, Ca 3 P-0 8 0. 0225 Calcic sulphate, CaSO 4 0.0204 Sod ie sulphate, Na c SO 4 0. 1248 Borax, Na^B'O 7 5.0040 Sodic chloride, NaCl 38.9900 Potassic chloride, KC1 2.2003 Potassic bromate, KBr 0. 0447 Organic matter 3.6184 Carbon dioxide, CO 3 0. 6H39 Total 80.8654 1 Geol. Survey California, Geology, vol. 1, p. 98. 266 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. When this analysis is compared with those of the waters of Sulphur Bank it is manifest that there is a very close resemblance. Taking into consideration also that the waters which must formerly have issued from Little Sulphur Bank flowed into Borax Lake, it may be -considered absolutely certain that the formerly active springs of Little Sulphur Bank furnished the supply of borax now practically exhausted, and that there will be no re- newal of this supply unless the Little Sulphur Bank should again become a flowing spring. To bore wells in Borax Lake is useless. Possibly, how- ever, a hole bored into the Little Sulphur Bank would bring about a re- newed flow of dilute solution of borax, which by concentration under the hot summer sun in Borax Lake would yield the salt in profitable quantities. FIG. 6. Dendritic sinter on the chore of Borax Lake. Dendritic sinter. Along the shores of Borax Lake are numerous isolated masses of calcareous sinter (Fig. 6). They all grow from the surface of the lake bottom, but some of them are partially submerged and some stood at the time of examination many yards from the actual edge of the lake. They consist chiefly of calcium carbonate, with small quantities of all the sub- [UHI7BRSITT) Jh DENDRITFC SINTER. stances detected in the water (excepting manganese and bromine) and, in addition, traces of cobalt and lithium. They also contain some organic matter which evidently consists in part of the pupa cases of insects. These sinter masses grow to a maximum diameteT of about four feet and a height of about three feet. The outlines assumed resemble those of an isolated clump of trees and bushes seen at a distance. They appear to grow laterally as well as vertically, and thus overhang the level, somewhat pebbly ground upon which they stand. Broken masses show a porous, sponge-like structure, but I detected no definite crystal forms. There appeared to be no opportunity to trace out the history of these masses, nor could I detect any definite nucleus. When once a small accretion of this sort has started, it would appear that the spongy mass draws up the brine from the moist ground and affords an opportunity for the evaporation of the fluid. Why the masses consist substantially only of calcium carbonate is not certain; but it seems not improbable that when first formed they contain a considerable excess of this rather insoluble compound, which separates out in a comparatively pure form, as is usual in cases of slow crystallization from mixed solutions, and that they are further purified by the winter rains. Though the inception of these masses has not been traced, it is easy to imagine how it might occur. Any small lump of pumice, fragment of wood, or other porous sub- stance partially immersed or lying upon the wet mud near the edge of the lake would tend to accumulate a crust of salts upon its upper surface through capillary attraction and evaporation, and the spongy accumulation would then continue to absorb the fluid. These sinter masses appear to answer to some of the tufas associated with the thinolite studied by Messrs. King, Russell, and E. S. Dana. They are certainly still forming and are all of recent origin. If any substitution has taken place in these sinters it must have followed almost immediately upon deposition and probably accom- panied dehydration. However this may be, it is an interesting and some- what important fact that sinters composed substantially of calcium carbon- ate can grow directly from a fluid containing large quantities of sodium carbonates and borax and which holds only small amounts of calcium car- bonate in solution. 268 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. Little Borax Lake, at the foot of Mt. Konocti, possesses a great deal of similarity to the larger body of mineral water near Sulphur Bank. It is snii.ll and shallow and frequently dries up entirely. The salts deposited are borates and carbonates of the alkalis, but no dendritic sinter is found along its shore. Evidences of the volcanic character of this basin were given in the preceding chapter, but no active solfatarism was observed. There seems no reason to doubt, however, that its origin is similar to that of the more important Borax Lake. Maggots. Borax Lake, like many similar pools, is infested by flies, the maggots of which appear to be the sole inhabitants of the brine. Speci- mens of these insects were sent to Professor Riley, who states that the larger part of the specimens are larvae of Epltijdra caltfortvcn Packard. The same insect is abundant at Mono Lake, where the maggots are used by the- In- dians for food. Some larger maggots were also found in Borax Lake, which Professor Riley determined as belonging to the dipterous genus Stratiomys. ADDENDUM TO CHAPTER VII. SOLUBILITY OF CINNABAR IN AMMONIACAL SOLUTIONS. As appears in part from the foregoiug chapter, repeated efforts were made to detect mercury iu the waters of Sulphur Bauk, but without success. Consequently, although the deposit is of such a character as to suggest very strongly that cinnabar is still being formed, such a deposition could not be definitely asserted at the time when this memoir was transmitted. The absence of mercury from these waters was not a little perplexing, for, as will be described in Chapter XV, I had found cinnabar soluble to a very considerable extent in artificial solutions not dissimilar to the waters of Sul- phur Bauk, aud everything pointed to the conclusion that the ore of this locality must have been deposited from waters like those which now flow from it. These waters, however, are ammoniacal, and experiments in my laboratory had proved that, under ordinary conditions, ammonium salts completely precipitate cinnabar from artificial solutions. Consideration of all the circumstances showed it very improbable that the waters had recently become ammoniacal, and I therefore inferred, as was mentioned on page 200, that cinnabar was probably soluble at high temperatures and pressures in am- moniacal waters, seeing, also, in this hypothesis an explanation of the remarkable fact that cinnabar nowhere appeared at the original surface of the bank. To test the matter I devised certain simple experiments, which were carried out after the transmission of this volume. A solution of mercuric sulphide was first made in a manner which will be described in detail in Chapter XV. The solvent is prepared by dividing a solution of sodic carbonate into two portions, saturating one of them with hydrogen sulphide and mixing the fluids. This liquid dissolves mercuric sulphide as a double sulphide of mercury and sodium. The solvent was charged with mercuric sulphide and filtered. Ammonium carbonate was then added till a large precipitate formed, and portions of the mixture were sealed in glass tubes, which were about half filled. These tubes were then heated to various temperatures above 100 C. At 120 the solutions still showed the dark tint due to the presence of unclissolved sulphide, but at 145 and at 175 the mercuric sulphide was entirely dissolved in less than an hour. On cooling, the black color again appeared, and it was found by appropriate tests that this coloration was due to reprecipitated mercuric sulphide. Ammonia in the presence of hydrosulphurioaud carbonic acids thus does not com- pletely precipitate mercuric sulphide at high temperatures and pressures, and waters 269 270 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. similar to those of Sulphur Bank, though incapable of dissolving cinuabar under the physical conditions existing at the surface, would hold it in solution at higher tem- peratures and pressures. Such waters rising toward the surface would deposit the entire quantity of cinuabar held in solution before reaching the atmosphere. This discovery seems to furnish an entirely satisfactory explanation of the absence of cinnabar from the original surface of the Sulphur Bank and of the failure to find mercury in the water; It also removes all reasonable doubt that the deposits of cur- dy, hydrous silica containing cinnabar are really as recent as they appear and that the ore is still accumulating at this interesting locality. The experiment furthermore affords an actual instance of the precipitation of an important ore by relief of temper- ature and pressure, a method of deposition the evidence of which is generally imperfect and indirect. CIIAPTKK VIII. DESCRIPTIVE GEOLOGY OF THE KNOXVILLE DISTRICT. [Atlas SUeet V.] General character. This district includes the point at which Napa, Lake, and Yolo Counties meet. It presents the usual characteristics of the Coast Ranges: low, rocky ridges, partially covered by brush and a scanty growth of trees and divided by narrow valleys. Though some pleasing views are to be had from the higher points, the region is not a picturesque one. It possesses great geological interest, however, for it affords an admirable opportunity for the determination of the age of the metamorphic series and for a studv of the processes of metamorphism. It also contains a series of quicksilver deposits which show instructive features and which bear signifi- cant relations to the metamorphic rocks and to basalt. The Knoxviiie series. Tlie area embraced in the detailed map contains fos- sils at a number of points, and study of the district shows that all of the sedimentary beds are probably of the same age, belonging to one division, the lower, of the Shasta group of Messrs. Gabb and Whitney. As has been explained in Chapter V, it is advisable to consider this series as wholly dis- tinct from the Shasta beds on Cottonwood Creek, in Shasta County. It is characteristically developed in the Knoxviiie district, where also it is the only series exposed, and Dr. White and I have therefore christened it the Knoxviiie group. The Knoxviiie beds form a very large part of the Coast Ranges and of the auriferous slates of the Sierra Nevada. A considerable portion of the rocks in this district are nearly or quite unaltered and consist of predominant sandstones interbedded with shales 271 272 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. and a little impure limestone. The beds stand at many angles, but their dip is usually very high, while the prevalent strike is in the direction of the ranges. Fossils are abundant at a few points, but are not very generally disseminated. By far the most frequent and the most important forms are two species or varieties of Amelia. These were not distinguished by Mr. Gabb, who collected specimens here and gave them the name A. Piochii, but Dr. White considers the more robust form as A. concaitricu and the more slender us A. mosquensis. These and the accompanying fossils have been fully discussed in Chapter V, and the conclusion was there reached that the beds carrying them are close to the line of division between the Jurassic and Cretaceous formations, but are probably to be considered as the earliest Cretaceous, and therefore as belonging to the Neocomian period. The study of these fossils when first collected led me to the belief that the beds carrying them could not be separated from the slates of the gold belt, which also carry AticeUa. This conclusion was afterwards fully confirmed by Dr. White. Mctamorphic rocks. The Coast Ranges are so scantily supplied with fossils that the determination of these beds and their correlation with those of the Sierra Nevada are matters of much interest; but of no less interest is the fact that this district affords abundant opportunities of tracing the passage of these beds into the metamorphic rocks. The microscopical evidence of these transitions has been set forth at great length in an earlier portion of this memoir, but the structural relations have been only briefly referred to. These are of great importance for two distinct reasons. One of them is that eminent geologists deny that large areas of ordinary sediments are converted into crystalline rocks and serpentine by secondary processes; in other words, they deny the theory of regional metamorphism. The second reason for a minute description of the occurrence is that the results of mere microscopic examinations of collections are not altogether trustworthy. The phenomena which specimens and slides from complex areas present are so multifarious that it is nearly always possible to draw various plausi- ble conclusions from them. Specimens may often be so arranged as to sup- port arguments either for connecting the most diverse rocks by transitions or for separating varieties which are in reality closely allied. When due METAMOEPHIC ROCKS. 273 regard is paid to the occurrence in the field, on the other hand, the number of possible hypotheses is generally reduced to one. There can be no question as to the regional character of the occurrence of crystalline rocks at Knoxville. A part of the area of the map, to be sure, is unaltered rock ; but from the westerly edge of the map westward the crystalline rocks and serpentine form an unbroken mass many miles in width ; indeed, it would probably be possible to proceed from Knoxville to the mouth of the Russian River, not in a perfectly straight line, but with no great deviations, without leaving this series. The crystalline rocks not eruptive. It is equally certain that these rocks are in fact neither of igneous origin nor crystalline precipitates from an ancient sea. No observer studying the rocks on the ground could fail to come to this conclusion; and, if conviction be not brought home to the reader, it will be due entirely to imperfect description. No area of more than a few yards can be examined without revealing evidence that the rocks are stratified. It is true that in a large proportion of cases there is entire discordance be- tween the planes of stratification of different portions of a single cropping, but fractures may often be detected between adjoining masses which bear this relation, and sometimes distinct plication accompanied by a more or less elaborately developed fissure system is apparent. In the granular and ser- pentinoid series no masses are intercalated which exhibit the common char- acteristics of eruptive rocks: a lack of stratification and a tolerably persistent granular or porphyritic structure. The only rock in this district possessing this character is the basalt, which is manifestly far younger than the strati- fied rocks. It has frequently been maintained that certain rocks, like gneiss, which show distinct stratification, are of eruptive origin. That a gneissoid structure may be produced by igneous action, at least over small areas, is certain. I have myself seen such a case in New England. A dike of some- what porphyritic diabase filled a fissure in unstratified granite, but at one point an irregularity in the fissure left a mass of granite projecting into the dike. This had been softened by the heat of the eruptive rock and molded by the pressure of the intrusive material. It had assumed a perfectly gneissoid structure without being separated from the wall of granular granite- But when an igneous origin is attributed to large areas of rock it must at MON xiu 18 274 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. least be shown that they possess a certain degree of uniformity ; for, though there may be gradual changes from point to point in a mass which has been reduced to a pasty state by imperfect fusion and which has been extruded through vents, a certain degree of homogeneity, more easily appreciated than described, is inevitable. This is entirely lacking in the rocks at Knox- ville, which often change from one structure to another in the most capri- cious manner and which frequently pass over into little altered, clastic rocks. Though there are single specimens and blocks of rock which might be sup- posed eruptive, the greater part of the rocks are not comparable with gneiss or with any eruptive rock and are manifestly closely allied to sandstones and slates such as no one would think of considering eruptive. As has already been remarked, no case of interbedded Pre-Tertiary eruptives has been met with in the investigations described in this volume nor any instance ia which the serpentine is eruptive or traceable to the alteration of an eruptive rock. These rocks not crystalline precipitates Tll6 Supposition that the granular and S6r- peritinoid rocks, though sedimentary in their origin, were originally depos- ited in approximately their present condition also requires careful consider- ation, particularly as this appears from the published evidence to be the most probable explanation of the genesis of* some similar rocks in other parts of the world. Were this the case at Knoxville, two possibilities would present themselves : Either the conditions necessary to the deposition of the crystalline rocks must have been general, in which case the ordinary sedi- mentary strata of the district are of a different age, or, on the other hand, it might be that the ordinary sediments and the crystalline rocks are of the same age and that local influences produced the differences in lithological character. The granular and serpentinoid rocks of the Knoxville district are of the same age as the ordinary soft, fossiliferous sandstones and shales, and this is shown independently by the structure of the country and by the transitions between the two classes. The structure can be particularly well studied in the neighborhood of the Reed mine, on the north branch of Davis Creek. To the northwest of the mine lies an area of unaltered rocks carrying Ancella and other fossils; another and larger area, also carrying , extends in a southwesterly direction from a point, about one tlion- METAMOBPHIC ROOKS. 275 sand feet south of the Reed mine. To the west of the mine, and again to the east of it, are large areas of serpentinoid rocks, which are connected by a neck a few hundred feet in width, cut by the creek near the mine. The strike of the unaltered strata in both areas is northwesterly, coinciding in general direction with the creek, and a large portion of these strata are inclined at high angles, most of those in the creek bed and a large part of those in the southern area being vertical or nearly so. Had the crystalline rock, including serpentine, been deposited before or after the ordinary sand- stones and shales, and conformably with them, the two unaltered areas would be continuous, instead of being divided by an isthmus of crystalline rock. If the crystalline rocks had been first deposited, but disturbed prior to the deposition of the sandstones, so that the latter were unconformably de- posited and afterwards folded up, it is difficult, but perhaps not impossible, to imagine relations such as those thus far described; but. this hypothesis is entirely inconsistent with another structural feature. The north branch of Davis Creek, from below the Reed mine to the northwestern edge of the map, follows the axis of an anticlinal fold, so that the strata on each side dip into the hills. The same structure is traceable to the south also, particu- larly on Eticuera Creek below the Redington mine. If, therefore, there is any difference in age, the crystalline rocks are younger than the sandstones and overlie them. But this is also impossible ; for, while the sandstones are comparatively little broken, the crystalline rocks show most abundant evi- dence of extremely violent disturbance, and evidently the upper portion of a series cannot be crushed while the lower portion remains intact. section on Davis creek. The following section on the north branch of Davis Creek was carefully worked out from numerous measured dips (Fig. 7). The evidence of anticlinal structure is clear, and, in view of the foregoing, it is cer- tain that the southwestern side of the anticlinal fold consists of a crystalline mass, while the northeastern side is composed of fossiliferous sandstones, shales, and impure limestones. Nearer the Reed mine both sides of the an- ticlinal are crystalline and only the highly compressed portion close to the axis is arenaceous. Transitions from ordinal'}' sediments to crystalline rocks are not lack- ing at Knoxville. Some of these are much more striking under the micro- 276 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. scope than in the field, for many rocks which were not suspected to be anything but somewhat indurated sandstones are shown by thin sections to be holocrystalline rocks, here called pseudodiabase and pseudodiorite. Usually, indeed, the transition is somewhat abrupt, and the rule is this: So far as evidence of crushing of the rock masses extends, these are more or less completely crystalline, while, where the rock preserves its continuity, it is generally an ordinary, more or less indurated sediment. The areas of crushed rock are naturally well defined ; for, where the force exceeded the cohesion, the rock broke, but, where the cohesion exceeded the stress, the rock could only be bent or molded. There is no difficulty, however, in finding along the edges of these areas cases of partial conversion to crys- talline material. FIG. 7. Partly metamorphosed anticlinal, north fork of Davis Crock. The relations of the crystalline rock to the anticlinal structure on the north branch and to the fissuring of the mass are so indicative that it is al- most superfluous to consider the hypothesis of local crystalline precipitates. This theory would not exclude transitions, but it is difficult to imagine that areas of crystalline and uncrystalline sedimentation should be so intimately associated with each other; The absence of fossils in the crystalline rocks would also indicate an equally remarkable distribution of areas fitted for animal life. The intense dynamical action evinced wherever the rocks are crystalline and the absence of similar action in the ordinary beds appear to prove conclusively that the crushing and the crystallization were asso- ciated phenomena. The microscope finally shows, in connection with the field studies, that the crystallization was a secondary process, the progress of which can be followed in great detail. serpentine. The granular and serpentinoid rocks cannot be sharply sep- arated from the unaltered sedimentary rocks, as has been pointed out above. SERPENTINE. 277 Still less sharp is the distinction between the serpentine and the other altered rocks, though, so far as practicable, the areas covered by each are indicated on the map by different colors. There is nevertheless abundant evidence that serpentinization was a distinct process at Knoxville, from the formation of granular pseudodiabase, pseudodiorite, and glaucophane schist, all of which were formed under similar conditions and at the same time. The ser- pentine was formed in part from these granular rocks, but in part also from sandstone, and the microscopical evidence of this fact has been full} 7 stated in Chapter III. This would be inferred from the occurrence in the field, but the difficulty of distinguishing partially altered sandstones from sandstones which have been converted into fine-grained, holocrystalline rocks is such that it would be impossible to make absolutely sure that a preliminary recrystallization did not invariably precede serpentinization. In a great number of occurrences at Knoxville serpentinization has evidently begun along cracks in rock retaining macroscopically the appearance of somewhat altered sandstone. When some progress has been made in the conversion, the structure may be illustrated by the following diagram prepared from sketches. Here the serpentine is represented by dark bands of nearly even width, but the corners of the intervening blocks are rounded, and it is evi- dent that, were the serpentine removed, the remaining masses would no longer fit together as they originally did (Fig. 8). When the process has been carried further rounded balls are formed and in some cases these have weathered out and strew the ground like water- worn pebbles. The process is mechanically strictly analogous to the formation of balls of basalt in the Sulphur Bank, of which mention was made in the last chapter, and a theory of the process has been given on page G8. The fibers of serpentine usually follow the direction of the veins separating the more or less cracta in the mas8 ' rounded masses which they include, but in a few cases stand vertically to the surfaces of the unserpentinized nuclei, and the lines of division then clearly mark the exact position of the original crack, as shown in Fig. 9. One very fine rase was found in which a subangular mass when broken 278 QUICKSILVER DEPOSITS OF TIIE PACIFIC SLOPE. open showed a rounded kernel of unserpentinized rock within a shell two inches or more in thickness composed of fibers of serpentine standing per- pendicularly to the surfaces. These phenomena seem to demonstrate that the conversion of other rocks to serpentine has been effected by the instrumentality of solutions reacting on the material of the rocks. The latter are acid, and the solutions must have been niag- nesian. Partially serpentinized shales also occur, no. o. serpentine ^forming from but I have nowhere seen any tendency to the normaTto the at tacked* surface formation of balls in this rock. This fact indicates that a portion of the constituents of the shale resisted serpentinization so that replacement of the rock as a whole could not take place, and only impregnation or the replacement of certain con- stituents was possible. Not a trace of any olivinitic rock could be found in Knoxville or its neighborhood, excepting the basalt, which is certainly far more recent than the formation of serpentine and has suffered little decomposition. Serpentine is attacked and removed by atmospheric agencies about as rapidly as partially altered sandstones. Where croppings of the latter are serpentinized in part, sometimes the sandstone and sometimes the serpentine may be seen standing in relief. On the whole, however, the serpentine appears to offer least resistance to weathering. On the map serpentinized and unserpentinized metamorphic rocks arc laid down in different colors. This division, however, must not be taken as absolute. Traces of serpentine are to be found in the unserpentinized area, and there are many small masses of other metamorphic rocks in the area colored as serpentinized. In the nature of the case an absolute division is impossible, but the colors represent the limits within which serpentine is the prevalent rock and serve to illustrate the approximate distribution of one phase of metamorphism. Chromic iron is found in the serpentine here, as at many other places in the Coast Ranges. At one locality, not far from the Royal claim, it forms a series of nodules around which the serpentine has weathered away. The NKW MINERALS. 279 ore forms a belt or seam, and a considerable quantity of it might be obtained \\ -ves the former existence of volcanic activity in this district, but empha- sizes a fundamental structural axis. The character of the metamorphic rocks shows that the line along which compression and upheaval took place in the early Cretaceous was about west by north, east by south The fold- ing of the Tertiary rocks shows that compression was repeated in the same direction at the close of the Miocene. The position of the rhyolite dike proves that the dislocation which opened a passage for this lava again fol- lowed a similar course. As for the age of the rhyolite, it is certainly Post- Miocene, for had it been earlier it must have shown the effects of the Post- Miocene uplift. Had the lava been ejected at the time of that uplift, it would probably have been so eroded that the croppings would present a different appearance, for the tufaceous modification is probably superficial. It is possible, however, that its position has in great measure protected it and that during the Pliocene it was covered with sediments. As a rule, the rhyolites of the Pacific slope are younger than the andesites, as was [jointed out by Baron von Richthofen, and if this rhyolite is younger than the ande- sites of Mt, Diablo and of Napa County it is Post- Pliocene ; but there is no direct evidence that this is the case. On the whole, the probabilities are. then, that the rhyolite is recent or late Pliocene, but. it is certainly known only that it is not older than the Pliocene. Mine minerals and rocks. TllC Ol'eS of this rCglOll {ll'C COlllpOSed of tllC 08118.1 association of minerals : cinnabar (sometimes accompanied by a little native MINERALS AT NEW ALMADEN. 315 mercury), pyrite, quartz, calcite, and dolomite, and more or less closely associated masses of bituminous matter. Accompanying the deposits is a small amount of chalcedony or opal, usually black in color; but this sub- stance is much less abundant here than in the greater part of the northern mines. Dolomite is more prevalent as a gangue mineral here than in most quicksilver districts, a fact probably not unconnected with the unusual quantity of limestone in the sedimentary rocks. The croppings of the de- posits are to a large extent composed of dolomite in botryoidal masses, instantly seen to be secretions, and not sediments. Besides the minerals enumerated, Prof. W. P. Blake reported mispickel in the upper working of the New Almaden. 1 This mineral was extremely abundant in the great Peruvian mine and its existence at New Almaden is not at all improbable. No one seems to have observed it here since 1854, however; for Prof. B. Silliman 2 in 1804, Mr. Goodyear 3 in 1871, and my party in 1885 failed to meet with it. Neither is it mentioned by Mr. G. Holland. 4 Professor Blake also states that gold has frequently been found in small quantities in this mine. This, too, is far from improbable, but it has not been verified The rocks associated with cinnabar in this district include every variety of the metamorphic series. Where the rock happens to be a per- meable sandstone, impregnations have resulted. Elsewhere the ore seems to occur exclusively in crevices in the rock, nor are the cracks invariably filled, so that quartz and carbonates frequently show surfaces covered with crystal faces. In some cases quartz reddened throughout by cinnabar occurs in this manner. I was unable to perceive any indication that ore had been deposited by substitution or that the rock had influenced the deposition of ore by its chemical properties. Ore is found with nearly equal frequency in contact with various rocks and the existence of fissures appears to have been the nccessarv and sufficient condition for the deposi- tion of cinnabar and gangue minerals. The rock, then, influences the occurrence of ore mechanically, though indirectly. Where disturbance of the country resulted in the formation of open fissures or of ground present- 1 Am. Jour. Sci., 2d series, vol. 17, 1854, p. 438. II. id., vo].:;s, H(M,p. 192. : (':!(>}. Survey California, Geology, vol.2, appendix, p. 99. * Anniile.s il>-s mines, vol. 14, 1.^78, p. :!84. 316 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ing a large amount of interstitial space, ore bodies were formed, but where the rock yielded to stress as a plastic mass no room was left for ore. Aitas. The ore in the New Almaderi mine seems never to occur except close to evidences of faulting. This evidence consists in the presence of layers of attrition products, so-called clays, full of slickensides and of frag- ments of rocks more or less rounded by attrition. These lavers of clav J V 4 usually occur on the hanging side of deposits and are known to the miners as altas, the Spanish term for hanging walls. The clays are impermeable to solutions and the ore usually forms on their lower side, as if the cinnabar had ascended and been arrested by the alias. That the solutions really took this course is clearly shown by the phenomena of other quicksilver districts, as well as by the relations observed in the New Almaden mine The miners very properly follow seams of alta in their search for ore. Sometimes, however, a second -mass of ore exists on the hanging side of the clay and is again limited by a second layer of alta, as I have myself observed. Such occurrences are to be expected in a country so irregularly disturbed as this. The alta is not a definite substance, though it is usually a dark or black mass, readily distinguishable even in hand specimens from the country rock. It is simply triturated country rock and varies in com- position 'with the material from which it has been produced. Its black color is in part due to the. presence of manganese. These layers of clay correspond exactly to those which were met with in the upper portion of the Comstock lode and against which many bonanzas were found to rest. The evidence of movement in the New Almaden mine is not confined to clays. Where the opposing walls were so nearly parallel that no consider- able quantity of trituration took place, polishing occurred, and some of the slickensides met with are as brilliantly polished as if the work had been done by a lapidary. Form of the New Almaden ore bodies While tllC evidence of tll6 existence of a fis- sure system is, if possible, more abundant in the New Almaden mine than in most other quicksilver deposits of the Pacific slope, the deposits them- selves are of various types. The commonest is the reticulated mass, or stockwork, consisting of irregular bodies of broken rock into which solutions of cinnabar and gangue minerals have filtered, cementing the fragments to- FISSUliE SYSTEM. 317 gether with ore. Where the disturbance has been less extensive and irreg- ular, clean-cut fissures may sometimes be seen filled with ore, and these can only bo classed as veins, though they are not persistent. As already mentioned, impregnations also exist where the ore-bearing solutions havo encountered permeable sandstones. The classification of the various portions of such a deposit under various names seems to me of very little interest, excepting as it serves to a certain extent as a basis of comparison between ore deposits of different regions. It is not long since it was customary to maintain that the deposits of cinna- bar were very different in character from those of other ores and that the genesis of quicksilver deposits was essentially unlike that of other metals. I have taken some pains therefore to show that no distinction can be main- tained as to form between the ore bodies of the quicksilver mines and well recognized types of gold, silver, and copper deposits. The only important mode of occurrence of ores which I have not encountered in the quicksilver mines is that of replacement. Lead ores have certainly in some cases re- placed limestone molecule for molecule. According to Prof, von Groddeck, cinnabar ore at Mt, Avala, in Servia, has replaced serpentine in a similar man- ner. Others also have been led to suppose analogous substitutions at Al- inaden and at Idria, but I have not met with them at those mines or any- where in California. Existence of a fissure system. While the reference of deposits to different heads of more or less artificial classifications is only of indirect interest, a compre- hension of the fundamental structural relations of the ore bodies of a mine is of the utmost importance to its conduct. From any one accessible stope of the New Almaden mine it is evident that the country has been intersected by fissures, that energetic motion has taken place along these fissures, that the adjoining rock masses have been shattered more or less irregularly, and that solutions entering the ground have deposited ore in such spaces as were vacant. It is also apparent from the relations of the ore to the clay that the solutions have entered from below, and it is almost a necessary inference that the fissures served as channels of ingress for the solutions. These con- clusions may be drawn in each of as many chambers as the observer can 318 QUICKSILVER DEPOSITS OF THE PACIFIC! SLOPE. reach, and he will find nothing to conflict with them in any portion of the mine. Certain features must be common to the ore bodies taken singly and to the ore-bearing ground as a whole. It would be impossible to suppose that each atockwork has an independent fissure system, and a mere glance at the mine maps shows that a connection between them exists. It is also a his- torical fact that the thin seams of ore (stringers or, as the Spanish miners call them,, hilos) have led from one ore chamber to another. There must be a general fissure system, in subordination to which the various ore bodies are arranged, and this system must stand in the closest relations to the gen - eral geology of the country. Such a system can result only from a some- what widespread disturbance and, it is superfluous to remark, must have been formed according to ordinary mechanical laws. If the rock of the country were thoroughly homogeneous and were level at the surface, a fissure caused by a simple disturbance would follow a straight line and would pass over at its extremities into a fold. Under a sufficient horizontal stress such a country would show a system of parallel fissures passing into a common fold at each end. Fissures thus tend to straight lines and parallel systems, but this tendency is modified by inequalities in the properties of the rock and in the configuration of the surface. It is often difficult to decipher the fundamental fissure system in a country of heterogeneous character, but this does not seem to be the case at New Almaden. The distribution of serpentine, the average strike of the nietamorphic strata, the compression of the Miocene beds, the position of the rhyolite dike, and the trend of the range, in short the whole structural geology of the region shows that the fundamental axis of disturbance must have a direction which is approximately northwest and southeast. It is along a fissure, or a system of parallel fissures, taking this general direction, but more or less deflected by local causes, that ore might be expected to occur in such a district. It is on such a line that the New Almaden, Enriquita, and Guadalupe deposits occur. In the New Almaden mine itself, also, there appear to me clear evidences of a fundamental fissure system. Plans and sections of the New Almaden TllC SUl'faCe and tllO WOl'kingS of tllC NeW Almaden mine have been surveyed with the utmost care by the officers of SECTIONS OF THE NEW ALMADEN. 319 the Quicksilver Mining Company, and data exist for the construction of any desired sections. A fine opportunity is thus afforded for a study of the structure of this very important deposit, and it has seemed to me worth while to illustrate the occurrence very fully by plans and sections. The mine maps and sections which I selected as best adapted to show the struct- ure were prepared for me from plans and notes in the office of the company by Mr. Frank Reade, who was surveyor of the mine at the time of my examination and who formerly assisted me in studying the Comstock Lode. The ore deposits being in my opinion comparatively recent, the rela- tions between their distribution and the present topography of the surface are of interest. On Atlas Sheet VIII the plan of the known ore bodies is shown beneath a contour map of the surface. It will be at once remarked that these ore bodies are divisible into four groups. Two of them, reached respectively by the Washington and Cora Blanca shafts, seem to be isolated. The other two groups, upon which the main mine has been opened, are very closely connected. The more important group of the ore bodies of the main mine reaches from the top of the Mine Hill nearly to the Santa Isabel shaft and is substantially continuous for the entire distance. The croppings at which Castillero and others before him found cinnabar, as was narrated in Chapter I, were at the top of Mine Hill. A monument at this point is used as the datum to which the contours and mine levels are referred. The other group of ore bodies of the main mine lies to the east of the Randol shaft. I shall have frequent occasion to distinguish these two sets of ore bodies and shall refer to them as the north and south groups. This map is printed on a scale of 300 feet to the inch and the contours are drawn at vertical intervals of 10 feet. The plan of the workings is given on Atlas Sheet IX, this and the succeeding sheets being drawn on a scale of 150 feet to the inch, or double that of the topographical map on Sheet VIII. The highly complex structure of the separate ore bodies is very apparent from this plan as well as the existence of certain surfaces along which the ore bodies are grouped. The colors and figures make explanations needless. I have not tried to indicate on this plan or on the sections the character of the wall rocks, for nothing could result from such an effort. The entire mass of the country rocks consists of metamorphosed sediments. Every stage of metamorphisin 320 QUICKSILVEK DEPOSITS OF THE PACIFIC SLOPE. is represented, and pseudodiorite, pseudodiabase, phtlianites, sandstone, sliale, and serpentine are mingled in inextricable confusion. Atlas Sheet X shows a section taken along the course of the south group of bonanzas. The line on which the section is made is shown on the mine map and was selected with a view of illustrating 1 the continuity of ore from the surface at the top of Mine Hill to the lowest workings. The group of ore bodies thus intersected is for the most part distinct from that to the east of the Randol shaft. It is manifest from this section that a fissure extends from the lower workings to the top of Mine Hill, a vortical distance of about 2,000 feet, and that ore has been deposited almost continuously along its entire course. This fissure is remarkably sinuous in vertical section, and a long tongue of ground north of Mine Hill has manifestly moved north- ward sufficiently to leave space for the deposition of ore. If one considers the character of the disturbance to which the fissure must owe its origin, it appears almost certain that this tongue of country rock overlying the fissure cannot have remained intact. One would expect to find one or more fis- sures intersecting it in a direction more nearly vertical than the south ore channel, because the tenacity implied in the movement of the entire hang- ing country without fracture would be improbably great, even were the rock much firmer than the materials of which the Coast Ranges are chiefly com- posed. Such a fissure intersecting the hanging country really exists, and a trace of it may be perceived on this section from the 1,500-foot level down- ward, where the stopes show that the ore occurs on parallel lines. The line of the northerly stopes in this region if continued upward would reach the surface near the point at which the Randol shaft appears projected. On Atlas Sheet XI two sections are shown, cutting the northern portion of the mine on parallel north and south planes. One of them is taken through the Randol shaft and the other 350 feet west of it. The two are to be considered together and as if they were superimposed. The western section shows the same group of bodies as is depicted upon Sheet X, but cut at a different angle. The relations of the section on Sheet XI are most easily appreciated by reference to their traces on the mine map (Sheet IX). The eastern section, through the shaft, on Sheet XI is very different. It shows only the edge of the south ore channel, or of that series of deposits SECTIONS OF THE NEW ALMADEN. 