DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY 

GEORGE OTIS SMITH, DIRECTOR 

. 

PROFESSIONAL PAPER 66 

THE 

GEOLOGY AND ORE DEPOSITS 

OF GOLDFIELD, NEVADA 

BY 

FREDERICK LESLIE RANSOME 

ASSISTED IN THE FIELD BY 

W. H. EMMONS AND G. H. GARREY 

'V ASHINGTON 

GOVERNMENT PRINTING OFFICE 

1909 

CONTENTS. 

·· Page. 

CHAPTER I.-Introduction ........................ __ . ___________ . __________ ._._. ___ ._._. _____ ....... _._ ... ·. 13 

Field work and acknowledgments ....... . ......... _ . ______ . _ .. ____________ . _____ . ___________________ . _ . 13 

Situation of the district.-~ ............... _ ..... ______ .. ________________________ ______ __ __ __ __ . ____ . :' ... 14 

Topography .................... ... · .. ..... ............ .... _._ ......... ______ ..... __ ........... _·_..... 14 

History of mining ................................... . __ .. _ ...... _ ....... _ .... _ ..... ... _ .. _ ........ ·... 16 

Production .... .................................................. _ ....................... ~ . ... ._. 23 

Literature .............................................. . ___ ............ _._._ ... _._........ . . . . . . . . . . . 24 

Geographic names ......... .. ............................ _._ .... .. : __ ._. __ ._. _____ ... . _.............. 26 

CHAPTER H.-Preliminary outline of the geology and ore deposits ..... _ ........... _______ ..... : .............. 27 

CHAPTER IlL-Description of the pre-Tertiary roeks ............. _ .. _ ......... _. _____ . ____ ... _ .......... _·_.. 32 

Cambrian shale .................... .. ................... ___ . __ . ____________ . . _ ........... __ . . .. _ ... .. - 32 

Alaskite and granite ... ... ............ _ .. _ ....... : ._ .. ________ ... _ ... _._. ___ ____ __ ... _............... 33 

Definition ..................... _ ............. ______ . _ . _ ...... _ ...... _ . _ . _ . _ . ______ . ____ . . . . . . . . . . . 33 

Distribution .............. ...... ..... . __ ............... _ . _ . ______ . ____ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 

Petrography .. . ...... .... ........................ _ ............................ _ . . . . . . . . . . . . . . . . . . . . 33 

Geologic relations ......................................................... _ .. _ .... _ ......... , . ~ . 34 

~~ge ......... . ......................................... : ................... : ... ·. _ . .. _. ......... ·... 35 

CHAPTER IV.-Description of the prelacustrine Tertiary igneous rocks........................................ 36 

Introduction ........... ................................................................. : ........ : .. 36 

Vindd~:~:a~~i~:!~t~; ~~-d ~~~~~~~~-- -- ~: ~: _-_-_-_ -- ~:::::::::::::::::::::::::::::::::::::::::: :·::::::::::: ;; 

Petrography ........................................... __ .. _._ . . .................... __ .. .~ ... _.... 38 

Lati te ............................... .. .......... _ ........ _ ........... . .. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 

General character and occurrence ...................................... . . . ... _ . . . . . . . . . . . . . . . . . . . . . 38 

Petrography ............... .......... _ .. _____ ..... _ ... ·. _ .... _ ....... _________ .-. ... _ . . .. . . . . . . . . . . . . 39 

Kendall tuff ................................... _ ..... ... . ..... . . _ ..... __ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 

Sandstorm rhyolite ....................... _ . ____ . ___ ....... , .. _ .... __ .. __ . __________ ... _ . _ . _ . _ . _ . _ .. . 

General character and occurrence ............................................ ... .................. . 

Petrography ........................... __ ... _ ..... . _ . _ . __ . ______ ..... _ .. _ . _ . __________ . __ . _ ...... . 

Morena rhyolite ............................. . ________________ . _______ . .. _ . ... . _ . _ . ________ . ___ . _. __ . 

General character and occurrence ...................... . ...................... _ . _ ................. . 

Pe-trography ................................. ___ . _ . _ . _____________ ... _ .. __ . ______ .. ___ .... _ . __ ... _ 

Milltown andesite .......... . ........................ : .......................... · ............... ·_ ..... . 

Introductory statement ........ .......... _ ... _._._. _______ . _____ .. .. _._._. ______ ... ___ ........... _ 

Distribution ........................ _ .... ___ _ ._. ___ ._._. ___ ._. ___ . __ . _ .. _: .. _. __ . __ ._ . __ ... _. __ .. . 

Petrography ................................ _ ....... _ ... _ . _ · .. . _ . .. _ . ____ . ____ ... .. _ . _ . __ .... _ . _ .. . 

General character of the formation ............. . ............. , ................................ . 

Hornblende-pyroxene andesite ................................... . ........................... . 

Pyroxene andesite ............................................ . ... . .......... . . . ....... ... ... . 

Hornblende-biotite andesite .............. ·_ . ...... _ ................ _ ....................... . . --. 

Tuff .................... ................ ____________ ...... ----------------------- ___________ _ 

Basalt .............. · ... _.:._ ...... _.· ...... _ ....... _ .. ____________________________________________ _ 

Geologic relations ...................... ... ............... ..... ..... : . ............................ . 

Dacite .................... .. .. ... .. .. ................... .. ....... . .......... .. ............ -.- ... ---. 

~~!~:~:t~~~ ~~~~~~~~~---_- -_- ~ ~::::::: -:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: 

Petrography .............. . . . _ . _ . _ . _ . ___________ . _ . ______________________ .. __ . _ . __ . _ . ____ . _______ _ 

Geologic relations .................... -. . _ .. _ . _ .... _____ . _____ ..... ... __ ...... _ . : ..... _ .......... . 

Dacite vitrophyre ................. . .... . ....... . .. ...... . _ . _ . _ . ... _ .................................. . 

General character and occurrence ............ ... ............. . ....... . ... . ..... , ............ _,_ ... . . 

Petrography ............... . ............ ... ... _ ... . . . . ... . _ ... _ ............ . .................. _ .. . 

Relation to the dacite .............................. . ............. . ... . ....................... -. -.. 

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4 CONTENTS. 

CHAPTER IV.-Description of the prelacustrine Tertiary igneous rocks-Continued. Page. 

Chispa andesite..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

General character and occurrence......................................... .. ..... .. ................ 6 

Petrography ..................................................................................... . 

Andesite dikes ................................................ . ... ... . . ........ . ---------------------

Meda rhyolite ................................ ..... ..... . ............... ...... --. -.... -----· ---· -· -· -· · 

General character a:rid occurrence.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Petrography.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

Andesite breccia ...... ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

CHAPTER V.-Rocks of the lake epoch...... . .... ...... ........................... ... .............. . ...... 6e 

Introduction..................... . ........................................ . ......................... 66 

Siebert formation ................................................ ......... ............... ·............. 66 

Distribution.............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 

Lithology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 

Thickness ............................. : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 

Conditions of deposition............................ ... ..... . ........... ........... ................ 68 

Stratigraphy ........................... .... ....... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 

Mira basalt .......................................... . . :. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 

Occurrence.......................... . ........... . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 

Petrography ...................................................... . . ... ... ......... . . ............ . 

Espina breccia ...................................................................... . ................ . 

CHAPTER VI.-Postlacustrine Tertiary rocks .............................. . ..... ... . ... .................... . 

Introductory statement ........ ~ ..................................................................... . 

Pozo formation .... · ................................................... . ... ... ................. . ....... . 

Spearhead rhyolite........................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . · 7 

Rabbit Spring formation......................................... ...... . .. .......... . .. . . ... ......... 7 

Malpais basalt.~ ..................................................................................... . 

CHAPTER VII.-Quaternary deposits .............. ... ................. .............. .......... ... . . ....... . 

CHAPTER VIII.-Geologic structure .................................... ... . ... .... " .. .. ... .. .............. . 

CHAPTER IX.-Geologic history and correlation .................................... ............. .......... . . 

Introduction .................................................. _ ........................... · ... _ ..... . 

Local geologic history .................................. ·_ .. ........... ....................... ... ... .... . 

Before Tertiary time .............................. . ....................... . . . ..................... . 

Tertiary prelacustrine epoch ................................................................. : ... . 

Lacu.strine epoch ............ _ . _ .............................................. c ••••••.•.••••••••••• 

Postlacustrine history ....................................................... ........ ............... . 

Correlation of the Goldfield rocks with those of the surrounding region_ .... . ............ ... .. ...... ..... . 

Introductory statement ............. . ................................ ... . .. .. . .. ........ ......... . 

Prelacustrine rocks........... ... ... ...... .......... .... ........... . . . ....... . ............. . ...... 92 

Lacustrine sediments ....................................................................... __ .... 95 

Tertiary chronology of the western part of the Great Basin ............................................. _ 10 

The eruptive sequence ....................................... · .. .'..................................... 105 

Tertiary climate ......... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i06 

CHAPTER X.-MiJ?-eralogy of the district ................................. r •••••••••••••••••••••••••••• -....... 108 

Introduction ....................... .. ........ ... .. . .. ......... ................... ,.................. 108 

Notes on the more important minerals associated with the ore deposits.................................... 109 

Sulphur ........... ........... ......................................... ........... ·. . . . . . . . . . . . . . . 109 

Gold .................. ........... . : ........................... .. ... . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 

Copper....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 

Bismuthinite ...... .... ... ............... . ........................................ · ... · ........... _._ 111 

Galena ...•........ .-................................................................... . ·. . . . . . . . . . 112 

Sphalerite.......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 

Cinnabar .............. ................ .. ...... ... ........... ... : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 

Chalcopyrite ........ ..... ..... .... ......... . . . ......................... .. ___ . . . . . . . . . . . . . . . . . . . . 113 

Pyrite ........ ... . ........ ...... ........ .... .............................................. _ ... ... 113 

Marcasite ..... ·..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 

Tellurides of gold .................... _ .... _ .................................. _ .. __ ............... 115 

Proustite. ~ ............. . .......... .... .. ... : .............................. ... ...... . .......... ... 116 

Polybasite ........... . ............... , ..................... _..................................... 116 

Gold:fieldite .................. . ".......... .. .. .................... ... ......... .. .... . ............. 116 

Enargite............................................................. .... ........................ 117 

Famatinite............ . ....................................... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 

Cerargyrite ...................... ... .................... :........................................ 119 
CONTENTS. 5 

CHAPTER X.-Mineralogy of the district-Continued. 

Notes on the more important minerals associated with the ore deposits-Continued. Page. 

Quartz ...................... _ .............................. _ ......................... ~ . _ ....... . 120 

Bismite ......... ............... · .......................................................... _ . __ . -·-. 121 

Tellurite. ___ ... ....................... , ................ · ...... , .............................. -.--. 123 

Massicot. _ .......... , ....... _ ............................................. ___ . __ . _ .... _ .. _ ..... _ . ,. 123 

Hematite.· ........ _ .... ___ ......................................................... _ .......... .. . 123 • 

Rutile .. _ ...... _ ...................... .. .............. __ .... __ ..... ___ . __ .......... _ .. _._ ....... . 124 

. Diaspore_ . __ . _ ................ _ ............... ..... ... _ . _ ....... : ................... -. --....... . 124 

Limonite .......... _ ... _ ... _ ... _. _ .............. . _ . . ___ . ____ · _________________ __ . _. __ ............ . 125 

Calcite ................................. _ .. _._. __ .. _____ _______________________ . _______ . __ ....... . 126 

Feldspars_ ... ___ ..... _ ....... ; ...................... _ . _ . ______________ . ___ ... _ ................. . 126 

Epidote __ . _ ... _ .... _ . _____ · ________ . : _____ . ____ . _ .... ___ . _ . ____ . __ . _________________ . ____ . __ . _ ... . 126 

Muscovite .......................... ·_ ...... . ........ .. . _. _ .. _______ .. ___ .. _ ........... _._ .. . .. _ .. . 127 

Kaolinite ........ _ . _ .. __ . . · _ . _ .. __ . _ .. _ ·. _________ . ____ . __ . ____________________ __________ . ____ .... . 127 

Barite ........... _ .. ____ . ___ .. _. ________ . _ .. ____ . _. ___ . ___ . _____________________ . _________ . ____ . _ 127 

Gypsum. __ ... _ .. ____ .. _. ________ .. __ .. _ ... ___ ._. _____ . _ .. _____________ . _____________________ .... 128 

Melanterite. _______ .. ___ ___ ___ ___ . ___ . ____ ___ ... _ . ____ _____________________________ . _____ __ .. __ _ 128 

Chalcanthite ..... _ .... __ . _. _. _ ............ __ . _. _ .. ___ . _. _. _____ . _________ ____ ___ . _________ . __ .. _. 129 

Halotrichite ............... _ .... _ ... . _. _-___ .. __ . ____ · __ . _. _. ___ .. __ . _. ___ . : ________________ _ . _ ... . 129 

Alunite ................................. , .... . .. .. _ . ....... _._ ............. _ ........... __ ....... . 129 

Jarosite ... _ .. _ ........ _ ....... _ ...... ______ . __ ... _. _______ .. __________________ ._. ____ . ____ ._ .... _ 133 

Emmonsite and durdenite ... ___ . _ ..................... .. _. _. _. __ .. _ .. _ ... _ .... ___ ... _ ........ __ . __ 133 

CHAPTER XL-The mines; a general account of their distribution, development, and operation, including ore 

treatment .............. _ ................... -........... _ . _ . _ .. _ . _ ... _ .................. __ 135 

Distribution and underground development. ................ __ .... _ ... ____________ .. ___ . __ . _ . __ . _ .... . 135 

Mining costs ....... ... _ ... _ ......... . ......... .......... _ .. __ . ___ .. ____ . ___ .. _ .... _ .... .- ............ _ 141 

Power ....... _ ... __ . _ .... .... .......................... _ ............... ..... ... _ .... _ .. . ............ . 142 

Water supply .......................... -....... ___ .. ______ __ ~ _. ____________ ___ . ___________________ . __ . 142 

Treatment of the ores .... __ .. _ .. _ ......... _ ............ _._ .. __ ... ___ . ____________ . ___ .. _ ... _· __ ... _._ .. 143 

CHAPTER XII .-The ledges .... _ ...... : . : . .... _ . ................ _____ . __ . _______ .. ____ .· ______ .. _ . _ .... _ .. . 150 

De:fini tion .... _ ....... _ ..... _ .. ___ . ____ .. _ . _ . ____ . ___ . .. __ . _ ... __ ._ . __ ___ . ______ . _____ . _ . _ . __ · __ . ___ : .. _ 150 

Distribution ..... __ .... . ........... _ ....... . ....... __ ............... ___ .... _._ ........................ . 150 

Trend or strike ... ___ .......... ____________ ___ . ___ . _ . __ · _____ . ______ ... ____ ... ____ . _ . _______ . ______ ... _ 152 

Dip ............. ' ..... ---- ..... ------ ................... .... ...... .... . .... :_ ............... _ .. __ ... . 152 

Shape._ .. _ .................... __ . ____ .. ___ . _____ ._. _____ ._. _________ ______ _______ ... ______ ___ . _____ .. 153 

Material and minor structures ................................... __ . __________________ . _______ .. _____ . 155 

CHAPTER XIIL-The pay shoots and ores ..... _ ... ____ . ___ . ___ . _____ .. __ . ____________ . __ _ . _____ .... _ .. _ .. .. 158 

Distribution ...... _ ................. _ .. __ .. : _ .. _. ____ . ____ .. ____________________________ . _______ ...... _ 158 

Relation to ledges ... _ .... _ ... : ............... __ . _ . __________________________ . ___ . ____________ . __ .. __ _ 158 

Shape._ ........... _ .. . ·-.......... __ . ___ .. __________ .. __________________ . ___________ . _. _______ ..... __ _ 158 

Relation to fissuring ... _ ...................... _ . _ .. __ .... _____ . ____ . _ . ___ .. ____ ... ___ .. ____ . __ .. ___ .. ,. 160 

Effects of faulting._ ........ _ ... _._ ........ _ .. _ .. _._ .... ___ .. __ ._. ________ . _________ . _. _• ________ . . __ .. _ 161 

Influence of country rock .................. _____ _____ . __ ._. ___ . __ : _____ ._. _________ . ______ ___ ._ .... _._ 163 

Mineralogical and chemical character of the·sulphide ores ... ... , ...... _. __ . ___ ._ .. ___ _ . __ ._ ... ___ .. _ .. . 165 

Paragenesis .. _ ........................... ___ . _ . . _ .. _ .. ___ . _ . ___ .... __ . _____________ .. _ . ______ . ___ .. . 169 

Mineralogical character of the oxidized ores ............. ___ ................................. _ . _ ....... . 170 

Value of the ores .......... _ ......... ......... .. .. ...... _ .. __ . ________ . ____________ . __ . ___ ______ . _ .... . 171 

Areal variations in the ores ..... _ ......... ~ ... ___ .. _ . _ . _ . ____ . __ . ___ . ___ . _ . ___ . __ .. _ . __ .. ____ .. _ ...... . 172 

Observed changes in depth ............... _ . . .............. __ . ___ . __ .. __ . _______ .. _____________ ...... . 173 

Original depth of the ores now visible ..... _ ........ : _ .. ___ . ____________ . _ .. _ . _ . _________ . ____ . __ ...... . 174 

Age of the deposits ............................. _ ... ____ . _ . _____ . ____ . ___ .. ___ .. ____ . _ . ___ ... __ ...... _ . 175 

CHAPTER XIV.-Metasomatic processes .... .................... ___ ............ _____ . ____ ...... _ ... _ ... _ .. . 176 . Types of alteration .......... _ .......................... · .. .. ____ ..... ______ .. ___ . ___ . ____ ._ ...... _ ... . 176 

Comparison of"fresh and altered dacite ................................................................ . 176 

Changes in other rocks •.... _ .................... . .. _ . _ ... __ . _ ... _ . ____ .. _____ . _____ ______ . _ . _ ........ _ . 182 

The ore-depositing solutions .................... __ ....... __ . _ _ _ .... ___ ... _ .. _ . __ . _ ..... _ . _ .......... _ 185 

CHAPTER XV.-Underground water and depth of oxidation ... ..... .... ...... _ .... ................... ....... . 187 

CHAPTER XVL-Genesis of the deposits ............ _ . . .................................................... . 189 

Statement of the problem .............. ... ...... . ... _ ... _ ......... __ .. __ .. __ .. _ . _ .. __ ... _ .... __ ...... . 189 

The direct volcanic hypothesis ............... ... . ...... _ .· ___ . ___ ... ______ ................ _ ......... _ .. 

Hypothesis of derivation of the sulphuric acid from the oxidation of pyrite .. _· .. _ ....... , ............... . 

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Hypothesis of simultaneous solfatari~m and oxidation ..... _____ ... __ ................... _ .. ~ ....... _ ... . 193 
6 CONTENTS. 

CHAPTER XVI.-Genesis of the deposits-Continued. 

Stages of deposition ............. . ........ . ............................................. . .......... -- : 

Summary of genesis .............................................................................. --.-.-

Ultimate source of the ore-bearing solutions .................................................... _ ...... _ 

Present absence of volcanic activity ............................................................ -.-.-.-

Goldfield type of deposit..... . ................................................................... ---

CHAPTER XVII.-Practical conclusions ........................................•................. ---.---.-

CHAPTER XVIII.-Detailed descriptions of the mines of the Goldfield Consolidated Mines Company .......... . 

Introduction ....................................... _- .................... . ..................... -- ... . 

Red Top mine ............................ . ...................... . .................................. . 

History ................................... . ...................................... . ............. _. 

Underground workings ........................................................................... . 

Geologic relations ..... · ................ . ...................... : ..... . ... · ......................... _. 

The ledge ................................................................................. . ..... . 

The pay shoots ......................................... . ..... · ................................... . 

Mohawk mine ............................................................... . . .. ................... . 

Introduction ............ · .................................................................. . ..... . 

~:~~~1~ :e~~t:~:~~~~-s_ .. · .· .· .· .· .· .· .· .· ~ ~ : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :_: : ·: : : : : : : : : : : : : : : 

Form and distribution of the ledges .................................... . .. . ...................... . 

Form and distribution of the pay shoots ... . ................................. · ..................... . 

Combination mine ........... _ ......................................................................... . 

History and production ...................................................................... . ...... . 

Underground workings ......... _ ............................... _ ................................ . .. . 

Geolvgic relations ...................... . ...................... . .... . .......................... . .. . 

Form and distribution of the ledges ......... . ........ . ·.. : ............ ! .... . ............. . . . .. . ... . 

Material of the ledges ................................... . ~ .. . .................................... . 

Form and distribution of the pay shoots ....... . .................................................. . 

Character of ore ........................... · .............................. . . . : . .................... . 

Underground water .................... . ............... . ................ •.................... . . . . 

January mine .................................................... . ....... . ... . ...................... . 

History ..................................... ... ...................... . . . ...... . ........... . ... . . . 

Underground workings ... . .......... . . . ................... .. ... . .. .. ............................... . 

Geologic relations ..................................... · ................ . .. .. . . .................... . 

Form of the ledge ........................... . .............................. . ..... : ........... . ... . 

Material of the ledge ....................................... . .. . .................................... . 

Form and distribution of the ore bodies .. __ ..... . . . ................. . ...... . .... . ..... . .. . ........ . 

Character of the ore ................. . ........................................................... . 

Underground water .................. · ...................... . .. . ................................. . 

Jumbo mine ........................................................................................ . 

History ................ . ........ . ............ . .... . ..................... . ....... . ........ . . . .... . 

~:~~:~;:~~--~~~~~~~s-- ~:: ~ ·_ ·_ ·_· _" ~: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 

The pay shoots ....................................... . ........................ . ...... . ..... . . . .. . 

Character of ore ............................................. . .............. . ..................... . 

Mines and prospects operated by lessees ........................... . ...................... . ............ . 

Introduction .............................. . . . ... . ..................................... . .......... . 

Five Friends lease ............................................. . ............. . .. . ........ . . . ..... . 

Mushett lease .............................. .. .................................................... . 

Mohawk-Red Top lease ................................. . .............. ~ .............. ... . . ..... . . 

Consolidated Red Top lease ......................... : .... . .... . .............. : ....... .. ....... . ... . 

Hazel-Goldfield lease ............ . ...... . .... . ............................ . .... . ................. . 

Other leases ............ . .. .. .......... . ......................................................... . 

CHAPTER XIX.-Detailed descriptions of the mines of the Florence-Goldfield Mining Company ................ . 

-i .,- Introduction ................................. . .. . ... . ........................... ~ ........... _ ...... . 

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Florence mine ......................... . ................... . ........ ... . . .. . ..... . ................... . . 

_:;·;; History ...... _ .... . .......... . .. · .. . ................... . .... . ......... ... ......................... . 

~:~~~1~o~~~ti:~:~~~~-s--~---_·_·_ _-_-_-_- .·::::::::::::::::: ::: : ::.:: ·::::::::: ::::::::::: : ::-:.:::::::::::::::::: 

;!1-:; i Form_ of the _Florence ledge ....•. . ........................................ . ........ . . . ............ 

,~ ;~ i Th~ _pay shoots .................... .. .. · .......... . ... ... _ .... . ..... . .. _ . _ .. . _ . .. .. ............... . 

qg1 Character ofthe ore .. . ...... , .. . .. . .. .. . ......................... . .......... .. ........ . ....... ,~ . . 

In\" pn~erground water ............ · ... :: .... ; .. , ..... ~;. ....... . · ....... · .... . ........... . ......... . 

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CONTENTS. 

CHAPTER XIX.-Detailed description of the mines of the Flo ence-Goldfield Mining Company-Continued. 

Min~~§\~~~e;:: ~: ~ ~ ::: : : : : : : : : ~ ~ :::: :::: r::: ~:::::::: : :: : : : :::: : : : : : ~ ~ ~ ~ ~ : : : : : : : ~: ~ ~ CHA~:~s~~~~!~~l·e-~ ~-e·s~~~~~i-o~s- ~~ ~~~-1-~s~~~ -~~~~~ -~~~ ~~s~~~t~-~f- ~~~-~~~~~~~~-~~~~~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Kendall mine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................... _ . _ ... _ ....... _ . ___ . .. _ . 

Conqueror mine ..... . . _. · ........ _ ....... . ............. .. .. ___ ._. ______ .. _ ......... _. ___ . __ ...... _._. 

Adams mine ................... _ .. _ ....... ____ .. _. __ . ___ . _________ J ____________ • _____ • ________ • _. ____ _ 

Kewanas mine ................. _____________________ ......... ___ . _____ .. _._ ......... ___ .- ......... ---. 

Goldfield Merger Company's mines ...... _ ................... ___________ _____ __ . __ ......... __ . _. _ ...... . 

Introduction ................................................ _. __ ........ _. ___ ....... -.-.- . .. ... . St. I ves mine._._._. _____ ._. __ ........ ___________ . _ .... __ . ______ . _________ . _____________ ......... . 

Codd lease ............ _ ........ __ ·_ .............. _ .. ______ . _______ . _________ ..... ·.-. __ ._._ .... .. . 

Velvet mine. __ . __ ............................... _ .. _. ___ . : __ . ________ ._ ....... ____ ............. . 

Jumbo-Extension Mining Company's Gold Wedge claim. __ ......... _ . _ .......... _ ............ _ .. ..... . . 

Combination Fraction mines ..... _ .............. __________ ._. ___ . __ ..... _____ ........................ . 

Atlanta group .. _ ......... ~ .................. _ ........ : ................ _ .... _ .......... . -.-- ........ . 

Gold Bar and Victor mines. __ ... .... ... _ ...... : . ....... _ ............ , ................................ . 

Blue Bull mine ..... _ .......................... _. __ __ ___ ______ . ___________ .. _ . . _ ........ _ . . ........ _ . 

Simmerone mine ............... . ... _ ............. .... _ ... _ . _ ... _ . _ . _ ..... _ ......... _ . _ ......... .. ... . 

Lone Star group .... __ ........ .. .. . . ·.- .. _. _____ . _______ . ___ . ..... ___ ... ___ ._ .. ___ ._ .... ..... _ ........ . 

Commonwealth mine ............................ _. _____ . __ .. _ .. _______ .... _._ ......... _ . . .. ~ ........ _ . 

. ~~~;:~::;:c~:::::::·.-·.·::::::::::::::::::::::::::::: j::::::::::.::::::::::::::::::::::::::::::::::: 

CHAPTER XXI.-Detailed descriptions of mines of the Diaiond:field group .. ~ .. _ ................... ... .... . 

. Diamond:field Black ~utte Consolidated mine ........... ·r ................ -: .......... -.-----------.----

INJ~~~~~i:t(~i:·Com)h··:-::::: :.;-:-U iii iii U iii iii i U iii iii U iii;;; i; i i /// 

7 

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ILLUSTRATIONS. 

PLATES. 

Page. 

PLATE I. . Topographic map of the Goldfield district .............. _ . ___ .... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . In pocket. 

II. Geologic map of the Goldfield district ................ _ ..... . __ ...... _ ..... _ .. _ ...... _ ..... _ In pocket. 

III. Goldfield topography: A, Goldfield; B, Black Butte ......................... __ .................... 16 

IV. Geologic reconnaissance map of the region adjacent to Goldfield.................................... 32 

V. A ,' Columbia Mountain; B, Cambrian shale cut by alaskite, south slope of Columbia Mountain...... 34 

VI. A, Intrusive contact between Morena rhyolite and Cambrian shale, west ~lope of Columbia Mountain; 

B, Goldfield................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. . . . . 46 

VII. Photomicrographs of volcanic rocks ...... ............................ ·_.......................... 62 

VIII. Geologic sections across the Goldfield district..................................................... 76 

IX. Combined plan of the underground workings of the principal mines near Goldfield.................. 136 

X. Map showing principal lease blocks in the vicinity of Goldfield.................................... 136 

XL A, Mal pais Mesa; B, Florence HilL .. ~ ....................... __ ....... ... : . . . . . . . . . . . . .. .. . . . . . . . 136 

XII. A, View northwest from Florence Hill; B, View east from Florence Hill ......................... ~- 136 

XIII. A, Sandstorm and Kendall mines; B, View from Morena Ridge eastward to Diamondfield and Blac'k 

Butte ......................... -... .... .......... ..... .................... . ......... .... .. ..... 138 

XIV. A, Ledge outcrops in Milltown andesite about 2 miles east of Goldfield; B, Ledge outcrop in dacite 

between the Blue Bull and Commonwealth mines............................................... 150 

XV. A, Ledge outcrops east of Black Cap Mountain; B, Ledge outcrops in latite on Banner Mountain.... 152 

XVI. Plans of the principal levels of the January mine, with a diagrammatic section showing relations of ore, 

ledge matter, and country rock .......................................... . .... , ............... 152 

XVII. Sections across the Combination ledge on lines shown on Plate XXXIV ........ ..... ..... ...... _._ .. 154 

XVIII. · Plans of levels of the Combination mine ........... ........................... __ ....... .......... 154 

XIX. A, Dacitic ledges on ridge near the Commonwealth mine; B, Dacitic ledge near the Blue Bull mine. 156 

XX. Ledge structure: A, Veinlets of compact quartz and kaolinite in altered andesite, Goldfield-Belmont 

mine; B, Sheeted dacite and low-grade ore, Jumbo mine........................................ 156 

XXI. A, Part of the Sweeney stope in the Florence mine; B, The Hayes-Monnette stope in 1906... . ..... 160 

XXII. A, The "glory hole" of the Combination mine; B, Ledge matter on the 150-foot level of the Florence 

mine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 

XXIII. Ore structures .......... .......... ...... ......................... . ............. , . . . . . . . . . . . . . . . 164 

XXIV. Ore structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 

XXV. Ore structures .............. ...... ............... ,_ ............................................ 166 

XXVI. Photomicrographs of ores....................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 

XXVII. Photomicrographs of ores............... . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 

XXVIII. Pllotomicrographs of alunitized rocks .. __ ·_ ........... . .... . __ .... . . .. ... __ ... __ ..... ~ .... __ ..... 178 

XXIX. Photomicrographs"showing alteration of dacite . ...... ................................. ·............ 178 

XXX. Photomicrographs illustrating alteration of rocks ...................... . .......... _............... 178 

XXXI. Photomicrograph of alunitized rhyolite........................................................... 184 

XXXII. Plan and section of the Red Top mine ...................... __ ...................... __ .. .'. .. ..... 202 

XXXIII. Plan of the Mohawk mine, showing also the workings of lessees on the Gold Wedge claim........... 206 

XXXIV. Plan of the Combination mine, including the productive part of the January mine....... ........... 210 

XXXV. Plan of the Florence mine, showing also some of the adjacent workings of lessee companies.......... 226 

9 

FIGURES. 

Page. 

FIGURE 1. Index map showing the position of the Goldfield district .............. _......................... 15 

2. Plan of the dacite mass near Goldfield .............. _._ ... _._ ..... _ ............. _ ... _........... 80 

3. Section across the Columbia Mountain fault at the Conqueror mine............................... 82 

4. Generalized columnar section of the rocks of the Goldfield district. ..... _ . _ . . . . . . . . . . . . . . . . . . . . . . . 90 

5. Columnar section of rocks of southwestern Nevada and eastern California.......................... 91 

5. Succession oflavas in the Great Basin and at Goldfield.......................................... 1Q6 

7. Characteristeric outlines of quartz phenocrysts in dacite......................................... 121 

8. Crystal form of bismite from Goldfield ..................................... ·_....... ............ 123 

9. Spherules of hematite with crystal facets ........................ _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 

10. Scheme of treatment in the Combination milL ................... ·. __ ....................... ... 144 

11. Scheme of treatment in the new Goldfield Consolidated mill ............... : ..................... - 147 

12. Plan showing distribution of ledges east of Goldfield.............................................. 151 

13. Plan of ledge matter and pay shoots on the 100-foot level of the Florence mine.................... 152 

14. Vertical section through an irregular flat ledge in the west wall of the Black Butte tunneL......... 152 

15. Sections across the Mohawk ledge on lines shown on Plate XXXIII.............................. 153 

16. Sections across the Reilly pay shoot............................... . ........................... 154 

17. Section across the Florence pay shoot near the main shaft...................................... 154 

18. Plan of the 350-foot level of the Mohawk mine ............................. _.................... 162 

19. Diagram showing the portions of the Goldfield district in which the rocks have undergone extensive 

alunitic alteration......................... . ........................................ .... ..... 177 

20. Diagram illustrating gains and losses of each chemical constituent in terms of percentage of mass of 

original fresh dacite. . . . . . . .. .. .. .. .. . . .. . . . . .. . .. . . .. . . .. .. . .. .. . . . . .. .. . .. . . . . . . . .. .. .. .. . 181 

21. Geologic plan of the 600-foot level of the Mohawk mine......................................... 206 

22. Diagram showing relation of the Mohawk ledge to the dacite-latite contact................ ....... .. 206 

23. Plan of part of the 130-foot level of the Combination mine ... _ ............ .. ........... ·_........... 211 

24. Diagram showing possible plan of the combined January and Combination ledges................. 212 

25. Sketch plan of the workings of the Five Friep.ds lease..................................... . ..... 223 

26. Plan of the workings of th~ Mushett lease. ___ .... _....... ...... ...... . .... . ..................... 223 

27. Sketch plan of the 420-foot level of the Mohawk Red Top lease .......... -.- ...... .............. 224 

28. Diagrammatic section through the Florence mine ..................................... : . .. -. . . . . 226 

29. Section through the Kendall mine .............. _ ... _............. .. ...... .... . . ..... . .......... 237 

30. Plan of the St. I ves mine .......................... . ........................ ... . .. .. . : . . . . . . . . . 240 

31. Plan of the Gold Bar and Victor mines... . ..... . ............................................... 243 

32. Plan of the workings of the Black Butte mine .................... .... ............. . .. -.. -. --. . . 246 

33. Plan of the workings of the Goldfield-Belmont mine ............................ -.---- ..... . -.-- 248 

34. Plan and longitudinal projection of the workings on the Daisy group ....... -.- ......... ---- .. -.. ·.. 249 

11 

THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD,. 

NEVADA. 

By FREDERICK LESLIE RANSOME. 

CHAPTER I. 

INTRODUCTION. 

FIELD WORK AND ACKNOWLEDGMENTS. 

During the summer of 1905 a topographic map of the Goldfield district, on a scale of 2,000 

feet to the inch (1: 24000), and covering approximately 31! square miles (82 square kilometers), 

was made by Mr. William Stranahan, topographer. With this map as a base, detailed geologic 

work was begun in September of the same year. Messrs. W. H. Emmons and G. H. Garrey 

assisted in the field work of the first season. In the main, the geologic mapping of that portion 

of the district lying in Nye County (see Pl. II, in pocket) and extending from Blackc~p Mountain 

to Black Butte is the work of Mr. · Garrey. The part lying south of a line drawn from Blackcap 

Mountain to Goldfield and west of the Goldfield-Tonopah freight road (i. e., the southern and 

western borders of the area) was mapped principally by Mr. Emmons. The field notes of both 

geologists have been used whenever it was necess~ry to supplement my own observations with 

details observed by them in their respective divisions of the field. All the geologic mapping 

·was done with traverse plane tables, each contact being followed and numerous points upon it 

·determined by intersections. 

A preliminary report a on the district was issued early in 1907 and the greater part of the 

·final report was finished by the end of the same year. The rapid development of the mines 

during 1906 and 1907, the large number of new ore bodies found, and the -important discoveries 

made at depths not reached when the first field work was brought to a close, rendered it clear 

that the disadvantage of a few months delay in the publication of final results would be amply 

-compensated for by a second visit to the field and by a study of underground workings opened 

.since the close of the year 1905. Accordingly a supplementary investigation of the district was 

carried on from June 11 to July 27, 1908. It was found necessary, moreover, in consequence 

of the many modifications in the cultural features (changes in roads, additional shafts and 

1:mildings, etc.) to thoroughly revise the topographic map published in 1906. Mr. W. M. 

:Beaman, topographer, was occupied with this revision during September, October, and part· of 

November, 1908. 

The assistance rendered us in the course of our investigation by all interested in the development of the district was hearty and general. It is a pleasure to record gratefully the generous 

cooperation of Mr. H. P. Henderson, geologist for the Goldfield Consolidated Mining Company, 

and of our professional colleagues, the local mining engineers, particularly Messrs. E. A. Byler, · 

George B: Church, F. A. Lucy, C. D. Wilkinson, A. E~ Barnes, W. Stranahan, F. J .. Siebert, and 

Charles J. Moore. Very helpful also was the active interest of the owners and superintendents 

of mines. 

a Ransome, F. L., Preliminary account of Goldfield, Bullfrog, and other mining districts in southern .Nevada: Bull. U. S. Geol. Survey No . 

. 303, 1907. ' 

13 
14. THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The various chemical tests and the analyses of minerals and rocks recorded in the following 

pages were made in the chemical laboratory of the Geological Survey by Messrs. George 

Steiger, W. T. Schaller, and Chase Palmer. 

A full and representative collection of the rocks and ores of the Goldfield district has been 

deposited in the National Museum, Washington, D. q., where it may be examined by anyone 

on application to the curator of geology. It is hoped that arrangements may be p1ade whereby 

a smaller. collection illustrative of this report may be placed on exhibition in Goldfield. 

All plans of mine workings and all plats of claims accompanying this report have been 

compiled from the maps of the various companies and are published with their permission. 

The standard of mine surveying at Goldfield is generally excellent and there is no reason for 

supposing that any of the maps here utilized are incorrect. The United States Geological 

Survey does not, however, vouch for their accuracy. 

SITUATION OF THE DISTRICT. 

The town of Goldfield, which, with the adjoining settlement of Columbia, has a population 

estimated at about 15,000, lies near the eastern border of Esmeralda County: il). southwestern 

Nevada. (See fig. 1.) It is about 28 miles (45 kilometers) nearly due south of Tonopah and 7 

miles (11 kilometers) a little north of east from the old mining camp of Montezuma. As may 

. be seen from Plate I, the eastern part of the Goldfield district, including Black Butte, lies in 

Nye County. 

Three railroads of standard gage enter the district. A branch of the Southern Pacific leaves 

the main line at Hazen and connects at Mina with the Tonopah and Goldfield Railroad, which 

enters Goldfield on the north by way of Tonopah and Tonopah Junction. Through trains are 

run over this route from San Francisco to Goldfield. The Las Vegas and Tonopah Railroad 

leaves the San Pedro, Los Angeles and Salt Lake Railroad at Las Vegas, Nev., and passes through 

the Bullfrog district, 60 miles (96.5 kilometers) south-southeast of Goldfield. The Tonopah 

and Tidewater Railroad branches from the main line of the Santa Fe system at Ludlow, Cal., and 

reaches Goldfield by way of Death Valley and the Bullfrog district. The northern route affords 

communication with San Francisco, and particularly with the works of the Selby Smelting and 

Lead Company wh~re a large part of the Goldfield ore has been treated. The two southern 

routes give access to Los Angeles and to the smelters of Utah. , 

TOPOGRAPHY. 

The hills in the vicinity of Goldfield form an irregular group (see Pl. I, in pocket), having 

no definite trend and belonging to no recognized mountain range. On the north, east, and south 

these hills slope down to broad, undrained sterile basins, each with its characteristic central 

playa-a gleaming level plain incrusted with salts, except ·when an occasional shower has spread 

a film of water over its surface. The average altitude of the playa floors above sea l~vel in this 

region is about 5,000 feet (1,524 meters). Such a basin, approximately 10 miles (16 kilometers) 

in width, separates the Goldfield Hills from Stonewall Mountain, a prominent landmark southeast of the district and visible in Plate XIV, A. A low, broad pass between this basin and one 

to the north of it connects the Goldfield Hills with the northwest end of the Cactus Range, 

Cactus Peak being 20 miles (32 kilometers) east-northeast from Goldfield. A similar inconspicuous divide, about 12 miles (19 kilometers) north-northeast of Goldfield, forms a slight 

connection between the Goldfield Hills and the hills of the Southern Klondike and Tonopah 

distl'icts. 

West of town a basaltic mesa (see Pl. II), at this latitude about 4 miles (6.4 kilometers) 

wide, stretches to the eastern base of Montezuma Peak, which is composed in part of rocks. 

similar to those of the Goldfield district. The old mining settlement of Montezuma lies n'ear the · 

summit of the peak, which is 8,426 feet (2,568 meters) in height and 7 miles (11 kilometers) a. 

little south of west from Goldfield. 
'TOPOGRAPHY. 15 

Goldfield is situated on the southern rim of one of the typical desert basins -of the region, 

which merges through a low pas~ 22 miles (35.4 kilometers) north of town into the still larger 

basin west of Tonopah. · (See Pl. IV.) This pass, through which the railroad runs from Tonopah to Goldfield, is between the Lone Mountain Range on the west and the Tonopah Hills on 

the east. 

The portion of the Goldfield Hills, which is particularly described in the present paper and 

which will for convenience be hereafter referred to as the Goldfield district, is shown in the 

accompanying map (Pl. I). The relief in this area ranges from 5,400 feet (1,646 meter~) in its 

FIGURE 1.-Index map showing the position of the Goldfield district. 

northwest corner to 6,635 feet (2,022 meters) on the summit of Preble Mountain, near the 

southeast corner. The culminating peak of the Goldfield IIills, however, known as Diamond 

Peak, is just east of the area represented in the map and attains an elevation of nearly 7,000 

feet (2,133 meters). A· large part of the district may be described as a rolling plateau (see 

Pis. III and VIII), ranging from 5,700 to 5,800 feet (1,737 to 1,768 meters) in general elevation and surmounted by many irregularly distributed peaks and knobs, of which Preble, Black-

, cap, Vindicator, Banner, and Columbia mountains are conspicuous examples. Not any of these 

hills are volcanic craters or local volcanic upheavals, as has been asserted in some descriptions 
16 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

of the district. They owe their height above the surrounding country merely to the fact that 

they are composed of material somewhat harder or more durable than the average rock of the 

region, and have thus succumbed more slowly to the general erosion that has carved the existing 

relief from a gently domed volcan!c series. The superior resistance of the hills is in some cases 

due to the original character of the rock of which they are composed; in other cases to a capping 

of young and fresh lava, but by far the greater number of the smaller knobs that stud the dis-

. trict, of which Black Butte, Plate -III, B, is an excellent example, are prominent because the 

rock has been hardened by intense local metamorphism in a manner that will be described in 

connection with the ore deposits. 

The fact that much of the district is a rolling plain diversified by rocky knobs has an 

important bearing in a region where detritus tends to accumulate on all but the steepest slopes. 

In the Tonopah district, and especially in the Bullfrog district, there is generally a fairly definite 

line between steep, bare, rocky hills and the gentle a1luvial slopes at their base. At Goldfield, 

however, the general gradients, as may be seen from Plate VIII, are so slight that detritus 

accumulates over much of the surface and interferes seriously with attempts to determine the 

distribution and structure of the underlying rocks. 

HISTORY OF MINING. 

At the beginning of the present decade the state of the mining industry in Nevada had 

so far declined as to appear but a feeble and flickering reminder of past splendor. The output 

of the great Comstock, a loqe which in fort.y years had yielded about $400,000,000 in gold and 

silver, had dwindled in 1899 to the relatively paltry sum of $171,677.90; and the whole State 

in that year produced only $3,740,790 (with silver reckoned at coinage value), nearly half of 

this coming from Lincoln County, in which the Delamar mine was the only large producer. 

Eureka, Pioche, Eldorado Canyon, and many places of less note had apparently passed from 

activity into tradition. 

With the opening of the year 1900, however, there were signs that some of the older camps 

were preparing to shake off their dusty lethargy. On the Comstock, particularly, some progress was made in freeing the deep levels from water and the production from this famous lode 

rose to $700,865. But the one event which transformed a gradual resuscitation of mining, the 

natural accompaniment of great national prosperity in all other branches of industry, into a 

movement almost explosive in its energy and suddenness, and resulted in the development of 

Goldfield, Bullfrog, Manhattan, Wonder, Fairview, and many other new fields, was the discovery, in 1900, of the Tonopah deposits by James L. Butler. In 1901 ore to the value of 

$576,145 was shipped from ~he Tonopah district, and prospectors were not slow in acting upon 

this striking demonstration of the fact that the State of Nevada, owing largely to its uncompromisingly desert character, had hitherto been very inadequately prospected. From Tonopah 

as a base prospectors scattered over the desert, and as the size and richness of the new bonanzas 

became known the number of explorers increased. Many of these, as well as prospectors of 

an earlier generation, must have walked over the low hills which lie east of Montezuma Peak, 24 

miles (38.6 kilometers) south of Tonopah. They could scarcely have failed to remark the dark 

siliceous outcrops; or combs, which are a notable feature of their topography and must have 

suspected the connection of these with ·ore deposition . . How gold ore of such unprecedented 

richness, lying so close to the surface in a region of such obvious volcanic and chemical activity, 

escaped detection when work was in progress at the old camps of Montezuma, Lida, and Silver 

Peak, is difficult to comprehend. The explanation is probably to be found in the fact that the 

earlier prospectors were looking for quartz veins of the normal type, particularly for silverbearing veins, and finding nothing of value in the projecting parts of some of these curious 

. rusty "blow outs" concluded that all were barren and passed on to what seemed more promis-

_ing localities. The gold pan was not at that time a recognized part of the outfit of a Nevada 

prospector, and the first attempts to use it at Goldfield were not successful because the pioneers 

panned the hard quartz broken from the croppings instead of the soft disintegrated m·aterial 

' which in this district generally contains the gold. • 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE Ill 

B. BLACK BUTTE; FROM POINT NEAR McLAUGHLIN'S WELL. 

knob of ledge matter rising above the gen e ral rolling surface. The white dump at the base of the butte 

rks the portal of the main tu n nel. To the right of it , extending o bliquely up the slope, are the cuts on the 

t vein. 

HISTORY OF MINING. 17 

It was not until late in 1902 that "float" gold was found on Columbia Mountain by Harry 

Stimler and William Marsh. After seeking in vain for the source of this gold the two prospectors worked northward, and on· December 2 of the same year located claims on and near the 

Sandstorm lode. A brief period of excitement followed their discovery, men thronging into 

the district on foot and in wagons and automobiles. No important ore bodies were immediately 

uncovered, however; interest flagged; and all but a few of -the more determined or more sanguine 

prospectors left the district, then known as Grandpa. Stimler and Marsh's ?riginal locations 

appear to have lapsed, the ground being afterwards relocate9. by others. Among those who 

remained were A. D. Myers and R. C. Hart, who, on May 24, 1903, located .the Combination 

lode. These two men had been "grubstaked'' by eight others and 'were under contract with 

their backers to do the assessment work. The early locations south of Columbia · Mountain 

were not based on direct discovery of ore, but were made with the view of securing claims as 

near as possible to the point at which gold was first found. They were originally speculative 

holdings merely. 

Hart soon sold his interest toT. D. :Murphy, who, with Myers, began to develop their property. Their pertinacity was rewarded· by the discovery of the Combination ore shoot, and to 

them and their associates undoubtedly belongs the credit bf the real opening of the district. 

It was at this time (June, 1903) that J. E. Spurr, then studying the geology of Tonopah, paid 

a hasty visit to the district and published a brief note a on the geology, which was supplemented 

by a fuller statementb made after a second visit in November, 1904. 

In October, 1903, after the existence of ore in the Combination ledge had been proved by a 

short tunnel, the ground was bonded to the Co:mbination Mines Company for $5,000 in cash and 

$70,000 to be paid in later instalments. In the following December this company began the 

shipment of ore. Prospecting was activtly resumed over the district in January and February 

of 1904, and before midsummer rich ore was being shipp~d from the Jumbo, Florence, and 

January mines. 

With the exception of the Combinatio:1,, all the mines which have attained any importance 

w.ere first opened and developed by the leas~g system, and so near the surface and so rich were 

many of the ore. bodies that numbers ·of tl:e successful lesses made ample fortunes in a few 

months or even in a few weeks. The royaltie; exacted usually ranged from 20 to 30 per cent of 

the net value of the ore extracted. At one tl;ne there were six sets of lessees working through 

as many shafts on the Jumbo lode. The bloc~ were !rom 100 to 300:feet (30.5 to 91.4 meters) 

in length, the most productive and best known being that generally referred to as the BowesKernick lease. 

The daily output from all of these workings n August, 1904, was estimated at $10,000, and 

t4e total to the expiration of the leases, early h 1905, amounted to considerably more than 

$1,000,000. Another famous lease was the Sweemy lease on the Florence mine, which expired 

on January 15, 1905, after a production amountng to $650,000. The Patrick lease on the 

January mine, probably the first important lease gnnted in the camp, produced about $500,000. 

Later, and in some respects more sensational than He leases just mentioned, was.that granted 

to B. J. Reilly and associates on No. 1 block of the 1'lorence ground. This lease, after having 

been successively abandoned by two earlier holders, w.:ts -taken up by Reilly and his partners in· 

April, 1905. Ore was found in the following June, blt it was not until August that the true 

richness of the body became apparent. In the short t:me then available before the expiration 

of the term, on October 19, 1905, nearly all of the ore W:lich the lease produced was mined and 

hoisted to the surface. The royalties paid to the Floren<e-Goldfi~ld Mining Company represent 

a total outputof $475,000. Most accounts, however, gi'e the production as $750,000. Some 

of this ore was of extraordinary richne1;ls, a lot of about~ tons,c ~ken out from the bottom of 

the workings during the last days of the lease, averaging, according to Mr. Frank Oliver, then 

superintendent of the Florence mine, between $6,000 and ~ ,000 per to!',. -

a Bull. U. S. Geol. Survey No. 225, 1904, pp. 118-119. 

b Bull. U.S. Geol. Survey No. 260, 1905, pp.132-139. 

c The tons referred to in this report are in every case'.' short tons " of 2,000 pounds. Since tJ.e short ton is equiva.ent to approximately 0.9 metric 

ton, conversion to the metric units is in ~ost cases unnecessary. 

79145-No. 66-09-2 
18 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Early in 1905 the district probably contained fully 8,000 people, ov~r two-thirds of whom 

were in the town of Goldfield. Late in the year, owing to the attractions of Manhattan and 

other recently opened camps and to a decreasing activity in prospecting, in leasing, and in the 

various more or less speculative transactions so characteristic of a new mining district, the 

population had somewhat declined. 

The completion of a railroad from Tonopah to Goldfield in September, 1905, gave the 

district a much-needed improvement in transportation, although freight charges were still 

maintained at unduly high figures. Another important event of the year was the discovery of 

a large body of rich ore in the Red Top mine, which had not previously been a productive 

property. On the whole, the year 1905 witnessed a slight ebb in the tide of prosperity, due to 

many causes. The rapid exhaustion of many of the rich shoots worked by lessees and the failure 

to immediately find other rich bodies at greater depth aroused forebodings which not even the 

record of the Reilly lease. could allay. The Jumbo mine, after making fortunes for lessees, was 

involved in litigation and became temporarily unproductive. The bottom level of the Combination 

mine had been allowed to fill with water and the bottom level of the Florence mine revealed as yet 

no shipping ore. New camps, particularly Manhattan, were coming into prominence and were 

drawing men away from Goldfield, which under all these circumstances could not avoid some 

reaction from the buoyant optimism of the preceding year. The entrance of the Red Top mine 

into the rank of producers at the close of the year did niuch to restore confidence, although no 

one yet realized what extraordinary riches still lay concealed within 250 feet (76 meters) of the 

surface in the little area of about a quarter of a square mile (0.6 square kilometer) which contained 

the Red Top, Combination, January, Jumbo, and Florence mines. 

During the first quarter of 1906 no very important cbanges took place in the general situation 

at Goldfield. Several new ore bodies were found and tie discovery of rich ore in the Sandstorm 

bet~een the 100 _and 150 foot levels proved encouragug in view of the shallow depth to which 

stoping had hitherto been restricted in this mine. The development of the Laguna mine, east of 

the Red Top, was begun, and a few tons of low-grade ore were found by lessees on the Mohawk 

claim. The various local mills and reduction works- were in active operation, including a new 

Kinkead mill on Columbia Mountain. The Com}ination mill was working 20 stamps and 

installing tube mills. 

In June differences between the mine owners and the miners' union threatened to become 

acute, being complicated by the introduction ino Goldfield of an organization of labor called 

the Industrial Workers of the World. The lat. er had declared a strike against the Western 

Union Telegraph Company which threatened 1o involve all the workmen in the district. A 

visit of Governor Sparks to Goldfield early in Ju1e, when he addressed the labor unions, appeared 

to avert the threatened trouble, but the spiritof unrest still smoldered. 

Ore was first discovered on the Hayes-N.bnnette lease of the Mohawk in April, 1906, at a 

depth of about 250 feet (76 meters). By thf end of the first week in June nearly 2,500 tons of 

sulphide ore averaging 2.7 ounces of gold pe: ton had been shipped, and in the following month 

the Mohawk ground began to attract much .:tttention and was actively worked by several sets of 

lessees. In the early days of the Hayes-Vfonnette lease considerable fruitless work had been 

done on the 150-foot level; and there, as hter developments showed, the main drift missed the 

great ore shoot by a few feet oniy. In September the ore shoot, there very rich, was opened 

from that level, and this one lease block vas soon shipping up to $60,000 worth of ore a day from 

two shafts. The original Hayfs-Monn£tte lease covered an area 700 feet (213 meters) long by 

,373 feet (113 meters) wide. About twr-thirds of this was sold to other lessees who met with less 

success than did the original holders en the retained third. 

On some of the Mollaw\: leases 1he miners were paid $5 for six-hour shifts. Mere wages 

in fact counted for little where the ?rime consideration on the part of the lessee was to raise 

as much rich ore as possible in a glven time and where the obvious aim of many employees 

·and others was to sttal the greatESt quantity possible. It is reported that miners in some 

cases refused $20 a dty on developnent work in order to accept $5 a day with the opportunity 
- HISTORY OF MINING. 19 

fo illegal perquisites in the Mohawk. The extent to which "highgrading," or the stealing of 

ri h ore, went on in 1906 is almost incredible. .Two shipments of stolen ore, valued at $60,000 

a d $150,000 were seized on the cars. Scores of so-called assay offices sprang up,, the main 

b iness of which was the traffic in dishonestly acquired "highgrade." It has been locally 

es imated that over $2,000,000 was stolen from the Mohawk, Red Top, and Jumbo mines alone 

u to the latter part of 1907. About $250,000 worth of stolen ore is said to have been \ . 

re overed in 1906. While these figures may be exaggerated they give son1e idea of the magnit de of the thefts. The 1

report of the Goldfield Consolidated Mines Company for the year 

e ding November 1, 1907, ~hows that stolen ore to the value of $30,896.98 was actually recover d between :May 1 and October 31, 1907 . . T. A. Rickard a states that the total stealings 

fr m this one company for th~ year 1907 were fully $1,000,000, and the same conclusion is 

re ched from a compar~son of the figures of mine productiQn, with those of the mint for that 

y ar.b . 

In October, 1906, thetown o£ Goldfield was in a very :flouris.hing condition. According to 

e local eorrespondent of the Engineering and Mining Journal there were· at that time over 

0 buildings in eourse of construction. There were 56 mining eompanies in operation, employi 2,250 men. There were 27 leases on the Mohawk, of whieh 12 were shipping ore. The 

p pulation of the district at the close of the year was estin1ated at 15,000. 

It is not surprising that the remarkable discoveries in the Hayes-Monnette and ~ittle 

F orence lease bloeks, coming at a tim~ when over the eountry at large a wave of speculation 

h d reached what we now know was nearly breaking height, should have led to overeonfidence 

a d inflation. In the prospectuses of promoters and in the minds of eager investors nearly 

e ery claim was a potential Mohawk. One mining company, the ground of whieh, so far as 

own, has never produced a pound of ore, is eapitalized at 2,000,000 shares with a par value 

o $1. Yet, notwithstanding this obvious overeapitalization these shares were· quoteq at one 

ti e at $1.80, corresponding to a total valuation of the property of $3,600,000. In October, 

1 08, the public, with chastened judgment, valued the same ehance for finding an ore body 

a $400,000. 

Overcapitalization is not eonfined to any one1company, but is so common as to be generally 

a cepted as a matter of course. Prospects irrespective of all probabilities are generally capit lized at $1,000,000 from the start, and it ~ a fair question whether the n1ines of one or two 

o the most important companies, in spite of their past productiveness, great known resources, 

a d reasonable expectations, warrant their· ve:r\y large capitalization. Even at a time of general ~ 

i :flation, such as that n,t the close of 1906, some of the most valuable of these stocks did not 

r ach par, although others having no basis of vclue other than expectation were quoted at high 

p emiums. As an investment mining stock du:ting the life of the mine should repay in divid nds to its holders the sum invested plus interest calculated at a rate considerably higher 

t an that customary in well-secured loans. The public, however, in buying mining stock is 

i :fluenced as a rule more by the prospect of immediate high returns than by the real value 

o the investment. That the speculative side of the transaction should be usually dominant 

f llows naturally from the great extent to which ch&nce enters into mining operations, particu1 rly where, as at Goldfield, the ore bodies are both rich and irregular. The buyer expects to 

s ll at an advance or to dispose of his holdings after the receipt of rich dividends at something 

ar their purchase price. 

Friction between miners and operators continued through the latter part of 1906, the 

age scale and the problem or preventing ore thefts b~ing prominent subjects of negotiation. 

I August an eight-hour day was agreed upon for all work with rates of $4 and $4.50 for ordiary and $5 to $5.50 for skilled labor. The .harmony, ho~ver, proved transitory. The attempt 

the operators to eliminate stealing by the use of change rooms for the men n1et with oppos tion from the miners and the regulation of wages becarre a recurring point of contention. 

a The great gold mines: Min. and Sci. Press, vol. 96, 1908, p. 161. , 

b Lindgren, W ., and McCaskey, H. D., Production of gold and silver in 1907: Mineral l~sources U. S. for 1907, pt. 1, U. S. Geol. Survey, 

1 , p. 122. 
'20 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

On -November 20, 1906, occurred the most important consolidation of interests yet effected 

at Goldfield. The Mohawk, Jumbo; Red' Top, and Laguna mines were consolidated under the 

title of the Goldfield Consolidated Mines Company, incorporated under the laws of Wyoming and 

capitalized at $50,000,000, in 5,000,000 shares, at $10 par value. In this transaction C. D. Taylor 

received $1~330,000 for his shares in the Jumbo and Red Top companies, at a rate of $2 a share. 

Mr. George Wingfield, who became president of the new corporation, with his associates received 

250,000 shares as their commission for effecting the amalgamation. The consolidated company 

also secured options on the Combination and January mines, which they subsequently acquired. 

The price paid for the Combination mine in March, 1907, was reported to be $4,000,000. 

The extent and development of the properties in the initial consolidation are shown in the 

following table issued by the company early in December. 1906: 

Acreage and workings of consolidated mines. 

Mine. Area. J Shafts. Drifts. Crosscu;s. j Raises. Winzes. ---------------------------------------------l------l----------1·----------------

Mohawk ........................................................................ . Red Top ..................................... . ....... ..... ... . ....... ... ........ . Jumbo .... . ....................... .. ....... . ... ... .. ..... ..................... . Laguna .............. · ............................................................ . 

Acres. 

42.227 

62.440 

18.690 

33.113 

Feet. Feet. 

3,140 2, 710 

300 1,670 

1,350 2,020 

140 ......... . 

. Feet. Feet. Feet. 

3, 715 1, 565 465 

1,545 530 35 1, 025 645 125 

360 .. · .................. . 

156,470 4, 930 6,400 1 6,645 1 2, 740 ,~ 

To the above were subsequently added over 200 acres embraced in the Combination and 

January holdings. The production credited to these properties at the time of consolidation is 

as follows: 

Production of consolidated nines. 

Mine. Gross value. Net value. Royalties. 

i 

$813,098 $201, 771 260,177 ........... . 3, 135, 426 705, 469 

Jumbo 

Red ............. . ........................ ...... ........ ·.... .... . . ......... ..... . .. .. ................. $1,607,342 

Mohawk.................................... Top. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308, 515 ... ....... ......... .... ........ .. .......... ................. 4,875,519 I 1--------1--------1·------ 6, 791,776 4,208, 701 907,240 

The market value of the Consolidated shares at the beginning of 1907 was about $7. On 

November 21, 1907, they were quoted at $3.95. The Hayes...:Monnette lease, after surpassing all 

records in the district for the value of ore shipped in less than a year's time, expired on ·January 

11, 1907. According to a statement issued by uhe Goldfield Consolidated Mines Company, the 

output of the Mohawk leases was as follows: 

Production of Mohawk leasesfom April18 to November 20, 1906. 

Ore in dry Gross tons. value. Net value. Royalties. Balances. Lease. 

I 

20,909 $2,597,845 $2,038,398 $458,640 $1,579,758 6,422 993,508 784,490 176,510 607,980 7,466 484,566 312,538 70,320 242,218 

Hayes-Monnette . ............. ..... ............... ............... .............. . Frances ............................... : ..................................... ·· Others ...................... . . . ... .. ................ ............ ··············· 

34,797 4,075,919 3,135,426 705,470 2, 429,956 

The foregoing table is not complete, as most of the leases still had from one to two months 

to run. The total gross production of the Hayes-Monnette, according to a statement by Mr. 

M. J. Monnette in the Goldfield News 1 amounted to $4,400,000. The gross output for October 

a,lone was approximately $1,300,000. Shipments continued to be made from the dump of this 

lease until late in 1907.. The average freight and treatment rate on ~re. s shipped to smelters in 

1906 was about $23.50 a ton. · 

Throughout the y~ar: 9Q7 the free development of the district ontinued to be hampered 

by friction between the mine operators and the unions. In April o e of the many short-lived 
HISTORY OF MINING. 21 

and parti2l strikes was settled_on the reported basis of recognition by the operators of theW estern 

Federatio p. of Miners and the withdrawal of the organization of the Industrial Workers of the 

World frc m the · district. In November the miners refused to accept part payment of their 

wages in hecks or exchange drafts-an expedient which the employers had adopted in consequence of the exceptional :finaneial conditions then prevailing throughout the country and the 

congestior in the -smelters' of the siliceous Goldfield ores, which prevented prompt settlement 

with the sihippers. Local samplers, who act as middlemen between some of the mines and the 

smelters, vere compelled to refuse the purchase of ore or to accept it only upon the understanding that payment therefor might be subject to delay. Under these unusual circumstances most 

of the large mines were compelled to store their rich ore or to curtail production. 

Abou"' 1,900 men struck on November 27. On December 6, at the request of the governor 

of Nevada~ in view of the fact that the State maintains no militia, 9 .companies of federal troops 

were orde ed into the district from San Francisco and Monterey. No actual violence appears 

to have been committed by the strikers prior to the call for troops, but the experience at Cripple 

Creek and other mining camps in theW est was held by the mine-owners to justify the conclusion 

that any ~ ttempt to reopen the mines with nonunion me~ would be followed by bloodshed and 

by the destruction .of property. 

On D cember 9 the Goldfield Mine Operators' Association announced the following changes 

in the scale of wages: 

Wages at Goldfield. 

Old. New. I Old. 

---- ---------------------~- -----l ----------------------~----1------ Miners .... . .... . . . ... . .. .. .... .. ................. . Machine men .. .. .. . .. .. ..... . .. .. .... . ... , .. . . ... . 

~~:~~~~~~~~-: :·:::: :::: :::::::::::::: ::::::A 

!?~?:~~::_ ~:: ::::::::: :·::::::::::::::::::::::::I 

$5. 00 5. 00 

5.00 

5.00 

5. 00 5.00 

$4.00 

4.00 

3.75 

3. 75 

4.00 

4.50 

$7. 00 5. 00-6. 00 Carpenters .......................... . ... . .... . .. . Machinists ....... ....... .. .. . ... . ......... . . . : .. . 5. 00-6. 00 

7.00 

Engineers ........... .... ..... . ... . .. .. .. . ....... . Electricians ...... . ................ . ..... . ... . .. . Blacksmiths .......... . .... . ..................... . 5.00 

5.00 

4. 00 Tool sharpeners ........ . . .. ... . . . : .. · .... .. ...... . Blacksmith's helpers ..... . .................. . ... . 

New. 

----

$5.00 

5.00 

5.00 

5.00 

5. 50 

5.00 

4. 00 

The n~w scale, however, was not immeiliately put into effect. Resolutions were passed, 

also, to th~ effect that no one affiliated with lhe Western Federation of Miners should be employed at he mines. 

Some r.orrespondence_ was carried on in Dec~mber between the governor of Nevada and the 

President< f the United States concerning the pr<u>riety of the call for troops and of their continued pre~ence in the district. Governor Sparks was urged to call the legislature together, in 

order that the State might take steps to maintain order within its boundaries or else formally 

eall· upon he Federal Government for assistance. On December 11 a federal commission consisting of ]~awrence 0. Murray, Assistant Secretary of Commerce and Labor, Charles P. Neill, 

Commissioper of Labor, and Herbert Knox Smith, Commissioner of Corporations, was sent to 

1

the distric to investigate the conditions there obtaining. Its members reached Goldfield and 

1

began the aking of testimony on December 15, 1907. In the meantime some of the mines were 

reopening fvith new men or with old employees who rer1ounced allegiance to the local union. 

I _ On D<: cember 30 the three c~m~issio~ers reported ~eir findings to the President. a They 

concluded hat there had been no JUStificatiOn for the callmg of federai troops and that the State 

pf Nevada ~hould ta~e upon itself the pre~ervat~on of order in the district. On January 4 a part 

pf the tro·cps was withdrawn, 2 comparnes being left at Goldfield. On January 14 the state 

egislature convened in specialsession, and on January 16 i\ passed a resolution asking that the 

federal troc ps be allowed to remain until a suitable state org'inization could be effected to police 

he district On January 24 the legislature passed a bill for L,he creation of a force of state eontabulary cpnsisting of a superintendent, an inspector, 25 subtrdinate officers, and 250 privates, 

and on the same day it requested the Mine Operators' Assochtion of Goldfield -to abolish the 

pard syste n of employment which discrirninated against ce;tain labor organizations. This 

a 60th Cong., 1st sess., House Doc. 607, 1908. 

\ ' 
• 

22 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

request was acceded to, with the result that competency and good repute became the sole 

qualifications demanded of the employee. The following rules, copies to be posted at each mine, 

were promulgated by the -mine owners: 

This mine is to be worked under the open-shop policy of the Goldfield Mine Operators' Association, hiring and discharging men without regard to whether they do or do not belong to any labor organization, and under the following 

rules and regulations: 

1. The time of each man on every shift belongs to this company and to no one else. 

2. No walking ·delegate or other representative of any labor organization is to be allowed upon these premises at 

any time or for any purpose. 

3. No soliciting of membership in any labor organization is to be allowed upon these premises at any time by an 

employee of this company or by anyone else: 

4. No discussion of labor questions, either for or against unions, or in any way connected therewith, is to be allowed 

during working hours~ or upon these premises at any time or under any circumstances. · 

5. No employee of this company is to be annoyed or interfered with by any other employee in his work in any 

way whatsoever because he may or may not belong to any labor organization, or for any other reason, and all employees 

are to work together harmoniously for the best interests of the company. · 

6. No employee of this company is to harass, intimidate, or interfere with any working man of the Goldfield mining district because he does or does not belong to any labor organization. 

7. All employees are requested to report any violations of these regulations to the management;and any employee 

found guilty of violating them, or any part of them, will be immediately d)scharged and be oisqualified from any 

further employment by this company. 

8. Any outsider violating any of these rules will be immediately ejected from the premises and prosecuted by law 

for trespass . 

On March 7, 1908, the last of the federal troops were withdrawn, and in April the Goldfield miners' union declared the strike at an end. 

Among the notable events of the year 1907 was the discovery of ore by lessees in the Little 

Florence mine, near Milltown, at a point about 600 feet south of the Florence claim, and in the 

Rogers lease on the Red King claim. These developments were important in that the new ore 

bodies occur in andesite, while the mines which had previously proved so productive are in dacite. 

Ore in andesite was found also in the Daisy mine, near Diamondfield. A prom:ising fe~ture of 

this year's development was the considerable depth, from 400 to 500 feet, at whi"ch some of the 

newly opened ore bodies were found. The Las Vagas and Tonopah Railroad, connecting Goldfield with the Bullfrog district, was completed in the latter part of October, giving the Goldfield 

mines an outlet by way of Las Vegas to the smeJters of Utah. A few months later the Tonopah 

and Tidewater Railroad also built into the diSLrict. In this year Goldfield became the seat of 

Esmeralda County. 

The year 1908 was mainly a period of siow recovery from the d-epression of 1907 ,and of 

preparation for extensive operations in the future. The Goldfield Consolidated :Mines Company confined its work chiefly to the development of the Mohawk and Combination mines 

and to the construction of its 100-stamp mill, on the west face of Sandstorm Ridge, at a cost of 

$750,000. The 600-foot level of the }rfohawk was opened, and there proved to be a large body 

of good ore at that depth. The Florei,lce Company did practically no underground work, but 

completed a pipe line and a 20-stamp miil. 

Lessees continued to be fairly actire. The Little Florence lease expired on April 26 and 

the Rogers Syndic.ate lease on July 11, 1908. Both were highly profitable. The gross production of the Little Florence is estimated at over $1,500,000 ($1,285,000 net) and of the Rogers 

Syndicate about $500,000. The suctess of these lessees has led to thorough exploration of 

the ground on the east, south, and west of Florence Hill and the sinking of more than a score of 

shafts in this vicinity to depths ranging from 300 to 500 feet. One result was the discovery 

of a ·small, although very rich, ore body in the Engineers' lease on the east side of the hill. 

On }.,fay 1, 1908, the St. I ves, Velvet, Potlatch, and Gold Horn mining companies consolidated as the Goldfield Merger Mines Company, with a nominal capital of $5,000,000. Up 

to the date of consolidation the St. Ives had produced less than $100,000 and the Velvet 

probably less than $25,000. 
PRODUCTION. - 23 

The character-of the Goldfield deposits is such th~t endless litigation might easily result 

were the law of the apex invoked with the same ingenuity and contested with the same bitterness as in Butte. ~'ort'unately for the-district the mine owners have been wise enough to avoid 

this danger by compromise or consolidation. A notable example of such foresight was shown 

in July, 1908, when the Goldfield Consolidated Mines Company and the Jumbo Extension 

Mining Company reached an agreement regarding the Wedge fractional claim of the latter 

company; which lies immediately northeast of the :Mohawk No. 2 claim. On February 18, 

1908, the Jumbo Extension Company and its tenants were enjoined from working the Wedge 

claim on the ground that the ore in this fraction had its apex in the property of the Consolidated Company. On July 24 the Jumbo Extension Company deeded the Wedge claim to the 

Goldfield Consolidated Mines Company and relinquished to the latter a one-fourth interest in 

the Vinegarone fraction, lying immediately northeast of the Red Top claim. On its side the 

Consolidated Company recognized\ existing leases on the Wedge claim and agreed not to claim 

more than one-half of any ore that' might in future be mined from veins on the Polverde claim 

apexing on Consolidated ground. This agreement is creditable to all concerned-to the engineers who established the facts, to the lawyers who interpreted the legal bearing of these, and 

to the companies who accepted them. 1 Its !ratification deserves to rank as one of the important 

events in the history of the district. 

According to the secretary of the Mine Operators' Association, the total number of miners 

employed in the latter part of June, 1908, was about 1,800, the monthly pay roll having a total 

of $200,000. 

PRODUCTION. 

The gross production of the Goldfield district from the beginning of mining to the end of 

1907 is shown in the following table, the ;figures being taken from the reports on the p~oduction 

of gold and silver published by the United S,tates Geological Survey. The silver is calculated 

at the average commercial value at New York for each year. As the figures represent gross 

output, no deductions have been made for freight, treatment, or loss in smelting. 

Production of the Goldfield district. 

Gold. 

Year. Ore. 

uantity. Value. 

Short tons. Fi?e ounces. 1903 . ...... . ...... . .... ... .. ... . . . . . . .. . ..... .. .. .. .. ... . 335 ~. 412.66 $70, 671) 1904 . ... ..... .. . . . . . .. . .. ..... : . .. ... . ... . . .. .. ....... ... 7,433 1U, 293. 23 2, 341, 979 

1905. · · ·· · ·· · · ··· · ······· ·· ····· ··· .. . ......... . .. · · · · · . . 19, 5481 91_087. 76 1,882,951 1906 .. . . .. . . ... -. .. . . ... . .. .. . .. · ···· ··· ... .. .... .. ...... . . 59,628 339,'S90. 20 7,026,154 1907 •. . .. .... . .. .. ·· · ·· · · ·· ··· ·· ·· · ·· · ·· ·· ... . .. . . ...... . 101,136 406, \56.16 8,408, 396 

188, 080 954, 4'6. 01 19, 730, 150 1 

Silver. 

Quantity. Value. 

Fine ounces. 287 $155 

19,954 11~ 374 8,589 5,188 

15,648 10,484 71, 710 47,329 

116,188 1 74,530 

Total 

value. 

$70, 825 2,353,353 

1,888,139 

7, 036,638 8, 455, 725 

19,804, 680 

Average 

value 

per ton. 

$211.41 

316.60 

96.58 

118.00 

83. 61 

105.29 

The decrease in 1905 is accounted for mainly by the expiration of many leases at the close 

of that year, by the necessity of more systematic tndergrQund development by the mining 

companies as a preparation for mining on their own .account, by the idleness of the Jumbo 

mine, which had contributed over $1,000,000 to the production of 1904, and by the tendency 

of the mine owners to hold their ore until railway tral.sportation and better milling facilities 

should decrease the cost of treatment. The remarkabh revival of successful leasing in 1906, _ 

particularly on the Mohawk No. 2 claim, and the impro~ed facilities for shipping and marketing ore are r~flected in the greatly increased production fer that year. 
24 'I' HE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA • 

. The following approximate figures, taken from the current reports of local correspo:Qdents 

to the mining journals, will give some idea of the size, value, and fluctuations of weekly ship-

~ents in the latter part of 1907: 

Weekly outputjrom Goldfield, 1907. 

Week ending- Tons of Estimated Week ending- Tons of Estimated ore. value. ore. value. 

t~l-•i __ -: ••-•:•: :::::::••:::::•·•• -·· ··•• --- -:~m- ····~miill· lf~~~··-· •:• •:•••••·• •• •• •• ••••• •• • ::::~!;: ::: ;~; 

t~~m:••· ::•: •::·::: ••: •:::: :: • ---i;~- --- --~\: ~ui~~•---· -• •• •: •• •• •• •· ·• •• •• 1:m m:m 

The following statement from the Mining and Scientific Press of November 9, 1907, shows 

the sources of the ore treated in the district or shipped from Goldfield during the week ending 

on November 3: 

Output of Goldfield minesjor the week ending No7!emb_er 3, 1907. 

r' 

·Tons. Value. Tons. Value. / ------------------------------- ----- 1------ ll -------- ~------------------ - --------

Mohawk.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 $125, 000 By railroad. 

Mohawk-Combination. . . . . ... ..... ... .. . . ..... . . . .. 768 53,700 Mohawk . . ..... ... . . ... .. . . ... . .... . ..... . . .. ..... . Begole lease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 29, 000 Begole lease .. . ~ .. .. .. . . ..... . ... . .... . . . . . .. .... . . . Rogers Syndicate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 9, 000 

Florence ....... . . .... .. , . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4, 600 Combination mill.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560 39, 200 

Kinkead mill! .. .. ... .... . . .. .. .. . . .. .. .. ..... ·. .. . .. 140 7, 000 

698 $100,000 

165 16,500 

3, 741 399,700 

Of the 101,136 tons of ore treated in 1907, 17,782 tons, of an average value of $44.90 a ton, 

were milled, yielding 434 tons of concentrates, which contained $195,231 in gold and $2,057 in 

silver. The 83,354 tons shipped had an average va]ue of $91.86 a ton. 

In June and July, 1908, the estimated value of the weekly shipments of ore and· concentrates from Goldfield ranged from $175,000 to $Xl0,000. Owing to causes noted in the preceding historical sketch, the output of the district for 1908 will probably b~ less than that for 1907. 

LITERATURE. 

The following list aims to include: (1) Pllblications of value for a general understanding 

of the geology of southwestern Nevada, particdarly those which treat of formations represented 

in the Goldfield district; (2) publications de~riptive of mining districts in the region adjacent 

to Goldfield; and (3) publications containing original and important contributions to our 

knowledge of the geology or ores of the Qoldfield deposits. Many short papers relating to 

the district are not included in any of these categories and · are therefore intentio:rially omitted. 

(1) WORKS O;f THE G*NERAL REGION. 

KiNG, CLARENCE. Systematic geology: U. S. Ged.. Expl. 40th Par., vol. 1, 1878. 

Contains a wealth of information on the ~ologic developm~nt of the whole region of which the Goldfield 

district is a part. 

SPURR, J. E. Descriptive geoJogy of Nevada sotth of the fortieth parallel and adjacent portions of California. Bull. 

U. S. Geol. Survey No. 208, 1905. 

Deals with the general region and may le regarded as supplementary to the work of King. 

BALL, S. H. A geologic reronnaissance in s01thwestern Nevada and eastern California. Bull. U. S. Geol. Survey 

No. 308, 1907. 

A further development and extension of the reconnaissance work begun by Spurr in 1899 (Bull. U. S. Geol. 

Survey No. 208, 1903). 

~-The post-Jurassic igneous rocks of s01thwestern Nevada. Jour. Geology, vol. 16, 1908, pp. 36-45_. 

Describes the petrography and relatimships of the intrusive granular rocks of pre-Tertiary age. 
LITERATURE. 25 

(2) DESCRIPTIONS OF MINING DISTRICTS IN THE GOLDFIELD REGION. 

SPURR, J. E. Ore deposits of Tonopah and neighboring districts, Nevada. Bull. U. S. Geol. Survey No. 213, 1903, 

pp. 81-87. 

Describes Southern Klondike, Silver Peak, Gold Mountain, and Hennepah districts. The Goldfield deposits 

were not yet known. 

--The ore deposits of Tonopah, Nevada. (Preliminary report) Bull. U.S. Geol. Survey No. 219, 1903. 

-- Preliminary report on the ore deposits of Tonopah, Nevada. Bull. U.S. Geol. Survey No. 225, 1904, pp. 89-110. 

-- Ore deposits of Silver Peak Quadrangle, Nevada. Bull. U. S. Geol. Survey No. 225,1904, pp. 111-117. 

-- Developments at Tonopah, Nevada, during 1904. Bull. U.S. Geol. Survey No. 260, 1905, pp. 140-149. 

--. Geology of the Tonopah mining district, Nevada. Prof. Paper U.S. Geol. Survey No. 42, 1905. 

--The ore deposits of the Silver Peak quadrangle. Prof. Paper U.S. Geol. Survey No. 55, 1906. 

BALL, S. H. Notes on ore deposits of southwestern Nevada and eastern California. Bull. U. S. Geol. Survey 

No. 285, 1906, pp. 53-73. 

RANSOME, F. L. A preliminary account of Goldfield, Bullfrog, and other mining districts in southern Nevada; with 

notes on the Manhattan district by W. H. Emmons and G. H. Garrey. Bull. U. S. Geol. Survey No. 303, 1906 ~ 

TAFT, H. H. Notes on souther~ Nevada and Inyo County, California. Trans. Am. Inst. Min. Eng., vol. 3'7, 1907, 

pp. 178-197. 

Chiefly hist.orical and descriptive of I¥ining development and some notes on geology. 

(3) PAPERS ON THE GOLDFIELD DISTRICT. · 

SPURR, J. E. Notes on the geology of the Goldfield district, Nevada. Bull. U. S. Geol. Survey No. 225, 1904, 

pp. 118-119. 

Notes occurrence of alaskite and rhyolite on Columbia Mountain, and describes their intrusion into dark siliceous 

sediments. Best assays then obtained (June, 1903) were $50 a ton: 

-- The ores of Goldfield, Nevada. Bull. U. S. Geol. Survey No. 260, 1905, pp. 132-139. 

Describes conditions in November, 1904. Gives additional notes on geology. The peculiar shape of the deposits 

and their mineralogical character are described in some detail. The ledges are regarded as products of meta-

. morphism by hot ascending water. 

MooRE, CHARLES J. The Goldfield mining district. Goldfield News, April21, 1905. 

Of interest as an early effort to interpret the geology of the district. · 

WINCHELL, HoRACE V. Notes on Goldfield, Nevada. Am. Geologist, vol. 35, 1905, pp. 382-385. 

Describes the ore deposits as silicified rhyolite dikes. Recognizes the evidence of solfataric action. 

BosQui, FRANCIS L. Ore treatment at the Combination . mine, Goldfield, Nevada. Min. and Sci. Press·;-vol. 93, 

1906, pp. 413-415 and 451-454. 

An excellent description of processes employed, with results and costs: 

TAFT, H. H. Notes on southern Nevada and Inyo County, California. Trans. Am. Inst. Min. Eng., vol. 37, 1907, 

pp. 178-197. 

Chiefly historical and descriptive of mining development with some notes on geology. 

HASTINGS, J. B., and BERKEY, C. P. The geology and petrography of the Gold'field mining district, Nevada. Trans. 

Am. Inst. Min. Eng., vol. 37, 1907, pp. 140-159. 

Presents a good account of the rocks and shows their distribution by a sketch map. The paper errs in citing 

Columbia, Knickerbocker (Preble), Black Cap, and other hills as volcanic necks or cones, and contains scant 

information on the age and structural relations of the various rocks. 

RANSOME, F. L. A preliminary account of Goldfield, Bullfrog, and other mining district~;~ in southern Nevada; with 

notes on the Manhattan district by W. H. Emmons and G. H. Garrey. Bull. U.S. Geol. Survey No. 303, 1906. 

CoLLINS, E. A. The Combination mine. Min. and Sci. Press, vol. 95, 1907, pp. 397-399 and 435-438. 

History of mine and methods of mining and treating the ore. Describes general character of the ore bodies. 

RANSOME, F. L. The association of alunite with gold in the Goldfield district, Nevada. Econ. Geology, vol. 2, 1907, 

pp. 667-692. 

Describes the alteration of the dacite in connection with ore deposition. Establishes the abundant occurrence 

of alunite as a characteristic mineral of the ores and altered country rock, and discusses the genesis of the deposits. 

SHARWOOD, W. J. Gold tellurides. Min. and Sci. Press, vol. 94, 1907, pp. 731-732. 

Drawings of thin sections showing relations of telluride, gold, and quartz. 

BROWNE, R. STUART. · Cyanidation in Nevada. Min. and Sci. Press, vol. 95, 1907, p. 677. 

Proposes to treat Goldfield ores by dry crushing, roasting, and final leaching with cyanide solution. 

RICKARD, T. A. Goldfield, Nevada. Min. and Sci. Press, vol. 96, 1908, pp. 559, 664, 738, 774, 840. 

General notes on. the district. The articles on the history of the district, on the moral effect of rich ore, and 

on metallurgical development are particularly good. 

BECKER, AR~OLD. Geological possiblities at Goldfield. Min. and Sci. Press, vol. 96, 1908, p. 846. 

An attempt to show that there is a second sheet of dacite below the one in which the rich Mohawk ore bodies · 

occur and that this lower sheet may prove productive. The supposed lower dacite does not exist. 
26 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

KING, 

Advocates 

LocHIEL M. Cyanid.ation in Nevada.. Min. and Sci. Press, vol. 96, 1908, pp. 123-126. 

dry crushing, roasting, and cyanidation of crude ore. 

KIRBY, 

Describes 

A. G. Cyanidation in Nevada. Min. and Sci. Press, vol. 96, 1908, pp. 836-839. 

mill tests on Combination and Mohawk ores. Believes that ores can be more economically 

by wet crushing, amalgamating, 

treated 

concentrating, and then roasting and cyaniding the concentrates 

than by roasting and 

in the district, 

cyaniding the crude ore. 

GEOGRAPHIC NAMES. 

petrographic 

A search for geographic names to distinguish successive eruptions of lava of the same 

soon

character (there are in the district, for example, five rhyolites of different age) 

-showed how few names in local use were available for this purpose. It became necessary 

these 

to apply names to certain topographic features in order that the rocks typically developed at 

which 

localities 

are 

might be appropriately designated. The difficulty of finding English names 

becomes 

appropriate, and which can at the same time be fitly applied to geologic formations, 

words 

evident on trial. In names chosen from the Spanish the ordinary meaning of the 

easily 

is 

pronounced. 

less obtrusive, and it is possible to find terms which are appropriate, euphonious, and 

their derivation 

The following list shows the new names employed in this report, with 

and usage: ' 

Name. 

Malpais Mesa ........... . 

Spearhead Point .•....... Pozo Canyon ........... . 

Mira Monn tain ..•• ____ .. Meda Pass .............. . Chispa Hills ............ . 

Espina HilL .......... .. Morena Ridge .......... . 

Names applied in this report to topographic features. 

Derivation and comment. 

Spanish The feature 

mal pais 

here (mltl pah-ees'), bad country. Popularly prononnced mltl'-a-pi. 

"the mesa." called Mal pais Mesa is locally referred to as "the Malapai" or 

Refers to shape of point .......................................................... Spanish pozo, well. Refers . 

source of water to fact that a well in this ravine was formerly the chief for Goldfield. Spanish 

From Goldfield 

mira (mee'-ra), Meda Mining 

look!, behold! Refers to view of Goldfield from the summit. Co., whose claims cover the pass ................... Spanish chispa, sparkle. Refers . 

hills. to the sparkling black mwa on the surface of the • Spanish espina (es-pee'na), spine. Refers to shape of hill ........................ Spanish morena (mo-ray'·na), . brown. Refers to color of the rhyolite ......... : .. . 

Geologic use. 

Malpais basalt. 

Spearhead rhyolite. Pozo formation (sedimentary). 

Mira basalt. 

Meda rhyolite. Chispa andesite. 

Espina breccia. 

Morena rhyolite. 
CHAPTER II. 

PRELIMINARY OUTLINE OF THE GEOLOGY AND ORE DEPOSITS. -. 

This chapter is not intended as a complete synopsis of the whole report. Its function is to 

give the reader such a preliminary and general view of the field as will enable him to follow 

more readily and, it is hoped, with greater interest, the ampler exposition of the succeeding 

chapters. 

The geologic structure of Goldfield, compared with that of most districts in which deposits 

of the precious metals are found, is simple. The district is essentially a low, _domical a uplift 

of Tertiary lavas and lake sediments resting upon a foundation of ancient granitic and metamorphic rocks. The erosion of this fiat dome has exposed the pre-:-Tertiary rocks at a number 

of places in the central part of the district and these outcrops are surrounded by wide concentric 

zones of successively younger formations. Some of the laterlavas were erupted after the dome 

had been elevated and truncated. 

The oldest rocks exposed in the district are found on Columbia and Vindicator mount'ains, 

and from Columbia or Goldfield are particularly not~ceable as conspicuous dark patches on the 

southern slope of the former peak. Originally thin-bedded limestones or calcareous shales, 

with subordinate beds of sandstone, the form_ation is now much contorted and metamorphosed. 

The calcareous beds have been changed to compact aggregates of quartz (j asperoid) crowded 

with microscopic black particles, probably carbonaceous, and the sandstone to hard, vitreous 

quartzite. These beds are probably Cambrian. 

The metamorphism is apparently due to the intrusion into these sediments of masses of a 

granitic rock composed essentially of quartz and orthoclase, a type for which Spurr has proposed 

the name alaskite. This rock is well exposed on Columbia Mountain and :makes up a large 

part of Vindicator Mountain. Smaller areas occur in the vicinity of Banner Mountain. Most 

of the alaskite contains a very little black mica and some plagioclase. In most exposures the 

mica is decomposed and scarcely noticeable, b:ut northeast of the summit of Vindicator Mountain the alaskite mass grades into a biotite granite. 

The alaskite was pro"Qably intruded at about the close of Jurassic time. It is certain that 

this event was followed by a long interval during which the region was eroded to the surface 

-of moderate relief subsequently covered by the irruption of Tertiary lavas. 

The sequence of Tertiary eruptions as exemplified by the rocks of the Goldfield district is 

,given in the following list, the oldest rocks being at the bottom. To prevent confusion between 

rocks of like petrographic character erupted at different periods,. recurrent kinds are distinguished 

by local geographic terms derived from places at or near which the corresponding rocks may 

be seen. 

a The word domal (from the Latin domus, a house) which means "belonging to a house" was originally an astrological term, but was later 

-applied to the roof-like planes of certain crystal forms. It has unfortunately slipped into some currency in geologic literature as a substitute 

for domical, which is the correct adjective in reference to a dome and is analogous to conical, spherical, and cubical. 

27 
28 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Sequence of the Tertiary eruptions. 

Formation or map name. Petrographic name. Occurrence. 

Malpais basalt ...... ::... Dolerite............................... Flow or flows, with a few small intrusions. Rabbit Spring formation. Breccia, conglomerate, and sandstone.. A variable and for the most part thin deposit; probably fluviatile. 

Pozo 

Spearhead formation.......... rhyolite....... Conglomerate......................... 

Rhyolite ... ..................... .. ... Flow or flows. 

Fluviatile deposit. Conformably underlies Spearhead rhyolite and unconform-

!

Siebert formation ....... Conglomerate, sandstone, tuffs, and 

Mira diatomaceous earth. 

Siebert basalt............. Quartz-bearing doleritic ba{lalt. ...... . 

Espina breccia........... 

formation ....... Con~lomerate, sandstone, tuffs, etc ... ·. Dacttic breccia ....................... Andesite breccia......... . Andesite breccia ...................... Meda rhyolite............ . Rhyolite ............................. . 

{

Dacite vitrophyre,...... Dacite vitrophyre .................... Chispa andesite . ......... Andesite .............. : .............. Dacite vitrophyre.. . .. .. . Dacite vitrophyre .................... . 

:::~~-a~~~~;~-----~~:::1 ::::i~~:::::::::::: ::::: :·:::::: ::::: 

Morena rhyolite.......... Rhyolite ............................. Sandstorm . rhyolite ........... do ................................ Kendall . tuff ............. Rhyolitic and andesitic tuff .......... . 

Latite.. .. . . . . . . . . . . . . . . . Latite ................................ Vindicator . rhyolite ...... Rhyolite ............................. . 

ably overlies the Siebert formation. Lake beds. 

Flow intercalated in Siebert formation. Lake beds. 

Roughly bedded deposit. Roughly bedded :pyroclastic deposit. Flow. 

Do. 

One or more flows in the dacite vitrophyre. Flows. 

Sheet-like 

the arj:la 

and 

mapped. irregular intrusive masses passing into flows and breccias east of 

Mainly 

breccia. flows, 

Locally 

but with some dikes and intrusive masses and with some tuff and 

at the surface. includes some effusive basaltic rocks which are not exposed 

Intrusive masses. Flows. 

Obscurely 

Sandstorm 

bedded and in part lenticular deposits closely associated with the rhyolite. Flow. 

Do. 

The 

A few 

Vindicator 

dikes of uncertain position in the sequence are not included in the foregoing list. 

cator Mountain 

rhyolite rests on Cambrian sediments and alaskite on the flanks of Vindicontains abundant 

and on the summit of Columbia Mountain. Much of it is greatly altered and 

alunite. 

meters) 

The 

in 

latite, 

diameter 

as may be seen from Plate II, occupies an area a little over 2 miles (3.2 kilocharacteristic 

in the center of the district, and a smaller area south of Columbia. Its 

tain, and on 

features may be well seen in the vicinity of McLaughlin's well, on BaiUler Moundull purplish 

the southern edge of the town of Columbia. The rock, nowhere fresh, is normally 

or greenish gray. A spotted or mottled appearance, due to flow brecciation, 

rather characteristic 

is 

Mountain. The 

and is well ~hown on a small hill half a mile north of the summit of Bannerblende, and mic~ 

freshest obtainable specimens of the latite show phenocrysts of feldspar, hornin a compact, streaky groundmass 

marked flowage 

that was evidentJy once a glass with wellalteration connected 

lines. 

with 

As a rule, the latite, when it has not been subjected to the intense local 

ore deposition, may be distinguished 

by the absence 

from the later andesitic rocks 

resembles 

of fresh phenocrysts and the peculiar streakiness of its groundmass, which 

the groundmass of a rhyolite rather than that of most andesites. 

Paleozoic 

The rock 

sediments, 

is a flow resting generally upon a clean and rather uneven surface of alaskite and 

although on Vindicator 

Its 

l\iountain it rests in part on the oldest rhyolite. 

rhyolite 

thickness is not known, but is clearly variable, as on Columbia Mountain the succeeding 

300 feet 

rests 

(91 meters); 

directly upon the alaskite. The maximum thickness is tentatively estimated at. 

it may be considerably more. 

series 

Overlying 

of thin, glassy 

the latite, or resting on the pre-Tertiary rocks where the latite is absent, is a. 

of Columbia Mountain. 

rhyolite 

This, 

flows which is best developed in the rounded white hills northwest " 

tuffs (Kendall 

the Sandstorm rhyolite, is closely associated with pale greenish. 

Morena 

tuff) of mingled latitic and rhyolitic character and is cut by masses of intrusive 

nation, and 

rhyolite. 

weathers 

The effusive rhyolite is usually nearly white, has conspicuous flow lamihills lying west of 

in thin, shelly flakes. This is the rock of the Sandstorm mine and of the, 

silicification, particularly 

the road from the mine to Columbia. It all shows some devitrification and 

this rhyolite acquired 

in the . vicinity of the ore deposits. Certain varieties or portions of 

weathered 

by flowage a very thin lamination, which gives the rock when somewhat 

a deceptive resemblance 

thicke~t in 

to indurated clay shale. The rhyolite appears to have been 

been found 

the 

southeast 

vicinity of Columbia Mountain and to thin out to the southeast .. None of it has; 

of McLaughlin's well. 
OUTLINE OF THE GEOLOGY .AND ORE DEPOSITS. 29 

The Kendall tuff associated with these early rhyolitic eruptions may be best examined 

along the southwest base of Columbia Mountain and directly west of the Kendall mine. Underground it is exposed in the west workings of the 100-foot level of this mine. 

The intrusive or Morena rhyolite that forms Morena Ridge extends north from the summit 

of Columbia Mountain to the Adams mine and cuts the shaly Sandstorm rhyolite at the 

Conqueror mine. 

After the eruptions of the earlier rhyolites the region was covered with successive flows 

of andesite, accompanied by subordinate layers of andesitic tuff. The products of thes;e eruptions, the Milltown andesite, constitute the most extensive formation in the district. (See 

Pl. II.) The total thickness of this deposit, as of most of the other volcanic formations in this 

district, can p.ot b~ determined, owing to the slight deformation of the rocks, their poor exposures, 

the comparatively slight topographic relief, and the absence of persistent datum planes, such 

as may usually be found in stratified rocks. It probably lies between 600 and 800 feet (183 

and 244 meters). 

. The dacite, whose eruption followed the andesitic period, is in many respects the most 

interesting rock in the district and is very important from an economic point of view. It 

occupies, as may be seen by reference to £late II, a considerable area east of Goldfield and 

Columbia and is the principal country rock of the larger mines. This mass appears to be an 

intrusive sheet about 700 feet (213 meters) in maximum thickness, but in most places much 

thinner. · 

A larger body of dacite extends southward from Tognoni Springs and forms some of the 

high hills just east of the m,apped portion of the district. This body, as may be seen from 

Plate II, makes up a large part of Preble Mountain, where it is probably intrusive into th.e 

:Milltown andesite. East of the area mapped, however, the dacite is undoubtedly effusive and is 

associated with volcanic breccia. Smaller .masses of dacite occur southeast of Black Butte and 

in the central part of the district. 

Mineralogically and chemically the dacite at Goldfield is merely a quartz-bearing andesite 

and is in no way similar to the more siliceous rocks called dacite by Spurr in his report on the 

Tonopah district.a 

Contemporaneously with, or shortly after, the dacite intrusion a rock classed as dacite 

vitrophyre was erupted as a series of flows and is now extensively exposed in the low hills in 

the southeast corner of the district. This rock is in most places a porous light-gray or greenish 

rock with abund~nt glistening scales of black mica and phenocrysts of fresh plagioclase. The 

dacite vitrophyre is associated with one or more intercalated flows of andesite (Chispa andesite). 

The eruption of the dacite vitrophyre was. followed by a flow of rhyolite (Meda rhyolite) and 

by eruptions of andesitic breccia. · 

After these eruptions the region was covered by an extensive body of fresh water in which 

were laid down 1,000 feet (305 meters) or more of bedded conglomerates, tuffs, tuffaceous sands, 

pumiceous ash, and diatomaceous earth. Th+e deposits cover a large part of the district, 

particularly in its outskirts. They underlie the town of Goldfield and stretch both northward 

and southward beyond the limits of the area stJdied. They also extend beneath Malpais Mesa 

southwest of town and are well exposed in the s~eep bluffs of Pozo Canyon. The beds here dip 

generally westward at angles ranging from 25° to 30°. 

As dacite vitrophyre and associated flows a~e present beneath the lake beds in only a small 

part of the district, and as the formation of the \lake indicates some• change in the. configuration 

of the region, there is at least a suggestion of er<!>sion between these eruptions and the lacustrine 

condition. Volcanism continued active durin~ the existence of the lake, as is. sho;wn by the 

prevailingly volcanic nature of the sedip1ents and the occurrence within them of a thick flow 

of quartz-bearing basalt (Mira basalt) and tliiJ flows of glassy rhyolite. The Mira basalt, as 

shown by wells, underlies the southwestern par~ of Goldfield and is exposed on the automobile 

road to the Bullfrog district. · I .• . . . . . . j . . .. . . 

. a Spurr's reasons for using the name .dacite for rocks which strictly s~ould receive other names are given in. Geology 1or Tonopah mining district,-

Nevad"' P<Of. Pap& U.S. Goo!. Survey No. 42,1905, p. 59, footnote. I 
30 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

In the eastern part of the district, northeast of Preble Mountain, are some bedded breccias 

and tuffs from 200 to 300 feet (61 to 91 meters) in present thickness. They rest upon dacite 

and andesite and are made up largely of fragments of these rocks, particularly of dacite mingled 

with abundant fragments of volcanic glass and some sandy tuffs. These beds, the Espina 

breccia, are possibly of the same age as the lake beds just described. 

The dacite vitrophyre is cut by dikes of andesite. Whether these were erupted before, 

during, or after the lacustrine episode is not determinable. · 

Lacustrine conditions were ended by uplift of the region, the domical structure being then 

initiated. After the lake beds had b-een beveled by erosion and entirely swept away from the 

central part of the district eruptions of rhyolite lavas again. began. 

The latest rhyolite, called the Spearhead rhyolite, is a light-pink or pale-green rock, rather 

porous and containing abundant pumiceous fragments. It comprises two flows about 100 feet 

(30 meters) in total maximum thickness, which are exposed in the bluffs southwest of Goldfield. 

It is this rock that is quarried for building stone at Rabbit Spring. The rhyolite is in some 

places overlain by a few feet of unconsolidated tuffaceous sand and volcanic gravel, called the 

Rabbit Spring formation. 

Finally, the volcanic history of the region was brought to a close by the eruption of one 

or more flows of olivine basalt. This is the dark rock that is conspicuous as the capping of 

Malpais Mesa southwest of town, and has accordingly been given the local designation of the 

Malpais basalt. It also forms the summit of Myers Mountain, Blackcap Mountain, and of 

several hills south and east of the area mapped. The larger areas of this rock represent remnants of flows which rest upon a nearly horizontal surface of older rocks; but some smaller 

masses, such as that shown on the east slope of Vindicator Mountain, are intrusive and may fill 

' orifices through which the basalt reached the surface to spread out as flows. 

The eruption of the Malpais basalt was followed by a period of erosion which, varied by 

slight deformations of the rocks, has continued to the present. 

There is no paleontological evidence upon which to assign the Tertiary formations at Goldfield to the recognized series of that system. For reasons later presented the prelacustrine 

volcanic rocks are provisionally regarded as Eocene, the lacustrine formations as Miocene, and 

the postlacustrine formations as Pliocene. / 

The sulphide ores of the Goldfield district are of complex mineralogical character, native 

gold and pyrite being accompanied by minerals containing copper, silver, anti~ony, arsenic, 

bismuth, tellurium, and other elements. In some ores the gold occurs free in fine particles, 

which as a rule are so closely crowded together in the characteristic flinty quartz gangue as to 

form yellow bands or blotches. The associated minerals are pyrite, marcasite, bismuthinite, 

a reddish gray cupriferous mineral which appears to correspond more nearly to famatinite 

than to any other known species, and a new. cupric sulphantimonite, which has been named 

goldfieldite. A concentric crustification is highly characteristic of the richest ores, fragments 

of silicified, alunitized, and pyritized rock being covered by shells of gold and sulphides. 

The most notable features of these ore bodies are their remarkable richness and their 

egyally remarkable irregularity. The ores are almost without exception associated with craggy 

outcrops of silicified vo canic rock, although only a very small proportion. of these outcrops, 

which are extraordinarily numerous and constitute the" most striking superficial features of 

the district, have been found productive. Associated with the silicification other processes of 

locally intense alteration, especially the formation of alunite, have also been active, producing 

in many cases a softening of the rock affected, and thus serving to accentuate the silicified 

portions under the selective action of erosion. The deposits have formed ·along [zones of fissuring, which for the most part are very irregular in trend, are rarely traceable in any one direction 

for more than half a mile, and are not planes of notable faulting. Branching and intersection 

are very common. Many of the outcrops show no linear character, being mere irregular knobs 

of siliceous and alunitic material. Some of these probably represent intense alteration at the 

point of intersection of two or more inconspicuous approximat~ly vertical fissures. Others 
OUTLINE OF THE GEOLOGY AND ORE DEPOSITS. 31 

:tre erosion remnants of nearly horizontal silicifi~d zones and, as in · the case of Black Butte, 

merely cap the hills whose summits they form. 

The most important ore bodies thus far found are in dacite, although some small, very 

rich pay shoots have been disc0vered in the Milltown andesite. 

Oxidized ores have supplied a large part of the gold produced during the first two or three 

years of exploitation, and in some mines, particularly the Sandstorm and Kendall, wp.ich are 

in rhyolite, no sulphide ores are as yet known. As a rule the oxidized ore is a soft, shattered, 

more or less earthy material, usually stained brown by oxide of iron. Fragments .of rusty 

porous quartz are mingled with kaolin, alunite, gypsum, alum, oxide of iron, and various 

earthy mixtures of no definite mineral composition. Some of the rich ore, as in the Sandstorm 

mine, is a nearly white, impure kaolin, gritty from the presence of minute crystals or grains of 

quartz, and containing all through it abundant specks of free gold. Barite, in crystals up to an 

inch (25 millimeters) in length, is abundant in this ore. In the January and Combination 

mines some of the most characteristic rich ore consists of porous· rusty quartz (silicified dacite), 

in which the pores and crevic~s are partly filled with yellow, earthy limonite and tiny pearly 

scales of bismite, the oxide of bismuth. In some specimens these scales form pseudomorphs 

after bismuthinite. They are usually a sign of rich ore, but are occasionally found in lowgrade or barren material. In the mines at Black Butte the richest oxidized ore usually shows 

little greenish-yellow specks of a ferric tellurite, either emmonsite or durdenite, and tellurite, 

the oxide of tellurium, was noted in a partly oxidized .telluride ore from 'the Goldfield-Belmont 

mine near Black Butte. Melantetite (hydrous ferrous sulphate), in some cases mixed with a 

very little chalcanthite (hydrous copper sulphate), occurs in the partly oxidized ore of the 

Combination and Florence mines. 

The valuable constituent of the oxidized ores is native gold. Native silver or halogen 

compounds of silver are not common. 

The time of deposition of the ores is not definitely known, but was probably Pliocene. 

They were deposited from acidified solutions and the deposits now exposed are believed to have 

been at no time covered by more than 1,000 feet (305 meter~) of rock. 
CHAPTER III. 

DESCRIPTION OF THE PRE-TERTIARY ROCKS. 

CAMBRIAN SHALE. 

The ·oldest rocks exposed in the Goldfield district are certain dark, fine-grained, and thinbedded sediments forming parts· of Columbia and Vindicator mountains. Those on Columbia 

Mountain are most conspicuously displayed on the southwest slope, appearing aR dark patches 

which, by their contrast with the light-hued alaskite and rhyolite, constitute a striking feature 

of the hill as seen from Goldfield or Columbia. In Plate V, A, which is a view of Columbia 

Mountain from a point between the two towns, this difference in shade is much less evident than 

in the actual view. 

The individual beds are thin, most of them less than 4 inches thick. The material is 

prevailingly aphanitic and of a dense flinty texture. The color is gray, so dark as to appear 

nearly black when seen in mass. The microscope shows that these beds are now composed. of a 

fine crystalline aggregate of quartz containing abundant opaque black microscopic particles, 

which are probably carbonaceous, and some minute crystals of pyrite. It is the presence of 

these inclusions that gives the rock its dark color. Some specimens show tiny grains and 

veinlets of a colorless anhedral mineral which has not been definitely determined, but which has 

the general optical characteristics of zoisite. 

This is the rock referred to by Spurr a as "jasperoid" and regarded by him as probably 

a silicified limestone. While such a derivation is not impossible it is thought more probable 

that the rock was originally a siliceous shale containing considerable organic matter and probably 

some calcite. On the south slope of Columbia ~1ountain these dark flinty shales are interbedded 

with a few thin layers of quartzite. · 

The shales occur in comparatively small masses which have beeh intruded by alaskite. 

Th~ original terrane of which they once formed a part has been greatly disrupted by the act of 

intrusion, and it is doubtful whether any extensive remnants remain beneath the Tertiary 

volcanic rocks of the Goldfield district. The visible bodies of shale in Columbia and Vindicator 

mountains probably rest upon alaskite in intrusive contact. Their internal strp.cture therefore 

has little bearing upon the present tectonic features of the region. It is sufficient to say that 

the beds have been greatly disturbed by the alaskite intrusion. Those on the west slope of 

Vindicator Mountain have a general strike of N. 20° W. and dip west at an angle of 75°. 

Whether this attitude represents folding prior to the granitic invasion there is no means of 

telling. 

No fossils have. been found in these shales and the only local clue to their age is the fact 

that they constitute a part of the eroded floor upon which the Tertiary rocks accumulated. 

The studies of H. W. Turner,b J. E. Spurr,C and S. H. Balld have shown, however, that north, 

west, and south of the Goldfield district are extensive areas of sedimentary rocks referable to 

the Cambrian period. These rocks are represented in the Southern Klondike district, 14 miles 

(22.5 kilometers) north of Goldfield; in the Silver Peak Range, of which Montezuma Peak, 7 

miles (11 kilometers) west of Goldfield, is a spur; and in some hills just east of the halfway 

station, 6 miles (9 .6 kilometers) south of Goldfield, on the stage road to Lida. Cambrian fossils 

a Geology of the Goldfield district, Nevada: Bull. U. S. Geol. Survey No. 225, 1904, p. 119. The ores of Goldfield, Nevada: Bull. U. S. Geol. 

Survey No. 260, 1905, p. 133. 

b Silver Peak folio (unpublished). 

c Descriptive geology of Nevada south of the fortieth parallel: B-ull. U . S. Geol. Survey No. 208, 2d ed., 1905, pp. 184-185. 

dA geologic reconnaissancein southwestern Nevada and eastern California: Bull. U.S. Geol. Survey No. 308,1907. 

32 
EO L O GI C AL SURVEY 

Con. tour in.te:rvallOO £ee-t . a;~;urn. U1 m,e;cov .~('/,// le-veL. 

1906 

PROFESSIONAL PAPER 66 PLATE IV 

LEGEND 

n . 

( ar:.,;;;z;;;J;{eW.,i:n1':~'f ~ IGNEOUS ROCKS 

l 

Fa: t 

~ ::f7to"PrONfJ f, 1\{( u:nmin.· Wnr tonP i.s now kfl,Own- a · t7rc Eldorado lirn&stnnf!, 
PRE-TERTIARY ROCKS. 33 

have been found at Silver Peak, a at Lida,b near Cuprite c (about 16 miles (25.5 kilometers) 

south of Goldfield), and at a locality 4 miles (6.5 kilometers) west-northwest of Montezuma 

Peak.d These Cambrian rocks comprise, according to Ball,e fine-grained dark limestone, shale, 

and quartzite, the shale and limestone in the Silver Peak Range being interbedded and grading 

one into the other. As shown in Plate IV, which is compiled chiefly from the geologic map 

(Pl. I) accompanying Ball's report, the situation of Goldfield with reference to the areas of 

Cambrian rocks which partly encircle the district is such as to render it reasonably certain that 

the metamorphosed beds of Columbia and Vindicator mountains are also Cambrian. They are 

regarded as probably metamorphosed remnants of the shaly be.ds belonging to that period as 

represented in the Silver Peak Range and elsewhere in this general region. 

ALASKITE AND GRANITE. 

DEFINITION. 

The name alaskite was proposed by Spurr! in HlOO to designate the group of holocryst~lline quartz and alkali-feldspar rocks to which the name aplite had previously been tather 

loosely applied by most petrographers. Aplite, however, had come into wide use as a textural 

term applied to rocks of many kinds, usually occurring as dikes, and the name no longer had 

any precise mineralogical significance. Rocks of granitic texture and habit, consisting· essentially of quartz with orthoclase or other alkali feldspar, have proved to be so widespread and 

to constitute such important masses, particularly· in Nevada, that Spurr's proposal is amply 

justified. The name alaskite is already familiar to the mining. men of that State. 

By the addition of black mica alaskite tnay grade into biotite granite (granitite), a transition which, as will presently be shown, is exemplified iri the Goldfield district. In a simple field . 

classification the alaskite might properly be called granite, this name in such usage designating 

any .quartz-feldspar rock of visible and even grain. · 

DISTRIBUTION. 

As may ·be seen from the geologic n1ap (PL II) the principal exposures of granitic rocks _are 

in the central part of the district, especially in the vicinity of Columbia, Vindicator, and Banner 

mountains. Two exceptional occurrences deserve mention, although they are too. small to · 

appear on the map. One mass, discovered in a prospect on the north slope of Black Butte, 

is apparently a block a few feet in diameter, inclosed in andesite. The other mass, the visible 

portion of which is about 10 feet (3 meters) in diaineter, occurs in the northwestern corner 

of the area mapped in Plate II, close to the small patch of rhyolite crossed by the line of the 

electric power company in section 15. This also may be a loose block, as it is surrounded by 

the sedimentary deposits belonging to the Siebert formation, which is probably some hundreds 

of feet thick at this point. This supposition seems more probable than the alternative one, 

that the mass is the top of a sharp alaskite hill projecting through the s~diments. The transportation of large blocks of pre-Tertiary rock by the lava flows which inundated the district at 

several periods in its later geological history is not inherently i1nprobable. Underground, 

alaskite has been cut in the Sandstorm 1nine on the 400-foot level, about 290 feet (88 meters) 

southeast of the shaft. 

PETROGRAPHY. 

The rock. of the Columbia Mountain areas is evenly granular, consisting wholly, so far as 

,can be seen without the microscope, of x(momorphicg crystals of quartz and feldspar. The 

a Walcott, C. D., Second contribution to the Cambrian faunas of North America: Bull. U.S. Geol. Survey No. 30, 1886, p. 38. 

b Spurr, J. E., Descriptive geology of Nevada s<mth oJthe fortieth parallel: B,ull. U.S. Geol. Survey No. 208, 2d ed., 1905, p. 185. 

c Ball, S. H., A geologic reconnaissance of southwestern Nevada and eastern California: Bull. U. S. Geol. Survey No. 308, 1907, p. 66. 

d Ball, S. H., op. cit., p. 57. 

~ Op. cit., pp. 51, 56, 66·. 

f Classification of igneous rocks according to composition: Am. Geologist, vol. .25, 1900, pp. 229-232. 

g So far as practicable the textural terms applied to rocks in this report are those proposed or recommended by Cross, Iddings, Pirsson, and 

Washington i1;1 their paper "The texture of igne~us rocks" (Jour. Geology, .vot 14, 1906, pp. 692-7Q7). · 

79145-No. 66-09--3 
34 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

average diameter of the grains is rather less than 5 :millimeters, although so:m·e of the feldspar 

crystals are occasionally larger and show a slight tendency toward porphyritic development. 

The prevailing color is light reddish, the tint being due to :microscopic flecks of hematite in the 

feldspars. Some of the rock, however, is nearly white. 

Thin sections show that over 95 per cent of the rock consists of quartz and microperthitic 

orthoclase. In addition to these minerals there is a little sodic oligoclase and small scattered 

plates of what was probably once biotite, but is now an aggregate of a faintly greenish :mica 

with the birefringence of muscovite, and epidote. The feldspars are fairly fresh and the rock 

has undergone no appreciable dyna:mo:metamorphism since its original solidification. It is a 

· typical alaskite. 

The alaskite of Columbia Mountain is cut by occasional aplitic dikes of lighter color and 

finer grain than the mass of the rock. Such of these as were :microscopically examined show 

essentially the same Jnineralogical composition as the alaskite, although oligoclase is perhaps a 

little more abundant in them. 

The main mass of Vindicator Mountain is composed of a moderately coarse reddish alaskite, 

closely resembling that of Columbia ~fountain and n1ade up chiefly of .quartz and orthoclase. 

In many places the rock is silicified or kaolinized. On the eastern slope of the mountain the 

alaskite passes gradually into biotite granite. This granite, which is well exposed along the 

road half a mile (0.8 kilometer) northeast of the summit of the mountain, shows a pronounced 

tendency toward a porphyritic texture, large rounded anhedral crystals of quartz and orthoclase 

being closely crowded in a rather fine-granular groundmass consisting of the same :minerals 

with oligoclase and biotite. Some of the quartz crystals show the embayed outlines characteristic of granite porphyries. Much of the granite is considerably decomposed, the biotite being 

altered to chlorite and epidote. The latter :mineral has also developed extensively in the 

feldspars. Titanite and zircon occur as accessory. minerals. 

A similar porphyritic variety, really a granite porphyry, is exposed in a ·shaft which goes 

through Vindicator rhyolite into the granite at a point half a :mile (0.8 kiiometer) east of the 

summit of Vindicator Mountain. This facies has a reddish tint from the abundant phenocrysts 

of red orthoclase. The other visible crystals are quartz and small dull greenish specks, evidently 

in part hornblende. The :microsope shows large turbid crystals of microperthitic orthoclase, 

rounded and embayed ones of quartz, some automorphic green hornblende, abundant pseudomorphs of chlorite and epidote after biotite, some irregular grains of titanite, and a little' 

plagioclase. There is also some pyrite. The orthoclase shows incipient sericitization. 

The alaskite of Vindicator Mountain, particularly on the ridge south of the suntmit, 

contains numerous small dikelike masses of an aphanitic rock which has a much-altered 

.and bleached appearance. The microscope shows a compact aggregate of quartz and other. 

secondary minerals with no recognizable igneous characteristics. The masses may possibly 

represent rhyolitic dikes but their original character can only be surmised. 

The rock of the various smaller areas shown on the geologic rna p (Pl. II) is in most cases 

too decomposed for satisfactory microscopical study. Most of them are composed of typical 

alaskite, with no mica. Biotitic facies occur, however, in the masses exposed north of Banner 

Mountain and east of Vindicator Mountain. 

GEOLOGIC RELATIONS. 

The alaskite and granite are intrusive into the Cambrian shale. (See Pl. V, B.) The 

intruding magma appears to have been highly viscous and some of the exposures on Columbia 

Mountain indicate that the alaskite had in some places solidified in contact with the shale 

before the general movement of the magma had ceased. In other words, the contact, while 

clearly of intrusive character, is accompanied by brecciation of both shale and alaskite. Whatever rocks may have overlain the shale at the time of intrusion were removed by erosion prior 

to the outbreak of Tertiary volcanism. The opening of that epoch found the Goldfield region 

'eroded to a tract ot'low relief floored with alaskite and granite, within which lay a few residual · 

patches of Cambrian shale. . 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE V 

A. COLUMBIA MOUNTAIN; FROM THE SOUTH. 

The top of the mountain is Vindicator rhyo lite. The two sharp knobs at the right are sil icified dacite. Dark areas 

near the base of the mountain are Cambrian shale. 

~outh slope of Co lumb ia Mountain . 
I 

j 
PRE-TERTIARY ROCKS. 35 

AGE. 

The age of the al skite and granite intrusion is not definitely determinable from local 

relations. These indica e merely that the rock is post-Cambrian and is older than the Tertiary 

eruptives. Clarence Ki ga many years ago advanced the opinion that the ranges of western 

Nevada and the Sierra evada are of contemporaneous origin and that their granitic intrusions 

are of early Cretaceou age. The post-Jurassic age of the Sierra Nevada batholith has long 

been well established, a d the reconnaissances made by J. E. Spurr b and S. H. Ball c with the 

study of the Humboldt region by G. D. Louderback d all support the view of King as to the 

contemporaneous age o the principal granitic intrusions of the Nevada ranges. The alaskite 

of the Goldfield district can therefore be considered with some confidence as belonging to the 

eaTly Cretaceous period. 

aU. S. Geol. Expl. 40th Par., v . 1, 1878, pp. 733-754. 

b Descriptive geology of Nevada south of the fortieth parallel: Bull. U. S. Geoi, Survey No. 208, 2d ed., 1905. See also, The ores of Goldfield, 

Nevada: Bull. U.S. Geol. Survey N . 260, 1905, p. 133. 

c A geologic reconnaissance in so thwestern Nevada and eastern California: Bull. U. S. Geol. Survey No. 308, 1907. 

d Basin' Range structure of the umboldt Region: Bull. Geol. Soc. America, vol. 15, 1904, p. 336. 
CHAPTER IV. 

DESCRIPTION OF THE PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 

INTRODUCTION. 

Definite assignment of all of the various lithologic units composing the volcanic series 

at Goldfield to the standard divisions of Tertiary time is not yet possible and may never b€ 

effected. The general post-Mesozoic age of the volcanic rocks of the Great Basin has, however) 

been so firmly established by von Richthofen, King, and later investigators as to be generally 

. accepted as one of the basal facts of the. geologic history of the region: In the vicinity of th€ 

· :fortieth parallel, King a was able,- by reference to the Miocene sediments of Pahute Lake and 

the Pliocene beds of Shoshone Lake, to determine the divisions of the Tertiary to which many 

of the lavas belong. 

In the Tonopah district Spurr, b by the help of the Siebert sediments, whi~h he tentativ~ly 

eorrelated with those of King's extinct Miocene Pahute Lake, was also able to reach some conclusions as to the age of the several eruptions. 

The extent to which similar results are attainable in the Goldfield region will be fully 

discussed in a subsequent chapter. For the present it is enough to keep in mind the fact that 

a group of lake sediments, equivalent to and very probably once continuous with the Siebert 

tuff of Tonopah, occurs in the Goldfield district. They record a distinct lacustrine epoch initiated 

and terminated by deformation and erosion. It is thus possible to divide the Tertiary rocks 

of the district into three natural groups divided by conspicuous unco~formity. These are: 

(1) the prelacustrine flows and intrusions, (2) the lake beds and associated volcanic rocks, and 

(3) the postlacustrine volcanic rocks. The correlation of these groups with the rocks of other 

districts and the discussion of their geologic chronology will be deferred until the rocks themselves ·have been described. 

The prelacustrine rocks in the order of their eruption are: (1) the Vindicator rhyolite, 

(2) latite, (3) the Kendall tuff, (4) the Sandstorm rhyolite, (5) the Morena rhyolite, (6) the 

Milltown andesite, (7) dacite, (8) dacite vitrophyre and the Chispa andesite, (9) the Meda 

rhyolite, and (10) andesite breccia. 

In the preliminary report con the district, written in advance of chemical and full petrographic study, the latite was called the "first or earlier andesite" and was made to include most 

of the altered rock now called Vindicator rhyolite. . ' 

In the present stage of the science of petrology the consistent treatment in an economic 

report of any varied eruptive series presents peculiar difficulties. The ordinary classification and 

nomenclature of igneous rocks which has grown up in the half century since Sorby applied the 

microscope to their study has the recognized defects of most structures built from old materials 

and added to at various times. It has become unsatisfactory both to the general geologist 

· and to the petrologist. The modern quantitative system of classification, while logical, refined, 

and accurate, is adapted rather to the needs of the specialist than to those of the field geologist 

or engineer. On the other hand, simpler schemes for classifying rocks without the use of the 

microscope, such as that recently presented by Pirsson, d are not adequate to express the facts 

developed in an investigation like the present, in which field observations have been supplemented by microscopical and chemical work. In view of these considerations the older petrographical classification, exemplified in the Elemente der Gesteinslehre and Mikroskopische 

36 

aU. S. Geol. Expl. 40th Par., vol. 1, 1878. 

b Geology of the Tonopah mining district, Nevada: Prof. Paper U. S. Geol. Survey No. 42, 1905. 

c Bull. U.S. Geol. Survey No. 303, 1907. 

a Pirsson, L. V., Rocks and rock minerals. New York and London, 1908. 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 37 

Physiographie of Rosenbusch, has, nothwithstanding its defects, been generally followed in 

this report. In addition, the position in the quantitative system has been given of such unaltered 

rocks as have been chemically analyz~d. 

VINDICATOR RHYOLITE. 

GENERAL CHARACTER AND OCCURRENCE. 

