DEPARTMENT OF THE IMTBEIOK

BULLETIN

UNITED STATES

GEOLOGICAL SURVEY

No. 182

SERIES A, ECONOMIC GEOLOGY, 12

WASHINGTON

GOVERNMENT PRINTING O If F I C E 

1901

UNITED STATES GEOLOGICAL SURVEY

CHARLES 1>. WALCOTT, DIRECTOR

A REPORT

ECONOMIC GEOLOGT7

SILVERTON QUADRANGLE, COLORADO

FREDERICK RANSOME

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1901

CONTENTS.

PART 1. GENERAL DESCRIPTION AND DISCUSSION OF THE ORE DEPOSITS.

Introduction and acknowledgments..._.......-.--..-............ .......... 13

Geographical position ...... ....................--..._ .................. 14

Literature.............. ..-._...-........---........ l ...... .................. 14

Historical sketch .....__......._...............................-..._._.:._ 19

Production..... ............................................. ............ 25

Climate....................... .......................................... 25

Vegetation ................ ................ .......... ............... .......... 26

Topography ....................... ...... ................................ 26

Outline of geology, by Whitman Cross........................... ........ 29

San Juan volcanic area .......................... ...................... 29

Geology of the Silverton quadrangle .........--.........-..-.-.-....I.. 80

Location with regard to the volcanic area ......... ...........:..... 30

San Juan formation . ...... ...'......--...-....................... 31

Silverton series ......................................... .......... 32

Potosi series ....................................................... 32

Stock eruptions..........-..-...........--...-...-...-....-..--....- 38

Other intrusive rocks.... ..... .................... ....... 33

Formations underlying the volcanics.. .. ... .................... 34

Prevolcanic surface and the Telluride conglomerate ....I........... 30

Structure of the pre-Telluride formations ........ . .............. 37

Faulting.... .. ....................................................'.... 37

Landslides. . . .......... .................../................:. 37

Methods of mining and treatment of ores....-....--. ...... ................ 39

Classification of the ore deposits .................................... ...... 43

The lode fissures........ .:.... .....-...-....-...-....-...--. ............. 43

Definitions ..'.............-..........-................-.. ....-.--.-.. 43

Distribution of the ore-bearing fissures. .............................. 44

Coordination of the fissures........................................... 45

Relation of fissures to kind of country rock and to rock structure..... 53

Displacement or faulting as an accompaniment of the fissuring ........ 55

Intersections and relative ages of fissures. ..-.......;..-..-..-.....-.. 56

Geological age of the fissures............ ................................ 60

Probable depth at which the portions of the fissures now exposed were

originally formed.......... ......................................." 60

Persistence of the fissures horizontally and in depth ................... 61

Origin of the fissures.................... .................................. 63

Structures of the lodes.......... .............. . . .................. ........ 67

The ores of the lodes......................... ..:.-.....................-.- 70

Mineralogy of the ores...... .......................... ................ 70

Gangue minerals .... ....................-.........:...-......-.. 70

Ore minerals ..... ..... ...... .................................... 77

Products of superficial decomposition .. ........................... 87

5
6 CONTENTS.

Page.

The ores of the lodes Continued.

Structure of the lode ores ............ ................................ £7

Megascopical structures .. ..... .-...............'..... ........... 87

Microscopical features ..... ..:...............-....-... ............. 92

Areal distribution of the lode ores ............ .. ..................... 94

Distribution of the ores within the lodes ........................ ...... 96

Relation of ores to kind of country rock... ...................... ...... 101

Secondary alteration of the lode ores... . ............. .._. ........... 101

Origin of the 1 ode ores.................................................. 102

Value of the lode ores...................... ......................... . 102

The stocks or masses ........................................................ 103

Definition and general description ...................................... 103

Distribution ........ ....................... ....................... 104

Origin of the spaces now filled with ore................... ............ 104

Character and structure of the ore........... ......................... 109

Changes in the ore with depth .... ......................_........... Ill

Value of the ores . ... . .......... .................................. 112

Mineral waters associated with the ore deposits:........................... 113

Metamorphism of the country rock in connection with ore deposition...... 114

Paragenesis of the lode and stock ores........... ............................ 131

Origin of the lode and stock ores .......... ............................ .. 132

The ground water .................................'......................... 141

Replacement depo;its.... .. ............................................... 141

Miscellaneous mineral resources ...... ...... ............................... 143

PART II. DETAILED DESCRIPTIONS OF SPECIAL AREAS AND INDIVIDUAL

MINES.

Introduction ........ ... ...... ..'........ ...... ................ ...... ....... 145

Lodes of Silver Lake Basin... ..................... ......................... 145

General features...... ................ .................... ............... 145

Silver Lake mine..... . -.-.-..--....-.---..-.-. ....................... 149

Iowa mine ........ ....^..................... ^. ...................... 157

Royal Tiger mine......................... ......--.....-....-.-....-. 159

Buckeye mine .....................----...-- ......................... 160

Titusville. mine ... .........--.--..-.---...-..-.................... 161

Lodes of Hazelton Mountain.................. ................ ............. 161

General........ .... ..................-.-...--......-..........-.,.:. 161

Aspen mine ..... ... .....,.-...--....----.-.--..---.-.............-. 161

North Star (King Solomon) group of lodes .............................. 163

General............ ...... ........................................... 163

North Star (King Solomon) mine ..................-.....-.'... ...'.*.... 163

Dives mine...... ............................................ ...-..--. 165

Mountaineer and Lookout mines....................................... 166

Big Giant lode and others .-..--.-.........-...--.-- ...-......-......-- 166

Little Giant lode . ..................................................... 167

Lodes of Cunningham Gulch.... ............................................ 167

General.......................................>.............. ........ 167

Highland Mary mine . ....-...............-...-.--.---.......-..-... ... - 167

Green Mountain mine ..................'......-.-.......-......-..-.-. 168

Pride of the West mine.......... ..................................... 169

Philadelphia, mine ....-.........-......,-..-.......--....-..-., ......... 170

Other lodes. .................. ................-............ -...... 170
CONTENTS. '<

Page.

Lodes of Galena Mountain and vicinity..._..... ._.......--......--..---- 170

General .... ......_.....,.._.. .....................---..........-.-.-.. 170

Antiperiodic mine..__-_..........._...__..._.._--.._.__..._..,.-....-.- 172

Ridg way mine........ .... ............. ..^........................... 172

* Gold Nugget claim ..................... .............................. 173

Little Maud claim ..................................................... 173

Hamlet mine .... .-.-.--.-.-.-.-..-.-..-._-..- .,.-..-.......:.-..- . 173

Other lodes....................... .................................... 174

Lodes of Burns Gulch .................................. ................... 174

General ....... ........................................................ 174

Tom Moore lode...............,.'............_................__.......... 174

Silver Wing mine ........ ............................................. 175

Lodes of Sunnyside Basin .................................................. 176

General... .................................................. ....... 17(1

Sunnyside mine ....-..-.--.....--...-.....---.-..------.-....-.-----.- 176

La Belle Creole claim...................-.....---....---...........'.._ 176

Lake claim ................ ........................................... 178

George Washington claim............................................. 178

Ben Franklin mine ............... .......',.........-............--.-.. 178

Placer Gulch and Treasure Mountain group of lodes....................... 179

General ....... ........... .................................... ..... 179

Sunnyside Extension mine.... ........................................ 180

Mastodon claim ..................... ...... .......................... 181

Silver Queen mine ... ......... ...................................... 181

Hidden Treasure, Pride of the Eockies, etc............................ . 182

Sound Democrat mine . ....... ........--.-...-..--...........-. ..... 182

Scotia lode ............................ ........._.................... 182

Golden Fleece vein ...-........-......,..........--......'.............. 188

San Juan Queen mine .-.---...,-.--.--..--...------ ................... . 183

Tolteclode..... ...................................................... 183

Mountain Queen mine .................................................. 183

Other lodes..... .............. ......................................... 184

Lodes of Mineral Point.................................................... 185

General............................................................... 185

Bed Cloud mine ........,.........--.-..-...-....-.--.......-..-- ...... 185

Ben Butler mine...................................................... 186

Uncompahgre Chief claim............................................. 186

Bill Young mine.................. ^..................................... 187

San Juan Chief mine. ................................................. . 187

Polar Star mine ...-.'..-----......-.....-.-...----..................... 187

Other mines ..... ................................ .................... 188

Lodes of Henson Creek ...................... ......... ..... .......... .... 189

General ............ ................................................. 189

Frank Hough mine-..-...-..-...-.-.....-...-- ........ .............. 189-

Palmetto mine .. ....... .......... ^............................... .. 189

Dolly Varden lode............................................ ........ 189

Other prospects ........................... ...........................'. 191

Lodes of Poughkeepsie Gulch............................................. 191

General ............... ..........-.....-.-....--......-.....----..... 191

Old Lout and Forest mines............................................ 192

Maid of the Mist mine ........................... .................... 193

Alabama mine.... .--..............-...--.-_.-.-........-.....---...... 191

Poughkeepsie mine ................................................... 194
b .CONTENTS.

Page.

Lodes of Poughkeepsie Gulch Continued.

Ainador mine ................ .. ...... ................. .......... 194

Saxon mine.. ....._-.--...-.--.......-_........_-.-. ....... -.-...._... 195

Alaska mine...-..... ........... .. _. ....................... ....... 195

Bonanza mine....... ................................................. 196

Other mines and prospects..-...._-._......._--.....:-..--. .'....-..-..-.. 196

Lodes of the Uncompahgre Canyon ...................................:..... 196

General ...... ...... .................-.'..._. ............................ 196

Michael Breen mine ....................... ....... ................... 196

Happy Jack mine..... ....'...... .................... ................ 197

Silver Link mine ..................................................... . 198

Silver Queen mine...... ............................................... 199

Lodes of Canyon Creek .... .............. ............................... 200

General ....:..... ................................................. 200

Camp Bird mine ..........._..._._.__......_.............._._-_.__...... 200

Hidden Treasure mine............................................ ...- 204

Hancock mine .........--.....-..............._..._...--_...-..__..._. 204

Yellow Rose mine ........................................................ 204

U. S. Depository mine ................................................. 204

Wheel of Fortune mine ................................................ 205

Bitnetallist mine ...... .................................. ....._....... 205

Lodes of Savage Basin......_._....._....._ ._...--.......:__--.....:.._...._. 206

General .... ............................. .... ........................ 203

Tomboy mine ......................................................... 206

Japan mine ........................................................... 211

Argentina mine . ....................................................... 213

Columbia mine. .... ................................................ 214

North Chicago mine.................................................... 214

Ore deposits of the Red Mountain region _.. ......_.............----.....__. 214

General.............. ........ ......_.:..___._._.._............_.....__ 214

Yankee Girl mine . ................... .............. .,..,.__.-. _....-_. 215

Robinson mine ........................................................ 220

Guston mine ....... .. ........................................ ........... 221

Genesee-Vanderbilt mine ..-.-..........-....----.--.................... 227

Alexandra mine .............................................. ..... 231

Grand Prize mine ............................................ .^~ --- 231

National Belle mine ................................................... 231

White Cloud mine..... .................... ............................ 236

Paymaster mine..-...:..................... . ................ .......... 236

Silver Bell mine ........... 1............:................. ............ 236

Congress mine............... ..... ..'........--.......................,... 238

St. Paul mine ..........--,-.---..............--...-..-.....---......... 238

Carbonate King mine ., ....... ......... .....-..---.-...... .......... 239

Midnight mine ............... ......................................... 239

Other mines .......................................................... 239

Saratoga m\ne.....................^.................................. 240

Baltic group........... .................................... ............ 244

Jay Eye See mine...-................................................. 245

Barstow mine .... ...................... ............................ 246

Silver Ledge mine ...... ...................._.........-..-.........-.._. 247

Magnet mine .......................................................... 249

Brobdignagclaim .................................................... 249

Zuni mine .. ... -.... .. .... .... .... ... .......... ...^.. .... ........... 249

Meldrum and Hammond tunnels ....--..............-.. .---......-..-. 250
CONTENTS. 9

Page.

Mines of Sultan Mountain ..... ....................... i.................. 251

North Star mine........... .......................................... 251

Belcher mine... ................................. .................... 252

Empire group ........................................ ............... 252

Other mines and prospects......................... .................. 253

Mines of Cement Creek .................................................... 254

General ...................... .................... .................... 254

. Gold King mine ..-...-....-......-.-...........-.-...'.......... ..... 254

Tungsten ore deposits ............................................... 256

Bed and Bonita mine .....-.........---....----....-...-.-.......... .. 256

Queen Anne mine .......-...........................'................. 257

Columbia mine.......................................................... 257

Ross Basin lodes....................................................... 257

Henrietta mine .................... ............. ....,..._..-.............. . 257

Other mines and prospects ............................................ 258

ILLUSTRATIONS.

Page. 

PLATE I. Bakers Park and the town of Silverton. from the south ........... 13

II. Index map showing position of the Silverton quadrangle........ 14

III. Outline map of the Silverton quadrangle, showing fissure systems

and mineral deposits ............... .......... ............. 26

IV. Preliminary geological map of the northwest portion of the

Silverton quadrangle............. ........................... 32

V. Map of the southern portion of the Silverton quadrangle ........ 34

VI. View of the principal Red Mountain mines from the north, looking up Red Creek ....................... ................... 38

VII. Sheeted structure in cliffs of San Juan breccia, canyon of the

Uncompahgre River, near the Silver Link mine................ 50

VIII. View of lodes exposed on south side of Lake Como .............. 52

I.. Normal vein-quartz structure: A, Stelzner lode; J3, 'Sunnyside

lode............ .................. .......................... 70

X. Vein-quartz structures: A, Finely crystalline from the Ridgway

lode; B, Gangue of rich ore, Camp Bird mine................... 72

XI. Ore structures: A, Radial ore, North Star lode, Dives mine; B, 

Massive structure, Iowa lode, Silver Lake Basin; C, Brecciated 

radial pyrite, Red Cloud mine .............. .................. 86

XII. Ore structures: A, Banded ore, Osceolaclaim, Cunningham Gulch;

B, Banded ore of Camp Bird mine............................ 88

XIII. Plat of the principal mining claims of Silver Lake Basin......... 146

XIV. View of the surface workings of the Camp Bird mine........... 200

XV. Plan of a portion of the underground workings of the Guston and

Robinson mines .......... ....................... . .......... 224

XVI. Plan of underground workings of the National Belle mine....... 230

Fig. 1. Diagram showing courses of some of the lode fissures of the Silverton quadrangle.................................... ............... 47

2. Horizontal sketch projection of the productive lodes west of Silver

Lake. ..........._.._.._.._.__ .............................. 51

8. Cross section of the New York City lode, Silver Lake mine........ 67

4. Sketch section of the Silver Crown lode, showing stringer lode structure ........... ............... ........ ....................... 68

5. Cross section of the Japan lode, showing structure produced by successive openings of the original fissure............................ 69

6. Diagram illustrating common occurrence of kaolin in the Red

Mountain region................. ................................ 74

7. Cross section of No-Name lode, Sunnyside mine.................... 88

8. Cross section of banded vein near the London shaft, Mineral Point. 89

9. Section through a rich ore band in the Camp Bird lode............. 90

10. Map of principal mining claims in the Red Mountain region ....... 105

11. Sketch section across the Silver Lake lode between levels 1 and 2,

showing probable faulting of the lode by a flat strike fault........ 152

11
12 ILLUSTRATIONS.

Page. 

Fig. 12. Plan and longitudinal section of the workings of the Aspen mine.

Hazleton Mountain ...... ...................................... 162

13. Sketch plan of underground workings of the North Star (King Solowon) mine .......... .............................^.^........... 164

14. Cross section of the Tomboy and Iron lodes through No. 2 raise, between the 600-foot and 200-foot levels . ............................. 209

15. Cross section of the Tomboy and Iron lodes through No. 12 raise on 

the Iron lode and a neighboring raise (projected) on the Tomboy 

lode _...................-........_. ...........................'. 210

16. Longitudinal and transverse sections through the G-uston mine.... 224

17. Plan of a portion of the underground workings of the GeneseeVanderbilt mine ..........._._......._............_.._.. ......... 228

18. Plan of fourth level of the Genesee-Vanderbilt mine, showing method

of prospecting for ore bodies with the diamond drill ............ 229

19. 'Sketch plan showing changes in position of the Genesee-Vanderbilt

ore bodies with depth ...................................... ...... 230

20. Sections through the National Belle mine, showing ore bodies sloped

and natural ore caverns............ ............................. 232

21. Sections through the Silver Bell mine, showing ore bodies stoped .. 237

22. East-and-west section through the Saratoga mine (after G. E.

Kedzie).....:..........-.. .......-.:...-........-....-. .......... 242

28. Diagrammatic east-and-west section, illustrating in a general way

the occurrence of ore in the Saratoga mine.... .................. 243
BULLETIN NO. 182 PL. I

AND THE TOWN OF SILVERTON, FROM THE SOUTH.

 Cement creeks; in the background is Boulder Mountain, between Cement Creek and the Animas 

and enter the gorge of the Animas near the lower right-hand corner of the picture. Photograph by 
ECONOMIC GEOLOGY OF THE SILVERTON QUADRANGLE, COLORADO.

Bv F. L. RAXSOME.

PART I, GENERAL DESCRIPTION AND DISCUSSION OF THE ORE DEPOSITS,

INTRODUCTION AND ACKNOWLEDGMENTS.

The field work upon which this report is based occupied the season 

of 1899 from the beginning of July to the middle of October. During 

that summer nearly all of the area was examined and most of the 

mines and prospects were visited.

The work was resumed in the autumn of 1900, with Mr. Alfred M. 

Rock as assistant, a period of six weeks in August, September, and 

October being devoted to those portions of the quadrangle that had 

not been thoroughly studied in the preceding year and to an investigation of such mining developments as had been effected during the 

winter.

It was at one time hoped that the report .of Mr. Whitman. Cross, of 

this Survey, on the general geology of the Silverton quadrangle, forming the Silverton folio of the Geologic Atlas of the United States, 

might be published in advance of this investigation of the economic 

resources of the district, but owing to various causes his field work is 

not yet finished. I am therefore unable to use or to cite his results 

in their entirety, or to reproduce his geological map as an adjunct to 

this report. This is to be regretted, as both a thoroughly satisfactory 

treatment and a proper understanding of the ore deposits require a 

knowledge of the geological relationships of the rocks in which they 

lie. This want has been partly supplied by a brief preliminary 

sketch of the geology, kindly furnished by Mr. Cross. This is necessarily an imperfect outline, to be later replaced by his final results. 

To Mr. Cross I owe, also, the privilege of publishing a preliminary 

geological map (Pis. IV, V) of a portion of the area. This map is based 

upon field work done by himself and his assistants. The geological

18
14 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [Bui,L.182.

boundaries shown are not final and will undoubtedly be spmewhat 

changed Avhen the field work in this region is completed.

To Mr. S. F. Emmons, geologist in charge of the investigation of 

metalliferous deposits, my thanks are due for various helpful sugges- 

.tions and criticisihs and for access to his unpublished notes on the 

Yankee Girl and Guston mines.

The descriptions of the abandoned mines of the Red Mountain district would be far more imperfect than they are were it not for much 

information courteously supplied by Mr. Bedford McNeill, of London, 

liquidator of the New Guston Company; Mr. T. E. Schwarz, of Denver, and Mr. Otto J. Schulz, of St. Louis, trustee of the GeneseeVanderbilt mines.

To the mining men of the region I am indebted for much cordial 

assistance and for courtesies which have many times been recalled 

with pleasure.

GEOGRAPHICAL POSITION.

The Silverton quadrangle, embracing one-sixteenth of a square 

degree of the earth's surface, lies between the meridians 107° 30' and 

107° 45' west longitude and the parallels 37° 45'. and 38° 00' north latitude. On the west it adjoins the Telluride quadrangle and on the 

south the Needle Mountain quadrangle. Its area is approximately 

235.3 square miles. It lies in southwestern Colorado, in the highest 

and most rugged portion of the San Juan Mountains, including a 

part of the continental divide. There are comprised within its boundaries the headwaters of the Animas River and portions of the headwaters of the Rio Grande, Gunnison, Uncompahgre, and San Miguel 

rivers. The principal settlement is Silverton, a town of about 900 

inhabitants. The position of the Silverton quadrangle with reference 

to the adjacent map units of the Geological Survey is shown in the 

index map, PL II. °

LITERATURE.

The published literature relating to that portion of the San Juan 

Mountains included within the Silverton quadrangle is not voluminous. 

It is chiefly comprised in the official reports of the members of the 

Hayden survey, who visited the region in 1874, 1875, and 1876; in 

descriptive notes of various travelers through the San Juan; in scattered descriptions of mines and minerals occurring in the district, 

and in references to the history of mining development found in the 

more general works on Colorado and its resources. The following 

bibliography includes most of the important publications concerning 

the Silverton region. The data contained in them have been freely 

used in the preparation of the following historical sketch, for the 

purpose of supplementing information obtained at first hand from 

those who actually participated in the development of the district.
B U LLETI N NO. 182 PI. II

- POSITION OFTHK SLLVKRTON

Scale of miles

10 20 3D 40 5O 60 70 80 90 100
RANSOME.] LITERATURE RELATING TO THE REGION. 15

BIBLIOGRAPHY.

RHODA, F. Report on the topography of the San Juan country :<' Hayel en Survey Report for 1874, p. 451. 

Contains a few notes on early history of the region. 

ENDLICH, F. M. Report on the San Juan region: Hayden Survey

Report for 1874, pp. 185-240.

Contains brief notes on 'the mines as developed at that time. He divides the 

veins into two systems one striking nearly northwest and southeast, and the 

other nearly northeast and southwest. The veins were formed at the close oi: the 

Cretaceous or beginning of the Tertiary.'

ENDLICH, F. M. Report on the San Juan region: Hayden Survey,

Annual Report for 1875, pp. 176-191. 

General notes on geology. 

ENDLICH, F. M. Report on the San Juan region: Hayden Survey,

Annual Report for 1876, pp. 120-121.

Brief notes on mines and ores.

FOSSETT, F. Colorado. Denver, 1876. 2d ed., New York, 1880.

Contains much useful data, chiefly of a historical character, in regard to the 

early settlement and development of the San Juan region.

KOENIG, Gr. A. On alaskaite, a new member from the series of bismuth 

sulphosalts: Proc. Am. Philos. Soc., Vol. XIX, 1881, pp. 472-477. 

Describes alaskaite from Alaska mine, Poughkeepsie Gulch.

COMSTOCK, T. B. Notes on the geology and mineralogy of San Juan 

County, Colorado: Trans. Am. Inst. Min. Eng., Vol. XI, 1882-83, 

pp. 165-191.

Discusses chiefly the character and distribution of the veins. Accompanied by 

a sketch map.

CROSS, WHITMAN. A list of specially noteworthy minerals of Colorado: Proc. Colo. Sci. Soc., Vol. I, 1883-84, pp. 134-144. 

Refers to occurrence of various minerals in the San Juan region. 

SCHWARZ, T. E. Remarks on occurrence of ore in mines near Silverton: Proc. Colo. Sci. Soc., Vol. I, 1883-84, p. 132. 

Describes principal deposits of the Red Mountain district. 

HILLEBRAND, W. F. Mineralogical notes: Proc. Colo. Sci. Soc., Vol.

I, 1883-84, pp. 121-123. 

Describes zinkenite from Brobdignag mine.

HILLEBRAND, W. F. On zunyite and guitermanite, two new minerals 

from Colorado: Proc. Colo. Sci. Soc., Vol. I, 1883-84, pp. 124-131.

HILLS, R. C. Kaolinite from Red Mountain, Colorado: Am. Jour.

Sci., 3d ser., Vol. XXVII, 1884, p. 472. 

Describes kaolinite from National (American) Belle mine.

HILLS, R. C. Extinct glaciers of the San Juan Mountains, Colorado: 

Am. Jour. Sci., 3d ser., Vol. XXVII, 1884, pp. 391-396. Also 

Proc. Colo. Sci. Soc., Vol. I, 1883-84, pp. 39-46. 

Notes on extent and location of former glaciers of San Juan region.-
16 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. inuLr.,.].KJ.

COMSTOCK, T. B. The distribution of San Juan County ores: Eng.

and Min. Jour., Vols. XXXVIII and XXXIX, 1884-85.. 

A series of brief papers.

HILLEBRAND, W. F. Miscellaneous mineral notes: Bull. U. S. Geol.

Survey No. 20, 1885, pp. 89-99.

Describes kaolinite from National Belle mine and zinkenite from Brobdignag 

mine, on Red Mountain Range, near Chattanooga.

HILLEBRAND, W. F. New mineral species from Colorado: Bull.

U. S. Geol. Survey No. 20, 1885, pp. 100-107.

Describes zunyite and guitermanite frojn the Zuni mine, Anvil Mountain, near 

Silverton.

EMMONS, S. F. Geological sketch of the Rocky Mountain division:

Tenth Census, Vol. XIII (Precious Metals), 1885, pp. 82-85. 

A general sketch of the San Juan region by counties. A table of mines, giving 

country rock, dip, and strike of vein and ore minerals.

EMMONS, S. F. Notes on some Colorado ore deposits: Proc. Colo.

Sci. Soc., Vol. II, 1885-1887, pp. 85-105.

San Juan region an excellent field for the study of fissure deposits. Points out 

that so-called "geyser mounds" of the Red Mountain district are merely masses 

of country rock bleached and altered by solfataric action.

EMMONS, S. F. On the origin of fissure veins: Proc. Colo. Sci. Soc.,

Vol. II, 1885-1887, p. 207.

Ascribes shape of Yankee Girl ore body to the formation of a shattered zone at 

intersection of three or more fissure planes.

COMSTOCK, T. B. The metallurgy of San Juan County ores: Eng.

and Min. Jour., Vol. XXXIX, 1885, pp. 69-71; also Vols. XLE

and XLII, 1886.

A series of brief papers dealing chiefly with causes of failure of various 

smelters.

IHLSENG, M. C. Review of mining interests of the San Juan 

region: Colo. State School of Mines, annual report of field work 

and analyses, 1886, pp. 19-63. 

General notes on the mines.

COMSTOCK, T. B. The geology and vein structure of southwestern 

Colorado: Trans. Am. Inst. Min. Eng., Vol. XV, 1886-87, pp. 

218-265.

Advances speculative views as to the origin of the ore deposits and divides the 

veins into groups. The Red Mountain deposits are supposed to occupy the 

throats of extinct geysers and the bowls of nonsintering hot springs.

LAKES, A. Geology of the Colorado ore deposits: Ann. Rept. State

School of Mines, 1887, pp. i-clix.

Contains scattered and unimportant references to veins of the San Juan Mountains.

REUSCH, H. Krystallizirter Kaolin vou Denver in Colorado: Neues

Jahrbuch fiir Mineralogie, etc., 1887, II, pp. 70-72. 

Description and chemical analysis of kaolin from National Belle mine. Red 

Mountain. '. ..
RANSOME.] LITERATUEE EELATING TO THE REGION. 17

KEDZIE, G. E. The bedded ore deposits of Red Mountain mining 

district,'Ouray .County, Colo.: Trans. Am. Inst. Min. Eng., Vol. 

XVI, 1887-88, pp. 570-581. 

Classifies deposits in northern San Juan County as fissure veins, "chimneys,"

and '' bedded "or " contact" deposits. Describes the deposit of the Saratoga mine

as of the latter class.

SCHWAEZ, T. E. Notes on the ore occurrence of the Red Mountain

district: Proc. Colo. Sci. Soc., Vol. Ill, 1888,'pp. 77-85. 

Ascribes Bed Mountain deposits to hot-spring action. Describes changes in ore

bodies, character of ores, and origin of ore caves.

EMMONS, S. F. Structural relations of ore deposits: Trans. Am. Inst.

Min. Eng., Vol. XVI, 1888, pp. 804-839.

Describes ore body of Yankee Girl mine and criticises the speculative statements of T. B. Comstock. Discusses fractures and their causes. Eet'ers to zones 

of sheeting in the rocks of the San Juan. Suggests that complicated systems of 

fractures there found seem to require torsional strains for their formation,

COMSTOCK, T. B. Hot spring formations in the Red Mountain district, Colorado: Trans. Am. Inst. Min. Eng., Vol. XVII, 1888- 

89, pp. 261-264. 

A reply to criticism by Mr. S. F. Emmons.

HILLS, R. C. Orographic and structural features of Rocky Mountain

geology: Proc. Colo. Sci. Soc., Vol. Ill, 1888-1890, pp. 362-458. 

A few references of general character to the geology of the San Juan region,

SCHWARZ, T. E. The ore deposits of Red Mountain, Ouray County, 

Colo.: Trans. Am. Inst. Min. Eng., Vol. XVIII, 1889-90, pp. 139- 

145. 

A careful general description of the peculiar deposits characteristic of the Red

Mountain "district. Some hypotheses are advanced, but the value of the paper

lies in the facts presented relative to the main ore bodies, which are no longer

accessible.

KELLER, H. F. Ueber.Kobellit von Ouray, Colorado, und iib'er die 

chemische Zusammensetzung dieser Species: Zeitschrift fur Krystallographie, Vol. XVII, 1890, pp. 67-72. 

Describes kobellite from the Silver Belle mine.

ARGALL, PHILIP. Discussion of paper by P. H. Van Diest: Proc.

Colo. Sci. Soc., Vol. IV, 1891-1893, p. 353.

States that in the San Juan region many of the mineral veins in the eruptive 

rocks occupy fissures of contraction and do not extend into the underlying rocks.

BANCROFT, H. H. History of Nevada, Colorado, and Wyoming; San

Francisco, 1890, pp. 495-503. 

Sketch of early history of San Juan region.

HILLS, R. C. Types of past eruptions in the Rocky Mountains: Proc.

Colo. Sci. Soc., Vol. IV, 1891-1893, p. 25.

San Juan Mountains said to correspond to Tushar type, of Powell, carved from 

thick volcanic masses in nearly horizontal attitudes.

HALL, FRANK. History of Colorado, Vols. II-IV; Chicago, 1890-1895. 

Early history of prospecting in the San Juan.

Bull. 182 01 2
18 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

HURLBURT, E. B. On alunite from Red Mountain, Ouray County, 

Colo.: Am. Jour. Sci., 3d ser., Vol. XLVIII, 1894, pp. 130-131.

RICKARD, T. A. The development of Colorado's mining industry:

Trans. Am. Inst. Min. Eng., Vol. XXVI, 1896, pp. 834-898. 

Contains brief historical notes on the San Juan region.

SCHWARZ, T. E. Discussion of paper by T. A. Rickard: Trans. Am.

Inst. Min. Eng., Vol. XXVI, 1896, pp. 1056-1060. 

Describes "ore break" of Genesee-Vanderbilt mine.

PURINGTON, C. W. Preliminary report on the mining industries of 

the Telluride quadrangle, Colorado: Eighteenth Ann. Rept. U. S. 

Geol. Survey, Part III, 1898, pp. 745-850.

A valuable study of the ore deposits lying immediately west of the Silverton 

quadrangle and including also a few mines, such as the Tomboy, within the 

former area. The general similarity of conditions obtaining within the Silverton and Telluride quadrangles renders the material of this report specially important, and it will frequently be referred to in the following pages.

CROSS AND PURINGTON. The Telluride folio: Geologic Atlas U/S.,

folio 57; U. S. Geol. Survey, 1899.

Maps and general geology of the quadrangle adjoining the Silverton quadrangle 

on the west. In this folio are defined and described many of the geological formations which extend into the Silverton area.

ENGINEERING AND MINING JOURNAL, Vols. XXIII (1877) to the

present.

"Numerous brief reports from correspondents in the San Juan region. Their 

value at the present time is in their historical data.

RAYMOND, R. W. Report on the Mineral Resources of the States 

and Territories West of the Rocky Mountains, Vols. I to VIII, 

comprising the years 1869-1876. 

Contains many notes on the mines of the San Juan.

BURCHARD, H. C. Report of the Director of the Mint on the Production of Gold and Silver in the United States, 1880-1884.

Contains numerous notes on the development and production of the mines in 

the Silverton quadrangle.

KIMBALL, JAMES P. Report of the Director of the Mint on the Production of Gold and Silver in the United States, 1885-1888. . Brief notes on the San Juan region, chiefly in regard to production.

LEECH, E. 0. Report, of the Director of the Mint on the Production

of Gold and Silver in the United States, 1889-1892. 

Brief notes on mines, chiefly in regard to production.

ROBERTS, GEORGE E. Report of the Director of the Mint on the Production of Gpld and Silver in the United States, 1897. 

Brief notes on mines and production of region, by counties.

LEE, H. A. Report of the State Bureau of Mines for 1897; Denver,

pp. 109-112. 

Gives production for year by counties and some historical data on San Juan County.

VAN HORN, FRANK R. Andesitic rocks near Silverton, Colorado:

Bull. Geol. Soc. America, Vol. XII, 1900, pp. 4-9. 