321 which crops out on Mine Hill. To this series belong the various Santa Rita " labores " exhibited on the southern part of the section, and the series of winzes extending from the Santa Rita to the 1,400-foot level of the Randol shaft, showing here and there a small slope, was sunk along the course of the same fissure. The main stopes on this section are on the north fis- sure, which divides the great body of rock forming the hanging country of the south fissure from the region north of the mine. Another view of the two fissures is shown on Atlas Sheet XII, where they are intersected by an east and west vertical plane. To the right ap- pears the south ore channel, including the O'Brien, Don Federico, and other bodies ; to the left is the north fissure. Existence of two principal fissures. The existence and position of the two fissures are not so evident and clear as would appear from the foregoing notes. The ore bodies lie upon complex curved surfaces. The result is that no vertical plane intersects both fissures at right angles throughout, and no single sec- tion affords indubitable evidence of two fissures. Views similar to those shown in the sections might be given of two channels along a single, doubly curved surface. Could one but represent the fissures by contours, the en- tire structure would be shown in three dimensions and would not be ambig- uous. A certain approximation to this result can be reached. As was mentioned above, the fissures are marked by clay seams or altas. It oc- curred to me that if one could lay down all the alta seams followed in the explorations the result would closely resemble a contour map of the fissures. Mr Reade, with the assistance of other officers, has 'compiled all the information available regarding the occurrence of altas in the northern part of the mine, and they are shown on the same scale as the mine map on Atlas Sheet XIIL The result, however, requires some discussion because of the irregularity of the lines and the distance which sometimes intervenes between the two ore channels. At the northwest the fissures come nearly together, and on the 1,930, the 1,850, and -the 1,735 foot levels it is plain from the position of the altas that there are at least two nearly parallel fissures. On the 1,650 the alta forks, probably indicating the existence of two fissures connected by a diagonal cross-course, for on the 1,5-10 and again at the 1,440 there are two altas nearly parallel and at a considerable MON XIII 21 322 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. distance from one another. On the 1,850 (1,832 to 1,847) it is the north- erly alta which extends to the north group. The same is true of the clays on the 1,735, and on the 1,650 it is also the north fork of the alta which has been followed to the neighborhood of the Randol shaft. On the 1,550 (1,540 to 1,547) there are three lines of alta, two of which are to the south- west and one to the northeast. From the continuities just mentioned on the three levels below this it is evident that the northerly alta of the 1,540 in the southwest region answers to the alta in the north group of ore bodies, and to emphasize this relation I have connected the two altas by a straight dotted line. A precisely similar relation exists on the 1,440. Thus for a vertical interval of 500 feet there is abundant evidence of two fissures, the outer or more northerly of which leads into the north group of ore cham- bers. The inner or more southerly fissure is certainly that upon which ore has been followed from the top of Mine Hill, as may clearly be seen by ref- erence to the section of this channel on Atlas Sheet X. The southerly or inner altas on the 1,540 and 1,440 levels form the hanging wall of ore body XLI, which appears on Atlas Sheet X, and this section shows that from this body to the top of Mine Hill the ore is substantially continuous. The outer or northerly alta appears on Atlas Sheet X as the hanging wall of the body XLVIII. These same altas in the north group overlie the bonanzas known as XXI, XLIV, XX, which appear on the section through the Randol shaft (Atlas Sheet XI), and from this section it is manifest that the fissure cany- ing these bonanzas is continuous up to the 900-foot level. Referring again to the plan of the altas (Atlas Sheet XIII), it is seen that the two groups of ore bodies are so far apart between the 1,440 and the 1,050 that from this plan alone no certain result could be reached as to the distinctness of the fissures within this interval. The lines of altas aro very tortuous as well as distant, and without the aid of the sections it might seem quite pos- sible that the altas of the same level were continuous in the two groups; but in the foregoing I have sluown that each of these fissures for the inter- val between the 1,440 and the 1,050 continues in depth and that at lower levels the fissures are distinct. It is true that the fissures might come to- gether above, though this would be an unusual structure. But on the 950 FISSURES OF THE NEW ALMADEN. 323 the altas of the two groups once more assume a position of approximate parallelism, which shows that they remain distinct throughout. Another test of the distinctness of the fissures can be applied, and, indeed, one which is of no small importance for the mine. The average strike of the north group in its upper portion is on a line not far from S. 50 W. magnetic, and, as shown by the north and south section through the shaft, if the north fissure were continuous it would reach the surface about four hundred feet south of the Randol shaft. Having arrived at this conclusion, I examined the surface, and did in fact find a line of dolomitic, botryoidal croppings north of the road leading from the office to the Randol shaft above the Randol group of bonanzas, and which seemed to strike for other croppings on which a little tunnel has been opened about four hun- dred and fifty feet south magnetic from the shaft. These croppings thus strike very nearly in the same direction as the altas of the Randol group of ore bodies on the 1,050-foot level, and are very close to the position indicated for a cropping of this fissure. In my opinion they represent such a cropping and complete the proof that the New Almaden mine pos- sesses two important fissures, along one of which the south group of bonanzas has been followed from the surface, while the north group lies upon the other. One fissure underlies the great tongue of hanging coun- try, the other intersects it. ore in the inclosed wedge. Between the two principal fissures a wedge of country rock exists. It is not uncommon for great masses of this description to be inclosed on both sides by ore-bearing fissures. Such was the case on the Comstock and also in the Ruby Hill mines at Eureka, Nev. Ground thus inclosed is seldom solid and subsidiary fissures leading into it are often ore bearing. In the New Almaden mine the ore is not confined to well de- fined fissures. It is true that ore can be followed from the top of Mine Hill downward to a depth of 1,600 feet practically without a break; but the sec- tions show that at many points the fissures are systems of associated open- ings rather than simple ruptures. The north and south section through the Randol shaft shows a section of the Velasco, Theatre, and several of the Santa Rita bodies, which is especially illustrative of this structure. The section shows that the wedge of ground between the principal fissures is 324 QUiCKSILVEE DEPOSITS OF THE PACIFIC SLOPE. not a solid mass, but that subordinate fissures and ore channels exist in it. This would be still more evident were all the ore bodies represented. Those which have been exploited since systematic work was begun are, I believe, all accurately given, but in the early days there were many openings, resembling burrows rather than mines, excavated from the surface between the Randol shaft and the top of Mine Hill. Mr. Reade has shown many of the dumps of these old workings on Atlas Sheet VIII. They produced considerable quantities of ore. One of them, the Juan Vega, which appears on the plan but not on the sections, I was able to explore. The stopes were of considerable size and the ore appears to have been very rich. It was associated with masses of dolomite similar to those found at the surface as croppings, but which are not met with in the lower levels. Evidently fis- sures carrying ore in solution must have readied the Juan Vega and other similar deposits. These fissures must have connected with great ore chan- nels, and must therefore intersect the wedge of country rock. The wedge of rock between the two principal fissures has contained ore bodies and the fissures leading to them must penetrate the wedge through and through. The entire mass should be regarded as potentially ore bear- ing and should be explored. It is not in the least likely that all the ore which it contains is known and, if other bodies are encountered, they will be mined at a greater profit than similar bodies at lower levels. This mass arid the lateral extensions of the main fissures constitute the promising ground in the mine. At the lowest levels reached there is little ore. There is no known reason why bodies of cinnabar should not be found at still greater depths, but I do not regard it as probable that the ore chambers beneath the 2,000-foot level will be as frequent as they were above Some further comments on the fissure system of this mine will be'made below. Cora Blanca and Washington deposits. -The WOl'luUgS of tllC WasllillgtOll shaft, which were formerly known as the San Francisco mine, are connected with the main mine of New Almaden, but the deposits were not being worked during my visit. The association of minerals and rocks is entirely similar to that of the main mine, and the deposits are also accompanied by clay seams or altas. The position of the deposits is shown on Atlas Shifts VIII, IX, and X. Ore has been followed in the workings to a depth of OTHER DEPOSITS NEAR NEW ALMADEN. 325 850 feet below the summit of Mine Hill, but below that level no ore bodies have as yet been met with. The strike of these deposits is at an angle of over 70 to the deep fissure of the New Almaden, and both fissures stand at considerable angles to the main axis of uplift. Near the New Almaden and the Washington is the Cora Blanca mine, the position of which, with a horizontal projection of the ore bodies, is shown on Atlas Sheet VIII. Portions of it were accessible to me, but no work was being done upon it. Though the rocks inclosing this deposit are members of the metamorphic series they are less modified than usual, and in part are but little contorted, though standing at a high angle. One of the strata, which is usually close to the ore, is a magnesian limestone. Some native quicksilver was found in the mine. The gangtie minerals accompanying the cinnabar are almost exclusively carbonates. There are clays and evidences of disturbances in the Cora Blanca, but less marked than in the New Almaden. The ore-bearing solutions have followed the bedding for the most part, and in places the deposits can be classed only as a bedded vein; but not infrequently the ore crosses laminaj and often fills chambers adjacent to the main ore-bearing surface. These are in part reticulated masses and in part impregnations in sandstones. The ore was followed to a depth of 750 feet below the summit of Mine Hill. The strike of this deposit is about N. 18 W. magnetic, or very nearly true north and south. The direction has doubtless been influenced by the fact that the partings between the beds offered a comparatively slight resistance to rupt- ure. The average dip is about 40 to the west. The Endquita. The Enriquita mine is also on the property of the company which owns the deposits described above. It has long been abandoned and no part of the deposits is accessible. The ore-bearing ground was about five hundred feet in length and had an extreme width of about sixty feet, the dip being nearly vertical. From a manuscript report of Mr. Louis Ja- nin, which he has kindly shown me, I see that the ore was found in lime- stone inclosed on. both sides by serpentine. The ore formed rich pockets, connected by stringers, and the lowest body, the San Jose, was the richest of all. The mine possessed reduction works and in a short time yielded 326 QUICKSILVEIJ DEPOSITS OF THE PACIFIC SLOPE. metal worth $350,000. It was producing in 18GO and is said / to have yielded about nine thousand flasks. The Guadaiupe. Over fifty thousand flasks of quicksilver have been pro- duced from the Guadalupe, which was closed at the time of my visit, though it had been working in the preceding year. Cinnabar has been found at a great number of points on this property over an area of about a half a mile square. -The only deposit of large size detected cropped out about one hundred and fifty feet north, of the creek and has been followed down- ward for over seven hundred feet. The strike of the main body was about east and west magnetic ; but to the east seams have been followed on a more northerly course which led to small bodies of ore. The dip is southerly and the greater part of the mine lies south of the creek. The ore and the associated substances are said to have resembled those of New Almaden, but I have been unable to obtain any particulars of interest. A small quantity of ore was obtained from the " Office mine," a small excava- tion on a cropping some two hundred and fifty feet north of that of the main mine. Some of the other numerous superficial workings have also yielded ore. These excavations have obscured rather than revealed the structure of the country, and I was. unable to make observations sufficiently definite to justify important conclusions. It certainly is improbable that the resources of the locality are exhausted. The most evident course to be pursued is further exploration along the fissures developed by the main mine. Were the old tunnels and superficial workings which dot the surface cleaned out, it is also possible that a careful study would reveal other fissures which might be ore bearing in depth ; but there is no certainty that the search for ore bodies would prove successful. Quicksilver deposition in the Coast Ranges has been very irregular and study of the geological phenomena shows that this is an almost necessary consequence of the structure. The only way for quicksilver miners to keep up the value of their property is to study the fissure system with the most earnest attention from day to day and to do their prospecting while in bonanza. Prospecting when all the vis- ible ore has been extracted and the old workings have become inaccessible is little better than guess-work and seldom meets with much reward. It is THE GUADALUPE. 327 only under exceptional conditions that ore bodies can be foreseen in the quicksilver mines, and predictions as to the quantity of ore in these mines, excepting so far as the ore is in sight, ore entirely valueless. Minor deposits. In addition to the mines UpDn which notes have been given above, there are a number of workings which have yielded cinnabar in quantities of little or no commercial importance, but which throw some light on the structure of the country through their position relatively to the more developed deposits. The America, to the westward of the New Almaden mine and a little south of the ridge, showe'd two small ore bodies. From the plan of the drifts it would appear that clays running to the northeast were followed. The Providentia, one quarter of a mile from the Enriquita, in the direction of the New Almaden, yielded ore of excellent quality, as I learn from Mr. Janin. The San Antonio mine was half a mile northwestward from the Enriquita, on the hillside northeast of Los Capitancillos Creek, and the San Mateo was a quarter of a mile farther in the same direction and in a similar topographical position. A mass of black opal, such as is so often associated with cinnabar in California, exists about 6,400 feet north magnetic from the Enriquita, be- tween the isolated patch of rhyolite and the continuous dike. I am not aware that cinnabar has been detected at this point, but it would not be surprising if search were to disclose at least a trace of ore. Age and genesis of the deposits. The croppings of Mine Hill have been exposed for a long time and there is a considerable quantity of cinnabar in the sur- face soil of the hill. The deposits have been formed since any violent dis- turbance of the country took place, however, for there are mere traces of dislocation in the ore bodies. The eruption of rhyolite must have been accompanied by very considerable movement of the country, and, had the deposits existed before the formation of the dike, they could hardly have escaped dislocation. There are no unquestionably Pliocene strata at New Almaden, but beds of this age have been considerably disturbed both to the north and to the south, though at distances of a number of miles. It is very probable, but not certain, therefore, that the deposits are Post-Pliocene, while it is certain that they are not Pre-Pliocene. 328 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Ore deposition followed the erupt'on of lava. The minerals deposited and the manner of their deposition are such as in the more northerly quick- silver districts were induced by volcanic springs. Though there are now no indubitable remnants of the volcanic activity Avhich certainly prevailed here since the beginning of the Pliocene, the analogies of the deposit, together with the presence of lava of approximately the same age as the ore, make any theory of deposition excepting from hot sulphur springs improbable. The source of the ore will be discussed in a future chapter. General fissure system. The rliyolite dike, of course, represents a deep fis- sure. The length of this dike shown on the map is about twenty thousand feet, but I have followed it beyond the map limit for a considerable dis- tance. The presence and the character of the range also indicate the existence of an axis of disturbance, though its direction is mpre or less ob- scured by irregularities in metamorphism and erosion. There can, further, be no doubt from the foregoing description that the cinnabar deposits occur along fissures. The question arises, what connection exists between the fissures upon which the various deposits are found ? It is hardly pos- sible to consider the relative position of the Guadalupe, San Mateo, San Antonio, Enriquita, Providentia, America, and Washington without coming to the conclusion that they form a substantially continuous series of de- posits. If the strike of the Guadalupe, the Enriquita, and the Washington be taken into account this impression is strengthened, for it is easy to draw a continuous line through the deposits which will coincide with the strike of each. This series leaves out the New Almaden and the Cora Blanca. The deep fissures of the New Almaden to the northeast of the Randol shaft are nearly straight, approximately vertical, and strongly marked by slicken- sides, clays, and other evidences of motion. They must be very profound and persistent fissures. They strike nearly for the workings of the Amer- ica. The fissures on the lower levels have been followed for about one thousand feet and to about twenty-two hundred feet in a horizontal direc- tion from the America. I cannot believe that these strong fissures can die out within this distance or that they can greatly change in general direc- tion. They might possibly be replaced by other fissures near to them and parallel with them, the two sets being connected by more or less indistinct GENERAL FISSURE SYSTEM. 329 cross-courses, but this would be substantial continuity. If I am right, the New Almaden deep fissures connect with the ore-bearing fissures south of the ridge and cross the ridge near the America. Considering the amount of disturbance on the New Almaden fissures~tliey would seem to represent the main line of fracture, and in that case the crack leading to the Washington is in the nature of a cross-course. The apparent strike of the America accords with this view, which is strengthened by the relations to the dike to be men- tioned presently. As for the Cora Blanca, the fact that the deposit is largely bedded or that it follows the stratification complicates its relations, for its strike is very likely to differ considerably from that which it would have if the structure of the country had not presented a local line of weakness. It may be that this mine is on a cross-course nearly parallel to the Washington, but the evidence is hardly sufficient to justify speculation. The following sketch shows the approximate positions of the several deposits of the ridge and of the dike. The strike of the main deposits is also indicated and a fine line is drawn through all except the Cora Blanca. The upper portion of the south fissure oflthe New Almaden is not represented on the sketch for lack of data. The Iroppings of this fissure probably curve rapidly toward those of its northern 1 - companion, but the soil and artificial disturbances obscure the line (Fig/ 13). FIG. 13. R, deep fissures of .the New Almaden near the Eandol shaft; W, Washington deposit: A, America; S, Cora Blanca; P, Proviilentia ; E, Knriquita; SA, San Antonio; M, San Mateo; a, GuaUalupe; dd rhyolite dike. The straightness and persistence of the dike seem to show that its crop- pings have the same strike as the main fissure through which it reached 330 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. the surface. I have shown that the deposits were probably induced by volcanic activity following the eruption of this lava, so that a not very remote connection exists between the ore-bearing fissures and that marked by rhyolite. At the time of the lava eruption the present range of hills existed much as it does to-day. Consequently the course of a fissure tend- ing to assume a strike nearly parallel to that of the dike and which was formed near the range of the hills would be affected by their presence. The hills would act as - a mass of considerable rigidity and would tend to deflect such a fissure, but if at any point this tendency were overcome the fissure would return more or less closely to the direction of the dike. Now, near the Guadalupe the line connecting the deposits is almost exactly par- allel to the dike ; as the ridge curves away from the dike the line of de- posits follows the high ground. After the angle between the ridge and the dike becomes large the line of fissure seems to me to cross the high land and to approach the dike again in the New Almaden ground at an angle of about 30. In crossing the ridge a branch fissure seems to have been formed leading to the Washington. I cannot, of course, pretend to have demonstrated the above explana- tion of the relations of the deposits. For this the exposures are insufficient. I offer it, however, as a working hypothesis which possesses considerable probability and may serve as the basis for a more exact theory to be elab- orated by the engineers in charge of the properties. It is probably needless to remark that if the hypothesis set forth above be true it shows where ore is to be sought, but ore will be found only at certain favored points or in certain channels at or near the fissures. If the Washington fissure actually meets that connecting the New Almaden and the America, great disturbances must have taken place at the junction and some ore will probably be found there. CHAPTER XT. DESCRIPTIVE GEOLOGY OF THE STEAMBOAT SPRINGS DISTRICT. [Atlas Sheet XIV.] character of the district. Steamboat Springs lies between the Sierra Nevada and the Virginia Range, at the western edge of the Great Basin. The forests and snows of the great Sierra ai-e in sight a few miles away, but in the neighborhood of the springs only sage brush grows without irrigation. The soil in the lowlands, however, is fertile, and sufficient water is avail- able to bring a considerable surface under cultivation. The hills are for the most part bare rock, as geologists love to see them. Many of the exposures are whitened or reddened by solfataric action, and on cool days tall columns of steam rise from the numerous hot springs, giving the local- ity a weird appearance. Steamboat Springs is -only six miles from the Comstock lode and lies at the northwest base of Mt. Davidson, on the eastern flank of which is the great silver vein. The intervening space is for the most part covered with lavas, one of the sheets of which seems to be continuous for the entire distance. All the rocks which occur at Steam- boat are also found in the immediate neighborhood of the Comstock, and the fissures of the two localities are approximately parallel cracks, with many points of resemblance. Steamboat affords fine opportunities for the investigation of massive rocks, and the occurrences here serve to throw much additional light on the rocks of the Washoe district, described by me in Vol. Ill of this series. The proximity of the areas permitted me to make direct comparisons during the present investigation. The spring 331 332 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. deposits also have long been known to be of extraordinary interest, because they contain metallic compounds, including cinnabar and gold. So much cinnabar is found here in areas still emitting steam and sulphur gases that mining operations were undertaken some years since and a furnace was run for a time on the ore. That quicksilver was produced is certain, though I was unable to ascertain how many flasks. A considerable amount of ore is in sight, and there is no apparent reason to doubt that were the price of the metal to rise to a dollar a pound the deposit might be worked at some profit. Here, if anywhere, the question of the mode of genesis of cinnabar deposits can be settled, and the study of the locality was undertaken on that account. The results of this study and of laboratory experiments suggested by it appear in this and succeeding chapters. Granite The Hthological character of the massive rocks of Steamboat has been described in Chapter IV, and the details do not require repetition here excepting in reference to the distribution of the rocks and their rela- tions to field habit, The granite, which is exposed to a large extent, mani- festly underlies the whole region. In external appearance it is thoroughly typical, and no geologist would doubt for a moment how to classify it. It is unstratified, much fissured, weathers irregularly, and sometimes crumbles to a coarse gravel, as granites often do. Some of it is coarse, and it dis- plays considerable irregularities in texture and mineralogical composition, as if it had never been thoroughly fluid. Plagioclase is occasionally visible with the naked eye, but the predominant feldspar seems to be orthoclase. Under the microscope this granite appears less typical, inasmuch as the quantity of triclinic feldspar seems in the slides unusually large, and one might well doubt whether to class some of the rock as orthoclastic or pla- gioclastic. This is one of the cases in which the appearance is less truthful under the microscope than to the unaided vision, and this is doubtless due to the fact that the plagioclase is recognized by positive characters between crossed nicols, while the presence of orthoclase is evinced chiefly by the absence of polysynthetic structure. Separation by specific gravity shows that the more plagioclastic specimens of the rock contain about as much orthoclase as plagioclase. The granite of Steamboat Springs is substan- SEDIMENTARY KOCKS AT STEAMBOAT. 333 tially similar to that which appears near the southern end of the Comstock Lode. The superficial exposure there is very small, but the rock extends into the workings of the mines at American Flat. Similar granite is found near Washoe Lake, some miles south of Steamboat, and large exposures of it exist between these points and Lake Tahoe, in the Sierra. The granite is intersected by distinct dikes of granite porphyry. So far as observed these dikes do not penetrate the sedimentary rocks and are probably older than the beds. The metamorphic scries. Upon the granite lies a considerable area of sedi- ments, which are in part very highly metamorphosed and in part but little altered. These beds are usually nearly vertical and strike with the trend of the Sierra. Attempts to make two series of them failed and only resulted in showing that the metamorphism was partial and irregular. The highly altered portions considerably resemble Archaean schists, but the partial character of the metamorphism seems to forbid their reference to a Pre- Cambrian age. They are certainly Pre-Tertiary, for there are Tertiary strata within a few miles both to the north and to the south which are far less disturbed and not at all metamorphosed. The only other sedimentary rocks known to exist near the eastern edge of the Great Basin in this lati- tude are those determined to be Jura-Trias by the paleontologists who dis- cussed the fossils collected by the geologists of the Geological Exploration of the Fortieth Parallel. Dr. White, on reviewing the evidence on which the assignment was made, thinks it insufficient to justify any conclusion more definite than that the beds in question are Mesozoic. The descriptions of these Mesozoic rocks accord very well with the strata found at Steamboat. Their metamorphism is perhaps an evidence that they are not younger than the Neocomian, for no more recent alteration of any such intensity is known to have taken place later than the Post-Neocomian upheaval so often re- ferred to in this volume. The upheaval is the same as that called the Post- Jurassic by Professor Whitney, and its existence was no doubt given due weight by the geologists of the fortieth parallel when they referred the Mesozoic beds of Nevada to the Jura-Trias. As this region is separated from the gold belt by a great range of mountains, however, it is not impos- sible that its metamorphism may have been subsequent to and independent 334 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. of that of California, though no known fact lends this supposition proba- bility. A prolonged, but wholly unsuccessful search was made for fossils, which are also very rare in the other Mesozoic rocks of Nevada. A portion of these rocks are conglomerates. Among the pebbles of these conglomerates are some of diabase, identical with the porphyritic diabase which forms the hanging wall of the Comstock lode. There can be little doubt that these pebbles formed a portion of masses which were erupted simultaneously with that at Virginia, and it is possible that they came from that very mass, though this is not certain. I did not succeed in finding peb- bles of the still older diorite of Mt. Davidson, which may perhaps have been buried under the diabase at the time when the conglomerates were laid down. The bearings of the occurrence of diabase pebbles at Steamboat on the geology of Washoe I have enlarged upon in another publication. 1 Earlier hornblende-andesite Tl>6 oldest of tll6 laVaS of tll6 district is llOm- blende-andesite. It overlies the metamorphic beds in part and is distinctly more recent than the date of their upheaval. All this lava is very compact and of a bluish tint, but it is divisible into three varieties: one extremely fine- grained and often of a slaty texture ; one a comparatively coarse-grained, porphyritic rock ; the last glassy. Of these the first is most common. It is also found near the Ophir grade at Virginia, and the two occurrences are indistinguishably similar. The coarse-grained, somewhat grayish porphyry is best represented at Steamboat, near the eastern edge of the map. At Virginia this modification is perhaps the commonest. The glassy variety, associated with the others, is found at the western edge of the map of Steam- boat Springs. In this area there also occurs a very small amount of a pyroxenic andesite which, after careful study, seems to me to represent a strictly local variation in mineralogical composition and to pass over into the hornblende rock by transitions. The fact that this andesite overlies the metamorphics seems to indicate that it is later than the early Cretaceous. The existence of glassy modifications forming a portion of the areas is evi- dence that it is much later than the Cretaceous. Indeed it is hard to under- stand how the glass can have failed to be removed if this andesite is older than the Pliocene. 1 The Washoe rocks : Bull. California Acarl. Sei. No. !i, vol.'J, 1887, p. 93. ASPEKITES AT STEAMBOAT. 335 Later andesites. More recent than the hornbleiide-andesites described above are other andesitic rocks. These are divisible mineralogically into three varieties, and are so laid down upon the map. They appear, how- ever, to have been ejected almost simultaneously. They are all so recent that extremely little erosion has taken place and only a few depressions arc marked by water- courses. The difference in this respect between the areas of later andesites and the metamorphic areas is readily seen from the map where the amount of sculpturing corresponds to the geological colors. All the later andesites are rough, soft rocks, in which the feldspars are much cracked. Some of them are laminated, the beds averaging perhaps an inch and a half in thickness, and this modification is physically indis- tinguishable from similar occurrences at Clear Lake. One variety of these rocks is highly pyroxenic ; a second is hornblendic, though not free from pyroxene, and sometimes contains mica, while often lacking this constituent. Between the pyroxenic and hornblendic rocks are transitions of the 1 most unmistakable kind, which I have designated by a separate color and have entitled for the purposes of this one map " transition andesite." In thesa areas the composition of the rock is curiously variable. Thus, in a little triangular patch nearly south of the mines and embracing considerably less than two acres, specimens can be collected which in the office might well be supposed to represent three distinct species: one a pyroxene-andesite, one a simple hornbleude-andesite without mica, and the third a micaceous liorn- blende-andesite. But the whole area is thoroughly exposed and certainly represents only a simple eruption. The different varieties of rock were found here and elsewhere within a few inches of one another on the same blocks of lava, Such occurrences show how hopeless is the attempt to reconstruct the geology of an eruptive district from collections alone. The area colored as later hornblende-andesite is covered with rock almost indistinguishable from the later hornblende-andesite near the Corn- stock ; indeed, a very large proportion of the region intervening between the two districts is occupied by this rock and the lava field seems to be continuous from the northern end of the Comstock area to the eastern edge of the Steamboat Springs map. In botli neighborhoods the quantity of mica is variable, but near Steamboat it is exceedingly capricious. Mica is 336 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. sometimes present in most unusual quantities, forming a large percentage of the entire mass, and such flows appear to have been the latest of all. Else- where the rock is scantily supplied with mica and over considerable areas the most diligent search failed to reveal a single flake. The non-micaceous portions of the later hornblende-andesites are dis- tinguishable from the pyroxene -andesite only by the relative abundance of the bisilicates, texture and habitus being identical and both of them trachytic. The hornblendic and the pyroxenic modifications of this rock are in con- tact at the eastern portion of the map. Neither is eroded to any considera- ble extent, though both areas are more or less covered with loose fragments. I was unable to make sure whether the eruptions had been actually simul- taneous or not. On the whole, the pyroxenic rock seemed a little earlier than the hornblendic lava. On comparing the occurrences here with those at Virginia I found that transitions occurred at the latter locality also, which I had overlooked when I mapped the geology of that region. The transi- tion rocks in the Washoe district occur along the ridge of which Mt. Kate forms a part and near that peak, and are present in small quantities only. 1 At Virginia the pyroxenic portion of the later andesites is older than that which carries mica. On the other hand, Mr. Lindgren found near Mono Lake flows of pyroxenic andesites, entirely similar to that of Steamboat, overlying micaceous, hornblendic andesites. The order of succession is thus not a fixed one. At Steamboat the two are very nearly and perhaps abso- lutely contemporaneous. Both of them are later than the earlier dense hornblende-andesite and have overflowed it. The area of the older ande- sites at the east of the map is also intersected by dikes of the later rocks. These dikes are in part micaceous and in part free from mica. Those por- tions of them which carry no mica are sometimes highly charged with horn- blende and sometimes carry comparatively large quantities of pyroxene. 1 Tho occurrence of these transitions shows that the pyroxeue-audesito of the Mt. Kato Range im- mediately preceded the later horublende-audesite adjoining it. Tho pyroxene-andesito of the Washoe district (laid down on the map as augite-audesite) is divisible into two eruptions, one much older than the other, though without any intervening outburst. Tho Washoe district contains three pyroxenic rocks of different ages: diabase, which was followed by a hornblcnde-amU-site, and two successive outflo ws of pyrox^ne-audcsite, both later thau this earlier horn blendc-andesi to. The pyroxene-andesites were again followed by later hornblende-andesite. Dr. Whitman Cross pointed out the prevalence of hypersthone in audesito after iny discussion of the lithology of Washacs was completed. Compare my paper, " Washoe rocks," cited above. [UNIVERSITY] AU..ITIB AT *&.& They are all of the trachytic type. Similar rocks occur aBImdantly in the surrounding region. Special mention may be made of the Hufaker Butte, which is an isolated volcanic mass about four miles north of Steamboat, in the valley. This seems clearly to represent a single eruption or a series of eruptions embraced within a short interval of time. The rock is all tra- chytic, in part highly micaceous and in part free from mica. While it is quite possible to distinguish varieties among these later an- desites, they pass over into one another in such a manner as to indicate that they form a natural group. The distinctions are, at least near Steamboat Springs, of little geological importance. As is pointed out in Chapter IV, similar rocks occur at Mt. Shasta and from Clear Lake to the Bay of San Francisco, Imt those of the latter area are remarkable because they usually contain mica and pyroxene, but no hornblende. All these andesites seem to be more recent than the close of the Pliocene and all have a similar physical character. Some contain pyroxene with a very little hornblende; some, pyroxene and mica, but no hornblende; some, hornblende with a little pyroxene and no mica; some, much mica, a little hornblende, and a trace of pyroxene. Every possible combination of these ferromagnesian silicates excepting those altogether excluding pyroxene is represented ; there is no known difference in mode of occurrence and the order of succession is variable. This group of rocks is the same which, before the reference of lavas to the microscope became habitual, were -regarded as trachytes. The name is indefensible, for the rocks are plagioclastic ; but the thing to which it was given is a geological entity. I have therefore proposed for this nat- ural group of rocks the name aspcritcs, which is etymologically an equiva- lent of trachyte, but of Latin origin. Basalt. The basalt of Steamboat is in no respect remarkable. Though it covers a considerable area, the amount of the rock is by no means great, for it is evident from some exposures that the sheet is only a few yards in thickness. 1 Kmbtless, however, the depth of the lava is variable. Basaltic breccias form a portion of the mass. The basalt eruption antedates the deposition of ore, at least in part; for where it adjoins the mine it is sol- fatarically decomposed and cinnabar has been deposited in crevices in the lava. The spring deposits, including the cinnabar, have formed close to MON XIII 22 338 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. the edge of the basalt, and I can see no reason to doubt that they result from the volcanic action of which the lava eruption was one manifestation. The springs. The present vents of the springs lie along a series of fissures about a mile in length, shown on the map nearly parallel to the railroad. These cracks have formed in a mass of sinter deposited from earlier vents and are in part choked up by detritus, in part covered by recent deposits, but they are nevertheless traceable for long distances. The vents in many cases retain their fissure character and the water may be seen and heard boiling in openings, evidently of great depth, from an inch to two feet in width and many yards in length. At other points the cracks are closed, with the ex- ception of pipe-like openings, through which the water reaches the surface. At vents of the latter class there often form smooth mounds of Winter, from the summit of which the water escapes continuously or fitfully. Some of the springs have a true geyser character, though on a very small scale, alternately disappearing from their basins and returning to them with noise and agitation at short intervals of time. It is said by the inhabitants that in some seasons the water returns to certain of the basins with sufficient violence to be thrown several feet into the air, but during my visits the maximum action did not exceed a plentiful overflow. It is very clear that these springs are short-lived. In the most active area they are to bj found in every approach to extinction. Some have completely covered their own vents with sinter, though when the crust is broken hot wator is still found below, while other mounds and cracks are completely cold. Some very active vents are also manifestly extremely recent and have only lately begun to form new deposits. The extinction and subsequent formation of springs has certainly been in progress for a long time and the accumulation of sinter is large. The upper line of vents is about one hundred feet above the railroad, which runs along the base of the mass of sinter. The ground beneath the sinter, however, evidently slopes outward from the hills, and the maximum thickness of the deposits is probably about fifty feet. Active springs formerly existed at many other points. The map extends eastward to the foot of the Virginia Range. The rocks of this range a little farther eastward are greatly decomposed, apparent- ly by solfataric action. There is also on the map east of the railroad one STEAMBOAT SPRINGS. 339 small area of sinter in which there is now no evidence of activity. Much of the main area of sinter is likewise cold and dry, but some three thousand feet due west of the active group of fissures is a second group, now nearly extinct, of which only one is shown on the map. From this small quantities of steam and other gases still escape at a few points. At the mine only small quantities of sinter exist and the fissures are not superficially defined as in the areas just mentioned, though it is clear that the lines of vent ex- tended in a direction nearly north and south. In some of the excavations the ground is moist and still hot enough to be painful to the touch. Gase-i, too, still escape, but no water flows. The entire area of sinter and decom- posed granite north and west of the basalt area is continuous and manifestly has a common origin. There can of course be no question that the thermal action of this locality is volcanic. The area of thermal activity is at the foot of a stream of comparatively recent basalt, which was the last rock ejected. The relations thus point very clearly to an immediate connection between the basalt eruption and hot springs. In discussing the solfatarism of the Washoe district I inferred that it was probably of later date than the eruption of later hornblende-ande- site, while of its time-relations to the basalt eruption there was no means of judging. 1 I was not then aware of the evidence that the activity at Steamboat was directly referable to the eruption of basalt. The thermal action on the Comstock has advanced somewhat farther towards extinction than that at Steamboat; for, while the water on the 3,000-foot level of the Comstock is charged with carbonic and sulphydric acids and has a tempera- ture of 76.7 C., most of the vents at the surface at Steamboat show still higher temperatures and the water at a distance of half a mile below must be greatly superheated. Nevertheless the thermal action in each of the districts must be of approximately the same age, as are also the basalt erup- tions of tin; two areas; and the fact that the origin of the spring in the one cast; is directly traceable to the eruption of basalt makes it extremely prob- able that in the other also the basalt eruption gave rise to the thermal ac- tivity. The relations of the lava to the springs at Steamboat are strikingly 1 Geology of the Comstock Lode, p. 207. 