siren nue fk naan se Boat ia irc ane ste earn a ne oie emerge Ste Saatumsam agen atin ae : : ete! : : : sie : = Bhatt ee wm — ~ ete cages senpatn canes he arwernennt te twee. varaaret ee wn Tres rset ee ne oe ae ena pre mente ae mos sone a ee ee Pee ae eh eae Be Sew Bee os SPSS re SLSR MIA aaa 2, nas at nsec oat Se me. - a Oe ae "ar fd hve ' Pee? Ghyivel, 4 te VOe ite Wala, ae ) ie Y he 1, Ud ASD VCR eS Baye EN a [Monograph XIII] The publications of the United States Geological Survey are issued in accordance with the statute approved March 3, 1579, which declares that— “The publications of the Geological Survey shall consist of the annual report of operations, geo- logieal and economic maps illustrating the resources and classification of the lands, and reports upon veneral and economic geology and paleontology. The annual report of operations 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 quarto series if deemed necessary by the Director, but otherwise in ordinary octavos. Three thousand copies of each shall be published for scientific exchanges and forsale at the price of publication; and all literary and cartographic materials received in exchange shall be the property of the United States and form apart of the library of the organizwtion: And th» money resulting from the sale of such publications shall be covered into the Treasury of the United States.” i On July 7, 1882, the following joint resolution, referring to all Government publications, was passed by Congress: “That whenever any document or report shall be ordered printe-l by Congress, there shall be printed, in addition to the number in each ease stated, the ‘usual number’ (1,900) of copies for binding and distribution among those entitled to receive them.” Except in those casestin which an extra number of any publication has been snpplied to the Sur- vey by special resolution of Congress or has been ordered by the Secretary of the Interior, this office has no copies for gratuitous distribution. ANNUAL REPORTS. I. First Annual Report of the United States Geological Survey, by Clarence King. 1880, 8°. | 79 pp. 1lmap.—A preliminary report describing plan of organization and publications. IL. Second Annual Report of the United States Geologisal Survey, 18897381, by J. W. Powell. 1882. 8°. lv, 588 pp. 61 pl. 1 map. Ill. Third Annual Report of the United States Geological Survey, 188182, by J. W. Powell 1883. 8°. xviii, 564 pp. 67 pl. and maps. IV. Fourth Annual Report of the United States Geological Survey, 1882-83, by J. W. Powell. 1884. 8°. xxxii, 473 pp. 85 pl. and maps. V. Fifth Annual Report of the'United States Geological Survey, 1883-84, by J. W. Powell. 1885. 8°. xxxvi, 469 pp. 58 pl. and maps. VI. Sixth Annual Report of the United States Geological Survey, 1884-’85, by J. W. Powell. 1-86. 8°. xxix, 570 pp. 65 pl. and maps. VIL. Seventh Annual Report of the United States Geological Survey, 1885-’86, by J. W. Powell. 1888. 8°. xx, 656 pp. 72 pl. and maps. x The Eighth and Ninth Annual Reports are in press. MONOGRAPHS. Monograph I is not yet published. jl. Tertiary History of the Grand Canon District, with atlas, by Clarence E. Dutton, Capt., U.S. A. 1882. 4°. xiv, 264 pp. 42 pl. and atlas of 24 sheets folio. Price $10.12. Ill. Geology of the Comstock Lode and the Washoe District, with atlas, by George IF. Becker. 1882. 4°. xv, 422 pp. 7 pl. and atlas of 21 sheets folio. Price $11. IV. Comstock Mining and Miners, by Eliot Lord. 1883. 4°. xiv, 451 pp. 3 pl. Price $1.50, V. The Copper-Bearing Rocks of Lake Superior, by Roland Duer Irving. 1883. 4°. xvi, 464 pp. 151. 29pl. Price $1.85. VI. Contributions to the Knowledge of the Older Mesozoic Flora of Virginia, by William Morris Fontaine. 1883. 4°. xi, 144 pp. 541. 54 pl. Price $1.05. VIL. Silver-Lead Deposits of Eureka, Nevada, by Joseph Story Curtis. 1881. 4°. xiii, 200 pp. 16 pl. Price $1.20. VII. Paleontology of the Bureka District; by Charles Doolittle Walcott. 1834. 4°. xiii, 203 pp. 241, 24 pl. Price $1.10. ; 1 IL ADVERTISEMENT. IX. Brachiopoda and Lamellibranchiata of the Raritan Clays and Greensand Marls of New Jersey, by Robert P. Whitfield. 19885. 4°. xx, 338 pp. 35 pl. 1lmap. Price $1.15. X. Dinocerata. A Monograph of an Extinet Order of Gigantic Mammals, by Othniel Charles Marsh. 1886. 4°. xviii, 243 pp. 561. 56 pl. Price $2.70. XI. Geological History of Lake Lahontan, a Quaternary Lake of Northwestern Nevada, by Israel Cook Russell. 1885. 4°. xiv, 288 pp. 46 pl. and maps. Price $1.75. XII. Geology and Mining Industry of Leadville, Colorado, with atlas, by Samuel Franklin Em- mons. 1886. 4°, xxix, 770 pp. 45 pl. and atlas of 35 sheets folio. Price $3.40. XIIL. Geology of the Quicksilver Deposits of the Pacific Slope, with atlas, by George F. Becker. 1888. 4°. xix, 486 pp. 7 pl. and atlas of 14 sheets folio. Price $2.00. XIV. Fossil Fishes and Fossil Plants of the Triassic Rocks of New Jersey and the Connecticut Valley, by John S. Newberry. 1888. 4°. xiv, 152 pp. 26 pl. Price $1.00. In preparation: XV. Younger Mesozoic Flora of Virginia, by William M. Fontaine. XVI. Paleozoic Fishes of North America, by J. 8S. Newberry. XVII. Description of New Fossil Plants from the Dakota Group, by Leo Lesquereux. —Gasteropoda of the New Jersey Cretaceous and Eocene Marls, by R. P. Whittield. —Geology of the Eureka Mining District, Nevada, with atlas, by Arnold Hague. —Lake Bonneville, by G. K. Gilbert. —Sauropoda, by O. C. Marsh. —Stegosauria, by O. C. Marsh. —Brontotheridxw, by O. C. Marsh. —The Penokee-Gogebic Iron-Bearing Series of North Wisconsin and Michigan, by Roland D, Irving. —Report on the Denver Coal Basin, by 8. F. Emmons. —Report on Silver Cliff and Ten-Mile Mining District, Colorado, by S. F. Emmons. —Flora of the Dakota Group, by J. 8. Newberry. —The Glacial Lake Agassiz, by Warren Upham. —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 are, however, num- bered in a continuous series, and may be bound in volumes of convenient size. To facilitate this, each Bulletin has two paginatious, one proper to itself and another which belongs to it as part of the volume. 1. On Hypersthene-Andesite and on Triclinic Pyroxene in Augitie Rocks, by Whitman Cross, with a Geological Sketch of Buffalo Peaks, Colorado, by 8. F. Emmons. 1883. 8°. 42 pp. 2 pl. Price 10 cents. 2. Gold and Silver Conversion Tables, giving the coining values of troy ounces of fine metal, etc., computed by Albert Williams, jr. 1583. 8°. 8pp. Price 5 cents. 3. On the Fossil Faunas of the Upper Devonian along the meridian of 76° 30’, from Tompkius County, N. Y., to Bradford County, Pa., by Henry 8. Williams. 1884. 8°. 36 pp. Price 5 cents. 4. On Mesozoic Fossils, by Charles A. White. 1884. 8°. 36 pp. 9pl. Price 5 cents. 5. A Dictionary of Altitudes in the United States, compiled by Henry Gannett. 1884. 8°. 325 pp. Price 20 cents. 6. Elevations in the Dominion of Canada, by J. W. Spencer. 1884. 8°. 43 pp. Price 5 cents. 7. Mapoteca Geologica Americana. A Catalogue of Geological Maps of America (North and South), 1752-1881, in geographic and chronologic order, by Jules Marcon and John Belknap 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°. 56pp. 6 pl. Price 10 cents. 9, A Report of work done in the Washington Laboratory during the fiscal year 188384. IF. W. Clarke, chief chemist; T. M. Chatard, assistant chemist. 1884. 8°. 40 pp. Price 5 cents. 10. On the Cambrian Faunas of North America, Preliminary studies, by Charles Doolittle Wal- cott. 1884. 8°. 74 pp. 10 pl. Price 5 cents. 11. On the Quaternary and Recent Mollusca of the Great Basin; with Descriptions of New Forms, by R. Ellsworth Call.. Introduced by a sketch of the Quaternary Lakes of the Great Basin, by G. K. Gilbert. 1884. 8°. 66 pp. 6pl. Price 5 cents. 12. A Crystallographic Study of the Thinolite of Lake Lahontan, by Edward $. Dana. 1884. 8°. 34 pp. 3pl. Price 5 cents. 13. Boundaries of the United States and of the several States and Territories, with a Historical Sketch of the Territorial Changes, by Henry Gannett. 1885. 8°. 135 pp. Price 10 cents. 14. The Electrical and Magnetic Properties of the Iron-Carburets, by Carl Barus and Vincent Stronhal. 1885. ¢°. 238 pp. Price 15 cents. 15. Ov the Mesozoic and Cenozoic Paleontology of California, by Charles A. White. 1885, 8°. 33 pp. Price 5 cents. : 16. On the Higher Devonian Paunas of Ontario County, New York, by John M. Clarke. 1885, 8°. 86 pp. 3pl. Price 5 cents. 17. On the Development of Crystallization in the Igneous Rocks of Washoe, Nevada, with Notes on the Geology of the District, by Arnold Hague and Joseph P. Iddings. 1885. 8°. 44 pp. Price 5 cents, ADVERTISEMENT. Ill 18. On Marine Eocene, Fresh-water Miocene, and other Fossil Mollusca of Western North America, by Charles A. White. 1885. 8°. 26 pp. pl. Price 5 cents. 19. Notes on the Stratigraphy of California, by George F. Becker. 1835. 8°. 28 pp. Price 5 cents. 20, Contributions to the Mineralogy of the Rocky Mountains, by Whitman Cross and W, I’. Hille- brand. 1885. 8°. 114 pp. Lpl. Price 10 cents. 21. The Lignites of the Great Sioux Reservation. A Report on the Region between the Grand and Moreau Rivers, Dakota, by Bailey Willis. 1885. 8°. 16 pp. 5pl. Price 5 cents. 22, On New Cretaceous Fossils from California, by Charles A. White. 1835. 8°. 25 pp. 5 pl. Price 5 cents. 23. Observations on the Junction between the Eastern Sandstone and the Keweenaw Series on Keweenaw Point, Lake Superior, by R. D. Irving ané ‘I. C. Chamberlin, 1835, 5°. 121 pp. 17 pl. Price 15 cents. 94. List of Marine Mollusca, comprising the Quaternary fossils and recent forms from American Localities between Cape Hatteras and Cape Roque, including the Bormudas, by William Healey Dall. 1885. 8°. 336 pp. Price 25 cents. 25. The Present Technical Condition of the Steel Industry of the United States, by Phineas Barnes. 1885. 8°. 85 pp. Price 10 cents. 26. Copper Smelting, by Henry M. Howe. 1885. 8°. 107 pp. Price 10 cents. 27. Report of work done in the Division of Chemistry and Physics, mainly during the fiscal year 182485. 1886. 8°. 80 pp. Price 10 cents. 28. The Gabbros and Associated Hornblende Rocks occurring in the Neighborhood of Baltimore, Md., by George Huntington Williams. 1836. 8°. 73 pp. 4 pl. Price 10 cents. 29, On the Fresh-water Invertebrates of the North American Jurassic, by Charles A. White. 1835. 8°. 41 pp. 4pl. Price 5 cents. 30, Second Contribution to the Studies on the Cambrian Faunas of North America, by Charles Doolittle Waleott. 1°86. 8%. 369 pp. 33 pl. Price 25 cents. 31. Systematic Review of our Present Knowledge of Vossil Insects, including Myriapods and Arachnids, by Samuel Hubbard Sendder. 1886. 8°. 128 pp. Price 15 cents. 32. Lists and Analyses of the Mineral Springs of the United States; a Preliminary Study, by Albert C. Peale. 1886. 8°. 235 pp. Price 20 cents. 33. Notes on the Geology of Northern California, by J.S. Diller. 1836, 8°. 23pp. Price 5 cents. 34. Onthe relation of the Laramie Molluscan Fanna to that of the succeeding Fresh-water Eocene and other groups, by Charles A. White. 1886. 8°. 54pp. 5pl. Price 10 cents. 35. Physical Properties of the lron-Carburets, by Carl Barus and Vincent Strouhal. 1885. 8°. 62 pp. Price 10 cents. 36. Subsidence of Fine Solid Particles in Liquids, by Carl Barus. 1885. 8°. 53pp. Price 10 cents. 37. Types of the Laramie Flora, by Lester FP. Ward. 1887. 8°. 354 pp. 57 pl. Price 25 cents. 38. Peridotite of Elliott County, Kentacky, by J.S. Diller. 1837, 8°. 3lpp. Lpl. Price 5 cents. 39. The Upper Beaches and Deltas of the Glacial Lake Agassiz, by Warren Upham. 15873 Se. 84 pp. pl. Price 10 cents. 40, Changés in River Courses in Washington Territory due to Glaciation, by Bailey Willis. 1887. 8°. 10pp. 4 pl. Price 5 cents. 41. On the Fossil Faunas of the Upper Devonian—the Genesee Section, New York, by Henry S. Williams. 1887. 8°. 12lpp. 4 pl. Price 15 cents. 42, Report of work done in the Division of Chemistry and Physics, mainly during the fiscal year 188586. F. W. Clarke, chief chemist. 1837. 8°. 152pp. 1pl. Price 15 cents. 43. Tertiary and Cretaceous Strata of the Tascaloosa, Tombigbee, and Alabama Rivers, by Eugene A. Smith and Lawrence C. Johnson. 1887. 8°. 159 pp. 21 pl. Price 15 cents. 44, Bibliography of North American Geology for 1886, by Nelson Hl. 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. Penrose, jr., with an Intro- duction by N.S. Shaler. 1888. 8°. 143 pp. Price 15 cents. 47. Analyses of Waters of the Yellowstone National Park, with an Account of the Methods of Analysis employed, by Frank Austin Gooch and James Edward Whitfield. 1838. 8°. 84 pp. Price 10 cents. 48. On the Form and Position of the Sea Level, by Robert Simpson Woodward. 1888. 8°. 88 pp. Price 10 cents. Numbers 1 to 6 of the Bulletins form Volume I; Numbers7 to 14, Volume IL; Nambers 15 to 23, Volume Il; Numbers 24 to 30, Volume LV; Numbers 31 to 36, Volume V; Numbers 37 to 41, Volume VI; Numbers 42 to 46, Volume VII. Volume VIII is not yet complete. Tn press: 49. On the Latitudes and 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. ae 51. Invertebrate Fossils from California, Oregon, Washington Territory, and Alaska, by C. A. ite. 52, On the Subavrial Decay of Rocks and the Origin of the Red Color of Certain Formations, by Israel C. Russell. 53. Geology of the Island of Nantucket, 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 I’ orm: ution, by F. H. Knowlton. — Mineralogy of the Pacific Co: ust, by W. H. Melville and Waldemar Lindgren. — Report of work done in the Division of Chemistry and Physies, mainly ‘daring the fiseal year 1886-87. —A Report on the Thermo Electrical Measurement and High Temperatures, by Carl Barus. — The Greenstone Schist Areas of the Menominee and Marquette Roagions of Michig: vn, by George H. Williams; with an introduction by R. D. Irving. — Bibliography of the Paleozoic Crustacea, “by ASIN: Vo; ades. — The Viscosity of Solids, by Carl Barus. — Anthor-Catalogue of Contributions to North American Geology, by N. H, Darton. -—On a Group of Voleanie Rocks from the Tewan Mountains, New Mexico, and on the occurrence of Primary Quartz in certain Basalts, by J. P. Iddings. — On the relations of the Traps of the Jura-Trias of New Jersey, by N. H. Darton. — Altitudes between Lake Superior and the Rocky Mountains, by Warren Upham. — Mesozoic Fossils in the Permian of ‘Texas, by C. A. White. STATISTICAL\PAPERS. Mineral Resources of the United States [1832], by Albert Williams, jr. 1883. 8°. xvii, 813 pp. Price 50 cents. Mineral Resources of the United States, 1333 and 1834, by Albert Williams, jr. 1885. 8°. xiv, 1016 pp. Price 60 cents. Mineral Ri sources of the United States, 1335, Division of Mining Statisties and Technolozy. 1886. 8°. vii, 576 pp. Price 40 cents. 5 Mineral Resources of the United States, 1835, by David T. Day. 1837. 8°. viii, 813 pp. Price 50 cents. Mineral Resources of the United States, 1837, by David T. Day. 1833. 8°. vii, 832 pp. Price 50 cents. In preparation : Mineral Resourees of the United States, 1888, by David T. Day. The money received from the sale of these publications is deposited in the Treasury, and the 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. WasHinGtTon, D. C., March 15, 1889. Series title, Author title, Title for subject entry. ADVERTISEMENT. LIBRARY CATALOGUE SLIPS. United States, Department of the interior. (U.S. geological survey). Department of the-interior | — | Monographs | of the | United States geological survey | Volume XIII | [Seal of the depart-» ment] | Washington | government printing office | 1888 Second title: United States geological survey | J. W. Powell, director | — | Geology | of the | quicksilver deposits | of the | Pa- cific slope | with an atlas | by | George I. Becker | [Vignette] | Washington | governmeit printing office | 1888 4°. xix, 486 pp. 7 pl. and folio atlas of 14 pl. Becker (George Ferdinand). United States geological survey | J. W. Powell, director | — | Geology | of the | quicksilver deposits | of the | Pacifie slope | with an atlas | by | George F. Becker | [Vignette] | Washington | government printing office | 1888 4°. xix, 486 pp. 7 pl. and folio atlas of 14 pl. {UNITED Starrs. Depariment of the interior. (U. S. geological survey). “Monograph XIII]. United States geological survey | J. W. Powell, director | — | Geology | of the | quicksilver deposits | of the | Pacific slope | with an atlas | by | George I’. Becker | [Vignette] | Washington | government printing office | L833 4°. xix, 486 pp. 7 pl. and folio atlas of 14 pl. [Unitep States. Department of the interior. (U.S. geological survey). Monograph XIIT]. V tile Re i ne DRUMS 1 6 tars ( ona | Las! yan = 4 ‘ ’ . be | U.S. GEOLOGICAL SURVEY : MONOGRAPH XII, PL.1I. SKETCH MAP SHOWING DISTRIBUTION OF QUICKSILVER MINES IN CALIFORNIA = Prmcipal Surveys e Other deposits referred to A Minor Surveys . o Traces of ore Scale 50 miles to linch . Ss orig be Steamboat Springs | \\\\\\\ a Ga are bie 2 y / or Virginia ° Carson Geo.F Becker, Geologist in charge. DEPARTMENT OF THE INTERIOR MONOGRAPHS OF THE UNITED STATES GEOLOGICAL SURVEY 1 VOLUME XIII WASHINGTON GOVERNMENT PRINTING OFFICE 1888 UNITED STATES GEOLOGICAL SURVEY aids J. W. POWELL, [IRECTOR GEOLOGY PCR Ey: DEPOSITS eee k ees [5 ©) Pi WITH AN ATLAS GEORGE F. BECKER WASHINGTON GOVERNMENY PRINTING OFFICE 1888 LETTER OF- TRANSMITTAL. DEPARTMENT OF THE INTERIOR, U. S. GrotocicaL SurvEY, CauirorniA 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, GeorGeE F. BEcKER, Geologist in Charge. Hon. J. W. Powe tt, Director U.S. Geological Survey. 1? | ea) ee | tay! aa - La 5 : * ” uff aS} CONSENTS: Page. EETLERIOR TRANSMUGT AL psec). Seis ec aie sepsetinenwe acinar Sek loa etie acura na taceiee ces acseceees eeee Vv RFE H AGRE pete maar a are cto fae tata Sas cas otelatstein Sieinio t= bin/e coaes Seo cic feb ce cece ne occewce ean tout eebeae XI BRD O ULEENE OMPRES MUNG temas sas naa See nome sas ot che sae een ots soe ce'ge ace oes mouemeseenemee XV (HUA Ri le SUALIS LICH MIN GUNIS COD gest: Bee ae ss clacendaaae + saaake Smee acescce Utcceeees ee aa oee 1 nN onesion oregon occurrences obiquicksilver.-+ casas -ecane oo a) ae es ee eee 365 Selva Discnasiontot,thetdcedepositess seas aes ss eee oe one eee ee ee eee eee). 387 XV. On the solution and precipitation of cinnabar and other ores..............--..---- 419 XV ehelonivinyo fadhe! Ones ss.) i2 soso ces 1 - osahaweioatec se ceiatecee boosie oasactewee --- 438 MVD SUM MALO te Tesi bse -siass = c1coytee ses eele cece cenee qzocaes chenedgswises Doges: eewaees 451 LISTON. oo. coocsa anbe SES Co SSO DO DANS Sec bEER BCH ODEO OS OCG DOE IIG Bars DSA OC ISO O50 -UntC eC One En 477 ly ne Ss a) a : d A \ 4 5 * 4 ’ oe i”) ’ y A a . Ap - . = = 7 i 1 bd i # ~ i : . s ‘ , > - i ’ rs ; \y ae . 5 Sa . . . s ° : ‘=~ 3 : f 5 > “ - i ar ; he al - a = b | * ‘ ; = c a : ' ; > ‘ ~ . ; ‘ > a ' P Se | 5 te Dead ay if y ae = ; SU AY alee ae [er The feet e er Ae J : ’ : ‘ » s a ™ « : : rh _ ‘ 7 . - U 1 Uy é 7 < | Ls 7) . fi & . . { a “a ILLUSTRATIONS. Page. PuateE I. Distribution of quicksilver mines in California. ....--.----+-.+---+ +2222 e22--+ Resi epiees II. Distribution of quicksilver deposits throughout the world ..-.--.-----------+-+------ 15 III. European and other foreign forms of Aucella ...--..----------+ ++ +2222 2 erste tteee 231 1V. American forms of Aucella.....------- ---- ---- --- 2-0 22 cere e ee eee e tenet tee cree 232 V. Geological map of Oathill .......--.-.------------ +--+ see eee eee eee cee cere terre 304 VI. Geological map of the Great Western district -....-.-.--------------+------+---- eee 8 VII. Map of the Great Eastern district ...-.....----. ------ -----+ e-++ eee ee crete rere ee 362 HiGH alee Zoisitemicrolites ose saeeeacecciss seen =e eis ae mee einecie = «lela Elman in oininia=io=ia)niataneininnm ata minein 78 2. Authigenetic augite in altered sandstone -...---..----.-------+ +--+ +--+ ++--2+---+- +--+ 88 3. Authigenetic hornblende in altered sandstone ....-...---------------+ +--+ --2+ +--+ +--+ 89 4. Clastic quartz partially converted to serpentine .-.--..-.---.----------. ---++-+-+-++--- 123 5. Ruptures produced by compression of strata .......---------------+----++ +--+ --2+-- 236 6. Dendritic sinter on the shore of Borax Lake....--....----------+---++-----+-+ ----++- 266 7. Partly metamorphosed anticlinal.........----.----- -----+ e+ 20+ 2-22 ee ee eee ee ee ree 276 8. Sandstone undergoing serpentinization .....-.--..-----.----+----++--++ +--+ - 222 serene 277 9. Serpentine forming from sandstone -....... ----- -------+ ---+- +++ oe 2222 eee eee eee 278 10. Diagrammatic vertical cross-section of the Redington mine....--...---------------7-- 289 11. Contact between metamorphic rocks and Chico beds.. -...----..-.--------- .----+----+- 296 12. Sketch of New Idria ore bodies .-.- ..--.. .-- 22. 2220 eee eee wo oe oe onan eee eens nee oe nae 303 13. Fissures of the New Almaden district .........-.-.--.------ +--+ 1-2-2 eee eee eee eee 329 14. Vertical cross-section of the Napa Consolidated mine. .....---.--.-------------------- 957 15. Vertical cross-section of the Great Western mine.........-....--.---------+ --------- 360 16. Vertical longitudinal section of the Great Western mine.........---------. .------=-- 361 7. Vertical cross-section of the Great Eastern mine..-.....--.. paupORCcOnSHaaee Spee csseu OOF: 18. Geological sketch map of the Mayacmas Range...--.-..----++----++---0 s+ +22) sere eee 369 TOMB INIGdev eins eral = nlelery-eisale r= atsta relat em ctnlaisceincawm~ s\=iaceitemisin wee dogos dosscese séctioneads 410 20. Simple fissure vein and chambered Vein ...00. sce cecceececeesseewee ceccescncece caceee 411 Ix y 7 _ is a 7 vee eer, i . ‘ ‘ Ng ra Le , >) Pee iigetaehe 7 4 ? ‘ 7) > ‘ aan ‘ PS OTe AAS. Skt EE ot SHEET I. Title. Il. Contents. III. Geological map of the Clear Lake district. IV. Geological map of the Sulphur Bank district. v5 Topographical map of the region of Clear Lake. ( Geological map of the Knoxyille district. VI. Geological map of the New Idria district. VII. Geological map of the New Almaden 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 Almaden mine. XII. East and west section of the New Almaden mine. XIII. Plan of clays, New Almaden mine. XIV. Geological map of the Steamboat Springs district. e P , ‘ ! vs oO . ‘ - id » * . [a = a. i a . , * . o> * - = J . P | a A b “4 bd i 7 ' “a - ’ ' : af ‘ - ‘= " ‘ . 4 ‘ ‘ F ° . ) . ~ J . U - re 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 experfments. 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 XI 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 andimportant. I could not without aid have accom- plished in a reasonable time so trying an investigation as that of the meta- morphie 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 these 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 this 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 respect 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 Pacifie 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 exvect to write more fully of them hereafter. Jus, 1887. BRIEF OUTLINE OF RESULTS. Quicksilver appears to be rather more ifian 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 yalue of the silver was about 16.4 times that of the quicksilver. The great quick- silver-producing localities of the world have been Almaden in Spain, Idria in Austria, Huancavelica in Peru, California, and the province of Kwei-Chau in China. No statisties are known to exist of the Chinese product. The total known products of the other regions take rank in the order in whch they are named above, but of late years Peru has prodneed nothing 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 1877, 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 discussious 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 these have been subjected to very intense metamorphism and have been con- yerted into thoroughly crystalline rocks, in part schistose. These rocks are of Cretaceous age and are grouped as pseudodiabase, pseudodiorite, glaucophane-schists, phthanites, and serpentine. Very elaborate field studies, 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 recrystalline. The conclusion reached is that dynamical action, tugether with warm waters carrying magnesian salts and silica in solution, effected the metamorphis o 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 will produce rounded nodules, like pebbles. The massiye rocks of the quicksilver areas include granite, ancient porpbyries, andesites, rhyolite, and basalt, A new group of andesites is discussed, for which the name asperites is suggested. It is shown that these rocks are of variable mineralogical composition, even in the same eruptions, while all of them share a trachytie habitus. The name is simply a latinized eanivalent of trachyte. Very remarkable andesitie and basaltic glasses occur near Clear Lake in areas of unusual size. These glasses are extremely acid, but contain alse 1 very high percentage of alkalis, and it is because of this peculiar chemical composition that 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 XVIL XVUI 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 remelted 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 Cretaceous beds containing a very eharac- teristic fossil of the genus Aucella. Soon after the era in which this mollusk lived —the Neocomian — occurred the great upheaval which induced the metamorphism, The next strata in point of age com- prise a hitherto undetected group of the middle Cretaceous called the Wallala beds. They were laid down unconformably 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 Téjon beds, which are here regarded as Eocene; but there was continuity of life and of sedimentation from the Chico to the Téjon, or from the Cretaceous to the Ter- tiary —a state of things detected nowhere else in the northern hemisphere, Upon the Téjon 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 voleanic 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 Aucella-bearing beds in Mariposa and Tuolumne Counties. This shell is of the same species as that in the Coast Ranges, and the first known upheaval of these mountains was contemporaneous with an important addition to the Sierra Nevada. A description of various forms of Auceila from different portions of the world, by Dr. C. A. White, with plates, forms an appendix to this chapter. Descriptive chapters follow dealing with the various districts of which detailed surveys were made. Each of these districts affords special facilities for the study of some special topic. The Clear Lake region contains fresh-water Pliocene beds, and in it the age of the andesites can be determined. It also contains remarkable areas of voleanic glass. At Sulphur Bank cinnabar is being precipitated from heated waters largely by the action of ammonia. At Knoxville, besides the ore deposits, there are admirable opportunities for determining the age of the metamorphic rocks and for studying the process of alteration. At New Idria the non-conformity between the metamorphic rocks and the Chico and the continuity between the Chico and Téjon appear. The New Almaden mine is particularly well adapted for the study of the structure of the ore deposits. At Steamboat Springs cinnabar is being deposited without the complications introduced by the presence of ammonia. In Chapter XII the Great Western, Great Eastern, and Napa Consolidated mines are described, and in the next chapter more or less information is given concerning each of over fifty minor deposits on the Pacific slope. Some of these have been productive mines, while others are mere prospects or possess only a geological interest. A general discussion of the deposits described follows, including the enumeration of the gangue minerals, the microscopical character of ores, ete. It appears that the cinnabar has been deposited solely in pre-existing openings, and never by substitution for rock. The fissure systems, which are always present, are very irregular, and deposits cannot be conveniently classified according to existing systems. A new descriptive term, ‘ chambered vein,” is suggested, which would include nearly all the deposits. A chambered yein is defined as a deposit consisting of an ore-bearing fissure and of ore bodies contiguous with the fissure which extend into the country rock. It appears that all of the deposits described have probably been deposited in the same way from hot sulphur springs. Chapter XV deals with the processes by which the ore has been dissolved and precipitated in nature. It is shown by experiment and analysis tliat cinnabar unites with sodium sulphide in various proportions, forming soluble double sulphides, and that these compounds can exist in such waters as flow BRIEF OUTLINE OF RESULTS. XIX from Sulphur Bank and Steamboat Springs either at ordinary temperatures or above the boiling-point. Metallie gold, iron pyrite, copper pyrite, and other minerals found with cinnabar are also soluble in the same solutions. A discussion of the origin of the ore concludes the investigation. It is shown that the quicksilver is probably derived from granitic rocks by the action of heated sulphur waters which rise through the granite from the foci of voleanic activity below that rock. For the convenience of those who consult the report the separate chapters are made as far as pos- sible independent of one another, a plan involving a certain amount of repetition. Further to facili- tate the use of the volume, the last chapter presents a summary of those which precede it. GEOLOGY OF THE QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. By GEORGE F. BECKER. CHAPTER I. STATISTICS AND HISTORY. Relative value of quicksilver—The exceptional physical and chemical properties of quicksilver give this metal a peculiar position in the markets of the world, which it is desirable to illustrate by comparison with that of other metals. The normal price of a metal is slightly, and only slightly, greater than the average cost of production; fur competition forces prices towards a minimum and in every industry there are individual establishments which, through errors in jadgment or want of foresight, work at an actual loss. For purposes of comparison if is fair to assume that the average cost of production is not far from 90 per cent. of the average price. From January, 1850, to Janu- ary, 1886, the average price of quicksilver may be taken at about 550 a flask, though the fluctuations have been so great and so frequent that a pre- cise mean could not possibly be reached. The average total cost has prob- ably been about 515, or say $1.30 a kilogram. It costs about twenty-nine times as much to produce a kilogram of silver and four hundred and sixty times as much to produce a kilogram of gold. These facts afford sufficient proof that quicksilver is a far more abundant metal than is silver. Were quicksilver and silver produced in exactly equal quantities and were the MON XI1I——1 1 2 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. extraction equally expensive, the cost of production would be substantially proportional to the abundance of the metals in nature. The weight of quick- silver produced is considerably in excess of the weight of silver. Were the quicksilver product about three-fifths of the actual amount and were the richer deposits only worked as a consequence of this restriction, the metal could be produced still more cheaply. The cost of reduction per kilogram, however, is trifling for quicksilver, but very considerable for silver. Making due allowance for this fact, it appears that quicksilver must be three or more times as abundant in nature as silver. The quantity of. metal produced bears an intimate but not a simple relation to the selling price. Higher prices would stimulate the production of quicksilver, but restrict consumption for certain purposes and to a certain extent. With some metals decrease of price brings with it a greatly in- creased consumption, but this has not hitherto proved to be the case with quicksilver, which is employed for very few purposes in large quantities. The consequence is that, in comparison with the quantity produced, quick- silver is the cheapest of metals; or,in other words, the value of the total productis very small. The total weight of quicksilver produced in the past thirty-six years is less than twice as great as that of silver, but the total value of the quicksilver is only one-sixteenth that of the silver. The world has yielded nearly one-sixteenth as much gold as quicksilver during the past thirty-six years, but the total gold product is worth thirty times as much as that of quicksilver. Tin is a metal sharing some properties with quicksilver, and, if one compares frozen quicksilver with tin, the likeness is much stronger. The tin produced in thirty-six years weighs about six times as much as the quicksilver; but, because the demand for tin is insatiable, the price remains sufficiently high to make the total value of the tin more than twice as great as that of quicksilver. These relations may be suecinetly expressed in a table such as the fol- lowing, which gives the total weights and values, the value of a kilogram of each metal, and the relative quantities when gold, silver, and quicksilver are each regarded as unity. Silver is now worth much less than the mint value; but, for a great part of the period which has elapsed since 1850, this metal VALUE AND USES. 3 has been at a slight premium. The mint value is thus sufficiently close to the average for the present purpose. The data as to the gold and silver products are compiled from figures given by Dr Soetbeer and Dr. Kimball.* The figures for tin are only approximations, but are close enough for the purpose. In estimating the total quicksilver I have supposed, with Mr. Randol, that the average yearly product, besides that of Almaden, Idria, and California, is 2,000 flasks? The mean value is assumed at 350 a flask. The world’s product of four metals from January, 1850, to January, 1836. u ? ’ ? | Total product. | Total value. Value per kilogram. (eae ee | ae ; ; | Kilograms. | Approximate EAUIOS?) Dollars. Approximate ratios.| Dollars. | Approximate ratios. [aaa | ae (Poa ee ee a Salat Fi THs | kale | Golden -cs = | 6, 484,922} 1. | 0.11 | 0.064 | 4, 309, 879, 161 2 1.79 | 29.3 | G6L 60 if 16. 458. | Silver.........| 58, 054, 906 | 8.9] 1. 0.57 | 2, 413, 203, 111 0.56) 1. | 16.4) 41.5676 | 0.063 | 1. | 28.7 Quicksilver...) 101,300,000 | 15.6} 1.74) 1. | 146, 800,0/0 | 0.03 | 0.06 | 1. 1.45 | 0.002 | 0.035| 1 |\Ringensaceeek| 620, 000, 000 | 95.6 10.7 6.12 322, 409, 010 | 0.97 | 0.13 2.2 0. 52 0. 0008 0. 013 0. 36 Uses for quicksilver—'The low value of quicksilver, which is abnormally small considering the comparative rarity of the metal, is due to its restricted use. It is true that the number of purposes to which quicksilver is applied is very great; but most of these applications imply the consumption of trifling quantities of the metal. A single flask of quicksilver in the form of mir- ror-backs, thermometers, or medicines goes a long way. The great mass of the metal is employed in the amalgamation of ores and in the manufact- ure of vermilion. As only certain silver ores can be economically amalga- mated, the demand for this purpose fluctuates greatly. The bullion of the Comstock was all extracted by this process, but amalgamation is not appli- cable to any of the ores of Leadville. The demand for vermilion also is limited by the competition of other red pigments. A few years since, Mr. J. A. Baur, of San Francisco, devised a means for the extirpation of phyl- loxera, which consists in intimately mixing clay with quicksilver (or “ex- 1 Report of the Director of the Mint, 1886, pp. 169 and 171. 2 They are estimated from data contained in Mr. J. A. Phillips’s Ore Deposits and statistics which I gathered at the Paris Exposition of 1875 (Reports of the United States Commissioners, vol. 4). 3 This for the later years is much too small. ‘The Tuscan mines are said to be producing about six hundred flasks a mouth. . 4 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE, tinguishing” quicksilver with clay) and adding this material, which is substantially blue mass, to the soil in which the vines are planted. The process seemed at first successful, but subsequently failed to give the de- sired result. Prof. E. W. Hilgard' has experimented on the process and found it entirely successful when properly carried out. No lead or oil should be added to the quicksilver, and the soil either must be sandy or, after im- pregnation with mercury, must be warmed in a hot sun or by artificial means, to saturate it with mercurial vapor. Should this process be widely introduced it would greatly enlarge the market for quicksilver and would correspondingly benefit the mining industry. Comparison between various mining regions. —()uicksilver has been produced in large quantities in but few localities. The principal productive regions have been Almaden in Spain, Idria in Austria, Kwei-Chau in China, Huancavelica in Peru, and California. Italy has yielded a little quicksilver for a long time and a considerable number of localities elsewhere have had a temporary or local importance, but none is to be compared with those enumerated in the last sentence. Peru is now producing uo quicksilver and the Chinese pro- duction is small, but it is certain that the Chinese deposits are not exhausted and Huancavelica may possibly resume production when the conditions for intelligent exploitation are better. Such geological interest as attaches to the occurrence of exceptionally large quantities of cinnabar is independent of the question of future produc- tiveness, and afew historical notes on the past yield may be welcome to the reader. The great quicksilver mine of the world is Almaden, which has been worked since at least 415 years before the Christian era, and perhaps still longer. What quantity of ore was extracted from it in ancient times and in the Middle Ages there is no means of knowing, further than that Pliny reports 10,000 pounds of cinnabar a year as brought to Rome from Almaden (Sisapo). The product was certainly never large until the amalgamation process was invented in 1557. Since that time the product has increased pretty steadily, and the output since 1850 is nearly equal to that of the entire eighteenth century. The deposit is said to grow richer in n depth ‘Science, vol, 6, 1885, p. 497, and vol. 7, 1886, p. 462. PRINCIPAL DISTRICTS COMPARED. 5 and is certainly far from being exhausted; on the contrary, in the method 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 authoritative 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 were discovered, according to some authorities, in 1490; according to others, in 1497. Since 1580 they have been worked by government officials for publie 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 365,000 florins’ 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 Almaden, 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, 1886, 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 has 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 are of considerable commercial importance. The product is given by Mr. A. d’Achiardi as follows, in kilograms: 1860. | 1870. | 1878. 1879. | 1880. | | | | | | | Ty | 3,500] 15, 000 | 120,563 | 129,600 | 115, 940 WENO U ARIE OB Ts ui)ae)s eee toe sie oe oer ome = aircie aioe leit ae Giclecebete ns | 30,256 | 31, 192 | 3, 080 2, 464 | () | | SUB CAIRO eee reeds eee ede ar eG wks eases Cums acoso se ‘Austrian paper money. A florin, silver, is $0.4878. ‘The value of paper fluctuates. At 45 cents the above yearly profit would be $164,250. 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 2,617 flasks a year. From 1850 to 1860 the average was probably con- siderably lower. Since 1880 it has been greater.’ 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 Huaneavelica 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. —T 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. H. Kuss*® and data furnished by Mr. J. B. Randol.’ 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 1800 and 1850. The product of Almaden for 1885 was 47,026 flasks. The 1 According to data furnished to me by the superintendents of the Siele and the Cornachino mines (the only ones 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 1886 was 7,478 flasks. * Annales des mines, vol. 13, 1878, p. 150. Mineral Resources U, 8. 1883 and 1884, p. 492. PRODUCTION. ( data for Idria up to January 1, 1880, are from an official publication. 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, and, 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 The production of Idria from 1800 The data for Huancavelica are to 1800 which appears in the table. onwards is from exact official figures.” taken from Mr. M. E. de Rivero’s memoir on the district.’ 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 districts, in Spanish flasks of 75 Spanish pounds or 34.507 kilo- grams. == = : = ae | | First record.