Petrographical descriptions and chemical analysesof various more or less altered 

specimens from the southeastern quarter of the Silverton quadrangle.
RANSOME.] EAELY HISTORY. 19 

HISTORICAL SKETCH.

Deeply covered with snow for a great part of the year, and standr 

ing remote from lines of transportation and points of supply, it is not 

surprising that the rugged San Juan Mountains should, until a comparatively late period, have discouraged the advance of prospectors 

into their lonely ravines. Prior to 1860 the area now included in the 

Silverton quadrangle had been visited by but few white men, and at 

a time when every gulch of the Sierra Nevada was a scene of picturfc'sque activity the Indian and the mountain sheep were as yet undisturbed in their possession of the San Juan. But no natural obstacles 

have ever long withstood the restlessness and indomitable perseverance of the seekers after precious metals. In 1860 (according to some, 

1861) a large party of miners, under the leadership of John Baker, 1 

penetrated to the little mountain-rimmed '' park" where the town of 

Silverton now stands. They .had hoped to find profitable gulch mining, but, overtaken by the heavy winter snows and harassed by the 

Ute Indians, many of the party perished miserably and the remnant 

escaped over the mountains only after suffering great hardships. For 

several years the memory of this unfortunate expedition seems to have 

discouraged further attempts at prospecting in the neighborhood of 

Bakers Park. It was not until the early seventies that reports of mineral wealth again began to draw the more adventurous miners into the 

San Juan region. Some gold was early obtained by washing in Arrastra Gulch, and this led, in 1870, to the discovery by a party of prospectors sent out by Governor Pile, of New Mexico, of the first mine 

which was successfully operated, the Little Giant, on the noi;th side 

of Arrastra Gulch. 2 This produced a gold ore, of which some 27 tons 

were treated in arrastres, yielding $150 a ton. The first shipment of 

ore from the district is said to have been from this mine. In 1872 

troops were sent into the region to keep out the miners, as their presence constituted 'a violation of the treaty of 1868, by which the Utes 

were secured in sole possession. In the same year a commission was 

appointed by Congress to negotiate a new treaty with the Indians to 

reduce the extent of their reservation. The Little Giant Company 

was organized in Chicago in 1872, and in 1873 the arrastres were 

replaced by an amalgamating mill equipped with a Dodge crusher, a 

ball pulverizer, and .five stamps. Power was furnished by a 12-horsepower engine. The mill was built 1,000 feet below the mine and the 

ore was brought down on the first wire-rope tramway built in the 

region. This year the mine produced about $12,000 out of a total of 

about $15,000 for the entire region. The pay shoot, however, began

1 Accounts differ as to the Christian name of this pioneer. Thus Bancroft (History of Nevada, 

Colorado, and Wyoming, San Francisco, 1890, p. 495) refers to him as John Baker; T. A. Rickard, 

in his paper on The Development of Colorado's Mining Industry (Trans. Am. Inst. Min. Eng., 

Vol. XXVI, 1890), gives his name as Jim Baker; while Frank Hall, in his History of Colorado, 

makes him Charles Baker. .

3 According to Rickard, opened by Miles T. Johnson in 1871.
20 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

to diminish, and after the milling of a few hundred tons of ore mine 

and mill were abandoned. Several lode., had by this time been opened 

in the region and some small amounts of rich ore had been taken out, 

but it was not until 1874 that the main rush to the country began. In 

September of the previous year a treaty, known as the Brunot treaty, 

had been drawn up with the Utes, whereby the San Juan Mountains 

were thrown open to settlement. The ratification of this treaty by 

the Senate in April, 1874, was followed by a sudden influx of miners, 

chiefly from the northern camps of Colorado, but including also a few 

from the south, and some even from the far West. It is estimated 

that about 2,000 men came into the district during the summer of 1874, 

and Endlich l reports that more than this number of lodes were then 

staked out. 2 At that time La Plata, Hinsdale, and Rio Grande were 

the only counties into which the former reservation had been divided. 

The chief settlement and the county seat of La Plata County was 

Howardsville; but in the autumn of 1874 the county seat was moved 

to Silverton, then a growing town of some dozen houses, admirably 

situated in Bakers Park. The nearest post-office at this time was Del 

Norte, about 125 miles distant. In 1876 San Juan County was formed 

from a portion of La Plata County, with Silverton as the county seat. 

At this time the town is said to have had a population of about 500 

voters. Ouray, San Miguel, and Dolores counties were subsequently 

formed by legislative enactment from the territory originally included 

in La Plata County.

In 1874 real mining began, principally on Hazelton Mountain, and 

several hundred tons of gray copper and galena ore were taken out 

from the Aspen, Prospector, Susquehanna, and neighboring claims 

during this and the immediately succeeding years. This ore was 

treated chiefly in Greene & Go's, smelter, which was erected just 

north of Silverton in 1874, but which was not successfully blown in

until the following year. The machinery was brought in on burros

from Colorado Springs, then the terminus of the Denver and Rio 

Grande Railroad. The product of the entire quadrangle for 1875 was 

about $35,000, and an estimate made in 1877 places the total product 

from the beginning of mining to the close of 1876^ at a little over 

$1,000,000. The Greene smelter was in intermittent operation until 

1879, and was the first successful water-jacket furnace in the State. 

Its daily capacity was about 12 tons, and it is said to have smelted 

nearly $400,000 worth of silver-lead bullion. The bullion was shipped 

by pack train and wagon to Pueblo. The cost of transporting it to 

the railway terminus was $60 per ton in 1876, $56 per ton in 1877, and 

$40 per ton in 1878. The average price for treatment was not far 

from. $100 per ton. During the seventies the chief route into the 

Animas mining district was by the trail from Del Norte on the Rio

1 U. S. Geol. and Geog. Surv. Terr., Report for 1876, pp. 120-123.

9 According to Bancroft, "more than 1,000 lodes claimed." LOG. cit., p. 501.
RANSOMS.] HISTOBICAL SKETCH. 21

Grande, by way of Antelope Park and Cunningharn Gulch. Over this 

route the first ore sold from the Pride of the West mine, in Cunningham Gulch, was taken out in 1874. It was not until 1879 that the 

wagon road from Antelope Park was completed by way of Stony 

Gulch, and ore could be hauled out to Del Norte by teams at $30 a 

ton.

The founding of Lake City, about the year 1875, and the establishment there by Crooke & Co. of a smelting, plant, afforded a market for 

the ores of the northeastern portion of the quadrangle. The first ore 

shipped out from this part of the district was from the Mountain 

Queen mine, at the head of California Gulch, in 1877. It amounted 

to 370 tons, and contained 64 per cent of lead and 30 ounces of silver 

per ton. It was carried by pack animals to the end of the road at 

Rose's cabin, at a cost of $3 per ton. Crooke & Co., of Lake City, and 

Matter & Geist, of Pueblo, both had ore-buying agencies in Silverton

in 1879. During this year about 500 tons of ore, worth about $60,000, 

were sent to the Lake City smelter, and about 185 tons went to Pueblo. 

The value of the latter was probably about $25,000.

In 1879 a road was completed from Silverton up Cement Creek to 

the head of Poughkeepsie Gulch, where prospecting and mining was 

going on with great activity on the Old Lout, Alabama, Poughkeepsie, Red Roger, Saxon, Alaska, Bonanza, and other claims. Chlorination and lixiviation works were erected at Gladstone about this 

time, to treat these ores by the Augustin process. Their capacity 

was.about 6 tons per day.

During the seventies the eastern and northeastern portions of the 

quadrangle were actively prospected, and nearly every lode which has 

subsequently proved valuable was then located. In some cases paying ore was taken out in large quantities, as from the North Star mine 

on Sultan Mountain and others already referred to. But this activity 

was in great part feverish and unwholesome. The success' of a few 

encouraged extravagance in the incompetent, and opened a rich field 

to unscrupulous and dishonest promoters. Smelting plants and mills 

were erected before the presence of ore was ascertained. Reduction 

processes were installed without any pains having been taken to 

ascertain their applicability £0 the particular ores to be treated. Thus 

in 1876 Anitnas Forks was a lively town of some 30 houses and 2 

mills, and in 1883 boasted of a population of 450. But there was 

never any real justification for its existence. Built upon hopes never 

realized, its decline was almost as rapid as its rise, and the town is 

now ruined and desolate. Its principal mill was put up in 1875 or 

1876 to treat ore from the Red Cloud mine, but was never successful. 

The Eclipse smelter, erected by James Cherry as late as 1880, at the 

mouth of Grouse Gulch, ostensibly to run on lead ores from the 

Mountain Queen and other claims, was also a costly failure. The 

Bonanza tunnel, a mile and a half west of the town, was run 1,000
22 ECONOMIC GEOLOGY OF SILVEKTON QUADKANGLE. [BULL. 182.

feet at the extravagant cost of $300,000 or $400,000, and then abandoned. Around Mineral Point probably $2,000,000 or $3,000,000 were 

squandered in mining operations which resulted in no permanent 

improvements or actual development. Numerous similar cases might 

be cited from this region, many of them unfortunately of much more 

recent date. Capital thus invested serves only to build monuments 

of failure, folly, and dishonesty, which may operate to delay for years 

such development and improvement as the mineral resources of a 

district really warrant.

In 1881 the remarkable deposits between Red. Mountain and Ironton were discovered, and in 1882 and 1883 prospectors swarmed into 

this new field. The Yankee Girl ore body was struck in 1882, and, 

with the Gustoii, shipped large quantities of high-grade silver ore for 

over fourteen years. These two mines alone have probably produced 

at least $6,000,000 or $7,000,000, but a very large amount of capital 

has been vainly expended in attempts to find other ore bodies in the 

vicinity equally large and rich. Nowhere else in the quadrangle has 

mining been carried on so extensively. In 1888 the railroad was 

extended from Silverton to Irouton, greatly facilitating the marketing 

of the ore. Red Mountain and Ironton were formerly thriving mining towns of 400 or 500 inhabitants, and the activity steadily increased 

almost up to 1893, when the fall in the value of silver and the exhaustion of the phenomenally rich portions of the ore bodies caused 

the boom to collapse. The Yankee Girl and Guston mines continued 

working until 1896, but the low price of silver and the increased 

expense involved in deep workings and in handling the troublesome 

corrosive waters of these mines, together with the lower grade of the 

ores in depth, finally compelled them too to shut down. From that 

time to the present Red Mountain and Ironton have remained practically dead camps.

Previous to the advent of the railroad in Silverton, ores running less 

than $100 per ton could seldom be.handled with profit, but with the 

completion of the Silverton branch of the Denver and Rio Grande 

narrow-gauge railroad in July, 1882, the rate of transportation on lowgrade ores was much reduced, and many mines hitherto unavailable 

became productive. Freight charges, at first $16 per ton to Denver 

or Pueblo, were soon dropped to $12, at which high figure they stood 

for some time. Over 6,000 tons of ore were shipped from Silverton 

during the first six months after the advent of the railroad. The 

Greeue smelter had some years previously (about 1880) come into the 

possession of the New York and San Juan Smelting Company, which in 

1881 moved the Silverton plant to Durango and in 1882 started the 

present smelter in that town. In September, 1887, the name was 

changed to the Durango Smelting Company, which operated until 

April 1,1888. From that date until May 1,1895, business was carried 

on under the name of the San Juan Smelting and Mining Company, a
RANSOME.I HISTORICAL SKETCH. 23

corporation organized through the consolidation of the Durango Smelting Company of Durango, and the Hazelton Mountain Mining Company, of Silverton, owners of the Aspen group of mines. The Martha 

Rose smelter, with a capacity of about 20 tons, began operations in 

Silverton in 1882, but after smelting about 11 tons of bullion shut 

down and was never successfully reopened.

The year 1883 was a busy one in Silverton, and the population of 

the town rose to over 1,500 inhabitants. Sampling works had previously been erected by E. T. Sweet and T. B. Comstock & Co. Late 

in the season a third plant was opened by Stoiber Brothers. The North 

Star on Sultan, the Belcher, Aspen, Gray Eagle, North Star on Solomon, the Green Mountain, as well as the Red Mountain mines, were 

all actively producing, while great strikes were announced in the Ben 

Franklin and Sampson mines. The' Silver Lake mine also came into 

prominence and shipped that year 72 tons of ore to Sweet's sampling 

works.

It was not until about 1890 that any real attempt was made to concentrate low-grade ores. The credit of thus initiating a procedure 

upon which largely depends the future of the whole district must be 

divided between J. II. Terry, of the Sunnyside mine, and E. G. Stoiber, of the Silver Lake mine. Both men have been successful, and 

Mr. .Stoiber in particular has shown how low-grade veins may be 

worked successfully on a large scale with a modern plant. About this 

time the North Star mine, on Sultan Mountain, put up the present mill, 

run by water power, and in 1894 Thomas Walsh and others erected 

the matte smelter just west of Silverton. Walsh treated by the Austin process the lower-grade Guston ore, and bought siliceous ores 

wherever he could obtain them. This smelter ran pretty steadily for 

three years and finally shut down. Its capacity was about 100 tons 

of ore a day for ten months in the year. In all, about 100,000 tons of 

low-grade siliceous and pyritiferous ores were treated. There was no 

further attempt made to smelt ores in Silverton until the construction 

in 1900 of the pyritic smelter, near the mouth of Cement Creek. The 

smelter at Durango, which was -leased in 1895 by the Omaha and 

Grant Company, and which on May 1, 1899, became the property of 

the American Smelting and Refining Company, has continued to handle the bulk of the ore and concentrates from the Silverton region. 

 With a few notable exceptions the mines of the Silverton quadrangle 

produce ores in which silver and lead are the predominant metals. 

Naturally the rapid decline in the value of silver in 1892 and succeeding years resulted in the closing of many mines hitherto productive, 

and in a general decrease of mining activity. At the present time, 

however, there are signs of a favorable reaction and a marked increase 

of activity. The success of Messrs. Stoiber and Terry in handling 

low-grade ores has demonstrated that when wasteful and inadequate 

methods are replaced by modern appliances and shrewd management,
24 ECONOMIC GEOLOGY OF SILVEKTON" QUADBANGLE. [BULL. 182.

mines carrying abundant low-grade ore may be made profitable, even 

with the present low price of silver. Probably, as in the past, periods 

of depression will sometimes retard mining improvements. Yet it is 

clear that the resources of the district have been far too often superficially, ignorantly, or wastefully exploited. Although examples of 

extravagance 'are still not hard to find, there is now a more general realization of the distinction between such wasteful expenditure 

and the legitimate and often large outlay that makes possible the 

economical working of known low-grade ore bodies. It is very probable that the future will see a great and permanent increase in the 

productive development of such large and persistent ore bodies of low 

average grade. The decline in the price of silver, and also in that of 

lead and copper, which are important constituents of most of the ores, 

has greatly reduced the margin of profit and rendered economical 

working imperative, as is illustrated in the following table:

Table shoiving the average annual prices of silver, lead, and copper, from 1880 to

1899.

Year.

1880 ..I... ..........

1881 ................

1882................

1883................

1884................

1885. .......... .....

1886................

1887.................

1888................

1889................

Silver, 

per fine 

ounce.

$1.145

1.138

1.136

1.110

1.113

1.065

.995

.978

.940

.936

Lead, 

per 100 

pounds.

$5.03

4.81

4.91

4.32

3.74

3.94

4.61

4.50

4.41

3.81/

Copper, 

per 

pound, a

$0. 216

.188

.185

.159

.139

.110

.110

.113

.168

.134

Year.

1890...........'.....

1891................

1892................

1893................

1894................

1895.... ......... ...

1896. .......... .....

1897. ..............'

1898. ............ ...

1899................

Silver, 

per fine 

ounce.

$1.050

.988

.874

.779

.634

.658

.674

.603

.588

.601

Lead, 

per 100 

pounds.

$4.a5

4.33

4.07

4.10

3.28

' 3.24

,2.97

3.60

3.75

4.44

Copper, 

per 

pound.a

$0. 156

.128

.115

108

.094

.107

.109

.112

.119

.177

a Lake Superior ingot.

The prices of silver are taken from the annual reports of the 

Director of the Mint. The lead and copper values are compiled from 

tables showing monthly prices and monthly range in the reports on 

mineral resources issued as parts of the annual reports of the Geological Survey.

Although the first mine to be worked in the district was a gold producer, yet it is an interesting fact that fOi- many years prospecting 

was practically restricted to a search for silver and lead ores. It was 

apparently owing to this adherence to an established routine that the 

Una and Gertrude claims in Imogene Basin, worked twenty years ago 

for silver and lead, were subsequently abandoned, with no knowledge 

of the remarkable gold ore which lay close alongside the argentiferous 

streak, and which was thrown out as waste. Masses of this rich ore 

were discovered by Thomas F. Walsh on the Camp Bird claim, and 

subsequently on the dump of the old workings of the Una and Gertrude, and he purchased the latter in 1896 for $10,000. It is to-day
RANBOME.] PEODUCTION AND CLIMATE. '25

one of the greatest producing mines in the quadrangle, arid certainly 

excels all others in the average richness and regularity of its ore bodies. 

Placer mining has never been extensively practiced within the 

Silverton quadrangle. In former years a little washing was done on 

the east side of California Mountain, in Picayune Gulch, and in 

Arrastra Gulch, but there are no extensive deposits of auriferous 

gravels in the district, and the total output from placer mining is 

probably insignificant.

PRODUCTION.

Accurate figures from which the total production of the Silverton 

quadrangle might be computed are not available. The area comprises portions of several counties, and has shipped ore to various 

'smelters. An attempt to ascertain and combine the products of the 

individual mines within the quadrangle has been only partially successful. In the case of some abandoned mines no records can be

found, and in two instances requests to the owners of active mines 

for confidential statements of total output have met with no satisfac- 

$ory response; but by combining actual figures with individual estimates it appears that the total production of the Silverton quadrangle 

from the beginning of mining activity to the close of 1900 has been at 

least $35,000,000. The greater part of this has undoubtedly been in 

silver, but during recent years, largely owing to the activity of the 

Camp Bird, Tomboy, and Gold King mines, and to the lower price of 

silver, the value of the gold output has predominated.

CLIMATE.

The climate of the Silverton quadrangle is, in general, somewhat 

rigorous. Meteorological records are lacking for this elevated region, 

and no accurate data can be given in regard to temperature and precipitation. The winters are long, the snowfall is heavy, and the temperature sometimes falls to 20° to 30° below zero. The first heavy 

snow usually arrives late in October, but heavy falls are not unknown 

in September. This earty storm may be followed by fine weather, 

lasting well into December. In midwinter snowshoes afford the only 

means of communication over most of the higher roads and trails. 

Snowslides are frequent and dangerous, and a winter seldom passes 

without loss of life and property from this cause. It is often late in 

June before the snow has disappeared from the higher trails, and on 

northern slopes, sheltered from the sun, patches frequently linger 

until long after midsummer. The period extending from the beginning of July to the middle of August is referred to by the inhabitants 

as the "rainy season." During this period in normal years showers 

are of almost daily occurrence, usually coming up early in the afternoon and lasting for an hour or more. It is during this season that 

the wild flowers in the upland basins, notably many species of gentians
26 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

and a magnificent lilac-colored columbine (Aquilegia ccRrulea) attain 

the height of their luxuriant beauty. The temperature at this time 

is changeable. The transformation from balmy air, genial sunshine, 

and humming insects to cold winds, dark clouds, and chilling rains 

is by no means uncommon, and may take place in an hour. The 

month of September is usually delightful. The rainy season has 

passed, and toward the end of this month the aspens assume their 

yellow and orange autumnal coloring, enlivening and softening for a 

brief period a landscape in which bleak grandeur is the rather too 

dominant element.

VEGETATION.

Most of the slopes, up to a timber line varying from 11,000 to 11,500 

feet, are covered with firs, spruces, and aspens, the. last flourishing 

particularly on the southern exposures and on the talus slopes. 

Although .unsuitable for good sawn lumber, the firs and spruces furnish round timber of sufficient size and strength for ordinary timbering in the mines. The basins, being mostly above 11,500 feet, are 

treeless, but are covered in summer with a luxuriant growth of grass 

and flowers.

TOPOGRAPHY.

For more complete accounts of the topography of the region the 

reader is referred to the general geological text of the forthcoming Silverton folio. The present sketch is confined to such considerations 

of topographic form as are necessary to enable the reader to fully 

understand the modes of occurrence of the ore bodies and the conditions governing their exploitation.

The lowest point within the quadrangle is found on its northern 

edge in the canyon of the Uncompahgre, where the contours (PI. IV) 

show an elevation of somewhat over 8,100 feeb. The highest point is 

Handles Peak, on the extreme eastern edge of the area, with an altitude of 14,008 feet. Between these extremes the region exhibits such 

abrupt and frequent variations in relief as to constitute a topography 

of the most rugged character. This assemblage of sharp peaks, jaggpd 

ridges, steep-walled basins, and deep canyons is the result of vigorous 

erosion, acting for the most part on nearly horizontal volcanic rocks. 

The present drainage system is apparently irregular or autogenous 

that is, uncontrolled to any recognizable degree by regular structure 

in the rocks and was undoubtedly established in essentially its present form prior to the epoch of glaciation. Of the character of the 

initial land surface, upon which the present streams began their work, 

we know very little. We may assume, with some degree of probability, 

that it was the surface of a broad, dome-like elevation extending 

beyond the bounds of the quadrangle, which, after its original structural doming, had been reduced by erosion to an irregular plateau 

near the end of the Cretaceous. This was buried to a depth of several
U.S. GEOLOGICAL SURVEY BULLETIN NO. 182 PL. Ill

OUTLINE MAP OF THE SILVER!ON" QUADRANGLE, COLORADO

Showing" areas c.ove-red. ~bv Plates IV a/nd. V 

Scale
RANSOME.] TOPOGKAPHY. 2T

thousand feet by volcanic accumulations in Tertiary times, and has:, 

been complicated by faulting and minor oscillations. No recognized 

trace of this surface remains. The topography, as we know it to-day^ 

is the product of stream erosion, modified by glaciation and the powerful disintegrating action of frost at these high altitudes. It is essential in all discussions relative to the lodes to keep in mind the fact 

that the entire topography is due to erosion, and that the. highest 

peaks are but residuals which owe their relative height to the resistant 

materials of which they are composed, or to their distance from the 

main streams, but in no sense to direct and local elevations.

With the exception of Bakers Park, Ironton Park, and perhaps the 

gently sloping bit of upland at the head of Henson Creek, commonly 

known as American Flats, no considerable areas of approximately 

level land occur within the quadrangle. The mountains rise in steep 

slopes, or in inaccessible cliffs, often from 3,000 to 4,000 feet in height 

from the bottoms of the main canyons. The smaller streams descend! 

these precipitous declivities in successions of waterfalls, or occupy 

small ravines or gulches of high gradient, such as Niagara Gulch near 

Eiireka, Porcupine Gulch, or the gulches northwest of Howardsville. 

The larger tributaries have frequently excavated long canyons of 

moderate gradient, such as Cunningham and Poughkeepsie gulches* 

but in these there is nearly always a point near the headwaters where 

a moderate gradient is succeeded by a much steeper one. Most of the 

streams, large and small, head in cirques, or "lasins" as they arelocally termed, which often contain one or more lakelets. These> 

basins form a very characteristic feature of the .topography, and their 

general shape and character are admirably illustrated by the amphitheaters just north of Sultan and Bear peaks (PI. V).

The rock floors of these basins, often of somewhat hummocky character, generally slope upward on three sides and pass beneath thetalus or " slide rock," with which they are always partly filled. Abovethe talus and inclosing the basin on three sides are usually more or 

less precipitous cliffs, from which have fallen the fragments making up 

the talus at their base. As may be seen from the maps, these cliffs 

are merely the sides of narrow ridges, surmounted by peaks and intersected by cols or saddles which separate adjacent basins. The talus 

frequently extends up to a saddle, and it is then possible to pass from 

one basin to another over the divide. At their lower ends the basinsare usually terminated by a precipitous descent to a gulch or to a. 

second basin at the lower level. This relation is well- shown in the 

case of Silver Lake Basin and Arrastra Gulch. When the connecting 

gulch is very short and steep, as Niagara Gulch, the basins have the 

form of hanging valleys. The talus that always lies against the cliffs. 

and slopes rimming the basins represents in some cases the gradual 

accumulation of comparatively small fragments, such as may frequently be heard rattling down the cliffs during the spring and sum-
28 ECONOMIC GEOLOGY OF SILVERTON" QUADRANGLE. [BULL. 182.

mer. But in many instances it is plainly the result of one or more 

Tock slides of some magnitude, by which large masses of the cliff have 

fallen and slid out onto the floor of the basin.

The lakelets lying in these basins or amphitheaters are usually rockrimmed and often of considerable depth. The existence of the lakes 

depends merely upon the characteristic form, of the main basins or

 cirques in which they lie. This form is immediately due to the eroding action of local glaciers which once occupied the basins. The outlet of Silver Lake flows over a sheet of hard, massive andesite, whose 

surface has been rounded and scored by the ice. The,lake basin itself 

has been excavated, however, in softer, more readily erodible volcanic 

"breccias. Ordinary erosion by running water would have been powerless to excavate such a basin below the level of its present outlet. 

Ice is the only eroding agent that could produce such a result.

The evolution of the topography has undoubtedly been influenced 

to some extent by the fissures and veins that are so abundant in this 

region. But it is difficult or impossible to reduce their effect to the 

form of a simple and general statement. Mineralized fissures are 

frequently lines of comparatively easy oxidation, rapid decomposition, and ready erosion. Thus very many of the lodes determine the 

position of the cols or saddles in the ridges, and can be distinguished 

from a distance by the yellowish color of their surface detritus. Yet 

this is by no means universally true. It often happens that in the 

present stage of erosion the croppings of a vein traverse an even

 slope or cross the summit of a high peak. As an example of the last 

may be cited the important Titusville vein where it crosses Kendall 

Mountain. It is plain that in some cases the fact that erosion has 

resulted in cliffs rather than steep slopes is due to the presence of 

nearly vertical fissures. A system of such fissures running nearly 

northeast and southwest is responsible for the cliffs which separate. 

.Silver Lake Basin from Arrastra Gulch.

In this elevated region the disintegrating action of frost and the 

.active erosion far outstrip the chemical processes of decay which in 

mild and moist climates are efficient in reducing the rocks to soil. As

 a consequence the high peaks and ridges are usually composed of bare 

rock, while their lower slopes are largely made up of talus or '"slide 

Tock," as it is locally called. This talus has concealed in a most 

effectual manner much of the rock once scoured clean by the ice, and 

has restricted most of the prospecting to the high peaks and ridges 

where the veins are exposed.

In the vicinity of Red Mountain and Ironton much of the topography has a peculiar hummocky character, which is the result of 

landslide action. This feature is particularly striking on the northern 

and western flanks of Red Mountain. Several of the Red Mountain 

mines, such as the Yankee Girl, Genesee-Vanderbilt, Guston, Silver 

Bell, Paymaster, and others, are in this landslide area. But the ore
RANSOME.] OUTLINE OF . GEOLOGY. 29

bodies of these mines appear to be in place. Apparently the landslide action is rather superficial, and the siliceous outcrops of the 

larger ore bodies have remained stationary, while the fractured and 

mineralized rock around them have slid in considerable masses down 

the slope. Obviously such sliding renders superficial prospecting very 

unsatisfactory. It is quite possible that some ore bodies have been 

covered by landslide material and entirely concealed. For further 

account and discussion of landslide areas in this and other portions 

of the quadrangle the reader is referred to the heading " Landslides " 

(p. 37), in the outline of geology given by Mr. Whitman Cross.

OUTLINE OF GEOLOGY.

By WHITMAN CROSS. 

SAN JUAN VOLCANIC AREA.

The complex of volcanic rocks within which the Silverton quadrangle is situated is one of the most extensive in the Rocky Mountains. It consists of a series, several thousand feet in thickness, of 

tuffs, agglomerates, and lava flows. The more or less distinctly horizontal surface volcanics have been penetrated by later stocks of various rocks, ranging in composition from gabbro almost to granite, and 

by numerous small dikes of a considerable variety of rocks. The 

eruptions began with the Tertiary and continued during the greater 

part of that era.

The area covered at the present time by these volcanic rocks is in. 

general well shown by the Hayden map of Colorada. The main peaks 

of the San Juan Mountains are situated in the western center of the 

area. From this point the volcanic series extends northward across 

the Gunnison River to the West Elk Mountains, eastward to the San 

Luis Valley, and southeasterly a broad arm. passes a considerable 

distance into New Mexico.

The former extent of the San Juan volcanics was very much greater 

than at present. There is evidence of enormous erosion, which was 

greatest along the western and southern sides, and it appears that 

very possibly the high mountains of the Telluride and Silverton quadrangles are near what was the center of the volcanic area at its maximum. Certainly the former border of the volcanic pile must have 

been located many miles farther west and south than at present.

The Hayden map of this region is only of general value. There is 

great complexity within the area of surface lavas and agglomerates, 

and the map shows in part quite incorrectly the relations of sedimentary and other formations on the borders of the volcanic rocks. The 

resurvey of this extensive tract has not progressed sufficiently to permit the preparation of a satisfactory outline of San Juan geology. In 

the Telluride folio, however, an attempt has been made to present 

the results of the more recent work in their general bearing.
30 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

From the western front of the San Juan Mountains one looks down 

upon a great plateau level which reaches for hundreds of miles westward. This level is nearly 2,000 feet below the base of the volcanic 

series. The isolated mountains which modify this plateau country in 

the zone bordering the San Juan Mountains are in all cases due to 

igneous intrusions which have in a measure protected the softer sedimentary beds from erosion.

The removal of the western part of the original volcanic complex 

has revealed a complicated structure in the underlying older formations, showing that the general center of volcanic activity has also 

been the site of several great disturbances in earlier geologic times. 

About a center not yet very well located, because covered by the 

remaining volcanics, the sedimentary formations of Paleozoic and Mes- 

. ozoic times have been upturned and eroded at several periods. This 

structure is well shown, in the zone bordering the present western 

projection of the San Juan Mountains and in the canyons cutting 

through the volcanics.

The first quadrangle in this area to be resurveyed was the Telluride, 

lying directly west of the Silverton. The main western front of the 

San Juan Mountains traverses this quadrangle from north to south' in 

an irregular line, and the fine exposures of the high peaks and deep 

canyons permit a clear understanding of the principal elements in the 

mass of the volcanic series, in this portion of the area at least. The 

sedimentary formations below are also very clearly shown in the Telluride quadrangle. The somewhat detailed text of the Telluride folio 1 

must be referred to for much general information which is applicable 

to certain parts of the Silverton quadrangle.

GEOLOGY OF THE SILVERTON QUADRANGLE.

Location ivith regard to the. volcanic area. The Silverton quadrangle 

lies almost wholly within the volcanic area, but two streams, belonging 

to the drainage of the Colorado River, have cut through the volcanics 

and disclosed the underlying formations.

On the north the Uncompahgre River with its tributaries, Canyo-n 

-Creek and Red Creek, reveal the Algonkian quartzites and the Paleozoic and Mesozoic formations underneath the volcanics. The lower 

members of the section appear in the Silverton quadrangle. From 

the south the Animas River has penetrated far into the quadrangle, 

and below Silverton it flows in a canyon excavated below the volcanics. This stream has cut a deep gorge through the Needle Mountains, 

which rise immediately south of the Silverton quadrangle to elevations of over 14,000 feet. These mountains are composed very largely 

of Archean and Algonkian rocks. On the west no stream has eaten 

back into the area of this quadrangle with the exception of the two

i Geologic Atlas U.S., folio 57,1899. ..
HANSOME.] OUTLINE OF GEOLOGY. 31

short tributaries of the San Miguel heading in Ingram and Savage 

basins. On the eastern border the Lake Fork of the Gunnison River 

has exposed a mass of granite which is entirely surrounded by volcanies, but as its boundaries are at least in part fault lines, it is possible that dislocations on these planes have produced this outcrop by 

local iipthrust. The structures observable in the formations beneath 

the volcanies show the Silverton quadrangle to be near the center of 

an area of repeated erogenic disturbance in Paleozoic and Mesozoic 

times. Some of the igneous phenomena seem also to center here, but 

it is as yet premature to conclude that the principal center of the 

entire volcanic activity was in this vicinity. There may have been 

several centers of eruption whose products combined to form the great 

complex known.

All of the principal members of the volcanic series thus far identified are exhibited in the Silverton quadrangle. There are also a 

number of intrusive rocks, most of them, having been previously 

observed in the Telluride quadrangle. The principal elements of the 

igneous complex will now be briefly described.