340 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. similar to those studied by Dr. Hector near Lake Omapere, in New Zea- land, where, too, the sinter contains cinnabar. (See page 50.) Diversities. The effects produced by the action of the heated waters and of the gases accompanying them in the various portions of the affected area differ very materially and in an interesting manner. The heavy masses of sinter near the railroad are to a considerable extent composed of carbonates and all effervesce with acids. Much of the mass is silica, however, in part crystalline and in part amorphous. The material is deposited in layers or bands, partly lining crevices and partly covering the adjacent country in more or less nearly horizontal sheets. The linings of the crevices have a ribbon structure precisely such as is found in veins and composed of sub- stantially the materials most common in veins, excepting indeed the hy- drated silica. In the northwestern part of the area carbonates occur only in small quantities. The deposits here are for the most part chalcedony, which also exhibits ribbon structure. In the neighborhood of the mine workings only small quantities of silica and carbonates have been deposited. Here, indeed, the quantity of material removed by the spring waters is greatly in excess of the deposits which they have formed. In the southern part of the ground, where mining has been carried on, an actual basin has been formed, with a low rim to the north, which, however, is not sufficiently high to be exhibited by the 20-foot contour lines. This basin, from which there is no drainage, is not artificial, and appears beyond question to have formed in consequence of the collapse of the decomposed granite, yet it contains not only cinnabar, but a thin layer of sinter composed of carbonates and silica There is no reason to suppose that the general character of the fluids and gases which have been active in the various portions of this area dif- fered qualitatively ; on the contrary, the entire character of the deposits and the distribution of decomposed granite indicate that the qualitative com- position was the same. Variations in the quantitative composition of the waters thus seems to have been sufficient to bring about either the deposi- tion of large masses of material or an actual subsidence of the surface. This important inference maysaom doubtful when drawn from this locality alone; for, though there is no indication of a qualitative difference in the SINTERS AT STEAMBOAT. 341 waters, the proof that the water which undermined the basin south of the furnaces was similar to that now issuing near the railway is negative. At Sulphur Bank, however, we have springs of similar qualitative composi- tion which are not depositing sinter to any extent and which are actually removing material by their solvent action. The difference at the two localities appears to depend largely upon the quantity of sulphuric acid generated. At Steamboat, also, the depressed basin contains sulphates, which have been formed by the action of sulphuric acid on the rocks, and I can see no reason to doubt that the quantity of sulphuric acid generated has determined deposition of sinter or removal of constituents of the rocks. The silica of the sinters. As has been stated, one portion of the sinter area consists almost solely of a flinty or chalcedonic mass. This is by no means ancient, for scalding steam still issues at one point, nor does it show any signs of erosion. Under the microscope the sinter is found to be composed of ordi- nary quartz crystals and fibrous, crystalline silica. No opal was detected with certainty by the microscope. This rock is almost absolutely identical with some of the chalcedonic specimens from Knoxville, which contain, in addition, cinnabar. The sinters from the springs now most active are finer grained than that just described. They are composed of silica and carbon- ates. The silica is certainly in part crystalline and does not remain dark between crossed nicols. To obtain further information about the existence of opal, water deter- minations were made of three specimens, care being taken to separate the water from other volatile constituents. One of the specimens was a rnilky- white, compact rock with dull luster; a second was a very dark slate-col- ored rock with a resinous luster; and the third, a pure-white sinter, earthy and friable in part. The water absorbed in a calcium chloride tube was in the order of the descriptions 0.72, 3.77, and 0.67 per cent. These ex- periments show that hydrous silica was present in three specimens and that they were true chalcedonies, if by that term is understood a mixture of crystalline and amorphous silica. 1 It is evident from these observations 1 Some remarks will be madt; in Chapter XIV ou another iise of the word chalcedony. 342 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. that crystalline silica, both fibrous and granular, forms from thermal springs at the earth's surface. cases. Besides steam, hydrogen sulphide, carbonic anhydride, and sulphurous anhydride escape from the springs and fissures. The quanti- tative composition of the gas manifestly varies from point to point, and therefore quantitative analyses were not made. In the qualitative analyses free hydrogen and hydrocarbons were looked for, but none was detected. Neither were oily hydrocarbons found here as they are at most quicksilver deposits, though low forms of vegetation flourish in the waters of the hot springs even at very high temperatures. The absence of hydrocarbons from the gases and deposits is a very important fact. The sinter rests upon granite, and through this rock the springs reach the surface. If the hydro- gen sulphide were a result of the reduction of soluble sulphates by organic matter, hydrocarbons would almost certainly be present, as was pointed out by Bunsen in his great memoir on the geysers of Iceland. The com- position of these gases, therefore, points to generation from inorganic material at the seat of volcanic activity far below the surface. Whether, under the unknown conditions there prevailing, hydrogen sulphide can be derived from sulphates without the intervention of organic matter by some reaction not yet discovered, or whether the sulphur comes from regions which have never been oxidized, is uncertain. The same gases are percep- tible at the mine as at the more active springs ; it is possible, however, that a portion of the sulphurous anhydride at the mine is due to the decomposi- tion of hyposulphites. The metalliferous deposits The springs now flowing emit no great quantity of water and many of the vents did not overflow at all during my visit ; neither does the water seem to be impelled toward the surface with an}- vio- lence and in most cases it is perfectly clear. The mass of sinter through which the water attains the surface is also many yards in thickness. The deposits formed in the vents, particularly when they are narrow cracks, con- sequently consist of substances which have been held in solution by the waters and which have been precipitated by cooling, evaporation, and, to some extent, by acidification Large quantities of these deposits were col- ORES AT STEAMBOAT SPRINGS. 343 lected at different points and were analyzed with the utmost care. In the waters themselves one could expect to find only those substances which were most abundant in the natural precipitates, because they represent the concentration of much larger quantities of water than it would be practicable to evaporate for analysis. The spring deposits were found to contain the fol- lowing metallic substances arranged as nearly as may be in the order of their quantity : Sulphides of antimony and arsenic, ferric hydrate, lead sulphide, copper sulphide, mercuric sulphide, gold, and silver, together with traces of zinc, manganese, cobalt, and nickel. In the spring water itself only antimony, arsenic, and traces of mercury were detected. In considering the analyses, it must be remembered that the greater part of the metallic deposits are not at the vents of the living springs, but to the west at the mine, where no springs now exist, though steam and solfataric gases in small quantities still escape. Metalliferous spring deposits Specimens I and II were from an old crevice in the plateau of sinter near the railroad. The crevice was sealed with sinter and the ground was entirely cold. When it was opened no water was found. The deposit was r true, simple fissure vein between walls composed of earlier sinters. It was brick-red in color, like almost all of the metalliferous de- posits of the plateau, the tint being due to red, precipitated sulphide of antimony, a mineral which I believe has received no name. 1 The color of some of these deposits is such as to suggest impure cinnabar, but in none of those near the railway did we find enough mercuric sulphide to account for the tint Qualitative analysis showed the presence of mercury, gold, silver, copper, lead, arsenic, antimony, iron, aluminium, manganese, zinc in minute quantity, traces of cobalt and nickel, lime, magnesia, lithium, sodium and potassium, silica and sulphur. A minute quantity of sulphates appeared to be present. Quantitative separations were made with very large samples. The object was to obtain weighable amounts of the metals, in order that an idea might be obtained of their relative abundance. The precise estimation, however, has only a general value, because the deposit 1 Dr. .1. Sterry Hunt desiring to mention this mineral in bis classification, I suggested metaslibnite (Proc. Am. Philos. Soc., vol. 25, 1888, p. l&J). 344 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. is manifestly of variable composition, results: The following figures give the i. II. Weight of sample Crams. 1 021 0000 Qramt. 3 403 0000 Gold oOOft 0034 Silver 0003 001 0.0014 0070 0. 0899 070 Cuprio sulphide 0.0064 0. 0424 78 0308 3. 5924 Specimen III was taken from a crevice at some points of which hot water and gas still escape, but from a portion of the fissure no longer active. Qualitative examination showed the presence of mercury, gold, lead, copper, antimony, arsenic, iron, aluminium, manganese, traces of nickel, lime, traces of strontium, magnesium, sodium, potassium, lithium, caesium, rubidium, free silica, and free sulphur. The bases were combined as sili- cates, carbonates, sulphates, sulphides, chlorides, borates, and phosphates, the last in small quantities. The color of the material showed that the greater part of the arsenic and antimony was in the form of sulphide. Special determinations of the mercury were made with portions of this deposit After drying and pulverizing, the carbonates were extracted with dilute chlorhydric acid and the heavy metals were dissolved in aqua regia The precipitate given by sulphureted hydrogen was leached with cold, yellow ammonium sulphide and the residual sulphides were weighed. A portion of this residue, heated in a closed tube with sodium carbonate and pure iron powder, gave a sublimate of metallic mercury. This sublimate was tested by uniting the globules to larger ones, by amalgamating gold, and by conversion into mercuric iodide in a closed tube. From another por- tion mercurous chloride and gold were precipitated by phosphorous acid. The gold produced the characteristic tint and a button of metallic gold in a pure state was finally extracted. Another portion of specimen III, ex- amined quantitatively, gave the following result: Grant R. Weight taken 2, !."i. 0000 Mercuric sulphide found 0.0024 Snl jib ides of arsenic and antimony 4.27 - J~> OEES AT STEAMBOAT SPRINGS. 345 Another sample (IV) from the same crevices which contained III, but from a point at which steam and sulphurated hydrogen bubbled through the hot water, showed an entirely similar composition; it contained mercury, lead, copper, arsenic, antimony, iron, aluminium, calcium, magnesium, sodium, potassium and lithium, free silica, and free sulphur. The bases were combined a>e silicates, sulphides, sulphates, carbonates, chlorides, borates, and to a small extent as phosphates. Specimen V was from one of the springs which had formed a basin, through which occasional bubbles rise to the surface. The sediment con- sisted of layers of gray and yellow material, the latter being tinted by sulphide of arsenic. It contained mercury more abundantly than those previously mentioned, and also lead, copper, arsenic, antimony, iron, and aluminium, a trace of cobalt, magnesium, sodium, potassium, caesium, lithi- um, free silica, and sulphur. The bases were combined as silicates, car- bonates, sulphides, sulphates, chlorides, and phosphates. At one point on the plateau a mud deposit is formed by deposition from streams issuing from two of the more active springs. Here mica scales exist, showing that in this case some material is brought up in sus- pension from the underlying granite, which must consequently b'e under- going decomposition ; for the feeble streams of water which rise through it are certainly incapable of wearing granite away at such a rate that the abraded portions would be visible to the naked eye. This mud must there- fore contain products of decomposition of granite, as well as any substances which may have passed through the granite in solution. Qualitative analysis showed that it had nearly the same composition as the other de- posits. The portion soluble in acid contained mercury, gold, silver, lead copper, arsonic, antimony, much iron, aluminium, a trace of cobalt, mag- nesium, calcium, and of course alkalis. The bases were combined as silicates, ca.i-bonat.es, sulphides, and to a small extent as phosphates. A warm spring, which is known as the Chicken Soup Spring, issues at the base of the plateau close to the railway, the water of which is drunk by visitors to the locality. No mercury could be detected in the sedi- ment; but sulphides of arsenic and antimony and free sulphur, as well as low vegetable forms, abound in it. 346 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Free sulphur occurs at many of the springs and also at tne mine. It is of course produced by the partial oxidation of hydrogen sulphides, either by atmospheric air or by sulphurous anhydride. The quantity is nowhere large, and I doubt whether more than a pound or two could be collected at any one spot. In this respect there is a great difference between this locality and Sulphur Bank, where a great quantity of sulphur was exploited. The sulphur is found chiefly at points to which the access of air is limited, as should be the case according to the thermochemical relations stated on page 255. The water. The water analyzed was taken from a spring at the eastern edge of the sinter plateau, which had formed a basin. The water in the basin seemed perfectly limpid and the overflow was gentle and nearly con- stant. The temperature of the spring was found to vary considerably, the extreme limits noted being 75 and 84.5 C. In order that the water might be free from solid impurities it was siphoned off from the basin into a covered funnel and was filtered directly into the demijohns used to trans- port it. In passing through the siphon the water was inevitably cooled, and it was found that the water on the filter paper had a temperature of from 30.5 to 33 C. In collecting 1 the water in this manner a very inter- esting fact was observed. Near the lower end of the glass siphon a red precipitate formed. Since neither air nor any other foreign substance had access to the water at this point, the precipitation could hardly be attributed to any other cause than cooling. The precipitate consisted of sulphides of antimony and arsenic and silica, the last being deposited chiefly on the upper part of the coated portion of the tube. Here, then, ores and one of the most important of gangue minerals were deposited in an opening by natural means, and I had the pleasure of watching the actual progress of the formation of an ore deposit. On the filter paper also a similar precipitate formed, but here the organic matter of the paper and atmospheric influences were at work, and floating dust came in contact with the fluid. Even the water in the spring basin must have contained organic germs, for at all the springs, so soon as the water has somewhat cooled, low forms of vegetable life flourish and form red and green, pulpy sheets of slimy matter. The germs of these organisms are no doubt abundant in the atmosphere and fall WATER OF STEAMBOAT SPRINGS. 347 into all the spring basins. On the inner walls of the siphon tube diatom- like structures were visible with the microscope. The cooling of the water was unquestionably. necessary to the development of these organisms, and in the absence of air it seems impossible to suppose that they can have grown sufficiently to have influenced the precipitation of the sulphides. An attempt was made to collect a considerable quantity of precipitate by simply cooling the water of this spring as described above, and for this purpose a number of long siphons were set in operation. But, though the precipitates in the tubes were very striking in appearance, the quantity of precipitate obtained in filtering 118 liters was only about nine milligrams. It was almost completely soluble in yelloAV ammonium sulphide, and, to my disappointment, not a trace of mercury could be detected. Perhaps this was to be expected in view of the proportion which cinnabar bears to the sulphides of antimony and arsenic in the other deposits. The following results were obtained from analysis of the water : Analysis of Steamboat Springs wahr. [Contents of 10 liters in grams.l Silica, SiO J 3. 10G5 Carbon dioxide, CO 2 1.7759 Boric anhydride, B 2 O 3 2.1741 Sulphuric anhydride, SO 3 1.0339 Hyposulphurous anhydride, S 2 2 0.0307 Sulphur combined, S as RHS 0.0327 Hydrogen sulphide, H 2 S 0.0055 Or sulphur, S 0.0052 Chlorine, Cl 9.5243 Antiniouious anhydride, Sb 2 O 3 0.0051 Arsenious anhydride, As'O 3 0. 0357 Phosphoric anhydride, 1 M O B 0. 0063 Mercuric sulphide, HgS Trace Alumina, Al-O' 0.0025 IVrvous oxide, FeO 0.0018 Lime, CaO 0.0958 Magnesia, MgO 0.0047 Soda, Na-0 9.1929 Lithia, Li J O.. 0.1541 Potassa, K Z O 1.2460 Caesium and rubidium oxides, Cs^O, Rb 2 O Trace The caesium and rubidium in this analysis were detected by the spec- troscope, but the quantity present was too small for determination. The 348 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. mercury was precipitated by phosphorous acid under conditions precluding the precipitation of any other metal. A faint cloudiness indicated its pres- ence, but no weighable quantity came. down. The basin from which this water was taken was small and contained perhaps no more than a cubic foot of water ; but the overflow was also small, and a part of the water in it must have been exposed to the air at a high temperature for a considerable time. Some decomposition was there- fore to be expected. If solutions of alkaline sulphides be allowed to oxi- dize, hyposulphites are well known to form. The analysis shows hyposul- phurous acid, and this, I think, must be attributed to decomposition, for its formation at great depths appears hard to explain, nor am I aware that hyposulphites have ever been detected under conditions which suggest their existence in nature at points removed from oxidizing influences of the air. The hyposulphurous acid is undoubtedly combined with sodium, and prob- ably represents a certain amount of oxidized sodium sulphydrate. The 'decomposition of sodium sulphydrate is well known to be attended by the formation of sodic hydrate. The antimony and arsenic were certainly in solution, and it is altogether probable that they were originally in the form of sulpharsenides and sulphantimonides of sodium. But in the presence of caustic soda these sulphides are partially decomposed with the formation of arsenites and antimonites- The sum of the quantities of sulphur found in combination with metals and in the free state or in combination with hy- drogen is just sufficient to form sulphantimonides and sulpliarsenide of sodium, and the presence of hydrogen sulphide is explained if one supposes the sulphosalts partially decomposed, as suggested above. In the table given below I have supposed the arsenic and antimony to be entirely in the condition of sulphosalts and that the hyposulphite is represented by sodium sulphydrate. As has been mentioned, silica is precipitated when this water is cooled ; but when the fluid reaches the surface there can be little doubt that it all exists in combination with the alkalis as an acid silicate. It is not improbable that this compound is the quadrisih'cate of sodium It is computed as such. Acid sodium carbonate is well known to be partially decomposed at high temperatures, and it is therefore by no means unreasonable to suppose WATER OF STEAMBOAT SPRINGS. 349 that a part of the sodium salt was neutral. This supposition also accords with that made with reference to the silica. The alumina was probably present as an alkaline aluminate, but the quantity found was so small that it did not appear worth while to coinpute~1ts hypothetical compounds. In Chapter XV it will be shown that the trace of mercury in this water is combined as a double sulphide with sodium, which is of the form HgS, ^Xa 2 S. The value of n in this case is probably four. No comments seem needful on the state of combination of the other constituents of this water. The suppositions made lead to the following scheme of composition as the most probable prior to the action of the atmosphere upon the fluid : Probable composition of the water prior to oxidation. Grams. Ferrous cai-bonare, FeCO 3 .................. , ................ 0.0029 Magnesium carbonate, MgCO 3 ............................... 0.0099 Calcic carbonate, CaCO 3 .................................... 0.1577 Calcic phosphate, Ca 3 P 2 O 8 .................................. 0.0137 Potassic chloride, KC'l ...................................... 1.9735 Lithic sulphate, Li 2 SO 4 ..................................... 0.5650 Sodic chloride, NaCl ........................................ 14.1475 Sodic sulphylrate, NaHS ................................... 0.0358 Sodic sulphate, Na 2 SO< ..................................... 1.1147 Sodic bicarbonate, NalICO 3 ................................. 2.9023 Sodic monocarbonate, Na 2 CO 3 .............................. 0.4314 Sodic biborate, Na 2 BO T .................................... 3.1368 Sodic quadrisilicate, Na a SW ............................... 3.9090 Sodic sulphantimonide, Na 2 SbS 3 ............................ 0.0100 Sodic sulpharsenide, Na"AsS 3 ................................ 0.0866 Alumina, AW ............................................ 0.0025 Sodium-mercury sulphide, HgS, jiNa^S ...................... Trace origin of the water. Old residents informed me that the quantity of water flowing from the springs varies from year to year, being greater in years of heavy rain-fall than in dry seasons and greater in spring than in autumn. If these statements be accurate, the supply must come from the surface and no very long time can intervene between precipitation and return to the surface. It is natural to suppose the great snowy range to be the source of supply. The fissures underlying the range may afford a downward pas- sage for the waters to the heated mass from which the basalt came, while the fissures associated with the channel through which the basalt was ex- 350 QUICKSILVER DEPOSITS OF TIIE PACIFIC SLOPE. traded furnish a shorter road back to the surface. 1 The water must be well filtered ou its course, since there is no evidence that organic matter is car- ried to the source of heat. The cinnabar deposit. The quantity of mercuric sulphide in the deposits from the active springs is very minute, and there is in this district nothing which could be called quicksilver ore in a commercial sense, excepting near the mine workings and furnace on the northern central portion of the area mapped. Cinnabar is deposited in considerable abundance only in the de- composed granite, though a few paints and seams have penetrated into the basalt at the southern end of the basin-like depression. By no means all of the decomposed granite, however, even in this area, shows any ore, the cinnabar occurring only as impregnations in the decomposed area, appar- ently along the courses of half-obliterated fissures in the soft material. The underground workings are now almost wholly inaccessible, and some prospecting would be necessary to ascertain anything definite with regard to the amount of ore available. The mode of occurrence of cinnabar indi- cates that the deposition did not proceed pari passu with the decomposition of the granite, but followed it. Had it been otherwise, cinnabar would be found generally over the decomposed area and the impregnated granite would be tolerably firm, instead of forming a gravel-like, incoherent mass. It is very probable that at depths of a hundred feet, more or less, the char- acter of the deposit would be found to differ markedly from that at the sur- face, for the phenomena here, as at Sulphur Bank, are complicated by the action of sulphuric acid due to the oxidation of sulphureted hydrogen. Mctais in the granite. The present springs are certainly decomposing granite to some extent, and decomposition of this rock on a large scale has occurred within no long period. It seemed probable that at least a portion of the heavy metals found in the deposits were derived from the granite and pos- sible that all of them had this origin. Rock from the area east of the rail- road was selected because it was fresh and well removed from springs, act- ive or extinct. Large quantities of granite, in one case 15.5 pounds, were finely pulverized and decomposed either by aqua regia, which does not 1 Compare my suggestion as to tbe source of the water entering the mines on the Couistock (Geol- ogy of the Comstock Lode, p. 243). METALS IN THE GllANITE. 351 decompose the mica, or by hydrofluoric and sulphuric acids. Both the resulting solutions were examined for heavy metals; and arsenic, antimony, lead, and copper were found in those prepared by each of the above meth- ods. but neither mercury nor gold could be detected in either. Experi- ments made with 50 grams of hornblende and mica separated from the rock also failed to detect mercury or gold. Lead almost if not quite always contains silver, so that the presence of lead in the granite points to the existence of silver in that rock, although the tests available were not suffi- ciently delicate to reveal it. Professor Sandberger has actually found silver in the micas of German granites, as well as arsenic, lead, copper, and other metals, lie has also detected zinc in the mica of gneiss. 1 Silver is rarely if ever found in nature unaccompanied by gold, and it is altogether prob- able that micas in which Professor Sandberger found silver also contained the sister metal. According to Mr. A. Simundi some of the Idaho granites, collected at long distances from any veins, carry determinate quantities of gold.- The granite of Steamboat Springs exhibits considerable variations in texture and mineral composition, as do most other granites. This and other phenomena indicate, as Scheerer and others have pointed out, that granite has never been thoroughly fluid and is not uniform in composition. It is therefore far from impossible that specimens of this rock from other points in the region of Steamboat Springs might have shown gold, silver, and zinc. Considering that the granite is certainly undergoing decomposition and partial solution by action of the springs and that the metals most abundant in the spring deposits are also found in the granite, it seems to me only reasonable to conclude that from the granite the springs derive the arsenic, antimony, lead, and copper which they bring to the surface. The other metals are found in the deposits in far smaller quantities than those just enumerated. Though not detected in the granite here, all of them except- ing quicksilver are known to occur elsewhere in granite or gneiss. It is also worth noting that silver, gold, and zinc, are very frequently associated in nature with arsenic, antimony, lead, and copper. The prevalence of this iilicr Ki/^iiuge, p. 25. Euimons and Becker, Statistics and Technology of the Precious Metals, p. 54. 352 (JUICKS1LVEU DEPOSITS OF THE PACIFIC SLOPE. association seems to point to the supposition that these metals are often derived from the same source. It is therefore much more probable that the silver, gold, and zinc also were derived from the granite at Steamboat than that they came from the unknown regions beneath it or from some mass of lava crossing it. As for the quicksilver, I am not a. ware that it has ever been detected as a constituent of a massive rock ; but it is found at very many points the world over in association with gold, copper, arsenic, and antimony, or some of them. All the circumstances at Steamboat seem to point to the granite as its probable source, and, so far as I know, nothing suggests a different origin. conclusions As Messrs. J. A. Phillips 1 and Laur 2 have pointed out, Steam- boat affords instances of the formation of true fissure veins by hot springs at the present da}'. While it is quite probable that some veins are formed in a different manner, it is substantially certain that many deposits have been generated in this way. The composition of the waters, with special experiments devised for the purpose, also leads to definite conclusions con- cerning the soluble compounds of the metals contained in the waters, as will be shown in Chapter XV. Steamboat Springs, too, affords a striking illus- tration of lateral secretion. This term is sometimes limited to segregations affected by cold solutions, but quite improperly, for the extraction and dep- osition of ore from the rocks adjoining fissures by hot solutions are just as much lateral secretion as if the prevailing temperature were low. The term is used by von Cotta without any limitation as to temperature. As it has been employed by Mr. S. F. Emmons and myself also, a limitation as to temperature has never been implied. comparison with the comstock. There are noteworthy similarities and differ- ences between the deposits of Steamboat and of the Comstock lode. At Steamboat gold is present in much larger quantities than silver, as it is in all the deposits of the gold belt of California. At the Comstock the pro- portion of gold to silver by weight is only about 1 to 20. At Steamboat arsenic and antimony, lead, copper, and mercury are the most abundant metals, while on the Comstock mercury is not found at all and the prevail- ing ore is auriferous argentite. As I showed in my memoir on the Com- 1 Ore Deposits, 1884. " Annalcs drs mines, vol. ;!, W>:'>, p. !.':;. STEAMBOAT SPKINGS AND THE COMSTOOK. 353 stock, it is probable that the ore was there leached from the diabase hanging wall by the action of ascending waters of very high temperatures, charged with alkaline solvents, and was not deposited by sublimation or distillation, as Baron von Richthofen surmised. THe difference in origin of the two ore deposits sufficiently explains their difference in character. It is of course possible that a part of the ore of the Comstock may have been derived from granite, and it is noteworthy that the ore of the Justice mine, which is near the granite area, was much baser than and quite different from that of the mines of Gold Hill and Virginia. I shall be obliged to return to this sub- ject in Chapter XVI. MON XIII 23 CHAPTER XII. DESCRIPTIVE GEOLOGY OF THE OATHILL, GREAT WESTERN, AND GREAT EASTERN DISTRICTS. In addition to the five districts described in the previous chapters, small areas surrounding the Napa Consolidated, Great Western, and Great Eastern mines were mapped. The topography of these maps was executed rapidly and without any effort to attain the degree of accuracy demanded in the larger maps. It is nevertheless very fairly done, and, excepting in some minute details, the localities are excellently represented. I intrusted the study of the geology of these districts to Mr. Turner. On going over the surface area and the mines with him, at the completion of his examina- tions, I could not see that anything had been omitted or misrepresented. This chapter is mainly prepared from his reports. OATHILL. The neighborhood of oathiii. The region including Oathill, the .97 flasks, but has not been worked of late years. The deposit upon which these two mines are situated is somewhat remarkable for its isolation. Not only is it above twenty miles from the nearest quicksilver mine, but it lies away from the cou-rse of any line of deposits. It is also somewhat distant from manifestations of volcanic activity, the nearest known lavas being about six miles east of the Great Eastern. Genai geology The district surveyed presents little interest from the point of view of general geology. The surface is exclusively occupied by the series of irregularly metamorphosed rocks so prevalent in the Coast Ranges. Slightly altered sandstones and shales, impure limestones, gran- ular metamorphics, schists carrying glaucophane and garnet, phthanites, and serpentine are all represented. So thoroughly mingled are these vari- ous substances, however, and so numerous are the transitions that it would be entirely impracticable to represent the varieties by colors on the map (Plate VII). Although a portion of the beds are so little altered that fossils might have been tolerably preserved in them, no organic remains could be detected. 8 g B n 2 M > y "-a | p K i|.is s Q B H w > rr F| H o 1 1 ' ? UII7BR3ITY GREAT EASTERN DISTRICT. 363 Consequently their age is a matter of inference. The fac.ts bearing on this question are as follows: Along the coast of Sonoma County, to the south of Ft. Ross and a little more than six miles from the Great Eastern, I found a series of unaltered sandstone beds lying -nconforma,bly upon the meta- morphic series. The overlying strata are fossilifereus at some points and have been named the Wallala beds. Dr. White has determined the fossils which they contain as Middle Cretaceous. The underlying metamorphic series is older, arid there can be little doubt that it is at least as old as the Knoxville series. It may possibly be older, but all the characteristics of the rock are absolutely identical with those of the material at numerous points from Colusa County to San Luis Obispo, in which Amelia has been found. There is, furthermore, nothing in this part of the country suggest- ing the presence of strata earlier than the Knoxville series. So far as there is any evidence as to the age of the rocks at the Great Eastern, therefore, they are to be regarded as Neocomian. Quicksilver r0 ck. In this district there are numerous occurrences of opal- ized rocks. Of these many are small, seemingly isolated patches. In two cases this material forms defined ledges, standing up from the surface on account of the resistance which it offers to decomposition and erosion. These ledges strike nearly east and west magnetic, which seems to be the prevalent strike of the strata also. In one of these are the deposits of the two mines. At the surface the metalliferous ledge is nearly vertical, but at lower levels it dips to the north. It lies between a hanging wall of sand- stone and a foot-wall of serpentine. ore deposits. It will be remembered that at the Great Western also a layer of opalized rock lies between serpentine and sandstone. At the Great Eastern, however, the ore is inclosed in the dark, opaline mass, instead of being adjacent to it. The ore body was continuous from the surface to the lowest workings, a vertical distance of 450 feet. The ore does not form a nearly vein-like sheet in the ledge, but an irregular pipe, the axis of which is inclined to the horizon at an angle of about 50. So far as it has been developed it is entirely embedded in the opalized rocks and does not touch either the sandstone or serpentine. The ore does not appear to have been deposited simultaneously with the amorphous silica, but in openings in the 364 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. material. It is accompanied by pyrite and quartz. Bitumen is also found, especially in covities in the opaline mass. The deposit of the Mt. Jackson seems to have been similar to that of the Great Eastern, but of smaller extent. The explorations do not appear to have been sufficient to decide whether there are or are not other similar pipes of ore in this layer of rock. The following- cut (Fig. 17) represents a vertical cross-section of the ledge upon which the ore pipe is projected : Flo. 17. Vertical cross-section of the Great Eastern mine. Scale, 150 feet to 1 inch. Probable history. The dark, opaline or chalcedonic " quicksilver rock" of this locality seems to have resulted from a silicification of several rocks, chiefly perhaps of serpentine. Both here and at the Great Western this silicification seems to have preceded the deposition of ore, though somewhat closely connected with it. The deposition of silica, in part amorphous, probably succeeded a movement attended by the development of hot springs. Renewed movements followed, dislocation taking place in tho opalized beds at the Great Eastern, close to those at the Great Western, and these later movements were succeeded by the deposition of ore. This interpretation of the structure is supported by the existence of other ledges of the opalized material in which no cinnabar seems to occur. CHAFFER XIII. OTHER DEPOSITS OF THE PACIFIC SLOPE. Besides the eight districts described in the foregoing chapter, there are many less important localities in which cinnabar has been found and from which more or less metal has been extracted. A considerable number of these have been visited by myself or by members of my party and others have been described by previous observers. Such notes on these occur- rences as are available w\\\ be presented in this chapter. Many facts con- nected with these deposits are of great geological interest, but, on the other hand, a large number of the deposits are so similar that it is impossible to avoid monotony in their description. The quicksilver belt. The quicksilver belt of California cannot be said to be continuous to the north of Clear Lake, for between that sheet of water and the- next deposit to the north there is a long stretch of country. It is possible, indeed, that cinnabar may yet be met with in this interval, which is very inaccessible and has been but little explored. The chances, how- ever, seem against it, for the volcanic phenomena which are associated with so many of the deposits to the south seem to be absent between Clear Lake and the neighborhood of Mt. Shasta. There are cinnabar deposits at the northern end of the Coast Ranges, however, in the northeastern corner of Trinity County, and some fifteen miles from the edge of the volcanic rocks of the Mt. Shasta region. Cinnabar again appears in the Cascade Ranges of Oregon, which, as is pointed out in Chapter V, I regard as a northern continuation of the united Sierra Nevada and Coast Ranges of California. These occurrences to the north are thus on a continuation of the group of profound dislocations which are marked by the ranges and 365 366 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. deposits to the south, and they show that the series of chemical phenomena leading to the deposition of cinnabar have been repeated at long geograph- ical intervals. At the north, as to the south also, the deposits are formed at no great distance from lavas. The entire belt of country from the mines of Douglas County, Oregon, to Santa Barbara is thus structurally continuous and is marked by irregularly distributed volcanic phenomena and cinnabar deposits. In a broad sense the entire zone, six hundred miles in length, may be considered as a quicksilver belt. It will be convenient to take up the deposits not described in the foregoing chapters in the order of their latitude, beginning at the north. North of ciear Lake The deposits of Douglas County, in Oregon, are sit- uated on the western flank of the Cascade Range, the base of which is composed of granite and metamorphosed sandstones precisely similar to those at Knoxville and other points to the south which have been minutely described in Chapter III. The crest of the range is occupied by lavas. The New Idrian mine is said to be the principal deposit. It was visited in 1880 by Mr. H. W. Leavens and it is reported by him to be a vein in sand- stone. The ore is cinnabar accompanied by iron oxides and, according to the report, by manganese oxide. 1 In 1882 fifty flasks of quicksilver are known to have been produced by the mines of this region. Near the boundary between California and Oregon, in Del Norte County, Rockland district, in the neighborhood of the Diamond copper mine, cinnabar and native quicksilver were described as occurring in a whitish-gray rock in 1874. 2 I know of no second notice of this occur- rence. . The quicksilver district of Trinity County, California, is in its north- eastern corner. The rocks are mainly metamorphosed sediments, largely serpentinized, but volcanic rocks are said to occur at intervals, and there are mineral springs directly at the principal mine, the Altoona (formerly called the Trinity). The rocks immediately associated with cinnabar are serpentine and sandstone. The ore occurs in part as a tabular impregna- ' Statistics and Technology of the Precious Metals, by S. F. Enimous and G. F. Becker, pp. 27 and 28. 'Mining ami Scientific Press, vol. 29, August 15, 1874. THE MANZ ANITA. 367 tion several feet in thickness and in part as narrow seams of rich ore. One observer describes the deposit as a replacement vein between serpentine and sandstone. The vein matter is decomposed country rock and the gangue is quartz. The strike of the deposit is nearly north and south. 1 coiusa county mines. One of the most interesting deposits in the world is the Manzanita mine, on Sulphur Creek, close to the hot sulphur springs now known as Wilbur Springs, but formerly as Simmons's Springs. The rocks are highly metamorphosed beds of the Knoxville series. At a dis- tance of about three-quarters of a mile from the mine is a bed of limestone, composed of shells of Rliyncliondla Whitneyi, held together by a small amount of matrix. Within a few yards of the mine itself I collected perfectly re- cognizable specimens of Aucella conccntrica. The age of 'the rocks is thus fully determined. The strata are thin-bedded, highly altered and con- torted, shaly sandstones, a part of them somewhat serpentinized. The waters of the hot springs, which are only a few hundred feet from the mine, are highly charged with sulphureted hydrogen and are very salt. They also seem to contain borax. The surrounding country shows that, as is so usual with springs of this class, the position of the vents has repeatedly changed and much of the rock in the neighborhood has been leached by sulphuric acid. Hot sulphur waters once issued from the mine itself, for it contains a large amount of free sulphur. The ore consists of cinnabar and gold, which are sometimes in direct contact, and some metacinnabarite. These minerals are accompanied by pyrite and marcasite, chalcopyrite, stibnite, calcite, and quartz. The gold is often visible in feather-like, crys- talline aggregates, sometimes in direct contact with cinnabar and some- times deposited directly upon calcite, which is more prevalent in the ore than is quartz. The cinnabar and gold are often separated by a layer of calcite an eighth of an inch in thickness. Oily and resinous bitumens are also tolerably abundant in the workings. The ores and gangue minerals do not form a regular deposit, but occur as thin seams, penetrating the rock sometimes along the partings between strata and sometimes cutting across the beds. It is evident on inspection 1 This information is derived from an unpublished report of Mr. C. A. Luckhardt, Report of the Mining Commissioners, 1876, and from Statistics and Technology of the Precious Metals, by Emmona and Becker. 