} Up to 1700. | 1700 to 1800. | 1800 to 1850. | 1850 to 1886. | Total to Jan., 1886. | | | Year. INI than adcoessabocadace= 1564 517, 684 » 221,477 1, 091, 675 | 1, 135, 576 | 3, 965, 812 Idria 1525 399, 861 608, 743 242, 226 301, 549 | 1, 552, 379 Huaneavelica. .-- 157 881, 867 | 543, 642 Mos OU ti eten entertain 1, 501,113 Califormia------2----2 =. aeaael TSS Ohl sen echn aeons | PorletSmeccnae: | Posoesetoecer | 1, 429, 346 | 1, 429, 346 | 1, 799, 412 | 2, 373, 862 1, 408, 905 | 2, 866, 471 8, 448, 650 i 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 'Das k. k, Quecksilberwerk zu Idria in Krain, 1831. 2In the 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 227,432 flasks. been good enough to supply me with the following figures, in flasks: The present director, Mr. Joh. Novak, has 1880. | 1881. TEPC IT eee eer ene aeeonnan are 10,510 | 11, 333 1882. 11, 652 1883, | 1gs4. | 1885. | 1886. | 13,153 | 13, 968 13, 501 | | 3 Memoria sobre el rico mineral de azogue de Huancayelica, Lima, 1843, 14, 495 | 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.’ 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 asserted 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 Sunol 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 Sutter’s Fort, passed through Santa Clara. The mysterious ere was shown to him, and he is 1 The notes on the history of the discovery of quicksilver in California are derived from the testi- mony in the case of The United States vs. Andreas Castillero, decided by the Supreme Court, December term, 1862. (Bluck’s 8. 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 quoting: About the latter part of November, oz first of December, 1845, I went into the mission of Santa Clara to dine with Padre Real, of the mission. Mr. Castillero was there. Our general conversation through dinner was about this mine and of experi- ments which Castillero had been trying to find out what the mineral was, He made aremark 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 fall of lighted coals. He took some of the powdered ore and threw it on the coals. After it got perfectly hot he took a tumbler of water and sprinkled it on the coals with his fingers. 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 with his finger and said it was quicksilver. He then said to-morrow he wouid 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 offered 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 caleulated to afford a demonstration of the presence of quicksilver without the use of reagents which were, perhaps, inaccessible to Castillero. By 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 sufliciently 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 as retorts. These insignificant reduction works have now grown to very imposing dimensions, but the o quantity 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 d?scovered 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 1874 and 1875 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 characteristies 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 quicksilver on the Pacifie Slope, in flasks of 764 pounds avoirdupois. | | | | | | ! | | | . ; ‘ ‘Ss ae 5 = 3 a. 5 eis oe ; =. Ae 2 a4 2 s + as Years. ae (ee en aa ‘a a eae |e ates a a i) ie = s uD o ez S = E & s =A a $ = as 5 S © © Ey ] 5 a 5 ao S = A | 4 4 n o oO iv a” RB 4 7,723 )) 33 13 Be 27, 779 || | | 3 Ee 15,901 || 4-5 E Ee 2,984 || SE Palle og ot ey or 30,004 || 32 || *8 2: =o =68 = 29,142 || <3 | Ge a 27, 138 és! é 28 es 28,202 | (a5 8 2: ae OSs ar Ea 25,761 || =a e Me ES Ban AS ie ami || a8 | EF 2 7, 061 | Ee 5 oe a BAFADO) ieee Eel |e toeanman|| ness eee. He £8 39,671 || 22° POE eae aie =s coed te ot 32, 803 | 225 B50) (Pees se | © &5 | Bt o) - ArAROhlilii sisi li|'s I) 91d |Peese see es bac) InCieral ey Sa ATL OAs) iota a (eer 3545) ees 2 | 2e aes S550) 6525 |) 2,954 |\2 2.2. =e 25 24,461 | 11,493 | - 7,862 ].. ...---.|| eg ar Lm] 25,628 | 12, 180 SiGBGH |e oo | ae Se 16,898 | 10,315] 5,018] ........ less ekg = °o 14,423 | 9, 888 AVGL6) Were eens BS ere| 18,568; 8,180] 2,128] ......... ES 25 A 18,574 8,171 S046 en eee = 255 11,042 | 7, 735 Beei ra) ose Sees Nie ges | = o 5 4 9,084 6,911} 6,678 573 |J a 13,648 | 8, 432 7,513 5, 372 3, 342 | 533 TR7G eet Peed 20,549| 7,272} 9,183| 8,367] 7,381 | 1, 979 1877.......-..-..---.| 23,996 | 6,316] 9,399 10,993] 6, 241 5,856 | 1,060) 2,229) 1,463 1,317 TV/}s2e= Soe cette 15,852 | 5,138] 6,686| 9,465) 9,072] 4,963 TOTS Mee S049) | Eee ae: 1,534 1879is--The Gold Fields of St. Domingo, 1860, p. i119. ‘Encye. Brit., 9th ed., article Hayti. ‘A note communicated to the Mining and Scientifie Press, San Francisco, January 16, 1875. I re- gret not having been able to obtain a copy of this author’s work, Memoria sobre las minas de azogue de America, 1872. ®On the authority of Mr. Lorenzo Castro: Eneye. Brit., article Mexico. ®S, Ramirez: Riqueza minera de Mexico, p. 91. . 7 Repts. Phila. Internat. Exh. 1876 to Parliament, vol. 3, London, 1878, p. 389. MEXICAN LOCALITIES. 17 mercury were observed in the porphyry at considerable distances from the vein.’ At Durasno, between Tierra Nueva and San Luis de la Paz, in the State of Guanajuato, he inspected a cinnabar deposit forming a layer? 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.* This district forms the subject of a paper by Mr. Ramirez,‘ 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.6 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 Noéggerath, 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 Guadaleazar. 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 Calzones and extends to Chichindara. I have not been able to find these localities on the maps. 2T shall use this word to translate the term manto, 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 horizontality is certainly not a necessary attribute of mantos as the term is used by Spanish-American mining geologists. Rivero, in describing the deposits of Huaneayelica, re- peatedly uses the expression manto 6 capa, and capa is the torm employed for a stratum of sediment- ary rock. According to F. A. Moesta (Ueber das Vork. der Chlor-, Brom- und Todverbindungen, 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 mantos, and both he and the Mexican geologists seem to me 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, ’ Castillo, loc. cit. ‘Anales del ministerio de fomento, Mexico, vol. 3, 1877, p. 339. ' Comptes rendus Acad. 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." The chief ore is cinnabar, often hepatic and sometimes accompanied by the seleno-sulphide guadaleazarite, 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 deserip- 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.” 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.* 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 1T suppose this mineral to resulf from the reaction of iron sulphate, produced by the oxidation of pyrite, on the limestone walls. ?Anales del ministerio de fomeuto, Mexico, vol. 7, 1382, p. 605. *Velten and Lehmann: Sitzungsber, k, bayer. Akad. Wiss., vol, 2, Munich, 1867, p, 202, 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 sulphide is considered as due to the probable solubility of mercuric sulphide in calcium sulphide. Quartz and gypsum are the gangue minerals.’ 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 Guadaledzar; 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 Cruces, 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.”* Humboldt mentions cinnabar as occurring in the province of Antioquia, in the valley of the Santa Rosa, to the east of the river Cuaca, and also between the towns, Ibague and Carthago. ' Sitzungsber. k. bayer. Akad. Wiss., Munich, July 3, 1875, *? Noggerath, loe, 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." 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 Chonta,’ in the western Andes, close to the frontier of Ecuador. Mr. Bugdoll’ 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.* 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 1H. A. Webster: Encyce. Brit., article Ecuador. 2 The deposits mentioned in Peru being somewhat numerous, the following table may be convenient to readers. The latitudes are only approximate: Localities. Provinces. Latitude. te} ’ Ghontaece oo ee eee ee eee eee aa ae era aera PUNT a amio\a see eee cote niae sinew ra oe sane en eee 4 30 CajAMACOa ano wense vim nece stem iel-mome eo mem ale miein = -.| Cajamarca 7 EY Aaa sem o PICE CE Od SOOO SS SE DSO CEE ae se race ne Ses ibertadyesasseseace- ee sae ae 7 30 Huacrachuco TITER OTe Sapte scene soos 8 Garameens uses sotieseees ee ATIDRCHS lens senescence nee n> eee eee ee eee eee eee 9 San telesales eee eee AN CACHS ase acwseeeeea = 9 TUE Wess cee ogo co soos = JSaSnSOSe: Soochesdsesss= PATI CACHE! cana ae eb sme aU denier cera eee eee ee eet 9 20 (Oven NG Gl St (nee SoanSoecr ccconc cc once Seca bococe 328-46 AUN Se ie econo ie ootoeco ce tears cocccses: 10 40 VATU her BR sO Da Ecos ensbe ss SEOs SESS Soo cess t= S° Sos ASU Ye ee er eorSeB ona SSEcOr et co rosssctssce 11 40 PEI AN CA VOLO oem cee otete ernie ee eee ee ere Maancavelica’=) s.sqc- one fone ate eee ee eee 13 TN EG et Aasspeae otcoo arses seer Coo sancosseceosesesacee: MUS ooepsotnoassss A aee ne ena eS eae eee 14 40 4G. vom Rath: Natnurwiss. Studien, Bonn, 1879, p. 372. HUANCAVELICA. 21 doubt hot springs. He also mentions this ore at Guaraz (Huaraz) and near Santa. In the province of Ancachs' mereury occurs in only a few deposits, which appear to be of little value. It is always found as cinnabar in veins, and mixed with other sulphides, such as galena, blende, pyrite, and gray copper. One of the principal mines is the Santa Cruz, near Caraz. The large amount of carbonic anhydride evolved in this mine renders its ex- ploitation difficult. There is a quicksilver mine in the great silver-mining district of Cerro de Pasco, atCuipan. The rocks of this region include granite and trachytie lavas, as well as more or less metamorphosed sedimentary beds.’ In the mineral district of Yauli, 75 miles northeast of Lima, close to the Punabamba ranch, in a valley of the Andes, hot sulphur springs reach the surface and deposit considerable quantities of sulphur. Above these springs are quartz veins carrying seams and pockets of cinnabar and pyrite. The inclosing rocks are schists and sandstones.’ For over two hundred years the district of Huancavelica (sometimes written Guancavelica) yielded almost as much, possibly quite as much, metal as the district of Almaden, and the recorded total product of Huan- cavelica considerably exceeds that of California. The district of Huanca- velica lies on the eastern slope of the western range of the Cordilleras. The rocks, according to Mr. Crosnier,* are of Jurassic age and are elevated to a nearly vertical position, but have a westerly dip. They strike north and south. The sedimentary rocks are the same throughout the district, and consist of argillaceous schists, conglomerates, sandstone, and limestone, alternating in thick beds. There are also, according to Mr. Rivero,’ por- phyries and trachytie lavas in the district, and granite is exposed at least at one locality. All traces of voleanic action have not disappeared from this 'Explotacion y beneficio de los minerales de Ancachs, Prof. M. du Chatenet: Anales constr. civ. y minas Peru, vol. 3, 1883, p. 3. 2 Alijandro Babinski, State engineer: Informe sobre el Cerro de Pasco, 1876. ®>Bugdoll, loc. cit.; Mineral de Yauli, por L. Pfliicker y Rico: Anales constr. civ. y minas Peru, vol. 3, 1883, p. 62. +Annales des mines, Paris, 5th series, vol. 2, 1852, p. 37. 5Memoria sobre el rico mineral de azogue de Huancavelica, por Mariano Eduardo de Rivero, Lima, 1848. 22 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. region. In the environs of the town are hot springs still depositing sinter, and so abundant is this material that the town is built of it. The most famous mine is the Santa Barbara, close to the town of Huancavelica, but there are over forty points at which cinnabar occurs, the most remote being 18 leagues (20 to a degree) from the Santa Barbara, and sixteen of them within 2 leagues. The department of Huancavelica contains silver, copper, lead, iron, and coal, as well as quicksilver. The deposit of Santa Barbara consists of impregnations of cinnabar, mainly in sandstone. Some observers have pronounced it a vein, but Mr. Rivero denies that this name is applicable and considers it a layer or bed running parallel with the beds of limestone, sandstone, and conglomerate. Humboldt points out that cinnabar occurs close to Huancavelica in two very different ways, in part in true veins (filons) and in part in strata (couches). In the Santa Barbara it occurs chiefly as impregnations in portions of the sandstone bed, though much of the sandstone is barren; but he states that in portions of the deposit the cinnabar forms stringers, which are sometimes reticulated, forming a true stockwork or irregular reticulated mass. Ac- cording to Crosnier profound disturbance of the rocks preceded the deposi-- tion of ore, and the deposit appears to me therefore to be a tabular impreg- nation intimately related to a fissure system. The difference between such a deposit and a bed vein does not seem great or important. Besides pyrite the mine carries much mispickel and realgar, differing in this respect from the other great cinnabar deposits of the world, though similar associations in smaller deposits are frequent. According to Humboldt the arsenic is found almost exclusively in the lower levels. He also mentions galena among the metallic minerals. Calcite and barite are the gangue minerals. The Santa Barbara was discovered in 1566 by Enrique Garcés, but it had long been known to the Indians, who called cinnabar Ilimpi and used it to paint their bodies. According to Mr. Rivero no historian has mentioned that they obtained quicksilver by the distillation of cinnabar. He states, however, that in the immediate neighborhood of the Santa Barbara there are remains of ancient, very small, retort-shaped furnaces in which the sub- jects of the Peruvian Incas reduced cinnabar. In this connection it is interesting to note that in the northern part of Chili, according to Mr. V. . SOUTH AMERICAN LOCALITIES. 23 Perez-Rosales,' the Indians of the present day extract quicksilver from cin- nabar in small, rudely made, earthen retorts (cornues en terre) and supply the demand of the gold mines of the region. Has this industry survived among the natives from the time of the Incas? It might also be asked what connection, if any, existed between the primitive furnaces of the Indians and the aludels of the Bustamente furnace which was invented at Huanea- velica in 1633 by Lope Saavedra Barba, a physician and prospector. Native quicksilver is found in the pores of a trachyte at Ayaviri, de- partment of Puno,’ and this is the most southerly locality in Peru of which I have notes. Bolivia—It is stated that cinnabar is among the ores of Bolivia and that quicksilver is frequently found associated with silver ores.* criti Mr. Crosnier, in discussing the deposits of Chili and Peru (loc. cit.), remarks that deposits of mercury appear to occur indifferently in stratified rocks and in granite. The Punita mine, in Chili, is in the latter. According to Mr. Rosales (loc. cit.) cinnabar occurs in the northern prov- inces, especially near Andacollo, in the province of Coquimbo. Near the town of Chili* cinnabar is found in dendritic forms, inclosed in quartz. Amalgams are well known to be frequent in the Chilian precious metal mines, especially at Arqueras. The Argentine Republi.— It has been asserted that traces of mercury have been found in the sandstones at La Cruz and at Santo Tomé. Professor Stelzner’ regards this occurrence as extremely problematical. These local- ities lie in the northeastern part of the republic. The northwestern corner of the country, adjoining portions of Peru and Chili known to contain mer- curial ores, does not appear to have been explored to any considerable extent. Brazil— There is no doubt that quicksilver occurs in southern Brazil, but the information concerning it is very indefinite and probably in part erroneous. In 1865 Dr. Bosquet, a resident of Paranagua, stated that at ‘Essai sur le Chili, 1857, p. 166. 2G. vom Rath, loc. cit. In view of the investigations of later years on the supposed trachytes of the Pacific Slope, it is not improbable that the two mercurial lavas of Peru are really andesites. 8J. A. Phillips: Ore Deposits, p. 620; Keith Johnston: Encye. Brit., article Bolivia. ‘Noggerath, loc. cit. I cannot find such a town on the maps. 5Geol. und Pal. Arg. Rep., 1885, p. 249. 24 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ; one of the extremities of the city a deposit of mercury existed so abundant that in the rainy season it flowed from a talus on the borders of the sea.! Mr. G. C. Broadhead states that mercury is found in rich quantities in the province of Parana, and is also found in Santa Catherina and, in the metallic state, in Sao Paulo.? In 1886 Mr. J. C. Gomes, of the Brazilian legation at Washington, wrote: ‘Mercury has been discovered at the Capao d’Anta, in the province of Parana, in quantities that will permit competition with mines of Europe, Peru, and California”*® Prof. Orville Derby, of whom I made inquiry, writes me that the only authoritative reference known to him is by W. L. von Eschwege. Cinnabar, according to this geolo- gist, occurs sparingly in rounded grains in gold sands in the bed of a stream flowing from the itacolumite mountain of Cachoeira, near Ouro Preto (formerly Villa Rica). It is not known that this locality has been re- examined. Professor Derby has visited two localities at which it is said that native mercury was found, but could detect none and is inclined to suspect an artificial origin.® He is of the opinion that the Capao d’Anta locality requires further investigation. The neighboring region is one of undisturbed Devonian shales and sandstones. The occurrence was reported by Mr. Keller, who visited it in 1864 or 1865, to be native quicksilver found in loose earth in a gully, and, so far as Professor Derby knows, only a few ounces have been collected as a curiosity. ICELAND. The Great Geyser—D uring his well-known investigation of the Great Gey- ser, Mr. Des Cloizeaux found metallic mercury and mercuric sulphide in the geyserite of which the basin of that remarkable spring is composed. At the time of this examination similar occurrences elsewhere were un- known or had been very imperfectly studied, and the probability that the presence of the metal was due to artificial transportation seemed so great ‘Bull. Soe. géographie, Paris, 5th series, vol. 9, 1865, p. 528. * Rept. Phila. Internat. Exh. 1876 to Parliament, vol. 3, London, 1878, p. 494. *Commercial and Emigrational Guide to Brazil, Compiled and Translated from Official Pablica- tions, Washington, 1886. ‘4 Beitriige zur Gebirgskunde Brasiliens, 1832, p. 283. °The localities are the island of Itaparica, in front of the city of Bahia, and the fagenda de Bon Successo, on the Rio das Vellias, mentioned by R. F. Burton (The Highlands of Brazil, vol. 2, 1869, p. 69). THE GREAT GEYSER. 25 as to deter Mr. Des Cloizeaux from mentioning the discovery in his memoir on the Great Geyser.’ He collected numerous specimens, however, some of which he was kind enough to show me, and noted the conditions in detail. During the last forty years quicksilver and its sulphides have re- peatedly been discovered in close relations to thermal springs, and it no longer seems intrinsically improbable that this occurrence was produced by deposition from natural solutions. Indeed, it has repeatedly been referred to in the later literature, though not by its discoverer, as if it were beyond question a natural deposit. The basin of the Great Geyser is about eighteen meters in diameter, and the point at which the quicksilver was found is within the rim exactly due east, magnetic, from the vent. Traces of the metal were detected over an area of about one square meter, and Mr. Des Cloizeaux roughly esti- mates the entire quantity of mercury which he collected at about half a pound. It occurred at depths from the surface of the sinter varying from one or two millimeters to about four centimeters. The specimens which I saw seem to show that the mercury was originally deposited in the me- tallic state, for liquid globules of the metal about two millimeters or less in diameter are often partially enveloped in crusts of black sulphide, mani- festly produced by the action of soluble sulphides on the inclosed metallic drops. Portions of the sinter, at some distance from visible globules of quicksilver, were stained black by mercuric sulphide, and at some points small quantities of the red sulphide made their appearance. The fact that cinnabar accompanies this quicksilver shows that the water of the geyser is capable of dissolving traces of mercuric sulphide; for, had not this been the case, only metacinnabarite could have resulted from the attack of metallic mercury by soluble sulphides. The investigations described in Chapter XV of this memoir also show that mercuric sulphide is soluble to a considerable extent in waters of a composition similar to that of this great spring. Such solubility is evidently a necessary condition of the hypothesis that the mercury was deposited from the water. On the other hand, there are circumstances connected with the occur- rence which seem to me to point somewhat strongly to an artificial origin. 1 Annales de chimie, Paris, vol. 19, 1847, p. 444. The information given in the text was verbally communicated to me by Mr. Des Cloizeaux. 26 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Judging from the specimens, it would appear, as already mentioned, that nearly or quite all of the quicksilver was originally deposited in the metallic state and that the sulphide accompanying it is of secondary origin. Now, though more or less native quicksilver often accompanies deposits of cinna- bar, the metallic mercury usually forms but a small proportion of the entire ore. To this rule there are some exceptions. At the Rattlesnake mine, in California, for example, a large part of the quicksilver was native, but here, and at other points in the same State at which native quicksilver was abun- dant, it was also accompanied by unusual quantities of bituminous oils, which were probably not without effect upon the form in which the metal was deposited. Near Montpellier, France, also, quicksilver has been found in some quantity, so far as I know unaccompanied by cinnabar. But the depo- sition of quicksilver, almost exclusively in the metallic state, from waters such as that of the Great Geyser, containing soluble sulphides and little or no or- ganic matter, is very hard to understand. It is also very difficult to account for the distribution of the metal on the supposition that it was brought to the surface in solution by the heated waters. The basin of the Great Geyser is extremely symmetrical; in other words, the deposition of mineral matter takes place with great uniformity on all sides of the vent. Now, although the quantity of quicksilver found was by no means inconsiderable at a single spot, it was detected nowhere else in the basin. It seems highly improbable that the metal should have been deposited from the water without any approach to symmetry of distribution. In the opinion of Mr. . Des Cloizeaux, it is not difficult to imagine circumstances under which a barometer might have been broken at the point where the mercury was found. The water sinks periodically into the vent, leaving the point in question bare, and returns again with a rush. An observer, taking the op- portunity to advance as close to the vent as possible, would have to fly for his life as the water returned, and might well drop his instruments. Professor Bunsen, who, as is well known, was engaged in investigating the geysers at the same time with Mr. Des Cloizeaux, also examined this occurrence of quicksilver, and has informed me that in his opinion it was certainly the result of an accident and was not a natural deposit. SPANISH LOCALITIES. oT EUROPE. Northwestern Europe. —Amalgams have been found at Kongsberg, in Nor- way,’ and at Sala, in Sweden,’ but no cinnabar has been discovered in Scandinavia, so far as I am aware. In the Scotch highlands, Black* re- ported an ore containing lead, copper, and a little silver, which, on distilla- tion, yielded some mercury. Possibly this may have been a tetrahedrite. According to Prof. R. Jameson, a quantity of quicksilver was found in a peat moss on the Scotch island of Isla about the beginning of this century. Some further search was made with no result! I should regard such an occurrence as almost certainly due to human agency. Portugal— A quicksilver mine is said to have existed in the latter part of the last century in gravels. The locality seems to be at Conna, on the Tagus, not far from Lisbon.° Spain— Near Mieres,° to the south of Oviedo, in Astunia, cinnabar deposits, which had been worked long ago, and probably by the Romans, were rediscovered soon after 1840. The country rock in this district is composed of carboniferous sandstones and schists. The crest of a range of hills is formed of a breccia, bounded on both sides by broken and con- torted beds of sandstone and schist, and composed of fragments of these rocks. In this breccia, or belt of extreme disturbance, occur cinnabar, pyrite, mispickel, and realgar. The ore is thus similar to that of Huan- cavelica. The cinnabar fills cracks and interstitial cavities and sometimes appears as impregnations Some streaks of ore are four to six inches in width. My authority speaks of no gangue mineral, but mentions a deposit of ferrous carbonate in one portion of the belt with the cinnabar, and, so far as gangue minerals are present, they are perhaps carbonates. The ore-bearing belt is forty-five to sixty-five feet wide and about four miles in length. It seems manifest, as Mr. Klemm concludes, that these deposits ‘Reports of the American Commissioners on the Paris Exposition of 1878, Mining Industries, by J. D. Hague, vol. 4, p. 270. ~ A. Noggerath, loc. cit. 3Néggerath, loc. cit., probably Joseph Black, who wrote various treatises towards the close of tho last century. 4 Mineralogical Travels etc., vol. 1, 1813, p. 153. 5V. d’Aoust, Comptes rendus Acad. sci., Paris, vol. 83, 1876, p. 289, and Noggerath, loc. cit. 6J. G. Klemm: Berg- und hiittenm. Zeitung, vol. 26, 1867, p. 13. 28 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. are more recent than the shattering of the mass in which they occur. At Santander, in the same province, cinnabar forms pockets in the lead and zinc ores.! Casiano de Prado mentions the occurrence of cinnabar and coal together from this province, the coal being unaltered. The mines of Almaden are not only the greatest quicksilver mines in the world, but have yielded a product exceeded in value by very few mines of any kind? The name given by the Moors (al maden, the mine) was therefore not inappropriate. Cinnabar from Spain is frequently mentioned by the ancient writers, and the indications are that it came from this locality. The accounts reach back to 415 B. C., when an Athenian, Callias by name, is said to have invented and made known a method of separating cinnabar from earthy matter and to have acquired a fortune by mining in Spain. Pliny describes the locality under the name of Sisapo in such a way as to leave no doubt that the mining district of Almaden is meant. A few tons of cinnabar were extracted yearly by the Romans for use as pigment. The mines were certainly worked by the Moors, but no details are now extant. Work on a considerable scale, so far as is known, was first initiated by the German bankers, the brothers Fugger, to whom the mines were farmed in 1525 and who retained control till 1645. The demand for quicksilver did not in fact reach large proportions until the discovery of the process of extracting silver from its ores with the help of mercury by Bartolomé de Médina, a Mexican miner, in 1557. Work seems to have been prosecuted from the earliest times on portions of the deposits which are still being ex- ploited. Various other deposits within a distance of ten miles have been 1G. Dewalque: Revue de géologie pour les années 1864 et 1865, vol. 4, Paris, 1866, p. 94. 2The principal authority on the geology of the Almaden mine is Casiano de Prado, Bull. Soc. géologique France, 2d series, vol. 12, 1855. The paleontological portion of this memoir is by Messrs. de — Verneuil and Barrande. All subsequent writers owe much to this important work. Valuable pa- pers have also been published by the following geologists and engineers: Bernaldez and Figueroa (Memoria sobre las minas de Almaden y Almadenejos, Madrid); A. Noggerath (Zeitschr. fiir Berg-, Hiitten- und Salinenwesen im preuss. Staate, vol. 10, 1862, p. 361); José de Monasterio y Correa (Rev. uniy. mines, vol. 29, 1871, p. 1); H. Kuss (Annales des mines, Paris, vol. 13, 1878, p. 39); and Caron (Zeitschr. fiir Berg-, Hiitten- und Salinenwesen im preuss. Staate, vol. 28, 1880, p. 126), More general is M. D. de Cortizar’s Resena fisico-geologica de la provincia de Ciudad Real. , Prof. R. Helmhacker has investigated the diabase and piedra frailesea of Almaden in Tschermaks mineralogische und petro- graphische Mittheilungen, 1877, and Prof. Salvador Calderon has studied the massive rocks of the dis- trict (Anales Soc. espan. hist. nat., vol. 13, 1884, p. 227). The account of Almaden given in the text was compiled before my visit to the spot, and I have added to it only one or two observations which seemed necessary to obviate misunderstandings. My own results will appear separately. ALMADEN, 29 discovered from time to time, but are said now to be exhausted or abandoned for other reasons. The prevailing rocks of the Almaden district are schists, quartzites, and sandstones, together with small quantities of limestone, all of Silurian and Devonian age. Intimately associated with the deposits, though seldom in direct contact with the ores, is a rock called piedra frailesca. According to de Prado this is a metamorphosed breccia, consisting of grains of quartz, calcium carbonate, dolomite, and fragments of schist cemented by dolomitic calcite. It occurs in lenticular masses intercalated in the schists and has been found to contain Silurian fossils. Messrs. Helmhacker and Calderon regard the rock as a diabase tufa. Cracks in this rock sometimes carry cinnabar, the deposition of which is therefore later than the brecciation. The district lies upon the northern flank of the Sierra Morena. In this range are extensive areas of granite, and a rock also called granite crops out at various points not many miles to the north of the mines. Di- abase, or melaphyre, has broken through the sedimentary rocks and oceu- pies considerable areas near the mine, and a small quantity of porphyry, regarded as trachytic by de Prado, but as Pre-Tertiary by more recent Span- ish geologists, exists some six miles northeast of Almaden. The sediment- ary rocks are nearly vertical and are said to be little disturbed by the diabase eruptions, which have naturally reached the surface along the planes of bedding. The strata carry enough fossils for a satisfactory de- termination of the age of the rocks as a whole, but the same beds seem to reappear more than once in the compressed folds, and it is often difficult to decide to which of the periods a particular stratum belongs. The Almaden district contains many deposits of cinnabar scattered over an area of about ten miles by six, but neither these nor the ranges of hills exactly follow the strike of the strata, which is very closely east and west. There seems to be some tendency, however, both with the deposits and the ranges, to arrangement in the same direction. The chief ore is of course cinnabar, accompanied by relatively small quantities of metallic mercury. Pyrite occurs in small quantities, and Caron detected chalcopyrite. Gangue minerals have been said to be al- most entirely wanting, but Noggerath detected a little heavy spar with the 30 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ore, and spots of bituminous matter are sometimes found. I found quartz gangue abundant both in the reserves and in the newer exposures. The deposits of the Almaden mine consist of three tabular masses of _ ore, nearly 600 feet long and from 12 to 25 feet in thickness. They stand almost vertically and nearly coincide in position with the surfaces of strat- ification. The southernmost body is called San Pedro y San Diego; then come the San Francisco and, still farther to the north, the San Nicolas. The first of the three consists of a stratum of sandstone (or quartzite, as it is called by some authors) impregnated to a large extent with cinnabar. ‘The impregnation differs in degree and is sometimes so complete that de Prado infers a partial replacement of the material of the rock by the metallic sul- phide. Most later writers have accepted de Prado’s view, but I could find no evidence to sustain it. In the two more northerly bodies the deposits consist of quartzite intersected by stringers and seams of cinnabar. The seams are sometimes parallel to one another and sometimes intersect the rock in every direction. Occasionally portions of the quartzite appear to be impregnated with cinnabar. The walls of the deposits are formed by quartzite and slate. When quartzite is the wall rock the ore dies out into it gradually, but scarcely a trace is to be found in the slate. Diabase in a highly decomposed condition is said to cut off the-San Nicolas and the San Francisco to the east. The ore does not always follow a single stratum, but, according to Kuss, sometimes passes abruptly from one stratum to another. Slicken- sides are noted in the schists by Caron, who also mentions small faults in the San Nicolas, which did not reappear in the San Francisco. There has been much difference of opinion as to the classification of these deposits. Early authors regarded them as veins; de Prado, who con- sidered that the ore was introduced from below after the formation of the beds, regarded the deposits as ore-bearing strata, but not as veins. Nodg- gerath assents to this opinion, pointing out that many phenomena common in veins are not found here. Caron calls them impregnations and denies that they are veins or beds. Kuss says: ‘So soon as one admits, with Mr. de Prado, that the mercury is derived from the earth’s interior, so soon as one recognizes that the deposits of Almaden form relatively narrow belts, SPANISH LOCALITIES. 31 following a single direction and having a determinate dip, we do not see how one can refuse them the name of veins.” For my part Lam not aware that any definition of vein has been proposed which would exclude the San Francisco and the San Nicolas as they are described, nor can I see how a definition could be given which would exclude these bodies without also excluding the greater portion of known veins. The San Pedro y San Diego would also seem from the descriptions to be a vein-like impregnation, differ- ing from the others chiefly in the size of the interstitial cavities, which, for the most part, the cinnabar has filled. It is a very remarkable fact that the Almaden mine appears to grow richer as the depth increases. No other known quicksilver deposit exhibits this valuable peculiarity excepting the Idria. It is also interesting to note that the other deposits of the Almaden district have given out in depth, though they occupied a similar position in the same rocks. The relations of cinnabar deposition to depth are thus evidently determined by purely local causes, and not by any general principle governing precipitation. Hence it is quite possible that deposits which grow stronger as distance from the surface increases may be found in any quicksilver district | Monasterio and Kuss believe the deposition of ore and the eruption of the diabase to be closely related. The province of Granada also contains quicksilver along the southern base of the Sierra Nevada. That range is composed of micaceous and chloritic schists and serpentine. The central mass contains little ore of any kind, but gold, lead, copper, zine, cobalt, and nickel ores are found along its edges. The quicksilver belt has been traced from Torbiscon, in Granada, to Purchena, in Almeria, and runs on a somewhat more northerly course than the Sierra. This strip of country contains numerous veins of cinnabar in talcose schists of Triassic age. The mercurial ore is accom- panied by gray copper, sulphides of nickel and cobalt, and oxides of iron. The veins are small and irregular. In the soft rocks there is a tendency to the diffusion of ore.t Mr. A. Heckmanns, a mining engineer of large experience in the mineral districts of Spain and Algeria, informs me that a distinct vein ’Guillemin-Tarayre, Comptes rendus Acad, sci., Paris, vol, 100, 1885, 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 6 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 Néggerath, 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.’ A mine is said to have been worked recently at Pruniéres, in the department of Isétre, somewhat over twenty miles from Grenoble. This statement, however, is erroneous. Mr. H. 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: Géol. appl., vol. 2, p. 130, FRENCH 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 Chalanclies, in the same department, it is found with sulphides of lead and zine in veins, in- closed by crystalline schists which contain traces of platinum. At Alle- mond, also in Istre, 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 Isére, lead, silver, and gold; in Hérault and Aveyron, tetrahedrite and galena.’ 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 ean- ton of Belgodére.” The Balagna is a district lying east of Calvi, on the north coast of Corsica, and its port is Ile 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 yeins, and arsenic has been detected. Mr. Hollande states that the fissures have been filled through the action of hot springs? ttaly— 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 whicli lies the Idria mine. ‘Burat: Géol. appl., vol. 2. 2Noggerath, loc. cit. °D. Hollande: Bull. Soe géologique France, 1575-1876, vol. 4, Paris, 1876, p. 31. MON 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.! 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 seem 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 eround-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 known 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 depositien 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 oceurrence of native quicksilver in contact with graphitic rock (and, so far as reported, there only) is suggestive of reduction. The copper depos- ITALIAN LOCALITIES. 30 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 L Traces of cinnabar are found in Lombardy in quartzite, but the quantity is nowhere considerable." ; 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 guadaleazarite, 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. ; Noéggerath 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 Geognosie und Schilderung der yulkanischen Erscheinungen, Berlin, 1838, 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 voleanie products,! 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 voleanic rocks, and cinnabar and stib- nite have frequently been discovered together. Prof. kK. de Chancourtois, in his lectures at the Ecole 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.” Cinnabar as a product of voleanic 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. ZEtna. 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* 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, de chimie, d’histoire naturelle et des arts, Jean Claude Lamétherie, Roi it 1794, p. 102. 2 Rolland: Bull. Soc. minéralogique, vol. 1, 1878, p. 99. 3 Archiv fiir Mineral., Karsten, vol. 22, 1548. 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' twice mentions among the ores Quecksilber-Mohr, though without any remark. This name is the German equivalent of dthiops 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 Lissnitz, 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 'Archiy fiir Mineral., Karsten, pp. 430, 463. 38 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 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—The 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 Survey, examined and mapped the country surrounding the mines in 1856. In 1867 he took charge of the mines, and in 1874 published a memoir on the geology of the deposits and of the surrounding region.’ 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 ! Jahrbuch k. k. geol. Reichsanstalt, Wien, vol. 24, 1874, p. 425. “Das k. k. Quecksilberwerk zu 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 astratum. 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 mereury. 