The oldest member of the volcanic series derives its name from Vindicator Mountain and 

is most extensively exposed on the flanks of that peak. As may be seen from Plate II, the 

central pre-Tertiary mass of the mountain is surrounded by the rhyolite on all sides except 

the southeast, the exposure attaining a width of nearly half a mile on the north. A small 

.mass of much-silicified rock, probably a remnant of the rhyolite, rests on the smnmit of the 

peak. What is supposed also to be a larger residual of the same flow caps Columbia Mountain. 

The rock is nowhere fresh, and · as a rule contains abundant alunite, the mineral being in 

many localities distinctly ~isible in freshly broken fragments of the rock as small pale-pink 

crystals. Much of the altered rhyolite is very hard and forms prominent outcrops, often with 

characteristic pitted surfaces, due to the solution and removal of the pseudomorphs of alunite 

after feldspar. ' 

As the basal member of the Tertiary volcanic series the Vindicator rhyolite rests upon 

an undulating surface of alaskite and Cambrian shale. The character of the rock shows it to 

have been effusive. The base of the flow is well exposed half a mile northeast of the summit 

of Vindicator Mountain, where a nearly white altered rock may be seen lying upon a slightly 

rolling surface of biotite granite. The latter shows only slight superficial weathering and 

appears to have been swept clean of loose detritus before the first Tertiary eruptive. The 

basal portion of the flow contains many fragments of the underlying granite as well as of the 

dark Cambrian shale. Considerable alteration has taken place in the volcanic rock near the 

contact, it being bleached to a delicate pale-green tint and in places int~nsely silicified. This 

silicification is related to a fairly reglilar system of fissures which strike nbout N. 30° W. and 

dip northeast, giving a sheeted structure to the rhyolite. These fissures do not show in the 

underlying granite. The solutions which effected the silicification probably worked their way 

along the contact between· the two rocks and ascended in the parallel fissures. The most 

intense alteration borders these cracks, ·.which are in ,many places very tnarrow and were not 

themselves filled with quartz. 

The rhyolite on the summit of Columbia Mountain was originally supposed to be part of 

the intrusive mass of Mor(}na rhyolite which forms the ridge to the north. It is, however, 

distinctly a capping;· and prospect shafts near its edge have shown it to ~est on the Cambrian 

shale. At the north end of the oval cap (Pl. II) a small pit, open in l905, exposed the base 

of the rhyolite, which is here separated from the shale by a foot or more of gravelly material 

containing fragments of alaskite and shale, evidently old surficial detri~us. Petrographically 

the rock of the summit is identical with that on the west slope of Vindicator Mountain, near 

the Lucky Boys shaft. On the other hand, no very distinct contact has been found between 

the rhyolite capping Columbia Mountain and the somewhat similar ~fiorena rhyolite to the 

northwest, which is known to be intrusive. The boundary as drawn on the geologic map 

(Pl. II) corresponds to an obscure line of j separation which is admittedly unsatisfactory. 

Nevertheless the preponderance of evidence f~vors the view that the capping of the mountain 

is the Vindicator rhyolite which has been intruded on the west by the younger but locally 

similar Morena rhyolite. A close, irregular intrusive contact between two similar rhyolites 

might be difficult to recognize even were th surface swept ·clean of all detritus. 

There are no exposures from which the tlicktiess of the Vin9-icator rhyolite can be directly 

measured. It is evidently far from uniform, s a glance at the map will ~how. The maximum 

thickness, as estimated from t~e general rela ions and structure 'illustrated by sections A-A' 

and D-D', Plate VIII, is probably about 200 feet (61 meters). 
' . 38 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

PETROGRAPHY. 

The weathered surfaces of the Vindicator rhyolite are generally some shade of light gray, 

although in places they are stained buff or brown by iron oxide. A pitted appearance, already 

referred to, is characteristic of the harder silicified outcrops. On fresh fracture the rock is 

white or light gray, usually with a faint pink tint due to the abundant alunite: Some varieties 

northeast of Vindicator Mountain are pale greenish gray. The rock is everywhere much 

altered, the only primary mineral recognizable, as a rule, being quartz in fairly abundant 

anhedral phenocrysts up to 5 millimeters in diameter. 

Under the microscope the Vindicator rhyolite shows rounded and embayed phenocrysts 

of quartz and pseudomorphs of alunite after feldspar, presumably orthoclase. Some thin 

sect~ons show alunite pseudomorphs also after phenocrysts whose outlines are suggestive of 

mica. The groundmass has the general structure characteristic of rhyolitic glasses, but has 

undergone complete devitrification and is now a fine-grained aggregate of quartz and alunite, 

accompanied in some varieties· of the rock by smaller quantities of kaolinite. Diaspore has 

been found in some thin sections, and calcite occurs in a richly alunitic variety of the rhyolite 

from the east slope of Vindicator Mountain. The general texture of the rock as it appears 

under the microscope is shown in_ Plates XXVIII and XXXI. 

A good place to study the alunitic alteration of the rhyolite is on the east shoulder of 

Vindicator :Mountain, about a quarter of a mile from the summit. Some of the rock here is 

nearly white, mottled with spots and rings of pale-pink alunite. Some specimens also show 

minute, faint-blue specks which have not been identified with any mineral observed in thin 

section. A chemieal analysis of this rhyolite (speeimen G. 333) is given on page 183 in connection with a full discussion of the character of its alteration. The rock capping Columbia 

Mountain also illustrates particularly well the pseudomorphous development of alunite after 

feldspar. (See Pl. XXVIII.) 

In the simple field classification suggested by Pirsson the Vindicator rhyolite would be 

called a felsite. The rock is too much altered to be assigned a place in the quantitative system. 

LATITE.a 

GENERAL CHARACTER AND OCCURRENCE. 

The latite, as may be seen from Plate II, occupies the greater part of an area a little over 

2 miles (3 kilometers) in diameter in the center of the district, and a smaller area south of 

Columbia. Its characteristic features may be well seen on Banner Mountain, in the vicinity 

of McLaughlin's well, and on the southern edge of the town of Columbia. This rock has not 

been found in a fresh condition. Its normal color is dull purplish or gr~enish gray. A spotted or 

mottled appearance, due to flow-brecciation, is rather characteristic and is well shown on a 

small hill half a mile (0.8 kilometer) north of the summit of Banner Mountain. The freshest 

obtainable specimens of the latite show phenocrysts of feldspar, hornblende, and mica in a compact, streaky groundmass that was evidently once a glass with well-marked flowage lines: All 

the phenocrysts have the dullness that indicates more or less thorough alteration, and the 

original glassy base is now devitrified. As a rule, the latite, when it has not been subjected to 

the intense local alteration connected with ore deposition, may be distinguished from the later 

andesitic rocks by the absence of fresh phenocrysts, and especially by the peculiar streakiness of 

its groundmass, which resembles the groundmass of a rhyolite rather than that of most andesites. 

Even intense alteration does not always obliterate this feature. The much-altered Iatite has 

frequently been mistaken for dacite, and probably no amount of experience will insure even a 

keen observer against occasional errors of this kind. The altered latite may contain blebs of 

secondary quartz, but these are usually of lighter tint and less homogeneous than the primary 

quartz of the dacite. ·Little vugs, with projecting quartz crystals, are rather characteristic. of the 

alunitized and pyritized latite. 

a The "earlier andesite ' ' of the preliminary report. 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 39 

The rock is apparently a flow resting up0n a rather uneven surlace of alaskite, Cambrian 

sediments, and Vindicator rhyolite. Its thickness is not known, but is probably very variable, 

as on Columbia Mountain the succeeding rhyolite rests directly upon the alaskite. The maximum thickness is tentatively estimated at 300 feet (91 meters). Although the ~atite is prevailingly massive or 2xhibits only moderate flow brecciation, a west crosscut on the 612-foot 

level of the Combination-Fraction shaft has exposed some altered pyroclastic rock which appears 

to belong to thi'3 formation. 

The latite underlies a large part of the district, but is exposed only where deformation 

followed by extensive erosion has stripped away the rocks that once covered it. As might be 

expected from its place in the local geologic column and the general domical structure of the 

district, the ro~k occurs in the central part of the area studied, encircling the exposed masses of 

alaskite, Cambrian shale, and Vindicator rhyolite. Banner Mountain lies almost in the center 

of the largest expa.nse of the latite. This tract , while roughly circular, . has a very irregular 

outline expressive not only of the usual inequalities of erosion, but also of the nearly horizontal undulating contact between this rock and those that overlie it .. 

A smaller area of latite is exposed just south of the town of Columbia, and a very small 

exposure at the northwest end of the same town is worthy of mention, since it shows the latite 

overlain by the Sandstorm rhyolite. 

When the district was studied in 1905 the presence of latite under the andesi~e soutll. and 

southeast of Florence Hill could only be inferred. At present several shafts go_ through the 

andesite into the latite ~ The Yellow Tiger, situated a mile southeast of Milltown, went into 

latite at a depth of about 510 feet (1.55 meters), showing that this formntion extends southward 

beneath the andesite for at lenst three-qunrters of a mile .(1.2 kilometers) from its nearest surlace 

exposure. The developments of the past three years have proved, moreover, thnt the latite in 

general underlies the dacite of the Mohawk, and other important mines near Goldfield at a 

maximum depth of about 700 feet (213 meters). 

The only part of the district where the base of the latite is visible is in the vicinity of Vin-

. dicator Mountain. The, contact with the underlying rocks, however, is so poorly exposed and 

so obscured by alteration that no detailed observations on its original character are possible. 

The fact that the latite in some places,. as on Banner Mountain, is in direct contact with the 

alaskite suggests that there may have been considerable erosion whereby the Vindicator rhyolite 

was in part removed prior to the latitic eruptions. On the other hand, the Vindicator rhyolite 

may never have covered all of the old alaskite surlace. It is possible, moreover, that the jux- · 

taposition of the latite and nlaskite along the south slope of Vindicator Mountain may be due to 

a fault nearly parallel to and northwest of the one shown (Pl. II) half a mile northwest of Banner 

Mountain. While the relation of the rocks suggests such a fault the evidence for its existence 

is hardly sufficient to warrant plncing it on the map. 

In regard to the relations of the latite south of Columbia to the older rocks little definite 

information is available. The mass is overlapped on the west, south, and partly on the east 

by the younger Siebert formation, under which it is known to extend for over half a mile (0.8 

kilometers) to the south. On the north it is in contact with Kendall tuff, the contact corre.: 

sponding to a fault. 

PETROGRAPHY. 

The normal tint of the latite is dull gray with a suggestion of lilac or ptirple. Some varieties, however, are dull mottled green and where local alteration has been intense the rock may 

be yellow, pale pink, light green, or white. More or less alteration has invariably take!). place, 

and none of the rock has the dark-gray color and glistening phenocrysts characteristic of the 

later andesitic and basaltic rocks of the region. Surlaces of fresh fracture show numerous 

small dull-white phenocrysts of feldspar, w~th much less conspicuous darker phenocrysts representing some altered fernie mineral, in a dense finely streaked groundmass, which on close 

inspection reveals the pasty flow-texture frequently found in rhyolite, but not common in 

latitic or andesitic rocks. At many localities, particularly in the vicinity of }..fcLaughlin's 
40 · THE GEOLOGY AND ORE DEPOSI',fS OF GOLDFIELD, NEVADA. 

well and north of Banner Mountain, the rock is deeidedly mottled, and close examination 

shows it to be a flow breccia in which the fragments are of the same general character as the 

matrix, although some slight difference in texture is sufficient to produce delicate color distinctions in weathering. In this respect also the rock resembles rhyolite. 

Under the microscope the latite shows a vitrophyric texture, phenocrysts of plagioclase, 

biotite, and hornblende lying in a glassy groundmass which shows the characteristic wavy 

and curled flowage lines associated with this textural type. Apatite, magnetite, and zircon 

are accessory constituents. 

The phenocrysts are never quite fresh. The plagiociase, which is andesine-labradorite 

with approximately the composition Ab1An11 is changed to quartz, alunite, calcite, sericite, 

and kaolinite. The relative proportions of these secondary minerals as well as the degree. 

of alteration or replacement varies in different specimens, even in those from the same locality. 

Quartz is the most abundant mineral formed at the expense of the feldspars, although calcite 

is scarcely less common. Sericite is decidedly subordinate to quartz and calcite, and kaolinite 

is rather rare except with alunite in cases of special alteration in the vicinity of ore bodies. 

lt is apt to be more abundant in the altered groundmass than in the phenocrysts. As a rule, 

·the feldspar is only partly altered, a portion of the crystal being replaced by quartz or calcite 

or both, while another portion remains as limpid and fresh in appearance as in the younger 

basalts of the region. The replacement is usually sharp and complete, with no intervening 

stage or zone of turbidity in the feldspar as seen under the microscope. The alteration does 

not necessarily proceed from the periphery of a crystal toward its center. Many feldspar 

phenocrysts, especially those which originally contained glass inclusions, are changed to quartz 

and calcite in their central parts while still retaining an outer shell of fresh andesine. 

Only a very few remnants of fresh biotite and no hornblende were found in the 40 to 50 

specimens of this rock microscopically examined. The most characteristic change in the biotite 

is a bleaching, whereby, the mineral becomes pale green or colorless and rerembles muscovite 

in birefringence. This form of alteration is associated with the developmf.nt pf particles of 

magnetite and hematite, which in some pseudomorphs are so thickly crowded as to render 

them practically opaque and in others are gathered into a dark periphera~ shell. This shell, 

defining the outline of the former phenocryst, is as a rule persistent an,d may remain when 

the rock has been wholly altered to a granular aggregate of quartz. The common alteration 

of biotite into chlorite interlaminated with lenses of epidote is also represented in some 

specimens. 

The former presence of hornblende as an original constituent of the rock is indicated by 

pseudomorphs of quartz, calcite and iron oxides possessing the .characteristic prismatic sections 

of that mineral. Most of these pseudomorphs, like those after biotite, are enveloped in dark 

shells of iron oxides. It is possible that some pyroxene may also have been present in the 

original rock, but no pseudomorphs definitely referable to this mineral have been detected. 

The groundmass of the latite was originally glassy, containing only incipient crystal 

forms. In the rock of the small outcrop at the northwest end of Columbia the groundmass 

shows a faint spherulitic structure. Elsewhere it exhibits the ordinary flow banding of a 

pasty microlitic glass. Very little, if any, of this glass now remains. It has not only devitrified, or become crystalline, through lapse of time and through conditions of pressure and 

temperature favoring such molecular rearrangement, .but has also been altered by the same 

agencies that have changed· the phenocrysts to aggregates of secondary minerals. The boundary between endogenous devitrification. and the processes that have altered the phenocrysts 

is not a sharp one. Simple devitrification, however, involves no essential change in the composition of the rock, whereas in the more pronounced phases of general alterations, such as 

have in some places changed the latite to an aggregate of quartz with very subordinate kaolinite and pyrite, there has been a notable change in the chemical constitution of the rock 

as well as in its mineralogical character. 

·The most abundant secondary mineral in the groundmass is quartz. Calcite also is common, while kaolinite and sericit'e are rather rare. 'Alunite is abundant in the vicinity of the 
PR.ELACUSTRINE TERTIARY IGNEOUS ROCKS. · 41 

ore deposits. Where the alteration has not been extreme, the groundmass shows little bunches 

of quartz and calcite interspersed through a faintly crystalline groundmass in which the constituent crystals are too minute for identification. Where alteration has been most thorough, 

thisgroundmass is transformed to a distinctly crystalline granular aggregate of quartz. 

' Owing to its generally altered condition the latite has not been subjected to complete 

chemical analysis. A partial examination by Dr. E. C. Sullivan, however, of a specimen 

· collected 1 mile northwest of McLaughlin's well affords the followingresults: 

Partial chemical analysis of latite. 

Si02 

•• -- •• - •• ____ ... ___ ~ _________________________________________________ __ . .. __________________ 61. 14 

CaO ..... __ . __ - ___ - ________________________________ · ___ : _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5. 60 

K 2

0 .. - ---. -_________________________________________________________ ___ __ . ___ . _________ . _ _ _ _ 3. 90 

N a2

0 _ ... __________________ . __ ... ________ . _ . ______ . _________________ . . __ . _______ . ____ . _ _ _ _ _ _ 3. 26 

The specimen analyzed (G. 348) has a dull olive-gray tint and is fresher than most of the 

rock. It contains phenocrysts of andesine or labradorite (Ab1An1) partly altered to calcite; of 

biotite changed to chlorite, quartz, epidote, and calcite; and of hornblende (and possibly augite) 

replaced by pseudomorphs of calcite, quartz, and magnetite. The groundmass is the usual 

obscurely crystalline aggregate resulting from the devitrification of a glassy base. The rock 

conr,ains a few minute crystals of pyrite. 

The partial analysis shows that it is a latite rather than an ordinary andesite, and the use 

of the special name is convenient to distinguish the rock from the andesites proper that occur 

higher in the volcanic series. ' 

The general alteration which the latite has undergone, while probably broadly related to 

the economic mineralization of the district, is not always intimately associated with individual 

ore deposits, nor is it confined to those particular parts of the district where ore bodies are 

known to be present. 

On the southern edge of the town of Columbia the latite has been altered to a white, porous 

chalky rock which has been quarried for building stone. Under the microscope this shows 

almost no trace of its original igneous texture, but is chiefly a very fine-grained aggregate of 

kaolin with some quartz, alunite, and sericite. 

Certain phases of intense or local alteration of this and other rocks, in the immediate 

vicinity of the ores, are reserved for fuller treatment in a later chapter in connection with the 

description of the ore deposits. 

KENDALL TUFF. 

The Kendall tuff, which takes its name from the Kendall mine, is of uniform character 

and as a rule is easily distinguished from the much younger tuffaceous beds of the Siebert formation, with which it is in ·places in contact. As taken from mine workings where oxidation 

has not penetratep., the body of the tuff is rather dark gray and has an andesitic appearance. 

This gray matrix ~is flecked with irregular pale-green spots, usually less than half an inch in 

diameter, of a s~ft waxy material which sometimes contains s1nall scales of biotite. When 

slightly weathere the tuff is a shade lighter in color and the green spots become yellowish. 

As exposed and arried on the north edge of the town of Columbia, the tuff is light gray with 

a rather faint gr enish mottling instead of the more distinct spots seen elsewhere. As a rule 

~he tuff contains few visible rock fragments, but pebbles of alaskite, andesite, and rhyolite 

have been found in it and in some places are :moderately abundant. Well-rounded bowlders 

of alaskite up to 6 inches (15 centimeters) in diameter were observed embedded in the tuff on 

the dump of the Winston lease shaft, on the Mohawk No. 1 claim, · southeast of Columbia. 

Similar bowlders as well as fragments of rhyolite, are common also at a depth of 213 feet 

(65 meters) in tHe tuff of the Gold Sovereign pro.spect, half a mile (0.8 kilometer) north of 

McLaughlin's well. 

The largest ·area of the tuff associated with the Sandstorm rhyolite is that partly under-

~ying the town of Columbia. Another body is inclosed in the rhyolite at the Kendall mine 
42 THE GE OLOGY AN D ORE DEPOSITS OF GOLDFIELD, NEVADA. 

and some smaller included masses occur on the lower western slope of Columbia Mountain. 

Tuffaceous beds or layers are also found in some of the shafts sunk in the Sandstorm rhyolite. 

The microscope shows the tuff to be everywhere more or less altered and to consist of 

fragments of glassy rhyolite and of latite or andesite. The rock is apparently of mixed derivation and can not properly be called either a rhyolite or a latite tuff. On account of the alteration it is not possible to identify the latitic fragments with certainty, but it is probable that 

they were derived from the latite of the district. The rhyolitic eruptions presumably broke 

through this rock at certain points with explosive violence and comminuted fragments of the 

latite were thus mingled with rhyolitic particles. The finding of occl:l,sional fragments of 

alaskite in the tuff lends support to this view. Many of the rhyolite particles in the tuff contain abundant quartz phenocrysts, and as such phenocrysts are not common in the Sandstorm 

rhyolite these particle~ may also have been derived from an older rock, probably from the 

Vindicator rhyolite. On the other hand, the tuff also contains angular fragments and blocks 

up to a foot (0.3 meter) or more in diameter of the Sandstorm rhyolite, as may be seen in the 

Black Rock shaft about 500 feet (152 meters) west of the Conqueror mine. 

The rhyolite-latite tuff is very closely associated with the Sandstorm rhyolite, next to be 

described, and is to be regarded as a practically contemporaneous deposit. It is apparently 

not a continuous formation, but probably accumulated in local basins at more than one period 

during the rhyolitic eruptions. The greater part of the tuff, however, is near or at the base 

of the rhyolite, and for this reason is first described. 

,The large area of tuff near Columbia is considered to occupy an approximately basal position with reference to the Sandstorm rhyolite, although were this the only body of the Kendall 

tuff it would be difficult to say whether it overlies or underlies the rhyolite to the north of it. 

It is possible t.hat the contact between the two may in part be due to faulting. The two small 

patches farther north, on the west slope of Columbia Mountain, appear to be small lenticular 

masses in the rhyolite. The body of tuff at the Kendall mine may also be a lens with Sandstorm rhyolite beneath it as well as above it but the base was not exposed in the mine workings 

at the time of visit. (See fig. 29, p. 237.) The main Sandstorm shaft, not accessible at the 

time of visit, is reported to have gone from Sandstorm rhyolite into Kendall tuff at a depth 

of 200 feet (61 meters) and to have continued in this rock for another 200 feet to the bottom. 

A shaft close to the road, about 500 feet (152 meters) east of the Sandstorm shafts, penetrates 100 feet (30 meters) of glassy banded rhyolite and exposes 25 feet (7.5 meters) of tuff at 

the bottom. The tuff is overlain nearly horizontally by the rhyolite but its base is not reached 

by the shaft . 

. The Black Rock shaft, 500 feet west of the Conqueror mine, exhibits a similar relation of 

rhyolite to tuff. The bottom of this shaft, which was about 100 feet (30 meters) deep at the 

time of visit, is in rhyolite-latite tuff, here containing large angular blocks of rhyolite. The 

tuff is overlain by about 80 feet (24 meters) of glassy spherulitic rhyolite and rhyolite flow 

breccia, including layers of the shalelike variety of the Sandstorm rhyolite. The rocks are 

devitrified and altered and the planes separating tuff from flow breccia and volcanic glass are 

indistinct, much of the glassy rhyolite having a clastic, sedimentary aspect. 

At the Gold Sovereign mine, already referred to, the shaft after going through a slight 

thickness of shaly Sandstorm rhyolite continued for 200 feet (61 meters) in greenish bedded 

tuffs which on account of their lithologic character and stratigraphic position are correlated 

with the Kendall tuff. The material here contains abundant fragments of alaskite and rhyolite with small particles of Cambrian shale in its lower part and rests on an uneven surface of 

granite or alask;te. As exposed in a crosscut east of the shaft on the 213-foot level the contact, 

which apparent y is not a fault, dips to the west at about 45°. The relations of the tuff to the 

latite and Vine icator rhyolite in this locality are not fully understood. While the oldest 

rhyolite appear: , in this part of the district, to have never covered or to have been eroded away 

from the granit .3 before the eruptio~ of the latite, it is difficult to account for _the local absence 

of the latter fo::.'mation at the Gold Sovereign mine, particularly as the latite is the prevailing 

rock for more han a mile (1.6 kilometer) north of McLaughlin's well (see Pl. II) and prior to 
PRELAOUSTRINE TERTIARY IGNEOUS ROCKS. 43 

the sinking of the shaft was supposed to continue under the small residual areas of Sandstorm 

rhyolite. It seems necessary to conclude: (1) That revision of the mapping would show some 

Kendall tuff outcropping around the edges of the small patches of Sandstorm rhyolite, a fact 

easy to overlook on account of the poor exposures and the general similarity of the weathered 

t,uff to some varieties of the latite. Such overlooked areas can not be large, inasmuch as typical latite occurs north of McLaughlin's well and both east and north of Banner Mountain. 

(2) That the old granitic surface is locally irregular and was in part exposed after the eruption of the latit~ and before the dep~sition of the Kendall tuff, the latter being laid down on 

a surface that was also diversified by hillocks and hollows. 

Excellent exposures of the Kendall tuff may be studied in the railway cuts. along the south 

slope of Columbia Mountain. The beds here have a dip of 45° SW. 

SANDSTORM RHYOLITE. 

GENERAL CHARACTER AND OCCURRENCE. 

Overlying the latite and most of the Kendall tuff or, in places where the earlier volcanics 

are absent, resting on the pre-Tertiary rocks, are some thin, originally glassy rhyolite flows 

which attain their greatest deyelopment in the rounded white hills northwest of Colrnnbia 

Mountain. This effusive rhyolite is usually nearly white, shows conspicuous flow lamination, and 

weathers in thin, shelly flakes. It is the rock of the Sandst~rm mine, whence its name, and 

of the hills lying west of the road from the mine to Columbia. It all shows some devitrification 

and silicification, particularly in the vicinity of the ore deposits. Certain varieties or portions 

· of this rhyolite acquired by flowage a very thin lamination, causing the rock when somewhat 

weathered to closely resemble indurated clay shale. This appearance is exceedingly deceptive, as may be seen at the Conqueror (Tonopah Club) mine. The town of Diamondfield is 

partly underlain by this shalelike rhyolite, and small residual patches of a similar material 

are scattered over the surface of the latite northeast of Banner Mountain. (See Pl. II.) The 

rhyolite appears to have been thickest in the vicinity of Columbia Mountain and to thin out 

to the southeast. None of it has been found southeast of McLaughlin's well. 

The largest- area of the Sandsto~m rhyolite is that extending front the vicinity of the town of 

Columbia northward to the south base of Kendall Mountain. Another body, probably connected with the Sandstorm mass under the intervening Milltown andesite (see Pl. II), contains 

the Adams and Tonopah Club mines, southeast of Kendall Mountain. The northwestern 

half of the roughly circular main area of latite is fringed with small patches of the Sandstorm 

rhyolite. This is for the most part the shaly variety and its outcrops are inconspicuous, the 

presence of the rock being indicated in most insta ces merely by the thin loose flakes, resembling gray shale, into which the rhyolite disintegrat son weathering. 

A rather more resistant variety forms some lo hills about half a mile southeast of Black 

Butte, and a few small residual outliers, chiefly of e shaly form, are. scattered over the latite 

north of McLaughlin's well. The area between D'amondfield and Black Butte, on the other 

· hand, is probably an inlier, a small rhyolite hill projecting through the younger Milltown 

andesite. 

That the Sandstorm rhyolite is younger than he latite was a conclusion reached in 1905 

from the relative distribution of the two rocks as hown in Plate II. At that time also the 

dumps of two abandoned shafts-one half a mil S. 5° E. from the summit of Vindicator 

:Mountain and just south of the road to McLaughli 's well, the other on the west slope of the 

mountain-indicated that the shaly San~storrn rhy lite had been penetrated and latite found 

below. In 1905 a shaft half a mile (0.8 kilomete ) southeast of the top of Vindicator, after 

going through about 50 feet (15 meters) of Millt own andesite, had continued for another 50 feet 

into soft, altered, rhyolitic flow breccia with strea of dark devitrified glass, the whole looking 

remarkably like a gray tuffaceous sandstone with thin layers of shale. The bottom at the 

time of visit was in shaly rhyolite. In 1908 this shaft had been abandoned, but the dump 

showed that the rhyolite had been penetrated and atite found beneath it. 
44 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The Sandstorm rhyolite north of Columbia probably rests for the most part on Kendall 

tuff, which in turn. appears to occupy one or more depressions in the alaskite. The irregularity 

of the pre-Kendall surface is well shown at the Mayne shaft, 1,500 feet (457 meters) northwest 

of the summit of Columbia Mountain, near the eastern edge of the largest area of alaskite. 

(See Pl. II.) Although only about 200 feet (61 meters) from the outcrop of the alaskite, this 

shaft was sunk 100 feet (30 meters) before reaching that rock. In the southeast crosscut on 

the 400-foot level of the Sandstorm mine the Kendall tuff, according to Mr. H. C. Cutler, the 

superintendent, was found resting upon a slope of alaskite, which dipped about 50° vV. ·To 

what extent this irregularity is the result of faulting since the eruption of the Sandstorm rhyolite 

can not be determined from the scanty data available. A.t the northwest end of Columbia town 

one small and rather obscure exposure shows rhyolite of the shaly variety dipping west and 

apparently overlying latite. The relation of these rocks to the Kendall tuff at this place is 

not clear. 

A.t the Sandstorm shaft the rhyolite has tt thickness of 200 feet (61 meters). This is not 

a maximum, as at least another hundred feet is represented by the hill which rises southwest 

of the shaft. A. single measurement, moreover, owing to the uneven surface upon which the 

rock rests and the disturbance introduced by the subsequent intrusion of the Morena rhyolitet 

throws little light upon the average thickness. It is thought probable that the Sandstorm 

rhyolite may attain a maximum thickness of 300 to 400 feet (91 to 122 meters) northwest of 

Columbia Mountain. Around Vindicator and Banner mountains it thins to less than 100 feet 

(30 meters), and southeast of McLaughlin's well disappears, the Milltown andesite resting upon 

the latite. · 

Although the Kendall tuff and Sandstorm rhyolite are separately mapped and successively 

described, their intimate relationship should not be lost sight of. They probably belong to the 

same eruptive epoch and are to some extent intermingled. 

PETROGRAPHY. 

A.s exposed in the principal area, northwest -of Columbia Mountain, the Sandstorm rhyolite 

is a nearly white rock with fine, often much contorted flow banding. Under the influence of 

weathering, the rhyolite splits along this flow lamination into thin shelly flakes, somewhat 

resembling disintegrated shale. Much of the surface of the low, rounded, white hills between 

Columbia and the Sandstorm mine is covered with this flaky detritus~ Locally, as near the 

Sandstorm and Kendall mines, the rhyolite is intensely silicified and outcrops as cellular masses 

of nearly pure quartz. Phenocrysts are small and inconspicuous, consisting chiefly of feldspar. 

The abundant groundmass was once highly glassy, and in some localities still shows small 

spherulites and lithophyses. The delicate fluxion lines in this groundinass are very characteristic of the Sandstorm rhyolite and, in connection with the paucity of quartz phenocrysts, 

serve to distinguish the rock from the younger and intrusive l\1orena rhyolite. The general 

<;lull-white appearance of the rhyolite is sufficient to show that the rock no longer retains its 

original glassy condition, but has crystallized into secondary aggregates. Microscopical investigation confirms this conclusion. · 

Seen in thin section under the microscope, the Sandstorm rhyolite shows phenocrysts of 

sanidine in a groundmass which, in addition to the wavy flow lines visible in hand specimens, 

frequently exhibits delicate reticulating and spiral cracks, the typical perlitic structure of 

siliceous volcanic glasses. The glass it~elf, however, as may be seen between crossed nicols, 

has devitrified and is now represented by an exceedingly fine-grained aggregate, consisting 

chiefly of quartz, but containing also some chalcedony or opal, kaolin, and probably other 

minerals not optically determinable. Some specimens show remnants of mica, probably biotite, 

and occasional altered crystals of sodic plagioclase. Quartz phenocrysts, while not entirely 

absent, are rare and inconspicuous. Zircon _occurs sparingly in the usual small rounded grains 

and prisms. 

A. large part of the rhyolite shows more intense alteration than can be ascribed to simple 

devitrification. Such rock, for example, as that which lies along the ridge between ~he Sand-
I 

I 

PRELAOUSTRINE TERTIARY IGNEOUS ROCKS. 45 

storm and Kendall mines and forms several craggy points sou~h of the former property, consists for the most part of a crystalline granular aggregate of quartz, which, although aphanitic, 

.is of less fine grain than the usual product of devitrification. With the quartz may occur 

considerable kaolin, silicification and kaolinization clearly having gone on simultaneously. 

Alunite is also fairly abundant and in some specimens occurs with quartz as. distinct pseudomorphs after sanidine. In the most altered varieties the phenocrysts and some of the ·glassy 

bands or streaks in the groundmass have been dissolved and the cavities thus formed lined 

with druses of quartz. Such rock is rough and cavernous. Being composed of almost pure 

quartz, it is resistant of decay and forms most of the prominent outcrops in the rhyolitic area. 

About 900 feet (275 meters) east of the Sandstorm mine, the rhyolite,· near its. contact 

with ' the overlapping Milltown andesit~, has a more regular lamination than· is usu?J. b. ) 

area just described, and splits, on exposure to the weather, into. thin gray flakes which might 

easily be mistaken for shale. Close observation, however, reveals irregularities in the lamination which show it to be a flowage phenomenon, and micr_oscopical examination renders it 

certain that the rock is a devitrified glassy rhyolite. A similar shaly facies occurs at the southern end of the main rhyolite area and is exposed in the Columbia Mountain No. 2 Tunnel, near 

its portal. This variety of the rhyolite, however, is much more abundant in an· area of the 

Sandstorm rhyolite presently to be described, namely, that extending from the Adams mine, 

about a third of a mile (0.5 kilometer) east of the Sandstorm, northeastward past-the Conquerer (Tonopah Club) mine. 

The rhyolite of the small area shown in Plate II, in the northwest corner of the region, is 

a partly devitrified spherulitic glass. This rock is fresher than in the other areas and contains some glass as well as a ·few phenocrysts . of sodic plagioclase. The principal secondary 

minerals are quartz, chalcedony, and opal. 

The lithologic . character of the shaly facies of the Sandstorm rhyolite is well displayed 

just north of the Conquerer mine. Much of the material here has the appearance of a white 

or light-gray shale with a dense porcelain-like texture grading in places into softer chalkylooking varieties. ~he microscope shows th~t these are devitrified glasses consisting of very 

fine grained aggregates of . quartz, kaolin, and possibly other minerals. Interlaminated with 

these aphanitic layers are rhyolite flow breccias containing fragments of white pumice and 

of devitrified glassy rhyolite. One of the shaly bands, about 1,500 feet ·east of the summit of 

Kendall Mountain and close to the contact with the Milltown andesite, contains abundant 

hollow spherulites or lithophyses up to several iriches in diameter. 

An unusual variety of 'the rhyolite outcrops prominently just west of the Adams mine. 

This is a rough porou~ rock evidently somewhat altered. The microscope shows it to be a 

devitrified and partly silicified spherulitic glass: Rock of the same character occurs north of 

the Conqueror mine, and both are probably alteration products of a variety of the rhyolite 

resembling that from the western edge of the district, described above. 

The rock of the small areas extending from the west side of Vindicator Mountain to Dia-

·mondfield is chiefly the gray shaly variety. Just west of Diamondfield, however, are some 

outcrops of rhyolite flow breccia. . I 

Between Diamondfield and Black Butte is an area of devitrified and silicified glassy rhyolite ranging from white chalky facies to nearly black flinty varieties. 

The area mapped as Sandstorm rhyolite between Black Butte and Tognoni Springs is 

occupied by much altered rock of somewhat doubtful character. Most of the area is littered 

with the shaly detritus indicative of the presence of the Sandstorm rhyolite and some of the 

specimens collected are devitrified glassy rhyolite such as .is known to occur in that formation. 

Other specimens, however, contain abundant quartz phenocrysts and resemble the later Morena 

rhyolite. Still others are undoubtedly much altered latite. It is certain, therefore, that· the 

·area as mapped includes rocks of more than one kind, although it is doubtful whether these 

can ~e separately mapped, owing to their general alteration and to the unsatisfactory character 

of the exposures. 
46 THE EOLO Y D ORE DEPO IT OI• GOLDI~IELD NE\'ADA. 

MOUE \. RII LITE. 

PETR H PJ lY. 

' ryv;h r bl ·h d or 
. 1. INTRUSIVE CONTACT BETWEEN MORE A RHYOLITE A 0 CAMBRIAN SHALE. 

W st slope of Columb1a Mountain. 

The sharp p •ak i Columbi Mounta1n. Th princip I mines l1 b yond h b sal capp d hill in th right for ground . 
·, 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 47 

MILLTOWN AND~SITE. 

INTRODUCTORY STATEMENT. 

The intrusion of the Morena rhyolite may have been followed by some erosion. Then came 

eruptions of andesite, which covered the region with successive flows. of this rock, with here and 

there local and subordinate accumulations of andesitic tuff. The products of these eruptions 

constitute the most extensive formation in the district. (See Pl. II.) The total thickness 

of this deposit, as of most of the other volcanic formations in this distri~t, can not be accurately 

determined, owing to the slight general deformation of the rocks, their poor exposures, the 

comparatively low topographic relief, and the absence of persist::nt datum planes, such as may 

usually be found in stratified ·rocks. It probably lies betvreen 600 and 800 feet (183 and 244 

meters). 

The petrographic study of the andesites shows that they contain phenocrysts of labradorite 

feldspar, hornblende, augite, orthorhombic pyroxene, and occasionally biotite in groundmasses 

ranging from hyalopilitie to vitrophyric in texture. The formation mapped as 11illtown ande-

. site undoubtedly includes more than one lava flow, with some pyroclastic and intrusive rocks, 

but it is quite impracticable in this field to discriminate individual flows in mapping the whole 

area. 

The local name of the formation is derived from the small settlement of Milltown, about a 

mile east of Goldfield. 

DISTRIBUTION. 

As may be seen from Plate II, the audesitic ten-ane occupies a very large part of the district. 

One broad, irregular belt stretches eas~w'1rd from the edge of the main valley north of Goldfield 

past Diamondfi~!d and beyond the eastern bJundary of the area mapped. Another belt extends 

from near Goldfield eastward beyond Preble and Blackcap mountains. These two belts are 

· prevented from meeting on the west and east sides of the central part of the district by exte~sive 

intrusive masses of dacite. Were it not for these intrusions the andesite would undoubtedly 

form a complete although irregular band around the central latite area, and thus still further 

accentuate the general concentric and domical structure of the district. 

The rounded andesitic hill which emerges from the Siebert formation near the railway, 2 

miles (3.2 kilometers) north of Goldfield, is probably an inlier, the andesite being continuous, 

under the later formation, with the andesite of Kendall Mountain and vicinity. Some small 

areas of the andesite similarly projecting through the Siebert formation are shown in the northeast corner of the geologic map (Pl. II). 

PETROGRAPHY. 

GENERAL CHARACTER OF THE FORMATION. 

The rocks mapped as the Milltown andesite in Plate II undoubtedly include more than one 

lava flow and exhibit greater variety in color and texture than any other formation in the 

district. In a few localities the superposition of one flow upon another can be recognized, as, 

for example, in the hill two-thirds of a mile (1 kilometer) northeast of Columbia Mountain, in 

another hill half a mile ( 0.8 kilometer) northeast of Kendall Mountain, and in the extreme 

northeast part of the district; but after sorne effort had been made to extend these local distinctions over the district the attempt was abandoned as impracticable. The actual petrographic diffe:vence between rocks belonging to successive eruptions is in some cases no greater 

than between the variations in texture and composition of individual lava flows. Since the 

exposures over all 'but a very small part of the district are such that the different flows would 

have to be discriminated solely by petrographic means, much of the andesite being altered almost 

beyond recognition, and since it is by no means certain that each flow extended over the whole 

district, the necessity for treating the andesite as a unit is. apparent. With the flows are associated some local deposits of andesite tuff, ~s already mentioned, and some intrusive bodies of 

small size, the whole constituting a typical volcanic complex. 
48 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The fresher varieties of the andesite range in color from nearly black to light gray. The 

altered forms are usually of lighter hue and may be gray, brown, red, yellow, green, or white. 

The darker fresh kinds are in most places dense ringing rocks with splintery fracture and an 

almost basaltic aspect. Such a rock, showing small phenocrysts of augite, occurs 1,000 feet 

(305 meters) northeast of the transformer station east of Columbia Mountain. A similar 

. andesite, but with the };Ilegascopic dark phenocrysts of hornblende instead of augite, forms a dike 

which is crossed by the road south of Vindicator Mountain. As a rule, however, the hornblendic 

varieties are lighter colored and less dense rocks than the pyroxenic ones, although, as will be 

shown, the two types are connected by· intermediate forms. Andesite with conspicuous pheno-

~rysts of hornblende is particularly abundant _in the part of the district lying northeast of Black 

Butte. A similar hornblendic variety occurs also in a hill 1,000 feet (305 meters) south of Diamondfield. Hornblende is present in many varieties of t)le andesite in which it is not conspicuous in hand specimens. It has in many such rocks undergone molecular change into aggregates of augite, magne.tite, and plagioclase, the abundance of augite being often in rough inverse 

proportion to the diminution of the hornblende by this process. While it can not be said that 

all of the pyroxene andesite in the district once contained hornblende or biotite, the evidence is 

clear that much of it did. The probability of such a derivation of some pyroxene andesites 

from originally hornblende-bearing magmas was pointed out by Von Lasaulx a some years ago. 

L~ter, H. S. Washington,b after showing that hornblende and biotite in molten magmas are stable 

only under plutonic conditions and undergo a paramorphic change into augite and magnetite in 

lavas not too quickly cooled, suggested that "some of the augite andesites, especially the more 

acid ones, may owe their augitic character to the alteration and subsequent disintegration of 

previously existing hornblendes or biotites, in accordance with the views of Von Lasaulx;" 

The pyroxenic andesites of the Goldfield district, even those containing enstatite or hypersthene, furnish a good example of such an origin. Not all of the pyroxene in them was formed 

by the paramorphic change of hornblende and biotite and the subsequent dispersal of the 

aggregates of augite and magnetite by the movement of the magma, but ~ost of the pyroxene 

andesites, had they been more quickly cooled and solidified, wou.Jd probably contain hornblende and perhaps biotite. 

The occurrence of plagioclase with augite and magnetjte as a result of the molecular disintegration of hornblende is not often mentioned. J. P. Iddings c notes it, however, and states 

that orthorhombic pyroxene may also be present in such paramorphic aggregates. 

In the course of the present investigation over 200 specimens of the Milltown andesite, from 

all parts of the district, have been microscopically studied. While the andesitic rocks are of too 

many kinds to be embraced in a single petrographjc description, it is impracticable; on the other 

hand, to describe in detail every one of the many varieties found. . Accordingly only certain 

representative or striking facies, including those of which chemical analyses have been made, 

will be fully described. Such description will be followed in each case by comments upon the 

.range, transitions, and affiliations of the variety described. 

HORNBLENDE-PYROXENE ANDESITE. 

By far the most prevalent type of andesite is one in which labradorite, augite, enstatite, 

and hornblende all occur as phenocrysts in a hyalopilitic or microlitic groundmass. Two fresh 

.specimens of this type, one (G. 316) from the summit of a hill two-thirds of a mile (1 kilometer) 

.northeast of Columbia Mountain, just north of the Goldfield-Diamondfield road, and the other 

(G. 59) from the area of andesite shown .in the northeast corner of the geologic map (Pl. II) 

about 1! miles (2.5 kilometers) northeast of Black Butte, were selected for chemical analysis 

and special description. The latter specimen was collected just outside of the area included 

in Plate II. 

a Ueber Vorkommen und Verbreitung der Augitandesite im Siebengebirge: Sitzungsber. Nieder-rbein. Gesellsch. in Bonn, vol. 41, 1884, p.155. 

b The magmatic alteration of hqrnblende and biotite: Jour. Geology, vol. 4, 1896, pp. 257-282. 

cRock minerals: New York and London, 1906, p. 341. 
PRELACUSTRINE TERT ARY IGNEOUS ROCKS. 49 

The specimen from the h~ll near Columbil Mount~in is a dark, reddish brown, evidently 

glassy r~ck, in which the naked eye can dete . minute phenocrysts of p~agioclase and black 

hornblende. · l · · 

under the microscope, phenocrysts of plagioclase up to a millimeters in length and smaller 

cry~tals of augi~e, orthorhombic pyroxene, horjblende, magnetite, and apatite appear scattered 

through an abundant glassy groundmass crow~ed with minute feldspa.r m!crolites. The texture of the groundmass is hyalopilitic. The rock is perfectly fresh. 

The feldspar phenocrysts,. save for inclusibns of glass, are clear, eXhibit the usual albite, 

Carlsbad, and pericline twinning and have an approximate composition of Ab3An7, corresponding 

to a rather calcic labradorite. The microlites are too small and are embedded in too much glass 

for satisfactory optical determination of their place in the isomorphous plagioclase series. In 

all of the Milltown andesite studied the phenocrysts are labradorite and range in composition 

from Ab " 3An4 to Ab1An4 • · · . 

The augite is faintly green in thin section, with a maxi1num measured extinction angle of 

40°. In other specimens of the andesite it is about 45°. The planes of the pfism zone are 

often well developed, but many crystals show only rounded outlines. The augite of the 

pyroxene-hornblende andesite specimens frequently shows the usual twinning on the plane 

(100). This·mineral decomposes readily, and in many specimens of the andesite in which the 

labradorite is still fresh the monoclinic pyroxene has been converted to pseudomorphs of 

calcite. · It is probably near diopside in composition. 

Orthorhombic pyroxene is rather abundant in small euhedral phenocrysts of prismatic 

. habit with blunt pyrarnidal terminations. Although nearly colorless, the crystals are faintly 

. pleochroic, rays vibrating parallel to X a giving a slight reddish tint and those parallel to Y and 

Z being faintly tinged with green. The birefringence is low and the optical character is apparrently positive, although some uncertainty attaches to the latter determination owing to the large 

optic angle and small size of the prism cross sections. The pyroxene is thus probably enstatite, 

hypersthene being o-ptically negative and having as a rule stronger pleochroism and birefringence. In many specimens of the pyroxene-hornblende andesite the orthorhombic pyroxene· 

is partly or wholly decomposed to a p~le yellowish green mineral of variable birefringence, the 

interference colors ranging from the usual gray or yellow of ordinary serpentine to those almost 

as brilliant as in biotite. In some · cases the mineral is distinctly an aggregate; but in most 

specimens it is optically homogeneous, with a fine fibrous structure parallel to the prism axis 

of the pyroxene. Such pseudomorphs exhibit parallel extinction, and the direction of least 

elasticity is that of the elongation of the fibers. The mineral, like iddingsite, which it sometimes resembles, is probably closely related to serpentine. The relation to ordinary serpentine 

of such strongly birefringent minerals as iddingsite and possibly other similar alteration products 

of the magnesian silicates is still obscure. The orthorhombic pyroxene becomes serpentinized 

during the early stages of alteration of the andesite, before the augite changes to calcite. 

The hornblende occurs in rounded anhedrons with narrow opaque reaction rims. The 

absence of extensive paramorphic change and the glassy character of the groundmass indicate 

co{nparatively quick cooling of the magma. Two varieties of hornblende are present, usually 

intergrown in the same crystal. One is pleochroic in brown and the other in green tints. 

Apparently in both, however, the ray vibrating parallel to X is greenish yellow. 

All of the Milltown andesite contains magnetite, probably with some ilmenite, and apatite. 

The latter occurs in the usual small stout hexagonal prisrns, many of which have a fibrous 

appearance due to lines of small dark inclusions parallel to the prism axis. Such crystals are 

faintly pleochroic. 

The second Tock, that from the northeast corner of the district, is dark gray and appears 

more crystalline. The phenocrysts of feldspar and hornblende are much more abundant. 

a Throughout this report the crystallographic directions of greatest, mean, and least elasticity will be designated, resp~ctively, as X, Y, and Z, 

instead of by the German a, b,andc,frequently used. This usage follows the example set by J.P. Iddings in his "Rock minerals," New York 

and London, 1906, and makes for clearness and convenience. 

7f:>145-No. 66-09~ 
50 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The microscope shows phenocrysts of the same minerals as occur in the other rock. Determination of some of the feldspars by the Michel Levy method gives compositions approximating 

to Ab1An4, corresponding to a calcic labradorite. The central parts of the crystals are often 

of spongy texture and full of glass inclusions, these cores usually showing sharp crystallographic outlines and being inclosed in a -shell of clear labradorite. The augite is. colorless or 

faintly green and shows a maximum extinction of about 35°. The hornblende is generally 

brown in thin section, the pleochroism being X greenish yellow, Y and Z ·yellowish brown. 

The absorption is Z> Y>X. Some of the hornblende shows no reaction rims orparamorphism. 

Other crystals have been partly or wholly altered, prior to the solidification of the rock, into 

aggregates of augite, magnetite, and plagioclase. Orthorhombic pyroxene occurs much as in 

the rock near Columbia Mountain and appears to be enstatite. The graundmass is glassy 

hyalopilitic. 

Chemical analyses of these two rocks were made by George Steiger in the United States 

Geological Survey laboratory, the results being as follows: 

Chemical analyses of pyroxene-hornblende andesite. 

1. 

Si02...... .. .. ...... .. .. .. . . . .. . .. . . . . . . 58.06 AhOa..... ...... ........ ........ .... .... 17.43 Fe20s................................... 3.83 FeO ..•................ : ................ 1.91 MgO..... .............................. 2.60 CaO...................... . .............. 6.33 

2. 

60.41 

16.59 

·3.18 

3. 

54. 66 H20 below 110° C ...................... . 17.53 H20 above 110° C ...................... . 3.18 Ti02--- ................................ . 3.52 C02 ................................... . 3.62 P20~ ............... · .................... . 7.33 MnO ................................... . 

1. 

Q. 97 

1.88 

..87 

None. .27 

.09 

2. 3. 

1. 94 0.59 

2.64 .69 .62 .99 

None. 1. 35 .31 .30 

Na20................................... .07 .12 3.34 

1. 70 

2.13 

5.26 

3.94 

1. 70 3.56 

2.22 K20 ................... ·................. 2.61 --------- 100.19 100.49 99.66 

1. Pyroxene-hornblende' andesite (G. 59), 1' miles (2.5 kilometers) northeast of Black Butte. 2. Pyroxene-hornblende andesite (G. 316), two-thirds mile (1 kilometer) northeast of Columbia Mountain. 3. Pyroxene-hornblende andesite, 1 mile (1.6 kilometers) northeast of Columbia Mountain. 

The norm. of analysis 1, calculated in accordance with the quantitative system of Cross, 

Iddings, Pirsson, and Washington, a is as follows: 

Norm of pyroxene-hornblende andesite 1~ miles 'R,OTtheast of Black Butte. 

Quartz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13. 26 Magnetite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 71 Orthoclase ................. _ ................ 15.57 Hematite.................................. 1. 28 Albite .................................... 27. 77 Apatite.................................... . 67 Anorthite .................................. 25.02 

97.

31 Diopside (CaO, MgO, Si02).................. 3. 46 Water ........... _ ......................... _. 2. 75 Enstatite (MgO, Si 0 2). • • • • • • • • • • • • • • • • • • • • • 4. 90 

Ilmenite.................................... 1. 67 100.06 

This affords 81.62 per cent of salic minerals against 15.69 per cent of fernie minerals, ~nd the rock belongs in the dosalane class of that system. It is dosalic, alkalicalcic, quardofelic; 

and dosodic, thus corresponding to the subrang tonalose. It is accurately described in terms 

of the quantitative system as a vitriphyro-tonalose. 

It may be noted that a very large proportion of the andesites of the western United States b fall in this same subrang, which is very near the hypothetical average igneous rock as calculated 

by F. W. Clarke,C H. S. Washington,d and Alfred Harker.e 

· The mode of the rock analyzed differs from the calculated norm in the presence of much 

glass, prob_ably richer in potassium than the crystalline part of the fabric, in the absence of recognizable orthoclase, in the presence of labradorite instead of albite and anorthite 1 in the absence 

of free quartz, probably in the occurrence of somewhat aluminous and fer~ginous microclinic 

pyroxene (augite) instead of diopside, and in the actual miner~logical functions of the Iron 

oxides. 

a Quantitative classification of igneous rocks, Chicago and London, 1903. 

b See Washington, H. S., Chemical analyses of igneous rocks: Prof. Paper U.S. Geol. Survey No. 14, 1903, pp 231-245. 

c Bull. U.S. Geol. Survey No. 22S, 1904, pp. 14-20. · 

d Op. cit., pp. 106-117. 

e On the average composition of British igneous rocks: Geol. Mag., new ser., 4th decade, vol. 6, 1899, pp. 220-222. 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 

The norm· of rock 2 is as follows: 

Norm of pyroxene-hornblende andesite two-thirds mile northeast of Columbia Mountain. 

Quartz .......... ·... . . . . . . . . . . . . . . . . . . . . . . . . . 17. 64 

Orthoclase ................................. 10. 01 

Albite ...................................... 33. 54 

Anorthite ........................ _. . . . . . . . . . 22: 52 

Diopside [(CaMg)O.Si02].. ....... . .......... 1. 30 

Enstatite ............................. ..... 4. 70 

Apatite....................... ....... ....... . 67 

Magnetite.................................. 3. 94 

Ilmenite ..... .. : . . . . . .. .. . .. . . .. . . .. .. . . . . 1. 22 

Hematite................ ... ................ . 48 

96.02 

\Vater..................................... 4. 58 

100. 60 

51 

This rock also is a vitriphyro-tonalose, but lies near the line s~parating this subrang from 

yellowstonose, the corresponding subrang in the persalane class. 

· The rock of analysis 3 was collected a few hundred yards east of rock 1, , and may belong to 

an underlying flow. It shows no hornblende in the thin section studied, and was selected as 

representative of the pyroxene andesite:- Subse uent examination of the hand. specimen, how--

ever, revealed a single phenocryst· of hornblende-, and the analysis is accordingly-discussed at this 

place. The rock well illustrates the close relation between the hornblende-pyroxene and pyrox-· 

ene andesites in this district. 

Under the microscope the rock appears perfectly fresh, the carbonate indicated in the analysis evidently occurring in a few small scattered amygdules. The phenocrysts are labradorite 

(Ab3 An4) , . augite, enstatite, magnetite, and apatite. The pyroxenes are more abundant th~n 

in the hornblendic varieties of andesite just described. The augite is faintly green, with extinction angles up to 43°. The orthorhombic pyroxene is particularly well developed in the usual 

stout prisms and is slightly more pleochroic than i1,1 the rocks previously described. It is 

probably near hypersthene in composition. The groundmass is hyalopilitic. 

The norm of this rock is as follows: 

Norm of pyroxene-hornblende andesite 1 mile northeast of Columbia Mountain. 

Quartz ..................................... 6.90 Apatite································"· 0.67 

Orthocl~e .............................. : ... 12.79 Magnetite ........ ......... _... ............. 4. 64 

Albite .................................... 29. 34 Ilmenite ....... .. _ .. _ ........ _............ 1. 98 

Anorthite .............. .. ................. . 

{

31Ca0.Si02} 

Diopside 26MgO.Si02 ........ - ........... . 

5FeO.Si02 . 

. ,J64MgO.Si02} 

EnstatitL12FeO.Si02 •• -------- •••••••••• 

25.85 97.07 

6. 92 C02.- .. -..... -................... - --. --.. - 1. 35 

Water .... : ................................. 1.28 

7.98 99. 70 

The rock in terms of the quantitative system is dosalic, . alkalicalcic, quardofelic, and 

dosodic, and is therefore, like the other two rocks analyzed, tonalose. 

Study of the distribution of the pyroxene-hornblende variety of the Milltown andesite 

shows that while it is certainly the dominant facies, and although it occu1·s here and there 

over the whole andesite area, yet it occupies no well-defined portions of that area to the exclusions of the other varieties presently to be described. In a few places the distinction between 

the pyroxene-hornblende facies and andesite free from hornblende or containing biotite is . 

sharp enough to indicate a contact petween two flows. This, however, is exceptional. As a 

rule the hornblende andesi~e grades into pyroxene andesite, and every step in the transition 

can be studied in thin sections from those in which hornblende is abundant . to those in which 

the mineral has undergone complete magmatic transformation into aggregates of labradorite1 

augite, and magnetite, or is so rare as not to appear in every thin section of the rock. In some 

pyroxene andesites these aggregates still preserve the rough outlines of the hornblende; in 

others the outlines are lost and the aggregate merges with the general fabric of the rock. As 

already pointed out, most or all of the pyroxene andesite once contained hornblende, the survival 

or· disappearance of this· mineral depending upon the rate and conditions of cooling. Furthermore, it is almost certain that hornblende may be present in one part of a flow and absent in 

another. · 
52 THE GE9LOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

PYROXENE ANDESITE. 

In every respect, except the absence of hornblende ana rather more abundant pyroxene, 

the pyroxene andesite is identical with the hornblendic variety just deseribed. Its chemical 

eomposition is probably well represented by analysis 3 on page 50, although, as stated, thi~. 

particular facies contains an occasional phenocryst of hornblen~e. 

A particularly glassy variety is exposed on the hillside just east of Tognoni Springs. This 

is a dark-gray rock, which on close inspection is seen to be composed chiefly of glass with a 

characte:r;istic oily luster. The material has a pronounced :flow structure, brought out in 

specimens by the alternation of bands of greenish-gray glass with nearly black layers. 

The microscope shows the rock to be a vitrophyre, the glass containing phenocrysts of 

labradorite and orthorhombic pyroxene . as well as tiny microlites of augite and plagioclase. 

The orthorhombic pyroxene is more strongly pleochroic than in most of the andesites of the 

district. The acute bisectrix corresponds to the direction of greatest elast_icity, X, and sections 

parallel to the macropimi.coid (100) give a biaxial interference figure. Th~ ~xial angle, also, is 

smaller than in the enstatite of the other andesites studied and the PY!'~~ne il3 in this case 

hypersthene. .·tt 

HORNBLENDE-BIOTITE AN:pESITE. 

A specimen from 1 mile (1.6 kilometer) northeast of Black Butte (G. 63) was selected for 

chemical analysis as. representative of the hornblende-biotite andesite. This is a light-gray, . 

somewhat porous rock showing abundant phenocrysts of hornblende, biotite, and feldsp~r in 

an aphanitic base. Most of the phenocrysts are less than 5 millimeters in length. 

Under the microscope the feldspar proves to be labradorite with the approximate composition Ab2An3, it being less calcic than in the pyroxenic varieties of the andesite. The hornblende is the common brown variety with narrow dark reaction rims consisting of magnetite, 

plagioclase, and ·a colorless isotropic material, probably glass. · Similar rims surround the 

sections of biotite, which has the optical character of meroxene. · The rock was evidently 

cooled too quickly to allow any molecular rearrangement of the hornblende and biotite. Among 

the smaller phenocrysts are rather abundant prisms of cloudy pleochroic apatite and grains of 

magnetite. The groundmass is glassy hyalopilitic, the plagioclase microlites being for the 

most part too minute for satisfactqry deter~nation of their precise character. No pyroxene 

appears in the thin section studied. 

The chemical analysis of this rockf by Mr. George Steiger, is as follows: 

Chemical analysis of hornblende-biotite andesite. 

Si02 •••••••••• _· . : .••••.••• : ••••••••••••.•• • 

Al20 3 •••••••••••••• _. _ ....•.•.••. •• •••••••• 

Fe20 3 ••••••••••••••.••• • •••••••••••••••••••• 

63. 16 H20 b~low 110° c: ................ .-.. ....... 1.12 

16. 74 H20 above 110° C................. . . . . . . . . . . . 77 

3. 94 Ti02 •••••••••.•••.•.••••••••••• ·•.•••.• .. ..• • 61 

FeO ..... . ............ · ......... · .......... . .47 C02 •••••••••.•••.................••........ None. 

MgO .............................. : ....... . 1.12 P20 5 ............................. ... ....... • 30 

CaO .. . ........................ : .......... . 4. 07 MnO ...... : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 04 

Na20 ............................. ···· .. : .. 3.88 • 

K 20 ..................................... . 3. 71 99. 93 

The analysis, as might ·have been expe<;ted, shows more silica and less iron oxides, magnesia, 

and lime than those of the pyroxenic andesites on page 50. · 

The norm calculated from this analysis is as follows: 

. Norm of hornblende-biotite andesite. 

Qu~rtz ............ · ........... • .............. 17.16 Ap.atite................................... . 67 

· Orthoclase .................... . ............. 21.68 Ilmenite ... : .... .. ..................... . ... 1.06 Albite .................................... _ 33.01 Hematite ....................... .. .......... 3. 65 Anorthite .................... _. ~ ......... _ 17. 24 

Diopside (CaO.MgO.Si02f. .................. . 43 

Enstatite .......................... ...... ... 2.60 'Vater .............. : ....... .. .............. 1.89 

97.64 

' ·Ti tani.te ... _ ....... _ .. _ ............... _ ..... ·. . 14 99. 53 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 53 

In this norm the proportion of salic' to fernie minerals is greater than 7 to 1, and the rock · 

falls in the persalane class. It is quardofelic, alkalicalcic, and sodl.potassic, although very near 

dosodic. The rock is accordingly amiatose but is exceedingly close to yellowstonose. 

The chemical analysis of this rock shows that it can not be regarded merely a~ a quickly 

cool~d part of a magma chemically identical with that which solidified t:,S hornblende-P,yroxene 

and pyroxene andesite. In other words, it indicates clearly that the mineralogical differences 

_ in the Milltown andesite can not all be explained as various steps in the change from the complex 

molecules of biotite anq hornblende to the rhore stable combination of augite, magnetite, and 

labradorite. 

A rather striking variety of hornblende-biotite:..augite andesite (G. 47) occurs 1 ~ miles (2.5 

kilometers) east of Black Butte, just outside of the area included in Plate II. This rock contains 

abundant small sparkling phenocrysts of hornblende and biotite and subordinate ·plagioclase 

in a light-gray aphanitic groundmass. The microscope shows that the majority of the phenocrysts are of sharp euhedral form. The hornblende shows no resorption. Its pleochroism is X 

light yellowish green, Y dark brownish green, and- Z brownish yellow. The absorption is 

Y > Z > x · and the extinction angle Z A Cis about 11°. Some crystals are. twinned repeatedly 

on the orthopinacoid ( 100). A colorless augite also occurs as phenocry~ts, often intergrown 

with hornblende and biotite. In this rock there is nothing to indicate that the constituents 

of the augite have ever crystallized, as hornblende. The plagioclase is labradorite. The groundmass is glassy, with microlites of plagioclase. The appearance of this rock in thin section is 

shown in Plate·VIt A. 

Hornblende-biotite andesite, free from pyroxene, occurs so far as known only in the northeast cor~er of the district and possibly in the ~mall hill 1,000 feet ( 305 meters) south of Diamondfield, the rock at the latter locality not being sufficiently fresh 'to permit the positive statement 

that pyroxene was never present. Biotitic andesite occurs half a mile west of DiamondfieldJ 

on the southeast slope of Blackcap Mountain, one-half mile (0.8 kilpmeter) south of Myers 

Mountain, about a mile ( 1.6 kilometers) northeast of Kendall Mountain and in a few other 

places in the district. At all the loct)lities mentioned, however, . the rock is pyroxene-bearing 

or is so decomposed ·as to leave the question of the possible former presence of . pyroxene in 

doubt. It thus appears that there is scarcely any more grou~d for a definite division of the 

Milltown andesite on the basis of the presence or absence of biotite than on the basis of the 

presence or absence of hornblende. There is a suggestion from the position of the biotitehornblende andesite in the northeast corner of the district that this rock belongs to a late flow 

in the Milltown andesite. This suggestion is supported moreover by the sirrtilarity in mineraiogical and chemical composition of the biotite-hornblende andesite with the dacite presently 

to be described. · TUFF. 

Deposits of tuff constitute a wholly subordinate part of the Milltown andesite. A small 

accumulation occurs near the east base of the hill three-fourths mile ( 1.2 kilometers) northeast 

of Columbia Mountain. Tuffaceous rocks are present along the eastern edge of the area, north 

of Tognoni Springs. These, however, like much of the massive andesite with which they are 

associated, are so intensely altered to white kaolinic aggregates that little can be determined 

regarding their original character or present boundaries. The hill two-thirds mile ( 1 kilometer) 

northeast of Myers 1vfountain is composed in part of much-altered tuff. . in ·view of the ease with · 

which clastic rocks of this character succumb to chemical attack their general altered condition 

· in this district is not surprising. It is probable that in other parts of the area than those mentioned rocks now bleached and metamorphosed beyond recognition may have been originally 

tuffaceous. 

In underground 'work andesite. tuff and breccia has been found in the Daisy mine as the prevailing rock on the 300-foot and 400-foot levels. The Crooks shaft of the Kewana Leasing 

Company, about half a mile (0.8 kilometer) southeast of the summit of Columbia Mountain, 

went through 140 feet ( 43 meters) of dacite, then through more than 100 feet ( 30 meters) of 

andesite into andesitic breccia. . The latter continued to a depth of at least 410 feet (125 

meters)-the bottom of the shaft at time of visit. 
'54 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, . NEVADA. 

BASALT. 

. In tne Portland mine, east of Goldfield, a crosscut to the east on the 250-fo9t level which 

was accessible in 1905 exposed a series of thin amygdaloidal basalt flows with associated tuffs. 

Nearly all the rock in this mine is much altered, and the ground in general is so soft and so cut 

up by gouge-filled fissures that prospecting was carr:ied on with difficulty. Such observations 

as were possible under these conditions showed that the basalt occurs near the base of the 

Milltown andesite and .just above the latite. The thickness of the basalt and basalt tuff could 

not be determined. What appears to be the saq1e amygdaloidal basalt has been cut in the 

Red Hills shaft, 800 feet (244 meters) southeast of the Portland. 

The material of the flows is an ordinary olivinite basalt with nothing noteworthy in its 

character. It is nowhere exposed at the surface, so far as known, and represents a very local 

eruption at the beginning of the andesite period. The old vent is probably somewhere beneath 

the :Milltown andesite in the vicinity of the Portland mine. . 

GEOLOGIC RELATIONS. 

The ·Milltown andesite overlies the Sandstorm and Morena rhyolites, or the ·latite where 

these are absent. While probably made up chiefly of gently inclined lava flows, only obscure 

traces of stratiform structure are visible. Here and there a hill rising above the minor undulations of the surface furnishes a suggestion of one nearly horizontal flow capping another. 

The general topography of the district, however, and the conditions of exposure are such that 

almost nothing of the internal structure of the andesite complex is revealed. 

One of the best places in the district to observe the effusive character of the andesite and 

to distinguish the superposition of flows is in the steep slope just east of the northernmost of 

· the three Tognoni Springs. The lower part of the slope is occupied by a poorly exposed and 

· rather decomposed andesite. Above this lies about 40 feet (12 meters) . of andesitic tuffbreccia, which is overlain by 50 or 60 feet (15 to 18 meters) of brittle, banded volcanic glass, 

an andesite vitrophyre, which has been described on page 52. This glassy lava is overlain by 

dacite, which at this place is probably a flow. 

Nowhere in the region adjacent to Goldfield is there, so far as known, a single definite and 

well-exposed contact between the individual flows ·Of the formation. Yet the occurrence of 

tuffaceous and glassy rocks and the variety in the andesite~ prove that the formation is really 

·complex. 

Andesitic dikes within the Milltown andesite may be present at many localities, but can 

not ordinarily be distinguished from the effusive members of the formation, owing to similarity 

in petrographic character and obscurity of exposure. 

As already stated, no acc11rate determination of the thickness of the Milltown andesite can 

be made. The Yellow Tiger shaft (see Pl. VIII, section F-F') goes through 510 feet (155 

meters) of this rock, and the total thickness at this locality prior to erosion is estimated at 

700 feet (213 meters). Whether this can be regarded ~s greater or less than the average for 

· the formation is not known. 

DACITE. 

INTRODUCTORY STATEMENT. 

The dacite, whose eruption followed the andesitic period, is in many respects the most 

interesting rock in the district, and is certainly the most important from an economic point of 

view. It occupies, as may be seen by reference to Plate II, a considerable area east of Goldfield and Columbia and is the principal country rock of the Mohawk, Combination, January, 

Jumbo, Redtop, and Florence mines. It is, a.t least in part, intrusive in the andesite. 

The dacite, of which typical and fairly fresh specimens can be collected on the little hill 

·500 feet . (152 meters) northeast of the transformer station, has the general appearance of 

rather dark andesite. It is usually more conspicuously porphyritic than the andesites of the 
I 

PRELACUSTRINE 'TERTIARY IGNEOUS ROCKS. 55 

district, but its essential distinction from them is the presence of phenocrysts of quartz. 

All of these ar~ angular fragments or crystals rounded by magmatic corrosion, and as a rule 

are neither very numerous nor very conspicuous. The rock consists of labradorite feldspar, 

hornblende, biotite, augite, and quartz in the usual andesitic groundmass. Chemical analysis 

of the dacite shows that it contains 60 per cent of silica, or only 2 per cent more than a hornblendic andesite from the northeastern part of the district. Mineralogically and chemically 

the dacite at Goldfield is merely a quartz-bearing andesite and is in no way similar to the more 

siliceous rocks called dacite by Spurr in his report on the Tonopah district.a 

DISTRIBUTION. 

The dacite that lies just east of Goldfield contains the principal mines of the district. 

(See Pl. II.) Another large mass of dacite extends southward from near Tognoni Springs to 

Preble Mountain. This body extends for some miles east of the area included in Plate II and 

forms the high hills east of Tognoni Springs. In this vicinity the ·rock is fresh but the 

southern extension of the mass, particularly that forming the greater part of Preble Mountain, is 

intensely altered, so much so that the dacite is distinguishable with much difficulty from the 

similarly altered andesite. Smaller masses of dacite occur just east of Black Butte, in the 

extreme northeast corner of the district, between Diamondfield and McLaughlin's well, and 

in the vicinity of Preble Mountain. 

The distribution of the dacite is much more irregular than that of the Milltown' andesite, 

the irregularity scarcely admitting any other explanation than that of intrusion. The outlines 

·Of the dacite areas, moreover, suggest that this rock cuts the andesite, a suggestion in harmony 

with the clearly effusive character of the Milltown andesite as a whole. 

In two places masses of soft altered latite have been observed which appear: to be included 

biocks in the dacite. One of these is in the Mohawk mine (seep. 207), and the other is on the 

500-foot level ·of the Win ton shaft on the Cornishman claim. The latter mass is about 10 

feet (3 meters) long and is exposed on one side of a drift which it does not cross. The dacite, 

which is also somewhat alt red, shows a platy structure parallel to the surface of the inclusion. 

PETROGRAPHY. 

The unaltered and t~pical dacite is a dark-gray rock in which the most obvious. char-

·

.acteristic, as compared wilh the Milltown. andesite, is a more conspicuous porphyritic texture. 

Phenocrysts of plagioclase from 5 to 10 millimeters in length are abundant, and in contrast 

with the dark-gray aphani ic groundmass give the dacite a decided speckled appearance, which 

is of use as a rough mean of recognizing exposures of this rock. Even where greatly altered 

the dacite, as may be see~ on the dumps of the Red Top, Mohawk, Combination, and ·other 

mines, still retains a spot ed appearance-due to the difference in shade between -the pseudomorphs after the feldspar phenocrysts and the altered groundmass-which is rarely found in 

the altered forms of the andesite. Associated with the phenocrysts of plagioclase are less 

.abundant ones of augite, ornblende, and biotite, the proportions and relative prominence of 

these ferromagnesian or ernie minerals varying in different localities. The• phenocrysts of 

quartz, which constitute he most useful and in many places the only petrographic means of 

di6tin.guishing the dacite from the andesite, are never abundant · and seldom conspicuous. 

·Close inspection of hand specimens;, however, will usua1ly reveal the rounded outlines and 

conchoidal fracture of the uartz which i5 often more noticeable in altered than in fresh varieties 

~f the rock. 

The appearance of t e fre~h dacite can be well studied on the hill immediately northeast 

.of the transformer statio east of Columbia, and in the steep hills just east of Tognoni Springs. 

A specimen (G. 97) taken half a mile (0.8 kilometer) northeast of Columbia ~fountain, 

near tP,e point where the dacite wedges @Ut against the Columbia Mountain fault (see Pl. II), 

a Spurr's reasons for using the nam dacite for rocks which should strictly receive other names are given in Geology of the Tonopah district, 

Nevada: Prof. Paper U.S. Geol. Surve No. 42, 1905, p. 59, footnote. 
56 ~ 

THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

was selected for chemical analysis as the freshest obtainable representative facies of this particular daCitic body. The rock a~alyzed is dark ,gray, with moderately abundant phenocrysts 

present, 

of clear plagioclase, up to a centimeter in length, · in a dark aphanitic groundmass. There are 

of 

also, less numerous phenocrysts of augite an.d biotite with occasional anhedral a grains 

quartz. The volumetric ratio of phenocrysts to groundmass is estimated at ·rather less 

than 1 to 3. 

Under the microscope the feldspar phenocrysts prove to be labradorite of the approximate 

composition Ab1An1

noticeable 

• They are perfectly fresh, with slightly rounded euhedrttl b outlines. A 

which 

feature is the presence in.many crystals of closely crowded minute inclusions of glass, 

center 

in some cases constitute cloudy cores or kernels, in others sharply bounded shells, the 

a maximum 

of the 

measured

crystal being clear. The augite crystals are roughly euhedral or subhedral, with 

· extinction angle, .Z 1\ c, of about 45°. The biotite occurs in the usual 

The

short, rather irregular pseudo-hexagonal p~isms. Both biotite and augite are entirely fresh. 

. 

Hornblende 

quartz phenocrysts are anhedral, with rounded, embayed, or sharply angular outlines. 

of 

is very abundant, but is confined almost exclusively to the groundmass, most 

the crystals being comparable in size rather with the feldspa,r microlites than with the phenoY 

crysts just described. The general color is yellowish green, the pleochroism being X yellow, 

nor 

yellow-green, and Z brownish green, and the absorption Z > Y > X. Neithe:r; the biotite 

blende 

the hornblende shows any magmatic resorption or pseudomorphism. The largest hornhowever, 

crystal in the thin section studied is about half a millimeter in length. It should be said, 

that in dacite from other parts of the district the hornblende occurs as phenocrysts. 

position 

The feldspar microlites in the groundmass are at least in part labradorite of as calcic comembedded 

as the phenocrysts. They, the hornblende, and a little magnetite and apatite are 

in an abundant glass, which in transmitted light is gray, with incipient crystals 

(crystallites). There is one crystal of titanite, 0.3 millimeter in length, in the thin section 

st1,1died. 

The chemical analysis, by Mr. George Steiger, is given below, under 1. 

Chemical analyses of dacite·. 

~!}:-

~~z:~ -: ~: : 

: 

: : : :: 

: : : ::: : f;J! ;Hf ~~~~:: - :- : : N~n~ :~~:~ Na20 .... . .....: : 

..

: : 

...............

: : : : :: : : : : :: :: : 

.....

: : : : : 

........

: : :·: : : :: ...

: : : 

...... 

: : : : : 

3.0i 

~: H 

3.19 

iJg I 

BaO 

!~:~:. .....

~:: : : 

..

: : 

..

: : 

....... 

: : : : : : : 

· ... 

: : 

: 

: : 

.

: 

.....

: : : : : 

..

: : 

.

: 

..

: : 

.

: 

....

:: : : 

.

: 

....

: : : : 

.

: 

......... 

::: :.: : N °~& · · · --:-~: 11 ....... . K20............... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 52 3. 23 1 SrO.......... . ... . . . . .. .... .. .......... . .............. . 13 . , . .. .. . H20 below ll0°C ... :. ... ~----------------- ---:.. .. ..... .95 1.08 H20 above 110° C..................................... 2. 00 1. 88 ----

99. 94 100. 15 

1. Dacite .( G. 97), one-half mile (0.8 kilometer) northeast of Columbia Mountain. Intrusive. 

2. Dacite (G. 83), Diarr.ond Peak. Effusive. 

The norm calculated' from analysis 1 is as follows: 

Norm of dacite· one-half mUe northeast of Columbia Mountain . 

. Quartz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17. 34 Magnetite ...............

Orthoclase 

.. .. ....... ·_ ... . . . . . 4. 87 

Albite 

............. ~ .. .. . . . . . . . .. .. .. . 15. 01 Ilmenite .... :....... . . . . . . .. .. .. .. . . . . . . .. . 1. 52 

.................

Anorthite 

. ............. _ .. __ . 25. 68 Apatite ... _._ .... : ........ _ ........ _...... . 34 

............. . _ . ................. 21. 96 

Zircon ................. · .................... 37 u r t 9

2

6·

9

9

5

3 

vv a er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diopside ..................... _ ....... ·. _ ... 5. 21 

Enstatite ............................... :.. . 4. 63 99. 88 

a Anhedral= without crystal faces, xenomorphic, allotriomorphic. See Cross, W ., Iddings, J.P., Pirsson, L. V., and Washington, H. S., 

. The texture of igneous rocks: Jour. Geology, vol. 14, 1906, p. 698. 

b Euhedral= bounded by crystal faces; idiomorphic, automorphic. 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 57 

· 'This dacite, like the andesite previously described, is a tonalose in accordance with .the 

nomenclature of the quantitative system. . It is, however, close to the sodipotassic subrang 

harzose in the same quardofelic orqer, austrare. 

Another specimen of daGite (G. 83) selected for .analysis comes from Diamond Peak, 

one-half mile (0.8 kilometer) east-southeast from Tbgnoni "Springs and just outside the area 

mapped in Plate II. Like most of the dacite in this part of the district, it is more conspicuously 

porphyritic than the rock just described, the dark-gray groundmass being thickly strewn with 

crystals of plagioclase up to a centimeter in length, with abundant sparkling phenocrysts of 

hornblende and biotite. The volumetric ratio of phenocrysts to groundmass is estimated at 

. nearly one to two. 

Under the microscope, the rock closely resembles the cite froPl near the transformer 

station. The plagioclase is labradorite ranging from Ab1An1 to Ab3An4• The hornblende is of 

the same character as in the facies last described, but in addition to occurring in the groundmass 

it forms phenocrysts up to 2 or 3 millimeters in _length. These crystals 'exhibit no magmatic 

resorption or paramorphism. The section, however, shows one or two aggregates of hornblende, 

augite, and magnetite that are suggestive of paramorphic change of an earlier generation of 

hornblende phenocrysts. · 

· Quartz occurs'in the thin section of this specimen in two or three small, rounded, embayed 

phenocrysts. It is more abundant and conspicuous in other speci:qlens from the same rock 

mass. 

The groundmass is a colorless glass crowded with crystallites and with microlites of p!agi· 

oclase and hornblende. No titanite was observed in this rock, the accessory minerals being 

magnetite and apatite. 

The chemical analysis of this rock is given under 2, on page 56. The calculated norm from 

analysis 2 is as follows: 

Norm of dacite from Diamond Peak. 

Quartz .............. _ ....... _ ....... _·._ .... 17. 10 Hematite.~_ · _________ . ____ .. _. ___ . ___ .______ 2. 40 

Orthoclase .. ______ ... ____ .. ___ ... __ . ________ 18. 90 Apatite .... ___________________ . _ _ _ _ _ __ _ _ _ . 34 

Albite ... ~ ... _ . _ .... _______ ........ ___ · __ . _ . 27. 25 

Anorthite .. ______ ._._ .. _____ . _____ ·- ____ . __ 19. 46 97.42 

Diopside ... _ . _ ..... _ ......... _____ . ____ . . . 5. 34 · Water._. ___ . ___ ._ ... _____ . _ • _ ·.' .. __ . ______ . _ 2. 96 . 

Enstatite ..... ___ .:._ .. _ ... ___ . _______ . _ .. _ _ 3. 40 

Ilmenite ..... ___ .. _._ .. ____ . ____ . __ .... ____ 1. 37 100. 38 

Magnetite ............ _._· ....... :_·_________ 1. 86 

This norm corresponds to a harzose, near tonalose. In the ordinary classification the rock 

is a dacite, close to quartz latite. · 

The mass of dacite which is partly mapped in Plate II as a small area in the extreme northeast corner of the district is eomposed of a very fresh rock of different appearance from the 

dacite near Goldfield or near Tognoni Springs. This variety is rather light gray with moderately 

abundant phenocrysts of plagioclase, hornblende, augite, and biotite in a ·dense aphanitic 

groundmass. · 

The microscope shows that this rock, 'in spite of its different aspect, is practically identical 

in mineralogical composition and texture with the ·dacite from Diamond Peak. The quartz . 

phenocrysts are few and small and might easily be overlooked in a casual examination of a thin 

section. Some of the hornblende and biotite crystals show incipient peripheral change to 

magnetit~ and augite. 

The groundmass consists of microlites of plagioclase and augite, with grains of magnetite 

in a pale-brown to colorless glass containing crystallites. The rock i~ ab.solutely fresh. 

In g~neral the fresh dacite, wherever found, is remarkably uniform in character, as seen 

under the microscope. The rock, however, has been extensively altered, and even moderately 

fresh rock is not the most common except in the northeastern part of the district. Much of 

·the dacite is so changed in appearance by this alteration that one unfamiliar with the various 

stages of the process and unable to resort to petrographical methods would be quite u-nable 

to identify it. · 
58 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

A comparatively incc;mspicuous mode of alteration consists in the change of the plagioclase and augite to calcite, which may be accompanied by quartz; of the biotite to epidote and 

chlorite with some form of iron oxide; and of the hornblende to dark aggregates of finely disseminated magnetite and quartz. Such alteration may usually be recognized by the lusterless 

greeni~h-gray tint of the rock and the dullness or opacity of the plagioclase phenocrysts: 

Another much more intense process of alteration, which is well exemplified in the vicinity 

of Preble Mountain and in the mines near Goldfield, changes the rock to a light-gray or white 

mass in which the occasional small phenocrysts of quartz are all that remain of the original 

minerals of the dacite. The feldspars, most of them still recognizable from their outlines, are 

no longer clear and vitreous, but are dull and chalky. The microscope shows that the principal constituents of such alte~d rock are quartz and alunite, the hydrous sulphate of aluminum and potassium. In some varieties kaolinite is present with the alunite; in still others 

the rock is chiefly ·quartz and kaolinite. A niore detailed account of this alteration and of 

the further stage of 'complete silicification will be given in Chapter XIV. 

GEOLOGIC RELATIONS. 

Most of the dacite within the area covered by the geologic map (Pl: II) is regarded as 

intrusive into the Milltown andesite and older rocks. As this important fact is not .obvious, 

and as the dacite is known to occur as an effusive rock associated with dacitic breccia just east 

of Tognoni Springs, the evidence bearing upon the question whether the dacite of the district 

is intrusive requires detailed consideration. 

At one point only within the district, so far as known, is a contact between unaltered 

dacite and andesite exposed. This is near the eastern border of the district, 1,300 feet ( 396 

meters) in a direction N. 26° W. from the sharp summit of Espina Hill. At this place a little 

saddle is occupied by dacite between an isolated area of andesite on the west and volcanic 

breccia on the east. (See Pl. VIII, section A-A'.) The andesite is a fine-gr:ained compact 

variety and looks younger and fresher than the dacite. The latter, however, contains fragments of the andesite and has a noticeably glassy selvage band within half an inch ( 12 millimeters) or less of the sharp irregular contact. · The dacite shows some flow structure near the 

contact, and the intrusion presumably took place very close to the then existing surface. 

The large body of dacite northeast of Goldfield has the general form of an irregular sheet 

with a present maximum thickness of about 700 feet (213 meters). Its outline is very irregular. Along the east side of Columbia Mountain the dacite ends against the Columbia Mountain fault. (See Pl. II.) South of the town of Columbia the rock extends westward across 

the line of the fault and is in part overlapped by the younger Siebert formation. Surface 

exposures in this vicinity throw no light whatever on the character of the contact between 

the dacite on the one hand and the latite and Kendall tuff on the other. The artificial exposures underground are scarcely more satisfactory. Some shafts sunk by lessees west of the 

Red Top mine might at one time have afforded valuable information; but in this district 

shafts from 200 to 400 feet ( 61 to 122 meters) deep are often put down and abandoned within 

a few months. They soon become inaccessible or unsafe, those who sank them disappear, and 

only the dump is left to perplex and tantalize the geologist. 

The workings of the Red Top, Mohawk, Combination, and January mines all show the dacite 

to be in contact along its western border with latite. On the whole, this contact, as illustrated 

in Plate VIII, section C-C', has a general dip east, the average angle being from 30° to 40°. 

The rocks in its vicinity are generally altered and soft. Partly in consequence of this condition 

they are disturbed · and are traversed by many seams of muddy gouge. There has been considerable movement along the contact, whatever its original character, and its present appearance 

in individual exposures is that of a fault plane. Detailed study of the mines shows, however, that 

these planes are not continuous and that the contact is more irregular than it should be were the 

dacite here bounded on the west by a fault. On the 450-foot level of the Mohawk mine the 

main latite-dacite contact is at the Mohawk shaft. From this shaft a w~st crosscut to the 

Mackenzie shaft goes through latite for 400 feet (122 meters), then enters dacite and continues 
PRELACUSTRINE TERTIARY IGNEOUS ROCKS. 59 

in this rock for 250 feet (76 meters) 'to the face. (See Pl. VIII, section C-C'.) As usual the 

contact is disturbed, but this dacite west of the Mackenzie shaft is thought to be a dike which / 

has come up through the latite and connects with the dacite sheet above. . 

In the lower levels of the. Moha:Wk mine and i~ part.s of the Cor;bination mine ore has been 

found at the contact, partly In dacite and partly In latite. In such places the contact, much 