San Juan formation. The earliest volcanic formation of this series 

revealed to the present time has been termed the San Juan formation. It is a more or less perfectly stratified series of tuffs and 

agglomerates of andesitic rocks, no lava flows having been observed 

within it. The character of the San Juan tuff and agglomerate in its 

greatest known development is very clearly exhibited on either side 

of Canyon Creek. It reaches there a thickness of fully 2,500 feet 

(PL IV). In many parts the San Juan seems to be a water-laid 

deposit, so fine is the stratification. The agglomerates are more or 

less chaotic, but exhibit distinct stratification when seen in large 

exposures. These tuffs and agglomerates are also exposed in typical 

development in the mountain group southwest of Silverton, of which 

Sultan Mountain and the Grand Turk are the most notable summits. 

The thickness is here, however, but 1,500 feet. On the east side of 

the Animas the San Juan tuffs are exposed in very irregular thickness on the slope of gneisses and granites descending from the Needle 

Mountains. Apparently, erosion was here extremely active in the 

period succeeding the San Juan fragmental eruptions.

On the eastern side of the Uncoinpahgre River the floor upon which 

the San Juan rests and also its upper surface dip rather abruptly 

southward, bringing the succeeding formation abruptly down to the 

level of the river, and the San Juan does not reappear in the canyonlike valleys of the streams in the eastern portion of the quadrangle. 

It is plain that in the entire valley of the Animas from Silverton to 

Animas Forks the volcanies rest upon a surface much lower than that 

which constitutes their base in Sultan Mountain. Whether this fact 

is due to an original depression in this area or to subsequent sinking 

has not yet been determined.
32 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Silverton series. The next volcanic series after the San Juan was 

termed the "Intermediate series" in the Telluride folio. It was 

very .much less developed there than either the San Juan below or 

the Potosi series above. The relations exhibited by the map (PL IV) 

in Potosi Peak and the mountains south of Canyon Creek are typical 

of what was observed throughout the Telluride quadrangle. But, as 

the map clearly shows, this formation increases rapidly in thickness 

eastward and covers, in fact, much the greater part of the Silverton 

quadrangle. It will therefore be known in future as the Silverton 

series, the undesirable term "Intermediate" being discarded. From 

a thickness of 300 or 400 feet in Potosi Peak the Silverton series 

increases to 4,000 or 5,000 feet in observed thickness near the center 

of the quadrangle. This series is a complex of andesitic flows and 

tuffs alternating with rhyolitic flows, flow-breccia, and tuff. In the 

Telluride quadrangle, and in raost places in the Silverton, its lowest 

member is a rhyolitic flow or flow-breccia of peculiar character. This 

is well seen in Potosi Peak, along the crest of the range west of 

Mineral Creek, and very near the summit of Sultan Mountain.

The relation of the different rocks to one another is very variable in 

different places. Rhyolite is seldom typical, and its largest masses 

are reddish flow-breccia that is to say, lavas of rhyolitic base containing many inclusions of both rhyolite and andesite. Very seldom 

indeed is the rhyolite free from these inclusions. The andesitic portion of the series consists of augite- and hornblende-andesites, and the 

relation of massive rock to tuff or agglomerate is extremely irregular. 

In all the central portion of the quadrangle the Silverton series 

appears to be principally composed of andesite, either fragmental or 

in flows. But in the Animas Valley the lowest exposed member of 

the complex, especially along the eastern side from Cunningham 

Gulch upward, is a rhyolitic flow-breccia of reddish or almost purplish 

color, so full of impurities that its character is not easily recognized. 

It appears either that these rhyolite flows were considerably eroded 

or that they piled up in quite irregular masses at eruption, for the 

surface upon which the succeeding andesitic rocks rest is extremely 

irregular, as will be shown by the final geologic map. The recurrence 

of rhyolitic material at various horizons within the series may be 

observed at many points. The Silverton series consists, then, of an 

irregular alternation of -two quite different rocks, erupted doubtless 

from different centers. They are grouped as one series, because the 

complex contrasts as a whole so markedly with the products of the 

San Juan epoch below them, which were purely andesitic and entirely 

fragmental as far as seen, and with the Potosi series above, which is 

almost entirely rhyolitic in character.

Potosi series. The uppermost series recognized in the Telluride 

quadrangle was termed the Potosi series from its occurrence in maximum development in the peak of that name, situated in the extreme
NAMES OF 

MINES AND PROSPECTS

ill ; J sS r ? m

5 | '
KANSOME.] OUTLINE OF GEOLOGY. 33

northwestern corner of the Silverton quadrangle. This series is distinguished as marking the beginning of an epoch of almost exclusively rhyolitic eruptions. For a time, at least, eruptions of more 

basic rocks were suspended. In Potosi Peak_itself, and, indeed, in 

the Telluride quadrangle, so far as this series was observed, the floor 

upon which the earliest Potosi lavas were outpoured was approximately level. But either the great development of the Silverton' 

series to the east or other causes have limited the distribution of the 

Potosi in this first observed simple relation to the other volcanics. 

No rhyolites which might be correlated with the Potosi series occur to: 

the east in the Silverton quadrangle until the rugged crest of the continental divide is reached. Here several summits, like Sheep Mountain, show light-colored, fluidal lavas at their summits, but they are 

not sufficiently like the Potosi rhyolites, as known to the westward, 

to fully justify at this time a certain correlation between them.

The rhyolitic lavas which occur in the higher summits of the northeastern portion of the quadrangle seem more nearly related to the 

Potosi type, but. further examination in the mountains of the Ouray 

quadrangle is necessary to show the true relations of these lavas to 

those of the Potosi series.

Stock eruptions. At a later period than that of the Potosi rhyolite 

there were in the western San Juan several eruptions of magmas; 

differing much in composition, and now seen in the form of rather, 

coarsely crystalline rocks penetrating the whole series of surface 

volcanics to the summits of the highest mountains.

In the Telluride quadrangle a series of these large stocks wero 

observed, in Mount Sneffels, and Stony Mountain, Ophir Neeclle.s, 

Grizzly Peak, and Mount Wilson, all of whose summits are in these 

stock rocks. There are also several stocks in the Silverton quadrangle,-, 

the largest being that of quartz-monzonite, the massive rock of the. 

mountains immediately southwest of Silverton. This stock has a 

very irregular outline. It extends from Copper Gulch on the west to 

the base of Kendall Mountain on the east, and the site of Silverton 

is eroded out of this mass. The northern boundary is very much 

concealed by talus slopes. The evidence that thfs stock cuts directly 

across both sedimentary and surface volcanics is clearly seen in. the 

exposures of the southern contact, on Sultan Mountain and Bear 

Peak. Smaller stocks of monzonite occur also in the lower part ot: 

Ounningham and Maggie gulches. A more basic rock of gabbroitic. 

character appears at the head of Henson Creek, where it is crossed 

by the wagon road leading to the divide.

Other intrusive rocks. The Silverton quadrangle is notable for 

several masses of a peculiar porphyry. This rock occurs in several 

small stocks; one of them forms a portion of the summit of Red, 

Mountain, another is on Bound Hill, while a third is seen at the head

Bull. 182 01 3
34 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

of Fflllmoon Gulch. A very completely decomposed mass of what is 

probably the same rock is seen on the north side of Mill Creek, and 

still another occurs to the west of Mineral Creek, between Mill Creek 

and the Middle Fork. This rock is characterized by large crystals 

of prthoclase which give it a very marked porphyritic structure. A 

very small occurrence of the same rock is found on the wagon road a 

short distance south of the Yankee Girl mine, and another in the knob 

north of the National Belle. Intrusions of rhyolitic, and probably 

of other rocks, are known in the surface volcanics of the northeastern 

part of the quadrangle, but their character has not yet been definitely 

ascertained.

A sheet-like mass of porphyry occurs at the eastern base of Sultan 

Mountain. It has been intruded in quite regular manner in the 

shales just above the Ouray limestone. Several other masses of 

porphyry, more or less distinctly in sheet form, with a few dikes, 

occur at the forks of Mineral Creek west of Silverton. In this 

vicinity all rocks are so extremely decomposed and are so extensively 

covered with glacial and other superficial material that the outline of 

the bodies is very difficult of determination.

A large body of porphyry of rude laccolithic outline occurs on the 

north side of Canyon Creek on the north border of the quadrangle. 

The representation of this mass on the map (PL IV) is provisional, 

for the topographic map of this region was revised after the porphyry 

mass had been examined. This mass is an intrusion in the Triassic 

beds and extends for some distance into the Ouray quadrangle. The 

cliffs of this mass are very notable as seen from the wagon road leading up Canyon Creek. The rock is usually very much decomposed.

Formations underlying the volcanics. As explained above, the 

volcanic rocks rest upon the greatly eroded surface of many older 

formations which have been repeatedly elevated and eroded at this

general center, producing a complex domal structure. The oldest 

formation displayed is the gneiss and schist series, in which the 

Animas Canyon is eroded for several miles, beginning about one rnile 

below Silverton. The rocks of this section have not yet been examined in detail, but will be studied in connection with the Needle 

Mountains quadrangle.

Associated with these gneisses and schists in the Needle Mountains is a series of quartzites and slates several thousand feet in 

thickness. These rocks cross the Animas a few miles south of the 

Silverton quadrangle line. A similar section is displayed in the 

picturesque canyon of the Uncompahgre from the north base of 

Abrams Mountain to Ouray. Here, too, there are some thousands 

of feet exposed, but neither the top nor bottom of the quartzite series 

is shown. On the south the earliest Paleozoic beds or the volcanic 

tuffs cover the quartzites and schists unconformably. On the north 

the Ouray limestone rests upon their upturned edges. This great
U.S.GEOLOGICAL SURVEY BU LLETI N No. 182 P L V

NAMES OF 

MINES AND PROSPECTS

BR08DIGNAG

ZUN1

YUKON TUNNEL

NORTH STAR

BELCHER (SULTAN MT.)

MONTEZUMA (FORMERLY BOSTON)

TUNNEL., HERCULES MINE 

EMPIRE TUNNEL, (HERCULES MINE)

KING 

MOLES

MABEL 

. MONTANA 

LITTLE RAY 

TITU9VILLE

31 SILVER LAKE MINE (MAIN ADIT 1

92 IOWA

23 ROYAL TIGER

84 BUCKEYE

25 NORTH STAR (KING SOLOMON)

26 DIVES

28 GREEN MOUNTAIN

23 PRIDE OF THE WEST

30 BIG GIANT

31 LITTLE GIANT

32 ASPEN

33 NEIGOLD

34 PHILADELPHIA

35 VETA MAORE

36 ANT1PERIODIC

37 BIG TEN

36 RIDGE WAY

39 HAMLET

40 GOLD NUGGET

42 LITTLE MAUO

LEGEND

Lode -Fi ssures

Mineral deposits other than 

' lodes, chiefly stocks

X Prospects

Nosharp distinctio 

between the two

S+rikeanddipof lodes

f Vertiical lodes

MAP OF THE SOUTHERN PORTION OF THE SILVERTON QUADRANGLE, COLORADO Economic features by F.L.Ran.0 me, 1899-1900

Scale

Contour interval 1OO feet
HANSOM*.! OUTLINE OF GEOLOGY, 35

series of old quartzites and slates has been assigned to the Algonkian 

period, chiefly from their lack of fossils, and because they may be 

thus plausibly correlated with the Algonkian rocks of the Grand 

Canyon of the Colorado.

The earliest Paleozoic formation is a quartzite with some sandj^ 

shales 100 to 200 feet thick, which is seen on the west side of the 

Animas from the rnonzonite contact to Molas Lake, and imperfectly 

on the east side of the Animas. This quartzite has been traced down 

the Animas to a point below Rockwood, and is called the Ignacio 

quartzite from its characteristic development on the bench where the 

lake of that name is situated. A southerly dip carries this quartzite 

onto the southern slope of the Needle Mountains, and there a few 

indistinct fossils have been found which indicate its Cambrian age.

The rather shaly beds, often calcareous, succeeding the quartzite 

have as yet yielded no fossils. If there are any Silurian strata in

this section they are probably represented by these calcareous shales 

and sandstones.

The next formation recognized is a heavy white limestone about 

200 feet in thickness, which is seen resting directly on the Algonkian 

quartzites just south of Ouray, and has been called from this locality 

the Ouray limestone. In the Animas region this limestone rests upon 

the calcareous shales just mentioned. A few .Devonian fossils were 

found in this limestone by F. M. Endlich during the Hayden survey. 

At the present time a quite characteristic Devonian fauna has been 

obtained from this limestone at various places.

Following the Ouray limestone there is a stratigraphic break. 

Some formation of Lower Carboniferous age should appear at this 

horizon, and some fossil evidence has been obtained to show that at 

least remnants of that formation may be found on careful search. 

But the great series of Upper Carboniferous rocks called the Hermosa formation come nearly or quite in contact with the Ouray limestone in many places. This series of alternating limestones, grits, 

and sandstones is about 2,000 feet thick and forms the imposing 

scarp facing the Animas Valley on the west side. The same beds 

form notable cliffs about the town of Ouray. From the limestone 

members a very characteristic Upper Carboniferous fauna has been 

obtained.

At Rico the uppermost division of the Carboniferous was found to 

be characterized by invertebrate fossils of the Permo-Carboniferous. 

Three hundred feet of strata have been grouped together as the Rico 

formation. Evidence is not yet sufficient to demonstrate the presence 

of the Rico strata in the Silverton quadrangle.

Following the Carboniferous comes the well-known series of reddish 

grits, sandstones, and conglomerates ordinarily known as the Red 

Beds. This series has been termed the Dolores formation from its 

occurrence along the Dolores River, and evidence of its Triassic age
36 ECONOMIC GEOLOGY OF SILVEKTON .QUADRANGLE. [BULL. 182.

has been found in the upper part of the formation. These strata are 

seen in Canyon Creek and in the southwestern corner of the Silverton quadrangle. All the Paleozoic and Mesozoic formations named 

exhibit a clomal structure by their prevailing dips to the north or to 

the south, away from the center in the Silverton quadrangle. Beyond 

the borders of this quadrangle the other formations of the Mesozoic 

appear.

Prevolcanic surface and the Telluride conglomerate. The Hay den 

map represents the volcanic complex of the San Juan as resting on 

a general plane surface eroded across many different formations. 

Over considerable stretches the base of the volcanics is represented 

as approximately level. A detailed examination of the Telluride 

quadrangle showed that the San Juan tuff was in that region everywhere underlain by a conglomerate free from volcanic material but 

containing pebbles of very hard sedimentary rocks, Mesozoic and 

Paleozoic, with schists, granites, and Algonkian quartzites, such as 

may be seen in the Needle Mountains; that is to say, this conglomerate contained in its pebbles the record of an enormous erosion, such 

as would be required to produce the surface upon which the volcanic 

formations in general rest.

This conglomerate below the volcanics was first called the San 

Miguel conglomerate. It is now necessary to replace that name by 

another, as it has been found that there is a prior use of that term for 

a Cretaceous formation in Texas. It is therefore proposed to rename 

this conglomerate below the San Juan tuff the Telluride conglomerate, or formation, on account of its typical exposures and relations, 

clearly seen about the town of that name and, indeed, throughout 

the Telluride quadrangle. The Telluride formation varies greatly 

in thickness; it is almost 1,000 feet thick in Mount Wilson, on the 

western border of the Telluride quadrangle. It is 700 feet thick in

Sheep Mountain, southwest of Trout Lake, and from that point thins 

gradually eastward to Sultan Mountain in the Silverton quadrangle, 

where, on the eastern slope, it has an average thickness of about 30 

feet. To the east of the Animas this conglomerate is not continuously 

developed, but is found occupying hollows in the surface of gneisses 

and schists. The San Juan tuffs resting upon it bury the small prominences separating these hollows, and the Telluride conglomerate is, 

as a rule, not conspicuous. It is very distinctly seen, howrever, 

beneath the San Juan on both sides of Whitehead Creek. The same 

thinning of the Telluride conglomerate occurs between Telluride and 

the exposures in Canyon Creek. The conglomerate is very clearly 

exposed upon the wagon road leading up the north side of Canyon 

Creek, and is probably continuous along its southern side to the valley 

of Red Creek, but beyond that to the east is seen only in disconnected exposures. It is thought probable that the same formation 

occurs beneath the volcanics in the lower country east of the Uncompahgre River in the Ouray quadrangle.
HANSOSIE.] OUTLINE OF GEOLOGY. 37

Structure of the pre-TeUuride formations. The domal structure 

which has been referred to is clearly seen in the Animas Valley from 

the Grand Turk Mountain southward. The formations here have a 

southerly or southwesterly dip, which prevails with some undulations 

to a point below Durango. Westerly dips prevail in general in the 

Telluride quadrangle, and northerly dips are seen in the Uncompahgre 

Valley from Ouray downward. A local structure of interest is seen 

directly east of Sultan Mountain in the Animas Valley, where the 

Ignacio quartzites, the Ouray limestones, and the lower Hermosa beds 

dip rather abruptty northward. The original extent of this fold is 

not now plain, for these beds are cut off sharply by the great quartzmouzonite stocks, beyond which only volcanic rocks are known for 

a number of miles. An interesting evidence of the structure of the 

Paleozoic beds is also seen in Ironton Park. The well-known deposits 

of the Saratoga mine seem quite clearly to be in the horizon of the 

Ouray limestone, resting upon Algonkian quartzites, as in the Uncompahgre Valley. They have a westerly dip, which carries them quickly 

below the level of the park, but along the road on the western side a 

very few feet of grits may locally be found beneath the San Juan tuffs.

These beds of Ironton Park are supposed to represent the known 

eastern limit of the sedimentary section which must be continuous 

beneath the volcanics and which reappears at Telluride, in the drainage of the San Miguel River.

Faulting. Displacements of the volcanic rocks by faulting are 

numerous, but it is in most cases difficult to ascertain the amount 

and character of the displacement. It is supposed that many of the 

faults seen in the eastern part of the quadrangle, especially in or near 

the valley of the Lake Fork, have a very considerable throw. In 

other parts of the area dislocation is, as a rule, comparatively slight. 

An exception to this statement is afforded by the faults bounding the 

rhyolite body of Porphyry Gulch, near the head of Mineral Creek. 

Here there appears to be a sunken block of Potosi rhyolite bordered 

"by faults, some of which are very clearly exposed. Minor faults 

occur particularly in the southern parts of the quadrangle, on either 

side of the Animas.

In that region there are faults which seem to be of an earlier date 

than the volcanic eruptions, but they can be identified as prevolcanic 

only where they are found- to stop at the lower surface of the San 

Juan. Two such faults are seen in Cunningham Gulch above the 

Highland Mary mine. Between these faults a block of Ouray limestone has been dropped, and outcrops of that formation occur on each 

side of the main gulch. These faults do not affect the San Juan tuffs 

above the Ouray limestone.

Landslides. The Telluride quadrangle is an area of important 

landslides, especially on the steep western face of the San Juan, where 

the Telluride conglomerate* rests on soft Cretaceous shales. Two' of 

these slide areas are several square miles in extent and huge blocks
38 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

have slipped en masse. Minor slides were also noted in several of the 

gulches of the mountains about Telluride.

The Silverton quadrangle has also been the scene of landslides on 

an unusually grand scale. The principal area of landslides, shown 

on PL IV, embraces the country oh both sides of Red Creek from, 

the lower end of Ironton Park1 to the head of Mineral Creek, and 

extends vertically up the adjacent slopes for several hundred feet, or 

in places 1,000 feet. That landslides have occurred in this region 

will be evident to all who carefully examine the topographic detail 

within the areas outlined. This detail is unfortunately too small to 

admit of expression on the scale of the topographic map. Apparently 

the movement has been very superficial in comparison with the greatslides of the Telluride quadrangle. It has taken place in hundreds 

of separate small blocks, which are now outlined by trenches or sinks 

back of the knolls representing the separate masses. When shadows 

are cast in the right direction the individual knolls of this slide area 

stand out very clearly. PL VI represents a small part of the landslide 

surface in the vicinity of the Guston mine.

The occurrence of such an area of landslide material is especially 

interesting in this case because of the fact that the Yankee Girl, 

Guston, Robinson, Vanderbilt, Paymaster, and other mines are in the 

heart of the area affected. Since in some cases the ore bodies were 

traced continuously from the surface downward to depths of over 

1,000 feet, it is plain that not all of the surface rock has suffered dislocation, but it is a notable fact that at each one of these mines there 

is a mound or hill of much-altered rock which stands up as an outcrop in place in the midst of the greatly fractured rock which has 

slipped downward to an unknown extent through the landslide 

action. The contrast between a hill of rock in place and the knolls 

representing landslide blocks surrounding it is very striking in the 

case of the hill above the Paymaster mine. A critical examination 

of the mountain side at this point clearly shows that this hill must 

have been a still more prominent point before the landslide epoch. 

The great multitude of small slide blocks descending from the higher 

slope have 'almost covered Paymaster Hill and have swept down oh 

either side to the level of the main gulch. Whether this landslide 

material may have entirely concealed mounds of altered rock corresponding to those so prominent at the mines mentioned is an interesting problem to which Mr. Ransome refers.

The evidence of landslide action is chiefly that of the topography, 

which is entirely irregular and can not have been produced by ordinary erosion. The mounds or knolls can not be regarded as roches 

moutonnees because of the completely fractured character of the rocks 

found in them and the fact that many of them are soft tuffs, quite 

incapable of having resisted moving ice to form a scoriated mound. 

It is also notably the case that rocks of entirely different character
U. S. GEOLOGICAL SURVE

VIEW OF PRINCIPAL RED MOUNTAIN MINES, FROM THE NORTH, 

The view shows the character of landslide topography. The Guston and Robinson mines ate on the left; the roof and smo

while beyond, on the sky line, is the knoll on which the National Belle is located. 
KANSOME.] METHODS OF MINING AND TREATMENT OF ORES. 39

and different states of preservation are found in juxtaposition, breaking the continuity which is normal where the formations were not 

thus dislocated.

Landside action of similar character has been very prominent about 

Rico, in the heart of the Rico Mountains. 1 The result is to produce 

broad topographic forms of rather gentle outline, modified by many 

small ridges, knolls, and trenches. Such fractured material is now 

necessarily in process of further disintegration. Indeed, certain parts 

of the landslide area adjacent to Ironton Park have been so smoothed 

out by the ordinary creeping down the slopes of the much-fractured 

rock that the landslide character is rather obscure. Landslide action 

on so gigantic a scale is at present attributed to violent earthquake 

shock. Only some such violent local force seems adequate to explain 

the enormous slides of the Telluride quadrangle, and the explanation 

is most plausible in view of the volcanic history of the region.

METHODS OF MINING AND TREATMENT OF ORES.

It is not proposed in this section to go into an exhaust.! A'e account 

of mining methods and metallurgical processes. Such a discussion 

would be outside the scope of the present report and would necessitate 

the collection of detailed data of a kind not contemplated in planning 

geological field work. A brief statement of methods and approximate 

costs may, however, be of use to readers having no practical knowledge of this district or of the modes of procedure followed in it.

Owing to the exceedingly rugged character of the country, the 

larger mines, with the exception of those in the Red Mountain district, 

are almost all worked through adit tunnels. Although involving, as 

a rule, greater initial expenditure, and, in the case of crosscuts, 

necessitating much "dead work," such adits have for large mines 

undoubted advantages in this region over shafts. They obviate the 

need of pumping, and when, as is commonly the case, there is vertical 

connection with the surface through old workings, they greatly simplify 

the problem of ventilation. In. a region so elevated as the San Juan 

an adit tunnel possesses great advantage in that it allows the mine 

entrance and buildings to be placed as low down as possible, where 

they can be better sheltered from the winter snow, and where water 

and timber can be more readily utilized. In several of the larger 

mines, such as the Silver Lake and Tomboy, shafts are sunk from the 

adit levels, and hoisting and pumping machinery are installed m 

underground stations.

The levels are usually, although not uniformly, about 100 feet 

apart, and the ore is worked out by overhand stoping. It is usually 

allowed to fall on canvas and roughly sorted from the waste. The 

stopes are sometimes left open, sufficient timbering being carried up

1 Geology of the Eico Mountains, Colorado, by Whitman Cross and Arthur Coe Spencer: 

Twenty-first Ann. Kept. U. S. Geol. Survey, Pt. II, pp. 129-151.
40 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [HULL. 182.

for working purposes. But the more approved practice is to nil in 

the stopes as the work proceeds, blasting out material from the walls 

if necessary. In many cases this filling is successfully combined with 

systematic prospecting of the wall rock on. both sides of the vein, often 

resulting in. the discovery of ore which would otherwise have, been 

overlooked. Underhand stoping is, however, practiced in a few mines, 

as in the Sunnyside, where the proportion of waste which it is necessary to move is small in comparison with the ore.

Machine drills are not generally employed, save in running long 

crosscuts. The progressive Silver Lake mine began, however, to 

employ several Siemens and Halske electric drills in its stopes in 1899.

In mines of moderate output the ore is taken directly from the ore 

chutes and run out in single cars pushed by a man or a boy. In the 

Silver Lake mine the ore collected from the various drifts and levels 

is all dumped into ore bins in the main underground station on the 

adit level, and thence taken out to the mill in a train of cars drawn 

by a mule. In the Revenue tunnel, which is over 7,400 feet in length, 

and from which the daily output is some 200 tons of crude shipping 

.ore and an additional amount of milling ore sufficient to furnish 30 to 

40 tons of concentrates, the ore is drawn out iii a train of cars operated 

by an electric locomotive. The tunnel is furnished with a double 

track, but practice has shown that even in an adit of this length a 

single track is amply able to accommodate a much greater output 

than that now handled.

Many of the mines being situated' above timber line in the high 

basins, frequently from 2,000 to 4,000 feet above the main roads, the 

proper location of the mill and the mode of transportation of the ore 

and concentrates to the nearest railway are problems which must be 

solved for each mine. Owing to the scanty and intermittent character 

pf the water supply, it is seldom practicable to mill the ores at the 

altitude of the adit tunnel. An exception must be made in the case 

of the Silver Lake mine, where water for the mill is obtained by pumping from the adjacent lake. But in most cases the mill is built any. 

where from a few hundred to several thousand feet below the mine. 

The primitive method of packing the ore down on backs of burros to 

the shipping point or to the mill is in use by nearly all the small mines 

and prospects. But. in well-equipped mines, located above timber 

line, the wire-rope tramwa}r performs an office which makes it indis- 

.pen^able in the mining development of so rugged a country. These 

tramways are of various patterns, from the lightly constructed Huson 

.;tram, with its small fixed buckets and single rope, to the substantial 

Bleichert, with large detachable buckets drawn over a fixed rope and 

supported by well-constructed towers of timber. The Bleichert. tramway of the Camp Bird mine in 1899 was running about 45 buckets, 

each bucket carrying about 700 pounds of ore. One man is able-to 

dispatch 350 buckets a day. This, however, is~ by no. means the'full
HANSOME.-] METHODS OF MINING AND TREATMENT OF ORES. 41

capacity of the tramway, it being restricted in this instance by the 

limitations of a small Htison tramway which was bringing ore down 

from upper workings to what is now the main adit. The expense of 

running these well-constructed gravity tramways is comparatiArely 

small, and they are remarkably smooth and efficient in operation.

The ores Of the Silverton quadrangle are commercially divisible 

into shipping ores, and milling ores. The former are shipped direct 

to the smelter as crude ore. They include such high-grade ores as 

can not be treated economically by simple milling processes and such 

ores as contain but a small proportion of worthless gangue. The 

milling ores include such gold ores as can be readily amalgamated or 

concentrated and those silver-lead ores in which .the valuable minerals are associated with considerable quartz or other gangue material. Most large mines produce both grades of ore, while the output 

of the smaller mines, without mills, is necessarily usually restricted to

shipping ore. Exclusive of the ore from the Revenue tunnel, which 

really comes from the Telluride quadrangle, the bulk of the crude 

ore at present shipped from the Silverton quadrangle goes to the 

American Smelting and Refining Company's smelter, at Durango. 

Heavy lead ores preponderate. The treatment charge varies from $2 

to $13, the higher rate being for siliceous or "dry" ores. An extra 

chare of 50 cents per unit (1 per cent of 1 ton) is made for ores running over 10 per cent of zinc.

The treatment of milling ores varies considerably with their character. Formerly many lixiviation plants, usually employing some 

modification of the original Augustin process, were installed in the 

region for the treatment of argentiferous ores. This process, involving a chloridizing roasting of the ore and subsequent leaching out of 

the chloride of silver by the use of strong brine, proved successful in 

treating the ore of the Polar Star mine, about 95 per cent of the silver 

being saved. In many cases, however, it Avas a failure, the ores not 

being adapted to its employment. At the present time it is no longer 

used. Mechanical concentration, coupled in some cases with amalgamation, has entirely replaced the various chemical processes, and the 

concentrates thus obtained are shipped to the smelters.

The silver-lead ores, carrying usually some gold and copper, are 

crushed by rolls or stamps and, after proper sizing in revolving 

screens, are concentrated by means of jigs and shaking tables. For 

this purpose the Wilfley table is most in use, although Woodbury, 

Bartlett, and Canimett tables and Frue vanners are also employed, 

and a special form of "end-shake" table is in use in the Silver Lake 

mill for saving the slimes. A^7 here the ore to be treated is. rich in 

galena the tendency in most of the newer mills is to substitute 

rolls for stamps. Huntington mills are frequently employed for 

regrinding tailings.

The richer ores, carrying free gold, require different treatment. In
42 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

the thoroughly modern mill of the Camp Bird mine the equipment is 

similar to that which has been found best adapted to the free-millinggold ores of California. The ore passes from the crusher directly to 

the stamps, weighing 800 pounds and dropping 90 times a minute. 

The pulp passes through a 40-mesh screen to the amalgamating 

plates, where from 75 to 80 per cent of the value is caught. It is 

then passed through classifiers and over Frue vanners, the latter 

being so arranged that the pulp before being allowed to escape as 

tailings passes over two vanners. The ore commonly run through 

this mill averages from $100 to $200 per ton and is frequently much 

higher. The tailings run from $3 to $5, part of which is recovered 

in a small auxiliary mill. 1 Considering the peculiar character of the 

Camp Bird ore, which will be elsewhere described in this report, this 

showing is rather remarkable. Between mills of this type and the 

more complicated equipment required for treating lower-grade argentiferous ores there are all gradations, as will appear when each mine 

is described in detail. At the Tomboy mine, which produces a gold 

ore, the ore is crushed by rolls and ground in Huntington mills before 

passing over the plates, no stamps being used.

The various mills will be described in the detailed accounts of the 

individual mines included in this report.

The conditions under which the several mines operate differ so 

widely that it is impossible to assign a definite lower limit to the value 

of ores which can be profitably extracted. Ores ranging in value from 

$6 to $12 a ton are perhaps as of low a grade as can be now worked, 

even on a considerable scale and with modern equipment. For many 

of the smaller mines, however, this limit must be doubled. The Red 

Mountain mines were expensive to operate on account of the irregularity in the disposition of their ore bodies, their corrosive waters, and 

the necessity of pumping and hoisting through shafts. In 1888 the 

New Guston, then beginning operations on an extensive scale, paid 

dividends on ore mined at a cost of $53.50 per ton. The lowest annual 

cost per ton was $9.60 in 1894 on ore worth only $12.80 per ton. Location, power, timber, water, kind of country rock, and character and 

amount of ore form a complex set of factors, which fully accounts for 

the range- in the limiting value between workable and nonworkable 

ore. Compared with $1.35 per ton, which in 1894 covered the entire 

cost of mining and treatment of the ore from the Alaska-Tread well 

mine, 2 or the $2.50 to $5 per ton which covers the similar expense.in 

many deep California gold mines, the figures given above seem high. 

But the difference is sufficiently explained by the difficulties inseparably connected with mining in so rugged and elevated a region and by 

the more involved processes required for the treatment of complex

1 In 1900 a modern cyanide plant was being erected to treat the tailings directly from the mill. 

It is now in operation.

2 Reconnaissance of the gold fields of southern Alaska, by G. F. Becker: Eighteenth Ann. Rept. 

U. S. Geol. Survey, Pt. Ill, 1898, p. 64.
RANSOME.] CLASSIFICATION OF THE ORE DEPOSITS. 43

ores, the concentration of which is often rendered troublesome by the 

presence of sphalerite and barite, and which almost invariably require 

smelting.

CLASSIFICATION OF THE ORE DEPOSITS.

The ore deposits of the Silverton quadrangle may be conveniently 

classified and described under three heads: (1) Lodes, (2) stocks or 

masses, and (3) metasomatic replacements. To the first class belongby far the greater number of the deposits that are being worked at 

the present time. To the second class are assigned most of the ore 

bodies formerly worked in the Red Mountain district, often locally 

known as "chimneys." In the third class, by far the least important 

in this quadrangle, are placed a few deposits occurring in limestone 

or in rhyelite.

In the classification of actual ore deposits it is usually found that a

given ore body presents features common to two or more Ideally distinct types. Thus a fissure vein may be accompanied by some replacement of the adjacent country rock, or it may be found impossible to 

draw any definite line between impregnation l .and total metasomatic 

replacement. The present field offers no exception to this general, 

difficulty, and the division of the ore deposits here made is not to be 

regarded as in all cases discriminating between totally different 

things. The aim is to group the deposits broadly, under most prominent characteristics of occurrence, in order that they may be conveniently and systematically described.