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 hepatie cinnabar. In one region a small quantity of fluor-spar has been detected with cinnabar and dolomite. Mr. Lipold regarded the asso- ciation 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- thia, 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. At in cracks in the schists at right angles to the bedding.' In specimens which I have examined cale-spar also is present The reader may be reminded that at Mieres, also, bodies of iron ore are found with cinnabar. Heagary— Though mercurial tetrahedrite 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.’ 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.* Ore has been found at six points near Mt. Avala. hese 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 millerite, finely disseminated, accompany the cinnabar, and in a single locality galena also occurs. The gangue 1Von Cotta: Erzlagerstiitten, part 2, p. 204. *Tbid., part 2, p.269. The average annual product of quicksilver in Hungary from 1864 to 1883, twenty years, is said to have been 26,65 metric tons, or 772 flasks, Spanish standard (Mineral Resources U. S. 1885, p. 293). 3 Zeitschr. fiir Berg-, Hiitten- und Salinenwesen im preuss. Staate, vol, 33. 42 QUICKSILVER DEPOSITS OF THE 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. Ina 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. Tf 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! 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 Seutari and about four miles from the river Drin. He also reports occurrences at Crescevo, in Bosnia. There is a town Kreshevo, perhaps equivalent to Crescevo, near Serajevo, in Bosnia. Mr. A. Conrad?’ 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- und hiittenm. Zeitung, vol. 32, 1873, p. 109, * Revue de géol., vol. 5, 1865-66, p. 115. LOCALITIES IN EUROPE AND AFRICA. 43 Mr. Fischbach 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 T'schermak galena is intimately mingled with the cinnabar.' 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 Arzrunt informs me. ‘There are ancient superficial mine workings on the metalliferous beds.” AFRICA. 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-taleose schists. In his opinion the metalliferous emanations were derived from the latter rock. This mine was patented in 1861 and abandoned in 1876. He also mentions a very regular mercuriferous vein at Taghit, in the valley of the Oued-Abdi. It occurs in the lower Cretaceous.’ 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 3$ per cent. The quicksilver is not recovered at present. 'Tschermaks mineral. Mittheil., vol. 7, 1885, p. 93. 2M. Hiriakoff: Geol. Foreningens Stockholm Férhandl., vol. 8, No. 6, 1886, * Texte explicatif de la carte géologique de Constantine, pp. 59 and 63, Also, Notice géol. et min., Dép. de Constantine, Exp. uniy. de Paris, 1878, pp. 22 and 23. 44 QUICKSILVER DEPOSITS OF 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.' ASIA. Southwestern Asia — Near Smyrna Mr. Fischbach (loc. cit.) found a rich vein of cinnabar accompanied sy 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.” Cinnabar occurs with gold in alluvial washings. Furthermore, cinnabar and native quicksilver are found in considerable 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 bea solfataric one, not dissimilar to those of California. In Afghanistan Captain Hutton* 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.’ 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.* 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.’ 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 'J, M. Safford: Rept Phila. Internat. Exh. 1876 to Parliament, vol. 3, London, 1878, p. 481. ? Jahrbuch k. k. geol. Reichsanstalt, Wien, vol. 31, 1881, p. 183. 3V. Ball: Economic Geology of India, p. 170. 4N. yon Kokscharow: Materialen zur Mineral. Russlands, vol. 6, 1870, p. 259. °C. Zincken: Berg- und hiittenm. Zeitung, vol. 39, 1880, p. 360. cos THE SIBERIAN MINE. 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 1797 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.! 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.’ 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, avery 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.? 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 Geologie, der Mineralreichthiimer und des Bergbaues von Transbaikalien, St. Petersburg, 1867. 2Dr. Henry Lansdell (Through Siberia, 1882) could learn of no quicksilver mine at Nertschinsk and cited other authorities to the same effect. ° 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, and believes that it represents an actual oceur- rence. He was not shown any cinnabar. china—Mr. R. Pumpelly discovered in Chinese literature records of 1 the occurrence of quicksilver in ten of the eighteen provinces.’ The only province certainly known to contain important deposits is Kwei-Chau. Of this locality Baron F. von Richthofen writes as follows:* 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 1334 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, ard 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-Fu). The mines there were scattered over an area of 10 Ji diameter [about 3$ miles] * * * Iwas 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 acccunt 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 eeologist of the first rank and o 5 oO 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, ' Geological Researches in China ete. The provinces are Shen-Si, Kan-Su, Shan-Tung, Ngan-Hwui, Sze-Chuen, Hu-Nan, Kwei-Chau, Cheh-Kiang, Kwang-Tung, Kwang-Si. °Letter VII to the Shanghai Board of Trade, 1872, p. 8L. Prof. J. D. Whitney has been kind enough to furnish me with a copy of that portion of this rare publication bearing on the province of Kwei-Chau, CHINA AND JAPAN. 47 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 there. 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. Pumpelly (loc. cit.) ascertained from Chinese records that Corea contained cinnabar deposits. Mr. Ernest Oppert' 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.? He found the province of Hwang-Haido (equivalent to Hoang-Hai) princi- pally oceupied 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.’ It would be interesting to know whether this is a rhyolite ora solfatarically decomposed eruptive rock of a more basic type. A quicksilver mine has been worked near Ainoura, on the peninsula of Hirado, in Matstira 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.* ; British India—ITt is said that quicksilver mines formerly existed in Cey- lon, near Colombo, and that the Dutch exported quicksilver from them to Europe.’ In the Andaman Islands, also, it is said, quicksilver used to 1 Voyages to Corea, 1880, p. 171. _ 2 Sitzungsberichte der Berliner Akademie, vol. 36, 1886. 5J.G. H. Godfrey: Quart. Jour. Geol. Soc. London, vol. 34, 1878, p. 555. 4H. 8S. Munroe: Trans. Am. Inst. Min. Eng., vol. 5, 187677, p. 299, * J. F, Dickson; Encye, Brit., 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." In 1880 the value of the quicksilver produced in Sarawak was $66,300. Mr. 8. B. J. Skertchly, formerly of 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 erystal- line schists, but not in quantities sufficiently large to warrant mining oper- ations.’ Quicksilver is also reported from the island of Java at Samarang.* Spanish India— Unimportant quantities of quicksilver ores are reported to occur in the Philippine Islands.° Australia— Rey. 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- 1A, H. Everett: Notes on the Distribution of the Useful Minerals in Sarawak, not dated, but seemingly written in 1874. 2 Mining Journal, London, 1882, p. 415. This value corresponded, at the London prices for 1880, to about 2,000 flasks. 3R.D.M. Verbeek: Beschr. Sumatra’s Westkust, 1883, p. 552. 4D’Achiardi, loc. cit. © This note is derived at second hand from J, Roth: Geologische Beschattenbeit der Philippinen. ® Mines and Mineral Statistics of New-South Wales, etc., Sydney, 1875, p, 201. AUSTRALASIAN LOCALITIES. 49 nabar occurs on the Cudgegong in drift lumps and pebbles, and is probably 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,' but in 1876 the official reports pass it over in silence. In 1878 specimens of cinnabar and quicksilver were exhibited in Paris,” 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.’ 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.* Mr. Néggerath 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 oceur in Victoria,® 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 1866 it was known that quicksilver occurs a few miles southeast of Omapere Lake, near the Bay of Islands. In 1870 Mr. F. W. Hutton’ 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, 74 1 Annual Report of the Department of Mines, New South Wales, 1875, Sydney, 1876, p. 31. 2 Repts. of the U. S. Commissioners Paris Univ. Exp., 1&78, vol. 4, p. 246. 3D. de Cortiizar, loc. cit. 4R. Acton: Encye. Brit., 9th edition, article Australia 5 Geol. Survey Victoria, Rept. Prog., 1876, p. 280. 6 Prepared for the Victorian exhibition, 1872. 7 Trans. New Zeal. Institute, vol. 3, 1870, p. 252. 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. Hutton. Dr. J. Hector’ 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, silicious 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* 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—F yom the crystalline schists, presumably of Archean 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. Lithological 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, serpentincs, and crystalline schists, as well as in basic and acidie 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 ' Rept. Geol. Explorations, 1874-1876, p. 5. °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 the sketch-map (Pl. IT) 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- ver 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 Kamtschatka 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 the 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 Pacifie 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 Guadaleazar 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 — he 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 Huancayelica. 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; realear 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 zine 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 of the deposits —[xcept in the case of gravels, | know of no ease 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 occur, 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 upon 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 voleanic 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 eut the beds. Humboldt’s descrip tion of Huancavelica shows that similar conditions there prevail. At Val- 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 OF THE ORE. 5D 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—"he 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 Te 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. CHAPTER III. THE SEDIMENTARY ROCKS. General character —'T'he 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 idea of the unusual advantages afforded by this area it is necessary to anticipate some 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 lithological 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 recrystallization has 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 metamorphies, and this series extends far to the north and to the 56 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 reerystallization, 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' 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 this 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 By metasomatisin I understand and desire to express a change effected by the action of mineral solutions having au extraneous origin, but not necessarily or usually involving a total replacement of the material acted upon. 58 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Hypotheses.— Students of the extremely difficult subject of metamorphism have, no doubt, in some cases been tempted to put forward hypotheses, to account for the existence of crystalline rocks, which were warranted neither by detailed observation on the actual series of changes nor by any known chemical principles. It would be a great mistake to assume, however, thit careful observations on actual transformations are valueless unless they can be accounted for by known chemical relations. Even the structural formulas of many most important minerals are still in doubt; much more so is the complete theory of their formation; while recent researches, particu- larly those of Dr. Woleott Gibbs, demonstrate the extreme complexity of many inorganic chemical processes. Though there can thus be no question as to the existence of transformations in altering rock masses for which no adequate explanation can be offered, it is equally true that observed facts are frequently capable of two or more explanations and that the relations of mingled products are often susceptible of misinterpretation. In the present investigation great care has been taken to avoid errors; and sev- eral hypotheses as to relations, in support of which considerable evidence can be adduced, have not been admitted on the ground that the appear- ances might after all be deceptive. It is believed that by this means the errors have been reduced to a minimum and that the residual observations and inferences recorded in the following pages afford a solid foundation for future inquiry. The results also seem sufficiently definite to form an important aid in the study of more complex metamorphic areas in other parts of the world. That the conclusions reached are applicable to other portions of California is almost certain, for the metamorphosed rocks of the gold belt are in part of the same age as those of the Coast Ranges and appear to be strikingly similar in lithological character. That region is now under investigation by my party, and it is believed that further interesting results, for the same class of metamorphic rocks at least, will be obtained in the near future.! 'Ttis probably impossible for any one to free himself from the influence of preconceptions. It may not be superfluous, therefore, to state that in beginning the investigation of the quicksilver belt I entertained no opinions on the character of the crystalline and serpentinoid rocks. I was quite pre- pared to find the former either eruptive or unaltered crystalline sediments and I entertained no preju- dice against regarding serpentine either as an original deposit or as an altered olivine rock. I still regard it as not improbable that crystalline schists and serpentine are sometimes original precipitates FRAMING OF HYPOTHESES. 59 It is well known that eruptive as well as sedimentary rocks are subject to metamorphic action, and, since sedimentary rocks are not infrequently of nearly the same composition as eruptive masses, they should yield analo- gous results under similar circumstances. The study of metamorphies should therefore throw light on the transformations of eruptive masses, a study most intimately connected with mining geology. It will appear in the sequel, as it does from the published investigations of other geologists, how much caution should be exercised in deciding, from slides of altered eruptive rocks, what mineral constituents are secondary. It is certain that the neglect of such caution has more than once led lithologists into grave errors, and the facility with which it appears that new mineral combina- tions take place, under conditions perhaps not greatly different from those usually prevailing, strengthens the probability that deceptive appearances are even more common than has hitherto been suspected. UNMETAMORPHOSED SEDIMENTARY ROCKS. Macroscopical character of the 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 quick- silver belt where unaltered are mainly sandstones of Cretaceous and Ter- tiary age. (See Chapter V.) The sandstone of the Coast Ranges often occurs in practically unin- terrupted series of beds many thousands of feet in thickness Indeed, the observer can hardly fail to wonder under what mechanical conditions such vast accumulations of sand can have gathered. This problem, presented in many regions, though perhaps nowhere else on so large a scale, has never I believe received a satisfactory solution. From the Neocomian to the Mio- cene the predominant rock of this class is of medium grain and light color, usually yellowish where exposed, bluish at some depth from the surface. The Téjon rock, however, is, as a rule, much lighter in color than the oth- ers, and often almost white. Induration is much more frequent among the and do not doubt that highly olivinitic rocks may decompose to a mass substantially composed of serpentine. For the Coast Ranges of California and in part for the gold belt, however, careful study has led me to very different conclusions; but I do not hesitate to believe that every mineral has been formed somewhere in nature by every possible method Real peridotitic serpentine occurs in the gold belt and has been carefully compared with the serpentine of the Coast Ranges. 60 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. older sandstones, but is not unknown among the Miocene beds; and of course where induration exists the tawny color due to oxidation penetrates to a much smaller depth than in the rocks of looser texture. Deep brown, highly ferruginous sandstone is frequent in the form of nodules, as are sin- gle narrow beds, particularly in the rocks of the Chico-Téjon group, but it seldom or never occurs in large masses. The sandstones of the Knoxville (Neocomian) group are in great part metamorphosed, and they give rise to the series of rocks which will be discussed in the following pages. The unaltered Knoxville sandstones, on the other hand, lithologically considered, do not materially differ from those of subsequent periods. This fact is not a source of confusion in field work, however, for the portion of the Knox- ville sandstones which has entirely escaped alteration is small, and, so far as observed, these are associated with greatly disturbed and intensely met- amorphosed rocks of the same period in such a way as to leave no doubt as to their age when once it is established, as will be done in a succeeding chapter, that the great epoch of upheaval and of metamorphism in the Coast Ranges preceded the Chico and Wallala periods. There is more difficulty in distinguishing the somewhat altered rocks of later periods from similar sand- stones of the Knoxville group, but associated silicification and serpentiniza- tion appear to be confined to beds not younger than the Knoxville series. Among the unaltered rocks impure limestones play an extremely sub- ordinate but still important part, since they contain the best fossils of the Knoxville group. More widespread are shales (sometimes calcareous), which form a connecting link between the sandstones with a calcitic cement and the limestones. The shales and limestones together form but a small portion of the entire mass. Origin of the sandston—ITt is found that the unaltered or very slightly al- tered sandstones of all ages may be discussed together from a lithological point of view. The first point which suggests itself for consideration is the internal evidence of their origin which these rocks present. One of the more important generalizations resulting from the field study of the quick- silver belt is that granite probably underlies the entire area of the Coast Ranges. ‘This inference has received unexpectedly strong confirmation from the microscopical study of the sandstones, for the entire series is thus ARCOSE. 61 shown to be composed of granitic detritus, or, in other words, to be arcose. In many cases, indeed, it appears from structural considerations improb- able that the sands were immediately derived from granite and altogether probable that they were formed by the disintegration of earlier sand- stones. The microscope shows, however, that some of these rocks consist of grains of such angularity and sharpness as to lead inevitably to the con- clusion that they were directly derived from granites— indeed, from granites at no great distance from the point of deposition. As a rule the grains are worn and rounded like ordinary beach sand, and in such cases the micro- scope fails to show whether the material was immediately or indirectly de- rived from the original granite. But the arcose character is persistent in all these rocks, and this points to short transportation; for the admirable ex- periments and observations of Mr. Daubrée prove that the feldspathic con- stituents of granite are rapidly triturated and decomposed in running water. I cannot recall any description in geological literature of a mass of arcose so immense as that exposed in the Coast Ranges. All the characteristic components of granite reappear in the sandstones, often in proportions differing but little from those which prevail in the parent rock, and it is very rarely the case that the sandstones contain any clastic fragments or allothigenetic minerals not identified in the granites still exposed in the Coast Ranges. Chemical analysis is not calculated to exhibit the origin of the sandstones, for in the course of disintegration and transportation a certain amount of material must have been reduced to impalpable powder, decomposing agencies cannot have been altogether absent, and a certain amount of mechanical concentration must have taken place, although this last influence was reduced to a minimum by the close approach of orthoclase to the density of quartz. It is manifest that the chemical indifference and superior hardness of the quartz establish a ten- dency to greater acidity in the sandstones than in the granites. Microscopical character —The quartz of the fresh and of the slightly decom- posed sandstones is exactly similar to that of the granite and commonly contains abundant fluid inclusions, those of small size and regular form showing active bubbles. The feldspars are often present in about the same quantities as the quartz. The predominant species is orthoclase, with char- 62 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. acteristic cleavages, extinctions, and twinning. Oligoclase is the most abundant triclinic feldspar, but in a few cases angles of extinction between 20° and 30° on each side of the twinning plane indicate the presence of more basic species. Biotite is also a constituent frequent in many of the sandstones. When it occurs it is usually allothigenetic, and this is shown by its relation to the structure of the mass, the scales being distorted by the pressure of the unyielding grains of quartz and feldspar about it. Occa- sionally biotites appear to have been bruised edgewise and very finely di- vided clastic material has silted in between the contorted foils. The biotite when fresh is dirty brown in color and in no respect differs from that of the eranites. That a white mica, probably muscovite, forms in the sandstones epigenetically from biotite is certain. It is also found in such a way as to suggest that it is allothigenetic, but it is not impossible to explain these cases by epigenesis. While it is altogether probable on general principles that the muscovite of the granite is represented in the sandstone, the nature of the case precludes absolute certainty on this point. Muscovite is a very subordinate constituent of the granite. Hornblende, exactly like the granitic hornblende, is tolerably common in the sandstones, usually in very small grains. Titanite in rounded grains, minute zircons, and occasionally epidote have heen observed. A strongly refracting, proved by chemical tests to be rutile. Tourmaline in large, brown, in- monochroitic mineral was detected, which, after separation, was tensely dichroitic grains was also found in the same sandstone as the rutile. Small apatites, especially included in the clastic quartz grains, are not un- common in the sandstones. Some of the slides of granite in the collection show more apatite in the quartz grains than do any of the slides of sand- stone, but apatite is rather irregularly distributed in the granite and some thin sections of this rock contain extremely little of it. The only allothigenetic material not derivable from the granite which appears with any considerable frequency consists of occasional black scales, sparsely distributed in some localities, from the Knoxville group upwards. In many eases these scales seem referable to carbonaceous shale; in others they at least suggest plant remains, such as are found in the schists of the Knoxville series. CHARACTER OF METAMORPHISM. 63 Alteration of the sandstones—'Ihe sandstones have been changed, under the conditions which have prevailed in the Coast Ranges, by several distinct processes of varying interest and importance. They are, of course, sub- ject to the ordinary decompositions known as weathering. Here the ferro- magnesian silicates are in part converted into chlorite and in part also into a ferruginous cement; the feldspars become carious, while the quartz is nearly or quite unaffected. Much more interesting is the process of meta- somatic recrystallization, which is in some respects the inverse of weather- ing. In rocks which haye undergone this process the clastic grains are transformed into ferromagnesian silicates, feldspar, zoisite, apatite, ete. A third process is that of serpentinization. This sometimes occurs in sand- stones in which metasomatic recrystallization has either not taken place at all or only to an insignificant extent. The recrystallized rocks, however, are also subject to serpentinization, and from them the greater part of the serpentine of the Coast Ranges appears to have been produced. A fourth process is silicification, by which shales have been converted into phthanites and sandstones into quartzites. The serpentines and crystalline metamor- phies also yield to a similar process and are converted into a dark, opaline substance known in some of the quicksilver mines as quicksilver rock, but this seems to be a phenomenon attending the process of ore deposition rather than that of regional metamorphism. A further rather unimportant process manifests itself in many localities by the presence of numerous stringers of calcite or gypsum intersecting the rocks, particularly the sand- stones, in all directions. This process has affected many of the younger rocks, as well as those of the Neocomian. It is important to remark that some of these processes are inconsistent with one another. Evidently chloritization of the ferromagnesian silicates cannot go on simultaneously with the formation of ferromagnesian silicates by metasomatic recrystallization, and this process is equally inconsistent with serpentinization. So, too, since serpentine is subject to conversion to chalcedony, serpentinization and silicification must go on under different sets of conditions. Weathering of the sandstones. —'[he weathering of the sandstones can be very briefly disposed of. The chlorite which forms in this process from the 64 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ferromagnesian silicates appears to be identical with that which results from the similar minerals of the recrystallized rocks. The nature of this chlorite will necessarily be discussed in connection with these rocks. Ser- pentine has not been identified with certainty among the results of weath- ering in these sandstones. It is possible, however, that it forms a very subordinate product of this process. The decomposition of the feldspars calls for no special comment, excepting that there is no considerable quan- tity cf well marked kaolin. CONCRETIONS. Analysis of anexample-—Qne of the most interesting changes which take place in the sandstones is the formation of concretions. These are very common in the Chico-T¢jon and Miocene groups. That they really repre- sent changes of composition within the rock mass is certain, for they often develop into a symmetrical, spheroidal shape, without disturbance of the stratification, which the formation of concretions does not wholly obliterate. That these concretions could not gradually be built up during sedimenta- tion is certain. They are usually much harder than the surrounding rock, darker, and of a redder color. In a great majority of cases no nucleus can be found at the center. Under the microscope the chief peculiarity of these concretions was found to consist in a brown cement between the elastic fragments of granitic origin. This cement does not effervesce with acid and is so unusual in character as to call for investigation. A concretion from the Chico beds of New Idria (No. 53) was selected for examination. One sample of the pulverized rock was treated with cold, dilute chlorhydric acid (1:10) and the resulting solution analyzed. Another sample was digested with stronger acid (1:1), at first at ordinary tempera- tures and then for twenty-four hours on the water-bath. The solution formed was analyzed and the residue was treated with a hot solution of sodic carbonate to extract soluble silica. Special determinations were made of carbonic acid, ferric oxide, ete. The following table shows the percentages soluble in weak acid and in strong acid separately. CONCRETIONS IN SANDSTONES. i6ys) | Tirst Second sample. | sample. ossiat 1000) (H 0 lec ce tae e ne aurea ceaeee ses emeeeasisse= = | 0. 855 Carbonic anhydride, CO” BE 952! pesos ee SUP SG i se Sia ei doeinecenoa de aaoccoscsasnooosun onaeenaoeeons | 0. 362 0.177 PNOSPhOViG Cie OS en gee eeeiebheniaaeeiels =e eae stator ss nie 0. 034 0.085 Atom ina (Al? O82 aes pore cecesncas cece aa cieies aes ceeeccimens' | 0, 326 0.385 Rerrigioxid ay bars seeenct: a aeeea eaatceaes see asst se seen = | 0.607 0. 783 Man rANOnS/OXIOOy NLU Oksce ten simac anita scleielaal= a eielaaieei-etaiaiaio 0.195 0. 162 TM | CAO cease wes clacicen ves eae ose eee cere seinen ceases oct ee | 11. 152 0.139 PAT ss oTIGR iA MO) eee soot ancora anna Sem a oitaan alae eee Sst cia | 0,315 0. 162 SANE? OV ee) eee en ee ERE so! 0.122 De EE ie ONE 3 ai ccSec ey Jas SoU Ee Serna SoS eo eoeeed asec 7 0.119 Silica extracted by Na?CO* 2. 865 Regi Use esses ee Sere ele een ieee sec aebac als ea cincs | 72.110 Potal\percentage: y-~=- =. eo ee oe ee oem acme jcttttteeee 99. 956 When the atomic ratios of this analysis are calculated it appears that the protoxide bases found in the first sample are slightly in excess of the amount required to saturate the carbonic acid. All excess of these bases, as well as the alumina and the iron (which is wholly in the ferric state), must be combined with phosphoric and silicic acids. Assuming that the phosphorus is as usual combined as triphosphate of calcium, the remainder is a silicate or a mixture of silicates. The atomic ratio of the sum of these silicates is: royigeysan ical oh 0.22688 : 0.09385 : 0.22695 ors sae. si" Die eno. If the water is taken into account, as it apparently should be, the ratio becomes 2: 5: 2: 5, indicating some form of a hydrous subsilicate. The cementing material of the concretion then is an intimate mixture of calcium carbonate with a hydrous subsilicate and a small but not incon- siderable amount of phosphate. The subsilicate may probably be regarded as an iron compound in which a portion of the iron is replaced by alumina and protoxide bases. How such a cement can be formed within the body of a sandstone is evidently a question of great interest; and in its answer lies the secret of the class of concretions of which the specimen investi- gated is an example. Action of a nucleus.— Since it is manifestly impossible that these concretions should be built up during the deposition of the sand, they must be due to MON X1I——) 66 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. the action of some substance embedded in the rock. The spherical form which they tend to assume and to which they often closely approximate indicates that this substance either exists or once existed at the center, and this simple inference is confirmed by the fact that the concretions are often separable into spherical shells, indicating a change in composition related to the distance from the center. Such concretions are common, for exam- ple, in the Chico beds near Lower Lake. So far as my observation goes, the central substance has utterly disappeared in a great majority of cases. In three or four instances I have found fossils at the centers of these con- cretions, but I have broken open great numbers of them without finding any visible difference in the substance at the center and elsewhere. Such was the case in the specimen investigated, and chemical tests also failed to detect any foreign substance. Thus, while fossils are occasionally found both in California and elsewhere at the centers of concretions in sandstone, such cases are so rare that one would by no means be justified from obser- vation in ascribing the concretions to the action of organic matter, nor am I aware that it has ever been shown how organic matter could effect such a result. Nucleus possibly organic— The analysis given above appears to me capable of interpretation in a manner calculated to throw light on the nature of the central substance. The cement of the concretion contains one-fourth of 1 per cent. of phosphoric acid, most of which must have come from the cen- tral substance, for the cement of the sandstone away from concretions is almost pure calcite. Taking the size of the concretions into account this indicates the existence of much phosphorus in the central substance. The possibly organic nature of the substance in question is thus strongly sug- gested. But is there any way in which an organic substance could give rise to the formation of hydrous ferric silicate? I think there is. It is well known that during the decomposition of organic matter various acids are formed, and that among them the group of humus acids frequently occurs. ‘These acids, or some of them, dissolve magnetite, and in this way sands underlying vegetable soils are frequently bleached.’ & CONCRETIONS IN SANDSTONES. 67 Some of these acids also combine with silica to silico-azo-humic 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 operandi— It is clear that a fragment of undecomposed 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, ete. 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—T'he 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 components of the concretion. It thus appears to me nearly certain that the concretions are due to the action of decomposition-products arising from 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 humic 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 oceurrences 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: y 1 3 4 - a 2,2 2,. x aot ears =o = 1S) =F z (37°—3r+1). NODULES. 69 The surface of the sphere is, say, S=4 77 and The surface of the material exposed to the action of the fluid per unit of volume of the shell acted upon, or S/V, may readily be seen from this equation to diminish rapidly as the radius of the sphere increases.' For example, if the radius is unity, or just equal to the depth to which the solid is permeable, S/V=3; if r=2,8/V=1.7; if r=4,S/V=133, and if the radius is infinite or if the attacked surface is flat, S/ V=1. 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 the 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.’ If, therefore, any comparatively dense, irregular body is acted upon by solvent or decomposing solutions, the portions the radii of curvature ''The portion of the sphere which is not reached by the fluid is essentially a positive quantity, and 4 when + becomes less than unity, . a (r—1)° disappears from the value of S/V, which thus becomes equal to 3/7. This is a hyperbola, asymptotic to both axes, and S/V is infinite forr—0. At the point at which r=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. ? 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 case this function and S/V must vary directly, and that both of tlem, therefore, vary inverscly as the radius of curvature. 70 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 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 be more slowly decomposed or dissolved. There will thus be 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.— he 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 NODULES. 71 results will clearly be those discussed above. An angular mass of such a rock will yield to the decomposing agencies directly as S/V, 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, while tufaceous masses and porous rocks decompose with 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 will 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 sue- cessively on all points of its surface will 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 (i QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. mass must tend to a spherical form, provided that it is of uniform composi- tion. If the body is permeable to different depths in differer-t 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 s#em so strange as it otherwise might. CRYSTALLINE METAMORPHIC 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 serpentinization 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 erystal- 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 isnot 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 metasomatie 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 METAMORPHIC ROCKS. 73 (4) Phthanites or schistose rocks which have been subjected to a process of silicification. There is seldom any doubt about the macroscopical determination of the third and fourth of these groups; ina 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 rocks, 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 —W hen 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 glaucophane schist from New Idria there is a great abun- dance of fine, nearly uniaxial biotite. Muscovite. —The epigenetic formation of white mica from biotite and from feldspar has long been recognized. In the recrystallizing sandstones of the Coast Ranges white mica is rather rare as an indubitably allothigenetie 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 allothigenetice. 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 metamorphic 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 MINERALS. 75 undergoing the process of metasomatic recrystallization, and which thus form alink 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 augites make their appearance in 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 erystallographic outlines. The usual occurrence of gar- net in metamorphic rocks indicates an entirely similar process of agerega- 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 reerystallized rocks are divisible with some sharpness into hornblendic 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 be 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. 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 eases 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 uralite, but 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. Glaucophane.— This is a prominent component of the micaceous schists* 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; 0, violet; c, ultramarine blue. The absorp- 'For some curious evidence bearing on this point, see my Geology of the Comstock Lode and the Washoe District, Mon. U. S. Geol. Survey No. 3, p. 60. 2 According to Mr. H. G. Hanks, glaucophane was detected by Mr. Michel-Léyy, 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, 1823-84, p. 182.) COMPONENT MINERALS. rir tion isc> b> 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 usually 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 erystals, which suggest the possibility of epigenesis of glaucophane upon actinolite. Iam inclined to consider this suggestion misleading, however, - because fibration and sensible difference of orientation would almost inev- itably result from such a process. zoisitc— 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 recrystallized 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- eated. ‘This irregular development of faces in the vertical zone is charac- teristic of zoisite.? 1 Liidecke found the specifie gravity of glaucophane from Syra, 3,101 (Roth: Allg. und chem. Geol., p- 21). *Dana’s System of Mineralogy, p, 290, 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 hornblendie rocks, though a faint greenish yellow may sometimes be observed. In the glaucophane rocks the color is usually deeper, and the pleochroism is then distinct in thin section, c being yellowish green to light grass green and a and b 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, but 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. Fic. 1. Zvisite microlites, a, b, and c, from a glancophane rock, No. 31, Sulphur Ba.k. a@ and b are magnified 175 diameters; c, 106 diameters; d is from minute quartz veins in phibanite (No. 51, Mt. Diablo) and is magnified 185 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 be expected. No. 98, Sul- ZOISITER. 