obscured by the mineralization, appears to be of the irregular kind characteristic of igneous 

~~~. . I 

On the whole, while much remains to be learned, the evidence relating to the dacite-latite 

contact west of the Red Top, Mohawk, and Combination mines is thought to indicate that it 

was originally intrusive and that it has since been modified by many local faults. As will later 

be shown, the whole body of dacite containing the principal mines has been -racked by movements which have transformed joints, contacts, and other planes of weakness into gouge-filled 

fissures. 

On the south the dacite is in contact with the Milltown andesite. When the preliminary 

report was issued it was thought probable that this contact dip~ed gently to the south, such a 

supposition being a reasonable conclusion from the general relation of the geologic boundary 

between the two rocks to the topography. The · Florence was then the only shaft that had 

penetrated the Milltown andesite in this locality and the exposures it afforded lent some support 

to such a view. (See Pl. VIII, section F-F'.) It is now known that the contact is in general 

very steep and that the andesite near Milltown rests not on dacite, but on latite. In the Florence 

workings the contact is much obscured by the alteration of the rocks. It is apparently close 

·to .the shaft on the 150-foot level and only 20 to 30 feet (6 to 9 meters) south of the shaft on 

the 250-foot level. (See fig. 2~). The Little Florence shaft, 500 feet (152 meters) south of the 

Florence shaft and 500 feet deep, is all in andesite. The Rosebud, Rogers, Florence Annex 

(Engineer's Lease), Pollard-Florence, and Florence-Extension No. 2 shafts, all 500 feet (152 

meters) deep, and all on the southeast slope of Florence Hill, show andesite as the prevalent 

rock to the bottom. It thus appears that in ·this loc·ality not only does the dacite abut against 

the Milltown andesite with a nearly vertical contact, but the latter rock extends to unusual 

depth (see Pl. VIII, section G-G') and probably occupies one of the fissures or conduits through 

which the andesitic flows i~sued. At one place on the 509-foot level of the Rogers lease a narrow 

slab of mineralized dacite between andesite walls has been drifted on for a short distance. It 

is probably a small dike. 

On the south slope of the little hill north of Milltown the Baltimore Belle shaft, 375 feet 

(114 meters) deep, is all in andesite. Farther east the Atlanta-Cherokee shaft, 500 feet (152 

meters) deep and, as shown on Plate II, very close to the dacite contact, is nearly all in andesite. , 

A little dacite was cut near the bottom, but this, probably an intrusive offshoot from the main 

body to the north, was penetrated and andesite was found belm:J it. ·The Garrison shaft, just 

northeast of the Atlanta-Cherokee, is in dacite at the surface, but the bottom, at 300 feet (91 . 

meters), is in andesite. Both dacite and andesite occur at the ~50-foot level, the relations of 

the two rocks being suggestive of irregular intrusion of the andesite by the dacite. Alteration 

and disturbance of the rocks, however, render interpretation of th~ observed relations uncertain. 

Near this shaft the contact crosses the ridge and swings north of the line of shafts, which continues southeastward along the crest to the Gold Bar and Victor mines. The Gold Bar workings, 

300 feet (91 meters) deep, are mainly in andesite and latite, the latter being the rock of the 300-

foot level. Considerable dacite is exposed on the 200-foot level, however, where it apparently 

occurs as irregular masses in the ande~ite. The roc~ in this mif e are generally much altered 

and disturbed so that contacts as a rule are very obscure. At one place, however, on the 200-

foot level, west of the shaft, a little intrusive tongue of dacite projecting into andesite was 

plainly discernible in 1908. AlthQugh both rocks were soft and altered the sharp irregular 

contact was distinct, and specimens have since been microscopically identified as andesite and 

dacite. · " 

Of the contact along the eastern and northern sides of the main dacite sheet little more 

is known than appears from the map (Pl. II) and structure sec ions (Pl. VIII). It is poorly 

exposed and has not been much explored underground. The boundary ·corresponding to the 
60 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

contact is sinuous, and in general defines the thin edge of the dacite sheet which rests for the 

most part on Milltown andesite, but in some places on latite or Sandstorm rhyolite. 

Practically nothing i~ known concerning the detailed character of the contacts of the other 

bodies of dacite, such as that near BJ.ack Butte and those in the vicinity of Preble Mountain. · 

These contacts are either not actually exposed or are so blurred by the intense alteration of 

the rocks. that the only information they furnish is such as is deducible from their courses on 

the map and from the relation of these to the topography. This information alone, · however, 

is demonstrative of' intrusion. , If the boundary of the dacite mass of Preble Mountain, for 

example, be supposed reasonably accurate, if· it be carefully considered with reference to the 

slopes which it traverses .(see Pl. II), and if the attempt be made to get from this inspection 

an idea of the shape of the mass, this shape is found to be consistent only with the hypothesis 

of irregular intrusion of the dacite into the andesite. 

Finally the dacite as a whole does not accord with the general concentric plan which has 

resulted from the doming and erosion of a series of originally nearly horizont.al lava flows. 

Reference to Plate II shows that it cuts across the annular area of Milltown andesite from 

west to east. 

So. far as the mapped area is concerned the evidence for the generally intrusive· character · 

of the dacite maybe regarded as sufficient. It appears, however, that the intrusion took place 

under a. cover of andesitic rocks which was comparatively thin, and that some of the dacite 

broke through and was erupted at the surface. The t~xtural uniformity of the dacite and the 

comparatively slight extent to which the hornblende and biotite have ·undergone paramorphic 

. change both suggest that the magm~ solidified under conditions of pressure and temperature 

such as would be "afforded by intrusion under-some load. · On the other hand, the comparative 

thinness of the former cover is indicated by the presence of some glass in the groundmass of the 

dacite and the absence of any recognizable contact metamorphism of the andesite by the 

invading rock. 

Some additional reconnaissance east of the mapped area in 1908 showed that in the neigh- · 

borhood of Tognoni Springs a transition takes place from intrusive dacite on the west to effusive 

d'acite on the east. .A mile or two east of these springs, on the east ~lope of the first high hill 

east- of Diamond Peak, are exposed the edges of a series of lava flows dipping gently to the west. 

At the base of the section observed is a flow of rather dense andesite overlain by a dark-gray 

andesite vitrophyre like that which may be seen on the slope just northeast of Tognoni Springs. 

(See p. 52.) Resting on this glassy flow is an unstratified dacitic breccia from 200 to 300 feet 

(61 to 91 meters) thick composed wholly of fragments of dacite and. containing ang~lar blocks 

. and bomblike masses up to 6 feet (1.8 meters) in diameter . . This deposit is overlain by a flow · 

of massive dacite of approximately equal thickness . 

.A mile (1.6 kilometers) or less east of the section just described another hillside exposes a 

flow of dacite resting on glassy andesite without any intervening breccia. .Above the typical 

dacite is a flow of volcanic glass, probably dacitic, and overlying this a flow of. rhyolite which is 

thought to be the Meda rhyolite. 

Diamond Pe.ak, which lies just east of the mapped area and is the culminating point of 

the steep slope east of Tognoni Springs, is composed mainly of dacite. This is apparently a 

flow, several hundred feet thick, which dips gently westward and pas~es directly, with no essential change in petrographic character, into the dacite south of . the springs. This in turn is 

directly continuous with the dacite of Preble Mountain, supposed to be intrusive. 

It thus appears that in the Goldfield district there is a remarkable transition from an 

in-trusive rock to an effusive one. The imaginary restoration of the conditions under which the 

eruption took place is somewhat difficult. The familiar conception of narrow vertical dikes 

connecting with overlying lava flows has no application here and no sharp distinction seems 

possible between the intruded and e·xtravasated dacite. The magma appears to have irregularly invaded the older rocks, to have lifted these in part as an overlying crust, and to have 

poured through various ragged rents in this comparatively thin cover. The locus of one such 

rent is supposed to lie between Preble Mountain and Tognoni Springs, most of the dacite west 
I 

PRELACUSTRINE TERTIARY IGNEOUS U.OCKS. 61 

I 

of this line being intrusive and most of that east of it effusive. The breccias to the east of the 

mapped area prove that the outbreak of dacitic magma was accompanied by explosive activity. 

That transitions similar to the one just described must have occurred countless times in 

the history of the. earth is obvious. It is rare, however, that erosion has progressed .just far 

enough to reveal but not obliterate them. It ·is the realization of these unusual conditions that 

has led to skeptic~} s~rutiny of the_ eviden_ce for intrusi_on in ~he easel of the ?acite near· Goldfield 

and to the presentatiOn of that ev1dence 1n more detall than would otherwise be necessary. 

DACITE VITROPHYRE.a 

GENERAL CHARACTER AND OCCURRK CE. 

The dacite vitrophyre is a volcanic formation, consisting of thin lava flows with one or 

more ash beds, which as a whole rests upon an uneven surface of !andesite and is overlain by 

the Meda rhyolite, andesite breccia, and deposits of the lacustrine epoch. Its age, so far as 

fixed by the general -geological succession, is thus the same as that of the dacite. The vitrophyre 

is liniited to the southern part of the district and e·xtends from the vicinity of :Myers Mountain 

southeastward past Blackcap Mountain and beyond . the boundary of the area mapped. With 

some Chispa andesite it forms a series of low, rounded, light-colored hills (Chispa Hills), crosseil 

by the freight road from Goldfield to the Bullfrog district and skirted on the north by the Gold 

Crat~r road. The details ·of· distribution may be had from Plate II. 

' PET~OGRAPHY. I 

Th~ most abundant and characteristic material of the formation is a very light gray or 

nearly white rock, often with a faint tinge of green or pink. The texture is apparently porous, 

although · the microscope shows this appearance to be in most ses misleading. The comparative softness of the material and the presence of blotches in the glassy groundmass give 

it considerable resemblance· to a tuff. The rock is, in most places, finely speckled with small 

scales of biotite and contains less noticeable crystals of feldspar and quartz. 

A typical specimen (G. 158) collected alongside of the Gold Crater road, 1 mile ( 1.6 kilometers) southwest of Blackcap Mountain, was selected for description and chemical analysis. 

The rock is light greenish gray with irregular greenish blotches. Flakes of biotite, a 

millimeter or two in diameter, and-larger phenocrysts of quartz and clear feldspar are dis-

. tributed through a dull aphanitic groundmass. Under the microscope (Pl. VII, B)· the rock 

shows a typical vitrophyric structure, phenocrysts of vitreous plagioclase, biotite, and quartz 

being embedded in a eutaxitic glass. The plagioclase is in part labradorite, near Ab~An3 in 

. composition, but other·varieties may also be present. There is, in the section studied, a single 

phenocryst of hornblende partly changed to an aggregate consisting chiefly of magnetite. 

~he groundmass is almost wholly glass, partly transparent, and ~artly gray and cloudy, with 

incipient crystal growths. Streaks of these different varieties of the glassy base, drawn out 

by flowage, give the rock its blotchy appearance in hand specimens and its eutaxitic structure 

as seen under the microscope. 

A chemical analysis of this rock, made in the Survey labora ory by George Steiger, is as 

follows: · Chemical analysis of dacite vitrophyre. 

Si02 ••••..••••• . • • • • • • • • • • • • • • • • • • • • • • • • • • • 59. 99 H 2 0 below 110° d .................. __ ... __ . _ 3. 35 

~~:~ -. -_ -_ -_ -_ -_ -_-_-_ -_ ~ ~:::::: ~:::::::::: :·:::::::: 1!: ~~ H20 above 110° d ................. . _ .. __ .. _. 4. 06 

Ti02 • • •••••••••••• •• • l ........ ....... _ .. . . . . 64 

FeO .......................... · ..... -:. ·_ . . . . . 13 002 •••• . • • •••••••• • _· . • •..•. _. _ .... _. ___ • _. _ None. 

MgO .......................... . .. . ... ~ . . . . . 1. 51 P20 5 • ~ • • • :· ••••••• • • • . . •..•..... _ • __ • ___ • _. _ • 24 

CaO ................... . ....... ·_ . . . . . . . . . . . 4. 17 MnO ... . .. . . · ....... _ . _ . . ......... . ~ . --. _ . _ . _ . 05 

N a20 ........... . ...... . ............ . . . . : . . 3. 04 

K20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 82 I 100. 56 

-----------------------------------------~------------~-------------------

a In the preliminary report (Bull. U. S. Geol. Survey No. 303, 1907, p: 18 , written before the rocj ks had been thoroughly studied, the f'Jrmation here designated dacite vitrophyre was provisionally called quartz-latite · · 

I 
PLATE VII. 

PHOTOMICROGRAPHS oF VoLcANic RocKs. · 

A. Hornblende-biotite-augite andesite (G. 47). Northeast corner of district, 1! miles east of Black Butte. Contains phenocrysts of labradorite (I), hornblende (h), biotite (b), and augite (not shown in iiection) in a glassy hyalopilitic 

groundmass (g). Ordinary light. Magnified 40 diameters. 

_B. Dacite vitrophyre (G. 163). Southern edge of district, 1-1 miles southwest of Preble Mountain. Contains 

phenocrysts of plagioclase (p) near oligoclase in composition, biotite (b), and quartz ( q), in a eutaxitic brown glass (g) 

containing shreds of clearer glass (g). This variety probably approaches quartz latite or rhyolite in composition. 

Hole in section (h). Ordinary light. Magnified 35 diameters. 

C. Olivine basalt (dolerite) (G. 2). Edge of Malpais Mesa above Rabbit Spring. Contains phenocrysts of anorthite 

(a), olivine (o) partly altered to red-b-rown serpentine and an occasional cryetal of hornblende (not shown). The 

holocrystalline groundmass (g) is composed of plagioclase (labradorite or a:r;wrthite), augite, olivine, magnetite, a little 

interstitial calcite, and apatite. Nicols crossed. Magnified 40 diameters. 

D. Mica basalt (dolerite) (G. 46). ·Northeast corner of district, 2 miles east of Black Butte. Contains anorthite (a), 

a bright ·chestnut biotite (b), augite (p), olivirie (not shown), calcite (c), magnetite and apatite. There is no sharp 

distinction between phenocrysts and groundmass_. The biotite projects into irregular miarolitic cavities, many of which 

are partly filled with calcite. The minerals are all fresh except the olivine, which is altered to deep red-brown serpentine. Hole in section (h). Nicols crossed. · Magnified 40 diameters. 

62 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE VII 

A. 

c. D. 

PHOTOMICROGRAPHS OF VOLCANI C ROCKS. 

PRELACUS1'RINE TERTIARY IGNEOUS ROCKS. 63 

A remarkable feature of this analysis, and one not easily accounted fo:r, is the unusual 

ratio between the ferrous and ferric iron. As the rock is perfectly fresh, containing no hematite and very little augite, it would seem that ferrous iron should be much more abundant ' 

than the ferric form, inasmuch as in biotite and magne-tite the ferric iron is normally combined 

with respectively greater and equal amounts of the divalent form. Three determinations of 

the iron were made by :Mr. Steiger and two additional determinations, by another method, 

were carried out by Doctor Hillebrand . . All agree so closely as to show that the abnormal 

ratio is not due to defective analysis. As there is apparently enough magnetite in the rock to . 

account for all the ferrous iron found it seems necessary to conclude that the biotite is of 

unusual composition and that probably some iron jn the ferric state is present in the glass of 

the groundmass. a 

The norm calculated from this analysis is as follows: 

Norm of dacite vitrophyre. 

Quartz ................ _ .................... 20. 76 Ilmenite.............................. .. . . . . 30 

Orthoclas3 ......... : ..... . .................. 16. 68 Titanite ......... . · .... . .. : ......... , . . -. . ... l. 18 

Albite ......... _ . _ . . . . . . . . . . . . . . . . . . . . . . . . . 25. 68 

Anorthit8 . . . . ..... . .......... . ......... . .. 18. 90 92.90 

Corundun ........ . .. . ... . .. . ............. l. 12 Water .. . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. 41 

Enstatite.... .. .. . .......... . .. . ........... . 3. 80 

Hematite.................... . . . ... . ........ 4. 48 100.31 

The rock is amiatose, in the persalane class, brit annare order, alkalicalcic rang and sodipotassic subrang, of the quantitative class:D.ication. It is practically on the line, however, 

between amiatose and the unnamed dopotassic subrang of the same rang and order. 

The only rock falling in this unnamed subrang in H. S. VVashington's tables of analyses b 

is a so-called retinite, described by V. Sabatini and analyzed by G. Aichino. · This analysis 

is here quoted for comparison with the dacite vitrophyre. 

Chemical analysis cj retinite. c 

Si02 •••••••••••.•...• • • • •.••• . • • •••••••.• • • 64.32 NaO .. . . . . . .... . ....................... . .. 1. 63 

Al20 3 .. • .••..••.•.. • • • •... . ... •• •••••••• . •• 17.87 K;jO ........... . ...... . ............. . ... . . 4. 52 

Fe20 3 • ••••• •• ••••..• • .. . .. • ••••• • •• : . • • • • • • 2. 55 H 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 19 

FeO . .. .. . . . .. ... . . . .. . . . . ...... Not determined . 

.M:gO .. . ......... -.. . .. . : . . . . . . . . . . . . . . . . . . Trace. 100. 14 

CaO............ . .. . ... . ... . ..... . ...... . .. 3. 06 

The interesting feature of the comparison is the considerabl9 difference between the 

analysis here quoted and that of the dacite vitrophyre, which very ~arrowly escapes falling 

into the same subrang. 

A mile and a half (25 kilometers) south of Preble Mou tain (on3-fourth mile outside of 

the area mapped) a quarry has been opened in a bed of white volcanic ash, and the material, 

although very soft, has been used for buildings in Goldfield. It is composed almost entirely 

of small particles of volcanic glass with a few crystals or fragments of biotite, feldspar, and 

quartz. No chemical analysis has been made of this tuff, but it prob bJy corresponds in composition to the dacite vitrophyre with which it is associated. 

RELATION T.O THE DACITE. 

As the dacite vitrophyre has not the slightest physical resemblance to the dacite, it was 

at first supposed that the vitrophyre was the younger rock--t he product of eruptions, that may 

have been separated from the dacit6 by a considerable interval of deforr.aation and erosion. This 

a Since this was written the Swedish chemist Robert Mauzelius has found that the ferrous iron of minerals may be partly oxidized during 

the grinding preparatory to analysis. W. F. Hillebrand (Jour. Am. Chern. Soc., vol. 30, 19b8, pp. 1120-1131), -in whose paper may be· found 

references to earlier work, has recently confirmed and extended the experiments of Mauzelius and others. This discovery may account in part 

for the unexpected ratio of ferrous and ferric iron in. the dacite vitrophyre, but there has been no opportunity to test this before the report goes 

to press. 

b Prof. Paper U. S. Geol. Survey No. 14, 1903, p. 183. 

c Sabatini, V., Descrizione geologica delle !sole Pontine: Boll. R. Comitato geol. ital., vol. Q4, 1893, p. 252. 
64 . THE GEOLOGY AND ORE DEPOSITS OF . GOLDFIELD, NEVADA. 

was the view expressed in the preliminary report.a Subsequent petrographic study, however 

has shown that the vitrophyric dacite has some mineralogical features in common with the 

intrusive dacite, and chemical analyses pro.ve that the two rocks are nearly identical in chemical 

composition. . In order to illustrate this chemical likeness, the analyses of the dacite rocks 

. are here given side by side. · 

(Jhemical analyses of dacite dnd dacite vitrophyre. 

[George Steiger, analyst.]· 

L _2.1 3: 

Si02.......................................... 59.95 59.99 61.25 AbO~ ................ ·......................... 15. 77 16.14 15.92 Fe20a .......... __ ... ______ . ________ . ___ . _ _ _ _ _ 3. 34 4.42 3. 75 .13 1.17 1. 51 2.28 

FeO .......... ...-- ______ ... _ .. .... .. ........... 2.34 MgO ........... _ . _ .............. ___ . __ . _ .. _ . . 2. 73 CaO .......... __ .. _. ___ . _. _. _. __ ...... _ ..... _. 5. 84 4.17 5.39 Na20 ............... :............... . ......... 3.07 . 3.04 3.19 K20 ............. ---- _ .. _ .... ........... : ..... : 2. 52 2.82 3. 23 H20 below 110° C .... _ ........ _ .. .. .. .. .. . .. . . 95 3.25 1. 08 H20 above 110° C ....... ___ . _ .. _ . . . . . . . . . . . . . 2. 00 4.06 1.88 

L Dacite, one-half mile (0.8 kilometer) northeast of Columbia Mountain. 

2. Dacite vitrophyre, 1 mile (1.6 kilometers) southwest of Blackcap Mountain. 

3. Dacite, Diamond Peak, one-half mile (0.8 kilometer) east-southeast of Tognoni Springs. 

The vitrophyre, owing to the abundance of glass, contains a .larger quantity of water than 

the more crystalline rocks. It has somewhat less iron, calcium, and magnesium, but the chemical difference is no greater than may obtain in rocks known to be the products of a single eruption. The vitrophyre, as has been shown, falls into ·the persalane class of the quantitative 

classification, while the dacite is in the dosalane clasE). · Both rocks, however, are near the border 

line between the. two arbitrary classes, and any such definite scheme of artificial grouping necessarily separates many rocks which are chemically very close together. 

Were the dacite and dacite vitrophyre separated in geologic time by an interval of erosion 

or by the eruption of some other lava, the resemblance would be regarded as a rather remarkable 

coincidence. As it is, the two rocks are known to be of nearly the same age. Whether they .were 

simultaneously erupted, the vitrophyre as an effusive equivalent of the dacite, can not be determined from the data available. The fabt that dacite known to be effusive east of Tognoni 

Springs has the same general habit as the intrusive dacite near Goldfield, whereas the dacite 

vitrophyre is a rock of wholly different aspect, suggests that the eruptions of the dacite and 

dacite vitrophyre were not strictly contemporaneous. · The vitrophyre is probably slightly 

younger. 

CHISPA ANDESITE. 

GENERAL CHARACTER AND OCCURRENCE. 

The Chispa andesite _occurs as flows intercalated in the dacite vitrophyre. A traverse of 

the Chispa Hills shows five of these flows, of which the northern ends of two only come into 

the area mapped (Pl. II). They dip to the southwest with the dacite vitrophyre at angles up 

to 50°. There is evidently some faulting in this vicinity, and it is possible that some of the 

apparently distinct. flows may be repeated exposures of the same lava sheet in successive fault 

blocks. All the dark andesite bands, which contrast in color with the light dacite vitrophyre, 

end rather abruptly on. the northwest in a manner suggestive of faulting. The larger of the 

two areas shown in Plate II is in contact along its northern border _with the Milltown andesite. 

This contact is covered by soil and wash and is further obscured by the deep decomposition of 

the rocks. Its position is uncertain and nothing is known of its characte::-. It may correspond 

to a fault. 

PETROGRAPHY. 

The Chispa ande~ite is generally a brownish-gray porous rock. The most abundant of 

the small phenocrysts are augite, and, with less conspicuous feldspars, are embedded in a brown 

aphanitic vesicular groundmass. The microscope shows the rock to be an ordi_nary fresh 

a Bull. U.S. Geol. Survey, No. 303, 1907, p. 18. 
PRELACUSTRINE TER'l'I.ARY IGNEOUS ROCKS. 65 

glassy augite andesite with no special .features. The phenocrysts of augite, plagioclase, and 

magnetite lie in a turbid microlitic glass. A few aggregates of smaller individuals of these 

minerals appear to re·present resorbed hornblende. 

ANDESITE DIKES. 

Cutting the Milltown andesite, dacite vitrophyre, and Chispa andesite in the southeastern 

corner of the district are a few dikes of a still yov.nger andesite. Possibly similar dikes occur 

elsewhere, but in most places it would be impossible to distinguish them if present from the 

mass of the Milltown andesite. Many exposures originally supposed to be dikes were found 

afterwards to be merely unaltered parts of the andesite, which in some localities outcrop from 

th softer disintegrated material around them in a manner strongly suggestive of younger 

In ruswns. 

The dike andesites are as a rule not particularly fresh, and no special petrographic study 

w s. made of them. Some show phenocrysts of hornblende, but the microscope proves them 

to be for the most part rather feldspathic rocks with subordinate fernie constituents. The 

gr undmass ccntain~ considerable glass, and a vesicular texture is not uncommon. It appears 

th refore that the parts of the dikes now visible were never far from the surface. 

MEDA RHYOLITE. 

GENERAL CHARACTER AND OCCURRENCE. 

The Meda rhyolite, which takes its local name from Meda Pass, is exposed in the vicinity 

of the pass and close to the road south of Myers Mountain. Two small areas of rhyolite in the 

n rtheast corner of the district, parts of a much larger area to the east, are supposed to represent 

th same epoch of eruption and are mapped as Meda rhyolite, although it is not certain that 

th y were ever continuous with the rhyolite near Meda Pass. The rock is a flow which northea t of Tognoni Springs rests on Milltown andesite and dacite and in the southern part of the 

di trict on dacite vitrophyre. It probably varies much in thickness. 

PETROGRAPHY. 

The rhyolite of the type locality near Meda Pass varies in color from light gray to pink. 

me of it has a well-marked flow structure which is accentuated by 1nany narrow lenticular 

st eaks of obsidian. Small phenocrysts of feldspar and quartz are abundant although not cons icuous. The microscope shows the rock to be a fresh glassy rhyolite vitrophyre in which the 

p enocrysts of quartz and orthoclase are accompanied by less abundant crystals of plagioclase 

a d biotite. The plagioclase is mostly oligoclase. Some of the rock northeast of Meda Pass is 

a ittle more crystalline than the variety just described and contains more abundant scales of 

b"otite. It is this latter facies that is exposed south of Myers Mountain. 

The rhyolite mapped in the northeastern corner of the district is a light reddish-gray variety 

w th abundant small phenocrysts of quartz which, with crystals of orthoclase and biotite, are 

e bedded in a eutaxitic groundmass. East of the area n1apped this rock grades into more 

c ystalline varieties. 

ANDESITE BRECCIA. 

About half a mile ( 0.8 kilometer) southeast of Meda Pass the northern end of a body of 

a desite breccia barely comes into the area mapped. This is .a bedded deposit and consists of 

f agments of andesite, mostly scoriaceous and more or less decomposed, firmly cemented in a 

atrix of andesitic tuff. The fragments are rarely over 6 inches (15 centimeters) in diameter. 

e breccia rests upon the Meda rhyolite, or where this is absent on the dacite vitrophyre. It 

d ps gently to the southwest and is overlain by tuffs supposed to be part of the Siebert formation. 

I is probable th~t this breccia was laid down GOntemporaneously with the intrusion of the 

andesite dikes noted above. , 

7D145-Ko. 66-09--5 
CHAPTER V. 

ROCKS OF THE LAKE EPOCH. 

INTRODUCTION. 

In the Tertiary lake that probably covered much of the district after the eruption of the 

dacite, dacite vitrophyre, Meda rhyolite, and andesite breccia, there were laid down over 500 feet 

( 152 meters) of bedded tuffs, . tuffaceous sands, pumiceous ash, conglomerates, and diatomaceous ~arth. These are the deposits known to the miners as "cement rock." Volcanism continued during the existence of the lake, as shown by the prevailingly volcanic character of the 

sediments and the occurrence within them of a thick flow of quartz-bearing basalt (Mira basalt) 

and a few thin flows of glassy rhyolite. The Mira basalt, as shown by wells, underlies the 

southwestern part ·of Goldfield and it is exposed on the automobileroad to Bullfrog. Lacustrine conditions were ended by deformation of the region, the domical structure probably being 

initiated by this uplift. 

The sedimentary .deposits of the lake epoch will in this report be called the Siebert formation, being regarded as the equivalent of the Siebert tuff of the Tonopah district, described 

and named by Spurr. a 

SIEBERT FORMATION. 

DISTRIBUTION. 

The beds of the Siebert f0rmation are prevailingly rather soft and disintegrate readily. 

Consequently they do not as a rule give rise to prominent outcrops. They underlie the town 

of Goldfield and occupy the valley to the north through which passes the railway to Tonopah. 

South of GoJdfield they cover a large area, Myers Mountain and similar eminences in that 

direction being made up of these beds capped by basalt. They also underlie much of the 

_ basaltic mesa southwest of Goldfield and some of the best exposures of them are in the steep 

sides o{the mesa near Pozo Canyon. (See Pl. II.) Other areas extend into the northern part 

of the district and deposits belonging to this formation undoubtedly underlie a large part of the 

desert plains which surround the Goldfield Hills. 

LITHOLOGY. 

The sediments of the Siebert formation exhibit a wide range of character, although they 

consist ·almost entirely of volcanic and diatomaceous material, the former greatly predominating. 

Most of the material exposed or penetrated in wells near Goldfield consists of soft, sandy 

tuffs alternating with beds of volcanic conglomerate or gravel. The bedding is in most places 

fairly regular, but in small exposures is not always clearly distinguishable from cross-bedding. 

In the 100-foot well of the Columbia Ice and Cold Storage Company the gravel or conglomerate beds are said to occur every 20 to- 30 feet ( 6 to 9 meters) and to be from 1 to 2 feet 

( 0.3 to 0.6 meter) thick. 

The soft, light-gray, sandy beds which constitute most of the formation as exposed near 

Goldfield and in .the valley to the north a:re composed almost entirely of volcanic ash. The 

constituent particles, as· seen under the microscope, are chiefly angular bits of transparent 

a Spurr, J. E., Geology of the Tonopah mining district, Nevada: · Prof. Paper U.S. Geol. Survey No. 42, 1905, pp. 51-55. 

66 
ROCKS OF THE LAKE EPOCH. 67 

glass. These show so little rounding as to indicate that the material either was transported 

only for very short distances by streams or else fell directly as ash showers into the waters 

of Siebert Lake. In some beds the minute size of the particles suggests that the material was 

blown from some vent as fine dust, such as might be carried for many miles by winds. 

With the tuffs are associated some thin beds of diatomaceous earth, distinguishable from 

the ash beds by their whiteness and lightness. There is in some places, however, a gradation 

from tuff into the organic deposit. The purest form of diatomaceous enrth was found in the 

northwest corner of the area mapped, near the point where the electric--power line enters the 

district. The material is cream color, exceedingly light, and splits into paper-thin leaves. A 

little of the powder when covered with a drop of water and examined under a high power of 

the microscope is seen to be made up entirely of the whole and broken cells, or frustules, of 

diatoms. The species of these tiny plants are probably the same as those identified by Dr. 

R. M. Bagg from the Siebert tuff at Tonopah. a Inasmuch as these low organisms, owing to 

their wide range through geologic time, are of little value in determining the age of the rocks 

with which they are associated, it seemed scarcely wort while to have specific determinations 

made on the Goldfield material. An impure and less thinly laminated diatomaceous earth 

0

1

ccurs just east of the railway, near the crossing of th electric-power line, and similar material, associated with soft, light-gray, pumiceous tuffs, un erlies much of the low ground between 

Myers Mountain and Meda Pass. · · 

. The conglomerates ass<;>ciatecl with the fine tuffs d infusorial earth contain pebbles of 

most of the prelacustrine rocks of the district, those of i: yolite being probably most abundant. 

The material . of the conglomerates, however, varies fro place to place. Some of the shafts 

sunk near the eastern side of the town of Goldfield show the Siebert formation to contain many 

fragments of dacite up to a foot ( 0.3 meter) or more n diameter. Still larger fragments of 

the same rock are abundant in the Siebert beds about a mile southeast of Myers Mountain. 

The dump of an abandoned shaft, a few yards northeast of the railway station in Columbia, 

shows that the basal part of the Siebert (which· here rests on the Kendall tuff) is a breccia containing fragments of dacite up to 18 inches ( 0.5 meter) in diameter. The matrix in whioh 

these blocks are embedded is composed of particles of volcanic rocks of various kinds, those 

of andesite predominating. Small pebbles of quartz also were noted in some of the conglomerates of the Siebert. . · · 

The flow of Mira basalt, shown south of Goldfield in Plate II, is overlain by beds of lightcolored ttiff which contain, near their base, vesicular blocks of the basalt. This phase of the 

Siebert is well exposed on the north slope of Spearhead Point, south of Goldfield. The beds; 

which dip 25° S., have in general a pale greenish yellow tint and are rather soft. They comprise fine-grained tuffaceous sandstones and small-pebbled conglomerates or grits, the latter 

showing cross-bedding. 

In the northeastern part of the district much of the Siebert formation is a soft, brown, 

sanely tuff, composed . chiefly of particles of feldspar, hornblende, and · other minerals found in 

the massive lavas. This material in places overlies a deposit made up of fragments of light 

vesicular glass, or pumice. , 

At Mecla Pass the :M:ecla rhyolite is overlain by a bed of white pumiceous tuff probably 

from •20 to 30 feet (6 to 9 meters) thick. The upper surface of this tuff is very uneven, the 

inequalitie·s being apparently clue in part to erosion and in part to subsequent minor faulting. 

Upon it rest clark friable sanely tuffs, which ·in the limited exposures available show very 

irregular lamination with diverse clips, but no true bedding. This material is really a basaltic 

or anclesitic sand in which the partially rounded grains of plagioclase, augite, magnetite, and 

brown glass have been cemented by calcite. It is closely associated with, and probably grades 

into, or is overlain by, coarser tuffs in which the cementing material of the basaltic fragments 

is also mainly crystalline calcite. The exposures in this part of the district are very ·unsatisfactory, but the tuffs just described are probably part of the Siebert. The beds which appara Spurr, J. E., Geology of the Tonopah mining district, Nevada: ;E>rof. Paper U. S. Geol. Survey No. 42, 1905, pp. 69-70. 
68 THE GEOLOGY AND ORE DEPOSITS OF · GOLDFIELD, NEVADA. 

ently overlie them and form the ridge between Meda Pass and Mira Mountain are exposed 

only in a few prospect pits. One such pit between bench mark 5813 and Mira Mountain showE 

·soft gray tuffs with layers of coarse angular conglomerate. The material is partly andesitic, 

but is of mixed derivation. Similar soft tuffs dip 35° to 40° W. under the basalt cap of the 

mountain. 

THICKNESS. 

The thickness of the Siebert formation has previo1:1sly been' given (p. 29) as "1,000 feet 

or more." This, however, may be under the mark. It is difficult to draw sections to scale, 

and in accordance with known surface relations, that do not give a thickness of over 2,000 

feet (610 meters') for the lake sediments in the vicinity of Goldfield. Exposures are far too 

poor to permit of ariy satisfactory measurement of thickness, and consequently we are forced 

to be content with estimates. The beds are certainly over 500 feet (152 meters) in thickness. 

Part of the apparent 2,000 feet, however, is probably due to faults and minor folds not visible 

at the surface. On the whole, 1,000 feet (305 meters) is probably as fair an estimate as can be 

made at present of the maximum thickness of the Siebert formation at Goldfield. Ball's map a indicates that the nearly horizontal Siebert beds which constitute the upper part of Montezuma Peak have a thickness of at least 1,000 feet, and the formation exhibits similar development in the Monitor Hills, b 25 miles (40 kilometers) northeast of Goldfield, and at the southern 

end of the Belted Range, c 60 miles (96.5 kilometers) to the southeast. 

CONDITIONS OF DEPOSITION. 

The variations in the Siebert formation from pure diatomaceous earth and fine volcanic 

ash to coarse accumulations of large angular rock fragments indicate that the Tertiary lake 

was of variable depth, and that parts of the district rose above its waters. On the other hand, 

the Siebert lake beds, as shown by the work of Ball d and of Spurr,e and as indicated by the 

probable correlation of them with the Pahute lake beds of King, have a wide distribution over 

western Nevada, so that the lake, in spite of the evidence of the existence of near-by land, can 

have been no local feature. It was probably an exceedingly irregular body of water, comparable in shape with the labyrinthine inland sea which would arise were the present desert 

valleys to re~eive a I~ainfall persistently in excess of evaporation. That the bottom of the lake 

was exceedingly uneven is shown not only by the relation of the beds to the present t9pography 

of the district, but by the reconnaissance work of S. H. Ball f over a much larger area. Above 

the waters of the Tertiary Siebert or Pahute Lake rose not only mountains of older rocks, but 

volcanoes in active eruption, which hurled angular blocks of lava into the w~ter, and must at 

times have covered parts of the lake with floating pumice and volcanic dust. Torrential rains 

probably aided in transferring the detrital products of eruption to their final resting place at 

the bottom of the lake, while in the intervals of quiet between eruptions, . or in sheltered spots, 

diatoms found in the temperature of the water and in its silica contents conditions favorable 

to their abundant development. 

STRATIGRAPHY. 

The stratigraphy of the Siebert rocks, owing to their prevalent softness, is very u:qsatisfactorily revealed. In general the beds dip away from the center of the district at low angles. 

Exposures in the bluffs southwest of Goldfield indicate a dip of about 18° W. in that part of the 

field. This, however, is probably steeper than obtains north of Goldfield and in the northern 

part of the district. · 

The beds have been subjected to some faulting, as may be seen along the edge of the mesa, 

southwest of town. This disturbance will be described in a subsequent chapter. 

a Ball, S. H., A geologic reconnaissance in southwestern Nevada and eastern California: Bull. U. S. Geol. Survey No. 308, 1907, Pl. I. b Op. cit., p. 97. · 

cOp. cit. , p. 143. 

d A geologic reconnaissance in southwestern Nevada and eastern California: Bull. U . . S. Geol. Survey No. 308, 1907. 

e Geology of the Tonopah mining district, Nevada: Prof. Paper U.S. Geol. Survey No. 42, 1905. 

fOp. cit., Pl. I, figs. 7· and 13. 
ROOKS OF THE LAKE EPOCH. 69 

MIRA BASALT. 

OCCURRENCE. 

The Mira basalt occurs as a flow, apparently about 100 feet (30 meters) in greatest thickness 

(see also geologic sections, Pl. VIII), intercalated in the Siebert sediments. This rock underlies 

the southern part of the town of Goldfield. The flow rises gently toward the south, capping 

Mira Mountain and some smaller hills_ in its neighborhood. (See Pl. II.) North of Goldfield 

the Mira basalt is partly concealed by the Siebert formation, a few small areas only having been 

uncovered by erosion in the vicinity of the railroad station. 

PETROGRAPHY. 

The basalt as exposed at the surface is prevailingly vesicul:tr and is characteriz~d :negascopically by the presence of rather large phenocrysts, up to three-fourths of an inch (1.8 

centimeters) in length, of vitreous feldspar, which are disseminated sparingly through the rock. 

Although these feldspars are often bright and fresh, the rock as a whole presents a somewhat 

more weathered appearance th.an the later olivine basalt which caps the large mesa southwest of 

Goldfield. Denser and fresher varieties are obtained, however, in some of the wells near the 

town. 

Under the microscope the rock appears as an ordinary olivinitic basalt, save for the rather 

sporadic occurrence of quartz phenocrysts. The plagioclase is labradorite. The olivine is in 

some facies completely serpentinized, in others only initially attacked. The quartz occurs in 

rounded or embayed anhedrons, which, in some specimens, are surrounded by narrow rims of 

augite. Not every thin section contains quartz, and where this :mineral is absent there · is little 

to distinguish this rock from the later basalt. This simiiarity is particularly marked in the case 

of specimens of the older basalt taken from wells in the southern part of town. The rock frorn 

some of these wells is a doleritic variety with much olivine and no quartz. In spite 'Of its 

resemblance to the basalt of the neighboring mesa (Pl. II), this doleritic facies is apparently 

part of the same flow as the vesicular quartz-bearing variety, and is so mapped. It must be 

said, however, that the geologic relations of the rocks in the valley around Goldfield are very 

obscure. There may be unrecognized faults concealed beneath the loose detritus which covers 

most of the surface. 

ESPINA BRECCIA. 

In the eastern part of the district, northeast of Preble Mountain, is a deposit of precciaand 

tuff which shows a rough nearly horizontal bedding, and is about 200 feet (61 meters) in thickness. The material is for the most part greatly altered so that its original character is in part 

doubtful. Fragments of dacite are abundant, particularly in the lower beds, while the upper 

beds contain much volcanic glass in bomb like masses up to a foot (0.3 meter) in diameter, 

mingled with fragments of glassy rhyolite. 

The breccia records explosive volcanic erupti9ns of rhyolitic material which has since been 

extensively altered to opal, secondary quartz, kaolinite, and perhaps alunite. Whether the 

stratification was effected beneath the waters of Siebert Lake or is the ;result of successive . 

showers of volcanic detritus upon a land surface is a question to which· the character of the 

m~terial affords no decisive answer. 

The Espina breccia may be part of the Siebert formation, but definite correlation is not at 

present possible and the deposit, therefore, has been given a local name. 
CHAPTER VI. 

POSTLACUSTRINE .TERTIARY ROCKS. 

INTRODUCTORY STATEMENT. 

With the close of the lake epoch the rocks of the district underwent deformation, followed 

by erosion. Consequently the postlacustrine rocks rest unconformably upon the older formations, as may be well seen in the cliffs bounding the mesa southwest of Goldfield, particularly 

in the vicinity of Pozo Canyon. Here the Siebert sediments are in some places tilted to. angles 

up to 30°, with the practically horizontal lavas which cap the mesa lying upon their eroded 

edges. The postlacustrine rocks comprise four distinct formations, which, from the base up, 

are (1) the Pozo formation, consisting of beds of volcanic conglomerate and sandstone; (2) 

two flows of rhyolite, which may conveniently be called the Spearhead rhyolite; (3) a thin 

layer of sandstone and conglomerate, here named the Rabbit Spring formation; and (4) one 

or more flows of olivine basalt (Malpais bft,salt), with some biotitic and hornblendic facies. 

POZO FORMATION. 

The Pozo formation is named from Pozo Canyon, where may be seen the only satisfactory 

exposure of these rocks in the district. At the bend in the ravine (see Pl. II), about threequarters of a mile (1.2 kilometers) southwest of the center of Goldfield, some 50 feet (15 meters) 

of the Pozo formation is exposed in a cliff section, capped with the Spearhead rhyolite, which 

in turn is overlain by the Malpais basalt. The Pozo consists of roughly bedded, imperfectly 

assorted conglomerates associated with some soft sandstone. The material is mainly of 

volcanic derivation, andesitic, basaltic, and pumiceous fragments being abundant. . The 

pebbles, which are not well rounded, range in size from sand grains to blocks a foot or two (0.3 

to 0.6 meter) in diameter. The larger blocks are not confined to any one part of the deposit 

and some are embedded in the fine sandy layers. The general bedding of the deposit is nearly 

horizontal, but in detail the stratification is irregular and as exposed in the cliff shows small 

local unconforinities. It is evident that after some of the sands were laid down currents 

changed, channels were scoured, and were later filled with gravel. The whole deposit is clearly 

of fluviatile origin. 

The base of the formation is not visible in the section just described. On the opposite 

side of the ravine, however, the conglomerate may be seen resting upon an uneven erbsion 

surface of the soft yellowish Siebert beds. The Pozo formation thins rapidly to the north, 

and at Spearhead Point the rhyolite rests directly upon the eroded edges of the Siebert strata. 

Partly consolidated gravels and sands referable to the Pozo formation are exposed in the 

railway cut a short distance south of Meda Pass. They conformably underlie the Spearhead 

rhyolite and doubtless rest uncomformably upon the tuffaceous Siebert beds, · although this 

contact is not exposed. The pebbles are subangular,. ill-assorted, and of many kinds. A few 

are of dacite which had u~dergone the characteristic alunitic alteration prior to the erosion 

that furnished the materials of the conglomerate. The total thickness of the deposit, which 

contains some sandy and tuffaceous layers, is probably between 50 and 100 feet (15 ·and 30 

meters). 

A little less than a mile (1.6 . kilometers) north of Black Butte is a ridge . capped with 

roughly bedded conglomerate with. some fine tuff near the base of the deposit. The conglomerate contains fragments of andesite arid dacite cemented by calcite. In its upper part the 

deposit contains many blocks, some as much as 6 feet (2 meters) across, of vesicular basalt of 

the same kind as that of the postlacustrine flows. 

70 
POSTLAOUBTiRIN:E TERTIARY ROOKS. 71 

The correlation of this material is somewhat in doubt, hut it is provisionally mapped 

with the Pozo formation. It is possible, also, that a small part of what has been mapped as 

Siebert in the northeast corner of the district inay really belm;tg with the Pozo, as the l2~tter 

formation had not been recognized when this part of the field was studied. It is questionable, 

however, whether the Pozo, if present northeast of Black Butte, could be there satisfactorily 

separated from the dominant and poorly exposed Siebert. 

SPEARHEAD HHYOLITE. 

The rhyolitic flows are well exposed at Rabbit Spring, west of Goldfield, and in Pozo Canyon. -

At Rabbit Spring they have a thickness of about 80 feet (24 meters), while at the southern 

boundary of the district m·apped they are altogether only about 20 feet (6 meters) thick. · In 

most places two distinct subdivisions are recognizable-an upper, thicker, pinkish member:. and 

a lower, thinner, brown member. These are thought to be distinct flows, but the rock of both 

members is essentially the same and no evidence of any erosion or deposition between the flruption of the two varieties has been found. 

At Rabbit Spring, w.here the upper rhyolite has been quarried for building stone, the rock 

is a rather soft, porous; pin~ish-gray rhyolite, containing so many fragments of pumice a.s to 

warrant the name of "flow brec~ia." These pumiceous fragments are everywhere present in 

the -Spearhead rhyolite, but they vary in abundanee from place to place. In some localities they 

are so numerous as to give the rhyolite the aspect of a tuff; in others the flow is comparatively 

compact and massive. 

Under the microscope the rhyolite shows phenocrysts of quartz and orthoclase and a curly 

eutaxitic glass, which, in some specimens, shows incipient devitrifaction. Among the rarer 

phenocrysts are biotite, hornblende, ttnd green pyroxene. These seldom occur as more than one 

or two imperfect crystals in any single section and may be entirely absent. 

The Spearhead rhyolite has been extensively used as a building stone in Goldfield and is the 

material of the court-house and of the town fire station. 

RABBIT SPRING FORMATION. 

The Rabbit Spring formation is exposed in the bluffs above the spring '~rhence it derives its 

name and in other places along the edge of Malpais Mesa. A deposit correlated with it occurs 

also beneath the basalt of Blackcap Mountain. 

As exposed near Rabbit Spring, the formation is from 10 to 15 feet (3 to. 4.5 meters) thick, 

and is consequently exaggerated as shown on the geologic map (Pl. II). It consists h~re of sandstone, apparently derived from the underlying rhyolite, with lenses of conglomerate, of which the 

pebbles are all of volcanic rocks. In its upper part the formation merges with the brecciated 

vesicular base of the overlying olivine ba.salt. The occurrence of this bedded sandstone and conglomerate indicates fluviatile action or a very brief recurrence of at least local lacustrine conditions just prior to the basaltic eruptions. 

At Blackcap Mountain the basalt cap rests :[n part upon a wedge of volcanic sandstone and 

conglom~rate, the pebbles of the latter being mostly andesite and basalt. This wedge is about 

25 feet (7 .6 meters) thick on the west face of the mountain, but thins to the east, and has not 

been seen on that side of the summit. (See Pl. II.) The lower 7 feet (2 meters) of the basalt 

is exceedingly vesicular and much brecciated by the movement of the flow. These sediments 

are correlated with those above Rabbit Spring, although it is by no means certain that they were 

laid down in one continuous body of water. The Siebert formation, if it ever covered this part 

of the district, was eroded away before the Rabbit Spring formation was laid down. The Spearhead rhyolite is also missing at Blackcap Mountain. 
72 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

MALPAIS BASALT. 

The youngest volcanic rock in the district is the dark oliv1nitic basalt which caps the mesa 

southwest of Goldfield, Myers, and Blackcap mountains, and many of the hills along the eastern 

border of the area studied. The same rock occurs also as small intrusive masses, such as that 

on the east slope of Vindicator Mountain and the small bodies mapped about a mile (1.6 kilometers) northeast of Preble Mountain (Pl. II). 

The basalt appears to have flowed over a somewhat diversified topography, covering considerable ~reas of plain and enveloping the bases of hills which rose above the general level of the 

country. As shown by sections D-D' and E-E', Plate VIII, there is nothing improbable in the 

supposition that most of the central part of the district, including Vindicator Mountain, was 

once covered by basalt, although erosion has left no remnants to testify directly to this extensive 

volcanic inundation. On the other hand, some of the high dacite hills just east of the area 

mapped and :Montezuma Peak, west of Goldfield, appear to rise above the level of the former 

lava flood. 

Whatever . . 

its former extent, the basalt has been much reouced by erosion and is represented 

to-day by a series of dissevered remnants. Of these the largest forms Malpais Mesa, near Goldfield, a desolate somber plateau some 4 miles (6.5 kilometers) in widtl;l and 12 miles (19 kilometers) 

in length from north to south.a A small part only of this basaltic table or mesa comes within 

the area represented in Plate II. The cliffs which bound the mesa on the east continue for several 

miles north of Goldfield to form the western wall of the valley in whi~h the town lies, until finally 

the escarpment turns to the west and the valley opens into the desert plain north of the Goldfield 

Hills. 

The basalt cap of the mesa is aoout 100 feet (30 meters) thick as exposed in the cliffs near 

Goldfield. On top of Myers Mountain is 200 feet (61 meters) of basalt and on Blackcap about 

100 feet. 

It is by no means certain that all of the olivine basalt belongs to a single flow or issued 

from one vent. The rock exhibits sufficient lithological variety to suggest that the lava may 

have come from more than one orifice and may not have been of entirely simultaneous eruption. 

Ball,b moreover, has shown that basalt was the last rock erupted over a wide region circumjacent to Goldfield, such as could have hardly been covered by a single flow. Within this 

region are basaltic cones, some of which are visible northeast of the railroad about 15 miles 

(24 kilometers) southeast of Beatty, indicating that the basaltic magma reached the surface 

through several conduits. 

The basalt of Malpais Mesa is a holocrystalline variety such as is properly designated 

dolerite. (Se.e Pl. VII, 0.) Vesicular facies, containing more or less glass, occur, however, at 

the base of the flow. The rock contains abundant phenocrysts of calcic labradorite (Ab1An2) 

·and olivine in a crystalline groundmass of the same minerals, with much augite and magnetite, 

a little biotite, and many small prisms of apatite. Filling the interstices between some of the 

subhedral labradorite crystals of the groundmass is a clear untwinned feldspar of distinctly 

lower index of refraction and weak birefringence. _This is probably orthoclase. It is not 

conspicuous in the thin•section and was evidently the last mineral to crystallize. It usually 

incloses delicate prisms of apatite. The minerals are all perfectly fresh except the olivine, 

which is partly altered to a red-brown serpentinous mineral (iddingsite). It is questionable, 

however, whether this alteration comes under the head of ordinary weathering. Its frequent 

occurrence in basalts exhibiting no signs of general decomposition suggests that this change in 

the olivine may in some cases follow very closely upon the solidification of the magma. A 

. chemical analysis of this olivine dolerite is given under 1 in the following table. The small 

quantity of carbon dioxide there shown comes from a little calcite which occupies some small 

interstitial spaces between the crystals of the groundmass and is not obviously a deco:mposition 

product of any particular mineral. 

a See Ball, S. H. , Bull. U. S. Geol. Survey No. 308, 1907, Pl. I. b Bull. U.S. Geol. Survey No. 308, 1907, PI. I. 
POSTLAOUSTRINE TERTIARY ROOKS. 73 

Chemical analyses of basalts. 

[George Steiger, analyst.] 

1. 2. 1. 2. 

48.20 48.59 H20 below 110° C .............. _.. .... .... . ... .. . . .. 0. 96 0. 76 Si02 ...... .................. . ...................... . AhOa .............................................. . Fe20a .. . ........................................... . 21.47 17.80 H20 above 110° C......... . . . .................. .. ... 1. 20 • 67 

FeO .... . .......................................... . 5. 89 8. 70 '.ri02. .. ..... .... ...................... . ............. 1. 34 1. 54 

MgO .......................................... .' ... . . 2.20 .93 C02... . .. ........ .. .. . ......... .. ............... .. .. .38 .55 

CaO ................................... c •••••••••••• 

3.33 4.85 P20; .... .... : . .. . .... . .................... . ......... .39 .43 

Na20 .............................................. . 10. 60 10. 49 MnO...................... . .. . ...................... . 11 . 14 

KtO ............................................... . 1. 33 1. 70 100. 50 100. 21 3. 10 3. 06 ---,--

1. Olivine dolerite (G. 2), Rabbit Spring, near Goldfield. 

2. Mica dolerite (G. 46), 2 miles (3.2 kilometers) east of Black Butte. 

The norm of the olivine dolerite, calculated from analysis 1, is as follows: 

Norm of olivine dolerite. 

Anorthite... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40. 87 Magnetite .... _ .. _ ......... _. _. ___ .. __ ... _ 

Albite .................................... ' 26. 20 Ilmenite._ .... _______ . ________ ..... _ ..... . 

. Orthoclase ......................... _..... 7. 78 

3.48 

2.43 

Quartz ................................. · .. 

Diopside ................................ . 

96.95 

7 

· ~: (Calcite ...................... _ . __ . . . . . . . . 90) 

· \Vater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 16 

Enstatite ..................... _._ ... ...... . 5.00 

Hematite ............................. _ . . 3. 52 100.01 

The rock is a hessose, in terms of the quantitative classification. 

The basalt of Myers Mountain, which is vertically columnar, contains phenocrysts of 

augite as well as of labradorite and olivine. The rock is a holocrystalline doleritic variety and 

is almost ideally fresh, the olivine showing only traces of serpentinization along irregular microscopic cracks. This serpentine is of the ordinary greenish yellow kind. Many of t_he olivine 

phenocrysts are magmatically embayed, much as are quartz phenocrysts in rhyolite. In the 

area of basalt just east of Myers Mountain the olivine is nearly all altered to the same orangecolored, strongly birefringent, serpentinous mineral as is found in the basalt of the large mesa 

to the west. 

Most of the cap of Blackcap Mountain is a fine-grained, even-textured basalt, which the 

microscope shows to be of the holocrystalline doleritic type. The olivine is all changed to 

serpentinous pseudomorphs of fibrous structure and deep reddish-orange color in transmitted 

light. The labradorite and augite are fresh, although the rock eontains a little interstitial 

calcite. The dolerite contains also a little orthoclase as the final produet of crystallization. 

Some specimens contain biotite. Whether these belong to a distinet flow or are merely faeies 

of one thiek lava sheet was not determined. The biotite is a light-eolored variety, the pleochroism being X pale buff, Y and Z yellowish chestnut brown. Highly vesicular faeies oeeur 

at the top and bottom of the flow, which can not have suffered much reduction of thiekness 

by erosion. 

The small body of basalt on the southeast slope of Blackeap Mountain is of the same kind 

as the rock which caps the mountain, but is too low down to be part of the same flow, in plaee. 

It is either intrusive in the andesite or-and this seems more probable-is a loose mass whieh 

has slid down to its present position in consequence of the disintegration and erosion of the 

underlying andesite. 

Several .hills about 1! miles (2.5 kilometers) east of Blaek Butte and just outside of the 

eastern boundary of the area mapped (Pl. II) are capped with basalt, the cappings ranging from 

100 to 200 feet (30 to 61 meters) in thiekness and exhibiting eonsiderable diversity in elevation and slope. The basalt is mueh like that on Blackcap Mountain, although mueh of it is 

less eoarsely erystalline as seen under the microscope. Glass oeeurs only in some of. the vesicular facies eharacteristic of the tops and bottoms of the floors, The olivine exhibits various 

stages of alteration to iddingsite or serpentine pseudomorphs. Two rather unusual varieties 

of the basalt call for brief description. 

). 
74 T HE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

One is a compact aphanitic rock, which caps a hill just outside of the extreme northeast 

corner of the district, as mapped in Plate II. Under the microscope this basalt. shows a striking flow structure, the small crystals of plagioclase, olivine, and augite being nearly all arranged 

with their longest dimensions parallel. 

The other, a somewhat porous, light-gray variety, is o:O: the hilltop just east of the area of 

rhyolite mapped in the northeast corner of the district. The most noticeable .feature of this 

rock, as seen in ha,nd specimens} is a bright golden-brown mica. The small scales of this mica 

arc particularly abundant in the irregular pores of the basalt, projecting from the walls of thl3se 

little cavities and frequently partly embedded in calcite. 

The microscope shows the rock to be a holocrystalline aggregate of calcic labradorite 

(near Ab1An2), augite, biotite, hornblende, magnetite, and apatite. (See Pl. VII, D.) Originally a little olivine was present, but this has been altered to a deep red-brown ferruginous 

serpentine or allied mineral. Calcite is fairly abundant, filling rough miarolitic or interstitial 

cavities. Although the calcite apparently began to crystallize in actual cavities in the rock, 

it has also directly attacked and replaced some of the contiguous labradorite. The line between 

calcite and labradorite is irregular but sharp, and the plagioclase crystals show no tendency 

to alter into calcite throughout their mass. 

The brown mica is biaxial with small axial angle. The plane of the optic axes lies in the 

plane of crystal symmetry as in common biotite and phlogopite. The pleochroism is .X light 

yellow, Y and Z bright-yellowish chestnut. The absorption scheme is Y = Z>X. The optical 

character indicates that the mica is either biotite (meroxene) or phlogopite, the color suggesting the latter material. Inasmuch, however, as the rock as shown by the analysis under 2 on 

page 73 is by no m~ans poor in iron, the mica is probably merely a biotite of rather unusual 

color. 

The norm of this mica-bearing dolerite, calculated .from analysis 2 on page 73, is as ~ollows: 

Norm of mica dolerite. 

Anorthite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 30. 02 Ilmenite __ • ____ _________________ . ___ . _ .. _ . __ 

Albite._. ________ : _ .... __ . ____ . _____________ 25. 68 Titanite. _____ .... ______________ . ___ ..... _ . . 

Orthoclase_ . _ ... ______ ... _ . _ . ____________ . 10. 01 

Diopside. 

Quartz.------------.-.- .... ----.--- .. --.--. . 18 (Calcite.-.-- .. -.-- .. -.--.---- ... -.. -- ... -

Hematite _. _. _ .. ______ ..... _________ -·-- _ .. 13. 61 Water _________ ._. ___ . __ . _____ . ___ ._._._ .. .. _· ______ . ___ . __________________ . 8. 70 

Enstatite. ______________ .. ______ ..... ___ ._._ 5. 80 

This rock also is a hessose in the quantitative classification. 

2.13 

. 98 

97.11 

1. 20) 

1.43 

99. 74 

On the east slope of Vindicator Mountain and near the eastern edge of the district, 1 t miles (2.5 kilometers) north of Blackcap Mountain, are small bodies of basalt that appear to 

be intrusive in the _older rocks, and may fill conduits through which some of the extrusive 

basalt reached the surface. 

The rock of the Vindicator Mountain areas is dark gray and compact, with small phenocrysts 

of plagioclase, augite, and hornblende. Microscopical examination leaves the character of the 

larger mass (Pl. II) somewhat in doubt, as the mineral supposed to have been olivine is entirely 

altered to calcite and serpentine and the groundmass is rather andesitic in texture. Some of 

the smaller masses shown, however, are clearly olivinitic basalt, with small phenocrysts ~f 

.labradorite, augite, and olivine in a dense partly glassy groundmass. 

The rock of the small areas north of Blackcap Mountain is compact and nearly aphanitic. 

It shows under the microscope abundant small phenocrysts of partly serpentinized olivine 

and of labradorite, in a groundmass of plagioclase, augite, magnetite, apatite, and a little glass. 
CHARTER VII. 

QUATERN:IRY DEPOSITS. 

The post-Tertiary deposits of the G:1dfield district comprise unconsolidated gravel 

belonging to two periods. The older gravels have been recognized chiefly to the south o . I 

Goldfield, along both sides of the automobire road to Bulliirog, being found in some placen 

500 feet (152 meters)- above the bottoms of neighboring ravi!nes. They are particular! 

abundant on the slopes of Mira Mountain. These gravels are apparently not well bedded~ 

are very poorly exposed, and owing to their tendency to roll down the slopes and mingle wit~ 

later detritus can not be accurately mapped~ They are not shown on Plate II. The pebble~ consist largely of rocks foreign to the distri t. Mr. vV. H . Emmons estimated that about 40 

per cent of them are of micaceous slate or p 1yllite, 20 per cent of dense dark-gray limestone! 

15 per cent of hard quartzite and 25 per cent pf andesitic and other dark volcanic rocks. Som~ of these rocks occur as bowlders a foot (0.3 et ) in diameter and nearly all are ·well rounded 

The maximum thickness of these gravels is not known, although a shaft in one place show . 

them to be at least 50 feet (15 meters) thic . 

It appears most probable that the mate ial of these gravels was brought from the southwest by a stream, which must at times have rrie d more water than is ever found in the vreseni 

arroyos. - · l 

The later gravels and sands are those o! the present stream courses, which, it should b : 

understood, contain running water only at r .re intervals and for brief periods. These gravelf 

are of local derivation and in most places can not be definitely separated from the loose 

the work of the prospector · or geologist. qn ·Plate II only the thicker and more extensiv 

. accumulations of alluvium are shown, for te reason that in this arid region the details of 

distribution of the superficial gravel and ubi uitous "wash" are ~f little importance compare 

with the _structure and distribution of the · nderlying rocks. The areas of alluvium show9, 

therefore, are merely t~ose w~ich are. so ~ck or so extensive as to prevent the underlyinr' 

rock structures from bmng satisfactonly de9rphered: · 

No attempt has been made, so far as k wwn, to work any of the gravels for gold, and i 

is doubtful whether they could be successful y exploited, even were abundant water availabl . 

For not only is the gold of the district very/_fine, but the concentration by running water ha 

doubtless been far less perfect than in those regions where a comparatively stable system f perennial streams has steadily concentrate~ the gold into narrow . and definite channels. I:p. 

an arid region like that of Goldfield the ch nnels are wide and ill defined and the process qf 

erosion is too erratic and intermittent for effective concentration. Moreover, the total deptf 

of erosion since the ores were deposited has been eomparatively small, as will be shown late '. 

75 
) 

CHAPTER VIII. 

GEOLOGIC STRUCTURE. 

The structure of the Goldfield district, as previously stated, is broadly simple. A Tertiary 

volcanic series resting upon the worn surface of much older rocks has been elevated into a dome 

of gentle curvature (see Pls. II and VIII), and this after some modification by faulting and 

igneous intrusion has been truncated by erosion so as to denude patches of the fundamental 

rocks in the central part of the uplift, leaving them surrounded by annuli of successively younger 

formations. This structure was afterwards covered, at least in part, by flows of lava which 

have in their turn been eroded from all but the outlying parts of the district. 

Banner Mountain may be taken as the approximate center of the domically uplifted area. 

(See Pl. II.) The uplift, however, is not symmetrical, and Vindicator Mountain appears to 

correspond structurally to a local protuberance on the dome. It is quite possible that originally 

there was a depression here in the pre-Tertiary surface, since the oldest of the lavas, the Vindicator rhyolite, is found mainly on the flanks of this mountain. The symmetry of the dome is 

further modified, as will later be shown, by irregular intrusions of the dacite and by the Columbia 

Mountain fault. (See Pl. II.) 

The scattered and relatively small areas of pre-Tertiary rocks now exposed throw little 

light on the structure of the old floor through which the lavas broke. The basal rock, in these 

exposures, is mainly alaskite, which has invaded and greatly disrupted a series of Cambrian 

sediments. It is probable that the alaskite or granite is the prevailing rock upon which the 

Tertiary rocks as a whole rest, but it is quite possible that included in this plutonic rock and 

forming parts of the floor may be masses of the Cambrian sedimentary terrane much larger 

than those visible on Columbia and Vindicator mountains. 

It is doubtful whether, with the information now available, the configuration of the preTertiary floor can be ascertained with any accuracy. The contacts between alaskite and the 

volcanic rocks in the vicinity of Vindicator and Banner mountains show no sharp rugosities, 

but on the other hand they scarcely suggest that the alaskite was worn down to a smooth plain. 

That. the old surface suffered considerable deformation in Tertiary time is evident from the 

relations shown on Columbia Mou.ntain, where Tertiary rhyolite is intrusive into alaskite and 

Cambrian sediments. Doubtless equal or greater deformation has affected parts of the floor 

now buried, and the occurrence of such local disturbance complicates the problem of an ideal 

restoration of the surface as it was before the Tertiary volcanic eruptions began. 

The fact that the pre-Tertiary rocks are exposed only in the central part of the eroded 

dome, or where, as on Columbia Mountain, faulting has modified the domical structure and 

brought the older rocks within the reach of erosion, indicates that the prevolcanic surface had 

low relief; otherwise knobs of alaskite or of Cambrian sediments would be found here and there 

projecting through the andesite. The pre-Tertiary floor was therefore in the main a rolling 

granitic surface diversified by rounded hills a few of which may have attained heights of 200 

to 300 feet (61 to 91 meters) above the general level. ~one of the exposures in the district 

aifords evidence of any considerable detrital accumulation on this old surface prior to the 

volcanic outbursts, although, as mentioned on page 37, there is a little such material beneath 

the Vindicator rhyolite on Columbia Mountain, and the basal part of the rhyolite generally 

contains many inclusions of Cambrian shale. 

Overlapping the pre-Tertiary core of Vindicator Mountain on its west and east sides are parts 

of the oldest lava in the district, the Vindicator rhyolite. This flow is at present not extensive, 

76 
S . GEOLOGICAL SURVEY 

RGE OTIS SM ITH , DIRECTOR 

lmo 

1mb ll 

ls 

.E 

:::E 

L. 

., 

c: 

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PROFESSIONAL PAPER 66 PLATE VIII 

Tma 

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500 50 

EXPLANATION 

T Shafts approximately '" 

the plane of section 

Shafts behind the 

plane of section 

,.- Shafts in front of the 

plane of section 

«l " 

" l; " l; .., -' .., l; 

.., l; " ., ~ 

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i 

Ts 

SECTION B -B ' 

SECTION 

Vindicaror Mtn Tvr 

SECTION 

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L---------------------------------------------------------------~----------------------------------------------------------------------------------------------------------------------------------------------------------~ 600 . c SECTION E -E ' 

i 

Td Tmo lme 

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SECTION F -F' 

Columbia Mt 

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SECTION 

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GEOLOGIC SECTIONS ACROSS THE GOLDFIELD DISTRICT, NEVADA 

BY F.L.RAN OME 

Horizontal and rti al scale z~~o 

lDOO 0 1DOO 2000 3000:& • 

t 

" 

FOR EXPLANATION OF COLORS 

SEE LEGEND ON GEOLOGIC MAP. PLATE II 

Tmb 
GEOLOGIC STRUC,TURE. 77 

for it does not appear around other areas of alaskite exposed to view in the vicinity of Banner 

and Columbia mountains. Whether it is the product of a small local outburst which never 

extended far from the site of Vindicator Mountain, where it perhaps accumulated in a hollow, 

or whether there was considerable erosion between its eruption and the latite inundation is 

not known. The maximum thickness of the Vindicator rhyolite is estimated at about 200 

feet (61 meters). The rhyolitic capping of Columbia Mountain is probably a remnant of the 

same flow. 

The latite flow, which rests in part upon the Vindicator rhyolite but mainly upon the preTertiary floor, now forms the surface rock over a considerable area in the center of the dome. 

The average diameter of this area is about 2 miles (3.2 kilometers), but its outline, as :may be 

seen from Plate II, is very irregular. This irregularity of outline, considered in connection 

with the def).nition of the bottom of the formation by the various areas of alaskite from which 

the latite has been stripped by erosion, and of the top by the residual patches of younger Sandstorm rhyolite which rest on the latite northeast of Banner Mountain, shows that the latite 

flow lies in a nearly horizontal position in the center of the dome, where it is· not generally of 

great thickness. The estimated maximum is about 300 feet (91 meters). 

Outside the main central area latite is exposed south of Columbia in consequence of the structural modifications of the dome brought about by the Columbia Mountain fault, as will be 

shown in subsequent pages. 

Following the latite as one of the concentric structural elements of the dome is the Sandstorm 

rhyolite and associated Kendall tuff. As shown in Plate II, the rhyolite is exposed in a numb_er 

of small irregular areas around the latite in the northwest half of the dome and occurs in small 

residual patches or outliers northeast of Banner Mountain. It is absent so far as known from 

the southeast half of the uplift. As in the case of the Vindicator rhyolite, it is not quite clear 

whether this absence is due chiefly to erosion or is a result of the original distribution of the 

flow. As will presently appear, however, there is reason to conclude that some erosion of the 

region took place after the eruption of the rhyolite and before the outbreak of andesitic lavas. 

Reference to Plate II will show that on the south side of Vindicator Mountain one small 

residual mass of Sandstorm rhyolite is almost in contact with t~e alaskite. This indicates 

that the alaskite mass of the mountain was not entirely buried by the latite, but stood out in 

part as an island in the volcanic flood. Otherwise there should everywhere be a wide band of 

latite separating exposures of the younger rhyolite from those of alaskite. 

It may appropriately be observed at this stage that in a volcanic sequence, such as is here 

dealt with, unconformities have not the same definiteness and significance as when they intervene between sedimentary rocks. In the latter case they usually record an elevation of the · 

area of sedimentation, a change of sea bottom into land, erosion of this land, subsequent submergence, and renewed deposition of sediments o:o the eroded surface. In the Goldfield region 

there is no evidence of general submergence at any time during the prelacustrine epoch. The 

area as a whole was a land surface, and erosion was undoubtedly active during the entire 

period of volcanic accumulation. Each flow as it was poured out was at once attacked by air,, 

rain, and streams. Such erosion was probably very uneven, and its results depended upon the 

character of the material erupted, the nature of the local topography, the length of time 

between eruptions, and probably other less obvious factors. In sedimentary rocks the existence of planes of stratification and the knowledge that originally these were nearly horizontal 

enables us to restore in imagination the surface initially exposed to erosion. No such restoration is possible in the case ·of the volcanic formations of Goldfield. We may not assume that 

the flows spread evenly over the whole district, that they were of uniform thickness, or that the 

topography at the close of each eruption was even approxin:iately a plain. It is as a rule 

impossible to say in how far the observable inequalities in the thickness and distribution of 

the various flows are due to original irregularity of deposit and how far to intervolcanic ero8ion. 

The thickness of the Sandstorm rhyolite is variable. In the central part of the area it 

is probably not over 100 feet (30 meters) thick, but west of the Columbia Mountain fault, in 

the vicinity of the Sandstorm mine, the formation, which here is apparently made up of a 
78 THE GEOLOGY AND ORE. D'EPOSITS OF GOLDFIELD, NEVADA. 

series of thin glassy flows, becomes considerably thicker. The workings of the Sandst'Jrm 

mine show that this rock extends to a depth · of 200 feet (61 meters) and is underlain by 

a~other 200 feet o{ Kendall tuff. The increased thickness of the Sandstorm rhyolite in this 

part of the district and its irregular intrusion by the closely following Morena rhyolite suggests 

that both eruptions broke through the pre-Tertiary floor in this part of the district. Consequently the bottom of the Sandstorm rhyolite north of Columbia Mountain may be very irregular, and the extrusive rock may pass in depth into facies not distinguishable from the Morena 

intrusive type. · 

The Morena rhyolite, whose intrusion closely followed in time the extravasation of the 

Sandstorm rhyolite, does not appear in the domical structure as displayed east of the Columbia 

Mountain ·fault. • 

The main mass of :Morena rhyolite that forms the northern spur of Columbia Mountain 

and the smaller bodies exposed in the vicinity of the Conqueror rriine clearly cut irregularly 

through the Sandstorm rhyolite and through the pre-Tertiary rocks. These intrusive bodies 

have been subjected to the same stresses that have produced the general domical structure 

of the 'district, but they have introduced by their intrusion local disturbances whose effects 

mask the more general tectonic relations. The same statement, as will presently be seen, 

applies also in less degree to a younger intrusive rock, the dacite. 

Although the contact between the two rocks is nowhere Clearly exposed, there is little 

doubt that the Milltown andesite normally overlies both the Sandstorm and Morena rhyolites. 

This shows, not only that the intrusive rhyolite was erupted before the andesite flows swept over 

the region, but that sufficient erosion must'have intervened to lay bare a rock, or a rock facies, 

that had solidified under some cover. · Additional evidence of such postrhyolitic erosion is 

afforded by the many places where the Sandstorm rhyolite has been cut out and the andesite 

rests directly upon the latite, as near Diamondfield and along the entire southeast side ofthe 

dome. The thickness of material removed in the course of this erosion can not be accurately 

determined, but there are reasons for supposing that it was not great. 

It has already been shown that prior to the outbreak of Tertiary volcanism the surface of 

the region was hummocky. The hills were neither high nor sharp, and the valleys were broad 

with gentle slopes. There was neither active erosion nor active deposition. After the latite 

flow had covered the region the surface was presumably mote nearly a plain than before. 

There is no reason to conclude that the addition of this mantle of volcanic rock greatly accentuated erosive processes, and no evidence has been found indicative of any trenching of the 

volcanic terrane by streams. 1 

Upon the latite, which probably underwent some local deformation at this time, was 

thrown out the Kendall tuff. This appears to have accumulated chiefly in basins or small 

valleys, and its deposition was immediately followed by the pouring out of the thin glassy 

flows of Sandstorm rhyolite, alternating in some places with small accumulations of tuff. The 

rhyolitic material probably accumulated to the greatest thickness near the vent or vents, which 

there is some reason to suppose lay north of the site of Columbia Mountain. Finally, the 

Morena rhyolite rose through fissures opened by earlier volcanic paroxysms and solidified as 

intrusive masses in the flows. There is nothing to indicate that the intrusive rock solidified 

under any other cover than the previously erupted Sandstorm rhyolite. 

Subsequent preandesitic erosion appears to have done little more than level off and carry 

away such rhyolitic accu1nulations as rose above the general level of the region. Possibly 

there was some local subsidence north of Columbia Mountain, which accounts for so much of 

the rhyolite being left in that part of the district, while elsewhere it was reduced to a thin layer 

or entirely removed. There is nothing to show that the postrhyolitic erosion was able at any 

point to cut deeply below the latite terrane upon which the rhyolite was erupted. If the region 

between the beginning of the rhyolitic eruptions and the beginning of the andesitic period had 

been deeply buried. it is improbable that erosion would have so nearly restored the general 

surface to its postlatite level and configuration. It seems reasonable to suppose, therefore, 

that the Morena rhyolite was intruded under a comparatively light load of extrusive (Sand-
GEOLOGIC STRUCTURE. 79 

storm) rhyolite, and that a very moderate erosion sufficed to level off the region to the gently 

undulating surface which was to receive the andesitic flows and tuffs. 

The distribution of the andesitic rocks has been described on pages 47 to 54. If the intrusive dacite be for the present disregarded, e andesite forms a broad ring, the outer annulus 

of the successive eruptive formations exposed in the truncated dome. As shown in Plate II, 

this band is of very uneven breadth, its in~er margin encroaching irregularly over the Sandstorm rhyolite and latite, and its outer border being determined by the still greater sinuosities 

of the edge of the overlapping Siebert formrution. Its shape is modified also by the Columbia 

Mountain fault. I 

· The Milltown andesite is the thickest of the eruptive formations entering into the structure 

of the dome. It is very difficult, however, o estimate this thickness, owing to the absence of 

any regular ·planes within the formation tlilat might be confidently taken as corresponding 

to the general dip of the whole. The only haft that has penetrated the andesite at a point 

where a direct section o{ the formation would throw light on its total thickness or general dip 

is the Yellow Tiger. The vertical section i~ this shaft gives 510 feet ( 155 meters) of andesite, 

which, as shown in Plate VIII, section F-F j, may correspond to an actual thickness of about 

600 feet ( 183 meters). The Milltown ande ite is certainly not a single flow, but is probably 

built up of several overlapping lava sheets,~ith a minor proportion of tuff and perhaps some 

intrusive andesite. In the few localities WI ere the composite character of the formation is 

shown the contacts between successive she ts are nearly horizontal. It is probable that the 

formation as a whole varies considerably in it dip at different-places, but has in general a centrifugal inclination with reference to the domica~ structure of about 10°. The thickness is roughly 

estimated at from 600 to 800 feet ( 183 to 244 meters). 

Th:e next tectonic element to be consi ered after the andesite is the dacite. This rock, 

while involved in the architecture of the d9me,. is so irregular in its occurrence as to obscure 

rather than to accentuate the structure of jWhich it is a part. The evidence of the intrusive 

relation of part of the dacite with referen9e to the andesite and older rocks is presented on 

page 58; it remains in this chapter to consider the form of . the intrusive masses and their 

relation to the general structure. 1 

The most important body of dacite fro:rh an economic point of view is that lying northeast 

of Goldfield and containing the principal nes of the district. Although the general form of 

the mass, particularly when considered with reference to the domical structure, leaves little 

room for doubt of its intrusive character, tp.ere are, unfor~unately, no exposures in which the 

relation of this body to the andesite is clearly displayed at any one locality. In most places 

the contact can be determined with an acc racy commensurate with the scale of the map (Pl. 

II), but the actual plane of separation bejeen the dacite and the rocks which it cuts is rarely 

visible or is obscured by alteration. The ass, as may be seen from-the geologic map, practically cuts across the andesite annulus fro east to west. It has the form of an irregular sheet .. 

The thickness of the dacite is least to the east, where the sheet. thins to an edge, and is 

greatest along a trough-like depression whibh extends from the vicinity of the Hazel-Goldfield. 

shaft. toward Florence Hill. (See fig. 2.) This depression (see also Pl. II; Pl. VIII, sections 

C-C' and D-D') is in the general line of prolongation of the fault southward, due allowance 

being made for the dip of the latter. Th~ depth of the bottom of the dacite along this line 

ranges from 685 feet ( 209 meters) at the Hazel-Goldfield mine, to 615· feet ( 187 meters) at the 

Clermont shaft. South of the Clermont sh ft the dacite has probably not yet been penetrated 

in its thickest part. West of this line thet bottom of the sheet in general rises at an average 

angle of about 30°, although as shown in ection C-C', Plate VIII, a part of the mass appears 

to extend as a dike to an indeterminate de th. It is possible that future exploration may not 

only establish this ab:yssal continuation bu may reveal other connections of the sheet with its 

deep-seated source. 

Along its southern boundary the dacit sheet ends with ·a steep irregular intrusive contact 

against the Milltown andesite. There is Iljothing to show that it does not extend indefinitely 

downward along at least the western part of this contact . . (See Pl. VIII, section G-G' .) 

--
80 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

That the under surface of the dacite is far from even is indicated by the data assembled 

in figure 2 and by the relation of the contact between this rock and the underlying formations 

south and southwest of Vindicator Mountain. The two deepest points yet found on the bottom 

of the dacite are, as already mentioned, at the Hazel-Goldfield shaft (685 feet or 209 meters) 

and at the Clermont shaft (615 feet or 187 meters). The Oddie shaft on the Combination 

Fraction claim has not penetrated through the dacite at 612 feet (187 meters), so that the 

thickest part of the sheet may be between this shaft and the Clermont. (S~e fig. 2.) Both 

east and west of this approximately north and south line, which may conveniently be referred 

to as the keel of the dacite mass, shafts pass out of the dacite at depths which, in a rough way, 

FRISCO I FJ\ CROOKS 

FJ D./SO C./30 1 0.40).140 

!! FIVE FRIENDS 

CONS. RED TOP 0!560 c:s60 + !! 0.300 C.300+ !!! KEWANAS 

MUSHETTFJ FJI HAZEL-GOLD IELD 

0.480 C.LJBO I 0.740 C.685 

1"1 LA~UNA RED TOP o . .1f0o C. 400+ 0.350 C.300:trl I I!! 

CHICAGOLVELVET 

0 .5261 C . 380 

I 

FJ MOHAWK4EDGE 

o. 700 c.l<fso 

MOHAWK-JUMBO : !! CLERMONT 

0 . 500 C.SOO+rl I 0.920 C.615 

I 

I 

0 1000 

N. 

2000 3000 feet 

I Line or maximum th/ckness or the dacite sheet 

I 

1:1 MOHAV\1K 

0.600 q450 CODD 0.500 C.400+ I FJ l!l ST.IVES 0.470 C.470+ 

rJ ODOlf£ 0.612 C. 612-tSIMBULL 

D.200 C.ISO±r:J 

FJ 

!! I COMBINATION rJ LIITTLE FLORENCE 

D. 380 c.zso ::1: I D. 600 c. ? 

MERGER 

o.aoo c.3t2 

I 

FIGURE 2.-Plan of the dacite mass near Goldfield, showing positions of shafts that penetrate it, their depths in feet (D), and the depths (C) at which they go into tae underlying rocks. 

vary inversely as the distance from the keel. There are, however, some notable irregularities, 

as is to be expected in an intrusive body. The Codd shaft on the St. I ves claim, for example, 

is in latite at 500 feet (152 meters) and is said to have gone through the dacite at about 400 

feet (122 meters) or less. The St. Ives shaft, a short distance farther east and 470 feet (143 

meters) deep, is still in dacite. A little farther east, the new G0ldfield Merger shaft, according 

to a letter .from Mr. II. P. Henderson, passes out of the dacite at 412 feet (125 meters). The 

collar of the St. Ives shaft, it is true, is about 15 feet (4.6 meters) higher than that of the Codd 

shaft and 25 feet (7.6 meters) higher than that of the Merger shaft. When these corrections 
GEOLOGIC STRUCTURE. 81 

are applied, however, the data furnished .by the three shafts show that the bottom of the dacite 

does not rise regularly to the east. 

Undoubtedly much remains to be learned regarding the configUJration of the under surface 

of the dacite. This has been reached now in over a score of shafts, but these are not all so 

placed as to afford the most geological information. In most plac s the rocks at the contact 

are soft and the shafts closely lagged, so that for information concerning the change of formation 

the geologist must depend upon the memories and observations of those who performed the 

work of sinking; elsewhere the rocks are mineralized, as in parts of the M"ohawk and Mushett 

mines, and their original character is thereby obscured. Some of the movements that have 

disturbed the rocks in this part of the district (in a mariner and to an extent presently to be 

described) have affected the under contact of the dacite and probably in part caused the local 

softening which is its prevailing characteristic. The soft, gouge-like material ("mushy stuff") 

in the Goldfield Merger shaft is reported to be about 12 feet (3.6 meters) thick. 

Without much question some of the irregularity in the lower ~urface of the dacite is due 

to a step-like structure produced by faulting. It is not possible at present to identify any of 

these faults at the surface or to trace· them from point to point underground . 

. East of the Red Top mine a tongu·e-like area of Milltown andesite is shown on Plate II and 

figur<3 2 as extending into the dacite toward the Velvet mine. The relations of the rocks are · 

here somewhat obscure. The andesite apparently underlies . the dacite in part, but is here 

rather thin and is underlain by latite. Several shafts, including the Alta, 418 ·feet deep in 1908, 

go through the andesite into latite, although the depth of the co:o.tact could not be ascertained. 

The Chicago shaft, just west of the Alta, is in dacite to a depth of 380 feet. The contact of 

the dacite with the·l\1illtown andesite and the latite must at this place therefore be very steep. 

It is not exposed and it is not known whether it is an intr11sive contact or a fault contact. Below 

380 feet the Chicago shaft went through about 30 feet of soft andesite or andesitic tuff and then 

into latite, which was the rock in the sump (410 feet) in July, 1908. . 

As regards the original upper surface of the dacite sheet little information is available. 

The small area of Milltown andesite on the hill above the 1\rfohawk mine is probably a remnant 

of the original cover of the laccolithic intrusion. This andesite is soft and decomposed, and 

since it was mapped in 1905 its surface has been largely covered up by dumps from the mines. 

It is evidently thin as it does not appear.in the present underground workings. 

Of the shapes of the other masses of dacite represented in Plate II little more is known 

than can be learned from a study of the mapped outlines, with reference to the topography. 

That they are for the most part very irregular in form is evident. Such irregularity, together 

with the distribution of the masses at variance with the rough concentric structure of the dome 

as a whole, is regarded as sufficient to establish the intrusive character of the dacite. Confirmatory evidence is supplied at a locality 1 i miles ea.st of McLaughlin's well, practically on the 

line of section 0-C', Plate VIII, where the dacite may be seen in close igneous contact with 

andesite, both rocks being comparatively fresh (see p. 58); and at various points along the . 

southern contact, as shown on page 59. · 

Although the dacite is for the most part ·unquestionably intrusive, there are some indications that the intrusion took place within a very moderate distance of the then existing surface. 

At the locality just mentioned the dacite not only shows glassy facies near the contact, but in 

some places exhibits flowage structure. Moreover, near Tognoni Springs the dacite, as previously 

shown, passes into a flow, showing that the lava in this part of the district actually broke 

through its thin cover and welled over the surface. Evidence of the same kind as that adduced 

in relation to the Morena rhyolite also supports the, conclusion that the dacite intrusion was not 

deep-seated. The dacite is older than the Siebert formation, and so could not have served 

as cover. The ·only rocks in the district w;hich can be supposed to have played this passive 

part are the andesite and older rocks cut by the dacite, and the dacite vitrophyre exposed in 

the southern part of the district. As stated on page 64, this dacite vitrophyre is supposed 

79145-No. 66-09-6 
82 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

to have been erupted at nearly the same time as the dacite intrusion. It undoubtedly covered a considerable part of the district north of its present exposures, and may possibly have 

· constituted a blanket of extrusive material under which the dacite solidified as superficial 

intrusions from the same magma reservoir that had supplied the vitrophyre. 

The important dislocation which has been called the Columbia Mountain fault demands 

some consideration at this stage, particularly as regards its relation to the dacite intrusion. 

The fault, as shown in Plate II, has been traced from a point nearly east of Kendall Mountain 

to the eastern end of the town of Columbia, a distance of 2 rniles. It dips to the east and has 

a normal throw, the Milltown andesite being relatively dropped against the older rhyolites 

and pre-Tertiary rocks of Columbia Mountain. 

The structural effect of the fault is . the uplift of the rocks west of it relatively to those 

east of it. As a consequence of the general erosion of the dome these locally uplifted older 

rocks, including the Cambrian sediments, alaskite, and rhyolites of Columbia Mountain, now 

appear at the surface, whereas in other parts of the district equally distant from the center 

of the dome they are buried under younger formations. The fault is very poorly exposed. 

It is followed by .an inclined shaft at the Conqueror mine, where the dip is from 20° to 25°. 

The shaly Sandstorm rhyolite which forms the foot wall is much disturbed and much of the 

Surface 

0 10 20 30 40 50 FEET 

andesite of the hanging 

wall is crushed to a 

soft gouge. Some of the 

crushed material contains 

pyrite and is said to yield 

assays up to $12 per ton. 

A crosscut from the bottom of the 55-foot vertical shaft of the Conqueror mine affords the 

section shown in figure 

3, where movement along 

the fault plane is recorded 

by a tough clay gouge and 

1nuch crushing of the andesite. The sarne gouge 

is reached in a prospect 

FIGURE 3.-Section shaft sunk through the across the Columbia Mountain fault at the Conqueror mine. , andesite just south of the 

Conqueror workings. From this shaft southward there are no exposures of the fault plane 

until the southec,'"tern slope of Columbia Mountain is reached. Here the Columbia Mountain 

No. 1 tunnel cuts through the fault plane, which separates crushed, fissured, and much-altered 

dacite from Cambrian sediments that are generally shattered and also show some fissuring 

approximately parallel with ·the main fault. The principal plane of dislocation appears to dip 

45° E. South of the tunnel and north of the water tank the outcrop of the fault passes through 

a saddle, and on the south slope of the mountain it coincides with a little ravine eroded in 

the soft, crushed material of the fault zone. A crosscut from the 200-foot level of the Booth 

shaft, just east of this ravine, is said to reach the fault, but this shaft was closed at the time 

of visit in 1908. 

The most southerly underground exposure of the fault is in the workings of the Consolidated Red 'fop Leasing Company. This shaft. is about 250 feet east of the outcrop of the 

fault, which is rather indistinctly exposed in a railway cut. The bottom of the shaft, 300 feet 

deep, is in soft crushed dacite. A crosscut to the west, 30 feet in length, is in Cambrian shale 

at the face, and from this point a drift has been run south along the fault. This drift is all in 

soft, much-disturbed ground, shale and Kendall tuff being mingled in great confusion. The 
GEOLOGIC/ STRUCTURE 83 

material is apparently all within the fault zone and it is doubtful whether the real foot wall has 

been reached. The position of the fault on this level taken in connection with the exposure in 

the railway cut gives a dip of 55° E. · 

When the preliminary report on the district was prepared, the most reasonable explanation of the obscure structure south of Columbia appeared to be the postulation of a transverse 

northwest-southeast fault which was supposed to offset the main fault. The latter was thought 

to continue southward beyond this offset past the January mine and to constitute the boundary 

between dacite on the east and latite on the west. Thorough revision of the geologic mapping 

south of Columbia Mountain in 1908, aided by the numerous shafts sunk in this part of the 

district since 1905, many of which gave definite information where previously the kind of rock 

beneath the mantle of surficial material could only be guessed, showed that the original interpretation was erroneous. The hypothesis of a transverse fault had t~ be abandoned. Moreover, as shown on pages 58 to 59, the evidence 'bearing upon the relation of the dacite to the 

. latite west of it, while not entirely conclusive, is more accordant with the supposition of an 

intrusive contact modified by many local fault slips than of juxtaposition e:tfected primarily 

and chiefly by faulting. 

The throw of the Columbia Mountain fault can not be accurately determined. It may 

amount to 400 to 500 feet (122 to 152 meters). (See Pl. VIII, section A-A'.) 

It was supposed at one stage of the investigation that the Columbia Mountain fault was 

younger than the dacite, but the evidence now available points to a different conclusion. Reference to the geologic map (Plate II) shows the fault as ending about 600 feet (183 meters) northwest of the Red Top mine. At this place the dacite passes westward across the line of dislocation. South of the end of the fault the dacite is much fissured and the great ore bodies of the 

Red Top, Mohawk, Combination, Jumbo, and Florence mines occupy a zone of great disturbance 

which lies in the general path of the Columbia Mountain fault. Throughout this entire zone 

the dacite is traversed by an extraordinary number of fissures which carry soft gouge and which 

in the aggregate undoubtedly record much movement. So numerous are these slips, so varied 

in trend, and so frequently do individual fissures exhibit unexpected departures from .a straight 

course'that it is at present impossible to group them systematically or to identify any particular 

exposures as parts of a single dominant fault zone. The most that can be said is that the more 

important ones have a general north to north-northwest course. Can this fissuring record the 

whole of the movement represented by the Columbia Mountain fault? I believe not. It is 

too .dispersed and irregular. There is at present no evidence that the dacite sheet as a whole 

has been displaced to anything like the extent it would have been had it been affected by the 

total movement represented by the Columbi~ :Mountain fault. The hypotheses suggested as 

best accounting for the facts at present known are: (1) That the dacite was intruded after the 

main movement along the Columbia Mountain fault had taken place; (2) that the intruded 

magma to some extent followed the fault, possibly in some places coming up along it, and 

spread out where opportunity offered into sheetlike or laccolithic form; (3) that the Columbia 

Mountain fault continued, after the intrusion, to be a line of structural weakness and movement; and (4) that such renewed movements along the fault produced in the dacite, lying 

athwart the path of the dislocation, stresses which were relieved by complex fissuring of the 

brittle mass. Other stresses probably also contributed to this result, but it is believed that 

this revival of movement along the Columbia :Mountain fault had a very important part in the 

fissuring and mineralization of the remarkable little area which has produced nearly all the 

gold thus far mined in the district. 

As stated on page 39, the boundary between the Kendall tuff and the latite, just south of 

. Columbia, is probably a fault. No geologic examination has been made of this contact, as 

it is not actually exposed at the surface, and the shafts in its vicinity had all been abandoned 

in 190R. This fault, like the Columbia Mountain fault, apparently ends at the dacite and is 

supposed to be older than that rock. South of it the Siebert formation laps over the prelacustrine rocks and little is known of their structure. Minor faults are certainly abundant in . 

this part of the area and it is not improbable that future development, such as is planned by 
84 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

the White Rock :Mining Company, may establish the existence of structurally important dislocations now concealed by t}le Siebert formation. 

The faults in the vicinity of" Vindicator Mountain are perhaps of the same. age as the Columbia 

Mountain fault, but there is nothing to show that they may not be considerably older or younger. 

They are normal faults of moderate displacement and are not very well exposed. There are 

1,1ndoubtedly other faults in the district that have not been mapped. Those only are shown for 

which there is satisfactory evidence. There are many places where structural relations might 

be explained by hypothetical faults drawn where exposures are wanting or where the general 

disturbance and alteration admit the possibility of a fault while at the same time they prevent 

any definite proof or disproof of its presence. 

Like the andesite, Sandstorm rhyolite, latite, and Vindicator rhyolite, the dacite vitrophyre 

· is one of the annular elements of the domical str:ucture, though apparently not a complete one. 

As exposed in the southern part of the district, it laps at a low angle over the andesite and is 

overlapped in turn by Meda rhyolite, andesite breccia, and Siebert formation. Its thickness 

is not accurately determinable, but is estimated at about 400 feet. If the dacite vitrophyre 

ever extended over the whole area now occupied by the Goldfield dome it has been eroded away 

from the northwestern half, where the Siebert formation rests directly upon Milltown andesite 

or older rocks. 

The youngest rocks that participated in the domical uplift are the sediments of the Siebert 

formation and the volcanic flows intercalated with them, particularly the Mira basalt. The 

Siebert beds are prevailingly soft and are readily eroded, so that in most places they are covered 

by detritus which has been derived in large part from the underlying formation. Consequently 

the detailed structure of the beds is generally concealed or is very 0 bscurely shown. 

Along the northern border of the district the Siebert beds show little disturbance other than 

a gentle tilt away from the center of the dome. In some places, as north of McMahon Ridge, , 

the erosion surface upon which the sediments accumulated appears to have been fairly even. 

In other places, as in the northeastern corner of the district, tuffaceous sands and beds of pumice 

seem to have accumulated in hollows amid hills. It is impossible, however, to distinguish with 

certainty between prelacustrine irregularities of surface and possible local deformation connected 

with postlacustrine basaltic outflows. 

Along the western border of the district, north of Goldfield, the Siebert rocks are too poorly 

exposed to throw much light on their structure. That they were laid down upon an unevenly 

eroded surface is jndicated by the character of the eastern boundary of the sediments as they lap 

up over the older volcanic rocks, and by the andesitic hill which rises through the lacustrine 

deposits near the Tonopah and Goldfield Railroad. · 

Southeast of Goldfield the Siebert beds are well exposed in the bluffs at the edge of the basalti~ 

mesa, where the prevailing dip is about 18° W. It is certain that in this part of the field the 

Siebert formation, as represented in sections D-D' and E-E', Plate VIII, has been thrown into 

open folds. Existing exposures, however, are insufficient to furnish the key to the details of 

this folding. If the former connection between the residual masses of :Mira basalt south of 

l\1yers Mountain and the main part of the intercalated flow south of Goldfield were restored, 

the whole would form a buckled sheet nearly horizontal or with a low dip to the northwest 

along its northeastern margin, but with a dip of about 18° W. where the Mira basalt passes 

under. the mesa. (See Pl. VIII, section E-E'.) 

On the east side of the Goldfield dome the annulus of Siebert beds is not complete. The 

andesite and dacite extend for 5 or 6 miles beyond the boundary of the area here described, 

and Ball's .map (see Pl. IV) shows that the Siebert formation, if present, is covered by Quaternary deposits which overlap the Tertiary lavas. 

With the post-Siebert deformation the Goldfield dome came into existence. Of the stresses 

which produced the . structure practically nothing is known. Was the region gently arched 

by lateral centripetal pressure or was the ascensional force mainly a direct vertical upthrust.? 

Were the rocks actually elevated or did the central part of the dome merely lag behind the 

rest of the region in a general subsidence? These are questions upon which some speculation 
GEOLOGIC STRUCTURE. 85 

is permissible provided the lack of real knowledge be not forgotten. we do know that throughout Tertiary time the entire region was the theater of volcaniJ activity and of crustal disturbances, the present results of . which differ greatly in characte i!f localities not necessarily far 

apart. The elaborate faulting described by Spurr at Tonopap, for example, has no counterpart in the structure at Goldfield, and this, in turn, has little inJ common with the faulting in the 

Bullfrog district. We may conclude with some reason that di, strophism or crustal movements 

and volcanism were genetically connected, and, with somewh,t 1ess confidence, that in general 

some subsidence followed the extensive transfer of lava from f'Ubcrustal regions to the earth's 

surface. As different lavas were erupted at different times in 8-ifferent parts of the region such 

subsidence, if it occurred, must have been intermittent and an scarcely be conceived of as 

proceeding at an equal rate over the entire tract affected by Tertiary volcanism. While one 

area was sinking an adjoining area might be quiescent or evep. rising; between the two would 

be developed stresses which might find relief in complex fau1tirig. Thus the development of 

domical and other flexures and of local fields of faulting is in a 4eneral way susceptible of genetic 

correlation with volcanicity. The actual mechanism in each case, however, is entirely concealed. 

After the Goldfield region had been domed, erosion appea~s to have reduced it to a surface 

of comparatively low reli(/f. This was partly covered by the postla.custrine flows, of which 

those of olivine basalt are most important. Subsequent erosion, extending to the present, 

has cut through and ·carried away the greater part of these flows, leaving the remnants as tabular cappings to buttes and mesas in outlying parts of the disbict. These remnants, as may 

be seen from Plate II, occur at various elevations and have perpaps suffered some changes in 

altitude by crustal warping of the region. The observed differences in elevation of the 

bases of the various remnants of the basaltic flows, however. arej not too great to be accounted 

for by the flowage of the lava over an originally uneven. surface. . . 

That son1e deformation has taken place subsequent to the basalt eruptions is shown by 

minor faulting southwest of Goldfield. The small hill at the mouth of Pozo Canyon is apparently part of a triangular fault block in which some of the rhyolite and basalt of the ·mesa have 

been dropped into the Siebert beds. Other minor faults are shown which slightly displace 

·the rocks capping the mesa. (See Pl. ·II.) . 

These faults are comparable in age and character with the post-Siebert faults so abundant 

at Tonopah. Dislocations of this epoch, however, are of very slight structural importance 

at Goldfield, although perhaps not entirely confined to the one locality southwest of town. 

Faults of similarly small throw occurring in the older volcanic • formations in the central part 

of the dome might escape recognition. 
CHAPTER IX. 

GEOLOGIC HISTORY AND CORRELATION. 

INTRODUCTION. 

Since the historical sequence has served in the preceding chapters as a framework for the 

orderly presentation of lithologic and structural description, the reader already has an insight 

into the geologic development of the Goldfield district. It is the purpose of the present 

chapter, however, to narrate the series of geologic events with greater clearness and with more 

regard to "their broader relationships than was possible while the attention has been occupied 

with descriptive details-with the slow inductive steps that have led, as it were, to the crest of 

an eminence whence the whole region previously traversed may be comprehensively viewed. 

It is believed that this purpose will be served most directly by first summarizing the local 

geologic history with as little reference as p~ssible t9 regional correlatior;. With the sequence 

of local events well in mind, the relations of the Goldfield. rocks to those of the surrounding 

region may then be considered, and finally such conclusions will be drawn as are permissible 

regarding the Tertiary chronology and the succession of the lavas in this part of the Great 

Basin. 

Such is the general· plan of this chapter. The pre-Tertiary rocks, however, have so little 

prominence in the part of the geologic record with which this paper has chiefly to do, that it 

seems best to depart, with respect to them, from a rigidly systematic treatment and to combine 

some suggestions <;>f correlation with the local narrative: This early clears the way for the concentration of an undivided attention upon the Tertiary. 

LOCAL GEOLOGIC HISTORY. 

BEFORE TERTIARY TIME. 

The records of what took place prior to the opening of Tertiary time are. fragmentary. 

During the early part of the Paleozoic, probably in the Cambrian, thin-bedded calcareous and 

quartzose sediments were laid down upon a surface of still older rocks. Of the pre-Cambrian 

surface no vestige is visible in the Goldfield district at the present time. Moreover, the reconnaissance of S. H. Ball a over a region more than 8,500 square miles (22,100 square kilometers) 

in extent, lying mostly south and east of Goldfield, has revealed no rocks certainly older than 

the Cambrian. The nearest pre-Cambrian rocks shown by J. E. Spurr on his earlier reconnaissance mapb are at the south end of the Kingston Range, in California, 150 miles (241 kilometers) 

south-southeast from Goldfield and in the Kern Mountains and Snake Range, 200 miles (322 

kilometers) to the northeast of the district. Ball c notes that the Cambrian Prospect Mountain 

quartzite in the Specter Range, about 95 miles (153 kilometers) southeast of Goldfield, contains pebbles of sedimentary rock and of granite, thus giving a clue to the local character of the 

vanished pre-Cam brian terrane. 

The masses of Cambrian rocks exposed in the Goldfield district on Columbia and Vindicator 

Mountains are mere fragments which probably belong in the upper division of the lower Cambrian as mapped by Ball-the Prospect Mountain limestone of Arnold Hague,d renamed by 

86 

a A geologic reconnaissance in southwestern Nevada and eastern California: Bull. U.S. Geol. Survey No. 308, 1907. 

b Descriptive geology of Nevada south of the fortieth parallel: Bull. U.S. Geol. Survey No. 208, 2d ed., 1905, Pl. I. cOp. cit., p. 38. 

d Geology of the Eureka district, Nevada: Mon. U. S. Geol. Survey, vol. 20, 1892, p. 36. 
LOCAL GEOLOGIC HISTORY. 87 

Walcott a the Eldorado limestone. Rocks belonging to this division, according to Ball/ are 

extensively exposed in hills to the north, west, and south of the Goldfield district and contain a 

lower shale member at least 1,000 feet (305 meters) thick, an overlying limestone several thousand feet thick, and probably a second shale member. The Goldfield masses are thought to represent remnants of the thick lower shaly member. I 

Although it is known that Ordovician, Silurian, and Carboniferous beds were deposited in 

. southwestern Nevada, no representatives of these periods occur within the Goldfield district, 

nor, so far as known, within a radius of 40 to 50 miles (64 to 80 kilometers). The history of 

Paleozoic time subsequent to the Cambrian is locally blank. Presumably there was deposition, 

the products of which were afterwards swept -away by erosion. The first authentic record 

following that of Cambrian deposition is supplied by the intrusion of the alaskite now exposed 

in the central part of the Goldfield dome. The geologic date of this intrusion, · which greatly 

disrupted the Cambrian beds, is not certainly known, but, as shown on page 35, the work of 

King and later observers affords a strong suggestion that it took place at the close of the Jurassic 

or beginning of the Cretaceous, being thus generally contemporaneous with the main granitic 

intrusions of the Sierra Nevada. 

As the alaskite has all the characteristics of a deep-seated or plutonic intrusive, it may be 

concluded that it solidified under a considerable thickness of other rocks. The undoubted 

deformation of the Cambrian rocks at the time of intrusion suggests that a mountain range may 

have come into existence in the Goldfield region at the opening of the Cretaceous. 

Clarence King,c thirty years ago, noted the absence of Cretaceous deposits from the section 

of the Great Basin lying between the ''V asatch and Sierra Nevada ranges, and subsequent work 

has all tended to support the conclusion that throughout this long period that part at least of 

the Great Basin included within the boundaries of Nevada was a land mass undergoing erosion.d 

The results of Spurr's and Ball's reconnaissances, as well as the local history recorded in the 

rocks at Goldfield, accord with this generalization. During the Cretaceous the region was · . 

greatly eroded. Whatever mountains may have existed on the site of Goldfield were destroyed, 

the once deeply buried alaskite 'was exposed over broad areas, and the country was characterized at the end of the period by a topography of low rounded hills, which swelled above rolling 

plains or merged into open, gently sloping valleys. There is no evidence of any extensive 

accumulation of soil or of any vigorous growth of vegetation upon this pre-Tertiary surface. 

So far as appears from the few exposures available, the slopes were of rock, here and there 

thinly veneered with stony detritus derived mainly from the metamorphosed Cambrian shales. 

The landscape at the close of the Cretaceous, could one have seen it, must have been expressive 

of long-continued crustal stability and of the waning power of denudation concomitant with 

the reduction of relief. It could have afforded little suggestibn of the next scene in the geologic 

drama. 

Although erosion reduced what is now the Goldfield district to comparatively low relief, 

Ball's work shows that no extensive peneplanation was effected over the surrounding region. 

His statement e is: 

A long period of erosion, extending at least to Eocene time, followed the post-Jurassic folding and consequent 

mountain building. This period was probably one of heavy rainfall and large rivers. No estimate can be formed of 

the amount of erosion, but it was sufficient to remove from the granite the covering beneath which it solidified. Notwithstanding the length of this erosion period, no peneplain was formed. From this it is inferred that the area was 

· t>ubjected to successive uplift'> while being eroded. \Vhere exposed beneath the oldest Tertiary formation, the Paleo- · 

zoic rocks appear to have been eroded into mountain ranges, many of which have a north-south extension. Some of 

these mountains of Paleozoic rocks-for example, the Kawich Range-were fully as higq and rugged as the present 

ranges. 

a Walcott, C. D., Cambrian geology and paleontology. No.5: Cambrian sections of.the Cordilleran area. Smithsonian Miscell. Col!. No. 1812, 

Washington, 1908, p. 184. 

b Op. cit., pp. 51-52. 

cU. S. Geol. Expl. 40th, vol. 1, Systematic geology, 1878, pp. 296-297. 

d See also Chamberlin, T. C., and Salisbury, R. D., Geology, vol. 3, 1906, figS. 379 and 388. 

e Qp. cit., p. 4.0. 
88 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Farther north, in the 'Humboldt region, G. D. Louderback a found that the post-Jurassic 

erosion resulted in a topography of very low relief, approaching a peneplain, and comparable,' 

apparently, with that developed in the Goldfield district. · 

TERTIARY PR~LACUSTRINE EPOCH. 

At a time which can not be definitely fixed, but which may provisionally be identified 

with the Eocene, lavas broke through the eroded surface just described, and their appearance 

marked the beginning of a period of active volcanism, which continued through the Tertiary. 

The first volcanic eruption in the Goldfield district is represented by the Vindicator rhyolite. 

This flow, as described on page 37, is expo~ed on the slopes of Vindicator Mountain and forms 

the summit of Columbia Mountain. Its original extent is unknown. It does not ,appear on 

the alaskite exposed near Banner Mountain, but its absence from that locality may be due to 

erosion prior·to the next volcanic outburst. 

The Vindicator rhyolite was followed in the Goldfield district by one or more flows of 

latite, which probably covered the older rocks completely. The vents whence the latite issued 

are entirely unknown. The prevalent alteration of the rock interferes with a complete determina~ion of its original character and renders comparison with rocks in neighboring . districts 

uncertain. 

There is, within the Goldfield district, no definite evidence of erosion of the latite prior to 

the succeeding eruptions. Ball, b however, reports an erosion unconformity in the Kawich, 

Amargosa, and Cactus ranges, in the Bullfrog Hills,. and in the Shoshone Mountains, c between 

rocks supposed to be the equivalent of the latite. and subsequent flows. In general accord with 

the views of Spurr, d he regards this unconformity as marking the division between the Eocene 

and Miocene, thus placing the Sandstorm and Morena rhyolites and the Milltown andesite in 

the Miocene. The question whether they belong there will be considered later. 

Following the latite·, with perhaps an interval of erosion, came the eruption of the Kendall 

tuff and Sandstorm rhyolite. e The tuff and the character of the rhyolite indicate the proximity 

of a local center of explosive eruptions which it is thought lay just north of the site of Columbia 

Mountain. Beneath the volcanic pile which probably rose in this part of the district were 

intruded the masses of Morena rhyolite and the solidification of these brought to a close the 

second epoch of rhyolitic eruptions. As described on page 78, erosion appears to have attacked 

with energy the volcanic accumulations and reduced them to such an extent that the intrusive 

Morena rhyolite was laid bare. 

The Milltown andesite flows which, with some tuff and a local outpouring of basalt, record 

the next volcanic disturbance not only are one of the most important formations in the 

Goldfield district but, as Ball's map shows, are part of the largest area of such rocks in the 

entire region covered by his reconnaissance. Their distribution suggests that these lavas were 

erupted from vents within the tract now corresponding to t4e Goldfield Hills. The andesites 

of Goldfield constitute a volcanic complex in which biotitic hornblendic and pyroxenic 

andesites are inextricably involved, the connection in many places being apparently through 

an actual gradation of one variety into another. 

After the cessation of the andesitic eruptions the series of ~avas was faulted and was 

invaded by dacitic magma. It is probable that erosion had already t>egun to attack the andesites before the intrusion of the dacite, but of this there is no clear evidence, and the two . 

periods ,of eruption were probably separated by an interval of time geologically brief. The 

reasons for supposing. that the dacite was a comparatively superficial intrusion which passed 

into extrusive flows to the eastward have been given on page 81. It has also been suggested 

(p. 64), although not demonstrated, that the dacite vitrophyre also represents a part of the 

dacite mag~a which, perhaps a little later, broke through the thin cover of andesite and 

a Basin range structure of the Humboldt region: Bull. Geol. Soc. America, vol. 15, 1904, pp. 307, 337. 

bOp. cit., pp. 32-33. 

c A small group of hills east of the Bullfrog district, in latitude 37° ; not the Shoshone Range of the Fortieth Parallel reports. 

d Succession and relation of lavas in the Great Basin region. Jour. Geology, vol. 8, 1900, p. 637. 

e On Ball's reconnaissance map the areas of Sandstorm and Morena rhyolite north of Columbia are colored as ;, middle Miocene rhyolite, ' ' which would make them later than the andesite and dacite of the Goldfield district. This is doubtless a mere oversight in the reproduction of the map. 
LOCAL GEOLOGIC HISTORY. 89 

poured over the surface as lava flows. There were also minor contemporaneous eruptions 

of andesite, for flows of this rock ( Chispa andesite) are associated with the flows of dacite 

vitrophyre in the southern part of the district. 

Next came the eruption of the Meda rhyolite, followed probably by the intrusion of the 

andesitic dikes whieh cut the dacite vitrophyre in the southern part of the district and whieh 

are provisionally. correlated with the eruption of the andesitic l;>reccia exposed at the southern 

edge of the mapped area. 

Whether there was any eonsiderable erosion of the daeite and earlier voleanic rocks before 

the initiation of the lacustrine conditions next to be deseribed is not dearly shown in the 

Goldfield district. 

LACUSTRINE EPOCH. 

Dp to the stage in the geologic history now reached there has been no indieation that the 

Goldfield district was at any time during the Tertiary an area of sedimentation. Erosion 

was presumably more or less aetive, but its products were either carried to the sea, whieh is 

known to have extended in Eoeene time into the Mohave Desert region,a or were deposited in 

lakes outside of the Goldfield area. 

After the daeitie eruptions, however, most of the area now known as the" Goldfield diktrict" 

was submerged beneath the waters of a lake. This body of water was no local feature, but, as 

will later be shown, probably eovered a large part of western Nevada and owed its existenee to 

conditions that changed the aspect of a wide region. Sinee the laeustral sediments at Goldfield attain a thiekness of probably 1,000 feet (305 meters), the lake was in all likelihood deep, 

· although to some extent deposition and submergenee may have gone on together. On the 

other hand, the charaeter of the beds indieates that they were laid down at no great distance 

from land, and some of them may be regarded as shore deposits. The inferenee is that the 

submerged topography was of strong relief. The lake probably possessed a deeply indented 

shore line and was diversified by numerous rugged islands and peninsulas. , 1

· 

There can be little doubt that on some of the mountainous islands and about the shores 

of the lake volcanoes were in intermittent eruption. Clouds of siliceous voleanie dust m11st at 

times have swept over the ruffled surfaee of this inland sea, and pumice either fell into the 

water or was brought down by streams from the voleanic slopes to drift about, to gaJther in 

sheltered bays, and finally to subside in a water-logged eondition to the bottom. Oecasionally 

flows of lava appear to have entered the lake and spread over part of the sediments previously 

. deposited on its bottom. These were ehiefly thin sheets of rhyolite, but at one time there was 

an important flow of quartz-bearing basalt. Throughout this epoch erosion was at~acking with energy the loose volcanic material supplied to the land. by the eruptions and was cutting 

also into the older rocks. Great quantities of sedimentary material were thus earried into the 

lake to mingl_e with an~ alternate with the produets of ash showers and the layers of Jdiatom 

frustules, wh1le coarse 1mperfeetly rounded fragments were dropped near shore by torrents 

which .rushed down the mountain sides. 

The prevalenee of diatomaeeous deposits in the Siebert formation shows that the lake was 

fresh throughout most of its existence. The beds exposed· in the distriet afford no suggestion 

of deposition under saline eonditions. 

Finally, through changes that were associated with, if not produced by, orographic. movements, the lake. was drained, its sediments were folded, perhaps faulted, and the doldfield 

dome eame into existenee. 

POSTLACUSTRINE HISTORY. 

With the disappearanee of the lake waters erosion began to attack the sediments, and soon 

stripped them away from part of the domical uplift, which, indeed, they may never have 

entirely covered. The final result of this period ·of denudation appears to have been the reduction of the region to .a surface of low relief, with at least some local peneplanation, as is shown 

a See Arnold, Ralph, and Strong, A. M., Some crystalline rocks of the San Gabriel Mountains, California: Bull. Geol. Soc. America, 1

vol.16, 1905, 

· p. 188, footnote. Apparently the first recognition of the Eocene age of these rocks was by W. P. Blake in the Pacific Railroad Reports, vol. 5, 

1856, map III. 
90 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

by the manner in which the ho.rizontallava flows of the mesa southwest of Goldfield lie upon 

the smoothly truncated edges of the old lake beds (Siebert formation). The accumulation of 

the fluviatile Pozo formation belongs to this period of erosion, which waS' followed by a renewal 

of volcanic activity, recorded by the two lava flows composing the Spearhead rhyolite. 

Overlying the Spearhead rhyolite is the Rabbit Spring formation, consisting of rhyolitic 

sandstone and volcanic conglomerate, with a total thickness of about 15 feet (4.5 meters). 

This .deposit may possibly have been laid down in a shallow transient lake, but the evidence 

for a return of lacustral conditions is far from conclusive. The deposit probably represents 

the action of shallow streams, which spread over the nearly horizontal surface of the lava flow. 

Whatever the origin of the Rabbit Spring formation, the time occupied in its deposition was 

brief, and the sed_imentary material was soon covered by the Malpais basalt. 

-------------.~~~~~------------------------------------ 1111 

I 

Malpais basalt. m r1111 

Ratlbit Spring formation. Plioeene! 1--::---::---=--:--,.:::-~,_ -----'------------------------- · · ,_: · v 1- ._.v v 7 v "- v -- I'.., ... ...:. ,... 7 v 11 <:: < 1\ 1 11 \ I-,Si':'pe=:a:-:<rh;-;:-e=ad=rhc::-y::-ol_it_e. ________________ -----'-------- ..J /' ~.; I'..., I' 1' }' .11 -z_ 7 ..., r 

1 ____________ 1 _ _:P_:::o::: zo:....:t:.:.·o:.:rm:::a:.:ti:.:.o.:::n·:__ _ ___:_ _____________ ------------ ~o~~tt ; · ... . :. ::. · .. :. 

Unconformity. 

Unconformity. 

•••••• 

• o I o * o 

0 • • 

Siebert formation. .... · ......... •. 

. . .. .. ........ . . . . . . . . . . . . . · ... · .·.·.·. Mira basalt. · 1ir · · · · · · 

Miocene! • ••• 0 •••••• • •• 

. . . ·.· ," .·.· .· . .. .. . ... ·.· .· .·.·. · . . • 

. • 

. • 

. • 

. • 

. 0 • • • 

. . . . . . . . . . . . . . . . . . . . . . . Siebert formation. 

Meda rhyolite overlapped · . . . • . . • • · · · Unconformity. t:..e. lY--=.acncc..::._ de:.;:.sJ:..:.· te.:__l__:_ w_::_ ec:..:. ·c-'-ia-'-. ----·--------- /\ v I" 11 .., ':'·" ;,·.4·.;:v:.,,. 

Eocene! 

Dacite vitrophyre. +++++++++ 

+++++++++ _..c_:C_h_is-'-'p-a_a_n_de_si_te_. ____________ ___________ · '~-' -:..-~~· ... -~~ ~-)~~..'~,,-... •~~-);-; 

+++++++ 

1-------------------------- + + + + + + + + + + +~,' \I I' (_I_:/-\-..._,, I -

Dacite vitrophyre. 

Milltown andesite and Intrusive dacite. 

1\lt/ -...;,,,.-{ 

, ..... , ...... __. ...... '-"'- 1,- \ ,,,;, -,'>'1 -I.... , I 1 I 1--/ '; ...... /,,..,-_ 

~ + + ++ + + + + + + + + +++++ + 

+ +++ + + 

+ + ++ + + 

+~g 

+,+,+._±~ 

----· .. ·--· ---' /1 ~ -''I'~ 

I, 

-----------------

7 - -------------------------- L~~~~~~~~~1 

Sandstorm rhyolite cut by dacite and Morena rl1yolite. 

Kendall tuff cut by dacite and Morena rhyolite. 

Latite eut by dacite and Morena rhyolite. 

Vindicator rhyolite. ~ 11 ~ ~ v" "v< ~ ~ ~ 7~ II J. 

1---------· ~~<7< "'L5;.,7 l------'--------------------------- 1 

_,_ ·-x· _1_ ~~~~~ 

Pre Tertiary. Alaskite and granite intrusive into Cambrian shale. 1 I 1 I 1 1.;, 

-:..:--·--:--·--:--·--:_-,--:--1- 1 ~ 

FIGURE 4.-Generalized columnar section of the rocks of the Goldfield district. 

Unconformity. 

Long erosion Interval. 

Since the basalt solidified the district has been subjected to some minor faulting and probably also to some unequal settling or warping of its surface. Erosion has cut through the basalt, 

dividing what was probably once a continuous sheet into the various remnants now capping 

mesas and flat-topped buttes, has excavated the broad valley in which the town of Goldfield 

lies, and has carved the hills into their present forms. As shown on page 75, there is some 

evidence in the shape of gravel deposits which indicates a stage in the erosion when the drainage was notably different from that now developed in the district. There is a possibility that 

this earlier drainage may have been associated with a brief lacustrine period, but the observable 

facts justify no more than this bare suggestion. 
LOCAL GEOLOGIC HISTORY. 91 

The general sequence of events in the Goldfield district is summed up in the accompanying 

columnar section (fig. 4). For convenience in subsequent comparison and correlation, Ball's 

general columnar section of southwestern Nevada is reproduced as figure 5. 

Basalt. 

Older alluvium. 

Basalt. 

Other alluvium, with Pliocene lake beds at base. 

Basic andesite. 

Second rhyolite, with min_or basalt flows. 

First rhyolite. 

Prospect M.ountain limestone. 

Prospect Mountain quartzite. 

FIGURE 5.-Columnar sectionofrocksofsoutllwestern Nevada and 

[The extension of the Pliocene down to include the Siebert 

(reproduced on page 93) and with the text of Ball's report, the 

The "Prospect Mountain" limestone is now known as the 

CORRELATION OF THE 

Throughout that part of the Great B 

time than the Jurassic are unknown, and, 

ances at the close of that period in all 

from the region. Thus definite paleonto 

case of persistent and fossiliferous marine 

to scanty fresh-water faunas or land floras 

preserved in lake sediments which, wha 

Un<;onformity. 

Unconformity. Unconformity. 

California. After S. H. Ball (Bull. U.S. Geol. SurveyNo.308, 1907,p.27). 

beds is clearly an oversight. To be consistent with the table of Bulletin 308 

of the Pliocene should coincide with the unconformity at the top bf the Siebert. 

limestone.-F. L. R.] 

WITH THOSE OF THE 

Y STATEMENT. 

included in western Nevada marine fossils of later 

has previously been sta.ted, the orogenic disturbbility resulted in the fmal exclusion of the sea 

cal correlation, such as is usually possible in the 

'ts, is not attainable. Recourse must be had 

yet of more or less doubtful determinatiiVe value, 

may have been their original areal rela~ions, are 
92 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

now scattered and isolated deposits. Under these circumstances the physical history of the 

region and the lithological character of the various eruptive rock& assume an importance not 

accorded them where more trustworthy means of correlation are available. That great physical 

events, such as the .post-JuraE;;sic deformation and erosion, have far-reaching effects and may 

legitimately be used as datum planes in correlation is of course true; but without any satisfactory paleontologic~! evidence it is not always possible for the observer to be sure that any 

event which has left a locally conspicuous record is also the mark of a geologic revolution regional 

'in its extent. In the case of' correlation by lithology the possibility of error is much greater, 

since carefully studied districts in Nevada reveal not only the prevailing complexity of the 

volcanic sequences, lavas of similar character being in some locaiities sev.eral times recurrent, 

but also the very small areal extent of many of the eruptions. 

In a comparison of the Tertiary portions of the various local geologic columns in southwestern Nevada two horizontal datum zones of wide regional extent are preeminently conspicuous. One is the unconformity between the Tertiary rocks and the rocks worn down by 

t~e post-Jurassic erosion interval. The other is the thick accumulation of lacustral sediments, 

known in different parts of the region as the Truckee group,a the Esmeralda formation,b Siebert 

tuff, c and Siebert lake beds.d The first datum is of so definite a character that it may be regarded 

chronologically as a horizontal plane. The second is less definite and, as will later appear, 

there is some question whether the base of these lacustrine sediments is not chronologica,lly as 

well as physically a very irregular boundary, here sagging deep do.wn into the earliest Tertiary 

and ·there rising into the latest part of that geologic period. However that may . be, without 

further anticipation of later discussion, it is possible in the meantime to make use of the lacustrine 

epoch, corresponding more or less closely with King's Pahute Lake, as a datum plane in preliminary correlation on physical and lithologic grounds. To the details of such correlation 

we may now pass. 

PRELACUSTRINE ROCKS. 

The Vindicator rhyolite, the oldest of the volcanic rocks at Goldfield, is perhaps the equivalent of a rhyolite described by Balle as forming the main mass of the Stonewall Range, 18 miles 

southeast of Goldfield, and regarded by him as representing the earliest Eocene eruption. This 

relation, however, does not necessarily imply that the rhyolite of the two localities ever formed 

a single continuous flow. According to J. E. Spurr/ rhyolite. of corresponding· age also occurs 

in the Silver Peak district, in the Panamint Range, in the Randsburg district, and near Daggett 

in the Mohave Desert. 

The latite of Goldfield appears to correspond in age and geologic position to rocks embraced 

under" monzonite and biotite andesite" in the correlation table of Ball,o here reproduced (p. 96). 

This would make it equivalent in time of eruption and magmatic origin to the monzonite porphyry of the Kawich Range h (50 miles (80 kilometers) east-southeast of Gold~eld) and to the 

hornblende-biotite latite of the intervening Cactus Range. Ball's i description of the latter 

rock indicates a very close resemblance to the Iatite of Goldfield, not only in original character 

but in mode of alteration. 

a King, Clarence, U. S. Geol. Expl. 40th Par., vol. 1, 1878, p. 412. 

b Turner, H. W., Twenty-first Ann. Rept. U.S. Geol. Survey, pt. 2, 1900, p. 197. 

c Spurr, J. E., Geology of the Tonopah mining district, Nevada: Prof. Paper U.S. Geol. Survey No. 42, 1905, p. 51. 

d Ball, S. H., A geologic reconnaissance in southwestern Nevada and eastern California: Bull. U.S. Geol. Survey No. 308, 1907. 

e Bull. U.S. Geol. Survey No. 308, 1907, pp. 32-33, 85. 

f Succession and relation of lavas in the Great Basin region: Jour. Geology, vol. 8, 1900, p. 633. 

gOp. cit., p. 33. · 

h Ball, S. H., op. cit., p. 104 

i Op. cit., p. 91. · 
CORRELATION. 

Correlations of Tertiary formations in various ranges of southwestern Nevada. a 

Eocene or I 

earlier. 

[Symbol X shows presence of formation.] 

Miocene. Pliocene. I Pleistocene in part. 

~ ~ g ~ ~ ~ uj ~ g ~ ~ § ~~ g ~ 

;S § ~l ~ :2~ .aQ)~ bO~ ~~ ~~§ 

Range. "O Q) ~~ • ~~ i ;S :8 ~~ ·;~i l~ ~u; ~-~:~-i~ ~~ 0 Q) $~ .i "0 "03 ~ ;;~ ~ ..<::1 ......:::: ~ Ol 0 ~'""' "0 ~ :5 q 0 s § § :;3 Q) q Q) :a ~~ ~ '; ~ ..... gj 1j.S 

.

$_· $ ~ _$_~ 8.2.= ~ :~ .2·§ ~ ~~ ~ .s ~~.a~ ·s ~ .. ~g ~ :§ ~ ::oo ~~~oo o ~ !SA~S--~ o s o -~ b.O C1J e ~ o,.q $..4 ~"0"0 ~ <:.) ~ s $..4 ~.s » ~=~ ~» ~-~.S "' .-. .a ~»~ "'o'O"' $ --~ g:JQ)Ql·-~ ~ ~ ~ ~ ~ ~ ~ ~ ~ j o .... .O j ~ >C..., A:> 

--1--------- ------ ------- ---1 -- --

Timber Mountain............. . .. . . . .. . . .. .. . ..... X . . ... _;fQ)g-g . .. . . . . . . . .. .. . .. . . .. . .. ~ I ..... -------: X 

Mount Jackson ................ ·· ·"· ............ g Q) <:ll X X I X A ' X? ------ 1 X 

~~~i~~~ffsi~:::::::::::::::: :: : :::::: -~-?-- gf ::~:: :::::: ~j~ ~~~~~~ :::·::: ::~:: :::::: 1:::::: :;::::! Q 

Specter Range .......... . ....... -- . . . . . . . . . . . . ~ ------ ------ a~ "' · · · · · .·. · · · -, X ~ ~ 

YuccaMountain .... · ......................... a X ...... - :>.l=i •.••• • ••• •.. ...... ....•. -_--_- -_--_--_- -__ :-__ .. ___ :· __ : __ : ,

1

· ____ Q_. ____ _ Reveille Range.... .. ............. . . . . . . . . . . . . S . X .... .. 13~: . .. . . . . . . . . . (b ) ..... . 

Lone Mountain foothills.······ ................... Q) -_ -_ -_-_ -_ -_ -- .---_ -_ -_-_ -~-"-;::;o'"'o"'_~=~o~_~ I X .I-.... _I x· 

..., 

al 

~~ 

~~N:~~r.;e~~cg:c·t~s-aitd:i{~~~ic;j;· ...... ·----- :~ ::::; : :::: : :: :::::::::::::::: : ~ Q) Q) ..<::1 

ranges 8 ~ X "O o ~ X .. . . . . . . . . . . .. . . . . X 

g~~M~:~!~:: _ __1-- , ~ ~~ Qx·--)_~-~-~-~_:_· !"0_;_ .. >< .. g 1::>: ::~::<~~~~ ~ g 

s h <!) 

0 

:> ~.8 X . ,o!:! s oal 

Pahute Mesa .. .... ... ........... ·!··· ......... ..., 0 I ..... X X X X X Kawich Range ........................ ~ X '§ 8 X X £-8 '0 X . . . .. . c X X . . . . . . X I X Amargosa Range............... .. ..... . X .£ ~ X X ..... 8£ ... ... ... ... X X X BullfrogHills .................. . ....... X i=lo X X ::~aJ'-' .•..... .. ... (d) ...... X X 

Cactus Range ................ , . . . . . . . . . X g..:: X ...... 

1 

~ :>. ~ X . . . . . . . . . . . .. .. .. ----.. X J X 

------- 0 '-<gj 

'i:1 X A ,a 

Q) 

M "'" J1 0 

0 ~ ~~uther~ ~ondik~ Hills ............... 

1

...... § ...... 

1 

...... ~~ ~ . . . . . . X X X __ ~ __ :::::: Q 

fif~:i~~~~~~ :: : : < I > 1 ··~·· :· ~:!~ J tT) - ------ - ~ §g~:%'~n~;:n':,-s.,;iiffiO~n;a;.;; i: I X ~ Q I ~ 8 ~~ I X X - ~ : ! Q 

X "0 X l=i 

~ 

~ ·X ~ ~ 

a After S. H. Ball, Bull. U. ~ Geol. Survey No. 308, 1907, p. 33. c Including shore formation. b Probably to north. d Shore formation only. 

The next physical event recognized by Ball (see his table above) is an erosion interval 

marked by unconformity which he has observed in the Kawich, Cactus, and Amargosa ranges, 

in the Shoshone Mountains, and in the Bullfrog Hills. This unconformity, which he considers 

as corresponding wi1jh the end of the Eocene or the beginning of the Miocene, is not distinctly 

shown at Goldfield. 

The Sandstorm and Morena rhyolites were apparentiy erupted contemporaneously with 

what Ball has called "early Miocene rhyolite," a formation which according to his reconnaissance map is of widespread importance in southwestern Nevada, making up the greater part of 

the Cactus, Kawich, Reveille, and Belted ranges and of the Bullfrog Hill~. It is also the principal 

rock of Timber and Yucca mountains east of the Bullfrog district. The rhyolite of some of 

these areas, according to Ball, is associated with contemporaneous flows. of dacite and hitite, 1 

a relation not exhibited at Gbldfieid. As rhyolites were erupted at ~east half a dozen times 

during the Tertiary in this general region it is evident that correlation of these lavas from 

one range to another is, in our present stage of knowledge, tentative. The difficulty experienced in distinguishing by detailed work the 4 or 5 different rhyolites occurring in the Goldfield 

district shows that nwre than rapid reconnaissance will be necessary before it can be definitely 

asserted, for example, that the Sandstorm rhyolite is in part the equivalent of the much thicker 

series of rhyolites in the Bullfrog Hills. . 

The Milltown andesite of Goldfield is grouped by Ball with the dacite, and this group is 

correlated by him with rocks in the Belted, Kawich, Cactus, and Silver Peak ranges. The 

oldest Tertiary rocks described by J. E. Spurr a in the Tonopah district, 30 miles (48 kilometers) 

north of Goldfield, are andesites which he designates "earlier" or "hornblende-biotite" andesite, 

and "later" or "biotite-augite" andesite. An interval of erosion is described between the 

two. These andesites may b~ of about the same age as the andesite at Goldfield, although 

a Geology of the 'l'onopah mining distrLt: Pr<~f. Paper U.S. Geol. Survey No. 42, 1905. 

·, 
94 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

the unconformity has not been recogpized in the latter district and the rocks of the two areas 

are not petrographically identical. 

In the Tonopah district also Spurr describes a series of dacites and rhyolites which correspond to a long period of eruptive activity and for the most part are older than, or are overlain 

by, the Siebert lake beds. He considers, however, that the dacitic eruptions and the lake 

beds belong to the' same general period (Miocene), and shows tha_t the lake beds after they 

had been folded, eroded, and covered by basalt were intruded by dacite. Thus there is a 

suggestion that the dacite of Tonopah may in part be equivalent to the dacite of Goldfield. 

Closer examination, however, renders this correlation questionable. In the first place there 

is no evidence at Goldfield that dacitieeruptions continued into the lacustrine epoch, although 

it can not be positively asserted that they did n,ot do so. In the second place the dacites of 

the two districts are distinctly different rocks; that of Goldfield is a quartz-bearing andesite 

or true dacite, while those at Tonopah, as Spurr a himself states, are not, strictly speaking, 

dacites at all, but are siliceous quartz latites and rhyolites. This difference is brought out in 

the following table qf chemical analyses: 

Chemical analyses of Goldfield and Tonopah dacites. 

Goldfield. Tonopah. 

1. 2. 3. 4. 5. 6. 

-------------=-----------------------------------

SiOz............................................................................... 

Alz03 59.95 59.99 61.25 71.71 73.00 75.56 

Fe203............................................................................. ............................ · .. ... ... ... . ... .... .. ." ... .. ....................... 15.77 16.14 15.92 14.00 ................... . 

FeO............................................................................... 3. 34 4. 42 3. 75 1. 06 ................... . 

MgO 2.34 .13 1.17 .51 ................... . 

CaO .............................................................................

........... · ... .......... .... . .... . . ........ . .. ~.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 73 1. 51 2. 28 . 43 ................... . 

Na20.............................................................................. ... 5.84 4.17 5.39 2.25 1.55 1.16 

K20. 3. 07 3. 04 3.19 3. 21 3. 50 4. 20 

H20 below 

. . . . . . . . 

110. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 52 2. 82 3. 23 4. 41 4. 71 4. 50 

H20 above 110° ° 

C 

C ....... : ...... . ..... ..... ... .. ..... . ....... ........ ............... . 95 3. 35 1. 08 . 44 ................... . ............................................................ TiOz..... .1..... 2. 00 4. 06 1. 88 1. 38 ................... . 

Zr02 ........ .. ....... .. ........ .. .. .. . . . . . ... .. .. ... ... ... .... ...... ... ...... .82 .64 . 71 .28 ... .. .. ... ......... . ...... ... ..... . .............. ... ..... . .... . .. .. .... ~.. .......................... .02 ................................................. P205 . 

Cr203 .... ........... .. ... ..... .. . .. . ... .. . . . .. . . ... .. ... .. ... .... ................... .26 .24 .22 .07 ................... . ...... ...... . . ......... .......... ........ .... .... .... .. .... .... ..... . ... ............................... MnO. . ........... . .......... . .. . .... .. . . ... . .. . ... .. .. ...... . .. . ... . .. . .. . . .. . ....... .... .. . ... . ....... .. ..... .. .. ... .09 .05 .08 ............................. BaO............ . .............. .. . . . . . . ... . . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . ... . . . . . .. . .11 ................................................. SrO....... . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 ................................................. . 

99.94j- 1oo.S6 110o.l5199.75i==i== 1. Dacite (G. 97), one-half mile (2.4 kilometers) northeast of Columbia Mountain, Goldfield district. George Steiger, analyst. 2. Dacite vitrophyre (G. 158), 1 mile (1.6 kilometers) southwest of Blackcap Mountain, Goldfield district. George Steiger, analyst. 3. Dacite (G. 83), Diamond Peak, Goldfield district. George Steiger, analyst. 

4. "Dacite," Brougher Mountain, Tonopah. George Steiger, analyst. (Spurr, op. cit., .p. 57.) 

5. "Dacite," Butler Mountain, Tonopah. E. T. Allen, analyst. (Spurr, op. cit., p. 57.) 

6. "Dacite," Golden Mountain, Tonopah. E. T. Allen, analyst. (Spurr, op. cit., p. 58.) 

Comparison of the three analyses of rocks from each district shows conclusively that the 

so-called dacites of Tonopah are quite distinct from the dacite of Goldfield. The Tonopah 

dacites, according to Spurr,b all fall into the subrang toscanose of the quantitative system. 

H. S. Washington's c tables include in this subrang 122 entries, of which 40 were originally 

described as granites, 31 as rhyolite, liparite, obsidian, etc., and 9 as quartz porphyry. Among 

the remaining 42 entries are trachyte, akerite, quartz monzonite, toscanite, latite, etc., but 

only one dacite. The positions of the Goldfield dacite and dacite vitrophyre in the quantitative 

system have been given on pages 57 and 63. 

It appears from the foregoing comparison that the dacite of Goldfield is not lithologically 

identical with the so-called dacites of Tonopah and that some of the latter are younger than the 

former. It is probable that some of the later of these Tonopah eruptions correspond in time 

with the thin rhyolitic flows known to be intercalated between the beds of the Siebert formation 

at Goldfield. On the other hand, some of the earlier "dacites" and rhyolites (i. e., I-Ieller 

dacite, Fraction dacite breccia, and Tonopah rhyolite-dacite) at Tonopah, which Spurr d shows 

a Geology of the Tonopah mining district: Prof. Paper U. S. Geol. Survey No. 42, 1905, pp. 365, 9. bOp. cit., p. 60. 

cChemical analyses of igneous rocks: Prof. Paper U.S. Geol. Survey No. 14, 1903, pp. 159-173. 

a Op. cit., p. 54. 
CORRELATION. 95 

to have been eroded before the deposition of the lake beds, although lithologically different, 

may be approximately equivalent in age to the dacite vitrophyre of Goldfield. 

The. merely tentative correlation thus far attempted in this chapter has had to do with 

volcanic rocks lying between t4e post-Jurassic erosion surface and the earliest Tertiary lacustral sediments. The extent to which these sediments, as now exposed in various areas, possess 

common lithologic, stratigraphic, and tectonic characteristics next demands attention, and 

the general discussion may be fitly introduced by a brief summary of the more important descriptive literature on the older Tertiary lake deposits of western Nevada. 

LACUSTRINE SEDIMENTS. 

King, a who applied the name Pahute Lake to th~ great body of water which he supposed to 

have covered western Nevada in Miocene time, outlines the distribution of the lacustral sediments (Tn1ekee group b) as follows:· 

The rocks of the group are limited on the east, within the boundaries of our exploration, by the one hundred and 

seventeenth meridian, and on the west by the abrupt wall of the Sierra Nevada. Northward they extend through 

Oregon and pass into Washington Territory, having their greatest development on Crooked River, the John Day, and 

the Malheur. South of our work they are well known in the valley of Walker River, but beyond that southward I am 

not aware of their having been observed. · 

King's description of a characteristic section of the Truckee group at a locality west of 

Carson sink, near the Southern Pacific Railroad, is as follows: c 

The most important and characteristic development of this series within our limits is at the Kawsoh Mountains and along the southern extremity of Montezuma Range. The northern and eastern portion of the Kawsoh 

Mountains and the valley which lies north of them, separating their broken detached group of hills from the end of 

Montezuma Range, together offer a section of about 2,300 feet of Miocene beds, noting from the top as follows: 

l. The upper 1,200 feet consist entirely of drab, mauve, gray, pale-buff, and white stratified trachytic tuff, intermixed with more or less detrital material. The beds are characterized by rapid changes of color and texture, are of 

very variable coarseness, and have a prevailing amount of glassy fragments, as if an enormous amount of the material were 

the glassy scoria and rapilli of violent and long-continued trachytic eruption. At intervals are beds of pure gray sand 

with a few seams of slightly marly clay. The microscope shows that this entire series is made up of angular and subangular fragments, many of them excessively small. There are some singular chalcedonic strata, 1 to 2 feet thick, 

of which the lower stratum plane is exceedingly rough, resting upon the trachytic tuff and including a great many 

minute fragments of the volcanic material, the upper surfaces being rudely botryoidal, the protuberances reaching 

the size of an egg. Toward the lower edge of this great series of trachytic tuffs, the upper limits of which are nowhere 

seen, the proportion of true detrital material-quartz and feldspar sand-becomes rapidly greater until the tuff is 

underlaid by2. Coarse, sandy grits, gray and yellow fragments, partially rounded, partially angular, with a 

slight proportion of calcitic m.ateriaL ........... . _ ..... _ .... _ .. _ i . .. . . .......... . ..... . 

3. Saccharoidallimestone, rich in fresh-water mollusks ............. . .... _ . . . .. ............. . 

4. Marly grits, yellow and drab, rather coarse ........ . .... . ............ __ ._. _ ............. . 

5. Fine-grained, friable, buff and gray sandstone, having a peculiarly sharp, gritty feeL .. . .. . 

6. Variable gray sandstones ...... ___ ___ .. ___ ... _. __ _ . . __ ... ___ ._ .. ___ ._ . . __ ....... _ ..... . 

Feet. 

250 

60 

40 

70 

100 

7. A marly grit ................... _._. ___ . . . __ . __ .. __ ._. __ __ . ___ _ . _____ _.............. 50 or 60 

8. White and yellow infusorial silica .......... __ ._ .. .. ____ . ___ . ______ ... .. . ___ . __ ._._ ...... 200 to 250 

9. Palagonite tuff, base never seen, 250 feet being ~aximum exposure. 

No lower members than the bed of palagonite tuff are observed in the Kawsoh Mountains, or in the southern end 

of the Montezuma; but :[n Warm Spring Valley, a small depression in the basaltic hills a few miles north of Hawkes's 

~tation, on Carson River, the palagonites, there remarkably well developed, are seen to be underlain by a light siliceous 

clayey bed made up of fine silt and comminuted infusoria. It is always far less pure than the white infusorial beds 

above the palagonites. Here, as everywhere, the series has an inclined position, dipping 15° to 20°. 

It is now well known that the rocks ca,lled trachyte in the Fortieth Parallel reports are mostly 

andesites, and consequently that the trachytic tuff referred to in the foregoing descriptions 

should be translated andesitic tuff. It may fairly be questioned, moreover, whether this 

a Geol. Expl. 40th Par., vol. 1, 1878, p. 413. 

b The name "Truckee group" is not a very happy choice. Although the lake beds at Verdi, on Truckee River near the California line, arc 

mapped as the Truckee group in the Fortieth Parallel Atlas, the typical and best exposures, according to King, are all to the east and south of the 

stream from which the formation presumably takes its name. 

cOp. cit., pp. 415-4i6. Reference to Arnold Hague's description of the Kawsoh Mountains (U. S. Geol. Expl. 40th Par., vol. 2, pp. 766--774) 

shows that King combined and generalized the actual sections there observed. 
96 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

change entirely expresses the facts and whether a reexamination of the section would not show 

·a large proportion of rhyolitic material in the so-called trachytic tuff. To the northeast of the 

section just described, in the foothills of the West IIumboldt Range, the sediments, according 

to King,a are less characteristically volcanic and consist largely of coarse sands and gravels. 

Louderback b descr~bes these as consisting of "slightly co.nsolidated granitic. sands, diatomaceous earth, et cetera," dipping at about 35° and overlain by basalt. King noted c that the 

Truckee beds are everywhere upturned from 10° to 25° and, where associated with basalt, 

are eut through and overflowed by that rock. . 

The lake beds west of Reno and under the town of Verdi, mapped as Truckee Miocene in 

the Fortieth Parallel Atlas, are deseribed by Arnold I-I ague as follows: d 

That portion of the Truckee Valley lying directly west of the Virginia Range is a broad open basin covered by 

a thick deposit of Quaternary sands and gravels obscuring all the Tef'tiary strata below; these appear, however, farther 

up the valley, just above the town of Reno, and extend thence westward to the California boundary. These Tertiary 

beds line the valley on both sides of the river, and form a distinct deposit quite unlike those described from the 

lower Truckee Valley. They lie inclined at angles varying from 10° to 15°, in general dipping ~o the southward away 

from Peavine Mountain, but considerably disturbed by local outbursts of volcanic rocks. Inasmuch as the beds are 

o highly inclined, and are older than many of the intrusive rocks of the region, they have been referred to the Miocene 

age, although they differ somewhat in lithological character from the Miocene strata of the Kawsoh Mountains and 

:Montezuma Range, having much less volcanic material in their composition. They consist mainly of sand tones, with 

interstratified beds of friable sands, clays, and thin shales of prevailing light colors. So far as known, no animal 

remains have as yet been found in these beds, although stems, leaves, and partially carbonized vegetable matter are 

abundant in certain layers of shale. · Perhaps the most characteristic feature of the basin, and one that suggests the 

Green River beds of the Elko region, is the presence of a number of seams of impure coal and carbonaceous shales. 

Outcrops of coal occur on both sides of the river north of the town of Verdi, dipping to the southward 10°. Another 

coal_seam has been opened a long time on Dog Creek, a short distance north of Crystal Peak, but, so far as known, 

none of the deposits have as yet proved of any economical importance. No accurate measurements of the thickness. of these Tertiary strata have been made, but there can not be less than 500 or 600 feet of conformable beds. 

West of the locality just noted, in Truckee Valley, California, Lindgren e has described 

Neocene lake beds consisting of yellowish sands and clays, the latter predominating, with 

brilliantly white beds, probably volcanic ash, containing diatoms. There are also severallaye.rs 

of coarse tuff and some seams of impure lignite. These beds, which show dips up to 10°, are 

capped in places with basalt, and are younger than the main andesitic eruptions of the Sierra 

Nevada. Lindgren suggests the equivalence of these depo~its with those at Verdi. 

D. T. Smith! has briefly described a series of Tertiary sediments about 1,200 feet (366 

meters) thick near Yerington in the valley of Walker River about 15 miles (24 kilometers) south 

of W abuska, or 45 miles (72 kilometers) south of the Kawich Mountains, which apparently 

have considerable resemblance to the Truckee group and are inclined at angles up to 40°. 

These beds have yielded ma.mmalian remains which W. J. Sinclair states are probably late 

Miocene or Pliocene and correspond to the faunas of the Maseall and Rattlesnake formations 

· of Oregon. 

In Gabbs Valley, about 60 miles (96.5 kilometers) southwest of King's type locality for 

the Truckee group, Spurr has noted lacustrine beds, which he describes as follows: g 

Near the center of the valley, just east of the low mountain spur which crosses it, and on the Reese River road, 

there. are low ridges of gray, stratified marl containing leaf remains, alternating with gravels and more solid conglomerates. Some of the conglomerate contains comparatively abundant silicified wood. The conglomerate, when examined microscopically, proves to be volcanic. The pe_bbles are made up in part at least of spherulitic glass. Some 

pebbles contain phenocrysts of feldspar, of species indicating that the lava is andesitic, in a glassy matrix containing 

broken feldspar and biotite. Some of the shaly beds associated with the conglomerate are feldspathic tuff, made up of 

fine fibrous material, with larger broken fragments of feldspar and some shreds of biotite. These beds strike north and 

south and dip about 8° E. -----------

a Op. cit., p. 414. See also Hague, Arnold, U.S. Geol Expl. 40th Par., vol. 2, 1877, p. 733. 

b Basin Range structure of the Humboldt region. Bull. Geol. Soc. America, vol. 15,1904, p. 301. 

c Op. cit., p. 413. 

d U S. Geol. Expi: 40th Par., vol. 2, 1877, pp 849-850. 

e 'fruckee folio (No. 39), Geol. Atlas U.S., U.S. Geol. Survey, 1897. 

f Geology of the upper region of the main Walker River, Nevada: Bull. Dept. Geology Univ. California, vol. 4, 1905, pp. 10, 13. 

g Descriptive geology of Nevada south of the 40th parallel: Bull. U.S. Geol. Survey No. 208, 2d ed., 1905, p 107. 
CORRELATION. 97 

Spurr correlates these sediments provisionally with King's Truckee group. 

A few miles south of Gabbs Valley, in the Candelaria Mountains near Sodaville, Spurr a 

notesa comparatively small area of brown, yellow, sometimes purplish, limy and sandy shales, argillaceous fine sandstones, and thin-bedded brown and yellow aphanitic limestones. This series strikes N. 65° E. and dips,65° NW. It 

is probably identical with the rocks of the Esmeralda formation a few miles to tP.e south, in the southern end of the 

Monte Cristo Mountains. 

The Esmeralda formation, described and named by H. W. Turner, b is well displayed 

in the Silver Peak district on the slopes of the Silver Peak and Montezuma ranges, about 15 

miles (24 kilometers) west of Tonopah and Goldfield. According to Turner,c "The beds are 

composed of sandstones, shales, and lacustral marls, with local developments of breccia and 

conglomerate on a large scale." He further describes the forma,tion as containing intercalated 

volcanic flows and, near the base, some coal. The beds, according to this observer, have the 

enormous aggregate thickness of 14,800 feet (4,511 meters), a:re folded, and are capped unconformably by basalt. .Turner suggests their correlatimi with the Truckee group of King. 

Spurr refers to the Esn1eralda formation as follows: d 

These Tertiary deposits flank the edges of the mountains and underlie, in ]part at least, the Pleistocene veneer of 

the valleys. On account of folding and faulting since their deposition they arch upward along the sides of the mountains, although according to Mr. Turner they have not been found within 2,500 feet of the highest elevations. They 

consist of soft shales, sandstones, marls, tuffs, volcanic breccias, etc., with interbedded layers of andesitic and rhyolitic 

lava. The thickness of the whole accumulation is very likely several thousand feet. This mass has not yet been 

satisfactorily differentiated into separate members, but it undoubtedly contains materials deposited under widely 

varying conditions. Some of the beds are lake sediments; some appear to have been deposited in running water and 

were probably distributed by stream action. Others bear the marks of dry, subaerial origin. Also there is probably 

.a great range in the period of deposition, as will be presently shown from a consideration of the fossil evidence. It is 

probable that practically the whole Tertiary, from the Eocene through the Pliocene, is represented. In short, it is 

probable that the beds are the record of the whole period of Tertiary sedimentation, beginning with the period when 

the Nevada land mass ceased to have free drainage to the ocean, at the close of the Cretaceous, through the whole of 

the climatically changing but in general arid Tertiary period, when the material eroded froin the mountains was 

accumulated in the valleys, in lakes, or in subaerial sheets, down through the Pliocene. Both the early and more 

recent Pleistocene accumulations of the region are ·of very much the sanie nature as many of these Tertiary beds, and 

probably form a direct continuation of them; but in the Pleistocene material the proportion of lake beds does not appear 

to be nearly so large as in the Tertiary formations. 

Eight miles (13 kilometers) north of Tonopah, near Ray, Spurr found "folded gravels, 

tuffs, lavas, and some white, thin limestones." He states that similar beds are found at several 

places between Ray and Sodaville and remarks that the-y are (were?-R. L. R.) probably 

continuous with a part of the Tertiary deposits of the Silver Peak and Monte Cristo mountains-that is, with the Esmeralda formation. 

The same writer characterizes the Siebert tuff at Tonopah rather briefly as follows: e 

The white stratified tuffs form a conspicuous feature of the geology near Tonopah. As a rule they are beautifully 

.and uniformly bedded, and composed of well-assorted material. vVhere beds of conglomerate_ occur the pebbles are 

perfectly rounded. Since these sediments do not vary in character for thicknesses of several hundred feet, it is plain 

that they were laid down in a large body of standing water that lasted for a considerable length of time. That this body 

was a lake is indicated by numerous general considerations derived from the study of the geology of the surrounding 

region and by the presence of numerous fresh-water infusoria in some of the strata. In contrast to the general regula-r 

stratification, cross-bedded strata may occasionally be found, and at one place markings like those made by rills on a 

sandy shore were noted. These are pr~bably shore and delta features. 

The Siebert tuff is unconformably overlain by basalt on Siebert Mountain, and both rocks 

.are cut by a late intrusion of "dacite." 

a Descriptive geology of Nevada south of the 40th parallel: Bull. U.S. Geol. Survey No. :!08, 2d ed., 1905, p. 114. 

b The Esmeralda formation, a fresh-water lake deposit: Twenty-first Annual Report U. S" Geol. Survey, pt 2, 1900, pp. 197-208; also Am. 

Geologist, vol. 25, 1900, p. 168. 

cOp. cit., p. 198. 

d Ore deposits of the Silver Peak quadrangle, Nevada: Prof. Paper U S. Geol. Survey No. 5~i, 1906, p. 19· 

e Geology of the Tonopah mining district, Nevada: Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 51. 

79140-No. 66-09--.7 
98 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

There can be no reasonable doubt that the Siebert tuff of Tonopah and the Siebert formation of Goldfield were once continuous deposits laid down in one lake. The two districts are 

less than 30 miles ( 48 kilometers) apart, the deposits are thick and lithologically similar, and 

the reconnaissance of Ball a has shown that the formation is well represented in the Klondike 

Hills, .about halfway between Goldfield and Tonopah. He found the Siebert beds making up 

a large part of Montezuma Peak, 7 miles ( 11 kilometers) west of Goldfield, where the faulted 

and folded lake beds attain an altitude of 8,426 feet (2,568 meters) on the summit of the peak. 

He also traced the formation westward to longitude 117 ° 30', where his area marches with the 

Silver Peak quadrangle, in which the Esmeralda formation was described in 1900 by Turner. 

Very curiously, Ball makes no reference to this-formation, nor does he point out what would 

appear to he a conclusion from his own work, namely, that the Siebert Lake beds were laid 

down with at least a part of the Esmeralda formation in a common basin. b Ball's description 

is as follows: c 

Prior to the deposition of the Siebert Lake beds the Cambrian rocks had a rugged topography. These beds, 17 

miles north of Lida, are coarsely conglomeratic, and inliers of limestone protrude through them, and· outliers of lake 

beds occur on the Cambrian rocks. The lake beds cover a considerable area on the western border of the region under 

consideration, a somewhat smaller area near Montezuma Peak, and a small area 5 miles south of Alkali Spring. The 

northern boundary of the largest area is approximately correct as mapped. The southern boundary is less accurately 

drawn and some Tertiary igneous rocks may lie between the Cambrian rocks and the lake beds. 

These beds, which are composed largely of rhyolitic material, consist of typically incoherent, unevenly granular, 

well-bedded sandstones. When unstained by iron, they are white in color, but brilliant reds and yellows are characteristic of many areas. Fine-grained beds alternate with conglomeratic layers containing pebbles of Gambrian 

rocks, quartz-monzonite porphyry, diorite porphyry, rhyolite, and igneous rocks of andesitic and basaltic affinities. 

The pebbles are well rounded or semiangular. Microscopic examination of several slides shows the presence of quartz 

and orthoclase crystals in a pyroclastic matrix. 

Locally the Siebert Lake beds have been indurated by silicification along joints and in irregular bodies. Quartz, 

chalcedony, and opal fill cavities. The silicified portions weather into wall-like masses along joints and into 

grotesque topographic forms where silicification has been less regular. 

Rhyolitic and dacitic flows are interbedded throughout the sediments, although they increase toward the bottom 

of the formation, and dacite appears to underlie it. 

The lake beds at Montezuma Peak are about 1,100 feet thick. On the western border of the area mapped they 

are probably 200 or 300 feet thicker. The formation was for the most part deposited in an inland lake, although some 

portions were possibly laid down subaerially by explosive volcanic action. 

Mr. R. H. Chapman found a piece of silicified wood at a point 4 miles west of Montezuma Peak. Mr. F. H. 

Knowlton, who kindly examined it, states that it is wood of a deciduous tree not older than the Tertiary. These 

sandstones are correlated with the Siebert Lake beds of Tonopah, described by Spurr. 

South of the Goldfield district Ball's map shows areas of lake sediments which he correlates with the Siebert formation extending into Death Valley in latitude 36° 30'. Ball refers 

to the lake beds on the west slope of the Funeral Mountains as follows :d 

The rather large mass of later rhyolite and biotite latite to the southeast of Staininger's ranch has between its flows 

layers of white or light-colored incoherent tuffaceous sandstone, which readily breaks down into sand. The section 

at this point is as follows: 

Se~tion southeast of Staininger' s ranch. 

Feet. Lava, largely biotite latite .......... : .......................... . .... _ ......... . . . ........ __ .. ____ 375 

Rhyolite flow:s and some tuffaceous sandstone ............... _ ..... ... ....... . _. ____ ___ . ________ . __ 100 

Tuffaceous sandstone and thin rhyolite flows ... ~ .... _.__ . . _ ... _. ____ _ . _. _. __________________ ___ 375 

Rhyolite flows ............................................ _ .. ... . . _ ..... ·_ ................ _. _ _ _ _ _ 75 

Tuffaceous sandstone ............................................ _·_ ................ . .......... _._ 225 

Between the lava and the sediments are minor erosional gaps, but these are probably current erosional unconformities, and the series is approximately all of one age. Bedding planes from 2 inches to 20 feet apart are well developed 

at some .places. 

a Geology of the Tonopah mining district, Nevada: Prof. P~per U.S. Geol. Survey, No. 42, 1905, p. 78, Pl. I. 

b A comparison of Ball's map (Bull. U.S. Geol. Survey No. 308,1907, Pl. n with the map of the adjoining region accompanying Spurr's report (Prof. Paper U.S. Geol. Survey No. 55, 1906, Pl. I), and purporting to be based on a manuscript map by H. W. Turner, shows that the area of Siebert Lake beds, which Ball maps for 6 miles along his western boundary, apparently changes abruptly to" Tertiary lavas'' on Spurr·sside of the line. This discrepancy, however it may in future be explained, is not likely to affect the general conclusion that the Siebert formation and at least a part of the Esmeralda formation were once areally continuous across the region now occupied by the Montezuma Range.- F. L. R. 

c Bull. U. S Geol. Survey No. 308, pp. 57-58. 

d Op. cit., pp. 165-166. 
CORRELATION. 99' 

Locally the tuffaceous sandstone lies unconformably upon folded Pogonip limestone. It is closely similar to · 

that of the Mount Jackson hills and, like it, is overlain by siliceous lavas. This formation is, without much doubt, 

the Siebert Lake beds. 

A number of small areas of conglomerate occur on the -eastern slope of the Amargosa Range, east of boundary post 

No. 94, southeast of Daylight Spring, and north of Willow Spring. The rocks, varying from loosely to rather strongly 

consolidated.material, consist of conglomerates and arkoses with a little shale. They range in color from green to red, 

yellow, or brown. Bedding planes, which are from 1 inch to 2 feet apart, are well developed. The pebbles in the · 

conglomerate, which are very well rounded and many of them highly polished, reach a maximum diameter of 4 inches . . 

They are derived principally from the Paleozoic rocks near by, with here and there a pebble of fine to medium grained 

granite, and in the area east of boundary post No. 94 some of earlier rhyolite. These rocks appear to be the shore 

deposits of a lake ii;l which waves swept with considerable force. Material was transported from considerable distances, 

since granite does not now outcrop in the vicinity. Since the conglomerate contains pebbles of rhyolite and none 

of basalt, the deposits are younger than the rhyolite (early Miocene) and older than the basalt (Pliocene-Pleistocene),_ 

and in consequence of middle or late Tertiary age, presumably Miocene. Th~y are approximately contemporaneous 

with the. lake in which the Siebert Lake beds were deposited, and it is believed that they are shore deposits of that 

bb. ' 

In that part of California lying east of the Sierra Nevada and north of the San Gabriel and 

San /Bernardino ranges Tertiary lacustral deposits have been described by G. K. Gilbert, a ' 

H. W. Fairbanks,b M. R. Campbell,c and J. E. Spurr.d i 

Spurr, writing of the Death Valley region just south of the area examined by Ball, describes 

the early Tertiary lake sediments as follows: e 

In the eastern part of the range, where the road crosses from the Amargosa Valley into Furnace Creek, there is found. 

a great amount of conglomerate, forming high hills. These conglomerates are very coa,rse and contain rounded pebbles 

and bowlders of all sizes, made up of reddish and white quartzite and black and gray limestones bearing the badly. 

preserved Paleozoic fossils above mentioned. , The conglomerate is as hard and firm as the rocks from which it is derived. · 

It is water laid and well stratified, and evidently a shore formation. The whole thickness exposed is estimated at 4,000 

feet. It is sharply folded, together with the limestones from which it is derived, but it abuts abruptly against these 

limestones on the west. 