THE LODE FISSURES. 

DEFINITIONS.

By fissure, as used in this report, there is meant a somewhat extensive fracture in the rocks. Such a fissure is not necessarily accompanied by recognizable faulting, nor by the production of visible 

open spaces, nor by mineralization. According to the classical definition of Von Cotta, 2 a vein is the filling of a fissure. As designating 

a simple type, of frequent occurrence, it seems very desirable that in. 

accurate description the term vein should retain this significance, 

i. e., a "true vein" or fissure vein. In mining speech, however, 

the word commonly has a broader meaning, and is made to include 

not only the filling of a preexisting fissure, but also, in many cases, 

more or less altered and impregnated country rock alongside the fissure. Frequently the " vein " of the miner is a sheeted zone, embracing several veins in Von Cotta's sense, or it may be a zone of more 

or less irregular ore-bearing stringers. For this reason, lode will be

1 As used in this report, impregnation is merely a structural term indicating the fine dissemination of ore particles through a rock mass. In the majority of cases it involves true metasomatic replacement.

2 Die Lehre voii den Erzlagerstatten, 2d ed., Freiberg,' 1859, p. 103.
44 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL.182.

consistently used throughout this report, as a more general term than, 

vein, to designate either a simple filled fissure or a zone of closely 

spaced fissuring with possibly more or less impregnated or replaced 

country rock. Lode thus includes what Yon Gotta and Von Grodtleck 2 have called complex A^eins (zusammengesetzte Gauge). 1

A similar usage has been followed by Emmons and Tower 2 in their 

description of the ore deposits of Butte, Mont., and to some extent 

by Purington 3 in describing the ore deposits of the Telluride quadrangle.

DISTRIBUTION OF THE ORE-BEARING FISSURES.

Fractures in the rocks, containing more or less ore, are widely distributed within the quadrangle, but are larger, more abundant, or 

richer in metalliferous contents in certain limited districts than elsewhere. Prospects occur thickly dotted over the whole area, but the 

important mines are found in more or less isolated groups. A partial 

idea of the distribution of the fissures may be gained from the accompanying map (PI. Ill), on which but a small proportion of the actual 

fractures are indicated. Moreover, in plotting the lodes the smaller, 

poorly exposed, and apparently nonworkable ones must necessarily 

be often disregarded, and the map can not therefore be taken as showing strictly the true distribution of all the fissures, but onty of those 

which are superficially conspicuous or which carry ore in sufficient 

quantity to be worked or prospected. As the map suggests, fissures 

carrying variable amounts of ore are less noticeable features in the 

southwest and southeast corners of the quadrangle than elsewhere. 

But they occur in all the rocks which possess any considerable, distribution within the area, from the Algonkian (or Archean?) schists, 

which constitute the basement formation of the region, to the latest 

monzonitic intrusions that cut the Tertiary .volcanic series. By far 

the greater number of them, however, are found in the volcanic rocks 

of the Silverton and San Juan series. This is apparently due chiefly 

to the fact that these rocks occupy the greater part of the quadrangle 

rather than to any special determining factor in the rocks themselves. 

It is admittedly difficult, however, to isolate such a possible factor 

from others more directly associated with the origin and accumulation 

of these rocks than with their texture and structure. Whether the 

productive ore bodies that fill some of the fissures are as impartially 

distributed in the various formations as the fissures themselves is a 

different question and will be discussed in another place.

The existence of local areas of especially pronounced fissuring and 

mineralization has already been pointed out. Silver Lake Basin may 

be cited as a center of one such areal group of fissures. Not only are

1 Die Lehre von den Lagerstatten der Erze, Leipzig, 1879, p. 35.

2 Geologic Atlas U. S., folio 33, Butte special.

3 Preliminary report on the raining industries of the Telluride quadrangle, Colorado: Eighteenth Ann. Eept. U. S. Geol. Survey, Pt. Ill, 1898, p. 772.
RANSOMS.] COORDINATION OF "THE FISSURES. . 45

the fissures within and around this basin exceedingly numerous, but 

many of them contain large and productive ore bodies. Another area 

is. that of Galena Mountain, where the fissures are well exposed and 

form a remarkable network, but have not hitherto proved to contain 

ore bodies of great value. As still other centers of conspicuous fissuring may be cited the heads of Treasure and Poughkeepsie gulches, 

Ross Basin, and Mineral Point. These last four local districts of vigorous fracturing are not distinctly separated, and should perhaps be 

included together as a single area over which fissuriug and..subsequent veining has taken place on an extensive scale. Finally, the 

region embracing Savage, Imogene, and Silver basins, in the northwest corner of th'e quadrangle, in which are located the Virginias and 

Smuggler-Union mines, may be regarded as part of a very important 

district of strong ore-bearing fissures, lying chiefly within the Telluricle quadrangle.

COORDINATION OF THE FISSURES.

By the coordination of the fissures is meant their arrangement in 

natural systems, based upon direction, size, persistency, or other 

features. In the present instance the trends of the principal fractures will first be discussed, and afterwards the coordination of minor 

local groups of fissures occurring in various portions of the quadrangle will be considered.

If fissures were always vertical and were bounded by plane surfaces, 

it would be possible to represent them on a map, such as PI. Ill, by 

straight lines. Moreover, a single careful observation along a short 

exposure of any fissure would afford sufficient data for accurately 

laying off the direction of the line on the map. It might then be 

possible to classify these fissures with mathematical precision and 

divide them into groups or systems, each system being characterized 

by a certain common direction.

But actual fissures seldom conform to these conditions. They 

stand at various angles to the horizon and are often curved. The 

existence of curves of large radii where it is evident that the mapped 

curvature is not the result of the combination of dip and topography 

is illustrated by several of the lodes plotted on the accompanying map, 

PI. III. The existence of minor curves may be well seen in almost 

any plan of the underground workings of a mine exploiting a fissure 

deposit. These facts interfere materially with the discussion and 

classification of the fissures of a given region as a simple problem in 

plane geometry. It is obvious that single observations of the course 

of a fissure in a drift can not be assumed as giving its general strike. 

Nor is it practicable to tabulate such observations at least in this 

region and thereby to set up A^arious systems of fractures traversing 

the region, each system narrowly confined and accurately distinguished from other systems by a difference of only a few degrees in 

trend.
46 ECONOMIC C4EOLOGY OF SILVEKTON QITADKANGLE. [Bur-r,.182.

In the Silverton region the important fissures have been mapped in 

the field with reference to the topography. The lines as shown are 

approximations to truth, requiring much allowance for necessarily 

limited observations and for imperfections of the topographic map. 1

Inspection of the map on which the prominent lodes are thus platted 

shows that the most conspicuous Assuring has taken place in a general 

northeast and southwest direction. The dip of these fissures is usually 

southeast at about 75°. But the angles of dip range from 40° to vertical, and a few of the lodes dip northwest. Perhaps slightly less 

marked, but thus far more economically important, are numerous 

strong lodes running in a general northwest and southeast direction. 

In the southeastern quadrant these usually dip northeast at angles 

varying from 50° to 90°. Else where they usually, although not invariably, dip southwest at high angles, as observed by Purington in the 

Telluride area. The existence of these two dominant directions was 

long ago pointed out by Endlich. 2 Purington, 3 in his description of 

the fissures of the neighboring Telluride quadrangle, concludes that 

"there are four general directions of fissuring: (1) East and west, and 

(2) northeast, best developed in the central and southeastern portions 

of the quadrangle, and (3) north and south, and (4) northwester^, 

best exemplified in the northwestern portion." It will be seen that 

the two most prominent directions of fissuring in the Silverton area 

coincide with Purington's second and fourth general directions in the 

Telluride quadrangle.

There occur in the Silverton quadrangle several approximately 

north and south, as well as nearly east and west, lodes, and if attention were restricted to certain small areas, such as Galena Mountain, 

it might be considered advisable to recognize one or both of these 

directions as characterizing distinct subordinate systems of fractures. 

Such a grouping, however, while valid for the very limited area named,

is lost when the various directions of all the fissures in the quadrangle 

are taken in-to account. The possible number of such subordinate 

systems then becomes so large as to obliterate the divisions between 

them. For accounts of these minor directions of fracturing the readeris referred to the latter part of this section, where their coordination 

is discussed, and to the detailed descriptions of the various local groups 

of lodes in the later pages of this report. It is sufficient in this place 

to point out that the fissuring of the rocks throughout the quadrangle 

has been so thorough and has taken place in so many directions that 

two of these only stand out as dominant. Even these show a certain localization within the limits of the quadrangle, the northeastsouthwest fissures notably predominating in the northeast quadrant,

1 The topographic map upon which most of the lodes were originally laid down was partly 

revised during the year 1900, and these lodes had then to be transferred and adapted to the new 

map in the office a procedure which may lead to occasional unavoidable errors of position 

 with reference to minor topographic features.

2 Hayden Survey, Ann. Rept. 1874, p. 232. 3 Loc. cit, p. 767.
KANSOMK.] COORDINATION OF THE FISSURES. 47

while the northwest-southeast fissures are the more persistent in the 

southeast quadrant.

In the accompanjnng diagram (ftg. 1) the lodes represented upon 

the map have been platted as straight lines passing through a common central point. In the case of moderately curved fissures the 

line represents the average general direction. A few sharply curved 

lodes have been treated as if they were formed by two intersecting 

fissures, and represented in the diagram by two lines. The figure

FIG. 1. Diagram showing courses of some of the lode fissures of the Silverton quadrangle.

brings clearly before the e}res the great variety of direction assumed 

by the relatively few fissures which have been mapped as lodes. It 

fails, on the other hand, to express the relative persistency and individual importance of the various fissures represented, and in so far 

only partially brings out the prominence of the northeast-southwest 

and northwest-southeast lodes: *

In a region traversed by such a great number of fissures, trending 

in so many different directions, it is not difficult to construct fanciful 

relationships. Few of the latter are more popular than that which
48 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [HULL. 183.

makes all the important lodes radiate from one or more points 

extinct volcanoes being generally preferred. That there is a certain 

radial disposition of the fissures will be presently shown, but this 

arrangement is very different from that which has been sometimes 

supposed, and which has been described in intendedly serious publications.

Having considered the various directions taken by the fissures in 

the region as a whole, it remains to discuss certain mutual relations 

in regard to direction exhibited by the fissures of several small areas. 

In spite of the wide'diversity of strike already dwelt upon, and illustrated in fig. 1, it is nevertheless true that in certain limited portions 

of the quadrangular area one or more systems of fissures, characterized ~by fairly accordant directions of strike, are easily recognizable. 

In many cases these parallel fissures are so small and carry so little 

ore or vein matter that they have not been indicated on the map. 

Moreover, they are at places so closely spaced as to render it impossible to show them on the scale here employed for the topographic 

mapping.

On the west side of Silver Lake Basin, in addition to the productive 

lodes, such as the Iowa, New York City, and Stelzner, the country 

rock is traversed by a great number of smaller fissures, striking from 

20° to 40° west of north, and resulting in a pronounced sheeting of 

the rock, generally parallel with the lodes mentioned, but without 

recognizable regular or rhythmical spacing. These fissures are nearly 

vertical, but one group of them sometimes exhibits a steep northeasterly dip, while another group dips southwesterly. Many of them 

are ore bearing, and it is not uncommon to see on a clean surface of 

rock a vein an inch or so wide composed of quartz and galena in 

about equal proportions. Such mineralized stringers may be seen to 

branch or to wedge out completely in a distance of 40 or 50 feet and 

be succeeded by an overlapping veinlet a few inches to one side. On

a smaller scale they repeat the phenomena observed underground in 

the nearly parallel lodes, such as the New York City, belonging to 

Group II of the Silver Lake Basin lodes. (See detailed descriptions, 

pp. 145-148.) They appear to belong to the same system and to have 

been formed at the same time as the latter.

Two prominent sytems of parallel fissures, intersecting nearly at 

right angles, are noticeable in the cliffs at the head of Arrastra 

Gulch. One system, with a strike .of about N. 32° W., and a dip of 

from 75° to 80° to the northeast, runs generally parallel with the 

trend of the gulch, and divides the compacted breccias of the Silverton series into great plates from a few inches to several feet in thickness. The width of this sheeted zone is from 30 to "40 feet. These 

fissures may perhaps be placed in the same system as those just 

described west of Silver Lake, and were possibly formed at about the 

same time. But they apparently contain neither ore nor quartz, and
EANSOME.] COORDINATION OF THE FISSURES. 49

may be of later date. The second set of fissures, with a strike of N". 

60° E., and a southeasterly dip of about 80°, crosses the gulch near 

its head, and may be seen also in Blair Gulch, in a considerably 

broader zone than the first set. Some of these fractures contain 

quartz, but, so far as observed, are not heavily mineralized and carry 

only a little pyrite. The relative ages of these two systems of intersecting fissures were not directly determinable in the field. It is not 

improbable that they were formed simultaneously as conjugate fissures. (See pp. 52-53).

Minor systems of fractures in parallel coordination may be well 

studied on Galena Mountain, a precipitous peak composed of both 

massive and fragmental andesite. The mass of the mountain is cut 

by very numerous fissures, many of them prominently indicated on 

the surface as lodes or veins. These maybe divided into four groups, 

the members of each group being characterized by approximately the 

following strikes: (1) N. 45° E., (2) N. and S., (3) K 25° W., and (4) 

1ST. 65° W. In each of these systems there usually occurs one or more 

fairly strong lodes accompanied by numerous smaller, nearly parallel, 

fissures, the rock being conspicuously sheeted. These associated parallel fissures are particularly abundant in the K. 25° W. system, as seen 

on the southern declivity of the mountain, in the vicinity of the Yeta 

Madre mine. They are generally nearly vertical, and rather closely 

spaced, a foot or less apart. They are usually occupied by small 

veins which sometimes carry ore minerals, chiefly -galena, sphalerite, 

and chalcopyrite, but which are seldom large enough or rich enough 

to be Avorked.

Another area within which the fissures exhibit striking parallel 

coordination is on Treasure Mountain and at the head of Placer Gulch. 

The dominant northeast-southwest fissure system of this portion of 

the quadrangle is exemplified by a series of strong, persistent lodes, 

represented by the Sunnyside and Scotia, with a general course of 

about N.-400 E. The dip of these is southwesterly at high angles. A 

second system of shorter, less conspicuous fractures crosses the first 

series almost at right angles, with a general course of about N. 55° W. 

These fissures are nearly vertical, but the majority of them dip southwest at high angles. In their trends these fractures ?Delong with the 

system of northwest-southeast fissures already recognized as a system 

characteristic of the quadrangle as a whole. It is interesting to note 

that here, however, they are not, as in the Silver Lake Basin, the 

master fissures, but are short, transverse, relatively unimportant fractures, forming a nearly rectangular network with the strong, continuous northeast-southwest lodes. A third local system of transverse 

veins, represented by the Golden Fleece, has a course of about N. 

75° E., with usually steep southerly dip. Still a fourth set of very 

prominent lodes is exposed at the head of Placer Gulch, with an 

average strike of about N. 25° E. Their dips are usually steep and

Bull. 182 01 4
50 ECONOMIC GEOLOGY OF SILVEETON QUADBANGLE. [BULL. 182.

easterby. There are several other fissures in this vicinity which do not 

strictly belong with any of the S37 stems noted. Several have a nearly 

east-and-west strike, and might, perhaps, be grouped together or 

possibly included with veins of the Golden Fleece system.

In the cairyon of the Uncompahgre, north of Mount Abrams, the 

thick masses of San Juan breccia and the underlying Algonkian schists 

and quartzites are cut by numerous nearly parallel fissures with a 

general trend of about 1ST. 5° "W. and a dip of about 80° to 85° to the 

ea,st. These fractures, which do not, as a rule, contain prominent 

veins, have divided the San Juan breccia into huge, nearly vertical 

slabs (PI. VII), and have thereby contributed to the preservation of 

the lofty cliff faces of this part of the canyon. A second, less prominent, system of fissures, usually carrying quartz stringers, has a 

general strike of about N. 60° W.

At the head of Porphyry Gulch, near the western border of the 

quadrangle, the Potosi rhyolite and underlying Silverton series are 

traversed by a conspicuous series of nearly vertical fissures, striking 

N 8° W., which do not contain workable ore bodies, so far as known.

A similar series of fissures is also very prominently shown in the 

steep walls of Canyon Creek northeast of the mouth of Richmond 

Basin. The general strike of these fissures appears to be about N. 

35° W.j and they usually dip steeply to the northeast. They belong 

ge'netically with the northwest-southeast system of lodes as developed 

in Silver Lake and Richmond basins. So far as is known ihey do not 

carry any workable ore bodies.

On the eastern side of Ironton Park are several fissures having a 

general northeast-southwest course and a steep southeasterly dip. 

Their formation was accompanied by considerable normal faulting.

The parallel coordinated fissures or sheeted zones hitherto described 

all possess considerable width and are characterized by the division 

of the countiy rock into slabs of relatively great thickness as compared 

with the resulting fissures. But this is not always the case. The 

fissures may sometimes be very small and also very close!}7 spaced, as 

in the col separating Lake Como from Cement Creek, where the thorough manner in which the rock, a much-altered andesite or rhyolite, 

has been sheeted is beautifully shown. This minor sheeting is generally parallel in strike with the larger lodes in the vicinity, and at 

the particular point where best shown the fracture planes dip westerly at about 60°. As many as fifty such planes may frequently be 

counted within the width of a foot. There has been some infiltration 

of silica along these minute fissures, which causes them to stand out 

on weathered surfaces as little parallel ribs. The local strike of this 

sheeting is about N. 35° E., but it is sometimes disturbed by irregular 

later cross fractures. No regularity or rhythm could be detected in 

their spacing.

Sometimes several nearly parallel fissures of considerable extent,
U. S. GEOLOGICAL SURVEY LLETIlM NO. 182 PL. VII

SHEETED STRUCTURE IN CLIFFS OF SAN JUAN BRECCIA ABOVE THE SILVER LINK 

MINE, CANYON OF THE UNCOMPAHGRE RIVER

The brecc.a rests upon the eroded surface of Algonkian schists and quartzites. Phoiograph by Whitman

" Cross.
RANSOME.] COORDINATION OF THE FISSURES. 51

originally containing open spaces ranging from a few inches to a foot 

or more in width, occur closely spaced Avithin a comparatively narrow 

zone boiinded by less fractured country rock. Such a sheeted zone 

forms a favorable place for the deposition of ore bodies, and, as will 

be shown later, the Camp Bird, Tomboy, and other lodes are chiefly 

of this type, illustrated in. figs. 9 and 14. Coordinate fractures of this 

simple character, in which the individual fissures maintain their individuality and essential parallelism for long distances, may pass without any line of demarcation into groups of fissures of the linked type, 

in which the nearly parallel fissures are arranged more or less en 

Echelon and connected by smaller oblique fractures. This structure 

is exemplified to some extent in the Tomboy mine, but is not a coniPrc. 2. Horizontal sketch projection of the productive lodes west of Silver Lake.

mon one in the Silverton quadrangle. With a still further shortening 

of the principal parallel fissures and an increase in the number and 

size of the linking fractures the fissure zone becomes a reticulated 

aggregation of irregular, curving fractures, which, when filled with 

ore, constitute what may be conveniently termed a stringer lode. Of 

this class is the North Star (King Solomon) lode. Finally, with yet 

greater increase in the number and irregularity of the fissuring, this 

type of fissure zone passes by insensible gradations into a breccia 

zone, such as a portion, at least, of the Polar Star lode.

Thus far the discussion has dealt with the parallel coordination of 

fissures into minor sj^stems and with the steps by which such groups 

of fissures, when confined to rather narrow zones, may pass into other 

less regular structures commonly associated with the deposition of
52 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

ore in lodes. It remains to consider another manner in which the fissures of this region are sometimes locally grouped, not in parallel, 

bnt in more or less radial, or, perhaps more accurately, branching, 

arrangement. This feature is well shown by the lodes of Silver Lake 

Basin. The accompanying diagram (fig. 2) is a horizontal sketch projection of the productive fissures worked in the Silver Lake and Iowa 

mines, compiled from maps of the underground workings. The relations of the lodes here shown are described on pp. 148-149, and it is 

only necessary in this place to call attention to the branching arrangement of the fissures and to the fact that all these lodes appear to have 

been formed at the same time. Another case of conspicuous branching occurs at the head of Placer Gulch, where several lodes having 

an average strike of about N. 25° E. split off from the main Sunnyside 

lode. The junctions in this case have not been exposed underground, 

but from the similar character of their filling it is highly probable 

that these fissures, like those of Silver Lake Basin, were all filled 

at the same time, and were therefore probably formed practically 

simultaneously.

Still a third and interesting case of branching fissures is that at 

Lake Oomo, partially and somewhat diagrammatically represented on 

the map (PI. III). A view of some of these lodes is shown in PI. VIII. 

In this instance,^ again, the lodes are all of similar character and all 

appear to have been formed contemporaneously.

Another mode of coordination sometimes observed in groups of fissures is that which Lindgren, 1 following Daubree, has described 

under the name of conjugated fissures i. e., in the particular region 

described by Lindgren, fissures having generally parallel strikes but 

dipping symmetrically in opposite directions. In the Silverton q uadrangle, however, the fissures usually stand so nearly vertical that 

such a relation, if it exists, can not be clearly made out. The difference of dip, which would determine to which subdivision of such 

a conjugated system, any given fracture would belong, is so slight, 

and may be so frequently found in various portions of one and the 

same fracture, that it does not seem practicable to recognize such 

systems. The low angle of dip at which most of the Grass Valley 

and Nevada City lodes lie makes the conjugated character of the 

fissure systems readily recognizable. It is to be noted, however, 

that in such conjugated fissures as those above described it is 

assumed that the rocks, in1 fracturing under tangential stress, yielded 

in a vertical direction, and that the prisms consequent upon the 

rupturing lie horizontal. But it is obvious that if, for some cause, 

the rocks could yield more easily in a horizontal direction, at right 

angles to the direction of thrust, then the resulting prisms would 

stand vertical and the conjugate fissures would, in this case, form two

1 The gold-quartz veins of Nevada City and Grass Valley, Gal.: Seventeenth Ann. Rept. U. S. 

Geol. Survey, Pt. II, 1896, p. 164.
U. S. GEOLOGICAL SURVEY

VIEW OF LODES EXPOSED ON THE SOUTH SIDE OF 
RAWSOME.] RELATION OF FISSUEES TO KIND OF COUNTED EOCK. 53

'intersecting systems of vertical fractures, with their obtuse angles of 

intersection "bisected by the direction of the applied stress. Thus 

systems of parallel fissures flatly dipping in opposite directions and 

systems of nearly A^ertical intersecting fissures may both result from 

compressive stress, and may both be called conjugated fissures. Further, all gradations are possible between these two extreme cases, 

dependent upon the relation of the present surface to the original 

direction of least resistance when the fracturing took place. It is 

quite possible that some of the steeply dipping fissures of the Silverton quadrangle which intersect nearly at right angles form conjugate 

systems in the sense of Daubree. The test of this lies in determining 

whether the intersecting fissures are of the same or different ages.

RELATION OF FISSURES TO KIND OF COUNTRY ROCK AND TO ROCK

STRUCTURE.

It has already been pointed out that fissures carrying ore in greater 

or smaller amounts occur in practically all the rocks found in. the 

quadrangle. Opportunities are rare, however, for observing directly 

the character of the fissures as they pass from rocks of one kind to 

another, and when such observations are possible no marked change 

is apparent. It has been stated by at least one observer, 1 that the 

lodes of this region occupy contraction fissures in the volcanic rocks, 

and do not extend down into the underlying schists or sediments. 

Nothing could be much farther from the facts than this assertion. 

Not only does the distribution of the fissures disprove it, but aj: the 

Green Mountain and Highland Mary mines, in Cunmngham Gulch, 

the lodes may be seen passing from the Algonkian schists up into the 

overlying volcanic rocks of the San Juan and Silverton series. In the 

case of the Green Mountain mine no difference was noted in the fissure 

itself, either in width, direction, or general character, in the older 

schists and the younger rhyolite ftow-breccia. The exact point at 

which the fissure passed from one rock into the other was not seen. 

The Highland Mary lode, where originally worked in Algonkian 

hornblende-schist, is a simple vein filling a clean-cut fissure 2 or 3 

feet in width. Toward'the northwest the lode passes into the volcanic rocks of the San Juan and Silverton series, and becomes a rather 

irregular zone of fissuring about 12. feet wide where observed at a 

point, some 1,500 feet in elevation above the mine. In general it is 

apparently true that the fissures in the Algonkian rocks tend to be 

simpler and narrower than those in the volcanic rocks of later age. 

The fissures as a rule cut the schists cleanly at various angles with 

the schistosity, which apparently exercised no influence upon the 

direction of the fracturing.

No very definite differences can be observed in the character of the

1 Philip Argall: Proc. Colo. Sci. Soc., Vol. IV, 1891-1893, p. 353.
54 ECONOMIC GEOLOGY OF SILVERTON QUADKAJSTGLE. [BULL. 182.

fissuring within the various volcanic rocks of the quadrangle. It is 

veiy rarely possible to study in. any one mine the passage of a given 

fissure from one rock into rock of a different sort, and thus the kind 

of observations which, could best establish such characteristic differences, if they exist, is wanting. The massive lavas and indurated 

flow-breccias seems to have a general tendency toward comparatively 

simple fissuring, such as results in fissure veins of moderate size and 

regularity or in sheeted zones. In the softer tuffs and volcanic breccias the fissuring tends to be irregular, resulting in stringer or breccia 

lodes. Irregular fissuring appears to be favored also by alternations 

of harder and softer members of the nearly horizontal volcanic 

series, as at the North Star (King Solomon) mine. In this instance 

the softer rocks were regarded by the miners as the more favorable 

for ore. According to Purington, 1 in the northeast corner of the 

Telluride quadrangle the fissures passing from the San Juan formation 

and massive andesite up into the Potosi rhyolite series contain there 

less ore, and appear to have originally formed with less open space 

than in the underlying andesitic rocks. There are no workings in the 

Silverton quadrangle which afford an opportunity to verif}7 this statement, but the Potosi rhyolite is generally regarded by the miners as 

unfavorable to ore in the region where it prevails. Near the head of 

Porphyry Gulch, however, a vein carrying galena and sphalerite ore 

up to 10 inches in width has been prospected in the Potosi rhyolite. 

The vein strikes N. 50° E. It can be followed for a short distance to 

the southwest, over the 'bare rhyolitic surface, when it either dies out 

or is cut off by a numerous series of small, nearly east-and-west fractures filled with white quartz and often showing excellent illustrations 

of linked-vein structure on a small scale.

In the intrusive stocks of monzonite, such as that of Sultan Mountain, the fissures are, as a rule, of simple regular character and 

moderate width. They are usually occupied by fairly simple fissure 

veins, subject to local contractions or enlargements, but seldom lose 

their simple linear character. As examples, may be cited the fissures 

of the North Star, Hercules, and Little Dora veins in Sultan Mountain, and of the Hamlet vein near Middleton.

The foregoing generalizations are admittedly based upon scanty 

data, and are to be considered rather as suggestions indicating lines 

of future inquiry than as authoritative statements of facts.

As a rule, local geological structure has had very little discoverable influence upon the fissuring. The lack of any regular relation 

between fissures and schistosity has already been pointed out. Contacts between rocks of different kinds and ages also appear to have 

had but little effect upon the fracturing and subsequent veining. 

This is partly due to the fact that the contacts are frequently nearly 

horizontal, while the fissuring took place along nearly vertical planes.

1 Eighteenth Ann. Kept. U. S. Geol. Survey, Pt. Ill, 1898, p. 774.
KANSOME.] FAULTING AS AN ACCOMPANIMENT OF FISSURING. 55

Search was made in Cunningliarn Gulch, along the TJncompahgre, 

and at other points for any evidence of the diversion of fractures and 

mineralizing solutions along the contact of the older schistose terrane 

with the volcanic series, but with negative results.

Lines of fissuring in this region are occasionally determined by 

igneous dikes. Thus the Magnolia, a superficially prospected northwest-southeast lode just northeast of Silver Lake, follows for some, 

distance an andesitic dike about 6 feet wide which curves across the 

gulch toward Round Mountain. Both this dike and a larger one 

which crosses it are irregularly fissured and traversed by poorly 

mineralized quartz stringers along the greater part of their exposed 

lengths. A similar occurrence was noted on the south side of Kendan Gulch about a mile a little east of south from Keudall Mountain, where a vein about 6 inches wide lies on the south side of a 

nearly east-aud-west andesitic dike. None of these fissures have yet 

proved of much economic importance.

DISPLACEMENT OR FAULTING AS AN ACCOMPANIMENT OF THE

FISSURING.

In a few cases only, and those of relatively unimportant lodes, has 

tangential dislocation been detected as a consequence or accompaniment of the original nssuring. The abandoned Moles mine, 3 miles 

south of Silverton, is On a vein about 2 feet wide which apparently 

nils a fault fissure of noticeable throw. The head of Deer Park 

Creek is crossed by a nearly north-and-south fault, with the downthrow on the west side, which is accompanied by some brecciation 

and veiniug of the schists along the fracture and with unimportant 

mineralization.

On the eastern side of Ironton Park, as shown in the Saratoga and 

Baltic mines, the formation of a parallel series of approximately 

northeast-southwest fissures has been accompanied by obvious faulting. These fissures, as a rule, dip steeply to the southeast. In all 

cases where it could be made out the faulting is normal, and the 

maximum throw, as observed on the Mono vein, can hardly be less 

than 100 feet. This fissure carries a body of low-grade pyritic ore.

In the northeastern portion of the quadrangle the field work of 

Messrs. Cross and Spencer appears to demand considerable faulting 

along some of the prominent vein fissures. But as there are no extensive underground workings in this portion of the area the evidences 

of such faulting did not come under my observation.

Notwithstanding the foregoing exceptions, it remains true that such 

displacement as occurred in connection with the formation of most of 

the principal productive lodes was slight in amount, although probably not wholly absent. Moreover, the peculiar branching arrangement of many of the fissures, described on page 52, and their disposition 

en echelon, as in the Silver Lake and Iowa mines (p. 157), would seern;
56 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [nuLL.182.

opposed to the idea that anj7 considerable tangential displacement of 

the walls had taken place during their opening. In the King lode, south 

of Silverton, and in other fissures cutting the schists, there is no recognizable displacement or throw of the individual schistose bands by the 

fissuring. Slickensiding of the fissure walls prior to the deposition *of 

the ore has been nowhere recognized. In the Telluride quadrangle, 

where the occurrence of workable lodes in nearly horizontal sediments 

gives better opportunities than are usually available in the Silverton 

area for detecting and measuring displacement, Purington * evidently 

saw little clear evidence of it. Beyond recording a vertical separation 

of 1 foot by normal faulting in the San Bernardo mine, and concluding from the shape of the ore bodies of the Virginius and SmugglerUnion mines that the spaces they occupy were probably formed by 

faulting of the same kind, he makes no further reference to faulting 

as accompanying the formation of the ore-bearing fissures, although 

pointing out the desirability of future study in this direction. In 

nearly horizontal rocks faulting in which the movement is confined 

chiefly to the horizontal component (offset or heave) is not readily 

detected when of small amount, and was noted only in the few cases in 

which later-filled fissures have cut productive lodes, displacing the 

latter.

The absence of considerable displacement as an accompaniment of 

the opening of lode fissures is not a special peculiarity of the Silverton 

quadrangle, but is of very common occurrence. In fact, it seems to 

be comparatively rare to find more than very moderate faulting in 

fissures which have formed productive lodes. 2

INTERSECTIONS AND RELATIVE AGES OF FISSURES.

In a region where the fractures are so numerous and possess such 

diverse trends intersections must necessarily be of frequent occurrence. But as veins at such points are particularly susceptible to 

disturbance by later movements of the rocks and to superficial disintegration, the study of these intersections is-often difficult. The presence of seams of clay or gouge, due to these later or postmineral 

movements and the entrance of oxidizing waters, may so obscure the 

original relationship at the junction of two fissures as to render any 

conclusive determination of relative age impossible when no conspicuous faulting of one of the fissures has taken place to give the desired 

information.

In many cases in the Silverton quadrangle intersecting fissures have 

been formed nearly or quite simultaneously and filled bygone process 

of vein deposition. This is true of the assemblage of brandling fissures worked in the Silver Lake and Iowa mines, and probably so of 

the Placer Gulch and Lake Como fissures. It is also possible that

1 Loc.cit..p.780.

2 Phillips and Louis: A Treatise on Ore Deposits. London, 1896.
BANSOME.] INTERSECTIONS AND RELATIVE AGES OF FISSURES. 57

many of the fissures intersecting nearly at right angles (conjugate 

fissures) were produced by a single principal stress. In the greater 

number of instances, however, in which lodes are known to intersect, 

the exposures are such as leave the actual character of the crossing 

and the relative ages of the fissures in doubt. They may or may not 

have been simultaneously formed.