7 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: Wiater-at above L009 EO sos. ssscescecn ce oecec -ceeie- se one 5.25 Silcan SOs’ cesta eee cee: seen ee cae 2 Seey-eivee ee! esas 39. 80 Mitaniciacid yl Os acm at weiss che teh weno rec acceeaeoes Trace Al nmina; cA Oe: secs ese cele naceyes ce ensosooo.ecen cso danga6 22.72 HerricioxideyHetOr seo. cisreaseate sree Aeeaeicee eeaieae en tei ose 4, 85 Herronstoxido se Olea 2 tess tenes cess wee ceecee ee cchee sce 1.49 Mang amousioxid eyMin © Seetse cesses sol ams soecseeee ate cee 0. 26 IDG (CH O)c RacGoasucn BoSOco bans onecer Buen Sosa Beano snes Ges jbo Magnesia, MgO ...-.... 38 dedecndesssb cep adond we seen ease 3aae 3.89 SOB WIEHO) a60 dogo coe eneO Ger ans bend oAae an SNC ORO Iso aeeeEe 4,09 IPotassan Ke Oke tecciecaeae ysis sisae cise caoe oo aeicaeiceerneee 0.12 LUNES Seocco coscoonspe cub ocasaa con Gao cage soneeoos 100, 02 The atomic ratio H’: RY” : KR": 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 specimea 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 be 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 to3:4:9:12. 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 suff- 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: Doss;above L00S MeO cece serene ates een metaceine ice ote eee ere 1,119 Silica, “SiOSon.,- -eec oe eee eee seeeer eee eee ee ieces 39, 196 Phosphonic! acid p20 oe ae areata = aati eel tele lerettte rat Trace Mit AMI AST Ay MUeILS) spel O zs ere ool wlolerelatetate le alee eae en 1.169 TNribet ly (NEO oe Son oae Soos pISeo a cod HOoUe Endo abasescoscne 22.760 Meni ChOxXide: Mhe62 Os een eee ce mae ce eee eens atte te eters 6. 487 HeTLOUSIO 106 CO hee eee se eee ete ents eerie 1. 783 IMPORT INO) edccoe secooseody soce He coSbocescese cuss sone Trace Man ranonsOxi de, Mm Oe ectcrie ace ria clea arate aia tained ole 0. 090 Tame; CaO meee qwes-sieq ee PGS sees eee ee see 22. 023 Magnesia, MoO) 21ccicnieietenisl= mle wleieie se eee) ee eee = 1. 643 Shyer NGO) Soe556 Stes ascend Sone sooopsbenoso coe eos suecaces 3. 382 Tet ER NCO) soe sn come esicnhoac cose to esoscont coco sone ores 0.575 Ut Ran See se Sect se soe don SeoSde soNrescs saqeasco 100. 227 This analysis gives the atomic ratio H’?: Rk”: RY: Six0.57: 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, 3:4: 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 light-green 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 erystals 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. Prelnite 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 ease did either test indicate the presence of prelnite, nor has prehnite been detected macroscopically. Zoisite in the recrystallizing sandstones not only forms in aggregates of reerystallizing 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 in 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 XI1I——6 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 as to forbid any suppo- sition except that it is authigenetic. The granites contain none. Saussurita—In 1859 Dr. T. Sterry Hunt’ showed that the saussurite of the euphotide of Monte Rosa corresponded in chemical composition and physical character to zoisite. After the application of the microscope to the study of lithology, saussurite was recognized as (ordinarily, at all events) a mixture. In 1883 Mr. A. Cathrein® showed that many saussurites were mixtures of zoisite and feldspar. Many of the metamorphic rocks of the Coast Ranges might be described as saussuritic, but it appears unadvisable to retain distinct names for mixtures of this description after their real com- position is established. In the California rocks this mixture is not a product of decomposition under ordinary conditions, but of a process of recrystallization inconsistent with ordinary decomposition. In Switzerland and elsewhere eruptive dia- basic rocks are supposed in some instances to have been converted into saussuritic masses, while in others decomposition has yielded no zoisite In any case the result of a chemical process must be that group of compounds the formation of which liberates heat most rapidly. It is consequently to be supposed that the saussuritic gabbros have been subjected to influences different from those to which such gabbros as have undergone ordinary de- composition have been exposed. Judging from the analogy of the rocks of the Coast Ranges, it may be conjectured that the saussuritic gabbros stand to ordinary rocks of the same species in the same relation as the zoisitic altered rocks of the Coast Ranges do to those which have merely weathered, or, in other words, that the saussuritic rocks are the result of a process of metamorphism acting upon rocks some of which are eruptive. Feldspars.—'The formation of feldspars is an almost invariable accom- paniment of the metasomatic changes of the rocks of the quicksilver belt, ‘Am. Jour. Sci., 2d series, vol. 27,1559, p. 336. * Zeitschr, fiir Kryst. und Mineral., Groth, vol. 7, 1883, p. 234. FELDSPARS. 83 and the only exception appears to bein the case of the amphibolites, which seem most rationally regarded as extreme cases of the dioritic group. The genesis of feldspar in the metamorphic rocks is certainly one of the most important changes, and it is also one which is very fully illustrated by the collections. The unquestionable authigenesis of minerals of this group is excellently seen in No. 11, Knoxville, an augitic rock intersected by minute, almost microscopic, veins. Portions of these veins are filled with well developed, striated feldspar prisms and irregular grains of plagioclase, seemingly oligoclase. In some portions carbonates are mixed with these crystals and appear to have crystallized at the same time with the feldspar. These crystals are more recent than the rock in which they are embedded, but they demonstrate that conditions necessary and sufficient to the forma- tion of feldspar in the wet way have existed in this region. The whole oe- currence is such as to exclude the possibility that these veins are of eruptive origin. There is also abundant evidence of the presence of authigenetic feldspar in the altered sandstones. The process usually commences in the fine detritus which often composes the cement of the sandstones. Here form slender, polysynthetic, plagioclase microlites, of such shapes and in such grouping that it is impossible to suppose them to be clastic constituents. The larger grains are attacked later than the cement, and both quartz and feldspar grains appear to be resolved into plagioclase, secondary quartz not infrequently forming at the same time. The corroded grains are often to o fo) be seen surrounded by a fringe of authigenetic plagioclase microlites, the nucleus remaining clear. The allothigenetie feldspar grains are also often recrystallized without any change in the external outline. In such cases an ageregate results which is usually microcrystalline, but often also includes or may be almost entirely composed of lath-like, hemitropic lamelle. There appears clear evidence of the process by which tolerably large plagioclases may be formed in the rocks which have undergone metaso- matic recrystallization. In some rocks which still retain an indubitably clastic character, plagioclase microlites may be seen forming in groups of almost identical orientation, but still separated by thin layers of minerals not belonging to the feldspar series. Even rough, erystalline outlines may be traced surrounding such groups. The hemitropic lamelle in such cases 84 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. usually have frequent offsets, and the crystallographic orientation, though nearly the same for the whole group, is not absolutely uniform. It is ex- tremely difficult to understand this building up of crystals from microlites; yet perhaps in no other way could the formation of garnets, tourmalines, and a long list of other minerals be explained in strata which can never have been reduced to a plastic state. The commonest feldspar species in the altered sandstones and the eranular rocks is oligoclase, but andesine is probably also common. Many angles of extinction, referable to andesine,-have been observed, and in one case a separation and chemical analysis showed the presence of this feldspar. Labradorite is found in the gabbroitic rocks and in at least one pyroxene rock where the bisilicate is not diallage. Orthoclase has been proved chemically to exist in one glaucophane rock, and albite in a feld- spar-augite-hornblende rock. There may be more albite than has been detected, since it cannot be recognized with ease by optical means in the presence of oligoclase. Rutilee—In some of the schists and amphibolites numerous masses of a bright-brown, anisotropic mineral were observed. Many of these masses are prismatically developed, though the edges and corners are somewhat rounded. They are monochroitic and extinguish light when parallel to the principal sections of the nicols. The interference colors are scarcely dis- tinguishable from those observed in ordinary light. A small amount of this mineral separated from an amphibolite proved on chemical examination to be titanic acid. The absence of dichroism and of brilliant colors of inter- ference shows that it is not brookite. The prismatic development excludes anatase,’ while its characteristics correspond exactly to those of rutile. Some of the masses of rutile are partially decomposed to a light-colored, clouded substance similar to leucoxene. umenite—T'itanie iron is very abundant in some of the groups of gran- ular, etamorphie rocks, and the associations are such as to lead to the sup- position that it has been formed at the same time with the bisilicates. The characteristic triangular grating of the ilmenite is much more common im these rocks than it usually is in eruptive masses. The ilmenite is frequently 1 See a report of an investigation by Thiirach: Neues Jahrbuch fiir Mineral., vol. 2, 1589, p. 398. COMPONENT MINERALS. 85 accompanied by clouds of leucoxene. ‘The appearance of this material is entirely accordant with the supposition that it is granular titanite. Titarite— Besides the clastic grains of this mineral in the sandstones, it appears in the glaucophane schists in characteristic rhomboid forms, the corners being wholly unabraded. In the same rocks it appears as more or less regular grains, embedded in zoisite and in entirely undecomposed glau- cophane. It is thus to be considered as an authigenetic component of these rocks, apparently replacing the ilmenite of the granular group. The colors in ordinary and in polarized light and the other optical properties, as well as the form, are entirely characteristic and require no comment. Apatite — This mineral having been detected by optical and chemical means as an authigenetic constituent in one slide, a special examination of the collection was made for fear that it might have been mistaken for zoisite. Tt was found in abundance in some of the pyroxene granular rocks and in two glaucophane schists. Minute prisms of this mineral appear also to be present in a few of the altered sandstones. Apatite is tolerably frequent as an inclusion in clastic grains. chiorites—(Chlorites are abundant both in the sandstones and in the recrystallized rocks which are undergoing weathering. As usual, it is dif- ficult to determine the particular species of chlorite; indeed, the specific distinctions between these minerals are far from satisfactory. All of the chlorite met with possesses the usual grass-green tint and is strongly di- chroitice. It is usually fibrous, but in a few cases shows irregular scales. The fibers always extinguish light when sensibly parallel to the principal section of the polarizing apparatus, while some of the scales appear to remain absolutely dark between crossed nicols. The interference colors of the fibrous aggregates vary greatly. When the mass is composed of felted fibers of minute size the colors of polarization are very feeble. In other eases dark-blue tints appear, and in some instances, which appear to be distinguished by unusually large quantities of parallel individuals, yellow interference colors make their appearance. By treatment through a per- forated cover with moderately strong, warm chlorhydrie acid, it was found that the ordinary fibrous chlorite of these rocks is not attacked. Portions of the same specimens, however (e. ¢, No. 26, Sulphur Bank), treated with 86 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE, boiling, concentrated chlorhydric acid, yielded a solution containing both alumina and magnesia. Clinochlor is thus absent. None of the specimens affords an opportunity of isolating the chlorite in sufficient quantities for quantitative analysis. Pennine is stated to occur characteristically in hexag- onal scales, which are readily attacked by chlorhydric acid." It is possible that the rather rare irregular foils mentioned above belong to this species; but the fibrous variety is certainly not easily attacked by the acid. Of the ordinary chlorites there remains only the ripidolite of Rose, which is Werner's chlo- rite and Dana’s prochlorite. It is to be hoped that the researches of Pro- fessor T'schermak will make future determinations more satisfactory than this. Epidote—Fpidote is not very abundant in the metamorphic rocks. In a single specimen, however (No. 119, Knoxville), it is developed in large crystalline grains with two cleavages, and in this case greatly resembles augite. The optical reference of this specimen was confirmed by a silica determination, which was 38.98 per cent. The usual occurrence of this mineral is in crystalline aggregates in association with chlorite, to which it often stands in relations strongly suggesting epigenesis from chlorite. No cases so fine as those described and figured in my memoir on the Comstock lode were met with. Professor Rosenbusch’ doubts my explanation of those occurrences, believing that they are not of such a nature as to pre- clude the’simultaneous formation of the two minerals. _ It is difficult to prove absolutely that they were not formed at the same time, because of the lack of persistent structure in the chlorite; yet, from the inspection of almost numberless cases, it certainly appears that epidote needles pierce aggre- gates of chlorite fibers freely, while the arrangement of these fibers does not bear any visible relation to the epidote crystals such as is familiar in ‘ases of simultaneous formation. When I first expressed my opinion on this subject I was unaware that other lithologists had reached the same conclusion. Both Dr. H. Francke and Prof. A. Renard anticipated me in what I still regard as the most probable explanation.’ ' Fouqué and Michel-Lévy: Min. micrographique, p. 438. 2 Neues Jahrbuch fiir Mineral., vol. 2, 1884, p. 187. 3 Dr. Francke’s paper, Studien iiber Cordillerengesteine, Inaug. Diss., Leipzig, 1575, I have not seen. The following is an extract from Mr. Renard’s paper on the diabase of Challes (Bull. Acad. roy. Bel- gique, vol. 46, No, 8, 1878, p. 289°): ‘‘Francke admits that the epidote is formed by the decomposi- tion of the viridite ineluded in the feldspars, the viridite itself arising from the decomposition of horn- ALTERED SANDSTONES. 87 Garnet—In the glaucophane schists garnets are not infrequent, though nowhere yery abundant, in crystals measuring from 0.3™ to 2™. The garnet is of a pale reddish-brown tint, perfectly isotropic, and includes zo- isite, titanite, and glaucophane. It decomposes to a coarsely foliated chlo- rite. Nothing answering to the kelyphite of Mr. A. Schrauf! has been observed, and it can only be supposed that the decomposition has been effected by the action of magnesian waters. Serpentine is also associated with the decomposing garnets, but not under conditions sufficiently pro- nounced in the material at hand to justify any positive assertions as to the relations of the two minerals. Other minerals —Zircon 1S common as an inclusion in clastic grains and is also probably present in some of the glaucophane schists. A careful watch has been kept for other minerals, such as andalusite, dipyre, prelnite, allan- ite, and zeolites. The last occur macroscopically in the New Almaden mine, but have not been observed in the slides. ALTERED 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? 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 Francke’s point of view are true also of the chloritie material derived from augite 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- spar sections not as pseudomorphie after feldspar, but as a result of the transformation of chloritic matter. There ave, furthermore, numerous instances of this transformation.” 1 Zeitschr. fiir Krys. und Mineral., Groth, vol. 6, p. 321. 2No. 8, Coast Range 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 125° 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 microcrystalline 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. Fic. 2. Authigenetic augite in altered sandstone, No. 8, Coast Ranges. A, angité; u, uralite; J, microcrystalline feld- spar; q, quartz grain; s, serpentine. Magnified 117 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 sides by microcrystalline, authigenetie 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 of feldspar can be observed. White mica is forming authigenetically, and perhaps also apatite. Decomposition has also set in and the slide contains some serpentine. These phenomena are better observed, however, in other cases. Fic. 3. Authigenetic hornblende in altered sandstone, No. 8, Coast Ranges. a, clastic quartz; b, clastic feldspar; ¢, authigenetic hornblende; d, authigenetic feldspar aggregate ; e, clear isotropic mass; s, serpentine. Magnified 170 diameters. No. 86, New Idria, is a coarse, bedded, dark greenish-gray sandstone, evidently altered, but manifestly a sandstone. Under the microscope the clastic character is clearly yisible, the original limits of the grains being defined by irregular streaks of brown or greenish color. Some of these streaks represent decomposed mica foils. In the clear masses separated by the colored streaks are embedded angular and rounded grains, many of which are quartz carrying abundant fluid inclusions, while others are feld- spar. Surrounding these nuclei are aggregates, chiefly feldspathic, and these aggregates are so related to the nuclei that it is impossible to doubt that they are composed of authigenetie minerals formed at the expense of clastic grains, only the central portions of which remain. Many of the residual grains are almost entirely surrounded by elongated microlites in positions nearly normal to the surface of the nucleus. The ends of the microlites do not merely abut against the nucleus, but penetrate it for a sensible dis- 90 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. tance, so that the edge of the grain seen in section is full of indentations, each the bed of a microlite. This relation is more clearly seen by revolv- ing the analyzer. In positions where the colors of the host are strong while those of the parasites are weak, the original mineral is seen to extend out among the microlites, while, when the relations of the colors are reversed, the nucleus appears limited nearly to the inner ends of the microlites. As the polarizer revolves, the visible limits of the parent mineral dilate and con- tract in a very striking manner. In many cases the nuclei are quartz and the microlites are poly- synthetic twins, which in favorable cases give the angles of extinction of oligoclase. In other cases the nuclei are feldspar, sometimes orthoclase and again plagioclase; the parasitic microlites, however, again appear to be chiefly oligoclase. That oligoclase should result under the same conditions from the attack of quartz and of feldspar is in the highest degree remark- able; but the observations made on this slide and confirmed by comparison with other thin sections admit of no other simple explanation. The process of alteration does not go on only at the surface of the quartz grains. In the granites quartz grains are frequently composite, the separate crystalline individuals sometimes exhibiting a barely perceptible difference in crys- tallographic orientation. The lines dividing the individuals must also be lines of weakness, and when the fractures which take place in the disinte- gration of the parent rock do not follow these lines they may often be seen to have afforded opportunities for the attack ,of the solutions and to be marked by narrow bands of microlites nearly perpendicular to the line of division. It is not always that the microlites resulting from the attack of quartz and feldspar in this rock are lath-like. In many cases they take the form of irregular grains indenting one another and assuming the granophyr-like structure mentioned in the slide from Jericho Creek. These grains are not polysynthetic, but evidently feldspathic, and are so associated with the elongated microlites as to make it probable that they are of the same or a closely allied species. This slide also contains small quantities of zoisite and some undeformed foils of white mica embedded in aggregates which have replaced clastic ALTERED SANDSTONES. 91 grains. Both of these minerals are authigenetic. There are also decompo- sition products, including a little serpentine. No. 134, Sulphur Bank, is manifestly a much altered, arenaceous rock, of a strong green tinge, intersected by minute veins of a feldspar-like min- eral. Under the microscope the clastic character is perfectly distinct, the clear or somewhat milky grains being divided by a net-work of thoroughly characteristic conformation. ‘The net is composed of green and brownish- ereen matter. The original clastic minerals have entirely disappeared. The thin section shows half a dozen minute veins, more or less continuous, and these are filled with feldspar, which is for the most part granular, but occasionally shows irregular, hemitropic lamellee. On the course of one of the veins, at a point at which the vein pinches, is a very remarkable feldspar aggregate of lath-like microlites extending over an area several times as wide as the adjacent vein. This aggregate has replaced, wholly or in part, several clastic grains the shape of which is faintly trace- able by brownish streaks. Three-fourths of the periphery of the aggregate is nevertheless bounded by straight lines. The aggregate is composed of polysynthetic, lath-shaped microlites almost exactly parallel to one another and giving low angles of extinction on each side of the twinning plane. The position of these microlites corresponds to the straight outlines and the entire aggregate appears to represent a porphyritic, authigenetic feld- spar cut nearly perpendicular to the brachypinacoid and showing two distinct terminal outlines at one end. The chief distinction between this and porphyritie feldspar in eruptive rocks is the frequent interruption of the hemitropic lamella. The traces of the original outlines of the clastic fragments still visible in the feldspar forbid the supposition that it is an allothigenetic mineral; neither is it possible that such a crystal should have been transported and redeposited without abrasion of its corners. The slide shows several other feldspars of similar character, but less perfectly developed. The greenish-brown net-work between the altered grains in this slide is chiefly composed of a non-dichroitic, fibrous mineral show- ing dull-yellow interference colors and thus corresponding to serpentine. There are no patches of it large enough to show the characteristic grate structure. 92 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. No. 212a, Sulphur Bank, is a dull-green saudstone intersected by quartz veins. Under the microscope it is seen to be a partially decomposed sandstone, containing numerous fragments of quartz, orthoclase, and pla- gioclase, the interstices being in part filled with serpentine. The slide is chiefly remarkable for the presence of zoisite in considerable quantities, growing into the quartz grains, The zoisite shows the characteristic extine- tions, interference colors, refraction, and cross-section. No. 15, Sulphur Bank, an ordinary gray, indurated sandstone, shows phenomena similar to those described in No, 86, New Idria. It also con- tains a great deal of zoisite, both in the granular and the prismatic form. The zoisite in this slide was tested with nitric acid to make sure that apatite had not been mistaken for it. An especially significant rock is No. 13, New Almaden, which is both macroscopically and microscopically unquestionably an altered sand- stone. In the slide, however, it is seen that the progress of the metaso- matic recrystallization has been somewhat irregular and that there are fields in the slide which could not be distinguished from an ordinary eruptive diabase, As the slide is moved, however, the structure and mineral compo- sition change gradually and by insensible degrees until the eruptive habitus is lost and the clastic character is clearly revealed. There is no suggestion of included fragments or dikes of eruptive rock in the specimen or slide. No. 13, Sulphur Bank, a slightly altered sandstone from the meta- morphic series, was selected for chemical analysis. Under the microscope the rock appears to be arcose, the grains being quartz similar to those of the granites, plagioclase, and unstriated feldspars, with the optical properties of orthoclase. The grains are cemented by newly formed aggregates which seem to consist in great part of triclinic feldspar. From inspection one would expect to find in this rock about equal quantities of soda and pot- ash. The following analysis, however, shows a very different and unex- pected relation : Tossa WOOO HR Oke seec. ccc wots cases a hodon soso aaeeee sate 0. 276 Toss above: 100S HzO Cs Saco Soe ee sa ace eee Peis Silica, SiO2: = 52 cee dasc cco cce- oan seh acees eee Seen ee 68. 500 Phosphoriciacidssh: Ose. oeascee ana se oie eeeeee eaeeee eee 0.163 Titanic acid) TiO assoc dec = ccieee = cas store ae sae eee eee 0. 600 GRANULAR METAMORPHICS. --~ i) PACITAIMMIN SAU AO)S water etree minataraeteets etcletaterctaeicierecim/ejeic sie etele's: siainie 12. 816 INEWNG GSC E, EOS mochoade pocn tole ce. someee UneoEs Good Socue 1. 293 HERTOUS OXI we Osan ee ae ate ee enfant ele teal one a)— =< 3.373 Manganousioxide; MnO) 2252 on sacee ca ceasciass-esesccs--~ 0. 023 Times Ca Oise ne seve cess casice cia ssl= Paceres celine vesenmeacisive,e ects 1. 823 Maoniegiane My Olea. ae ccse teste sa enaewtats se eee mitee(areis sche oS oye ess 2. 206 Swi NEVO) so8 cease cessed Doce dadbos ceacne sanecdnaas BoSeec 6. 033 Po tasgar tke @) vie. socio aie cial e ciate leis viele wcieie ais eveisiwisinietcisievsinic. stare 1, 259 100. 478 The atomic ratio represented by this analysis is H?: RY”: R": Six 0.266 : 0.490 : 0.801 : 4.567. How the soda can be so greatly in excess of the potash in such a rock I cannot explain. The cementing feldspathic mass may be very rich in soda and possibly some of the unstriated feld- spars are triclinic. It is also possible that the orthoclase is abnormally sodic. These examples show that nearly all of the most important metaso- matic processes can be traced in rocks the clastic character of which could be questioned by no one for a single moment. It is only necessary to sup- pose the same processes carried further to obtain a product in which the clastic character is obscured or obliterated, and the altered sandstones, under the microscope no less than in the field, thus form transitions from the clastic series to the holocrystalline rocks. The enlargement of clastic grains by erystallization from infiltrating solutions, which has been shown by several geologists! to be not infrequent in some regions, and of which I too have studied fine examples, has not been observed in the rocks here described. The general nature of the changes here consists in the attack of clastic constituents, not in the addition of mineral matter of the same kind. GRANULAR METAMORPHICS. Nomenclature—'There are in many parts of the world metamorphic rocks very closely resembling diabase and diorite in mineral composition- These rocks have sometimes been called, by myself as well as by others, metamorphic diabases and metamorphic diorites; but there are serious ob- Jections to these terms. A diabase would be defined by most geologists as a Pre-Tertiary eruptive rock, mainly composed of plagioclase and pyrox- ene. This is also the historical meaning of the term. To those who have 1See Hunt, Origin of Crystalline Rocks, § 116. Q4 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. this definition in mind the name metamorphie diabase would not convey the idea of a metamorphic rock resembling a diabase, but of an eruptive rock changed by metamorphic processes. Even if diabase were usually understood to signify a rock of a certain age and a particular mineral com- position, irrespective of origin, the term metamorphic diabase would be inconvenient on account of its length. If it were in frequent use, it would often be contracted to diabase, and this term would lead to misunderstand- ings. It seems eminently desirable to retain for diabase and diorite the meanings which they have long conveyed to geological readers and to limit their application to eruptive masses. Metamorphic rocks which resemble them in mineral composition may then fitly be called pseudodiabase and pseu- dodiorite, and these terms will be employed in the remainder of this report. Groups of granular metamorphic rocks— The granular crystalline rocks of the Coast Ranges are divisible according to their mineralogical composition into several more or less well-defined groups, between which, however, there are transitions, as there also are between the granular and the schistose rocks. The chief divisions are pseudodiabase and pseudodiorite. The pseudodiabase is sometimes met in gabbroitic modifications and in a few cases contains so much zoisite that it might without impropriety be denominated a zoisite pseudodiabase; for, since it has been shown that saussurite is either mere zoisite or a mixture of zoisite and plagioclase, there appears to be no reason for retaining that name. The pseudodiorite passes by gradations into a mass so highly hornblendic as to deserve the name of amphibolite. There are also a few rocks in which no augite or amphibole appears, and which are thus composed of feldspar, quartz, zois- ite, ete. These appear to represent pseudodiabase or pseudodiorite in ex- treme forms, since they are locally associated with these rocks, as are also the slightly altered sandstones. The schistose rocks are all characterized by tne presence of glauco- phane and zoisite. They are usually micaceous, but sometimes not. PSEUDODIABASE. Pseudodiabase is much the commonest of the crystalline metamorphic rocks of the Coast Ranges. When sufficiently coarse in texture it is readily PSEUDODIABASE,. 95 seen with the naked eye to be a crystalline mass, though it could rarely be mistaken for an eruptive rock. It then shows dark-green bisilicates and sometimes, also, feldspar grains. The absence of visible feldspar grains corresponds to a microcrystalline groundmass. Very frequently the rock is fine grained, and then it sometimes retains the appearance of an altered sandstone so perfectly that it is impossible to discriminate between this and pseudodiabase without the aid of the microscope. Under the microscope it is found that at least a portion of the augite exists in comparatively large grains or crystals, while the feldspar may be granular or microcrystalline. In other words, as sometimes happens among eruptive rocks, both granular and somewhat porphyritic forms of pseudodiabase are common and are intimately associated. Under the cir- cumstances a difference in chemical composition appears to be a necessary inference from this difference in structure. Orthoclase has not been detected in the pseudodiabase. Plagioclase usually forms the greater portion of the rock. In those rocks in which the feldspathic mass is microcrystalline it forms a mass of minute interlocking grains, sometimes resembling granophyre. These minute grains seldom ex- hibit polysynthetic structure and cannot be referred to their proper species by optical methods. A separation and partial analysis of a typical occur- rence of this material, No. 105, Knoxville, showed that it approaches an- desine in specific gravity and composition. In the rocks in which the plagioclase grains reach 0.1" and upwards in length, twin structure is usual and lath-shaped individuals are common. The hemitropic lamellee are often irregular, showing breaks and offsets. The extinctions refer them to oligoclase or andesine. Porphyritic feldspars are uncommon, but not wholly wanting. Altogether the most ordinary inclusion in the feldspar consists of grains and prisms of zoisite. These are not products of the decomposition of the feldspar, but of contemporaneous development, both minerals being often perfectly fresh. When the pseudodiabase has not been subjected to serpentinization the feldspars are often affected by a decomposition process resulting in the formation of irregular grains of a colorless substance which gives orange tints between crossed nicols. Its 96 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. nature is uncertain. Distinctly developed nacrite has been detected in only one of the rocks. Much of the quartz in the pseudodiabases is secondary, but in a few cases quartz grains appear to have formed contemporaneously with the feldspars. They carry a few fluid inclusions. No rhombic pyroxene has been detected. In the extremely rare cases in which erystals of pyroxene extinguish light when parallel to the princi- pal nicol sections, there appears no difference between their dichroism or other properties and those of the other pyroxenes in the same slide. The proportion of cases in which the extinction of the pyroxene crystals sensi- bly coincides with the principal axis is very small and not greater than might be expected in the case of a monoclinic mineral. Both augite and diallage occur, but no sharp line can be drawn between them. In nearly all cases the clinopinacoidal cleavage of the larger crystals seems well developed. Pyroxene evidently develops early and vigorously in the rocks undergoing recrystallization and tends to the formation of porphyritie crystals. Well-developed crystals are not very common. Amphibole occurs as brownish-green crystals, formed contemporane- ously with the augite and more abundantly ‘as unmistakable uralite. A few of the pseudodiabases also carry glaucophane. Examples — No, 21, Coast Ranges, from near Mt. St. Helena, is a gray, rather fine-grained rock, which, on close inspection, appears crystalline.. Under the microscope it is seen to contain much augite and hornblende, together with feldspar, both polysynthetic and monosynthetic, and an unu- sually large quantity of zoisite. It is also unusually free from decomposi- tion products. This rock represents both the pseudodiabase and pseudo- diorite, between which there is no sharp division. The hornblende is in part of a clear, light, but not vivid, brown color, with very moderate dichroism. This variety occurs in well developed crys- tals, giving normal extinctions and cross-sections. Curiously associated with it is a light-green variety. Many of the crystals are in part brown and in part green, the division being a sharp, straight line. The different portions of such composite crystals extinguish simultaneously, but usually give very different interference colors. The cleavages are continuous from PSEUDODIABASE. 97 one portion to the other, nor does the green mineral exhibit greater fibra- tion or any other structural peculiarity. In some cases the line of demar- kation is curvilinear, but nowhere does the green color follow cleavages or cracks or penetrate the brown by sharp indentation, as products of altera- tion usually do. There seems nothing to indicate that the two varieties have notformed simultaneously, and even on this supposition the sharpness of de- markation and the character of the limits are difficult to understand. There is a little ordinary chlorite in the slide, produced by decomposition of horn- blende. The augite possesses no peculiarity excepting its relations to the horn- blende. There is some ordinary uralite, but there are also augite masses ; partly surrounded by brown hornblende in such a way as to suggest a brown uralite. The relation of the brown hornblende to the augite, however, is similar to that which the green hornblende bears to the brown, and I cannot satisfy myself that it is really epigenetic. The feldspar is for the most part clear and fresh, and a large portion of it shows polysynthetic structure. The extinctions observed indicate the presence of oligoclase. To test the character of the feldspar, a separation was made by the Thoulet method. At a density of 2.85 a large precipi- tate of bisilicates and zoisite fell, carrying a portion of the feldspars with it. On reducing the specific gravity of the solution gradually, 5 per cent. fell at, 2.65, which appeared under the microscope to be pure feldspar. Between 2.65 and 2.58 there was no precipitate. From 2.58 to 2.56, 7 per cent. of pure feldspar fell. This was found to contain 11 per cent. of soda, and the rock, therefore, contains both oligoclase and albite. The zoisite occurs in part in prisms with characteristic properties, but mainly as granular masses, which are nearly colorless and monochroitic, but otherwise not unlike epidote in appearance. Exactly such zoisite was isolated from a Mt. Diablo specimen and chemically tested. The greater part of the zoisite is embedded in the clear feldspar, but it also fills interstices between feld- spars, so that the formation of the two minerals must have gone on simul- taneously. MON, XIII——-7 98 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Ilmenite in part converted to leucoxene is abundant in this as in most of the pseudodiabases and pseudodiorites. A complete analysis of this rock gave the following result: Loss at 100°, H2O ...--. 0... ------ -- 22 2 ne woe enn ore r ne 0. 275 Loss above 100°, H?0.......--- -----. ..-<<. See Soe eae rales 1,179 Silica, SiO? so nee wooo cee nn tna miele em emia ee 49. 080 Phosphoric acid, P?O° ..--...----------+ -++--+ +++--+-------- 0. 232 Titanic acid, TiO?........---. ..---.------------------ ------ 1.721 Amina, Al? Os eee eae BS emoe Sano ase Cno Deca suadde cocnacss 14. 685 Ferric oxide, Fe203. ....-. .----- .----- ------ 2-222 eee eee =e 1. 946 Ferrous oxide, FeO. .-.---.----. ---- ------ --- 2-5 +----~ -- 5 -- 9. 632 Manganous oxide, MnO ..-.-..----. -----------+ +--+-+------ 0. 154 IMGs (Of Ob geseee cece. o2a0 esr soaacoSstSobeces ds oceeeteeen ae 10, 091 Magnesia, MgO ..-.------ ------ ----++ --++ +2202 eee eee 6. 693 Soda, Na?O_..--.. 2... 2. - <0 --2- eee ne conn on ne nnn ww = 4.597 (Potassa eke Omeem eae eee Kaa winioeiec sie sistant eines 0,199 Total oa-aes coc sices clean eeeiseeic oe eee sales pee ae 100. 482 The atomic ratio deduced from this analysis is H?: R’: RY: Six O62 AIG 0.935 23.202: No. 11, Knoxville, appears macroscopically a green, much-altered sandstone, intersected by numerous minute veins of white mineral. Under the microscope it is found to be a holoerystalline pseudodiabase consider- ably decomposed. The feldspars are in part granular, but chiefly lath- shaped crystals from 0.1™ to 0.4" 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 with calcite. The augite occurs as imperfect prismatic crystals and grains, either included in the feldspars or between the erystals of the latter. Its color is very faint; it is not dichroitic 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. No, 36, Sulphur Bank, is a dark-green, fine-grained, crystalline rock, in which feldspars and bDisilicates 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: HboOsstaite OOS WHE Ose see ee ences. RODEO RedeasnU SCS Cams 0, 389 JOSS ADO EEL OOS Ee O ks poe see susniscteja nic ava sess see See ae eee see 2.965 SHIGE TSO Gaceop shes Docerb eae se nC oe COS EE ee Ce ee ee neee 51. 278 nhosphoricvacid We2O tessa oes eee ceisee = soe eee see ce neeke 0.131 PLisanicracid si Oise assninnt seen ee ese blea meeeeen ieee eee oe 1.330 Alumina; -APOS= 2. cence aae Sond eA ee nn aeree --- 15,048 IBELILO(OKO One RE2Z OS ame teaawcau ree ae ecu caoees sass osk eee lees 2.415 HMErROURFORICO WOO) eis cecetee aan a-teneroon = suctcic oe Se ee O14 MACK Omide yNIO) soseesase ian ea aatcacaee cote cele een weer 0. 098 Maneanonsoxide ein Omen sen ease eects. eee en eece cele. 0, 251 MIME CAO mrss ae cenc nt ae oe woes vectee Ck eases se clock 7. 079 Maenestal Mic Oren weer nce eee eee races cuss eee ees ocee esse 6. 