Besides these rocks there o<;cur, as parts of the same series, semiconsolidat~d gravels, with clays partially hardened 

to slaty shales, limy clays partially consolidated to argillaceous secondary limestones, and sands partially hardened to 

cherty and limy sandstones, all interbedded. All these, including the conglomerate and the limestone tuia, have ageneral light-yellow, often greenish, color, characteristic of the series. 

This sedimentary series makes up the greater portion of the Funeral Range. Along Furnace Creek Valley and on 

both sides of it the mountains consist chiefly of yellow-green strata capped by basalt. The lava seems to occur interbedded with the sedimentaries, as well as overlying them. The series is here consolidated into a hard clay rock, with 

occasional thin sandstone, and the general yellow-green color is changed in places to reddish, yellowish, and pinkish. 

The rocks are often gypsiferous and contain abundant grass remains, which are, however, indeterminable. From the 

yellow-green Tertiary series in the hills just east of the mouth of Furnace Creek there has been. taken much borax, which 

occurs as borate of lime in beds in the strata. . 

Near the summit of the pass, just east of Furnace Creek, there come in above the yellow-green Tertiary series softer, 

dark-brown, honeycombed conglomerates, recalling the similar rocks of Meadow Valley Canyon. Thin sheets of basalt 

are interbedded with the conglomerates, but the great sheets lie on top. Patches of this same upper conglomerate series 

·were else'where observed, and at one place its contact with the underlying yellow-green series appeared slightly discordant. The conglomerate contains pebbles and bowlders which are chiefly of lava and must have· been derived from 

the sheets of basalt which were periodically poured out during the deposition of the beds. 

A rough estimate of the thickness of this whole series of slightly consolidated beds and volcanics puts it at not less 

· than 4,000 feet, and the nature of the sediments shows that they must have been deposited in standing water. The· 

presence in some of the beds of gypsum, borax, and calcareous tufa shows that at some periods the waters in which the 

sediments were deposited were evaporated. · They were, therefore, those of an inclosed lake, which was probably of · 

great dimensions. It is likely that a large portion of the beds were deposited in fresh water at a period different from 

that in which the chemical precipitates were laid down. 

Northward from Furnace Creek, at Silver Peak, are found beds of the Esmeralda formation, which are entire~y 

similar in nearly every respect to those at Furnace Creek. Moreover, the fossils found in the Esmeralda beds indicate 

a nearly similar age to that indicated by fossils found in the Tertiary strata of the Mohave Desert, just west of Cajon Pass. 

Spurr considers it probable that the ·beds at Furnace Qreek represent nearly the whole of the 

Tertiary period. They are capped by basalt, which he considers may have been poured out in 

a Rept. Geog. and Geol. Surveys W .lOOth mer., vol. 3, 1875, pp.l42-143. 

b Geology of eastern California: Am. Geologist, vol. 17, 1896, pp. 67-69. 

c Reconnaissance of the borax deposits of Death Valley and Mohave Desert: Bull. U. S. Geol. Survey No. 200, 1902. 

d Descriptive geology of Nevada south of the fortieth parallel and adjacent portions of California: Bull. U. S. Geol. Survey No. 208, 2d ed. , 1905. 

e Op. cit., pp. 189-191. · 
100 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA, 

Q,uaternary time. In the same report are described similar la<;mstral deposits in the Panamint 

and other ranges of this region. 

The general conclusions which may be drawn from the observations brought together in the 

foregoing pages are as follows: 

There is in western Nevada, extending from the fortieth parallel down to about the thirtyfifth parallel, a chain of remnants of Tertiary lacustral deposits. These deposits are of great 

I VOlUme, estimates of total thickness in the VariOUS placeS Where the beds are Well represented 

ranging from a minimum of at least 600 feet (183 meters) at Tonopah a to 14,800 feet ( 4,511 

meters) at Silver Peak.b The materials vary from place to place, but are preponderantly 

volcanic. They include true tuffs, largely rhyolitic, and detrital rocks of a wide range of coarseness derived from all the prelacustrine rocks and probably also from volcanic masses piled up 

~nd eroded during the lake period. Diatomaceous beds appear to be rather characteristic of the 

deposits north of the Death Valley region, while in and south of Death Valley descriptions indicate a greater abundance of clays with associated beds containing gypsum and borax. Lignitiferous beds, apparently in all cases in the basal part of the d~posits, occur from Truckee River 

~southward to the Mohave Desert. The beds are everywhere folded and faulted and in many 

places sheets of basalt have flowed over their eroded edges. It is clear that since the period of 

lacustrine deposition the region has undergone such deformation and erosion as to entirely 

remodel the topography; lake beds, for example, now forming the summit of Montezuma Peak, 

west of Goldfield. 

Two opposed views have been held regarding these Tertiary lacustrine deposits. Clarence 

King c regarded those with which he was familiar near the fortieth parallel as having been laid 

down in a single great Miocene lake which he called Pahute Lake, giving the name Truckee 

group, as we have seen, to the sediments. He believed that this lake stretched northward into 

the John Day basin in Oregon, and suggested that it extended also into the Mohave region of 

California. Most recent writers on the earlier. Tertiary lacustrine deposits of western Nevada 

appear to have accepted King's conclusion that they were for the most part laid down in a single 

great lake. M. R. Campbell, however, writes as follows: d 

From the observations noted above and from descriptions of other geologists, it is apparent that lake sediments 

occur throughout a wide extent of territory in the Great Basin region. Some writers have supposed that the various 

outcrops are parts of one extensive sheet of sediment which was deposited in a widespread but shallow lake, and consequently that they are all of the same age. 

The data gathered during the present reconnaissance show that such is not the case. From the character and 

arrangement of the material composing these beds, it is apparent that most of the lakes occupied valleys, the bounding 

walls of which may be seen to-day with the coarse detrital material of the lake beds at their feet. As previously mentioned, the lakes undoubtedly existed at differ~nt geologic epochs, and from data now at hand it seems probable that 

lake-forming conditions existed practically throughout the Tertiary period (Eocene, Miocene, and Pliocene); but 

sedimentation was interrupted at intervals by violent crustal movements that tilted the earlier sediments and materially 

changed the topography of the country. 

The truth of the matter is that it is impossible to demonstrate at the present time that a 

single lake covered the greater part of western Nevada in early or middle Tertiary time. 

Deformation and erosion have destroyed, beyond . possibility of conclusive restoration, such 

continuity of sediments as may once have existed. Nevertheless the distribution, thickness, and 

character of the remnants are such as to lend strong support to the view that the greater number 

of them were deposited in one great water body corresponding to King's Pahute Lake. It is 

probable that there were other smaller lakes also, contemporaneous with Pahute Lake. Moreover, submergence and sedimentation may have been going on in certain greatly depressed 

parts of the lacustrine basin while erosion continued long in progress over other parts much 

later covered with water. Whether Pahute Lake extended, as King supposed, into Oregon is 

a Spurr, J. E., Geology of the Tonopah mining district: Prof. Paper U.S. Geol. Survey No. 42, 1905, p. 53. 

b Turner, H. W., The Esmeralda foFmation: Twenty-first Ann. Rept. U.S. Geol. Survey, pt. 2,1900, p. 202. 

cU. S. Geol. Expl. 40th Par., vol. 1, 1878, pp. 413, 454. 

d Reconnaissance of the borax depo::oits of Death Valley and Mohave Desert: Bull. U. S. Geol. Survey No. 200, 1902, pp. 21-22. 
TERTIARY CHRONOLOGY. 101 

yet unknown. · Between the Goldfield-Silver Peak region and the Death Valley-Mohave Desert 

region there is a considerable gap in the chain of lacustral deposits. There is also a change in the 

character of the sedjments, those of the southJrn region containing beds indicative of saline 

periods which apparently are not represented ih the sediments of the northern region. This 

difference suggests that the older lacustrine de osits of Death Valley and the Mohave Desert 

were laid down in a body of water which, during /part of its existence at least, was not connected 

with Pahute Lake. I 

Aside from the still doubtful extension of /the Truckee beds northward into Oregon it is 

clear that Pahute Lake was a vast sheet of wat~r, fully comparable in size with Lake Superior. 

King estimated the maximum thickness of the acustrine deposits[ as at least 4,000 feet ( 1,219 

meters), and it has been shown (p. 68) that the/_ thickness of the b

1

eds in the Goldfield region is 

probably in the neighborhood of l,OOOfeet (305 rp.eters). Conseque . tly, although deposition and 

submergence probably went on at the same time~ there is reason to suppose that the lake was by 

no means generally shallow. On the other han~, the submerged opography was undoubtedly 

fied by numerous islands. 

TERTIARY CHRONOLOGY OF THE W~STERN PART F THE GREAT BASIN. I . 

As has previously been seen, the initial da um plap.e from whJich the beginning of Tertiary 

history must be reckoned is the interval of post Jurassic deforniat on and erosion. The second 

and much less definite or satisfactory epoch is that of Pahute ake. Knowledge of the age 

of the lacustral beds thftt in this report are ovisionally corre~ ted with the Truckee group 

would be a great step toward a clear understan ing of Tertiary hiftory in western Nevada. 

Pahute Lake was supposed by King a to have come into exisyence at the dawn of the Miocene. This conclusion was based mainly upo1 the supposed dir ct continuity of the Truckee 

group with the John Day formation in Oregon1 

b the geologists of the Fortieth Parallel Survey 

realizing clearly that the scanty fresh-water fauna in the True ee group in Nevada was not 

distinctive enough to determine whether the ds are :Miocene or liocene. b The Infusoria collected by Spurr c from the Siebert beds at Ton pah are of no grea er distinctive value, although 

he appears to have accepted without questio~ the Miocene age of Pahute Lake. As no one 

has yet actually established the supposed connection of the Ttu9 ee group with the mammalbearing Miocene beds of the John Day basin, i/t must be admitt d that the assignment of the 

Truckee group to the Miocene rests upon evi~ence that is far frpm satisfactory. Spurr d and 

Balle accept the view of King, but G. D. Louderback t is inc ned to regard the group as 

Pliocene. I 

The opinion of the last-named author is pe/rhaps based in pa t upon the work of Lindgren,u 

who showed that lake beds in Truckee Valley, California, which le regards as probably equivalent to the lake beds at Verdi, Nev., are younger than the m in andesitic eruptions of the 

Sierra Nevada, a conclusion which is suggestiire of a late Tertia y age of at least some of the 

beds originally mapped with the Truckee group. In the lake deEsits south of Wabuska, also, 

D. T. Smith, h as before noted, found mammal" an remains, from hich W. J. Sinclair concludes 

. that" the beds are probably late Miocene or Plfocene, correspond ng to the Mascall and Rattlesnake formations of Oregon; but the material is not complete enJugh to determine these points 

with certainty." 

aU. S. Geol. Expl. 40th Par., vol. 1, Systematic geology, 18'i118, p. 691. 

b King, Clarence, op. cit., p. 423 . . 

cOp. cit., pp. 69-70. 

d Prof. Paper U.S. Geol. Survey No. 42, 1905, p. 70. 1 

eBull. U.S. Geol. Survey No. 308,1907, p. 33. 1 

/Basin Range structure of the Humboldt region: Bull. Gedl. Soc. America, vol. 15, 190 , p. 337. 

g Truckee folio (No. 39), Geol. Atlas U.S., U. S. Geol. Surv y, 1897. 

h Geology of the 11pper region of the main Walker River, Nrvada: Bu!l. Dept. Geology niv. California, vol. 4, 1904, p. 10. 
102 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIE~D, NEVADA. 

On the other hand, in the beds near Ray, Spurra found fresh-water shells concerning 

which W. I-I. Dall reported: 

According to the literature the fresh-water beds from which these fossils came have been referred by Doctor White 

and 

Eocene 

Meek to the Wasatch, or Bear River Laramie, Eocene, which is believed to be nearly the equivalent of the lower 

or Chickasawan marine Eocene (Lignitic of old authors) of our southeastern coastal plain. 

Dalllists only three forms and is not certain of the identity of these. Consequently the 

paleontological evidence can scarcely be regarded as establishing the Eocene age of the beds. 

The Esmeralda formation has furnished molluscan, fish; and plant remains/ but these do 

not fix the age of the beds, although Turner concludes that the formation as a whole is probably Miocene. Spurrc believes that the Esmeralda formation was deposited under a wide range 

of varying conditions and probably represents the whole of the Tertiary. 

In the El Paso Range, California, H. W. Fairbanksd found fossil leaves which, according to 

F. H. Knowlton, are undoubtedly Tertiary and "seem to belong to the Eocene." 

On the whole, therefore, paleontological data for the determination of the age of the Truckee 

group and its probably correlative deposits are both scanty and unsatisfactory. No evidence 

has yet come to light which discredits King's conclusion that extensive lacustrine deposition 

began with the Miocene. On the other hand, the basis for this conclusion must be admitted 

to be none of the surest, and the possibility that lacustrine conditions began in the Eocene 

can not be excluded. Paleontological evidence having been found inconclusive, the bearing of 

physical history upon the problem of the proper time subdivision of the Tertiary rocks may 

next be considered. 

In discussing the correlation of the lavas in that part of the Great Basin adjacent to the 

fortieth parallel, King e stated that the propylites are probably pre-Miocene and that the hornblende andesites are distinctly earlier than the Miocene strata(Truckee group), since these abut 

against eroded andesitic mountains. He concluded that the dacites also probably belong in 

Miocene, 

Eocene time. On the other hand, the so-called trachytes were thought by him to belong in the 

because the sediments of the supposedly Miocene Pahute Lake were thought to be 

largely composed of "trachytic" tuffs. For a similar reason some of the augite andesites were 

also placed in the Miocene. Mterward G. F. Beckert showed that the propylite was merely 

would 

an altered andesite. He als_o suggestedu that the trachytes of the Fortieth Parallel report 

turn out to be mainly an9-esites, -a result soon after fully established by Hague and 

. Iddings.h . As Spurr i has pointed out, the dacites of the earlier classification are in part rhyo-

. lites and in part latites. Moreover, it is clear from later work in the Great Basin that King's 

distinction between augite andesite and hornblende andesite is largely imaginary and certainly 

is not applicable as a criterion for determining the chronological succession of lavas over a wide 

region. Hague and Iddings i showed that the so-called augite andesites of the Great Basin 

nearly all contain hypersthene, and the descriptions given in Chapter IV of this report serve 

to illustrate what close connection and gradations between bio.titic, hornblendic, and pyroxenic 

andesites may obtain in a small area. Thus the broad generalization regarding the succession 

King 

of volcanic rocks propounded by Von Richthofen and adopted with some modification by 

has crumbled to pieces. The exceptions to so simple a sequence are too numerous to be 

_ignored. The later attempt of Spurrk to determine the general law of succession of the lavas 

of the Great Basin will be referred to in its proper place. The fact of present importance is 

a Geology of the Tonopah mining district: Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 66. 

plants 

b Turner, 

of the Esmeralda 

H. W., The 

formation: 

Esmeralda formation: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, pp. 203-204. Knowlton, F. H., Fossil 

pp. 223-224. 

Idem, pp. 209-220. Lucas, F. A., J;>escription of a new species offossil fish from the Esmeralda formation: Idem, 

cOre deposits of the Silver Peak quadrangle, Nevada: Prof. Paper U. S. Geol. Survey No. 55, 1906, p. 18. 

d Geology of eastern California: Am. Geologist, vol. 17, 1896, p. 68. 

e Op. cit., pp. 691-693. 

f Geology of the Comstock lode: Mon. U. S. Geol. Survey, vol. 3, 1882, pp. 81-90. 

gOp. cit., p. 374. 

h, Volcanic rocks of the Great Basin: Am. Jour. Sci., 3d ser., vol. 27, 1884, p. 456. 

i Geology of the Tonopah mining district: Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 59. 

i Loc. cit. 

· k Succession and relation of lavas in the Great Basin region: Jour. Geology, vol. 8, 1900, pp. 621-646. 
TERTIARY CH~ONOLOGY. 103 

I 

that King recognized a considerable group of andesitic rocks as distinctly pre-Miocene-that 

is, as prelacustral-and another group of rock now known to be also andesitic, as belonging to 

the period of the Miocene Pahute Lake, because supposedly corresponding tuffs were deposited 

in that body ·of water. As has been shown, however, the Siebert formation at Tonopah and 

Goldfield is not essentially andesitic. 

Apparently having uppermost in his mind the fact that the supposedly Miocene trachytes 

of King have turned out to be mainly andesites, Spurr a makes the andesitic eruptions begin 

just before the opening of the Miocene. He designates the andesites at Tonopah as "earlier" 

or ('hornblende-biotite" andesite and "later" or "biotite-augite" andesite and assigns both 

to the :Miocene, although he describes an interval of denudation and an extensive Geries of 

"dacite-rhyolite" eruptions between the · eruption of the later andesite and the formation of 

the Miocene lake in which the Siebert beds were deposited. In view of this interval, his statement b that the eruption of the hornblende-biotite-pyroxene andesites was contemporaneous 

with the Miocene lakes is not clear. Spurr's general summary of the geologic history at 

Tonopah is as follows: c 

The oldest of the Tertiary rocks :within the area of the Tonopah map are probably early Miocene, and so far as 

known the volcanic manifestation began with an eruption of andesite. In this andesite were formed fracture zones, 

along which heated waters ascended and deposited the valuable veins of the region. Another extensive eruption of 

similar but slightly more basic andesite followed, and then there was probably a period of volcanic rest and of denudation. Eruption was resumed by the outbreak of volcanoes, which alternately ejected siliceous dacite and poured 

out volcanic mud and frequently pumiceous lava. Some of the material may have been accumulated in water; most 

of it was probably deposited upon the land. Later, more glassy dacite of a slightly different composition ascended from 

below in irregular channels and poured out on the surface as thin sheets, or exploded and formed tuffs. Heated 

ascending waters followed the intrusive contacts of this lava and formed a group of quartz veins which contain gold 

and silver, but which are less important as regards strength and values than the veins formed after the eruption of 

the earlier andesite. 

As these dacite-rhyolite ert~ptions quieted down a lake was formed in a basin, which may have been due to a 

depression of the crust consequent upon the previous copious eruptions. In this lake there accumulated quietly 

several hundred feet of sediments, with occasional light showers of ash from volcanoes, and, in the lower portions, 

some thin flows of dacite lava. Then the beds were lifted and became dry land. This uplift may have been due to 

the accumulation of additional volcanic material beneath this portion of the crust. Streams began to cut into the 

lake beds, the uplift was continued, and the whole district was tilted bodily to the west a~ an average angle of 20°. 

After this there were renewed outbursts, from probably new vents, which doubtless corresponded, in part at least, 

to the present mountains. On Brougher and Butler mountains explosive eruptions occurred, the material being 

dacitic, like that immediately preceding the lake deposits. Cones of ash, cinders, and bombs were built up, and there 

were occasional very thin and scanty glassy flows. On Siebert Mountain there was an explosive outburst of basaltic 

material, followed by a thin basalt flow. Subsequently columns of liquid lava welled up and stood in the vents of 

the .volcanoes, but aid not overflow. Some of these were composed of dacite, some of rhyolite. As these columns 

cooled, heated waters rose along their contacts and deposited chalcedony and other minerals, and mud dikes were 

injected into the soft intruded rocks. The explosive outbreaks and the intrusion of these large necks must have 

broken the rocks into blocks and displaced the blocks, for at this time many faults were formed. 

On the cessation of this dacite-rhyolite period of volcanic activity there was a collapse or depression around the 

vents. This sinking took place largely along the fault planes, and was especially prominent around the volcanic 

necks, which, as they sagged, dragged down blocks of the intruded older rocks with them. 

Since this time, which was probably somewhere in the Pliocene, erosion has been active, stripping away the 

debris covering from the dacite-rhyolite necks, and leaving them as hills, and in general removing the surface layers 

from the hills to the desert valleys. 

In opposition to this view of the essential contemporaneity of the andesites and lake 

sediments stand not only King's recognition of andesites distinctly older than Pahute Lake, 

but Spurr's oWn work at Tonopah, in which he shows clearly that a notable interval of erosion 

separates the "later andesite" from the Siebert lacustrine epoch. 

At Goldfield there is an extensive series of lavas, including the andesites, which are certainly older than the lake sediments. The reconnaissance of Ball also, as appears from the 

a Succession and relation of lavas in the Great Basin region: Jour. Geology, vol. 8, 1900, p. 637; Geology of the Tonopah mining district: Prof. 

Paper U. S. Geol. Survey No. 42, 1905, p. 69. 

b Prof. Paper U. S. Gool. Survey No. 42, 1905, p. 69. 

c Goology of the Tonopah mining district: Prof. Paper U. S. Geol. Survey No. 42, 1905, pp. 67-68. 
104 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

table on page 93 and the columnar section on page 91, shows that in the area studied by him 

that part of Tertiary time antecedent to lacustrine conditions was long enough for the eruption 

of Inany kinds of lava, including the andesites, and for the dev~lopment of two erosion 

unconformities. 

The situation may be summed up by saying that in the Goldfield region, and probably in 

other parts of southwestern Nevada, extensive eruptions of andesite took place after the 

extravasation of lavas which most workers in the region have tentatively assigned to the Eocene 

and before the formation of Pahute or Siebert Lake, which has been considered Miocene by 

King, Spurr, and Ball. Are these andesites to be placed in the Eocene or do they belong to 

the Miocene? 

To this question, it must be admitted, no definite answer can yet be made. We know 

merely that a series of effusive and intrusive rocks intervenes between a pre-Tertiary terrane 

and a series of lake sediments and intercalated flows of questionable Miocene age. Kinga 

regarded the beginning of the lake as coinciding with the dawn of Miocene time. The prelacustrine series is divided at certain horizons by unconformities and is unconformably overlain by the lake beds. No direct paleontologic evidence is available, and for the determination 

of the plane between the Eocene and Miocene, supposing Pahute Lake to have been Miocene, 

recourse must be had to local physical history. Spurr and Ball carry the Miocene back into 

the prelacustrine series, the latter making the division between the two periods coincide with 

an unconformity which, in the local sequence at Goldfield, comes between the latite and the 

Sandstorm rhyolite. My own preference is to regard the initiation of lacustrine conditions as 

the most significant physical revolution and, with King, to make that event mark provisionally 

the beginning of the Miocene, or, in any case, to regard it as one of the principal division planes 

in Tertiary chronology. I fully realize, however, that the physical event which appears most 

significant and epoch-making to one student may, in the opinion of another worker, take 

secondary rank. Moreover, new paleontologic evidence may at any time show that the 

beginning of the Miocene, and what appears to be the most important break in the continuity 

of physical history, are not necessarily coincident. Besides, although the andesites of Goldfield 

and Tonopah are distinctly older than the lake epoch, this proposition can not be asserted with 

equal confidence in regard to the dacite and dacite vitrophyre of Goldfield and the earlier of 

the so-called dacites of Tonopah. Still further, the beginning of the lacustrine conditions, as 

has been shown, may have been far from synchronous over the whole region. 

So far as it goes, the evidence for an important prelacustrine epoch of volcanism and erosion supports the view that the lake sediments are at least not older than the Miocene. It 

may be considered very doubtful, however, whether it will ever be possible to correlate with 

,recision the Tertiary events of the Great Basin with the well-recognized divisions of the marine 

deposits of the same period. Whether any close parallelism ever existed between the deposition of sediments known as Eocene, Miocene, and Pliocene along the Pacific margin and the 

complex manifestations of local volcanic activity, erosion, and lacustrine sedimentation that 

make up the history of the interior province is open to serious question. 

The second great division of Tertiary time in western Nevada, provisionally called 

Miocene, came to an end with the disappearance of the lake and the folding of its sediments. 

Masked and confused as it is in some localities by later disturbances, this folding, accompanied 

by faulting, is recognizable as a generally synchronous revolutionary movement for the whole 

region and was possibly contemporaneous with the post-Miocene uplift of the Coast Ranges. 

In the t.q.ird division of the Tertiary, the provisional Pliocene of the Great Basin, King b 

plaeed the sediments of his Shoshone Lake, calling them the Humboldt group. Russell c 

aftern:ard showed, however, that all the deposits described and mapped in the Fortieth Parallel 

reports as the Pliocene Humboldt group are really the deposits of Lake Laho~tan and are 

a Geology of the Tonopah mining district: Prof. Pap"r U. S. Geol. Survey No. 42, 1905, p. 691. 

bU. S. Geol. Expl. 40th Par., vol. 1, 1878, pp. 434 et seq. 

' cLake Lahontan: Mon. U.S. Geol. Survey, vol. 11, 1885, p.145. 
TERTIARi CHRONOLOGY. 105 

Quaternary. Thus King's Pliocene Shosho Lake, robbed of its sediments, has with progress 

of time become more nearly mythical than Spurr a and Ball,b to judge frbm their publications, 

appear to be aware. It is true that Spurrlc has noted deposits which are at altitudes above 

the highest known level of Lake Lahontan knd which he believes were d1

eposited in a Pliocene 

lake; but these observations alone appear I carcely sufficient to resuscitate King's conception 

of the vast Lake Shoshone. If Russell is right, Lake Shoshone was d.erely Lake Lahontan 

and was Quaternary. - I 

At all events there are no deposits in he Goldfield district definitely referable to a great 

Pliocene lake. The Spearhead rhyolite, thy. Rabbit Spring formation, and the Malpais basalt 

are provisionally placed in the Pliocene b, cause they are later than the folding and erosion 

of the supposed Miocene lake beds and ha ~ themselves suffered some deformation and much 

erosion. Finally, the gravels referred to o page 75 are supposed to co_rrespond to the Quaternary epoch of expanded lakes represente by Lakes Lahontan and Bonneville. The shore 

features of this epoch are well displayed abf ut Walker Lake, but it is not clear whether actual 

lacustrine conditions prevailed during the P eistocene over the Goldfield region. 

. THE ERU,TIVE SEQUENCE. 

For convenience of comparison the general succession of lavas in the Great Basin region 

according to Spurr d is in figure 6 placed side by side with the observed ~uccession in the Goldfield district. The order of age is from the bottom up. 

The two columns in figure 6 show some general agreement in that the first rocks erupted 

were rhyolites and the last rhyolites and basalts. :Moreover, between these earliest and latest 

products both columns show lavas of intermediate character. Spurr presents an elaborate twocycle scheme of regional differentiation into which it is possible to ~t most of the locally 

observed sequences, under the supposition that each of these repres~nts only a part of the record. 

If a basic rock appears in the wrong place in one line of descent from the parent andesitic magma 

it may be fitted into the other divergent line; thus if the local sequence be not too full it matters 

little, so far as conformity with the diagram is concerr:ed, in ':hat order he llitvas. were erupted. 

Even the rather full sequenc_e at Goldfield can, by d1sregard1ng the quartz-beanng basalt and 

the basalt of the Portland mine, be shown fO have a certain conformity to this scheme. Thus 

"1. Rhyolite" at Goldfield may be considered equivalent to "1. Biotite rhyolite and tordrillite; ' " 2. Latite" at Goldfield to "2. Latite(?)" in Spurr's scheme ; "3. Rhyolite" and " 4. 

Rhyolite" at Goldfield to "3. Biotite rhyolite ;" "6. Andesite " at Goldfield to the andesitic 

part of Spurr's fourth group; the dacitic rocks at Goldfield to the biotite-hornblende dacite of 

Spurr's fourth group; and "12. Rhyolite" and " 13. Olivine basalt" at 1

Goldfield to the corresponding rocks in the fifth group of Spurr's succession. Furthermore,f the Goldfield column 

may be inverted or its members may be transposed in various ways and it will still fit into the 

same plan of recurrent general differentiation. 

To some minds the conformity here shown may appeal as corroborative, but to others, 

impressed by the scanty representation of the numerous members of the ideal succession in any 

given locality, t he capacity of the scheme for assimilating not only observed sequences, but 

imaginary ones, raises doubt whether it really represents natural processes. The basal assumption that every observed local sequence is a fragmentary expression of a regional two-cycle 

differentiation of a common magma having the composition of pyroxene-hornblende andesite 

is the uncertain foundation upon which the whole structure rests. 

a Origin and structure of the Basin Ranges: Bull. Geol. Soc. America, vol. 12, 1901, p . 246. See also, Louderback, G. D., Bull. Geol. Soc. 

America, vol. 15, 1904, p. 339, footnote. · 

b Geologic reconnaissance in southwestern Nevada: Bull. U. S. Geol. Survey No. 308, 1907, p . 34. 

c Geology of Nevada south of the <iOth parallel: Bull. U. S. Geol. Survey No. 208, 2d ed., 1905, pp. 107, 117, 123-125 

dSuccession and relation of lavas in the Great Basin region: Jour. Geology, vol. 8, 1900 p. 643. 

I I 
106 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Study of the Goldfield district, moreover, does not indicate such parallelism between 

sequence and miner~logical composition as is presented by Spurr for the andesitic rocks, particularly in the fourth group of his synopsis. 

Great Basin (J.E.Spurr) Goldfield 

5{ 

Olivine\asalt Ultra acidic rhyolite or tordrillite 13. Olivine basalt 

Biotite r'olite 

(Malpais basalt) 

Augite \salt 

Biotite-horn,(.nde rhyolite 

12. Rhyolite 

Hornblen~ basalt (Spearhead rhyolite) 

Pyroxene-oli~ne aleutite Hornblende(biotite latite 11. Olivine basalt 

· Pyroxene ~eutite Biotite-ho~lende dacite 

(quartz bearing . 

Mira basalt) 

Hypersthene-hornble~e aleutite Biotite-augite-,rnblende-quartz latite 10. Andesite 

4. \ Augite-bio~e-hornblende latite 

(breccia and dikes) 

Hornblende-pyroxene-biotite aleutite 9. Rhyolite 

Pyroxene \desite Hornble~e-pyroxene andesite 

(Meda rhyolite) 

{Dacite vitrophyre 

Pyroxe~-hornblende Ldesite 

s. Andesite 

(Chispa· andesite) 

7. Dacite 3. Biotite'\hyolite Olivi/ basalt 

6. Andesite 

L~tite (?) 

P=xeneL 

(Milltown andesite. 

Generally contemD~ite(a) poraneous biotitic, 

hornblendic, and 

. \ . pyroxenic varieties) Hornblende-quartz andesite 

Biotit~ndesite 5. Olivine basalt 

2. (of Portland mine) 

Hornble~ andesite 

4. Rhyolite 

Hornblende-p~\e andesite . 

(Morena rhyolite) 

3. Rhyolite 

(Sandstorm rhyolite) 

Pyroxene~hornblende andesite 2. Latite 

1. Biotite rhyolite and tordrillite 1. Rhyolite 

(Vindicator rhyolite) 

(a) Spurr's use of this name in the Tonopah report leaves the reader in some 

doubt as to what rock is here meant.-F.L.R. · 

FIGURE 6.-Succession of lavas in the Great Basin and at Goldfield. 

TERTIARY CLIMATE. 

With the advance into the Tertiary the. problem of climatic changes strongly challenges 

attention, not only on account of its obvious bearing on the discussion of erosion and lacustrine episodes, but also, as will later appear, in view of its being a possible factor in the process 

of ore deposition. 

Clarence .King states a thatthe Eocene, as a whole, was remarkable over the Fortieth Parallel area for the intensity, rapidity, and grandeur of ita 

processes of disintegration and removal. Like the deposits of the Alps and the enormous Eocene field of Asia, it stands 

out in the Tertiary as a great interval of degradation and sedimentation. 

Presumably; therefore, the climate in the Great Basin region during Eocene time was comparatively humid. The coal and fossil leaves described by H. W. Fairbanks b in the El Paso 

aU. S. Geo. Expl., 40th Par., vol. I, Systematic geology, 1878, p. 692. 

b Geology of eastern California: Am. Geologist, vol. 17, 1896, p. 68. 
TER'l'IARY CLIMATE. 107 

Range, California, and by H. W. Turnera at the north end of the Silver Peak Range, point to 

the same conclusion1

! although the age of these coal-bearing beds is still not definitely known, 

and there is a possibility that they are Miocene. 

Although Tertiary lacustrine conditions appear to have begun in a period sufficiently humid 

for the growth of coal-producing vegetation, there are clear indications in the beds of borax . 

and salt in the southwestern part of the Great Basin that in that part of the region at least, 

periods of comparat~vely abundant water alternated with intervals of aridity. Thus throughout the Tertiary the climate of the Great Basin probably swung back and forth between moderate humidity and pronounced aridity. In this connection it is important to· remember that 

under the physiographic conditions which appear to have characterized the Great Basin since 

the beginning of the Tertiary the existence of extensive lakes is consistent with only moderate 

humidity. A very slight persistent increase of precipitation at the present time, for example, 

would materially enlarge the existing lakes, whose levels are determined by a delicate, fluctuating balance between evaporation and rainfall. As Russell points out, the Quaternary climate 

in the Great Basin at the time of the greatest expansion of Lake Lahontan must still have 

been comparatively 1 

arid, since the lake never overflowed. The life history of the former lake 

shows "that its shores must have ' been. at least as desolate and lifeless as the borders of the 

existing lakes of th~ same region.'' b 

a The Esmeralda formation: Am. Geologist, vol. 25, 1900, p. 168. 

b Russell, I. C., Geological history of Lake Lahontan: Mon. U.S. Geol. Survey, voi. 11, 1885, p. 261. 
CHAPTER X. 

MINERALOGY OF THE DISTRICT. 

INTRODUCTION. 

The accompanying table . presents in alphabetical order the minerals recognized in the 

Goldfield district. Those of doubtful occurrence are printed in italics. Following the tabular 

statement are fuller notes on the more important minerals taken up in the same order as that 

followed in Dana's System of Mineralogy. 

One mineral listed, namely, goldfieldite, is a new species; and it is possible that the 

minerals described as famatinite and bismite may also be species not hitherto recognized. 

Knowledge of these, however, is not as yet sufficient to justify the application to them of new 

names. 

Minerals occurring in the Goldfield district. 

Mineral. F<'rmula. 

Albite .............. NaAlSiaOs ............................ . 

Alum (kalinite)..... K2S04.Ah(S04)3+24H20 ............ . . 

Alunite ............ K(Al0)3(S04)2+3H20 ....... .. ....... . 

Amphibole ... . . . .. . Andesine .••....... . 

Apatite .......... . . Augite .. .. ...... .. . Azurite ............ . 

(See Hornblende.) Variable mixtures of the albite and 

anortll.ite molecules ranging from 

AbaAn1 to Ab1An1. 

(CaF)Ca,(P04)a or (CaCl)Ca,(P04)a ... . Variable. Complex silicate ........... . . 2CuCOa.Cu( OH)2 ............... . ..... . 

Barite ............. . BaS04 ................................ . 

Biotite ....•..... .. . Complex silicate of H, K, Mg, Fe, and AI. 

Bismite............ BhOa ............................... .. . 

Bismuthinite. .. .... Bi2Sa ............... .. ............... . . 

Bytownite . .. ....... Variable mixtures of the albite and 

anorthite molecules ranging from 

Ab1Ana to Ab1An5. Calcite............. CaCOa ....... .. . . ..................... . 

Cerargyrite ......... AgCL .............................. ... . Chalcanthite..... . . CuS04+5H20 ......................... . 

Chalcopyrite. . . . . . . . CuFe82 ............................... . Chlorite .... .. ..... , Complex silicate of H, Fe, Mg, and AI. 

Variable. Cinnabar........... HgS ................. . .......... . ..... . 

Copper ...... . ...... Cu ...... .. ....... . .................. .. . Diaspore .... ....... AIO(OH) ............................. . Durdenite .......... Fe2(Te0a)a+4H20 .................... . Emmonsite........ Not known ........................ . .. . Enargite...... . .... acu2S.As2Sa ..... ... ..... . .. . ....... .. . . 

Enstatite ......•.. ! . (Mg, Fe)SiOa ........... .. ...... ..... . . Epidote ............ Complex silicate of Ca, Fe, and A L . .. . Famatinite . . ....... Cua(Sb,As)S4 ................ .. .... . .. . Galena............. PbS .................................. . 

Gold ............ ... Au ............. .. ........... . ........ . Goldfieldite (new 5CuS.(Sb,Bi,As)2(SeTe)a .............. . species). 

Gypsum............ CaS04+2H20 ........... . ... ... ....... . 

Halotrichite........ Fe0.Ah0a.4S0a+24H20 .............. . Hematite . ......... Fe20a ................. .. .............. . 

Hornblende ........ Variable. Complex silicate ........... . Hypersthene ....... (Fe,Mg)SiOa .......................... . Jarosite ... ........ . K2(Fe(OH)2)6(S04); .................. . 

Occurrence. 

As microperthite in alaskite. Possibly also in some of the andesitic and rhyolitic lavas. 

Not definitely recognized, but probably occurs in some mines in lower part of zone of oxidation. 

Abundant as constituent of altered volcanic rocks and in soft massive form with ores. 

Probably present with other feldspars in dacite and andesite. 

As microscopic constituent of andesite, dacite, and basalt._ As constituent of andesite, dacite, and basalt. 

Very sparingly as blue stain in some oxidized ore. Reported from Florence and Reilly mines. 

Abundant with ore in Sandstorm and Kendall mines. Sparingly present in Reilly, Consolidated Red Top, and Commonwealth mines. In dacite and dacite vitrophyre; in some of the varieties of andesite and basalt; in granitic facies of alaskite. 

Minute pearly scales in oxidized ore of Combination, January, Sandstorm, and probably other mines. 

Acicular crystals in ore of mines near Goldfield. Usually associated with famati- nite and gold. Probably present in some of the andesites and basalts with other plagioclases. 

In some unimportant veins; as cement of some tuffs and sediments; lamygdules in basalt; in propylitically altered rocks; with alunite in altered hyolite on Vindicator Mountain as a microscopic constituent. In oxidized ore near Diamondfield. 

Spari]lgly present near base of oxidized ore in most of the large mines near Gold- field. 

Reported from Sandstorm, Ken(iall, Combination, and Florence mines. As alteration product of biotite in propylitic dacite, latite, and andesite. 

Disseminated through altered andesite or andesitic tuff 1~ miles east of Black Butte. 

Native. Reported in surface panning. As microscopic constituent with alunite in altered rocks. In oxidized ores near Diamond field. Not certainly distinguishable from emmonsite. In oxidized ores near Diamondfield. Not certainly distinguishable from durdenite. In ore of the Gold Bar and Victor mines. Some of the material called famatinite in this report may be enargite. See page 117. As microscopic constituent of some varieties of andesite. In propylitically altered dacite, andesite, and latite. Characteristic of rich sulphide ore with native gold in mines near Goldfield. Not known in ores of the principal mines. Occurs in January-White Rock lease, just east of Goldfield, and in Mushett and Consolidated Red Top leases north of the Mohawk mine. 

Native. The principal valuable constituent of both sulphide and oxidized ores. Occurs intimately associated with gold, marcasite, and famatinite in some of the richest ores. Widely distributed in ores and altered rocks. Particularly associated with soft crushed material along fissures. As superficial deposits in southern part of dis- trict. 

As efflorescence in disused workings. As minute crystals in workings of Hat lease; probably with limonite in some iri- descent coatings on rock surfaces. 

Constituent of dacite, latite, and some varieties of andesite. As microscopic constituent of some varieties of andesite. In altered tuff ! mile south of Myers Mountain. Kalinite ............ (See Alum.) Kaolinite ... .... ... . H4AhSh09 ............................. In altered rocks near ore bodies. As soft white masses with ore. Often asso- ciated with alunite. 

108 
MINERALOGY. 109 

Minerals occurring in the Goldfield district-Continued. 

Mineral. Formula. 

Labradorite........ Variable mixtures of the albite and 

anorthite molecules ranging from 

Ab1An1 to Ab1Ana. 

Limonite ... --- ..... H6Fe409 .................... __ .... . ... . 

Magnetite ... _ .... . _ FeaO •. ______ .. _ ....... _. __ .. __ ... _____ _ Malachite .......... CuCOa.Cu(OH)2 ....... ___ ............ . Marcasite ......... _ FeS2 ............. ... _ ..... _ ........... . 

Massicot .......... _ PbO ...... __ _ . _. _. _. ___ . ___ .. _________ _ Melanterite ..... .. .. Fes0.+7H20 ... __ .... _ .. __ .... __ ..... . Muscovite ......... _ H2KAiaSia012- ........................ . 

Oligoclase.......... Variable mixtures of the albite and 

anorthite molecule ranging from 

Ab6An1 to AbaAn1. 

Olivine ...... ------- (Mg,Fe)2Si04 ...... ___ _______ ..... ____ _ Orthoclase......... KAlSiaOs .... _____ .. __ ............ _. _. _ Petzite. _. _ .. ______ . _ (Ag,Au)2Fe ..... _. ___ ..... _ .. ___ .. ____ _ Polybasite . ...... _ . _ Ag9SbS6 ............ _ ... _ ..... _ ....... . Proustite ..... ...... Ag2AsSa .......................... ____ . Pyrite .............. FeS2 .............................. _. _ .. Pyroxene .......... (See Augite.) 

Quartz ...... _. ___ ._ Si02 .......... _ ......... ___ ........... _ 

Rutile . . ... _________ Ti02. ···········---------------------- _ 

Scapolite ........... Silicate of Ca, Na, and AI. Composition variable. 

Serpentine ......... H4MgaSi209 ............. ______ .. . . __ . __ Sphalerite .. ___ .____ ZnS .............. _ ....... _______ . ____ _ 

Sulphur ....... _._._ S ....... ______ .. ___ . __ .......... ____ .. _ 

Tellurides ........ __ (See Goldfieldite and Petzite) .. _. _. ___ _ 

Tellurite .... _ .. _ _ _ _ Te02 ... _ .. _. ____ ... _ ........... _ ..... _ Titanite ..... __ .. , .. CaTiSiO;. __ ... ___ .......... _. _. _____ .. Zircon ... _____ ...... ZrSiO •... ________ ......... _ ... ___ .. ___ _ 

.Zoisite ... ........... Ca2(AIOH)Ah(SiO.)a . .. ....•......... _ 

Occurrence. 

The most common and abundant feldspar in the andesitic and dacitic rocks. Oc- curs also in basalt. 

Abundant in earthy form in oxidized ores. As crusts on .the croppings of some ledges. 

As microscopic constituent of the igneous rocks, especially basalt. 

As stains in some partly oxidized ore. Not common nor abundant. 

With pyrite, famatinite, goldfieldite, and bismuthinite in some rich sulphide ores. In crushed rock and gouge along fissures. Yellow incrustations. Commonwealth ground, 2 miles east of Goldfield. 

In partly oxidized ore of Combination mine. 

As variety known as sericite. Sparingly present in altered rocks with alunite 

and kaolinite. 

As constituent of alaskite and of some of the rhyolitic rocks. 

As constituent of basalt. 

As constituent of alaskite and, as variety sanidine, of some of the rhyolites. 

Not identified, but may occur in ores near Diamondfield. 

Possibly in ore from Florence mine. 

Do. 

Widely disseminated through altered rocks. Most abundant sulphide in ores. 

A constituent of alaskite, rhyolite, dacite, and of most of the sediment~try rocks. 

In cryptocrystalline form is the principal constituent of the ledges. Occurs 

sparingly in quartz-basalt. . As a microscopic constituent with alnnite, diaspore, quartz, and pyrite in altered 

dacite. 

Possibly as rare microscopic constituent in altered Sandstorm rhyolite. 

As alteration product of.olivine in basalt. 

Very sparingly in ores of the principal mines. Rather abundant in ?.Iushett and 

neighboring leases. . In altered andesite or andesitic tuff, 1 mile east of Tognoni Springs. Reported 

from croppings on Blue Bull claim 

Tellurides of gold occur in some rich ore, but have not been found in a form to admit specific determination. 

Sparingly with a telluride of gold in the Goldfield-Belmont mine. 

Occurs sparingly as an accessory constituent of some of the igneous rocks. 

Occurs sparingly as an accessory .constituent of some of the igneous rocks, especially alaskite. 

Not certainly identified, but may be present in some of the metamorphosed Cam 

brian sediments. 

NOTES ON THE MORE IMPORTANT MINERALS ASSOCIATED WITH THE ORE 

DEPOSITS. 

SULPHUR. 

Native sulphur occurs about 1 mile due east of Tognoni Springs as irregular interstitial bunches in a greatly shattered and much-bleached rock which appears to have been 

originally an andesite or andesite tuff-breccia. In places the sulphur serves as a matrix for the 

fragm.ents of altered rock, which now consist almost wholly of cryptocrystalline quartz. Associated with the sulphur is some white pulverulent material which the microscope shows to consist 

of minute, rough, doubly terminated cryst~ls of quartz. This crystalline powder is thus very 

sin1ilar to some in the Lone Star mine, described on page 244. The sulphur is massive and 

much of it occurs in lumps large enough to1 be easily sorted from the waste rock. Such prospecting as has been done, however, shows that the mineral is very unevenly distributed and the 

deposit is therefore of doubtful commercialjimportance. The sulphur was without much question deposited in connection with fumarolic activity or by hot sulphurous waters. 

According to Mr. H. C. Morris, a little sulphur has been found in the croppings on the Blue 

Bull claim. Whether in this case also it records extinct solfataric action is not so clear. 

Sulphur in considerable quantity occJrs near Cuprite, 12 miles (19 kilometers) south of 

Goldfield. There are two main deposits. One, about 1! miles (2.4 kilometers) northwest of 

the railway stationJ is on the summit of an oval hill composed of nearly horizontal beds of angular 

conglomerate probably belonging to the Siebert formation. These beds are in part silicified 

and contain abundant opal. Overlying these beds near the top of the hill is a nearly horizontal 

stratum of dazzling white ashy material, through which the sulphur is distributed in considerable 

masses. This bed is overlain by a layer of chalcedonic brecci~, which was probably originally 

a layer of pumice. The rocks show evidence of strong solfataric action, which has bleached and 

silicified them, and has deposited the sulphur. The pulverulent material containing the sulphur 
110 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

was probably a rhyolitic glass or tuff now altered to pulverulent silica and alunite. The deposit 

is of oval plan and about 600 feet (183 meters) long, the thickness of the deposit being unknown. 

The sulphur apparently lies generally under the chalcedonic capping and would have to be 

mined by tunneling. A car or two of the material has been sorted and shipped from the various 

prospecting pits. 

The second deposit is about half a mile northeast of Cuprite in solfatarically altered rhyolite 

pumice containing alunite. It is smaller than the one first described. 

GOLD. 

Over 95 per cent of the gold obtained in the district occurs in the free or native condition. 

Some tellurides are present, for tellurium was detected chemically by W. F. Hillebrand in 1905,a 

and auriferous tellurides have been found in the Gold Coin and Goldfield-Belmont mines near 

Diamondfield. The presence of a ferric tellurite (emmonsite or durdenite) and the mineral 

tellurite in the Black Butte ores was noted in the preliminary report of 1907. b Gold tellurides, 

however, have not been satisfactorily identified as visible constituents in the rich ores of the 

mines near Goldfield. A large part of the tellurium of these ores certainly belongs in the mineral 

goldfieldite, in which the gold is apparently embedded in the native state, not as a telluride 

of gold. 

Although the particles of gold are uniformly very small they are usually visible on close 

inspection in all but the lower grades of ore. In the unoxidized ore the tiny specks of gold 

may be clustered so thickly in quartz as to give a yellow tint to the aggregate. Such ore is shown 

in Plates XXIII. XXV and XXVI. In 1nore scattered and frequently in rather larger particles 

the gold may be embedded in famatinite or bismuthinitc, or, as first shown by W. J. Sharwood,c 

in a material supposed by him to be a mixture of tetrahedrite and a telluride, put which is 

probably the new mineral goldfieldite. 

· "TJlile there is evidently a very close association in this district between gold famatinite 

.and bismuthinite, the precious metal appears to exist in these sulphur-bearing minerals as 

mechanical inclusions, and not as a chemically combined element. It is likely that a similar 

statement applies to the gold associated in n1uch smaller proportion with pyrite in the lowergrade ores. In the pyrite, however, the gold is in a state of such minute division and is present 

in such small quantity that it has not been recognized under the microscope. 

The gold thus far obtained from the mines has been, on the whole, unusually fine. An 

average of 34 assays of rich ore from the Mohawk mine, made for Mr. J. W. Finch, gave 330 

ounces of gold, and 46.5 ounces of silver, to the ton. Probably not all of this silver was present 

in the native gold, since some of the other minerals in the ore may be argentiferous. The 

bullion from oxidized ores as deposited in the Carson City branch mint in 1904 was in some 

instances 0.9915 fine, worth $20.498 an ounce.d 

The most common gangue of the gold is cryptocrystalline quartz. · In some varieties of 

ore the gold and quartz incrust fragments of altered dacite or andesite, as described on page 165 

and are incrusted in turn by sulphides. Such is some of the rich ore of the Combination mine, 

shown in Plates XXIII, A, and XXVI. In other varieties the inner crust is composed of 

sulphides, and the gold is mainly in an outer envelope of gray flinty quartz, inclosing· needles of 

bismuthinite (Pl. XXIV, A). .In some of the rich ore from the Engineers' lease a twofold deposit 

of gold was observed, a thin layer on the surface of a fragment of altered andesite, then a shell 

of quartz and bismuthinite, and then a broader crust of gold covered by a drusy film of the 

quartz. (See Pl. XXV, B.) In still other kinds of ore the gold, quartz, famatinite, bismuthinite, and pyrite are less regularly distributed. In the January mine, for example, some of the 

best unoxidized ore is a porous mass of gray flinty quartz, in places showing traces of. former 

dacitic character, through which the gold and. sulphides occur irregularly in specks and illa Spurr, J. E., The ores of Goldfield, Nev.: Bull. U.S. Geol. Survey No. 260, 1905, p. 137. 

b Bull. U. S. Geol. Survey No. 303, 1907, p. 36. · 

c Min. and Sci. Press, June 8, 1907, p. 731. 

d Rept. Director of the Mint on production of the precious metals in the United States during 1904, Washington, 1905, p. 142. 
MINERALOGY. Ill 

defined bunches. The gold is not evenly apportioned through the mass, but is concentrated 

in the immediate vicinity of the sulphides, although the minute particles of gold are themselves 

usually embedded in quartz. In order to test the apparent affinity of gold and sulphides, a 

lump of this ore was crushed .and picked by hand into two parts, one containing most of the 

famatinite and the other most of the quartz. The sample having most famatinite afforded 

on assay 15.7 ounces of gold and 25 ounces of silver to the ton. The other portion gave 9.32 

ounces of gold and 11.08 ounces of silver to the ton. It should be said that the poorer sample 

still contained much famatinite, bisrnuthinite, and pyrite, it being impossible to effect more 

than a very rough separation of the ore into quartzose and sulphide portions. 

As seen by incident light with high microscopical power, the gold of the unoxidized ores 

appears as bright yellow hackly particles, with usually little more than a suggestion of crystalline aggregation. In a few instances particles suggestive of distorted or modified octahedrons 

have been observed strung together like beads into filiform aggregates, and rarely suggestions 

of octahedral planes and form can be detected in the smallest isolated specks embedded in 

quartz. The microscope shows that the gold and famatinite may be intimately intergrown, 

with no indication of one mineral being later than the other. A similar microscopic intergrowth of gold with a telluride was noted in ore from the Gold Coin claim, near Diamondfield. 

In the oxidized ores the gold has the same general character as in the sulphide ores, being 

invariably in a state of fine divi'sion. One sometimes hears the gold referred to as "rusty," 

but this is usually a misnomer. The term appears to be often applied to gold in particles so 

small as not to be individually visible to the naked eye. fuch particles when seen through a 

lens or microscope are clean and bright. The peculiar rus~y-looki 1

g 11ggregates of gold, such 

as results from the oxidation of calaverite in the Cripple C~eek .dist ict, have been observed in 

the Goldfield district only in some of the ore of Black Butte. 

In the ores of the oxidized zone the gold is associated with imonite, quartz, kaolinite, 

alunite, barite, bismite, and in a few places with emmonsite or durde ite, tellurite, and hematite. 

COPPER. 

No native copper was observed in the mines, although its occu renee in minute quantities 

in the lower parts of oxidized ore bodies is not improbable. A few particles of copper are 

reported to have been found by panning near Diamondfield and on the Combination Fraction 

claim. 

BISMUTHINITE. 

The mineral bismuthinite is the · trisulphide of bismuth (Bi2S3 ) and occurs In lead-gray 

acicular crystals belonging to the orthorhombic system . 

. Bismuthinite is present in much of the rich ore of the January, Combination, and Florence 

mines, and in the ~1ushett, Reilly, Engineers', Little Florence, and Rogers leases, as slender 

crystals embedded in cryptocrystalline quartz and associated with famatinite and free gold. 

The crystals are frequently intergrown with both the gold and the famatinite. The appearance 

of the bismuthinite in specimens of rich ore is shown in Plates XXIII, 0, and XXIV, A, and 

in thin section under the microscope in Plates XXVI, A, ·and XVII, A. The crystals are usually 

slender, ranging from delicate hair-like or capillary forms up to prisms a millimeter in breath. 

Crystals larger than are common occur in the Mushett and Little Florence leases. Th~ prisms 

are often curved. In no case have terminal planes been observed, the ends of the crystals 

being irregularly pointed or frayed. The planes of the prism zone are also indistinct arnd apparently striated, much as in stibnite, which bismuthinite resembles in habit. They have one 

perfect cleavage, presumably that parallel to the brachypinacoid (010). 

That the material of the crystals is sulphide of bismuth was proved by W. T. Schaller in 

the United States Geological Survey chemical laboratory. · 

In the Florence mine bismuthinite needles are abundant in nodular ore near the 300-foot 

level. With their cryptocrystalline quartz matrix they form a shell around famatinite, which 

incrusts fragments of altered dacite, as described on pages 165 and 229. In this place they 
112 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

are accompanied by abundant visible specks of native gold. In the rich ore of the Combination 

mine the shell of bismuthinite and quartz envelops a shell of quartz and free gold, as shown in 

Plates XXIII, A, and XXVI, A. In the January mine the bismuthinite is rather irregularly 

crystallized with quartz, famatinite, pyrite, and gold. Occasionally some regularity of arrangement is observable, however, as in the specimen of ore illustrated in Plate XXIII, 0, where a 

banded structure is recognizable. In the Mushett lease the prisms of bismuthinite in some 

places form nearly solid crusts, which are u.sually associated with sphalerite. 

While the needles of bismuthinite often run in all directions through the quartz and associated minerals, a radial or sheaf-like aggregation is rather characteristic, especially when the 

crystals are slender. 

The mineral is so uniformly associated with gold in the Goldfield deposits as to afford by 

its presence one of the most reliable indications of rich ore. 

In the process of oxidation the bismuthinite is changed to bismite. 

Bismuthinite is not a very common mineral in deposits of the precious metals, and is not 

mentioned by Lindgren a in his list of "minerals formed in ore deposits under varying conditions." It occurs with gold, chalcopyrite, and pyrite in the Gold Hill mine, Rowan County, 

N.C., band with speculafite (crystalline hematite) in quartz at the Neigold mine near Silverton, 

Colo. c It is reported d to occur also with almandine garnet and barite in the Granite mining 

district, Beaver County, Utah, and in Mono and Fresno counties, Cal. Its mineral associations 

in the Utah and California localities do not appear to have been fully described. 

The mineral has been prepared artificially by Senarmont, e who heated precipitated sulphide 

of bismuth with an alkali sulphide and water in a sealed glass tube; by Durocher/ who conducted sulphydric acid and vapor of chloride of bismuth through a tube heated to redness; by 

Schneider,g who fused together sulphur and bismuth in proper proportions; and by Carnot,h 

who passed a current of hydrogen sulphide over a salt, oxide, or precipitated sulphide of bismuth at a dull red heat. It is of interest to note also that bismuthinite has been known to 

form in sedimentary beds from the distillates of burnjng coal seams.i 

GALENA. 

During the first few years of mining at Goldfield galena was unknown. It does not occur, 

so far as can be ascertained, in any of the large mines. It is found, however, in latite in the 

January-White Rock lease on the eastern edge of Goldfield, in the same rock in the MohawkRed Top lease just east of the Red Top mine, and according to recent reports is present in 

comparative abundance in parts of the Consolidated Red Top lease, one assay affording 12.5 

per cent of lead. The ore of the Mushett. lease also has a little galena associated with sphalerite, famatinite, bismuthinite, pyrite, gold, and goldfieldite. The mineral occurs also in the 

Five Friends lease. 

SPHALERITE. 

I 

At the time of first visit, in 1905, the only occurrence of the sulphide of zinc known was a 

small speck which Mr. W. H. Blackburn had found in the Goldfield-Belmont mine near Diamondfield. Like galena, it is still a comparatively rare mineral in this district and has not been 

recognized in the ores from the large mines. It has proved latterly to be rather abundant, 

however, in the rich ore of the Mushett lease. Here it has generally been one of the later 

minerals to deposit and forms botryoidal crusts over the other sulphides. According to Mr. H. P. 

Henderson, some of this sphalerite afforded on assay 55.6 per cent of zinc with 1.8 ounce of 

gold and 7 ounces of silver per ton. 

a The relation of ore deposition to physical conditions: Econ. Geology, vol. 2, 1907, p. 125.. 

b Genth, F. A., Rep. Geol. Survey North Carolina, vol. 1, 1875, appendix C, p. 58. , 

c Ransome, F. L., Economic geology of the Silverton quadrangle, Colorado: Bull. U. S. Geol. Survey No. 182, 1901 (reprinted in 1903), p. 82. d DanJ, J.D. and E. S., System of mineralogy, 6th ed., New York, 1895, p. 38. 

e Sur la formation des mineraux par voie humide dans les gites metalliferes concretionnes: Annales de chim. phys., vol. 32, 1851, p. 161. f Production artificielle, par voie seche, des principaux mineraux contenus dans les gites metallifere~: Com pt. Rend., vol. 32, 1851, pp. 823-826. g Untersuchungen tiber das Wismuth: Pogg. Annalen, vol. 9, 1354, pp. 404-427. 

h Fouqoo, F., and Michel Levy, A., Synthese des mineraux et des roches, Paris, 1882, p. 319. 

i Brauns, Chemische Mineralogic, Leipzig, 1896, p. 299. 
MINERALOGY. 113 

Sphalerite occurs also in the Mohawk-Red Top and Five Friends leases and probably in 

other 1essee workings north of the Mohawk mine. It has also been noted· in a small stringer 

in alaskite in the Lucky Boy prospect on Vindicator Mountain and in the ore of the Loftus 

and Davis lease on the Great Bend, northwest of Diamondfield. 

CINNABAR. 

The very characteristic sulphide of mercury (HgS), with its cochineal-red color and adamantine luster, occurs in the northeastern part of the district, but is not known in the gold 

deposits. The cinnabar rock outcrops on the Brooklyn claim, about 1 ~ miles east of Black 

Butte. The mineral forms irregular crystalline aggregates, up to an inch in diameter, rather 

abundantly disseminated through material which was probably once andesite or andesite 

tuff, but which has been intensely altered and is now a mass of cryptocrystalline secondary 

quartz, . mottled with cinnabar and limonite. The deposit apparently is not of economic 

importance. 

The occurrence of cinnabar in the Goldfield district, in view of the well-known association 

of this mineral with volcanic activity, is of interest in connection with the problem of the 

genesis of the gold ores, as will be more fully shown in another place (p. 174). 

CHALCOPYRITE. 

The tetragonal copper-iron sulphide (CuFeS2), sometimes called "copper pyrite" or "yellow copper," is very rare in the Goldfield district. It has been reported in small quantity in 

the Sandstorm and Kendall mines, but was not seen in the course of the present investigation. 

E. A. Collins a states that it has been found very sparingly in the Combination mine. A speci.., 

men of rich ore, said to be from the Florence mine, and in the possession of Mr. F. 0. Altinger, 

of Goldfield, was examined by Mr. G. H. Garrey, who noted the occurrence of minute crystals of 

chalcopyrite lining small vugs and associated with bismuthinite, ruby silver (proustite ~), and 

a mineral resembling polybasite in crystallization. 

The rarity of chalcopyrite at Goldfield is remarkable, as most of the ores contain copper, 

and both sphalerite and galena, which often accompany this mineral in other districts, have 

been found in the leases north of the :Mohawk mine. 

PYRITE. 

Common pyrite, the isometric disulphide of iron (FeS2 ) is the most abundant and ubiquitous sulphide in the district. It is a constituent of practically all the rocks in the region except 

some of the later rhyolites, basalts, and lake sediments. It is disseminated through the propylitically altered andesite, dacite, and latite, where it has formed from the action of sulphide 

solutions upon biotite, hornblende, augite, and magnetite. As shown on page 179, it makes up 

a considerable percentage of the dacite that has undergone alunitic and kaolinitic alteration, 

particularly in the vicinity of the ledges. It is also finely disseminated through the altered 

rhyolites, although less abundant in these rocks than in those originally richer in iron-bearing 

silicates. 

Within the ledges, pyrite occurs disseminated through the altered siliceous rock forming 

the gangue of the ore, in the form of small bunches and metasomatic veinlets, and as crusts with 

gold, goldfieldite, famatinite, bismuthinite, sphalerite, quartz, alunite, and kaolinite around 

fragments of altered rock. 

In all of these occurrences the mineral usually forms aggregates. Individual crystals of 

free growth and large enough for the recognition of crystal habit are rare. Such faces as are 

visible indicate that the prevalent form is the pyritohedron, variously modified. When the 

crystals have been able to grow without mutual interference, as is the case in small vugs filled 

a The Combination mine: Min. and Sci. Press, Sept. 28, 1907, p. 398. 

79145-No. 66-09--~ 
114 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

with spongy friable quartz or in soft massive kaolinite or alunite, the usual form assumed is a 

sharp octahedron, in some cases modified by small cubic and dodecahedral faces. Such octahedral crystals were noted on the 250-foot level of the Florence mine. Small brilliant crystals 

embedded in alunite, from the 230-foot level of the Combination mine, show a dominant octahedron modified by sma1l faces of the cube, dodecahedron and pyritohedron. Beautiful clusters of sharp, brilliant crystals from the Mushett lease show a similar combination, but with the 

· pyritohedral faces dominant. The well-formed individual crystals are invariably small, most 

of them being less , than a millimeter in ·diameter. 

Pyrite with alunite, forming pseudomorphous aggregates after orthoclase, occurs in the 

Morena rhyolite at the Conqueror mine. Crystallized wi.th gypsum it is found on the 150-

foot level of the Goldfield-Belmont mine. 

While pyrite is widely distributed in the . Goldfield district, few observers familiar with 

other mining regions can fail to note the absence from the known Goldfield deposits of any 

considerable masses of this mineral. It is everywhere present but nowhere aggregated into 

bunches or veins of any notable size or purity. This is undoubtedly due to the fact that the 

pyrite has formed mainly from the ferrous si~icates and magnetite in the rocks and has undergone very little transportation or segregation. The fissuring, moreover, was not of a character to favor the accumulation of large solid masses of sulphides. The mineral is not all of one 

generation, as will be shown in the section on paragenesis on page 170. 

Whether the pyrite in the Goldfield deposits is auriferous is not easily determined. That 

it is not highly so is certain, since assays of the most pyritous ledge matter often show very 

little gold, and abundance of pyrite is generally a sign of poor, rather than rich ore. On the 

other hand, it is difficult to establish the absence of an· gold from the pyrite, owing to the 

impossibility of obtaining this sulphide entirely free from other constituents of the ore in which 

the gold might be held. Undoubtedly pyrite might be obtained in the district which contains 

practically no gold; but the pyrite to which most interest attaches is that in, or close to, rich 

ore, and it is this selfsame pyrite which can not be separated with certainty from its associated 

minerals. Famatinite and bismuthinite, for example, which are known to contain particles 

of gold, may iii turn be embedded in pyrite. 

In order to obtain some light upon this problem, samples of pyritized dacite w~re collected 

from various mines and assayed. All the samples were taken within the general boundaries of 

the ore-bearing zones, the aim being to obtain material in which pyrite was the only sulphide 

and which at the same time lay as close as possible to ore. The pyrite in all of the specimens 

is disseminated in varying abundance through a gangue consisting chiefly of quartz and alunite. 

The assays were made by Ledoux & Co., New York. 

Assays of pyritized dacite. 

[Ounces per ton.] 

Specimen. Locality. Gold. Silver. Remarks. 

G. 624 ...... · ........ Florence mine, 250-foot level, north end............. 0.075 

G. 819 .............. Combination mine, 230-foot level, near vertical shaft. .030 G. 818 .............. Combination mine, 230-foot level.................... .68 G. 714.............. Red Top mine, 160-foot level........................ . 55 G. 713 ................... do.............................................. .145 

0. 70 Pyrite in minute crystals, abundantly disseminated . . 13 Similar to above. 

2. 60 Pyrite very abundant. . 05 So-called low-grade ore. .20 Do. 

The results of these assays accord with the statement just made, that the pyrite is not 

rich in the precious metals. This is to be expected from the fact that most of the mineral was 

formed by the action of hydrogen sulphide on iron compounds already present in the rocks 

and not . wholly from materials i11-troduced by the ore-depositing agencies. 

MARC.A.SITE. 

The orthorhombic disulphide of iron (FeS2) is not always readily distinguishable from 

common pyrite, inasmuch as the latter mineral sometimes occurs in fibrous radial aggregates 
MINERALOGY. 115 

similar to those characteristic of marcasite. Specimens of 1narcasite usually decompose more 

readily than those of pyrite, but this test is not altogether reliable. In fact, as H. N. Stokesa 

has shown, there is no simple test, in the absence of recognizable crystal form, that will invariably distinguish the two minerals. Stokes's own method, based on. oxidation coefficients, is 

decisive, but requires special chemical apparatus and careful preparation of the sample to be 

tested. This method has not been applied to any of the material from Goldfield, and some· doubt 

may therefore attach to the determination of ~ndividual specimens of iron sulphide as marcasite. 

On the other hand, there is evidence enough to establish the fact that a subordinate part of the · 

iron sulphide associated with the ore bodies is of this species . . 

A specimen of rich ore from the Combination inclined shaft between the 180-foot and 

230-foot levels shows native gold and · quartz incrusted by pale yellow iron sulphide with a 

fibrous radial structure and mammillary surface. This is probably marcasite~ although it 

shows no vitriolization after the lapse of a year since it was taken from the mine. Crystals 

with characteristic marcasite planes and twinning collected by Mr. Lindgren from the Florence 

mine have proved equally stable. ~1any of these crystals, which incrust alunitized dacite, 

appear to be unmodified unit pyramids. Others are twinned, probably with a prism face (110) 

as twinning plane, although this is not clearly shown on the specimen .. Crusts of marcasite and 

goldfieldite are closely associated in some of the richest ore in the Mohawk mine. This marcasite, 

which does not decompose as readily as some varieties, shows a generally prismatic habit, 

the sides of the closely crowded prisms being irregular and strongly striated. Terminal faces 

are rare and no measurable forms have been isolated. 

Like gypsum, marcasite is rather characteristic of soft, cr:ushed ore and of gouge, ap.d 

appears in many places to be of later origin than most of the other sulphides. It occurs as 

concentric radially fibrous shells in soft, dark, and probably secondarily enriched ore streaks in 

the Combination, Reilly, and Florence ore bodies. . As a rule these shells disintegrate on exposure to the air, with the formation of yellow films, apparently containing a little free sulphur, and 

.of a brown fibrous effiorescence of iron sulphate. It is very abundant in soft gouge in some 

workings (Harrison shaft) opened by lessees just north of the Red Top mine and in leases on the 

February claim, south of the January mine. 

On the 146-foot level of the Oddie lease workings in the Mohawk mine the ore body is 

traversed by a narrow regular fissure. The walls of this are covered by a botryoidal incrustation of iron sulphide which is supposed to be marcasite, although the crystal form is not very 

clearly shown. · 

TELLURIDES OF GOLD . . 

No tellurides of gold have been satisfactorily identified in the mines near Goldfield, although 

the presence of some tellurium in the ores has been shown by W. F. Hillebrand.b In the preliminary report c issued in 1907, attention was called to the occurrence of emmonsite or durdenite and tellurite at Black Butte and to the conclusion that these ores prior to oxidation 

must have contained tellurides. It was also shown that a dark-gray mineral in irregular particles embedded in quartz and alunite forms part of the ore of the Gold Coin claim near Diamondfield. Tests by Mr. W. T. Schaller showed this mineral to contain much gold and tellurium, 

but no silver nor lead. It is thus probably a gold t~lluride , but the small size of the grains and 

the absence of crystal form rendered specific identification impracticable. A similar telluride 

occurs sparingly in the Goldfield-Belmont and probably also in other mines and prospects of 

this portion of the district. 

'Vith the opening of the Mohawk oce body in the Hayes-Monnette lease it was found that 

the gold of the rich ore is associated with notable quantities of tellurium.d 

a On pyrite and marcasite: Bull. U.S. Geol. Survey No. 186, 1901. 

b Spurr, J. E., The ores of Goldfield, Nevada: Bull. U.S. Geol. Survey No. 260, 1905, p. 137. 

c Ransome, F. L., Garrey, G. H., and Emmons, W. H., Preliminary account of Goldfield, Bullfrog, and other mining districts in southern 

Nevada: Bull. U. S. Geol. Survey No. 303, 1907, p. 36. 

d King, L. M., The sampling and assaying of a car of bonanza ·ore: Min. and Sci. Press, vol. 94, 1907, p. 241. In an editorial in the same 

number the statement is made that calaverite occurs in the Mohawk ore. The method of identification is not given and the statement is probably 

a conclusion from the ratio of gold and tellurium found in the ores, since no distinct crystals of this mineral have been found at Goldfield so far as 

can be Jearned. 
116 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

In June, 1907, W. J. Sharwood a published a drawing of a thin section of Mohawk ore in 

which he shows particles of native gold embedded in a dark '' sulpho-telluride," which he foundgave strong reactions for sulphur, tellurium, copper, and iron, also for arsenic, antimony, gold, and silver (about 6 per 

cent and 1 per cent, respectively, of the two last)-a composition agreeing with the admixture of tetrahedrite and 

telluride suggested in the editorial referred to. To all outward appearance, however, the material seems to be uniform 

in character and gives no evidence of being such a mixture. 

In a thin section of another specimen of Goldfield ore Sharwood detected particles resembling 

sylvanite associated with native gold. The dark-gray mineral supposed by Sharwood to be 

a mixture of tetrahedrite and calaverite is further described under "Goldfieldite." The particles thought to be sylvanite may have been marcasite, the resemblance of the marcasite of this 

ore to sylvanite in color, luster, and striations being deceptively close. 

PROUSTITE. 

Ruby silver (Ag2AsS3) has been noted on only a single specimen, purporting to come from 

the Florence mine, and preserved in a private collection in Goldfield. The identification of 

the mineral was made by Mr. Garrey, who examined the specimen but was unable to obtain it 

for confirmatory tests. The occurrence of proustite in the district can not, therefore, be regarded 

as established. 

POLYBASITE. 

The mineral polybasite, essentially a sulphantimonite of silver (Ag9 SbS) 6, has not been 

identified with certainty in the Goldfield ores. Crystals of a form and color resembling polybasite were observed by Mr. Garrey, associated with a little ruby silver, in the specimen of ore 

referred to i,n the preceding paragraph. The ore was said to have come from the Florence mine . 

. GOLDFIELDITE. 

At the time of second visit to the district, in 1908, specimens were secured of the dark 

tellurium- and gold-bearing material from the Mohawk mine for the purpose of determining 

its mineralogical and chemical character. A piece of rich ore from the Mohawk-Combination 

lease (a consolidation of the Sheets-Ish and Kalfus leases) was broken up and the fragments 

of the dark telluri.c crust picked as free as possible from the gangue. These were crushed to 

pass through a 40-mesh screen and freed from fine dust. The grains were picked over several 

times under a lens and a separation effected into (I) yellow grains, (2) gray grains, and (3) 

mixed grains and gangue. The yellow grains proved to be marcasite. · 

The gray· portion when examined under the microscope appeared homogeneous with · the 

exception of a few minute specks of gold embedded in the gray mineral. The latter is dark 

lead gray with a high metallic luster. It is brittle, breaks with a conchoidal fracture, and ha~ 

a hardness of 3 to 3.5, although on account of the brittleness of the material it appears to be 

sornewhat softer when crushed. No crystal faces have been detected. The small quantity of 

purified material, only 1.2 grams in a.ll, was analyzed by Doctor Palmer with the following result: 

Preliminary chemical analysis of golqfieldite. 

Copper.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33. 49 Gold.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 51 

Sulphur..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21. 54 Silve:-............. . . . . . . . . . . . . . . . . . . . . . . . . 18 

Tellurium.............................. . .. 17.00 Gangue................................... 2. 00 

Antimony........... . . . . . . . . . . . . . . . . . . . . . . 19. 26 

Arsenic................................... . 68 

Bismuth .............. '.................... 6. 91 

101. 57 

Of the gold about 0.40 per cent in terms of the whole analysis is combined, presumably 

with tellurium, and 0.11 per cent is native. 

Doctor Palmer states that the mineral is essentially a cupric sulphantimonite in which part 

of the antimony is replaced by arsenic and bismuth and part of the sulphur by tellurium. He 

a Gold tellurides: Min. and Sci. Press, vol. 94, 1907, p. 731. 
MINERALOGY. 117 

suggests that the analytical results approximate closely the formula 5CuS. (Sb,Bi,As) 2 (S,Te)3. 

The minerals geocronite (5PbS.Sb 2S3) and stephanite (.5Ag2S.Sb2S3) have analogous formulas 

whereas the known copper su]phantimonites and sulphantimonates are all cuprous salts. 

As bismuthinite is a common mineral in these ores, the possibility that the material analyzed 

might be an intimate mixture of bismuthinite with some other mineral has been considered. 

If the analysis be calculated in molecular proportions, and the constituents of bismuthinite 

(Bi2S3) be subtracted, the following molecular quantities remain: 

Cu .............. ___ .. _ ........ . ........... 0. 527 · As._ ... _ .... _ . . ..... . _ .................... 0. 009 

S ........................ __ .... . ... , . . . . . . . . 624 Au .... _ ..... . . .. _ . . . . . . . . . . . . . . . . . . . . . . . . . . 002 

Te ....................... . ............. . .. . . 133 Ag ............ . ....... . .................... 001 

Sb ...................................... _. . 160 

For famatinite the theoretical proportions are: Cu, 0.-6; , S, 0.6; Sb, 0.2; so that the residue 

after subtraction of bismuthinite does not correspond very closely to famatinite, even if the 

tellurium be ignored. This constituent, it is to be observed, is far in excess of any quantity 

which could be accounted for as combined witll the gold and silver, and a part of the gold is 

known to be free. 

While determinative work on minerals such as the sulphantimonites, which rarely show 

crystal form and are often intergrown with other minerals, is as a rule more or less unsatisfactory, there seems to be no escape from the conclusion that the present mineral is a new species. 

It is provisionally so regarded and "goldfieldite" ~s suggested as an appropriate name. It is 

hoped that additional material can be secured for further analytical and microscopical investigation in the near future. 

In some ore, especially that of the Mushett lease, the association of goldfieldite and famatinite is very close, and it is possible that such ore may contain intermediate species or varieties. 

ENARGITE. 

Crusts of a dark-gray brittle compound of copper, arsenic, antimony, and sulphur are 

characteristic of the ore of the Victor and Gold Bar mines. The substance is similar in habit 

and appearance to a mineral which is commonly associ~ted with the rich ores near Goldfield 

and which, as will be shown, appears to correspond more nearly to famatinite than to any. 

other known species. It presents some differences, however. It lacks for the most part the 

reddish tint of the famatinite, is rather more brittle, ·shows more tendency toward crystalline 

structure, and is not associated with rich ore. The crystal habit of the mineral is prismatic, 

the faces being longitudinally striated. It has at least one cleavage, although the crystals are 

too few and imperfect to permit determination of its crystallographic orientation. Mr. W. T. 

Schaller was able to isolate one crystal with rather uneven faces, which gave the following 

goniornetric readings in the prism zone: · 

100 /\ 110= 41° 30' 

100 A 120= 60° 30' 

roo A 1ro= 40° 30' 

roo A 100= 179° 30' 

These agree fairly well with the calculated angles for enargite, which ar~-

100 A 110= 41 o 04' 

100 A 120= 60° 09' 

roo A 1ro= 41 o 04' 

roo A 100=180° oo' 

As enargite and famatinite are isomorphous, however, the measurements serve only to 

rule out tetrahedrite, which contains the same constituents as famatinite or enargite, although 

in different proportions. It will presently be shown that the composition of the mineral called 

famatinite in this report is not normal, but indicates' a variety between that mineral and its 

isomorph, enargite. It is likely that at Goldfield there are vanous representatives of the 
118 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

enargite-famatinite series separated by no sharp differences in composition. The mineral from 

the Gold Bar and Victor mines is probably nearer to the enargite end of the series than most 

of these varieties. Not all of the cupriferous material from the Gold Bar mine is of the same 

kind as that just described. Some of it is indistinguishable from the famatinite of the Florence 

and other mines nearer Goldfield. 

FAMATINITE. 

Forming part of the rich sulphide ore in most of the mines near Goldfield is a massive 

metallic mineral of dark-gray color, with a tinge of copper red. This has been commonly called 

"bornite." In the preliminary report on the district a it was shown that the so-called "bornite" 

contained antimony, and accordingly it was there provisionally referred to as tetrahedrite, 

although attention was called to the possibility of its being famatinite. 

In order to determine if possible the species of the minerai; a specimen of ore from the 

January ~ine was broken up, and material for chemical analysis was carefully picked out under 

:a lens. The selected particles contained considerable quartz, a very little intergrown pyrite, and 

still less bismuthinite. The analysis is as follows: 

Chemical analysis of mineral from January mine. 

[By W. T. Schaller.] 

Quartz gangue (99 per cent Si02) •••••••••••••••••••••••••••••••••••••••••••••• _. _. _. _. ___ • _ 54. 60 

Copper ....................................... : ................... ·_ ....... __ . ___ •• _. _____ . _ 20. 05 

Sulphur ........................................ _ ........... _ ...... __ .... _ ... __________ •.. 13. 64 

Antimony ..................................................................... _. _ ... _ .. _ _ _ 5. 09 

Arsenic ... _ ............... ·........................ _ ..... _ ......................... _ ..... _ . 4. 61 

Iron .. ............................. •. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . 1. 46 

Manganese ..... ·.· ................. , .......................................... _._._ ....... _ . 02 

Silver ................. . ....................................................... :._ .. _: .... None. 

Bismuth, lead, zinc ............................................................... _ ... _ .... Trace(?). 

Water at 110° C ••............................................................... __ ......... .· 32 

99. 79 

By elimination of the silica and obviously unessential or negligible constituents, and by 

recalculation to 100, the analysis may be more simply stated as follows: 

Composition of mineral jro'f(l, .January mine. 

Copper .................................................................... -•. -..... ---. -... - 44. 8 

Sulphur ................................................................... -... --- .. -. . . . . . . . 30. 5 

Antimony................. . . . . . . . . . . . . . . . . . . . . . . __ ................... · ...... --............... 11. 3 

Arsenic ...................................................................................... 10.2 

Iron......................................................................................... 3. 2 

100.0 

For comparison the theoretical compositions of tetrahedrite, tennantite, enargite, and 

famatinite are given below: 

Theoretical compositions of tetrahedrite, tennantite, enargite, andfamatinite. 

Tetrahedrite. 

Cu....... ...................................................................................... 52.1 As ..••.•........•.•..••.•...•..•. . ............••.•.•••••••••••••••••........................... -······-· · --

Tennantite. Enargite. 

57.5 48.3 17.0 19.1 

Famatinita. 

43.3 

~~::: ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ~: y -.--.- "25:5- -.---. "32: 6" ~:: 1-------l--------1-------l-------- 100. 0 100. 0 100. 0 100. 0 

In nature, however, the antimony and arsenic mutually replace each other, giving rise to 

intermediate chemical compounds. Most analyses of enargite and famatinite show a little iron. 

a Bull. U. S. Geol. Survey No. 3i8, 1907, p. 34. 
MINER4LOG Y. 119 

While it is possible that in some varieties of these minerals the iron may be chemically combined, the Goldfield material is known to contain a little inseparable pyrite, and it is probable 

that a:ll the iron found in analysis is present as pyrite. By eliminating the constituents of this 

pyrite and recalculating the analysis to 100 the following figures are obtained for the composition of the Goldfield mineral: 

Composition of famatinite or enargite from Goldfield. · 

Cu ...... _______ .. _ . .. . ___ _____ ____________ ·_. ___ . __ . ___ ___ . _ .. ___ __ . _ . _____ · _____ .... _. . .... 48. 0 

As .... ___ . _ . _ . __ . . . . . _ . _ . __ . .. _ . . _ .... . .. . __ . ______ . ___ .. _ . ______ ___ . . __ ......... __ . _ . . . . . . 11. 0 

Sb ... _ . _ .. _ .. _ .. _____ _______ _ . _ . ___ . _ . ____ _______ .. __ ____ _________ __ _ . __ _____ . _ . _ ........... _ 12. 2 

S ............. _______ .. _____ . __ ___ . ___ · ... _____ . _____ __ . _. ___ . ______ ______ . __ .. _ .. _. __ . _. _, .. . 28.8 

100. 0 

This composition is intermediate between theoretical enargite and theoretical famatinite. 

As both minerals are orthorhombic and isomorphous, the occurrence of an intermediate variety 

is not surprising. Attempts to calculate a simple formula corresponding to the foregoing per-· 

centage composition have not been successful, and it is not clear whether the copper is in the 

cupric or the cuprous condition. The atomic ratio of copper to sulphur in the Goldfield mineral 

is approximately as 7 to 8. In a formula of the stephanite type it should be as 5 to 8, in one 

of the famatinite type as 6 to 8, and in ·one of the tetrahedrite type as 9 to 8. 

The Goldfield material can not be definitely assigned to either enargite or famatinite. Its 

massive habit, reddish-gray color, and slight preponderance of antimony over arsenic suggest, 

however, closer affinity with famatinite than with its corresponding arsenical isomorph, and as 

knowledge of the variety is insufficient to justify the application to it of a new name, it will be 

referred to as famatinite in this report. 

The famatinite is comparatively abundant in the Florence, Jumbo, Combination, and 

January mines, where it is usually associated with rich ore and often contains visible particles 

of native gold. 

- Although gold does not appear to enter chemically into the constitution of the famatinite, 

the association of this mineral with the richest ore is often very marked. A specimen of ore 

from a winze a few feet below the 250-foot level of the Florence mine was broken up and separated into two parts, one containing most of the pyrite (more abundant in this specimen than 

usual), the other most of the famatinite. The portion containing the most pyrite gave on assay 

2.31 ounces of ·gold and 1.8 ounces of silve'r to the ton; the portion richer in famatinite gave 

53.37 ounces of gold and 3.17 ounces of silver. This result is rather remarkable, as this particular 

ore shows. no native gold under a hand lens. A similar separation was made of some ore from 

the January mine, although in this case the portion containing the less famatinite was mainly 

quartz, with probably no more pyrite than was present in the other portion. The portion with 

the most famatinite afforded on assay 15.70 ounces of gold and 25 ounces of silver to the ton; 

the quartzose residue gave 9.32 ounces of gold and 11.08 ounces of silver. 

On the other hand, a sample from the 200-foot level of the Jumbo mine containing rather 

abundant famatinite was found on assay to contain only 0.26 ounce of gold and 0.25 ounce of 

silver to the ton. Thus famatinite and a high proportion of gold are not invariably associated. 

CERARGYRITE. 

Halogen compounds of silver appear to be very rare at Goldfield, owing doubtless to the 

fact that the proportion of silver in the ores is small. Nevertheless, it might have been expected, 

a priori, that in the oxidation of ores of such remarkable richness, in which the silver, though 

relatively unimportant, rises in soine cases to over. 60 ounces to the ton, noticeable quantities 

of cerargyrite would form. 

The only mines in which any chloride of silver has been distinctly recognized are the workings of lessees on the Gold Coin claim of the Jumbo-Extension Company and the Toplitz lease 

<Jn the Daisy No. 1 claim, both near Diamondfield. Cerargyrite occurs in the oxidized ore of 
120 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIEJ.,D, NEVADA. 

the Gold Coin as minute, waxy, olive-green crystals implanted on limonite or rusty ledge matter. 

Owing to the high specific gravity of the mineral it can be separated with the free gold by 

panning. Associated with the gold, cerargyrite, and limonite are kaolinite and small quantities 

of an obscurely crystalline yellow mineral, which is a ferric_ tellurite, probably emmonsite or 

durdenite. · · 

The ore from the Gold Coin claim is more argentiferous than most of the Goldfield ores, 

some assays showing nearly 2 ounces of silver to 1 of gold. This fact probably accounts for the 

presence of cerargyrite in the oxidized part of the deposit. 

A few minute specks of light-green color noted in the ore of the Toplitz lease are probably 

embolite or bromyrite. The material was insufficient for chemical tests. 

QUARTZ. 

The quartz of the Goldfield district is a gray, aphanitic, 'flinty material bearing little resemblance to the white, coarsely crystalline variety characteristic of typical quartz veins the world 

oveF. The coarsely crystalline mineral, such as forms the gangue of the California gold veins, 

has filled open fissures, having been deposited from siliceous solutions. The• greater part of 

the Goldfield quartz, on the other hand, occupies space once filled by shattered or fissured 

rock. To say that this rock has been silicified .only partially expresses the facts. The quartz 

is in large part the silica of the original dacite, andesite, or rhyolite, as the case may be, left 

mass, 

behind, as a more or less porous mass, in the removal of other constituents. In parts of this 

where fissures are most abundant, additional silica has been metasomatically introduced. 

A further increment of silica has crystallized as quartz druses on the walls of cavities which are 

in 

mass 

part interstitial and in part the result of the removal of phenocrysts by solution. In such a 

of quartz the pyrite is probably in large part derived from ferrous silicates and magnetite 

in the original rock. It has, however, undergone some migration and segregation. The other 

sulphides and the gold have ·been for the most part metasomatically 

minor 

introduced, although to a 

extent they fill small cavities. 

The steps in the conversion of rock into quartz are fully described in the chapter on metasomatic alteration, pages 176 to 186. 

In the Goldfield ores, quartz rarely occurs in crystals of such size as to be distinctly visible 

with the naked eye ~ They are mostly microscopic. Even in the druses of open cavities a 

lens is usually necessary to distinguish the individual faces of the crystals. 

Under the microscope the flinty quartz appears as a finely crystalline mosaic of-· quartz 

grains. This may show no trace of the texture of the original rock, but quartz of the kind 

described is connected by insensible gradations with aggregates of quartz, alunite, kaolinite, 

and pyrite, in which the porphyritic structure of the dacite, andesite, or rhyolite is still recognizable. The microstructure of this cryptocrystalline quartz is illustrated in Plates XXVI and 

XXVII. 

In the Goldfield-Belmont mine the altered andesite in places is traversed by dull-white 

stringers composed of a cryptocrystalline aggregate of quartz and kaolinite. Some of these 

vei:rilets grade into soft, nearly pure kaolinite. In the same mine is some white quartz, carrying 

most 

a little pale-green sericite, which more closely resembles ordinary vein quartz than does 

of the mineral in the district. Close inspection, however, shows that this materia1 is a 

very finely crystalline granular aggregate. Some of it is porous with a structure suggesting 

incrustation of a prismatic mineral since entirely dissolved. This, however, is little more than 

a suggestion furnished by the resemblance of the material to quartz pseudomorphs after celestite at Cripple Creek. a The quartz in the upper workings of this mine has in places been crushed 

to a loose sugary condition. 

An unusual -variety of quartz is found in the Gold Coin workings of the Jumbo-Extension 

Con1pany, near Diamondfield. This is dark gray and cryptocrystalline. Its peculiar feature 

1906, 

a 

p. 

Lindgren, 

125. 

W .. , and Ransome, F. L., Geology and gold deposits of the Cripple Creek district, Colorado: Prof. PaperU. S. Geol. SurveyNo.54, 
MINERALOGY. 121 

is a vesicular structure, the vesicles being smooth and spherical and ranging up to half an inch 

(12 millimeters) in diameter. Most of them are empty, but some are filled with alunite or 

kaolinite. The material is probably an altered, vesicular glassy volcanic rock. Whether it 

was originally a local vitreous facies of the and~site, which is the general country roek,. or an 

included mass. of rhyolite is not clear. The mieroscope shows a spotty quartz mosaic with faint 

suggestions of a former igneous texture. 

As will be shown in the section on paragenesis, the quartz associated with the ores is not 

all of one generation. 

In addition to its occurrenee in the ledges, quartz is an original constituent of some of the 

igneous rocks of the district, partieularly of the alaskite, rhyolites, and dacite. In the rhyolites and daeite it is present as rounded and embayed phenocrysts which, as they usually remain 

unchanged in the . alteration conneeted with ore deposition and are readily distinguished from 

the fine-grained later quartz, serve as useful and reliable means of determining the original rock 

from which much of the ledge matter has been derived. On this account sections of some of 

the larger and more irregular quartz 

phenocrysts from altered dacite are 

shown in figure 7. Quartz also oeeurs 

a.s phenocrysts in the Mira basalt. (See 

p. 69.) 

BISMITE. 

The artificially prepared trioxide 

of bismuth (Bi20 3) crystallizes in the 

orthorhombic system, although according to Dana a the natural mineral is not 

crystallized, but is found in massive, 

disseminated, or earthy condition. 

In the Goldfield district, bismite 

occurs in the January, Combination,. 

Sandstorm, and probably also in other 

mines, as minute pearly scales with 

brilliant luster and of silvery whiteness. The luster of the scales is almost 

metallic and suggests at first glance 

- ·delicate and untarnished crystals of 

native silver. The mineral is limited 

o z millimeters ~----------~----------~ 

FIGURR 7.-Characteristic outlines of quartz phenocrysts in dacite. 

to the oxidized zone, is usually accompanied by limonite, and is frequently associated with rich 

ore. It occurs as single glittering scales or specks on the walls of eavities in spongy limonite 

or rusty ledge matter, as delicate frost-like films on the same materials, and as spongy aggregates with quartz. In the last-named form it is clearly pseudomorphous after bismuthinite, 

the material having consisted originally of a mass of bismuthinite prisms held together by a 

siliceous gangue. The prismatic structure of the bismuthinite is retained as hollow easts in the 

quartz, lined or partly filled with scales of bismite. 

As natural crystals of bismite do not appear to have been found hitherto and as the mineral 

has been assigned to the orthorhombic system in Dana's and Hintze's mineralogies on the 

basis of Nordenskiold's work on artificial crystals in 1860 and 1861, eonsiderable interest attaches 

to the Goldfield occurrences on account of the crystallinity of the material. 

When examined under the microscope in gently powdered material the erystals appear as 

thin colorless scales, with occasionally a suggestion of hexagonal outline. On aecount of their 

tenuity, it is rare that an edge view of a scale is obtainable. Th~ larger flat-lying scales are 

dark in all positions between crossed nicols and give a negative uniaxial figure with convergent 

light. There are no colorea rings and the double refractiOn is apparently not great. The 

a System of Mineralogy, sixth ed., New York, 1895, p. 200. 
122 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

refractive index, on the other hand, is rather high, being greater than that of anorthite. The 

mineral has. a perfect basal cleavage, and the scales, viewed without the analyzing nicol, commonly show delicate interference colors due to the refraction and reflection at the surfaces of 

the exceedingly thin cleavage sheets. 

Some of the best material obtainable was analyzed in the United States Geological Survey 

laboratory by W. T. Schaller, as follows: . 

Chemical analysis of bismite. 

Insoluble in hydrochloric acid; mostly quartz gangue ..... . ................................... . 

Bi20 3 •••••••••••••• • ...••.•..•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••.. 

Fe20 3 ••••••.•••••........... . ... • •.. _ • •..•....•..•..•.....•••...•..••...•••.•••.•.••• •• ... . Loss on ignition ......................................................................... . .. . 

78. 94 

i7.04 

. 36 

3.96 

100. 30 

The results show that the mineral is either bismite or else a hydrous oxide of bismuth. If 

the latter be the case the mineral is a new species. Attempts to isolate a sufficient quantity 

of the pearly scales from the gangue for separate analysis were not successful. 

Mr. Schaller has kindly furnjshed the following crystallographic note: 

The minute, tabular crystals are too incomplete to allow of a determination of their geometrical form by crystallographic measurements alone. From the uniaxiality of the crystals, their hexagonal outline, triangular markings 

on the base, and distribution of faces as far as seen, one seems justified in referring them to the rhombohedral division 

of the hexagonal system. · · 

As given in detail further along, the c axis is 0.5775. Seven faces were determined as present; the base, five 

positive and one negative rhombohedra. Besides these, there were indications of two more positive rhombohedra. 

Below is given a brief description of these forms. 

c (0001). Always very large, even, and highly polished. Sometimes shows triangular markings or strire, the faces 

parallel to these markings being taken as positive. 

o (1016). Occurs on two crystals, as broad faces giving, however, poor reflections. One face was considerably 

striated, giving two signals a degree apart. 

q (1015). Broad faces giving fairly good reflections. 

u (1014). Narrow faces, one striated with a fair reflection, and one as a line face giving a very poor reflection. 

k (1013). Usually as a line face, striated and giving a very poor reflection. 

·a? (2025). A doubtful face, narrow, giving no distinct signal. 

? (1012). Another doubtful face, broad, giving no distinCt reflect~un. 

y (2021). Line faces, giving exceedingly faint reflections. 

z (0111). The only negative rhombohedron observed. Very faint line faces, giving no reflection. Its negative 

position could be determined only on crystal No. 6. 

The measurements of the forms are shown below: 

(0001):(1016) .................... .. . . ........ .. ....... .. ... . .............. . .... .. ......... . ...... . . . ................... . (0001):(1015) ... . ..... .. .... . .. . ...... . ...... -.............. . .. -... -... -- .... -- .. . ......... . ... . . -... -... -. -.- . ... . . . . -. 

~:gagii~::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::: ::::::::::::: :::::::::::::::: ::: 

Doubtful 

gggg~~m: forms: 

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :·: ::::::::::::::::::::::::::::::::::: · 

Measured. 

6° 37' 6° 41' 

7° 33'; 7° 36' 

9° 31'' 9° 31' 12° 11' 12° 26' 

13° 18<12°-14° 

54°,54° 

35°,32!0 

(0001):(2025) ..... -.. -.-- ..... . .. . ......... .. .. -. . -- ...... -. . -. . -.... -. : -.... -.- ...... --. -.. --. . . . .... -.- ... -.. -- .. - 15° (0001):(1012) ............. . ............. . . . .. . ...... .... . . .......... .. ... . ...... . ................................... 16°-20° 

Calculated. 

6° 21' 

7° 36' 

9° 28' 

12° 32' 

53° 08' 

33° 42' 

The value for the c axis was obtained from three measurements that were considered as the most accurate. The 

others gave values agreeing fairly well with the one adopted, as is shown below. The crystals were measured on the 

two-circle goniometer, and the p angle for these forms is the angle between that form and the base. 

The three best measurements are: 

p (1015)=7°. 33/ 

p (1015)=7° 36/ 

p (1014)=9° 31" 

. ·. p0 =0.6627 

p0= .6672 

p0= .6706 

Crystal No.1 . 

Crystal No. 4. 

Crystal No. 2. 

Average p0 = .6668; c=0.5775. 
MINERALOGY. 123 

An average of the other measurements gave values closely agreeing. Thus: 

p (1016)= 6° 37" 

p (1016)= 6° 41" 

p (1014)= 9° 31" 

p (1013)=12° 11" 

p (l013)=12° 26" 

p (1013)=13° 18" 

. ·. p0 =0.6960 

p0 = .7031 

Po= .6706 

p0 = .6477 

p0 = .6614 

p0 = .7102 

Average = . 6815 

Crystal No.3 . 

Crystal No. 6. 

Crystal No. 6. 

Crystal No.6. 

Crystal No.4. 

Crystal No. 1. 

The following measurements of faces giving no distinct reflections also showed close agreement. 

p (1013)=12°-14° (av. 13°) p0=0.69 Orystal No. 1. 

p (2025)=15° Po= . 67 Crystal No. 2 . 

p (1012)=16°-20° (av. 18°) Po= .65 Crystal No. 1. 

p (0111)=35° Po= . 70 Crystal No. 5 . 

p (0111)=32z0 Po= . 64 Crystal No. 6 . 

p (2021)=54° Po= .69 Crystal No. 1. 

p (2021)=54° Po= .69 Crystal No.6. 

The values for Po just given show that the interpretation of the forms is the correct one. 

Of the six crystals (all incomplete) that were measured, only two are here figured. In figure 8 a is an orthographic 

projection of a crystal (No. 1), showing the trigonal distribution of the rhombohedra and the triangular marking on the base. b shows a similar projection 

of crystal No.6, with a negative rhombohedron. 

An odd feature of these crystals is that the development of the faces is so 

uneven that no two faces of the same form are present on the upper half of a 

crystal, though this is in part due to the incompleteness of each crystal. 

From the foregoing observations it appears that the natural 

bismite is not orthorhombic, but belongs to one of the uniaxial 

systems, probably the hexagonal. Its presence in oxidized ore 

appears to be uniformly indicative of bismuthinite in the original 

sulphide ore. Some migration, however, has taken place during 

oxidation, and ·the scales of bismite do not always occupy the 

exact positions of the parent needles of bismuthinite. 

TELLURITE. 

The oxide of tellurium (Te02) occurs sparingly with a telluride of gold in the Goldfield-Belmont mine, north of Diamondfield, as a crystalline honey-yellow mineral with subadamantine 

luster. Only one small speck of the mineral was obtained, which 

was determi_ned chemically by Mr. W. T. Schaller. 

MASSICOT. 

A little lead, apparently in the form of the yellow oxide·(PbO), 

occurs in the workings of the No. 3 lease on the Commonwealth 

c 

a 

ground, a little m.ore than 2 miles east of Goldfield. The sup- f . 0 

posed massicot, with probably various impurities, forms porous, FIGURE s.-Crystal form of bismite from 

sinter-like, yellow incrustations in the interstices of shattered and Goldfield. 

silicified latite, associated with kaolinite and alunite. Mr. W. T. Schaller found on chemical 

tests that the yellow material contains a little lead. The evidence fthat the metal in this earthy 

mixture is really in the form of massicot can not be regarded as cob..clusive. 

. I 

HEMATITE. . I 

The anhydrous oxide of iron (Fe20 3) occurs in nature a~ th~ crystalline (rhombohed.ral) 

variety known as "specularite" and in various fibrous, botryoidal ~ massive, and earthy forms. 

The latter are generally distinguished froni the hydrous oxide, limbnite (2Fe20 3.3H20), by a red 

I 
124 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

instead of a brown or yellow streak or powder and of course by the absence of a_ny notable 

quantity of combined water. Between limonite and hematite, however, are the in'termediate 

species gothite (Fe0.H20) and turgite (2Fe20 3.H20). As these various minerals frequently 

occur together, the determination of the mineral species represented in a massive aggregate of 

partially hydrated iron oxide is not always a simple matter. It is probable that some of the 

brilliant iridescent films described later under "Limonite" are in part hematite. Although 

apparently none of them is quite anhydrous, they for the most part give dark-red streaks. 

In the crop pings of what is known as the "Hat lease" on the Blue Bull ground, earthy red 

hematite associated with ocherous and botryoidal limonite is abundant as a cement of brecciated 

and silicified andesite. Close inspection of this material shows that some of the fragments are 

coated with thin glistening black films, which give a red streak like that of hematite. The microscope resolves this film into minute crystals of specularite, about 0.05 millimeter in diamet~r, 

implanted on a brown, finely botryoidal surface of a crust of limonite. These little crystals are not 

perfect. Some are mere rough black spherules with no distinct crystal planes. Others show one 

lustrous face, usually at the top of the spherule, while still others show combinations of several . 

faces belonging apparently to flat rhombohedrons or to combinations of rhombohedrons with the 

basal pinacoid. Sketches of some of these faceted spherules are shown in figure 9. The crystal 

faces have the splendent luster of specularite. 

In the workings of the same lease minute specks of iron oxide occur distributed through a 

massive fine-grained, sandstone-like aggregate of alunite. The specks give a red streak when 

the material is picked or struck, and may be hematite. Turgite (2Fe20 3.H20) has a similar 

streak, however. A similar oxide occurs with jarosite or alunite on the south slope of Myers 

FIGURE 9.-Spherules of hematite with crystal facets; X300. 

Mountain. The particles show no crystal 

form under the microscope and it is not possible to determine whether they are hematite 

or turgite, or, possibly, gothite. A similar 

mixture of red iron oxide with alunite and 

native gold forms part of the ore of the 

Simmerone mine. In the Lone Star mine, 

alunite, red oxide of iron, and quartz in small rough doubly terminated prisms form soft sandy 

aggregates. 

RUTILE. 

Rutile (Ti02) forms microscopic crystals with alunite, quartz, and sulphides in some of the 

altered dacite of the Combination and Florence mines. It is probably distributed sparingly 

through much of the alunitized rocks of the district as an alteration of titanite or ilmenite by 

ore-depositing solutions. 

DIASPORE. 

The hydrous oxide or basic hydrate of aluminum, AIO(OH), crystallizing in the orthorhombic system as the mineral diaspore, has rarely been noted in connection with ore-bearing 

veins. It is a characteristic alteration product of corundum, and its best-known occurrences 

in this country are in the intensely metamorphosed rocks of Chester, Mass., Chester County, Pa., 

Macon County, N. C., and near Trumbull, Conn. According to Van Hise,a biotite, gibbsite, 

hauynite, muscovite, nephelite, noselite, phlogopite, scapolite, and sodalite, as well as corundum, 

may all give rise to diaspore in the belt of weathering. 

Diaspore was found by Cross b associated with alunite, quartz, and kaolin in the altered 

rhyolite of the Rosita Hills, Colorado. It occurs also with quartz and kaolinite in altered latite 

in the Silverton district, Colorado. c 

These occurrences in altered volcanic rocks in Colorado led to a search for diaspon~ in 

the · alunitic and kaolinitic rocks of Goldfield. The mineral proved to be rather widely distributed as a microscopic constituent, although not present in great quantity at any one place. 

a A treatise on metamorphism: Mon U.S. Geol. Survey, vol. 47, 1904, p. 232. 

b Geology of Silver Cliff and the Rosita Hills, Colorado: Seventeenth Ann. Rept. U.S. Geol. Survey, pt. 2, 1896, pp. 316-317. 

c Ransome, F. L , Economic geology of the Silverton quadrangle, Colorado: Bull. U. S.Geol. Survey No.182, 1901 (reprinted in 1903), pp.121-124. 
MIN ERA LOGY. 125 

It has been found with alunite and kaolinite in Sandstorm rhyolitE) near· the Sandstorm mine; 

in altered rhyolite from the west slope of Vindicator Mountain; with quartz, alunite, and a 

little rutile and sericite in altered dacite on the south slope of Preble Mountain; and with 

alunite, quartz, and pyrite in altered dacite from the Florence mine. In the last-named place, 

the pyrite, alunite, and diaspore are intimately crystallized tog~ther and are clearly of contemporaneous origin. 

Diaspore occurs in the Goldfield rocks as rounded, colorless, anhedral grains which rarely 

exceed 0.5 mm. in greatest diameter. These have one ;veil-marked cleavage which is parallel 

to the plane of the optic axes. Sections transverse to the cleavage give a biaxial interference 

figure. The optical character of diaspore is positive, but owing to the large optic angle 

(over 84°) it is not always clear when dealing with small irregular grains whether the interference 

figure obtained corresponds to the acute or the obtuse bisectrix. Consequently attempts to 

determine the optical character from interference figures are likely to yield negative results on 

some grains and positive on others.a The index of refraction of the Goldfield mineral is about 

1.7 and the birefringence is such as to give green, yellow, and red of the second order in sections 

about 0.02 millimeter in thickness, thus corresponding closely to r- a= 0.048, the figure given 

for diaspore in Michel Levy and Lacroix's table o[ birefringences.b · 

The optical properties leave little doubt of the identity o~ the mineral with diaspore. 

Additional assurance, however, is afforded by tests by Mr. Schaller in the United States 

Geological Survey chemical laboratory. E~e pulverized the rock from the Florence mine, and 

after removing the pyrite treated the powder with hydrofluoric acid. The undecomposable 

residue was microscopically examined and found to consist of particles of the mineral under 

investigation. These proved to have the chemical composition of diaspore. 

LIMONITE. 

The common brown or yellow hydrous oxide of iron (2Fe20 3.3H20) is present in varying 

quantities in practically all of the oxidized ores of the Goldfield district and is the most characteristic product of the weathering or oxidation of pyrite. As pointed out on page 124, it is 

sometimes mixed with hematite and it is not always possible in any given ferruginous mixture 

to determine exactly what proportions of the various hydrated @xides are present. 

Limonite as a rule is more abundant in ores having dacite or andesite for country rock 

than in those inclosed by rhyolite. This difference is partly accounted for by the fact that 

the oxidized dacitic and andesitic ores were originally more pyrit~c in consequence of the lar.ger 

quantity of iron available in the fernie 1ninerals of these rocks than in the more siliceous 

rhyelites. As indicated on page 181, the pyrite of the Goldfield ores has not been introduced 

bodily as sulphide of iron by the ore-bearing solutions, but has to a great extent been generated 

by the attack of sulphurous waters upon iron silicates already present in the rocks. 

The limonite of the Goldfield ores is generally earthy and mix d with kaolin, quartz, alunite, 

and other impurities. Often it is a mere rusty film on fragment~ of ledge matter. In a few 

places, as in some nearly horizontal seams on the 50-foot level of the Watson lease on the Florence 

claim, nearly pure limonite forms spongy masses suggestive of bog ore. 

One of the most characteristic and conspicuous occurrences of limonite in the Goldfield 

district is that of thin coatings on the surfaces of some of the srliceous outcrops of the ledges. 

Such coatings are exceptionally well developed on the hilltops just east of the Blue Bull mine 

and on Banner Mountain, but may be observed at many other places. 

The films are in some places dark steel gray with rounded, highly lustrous and finely 

botryoidal surfaces. In other places they exhibit gorgeous iridescence, the play of colors, due 

to the refraction of light by thin films, ranging from deep blu~ through purple, crimson, and 

orange to bright green. These films envelop loose fragments pf the croppings or cover the 

surface of rock in place as brilliant expanses sometimes several ~quare feet in unbroken extent. 

a A supposed negative mineral resambling diaspore, referred to in an earlier paper (The associatjon of alunite with gold in the Goldfield district, 

Nevada: Econ. Geology, vol. 2, p. 673), turns out to be diaspore in which the obtuse was mistaken for the acute bisectrix. 

b Les mineraux des roches, Paris, 1888. Reproduced also in Idding's Rock Minerals, New Yo k and London, 1906. 
. 126 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Such extensive coatings are often visible on the walls of joints which have gaped in consequence 

of the partial undermining of the siliceous croppings by the erosion of the softer country rock 

around and under them. 

The iridescent limonite films are not confined to surface exposures, but occur in the oxidized 

ore of some of the mines, including the January and Combination. The Columbia Mountain 

No. 1 tunnel, on the east side of the mountain, extends for 300 feet through shattered Cambrian 

sediments in which the fragments are encrusted and cemented by iridescent botryoidal films 

of iron oxide. 

The material of many of these films has a red streak and gives off less water in a closed 

tube than does ordinary limonite. It is probable that it consists in part of hematite, with perhaps some admixture of the hydrous oxid~s gothiteJ turgite, or limonite: 

CALCITE. 

The common rhombohedral carbonate of calcium (CaC03) is not an abundant mineral in 

the Goldfield district, and is absent, so far as is known, from the ore deposits. 

Veins of yellowish, massive, and impure calcium carbonate, carrying a little oxide of manganese and small vugs and veinlets of clear crystalline calcite, traverse the beds of the Siebert 

formation on the west slope of Myers Mountain. They apparently contain neither sulphides nor 

gold and are probably later in age than the ore deposits: Similar veins occur in dacite, about a 

mile southeast of McLaughlin's well. Some of the material is porous and rusty, and the vein 

. may prove to contain pyrite at greater depth. · 

Calcite serves as cement for some of the tuffs and conglomerates of the Siebert formation, 

and is a microscopic constituent of some of the propylitically altered andesite, latite, and dacite, 

as an alteration product of feldspar and augite. It occurs also as amygdules in some of the 

basalts and in interstices between the crystals in the same rocks. In the basalts the presence 

of calcite is not necessarily connected with noticeable. decomposition of the primary minerals, 

and it is evident that in these rocks carbonate of calcium can be deposited in vesicles and miarolitic cavities within a comparatively short time after the solidification of the lava. 

Calcite is also a microscopic constituent of alunitized rhyolite on the east slope of Vindicator 

Mountain. This is the only rock _in which calcite and alunite have been found together in this 

district, and the association is probably not common. Its significance is discussed on page 194., 

FELDSPARS. 

The pseudomonoclinic potassium feldspar orthoclase (KA1Si30 8 ) is an important constituent mineral of the alaskite. In this rock it is usually microscopically intergrown with albite 

in the form of perthite. 

As the clear variety known as sanidine it is abundant in the younger rhyolites. In the 

older rhyolites, such as those of Columbia and Vindicator mountains, it has been extensively 

altered to alunite. It does not always succumb to alteration in these rocks as readily as might 

be expected, however; a facies of the Morena rhyolite northwest of the Conqueror mine still 

contains much fresh sanidine, although the rock is full of secondary quartz and the original 

quartz phenocrysts show broad optically continuous accretions of the same mineral. 

Th~ most abundant calcium-sodium feldspars in the district are those ranging from andesine 

to anorthite. The anorthite occurs in the olivine basalt, and labradorite is the principal species 

in the dacite and andesite, and probably also in the latite, although the feldspar in the lastnamed rock is never fresh. 

In the vicinity of the ore deposits the feldspars are invariably decomposed and have given 

rise to aggregates of alunite, kaolinite, quartz, pyrite, and diaspore. In the propylitically 

altered rocks they have usually been changed to calcite and quartz. 

EPIDOTE. 

Epidote, a somewhat complex basic orthosilicate of c·alcium, iron, and aluminum (HCa~ 

(Al,Fe) 3Si30 13) crystallizes in the monoclinic system and has a characteristic yellow-green ·color. 
MINERALOGY. 127 

It occurs at Goldfield with calcite, chlorite, and pyrite as a microscopic constituent of propylitically altered dacite, andesite, and latite, particularly as an alteration product of augite and 

biotite. It is not present as a rule in the in1mediate vicinity of ore, but is best developed in the 

greenish altered dacite northeast of McLaughlin's well. In some of these rocks the aggregates 

of epidote pseudomorphous after the original fernie ~inerals are visible with the naked eye. 

Where formed at the expense of biotite, the epidote usually occurs in lenticular lamelloo alternating with chlorite. 

MUSCOVITE (INCLUDING SERICITE). 

The white potassium mica (H2KAl3Si30 12 ) occurs very sparingly in some of the alaskite, 

apparently as an alteration product of biotite and usually associated with epidote. 

The fine scaly variety known as sericite, abundant in close association with some of the 

largest and most important classes of gold-quartz veins, is rare in the Goldfield district, and its 

occurrence is sporadic and exceptional rather than characteristic. It is found .with quartz at 

the Goldfield-Belmont mine and imparts a pale-green tint to that mineral. As a subordinate' 

microscopical constituent it is present with alunite in altered dacite from the south slope of 

Preble Mountain. It occurs also as an alteration product of felds.par in pyritized andesite near 

the Florence mine. 

KAOLINITE. 

The hydrous silicate of aluminum known as faolin or kaolinite (Al20 3.2Si02.2H20) crystallizes in the monoclinic system, but commonly O~fCUrs in soft, white massive form, in which 

the individual crystals are too minute for the n!cognition of crystal form, even under the 

microscope. 

Kaolinite is abundant in the Goldfield distri t, 'particularly in oxidized ores. It is not 

confined to the belt of wea~hering, however, but o1curs also in the sulphide zone and as a constituent of unoxidized country rock in the vicinity of the ore bodies. The dacite from the 

230-foot level of the Combination mine, of which an analysis is given on page 181, contains, 

for example, 24 per cent of kaolinite by weight. In such altered rocks the kaolinite forms 

very minutely crystalline aggregates of feeble bir~fringence as seen in thin section under the 

microscope. These aggregates have rather ill-depned boundaries and the kaolinite is intimately and contemporaneously crystallized with j quartz, alunite, and pyrite. A very large 

part of the altered dacite in the vicinity of the or' bodies near Goldfield consists of these four 

minerals in varying proportions. A similar alte ation has affected the latite penetrated by 

the workings west of the shaft on the. bottom level (280-foot) of the January mine. Specimens 

from a zone of mineralization in this rock consist of quartz, kaolinite, and pyrite. 

In the Goldfield-Belmont mine dull-white, fin -grained aggregates of quartz and kaolinite, 

associated with gypsum and pyrite, form veinlets ih altered andesite below.the level of oxidation. In parts of the ledges, in the sulphide zone, articularly in the Combination and Florence 

mine, kaolin and pyrite form irregular bunches, such material as a rule being of little or no 

value as ore. With alunite, quartz, and a little tliaspore, kaolinite occurs in altered rhyolite 

in the vicinity of the Sandstone ledge, and with ~uartz, alunite, and a little calcite in rhyolite 

on slopes of Vindicator Mountain .. The occurrenpe of kaolinite with alunite in tht3 Commonwealth No. 3 lease has been descr1bed on page 1~0. · 

Within the oxidized ores, kaolinite is someti.nles very abundant. It occurs in soft pulveru,lent condition, mixed with alunite and slightly cblored with yellow oxide of iron, in the Combination mine. Similar impure kaolinic material,j often gold-bearing, is present in most of the 

, oxidized ore bodies near Goldfield. In some plac~s, as in the Red Top mine, pure, white, waxy 

kaolinite forms irregular veins and masses in limonitic, oxidized ledge matter. In the oxidized 

ores of the Sandstorm and Kend9Jl mines there ~ s much soft whit~ kaolinite associated with 

barite and native gold. 

BARITE. I 

The orthorhombic sulphate of barium (BaS~ ) is abup.dant in the ore of the Sandstorm 

and Kendall mines associated with kaolini~e. · l he crystals, whic~ !tre occasionally over an 
128 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

inch in length in the Kendall mine, are usually attached to silicified rhyolite, their free ends 

being embedded in the kaolinite. Some, however, are entirely surrounded by the latter mineral. 

The crystals are of simple tabular habit, being bounded by the unit prism (110) and the basal 

pinacoid (001). They are clear and colorless, with perfect cleavages parallel to the prism 

base. The association of the barite with kaolinite and oxidization in the Sandstorm and Kendall mines suggests that it may have been formed by the action of cold, percolating meteoric 

water. 

In much smaller crystals, barite occurs with kaolinite in the Commonwealth No. 3 lease, 

2 miles east of Goldfield, and with alunite and pyrite in the Reilly workings. The crystals 

in both these places are barely recognizable with the naked eye. Tubular crystals up to 2 

millimeters in length embedded in soft alunite with pyrite or marcasite o·ccur in the ore of the 

Con~olidated Red Top lease. 

As barite is known to form, independently of any thermal activity, in cavities in limestone 

and in boxes and pipes carrying certain mine waters, and as it is also deposited from the 

waters of both hot and cold springs,a its mere occurrence throws little light. upon the source 

of the solutions from which it was precipitated. 

GYPSUM. 

The monoclinic hydrous calcium sulphate (CaS04 + 2H20) occurs in various forms in the 

Goldfield district. 

About a mile southwest of Blackcap Mountain, near the Gold Crater road, are some superficial deposits mapped in Plate II. These are composed of very soft, porous, cream-colored 

material, somewhat resembling a light volcanic ash or some forms of impure diatomaceous 

earth. The deposits prove to be earthy gypsum and were probably formed by the evaporation 

of the waters of a spring now extinct or of some temporary pond in which was accumulated 

water rich in sulphate of calcium derived from the surrounding rocks. 

A deposit of similar material lies about half a mile (0.8 kilometer) east of Blackcap Mountain. Here the gypsum has a very porous fibrous structure strongly suggestive of the fragile 

frost crystals which may be seen sprouting from moist ground in winter. This a:tso is probably 

a local spring deposit. . 

In the form of clear crystals or broad plates of the variety known as selenite, gypsum is 

abundant at. the surface along the outcrops of fissures, particularly along those accompanied 

by much crushed rock or gouge. Broad lustrous plates of the mineral may be obtained along 

the Columbia Mountain fault on the south slope of the mountain. Underground, gypsum 

i~ found in most of the mines, particularly in gouge seams and in soft crushed ground, sometimes accompanied by marcasite. Its occurrence underground is not limited to the oxidized 

zoE.e. It is found in the Goldfield-Belmont mine, on the 150-foot level, or 50 feet (15 meters) 

below the natural water level, crystallized with quartz and pyrite, and may be noted in small 

nests in the soft pyritized andesite or dacite of many prospecting shafts. The mineral forms 

small veins in altered andesite about three-fourths mile (1.2 kilometers) northeast of Myers 

Mountain. It also occurs in seams in partially oxidized ore on the 50-foot level of the Jumbo 

mine. 

Gypsum is not a conspicuous or characteristic constituent of the Goldfield ores, but the 

mineral is widely distributed over the district and occurs near the surface in connection with 

all the Tertiary rocks with the possible exception of the rhyolites and the fresh olivine basalt. 

MELANTERITE. 

Nat ural ferrous · sulphate (FeS04 + 7H20) or iron vitriol forms in small quantities in the 

lower part of the zone of oxidation by the oxidation of pyrite and marcasite. It was noted as 

bluish-green vei:alets on the 130-foot level of the Combination mine and as a silky white effiora Headden, W. P ., The Doughty springs: Proc. Colorado Sci. Soc., vol. 8, 1905, pp. 1-30. 
MINERALOGY. 129 

escence in the unused workings of the Vernal mine, now part ' f the Goldfield-Belmont. The 

nor1pal color of the sa1t is green, but it loses water on exposure and turns white. The material 

assumes its original color on moistening. 

CHALCANTHITE. 

_ Hydrous cupnc sulphate (CuS04 + 5H:

20) is sparingly ·p esent in ·some places near the 

base of the oxidized zone. It may readily be distinguished u derground from melanterite by 

taking up a particle on a bright moistened knife blade. If a y chalcanthite is present a film 

of copper will at once be deposited on the steel. 

HALOTRICHITE. 

White or slightly yellowish fibrous incrustations, having he astringent taste common to 

the alum group, occur in some of the mines near Goldfield, articularly in disused workings 

above the water level. Such efflorescent crusts were observe l in abundance on the 190-foot 

(intermediate) level of the January mine in 1905. Samples of t e mineral collec.ted at that time 

were found by Mr. W. T. Schaller to contain sulphuric acid and rnuch ferrous iron, but .no · 

potassium, and to correspond in other respects to halotrich'te (FeO.Al 20 3 .4S03 +24H20), a 

monoclinic or triclinic member of the alum group. The potas iurn alum, ka.linite (K20.Al20 3.4 

S03 + 24H20), is also a mineral likely to occur in deposits ori · inally containing much alunite, 

but it has :riot been definitely recognized in the Goldfield district Alunogen (Al 203 .803 + 18H20) 

is another mineral of probable although not yet demonstrated ccurrence in this locality. 

ALUNITE. 

The hexagonal (rhombohedral) hydrous sulphate of pota sium (K20.3Al20 3 .4S03 .6H20 ),a 

known as alunite or, in massive form, as alumstone, is so a bun ant in 'the Goldfield district and 

so generally associated with the intense alteration of the rocks in the ,vicinity of the ore bodies 

that it must be regard~d as one of the most characteristic mi erals of the gold deposits. It is 

riot limited, however, to the immediate vicinity of the ore d posits, but, as will be shown in 

the chapter on metasomatism, occurs in pr~ctically all of the Morena rhyolite, in the rhyolite 

about Vindicator Mountain, in the dacite and andesite of Preble Mountain, and elsewhere. 

Alunite occurs at Goldfield chiefly in two forms: (1) as a oft, white or slightly pink material, closely resembling kaolinite, and like that mineral filling cavities in ledge matter or ore, 

and (2) as an integral constituent of altered rocks. 

In the earthy, massive form, alunite is very abundant i the January and Combination 

mines, where it plays much the same part in the sulphide zone that kaolin does in the oxidized 

zone. It has been found in considerable quantity also in the one Star mine arid in leases on 

the Commonwealth claims, about 2 miles east of Goldfield, an is probably not entirely absent 

from any of the·ore bodies in dacite. 

In the Combination mine much of the interstitial mate ial between the 'nodules of rich 

native gold and sulphide ore near the 230-foot level is aluni e. As a rule, the pure massive 

alunite can be distinguished from the pure kaolinite by a fa nt pink tint. The crystallinity 

of alunite, too, is usually greater than that of kaolinite, an examination with a hand lens 

shows tiny crystal faces with pearly luster. . The texture of kaolinite on the other hand is 

normally too fine to show crystal planes, even under the microscope, ·and with a hand lens it 

appears uniformly dull and earthy. Inasmuch as alunite is a sulphate, its distinction from 

kaolinite or sericite may readily be made by simple chemical t sts. 