368 QUICKSILVER DEPOSITS OF TOE PACIFIC SLOPE. that the reck has been greatly disturbed and that wherever a fissure was produced the ore-bearing solutions penetrated. The fact that native sulphur occurs in the mine in considerable quanti- ties, taken in connection with the adjacent springs, is sufficient proof that the deposit is due to the action of hot sulphur waters. In mineralogical composition the ore is similar to that of most of the quicksilver mines, except- ing in the fact that it carries gold in such quantities that the mine has been worked for this metal As has been seen in former chapters, gold occurs in much smaller quantities at Sulphur Bank, Knoxville, and Steamboat Springs. The Manzanita forms a link between cinnabar and gold mines and shows that both minerals may be deposited from the same solutions, not merely in traces, but in notable quantities. No volcanic rock is known to exist within several miles of the Manzanita, but the very hot sulphur springs seem ample evidence of volcanic agencies. It is important to note that this manifestation of volcanic activity with attendant ore deposition is found at a distance from lavas, so that, were the springs to dry up and the country to be somewhat eroded, no direct evidence would remain that any connection ever existed between this deposit and the eruptive phenomena. The Buckeye and the Abbott's mines are near the Manzanita, and each of them has produced some quicksilver, the latter over two thousand flasks. Mr. W. A. Goodyear visited these mines. He describes the ore as consist- ing of cinnabar accompanied by pyrite, marcasite, and chalcedonic silica. The ore lines cracks and seams and impregnates earthy matter. Associated with the ore is a considerable quantity of the black oval so often referred to in the preceding pages. 1 The Baker mine. This mine lies about half-way between Lower Lake and Knoxville. It was visited by Mr. Goodyear, who found metacinnabarite in the ores. A specimen of marcasite which I collected at this mine was ex- amined for gold and was found to contain it, the quantity being about one dollar per ton. The Mayacmas district. A very large part of the many cinnabar deposits north of the Bay of San Francisco are found along the Mayacmas l\ange, which extends in a northwesterly direction from Mt. St. Helena. Two 1 Geol. Survey California, Geology, vol. 2, appendix, p. 1_M. THE MAYACMAS BELT. 369 of the deposits of this district, the Great Western and the Napa Consoli- dated, have already been described. Mr. Turner was instructed to make a reconnaissance of this district as a whole, and the following 1 information is chiefly derived from his report. The underlying rock of the entire district appears to consist of metamor- phic strata. At the southeastern end of the district some of these beds contain Aucella concentrica, and are certainly, therefore, members of the Knoxville series. 1 The lithological and physical character of the metamor- phic rocks throughout the remainder of the region is identical with that of the rocks immediately associated with these fossils here, at Knoxville, and elsewhere, and there is no reason to suspect the presence of strata of other age than the Neocomian in the met- amorphic series To the north of the Oathill mines is a small area of un- altered rock carrying very imperfect fossils, the age of which is uncertain. Upon the metamorphic rocks lie great quantities of andesite and basalt. The andesite is for the most part glassy when fresh, though asperites are al- so found. This rock constitutes the greater part of the mass of Mt. St. 'The exact locality is on (lie cast bank of Pope Creek, at the point at which the road from Lidell to Knoxville crosses it. MON XIII ->-! 370 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Helena and covers large areas to the north, east, and southeast of that mountain. The summit of Mt. Cobb is also andesitic. Tufaceous forms of andesite, usually much decomposed, are also abundant, especially to the south. At the southern end of Mt. St. Helena there are argentiferous quartz veins in andesite from which a considerable amount of ore and, it is said, $90,000 of bullion have been extracted. About one and a half miles north of Calistoga, in King's Canon and on a small ridge to the north of it, there are argentiferous quartz veins in andesite. Two of these strike northeast and southwest and two others cross them, striking nearly north and south. One of these latter is called the Elephant and carries ore of great interest, both cinnabar and pyrargyrite being visible in it, as well as pyrite. Tin- cinnabar was chemically tested and the silver ore was analyzed. The latter contained antimony, with a mere trace of arsenic, sulphur, silver, copper, arid a trace of lead. Here, then, is a true vein, carrying almost precisely the same ingredients as the deposits of Steamboat Springs. This is also the only case known as yet on the Pacific slope, excepting Steamboat Springs, where lead and quicksilver occur together. This vein is certainly a com- paratively recent one, for the greater part of the andesites of the region are Post-Pliocene. In ore from one of the other veins (the Grigsby) cinnabar and pyrite were found together. Large quantities of basalt were erupted at a much later period than that of the andesites. It occupies large areas to the north of Oathill and the igneous region east of Middletown is mostly basaltic. Some of the rock last mentioned produces a marked effect upon the needle and contains much magnetite. In some cases andesitic hills are capped by basalt. There are immense quantities of tufa to the southeast of Mt, St. Helena, and embed- ded in it are fragments of compact basalt, showing that the tufa belongs to the basaltic series of eruptions. The tufa is especially abundant in the neighborhood of the North Cone and South Cone and it often forms dis tinctbeds, which are sometimes considerably inclined. It not infrequently includes great quantities of metamorphic pebbles. The drainage and triangulation of the accompanying sketch map are mainlv compiled from surveys by Mr. (J. F. Hoffmann, but this material has THE MAYAOMAS BELT. 371 been supplemented by observations by Mr. Turner. While the foregoing notes indicate in a general way the distribution of andesite and basalt, no attempt was made to map the two lavas separately. The areas marked as igneous are to be considered as only approximately correct, the cartograph- ical base not being sufficiently good to permit of much detail. The area not occupied by igneous rocks is metamorphic. The most southerly mine of this district is at Lidell and is known as the Valley claim. Lidell is resorted to by invalids for the sake of the hot sulphur baths, supplied by a spring which issues from the old workings of the Valley mine. Cinnabar may still be seen in the silicified and opaline rocks. The mine never paid for working, but is interesting for the direct association which it presents between cinnabar and hot springs. The ^Etna property is a mile distant from Lidell and comprises sev- eral claims between which are marked differences. The Phoenix, which has yielded large quantities of quicksilver indeed, most of the product of Pope Valley is entirely in sedimentary rocks consisting mainly of serpen- tine and other highly metamorphosed strata, though unaltered sandstones also appear in the workings and in parts of the mine are in direct contact with the metalliferous ground. The rock directly inclosing the ore from the surface downward was highly silicified slate and black, opaline chalcedony. The cinnabar occurred in stringers in this material and as impregnations in the softer rock and in the attrition products accompanying it. There are manifold evidences of the existence of a fissure system and of motion in the ground, so that in some places well defined walls exist. The ore was first found at the surface and was followed down for about one hundred and fifty feet. This upper ore body yielded about seventeen thousand flasks of quicksilver and then gave out completely. Vigorous prospecting below the old ore body of late years has disclosed the existence of more oi'C in depth. The Phoenix appears to belong to a group of deposits of cinnabar, instances of which are very numerous. The ore-bearing solu- tions have ascended along a fissure system, formed in very heterogeneous material, and have penetrated the wall rock with corresponding irregularity, producing irregular stockworks and impregnations tending to a tabular form. In the upper levels the ore contains some native quicksilver, which 372 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. disappeared as depth increased. Besides the usual pyrite and marcasite, millerite is found in fine, bronze-colored needles on the 300-foot level. This mineral has been observed as microscopic crystals in the slides of ore from several of the mines in California, but not elsewhere in crystals visible to the naked eye, so far as I know. Napaute. The mine contains much yellow, bituminous matter, usually of a consistency similar to that of shoemaker's wax; indeed, it has actually been employed as a substitute for that useful material. It has been exam- ined by Dr. Melville and turns out to bo a new mineral. The substance is dark reddish brown and shows green fluorescence by reflected light; by transmitted light, brilliant garnet red. It is interesting to note that the green fluorescence disappears in a great measure on ex- posure to the air, evidently with a loss of some very volatile constituent. The specimens from which the material was obtained for analysis had un- dergone this change, only a few smaller fragments exhibiting the original color. The ethereal solution is reddish brown, with green fluorescence, and both this solution and the solid resin are highly refracting. The luster is resinous and the hardness about 2. Ibis brittle, but by the warmth of the hand mav easily be molded and drawn into long threads. It is not elastic. / / The fracture is conchoidal. It begins to fuse at 42 C. and becomes liquid at 46 C.; it boils above 300 C.; at 130 C. a heavy, colorless oil distills over, yielding an aromatic odor ; then at a higher temperature yellow- brown vapors rise with a peculiar suffocating odor, and finally a heavy, dark red oil condenses, much resembling coal-tar in smell. The boiling- point of this last product is not far below the temperature of 350 C. Many intermediate products were obtained by fractional distillation, but the yield was very small below 236 C., above which colored distillates were collected. At the temperature of softening of the glass boiling-flask a small amount of carbonaceous matter remains, showing that decompo- sition in part results Bromine attacks the resin with deposition of carbon. Ether dissolves it completely in the cold; so, also, does oil of turpentine, but not so readily; cold alcohol takes up but a small quantity. It is com- bustible and yields absolutely no residue. A small amount of sulphur was detected in one sample, but its absence in others proved that its origin was V*" o UJTI7BRSIT7 373 in the sulphurets sparingly disseminated throughout the rock specimen. It is associated with pyrite and millerite in vesicular quartz. The specific gravity is 1.02. The following analyses were made on three different samples : (I) Pure material selected from that in the rock specimen ; (II) material dissolved in ether filtered, and the filtrate allowed to solidify spontaiieously ; (III) ma- terial fused at a low temperature and allowed to flow away from small frag- ments of rock : 1 - II. III. i Carbon, C 89.84, f9.54 89.35 Hydrogen, H | 10. 1" | 10. 36 | 10.11 100.01 99.90 i 99.46 The resin is therefore a hydrocarbon, and the analyses correspond closely to the formula C 3 H 4 , which would contain 90 per cent, of carbon. Since it is decomposed by heat its vapor density cannot be determined, and its structural formula could not be ascertained without a more elaborate investigation than was practicable. This mineral has not been described, and must therefore be named. The term napalite seems unobjectionable. On the 150 and 300/oot levels inflammable gas issues from cracks. As shown by the following analyses by Dr. Melville, the chief component is marsh gas : Carbonic uuliydrido 0.74 Marsh gas 61.49 Nitrogen 31.44 Oxygen G.33 100. 00 The Starr deposit, belonging to the same company, is said to have produced five thousand flasks of quicksilver and is of peculiar geological interest. It occurs at the contact between a basalt dike and the sandstone through which the lava has broken. The ore occurs both in the sandstone and in the basalt along the contact. The workings extend to a depth of 400 feet from the surface and the ore is not yet exhausted. Similar to the last and also on the property of the ./Etna Company is the Silver Bow. So far as observed, the ore in this mine is wholly in the 374 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPI]. decomposed basalt close to its contact with the sandstone. This dike is typical, standing up as a ridge above the inclosing rocks and showing a double columnar structure, one set of columns being transversely arranged, while the other, at the croppings, is nearly vertical. The existence of these superficial vertical columns shows that little erosion can have taken place since the eruption of the rock. The yEtna property also comprises two other claims: the Washington, containing alluvial deposits of cinnabar as well as native quicksilver along clay seams, and the Pope claim, which contains a deposit of cinnabar in contorted and silicified shales. The ^Etna mine is included in a belt com- posed of serpentine, which can be followed almost without interruption as far as St. Helena Creek, a distance of about seven miles. In this belt crop- pings of opaline matter, which is largely opalized serpentine, form an almost continuous ledge, with traces of cinnabar at many points. At one point, the No. 2, or Phoenix No. 2, some work has been done. Mr. Luckhardt describes this mine as opened upon a layer of slate three to seven feet in width and carrying seams of ore of six to eight inches in width. The deposit seemed unusually regular, but ore appears not to have been sufficiently abundant to repay exploitation. All of the deposits mentioned above, as well as the veins of cinnabar belonging to the Napa Consolidated Company, which have been described in a previous chapter, are within three miles of the hot springs at Lidell and within a triangular area measuring less than a square mile. Among them are deposits in unaltered sandstone, in highly metamorphosed strata, and in eruptive rocks. The} 7 embrace regular veins, impregnations, and re- ticulated masses. Three of the deposits show unquestionable connection with very recent volcanic activity, for one of them occurs in basalt, the second is in contact with the same lava, and a very hot mineral spring flows from the third. There is no i*eason to suppose that different genetic proc- esses have been at work in this small area; on the contrary, there is every reason to suppose that the deposits, embracing all the principal types of occurrence, have been precipitated from waters heated by volcanic action, in a manner similar to that by which the ores of Sulphur Bank and Steam, boat Springs have been produced. GREAT EASTERN AND GREAT WESTERN MINES. 375 The next deposit to the north of the Pope Valley group of mines is the Great Eastern, in Lake County, on St. Helena Creek. 1 This deposit was remarkable for the richness of its ores, but the quantity of quicksilver produced was small and the mine has been abandoned for several years. The specimens obtained from the dumps show that the ore was accompanied by opaline rock and that an oil was present, associated with dolomite. A large amount of unaltered sandstone on the dumps suggests a wall of this rock. Just northeast of this claim, on the opposite side of the creek, is Bradford's Prospect, in which also the cinnabar is associated with opal. Difficult drainage, due to the proximity of the creek, is said to have inter- fered with the development of this deposit. It is stated that since I visited this locality a shaft has been sunk and that a considerable ore body has been developed. The next deposit to the northwest is the Great Western, described in detail in the preceding chapter. The district between the Great Western and Pine Mountain has been actively prospected, and many claims have been taken up and again abandoned. It is not possible to get much infor- mation about these deposits, none of which has been extensively developed and in none of which extensive ore bodies were found. The Wall Street is on a layer of opaline, metamorphic rock. Glaucophane schists occur in this mine and it was in specimens from this locality that glaucophane was first detected in California. Native quicksilver existed here as well as cinnabar. The American mine was located upon a ledge of indurated strata which form croppings of considerable height. The rock consisted of alternating beds of sandstone, siliceous slate, and partially serpentinized sandstone, and underlying the ore-bearing strata was dense serpentine. The cinnabar sometimes impregnated disintegrated and ocherous material, but was mostly found in seams and bunches in the siliceous rocks. Quicksilver, pyrite, and bitumen accompanied the cinnabar. The deposit appears to have been an impregnated series of strata'and the ground must have been charged with ore after the metamorphism of the rock. 2 According to Mr. D. de Cort;izar 3 specimens containing selenide of mercury were obtained from this mine. 1 A more important mine of the same name in Sonoiin Comity has been described 1u the preceding chapter. 1 Unpublished report of L. Janin. 'British Reports on thr rhilnrirlpliia International Exposition of 187(1, vol. 3. 376 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE The Flagstaff is a claim adjoining the Pioneer and very similar to it. The ore-bearing ground is a stratum of argillaceous sandstone impregnated with metallic mercury, which is accompanied by a little cinnabar. 1 Pro- fessor Whitney visited the region in 1861, when some of the mines were being worked, and has published the following notes concerning them: 2 The Cincinnati is on the bill-side near a steep canon, northeast of Pine Mount- ain ; from it Mt. St. Helena bears S. 3^ E., and tbe mine was estimated to have an altitude of about two thousand five hundred feet. The prevailing rock is serpentine, filled with threads and veinlets of quartz, running through it in every direction, pre- senting a rather peculiar appearance, as some of the quart/ is in a crystallized form. Both cinnabar and native mercury have been found here, but there was little appear- ance of regularity in the deposit and uo large mass of ore had been discovered. * * The Dead Broke lies about one mile west of the Cincinnati. The rock here con- sists of alternating layers of dark and light colored and partly decomposed quartzite ; the strike is about N. 5 W.-S. 5 E., and their dip, which is to the west, about 45. On the east side of the ridge imperfect serpentine was seen, and a level had been driven in it for 265 feet. The cinnabar, of which rich specimens had been procured, was contained in a stratum about four inches wide and parallel with the formation. The Pittsburg claim is one half a mile N. 15 W. from the Dead Broke, and some cinnabar has been found here in serpentine. The Pioneer mine, which is south of Mt, Cobb and not far from the Little Geysers, was also visited by Professor Whitney, who says : The rock most nearly associated with the ore is the same peculiar siliceous variety usually seen at the cinnabar mines of California, and it is inclosed on both sides by serpentine. The strike of the metalliferous lode or vein was nearly northwest and southeast. The metal exists here both in the form of the sulphuret, as cini:abar, and in the native state; indeed, so far as we know, it is one of the most remarkable local- ities of native mercury ever discovered. The metal occurs disseminated in fine glob ules through the veiri-stoue, or in larger quantities in the interior of quartz geodes or pockets. Over six pounds have been saved from a single pocket, and one of the first cavities broken into yielded four pounds three ounces of the metal, besides what was unavoidably lost in collecting. These facts are stated on the authority of Mr. B. C. Wattles, the superintendent. * * * Considerable bituminous matter occurs here, as in most of the other mercury mines of the State, and some of the quartz geodes contain bitumen. From Pine Flat, in- Sonoma County, a definite belt of deposits extends in a direction which is about 25 west of north. It is very noticeable on the sketch map that this belt of deposits occurs at a considerable distance from any volcanic rock, while, on the other hand, it passes within a mile of 'Unpublished report by L. Juiiin. 3 Geol. Survey Culiforiiin, Geology, vol. 1, p. 89. OAKVILLE AND BELLA UNION MINES. 377 the group of hot sulphur springs miscalled geysers. Some of these springs reach the boiling-point and emit steam. They are very numerous and active and are regarded as one of the sights of California. Their character is such as is almost universally attributed to volcanic activity. Their presence near the quicksilver mines therefore indicates that the remoteness of the deposits of cinnabar from the nearest lavas does not preclude a relation between vol- canic activity and ore deposition. The mines of this group are the Sonoma, the Rattlesnake, the Little Missouri, the Oakland, the Kentucky, and the Cloverdale. The Rattlesnake produced only about sixty-five flasks of quick- silver, but it is a noteworthy fact that this product was obtained almost entirely from native quicksilver disseminated in a friable sandstone. An unusual quantity of oily bitumen accompanied this ore, and it is recorded that there were special arrangements to burn the hydrocarbons because of the quantity of soot which they formed in the condensers. 1 Though most of the ore was an impregnated unindurated sandstone, the usual opaline rock also occurred here and sometimes showed geodes containing oil. The Oakland mine, as stated in the table of production, Chapter I, produced G,831 flasks, and may perhaps be reopened under favorable circumstances The product of the Cloverdale was 2,GG1 flasks, but the Kentucky only turned out 54 flasks. Another small mine, beyond the limits of the map, is the Livermore. It lies two miles west of the junction of Pluton Creek and Sulphur Creek. oakviiie ana Beiu union. Small quantities of cinnabar occur in the hills bounding Napa Valley on the west, about half way between Calistoga and Napa City. The principal deposits are on two adjoining claims, the Bella Union and the Oakviiie. The rock is siliceous slate, associated with serpen- tine. The slates strike north and south and dip at 60 or 70 westward toward the summit of the range. The ore is exclusively cinnabar, accom- panied by pyrite and calcite. It forms seams in the slates and irregular o bunches connected by narrow stringers of ore. The Bella Union has pro- duced some metal. 2 T. Egleston, Trans. Am. Inst. Min. Eng., vol. 3, p. 273. 8 The information concerning these mines is derived from an unpublished report of Mr. C. A. Luck- hardt. 378 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. county. The most southerly of the mines north of tlie Bay of San Francisco is the St. John's, four miles northeast of Vallejo. It is situated in an isolated ridge of metnmorphic rock trending from northwest to southeast and lying in Sulphur Spring Valley. The surrounding region is unaltered. In the metamorphic area also there are portions of little modified rock, and at two points on the ridge Mr. Turner found Aucclla moxquensis. One of these localities is in the main tunnel of the St. John's mine, and the shales in which the fossils occur seem beyond doubt the same which, at a distance of 150 feet from the fossils, are indurated and contain cinnabar. The second Aucclla locality is three-quarters of a mile southeast of the mine on the same ridge. At this point the shells occur in calcareous nodules in shale. These fossils of course determine the rocks as belonging to the Neo- comian formation. The ore was found at the croppings and is said to have been discovered as early as 1852. The ore body exposed at the croppings extended down- ward about four hundred feet and furnished most of the metal which this mine has produced. Much of this ore was inclosed in a white, greatly decomposed rock, which is probably a metamorphosed sediment, further altered by the action of sulphuric acid and other reagents. At one point it crosses the tunnel very like a dike. There is nothing suggesting the pres- ence of eruptive rocks on the surface. According to Mr. Neate, the owner of the property, an open fissure exists in proximity to the main ore body, but the position of this fissure is now inaccessible. Like most of the quick- silver mines, the St. John's carried some bituminous matter. In the west- ern mine workings cinnabar occurs in highly siliceous, apparently chalce- donic rocks, and close by is serpentine, forming a wall to. the ore-bearing ground. As appears from the table of production, this mine has yielded 8,598 flasks of metal. MI. Diablo. Cinnabar is found on the eastern slope of the north peak of Mt. Diablo, associated with the usual black opal and chromic iron ore. It is said that some thousands of dollars' worth of the metal was extracted from this locality. In the ravine just below the mine is a sulphur spring, and farther down the slope is another mineral spring which must formerly have been very active, for it has deposited a large quantity of calcareous sinter. PANOCHK DISTRICT. 379 To the south of this spring deposit in a hill of asperite and at the con- tact between this lava and the unaltered shale Mr. Turner found cinnabar. It is associated with copper pyrites and calcite and in some cases is so in- termingled with the latter as to show simultaneous deposition. There seems to be no quartz or opal at this point. This is the third locality in California at which cinnabar is found associated with andesite, and the circumstances are such as to leave little or no doubt that the deposition took place from hot sulphur springs, induced by volcanic action. Traces of cinnabar The discovery of cinnabar at Point Reyes was reported in 187;").' There is no improbability in the statement, but I have heard of no confirmation of the report and hesitate to enter it on the map. Pro- fessor Whitney states that small quantities of cinnabar and mercury were found in early days near the Mission, in San Francisco, in rocks of the usual type. Santa clara county. Besides the New Almaden, Euriquita, and Guadalupe, which form the subject for Chapter X, a small mine called the San Juan Bautista was worked in former years. It is in the northeastern portion of an isolated range or cluster of hills bearing the same name and is about four miles southeast of San Jose. The hills are composed of metamorphic rocks, largely serpentine. The ore deposits were irregular, but seemed in a general way to follow the stratification. Mr. Goodyear (loc. cit.) notes the presence of chalcedonic silica and of a hard, dark-gray, granular, crys- talline rock, which was probably pseudodiabase. My party has not visited this deposit panoche district Paiioche Pass, which is near the junction of Fresno, Merced, and San Benito Counties, leads from the area drained by the Pajaro River to that drained by the San Joaquin. The divide forms a por- tion of the somewhat irregular mountain system called by Professor Whit- ney the Mt. Diablo Range and is composed of rocks identical in character with the central metamorphic mass of Mt. Diablo. There is no reason for supposing these rocks to be of different age from those of Mt. Diablo and Knoxville, and there is considerable evidence that like them they are Neo- comian, but no fossils were found in them. The surrounding country con- 1 Mining and Scientific Press, February 27, 1875. 380 QUICKSILVER DEPOSITS OF THE PACIFIC! SLOPE. tains Miocene sandstones and heavy gravels supposed to be Pliocene. Both of these formations have been greatly disturbed and often stand at high angles. The metamorphic rocks near Panoche Pass contain a number of deposits of quicksilver, some of which have yielded metal. The Stayton mines was the name given to a group of fourteen prospects, which are remarkable because they contain stibnite in quantities equal to or greater than those of cinnabar. At one time quicksilver was reduced in a retort at this locality and at another the antimony ore was smelted. The mines have not been in operation for some years and little could be seen at the time of my visit, excepting that both minerals occurred in proximity, chiefly with quartz gangue, in siliceous and serpentinized rocks of the usual type. I saw no indications of a large or a regular deposit. The Wonder quicksilver mine was close to the Stayton and is said to have been similar. About eleven miles west of Panoche post-office, near the main high road, is a prospect called the Cerro Gordo. It is remarkable for the presence of metacinnabarite in the ore, which contains, besides, cinnabar, pyrite, and bitumen, associated with opal and crystalline silica. The inclosing rocks are of the metamorphic series and contain titaniferous magnetite. The material on the dumps seemed to me of a promising character. The Little Panoche mine is in a canon at the north end of Little Pano- che Valley. The workings were never large and are now for the most part inaccessible. The rock is metamorphic sandstone, highly silicified, but ac- companied by only trifling quantities of serpentine. The ore, as shown by the dumps, consisted of cinnabar and pyrite in a quartz gangue, with meta- morphic sandstone. I saw no evidence of a defined vein, though the work- ings may have disclosed something of the sort. The Cerro Bonito, sometimes called the Panoche Grande, is about three miles by road from Panoche post-office, in the northwestern corner of Fresno County. It lies close to a basalt area of considerable size, the only one of the kind known to me in this part of the country. The mine is in metamorphic sandstone, accompanied by serpentine, and the ore is associated with quartz and calcite. Very little pyrite exists in the dumps and the ore was dull, unpromising-looking material. According to Mr. L. Janin, the ore followed the stratification. The most promising ore-bearing SAN LUIS OBISPO DISTRICT. 381 ground was a vein-like formation from two to five feet in width, consisting of earthy decomposed rock, in which occurred threads and bunches of cin- nabar. Bowlders, too, were included in the matrix; they were impregnated with cinnabar to a greater or less extent. san Luis obispo. The mines of the San Luis Obispo are on the Santa Lucia Range, which extends from near Monterey southward along the coast. TUs range is chiefly composed of metamorphic rocks and Miocene beds. The metamorphic rocks are lithologically identical with those farther north and are also of the same age. Five miles from the town of San Luis Obispo, on the road to Santa Margarita, in a patch of comparatively little altered shale inclosed in the metamorphic series, Mr. Turner found an ex- cellent specimen of AuceUa mosquensis. This is the most southerly locality at which this characteristic fossil of the Knoxville series has been encoun- tered, and it is nearly three hundred miles in a direct line from the Man- zanita mine, in Colusa County, where AuceUa was also found. This inter- val is equal to three-fifths of the entire length of the Coast Ranges from Ft. Tejon to Shasta City. There is a considerable extent of Miocene rocks in this region, as well as a volcanic range which trends in a westerly direction and ends, according to Professor Whitney, in the Moro rock off the coast. It seems to consist of asperites. Hot springs are said to exist in abundance in the quicksilver district of San Luis Obispo, and extinct springs, evidently similar to those now active, are stated to occur close to the most productive of the mines, the Oceanic. The hot sulphur springs of Paso Robles are not far from this group of mines. The Rinconada mine is sunk on a deposit in metamorphic rocks among which is serpentine. These rocks are not distinguishable from those at New Almaden and other more northern districts. The deposit is partly in slaty material, accompanied by black opal, and partly in indurated sand- stones. Pyrite, calcite, dolomite, quartz, and organic matter accompany the ore. It is to some extent disseminated, but usually occupies cracks in the rocks, which it often only partially fills. The crevices sometimes cross the beds and sometimes follow them. The deposit has not as yet proved of any commercial value. It is interesting because its general character is so 382 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. like that of many deposits to the north in mineral association, in structure, and in the age of the inclosing rocks. Judging from reports of Mr. Janin, the Ocean View, Keystone, Jose- phine (also called Sunderland and Luckhardt), and other mines seem to have been essentially similar in the mode of their occurrence to the Rin- conada and to a great proportion of the other quicksilver deposits of Cali- fornia. The Oceanic was more exceptional, for its deposit consisted of a stratum of unaltered sandstone impregnated with cinnabar. The width of the stratum was several yards and at one time the entire body of rock paid for extraction and reduction. Specimens show that the cinnabar is asso- ciated with quartz as a gangue and that stringers of ore and gangue as well as impregnations occurred. A coarse conglomerate, said to form the " cas- ing of the vein," contains metamorphic pebbles, showing that the rock is at least as late as the Chico and probably Miocene, but no fossils are known to have been found in it, There is nothing improbable in the hypothesis that this rock is Tertiary ; for it has been shown in this report that in Cali- fornia cinnabar is associated with many rocks, both Pre-Miocene and Post- Miocene, and that it is known to exist in Tertiary strata in other parts of the world. The appearance of one specimen from the Oceanic suggests that the works have struck metamorphic rock beneath the sandstone. The Sulphur Spring claim adjoining the Oceanic on the west yields specimens of rich cinnabar. In the northwest portion of San Luis Obispo County good ore occurs at the Polar Star mine. Santa Barbara The Los Prietos is on the northern flank of the Santa Inez Range, some five miles northerly from the town of Santa Barbara. A belt of quicksilver-bearing rock is said to extend from this point for about six miles on a course south 50 east, or approximately in the direction of the range, and upon it several claims have been located. The occurrence is of the usual kind seams and bunches of cinnabar in metamorphic rocks, including serpentine and serpentinoid rocks. Specimens also show light- colored limestone with cinnabar. These mines have turned out a small quantity of ore, some of which has been reduced. 1 Hot springs occur at several points along this range of mountains. 'This information is derived from Mr. Janin. QUICKSILVER ON THE GOLD BELT. 383 other traces ot dnnabar. The occurrence of traces of quicksilver has been re- ported a number of times near Lake Elizabeth, in Los Angeles County, and the report is credited by persons whose opinion is entitled to respect. Cin- nabar also occurred near San Bernardinor -A small deposit is said to have worked out long since, and new discoveries were announced in 1873. 1 According to Mr. Schmitz, a mine superintendent, gold amalgam was found at many points on the gold belt in early days. He found one occur- rence in stringers in ''greenstone" five feet below the surface, which was analyzed by Sonnenscheitr and gave the formula AuIIg 3 . The exact locality is not given. Three extremely interesting occurrences on the gold belt of California are described by Professor Whitney. One of these is in Mariposa County, on the north bank of the Merced River, near Horseshoe Bend. Here an auriferous quartz vein six inches wide and resembling other such veins in most respects carried on its foot-wall a thin seam of quartz containing cin- nabar in crystalline plates and bunches. The seam was about an inch wide and appeared to be continuous. 3 Mr. C. L. Mast is now the owner of a ledge on the hillside east of the Merced River, near the mouth of Maxwell Creek, not far from Coulterville, which is probably the same vein referred to by Professor Whitney. The country rock is of the kind called by Professor Whitney greenstone and by Professor Wadsworth diabase tufa. The cinnabar occurs in crystals of unusually large size embedded in quartz and accompanied by very little pyrite. This ore was sold to the Chinese between 1850 and I860. Mr. J. W. C. Maxwell informs me that many years ago extraordinarily well crystallized cinnabar in a quartz gangue used to be brought from the country back of the town of Merced and sold to the Chinese as vermilion at a hi-h O price per ounce. This cinnabar may have come from the vein just described or possibly from some similar locality now unknown. In Calaveras County, near Murphy's, a quartz vein assaying well for gold also carried cinnabar in small quantities, according to Professor Whitney, with traces of vitreous copper ore and copper carbonates. The same geologist has also seen speci- 1 Mining and Scientific Press, vol. 27, 187:!, p. 1GG. "Zeitschr. Dnilscli. gcol. (icsell., vol. C>, 1854, p. 24;!. "Geol. Survey California, Geology, vol. 1, p. 2;iO. 384 QUICKSILVER DEPOSITS OF TBE PACIFIC SLOPE. mens of gravel from near Placerville, El Dorado County, containing gold and rounded grains of pure cinnabar. 1 This is probably at or near the locality, three miles south of Shingle Springs, from which not only float cin- nabar, but a ledge carrying this ore, was reported some years since. 2 Mr. Turner has visited this locality, which is at Cinnabar City. The deposit is a bedded vein in slates and quartzitic rocks. The cinnabar, accompanied by pyrite, occupies interstitial spaces. A furnace was built here and some quicksilver was produced. According to the county sur- veyor, Mr. G. W. Kemble, cinnabar also occurs in place in the ravine of Hastings Creek near its mouth and in the ravine of Clark's Creek about one mile from its mouth, the two localities being presumably on the same ledge. Hastings Creek empties into the south fork of the American River from the north about three miles from Coloma. Clark's Creek flows from the south into the same river about four miles northwest of Coloma. Gold amalgam is reported from British Columbia. 3 Mr. H. G. Hanks has also analyzed arquerite (silver amalgam) from Vital Creek, British Columbia, in latitude 53 north. 4 The only cinnabar deposit in British Columbia upon which any work has been done is at Kicking Horse Pass (lat. 51 20', long. 116 30'), two and a half miles east of Garden City. It is called the Ebenezer and is described as a vein of calcite flecked with grains of cinnabar. The ore is accompanied by pyrite and contains traces of gold. 5 Dr. G. M. Dawson reports that float cinnabar has been found in the gold washings on the Eraser River, near Boston Bar. Rich specimens containing cinnabar and native metal are said to have come from the west side of the Eraser, near Clinton, and the silver ores from Hope, on the Eraser, are stated to contain mercury. A well denned lode containing rich cinnabar ore is also said to occur on the Homathco River. 6 Mr. W. H. Dall informs me that in 1865 he saw a large piece of cin- nabar in the Colonial Museum at Sitka, Alaska, which was said to have been 1 Auriferous Gravels, p. 367. ^Mining .and Scientific Press, vol. 31, 1875, p. 118. 3 GeoI. Survey Canada, Geol. Canada, 18G3, p. 518. * Kept. State mineralogist California, vol. 4, 1884, p. 12. "Ann. Kept. Geol. Survey Canada, 18*ti, pp. !> T and 40 D. 6 Kept. Progress Geol. Survey Canada, l-7i'-'?7, p. l:!;i. QUICKSILVEE DEPOSITS IN THE GREAT BASIN". 385 brought in by the Indians from some portion of the Alexander Archipelago. It has since been reported as occurring on the Kuskokwim River. There seems to me no reason to doubt that cinnabar really does occur in Alaska, though more definite information is to fee-desired. In the Great Basin quicksilver ores occur at several points besides Steamboat Springs. In Idaho considerable quantities of float cinnabar have been found in Stanley Basin, at the eastern extremity of Boise" County, and along the Salmon River between the mouth of Yankee Fork and the town of Sawtooth, but the ore has not been found in place. 1 Prof. W. P. Blake wrote in 18i7: 2 Ciunabar of a beautiful vermilion color is fouud in Idaho abundantly spread through a gaugue of massive compact limestone or marble. No quartz or other minerals are visible in the specimens. Professor Blake writes me that these specimens were water worn or rounded fragments about the size of one's fist, and he thinks it not im- probable that the}- formed portions of a calcite vein in some other rock. Judging from the frequent occurrence of cinnabar with calcite in fissures in many parts of the world, this also appears to me probable. He cannot recollect ever having been informed as to the precise locality from which the specimens came, and they are most likely therefore to have been found in one or the other of the regions referred to above. Cinnabar, then, so far as known, has never been found in place in Idaho. Mr. Janin informs me of a very interesting occurrence of cinnabar in the Belmont district, Nevada. Rich seams of nearly pure cinnabar were found here in the Barcelona silver mine, following along the vein of argen- tiferous ore. Cinnabar has also been reported from Humboldt County and from the southeastern corner of Nevada, but with no details as to occurrence. In Utah the Lucky Boy claim, Mt. Baldy district, Piute County, con- tains bunches of tiemannite (mercuric selenide) in limestone. 3 In Feb- ruary, 1887, a mine was at work in the Lucky Boy claim upon a body of this rare ore about four feet in thickness. The ore sometimes contains 70 per cent, of mercury and is said to average 10 per cent. Three retorts were running and producing enough quicksilver to pay expenses. The 1 Kininous and Hecker, op. cit., p. 55. 'Emnions and Becker, loc. cit., p. 463. 2 Am. Jour. Sci., 2d sciies, vol. 4:?, 1867, p. 125. MON XIII L'u 386 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. product for the last quarter of 188G was 87 flasks. A furnace was being built. 1 This is, I believe, the only case in which tiemannite has ever been mined and reduced on a commercial scale. A body of low-grade cinna- bar is said to have been found near this mine. I also learned from Mr. J. E. Clayton, through Mr. D. T. Day, that cinnabar is found in the Camp Floyd district, near Lewiston, in the Oquirrh If jinge, about sixty miles south- west of Salt Lake City. The ore is said to occur in bunches and seams in calcareous shales of Carboniferous age and to be accompanied by heavy spar. The deposits at this locality can be followed for a mile or more, but the ore is of low grade and has not been worked. Cinnabar has been reported from New Mexico, but I have seen no definite locality given and no particulars. Many years since, remarkable specimens of ore containing cinnabar with gold, silver, and copper ores were shown in San Francisco, which it was said came from Arizona. 