069 SOG Ap Naa O) meme aston ce tsee reeeene teers eee ea) Ae 493 OUR SS Sy Ohler eretccoteys ote stare meat ea sete cin cans es coae 0. 123 Total...... Saeclow slewiteinictes (cities scsl ccs oe eens Sa eae 99. 623 The atomic ratio deduced from this is H?: R’” ; RY: Si—0.373 - 0.931 POO TAN 341.9) PSEUDODIORITE. 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 itis only when the bisilicate 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 in a fine-grained, colorless ground- mass. When well exposed this groundmass shows a faint net-work of grecn- 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 foreibly while forming. The groundmass is very fine-grained, the individuals ranging from 0,01" 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 inthe rock. Included in the actinolite are also grains of titanite, brown, somewhat pleochroitice prisms of rutile, and sinall 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.......- See see ice te meSe ae senses euccws 0, O68 TrosstalvowewlOQO HO) tes terse oe nayee rarer inisinier ieee ale iaele winless. 0, 916 SiliG ats Ok eee ep ae eeetee wens ane oe acitenceicenaaisnrams 50. 437 PAM Min AC MATA OF Seen en emioe eee se cas felsainyo= aia\ee a=ysise/or so ieiee e's &. 183 Chromic’oxidesCr-O8". 22s emis rocnse {don Shosccoscdecosoc 0. 480 Perricioxid es We Oe sees sam ehcic ete ceinies somes tide ctessaseccete 1. 059 ELLONS TOXICS wile Ones camiiseeeeisseleiaesci ce riacsaiccecies =a 0 6. 285 Man canons, 0x1 ern Olen enemas ciacsiereee eaeeierimccsisesia 0) Oneld ‘ Lime, CaO Serer rin ta Jette shee aon ease maamcina cece seas 11.550 Marries am MOO mare ete matte erties uae eine pine Stenilace oaks 17. 628 SoG, IMGHO) Sosne cobasbe cone poscebo one Senos Sp Sacc0B aod S05 2. 982 IR OLASS ame (Daan eat eee aia rete hee iars talc, Satan's oncielersle ete 0. 503 Motallee sass ynieihes esse ana e ale abe ace eceaewenisces 100, 304 The atomic ratio deducible from this analysis is H?: RY : RY: Six O109%; 2573 2 0:539'< 3.362. GABBROITIC PSEUDODIABASE. While a tendency to the development of the clinopinacoidal cleavage of the pyroxenes of the pseudodiabase las 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 phthanites. 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. Ina few places a decomposition-produet, similar in appearance to the ferruginous cement of the sandstones, appears to have formed from the diallage. The feldspars are clear and give extine- tions as high as 30° on each side of the twinning plane, indicating the pres- ence of labradorite. 102 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 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 eabbros. There appears to be no reason to consider the above-described rock as anything more than a variety of the pseudodiabase. -secen oes ore osae ocean cen eac rae ences | 3.043 2.524 Silica SiO8 & Pt cee tee cee) Ae ee 40.53) 66.42. Titanie acid, TiO? 1.80 0.31 Alumina, Al‘O? /MRentiGOS10G (NGO fn nee eene ae nee eceie ee esaasseemeneaeise 1.02 2 AGE errand 0S lets QO) cases cece ser sean ane ane sane eee ener 11.07 5 Manganous oxide, MnO 0.16 Trace HERES WIN FRO) a Soe po Re Se cco seorceSecsececHce nse 8. 02 1.30 | Lime, CaO 14. 62 1.19 Soda, Na20 ae 2.87 6.09 Pn eth) REID SEO) eee Sep eS ee SEER ses amti CEST OC ECOSOC SS 1,95 7. 36 Phosphoric aod, R205 <2 ooo eww awa een cetecenees ows ene a- = } 2G ye eres | Carbonic acid, CO? as (hel eae tes | WWI S ELOY ak oa 83 oe en erie occ = 1.44 0. 73 99.86 100. 13 { 1 Zeitschr. Dentsch. geol. Gesell., vol. 17, 1855, p. 413. 2 About 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 Neues Jahrbuch fiir Mineral., V. Beilage- Band, 1887, p. 381. He regards the whole mountain as asingle 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 Jess glassy. A very pure glass from Fosso del Diluvio gave: Sp.gr., 2.346; SiO2, 73.57; CaO, 0.99; MgO, 0.26; Na?0,3.09; K20, 5.74. An analysis of typical trachyte from the Poggio Traburzolo gave: Sp. gr., 2.562; SiO®, 64.76; CaO, 3.24; MgO, 1.74; Na?O, 2.67; K°O, 5.49. Asin 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 the glass was prevented from erystallizing by peculiarities of composition, not of the physical condi- tions to which it was subjected. : 3 Neues Jahrbuch fiir Mineral., 1869, p. 36; ibid., 1873, p. 587, 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 mineralogical 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 xuI—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 Disilicate, 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 by these or by other substances, such as titanium. Granitoid and porphyritic texture— While the obsidians of Clear Lake and 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 erystallized. 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 crys- tallographie development. This follows both from theory and experiments familiar to every chemist. If the cooling of such fluid 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 ROCK 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 exactiy 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 sucha 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 general the result of pressure, for, while it is certain that some cannot be in ¢ 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 Archean, 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 porphyritie 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.’ 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- !T have discussed this subject more fully ina paper on The texture of massive rocks:"Am. Jour. Sci., 3d series, vol. 33, 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. Mit- theil., 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 tendency to crystallization. He points out the high alkali contents of the ylasses 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 does also their simultaneous precipitation from supersaturated solution, ORIGIN OF MASSIVE ROCKS. 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 depth 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 been 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 upheavals. 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 clear that, if. Professor Dana’s theory 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 this 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 regions. In regions where the total erosion has exceeded the total sedimentation, the original crust must almost certainly be exposed. Bearing of principle of hydrostatic equilibrium.— Nothing in geology is more certain than that the earth is very nearly in a condition of hydrostatic equilibrium,’ 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. ¢., 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.” 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 arez 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, and 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. ' Babbage, I believe, was the first to point out this now familiar fact. 2Tn discussing the question of the solidity of the earth, geologists seem sometimes to forget that time enters into the conception of viscosity. The earth may be as rigid as steel with reference to forces which rapidly change their directions like those exerted by the sun and moon, but as plastic as putty to 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 surface. 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 —The 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 EROSION. 169 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—The average thickness of the 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- ereased 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.’ 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? Ido 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 half a mile, Leipoldt’s estimate for Europe is 297 meters, or 975 feet, say a sixth of a mile, 170 QUICKSILVER DEPOSITS OF 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 not 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. 7a 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 — The oldest sedimentary rocks compose the Archean 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 tocks, 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, ete. 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 OF THE PACIFIC SLOPE. The foregoing paragraph contains no novel statement. Scrope,! in 1825; MacCulloch,” in 1831; and Elie de Beaumont,’ in 1847, all maintained that the primeval rock from which the strata are derived must have been granitic. In 1859 Mr. Daubrée* entered more fully into the physical theory of the formation of the primitive rocks. Taking as a basis Humboldt’ 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 was further augmented by other vapors and gases. The purely igneous rocks formed prior to the condensatien of any water, as Daubrée infers, must haye 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. Daubrée, 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 ' Considerations on Voleanoes Leading to the Establishment of a New Theory of the Earth, quoted by Dr. Hunt, Origin 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.” * Bull. Soc. géologique France, 2d series, vol. 4, pp. 1321 et seq. He regards granite as formed by_ igneo-aqueous fusion and speaks (p. 1327) of ‘the first granitic crust of the terrestrial globe.” 4 Btudes et expér. synth. sur le métam: Ann. des mines, 5th series, vol. 16, p. 471. 5 Dr. Kriimmel’s revision of the question of the total quantity of water in the ocean (extract from a note to the Géttingen Academy, Nature, vol. 19, 1879, p. 348) leads to about 3,584 pounds per square inch. ® Quart. Jour. Geol. Soc. London, vol. 36, 1880, p. 112. PRIMEVAL ROCKS. 173 deduced the conditions as Daubrée 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 1gneous super- ficial layer of 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.’ 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 eranite 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 been highly charged with mineral matter. It is to this later period that Dr. Hunt, who accepts Dau- brée’s exposition of the action of the earliest condensed water, ascribes the formation of the Archean schists as chemical precipitates. In the text I am not concerned with the formation of the erystalline schists, but I wish to state that it appears to me impossible to suppose no crystalline precipitates to have been deposited. Ido not doubt that such were formed in amanner 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 Archean 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 begiven. At present general evidence only is attainable. California granites. — (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 ongranite. The granite of the Coast Ranges has been covered by sediments a large part of the time which has elapsed since the Paleozoie 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 can 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 Archzean, 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 eneissoid 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. California tavas——The lavas have unquestionably come up through the granite and are of infragranitie origin. There is no direct evidence what- ‘A portion of the 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 the clastic rocks. If Professor Lagorio is correct, as he seems to me to be, in asserting that sodinm silicates separate from magmas more readily than potassiam compounds, it would seem that orthoclase should have predom- inated in the outer crust of the earth, or in the primeyal granitic rocks, and that plagioclase should have predominated in the infragranitic rocks, or in the lavas. This, of course, accords with observation, CALIFORNIA GRANITE. 175 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 voleanic 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 feom 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, it 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. 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 inelosing 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 areas follows: The Coast Ranges experienced a great upheaval (the first traced) probably about the close of the Neocomian, this being the same disturb- ' Messrs. Antisell, Blake, and Newberry 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 known 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 Cenozoic Paleontology of California, by C. A. White (Buil. U. S. Geol. Survey No. 15); On New Cretaceous Fossils from California, by C. A. White (Bull. U. S. Geol. Survey No. 22), and Notes on the Stratigraphy of California, by G. F. Becker (Bull. U. 8, Geol. Survey No. 19). I have also used facts aud arguments adduced by me in a paper entitled “The relations of the mineral belts of the Pacific Slope to the great upheavals” (Am. Jour. Sci., 3d series, vol, 28, 1834, p. 209) and in Statistics and Technology of the Precious Metals, by S. F. Emmons and 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. MRE 7 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. The peculiarity of these thin-bedded, plicated, metamorphic rocks was observed by Professor Whitney. AGE OF THE METAMORPHICS. 183 that as a rule the hills of metamorphic rock are synclinal,’ 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 mollusean 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 Piochii, and close by are beds of limestone full of Rhynchonella Whitneyi? The metamorphic rocks of this region are serpentinized and silicified, and 1 Also observed by Professor Whitney: The Auriferous Gravels, Mem. Mus. Comp. Zoél. Harvard Coll., vol. 6, No. 1, 1880, chap. 1. 2These specimens were determinel by direct comparison with specimens in the collection of the State survey. The figure given in Geol. Survey California, Paleontology, vol. 2, Pl. 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 metamorphic 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 ete. 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 both sides by highly metamorphic strata. At Autna Springs, in Napa County, near the Aitna 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 with the metamorphic beds near the St. John’s mine, Solano County, 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 Aucella 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 metamorphies 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. Aleatraz 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 TERTIARIES. - 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 directly determinable by paleonto- logical evidence. Mr. Gabb also found Aucella 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 oceur abundantly in rocks of all ages. In the Arroyo de la Penitencia, above Alum Rock, near San José, there is also an area of altered Miocene sandstones referred to by Professor Whitney.! The rock here is much indurated and is full of veins of calcite. No objection can be made to its description as metamorphic oy 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 tle 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? 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 metamorphic is referred by us to the Cretaceous formation from general analogy rather 'Geol. Survey California, Geology, vol. 1, p. 51. *Tbid., p. 196; The Auriferous Gravels: Mem, Mus. Comp. Zoél. Harvard Coll., vol. 6, No. 1, 1880; p. 19. 186 QUiCKSILVER DEPOSITS OF THE PACIFIC SLOPE. 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 ean have little bearing upon the age of the metamorphies 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. his faet 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 aecom- 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 metamorphie 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 New 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. ERAS OF METAMORPHISM. 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 shoald properly be considered as even tending to prove the age of either.’ I go further, and refuse to regard the metamor- phism of the rocks of Butte 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 Tcjon 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 metamorphic 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 metamorphic 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 A The resemblance ee een the pieocoaes poderonce aad the Molasse of Sw feenandl was advanced by Mr. Jules Marcon (loe. 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 Archean rocks. Mr. Marcou attributes to ignorance of lithology my failure to appreciate if as an 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 Classification and Nomenclature, 1828, p. 52). I am very sorry that my work produces so bad an impression on this veteran geologist. 188 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. maintained that the violent upheaval and metamorphism which followed the Knoxville 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 metamorphie 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] 1ad the proof of this non- 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 acertain 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 Archean 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 adescription, actually oceur 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 distinet 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 macroscopically 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. amorphie 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 this respect is superior to any but that NON-CONFORMITY BELOW THE CHICO. 191 furnished by the very best local exposures of unconformable contacts; for every geologist must have observed cases where unconformable exposures are closely 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 Ranges 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. he 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, Téjon, 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 first range of elevations opposite portions of the shore, which 192 QUICKSLLVER DEPOSITS OF THE PACIFIC SLOPE. are composed of the metamorphic rocks. 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 uncomformably upon the metamorphic between the Guada- lupe mine and Forbes’s mill, and also near McCartysville,’ as well as north of the Golden Gate,* for instance, near Tomales,’ while, in speaking of the neighborhood of Suscol, he says:* “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 does not occur between the Knoxville and the Chico, it must be sought between the Chico and the Téjon or between the Téjon 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 Téjon and the organic remains prove that there was continuity of life. The great non-conformity cannot, therefore, have been between these groups. Between the Téjon and the Miocene there is at least no general non-conformity.? Near New Idria and at Mt. Diablo, for example, the Mio- ' Geol. Survey California, Geology, vol. 1, p. 69. a Thid!., p. 79: STbid., p. 83. ‘Tbid., p. 103. * Professor Whitney (Aur. Gray., p. 26) writes: ‘‘The Miocene and the Cretaceous seem everywhere to be conformable with each other.” The Cretacecus here referred to is of course the Téjon. Mr. J. NON-CONFORMITY BELOW THE CHICO. 193 cene seems as strictly conformable with the Téjon 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 been a great upheaval, accom- panied by intense metamorphism, between the Téjon and the Miocene, it seems impossible that no Chico or Téjon 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 Chieo. Add to this the direct evidence at New Idria and Ft. Ross, and the conelusion appears irresistible, irrespective of the paleontological 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 sedimentation, which could hardly be the case with the class of sediments composing the Coast Ranges, the region of Mt. Diablo must have been above water for at least one-half of the interval between the close of the Knoxville and the beginning of the Marcou in his paper on geological classification, 1883, p. 49, asserts that there is a great break between the Téjon and the Miocene near Ft. Téjon. In the description of the locality to which he refers (Ann. Rept. Geog. Surv. West of the 100th M., 1876, p. 167), 1 find no mention of this non-conformity. In the text I am concerned to show only that there was no disturbance at this epoch great enough to corre- spond to the metamorphism. : MON XIII——15 194 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Chico. Now this interval is an enormous one, comprising nearly the whole of the Cretaceous pericd. The Chico represents only a small portion of the Cretaceous, yet its sediments are thousands of feet in thickness. The same is true of the Wallala, which represents a different portion of the Cretaceous. On the most unfavorable supposition, therefore, Mt. Diablo must have been ex- posed for a sufficient time and at a sufficient elevation to allow of the ero- sion of thousands of feet of strata between the Knoxville and the Chico periods, thus indicating not a gentle oscillation, but a great uplift. Applied to the quicksilver belt in general the argument ts less precise and indeed negative; for, while an enormous interval of time elapsed be- tween the epochs at which the Knoxville and Chico faunas flourished, it might be possible to find other intermediate groups as well as the Wallala. To account for the conditions except on the theory of a non-conformity, however, it would be essential to find such faunas in beds stratigraphically intercalated between the Knoxville and the Chico, and even such a discovery would not disprove a non-conformity. Now, although the geology of the Coast Ranges has by no means been exhaustively studied, they have been carefully examined at a great number of points by many geologists hold- ing diverse views, and no one of them has ever discovered a trace of fos- siliferous beds stratigraphically intercalated between the Chico and the Knoxville series. It is therefore very improbable that a substantially full series filling the gap between the Knoxville and the Chico exists in any one locality, and mucli more so that this is the general condition and that Mt. Diablo is merely a local exception. The paleontological argument, though negative, is thus so strong as to give to the hypothesis of a great non-conformity between the Knoxville and the Chico a very high degree of probability without any aid from direct observations of non-conformity or from observations on the age of the metamorphosed rocks. A similar argument applies, though with less force, to the relations existing between the Knoxville and the Wallala, for here, too, a long inter- val is indicated between the eras of the respective faunas; but the relations of the Knoxville and Horsetown beds cannot as yet be thus elucidated, be- NON-CONFORMITY BELOW THE CHICO. 195 cause their relative age is not sharply enough defined. Unfortunately, pos- itive structural evidence on this point also is as yet wanting. The evidence of the existence of this important non-conformity may be recapitulated in a few words. The pebbles in the conglomerates of the Wallala and the Chico groups show that metamorphic 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 metamorphism and upheaval of the Knoxville beds must have preceded the Wallala period and there must be an unconformity. Again, the strati- eraphical 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 Téjon or be- tween the Téjon 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— The gold belt of California, as hitherto 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.’ Some years after Mr, Meek had referred the Mariposa beds to the Jurassic Mr. Gabb redescribed Inoceramus Piochii as Aucella Piochii,’ 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-bearing beds of the Coast Ranges must be members of that system, while if these Aucella beds are Cretaceous Au- cella is not a distinetively 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 specifie distine- 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 ; ‘Geol. Survey California, Palieontology, vol. L. 2Tbid., vol. 2. 31. am perfectly satisfied of the existence of this non-conformity, though the localities where the Chico beds have been found resting ou the upturned edges of the anriferous 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 ani are nearly horizontal. The Mariposa beds are almost vertical. _ AGE OF THE MARIPOSA BEDS. 197 but I find no record of any such bed so low as the Knoxville group.’ All the fossils recorded in this position are Chico. This does not, indeed, pre- clude a possibility that the Mariposa beds 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 has been traced in the preceding pages as existing in the Coast Ranges; and, evenif the species of Awcella 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 1s 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 this 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 ‘The shell from Tuscan Springs recorded as Inoceramus Piochii (Geol. Survey California, Geology, vol. 1, p. 207) is redetermined as a Mytilus in ibid., vol. 2, p. 191. 198 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. remainder of the immense thickness of similar and apparently conformable slates." The Knoxville and Mariposa series. Though the beds of the Knoxville and Mari- 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 were published by Mr. Gabb: Belemnites impressus Gabb. Liocitum punctatum Gabb. Paleatractus crassus Gabb. ; Modiola major Gabb. Cordiera mitreformis Gabb. Aucella Piochii Gabb. Atresius liratus Gabb. Rhynchonella Whitneyi Gabb. Ringinella polita Gabb. Pecten complexicosta Gabb. ‘Mr. J. Marcon stated that these schists ‘sont souvent trés rapprochés des veines métalliféres, sans toutefois jamais en renfermer” (Bull. Soc. géologique France, 1883, p. 410). He now accepts without objection my statement that gold quartz veins occur between the slates of the Mariposa beds, and not simply near them. It does not follow, he thinks, that because the Mariposa beds, which in his opinion are Triassic, form an integral portion of the auriferous series, the apparition of gold in the Sierra Nevada is to be put as late as the Jurassic. This, in his opinion, took place not later than the Lower Paleozoic. ‘The extrication of gold from the quartz matrix being due to pressure, naturally gold dust entombed in the Triassic marl of the Mariposa may have been united into small nuggets dur- ing the process of lamination and crushing” (American Geological Classification etc., 1888, p. 37). I must confess myself unable to follow this reasoning. 2The paleontological statements are all on the authority of Dr. White and are in part extracted verbatim from Bull. U. 8. Geol. Survey No. 15, / FAUNA OF THE KNOXVILLE SERIES. 199 Three other species, viz, Ammonites ramosus Meek, Potamides diadema Gabb, and Lima shastuensis Gabb, the types of which Gabb obtained in the Horsetown beds, Dr. White thinks probably, but not certainly, identical with specimens obtained by my party from Knoxville. In addition to these published species the following have been gener- ically recognized among the collections from Knoxville, all the specimens of which are, however, too imperfect for specific determination: Ammonites ?, Margarita ?, Dentalium, Arca, Nuculana, and Rhynchonella. Besides all these forms there are fragments among the collections from Knoxville which indicate two or three other molluscan species not considered in the enumer- ation of the fauna of the Knoxville beds. The specimens which have been referred to as probably representing a species of Ammonites are only a few small fragments, which show only portions of the sides and periphery of the shell. These seem to indicate a species related to the A. Newberryi of Meek. The Dentalium is probably undescribed, as are probably also the Arca and Nuculana. The Rhynchonella is apparently an undescribed species and seems to be identical with one which Dr. White discovered at Horse- town.’ The collection contains only one fragment of a shell which he refers with doubt to Margarita. The specimens of Ammonites which in the foregoing list of published species are referred with doubt to A. ramosus Meek consist only of the small inner whorls, none of them reaching an inch in diameter. The form, surface markings, and septa of the shell, so far as these characters are shown by the Knoxville specimens, seem, however, to agree well with those of the species as it is described by both Meek and Gabb. Meek’s type specimens came from Vancouver Island, but Gabb identified the species in the Horse- town beds of the Shasta group of California.” The specimens of the shell which in the foregoing list are referred with doubt to the Potamides diadema of Gabb are embedded in compact rock, so that all its characters cannot be observed. They are probably identical with Gabb’s species which he de- scribes as coming from the Horsetown beds. Finally, so far as the specific identity of any Belemnites can be determined, there seems to be compara- 1 This form is closely like the R. oxyoplheata Fischer, from the Jurassic of Moscow. 2See Bull. U.S. Geol. Sur. Terr. (1876) No. 2, p. 371, Pl. V, Fig. 1; also, Geol. Survey California, Palxontology, vol. 1, p. 65, Pl. XI, Fig. 13, and Pl. XII, Fig. 120. 200 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. tively little reason to doubt that the specimens which have been found in the Horsetown and Knoxville beds, respectively, and referred to Belemnites impressus Gabb, are specifically identical. Comparing the nineteen species of fossils now known to exist in the Knoxville beds with those from the Horsetown beds, or, in other words, with all the other species which Gabb refers to the Shasta group," it appears that all except six of them are certainly different from any of the latter. One of these six, the Ammonites Newberryi??, offers only a mere suggestion of identity ; four are probably, but not certainly, identical, namely, Am- monites ramosus?, Potamides diadema?, Lima shastaensis?, and Rhynchonella ?; and the specifie identity of one, Belemnites impressus, has been regarded as certain. The fact that the Belemmnites, asa 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 Aucella Erringtonii and A. Piochit 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. He has not only examined the original types of those two forms, but hundreds of other specimens of A. Piochii 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 4. Erringtonii 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 orbiculata of Gabb, others that represent a species of the Pectinide (perhaps the Amussiwn aurium of Meek), and still others which are undeterminable. On adding to these the Belemnites pa- cificus 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” 1Geol. Survey California, Paleontology, vol. 2, pp. 209-254. 2Some of the specimens found in the anriferous slates of the Mariposa estate show more or less distinct, radiating lines, and the same peculiarity has been observed among examples from the Knox- ville beds, as well 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 Aucella and other 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 River, Mariposa County, Cal., 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. We did not obtain any Lelemnites from the auriferous slates, as King and Gabb did, nor has Dr. White seen Gabb’s B. pacificus, obtained from this formation, but not figured. From the description it is supposed to be identical with B. macritatis White,’ obtained by Mr. Dall from Alaska and found associated with an Aucella regarded as of the same species as A. Erringtonti and A. Piochii. That the Mariposa beds and the Knoxville beds are of the same age is considered as proved by the identity of Aucella Piochii and A. Erringtonii, supported by the generat character of the other fossils which the strata of both respectively bear. Itis 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 ‘See Bull. U. S. Geol. Survey No. 4, p. 15, Pl. 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 Aucella, 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 Avucella Piochii 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 Kichwald, 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, Kichwald? recognized all the forms of Aucella which Keyserling had published as oceurring in Russia, namely, A. concentrica Fischer, A. mosquensis von Buch, A. pallasii, and A. crassicollis Keyserling. The last two he considered as only varieties of A. concentrica. Dr. Fischer recognized only one species among Pinart’s Alaskan collections,’ which he referred to 4. 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 Aucella concentrica* Myr. Whiteaves (loc. cit.) recog- nized only one species among the collections from British Columbia, and this he referred to Aucella mosquensis. In the Knoxville beds of California there are two recognizable varieties of Aucella, which are connected more or less closely by intermediate forms, 1 See Trans. Royal Soc. Canada, sec. 4, 1832, p. 34. 2 See Geognost.-palaeont. Bemerkungen iiber die Halbinsel Mangischlak und die aleutischen Inseln, 1871, pp. 185-187, Pl. XVII. 3See Voyage A la céte nord-ouest de VAmérique, par M. Alph.-L. Pinart, pp. 33-36, Pl. A. +See Bull. U. 8. Geol. Survey No. 4, pp. 13,14, Pl. 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 the other variety are smaller, more slender, and have a more delicate appearance. They seem to correspond more nearly with the type of A. mosquensis. 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. mosquensis, A. pallasii, A. crassicollis, A. Piochii, and A. Erringtonii. However, it will be convenient, when discussing the Awcella-bearing 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 is 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," in northern Siberia,’ on the island of Spitzbergen," on Kuhn Island (off the east coast of Greenland),‘ 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 Eichwald’s Geognost.-palaeont. Bemerkungen tiber die Halbinsel Mangischlak und die alentischey Inseln, 1871, p.53. *See Middendorfi’s Reise in den fiussersten Norden und Osten Siberions, vol. 1, part 1, p. 255. ®See Lindstr6m: Om Trias- och Juraférsteningar frin Spetsbergen, Kongl. svensk. Vet.-Akad. Handl., vol."6, No. 6, 1867, p. 14. *See F. Toula, Die zweite deutsche Nordpolarfahrt, vol. 2, 1874, pp. 497-505; also Quart. Jour. Geol. Soe. London, vol. 34, 1876, p. 560. 204 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. The age of the Avucella-bearing 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. 30th Kichwald and Whiteaves contend that all the strata which bear Aucella concentrica 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 Aucella as an exclusively Jurassic genus. Even so late as the year 1884 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 bear Aucella concendrica, as the earlier Russian geologists also did.! Dr. White thinks it not impossible that Aucel/a occurs in the Jurassic in some regions and in the Neocomian in others, just as a number of Lower Carboniferous species of Kurope are found in the Upper Carboniferous of North America and as certain species are known to pass from the Devonian to the Carboniferous. THe 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 Aucella. 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 Aucella, which appears as an appendix to this chapter. — a 1 See Bull. Soc. géologique France, 3d series, vol. 12, 1884, pp. 686-696. HORSETOWN BEDS. 805 The Horsetown beds.— The Ilorsetown beds, as it seems convenient to call the group which occurs near Cottonwood Creek, Shasta County, are con- fined to that locality, so far as known, and their stratigraphical 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- amiued 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 metamorphism 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.’ 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 MKnoxville series. Though the Horsetown 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 ! Geol. Survey California, Geology, vol. 1, p. 321. 206 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, silicified, 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 certainly Mio- cene, for, though we found no fossils ourselves, Dr. White examined ex- Fe g tensive collections of Miocene shells in entirely similar rock made by Rey. 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.’ 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 Aucella 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.” Butshore 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 ‘In answer to an inquiry, Prof. Joseph Le Conte states that his remarks concerning the lower por- tion of the Cascade Range ia Am. Jour. Sci., 3d series, vol. 7, p. 177, were not from personal observa- tion. He there suggested that the Cascades were a continuation of the Sierra. 2U. S. Geol. Expl. 40th Parallel, Systematic Geology, vol, 1, p. 452. THE CASCADE RANGE. 207 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 Rivers 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 20 feet higher, relatively to the land, than it is now.’ 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 the 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 epee ne main structtiral continuation of — the united Coast Ranges and Sierra Nevada to the southward appears to be the peninsula of Lower California. Mr. Gabb,’ 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 “Prof. Coe rayon nny traced from ioe er California to Alaska the terraces which line the western coast (Proc. California Acad. Nat. Sci., vol.5, p.90). 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 at 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. 2Geol. Survey California, Geology, vol. 2, appendix, p. 187. 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 to justify any extended speculation on this subject. Pre-Cretaceous upheavals and metamorphism.— [wo important areas of serpentinized 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 erystalline 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 question therefore at once arises whether their upheaval and metamorphism are ascribable to the same period as the uplift and alteration of the Mariposa and Knoxyille 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- eal 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 Pacifie 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 ouward, 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 X11I——14 210 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. posing at least a partial separation of these areas during 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?! and his colleagues, who were led to infer the existence of a conti- nental area during the Paleozoic west of longitude 117° 380’, 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- LU. S. Geol. Expl. 40th Parallel, vol. 1, Systematic Geology, p. 534. ; THE COAST RANGES AND THE SIERRA. PALL 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 has already been 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 about 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- tinectly 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 jest before the beginning of the Chico, admitting the ocean over a great part of the Coast Ranges and over Pile, QULCKSILVER DEPOSITS OF THE PACIFIC SLOPE. considerable areas at the base of the Sierra. Both appear to have risen partially and gently before the Téjon, 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 Téjon 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 haye 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.—Ihere seems every reason to suppose that tne upheaval of the Knoxville and Mariposa beds was substantially con- temporancous 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 Gault. This, however, is more probable than the alternative hypothesis, for the limited occurrence of the Horsetown beds seems to indi- WALLALA BEDS. 213 eate that an uplift, though possibly a gentle one, occurred between the Neocomian and the Gault; so that, if it should prove that the Horsetown beds were involved in the metamorphism, there were probably two distinct uplifts between the Knoxville and the Wallala, and of these the later must have been much the more violent. his appears less likely than that a single great movement took place at the close of the period characterized by the presence of Aucella and prior to the Gault. The Wallala series —Along the coast in Sonoma and Mendocino Counties, from a little below It. Ross to beyond the town of Gualala or Wallala,} 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- ceranus, 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: Coralliochama Orcutti (gen. et sp. nov.). Trochus euryostomus, 0. sp. Nerita — ?. 