While alunite is· not entirely absent from the complete! oxidized ores, most of the soft 

white material found filling crevices in the weathered zone ha proved to be kaolinite. Kaolinite and limonite often occur together, but the association o alunite with an oxide of iron is 

a Or, as written by Hillebrand and Penfield in Bull. u, S. Geol. Survey, No. 262 1905, p. 38, K 2 [Al(OH)2] 6 (S01]1. 

79145-No. 66-09-9 
130 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

comparatively rare. Kaolinite and alunite occur together, however, in some of the oxidized 

ore of the Combination mine. The material is pulverulent and slightly yellow, the color lteing 

perhaps due to the presence of some jarosite, a mineral isomorphous with alunite, but differing 

from the latter in containing iron instead of aluminum.a The massive alunite in 1nany places, 

particularly in the Combination mine, contains abundant small, embedded crystals of pyrite. 

A somewhat unusual occurrence of massive alunite. was observed in 1905 in a 95-foot 

shaft on the Commonwealth No.3 lease, about 2 miles (3.2 kilometers) east of Goldfield. The 

country rock is silicified latite. This has been irregularly fissured and the fissures and irregular 

interstices are filled with faintly pink alunite, within which are embedded spherical nodules of 

snowy kaolinite ranging in size from that of a pea to that of a small marble. 

In the Dixie mine, on the west slope of Preble Mountain, massive alunite, which in 

some places is very compact, with almost the texture and hardness of some varieties of opal, is 

abundant on the 110-foot level, filling fissures and irregular crevices in porous silicified dacite. 

The most coarsely crystalline form of the mineral found is in an irregular veinlet, from a 

half to 3 inches (1.2 to 7.6 centimeters) in width, in altered dacite on the northeast slope of 

Preble Mountain. This material, as exposed at the surface, is a buff-colored aggregate · of 

platy, irregulat crystals, and resembles some forms .of coarse dolomite. 

The greatest interest attaches to the alunite as a rock constituent. Attention was first 

directed to its occurrence in this form by the finding of small nests or crystalline aggregates, up 

to 5 millimeters in diameter, of a pale-pink mineral in a greatly altered nearly white rock 

exposed on the east shoulder of Vindicator Mountain, about 2 miles northeast of the town 

of Goldfie.ld. The rock contains quartz phenocrysts and was probably originally a rhyolite. 

The m.icroscope shows that the feldspar phenocrysts, as well as the groundmass, have been 

altered to an aggregate of quartz and alunite, the optical determination of the latter mineral 

being checked by chemical tests in the United States Geological Survey laboratory by Mr. 

George Steiger. With the alunite is associated a subordinate quantity of diaspore. 

Microscopical study of the bleached altered rocks of the district soon showed that alunite 

is present in nearly all of them. The rhyolite forming the summit of C9lumbia Mountain, just 

north of the towns of Goldfield and Columbia, has been altered to a quartz-alunite rock, the 

alunite with some quartz forming pseudomorphs after the feldspar phenocrysts, which probably were originally orthoclase. Alunite is very abundant in the altered andesite and dacite 

of Preble Mountain and vicinity, and is present, down to the deepest workings, in practically 

all of the altered dacite which forms the country rock of the Mohawk Combination, Florence, 

January, Red Top, Jumbo, and other mines near Goldfield. Its characteristic appearance in 

thin sections is illustrated in Plates XXVIII, XXIX, and XXX. It is also abundant directly 

associated with the sulphide ores in these mines, and is in many cases intercrystallized with 

pyrite, as shown in Plate XXIX, D. . 

As a constituent of altered rocks in the Goldfield district, the alunite does not have com.;. 

plete crystal form. It is usually tabular in habit, the basal pinacoid being well developed and 

the rhombohedral faces being absent or indi~tinct. In thin sections (see plates above referred 

to) it shows distinct cleavage parallel to the basal pinacoid and parallel extinction with 

reference to the cleavage. The birefringence is apparently rather stronger than the difference 

. r- a= 0.018 given in the table of Michel Levy and Lacroix/ the interference colors in good 

thin sections being mostly yellow, but rising in places to red or blue of the first order. 

The mineral gives a positive uniaxial interference figure in sections showing no cleavage. 

The index of refraction is distinctly higher than the balsam of the slide ( 1.54), that given 

for the alunite of Tolfa being w= 1.572 .and s= 1.592.c 

In some thin sections alunite might, on superficial examination, be mistaken for sericite. 

The latter mineral, however, has higher double refraction with the color mottling characteristic of the micas, has finer cleavage, and is optically negative. The difference in optical oriena See Hillebrand, W. F., abd Penfield, S. L., Some additions to the alunite-jarosite group of minerals: Bull. U. S. Geol. Survey No. 262, 1905, 

pp. 32-41. 

b Les mineraux des roches, Paris, 1888. Also Iddings, J.P., Rock minerals, New York and London, 1906. 

c Iddings, J. P. , op. cit., p. 476. 
MINERALOGY. 131 

tation is most quickly detected by the use of gypsum plate o q~artz wedge. In alunite the 

higher colors appear when the basal cleavage is parallel to th direction of greatest elasticity 

in the plate or wedge. In sericite the higher colors occur in th transverse position. 

The minerals most commonly associated with the alunit as constituents of the altered 

rocks are quartz and pyrite. Some of the andesite on the outh slope of Preble Mountain 

has been altered to a nearly white-, fine-granular aggregate c]sisting almost wholly of quartz 

and alunite. The altered dacite forming the country rock f the Goldfield ,group of mines 

consists of quartz, alunite, pyrite, and kaolinite in various pr portions. In many varieties of 

the rock these minerals are accompanied by small quantities f diaspore. 

The gold, fa1natinite, bismuthinite, and other constituent~ of th-e richest ore. _are generally 

inclosed in quartz, not alunite. The latter mineral, howeve , frequently occurs in the same 

microscopical section less than a millimeter distant from the mftallic minerals. In ore from the 

Jumbo-Extension mine, near ~iamond~eld, alunite an.d _a . tflluride of gold are crystallized 

together, as was found by the miCroscopiCal study of thin sect ons. -

Calcite and alunite do not ordinarily occur together, bu microcrystalline calcite, a little 

sericite, and probably some kaolinite have been found associ ted with much larger crystals of 

alunite in an altered rhyolite from the east slope of Vindi ator Mountain. The molecular 

ratio of soda to potash in this alunite, as determined by Dor.t r Hillebrand, is as 40 to 45. It 

is possible, however, ·that the result obtained for potash ay be high in consequence of 

some decomposition of the sericite by the sulphuric acid use to dissolve the alunite. 

The occurrence together of alunite and calcite, appar ntly developed -simultaneously, 

shows that the alteration took place under conditions which id not permit the free escape of 

carbon dioxide. It is scarcely conceivable, for example, tha calcite could form in the presence of sulphuric acid percolating down from an overlying de osit of oxidizing pyrite. . 

As shown above, part of the alunite contains considerabl · .sodium, and the ca~culations of 

the mineralogical compositions of some of the altered rocks rom their chemical analyses, as 

will appear in the following chapter, indicate that most of t e mineral occurring in the Goldfieki d~strict is not the pure potash salt, but is intermediate b tween alunite proper and natroalunite.a 

Alunite differing in habit from most of the mineral thu1 far found near Goldfield occurs 

-in the Hat lease on the Blue Bull Mining Company's ground, 1! miles ( 1.4 kilometers) east of 

Goldfield. The country rock here is andesite. This has bee locally brecciated and the fragments are silicified. Between the fragments, and cementin them together, is much bright 

red hematite, which in the croppings is partly changed to li onite. The workings when visited were only about 50 feet ( 15 meters) deep and the hemati e extends at least to that depth. 

Occurring as irregular bunches and streaks in this. hem titic breccia is much soft, finegrained material of light-gray color with irregular reddish gr y bands. In texture this material resembles a :fine sandstone. It is firm, but can be crurnb ed between the fingers, and gives 

a reddish streak when struck with a pick. 

Under the microscope -the powdered material proves t be made up of small, sharply 

bounded, colorless crystals, the largest being less than o.oa illimeter in diameter. The crys_-

' tals are apparently octahedral, but in reality are probably ombinations of a rhombohedron 

an~ basal pinacoid. They are doubly refracting and can not, therefore, belong to the isometric 

system. 

Chemical tests by Mr. W. T. Schaller show the presen e of alkalies and sulphuric acid, 

and the mineral is without much doubt alunite, natroaluni e, or an intermediate variety of 

this isomorphous group. The crystals are associated with icroscopic rosettes of hematite, 

the latter giving the red streak when the material is scratch d. Such ore as had been sacked 

for shipment at the time of visit consisted mainly of this alu itic material. . 

The mineral is also abundant, with sulphur in altered r yolitic pumice, near Cuprite, 12 

miles-south of Goldfield. 

a Hillebrand, W. F., and Penfield, S. L., op. cit., p. 38. 
132 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

As alunite is still a co~paratively rare mineral, as it has not been recognized hitherto as 

an important mineral in ore deposits, and as its presence with the rich ores at Goldfield sug-· 

gests problems of great interest connected with the genesis of epigenetic ores, some reference 

to other occurrences and to opinions held as to the origin of the mineral may not be amiss. 

Alunite was first noted at Tolfa, near Rome, where it was used as early as the fifteenth 

century for the manufacture of potassium alum (K20.Al20 3 .4S03 .24H20). a This salt, containing 2 parts less of Al20 3 with 18 parts more of water, is obtained from the alunite by roasting 

and lixiviation. The mineral is found also on some of the islands of the Grecian Archipelago, 

near 1iuszay in Hungary, on Mount Dore in France, and in a few other localities in Europe, as 

well as with the opal"of Queretaro, in Mexico. In the United States it has been described in the 

Rosita Hills,b on Calico Peak, near Rico,C in the National Belle mine near Silverton,d and at 

Cripple Creek,e all in Colorado. It occurs also at Tres Cerritos, Mariposa County, Cal./ W. 

Lindgren u found alunite in the Ryerson, mine near Morenci, Ariz., associated with pyrite and 

kaolin. He regarded it as formed by the attack of descending sulphuric acid solutions upon 

sericite away from free oxygen. In Nevada alunite has been described by G. I. Adamsh as 

associated with sulphur and cinnabar at the Rabbit Hole mines, and by S. H. Ball as in a silicified rhyolite of the Cactus Range, east of Goldfield.i 

Until recently, geologists and mineralogists have regarded alunite as formed exclusively 

by the attack of sulphurous fu:marolic vapors upon feldspathic rocks. i At Cripple Creek, however, the mineral was found only in the oxidized ore, and, like the kaolinite of that district, is 

probably secondary with reference to the original telluride ores. ·De Launay,k moreover, has 

recently maintained with cogency that the alunite of Tolfa is probably not, as commonly supposed, 

a solfataric product, but is due to the action of percolating surface w~ter, charged with sulphuric 

acid by the oxidation of pyrite, upon a particularly feldspathic facies of .the trachyte. It is 

accordingly no longer justifiable to regard the occurrence of alunite as proof of former fumarolic 

activity. The mineral may form under very different sets of conditions, and it is necessary in 

seeking the explanation of any occurrence of it to keep alternative hypotheses in mind. 

· In all four of the Colorado localities the alunite occurs in regions which contain ore deposits. 

In the Rosita· Hills and in the Rico and Silverton districts it is apparently not a product of superficial oxidation. No close kinship between this mineral and the ores, however, has been shown, 

although it was doubtless recognized by all the workers in those districts that there might be 

some genetic relation between the metallic sulp.p.ides and the volcanism of which the sporadic 

solfataric metamorphism of feldspathic rocks to quartz-alunite aggregates was one manifestation. 

It is worth noting in ~his connection that the indexes of two of the best and ·most recent worksl 

on ore deposits contain no reference to alunite, showing that the mineral has not been commonly 

recognized as one intimately associated with ores. Neither is it mentioned, so far as I am aware, 

in C. R. Van Rise's work on metamorphism.m J. H. L. Vogt,n however, in discussing rnetasoa For the latest account of this celebrated locality, with a bibliography, see De Launay, L., La metallogenie de l'Italie. X. Geol. Cong., Mexico, 1906, pp. 125-132. 

b Cross, Whitman, Geology t>f Silver Cliff and the Rosita Hills, Colorado: Seventeenth Ann. Rept. U.S. Geol. Survey, pt. 2, 1896, pp. 52-56; also Am. Jour. Sci., 3d ser., vol. 41, 1891, pp. 466-475. 

c Cross, W., and Spencer, A. C., The geology of the Rico Mountains, Colorado: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, pp. 92-94. . d Hurlbut, E. B., On alunite from Red Mountain, Ouray County, Colorado: Am. Jour. Sci., 3d ser., vol. 48, 1894, pp. 130--131. Also Ransome, F. L., A report on the economic geology of the Silverton quadrangle, Colorado: Bull. U. S. Geol. Survey No. 182, 1.901. 

e Lindgren, W ., and Ransome, F. L., Geology and gold deposit~ of the Cripple Creek district, Colorado: Prof. Paper U.S. Geol. Survey No. 54, 1906, p. 125. . f Turner, H. W., Rocks and minerals from California: Am. Jour. ScL, 4th ser., vol. 5, 1898, pp. 424-426. 

g The copper deposits of the Clifton-Morenci district, Arizona: Prof. Paper U.S. Geol. Survey No. 43, 1905, pp. 119-120, 169, 193-194. h Adams, G. I., The Rabbit Hole sulphur mines near Humboldt House, Nev.: Bull. U.S. Geol. Survey No. 225,1904, p. 500. i Ball, S. H., A geologic reconnaissance in southwestern Nevada and eastern California: Bull. U'. S. Geol. Survey No. 308, 1907, p. 48. i Cross, W., Geology of Silver Cliff and the Rosita Hills, Colorado: Seventeenth Ann. Rept. U.S. Geol. Survey, pt. 2, 189G, p. 314. Cross, W., and Spencer, A. C., Geology of the Rico Mountains, Colorado: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2,1900, p. 33. Iddings, J.P., Rock minerals, New York, 1906, p. 476. Hillebrand, W. F., and Penfield, S. L., op. cit., p. 40. 

· · k Op. cit. . 

l Beck, Richard, Lehre von den Erzlagerstatten~ Berlin, 1901. Stelzner, A. W., and Bergeat, A., Die Erzlagerstatten, Leipzig, 1904-1906. 

m A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904. 

n Problems in the geology of ore deposits: Trans. Am. Inst. Min. Eng., vol. 31, 1902, p. 150. 
MINERALOGY. 133 

matic vein processes, has remarked: "I would mention also the ormation of alum-stone, quartzalunite rocks, quartz-diaspore rocks, etc., and also the format' on of. bauxites, etc. But I do 

not know that these changes have been anywhere observed in g etic relation with ore veins." 

~AROSITE •. 

The mineral jaros_ite is closely related, chemically and erystallographically, with alunite. 

The formula of jarosite proper is K20.3Fe20 3.4S04.6H20 or [F~(OH) [S0 4 ·and the crystalli- . 

zation, like that of alunite, is rhombohedral. As Hillebrand land Penfield a have shown, the 

potassium jarosite ~s merely one member of a series of which the other known members are 

natrojarosite, N a2[Fe(OH) 2] 6[S04] 4, and the remarkable plumboj · rosite, Pb[Fe(OH) 2] 6[S04] 4• 

In view of the great abundance of alunite in the Goldfield district, it might be expected that 

some men1ber of the related jarosite group would be not unco 1 mon. Such expectation, however, has not been fulfilled. It is not even certain that the mi eral presently to be described is 

really jarosite. 

Half a mile south of Myers Mountain Mr. W. H. Emmons ollected from the Siebert forma-

. tiona specimen of tuff which proved to be of unusual character it has the general appearance 

of a yellowish, sandy tuff which weathers red on exposed sufa es. Like the material from the 

Hat lease, it gives a hematite streak. A thin section shows t e rock to be a tuff in which the 

larger fragments are irregular cuspate particles of clear volcanic glass. The bulk of the material, 

however, is a friable mass of microscopic yellowish crystals·. P,e crystals are sharply bounded, . 

and when seen in the pulverized ·material under the microsco e resemble octahedrons. They 

are not isotropic in all sections, however, and are probably corn inations of a basal pinacoid with 

a rhombohedron, giving a pseudo-octahedral form similar to hat sometimes assumed by the 

mineral coquimbite.b The crystals are n1inute, rarely exceedi g 0.025 millimeter in diameter. 

Their color is light yellow. ' 

Chemical tests by Mr:. W. T. Schaller in the United Sta es Geological Survey laboratory 

showed the presence of alkalies and sulphuric acid, so that t e mineral belongs without much 

question to the alunite-jarosite series. The yellow tint and th tendency of the rock to redden 

on weathering indicate that the crystals contain iron, and t at therefore they are probably 

jarosite or some variety intermediate between jarosite and alu ite. A little scattered hematite 

occurs with the jarosite. 

The tuff has evidently undergone alteration as a result of wP,ich the finer particles of volcanic 

glass have been changed to an aggregate of jarosite or soiie closely related mineral. The 

alteration has only slightly affected the larger glass sherds, hich, as a rule, still retain their 

characteristic clastic outlines. Some of them, however, have1 been peripherally attacked, the 

glass being sep~rated from the jarosite aggr~ga~e b~ ~e y jagged suturelik.e boundarie. s. 

Cracked or pumiCeous fragments usually contain· Jarosite In the cracks ot vesicles. 

· There is no evidence that the tuff ever contained any no able quantity of pyrite, and the 

sulphide solutions which effected the metamorphism must ha e had their source outside of the 

rock itself. 

It is not improbable, as pointed out by W. F. Hillebran ,c that a yellow coating on some 

oxidized ore collected in the district by Spurr is jarosite. 

EMMONSITE AND DURDENITE. 

Both emmonsite and durdenite are greenish-yellow or yepowish-green minerals of obscure 

crystallization and somewhat uncertain composition.d The are essentially hydrous ferric 

tellurites, in which part of the tellurium may be replaced by selenium. The theoretical composition of durdenite is Fe20 3 .3Te02.4H20. 

a Some additions to the alunite-jarosite group of minerals: Bull. U.S. Geol. S rvey No.-262, 1905, pp. 32-41. 

b See Dana, J.D. and E. S., System of mineralogy, 6th ed., New York, 1895, p i 956, fig. 2. 

c Bull. U .S. Geol. Survey No. 260, 1905, p. 137. 

d See Hillebrand, W. F., Two tellurium minerals from Colorado: Bull. U.S. Geol. Survey Ko. 262, 1905, p. 56. 
134 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

At Black Butte a greenish-yellow mineral belonging to this group occurs in the oxidized 

parts of the ore bodies, particularly in connection with good ore. It forms tenuous crusts, 

often little more than a stain, along cracks in the ore, or is implanted on the walls and cavities 

as thin rosettes, resembling lichen growths and showing minute fibrous crystallization. It is 

associated with free gold, limonite al~nite, and perhaps kaolinite. The mineral was determined 

by Dr. W. F. Hillebrand to be a seleniferous ferric tellurite. 

A canary-yellow variety, also seleniferous, occurs in similar thin incrustations and specks 

with limonite, cerargyrite, and. native gold in the oxidized ore of the Gold Coin claim near 

Diamondfield. Other occurrences will doubtless be noted with the increase in mining development near Diamondfield. 

The mineral, as at Cripple Creek, results from the oxidation of ores containing tellurides. 

In the Gold Coin workings the original mineral is a telluride of gold of undetermined species. 

In Black Butte· the p~rent mineral has not been recognized. 
CHAPTER XI. 

THE MINES: A GENERAL ACCOUNT OF THEIR DIST IBUTION, DEVELOPMENT, 

AND OPERATION, INCLUDING ORE IREATMENT. 

DISTRIBUTION AND UNDERGROUND DEVEL PMENT OF . MINES. 

The important mines of the Goldfield district will be c nsidered in two areal divisions, 

which may be conveniently designated the "Goldfield" and 11 iamondfield" groups, Of .these 

the first has supplied over 95 per cent of the output of the district and includes such well-known 

mines as the Mohawk, Combination, Florence, Jumbo, January, Red Top, and Sandstorm. 

The belt of productive mines of the Goldfield group sweeps from Kendall :Mount~in on the 

north in a gentle curve, concave to the northeast, past Columbia Mountain and Milltown, to a 

point about half a mile southeast of the latter settlement. It may be subdivided into a cluster 

of mines on the north, including the Sandstorm, Kendall, a~d Conqueror, which are in rhyolite; 

a very important aggregation northeast of Goldfield, which is mainly in dacite, and includes the 

Red Top, Mohawk, Combination, January, Jumbo, and part of the Florence mines; and, finally, 

some mines, principally lessee workings, east of Goldfield, in the Milltown andesite. The principal underground workings of the mines near Goldfield are shown in Plate IX, and the situation 

of most of the important leases may be seen from Plate X. 

The mines of the Diamondfield group are aligned along McMahon Ridge north of the town, 

and stretch from Black Butte on the east for a distance of about a mile to the west. These are 

mainly in the Milltown andesite. 

Although the positions of the mines are given on Plate I, some verbal and pictorial description will perhaps help the reader to visualize the conditions at Goldfield and to follow with 

greater interest a presentation of the ore occurrences which necessarily falls far short of reality. 

On a quiet morning when the winds are not whirling clouds of desert dust through the 

town, one standing on :Mira Mountain, about 1! miles south of Goldfield, and looking nearly 

due north has before him the scene shown in Plate VI, B. The sharp peak conspicuous in 

the middle ground is Columbia Mountain. · Southwest of it are the towns of Columbia and 

Goldfield, beyond which, to the north, shimmers the desolate valley followed by the railroad 

to Mina and Hazen. In the distant hills behind the mountain and a little to the left of its 

summit is Tonopah, 30 miles (48 kilometers) away. The buildings visible on the hill just west 

of Columbia Mountain are at the new 100-stamp mill of the Goldfield Consolidated Mines Company, of which only the foundations were completed when the view was taken. Just beyond 

them, but not in sight, are the Sandstorm and Kendall mines. A little east of south from the 

mountain and over the small basalt-capped hill in the foreground are the principal mines of 

Goldfield, the mill and head frame of the Florence mine being almost in line with the summit 

of the intervening hill. The large white dump at the right-hand side of the picture is that of 

the Little Florence on the south side of Florence Hill. If, before leaving Mira Mountain for a 

nearer view of the mines, the visitor turn to the west he may look over the basalt top of Mal pais 

Mesa · (Pl. XI, A) to Montezuma Peak, about 8 miles (1 3 kilometers) . away. On the slope 

under the basalt may be seen exposures of the Siebert formation and in the middle ground the 

·road fr01n Goldfield to Lida and Rhyolite. 

Leaving Mira Mountain and walking north over the Siebert beds and Milltown andesite, 

which is covered in most places by soil and stony detritus, the visitor who approaches the 

Florence mine has the view shown in Plate XI, B . . In the foreground is soil-covered Milltown 

andesite. The near dump to the left is that of the Black Eagle lessee shaft, 290 feet (88 meters) 

135 
136 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

deep, the last rock on the dump being the latite which underlies the andesite: The shaft just 

behind this dump is the Rosebud, on the 0. K. lease, 500 feet (152 meters) deep. Beyond it 

is Florence Hill, crowned by the Little Florence shaft, 555 feet (169 meters) deep, with five 

short north-south levels and lateral crosscuts to shafts on each side of the hill. This is one 

of the famous Florence leases a and produced about $1,500,000 from ore in the Milltown andesite. 

Below the Little Florence dump, and in front of a dark ledge outcrop on Atlanta ground, is 

.the 500-foot Rogers shaft on another rich lease block of the Florence-Goldfield Mining Companies' ·ground, and to the right of this are a number of shafts, most of them about 500 feet . 

deep, which have been sunk in the hope of finding some continuation of the rich ore mined in 

the Little Florence and Rogers leases. . Beyond and just to the left of the hill are the head 

frame and mill of the Florence mine. · 

The visitor may now go to the top of Florence Hill and look northwest at the view shown 

in Plate XII, A. Near at hand to the right is the Florence head frame. This shaft is 350 feet 

(107 meters) deep, with levels running generally northwest and southeast. Two levels, the 

. 150-foot and the 250-foot, are connected with the Reilly lease shaft, which appears in the middle 

ground, just to the left of the center of the picture. This was a profitable lease in the northwest 

corner of the Florence claim and produced ore to the value of nearly half a milli.on dollars in 

. 1905. On the hill above and to the left of the Reilly are the Combination mine and mill. The 

Combination shaft, 380 feet (116 m.eters) deep, is connected by extensive levels with the Reilly 

shaft, with the January, of which the disused head frameb appears just beyond the Combination 

buildings, and with the Mohawk workings, which ramify through the low hill to the right of 

the valley in the middle ground. The top of the head frame of the Mohawk shaft, 600 feet 

(183 . meters) deep, barely shows over the crest of this hill. The Mohawk has levels at 245, 

350, 450, and 600 feet (74, 107, 137, and 183 meters). These connect with an irregular maze 

of lessees' workings, mostly above the 250-foot level, and extending over the greater part of 

the Mohawk No. 2 claim. In the valley to the right of the Reilly and in order from southeast 

to northwest are the Florence-Wheeler, the California-Florence, the Combination Fraction, and 

the Burns shafts.· (See also Pl. IX.) Beyond them, near the high trestle which leads to the 

Mohawk ore bins, are the dumps of the Hayes-:Monnette and 'other famous lease shafts on the 

Mohawk ground. These shafts have been dismantled, and their dumps are being culled over 

and shipped. The largest dump visible on the south side of the Mohawk hil~ is that of the · 

Loftus-Davis lease shaft on the Combination Fraction claim, which connects through stopes 

with the Mohawk workings. Below it and to the left of the Florence head frame is the Oddie 

shaft, 612 feet (186 meters) deep, also on the Combination Fraction. Concealed by the Mohawk 

hill and between it and Columbia Mountain are many lessees' shafts on the Mohawk and Gold 

Wedge claims and the main shaft of the Red Top mine. The most important lease on the 

Goldfield Wedge claim is the Mohawk-Jumbo, with a shaft 500 feet (152 meters) deep, and 

extensive stopes on the deeper part of the Mohawk ledge. Just north of it is the Mohawk Ledge 

shaft, 700 feet deep. The Jumbo mine, 500 feet deep, is at the extreme right of the view, 

concealed by the Florence head frame. The shaft is now dismantled, and the old workings 

will be undercut from the 600-foot Mohawk level and from the Goldfield Consolidated Mines 

Company's new .Jumbo or Clermont shaft, 860 feet (262 meters) deep in January, 1909, which 

is about 1,000 feet (305 meters) north-northeast of the old Jumbo shaft. Beyond the Jumbo, 

to the north, are the Mushett (480 feet, or 146 meters, deep), Five Friends (560 feet, or .170 

meters, deep), Hazel-Goldfield (740 feet, or 225 meters, deep), Mohawk-Red Top, and other 

leases on the ground of the Goldfield Consolidated Mines Company. The long dark building 

in the middle distance is the Goldfield Cl c mill. 

If the visitor, still standing on Florence Hill, will now turn to the east, he will see (Pl. XII, 

B) just below him to the left the Florence-Annex shaft, 500 feet (152 meters) deep, through 

would 

a The word" lease" is so generally used in the district to designate not merely a contract but a mine worked by lessees that to avoid such use savor of pedantry. 

b f)ince removed. 

cThe company uses this, the chemical symbol of chlorine, in its corporate name. 
S. GEOLOGICAL SURVEY 

RGE OTIS SMITH. DIRECTOR 

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I O.K . L~S~ 

I L_________ BLACK EAGLE I 

~ Q?' I SP~AGUE AND STEIN I MINING AND LEASING I 

w ~ I LEASE I COMF>A I .J 1- I COM ...1. '"'NY S ~ 1-------~L~E_.J(I ON No 3 ~ I ---r-----·-- I 1- - I MITCJ1ELL-rAI"''" I I ~ ~ I ro;rlf:LO I ~ 1 LEA s~ 1 1- I I 

0 300 600 900 1200 1500 FEET 

c===~====~==~====~==~ 

MAP SHOWING PRINCIPAL LEASE BLOCKS IN THE VICINITY OF GOLDFIELD. 

Based on J ohn Hagel 's lease map for May, 1go8. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XI 

A . MALPAIS MESA; FROM MIRA MOUNTAIN . 

B yond the m sa is Montezuma Peak, composed largely of beds belonging t o the Si eb rt for m ation. T h same 

formation sho w s also in t he steep slope belo w t he basal t cap of t he mesa. 

U. FLORENCE HILL; F ROM THE SOUTH . 
U. S. GEOLOGICAL SUR VEY PROFES 10 AL PAPER 66 PLATE 

.t!. 

lJ. 

VIEWS FROM FLORENCE HILL. 

A , Looking nort h w st; 1 , Loo k ing ast. 
DISTRIBUTION .AND DEVELOPMENT Ol!' MINES. 137 

which was hoisted· rich ore from the Engineers' lease to a gross value of over $1,000,000. To 

. the right is the group of board buildings known as Milltown, and beyond the railroad is the 

ridge with typical ledge crop pings which ·extends eastward beyond Pre9le 1\fountain. Nearly 

all the shafts visible on this ridge are prospects on the ground of the Atlanta Mining Company. 

Most of them are from 300 to 500 feet (91 to 152 meters) deep, with short exploratory levels. 

About a quarter of a mile (0.4 kilometer) beyond the shafts on the extreme .right are the Gold 

Bar and Victor mines, about 300 feet (91 meters) deep, which thus far have .been the most 

easterly productive mines of this belt. In the distance are the high dacitic hills, just outside 

of the mapped area and southeast of Tognoni Springs. 

One who wishes further to overlook the district before examining the individual mines 

will do well to continue his walk northward and climb Columbia Mountain. Thence, looking 

southward, he may see Goldfield spread out, with the dark edge of Malpais Mesa behind it, and 

will see, a little east of the town, most of the mines visible from Florence Hill, with others which 

are concealed from that point by the hill southeast of the Mohawk mine. If the walk be extended 

northward .along 1v.t:orena Ridge, the Sandstorm and Kendall minescome into sight to the northwest (Pl. XIII, A), and to the east is an uninterrupted view (Pl. XIII, B) over lower country, . 

underlain chiefly by Milltown andesite, to Black Butte and the town of Diamondfield. McMahon 

Ridge, seamed with trenches cut by prospectors, shows to the left of the town and ·butte. 

The Sandstorm shaft is 400 feet (122 meters) deep, but all the ore from this and the Kendall 

mine, most of which has been shipped by lessees, has come from superficial workings. The 

deepest shaft in the Diamondfield group is the Daisy, 400 feet deep. The lateral work in this 

group is not extensive. In the mines near Goldfield, on the other hand, it was possible in 1908 

to travel underground from the north corner of the 1\fohawk No. 2 claim by way of the Combination mine to the south end of the Florence claim, a distance of nearly 4,000 feet (1,219 meters), 

with the oppO'rtunity of making long detours in the mines passed through. 

The following reference list, which is intended to summarize the principal shaft develop- · 

ment in the district and to aid the reader as· a key to Plate I and in looking up details regarding any particular shaft, aims to include, with a few exceptions, only those of 200 feet (61 meters) 

or more in depth. Even as regards these it is not complete, as there are many abandoned 

shafts in the district of which the depths, not ascertainable, may exceed 200 feet. There are 

also many prospect shafts of less than 200 feet in depth scattered over the district. Of these 

no account is taken. In general, the shafts listed are those whose positions are shown on Plate I. 

The depths and geologic information given were ascertained in July, 1908; although where 

later information has come to hand it has been used. . The names listed are in most cases those 

by which the shafts are genera1ly known rather than the official designations of the companies 

operating them. There is considerable confusion introduced into the naming of shafts through 

the practice by some lessee companies (for example, the Little Florence and Frances-Mohawk) 

of transferring their names from the original lease to other leases in different parts of the district. Some shafts also are known under more than one name, and changes in designation are 

not uncommon. The list illustrates well the remarkable energy ~hat has been displayed in 

searching for the rich Goldfield ore bodies. These shafts alone, regardless of all drifting and 

·crosscutting and of the numerous unlisted openings less than 200 feet (61 meters) deep, would, 

if put together, have a total length of over 80,000 feet (24.4 kilometers); they represent an expenditure of about $2,000,000. 
138 . THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. ' 

Principal shafts in the Goldfield district. 

[A plus sign ( +) in the column of depths indif!ates that sinking was in progress ·when the figure was obtained or that there is reason to believe that the sbaft has since been deepened.] 

Name. 

I 

Number on Plate I. Claim. Section. 

Depth I 

in 

feet. 

Surface rock. Changes in general formation. 

Adams................

Albemarle ..... . . .......... . ........... ~....... 316 

67 Adams....

Huntch B . ........... 25 ........ Sandstorm rhyolite .... Into Morena rhvolite. ell No. 4.... 5 300+ Milltown andesite.. . .. Into latite. · 

American.......................... 

it~~-~--· ·.-_-:·. .·.·.~~:::~ :: ::: ~: :::::: : 1~ ~~fJ':{_ ~~-~~~:: :: ::::: ~~ ... 4is+ . Mtlito~ri" andesite.:: :: Into latite above 300 feet. 

AtlantaB.andM................. 76 Johnson No.1......... 29 . . . . . . . . Latite ................ . 

Atlanta Boom.... 292 BlackBear............ 1 200 Dacite ................. None. 

Atlanta-Cherokee.... . ................ 275 Union Jack........... 1 300 ..... do................ Do. . ...... . ...... 277 Black Bear............ 1 500+ Milltown andesite. . ... Some dacite near bottom. 

~;~~t;i~~~~~-~~~~~~~~i-~i~~ Baltimore Belle................... 

.~."~:: ······260·. c·orni.sii~an~::: ::::::: ....••• T ... 400·· ·nacite."."::::: ::::::::: None. 

Barnes (Mountain Crown)......... 

257 Bee Fractiop.. . ..... .. . 1 375+ Milltown andesite..... Do. 

Baumgarten.. .. ........ 234 Rustler Fraction...... 1 300+ ..... do ................ Into latite at 260 feet. 

Begole............................. . .......... 40 Black Butte No.2. .... 20 ............. do................. None. 

Belcher............................ 128 Mohawk No.2........ 36 200 Dacite ...... ·.......... Do. 

Belmont........................... 24 Daisy Triangle........ 19 . . . . . . . . Milltown andesite..... Do. 

Berlin............................. 35 Vernal No.2.......... 20 150+ ..... do...... . ......... Do. 

Black Butte Bonanza.............. 204 Berlin... . ............. 33 ........ Dacite.... . ........... Do. 

Black Butte Consolidated....... 45 Black Butte Extension 20 ........ Milltown andesite .. : .. Do. 

Black Butte Extension............ . . 39 Black Butte No. ·2..... 20 150 . . ... do................ Do. 

Black Eagle ....................... 48 Daisy...... . ...... . ... 20 ....... ...... do................ Do. 

Blake ............. . ........... 231 Combination No.3.... 1 290+ ..... do ................ Into latite at 280 feet. : ... 266 Atlanta............... 1 320 Dacite ................ None. 

Booth.

~}~~~~H~~~~s~~ik:::::::::::: ~~ -~i~_-cto."."."::::::::::::: ~ ---~~- :::::~~:::::::::::::::: Do. 

Bulldog.

.,.

.....................

........................ . ..... 140 Booth.. . . . . . . . . . . . . . . 36 200+ ..... do................ Do. 

Burns............................. 47 Bulldog Fraction No.2 20 . . . . . . . . Milltown andesite..... Do. 

California-Florence............... 219 Combination Fraction. 1 380 Dacite................ Do. 

Camp............ 223 Florence. ............. 1 400 ..... do ............... . Into latite (?). 

Century.............. . ................ 29 Daisy No.2........... 19 130 Milltown andesite . . .. None. 

Chicago-Florence ................... . ........ . ... 271 Union Jack........... 1 350 Dacite. ............... Do . 

Ch!cago-Goldfield · 245 Red King............. 1 400 Milltown andesite..... Do. 

Ch1cago-Velvet............... ... ,.. . ........... 107 Pipe Dream........... 35 Sieb_ert................ Into latite. .. . .. 157 Velvet................ 36 526+ Dac1te ............... . Milltown andesite at 380 feet; 

Cleary ... : ...... . ....... latite at 410 feet. . ......... . 30 Cleary ............... . 20 

36 

1 

36 

Clermont (Ne.w Jumbo) Milltown andesite ..... None. 

C.O.D ... .. ........................ 

. .. . 150 Clermont ............ . 920+ Dacite ..... . ........ . . Into latite at 615 feet. · 

Codd (St. Ives Leasing Co . ..... . 298 C.O.D .............. . 300 Milltown andesite. .. .. Probably none. .) ....... . 168 St. Ives .............. . 500 Dacite.... . . . . . . . . . . . . Into latite between 350 and 400 

Combination ........... .. . ....... . Combination Extension .......... . Combination Fraction ............ . Combined .............. . ......... . Do ..... ....... · .. . ............ . Do ............ . .............. . Commonwealth ..... .. .. . ......... . 

212 

229 

221 

26 

173 

152 

196 

Combination No.2 . .. . 2 380 ..... do ............... . August .. . ........... . Combination 1< raction. 1 400 Milltown andesite .... . 1 431 Dacite ............... . Daisy No.1. ......... . Sunflower .. . ......... . 19 . . . . . . . . Milltown andesite .... . 36 .. ...... Dacite ............... . Curly George ......... . Tokop ... . ........... . 36 ............. do ............... . 31 400 . .... do ............... . 

Crackerjack........................ 

Consolidated Red Top Lease....... 137 Red To:p. . . .. . ... ..... 36 300 ..... do ............... . 

Crooks............ 66 CrackerJack....... .. .. 25 .... . ... Morena rhyolite ...... . 

Crown............................. . .. . ... . ......... 165 Kewana No.3......... 36 400 Dacite ............. . . . 

Curtis....... 294 Crown rraction. . . . .. . 1 ........ . .... do .............. . . 

Do. . ........ . ............ 123 Mohawk No.2........ 36 365 ..... do ............... . 

Curtis-Frances....... . .......................... 151 Jumbo.... . ...... .. ... 36 ... . .. .. ..... do ............... . 

Daisy (Main or Truett).. . ............. 126 Gold Wedge.......... 36 .......... . .. do ............... . 

Daisy No.1.......... . ......... 28 Daisy No.1........... 19 400 Milltown andesite .... . 

Daisy Annex.......... ............ 32 Daisy No.2........... 20 210 ..... do .. · ............. . 

Daisy-Florence........ . ........... 23 Spokane.............. 19 .... . .... . ... do ............... . . ........... 256 Cornishman........... 1 320 ....• do ............. .. . 

~!I!~~~ Desert 

.. ~~~~~~:~:o:~~i~~~:::::::: ···---~~f 8~fl~~~~:::::::::::: ....... if:::::::: -~~rt:~:~~~~~~::::: 

Desert Rose....

Chief... . ................... 75 Angelus............... 30 . . • • . . . . Vindicator rhyolite ... . 

Diamond . .... . ............. 58 Desert Rose........... 26 . . . . . . . . Sandstorm rhyolite ... . 

Dixie............... ....... , .. :............... 69 Black Diamond..... . . 25 . . . . . . . . Milltown andesite .... . 

Eassie.. . .... . ....... . . 320 Tin Horn......... . ... 5 300 Dacite ........... . ... . . ....... . .................. 179 Kewana No. 3.... ..... 36 285 . .... do ............... . 

Eureka..

~~~!~1d'~.~s-~~ . .........

-~~~~~~~~~~~~~>. ... ... . ....

~: · · · · · · ··9o· · cia~a~~:::::: :::::::::: · · · · · · · 35· :::::::: · siei>ei:i·.-.-.~::: ~:::::::: 

Fargo (see Goldfield-Fargo) . .. .. 34 Yucca No. 1.. .. . . . . . . . 20 . . . . . . . . Milltown andE',site .... . .................. . ................................... February-Atlanta........ . .. . .... . .............. . ..... . 

Five Friends.......... . ........ 280 Atlanta..... .. ........ 1 . . . . . . . . Milltown andesite .... . 

Florence...... . ........... 163 Last Chance........... 36 560 Dacite ............... . 

Florence-Anne

.

x 

... . ................ 254 Florence.. . ..... .... .. 1 350 Milltown andesite .... . 

Florence-Annex (Engineers')...... 

No.2............. 253 Cornishman........... 1 500 . . ... ~o ..... .... ....... . 

Florence-Aurelia................... 258 ..... do................. 1 ........ Dac1te .......... ..... . 

Florence-C. 0. D 251 Firelight.......... . ... 1 330 Milltown andesite .... . 

Florence Consolidated............. . ..... . ... . ..... . . 301 C. 0. D............... 1 ....... . ..... do ................ . 

Florence Extension No.1.......... 

262 Cornishman.... . ...... 1 .... . .. . Dacite .... . .... . ..... . 248 Red King Fraction 1 320 Milltown andesite .... . ' No.1. Florence Extension No.2.. . ...... . 236 Rustler No.2 ........ . Florence-Goldfield Red King...... 243 Red King ............ . 500 

450 . . ... do ................ . ..... do ................ . 

Florence-Hopkins................. 282 .. . .. do................. Florenc . 345 ..... do ............•.... e-Jumbo................... 259 Florence.............. Florence-Kirby.................... 250 Dacite ............... . 

Florence L. and M

246 Red King............. 1 .. .. . .. . Milltown andesite ... .. . (see Little Flor- ......... . . . ..........................••................................... ence) - . Florence-Mohawk................. 

Florence-Wheeler.................. 108 January............... 35 ........ Siebert .............. :. 225 Florence.............. 1 480 Dacite ............... . 

Fr ~~-~~~~':".~:::::::::::::::::: ~i~ ¥i?a~~':sk:O~l~::::::: ~ ~ ·Miii~Wli-anCies.ite::::: 

feet. Into latite at about 250 feet. 

Into latite at unknown depth. None. 

Do. 

Do. 

Do. 

Into latite at probably less than 100 feet. None. 

Into andesite at 140 feet. 

None. 

Do. 

Do. 

Do. 

Do . . Do. 

Do. 

Into dacite. 

None. 

Do. 

Do. 

Do. Do. 

Do. 

Into Milltown andesite. 

Into latite at unknown depth. None. 

Do. 

Do. 

Do. 

Do. 

Do. Do: 

Do. 

Into latite at unknown depth. 

None . Into latite between 350 and 400 

feet. Into latite, depth unknown. 

None. 

Do. 

Do. 

Do. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE X III 

A. S,ll,NDSTORM AND KENDALL MINES. 

From Morena Ridge, north of Columbi a Mo untain . 

B. VIEW LOOKING EASTWARD FROM MORENA RIDGE TO DIAMONDFIELD AND BLACK BUTTE. 

Th e principal mines near Diamondfiel d are on the ridge extending from Black Butte to the trenched summit of 

McMahon Ridge (on the left). 

DISTRIB T N .AND DEVELOPMENT OF 1\iiNES. 139 

Princi al s afts in the Goldfield district-Continued. 

Name. Surface rock. Changes in general formation. 

I 

Nu::;;ber !aim. Section. D~~th I 

Plate I. feet. 

---------------: 1--+-44------1 ----------

138 B ot~h-.............. : 

268 J mbo .............. . 291 Black! ear ........... . 68 en. ashington No. 2 

228 C m · ation No. 3 ... . 300 old !B r .... . ___ ..... . 

~g~ g{g~~t~~~i_o_~ ~: ::: 

2 oldrrlg ... .. . ....... . 

'D -2:ii:; :: : 

Frisco .... _ .. ____ ------- .. -- .. ----. 

Fuller ..... ·- -·----- --- ---···· · ·--· Gauison ...... _____ _____ ____ ______ _ 

General Washington ... __ ____ . __ . __ Gibraltar .. _ ..... _______ ....... . .. . Gold Bar .. _ ..... _ ... ________ ... __ _ Gold Bar Fraction .... ______ ...... . 

Gold Bar M. and L ... _ ------------ Goldbug ... _ ..... ____ _ . ___ .... _ .. __ Gold Coin. _ . _________ . . __ .. . .. ... . 

Do ... . ----- -----·-··· -···· ·· ·· Gold Crown .......... __ -·-··-···-_ Golden Daisy .... _ . ___ .... . _ ..... __ Goldfield-Bullion .. _ .... ___ .. __ .. _. Goldfield-Columbia Mtn. Annex._. 

36 

1 

1 

25 

1 

1 

1 

1 

13 

20 

2 ' 35 

19 

33 

35 

150+ Dacite ... ___ . _. _ .. _ .. . 

200 ... . . do . .. _____________ _ 

300+ .. _ .. do . ... ____ .... _ .. __ . . .. _. __ Milltown andesite .. _._ 350+ .. _ .. do . ...... ______ ._._ 300 ..... do ... _____ ________ _ 

__ ... .. . _ .... do ........ : ....... _ 475+ ... _.do ..... . _ .. _._. ___ _ ............. do . .... ... ... ... ... . 150 ..... do ... _____________ _ 

420 .. ... do ..... . . ......... . Latite ..... . _. __ _ .. -.-- Milltown andesite._._ . 500 Dacite ............... . Latite ... ___ . . ___ ---.--

Into Kendall tuff or latite at 130 

feet. None. , Into andesite below 250 feet. None . Into latite at 340 feet. Into latite, depth uncertain. 

At dacite contact. None. 

Do . Do. 

Do. 

Do. 

. Do. Into latite at unknown depth. 

Close to contact with K endall 

tuff. 

None. 

2g; I~e~,~~~: ::::::::: ~: Goldfield-Dominion ________ . _ .. _._ 7 a o~ ..... _. _____ .. . 23 Milltown andesite .. __ . Goldfield-Fargo.................... 296 0. :··-·-·----··-· 1 415 .. ... do., ...... . ........ . Goldfield-FederaL ... _ ... ____ . ___ . 79 'onnt m Rat......... 28 _ ............ do . ... _. ___ ... .. _.. Do. GoldfieldMerger ... __ ____ ______ ____ 305 oons ine... . ........ 1 600 Dacite ______ ____ ___ ___ Intolatiteat312feet. 

Goldfield M. & Ore Red. Co .... .. _ 288 ond r.. _ .. _. _. ___ ... 1 350 Milltown andesite..... None. 

Goldfield-RedBillsM.&L........ 249 epte ber............ 1 300 ..... do .............. . .. Latiteat260feet. 

Goldfield-RedKingM.&L....... 232 om i ationNo.3.... 1 ··-····- .. .. . do ....... ... .. . .. . . Goldfield-Rosebud (see Rosebud) .... _ .. ... _ .... _. .. -.- _ ......... _ ... _ . ................ .. .... _. ______ .. _. _ ._. .. __ . 

Goldfield-Tomboy................. 65 lg l e .... : -······-· 25 ........ SlJ:ndstormrhy?llte .... None. 

Goldfields-Chedd .. __ .. .. __ .. . _ _ _ _ _ 252 im~ FractiOn....... 1 . . . . . . . . M1Utown andesite._ ... Do. 

g~~~ i/~;li-(see-i.ewis)-_-_- _- _-::::: ::: . ______ :~. _ --~~~ -~-~~:: :::::: ~ : ::: _____ --~~-: ~~:: ::: _: ~: :~~:.-::: ~:: ~::::: ~: GoldMountain.......... . ..... .... 287 oleo da..... .. ...... 1 ........ M1lltownandesite ..... None. 

Gold Sovereign . . __ __ .. --- ... -.. . . . 198 ohns n No. 2......... 32 213 Sandstorm rhyolite... Into Kendall tuff. 

Gold Star ....... _ .... .. .. . _ ... _... 289 oldj tar Fraction.... 1 Milltown andesite ..... None. 

Goodfriends ... _____ .. __ . __ .. _ ... _. 193 ilv~r ip.... .. .. . . . .. 31 Dacite .. ... _ ......... . Gordon and Ostetter.............. 41 olip y Fraction..... 20 .. _. _. _. Milltown andesite..... Do. 

Gotwaldt ......... :. ............... 226 omp nationNo.2.... 1 300+ ..... do .. . ............. Into dacite at 80 feet. Into 

Graham .. ---·-.--.-- --.-.- .. ---- ... 31 aisy±o. 2.--- ---- -.. 20 100 .. -.. do.-.--- ... -.... -- N~;~~e at 250 feet. 

Grandma...... ... ................. 180 ran a............. 36 ·--- ---- Daeite ................ Into Milltown andesite at slight depth. 

GreatBend(old).................. 16 reat endNo.2..... 19 300 Milltownandesite . ... . None. 

Gre-at Bend (new) ... _. _ ... _....... 15 .e.d.d~u-.t.te-.N .. 

0

._.

1 

___ ._ . __ · ._ ._ 19 .... . .. .. _ .. . do ....... ..... .. -. Do. GreatBendAnnex. . ..... ......... 10 19 ............. do .. .............. Do. 

Great Bend Diadem .. _ .. _......... 17 re t Bend No. L.. .. 19 400 ... .. do . .... . ....... . _. Do. 

GreatBendExtension............ 19 alae······-·-······· 19 ... .. ........ do ............ :... Do. 

GreaterNevada........ . ......... . 72 es ian______ ___ ____ 30 ------·- Vindicatorrhyolite.... Do. 

Hall-Florence ..................... 242 ed ing... .. 1 300 Milltownandesite ..... Do. 

~:;es~i1-orineite·:N·o: i: ::::::::: ::: f~~ ~tj~· "k No~ :i:::::: :: 3~ ~~~ ·ria~~~~~·_ ·_::::::::: : Do. 

Hayes-MonnetteNo.2.. ...... ..... 119 _a_s_ h··a·n·c·e·_-_·_-_.-_.: __ ::_._-_ 36 270 ..... do................ Do. 

Hazel-Goldfield........ ..... . .... . 161 36 740 ... . . do . .. .... ......... Intolatiteat685feet. 

Higginson.... . .... .. ....... ... .... 131 old edge ....... : .. 36 ............. do ... ...... ... ... . None. 

Do.................. .......... 74 {.u Silver.......... 30 ... .. ... Vindicatorrhyolite . ... Intoalaskiteatslightdepth. 

~~~~!~~ailiiiiii."." :: ::: ::: :::::::: 2~i fac ~~ar~::::::::::: ~ ---32o+ ~fl~~~ewn-ande-siie: :: :: None. 

ImperiaL......... . ............... 273 nip Jack.. . .. 1 375 · Dacite ........ . ..... .. · Do . 

. !lf~;~~r.~:·&c:;:Whito: ·· ··-~- :~~~,,.::I• III•:: ·······ii· ::::::: •. :~1i:i:•::::•::::•:: =·l;tltoat,Mfoot. 

~~~re~ ~~~~~~-~-~~-~ :_ ~::::::::::::: i~i ~~WJ{~t;~~:::::::::: ~i :::::::: : ~i1JJ~~: ~~~:~sii~::::: g~: Kalfus ......... . -.- ....... · .. -... .. 127 Mo'tllk No.2........ 36 270 Dacite . ....... _ .. __ ._ : Do. 

KansasCity.... .. .. ..... . .. ....... 297 C. O.ID............... 1 300 Milltown andesite ..... Probablyreacheslatite. 

Keane.- .- ....... _. _.. .. ........... 12 Great Bend ..... _..... 19 ..... ... _._ .. do ...... _._. ______ None. 

Keelyn G. & G.................... 283 Zoe . ...... .. _ .. _..... 1 500 _._ .. do .... ... _._ .... _. Into latite between 300 and 400 

Kett ..... .... . ................... . Kewanas .. __ .. ..... ... _ . _ ........ . Laguna (old) ... _ .. _ .. _ ......... _ . . Laguna (new) ..... _ ............. _. 

t~~~~~~::::::::: ::::: :: ::::::::: I 

Little Florence (Florence L.& M.). 

~:::;;::~~~~~ -(~-~ ~~~~~ -~~:~·_::: I Loftus-Davis .... ___ .. ____ . ____ ... _ 

Do .. ·-- · -···- ···----- ---- ·-· -- LQne Star ..... _. _. ___ . . . .... ..... _ Lucky Boys ........ __ ..... _._ .... _ Los Angeles ..... . . _ ..... .. __ ..... . M. and H .......... .............. . Mackenzie ........................ . 

279 

162 

144 

146 

272 

274 

241 

222 

284 

122 

61 

189 

182 

111 

92 

117 

Polvtde_ ............. . Zo(j . ... ......... .... . 

Ke alL. .. __ . _ .. _ ... . 

Re ing ............ . 

::f{:~~:'·· Moo~, shine .. _._ ...... . Re ing. _ .......... . Co ination Fraction 

Golc nda. _ .. __ . . ..... . Co¥1 inatiol). Fraction 

~~~r ~~~~:::::::: :::: 

~~ ~e~~~ ·_ ~ ~ ::: ::::: 

Silp r Pick ........... . Moh wkNo.2 .. . .... . 

feet. 

36 

1 

Dacite._ ...... . . _ . . ___ None. 

408 Milltown andesite .... .. Into latite between 300 and 400 

feet. 

26 368 Sandstorm rhyolite .. _. Into Morena rhyolite at about 

1 Milltown andesite._ . _. 36 500 Dacite ____ ___________ _ 36 ........ __ .. . do ... ____________ _ 

36 400 . __ .. do ..... __ .. .. .... . 1 ............. do ............... . 1 ________ .. . .. do ........... . ... . 1 5:>0 Milltown andesite. ___ . 1 600 Dacite ............... . 

1 

36 

26 

31 

36 

35 

35 

36 

420+ 

531 

250 

100 

360 

300 

300 

Milltown andesite ... _. Dacite .... _ ... _ ..... _. Sandstorm rhyolite ... . Dacite .... ___ ........ . Cam brian shale ..... _ . Dacite . .. __ .. ... ... .. . La tite .. . _ ... ......... . Dacite ............... . 

150 feet. 

None. 

Into lati.te; depth uncertain. 

None. 

Do. 

Do. 

Do. 

Do. 

None to 450 feet; record below 

that unknown. 

None. 

Do. 

Into latite near bottom. 

Into alaskite. 

Into latite at unknown depth. 

None. 
140 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Principal shafts in the Goldfield district-Continued. 

Name. 

Changes in general formation. 

I 

Nu:ber Claim. Section. ' DT~th Plate I. feet. Surface rock. 

Madonna 

- -------------- l-----------l----------- ---------1--------------

......................... . Magnet. .......................... . Majestic .......................... . Maloney .......................... . . Do .................. · ......... . Mammoth ........................ . Mayne ........................... . Do .......................... .. McNaughton ..................... . Midnight-Pawnee ................ . Milltown Fraction ................ . Mitchell-Fairfield (Stoneham) .... . Mohawk ............... .......... . Mohawk-Annex .................. . Mohawk Consolidated ............ . Mohawk Consolidated M. & L .... . Mohawk-Florence ................ . Mohawk-Jumbo .................. . Mohawk Leasing Co. No. L ...... . Mohawk Leasing Co. No.2 ....... . Mohawk Ledge ........ : .......... . Mohawk-Red Top ................ . Mohawk Syndicate ............... . Montezuma Lou Dillon ........... . Moore ............................ . Morrison ......................... . Mushett ...... · .................... . Nevada Amalgamated ............ . Nevada Exploration ............. . 

~f;~~~~i~~:::::::::::::::::::::: Norcross ............... ~ _ . _ ....... . Oakes ................ . ............ . Oddie ............................ . Do ........................... . Oddie-Rose ....................... . O'Keefe ........... : ............. .. Old Kentuck ..................... . 

Original Atlanta .................. . Original Velvet ................... . Oro .............................. . Palace . ........................... . Parker .............. ___ ....... . _ :. Parkinson ........................ . Penn (Winston) ...... . .......... . Peterson's Silver Pick ........... . . 

Pieri:e and Pugh .................. . Pittsburg-Nevada ................ . Pocahontas ....................... . Pollard-Florence ................. . Portland ......................... . 

Portland-Florence ... : ............ . Quartzite ....... : ................ . Red Hill ......................... . 

319 Bonanza ............. . 200 Gold King ........... . 203 Hobo ............... .. 164 Kewana Fraction .... . 267 Atlanta .............. . . 50 Amazon .............. . 54· Gem ................. . 56 Denver .... _ .......... . 132 Mohawk No.2 ....... . 46 Midnight Fraction._ .. 322 Milltown Fraction .... . 230 Combination l\o. 3 ... . 124 Mohawk No.2 ....... . 89 Dewdrop .......... . .. . 109 Mohawk No. L ...... . 110 ..... do .............. .. 240 Red King ........ _ .. .. 125 Gold Wedge ......... .. 113 Mohawk No. L ..... .. 112 ..... do ............... . 130 Gold Wedge .......... . 147 MissJessie .......... .. 102 Mohawk No. L ..... .. 77 Lou Dillon ... __ ...... . 227 Combination No.2 ... . 27 Daisy No.1. ........ .. 145 Miss Jessie ........... . 101 MohawkNo.1 ....... . 290 Golden Eagle ........ . 201 North Star. .......... . 142 East Side ........... .. 166 Black Rock .......... . 8 Oakes ............... .. 220 Combination Fraction 

118 Mohawk No.2 ....... . 129 · .. _ . . do ........ _ ...... . 159 Kewana No. 2 ....... .. 190 Economist.._._ ...... . 

276 

156 

143 

11 

309 

235 

264 

104 

21 

323 

85 

247 

233 

Union Jack .......... . Velvet ......... __ ... .. Midnight Fraction .. .. Rabbit's Foot ........ . Neglected ............ . Rustler Fraction ..... . Cornishman .......... . Deserted ............. . 

Thanksgiving Gift ... . Mayflower ........... . Valley View ........ ,: Red King ........... .. Bull Con._ ....... __ .. . 

277 Emma Fraction ...... . 43 Quartzite No. 1 ...... . 

5 Milltown andesite .... . 32 Latite ..... _ .......... . 33 Milltown andesite .... . 36 195 Dacite ........ _ ...... . 1 300 Milltown andesite .... . 21 ............. do .............. .. 26 .. .. .. .. Alaskite .............. . 26 .. .. .. .. Sandstorm rhyolite ... . 36 283 Dacite .............. .. 20 ............. do .............. .. 7 .... _ ... Milltown andesite .... . 1 220+ ..... do .............. .. 36 600 Dacite ............... . 35 ........ Siebert ............. .. 35 ........ Dacite . .' ............. . 35 200 ..... do ............... . 1 300 Milltown andesite .... . 36 500 Dacite ............... . 35 ............. do ............... . 35 ............. do .............. .. 36 700 ..... do .............. .. 36 420 ..... do ............... . 35 300 Kendall tuff .......... . 29 ........ Milltown andesite .... . 1 ............. do .............. .. 19 - 370 ..... do ............... . 36 480 Dacite .............. .. 35 Kendall tuff ......... . 1 300 Milltown anuesite .... . 32 Latite ............... .. 36 ........ Dacite .............. .. 36 ............. do .............. .. 24 ........ Milltown andesite .... . 1 612 Dacite .............. .. 36 300 ..... do ............... . 36 230 ..... do .............. .. 36 300 ..... do ............... . 31 ........ Milltown andesite .... . 

1 275 Dacite ............... . 36 300± ..... do .............. .. 36 ............. do ............... . 19 .. ...... Milltown andesite .... . 6 ............. do ............... . 1 ............. do ............... . 1 500 Dacite .............. .. 35 ........ _ .... do ............... . 

19 100 Milltown andesite .... . 8 ............. do ............... . 35 Alluvium ............ . 1 500 Milltown andesite .... . 1 440 Siebert ............ ~ ... 

1 250 Milltown andesite ... . . 20 200 ..... do ............... . 1 ............. do ............... . 

None. 

Do . 

Do. 

Do. 

Into alaskite at 100 feet. 

None. 

Do. 

Do . . Into latite at 450 feet. 

None. 

Do. 

Do. 

Do. 

Do. 

Do. 

Into latite near 470 feet. 

Into latite at 365± feet. 

Into Cambrian shale at 280 feet. None. 

Into latite. 

None. 

Into latite near 480 feet. 

Into alaskite. 

None. 

Do. 

Do. 

Do. 

Do. 

Do. 

lnto latite. 

Into Sandstorm rhyolite at 50 feet. Into latite below. 

None. 

Do. 

Do. 

Do. 

Do. 

Latite somewhere below 60 feet. 

None. 

Do. 

Into Siebert. 

None. 

Into Milltown andesite within a few feet of surface. Into latite near 250 feet. 

Kone. 

Do. 

Red King ........................ . 250 September .. __ . _ . __ .. _ 

Red Top ......................... 244 Red King ...... _ ...... 1 ............. do................ Do. . 135 Red_Top. ______ . _ .. _. _ 36 350 Dacite................ Into latite between 260 and 350 

Red 

Do............................ 

Top Fraction.. .. .. .. . .. .. . . .. 100 Red Top Fraction ... ·_ _ 35 Alaskite ............. . 

Reilly............................. 148 ..... do................ 36 360 Dacite ............... . 

RickardNo.L.................... 224 Florence.............. 1 210 ..... do .............. .. 

Rickard No.2..................... 134 MohawkNo.2........ 36 200 ..... do .............. .. 

Rochester. .... . _ .. __ .............. 114 ..... do................ 36 200 ..... do .............. .. 

Rogers............................ 205 Lone Star............. 33 .... _ .. ____ .. do ........ . ...... . 

Rosebud(O.K 239 Red King .. _ .. __ ...... 1 •500 Milltown andesite .... _ 

Sandstorm (old) .).................. 

.... ___ 238 RustlerFraction...... 1 500 ..... do ............... . 

Sandstorm (new or Kruger)....... . ___ .. _..... 62 Sandstorm .. __ .~ __ .... 26 400 Sandstorm rhyolite .. .. 

Sheetz-Ish......................... 63 Kruger............... 26 150 _._ .. do ............... . 

SilverPick........................ 115 Combination No. L... 35 150 Dacite .............. .. 

Silver Pick Extension............. 106 Deserted.............. 35 175 ..... do ............... . 

Simbull........................... 88 Wh1te Streak......... 35 .... _ .. _ Latite ............... . 187 Kee ... . .. .. ........... l 31 200 Dacite ............... . 

Simmerone........................ 188 Simmerone........... 31 250 ..... do ............... . 

Spokane 

!~J~~ie~!~s3~~~:~~~~i~i~~i_:: :: :::::: :~~: :~~~~~;~~~:~:~-: ~::::: :: :::::: :~~: :::::::: : ~~~~;~::: :::::::::::::: 

Sprague-Stein..................... .. __ __ ............ :........ 14 Spokane No.2........ 19 ........ Milltown andesite .... . 

St.Ives............................ 237 Combination No.3 ... _ 1 .. ____ ....... do ........... : .. .. 169 St.Ives............... 36 470 Dacite ............... . 

Tacoma 

!~I5!wt~~~~~i~~~~~~~~!~~~::::: :: ::::: :~i~: :~~il:i~:~~-: i:::::: ::::: ::::::: :~: :::::::: :~i:l;f~~~:~~~~sii~:: ::: 

Texas-Golconda . ...... _ 

..... 

.. _ ............... 

__ _ 3 Tacoma._............. 13 ... _ ... _ ..... do ................ . 

ThirdChance ............ 286 Golconda ............ _ 1 300 ..... do ................ . 

Toplitz (Daisy .. 

L. 

,..... & M.) 

. ............. 

.......... _ 295 ThirdChance......... 1 -------- ..... do ............... . 

Truett... ___ .................. 18 Daisy No.1........... 19 250 ___ .. do .............. __ 

United Mines ... __ ._ .. _ __ ... 120 Mohawk No.2........ 36 275 Dacite ............... . 

Velve.t(KansasCitylease)......... ....... ____ . 192 Hansbros. No.2....... 31 . _ ...... Latite ................ . 

Vencendor ....................... 172 Sunflower.. :.. ........ 36 ........ Dacite ............... . 

Victor.. ........... , 303 Combination.......... 1 415 Milltownandesite .... . 

Vindicator......................... ........ ........ 302 Victor................. 1 300 ..... do .............. .. iO Vindicator ... _........ 25 Sandstorm rhyolite .. . 

feet. 

None. 

Do. 

Do. 

Do. 

Do. 

Do. 

IntoDKendall tuff at 200 fee f. 

Into Kendall tuff at bottom. 

None. 

Do. 

Do. 

Into latite between 75 and 200 feet. 

Into latite at unknown depth. None. 

Do. 

Do; 

Do. 

Do. 

Do. 

Into latite at 290 feet. 

Dump shows dacite. 

None. 

Do. 

Close to dacite contact. 
OPERATION OF MINES. 141 

Principal shafts in the Goldfwld district-Continued. 

. Name. 

I 

Nu~ber Claim . Depth 

Section. in Surface rock. Changes in general formation. 

Plate I. feet. 

----------------------: I • 

White Rock No . 2.............. ... 209 White Rock........... 2 300 Siebert__ .............. Into latite at lOOfeet. 

White Rock No.3................. 213 White Horse.......... 2 ..... . ....... do ...... . ......... Into latite; depth not ascer-

~~:~:ii:~Ng."lUanuary:w:ii:)· ~i: :: :::~~:::: :::::::::::: ~ ···4aa·· :::::~~:::: ::::::::::::1 tagF· 

WhiteRockNo.6................. 216 BlueJay., ...... : ..... 2 ........ .... . do ..... ..... ...... l Do. 

White Rock No.7................. 207 Alpha................. 2 520+ ..... do ................ Into latite at 280 feet. 

~n~~-~s~~-~~~i-t~-~~~~-~~:::~ ::: ·······i;o· ·sands~orm:::: :: ::::: ······-26' :::::::: .Mflito~n-and.esiie::::: Close to contact with Sand- storm rhyolite. 

Yellow Tiger...................... 310 Lindsay............... 6 600+ Milltown andesite .. ·... Into latite at .'110 feet. Zion-Florence..................... 263 Cornishman . . · .· ... · .... 

1 

.1 ........ Dacite .......... ... ... None. 

The names of the following shafts were not ascertained: 

No.on I Plate I. . Claim. Section. I No.on I Plate I. Claim . S9Ction. 

191 Alhambra ............................. , ........ . 73 Atlanta ........................................ . 36 Black Butte Extension ..... , ................... . 38 Black Butte No. 1 ......... . ........... . ........ . 217 Butte ........................................ __ _ 25 Daisy Triangle? .. . ............ . · ............... . 324. Davoren Boy ..... . ... : ......................... . 105 Deserted ................... .................. _ . _ 103 ..... do .................................... _ .. ___ . 184 Frisco ... .... . .................... . ............ _ .. 99 Gold Banner ................................... . 285 Golconda ...................................... . 13 Great Bend No.2 ......... , .. ......... ......... . 311 Hidden Treasure .. ............................. . 199 JohnsonNo.2 .......... ............... : ........ . 55 Joshua ... · .... ............................. _ ... _. 181 Kewana No.3 ................. .. ............... . 183 Lazy George ................ . . .. ................ . 197 Little Brownie ................................. . 9i Lou Dillon .................................. . _ .. 

31 

30 

20 

20 

2 

19 

8 

35 

35 

36 

35 

1 

19 

6 

32 

26 

36 

36 

32 

35 

5 . Lucky Strike No.3 .... . ............ .. . --.· ...... . 321 Nevada Eagle ....... . .................. . ....... . 95 Piedmont Fraction ............................. . 98 Plaza Fraction ................................. . 167 Pol verde . .. . . . . : ............................... . 153 ..... do ...... ... ................................. . 9 Red Butte No.1. .............................. . 51 Red Rock ...................................... . 57 Rex ............................................ . 185 Rosebush .......... . ........ ; .................. . 194 SilverTip ...................................... . 44 South Quartzite ................................ . . 170 St. Ives ... .......... . .................... : . ... · .. 171 Sunflower. ............. . ....................... . 176 ..... do ......... . . . .... . ........................ . 208 Triangle . . ...................................... . 175 Velvet. ........................................ . 

,:: ~~~""-'• ••• ·•·••••••••••·••••• •I 

MINING COSTS. 

16 

4 . 35 

35 

36 

36 

19 

21 

26 

36 

31 

20 

36 

36 

36 

2 

36 

35 

2 

36 

The only mine that .has recently afforded full and significant data on mining costs is t~e 

Combination. According to the report of the Goldfield Consolidated Mines Company for the 

year ending October 31, 1907, the normal average costs from June to October of that year, a 

not very favorable period, were as follows: 

Costs per ton at Combination mine. 

Mine expenses ...... _ ................ : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . $4. 369 

Office expenses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 778 

Total mining costs. . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 6. 14 7 

Milling ............ . .......... ~ ........................ __ . _ ..... _ ..... ~ . . . . . . . . . . . . . . . . . . . . . . 7. 142 

13.289 

For September, 1908,· the mining costs were brought down to $3.15 and the milling costs 

to $6.13, a total of $9.28. 

The company expects in the near future, when the new mill is in operation, to reduce the 

total mining and milling cost to about $5 a ton and to be able to handle $8 ore at a profit. 

This is probably a somewhat optimistic estimate, .although in July, 1908, ore was being broken 

in some of the Combination stopes at a cost of only 33 cents a ton. 

In the year ending November 1, _1 907, the average cost of all development in the Red Top 

mine was $9.02, and in the Mohawk mine $11.42, a linear foot. . 

Shaft sinking as a rule is rapid at Goldfield and costs from $20 to $30 a foot. At the end 

of 1905 the deepest shaft in the district was the old Jumbo, 450 feet deep, and the deepest 
142 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

level then being worked was the 280-foot level of the January mine. In July, 1908, there were 

at least 4 shafts 600 feet or more in depth, 18 shafts from 500 to 600 feet in depth, 22 shafts 

from 400 to 500 feet in depth, 39 shafts from 300 to 400 feet in depth, and probably at least 50 

shafts from 200 to 300 feet in depth. As shown by the preceding table, much work has been 

done since that time. The Little Florence shaft, containing two hoisting compartments, with 

separate manway and fully timbered, was completed in thirty-nine and one-half days. In this 

case it was possible to work both by sinking and raising. The main Combination shaft, 380 

feet deep, is said to have cost $22 a foot for the original two compartments. (The shaft has 

since been enlarged.) Recently the Gold Bar Fraction Mining Company contracted for 250 

feet of shaft sinking at $26.50 per foot, the contractor to furnish all materials, tools, and labor. 

Tunneling or crosscutting usually costs from $4 to $5 a linear foot. 

POWER. 

Horse whims were used on some of the early leases in Goldfield, but were soon supplanted 

by the more economical and much more efficient gasoline hoists. In 1905 these hoists, ranging 

from 12 to 30 horsepower, were in almost universal use. The Combination and January mines 

at this time were hoisting with steam, the former using wood at $11 a cord for fuel, and a few 

mines had begun to use electric power generated at Bishop, Cal. At present this is the most 

generally used power in the district, and will run the new mill of the Goldfield Consolidated 

Mines Company. Hoisting at the main Mohawk shaft is at present done by air compressed 

by electric power. The air on its way to the hoist passes through the boilers, which are partly 

filled with water warmed by a low fire. It is the intention, however, when active work is 

resumed and more air is needed underground, to hoist with steam, using oil as fuel. 

Electricity is supplied to the Goldfield district by the Nevada-California Power Company, 

which has displayed much enterprise in utilizing the water power at Bishop, Inyo County, Cal., 

and in carrying transmission lines across wide stretches of desert. At Bishop Creek, 98 miles 

(158 kilometers) from Goldfield and 104 miles (167 kilometers) from Tonopah, the company 

has built large reservoirs and has installed dynamos capable of generating 16,000 horsepower. 

There a,re two separate transmission lines to Goldfield and Tonopah, each capable of carrying 

the full load, and thus providing against any long interruption of the current. The electricity 

is sent over these lines at 50,000 volts, is distributed to the mines at 6,600 volts, and is used 

for motor driving at the standard voltage of 440. In July, 1908, the power consumption in the 

Goldfield district was 3,500 horsepower. The power company estimated that 2,500 additional 

horsepower would be utilized at the beginning of 1909, when presumably the Goldfield Consolidated mines and mill, the Florence mine and mill, and the Goldfield Cl mill will all be in 

operation. The rates for continuous service, based on peak loads measured on the motor side 

of transformers, are as follows: 

Net rates for electric power per horsepower per month. 

1 to 10 horsepower __ . ____ _ .. _ . _ . __ . ___ ..... _ ... _ . _ ....... . ... -. ___ ... -...... ____ .. . __ ... . ___ . $20. 00 

11 to 20 horsepower __ .. ___ . __ .. __ ... _ . __ . _ ... -.. - - -........... - _ - _ .. -...... _____ .. ___ ... _ _ _ _ 15. 00 

21 to 50 horsepower, $15 less 10 per cent. ___ ... _-_- ........ __ ... ___ ... _____ ._ .. _ .. ~ .. __ .. __ .. _ 13. 50 

51 to 75 horsepower, $15 less 15 per cent. ___ .. _ ... __ ... ____ .. ___ .. _._ .. _. _._ . .. . _._._._. __ .... 12. 75 

76 to 100 horsepower, $15 less 20 per cent.. ___ .... ---_ ... :- . ... . - __ ...... _._. _ . . ....... __ ... _. 12. 00 

101 to 200 horsepower, $15 less 25 per cent. ___ -_-.-.- __ .. __ .. _ ... __ ..... ___ .... __ ....... _____ . 11. 25 

201 horsepower and upward, rates fixed by special contract in each case. 

Users -of the power are required to furnish transformers and other connecting apparatus. 

WATER SUPPLY. 

The water supply of Goldfield was originally obtained from a well 90 feet (27 meters) 

deep, with lateral drifts, situated near the mouth of Pozo Canyon. This was yielding about 

15,000 gallons (56;250 liters) a day in 1905, but experience with shallower wells in this vicinity 

had shown that the available water at any given depth was exhaustible. The present supply, 

furnished by the Goldfield Consolidated Water Company, comes from springs near Lid a, which 

_ the company estimates can be made to yield from 500,000 to 1,000,000 gallons (1,875,000 to 
TREATMENT OF THE ORES. 143 

3,750,000 liters) in twenty-four hours. The 7-inch riveted steel pipe line is about 30 nliles 

(48 kilometers) in length and has a capacity of 450,000 gallons (1,687,500 liters) in twentyfour hours. This line was completed in October, 1907, and is at present (November, 1908) 

delivering 250,000 gallons .(937,500 liters) per diem. The water flows to a point about 3 miles 

(5 kilometers) from Goldfield and is thence pumped over Malpais Mesa. 

The water supply of Columbia, which is of good quality, comes from Rabbit Spring and 

from a well 180 feet (55 meters) deep, just south of the old Goldfield Reduction Company's 

(Gardiner) mill. This well was yielding about 10,000 gallons (37,500 liters) per diem in 1908. 

The greater part of the water comes in from the sides above 100 feet (30 meters) in depth and 

at the time of visit stood within 2 feet (0.6 meter) of the surface. 

Since 1905 the Combination mine has had an independent water supply derived fron1 

Alkali Springs, situated 10 or 11 miles (16 to 18 kilometers) northwest. The springs are warm 

(about 60° C.) and the water collected by tunnels is discharged into a concrete tank of 200,000 

gallons (750,000 liters) capacity, whence it is pumped to the -mine. The flow from the springs 

is 67,500 gallons (253,125 ·liters) in twenty-four hours. A . partial analysis of this water by 

A. A. Hanks shows the following constituents: 

Partial analysis of tcater from Alkali Springs. a Parts per million. 

Silica (Si02

) . ______ . ______________ _ ________ __ .. _ _ . _ _ _ _ ___ • _. _______ _ ___ _ ____________________ - ·- 42 

Oxides of iron and aluminum (Fe2

0 3

+Al2

0 3

) . ____________ .. ____ • _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5. 3 

Calcium ( Ca) ____ . ___________ - -- __ ____ _______ _____ ___ . _ ~ _______ -. ________ ____ ___ __ . __ ... _ . : _ _ _ _ 46 

Sodium (N a)_._ .. ___ . _ . ________ _.. ___ _______ . __ . __________ ___________ . ___ ______ ____________ . _ . 282 

Bicarbonate radicle (HC0 3

) ______ • ________________ _ __ _ __ _ ________ _ ____ _ . _ . _ . • • • _ ____ _ __ · _ _ _ _ _ _ _ 142 

Sulphate radicle (SO 4

) _______ •• __ • _ • ________ . ___ •• _ _ ____________________ _ ___ _ _______ _ ____ • _ _ _ • 501 

Chlorine ( Cl) _________ . __ . ________ . _ . ___ ... _____ ___ . . __ . ___ .... _____ _______ .. ____ . _ _ _ _ _ _ _ _ _ _ _ 64 

The Florence-Goldfield Mining Company has recently constructed a pipe line from Indian 

Springs, about 5~ miles (9 kilometers) west of Goldfield'. _ This line, which is partly of wood 

and partly of steel, is expected to supply about 100,000 gallons . (375,000 liters) per twentyfour hours. No pumping is necessary. 

TREATMENT OF THE ORES. 

The first important production from the district came from the Combination mine, and 

from December, 1903, to May, 1905, the ore was shipped to the smelters, being hauled by 

wagons first to Candelaria, 65 miles (104 kilometers) away, and later to Tonopah, 30 miles (48 

kilometers) distant. The total shipping and treatment charges on Combination ore in 1904 

averaged $57.24 a ton on ore of an average value of $419.24 a ton. During this year careful 

tests were made by F. L. Bosqui,t> following which a 10-stamp mill was built. This was designed 

originally for oxidized ore only, and was built in tw<;> symmetrical parts, the intention 'being to 

use one-half for custom work. The scheme of treatment is shown in figure 10, compiled from 

Bosqui's paper. Afterwards, when sulphide ores were found, 10 more stamps and the equipment 

sho:wn on the right-hand side of the diagram were added. Wet crushing, amalgamation, concentration, and cyanidation of the tailings is the general process employed, full details of which 

may be found in the paper above referred to and in a recent article by T. A. Rickard.c The 

concentrates are shipped to the smelters. 

The Combination mill, although not without· some recognized defects in plan, has proved 

very successful when the character of the ore and the conditions under which milling is carried 

on at Goldfield are considered. According to Bosqui the total cost of milling and cyaniding 

in January, 1906, was $10.268 per ton, and in May of the same year $5.828. It was expected 

that the cost would be still further lowered, but from June to October, 1907, it averaged $7.142 

per ton, and in September, 1908, was $6.13 per to~. The average recovery is 90 per cent and 

the daily capacity about 70 tons. 

a Ball, S. H., op. cit., p. 19: The analysis has been recalculated to the standard form now employed by the Survey. 

bOre treatment at the Combination mine: Min. and Sci. Press, vol. 93,.1906, pp. 413-415, 451-454. 

c Goldfield, Nev., V: Min. and Sd. Press, June 20, 1908, p. 840. · 
~ 

I 

I 

" belt onveyor 20 0 - - - - - - - ----------==-.:---:~~"----- - - / I ' - - 12 

-

___ <:- - - - - - -

_ ---Adjustable distributing carriage - ---

. ., I ' 88:8 1 I I I 

.i. 

Amalgamating 

plates 

Amalgamating 

plates 

I 

,.. 

Amalgamating 

plates 

~-:::bin I 

Amalgamating 

plates 

/7 7\ 

: I J : 

. . --------vJ---------

V' ---- 

~ ___ .,.~ -

I \ I I \ ';..,. .,-' I 

', '-.......... .... .... ;..' /1 ' 

.... / / ',, g'/ _,./' ' / 

', _,~ryan mill 

/f, /Ill 

,,,, 

I Receiving cone / • I ',. : r- Frue vanner \ · 

1 

',,, --- -- OE!e

·--------' 

----

9-------------j ~ ~/I\\ I I . 

. I 

L-------~ ._£i,:: V ??-? Classlli.,.. [ ! \, j ' ' Y : (- vanner vanner 

1 

--- 

' 

)'y.~-------,. 

I : 

,,.----~ Classifier ----'4---- i 

~::::.-::'=.:::-:.

=::..;·x~~-P---------¢~~; I --... ,, I I I I,:,-' I I "' lr---------~ I I I J ', 

,..-- - - - - 7 

_1____, I '--... I ' I 

' 1 To a duplicate of the I ', 4 settling and 

4leaching 

tanks 

Cyanidation 

: system supplied by 1 ', : · other pump on the 1 . ', _____ _, ___ ____ ...

1 left '--- ___ j ; 

I 

-----

_____ .1 

Slime 

reservoir I 

FH~~x I 

, _____________ f 

OXIDIZED ORES 

SULPHID

FIGURE 10.- Scheme of treatment in the Combination mill, 
TREATMENT OF 'l'HE ORES. 145 

Up to the latter part of 1908 the Combination mine was the only property equipped with 

its own mill in actual operation. The new 20-stamp mill at the Florence mine was then practically complete, but was not running. 

At the time of first visit, in 1905, there were four custom mills and one sampler in the 

district. The pioneer mill was that of the Goldfield Reduction Company (Gard~ner mill), situated about 1,000 feet (305 meters) northeast of Rabbit Spring. The New Western Reduction 

Company paid 85 per cent of the assay value for ore, subtracting a charge of $12 a ton for 

milling. The Nevada Goldfield Reduction C mpany, popularly referred to as Frank's mill, 

bought ore outright and milled it, or, in the case of ore from the January mine, paid 95. per cent 

of the assay less $12 a ton for treatment. The American :Milling and Water Company bought 

ore or milled it at an average charge of $12 a ton. The Columbia Sampling and Ore Compa~y 

acted as sampler or purchaser only, shipping the ore out of the district for treatment. The 

total maximum capacity of the three custom mills running in 1905 was about 70 tons a day. 

The processes employed in these mills were similar to that used in the Combination mill, but 

the American :Milling and Water Company's plant was the only one equipped for cyanidation. 

According to an estimate made by Francis A. Thomson, superintendent of the New Western 

Reduction Company, and published in the Goldfield Sun of September 14, 1905, the average 

daily production of the Goldfield mines at that time was 70 tons of shipping ore, of an average 

value of $200 a ton, and 100 tons of milling ore, at an average value of $40 a ton. In general, 

ore of lower grade than $100 a ton was milled in the district. The Combination :Mines Company 

milled all of its ore except that exceeding $.600 a ton in value, which was shipped. 

The freight rates on ore to San Francisco, Salt Lake City, or Denver in 1905 ranged from 

$8 a ton for ore under $25 in value to $22 for $300 ore. For richer' ores, from 3 to 5 per cent 

of the value per ton in excess of $300 was added to the· $22 rate. For example, on $2,000 ore 

the freight would be $22 plus 5 per cent of $1,700, or $107 a ton. Smelting charges were $10 

a ton on all siliceous ores, with an additional charge of $1 a ton if the silica were unusually high. 

With the exception of the Combination, the mines either shipped their ore directly or 

disposed of it to one of the four reduction or sampling companies in the district. 

At the time of second visit, in 1908, the Combination mill was running practically as in 

1906, the Florence Company had completed a 20-stamp mill, and the construction of a 100-stamp 

mill for the Goldfield Consolidated Mines Company, to cost $750,000, was well advanced. Some 

changes had taken place in the custom plants. The works of the Columbia Sampling and Ore 

Company, northwest of Columbia, had been remodeled by the Western Ore Purchasing Company, which samples and buys ore, selling it ~o the smelters. No schedule of rates was obtained 

from this company, but their charges on 5-ounce ore from one lease in July, 1908, are known 

to have been $25 a ton for freight and treatment, the gold being paid for at 95 per cent of the 

total value figured at $20 per ounce. The Nevada Goldfield Reduction Company, although 

changed in personnel, was still in operation, but the other mills had closed. The following 

description of the Nevada Goldfield Reduction Company's plant is taken from Rickard's 

article (p. 841) : 

This plant includes a sampler with a capacity of 450 tons per diem and a cyanide mill treating 100 tons per diem. 

The surplus ore is sold to the smelting companies. The equipment of the mill includes 20 stamps, of 1,250 pounds 

each, by which the ore is crushed to 12 mesh in a 0.50 to 1.25 pound KCy solution. The pulp on issuing from the 

mortar goes over amalgamating plates and then to eight Wilfley concentrators, classifying into three products, namely, 

concentrate, sand, and slime. The concentrate assays from $200 to $1,000 per ton, and is shipped to the smelters; 

the sand goes first to an Allis-Chalmers tube mill, 5 to 22 feet, reducing it to a screen size of less than 100 apertures 

per linear inch; from the tube the reground product passes over supplementary amalgamating plates and then to classifiers, the oversize from which is reground after going over a Wilfley. The leachi~g plant, which receives the pulp after 

the free gold and rich sulphides have been partly extracted by concentrators, includes eight vats of 22 by 5 feet and 

three agitator vats of 24 by 16 feet. Three vacuum filters of the Butters type strain the gold-bearing solution, which 

is further clarified by passage through a 5-ton American filter press, remodeled by E. S. Leaver, the superintendent 

of the mill. 

79145-No. 66-09--10 
146 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

A new plant, designed by John E. Greenawalt, had been built by the Goldfield Cl Mill Company northwest of Columbia, but was not yet open to custom. In Mr. Greenawalt's absence 

from Goldfield I was unable to examine these works. Mr. Rickard's visit was more fortunately 

timed, and his account a is here quoted: 

The roasting furnace is a rabble roaster of the muffie type; it has a porous hearth and is heated with producer gas 

manufactured from coal (coming from Helper, in Utah) enriched with crude oil (from Bakersfield, Cal.). From this 

furnace the roasted ore goes to a cooling cylinder, at the end of which it is moistened before delivery into a bin. From 

the bin it is transferred to large vats by means of a grab bucket of 60 cubic feet (nearly 3 tons) capacity, operated by 

a traveling electric crane. The chlorination vats are of wood, sealed by a wooden· cover, dipping into a launder filled 

with water. When silver ore is being treated 2 per cent salt is added before crushing, so as to get a good mixture. 

The leaching in the vats is done by a strong solution of chlorine in water-7 to 8 pounds free chlorine per ton of solution. 

Leaching requires three to four days. The seven vats are each 22 feet diameter and 8 feet deep. The gold solution is 

withdrawn by gravity and pumped into a storage vat, and thence drawn to the precipitating boxes, resembling the 

zinc box of a cyanide plant. The precipitation of the gold is effected electrolytically, the anode being graphitized 

carbon and the cathode lead shaving containing 1 per cent zinc, the presence of the zinc hastening the corrosive action. 

The slime of lead, gold, and silver while still moist is mixed with flux and briquetted. The briquets are melted in a 

reverberatory furnace and then refined in a cupel. 

The chlorine is generated electrolytically. At first salt was obtained from Hazen, in Nevada, but it was found 

to contain over 5 per cent silica, from sand blown across the dry lake; the salt now used comes from Salt Lake and costs 

$16.25 delivered. The solution of chlorine water is made in an absorbing tower; this consists of two sheet-iron stacks 

lined with glazed sewer pipe, with cement between the pipe and the outer iron. Inside is placed a filling of hollow 

clay balls, each of them having eight perforations. The chlorine gas is i~troduced at the bottom of the stacks and 

water is made to trickle down from the top, the large surface thus offered facilitating absorption. 

The mill has a nominal capacity of 100 tons per diem. The ore is crushed to 14 mesh and the roaster is 100 feet long. 

In the summer of 1908 the Goldfield Consolidated Mines Company were conducting experiments in the small Kinkead mill on Columbia Mountain for the purpose of devising a mode of 

treatment for the concentrates which would make the company independent of the smelters. 

The experiments were successful and the ·company is building a special plant on the lines suggested by them. According to a statement courteously furnished by Mr. J. H. Mackenzie, the 

general manager, the process depends on fine grinding and cyanidation. Its only p·eculiarity 

is a preliminary treatment of the concentrates to prevent the destruction of the cyanide solution 

by the sulphides. 

The new mill of th!s company, situated on the west slope of the ridge south of the Sandstorm mine, will probably be in operation by the end of 1908 and should greatly increase the 

output from the Consolidated group of mines. The flow sheet of this mill is shown as figure 11. 

The rich ore shipped by lessees is usually hand sorted at the surface, although in some 

cases, as at the Engineer's lease, the ore is so free from waste that it is shipped just as it comes 

from the stopes. Sorting as practiced by lessees is generally a rough and wasteful process. 

The coarse pieces after passing over grizzleys are picked over and cobbed without any preliminary washing, so that many rich lumps go on the dump. The waste piles of the successful leases 

are consequently valuable and are nearly always reworked, being, as a rule, picked over again 

by hand. The Little Florence dump, for example, was sold for $10,000, and the purchaser 

realized $16,152.83 from the ore culled from it between June 1 and November 30, 1908. In 

this case water was available and hose _was. used advantageously to clean the lumps before 

sorting. 

Most of the crude ore and concentrates shipped from Goldfield has gone to the smelters 

on San Francisco Bay and in the Salt Lake Valley, Utah. The freight rates to these points 

are the same, and where ore is diverted to other smelters the difference in freight, if any, goes 

to the account of the smelte_r receiving the shipment. Prior to September, 1907, the freight 

schedule was as follows: 

a Goldfield, Nev., V: Min. and Sci. Press, June 20, 1908, pp. 841-842. 
TREATMENT OF THE ORES • 147C 

. Freight rates from Goldfield to San Francisco and Salt Lake Valley prior . to September, 1907. . ' '' ~ 

Actual value per ton.l! Freight 

per ton. Actual value per t?n.a 

Up to $40 ......... .... .. ....... . . . . . ..... . .. ............ · ... . $7.80 

10.95 

11.55 

12.90 14.25 

15.60 

$90 to $100 .............. 1 

.................................. . $40 to $50 .................................................. . $100 to $150 . ...... ... . .... . .. .. .. : .... : .................... . $50 to $60 ......... .. ........ . ......... . ................. . .. . $150 to $200 ......... .............. ... . ................... : .. $60 to $70 .... .. ... . .. .. ...... . .. .... ...... .. ... .. . ......... . $200 to $250 ................................... : . ........... . $70 to $80 .................................................. . $250 to $300 .......... . ............................ . .. .. .... . $80 to $90 .................................................. . $300 to $1,000 . . .... . . .. . .. .... .......... ... .... .. .. ... ...... . 

a Gross assay value less the charges for assaying, smelting, and handling at the smelter. b Add to rate for $300 ore 2 per cent of the value above $300 per ton. 

CONCENTRATION SCHEME OF THE GOLDFIELD CO-NSOLIDATED MILL 

Anialg,J. =plates 

AmalgJn traps 

Hxdraulic ~classifiers 

~mmder ft;strib\rtor 

(G)Dorr tlassiftcrs 

(G) tuhe'tnJJs 

cm.lfl~.~·--------~·~+ 

Lmmder$ mstribntor TTenier sand '=:P 

. U4) 5'by16' a:rnal¢:am plates 

Amalgl, 1:r8j>S. 

Pulp tlrlckeners 

(78) 6-fuot Di;,stef' tables 

us> s.!ttn{g tanks 

Launder distributor 

(lo) ·tJOr,. 

, LlunaJ di..~tnr 

(; sets)Butt.ers der frames 

Launder~ distributor v'acuum ~pumps ,..-------+----+--------~==L:..mm...;;.:;;,;;der:.=di;;;·;,;_,_~ Gold solu\on sump 

l 

+ • '+' ' :j. .. 

t 

· S""urp;..=fu;:;..s wa....:~-"'ter;;..iank= S=Jus solUtion tmk Smylus ppP tank li-=amerfilt;;;;.er~yres=s.;;:;es:...;;fut;;;;...::~:::; • • 

L. --~~----'-----------------'-*-----·o--'-·------t r -~ La:m1~bibutor . J L~aer~stt-Hmtor . 2fnc~yrecipitation1arik(weak) Z"meilust~tiont.ariks(strong) A:rnalgam ha:n-el 1 :n:-J.e zinc dust pt'eclpitalion yresses , 

I 

Freight 

per ton. 

$17.15 

18.05 

18,85 

19.90 

20.90 

(b) 

Am:tljam press J?ryl:nB furna£e for precipitate Lannife:r~tnr 

~ DiSti4Utm: Stor e tak(we~ solution) ==:.===,;::;;z:a.;;;;So;:;iluti=·on=), 

' ' ~ <51Fal>erdu Fanrf '~ lJr~· • 

. 

Bullion furna.ee . l l___.solatWn re(urn.ed fD sett.lers a:nd agtta.tors 

'->------~:··Slag to smelter 

'---+----------------------"---------------'------------B.uU:ion tn m.Ud: 

: : J (/rncksilver 

! r~~w~ 

~----------~~-----------~--+---~'·-------w~~~~~ 

FIGURE 11.-Scheme of treatment in the new Goldfield Consolidated mill. 
148. THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The smelter charges at this time were as follows; 

Smelter schedule prior to September, 1907. 

Assay value of gold and silver per ton. Charge per Price paid ton for for gold treatment. per ounce. 

--------

~~ i~ :rgo .- .- .- .- .- .- .- ~: :::: ::: :: : : ::::: : : : : : : : : : : : : :: : : :: : ::: : : : : :: : ~ :: : : :: ::: : :: : : ::: ::: ::::: ::::: :::: ::: ::: :: : : :: . : :: :: : : : $6 

7 

8 

9 

$19.00 

19.00 

19.50 

19.75 

$100 to $300 .... . .. . _ ...... .. ............................................................................................ . Over $300 ........ . ........... ..... ......... ; . . . . .................................................................... :. 

In October, 1907, owing to the general financial situation, the rates were raised until the 

total freight and treatment charges on $100 ore amounted to $45.35. 

On December 13, 1907, the following freight schedule went into effect and was still in force 

in June, 1908: 

Freight rates from Goldfield to San Francisco and Salt Lake Valley December 18, 1907. 

Actual value per ton. 

Up to $20 ................................................... . $20 to $30 ................. . . .... ..... ..... ... .. ........ ... . . $30 to $40 ..•...... . .......... ..... ..... . ...... . ........ ... .. $40 to $50 ......... .... ................. ... .......... -.. .... - $50 to $60 ...... . ... ......... ............ . .................. . $60 to $70 .................................................. . $70 to $80 •..... " .......................................... . 

Freight 

per ton. 

$6.00 

7.10 

7.80 

10.00 

11.00 

12.00 

13. 00 

Actual value per ton. 

$80 to $90 ................................... ........ . ...... . $90 to $100 . ................................................ . $100 to $150 ............................ .. .... ... ........... . $150 to $200 ................................................ . $200 to $250 ................................................ . $250 to $300 ................................................ . $300 to $1,000 ............................................... . 

Freight 

per ton. 

$14.00 

15.00 

16. 50 

18.00 

19.50 

20.90 

(a) 

a Add to rate for $300 ore 2 per cent of the value above $300 per ton. 

In this schedule freight agents are instructed to refer shippers offering ore of greater 

value than $1,000 per ton to the express companies. If accepted as _freight, the following 

additional charges are levied: 

Freight on exceptionally rich ore. 

Actual value per ton. Freight per ton. 

$1,000 to $1,500..... . ........................................... . . . . . . . . . . . . .. . . . . . . . . . . . . . . $20.90 plus 3 per cent of excess value over $300. $1,500 to $2,000......... . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $20.90 plus 4 per cent of excess value over $300. Ov~r $2,000 ........ .. .......... ............ .. .................... ... .......... .. ............ $20.90 plus 5 per cent of excess value over $300. 

It is evident from a casual inspection of these rates that they are based, not on the cost 

and responsibility of the service performed, but o.n the expectation of what the shipper may be 

made to pay. The railroads, unless forced to by legal proceedings, assume no greater responsibility on ore above $100 per ton in value and exact the additional rates for rich ore, even when 

expressly released from special liability.a 

a As this report goes to press announcement is made of a new freight schedule promulgated by the Tonopah and Tidewater Railroad. As given 

in the Mining and Scientific Press for December 26, 1908, the new rates are as follows: 

Ore assaying-

$20 ........................................ ................... $3. 50 

30 ...................... ...... .. ········ .... ····· · · ·· · -~ ..... 3. 90 40 ....................... . ..... ...... ..... ········ ........... 4. 40 50........................................................... 4. 80 GO. .................. . ......................... ......... .. ... 5. 25 

70........................................................... 6. 75 

80 .......................... ······· · ··· ...... · ······ · ......... 7.50 

Ore assaying-

$90 ........................................................... $8.25 100........ .. .................... .......................... .. . 9. 00 

150 ........................................................... 10.10 200 .... . ....... .. .... ... . .. .......... ... .. ' .. . ! . . . . . . . . . . . . . . . 11. 25 250 ........................................................... 12.40 

300 ..........................................................• 13.50 
,. 

TREATMENT Off THE ORES. 149 

I 

On February 6, 1908, the following smelter schedule became effective· 

I Smeller schedule of February 6, 1908. 

GOLDFIELD ORES. 

Assay value of gold and silver per ton. ton for for gold ·Chllrge ·per I Price paid 

----------------------------------!,treatment. perounce. 

~g {g :gg~: ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::.......... $~:~81 $i~:~ 

m:.~i••••••••·••••·•••••·• ••··••·•••·••••·•··•·•••···•••·••••••·•·· ••••·•····•••···•••••·• ••·•·••··•··•••·•·•••l J~ I l!~ . In addition to above treatment charges, where gold contents exceed 5 ounces per ton, add $0.50 for each ounce 

or fraction thereof in excess of 5 ounces. ' 

Silver to be paid for, if 1 ounce or over, at 95 pe~ cent bf New York quotation. 

On ores under $60 gross value a charge of $0.25 will be made for each per cent of sulphur in excess of 3 per cent. 

GOLDFIELD CONCENTRA'J'ES . 

. 

Assay value of gold and silver per ton. 

Under $100 .............................................................. [ . . .. . .. ..... . ... ...... ..... . . .......... ..... . $100 to $300. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........... .. .. ! . ............. . . ... · .... ....... . . . ........... . Over 1)300 ....... ~ ............. .. ........................... .. . .... . .. ...... ... .... .. ... .. . .. . ......................... . 

Charge per ton for 

treatment. 

$10.50 

J\.50 

12-50 

Price paid 

for gold 

per ounce. 

$19.00 

19.50 $19. 75-20.00 

In addition to above treatment charges, where gold contents exceed 5 ounces per ton, add $0.50 per ton for each 

ounce or fraction thereof in excess of 5 ounces, and where gold is under 5 ounces per ton add $1.50 for each ounce or 

fraction thereof under 5 ounces. 

The treatment charges in the foregoing table are those upon which the American Smelting 

and Refining Company bases its contracts. Thle actual charges for treatment are 50 cents less 

in each case-viz, $6 instead of $6.50, etc.-the not altogether luminous explanation being 

current that the sampling works, which act as I brokers or buyers for the smelters, charge the 

lower rate and the smelter company "protects," them. Attention may be called also to the 

modifying addenda which follow the tabular parts of the schedule, particularly that under concentrates. Here the rate for $100, or 5-ounce, concentrates is $10.50. For concentrates containing a fraction of an ounce less than 5 ounces of gold per ton the charge becomes $10.50 plus 

$1.50, or $12. For concentrates containing a fraction of an ounce over 5 ounces of gold per 

ton the charge becomes $11. 

In addition to the freight and smelting charges the shippers have to pay from $1.50 to $2 

a ton for the sampling. · 
CHAPTER XII. 

THE LEDGES. 

DEFINITION~ 

The Goldfield deposits, in all that pertains to the genesis of the ore, are most closely allied 

to metasomatic fissure veins. Yet they can scarcely be included within that class. They are 

intimately related to fissuring, but only a small part of the ore has actually filled fractures 

(spaces of discission). These fractures, moreover, rarely show that regularity in form and that 

persistency in strike and depth which are connoted with the term "vein" or "vein fissure." . 

Structurally the deposits are irregular masses of altered · and mineralized rock traversed by 

multitudes of- small, irregularly intersecting fractures, such fracturing passing in many places 

into thorough brecciation . . There are exceptions to this character. Certain deposits exhibit in 

part more regularity of form and there is reason to suppose that at depths greater than those 

now reached such approaches to lode-like form may become more numerous. But within the 

mass of rock extending from the surface to a depth of 600 feet (183 meters), a mass which 

includes all the ore bodies thus far exploited, the deposits can not be called lodes or veins without giving to these words unusual meanings or without tacitly ascribing to the mineralized 

bodies a tabular form that they rarely possess. 

In view of these considerations, the word' 'ledge,"a already in use by miners in a less definite 

sense than "vein," will be employed in this report to designate the masses of silicified or otherwise altered rock in which the ore bodies are found. This word, although suggested by the 

outcrops of such material, will be applied at all depths where any distinction is possible between 

an alteration intimately associated. ~ith the ores and a more extensive alteration of country 

rock. It will be applied, moreover, to rock which has undergone alteration of the kind charteristic of the immediate vicinity of ore bodies, whether or not ore is known to be present. 

The actual ore bodies or pay shoots occur within, but are seldom coextensive with the 

ledges or ledge matter. · 

The proposed usage of ledge is not intended to restrict the word to a special technical 

meaning but rather to avoid the use of vein and lode, which, while broadly used by miners, 

are employed with some definiteness in scientific writing. 

DISTRIBUTION. 

The ledges, considered as topographic features and independently of ore bodies, are extraordinarily abunqant in the Goldfield district. To them the topography owes most of its minor 

roughness; many small knobs are crowned with iron-stained masses of ledge matter and the 

slopes qf the larger hills are ridged and studded with the same material. As stated on page 16, 

these rough outcrops are in most, if not all, cases purely residual, and stand out, like pebbles in 

a clay bank, because the softer rock has been eroded from around them. Many of them in 

fact rest like giant pebbles on the tops of knobs and have no downward continuation into the 

soft rock beneath them. Some of these loose superficial masses of ledge matter east of Goldfield are shown in Plate XIV, A. Prospecting tunnels have been driven directly under some 

of them. · 

a" In mining, ledge is a common name in the Cordilleran region for the lode, or for any outcrop supposed to be that of a mineral deposit or vein . It is frequently used, as reef is in Australia, to designate a quartz vein."-Century Dictionary . 

. "A rocky outcrop or reef. * * * Mining. A metal-bearing rock stratum; a quartz vein."-Standard Dictionary. 

150 
U. S. GEOLOGICAL SURVEY 

A. LEDGE OUTCROPS IN MILL TOWN 

B. LEDGE OUTCROP IN DACITE BETWElN 

The consp icuous white dump is alu nitic material frpm a 

sky line near the right side 

I 

PROFESSIONAL PAPER 66 PLATE XIV 

ABOUT 2 MILES EAST OF GOLDFIELD. 

E BLUE BULL AND COMMONWEALTH MINES. 

lease on the Lon e Star ground. The rough knob on the 

the view is Banner Mo untain . 

151 

On the geologic map, Plate II, an atte pt ~as been made to show the.general distribution 

of the ledges by plotting the principal out c ops in the field with a plane table. The result at 

best is only an approximation to the tr.uth as the boundaries between ledge matter and soft 

altered country rock are often indefinite a d are seldom clearly exposed at the surface. For 

this reason, and to avoid obscuring the oth r geologic features of the map, the generally linear 

outcrops are indicated by lines and round o · 

irregular bosses by dots. No attempt has bee 

made to indicate the relative size of outcrop . 

Moreover, many small outcrops are omitte , 

while in some places, as on the east side f 

Vindicator Mountain, the alteration to led , 

matter has affected areas so broad that the 

could only be properly indicated by washes f 

color or by some device of shading. But whi e 

rigid accuracy in the cartographic represent -

tion of them is thus unattainable, the m.a 

serves to bring out the genera-l distribution an 

some of the peculiar features of the ledge . 

The ledge outcrops east of Goldfield are sho 

on a smaller scale in figure 12. ~ 

Plate II shows that a conspicuous lbe t ~ 

of ledges, about a mile wide, stretches fro 1 ~ 

0 

the vicinity of Columbia and Goldfield ~ 

a gentle curve, at first nearly southeast b t g 

gradually sweep in? to the east, past Preble a~d f ., · 

Blackcap mountains and beyond the eas1 n · 

boundary of the area subjected to detail d i 

study. As shown in Plate XV, A, which is a [ 

view eastward from Blackcap Mountain, t e §' 

characteristic ledge topography continues f r ~ 

a mile or two beyond that summit, and me·rg s i 

finally into the desert• plain that separates t e a> 

:· 

/ 

~ Goldfield Hills from the Stonewall and Caet s 2.. 

ranges. Nowhere in the belt are the ledg s 2? 

more numerous or conspicuous than betwe n A.~ 

Milltown and Blackcap Mountain, yet alo g 

this stretch no mines of the first rank ha~ 

been developed. On the other hand, frmn t e 

comparatively few ledges between Millto 

and Columbia has come over 95 per cent of t e 

gold sent out from the district. As rega;s 

geologic distribution, it is to be observed t at 

most of the productive ledges ate in the a ea 

of dacite northeast of Goldfield; a very la ge 

number, of which only a few near Milito n 

have proved productive, are in andesite; o hers, of which a few have been found to cont in 

a little ore, are in the .dacite mass of P;re le 

( 

I 

;, ::· ... : 

)z 

I. ·: '/ 

/ 

1 • -;:· 

(/) 

0 r.JI-Q) 

Mountain; and a few of no known economic · mportance are in the area of Espina breccia, northeast 

of Preble Mountain. Isolated ledges in a,n esite occur south of the main belt, up to the northern 

edge of the dacite vitrophyre, and there nr a .few not very prominent ones in the latter rock .. 

A second belt of ledges is recogniznb e extending in a general easterly direction from the 

vicinity of Kendall Mountain through :Me ahon Ridge and Black Butte to the eastern border 
152 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

of the district. This belt is much less pron1inent than the southern or Preble Mountain belt. 

At its eastern extremity it spreads and becomes indefinite. It is connected rather loosely with 

the southern belt by scattered ledges in the neighborhood of Tognoni Springs and in the dacite 

east of McLaughlin's well. 

The northern belt of ledges is mainly in the Milltown andesite, although it crosses a mass 

of dacite near Black Butte. It contains some productive ore bodies in l\1cMahon Ridge and 

Black Butte but no mines of the first rank. 

In addition to these principal belts ledges are distributed, without any particular alignment 

or regular grouping, over the central part of the district between the two principal belts, Banner 

N 

1 

~ 

Mountain being traversed by many of more than usual conspicuousness and regularity (Pl. XV, B). Others outcrop 

between Banner Mountain and Diamondfield. Vindicator 

Mountain exhibits much metamorphism of the ledge-forming 

type and many isolated outcrops of ledge matter; but distinct linear ledges are not so well developed here as on Banner 

Mountain. Most of the scattered ledges and groups of Jedges 

in the centnd part of the district are in latite and none of 

them has yet proved productive. 

The Sandstorm, Kendall, Adams, and Conqueror ledges 

in rhyolite, north of Columbia Mountain, are perhaps best 

regarded as a group by themselves. As regards position, 

however, they are not sharply marked off from the northern 

or Black Butte belt. 

TREND OR STRIKE. 

The greater number of the ledges are irregular masses 

of no definite trend. Others, of which the proportion appears 

magnified by the method of representation adopted in Plate 

Ledge matter Pay shoots II and figure 12, have linear outcrops and are evidently 

0 50 scALE 100 

IN FEET 150 related to fissures or fissure zones of some persistency, 200" 

Country rock 

c;;;;c::e:~c:::s===::::ES:============::::::::i attaining in extreme cases a length oi a quarter of a mile FIGURE on the 

13.-Plan 

100-foot 

of ledge matter and pay shoots (0.4 kilometer). These, as a glance at Plate II will show, level of the Florence mine. 

exhibit great diversity of direction and in some parts of the 

field, particularly near Milltown, ledges of various trends are linked together in complex chains. 

Most of the productive ledges near Goldfield have a north to northwest strike. 

Although diversity of strike is one of the most conspicuous features of the ledges as a 

whole, there is some approach to uniformity in the tendency of the longer ledges to conform in 

direction to the general trend of the belt in which 

they lie. 

The linear ledges are in most cases straight 

or but slightly curved. Others, such as the January and Florence ledges, are sharply bent. (See s 

Pl. XVI and fig. 13.) 

DIP. 

N 

Scale 

2 3 .. 

Accurate data on the · dip of a ledge are ob-

. tainable only where n1ining has been carried to 

some depth. A large number, probably most of FIGURE 14.-Vertical section through an irregular flat ledge, as seen in the west wall of the Black Butte tunnel. the ledges, have nearly vertical dips. Others, 

such as the mass of ledge matter capping Black Butte, and the so-called Flat vein in the sa:r1fe 

hill, are nearly horizontal. (See also fig. 14.) The Mohawk ledge as a whole (see fig. 15) has 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XV 

B. LEDGE OUTCROPS N LATITE ON BANNER MOUNTAIN. 

U. S. GEOLOGICAL SURVEY 

_,);< 

A¥::cz;:~·; cc···c ',--;;:?:~?'·;;i/: 

JANUAR~

~~ 

SHAF~:..

'~--:N 

,~:%.:~. '~ ;<:~.{'f:t~~~~;.~;~:~~f~:¥~ '' 

Fig. A '...._';, ~,~~, -~!)k 

Fig.D 

Fig.B 

Fig.E 

- ' 'c;: ', ~:;' ?~~\ ;J,;p}t''; 

,,,-

/,;\ ~1 , ,, __ .~ 

c ~ .. ~:~'-~!!:{;;Y > .· ····. ~ Fig.C 

N 

1 

Fig. F 

¢ 

PLANS OF THE PRINCIPAL LEVELS OF THE JANUARY MINE, WITH A DIAGRAMMATIC SECTION, SHOWING 

AND COUNTRY ROCK. 

a dip of 35° to. 45° to the east. 

The Combination ledge, while 

very irregular, also dips to the 

east, the angle of dip becoming 

very low on the deeper levels. 

(See Pl. XVII.) Most of the 

ledges that have been followed 

down for a few hundred feet 

shovr changes in dip such as are 

rarely found in typical veins or 

lodes. These changes are well 

illustrated in the January, Combination, Reilly, and Florence 

workings. (See Pls. XVI and 

XVII and figs. 16 and 17.) 

SHAPE. 

The shape of the ledges has 

been partly indicated in the preceding description. It has been 

shown that they range from· 

roughly equidimensional, irregular masses to nearly vertical 

or inclined, undulating, lodelike 

plates or sheets. Vertical pipes, 

of generally circular or elliptical 

section, such as the Anna Lee 

chimney of . the Portland mine, a 

may occur in the Goldfield district, 

but mining operations have not 

yet revealed any good example of 

this form of deposit. 

As examples of fairly regular, 

lodelike ledges may be cited parts 

of the main ledge of the Combination mine (described on p . 

211), theJumboledge (p.221),and 

the Little Florence ledge (p. 223). 

The Mohawk ledge as a whole is 

generally lodelike, but is a very 

broad ill-defined mass, whose 

boundaries are as yet imperfectly 

known. Regularity observable 

on a given level is no guaranty of 

vertical regularity or persistence, 

as is shown by the sections of the 

Combination mine (seep. 212 and 

Pl. XVII) and by the changes in 

dip of the Combination and Reilly 

ledges. 

a Lindgren, W., and Ransome, F. L., Geology 

and gold deposits of the Cripple Creek district, Colorado: Prof. Paper U.S. Geol. Survey No. 54, 1906, 

p . 447. 

TBjE LEDGES. 

---,--.,-------MACK£NZI£ SHAFT 

SECTION A- A" 

MOH AWK SHAF1 

153 

MOHAWK-JUMBO SHAFT 

'- ~:[~<·. ::.\.·:·:: ):·:/:/7.~. ~ 8 8 

. .... . 0 I H ~f-

.... 

0 ---~~.~ ~~~~~~~~~~--~----

~ ~ 

l:..J 0 

~g ~ 

'----- ~1-­

::;. 

"' 0 

iii 

77~~~~~~~~~~;~-----"'---

I 

I SEC TION B- B" 

I 

S ECTION C-C" 

FIGURE 15.-Sections across the Mohawk ledge on lines shown on Plate XXXIII. 
154 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

S01ne ledges, like that of the Florence, while showing a fairly rectilinear outcrop, prove on 

exploitation to be exceedingly irregular in plan and to change in direction from level to level, 

as illustrated by the map of the Florence .workings (Pl. XXXV) and by figures 13 and 17. The 

w. 

-

Stapes 

COMBINATION 

5HAFTN0,5 

Surface! 

o~------~·o~o------~zo0foot 

EJI2] 

Ore body 

FIGURE 16.-Sections across the Reilly pay shoot. 

E 

January ledge, described in detail on page 217, best exemplifies a curved ledge and illustrates well 

the manifold irregularities of form characteristics of the Goldfield deposits. (See Pl. XVI.) 

The moc;lifications in form manifested by the ledges with increase in 'depth are not only of 

w. SHAFT 

./00-root level 

!50.:..root level 

zoo-"f'oot level 

250-root level 

.350-root level 

much scientific interest but are of great practical signifie:. cance. The study of this feature of the deposits is hampered by the fact that below the zone of oxidation the 

distinction between ledge matter and the general country 

rock of the mines is less well marked than on those levels 

where original differences in composition and structure have 

been accentuated by the selective action of weathering. 

Moreover, the number of mines that have attained sufficient 

depth and horizontal extent to throw much light on this 

question is still small. 

The -available data favor the view that silicification, 

which is the principal chemical distinction of the ledge matter as a whole, becomes less as the depth increases. Accompanying this change is a tendency of the ledges to become 

narrower and more lodelike. The change is not entirely 

regular and does not take place everywhere at the same 

depth. 

In the January mine the ledge on the 283-foot level still . 

shows some silicification, but is much narrower than above 

and is straighter and more lodelike, as shown by Plate 

XVI. A similar simplification of form with narrowing and 

a notable decrease in silicification appears in the Florence 

ledge below the 250-foot level. (Seep. 227.) In the St. I ves 

50 0 50 IOOfeet ~~~~----~~----~ 

mine the levels above the 150-foot show broad irregular 

1nasses of silicified ledge matter, while the 250-foot level is 

FIGURE near 17.-Section 

the main across the Florence pay shoot in soft fissured pyritized dacite showing only partial silicifi- shaft, showing changes in dip. 

cation along the fissures. In the Mohawk mine the ledge 

on the 600-foot level, so far as could be determined from the limited exposures of it in 1908, 

is narrow and more lodelike than on the upper l~yels. ' 

Quite independently of ore and valqe, then, the ledges, as structures differentiated from the 

country rock by silicification, tend to become narrower, simpler, and more rectilinear in plan with 
U. S. GEOLOGICAL SURVEY 

80-foot level 

130-foot level 

180-foot level 

230-foot level 

280-foot level 

380-foot level 

380- foot level 

A-A' 

Surface 

Latite 

~ 

D-IJ' 

B-B' c-c' 

~!!jJi~,, 

·:·&IB?·R~s~ 

'~~i::n 

< •• ~~;;s; ~t,~i::;l 

.. ····· 

'/~ ·;~.~. ··:.::· . .-: . 

<.'> 

Latite 

0 'lij:~t~~f\ 

E-E' 

SECTIONS ACROSS THE COMBINATION LEDGE ON LINES SHOWN ON PLAT

U. S. GEOLOGICAL SURVEY 

A' 

A E 

LEGEND 

1-<lRich ore originally foll owed 

:·~:; ;-::·?f:.wiOre bodies as known in 1905 

Stap es in 1908 

[':).}:::i{.).JLedge matter; in partore 

A - - ------- ---A' 

5ection l ines 

0 100 200 3 00 400 500feet ~~~~=====E~~~======~~~~ 

PROFESSIO AL PAPER 66 PLATE XVIII 

PLANS OF LEVELS OF THE COMBINATION MINE, SHOWING APPROXIMATE HORIZONTAL DISTRIBUTION OF LEDGE MATTER AND ORE. 
THE LEDGES. 155 

increase of depth. This suggests that below a depth of about 500 feet (152 meters) most of 

the ledges will show a gradual change to sulphide impregnations, or metasomatic veins, along 

zones of fissuring. · 

Ledges having the form of nearly horizontal she'ets occur in the district, but have not proved 

of much economic importance. Figure 13, page 155, illustrates a small ledge of thi~ type in Black 

Butte. Another, from which ore has been stoped, is the Flat vein on the south side of the 

same butte, described on page 247. 

In this connection attention may be directed to the tendency of the Mohawk and Combination 

ledges to flatten out to the east as they reach the bottom of the dacite (see fig. 15 and Pl. XVII). 

This behavior is extremelyinteresting; and the bottom level of the l\1ohawk, as shown on page 206, 

just fails to answer the· important questions suggested by this relation of the ledges to the dacitelatite contact. It is known that a short distance east of the ·Mohawk workings the bottom of the 

dacite in general rises toward the east. The 600-foot level of the Mohawk apparently cuts the 

ledge very near what may be called the keel of the dacite mass. To the west of the ledge on 

this level the bottom surface of the dacite dips to the east. I A short ·distance to the east of the 

ledge on the 600-foot level the bottom surface of the dacite dips to the west. What becomes 

of the ledge below this leveH Will it steepen and go dowr through the latite with probably 

some change in mineralogical character~ Is there in the latite a dike of dacite which the ledge 

will accompany downward~ Or will the ledge be no lo ger traceable for any considerable 

distance below the main dacite sheet~ The importance of these questions is obvious, but unfortunately they can not be definitely answered until morJ underground work is done. The 

probabil~ty is that the ledge will continue down into the ,latite as a low-grade metasomatic 

fissure vein with pyrite as its principal metallic constituent. a · 

MATERIAL AND MINOR STRUCTURES. 

As the most important ledges are in dacite, the material of those in this rock appropriately 

receives first attention. 

Within the zone of oxidation, the ledge matter is usually fl. rusty, shattered, or brecciated 

mass that comiP .mly contains, here and there, bunches and st- .aks of kaolinite, which may be 

mixed with limonite or alunite, or both. The fragments of 1e breccia may be loose, with 

cons;dcrable interstitial limonitic or kaolinitic material, or may be cemented by quartz, limonite, 

or hematite. Excellent examples of such hard cemented breccias may be studied on the ridge 

east of the Blue Bull mine, and views of them are ·given in Plate XIX. The fragments of the 

breccias vary much in size, and it is impossible to draw any definite line between brecciation 

and close irregular fissuring. In many places the rock appears to have been shattered without 

any noticeable displacement, rounding, or trituration of the fragments. 

The ledge matter as a whole is porous and permits the downward percolation of atmospheric water, while the soft pyritized dacite on both sides is relatively impervious. Hence, 

oxidation extends much deeper in the ledges than in the adjoining country rock and gives rise 

to a sharp color-distinction between rusty ledge matter and gray pyritized dacite. 

The. fragments in the 04idized ledge matter, which were originally dacite, are usually 

stained with iron oxide and now consist of gray, flinty, aphanitic quartz with a porous texture . 

. Close inspection of this material shows occasional phenocrysts of quartz which have persisted 

practically unchanged while other minerals have altered to secondary aggregates around .them. 

The pores are spaces once filled by feldspar and by fernie (ferromagnesian) minerals in the 

original dacite. These minerals were first changed, during ore deposition, into aggregates 

consistmg chiefly of alunite and pyrite, respectively. Later, during the progress of oxidation, 

the pyrite and alunite were removed and the spaces they once occupied were iined with drusy 

films of quartz. The removal, however, is complete only near the surface. In much of the 

aSince this was written the mining periodicals report (January, 1909) that the Clermont shaft has cut the Mohawk ledge at lJ. depth of 856 

feet (261 meters), or 241 feet (73 meters) below the bottom of the dacite. 'rhe ore found here is said to assay $22 per ton. T}le character of the 

ledge matter is not stated. 

• 
156 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

rusty ledge matter the fragments, when freshly broken, show pyrite and alunite. Not all of the 

pyrite and alunite are distinctly pseudomorphous, but these minerals are in part disseminated 

in minute crystals through what was once the groundmass of the dacite. 

Below the limit of oxidation the ledge matter is usually less siliceous, less porous, and of 

course is not discolored by oxides of iron. The many small fissures and interstices in the mass are 

commonly filled with a soft white substance which is usually alunite or a mixture of alunite 

and kaolinite. The material of the fragments, or between the fissures, shows more clearly than 

in the oxidized zone that it is altered dacite, the feldspar phenocrysts being represented by 

aggregates of alunite instead of by quartz-lined cavities. These changes will be more fully 

treated in the chapter on metasomatism (p. 176). 

Sheeted structure, suggestive of that in the Cripple Creek district,a characterizes some 

parts of the Red Top, Mohawk, January, and Jumbo ledges, but is not common in the district. 

A small section of the Jumbo ledge in which this structure is well developed is shown on Plate 

XX, B. The nearly parallel fissures are for the most part mere crac~s rendered more prominent 

by silicification of their walls. Some are perceptibly open, their walls being lined with drusy 

films of quartz. The plates of dacite between the fissures are partially silicified and contain 

pyrite and alunite. Well-marked sheeting is displayed also in the Lone Star ledge. 

In some ledges and parts of ledges there is no evidence of more than one period of fissuring 

and mineralization; others have had a more complex history and contain fragments which show 

signs of an earlier fissuring and silicification. In the latter case, the ore is associated with the 

younger disturbance. Some ledges, also, have undergone some fissuring after the primary 

-ore deposition, · as will be shown in subsequent pages. 