. Fairly clear evidence of the intersection of an earlier vein-filled 

fissure by a later one without recognizable faulting was obtained at 

several points. The prominent lode outcropping along the crest of 

Green Mountain crosses and is distinctly younger than a strong vein 

of barren quartz, about 10 feet wide, which is accompanied by several 

parallel minor veins and strikes about N. 60° E., dipping 80° to 85° 

southeasterly. The younger lode has a general strike of about K 30° 

W. and a steep southwesterly dip. The intersection is thus approximately rectangular, and is not accompanied by faulting, so far as

could be seen. In the complex network of Galena Mountain it was 

found that at least one of the several north-and-south veins was cut 

by at least one of the numerous veins striking nearly N. 25° W., and 

these in turn are apparently intersected in several instances by lodes 

trending about N. 65° W. One of the latter was also observed to cut 

a lode striking about N. 30° E. In none of the cases mentioned was 

the intersection accompanied by visible results of faulting. Other 

probable examples of northwest lodes cutting northeast lodes occur, 

on Treasure Mountain, but the exposures were not such as to place 

the question of relative age beyond doubt.

The shaft of the San Juan Chief mine was sunk at the crossing of 

two lodes, but it is by no means clear that they are of different age. 

The main lode, striking about N. 40° E., formerly produced some ore 

from surface workings. The fact that in their underground development the owners of the mine appear to have inadvertently drifted 

along the barren intersecting lode, striking about N. 60° E., is theonly indication that the latter may be younger.

In three places only were lodes found to be faulted by later transverse vein-filled fissures. The King lode, in Cataract Gulch, 2 miles 

south of Silverton, with a strike of N. 6° W. and a dip of about 80° 

to the west,, is faulted by a small approximately east-and-west quartz 

vein, dipping south at about 50°. By this faulting the northern portion 

. of the King lode is thrown about 12 feet to the westward. In the 

Silver Lake mine the important New York City vein, with an average 

strike of about N. 20° W., and dipping generally northeast at about 

80°, is cut by a faulting lode, which, where best exposed, is a breccia 

zone about 6 feet wide, composed of sharply angular fragments of 

country rock cemented by quartz carrying a little worthless ore. 

This fault fissure strikes apparently about N. 73° E. and dips about 

75° to the south. The New York City vein is displaced in the same 

way and to about the same degree as the King lode. In the Ridgway
58 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

mine the main lode, with a strike of about N. 40° E., is faulted by the 

Alaska lode, with an average strike of about N. 25° W. The fault 

here is apparently of the same kind as those just described an offset 

of the northern portion of the main lode to the westward, but the 

developments in the Ridgway mine were not sufficiently extensive in 

1899 to clearly show the relations. It is interesting to find that the 

three observed cases of faulting of one lode by another are of like 

character. In each case the lode running most nearly north and 

south has been faulted by barren or low-grade lodes trending more 

nearl3r east and west. While the number -of observations is at 

present too small to serve for the formulation of a general rule for 

the quadrangle, their unanimity is suggestive of the possibility that 

such a rule may be laid down in the future. Even now, in the event 

that a productive lode in the southeastern portion of the quadrangle 

should be found, on drifting northward, to be cutoff by a more nearly 

east-and-west lode with southerly dip, the miner, in the absence of 

other clues, is not utterly at a loss, but may reasonably hope to 

regain his ore by crosscutting westward after drifting beyond the 

interruption.

That, after the original deposition of the important ore bodies, 

there was at least one period of minor fissuring, followed by fresh 

deposition of quartz, is abundantly shown in many of the lodes of the 

region. Thus, in the Royal Tiger, the Dives, the Tom Moore, the 

Sunnyside, the Red Cloud, the Polar Star, and various other mines 

and prospects the original ore has been fissured or brecciated, and 

subsequently healed with generally barren or low-grade quartz. In 

the Tom Moore the later veinlets are notable in carrying small 

amounts of native copper in the quartz. This later fracturing is not 

always conspicuous, but small stringers of quartz, sometimes with 

rhodonite and carbonates, can usually be detected cutting the ore when

the latter is examined in considerable masses. This is by no means 

a rare phenomenon in lodes in general, which are in most cases complex structures, resulting from successive fissurings and fillings. 

Such complexity, other conditions being the same, is more likely to 

be prominent in lodes of which the initial fractures were opened at 

an early geological period. The lodes of the Silvertou quadrangle 

show much less evidence of repeated movements and filling than do 

the auriferous lodes of the Sierra Nevada, which were probably initiated at the close of the Jurassic or in early Cretaceous time.

Still younger than any of the fractures hitherto described are numerous fissures, usually noticeable only in mine workings in which neither 

quartz nor ore has been deposited. These are the "slips," "gouge 

seams," or "breaks" of the miners. As these names partly indicate, 

the fissures are generally filled with a wet, plastic, grayish clay, or 

gouge, which is, as a rule, merely altered and ground-up country rock, 

resulting from the attrition of the fissure walls. The presence of this 

unctuous gouge, when sharply limited by harder country rock or vein
RANSOME.] INTERSECTIONS AND RELATIVE AGES OF FISSURES. 59

filling, is taken to indicate relative movement of the walls, not necessarily resulting in any great net displacement. In other words, they 

are fault planes of greater or less movement, possibly oscillatory. The 

width of these post-mineral fractures, as they are sometimes conveniently called, may vary from a narrow, scarcely noticeable clay 

seam, up to zones 12 feet or more in width, in which the gouge is 

mingled with masses of shattered country rock, and of which the most 

notable example is found in the zone of so-called "broken ground" 

in the Silver Lake mine (see p. 154). Occasionally the fine clayey material is lacking and the fracture is the course of a copious stream of 

water. Such a fissure was encountered in the Silver Lake mine in 

crosscutting to the New York City vein on level C, and the same or a 

similar water-bearing fracture was subsequently cut in the Unity tunnel about 400 feet loAver. Since these post-mineral fractures can be 

Studied, as a rule, only in the vicinity of the lodes, and as they are 

frequently directly connected with the latter, they may be conveniently classed as follows:

(1) Strike fractures generally parallel with the lode. These are most 

commonly seen as gouges next the hanging or foot wall or in the 

country rock near to and approximately parallel with the lode in strike 

and dip. Gouge seams of this class, although not generally characteristic of the lodes of the Silverton quadrangle, are frequently well 

exhibited. They are found on both foot and hanging wall of the Silver 

Lake lode, particularly the latter, and also in the country rock for a 

distance of several feet on either side of the main fissure. When such 

later fractures have followed a previously existing vein or stringer 

the}7 usually contain crushed vein quartz mingled with the gouge.

(#) Strike fractures dipping at considerable angles with the lode. 

These are not so common as the foregoing, but sometimes occtir. The 

ore in this case will be found to rest locally on a bench or step of 

country rock, separated from the latter by a clay seam of varying 

thickness. An example of this structure was noted in a stope on the 

Silver Lake lode (see p. 152, fig. 11). Such an occurrence needs to be 

carefully distinguished from the steps or benches of ore formed by the 

original opening of a somewhat irregular fissure by thrust faulting. 

In this case there should normally be no gouge between the ore and 

the country rock upon which it rests.

(3) Cross fractures differing from the lode in both'strike and dip, 

and cutting it at an appreciable angle. These are observed in nearly 

all extensive workings, and are sometimes fairly abundant and regular, as in the case of those which cut the Silver Lake lode (p. 151).

Besides the three classes noted, various irregular fractures occur in 

almost all lodes which can not be definitely grouped.

The post-mineral fractures are simply of local importance to individual deposits, and it has not proved practicable to discuss and 

classify them with reference to the quadrangle as a whole. Their
60 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

possible bearing upon secondary enrichment of the primary ore 

deposits will be discussed in another part of this report.

To briefly recapitulate, while many of the fissures in the Silverton 

quadrangle, including some which differ widely in direction, were 

formed at substantially the same time, there have been later periods 

of fissuring, also followed by vein deposition. The oldest fissures 

known have a course somewhat east of north, and appear to have 

been successively cut by later fissures approaching more and more to 

an east-and-west strike. This generalization, however, should not be 

taken too rigidly, as it is very probable that whenever a prominent 

set of nearly parallel fissures were formed, other fissures intersecting 

the dominant set at various angles were produced at the same time. 

Lastly, there has been fissuring not followed, as far as known, by any 

deposition of quartz or ore in the resulting fractures.

The evidence afforded by the intersections as to the possible conjugate character of the dominant northeast-southwest and northwestsoutheast fissures is unfortunately inadequate, owing to lack of satisfactory exposures of such junctions to determine the question one 

way or the other.

GEOLOGICAL AGE OF THE FISSURES.

Beyond the statement that the ore-bearing fissures of the Silverton 

quadrangle are of Tertiary and probably of late Tertiary age, it is 

not at present possible to fix the exact geological time at which the 

first considerable fracturing took place. More precise knowledge 

waits upon a determination of the exact age of the Telluride conglomerate and the San Juan and later volcanic formations. The Telluride 

formation, which, when present, underlies the volcanic rocks,. has 

faeen provisionally referred to the Eocene by Cross. 1 It is difficult to 

conceive of its being older than this, as it has been found by Cross to

rest imCOllf ormably on the Colorado Cretaceous shales. The Telluride 

formation and the younger volcanic series have been cut by seA^eral 

great intrusive masses of mouzonite, such as the Sultan Mountain 

stock, which is thus the most recent rock in the quadrangle and can 

hardly be older than the Neocene. Since the lodes occur in the monzonite as well as in other rocks of the area, their formation probably does not antedate the latter part of the Tertiary, and may, 

indeed, have extended into the Pleistocene.

PROBABLE DEPTH AT WHICH THE PORTIONS OF THE FISSURES NOW 

EXPOSED WERE ORIGINALLY FORMED.

According to Cross, 2 'the maximum thickness of the volcanic rocks 

in the Telluride quadrangle was, in round numbers, 5,000 feet. 

Owing to the varying thickness of different members of these series

1 Geologic Atlas U. S., folio 57, Telluride, Colorado; also Proc. Colo. Sci. Soc., Vol. V, 1894-1896, 

pp. 235-341.

2 Telluride folio.
RANSOME.] PEKSISTENCE OF THE FISSURES. 61

in the Silverton quadrangle, no very close estimate can be made of 

the average thickness of the volcanic accumulations over the quadrangle as a whole. It may provisionally be estimated, however, as 

from 5,000 to 6,000 feet. As no traces of any extensive later deposits 

have been found in the San Juan, it may be assumed that this thickness represents practically the total deposition from the beginning of 

Tertiary time. As most of the lodes worked at the present day occur 

within the volcanic series, and often from 1,000 to 3,000 feet above its 

base, it is evident that the portions of the fractures now accessible 

must have been formed at geologically moderate depths that is, probably under 6,000 feet. When, further, it is remembered that erosion 

proceeded concurrently with the fissuring and probably made rapid 

headway during the progress of ore deposition, it appears that many 

 of the ore deposits must have been formed well within depths frequently reached by mining operations. It might be expected that 

under these circumstances there would be a recognizable, although 

probably not very intimate, relationship between the ore as originally 

deposited and the present topographic surface. The full discussion 

of this subject, however, brings up questions whose solution properly 

belongs in another place, and which are treated in the section on the 

origin of the lode and stock ores.

PERSISTENCE OF THE FISSURES HORIZONTALLY AND IN DEPTH.

Fissures are not of indefinite extent either horizontally or vertically. 

No fixed limit, however, can be assigned to the length which a given 

fissure may attain. It depends upon the magnitude of the stress that 

produced the fissuring and upon the relative movement which has 

taken place between the walls. Great relative movement results in a 

long fissure, but as profound faulting appears to be usually not favorable to the subsequent formation of a lode, there is a certain variable 

limit beyond which length is to be regarded as an unfavorable factor 

in the productiveness of a fissure lode. There are, however, certain 

notable exceptions to the foregoing general rule that should not be 

ignored. Thus the Merrifield-Ural lode, near Nevada City, CaL, occupies, according to Lindgren, a thrust-fault fissure of probably over 

1,000 feet throw. 1 In the Silverton quadrangle fissures vary greatly 

in length. Those having a length of 2 or 3 miles are certainly not 

uncommon, and it is very probable that some of the fractures extend 

continuously for as much as 6 miles. That great length is not necessary for the formation of a productive deposit is shown by the occurrence of such lodes as the Iowa, Steezner, and East Iowa, which can 

scarcely be longer than a quarter of a mile, and which die out at their 

southern ends in small branching fractures. The exact length of a 

fissure is, of course, rarely determinable, as practical exploitation seldom follows a lode to its total disappearance.

1 Gold-quartz veins of Nevada City and Grass Valley districts; Seventeenth Ann. Rept. U. S. 

Geol. Survey, Pt. II, 1896, p. 167.
62 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

The formation of fractures is limited vertically by that depth below 

which the rocks are under such pressure that no fissures can form. 

As the zone of fracture, according to Hoskins and Van Hise, 1 has a 

depth of about 10,000 meters (33,000 feet), and as fractures may also 

form in the still deeper zone of combined fiowage and fracture, it is 

plain that this limit will never be reached in mining operations. But 

many fractures undoubtedly die out long before reaching this ultimate limit. The longer horizontal and the vertical dimensions of the 

fissures were probably originally nearly the same, and it is not likely 

that the present depth of any fissure very greatly exceeds its length. 

The depth will at least be roughly proportional to length. But the 

depth to which fissures extend is rarely actually determined, as the 

value of the ore body nearly always falls below the limit of profitable 

working long before the fissure itself disappears. But that many 

smaller fissures do die out at moderate depths is a well-attested fact. 2 

In the Silverton quadrangle, where mining development is as yet 

restricted to moderate or slight depths, no well-authenticated case is 

yet known of the actual dying out in depth of a fissure which carried 

workable ore at a higher level. The ore may change in character, or 

may disappear, as in the North Star (King Solomon) mine, but the 

fissure still continues to an unknown depth.

In such instances as the last many considerations enter into the 

question as to whether it is advisable to follow 'the pinched fissure to 

greater depth in the hope of finding new ore bodies. The first step 

in such an issue is to determine whether the pinch is merely a constriction in a fissure extending to greater depth or whether it signifies 

the final diminution of the lode. This can be decided only by a careful consideration of the length and strength of the fissure as exposed 

above, of the possible faulting which accompanied its formation, and 

of the behavior of the fissure in those portions already mined. If the 

length of the croppings be several times the depth attained, if the 

fissure be usually strong, if it has been opened by faulting, and if it 

has been found subject to local pinches above, it may safely be concluded that it will persist and open out again with increased depth. 

But equally important is the question of the character of ore that may 

be found below, even if the fissure continue, for, as Avill be fully discussed later on, the ore contents of a given fissure are not constant at 

all depths, either in kind or in value. Lastly, in connection with these 

factors must be considered the costs involved in mining the ore from 

an increased depth.

The foregoing relates to simple fissures. Lodes in general,exhibit 

similar characteristics, but their persistency will in the main be 

greater than that of a simple fissure. They are subject to the same 

general laws as the individual fractures of which they are composed.

Principles of North American pre-Cambrian geology; Sixteenth Ann. Rept. Q. S. Geol. 

Siirvey, Pt. 1,1896, p. 593. 

2 Lindgren, loc. cit., p. 162.
THE LODE FISSURES. 63 

ORIGIN OF THE FISSURES.

The attempt to explain the origin of so complex a network of fissures as occurs in the Silverton quadrangle presents many difficulties. 

No explanation that can be at present proposed is to be regarded as 

complete or as free from various necessary assumptions. Our knowledge as to the degree of homogeneity of the various rock masses under 

strain, the depth at which the fissures were originally formed, then 

exact .extent, direction, and distribution, the geological conditions 

obtaining at the time of Assuring, and numerous other essential data 

are far too fragmentary to permit of anything like rigid analysis leading to irrefutable results. And yet the problem is not so hopelessly 

insoluble but that it may be reasonabl}-' taken up in the hope of finding at least a working hypothesis to account for major features.

Fissures in which ore deposits occur are very commonly regarded as 

produced by tangential compressive stress transmitted in nearly horizontal planes by the rocky envelope of the earth, within what Van 

Hise 1 has termed the zone of fracture, limited by a depth of 10,000 

meters. In many districts this is, without much doubt, the immediate 

cause of the fracturing. Thus, in the Grass Valley and Nevada City 

region of California the conjugated systems of flatly dipping regular 

lodes, opened with the accompaniment of more or less thrust faulting, 

were probably, as Lindgren concludes, "produced by a succession of 

compressive stresses applied in different directions, chiefly from east 

to west and from north to south." 2

In accounting for the fissures of the Telluride quadrangle, Purington 3 arrived at somewhat similar conclusions. He states:

From all observed phenomena it seems probable that the fissuring was made by 

forces acting at time intervals not far apart and at localities not 1'ar removed from 

one another. Since the fissuring is later than all the rocks of the quadrangle 

[Telluride], volcanic disturbances whose product is now visible can not be cited 

to account for it, but it is entirely possible that later disturbances of volcanic 

nature, which did not result in surface flows of lava, have produced a straining to 

the point of rupture in the tract under consideration. It is thought, with great 

reason, that in the area directly east and northeast of the Telluride quadrangle 

there are centers and necks of volcanic eruption. Such evidence as has been collected in the present investigation points to those quarters as the source from 

which the pressure came.

Since the fissures of the Telluride and Silvertou quadrangles were 

formed at the same time arid undoubtedly had a common origin, 

Pnrington's results have an important bearing on the problem in hand, 

and it becomes necessary to scrutinize them closely. The geological 

mapping of the Silverton quadrangle and reconnaissances to the north 

of it, accomplished bj7 Cross and Spencer since Purington's report was 

written, have failed to identify the actual "centers and necks of

1 Loc. cit., p. 589. 

3 Loc. cit., p. 170. 

!l Eighteenth Ann. Rept. U. S. Geol. Survey, Pt. Ill, 1898, p. 770.
64 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

volcanic eruption " referred to as the possible sources of the compressive 

stresses supposedly effective in fissuring the rocks of the Telluride 

quadrangle. There is, however, ground for believing that there may 

have been local manifestations of volcanisin in the Red Moimtain 

region. It is not impossible that the plug-like masses of porphyry 

mapped by Mr. Cross (PI. IV) may occupy conduits through which 

volcanic materials reached a former surface some thousands of feet 

above the present one. The character of the ore deposits, the intensity 

of the associated metamorphism, and the geological distribution of 

the Tertiary volcanic rocks all strongly suggest that one or more centers of former volcanic* activity underlie the Bed Mountain region. 

This, of course, does not mean that any trace of volcanic form remains 

in the present topography. Cones or craters, if they existed, have 

been obliterated in the evolution of the erosional forms of to-day.

In the Silverton, however, no less than in the Telluride area, the 

greater part of the fissuring is not only post-volcanic, but is later 

than the monzonitic intrusions which cut the volcanic series. Thus, 

although the vast volcanic accumulations of the San Juan must have 

issued from local vents, the reference of the forces which produced the 

fissures to one or more centers of eruption immediately east or northeast of the Telluride quadrangle as their source is as jet scarcely 

warranted by the facts. In this connection it may be noted that the 

intrusion of the great stocks of inozonite into the rocks of both quadrangles brings up the rather perplexing problem of the mechanics of 

such intrusions and the dispositi6n of the rocks which formerly occupied the space now filled by the intrusive mass. He would be rash 

who would assert that the intrusion of. these stocks was not accompanied by strains and fissures in the surrounding rocks, and yet the 

fact is clear that the principal ore-bearing fissures of the region were 

formed after the monzonite had solidified, since they cut the latter as 

well as the adjacent formations. ^

But leaving aside for the present the question of their source, it is 

necessary to investigate more fully the extent .to which tangential 

stresses of the kind indicated may be regarded as an effective cause 

of the fissuring of the Silverton quadrangle. Normally, in hoinogeaieous rocks, such .stresses might be expected to produce systems of 

conjugated fissures of parallel strike, with dips not far from 45°, and 

accompanied by some, although not necessarily great, thrust faulting; 

i. e., reversed faulting. The actual fissures do not conform even 

approximately to these conditions. Assuming that the direction of 

least resistance was vertical, it is inconceivable that fissures so nearly 

vertical and showing so little evidence of thrust could have been 

formed by tangential stress. Moreover, such evidence of faulting as 

Purington was able to obtain in the Telluride quadrangle indicated 

normal faulting and not thrust faulting.

If, on the other hand, the direction of least resistance was not ver-
RANSOMB.] ORIGIN OF THE FISSUEES. 65

tical, but horizontal, then tangential stress might produce systems of 

nearly vertical fissures intersecting nearly at right angles conjugate 

fissures. As shown by Daubree's l classic experiments, such fractures 

would be undulating, not strictly parallel, and might branch as do the 

fissures of the Silver Lake Basin. Moreover, as shown by Daubree's 

illustrations, the walls of such fissures will not necessarily be always 

slickensided, nor need the faulting be in all cases perceptible. Such 

faulting as took place would result mainly in horizontal displacement, 

or offset, and, not being necessarily great in amount, might be easily 

overlooked. It is possible in this way to account for much of the 

fissuring of the Silverton quadrangle, and perhaps this view best 

explains the two dominant directions of fissuring intersecting nearly 

at right angles.

This hypothesis that the dominant northeast-southwest and northwest-southeast fissures were formed by compressive stress, acting 

nearly horizontally, although the direction of least resistance which 

it presupposes is not that which would appear most probable, seems 

to offer fewer serious objections than any other that has been devised. 

Fissures of contraction they certainly can not be, for they cut indifferently rocks of most diverse age, character, and origin. Fissures 

originating from tensional strains would probably be more irregular 

and would not be associated with close parallel sheeting of the rock. 

Tension would find relief in a single fissure rather than in a series of 

closely spaced parallel fractures. Shearing strains due to differential elevation "or subsidence might culminate in fissures, but these 

could not be expected to show the general regularity and the persistency of the principal fissures of the Silverton quadrangle, and 

would probably reveal evident faulting. Faults probably due to such 

forces occur within and about the quadrangle, but they rarely contain ore deposits. Torsional stress, which by Daubree 2 is regarded 

as a system of pressures, and 'by Becker 3 as a system of tensions, is 

capable of producing systems of parallel fissures intersecting at 

nearly 90° as well as radial fissures. It may at times be impossible 

to distinguish, such fissures from those formed by simple pre£sure. 

But the fissures produced by torsion are in general decidedly curved, 

with a more strongly marked radial disposition. Their characteristics are given in detail by Becker in the paper cited. In a homogeneous block subjected to pressure, there are formed, in addition to 

the main conjugate fractures, A^arious more or less irregular fractures, 

making angles of less than 45° with the direction of pressure, and 

frequently branching from the main fissures (see Daubree, loc. cit., 

PI. II). Such fractures are comparable witli the branching fissures 

of Silver Lake Basin and Placer Gulch. For this reason, and on

1 Etudes Synthetiques de G6ologie Experiinentale, Paris, 1879, PI. II.

' 'Loc. cit., p. 321.

3 Torsional theory of .joints: Trans. Am. Inst. Min. Eng., Vol. XXIV, 1894, p. 137.

Bull. 182 01 5
66 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

account of the preponderance of nearly horth-and-south fractures 

over nearly east-and-west fractures, it is thought that the effective 

stress producing the principal fissuring of the quadrangle may have 

acted in a north-and-south direction. Further, since there is no 

known source of such stress exterior to the quadrangle and immediately adjacent region, it is thought probable that the stresses \vere 

generated chiefly within the quadrangular area, by slight vertical 

movements following the enormous transfer, in Tertiary time, of volcanic material from an intratelluric to a superficial position, and that 

the surrounding country merely acted as a relatively passive buttress 

against which the thrust was directed. In other words, it is believed 

that the stresses were due principally to local gravitative readjustment. Some genetic connection between the volcanism. and the subsequent fissuring, mineralization, and veining can scarcely be doubted, 

as these phenomena rapidly diminish in intensity away from the volcanic district of the San Juan Mountains. It does not seem possible 

at present to do much more than suggest that hypothetical relation 

which seems to adhere most closely to the known facts.

In addition to the principal stress outlined, there were doubtless 

many minor directions of stress set up at various times, some contemporaneous with the principal north-and-south stress and others earlier or later, frequently leading to the production of minor local fissure 

systems. These also were probably in part compressive tangential 

thrusts, and it is the existence of these widely differing directions of 

effective stress that furnishes one of the strongest arguments against 

seeking sources for the latter outside of the region itself. It is exceedingly improbable that there should have been set up at various widely 

separated points in the relatively undisturbed regions inclosing the 

Arolcauic area, stresses which were to find their most energetic expression in the fissuring of the area itself. It seems likely that torsional 

strains also had their place in the readjustments following volcanism. 

Such a complex of fissures as that around Lake Como seems hardly to 

admit of any other satisfactory explanation. The probability that 

torsion has been a factor in the minor fissuring of this region has been 

suggested by S. F. Emmons. 1 It seems not unlikely that earthquake 

shocks, to which there is good reason to suppose the region was subjected during the faulting and principal fissuring accompanying postvolcanic readjustments, may have, in some instances, transformed 

torsional strain into actual fissuring, as suggested by Crosby. 2

In conclusion, it may be well to recall the complex forces and results 

that enter into the fissuring under simple pressure of a block of what 

is commonly called homogeneous material. The geological conditions 

under which rocks are fractured are vastly more complex, and, as Dr. 

Becker 3 has remarked, "it is entirely safe to presume that every p'os1 Structural relations of ore deposits: Trans. Am. lust. Min. Eng., Vol. XVI, 1888, p. 804.

2 The origin of parallel and intersecting joints: Am. Geologist, Vol. XII, 1893, p. 308. 

3 The torsional theory of joints,:" Trans. Ani. Inst. Min. Eug., Vol.'XXIV, 1894, p. 130.
RAXSOME.] STEUOTUKES OF THE LODES. 67

a b c

sible mode of deformation and rupture is exemplified," and, it may 

be added, frequently in a single limited field of fracture. The best 

that can be hoped for in any case is to ascertain the dominant mode 

in which fracturing has taken place.

STRUCTURES OF THE LODES.

The larger structural features of the various lodes depend mainly 

upon the character of the fissures in which they Avere deposited. 

Where the original fracture was a simple, clean dislocation, the resulting lode is a fissure vein. Most of the lodes of the Silverton quadrangle are of this character nearly vertical plates of gangue and ore 

confined between definite walls. They sometimes show local irregularities and may divide into numerous branching stringers (stringer, 

lodes) at their edges, but in the essential character of their workable 

portions they are veins, in the original 

sense of Von Cotta. Such are the veins 

of the Empire group on Sultan Mountain, the New York City (fig. 3), Stelzner, Royal, and Iowa veins of Silver 

Lake Basin, the Green Mountain vein, 

most of the veins of Galena Mountain, 

the Hamlet vein, and many of the lodes 

in the northeast portion of the quadrangle. The width of the Avorkable 

veins usually varies from a few inches 

up to 10 or 12 feet. Lodes attaining 

greater width than this are rarely simple veins, although some of those near 

Sunnyside Basin, with widths of from 

30 to 50 feet, appear to have filled simple open fissures. A width of 2 or 3 feet 

is perhaps a rough characteristic average of the productive veins of 

the Silverton region. T-he vein filling usually fits snugly to the 

fissure walls and is frequently adherent to them "frozen," as the 

miners say. Quite commonly, however, there has been sufficient 

movement along the fissure to cause the ore to come away readily 

from one or both walls, and sometimes there is a gouge or selvage 

present. This is rarely thick or extensive. Fissures sometimes contract, or pinch, and the vein then becomes much reduced in width 

and may be entirely absent. Such pinches, where the fairly solid 

walls are separated by a mere crack, were encountered on the New 

York City, Stelzner, and other veins, and on the Camp Bird lode. 

It is often difficult, when such a pinch is passed through by a crosscut, 

to believe that it really represents a lode which is elsewhere wide and 

productive. Many crosscut tunnels have on this account overshot the 

vein sought for. Careful systematic surveying and mapping is the

feet

FIG. 3. Cross section of the New 

York City lode, Silver Lake mine, 

a, country rock; b, miners' wall; c, 

broken country rock; d, ore, chiefly 

galena, chalcopyrite, and sphalerite; 

e, ore and country rock; /, ore and 

quartz.
68 ECONOMIC GEOLOGY OF SILVEKTOIST QUADBANGLE. [BULL. 182.

safeguard against such mishaps and is the prerequisite of all intelligent and extensive prospecting.

As a rule the country rock adjoining the .veins is not strikingly 

altered and retains practically the original form of the fractured surfaces. In some veins in rhyolite, however, there has been some 

replacement of the rock by ore, as may be seen in the Tom Moore 

mine.

Veins of the simple type described are connected by many transitional forms with lodes occupying closely spaced sheeted zones and 

consisting really of several parallel veins. Such are the small lodes 

of the Micky Breen and the important lodes of the Camp Bird and 

Tomboy mines. In both the Camp Bird and Tomboy, however, the 

parallel veining resulting from sheeting of the country rock is assofeet

FIG. 4. Sketch section of the Silver Crown lode, showing stringer-lode structure, a, andesite; 

6, quartz; c, andesite and quartz stringers; d, ore.

ciated with the less regular linked-vein structure, in which the lode is 

made up of nearly parallel or slightly diverging veins connected by 

linking stringers (Trummer) and with the yet more irregular stringerlode structure, in which the lode consists of a mass of stringers without noticeable parallelism among themselves. In these mines the 

more regular structure is usually found with the gold ore separated 

from the hanging wall by a little gouge, while the more irregular 

structures characterize the foot-wall portion of the lode, carrying a

low-grade galena ore and sending off irregular stringers into the

country rock, and being thus without regular foot wall.

The stringer-lode structure is perhaps best exemplified in the North 

Star (Solomon) lode, in portions of the Royal Tiger and of the Pride 

of the West lodes, in the upper part of the Forest lode, and in the 

Alabama lode. But it may frequently be well studied in surface out-
RANSOME.] STKUCTURES OF THE LODES. 69

crops, notably those which stand out on the steep slopes of Dome 

Peak, north of Howardsville, and in particular near the head of Mill 

Creek, west of Chattanooga, where the Silver Crown lode is beautifully exposed in the bed of the stream, and the details of its structure 

may be seen through the clear water. Fig. 4 is a sketch of the lode 

as seen at the bottom of a clear pool in the creek. In minor development it is to be seen in nearly every fissure deposit in the quadrangle. 

The most regular of the veins will sometimes locally split up into a 

stringer lode, particularly where the fissure is seen about to die out 

in the country rock.

Breccia lodes that is, lodes in which the ore and gangue originally 

filled the spaces in a zone of brecciated country rock, do not appear 

to be common. The only deposit 

seen which would appear to be 

characterized chiefly by this structure is that of the Silver Queen 

mine on Bear Creek, near the northern edge of the quadrangle. Here 

the rjay streak, from 3 to 6 feet 

wide, lies in a brecciated zone about 

12 feet wide in the San Juan formation. Judging from the materials 

seen on their dumps, the Polar Star 

and Red Cloud lodes also were in 

part deposited in breccia zones.

To a certain extent the lodes as 

originally formed have had their 

structure modified by later movements, resulting in fractures in the 

ore already deposited, followed by 

a secondary veining, usually of 

quartz. It could not be proved 

that this process has exerted any 

important influence upon the ore. 

are small and relatively barren.

/foot

FIG. 5. Cross section of the Japan lode, 

showing structure produced by successive 

openings of the original fissure, a, country 

rock; b, quartz; c, ore.

As a rule the secondary stringers 

In the Tom Moore lode the later 

stringers carry a little free copper, but the amount is insignificant 

from a commercial point of view. In the Polar Star and Red Cloud 

mines an earlier deposition of quartz carrying pyrite was certainly 

brecciated and followed by renewed veining. But there was no means 

of determining in 1899 to which period of deposition the ore of these 

mines belonged. The Japan lode, a section of which is shown in fig. 

5, appears to have been formed by successive openings of the original 

fissure. The main ore streak of banded galena and sphalerite ore was 

first deposited. Later, nearly barren white quartz, with well-marked 

comb structure, was deposited in fresh openings on each side of the 

original vein.
70 ECONOMIC GEOLOGY OF SILVERTQN QUADRANGLE. [BULL. 182.

The internal structure of the fissure fillings, such as banding and 

comb structure, and the size and shape of pay shoots, while, strictly 

speaking, embraced under the head of lode structure, will be more 

conveniently described in the following sections on the ores of the 

lodes.

THE ORES OF THE LODES.

MINERALOGY OF THE ORES.

GANGUE MINERALS.