1 The name of this town and of the river which there empties into the Pacific is variously spelled Gualala, Guadala, Walhalla, and Wallala. It is of Indian origin, and 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 eyentually be adopted on maps of the Coast. 214 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Cerithium Pillingi, v. sp. Cerithium totium sanctorum, n. sp. Solarium wallalense, n. sp. The collection from Mendocino County included the first and the last of these and also imperfect specimens of an Inoceramus about a foot in length, Ostrea, Pecten, and Turritella. Dr. White believes this fauna to indicate the middle Cretaceous and in some respects it reminds him of the Gossau.! 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.” 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-T¢jon 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. ? The branches of bushes growing close to croppings of these sandstones often wear grooves into the rock which are sometimes as much as three inches in depth. CHICO-TEJON SERIES. 215 New 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 Téjon 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 Cation, 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 Téjon 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 Téjon and Miocene any fossiliferous strata or any barren strata which might represent an interme- diate age, for Messrs. Whitney and Gabb, regarding the Téjon 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 Téjon conformable here, as they usually are elsewhere, and traced the fossiliferous Téjon beds so close to the fossiliferous Miocene beds as to leave no room for an intermediate series. The age of the Chico-Téjon series has been much discussed. Conrad first determined fossils from the Téjon which were collected by Prof. W. P. Blake near Ft. Téjon.' Of these specimens Conrad wrote: “The Eocene period is unequivocally represented by the beautifully perfect shells from the Canada delas Uvas.” Either through a misunderstanding or a difference of opinion these are referred to in the reports of the State survey asa “‘tew imperfect fossils.”? Conrad repeatedly reasserted, but never retracted, his i Pacific Railroad Reports, vol. 5, p. 315. 2Geol. Survey California, Geology, vol. 1, p. 191. 216 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. view.’ Gabb* vigorously maintained the Cretaceous age of the Téjon in his contributions to the State geological reports and elsewhere Prof. J. D. Dana considers the Téjon as probably Lower Eocene and gives a list of the Téjon genera to show the Tertiary character of the fauna? Prof. Jules Marcou asserts the Tertiary character of both the Chico and the Téjon on paleontological and apparently on lithological grounds* Prof. Angelo Heil- prin, who has charge of Gabb’s types, has ably reviewed the Téjon ques- tion and pronounces emphatically for its Eocene age’ Finally, Dr 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 Téjon dis- tinetly 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 Téjon 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 Eu- 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 1 Am. Jour. Conchol., vol. 1, 1865, p. 362; ibid., vol. 2, 1866, p, 97; Am. Jour. Sci., 2d series, vol. 44, 1867, p. 376. ?Am. Jour. Conchol., vol. 2, 1866, p. 87; Am. Jour. Sci., 2d series, vol. 44, 1867, p. 226; Proc. California Acad. 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. 8. A., 1876, p. 387; Bull. Soe. gévlogique France, vol. 2, 1883, p. 407. 5Proc. Phila. Acad. Sci., 1882, p. 195; Contributions to the Tertiary Geology and Paleontology of — the United States, 1884, p. 102. CHICO-TEJON SERIES. PINT 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-Téjon series. In correcting their opinions Dr. White and I have simply taken advantage of the advances which geological sci- ence has made since their day. Dr. White sums up the evidence as follows: ' 1 The Maestricht, Faxoe, and other beds of Europe, although they are intermediate between the Upper Chalk and the Eocene, are too closely related by specifie and ge- neric forms to the Chalk to be regarded as separate from the Cretaceous proper. Their faunal 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 New 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. I think the evidence which has been adduced to show the Eocene age of the upper or Téjon portion of the Chico-Téjon series is as conclusive as any evidence of that kind can be. Now, 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 Téjon 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.? An examination of the figures and descriptions of the fossils which Mr. Gabb has referred to the Chico group, together with his catalogue of California Cretaceous fos- sils,? 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 one or two Mesozoic types of cephalopods pass up from these strata into those of the Téjon portion does not necessarily prove that the latter ought also to be 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. 8. 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. 209-254, for the catalogue. 218 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE, Thednutimate relation to each other of all the strata of this great Chico-Téjon 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 toa 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 Téjon 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 Téjon 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 Téjon and the Miocene.'’ 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 unusuaily 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— The Pliocene of the Coast Ranges is of very 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, and it may be added that still later uplifts further confuse the structure of the Coast ' Since this memoir was anerehied Mr. ap ives ou states that he has ceed 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°." The same upheaval was felt thoughout western Oregon, where it had the same comparatively gentle character as in the Coast Ranges. Pliocene and Post-Pliocene 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,? 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.’ These beds appear to have a great thickness when meas- ured perpendicularly to the dip, which varies from 10° to 40°, and the up- ‘King: Op. cit., p. 455. 2 This occurrence is referred to by Professor Whitney, who discovered no fossils in it (Auriferous Grayels, p. 23). 3 See page 64. 2290 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. wahlamatensis. 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 M1. 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 ereat periodical variations in the quantity of sediments emptied into it. In Mr. Stearns’s opinion this shell imphes 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 FRESH-WATER PLIOCENE. 22 from living specimens from the modern Clear Lake. A third abundant species is Bythinella intermedia Tryon. 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 abditum Hald., is not perfect enough for specific identification, There are several similarly imperfect specimens of /elisoma ? anmon Gould and an imperfect Physa, which is either P. gyrina or P. heterostropha. 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. O. 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 aboye, 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.—'T'he 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 conelusion 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- yacmas 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 Pinos. 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. Pisgah 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-T¢jon 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-Téjon 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 back 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. 2a now rests in places upon the older fresh-water strata. The beds immediately below the andesite 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. In 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 voleanic 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 OF 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! 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 vi0- 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 peinted out on a preceding page, 1 Professor Whitney’s parties met with no yoleanic rocks in the Coast Ranges proper northward from Clear Lake. “ORE DEPOSITS. 229 are probably far older The distribution of voleanic 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 1s sufficient to say that ore deposition has taken place only since the earlier voleanie eruptions and seems in all cases to have been brought about by heated solutions of voleanie origin. Cinna- bar oceurs 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 xluI——15 APPENDIX TO CHAPTER V. REMARKS ON THE GENUS AUCELLA, WITH ESPECIAL REF- ERENCE TO ITS OCCURRENCE IN CALIFORNIA. By CuHarues A. WHITE. The fossil shells of the genus Auwcella, although presenting no features which especially attract the attention of the ordinary observer, haye come to possess unusual interest in certain fields of paleontological 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 Aviculidie, the family to which Aucella be- longs, are not so clearly definable and distinguishable from one another as conld 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 Awcella 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 Aviculidx, 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 iofolded 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 in 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 they are of course found to be without the transversely grooved hinge area and prismatic shell strueture which characterize Inoceramus. The genus Aucella has 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 in 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! and the other in the proy- ince of Sergipe, in Brazil.2 In both these eases the recognition of the genus has not been so complete and satisfactory as could be desired, because of the imperfection of the only speciinens 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 von Zittel seem to have been few as well as imperfect and in 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 Aucella under various specific names. The geographical distribution of Aucella in the northern hemisphere is cireumpolar, 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 in 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,’ when it was referred to the genera Inoceramus aud Mytilus, and afterward in Petschora Land,! when Keyserling proposed the generic name by which itisnow known. Subsequently it was discovered upon the eastern shore of the Caspian Sea,’ in northern Siberia,’ upon Nova Zembla,’ Spitzbergen® and Kuhn® Islands (the Palaeont., p. 32, Pl. VIII, Figs. 4, a, b, ¢. 2C, A. White: Contribuigoes a Palaeontologia do Brazil (in both Portuguese and English), Archivos do Museu nacional do Rio de Janeiro, vol. 7, p. 56, Pl. ILI, Figs. 11, 12, and 13, 3 Fischer De Waldheim: Oryctographie du gouvernement de Moscou, p.177, Pl. XIX, Fig. 5.and Pl. XX, Figs. 1, 2, and 3. 4A, Keyserling: Wissenschaftliche Beobachtungen auf einer Reise in das Petschora-Land, pp. 297- 301, Pl. XVI, Figs. 1-17. 5E. Eichwald: Geognost.-palaeont. Bemerkungen tiber die Halbiasel Mangischlak und die aleut- ischen Inseln, p. 53, Pl. VI, Figs. 10 and 11. 6 Middendorff: Reise in den iiussersten Norden und Osten Siberiens, vol. 1, No. 1, p. 255. 7S. A. Tullberg: Bihang till kongl. svensk. Vet.-Akad. Handl., voi. 6, pp. 1-24, Pl. Il, Figs. 9-18. 8G. Lindstrém: Om trias- och Juraférsteningar fran Spetsbergen, Kong. svensk. Vet.-Akad. Handl., vol. 6, No. 6, p. 14, Pl. IL, Figs. 3 and 4. 9F. Toula: Die zweite deutsche Nordpolarfahrt, vol. 2, pp. 497-505; also, Feilden and de Rance: Quart. Jour. Geol. Soc. London, vol. 34, 1876, p. 56. 10F, Stoliczka: Pal. Indica, vol. 3, p. 404, Pl. XXIII. 228 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. in Alaska,! British America,? and in various parts of California.? In the latter region the first-discovered examples were referred to the genera Inoceramus and Lima, re- spectively, and their relation to the Awcellas 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 circumpolar 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, 1s so great that no less than nine specific and several varietal names have been proposed by different authors who have studied them. The 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 mollusk, 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 are 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 for 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- ischen Inseln, pp. 185-187, Pl. XVII, Figs. 1-17; P. Fischer: Voyage ala céte nord-ouest de Amérique, par M. Alph. Pinart, pp. 33, Pl. A, Figs. 4and5; C. A. White: Bull, U.S. Geol. Survey No. 4, pp. 10- 14, Pl. VI, Figs. 2-12. 2 J. F. Whiteaves: Proc. Trans. Royal Soc. Canada, vol. 1, 1883, p. 54. 3W.M. Gabb: Geol. Survey California, Paleontology, vol. 1, 1864, p. 187, Pl XXV, Fig. 173; ibid., vol. 2, 1868, p. 194, Pl. XXXI, Fig. 92; Proc. California Acad. Nat. Sci., vol. 3, i885, p. 173; F. B. Meek: Geol. Survey California, Geology, vol. 1, 1865, p. 479, Pl. I, Figs. 1-5; C. A, White: Bull. 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, I 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 Aucellas 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 been 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,! but this does not fully meet the broader question of cireumpolar and st il] 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- mains 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 Awcella-bearing 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 thinkour present knowledge of 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 Cretaceous, and there are apparently good reasons for believing that such was really the case. The genus Aucella has been regarded by the majority of authors who have written upon it as diagnostic of the Jurassic age of the strata which bear if; but certain authors whose opinions are worthy of consideration are equally confident that all sueh strata should be regarded as of Neocomian age. Professor von Zittel refers his A. plicata from New 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. brazilien‘is, is from strata that I have referred to the Neocomian and there seems to be no possible reason to question the Cretaceous age of the Indian species described by Stoliezka, It is Professor Eichwald more especially who has contended for the Neocomian age of the Aueclla-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 Aucella-bearing strata of British Columbia. In California, although a part of the strata which bear Aucella have been referred to the Jurassic, those which bear 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. | Bull. Soe. géologique France, 3d series, vol. 12, 1634, pp. 686-696. 230 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. We do not yet know enough of the general geology of Alaska to speak confidently of the stratigraphical relations of the Auwcella bearing strata there; but there seems now to be no reason to doubt that all such strata in other parts of western North America ought to be referred to the opening epoch of the Cretaceous. I do not think, however, that the question of the exact geological age of these strata is of great im- portance in this connection, but no reasonable doubt can be entertained that a large proportion of the discoveries of Aucella have been made in strata of unquestionably Cretaceous age. Tn the year 1864 Mr. William M. Gabb published specimens of Aucella from two separate localities in California and, as was then supposed, from two separate forma tions. The first of these was published under the name of Znoceramus Piochii! and the other under the name of Lima Erringtonti.2. The first-mentioned fossils were afterward published by him as Aucella Piochii,’ and Mr. Meek afterward republished and illustrated the others under the name of Aucella ErringtoniiA Mr. Gabb never doubted the Cretaceous age of the first-mentioned forms; but it seems that he regarded the strata from which came his Lima Erringtonii as of Jurassic age. Mr. Meek agreed with him in this respect, as did also other authors. Upon an examination of the collections made in California by the division of the U.S. Geological Survey in charge of Dr. Becker, which were submitted to me in 1884, I became satisfied that the Aucella Piochii and A. Erringtonii of Gabb belong to one and the same species and that that species was no other than the one which had long been known under the various names of A. concentrica, A. mosquensis, A. pallasii, A. crassicollis, ete. (see Bull. U. S. Geol. Survey No. 15, p. 23). As Aucella Erringtonii was obtained from the auriferous slate series in California, this conclusion of course involyed the opinion that at least a part of that series is equivalent to the Knoxville division of the Shasta group, and therefore of Creta- ceous age. This conclusion was supported by the personal discovery in the auriferous slates of the Mariposa estate, in company with Dr. Becker and his assistant, Mr. Turner, of specimens of Avucella that are plainly identical with the A. Piochii of Gabb, which is found abundantly in the Knoxville division of the Shasta group. These and other facts bearing upon the relations of the Avzcella-bearing strata of different districts in Cali- fornia are discussed by myself in Bulletin No. 15 of the U. 8S. Geological Survey and by Dr. Becker in Bulletin No. 19. So far as I am aware, no other forms than those mentioned in this article are properly referable to the genus Aucella. It is plain that neither the A. contracta nor the A. impressa of Quenstedt belongs to this genus.° Itis also evident that the greater part of the species which Stoliczka ranged under the genus Aucella were not intentionally so placed by him.® EXPLANATION OF THE PLATES AND COMMENTS. In the foregoing paragraphs I have expressed serious doubt whether more than one clearly definable species of Aucella is yet known, at least in the northern hemi- 1 Geol. Survey California, Paleontology, vol. 1, 1864, p. 187, Pl. 25, Figs. 173, 174. 2 Proc. California Acad. Nat. Sci., vol. 3, 1868, p. 173. 3 Geol. Survey California, Paleontology, vol. 2, 1869, p. 194, Pl. 32, Fig. 92, a, b, e. ‘Geol. Survey California, Geology, vol. 1, 1865, pp. 479, 480, Pl. I, Figs. 1,2, 3,4, and 5, * Der Jura, p. 501, Pl. 67, Fig. 2, and p. 582, Pl. 73, Fig. 47. > ®Pal. Indica, vol. 3, index, p. 513. MONOGRAPH XIII PL w i w REMARKS ON THE GENUS AUCELLA. 231 sphere, with perhaps the exception of the species from southern India. 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, whieh is finally recognized as the true one. But Ido 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 Aucella. 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 Pl. III are mostly copies of those which represent the different forms that have been recognized in Europe, together with those from southern India, New Zealand, and Brazil. Those upon Pl. LV 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. Fic. 1. A copy of Keyserling’s figure of Aucella concentrica, from Reise in das Petschora-Land, PI. XVI, Fig. 16. Fics. 2and 3. Copies of Keyserling’s figures (loc. cit., Figs. 13 and 14), representing 4. concentrica var. sublevis. Fics. 4 and 5. Copies of Keyserling’s figures of 4. crassicollis (loc. cit., Figs. 9 and 11). Fics. 6, 7, and 8. Copies of Tullberg’s figures of A. mosquensis, from Nova Zembla (Bihang till kongl. svensk. Vet. Akad. Handl., vol. 6, Pl. If, Figs. 16, 17, and 18). These figures are regarded by Tullberg as representing the form which Keyserling gave as the type of 4. mosquensis. Keyserling tig- ured only the right valve of one example, and, as the left valye was not illustrated, several authors be- sides myself have hitherto regarded 4. mosquensis 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. Frc. 9. A copy of one of Keyserling’s original figures of his 4. pallasii (loc. cit., Fig. 4). The ra- diating lines shown on this figure are often, but uot 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. 8. National Museum from the vicinity of Moscow. It appears to belong to the form 4. pallasii. Fras. 12 and 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 4. pallasii, although some authors would probably regard it as quite as near to d. mosquensis. This uncertainty of specific recognition by 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 16. Copies of Professor yon Zittel’s figures of his 4. plicata from New Zealand (Reise der dsterreichischen Fregatte Novara, Geol. Theil, vol. 1, part 2, Paleont., p. 32, Pl. VIII, Figs. 4, a, }, ¢). Figs. 17 and 18. Copies of original figures of A. braziliensis White (Contribuigdes & Palaeontologia do Brazil, Archivos Museu nac. do Rio de Janeiro, yol. 7). The narrow, rough seam along the middle of the figure is a mineral vein, and not a natural feature of the shell. Fics. 19 and 20. Copies of Stoliezka’s figures of his 4. parva (Pal. Indica, vol. 3, Pl. XXXII, Figs. 2a and 3). PLATE IV. Figs. 1 and 2. Copies of Gabb’s original figures of his Inoceramus { Aucella] Piochii (Geol. Survey, California, Paleontology, vol. 1, Pl. XXV, Figs. 173 and 174). 232) QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. fies. 3, 4, and 5. Copies of Gabb’s subsequent figures of Aucella Piochii (Geol. Survey California, Paleontology, vol. 2, Pl. XXXII, Figs. 92, 92a, and 92b). fies. 6, 7, 8, 9, and 10. Copies of Meek’s figures of Aucella Erringtonii (Lima Erringtonii Gabb) (Geol. Survey California, Geology, vol. 1, Figs. 1, 1a, 2, 2a, and 5e). The radiating linesshown on thcse specimens seem to have been somewhat exaggerated by lateral pressure. Figs. 11, 12, 13, 14, and 15. Copies of the author’s figures of specimens from Alaska, published in Bull. U. S. Geol. Survey No. 4, Pl. VI, Figs. 2, 3, 8, 9, and 10. Fies, 16 and 17. TWo views of a remarkably ventricose left valve from the Knoxville division of the Shasta group near Knoxville, Cal. Figs. 13 and 19. Lateral views of two left valves from the Knoxville division of the Shasta group near Knoxville, Cal. These examples have suffered no lateral pressure, but the radiating lines have been made a little too distinet by the artist. Fie, 20, A right valve from the same locality. Fig. 21. A left valve from Washington Territory, collected by Prof. Thomas Condon. These figures of North American specimens of Aucella show, if possible, a greater range of variation than do the figures given on P]. III. The forms known by the specific names of concentrica, pallasii, and crassicollis, respectively, are readily recog- nizable among these figures of American Aucellas. There is, however, one form among them which has apparently not been recognized outside the limits of North America, and yet it is probable that it exists elsewhere. Figs. 16 and 17 represent an extreme example of this form or variety from California and Figs. 14 and 15 repre. sent a less pronounced example from Alaska. On the other hand, the form which Tullberg figures as A. mosquensis, of which Figs. 6, 7, and 8, Pl. III, are copies, does not appear among the North American forms which are here figured, and it is probably rare in North American strata. Figs. 4, 13, and 21 may be taken as representatives of the form A. crassicollis, and yet in each case the specimens represented by these figures were found com- mingled and embedded with other forms. Figs. 6, 7, 8, 9, and 10 are apparently referable to the form A. pallasii, as represented by Fig. 9, on Pl. III. Figs. 18, 19, and 20 ought probably to be regarded as varieties of that form, although there seems to be quite as much reason for referring them to A. mosquensis. The radiating lines which appear upon some of these figures, as well as those of some European examples, are oftener seen upon the form A. pallasit than upon the other forms; but such markings are not exclusively confined to,any one form. There is also much difference observable in the strength of the concentric markings of all the forms; but this cannot be regarded as even a varietal character. Many of the specimens appear unnaturally smooth, because of the fact that a large part of the examples discovered are casts of the interior of the shell, the test itself having been destroyed or removed. U, 5. GEOLOGICAL SURVEY YOGRAPH XIII PL. IV AMERICAN FORMS OF AUCELLA CHAPTER VI. DESCRIPTIVE GEOLOGY OF THE CLEAR LAKE REGION. {Atlas Sheet LII.] General character. Clear Lake is an irregular and picturesque sheet of water, lying at an elevation of 1,310 feet* in the heart of the Coast Ranges. Many of the surrounding hills rise to an elevation of about one thousand feet above the level of the lake, but the dominant feature of the scenery is the prominent mass of Konocti (or Uncle Sam), the summit of which, as measured by Mr. J. D, Hoffmann, stands 2,936 feet above the lake at high water (March, 1884). Konocti is a group of volcanic cones considerably eroded, but retaining clear traces of its original form, to which it approxi- mates as nearly as do Mt. Shasta and Mt. Hood. Like those mountains, too, it is composed of andesites of the group called asperites in-a preceding chapter and is probably of very nearly the same age. The peaks are rocky and the declivity toward the remarkable basin of Little Borax Lake is precipitous. The eastern flank also is steep and the rock is exposed to view over a wide area. Here it is scored with three sets of concentric lines, which sweep across the mountain side in graceful curves and mark series of bedded flows of the lava composing the mass. The lower portions of Konoeti and a very large proportion of the ranges of the district are densely clothed with brush, chiefly dwarf oaks, chamisal, and manzanita. These remain green throughout the summer and mitigate the impression of drought which the scenery in general creates. They also afford a refuge 1 Petermined by Mr. R. K. Nichols for the Clear Lake Water Company. 2 See my paper “On the geometrical form of volcanic cones,” Am, Jour. Sci., 3d series, vol. 30, 1885, p. 283. 233 234 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE, for numerous deer and other wild animals, but neither the topographer nor the geologist can contemplate these smooth, green surfaces with any sat- isfaction, for the brush is often impenetrable for men or horses, while the matted roots and accumulated mold seldom allow an inspection of the underlying rock. The growth of the brush seems capricicus and is not altogether dependent on either the exposure or the soil, for often a portion of a slope is densely covered with brush while the remainder is wholly free from it. The distribution, however, is probably governed to a great extent by the amount of moisture, for the southern exposures are much less often obstructed than the northern ones. The valleys, on the other hand, are usually free from brush and, like a portion of the hills, are studded with fine oaks, growing as a rule at distances of one or two hundred feet from one another and often as pieturesquely disposed as if set out by a skillful landscape gardener. This portion of California is full of mineral springs, and Clear Lake possesses its share, of which the warm chalybeate rising through the waters of the lake at Soda Bay is the best known and, with the charms of scenery, yearly attracts a number of visitors. Of more scientific interest are the two borax lakes—pools without outlets—in which borax has concentrated and accumulated to such an extent as to have yielded a large quantity of this salt to commerce. But by far the most remarkable locality in the region is the Sulphur Bank, where extremely hot springs and large accumulations of native sulphur were long ago known to exist. When this sulphur came to be exploited it was found that underlying and in part mingled with it there were large quantities of cinnabar. As may be seen from Chapter I, the production of quicksilver at this locality has reached a large total, though it has not proved the almost inexhaustible source of supply it was once supposed to be. Geologicai map—The Sulphur Bank lies at the extreme northwest limit of the area investigated by Professor Whitngy and his assistants, and its gen- eral geological relations were so little known at the time when this investi- gation was undertaken that it was found indispensable to a clear understand- ine of the occurrence of ore to submit a district of considerable size to ex- to} amination. The oldest rocks in the neighborhood of Clear Lake belong to MAP OF CLEAR LAKE. 235 “= the Knoxville group. They occupy the greater portion of the surface and are in great part highly plicated and metamorphosed or silicified. On this foundation rest Chico-Tjon beds, Pliocene strata, and volcanic rocks, with the last of which are associated the quicksilver deposits. The distribution of the rocks is shown on the recounaissance map (Atlas Sheet III). The topography of this map was not prepared for the Survey, the necessity for the examination of so large an area not having been apparent until the detailed examination of the Sulphur Bank had begun. It was compiled by Mr. C. F. Hoffmann from the published work of the former State geological survey, from plats in the surveyor general’s office, private surveys by Mr. R. K. Nichols, of Lower Lake, the detailed map of Sulphur Bank prepared for this volume, private notes of the compiler, and a little supplementary work by Mr. J. D. Hoffmann. While it makes no pretension to the detailed accuracy of the special maps prepared by the geographical division of the Survey, it represents the country fairly well, perhaps as accurately as the present needs of this section of the State de- mand. The geology is represented upon it as minutely as the character of the map will permit, preference of course being given to the indications of the topography rather than to the bearings of known points wherever there was a slight discrepancy. The data are on record for still more accurate plotting, should the preparation of a detailed map ever be undertaken. The Knoxville series.— No fossils of the Knoxville group were discovered in the immediate vicinity of Clear Lake, but the series was followed almost without a break to the Manzanita mine on Sulphur Creek, Colusa County, where Aucella concentrica and Rhynchonella Whitneyi ave abundant. The lithological character of the altered rock of Clear Lake, its structural pecu- liarities, and its relation to the Chico-Téjon series, when compared with those of fossiliferous occurrences elsewhere, all indicate beyond any rea- sonable doubt that it belongs to the Knoxville group. The Knoxville beds of the Clear Lake region have undergone very violent disturbances. A great deal of time and pains were spent in a sys- tematic investigation of the dips of these rocks in the area shown on the map of Sulphur Bank for the purpose of constructing sections, but this was found wholly impossible. The entire mass has been shattered, and the 236 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. blocks are very frequently so displaced that there is an utter discordance between the various dips observable in a single cropping of a few feet in diameter. That there may be predominant faults (Daubrée’s paraclases), as well as the innumerable piesoclastic fissures, is not improbable ; but between the extreme disturbance shown by the exposed rock and the proportion of the surface covered by soil this could not be determined. Only one result was obtained by the study of dips. his is, that the ridges are mainly synclinal folds, so that the prevalent dip of the Knoxville beds is into the hills. This result is not unimportant, because it shows that the region is deeply eroded and establishes another point of resemblance between the rocks of this group here and elsewhere. The degree of metamorphism of the Knoxville beds of Clear Lake varies greatly. Some of the sandstones are extremely little altered and are characteristic micaceous arcose. Granular metamorphies, glaucophane schists, and serpentine also occur; but the transitions are so frequent and seemingly so capricious that it would be impossible to define the different varieties by areas. Fic. 5. Ruptures produced by compression of strata. Structue of the ranges. —T'he regularity of some of the ranges is in strong contrast to the irregular disposition of the strata and is possibly due to the combined effect of plication and metamorphism. If a series of beds is thrown into folds, as in the accompanying diagram (Fig. 5), it is clear 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 synelinals. If metamorphism is then induced by rising waters holding mineral matter in solution, such as silicie acid, the compressed under surface of the anti- clinal will offer a resistance to percolation, while the fractured under sur- CHICO-TEJON SERIES. 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 the relief and the fractured surface of the anticlinals tend to their degradation, but the resistance of the synclinals will be increased by the silicification 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 metamorphism alone influenced the course of degradation.! The Chico-Téon series. —'Toward the southern end of the map the Chico-Téjon series 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 ouly mineral which will long retain the form of pebbles. Concretions are common in these rocks, oceasionally 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-Téjon 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-Téjon series does not come in contact with the metamorphic rocks in such a way as to demonstrate a non-conformity, alluvium and lava intervening on the surface; but the sudden change in lithological character and the comparatively trifling disturbance of the unmetamorphosed rocks 'See Dana, Manual of Geology, p. 750. 238 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. are sufficient to suggest a non-conformity. When this relation has 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 Téjon (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 Chico-Téjon 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 asmall 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 lithological 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 sand 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 prevaient 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 ITI. 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 uaable either to comprehend this or to ignore its significance. There is 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 the 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 Lake 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 Pacifie 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 Anodon, 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 has 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. This consists in depositions of ecalea- reous matter, silica, and ferric hydrates, apparently through the action of hot springs or of water heated by contact with the voleanic 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 has been pointed out, the identity of the shells in the two and other circumstances MON XUI——16 942 QUICKSILVER DEPOSITS OF TilK 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 eruption 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 andesitic 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.’ The lamin 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 voleanic. Where heavy masses are cut through, columnar structure is sometimes seen. It is 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. Elcte the obsidian and pumice are interbedded with the porphyr ritic ande- ‘Tn Geol. Survey California, Geology, vol. 1, p. 96, Professor Whitney states that, as seen from the opposite side of the lake, Uncle Sam appears to be made up of a closely folded, synelinal mass, prob- ably of somewhat metamorphie Cretaceous sandstones. This impression he certainly received from the exnosed edges of these flows. In Auriferous Gravels, p. 23, this mountain is correctly mentioned as voleanic. ASPERITE. 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 eut 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 andesitie 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 Kelseyville, 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 volea- 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— [xcepting the 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 altered Cretaceous strata appear under the voleanie rock at the ex- tremity of Elgin Point (“Snake Rocks”) and at Bailey Point. The pres- ent topography of the country between Konocti and Thurston 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 voleanie 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 andesitie 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 tm] MINES IN ANDESITE. 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 voleanic 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, even 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 forins 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 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 suft- 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. 247 Sulphur Bank, on Indian Island, on Red Hill, and west of Lower Lake contorted masses of lava remain on the surface, where they chilled after oozing from yents 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 voleano now active is very faraway. 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. clear 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 would 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 insuff- 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 orographical causes haye 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 sucha 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- ination 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, CHANGES OF SURFACE. 249 separated from the beach by a few feet of open water. Even when the lake is ina 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 PACIFIC 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. 8. 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. 8S. 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.] Sedimentary rocks of the 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 metamorphism. 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- 251 252 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-Téjon 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. Basatt—T'he only voleanic 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 3ASALTIC 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 Svlphur 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 southern half of the small basalt area in which it lies, including 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 cuis, with little regard to system. Its 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.—T'o 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 isa 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 voleanic 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.’ 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 hydrosulphurie acid is evident from the smell. The formation of sulphur and sulphuric acid from hy drosulphuric acid by oxidation is one of 1 These eiciied roots ai ane fae ae PRED bear a strong Pesamiiance to Caulinites, and my specimens, in the absence of sufficiently full information, have been described and figured by Mr. Leo Lesquereux as a new species of that genus (Proc. U.S. Nat Maus., 1837, p. 36). SULPHUR 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 thermo-chemical standpoint, for the reaction H?S + 40= H’SO! liberates 201,500 calories and H’°S+ 0=H°O-+58 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- een is deficient, as it must be a short distance from the surface, a single atom of oxygen by combining with 4H°S to {H°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 suftocatingly strong, even at some distance from the Hermann shaft. The sulphurous acid undoubtedly comes up with the other voleanic 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 inerustations 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 chiefly effected by the sodium carbonate brought up in the hot 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 68) 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.* 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 ! Text Book of Geology, Ist ed., Fig. 86. 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 shatt 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- nabar. The cinnabar in these cases has crystallized on the rock fragments, exactly as quartz often does, and frequently leaves hollow inclosed spaces.’ 