1 This iuformatiou was obtained from Mr. P. Cope, general freight ageut of the Utah Central Kail- way. CHAPTER XIV. DISCUSSION OF THE ORE DEPOSITS. Purpose of the chapter. The various cinnabar deposits of the Pacific slope have many features in common ; indeed, it does not appear to me practi- cable to divide them into two or more groups. Each mine, however, affords special facilities for the study of particular characteristics and comparisons are essential. This chapter will be devoted to comparative descriptions of the deposits and I shall also endeavor to include in it such information with reference to the occurrences as seems likely to be welcome to readers who desire a general knowledge of the quicksilver deposits of the Pacific slope rather than full particulars of any one property. It will include studies of the ores, gangue minerals, and inclosing rocks, a discussion of the place which these ore bodies occupy in the general classification of deposits, and remarks on the relations which they bear to metamorphic areas and to volcanic rocks. The origin of the ores and the manner in which they were dissolved and precipitated will be discussed in separate chapters. MINERALOGICAL CHARACTER OF THE DEPOSITS. ores. Quicksilver is obtained on the Pacific slope from four minerals, cinnabar, metacinimbarite, native quicksilver, and tiemannite (mercuric sel- enide). The last occurs in quantity only near Marysville, Piute County, Utah. Reduction works are in operation, and, it is said, at a profit. Cin- nabar is the chief ore in the United States, as it is elsewhere, and only a small portion of the metal is obtained from mctacinnabarite or in the native state. In the Kedington, Reed, and New Idria mines, however, large quan- tities of metacinnabarite were obtained from the higher levels, but large masses of this ore have not been seen in place during the present investiga- 387 I 388 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. tion. Native quicksilver in small and variable quantities is met in many of the mines. It is naturally oftener found in the lower portions of ore bodies than elsewhere, because of its fluidity and its high specific gravity, just as it permeates the earth far below the foundations of reduction furnaces when special means are not adopted to obviate its percolation. Hence miners do not welcome the appearance of native quicksilver. Gangue minerals. Dense masses of cinnabar, of considerable size, are found in most ore bodies, but the larger part of the ore is mingled with gangue minerals. These are few in number and are substantially the same in all the deposits. They are crystalline silica, opal, calcite, and dolomite. Asso- ciated with the cinnabar is also invariably pyrite or marcasite (sometimes slightly auriferous): millerite, too, in small quantities is common; and traces of copper as sulphide or carbonate are occasionally seen. Bituminous mat- ter is present in all the mines examined excepting Steamboat Springs. This substance, though sometimes disseminated through ore, is usually found in spots in the country rock. Sulphur occurs at the surface of three of the most recent deposits, and in the Maozanita mine, Colusa County, native gold and cinnabar are mingled. Cinnabar is also met with in some of the gold quartz veins of the gold belt. 1'yrargyrite and cinnabar are associated near Calistoga and this ore also contains arsenic and lead. At the Barcelona silver mine in Nevada cinnabar was found. A mixture of cinnabar with gold, silver, and copper ores is reported from Arizona, and at Steamboat the deposits con- tain gold, silver, lead, copper, arid zinc I know of no other case on the Pacific slope where zinc is found with quicksilver, but this association is not unknown in Europe. .The bitumen posepnyte was recognized at the Great Western mine and a new bituminous mineral, christened nj>ulilc, was found at the Phoenix mine. other associated minerals. Various other minerals have been identified in the mines, less important than the above or less closely associated with the ore. Gypsum is found with ore at Sulphur Bank. Magnesite occurs in the New Almaden, and perhaps elsewhere, with calcitic carbonates. Barite is found with cinnabar in the Oathill, and this is the only case known of the occurrence of barite with cinnabar in California. 1 Apophyllite in fine 'Au erroneous statement with reference to an occurrence of barito in this State will bo oxplai 1 further along. It is also reported with cinnabar in Utnli. ASSOCIATED MINERALS. 389 crystals occurs in the New Almaden, though at some distance from ore, in a geode, accompanied by bitumen. Specularite is found in hard crusts with pyrite and cinnabar in the Rinconada and limonite is naturally common near croppings. Melanterite often forms in the drifts of the mines. Copi- apite occurs both at Redington and at Sulphur Bank, as was proved both by quantitative analysis and by crystallographic properties. Among the efflorescences in the mines are epsomite from the Redington mine, of which a quantitative analysis was made, ammonia-alum from Sulphur Bank, and borates from the s:nne locality. Pyrolusite is found at the San Carlos and the alta of the New Almaden contains manganese. Morenosite coats one specimen of millerite, and nickel silicates are found at the St. John's and at the I'lKenix, but no nickel carbonate has been observed. Stibnite occurred with cinnabar at the Manhattan, the Manzanita, and at the Stayton mines. The red sulphide of antimony, for which I have suggested the name meta- stibnitc, and arsenic sulphides are abundant in the deposits of Steamboat Springs. Chromite is abundant in the serpentine of the Coast Ranges, and hence occurs also near cinnabar, though probably formed long before the ore. In the New Almaden some of the gangue is stained green with chromium sili- cates. The green stains were tested chemically; under the microscope they appear as greenish, cryptocrystalline grains. Two new hydrated chromium sulphates were found in the Redington mine at the point where solfataric gases issue, and they are doubtless the result of the action of these gases on chromite in the serpentinoid rocks. It is proposed to call the more highly hydrated compound redingtonite and that with loss water knoxvillite. It is needless to point out that a considerable number of the minerals enumerated above are products of decomposition processes which have taken place since the original deposition of the ore and gangue. Microscopical character. Many thin sections of the ore from different mines have been cut, but under the microscope they give results so uniform that the information thus obtained can be very briefly stated. The cinnabar is transparent only when the section is unusually thin. It is ordinarily only faintly translucent, transmitting dark-red rays, and is much better observed by reflected than transmitted light. As a rule the cinnabar seen in slides forms aggregates with only occasional crystalline outlines, which are usually 390 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. traces of prismatic faces. A few isolated and well developed crystals have been found showing 1 , in addition to the prismatic faces, terminal rhombo- hedrons. Cinnabar is often met with in dust-like aggregates disseminated through quartz, and with high powers this .dust often resolves itself into beautiful arborescent and capillary forms. In some hand specimens, too, quartz may be seen reddened throughout the mass by disseminated ore. These fibrous forms of the mineral are usually associated with concretionary structure and the ore is often deposited in concentric layers parallel to those of the accompanying quartz or at the centers of geodes. Good crystals vis- ible with the naked eye are very uncommon. Some such occurred in the upper portions of the New Idria mine and were secured for the collection by the courtesy of Mr. J. W. C. Maxwell. These are tabular and present some remarkable characteristics, which will be discussed in a separate paper. Vast quantities of silica occur with cinnabar at most of the California mines, and a large part of this material consists of mixtures of opal and crystalline silica. Such mixtures have long been known in geological liter- ature as chalcedony, and the term is used in that sense in this volume. Professor Rosenbusch has shown, however, that the fibrous silica crystals so common in these mixtures possess negative double refraction and are distinct from quartz. He calls this mineral simply chalcedony. 1 It seems to mo that the adoption of this name for this purpose will lead to much confusion, since chalcedony has been freely employed in literature in the other sense. A very slight modification of the term, however, would obviate this objection and would seem to escape any fresh ones. Cltulci'il- finitu at once suggests a mineral characteristic of chalcedony, yet not iden- tical with it. So far as I know it has not hitherto been employed in any- sense, and I venture to propose it for the anhydrous silica with negative double refraction described by Professor Rosenbusch. In a great majority of cases the minerals immediately accompanying the cinnabar are quartz and chalcedonite, and no case has been observed in which the cinnabar particles were directly embedded in opal, although the greater part of the area of some slides is occupied by the last-named mineral. Minute cracks in the opal are often filled with crystals of cinna- ' Mik. Phys., vol. 1, 1685, p. 345. MICROSCOPICAL CHARACTER OF ORE. 391 bar and of silica, and these indicate that the deposition of opal preceded that of such cinnabar and the accompanying quartz and chalcedonite. The mixture, however, is sufficiently intimate to compel the conclusion that opal deposition cannot have been an independent process, but only an early stage of the same process by which cinnabar was ultimately deposited. It is possible that there ma}- be cases in which cinnabar is directly embedded in opal, though this association is not represented among the slides, and it is certain from field observations that very little of the cinnabar can occur in this way. It seems more probable that the conditions attending the actual crystallization of the cinnabar were also favorable to the crystallization of the silica. Calcite and dolomite, especially the former, are found in a large proportion of the slides. The deposition or formation of more or less dolo- mitic carbonates appears from the slides to have preceded the deposition of opal, quartz, chalcedonite, and cinnabar in most cases, but in some instances the carbonates fill interstices in chalcedony, showing that carbonates were deposited at distinct periods. Cinnabar is sometimes deposited in direct contact with the carbonates, but occurs in this way much more rarely than in quartz. Field observations also show an irregularity corresponding to that observed under the microscope. In most of the mines silica predomi- nates in some portions and carbonates in others. This variation is not only. characteristic of the deep mines, but also of Steamboat Springs, where some areas of the spring deposits are almost pure chalcedony, while others consist largely of carbonates. The intimate association of cinnabar with opal and carbonates is of course sufficient to show that the ore is deposited from solutions. inclosing rocks. The country rock of the cinnabar deposits is of the most varied character, and I am unable to see that, excepting from a mechanical point of view, the rock has exerted any influence on deposition. The old- est rock in which cinnabar occurs is granite, in which the main part of the deposit at Steamboat Springs is found. The ore occurs in every variety of the early Cretaceous rocks, in unaltered sandstones, and also in phthanite, pseudodiabase, pseudodiorite, glaucophane schists, and serpentine. The most important deposits occur in the metamorphosed rocks, but this seems to be due only to their hardness, as will be explained a little later. Chico 392 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. sandstones not considerably altered contain cinnabar at New Idria. In San Luis Obispo County the ore is found in unaltered sandstones believed to be Miocene; at Sulphur Bank rich ore was found in modern lake beds; the andesite of Clear Lake contained deposits; so, also, does the andesite near Calistoga ; and the same association occurs at Mt. Diablo; traces of cinnabar occur in the basalt of Steamboat, and a large part of the best ore of Sulphur Bank was found in this recent lava. On the /Etna property ore is also found in basalt. Alteration of the rocks. The rocks adjoining ore deposits have in many cases been greatly modified. Metamorphic rocks often appear to have been con- verted into or replaced by more or less dolomitic carbonates by the action of solutions. This is inferable both from field and laboratory observations; for, while limestone is extremely rare in the Coast Ranges as a whole, large masses of more or less impure carbonates appear in the mines. This is especially noticeable at New Almaden, where also the concretionary struct- ure of a part of the material shows the foreign origin of the mineral. The metamorphic rocks converted into carbonates are usually stained brown by ferric oxide and ferrous carbonate and retain the general habitus of the associated metamorphic rocks which have not undergone this change; but it is often difficult to determine the exact character of the original material. The metamorphic rocks where they are unaffected by carbonate solutions vary so capriciously that the immediate association of psendodiabase with carbonated rock does not prove that the latter is an altered form of the former. Under the microscope it is found, too, that the alteration by car- bonate solutions so quickly obliterates the character of the rock modified that satisfactory transitions are comparatively rare. Both serpentine and the granular metamorphic rocks seem to be subject to this conversion. siiicification. In the third chapter I have referred to a widespread partial silicification of the Coast Ranges, which seems to have formed the latest phase of the Post-Neocomian metamorphism. In connection with the ore deposition there has also been localized silicification, sometimes on a large scale. The products of the two periods of silicification are ordinarily very distinct, though doubtless there are cases in the neighborhood of mines in which it might be impossible to refer the silica with certainty to one or the SILICIFICATIOff. 393 other period. The Post-Neocomian silicification altered a portion of the shales to jaspery masses or phthanite and formed in these and other rocks innumerable minute veins of quartz. The silicification attendant upon ore deposition at a much later date resulted m the formation of great quantities of opal, accompanied by a small amount of crystalline silica. The opal is usually colored, and, as seen in hand specimens, is often deep black, so that it considerably resembles some varieties of obsidian. It occurs in meta- morphosed rocks sometimes as small spots and, again, near ore bodies in large quantities. It is much more frequent in the mines to the north of San Francisco than to the south, though few deposits are unaccompanied by small quantities of this material. I am not aware that it is found any- where far from known traces of cinnabar and I look upon it as an indica- tion of the probable presence of quicksilver wherever found. Its intimate relation with metalliferous solutions is shown by the fact that it is seldom if ever free from sulphides of iron or nickel, which may sometimes be seen under the microscope when they are macroscopically invisible. The opal is seldom absolutely free from quartz and chalcedonite, and sometimes a small amount of carbonates appears in it. The chalcedonite and quartz microlites in the opal are not infrequently radially arranged, forming- globules which dot the entire field. Sometimes a perfect net of minute bands of quartz traverses the opal. This net has, however, nothing to do with serpentine, for, while net structure does not occur among the serpentines of the quick- silver belt, it is manifest under the microscope that this quartz net repre- sents an infiltration into fissured opal. The opal usually carries a few fluid inclusions and microlites of an indeterminable character. Some of the opal or opaline chalcedony has certainly been deposited in pre-existing openings, but a large part of it must have been deposited by sub- stitution for rocks. This conclusion was drawn from observation in the mines, where the shape of the opaline masses and the manner in which it was min- gled with country rock, particular!}' serpentine, forbade the supposition that it had filled cavities or fissures. Many slides present no evidence of pseudo- morphism, being entirely occupied by opal, with trifling admixtures of quartz etc. Others, however, show clear transitions to serpentine and, in particular, distinct remnants of the . 593. 3 Ibid., 4th series, vol. 7, l-.~>(>, p. 7(1. Jour, prakt. Chemie, vol. 9:5, 1864, p. 2:30. 6 For example, Graham-Otto, fifth edition, part 3, vol. 2, p. 111!). s SOLUTION OF CINNABAR, 421 mixtures containing- free hydrate. A probable explanation of this apparent neglect of careful investigations will appear a little further on. In 1876 Mr. M. C. Mt'hu 1 examined the soluble, crystalline mercury-sodium salt cor- responding to Brunner's potassium compound. He found mercuric sulphide insoluble in sodic hydrate or in the simple sulphide of sodium, but highly soluble in mixtures. One part of mercuric sulphide with two parts of the crystallized sulphide of sodium and two parts of a solution of sodic hydrate of specific gravity 1.33 form, he found, a perfect fluid, which absorbs car- bonic acid and gradually precipitates at first sodium carbonate containing mercuric sulphide and later crystals of cinnabar. Alkaline pentasulphides convert amorphous quicksilver sulphide di- gested with them into cinnabar, 2 and this process implies a certain degree of solubility. Mr. Barfoed, however, found mercuric sulphide insoluble at ordinary pressures in sodium sulphydrate to which sulphur had been added, and the solubility in the pentasulphide is probably slight. The conversion of the black into the red sulphide does not appear to imply more than a mere trace of solubility, for Messrs. IT. Sainte-Claire Deville and Debray produced rhombohedral crystals of cinnabar by heating precipitated sulphide with chlorhydric acid to 100 C. in a closed tube. 3 No statement is made in the account of this experiment of any means being employed to produce any great pressure. Mr. S. B. Christy 4 found that at pressures of from 150 to 500 pounds per square inch and temperatures of from 180 to 200 various liquids heated with precipitated mercuric sulphide convert it into vermilion. He experimented with polysulphides of potassium, potassic sulphydrate, acid sodic carbonate charged with sulphydric acid, and a spring water containing acid^odic carbonate which he charged with sulphy- dric acid. He reached no conclusions as to the state of combination of the mercury in solution. The fact that glass is greatly attacked at high pressures and temperatures by alkaline solutions of course leaves many possibilities open. Prof. H. Wagner 5 has shown that mercuric sulphide is 'Russian Jour, of Phariu., reported in Jahresbericht dor Cliemie, 187t>, p. 282. Gmeliu-Krant: Handlmcli dor Cheinio, Anorganischo Cheinie, vol.3, p. 758, where many refer- ences may be found. "Fouqno" and Michel-LoVy : Syntliese des min. et dcs roclics. p. 31:!. :',. 422 QUICKSILVER DEPOSITS OF TQE PACIFIC SLOPE. soluble in barium sulphide and Professor Roth 1 thinks it probable that cal- cium sulphide possesses a similar power. soiuwiity of HgS in mixtures of Na's and NaoH. A series of experiments was made in my laboratory with a view of testing the relative effect of the quantity of sodium sulphide and sodium hydrate on the quantity of mercuric sulphide which a given mixture of the solvents would take up. It is almost impos- sible to make experiments of this kind with the same accuracy which can easily be attained in precipitations, because, if one or more drops of either fluid reagent be added to a mass consisting of mercuric sulphide partially dissolved in the menstruum, it is not practicable to say how long a time will elapse before the additional drop will have become saturated. Approximate results are, however, readily obtained, and these appear in the present case to be sufficient. It was found that, provided a small quantity of free hydrate exists in the mixture, the solubility of mercuric sulphide depends upon the quantity of sodium sulphide in the solution, or, in other words, that, if to a mixture of Na 2 S and NaOH more sodic hydrate be added, the solvent power of the mixt- ure is neither increased nor diminished thereby. For example, three solu- tions, containing, respectively, 0.95, 1.38, and 2.29 grains of sodic hydrate, and each containing almost the same quantity of sodic sulphide (about 0.7 gram), each dissolved the same quantity of mercuric sulphide. A very small quantity only of the hydrate is sufficient to secure to the alkaline sulphide its maximum solvent power over mercuric sulphide. The greater part of the experiments made to test the maximum solubility of HgS in Na 2 S in the presence of NaHO shows that the relation of the weights of the two substances is very nearly in the proportion of one molecule of HgS to two molecules of Na 2 S. The average of fourteen such experiments gives iHgS to 2.03Na 2 S. From the nature of the experiments a slight excess in the quantity of the solvents employed is to be expected. One experiment was made by mixing mercuric and sodic sulphide in the proportion of two molecules of the latter to one of the former and adding a few drops of caus- tic soda. A mere trace of the metallic sulphide remained undissolved and 1 Allg. nnd chem. Geol., vol. 1, 187'J, p. 204. SOLUBLE SULPHOSALT OF MERCURY. 423 this completely disappeared on the addition of a single drop of a solution of alkaline sulphide, so that less than one drop completed the solution. Chemists, of course, regard cases of solution such as that under dis- cussion as due to the genesis of soluble double salts, which are formed according to ordinary laws of composition. The above experiments show that this soluble double salt can be represented only by the formula HgS, 2X;rS and that it is soluble in dilute caustic soda. The soluble mixture given by Mehu appears to be intended to repre- sent the maximum solubility of mercuric sulphide, for he states that sulphy- dric acid instantly produces a precipitate in it. As previously stated, it con- tains two parts of crystallized simple sodic sulphide (Na 2 S, 9II 2 0) to one of IlgS, which .answers to HgS + 2.07Na 2 S and is thus, so far as it goes, confirmatory of the above experiments. solubility of H g s in Na's. The most carefully prepared solutions of sodium sulphide dissolve mercuric sulphide' freely. This statement is directly con- trary to that which some of the chemists referred to have made, and it would be a rash one if the evidence to be adduced for it depended simply * upon bringing solutions of sodic sulphide into contact with mercuric sul- phide, for it is impossible to make certain that there is no trace of free caustic alkali or of sulphydrate in solutions of Na 2 S, however closely its analy- sis may correspond to its theoretical composition. If, however, a solution of sodic hydrate be treated with sulphydric acid, it is gradually converted into sodic sulphydrate and passes through a point at which the only com- pound present is sodic protosulphide. If mercuric sulphide be dissolved in a mixture of sodic sulphide and sodic hydrate and the clear filtrate treated with hydrogen sulphide, the mercuric sulphide begins to. be precipitated when very little free caustic alkali is left, and it is continuously precipitated until the entire amount of sodium present is converted into the sulphydrate. The purest preparations of sodic sulphide (Na 2 S) which we have been able to make, dissolve mercuric sulphide less freely than mixtures of sodic sul- phide and sodic hydrate, but more freely than mixtures of sodic sulphide and sodic sulphydrate. Different preparations, however, shown by most careful analysis to correspond very accurately to the formula Na 2 S, give somewhat different results, possibly indicating a minute variation from ab- 424 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPI*}. solute purity. It does not seem a priori improbable that the soluble salt when the sodic sulphide is absolutely pure is IlgS, 3Na 2 S, and one of our preparations gave almost exactly this result. It may also be that the mixt- ures of HgS, 2Na 2 S and HgS, 4Na 2 S are formed in proportions varying with other conditions than the purity of the sodium sulphide, such as tem- perature and concentration. insolubility of H g s in coid NEKS. Repeated experiments and analyses under- taken during this investigation have shown that mercuric sulphide is totally insoluble, in sodic sulphydrate at ordinary temperatures and that any prep- aration of this compound which will dissolve a trace of mercuric sulphide can be shown by analysis 1o fall short of complete saturation. A long time and an enormous quantity of hydrogen sulphide are required to completely saturate even a small amount of caustic soda with sulphur. As already mentioned, both Weber and Barfoed were aware of the insolubility of mer- curic sulphide in sodic sulphydrate at ordinary temperatures. It will be seen later that the behavior of these compounds varies with the tempera- ture. If mercuric sulphide be left in contact with cold sodium sulphydrate for twenty-four hours, just a trace of mercury goes into the solution. This is due to the spontaneous loss of hydrogen sulphide which the sulphydrate is well known to undergo. The absolute want of power of a preparation of sodium sulphydrate to dissolve a trace of mercuric sulphide is perhaps the best known test of its freedom from the alkaline protosulphide. This test does not show the absence of polysulphides, however, for we have frequently found mercuric sulphide totally insoluble in solutions of sodic sulphydrate which possessed a yellow color and which were proved by analysis to contain an excess of sulphur. This corresponds to Barfoed's observation. The occurrence of alkaline polysulphides in nature, excepting near the surface of the earth, seems so improbable that I have undertaken no investigations of the con- ditions under which they dissolve mercuric sulphide. Solubility of HgS in mixtures of Na^S and Na'S, H'S. For tll6 pUl'pOSB of determining the character of solutions of mercuric sulphide in mixtures of sodium sul- phide and sulphydrate, clear solutions of mercuric sulphide in sodium sul- phide and sodium hydrate were made, all of the reagents being carefully SOLUBLE SULPHOSALTS OP MERCURY. 425 prepared for the purpose, and sulphureted hydrogen was passed through the solution until a large permanent precipitate of mercuric sulphide had formed The mass was then filtered, and of course the filtrate represented an absolutely saturated solution of mercuric sulphide in a mixture of sodic sulphide and sulphydrate. A portion of this solution was analyzed. The remainder was treated further with hydrogen sulphide, the precipitation being arrested before the separation of mercuric sulphide was complete, and the second filtrate representing a second saturated solution of the metallic sulphide in a mixture of alkaline sulphide and sulphydrate, but one contain- ing much less mercuric sulphide than the first was also analyzed. Two such analyses gave the following results per 100cm 3 of solution: A. B. Mercury, Hg Grams. 1.4417 Grams. 4976 Sodium Na 4. 7990 4 7790 Sulphur S 5 9"W) 6 4220 It will readily be found that each of these analyses corresponds closely to the formula HgS, 4Na 2 S + Na 2 S, IPS. 1 The degree of correspondence can best be seen by supposing all the errors of measuring, weighing, spontaneous decomposition, and of the ana- lytical methods employed to be concentrated in the determination of the sulphur. Had the sulphur found been 5.9848 in A and 6.4102 in B the analyses would correspond accurately to the following : (A) HgS + 4Na 2 S + 10.473 Na 2 S,H 2 S. (B) HgS + 4Na 2 S + 37.757 Na 2 S, H 2 S. The error here supposed in the sulphur determination of B is less than one-fifth of 1 per cent, of the entire sulphur found, and, considering the quantities actually weighed, it comes within the legitimate inaccuracies of analysis. The error supposed in A is somewhat less than 1 per cent, of the entire sulphur, and, when it is remembered that it really represents the 1 The mercury is of course saturated with sulphur. The sodium may also be regarded as combined in the form of Na-S. Deducting the corresponding quantities of sulphur, a remainder is left, which is the sulphur combined with hydrogen in the sulphydrate Na 2 S, H 2 S. 426 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. sum of all the errors of experiment and analysis, 1 the variation is not great. In another analysis of this solution, devised for the purpose of deter- mining separately the sulphur combined with the hydrogen and that directly united with sodium (an attempt which was only approximately successful), the total sulphur also actually came out somewhat higher than in that cited. These analyses, which formed the conclusion of a tedious series of experiments, appear to me to show beyond any reasonable doubt that there is a compound HgS, 4Na 2 S which is soluble in the presence of Na 2 S, IPS and which is decomposed by hydrogen sulphide in the presence of sulphydrate by the reaction HgS, 4Na 2 S + 4H 2 S = HgS + 4Na 2 S, H 2 S. conclusions from the experiments. It appears from the above that there are at least three double salts of the form HgS, Na 2 S where n may be 1, 2, or 4, and, judging from the analogy of the potassium compounds, there is probably also a compound of this group where n is . The possibility of a case in which n is 3 has also been adverted to. Thus mercuric sulphide readily enters into combination with sodic sulphide in various proportions, while all the best known soluble compounds of mercuric sulphide and sodium have the same general formula, The presence of carbonates of the alkalis is also known, especially from Mehu's results, to be compatible with the ex- istence of these compounds. The question therefore arises whether such double sulphides may not exist in natural waters. Possible existence of Na'S in natural waters. This question I'CSOlveS itself HltO tWO. It is to be considered whether sodic sulphide may exist in natural waters as such. In that case such waters must dissolve mercuric sulphide. It is also possible that alkaline monosulphides cannot exist as such in these waters, but that the affinity of the compounds Na 2 S and HgS is sufficient to overcome the obstacles to the formation of sodic sulphide and that this compound will form when mercuric sulphide is present. The latter possibility is the more important, but the former is manifestly one of interest to chemical geology. It seems commonly to be assumed that only the acid carbonate of sodium exists in natural waters. I know of no warrant for this assumption. The 1 Among other sources of error in working with these compounds is the absorption of carbonic acid and the liberation of H 2 S. The solutions never cease to smell of the latter. ilTIBSXTY SODIUM SULPHIDE IN NATUI%l^ 7 ATBIfS^tV/ 427 ^^WFOr.?)^ ^ ^^^^ neutral carbonate and the sesquicarbonate are known to crystallize from many natural waters. It is even difficult to produce the acid carbonate free from the neutral salt, and the acid carbonate of commerce, though designed to be pure, invariably contains a considerable amount of the more basic compound. Hot solutions of acid carbonate lose carbonic acid rapidly and cold solu- tions evaporating in dry air also lose a large part of their acidity, so that the neutral carbonate and carbon dioxide may coexist. In my opinion it is only safe to regard natural waters as in general containing both carbonates. When hydrogen sulphide is passed through waters containing neutral carbonate at ordinary temperatures the following reaction is known to take place: Na 2 C0 3 +H 2 S=NaIIC0 3 +NaHS ; so that, if the solution of the neutral carbonate be moderately strong, a portion of the less soluble acid carbonate is precipitated by hydrogen sulphide. If hydrogen sulphide be passed through the solution until it is only semi-saturated or if a saturated solution be added to a solution of the neutral carbonate, the composition will be Na 2 C0 3 +NaIIC0 3 +NaHS. It is evidently conceivable that the neutral carbonate should react upon the sulphydrate, producing sodium sulphide and acid carbonate. This reaction cannot take place under ordinary conditions, however, for the thermal effect of Na 2 C0 3 +NaHS = NaHC0 3 +Na 2 S is negative. It does not follow that this reaction may not take place at temperatures approach- ing 100. Indeed, in connection with the known facts as to the solubility and hydration of sodium carbonate at different temperatures, it is a conse- quence of a somewhat complex train of reasoning on the thermal effects of the formation of the compounds involved that the following reaction must give a positive thermal effect when the temperature exceeds 80: 2Na 2 CO 3 + 2NaIIC0 3 + 2NaHS = 2NaHC0 3 , Na 2 CO 3 + NaHCO 3 + NaHS +Na 2 S. If this reaction actually takes place, a mixture of the two carbonates with the sulphydrate, raised to a temperature of above 80, yields a portion of the simple sulphide of sodium. This appears to give a greater thermal effect than any other reaction which can be devised between the ingredients. It does not of necessity follow that it takes place ; for the salts may possibly present unknown resistances to combination similar to the resistance which 428 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. prevents the combination of free hydrogen and oxygen at low temperatures. There is, however, nothing to indicate such anomalous resistances, and in any event the considerations adduced demonstrate a tendency to the forma- tion of sodium sulphide. On the other hand, though many efforts have been made, neither Dr. Melville nor I have succeeded in devising an ex- perimental method proving the presence of sodic sulphide, as such, in solutions of this kind. If it does exist, of course mercuric sulphide must immediately dissolve in the solution without the evolution of gas. The theoretical results given in the last paragraph were worked out before a single one of the experiments described in this chapter was made, and, in fact, formed the basis of the entire investigation. When the attempt was made to dissolve mercuric sulphide in the mixture, at the temperature indicated, in open vessels, it was found to go into solution without evolution of gas, thus behaving as if free sodic sulphide were present. This, however, in view of the facts afterwards ascertained, does not prove the actual pres- ence of free sodic sulphide. Formation of Na*s in the presence of Hgs. When, in addition to the tendency towards formation of sodic sulphide discussed above, the affinity of mercuric sulphide for this compound is brought into play, it can be proved experi- mentally that sodic sulphide is formed. We found that at a temperature of about 90 C a mixture of the two carbonates and the sulphydrate dissolves mercuric sulphide freely without a sensible evolution of gas. If the solvent does not contain sodic sulphide, it must contain the sulphydrate. Hence it becomes important to ascertain the behavior of mercuric sulphide to so- dium sulphydrate at moderately elevated temperatures. While sodic sulphydrate will not dissolve a trace of mercuric sulphide at ordinary temperatures, if mercuric sulphide be added to a solution of so- dium sulphydrate which stands upon the water-bath, hydrogen sulphide is evolved and mercuric sulphide goes into solution. The fact that hydrogen sulphide is evolved demonstrates that sodic protosulphide must be formed. Cooling does not reprecipitate the mercuric sulphide, and the compound dis- solved is therefore of the form HgS, Na 2 S. Though the solubility of mer- curic sulphide in warm solutions of the alkaline sulphydrates at ordinary pressures has, so far as I know, never been explicitly stated, I have no FORMATION OF MERCURIC SULPHO3ALT. 429 doubt that chemists have observed it, and that, in consequence of this ob- servation, the general statement of the solubility of mercuric sulphide in alkaline stilphydrates h;is remained in chemical literature in spite of the observations of Weber and Barfoed. The preparation in which I origi- nally observed this important reaction was one from which mercury had already been removed by precipitation with hydrosulphuric acid The ex- periment was afterwards repeated by Dr. Melville with several preparations of sulphydrate which had been accurately analyzed and had been tested in numerous ways. Now, in a mixture of the carbonates and sulphides at the temperature of the water-bath, .either sodic sulphide or sulphydrate is present, or, more probably, they coexist. If, then, mercuric sulphide be added to such a so- lution, either sodic .sulphide combines directly with mercuric sulphide or sodic sulphydrate is decomposed by mercuric sulphide, setting free hydro- gen sulphide, which must be immediately absorbed by sodium monocar- bonate. Hence, in any case the salt dissolved in the solvent must be of the form HgS, Na*S. Effects of dilution. Laboratory experiments are usually made with solutions which are more concentrated than those found in nature. Hence the effect of dilutions on solutions of HgS, wNa 2 S is important. Whether mercuric sulphide be dissolved in a mixture of sodium protosulphide and sodium hy- drate or of the former and sulphydrate, dilution with cold water precipi- tates mercuric sulphide. The process is gradual, yet progresses in stages. Thus a mixture of solutions of sodic sulphide and sodic hydrate of a vol- ume of' 3.9cm 3 was nearly saturated with mercuric sulphide. The mixt- ure was represented by the formula HgS + 2.04Na 2 S + 1.38NaHO + aq and contained 0.3349 gram of mercuric sulphide. Supposing no change of volume to have taken place, this is equivalent to 80 grams of mercuric sulphide per liter. On dilution no precipitate was observable until 25cm 3 of water had been added, or until the contents were reduced to 11.6 grams of mercuric sulphide per liter. Precipitation appeared to continue until about 100cm 3 of water had been added. There then remained in solution 0.0753 gram by weight, or 0.724 gram per liter. The filtrate remained clear until enough water had been added to reduce the strength 430 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. of the solution to 0.29 gram per liter. Then the liquid began to grow darker and the color deepened, until the entire quantity of sulphide pres- ent was about 0.12 gram per liter. The precipitated material was so finely divided that it would not settle and could not be filtered out, and it was therefore impossible to say where, if at all, the precipitating effect of water ceases. Similar experiments yielding analogous but not numerically iden- tical results were made with other solutions. The cause of this precipitation is clear. It is known through the in- vestigation of Messrs. Kolbe, Thomson, and others that, while in moderately concentrated solutions NaHS + NaIlO=:Na"S + H 2 O, this reaction is par- tially reversed on dilution, or that in the presence of much water sodic sulphide is decomposed by water, the proportion of the sulphide under- going this decomposition increasing gradually with the dilution. It is evi- dent that the decomposition of HgS, Na 2 S is effected in the same way, more and more of the protosulphide in combination being converted into the sulphydrate as the dilution increases, probably without any limit. Since mercuric sulphide decomposes hot sodic sulphydrate, the effect of dilution in hot solvents will evidently be less than in cold ones. Brunner found that dilution of solutions of such a salt precipitated a black mass, in which, on examination with the lens, minute globules of mercury were visible. The quantity of mercury was extremely small, so that the precipitate, on analysis, corresponded very closely indeed to the composition expressed by the formula HgS. Gmelin-Kraut 1 appear to have some independent confirmatory evidence on this point. If metallic mercury be precipitated in diluted solutions, of course sulphur is liberated, and, as shown above, alkaline hydrate must also be present. Now, when these two substances are brought in contact, sodic hyposulphite forms Accordingly Brunner found hyposulphite in solution forty years before the decomposition of alkaline sulphide in dilute solution had been eluci- dated. As Brunner experimented with HgS, K 2 S, I thought it best to com- pare the action of HgS, 4Na 2 S. A very concentrated, perfectly clear solu- tion of freshly prepared mercuric sulphide in a mixture of sodic sulphy- 1 ll.-milliiirli iler Clicmie, vol. :!, i>. ".">!. EFFECT OF FOREIGN SUBSTANCES. 431 drate and sodic hydrate, containing very little of the latter, was suddenly diluted with cold water to two hundred times its volume and rapidly filtered. Minute globules of mercury could be seen with the black sulphide on the filter. On digestion (after thorough washing) with very dilute nitric acid, a solution was obtained from which sulphydric acid precipitated black sul- phide. The decomposition thus appears to be the same in solutions of each of the compounds HgS, K 2 S and HgS, 4Na 2 S. influence of foreign substances. The fact that sodium carbonates do not pre- vent the solution of mercuric sulphide is evident both from Mehu's result and from our own. As was mentioned above, mercuric sulphide dissolves abundantly in a solution containing these carbonates and sodic sulphides. The chief constituents of the waters of Steamboat Springs and Sulphur Bank, besides alkaline carbonates and sulphides, are borax and salt. Ex- periments show that borax solutions precipitate a portion of the mercury from solution, but not the whole. The precipitation does not appear to be progressive, like that accompanying dilution, but to reach a sharp limit beyond which further additions produce no effect. A large amount of bo- rax added to a concentrated solution "of sodic sulphide and sodic sulphy- drate does not rob it of the power to dissolve mercuric sulphide. It is easy to imagine reactions by which borax may precipitate a por- tion of the mercuric sulphide. It seems possible, for example, that neutral borate is formed at the expense of the sodic sulphide combined with the mercuric sulphide. The sodic sulphide would then be converted to sulphy- drate and mercuric sulphide would precipitate. But the behavior of solu- tions of borax to sulphydric acid and to alkaline sulphides is very peculiar, and, so far as I am aware, has not been thoroughly investigated. 1 Very concentrated solutions of sodium chloride do not precipitate mercuric sul- phide from strong solutions in mixtures of sodic sulphide and sulphydrate, and they even appear to delay, but not to prevent, precipitation by dilution. The waters of Steamboat Springs contain no ammonia and probably no organic matter. Those of Sulphur Bank carry ammonia, and all of the mines examined in California show more or less organic matter. It is highly probable, therefore, that during the period of ore-deposition more or less 1 Gmelin-Kraut, loc. clt., vol. 2, p. 160. 