Under this head are included those mineral constituents of the lodes 

which commonly make up the matrix of or are intimately associated 

with the metallic ore minerals. The term is a somewhat relative one. 

Thus pyrite is often a matrix for free gold, and has sometimes been 

treated, with chalcopyrite, etc., as a gangue mineral. 1 But in the 

present report the term gangue will be restricted to the so-called nonmetallic minerals, 2 chiefly oxides, carbonates, sulphates, and silicates, 

while the compounds of the heavy metals, largely sulphides, sulpharsenites, -sulpharsenates, sulphautimonites, or sulphobismuthites, all 

commonly possessing metallic luster, will be treated as ore minerals, 

although they may not in all cases be valuable. This is but following 

the convenient distinction laid down by such classical writers on ore 

deposits as Von Gotta and Von Groddeck, and is in accordance with 

the usage of Lindgren, 3 PhrRips, 4 and others.

In the brief resume of physical properties given with each mineral, 

the aim has been simply to give those features of color, form, etc., 

which will enable one to recognize the minerals as they occur in this 

particular quadrangle. The same minerals occurring in other regions 

may differ in the properties named.

Quartz. Si02 . Khombohedral. Massive, or in hexagonal prisms

terminated by rhombohedvons. Usually white or colorless. Hardness, 

7. Specific gravity, 2.6.

This, as a rule, exhibits the usual character of' vein quartz common 

in most mining districts. It varies from semiopaque, milk-white varieties to those which are vitreous and transparent. The latter occur 

in the Camp Bird and Tomboy lodes carrying free gold, usually in 

minute particles. In the Tomboy the occurrence of the gold iii 

quartz of that particular vitreous appearance which is elsewhere commonly regarded as a sign of worthless vein matter has been commented upon by Purington. 5 The quartz of the veins is generally 

massive, and in thin section under the microscope is seen to be com1 Mining industries of the Telluride quadrangle, Colorado, by'G. W. Purington: Eighteenth 

Ann. Kept. U. S. Geol. Survey, Pt. Ill, 1898, p. 781.

2 Von Groddeck. Lagersttitten der Erze, p. 58, Leipzig, 1879.

3 Gold-quartz veins of Nevada City and Grass Valley districts: Seventeenth Ann. Rept. U. S. 

Geol. Survey, Pt. II, 1896, pp. 114-119. .

4 Treatise on Ore Deposits, 2d ed., pp. 1-2 and 85, London, 18%.

5 Loc. cit.,p. 840. . .
AJ. S. GEOLOGICAL SURVEY BULLETIN NO. 182 PL. IX

Ji. Sunnyside led

NORMAL VEIN-QUARTZ STRUCTURE.

Magnified 1 1 diameters; nicols crossed ; black areas, c ha I copy rite ; Q. qua r tz C, chloiite ; G, galei

S, sphalerite.
RANSOME.] GANGUE MINEKALS. 71

posed of interlocking grains with incomplete crystal boundaries (see 

PL IX, A and J3). Distinct crystals are found only in small vugs 

and are never of large size. A radial arrangement of the imperfectly 

formed crystals was noted in the Dives, Magnet, Camp Bird, and 

Tomboy mines. The quartz of the Silver Lake lodes frequently 

incloses chlorite, which gives it a green color, usually regarded as an 

indication of good ore. In some of the lodes the presence of minute 

included crystals and grains of galena, sphalerite, tetrahedritc, argentite, various sulphobismuthites, and other ore minerals results in a 

dark-clouded quartz in which the ore minerals are not recognizable 

with the naked eye. Such is the richest ore of the Ridgway mine 

(PI. X, A). Microscopic fluid inclusions are common, usually with 

gaseous bubbles. They are frequently arranged along irregularly disposed curved surfaces in the quartz.

In addition to quartz of the foregoing character, which has crystallized in open spaces, there occurs within and adjacent to many of the 

lodes, and especially in connection with the stocks of the Red Mountain district, a much more finely crystalline quartz, sometimes resembling a fine-grained quartzite, which has resulted from a partial or 

complete replacement of country rock by silica. As seen in thin section under the microscope, this quartz is associated with more or less 

sericite or kaolin, and sometimes alunite, in a cryptocrystalline 

mosaic. Such a mosaic often reveals the outlines of the former crystals of feldspar, which have been metasomatically replaced, as more 

fully described on pages 114-131. " f;

As vein filling, with other gaiigue minerals and ore, quartz occurs 

in nearly all the productive lodes of the quadrangle, but the relative 

amount of quartz and ore minerals varies widely between the highly 

siliceous gold ore of the Tomboy, showing to the eye insignificant 

mineralization, to the coarsely crystalline, heavy lead ore of the Royal 

Tiger and Iowa mines. In a few of the lodes occurring in rhyolite, 

vein quartz may be practically absent. It did not occur to any considerable extent with the ore stocks of the Red Mountain district, 

where the quartz is chiefly the result of metasomatic replacement of 

the country rock.

Barite. BaS04 . Orthorhombic. Massive, or in groups of diverging tabular crystals. Cleaves perfectly in three directions. White. 

Transparent to opaque. Hardness, 3. Specific gravity, 4.5; Avhence 

common name "heavy spar."

This is not nearly so important a gangue mineral in the Silverton 

quadrangle as quartz, but it occurs massive with the latter mineral 

in the A^eins in the Sultan Mountain monzonite mass, in the Royal 

Tiger, Melville, and probably other lodes in Silver Lake Basin, as a 

heavy vein in the Dives and Potomac claims, in the veins of Galena 

Mountain, where it has sometimes been replaced by pseudomorphons 

quartz, and in the Bonanza, Alaska, Tempest, Alabama, Old Lout,
72 ECONOMIC GEOLOGY OF SILVERTOIST QUADEANGLE. [BULL. 182.

and other lodes in Poughkeepsie Gulch. In practically all the stocks 

of the Red Mountain district barite was found in close association 

with the argentiferous copper ores. Thus in the Guston and Yankee 

Girl the bornite or chalcocite often incloses numerous isolated crystals of translucent barite, and it is to be found on nearly every mine 

dump in this vicinity. It also occurs in the Zuni mine, on Anvil 

Mountain, embedded in kaolinite, and with zunyite in guitermanite. 

Where occurring in lodes, the barite is very commonly associated with 

gray copper (tetrahedrite). In the Mastodon claim, on the Sunnyside lode, barite forms with quartz a finely crj^stalline aggregate 

which constitutes the gangue of a highly argentiferous lead sulphobismuthite.

Calcite. CaC03 . Rhombohedral. Commonly massive or in rhonibohedrons, scalenoheclrons, or prisms. Cleaves perfectly in three 

directions, affording rhombohedrons. White. Transparent to opaque. 

Hardness, 3. Specific gravity, 2.71. Effervesces freely with cold 

dilute acid.

Calcite is less abundant than barite in the productive lodes, but is 

nearly always present in small amount, particularly in small vugs and 

in minute veinlets cutting the ore. As the principal filling of mineralized veins it was noted at the Oneida, a prospect at the head of 

American Basin, where it carries sphalerite with a little pyrite, chalcopyrite, and galena, and at the.Yellow Jacket claim on Bear Creek, 

on the northern edge of the quadrangle, Avhere also it contains abundant sphalerite. In both cases the ore is too poor to work. As an 

important gangue constituent it Avas noted in some of the copperbearing lodes north of Hanson Creek. At the Osceola claim in Cunuinghani Gulch it occurs pseudoniorphous after tremolite. In the 

Camp Bird mine it is fairly abundant, filling vugs and spaces in the 

quartz left by comb structure. As a microscopic constituent calcite

is found almost invariably in the Avail rocks near the lodes, except 

Avhere the rock has been silicified, in small amount with rhodonite and 

rhodochrosite in the so-called "pink spar" (chiefly rhodonite) of the 

Suniiyside and other mines, and with fluorite and quartz in a palegreen cryptocrystalline aggregate accompanying and forming part of 

the rich streak in the Camp Bird lode.

As limestone, impure massive calcite occurs at several points in the 

quadrangle, and on the east side of Sultan Mountain and at the 

Saratoga mine in Ironton Park is directly associated with deposits 

of ore.

Dolomite. CaMg(C03 ) 2 . Rhombohedral. Usually massive or in 

curved rhombohedra. Cleavage like calcite. White to brownish. 

Milky to opaque. Hardness, 3.5. Specific gravity, 2.88. Effervesces 

with cold dilute acid only Avhen finely powdered.

This mineral is not abundant or important in connection with the 

ore deposits, but occurs as a microscopic constituent with rhodonite 

and rhodochrosite.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 182 PL. X

. Finely crystalline ore from the Ridgway mine. Magnified 17 diameters; nicols crossed; large blacU 

areas, pyrite : small black areas, argent'tes, with a little sphalerite and galena; shaded areas, quartz.

7>*. Gangue of rich ore, Camp Bird mine. Magnified 1 7 diameters ; nicols crossed ; black areas, fluorite ; 

shaded areas, quartz; cross-hatched areas, calcite.

VEIN-QUARTZ STRUCTURE,
IIASSOME.] GANGUE MINERALS. 73

Wiodochrosite. MnC03. Rhombohedral. , Massive or in small 

rhombohedra in vugs. Cleavage like calcite. Usually some shade of 

pink. Hardness, 3.5-4.5. Specific gravity, 3.5. Effervesces freely 

in powdered form with dilute acid.

Occurs abundantly in massive form as gangue in the Titusville 

lode, and in small amounts in the A^eins of the Empire group on Sultan 

Mountain, and in most of the lodes in the northeast quarter of the 

quadrangle, where it may usually be observed as minute rliombohedral crystals lining small vugs. In small quantity it always 

occurs in the veins containing rhodonite. In the Golden Fleece vein 

it forms, with quartz, the gangue of the rich free-gold ore, and also 

occurs in small amount in the Camp Bird lode. It is found in beautifully colored rhombohedral crystals in the Grizzly Bear mine on Bear' 

Creek, just within the northern boundary of the quadrangle.

Kaolinite. K4Al2Si 2 09 . Monoclinic. Massive, or in a loose powder consisting of microscopic crystalline scales. White. Hardness, 

2-2.5. Specific gravity, 2.6. Can be scratched with the finger nail. 

Smooth to the touch..

This mineral occurs in. very pure form in the National Belle mine 

as a snowy white powder, made up of minute crystalline scales. As 

seen in the upper A\7 orkings in. 1899 it occurs filling fissures in the 

country rock or as a filling between the fragments of brecciated zones 

near the ore bodies. It was apparently in these cases deposited later 

than the ores, partly taking the place in this mine of the clay gouge 

commonly associated with post-mineral movement in other localities.

As an original constituent accompanying the ores,'kaolin occurs 

abundantly in the stock deposits of the Red Mountain district, as 

shown by the materials now visible on their dumps. This is usually 

a firm, compact variety, intimately associated with pyrite. A characteristic form is that in which the kaolin is traversed by numerous 

anastomosing veinlets of pyrite, giving it a spotted and sometimes a 

schistose appearance (fig. 6). It was not possible to investigate the 

occurrence of kaolin in any of the deeper workings of the Red Mountain mines, but from what could be seen it appears to haA^e accompanied the ores to the greatest depths there attained about 1,300 

feet. It Avas evidently derived from the country rock adjacent to the 

ore bodies as a product of its alteration by the thermal waters.

In the Zuni mine, on Anvil Mountain, compact kaolinite is abundant and is directly associated Avith pyrite, barite, and small nests of 

enargite to form the lower exposed portion of the ore body. The 

pyrite is often beautifully crystallized in very slightly modified octahedra, Avhich are thickly embedded in the Avhite kaolinite.

As a soft Avhite powder kaolinite occurs Avith the gold quartz of 

the Tomboy and Camp Bird mines. In the Tomboy the kaolin is 

sometimes mixed with sericite. 1

1 Purington, loc. cit.,p.840.
74 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

As an alteration product of the wall rock, more particularly of the 

feldspathic constituents, kaolinite is extremely, common; but it is 

often impossible, without a chemical analysis, to distinguish it from 

sericite. Both minerals occur in similar fine aggregates, and they 

sometimes occur together. In such cases the microscope will not 

always serve to distinguish them.

Fluorite. CaFl2 . Isometric. Massive, or in variously modified 

cubes and octahedra. Cleaves in four directions, forming octahedra. 

Colorless, or pale green or lilac. Hardness, 4. Specific gravity, 3.1.

Pale-green fluorspar is abundant on some of the dumps of the Aspen

FJG.O. Diagram illustrating common occurrence of kaolin in the Red Mountain region. The 

kaolin is traversed by a network of pyrite. From Zuni mine. Natural scale.

mine, but was not seen in place. In a massive condition it forms a 

vein which has been superficially prospected on the north side of Picayune Gulch, near its mouth, and was seen in a prospect near the 

Mountain Queen mine, in California Gulch, and in another prospect 

just east of Lake Como. It was also noted in the dump of the upper 

tunnel of the Micky Breen mine. Well crystallized with quartz, 

fluorite occurs in a prospect just north of the Old Lout mine, and in 

the Indiana tunnel in Grey Copper Gulch. In the Sunnyside lode, 

fluorspar, usually of a lilac tint, accompanies the best ore and is used 

by the miners as an indicator for free gold. Pale-green fluorite occurs 

with calcite in the quartz of the Tomboy lode and as a microscopic
RANSOMB.] GANGLTE MINERALS. 75

v

constituent in some of the rich Camp Bird ore. It probably occurs 

also in visible masses in portions of the latter lode, although none was 

seen at the time of visiting the mine. It is abundant in the Morning 

vein of the Japan mine, and in the Empire-Victoria vein with hubnerite. This latter association, however, is much more strikingly 

shown on the Adams claim, near Gladstone, as described on page 25G. 

On the whole, however, it is not a common gangue mineral in this 

quadrangle, and when not too abundant is frequently associated with 

free gold.

Rhodonite. MnSi03 . Triclinic.' Occurs only in cryptocrystalline 

massive form in Silverton quadrangle. Color, rose pink, fading and 

then turning black on exposure to the weather. Hardness, 5.5-6.5. 

Specific gravity, 3.5.

The silicate of manganese, comprising much of the so-called "pink 

spar" of the miners, occurs in many of the larger lodes of the northeast quarter of the quadrangle as a fine-grained pink material, very 

hard and tough, forming partitions between the ore-bearing portions 

of the lodes, as elsewhere described. It is a conspicuous and abundant constituent in the Sunnyside lode, in the neighboring lodes in 

Placer Gulch, and on Treasure Mountain, particularly in the dominant northeast fissures, and occurs much less abundantly in other 

lodes of the northeast quadrant. It is also found in the Saratoga 

mine, near Ironton, where it has partly replaced limestone. It is 

often difficult to distinguish this mineral by inspection and ordinary 

physical tests from the pink carbonate of manganese, rhodochrosite, 

when both are massive. This is due to the fact that the rhodonite isseldom pure, but is associated with quartz, calcite, and rhodochrosite 

in grains or crystals of microscopic dimensions. The massive rhodonite, when powdered, often effervesces slightly with acids, due to this 

slight admixture of carbonates. The greater part of the pink pOAvder 

remains insoluble in dilute, boiling hydrochloric acid, and this fact 

and an examination of thin sections under the microscope show that 

the so-called "pink spar" of the Sunnyside and neighboring mines is 

the manganese silicate, rhodonite.

Zunyite. A very basic orthosilicate of aluminum. (A1(OH,F, 

Cl^uALjSigO^. Isometric, tetrahedral. Colorless. Hardness, 7. Specific gravity, 2.8.

This mineral, which was first described and named by Hillebrand, 1- 

from the Zuni mine, is limited in its occurrence, so far as known, to 

the Zufii and to one or two adjacent prospects on Anvil Mountain. 

It occurs as small tetrahedral crystals up to 5 millimeters (threesixteenths of an inch) in diameter, embedded in guitermanite or its 

oxidation product, lead sulphate, and associated with pyrite, enargite, bournonite, kaolin, and barite. The chemical composition of

'On zunyite and guitermanite, two new minerals from Colorado: Proc. Colo. Sci. Soc., Vol. I,. 

1884, pp. 124-129. Also Bull. U. S. Geol. Survey No. 20,1885.
76 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

.zunyite given by Hillebrand as the mean of eleven partial analyses

is as follows:

Analysis of zunyite.

Constituent.

;SiOo. ......... ............ .:. ...........

TJlrt |~\

AloOg- ------ ............................

KoO... ...............................

NaoO.-. ...... .......................

Li»O -...... . ......................

B.«O. ....................................

Per cent.

24.33

.20

57.88

.10

.24

Trace. '

10.89

Constituent.

P205 ................................

F. ........................................

Cl ......................................

Per cent.

.60

5. 01

2.91

102. 76

3.02

99.74

Although, of much scientific interest, the mineral at present has no 

 economic importance.

Other minerals'. Sericite, epidote, chlorite, and zircon occur in 

.some of the ores, often merely as microscopic constituents. In the 

mines of Silver Lake Basin, chlorite, with the usual green color and 

minute radially foliated structure, occurs as nests in the vein quartz. 

The spots of chlorite are commonly regarded as an indication of good 

ore. It is abundant, also in ore from the Silver King tunnel, on Mill 

Creek, and in vein quartz carrying pyrite in the Barstow mine. Sericite is often associated with kaolinite in ores formed ~by partial replacement of rhyolite and related potash-bearing rocks. A little chalcedony 

was noted in the Camp Bird ore. Alunite, although occurring in 

the National Belle mine and as an alteration product of some of the 

volcanic rocks of the Red Mountain range, has not been noted as a 

true gaugue mineral. Gypsum occurs occasionally as small crystals 

in vugs of the Red Mountain ores.

In a fissure in the Silver Ledge mine there is a considerable quantity of a soft white material which, when moist, has a beautiful 

faint-green tint. When dry the substance is a snow-white powder, 

.apparently of great purity. A partial analysis of this substance by 

Dr. Hillebrand gives the following approximate chemical composition:

Constituent.

SiOo ....................................

AloO3 (with trace of Fe2 03 ).-.. ........

H»O.. .................................. .

 S03 -- ..... -........... ........

Per cent.

14.83

39. 42

40.25

4.26

Constituent.

Alkalies (largelv K»O) .. .'.......'...

CaO. ...................................

Per cent.

.20

0.68

.53

100. 17

This may be calculated as a mixture of allophane, aluminite, gibbsite, alunite, and calcite, in the following proportions, by weight:

Per centAllophane (hydrous silicate of alumina) .................................... 58.0

Aluminite (hydrous sulphate of alumina) .t ................................. 15.5

 Qibbsite (hydrate of afumina) .............................................. 16.2

Alunite (hydrous sulphate of alumina and potash) ........................... 2.0

Calcite........-...........--...-'......-.................................... 1.2

92.9
BANSOME.] ORE MINERALS. 77

There remains over 5 per cent of superfluous water, which is not 

included in the foregoing calculation. The chemical analysis, however, does not pretend to be more than approximate, and the mineralogical composition deduced from it is of similar character.

ORE MINERALS.

Under this head are included minerals generally mined as ores, 

together with some compounds of the heavy metals not of commercial 

value in this region. Unless otherwise stated, these minerals arecharacterized by a metallic luster.

Pyrite. Iron disulphide (FeS2 ). Isometric, pyrifcohedral. Massive, granular, or in pentagonal dodecahedrons (pyritohedrons), octahedrons, or cubes, or in combinations of these forms. Pale-brass, 

yellow. Hardness, 6. Specific gravity, 5.

The isometric sulphide of iron is common in all the ores of the district, and impregnates to a varying extent all of the country rock ill 

the vicinity of the ore bodies. In some cases this impregnation has 

involved huge masses of rock, as in the Red Mountain range, which 

owes its color to the oxidation of the pyrite that is scattered in minute 

crystals throughout the altered andesites and other rocks which 

compose the range. Large bodies of pyrite, formed in part by 

replacement of country rock, are known to exist in the lower workings of many of the abandoned mines of the Red Mountain district. 

Other large masses of crumbling granular texture occur near Ironton, 

in the Saratoga and Baltic mines, in great part replacing limestone. 

Pyrite, in beautiful octahedra embedded in kaolin, is abundant in the 

Zuni mine, on. Anvil Mountain. As a rule the pyrite, when occurring 

in large bodies with little or no quartz, is not of sufficient value to 

pay for working. When, however, as in the Henrietta mine, it is 

associated with a considerable amount of chalcopyrite, it can sometimes be mined at a profit. Associated with true vein quartz, especially when the latter carries some free gold, the pyrite itself is 

usually sufficiently auriferous to repay treatment. In the Tomboy 

and Camp Bird mines the gold occurring in the pyrite is less in 

amount than that occurring free in the quartz. In the Gold King, 

however, the reverse is true. A large part of the gold in the Silver 

Lake mine is known to occur in pyrite.

Pyrite in radially fibrous spherules, and at first supposed to be the 

orthorhornbic sulphide of iron, niarcasite, was noted in the dumps of 

the Red Cloud and Old Lout mines, and also occurred as small stalactites in cavities in the Genesee-Vanderbilt ore body. It was noted in 

radial spherules embedded in calcite at the Yellow Jacket claim on 

Bear Creek, near the northern edge of the quadrangle. Dr. H. 1ST. 

Stokes, in the course of a chemical investigation on the iron sulphides, 

has shown that the foregoing radial forms are not niarcasite but
78 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

common pj^rite. Dr. Stokes has kindly furnished the following note 

in regard to his method of determination:

Siipposed marcasite from the Red Cloud mine, Colorado. Carefully selected portions of the mineral, as free as possible from foreign substances,gave the ''oxidation number " 65, that of pyrite being 60, and of marcasite 17. There can be noquestion, therefore, that the substance is pyrite, the excess of 5 over the normal 

figure being accounted for by small quantities of As, Pb, and Cu, which were found 

on analysis, the effect of these being to raise the "oxidation number." - .

The "oxidation number : ' may be thus denned: When a sulphide is boiled with 

a .solution containing 1 gram ferric iron per liter, Fe'" is reduced to Fe". and iron, 

if present in the mineral, goes into solution. At the same time more or less S is 

oxidized .to S03. In the case of FeS2 this is expressed by

G.333 b . , , , .,. , [60 for pyrite 2o=per cent of sulphur oxidized=<. ., 

a 117 for marcasite

where a=amount of iron dissolved,

6=amount of Fe" produced by reduction. £

7

When other sulphides are present the effect is to contribute to b but not to a, 

thus increasing the apparent percentage of sulphur oxidized, as in the present case.

Tetrahedrite (gray copper}. Sulphantimonite and sulpharsenite of 

copper. The composition of tetrahedrite proper is 4Cu2SSb2S3 , corresponding to 52.1 per cent of copper. For tennantite, the arsenical 

variety, it is 4Cu2SAs2S3 , corresponding to 57.5 per cent of copper. 

These two varieties are connected by various intermediate compounds. 

Isometric, tetrahedral; commonly massive. Color, gray. Streak, 

brownish or reddish. Hardness, 3-4.5." Specific gravity, 4.4-5.1.

This mineral rivals galena in this region in importance and abundance as an ore constituent. Its high percentage of copper, with the 

fact that it often carries a large amount of silver replacing part of the 

copper, gives it its value. Most of the varieties seen contain both 

.arsenic and antimony, but the latter predominates, especially in the 

highly argentiferous varieties sometimes known as freibergite (the 

typical freibergite from Freiberg contains over 30 per cent of silver), 

which is usually of a lighter gray than ordinary tetrahedrite. Moderately argentiferous tetrahedrite occurs in the North Star, Belcher, 

Empire, Little Dora, and other lodes on Sultan Mountain, in the 

Aspen mine on Hazelton Mountain, and in the Royal Tiger and other 

mines in Silver Lake Basin, associated with galena, chalcopyrite, 

sphalerite, pyrite, quartz, and barite. An antimonial variety rich in 

silver, probably to be referred to freibergite, constituted the principal 

ore of the North Star (King Solomon) mine. Tetrahedrite has been 

found in the Pride of the West, Philadelphia, and Highland Mary 

mines, in Cunningham Gulch, and usually constituted the richest ore. 

It occurs in most of the lodes of Picayune and California gulches, in 

the Tom Moore lode, in the Mickey Breeu, Poughkeepsie, Bonanza, 

and other mines in Poughkeepsie Gulch, and in many other mines 

and prospects in various parts of the quadrangle. In some, such as 

the North Star (King Solomon), Tom Moore, and Mickey Breen, it is
ORE MINERALS. 79

the principal constituent of ore bodies of some size and continuity, 

but in others, especially in those lodes carrying much galena, the 

tetrahedrite often occurs as bunches in the other ore. A little lead 

may sometimes replace part of the copper, as was found to be the 

case Avith a tetrahedrite carrying both arsenic and antimony, from 

the Black Diamond claim, on California Mountain. Tetrahedrite was 

present also in the ores of the Yankee Girl, Silver Bell, and other 

Red Mountain mines.

Enargite. Sulpharsenate of copper (3Cu2S.As2S5 ). Contains 48.3 

per cent of copper. Orthorhombic. One perfect cleavage. Grayish 

black to iron black. Hardness, 3. Brittle. Specific gravity, 4.4.

Enargite is of somewhat frequent occurrence in the ores of the Red 

Mountain range. It was found abundantly in the Zuni and Congress 

mines, and formed the principal ore of the National Belle. Handsome clusters of prismatic crystals incrusted with malachite and 

quartz were seen from the now inaccessible Avorkings of this mine. 

According to Mr. Emmons, enargite occurred in the Yankee Girl.

The enargite of the Zuni mine is said to have carried over 200 

ounces of silver per ton. In the National Belle it was probably of 

much lower grade.

Clialcociie. Cuprous sulphide (Cu2S), corresponding to 79.8 per 

cent of copper. Orthorhombic, commonly massive. Blackish leadgray. Hardness, 2.5-3. Specific gravity, 5.5-5.8.

Stromeyerite. Sulphide of silver and copper ((AgCu2 )S). Form 

and physical properties like chalcocite, except slightly higher specific 

gravity 6.1-6.3.

These two closely related species do not always admit of sharp distinction. Stromeyerite may be regarded as chalcocite in which about 

half of the copper is replaced by silver. Chalcocite is itself a valuable ore mineral on account of its high percentage of copper, but 

Stromeyerite, which may contain over 50 per cent of silver, is particularly valuable. The two minerals are probably connected by intermediate varieties.

Chalcocite, more or less argentiferous, was noted on the dump of the 

Frank Hough mine, and bornite in the Silver Link and John J. 

Crooke. Stromeyerite is reported to have been formerly an abundant 

ore in the Yankee Girl and Guston mines, where it occurred above a 

depth of 600 feet, between galena above and bornite below. One lot 

of 6 tons of this rich ore from the Yankee Girl contained over 5,-300 

ounces of silver per ton, 1 while one small lot from the sixth level of 

the Guston is stated to have contained 15,000 ounces of silver per ton, 

which corresponds roughly to the percentage of silver in pure Stromeyerite. None of this ore could be seen in 1899 or 1900.

Some of the richest ore in the New York City lode, in the Silver 

Lake mine, contains small quantities of a black amorphous substance,

1 Schwarz: Trans. Am. inst. Min. Eng., Vol. XVIII, 1889-90, p. 145.
A

80 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

associated with chalcopyrite and pyrite. It was at first supposed to 

be,black oxide of copper, but upon closer investigation proves to be 

a copper sulphide, probably chalcocite.

Bornite. Sulphide of copper and iron (3CusS.Fe2S3 ). Contains 

55.5 per cent of copper. Isometric. Commonly massive. . Copper 

red or pinchbeck brown on frssh fracture, but soon becomes iridescent from tarnish, whence the name "peacock ore." Hardness, 3. 

Brittle. Specific gravity, 4.9-5.4.

This mineral, often highly argentiferous by the replacement of a 

portion of the copper by silver, was a very important constituent of 

the large ore bodies formerly worked in the Red Mountain district. 

According to T. E. Schwarz, it was the "principal ore for large 

masses" l in the Yankee Girl. It formed large solid masses in the 

Guston mine, associated with barite, the crystals of the latter being 

often embedded in the bornite. It also occurred in the GeneseeVanderbilt mine. It is usually intimately associated with chalcocite 

and chalcopyrite. With quartz it occurs in bunches in the Silver Link 

mine and also in the John J. Crooke, a prospect north of Hensen 

Creek, associated with chalcocite.

Chalcopyrite (yellow copper}. Sulphide of copper and iron (Cu2S. 

Fe2S3 ), corresponding to 34.5 percent of copper. Tetragonal, sphenoidal. Commonly massive. Brass yellow. Hardness, 3.5-4. Brittle. 

Specific gravity, 4.1-4.3.

This is a common ore mineral throughout the quadrangle, and is 

sometimes auriferous, as in the Sound Democrat, or argentiferous 

(carrying also a little gold), as in the Yankee Girl, Guston, National 

Belle, and other Red Mountain mines, and in the Guadaloupe mine 

on Abrams Mountain. It is very abundant in the Titusville mine, 

in the New York City lode of the Silver Lake mine, and in the Hamlet mine. Associated with pyrite, it forms the ore of the Henrietta 

mine, and with tetrahedrite much of the ore of the Tom Moore 

lode. It is always present in ores carrying galena, sphalerite, and 

pyrite, although the amount varies widely in different occurrences. 

In the Saratoga mine it occurs with pyrite and galena, replacing 

limestone.

Galena. Lead sulphide (PbS). Isometric. Rarely showing external crystal form, but characterized by its perfect cubic cleavage. 

Lead gray. Hardness, 2.5. Specific gravity, 7.5.

This very important ore mineral, which when pure contains 86.6 

per cent of lead, occurs in nearly every ore deposit in the quadrangle, although in extremely varying amounts. In the lodes of 

the Silver Lake Basin and vicinity it occurs in coarsely crystalline 

masses, associated with quartz, sphalerite, chalcopyrite, pyrite, and 

sometimes barite and tetrahedrite. Such coarsely crystalline varieties carry in this region relatively low silver values. In other lodes,

1 Personal letter.
HANSOMK.] QBE MINERALS. 81

in Maggie, Picayune, and Placer gulches, and around Mineral Point, 

the galena sometimes occurs so minutely crystallized as to give 

merely a dark color to the quartz in which it is inclosed. This 

finely crystalline galena is often, but not invariably, highly argentiferous, as in the Sound Democrat mine in Placer Gulch. In the 

Sunnyside mine the foreman, J. James, informed me that he had 

seen free gold embedded in galena.

Sphalerite (zinc blende). Zinc sulphide (ZnS). Isometric, massive, and tetrahedral. In variously modified tetrahedral forms. Perfect dodecahedral cleavage. Luster resinous. Color, various shades 

of yellow or orange to dark brown or black. Hardness, 3.3 to 4. Specific gravity, 4.0.

This is a very common mineral in this region and always accompanies galena. It is not, however, worked as an ore of zinc, and 

its presence in the ore often involves additional cost in concentrating and smelting. The light-yellow varieties, commonly termed 

"rosin zinc" by the miners, are often associated with the occurrence of gold. An orange or red sphalerite is common in the ores 

of the Red Mountain range. In the Yellow Jacket, a prospect on 

Bear Creek near the northern edge of the quadrangle, sphalerite 

occurs abundantly in a peculiar form, viz, as cylindrical aggregates 

of radial structure, thickly embedded in a gangue of calcite. These 

aggregates, which occur in all sizes up to an inch or so in diameter, frequently contain small specks of galena and chalcopyrite. 

Spherules of marcasite also occur occasionally embedded, like the 

sphalerite, in the calcite. When the calcite is dissolved in acid 

the sphalerite remains as a loose mass of cylindrical rods lying in 

all directions. In nearly all cases these rods are broken sections, 

as if they originally formed a loose mass of small shattered stalactites which were subsequently cemented by calcite.

Bournonite. Sulphantimonite of lead .and copper (3(PbCua )S. 

SbaS3 ). Orthorhombic. Steel gray, lead gray, or black. ' Hardness, 

2.5 to 3. Rather brittle. Specific gravity, 5.8.

According to Mr. S. F. Eminons's unpublished notes, this mineral 

is reported as having been found in the Yankee Girl mine. A leadcopper sulphantimonarsenite, probably bournonite with some arsenic 

replacing the antimony, occurs at the Zuni mine, in small vertically 

striated prisms with pyrite and zunyite.

Zinkenite. Sulphantimonite of lead (PbS.Sb2S3 ). Orthorhombic, 

but occurs chiefly massive. Steel gray. Hardness, 3 to 3.5. Specific 

gravity, 5.3.

Described and analyzed by Hillebrand l from the Brobdignag claim, 

where it is said to occur sparingly with barite. None could be seen 

in 1899 or 1900.

J Mineralogical notes: Proc. Colo. Sci. Soc., Vol. 1,18S4, pp. 121-123.

Bull. 182 01 6
82 ECONOMIC GEOLOGY OF SILVEETON QUADKANGLE. .[BULL. 182.