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 ‘See an illustration of such a specimen in Le Conte and Rising’s paper on this locality (Am. Jour. Sci., 3d series, vol. 24, 1882, p. 29). 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. Solfatarie 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? ...... .--- .-- 225 enon ---- 2 epee ene e noe = 89. 34 Hydrogen sulphide, H°S ..--..---..------- -- -2-220 +--+ eee eee 0. 23 Marsh gas, CH* ...... 220-2 -- 2-2 oe wen ne nn ee on wn on sn en ee 7.94 INitropeny IN soon cemceclece ea ane ais alae sameeren lalate 2.49 Motaleomeee ewes ee ERO SOS NCES oSSpSSascSe 100, 00 ¢ HOLT 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 shows only BOC. 16° B).- 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 any 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 zine, 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 © rue, 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 1 believe has received no name.! 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. J. Sterry Hunt desiring to mention this mineral in his classification, I suggested metastibnite (Proe. Am. Philos. Soc., vol. 25, 1888, p. 163). 344 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. is manifestly of variable composition. The following figures give the results: 1g I. | Grams. Grams. WATER SO) JT 01) CSG es Bee enc secon ascrosncs = sad 1, 021. 0000 | 3, 403. 0000 Golde eae a eee na ile ane ee 0.0009 | 0. 0034 Sikwer <5: <.5.. 325-5 505-cs eeeenee eee 0. 0024 Sulphides of arsenic and antimony ..................--5 4, 2725 ORES AT STEAMBOAT SPRINGS. . 345 Another sample (IV) from the same crevices which contained ITI, but from a point at which steam and sulphureted 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 as silicates, sulphides, sulphates, carbonates, chlorides, borates, and to a small extent as phosphates. Specimen V was from one of the springs which had formed « 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, cesium, 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 be 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, arsenic, antimony, much iron, aluminium, a trace of cobalt, mag- nesium, calcium, and of course alkalis. The bases were combined as silicates, carbonates, 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 mereury 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 tae 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 ease 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 83° C. In collecting the water in this manner a very inter- esting fuct 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 organie 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. ‘I'he 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 yellow 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 ihe water : Analysis of Steamboat Springs water. [Contents of 10 liters in grams.] DLL Ca SL Os Meee Re ae ee one aa eset ee or ie cs 3. 1065 Carhonidioxide, CO2=5, s-aeeeeena-apinseia< sess B Gas scuBos ace 1.7759 Borresamby anid orbs? Ostet se este aaa laels sielalalst c= ale leetatain sp aatatet <1 2.1741 Sulphumcranhydride SOF seen ese a see cnet eee 1. 0339 Eyposulphurous;anhydride;(S?O7 22 o-) cen <= oes SoeEoa 0. 0052 Ohiloninest Clbsee Meer ce anaicide sce ses eereciceice cece areseaete- 9, 5243 Antimonious anhydride, Sb?03.-.--...---. ..---..--.-----:-- 0, 0051 ATSenlousranihy dricle:eAs? Os emes ae seme ase a toile sen aninisaiel ia o> 0, 0357 Bhosphoricsanby rides 2 OS) 22a eases ciem nas anise sass ces 0. 0063 WYRE MOO Sele WEIS Rees ene coones poSenondedeSnHeses Trace PAU TA TIRETI UAL Ot ape ntaere a S craintaratel cisieleteaeepeimiaie stata\n ajay aia avalistefeleicis 0. 0025 MerrousOxides MEO reac one ceseneseeccwetiswsce cecwen actis sous 0, 0018 IWiwet®y CROs HoGces paddannd scocehcd neo endOo Se SODOARBABaCa Baas 0, 0958 WIG RATGSTE) NOY Ae 65-58 pie SciS6 (CSCO COC ROBOO SES ONDA SONESeErr 0. 0047 Sloysl, MHC) oSqdbGase. oebaneconoss CHE oso Goan acousboseeeaeced 9, 1929, TERN, FORE O)E. baicic GAR See OGe roel aaa ee 0.1541 IBD TABS Ke Obreaeate sama stan ate rae eet aie it= cela <\n'e'aie aielaialele 1. 2460 Cesium and rubidium oxides, Cs?O, Rb°O .-.....---..--.-.-. Trace The exesium 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 ata 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 hypesul- 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 sulpharsenide 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 quadrisilicate 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 3, 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 compute its 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 Hes, nNa’S. The value of x 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 carbonate, FeCO*.......--. Hes ceesecs celucsaee. sscep's 0. 0029 Magnesium carbonate, MgCO3........-....-----.------------ 0, 0099 @alcieiecarbonate, CAC Osi eco occas ccce es scwces ceae seceieacs 0. 1577 Calcic phosphate, Ca%P?0® ...--. .....----- -------2---------- 0, 0137 IS Mee ee Ge IM 0) le Seon cose hocedo canbe HSB cospcssers sade 1.9735 Lithie sulphate, Li?SO# ..--. 5 BSS ad E COCO STOO Sa BcoD HEao Bese 0, 5650 SodicrchlonideyNa Chics. scence cect omnes oan aw amc eeslcweseciaces 14. 1475 Sodic sulphydrate, NaHS). --2--.-- 206). - 2-2. cena caceewosccoe- 0. 0358 Sodic sulphate, Na?S0‘ ... 22. .----- 22. - cee one cennee ------ 1.1147 Sogicriicanponato Nal Os peemme atest ete = saeeeeeeese 2, 9023 Sodie monocarbonate,, NatCOn o.oo eo coe ce ce sceeee weeeen 0.4314 Sodicubiovate Nats Olea weecie sisi ceeinae oan eiemne leans am 3. 1368 Sodic quadrisilicate, Na®SitO0®..--...... Deo c ose e ona cee ae 3.9090 Sodic sulphantimonide, Na*SbS* .......-.--.---..----.------ 0, 0100 Sodic sulpharsenide, Na®AsS?...--....--.-----.------ -------- 0. 0866 J Nlnriing, JNEOO acencoscoqsocec Shao cage ger eten Ceee ee eeae 0. 0025 Sodium-mercury sulphide, HgS, nNa*S.-....---. .----.------ Trace Origin of the wate.— 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 THE PACIFIC SLOPE. truded furnish a shorter road back to the surface.! The water must be well filtered on 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 inaecessible, 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. Metals 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 the source of the water entering the mines on the Comstock (Geol- ogy of the Comstock Lode, p. 243). METALS IN THE GRANITE. Bb yl 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, aud other metals. He has also detected zine in the mica of gneiss.' 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 determinable 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 zine. 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 zine are very frequently associated in nature with arsenic, antimony, lead, and copper. The prevalence of this ' Untersuchungen iiber Erzgiinge, p. 25. 2? Emmons and Becker, Statistics and Technology of the Precious Metals, p. 54. Bap QUICKSILVER 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 zine 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 aware 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'and Laur* have pointed out, Steam- boat affords instances of the formation of true fissure veins by hot springs at the present day. 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. 8. 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- ' Ore Deposits, 1884. 7 Annales des mines, vol. 3, 1863, p. 425. STEAMBOAT SPRINGS AND THE COMSTOCK. aDe 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 Oathit!— The region including Oathill, the AEtna mines, and the hot springs of Lidell, an area of, say, four miles by three, is one of the most interesting in the entire quicksilver belt, and, had its character been sufficiently understood at an earlier period, an atlas sheet would have been devoted to it. The deposits are numerous and differ very greatly from one another in external form and in the character of the inclosing rocks; some of them are also manifestly connected in the closest manner with volcanic phenomena. ‘These circumstances lend the deposits special significance. The ‘tna mines will be described in the next chapter, where also a sketch map showing the relative positions of the deposits will be found; but a few notes on these occurrences are needful to a proper appre- o- 304 MONOGRAPH XII, PL.V Shi; Sal Lyin gy GILES THO A LIBERTY PRINTING CO NY ILW. Turner, Geologist OAT HILL MINE, NAPA COUNTY.CAL. © Triangulation Points Scale: 1250 ft.. linoh ie 2000 S009 Fr. OATHILL DISTRICT. 355 ciation of the Oathill mines. Hot sulphur springs issue from an opening of the abandoned Valley mine at Lidell. The rock is highly metamorphic and shows small quantities of cinnabar associated with black opal. The ZEtna Company’s deposits are in part in metamorphic rocks, showing at present no evidence of volcanic action, unless the evolution of large quan- tities of inflammable gas is to be regarded as due to causes coming under this category. These metamorphic rocks, as well as the strata at Oathill, are members of the Knoxville series. Two of the ore deposits are in part impregnations and in part of the irregular, reticulated type. In two of the mines of the Autna Company the deposits form veins or vein-like impreg- nations at the contact between the basalt dikes and sandstone, the ore occurring both in the decomposed basalt and+in the adjacent sedimentary material. No hot water or gas now reaches these veins, though they must be of very recent origin. ‘There is no reason whatever to suppose that the various deposits of this small district are due to essentially different causes, and the common cause seems beyond question the action of thermal springs. Strata of Oathill—The deposits of Oathill are inclosed in a gray, rather friable sandstone, which is comparatively little altered or disturbed in the neighborhood of the mines, but passes over into intensely metamorphosed rocks in all directions. Veinlets of quartz, however, intersect the sandstone in some places, indicating that the general metamorphism of the country was feebly felt even here. The sandstones are not fossiliferous, though Aucella concentrica oecurs at no great distance and evidently in the same series of strata. A small amount of shale accompanies the sandstone. The area of unaltered rock is small, the ridge at the north end of the map (Plate V) being highly silicified, while the southern border is in serpentine, which forms a part of the belt of this rock, extending from the Adtna mine north- westerly to St. Helena Creek. vavas— The hill in which the deposits occur is covered over with a thin layer of basalt. This sheet is cracked up into large bowlders, many of them weighing many tons each, and the underlying sandstone is exposed at a num- ber of points. The basalt is for the most part gray and vesicular, but is found in the more usual dark, compact form at a few points. At the northwest cor- 356 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. ner of the map this thin sheet is in contact with a plateau of basalt, in which the rock is of much greater thickness. This mesa is about a mile square and is bounded on all sides by precipitous walls. To the north of the mines is a larger area of pyroxene-andesite, a tongue of which enters the region mapped. Deposits of the Napa Consolidated —'The deposits of Oathill are the Mercury vein, the Manzanita vein, and the Accidental vein, which are the property of the Napa Consolidated Mining Company, and the Eureka claim, which contains a deposit similar to those of the Napa. .The principal mine is upon the two veins first mentioned. The Mercury and Manzanita deposits are on two nearly parallel fissures in the unaltered sandstones’ of Oathill. They strike northwest-southeast magnetic and dip at a high angle, usually more than 45°. The strata, both in the mine and outside of it, are nearly horizontal, excepting close to the fissures. Here the faulting which has taken place between the walls of the fissures has flexed the strata. Those of the hanging wall are bent upward toward the fissure and those on the foot-wall are flexed downward, thus indicating the direction of the movement. The walls of the fissures are almost everywhere well marked by slickensides and the interval between them is chiefly filled with products of their attrition, sometimes in the form of clay.’ Often also fragments of sandstone and shale, showing the original stratification, are found between the walls.’ The attrition mixture is im- pregnated with silica, calcite, pyrite, and cinnabar. The silica is found mainly in stringers, which intersect the vein matter in surfaces parallel to the walls and sometimes give a cross-section of the vein a stratified appear- ance. nated with native quicksilver was found. . Pyrite Fic. 15. Vertical cross - section through shaft No. 3, Great Western jg abundant. Some of the cinnabar is so embedded mine. Scale, 200 feet to 1 inch. in quartz as to show that the deposition of the two minerals was simultaneous. Bitumen occurs, particularly in cavities in the opaline belt. The new, seemingly very ill defined species of bitumen, posepnyte, was described from this mine by Schréckinger. This bitumen is said to consist of a mixture of ozocerite and a substance soluble in ether which has the formula C?H*O*. Specimens collected at the Great Western were examined by Dr. Mel- ville with the following results : : The substance is reddish brown, resinous, soft, elastic, has a specific gravity of 0.985, and is highly electrified by friction in an agate mortar, On platinum foil it volatilizes partially at low temperatures with a rather suffocating, aromatic odor; at a higher temperature it becomes black and fuses and boils like rubber; at adull-red heat an incombustible, light-brown ee ‘tiem > wa” ~GREAT WESTERN MINE. 361 ash remains. In a closed tube a yellow-brown oil distills off with an odor somewhat like burnt rubber, leaving a black, carbonaceous residue. Noth- ing volatilizes at 190° C., so far as could be determined. In the retort a light-colored, brownish-yellow liquid distills over considerably below red heat; at about low red heat a dark-brown liquid comes over and a black residue remains. Both liquids are heavy and viscous. The lighter-colored \« 8 ROT KKK OTT KKK: | AI NAG AQ \\ \\ oe | A L/ We Wr “NVQ vy \S age aR : kernel NRG Scale of Feet wos 40 25 0 0 TG. 16. Vertical longitudinal section of the Great Western quicksilver mine, N. 65° W. Scale, 200 feet to 1 inch. liquid yields vapor at 140° C., rapidly at 190° C., the product smelling like coal-tar oils, while carbonaceous matter remains after complete distillation at temperatures gradually rising above 190° C. All these facts indicate decomposition by heat. Aleohol dissolves the substance partially. The alcoholic extract when evaporated yields an oil. Ether removes an olive- colored oil, the substance not wholly dissolving. No nitrogen or sulphur was detected. Carbon, hydrogen, oxygen (by difference), and ash (silica and ferric oxide) were determined with the fol- lowing result : j Per cent CanhonBramassra nan taea count toate ee se an sk sa eeslecenes 85. 60 Hiyidio xenitemcme lenses ans tron eas see setiss Sento s vac es els ci « ae 10.71 Ose O Ohi ae eis ac ape netsh ala clan nanis cial sio\t Satsic ce ctaclac soc seers ce 3. 22 Agi oc cose cane succes Retnerete aierate = aatalelsionaraiaiaiefieia(aleiota'sielamiereistaiat= 47 ~ 100, 00 362 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. This mineral is doubtless posepnyte, although many of its physical characteristics are not altogether like those ascribed to that mineral. The deposit of the Great Western appeared to be a tabular, reticulated mass, connected with a fissure system. It was certainly precipitated from solutions, and these were probably dependent upon volcanic action which attended the eruption of the adjacent lavas. No hot waters or gases, how- ever, now enter the mine. THE GREAT EASTERN, Importance and position—'This mine is in Sonoma County, about three miles north of Guerneville. There is another mine of the same name in Lake County, near the Great Western, which will be referred to in the next chapter. The Great Eastern of Sonoma County has a considerable eco- nomic importance, having yielded over eleven thousand flasks of metal and having been able to continue production in spite of the great depression in the price of quicksilver during the past few years. The Mt. Jackson mine, which is on the same ledge as the Great Eastern, has also produced 597 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 course 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. General geology— I'he 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 metamorphies, 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. OLOGICAL SURVEY, MONOGRAPH XI, PL.vil > ° San ~_-NINEYARD =s_> Ne \ GILES UTHO & LIBERTY PRINTING CON Y GREAT EASTERN QUICKSILVER MINE, © TRuNautarion roinrs . = HOUSES SONOMA COUNTY,CAL. Scale: 1250 ft... limch . 1900 o 1000 2000 3000 4000 5000 FT. J. Ahern, Assist. Topog? (METAMORPHIC NEOCOMIAN J we FY GREAT EASTERN DISTRICT. 363 Consequently their age is a matter of inference. The facts 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 unconformably upon the meta- morphic series. The overlying strata are fossiliferous 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, and there can be little doubt that it is at least as old as the Knoxville series. It may possibly be older, but ali 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 Aucella 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 faras there is any evidence as to the age of the rocks at the Great Eastern, therefore, they are to be regarded as Neocomian. Quicksilver rock—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 cavities 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 ove 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: SANDSTONE - TOOT WALL SERPENTINE RANGING WALL LEDGE OF QUICKSILVER ROCK Tic. 17. Vertical cross-section of the Great Eastern mine. Scale, 150 feet to 1 inch. Probable history— The dark, opaline or chalcedonie “ 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 the 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, CHAPTER 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 will 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 quicksitver beit— 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 cimmabar 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 voleanic phenomena and cinnabar deposits. Ina 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 Clear 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 HI. 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.’ 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 oceur- rence. The quicksilver district of Trinity County, California, is in its north- eastern corner. The rocks are mainly metamorphosed sediments, largely serpentinized, but voleanic 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- 1 Statistics and Technology of the Precious Metals, by S. F. Emmons and G. F. Becker, pp. 27 and 28. 2 Mining and Scientific Press, vol. 29, August 15, 1874, THE MANZANITA. 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.’ Colusa 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 Rhynchonella 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 concentrica. ‘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 ealcite 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 '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 Emmons and Becker. _ 368 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. that the rcck 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 chalcedonice 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.’ 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 distric— A very large part of the many cinnabar deposits north of the Bay of San Francisco are found along the Mayacmas Range, which extends in a northwesterly direction from Mt. St. Helena. Two ‘Geol. Survey California, Geology, vol. 2, appendix, p. 124. THE MAYACMAS BELT. 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 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.| 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 the east bank of Pope Creek, at the point at which the road from Lidell to Knoxville crosses it. MON XIII——2 369 Zz ' , By “yd unyding “OL peLsourg 33 “snoaus| ze SPL JO PLB9S anu sumouteyy oq} Jo duu qojays [warmopoarn “gt 3 ‘youl | 0} soptm g ‘ayBag BYTES ae aval), | a \ SS KK / L/L B/EORIAOS: x 3 XS = 1 w « 2 25 eae < \ 1 . Agi et \ VR = RNS BT 5 E Sele BH 3 <; > 2 @; cl 38 t ER) 2 a BPS H > ae ‘ |S ¥ © ce) ean Bie: Sa 3 Ny & BU/U UPILIBUY @ Oi 2BU Oly as eausw aesseay TO 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. The cinnabar was chemically tested and the silver ore was analyzed. The latter contained antimony, with a mere trace of arsenic, sulphur, silver, copper, and 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 oceur 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 tinct beds, which are sometimes considerably inclined. It not infrequently includes great quantities of metamorphic pebbles. The drainage and triangulation of the accompanying sketch map are mainly compiled from surveys by Mr. C. I’. Hoffmann, but this material has THE MAYACMAS 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 neyer 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 ore 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. Napalite —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 be 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. Itis brittle, but by the warmth of the hand may 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 180° 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 NAPALITE. 373 in the sulphurets sparingly disseminated throughout the rock specimen. It is associated with pyrite and millerite in vesicular quartz. he specific gravity is 1.02. The following analyses were made on three different samples: (1) Pure material selected from that in the rock specimen; (II) material dissolved in ether filtered, and the filtrate allowed to solidify spontaneously ; (II) ma- terial fused at a low temperature and allowed to flow away from small frag- ments of rock: = aie Ganbonn GO secession ae sec caawe nin ces sels mn -innmiwinwialmm me, ae 89, 24 £9. 54 89. 35 Miydroceny Mie. The formation of etacinnabarite by dilution has already been suggested by Mr. 8. B. Christy, DEPOSITION OF 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 cases 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 have shown that cinnabar and some of the accompanying minerals are dissolved as sulphosalts. 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 sulphydrie 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, ete , 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.— Since silicates of the alkalis and the 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’ 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 voleanic emanations, both gaseous and fluid, on the other hand, hydrocarbons are wholly wanting. Hence he concludes that in these eases the sulphur and hydrogen sulphide are in no way dependent upon organic matter. Prof. H. Credner’ 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 T'schermak* and KE. Reyer‘ hold similar views. From the point of view of the nebular hy- 1 Poggendorff, Annalen, vol. 83. 3 Neues Jahrbuch fiir Mineral., 1877, p. 857. 2 Elemente der Geol., 1887, p. 170. 4Pysik der Eruptionen, 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 oceurring 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 voleanic 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 voleanic phenomena is due to the reduction of soluble sulphates by organie 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 that this gas reaches the surface from ¢ siderable 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. 44] phur Bank, where the associated voleanic 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 lave covered with dry rock of a very 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 voleanic 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 ereat depths. On the Comstock lode the heat increment is £° 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 »vart 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! 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 Neocomian strata; at Oathill and to a slight extent in Knox- ville, in unmetamorphosed Neocomian strata; at New Idria, in the meta- ! Compare ‘Origin of the 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 of the ores. —In the 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 beimg 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 upheayal 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 froma 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 — F'jve distinct theories have 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 uaknown origin, have been deposited from solution or by distillation. The ascension theory also includes eases 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 fn 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 evidence 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 of 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; (b) By deposition from hot solutions; (c) By distillation, with or without steam. (2) From known sources: (a) From the original interior of the earth: (@), (0), and (¢), as above; (£) From underlying rocks: (a), (0), and (ce), 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 yon 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. Itis 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, (@) source contiguous, (b) source remote; (2) By distillation, (a) source contiguous, ()) source remote; (3) By hot solutions, (a) source contiguous, (b) source remote; (4) By cold solutions, (a) source contiguous, ()) source remote, From the earth’s interior: (1) By unknown means; (2) By distillation; (3) By hot solutions. Objections to an infragranitic origin —As has been abundantly proved above, 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 alinost 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 alse extremely unstable, their sulphides 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 Pacifie Slope. Hypothesis of derivation from granite. —If, on the other hand, one supposes 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, ete., 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 voleanic 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 CINNABAR FROM GRANITE. 447 with volcanic eruptions, are known in many cases to reach the surtace 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 metals 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 solfatarie 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. ern 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 solfatarie 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 comparison has been made 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,' 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.’ {See Geology of the Comstock Lode and Bull. California Acad. Sci. No. 6, 1886, p. 94. ° 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 other hand, Becker supposes the concentration to have been effected by surface waters flowing laterally through the igneous rocks, gathering the precious metals and depositing them in the fissure.” The inaccuracy of this statement may be seen from the following qnotatious. Baron Richthofen writes (see The Comstock Lode: Its Character ete. or Mon. U. S. Geol. Survey No. 3, p. 19): © 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. Now, if the ores of both localities came from intragran- 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 metals 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. Zine also has been found in gneiss-micas. Arsenic, antimony, lead, and copper are so frequently associated in nature with gold, silver, and zine 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. Conelusions— The evidence is overwhelmingly in favor of the supposition that the cinnabar, pyrite, and gold of the quicksilver mines of the Pacifie slope reached their present positions in hot solutions of double sulphides, the metals have a great affinity 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 filled, from its upper portion downwards, with all the elements which we find chemically deposited in it.” In my report, page 286, I wrote: ‘‘ Floods of heated waters now rose from a depth of two or more miles, certainly carrying carbonic and sulphydrie acids, and possibly other active reagents, in solution. The water followed the course of the main fissure as closely as circumstances permitted, but was de- flected toa great extent into the fractured mass of the east country, where decomposition resulted. Silica and metallic salts were set free from the mineral constituents of the rock, and were carried into the cumparatively open spaces near the main fissure, where they were redeposited” (see, also, ibid., pp. 226, 283, 386, 390). Professor Newberry attributes to von Richthofen and himself approves the very theory which I was at great pains to support. The hypothesis which yon Richthofen advocates New- berry seems entirely to have overlooked (see, also, The genesis of certain ore deposits, by S. F, Emmons: Trans. Am. Inst. Min. Eng., vol. 15, 1887, p. 125). MON XIII——29 450 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. which were leached out from masses underlying the granite or from the ‘oranite 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 infragranitie origin of the quick- silver and the gold, I consider it tolerably well established that both were actually derived from the granite. IT 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 chapte-——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 mereury, 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 in 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 THE PACIFIC SLOPE. duced more than any one of the other three. Idria, Huancaveliea, and Cali- fornia have each yielded pretty nearly the same amount 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 1) shows the dis- tribution of some of the mines. Punenal oventencrs of) quickuiver he sACcomut given of deposits known to oceur 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 Archzean 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 metamorphic 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 is scarcely supposable 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 name 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 mareasite 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 voleanic 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 seem 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. Excepting the light cream-colored schists of Miocene The sedimentary rocks. 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 Téjon (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 unaerlain by granite. The microscopical examinations have given this in- ference unexpectedly strong confirmation, for, though on struetural 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 granitie 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 SUMMARY. 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 defined 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 glaucophane schists, derived from certain shales, much as the granular metamorphies are produced from sandstone. The plithanites ave a series of more or less caleareous, schistose rocks which have been subjected to a process of silicification, resulting in chert-like masses, whieh 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 OF 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 metasomatie recrystallization can be traced in the altered sandstones, rocks whose clastic origin could not be doubted for a moment. In many eases 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 for a 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 metasomatie 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 miecro- 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 pseudodiabase. The pyroxene sometimes assumes the form of diallage. Another class contains amphibole instead of SUMMARY. 457 pyroxene, and I call this rock pseudodiovite. No metamorphic rocks have been found in place which carry olivine. Glaucophane occurs in both the pseudodiabase and the pseudodiorite. The quantity of zoisite in these rocks is very variable and in some cases is so great that with feldspar it forms almost the entire mass. The schistose metamorphies, 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 metamorphies. 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 New 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 metamerphism, soon after the close of the Neocomian, was probably a moderate one, perhaps two thousand or three thousand feet. Ata 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 Archzean schists are found in the metamorphosed rocks of the Coast Ranges. The quantitative relations indeed are different, especially those of the feldspars; for, while orthoclase predominates in the Archzean, 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 Archzean 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 the 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 percentage. 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 forma natural group, which should be recognized. I have proposed the name asperite to suggest their resemblance to trachyte. As- perites, 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 primeyal rocks. 460 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 erust 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 Azoie 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—ereat 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 Aucella concentrica and Aucella 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. 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 unconformably 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 T¢jon series. The non-conformity between the Chico and the underlying rocks and the continuity of the Chico and Téjon were first established in this investigation. Between the Eocene and Miocene there is a sharp faunal distinction, but there is no general corresponding non-contformity. 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 is consists of lake deposits. It is of course uncon- 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. Andesites 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- canie 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- parent influence on the ore. ciear Lake district. —The region of Clear Lake is a picturesque one, lying at the northwestern extermity of a belt of lavas which extend southward as far as the Bay of San Francisco. Extinet voleanic 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 Chico-Téjon oceurs. 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 cen- 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 in 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 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 solfatarie springs reach the surface, owing their heat to the vol- eanie action of which the lava eruption was an earlier manifestation. The springs contain much sulphydrie acid, which, oxidizing more or less fully at and near the surface, has yielded native sulphur and sulphuric acid. The latter has 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 mareasite 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. 464 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. Very large quantities of quicksilver have been taken from this prop- erty, but it has 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 californica and of a species of Stratiomys live in the lake. ; The Knoxville 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 metamorphic 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 erystalline 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 Aucella concentrica and A. mosquensis. The series carry- ing these shells are called the Knoxville group from the name of this locality. Excellertt 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. 465 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 may be 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 xIlI—-—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 -Téjon 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 Téjon 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 Téjon beds contain coal seams which were exploited on a small seale for many years. No lava exists in the district, but there is a considerable area of basalt just north of Vallecitos Canon, 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 Carlos, 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. AG7 where in this region is there any evidence of the substitution of ore for rock. New Almaden district—The first discovered and the most productive of the quicksilver mines of North America is the New Almaden, 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 Almaden Mr. Gabb found Avcella, 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 Almaden 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-Plocene. The New Almaden 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 mareasite, with rare crystals of chalcopyrite. The gangue is quartz, calcite, 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 stockworks; but they are arranged along definite fissures and the deposits as a whole have avein-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 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 alta. The other mines of the district contained similar ores in similar rocks. The Guadalupe 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 Comstock 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 voleanic 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 are chalcedony, 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- eraph. 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 Aucella. 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 eases 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 oceurs. Small quantities of barite are also found, and this is the only ease 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 ef the above mines haye 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. AT1 mine. There is no lava in the neighborhood. In the Stayton mines, San Benito County, large quantities of stibnite were associated with cinnabayr. 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 yeins 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 ties 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 ease 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 mareasite, silica and carbonates; but sulphur ocewrs 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 zine 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 rocks 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 vei 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. — The waters 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 zine; 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 sodie 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. Sodie 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 sodie 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 of sodic sulphide and sodic sulphydrate 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 145° C. These facts suffice to lead to important conclusions with reference to spring waters, such as those mentioned above. When neutral sodie carbonate is treated with sulphydric acid at ordinary temperatures, sodic sulphydrate 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 sodie carbonates will not prevent solution. These conclusions were amply verified by direct experiments. Mercurie 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 were found to be soluble in solutions of sodic sulphide and in solutions of the carbonates to which sulphydrie 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 sodie 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 produeed 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 the strongest evidence for the supposition that the cimabar, pyrite, and gold of the quicksilver mines of the Pacific slope reached their present positions in hot solutions of double sulphides. Hither the metals must have been leached from the 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 voleanic activity, cinnabar would often be met with in craters. Though it is often found associated with voleanie 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. 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. q 4 erro a END E28 A. Page. Abbott's mine, Colusa County ..----------+----------- 358 Achiardi, A. d’, cited , Acton, R., Cited ......--2+- ---202----2- eee eter eens Aden, Arabia, ciunibar at ..-.------- +--+. eeeser errr ee 44 JEtna mines, Napa C unty...-.