432 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ammonia was present in many cases. Very small quantities of ammonium carbonate precipitate all the mercury from the solutions discussed above at ordinary pressures and at temperatures not exceeding- the boiling-point. At temperatures of 145 or more and corresponding pressures, however, mer- curic sulphide dissolves freely in ammoniacal solutions, but it is repre- cipitated on cooling. The entire absence of cinnabar from the original surface of Sulphur Bank shows how complete this precipitation must be and that a "quantitative" separation of mercuric sulphide has there taken place (see page 269). solubility of PCS' The sulphide which is most frequently associated with cinnabar is pyrite or marcasite ; indeed, these minerals in greater or smaller quantities are to be found in nearly every hand specimen of ore and occur very abundantly in most quicksilver mines. It seems impossible to avoid the conclusion that the iron sulphides are soluble in the same natural solu- tions which carry cinnabar. Pyrite, however, is a mineral which is so refractory to most chemical solvents that neither Dr. Melville nor I felt any confidence that sodium sulphide would attack it. On making the- experi- ment I was accordingly surprised to find that pyrite, marcasite, or precipi- tated ferrous sulphide, when warmed with a solution of sodic sulphide, diminished in quantity, while the solution changed color. The filtrates gave strong reactions for iron. Pyrite dissolves in cold solutions of sodium sulphide without any evo- lution of gas. Ten cubic centimeters of an irreproachable solution of sodic sulphide containing 1.0955 grains of the alkaline sulphide dissolved six- tenths of a milligram of pyrite at the ordinary temperature of the laboratory. Thus over eighteen hundred parts of sodic sulphide are required to dissolve one part of pyrite. The solvent power seems to increase with the tempera- ture. Pyrite, like cinnabar, appears to be totally insoluble in cold sodium sulphydrate, and, like cinnabar, pyrite dissolves to some extent in hot solu- tions of the sulphydrate. Pyrite is also soluble in solutions of sodium car- bonate partially saturated with Irydrogftn sulphide, both hot and cold. A solution of 407 parts of the neutral carbonate, after being semi-saturated with hydrogen sulphide, dissolved one part of pyrite at the ordinary temperature of the laboratory. The mineral dissolves morn easily in hot solutions than in SOLUBILITY OF GOLD. 433 cold ones. Marcasite is more easily soluble than pyrite, and the simple precipitated sulphide goes into solution most readily of all. I think there can be no doubt that pyrite and marcasite form double salts with sodium sulphide entirely analogous to the soluble compounds of mercuric sulphide. Marcasite is more easily attacked than pyrite, just as metacinnabarite is more susceptible to the action of reagents than is cinnabar. soiuwiity of gold. The association of gold and pyrite is world-wide. Ac- cording to Gahn 1 there is no pyrite which does not yield traces of gold when carefully tested. This, indeed, does not accord with my experience, for extremely careful tests of some pyrite in my laboratory have failed to reveal any indication of gold. Gold is associated with quicksilver, however, at Steamboat Springs, at some points on the gold belt of California, at the Manzanita mine, at the Redington mine, and some other localities. From these facts I concluded that gold should be soluble in sodic sulphide. On warming chemically pure precipitated gold dust with a solution of sodic sulphide the glittering scales of gold gradually disappeared. The filtrate after a proper manipulation yielded a purple precipitate with phosphorous acid. 2 A solution containing 843 parts of sodic sulphide (Na 2 S) by weight dissolves one part of gold at the ordinary temperature of the atmosphere. Gold also dissolves in sodic sulphydrate and in solutions of sodic carbonate partially saturated with sulphydric acid at ordinary temperatures. The solubility appears to be increased and facilitated by heat. solubility of cus. Cupric sulphide dissolves less readily than pyrite. Ex- periments were made by keeping CuS in contact with the solvents in bottles at about 20 C. for two weeks, the bottles being shaken from time to time. A little less than five thousand parts by weight of sodic sulphydrate are required to dissolve one part of copper sulphide. About eight thousand 'BischoPs Cbeui. uud phys. Gcol., vol. 3, I860, p. 939. Bischof long since remarked that, were the existence, of sulphide of gold in nature proved, the possibility of double sulphides of this metal; such as can be artificially produced, and of their deposi- tion from aqueous solutions would be ascertained (ibid., p. 838). So, also, Prof. T. Kgleston has found that gold kept in contact v.'ith alkaline sulphides produced solutions giving reactions for gold (Trans. Am. Inst. Min. Kug., vol. 9, 1831, p. (HO). He did not show, however, how such sulphides or tliei; iM|iiivalents could form or exist in nature, ami seems to conclude that the compound existing in natural solutions is the chloride. MON XIII 28 434 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. parts of sodic sulphide in the presence of caustic soda are required to pro- duce the same effect. Cupric sulphide is also soluble at 20 in the solution of sodium carbonate to which sulphydric acid has been added. Over two thousand parts of neutral sodium carbonate which had been semi-saturated with hydrogen sulphide were required to dissolve one part of cupric sul- phide at this temperature. Cupric sulphide is also soluble in each of these solutions when hot. solubility or zns. The experiments on zinc sulphide were made in the same manner as on cupric sulphide. Zinc sulphide is more soluble in a mixture of sodic sulphide and caustic soda than in sodic sulphydrate. A solu- tion containing a little less than a thousand parts of Na 2 S and about one hundred parts of NaliO dissolved one part of ZnS at 20. The sulphydrate dissolves only a very small quantity of zinc sulphide. Sodic carbonate par- tially saturated with sulphydric acid also dissolves zinc sulphide. Over one thousand parts of neutral sodium carbonate which had been semi-saturated with hydrogen sulphide were found necessary to dissolve one part of zinc sulphide at 20. soiuwuty oi AS'S' and sb's'. It is, of course, perfectly well known that the sulphides of arsenic and antimony dissolve freely in sodic sulphide without evolution of gas and in sodic sulphydrate with the evolution of hydrogen sulphide. In cold solutions of sodic carbonate partially saturated with sulphydric acid they dissolve freely without liberation of gas, because the hydrosulphuric acid set free immediately combines with sodic carbonate. insolubility of pbs and Ag^s. The sulphides of lead and silver seem to be en- tirely insoluble in solutions of sodic sulphide, of sodic sulphydrate, or in solutions of sodic carbonate partially saturated with hydrosulphuric acid. We have obtained no evidence of solution with these sulphides even when heated above 100 with the reagents in closed tubes. Galena is rarely found in quicksilver mines and distinct silver minerals are still more seldom found associated with cinnabar. Very little galena occurs in the gold mines of California, and lead deposits usually differ widely in character and mode of occurrence from either quicksilver or gold deposits. These facts seem to indicate that the best natural solvent for lead is different from that which is most effectual in dissolving cinnabar and gold. Mr. de Senarmont 1 produced e> di- cliiinic, I'uris, vol. '.ti, 18.">l,]>]>. ITi" 1 , 171. PRECIPITATION IN NATUEE. 435 galena by the solvent action of water supersaturated with sulphydric acid in closed tubes at high temperatures and pressures, and also obtained ruby silver, both arsenical and antimonial, by heating alkaline sulpharsenites with silver salts dissolved in solutions of acid sodic carbonate at temperatures of from 250 to 350. There is, therefore, nothing strange in the fact that lead and silver accompany the other minerals at Steamboat Springs. Natural solutions and precipitations. The foregoing analyses and experiments show that there is a series of compounds of mercury of the form HgS, wNa 2 S, one or the other of which is soluble in aqueous solutions of caustic soda, sodic sulphydrate, or sodic sulphide, and apparently also in pure water at various temperatures. These solutions subsist, or subsist to some extent, in the presence of sodic carbonates, borates, and chlorides. There is the strongest evidence that the waters of Steamboat Springs contain mercury in this form and that the waters of Sulphur Bank still carry it in solution. Sulphides of iron, gold, and zinc form double sulphides with sodium, which appear to be entirely analogous to those of mercury. Copper also forms a soluble double sulphide, but combines more readily with sodic sulphydrate than with the simple sulphide. All of these soluble sulphosalts may exist in the presence of sodic carbonates. Mercuric sulphide is readily precipitated from these solutions. Any substance is more soluble in hot solutions than in cold ones, provided that increase of temperature does not resolve the fluid molecules into others which are less soluble, as happens with sodium chloride, neutral sodium car- bonate, etc. Diminishing temperature is thus a cause of precipitation, and diminishing pressure appears to act in a similar way. At Sulphur Bank cinnabar is precipitated at a short distance from the surface, partly at least in consequence of the action of ammonium salts. There are also other methods of precipitation which may be carried out under natural conditions. If a natural solution of mercury comes in contact with a strong solution of borax, or with sulphydric acid or any stronger acid, it will lose a portion of the more uric sulphide in solution, and, if the precipitation be a rapid one, the black sulphide will probably be thrown down. At Steamboat Springs and Sulphur Bank large quantities of sulphuric acid are found near the sur- face and, percolating downward, must precipitate mercury. The acid waters 436 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. penetrate to a depth of at least twenty or thirty feet, and this helps to ex- plain the fact that the water reaching the surface carries so little quick- silver. These same causes, or some of them, must also induce precipitation of the other ores and of gold from solutions. Another method by which mercuric sulphide may be precipitated is, as has been seen, mere dilution. Now, ascending solutions of quicksilver must sometimes meet with springs, and, when they do so, metacinnabarite or black sulphide will be precipitated, and with it also a small amount of me- tallic quicksilver. In nearly all mines a small quantity of virgin quick- silver is found, and in most it constitutes a very small proportion of the entire ore. 1 Accompanying this precipitation is the formation of sodic hypo- sulphite, which actually occurs in the waters of Steamboat Springs. Dilu- tion of solutions, of quicksilver with extraneous spring waters thus affords one method of explaining the occurrence of metacinnabarite 2 found in at least five of the mines of California, and also that of native quicksilver. Native quicksilver, however, occurs in many mines in which no metacin- nabarite has ever been seen. This does not preclude the supposition that the metal has been isolated by dilution, for black sulphide in the presence of solutions of mercury might readily be converted into the allotropic modi- fication, and I know of no reason for denying that much of the cinnabar of the ore deposits may have been deposited in the amorphous state. Cinna- bar and metacinnabarite are sometimes found mixed, as if a conversion to the red mineral were incomplete. In one of the abandoned drifts near the exhausted ore bodies of the New Idria mine the walls were covered with incrustations of secondary- salts over an inch in thickness. In this mass, */ which had been deposited since the drift was opened, I found a tiny vein of cinnabar, about three inches in length and perhaps a quarter of a milli- meter in thickness. The existence of this very recently formed veinlet evi- dently indicates the presence in the mine of solvents of mercuric sulphide in trifling quantities, which might be quite sufficient, however, to convert black ore into cinnabar. Professor Sandberger has described a series of 1 It is a very curious fact that from ancient times to tbe beginning of the last century virgin quick- silver was supposed to possess qualities superior to that of the metal reduced from cinnabar (Briick- mann, Magualia Dei in Lm-is Subterraneis). -'The formation of metuciunaUarite by dilution has already been suggested by Mr. S. H. Christy. DEPOSITION OP CINNABAR. 437 specimens from Huitzuco, in Mexico, which also seem to indicate a transfor- mation of metacinnabarite into the red sulphide by the action of solvent fluids (see page 19). The mercury found at the Great Geyser of Iceland is also surrounded by black sulphide, which at a greater distance from the metallic globules passes over into the red modification. While dilution will produce metallic mercury and a causa vera of its existence is thus detected, there may be other ways besides this in which it is produced in nature. Thus sulphydric acid precipitates a mixture of quicksilver and mercuric sulphide from mercurous salts. Whether soluble mercurous salts can occur in nature, excepting near the earth's surface, is another question. But even light is well known to decompose this feeble sulphide, and it is not impossible that the decomposition of organic matter associated in most cises with cinnabar deposits, and which seems to be especially abundant in those mines in which metallic mercury most prevails, may lead to the isolation of metallic mercury. conclusions. The conditions of the solution and precipitation of ores traced in this chapter appear beyond doubt those mainly instrumental in. forming the deposits of Steamboat Springs and Sulphur Bank. Most of the other quicksilver mines in California show ores and gangue minerals of similar composition to these, and many of them are accompanied more or less closely by warm springs containing much the same salts in solution. Some of the gold veins also appear to bear so considerable a resemblance in many particulars to these deposits as to lead to the belief that they too were formed by precipitation from solutions of soluble double sulphides. That pyrite, gold, and other ores are sometimes produced in nature by other methods is absolutely certain, for some auriferous pyrite is known to have resulted from the reduction of iron sulphate by organic matter. This particular process is probably confined to short distances from the surface, for I know of no indication of the formation of iron sulphate far from the oxidizing influence of the atmosphere. But there may be other solvents yet for these and other minerals which can form at great depths, and, if such there be, I am convinced that there are cases in which these solvents, and not those which it has been my good fortune to trace in the foregoing pages, have been instrumental in the segregation of ores. CHAPTER XVI. ORIGIN OF THE ORE. Solvents possibly due to reduction by carbon. I luiV6 sllOWll that Cinnabar and 801116 of the accompanying minerals are dissolved as sulpliosalts. It is now desir- able to consider how the alkaline sulphides essential to these solutions are formed. The alkalis found in thermal springs are easily explained, inasmuch as feldspathic rocks afford an inexhaustible supply of sodium and potassium. The source to which sulphur must be attributed is less clear. Many geo- logical chemists, among them Bischof, maintain that sulphides and free sulphur are ultimately referable to the reduction of soluble sulphides by organic matter. That sulphides and sulphur are frequently produced in this way is entirely beyond question, for the reduction has been effected experimentally and has been observed many times under natural and arti- ficial conditions. Gypsum, for example, in contact with water and carbon, yields hydrogen sulphide and acid calcium carbonate, or calcite and car- bonic anhydride. If salts also be present which may be decomposed by sulphydric acid, sulphides will be formed. Soluble sulphates exist in the greatest abundance in nature, being found in nearly all spring water and forming some of the principal constitu- ents of sea water. There can also be no doubt that a very large part, if not the whole, of the water flowing from thermal springs and ejected by volcanoes is of superficial origin and must have carried soluble sulphates with it to the depths at which its temperature was raised to a maximum. Organic matter is also held in solution or mechanical suspension in many 438 SODIUM. 439 waters. Besides direct observations on this point, it is a well known fact that below the permanent water-level of a country reducing agencies are at work, so that the heavy metals occur as sulphides and the clays are com- monly tinted blue from the presence of ferrous compounds. Of course sedi- mentary rocks of all ages also retain carbon, sometimes in large quantities, as graphite, coal, petroleum, etc , so that reducing matter is provided at all depths to which sedimentary strata extend. Organic matter is also said to be present in hot springs issuing from granite. In some cases granite un- doubtedly overlies sedimentary rocks and some granites are beyond ques- tion metamorphic. It appears to me possible, however, that some hot springs issuing from granite and seeming to carry organic matter do not really bring such compounds to the surface ; for at Steamboat Springs, in spite of the very high temperature of the water, living organisms of low forms are abundant and grow luxuriantly close to the vents. A description of the circumstances has been given in the chapter on that locality. Solvents probably independent of carbon SittCC silicates of tll6 alkalis and tll6 earths are decomposed by carbonic acid and by hydrogen sulphide, the hy- pothesis that these reagents are due to the interaction of soluble sulphates and organic matter, more or less metamorphosed, affords a method of ac- counting for the existence of solvents for the ores. It is by no means cer- tain, however, that the conditions are thus adequately explained. In his great memoir on the Icelandic geysers, Bunsen 1 called attention to the fact that in gases evolved by the help of organic matter, either in nature or by artificial processes, hydrocarbons are almost invariably present. In a very large part of the volcanic emanations, both gaseous and fluid, on the other hand, hydrocarbons are wholly wanting. Hence he concludes that in these cases the sulphur and hydrogen sulphide are in no way dependent upon organic matter. Prof. II. Credner 2 believes that most of the gases emanat- ing from volcanoes, including sulphurous acid and hydrogen sulphide, are disengaged from the fluid interior of the earth in which they have existed since the original formation of the globe. Professors Tschermak 3 and E. Reyer 4 hold similar views. From the point of view of the nebular hy- 1 Poggendorff, Annalen, vol. 83. 3 Neues Jahrbuch fur Mineral., 1377, p. 857. 2 Elemente der Oeol., 1887, p. 170. * Fysik der Ernptioncn, 1887. 440 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. pothesis it is certainly difficult to conceive that all the sulphur compounds should be confined to the surface of the earth or that all the sulphur com- pounds not occurring near the surface should be oxidized. Borax is another component of the spring waters which it is difficult to account for, except on the hypothesis that the waters derive a portion of their mineral constituents from beneath the granite. Ordinary surface waters seldom, if ever, contain more than a mere trace of borax, so that it is highly improbable that currents descending toward the source of heat carry a large percentage of borax with them. The only boron mineral which is anywhere abundant in granite is tourmaline, but this mineral is so rare in the granites described in this memoir that not a single grain of it has been detected in the slides. It is somewhat improbable, therefore, that the waters ascending through the granite have derived the large quantities of borax which they contain from that rock. This improbability is strength- ened by the well known fact that boric acid accompanies the direct sul- phurous emanations of many volcanic vents It is indeed conceivable that the borax should be derived from sedimentary rocks, but on the one hand there is no reason to suppose that the granite of Steamboat Springs overlies any sediments and on the other hand it seems doubtful whether strata ever contain any considerable quantity of borax except where they have derived it from volcanic emanations in the neighborhood. It is usual, and appears rational, therefore, to ascribe the borax of hot springs to a volcanic source the character of which is unknown. The waters of Steamboat Springs and Sulphur Bank, it will be remembered, contain relatively large quantities of borax, which is also present in the Knoxville mineral springs. Depths at which solvents are found Whether the hydrogen sulphide of those thermal springs which are associated with other volcanic phenomena is due to the reduction of soluble sulphates by organic matter by some unknown process not involving the production of hydrocarbons, or whether it is due to purely inorganic reactions not yet elucidated, as seems to me more prob- able, it is evident tint this gas reaches the surface from considerable depths, at which the waters percolating from the surface meet with rocks of greatly elevated temperature. In cases like those of Steamboat Springs and Sul- POSITION OF THE SOURCE OF HEAT. 441 phur Bank, where the associated volcanic phenomena are of considerable age, probably thousands of years, the depths at which these heated rocks lie must be great. It is true that a body of lava covered with dry rock of a verv moderate thickness would remain hot for a very long time; but, at the localities mentioned above, constant and copious streams of cold water from the surface are heated and returned to the surface. In both localities, also, this very effectual cooling process has been in operation for ages, and probably from the era of the latest volcanic outbursts. The rocks hot enough to heat rapid water currents to such an extent that they reach the surface with a temperature of nearly or quite 100 must therefore lie at great depths. On the Comstock lode the heat increment is 1 F. for every 33 feet. If the same increment obtain for Steamboat Springs and if the rock mass which heats its waters be at a very low red heat (about 500 C.), the depth of the mass below the surface is, in round numbers, five miles. The Sierra Nevada has been a land area from the Carboniferous onwards, and during a great portion of this immense interval it has been a mountain range undergoing rapid erosion. Its granitic surface must for the most part be extremely ancient, and at a depth of five miles from the surface it is very questionable whether there can be any rock which has ever been exposed to daylight. 1 The waters rising from a depth of five miles, and very possibly more, pass through granite which bears no evidence of meta- morphic origin, and possibly through other rocks. Relations of the deposits to various rocks. Granite is the deep-seated rock beneath all the ore deposits mentioned in this volume. This has been alluded to in former chapters, in which it was shown that granite underlies the entire Coast Ranges and supplied the material of which the sedimentary rocks of that region are composed. The ore deposits themselves are found in various rocks : At Steamboat Springs, in granite and to a small extent in basalt ; at Sulphur Bank, in basalt, in Neocomian sandstone, and in recent lake deposits ; at Mt. Konocti, in andesite ; at Knoxville and New Almaden, in metamorphosed Neooomian strata ; at Oathill and to a slight extent in Knox- ville, in unmetamorphosed Neocomian strata; at New Idria, in the meta- 1 Compare "Origin of thci massive rocks," Chapter IV, p. 164. 442 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. morphic series and in the Chico ; and in San Luis Obispo County, appar- ently in Miocene sandstones. Possible sources O f the ores. In tile two cases just mentioned, in which cinnabar has been found in basalt, this lava forms a thin sheet covering earlier rocks, and in each case the ore is found below as well as in the basalt. The ore certainly is not derived from basalt. Leaving the interesting but very small deposits in andesite out of the question, it appears that all the other deposits must have been derived from granite, or from rocks composed of granitic detritus, or from some source below the granite. This is manifestly equiv- alent to the statement that quicksilver prior to its solution must either have formed a constituent of the granite or must have dissolved below the granite and have traversed the entire thickness of that rock without being pre- cipitated. Observation affords no clew to the material which underlies the granites of California. Professor Whitney is of the opinion that a portion of these granites is comparatively modern and I am by no means prepared to con- trovert this assertion, but it is certain that long before the Post-Neocomian upheaval granite formed the bed rock of a great part of that State and of western Nevada, as it still does. The fact that neither in California nor else- where do we know anything from observation of what underlies the granite on which the older strata rest shows that the massive rock is of enormous thickness, if indeed granite and granitoid rocks did not, as elder geologists supposed and as is maintained in Chapter IV, form the original crust of the earth. Before undertaking to consider whether it is more probable that the cinnabar and accompanying minerals were derived from the granite or that they came from a source inferior to it, it seems desirable to allude briefly to the general theories held by geologists with regard to the origin of ore deposits. Brief statement of the theories of the genesis of ore deposits. Five distinct tlieOl'IeS liaVC been maintained in geological memoirs respecting the methods by which the ores occurring in an unstratified condition (as veins, stocks, and the like) reached the positions in which they are found. These are known as the theories of simultaneous formation, descension, injection, ascension, and lateral secretion. The first two have been abandoned for many years, THEORIES OF ORE GENESIS. 443 and the theory of injection, so far as ores are concerned, is limited to some very subordinate phenomena. Those remaining are variously subdivided as occasion may require. With appropriate modifications there is every reason to suppose that they include all important probable cases. It does not follow that they present the subject in the most advantageous manner. The least satisfactory form of the ascension theory asserts that the origin of the ores lies below the deposits in some unknown position from which translocation has been effected by unknown means. Lack of facilities for investigation may in some cases justify no more definite conclusion. In other instances the nature of the occurrence may point to the conclusion that the ores, though of unknown origin, have been deposited from solution or by distillation. The ascension theory also includes case's in which there is evidence, more or less satisfactory, as to the source whence the ore was derived. This may be the interior of the earth, as is maintained by many geologists, for some veins found in close connection with active volcanic phenomena, or the origin may be sought In deep-seated rocks, stratified or massive, but similar to those which are found at the surface. In either case there may or may not be sufficient evidenca to justify conclusions as to whether the ores during their ascent were gaseous or in solution. The lateral secretion theory, as usually defined, is that ores are segre- gated from rocks contiguous with the deposit. The statement that the lat- eral secretion theory is applicable to a certain case does not convey any implication as to the particular side from which the ore is derived. All ore deposits are finite and any finite space may be filled from any one of six directions. Neither does the lateral secretion theory, as such, involve any conclusion as to the temperature of the solutions from which the ore has been deposited. It is even possible that certain valuable minerals have been laterally secreted by means of distillation, though this is no doubt an exceptional and limited possibility. The modifications ot these two theories are best grasped in a tabular form. 444 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Ore deposits are formed By ascension (1) From unknown sources: (a) By unknown methods; (1} By deposition from hot solutions; (c) By distillation, with or without steam. (2) From known sources: (a) From the original interior of the earth: (a), (i), and (r), as above; (/?) From underlying rocks: (), (?/), and (r), as above. By lateral secretion (from contiguous rocks on any side) (1) Due to heated waters rising from below, charged with reagents; (2) Due to cold surface waters, which become charged with reagents in permeating the rocks; (3) Due to distillation (a rare and unimportant case). It will be observed that the difference between the lateral secretion theory and the ascension theory depends simply on contiguity, so that, as von Cotta pointed out, the ascension theory, as applied to rocks contiguous to an ore deposit, becomes a case of the lateral secretion theory. For the present purposes of economic geology the nomenclature of the theories is not well chosen. Many investigators are at present anxious to trace those cases in which ores are derived from rocks accessible from the surface, and the main question with mining geologists is now whether or not it is possi- ble to prove the derivation of given ores from rocks existing in the neigh- borhood of the deposit, and, if so, how the solution and deposition have been effected. It is a matter of detail whether the ore deposit is actually in contact with the rock from which it has been derived or is separated from it by masses of rock which exert no sensible effect upon the solutions. It is very easy to regroup the special forms of the lateral secretion and ascension theories with reference to this point, and the subject seems to gain considerably in simplicity by this step, as shown in the following state- ment: THEORIES OF ORE GENESIS. 445 Ores are derived From unknown subterranean sources: (1) By unknown means; (2) By distillation ; (3) By solution, hot or cold, and reprecipitation. From rocks such as occur on the earth's surface: (1) By unknown means, (a) source contiguous, (6) source remote ; (2) By distillation, () source contiguous, (&) source remote; (3) By hot solutions, (a) source contiguous, (6) source remote; (4) By cold solutions, () source contiguous, (6) source remote. From the earth's interior: (1) By unknown means; (2) By distillation; (3) By hot solutions. Objections to an infragranitic origin As liaS bcCll abundantly pl'OVed abOV6, either the quicksilver deposits of the Pacific Slope are derived by means of hot solutions from the granite, which is contiguous to the deposit in the case of Steamboat Springs, but more or less remote in all other instances, or else they are derived as heated solutions from the earth's interior (the region below the granite). Of this region we know but little. It sends to the surface eruptive rocks and volcanic emanations, gaseous or in solution. These emanations almost invariably escape in large quantities from the same vents from which the lavas flow, but also often escape through fissures at considerable distances from craters. Eruptive rocks sometimes contain gold, silver, lead, and other metals, and it cannot be asserted that they may not also carry quicksilver. But, were the source of quicksilver nearly or quite identical with the source of the" lavas, one would expect to find more or less quicksilver within the craters of the volcanic vents, from which sul- phurous, boracic, and alkaline emanations must have issued. This is not the case. At Sulphur Bank are three unmistakable craters, none of them showing any trace of cinnabar, and there are very numerous eruptive masses throughout the quicksilver belt unassociated with quicksilver. So- lutions of the heavy metals are also extremely unstable, their sulphides (UKIVBRSITT) 446 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. being soluble in a very limited class of solvents, and it is difficult to imag- ine a solution of cinnabar rising through several miles of rock at constantly diminishing temperatures and pressures without losing a large part of its contents. If high pressures and temperature have in this case anything like the effect which the theory of solutions and experiments on the solu- bility of substances at high pressures lead one to suppose, solutions which below the granite would be only partially saturated would become super- saturated long before they reached the surface, and cinnabar deposits thus formed, if they cropped out at all, would extend down into the granite, probably growing stronger with increasing depth for long distances. This is emphatically not the case with the deposits of the Pacific Slope. Hypothesis of derivation from granite. If, On the Other hand, O11C SUppOSCS that the granite is the original habitat of the quicksilver, the observed relations become simple and natural. The solutions of sodium sulphide accompanied by carbonates, chlorides, etc., which followed the actual course of lava cur- rents, would then have no opportunity to take up quicksilver ; while simi- lar solutions which diverged from the course of the lava into the surround- ing country rock would decompose the metalliferous components of the granite, forming and dissolving mercuric and ferric sulphides and bringing them to the surface in greater or smaller quantities, according to the course of the currents and the composition of the granite. Deposits would then form, not in volcanic vents proper, but at the points where thermal springs due to volcanic action issue from the country rock. Such deposits would be of very variable size. Where the channels leading up to the springs were simple and of small extent, mere traces of ore would reach the sur- face ; while, when a limited system of openings at the surface gave exit to waters which had flowed through extensive masses of shattered metallifer- ous granite, larger deposits would be produced. Now, in fact, the localities in which cinnabar is found on the Coast Ranges are numberless ; they are characteristically associated with hot springs ; they do not occur in volcanic vents, but are usually at no great distance from such vents. Of all the more important mines New Idria alone is not in the immediate neighbor- hood of lavas, the nearest mass of basalt known being some ten miles dis- tant. But hot, alkaline springs, similar to those immediately associated DERIVATION OF CINNABAK FEOM GRANITE. 447 with volcanic eruptions, are known in many cases to reach the surface at distances as great as this from lava vents. Though the cases in which cin- nabar in greater or smaller quantities occurs close to hot springs in the Coast Ranges are numerous, not all such -springs are known to be accom- panied by quicksilver. If the granite be supposed to be the source of the metal, this may at first sight seem strange. But granite is by no means a homogeneous substance, and, as I have pointed out in Chapter IV and else- where, was probably never thoroughly fluid. With reference to the small quantities of heavy metals which this rock is known to contain in various European localities, the composition is known to be capricious. It is alto- gether probable, therefore, that some parts of the granite underlying the Coast Ranges may contain much more quicksilver than others, and this irregularity of diffusion, in combination with the want of uniformity in the amount of granite leached by different hot springs, would be sufficient to explain all the observed diversities in the deposits of cinnabar. Evidence at steamboat springs. At Steamboat Springs a variety of melals oc- cur in the deposits from the active springs, and two concurrent quantitative analyses, together with many partial analyses, show that the relative quan- tities of the metals are as follows, beginning with the largest: antimony, arsenic, lead, copper, quicksilver, gold, and silver. The quantity of copper found was five times as great as that of quicksilver. If these same metals could be found in the granite it would establish the highest probability that the metals of the deposits were derived from the granite. Analyses of large quantities of very fresh granite, showing no effects of solfataric action and collected half a mile from any solfatarically decomposed material, failed to show all of these metals, but succeeded in revealing the presence of those most abundant in the deposits, viz : antimony, arsenic, lead, and copper. No mercury could be detected; yet the fact that four metals are common to the deposits and the granite and the coincidence that these metals are the most abundant in the spring deposits are highly suggestive of derivation from the granite. There is some evidence that the failure to find quicksil- ver in this granite was due to irregularity in the composition of the massive rock. The only portion of the solfatarically decomposed area of Steamboat in which cinnabar is abundant enough to be visible is at the extreme west 448 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. em edge of the deposits. The quantity of quicksilver at their eastern edge, where the principal active springs now exist, is very minute, and this may be due to the composition of the underlying granite. Now, the granite subjected to analysis was collected about half a mile still farther east than the active springs, and consequently a mile and a half from the mine If the granite contains quicksilver, but in diminishing quantities as one proceeds to the east, it might well be that the quantity at this point would be imperceptible. On the other hand, it might be argued that the presence of antimony, arsenic, lead, and copper in both the granite and the spring deposits is a mere coin- cidence, that the infragranitic source of the ore has been gradually ex- hausted, and that consequently only the older deposits show considerable quantities of mercury. This argument would not, however, quite fit the facts, for, while steam and hot gases still issue in small quantities from the mine, there is a belt of solfataric matter at the very eastern edge of area mapped at Steamboat. The springs here were evidently a portion of the same system now active, but here neither water nor steam now issues. These eastern springs were the oldest of the group, yet no trace of quick- silver has ever been detected in the decomposed mass. If the quicksilver were derived from a limited infragranitic source, these eastern localities should show ore more abundantly than any other. Comparison between Steamboat and the Comstock A COmpaiMSOn llHS bCCll HUlde on page 352 between the character of the deposit of Steamboat Springs and that of the Comstock lode, six miles distant; which is also significant in the present connection. The hanging wall of the Comstock is diabase, 1 and I have adduced much evidence going to prove that the main source of the ore in this lode is this Pre-Tertiary eruptive mass, from which it was ex- tracted by intensely hot waters rising from great depths, charged with sul- phides and carbonates of the alkalis. 2 1 See Geology of the Comstock Lode and Bull. California Acail. Sci. No. C, 1886, p. 94. s Prof. J. S. Newberry has made a curious criticism of my theory of the ore deposition on the Com- stock (School of Mines Quarterly, vol. 5, 1884, p. 338). He says : " Richthofen, who first made a study of the Comstock lode, suggested that the mineral impregnation of the vein was the result of a process like that described, viz, the leaching of the deep-seated rocks, perhaps the same that inclose the vein above, by highly heated solutions, which deposited their load near the surface. On the oth'T hand, Becker supposes the concentration to have been effected by surface waters (lowing laterally through the igneous rocks, gathering (lie precious metals and depositing them in the fissure." The inaccuracy of this statement may be seen from the following quota! ions. Baron Richlliofen writes (see The Comstock Lode: Its Character etc. or Mon. U. 8. Geol. Survey No. :t, p. !'.') : '' Fluorine and chlorine are the most power- CONCLUSIONS. 449 The water issuing from Steamboat undoubtedly comes from the Sierra Nevada, and this is also the probable origin of the water of the Comstock lode. In each case the water descends to great depths before rising to its point of issue. No\v, if the ores of both -localities came from infragran- itic sources, these sources must be very near together, but of very differ- ent characters. For this difference it is not easy to account. But if only the solvents came from below the granite and the metals from the rocks comparatively near the surface, it is easy to see why the two deposits differ as they do. Heavy metais in granite. "While in the granite investigated for this memoir only arsenic, antimony, copper, and lead have been found; lead is almost or quite always argentiferous and silver is rarely, if ever, free from gold. Silver has been detected by Professor Sandberger in the mica of German granites and Mr. Simundi has found gold in the granites of Idaho. Gold is always accompanied by silver. Zinc also has been found in gneiss-micas. Arsenic, antimony, lead, and copper are so frequently associated in nature with gold, silver, and zinc as to lead to the supposition that they often have a common source. Mercury is not yet known as a component of granite or gneiss, but all the metals associated with it have been detected in these rocks. The probability that the quicksilver alone is derived from an infragranitic source is exceedingly small and is not supported by a single known fact. conclusions. The evidence is overwhelmingly in favor of the supposition that the cinnabar, pyrite, and gold of the quicksilver mines of the Pacific slope reached their present positions in hot solutions of double sulphides, i'nl volatili/ers known, and form volatile combinations with almost every substance. Besides silicon, the metals have a great at'linity with them. All those which occur in the Comstock vein could ascend in a gaseous .state in combination with one or other of them. They must then be precipitated in the upper parts as metallic oxides or chlorides, and in the native state. Thus the fissure was gradually tilled, from its upper portion downwards, with all the elements which wo find chemically deposited in it." In my report, page iiHli, I wrote : " Floods of heated waters now rose from a depth of two or more miles, certainly carrying carbonic and sulphydric acids, and possibly other active; re;igeuts, in solution. The water followed the course of the main fissure as closely as circumstances permitted, but was de- llectcd to a great extent into the fractured mass of the east country, where decomposition resulted. Silica and metallic sails were set free from the mineral constituents of the rock, and were carried into the comparatively open spaces near the main fissure, where they were redepositcd" (see. also, ibid., pp. if>. ii83, ;!8fi, 3'JO). J'roi'essor NY wherry attributes to von Kichthofeii and himself approves the very theory which I was at great pains to support. The hypothesis which von Kichthofeii advocates New- berry seems entirely to have overlooked (see, also, The genesis of certain ore deposits, by S. F. Emmous : Trans. Am. last. Miu. Kng., vol. 15, 1H-7, p. 125). MON XIII 29 450 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. which were leached out from masses underlying the granite or from the granite itself. No one fact or locality absolutely demonstrates whether the metals were originally components of the granite or came from beneath it, but the tendency of the evidence at all points is to show that granite yielded the metals to solvents produced by volcanic agencies, and, when all the evidence is considered together, it is found that this hypothesis explains all the known circumstances very simply, while the supposition of an infra- granitic origin leads to numerous difficulties. Though no one of these may be by itself fatal, when taken as a whole they appear to be so. As there is no known direct evidence pointing to an infragranitic origin of the quick- silver and the gold, I consider it tolerably well established that both were actually derived from the granite. I regard many of the gold veins of California as having an origin entirely similar to that of the quicksilver deposits. I also have some reason to sup- pose that some of the gold deposits were formed by the leaching of their walls by surface waters. The auriferous area is now under examination, and the investigations on ore deposits described in this volume will be continued and extended in connection with my survey of the gold belt. CHAPTER XVII. SUMMARY OF RESULTS. Purpose of this chapter. A very large portion of the foregoing pages is nec- essarily occupied by detailed descriptions, written in order to enable readers to judge whether the facts warrant the opinions expressed, and by discus- sions of a somewhat technical character. There may be those, however, who will be interested to know in brief what conclusions have been reached, but who have no inclination to undertake the somewhat serious task of weighing the evidence adduced and of following the arguments in detail. For such readers this chapter is written ; but it must be understood that for full and fully qualified statements reference must be made to the body of the report. statistics and history. The commercial status of quicksilver is peculiar. It seems to be three or more times as abundant in nature as silver, and since 1850 the weight of silver extracted is about six-tenths that of quicksilver; but the total value of the latter is less than one-sixteenth that of the former metal. This is due to the limited demand for mercury, which is employed in large quantities only for amalgamating gold and silver ores and for the man- ufacture of vermilion. If it should prove practicable to extirpate phylloxera with mercury, this application will greatly benefit the quicksilver miners as well as the vine-growers. Five regions iu the world are yielding or have yielded great quantities of this metal. They are Almaden, in Spain; Idria, in Austria; Kwei-Chau, in China; Huancavelica, in Peru, and the Coast Ranges of California. Of the Chinese region little is known, except that it is extremely rich; in the opinion of a very competent judge, the richest of all. Almaden has pro- 451 452 QUICKSILVER DEPOSITS OF TBE PACIFIC SLOPE. duced more than any one of the other three. Idria, Huancavelica, and Cali- fornia have each yielded pretty nearly the same aniount from the dates of discovery of the deposits to the present day, California taking the lowest rank. But considering only the period which has elapsed since the mines of the Pacific Slope were first opened the case is different. Peru produced nothing from 1850 to 1886; Idria, in round numbers, 300,000 flasks ; Alma- den, 1,140,000; and California, 1,400,000, or nearly half the entire product of the world. But California does not seem likely to maintain the same rank among quicksilver producers in the future. Quicksilver was first recognized in California as occurring at the crop- pings of the New Almaden mine by Andreas Castillero in 1845. His means of testing the ore were quaint, but effectual, and he immediately began production on a small scale. A large number of other deposits were discovered at later dates, and some forty mines have produced metal, though from some of these the yield has been trifling. Half a dozen of them have yielded from 40,000 flasks upward and New Almaden has turned out over 853,000. The sketch map of California (see Plate I) shows the dis- tribution of some of the mines. Foreign occurrences of quicksilver. TllC aCCOlint givetl of deposits kllOWIl tO occur in foreign countries will not bear condensation, being in itself a brief digest. The rocks inclosing quicksilver deposits are of very diverse ages, ranging all the way from Archaean granites and schists to recent strata and lavas. The lithological variety of the inclosing rocks is equally great, including limestones, sandstones, and shales, many kinds of metamorpliic strata, and massive rocks of acid, neutral, and basic types. Cinnabar does not even seem to exhibit any preference for one class of rocks rather than another. It is clear that the mere age of the surrounding material is with- out influence on the deposition of the ore and that the ore cannot in gen- eral be derived from the walls of the deposits, for it isVarcely auppoaable that this metal forms an original constituent of all sorts of rocks. A glance at the map (Plate II) shows that the quicksilver deposits occur along the great axes of disturbance of the world. One of these is on the line of the principal mountain system of Kurasia, for which I suggest the Hi; me of Alpimalayan chain, because it includes the Alps and the Hima- SUMMARY. 