Fissures filled with gouge which may contain gypsum, pyrite, and marcasite occur in some 

ledges, often as local division planes between ledge 'matter and country rock. The age of such 

fissures is not always .determinable. A gouge seam may be formed very early in the history 

of a deposit and is likely to remain as a permanent feature, owing to the fact that gouge is 

relatively impervious to solutions and often retains its soft plastic character, while fissured 

rock alongside of it is profoundly altered. Such gouge-filled fissures remain planes of relatively 

easy movement and the material within them may be slowly squeezed and kneaded throughout 

the entire period of ore deposition. They may even continue to register such adjustments and 

.displacements as take place in the ledges up to the present time As pointed out in ano~her 

place, b the soft condition of gouge is no proof of recent origin. In many cases it appears to 

be the record of continued movement which was initiated before ore deposition and continued 

after it had ceased. Still other fissures are plainly later than the first ore deposition and 

appear in the ore bodies as streaks of soft dark material, often carrying more gold than the 

adjacent ore. 

Ledges in andesite have not been so fully explored as those in dacite, but they exhibit 

sirllilar structural features. They are exemplified by the ledges worked in the Engineers', 

Little Florence, and Rogers leases in Florence Hill. The discovery of these ore bodies trom 

1906 to 1908 shows that andesitic ledges may contain ore fully as rich as those in dacite. The 

ledges near Diamondfield are mostly ·in the Milltown andesite. Their character b~low the 

zone of oxidation appears to be different from that of the ledges near Goldfield. They are less 

siliceous, being as a rule soft, crushed masses, with none of the structures so characteristic of 

the pay shoots of the Goldfield group of mines, presently to be described. In their oxidized 

·portions, however, these andesitic 'ledges are as hard and siliceous as any in the district. 

The only rhyolitic ledge in which extensive work has been done is that of the Sandstorm 

and Kendall mines. Within the oxidized zone, the fissured rhyolite is thoroughly silicified 

and the walls of fissures and the surfaces of fragments are often encrusted with barit.e. The 

intersti~es are filled with kaolinite, usually more or less rusty and containing in many places 

a See Lindgren, W.,and Ransome, F. L., Geology and gold deposits of the Cripple Creek district: Prof. Paper U.S. Geol. Survey No. 54, 1906, p. 160. 

b Ransome, F. L., and Calkins, F. C., The geology and oredepositsoftheCreurd' Alene district, Idaho:. Prof. Paper U.S. Geot Survey No. 62 1908, p. 120. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XIX 

A. DACITIC LEDGES MEETING ON RIDGE NEAR THE COMMONWEALTH MINE. 

B. NEAR VIEW OF DACITIC LEDGE NEAR THE BLUE BULL MINE; SHOWING STRUCTURE. 
.. 

• 
THE LEDGES. 157 

crystals of barite. Below the zone of oxidation there is little to distinguish ledge material 

from the altered rhyofite in the vicinity of these mines. 

The origin of the fissuring constitutes a problem that will be attacked in a later chapter. 

It may be pointed out at this place, however, that fissuring of the kind described has all the 

characteristics of fracturing that has taken place close to _ the surface or under very slight load. 

The multitude of small fractures, becoming noticeably Jess abundant and individually more regular 

within a depth of a few hundred feet, is clearly the comparatively superficial expression of 

more deep-seated and regular dislocation. Such complex fractures, as T. C. Chamberlin a has 

well emphasized, are secondary phenomena related to more profound and more simple movements, and from the point of view of dynamics they are accessory, not essential. A similar, 

although less pronounced, change in the fissuring of the rocks at Cripple Creek at various depths 

has been pointed out and has received like explanation.b At Goldfield the rocks when ruptured appear to have been under less load than at Cripple Creek. 

The evidence furnished by the fissuring is thus in full accord with that derived from the 

geologic history of the Goldfield region as presented on page 86. 

a The fault problem: Econ. Geology, vol. 2,1907, p. 590. 

b Lindgren, W ., and Ransome, F. L., Geology and gold deposits of the Cripple Creek district, Colorado: Prof. Paper U.S. GeoL Survey No. 54, 

1906, p. 167. 
CHAPTER XIII. 

THE PAY SHOOTS AND ORES. 

DISTRIBUTION. 

In a broad way the general distribution of the ores with reference to the various rock 

formations has been indicated in the preceding chapter. It is safe to say that over 80 per cent 

of the gold obtained in the district has come from the intrusive body of dacite that lies just 

northeast of Goldfield. In this rock chiefly are the Red Top, Laguna, Mohawk, Combination, 

January, and Florence ore bodies. Next in importance are the ore bodies in andesite, a class 

of more recent development, which includes the pay shoots of the Little Florence, Rogers, and 

Engineers' leases, a~d the deposits near Diamondfield with the exception of the Flat vein on 

the south side of Black Butte, which is in dacite. The only ore bodies of proved importance 

in the rhyolite are those of the Sandstorm and Kendall mines, and these are superficial. 

RELATION TO LEDGES. 

In some deposits ore and ledge matter are practically coextensive; but usually, and particularly in the larger deposits, the ore constitutes a small part of. the entire ledge. This is 

particularly true in the oxidized zone, where . the ledges are wide and irregular and where more 

or less· secondary concentration of the gold has taken place. In such ledges the ore may occur 

within the mass as irregular pods or bunches, or it may lie on one side of a body of ledge matter, 

with the country ·rock forming practically one wall. (See Pls. XVI and XVIII.) 

.SHAPE. 

Description of the shape of the Goldfield ore bodies is difficult because the ore bodies themselves are inherently vague. The pay shoots as a rule have nothing to distinguish them structurally from barren ledge matter. They have no boundaries other than the invisible limit~ 

beyond which the assayer's returns show stoping to be unprofitable. The change from very 

rich ore to practically barren ledge matter may take place within a short distance, but it is 

nearly always a gradation, not a definite boundary. The siz~ of pay shoots, and to some extent 

their shape also, depend, therefore, upon conditions which determine the grade of ore that can 

be profitably treated at any given time. If the economic boundary between ore and waste 

be placed at $25 a ton, a given ore body will have a definite shape and size. If the limiting 

value be reduced to $20 a ton, the same ore body will be larger. We may assume that its shape 

will be somewhat similar to that defined by the higher value, but beyond this we can not go 

without such detailed and systematic exploration of pay shoots as is hardly ever practicable in 

this district. In reading the following statements as to the form and dimensions of pay shoots 

these conditions should be kept in mind. 

In general, the pay shoots are fully as irregular as the ledges with which they are associated. 

Some of them are roughly equidimensional masses, others are lenticular, some are approximately spindle shaped, with the large axis nearly vertical, and still others are tabular or platelike, although such sheets of ore are often curiously twisted or warped. The striking feature 

of the ore bodies as a whole is the absence of, rather than the approximation to, any regularity 

of form. While many of the pay shoots conform to the trend of the inclosing ledge, others 

do not. 

Some idea of the shapes of pay shoo.ts as determined by stoping may be had from Plate 

XVI, which shows plans of the ore bodies on successive levels of the January mine, with a 

158 
PAY SHOOTS AND ORES. 159 

generalized section through the workings.· The change in form in passing from one level to 

another is very striking, although the levels are only 50 feet (15 ,meters) apart. Similar changes 

are shown in the Combination mine, as illustrated in Plate XVIII. In both these mines the tendency of the pay shoots to become narrower and more regular with increase of depth, corresponding to the tendency already noted in connection with the ledges, is well marked. The richest 

ore on the upper levels of the Combination mine occurred. in chimney-like shoots of short stope 

length. These either pinched out at slight depth (see p. 213) or merged below with shoots of 

different form. When the mine was revisited in 1908 it was found that the outlines of the 

original rich shoots had been in most places obliterated by the enlargement of the stopes in 

consequence of the lower grade of ore that it is now possible to mill at a profit. Details of the 

pay shoots of the January and Combination mines will be found on pages 211 to 219. 

Beyond the fact that their longer dimensions usually lie nearly in the general plane of the 

ledge the Mohawk pay shoots have little regularity of formJ particularly on the upper levels. 

This may well be seen in the Hayes-Monnette stope (Pl. XXI, B), easily reached from the 

245-foot level of the main shaft. This is a great chamber, or rather a series of chambers, one 

opening unexpectedly into another, and without special illumination the visitor finds it difficult 

to realize its shape or. size. It is over 100 feet (30 meters) in height and of very irregular plan, 

the total stope length being about 75 feet (23 meters). Below the 245-foot level the HayesMonnette shoot merges with. other pay shoots stoped from the Truett and Frances-Mohawk 

lease shafts (see Pl. XXXIII) and with an irregular chain of ore bodies extending down to the 

bottom of the main :Mohawk workings. Only by long familiarity with the mine or by the aid 

of a carefully constructed model is it possible to gain any satisfactory conception of the shapes 

of these pay shoots as indicated by existing stopes. That they are on the whole of flat form 

and lie generally with the ledge and not across it is shown by figure 15 and Plate XXXIII. 

Among the pay shoots which approach tabular form may be mentioned the southern 

part of the main shoot of the Combination mine above the 130-foot level. As worked on this 

level in 1905, the pay shoot, then known as the No. 2 shoot, was near the hanging wall of the 

ledge and had a maximum width of about 6 feet (1.8 meters) and a length of 300 feet (91 meters) 

or more. In 1908, however, the whole ledge had been stoped to a wid.th of 40 feet (12 meters). 

In spite of the regularity of the ore on this part of the 130-foot level the pay shoot, as shown 

by Plates XVII and XVIII, does not extend directly down to the lower levels. 

The Reilly pay shoot is also of tabular or flat lenticular form, but shows striking changes 

in dip and strike, as illustrated in figure 1 () and Plate XXXV. In the Florence mine the principal pay shoots are roughly lenticular masses of which the stope length rarely exceeds 100 

feet (30 meters). The maximum stoping width of the large Sweeney shoot was about 18 feet 

(5.5 meters). These masses occur in a very irregular ledge (see pp. 227 to 229) and are 

not of great persistency in the line of pitch. Even the relatively large Sweeney shoot has 

a vertical range of little more than 100 feet (30 meters). (See fig. 17.) The pay shoot of the 

Jumbo mine appears to have more regularity than is usual in this district, but not much is 

yet known as to its behavior below the 250-foot level. Near the surface the ore body has a 

practically continuous stope length of over 500 feet (152 meters), and in one or two places is 

as much as 20 feet (6 meters) In width. 

Flattened shoots lying in the plane of the ledge, but with stope lengths so short as to suggest the pipelike or chimney-like form, occur in the :Mushett and Engineers' leases. In the 

latter mine the pay shoot apparently does not extend below the 300-foot level. The pay shoots 

of the original Little Florence lease also are roughly lenticular with short stope lengths, and, 

so far as known, do not extend below a depth of 500 feet (152 meters). 

In addition to the larger pay shoots, small, irregular, isolated bunches of ore, often of 

high grade, are rather characteristic of the district. Such were the bodies mined during the 

early days of Goldfield in the Velvet, St. lves, Commonwealth, Lon~ Star, and Simmerone 

mines and in some of the mines in and near Black Butte. The sudden springing into notice 

of some hitherto obscure mine in consequenee of the discovery of a rich bunch of ore; glowing 

descriptions of high-grade shipments in the local newspapers; and,. in a few weeks or months, 
160 THE GEOLOGY AN D ORE DEPOSITS OF GOLDFIELD, NEVADA. 

the cessation of shipments and an unheralded return to prospecting and development-these 

are the familiar stages of an oft-repeated story in the Goldfield district. 

The oxidized ore bodies hitherto worked in the Sandstorm and Kendall mines differ from 

most of the pay shoots of the other mines in that they do not pass downward directly into 

sulphide ores. As a rule, the ore bunches, which are very irregular, rest upon an uneven although 

generally nearly horizontal floor of hard, silicified rhyolite, which shows little sulphide mineralization. Some of these shoots extend from this floor to the surface as nearly vertical pipes. 

Others are flat-lying masses in which the horizontal dimensions exceed the vertical. Up to the 

end of 1908 no ore had been found in these mines below a depth of 80 feet (24 meters). 

As compared with ore bodies of other gold districts, such as Cripple Creek, those of Goldfield are small, although the disparity in size would undoubtedly be less if the definitions of 

ore and waste were the same in the two districts. One of the largest stopes in the Goldfield 

district at the end of 1905 was the curved opening on the northern part of the· January ledge, 

which extends from the surface nearly to the 160-foot level. The maximum stope length of 

this body was about 200 feet (61 meters) and the greatest width of ore about 25 feet (7.6 meters). 

Another large opening is the Sweeney stope in the Florence mine (Pl. XXI, A). From this 

. a lenticular body of ore about 100 feet (30 meters) in diameter and up to 18 feet (5.5 meters) 

in width was extracted. 

Of late years some large stopes have been opened in the Combination mine. The so-called 

"glory hole,'' of which a view is shown in Plate XXII, A, is an Irregular opening probably over 

100 feet (30 meters) long, up to 75 feet (23 meters) wide and 80 feet (24 meters) deep, while 

below it, as shown in Plate XVII, are continuous although narrowing stopes down to the 280-foot 

level. Another large · stope is that east of the main shaft, which on the 130-foot level is 

nearly 500 feet (152 meters) long and up to 40 feet (12 meters) wide, its height being from 

100 to 150 feet (30 to 46 meters). The Hayes-Monnette stope in the Mohawk, as already 

described, is also a large one, and when the new mill of the Goldfield Consolidated Mines Company is in operation some very large openings will undoubtedly be made in the ~1ohawk ledge, 

which as yet has supplied only high-grade ore. 

In comparison with such bodies of ore as were taken from stopes in granite in the Portland, Stratton's Independence, and Ajax mines at Cripple Creek, the largest known pay shoots 

at Goldfield are small. The tenor of the ore mined, however, is much higher than in the Colorado district. 

RELATION TO FISSURING. 

Although, as will be fully explained in a later chapter, metasomatic replacement has played 

no small part in the formation of the ore deposits as a whole, that process and the ores themselves are very closely controlled by fissuring. Such complete replacement of rock by masses 

of sulph-ides as takes place in some limestones, a replacement which in that rock may extend 

for considerable distances from the fissures supplying the active solutions, is not found at Goldfield. There-- fissuring, not relative solubility or chemical instability of the country rock, has 

determined the shape of the deposits. The irregularity of the ore bodies, like that of the ledges, 

is consequent upon the unusual complexity of the fissuring. In any ore-bearing ledge the 

ore is found where the fissuring has been most intense and where originally there were abundant openings to admit the depositing solutions. .The favorable conditions are clearly rather 

loose, open fissuring or shattering, not followed by any such extensive movement as would 

squeeze the shattered material together and clog the interstices between the fragments with 

impervious gouge. In many places there appears to be a close connection between ore deposition and the intersections or junctions of divergent zones of fissuring. Good examples of this 

feature are found on the SO-foot and 130-foot levels of the Combination mine (see Pl. XVIII), 

and in the Rogers, Sandstorm, and Kendall mines. As stated on page 156, some ore bodies 

show recurrent fissuring; where ore is traversed by later fissures, these and the material adja- • 

cent to them are usually richer than the rest of the ore. Such later fissuring may thus modify 

the original shape of an ore body. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XXI 

A. PART OF THE SWEENEY STOPE IN THE FLORENCE MINE. 

Note shattered ledge matter and absence of any regu(ar boundary between ore and waste. 

B. THE HAYES-MONNETTE STOPE IN 1906. 

Afterward much enlarged. Photograph by P. E. Larson. 

U. S. GEOLOGICAL SURVEY 

A. THE '·GLORY HOLE" OF THE COMBINATION MINE. B. LEDGE MATTER ON THE 150-F

PAY SHOOTS AND ORES. 161 

Mere character of fissuring, however, as visible within a few hundred feet of the surface, 

is only one of several factors determining ore deposition. The district abounds in illustrations 

of the fact that fissuring, apparently of the most favorable kind, is not necessarily followed by 

the accumulation of an ore body. The fissure complex must evidently be connected with still 

deeper channels in such a way a~ to · give a·ccess to ore-bearing solutions, and probably also 

with lateral and superficial channels through which other solutions could pass to mingle with 

the waters of deep origin -and precipitate their valuable constituents. Thus locality and the 

features of a former topography were probably both of great importance in determining whether 

a given mass of shattered rock should become an ore body. 

That some further modifications of the original shapes of pay shoots take place in the 

course of oxidation is highly probable, although the steps of such change can not usually be 

traced. Oxidation implies changes in volume of the constituents of the .mass with more or 

less gravitative readjustment or settling, minor fissuring, and some migration of material by 

resolution and redeposition. ' 

EFFECTS OF FAULTING. 

So far as known the ore bodies have not as a rule been greatly modified by faulting subsequent to ore deposition. In this respect they differ in striking fashion from the veins of 

Tonopah. It must be pointed out, however, that the difficulties in the way of the recognition 

of notable faulting at Goldfield are very great. The ability to recognize important dislocations 

depends very largely upon the degree to which the faulted structures were initially regular and 

persistent. When, for example, a well-defined regular vein which has been followed for some 

hundreds of feet ends abruptly at a fissure filled with attrition products, faulting is at once 

suggested and in many cases is easily demonstrated. At Goldfield, however, the initial regularity is lacking. It is known that ore bodies in this district show unexpected and erratic 

changes in direction . and may terminate abruptly without faulting. There is in many cases no 

a priori ground for supposing that beyond the apparent end of an ore shoot is another body, 

once continuous with it, but now displaced. The evidence of movement both in and around 

the Goldfield ore bodies is abundant, but the interpretation of this movement-the discrimination between slips of structural importance and those whose total displacement is measurable 

in inches rather than feet-is as a rule impossible or inconclusive. If a pay shoot ends at a 

seam of gouge, and if a few hundred feet away another pay shoot is found on the other side of 

a similar gouge-filled fissure, there is as a rule no means of identifying the two bodies as originally part of the same mass, nor can it be assumed in this district, where gouge seams are known 

to bend through angles of 90° or more, that the gouge in contact with the two masses of ore 

occupies one continuous fissure. 

The difficulty in the way of "identifying gouge-filled fissures from point· to point by means 

of a few isolated exposures is well illustrated by the plan (fig. 18) of t~e 350-foot level of the 

Mohawk mine, a level on which the so-called hanging wall of the ledge is visible at more places 

than elsewhere in the mine. Near the upper Curtis shaft this wall, which is defined by a gouge 

seam dividing ore or ledge matter from soft, altered dacite, has a curved but generally northerly 

course. Near the Mohawk shaft the hanging wall swings to the east and a similar seam of 

gouge tFaverses the ledge matter, passing through the shaft. The two fissures must join or 

intersect about 100 feet 'south of the main shaft. Near the Mohawk-Jumbo stope the hanging 

wall turns northwest. As a whole it is a very sinuous curve. The hanging wall is probably 

not a single fissure, but a series of fissures, each one of which serves as hanging wall for a short 

distance and then passes either into ledge or country rock. The significance of this is that the 

hanging wall is probably as erratic in section as it is in plan. Neither in plan nor section can 

its true course be drawn from a few isolated exposures. 

The conditions as regards faulting may perhaps be best understood by keeping in mind 

the facts that the ledges as a whole are hard, brittle masses of irregular contour, and that the . 

altered country rock in which they lie is as a rule soft and plastic. The result of any competent compressive stresses applied to the whole system would be to cause IIl;Ore or less slow 

79145-No. 66-09--11 
162 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

flowage of the soft country rock arou:p.d the masses of ledge matter, and in some degree to deform 

the latter by fracturing or, if the system were much strained, by faulting. On a small scale 

the process is illustrated by the conditions in some serpentine masses, such as those in the Coast 

Ranges of California, where the pressure due to the increase of volume consequent upon serpentinization of the original peridotite has caused the softer portions of the mass to flow around 

the harder slickensided nodules. Such a conception, it is believed, best explains the prevalent 

fractured condition of the ledge matter and its frequent separation from the neighboring soft 

country rock by curved seams of gouge. That the entire mass of country rock (dacite, latite, 

and andesite) near Goldfield, with its included ledges, has been subjected to stresses capable 

of effecting such a result will be evident to anyone who examines the exploratory workings of 

the Kewanas, Combination, Fraction, or Portland s4afts, or who studies the longer crosscuts 

into country rock in the principal productive mines. It is the general squeezing which such 

rock ha,s undergone and the abundance of gouge-filled fissures that constitute one of the chief 

difficulties in tracing any structurally important fissures through it. 

0 100 zoo 300 FEET 

\ 

\ 

\ 

\ 

\ 

------------·-----~ FIGURE 18.-Plan of the 350-foot level of the Mohawk mine, showing irregularity of the so-called hanging wall. 

A few faults of small throw have been recognized in the Mohawk and Combination mines, 

but these do not materially affect the shapes of the ledges and pay shoots. There is a possibility, 

as pointed out on page 212, that the irregularity of the Combination ledge below the 180-foot 

level, shown in Plate XVII, may be in part due 'to faulting generally parallel to the eastwarddipping dacite-latite contact, but this is a mere suggestion. Probably the strongest indication 

of important faulting of ore bodies comes from the relation of the Florence ledge to that of the 

Engineers' lease, which is described on page 232 and illustrated in Plate XXXV. In this case it is 

reasonable to suppose that the Engineers' ore body is displaced about 50 feet (15 meters) to 

the northeast from the Florence ledge by a curved fault, which dips to the southeast. (See 

fig. 28, p. 226.) Whether there is a correspohding displacement in the opposite direction between 

the Engineer:s' ledge and that of the Little Florence lease is not clear. 

In conclusion, the possibility that some of the other ore bodies have been extensively displaced by important faults is not denied. It does not appear, however, that there is any evidence 

now available which adequately supports such a supposition. 
PAY SHOOTS AN 0 ORES. 163 

INFLUENCE OF COUNTRY ROCK. 

· The fact th~t so -many of the larger and better ore ~odies are in dacite has naturally made 

that rock a great favorite with prospectors, and in many cases anxiety to prove its presence has 

led to the erroneous identification of andesite or latite as dacite. The presumption in favor of 

dacite as an ore carrier was, however, far greater in 1905 than now, since the Little Florence,. 

Rogers, and Engineers' leases have proved that just as good ore may be found in the Milltown. 

andesite as in the dacite. It has always oeen difficult to see in what inherent properties the 

dacite had any advantage over the Milltown andesite. The chemical difference between the 

two rocks, as has been shown on pages 50, 52, and 56, is very slight, and the only constant mineralogical difference is the presence of scattered phenocrysts of quartz in the dacite. That the 

Milltown andesite can be silicified and form ledges to as great an extent as the dacite is shown 

by the hundreds of outcrops east of Milltown, and by the strong flinty ledges of Kendall Moun- · 

tain, McMahon Ridge, and Black Butte. It is true that the fresh dacite is a slightly more brittle 

rock than the average Milltown andesite, and perhaps on this account afforded better channels 

for the ore-depositing solutions in the early stages of mineralization. Its generally larger 

. porphyritic crystals of feldspar may also be somewhat in its favor as regards ore deposition. 

The phenocrysts of quartz may have served as nuclei or centers of precipitation of silica from· 

the ore-bearing solutions. · While these slight differences may make the dacite a slightly better 

depository for ore than the Milltown andesite they do not seem sufficient to account for the 

overwhelming preponderance of the ore bodies in this rock, particularly as some ore equally 

good . occurs in andesite. As regards areal distribution this preponderance is probably a matter 

of locality rather than petrography. In other words, the large ore bodies of the Mohawk and 

Combination mines occur where they do, not because the country rock is dacite instead of andesite, but because some conditions outside of the visible dacite mass determined the influx of 

highly auriferous. ·solutions to those particular places. 

As regards thelatite also, recent developments in the larger mines and in the Hazel-Goldfield 

lease have tended to remove some of the prejudice against this rock based upon the fact that 

no ore bodies of any consequence have yet been found wholly within it. That ledges of the 

ordinary Goldfield type may occur in th.e latite is well shown ·on Banner Mountain and elsewhere, but, perhaps owing mainly to its texture, the rock appears rather less susceptible of 

silicification than the dacite and andesite. The ordinary change observable near Goldfield is 

to a soft alunitic mass carrying abundant disseminated pyrite. Nevertheless, as described on 

pages 206 and 214, some excellent ore has been found in the latite near the dacite contact in the 

Mohawk and Combination mines: According to Mr. H. P. Henderson,a the Hazel-Goldfield 

lease, also, has opened some ore in latite at tlie 718-foot level.b This, while encouraging as 

regards the future of the mines below the dacite, still does not_offset the fact that the latite near 

the surface and away from the dacite has thus far proved barren. The evidence from experience suggests that the latite is a less favorable rock for ore deposition than either the dacite 

or the andesite. 

The only ore of consequence found in rhyolite is that of, the Sandstorm, Kendall, and 

Conqueror mines. This is oxidized ore, and all efforts to trace it down to workable bodies of 

sulphide ore have been futile. The probability that large or persistent bodies of ore will be 

found in any of the rhyolites appears to be small. The ore-bearing capacity of the pre-Tertiary 

rocks is problematic. As exposed at. the surface they contain nothing of value so far as known. 

It is likely that the larger mines near Goldfield will have to sinK to a depth of 1 000 feet (305 

meters) or more before reaching the Cambrian shale or the alaskite. The probabilities at that 

depth are discussed on page 200. 

a Personal letter, December 6, 1908. b See also the footnote on page 200. 
.. 

PLATE XXIII. 

ORE STRUCTURES (N ATUE,AL SIZE). 

A. Very rich ore (G .. 604). Combination mine. Polished face of altered dacite (d). Part of a fragment coated with gold and sulphides. The inner dark band t~ the right is gold in quartz. The outer dark band, separated from the gold by a narrow indistinct film of quartz, is famatinite. The external coating is chiefly alunite and pyrite. The photomicrograph of Plate XXVI, A, is from the same specimen. 

B. Marcasite (G. 643). Florence min,e. Incrusts a fragment of altered dacite. The white material partly cov- ering the botryoidal marcasite is alunite . 

C. Rich ore (G. 809). January mine. Polished face. The gray matrix is quartz. The irregular dark inclusions in the right-hand third of the specimen are famatinite; those in the left-hand third are bismuthinite; those in the middle zone are mostly bismuthinite, but some are famatinite. 

D. Rich ore (G. 641). Florence mine. Polished face. Shows fragments of altered dacite coated with gold and sulphides. Interstices are filled with spongy quartz. Order of deposition from within out is gold, pyrite, famatinite, 

quartz. Gold is not visible in all of the fragments and in none of them forms a complete envelope. The specimen illustrates modification of shape of original dacite fragments by alteration and solution. Most of them have, inside of the sulphide shells, a shadowy envelope of cryptocrystalline quartz. This grades irregularly toward the center into alunitized dacite) which still retains traces of its original texture. The gold particles are for the most pa,rt clustered in this siliceous envelope. 

E. Ore (G. 628). Florence mine. Polished face. Shows part of a fragment of altered dacite with shell of sul- phides and quartr; on left-hand side. The dacite fragment records at least two periods of fissuring and quartz depo- sition prior to the deposition of the sulphide shell. 

F. Ore (G. 88). January mine. Polished face. Shows a fragment of altered dacite with outline modified by solution, incrusted with quartz, famatinite, bismuthinite, and pyrite. Gold is probably present, but is not visible. The dacite kernel contains alunite pseudomorphs after feldspar and, like the specimen illustrated by figure E, was fissured and at least partly altered prior to the envelopment of the fragment by sulphides. The peripheral shells, from within out, are (1) a thin film of quartz, (2) a thin film of pyrite, and (3) an aggregate of quartz, bismuthinite, and famatinite much like that in figure C. 

PLATE .XXIV. 

ORE STRUCTURES (NATURAL SIZE). 

A. Rich nodular ore (G. 642). Florence mine. Fracture surface. A kernel of altered dacite is enveloped (1) by a not wholly continuous film of pyrite, (2) by a shell of famatinite, and (3) by a thick crust of dark cryptocrys- talline quartz carrying famatinite, bismuthinite, and native gold. 

B. Oxidized ore (G. 718). Red Top mine. Shows cavernous texture of cryptocrystalline quartz. 

164 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XXIII 

c D 

E F 

ORE STRUCTURES. 

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XXIV 

A 

B 

ORE ST RUCTURES. 

PAY SHOOTS AND ORES. 165 

MINERALOGICAL AND CHEMICAL CHARACTER OF THE SULPHIDE ORES. 

The typical unoxidized ore as it occurs in the dacite or andesite near Goldfield, particularly in the mines south of the Mohawk, consists of pyrite, bismuthinite, and a reddish-gray 

cupriferous mineral having the general composition of an arsenical famatinite (seep. 118), in 

a rather dark gray, flinty, quartz gangue. Native gold is usually associated with these minerals, particularly with the bismuthinite and famatinite, and in the rich ore may be easily 

visible. In ore of the Mohawk type, however, the gold is as a rule less conspicuous. The 

native gold is in many ores embedded chiefly in the quartz, but it may occur also in minute 

particles in bismuthinite, goldfieldite, or famatinite. 

Concentric shells of ore minerals about greatly altered rock fragments are rather characteristic of the best ore. (See Pls. XXIII, XXIV, and XXV.) Specimens from the Combination mine (Pl. XXIII, A.) show an inner zone of free gold and quartz up to an eighth of an inch 

in thickness. This is covered by a shell of famatinite and this by an outer crust of -pyrite. In 

the Florence mine similar fragments (Pl. XXIV, A) show, first, a shell of pyrite, then one of 

famatinite, and, finally, a thick crust of quartz speckled with native gold, famatinite, and 

pyrite, and transfixed by needles of bisn1uthinite. Some of the particles of gold are embedded 

in the compact quartz, others are inclosed in the bismuthinite. The different crusts are not 

in every case sharply defined nor are they necessarily continuous. 

· In the ore of the. Engineers' lease two distinct crusts of gold have been observed. Thus 

in the specimen illustrated in Plate XXV, B, there is, next to the fragment of altered andesite, 

a thin discontinuous film of famatinite covered in places by a similar film of gold. Outside of 

this is a relatively thick layer of quartz and bismuthinite needles. Incn-sting this is a second 

shell of gold particles in quartz about one-sixteenth of an inch in thickness. This in turn is 

covered by a skin of drusy quartz or is succeeded by a mass of cemented fragments of flinty 

quartz containing gold, famatinite, bismuthinite, and pyrite irregularly distributed through it. 

Another specimen from the same lease is shown in Plate XXV, A. Here the andesite fragments, which are silicified and full of fine pyrite, are coated first -with pyrite, then with 

famatinite, and then with bismuthinite, all in very thin shells. Outside of these is an envelope 

of gold and outside of this envelope a thick shell of dark-gray dense quartz carrying gold ~nd 

needles of bismuthinite. Both specimens are shown in natural size. 

The native gold of these ores is often in particles so fine and so closely crowded in the gangue 

that the precious metal resembles a streak of yellow ocher, and it is only under a lens that 

the luster of the particles appears truly metallic. 

Opportunities for examining the richest Mohawk ore in place were not pa1 ticularly good 

at the time of the visit in 1908. Specimens which were seen, however, show ·the same habit 

of crustification around fragments of rock as has been described. In the Mohawk ore, however', 

the most valuable crust is not a yellow aggregate of quartz and gold, but a dark-gray mixture 

of goldfieldite, and native gold, closely associated with marcasite, as described on page 116. 

The ore of the Mushett .lease on the Miss Jessie claim northeast of the Red Top mine is _ 

structurally and mineralogically one of the most interesting in the district. The proportion 

of sulphides to gangue is greater than in most of the mines. The metallic minerals noted are 

pyrite, famatinite, bismuthinite, sphalerite, and a dark-gray mineral identical in appearance 

with that analyzed and described on page 116, and probably like it the new species goldfieldite. 

This material is rich in gold, specimens which to the naked eye show not a particle of the native 

metal yielding over $8,000 a ton on assay. The crustification in the Mushett ore is not very 

regular, but the minerals have formed in the following general succession: ( 1) Pyrite; (2) famatinite, bismuthinite, goldfieldite; (3) sphalerite; and (4) pyrite. The sphalerite in some places 

forms botryoidal crusts over the prisms of bismuthinite, which attain a larger size in this ore 

body than in other known occurrences in the district. 

The material forming the extreme outer crust of the nodular ores of Goldfield or filling 

interstices between the altered and incrusted rock fragments is in most places a soft mixture 

of alunite and pyrite. 
166 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, N~V ADA. 

The appearance of some of the typical rich ores in thin section under the microscope is 

illustrated in Plates XXVI and XXVII, which are accompanied by full descriptive notes. 

The very fine grain of the flinty quartz gangue is shown in these photomicrographs. 

The proportion of silver in the Goldfield ores is usually rather small, the average of 34 assays 

of rich ore from the Mohawk mine, made for Mr. J. W. Finch, at one time general manager, 

· giving 330 fine ounces of gold and 46.5 ounces of silver to the ton. In the Florence mine the 

ore of the deeper levels contains more copper and silver than that near the surface. A shipment 

from the 250-foot level in 1905 contained 100.8 ounces of gold and 3.5 ounces of silver per ton, 

and 3.5 per cent of copper. The highest silver assays from the upper levels, according to Mr. 

Frank Oliver, formerly superintendent of the mine, was less than 2 ounces per ton. There are 

some indications of a similar change in the Combination mine as regards the relation of silver 

and gold. A specimen of heavily pyritized dacite collected in 1905 from the 230-foot level 

was sent to E. E. Burlingame & Co., Denver, for assay. This material, apparently consisting 

entirely of pyrite, quartz, and a little alunite, afforded 0.68 ounce of gold and 2.72 ounces of 

silver per ton. The sample was chosen in an attempt to find material representative of a type 

of ore likely to prevail at greater depths than 500 feet (152 meters). The ores near Diamondfield generally contain a larger proportion of silver than those near Goldfield. 

Tests and chemical analyses of the ores made for scientific and technical purposes have from 

the first nearly all shown a little tellurium, although no tellurium mineral was recognized in 

the mines close to Goldfield until the discovery of the Mohawk ore bodies. Tellurides of gold, 

not sufficiently well crystallized for a determination of their species, occur in the Jumbo Extension and Goldfield-Belmont mines, near Diamondfield, and both tellurite and emmonsite (or 

durdenite) were found in 1905 in the oxidized ore of neighboring properties. a W. F. Hillebrand 

has detected some selenium with the tellurium of these minerals. The tellurides are· in some 

cases int~rgrown with native gold. 

Most of the analyses of Mohawk ores made in connection with the prosecution of ore thieves 

show about 2 per cent of tellurium, which. as explained on page 116, is probably due mainly to 

the presence of goldfieldite. 

The first sphalerite found in the ores of the district appears to have been a small speck noted 

in the Goldfield-Belmont mine by Mr. W. H. Blackburn in 1905. The mineral has since been 

found to be abundant in the Mushett and neighboring leases near Goldfield, where it formed subsequently to the rich ore. 

Galena was unknown in the Goldfield district in 1905. It has latterly been observed in 

several leases, as noted on page 112._ 

Chalcopyrite, a common mineral in most mining districts, was not found at Goldfield in the 

course of the present investigation, but it is said to occur sparingly in the Sandstorm and Florence 

mines. E. A. Collins b notes very small quantities of chalcopyrite and zinc blende in the Combination ore. · 

The common gangue of the unoxidized ore is quartz. This is usually compact, almost 

flinty, in texture, although porous in mass, and in most cases bears unmistakable evidence of 

having resulted from the silicification of dacite, andesite, or latite. Large vugs and conspicuously crystalline quartz, such as are found in typical veins the world over, are practically absent 

from the Goldfield district, where the free development of quartz crystals in open spaces is represented only by drusy films, lining pores left by the solution of phenocrysts, or incrusting small 

interstitial cavities in brecciated material. The appearance of typical quartz gangue as seen 

in thin section under the microscope is shown in Plates XXVI and XXVII. Even where the 

quartz, as in Plate XXIII, C, does not appear to have directly replaced a mass of rock, it is 

always cryptocrystalline and is usually full of little vugs. In such cases it appears to have filled 

spaces an inch or two across by the slow concretion of thin films on projecting crystals of bismuthinite and by the final coalescence of these films, leaving only a few small vugs. In other 

a Ransome, F. L., Preliminary account of Goldfield, Bullfrog, and other mining districts in southern Nevada: Bull. U. S. Geol. Survey No. 

303, 1907, p. 36. . 

b The Combination mine: Min. and Sci. Press, September 28, 1907, p. ;398. 
• 

' 
PLATE XXV. 

ORE STRUCTURES (NATURAL SIZE) • 

.A.. Rich nodular ore (G. 995). Engineers' lease. Polished surface. Fragments of altered andesite, silicified and pyritized, with an envelope of at least six layers. Next to the andesite is a thin irregular shell of pyrite. Outside of this is a shell of famatinite. Outside of the famatinite is a nonmetallic film, probably alunite and quartz, which 

shows as a white line in the illustration. Outside of this is a thin layer of quartz containing particles of famatinite. 

Enveloping this is another shell of quartz containing minute gray needles which are probably bismuthinite. Oovering this is a yellow envelope of quartz and gold. Last is a thick outer shell of quartz, bismuthinite, and gold. 

B. Rich ore (G. 994). Engineers' lease. Polished surface. At top is a fragment of altered andesite. Under 

this is a thin film of famatinite, gold, and quartz. This is succeeded by a broad dark band, which is an aggregate of 

quartz and bismuthinite. Below this is a second band of gold and quartz. The lower part of the specimen is a mass 

of cemented flinty quartz fragments carrying famatinite, bismuthinite, pyrite; and gold. The white areas are alunite • 

• 

., . 
DROFE.SSIO • 

. \ 
PAY SHOOTS AND ORES. 167 

· cases the films have started from fragments of rock lying in the cavity or fissure and have 

gradually thickened until the space became filled. . 

Associated with the quartz in much of the ore are soft white substances, such as theminers 

commonly call "talc." Chemical ·and microscopical tests of the white material show that in 

most cases it is either alunite or kaolinite or a mixture of the two. a Sericite, supposed when the 

· preliminary report b on the district was written to be also abundant, proves on further study 

to be very rare and is certainly nowhere an abundant or characteristic mineral in the ore 

deposits. Gypsum, while not known with actual sulphide ore, is very abundant in th~ altered 

rocks within a hundred feet or so from the surface; and does occur crystallized with quartz 

and pyrite in the Goldfield-Belmont mine, below the belt of oxidation. 

As a rule, the gold and auriferous sulp4ides are embedded in quartz. Alunite, however, 

is often so close to the gold as to appear in the same microscopic field, and the telluride of gold 

in the Jumbo Extension mine is partly embedded in alunite. 

Some idea 1

of the · chemical composition of typical ric:h da,cite ore may be had from the 

following analyses of unoxidized ore from the 'Mohawk mine kindly furnished by Mr. J. W. 

Finch, consulting geologist for the Goldfield Consolidated Mines Company, and by Mr. Charles 

S. Thomas, jr. These analyses are given in the form reported by the analysts to the company, · 

since in most cases they contain ambiguities, like "iron oxide," not safely translatable into 

more scientific expressions. 

Analysis of composite sample of nine lots of Moha'wk ore shipped early in 1907. 

I. [Lochiel M. King, analyst. Rep~rted February 13, HI07.] 

Water (combined)........ . . . . . . . . . . . . . . . . . . 7. 00 

Silica (Si02)............... • • • • • • • • • • • • • • • • • 66. 30 

Copper ( Cu) ........................ . . , . . . . . 2. 08 

Bismuth (Bi).................. . . . . . . . . .. . . . 35 

Tellurium (Te)... . ...... . . . . . . . . . . . . . . . . . . . 2.' 42 

Antimony (Sb) . . . . . . . . . . . . . . . . . . . . . . . . . . . Traces. 

Iron (Fe)...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 83 

Alumina (Al20 3). . ....... . • . • • .. • • • • .. .. .. • 9. 09 

Zinc (Zn) .......... . .......... Very slight traces. 

Lime ( CaO). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0. 00 

Magnesia (MgO) ...................... :. . . . . . . 24 

Sulphur (S).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. 30 

Gold (Au)-------------------------- ------- . 2. 00 

Silver ( Ag)........ .. . . . . . . . . . . . . . . . . . . . . . . . . . 25 

Unaccounted for............................ . 14 

100.00 

It may be noted in connection with the foregoing analysis that 2 per cent of gold is equivalent to 40 pounds avoirdupois, or 541.4 fine ounces per ton. ' '( 

Analys s of Mohawkore. 

[W. D. Arnett & Co., analysts. Reported December 17, 1906.] 

1. 2. 3. 4. 5. 

- --- - - ---,--- 66.65 77.08 65: 87 63.63 

I 

51.31 6.05 5.18 4.29 3.96 7.80 9.27 4.96 6.20 11.62 11.28 

Silica ..... ........... ... ... ... . ..... . . .. ... · ... ... . .. ..... . ... . . .. ... ..... _ . _ . . _ . __ _ . .. .. . . .. . . Iron oxide .•............ ... .. . . .. _ . _ .... . ..... . . . _ .. ___ . ___ . _ .. __ . . . . _ .. . _ .. __ .. _ . ___ .. _ .. _ .. _ Aluminum oxide ... ______ ... _. _. _ ... . _. __ . _. _. __ _ ._ ._ . . __ ._ . .. ... ____ _ .. __ .. _. _. _. _. _ .. _. _ . .. . 

.054 .067 .04 .068 .072 ~:~::: ~~~:_-_ -_-_ ~ ~ ~ ~ ~:::: :::: ::::: :::: ::::::::: :: ::::::: :: :::::::::::: :: ::::::::::::: .18 .15 .22 .16 .34 Calcium oxide ...... ... _ .. ... ........ .... ... .... .. . ..... . ... . .. _ ....... _ .. :. _ .. . ... ___ .. ___ .. . .95 .71 .58 1.17 1. 34 Potassium oxide .... _ .. __ . .. ·_ ... .... _ . . . .. _ . ... _ . . _ . . __ .. .. . _. _ .. . .. _ . . . . _ ... .. ........ .. . . . . 2. 71 1.42 1. 66 1.50 1.82 Sodium oxide ... _ . . . .... .. . . .. . . · .. .. _ . . .... . . . _. _ .. ... . . .. . ..... .. ..... . ... .. __ __ ._ . _._ . _ . .. . 3.16 3.22 3.21 4.07 4. 66 1. 76 .37 1.548 1. 014 2.563 &~Yr~:::: :::: ::::: :::: :::: ::: :::::: ::::: ::: ::: :::: :::::: ::: :::::::: :::::::: ::: 1. 004 . 45 1.062 .633 • 733 Silver .... . . . ..... .... .. . . .. . ... ... ...... . .. . .. .. .. . ........ .. . . .... . .. . . .. . . .. .. ... .. . . .. ... . .078 .07 .084 .111 .185 Bismuth . .. ... . .. . ... __ ._ : .. . ..... . . .. . . ... __ ___ _ ... . .. .. _ ..... .. . ...... ___ . . _. __ . .. ___ .. . .. . .67 Trace. .82 1. 09 2.91 

Tellurium . .. . _ .. .. _ .. __ .. ...... . .. . ......... . ...... . . _ . .. _ ..... . . ·- .. ..... ... ..... _ .... . .. _ ... . 42 .14 • 74 1. 21 1.07 Water .... _ .. _._ . _ . . . __ . . __ . __ ... _. __ . . _. __ _ . . __ _ .. ____ ___ __ . __ . . . _._._ ._ .. . __ ____ : _· ____ _____ _ .71 .64 • 73 .63 • 76 Carbon dioxide ... .. _ . ..... .. .. ..... ... . ........ _ . ... .. . .. ..... . .... ....... _ .. _ .... . _ . _ . . _ . __ . . 61 .93 .66 . 72 1. 74 Sulphur .. . . ....... . . _ ... . .. ... . _ .. _ . . .... . .... . .. _ . _ . . . _ . .. . _ . . ... . .. _ . . __ __ . _____ . ___ __ .. . _ . 5. 76 4. 80 12. 69 8.86 11.98 

lclO. 036 1 100. 187 ---

100.354 100. 446 1 100.563 

a E. A. Collins, in his recent good description of the Combination mine (Min. and Sci. Press~ vol. 95, 1907, p. 398), refers to the ore as "a mixture 

of soft kaolinized material and hard dacite." The '' kaolinized material" is chiefly alunite. 

b Bull. U.S. Geol Survey No. 303, 1907, p. 35. 
PLATE X·XVI. 

PHOTOMICROGRAPHS OF ORES • . 

A. Very rich ore (G. 604). Combination mine. 

Right-hand side of seCtion shows altered dacite, consisting of quartz, kaolinite (k), aiunite, and finely disseminated 

pyrite: To the left of this is a band (about 3 inches wide in the illustration), consisting of finely divided native gold, 

famatinite, and bismuthinite in a gangue of minutely granular quartz. The gold, famatinite, and bismuthinite all 

appear black in the microphotograph, but over 75 per cent (:>£'these black areas represent gold. To the left of this band 

the quartz is a little more coarsely crystalline and contains bismuthinite and famatinite, with subordinate native gold. 

The specimen from which this section was made is shown in Plate XXIII, A. Nicols crossed. Magnified 40 diameters. 

B. Rich ore (G. 389). Combination mine, 180-foot level. 

The large black area, a little to the right of the center of the photomicrograph, is chiefly pyrite (p). The smaller 

black areas above it, howev:er, are famatinite ( t), inclosing particles .of native gold. Some of the smaller black specks 

are gold. alone. Tlie matrix or gangue is dacite, altered to an aggregate of quartz, alunite, and probably some kaolinite. 

A few-of the original quartz phenocrysts ( q) appear in the illustration, while larger and more characteristic ones occur 

in parts of the thin section not included in the photograph. Nlcols crossed. Magnified 40 diameters. 

PLATE XXVII. 

PHOTOMICROGRAPHS OF ORES. 

A. Rich ore (G~ 627). Intermediate or 309-foot level of Florence mine. The order of deposition is from the 

lower left-hand corner of the photomicrograph to the upper right-hand corner. The large black areas in the lower 

left-hand corner are i)yrite (p) and famatinite ( t), forming a crust on silicified dacit@ ( dq). The famatinite generally 

envelops the pyrite. Deposited upon these is a crust of fine granular quartz ( q) and irregular prismatic crystals of 

bismuthinite (b). Holes in section (h). No gold is visible in this particular section. Nicols crossed. Magnified 

40 diameters .. 

B. Ore (G. 87). January mine. Illustrates structure resulting from silicification of much brecciated dacite. 

The.blaGk areas are famatinite(t)and pyrite (p); in many places intergrown. These are surrounded by a very finegrained aggregate of quartz. The more coarsely crystalline quartz (q) contains a few vugs (h). Nicols crossed. Magnified 40 diameters. 

168 
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XXVI 

A. 

B. 

PHOTOMICROGRAPHS OF ORES. 

PAY SHOOTS AND ORES. 169 

Analyses of Mohawk ore-Continued . 

lVon Schulz & Low, analysts. Reported February 27, 1907.] 

I 6. 7. I 8. . 9. 

-Si-li-ca-.-.. -.-.. -.-.. -.-. . -.. -.-.. -.-.. -.-.. -. -.. -.. -.-.. -.-.. -.-.. -.. -.-.. -.-.. -.-.. -.. -.-.. -.-.. -.-.. -.. -.-. . -.--.. -.-.. '/ . . --.-.. -.-.. -.-.-.-. -.. -.. .. -. ·.-_-__ - __ ~ ~----;,; ~ 

Iron ... . ____ .. _. __ . __ .. .. . ..... ___ ._. __ . ___________ ._._ . . _. : _. _ .. __ ...... _ . .. _. ___ . ____ ._ . ___ . . . __ ... _._ 5. 55 5. 82 5. 35 5. 65 

Alumina ..... __ .. __ ... _ . .. .. __ . _____ . __________ . ____ . __ .. _ ......... _. _. _______________ . _______ . . . . . . . . . 5. 85 5. 02 5. 34 5. 25 

Manganese ..... __ .... _ ....... --· ____ .. ____ __ ___________ . __ .. ............... ___ . _________ _ .. _-·-.... .... .14 . 10 .14 . 12 Bismuth ...... . ........ .... ..... . .. . .... ..... . ... ................... __ ___ ____________________________ .. 1.20 1.25 1.27 1.32 

Lead .... ... _ .. . _. ____ . ___ __ ....... _ .. __ .. __ _ . ______ .. .... .. __ _ . __ .. __ _ . ___ . ___ .. __ . ___ . _. __ __ _ .. . .. __ . _ Trace. Trace. Trace. Trace. 

~~EF:r and cobalt·.·.·.-.-.-::::::::::::::::::::::::::::::::::::::::::::::::::: :1::::::::::::::::::::::::::::: 2

: ~~ 2

: g~ 2

: g~ 2

: g~ Arsenic ..... .. . ____ . __ __ ___ ...... _ ....... ............... _. ____ . _____ __ . ____ .. . . __ . _._. ____ . __ ._._._ .. . _ .14 .10 .15 . 14 An tirnony. __ . ...... .. _ . _ L _ . ___ . __ _ .. _ .. _ .. _ . ___ .. ________ . . __ . _ .. _ ...... J __ _____ • __ .•. _ .. ___ • ____ .... _ . 26 . 21 . 32 . 32 Gold ...... ___ . ___ . _ ............. __ . _ . _____________ . _ . _ ...... _ .. .... __ . _ . _ .. __ . ___ . __ ....... __ .. ____ __ . _ 1. 20 1. 21 1. 24 1. 22 

Silver ....... .. . .. __ .. ______ ... .. _ ... ................ .. .. _ ... ____ .. ___ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 . 23 . 23 . 24 Zinc. . .............. ... ... .. ........ . ... ........... . ............................... . .................... . 13 . 16 . 11 .19 

Magnesium oxide .. ... ............................................. . .... .. J.... .. . . ... .................. . 14 . 20 .12 . 19 

Calcium oxide ............... .. ...... .. .. . .. .. .......... .. ...... . ..... .. .... . ...... : ............ .. ..... . . . 45 . 42 . 41 . 47 Sodium oxide . . . ........... ...... .. .... .... . ............................. !. .......................... . . .16 . 15 .12 .14 

Potassium oxide ....... . .... ...................... . ... . ... .. . ........ ... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 . 22 . 28 . 22 Barium oxide ....... ... ....... .. ........... .. ........ ... ........... . ....... .. _...................... . .. . 10 . 27 . 24 .17 

Sulphur ..................................... ...... ............................. ... ... . .............. _ . . 5. 44 5. 33 5. 46 5. 38 Phosphorus ................ ... ....... _ .................... .. .... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 06 . 08 . 07 . 08 Tellurium ........... . .................. . .. . .. . .............. _.......................................... 2. 03 2. 21 2. 07 2. 11 Moisture (at 110° C.) ....... . . ........ ·_ .. . ......................... . ... _ . . ... . ......... . ............ , ... . 02 . 01 . 04 . 02 Undetermined a....................................................................... . ................ 7.15 7.19 7. 77 6.19 

1oD.OO 1oD.OO -wo:ool 100. 00 

a This is probably in part combined water and in part oxygen combined with various bases.-V. S. & L. 

All of the foregoing analyses were made on material recovered from thieves or "highgraders." Those which follow were made on or~ taken by Mr. Thomas from the 220-foot level 

of the Hayes-Monnette workings. 

Analyses of Mohawk ore. 

[Von Schulz & Low, analysts. Reported April 22, 1907.] 

10. 11. 12. 13. 14. 15. 

---------------

Silica ................................... . ..... ... .. ............................... . 64.28 68.46 67.27 68.40 67.20 67.98 

Iron .. ... . .......................... .. .............. · ............... . ..... _,_ ....... . 6.92 5.21 5. 82 5. 61 5. 47 5.28 

Alumina ...................... . .. .......... . ....... ... ........................... . 6.18 5.04 5.65 5.44 5. 82 5.86 

Manganese .............. ..... ......... _ ... ..... .. ............................. . .. . . 12 . 12 .18 .15 .10 .11 

Bismuth ... . .......................................................... . .......... . 1. 22 1. 25 1. 36 1. 21 1.18 1. 20 Lead ........................... ..... ...... ........ . .. ....... . ............ . ....... . Trace. Trace. Trace. Trace. Trace. Trace. 

~~E~:r and cobalt·.~::::::::::::::::::::::::::::::::::::::::: :: :::::::::::: :::::::: 2.35 2. 42 2.29 2. 49 2.36 2.39 . 06 .05 .08 . 07 .07 .06 

Arsenic .................... .. ............................. ..... ... .. .... . ... . ..... . .11 .10 .15 . 12 .15 .15 

Antimony .. . ................. . . ...... . ....... ............. ... ........... : . . ...... . Gold ..... .. ........................ . .............. ... .. . .................. . ....... . . 30 .25 .36 • 28 .26 .35 1. 22 1. 30 1. 49 1.33 1. 37 1. 34 Silver ... . .. : .............. . ... . ................................ . ......... ! ........ . .28 .25 .29 .25 . 25 .26 

Zinc ...... ....... .... ................... ....... . .... . . .... .. . ............... . . .... . .14 .11 .16 .19 .17 .14 

Magnesium oxide ....... . ... .......... .. ............ .. ................ . .... ...... . . Calcium oxide .. ................. . .............. ........... ........... . ........... . .19 .17 .20 .19 .10 .18 . 49 . 45 . 45 . 42 . 46 .46 

Sodium oxide ........... . ............ .. ........ ... ................................ . .12 .12 .15 .14 .11 .14 

Potassium oxide ...... ...... . ... ... _ ..................................... l ........ . . 27 .26 .26 . 25 .24 .27 

Barium oxide ....................... . .... _ ..... .. ........... . ..................... . .19 . 21 .14 . 21 .24 .20 

Sulphur ................................ .. ..... . .. . .. ........ ........... . .. . ...... . Phosphorus ................................. .. ........................... _ . ...... _ . Tellurium ......... . ................................. . .... _ ......... . ............. . 

5. 39 5.24 5.26 5.48 5. 44 5. 45 . 07 .08 .05 .06 .06 .08 

2.11 2.10 2.27 2.06 . 2.14 2.12 

Moisture (at 110° C.) ................................................ . ............. . .03 .02 .02 .04 .03 . 03 Undetermined ............ .... .... .. .. . .... .. . .. ........ ........... ........... .... . 8.16 5. 79 6.10 5. 61 6. 69 5.98 

. I ------------------- 100.00 100. oo I 100.00 100.00 100. 00 100.00 

PARAGENESIS. 

1 'rhe paragenesis or order of formation of the minerals in the unoxidized ores is, as in most 

ore bodies, complex. In general the deposition of pyrite, quartz, and alunite appears to have . 

gone on throughout the entire period of ledge formation. On the other hand, there is abundant 

evidence to show that much of the gold, tellurides, bismuthinite, goldfieldite, marcasite, and 

famatinite were introduced after considerable progress had been made in the special kind of 

rock alteration which produced the ledges. It appears that some at least of these siliceous 

masses were fractured and that the richest ores were deposited in the shattered portions. 
170 THE GEOLOGY AND ORE :OE;POSITS OF GOLDFIELD, NEVADA. 

The following sequences have been observed in the rich crustified ore: 

Combination mine: (1) Altered latite; (2) marcasite and goldfieldite; (3) gold and quartz; ( 4) famatinite and bis- muthinite. 

(1) Altered dacite; (2) pyrite; (3) quartz; (4) pyrite; (5) alunite. 

(1) Altered dacite; (2) gold and quartz; (3) famatinite; · (4) bismuthinite and quartz. 

(1) Altered dacite; (2) gold and quartz; (3) famatinite, bismuthinite, famatinite, and gold in 

quartz; (4) pyrite and alunite. 

Florence mine: (1) Altered andesite or dacite; (2) pyrite; (3) famatinite and gold; (4) bismuthinite, gold, and quartz 

with some pyrite and famatinite. 

(1) Altered dacite; .(2) pyrite; (3) famatinite and quartz. 

(1) Altered dacite or andesite; (2) pyrite; (3) famatinite; (4) bismuthinite and quartz; (5) pyrite, 

quartz, and alunite. 

Mushett lease: (1) Altered dacite; (2) goldfieldite; (3) famatinite, bismuthinite, and quartz; (4) pyrite, sphalerite, and alunite. 

(1) Altered dacite; (2) pyrite; t3) sphalerite; ( 4) alunite. 

(1)'Bismuthinite; (2) pyrite, sphalerite, and alunite; (3) sphalerite; (4) alunite. 

(1) Bismuthinite, telluride (?), and famatinite; (2) sphalerite; (3) pyrite and alunite. 

Engineers' lease: (1) Altered andesite; (2) famatinite; (3) pyrite and famatinite in massive aggregate. 

(1) Altered andesite; (2) famatinite; (3) bismuthinite, quartz, and a little gold; (4) gold and quartz; 

(5) gold, bismuthinite, and quartz. 

(1) Altered andesite; (2) famatinite; (3) gold and quartz; (4) bismuthinite and quartz; (5) gold and 

quartz; (6) quartz; (7) alunite. · 

Rogers lease: (1) Altered andesite; (2) gold and quartz; (3) bismuthinite, famatinite, gold, and quartz. 

(1) Altered andesite; (2) gold and dark quartz; (3) white quartz. 

Little Florence lease: (1) famatinite; (2) bismuthinite and quartz; (3) gold and quartz; (4) pyrite and alunite. 

(1) pyrite, quartz, and alunite; (2) famatinite; (3) bismuthinite and quartz. 

Consolidated Red Top lease: (1) pyrite and quartz; (2) famatinite; (3) pyrite or marcasite, alunite, and barite. 

Attempts to fit the foregoing observations into a single definite general sequence have not 

been successful. In some specimens there are repetitions not found in others. In some specimens certain of the minerals have formed in de.finite succession while in others these same 

constituents have crystallized together in a single crust. T,he altered rock on which the first 

crust is deposited generally contains abundant alunite and disseminated pyrite. In some 

varieties of ore the boundary between this nucleus ·and the first crust is definite (see Pl. XXIII) ; 

in others there is more or less gradation, the disseminated pyrite in some cases becoming more 

abundant near the surface of the rock fragment and merging with the first pyritic crust. As 

a rule famatinite has formed before the bismuthinite, although both minerals are indiscriminately distributed through some crusts. · When marcasite is present as a constituent of rich 

ore it is closely associated with famatinite or goldfieldite. The free gold and bismuthinite are 

generally in close association, although in some specimens the greater part of the gold :ls of 

earlier generation than the bismuthinite and in others is later. Sphalerite, galena, and marcasite, where present with rich ore, belong to a period· of deposition later than that of the gold 

or gold-bearing constituents. 

MINERALOGICAL CHARACTER OF THE OXIDIZED ORES. 

Oxidized ores have supplied a large part of the gold produced, and in some mines, particularly the Sandstorm and Kendall, no sulphide ores are as yet known. As a rule the oxidized 

ore is a soft, shattered, more or less earthy material usually stained brown by oxide of iron. 

Fragments of rusty porous quartz are mingled with kaolin, alunite, gypsum, alum (halotrichite), 

oxide of iron, and various earthy mixtures of no definite mineral composition. Some of the 

rich ore, as in the Sandsto:r:m mine, is a nearlly white, impure kaolin, gritty from the presence of 

minute crystals or grains of quartz, and containing all through it abundant specks of free gold. 

Barite, in crystals up to an inch in length, is abundant in this-ore, but may be an original constituent. In the Red Top mine some of the :richest ore being taken out in 1905 was a firm gritty 

ocher, of bright yellow color, containing abundant very fine particles of gold. This yellow 
PAY SHOOTS AND ORES. 171 

material is perhaps in part jarosite.a In the January a:nd Combination m.ines some of the 

most characteristic rich ore consists of porous rusty quartz (silicified dacite), in which the 

pores and crevices are partly filled with yellow, earthy limonite and tiny pearly scales of 

bismite, the oxide of bismuth. In some specimens these scales form pseudomorphs after 

bismuthinite. They are usually a sign of rich ore, but are occasionally found in low-grade {)r 

barren material. Halotrichite, a member of the alum group, and alunite are rather abundant 

in the oxidized ore of the January mine. In the J;D.ines .at Black Butte the richest oxidized ore 

usually shows little· greenish-yellow specks of a ferric tellurite, which Dr. W. F. Hillebrand 

has determined to be either emmonsite or durdenite. The pres~nce of this mineral shows . 

that the original sulphide ore contained ~ne or more tellurides. Tellurite, a honey-yellow 

crystalline mineral, which is the oxide of tellurium and should not be confused with the salts of 

tellurous acid known to chemists as tellurites, was noted in a partly oxidized telluride ore from 

the Goldfield-Belmont mine near Black Butte. Melanterite (hydrous ferrous sulphate), in 

some cases mixed with a very little chalcanthite (hydrous copper sulphate), occurs in the partly 

oxidized ore of the Combination and Florence mines. 

The valuable constituent of the oxidized ·ores is native gold. Native silver and halogen 

compounds of silver have not, so far as known, been noted in the mines of the Goldfield group, 

but cerargyrite and probably a little embolite occur in some of the Diamondfield ores. The 

gold, which has undoubtedly undergone some concentration in the process of oxidation, is in 

most of the ores finely divided, and even in the richest ores might easily be overlooked by one 

not accustomed to its appearance. Some of the Sandstorm ore on close examination resembles 

.a fine, somewhat rusty sandstone having gold as the cementing material. 

VALUE OF THE ORES. 

As a ·whole. the ores thus far mined at Goldfield are unusually rich. Prior to January 1, 

1905, the Combination mine shipped a total of 1,166 tons of ore, having an average assay value 

-of $419 per ton. This ore averaged 20.22 ounces of gold and 2.68 ounces of silver per ton. 

The best ore from the mine was taken from the small No. 3 shait, which afforded about 309 

.tons, valued at $159,000, or $514 per ton. Approximately 59 tons of this averaged, according 

to Mr. Edgar A. Collins, 54.8 ounces of gold per ton, which is equivale:o.t to a value of nearly 

.$1,100. This ore, which was oxidized, contained only 1 ounce of silver to each 20 ounces 

.of gold. 

J. E. Spurr b estimated in 1904 that the average value of the ores mined in the Goldfield 

district was from $200 to $300 per ton or more. In 1905 the average value of shipping ore was 

about $200 per ton and of milling ore from $40 to $50 per ton. 

Shipments averaging ov~r $1,000 per ton are by no means uncommon. One of 14! tons 

·from the Kendall mine is said by Spurr c to have yielded $45,783 net in the preliminary milling, 

while the tailings still contained about $1,000 a ton. A shipment of sulphide- ore from the 

Florence mine, made in 1905, just before the date of visit, averaged 100.8 ounces of gold, 3.5 

ounces of silver, and 3.5 per cent of copper, giving a gross value of over $2,000 per ton. The 

silver in this shipment was unusually high for an ore from this part of the district. 

Some extremely rich ore was obtained from the Reilly lease; occasional specimens several 

inches in diameter being nearly one-half gold. Several shipments from this· lease are said 

to have assayed $20,000 a ton, and, according to Mr. Frank Oliver, one lot of over 4 tons was 

worth $6,000 to $7,000 a ton. · 

Some of the ore from the vicinity of Diarnondfield carries a greater proportion of silver 

than that from the mines near Goldfield. A specimen containing famatinite, taken from the 

Quartzite mine of Black Butte, yielded on assay 11.06 ounces of gold and 115.70 ounces of 

silver per ton. Samples of mineralogically similar ore _from the Goldfield-Belmont mine assay, 

a Spurr, J. E., Ores of Goldfield, Nev.: Bull. U.S. Geol. Survey No. 260, 1905, p . 137. 

b Bull. U.S. Geol. Survey No. 260, 1905, p. 136. 

cOp. cit., p. 136. 
172 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

silver 

according 

per 

to Mr. W. H. Blackburn, yielded 1 to 2 ounces of gold and from 30 to 60 ounces of 

mine. 

ton. A similar high proportion of silver is found in the ore of the Jumbo Extension 

one 

Some bunches of ore in the Blue Bull n1ine also show a very high proportion of silver, 

Bull 

assay giving 382 times as much EJilver as gold.a Some ore from the fiat lease on the Blue 

ever, 

ground assayed 174 ounces of silver and 4 ounces of gold to the ton. Such ratios, howare very uncommon. 

dized, 

Although, as is to be expected in a new district, much of the very rich ore has been oxiyet some of the sulphides in the mines near Goldfield have exceeded in value anything 

found 

and 

in the oxidized zone above them. Such was the case in part of the Combination mine, 

of 

in the Reilly ·workings. A still more striking example of the wonderful richness of some 

discovered 

the sulphide ores· is furnished by the Hayes-Monnette Mohawk lease. From the ore body 

Lead Company, 

by these lessees there was shipped in January, 1907, to the Selby Smelting and 

ore was 

the richest carload of ore ever sent out of the district. The net weight of this 

per 

95,537!- pounds. It assayed .(dry) 609.61 ounces of gold and 75.38 ounces of silver 

an ounce, 

ton. The gold was paid for at $20 an ounce on the assay return; the silver at 68! cents 

per 

after deduction of 5 per cent for loss in smelting. Cost of treatment was $10.50 

proceeds 

ton, sampling and assaying $150, refining $327.22, and expressage $8,810.50. The net 

Even 

received by the shippers from t~e smelter were $574,958.39 for the single car of ore. 

richer ore (620 ounces of gold to the ton) was being· sacked under the old Reilly workings,. 

on the 280-foot level of the Combination mine, in 1908. 

of 

One of the richest carloads of unsorted ore shipped from the district was from the lease. 

1907. 

the Florence 

This 

Annex Company on the Cornishman and Firelight Claims in the latter part of 

lot weighed 40 tons and assayed.$948 per ton, corresponding 

of $37,920. 

to a total gross value 

AREAL VARIATIONS IN THE ORES. 

common, 

Although all of the Goldfield ores have certain mineralogical and chemical features in 

Some 

there are some well-marked differences in the ores from different parts of the district. 

of the most interesting and important changes are those which may be observed in passat 

ing from the Rogers lease at the south end of the Goldfield bonanza belt to the Mushett lease 

ore 

the north end, a distance of a little less than a mile. By this it is not meant that no rich 

productive 

occurs north or south of these lea,ses, but merely that these mark the limits of the most 

ore of 

area as at present known. From the Rogers lease to the Combination mine the 

slight 

the rich pay shoots is all much alike, although as a rule the product of each mine has 

individual peculiarities whereby one thoroughly familiar with the different workings 

can identify it. The essential characteristics of this ore are the presence of visible native gold,. 

so distributed through the flinty quartz as to form the dull yellow crusts already described, 

the presence of abundant bismuthinite and famatinite, and the absence of recognizable telluRogers 

rides, sphalerite, or galena. The quartz varies in color from nearly white, as in some of the 

ore, to a dark gray, as in some of the Engineers' ore. The famatinite or bismuthinite 

are not equally prominent in all of the ore, nor is the relation of the gold to these minerals 

most 

exactly the same in each pay shoot. The gold in some stopes may occur in the hardest and 

Combination 

flinty parts 

mine, 

of the quartz; . in others, as in the Reilly stope on the 280-foot level of the. 

crul!lbled 

part of the free gold may be in a mixture of alunite and pyrite which can be. 

in the fingers. Notwithstanding 

Reilly, 

these differences the rich ore of the Combination, 

With 

Florence, Engineers', Little Florence, and Rogers mines is as a whole very similar. 

the opening of the Mohawk mine ore of a different type was found. In the typical 

· 

mines 

rich Mohawk ore native gold, bismuthinite, and famatinite are less conspicuous than in the 

to the south. So far as I am aware this mine has never produced specimens showingsuch broad bands of finely divided yellow gold as have come from the other mines mentioned 

and as are figured in Plates XXIII and XXV. Instead, the best ore has the dark telluric 

may 

crusts 

or 

described 

may 

on page 116, .which are mixtures of goldfieldite and marcasite. Free gold. 

not be visible. 

a Spurr, J. E., op. cit., p. 137 (footnote). 
PAY SHOOTS AND ORES. 173 

The change between the typical Combi.nation ore · and the typical Mohawk ore is not 

entirely abrupt, for ore. of the Mohawk character has been found in what is known as the 316 

stope on the 280-foot level of the Co.lllbination mine. From the same stope, also, has come ore 

intermediate between the two types. 

North of the Mohawk mine there is a change to ore of the Mushett type, in which goldfieldite is associated with sphalerite and a little galena. 

From the Mushett lease to the mines near Diamondfield there is an interval of about 3 

miles, in which no rich sulphide ores of any consequence have been found. Mineralogically 

the Diamondfield ores resemble those of the Mushett and neighboring leases rather than those 

of the :mines south of. the 1\tfohawk. Most of them, however, are soft c.rushed masses with 

little of the interesting crustification which is so marked a feature near Goldfield. The proportion of sulphides to gangue is less at Diamondfield than in the Mushett lease. 

East of the Rogers lease is another gap of three-quarters of a mile to the Gold Bar and 

Victor :mines, which have still another variety of ore. The best of this is of relatively low 

grade. The cupriferous constituent, which is abundant, is apparently nearer to enargite than 

to famatinite. No tellurides have been recognized, and neither visible native gold nor bismuthinite is common. 

OBSERVED CHANGES IN DEPTH. 

Observations to determine what changes, if any, take place in the unoxidized ores with 

increase of depth are limited to a vertical range of about 450 feet (137 meters), which is the 

distance from the base of the oxidized zone to the bottom of the Mohawk nLine. Within this 

rather short range the mineralogical changes are not very :marked~ The minerals associated 

with the very rich ore at depths of 200 or 300 feet (61 or 91 meters) have been found also at 

lower levels. Alunite, as a constituent of the altered rocks, is as abundant in the deepest 

parts of the ledges yet reached as it is nearer the surface, and it appears from this that there 

was no essential change in the general chemical character of the ore-bearing solutions. As a 

soft interstitial filling, however, the mineral is slightly less abundant on the 600-foot level of 

the Mohawk than it is at higher levels in this and other :mines. The explanation of this is 

thought to be physical rather than chemical. It is to be expected that spaces formed by 

fracturing in the deeper parts of a ledge would be smaller and less numerous than where the 

strained material is under a lighter load. 

Some pay shoots have shown a decided diminution in value before reaching a depth of 

500 feet (152 meters), but the changes in both horizontal and upward directions from the 

kernel of a bonanza may be fully as notable, and where deposits have shown themselves to be 

so irregular as those of Goldfield caution is prescribed in deducing a general law from a few 

examples. To assume, because one pay shoot ends at a depth of 200 feet (61 meters), that 

no more ore will be found below it would, in this district, be much like relinquishing as useless 

all prospecting beyond the horizontal limits of the same body. From the condition of the 

mines in the latter part of 1905 an observer would have had some ground for supposing that 

little if any ore of 5-ounce or bett~r grade would be ~ound belJ~ a depth of 300 feet (91 meters). 

Subsequent events have shown that such a sweeping concl 1

swn would have been erroneous. 

A tendency, however, toward a decrease of tenor below a depth of about 300 feet was noted 

in the preliminary report on the district, a where it was also ~tated that "there is considerable 

evidence in favor of the conclusion that ores of the grade nbw required for shipment are not 

likely to extend to as great a depth as 1,000 feet." These fi~ures obviously were not intended 

to represent actual depths below the collars of individual shafts, but are round figures referable 

to a mean or generalized surface. Later observations are in ull accord with this earlier statement, which is far from an assertion that no rich ore occurs /.at a greater depth than 300 feet 

(91 lneters). In the Mushett lease very rich ore is known Ito extend to a depth of 429 feet 

(131 meters) and in the Rogers lease to 550 feet (168 mete~s). These deposits, however, are 

thus far rather exceptional. There is good ore on the 600-f<i>ot level of the Mohawk, but it is 

a Bull. U. S. Geol. Survey No. 303, 1907, p. ~. 

I 
174 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

of much lower grade than that shipped from the Hayes-Monnette stope above the 250-foot 

level. Ore has recently been found also at 718 feet (219 meters) in the Hazel-Goldfield lease, 

but its character and quantity are as yet undetermined. 

On the whole, observation indicates a general although not uniform decrease in the tenor 

of the ores in the deeper workings. The gold, goldfieldite, bismuthinite, and, to a less extent, 

famatinite. become less conspicuous~ while pyrite is relatively more abundant. The bearing of. 

this change and its interpretation as regards the future development of the mines will be considered in a subsequent chapter. 

ORIGINAL DEPTH OF THE ORES NOW VISIBLE. 

It is important, before . taking up the problem of genesis, to obtain if possible some idea 

of the relation of the present surface to that which existed when the ores were precipitated. 

How many vertical feet of rock, in other words, have been removed since ore deposition began~ 

As a rule the investigator of a mining district is fortunate if he can form an estimate of such 

erosion that he is reasonably sure comes within a few thousand feet of the truth. At Gold-

. field the data permit a probable approximation within a few hundred feet. 

The dacite near Goldfield rests partly on the Milltown andesite, but mostly on latite. 

Immediately after its intrusion, therefore, the dacite may have been covered by the greater 

part, possibly 700 or 800 feet (213 or 244 meters), of the Milltown andesite. This cover was 

doubtless much broken by the force of the intrusion, and in consequence was easily eroded. 

The presence of abundant dacitic fragments in the basal part of the Siebert formation between 

Goldfield and Columbia indicates that before the lacustral epoch closed the dacite had been. 

laid bare and was being actively eroded. The presence of this coarse littoral material suggests 

further that the site of the future mines· was not one of the deepest parts of the lake, but for a 

time at least was unsubmerged land. At the close of the lake epoch, therefore, the present 

productive area of dacite must have been buried under considerably less than the 1,000 feet 

(305 meters) of sediments estimated on page 68 as the maximum local . thickness of the formation. With the disappearance ·of the lake, erosion began, and this may have further thinned 

the overlying sediments before ore deposition ceased. At the most, however, this erosion did 

not reduce the surface below the general level of the peneplain at the base of the Spearhead 

rhyolite (see Pl. VIII, sections D-D' and E-E'), since the completion of the peneplain, as shown 

by the alunitized. fragments in. the Pozo formation already referred to, must have been subsequent to ore deposition. A rough restoration of this plain over the site of the present mines 

would carry it about 300 feet (91 meters) above the existing surface of the dacite, indicating 

at least that amount of erosion since the ores were deposited. 

On the whole, therefore, and without referrence to any regional changes of level, it appears 

that the surface of that part of the district containing the principal ore bodies was not more 

than 1,000 feet (305 meters) higher than at present, and the difference may have been some 

hundreds of feet less. The general geologic relations of the deposits, therefore, indicate 

comparatively superficial origin. 

The structure and the mineralogical character of the deposits point to the same conclusion. 

The intricacy, irregularity, and lack of persistency of the fissuring are indicative of rupture 

under small load. The change in tenor of the ores at moderate depths is suggestive of deposition controlled in part by proximity to the surface. The presence of cinnabar and native 

sulphur not, it is true, in the ore deposits themselves, but in the same province or region, is, 

as De Launay a has shown in his study of the Italian metallogenetic provinces, and Villarellob 

for the metalliferous regions of Mexico, in harmony with the view that the ore deposits were 

formed in a comparatively superficial zone. The presence of abundant antimony, bismuth, 

and tellurium, and the extraordinary richness of the Goldfield ores have similar significance. 

Like the deposits at Cripple Creek, those of Goldfield exhibit a mineralogical character that 

a La metallogenie de l'Italie: Cong. geol. intern., Mexico, 1906, Com pt. Rend., vol. 1, 1907, p. 561. 

b Sur le remplissage de quelques gisements metalliferes: Cong. geol. intern., Mexico, 1906, Compt. Rend., vol. 1, 1907, p. 548. 
PAY SHOOTS D ORES. 175 

is suggestive o origin through processes connecte with volcanism and active at moderate or 

slight depth. The original surface at Cripple Crkek was probably from 2,000 to 5,000 feet 

(610 to 1,524 meters)" above the present one. ihe erosion at Goldfield has certainly been 

much less. 

AGE OF THE 

The gold deposits are obviously younger tha the dacite. As the postdacitic rocks have 

been eroded from the productive part of the dis rict the relation of the ores to them is not 

directly shown. · 

On the north slope of Mira Mountain, and at few other places along the southern ~order · 

of the district, the beds of the Siebert formation fhow some alun.itic alteration similar to that 

characteristic of the Goldfield ledges. A few mil s west of Goldfield, between :Mesa and 1!ontezuma Peak, the Siebert beds are sufficiently mi eralized to have induced considerable prospecting at the Red Peak, Houlihan, and Sassy Sal mines. Some of the beds contain disseminated pyrite, and one layer, apparently once pucliceous, has been changed to a mass of· opal 

and chalcedony. The alteration appears to have een effected by thermal or solfataric action. 

Whether alunite also occurs at this locality is nol known, although the appearance of some of 

the altered rocks suggests its presence. Near Cu~rite, about 12 miles south of Goldfield, both 

alunite and sulphur occur in association with op~lized material similar to that just described 

and supposed also to belong to the Siebert formarion. The depo. sition of the sulphur and the 

associated alteration are believed to be indicative of solfataric action. 

It thus appears that considerable minerali~ation occurred after the deposition of the 

Siebert formation, and although, so far as is kno,n, no valuable deposits of gold are contained 

in these beds there is a suggestion of similarity between the mineralizing processes which have 

affected that formation and those recorded in the Goldfield ledges. 

No fragments of alunitized rock or of ore h ve been found in material known to belong 

to the Siebert formation. This purely negative evidence is, of course, not of much value, 

but it is mentioned in order that observers in fut re may be on the watch for such ~n occur.:. 

renee. A fragment of dacite with alunitized fe dspars, ·or, better still, a bit of the characteristic Goldfield ore found in any shaft known o be in unaltered Siebert beds, would show 

that the ·ore deposits were formed before these deposits were laid down. Such evidence as 

is available, while very unsatisfactory, favors the view that the ore deposits are younger than 

the lacustral sediments. . l 

On the other hand, the Pozo formatibn is ertainly younger than the ore bodies, for as 

exposed near Meda Pass the partly consolidated ~ravels of this deposit contain abundant fragments of alunitized dacite. The Spearhead rhyqlite and the Malpais basalt are th.us yo_unger 

than the ores. I 

How merely tentative is the application of the Tertiary chronologie scale to the Goldfield 

deposits has already been pointed out. I_n terms of this provisional usage the age of the ores 

is late Miocene or early Pliocene. 
CHAPTER XIV. 

:METASOMATIC PROCESSES.a 

TYPES OF ALTERATION. 

Three types or stages of alteration are recognizable. Where the chemical activity has 

been most intense the rocks have been changed to porous, fine-grained aggregates consisting 

essentially of quartz. This is the material of which are composed the hundreds of craggy 

points and ledges that are characteristic of the topography of the district. Although most 

of these ledges, so far as known, contain no ore bodies, yet until recently no ore has been found 

that was not in or alongside such quartz rock. Some of the discoveries made in 1906, however, 

show that very rich bodies of ore may occur at places where there is no siliceous outcrop. 

The second type of alteration is one in which the rock is changed to a comparatively soft, 

light-colored mass of quartz, kaolinite, alunite, and pyrite. At any given locality the boundary 

between the rocks representing the two kinds of alteration may be fairly sharp; but the proportions of quartz, kaolinite, and alunite vary widely, and consequently, over the field at large, 

gradations in composition and hardness may be found between these two typical metamorphic 

products. Both types are usually associated with the ores and are most conspicuously displayed 

over a belt of country stretching east from Goldfield past Preble Mountain. This mountain, 

in fact, is composed chiefly of andesite and dacite that have undergone alteration of the kinds 

described. 

The third type of alteration has effected less conspicuous results than the other two, and 

its products are not closely associated with the ores. It consists in the development of calcite, 

quartz, chlorite, epidote, and pyrite at the expense of the original minerals and groundmass, 

and is thus propylitic in character. Rocks which have undergone this form of alteration, 

chiefly andesite, latite, and dacite, still retain something of their original color and texture, 

the principal external sign of change being a greenish tint instead of the usual dark gray of the 

fresh rock, and a lack of luster in the phenocrysts. 

The propylitic type is rather sharply marked off from the alunitic type by the presence of 

calcite and by the usual absence of alunite, these minerals having been observed together only 

at one place, on the east slope of Vindicator Mountain, where very minutely crystalline calcite, 

sericite, and probably some kaolinite have been found associated with much larger crystals of 

alunite in altered rhyolite. The occurrence together of alunite and calcite, apparently developed simultaneously, shows that the alteration took place under conditions which did not permit 

the free escape of carbon dioxide. It is scarcely conceivable, for example, that calcite could 

form in the presence of sulphuric acid percolating down from an overlying deposit of oxidizing 

pyrite. 

The alteration of the alunitic type is not confined to the vicinity of known ore bodies, but 

is prevalent over wide areas not recognized as ore bearing. The general relation of ore bodies 

to alunitization is shown in figure 19, in which the area affected by alunitic alteration is indicated with as much accuracy as is possible where there is no real boundary to be shown. 

COMPARISON OF FRESH AND ALT~RED DACITE. 

Inasmuch as the largest and richest ore bodies are in the dacite and as the rock is uniform 

in character, it was chosen for a close study of the alteration effected by the ore-depositing 

agencies. Such comparison is especially favored by the fact that the most intense alteration 

(Econ. 

a The 

Geology, 

greater 

vol. 

part 

2, 

of 

1907, 

this 

pp, 

chapter 

667-692). 

was published as a paper entitled "The association of alunite with gold in the Goldfield district, Nevada" 

176 
METASOMATIC PROCESSES. 177 

is often local, and consequently it is possible to obtain specimens ·of fresh and ~ltered rock 

within moderate distances of each other. The two specimens of dacite analyzed and compared 

were taken about 1 t miles (2 kilometers) apart. 

The fresh dacite has been fully describedon pages 55-88. 

I 

I 

·····················-!-················ ..................... L ...... . I . 

.. .... J .. .................... ~ ......................... . I . 

I . ............. ,:-.......................... ..,.~/·/-.,f·/·,-r-/ ,'--!-- ...... j ........................... , .............. ......................... (...... • ..... , ...................... ! ................................. . 

I 1 

·~~ b 

b 

Tognoni Sprs 

,' ~~:Vindidator Mtn ; I •.••.•...••. ( .................................. ._,..,.,1}·.-:-r .. ,r .. ~~ ....... ~············ ~:~Yd. ...... ~~~-~n ·t ·-· ..... ·:············· ·······~········ 

«'i I : ~ 

i"~~~~u ~ 

............ i··· ........... .. 

···········~······· ................................ ···~···· ........... .. ................... ·i .. I l 

1 ............................. j... . .. .. .. ...... 1 .. · ...... · .... · ...... ~ 

Generally ~ alunitized areas Known productive areas. 

FIGURE 19.-Diagram showing the portions of the Goldfield district in wnich the rocks have undergone extensive alunitic alteration. 

The altered dacite, of which a chemical analysis by Mr. George Steiger is given under 2 

(p. 181) was t~ken from the 230-foot level of the Combination mine, in a place to which oxidation had not extended. The original water level in this mine appears to have been at about 

130 feet from the surface, near which depth the oxidized ore gives place to sulphides. The rock 

analyzed is the typical wall rock of this and adjacent mines. 

79145-No. 66-09--12 
PLATE XXVIII. 

PHOTOMICROGRAPHS oF ALUNITIZED RocKs. 

A. Vindicator rhyolite (G. 26). Summit of Columbia Mountain. Shows alteration of feldspar phenocrysts, 

probably chiefly orthoclase, to aggregates of alunite (a}. The originally glassy groundmass (g) is now a :fine-grained 

aggregate of quartz, kaolinite, and alunite. The black areas in the photomicrograph are an opaque white substance 

resembling eucoxen~, an alteration product of ilmenite. There are two small phenocrysts of quartz (q). Holes 

in the section are indicated by H. Ordinary light. Magnified 40 diameters. 

B. Same as A. Nic.ols crossed, bringing out more clearly the aggregation of the secondary minerals. 

C. Dacite (G. 398). Combination mine, 230-foot level. Typical country rock showing large alunite pseudomorph after labradorite. With the alunite (a) is an isotropic material, probably opal (o). The black areas are mainly 

pyrite, in part disseminated -through the groundinass and in part aggregated into pseudomorphs after biotite and 

other ferromagnesian constituents. The groundmass (g) is a fine-grained aggregate of quartz, alunite, and pyrite. · 

Holes in section (h). Ordinary light. Magnified 40 diameters. 

D. Same as C. Nicols crossed. · . \ 

PLATE XXIX. 

PHOTOMICROGRAPHS SHOWING ALTERATION OF DACITE. 

A. Fresh dacite (G. 97). Half a mile northeast of Columbia Mountain. See chemical analysis on page 56. Contains phenocrysts of labradorite (1)~ biotite (b), augite (not shown), and abundant smaller crystals of hornblende (hb) 

in a hyalopilitic groundmass. Hole in section (h). The rounded and embayed quartz phenocrysts are not abundant. 

None appears in the part of the section photographed. The labradorite phenocryst at the bottom of the :figure exhibits 

a characteristic border of glass inclusions. Ordinary light. Magnified 40 diameters. 

B. Altered dacite or ledge matter (G. 712). Red Top mine, 160-foot level. The original structure of the dacite is 

still recognizable, but the rock is now an aggregate of quartz and pyrite. The feldspars, or their pseudomorphs, have 

been carried away in solution, leaving cavities (h). The black areas and specks are pyrite, in part aggregated as pseudomorphs after biotite and hornblende. The original quartz phenocrysts ( q) are alone unchanged. The former hyalopilitic groundmass has become a fine granular aggregate of quartz, sprinkled with pyrite. Nicols crossed. Magnified 

40 diameters. 

C. Alter~d dacite country rock (G. 393). Combination mine, 230-foot level. See chemical analysis on page 181. 

Rock is entirely recrystallized, with the exception of the quartz phenocrysts (not shown) to an aggregate of quartz, 

alunite (a), kaolinite, and pyri~e. The rock, when examined with low power, still shows traces of its original structure. 

Original ferromagnesian constituents are represented by patches of pyrite and feldspars by areas of alunite. Such an 

aggregate of alunite appears at the bottom of the figure. Nicols crossed. Magnified 40 diameters. 

D. Altered dacite (G. 634). Florence mine, 200-foot level. Large areas of the section, seen under low power, 

show vestiges of original structure. The part of the section figured illustrates chiefly the development of alunite 

throughout the groundmass and the crystallization of this mineral with pyrite (black). The rock consists essentially 

of alunite, quartz, and pyrite. Ordinary light. Magnified 40 diameters. • 

PLATE XXX. 

PHOTOMICROGRAPHS ILLUSTRATING ALTERATION OF RoCKS. 

A. Dacite country rock (G. 653). Florence mine, 350-foot level. The phenocrysts of labradorite have been 

altered to aggregates of alunite (a) and a veinlet of alunite extends diagonally across the section. The black spots 

are almost all pyrite. The groundmass (g) is an aggregate of quartz, alunite, kaolinite, and pyrite. Ordinary light . 

. Magnified 40 diameters. 

B. Ledge matter (G. 397). Combination mine, 230-foot level. Low-grade ore. Illustrates extreme alteration of 

shattered.or crushed dacite. Original structure obliterated. The black areas are pyrite in a gangue of microcrystalline 

quartz. · "Nicols crossed. Magnified 40 diameters. 

C. Altered andesite (G. 766). Goldfield-Belmont mine. Original structure of andesite has been obliterated. 

Rock is now an aggregate of quartz ( q), kaolinite (k), and pyrite. It was shattered prior to alteration and is traversed 

by white veinlets (not shown) of crystalli!le quartz and kaolinite. Nicols crossed. Magnified 40 diameters. 

178 
U.S. GEOLOGICAL SURVEY 

A. B. 

• 

c. D. 

PHOTOMICROGRAPHS OF ALUNITIZED ROCKS. 
,· 
METASOMATIC PROCF.SSES. 179 

The altered rock is light gray, flecked with numerous dull white spots which represent the 

original feldspar phenocrysts. The few quartz phenocrysts are unchanged, but the ferromagnesian, or, more briefly, fernie, minerals have wholly disappeared. Pyrite, in small, disseminated crystals, is abundant. 

Under the microscope, it is seen that the only original constituents are the quartz phenocrysts, even these showing some development of pyrite along irregular microscopic crack~, and 

an occasional small crystal of zircon. The feldspars are changed to aggregates of minutely 

crystalline kaolinite and tabular crystals of alunite, some of the latter being arranged in sheaflike bunches (see Pl. XXVIII). The alunite has the form characteristic of it in this district, 

sections cut at large angles with the basal pinacoid having the shape of narrow laths with irregular ends. The length of these lath-shaped sections rarely exceeds · half a millimeter.· The 

alunite, when cursorily examined under a low-power lens, may easily be mistaken for sericite 

(mu.::;covite), although of qourse this error is quickly dispelled on closer study, ·sericite being 

optically negative · and alunite positive. The interference colors, moreover, although bright, 

particularly in the larger crystals, are of a lower order than those of ·sericite. Quartz also 

accompanies the alunite and kaolinite in some of the pseudomorphs after labradorite. Diaspore, while not present in the rock analyzed, occurs in the alunitized dacite of the Florence 

mine and elsewhere. (See p. 125.) 

The form~r fernie constituents can be recognized from the fact that they contain little or 

no kaolinite, the quartz and alunite being here associated with abundant pyrite. In some 

cases the pseudomorphous aggregate still preserves a suggestion of the former cleavage of the 

biotite or of the outlines of hornblende. 

The groundmass is changed to a fine-grained aggregate of kaolinite, quartz, alunite, and 

pyrite. The last-named mineral occurs also in irregular microscopic veinlets. 

As the rock is wholly crystalline and is made up of minerals of approximately constant 

composition, it is possible to calculate with some precision the actual mineralogical constitution from the chemical analysis. This, in perce~tages of mass, is as follows: 

Mineralogical composition of altered drzcite. . Per cent of mass. 

Quartz (Si02) •••• : ••••••••••••••...••.• • _ • _____ • _ ••••• _ •••••••• _ ••• __ • • • • • • • • • • • • • • • • • • • • • • 49. 38 

Kaolinite (Al20 32Si02.2H20) ....................... _ ......................... _ .. ___ .... _. __ . 23.99 

Alunite (K20.3Al20 3.4S03 .6H20)a_.......................................................... 15. 73 

Pyrite (FeS2) •••••••••••••••••••••..•.•••••••••••••• _ ••••••• : ••••••••••.••• • •.. __ ••• ••••••• . 7. 20 

Water (H20) ......................... _ .. ___ ... _ ............... _ ... _. __ .. _ .... _ ...... _ . .... _. 2. 53 

Other _constituents ............... _. __ . ____ ........ __ ._ ................ _ .. __ ._. _____ ._........ 1. 17 

100.00 

The various stages and va~iations in the alteration of the dacite, as seen in thin section 

under the microscope, are illustrated in Plates XXVIII to XXX, which are accompanied by 

full descriptive notes. 

Compared as they stand,. the two analyses show close agreement in silica, alumina, titanic 

oxide, and phosphorous pentoxide. When all the iron in both analyses is calculated as ferrous 

oxide, that of the altered rock shows a loss of only 0.7 per cent, so that in this respect also the 

two analyses are very close together. On the other hand, the analysis of the altered rock shows 

a loss of practically all the lime and magnesia, most of the soda, and one-half of the potash. 

It has gaine·d a large quantity of combined water, nearly 6 per cent of sulphuric anhydride, 

and nearly 4 per cent of sulphur. 

Such a direct comparison of analyses, however, while indicating in this case the general 

character of the change that has taken place in the dacite, is really a comparison of equal 

masses of the two rocks, or, more strictly speaking, of the two powders as prepared and weighed 

a The molecular proportions of potash and soda as calculated from analysis 2, page 181, are respectively 11 and 14. All of the potash and 8 of the 

soda molecules are needed to satisfy the 75 molecules of SO~. Consequently the Goldfield alunite is a soda-bearing variety. In an altered rhyolite 

from the east slope of Vindicator Mountain, the molecular ratio of soda to potash in the alunite, as determined by Doctor Hillebrand, is as 40 to 45 

This rock, however,contains a little sericite, and it is possible that the result obtained for potash.may be high inconsequence of some decomposition. 

of the sericite by the sulphuric acid used to .dissolve the alunite. 
1 THE Y .L ·D RE DEP lT' F ' L FIELD. ;\ E\'.\ D.\. 

,'imply if th 

Th a lt r 1 

wc.'lling w uld 

pa 
]. 

•... .... . . ..... .... . 

F ··· · · · · ··· ··· · ·· · · ··· M n .............. .. . 

r o_-_-_-: ::::::::::::::1 

99 .. .j 

:.\f TA )1 TI 

n h ti u nt in 1 

y nndtipl~ in O' th p r ntnO' 

1 1 

ubi n -

fi gur s in 

inl di: tun lwl\\ t •n 

to fonu all th' pyrit ' in th ~ nlt r •d ro + I ut lt11 : 

2. 

60. 53 lo. 32 

. 20 

.14 

7. 20 1 .00 

. 41 

. 4 

]. 

1. 33 6 . 

. 0 

. 01 

h mical ulteration of daril 

on . .. . ......... ......... .. .. .. .. ... 1 •••••••••••.••• ••• •••••••••••••••••••••• 

rr~F 1: :: ~~:: : ::~·:::: ~~ ~: :1:: ~~-:~~ :1: ~:~~1:: : :: ~~- ~~ : :: ~~- ~~ : ::: ~-:i::: :::::::::· 'rrac . ... .... ............. ... .. ... ... . .......................... . ............. . .()(i ............... ..... .. .... .. ............................................ . 

. ·oi look for. 

100. !()(). 00 100. 00 2Cl5. 40 2iG. CO 2f3. 00 249. 00 - 14.00 - ."i.:l2 ......... . 

·:u.a . • !)e(:ill gravit of rock m · 2.49. 
~82 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Compadsons of fresh and altered rocks are sometimes made by assuming the constancy of 

one constituent and recalculating the analysis of the altered rock accordingly. Such a method 

in the present case would give erroneous results. 

The metamorphic agent was evidently a strongly acid ·solution carrying sulphydric and 

sulphuric acids, and possibly sulphurous acid. Whether the sulphuric acid which was doubtless 

the direct agent in the formation of the alunite was present in the original solution from the 

fust, or whether it was derived from the hydrogen sulphide, by oxidation at some stage in 

the movement of the solution toward its point of attack upon the rocks now visible, is a question 

which will be discussed in Chapter XVI. The absence of sulphates from contact ore deposits 

indicates, however, that oxygenated sulphur compounds are not given off directly from solidifying magma~: The solution was capable· of decomposing the silicates in the rocks, carrying 

part of their constituents away, reacting with the iron of the magnetite and silicates to form 

pyrite, with the potassium and aluminum to form alunite and with the aluminum to form 

kaolinite. The large percentage of loss in calcium, potassium, and sodium shows . that the 

active solution was far below its saturation point for these elements, and was therefore, within 

the range of depth investigated, entirely different in character from the alkaline solutions 

which deposited the large class of sericitic and calcitic gold-quartz veins exemplified by those 

of California. 

Not all of the dacite is altered to exactly the same product as that just described. Some 

varieties contain diaspore as a microscopic constituent. · Others, which may be classed as 

ledge matter or ore rather than country rock, contain more quartz and pyrite. On the south 

slope of Preble Mountain, near the summit, the dacite in some places has been altered to a 

white fine-granular rock, not unlike quartzite or marble in general appearance. This is a 

nearly pure aggregate of quartz and alunite, with very little pyrite. The original texture of 

the rock, except for the presence of an occasional phenocryst of quartz, is entirely obliterated. 

CHANGES IN OTHER ROCKS. 

The metasomatic changes effected by the ore-depositing solutions in the latite, andesite, 

and rhyolite of the district have not been studied in the same detail as that in dacite. Even 

were conditions for close comparison of fresh and altered rock as favorable as in the case of 

dacite, such study would not be likely to throw any new light on the general nature of the 

process. The andesite differs but slightly from the dacite in chemical and mineralogical 

composition and alters to products not always distinguishable from those derived from. the 

dacite. A similar statement applies to the latite, alunitized modifications of which may be 

studied on the lower levels of the deeper mines, in various shafts northeast c:i Goldfield, and 

in the quarry on the south edge of Columbia, where the original rock has been changed to a 

soft, white, porous mass which is chiefly alunite. 

The altered forms of rhyolite differ from those of other rocks mainly in the presence of 

less pyrite, owing to the fact that the rhyolite originally contained little iron in the form of 

oxides and silicates. Alunite is very abundant in the altered rhyolite, and, as shown in Plate 

XXXI, forms comparatively coarsely crystalline aggregates pseudomorphous after orthoclase. 

Such aggregates may be well seen in the rhyolite capping Columbia Mountain, near the Conqueror mine, and on Vindicator Mountain. 
METASOMATIC PROCESSES. 

A chemical analysis of altered rhyolite from the eastern shoulder of Vindicator Mountain, 

one-fourth mile (0.4 kilometer) from the summit, is given below : 

Chemical analysis of altered rhyolite. 

[George Steiger, analyst.] 

Si02 • - •• - ••••••••••••••••••••••••••••••• 75. 78 

Al20 3 - • • • • • • • • • . • . . . • • . • • • • • • • • . • • • . • • • • 10. 65 

Fe20 3 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 68 

FeO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

MgO ..................................... None. 

CaO...................................... 1. 67 

NazO .................... ·................. . 22 

K20 ................. ....... .......... _ . . . 96 

H20 below 110° C. . . . . . . . . . . . . . . . . . . . . . . . 1. 16 

H20 above 110° C. . . . . . . . . . . . . . . . . . . . . . . . 3. 54 

Ti02 •••••••••.•••••••••••••••••••••••• • • • 12 

Zr02 •••• ___ • • • • •••••••••••••• ------·----

C02 .. _______ _._ ............ --------------

PzOs--- ---- -·· .... ---· ----- ... -.. -------

803 ....... ........ .. ·-·-- ... ---- .. -------

F . ., . · ........................ , .. .... . .... . 

MnO ............. : ..................... . 

BaO ... - ---- -----·----------------·-··--

SrO ... -------- .. -- ·------- ---------------

0.02 ' 

. 76 

. 02 

4. 73 

None. 

None. 

. 02 

None. 

100.49-

The rock analyzed (G. 333) is nearly white and shows small spots of light-pink alunite. 

Under the microscope, in ordinary light, it shows embayed quart:T. phenocrysts and the outlines 

of feldspars, in a groundmass which still retains much of the fluidal structure of a glassy rhyolite. 

Between crossed nicols, however, the whole rock, with the exception of the quartz phenocrysts, 

is seen to have undergone recrystallization. In the new aggregate, alunite forms the largest 

crystals. These have grown partly in. the groundmass, partly in the· original feldspar phenocrysts. Many of the latter, however, are altered to extremely fine-grained aggregates, in which 

it is difficult to identify the constituent minerals. Most of the calcite shown by chemical tests 

and analysis to be present in the rock appears to be in these fine aggregates, as the mineral is 

very inconspicuous in the thin sections. Some of these aggregates certainly contain sericite 

and kaolinite. Relatively large plates of alunite inclosed in these fine-grained pseudomorppic 

aggregates are common. The groundmass is mainly a very fine-grained mixture of quartz, 

kaolinite, calcite, sericite, and a little iron oxide, probably from pyrite. The secondary minerals, except the iron oxide, so far as inicroscopic examination shows, were all formed contem-

. poraneously. 

The calculation of the mineralogical composition of this altered rock from its chemical 

· analysis, in terms of microscopically recognized minerals, is not entirely satisfactory. The 

carbon dioxide of the analysis is too low to combine with all the lime as calcite, while the alkalis 

do not quite suffice to satisfy the sulphuric anhydride for aly.nite, and no potassium is left for 

the sericite known to be present. Consequently, all of the alumina, after that necessary for 

alunite is taken out, must be calculated as kaolinite, whereas some of it should undoubtedly be 

combined in the sericite molecule. These conditions, since the chemical analysis may be 

regarded as trustworthy, suggest the presence of gypsum (CaS04 +2H20), which, if it occurs 

in the fine aggregates With kaolinite, can not be satisfactorily identified by microscopical methods. 

By calculating all of the carbon dioxide as calcite, the balance of the lime as gypsum, the balance 

of the sulphuric anhydride as alunite, the balance of the potash as sericite, and the residual 

constituents as quartz, iron oxides, and water, the following is obtained as the approximate 

mineralogical constitution of the altered rhyolite: 

Mineralogical composition of altered rhyolite; Per cent of mass. 

Quartz (Si02) ............................................... _·_ .............................. 67. 62 

Sericite (2H20.K20.3Al20 3 .3Si02)............................................................. . 79 

Kaolinite (Al20 3 .2Si02.2H20). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16. 77 

Alunite ((KNa)0.3Al20a.4S03 .6H20) ................ ...... .......... ....................... 9. 93 

Gypsum (CaO.S03 .2H20) .... --.............................................................. '1. 63 

Calcite (CaO.C02) ....................... .................. : ........................ _. _...... 1. 70 

Iron oxides (FeO .Fe20 3) •••••.••••••••••.•...•••••••••••••••••.••••.•••••..•.••••••••• -.- : •••• _ • 84 

\Vater (H20).. ... .. ............. .. ................ ........ ... ...................... .......... . 59 

99. 87 
PLATE XXXI. 

PHOTOMICROGRAPH OF ALUNITIZED RHYOLITE. 

A. Vindicator rhyolite (G. 326). West slope of Vindicator Mountain. Shows alunite (a) pseudomorphs after orthoclase. Quartz phenocrysts ( q) are unaltered. Black areas are opaque, white, earthy pseudomorphs after biotite. The groundinass (g), which retains its original flow structure, has been altered from a glass to an aggregate of quartz, kaolinite, and alunite. The rock contai~s a little diaspore, not shown in this section. Ordinary light. Magnified ·40 diameters. · 

B : Same as A. Nicols crossed, showing aggregation of alunite and devitrifi.cationof the groundmass. 

184 

_,...... . 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 66 PLATE XXXI 

A. 

B. 

PHOTOMICROGRAPHS OF ALUNITIZED RHYOLITE. 

METASOMATIC PROCESSES. 185 

This result is not entirely convincing, as the quantity of sericite obtained by calculation 

appears to be ·a little less than is actually present in the rock, and the occurrence of gypsum 

is not established beyond question. 

In the presence together of calcite, alunite, and sericite, this rock is exceptional. Other 

specimens from the same locality show much quartz, alunite, and kaolinitE}, with some diaspore, 

but no calcite or sericite. ' 

The rhyolite, as might be expected from its originally siliceous character, tends to become 

completely silicified in the vicinity of fissures, as is exemplified in the neighborhood of the 

Sandstorm mine. 

THE ORE-DEPOSITING SOLUTIONS. 

The mineralogical character of the Goldfield ores and the alteration of the wall rock show 

that the solutions or vapors which deposited them carried gold, copper, bismuth, antimony, 

a little arsenic and tellurium, hydrogen sulphide, and probably sulphurous and sulphuric acids. 

The solvent action of the solutions upon quartz was comparatively slight, as shown by the fact 

that the original phenocrysts of the dacite still retain their characteristic embayed outlines when 

the rest of the rock is altered to quartz, alunite, and kaolinite. The quartz set free by the 

decomposition of the -silicates has for the most part recrystallized as fine-grained aggregates. · A 

small proportion, as we have seen, has been carried away in solution, perhaps in part to be 

recrystallized in small neighboring fissures, and in part permeating the surrounding less-altered 

rocks. Large masses of coarsely crystalline vein quartz are absent from this district, and it seems 

necessary to conclude not only that the ore-bearing solutions were poor in silica but that, in 

spite of their energetic attack upon the rocks, they were not good solvents for quartz. The 

apparently intense silicification of the country rock in proximity to fissures appears at first glance 

to point to a different conclusion. The conversion of a rock containing 60 per cent of silica 

to a fine-grained pyritic quartz aggregate does not, however, necessarily imply the direct addition of 40 per cent of silica. The result may be attained by the removal of most of the bases, 

the conversion of the iron to pyrite, and the development of a porous texture such as js favorable 

for ore deposition and is characteristic of the Goldfield ledges. Moreover, it is probable that 

some of the silica shown to have been abstracted from the altered dacite may have been concentrated in the immediate vicinity of the fissures. Certainly, whatever silica was originally 

in the solutions did not travel far from 'the fissures through which they rose. 

Whether the solutions were notably ferruginous is doubtful. As compared with other 

districts, the pyrite at Goldfield is not abundant, and all of that in the country rock can, as has 

been shown, be accounted for without any addition of iron. There has, in fact, been an abstraction of iron which may have been sufficient to form the pyrite in the actual ore, upon the supposition that the dissolved iron, like the silica, migrated toward the fissures. 

In general the heavy metals brought in by the solutions remained within or very close to 

the multitude of small, irregular fissures that afforded opportunity for the depositional process. 

The sulphur acids, on the other hand, penetrated the wall rock for con~iderable distances. 

It is very probable that the ore-bearing solutions contained carbon dioxide, although the ores 

and the rock adjacent .to them are free· from carbonates. Field evidence in this district, as well 

as in the Camr d'Alene districta in Idaho, indicates that this constituent, when of volcanic 

origin, becomes active in the formation of carbonates only at comparatively low temperature, 

and that it tends to penetrate to greater distances from the source of supply than some of the 

other constituents. The third, or propylitic type of alteration described o.n page 176, is thought 

to be largely due to the extensive permeation of the rocks by solutions containing carbon dioxide. 

It thus constitutes an outer aureole to the more intense metasomatism associated directly with 

the ores. 

a Ransome, F. L., and Calkins, F. C., The geology and ore deposits of the Creur d'Alene district, Idaho: Prof. Paper U.S. Geol. Survey 

No. 62,1908. 
186 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

It may be recalled, in this connection, that Sainte-Claire Deville and Leblanc, a in their studies 

of Italian volcanic gases, found that sulphurous and carbonic acids never occurred together, 

although the association of sulphydric and carbonic acids was frequent. They concluded that, 

as a rule, the emanation of carbon dioxide marks a later and cooler stage of solfataric activity. 

The transition from one type to the other, however, can hardly be abrupt. 

Just what became of the lime and magnesia removed from the altered dacite has not been 

determined. A part, at least, of the calcium was probably taken into solution as hydrous 

sulphate and deposited in fissures as gypsum, this mineral being known to occur in the district 

in places where its formation can scarcely have resulted from the action of surface waters. 

Still another part and some of the magnesium may have been carried as carbonates into the 

rocks affected by metamorphism of the third or propylitic type and there deposited_ metasomatically as calcite or dolomite. ·It has not yet been ascertained, however, whether there has actually 

been any addition of calcium or magnesium to these carbonatized rocks. 

a Memoire sur la composition chimique des gaz rejetes par les events volcaniques de l'ltalie meridionale: Annales chim. phys., vol. 52, 1858, p. 45. 
CHAPTER XV. 

UNDERGROUND WATER AND DEPTH OF OXIDATION. 

When mining began, the average level of underground water in the district was from 100 

to 150 feet · (30 to 46 meters) below the general surface. The Combination mine first had water 

at 130 feet (40 meters), tlie January at 180 feet (55 meters), the Red Top at 140 feet (43 meters), 

the Silver Pick shaft, near Columbia, at 100 feet (30 meters), and various shafts near· Diamondfield at about the same depth. As is usually the case, water was found at less depth in low ground 

than on high, the Dixie shaft on Preble Mountain being dry at 300 feet (91 meters), as is also . 

the Lucky Boys shaft, 360 feet (110 meters) deep, on Vindicator Mountain, while some wells near 

town have furnished water at 40 or 50 feet (12 to 15 meters). At Rabbit and Tognoni springs, 

and at a spring near the mouth of Pozo Canyon, water comes to the surface. All these are 

ordinary hillside springs, the water seeping from the higher ground in their vicinity. 

In none of the mines has the flow ·of water been so large that it could not be easily kept 

down by bailing or with ordinary pumps. When the Combination was the deepest mine, the 

quantity of water hoisted to· keep the 280-foot level free was probably not over 3,000 gallons 

(11,250 liters) in twenty-four hours. The V\Thite Rock prospecting shaft in the northern part 

of the town of Goldfield is one of the wettest in the district. It was 520 feet (158 meters) deep 

in July, 1908, and goes through 280 feet (85 meters) of Siebert beds and overlying wash into 

latite. It thus drains a thick mass of porous sediments and at times it has been necessary to 

hoist 30,000 gallons (112,500 liters) in twenty-four hours to keep down the water. 

Most of the wells in the district are in the Siebert beds or in the intercalated tlow of Mira 

basalt. The latter is the principal water-bearing horizon for domestic wells of moderate depth 

(50 to 70 feet, or 15 to 21 meters) in the southern part of town. In 1906 the Goldfield brewery 

derived its water supply entirely from a 50-foot (15-meter) well in the basalt. The supply from 

wells in the Siebert beds is uncertain and is not always proportional to depth. In the latter 

part of 1905 the Goldfield Reduction Company was getting about 4,500 gallons (16,875 liters) 

in twenty-four hours from a 200-foot (61-meter) well and the New Western Reduction Company 2,000 gallons (7,500 liters) or less fron1 a 250-foot (76-meter) well. The well at the ice 

works, 100 feet (30 meters) deep, yielded 4,000 gallons (15,000 liters) per diem in June, 1905, 

but only 2,000 .gallons in the following October. A well sunk in 1908, just south of the Gardiner 

mill, is 180·feet (55 meters) deep, and is said to yield about 10,000 gallons (37 ,500 liters) in twentyfour hours, most of which comes in at points less than 100 feet (30 meters) deep. This well is 

rather remarkable in that the water rises to within a few feet of the surface, showing that it is 

under some artesian head. It undoubtedly taps the same flow that gives rise to Rabbit Spring. 

The town water supply came originally from wells in Pozo Canyon. The first well yielded 

about 8,000 gallons (30,000 liters) per diem in August, 1904, at a depth of 25 feet (7.6 meters). 

This soon diminished, and in November the well was deepened 10 feet (3 meters) and horizontal 

drifts were run from the bottom. The supply then rose to 15,000 gallons (56,250 liters), but fell 

off again when a new well was sunk lower down the canyon. This second well at first gave 

20,000 gallons (75,-000 liters) per diem, but in September, 1905, was furnishing only 15,000 gallons, the well being 90 feet (27 meters) deep·, with drifts. Both wells are in the Siebert beds. 

The Pocahontas well, at the roundhouse of the Las Vegas and Tonopah Railroad, is 840 

feet (256 meters) deep. Its yield is about 24,400 gallons (91,500 liters) in 24 hours. Water 

was first found at 94 feet (28 meters), but the flow was small and no increase w·as noted until 

a depth of 450 feet (137 meters) was reached. 

187 
188 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The ground water of the district without question represents m"erely the storage of that 

small part of the scanty local precipitation which is not evaporated before it can sink into the 

ground. Extensive pumping soon lowers the water in any one place and the subsequent influx 

is small. There is a permanent seepage from Malpais Mesa, as shown by springs and by some 

of the wells, but the quantity of water thus supplied to the sediment-filled basin under Goldfield probably does not average more than 20,000 gallons (75,000 liters) per diem and may be 

considerably less. The general level of the ground water is being steadily lowered by n1ining 

operations, and there is no suggestion whatever of any influx of thermal or abyssal waters at 

the present time. 

The character of the underground water varies. That from the wells and springs is fairly 

good as desert waters go and is not so strongly charged with salts as to give it perceptible taste. 

The water from many prospect shafts also is potable. But in mines where bodies of ore are 

·in course of oxidation the water, as shown by the analysis of that from the January mine on 

page 220, is heavily charged with sulphates and probably in many places with free sulphuric 

. acid. The quantity of sulphides in the Goldfield deposits is not great, and in more humid 

regions their oxidation probably would not give rise to such concentrated solutions. At Goldfield, however, the ground water has little natural circulation, receives only slight accessions of 

fresh water, and has a correspondingly slow underground run-off. 

In general, the bottom of the oxidized ore corresponds closely to the original ground-water 

level. In comparison with most deposits· in arid regions, therefore, the vertical "'range of oxidation is short, being only about 150 feet (46 meters). The change from oxidized to sulphide ore 

is as a rule sharp, and there is no evidence of any large fluctuation in the ground-water level. 

The character of the oxidized ore has been described on page 170. The questio:p. whether oxidation has been accompanied by notable enrichment of the sulphides below is so closely 

connected with the whole problem of ore genesis that its consideration belongs rather to the 

next chapter. 
CHAPTER XVI. 

GENESIS OF THE DEPOSITS. 

STATEMENT OF THE PROBLEM. 

Since the preceding chapters contain an ample presentation of the problem now awaiting 

solution, only a brief recapitulation is needed of some of the most significant facts with which 

an adequate explanation of ore genesis must harmonize. 

Beyond all question the intimate association of unusually rich gold ores with the mineral 

alunite is the most remarkable feature of the deposits and is the one that promises to shed 

most light en their origin. Alunite is not a common mineral, and although it was recognized 

in small quantity in the oxidized zone at Cripple Creek it is at Goldfield alone, so far as is at 

present known, that it is found with sulphide.s and tellurides as a characteristic mineral of 

unoxidized gold ores. The presence of this mineral and the kind of alteration undergone by 

the rocks containing it prove, as shown in Chapter XIV, that the ores were deposited from 

solutions containing sulphur~c acid. Whether this acidity was an original property of the 

gold-bearing solutions or whether the solutions, primarily of different character, ·became acidic 

at t_he place of preqipitation, or during their journey thither, are questions presently to be 

considered. · 

Other chemical and mineralogical features of the ores to be kept in mind are the occurrence of telluride and selenide of gold, sulphide of bismuth, and compounds of copper, sulphur, 

antimony, and arsenic (enargite, famatinite, and goldfieldite) of which the mineral species is 

not in every case determinable, the cryptocrystalline character of the qu_artz, and the extraordinary concentration of the gold. Due consideration must be given also to the volcanic history 

of the region, the recent age of the deposits, the slight depth at which they were formed, and, 

as a corollary of these facts, the brief time and the short vertical distance available for any 

secondary concentration that may be postulated in connection with erosion. 

Attention will first be directed to t,he question of the source of the sulphuric acid, since if 

it can be satisfactorily answered the other phases of the main problem should crystallize clearly 

about this nucleus. 

THE DIRECT VOLCANIC HYPOTHESIS. 

That some fumaroles emit sulphur dioxide has long been known. As early as 1858 SainteClaire Deville and Leblanc a found it in gases from Vesuvius and other Mediterranean volcanoes. 

From one fumarole in the crater of Vesuvius they collected a gas which proved to contain 

hydrochloric acid and sulphur dioxide in the ratio of 86.2 parts of the former to· 13.8 parts 

of the latter, together with water vapor and the constituents of ordinary air. They concluded 

from their investigations that carbon dioxide and sulphur dioxide never came simultaneously 

from the same fumarole. This, however, does not accord with the results of some other 

workers, as is shown by the following table prepared by F. C. Lincoln/ which is of theoretic 

-interest, from the fact that calcite and alunite occur together at one place in the Goldfield 

district. (See p. 183.) 

aM~moire sur la porn position chimique des gaz rejetes par les events volcaniques de l'ltalie meridionale: Annales chim. phys., 3d ser., vol. 52, . 

J>. 45, 1858. 

b Econ. Geology, vol. 2, 1907, p. 802. 

189 
190 

No. Volcano (or locality). 

THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Fumarole gases containi~~g both C02 and S02 • 

Spot. ture. 

~~~~ 

- -!-------:----------------------·---------------·- ·--

~ ~~~fae~~~~:: ' oc. ::::::: a;~~tmc~~{;r~ .e~~~i~~:::::::::::::::::::::::::::::::::::::::: :::::::1 .... -~~-

5 

~ . 

-~~~~~i-~~:: _._.do .. ___________ :::::::: At 

iroa~i:~i~~-:ui>iive eruptive center ______ .craie______ 

r.·: ~:: . __::::::::::::::::::::::::::::::::::::

_ ._ ..... _._. _._ .. _________________________ 1 ... -~~~- 6 ___ .. do .. _______________ _ .do. _________________________ ___ · _______________ : _________________ , _______ _ 

8 

7 _____ 

Vulcano. do .. -----------

__________ _____ 

Interior do. ___ 

of ------- _______ .--- --- __ ____ . __________ _ ------ ________ -----'-------- great crater ____________ ________ _________ ________ _______ __ .I 360 

12 

~~ : 

____ 

~~~!t~~::: .do.____________ 

::::::: :~66:!t~is: On ii~~~~~~ ~f: b:i~~~i~~:::::: :::::::::::::::::::::::::::::::1 Hg slope between Giorgios and lava stream_________________________ 110 

93.5 

2.44 

5. 38 

4. 90 

1. 42 

3.00 

3. 97 

23.40 

22.00 

59.62 

68.5 

98.5 

Trace. 0 

1. 54 0 Trace .. ___ . __ . 

3.40 -------- 2.61 2. 14 

2.25 3. 00 

1. 32 1. 98 

Trace. 73. 80 

Trace. 66. 00 

Trace. 27. 19 

12.0 19.4 

0. 4 1. 0 

6.5 0 81.81 14.21 

79.16 18.46 

73.48 18.13 

76.22 17.61 

73.71 18.04 

70.88 21.85 

2. 28 0. 52 

9. 60 2.40 

10.99 2. 20 

1853, 

Authorities: 

p. 259. (3) 

(1) 

Franco, 

Boussingault, 

Compt. Rend., 

J. B., Annales chim. phys., 2d ser., vol. 52, 1833, p. 21. (2) Bunsen, R. W ., Annales chim. phys., 3d ser., vol. 38, 

4th ser., vol. 30, 1873, pp. 

vol. 66, 1868, P- 159. (4) Franco, Compt. Rend., vol. 66, 1868, p. 1352. (5-7) Franco, Annales chim. phys., 

98-99. (8-10) Fouque, F., Compt. Rend., vol. 61, 1865, p. 565. (11-12) Gorceix, H., Compt. Rend., vol. 75, 1872, p. 270. 

Van Hise a states that in the gases emitted from fumaroles and solfataras sulphur dioxide 

is probably next in abundance to steam. This, however, does not appear to accord with the 

testimony of published analyses of volcanic gases. F. C. Lincoln, b on the basis of 50 selected 

analyses, concludes that, after steam and nitrogen (the latter being difficult to rank owing to 

the possibility of admixture of air), carbon dioxide is the most important gas, followed by 

hydrogen sulphide and sulphur dioxide. 

Sulphuric acid ~H sulphuric anhydride is apparently still less common in volcanic emanations 

than sulphur dioxide. Geikie c states that "occasionally, also, the production of sulphuric acid 

is observed at active vents," which probably means merely that the acid is formed superficially 

by oxidation of sulphur dioxide. In the i.nteresting crater lakes of Taal volcano described by 

R. F. Bacon d free sulphuric acid is present in large quantities. It is apparently formed, however, by the oxidation of fumarolic sulphur dioxide which bubbles up through the boiling water. 

On the whole, it appears to be very doubtful whether sulphuric acid or sulphuric anhydride 

is actually emitted from the deeper part of any volcanic vent. There is a strong suggestion,. 

moreover, that the sulphur dioxide which streams from some fumaroles is not all of deep-seated 

origin, but may in part be due to an admixture of air with the true telluric gases, particularly 

with hydrogen sulphide. Here we are confronted, however, with the difficulty of distinguishing 

sharply between primary and secondary volcanic products. At what depth, for example, must 

water or oxygen be introduced in order to be classed as a primary volcanic product~ By magmatic water do we mean only such as has been locked in the earth's interior since the planet 

tookits present form, or may we mean also water that the magmas have subsequently absorbed 

in some such manner as that advocated by S. Arrhenius~ e ~1ay not the water emitted from 

volcanoes be both magmatic and meteoric as these terms are used by most writers~ This is 

still a vexed question, although the available evidence favors the view that meteoric water does 

not reach the sources of magmas./ Granted t.hat the water of volcanic eruptions, however 

introduced or formed, comes mainly from the molten magma, there is no a priori difficulty ~ 

postulating the emission of oxygen compounds of sulphur, since Fouqueu has shown tha_t in 

some cases the constituent gases of-water are dissociated and the liberated oxygen might under 

some circumstances unite with sulphur. As a matter of fact, however, the oxides of sulphur 

are not nearly so common or abundant, and when they do occur are not so clearly of deep derivation, as is hydrogen sulphide. 

a A treatise on metamorphism: Mon. U.S. Geol. Survey, vol. 47, 1904, p. 491. 

bMagmaticemanations: Econ. Geology, vol. 2, 1907, pp. 261-264. 

c Text-book of geology, vol. 1, 1903, p. 268. 

d Philippine Jour. Sci., vol. 2, 1907, p. 115. 

~ Zur Phy;;ik des Vulkanismus, Geol. Foreningens. Stockholll} Forhandl., vol. 22, 1900, pp. 395-419 

1908, 

f 

p. 

For 

69. 

a recent discussion of this problem see Chamberlin, R. T ., The gases in rocks, Carnegie Institution of Washington, Publication No. 106. 

u Santorin et ses eruptions, Paris, 1879, p. 230. 
GENESIS 01!' THE DEPOSITS. 191 

There is evidence also of the deep-seated formation of sulphuric acid in the presence of 

sulphates, such as barite and celestite,a as primary minerals ~n some veins. Recently, too, 

Lindgren b has called attention to the occurrence of anhydrite as a primary mineral with tourmaline and chalcopyrite at the Cactus mine in the Frisco district, Utah. The presence of the 

minerals hauynite [(Na2

Ca) 2 (NaS04Al)Al2 (Si04) 3] and noselite [(Na4 (NaS04Al)Al2 (Si04 ) 3] in 

phonolitic rocks proves that under some circumstances sulphur trioxide may be present in 

molten magmas, and consequently may exist in magmatic solutions. There are, however, no 

phonolitic r.ocks known at Goldfield. 