G-uitermanite. Snlpliarsenite of lead (3PbS.As2S3 ). Massive, 

compact. Bluish gray. Hardness, 3. Specific gravity, 5.9.

This mineral, with zunyite, was first described and named by Dr. 

Hillebrand 1 , and occurs, as far as known, only in the Zuni and adjacent claims. It always incloses the minute, sparkling tetrahedrons 

of zunyite, and is intiinatety associated with pyrite, enargite, kaolin, 

and barite. It alters superficially to anglesite. As it contains about 

66 per cent of lead, and probably some silver, it is a valuable ore.

Stibniie. Antimony sulphide (Sb2S3). Orthorhombic. Usually.in 

clusters of radiating prisms. Perfect cleavage in one direction. 

Lead gray. Hardness, 2. Specific gravity, 4.5.

A single specimen of this mineral was seen, which was stated on 

reliable authority to have come from the North Star mine on Sultan Mountain. It is readily distinguished by its lustrous cleavage 

surfaces and softness, being easily scratched with the finger nail.'

Polybasite. Sulphantimonite of silver (9AgS.Sb2S3 ), with part of 

silver replaced by copper and part of antimony by arsenic. Orthorhombic., In characteristic, short, six-sided tabular prisms, with triangular striations and beveled edges. Iron-black. Hardness, 2 to 3. 

Specific gravitj-, 6.1.

This rich silver ore is known to have occurred in the upper workings of the Yankee Girl, and probably in other mines of the Red 

Mountain district. Well-crystallized specimens from this region are 

preserved in the museum of the Bureau of Mines, Denver, and in 

various private cabinets.

Proustite (ruby silver). Sulpharsenite of silver (3Ag2S.As2S), corresponding to 65.4 per cent of silver. Rhombohedral, hemimorphic. 

Luster, adamantine. Transparent to translucent. Color, scarletvermilion, but somewhat masked by brilliant luster. Hardness, 2.25. 

Brittle. Specific gravity, 5.5 to 5.6.

Few of the ores now mined show this mineral, although it was seen 

in the Beii Butler mine, associated with galena and perhaps argentite. It is also known in the Ridgeway mine and has been reported on 

good authority from the Red Cloud, Polar Star, Mammoth, Annie 

Wood, Palmetto, and Wheel of Fortune mines. It is known, to have 

occurred in the Yankee Girl, and a specimen was seen which was said 

to have come from the Genesee-Vanderbilt mine. It characterizes 

the upper portions of argentiferous ore bodies and is not known at 

depths over a few hundred feet.

Bismuthinite. Sulphide of bismuth (Bi2S3 ). Orthorhombic. One 

perfect cleavage. Lead-gray. Hardness, 2. Somewhat sectile. Specific gravity, 6.5.

This sulphide of bismuth occurs in slender prismatic crystals, with 

specularite in quartz at the Neigold claim on the south slope of Galena 

Mountain.

1 On zunyite and guitermanite, two new minerals from Colorado: Proc. Colo. Sci. Soc., Vol.1, 

1884, pp. 129-131. Also Bull. U. S. Geol. Survey No. 20, 1885.
MANSOME.] ORE MINERALS. 83

Argentite. Silver sulphide (Ag2S), containing 87.1 per cent of silver. Isometric. Blackish lead-gray. Hardness, 2 to 2.5. Sectile. 

Specific gravity, 7.3.

This valuable ore of silver, which is readily distinguished by the 

ease with which it can be cut with a knife without breaking or splintering, is not abundant in the Silver-ton quadrangle. It was distinctly 

recognized only at the Ridgway mine, where, curiously enough, it is 

called " brittle silver." Here it constitutes the richest ore, and is evidently "one of the most recently formed of all the ore minerals, as it 

occurs characteristically in vugs, incrusting or filling the interstices 

between the quartz crystals. It probably occurs also in the Gold Nugget and other prospects in Maggie Gulch, and is said to have constituted a large part of the rich ore formerly extracted from the Polar 

Star mine, oh Engineer Mountain, and from the Palmetto mine, in 

American Flats.

Molybdenite. Molybdenum disulphide (MoS2 ). Probably hexagonal.

Occurs in scales, with eminent basal cleavage, or compact. Laminae 

flexible, but not elastic. Lead-gray. Leaves a bluish-gray mark on 

paper. Feel, greasy. Hardness, 1 to 1.5.

This mineral occurs in the Sunnyside Extension mine, where it has 

been mistaken for graphite. Here it frequently contains free gold. 

It has not been recognized elsewhere within the quadrangle.

Hematite (specula-rite). Ferric oxide (Fe2 03 ). Rhombohedral. 

Lamellar or in thin scales. Color, steel-gray or iron-black. Streak, 

cherry-red or reddish -brown. Hardness, 5.5-6.5, but often apparently 

much softer on account of its scaly structure. Specific gravity, 5.2.

The variety of hematite known as specular iron is frequently met 

with in small quantities in the lodes of the Silverton quadrangle. It 

occurs, for example, in the Crown Point lode on Silverton Mountain, in the Little Giant lode (on the dump), in the Neigold claims on 

Galena Mountain, and in the Daniel Webster prospect in Maggie 

Gulch. In all cases observed it is a vein mineral inclosed in quartz. 

It is of no economic importance, but is frequently mistaken for more 

valuable minerals in one case for "brittle silver." It is easily recognized by its scaly structure, brittleuess, and red color when crushed.

Sulpliobismutliites. These include cosalite (2PbS.Bi2S3 ), galenobisrnuthite (PbS.B.i2S3 ), alaskaite ((PbAg2 )S.Bi2S3 ), beegerite (6PbS.Bi2S3 ), kobellite (2PbS.(Bi,Sb) 2S3 ), and possibly other species..

Sulphobismuthites of lead, carrying usually considerable silver and 

sometimes a little copper, are of frequent occurrence, particularly in 

the northern half of the quadrangle. As most of the above-named 

minerals resemble one another very closely in physical properties and 

as a rule occur massive, their specific identification is impossible 

Avithout a quantitative chemical analysis in each case. Nor is this 

method often available, for the association of these Sulphobismuthites 

with other ore minerals is usually such that pure material suitable
84 ECONOMIC GEOLOGY OP SILVERTON QUADRANGLE. [BULL. 182.

for chemical analysis can not be obtained. They are nearly all leadgray in color, with hardness varying from 2.5 to 4.

The argentiferous galenobismuthite named by Koenig 1 alaskaite 

occurs abundantly in the Alaska mine and in the Acapulco claim 

adjoining it on the east. Its occurrence and accompanying minerals 

are described on page 195.

Cosalite, from the Yankee Girl mine, with more or less of the lead 

replaced by silver, has been analyzed by Low, 2 and probably occurs 

in other mines of -the vicinity. It has been reported also from the 

Alaska mine. Kobellite has been analyzed and described by Keller 3 

from the Silver Bell mine, and beegerite, from Poughkeepsie Gulch, 

by Koenig. 4 The naming and identification of these species from the 

Silverton quadrangle rests upon chemical analysis of massive, more 

or less impure material, and these results have not yet been confirmed 

by any investigation of crystal form.

In the course of the present investigation sulphobismuthites have 

been met with in many of the ores, but never with external crystal 

form nor in such amount or purity as would warrant complete chemical analysis, whereby alone they can be specifically determined.

At the Barstow mine the richest ore is a bright lead-gray mineral, 

of hardness 3 to 3.5 and specific gravity 7.04 at 30° 0. (Hillebrand). 

It shows indistinct crystal forms, suggestive of isometric symmetry, 

and is very intimately intergrown with pyrite.

The purest material that could be picked out proved to be a mixture 

of a lead sulphobismuthite with pyrite and a telluride. According 

to Dr. Hillebrand the following may be taken as a rough approximation to the chemical composition of this mixture:

Approximate chemical composition of material from Barstow mine. .

Constituent.

Pb -.....-- . .--.-.........-- 

Bi. ............................ .... ......

Ag.... ................................

Au....... ...............................

Cu .-. ..............-..-.--...... 

Per cent.

45.5

22.5

6.0

.06

.3

Constituent.

Fe. ............... ..........:...........

Te. .....................................

S ......... ........... ....................

Per cent.

2.8

3.5

14.1

1.5-2.0

Had pyrite been the only mineral present with the sulphobismuthite 

it might have been easily deducted from the completed analysis. 

But the presence of tellurium shows that there is present also some 

telluride of unknown composition which can not be thus allowed for. 

The idea of a quantitative analysis was therefore abandoned. The 

above rough approximation indicates the probable presence of a mineral of the composition of beegerite, mixed with pyrite and perhaps 

an auriferous hessite (telluride of silver).

i Proc. Am. Philos. Soc., Vol. XIX, 1881, pp.

472-477. 

2 Froc. Colo. Sci. Soc., Vol. I, 1883-84, p. 111.

3 Zeitschr. fiir Kryst., Vol. XVII, 1890, pp. 67-72.

4 Loc. cit.
BANSOMK.I ^ QBE MINERALS. 85

In the Sunnyside Extension mine a sulphobismuthite of lead and 

silver, showing no distinct crystal form, occurs intimately associated 

with molybdenite and free gold in an ore containing quartz, barite, 

sphalerite, pyrite, and galena. In the Mastodon, which adjoins the 

Sunnyside Extension on the north, an argentiferous sulphobismuthite 

of lead showing indistinct prismatic crystallization occurs so finely 

disseminated in quartz as to give the latter a dark clouded appearance.

In the Ouster claim on California Mountain an argentiferous lead, 

sulphobismuthite, forms the richest ore, and similar bismuthiferous 

compounds occur in the ores of the Sound Democrat and Silver Queen 

mines in Placer Gulch.

A lead-copper sulphobismuthite, probably argentiferous, occurs in 

small, ragged prisms, frequently forming star-like radial clusters, in 

quartz with pyrite at the Uncompahgre Chief, near Mineral Point.

At the Silver Bell mine, between Irontori and Red Mountain, the 

richest ore was a massive argentiferous lead sulphobismuthite carrying up to 1,000 ounces of silver per ton. Massive argentiferous lead 

sulphobismuthites, of probably more than one species (one of them 

cupriferous), occurred in the Genesee-Vanderbilt ores, intimately associated with barite and pyrite. A massive lead sulphobismuthite (with, 

perhaps, a little copper) has been found in the Silver Queen mine on 

Bear Creek. In the Neigold group of claims on Galena Mountain a 

lead sulphobismuthite, carrying a little silver and perhaps some copper, occurs as small indistinct prisms and specks in quartz with pyrite, 

specularite, and bismuthite. Lastly, it is known that rich bismuthiferous ores, probably argentiferous lead sulphobismuthites, were formerly mined in the Old Lout and Poughkeepsie mines, and are 

probably present in varying amounts in most of the lodes of Poughkeepsie Gulch?

Tellurides. The occurrence of tellurides of gold or silver has been 

noted at only four localities within the quadrangle, and at each of 

these in small amounts only. In some of the rich ore of the Camp 

Bird mine a little tellurium, probably occurring as a telluricle, has 

been detected chemically by Dr. Hillebrand, although no tellurium 

mineral has been recognized. In the Barstow mine small amounts of 

an unknown telluride are intimately associated with an. argentiferous 

lead sulphobismuthite and pyrite. Its presence can be detected only 

by chemical means. At the Silver Ledge mine a small amount of a 

telluride resembling calaverite was found, with free gold in a single 

small pocket. At the Magnet mine telluride of silver, probably hessite, occurs, intimately associated with argentiferous galena and a little 

free gold in a quartz gangue.

6roZcZ. Isometric, but rarely showing crystal form. Usually in 

irregular hackly particles. Gold yellow. Hardness, 2.5-3. Very 

malleable and.ductile. Specific gravity, 15.6-19.3.

Free or native gold occurs in arborescent sheets in quartz and 

rhodonite in the Golden Fleece vein (see p. 183). In the Sunnyside
86 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

Extension mine it has been found, scattered through masses of spongy 

quartz, as implanted crystals on the faces of quartz crystals in vugs, 

and embedded in yellow sphalerite and molybdenite. It is also sometimes present in the ores of the Sound Democrat and Silver Queen 

mines of Placer Gulch. . In the Sunnyside mine it occurs intimately 

associated with quartz, rhodonite, fluorite, yellow sphalerite, and 

galena, and has been found embedded in the latter. In the Camp 

Bird it is inclosed as small particles with galena, sphalerite, pyrite, 

chalcopyrite, and traces of some telluride, in quartz and fluorite (see 

p. 90). In the Tomboy it is found with pyrite in quartz, but only 

rarely in visible particles. Visible particles are also met with in 

bunches in the quartz in the Gold King mine. In the mines of the 

Silver Lake Basin free gold is very rarely seen, and only one specimen 

has been noted in the Royal Tiger.

One small bunch of free gold, associated with a telluride (probably 

calaverite), has been found in the Silver Ledge mine. Rich pockets 

of free gold are reported to have been mined in early days in the 

Whale and Argentina lodes in Savage Basin, and it was the free gold 

of the Little Giant in Arrastra Gulch which in the early seventies 

first called attention to the San Juan region.

Silver. Isomeiric. Commonly filiform (wire silver). Silver white, 

but sometimes black through tarnish. Hardness, 2.5-3. Ductile and 

malleable. Specific gravity, 10.1-11.1.

Native silver is very rarely seen in the ores worked at the present 

day. But in the form of wire silver it was formerly found in the 

Pride of the West, Aspen, Ben Franklin, and Sunnyside Extension 

mines. It occurs occasionally in the Aspen and in the Antiperiodic 

mines, and, as small hackly particles and plates solidly embedded in 

limestone (probably Devonian), on the Fairview claim on Sultan 

Mountain. It is probably in all cases of secondary origin, resulting

from the oxidation of other silver minerals.

Copper. Isometric. Occurs in irregular plates and branching 

forms. .Copper red. Ductile and malleable. Hardness, 2.5-3. Specific gravity, 8.8-8.9.

Occurs in small amounts in the Royal Tiger, T6m Moore, and Sunnyside Extension mines. It is confined, as far as known, to the superficial 

portions of the lodes and is of later formation than the bulk of the 

ore. In the Tom Moore it occurs in a stringer of quartz which contains small crystals of hiibnerite and cuts the ore.

Hilbnerite. Tuugstate of manganese (MnW04 ), usually with some 

iron. Monoclinic. One perfect cleavage. Usually in bladed prisms; 

often radial. Brownish red to black. Luster, submetallic or metallicadamantine. Hardness, 5-5.5.

This mineral occurs rather widely distributed over the Silverton 

quadrangle as a vein mineral associated with quart/ and fluorite. It 

is most abundant at the Adams lode on Bonita Mountain, where it 

forms striking radial clusters of brownish-red crystals embedded in
U.S.GEOLOGICAL SURVEY BULLETIN No. 183 PL. XI

ORE - STRUCT!TIES
RANSOME.J PRODUCTS OF SUPERFICIAL DECOMPOSITION. 87

quartz and pale-green fluorite. It is also found in a quartz lode in Dry 

Gulch, but in smaller crystals. In the Tom Moore lode it was noted 

as minute brown prisms in quartz. On Sultan Mountain it has been 

obtained from the North Star mine, and occurs in moderate abundance in the Empire-Victoria lode. The mineral from the last-named 

locality is nearly black and probably contains considerable iron, thus 

approaching wolframite in composition. It is embedded in quartz and 

pale-green fluorite.

This mineral, if found in sufficient quantites, would be valuable as 

an ore of tungsten. It is doubtful, however, whether any of the 

above-mentioned deposits contain it in sufficient abundance to render 

possible its commercial extraction.

PRODUCTS OF SUPERFICIAL DECOMPOSITION.

Owing to the vigorous erosion to which, the Silverton region has been

subjected, oxidized ores have seldom had opportunity to accumulate 

to any great depth, and play a small part in mining operations. Small 

amounts of the carbonates of copper, malachite, and azurite, and the 

carbonate of lead, cerussite, can be found in the croppings of most of 

the lodes, and cerussite was mined to some extent from the upper 

levels of the Silver Lake mine. Anglesite, or sulphate of lead, also 

occurred near the surface in the Silver Lake and Whale lodes and 

formed an important part of the ore body of the Zuni mine, where it 

resulted from' the oxidation of guitermanite. Anglesite, resulting 

from the oxidation of galena and often containing kernels of the sulphide, occurs in the Anaconda mine about three-fourths of a mile 

south of Cinnamon Pass, whence four or five carloads, carrying 55 per 

cent of lead and 14 to 18 ounces of silver per ton, have been shipped. 

In the Saratoga mine the greater part of the ore has been mined comparatively near the surface, and consisted of a soft mass of ferruginous 

clay carrying carbonate of lead and silver, probably native or as 

chloride.

Under some circumstances partial oxidation has extended to depths 

of several hundred feet. In the Silver Lake mine more or less oxidation 

has taken place where the lodes of Group II join the Silver Lake lode. 

Subsequent movements have allowed surface waters to descend at the 

intersections of the planes of weakness determined by the lodes. The 

partial oxidation of the Tomboy and Camp Bird lodes at considerable 

depth, and the deposition within them of black oxide of manganese, 

are apparently due to fracturing of the original lode filling, thus 

allowing the downward seepage of oxidizing waters.

STRUCTURE OF THE LODE ORES.

MEGASCOPICAL STRUCTURES.

Six kinds of ore structure have been recognized in the-lode ores of 

the Silverton quadrangle: 

1. Massive structure. The quartz, galena, sphalerite, chalcopyrite,
88 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

pyrite, and other minerals are all crystallized irregularly in the fissures 

without external crystal form and without definite arrangement. As 

a rule the constituent minerals appear to have crystallized practically 

simultaneously.

This structure is exceedingly common and is the characteristic one 

of the quadrangle. It is typically exhibited by the ores of the Silver 

Lake, Royal, Stelzner, New York City, Iowa, and East Iowa lodes of the 

Silver Lake Basin (PI. XI, B}. The quartz sometimes incloses empty 

spaces, either as minute interstices between interlocking quartz prisms 

or as small vugs lined with quartz crystals. Occasionally, instead of 

being perfectly massive, the ore exhibits indistinct traces of the structure next to be described. The two are connected by intermediate 

forms.

2, Banded structure l)y deposition. The ore and gangue minerals 

have been, deposited in more or less parallel sheets, distinguishable

PIG. 7. Cross section of No-Name lode, Sunnyside mine, a, country rock; b, ore, chiefly galena 

with quartz gangue; c, rhodonite.

from each other by the fact that they contain the constituent veinforming minerals in different proportions.

This is far less common than the preceding, but it is found in many 

small, and unproductive veins and in some of the more important 

lodes, such as the Gold King, where the pyrite has been deposited in 

bands alternating with white quartz. On the large scale it is perhaps 

exemplified in the'Sunnyside lode, where the ore streaks, themselves 

of massive structure, consisting of galena, sphalerite, chalcopyrite, 

pyrite, tetrahedrite, and free gold in a gangue of quartz, rhodonite, 

and a little fluorite, are separated by plates or lenses of relatively 

barren rhodonite. This structure is illustrated by fig. 7, which is a 

section of the No-Name vein in the Sunnyside ground.

In the smaller veins and stringers carrying galena and quartz the 

galena frequently fills the medial suture formed by the opposing 

pyramidal ends of the quartz crystals which have grown out from the 

walls of the fissure. This is well seen in some of the veinlets of the 

Silver Lake Basin. Even the larger lodes, with prevailingly massive
U.S.GEOLOGICAL SURVEY BULLETIN No. I8E PL. XII

ORE - STRIJCTU11E S
BANSOME,] STRUCTURE OF THE LODE ORES.

structure, not infrequently reveal a tendency toward a final crystallization of the galena in the middle portion of the vein, as may be seen 

in parts of the Iowa lode and in the Idaho claim, on the Titusville 

lode. This same tendency is also illustrated in fig. 8, which is a 

sketch of a small regularly banded vein prospected by the roadside 

half a mile north of Houghton Mountain and close to the London 

shaft.

Remarkably fine and regular banding was observed in the ore 

thrown out on the dump of a small deserted tunnel on what is probably the Osceola claim, in Cunningham Gulch, about half a mile above 

Stony Gulch. In its most perfect form this banding consists of dark 

sheets of finely crystalline sphalerite and galena about one-half millimeter in thickness, separated by plates of vitreous quartz about 2 

millimeters in thickness. The result is a remarkably regular and 

striking fine banding (PL XII, A}. The little sheets of quartz frequently show comb structure and have apparently crystallized in

FIG. 8. Cross section of banded vein near the London shaft, Mineral Point. «, country rock; 

b, quartz and chalcopyrite; c, tetrahedrite; d, d', quartz; e, galena.

open spaces. In some facies with rather wider banding chalcopyrite 

occurs, chiefly in the quartzose bands. The cause of such fine and 

regular banding is not known, but is probably connected with 

metasomatic replacement. The ore is apparently of too low grade 

for profitable working and was not seen in place.

Another form of original banding is that exhibited l>y the rich gold 

ore of the Camp Bird mine (Pl.° XII, J3). As elsewhere described, the 

rich portion of this lode is a sheeted zone in San Juan andesitic 

breccia and lies next the main hanging wall of the lode. Within the 

individual fissures of this zone the quartz has crystallized freely in 

open spaces. Thus, in the specimen illustrated, which represents a 

characteristic cross section of one of the richest ore streaks, the quartz 

crystals are implanted at their bases on a thin seam of chalcedony and 

carbonates carrying a little finely divided galena and sphalerite and 

associated with pulverulent white kaolin. The thickness of this seam 

of chalcedony and kaolin varies from 1 to 2 centimeters. From this 

&s a foundation the quartz crystals grew out into the fissure. But
90 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

ftlBifc^-

liii^r^iiiy fSSte^-Sii!

after they had attained a length of 2 or 3 centimeters there was an 

enrichment of the depositing solutions, as is shown by an undulatingdark band traversing all the crystals in a general direction at right 

angles to their direction of growth and parallel to the walls of the 

fissure. This dark band, which is usually about a quarter of a centimeter in thickness, is made up of free gold, galena, sphalerite, and a 

minute amount of some unknown telluride, all in'very small particles 

embedded in the quartz. After this the quartz crystals continued to

grow outward for another 2 or 3

3 I c ~0 a centimeters, containing in this

portion only scattered specks and 

bunches of ore minerals. The 

direct outward growth of the 

quartz crystals now stopped and 

there was deposited upon the wavy 

surface defined by their pyramidal 

terminations a succession of at 

least 6 distinct coatings, differing 

in color, composed of cryptocrystalline aggregates of quartz, calcite, fluorite, sericite, and a little 

chlorite, aggregating in thickness 

about one-fourth centimeter. 

Upon these coatings there was 

next deposited a layer, about onehalf centimeter thick, consisting 

chiefly of finely divided particles 

of sphalerite, galena, and possibly 

other ore minerals. This is the 

most conspicuous dark band seen 

in the illustration. This band is 

succeeded by a delicately mottled 

pale-green aggregate of quartz, 

the grains of which sometimes 

contain free gold, calcite, sericite, 

and fluorite, with dark patches of 

ore. This aggregate does not 

exhibit the characteristics of material that has crystallizeJf freely in open spaces and is probably, in 

part at least, altered and replaced country rock. Variations from 

the foregoing structure are met witti in various parts of the Camp 

Bird lode, but the specimen described is thoroughly characteristic of 

the richest ore and illustrates well its curious and beautiful banding 

(fig. 9). The conspicuous dark band, locally designated "the worm," 

is the miners' sign for good ore in this mine.

In the Tom Moore mine the pay streak frequently consists of challlneh

FIG. 9. Section through a rich ore band in the 

Camp Bird lode, a, quartz, fluorite, calcite, 

etc.; b, ore particles including free gold; c, 

quartz.
UAN30MB.] STRUCTURE OF THE LODE ORES. 91

copyrite in the middle with tetrahedrite on each side, the latter fading 

off into the altered country rock. '

S. Brecciated structure. Ore formed at an earlier period of deposition has been broken into angular fragments by renewed movement 

along the fissure, and reeemented by fresh deposition of the ore or 

gangue.

Ore so shattered as to come under this head has not been noted as 

a conspicuous feature of any important deposit,, although some brecciation can often be detected. The structure, however, is best exemplified by material from the dump of the Red Cloud mine, in which 

an original deposit of radially fibrous pyrite has been broken up and 

held together by a younger accumulation of vein quartz carrying a 

little sphalerite and galena (PI. XI, C), and also by vein filling from 

the Polar Star -and Palmetto mines. In the Red Cloud occurrence 

not only have the concentric shells of pyrite been broken up, but in

some cases exceedingly thin coatings or sheets of the sulphide have 

been floated or moved out into the quartz, and in the polished specimen from which PL XI, C was made these delicate curved films 

embedded in the quartz resemble the finest cloisonne work of the 

Japanese.

4. Cellular structure. The quartz or other vein material has crystallized as a mass of irregularly intersecting septa, leaving numerous 

drusy cavities separated by relatively thin walls.

This is not a structure characterizing any important ore deposit, 

and was not seen in place. But it is of interest in view of the possible light that it may throw on the processes by which the veinforming materials are deposited. The structure is best exemplified 

by fragments on the dump of the Pride of Syracuse mine and on an 

upper dump of the Empire- group, Sultan Mountain. In the latter 

case the septa are composed chiefly of sphalerite and galena, arid the 

cells are lined with drusy quartz and in some cases filled with rhodochrosite. Beautiful little crystals of amber-colored sphalerite and of 

tetrahedrite were observed in some of the cells, implanted upon quartz. 

It is possible that this cellular structure may have resulted from some 

kind of pseudonlorphous replacement coupled with the solution and. 

removal of some unknown mineral.

5. Splierulitic structure. The quartz of a vein has crystallized in 

prisms, often imperfectly formed, which show a marked tendency to 

group themselves in radial fashion about local, centers of crystallization. It is not intended to treat specially under this head such minerals as treinolite, which exhibits characteristicall}7 a radial structure.

A rough spherulitic crystallization, previously described by Purington, 1 was noted in the gold quartz of the Tomboy mine and, in. 

connection with banding, in the Camp Bird lode. It is also a notable 

feature of the North Star lode, where worked in the Dives mine (see

1 Preliminary report on the mining industries of the Telluride quadrangle, Colorado: Eighteenth Ann. Rept. U. S, Geol. Survey, Pt. Ill, 1898, p. 840.
^)2 ECONOMIC GEOLOGY OF SILVEKTON QUADBANGLE. [BULL. 182.

PL XI, A), and of the Magnet lode. The quartz in this case has often 

.grown radially outward, from kernels of tetrahedrite. Less conspicuous radial structure was noted in the Silver Queen, at the head of 

Placer Gulch.

MICROSCOPICAL FEATURES.

In the larger lodes, with massive structure, particularly those carrying much galena, the crystallization is, as a rule, so coarse that 

microscopical study is of use only in furnishing details of miueralogical structure. The quartz of such lodes shows the usual character

 of vein quartz, and has crystallized in large, irregular grains, interlocking with one another and with the principal ore constituents. The

 structure, when sufficiently fine to be embraced in a thin section, 

is typically hypidiomorphic granular (PI. IX). Microscopic fluid 

inclusions with gaseous bubbles, often arranged along curved surfaces within the quartz, are always present. No special investigation 

of the hermetically inclosed liquids of these minute cavities has been 

made for this region, but they are probably solutions of calcium and 

alkaline sulphates, with some chlorides, and veiy likely carbonic acid. 1 

Interstitial or miarolitic cavities into which the quartz crystals sometimes project are common, and are often filled with calcite, or, in the 

Silver Lake Basin, with chlorite (PI. IX, A).

Vein quartz varies widely in the size of the constituent crystal, 

grains. In the Sunnyside and neighboring lodes the galena, sphalerite, and chalcopyrite are distributed through the gangue in smaller 

particles, and the quartz grains themselves are correspondingly smaller 

than those in the Silver Lake veins. PI. IX, B, shows a typical thin 

section of Sunnyside ore, in which chalcopyrite and sphalerite happen 

to be the dominant ore minerals.

Still, other ores, of which that of the Ridgway mine may be taken 

as a type, exhibit throughout much finer crystallization. The quartz 

occurs in small interlocking grains, and the ore particles, which in 

hand specimens are often so small as to render the quartz cloudy or 

black, without being themselves individually noticeable, are seen 

under the microscope to be thickly sprinkled through the gangue 

and to be very irregular in shape. They occur both in the sutures 

between the quartz grains and within the grains themselves (PI. 

X, A). Such ore is almost invariably said by the miners to contain 

brittle silver. But neither chemical tests nor the microscope reveal

 stephanite. In the Ridgway ore the particles are chiefly argentite with 

some pyrite, a little sphalerite, and sometimes a little galena. These 

finely crystalline ores are worked for silver and gold, as the galena is 

rarely abundant enough to pay for extraction. But they are by no 

means equally rich. In some cases the finely disseminated ore parti1 Gold-quartz veins of Nevada City and Grass Valley districts, by Waldemar Lindgren: Seventeenth Ann. Rept. U. S. Geol. Survey, 1896, Pt. II, p. 131.
RANSOME.] STKUCTUKE OF THE LODE ORES. 93

cles are chiefly argentiferous galena, sometimes a lead sulphobisnmthite, and occasionally tetrahedrite. Proustite (ruby silver) wasnoted in the Ben Butler mine, with finely crystalline galena, which 

is erroneously called brittle silver by the miners.

The gangne of the rich ore of the Camp Bird mine shows several 

interesting variations in its rnicrostructure, and differs from that of 

any other lode known in the quadrangle. A characteristic structure 

and mineralogical composition is that shown in PI. X, .£>, where quartz, 

calcite, and fluorite are crystallized together. This is a common 

appearance of the pale-green, finely crystalline aggregate which has 

crystallized concentrically outside of the dark, wavy ore band shown 

in PI. XII, B. The quartz here shows a distinct tendency toward idiomorphic form, and in sections transverse to the prism usually reveals, 

in polarized light, a zonal structure the outer shells of Avhich are 

composed of shadowy sectors differing in their interference tints (PI.

X, B). These quartz grains contain inclusions of chlorite and a mineral in acicular crystals too small for identification. The inclusions 

are most abundant near the center of the crystal. The fluorite is not 

always present, and the gangue is frequently much more finely crystalline and often shows nests of sericite. This portion of the gangue 

has evidently crystallized in part in open spaces, fyit it has also 

undoubtedly in part resulted from a metasoinatic replacement of the 

San Juan breccia adjacent to or included within the main fissure 

zone. The microscope shows the free gold to occur in nests of minute 

hackly particles solidly embedded iii quartz. It is apparently most 

abundant in the coarsely crystalline, vitreous, radial quartz (see PI. 

XII, J5), but also occurs in the quartz just outside of the dark ore band 

already referred to. As seen under the microscope this ore band consists of particles of galena, light-yellow sphalerite, and chalcopyrite 

in quartz. The gold was not seen in the dark band itself, but is 

nearly always AVI thin a few centimeters of it, usually associated with 

a little galena and sphalerite.

Although as a rule the ores occupy filled fissures, yet in a few cases 

the gangue in which the ore occurs is composed wholly or in part of 

country rock which has been altered to an aggregate of quartz, and 

usually one or more of the following minerals: Calcite, sericite, kaolinite, chalcedony, nuorite-. Such aggregates generally differ from true 

vein filling in showing under the microscope a much finer crystallization of their constituents into a mosaic which is more or less cloudy 

when seen between crossed nicols. The grains of quartz seldom 

exhibit the clear, definite boundaries seen in vein filling, such as is 

shown in PL IX. Moreover, the sericite and calcite are often 

grouped in areas whose form is that of former feldspathic phenocrysts. This structure, however, will be more fully described in the 

section on the nietamorphism of the country rock.
94 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182. 

AREAL DISTRIBUTION OF THE LODE ORES.

The various mineralogical and structural types of ore are not distributed at random over the quadrangle, but a given portion of the 

area is often characterized by ore of a certain kind, differing from 

those which preponderate in other portions. These areal subdivisions 

are not sharply bounded, and it often happens that in a district in 

which most of the lodes contain a certain type of ore there will occur 

other ores which are more characteristic of some other district in the 

quadrangle.. But, notwithstanding these transitions and exceptions, 

the localization of ore types is a striking feature of the region.

The lodes traversing the mass of Sultan Mountain are quite commonly filled with rather coarsely crystalline vein filling, carrying 

galena, tetrahedrite, and chalcopyrite, with some sphalerite andpyrite, 

in a gangue of quartz and barite. Their chief value is in silver. The 

most productive of these lodes has been the North Star, which produced an ore running about 40 per cent lead and 70 ounces of silver. 

This lode is in monzonite, but mineralogically similar ore is found in 

the King lode in Algonkian schists, said to carry about 0.1 ounce of 

gold, 55 ounces of silver, and 15 per cent of lead. The ore of the 

Empire group of veins is generally similar in character.