453 layas. The other coincides with the western ranges of the Cordillera system of America. In many parts of the world volcanic phenomena are intimately associated with these axes of disturbance and with the quicksilver deposits. The minerals which occur in considerable quantities with quicksilver ores are few in number. Pyrite or marcasite is nearly or quite always present, arsenic and antimony are found at many localities, and copper ores sometimes accompany cinnabar. Other metalliferous minerals are comparatively rare. The principal gangue seems to be invariably either silica, sometimes hydrous, or carbonates, chiefly calcite. Cinnabar occurs in true, simple fissure veins, in impregnations, and stockworks. The forms which its deposits take do not apparently differ in any essential respect from those which deposits of other metals assume; but ore bodies precipi- tated by substitution do not appear from the descriptions to be common. In all cases a fissure system seems probably associated with the deposits. The facts recorded point to the supposition that most of the quicksilver deposits, if not all of them, have been formed in a similar manner. They have all been deposited from solution, for the gangue minerals could have been formed in no other way. Cinnabar has certainly been deposited by thermal springs of very high temperature at Puzzuoli, in Italy, and at Lake Omapere, in New Zealand, and is most intimately associated with hot springs and other volcanic phenomena at a large number of other points. It has, perhaps, always been deposited by heated waters. It must be derived from some deep-seated substance of world-wide distribution, which has been exposed to the action of volcanic solvents by profound disturb- ance. The fundamental granitoid rocks answer this description, for they si-cm everywhere to underlie all other rocks ; they are of great but unknown thickness, and they certainly in part overlie the centers of volcanic activity. Geological investigations have as yet revealed no other substance of similar distribution. There is no other rock from which it is equally probable that the quicksilver is derived. The sedimmtary rocks. Excepting the light cream-colored schists of Miocene age, which occupy a narrow strip along the coast of California from the neighborhood of Santa Cruz southward, the rocks of the Coast Ranges where unaltered are mainly sandstones of Cretaceous and Tertiary age. 454 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Sandstones often occur here in practically uninterrupted series of beds many thousands of feet in thickness. The unaltered sandstones of the Coast Ranges are very much alike, whatever their age. The Tejon (Eocene) beds, however, are of a much lighter color than the Chico (late Cretaceous) or the Miocene rocks. The Chico again is usually more indurated than the Miocene. While the Knoxville (Neocomian) sandstones where unaltered closely resemble those of later periods, no case is known in which unaltered Knoxville beds are not intimately associated with greatly disturbed and metamorphosed rocks of the same age, so that there is no difficulty in dis- crimination when once it is established that the epoch of violent upheaval and metamorphism followed soon after the close of the Knoxville. Field study showed that the Coast Ranges are probably everywhere underlain by granite. The microscopical examinations have given this in- ference unexpectedly strong confirmation, for, though on structural grounds it appears certain that a portion of the later sandstones were formed at the expense of earlier arenaceous beds, they all exhibit unmistakable evidence of granitic origin. They are thus so similar that they may be discussed together lithologically. The microscope shows that the main constituents are quartz fragments (containing abundant fluid inclusions and in other respects resembling the quartzes of the underlying granite), orthoclase, the same plagioclases found in the granite, and biotite. Most of the less impor- tant constituents of the granite are also found in the sandstones. The pro- portion of quartz in the sandstones is, as a matter of course, greater than in the granite. The grains are commonly rounded like ordinary beach sand, but are sometimes extremely sharp. The cement is largely calcite. The sandstones are subject to the ordinary decomposition known as weathering, by which the ferromagnesian silicates are in part converted to chlorite and in part to a ferruginous cement The unmetamorphosed late Cretaceous and Miocene sandstones show numerous concretions. These in rare instances contain fossils as nuclei. A representative concretion in which no organic remains existed was inves- tigated. It was found that the cementing matrix contained a considerable amount of phosphoric acid, but was chiefly composed of a mixture of cal- cium carbonate and a hydrous subsilicate of iron. It is shown that this SUMMAKY. 455 composition points to the action of organic acids, especially the humus acids, and that the class of concretions of which this is a type must have contained nuclei of organic matter which have decomposed and disap- peared. Rounded nodules resulting from the action of decomposition processes on angular masses are discussed, and it is shown that the rapidity of attack must be in an inverse ratio to the radius of curvature of the mass. This explains the fact that such nodules tend to a spherical form. The rounding of pebbles and of sand grains is shown to depend on the same mathemat- ical law. Sharply denned limits cannot be drawn between the various early Cre- taceous metamorphosed rocks of the Coast Ranges; they pass over into one another by degrees. For purposes of description, however, it is desirable to consider certain types as distinct. The divisions which appear to satisfy best both their field occurrence and their microscopical character are as follows : Partially metamorphosed sandstones, in which, although a process of recrystallization has begun, the clastic structure as seen under the micro- scope is not obliterated, but is often more or less obscured. This class will be referred to hereafter for the sake of brevity as altered sandstones. Gran- ular metamorphics, in which metasomatic recrystallization of sandstones has transformed the mass into a holocrystalline aggregate, form another group. The third class embraces the ylaueopliane schists, derived from certain shales, much as the granular metamorphics are produced from sandstone. The plif/Hiiii/ex are a series of more or less calcareous, schistose rocks which have been subjected to a process of silicification, resulting in chert-like masses, which retain schistoid structure and are intersected by innumerable quartz veins. They usually carry more or less zoisite. Finally the serpentines, which have resulted in part from the direct action of solutions on sandstones and in part from alteration of the granular metamorphics. A considerable number of minerals have been generated in these rocks by metasomatic processes and weathering. These are biotite, muscovite, augite. hornblende, glaucophane, labradorite, andesine (probably), oligo- clase, albite, orthoclase, quartz, zoisite, rutile, ilmenite, titanite, apatite, garnet, nacrite, chlorite, epidote, serpentine, and chromite. The most inter- 456 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. esting and in some respects the most important mineral found is zoisite, which has been repeatedly analyzed and tested. All the more important processes of metasomatic recrystallization can be traced in the altered sandstones, rocks whoso clastic origin could not be doubted for a moment. In many cases one of the first stages in the process is the resolution of the clastic grains into crystalline aggregates from which new minerals are again built up. Augite, hornblende, and plagioclase have been observed which had formed in this manner. The feldspars also crystallize along tiny veins in the slides. A frequent occur- rence is the resolution of quartz grains into plagioclase microlites. The reaction begins on the surface of the quartz grains and produces a fringe of twinned feldspar microlites in positions approximately normal to the surface of the residual kernel. The microlites do not merely abut against the ker- nel, but penetrate it fora sensible distance like closely set pins in a cushion. Zoisite is present in nearly all the altered sandstones. It forms in the ag- gregates which result from the clastic grains, and its microlites sometimes pierce quartz grains from the outside. It is abundant in the granular as well as in the prismatic form. This hydrous mineral forms simultaneously with the other products of metasomatic recrystallization, and does not here represent a decomposition process in rocks already recrystallized. It is only necessary to suppose the processes indicated above carried further to obtain a product in which the clastic character of the rocks would cease to be evident. The altered sandstones thus form under the micro- scope, as they do in the field, transitions from the clastic series to the holo- crystalline rocks. The granular metamorphic rocks of the Coast Ranges are separable under the microscope into several groups, but this is not practicable by unaided vision ; indeed, there are many cases in which specimens which appear to the naked eye to be not greatly altered sandstones prove under the microscope to be holocrystalline rocks, with none of the microstructure of a sandstone. The most important class of the granular rocks is chiefly composed of plagioclase and augite. It sometimes resembles true diabase, and may conveniently be called pseiiilixlidbase. The pyroxene sometimes assumes the form of diallage. Another class contains amphibole instead of SUMMARY. 457 pyroxene, and I call this rock pseudodiorite. No metamorphic rocks have been found in place which carry olivine. Glaucophane occurs in both the pseudodiabase and tire pseudodiorite. The quantity of zoisite in these rocks is very variable and in some cases is so grealthat with feldspar it forms almost the entire mass. The schistose metamorphics, not including- phthanites, are all characterized by the presence of glaucophane. In every case but one, zoisite is associated with the glaucophane in this group and either muscovite or biotite is usually present. The phthanites or silicified shales form a very distinct group readily distinguishable from the granular metamorphics. They are usually green or brown and are intersected by innumerable quartz veins. They con- tain microscopic organic remains, and embedded in the quartz veins or pro- jecting from their walls are often numerous zoisite crystals. All of these rocks are best represented by detailed descriptions of special examples, for which there is no -space here. Serpentine in a comparatively pure state occurs throughout the quick- silver belt in irregular areas. As nearly as can be estimated these areas amount to somewhat over one thousand square miles between Clear Lake and Xew Idria. Serpentine is also one of the mineral constituents of many of the altered sandstones and of the granular metamorphic rocks. It is a biaxial variety, often just perceptibly dichroitic, and rarely shows differ- ences of tint as great as those characteristic of chlorite. It might be called antigorite if it seemed needful to separate the biaxial serpentines. The net structure so usual, though not invariable, in serpentine formed from olivine has nowhere been detected. Where any considerable quantity of serpen- tine is present it usually shows the now well known grate structure. No considerable portion of the serpentine of the Coast Ranges has resulted from the decomposition of olivine. Only in one district have pebbles of olivine gabbro have been found, and these contain a mere trace of serpentine, while the origin of the serpentine has been traced in a great number of cases to rocks containing no olivine. Field observations show most conclusively that the great mass of the serpentine of this area is derived from the sandstones, either immediately or through an intermediate granular metamorphic rock. 458 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Under the microscope it can be shown, as I think beyond question, that all of the principal components of the sandstones and granular meta- morphic rocks are subject to serpentinization. Not only are the augite and hornblende subject to this kind of decomposition, but feldspar, quartz, apa- tite, and probably other minerals are also converted into serpentine. In the present state of opinion it is not superfluous to insist upon the derivative character of the holocrystalline metamorphic rocks and the ser- pentine of the quicksilver belt. There are in fact two independent lines of evidence leading to this conclusion, for the known occurrences of zoisite and its composition indicate that rocks containing it otherwise than as a product of decomposition are metamorphic, while, even if zoisite were a common constituent of undecomposed lavas, the proof of the metamorphic character of these rocks would still be ample. The depth at which the rocks now exposed were buried at the epoch of metamcrphism, soon after the close of the Neocomian, was probably a moderate one, perhaps two thousand or three thousand feet. At a sufficient pressure rocks appear to be molded by dynamic action rather than crushed, and Dr. Lehmann has shown that under such conditions even crystals may be bent. In the Coast Ranges no such phenomenon has been observed. On the contrary, the amount of fracturing is really astonishing. The re- crystallization of the sandstones and the serpentinization and silicification are regarded as due to the action of solutions rising from the underlying granite; and these solutions were heated, charged with mineral matter, and driven to the surface as a result of the same dynamical causes which produced the uplift. In conclusion it may be noted that all the more important minerals of the Archaean schists are found in the matamorphosed rocks of the Coast Ranges The quantitative relations indeed are different, especially those of the feldspars; for, while orthoclase predominates in the Archaean, plagio- clase is much more common in the Coast Ranges; but it is evident that, under conditions not greatly dissimilar to those which prevailed in Califor- nia at the close of the Neocomian, rocks not distinguishable from those of Archaean areas might have been formed. SUMMARY. 459 : The massive rocks. The massive rocks met with in this investigation are granite, diabase, diorite, andesites, rhyolite, and basalt. The granites seem to underlie the entire Coast Ranges and to form the lower and central por- tion of the Sierra Nevada. They are on fhe~whole pretty uniform and pre- sent no known peculiarity. Diabase occurs in the Mesozoic conglomerates of Steamboat Springs and seems to be identical with the diabase which forms the hanging wall of the Comstock lode. Diorite is represented chiefly by pebbles in the Neocomian conglomerates of the Coast Ranges. The andesites are divisible into two groups, an older and a younger. The younger group is found at Steamboat Springs and elsewhere in and near the Sierra Nevada, at Mt. Shasta, and from Clear Lake to Mt. Diablo. It presents several varieties : one containing pyroxene, a mere trace of hornblende, and no mica; a second containing pyroxene and mica, but no hornblende; a third containing hornblende, with very small quantities of .pyroxene, together with mica in quantities ranging from nil to a very large perrontage. All of these pass over into one another, sometimes within a few feet, and in masses evidently not due to separate eruptions. Nearly or quite all of them are rough, soft rocks, such as were formerly supposed to be trachyte. They form a natural group, which should be recognized. I have proposed the name axperite to suggest their resemblance to trachyte. As- pcrik's, then, are a group of andesites with external characteristics similar to those of trachyte. Both the asperites and the basalts near Clear Lake pass by transitions into enormous masses of obsidian. The transitions have been traced in the field, in the chemical laboratory, and under the microscope. The glasses are more acid than the crystalline rocks into which they pass, but they contain much more alkali and much less lime and magnesia; their specific gravity is also much smaller. They have cooled as glasses, instead of as crystalline \ aggregates, because of their peculiar composition, and not because they have been subjected to different physical conditions from the associated, sensibly holocrystalline lavas. The origin of the massive rocks of California is discussed in Chapter IV. It is shown to be probable that portions of the granitic rocks repre- sent parts of the original crust of the earth^or that they are primeval rocks. 400 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. That the primeval rocks must underlie all others is self-evident and the lowest rocks we know of are granitic. It has never been shown how the original crust could be wholly buried beneath its own ruins, and simple arguments are adduced to show this utterly improbable. It follows that a part of the granite must be Azoic and that the lavas which have broken through the granite cannot be remelted sediments. Historical geology. The following outline states in the briefest terms the main events in the geological history of the Coast Ranges, so far as they have been elucidated by former observers and by myself. Prior to the opening of the Cretaceous the region of the Coast Ranges seems to have been chiefly occupied by granite. During the first period of the Cretaceous the Neocomian great quantities of sediments derived from the granite were deposited on the quicksilver belt. These were chiefly sands, though shales and calcium carbonate were also found. The sea must have been shallow and many islands must have existed in it. The most characteristic animals of the period were Ance.Ha concentrica and Anc/'Ha mosquensis, of which a description, with illustrations, by Dr. C. A. White, is given in Chapter V. At the close of the Neocomian an upheaval took place with extraordinary violence, folding and crushing the rocks and pro- ducing the first ranges along the coast of California of which any record remains. It is probable enough that earlier ranges existed, but had been obliterated. The same upheaval affected the Sierra Nevada and added to its western side, along a part of the gold belt, an immense mass of Neo- comian rocks, which were driven into a nearly vertical position. Accom- panying this upheaval was a vast expenditure of energy. The heat into which this energy was converted brought about the solution of some components of the underlying granite, particularly of magnesia and soda. These solutions, acting on the Neocomian rocks, converted them into the metamorphic product mentioned in preceding paragraphs. During the Middle Cretaceous (the Turonian) the shore of California seems to have been nearly in the same position as it now is, and a series of beds discovered during this investigation, the Wallala group, was de- posited. They are composed of granitic, detritus and fragments of meta- morphosed Neocomian beds and certain fossils. 1 SUMMARY. 461 Late in the Cretaceous a great part of the Coast Ranges was again under water and the sea once more reached the flanks of the Sierra Ne- vada. The sediments laid down at that time, and now known as the Chico series, were of course deposited unconforuiably upon the metamorphosed and eroded Neocomian rocks. There was no disturbance at the close of the Cretaceous, and sedimentation and the gradual development of the ma- rine fauna went on undisturbed through the Eocene, which, in California, is represented by the Tcjon series. The non-conformity between the Chico and the underlying rocks and the continuity of the Chico and Tejon were first established in this investigation. Between the Eocene and Miocene there is a sharp faunal distinction, but there is no general corresponding non- conformity. At the close of the Miocene an important upheaval took place, though one which was much less violent than the earlier uplift. Professor Whitney first studied this Post- Miocene disturbance. Only a small amount of Pliocene territory exists in this region, and part of ii consists of lake deposits. It is of course uncou- formable with the Miocene. After the close .of the Jurassic no eruptions seem to have taken place in the Coast Ranges until the close of the Miocene, or possibly a little later. Avuk'sites were then ejected and outbursts of these rocks recurred at intervals to the close of the Pliocene. The asperites of Clear Lake and of Mt. Shasta date from the end of the Pliocene. Only one dike of rhy- olite is known to exist in the Coast Ranges. It is close to the New Alma- den mine. It is probably later than the andesites, but its date is not cer- tain. During the Quaternary and down to very recent times there have been many basalt eruptions. The formation of cinnabar deposits was confined to the period of vol- canic eruptions with which they are most intimately connected. Almost all the massive and sedimentary rocks of the region inclose bodies of cin- nabar, and the age and the chemical character of the rocks are without ap- parer.t influence on the ore. ciear Lake district. The region of Clear Lake is a picturesque one, lying at the northwestern extermitv of a belt of lavas which extend southward as far .' as the Bay of San Francisco. Extinct volcanic cones, borax lakes, hot 462 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. mineral springs, and deposits of sulphur and cinnabar form its most note- worthy features. Metamorphic rocks of the Neocomian series underlie the whole country so far as known, though the existence of granite pebbles in the stream which drains the lake suggests that this rock is exposed at no great distance. Upon a part of the metamorphic area about Lower Lake the Ghico-Tejon occurs. The latter series is comparatively little disturbed and not meta- morphosed. The earliest eruptions .in the district seem to have been that of Chalk Mountain, on the north fork of Cache Creek, and some of the rock near Thurston Lake. This lava was a dense pyroxene-andesite and the eruption seems to have occurred about the beginning of the Pliocene. Soon, and perhaps immediately afterward, a large body of fresh water formed, which I have called Cache Lake. It lay mostly to the east of Clear Lake and con- tinued in existence up to the end of the Pliocene. At this period fresh erup- tions of andesites took place. They are the asperites of Mt. Konocti (or Uncle Sam) and the neighborhood. A part of the lava flowed over a portion of the bed of Cache Lake, and the orography was so modified as to shift the position of the water to the new Clear Lake, which overlaps part of the more ancient bed. The change must have been somewhat gradual, for the same mollusks which lived in the earlier body of water also flourished iu the new one and the forms are lacustrine. The asperitic andesites of Mt. Konocti are interesting because they contain pyroxene and mica, but no hornblende, which is unusual, and be- cause they pass over into acid glasses. The asperite is often almost wholly crystalline, though it has been subjected to substantially the same physical conditions as the glass, and the latter has remained vitreous because of its divergent chemical composition. The mountain nearly coincides in form with the theoretical shape of a volcanic cone and its highest point is 2,936 feet above the lake at high water. The lake is 1,310 feet above sea-level. Much later than the andesite came basalt eruptions, which extended to modern times. A part of this rock also is glassy. All the springs which now issue at a high temperature are probably due to the basalt eruptions, and the borax, sulphur, and cinnabar are referable to the same source. SUMMARY. 463 X sulphur Bank. The general geology of the Sulphur Bank is indicated in the notes on Clear Lake. The bank itself is a small basalt area, through which hot solfataric springs reach the surface, owing their heat to the vol- canic action of which the lava eruption wa.s an earlier manifestation. The springs contain much sulphydric acid, which, oxidizing more or less fully at and near the surface, lias yielded native sulphur and sulphuric acid. The latter lias attacked the basalt in part, extracting the basis and leaving a mass of more or less pure silica, in which rounded nodules of undecomposed rock remain. The rounded form of these nuclei is certainly due to the more rapid corrosion of the edges and corners of the basalt blocks, not to any structural peculiarity of the rock. The lava is bleached to an average depth of about twenty feet. In the lower portion of the decomposed layer of rock the sulphur is mixed with cinnabar. Near the bottom of this rock layer the sulphur dis- appears and the ore is richer, while the most extensive bodies are found at depths beyond the limits of the action of acid. The ores at one portion of the ground continued down for several hundred feet into the underlying recent lake beds and the metamorphic sandstones. Quartz, chalcedony, calcite, pyrite, and marcasite are the usual gangue minerals, but many other minerals are found in small quantities. The marcasite contains minute quan- tities of gold and copper. Bituminous matter is widely disseminated. The ore has been deposited exclusively in cavities, and not by substitution. The ore of the lower workings is exactly like that of most other quicksilver mines. The gases escaping from the waters are carbon dioxide, hydrogen sulphide, sulphur dioxide, and marsh gas. The waters contain chiefly car- bonates, borates, and chlorides of sodium, potassium, and ammonium ; but alkaline sulphides are also present. At the ordinary pressure the water does not dissolve cinnabar, on account of the presence of ammonia, but I have proved that at somewhat higher pressures it would effect solution. It is beyond question that the cinnabar has been deposited from waters of almost exactly the same composition as those now issuing from the mine and that the formation of ore is still in progress. Deposition of the ore seems to have been effected chiefly by relief of temperature and pressure in the presence of ammonia, not by acidification of the solutions. 4G4 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPIS. Very large quantities of quicksilver have been taken from this prop- erty, but it lias not been worked with system and has been insufficiently prospected below the basalt. There is no reason to suppose, however, that it is nearly exhausted. Close to Borax Lake lies a very interesting area of glassy basalts, ranging all the way from a nearly normal olivinitic rock to a pure glass. As is the case with the andesites across the lake, the glass is very acid and contains little lime, but much alkali. Borax Lake is a shallow pond, without an outlet, into which springs similar to those now flowing from Sulphur Bank once drained. These springs came from the obsidian area, and to them the borax contents of the lake is due. They issued at the point called Little Sulphur Bank, which is still hot and moist and shows native sulphur. It is stated on excellent authority that cinnabar in small quantities was found here. Maggots of Ephydra calif arnica and of a species of Strat'tomy* live in the lake. The Knoxviiie district. The region about Knoxville consists of metamor- phosed and unaltered rocks of Neocomian age, through which a small basalt eruption has broken, and contains a number of quicksilver mines and pros- pects. I know of no other district so favorable as this for the determina- tion of the age of the metamorphie rocks .and for a study of their character, excepting Mt. Diablo. Rocks occur in all stages of metamorphism, and the transitions, together with the structural relations, show that even the serpentine is not of eruptive origin. The metamorphosed and unaltered rocks are also so related as to preclude the supposition that the former are crystalline sediments. One side of an eroded anticlinal is metamorphosed, while the other is unchanged and fossiliferous. Fossiliferous strata in a nearly vertical position pass over into metamorphic rocks in the direction of their strike, and patches of unchanged rocks remain in metamorphosed masses. The fossils of the unaltered strata are of Neocomian age and the principal species are Amelia concentrica and A. int>*<[nr>iKis. The series carry- ing these shells are called the Knoxville group from the name of this locality. Excellent opportunities are here afforded for studying the passage of sandstone into pseudodiabase and pseudodiorite and the alteration of these rocks to serpentine. The direct change of slightly altered sandstones to SUMMARY. serpentine may also be seen in a very striking manner. Serpentinization takes place from cracks in the sandstone just as it does in olivines, excepting for the difference of scale. The meshes of the net in sandstone croppings are often about a foot across, while those in olivine are microscopic. The ore deposits occur at half a dozen points in the district, all of them near the basalt area, which is as nearly as possible in the center of the group of ore bodies. Ore is stated on good authority to have been found also in the Lake claim, at the contact of a basalt dike with the in- closing metamorphic rocks. Many mineral springs exist around the basalt area close to the mines and some of them carry borax. Solfataric gases still issue in small quantities at one point in the Redington mine and the upper portions of the ore deposits are of such a character as to indicate that they were deposited near an original surface. All of these facts indi : cate that the deposits are indirectly due to the basalt eruption and that the nature of the process was similar to that at Sulphur Bank. The upper part of the famous Redington mine was an extremely rich bonanza of great size and irregular form. It carried much metacinnaba- rite. Leading up to this mass from below were three regular fissures, and two of them were filled with ore, forming well defined fissure veins. This is particularly interesting as a proof that true, simple fissure veins maybe formed by hot solfataric springs, which has been doubted by some geol- ogists. The California or Reed mine, the Manhattan, the Lake, the Andalusia, and several prospects, as well as the Redington, lie in this district, but of late years only the last has been worked. Metacinnabarite was the princi- pal ore of the California Stibnite occurs on the Lake and Manhattan claims and is said to have been found in contact with cinnabar. New idria. The New Idria mining district lies among some of the highest peaks of the Coast Ranges, at the southern end of the Mt. Diablo Range. The views are very extensive and the scenery is picturesque, but it is in part very forbidding, the portion of the Coast Ranges lying to the northeast of the district being a mountainous desert. The higher portion of the Mt. Diablo Range is here, as for the greater part of its length, composed of highly metamorphosed -rocks of the Knox- MON xm 30 466 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ville series. No fossils are known to occur in it here, but at the northern end of the range they are abundant, and they are found again at San Luis Obispo, to the south, in precisely similar rocks. On the northeastern flank of the range lie the rocks of the Chico -Tejon series. These are tilted at angles averaging about 45, but are only slightly flexed. The lower part of the series lies unconformably upon the meta- morphic beds, as is proved by the structure and by the presence of meta- morphic pebbles in Chico conglomerates. The Chico and Tejon are absolutely conformable at New Idria and sedimentation went on continuously from one period to the other. Fossils are not numerous, but are present in sufficient number fully to identify the age of the rocks. Both portions of the series show many of the concre- tions mentioned above as due to induration by decomposing organic matter. The Tejon beds contain coal seams which were exploited on a small scale for many years. No lava exists in the district, but there is a considerable area of basalt just north of Vallecitos Caflon, about ten miles from the mine. There are cold sulphur springs, but no hot ones. Next to the New Almaden, the New Idria has been much the most pro- ductive quicksilver 'mine in North America. The ore contains the usual mixture of cinnabar, pyrite, and quartz, accompanied by some bitumen ; metacinnabarite also was found in the New Hope lode in very large quan- tities and in less abundance at another point in the mine. The structure is extremely complex, but typically developed stockworks, veins, and impreg- nations all occur. Faults and cross-courses make successful explorations very difficult and uncertain. The ore is almost entirely deposited in Neocomian rocks, but to a small extent also in the Chico beds. The deposition has taken place since the Post-Miocene upheaval and is seemingly referable to about the same period as the other deposits. The analogies point to the action of hot springs, but there is no direct proof that the solutions were of high temperature. The San Ciirlos, Aurora, Picacho, and other mines which have yielded small quantities of ore lie at no great distance. In all of them the ore has been deposited in shattered rock masses of the metamorphic series. No- SUMMARY. 467 where in this region is there any evidence of the substitution of ore for rock. , -*T New Aimaden district. The first discovered and the most productive of the quicksilver mines of North America is the New Aimaden, and in the same district the Guadalupe, Enriquita, and other mines have yielded quicksilver. The district is well watered and wooded and is more attractive than any other of the quicksilver camps. Upon highly metamorphosed rocks lie Miocene sandstones, which were sharply folded at the Post-Miocene upheaval. They are not conformable with the lower series and contain pebbles from these older beds. In the older rocks near New Aimaden Mr. Gabb found Aucella, proving the pres- ence of the Knoxville series. In this district is the only mass of rhyolite thus far found in the Coast Ranges. It forms a dike nearly parallel to the line connecting the New Aimaden and the Guadalupe. It is almost continuous, and I have followed it for a distance of several miles. It is certainly Post-Miocene and prob- ably Post-Pliocene. The New Aimaden is a very extensive mine, said to contain as much as 40 miles of galleries. Much of this length is open, and admirable op- portunities are afforded for study of the ore and structure. The ore is cinnabar, with occasional traces of native quicksilver, accompanied by pyrite and marcasite, with rare crystals of chalcopyrite. The gangue is quartz, calcitc, dolomite, and magnesite. These materials are deposited in shattered masses of pseudodiabase, pseudodiorite, serpentine, and sand- stone. There is no deposition by substitution and impregnations are very subordinate. Considered in detail, the ore bodies are stock works ; but they are arranged along definite fissures and the deposits as a whole have a vein-like character and answer to the " chambered veins " defined in a subsequent paragraph. The workings have developed two main fissures. One of these dips from the surface at a high angle and in a nearly straight line. The other strikes in nearly the same direction as the first, dips steeply from the surface, then flattens and approaches the first fissure rap- idly, again becomes very steep, and in the lowest workings almost coincides with the first. In vertical cross-section the two fissures form a figure 468 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. resembling 1 a V. The great ore bodies are distributed along these two fissures, making irregularly into the walls. The wedge between the fissures also contains ore bodies. They are always accompanied by evidences of motion and by a mass of attrition products of various rocks clay in a mining but not in a mineralogical sense. This clay is usually on the hanging wall and is called alia. The other mines of the district contained similar ores in similar rocks. The Gtiadalupe was the most productive, but was not at work and was full of water during my visit. All the deposits of the district appear to occur along a rather simple fissure system. The main fissure is nearly parallel to the rhyolite dike at the Guadalupe. It follows the direction of the hills, the axis of which curves gradually away from the dike for a certain distance. Passing through or near the San Antonio and Enriquita, it seems to break across the ridge at the America and enters the Almaden on the strike of its two great fissures. It is near this fissure that new ore bodies are most likely to be found. The Washington seems to be on a branch of the main fissure. This fissure was probably formed at the time of the rhyolite eruption, to which also I ascribe the genesis of the ore. steamboat springs. This curious thermal area lies just within the desert Great Basin, in full sight of the forests and snows of the Sierra Nevada. It is only six miles in a straight line from the (Jomstock lode. Granite underlies the district and much of the area exposed is of this rock. Upon it lie metamorphosed rocks of the Jura-Trias series and lavas. Older andesites and younger asperites, described in a former paragraph, cover a large space, and there is a considerable area of basalt, which repre- sents the last eruption. The springs are numerous and some of them reach the boiling-point. They are unquestionably of volcanic origin and due to the basalt eruption. They reach the surface in the granite area. The flowing springs are con- fined at present to a small group of fissures, but steam in small quantities issues at many points in the region marked by evidences of solfataric action, and this region is substantially a continuous one. In some portions of it the sinters arc clralcedony, in others they consist to a considerable extent SUMMARY. 469 of carbonates, and in one portion (at the mine) the deposits of sinter are insignificant in extent, the chief effect having been decomposition of granite and the precipitation of sulphur and cinnabar. In this part of the area also steam and gas still issue in small quantities. The amount of cinnabar is considerable. The ore was mined and reduced a few years since, but mining would not pay at present prices. Quicksilver in very small amounts is being deposited by the springs now active, together with gold and several other metals. They are dis- solved as alkaline sulphosalts, as will be explained in a subsequent para- graph. The waters and gases are similar to those of Sulphur Bank, except- ing that ammonia and organic compounds are absent. The four metals most abundant in the present spring deposits, anti- mony, arsenic, lead, and copper, exist in the granite, but I was unable to detect quicksilver. This may be due to the small quantity of quicksilver in the average granite or, as I think more probable, to irregularity in the composition of that rock. The granite is the probable source of the mercury. The Oathill, Great Eastern, and Great Western districts The neighborhood of Oathill is a most interesting one and contains many quicksilver deposits within a small area. The underlying rock is of the Knoxville series, identified by the presence of Aucdla. It is in part metamorphosed and serpentinized and in part unaltered. Andesite and basalt have broken through it. The basalt eruption gave rise to hot springs, one of which still ex- ists at Lidell, issuing from the workings of a now abandoned quicksilver mine. In two cases also cinnabar deposits occur at the contact between basalt dikes and the adjoining rock, forming veins. Irregular stockworks of the more usual type also occur. The Oathill mine is the principal one of the mines belonging to the Napa Consolidated Company. It is in unaltered sandstone, the strata of which are nearly horizontal. The deposits are true veins, cutting the strata at an angle of 45. From these veins ore bodies sometimes make out into the country, following the stratification. These are impregnations. The ore is the usual mixture of cinnabar, pyrite, silica, and calcite, and bitumen also occurs. Small quantities of barite are also found, and this is the only case in which this mineral is known to accompany cinnabar in California. It is also found at Almaden, 470 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The Great Western lies near the extinct andesitic volcano called Mt. St. Helena. The country rock is of the metamorphic series, and both ande- site and basalt have broken through it, A layer of opalized serpentine accompanies the ore-bearing ground. The ore is chiefly cinnabar, but at one point rock impregnated with native mercury was found. The cinnabar was deposited simultaneously with pyrite and quartz. The bitumen posep- nyte was first described from this mine. The deposit consists of a tabular, reticulated mass connected with a fissure system and it lies at the contact between serpentine and nearly unaltered sandstone. If it does not come under the common definition of a vein, it is closely related to that class of ore bodies. The Great Eastern lies in Sonoma County, far from other quicksilver deposits and six miles from lava. The rock is the ordinary metamorphosed material of the Coast Ranges The ore occurs in black, opalized serpentine, which here forms a definite ledge. The ore seems, as usual, to be of some- what later date than the formation of opal and is accompanied by pyrite, quartz, and bitumen. The ore seems to form a pipe, which is continuous from the surface to a depth of 450 feet. This pipe I believe to lie on a continuous fissure. All of the above mines have produced important quantities of quick- silver. other quicksilver deposits So far as I know, the most northerly cinnabar deposits on the west coast south of British Columbia are in Douglas County, Oregon. In the northern part of Trinity County, California, there is also a mine. These widely, separated deposits both lie on the northerly continua- tion of the middle Coast Ranges, where most of the deposits occur. From Clear Lake to Santa Barbara, as is shown on the map of California accom- panying this report, the deposits are thickly scattered. Of the very many deposits briefly described in Chapter XIII, only a few can be mentioned here. The Manzanita mine, Colusa County, is very remarkable for the association with cinnabar of free gold, often in feathery crystals. Pyrite accompanies the ore and the gangue is chiefly quartz. There is free sulphur also, as well as other evidence that the ore was deposited by hot sulphur springs, such as still issue within a few hundred feet of the SUMMARY. 