While these occurrences are to be regarded as favoring the view that sulphuric acid can 

form at volcanic centers, their testimony, as regards importance in ore deposition, is opposed 

by the abse:rice of sulphates from contact metamorphic deposits and of sulphuric acid from 

most hot springs. Springs carrying sulphuric acid are, it is true, not unknown. The water 

of a hot acid spring at the so-called geysers of Sonoma County, Cal., according to an analysis 

by Thomas Price, contains 145 grains of free sulphuric acid per gallon.c Other springs at the 

same locality contain smaller quantities of the same acid. All these waters, however, are · 

saturated with hydrogen sulphide, and it is possible that the sulphuric acid may have been 

formed by the oxidation of the sulphydric acid within the zone penetrated by surface waters. 

Hot sulphuric acid springs occur also in the Coso Range, Inyo County, Cal., accompanied by 

deposits of sulphur containing hydrogen sulphide. a Sim-ilar acid springs carrying hydrogen 

sulphide issue from sulphur deposits near Maverick Springs, El Paso County, Tex. The water 

from one of these, according to E. M. Skeats, e contains 136 parts per 100,000 or 79.08 grains per 

gallon of free sulphuric acid. W. T. Lee has described a similar occurrence at Sulphurdale, 

Utah/ Analyses of 11 other springs' waters containing less sulphuric acid than those above 

mentioned are given by F. W. Clarke.Y 

The chemical activity of free sulphuric acid in spring water would of course lead to the rapid 

formation of sulphates during the upward course of the water and to consequent neutralization 

of the free acid. But there is a limit to such rapid neutralization and in persistent and copious 

springs it might be expected that some free acid would in most cases be brought to the surface 

were it commonly generated below. Furthermore, if sulphuric acid were formed in any considerable quantity at great depth during volcanic activity we should expect to find alunite a more 

common constituent of rocks which have been uncovered by erosion than experience indicates. Moreover, it is questionable whether waters rich in sulphuric acid would be efficient 

carriers of gold, sulphides, and tellurides. It is probable that they would precipitate these constituents from the alkali sulphide solutions, of which the solvent efficiency has been repeatedly 

shown by experiment h and by geologic evidence. 

In view of these considerations, and of others presently to be brought forward, the hypothesis, suggested with some favor in a preliminary paper/ that the ore-depositing solutions may 

have come from below already charged with sulphuric acid, has been abandoned. 

HYPOTHESIS OF DERIVATION OF 'J.."'HE SULPHURIC ACID FROM THE OXIDATION OF PYRITE. 

The hypothesis that the alunitization of the rocks at Goldfield was effected by cold sulphate solutions percolating generally downward from masses of oxidizing sulphides, principally 

pyrite, has some facts in its favor. The small quantity of impure alunite found at Cripple 

a Lindgren, '"·• and Ransome, F. L., Geology and gold deposits of the Cripple Creek district, Colorado: Prof. Paper U .S. Geol. Survey No. 54, 

1906, pp. 22o-221. 

b Oral communication before the Geological Society of Washington. Abstract in Science, n. s., vol. 28, 1908, p. 933. 

c Anderson, Winslow, Mineral springs of California, San Francisco, 1892, p . 150. 

d Anderson, Winslow, op. cit., p. 254. 

eBull. Univ. Texas Min. Survey No.2, 1902, p. 34. 

/Water resources of Beaver Valley, Utah: Water-Supply Paper U.S. Geol. Survey No. 217, 1908, pp. 19-20. 

g Data of geochemistry: Bull. U. S. Geol. Survey No. 330, 1908, pp. 155--157. · 

hAs regards tellurides see Lindgren, W., and Ransome, F. L., Geology and ore deposits of the Cripple Creek district, Colorado: Prof. Paper 

U.S. Geol. Survey No. 54,1906, pp. 223-224. 

i The association of alunite with gold in the Goldfield district, Nevada: Econ. Geology, vol. 2, 1907, p. 688. 
192 THE GEOLOGY ·AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Creek was undoubtedly formed in this manner, and observations indicate that a part of the 

alunite at Goldfield, namely, some of the soft varieties which fill interstices in the partly oxidized ore, may have been, if not originated, at least dissolved and redeposited during oxidation. 

According to De Launay a the alunite at· the classic locality of Tolfa is the product of such 

solutions acting upon a particularly feldspathic trachyte. ';l'he formation of alunite by cold 

percolating solutions probably requires these to be more strongly acid than is necessary for 

the p:r:oduction of kaolinite. 

The intimate association of the alunite with kaolinite at Goldfield has a bearing on the 

problem. The origin of this mineral has been the subject of much recent discussion, b the general 

trend of which is to emphasize the connection between kaolinization and weathering. Lindgren c has recently intimated that although he himself formerly referred to the mineral. as 

characteristic of certain classes of veins, kaolinite should not be considered as a gangue mineral 

of any class of ore deposits except those formed under the influence of oxidation. In a subsequent paragraph he somewhat modified this statement by the expression of belief that ''kaolin 

is rarely formed by alkalir;le hot water at any considerable depth below the surface." The 

preponderant weight of careful observations made during the last few years is unquestionably 

on the side of the thesis thus moderately stated; and the occurrence of k~olinite at Goldfield, 

where the intimate association of the mineral with the alunite, gold, sulphides, tellurides, and 

sulphantimonites, as determined by microscopical work, shows that all were formed at the 

same time and by one general process, is an additional point against what has been called the 

direct volcanic hypothesis. 

Much kaolin originally described by various authors as formed by the solutions which 

first brought up the ores associated with it has later been proved to have resulted from oxidizing processes, it being one of the most characteristic products of the action of percolating, 

weakly acid solutions upon aluminous rocks. The kaolin at Cripple Creek is a good example. 

Much so-called primary or pneumatolytic kaolin, moreover, has been shown to be sericite, 

and some is perhaps alunite. 

On the other hand, these facts seem scarcely to warrant the total elimination of kaolinite 

from the list of gangue minerals found in ore deposits, the connection of which with oxidation 

is at least not obvious, and which are certainly not affected by ordinary weathering. The mineral 

occurs as an original constituent of .some of the ores of the San Juan Mountains, Colorado,a 

and W. H. Weed e has described it as a product of the metasomatic action of the waters of 

Boulder Hot Springs, Montana, upon granite. Kaolinization has also been noted by Bela 

von Inkey f in the dacitic country rock of the N agyag veins, the material being afterwards 

investigated by F. Kollbeck,u whose analysis indicates a mixture of kaolinite and sericite. 

The principal obje.ctions to the view that· the alunitization at Goldfield is connected with 

the oxidation of older pyritic ores are based largely on what appears to be the quantitative 

insufficiency of the proposed explan~tion. No such available primary masses of sulphides 

are known, and study in the district has failed to bring to light any bodies of sulphides that 

are distinctly older than the ores and that are not accompanied by alunite. There is no evidence yet found which indicates the superposition of a distinctly younger phase of deposition 

characterized by the formation of alunite upon an older phase not associated with that mineral. 

The mines at Goldfield are still comparatively shallow, but they have penetrated about 500 

feet below the bottom of the weathered ores, and if the alunitization were the result of ordinary 

weathering it is likely that secondary products would somewhere have been found distinctly 

imposed upon earlier nonalunitic material. It is probable that at a depth greater than that 

aLa metallogenie de l'Italie: Cong. geol. intern., Mexico, 1906, vol. 1, 1907, p. 681. 

b See especially Zeitschr. prakt. Geologie, 1907 and 1908. 

c The relation of ore deposition to physical conditions: Econ. Geology, vol. 2, 1907, p. 120. 

dRansome, F. L., Economic geology of the Silverton quadrangle, Colorado: Bull. U.S. Geol. Survey No. 182, 1901, p. 73. 

e Mineral vein formation at Boulder Hot Springs, Montana: Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, p. 253. 

/Nagyagund seine Erzlagerstatten, Budapest, 1885, p. 143. 

uUntersuchungen 

vol. 36, 1888, 

iiber die Zersetzung des Quarztrachyts neben Goldersgangen von Nagyag: Oesterr. Zeitschr. f. Berg- und Huttenwesen, 

pp. 25-27. 
GENESIR OF THE DEPOSITS. 193 

now attained alunite will become less abundant, but the change will, it is believed, be gradual, 

and there is nothing to indicate- that it will exhibit such a definite relation to the general 

ground-water level as might fairly be expected under the hypothesis now under consideration. 

The alunitization of the rocks, as shown on page 176 and by figure 18, is very extensive 

and is by no means confined to the immediate vicinity of known ore bodies. Except in the 

zone of superficial oxidation the alunite is crystallized with pyrite and consequently has not 

formed under conditions involving the destruction of this sulphide in the zone now accessible. 

To account for the alunid.zation by the oxidation of pyrite would require the assumption that 

the material stripped from the district by erosion was much more .heaVily pyritized than the 

rocks at present visible. The thickness of this vanished overburden, as has been shown, can 

scarcely have exceeded 1,000 feet (305 meters) and probably was very much less. Moreover, 

the period available for alunitization was geologically very brief, since the process had already 

taken place when the Pozo formation was laid down. We are thus confronted by the contrast 

. of a process remarkable for the extent and intensity of its action with conditions which, if not 

markedly unfavorable, Were at least not such as would be expected to produce the observed 

e6'ects under the present hypothesis. The remal:1 kable concentration of the gold and asso. cia ted 

minerals in these deposits appears to be out of all proportion to any leaching action possible 

within the time and distance available. This discrepancy will, it is believed, become more 

marked when the character and genesis of the metallic minerals of the ores are considered, as 

they will be in connection with the next hypothesis. 

HYPOTHESIS OF SIMULTANEOUS lsOLFATARISM AND OXIDATION • . 

The third hypothesis to be tested postulates that the ore constituents were brought up in 

hot solutions charged with hydrogen sulphide, a little carbon dioxide, and probably also with 

some alkali sulphides; that the hydrogen sulphide was oxidized at and near the surface to 

sulphuric acid, which percolated down through the warm rocks to mingle with the uprisibg 

currents carrying sulphydric acid; and that the precipitation of the richest ores took place j in 

the zone where the two kinds of solutions mingled and as a consequence of such mingling. jAs 

Van Hisea has pointed out, the chemical reactions of weathering and of solfataric action are 

not so diff. erent as might be supposed, and this process differs from that of the second hypothe~sis chiefly in greater intensity of action and in the smaller demands that it makes on time 31 d 

erosion. The hypothesis differs from the first one considered mainly in that the sulphuric a id 

acted as the precipitant rather than as the carrier of the ore constituents which came up/ in 

sulphide solutions. This latter view has the initial advantage of being in much better accJrd 

with all that has been learned of the chemistry of natural sulphide deposition than is the first 

supposition. Any explanation of the origin of the Goldfield deposits which calls for natu al . 

solvents radically different from those which carried the carefully studied ores of Tonopfh, 

the Comstock, Grass Valley, Cripple Creek, and many other districts in this country and abroad 

is burdened at the outset with presumptive improbability. -, 

In accordance with the third hypothesis the hot ascending waters carried abundant hydrogen 

sulphide, as shown by the extensive change to pyrite of the iron originally present in the 

dacite and ot4er rocks as a constituent of magnetite and silicates. This change was not confiled 

to the rocks now alunitized, but extended outward to what has been called the propylitic aureele 

of alteration . . The experiments of Beckerb and Doelter,C supported by studies of metaromatically altered wall rock in various districts, suggest that the sulphur of the original solutiT.ns 

was in part combined with or accompanied by sodium and potassium. The changes in the da ite 

investigated in Chapter XIV, notwithstanding the development of the potassium- and sodi mbearing mineral alunite, do not show any addition of alkalies to the original rock, but such ne ative evidence does not prove that no alkali sulphides were present in the primary solutio s. 

a A treatise on metamorphism: Mon. U.S. Geol. Survey, vol. 47, 1904, p. 494. 

b Geology of the quicksilver deposits of the Pacific slope: Mon. U. S. Geol. Survey, vol. 13, 1888, chap. 15. 

c Einige Versuche uber die Loslicbkeit der Mineralien: Tscbermak's Min. n. petr. Mittb., vol. 11, 1859, p 319. 

79145-No. 66--{)9--13 
194 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

They may have been largely oxidized to sulphates and carried away to accumulate in the playa 

deposits of. the region, just as is happening at the present day at Alkali Spring. (See p. 143.) 

If so, it is to be expected that at greater depth than is now reached at Goldfield the feldspars 

of the rocks are extensively sericiti~ed with some addition of alkalies. That the ore-bearing -

solutions contained carbon dioxide is indicated by the alteration of calcium-bearing silicates 

to calcite in the propylitic zone. It is not to be supposed that calcite would form abundantly 

in rocks soaked with sulphuric acid. It does occur, however, with alunite in rhyolite on the 

east slope of Vindicator Mountain, and this association of minerals is probably the result of local 

conditions which retained under pressure and fixed in combination the carbon dioxide that 

otherwise would have escaped in the presence of the acid solutions necessary for the production 

of alunite. Such local conditions of pressure are more readily conceivable in connection with 

hot uprising waters than under the circumstances of ordinary weathering. 

In addition to sulphydric and carbonic acids the solutions carried the following, either as 

compounds or in ionized condition: Gold, silver, copper, zinc, lead, bismuth, antimony, arsenic, 

tellurium, and selenium. They probably contained also some iron and silica, although the study 

of rock alteration recorded in Chapter XIV shows subtraction, not addition, of these constituents to the wall rock. On the other hand, the actual ledge matter contains more silica and pyrite 

than was in the original rock. How much of this excess was contributed by the uprising solutions directly and how much was merely concentrated from the surrounding country rock is not 

determinable. There was probably some direct addition, however, from deep-seated sources 

in th.e immediate vicinity of the fissures .. 

It has been shown that the fissuring of the district was very complex and irregular, affording innumerable devious channels for the passage of solutions. Thus the hot solutions presumably reached the surface at many places, and this distribution of the outflow must have 

been far more favorable to oxidation of the hydrogen sulphide to sulphuric acid and to the 

subsequent activity of the latter than if the uprising waters had flowed from a single vent. 

There is reason to believe (see p. 107) that the climate at the time the ores were deposited 

was comparatively arid. It is likely, therefore, that the mineral-bearing solutions, upon reaching the surface, were not only oxidized but were concentrated by evaporation as they flowed 

over the surface or percolated down through the rocks. The sulphuric waters as they penetrated downward must have exerted a strong leaching action on the superficial rocks similar 

to that observable at Sulphur Bank, Cal., at the present day, where basalt has been altered to 

spongy masses of snowy silica by the removal of its basic constituents. At moderate depth 

the acidic descending solutions Inet uprising solutions charged with hydrogen sulphide and 

ore constituents, and mingled with them in a zone characterized by the presence of sulphydric, 

sulphurous, and sulphuric acids and by the simultaneous development of alunite and sulphides. 

The vertical range of this zone must have been considerable- probably 1,000 feet (305 meters) 

or more. The mixing of the solutions may have been effected partly by differences in density 

between the hot ascending currents charged with gases and the cooler descending waters, partly 

by convection, partly by diffusion, and perhaps partly by osmotic action. The sulphuric acid 

solutions would in general have greater power of penetrating the substance of the country rock 

than would the si1ica and the in part colloidal bases of the uprising solutions. a It is to be 

remembered also that the rocks at the time of ore deposition were as a whole hard and brittle, 

had been recently fractured, and :were much more generally permeable than at present, when 

much of the country rock, softened by alteration, is incompetent to maintain open fissures. 

Evidently, ·with the process once initiated, the waters reaching the surface would no longer 

represent the original ore-bearing solutions, but would be mixtures of these with s-alphate waters 

and would contain various constituents abstracted from the rocks during alunitization, as 

shown in Chapter XIV. 

At no time in their history were the depositing solutions, if we may judge from their work, 

strong solvents for silica, and the quantity of this constituent transported by them was small. 

a See Sullivan, E. C., Experiments on the separation of the constituents of a solution by filtration through a mineral filter: Econ. Geology, 

vol. 3, 1908, pp. 750-756. 
GENESI8 OF THE DEPOSITS. 95 

The ledges, it is true, are siliceous, but most of the quartz was derived from the rock now alt~red 

to ledge matter and from the alunitized rock in the vicinity. Some silica doul?tless camel up 

with the solutions, but had these been very siliceous it is to be expected that they would hf.ve 

filled all interstices with solid crystalline vein quartz of the usual kind. On the contrary, !the 

quartz at Goldfield is flinty or cryptocrystalline, and occurs either as a metasomatic minrral 

replacing the country rock or as porous vuggy fillings formed by the accumulation of succesfive 

thin crusts, the process having rarely gone far enough to produce a solid m~ss of quartz. In this 

respect the deposits at Goldfield resemble those of Cripple Creek. It is possible that the ctystallinity of vein quartz does not depend wholly or chiefly on the supply of silica available !but 

is largely a function of pressure and temperature. At one end of the series may be the coarkely 

crystalline quartz of the pegmatite dikes or veins; at the other end the cryptocrystalline qurrtz 

of deposits formed close to the surface. If so, the character of the quartz at Goldfield is t1 be 

added to the other evidence in favor of superficial origin of the deposits. 

It is believed that the process outlined as the third hypothesis best explains the abun ant 

formation of alunite, with subordinate diaspore, and the intimate association of these min /rals 

with the sulphide ores and especially with the pyrite in the altered rock which surrounds the 

ores. This explanation of the genesis of the alunite is in accord with the experiments of Sa!fteClaire Deville, a who produced the mineral artificially by subjecting, for several months, frl agments of volcanic rock, suspended in water, to a stream of hydrogen sulphide mixed with air. 

By providing an efficient precipitant (sulphuric acid) supplied continuously to .a definite ~one 

traversed by the uprising metalliferous solutions, the hypothesis .appears to account wel~ for 

the remarkable concentration of the gold and associated constituents in this zone. As already 

mentioned, it is difficult to harmonize the extent and intensity of the alunitization with! the 

hypothesis of oxidation of lean deposits during erosion. It is still more difficult to explaid by 

such secondary enrichment the unusual concentration of the gold with so much tellurium and 

bismuth as are present in the Goldfield ores. 

Many of the important minerals of epigenetic deposits, as is well shown in the useful t~bles 

compiled by W. Lindgren band W. H. Emmonsc can be formed under different conditions land 

by solutions of diverse origin. The individual minerals that can be accepted with confidence 

as characteristic of a single bathymetric zone and of a single mode of genesis are certainly r ery 

few. Taken altogether, the minerals of the Goldfield ores suggest deposition at moderate or 

slight depth. They are not, however, as a group eharacteristic of what is ordinariiy undersfood 

as secondary enrichment. The tellurides particularly, in view of the recent investigatiop. at 

Cripple Creek,d are more indicative of deposition from uprising hot solutions than of enrichment 

by cold descending waters. ~ STAGES OF DIGPOSITION. 

It has been shown in the descriptive portions of this report that some of the richest o e is 

of later deposition than some of the siliceous ledge matter. The relation of this fact to1 

the 

various hypotheses suggested may appropriately be considered at this place. As regard~ the 

sulphide ores at least three depositional stages have been reeognized. These are (1) depos}tion 

of pyrite with famatinite, and probably also with some bismuthinite, gold, quartz, and alunite 

along zones of fissuring, associated with alunitization and pyritization of the neighboring coJ;_try 

rock; (2) deposition of rich nodular ores in zones of shattering in the previously formed l~dge 

matter; (3) deposition of narrow streaks of soft, dark, amorphous ore, often very rich in fl old, 

along fissures in the main ore bodies. These stages are not everywhere recognizable. More ver, 

it is doubtful whether they tell the whole story. It is highly probable that fraeturing foll~wed 

by renewed deposition has been repeated 1nany tin1es in the course of the formation of the ost 

a De !'alteration, par voie naturelle et artificielle, des roches silicatees, au moyen de l'acide sulfhydrique et de la vapeur d'eau: Compt. Rend . 

vol. 35, 1852, pp. 261-264. 

b The relations of ore deposition to physical conditions: Econ. Geology, vol. 2, 1907, p. 125. 

c A genetic classification of minerals: Econ. Geology, vol. 3, 1908, pp. 618-622. 

d Lindgren, W., and Ransome, F. L., Geology and gold deposits of the Cripple Creek district, Colorado: Prof. Paper U.S. Geol. 

No. 54, 1906, p. 204, and Chapter XI. 
196 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

important masses of ore, introducing a complexity which makes the record undecipherable. To 

determine whether a given mass of rich ore, with its characteristic concentric crustification, 

represents one or more periods of mineralization is by no means ·always easy. The mere fact 

that the gold, tellurides, and sulphides form shells around masses of dacite or andesite which 

have been changed to aggregates of quartz, alunite, and pyrite is not proof that the kernels 

had been altered before the crusts enveloped them. Many of the fragments, in fact, show by 

their rounded contours and by· slight textural and chemical differences in radial directions that 

the solutions which deposited the ores acted also upon the kernel which they were incrusting. 

(See Pls. XXIII to XXV). On the other hand, specimens such as those figured in Plate XXIII, E, 

prove that crusts of gold and sulphides may be deposited around fragments of rock that have 

been at least twice fissured and twice subjected to the action of solutions that deposited quartz, 

alunite, and pyrite. In other ore bodies there is no clear evidence of more than one period of 

mineralization. 

The third stage of deposition referred to, that which produced narrow seams of soft, dark, 

rich ore in some of the ore bodies, is not quantitatively of great importance. These seams may 

be very rich, but they are generally less than an inch (25 millimeters) in width and are filled 

with a mixture of attrition material and sooty sulphide mixtures of no definite mineralogical 

character. They are probably due to recent enrichment by the chemical action of the present 

ground water. This, as has been shown on page 220, is !n some places strongly acidic and is 

probably capable of dissolving and redepositing alunite and some of the sulphides. 

SUMMARY OF GENESIS. 

In accordance with the hypothesis of simultaneous solfatarism and oxidation it is believed 

that after the intruded dacite had solidified, but possibly beiore it had entirely cooled, the 

district and part of the surrounding region was subjected to stresses of unknown origin. These 

found relief in a very complicated system :of fissures, which were unaccompanied by any 

considerable displacement of the rocks. Hot waters carrying abundant hydrogen sulphide with 

some carbon dioxide and the various metallic constituents of the ores rose in these fissures. 

The dissolved hydrogen sulphide was oxidized in part to sulphuric acid in the upper parts of the 

fissu~e zones and at the surface. The resulting acidic solutions percolated down through the 

shattered rocks, changing their feldspars to alunite, mingling with the uprising sulphide solu- , 

tions, and precipitating the greater part of their metallic load as ore. The original solutions 

apparently were not everywhere equally rich in gold, since in many parts of the district ledges 

. were formed which have not proved to be of any value. · The most highly mineralized waters 

rose along a north-south belt about three-quarters of a mile in length and along the line of the 

Columbia Mountain fault, near Goldfield. Just what significance should be attached to this · 

coincidence of fault and mineralization is not clear. As suggested on page 83, the fissuring 

along this belt may have been occasioned by a renewal of movement along the predacitic fault . 

line. The presence of the fault fissure may also have favored deep connection with the ore 

sources. These suggestions, however, are not susceptible of proof and would have more weight 

did not some good ore occur in other parts of the district. 

It is believed that during this first stage of deposition most of the ledges were formed, 

much of the country rock was softened and alunitized, other parts farther from the fissures 

were propylitically altered·, and some masses of good ore were deposited. 

The ledges at this time were presumably harder than the . altered rocks which inclosed 

them, and it would seem at first thought that any subsequent fissuring would avoid the siliceous 

masses and pass through the softer material. To some extent it probably did so, the stresses 

finding relief in gouge-filled, curved, and irregular slips through the country rock. Movements 

in the soft country rock, however, which is more or less plastic near the ledges, could not fail 

to exert on these rigid brittle masses stresses which would deform them, like. the quartz pebbles 

in some squeezed and schistose conglomerates, by many small fractures rather than by a few . 

.simple fissures. The fractured ledge masses would be pervious to solutions, while the surround-
GENESIS OF THE DEPOSITS. 1 7 

ing squeezed country rock would be relatively imperviou:'· Some ledges after fracturing re perhaps cut off from communication with the rising mineralizing solutions and are to-d!ay 

comparatively barren. Others to which these waters had a~cess, particularly those in which 

considerable sulphide deposition had previously taken place, were enriched by the revival of ~he 

circulation of hot ascending sulphide solutions and cooler descending sulphate solutions mingl,ng 

in the manner already described. The conditions during this second stage of mineralization 

would probably be more favorable for the concentration and deposition of very rich ore tHan 

during the first stage. The shattered ledges may be likened to great sponges in the pores/ of 

which were provided ideal conditions for chemical reactions and precipitation, the sulphitles 

already formed probably aiding directly in withdrawing gold and fresh sulphides from soluti9n.a . 

It is not necessary to suppose that all the ledges were subjected simultaneously to this second 

fissuring or that all were affected by the same number of recurrent depositions. The ric~est 

ore bodies probably occur in those ledges which: were most often fractured and which at ~he 

same time retained nwst continuously an open connection with the deep source of the hot· 

sulphide waters. Movements in the ledges have continued up to very recent times and rna~ be 

still in progress. They are no longer followed, however, by any manifestation of thermal act~on, 

although they have afforded opportunity for some minor enrichment by waters which hfve 

passed downward through the belt of weathering. · 

Objection may be made to the foregoing hypothesis on the ground that, although the . ul-

. phur and cinnabar deposits of Sulphur Bank, California, exhibit a mode of deposition simila to 

that suggested for the Goldfield ores, no other important gold deposits are known to h~ve 

formed in this manner. It may be said, in reply, that no gold deposits comparable__ with t~ose 

of Goldfield are known, and it is no valid ground for surprise that their unique character ~ads 

to an explanation different from that applicable to gold veins such as those of the Mother ode 

belt in California. If the explanation here given is correct it follows that the conditions for the 

formation and preservation from erosion of deposits of the Goldfield type must be rare. Cli ate 

- alone may exert a controlling influence. If the original sulphide solutions rose in a regio~ of 

abundant rainfall, deep sqil, and luxuriant vegetation, oxidation of the hydrogen sulphide to 

sulphuric acid would take place less rapidly, and most of the a.cidic solution, instead of sinl1 ing 

deep into the ground, might flow off in streams. Such part as did seep down and survive the 

reducing action of organic compounds would mingle with a ground water diluted by cop ous 

rains and too rapidly renewed by run-off and additions to be of great chemical activity. 

In a region of rapid erosion the entire zone of alunitiz.ation might be removed in a eologically short time and deposits of no unusual character be left. 

ULTIMATE SOURCE OF THE ORE-BEARING SOLUTIONS. 

What was the ultimate source of the solutions that brought up the ores? Consider 

of this question takes us into a region where facts and hypotheses, inference, and specul tion 

are distinguishable with great difficulty, and where, in c~nsequence, dogmatism finds cong,nial 

soil. A genetic connection with volcanicity is strongly suggested by the geologic history of the 

region and is well-nigh pr.oved by the chemical character of the solutions and by the presum~bly 

high temperature at which they issued. This connection is indicated also by some points of 

similarity, particularly the presence of tellurides, between the Goldfield ores and those of Cdpple 

Creek, for which deposition from hot magmatic solutions appears more nearly demonstJable 

than for any district yet studied in equal detail. The thesis that the hot uprising solutiols at 

Goldfield emanated directly and solely from some crystallizing magma is, however, s~il far 

from proof. · -

The possible share, in much ore deposition, of water that at some time in its histo was 

precipitated from the atmosphere is not to be lightly dismissed. The argument, frequ,ntly 

advanced, that the dryness of most very deep mines precludes the primary concentrati~n of 

ores by meteoric water is not of great cogency. Its validity depends on the assumption /that 

a See Clarke, F. W., The data of geochemistry: Bull. U.S. Geol. Survey No 330, 1908, p. 558. 
198 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

the present conditions of permeability in the rocks are the same as when the ores were deposited. 

This obviously is not tnie. If it were, deposition by water from any source would have been 

impossible. The fracturing which permits the ascent of hot solutions also in most cases favors 

the descent of surface water. According to Arrhenius a there is no reason why this descending 

water should not penetrate to, and in the gaseous state be absorbed by, molten magmas. 

Evidence has already been presented which ·shows that during the deposition of the ores the 

rocks at Goldfield were more permeable to descending water than at present, or alunitization 

\vould probably never have extended so far and so .deep. It is supposed that this downwardmoving water was for the most part water that had first risen to the surface, but who can say 

how much rain water mingled with this and how deep the resulting mixture actually penetrated~ 

The work of Gautier,b also, shows how volcanic action, by heating masses of solid rock 

and generating therefrom large quantities of water and of the same gases as are emitted from 

fumaroles, may play a part in ore deposition . which is not dependent on the original water 

content of the intruding magma. · 

Although not inclined to deny the very important part played by volcanism in ore deposition, and while convinced that volcanic emanations have been largely responsible for the 

formation of the Goldfield ore bodies, I believe that we are not in a position to insist on the 

all-sufficiency of hypogene waters (that is, juvenile or original magmatic waters) to account 

for the deposition of most epigenetic deposits. The cooperation of water from different sources 

is not a negligible possibility and in the complex conditions and delicate adjustments incident 

to such cooperation is perhaps a suggestion of the reason why ore deposits are exceptional 

rather than invariable accompaniments of igneous intrusion. The mineralizing capacity of 

cold artesian solutions is ordinarily slight. Most masses of intrusive· rock, on the other hand, 

are not associated with productive mineral deposits. It is possible, however, that conditions 

most favorable for ore deposition may result when magmatic and meteoric water, and perhaps 

water of other kinds than is usually implied by these terms, contribute to the final result 

PRESENT ABSENCE OF VOLCANIC ACTIVITY. 

So far as can be determined from existing mine workings volcanic activity, notwithstanding its geologic recency, has completely died out at Goldfield. The mines receive no hot or 

warm water and no gases such as at Cripple Creek mark the final stage of expiring volcanism. 

This is rather remarkable, since many of the springs in this part of Nevada are thermal, and 

Spurr c found that at Tonopah the temperature increases downward at more than the normal 

rate. The highest rock temperature recorded by him was 78 ° F. (25.6 ° C.) at a depth of 766 

feet (233 meters) in the Ohio Tonopah shaft. Recently, however, water at a temperature of 

86° F. (30° C.) has been encountered at a depth of 1,250 feet (381 meters) in the Mizpah shaft.a 

Although no appreciably warm water occurs at Goldfield it is possible that refined temperature observations in the deeper shafts lately available might show a trace of the former heat 

in a temperature gradient somewhat higher than the normal for nonvolcanic regions. It is 

to be remembered that the waters of the Comstock lode had a temperature of only 70° F. at 

the 600-foot level. e 

It does not appear possible to connect the volcanic contribution to the Goldfield deposits 

with a magma corresponding definitely to any of the eruptive rocks in the Tertiary sequence. 

The supposition that the ·principal metallic constituents (with the exception of the iron) and 

some at least of the water in which these were carried issued from · a body of dacitic magma is 

. an attractive one, but has little real evidence in its favor. It may be remarked in this connection 

that a chemical analysis of the glassy, extrlisive dacite vitrophyre shows 3.35 per cent of water 

a Zur Physik des Vulkanismus: Geol. Fi:ireningens Stockholm Fi:irhandl., vol. 22, 1900, pp. 395-419. 

b La genese 

. 

c Geology of 

des eaux thermales, etc.: Annales des mines, 6th ser., vol. 9, 1906, pp. 316-370. Translated in Econ. Grology, vol. 1, 1906, p. 688. 

the Tonopah mining district: Prof. Paper U.S. Geol. Survey No. 42, 1905, p. 263. 

~Letter from Mr. W. H. Blackburn, superintendent of the Tonopah Mining Company. 

e Becker, G. F., Geology of the Comstock lode: Mon. U.S. Geol. Survey, vol. 3,1882, p. 252. 
. GENESIS 0]' THE DEPOSITS. 199 

driven off below 110° C. and 4.06 per cent lost above that temperature, a total of 7.41 per ce4t. 

The intrusive dacite, on the other hand, contains 2.95 per cent of water, 2 per cent being drivfn 

off above 110° C. It is not quite certain that these two rocks had the same magmatic origin, 

·but if so the dacitic magma originally contained a large quantity of water, much of which s expelled during the solidification of the more crystalline facies, as shown by the difference ~f 

over 4 per cent between the water of the two analyses. If the ore solutions came from t~s 

magma they presumably rose from portions solidifying at such depth as would develop a ill 

higher P.egree of crystallinity than in the visible dacite and lead to a further expulsion of wa~er 

and mineralizing constituents. It is quite possible, however, that the ores emanated frol 1l a 

magma differing in composition from any one of the eruptive rocks in the district. 

GOLDFIELD TYPE OF DEPOSIT. 

The recognition of alunite as a characteristic constituent of the Goldfield ores and 1lhe 

demonstration of its genetic relation to them ablishe~ a new type-that of alunitic ar d 

kaolinitic gold-quartz veins-in the classification of epigenetic deposits based upon the kind/ ?f 

metasomatism effected in the wall rock by the ore-depositing solutions. While the Goldfield 

deposits are probably too irregular in form to come under the usual definition of vein, yet in all that relates to genesis of the ores there is no essential difference between them and wha is 

usually termed a metasomatic fissure vein. · 

According to Robert T. Hill,a mineralization very similar to that at Goldfield has affec eel 

the rocks in the mining district of Alunite,b 22 miles (35 kilometers) southeast of L. as V11

as, 

Nev. Prospecting is in progress but no ore bodies of importanpe have yet been found. 

This chapter may fittingly be closed by recalling to mind how complex is the proble of 

genesis of most deposits of the precious metals and how uncertain in character are the data 

available for its solution. These are fragmentary and only in small part consist of defi+te 

facts wi~h kno~n quantitative va.lues. A careful siftin¥ of more or less doubtful evidencr is 

all that Is possible and the result Is usually a matter of Judgment rather than of mathematical 

proof. As regards Gol~field the evidence has been presented without conscious bias and he 

conclusions are submitted to the reader with full realization that no one of the three hypotheses 

suggested is certainly impossible. Were the question referred to a geological court its deciJion 

might .not be unanimous. 

a Camp Alunite, a n ew Nevada gold district: Eng. and Min. Jour., vol. 86, 1908, pp. 1203-1206. 

b A new name for a district prospected years ago and formerly known as Railroad Pass. 
CHAPTER XVII. 

PRACTICAL CONCLUSIONS. 

deposition 

If the genesis of the Goldfield deposits has been correctly inferred it follows that the 

not 

of rich ore is connected with alunitization. It follows, further, that at some depth 

yet determined the alunitic phase of alteration is replaced by metasomatism of a different 

meters) 

kind, probably sericitic, accompanied by ores of lower grade. To a depth of 600 feet (183 

there is little if any decrease in the abundance of alunite, but there are indications 

ment, 

of generally lessening tenor of the ores. There may be individual exceptions to this last stateof 

but few thoroughly familiar with the underground workings in the district and capable 

impartial judgment are likely to question its· essential truth. 

Even if the rocks below the depth of 600 or 700 feet (183 or 213 meters) were the same 

be 

as those above, it is believed that considerable changes in the character of the deposits might 

looked for in the next 300 or 400 feet (91 or 122 meters) of vertical development. The 

which 

rocks, however, are not the same, and this fact renders prediction very uncertain. The latite, 

bearer 

generally underlies the dacite and Milltown andesite, may prove neafly as good an ore 

principal 

as 

mineral 

the latter two rocks. This, however, is a little doubtful. Most of the shafts in the 

brian 

belt may at any depth below 1,000 feet (305 meters) enter rhyolite, Camshale, or alaskite, and although no one can with certainty assert the barrenne$s of these 

formations their present record in this district is not encouraging. 

The tendency of the main ledges near Goldfield to flatten out to the east on the lower 

understood 

levels is also rather disconcerting, although .the significance of this feature can not be fully . 

until the deep levels are fur..ther developed. This behavior does not prove that the 

ledges may not somewhere regain a steeper dip and continue down 'through the predacitic 

exploitation, 

rocks, but it defers. the confirmation of that hopeful supposition, increases the difficulty of 

and introduces greater possibilities of losing pay shoots by faulting.a 

great. 

Above the 500-foot (152-meter) plane the productive possibilities of the district are still 

although 

In 

most 

the principal mines there are large reserves of ore which can be milled at a profit, 

of the richest portions have been mined by lessees. In the announcement of 

the Goldfield Consolidated Mines Company at the end of 1906 the ore reserves of the Mohawk, 

Jumbo, Red Top, and Laguna mines were estimated at $7,750,000. This was said to be" exclusive of low-grade ore," and did not include the Combination ~nd January mines, later acquired. 

In the same announcement 

known 

it is estimated that at least $30,000,000 gross may be produced from 

ore shoots in the Mohawk mine alone.- The quantity of ore available is undeniably 

large, but in no district are the difficulties in the way of estimation greater, owing to the irregular 

shape, erratic distribution, and wide range in tenor of the pay shoots. 

:Many new ore bodies are likely to be found in the rich belt near Goldfield, although so 

of 

thoroughly has this part of the district been explored that it is not probable that any deposit 

ductive 

the importance of the Mohawk ledge has escaped detection. On the other hand, the promuch 

areas are steadily being enlarged by the discovery of new ore bodies, and in spite of 

unproductive 

fruitless prospecting over the district at large the possibility of success in some hitherto 

localities is still open. 

p1ining 

There is, and probably always will be, a large element of chance in the discovery .and 

of deposits of the prec!ous metals, and it is· vain to expect that geologic study, no 

a According to the Engineering and Mining Journal of January 2, 1909, the Clermont shaft has cut the Mohawk pay shoot at 856 feet (261 meters), 

or 241 feet (73 meters) below the bottom of the dacite . . The ore is said to assay $22 a ton. This is encouraging as regards the possibilities in the 

Iatite. 

200 
PRACTICAL CONCLUSIONS. 201 

matter how conscientiously and ably pursued, can eliminate all of the risks of the search. The 

obscure conditions that determine the movements of underground solutions and influence the 

precipitation of their contents can rarely be discovered from the relations of the rocks at the 

surface. Geology can seldom do more than suggest intelligent trial; and he who undertakes 

extensive prospecting without a realization of the ratio of success to failure and without being 

prepared to shoulder the latter, is playing desperately against chance. On the other hand, 

it must be admitted that were prospecting . in general conducted with the same caution and 

With the same careful scrutiny of probabilities as obtains in ordinary business many deposits 

which have yielded fortunes to their discoverers would never have been found. There are 

few gold districts that are not indebted to some man's blind good fortune. This has been 

well illustrated at Goldfield, and the brief but eventful history of the district teaches that 

surprises may be in store for one who presun1es to say with assurance what ground is ore 

bearing and what ground is not. · 

Local experience has shown a close conneetion between rich ore and alunitization. This 

association is of value as indicating the better chances of a prospect in alunitic material than 

of one outside of it. On the other hand, the presence of alunite is no proof of the presence of 

gold, even in this district, as many have learned to their cost, and the hasty generalization 

that alunitized rocks; wherever found, must be gold-bearing rocks is wholly unwarranted. 

The occurrence of this mineral means simply that rocks containing some potassic and aluminous 

silicate have been acted upon by sulphuric acid. A second deduction is that these rocks must 

have contained pyrite or else have been subjected to solfataric action. In either case mineralizing 

processes have been active and gold or other metals may have been concentrated. The reasonable conclusion is merely that the locality is worthy of some prospecting. 

Local experience at Goldfield has shown also that the rich ores are more or less intimately 

associated with the craggy siliceous outcrops characteristic of the district. . This does not 

mean that all such are auriferous, nor does it mean that no bodies of ore occur under topographic depressions floored with soft rock. It is evident that the dip of a ledge or pay shoot 

must carry it in places under rock whieh is soft at the surface. Experience does suggest, however, that exploration near ledge outcrops is more likely to yield results than shafts sunk at a 

distance on low ground or in areas covered deeply by lacustrine or alluvial deposits, unless 

such shafts are put down to cut a known ledge on the dip. 

With reference to the areal distribution of the deposits, no part of the district appears 

likely to surpass in richness the small elongated area containing the Red Top, Mohawk, Combination, Jumbo, and Florence mines. The geologic conditions which have determined the 

remarkable preeminence of this limited area a:re not certainly known, although, as suggested 

on page 83, the relation of the Colun1bia Mountain fault to the dacite may partly account 

for the exceptional concentration of gold. As regards general geologic features the belt of 

conspicuous outcrops stretching from the vicinity of Milltown past Preble Mountain appears 

prom1smg. It has been very persistently prospected, however, with but indifferent or 

negative results. 
CHAPTER XVIII. 

DETAILED DESCRIPTION OF THE MINES OF THE GOLDFIELD CONSOLIDATED 

MINES COMPANY. 

INTRODUCTION. 

The mines to be described in this chapter, in general order from north to south, are the 

Red Top, ~t[ohawk, Jumbo, Combination, and January. The history of the consolidation of 

this group has been given in Chapter I, and the relative positions of the mines are described 

on page 136 and shown in Plate IX. The close connection or proximity of the various underground workings, not only of those belonging to this group, but of the workings of other companies and of lessees, alth<?ugh it increases the difficulties of systematic treatment, has a compensating advantage in that it saves some repetition of descriptive details. Certain features 

well displayed in one mine will be fully described, while the same characteristics occurring less 

conspicuously in another member of the group will merely be briefly noted. The 8pace devoted 

to the description of each mine depends less upon the size or productivity of the property than 

upon the information its workings supply relative to the geologic occurrence and genesis of the 

Goldfield ores. 

RED TOP MINE. 

HISTORY. 

The Red Top mine, although older than the :Mohawk, was late in development in comparison with the January, Combination, and Jumbo mines. In April, 1904, some ore was found by 

lessees, but this apparently was not of great extent, for the mine attracted tittle funher attention 

until February, 1905, when the main ore shoot was opened by the Red Top Mining Company. 

By November in the same year the mine had produced ore to the value of $60,000, and in 

December it became one of the principal mines in the district. Its total gross production up 

to the consolidation in November, 1906, was $308,515.60. Under its present ownership the 

mine produced ore of the gross value of $201,025.51 from December 1, 1906, to October 31, 

1907. At the time of last visit, in July, 1908, no work was in progress in this property, although 

mining will undoubtedly be resumed when the company's new mill is in operation. 

UNDERGROUND WORKINGS. 

At the time of first visit, late in 1905, the Red Top shaft was 180 feet deep, with levels at 

100 and 165 feet. These two levels, which were short, ran generally north-northwest and southsoutheast. There had been no stoping at the time the mine was studied, all the ore having been 

taken from drifts and from a raise above the 100-foot level. At the time of second visit the 

workings had been developed as shown in Plate XXXII . . Unfortunately, the levels above the 

165-foot level · were riot accessible at that time, and some of the long crosscuts to the west on 

the lower levels, which probably pass from dacite into latite, had caved. The ground in the 

vicinity of this contact is in most places very soft, constant attention being required to keep 

it from falling. 

Extensive stopes have been opened in the oxidized ore between the 165-foot level and the 

surface, but practicaJly no attempt has been made as yet to handle the sulphide ores below that 

level. 

202 
U . S . GEOLOGICAL S URVEY 

N 

SECTION ON LINE A-A' 

( largely conjectural) 

Q\ 

\ 

0 \ < -· 1 ...... \ ~ 

<D ' 

0 100 200 feet 

P ROFESSIONAL PAPER 66 PLATE XXXII 

Shaft 

\ so-ft . level 

100-ft. level 

PLAN AND SECTION OF RED T P MINE 
MI EH OF THE L FIELIJ ON.' L[D TED liNE O)[PANY . 20 

OE )L()(;J(' l ELATl -

Th haf 

TilE LEO<H .. 
204 

30 

en 

THE Y Ai' ORE DE 0 TT F ,OLDF rELD :rE AD . 

TIJ E 1 \ Y SH T 

ldfi 1cl min 

tudy th 

MOil\." K !fiXE. 

ISTR 

om J atw· of the production of the Jfohav·k min . 

a lculated from royaiLi at 224 p r ot . 

c nne time pnrtlj ftllcd with 

C;l jti w rc lin('d wi h 

70.'),469. 5 117. 10 
MINE F THE GOLDlfiELD ON LIDATE D 

Royaltie , oldfi ld Mohawk Mining ompany y ar ending ctob r 1 1907. 

<•, t' footnOI ('. p. :!00. 

370, 02. 71 

9 7.62 

205 

f 
2 6 'I HE Y L ' D RE DEP IT F 'OLDFIELD ~.E\ AD • 

FI RE 21.- ; logi plnn of th tiOO-foot I v I f th Mohawk min . 

1 i

nT~p of level 

, 

, 

Daditic I 

I 

: 

I 

' ' ' I 

I 

I 

matter \:. : c,oro-taC 

1 Latit.ic 

ledge matter 

E.------~~8-o-tt=om=-o~f-le~v-ei--------------W 

0 5 10 FEET 

lO lh(' 
U. S . GEOLOGICAL SURVEY PROfESSIONAL PAPER 66 PLATE XXXIII 

PLAN OF THE MORA WK MINE, ROWING AL THE WORKING F LE SEE ON THE OLD WEDC.E LAIM 
MINE .B' THE U L l:!'IEL C r :40LID \ TED )ll N K C >)li'ANY . 2 ,., 

On non )f the l 

f th dn 

a rna 

F lDf .\XD DI, TJ rnrTJOX OF TilE u --:n E . . 

The w r , n. sjngl w IIdir 
20 . DFTELD E D~. 

f xi lati n, ·whi l in uot 

plan (Pl. :xx:..l"TIII) . m t t 'r int whi h 

rd r n· m d, 
:\I P • Y. 

u ing th r M gr 'ill<'r d< pth . Tlws on• hodic f >rill pn1 ·Litnlly n 

·onn c ·t di n• ·tl_,. xith h, t n>rkcd in th li n~·(' -.JJonn iff' l <ts and hn b({'ll xpl >r l d \\'ll to 

t h 60 -fo) l<>n"' l r h .Jl ha\\'k. ' outh f t h e Jn;lin . lwft , )Jl the; ;)0-font J. \ ' ( l th !'(' i.' il 

f n· a, di tnnC' of 1tb ut ;j -0 f t. nth -~:.-0-foot h Y I on in 

OMBIN . 'riO :r MI E . 

H I T( l Y .L · n P l 

"Tlw <'omhination min ~fin . nnd .d. l r s ,·ol. .. , 190i, p. 397. 
21 T lT h ' EOU ; ¥ .\"X J) HE I Fl ~lT~ OF (i LDFf E Ll , \ EV.\DA. 

f t ht' 

and 11 

rl hi.• 

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:3 ft>f't d ('p wilh .- I<' l . 'I'h 

nfln <I 

XJH l 11 t•. · n W >RKIXO . . 
U. S . GEOLOGICAL SURVEY 

PROFESSIONAL PAPER 66 PLAT£ XXX IV 

R E N C E 

S L M J M · ......... ·· L I N E 

\ 

C 0 M 8 N A T 0 N N 0. 

C 0 M 8 N A T 0 N N 0 . 2 

J 

R u A R y 

ENOAAV£0 AND PRINT£ 0 BY nu: IJ,S OEOlOGI 1.. SORVtY 

PLAN OF THE COMBINATION MINE AND THE PRODUCTIVE PART OF THE JANUARY MINE 
MlNb:S OF THE GOLDFIELD CONSOLIDATED MINES -<JOMPANY. 211 

GEOLOGIC RELATIONS. 

The general geology of the mine is simple. The 80-foot and 130-foot levels are entirely in 

dacite. In the early days· of mining' the ledge matter produced by the alteration of this rock 

was often called rhyolite. Latite appears first on the 180-foot level (see Pl. XVIII), a.nd as the 

contact dips to the east more and more of thi-s rock is exposed on successively lower levels. The 

details of this contact are not well known. The dip 

varies from place to place. On the line of section 

D-D' (Pl. XVII) the average dip is probably not over t 

30° and on the 380-foot level is not over 15°. Farther ~ I:'J 

southeast the dip increases, as shown in the sections ~ 

of Plate XVII, which, it should be borne in mind, are ~ 

not at right angles to the general strike of the contact. § ~ 

Where the rocks at the contact are soft some slipping ! ~ 

has as a rule taken place. Where, however, an ore ~ ~ 8, body lies at the contact the latter is close and irreg- .... £ ::T 

ular. Although its original character is largely oblit- ~ 

erated by the mineralization the contact at such ~ 

places (for example, stope _No. 316 on the 280-foot ~ 

level) suggests igneous intrusion. [ 

Some faulting l1as probably taken place since the : 

ore bodies were forn1ed, but, as in the Mohawk, seams g 

~ of soft gouge occur at so many places that it is impos- s 

$ible, without undertaking special development work S: 

~ 

for the purpose, to trace any given seam through from g· 

level to level. No evidence is yet available that s 

s· 

indicates any extensive displacement of the ore -: 

bodies. 6 

~- FORM AND DISTRIBUTION OF THE LEDGES. (1Q 

0. 

;· 

The Combination claims were located on one of ~ 

~ the rusty siliceous ledges common in the district, the ~ 

actual pay shoots or ore bodi~s, as subsequently [ 

found, constituting portions only of the ledge matter. ~ 

In the following pages the ledges will first be de- [ 

scribed and then attention will be directed to their ~ s· 

inclosed or associated pay shoots. ~ 

8, As exposed at the surface the main ledge appears p; 

to have a simple linear character and to trend ~ 

N. 50° W. It can. be traced for a distance of about ~ g;. 

1,000 feet, the Combination shaft being nearly in the ~ 

middle of the line of outcrop. To the northwest the ~ 

ledge has not been followed beyond its junction with [ 

the curved January ledge. To the southeast it be- ~ 

comes indistinct near the Reilly shaft, although the s· 

ledge appears to lie in the same zone of fissuring that ~ is.conspicuous in the Florence mine, southeast of the 

Reilly shaft. 

0 

Ul 

0 

)> 

_r 

arrl 

oN 

0 

0 

z 

(_ 

ibg(jit. O.c I 00.0> I I 

Cb, 1 I 

'< I 1. 

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I I ,--..._; I 

(_,.... ......... ,I 

'I 

I I 

I I 

I I 

I'· 

(DW 

~en -::r 

; 0> 

.:!? 

The underground workings of the Combination mine show two ledges, between which no 

direct connection has yet been established. These are best displayed in the plan of the 130-

foot level. (See Pl. XVIII.) On this level the main ledge has been developed from a point 

about 150 feet northwest of the shaft southeastward into the Reilly workings. When the mine 

was first ·studied in 1905 this main ledge was not known to be continuous underground, the 

~· 
212 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

conditions then obtaining being illustrated in figure 23, taken from the preliminary report. 

Since that time large stopes have been opened in the ground between what were then known 

as the Combination shoot and the No. 2 shoot (see fig. 23) and the continuity of the main ledge 

established, as shown in Plate XVIII. · 

The northwest part of the 130-foot level goes through about 200 feet of generally soft 

altered dacite into the January ledge, which has not yet proved very productive within the 

Combination mine. This ledge, as is shown on page 127 and in Plate XXXIV, curves in the 

January claim so that the southeast end of the January workings is in line with the main Com-

.bination ledge as developed on the 130-foot level. The intervening ground has not been 

;explored, and it is possible that the Combination and J~nuary ledges may yet be found united. 

If so; the ledge as a whole on the ~ 130-foot level has the remarkable plan shown in figure 24. 

Below the 130-foot level the Combination workings do not reach the January ledge, nor do they 

as yet satisfactorily reveal the outlines of the Combination ledge. So far as possible these 

:outlines are approximately shown in Plate XVIII. 

! The Combination ledge as a whole dips to the east, but as may be seen from the sections 

of Plate XVII the mass is exceedingly irregular. The general dip to a depth of about 250 feet 

N. 

1 

100 0 100 200 3oofeet ~~~~----~----~----~ 

FIGURE 24.--Diagram showing possible plan of the combined January and Combination ledges. 

is from 60° to 70°. Below this, near the contact of the dacite with the latite, the dip decreases 

and the ledge shows a tendency to flatten toward the east. Very little is known of the hangingwall side of the ledge matter on the lower levels. 

The boundary between ledge matter and dacite or latite is in some places a gouge seam 

or fault. The hanging wall of the ledge on the 130-foot level is in general well defined by a 

seam of tough leathery gouge up to an inch in thickness. This seam is particularly distinct in 

the vicinity of the Reilly workings. In some places it contains well-formed crystals of gypsum 

which must have · crowded aside the tenacious clay to make room for themselves. In many 

parts of the lower workings there is a gradual change from ledge matter to country rock. An 

.attempt has been made to indicate such a transition in the sections of Plate XVII. As in the 

Mohawk mine, the shape of the ledg~ has probably been somewhat modified by faulting, but 

the data for discriminating such modification from the great initial irregularity of the mass are 

not available. There is a suggestion that some of the irregularity of the ledge between the 

180-foot and 280-foot levels (see Pl. XVII, sections E-E', F-F', and G-G') may be due to faulting nearly parallel with . the contact. 
MINES OF THE GOLDFIELD CONSOLIDATED MINES COMPANY. .213 

MATERIAL OF THE LEDGES. 

The typical ledge matter of the upper levels is a loose porous mass of rusty angular fragments of altered dacite. There are all gradations, from material which is merely traversed 

in all directions by C!acks to loose rubble-like masses with many open interstices between 

the fragments. The interstices are often partly filled. and the fragments coated with yellow· 

or brown ocher, sometimes associated with much kaolinite. The fragments themselves, when 

broken, prove to be hard masses-of gray porous quartz of generally flinty texture, but showing, 

in spite of intense alteration, the original quartz phenocrysts of the dacite. The pores are in 

part irregular in shape, but in part they represent spaces left by the removal of the ~eldspars 

and of pyrite. They are usually lined with small quartz crystals, and when the rock is broken 

open are found to contain water, even in dry parts of the mine. The pyrite in these fragments 

is seldom completely oxidized, small disseminated crystals being abundant in the denser portions of the flinty quartz. Small pearly scales of bismite are associated with the ocherous 

limonite in some parts of the ledges, particularly in the January ledge and in the southeastern 

part of the Combination ledge. While often associated with rich ore the bismite also occurs in 

ledge matter· of no value. 

Below the zone of oxidation in the Combination the marked distinction between ledge 

matter and the alunitized and pyritized dacite vanishes. The contrast in color between the 

rusty ledge matter and the unoxidized country rock in the upper levels of course disappears 

in the sulphide zone, but more is involved than mere loss of color distinction. In the lower 

levels the sulphides are associated with mu.ch alunite, and the ore and l(3dge matter is in many 

places apparently less siliceous and softer than in the oxidized zone. Whether, however, there 

is really less silica in a cubic meter of this softer unoxidized material than in the harder but much 

more porous ledge matter of the upper levels is a nice question and one not to be answered offhand. In other words, it is doubtful whether or not the unoxidized ledge matter which grades 

insensibly into the country rock in the deeper levels could be converted by the mere removal 

of some constituents into a mas~ as hard and siliceous as the ledge matter of the oxidized zone. 

The pyritized dacite, even when close to rich ore, carries very little gold, assays of such 

material seldom giving over 40 to 50 cents "to the ton. The disseminated pyrite is clearly very 

slightly auriferous. 

FORM AND DISTRIBUTION OF THE PAY SHOOTS. 

The pay shoots in the Combination mine are such portions of. the ledges as cont_ain enough 

gold and silver to be classed as ore. As a rule, it requires a trained eye to distinguish ore from 

barren ledge matter, and some ore. is recognizable as such only by panning or assaying. There 

is no real boundary as a rule between ore and mere ledge .matter. 

Under these circumstances it is a difficult n1atter to describe the form of the ore bodies, 

inasmuch as this varies from time to time. Originally only the rich streaks of ore were stoped, 

but afterwards, as improved milling facilities rendered possible the treatment of lower grade 

material, these stapes were greatly enlarged. Descriptions of ore shoots based upon the stoping 

down prior to 1906 are not applicable to present conditions. Detailed descriptions of form suggested by existing stapes would likewise be of little value a few years hence. 

In Plate XVIII, showing the plans of the levels, an attempt has been made to illustrate 

some of the changes made in the apparent shapes and sizes of the pay shoots in the course of 

development. The illustration shows the streaks of rich shipping ore known in 1905, the 

approximate outlines of the stapes at the end of that year, and the present stapes. From this 

plate and the sections of Plate XVII, the reader may gain a better idea of the irregular shapes 

and distribution of the ore bodies than can be given by words. He should bear in mind the 

gradation of ore ·into ledge matter ~nd the probability that in a few years many stapes now 

separate will coalesce. . 

The original Combination pay shoot_ came to the surface near the old inclined shaft and 

according to Mr. Collins had a stope length of 120 feet and a width of from 30 to 50 feet. This. 
214 . THE G~OLOGY AND ORE DEPOSITS OF . GOLDFIELD, NEVADA. 

has been mostly stoped, leaving an open pit or "glory hole" (Pl. XXII, A), which is being 

steadily enlarged. Probably a large part of the ledge matter exposed on the present 80-foot 

level will finally go through the mill. 

On the 130-foot level the best ore near the shaft in 1905 occurred on short, nearly northsouth fissure zones which cross the general trend of the ledge. The very richest portions, 

although irregular, showed a tendency to form vertical pipes or" chimneys.'; 

The first pay shoot' discovered in the southeast part of the mine in what was known in 

1905 as the No~ 2 ledge (see fig. 23), was found in the No. 3 shaft, which goes down in. the footwall side of the ledge. This little shoot was elliptical in plan and was practically confined to 

the shaft. It pinched at 30 feet in depth. The ore was not particularly rich at the surface, 

but at a depth of 15 feet ore was found which in places carried 150 ounces of gold to the ton. 

In all, this small shoot of oxidized ore produced about $65,000. 

When the ore gave out in this shaft, a crosscut was run to the hanging wall of the No. 2 

ledge, and this opened up the main No. 2 pay shoot. This, as worked on the 130-foot level in 

1905, was a fairly regular streak of oxidized or~ lying within the -ledge matter, but close to its 

hanging wall, which dips at angles ranging from 60° to 7 5° NE~ The ore had a maximum 

'width of about 6 feet, but it passed with no plane of separation into ledge matter, and the 

width of ore stoped was determined solely by the conditions of economic mining at that time. 

This pay shoot had been stoped at the time of first visit to a length of about 300 feet. It is 

not actually continuous with the Reilly shoot, but the two are connected by a distinct zone of 

fissuring. Since 1905, as shown in Plates XVII and XVIII, stopes have been opened along 

the foot-wall side of the ledge in this part of the mine and have in places been carried across 

the full width of the ledge. They have also been carried northwest until they are almost continuous with the stopes north of the shaft, on what was formerly supposed to be a distinct 

pay shoot. (See fig. 23.) 

Comparison of Plates XVII and XVIII bdngs out some interesting features regarding the 

behavior of the pay shoots with increase in depth. It appears that the ore bodies are fully 

as erratic in a vertical direction as they are in horizontal directions. The large ore body, for 

example, on the 130-foot level, cut by sections B-B', D-D', and E-E', does not extend in 

full strength to the 180-foot level, and on the 230-foot level is unknown. While good ore has 

. been stoped from the 280-foot level, the value o.f the ledge below this, where it flattens with 

the dacite-latite contact, has not yet been determined. Although some good ore in latite 

has been opened on the 380-foot level east of the shaft, the extent of the body had not been 

ascertained at the time of visit in 1908. 

CHARACTER OF ORE. 

The ore of the Combination mine includes oxidized and unoxidized varieties. The typical 

rich sulphide ore is a rather loose mass in which the fragments consist of altered dacite and are 

surrounded by thin shells of gold and sulphides. These fragments vary greatly in .size and shape~ 

Most of them, however, are probably less than 6 inches in diameter. Many are much smaller, 

and having been rounded by chemical action give the ore a decided nodular appearance. 

The dacite of these fragments, some of which show signs of an earlier period of brecciation 

and cementation, exhibits various stages of alteration. Some of it is changed to a dense flinty 

quartz with irregular drusy pores. Other fragments, and these are apparently the more 

numerous, ~ontain much alunite with the quartz, the alunite appearing partly as soft white 

pseudomorphs after feldspars. Minute crystals of pyrite are nearly everywhere abundantly 

disseminated through this altered dacite, but they certainly do not carry more than a very 

small part of the gold in the ore. 

The outer, highly mineralized crust of these fragments varies from a few millimeters to a 

centimeter in thickness. The metallic.minerals are not everywhere arranged in precisely the 

same sequence nor developed in the same relative abundance. In what may be regarded as 

typical rich ore, however, the inner layer of the auriferous envelope is a somewhat indefinite dull 
MINES OF THE GOitDFIELD CONSOLIDATED MINES COMPANY. 215 

yellow band which close examination shows to consist of fine particles of gold embedded in qqartz. 

In the richest specimens this hand may bP- as much as 5 millimeters in width. A section of these 

bands as seen under the microscope is shown in Plate XXVI, A. 

As seen in hand specimens of ore, there is no definite boundary between the auriferous band 

and the kernel of altered dacite: It appears, in fact, as if the gold had penetrated the substance 

of the rock and crystallized metasomatically at the expense of some of the rock constituents. 

The microscope shows, however, th.at there is a distinct surface of demarcation between the 

golden envelope and the dacitic kernel. The kernel contains disseminated pyrite, while the 

auriferous band is usually free from this mineral, the irregular hackly particles of gold being 

intimately associated with famatinite and bismuthinite. The microscope shows also that the 

gold and associated metallic minerals are embedded in an exceedingly fine-grained aggregate of 

quartz with a little kaolinite, the aggregate bec\ng noticeably finer grained than that resulting 

from the alteration of the dacite in the kernel. It is also free from quartz phenocrysts, as far 

as seen.. The minute quartz granules of this aggregate exhibit shadowy, wavy extinction, suggestive of an extremely fine fibrous or chalcedonic structure. The contact between this aurifer-

-ous envelope and the material of the kernel, which is still recognizable as altered dacite, while 

definite, is ragged in detail and is not such as would result from the mere accretion of material 

upon a smoothly rounded surface. Nevertheless, the form of the frag1nents shows that some 

preliminary rounding did take place, this being effected by attrition probably aided by solution. 

Subsequently the auriferous envelope was deposited, neither by direct accretion nor by partial 

penetration and metasomatism, but by a narrowly confined process which appears -to have 

involved complete recrystallization of a thin peripheral part of each fragment with the jntroduction of much gold and probably the removal of some constituents originally present. The 

extreme fineness of grain of the quartz which constitutes the immediate matrix of the gold 

indicates that the auriferous solution was a poor solvent for silica. Whether the alteration of 

the dacite kernel, with the development within it of alunite, took place while the fragments were 

receiving their initial rounding, or while the gold was being deposited, is· in most cases an indeterminate question. As will presently appear, this alteration may have been taking ·place during 

both periods and may have continued to a later stage of ore deposition. 

Outside of the envelope of native gold there is, on most fragments, a layer of faniatinite. 

This varies much in thickness, and where it is not present its place is taken by pyrite or marcasite. The latter two minerals are not always readily distinguishable, as pyrite frequently 

occurs in radial crusts such as are characteristic of marcasite. Where the crystal form is not 

sufficiently well developed to serve as a means of distinction, the tendency of marcasite to disintegrate after specimens have been kept for a few months may be utilized. Such specimens 

show an efflorescence -of sulphur, and the sulphuric acid formed attacks the paper label or tray 

upon which the material may be resting. The iron sulphides in some cases coat the famatinite 

directly; in others they rest upon an intervening crust of drusy quartz. 

In Plate XXIII, A, is illustrated some very rich ore from the 230-foot level. In this the 

band of gold is from 2 to 4 millimeters in diameter. The fragment which it incrusts is clearly 

itself a breccia and must have been cemented into a firm rock again prior to the deposition of 

the gold. The microscope shows this older breccia to be now an aggregate of fine crystalline 

quartz, with pyrite and kaolinite. Alunite does not happen to be present in any considerable 

quantity in this specimen. 

The interstices between the larger fragments such as have been described are usually filled 

with smaller, less distinct fragments, similarly incrusted, with bunches of famatinite and with 

much alunite. Some kaolinite may be mixed with the alunite, and both minerals generally 

contain embedded crystals of pyrite. Such pyrite crystals often exhibit the common pyritohedral habit, but in many specimens they are all octahedral. Films of drusy quartz are not 

uncommon in the ore, but nowhere in the mine were any quartz crystals seen of sufficient size· 

to permit recognition of their crystal planes without a lens. Solid masses of vein quartz are 

entirely absent. 
216 THE G~OLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

Ore of the kind described has in some places been subjected to later crushing and brecciation. Such material often shows dark, soft streaks of obscure sulphides, and some of it is rich 

in gold. 

By way of summary, it may be said that the unoxidized ore of the Combinatio~ mine 

·shows at least three stages of chemical and physical activity. These are asfollo~s: (1) Brecciation of the dacite and cementation by fine crystalline quartz apparently formed by recrystallibelongs 

zation of the silica in the rock. How much of the pyritiz!Ltion and ·alunitization of the rock 

to this period is difficult to say. (2) Rebrecciation, rounding of fragments by attrition 

marcasite, 

and solution, and deposition of gold, famatinite, and bismuthinife, associated with pyrite, 

crushing 

alunite, kaolinite, quartz, a little telluride of gold, and some silver. (3) Later 

along fissure zones and some secondary concentration of the gold, probably by descending waters. There is no evidence that the first stage contributed any valuable constituent to 

the deposit. The gold, silver, bismuth, copper, tellurium, etc., appear to have been introduced 

in the second stage of the process. 

With 

. 

ore 

the exception of the small shoot· of oxidized ore found in the No. 3 shaft, the richest 

near 

in the mine has been the first hundred feet of the unoxidized ore in the original No. ·1 shoot, 

the main shaft. 

While it was known in 1905. that the unoxidized ore of the Combination contains some 

tellurium, . no mineral recognizable as a telluride had been detected. Since then rich · telluride 

280-foot 

ore, closely resembling that of the Mohawk mine, has been found in stope No. 316, above the 

level, about 150 feet east of the shaft. 'This ore occurs partly in latite. 

··:I The oxidized ore, as already mentioned, is not readily distinguished from ordinary oxidized 

ledge matter. The gold is visible at some places, but at more it is masked by yellow ocherous 

oxidized 

limonite from the decomposition of pyrite or marcasite. Kaolinite is rather abundant in the 

ore, while alunite is rare. The hydrous copper carbonates are rarely seen in the 

thoroughly oxidized ore, although they occur in small quantities in the zone of partial oxidation. Alum, gypsum, and melanterite (ferrous sulphate), the latter sometimes mixed with a 

little c~alcanthite, occur usually in seams or as efflorescent coatings in or just. below the oxidized 

zone. 

of 

The change from oxidized to sulphide ore in the Combination mine takes place at a depth 

about 140 feet. · 

UNDERGROUND WATER. 

'Vater was reached in the Combination mine at approximately the 130-foot level. In 1905 

when 

from 1,500 to 2,000 gallons were hoisted daily to keep the water below the 230-foot level, and 

making 

the 280-foot level was open the quantity raised was greater. In 1908 tne mine was 

practically no water, being drained by deeper adjacent workings. 

JANUARY MINE. 

• HISTORY. 

was 

Prior to its absorption by the Goldfiehl Consolidated Mines Company, the January mine 

January 

owned · by the Goldfield Mining Company, their holdings comprising, in addition to the 

and February claims just west of the Combination ground, .5 claims in other parts of 

one 

the district. 

year 

At the beginnihg of the year 1904, a lease on the January claim was granted for 

to L. L. Patrick and others, who within a month began to make shipments. The 

wcrth 

lease is reported to have produced 1,000 tons of high-grade ore, yielding $199,489 and $286,000 

operate 

of ore, ranging from $30 to $100 per ton. In January, 1905, the company began to 

the property themselves, with notable success. In 1906 the mine was merged with the 

January 

:Mohawk, Combination, Jumbo, and Red Top. The present owners were not operating the -

in 1908 and had abandoned the old shaft. Future work will be from the Combination 

shaft. · 
MINES OF THE GOLDFIELD CONSOLIDATED MINES COMPANY. 217 

UNDERGROUND WORKINGS. 

:t *¥. 

.The January mine was worked through a vertical shaft about 300 feet deep, connecting 

with six rather irregularly spaced levels, as shown in Plate XVI. The general- plan of these 

levels is crescentic, with the concave side to the east. The workings are remarkably compact 

and all the ore thus far mined lies within the space between the outer curve of the crescent · and 

the chord formed by the east side line of the January claim. Some of the ore bodies,· however, 

undoubtedly extend eastward into the Combination claims. Since the mine was studied the 

110-foot, 232-foot and 283-foot levels have been extended as shown in Plate XXXIV, but 

these later w.:orkings could not be seen in 1908. The following description relates to the mine 

as it was when in active operation at the end of 1905: 

GEOLOGIC RELATIONS. 

. The main workings of the January mine are in the same dacite that forms the country 

rock of the Combination mine. At the 283-foo"t level, how~ver, the shaft cuts a fissure filled -

with soft crushed rock. Owing to the softness of the ground shaft and drift had to be closely 

lagged, and the fissure was not well exposed at the time of visit. It apparently dips steeply 

northeast and separates dacite on that side from latite on the southwest. Both rocks, particularly the dacite, show great disturbance in the vicinity of. the fissure and are thoroughly 

altered, containing abundant alunite and disseminated pyrite. 

FORM OF THE LEDGE. 

The January ledge is one of the most remarkable that have been exploited in the district. 

Its peculiar form can best be understood by reference to Plate XVI. In the first three levels 

the ledge curves from a course of about N. 70° W. to one bearing N. 55° E. It thus turns 

through an angle of about 125°, the shaft being situated at the elbow. 

So decided a change in strike suggests that the ledge may be due to the intersection of two 

distinct zonee of fissuring. This, however, is not the case. The outer curve of the ledge is 

smooth and regular and the distinction between ledge and country rock, particularly on the 

upper levels, is sharp. That the country rock which bounds the ledge on the northwest, west, 

and southwest should be entirely free from fissuring is of course not to be expected. Such 

fractures as occur, however, are small and have rather the character of irregular jointing than 

of fissure zones which could be taken as the straight continuation of either limb of the crescentic 

ledge through and beyond the bend at the shaft. In fact the minor fissuring observable in 

the dacite at the shaft appears in most instances to be tangent to the bold sweep of the ledge, 

and the smooth outline of the curve as visible in the empty stopes of this part of the mine 

affords no suggestion of any break in the dacite wall such as would be expected were the turn 

in the ledge the result of the intersection of two rectilinear fissure zones. 

As the general map of the workings shows, the part of the ledge northeast of the shaft 

dips to the northwest, the angle of dip becoming lower as· the ledge is followed northeast. The 

ledge south of the shaft, on the other hand, dips to the northeast. In other words, each successively lower level shows a slight rotation, in a direction contrary to the hands of a watch, about 

the shaft as a vertical axis. :Moreover, below the 109-foot level the whole ledge pitches to the 

east, as shown by the increasing length of the crosscuts from the shaft in Plate XVI. On the 

232-foot and 283-foot levels the ledge is apparently becoming more nearly rectilinear in strike. 

It thus appears that the January ledge, even when stripped of minor complexities of form, is 

by no means simple in shape. 

The minor complexities referred to arise ]rom the variations in width of the ledge and 

the irregular-projections of ledge matter into the countvy rock on its concave side. These 

latter are so abundant and so irregular that any section such as that shown in Plate XVI is 

necessarily diagrammatic, the mine levels, close as they are, being too far apart to reveal every 

detail of structure. 
. . 

, 

218 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

In general, the distinction between siliceous ledge matter and the soft alunitized and pyiitized 

contact 

country rock is fairly sharp in the January mine. In the oxidized zone, especially, the 

is almost a geometric surface. There is very little evidence of movement, however, 

division. 

between ledge matter and country rock, and there is seldom any gouge to mark the plane of 

have 

Small streaks or lenses of ledge matter, apparently not connected with the main ledge, 

been found in crosscuts west of the shaft. That on the 283-foot level is a lodelike mass 

in latite. 

MATERIAL OF THE LEDGE. 

described 

The material of the oxidized portion of the ledge is of the same general character as that 

in the Combination mine. Below the oxidized zone the ledge matter is perhaps a 

little more readily distinguished from the ordinary country rock than in the Combination mine, 

the ledge being, as a rule, harder and apparently more siliceous than the country rock. Minerchiefly 

alogically, however, there is little difference between the two forms of altered dacite. Both are 

quartz and alunite with more or 1ess pyrite. The ledge usually shows more fissuring 

bottom 

and brecciation and contains small quartz-lined fissures or cavities. In some places on the 

level (283-foot) of the January the ledge is a sheeted zone, showing tiny vuggy veinlets 

alunite. 

of quartz between slabs of dacite in which the feldspars are altered to faint-pink aggregates of 

The pyrite in such ledge matter may be no more abundant than in the softer country 

rock through which it is universally disseminated. Much of the alteration to ledge matter, on 

· 

usually 

the lower levels, has been clearly facilitated by close sheeting of the rock; the fissures being 

less than an eighth of an inch in width. They can in places be seen crossing alunite 

been 

pseudomorphs after feldspar without perceptibly faulting them. In other places the dacite has 

shattered to fragments. The feldspars in these fragments have been changed to alunite 

and the latter mineral is in places very abundant as an interstitial filling between the fragments. 

crusts 

In addition to their internal alteration the fragments in some places show peripheral layers or 

ments 

of quartz, alunite, and sulphides. These are not all mere incrustations. Some fraghave been rounded, apparently by chemical action, and have a whitish outer layer which 

the microscope shows to be a very fine-grained aggregate of quartz and alunite. This differs 

from the quartz-alunite-aggregate of the central part of the fragment in being of finer and more 

even grain and in retaining no trace of the dacitic texture. It is apparently a secondary crystallization 

attacked 

of the already altered rock, in the course of which even the quartz phenocrysts are 

and merged into the fine resulting aggregate. Other fragments, of more or less 

rounded 

This 

outline, are encrusted by a thi:ri dark layer of pyrite (with perhaps other sulphides). 

is coated with a crust of drusy quartz and this in turn covered by and the whole nodule 

embedded in soft pulverulent alunite, which in places carries crystals of pyrite. Such material 

resembles some of the rich ore in the Combination mine, but where studied in the north .drift of 

mine, 

the 230-foot level of the January mine the material is of little value. As in the Combination 

there is a noteworthy absence of any quartz crystals large enough to allow the recognition 

of distinct crystal planes w1th the naked eye. Whatever processes may have been at work in 

places 

the formation 

where 

of the ledge matter, their capacity for dissolving silica and transporting it to 

crystals of some size might develop was exceedingly slight. 

FORM AND DISTRIBUTION OF THE ORE BODIES. 

Probably a better idea can be obtained of the distribution and form of the January pay 

shoots from Plate XVI than from any verbal description. They differ from the rest of the 

ledge matter in no essential respect save that of richness, and as a rule are without definite 

boundaries. On the first three levels there is a fairly regular curved pay shoot which conforms 

pay 

to the general curvature of the convex side of the ledge. Except for the curved strike this 

t~ a 

shoot 

maximum 

has a 

width 

lodelike form, and in the part of the mine northeast of the shaft has been stoped · 

of about 15 feet. Just above the 160-foot level this pay shoot dies out. 
MINES OF THE GOLDFIELD CONSOLIDATED MINES COMPANY. 219 

There is a similar shoot of sulphide ore, however, on the 232-foot and 283-foot levels, but it has 

not yet been opened to as great a length as in the oxidized Zione. 

In addition to these pay shoots which follow the outer curve of the ledge, there are a number 

of smaller, irregular shoots distributed with little uniformity through the inner or concave part 

of the ledge. These are irregular bunches of ore which trend in various directions and rarely 

extend continuously from one level to another. · 

It is noteworthy that the poorest level in the mine, the 160-foot, is the one nearest the 

original water level. No ore bodies are known on this level. 

CHARACTER OF THE ORE. 

The oxidized ore is of the same general type as that described in the Combination mine. 

The oxide of bismuth, bismite, is rather abundant in the oxidized zone of the January, and 

usually accompanies ore of high grade. It is present, however, on the barren 160-foot level. 

The bismite occurs in some places as minute pearly scales in loose limonitic material, 1

but in 

some varieties of the ore is clearly pseudomorphous after the needles of bismuthinite, from 

which it has been derived by oxidation. 

The typical sulphide ore consists of highly siliceous altered dacite containing specks and 

irregular bunches of reddish-gray famatinite, accompanied by pyrite and needles of bismuthillite, the latter being usually inclosed in the famatinite. 

In varieties of the ore pyrite is abundant. In others it is decidedly subordinate to the 

famatinite and bismuthinite. All three sulphides are so closely intergrown as a rule that it is 

almost impossible to effect a mechanical separation of them. 

In some places the sulphides and minutely crystalline quartz form small veinlets, a section of 

one of these being figured in Plate XXIII, 0. Such material seems to have resulted from the 

alteration and mineralization of crushed dacite rather than from the filling of an open crevice. 

The entire process of ore deposition illustrates very feeble capacity for the filling of open spaces, 

the-ore containing many small cavities which have never been filled with either quartz or sulphides. . 

The altered dacite of the gangue shows original residual phenocrysts of quartz. The feldspars are partly dissolved or obliterated, partly altered to pinkish-white aggregates of alunite. 

The material is porous, being full of small irregular vugs lined with quartz druses and in some 

instances filled with alunite. These pores usually contain water when the rock is freshly 

broken. 

Such ore evidently represents the alteration and mineralization of a shattered portion of 

the dacite. It is in some places traversed by seams of secondary crushing, which carry streaks 

of soft dark sulphides of obscure and probably mixed character. Such seams are generally the 

best part of the ore, and indicate some enrichment subsequent to the deposition of the bulk of 

the ore. -

In another form of ore the dacite has been sheeted prior to mineralization, instead of being 

brecciated. Such ore as a rule contains less sulphides than the other kind and is probably 

never of so high a grade. The famatinite and bismuthinite particularly occur chiefly where 

the dacite has been thoroughly shattered, and experience has shown that the gold is 9,ssociated 

with these two sulphides. 

The richest ore in the mine has been found in the oxidized zone. The original water level 

in the January was at a depth of 160 feet. This may have been lowered somewhat by previous 

work in the Combination mine. But even if some allowance be made for such artificial depression, the fact remains that the poorest level in the mine is that nearest the old water surface. 

The best sulphide ore on the 283-foot level at the end of 1905 had a gross value of about $1.50 a 

ton, and the highest assays were obtained from soft dark streaks traversing the mass of the ore. 
220 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

UNDERGROUND WATER. 

only 

At 

water 

the 

~;tctually 

end of 1905 a small pump sufficed to keep the 283-foot level free from water. The 

this level. 

observed flowing into the mine was a small stream at the north face of 

Chicago, 

A sa~ple of mine water was analyzed in December, 1905, in the Dearborn laboratories, 

boilem. 

by 

The 

Edgar & Carr, chemists, for the purpose of testing its suitability for use in the steam 

analysis is as follows: 

Analysis of water from January mine. 

Silica ................................................................................. 

Grains per gallon. 

Sulphates of 

_. __ . 2. 990 

iron and aluminum (principally iron) ..............................

Carbonate of 

.... ......... . 

lime ...................... _ . __ ... _ . _ ....... ~ ... _ ........................ 

Sulphate of 

__ .... . 

Carbonate 

lime .............. _ .. _ ......... _._ .... _ .. _._ .·_ ...... _. __ .... _._._._._ ...... _·_._. 

of magnesia ............... _ .. _ ............................................

Sulphate of magnesia 

... ... . 

...................... 

Sodium 

_ .. __ .. __ .. . _ ... _ .. _ ........ _ .......... _ .. _ ..... . 

and potassium sulpliates ............ · ................................. 

Sodium and 

__ ............. . 

potassium chlorides ..........................................

Loss, etc 

.. ........... _ .. _. 

....... ~ .................................................................. _ ....... . 

80.200 

None 

58.455 

None 

22. 971 

72. 194 

11. 880 

1.145 

Total soluble solids ...................................................... 

Suspended matter. 

-............ 249. 835 

Free sulphuric acid 

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41. 580 

..................................................................... _... Trace 

Total 

Total 

soluble 

soluble 

nonincrusting 

incrusting solids ...... _ . _..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141. 645 

solids ................................................... 

Pounds soluble 

_ . . . . . . . 108. 190 

Pounds soluble nonincrusti.ng 

incrusting solids per 1,000 U. S. gallons .... _"_ ........................ _....... .. 20. 23 

solids per 1,000 U. S. galions ............ _..................... . 15. 45 

The analysts remark that the waterStates 

contains 

wine 

a little 

gallon 

less 

of 

than 

231 

250 grains of solid matter in solution and a little over 41~ grains in suspension, per United 

cubic inches. It also contains a trace of sulphuric acid. Undoubtedly 

original condition carried a

this water in its 

in a can, it has been materially 

·considerable quantity of free sulphuric acid, but due to the fact that sample was shipped 

for the large amount of 

neutralized by the iron of the can itself, producing sulphate of iron, which accounts 

same above given. a 

of 

The analysis is accordingly very inaccurate and is of value only as affording some indication 

discharge 

the general character of the water. The sample analyzed was probably taken from the pump 

which 

and represents a mixture of the normal ground water of the district with solutions 

lower 

have trickled down through the oxidizing ore. Much of the percolating water on the 

levels contains aluminous salts, as shoWn by its taste and by the deposition of halotrichite 

in efflorescent form on the walls of drifts. 

JUMBO MINE. 

HISTORY. 

north 

The 

of 

Jumbo mine lies just north of the Florence, the main Jumbo shaft being half a mile 

of 

the Florence shaft and the same distance east of the Combination shaft. The holdings 

Clermont 

the Jumbo Mining Company in 1905 comprised the Jumbo, Lucky Boy, Grizzly Bear, and 

claims, all forming a compact group. Practically all the development 

claim, which was 

is on the Jumbo 

property was 

located by C. D. Taylor on May 19, 1903. In the following October the 

ore 

bonded for $100,000, but crosscuts at a depth of 50 feet having failed to open up 

and 

the 

during 

bond was relinquished. In March, 1904, the Jumbo Mining Company was organized, 

the 

the following spring leases were let to six or more different sets of lessees. Most of 

Curtis 

lease blocks extended ·for -100 feet along the lode, although the northernmost, or Ridgeof great 

lease, was 300 feet in length. The lessees soon found ore and the ledge became an object 

activity, each block having its own shaft. The daily output from all leases in August, 

a Report to Goldfield Mining Company. 
MINES OF THE GOLDFIELD CONSOLIDATED MINES COMPANY. · 221 

1904, was estimated at $l0,000 a da,y.a The total gross prqduction from these leases to their 

expiration early in 1905 was approximately $1,100,000. The most productive single lease ·was 

the Bowes-Kernick, near the middle of the claim, which expired October 31, 1904, after a net 

productio'n of $258,000. The royalty paid by the lessees to the company was 20 per cent of 

the gross output. 

Throughout the greater part of 1905 the Jumbo mine was involved in litigation and no 

ore was mined. In 1906 it was included in the consolidation with the Combination, January, 

Red Top, Mohawk, and other mines and is now the property of the Goldfield Consolidated 

Mines Company. Nothing has been done in the old workings since the consolidation and the 

shaft has been allowed partly to fill with water. It is the intention of the company to reach 

the ore body from _the Mohawk and new Jumbo (Clermont) shafts. 

UNDERGROUND WORKINGS1

. 

As each lease block was worked through an independent shaft and as the levels were not 

run at uniform intervals and do not .all connect with those of adjoining blocks, the underground workings of the Jumbo mine are in a rather chaotic condition. The section of ledge 

worked by the lessees is about 600 feet in length and their operations extended to a maximum 

depth of 250 feet. The deepest level in 1905 was the 250-foot level on the Bowes-Kernick 

lease, near the middle of the productive ledge. This connects with a vertical shaft sunk in 

the country rock just west of the ledge. After the expiration of the leases the company made 

this the main shaft, and by the end of 1905 had sunk it to a depth of 450 feet. The ledge, however, had not then been crosscut below the 250-foot level. A general plan of the principal levels 

is shown in Plate IX. 

THE LEDGE. 

The Jumbo ledge, which so far as developed is ·entirely in dacite, outcrops prominently 

for a distance of about 700 feet. Its general course is about N. 16° W. Underground development shows it to be nearly vertical on the upper levels, although the east side is commonly 

called the hanging wall, and the 300-foot level, not accessible at the times of visit, indicates an 

eastward deflection of the ledge at that depth. The deposit is more regular and lodelike in 

form than most of those in the district, much of it being a distinct zone of parallel sheeting in 

the dacite, resembling some of the typical lode structure of Cripple Creek. The beFt of regular 

sheeting is in most places from 4 to 6 feet wide, ·but the alt~ration and mineralization, as shown 

by stopes, may attain a width of fully 20 feet. Breccia don of the rock, so characteristic a feature 

of the Combination, January, and Florence ledges, is notably absent from the Jumbo. The 

sheeting, as at Cripple Creek, has been effected with very little slipping of one sheet of rock 

past another, and no gouge seams were noted in the workings accessible in 1905. The ledge 

has no true walls, the sheeted structure and the more intense alteration of the dacite which 

accompanies it grading into -the usual softer country rock, which contains much alunite and 

disseminated pyrite. 

Within the ground opened by lessees the sheeting is more regular toward the north, the 

structure being excellently shown at the north face of the 200-foot level of the Fuller-Macdonald 

lease (Pl. XX, B). In the Vermilyea and Zinn leases, to the south of the Bowes-Kernick lease, 

the lode divides into at least two branches, the sheeting is less regular, and at the south end of 

the Zinn workings the le-dge becomes rather indistinct. 

In general, the distinction between ledge matter and country rock is less easily made in 

this mine than in most of those described, owing to the gradual passage of one into the other. 

THE PAY SHOOTS. 

Near the surface the Jumbo ledge proved 'almost continuously productive for a distance of 

500 to 600 feet along the strike. The stopes ranged from 2 or 3 up to 20 feet in width. Too 

a Goldfield Sun, August 19, 1904. 
222 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

little 

of oxidation, 

systematic work has yet been done to determine the limits of the pay shoot below the zone 

been 

which extends to a depth of about 200 feet. A little stoping on sulphide ore has 

done near the 250-foot level, but the ore apparently is not there of high grade. At the 

south end of the ledge the two main branches into which the ledge divides both carry ore. At 

the north end of the productive zone, in the Ridge-Curtis lease, about. $200,000 woFth of ore was 

stoped between the surface and. the 50-foot level. Below that level no ore was found, although 

prospecting was carried to a depth of 200 feet. 

In the Bowes-Kernick lease, on the other hand, the stopes on the 150-foot level were carried 

the 

250-foot 

full length of the block, 100 feet. Below this they shorten and come to a point on the 

level. 

CHARACTER OF ORE. 

which 

The oxidation in the upper levels has followed the fissures of the sh-eeted zone. These, 

consisting 

are rarely more than a small fraction of an inch in width, are filled with rusty ~aterial 

extended 

of limonite, kaolinite, gypsum, and probably some alunite. Oxidation has also 

from the fissures for varying distances into the intervening slabs or sheets of dacite, 

of 

converting 

visit, 

the disseminated, pyrite into limonite. No gold was seen in the stopes at the time 

but it is said to have o_9curred mainly in the rusty seams of the sheeted zone. 

being 

Below the zone of oxidation the fissures are lined with films of quartz, the middle part 

nated 

empty or filled with alunite. Pyrite is apparently not abundant except as finely dissemihowever, 

crystals in the dacite. On the 200-foot level some of the seams carry famatinite. This, 

did not appear to be associated with much gold, an assay of a sample from the south 

face affording only 0.26 ounce of gold and 0.25 ounce of silver to the ton. 

· The rock between the fissures is dacite which has been changed to an aggregate of quartz, 

phenocrysts 

alunite, and pyrite, the alunite chiefly pseudomorphous after feldspar. The original quartz 

This 

of the . dacite are the only constitutents not affected by this kind of alteration. 

ledge rock differs from the general country rock·in containing more quartz and consequently 

in being of superior hardness. 

Bowes-Kernick 

Much of the ore shipped by lessees was of very high grade. One lot of 14 toris from the 

shipped 

lease netted $36,000, or $2,571 a ton. The smelter settlement on 14 sacks of ore 

Kernick 

in November, 1904, from the Richard lease, which was immediately south of the Boweslease, was at the rate of $4,960 a ton. 

As shown on Plate IX, considerable exploration has been carried on by lessees on the 350-

ore 

foot level of the Jumbo Ledge or Becker shaft, in an attempt to find a continuation of the rich 

formerly worked through the Zinn shaft. In 1908 this level was mostly in soft disturbed 

dacite, containing some large irregular masses of ledge material but no visible ore. 

MINES AND PROSPECTS OPERATED BY LESSEES. 

INTRODUCTION. 

Company 

The principal 

were 

mines operating in 1908 under leases from the Goldfield Consolidated Mines 

the Five Friends and Hazel-Goldfield on the Laguna and Last Chance claims, 

the Mushett and Mohawk-Red Top on the Miss Jessie claim, and the Consolidated Red Top on 

Plate 

the Red 

X. 

Top claim. All these are situated north of the Mohawk workings, as may be seen from 

None 

Southeast of the Combination mine shafts were being sunk by many groups of lessees. 

nected 

of 

with 

these shafts was in ore in 1908, and with the exception of the Rosebud none was conMoore, Gibraltar, 

any extensive lateral development. Among them may be mentioned the Gotwaldt, 

Stein, Mitchell-Fairfield, Rosebud, Black Eagle, Liverpool, Texas-Golconda, 

Consolidated 

and Facer shafts. The positions of these leases are shown in Plate X. The Mushett and 

Red Top leases were shipping ore in 1908. 

FIVE FRIENDS LEASE. 

by Mr. 

The 

H. 

shaft of the Five Friends lease was 350 feet deep at the time of visit, but, as reported 

A plan 

P. Henderson, it had been deepened to 560 feet at the beginning of December, 1908. 

of the levels i~ shown in figure 25. The country rock of the lease is dacite of the usual 
MINES O:B' THE GOLDFIELD CONSOLIDATED MINES COMPANY. 223 

character. No ore has yet been found, although the north-south drifts on the 27 5-foot level 

follow a narrow seam which dips 30° to 40° E. and carries a little crumbling sphalerite and 

gakna. ' · 

MUSHETT J,EASE. 

At the time of visiting the Mushett lease the principal level connected with the bottom 

of the 430-foot shaft. A plan of the workings is shown in figure 26. The 429-foot level at 

350-fi. level 130-f't. level 

N. 

I 0 50 100 200 FEET 

FIGUI!E 25.-Sketch plan of the workings of the Five Friends lease. 

the time of visit was wholly in dacite, which, near the ore body, shows the usual alunitic alteration. The main drift runs nearly north and south and follows a mineralized streak in the 

dacite, which at one place widens to a pipelike ore 

body. The narrower part of the mineralized streak 

is chiefly remarkable as c'arrying rather abund,ant 

sphalerite, a mineral which has hitherto been remarkably rare at Goldfield. A sample of this 

sphalerite assayed for the Goldfield Consolidated 

Mines Company gave 1.8 ounces of gold and 7 

ounces of silver per ton, with 55.6 per cent of zinc. 

The ore body, as shown in figure 26, dips from 

25° to 35° E., and pitches north. Its stope length 

varies from 12 to 20 feet an"d the width from a few 

inches to 7 feet. The ore is of high grade, some 

assays showing a tenor of $8,000 a ton. Mineralogically the ore is unique in this district. It contains abundant sphalerite, pyrite, bismuthinite in 

crystals unusually large for this district, famatinite, 

and some telluride rich· in gold. Alunite is abundant, both as a constituent of the altered dacite, 

as the filling of small fissures, and as a soft interstitial material in the ore. Further particulars of 

theMushett ore are given on pages 165 and 170, and 

in the chapter on mineralogy under the various 

minerals mentioned above. 

Since the date of visit (July, 1908) the contact 

between the dacite and latite has been cut on the 

429-foot level at a point about 160 feet west of 

the shaft. Both rocks are said to be altered to 

l ___ _ _,------ ,,,' 

/ 

,,,,'' 

,-'' ~ 

/--------~/ '(0 f_-r----:----1 

I 5 

I 

. 

. 

' " ....... ~ .. " 

... .. _____ ....... '' 

25 0 25 so feet ~~~~~------~----~ 

FIGURE 26.-Pian of the workings of the Mushett lease. 

ledge matter near the contact. On the new 480-foot level the contact, according to a letter 

from Mr. H. P. Henderson, appears to be about . 50 'feet east of the shaft, and is in ledge 

I . 
224 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

rnatter. These observations indicate a dip of about 15° E., and are of interest as showing the 

tendency of the ledge to fiatten out and follow this contact for a way instead of continuing 

straight down into the latite. · ' 

MOHAWK-RED TOP LEASE. 

The Mohawk-Red Top workings at the time of visit consisted of one level at the bottom 

of the 420-foot shaft. This level, shown in figure 27, is in latite, and the shaft is said to have 

passed out of dacite at a depth of. about 365 feet. The latite shows considerable mineralization, being partly silicified and containing pyrite and alunite. It is traversed by many approximately parallel fissures which strike generally north and dip at angles of 40 ° to 50 ° E. One 

such fissure followed in the eastward drift contains a little crumbling sphalerite and galena, 

which, although in a different rock, resembles the material in the Five Friends lease. 

CONSOLIDATED RED T<)P LEASE. 

The Consolidated Red Top shaft is 300 feet deep, with levels at 200, 225, and 150 feet 

below the surface. There are also some short, abandoned upper levels driven by earlier lessees. 

The shaft is in dacite, which, near the bottom, is much crushed, having in part the consistency of gouge. This conditiop. is due to movement along the Columbia Mountain fault, 

N. 

r. 

for the Cambrian shale appears on the 300-foot level just 

west of the shaft. The shale itself is greatly disturbed, 

and the level, which extends westward for about 30 feet, 

probably does not reach the foot wall of the fault zone. 

A drift has been run south along the fault and shows 

black shale and Kendall tuff, bo.th much crushed a~d 

disturbed. No ore has been found on this level. 

\ On the 150-foot level a strong ledge is exposed. This 

. & strikes N. 20° Vv. and dips 40° to 50° .E. It consists of 

( the usual altered dacite, which, near the indefinite ha·ngJ j j ing wall, has a sheeted structure, while near the foot wall 

lj this grades into a brecciated rubble-like mass. The whole 

· ledge on tl;lis level is about 80 feet wide, but like all 

. 

o so •oo FEET similar deposits in Goldfield is irregular. Some traces of 

L......L......__._-l........J.___--' ore having been found on this level, the lessees started a 

FIGURE 27.-Sketch 

Mohawk-Red 

plan of 

Top 

the 420-foot 

lease. 

level of the new level at 225 feet, and in July, 1908, found a body of 

good ore about 100 feet east of the shaft. This ore, like 

that of the Mushett, contains much sphalerite, which forms friable crusts around fragments 

of silicified and alunitized dacite. Associated with the sphalerite are free gold, pyrite, famatinite, galena, and probably some tellurium compounds. Some of this ore assayed in the latter 

part of 1908 gav(j 42.} ounces of gold and 34.5 ounces of silver per ton, with 5 per cent of copper 

and 12.5 per cent of lead. This, it will be seen, is a remarkable ore for this district. 

HAZEL-GOLDFIELD LEASE. 

The Hazel-Goldfield lease on the Last Chance claim was not in ore at the time of visit, 

the shaft being then 415 feet deep. According to Mr. Henderson, the shaft was 740 feet deep 

on D'ecember 6, 1908, and passed into latite at 685 feet. He reports that the contact wh~re 

cut in the shaft dips about60° NW. This, as he remarks in his letter, is probably local and 

may be a minor fault plane. A new level at 718 feet is entirely in latite, much of which is 

ledge matter. Some good assays (from $200 to $300) have been obtained on this level, and at 

last report the lessees were shipping some ore. 

OTHER LEASES. 

The other leases on the Goldfield Consolidated }.1ines Company's ground call for no special 

description. Those which afford information on the geologic structure of the district are 

. referred to In the appropriate places in Chapter VIII. 
CHAPTER XIX. 

DETAILED DESCRIPTION OF THE MINES OF THE FLORENCE-GOLDFIELD 

MINING COMPANY. 

INTRODUCTION. 

The principal mine of the Florence-Goldfield Mining Company is the Florence, situated 

just east of Goldfield on the north side of Florence Hill. The company owns the Florence, 

Red King, Cornishman, Firelight, &nd Emma claims, forming a compact group, as is shown 

in Plate XXXV. This ground as a whole has been very productive and is remarkable for the 

number of highly successful leases which have been taken upon various parts of it. The most 

notable of these were the Sweeney (in the Florence mine proper), Reilly, Little Florence, Florence Annex, Rogers, and Engineers' leases. (See Pl. XXXV.) The approximate gross production of these leases is as follows: 

Gross production of Florence leases. 

Sweeney and other early leases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $650, 000 

Reilly ............... . ......... . ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475, 000 

Little Florence ............. . ................. .. ... . ............... . ............ . ....... . a 1, 500, 000 

Florence Annex ..... ....... . ... . . . ...... ·. . . . . .......... . . . ......... .. . . .... . .. . ...... .. . 169,000 

~~!~~:~~-, ~ ·. ·. • .· .· ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ : : ~ ~ ~ ~ : ~ : : : : : : : : : : : : : : : : : : : ~ 1, ~~~: ~~ 

4,555,000 

For over a year practically no underground work has been done in the Florence mine . • The company has been building a mill,· laying a pipe line, and improving its surface equipment. 

In the meantime lessees have been taking out rich ore up to within 300 feet of the main shaft. 

FLORENCE MINE. 

HISTORY. 

The Florence claim was located on May 19, 1903, ·by Charles D. Taylor, but shortly afterward passed into the control of T. G. Lockhart and A. D.· Parker. As was the case with all of 

the important mines except the Combination, the first ore bodies were found and exploited by 

lessees. The most successful of these early leases was that granted to Sweeney, Nixon, Wingfield, and Hennessy, usually known as the "Sweeney lease." These lessees found little to 

encourage them and after exploring the ledge at a depth o.f 50 feet they relinquished the work 

to Durgan, Elkins, and others, but retained a half interest in the lease. Shortly afterward 

the 100-foot level opened up the south pay shoot and penetrated the top of what subsequently 

proved to be one of the largest single ore bodies yet worked in the district. Shipments began 

in the summer of 1904, and according to Mr. Frank Oliver, superintendent of the Florence mine, 

the total production from leases prior to January 15, 1905, when the company began to operate 

the mine, was $650,000. Some of the ore mi:q.ed by the lessees was very rich, although far 

~urpassed by later shipments from the Mohawk mine. One lot of 75,678 pounds, treated by 

the Western Ore Purchasing Company in August, 1904, had a value of $40,170.80, corresponding to about 53 ounces of gold per ton. Another lot of 1,855 pounds was valued at $7,350.45, 

equivalent to 396 ounces per ton. 

a This is merely a rough and conservative estimate from the known net production, which was $1,285,000. 

7~145-N o. 66-09--15 225 
226 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

The Florence-Goldfield Mining Company was capitalized at $1,250,000, and the total 

gross output of the mine up to the end of 1905 amounted to about $1,500,000. 

UNDERGROUND WORKINGS. 

. At the end of 1905 the Florence mine was developed to a depth of 350 feet. It was worked 

. · through a vertical shaft with levels at 50, 100, 150, 200; 250, and 350 feet, and an intermediate 

level at 300 feet below the collar of the shaft. These levels have a general trend of about N. 

15° W., but they are most of them exceedingly tortuous, as may be seen from Plate XXXV. , 

They somewhat resemble the workings of the January mine in showing a sharp elbow-like 

curve on the upper levels, which becomes less pronounced with increasing depth. 

At the time of second visit, in 1908, the mine was idle. The 150-foot and 250-foot levels · 

had been driven out to the Reilly shaft, but otherwise the workings were practically the same 

as in 1905. 

The chief feature of geologic 

dacite and the Milltown andesite. 

I 

I 

I 

\ 

\ 

\ 

\ 

\ 

\ 

GEOLOGIC RELA'l'IONS. 

interest in the Florence mine is the contact between the 

Most of the Florence workings are in dacite. On the other 

. Surface 

Andesite 

• 

----------'-...l.---~'------~-350feet 

5.28°E. 

hand the Engineers', Little 

Florence, Rogers, and 

Rosebud workings are in 

andesite. At the surface 

the rather obscure contact 

appears to be about 250 

feet north of· the Florence 

shaft. The 50-foot level 

(a short one not shown in 

Pl. XXXV) is probably 

entirely in Milltown andesite, although the alteration of the rock leaves its 

original character uncertain. At the 100-foot level 

the shaft is still in andesite. The dacite in the 

Florence mine, especially 

FIGURE 28.-Diagrammatic section through the Florence mine showing the cross fault and the dacite- near the contact with the 

andesite contact. Plane of section passes 20 feet southwest of shaft. andesite, is usually finer 

0 200 FEET 

grained and less porphyritic than elsewhere, quartz phenocrysts are less abundant and conspicuous, and the two rocks in their altered condition may be exceedingly difficult to distinguish. 

Fnr some distance north of the shaft on this level the character of the country rock is in doubt. 

Dacite certainly occurs on this leyel at a point 180 feet in a straight line northwest of the 

shaft. The rock south of this is ·believed to be mainly andesite, although it m.ay contain some 

intru_ded tongues of dacite. On the 150-foot level the contact is just south of the shaft. It 

could not actually be recognized, but the shaft itself is certainly in dacite, and undoubted andesite 

occurs in the drift leading south from the station. On the 200-foot level the contact is obscured 

by mineralization, but appears to be less than 20 feet south of. the shaft. On the 250-foot level 

the workings south of the shaft had caved in 1908, but observations made in 1905 showed that 

the south drift passes from. dacite across an obscure contact into rock which is certainly 

andesite. The 350-foot level examined in 1905 is probably nearly all in dacite, although some 

andesite may appear at the extreme south end. This part of the workings could not be seen in 

1908. The facts available from the Florence mine indicate that the dacite ends against the 

andesite with an igneous contact, and that this contact, below the 150-foot level, as illustrated 

in Plate VIII, section G-G', and in figure 28, has a steep dip to the south. 
U.S . GEOLOGICAL SURVEY 

F L 

R 

C 0 M B N A T 

c 0 R N s H M A N 

E N c E 

U OHAWK- rLORE:NCE: A c T 0 S H A FT 

0 N N 0. 2 

PLAN OF FLORENCE MINE, SHOWING ALSO SOME OF THE ADJACENT 'VORKINGS OF LESSEE COMPANIES 

PROFESSIONAL PAPER 66 PLATE XXXV 

~ 

.... 

HA L L- rLORt:NC£ 

SHAFr 

t:NQIVo.V£0 A 0 PRINTf.D (II '( Tt-l f. U.$ !:0\..0GICA~ SUII'VE.V 
MINES OF THE FLORENCE-GOLDFIELD MINING COMPANY. 227 

About 100 feet south of the shaft the 100-foot level passes through a seam of gouge which 

strikes N. 55° E. and dips southeast. This seam limits the main mass of ledge matter on this 

level, as shown in figure 13, and apparently fills a fault fissure. Similar seams are found at the 

southern ends of the 200-foot, 250-foot, and 350-foot levels, as illustrated in Plate XXXV. 

The strike and dip as observed at these various exposures vary, but when plotted in section, 

as in figure 28, the points of observation determine a line of slight curvature. This, without 

much doubt, corresponds to a single fault which in general cuts off the Florence ledge on the 

south. As may be seen from Plate XXXV the change in strike is progressive from level 

to level. The observed dips at the various levels agree also 'fith the dips indicated by the 

curve plotted in figure 28. The fault is in the andesite, and lies as shown in figure 28, southeast 

of the irregular dacite-andesite contact. . 

As exposed at the south end of the 350-foot level the fault plane has a dip of 40.0 at the 

southwest end of the exposure, but gets steeper toward the northeast. The fissure carries a< 

few inches of soft gouge and is accompanied by considerable disturbance of the adjacent andesite, which in the hanging wall is soft and pyritized, with some narrowly spaced sheeting near 

the fissure. There is pyrite in these fractures, showing that some mineralization has taken 

place since the faulting. 

The direction and amount of displacement along this fault are not determinable from the 

Florence workings. About 140 feet north of the main fal!lt, on the 350-foot level! an approximately parallel fissure has offset the part of the ledge south of it about 6 feet to the east. This 

suggests that the effect of the larger fault has been to throw the ledge south of it to the east also. 

Some additional light on this question is furnished by. the workings of the Engineers' lea~e, 

which will be described later. 

FORM OF THE FLORENCE LEDGE. 

At the surface the Florence ledge appears as a line of rusty siliceous outcrops, which extend 

from the vicinity of the shaft north-northwest toward the Reilly and Combination mines. 

The ledge, however, does not actually join that of the Reilly, but ends, superficially at least: 

just north of the line of contact of dacite with andesite. (See Pl. II.) From this ledge some 

outcropping spurs run off to the east, one of them being indicated on Plate II. 

The general shape of the Florence ledge, as explored underground, is probably more irregular than that of the January mine, and its boundaries are not so well determined by existing 

workings. On the 50-foot level (Pl. XXXV) the curved northeast-southwest drift is in oxidized 

ledge matter of unknown width, and apparently follows the line of greatest shattering in the 

country rock. The crosscut northwest of the shaft is in soft altered andesite containing much 

kaolinite and probably alunite. · The whole level shows much fracturing and disturbance of 

the rock, and all the material is oxidized. On the 100..:foot level the ledge assumes more 

definite form. It is generally oxidized, while the less pervious pyritized and alunitized country 

rock shows practically no limonite. Ledge matter and country rock thus contrast sharply in 

color. The plan of the ledge matter on this level, so far as it can be determined from existing 

workings, is shown in figure 12. The contact between ledge matter and country rock is almost 

everywhere sharp. In a few places there is a seam of gouge between the two kinds of material, 

but as a rule there is no dividing fissure or gouge recognizable. On the south the ledge is cut 

off by a fault, as already described. On the 150-foot level the ledge is narrower and less definitely bounded, there being insufficient oxidation at this depth · to accentuate the difference 

between the two kinds of material. The general dip of the ledge down to this level is to the 

west, at an angle of about 75°. 

Near the 150-foot level the dip flattens, and between the 150-foot and 200-foot levels 

expands to a maximum width of about 18 feet in the part of the mine adjacent to the shaft. 

(See fig. 17, p. 154.) Here was the large body stoped under the Sweeney lease. This wide 

part of the ledge continues down to the 200-foot level with a dip of 35° to 40°. It then steepens, narrows, and as shown in figure 17, dips east down to the 250-foot level. Near this level it 
228 THE GEOLOGY AND ORE DEPOSITS . OF GOLDFIELD, NEVADA. 

again turns and dips west at a high angle. In other parts of the mine the changes in dip from 

level to level are less well known. The plan of the workings, Plate. XXXV, indicates that they are 

as great as those shown in figure 17, but vary in direction on any given level in different parts 

of the mine. In the southern part of the workings the general dip is northeast. 

The long P.rifts to the Reilly shaft on the 150-foot and 250-foot levels are largely-in ledge 

matter, but this is irregular and is not continuous along the drifts, which here and there cut 

through masses of soft altered dacite. The irregular distribution of the ledge matter is in part 

original, but is in part due to minor faulting. 

THE PAY SHOOTS. 

The first pay shoot of any importance in the Florence mine barely reaches the 50-foot 

level, near the end of the south drift, the ledge from this level to the surface being practically 

·barren. This ore body was fo~d to increase in size downward and on the 100-foot level has · 

been stoped for a length of about 40 feet and to a width of 3 feet. This was all oxidized ore. 

Another pay shoot appears on this level just east of the shaft and is apparently the top of the 

large body stoped below the 150-foot level. On the latter level the ore shoot south of the shaft 

has apparently pinched out. Just north of the shaft, however, the 150-foot level enters a pay 

shoot which, prior to the Mohawk discoveries, was of unusual dimensions for this district. The 

stope length of this shoot on this level is about 50 feet. The ore pinches above the level and 

apparently has not been followed through to the small stope on the level above. Below the 

150-foot level, however, the ore body flattens in dip and has been stoped to a maximum width 

of 18 to 20 feet. The. width, however, varies greatly and the ore has no walls. (See Pl. XXI, A.) 

In parts of this body the rich ore is divided into two layers by a thin sheet or hor~e of low-grade 

ore. Near the 200-foot level the ore body steepens with the ledge and becomes nearly vertical. 

The stope length on this level is 75 or 80 feet and the greatest width about 12 feet. The ore 

varies much in width, however, and extends irregularly and without definite boundaries into 

the shattered and altered dacite. This pay shoot appears to end just above the 250-foot level. 

At the time of visit, in 1905, neither of the principal ore bodies known in the upper workings appeared to reach the 250-foot level. At the south end of the level, however, a stope 

about 90 feet in length had been opened on ore up to 7 feet in width. This width probably 

corresponds only to the ore of shipping grade, much low-grade or milling ore being left in the 

walls of the stope. This pay shoot evidently does not extend up to · the 200-foot level and is 

probably not directly connected with the ore body stoped south of the shaft, above and for a 

short distance below the 100-foot level. A winze has been sunk on it and some stoping done 

from the 300-foot or intermediate level. High-grade ($500-$600) sulphide ore has been taken 

out from this stope to a width of 6 feet. The deposit here is lodelike, although without definite 

walls. It dips to the northeast at about 80°. Below the intermediate level the ore decreases in 

value and it is questionable whether it continues to carry ore of shipping grade -down to the 

350-foot level. No stoping had been done from this level at the time of visit. The most mineralized part of the ledge showed a sheeted structure, the slabs of pyritized, alunitized, and silicified 

dacite being separated by very narrow veinlets of quartz. 

The pay shoot just described lies south of the Sweeney ore shoot, of which no direct downward continuation has yet been found on the 250-foot level. It is .in line with the Sweeney 

shoot, however, and , it is possible that the ore of the two shoots may prove to be connected. 

If so, the combined pay shoot pitches very strongly to the southeast between the 200-foot and 

250-foot levels. 

In the development of the workings to the north, some or_e was found late in 1905, at the 

end of the 250-foot level. This ore, while in the . general Florence ledge zone, is not directly 

connected, so far as known, with the ore shoots just described and is probably a separate shoot. 

Its limits have not yet been determined. _ 

In the Florence, as in the other mines described, it is· clear that the ore is not coextensive 

with the ledge, nor does it accompany the ledge to the same extent or with the same regularity 
MINES OF THE FLORENCE-GOLDFIELD MINING COMPANY. 229 

and persistence as do the pay shoots of typical veins their ~ssures. It forms irregular rich 

bunches or bonanzas of comparatively short stope length and ot no great individual persistency 

in depth. There were indications in 1905 that in the bottom or the mine the ledge was taking 

on the character of a metasomatic fissure vein with greater j egularity of mineralization, but 

with a notable decrease in the value of the ore. 

The study of the Florence pay shoots in 1905 was unsatisf ctory on account of the absence 

of accurate stope maps and even of good plans of the levels. In 908 better maps were available, 

but the condition of the mine was not then favorable to examr· ation. 

CHARACTER OF THE ORE. 

The oxidized ore of the Florence mine was never very ab ndant, and was practically confined to the south ore shoot, which was stoped between the 50-foot and 100-foot levels. Very 

little of this ore was visible in 1905. It appears not to have b¢en essentially different from the 

oxidized ore of the Combination and January mines. J. 

The ore of the large stope worked between the 150-foot and 200-foot levels under the 

Sweeney lease was mainly sulphide materia). The low-grade pbrtions of this body, which alone 

were available for examination in 1905, consist of rock whiciwas· probab. ly originally dacite, 

although it is altered so thoroughly that there is no certain means of distinguishing it fron1 

andesite. The material is now a fine-grained aggregate of qu rtz and alunite, with much disseminated pyrite in small crystals. It is minutely fissured, m . ny of the fissures being approximately parallel and giving the deposit a sheeted structure par llel to the greater dimensions of 

the ore body. There are no definite walls, the ore grading wirlhout any break into the country 

rock. The smaller fissures are filled chiefly with cryptocrys alline quartz, the little veinlets 

being rarely more than an eighth of an inch in width. Larger fissures and irregular interstices 

where the fracturing is less regular are lined with drusy quartz and filled with alunite. Pyrite, 

besides being disseminated through the rock, occurs also in he fissures, where it often forms 

films which lie next to the walls and are covered by quartz. j It also occurs embedded in the 

quartz and alunite. Minute white crystals, probably barite, a:rre also present in the soft alunite, 

which in some places is probably mixed with kaolinite. No ee gold was seen in this material, 

although it was presumably visible in sqme of the rich ore takJen from. this stope and may have 

been associated with famatinite. The dependence of minJralization upon fissuring is well 

illustrated in the low-grade ore left in the stope, pyrite bein1

1 most abundant in and near the 

fissures. . 

The ore stoped between the 250-foot and 300-foot levels is nodular, somewhat Tesembling 

some of the rich ore in the Combination mine. Fragments pf altered dacite, whose contours 

have clearly been modified to some extent by the chemical action of the depositing solutions, 

have been incrusted with sulphides. The inner crust is gener, lly pyrite and is usually less than 

0.1 inch in thickness. Outside of this is a crust of famatinite 1P to a quarter of an inch in thickness. This in turn is enveloped in a layer of cryptocrystallife quartz transfixed by needles of 

bismuthinite and containing also a little pyrite and famat nite. The outer surface of this 

siliceous envelope is rough or botryoidal with small quartz c ystals and is coated with alunite. 

Small octahedral crystals of pyrite occur in this drusy crus and in the alunite. The latter 

mineral, perhaps in some places mixed with kaolinite, fills th,e interstices between the nodules. 

It also occurs in the kernels of the nodules as an alteration product of the original feldspars of 

the dacite. The appearance of a typical rich nodule is shown in Plate XXIV, A. In the richest 

specimens much free gold is visible. It oceurs chiefly in e quartz and bismuthinite zone, 

embedded in bot.h these minerals. The succession of mineraf , it will be observed, thus differs 

from that in the rich nodular ore of the Combination mine, in hich the gold is deposited mainly 

in the siliceous crust next to the dacite kernel. 

Not all of the ore in this pay shoot shows the nodular chl}racter in equal degre~. In places 

where the dacite has been much shattered prior to mineraliz tion and where consequently the 

solutions have acted upon finely broken material, the pyrite famatinite, bismuthinite, quartz, 
230 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

and gold have crystallized into more irregular aggregates. The nodular structure appears to 

have been best developed where the fragments acted upon were of moderate size and where the 

> • interstices between them were not packed with ·comminuted material. 

The nodular structure is not confined to rich ore. Fragments of dacite coated with pyrite 

that is in turn covered by quartz druses, with a little famatinite, occur on the 250-foot level 

where the ledge is of low grade. No bismuthinite, however, was noted in this material. 

A notable increase in copper has been noted . on the 250-foot and 300-foot levels in the 

Florence mine as compared with the upper levels. The proportion of silver, also, is said to 

increase with the copper. A shipment of ore from the 250-foot level made late in 1905 carried 

100.8 ounces of gold and 3.5 ounces of sil~er to the. ton, with 3.5 per cent of copper. This is the 

most silver per ton yet found in the ore, according to ~1r. Oliver, formerly superintendent, the . 

usual qua.ntity of silver in ores from the higher levels being from 1 to 1.5 ounces per ton. Even 

3.5 ounces of silver to 100.8 ounces of gold, however, must be regarded as a very small proportion. It is only about one-fifth of the propo:r;tion of silver to gold in the rich ore shipped from 

the Hayes-Monnette lease on the Mohawk mine, for example. 

None of the ore on the 350-foot level of the Florence mine at the end of 1905 -was of shipping 

grade. The highest assays afforded about $60 a ton, the greater number giving only $25 to $30. 

Pyrite was the only sulphide seen on this level at the time of visit. . 

UNDERGROUND WATER. 

Comparatively little water enters the Florence mine, the lowest level in 1908 being kept free 

by hoisting from 30 to 40 buckets of water each' day. 

MINES OPERATED BY LESSEES. 

REILLY LEASE. 

The Reilly mine, or "lease," as it more often called, is at the northwest corner of the Florence claim, in what is known as lease block No. 1 of the Florence ground. The workings adjoin 

those of the Combination and are on the same general ledge. The lessees' stopes were carri~d 

into the ground then owned by the Combination Mines Company, and a dispute arose, which 

was settled by a compromise, as described on page 210. The Reilly mine has. not been operated 

for over two years. The Goldfield Consolidated Mines Company, however, has carried its 

280-foot level under the bottom of the old stopes and was taking out some very rich ore in the 

summer of 1908. 

The first lease on block No.1 was taken by F. G. Lockhart, one of the owners of the Florence 

claim, and George McClelland. They found no ore and relinquished the lease. Later a second 

group of lessees met with little better success. They opened a small shoot of ore on the 60-foot 

level, but missed the main ore body. In April, 1905, B. J. Reilly secured a six months' lease of 

the ground. On June 21 he found some ore, but it was not until August that the extent and 

richness of the bonanza was realized. Messrs. McKane and Campbell were taken into partnership about this time, and their united energies were bent to the task of extracting as much 

ore as possible before the expiration of the lease on October 19, 1905. The royalties paid by 

these lessees to the Florence-Goldfield Mining Company correspond to a gross production of 

$475,000. The estimate that an additional $60,000 worth of rich ore was stolen is probably a 

conservative one. 

When visited in 1905, just after the expiration of the lease, the Reilly workings (Pl. XXXV) 

comprised a crooked shaft 210 feet deep with four levels, the important drifts being all north of 

the shaft. On the 60-foot level crosscuts were run northeast and southwest, but revealed nothing of value. A drift to the northwest follows what appears to be the northeast wall of the Com-

.bination ledge. It opened a small body of ore, which apparently was not connected with the 

main shoot afterwards found. The 11 0-foot level passed under this small ore body and w,as 

then turned to the north until it cut a fissure containing a tough, leathery clay gouge containing 
MINES OF THE FLORENCE-GOLDFIELD MINING COMPANY. 231 

crystals of gypsum. This fissure, followed to the northwest, led into the mai.n ore shoot, which 

was stoped for about 60 feet on this level and for about 30 feet above it. 

The 160-foot level was first run as a crosscut to the southwest. It was then turned northwest and at a point about 100 feet a little north of west from the shaft came into an irregular 

body of ore. A crosscut of 50 feet to the north finally reached the main ore shoot. (See Pl. · 

XXXV.) 

The 210-foot level pursues a still more devious course. After first running west, it turns 

into a north crosscut of 90 feet in length. It then follows a gouge-filled fissure for 35 feet to 

the northwest and "then crosscuts back southwest to the main ore body. 

The Reilly workings are entirely in dacite and present no geologic features of special interest. 

The dacite is for the most part soft, with much disseminated pyrite and abundant alunite. It 

is traversed by numerous fissures, of which the more persistent have a general northwestsoutheast course. Some of these fissures carry clay gouge, some are associated with irregular 

segregations of pyrite. Most of them appear to have no close association with ore bodies. 

The ledge matter in the Reilly workings is irregularly distributed through the soft altered 

dacite and is not nearly so well defined a belt as is the ledge on the southeast part of the 130-

foot level of the Combination mine. Crosscuts driven across the general line of the ledge in 

v~rious places have shown only gouge-filled fissures in soft alunitized dacite, with here and 

there streaks and bunches of harder material such as might be termed ledge matter. The body 

of ore found on the 60-foot level and the one found nearest the shaft on the· 160-foot level are 

associated with masses of ledge material which apparently are mere irregular bunches in the 

soft dacite. _The ore of the main pay shoot is in most places inclosed in disturbed alunitized 

dacite with the usual disseminated pyrite. Distinct and persistent zones of characteristic ledge 

matter, such as the one which accompanies the pay shoot on the 130-foot level in the Combination mine, are absent in the Reilly workings. 

The main Reilly pay shoot, as shown in Plate XXXV.and figure 16, is a curiously warped 

or twisted sheet of ore, which does not reach the surface and varies much in stope length on 

different levels. Above the 160-foot level the general dip is northeast, while below that level, 

at least to the 210-foot level, the dip is reversed and the ore is inclined t<;>ward the southwest. 

As a rule the ore has no definite walls and the maximum width of the stopes in 1905 was about 

15 feet. Undoubtedly; under the exigencies of the lease ·much low-gracie ore was left standing. 

On the northeast side of the ore there is a rolling gouge-filled fissure which on the upper 

levels appears to serve here and there as a hanging wall. In many places, however, the ore 

apparently does not extend to this gouge. The smaller ore body shown near the third level 

is apparently an isolated mass inclosed in soft alunitized dacite. 

Both oxidized and sulphide ore are found in the Reilly mine, but the conditions for observing either in place were not favorable at the time of first visit. Practically all of the rich ore in 

sight had been extracted, and development for the opening of new bodies had not begun. Rich 

sulphide ore was known to exist in a winze below the 210-foot level, but this was filled with 

water. Some of the sulphide ore from this winze carried over 300 ounces of gold to the ton. 