-------------+-+++++-- 354 371 Afghanistan, cinnabar in --.-~--------0-+++++2++2----- 44 Africa, cinnabar in...-.. ---------++--2+2+ sreee ere 43 Age of strata in icated by resemblances ....--..----- 187 Alaska, Aucella in.......----+:+--+- 2200 seer se ress ee 201 CINDADAL AM: coc neck veers tanase oc sin vaccwne r= 334, 385 Aleutian I lands, Awcella in ......------2-++-++-2---- 20. Algeria cinmabar in .----.-------------- 43 Alkaline sulphides, action of, en cinna’ ar- Al'anite ....-----------------+-------++--+° Al. aden, Spain, cinnabar deposits at-. description of .....--.------------ historical notes on .-- no substitution at...- Alta at New Almaden ...-..----------------+++++---- 33 Altoona mine, Trinity County...-------------------+- 363 Amalgim, from Bri ish Columbia. -------------------- 384 from heGold Bet. ....-----..-----+---++-++-+--- 383 Amalgamation proce s, invention of .-.-------------- 4 quicksilver consumed in.---.-.-------+++++--++->> 3 America mine, New Almaden district ....--.--------- 327 ‘Amiata, Monte, in Tuscany, glassy trachyte from. .-.- 159 Ammonia, at Sulphur Bank .--...-- ------+---+-+--- 259 etfect of, on s lutions of cinnalar-.-..---- 431 precipitates cinnabar at Sulphur Bank 260, 269 Andaman Islands, cinnabar in the...---- Andesite, analysis of .......-..---------- SASL at Clear Lake.-.-...........---------= 238 at Great West2 n mino .-........---- 329 i COR Th eS Se Ae aos bea OSE 336: cinnabar depos‘ts in ......----------- 245, 379 of Mayacmas dis‘rict.....----..------ 3.0 Andesites, age of the....-... 222 classification of the ---.. 149 of Steamboat Springs... -- 146, 334 of Washoe district. ....- a 119 Andesitic obsidian - -. 2, 153 analysis of.-.....--.--.--- souewy LOL Anticlinal, partially mteamorphoned Saas 276 Antigorite in metamorphic rocks----------.---------- 113 Antimony sulphides, solubility of. -- 434 Antisell, T.. cited --.---......-----6----+--02eee-eeee= 176 ANIC L WiG CGD ee er Pee 17, 27 Apatite, conversion of, to serpentine --. --...--..--- ¥24 occurrence of, in metamorphic rocks .-.-.-..--.-- 85 Aragolite at Knoxville ......-..---------------++-+--- 286 Archean rocks, compared with metamorphies .-..-- 138, 458 in Cal.foruia 177 Arcose sandstone 61 47 | Page. Argentine Republic, cinnabar in the .---..---..------ 23 Argentite, insolubility of ......-...--.-.----++---+---- 434 Arsenic sulphides, solubility of....- ekececmeneaen ee hd PAPZENMICANS C1UGO) c= + saeco aa nees seem BRS OSII SESS 42, 43,44 Ascension theory....----.-- 442 Asia, Aticella in.....-----.-- 203 cinnabar in .......... = 44 Asperites = 2.2.5 o2.22-2- Secs cacencocanercesbecssna- ~ 151, 459 at Clear Lake. - -221, 242, 243 ab Mit. Shasta cases. caccesiccemerececuneev er nermn 150 ati San LnistObispo' - <<< 4: Seve -elnccenn se seu esas cinnl= 381 at Steamboat Springs -..-.--.0----------00 ---=-- 335 distribubionob the so-- se. aie seen senna = name 22 Aucella, age Of -..---2---6-sece0 -2-- +e enero --oo oe L9G, 201, 229 ERRNO XVI pe see wena lero eels elas ple ieee 272 Pin OPAATN pos eto a SeoaapaOnCOUo I borocosstae 355 Qharacteristics Of .-- cee .--cee- sc see eee aeenenes= 226 Gistribitbion Of =-—-ecseree- sense ane oee = 201, 203, 227, 460 figures Of ..-. 22. 2-20-2222 ene e eee eee nen e ee nnnes 230 first discovery of, iu California ..............--.-- 178 ATR AU AS Kee oie ale wie tate ane seein mle asm 201 in Colusa County..-..-.--..----. Scoesascee 235, 367 in San Luis Obispo County .....--..--..---- 381 in Solano County .--:.--------..- 378 Helis tien ets) losererteroreocspros -- 208 in Washington Territory.-.... Spe PX}! localities -.....-... SBA --183, 198 near Pope Valley, ane County. - 369 not yet known in Cascade Range 206 occurrence near New Almaden . 310 remarks of C. A. White on -. 226 BPOCiIES Of ona =, oe Leta e -noniss/s- awe wen see 228 Augite, development of, in metamorphic rocks- 88 occurrence of, in metamorphic rocks .-.... ve Aurora mine, New I@ria district ..-.-...-.-----..---- 309 Australia, cinnabarin ....-..-------.--.-----.-------- 48 Austria, cinnabar in...... 38 Avala, Mt.,in Servia, cinnabar at ..-..-.....--+------ 41,317 B. Babbage, C., cited...... Donna oagoceosacnducenSceEese 167 Babinski, A., cited .--..--.2-.----se200---2-2eee eee nees 21 Baker mine, Lake County .--..--...--------.-2-+-=-=-= 368 Va Vicn GG Bape eee enscses EROS RES 44 Ball structure iu basalt.....-- esengsntScee assan cess se 256 Barba, L: S:, cited .--.-- ... 60. -- =~. -on-ne one -- ---e= 23 Barcelona silver mine, Nevada, contains cinnabar.... 385 Barfoed, C. T., cited ....-. .-..---------- 2. -2---2- == 420, 429 Barite, in Oathill mines. -....-..---..-----+---------- 469 occurrence of, with cinnabar. .....-.-- . .386, 388, 469 pseudomorphs of cinnabar after - 397 Barrande, J., cited........------.-. 28 ASAlt aA LOL seen aa 2 223 RtiOlean AKG cose eer sie ss te sie mieleciew ween === 245 478 Page. Basalt, at Knoxville ......-......sscescees Sacer 280 at Knoxville, analysis of --- <2... -cscesce---ccecn-+ 159 at Oasthill)...-2--<.2<. a = 355 at Steamboat Springs. ............---------------- 337 atiSalphur Banks < <2 sn see a ee eee reer aee eee 252 at Sulphur Bank, decomposition of.......-.-...... 256 at Great Weatern;mine --22...-2---s-c: +. 6.-----2 359 distribution and character of ............----.-.-- 156 glass; origin ofS o2 220 eo Sapo aas selene 161 glass at Sulphur Bank, analysis of-. - -158, 159 glass from the Rossberg .......-----.. oenaetectete 160 MBA NG Ws TOTIAi ae conan ns sn a ntaye oe oe eeneaeeeaas 300 occurrence of, with cinnabar 373 of Mayacmas district .-....-...... 376 Bastite in metamorphic rocks......... 114 Bar, TAs ited aoe. s co paces as oecce ce cece onue seen = 3 Beaumont, {de citedes hae 22 soe ee oe ee 172 Boecke; By oted:)2- 2225. cee ee Jone 109, 115 Belemnites in the Coast Ranges 196 Bella Union mine, Napa County 77 Bernaldez v Figueroa, cited... -....-...--.s.-0+.--.- 28 Biotite in metamorphic rocks ............. ...-.-.... 74 Bischof, G., cited .............- =. «ne-e~-120, 124, 433, 438 Bitumen; AG mKnOxwille = \=0e we - - ee ese oe 286 at Sulphur Bank. .................-- 2357 at the Great Western mine...... -..... .. 360 at the Manzanita mine.................. 5 ~ 3b7 in Miocene schists 218 new species of, in the Phoenix mine ...._-........ 372 Black, J; (Ued ss os - a. osS22 occ eocace Blake! W.'P.; cited. 2.2.52. cose. se2en< Plies ARO n ERIN fora Santas eee snes 206 Blum, J. R., cited. ...-... 307 Bohemia, cinnabar in... 40 Bolivia, cinnabar in ... 23 Borax, at Knoxville-- <<. 22532550. 25 scene 281 ‘at Steamboats-2:. +---+ sac. see ences 346 aL Dolphin Bam. = sos. ssnm “casas ae naa ee 259 effect of, on solutions of cinuabar ................ 431 ORIOUI: OF (aera te = aoa aes mea aon eee eee 440 Borax Lake, described (see, alsu, Little Borax Lake) . .261, 464 AROS AN oo ae ase eis one aia eee, OER origin of borax in 266 water, analysis of 265 ome, cinnabarin.25<2ssesace a. ate socesee se ee 48 Boaquot, cited! 2.2: ce cance santo nce p ee tee eee 23 Brazil, cinnabar in....... 23 Breislack, S., cited ...... 35 Breithaupt, A., cited..... 118 Brewer, W. H., cited 176 British Columbia, amalgam in................-....--- 384 Arica i. 22. Pichon 32 siete wes soe saan eae ee 201 cimnabar in: -2 = <<< <2 25+: 5 cae eae ee eee 117 Buckeye Mine, Colusa County.........-.-.---------=: 368 Rupiall cited! ::.52 3 Se eee 20, 21 Bunsen, R, cited -- wicca TBORAG A: | Cited +22. coed .c5.0 een ee ee 32, 33 Barton st. i cited: 25-0 5..0-nvacesenc one eee eee Cc. Cache Lake, conglomerates of ..................-..-.. 152 described OFigin Of --=--- 5. <¢ DUBceriescen ree Calderon||S. cited =-sc.c-cse- see eee California, discovery of quicksilver in .......... California coast, recent elevation of ..... California mine, Kuoxville district-..........-.....-- 4 California mines, geographical distribution of -.. .-. 13 quicksilver produc& in —.25- 255-5 =--22---a-e= Callias of Athens --....... Sass SERS HESS Cantua Creek, nonconformity at Cap:chambers s.2- 222s sS2o20.6 Seas een ee eee Carbonates, conversion of rocks to- 392 effect of, on solutions of cinnabar. 431 Carboniferous formation in California 5 77 Carboniferous fossils in the gold belt .-....-......----- 195 Carboniferous metamorphic rocks --........---------- 208 Garon, cltcde-f. ooh. eee = 28 Cascade Range.... .......- 205, 365 Castillero, A., cited eet Bf) Castillo, A. del, cited 16, 17,18 Castro; Ts.; cite 2 ae cee nce oe eres soa 16 Cathrein, A., cited ........ a 82 Caulinites at Sulphur Bank... - 234 | Cerro Bonito mine, Fresno County ..--...--------- 380- Cerro Gordo mine, Fresno County .-...----.-.... ceere | ech) Ceylon; cinnabarin,.--te-2>- 2 eee eee 47 Ghaboya:l,. (cited’is..<22s2--4 22. SRR ree 8 Chalcedonite 390 Chalcedony at Steamboat Springs-.............--..--- 341 / (See, also, Opal.) Chalk Mountain, andesite of -.--....--.....--2.2220- 152, 238 CGlinmibered/ veins] 2250 ss eee a aetna eee LOZ Champlin) J; Diy citet ae see ao eens Se eeeencesen 16 Chancourtois, E. de, cited .... Chatenet, M. du, cited ---..-..-.. Chico beds at New Idria.-..-..-- Chico gtonp 2 -s-sos2 = oe ao een sence aoe eee Chico atrafa inc pon>.<2-2) 4-89 3-2 eee soe ee eseee Chico-Téjon series, described .. - 214 atClear- bake. (25. ...5=: 237 Chili, cinnabarin -.- es 23 China; cinnabar'in*. << 222-02. 0e eae 46 Chlorides, effect of, on soiutions of cinnabar....... ... 431 Chlorites in metamorphic rocks. .-.--.-..... Sscc025s- 85 Christy, S:\B:; cited 22.0 =< os. toon ee eee ee 421, 436 Chromic iron, at Knoxville 278 OCING Wy LGR rasa ce taal te ke eee 294 in werpentinG <--<~-<>..2-2.-22-scasca-coeeene nee 116 Chrysolite, occurrence of.-..-...-- 114 Cincinnati mine, Lake County 376 Cinnabar, at Knoxville............- 281 at New Almaden <.--.......---.-..-. 314 at Now iliy acer sas an eee ae 301 at Sulphur Bank 257 at Steamboat Springs --....-..---..--. --....-.--- 350 conclasions as to foreign occurrences of =- 50 erystala’ofc. 225 =e eee ele eee eee 390 eralof deposition s< ssa. cee sega nie eee eee 417 inl Basal fsa cece ea ee ee 257, 282, 337, 373 in OPan LO ses—- 3 et een ae eee ee 330 in metamorphic rocks, passim et............---.-- 391 in sedimentary rocks -......--.---- -301, 382, 391 known to the ancient Peruvians -.-..--..-.....--. 8 natural solutions and precipitations of..........-. 435 occurrence of, in andesite........---.-...-... 264, 370, 379 origin'ofs.- $222: - 2326 -ss-seesa - -59, 438, 445 possible sources cf ....--.-...---. eg ee) precipitation ef, at Sulphur Bank......-......----- 261 INDEX. » . INDEX. AT9 Page. | Page, Cinnabar, reJations to rocks...-.....-....20-----0+ +--+ 441 | Cope; F., cited ...........--..« avenceews aeesuivcese uae. 386 soluble in ammoniacal solutions. 431,269 | Copper accompanying cinnabar...... ...---. 257, 253, 343, 386 solution and precipitation of .---.419}473 | Credner, H., cited.......... 22. --.-c00- aes nesensece 439 supposed substitution of, for rock .......-.--------42,399 | Crosnier, L., ClO aaa aa oaynk enon eine sp Comer eta aree 21, 23 WOIDS OF cas cec ce cece ceeecn Cocccecivee vice sevice 208, 007,414 | CxO8S, Ws, CILOMs ~~. - 2.2205 nen oe cceense coseuwesces ass 336 With barite..-..----+. +--+ 22+ +--+ seer eee n rere 386, 39’ | Crystalline metamorphic rocks 455 with gold .....-.---- + +2200 eee2e eee eee ee ee eee e ee 367, 383 (See, also, Metamorphic rocks and Massive rocks.) with pyrargyrite ..--.------- +++ ee ee ee eee eee 370 | Crystalline rocks at Knoxville, age of...... ..---.---- 274 with silver not eruptive...... --- 273 with stibnite ...........----...---------- not precipitates 97. (See, also, Ore deposits.) Cuprie sulphide, solubility of 433 Cinnabar City, El Dorado County, deposit at ..-.------ Bef Curtishdk Sapoitediss--+-ess-=-- aaa 398 Cinnabar deposits, age of rocks inclosing .-.--------- 50,416 Cora Blanca mine, New Almaden district ...-..--.-- 319, 324 at Almaden. 2c. <00.-2 cece ccce-n 2 an eeen en sennnns 28,399 | Corea, cinnabar in ~ at Huaneavelica _ Corsica, cinnabar in. - at Idria .-...-----. | Cortizar, D. de, cited at Monte Amiata . 35,290 | Cotta, B. von, cited... ; at Vallalta Se cGouriney, Wey Cited 2-2. noc ea seas ecere ane eee 16 character of inclosing rocks .-.....--..--.------.-50, 391 form and classification of .-...--.....--++---..--- 53, 416 D. from SOlUtIONS. ~~... 0... 202 ee nen ne cere eee ne ce eee 55,435 Dall, W.H., Cited... ..- 1-0-2. eee ee eee eee eee ee 384 TVA ARICA main wen cieicivin!= «=)nin'e Bere ab cdoseteeso3scae $81 | Dana, E.S., cited......-----..-------. 22+ seen eee eee 267 jn ATIZONG 2-5. cwecew sens ee row renn Seite Sen sfoisieininls 386 | Dana, J.D., cited...... 15, 77, 108, 113, 118, 124, 129, 166, 216, 237 in British Columbia..-....-..----+ nascerocsognaone 384 | Darwin, G. H., cited......-..--.------ 22-228 eens eenee 167 in’ California ----<- 25s. 02sec enc ce nsceeenene ses 365 Daubrée,G.A., cited....-. .--.------- 61, 107, 136, 172, 182, 306 THON O een ole ohare ora io linlara nia en iain wisi ain a mime 385 Davidson, G., cited....-..---.-----.+ 2222+ eee eee eee ee 207 in Nevada .--. .-s- ce scenace---0--ceecses Sc 385 | Dawson, G. M., cited ...---..----.----------22- 202+ ==> 38k in New Mexico ...-...-.----..--.0-.---2-- 386 | Day, T. D., cited...-.-...------------ +--+ eee eee eee ee 386 RIN ONG RON eases to aeiee = lane ee=-n= meeee 366 | Dead Broke mine, Lake County...-....-.------+------ 376 SATO Ea ere Oe eee eeeite oe se enon gales 3g6) | Debray, Hs. Citeds-----<--.---=+-0se=- cecicesces 377 Gibbs) Weyoited ceeee een nse CrscecsSchene 53 Gilbert, GK. cited. =<. 2-2. 22. 209 Glaucophane, in metamorphic rocks 76 Glaucophane-schist...-............ 102 analysis\(Of-- 6.202053 .deeescvectecccncesesasssacece 101 AtiWelliStrect mines sac. -e- scene ceeee eee eceaats 375 GmelinsKrant) ‘cited sor. ccsce sate seecemena cio meses 430 Godfrey Wis Gol aeescease sehen soe eee eee eee 47 | Gold, extracted from quartz by pressure... 198 genesis of deposits of ...-........-..-.-...-- 450 product compared with that of quicksilver. 3 solubility of.........-..- Rte argc ee sesso oe 433 | Gold accompanying cinnabar, at Baker mine 368 Phii@iterg 7 GL eos soe ees S55 sho esec as at Manzanita mine... at Picacho mine .-.-.... at Steamboat Springs | Bip S0 PR U0 Usa Re eeeee teresa eee aan Goldtbelirdofined S2osecec=-— eae eee eee Gomes, J.C. citedsc sc 2. cass. sss. cee asw sions esses Goodyear, W. A., cited... GotischeGaciteds.- =a eee nese ese eae neaaaeeeee Gower, cited Granite, age of the at) NG@waA mad en a ass cee nae nee e neat ate distribution of : intrusive of California in part primeval 174 of Lower California. ........-..-... 207 PU UPN 7 esbese SooecoLer pence sce echoes oe ee 143 relations of, to other rocks -.----..---- - 170 the probable source of quicksilver underlying the Coast Ranges ........-. i Granite at Steamboat Springs .--........-..-...----- metals in...-..--- Asengse aso obs as sosonaascecas Grate structure, in opal... in\Kerpenbine!rs=.- saan eens ee Great Eastern district, geology of Great Eastern mine, Lake County Great Eastern mine, Sonoma County = 262 Great Geyser, Iceland .........--- Speen cen Qanicn an SHS 24 Great valley of California, elevation of ...... SS 2825556 206 Great Western district, geology of..-.. -- -- 338, 469 Greenland, Asicellaan- =~ ~~~ =~ o-oo nce nies ....20], 203 Groddeck, A. von, cited .-...--....--. 41, 317, 400 Guadalcdizar, Mexico, cinnabar at --...-...--......--. 17 Guadalupe mine! s2snes 2. eee a= aeons 326 Gualala, Mendocino County, fossils near........-..--. 213 Guancayelica. (See Huancavelica.) | Guatemala, cinnabhnin)--.2--2ses oe. --sseeee ee eee ee 19 Guillemin-Tarayro, E., cited) 22-- --- > =~ asian en 31 Gitobels CG. Wi Cited cane ete a encom stances Sea sy! ll. Hague, J. D., cited ..... econ cee + eceeerece daceceunscnr= 27 Hagne and Iddings, cited ........ ....----- 145, 146, 147, 157 INDEX. Page. Hall, J., cited....--..-eeeecccceesnereeeene veneer eecees 210 Hall) T. J., cited.-.-. .-. Hanks, H. G., cited .--. Haushofer, K., cited ........------------ Hautefeuille, P., cited ...--.....------++-- Haiiy, R. J., cited ----... Hawkins, R. R., cited ......--.-..ccseee- ee eee -eeeee Heat of thermal springs, origin of. 441 | Heckmanng, A., cited ......-..--..--.--- +++ | Hector, J., cited.....--...--+-----+---- ++ Heilprin, A., cited... - Helmhacker, R., cited -......-.---.----- Hilgard, E. W., cited -. Hiriakoff, M., cited <.----- .-- se -n-cee-carcecensws -=- Historical geology. .-----.----- +--+. s+ee22-eeeeeeees 176,460 | History and statistics of quicksilver ....--------.----- 1, 451 Hoffmann, F., cited .--...--.--- -eeee--e-ee eee eee eee 35 Hoffmann, F.C., cited . Senne . -235, 370 Hoffmann, J. D., cited ---.... 2.000 ceoees eee eee eee 2338, 298 Hollande, D., cited ........---...- sees ees cee e ee reer eee 3 Holzapfel, I, cited ..------..-++ +++. ee seer ee eee renee 231 Homathco River, cinnabar near .......----- ----- --- 384 | Hornblende, in metamorphic rocks ...--..-------+---- 75 metasomatie development of .....----------------- non-confurmity beneath the......-...--.---------- 205 reterred to the Gault...........-..----.------+---- 205 | stratigraphical relations of. ...-..---.------------ 194 Hot springs, association of, with mines..-....--.. 381, 382, 402 source of heat of 441 | Sow, H., cited.----.- 16 Huancayvelica, Peru : 4,6, 21 Huitzuco, Mexico, cinnabar at....---..-----.--------- 18 Humboldt, A. von, cited-.--.---------. 16, 17, 19, 20, 22, 54, 172 Humic acid, concretions due to ..--..--..---.---- 67 Hungary, cimnabar in..----.-------------- ++ adh 41 Hunt, T.S., cited....-.- 82, 117, 119, 120, 186, 172, 343 | Hussak, E., cited .--..--------+----2+---+-22222 e226: 109,113 | Hutton, Captain, cited ........--------------+-+------- 44 | Hutton, F. W., cited .....--.----------------- 49 | Hydrocarbons, absent at Steamboat Springs. 342 | absent in many volcanic emanations ----.. 439 Hypersthene in basalt .--.----.------+----+eeeeereeeee 157 Hyposulphites, formation of ....--.-------+--+++------ 430 at Steamboat Springs 348 at Sulphur Bank ...---.-----.---++----22-eee-+---- 260 it Ice, behavior of, in melting -- 70 Iceland, cinnabar in.......--.-.----+--------20+-2-2--- 24 | Idaho, cinnabar in ......------.----+----++ -+e0+--++-+ 385 | Iddings. See Hague and Iddings. | Idria mine, Austria ...... --..--------- | Tidekansk mine, Siberia Ilumination of tunnel by heliostat.... --...-..--.---- Ilmenite in metamorphic rocks..-.--..----------- Impregnations of cinnabar India, British, cinnabar in India, Dutch, cinnabar in India, Spanish, cinnabar in Injection theory of ore deposition Tnoceramus, occurrence of Inoveramus Piochit Italy, cinnabar in Tyanhoe claim, Oathill MON xI1I-—3l | Later hornblende-andesite J. | Page. Mek CRON ky) CLLOU nen wee ene sec weer ee eee ane esas canes 27 | Janin, L., cited...........------- xiv, 325, 327,375, 380, 382, 385 Japan, cinuabar in 47 PEO VA ACIOUAD ADIN. nis cans ocicers occesoasienemnsina 48 Johnston, K., cited.......-...... oe 23 Josephine mine, San Luis Obispo County 382 ILE N Aes AGO LUE Mite mnie nnn wine sas an ene = an «oak acon 66 Jurassic fossils in Genesee Valley .--..--..----------- 195 Jura-Trias at Steamboat Springs....-.....--- anes 128, 333 K. Kamtschatka, cinnabar in-....... cee sneccesceees cae Keller, cited Kemble, G. W., cited .-. Kennan Grjolteleces: ceeanaesiceaacese sass aacemre ss Kentucky mine, Sonoma County KWoyserling Ay (Cited ia -ncn'saqmcvicissalmeicenielns Keystone mine, San Luis Obispo County. . Ose Kicking Horse Pass, cinnabar at .....-...-----.--.---- 384 HOTTA ES 5 1D a0 eee cacet oo seccacogee SpSa ise aos 3 King, Clarence, cited...........-. 176, 178, 201, 206, 210, 219, 267 acOHNOf Gee CitOU oe aascesscnsis saa enn ese ance os 420 Klemm, J. G., cited 27 Knoxville beds, at New Idria 292 at Knoxville.-..--. woe orcas eee 271 ati Sulphnr Banks. ses ccwinccrcnswesns==e~a==ee ee 251 BL Glearesake some n ema eee cerita esses eats 235 Aucella in 230 defined ...-.... 140 Fa Ofeeases= teeta ote eeincc ema! 198 | Knoxville district, descriptive geology of..-.-...---. 271, 464 Knoxvillite, new mineral.......-.----.20. 2.0. --2--. 0 279 AIKOKECRALOWsIN-.WOUNCIUED oacienc eo ssc eencsie aaa 44 VOSS GON | Se Se esac ment co se oO Io ae Konocti, Mount.......---- Krantz, A. (?), cited Kriimmel, O., cited......., Kuss, H., cited: -..-- .---.. Kwei-Chau, China, cinnabar Lagorio, A., cited Laguerenne, T. L., cited Lake Elizabeth, cinnabar near .. Lake mine, Knoxville district. Lansdell, H., cited. .-.---.--..- Lateral secretion theory avr we Ciel y arse me eee eee = oleae mee meee 352 LIB CER Osan pecoseneoosceecac “525 145 age and distribution of the 221 of California not fused sediments . . 174 Lead sulphide, insolubility of...........-...-.-------- 434 TapaAmOns sos Wiss (CALh( see me ence een eeeeeepaclenanas == 366 EMOONLG 1) 24 ClLCU ec set cere Moc cae cease a = 206, 209, 257, 263 HSGESG ea by, ClLLEd Genoa ean an ecee's|sse ese z 3 Lehmann, J., cited. : 132 TS COT as ee Sse aa eae acess 169 WeiieHgmereUx, 1s, CltCW 222.-5-9cr se aceerecone=-eneacc=se 254 Lidell hot springs ........---------------+-++---------- 371 Limestone, of Gavilan Range -..-..---------.--------- 181 of Neocomian age...-..-------seee+---2--220se2ee= 60 of New Almaden. --..--- = sess6 31L Lindgren, W., cited .- .-Xiv, 149, 279, 336 Lindstrom, G., cited ......-- 22-2... -ceeee- eee ee eee 203, 227 482 INDEX. Page. | Page. Linked veins... waves swassesceveess 409 | Metamorphic rocks, at Great Eastern miné,.......---- 362 Lipold, M. V., cited = --5, 38, 42, 54, 398, 400 | -at Great Western mine.-... 858 Dittle Borax Lake: =~ -cscecsso-cec secs coruscees «--0- «244, 258 | at Knoxville, age of...... -272, 274 Little Missouri mine, Sonoma County ..... onsen Sos4 377 | at New Almaden......... = Little Panoche mine, Fresno County .......... -----. 380 ati Now, Iarid.--iccceucceseut ees sseean ee eeene 393 Witte Salphur Bank weno. seaasaseodneeerelse es ce oes = 264 BtiOsthill ese ssteseseen Uae Telos Fee aade aes neces 355 Livermore mine, Sonoma County .....--.-.. 377 | at Steamboat... - 128, 333 Liversidge, A., cited......-....... 50 at Sulphur Bank 251 Los Prietos mine, Santa Barbara County 382 | Carboniferous. -----s.22ass- ce 208 SOD Eilaky Sa CN GEL eaten ercter mr ea eel araim cnt siaim nara ois ieiere'alcis miei seis 35, 118 | comnared with the Archwan_....-.-..... paseacsses 138 Lower California, character of ............... Gactcise ct 207 ersstalline, classified osc foc seseeece see soe aera 72 Wallala beds in.......... ao ele decomposition of the... ..--.-<--<- 2... ° 369 in Solano County .....--..----+-e++eeeee cere eeeeee 378 BEACH aera ore eee ecinns ic jele oa ialciminini Smale acale aim mieiwin 198, 460 (See, also, Metamorphic rocks and Aucella.) Nertschinsk district, Siberia, cinnabar in...-. ..----- 45 Net structure i New Almaden district, geology of --.-..------------- 310, 467 fissure system Of.......--..----2--+--+-eeeee 2220+ 328 New Almaden mine, discovery of.....--------- ------ 8 318 plans and sections of Newberry, J.S , cited ..- | Ore deposition, theories of Ore deposits, age of at Great Eastern mine at Great Western mine ..........-...---.---+----- at Knoxville .............. at Manzanita mine at New Almaden SUGANO vapLGL UG Shaeetetsiercts stele lalate wtetei=(= =e'c(tiv winis)==in'=n'ole aie BUSTER DOR ete aeteeied ase eins aiaieanio ols wine rales slate at Sulphur Bank... character of ...... discussien of.......----- 5 furmiOfe posence cee sesamiae sence esescnewee~ == sin = MINGTAIS My ae we oe ees ee al etelen a wnale ea'eln ote siniminin minor, descripsions of ......-.....-.ee eneeee---- OLUP ING OL jets ctes as cree sate aloes mae eie aelalal es hmslalaietacetaet c 3 relations of, to general geology.--... - 225 WELL ROCKS! Ofte ccle = lames a tice am ste 391 Oregon, Chico beds in. ....--...---------- 206 CinnaADan AM) sees ole cee ee ccacmlceiay «sip e'n= 366 | Organic matter, eanerelivns CUG {00 io awer cic earls annem 66 OBOLS KU AT CLUOC as cle teate aiee wialeicvie icrotewe'p,<]~ seslwinlains sins 45 ie Pan OCHeistuiCtiesene-- seen oo = ates cieaetens Boe 7 Bit) Panoche Grande mine, Fresno County ..-.--------.--- 380 Paso Robles hot Springs). s-20.2 -2-- 2 oe eewsecerecer=n~ 381 PAVLOV Avy CLUC Cl arereteteraln Su lerein ete met asa o'ei vin leiriaiem eletninisl iar 204, 229 Pebbles, formation Of... s.cscasaa\a-sseocechnaneh == 71 New Idria, Chico-Téjon series at ..--.-------- ------- 215 district, geology of ....-...----+++--20-220- 222 0° 291, 465 ONG pee es etal tn 301 non-conformity at 189 sandstone concretion from ...--.----------+++----- 64 New Idrian mine, Douglas County, Oregon...-------- 366 New Zealand, cinnabar in .......----------+-+-020+°-° 49 Nicholas, W., cited ........-.------------ 2 scree teeeee 49 Nichols, R. K,, Citeduea dese esassece pos eae 233 Nodules and pebbled, theory of fanaiation’ eu 68, 455 Noggerath, A., cited .....-..-. 15, 19, 23, 27, 28, 32, 33, 35, 45, 49 Non-conformity, between the Téjon and Miocene -.--- 218 | Post-Miocene .....-.--------- ----2e2- ee steers 218, 461 Non-conformity, Post-Neocomian...---.--.------ 177, 188, 460 at New Almaden.........--------- -e-eee eee reee ee 313: | at New Idria..........-..----- .----+ -<--+"-- 295 indirect evidence of....-.-.----------+++---- 192 on the Gold Belt.......---- 196 paleontological evidence of. 193 INGWOIG Ue cited ease omens a 7 Nova Scotia, cinnabar in.......--.-----0+- 02 -ee2e eee: 16 0. Oakland mine, Sonoma County ...-- Bee cniaistetee ctalsieimta =I 377 Oakville mine, Napa County.....-.----+--++---++----+ 377 Oathill district, geology of .......---------++----- -. 854, 409 Obsidian, andesilic .......-..---------+----+-+ --++-- BUSAN Caeser se ose ninise seals fae B= == = Oceanic mine, San Luis Obispo County..-...- Ocean View mine, San Luis Obispo County -- Olivine in andesite Onofrite at Knoxville ... Opal at Great Eastern mine, Lake County at Great Eastern mine, Sonoma County. at Great Western mine .. at: Knoxville.-......... at New Almaden.... at Steamboat Springs - Oppert, E., cited Orbigny, A. D.d’, cited Orcutt, C. R., cited Ore, description of ....-.--..-------+-+ aan microscopical character of origin of (See. also, Cinnabar.) Ore deposition, at Steamboat Springs..... saaaeaense es at Sulphur Bank ......... --.-+-4-----+-+--++ hee Pence’s Ranch, Carboniferous fossils at Perez-Rosales, V., cited Perowskite in opal Peru, cinnabar in Petersen, T., cited. - Pfliicker, L., cited . =e Philippine Islands, etaaicn injee=a PHUlips yeas ClLCd seca ate sean seen a Phoenix mine, Napa County .-..-............-.-..-.-- Phoenix No. 2 mine, Napa County . Pholas borings - : NtRaM te wees aan ene Phylloxera, quicksilver ased to kill..........-.....--. 3 Picacho mine, San Benito County ..--.... .-----.----- 309 Ringrtw Ay WCicedlscoe~ ama ssc e eo 202 Pioneer mine, Lake County.....--- 376 Pipe veins'--.---.----.-.-..-.-... 411 Pittsburgh mine, Lake County -- 376 Pliny, (cifed!- sos ccwe-pe~en==en 4, 28 PUIG CONG nse saeco oe ans aoc eewemiee eens 219, 238 probable at New Almaden ...--....--.---..------- 314 Point Reyes, cinnabar at....-..------.++..---- 379 Polar Star mine, San Luis Obispo County 382 Pope mine, Napa County .-----.--------.--- 74 Portugal, cinnabar in: -...-.-<---s-0s---conseceeeen nes Pyt Posepnyte at Great Western, analysis of......-.------ 360 Post-Pliocene described ....-...----.--- +----+ 219 Potassic sulphide, action of, on cinnabar -.-.-... 419 Potassic sulphydrate, action of, on cinnabar 419 Prado, C. de, cited. 18, 42, 397, 399 Primeval rocks ..- 171 Pseudodiabase ........5.seecceccnc-nne cence seeenenen ane 94 analysis of .......... any Conese Deanae daniastecets <9 98, 99 Pseudodiorite ......-....-.----- Cosa OSH aIcsS analysis of ...-...--...--- ieee deena naan Pseudomorphism and substitution... Pseudomorphs, cinnabar after barite -- 484 Pseudomorphs, cinnabar after magnesite galena after calcite .............-..-.------------- Pumpelly, R., cited.......--..--. eae oeee essen seen! Pyrargyrite with cinnabar.......--...-..--.------+--- Pyrite, solubility of. ............---------++----+++---- Q. Quartz, conversion of, to serpentine -.......-...-..--- 123 Quicksilver, average price of.......------------------- 1 DOLG: ee on ee eee en ee ecenese as aoa artinae ae 365 Castitlerostestfor.... -..--.... .--s..--<--. 9 deposits in andesite. ................--..-.--- 245 discovery in California --. 7 historical notes on - 1 in Scandinavia -..- 27 in Scotland..---. ----.-..- 27 in Steamboat Springs water-.-.-..... 347 mines of California, distribution of. - = 13 mining, future of -......-...-.------ 417 native. formation of... 436 foreign occurrences of -.-.......-. 4 often found with gold and silver .--...---..--.---- u) ores, conclusions as to occurrence of ..-..--..----- 50, 416 product at Steamboat.......--.-------......-.---. 332 product in California.......-.....----..--.-------- 10 product in Hungary .......--.....----- sSansistbes3 41 pradoctanvluscany- 2-20 seen ens eee ean nena 6 products of districts compared ...........-.--.--- 7 relative abundance of, in nature .-.--.....-.-.-.-- 2 TEIALive waluelof cape se eee aeaeencese te ae e ene 1 TOCK. (see. Gix0, | Ojynl)i-aa- == 3 --- oe anes eee conn 63 BEALS CS fos tee anys Soca aaa a 1 USG8 (0 fesse ene eee oe ieee 3 value of product of, since 1850... 3 world’s product of, since 1850 ...--...:-----.--:--- 3 R. Te ATATN OTS @e\p OG LEE 9 ee OR Ee eee es 20 Ramirez, S, cited... 16, 17,18 LATO TOSS Joa oe el 0 PER Ae Bes es aoc on cigsaecose as 3, 6,10 Bath, G.ieOmiy Clee == ens ee see ne= == eee ee 20, 23, 34, 118, 159 TN Ce rts le Ae esa ts xiv, 319, 321 Redingtonite, new mineral.......-..-..-...--.-------- 279 Redington mine. ........-2....-----...---..--+.----=-261, 284 discovery of 10 Reed mine (or California mine), Knoxville district -..281, 283 Vey Ga tri ee eee eS a er ae 86, 106 Results, brief outline of--.....-..... 02... ~.---.------ XVii Reticulated veins of cinnabar......-.----------------- 54 RRONSS Acie ClO een eaes sence = aee en ene cone ase ann 398 Reyer ss Clted nao ee ec oae saan ee oes nneem meinen 441 Rhynchonella, in Colusa County ..-...-..------++----- 235 Oconrrence! Of oo oeese cee eee, 183 Nevolite .....- EES =Os eae 156 age of..-..,.- 223 dike at New Almader.........-...-.-.----------- 313, 329 Richthofen, F. von, cited --. -6, 46, 313, 353, 448 Rigidity of the earth......-- see sg aR RVG yO. sin, ClUe Ca eee - 268 Rinconada mine, San Luis Obispo County ae food Rising, W.B., cited .:-... ... 220. -.0ceccneennee-ann--> 257, 263 Rivero, M. E. de, cited. . 9, 17, 21, 22 Roach, J., cited... 22. noe nie cence enna = enna nnn=nw £09 Rockland district, Del Norte County, cinnabarin --.. 366 Rocks, sedimentary .....-.--.-.--.4--- see eeecee -0----06, 453 MMASIVG -casmcs one ccusss aeons Stee ead eer etseee ee 140, 459 INDEX. Page. Rotnd. Ge Creed —- ee se new ae eee ee ee 36, 315 Rosenbusch, H., cited. 86, 109, 118, 390 Rossberg, basalt from the ..-------.------------------ 160 Roth dc, Clie’ = 4. sonceese se = aaa 48, 66, 77, 118, 422 Russell, L., cited eco AV Russia, A UcallG Wie sae nema ee ee ee 202 CINNSADAT IN aso ae se mae eee temas ae eae eee 43 Rutile in metamorphic rocks .-...-----.-------------- 84 Ss. Safford: Sec, Gilet! sosee aerate te eee eee 44 St. Johu’s mine, Solano County .--- 378 San Antonio mine, New Almaden district 327 San Bernardino, cinnabar at .--...-..----------------. 383 San Carlos mine, New Idria district .....-...------.-. 308 Sandberger, F., cited ...... .-----.-.----------- 18, 118, 251, 436 Sandstone, alteration of the i] altered, development of minerals in......--.------ 87 analysis of ....=-------- 92 component minerals of 62 derived from granite -.....-----...----..--------- 60, 61 interstitial space in.......-.2.--=-+--.02------=-- 399 microscopical character of ..-.-....--------------- 61 transformation of, (o serpentine . -121, 277 weathering of the -.----.--.-.--- : 63 San Francisco, cinnabar at.--....--..--------- 379 San Francisquito Pass, metamorphic rocks of --- 185 San Juan Bautista mine, Santa Clara County-- Ss 879 San Mateo mine, New Almaden district --- 327 | Santa Cruz, terraces at 207 Santo Domingo, cinnabar in...---....- aecace ewe ease 16 Saussurite in metamorphic rocks..-..-.---..---------+ 82 Scandinavia, quicksilver in.......--..-.....+--------- 27 Scapolite ....-....---.----------.0+-s000 esos accse=3 129 Scheerer, T. , cited - 119,163,173 Schindler, A. H., cifed -.-.....--..5.s2-.-2-- Saeoe 44 | Schmitz, (cited|--.---q---4-----euens 5 ee 383 Schrauf: A., cited =..-..-.-2. i. cesses Ben oo cor 87,127,394 Schréckinger, J. von, cited-......... Se ccsoren 360 | Scotland, quicksilver in.--. --..---.+.--..+ Reser saa 27 Scrope, G. P., cited.-...-.---.-....50. eaesb anne eas 72 Sedimentary rocks) 2---2.-+---=---0npstsbese-==n--- 56,59,453 Senarmont, H. de, cited .-.....-.--...-..-.-- 434 Serpentine ..-...--..----------+--2+--2----5+++ ~- 108,457 analyses Of <<< <5. ce .enne=-neenn === =e -- 110,111 at Great Western mine...--. or Ae. - 309 at Knoxville .....-.--..- - 2G at New Almaden .-.--.-. 31l at New Idria-.-.-.- = 203 at Sulphur Bank.. 251 Carboniferous. ---- - 210 colloid ............ 115 decomposition of . .-. 127 derived from olivine 115 derived from peridotite ........-...--.--------2 59 derived from sandstone .-.......-..------------+-- 277 grate structure ip 115 microstructure of 14 mineralogical character of ...-.-.-------. “108 minerals yielding 118 net structure il .-....-.2. .---------------- 2-2 2ne- 115 origin Of .-.---.---..----.---s0---0---- 117 pseudomorphs of......----. ne 118 relations to olivine rocks... 312 Serpentinization, course of .... 126 Servia, cinnabar in.....-.... a Dire eds ee 41 INDEX 485 Rare. | Shasta group..------------++--+-2+ sees ee eee eee 179,180 | Sulphurous acid at Sulphur Bank 5 Siberia, cinnabar in.....---.---------+-- --+----225-- 44 | Sulphur springs, hot, at the Manzanita 207 Sierra Nevada, persistence of the.-...-....-.-----.--- 209 | Sumatra, cinnabar in 48 structural relations of the, to other ranges .....-. 208 | Summary of results. - 451 Silica of sinters at Steamboat Springs ..--.--.--- 341 | Sunderland and Luckha mele! MiN@ wae scenes see ete eee 382 Silicification, at Knoxville ...... Cocdncoaseacasa. Palin|), Sine k es (1a Se oeesaroaac peaoces a Sonn asa acc 8 opaline ...-----.-------------ee-22-2-+--- 392 Synclinal hills in metamorphicrocks .......----+------ 183 Sillem, cited ............-..--.---------+----- JORIS ZADO NRC LLCO meeee seme = meee ace Coon cinrcncccistom linen 118 Silliman, B., cited 6 Bcc 315 mn Silver, abundance of, in nature relehively to quic i i BI Olea oe neae cena ae conc e nicn cn nine scimese'enn=~ 2 Tale in metamorphic rocks....--.-.--- ----- 113 accompanying cinnabar ...-.....----. 19, 309, 370, 389, 38 Téjon, at New Tdnin: -.. os. e-.2. seceeneeewnecenee---- 299 product compared with that of quicksilver ..-- .- 3 Meds) aPelOL the) <= --.2--cceccnwencercqs= 177 sulphide, insolubility of -..---.------+-----+ --++- Ded SWlIsCusSe Cues enna siecle neem ccele mame = 214 Silver Bow mine, Napa County.’ | conformable with the Chico .......---..-----..--- 192 Simundi, A controversy as to age of ....... 215 Sinters, absence of, explained .- determined as Bocene...... --- 217 dendritic, at Borax Lake.......-...-...----------- PLOUDECee ee edenaas a 179, 180 at Steamboat Springs .--------...------+----+++--- Terraces of California coast 207 Sisapo, ancient name for Almaden ....-..--.---------. 4 | Texture of massive rocks. - 162 Skertchly, S. B.J., cited .....---------+-------++ee-0 ++ 48 | Thenard, P., citéd)-.-.-.. 2 187 Smyth, R. B., cited 49 | Thermochemistry, Erolcaton of. 427 Sodic hydrate, influence of, on the solubility of cin- new lawof .... 119 MDMA cae so = oa Seen sane enue ana sininsioce nes 422 Thibet, cinnabar in 47 Sodie sulphide, in nature. .-.--.---- TESCOC Ona eM CHAERECO GEL || Why) HG oeee anes 267 solubility of cinnabar in... ..-.----++--++-+++--- 419,423 | Thomsen, J., cited 430 solubility of pyrite in........--...-----+---------- 432 | Thomson, W.., cited 167 Sodic sulpkydrate, behavior of, to cinnabar..--- 419, 424,428 | Thiivach, H., cited.......----+----0+---+-+ +e eee eee eee BL Soectheer, A., cited......-..---.-------+-+--------- 3) )) Wurston ake! 22 . .<-- Soe ce cee oman nninnn awn wwenee==-= 244 Solutions of cinnabar, effects of dilution on ES AsgHeeDiemanniteanyO tal oe) oot= 2 an tone eelen == 385 effects of other substances on..--.. - 431 | Tin product compared with that of quicksilver .....- 3 Sonnenachein, F. L., cited.....--. Sey NBER Guiseteicn J2\ee Wiles ceeemohosooa rsa eassropeeoncaS 43 Sonoma nine, Sonoma County -.----..---------- ----- 377 | Titanite in metamorphic rocks........---.------.----- 85 Sonth America, cinnabar in.......--..-.--+ ----+---- 1) | Todos Santos Bay, Wallala beds at......-.-- 213 Southern California ...-.. ----.-+.---- 140) || Lonla; H:; cited. =. .----- SseacdEtts - -203, 227 Spain, cipnabar in .-... Pfs at Le Wi hsLts oeee siete ae Ase ASS SE DOScIC NSS OSr OS --- 150,155 Spitzbergen, Avcclla in. ----.5----+- ----+--++ +-+---- 203 | Transition andesites.-.- - 148 Springs at Steamboat.-...-..---.------- 338 | Trask, J. B., cited. .-.-- a ent Star mine, Napa County 373 | Trautschold, H., cited... Zs a 20k Statistics and history of quicksilver .....-----.--..--- | Trinity Connty, cinnabar in .... -- 366 Stayton mines, San Benito County..-.---------- - )Erinity wine eee e-sse 2 2- ose ---c=> 366 Steamboat Springs district, ceology of ......---- | Triassic fossils at Genesee Valley -..-...--.---+ --+++ 195 Giabaseiat. ...-2ce--5f 22.22.22. i) Dringsic inl Oalitonnla tess en a2 o= peat em ecileee mma 178, 198 granite of...-------.....-------- | Tschermak, G., cited.-.---..-.--..-.------- 43, 86, 118, 143, 439 metamorphic rocis of .-..---.--- | Tule roots, silicified, at Sulphur Bank..--. -.--------- 254 Stearns, R. E. C., rited.-..-.---.---- Wem bers SA C1ted)c aa. esse snceane wala enaae es 227, 231 Stein, W., cited._........ Manis; Ch@navAL iN ssasslo4 eeews hs sh ecese esse ences 44 Stetzner) A., Cived . Minuicoy? GINS MA e sere saniseewee emeeneteaae= saa 42 Stibnite 4-=>- .----- 2 367, 380, Seo lw Tarnorsh: We, citedea-ceasssstarsaasrenesteeeue o- =. xiv, 354 Stoliezka, F., cited .--..-- --.-+++--227, 231 | Tuscan mines, product of.......-.-------+--+-+-++2--00 6 Stratiomys at Borax Lake... Stee aetna inom aotae 268 | Tuscan Springs, Inoceramus at.......--------+--++--+- 197 Substitution of cinnabar for rock -..---. 286, 315,317, 394, 399 | Tuscany, cinnabar im .......-000+.----00 eens eee e ee eee 35 Sulphides, associated with cinnabar ...----..----+.--- 388 | origin of 438 Ue Sulphur, at Manzunita mine 367 | Uncle Sam Mountain (Konocti) -...-..-..-.---.------ 233 at Steamboat. ..--...--.-s-<20.-2:----- 00-005 -- anes 346 | United States cinnabar in, confined to Pacific slope.. 15 at Sulphur Bank.....-------------+--+-+-+-+-++--+ 254,463 | Upheaval, Post-Miocene .-...- .--..------------ 218 Sulphur Bank, descriptive geology of.......---.------ 251 Post-Neocomian ...-.-.--.,--.--+-------- - 188 discovery Of .......---------- 200 -- nn ne ence ee cwnene 10 | Upheavals, exposure of primeval rocks by...-------- 166 future prospects of ..-...------.2-- 20 eee eee ete 264 | Uralite in metamorphic rocks ..... AASenaSeoocer OSTcs 25 high temperature at ....--.---.----------------+-- 259 | Utah, tiemannite and cinnabar in....... ...-.-------- 385 resemblance of, to other deposits...--..--..----- 263, 402 | y Sulphur Bank mine ......----.----------+-----+---- 253, 263 | ; Sulphur deposition, at Knoxville 287 ~-Vallalta, description of -...--...-- Beye oa nneaasaal owas s 34 at Sulphur Bank..-..-----------.--------- 254 principal mine in Venetia. ..-...-,---.--+--+0+ -- 5 Sulphuric acid at Sulphur Bank, genesis of 255 Valley mine, Napa County.......0. ---.---+ OCCHERDS 355, 371 486 Page. Vieatoh:d.:A:., Cited s.asc Seiekeas maps ooh ee Meee eee 265 Vegetable growths in springs at Steamboat Springs... 346 Weilnicham bers ins sceon eee tere mene eie ema same eet tate 412 Veins! ati Oathillisoseases nts rene las tenner ccemsee a =e 356 CISCHESGU cee enone eee eee nee eee omnes 407 OPE TOM EL teen anno Sooen esos cre ncn Sanne eee 406, 472 of cinnabar at Knoxville............ ne Se noceeaoe 288 of emnabar in foreign countries. - 53 recent, at Steamboat Springs... 340 Velten and Lehmann, cited. ...... 18 Werbeok ReiD sir Cited ecm aces onion felt cin 48 Vermilion, nse of quicksilver in manufactare of. 3 Verneuil, P. E. P. de, cited 28 WiRCOSIGy ObsbHENGATENS cae ose oe cee ne nee 202, 204, 228 Whitney, J.D., cited ...46, 121, 140, 155, 176, 179, 185, 192, 215, 218, 224, 242, 265, 313, 376, 383 DV ilkinms Oe Ws sCxbC dis nec eron ete ea canis cease 160 Z. AIBGkeny CO. Oiteds snr se casas Secon pectin clateee 44 Zinc sulphide, solubility of ....----.--- 25. -2.--e-coeee= 434 Zircon in metamorphic rocks ...........--..------.-- 87 Zirkel ks \ciied oe: 0) Sie oc y, aa cam th f ‘ j . WAIT ay ey / ie rc a N N o o o ~ of 0 fe) So ao o