471 mine. There is no lava in the neighborhood. In the Stayton mines, San iienito County, large quantities of stibnite were associated with cinnabar. The Oceanic, in San .Luis Obispo County, is in unaltered sandstone, sup- posed to be Miocene. Most of the other -deposits occur in shattered rock masses of the Knoxville group, forming stockworks. In some cases they seem to be accompanied by true veins, and sufficient exploration would doubtless show a fissure system connected with each of them. The usual mineral association is the same so often described above. On the gold belt of California cinnabar occurs in pebbles, in aurifer- ous gravels, and in true gold quartz veins, so that there are mercuriferous gold veins as well as auriferous deposits of cinnabar. In the Barcelona sil- ver mine, Belmont, Nev., cinnabar was found with silver ore in the vein. Cinnabar also occurs in a silver vein near Calistoga, Cal. In Idaho float cinnabar has several times been found, in some cases with a calcite matrix. A statement repeatedly made in the literature reads as if this ore had been found in place in Idaho, but this is not the case. In Utah, near Marysville, a deposit of the selenide of mercury, tiemannite, was being mined and re- duced early in 1887. So far as I know this is the only case in which this mineral has been found in sufficient quantities to form the basis of commer- cial exploitation. None of the other deposits requires special mention in this abstract. Discussion of the ore deposits. The general results of the observations on the various mines are discussed in Chapter XIV. Microscopical examination of the ores shows that cinnabar is usually deposited in immediate contact with quartz, and that, though opal and chalcedony are frequently found very near the particles of cinnabar, there is seldom, if ever, actual contact. More rarely the cinnabar is directly embedded in calcite. The evidence of the microscope also goes to prove that the ore is always deposited in fissures in in dense rocks or in the interstitial spaces of porous sandstones. Macro- scopically the same conclusion had been reached. The assertion often made that cinnabar has been deposited by substitution for wall rock at Almaden in Spain is certainly incorrect, and, in my opinion, no such case has been adequately proved to exist. The only substance, excepting metallic sulphides, which cinnabar is known to replace is organic matter, and this seems to be very exceptional 472 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The usual mineral association consists of cinnabar and traces of native mercury, with pyrite and marcasite, silica and carbonates ; but sulphur occurs at three mines, chalcopyrite is not very uncommon, stibnite is found (though rarely), gold or auriferous pyrite occurs in a few cases, millerite in a number of instances, and barite in one. These substances and their decom- position-products are rare. Excepting in Steamboat Springs, at Calistoga, and in the Barcelona mine, I do not know of silver, lead, or zinc minerals accompanying cinnabar in the western United States. A new bitumen, two new chromium minerals, and a red antimony sulphide have been detected with cinnabar in this investigation. The great similarity of the deposits points to a common history for them all. The evidence is strong in many cases that they have been deposited from hot sulphur springs and the remainder have probably been produced in the same way. The inclosing rock* have been without effect upon the deposits, for nearly all the rocks in the Coast Ranges inclose ore bodies. These facts point to a common, deep-seated origin. It has often been asserted that quicksilver ores do not form deposits similar to those of the ores of other metals, but I can find no evidence of this Stockworks, impregnations, and regular veins all occur, and no other or peculiar form of deposit is known to me. Many of the discussions as to whether or not deposits are veins depend on the various uses of this word. To miners it usually means deposits along, or directly connected with, a distinct fissure ; to a geologist a vein means a deposit between well defined, nearly parallel walls which have once been in contact. Irregular bodies of ore, even those connected with distinct fissures, are known to him as stocks, stockworks, or by some similar name. I propose to call the contents of dis- tinct fissures with very irregular walls chambered veins and the irregular openings or ore bodies connected with a main fissure vein chambers. A chambered vein may then be defined as a deposit consisting of an ore- bearing fissure and ot ore bodies contiguous with the fissure, but extending into the country rock. The greater part of the cinnabar deposits would come under this definition, which would also apply to many deposits of other ores. If this term were adopted, simple fissure vein would still describe the form of deposits now known to mining geologists as veins. SUMMARY. 473 Solution and precipitation of cinnabar and other ores. TllC Wcltei'S of Steamboat Springs are now depositing gold, probably in the metallic state; sulphides of arsenic, antimony, and mercury ; sulphides or sulphosalts of silver, lead, copper, and zinc; iron oxide and possibly also iron sulphides; and manganese, nickel, and cobalt compounds, with a variety of earthy minerals. The sulphides which are most abundant in the deposits are found in solution in the water itself, while the remaining metallic compounds occur in deposits from springs now active or which have been active within a few years. These springs are thus actually adding to the ore deposit of the locality, which has been worked for quicksilver in former years and would again be ex- ploited were the price of this metal to return to the figure at which it stood a few years since. At Sulphur Bank ore deposition is still in progress. The waters of the two localities are closely analogous. Both contain sodium carbonate, sodium chloride, sulphur in one or more forms, and borax as principal constituents, and both are extremely hot, those at Steamboat Springs in some cases reaching the boiling-point. In attempting to deter- mine in what forms the ores enumerated can be held in solution in such waters, it is manifestly expedient to begin by studying the simplest possi- ble solutions of the sulphides, and particularly of cinnabar. The statements in the previous literature of this subject are incomplete and in part discordant, so that the subject required reinvestigation, particu- larly as to the sodic solvents. It was found that, provided a small quantity of sodic hydrate be present, one molecule of mercuric sulphide unites with two molecules of sodic sulphide to form a freely soluble sulphosalt and that an excess of sodic hydrate is without effect upon the solubility. Even when sodic hydrate is entirely absent, mercuric sulphide is freely soluble in aque- ous solutions of sodic sulphide, though the contrary has repeatedly been asserted; but either one molecule of mercuric sulphide then unites with three of sodic sulphide, instead of two, or a mixture of sulphosalts nearly corresponding to this compound is formed. Sodic sulphydrate when cold is absolutely without effect upon mercuric sulphide, but when the mixture is heated on the water-bath the sulphydrate is decomposed and sodic sulphide is formed; it unites with the mercuric sul- phide in the proportion of four molecules of the former to one of the latter. A perfectly limpid solution results. The same compound is produced when 474 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. mixtures oi' sodic sulphide and sodic sulpliydrate are brought in contact with mercuric sulphide. The presence of sodic carbonates diminishes the solu- bility of mercuric sulphide, but does not prevent solution. Ammonium carbonate completely prevents solution at temperatures below the boiling- point, but not at 14*) C. These facts suffice to lead to important conclusions with reference to spring waters, such as those mentioned above. When neutral sodic carbonate is treated with sulphydric acid at ordinary temperatures, sodic sulpliydrate forms. At temperatures approaching the boiling-point, it is probable that a certain quantity of sodic sulphide is also produced. At these higher temperatures either of these sulphur compounds will dissolve cinnabar, and the presence of sodic carbonates will not prevent solution. These conclusions were amply verified by direct experiments. Mercuric sulphide may be wholly or partly precipitated from solutions of the sulphosalts in many ways: by excess of sulphydric acid or of other acids, by borax and other mineral salts, by cooling (especially in the presence of ammonia), and by dilution. In the last case a certain quantity of metallic quicksilver, as well as mercuric sulphide, is formed, and this is very probably one of the methods by which native quicksilver has been produced in nature. Metallic gold, iron pyrites, cupric sulphide, and zincblende we.re found to be soluble in solutions of sodic sulphide and in solutions of the carbonates to which sulphydric acid had been added. All of them appear to form sulphosalts with the alkaline compound. It has long been known that sulphides of arsenic and antimony are soluble in sodic sulphide. They also dissolve in mixtures of the carbonates and sulphides of sodium. Natural solutions of sodic carbonates and sulphides, which are common components of hot spring waters, are thus capable of dissolving at least five of the principal metals, as well as sulphur, arsenic, and antimony. Combi- nations of these elements form a large part of the minerals found in mines. There is little or no doubt that the cinnabar of the California deposits has been dissolved and precipitated as indicated above and that at least a part, of the gold of that State has been produced in a similar manner, but I by no means assert that natural deposits of cinnabar and of gold have never been produced in any other way. SUMMARY. 475 origin of the ore. There is tli o strongest evidence for the supposition that the cinnabar, pyrite, and gold of the quicksilver mines of the Pacific slope reached their present positions in hot solutions of double sulphides. Either the metals must have been leached fronrtlre granite or they were derived from an infragranitic source, for examination of the conditions of occurrence shows it utterly improbable that they were extracted from any volcanic rock at or near the surface, while the sedimentary strata of the region are composed of granitic detritus. No one fact or locality absolutely demonstrates whether the metals were originally components of the granite or came from beneath it, but the tendency of the evidence at all points is to the supposition that the granite yielded the metals to solvents produced by volcanic agencies, and when all the evidence is considered together it is found that this hypothesis explains all the known circumstances very simply, while the supposition of an infragranitic origin leads to numerous difficulties. Though no one of these may be in itself inexplicable, when taken as a whole they appear to me to be so. Had solutions of quicksilver been formed in com- pany with other products at the foci of volcanic activity, cinnabar would often be met with in craters. Though it is often found associated with volcanic effects, it perhaps never occurs in craters. Were the solutions formed below the granite, ore deposition would also almost certainly take place in part within the granite, and most ore deposits would continue down into that rock, probably growing richer with increasing depth. On the other hand, the distribution of the deposits relatively to volcanic vents is such as would be anticipated if the ore were known to be leached from the granite by hot waters of volcanic origin. The varying richness of the different deposits also corresponds to the irregularity in the composition of the granite and in the extent of surface exposed along the underground passages through which the waters must have reached the surface. I Finally, at Steamboat Springs, at least, the composition of the granite answers to that of the deposits of springs which are still depositing small quantities of quicksilver. It thus seems fairly certain that the quicksilver and gold are derived from the granite. I entertain little doubt that many of the gold veins of California have a similar origin, while others have probably been produced by the action of cold surface waters. INDEX. Page. Abbott's mine, Culnsa County Arhiardi, A. d 1 , cited 5, 15, 35, 47, 43, 3 Acton. K., cit.-d *9 Aden, Arabia, ciuuibar at 44 ^Etna mines, Napa C nnty 354 371 Afgbauistou, cinnabar in 44 Africa, cinnabar in 43 i Age of strata in Seated by resemblances 187 | Alaska, A ucella in 201 I cinnabar in 3S4, 385 Aleutian I lands, Aucttta in 20- | Algeria cinnabar in 43 Alkaline sulphides, action of, < n cinua' ar 419 Alanite 119 ! Al i aden, Spain, cinnabar deposits at 390 description of xv i 28 historical notes ou ^ ( no substitution at 399 Albtat New Almaden 3:6 Altooua mine, Trinity County 36i Amalgim, from Bri i 412 Carbonates, conversion of rocks to 392 effect of, on solutions of cinnabar 431 Carboniferous formation in California 177 Carboniferous fossils in the gold belt 135 Carboniferous metamorphic rocks 208 Caron, cited 28 Cascade Range 205, 365 Castillcro, A., cited 8,9 Castillo, A. del, cited 16,17,18 Castro, L., cited 16 Cathrein, A., cited 82 Caulinitesa.1 Salphur B.mk 254 Cerro Bonito mine, Fresno County 380 Cerro Gordo mine, Fresno County 380 Ceylon, cinnabar in 47 Chaboya, L., cited 8 Cha'.cedonite 390 Chalcedony at Steamboat Springs 341 (See. also. Opal.) Chalk Mountain, andesitc of 152, 238 Chambered veins 410,472 Champlin, J. D., cited 10 Chanconrtois, fi. de, cited 30,52 Chateliot, M. du, cited 21 Chiro licils at New Idria. 294 Chicogroup 179 Chico strata fn On gon 206 Chico-Tejin series, described 214 at Clear Lake 237 Chili, cinnabar iu 23 China, cinnabar in 46 Chlorides, eifect of, on solutions of cinnabar 431 Chlorites in metamorphic rocks 85 . Christy, S. B., cited 4J1.436 , Chromic iron, at Knoxville 278 at New Idria 294 in serpentine 116 Chrysolite, occurrence of 114 Cincinnati mine, Lake County 376 Ciintalur, at Knox villi- 281 at N'cw Alinaden 314 at New Idria 301 at Sulphur Bank 257 :,t Steamboat Springs 350 conclusions as to foreign occurrences of 50 crystals of 390 era of deposition 417 in basalt 257,282,337,373 in granite 350 iu nii'tjiunrpliic rocks, passim et 391 in sedi ntary rocks 301,382,391 known to the ancient Pel uviaus 8 natural solutions and precipitations of 4:i:> occurrence of, in andesite 264,370,379 oiigmof. . 55,438,445 possible son l re.s c.t' 442 precipitation of. ill Sulphur Bank 261 INDEX. 479 Page. Pago. Cinni-bar, relations to rocks 441 j Cope, F., cited 3.S8 soluble in ;un mnnuit.il solutions 431,269 Copper accompanying cinnabar 257,283,34:1,386 solution and precipitation of 419,473 Credner, H., cited 439 supposed substitution of, for rock 42,399 Crosnier, L., cited 21,23 veins of 284,307,414 Cross, W., cited 336 withbarite 386, 39 T ; TTrygtaUinp mctaiuorpliic rocks 455 with gold 367,383 (s,-e, also, Metamorphic rocks and Massive rocks.) with pyrargyrite 370 Crystalline rocks at Knoxville, ago of 274 with silver not eruptive 273 withstibnite 282, 367, 380. :.s!i not precipitates: > 274 (See, also, Ore deposits.) Cuuric sulphide, solubility of . 433 Cinnabar City, El Dorado County, deposit at 384 ; Curtis, J. S., cited... 398 Cinnabar deposits, age of rocks inclosing 50,416 Cora Blauca mine, New Almaclen district .319,324 at Abnarten 28,399 Corea> cinnabar in 47 at Huancavilica 21 Corsica, cinnabar in 33 atldria 38,290 Cortazar, 1). de, cited 16,28,49,375 at Monte Amiata 35,290 ! Cotta| B . TOn , c i to d 36,41,305,357 atVallalta 34 Courtney, \V. S., cited 16 character of inclosing rocks 50,391 form and classification of 53,416 D. from solutions 55,435 Dull, \V.U., cited 384 in Alaska 381 Dana. E. S., cited 267 in Arizona 386 Dana, J. D., cited 15,77,108,113,118,124,129,166,216,237 in British Columbia 384 Darwin, G. H., cited 107 in California 305 Daubree, G. A., cited 61, 107,136,172,182,306 in Idaho 385 Davidson, G., cited 207 in Nevada 385 Dawson, G. M., cited 381 in New Mexico 386 Day, T. D., cited 380 in Oregon 366 Dead Broke mine, Lake County 376 in Utah 386 ] Debray, H., cited 421 minerals found with 52 : Dcchen, II. von, cited 36 minor, of the Pacific Slope 470 ! Decomposition, concentric 255 of Africa 43 ; Delesse, A., cited , 119 of Asia 44 Del Norte County, cinnabar in 366 of Australasia 48 Deposits of cinnabar, similarity of 401 of Europe 27 Derby, O., cited 24 oflceland 24 Des Cloizranx, A., cited 24 of North America 15 i Deville, H. Ste.-C., cited 421 of South America 19 Dewalque, G., cited 28 relations of, to lines of disturbance 51 Diabase, at Steamboat Springs 145 relations of, to volcanic phenomena 52 at Virginia City 145 Clarke, W.B., cited 48 ! tufa on the gold belt 383 Clayton, J. E., cited , 386 Diallage in metamoiphic rocks 75 ClearLako 247 Dicksou, J. F., citod 47- district 461 ] Dilution, cllcct of, ot> cinnabar solutions 429 fauna of 220 | Diorito in the Coast Ranges 141 originof 222 ' Doelter, C., cited 394 region, descriptive geology of 233 ; Dolomieu.D., cited 35,52 Cloverdale mine, Sonoma County 372 Dolomite, at Xcw Almaden 315 Coast Ranges, andosites of the 157 pscudomorphs of cinnabar after :;n7 dioriteoftlie 144 Doroschin, P., cited 2ni> granite of the 144 Drasche, R. von, cited 109, 115 history of the 211 Durand, E. F. , cited 285,286,31)7 structural relations of the, to other ranges 208,211 Colusa County, cinnabar in 367 '' Conistock Lode, andejitcs of the 336 Earth, rigidity of I he 168 compared with Steamboat 331,352,448 viscosity of the 107 criticism of theory of the geology of the .note, 448 Ecuador, cinnabar in 20 diabase of the 144 Egleaton, T., cited '. 377,433 origin of ore in the 448 Eichstiiilt, F., citod ion, 113, 115 Concretions 4 -, 4 Eiclivrald, E., cited 202,204,237 inChicobeds. 214 ' Elephant vein, Napa County :(70 in sandstone at New Idiia 64,294,300 Elliot, G. H., cited ],.,! theory of formation of 6j Ennnons, S. F., cited !,', 176,352,306,385,39s Condon, T., citod 202,232 Enricpiita mine, New Almaden district 325 Conrad, T. A., cited 42,215 Eon no age of Tojon beds 217 480 INDEX. Page. Eocene at New Idria. 2'J9 Ephydra, larvae of, in Borax Lake 268 Epidote iu metamorphic rocks 86 Equilibrium, hydrostatic, of the earth 167 Erosion, bearing of, on origin of massive rocks 109 Errington, Miss, cited 200,178 Eruptions, traditions of, at Clear Lake 247 Eruptive rocks, Pre-Tertiary 222, 274 not mingled with metamorphica 131 (See, alto. Massive rocks.) Eschwege, W. L. von, cited 24 Eureka mine, Oathill 356 Europe, cinnabar deposits iu 27 Everett, A.H., cited 48 F. Farallone Islands, granite of 140 terraces of 207 Feldspars, conveision of, to serpentine 122 in metamorpbic rocks. 82 specific gravity of 14:! Fischbach, W., cited 42,44 Fischer, P., cited 202 Fischerde Waldheim.G., cited 227 Fissure system, at New Almaden 317, 321 at various mines 414 Fissures, discussion of 407 formation of, under great pressure 414 Flagstaff mine, Lake County 376 Floyd, R. S., cited 250 Foreign occurrences of cinnabar 14, 432 Formations, found iu California 1~7 of California, classified by Whitney and Gabb 179 Fossils, Chico, at New Idria 291 of Cache Lake Pliocene 220 of the Wallala beds 214 Tejon 215 Tertiary, at New Almaden 312 Fouqu6 and MicheLLevy 86, 109. 114, 115, 129,421 France, cinnabar in - 32 Francke, H., cited - 86 Fraser River, cinnabar and gold uear 384 Fugger Brothers controlled Almaden 28 Furnace, tirst continuous quicksilver 309 G. Gabb, W. M., cited . . .16, 176, 178, 179, 184, 196, 198, 205, 207, 215 228, 231, 237, 310 Gabbro, metamorpbic 101 olivinitic, at Now Almaden 312 Gahn,J.G., cited 3 Galena, insolubility of 434 Gangne minerals, at Knoxville 279,285 at New Almaden 314 at Sulphur Bank 257 in cinnabar deposits 388,472 Gaugzng 410 Gannett, H., cited 163 Garces, E., discovered Huancavelica "1 Garnet in metaniorphic rocks - 87 Gases, at Xe\v Iilria ' 308 at Phomix mine, analysis of 373 at Steamboat Springs 342 at Sulphur Biink, analysis of 238 soll.itari. , at Knoxville 287 (fault, IIorsHowti l> ill referred to the 20~> Page. Uavilau Kange, limestone of the .... 181 rocks of the l.'H Geikie, A., cited : 256 Genesee Valley, fossils in 195 Genesis of cinnabar 401 at Pope Valley 374 Geology, importance of, to mining 418 of the quicksilver belt 176,460 Germany, cinnabar in 36 Geysers, the 377 Gibhs, W., cited % 53 Gilbert, G. K., cited 209 Glaucopbanc, in metamorphic rooks 76 Glaucophane-schist 102 analysis of 101 at Wall Street mine 375 Gmelin-Kraut, cited 430 Godfrey, J. G. H 47 Gold, extracted from quaitz by pressure 198 genesis of dcposi ts of 4 30 product compared with that of quicksilver. 3 solubility of 433 Gold accompanying cinuabar, at Baker mine 3C8 at Knoxville 381! at Manzanita mine 307 at Pica^ho mine 309 at Steamboat Springs 344 at Sulphur Bank 257 Gold belt defined 195 Gomes, -I. C., cited 24 Goodyear, W. A., cited 207, 28.', 283, 309, 315, 368, 379 Gottschc, C., cited 47 Gower, cited 47 Granite, age of the 141 at New Almaden 311 distribution of 140,180 intrusive 141 of California in part primeval 174 of Lower California 207 porphyry 143 relations of, to other rocks 1 70 the probable source of quicksilver 446 underlying the Coast Ranges 60 Granite at Steamboat Springs 332 metals in 350 Grate structure, in opal 393 in serpentine 115 Great Eastern district, geology of 302,469 Grt at Eastern mine, Lake County 375 Great Eastern mine, Sonoma County ?62 Great Geyser, Iceland 24 Great valley of California, elevation of 200 Great Western district, geology of 358,469 Greenland, Amelia in 201, 203 Groddeck, A. von. cited 41,317,400 Guadalcazar, Mexico, cinnabar at 17 Guadalupfmiue 326 Gualala, Mendocino County, fossils near 213 Gnancavelica. (Ore llmm-m lica.) Guatemala, cinnabar in 19 Guillemin-Tarayre. E., cited 31 Giimbcl, C. W., cited 151 II. Hague, J. D., cited lla^u and Iddinss. cited 27 145, MB, 147, 157 INDEX. 481 I'";;''. J. Hull, J.. cited 210 . Page. Hall, T.J., cited 283 Jameson, B., cited 27 Hanks, H. G., cited 76, 113, 3d4 Jauin, L., cited. xiv,325, 327, 375, 380, 382, 385 Haushofer, K., cited 112 ! Japan, ciuuabar in 47 Hnutefeuille, I 1 ., cited : 15 'lava, cinnabar in .48 Hatty, R. J., cited 100 Johnston, K., cited 03 Hawkins, R. K., cited 19 Josephine mine, San Luis Obiapo County 382 H.-at of thermal springs, origin of 411 Julicn, A. A., cited 66 Heckmanne, A., cited 31,43 Jurassic fossils in Goneseo Valley 195 Hector, J., cited 50, 340 Jura-Trias at Steamboat Springs _. 128, 333 Heilprin, A., cited 216 Helmhacker, R , cited ; 28 Hilgard, E. W., cited 4 Kamtschatka, cinnabar in 45 Hiriakoff, M., cited 43 Keller, cited 21 Historical geology 170,460 ' Kemble, G. W., cited 3gj History and statistics of quicksilver 1,451 Kennan, G., cited 45 Hoffmann, F., cited 35 Kentucky mine, Sonoma County 377 Hoffmann, F. C., cited 235, 370 Koyserling, A,, cited 202, 201, 227 231 Hoffmann,.!. I)., c itul 233,298 Keystone mine, San Luis Obispo County 382 Hollands, I)., cited 3:1 Kicking Horse Pass, cinnabar at 394 Hol/.apfe', E . cited 231 Kimball, J. P., cited 3 Homatlico Kivor, cinnabar noar 384 , King, Clarence, cited 170,178,201,200,210,219,267 Hornblende, in metamorpliic rocks 75 Kirchhoff, G. S. C., cited 420 metasomatic development of 89 Klemm, J.G., cited 97 Hornblende-mica-andesite 147 Knoxville beds, at New Idria 2D2 Horsetown beds, defined 180 at Knoxville 271 fauna of COii at Sulphnr Bank 251 non-conformity beneath tlio 205 at Clear Lake 235 referred to the Gault 205 Aurrlla In 230 straligraphical ivlations oj UH defined 1^0 Hut springs, association of, with mines 381,382,402 : fauna of 11)8 wuirccof heat of 411 Knoxville district, descriptive geology of 271,401 ::. H., cited 16 Knoxvillite, new mineral 27D Huancaveliea. Peru 4,C,2t Kokscharow, N. von, cited 44 Huitzuco, Mexico, cinnabar at 18 . Kolbe, H., cited 430 Hun'bolclt, A. von, cited 16, 17, 19,20,22,54, 172 Koiiocti, Mount ! 233 Hamic acid, concretions due to 67 Krantz, A. {?), cited 393 Hungary, cinnabar in. 41 Kriimmel, O., cited 170 Hunt, T.S., cited 82,117,119,120,130,172,343 ! Kuss, H., cited 6,28,32,42 Ilussak. E., cited 10^, 113 Kwei-Chau, China, cinnabar in 4,6,46 Hut ton, Captain, cited 44 Hntton, F. W., cited 49 Hydrocarbons, absent at Steamboat Springs... 342 r Lagorio, A., cited . absent in many volcanic emanations i - ;o Laguereuno, T.L., cited... 10 Hypersthene m basalt 157 Hvposulphites, formation of 4 30 ''t '^>. ^1> near 383 at Steamboat Springs 8 8 Lak 7".Knoxv,lIe district 2 82 at Sulphur Bank.. Lilns<1 f H " "^ 45 Lateral secretion theory 352,442 Later hornblende amlcsite Ice, behavior of, in melting 70 Laiir, P., cited 33 , Iceland, cinnabar in 24 Laras Idaho, cinnabar in 285 age and distribution of the ..] Idilings. See Hague and ladings. of California not fused sediments '.".'.'.'. 174 Idria mine, Austria 4,5,7,38 , Lead sulphide, insolubility of Ildekansk mine, Siberia 44 Leavens, II. W., cited .";"; 36G Illuminationoftuunelbyheliost.it 308 Le Conte, J., cited .206, 209' 257 263 Ilmenitein metamorpliic rocks 34 Lecso, J. P., cited Impregnation! of cinnabar 5J, 4;o Lehmanu, J., cited, 13 o India, British, cinnalur in 47 Leipoldt, G., cited .^.......... 169 India, Dutch, cinuabir in 48 L,s,,uc. TUX, L., cited .'.".".' 2 5i India, Spanish, cinnahai in 4g ! Lidell hot springs 371 Injection theory of ore deposition 442 \ Limestone, of Gavilan Range igi Inoceramus, occurrence of 181 of Neocomian age CO Inntcramus Piochii 1%, 1:17 of Now Almadon 31 1 Italy, cinnabar in 33 Lindgi en, W., cited ......xiv, 119,273330 Ivanhoe claim, Oathill ::,i^ Lindstrom, G., cited 203 ? 227 MON XIII 31 482 INDEX. Page. Linked veins 409 Lipolil, M. V., cited 5,38,42,54,398,400 Little Borax Lake 241 238 Little Missouri mine, Souoma County 377 Little Paaocho mine, Fresno County 381) Little Sulphur Bank 264 Livermore mine, Sonoma County 377 Liversidge, A., cited 50 Los Prietos mine, Santa Barbara County 382 Lotti, B., cited 35,118 Lower California, character of 207 Wallala beds in 213 Luckliardt, C. A. .cited 307,374,377 Lucky Boy claim, Piuto County, Utah 385 Liidecke, 0., cited 77 Lycll, C., cited 217 M. MacCulloch, J.,citcd 172 Maggots in Borax Lake 268 Mallet, E., cited 172 Manhattan mine, Kuoxvillc district 282 Manzanita mine, Colusa County 307 Marcasite, solubility in sodium sulpbiuo 432 Marcou.J., cited 176,187,193,198,216,218 Mariposa beds 180 Amelia in 230 auriferous 198 determined as Cretaceous 204 determined as Jurassic 196 determined as Triassio 198 fauna of 11.8 identical with Kuoxvillc beds 195,197 Mariposa estate, fossils on the 178 Marmolite i 114 Marsh, O. C., cited 221 Martinez group 179,180 Massive rocks 140.459 origin of the 164,168 primeval 171 texture of 162 Mast.C.L., cited 383 Maxwell, J.W.C., cited 302,308,383,390 Mayacmas district, geology of the 368 Medina, B. de, invented amalgamation process 28 Meek. F.I!., cited 178,190,232 Mthu, M.C., cited 421 Melville, W. II., cited xiii, 360, 372, 430 Meudelojeff, C., cited 171 Mercuric sulphide, solution anil preparation of ..26!), 419,435 (See, also, Cinnabar.) Mercury, sulphosalts of 422, 425, 4.'6, 429 Mercury and Manzanita veins, Napa Consolidated mine 350,415 Metacinnabarite, at Baker mine 28^,308 atKnoxvillo 284 atNewIdria 302 formation of 436 in Mexico 19 in New Zealand 49 in the Bavarian Palatinate 37 Metals in tin; Stra]nl">;it Springs deposit 313 Metamorphic pebbles in Chico and Miorene b::ds. . 18f>, 190. 2!)5 Metauiorph ic rocks 56, 4.~>5 ngeofthe 57,183,188 Page. Metamorphic rocks, at Great Eastern mine ............ 362 at Great "Western mine ............................ 358 at Knoxville, age of .............................. 272,274 at Xew Almadcn ............. . ............... _____ 319 atNcwIdria ..................................... 393 at Oathill ......................................... 355 at Steamb jat .......................... : .......... 128, 333 at Sulphur Bank ................................. 251 Carboniferous .................................... 208 compared with the Archojan ...................... 138 ci'i stalline, classified ............................. 72 decomposition ofthe .............................. 105 granular ........................................ .. 93 minerals formed in ................................ 74 of Gavilan Range ................................. 1-8 of Neocomian age ......................... ....... 60 eerpentinizatiou of ............................... 121 (See, also, Neocomian and Serpentine.) Metamorphism, chemical character of ............... 134 conditions attending .......... .. .................. 129 dynamic conditions of ............................ 133 eras of .................................... 57,131,187,210 influence of, on erosion ............................ 23G in the Coast Kanges ............................... 181 of eruptive ro=ks ................................. 59 Pre-Cretaccous ........... ....................... 2C8 pressure attending ............................. ... 132 proofs of .......................................... 129 theories of ........................................ 58 Metasomatism ........................................ 57,453 Mctastibnito ........ ................................ 343,383 Mexico, cinnabar in .................................. 16 Michel-Levy, A., cited ................................ 76 (See, also, Fouqne and Michel- Levy.) Middendoiff, A. T. von, cited ........................ 203,227 Milierite, at Knoxville ............................... 286 in the Pko>uix mino. ____ . ............ . ........ .... 372 Miucnkoff, cited ....... .............................. 43 Minerals, converted to serpentine ......... . ........... 122 found in metamorphic rocks ................... .... 74 resulting from metasomatism ..................... 455 Mines, various, comparison between .................. 401 Miocene, at New Almadcn ........................... 312 conformable with the Tejon ....................... 19i discussed ....................................... 218, 461 metamorphosed near San Jose ................... 185, 180 uucouformable with the Tejon ...... . ............. 193 uncouformablo with the Ncocomian ............. : 192 Mispickcl at \c\v Almadcn .......................... 315 Moesta, F. A., cited ............ ..................... 17 Mohelhel, Ibn, cited .................................. 44 Molasse compared with California rocks .............. 187 Moncasterio, J. de, cited ............................. 28,42 Monte Amiata, Tuscany, ul;issy trachyte of .......... 159 Moore, G. E., cited ............................... 37,49,283 Mt. Diablo, andesito at ...... ..... .................. 155 cinnabar at ......................................... 373 Mt. Jackson mine, Great Eastern district ............ 362,304 Mt. Shasta, aspwritps of ............................... 336 Munroe, 11. S., cited .. ............................. 47 Muscovite in mrtamorphic roeks. ..................... 74 N. Na;i:i Consolidated mines Xapaliti-. a m-w bitumen Xativo ipiicksilver. at Pi-ii 334, 356 372 376 INDEX. 483 Page. ! Page. Native quicksilver, at Rattlesnake mine 377 Ore deposition, theories of 442 at Wall Street mine 375 Ore deposits, age of .. mode of occurrence 3P8 at Groat E.isteni mine 30:1 precipitation of 4:! ' at Great Western mine 3.~>9 Neocomian, at Knoxvillo 271 at Knoxrille 281 at O.vthill :; '' at ManMinita mine 307 in Jt'ayacroas district a09 at New Alraaaon 314,310,323,327 in Solano County 378 at New Idria 301 strata , 193,400 at Steamboat 342 (See, also, Meta-norphic rocks and AttceUx.) at Sulphur Bank.. 257.203 Nertschinsk district, Siberia, cinnabar in 45 character of 410 Net structure 115.401 discnssicii of 387,471 New Al.Na.'.eiidistrict.u.-i'logy "'' ....3IO,4ii7 form of 40:, lissare system of -3- 8 minerals in 387 XY Almadfii mil,,.. .llKOVeryof minor, descriptions of 305,470 plans ami sections of 318 j origin of 438 Newberrv, J. S , cited 170, 448, nu( relations of, to general geology 2.'5 New Idria., Cliico-T.'jon scries at 215 wall rocks of 391 distiict, geology of 201,105 Oregon, Chico beds in 200 mine 301 ; cinnabar in 360 non-conformity at l> Organic matter, concretions duo to 60 s.,nd-tono concretion from ^ Oscrskij, A., cited 45 New Idiian mine, Douglas County, Oregon 360 New Zealand, cinnabar in 49 Nicholas, W., cited Panoche district 379 Nichols R.K. cited 233 Panoche Grande mine, Fresno County 380 Xo,liil,.and pebbles theory of formation of 68,455 Paso Roblca hot springs 381 Xoggeratli. A., eited '....15,19,23,27,28,32,33,35,45,49 Pavlow, A., cited 204,229 Non-conformity, between the Tejon and Miocene 218 i Pebbles, formation of 71 Post-Mioccno ... 218,461 Ponce's Ranch, Carboniferous fossils at 195 Non-conformity, Posi-Ncocomian 177,188,460 Perez-Eosales, V., cited 23 atNewAlmadcn 313 Perowskito in opal 394 atNew Idria 295 Peru, cinnabar in 20 indirect evidence of 192 , Pctersen, T., cited 160 on the Gold Belt 196 Pniicker, L., cited 21 paleontologicnl evidence of 193 ! Philippine Islands, cinnabar in 48 Novak,, I, cited 7 Phillips, J. A., cited 3,23,352 Nova Scotia, cinnabar in 16 Pl'ff nix mine, Napa County 371 Pluemx Xo. 2 mine. Napa County . 374 1'kolas borings 207 I'hthanite 105 Oakland miuo, Sonoma County 377 Phylloxera, quicksilver us.d to kill 3 Oakvillc mine, Napa County 377 Picaoho mine, San Benito County 309 Oathill district, geology of 354,409 Pinart, A. L., cited 202 Obsidian, andesilic 153,242 Pioneer mine, Lake County 376 basaltic 158,252 ; pi po veins 411 Oceanic mine, San Luis Obispo County 382 ! Pittsburgh mine, Lake County 378 Ocean View mine, San Luis Ohispo County 3S2 ! , Pliny, eited 4,28 OH vine in andesito 153 Pliocene 219, 238 Onofrite at Kuoxville 285 probable at Now Almaden 314 Opal S90, 392 Point Reyes, cinnabar at. 379 at Great Eastern mine, Lake County 375 Polar Star mine, San Luis Obispo County 382 at Great Eastern mine, Sonoma County 363 Pope mine, Napa County 374 at Great Western mine 360 Portugal, cinnabar in 27 at Knoxville L81, 286 Posepnyta at Great Western, analysis of 360 at New Almaden 327 Post-Pliocene described 219 at Steamboat Springs 341 Potassic sulphide, action of, on cinnabar 4!9 Oppcrt, E., cited 47 Potassic sulphydrate, action of, on cinnabar 419 Orbigny, A.D.d'.cited 204 Prado, C. de, cited 18,42,397,399 Orcutt, C. K., cited 213 Primeval rocks 171 Ore, description of 387 ! Pseudodiabase 94 microscopical character of , 389 analysis of 98,99 origin of : 438,475 Pscudodiorite 94,99 (See. also, Cinnabar.) analysis of 101 Ore deposition, at Steamboat Springs 346 Pseudomorphism and substitution 396 at Sulphur liank 269 Paeinbimorph . einnaKi: after h.vilc 397 484 INDEX. 1 365 9 245 Page. Pseudomorphs, ciuuabar after magncsite ..... ......... 397 galena after calcito ............................... 398 Pumpelly, R., cited ................................. 46, 47, 51 Pyrargyrite with cinnabar ........................... 370 Pyrite, solubility of ................................... 432 Q. Quartz, conversion of, to serpentine .................. 123 Quicksilver, average price of belt C'astillero's test for deposits in andcsite discovery in California historical notes on. .......................... in Scandinavia in Scotland ............... , ...... in Steamboat Springs water mines of California, distribution of ............ mining, future of native, formation of ................. . ........ .'. foreign occurrences of ........................... often found with gold and silver .................. ores, conclusions as to occurrence of .............. 50, product at Steamboat ............................. product in California .............................. product in Hungary ............................... product in Tuscany .............................. products of districts compared ................... relative abundance of, in nature .................. relative value of .................................. rock (see, also, Opal) .............................. statistics .............................. ___ ........ uses of .................................... . ....... value of product of, since 1850 ..................... world's product of, since 1850 ................... . . 27 :147 13 417 436 U 9 410 '.'">- 10 41 C 7 2 1 63 1 ;j 3 3 K. Raimondi, A., cited ................................... 20 Kamirez, S, cited ................................... 16,17,18 Rando), J. B., cited .......................... . ....... 3,6,10 Rath, Q. vom, cited ......................... 20,23,34,118,159 licude, F., cited ................................. xiv, 319,321 Rcdingtonite, now mineral ............................ 279 Red i ngton mine ...................................... 281, 284 discovery of ...................................... 10 Kccd mine ( or California mine), Enoxville district ...281,283 Kcnatd, A., cited ..................................... 86, 106 Results, brief outline of ............................... xvii Reticnl.ited veins of cinnabar ......................... 54 Kettss, A. E., cited ..................................... 398 Reycr.E., cited ....................................... 441 Rhynchonella, in Colusa County ...................... ' 235 occurrence of ..................................... 183 Riyollle .............................................. 156 age of ............................................. 223 dike at Ne\v Almaden .................. .......... 313,329 Richthofen, F. von, cited .................. 6,46,313,853,448 Rigidity of the earth .................................. 168 Kilc.y, C. V., cited ..................................... 268 Riuconada mine, San Luis Obispo County ............. 381 Uising, W. B., cited .................................. 257,203 Rivero, M. E. de, cited ............................. 7,17,21,22 Roach, J., cited ....................................... SOS Rockland district, Del Norte County, cinnabar iu .... 366 Racks, sedimentary ................................... 56, 453 massive. ......................................... 140, 159 Tag,-. Holland, G., cited 36,315 Kosenbti8c.li, H., cited 86, 109, 118, 390 Uo-^lMTg. basalt from the 160 Roth, J., cited 48,66,77,118,422 Russell, I., cited 267 Russia, Aticella in 202 (imiahnrin 43 Rutile iu metaiDorpUlc rocks 84 S. Sain.nl, J. M., cited 44 Sr. Jolm'.s mine, Solano County 378 San Antonio miue, New Almailen ill strict 327 San Bernardino, cinnabar at 383 San Cailos mine, NVw Idrin district 308 Sandberger, F., cited 18,118,351,436 Sandstone, alteration of the 63 alte: (', :!so product compared with that of quicksilver 3 sulphide, insolubility of 431 Silver Bow mine, Napa County.' 373 Simnndi, A 351,419 Sinters, absence of, explained 405 dendritic, at Borax Lake 266 at Steamboat Springs 340 Siaapo, ancient name for AlmaJen 4 Skertclily. S. B.J., cited 48 Smyth, 11. B., cited 49 Sodic hydrate, influence of, on the solubility of cin- nabar 42.' Sodic sulphide, in nature 473 solubility of cinnab.ir in 419,423 solubility of pyrite in 432 Sodie snlpl'ydrate, behavior of, to cinnabar 419,41>4,428 Soctboer, A., cited 3 Solutions of cinnabar, effects of dilution on 429 eft'ects of other substances on 431 Sonuensehein, F. L. , cited 383 Sonoma mine, Sonoma County 377 Soutb America, cinnabar in II Southern California 140 Spain, cinnabar in 27 Spitsbergen, Aucetta in 203 Springs at Steamboat 338 Star mine, Napa County 373 Statistics auil history of quicksilver 1,451 Stay ton mines, San Beuito County 380 Steamboat Springs district, geology of 331,463 diabase at 144 granite of 141 raetamorpbic rocks of 128 Stearns, R. E. C., cited 220,240 Stein, W., cited 420 Stotzner, A., cited 23 Stibnitc 282,367,380,389 Stoliczka, !'., cited 227,231 Ulriitiiiniiiiiat Borax Lake 2(i8 Substitution of cinnabar for rock . 288, 315,317, 394, 399 Sulphides, associated with cinuabar 388 origin of 438 Sulphur, at Manzanitamiue 367 at Steamboat. ..'. 346 at Sulphur Bank 254, 463 Sulphur Bank, descriptive geology of 251 discovery of 10 future prospects of 264 high temperature at 259 resemblance of, to other deposits 263,402 Sulphur Bank mine 253,263 Sulphur deposition, at Knoxvllle 287 at Sulphur Bank 254 Sulphuric acid at Sulphur Bank, genesis of 255 Page. Sulphurous acitl at Sulphur Bank 255 Sulphur springs, hot. at tho Mauzauita 367 Sumatra, cinnabar in 48 Summary of results 451 Similrrlandaud Luckhardt mine 382 Suiiol, A., cited 8 Synclinal hills in metamorphic rocks 183 Szabo, J., citod 118 T. Talc in metamorphic rocks 113 Tejon, atNewIdiia 299 beds, age of the 177 beds discussed 214 conformable with the Chico 192 controversy as to age of 215 determined as Eocene 217 group 179,180 Terraces of Californ ia coast 207 Texture of massive rocks 162 Thenard, P., cited 67 Thermochemistry, application of 427 newlawof 119 Thibet, cinnabar in 47 Thinolite 267 ' Thomsen, J., cited 430 Thomson, W., cited 167 Tbuiach, H., cited 84 TlmistonLake 241 Ticrnanuite in Utah 385 Tin product compared with that of quicksilver 3 Tissot, A., cited Titauite in metamorphic rocks...... 85 Todos Santos Bay, Wallala beds at 213 Tonla, F., cited 203,227 Trachytes 150,155 Transition andesites . 148 Trask, J. B., cited 177 Trautschold, II., cited. 204 Trinity County, cinnabar in 366 Trinity mine 366 Tri;issi<- fossils at Genesoe Valley 195 Ti-iassic in California 178,198 Tschermak.G., cited 43,86, 118, 143, 43!) Tulo roots, silicifled, at Sulphur Bank 254 TuUborg.S. A , cited 227,231 Tunis, cinnabar in 44 Turkey, cinnabar in 42 < Turner, II. W., cited xiv,354 Tuscan mines, product of 6 Tuscan Springs, fiioctramux at 197 Tuscany, cinnabar in 35 U. Uncle Sam Mountain (Konocti) 233 United States, cinnabar in, confined to Pacific slope.. 15 Upheaval, Post-Miocene 218 I'ost-N'eocomiiui 1!;8 Upheavals, exposure of primeval rocks by 166 1'ralite in metamorphic rocks 75 I'tali, tirmannlte and cinnabar in 385 V. Vallalta, description of 34 principal mine in Venetia ... 5 Valley mine, Napa County 355,371 486 INDEX. Page. Veatch.J. A., cited 205 Vegetable growths in springs at Steamboat Springs.. 340 Vein chambers 412 Veins, at Oathill 350 discussed 40" of cinnabar 4(16,472 of cinnabar at Knqxville 288 of cinnabar in foreign countries 53 recent, at Steamboat Springs 340 Velten and Lehmaun, cited.. 18 Vcrbeek. R.D.M., cited 48 Vermilion, use of quicksilver in manufacture of 3 Verneuil, P. E. P. do, cited 28 Viscosity of the earth. -- 167 Volcanic action evinced at various mine's 401 Volcanic cones, form of, at Sulphur Bank 253 Volcanic rocks, rel:it'on of deposits to 417 W. Wadsworth, M. E., cited 383 Wagner, R., cited 421 Wahsatch range 209 Wallala, etymology of 213 Wallala beds, composition of 140 discussed 213 uncon form able with Neocomian 191, 191 Wallala group 179 Wall rocks 391,410 WallStreet mine, Lake County 375 Page. Walker, G. T., cited 19 Washington mine, Napa County 319,324,374 Washington Territory, Amelia in 201 Washoe district, Nevad:v, audcsites of 149 diabase of 14."i Washoe rocks, nodules in 71 Water, of Borax Lake 265 of Steamboat Springs 346 of Sulphur Bank 259 Weber, K., cited 420, 42J Webster, H. A. .cited 2tf Weigaud, B., cited 109 White. C. A., cited xiii, 17ti, 198, 'JOt, 209, 213, 333, 460 Hcuuirks on the genus Aucrlla by 226 Whilcaves. 3. P., cited 202,204,228 Whitney, J. D., cited ...46,121,140,155,176,179,185,192,215, 218, 224, 242, 265, 313, 376, 383 Williams, J. F., cited 180 Z. Zincken C., cited 44 Zinc sulphide, solubility of 434 Zircon in metamorphic rocks 87 2irkcl, F.. cited " Zittel,K.A.,cited 227,231 Zoisite, analysis of 79,80 an evidence of metainorphism 129 in metamorphic rocks 77 UNIVERSITY 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. .Renewed books are sub RECEIVED ICLF (N) NUV/5'66-10AM ^ %-"-< i LOAN DEPT. ir~ t ,rro * MAYI-: 19 8 o RECE/yrrQ M/1V v TO Siftl h -C DM A.JSI f~$ m~ LIBRARY USE JULl Y 1 LD 21A-60m-7,'66 (G4427slO)476B General Library University of California Berkeley to VE 1 OI849 ' '-/> r UNIVERSITY OF CALIFORNIA LIBRARY ' :