In June, 1908, the Goldfield Consolidated Mines Company were stoping under the bottom of 

this winze on the 280-foot Combination level. This ore lies close to the hanging-wall gouge, 

whic}:_l. here dips to the west and is thus locally the foot wall. The rich ore streak as then 

exposed came into the drift obliquely from the southwest and wedged out against the gouge. 

It is a narrow shattered zone in siliceous ledge matter with much interstitial alunite and 

pyrite, the best ore as a whole being soft and friable. It contains abundant native gold, some 

of the ore carrying up to 620 ounces to the ton. 

Much of the rich ore shipped by the lessees was nodular in character, concentrically coated 

fragments of altered dacite · being embedded in so-called "talc/' which was probably chiefly 

alunite. Other specimens show pyrite, famatinite, bismuthinite, and free gold in a porous 

cryptocrystalline quartz gangue. Such ore appears to have resulted from the alteration of 

finely crushed dacite. Some of the richest of such masses consist of little else than gold 

and white quartz, the gold being so abundant and in such fine particles as to give a general 
232 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

yellow tint to the quartz. One unfamiliar with Goldfield ores might readily mistake this 

golden pigment for a superficial ferruginous stain. In some specimens small crystals of barite 

are embedded in alunite, which encrusts fragments of altered dacite. Other varieties of the 

ore show a firm interstitial filling or cement of fine-grained porous quartz with pyrite, famatinite, bismuthinite, and gold. The fine-grained texture and minutely vuggy character of this 

filling indicates that it has not filled entirely open spaces but has replaced finely comminuted 

dacite. Marcasite, as well as pyrite, occurs in some parts of the ore body. It is of later origin 

than at least a part of the pyrite. ' 

The ore of the body stoped west of the shaft on the 160-foot level consists of shattered 

dacite, the interstices between the fragments being partly filled with alunite. The· fragments 

themselves are hard, dense aggregates of quartz, alunite, and pyrite, the original plagioclase 

phenocrysts being now pseudomorphs of alunite, and the original fernie minerals being now 

chiefly pyrite and quartz. · The quartz phenocrysts alone remain unchanged. The surfaces of 

these fragments are incrusted and partly penetrated by a thin envelope of dark sulphides. A 

lens shows these to consist of the usual association of pyrite, famatinite, bismuthinite, and free 

gold. · 

The oxidized ore seen in. the Reilly workings presents no characteristics calling for special 

description. The lower limit of oxidation is irregular, mixed oxide and sulphide ore occurring 

on the 160-foot level. 

ENGINEERS' LEASE. 

The Engineers' lease block, as shown in Plates IX and X, lies in the southeast corner of 

the Florence claim. The first work in this vicinity was done by the Florence-Annex lPasing 

company, who sank a shaft on the Cornishman claim, crosscut west on the 300-foot level, and 

stoped ore to the value of about $169,000 from the northeast corner of the Red Kin5 claim. 

One shipment of 40 tons of this ore in November, 1907, averaged $948 a ton. The shaft is 500 

feet deep and considerable work has been done on the 400-foot and 500-foot levels. The only 

ore bodies so far discovered, however, are above the 300-foot level. The Florence-Annex lease 

expired on February 12, 1908, and early in the following May H. P. Taylor and L. Price began 

work on the Engineers' lease through the Florence-Annex shaft. On June 15 they broke into 

a body of ore on the 300-foot level, a short distance north of that stoped by the former lessees. 

At the time of visit at the beginning of July, 1908, the lease had already produced about $60,000, 

and at its expiration on November 8, 1908, it had paid over half a million dollars in dividends 

and was credited with a total gross production of $1,100,000. 

The country rock of the mines is andesite. This is cut by two fault fissures which limit the 

ore-bearing ground to the north and south. (See Pl. IX.) The northern fault dips south at 

about 55 ° and is supposed by Messrs. Taylor and Price to be the same fissure that cuts off the 

Florence ledge, as described on page 227. This is probably true, although, as shown on Plate 

IX, there is a considerable difference in strike, probably about 40°, between the fault in the Florence mine and the fissure in the Engineers' lease. Such curvature, however, is by no means 

unusual in the fissures of the Goldfield district. The 300-foot level, after passing north through 

the fault gouge, turns east and continues to the end in a soft mass of crushed andesite, which 

is probably within the f~ult zone. The fault which cut off the ore at the south end of the 300-foot 

level has been recognized only at this one place, and its trend is not known. It apparently 

runs in a nearly east and west direction and has a dip to the south. 

The Engineers' pay shoot lies just south of the northern fault, although the ore did not 

extend quite to the fissure. Its stope length was about 50 feet, the average width was about 

2 feet, and the height of the stope at the time of visit was 110 feet. The strike of the ore body 

was about N. 30° W. The dip was 80° NE. It was thus a nearly vertical pipelike mass, of small . 

elliptical cross section, and was one of the richest bodies of its size yet mined in the district. 

In the drift on the 300-foot level the only suggestion of ore was a mere seam of kaolinite 

or alunite. A raise was put up on this and soon reached the pay shoot, which continued to 

improve in value upward. At the time of visit the ore being taken from the top of the stope 

averaged about $2,000 a ton. 
MINES OF THE FLORENCE-GOLDFIELD MINING COMPANY. 233 

The best ore was much shattered and somewhat slickensided material in which many of 

the fragments were concentrically coated with gold, bismuthinite, famatinite, and pyrite. The 

stope showed very clearly that the rich ore had been deposited after the andesite had already 

undergone silicification. Specimens of this ore are illustrated in Plate XXV and described on 

page 165. It is very similar to.some of the rich ore of the Florence and Reilly workings. 

LITTLE FLORENCE LEASE. 

The Little Florence lease lies immediately south of the Engineers' lease and the main Florence 

workings, the relative positions of the three mines being shown in Plate IX. The main shaft of 

the lessees was sunk only a few feet south of the summit of Florence Hill. Work was begun early 

in 1907, and at the expiration of the lease on April26, 1908, the total gross production amounted 

to at least $1,500,000. 

The main shaft is 555 feet deep, with levels at 213, 268, 316, 442, and 555 feet below the 

collar. The 268-foot and the 442-foot levels, as shown in Plate IX, connect with an inclined 

shaft on the east slope of the hill and the 213-foot and 316-foot levels with the Mohawk-Florence 

shaft on the west slope. These latter shafts were the original workings, and it was while making 

a connection betwee11 them for air that the rich ore was discovered. Subsequently the main 

shaft was completed by simultaneously sinking and raising. At the time of visit in 1908 no work 

was in progress and only a brief examination could be made. 

The country rock of the Little Florence is andesite throughout. The ore body, while 

far from regular, is more veinlike in form than most of those• exploited in the district. The 

ore was found at a depth of about 250 feet and the pay shoot did not extend quite to the 213-

foot level. It was about 5 feet wide where first cut and averaged about $400 a ton. The pay 

shoot strikes north and south and was stoped in this lease for a length of about 200 feet. On 

the south it continues into the Rogers lease. On the north too little work has been, done to 

determine what becomes of the ore in that direction. Until the ground between the Little Florence workings and those of the Engineers' lease and Florence mine is thoroughly explored it 

will be impossible to determine how far irregularity of deposition and how far subsequent 

faulting are responsible for the lack of continuity between the ore bodies of these three mines. 

The Little Florence ore body between the 213-foot and 268-foot levels is short and narrow, 

dipping to the east at 75 °. Below the 268-foot level it becomes longer and divides into two rich 

streaks separated by a horse of siliceous ledge matter about 15 feet wide. The east shoot is 

the better on the 316-foot level. On an intermediate level 40 feet below the 442-foot level the 

two streaks of ore come together and form the widest mass of ore in the mine. On the 555-foot 

level there is abundant ledge matter, but this is bunchy and of low grade. Gouge seams are 

numerous and in places the ledge matter is cut off by faults. 

The rich ore stoped from this lease appears to have been similar to that of the Engineers' 

and Florence mines. The only place where any' of the better grade of ore was visible in 1908 was 

at the north end of the 316-foot level. This shows the nodular character so common in the rich 

ore of the Goldfield mines, and contains native gold, bismuthinite, famatinite, pyrite, quartz, 

and alunite. Some of the bismuthinite from the Little Florence is as coarsely crystalline as 

that in the Mushett lease. 

ROGERS SYNDICATE LEASE. 

The Rogers lease adjoins the Little Florence to the south (Pl. IX) and is on the same 

ledge. Ore was found in October, 1907, on the 409-foot level, and the lease expired on ,July 

11, 1908, after a gross production of about $660,000 from 7,000 tons of ore. The average value 

per ton was about $95, although some was very much richer. 

The workings consist of a shaft about 520 feet deep, with levels at 165, 309, 409, and 

509 feet, and a sublevel at 559 feet. (See Pl. IX.) The principal stoping was done from the 

409-foot and 509-foot levels and from the sublevel. 

The general country rock of the Rogers lease is the Milltown. andesite, which, where not 

transformed into ledge matter, is as a rule soft and much altered. The shaft is in this material 
234 THE GE OLOGY AND ORE DEPOSITS OF ·GOLDFIELD, NEVADA. 

and the principal levels crosscut through it for about 150 feet west-northwest to reach the 

ledge. This, which is a continuation of the Little Florence ledge, is exceedingly irregular and 

practically comes to an end in the Rogers lease. In some places it grades into soft andesite, 

but in others there is a definite seam of gouge between ledge and country rock. These seams 

vary greatly in dip and strike and are apparently local slips between hard and soft material, 

not persistent faults traceable from level to level. -

What may be called the Little Florence pay shoot, although it is not absolutely continuous, 

but rather a zone of rich bunches of ore, extends into the Rogers lease for about 75 feet, and 

has been stoped in places above the 409-foot and 309-foot levels. These bunches of shipping 

ore are small and occur where the 1edge matter is cut by intersecting fissures which are clearly 

later than the primary silicification. The shoot as a whole is nearly vertical, and with its containing ledge matter ends irregularly near an east-west vertical plane passing through the 

shaft. 

The second and more productive pay shoot is not so obviously a continuation of that 

known in the Little Florence. It was first cut about 275 feet west of the shaft on the 409-foot 

level and near the Red King side line. The ore body, as shown by the stope in Plate IX, went 

very little above the level, but grew longer downward and on the 509-foot level had a stope 

length of 90 feet. It extends for at least 50 feet below the 509-foot level, but how much farther 

is not kn'own. The grade is not as good on the sublevel as above. The width of the ore is 

not uniform, ranging from a few inches up to 4 or 5 feet. · The general dip is between 45 ° and 

50 ° E. Thus although on the 409-foot level this pay shoot appears to be separated from the 

Little Florence shoot, they must, if both persist, come together below the 509-foot level. There 

is probably at least some ledge matter joining the two. · 

The same zone of ledge matter that contains the main Rogers pay shoot continues into 

the 0. K. or Rosebud lease, where it has been explored northeast of the shaft. It appears as 

the blu1;1t irregular end of a wide zone of sheeted, silicified, and afterwards brecciated andesite 

in much-disturbed soft rock, originally of the same kind. The best assays of this ledge matter, 

although the rich ore of the Rogers lease came almost to the dividing line between the two 

leases, do not give over $20 per_ ton. 

OTHER LEASES. 

There are many other leases on the Florence in the vicinity of the Rogers and Engineers' 

leases, some of which, as the Pollard-Florence, have deep shafts and considerable lateral work, 

but no ore. Such geologic information as these workings afford has been referred to in the 

appropriate places. Description of each prospect in detail is unnecessary. North of the 

Florence shaft, also, there are a number of leases on the Cornishman claim, of which the workings 

are not shown in Plate IX. Most of these are on nearly vertical zones of sheeting and silicification in the dacite, with trends a few degrees west of north. Such for example is the Baby 

Florence, which has produced some ore from rich bunches in a ledge of this character. Considerable work has been done in this mine to a depth of 400 feet, but the ore thus far found is 

all above the 150-foot level. These ledges appear to occupy not very persistent zones of minor 

fissuring in the hanging wall of the main Florence ledge. 
CHAPTER XX. 

DETAILED DESCRIPTIONS OF THE LESSER MINES AND PROSPECTS OF THE: 

GOLDFIELD GROUP. 

SANDSTORM MINE. 

The Sandstorm claim, situated about 2 miles north of Goldfield, was staked on December 2, 

1902, by Messrs. Stimler and Marsh, and according to popular tradition was the first mining 

location in the district. But although claims were probably first laid off in this vicinity there 

is some doubt whether the distinction of primacy belongs strictly to the Sandstorm. Other 

claims in the group owned by the Sandstorm :Mining Company are the Kruger, Magnolia, and 

Stimler fraction. Efforts to find ore were at first unsuccessful, and it was not until December, 

1904, that J. R. Davis, J.P. Loftus, and A. H. Mayne, lessees, found rich ore and began shipping. 

Some of the best ore from these leases (No. 5 and No. 6 blocks) has carried as much as $4,600 

per ton. The royalty paid was 30 per cent of the net value of the ore extracted. In 1905 the 

Sandstorm Mining Company began working No. 6 block. The total production fro~ the Sandstorm mine to the end of that year has been locally estimated at about $250,000. Very little 

. work was in progress. in 1908, and the following account is based mainly on what could be · 

seen at the end of 1905. 

As is usual in mines worked in small blocks by lessees, the underground workings of the 

Sandstorm do not accorc with any general plan of development. On No. 5 block, which was 

being worked by Messrs. Loftus, Davis, and Mayne in 1905, there is a shaft 130 feet deep, sunk 

on the dip of the ledge, which is 68 ° E. No stoping had been done below the 50-foot level in 

1905. At 138 feet a crossyut has been driven through the ledge into the hanging-wall country. 

This shaft was being sunk to a depth of 1.50 feet in compliance with the terms of the lease. 

On the No. 6 block, which lies just south of No. 5, is a vertical shaft which was about !35 feet 

deep at the end of1905. All stoping in this block at the time of first visit had been above the 

50-foot level. A station had just been cut, however, for an 80-foot level, in which some rich 

ore was exposed. Above the 50-foot level short drifts and stopes have been run at various 

grades and levels wherever the ore led. In 1908 the main shaft was about 400 feet deep. 

Extensive exploration, however, on the 200-foot and 400-foot levels has revealed no ore, and 

these are· for the present abandoned. 

The upper Sandstorm workings are all in the Sandstorm rhyolite, and this was the only 

rock visible at the time of first visit. The main shaft, however, is said to go through this at 

a depth of about 200 feet into Kendall tuff, and a crosscut from this shaft southeast reaches 

alaskite. 

The Sandstorm-Kendall ledge, shown in Plate XIII, A, outcrops boldly as a zone of strongly 

silicified rhyolite, 40 to 50 feet wide. The outcrop is of lodelike character and can be followed 

without difficulty for at least a quarter of a mile. Its strike is about N. 8 ° W. Where crosscut 

on the 138-foot level in the Sandstorm mine its width is from 35 to 40 feet, but the workings 

are not yet extensive enough to afford much information concerning the size and shape of the 

ledge underground. 

The material of the ledge differs from that of the dacitic ledges in containing comparatively 

little iron oxide; it is not conspicuously rusty. This difference is evidently due to the fact that 

the rhyolite before its conversion into ledge matter contained few ferromagnesian IJlinerals, and 

235 
236 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

consequently there was little iron in the rock to be converted into pyrite, such as by subsequent 

oxidation gives the rusty character of the ledges in dacite and andesite. In the typical Sandstorm ledge matter the rhyolite has been converted into dense cryptocrystalline quartz. This 

is full of small irregular cavities lined with crusts of tiny quartz crystals. Much of the material, 

in fact, has a decidedly.spongy texture. Within this hard silicified rhyolite are irregular masses 

of softer kaolinitic and limonitic material, and it is in such softer portions of the ledge that the 

ore occurs. 

microscope 

Alunite is not so abundant in the Sandstorm ledge as in the mines nearer Goldfield. The 

shows the hard silicified material to consist of finely granular quartz, which in some 

places contains microscopic disseminated crystals of pyrite. Much alunite, however, occurs in 

the altered rhyolite near the Sandstorm and Kendall mines, especially in some of the Morena 

rhyolite, which is cut in the bottom of the Kendall mine. It is not always easy to say whether 

this alunitic material should be called ledge or country rock. 

The ore bodies of the Sandstorm consist entirely of oxidized material. The deepest ore 

found up to the end of 1905 was at 80 feet. This shows a little pyrite under the microscope, 

although the gold itself is associated with limonite and kaolin. Practically all the stoping had 

been done at depths of less than 50 feet. The pay shoots are irregularly distributed through the 

ledge zone and are usually associated with zones of transverse fissuring. The best· defined of 

these fissures runs east and west and on the whole is nearly vertical, although the dip is not 

uniform. It crosses the Sandstorm lode 30 or 40 feet north of the No. 6 shaft and is apparently 

of later origin than the metamorphism which produced the ledge. It varies from a few inches 

to 3 feet in width and is filled with triturated material. Some of the fragments have been 

rounded to pebbles by movement along the fissure. Some ore occurs in the fissure, but the 

principal masses extend out from it into the ledge matter. As a rule these bunches are very 

irregular in form, but most of them appear to rest upon an uneven although generally nearly 

horizontal floor of hard silicified rhyolite. This floor is apparently barren and exhibits no 

particular mineralization, although it, like most of the unoxidized ledge matter, contains a little 

very finely disseminated pyrite. There is apparently no gradation from the rich oxidized ore 

into this hard underlying material. Some of the pay shoots extend from this floor up to the 

surface as irregular pipes or chimneys; others rest upon it as flat-lying masses and are overlain 

by barren or low-grade ledge matter. 

As already mentioned, all the ore thus far found in the Sandstorm mine is oxidized. It 

1 

consists usually of a rather soft earthy mixture of. kaolinite, quartz, limonite, and free gold, 

the latter in some of the richest lumps of ore constituting a considerable part of the mass, 

through which it is disseminated in small particles. Singly these are barely visible with the 

naked eye, but their abundance in some cases gives a yellow tint to the ore. Crystals of barite 

are fairly common. They are generally implanted upon the surfaces of the hard silicified 

rhyolite and project into the softer and richer material of the ore, which fills crevices in the 

rhyolite or envelops loose fragments of that rock. Some of the ore contains pearly scales of 

bismite, indicative of the former presence of bismuthinite. 

Some of the oxidized ore shows slight copper stains, and Mr. C. D. Wilkinson reports that 

he has seen a little chalcopyrite in the main cross fissure. It is probable that some famatinite, 

or possibly goldfieldite, accompanied the bismuthinite in the sulphide ore, as in the mines near 

Goldfield. The best ore shipped from the Sandstorm prior to 1906 -is said to have carried 

about $4,600 (230 ounces) in gold to the ton. 

It is probable that the Sandstorm ore bodies were originally masses of sulphide ore with 

very nearly their present shape-that is, they were comparatively small, rich bunches surrounded by ledge matter and having no direct downward continuation. The original ore 

presumably contained pyrite, free gold, bismuthinite, and some cupriferous sulphur-bearing 

mineral. Oxidation of the known ore bodies has been practically complete, and in the course 

of that oxidation there has probably been some secondary concentration of the gold. 
.. 

KENDALL MINE. 237 

KENDALL MINE. 

The Kendall claim adjoins the Sandstorm on the north and, with the Argosy and Oregon 

claims, is the property of the Goldfield Kendall Mini,ng Company. The principal workings 

are on the Kendall claim and on the same ledge as those of the Sandstorm. The mine was 

first worked by lessees, but was being operated by the company in 1905. The total production 

to the end of that year was about $100,000. Little work has been done on the Kendall of late 

years, and the following description applies to the mine as it was in 1905. 

The main shaft of the Kendall mine is vertical, and at the end of 1905 was about 200 feet 

deep, with levels at 60 and 100 feet. Sinking was then in progress. Above the 60-foot level 

are some small tunnels and some irregular stopes and drifts. All the stoping at the time of 

visit had been done between the 60-foot 1evel and the surface. 

The Kendall shaft is sunk in Sandstorm rhyolite, which, as shown in Plate II, here forms 

a narrow strip between an area of Kendall tuff on the west and the Milltown andesite on the 

w. SHAFT 

I _.... ,_1 \ 1 I I 

.. ";,'.:::'.,..."'' /1_, ....... ,, _\/ ·.t>:: : '\ / \ I \ '\ I _.... 1 \ ""~ \ ", I 1 

. :v·: ~./I"/ \I - ~ \ _.... I I" I I \ I \-

'.-. .' :' ·: _.' 'I~ I~ I~ I'll ' 1

/ '__ 

· :tl .. ~ . · . ; · __. -.. I / \ l - \ ' / \ f__ · .. ... u. I..._ I I- -.....I 

· •. ll · .. ~ : : : · : D .

1 / \ 1 ' 1 - \ I \ __. I " ·.· ·. .·.~?_·.· .- -1 ';-/ ;\ / 'I> .. ·t> . . 6.: . I I '- I I I - I \ . .' :: : : ~: : . ... ,..(\ \ I '- I'\ I -..... .--

. · t:>.:. · ~ :·;. <:;>) ~ ,' I ..._ _.... I I , . . . t, .. . t>' : .. v1< / I I - I -

Kendall tuff. <1 . · .<:1 ·: • \ 

.:/:thi~.· .. : ~ ~~ 

t4l~[ft~; .. v"' II v ",._v.JII 

7 v 1\ ...J 

Morena/\ "_., t'-7 

777 

..., " 

0 25 

FIGURE 29.-Section through the Kendall mine. 

E. 

50 75 FEET 

east: At a depth of about 135 feet the shaft passed into this tuff and continued in it for about 

20 feet. It then passed into rhyolite of the intrusive Morena type, and continued in this rock 

to the bottom. The exact thickness of the tuff where it is penetrated by the shaft is not measurable, as ·the lagging of the shaft conceals the contacts. The general relation of these rocks 

is shown in section in figure 29. 

The tuff, as exposed at the surface, appears to pass beneath the Sandstorm rhyolite on the 

north, west, and south, but to be cut off on the east by a fault. (See Pl. II.) This fault is 

well exposed on the 60-foot level, about 27 feet west of the shaft. There is not much brecciation of either rock, but the plane of movement is marked by a distinct gouge. The fault plane 

at this place dips about 40° E. It truncates the flow banding of the rhyolite, which dips about 
238 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

25° W. The tuff probably rests upon Morena rhyolite about 150 feet below the surface. This 

rhyolite is doubtless intrusive into the tuff, but the contact has not been exposed except in the 

shaft. 

On the 100-foot level a crosscut has been driven east through the Sandstorm rhyolite into 

the andesite, as shown in figure 29. The contact lies about 135 feet east of the shaft on this 

level, and appears to be the result of faulting. The andesite is soft and altered and is either 

tuffaceous or has beep. brecciated by movement. ·The faulting is probably local and is thought 

to represent minor displacement along a contact which originally was a rhyolitic surface over 

which the andesite flowed. 

This same plane of movement, which dips about 35° E., is exposed in a tunnel just north 

of the main Kendall shaft. Near the mouth of this tunnel a shaft goes down through about 95 

feet of andesite to the same contact. This shaft was not in good condition in 1905, but the 

dump indicated the presence of soft gougelike material at the base of the andesite and showed 

considerable pyritization of this rock in its lower part. 

The Kendall ledge is the same as that of the Sandstorm mine. It is an indefinitely bounded 

zone of silicification in the effusive rhyolite. It was doubtful at the time of visit whether the 

ledge could be recognized at all below the point where the shaft enters tuff. The rhyolite in 

the bottom of the shaft contained much alunite, but this kind of alteration is so widespread in 

the Morena rhyolite as to be practically useless as a means of distinguishing typical ledge mat- . 

ter from country rock. 

At the time of visit, near the end of 1905, no ore had been found below the 60-foot level. 

Considerable rich ore was found by lessees at the surface, pockets of soft auriferous material 

having been gouged out from the hard, low-grade, siliceous part of the croppings. Subseque~tly ore was found, much as in the Sandstonn, in the form of small irregular bunches very 

erratically distributed through the ·ledge. The dependence of these rich bunches, however, 

upon transverse fiSsures was clearly shown, these fissures, which are neither regular nor persistent, having generally northwest-southeast trends. 

The ore is entirely oxidized and no sulphide ore has yet been discovered beneath it. It is 

usually a soft mixture of kaolinite, quartz, limonite, and native gold, with abundant barite 

in crystals up to an inch or more in length. As in the Sandstorm mine, the barite crystals are 

usually implanted o:ri silicified rhyolite with their free ends embedded in kaolinite or kaolinitic 

ore. No alunite has been noted in the Kendall ore, although this mineral is abundant in' the 

bottom of the shaft. 

CONQUER~R MINE. 

The Conqueror or Tonopah Club mine embraces the Tonopah Club and Bonanza claims, 

owned by the Conqueror :Mining Company. The principal workings lie about half a mile eastnortheast of the Kendall mine. Ore to the value of a few thousand dollars was obtained near 

the surface in 1904 and 1905, but the property has not since been an important producer. No 

w<;>rk was in progress in 1908. ' 

The principal workings (1905) are an incline about 100 feet in length run on an angle of 

20° to 25°, and a vertical shaft about 50 feet in depth, with a crosscut from the bottom. All 

the stoping has been within 10 or 15 feet of the surface. 

The geologic relations at the Conqueror mine are more complex than in most of the mines 

in the district. At the surface is e~posed an oval area of Morena rhyolite. This is intrusive 

into Sandstorm rhyolite, which here has a most deceptive similitude to a gray shale. Just east 

·of the mine openings and dividing Sandstorm rhyolite on the west from andesite on the east is 

the line of the Columbia Mountain fault. · This fault dips to the east at a low angle (see fig~ 3) 

and is followed by the inclined shaft previously mentioned. A well-marked zone of silicification 

or ledge, having a course of a few degrees east of north, traverses the oval area of Morena rhyolite. The ore has been found, not ill this ledge, but between its southern end and the andesite 

to the east. 
GOLDFIELD MERGER MINES COMPANY's MINES. 239 

The mine workings show shaly Sandstorm rhyolite irregularly intruded by Morena rhyolite. 

All the ore thus far found was in the shaly masses of the older effusive rhyolite. The Columbia 

Mountain fault, as shown by the incline shaft, contains much-crushed shaly rhyolite, much of 

it reduced to a tough, claylike gouge. This soft material is full of small crystals of pyrite and 

is said to afford assay values up to $12 per ton. 

ADAMS MINE. 

The Adams mine, which, like the Conqueror mine~ has furnished a little ore from surface 

workings, closely resembles the latter in geologic relations. It is situated rather less than half 

a mile east of the Sandstorm. The country rock is Sandstorm rhyolite, which is underlain and 

irregularly intruded by Morena rhyolite, which comes to the surface just south of the mine, as 

shown in Plate II. The Adams, like the Conqueror, is close to the Columbia Mountain fault, 

but the workings had not extended to the andesite in 1905. The effusive or Sandstorm rhyolite 

is much disturbed and altered, but exhibits comparatively little mineralization. None of the 

irregular workings had attained a depth of 100 feet in 1905. In 1908 the mine was idle and 

was not again examined. 

KEWANAS MINE. 

The Kewanas mine is situated about 1-! miles northeast of the center of Goldfield and 

three-eighths of a mile south of the Nevada-California Power Company's transformer station. 

The country rock near .the surface is dacite. The workings comprise an inclined shaft a whidh 

goes down to the east for a distance of 500 feet at an angle of 45°. There are levels at 100, 200, 

400, and 500 feet from the collar. 

The rock of the mine is generally much altered, partly to ledge matter, but more extensively to soft decomposed material which soon caves when a drift is abandoned, and which, as a 

rule, is difficult to identify petrographically. At the 200-foot level the shaft is in decomposed 

andesite or andesitic tuff, but the general country rock in the drifts which extend north and 

south for a total distance of about 250 feet is dacite. The relation between the two rocks is 

nowhere clearly shown. On the 400-foot level the main country rock is soft altered latite, but 

here and there in the level, which explores the ground for a distance of about 400 feet from 

north to south and 300 feet from east to west, are ill-defined masses of fine-grained decomposed 

andesite, and in a few places some dacite. The 500-foot level is chiefly in latite, which is either 

silicified to ledge matter carrying some pyrite or else is in a soft, gougelike condition. 

The conditions for geologic study in this mine render it impossible to determine the 

structural relations of the much-altered rocks therein exposed. Probably the observed masses 

of andesite and dacite are in part dikes in the latite. The soft, disturbed character of- the 

ground, moreover, suggests the possibility of considerable faulting, which can not be worked 

out from present exposures. As noted on p~ge 53, some of the shafts just north of the Kewanas 

go through dacite into andesite breccia of considerable thickness. Evidently the :Milltown 

andesite underlying the dacite in this vicinity is not uniform in character, and this adds to the 

difficulty of interpreting what may be seen underground. 

The Kewanas mine has shipped no ore and is essentially a prospect. 

GOLDFIELD MERGER MINES COMPANY'-8 MINES. 

INTRODrCTION. 

In June, 1908, the St. I ves, Velvet, Gold Horn, and Potlatch m1n1ng companies consolidated their buildings under the title of the Goldfield Merger :M:ines Company, capitalized at 

$5,000,000. At the time of consolidation the St. Ives and Velvet mines had small productions 

to their credit, mainly from the workings of lessees. Recently the company has sunk a new 

shaft from which to explore its ground. 

a Since the mine was visited this has been abandoned and a new, vertical shaft sunk. 
240 THE GEOLOGY. AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

ST. IVES MINE. 

The St. I ves mine is situated a little more than a mile east-northeast of Goldfield, and half 

a mile north of Milltown. The property was worked by lessees in 1904, and the results of their 

operations are summarized in the following statement, which is of interest as illustrating the 

conditions under which ore was marketed in the early days of the camp. 

Operations in St. Ives mine, 190-J .. 

Gross weight of ore shipped ........ __ .......................... ... ................... 

Net weight 

tons.. 49.34 

of ore shipped ................. .. ...................................... 

Gross 

do.... 47.87 

contents of ore shipped ..... ............................

Gross 

•..... ... . .. ...... ounces.. 535. 7 

value ............................... .. ..... .. ...................................... 

Treatment 

$10,683. 22 

charges ...................... .... .... ...... ................... ..... .. $287.34 

Loss in smelting, 2~ per cent.................................................... 56. 73 

Freight. ......................

Agent's 

.. ...... . .. .. .... ,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 302. 97 

charges .......... : ...................................................... 

Assays........................................................................ 

5. 50 

6. 00 

Exchange on draft ........... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 25 

1, 661.79 

Total net value ................. _ ................................................ _ .. __ .. __ 9, 021.43 

7,217.15 

Lessees' share (80 per cent) ........................................................ _ ... _._ 

Company's share (20 per cent) ............ -.- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ ___ . _ . 1,804.28 

The gross value of the ore per ton was $223.14 and the net value $150.74. 

In February, 1905, the first lease expired, and the company began operations on its own 

most 

account. The ore shipped by lessees was stoped between the 100-foot level and the surface, 

of it coming from near the 50-foot level. 

l 

0 

FIGURE 30.-Plan of the St. Ives mine. 

When visited late in 

1905, the workings comprised a vertical shaft 250 

feet deep, with levels at 50, 

100, 150, and 250 feet. 

These are shown in plan in 

figure 30. No work was in 

progress in 1908 and the 

mine was not revisited. 

The St. I ves ledge, 

which is in dacite, outcrops 

boldly, forming the crest of 

a small north-south ridge, 

as may be seen from Plate 

II. It has many branches 

and is part of a complex 

50 FEET chain of ledges extending 

southeastward past Milltown to the Gold Bar mine. 

The main ledge at the St. 

I ves mine strikes north-northeast, but the shaft is sunk at. a point near which branches .run out 

to the _east-northeast and to the northwest, as shown on Plate II. Most of the 50-foot level 

(fig. 30) is in ledge matter, all more or less rusty from oxidation. The general trend of the 

siliceous zone on this level is northeast. The 70-foot and 100-foot levels are also almost wholly 

in oxidized ledge matter. The 70-foot shows nearly the same strike as the 50-foot, but on the 

100-foot level the trend of the ledge becomes almost due north and south. In other words, the 

dip of the ledge in the southern part of the workings is about 45 °, while in the northern part it 

is nearly vertical. On the .150-foot level, which is below the limit of oxidation, the ledge is 
GOLDFIELD MERGER MINES COMPANY'S MINES. 241 

very obscure .. Beginning at a point about 30 feet east of the shaft the dacite for a distance of 

50 feet. shows irregular bunches and streaks of partially silicified material alternating with soft 

pyritized and alunitized dacite. In some places the dacite has been shattered and contains 

considerable pyrite and alunite, such material having the characteristic~ of unoxidized ledge 

matter. On the 250-foot level the ledge is still more obscure. A crosscut east from the shaft 

was about 100 feet in length at the time of visit. This showed soft pyritized alunitized dacite, 

with slight-silicification along some of the fissures. The highest value obtained by assay from 

any of the material on this level did not exceed $5 a ton. On the whole the St. I ves mine 

illustrates w~ll the fact of a decrease in silicification with increase in depth: 

The ore bodies stoped in the St. I ves mine were mainly near the 50-foot level and were 

oxidized. They were irregular in outline and of small size. The largest body (see fig. 30) was 

about 50 feet south of the main shaft. It extended about 20 feet, on the dip, above the 50-foot 

level and for a short distance down the winze to the 70-foot level. 

CODD LEASE. 

The Codd lease is on the St. I ves ground and is worked through a shaft 500 feet deep, situated a short distance west of the St. I ves shaft. The upper ·levels are· in dacite, but somewhere 

between 350 and 400 ·feet in depth the shaft goes into latite. Oxidized ore of a gross value of 

about $11,000 was mined in 1907 from small irregular pay shoots in the dacite above the 50-foot 

level. The ore trends nearly north and south and dips west. The total length of the stopes 

is about 100 feet. As in the St. Ives proper, the deeper levels have not proved encouraging. 

VEL VET MINE. 

In 1904 a bunch of oxidized ore found practically at the surface yielded lessees about 

$10,000. Since then a number of shafts have been sunk near the original discovery, about half 

a mile northeast of Goldfield. Two of these, the Alta shaft, 418 feet deep, and the ChicagoVelvet shaft, 526 feet deep, were in operation in 1.908. The geologic features of these workings 

are referred to on page 81. They are not in ore. 

JUMBO-EXTENSION MINING COMPANY'S GOLD WEDGE CLAIM. 

The Gold Wedge, a3 may be seen from Plate IX, is a fractional claim lying on the · northeast side of the Mohawk No. 2 claim. On it is a line of lessees' shafts, which from north to 

south are the Jumbo Annex, Higginson, Mohawk Ledge, Frances-Mohawk, and MohawkJumbo shafts. At the time of second visit to the district, in 1908, these workings were all 

closed by injunction and were not examined. The dumps showed that all the shafts at that 

time were wholly in the dacite. Lease blocks in the Goldfield district are bounded by vertical 

planes, and consequently the lessees on the northern part of the Gold Wedge are confined 

within narrow limits. In the Mohawk-Jumbo workings, however, at the south end of the claim, 

large stopes have been opened o'n the same pay shoots that are stoped at higher levels in the 

Mohawk mine. . (See Pl. IX.) This shaft at last report was 685 feet -deep, making it one of 

the deepest in the district. The settlement finally reached between the Goldfield Consolidated 

Mines Company and the Jumbo Extension Company over the Gold Wedge claim is described 

on page 23. 

COMBINATION FRACTION MINES. 

The Combination Fraction Mining Company owns a nearly square fractional claim between 

the ends of the Mohawk No. 2 and Florence claims, and northeast of the Combination mine. 

In it are 5 sets of workings. In the south corner is the company's shaft, with extensive exploratory levels down to .±Ql,...feet in depth. (See Pl. IX.) These workings were closed in 1908 

and were not studied. J'hey are probably all in dacite and the ground is said to be generally 

soft and disturbed. No ore has been found. In the northwest corner of the claim is the Burns 

79145-No. 66-09-16 
242 THE GEOLOGY AND ORE DEPOSJTS OF GOLDFIELD, NEVADA. 

shaft. The ground here also is soft and the drifts soon close. Northeast of the Burns shaft is 

the Loftus-Davis lease shaft. From this stopes were opened on the .Mohawk ledge in 1906 and 

1907. This shaft had been dismantled in 1908, although it was possible to enter the stopes 

from the Mohawk workings. The 531-foot level (Pl. IX) is reported to follow a nearly vertical 

fault which is supposed to cut and displace the Mohawk ledge. This level could not be reached 

in 1908. The displacement is certainly not great, as a short distance north the ledge has been 

found generally continuous down to the 600-foot level of the Mohawk. · 

East of the Loftus-Davis shaft is the Oddie shaft, originally sunk by lessees, but now being 

operated by the company. Its depth is 612 feet. It was sunk without any lateral exploration above the bottom level, with the expectation that the Mohawk ledge would be cut at a 

depth of about 600 feet. Subsequent work ih the Mohawk mine shows that this expectation 

was justified, but the lessees failed to find ore. A part only of the 612-foot level was accessible 

in 1908. ·It is apparently mostly in latite, the contact, which locally at least seems to be a 

fault with steep dip to the east, being a few feet west of the shaft. The rock in the vicinity of 

the contact is soft and decomposed. A part of the latite on this level is distinctly a pyroclastic 

rock. · 

The 427-foot level shows a north-south dacite edge with easterly dip. The width of this 

had not been determined at the time of visit. 

The principal work in progress in 1908 was on the 285-foot level, where ore in dacite, very 

similar in character to some of the lower-grade Hayes-Monnette ore, had been opened in two 

places. Dacite is the only rock on this level. Too little work had been accomplished at the 

time of visit to reveal the size or shape of the ore body, which is probably an irregular mass in 

the hanging wall of the main Mohawk ledge. 

About 250 feet southeast of the Oddie shaft is the shaft of the Little Florence Leasing 

Company. At the time of visit no ore had been found in these workings, which are in dacite. · 

ATLANTA GROUP. 

The Atlanta group includes the Atlanta Union, Black Bear, and Bismark claims and lies 

directly east of the Florence-Goldfield Mining Company's ground. The Atlanta Company has 

done comparatively little development, but the property has been most persistently explored 

by lessees, with very little encouragement. Among the shafts on this ground, most of them 

ranging from 300 to 500 feet in depth, are the Jumbo ledge, Blake, Maloney, Chedd, Lucky 

Swede, Century, Imperial, Atlanta-Cherokee, and Garrison. The lateral development from 

most of these shafts is small. 

GOLD BAR AND VICTOR MINES. 

The Gold Bar and Victor mines of the C. 0. D. Consolidated Mining Company lie southeast of the Atlanta group. (See Pl. X.) The main company shaft is the Gold Bar, 300 feet 

deep. About 400 feet east-southeast of this is the Victor shaft, operated by lessees, and about 

the same distance in the opposite direction is the C. 0. D. shaft, no longerin use. These three · 

shafts are connected by the 200-foot Gold Bar level, as shown in figure 31. · 

·The country rock in the upper level is the Milltown andesite, but the 300-foot level and a 

large part of the 200-foot level east of the shaft are apparently in latite, although the rock is 

too much altered for satisfactory identification. Dacite appears at several points on the 200-

foot level, probably as intrusive tongues in the latite and andesite. In spite of the prevailing 

alteration this intrusive character of the dacite is well shown at one place on the south side of 

the main west drift of the 200-foot level. Both rocks are soft and greatly altered, but the 

original irregular contact does not appear to have been disturbed. 

A large part of the workings are in ledge matter. While this is largely altered andesite 

and partly latite, there is a rather close association between ledge matter and dacite. The 

latter penetrated in ragged protrusions into the older rocks, and the subsequent silicification 

and mineralization have taken place chiefly in the vicinity of these intruded masses. 
BLUE BULL MINE. 243 

Shipments aggregating about $25,000 in gross value have been ;made from time to time 

from a chain of very irregular bunches of ore: extending eastward from near. the Gold Bar shaft 

down to the 200-foot (250-foot Victor) level near the Victor shaft, and some ore was produced 

from a body of oxidized ore near the surface at the C. 0. D. shaft. The unoxidized ore is characterized by an abundance of a dark-gray brittle ;mineral, which resembles the fa;rnatinite of 

the Florence and other mines near Goldfield. Like that mineral, it contains copper, sulphur, 

and antimony, and forms crusts around partly rounded fragments of silicified andesite or 

dacite. It has not the reddish tint of the famatinite, hmvever, and unlike that ;mineral elsewhere in the district is not associated with particularly rich ore. It is possibly enargite. As 

pointed out on page 117, the distinction between enargite and famatinite is impossible without quantitative chemical analysis of pure material or the presence of satisfactory crystal 

form. 

The Kansas City lease, northwest of the C. 0. D. shaft, is not i~ ore and was not examined. 

North of the Gold Bar shaft is the shaft of the Gold Bar Leasing Con1pany, 475 feet deep 

at the time of visit, ·but not in ore. The country rock is all Millto\vn andesite. The workings 

N. 

l 

0 

FIGURE 31.-Plan of t he Gold Bar and Victor mines. 

show irregular masses of ledge matter with abundant pyrite, partly dissen1inated and partly 

as crumbling stringers. The best assay obtained prior to the ti;rne of visit was $1.80. 

BLUE BULL MINE. 

The Blue Bull Mining Company .owns about 7 claims, lying in a compact group about 1 t 

miles east of Goldfield. On the Blue, Bull claim, which is the northeast member of the group, 

the company has sunk a shaft 110 feet deep, and has crosscut from the bottom of this for 

about 400 feet, under some bold ledge outcrops which crown the hill just east of the shaft. 

The dacite penetrated by this crosscut is cut by two sets of conjugate fissures with a com;rnon 

northeast strike. One set dips northwest at various angles up to 60°; the other dips southeast 

at rather lower angles. The fissures with northwest dip are generally the stronger, and considerable silicification has taken pla.ce along the;rn. The great east-west ledge which outcrops on 

the ridge east of the shaft (see Pl. II) had not been satisfactorily exposed in the crosscut at the 

time of visit. It appears to correspond to a series of east-w~st fissures, concerning which the 

;mine workings as yet afford very little information. This ledge has been crosscut by a tunnel 
244 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

near the crest of the ridge, where it proved to be about 25 feet wide. A small bunch of ore was 

fmmd in shattered kaolinized dacite, about 50 feet from tJ:le surface, on the south side of the 

siliceous ledge, but the Blue Bull n1ine has never n1ade any shipments. This shaft had been 

abandoned in 1908, and a new shaft, which was not visited, had been sunk about 800 feet south 

of the old one. · 

On the Hat claim, which is at the south end of the Blue Bull group, lessees at the end of 1905 -

had taken out a little oxidized ore from workings about 50 feet in depth. Additional work has 

since been done on this lease, but the shaft, like others in the vicinity, was closed at the time 

of second visit. The country rock here is the :Milltown andesite, and the ore as seen in 1905 

occurred in a pron1inent ledge containing abundant red oxide of iron. The character of the 

ore is described on page 124. 

SIMMERONE MINE. 

The Simmerone is situated about 2 miles east of Goldfield, near the eastern border of the 

central dacite area. The n1ine was not producing in 1905, although a small bunch of rich 

ore had previously been stoped from near the surface, yielding about $5,000 gross. . 

The n1ine in 1905 had a vertical shaft 50 feet deep and a 44° incline about 110 feet in 

length. The country rock, which is dacite, is traversed by n1any fissures, which in general 

strike north and dip 45° W. These give the rock a pronounced sheeted structure, and along 

some of then1 considerable silicification has taken place. 

The body of ore stoped was found in the incline and extended to a depth of 60 feet. It 

was an irregular pipe of small horizontal section. The ore is a firm fine-grained material, 

much of which is pink or light red, irregularly streaked with gray. This material is chiefly 

alunite, mixed with kaolinite and iron oxide. The gold ·is distributed unevenly in small hackly 

particles through the impure alunite. 

Since the first visit a new shaft has been sunk, which goes through the dacite into the latite. 

The shaft was not in operation in 1908 and no information regarding it could be obtained. 

LONE STAR GROUP. 

The Lone Star mine is about 2 miles·east of Goldfield, just north of the ridge on which are 

the Blue Bull, Simmerone, and Commonwealth workings. The total gross production to the 

end of 1905 was approximately $10,000, from ore mined by lessees who expended about $15,000 

on the property. So far as known there has been no subsequent output. · 

The Lone Star ledge, shown in Plate XIV, B, outcrops boldly, the exposed part consisting 

of strongly silicified dacite sheeted by closely spaced north-south fissures. This zone of sheeting 

and silicification is at least 50 feet wide at the surface. The ledge strikes a few degrees east 

of north and dips 60° E. · 

An inclined shaft has been sunk by lessees on the foot-wall side of the ledge and levels 

run at 80, 150, and 220 feet below the surface. The principal ore body was followed from 

the 80-foot level to a point about 20 feet below the 150-foot level. The maximum stope length 

of the shoot was 20 feet and the greatest width of ore 5 feet. The shoot was accordingly of 

pipe {orm. The ore all showed some oxidation and apparently consisted of iron-stained alunite, 

·with probably some kaolinite, carrying native gold. A specimen taken from the bottom of a 

winze below the 150-foot level, at the point where the ore shoot ends, is a rather sandy aggregate 

in which the constituents are chiefly rough, doubly-terminated, microscopic crystals of quartz. 

The average value of the ore shipped, according to the lessees, was $290 a ton. 

Alunite is abundant in the Lone Star ledge and in some places forms soft, snow-white or 

faintly pink masses, with practically no impurities. 

The holdings of the Lone Star Mining Company cover an extensive area and embrace 

about 16 claims. The principal company workings are on the Patrick claim, west of the lessee 

workings just described. The shaft is only 100 feet deep, but the drifts and crosscuts at this 

depth are unusually extensive. They have revealed no ore. The rock is generally 1nuch 

altered and shows considerable disturbance. The bottom of the shaft is just in latite, the 
PORTLAND MINE. 245 

contact with the overlying dacite as seen in the 100-foot station being nearly horizontal. Else-

. where in the workings .dacite appears to cut both latite and andesite, but the information 

afforded by the ·exposures is nowhere definite. The general relations of the rocks are similar 

to those observed in the Kewanas workings, although the thickness of the dacite is much 

less at the Lone Star shaft. 

COMMONWEALTH MINE. 

For the past three or four years lessees have been shipping small lots of ore from superficial 

workings on the north slope of the ridge east of the Blue Bull and Simmerone mines. This 

locality, as may be. seen from Plate II, is near the eastern edge of the main dacite sheet, and 

with the exception of the Diamondfield mines is the farthest point east at which any important quantity of ore has been found in this ditrict. The ore thus far mined is all oxidized and 

occurs in the usual irregular masses in dacitic ledge matter. Below the tunnels from which 

the ore has been stoped the Commonwealth shaft has been sunk to a depth of 400 feet. The 

shaft apparently goes into latite somewhere above the 1 00-foot level, but the exact depth of 

the change could not be ascertained, owing to the close lagging of the shaft. The shaft 

was not in operation in 1908, and the water stood at the 300-foot station. So far as could be 

ascertained no ore was found in these workings. 

PORTLAND MINE. 

The Portland mine is situated about a mile east-southeast _of the center of Goldfield and 

a little less than half a mile south of the Florence mine. It has never shipped any ore. The 

principal development in 1905 was on the bottom level, 250 feet below the surface. Since 

then a level has been run at a depth of 400 feet, but none · of the lateral work was visible 

in 1908 owing to the caving of the soft heavy ground. An attempt to put down a diamoncdrill hole below this level was abandoned before the bottom of the latite had been reached. 

The geologic features in this mine are especially interesting. As may be seen in Plate II, 

the Portland shaft is sunk through a small lobe of the Siebert formation, which apparently 

rests on andesite. It is not known at what depth the shaft passed out of the Siebert sediments, but it was probably very close to the surface. From the collar of the shaft to the 250-

fcot level there was no point at which the rocks could be satisfactorily examined in 1905. 

From the bottom of the shaft a crosscut has been driven for about 350 feet to the east. From 

al~ that was previously known of the structure of this part of the district it was to be expected 

that the rock in this crosscut would be andesite. It consists, however, of amygdaloidal olivine 

basalt flows with basaltic tuffs. In general these are soft and much altered and contain 

much disseminated py::rite. The depth at which these rocks occur appears to rule out any 

attempt to correlate them with the quartz basalt exposed south of Goldfield or with the later 

olivine basalt capping Myers Mountain. The most probable hypothesis is that they represent 

local basaltic eruptions within or immediateJy preceding the andesite period. -

The dump of the mine shows that at some point between the 250-foot and 400-foot levels 

the shaft went into latite and -continued in t his rock to the bottom. As a whole the rock of 

the Portland mine is soft, much of it being little firmer than mud. ' 

The Portland was for some years the only deep shaft south of Florence Hill. Recently 

a number of prospecting shafts, som-e of which exceed it in depth, have been sunk in its vicinity. 

These all go through andesite into latite at a depth of about 300 feet. 

OTHER PROSPECTS. 

The White Rock, Silver Pick, and numerous other companies owning claims in the vicinity 

of Goldfield have prospected their ground fully as extensively or even more so th~n some of 

those mentioned in the preceding descriptions. To describe in detail all these workings would 

add to the bulk of this report without increasing its interest or usefulness. Such geological 

information as is furnished by these various shafts has been incorporated in earlier chapter8. 
CHAPTER XXI. 

DETAILED DESCRIPTIONS OF MINES OF THE DIAMONDFIELD GROUP. 

DIAMONDFIELD-BLACK BUTTE CONSOLIDATED MINES. 

The Quartzite and Black Butte mines, with workings mainly on the north side of Black 

Butte, were consolidated as the Diamondfield-Black Butte Consolidated Mines in 1905. Prior 

to that a· considerable body of ore had been stoped by lessees, mainly from the original Quartzite 

ground. 

A plan of the combined workings is shown in figure 32. The Quartzite shaft is about 200 

feet deep, with four levels 50 feet apart. The Black Butte shaft is 150 feet deep, with three 

No.2 tunnel 

-----~~ 

100 200 300 F'EET 

Levels, which are about 

10 feet below the corresponding Quartzite 

levels. · A tunnel 545 

feet in length penetratesBlackButte from 

the south and connects 

through a 25-foot winze 

with the 50-foot level of 

the Black Butte workings. East of the portal 

of this tunnel is a chain 

of nearly horizontal 

stopes on a :flat vein. 

The general country rock of the mine is 

andesite, which is cut by 

a few ill-defined masses 

of dacite. Both rocks 

are in most places py- .FrGuRE 32.-Plan of the workings of the Black Butte mine. ritized and rather soft, 

containing much gypsum in gouge seams and in all the joints and crevic-es. Fissuring in nearly 

horizontal planes is a notable feature of the country rock and has resulted in the formation of 

sh.eets of brecciated and more or .Jess silicified material. The massive ledge which caps Black 

Butte (see Pl. III, B) is clearly a remnant of such a sheet, since the tunnel passes directly under 

it. Similar but smaller silicified sheets are exposed in the tunnel, and, as may be seen from figure 

14, these maY' be very irregular. In some places the horizontal fissuring has produced a sheeted 

instead of a brecciated structure. Such in the main is the :flat vein stoped along the south 

side of the butte. As a rule, most of these horizontal ledges contain·a little ore, but it is very 

bunchy and erratic in its occurrence. The ledges themselves, moreover, are apparently not 

very persistent. 

The ore body stoped by the lessees on the north side of. the butte was a very irregular but 

generally lenticular mass, with north-south trend and a dip to the west, the lens being nearly 

on edge. Its maximum stope length was about 100 feet and its greatest width about 25 feet. 

In its widest part the ore was divided longitudinally by a slab of waste or low-grade ore. The 

extreme vertical range of the ore was about 100 feet, its bottom limit being near the 100-foot 

level. It became poorer and narrower close to the surfa~e. On the north the ore ended against 

246 
MINES OF THE DIAMONDFIELD GROUP. 247 

a seam of gouge. At the bottom it graded into soft barren andesite. All of the ore appears to 

have been partly oxidized, the bottom of the pay shoot coinciding roughly with the lower limit 

of oxidation. The best part of the ore was between the 50-foot and 1 00-foot levels. . 

The ore, as shown by the little left in the stope, was a much-shattered mass of andesite, in 

which all the smaller fragments and part of the larger ones had been replaced by cryptocrystalline quartz carrying pyrite and famatinite. Doubtless native gold and probably a telluride of 

gold were present in the richer ore prior to the oxidation. The greenish-yellow ferric tellurite, 

emmonsite or durdenite, is said to have served as an indication of good ore. Alunite is abundant, both as a seco!ldary constituent of the altered fragments of andesite and as a filling in 

crevices and vugs in the sulphide ore. Within the generally silicified material of the pay shoot 

near the bottom of the ore are some masses of andesite which have been changed to soft, crumbling aggregates, consisting chiefly of alunite and pyrite. 

Practically all of the material available for examination in 1905 was sulphide ore, which in 

this mine has proved of low grade, rarely carrying over $15 a ton. Whether the partly oxidized 

ore taken out by lessees owed its greater richness to secondary concentration or whether the 

sulphides from which the extracted ore was derived were originally richer than those remaining, , 

it is impossible to say. The relations are suggestive of secondary enrichment during oxida- · 

tion, but bunches of unusually rich unoxidized ore are in this district so common as to throw 

the burden of proof upon the enrichment hypothesis. 

The boundary between the ore and the country rock appears in this deposit to have been 

unusually definite and in many places is marked by a seam of gouge. Similar seams were sometimes found within the ore. · 

All attempts to find a downward continuation of the rich ore shoot have proved futile, 

although, as shown in figure 32, two levels have been driven directly under the old stope. They 

show altered pyritized country rock. Exploration in depth has revealed only a few small 

podlike masses of ore separated by curved seams of gouge from the surrounding soft andesite. 

Ot her ore bodies, however, occur in Black Butte, as shown by the discovery of rich ore at the 

surface, on the south slope, in December, 1905. This was in one of the numerous nearly horizontal fissure zones, and at the time of visit, shortly after its discovery, the ore body had been 

followed into the hill for a distance of 20 to 30 feet. This ore, which was from 18 inches to 2 feet 

in thickness, showed native gold of unusually rusty appearance, associated with a greenishyellow ferric tellurite and cryptocrystalline quartz in a nearly white, alunitized rock, which 

appears to have been originally dacite. (See Pl. II.) The gold resembles, more than does 

most of the native metal in the district, the gold derived from tellurides in the Cripple Creek 

district, and without much doubt existed in part as a telluride prior to oxidation. Small 

brighter specks within the dull gold probably represent original· inclusions of native metal in 

the telluride. 

When visited again in 1908 this ore body had been practically stoped out, although some 

lessees were still stripping the sides of the stopes. The deposit proved to be nearly hori~ontal 

near the surface of the hill, along which it has been stoped for a distance of about 300 feet. 

The ore was followed · into the hill for a maximum distance of nearly 100 feet. The dip in this 

direction became steeper and the ore gave out. The better part of the body occupied a nearly 

horizontal zone of sheeting in dacite, the latter rock, as shown in Plate II, extending as a_n 

intrusive tongue into the andesite of Black Butte. The width or thickness of the sheeted zone 

amounts in some places to several feet, but the average thickness of the ore is between 6 and 10 

inches. This blanket ledge is cut by a few faults, with throws up to 8 feet. No sulphide ore was 

found. 

GOLDFIELD-BELMONT MINE. 

The Goldfield-Belmont mine lies half a mile northwest of the summit of Black Butte, in 

ground formerly owned by the Vernal Mining Company. The Vernal workings, from which 

lessees took some ore in the early days of the district, are about 750 feet north of the present 

Goldfield-Belmont shaft. Very little ore had been shipped from the new workings up to the 

end of 1905. At the time of second visit in 1908 all work had been abandoned. 
248 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

A general plan of the developm~nt of the mine is shown in figure 33. There is a main vertical shaft with levels at 62 and 150 feet below the surface. There are also some shallow shafts 

and irregular drifts above the 62-foot level. Whether the workings were carried deeper after 

1905 is not known. 

The country rock of the mine is a fine-grained andesite which is considerably altered and 

is usually soft. The ledge is a broad zone of partly sheeted and partly irregularly fissured and 

shattered rock of not very prominent outcrop. The strike is approximately north-south and 

the general dip about 40° W. There are no definite walls to the ledge as a whole, although an 

approximate hanging wall is defined by a zone in which the andesite is very, soft and is in some 

places sheared to the consistency of gouge. 

Such ore as has been found was between the 62-foot level and the surface. On that level, 

on the foot-wall side of the ledge, is a vein of soft, sugary, white quartz carrying small quantities of famatinite, gold telluride, and pyrite. Within this soft material are fragn1ents of quartz 

and a silicified rhyolite. Much of the firm quartz in this part of the ledge has a porous texture 

and appears to be in part pseudomorphous after, or to have incrusted, some mineral which has 

been carried away in solution. Some of-the vein material has a green tint, due to the presence 

· of scales of sericite. On the 150-foot level 

100 

N. 

l the ledge, about 40 feet in greatest width, is 

a zone of irregular white stringers in finetextured, p'artly silicified andesite. The general structure, unlike that of other deposits 

t:/ seen in the Goldfield district, might be charZOO FEE:r 

acterized as a stringer lode. The irregular 

stringers or veinlets fill fissures up to 4 inches 

in width. The vein material is a fine-grained 

mixture of quartz and kaolinite, grading in 

some places from soft kaolinite to nearly pure 

hard quartz. Pyrite, the only sulphide found 

on the 150-foot level, occurs in the veinlets 

and in the altered andesite. Many of the 

small vugs in the veinlets .contain gypsum, FIGURE 33.-Plan of the workings of the Goldfield-Belmont mine. SOme of which is intergrown with pyrite. • 

The ledge material as seen on the 150-foot level shows at least two periods of fissuring and 

veining, which are distinguishable on structural grounds, although not by the nature of their 

products. . 

No ore had been found on the 150-foot level to the end of 190.5. The chief features of 

scientific interest in the mine are (1) the occurrence of distinct fissure fillings; (2) the unusual 

character of the vein material, much of which is a porcelain-like aggregate of quartz and 

kaolinite; and (3) the occurrence of gypsum with pyrite below the belt of oxidation. 

The sugar quartz of the upper level was doubtless originally a mass of stringers carrying 

quartz and kaolinite. With the removal of some of the kaolinite a-nd perhaps other constituents the resulting porous mass was crushed to its present condition. Alunite has not been 

seen in the few thin sections studied, but is probably not entirely absent from the altered 

andesitic country rock. 

DAISY MINE. 

The Goldfield Daisy Mining Syndicate. owns the three Daisy claims along the crest of 

McMahon Ridge, north of Diamondfield. A general plan and a longitudinal projection of the 

workings ar~ shown in figure 34. In ali, the property had produced-about $60,000 gross up to 

July,-1908. 

The country rock of the Daisy is the Milltown andesite; Four general ledges are recognized, namely, the North, Middle, South, and Fault "veins." The general courses of these are 

shown in figure 34. They are not continuous, at least in outcrop, but are marked by bunches 

of ledge matter along zones of fissuring. The so-called Fault vein strikes northeast and dips 

55° NW. It is probably the same as the Belmont ledge. Most of the ore hithert'o shipped from 
JJflJS l'" 200-f"t.leYel 

] [300-f't.leve/ 

K 400-ft.leve/ 

Jl 0· 3 ~ ~ ~ a~.. 

<:."-

,_,., 

~~ ~ ~ 100 

]'I 

\ 

\ 

G,AL£3fl,At1H 

Lf,ASf 

____ ,---"\ 

--- \\, 

PLAN OF WORKINGS 

100 200 300 400 500 FEET 

iQ ~ ~~ 

,..._ 

~~ 

~"> ~ tt 

LONGITUDINAL VERTICAL PROJECTION 

· 1-IGURE 34.-Plan and longitudinal projection of t!:tc workings on the Daisy group. 

• 

\ 

\\, 
250 THE GEOLOGY AND ORE DEPOSITS OF GOLDFIELD, NEVADA. 

the Daisy has been oxidized material from this "Fault vein." According to Mr: C. W. Geddes, 

the superintendent, the ore from this pay shoot averaged about 5 ounces of gold and 3 ounces 

was 

of silver to the ton. No work was in progress on this ledge in 1908, and the old Daisy shaft 

not in a condition to give safe acces·s to the levels. 

West of the old shaft the main work on the Daisy No. 1 claim has been o:ri the Middle ledge, 

which is fairly distinct at the surface up to the highest point on the ridge. Here all the andesite 

between the courses of the two ledges is intensely silicified and at the surface forms a single 

broad mass of ledge matter. The main Daisy shaft (originally the Truett lease shaft) was 400 

feet deep at the time of visit, !n July, 1908, with crosscuts running south to the Middle ledge 

on the 300-foot and 400-foot levels . . This lies about 80 feet south of the shaft on the 300-foot 

level and dips about 65° S. It is a broad soft zone of crushed andesite, showing much less 

silicification than the typical ledges in the dacite near Goldfield. The material apparently is 

not heavily mineralized, pyrite being the only sulphide seen. According to Mr. Geddes the 

average value of this shoot for a width of 5 feet is $50 per ton. The pay shoot on the 400-foot 

level is of the same general character. On both levels the soft ore-bearing zone is apparently 

on the foot-wall side of the main ledge, or zone of most intense silicification. A crosscut was 

being run at the time of visit ~o cut the North ledge on the 400-foot level. , 

Milltown 

The country rock of the 300-foot and 400-foot levels is an andesitic breccia, part of the 

andesite volcanic complex. 

West of the company workings, on the' Daisy No. 1 claim, the Morrison and Toplitz leases 

were being worked in 1908. The Morrison shaft at that time was 370 feet deep, with a crosscut 

from the bottom 225 feet to the south. The rock exposed in this crosscut is altered and pyritized 

andesite and andesitic ·breccia, containing streaks and bunches of oxidized ledge matter but · 

no ore. 

The Toplitz shaft, about 700 feet west of the Morrison, was down 250 feet. A streak of 

good 

mere 

oxidized ore up to a foot in width was being stoped near the 200-foot level. This was a 

streak in a great oxidized siliceous ledge fully 100 feet wide. The ore showed free gold, 

cerargyrite, and specks of an undecomposed gray telluride. 

JUMBO EXTENSION (GOLD COIN) MINE. 

The Gold Coip. claim 9f the Jumbo Extension Mining Company's ground, on the south 

slope of ~ifcMahon Ridge, and south of the Daisy mine, was being worked by lessees in 1905. 

At the time of visit, in November, the shaft was 150 feet deep with 3 levels. It is sunk on a 

lodelike, nearly east-west ledge from 2 to 3 feet in width, which is probably the "South vein" 

of the Daisy. Down to the 100-foot level the ledge dips 75° N; but south of that level the dip 

is apparently in the other direction, although too little work had been done on the 150-foot level 

to establish the position of the ledge. The country rock is andesite. 

Most of the ore shipped prior to 1906 was partly or wholly oxidized and came from small 

stopes above the 100-foot level. It consists of cryptocrystalline quartz, formed by replacement 

of andesite, associated with limonite. Within the quartz are specks of a dark-gray telluride 

of gold, associated with native gold and microscopic crystals of alunite. In the limonitic part of 

the ore are native gold and cerargyrite associated with a yellow-green ferric tellurite. Some 

of the ore contains an unusually large proportion of silver, assay certificates in the possession of 

the lessee.s showing in one case 48.2 ounces of gold and 88.1 ounces of silver per ton; in another 

case 814.65 ounces of gold and 579.85 ounces of silver. ·Presumably, therefore, the dark 

mineral 

telluride is argentiferous as well as auriferous, for most of the unoxidized ore contains no other 

likely to yield much silver, although a few specks of what appeared to be famatinite 

were noted above the 100-foot level. The 150-foot level, as Q.eveloped at the end of 1905, showed 

practically no ledge matter and no ore. 

No work was in progress in 1908. 
MINES OF THE DIAMONDFIELD GROUP. 251 

TRIANGLE MINE. 

The Triangle workings are immediately northwest of the Gold Coin, and appear to be on 

the same ledge. The shaft at the end of 1905 was 100 feet deep with 3 levels. The strike of 

the ledge in the Triangle workings is N. 50° W. The dip is northeast and, although variable, 

approximates .to 75°. The country rock is andesite. 

The ledge is a well-defined plate of silicified andesite generally from 1 to 2 feet in width 

or thickness. A little oxidized ore has been shipped from the 40-foot and 70-foot levels, but 

the ledge as exposed on the 100-foot level in 1905 contained only low-grade pyritic material, 

none of which, in all probability, was worth Inore than $30 a ton. 

No work was in progress in 1908. 

GREAT BEND MINE. 

On the Great Bend claim, which ·adjoins the Daisy No. 1 on the west, the principal work 

in progress in 1908 was on the Loftus & Davis lease, on the westward continuation of the Daisy 

ledge zone. An inclined shaft had been sunk 300 feet on the ledge at a 65° angle, and some good 

ore has been stoped from very soft pay shoots resembling that of the Daisy. The ore consists of 

tiny stringers and bunches of quartz in alunitized andesite, the whole being as a rule soft enough 

to pick. Most of the ore has come from the hanging-wall side of the ledge, but some bunches 

have been fou:qd next to the foot wall. The best ore shows small crystals of pyrite and sphalerite, with specks of a telluride in a nearly white, shattered, alunitic matrix which can be crumbled 

between the fingers. Firm masses of flinty ledge matter, such as are common in the mines near 

Goldfield, do not occur, apparently, in the Daisy and Great Bend ores, which are prevailingly 

soft structureless masses and have evidently undergone comparatively recent crushing. 

A new vertical shaft was being sunk just south of the incline in the summer of 1908. 

INDEX. 

A. Page. 

Acknowledgments to those aiding ................................ 13-14 

Adams mine, description of .... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 

Alaskite, age of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 

character and distribution of ............ .... ....... : . ........ 33,87 

geology of... .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. . . .. .. .. . 34 

intrusion of ............... , . ................. .... ........... . 27,37 

petrography of. ......................................... ~ . . . 33-34 

view of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34, 46 

Albite, occurrence and character of. ................... ·.. ......... 108 

Alkali Springs, water from. .. . .. .. .. . .. .. .. . .. .. .. .. .. .. .. .. .. .. . 143 

water from, analysis of.................. . .................... 143 

Arteration. See Metamorphism. 

Alum, occurrence and character of........ .......... ............. 108 

Alunite, association of, with kaolinite ............ ... ............. 192 

association of, with ores. . . . . . . . . . . . . . . . . . . . . . . . 132-133, 189, 199, 201 

formation of.. .. ......... .. . . ................. 30, 38, 132, 191-192, 195 

occurrence and character of. . . . . . . . . . . . . . . . . . . . . . . . 108, 129-133, 167 

Alunite, Nev., rocks at ........ . ................................. : 199 

~\lu nitic veins, type of..................... ... .. .. .... .. ......... 199 

_\!unitized rocks, area of. . .. . . .. . .. . . .. . .. .. .. . .. . .. . . .. .. .. .. .. . 193 

area of, figUre showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 

photomicrographs of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178, 184 

production of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17G 

Amphibole, occurrence and character of..... .. ................... 108 

Andesine, occurrence of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 

Andesite, age of. ........................ · ................... :.. . .. 104 

alteration of. ........... .. ................ _. . ................. 182 

photomicrograph of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 

breccia of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

correlation of. ........................................ _ ..... 102-104 

dikes of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G5 

ledges in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151, 156 

ores in .... .. .... : . .................................. .... .... 31, 163 

veins in, photomicr.ographs showing .............. __ ....... ___ 156 

See also Milltown andesite; Chispa andesite. 

.J..northite, occurrence of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 

Apatite, occurrence of........... ... . .. . .. .. . .. .. . . .. .. .. .. .. .. .. . 108 

Arnett, W. D., & Co., analyses by................................ 167 

Atlanta group, mines of............. ...... .... .. ................. 242 

Augite, occurrence and character of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 

Azurite, occurrence and character of................. .. .. . . . . . . . . . 108 

B. 

Bacon, R. F.,onfumarolegases.... ............... ............... 190 

Ball, S. H ., correlation by ..................... _ .................. 92-93 

on erosion of region .......................................... 87,88 

on Funeral Mountains ............................ :. . . . . . . . . . 98-99 

on pre-Cambrian rocks............................ ... ...... .. 86 

on Siebert Lake beds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98-99 

Banner Mountain, rocks of and near........................... . . 27, 

28, 33,38-39,43,44, 76-77, 88, 152, 163 

rocks on, view of................. . .. .. .. . . .. . . .. . .. .. .. .. .. . . 152 

Barite, occurrence and character of. ........................ 108,127-128 

Basalt, alteration of....... . .. . ...... . .................. ... ....... 194 

character and distribution of. .. . . .. . .. . .. .. . .. . . . .. .. . . . .. .. . 54 

Beaman, W. M., work of....... . ................................. 13 

Becker, G. F., on Nevada rocks........................ .. ........ 102 

Bibliography of region ............. ... .... .. ... ..... .. .. . . ....... 24-26 

Biotite, occurrence and character of. . .. .. . .. .. .. .. .. . . . . . . .. .. .. . 108 

Bishop Creek, CaL, power from.. . .. . .. .. .. .. . .. .. . . .. . .. . . .. . . . . 142 

Bismite, analysis of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 

occurrence and character of. ........................... 108,121-123 

crystals ?f, figure showing.................................. .. 123 

Page. 

Bismuthinite, occurrence and character of. . .. ...... .. .. .... 108,111-112 

synthesis of .................... ... ... . ......... _-_ . . . . . . . . . . . . 112 

Black Butte, ores at. ........................ .............. ..... _ 31 

rocks of and near. ............ 16, 33, 43, 45, 48, 56, 60, 70-71, 73, 151-152 

photomicrograph of .. '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 

view of . ... . ................. ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 

Black Butte mine, description of. ........... . .................. 24~247 

ledge in .. ....................... :. . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 

section of, figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 

plan of, figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 

Blackcap Mountain, rocks of and near . . . . . 30, 47, 53, 61, 71, 72, 73, 74, 151 

rocks on, view of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 

Blue Bull mine, description of ... _ .... . ....... .... .. . .......... 243-244 

ores of..----.- .. -.. -.. -.-. -.... -- .. -.... -. .... ........ -. . -- 172,244 

silver in........................... . .... . .. . ...... .. .......... 172 

Bonanzas, occurrence of. . . .. . . .. . .. . . .. . .. .. . .. . . .. . . .. . .. .. . .. 159-160 

Bosqui, F. L., combination mill devised by... . ....... . .......... 143 

Butler, J. L., gold discoveries by.... ..... ........................ 16 

Bytownite, occurrence of. . . .. . . .. . .. .. . .. . .. . .. .. . .. .. . .. .. .. . .. 108 

c. 

Calcite, occurrence and character of ......... , . . . . . . . . . . . . . . . . . . 108, 126 

California, sulphuric acid in springs in........................... 191 

Cambrian shale, character and distribution of ...... . ............. 32-33 

geologic relations of. .. .................................... ... 32,34 

views of. ............................ : ........................ 34,46 

Campbell, M. R., on lakesediments...... . . .... .. . . ... .. .. ....... 100 

Capitalization, inflation in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Cerargyrite, occurrence and character of ...... .... ......... 108,119-120 

Chalcanthite, occurrence and character of . . ................ 108, 129, 171 

Chalcopyrite, occurrence and character of. .................. 108,113,166 

Chispa andesite, character and distribution of. ............. . . . 28-29,64 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64-65 

Chispa Hills, rocks of. .... . ...................................... 61,61 

Chlorite, o·ccurrence of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 

Cinnabar, occurrence of ........................................ 108,113 

Climate, Tertiary, description of. ............ ..... . .... ........ 10~107 

Codd lease, description of. . . . .. . . .. .. .. . .. .. .. .. .. .. .. .. .. . .. . .. . 241 

Collins, E. A., on Combination mine ............ ..... ... . ...... 167,171 

on occurrence of chalcopyrite.. . .. . . .. . . . .. . . . . . .. .. .. .. .. .. 113,166 

Columbia, rocks near ...................... 38,39,41,42,43,44,55,58,151 

water of..................................................... 143 

Columbia Mountain, gold on.......... .. ............ . ... ..... . ... 17 

rocks of. .. .. . . ............ 27-34,38,41-49,53,55,58, 7~77,88, 152,183 

views of. ............................ ......... ......... . 34,46 

view from...... ..... .. ....................................... 137 

description of. .. . .. .. .. . .. .. .. .. .. .. .. .. . .. .. . . .. .. .. .. .. 137 

view of. ........ _. ........................ . . .................. 34 

Columbia Mountain fault, figure showing........................ 82 

location and character of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82-83 

relation of, to deposits...................................... . 201 

Columnar sections, figures showing .......... ............. ... . ... 90,91 

Combination Fraction mine, description of. ........ . , ......... 241-242 

Combination mill, ore treatment in ............................ 143-145 

Combination mine, geology of.. . . . . . . .. . .. . .. . . .. . .. . . .. .. .. . . . .. 211 

glory hole in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 

view of. . . . . . .. . .. . .. . . . .. .. .. .. .. . .. . .. . .. . .. .. . .. . . . . .. 160 

history of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209-210 

location of............ ... .... ..... .... . ..... .... ............ . 17 

mining costs at.............................................. 141 

ledges of. .................................................. 211-213 

figure!> showing ............. . .......................... 211,212 

253 
254 INDEX. 

Page. 

Combination mine, ores of ............ .. ... 31,170,171,172-173,214-216 

ores·of, photomicrographs of._. _________ .. ____ . __ .. _______ . 164,168 

treatment of. ........ ...... _._ ..... ________ . _____ . __ . __ 143-145 

pay shoots in .......................... .......... ___ .. . 159,213'-214 

plates showing .. _·_ .... _ ...... __ .. _. ______________ . _ .. _ _ _ _ 154 

production of. ....... . .... _ . . __________ .. _____ . _. ______ .. _... 210 

rocks in .... __ ................ _ .. -_ ... _____________ . _ .. __ .. _ . _ . 58--59 

section of, plate showing .. ~ ........... . _· ___ . __ . ______ . ______ . 154 

water supply of._ .. __________________________ ............ _... 143 

water in ........ _ ...... ______________________ . __________ . __ 187,216 

workings of. ... ________ _____ _ . _______ _- _______ .. _._ ... ... . 18,22,210 

plate showing .. _ . ______ __ .. ____ ... ___ .... ___ . _ _ _ _ _ _ _ _ _ _ 154,210 

Commonwealth mine, description of. ____ .. __ __ ._ .. _ ...... _._.___ 245 

Comstock lode, production from .......... __ . .... _. _. ______ ___ ... 16 

Conqueror mine, description of... _________ , __ :. ____ . ____ ... _._._ 238--239 

Consolidated 

section at, 

Red 

figure showing- - - - -- ------------------------------ 82 

Top lease, description of. .. ____________________ 224 

Constabulary, organization of. . _ . _________ . _ . _ . . . . . . . . . . . . . . . . . . . 21 

Copper, occurrence of._ ................ __ .. _ ... __ . __ .. ______ ._. 108,111 

Correlation, discussion of.._ ...... _ ... __ .. _._ .. __ ,_. ___ . __ . __ . __ . 91-101 

methods of. ______________ . _ .. _ . _ .. _ . ... _ ... _ .. _ .......... _ . _ _ 91-92 

Country rock, effect" of, on pay shoots._ .... __ . ___ .. _____ . _______ . 163 

Cretaceous time, events in..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 

Cuprite, sulphur near __ ............. _ ...... _ .. _ .. __________ 109-110,175 

D. · 

Dacite, alteration of. ..... _ ............. _ .. . ___ ..... __ ..... _____ 176-177 

alteration of, photomicrograph showing ..... ____ . _____ ... ___ . 178 

results of, analyses of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179, 181 

description of .................. . ......... . _ . _ .... _ _ 176-182 

diagram showing ............................... _ . _ . . . 181 

analyses of. ........ _ ... . .. __ · .. _. ..... _ . .. _ ... _ . . 55, 56, 64, 94, 179, 181 

assays of. __ ...... _ ................. . ... : ..................... 114 

character and distribution of. _ .......... _ . .. ..... .. _ . . . 54-55, 79-81 

correlation of. ..... _ .. ... _ ...... _ .. _ ... . _ .•.......... _ . . . . . . . . 94-95 

distribution of, map showing.................. ...... ......... 80 

geology of. ..... _ ............ _ ............. __ . __ ._ ..... _. __ .... 58-61 

inclusions in ..................................... ~ ......... 55,207 

intrusion of. ....... . ................ _._ ... _ . ... _ ....... _ .. : .. 88--89 

ledges in ... . ... . ........ : ......... __ .............. ____ . 151,155-156 

ores in ................. . ........... ..... .. .. ...... . ..... 31, 158, 163 

analyses of. .............. : . ........................ _ . . . . . 167 

petrography of. ........................ _._ ... _ ........... _... 55 

relations of. ......................................... _ . . 63-64, 79-81 

veins in, photomicrographs showing ............. _._. ______ ... 156 

views of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150, 156 

Dacite vitrophyre, analyses of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61, 64, 94 

character and distribution of. ........... _ ... __ ....... __ . __ 61,81-82 

correlation of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94-95 

eruption of ...... __ .. _. : .. _ ..... ~ ........ ... ... : .. _. _ .. _ ...... 88-89 

ledges in ..... _. ___ ..................... _ .... __ . _ . . . . . . . . . . . . 151 

petrography of ........................ . ........... _ ... _. _ _ _ _ _ 61-63 

photomicrographs of. ___ .......... . ___ . ___________________ . . . 62 

relations of. ................................. 

Daisy 

_ ......... _ . . . 63-64, 84 

mine, description of. . __ . _ .. : ..... _ .. ____ . __ . ____ . __ . ___ . 248-250 

discovery of. ........................................... __ ·_... 22 

rocks in ... _ ..... _ ... _ . ... .... .. . .. .... ......... . . _ ......... _ _ 53 

workings of. .............................. . .... ___ .. _. _____ 137, 248 

figure showing ..................... . .......... ·. . . . . . . . . . . 249 

Dall, W. H., fossils determined by ............. __ .. _ .. _ ..... ___ .. _ 102 

Datums, description of._ ................... _._._._ .. _ ... _._._.... 92 

Deposition, stages of. .. ............................ . ........ 195-196 

See also Ores. · 

Depth, relation of, to ores .. . ...... _. __ .. .... ____ .. _ ... .. ... 173-174,200 

Depth, original, of ore deposits ............................. 174-175, 193 

Deville, St. Clair, experiments of. .... .... ................ . _._____ 195 

Deville and Leblanc, on volcanic gases _ .... .. _ .. __ . _ _ _ _ _ _ _ _ _ _ _ _ 186, 189 

Diamondfield, rocks at and near .............. 43, 45, 47, 48, 53, 56, 78, 152 

view of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 

Diamondfield group, mines of. .. __ ...... __ ................... -.. __ 135 

mines of, descriptions of. ................... _ .... _. __________ 246-251 

ores of. .... _ . __ .. , _ ..... _ ... _ ... _ . __ . __ ..... : . ... _ ... _ . __ . _ . . . 173 

silver in.:_ ...... _ .......................... .. ....... _ ...... 166, 171 

Diamond Peak, altitude of ... .... ................ . _ .. ..... __ ..... 15 

rocks of. ..... _ .. _ ... __ .. ................. ~ .. _. __ ............. 57,60 

Diaspore, occurrence and character of. . . . . . . . . . . . . . . . . . . . . . 108, 124-125 

Page. 

Dikes, andesites, character and,distribution oL.................. 65 

Domical, use of word ....... __ ._. ______ .. _ ....... __ .......... __ ... 27 

Durdenite, occurrence and character of. ........................ 108, 17i 

E. 

Edgar & Carr, analysis by. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 

Eldorado limestone, occurrence and character of. ................. 86-87 

Electric power, use and cost of. __ ........ .. .. ......... ........... 142 

Emmons, W. H., on Mira Mountain .. __ --- -------- -- ------------ 75 

work of .... . _____ . _ .. _ ..... _ . _ ... __ . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

Emmonsite, occurrence and character of. .......... .... . . ...... 1Q8, 171 

Enargite, analyses of. ............................ .............. 118, 119 

occurrence and character of. ____ ....................... 108,117-118 

Engineers' lease, description of ....... ..... .... . .... ....... ..... 232-233 

ores 1 

in .. . . ___ .. __ . _ ....... _ .... _ ...... _ . _ ~ __ .... 22,"165, 170, 232-23:5 

Enstatite, occurrence and character of............................ 108 

Epidote, occurrence and character of. ......... .. ........... 108, 126-127 

Erosion, amount of. ............. .. . . ...... .. .................. 174-175 

differences in .. ______ ... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

results of. ....... _._ ......... __ ._ ...... __ ._ .... __ .......... 27, 79,87 

Eruptive sequence, description of. ................ _, _ . . ........ 105-100 

Esmeralda formation, age of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 

character and distribution of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 

Espina breccia, character and distribution of .................. 28, 30, 69 

correlation of. ........................................ _._...... 69 

ledges in ....... _ . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 

Espina Hill, rocks on ....................... ... ..... ; . . . . . . . . . . . . 58 

F. 

Fam!!-tinite, analyses of.._ ...... _ ...................... __ ._ ... _ 118--119 

occurrence and character of ............... .. ............... 108, 118 

Faulting, effects of. __ .......... _ ....... .................. __ ._ .. 161-162 

occurrence and character of. ...... ..... .. . .. ......... 83-85,161-162 

relation of, to ores .......................................... Field work, 196, 201 

nature of.._ ... ________ . _____ .... __ ._._. ___ ._. __ ..... 13 

Fissuring,nature of .. __ ._ ........... ................. . .... _ 157,194,196 

relation of, to pay shoots ................................... 160...161 

Five Friends lease, description of. ................ -............. 222-223 

workings of, figures showing...... ... . .... ............ .. ..... 223 

Florence-Goldfield Mining Co., mines of, description of ___ ..... . 225-234 

Florence Hill, view from. ___ ...................... __ ........ __ ... 136 

vie·.v fro::ri, description of. . ............................ _. . . . 136-137 

view of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 

description of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135-136 

Florence mine, faulting in ..................................... 162,227 

geology of .................................................. 226-227 

figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 

history of .............. . ......... : . . ....................... 225-226 

ledge in .................................................... 227-228 

section of, figure showing..................................... 152 

view of. ...................... ·-........................... 160 

mill of. ................ . ........... :·. . . . . . . . . . . . . . . . . . . . . . . . . 145 

ores of. ........... _. ......................... 31, 166,170,225,229-230 

photomicrographi of .............. -.................... , 164, 168 

pay shoots in .......................................... 159,228--229 

section of, figure showing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 

rocks of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 

stope in, view of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 

water in .......... . .. ... .............. . ................. _____ . 230 

workings of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 

plate showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 

Formations, sequence of. ........................................ 27-30 

Fossils, lack of._ ........................... . ............. 91-92,101-102 

Frances lease, production of. .................. .. ................ _ 20 

Freight, rates for ................. ...... · ..................... 18,147,148 

Fumaroles, sulphuric acid in .... . ........... . ... : . .. ............ 189 

G. 

Galena, occurrence and character of. . . . . . . . . . . . . . . . . . . . . . . . 108, 112, 166 

Garrey, G. H., workof. .. ------------- --------------------------

Geikie, 

13,113 

A., on fumarole gases.......... .. ........... ..... ......... 190 

Geographic names, application of.. .. ____ ......................... 26 

Geologic history, outline of ........ . ..................... . ........ 86-91 

Geologic maps of district. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32, Pocket. 

Geologic names, derivation of. ............... . ---.-.............. 26 
INDEX. 255 

Gold, occurrence and character 

production of. ............ . 

Gold Bar mine, description of.. 

ores of. ................... . 

plan of, figure showing .... . 

rocks of ........ ___ ........ . 

Page. 

f- ------- --- ---- ---- --- --- - 108, 110-111 

------ --- ----- -- -- -- ----- ---- 23-24, 145 

------ --- ---- --- ----- --- ---- --- 242-243 

------------------------------- 173,243 

--------------------------------- 243 

59 

Gold Bar Fraction mine, shaft ~nking at, cost of................. 142 

Gold Coin mine, description of_ L __ ........... _ ..... _ ..... _....... 250 

Goldfield, histocy of. ............................................. Hi-23 

location of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

location of, map showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

View of.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 46 

description of. . . . . . . . . . ............. ___________ .... _ .. _ _ _ 135 

Goldfield-Belmont mine, description of. .. ______ . _______ .... ___ . 247-248 

ores of. ... _ . __ . ___ _ . _ . ___ . _ _ ... _ ... ___ ..... _ . _ . . . . _ _ _ _ _ 171-172, 248 

plan of, figure showing .. ~ _ .. _ .. _ .. ____ . _ .. __ . ___ .. ·_ .. _ .. __ . . 248 

veins in ..... __ . _ . _ ... _ . _ _ _ _ ___ . _ . ___ .... _ . _ . _ . __ __ ... _. _ . _ . _ 248 

photomicrographs sho ing _ . __ . _ ...... _ ..... _. . . . . . . . . . . . 156 

Goldfield Cl Mill Co., mill of... . . ____ ... _ ... _ . _ ..... _ ... _ . . . . . . . . 146 

Goldfield Consolidated Mine C ., mines of, descriptions a.f. _____ 202-224 

ore treatment plan of.. ... _ . ____________ . ________ . __ . _ __ __ _ _ _ 147 

organization of. . _________ ... __ .. _ ... _ . _. __ ..... _ . ___ . _____ . _ . 20 

plant of.. ____ ._ .. __ ....... . . _ ........... _ .. ____ .. __ .. _ _ _ _ _ _ _ 146 

report of .... ___ .. _ .. _ . ____ ... _ ..... _ ..... ___ . . ____ . _ . _____ . _ _ 200 

Goldfield dome, formation of._ . __ . _________ . _____ . ____ . __ __ ._. 76,84-85 

structure of. ... ____ . _____ ... _ .. _ ... _ .. __ . __ : __ . ____ . ______ . _ _ 76-85 

Goldfield group, mines of. .... _. __ ._. _______________ . __ .. ____ . _... 135 

Goldfield Hills, rocks of. . _. _ .... _. _. __________ . ___ . ___ ......... . 72, 151 

Goldfieldite, analyses of.. ____ . _._ ............ _ .. ____ . __ .. _ .. __ . 116-117 

occurrence and character o _ ..... __________________ .. . . . 108, 116-117 

Goldfield Merger Mii;J.eS Co., m nes of, descriptions of. .... _._. ___ 239-241 

organization of. : ... : _ . _ . _ . _ .. _____________________ . _ . ___ . _ _ 22, 239 

Gold Sovereign Mine, rocks of . _____ . _____ . ___ .... _.... . . . . . . . . . . 42 

Gold We~ge claim, descripti?IJ- of. ... _ .... __ . _____ ._ ..... _ .. __ ... 241 

workmg~of, plates shown]g_. ______ :· ___ . _. ___ ...... -------.. 206 

Gouge, formation of. .. _ .. _ . _ . ___ . _ ........ _ .. _ ................. _ 156 

Granite. See Alaskite. 

Great Bend mine, description of. ...... __ .. _ . __ ... _ . . . . . . . . . . . . . . 251 

Greenawalt, J. E., mill designfd by.............................. 146 

Gypsum, occurrence and chir ter of. . . . . .. .. . .. .. .. .. .. .. 108, 128, 167 

H. 

Hague, Arnold, on lake sedi nts ......... __ . . . . . . . . . . . . . . . . . . . . 96 

Hague, Arnold, and Iddings, { P., on Nevada rocks._._ . .... _... 102 

Halotrichite, occurrence and ~haracter of. . ... _______ ... _ ... 108,129,171 

Hayes-Monnette lease, ores of. ........... . ....... _ .............. _ 172 

prod action of. .................... _ .. _ ~ .. _ .. .. .. .. .. .. .. .. 18, 20, 205 

stope in. . . . . . . .. .. . . .. . . . .................. _ . ___ ........... _ 159 

Hazel-G:!~;e~~- i~~~: d~~r-i~li~~-~f~:::::: ::::::::::::::::::::::: ~~~ Hematite, figure showing.. . . -. _................................. 124 

occurrence and character f. ....................... __ .. 108, 123-124 

Henderson, H. P., on ore in I tite ......................... __ ..... 163 

on sphalerite ... ______ .. _ __ ... _ .. _. ___ .. __ ... _. _ ... _. __ .... _ _ 112 

Highgrading, prevalence of ................... _____ .......... ___ .. 19 

Hill, R. T., on alunite rocks .................................... _ 199 

Hillebrand, W. F., work of. ................... 63, 110, 115, 133-134, 165 

Historical geology, outline of1 

•• _. __ • __ . _____ • __ ...••••. _. ___ • ___ • 86-91 

Hornblende, occurrence and character of. ... ____ . _ .......... _ _ _ _ _ 108 

Hornblende-biotite andesite, analyses of. .. _ .... _ .. ___ ...... __ .. _. _ 52 

petrography of. .. _______ . __ _______ ________ . ___ __ ..... _ .... ___ 52-53 

Hornblende-pyroxene andes te, analyses of. ........ __ ... __ : ....... 50-51 

petrography of. .. ______ .. ___ . _ .. _ ... . __ . _____ . _ . _ ..... . _ . . . . . . 48-51 

Humboldt group, correlatio1 of. ............................. 104-105 

Hypersthene, occurrence an character of .... _ . __ . . . . . . . . . . . . . . . . 108 

I. 

Iddings, J. P ., on plagioclas~- ________ . __ ........ _. __ .. _ ..... ___ .. 48 

Iddings, J. P ., and Hague, mold, on Nevada rocks . .. . .. .. .. .. . 102 

Igneous rocks, classification L.................................. 36 

See also Prelacustrine rocks. 

Indian Springs, water from .... ·_................................. 143 

J. 

January mine, geology of.. . _................................... 217 

history of. ... ____ . . _ . __ . _ ...... __ ..... ___ ....... . . _ ....... _ .. 216 

ledge of. ............. ___ .... _ ... _· .................. ... ...... 217-218 

Page. 

January mine, ores of .......................................... 31,219 

ores of, photomicrographs of. .............................. 164, 168 

pay shoots in ....... .. .................................... 218-219 . 

rocks of ___ . ___ . __ . __ . ___ . __ .. _ . __ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 

section of, plate showing..................................... 152 

water in ...... _ .. _ . _ . __ ... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 

analysis of ..... ______ . _ .. _ .. _ . ___ . _. . . . . . . . . . . . . . . . . . . . . . 220 

workings of. __ . __ ._._._ ... _. __ .. _._ ... _ .................... 142,217 

plate showing_ . ______ . ___ .. ________________ ..... _ .. _ . _ . 152, 210 

Jarosite, occurrence and character of ....................... 108,133,171 

J asperoid, description of. ................... __ ................... 32 

Jumbo Extension Mining Co.'s mines, descriptions of. .. ___ .. __ 241,250 

Jumbo mine, history of.. _ ... ___ ... __ .......................... 22G-221 

ledge in. _. __ . __ . __ .. _ .. _. __ . _ ... _. _ ........... _ ......... _.... 221 

ores of ................. __ .... ___ . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 

pay shoots of._ ........ ___ .. ______ ..... ____ ............ 159,221-222 

production of. ... __ .... _ .. ____ ........ __ .................... 18,221 

veins in, photomicrographs showing. . . . . . . . . . . . . . . . . . . . . . . . . 156 

workings of. ..... . .... _ ....... __ .. __ . .. . .. .. .. . .. . .. . .. . 20, 141, 221 

K. 

Kalinite, occurrence and character of.._ . ......................... 108 

Kaolinite, association of, with alunite............................ 192 

occurrence and character of. ... _ ....................... 108,127, 167 

Kendall mines, description of_ ................................. 237-238 

ores of_ ...... ____ .... _ .. __ . __ .. ____ .................... 170,171,238 

rocks in- -- --- --- -.... --. --. --- --- ----- . --- -- -- -- -- --- - 41-42, 46, 237 

view of ...... . . _____ . __ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 

workings of .... __ ...... __ . _................. . ................ 237 

figure showing_. . .. .. .. . .. .. . .. .. .. . .. .. . .. . .. . .. . . .. .. . 237 

Kendall Mountain, rocks near._ .. _ .... _ .. _ ............ 43, 44, 47, 53,151 

Kendall tuff, character and distribution of_ .... _ ........ 28-29,41-43,78 

eruption of ... __ .. __ . _ ... ___ ... _ ............. _ . . . . . . . . . . . . . . . . 88 

relations of. .................................................. 83-84 

Kewanas mine, description of_ ............................ _ . . . . . . 239 

King, Clarence, on age of Nevada ranges ............ __ -.-_ ...... _.. 35 

on Great Basin rocks. . . . . . . . .. .. .. .. .. . .. .. . .. .. .. .. .. .. .. .. 87 

on lavas ................. .. ................................ 102-103 

on Pahute lake sedin1ents _ .... _. _ ............. _ ... _ .. 9.')-96, 100, 101 

on Tertiary climate .... __ .. __ . _ ....... _ ..... _ ..... _. _ ... _.... 106 

King, L. M., analysis by.. .. .. .. .. .. . .. .. .. . .. . .. . .. . .. . .. . .. . .. . 167 

Knowlton, F. H., fossils determined by ........... -.-............. 102 

L. 

Labor, troubles with ........... ' ............................ 18, 19,20-22 

Labradorite, occurrence and character of .... _ ............... _._.. 109 

Lacustrine sediments, age of. . . . .. . .. .. .. .. .. . .. . .. .. .. .. .. . .. . .. 104 

character and distribution of ...................... 36,66-69,100-101 

correlation of. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95-101 

Lahontan, Lake, climate oL.. .. ............................. . .. . 107 

correlation of. .............................. ..... . ......... _ . . 105 

Lake beds, datum marked by.................................... 92 

deposition of ... __ .. ___ _ . _ ... _ ............. . _ ........ _ ... _ .. _ . 89 

Laguna mine, development of. .............. _ ..... _ ... __ .... . .. __ 18,20 

Lake, Tertiary, character of. ............................ --;-- ..... 89 

Latite, alteration of.............................................. 182 

analysis of ... _. __ . ____ ___ ._._._ ......................... _.___ 40 

character and distribution of. ............................. 38-39,78 

correlation of. ........................ ·........................ 92 

eruption of.. . ..................... .. ........................ 88 

ores in. ____ ._ ....................... . ...................... 163,200 

petrography of ... ___ . _____ . __ ........................ : .. _ . _. _ 39-41 

relation ofledges to........ . ... . .............................. 155 

relations of. ............................................ . _. __ . 83 

view of. ........... .. ...... . ..................... . ". . . . . . . . . . . . 152 

Lavas, succession of._ . .. __________ ._ .. _ ...................... . .. 105-106 

succession of, figure: .showing __ ................................ 106 

Lease blocks, map showing .. __ . . .. .. . . .. .. .. . .. .. . .. .. .. .. .. . .. .. 136 

Leasing, practice of._ .......... . .... :. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Leblanc and Deville, on volcanic gases .......... _·_ ............ _ 186,189 

Ledges, composition of. ........................................ 155-157 

definition of. .......... : . . . . . . . . . . . . . . . . . . . .. . . . . . . .. .. .. .. . . . 150 

~!;t~i~~ti~~:::::::::::::::::::::::::::::::::::::::::::: ~~~~~;: ;~~ plate showing ........ _____ .. _ ... ____ . ___ .. _ .. _ ..... 151, pocket. 

pay shoots in ................... ~ ....................... 150, 158,200 

persistency of. ......... _ .. . . .. . .. .. .. . .. . .. . .. . .. .. .. .. . . . .. 200 

resemblance of,_ to fissure veins............................... 150 
256 INDEX. 

Page. 

Ledges, shapeoL .............................................. 153-155 

shape of, figures showing ... _. _____ ._ .. ________________ . __ .. 152-154 

strike of. ...................................... : .............. 152 

structure of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155-157 

photomicrographs showing ............................ _.. 156 

type of....................................................... 199 

Lida, water from ............................................... 142-143 

Limonite, occurrence and character of. ..................... 109,125-126 

Lincoln, F. C., on fumarole gases ............................ : .. 189-190 

Lindgren, W., on lakesedime:nts .. _ ............................. 96, 101 

on occurrence of anhydrite.................................. 191 

Literature, review of .............. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-26 

Lithology, correlation by ............. ·_........................... 92 

Litigation, avoidance of.......................................... 23 

Little Florence lease, description of ..... _. . . . . . . . . . . . . . . . . . . . . . . . 233 

ores of... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170, 233 

pay shoots of. ........ . . ......... ........................... 159, 233 

production oL .............................................. 22,233 

workings of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142, 233 

Location of district.. .. .. .... .......... . ............ _...... . . . . . . . 14 

map showing ................... _.............................. 15 

Lone Star group, description of.. .............................. 244-245 

Louderback, G. D., on erosion................................... 88 

on lake sediments....................... . . . . . . . . . . . . . . . . . . . . . 96 

M. 

McMahon Ridge, rocks of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

Magma, water in ... · ... · ......................................... 198-199 

Magmatic water, nature of. ................... . ..... ·....... . ..... 190 

Magnetite, occurrence and character of ... . ......... .. ......... _ . _ 109 

Malachite, occurrence and character of. _ . _ ..... _. __ ........... _.. 109 

Mal pais basalt, analyses of. ....... _. ___ . __ . __ . ·_. _. _ ..... ___ ...... 72, 73 

character and distribution of. .. _ . _ ... . ..... _ . ____ ....... _ . 28, 30, 72 

correlation of. ..... _ . .... ___ . ____ .. _ .. __ . ___ ._................ 105 

extension of. ........................ _ . . . . . . . . . . . . . . . . . . . . . . . . 90 

petrography of ....................... . ....................... 72-74 

Mal pais Mesa, rocks of. .. .... .. ... _ .............................. 71, 72 

rocks of, photomicrograph of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 

seepage from. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 

view of .................. , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 

description of. . ..... .... . . :. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 

Manhattan district, boom in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Map of district ................................................. Pocket. 

Map, geologic, of district.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32, pocket. 

Marcasite, occurrence and character of ...... . ........ ..... . lOll, 114-115 

Marsh, William, gold discovered by ............................. _ 17 

Massicot, occurrence and character of .......................... 109, 123 

Mauzelius, Robert, work of •............................. : . ... _. . 63 

Meda Pass, rocks in and near. ................... _ ........ 65, 67, 70,175 

Meda rhyolite, character and distribution of. ................. _ 28-29, 65 

intrusion of ............................ ·. . . . . . . . . . . . . . . . . . . . . . 89 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

Melanterite, occurrence and character of ................ 109,128-129,171 

Metamorphism, cause of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 

knobs due to .......................... __ ................ ~ . . . 16, 1 50 

view of.................................................. 1£0 

;::~~::~-~!_._-_-_ ~:::::::::::::::::::::: :-::::::::::::::::::::: -~76, ~~~ photomicrographs showing ........ _ . . . . . . . . . . . . . . . . . . . . . . 178 

types of ........................................... : . . . . . . . . . . 176 

Mills, construction of. .................. ,.. . ................... .. . 145 

ore treatment in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 

Milltown, rocks near............................................. 151 

Milltown andesite, character and distribution of. .. : ..... __ . 28-29,47,79 

correlation of. ......... : ...................................... 93-94 

eruption of.................................................. 88 

ores in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31, 152, 163 

petrography of ............................................... 47-53 

view of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 

See also Andesite. 

Mineralogy of district ....................... . ..... ..... .. .... 108-134 

Minerals, paragenesis·of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169. 

Mines, detailed descriptions of._, ..... . ............. .. ... .... .. 202-251 

distribution of. ........ .................. .. ............. ... 135-144 

shafts of, depths of. ...................... _ .......... · ....... 141-142 

list of. .................... . ............................ 138-141 

water in ................................................... 187-188 

character of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 

Page. 

Mines, workings of, plate showing................................ . 136 

Mining, costs of. ....... . ...... : ............... .......... ~ ...... 141-142 

history of . . . : . ...... ..... _ . ...... . . ·-. . . . . . . . . . . . . .. . . . . . . . . . . . 16-23 

power for. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 

Mira basalt, character and distribution of ........ ·_ ......... 28-29,66,69 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 

Mira Mountain, rocks of. . ......................... ....... .... 69, 75,175 

Mohawk mine, development of. ............................... 18,20,22 

faulting in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 

figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 

geology of ..... _ ........ : .. ...... ........................ ... 206-207 

latite under, relation of ledges to. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 

leases on, production of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

ledges of. .................................................. 207-208 

sections of, figures showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . 153, 206 

mining costs in ............ _ .. .. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 

ores of. . ............................ 18,167,169,172-174,200,208-209 

analyses of ............ _....................... ............ 167 

pay shoots in .............................................. 208-209 

plan of, figures showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 

production of. ....... ....... . .. ... .................. ....... 204.205 

rocks of .................................. .- ...... ... .... ... 55, 58-59 

workings of. ...... . ........................................ 2(1(), 205 

Mohawk-Red Top lease, description of.......................... 224 

plan of, figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 

Montezuma, location of. ........................... ~....... ...... 14 

Montezuma Peak, rocks of. ..... _ .. . ....................... ...... 68,98 

Morena rhyolite, character and distribution of ............. 28-29,46, 78 

correlation of. .................................... ·_ . . . . . . . . . . . 93 

intrusion of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 

view of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 

Morena Ridge, rocks of. ... ....... ....... . ......... .-.............. 29,46 

view from.. .... .............................................. 138 

description of. . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 

Morris, H. C., on occurrence of sulphur........................... 109 

Muscovite, occurrence and character of . ........................ 109, 127 

Mushett lease, description of. ... , .............................. 223-224 

ores of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165, 170, 173,223 

plan of, figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 

Myers Mountain, rocks of and near .......... 30, 53, 61, 65, 66, 67, 72, 73,84 

N. 

National Museum, Goldfield rocks in............................. 14 

Nevada, bibliography of . .. .... ............................... ... 24-25 

columnar section of, figure showing.......................... 91 

correlation of. .......... .. ... ... .. . ·.... ... ................... 93 

mining in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Nevada Goldfields Reduction Co., mill of........................ 145 

Nomenclature, determination of................................. 26 

0. 

Oligoclase, occurrence of ........... . :. . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 

Olivine, occurrence and character of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 

Open shop, maintenance of...................................... 22 

Ore deposition, solutions in .................................... 185-186 

Ores, age of. ..... . . .. .. ....... .. _ ..... .... .. ~.......... .......... 175 

alunite and, association of. ......... . ........ 30,132-133,189,199,201 

areal variations in ..................................... 172-173,201 

character of. ................................. _. . . . . . . . . . . . . . . . 3Q-31 

climate and, relations of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 

deposition of. ........................................... 31,195-196 

deposits of, genesis of. ..................................... 189-200 

depth and, relation of. ..... ............................ 173-174,200 

minerals in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Q-31 

original depth of. .......................................... 174-175 

paragenesis of ............ ' ...... ...... ............. 169-170, 195-196 

photomicrographs of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 

relation of, to country rock................................. . . 163 

shipment of. .... .... ... ... ....... ....... .. ........... . :

1 •••• 143, 146 

structures of, plates showing .. ....... . ........ . ....... .... 164,166 

tenor of. ................................................ 17,171-172 

treatment of. .............................................. 143-149 

costs of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 

figure showing ........................................ -.·. 144 

See also Pay shoots; Sulphide ores; Oxidized ores. 
INDEX. 257 

Page. 

Orthoclase, occurrence and ch acter of. ............. . ......... 109,126 

Oxidation, depth of .... ~. .......... .... ....... .. .. ... ... ..... 188 

solfatarism and, results of. ............ .......... .......... 193--195 

Oxidized ores, character of. ........... ............ . .... . .... 31,170-171 

minerals in. . . . . . . . . . . .. .. . . . .. . . .. . .. . . . .. . . .. .. . 31 

See also Ores. P. 

Pahute Lake, age of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 

datum marked by. . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92, 101 

situation and extent of. .. ....................... . ... ... 95,100-101 

Paleontologic evidence, scanturess of. ............... ..... 91- 92, 101- 102 

Paleozoic time, events in ..... ................ .. .... .. .... .. .. .. . 86-88 

Palmer, Chase, on goldfieldite ...... ...... ..... . .... .. ........ . 116-117 

workof....... .... ....... ................................... 14 

Paragenesis, discussion of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169-170, 195--196 

Patrick claim, workings on . . ................... ............. 244-245 

Patrick lease, production of. . . .. .. .. .. . .. .. .. .. .. . .. . . .. .. . .. .. . 17 

Pay shoots, distribution of .. '.J. ... .. , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 

relation of, to country rocr . ........ .. .. ................... .. 163 

to depth ............. . ................... · .... .. ....... 173- 174 

to fissuring ............ .. .. . . ... .. ..... .... . . ... . . .. . . 160-161 

sha~ !~~~~~ ~ ~ ~:: :::::: J :::::::::::: :·: :::::::::::: ::::::: ~:~~~ plate showing ......... :. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152, 154 

similarity of, to barren m tter....... . .. ... .... . ... .. ......... 158 

See also Ores. 

Petzite, occurrence and chara ter of... ............ ..... .. . .. .. .. . 109 

Pocahontas well, flow of. . .. .. . . .. .. . .. .. . .. .. .. .. .. .. . . .. .. .. .. . 187 

Polybasite, occurrence of ... .. ................................. 109, 116 

Population, data on ..... . ... .. ................ .. ...... _ .... 14, 18, 19,23 

Portland mine, description o ... .... .. .' ... .. _ ..... _ .. _ .... _.. ..... 245 

rocks of. • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 54 

Postlacustr~ne r?cks, charac~ r and distribution of . . .. ...... ..... . 70-74 

Postlac~trme t1me, e:ents 1, .. . _ .. __ . _. _ .. _ ... . .. ........... : . .. 89-91 

Power, kmds and costu of. . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 142 

Pozo Canyon, rocks in ... .... .......... ...... .... . ...... ... 29, 66, 70, 85 

water from ...... _ ......... .. . ..... _ . .. . . .... .... .... _ ... ... 142, 187 

Pozo formation, age of. ........ _ .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 175 

character and distribution of. ........ _ . _ ...... _ ............... 28, 70 

correlation of ........ ....... ... _ ........ . ................ :.... 71 

deposition of. .. . .. _ .. __ ... _ ... _ . .. ... . __ ................... . . 90 

Preble Mountain, altitude of .. _.. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

rocks of and near .. .. ... _ ..... .. . ..... . 29,30,47, 56,58, 60,63,151-152 

photomicrograph of. .......... ..... ..... ... .. ..... .. _ . . . . 62 

Prelacustrine rocks, correlation of. .... ... ..... .... _ .. _ ........... 92-95 

description of. ... . ... . .. .. .... .. ..... ... . . ... .. ... .. 1 

......... 36-74 

Prelacustrine time, events in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88--89 

sequence of.... .... . . ..... ... . .. .. .. .. .. .......... . .......... 36 

Pre-Tertiary rocks, description of ..... .... _ ..................... _ 32-35 

Production, data on ............... -.· . . .... : ... ... . .. ... . _ .. _. 23-24,145 

Propylitic rocks, character of ... ........ _.. . ............ .. .. .. ... 176 

Prospect Mountain limestone, occurrence and charactEir of .. __ . .. . 86--87 

Proustite, occurrence of. .................... ...... _ ........... _ 109,116 

Pyrite, assay of. ............................................ _.... 114 

occurrence and character of. ..... .... ............ ... ... 109, 113-114 

oxidation of, sulphuric acid from ... -.. .. .. .... --- ..... -... - 191-193 

Pyroxene, occurrence and character of ... ... .. _. . . . . . . . . . . . . . . . . . 109 

Pyroxene andesite, derivation of.... .... ...... .. ..... . 48 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 

Q. 

Quartz, alteration of rocks to ............. ...... .. . .... . ... _ ... _.. 176 

occurrence and character of .................... 109,120-121,166-167 

phenocrysts of, figure showing ........ .. .. .... _ . .. .. .. .. .. .. . 121 

Quartzite mine, ores of.. ... .... .... ... .... ...... ...... ....... .... 171 

Quaternary deposits, character and distribution of ..... . . _. ... .. 75 

R. 

Rabbit Spring, rocks at ................ _ ........ _. . .. ............ 71 

water from .. .. . .... .. ........... . . ................. ·.·.... ..... 143 

Rabbit Spring formation, character and distributicn of .... ... . 28, 30,71 

correlation of .. .. _ . .. .. .... _ ..... _ . ... ..... __ . __ .... ... ·....... 105 

deposition of. ........ : ....... . , .... ........... ~. . . . . .. . . . . .. . 90 

Railways, access by .. _ .. _ ..... _ ..... ... ....................... 14, 18,22 

Red King claim, discovery on .. __ ...... _ .. _ .... . , . . . . . . . . . . . . . . . . 22 

Red Top mine, development of...... ...... . ....... ...... ..... .... 20 

7914&--No. 6~9-17 

Page. 

Red Top mine, discovery of ............... .. . ................. , . . . 18 

geology of. .. . ....... _. __ . .. _ . . . _ . ........... .... .. ......• ·'-... 203 

history of . .. . : .. .. . .. . ... ..... . . . ..... . .. . . _ . ___ . __ . . . . . . . . . . . 202 

ledge in ................... . ................. . _ ........ ..... 203--204 

mining costs in ....... _ ......... . ... .. ... ,............... ..... 141 

pay shoots in .. _ . ...... _ ... _ ...... _._ .......... .. . . .. ..-.. .. .. _. 204 

plan and section of, plate showing.... ............ ............ 202 

ores .of. ....... _ . ... ... _ . _ . _ ........ _ .. _ . . . . . . . . . . . . . . . . . . . . . . . 170 

photo:nicrograph of .................... .. _. _. _ .. _.. ... .. . 164 

workings of. ... ........ ..... :·.. . . .. . . . .. . . . . .. .. .. . . .. . .. . . .. 202 

Reilly lease, description of ........................ . ...... .. . ... 230- 232 

ores of. ..... . .............. ...................... .. .. 171,172, 231-232 

pay shoot of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159, 231 

section of, figure showing....... .. .. .. .. . ...... .. ...... ... 154 

productionof. . . . ... ~- --· ·· ·· ······· ············· ··· ······· 17,230 

Retinite; analysis of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 

Rhyolite, alteration of .................. _ ...................... 182-185 

ledges in .. .................. .......... .... ...... .... , ...... 156-157 

ores in ............... _ ..... ... ... . _ . .... __ .... ... .. . _ . . . . . . . . 163 

See also Meda rhyolite; Sandstone rhyolite; Morena rhyolite; 

Spearhead rhyolite; Vindicator rhyolite. 

Rhyolite, altered, analyses of .. .. . . . . . . .. . .. . .. .. . .. .. .. .. .. .. .. 183 

photomicrograph showing. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 

Rickard, T. A., on mills ........................................ 143--146 

on highgrading .... . . .. ..... ... ..... _ . . . . . . . . . . . . . . . . . . . . . . . . 19 

Rocks, sequence of. .............................................. 27-110 

Rogers Syndicate lease, description of .............. . . . .......... 233- 234 

oresoL ... . ................. .... ... ..... ...... ..... 170,173, 233,234 

production of............... . . ...... ....... . .... . ...... ...... 22 

rocks of. . .. . . .... . ...... .... . .. ... .... ... .. .. . .......... 59,233-234 

Rutile, occurrence and character of. ..... .... .................. . 109, 124 

s. 

St. Ives mine, description of. .......... . ....................... 240-241 

plan of, figure showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 

production of .................. __ . ................. ...... .. 22,240 

Sampling, cost of... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 

Sandstorm mine, description of. ....... .. .. .. ........ ............ 235--236 

oresof. ... ... ..... ....... . .. .... ............ ............ 18, 170, 236 

rocks of _ . .. . .... .. ..... ... .. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 

view of..... . ... . ..... .. .. .. . ... . .. . . . .. ..... .. .......... .... . 138 

workings of. . _ ............. ... ............................. 137,235 

Sandstorm rhyolite, character and distribution of ... ... . 28, 43-44,77-78 

correlation of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 

eruption of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 

petrogmphy of. .. _ ......... .. ........... . ...... .. ............ 44-46 

Sanidine, occurrence and character of. . . .. .. .. . .. .. .. .. .. . .. .. . .. . 126 

Scapolite, occurrence and character of. .. • . .. . .. . .. .. .. .. .. .. .. . .. 109 

Schaller, W. T., on bismite .. ... ...... .......... ............ .... 122-123 

work of .. ....... ...... .. ............ .. ......... : 14,111,115,131, 133 

Secondary enrichment, inadequacy of. ... ... ...... . ........ 191-193,195 

Sections, geologic, plate showing . . . .. . . .. . .. .. .. .. . .. .. .. .. .. .. .. 76 

Sericite, occurrence and character of ... ... . .................... 127,167 

Serpentine, occurrence and character of ......... , . . . . . . . . . . . . . . . . 109 

Sharwood, W.J.,onminerals ............. .. .......... .. ....... 110,116 

Sheeted structure, occurrence of. ............ •.. . .. .. . .. .. .. .. .. .. . J56 

plate showing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 

Shoshone Lake, existence of.. ...... ...................... ... ... 104--105 

Siebert formation, character and distribution of. . 28, 66,68,84,89, 97,175 

Siebert tuff, cot·relation of .. . ............................... 36, 68, 94,98 

deposition of. ... .. .............. .. ·.. . ........................ 68 

lithology of. .......................... -. -.. -.. .. ............. 66-68 

relations of. .. ..... ~. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

water in . ... . .. . . ......... , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 

Silver, occurrence of.. ................ .. ..... .. ........ .. 31,166,171-172 

production of. ..... . ................................ '........ 23 

Simmerone mine, description of. ... · .............. . ..... ....... ~ . 244 

Sinclair, W. J., fossils determined by ...... .. .' ......... ~ ......... 96,101 

Smelting, costs of. ............................................ . 148-149 

Smith, D. T., on lake sediments· ..................... ........... 96 

Solfatarism, oxidation and, results of .... : ...... .. ..... . ........ 193-195 

Solutions, 9re-depositing, character of. . ............. .. . 185--186,191-197 

source of ...................... .. . .. .. .......... . ...... ... .. 197-198 

Spearhead Point, rocks of ........ _ .. . · ........................... 67,70 

Spearhead {hyolite, character and distribution of. .......... -.·. 28, 30,71 

correlatiion of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 
258 INDEX. 

Page. 

Spearhead rhyolite, extension of . _____ .. _ .. _ ............. _....... 90 use of, for building ___ _____________ ___________ . __ . __ . _ _ _ _ _ _ _ _ _ 71 

Sphalerite, occurrence and character of ________ ..... _. __ 109, 112-113,166 

Springs, sulphuric acid in ____ __ . ____ ____ _____ ____ ____ __________ _ . 191 

Spurr, J. E., correlation by_ .. _ .. __ ... ___ ____ _ ...... ... _._. __ 92, 94,105 

on beds at Furnace Creek .... __ . ____________ . __ . ______ ~- ___ . 99-100 

on Goldfield ores ... _ .. J ••• __ •••••• __ • • __ __ •••• ____ _ ____ • _.... 171 

on lake sediments .. ___ ____ .... _ .. __ ... _ . _ . __________ . 96-97, 102, 105 

on lava sequence ....•. ___ .. .. _ .. __ ______________ . . _________ 105-106 

on Nevada rocks ................... _ . . . ...... _ .... 92-95,97,102,103 

on pre-Cambrian rocks .... _ ... __ .... -.... _ ..... __ ......... , .. . 86 

on Siebert tuff ..... _ . ______ ...... _ ...... . .. _ .... _________ . . . . 97 

on Tonopah rocks ...... . . . _____ ..... _ ... _..... ............... 103 

on Tonopah underground temperature ..... _ .. __ . __ . . . . . . . . . . 198 

work of. ..... ______________ . ____ ... . ... ________ .. ______ .. ___ .. 17 

Stealing, prevalence of. ................... _ ......... __ .. __ ....... 18-19 

Steiger, George, analyses by ........ .. ...... .... ...... 50,52,56,61,63, 73 

work of. ..... _ ... _________ ........ ·_ .. _._._._·_. __ . ____ ... __ . . 14,130 

Stimler, Harry, gold discovered by............................... 17 

Stokes, H. N ., on marnasite. ____ .......... ____ . ___ ... _ .. _ ... ___ . _ 115 

Stratigraphy, columnar sections showing .............. _ .......... 90,91 

outline of ........... _ ....... _ ... _ ..... ___ . ___ .. _. ________ .... 27-30 

Structure, description of. ........ _._ . .. .... _ . ..... ........... , 27,76--85 

Sullivan, E. C., analysis by ................. _ .. __ .. _ .. _ ... ___ .... 41 

Sulphide ores,characterof. ....... ____ ...... __ .... _ ... _ .. 3()-31,165-169 

minerals in. _ ....... _ ..... _ . _. _ .......... _ .. _. _. _. _ . ___ . . . . . . 30 

See also Ores. 

Sulphur, occurrence and character of. ... _ .......... _ .. _ . . . . . . . . . . 109 

Sulphuric acid, source of .................... _. __ . ... ___ ........ 189-195 

Sweeney lease, production of. ....... ... ..... _. . . . . . . . . . . . . . . . . . . . 17 

T. 

Talc, so-called, nature of. .................. __ . .. .. _.............. 167 

Tellurides, occurrence and character of. ............ 109,110,115-116,166 

Tellurite, occurrence and character of ....... _._ .... __ ...... 109,123,171 

Tennantite, composition of. ...................... _.............. 118 

Tertiary rocks, sequence of. ........... . _ ............ _____ ._._ .... 27-30 

subdivision of. . . ...... _ ........... __ .. ___ . ________ . __ ... ..... 36 

Tertiary time, climate in .... .. _ ..... _ ..... __ .. __ .... ______ .. _ .. 106--107 

events in .......................................... _ . __ . . . . . . 88-91 

Tetrahedrite, composition of. ............... _ ........... _........ 118 

Texas, sulphuric acid in springs in ........... ______ ._._. ___ . ___ .. 191 

Titanite, occurrence and character of. .................... __ ...... 109 

'l'ognoni Springs, rocks near ........ _ ... _ 45,53,54,[15,57,58,60,65,81,152 

sulphur near ........................ _ ... _ ..... : ....... _ . . . . . . 109 

Tonopah, dacite from, analyses of ............... __ .. .... ... .. ___ 94 

discoveries at ......................... ____ .................•. 16 

rocks at .............................. . ___ . . . . . . . . . . . . . . . . . . . . 103 

Topography, description of ..••............................. . 14-16,150 

u 

Page. 

Triangle mine, description of ... _ ..... _. __ ..... _........ ..... ..... 251 

Truckee group, character and distribution of ...................•. 95-96 

correlation of.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 

Tuff, petrography of ........ _ .. _ .... ..... __ .. __ .................. _ 53 

Tumer;H. W., on Esmeralaaformation .•................. :..... 97 

u. 

Unconformity, datum marked by ....... .. _ .. _................... 92 

United States Government, investigation by .. __ ........ ......... 21 

v. 

Van Rise, C. R., on fumarole gases .... .. ... . __ ._........... ...... 190 

on solfatarism.......... . .. .... .......... ............ ......... 193 

Velvet mine, description of ...................... ·-. . . . . . . . . . . . . . . 241 

production of. ...................... . ..... .... ... ........... 22,241 

Victor mine, description of ............... ..... ................. 242-243 

ore of ...... _ ............................................... 173,243 

plan of, figure showing .................... __ ................. 243 

Vindicator Mountain, faults 'near ....................... _. _...... 84 

rocks of ............... 27-34, 38-39,43-48, 72, 74, 76--77,88, 152, 176, 182 

Vindicator rhyolite, alunitization of, photomicrograph showing. 178,184 

character and distribution of .. _ ... _______ . __ ........ 28, 37-38, 76--77 

correlation of. ............................. __ . . . . . . . . . . . . . . . . . 92 

eruption of. .............. _ ........ :: . .... . .. _ . . . . . . . . . . . . . . . . . 88 

petrography of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 

Vogt, J. H. L., on alunite ........... __ .... •... __ ............... 132-133 

Volcanic ash, quarry in. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 

Volcanic rocks, photomicrographs of. ........ _ . . . . . . . . . . . . . . . . . . . . 62 

Volcanism, disappearance of. .................... . .. ........... . 198-199 

relation of, to mineralizing solutions ..... _ . . . . . . . . . . . . . . . . . . . . 197 

Volcanoes, prevalence of, in lacustrine epoch... .. .... ... ......... 89 

Von Schulz & Low, analyses by ... __ .... __ .. ____ ................. 169 

W. 

Wages, scale of ....•.................... __ ..................... 18-19,21 

Washington, H. S., on derivation of pyroxene andesites.......... 48 

Water, supply of.. ............................................. 142-143 

Water, magmatic, nature of............. ............. ............ 190 

Water, meteoric, relation of, to mineral solutions .............. 197-198 

Water, underground, character of................................ 188 

depth of... • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 

White Rock shaft, water in ............... .......... ----......... 187 

Y. 

Yellow Tiger mine, rocks of. .......... . __ ..................... 39,54, 79 

z. 

Zircon, occurrence of. •.......... . .. ..... -....................... 109 

Zoisite, occurrence of. ••.............................. ---........ 109