 Southeast of Silverton, in the vicinity of Deer Park, are numerous 

mineralized fissures cutting the schists and granites, and in-some 

cases the overlying San Juan breccia. These are occupied, as anile, 

by quartz veins carrying pyrite, with a little galena, sphalerite, and 

chalcop37 rite. They are prospected for gold, which occurs free in 

small pockets. Compared with most of the lodes in the quadrangle 

these veins are not heavily mineralized, and are not mined on an 

important scale.

The lodes of Silver Lake Basin are'characterized by coarse, massive 

structure and are heavily mineralized. Galena often exceeds all

 oth,er constituents of the vein filling in amount, and lead is an important factor in the output. Sphalerite and chalcopyrite accompany 

the coarsely crystalline galena, and there is usually some pyrite 

present. The gangue is quartz, often containing chlorite. Tetra- 

. hedrite occurs sporadically in many of these lodes, and barite was 

noted in the Royal Tiger workings. These are generally loAv-grade

 concentrating ores, averaging from $8 to $15 per ton. Free gold is 

rarely seen, but the gold tenor in some of the lodes of Group II (see 

p. 147) may rise to 2 or 3 ounces per ton. In the Silver Lake mine 

about half the value of the output is from the gold; the remainder 

"being in silver, lead, and copper. The other mines contain less gold, 

and the Royal Tiger mine depends chiefly upon its lead. Most of the 

ore of Hazelton Mountain appears to have been of the general type 

.just outlined. A thousand tons from the Aspen mine is said to have 

produced 110 ounces of silver per ton and 60 per cent lead, although 

the average tenor was somewhat less than this. An exception of the
BANSOME.] AREAL DISTRIBUTION OF THE LODE ORES. 95

sort referred to at the beginning of this section is afforded by the 

.Little Giant lode, on the north side of Arrastra Gulch, which produced a free-gold ore.

In Maggie Gulch the greater number of the lodes contain siliceous 

ores, of which that of the Ridgway mine may be taken as the general 

type (PI. X, A). In these ores the quartz is finely crystalline and 

the ore minerals occur as minute dark specks, which, when abundant, 

give the gangne a dark, clouded appearance. In the Ridgway, the only 

mine working these ores on a commercial scale, the ore particles are 

chiefly argentite. But in other cases they are galena, and apparently 

not always very argentiferous. The erroneous belief of the prospectors that these minute ore particles are nearly always "brittle 

silver" has in some cases resulted in much fruitless labor. In one 

instance a prospecting tunnel of considerable length was being run 

on expectations excited by a few minute bunches of "brittle silver,"

which were in reality worthless specular-He. Ores generally similar 

to those of Maggie Gulch occur at various points in the northeastern 

part of the quadrangle, particularly in the vicinity of Mineral Point.

In Snniiyside Basin and at the head of Placer Gulch the ores are 

commonly of moderately coarse crystallization and carry abundant 

galena, sphalerite, and chalcopyrite. They are almost invariably 

associated with abundant rhodonite. Of low grade as a Avhole, they 

sometimes contain bunches of rich ore, which, in the Sunnyside Extension mine, are known to have carried, in carload lots, as much as 74 

ounces of gold per ton, mostly free. The ore of the Sunnyside mine 

may be considered as typical of this district.

In Poughkeepsie Gulch'-the ores partake somewhat of the characteristics of those of the Sunnyside Basin and of Mineral Point. But 

their most characteristic feature appears to have been in the occurrence of the lead and silver in some combination with bismuth, usually 

as an argentiferous sulphobismiithite of lead. The ore of the Alaska 

mine is a well-known example and has been described on page 195.

In the extreme northeast corner of the quadrangle many of the 

prospects and some of the mines formerly worked are characterized 

by argentiferous copper ores, usually chalcocite or bornite, with some 

galena and chalcopyrite.

What may conveniently be termed the Red Mountain Range, 

embracing the region bounded by Cement, Grey Copper, and Mineral 

creeks, is characterized by the predominance of the stock deposits 

and their peculiar ores, which will be described in subsequent-pages.

Lastly, in the northwest corner of the quadrangle, ores carrying 

much galena, and recalling in some of their features those of Silver 

Lake Basin, are associated with gold ores such as those of the Camp 

Bird and Tomboy, mines.

As far as could be determined, the distribution of ore tj^pes as briefly 

sketched in the foregoing paragraphs is purely areal and is not
96 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182,

dependent upon kind of country rock or direction of Assuring. Finally,, 

emphasis should again be laid upon the fact that there is much overlapping and intermingling of types, and that ores of many kinds may 

occur in any given limited district. Free-gold ores, in particular, may 

be expected to occur in any part of the quadrangle.

DISTRIBUTION OF THE ORES WITHIN THE LODES.

Lodes are seldom equally well mineralized in all portions. Those 

parts of a lode or vein which are sufficiently large and rich to be 

profitably worked are commonly known as pay shoots or ore shoots, 

sometimes spelled ore chutes. The first term is regarded as preferable, inasmuch as it expresses concisely the thing meant, and cannot 

be confounded with the ore chutes or mill holes of timber through 

which ore is drawn from the stopes into the mine levels. A pay shoot 

is obviously not a thing capable of exact delimitation. Its size and 

shape depend to some extent on fluctuations in the metal market 

(unless purely a gold ore) and on variations in the operating expenses 

of the mine. But the concentration of ore in certain portions of a* 

lode separated by unprofitable lode matter is a very important phenomenon, and one that can, as a rule, be studied and discussed only 

as it is revealed in the exploitation of pay shoots by actual stoping.

A complete study of pay shoots requires good'stope maps, carefully 

revised to date, and an advanced stage in the development of the 

lodes. Except for a few localities, these favorable conditions are not 

found in the Silverton quadrangle. The advantage in all future 

development of having a record of past work is not always fully 

realized, and the miner is too often content simply to follow his ore 

where he finds it, adapting his work merely to the needs of to-day. 

In simple lodes with continuous pay shoots this rough-and-ready

mining may succeed well enough. But in complex lodes, or in groups

of lodes, such as those of the Silver Lake mine, systematic mapping 

and the adaptation of the development to future probabilities may 

mean success where the more ordinary method would result in failure. 

On account of the general absence of accurate stope maps and the 

small depth of most of the mines operating in the quadrangle the 

following observations on the pay shoots are fragmentary and often 

unsatisfactory.

In mosj] of the workable veins and simple lodes, such as those of 

Sultan Mountain and Silver Lake Basin, pay ore is usually, although 

not invariably, found wherever the fissure is wide enough to hold an 

ore body. This appears to be particularly true of the New York City, 

Stelziier, Royal, and Iowa veins. Thus, in these veins, distinct pay 

shoots, separated by stretches of barren lode, do not properly occur, 

or have not been demonstrated by mining operations. The pay shoots 

take their shape, as a whole, from the form of the fissure. A partial 

exception to this is found, however, in the impoverishment of the
RANSOME.] DISTRIBUTION OF OKES WITHIN THE LODES. ' 97

lodes of Group II as they approach the Silver Lake lode, which is 

itself of lower grade, and in occasional spots where the lodes retain 

their width but are too low grade to work. The pay shoots of these 

lodes also grow longer with depth, which is apparently due to the 

increasing length of the fissures in connection with the dip of the 

Silver Lake lode. In the Silver Lake lode the pay ore is found in 

bunches of varying size; but as these bunches usually occur wherever 

the filling of the fissure is wide and firm they probably do not constitute a marked exception to the foregoing general rule. In the Royal 

Tiger mine not enough work has been done to reveal the real shape 

and extent of the ore body. In the North Star mine, on Little Giant 

Mountain, the ore occurred irregularly in a stringer lead, but the old 

stope maps show the pay shoot as a whole to have been about 700 feet 

in length on the levels and to have pitched to the southeast. Other 

small ore bodies were found farther in the mountain, to the northwest. 

In the Sunnyside and Suimyside Extension mines the pay shoots are 

mainly lenticular bodies 30 or 40 feet in length, lying on the hanging 

or foot wall side of the lode, or between plates of rhodonite. Owing 

to the lack of maps, the exact sizes and shapes of these ore bodies are 

not known.

In the Silver Queen mine, on Bear Creek, the ore occurs in three 

separate pay shoots, pitching south and separated by from 12 to 15 

feet of lean quartz. The northern pay shoot consists of low-grade 

chalcopyrite, with subordinate galena and tetrahedrite. The middle 

ore body is rich in an argentiferous sulphobismutliite of lead associated with galena, but changed to chalcopyrite in stoping upward from 

the tunnel level. The south pay shoot is almost wholly galena. The 

development of this mine is very superficial and the three pay shoots 

may, with more extensive workings, be found to be simply portions 

of one ore body.

In the Camp Bird mine the pay shoots, so far as known, appear to 

be coextensive with the lode, disappearing only where the fissures 

locally contract to a mere crack. What is known as the west pay 

shoot is about 1,200 feet in length, and others occur along the lode, 

separated by pinches. The pay shoots are stated to be increasing in 

length with depth. As previously pointed out (p. 89), the auriferous 

portion of the lode lies next the hanging wall, with a silver-lead streak 

near the foot wall.

In the Tomboy, also, the pay shoots, as indicated by the stopes, are 

long, and are practically identical with the lode itself, disappearing 

only where the latter is pinched. According to Mr. John Herron, 

superintendent, the pay shoots lie flat in the lode, one above another, 

and extend diagonally across from wall to wall. They are said, moreover, to be often connected with certain post-mineral fractures which 

cross the vein diagonally in the same direction (see p. 209). There 

was no means of verifying these statements, and such minor pay

Bull. 182 01 7
98 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE.

shoots, with the intervening lower-grade quartz, are all stoped out in 

working and would not appear in an ordinary stope map. It is 

beyond- question, however, that in this mine the best ore occurs in 

quartz which has been crushed by movements subsequent to its 

original deposition. The solid, unbroken, unstained quartz is invariably of somewhat lower grade. As in the Camp Bird, the auriferous 

ore is next the hanging wall, a silver-lead streak lying near the foot 

wall.

From large, regular pay shoots, such as are found in the New York 

City, Camp Bird, and Tomboy lodes, all gradations may be found 

through smaller, more irregular ore bodies down to the occasional 

small pockets of rich ore encountered in some of the lodes of Deer 

Park and Maggie Gulch.

The changes which take place in pay shoots with depth are exceedingly important in mining operations. Unlike the auriferous lodes of 

California, which rarely show any progressive or regular change in 

the character of their ores even to depths of 2,500 feet, the pay shoots 

of the Silverton quadrangle are less constant. It is a common belief 

among mining men of this region that lead ores do not go down to 

great, or even to moderate, depths. In part this opinion is plainly 

traceable to the experience gained in exploiting the stocks of the Bed 

Mountain district, which will be described in subsequent pages; but 

it is pertinent here to see how far it is justified by the known facts in 

regard to the lodes.

In the Aspen mine there are said to have been several veins near 

the surface which came together at moderate depth. Below a depth 

of 800 feet the galena, which \Aras very abundant in the upper levels, 

is said by Mr. W. H. Thomas to have so diminished in amount as to 

make further work unprofitable. According to the same informant 

the ore of the Belcher mine, on Sultan Mountain, earned abundant

galena of good grade in the upper workings, but this decreased in 

amount and value in the lower levels, while sphalerite grew more 

abundant. Actual verification of these statements by observation is 

not.now practicable, but Mr. Thomas, who had been connected with 

both mines, was undoubtedly himself convinced of the truth of his 

statements. In the Royal, Stelzner, New York City, Iowa, and East 

Iowa lodes there is no present indication of any diminution of galena 

or of any other regular change in the ore with increasing depth. The 

ore of the New York City lode where cut by the Unity tunnel, about 

1,200 feet below the croppings, shows abundant galena, and is similar 

to the ore in the same vein on levels C and J, 400 and 700 feet, 

respectively, above the Unity level. If anything, it is of higher 

grade. The Buckeye lode (part of the Titusville lode) has not been 

exploited to great depth, but tetrahedrite was undoubtedly more 

abundant in the upper than in the lower tunnel. In the North Star 

mine, on Little Giant Peak, a change in the character of the ore is
HANSOME.] DISTRIBUTION OF ORES WITHIN THE LODES. 99

well authenticated by Mr. W. Crooke, the manager. For 200 feet 

below the croppings the ore was largely sulphate of lead (anglesite) 

with some galena, and did not carry much silver. Below that level 

it changed to unoxidized galena. With increasing depth the place of 

the galena was largely taken by argentiferous tetrahedrif-e, and in the 

lowest workings, about 600 feet below the cropping, there was very 

little galena found. The bottom of the pay shoot is said to have been 

reached in the lowest workings, although the fissure zone continues 

to an unknown depth and probably contains other pay shoots, which, 

however, may not be large or rich.

In the Polar Star mine, on Engineer Mountain, the ore, consisting 

of argentite and proustite, is said by Mr. W. Crooke to have changed 

abruptly to iron pyrite, carrying about 12 ounces of silver per ton 

and no gold. According to Mr. Crooke, this change was generally 

encountered atabont the same level in all of the mines on this portion

of the mountain. The exact depth at which the change took place is 

not known, but it must have been moderate, probably not more than 

500 feet. In the Palmetto mine, on the northeastern extension of the 

Polar Star lode, the ore near the surface ran as high as $500 per ton, 

and contained ruby and so-called, "brittle " silver (probably proustite 

and argentite), resembling that of the Polar Star mine. The lode 

struck in the shaft at a depth of 400 or 500 feet was of low grade, and, 

as the dump shows, contained much pyrite. In this, as in the case of 

the Old Lout and Pride of Syracuse, it is sometimes asserted that the 

lode found in the deeper workings was not the same as that which 

had been productive above. While a mistake of this kind is not 

impossible in individual cases, the threefold repetition of such a mischance in theSilverton region maybe set down as highly improbable. 

The histories of the Pride of Syracuse mine on Engineer Mountain 

and of the San Juan Chief mine are almost repetitions of that of the 

Palmetto.. The Old Lout lode, which produced rich bismuthiferous 

ore to the extent of several hundred thousand dollars from a shaft 

sunk on the lode, proved too poor to work when crosscut by a long 

tunnel from the bottom of Poughkeepsie Gulch, about a thousand feet 

below the croppings. The ore from this lowest level shows galena, 

chalcopyrite, sphalerite, and pyrite, about equally distributed in a 

gangue of quartz with a little barite. The U. S. Depository lode, in 

Richmond Basin, produced some galena ore in the upper workings, 

but where cut by a tunnel, at a depth of something over 500 feet, the 

lode proved worthless. In this case the lode is well defined, but shows 

scarcely any mineralization in the lower workings. In the Uncompahgre Chief, a prospect near Mineral Point, a shaft 50 feet in depth 

has passed through ore containing an argentiferous sulphobismuthite 

of copper and lead, into an ore of which pyrite is the chief mineral 

constituent. In the Dolly'Varden mine, north of Rose's Cabin, according to Mr. James Abbott, good ore containing tetrahedrite and
100 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

"brittle silver" (?) was found in the shaft, but no pay ore was encountered in a lower crosscut tunnel.

From the foregoing it appears that in this region pay shoots containing chiefly ores of lead, silver, and copper may change in mineralogical character and in value within very moderate depths. But 

while galena in one case has been succeeded by tetrahedrite and in 

another case partly by sphalerite, in other lodes containing silverlead ore tetrahedrite (Royal Tiger and Buckeye mines) and sphalerite (Iowa lode) have been more abundant in the upper than in the 

lower workings. Thus the facts, as at present known, do not justify 

the general statement that galena passes into gray copper with depth, 

or vice versa. The change from galena to sphalerite with increasing 

depth is a well-known phenomenon in the lead and zinc deposits of 

southwestern Wisconsin, and is explained -by Van Hise 1 as a result 

(I) of a first concentration by ascending waters and (2) of a second 

concentration by descending waters. It is possible that the change 

recorded in the Belcher is of this character. But the occurrence of 

abundant argentiferous galena and tetrahedrite in the Virginius lode 

at the Revenue Tunnel level, over 2,0.00 feet below the croppings, and 

of galena in the deepest workings on the New York C\ty lode, indicate 

that both tetrahedrite and galena may occur abundantly and retain 

their values at far greater depths than were reached in the Aspen, 

North Star, and other mines of the Silverton quadrangle, in which 

the pay shoots are reported to have diminished in value or to have 

disappeared entirely. As applied to the lodes, therefore, the oftenheard arbitrary dictum that galena and tetrahedrit'e "do not go 

down," in so far as it relates to the depths ordinarily met with in 

mining, is a generalization based on insufficient premises, although, 

as will appear in the discussion of the origin of the ores, there are 

theoretical reasons for supposing these minerals less likely than.certain other sulphides to be found in abundance at great depths. With 

regard to the rich silver ores argentite and proustite, the known facts, 

incomplete as they are, seem, to warrant the conclusion that these 

minerals occur in the upper portions of the lodes only, and do not 

extend to great depths, probably rarely over 500 feet in this region. 

This is in general accord with observations in other districts where 

these and other rich silver minerals occur, and, as will be later shown, 

this fact has an important bearing on the question of the genesis of 

the ores.

The vertical range of the argentiferous sulphobismuthites of lead 

occurring in the Silverton region is not known, but there are some 

indications that they do not extend to great depths.

The free gold ores have not yet been worked to a sufficient extent 

in the Silverton quadrangle to furnish any very reliable data as to

'Some principles controlling the deposition of ores: Trans. Am. Inst. Min. Eng., Vol. XXX,. 

1900, pp. 104-109.
RANSOME.] SECONDARY ALTERATION OF THE LODE OEES. 101

their possible changes in value with depth. The indications, however, 

are in favor of a varying, but on the whole more nearly constant, 

'tenor as they are mined to greater depths, 'than in the case of silverload ores. It is fair to assume that the considerable depth to which 

the lodes of California have been mined without revealing any regular 

increase or decrease in the tenor of the pay shoots below the zone of 

oxidation is something more than a mere local phenomenon, and 

holds for gold-quartz lodes somewhat generally, provided that the 

fissures are continuous and the country rock is uniform.

RELATION OF ORES TO KIND OF COUNTRY ROCK.

As far as known, the influence of the country rock upon the deposition of the lode ores in the Silverton quadrangle is small. Extensive 

productive ore bodies occur in monzonite and in the volcanic rocks of

both.the Silverton and San Juan series; and, although none are worked 

in the Algonkian schists, there is no indication that, given a suitable 

fissure, ores would not be deposited as readily in these as in other 

rocks. The influence of the wall rock upon ore deposition appears to 

be limited to a tendency toward impregnation and replacement in the 

deposition of ores in some of the rhyolitic and andesitic flow breccias 

and tuffs. This, however, is a phenomenon relating to the form of the 

deposit, and to the subject of the alteration of the wall rocks rather 

than to the character of the ores themselves.

SECONDARY ALTERATION OF THE LODE ORES.

Owing to the fact that erosion in this high region is effected by 

mechanical disintegration rather than by secular decay, the oxidation 

of the ores is not, as a rule, very extensive, and is sometimes negligible. In the North Star mine, on Little Giant Peak, oxidized ore, consisting chiefly of anglesite, is reported to have extended to a depth of 

200 feet. Ordinarity, however, complete oxidation is Arery superficial, 

although traces may be found at much greater depths 'than 200 feet. 

Carbonate and sulphate of lead and carbonates of copper, often associated with the unaltered sulphides, occur in the croppings of most of 

the lodes carrying galena and. tetrahedrite or chalcopyrite. In the 

Silver Lake mine sulphate and carbonate of lead occurred abundantly 

in the highest level (No. 4) with unoxidized ore. At the level below, 

however, the secondary ores were unimportant. As is commonly the 

case in this region, there is no sharp line separating an upper zone of 

oxidation from the sulphide ores. The decomposition of the original 

ore minerals has penetrated irregularly downward wherever oxidizing 

waters found opportunity to descend, and is seldom limited by a distinct water level. Very commonly the level of permanent water lies 

far below the oxidized portion of the lode. In the Tomboy and Camp 

Bird mines black oxide of manganese occurs in the deepest workings 

and usually indicates good ore. In these cases the oxide appears to
102 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

be associated with post-mineral fracturing and crushing and to have 

been deposited later than the bulk of the ore. In the New York City 

lode of the Silver Lake mine a sooty, amorphous sulphide of copper 

occurs with pyrite, chalcopyrite, galena, and sphalerite. This is 

probably of secondary origin, and although not a product of ordinary 

oxidation is yet considered as due to descending waters percolating 

downward from the zone of weathering above.

ORIGIN OF THE LODE ORES.

Although the ores of the lode present many features not found in 

the stock deposits of the Red Mountain district, yet in the essential 

points of their origin they possess so much in common that it would 

be impossible to treat the two forms of deposit separately without 

much overlapping. Accordingly the question of the origin of the lode 

ores will be left in abeyance until the stocks have been described.

VALUE OF THE LODE ORES.

Generally speaking, the lode ores of the Silverton quadrangle are 

of low grade and require careful mining and milling to yield profitable returns. The ores which are or have been worked vary in value 

from a probable minimum of about $6 to several thousand dollars per 

ton. The extremely high values, however, are for ores carrying free 

gold occurring only in small amounts in pockets in otherwise lowgrade lodes, or in very small veins, such as the Golden Fleece. From 

the Sunnyside Extension mine, however, ore was obtained in carload 

lots carrying $1,500 per ton in gold alone, as shown by the smelter 

returns. In the Silver Lake Basin the ores worked probably vary 

from $8 or $10 to $60 or $70 per ton, according to the proportion of 

lead, silver, or gold which they contain. The average of the ore from 

the Iowa mine is not far from $12 per ton, although in places it may 

contain from 2 to 3 ounces of gold, thus affording much higher returns. 

The general average of the Silver Lake mine is probably higher, as 

half the value of its output is in gold. The ore of the Royal Tiger is, 

on the other hand, somewhat lower, the product being chiefly in lead. 

The North Star mine, on Sultan Mountain, was producing quantities 

of ore in 1882 carrying, according to the Mint reports, 40 per cent of 

lead and 70 per cent of silver. At the commercial values for that 

year this would mean an ore of about $120 per ton, gross value, or, at 

present prices, about $72 per ton. The Aspen mine is said to have 

produced one lot of 1,000 tons of ore containing 110 ounces of silver 

and 60 per cent of lead, which at present prices would correspond to 

about $110 per ton. The average value of the ore from this mine was, 

however, probably less than half this. The shipping ore from the 

Ridgway mine, containing finely disseminated argentite, is reported 

to average about $110 per ton, of which about 3 ounces is in gold and 

the rest in silver. The free-gold ore of the Tomboy mine averages 

about $20 per ton, of which $19 is in gold. The most uniformly rich
RANSOME.] THE STOCKS OE MASSES. 103

ore now worked in quantity in the quadrangle is undoubtedly the 

gold ore of the Camp Bird. This is all milled, and averages from $40 

to $200 per ton as delivered at the stamps. The gold ore of the,Gold 

King mine is generally of low grade and can be worked to about as 

low a limit as any in the quadrangle.

THE STOCKS OR MASSES. 

DEFINITION AND GENERAL DESCRIPTION.

As defined by Yon Ootta, 1 ore stocks are irregular bodies of ore 

possessing, distinct boundaries. They differ from veins or lodes in 

the absence of a characteristic tabular form, and from impregnations 

in being fairly solid masses of ore with definite limits, or, in the case 

of stockworks (Stockwerke), of a great number of small veins or ore 

bodies constituting a mass which is worked as a whole. Phillips 2 

has translated Von Cotta's Stocke as "masses," but this word is SO 

general, in its scope and lias been used in so many classifications with 

varying significance that it is here discarded as a definite descriptive 

term. The nearly vertical ore bodies of the Red Mountain district, 

sometimes locally known as ''chimneys," are substantially what Von 

Cotta has described and defined as standing (or upright) stocks.

The stocks of the Silverton quadrangle are nearly vertical, irregularly lenticular or spindle-shaped bodies of almost solid ore, surrounded by an envelope of much altered, partly silicified .country 

rock, which is usually impregnated with pyrite. Neighboring ore 

bodies are commonly connected by fissures, usually filled with wet clay 

gouge or kaolin. The sizes of the individual ore bodies vary greatly. 

In plan, lengths of 40 or 50 feet and widths of 10 or 15 feet appear to 

have been not uncommon. Accurate sections of actual stocks are not 

now available, but individual, ore bodies appear to have been followed 

in many cases through several levels, and therefore to have had a 

nearly vertical maximum dimension of several hundred feet. vVlthough 

sometimes nearly circular, the ore bodies generally showed a more or 

less elongated or elliptical plan, the longer axis of which usually lay 

more nearly north and south than east and west. The direction of the 

longer axis was not, however, always constant for all depths of a 

given stock.

The ore bodies, particularly in the deeper workings, were usually 

found within nearly vertical zones of fractured, altered country rock; 

locally known as "ore breaks." Mr. T. E. Schwarz, who appears to 

have originated this term, says:

The ore bodies of the Red Mountain district occur as chimneys or chutes, having great persistence in depth and varying greatly in dip and cross section, but 

ramifying toward the surface. The outcrops of these ore chutes occur along lines 

of alteration of the andesite or inclosing rock, and such lines were undoubtedly 

fracture planes of greater or less extent. These fracture planes or belts of metamorphosed andesite were in the early days of the district termed by me "ore

1 Erzlagerstiltten, p. 191, Freiberg, 1859. a Op. cit., p. 4.
104 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. IBULL.182.

breaks," to signify the character of the rock along the line of which the ore chimneys occurred or might be expected to occur. They were not fissure veins, in that 

the ore bodies did not confine themselves to any given plane, and in following 

them no definite course either laterally or vertically could be counted upon ahead 

of exploration. The course of an ore break I have frequently found to change 90° 

in a depth of several hundred feet. 1

DISTRIBUTION.

The stocks do not occur in all portions of the quadrangle, but are 

limited to a small, well-defined area, which corresponds mainly to the 

crest and westerly slope of what may be termed for convenience the 

Red Mountain Range. This district is bounded on the northeast by 

Grey Copper Creek, on the northwest by Red Creek, on the west and 

south by Mineral Creek, and on the east, with one or two exceptions 

near Red Mountain, by the ridge crest extending from Anvil Mountain northward to- Red Mountain and thence northeast to the saddle at 

the head of Grey Copper Gulch. The area thus outlined has certain 

characteristic features, apparent to the most unobservant eye. There 

is scarcely an exposure of rock within it which has not been bleached, 

silicified, or otherwise altered, and the whole has been more or less 

thickly impregnated with fine crystals of pyrite. The iron originally 

contained in this pyrite, through weathering and oxidation, has given 

to the Red Mountain Range the beautiful coloring for which the region 

is noted, blending from the deepest red, through vermilion and orange 

tints, to the most delicate yellows and graj^s.

. The greater part of the deposits, and all of the more important ones, 

are closely grouped in the northwestern part of this area, in a belt less 

than a mile wide and about 4 miles long, extending from Ironton to a 

point about a mile south of Red Mountain village.

Although no continuous fissures or veins can be detected on tli9 

Surface, it is noteworthy that the St. Paul, Congress, Senate, Hudson, 

Enterprise, Charter Oak, Genesee-Vanderbilt, Yankee Girl, Robinson, Guston, White Cloud, and Silver Bell mines all lie close to a 

straight line bearing about 1ST. 21° E. The National Belle, Paymaster, and Grand Prize mines, and a host of less-noted claims, are 

apparently irregularly disposed on either side of this line. (Fig. 10.)

South of the vicinity of Red Mountain the stock deposits are scattered and have not proved of much importance. The only one which 

has produced ore^in important amounts is that of the Zuni mine, on 

Anvil Mountain, which, however, is interesting chiefly as the source 

of the minerals guitermanite and zunyite.

ORIGIN OF THE SPACES NOW FILLED WITH ORE.

In seeking the origin of the ore spaces, there are, in spite of the 

present obstacles in the wfiy of complete investigation, certain facts

1 Trans. Am. Inst. Miu. Eng., Vol. XXVI, 1896, p. 1057.
PIG. 10. Map of the principal miuiug claims in the Bod M
106 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

which may be considered as established and which bear directly upon 

the problem. No solution can be considered as satisfactory which 

does not take them into account. They will therefore be briefly summarized.

The greater number of the productive ore bodies in the Red Mountain district, such as the Congress, Hudson, Yankee Girl, Guston, and 

Silver Bell, lie on or close to a line bearing about N. 21° E., which is 

probably a line of dominant fracturing. It is very probable, if not 

demonstrable, that a second nearly parallel zone of fractures extends 

through the ground of the National Belle mine southwesterly, past 

Summit and down Mineral Creek, to the Silver Ledge mine, near 

Chattanooga. The general course of this line is N. 30° E. The ore 

spaces are more or less irregularly spindle-shaped or ellipsoidal, with 

the longest axis commonly nearly vertical. The country rock .in 

the vicinity of the ore spaces is usually much, and rather irregularly, 

fissured. Neighboring ore bodies are commonly connected by fissures, 

and this fact was taken advantage of in prospecting. When the ore 

spaces are elongated or elliptical in plan, the longer axis generally, 

although not always, lies a little east of north. In the.Guston claim 

the ore spaces usually occur in what is called the "ore break," a zone 

of fissured country rock striking N. 20° or 30° E. Similar "ore 

breaks" were recognized in the Genesee-Vanderbilt and in other 

mines. The country rock adjacent to the ore spaces is much altered, 

as described iinder metamorphism, pages 124-131, and is often thickly 

impregnated with fine pyrite. Mr. S. F. Emmons has recorded what 

seemed to him to be undoubted replacement of country rock, especially of the Silverton breccia, by ore, and even the limited observations now possible show that some replacement undoubtedly took 

place in both the Yankee Girl and Guston mines.

It is believed that the explanation most consistent with the facts

above stated and with others presented in the detailed descriptions of 

the mines is that the ore spaces were formed primarily by complex, 

intersecting fissuring, and were enlarged both by solution and by 

metasomatic replacement. The dominant fissuring seems to have 

been in a direction between 20° and 30° E. of N., and is well shown 

along two principal zones. But there was also much minor fracturing in various other directions. Ah the intersections of two or more 

of these fissures the country rock was usually brecciated and furnished channels for the ascending currents of warm or hot mineralbearing waters which effected the pronounced hydrothermal metamorphism so conspicuous in the rocks of this particular district. 

That such waters were capable of considerably enlarging the irregular 

conduits through which they circulated, either prior to or during the 

deposition of the ore, seems likely when the shape of the ore spaces 

and the extent to which the rocks in their vicinity have been altered 

are taken into account. It must'be admitted, however, that in the case
RANSOME.] THE STOCKS OR MASSES. 107

of the small Zuiii ore body no such solvent action was detected. The 

foregoing explanation is essentially that proposed by Emmons 1 in 

1888, when he pointed out the similarity existing between the Yankee 

Girl mine and the Bull Domingo and Bassick mines in the Silver Cliff 

district, Colorado. As described by L. R. Grabill, 2 the Bassick ore 

body fills an irregular opening nearly elliptical in plan and varying 

from 20 to 30 feet on the shorter diameter to nearly 100 feet on the 

longer. It extends vertically downward for nearly 800 feet. No 

walls have been found, and there is no distinct boundary between ore 

and country rock. Emnions 3 concluded that the ore body was due to 

fumarolic action in the throat of a volcano after all explosive action 

had ceased. He remarks, however:

It would appear * * * that it was the intersection of certain fracture 

planes that determined the course of the ore-bearing channel, and that the ore 

body is not necessarily the center of tho volcanic vent, but that, as a second ore

chimney has already been discovered on one side of the first, it is by no means 

impossible that other chimneys or ore shoots may exist in the body of the agglomerate, which might be discovered by judicious and systematic exploration in the 

direction of the principal fracture planes.

In the Bassick mine the ore was deposited in the agglomerate, 

replacing the fine interstitial tuff and partly replacing the larger 

volcanic fragments. 4 It will be recalled that a somewhat similar 

replacement of the San Juan breccia by ore was noted by Mr. 

Emmons in the Yankee Girl mine (p. 216). In the Bull Domingo mine 

"the ore occupies a nearly vertical chimney-like channel in a conglomerate or breccia mass, and the minerals are deposited in concentric scales around the bowlders or rock fragments." 5 This ore 

channel "was primarily formed by a complicated intersection of a 

number of fracture planes which produced a zone of broken country 

rock, in which the included fragments may have been somewhat 

rounded by attrition, but whose final rounding was more likely completed by the solvent action of percolating solutions." 6

It is evident from the descriptions given of the Red Mountain 

stocks that the term "chimney" applied to them is somewhat misleading. They are not simple vertical pipes of ore extending from the 

surface to indefinite depths, but are separate bodies of irregular, 

lenticular, or spindle-shaped form, often completely inclosed by 

country rock, but linked with neighboring stocks by fissures which 

are often small and which carry little or no ore. There is no evidence whatever to indicate that they occupy the necks of former 

volcanoes. Although they occur in volcanic breccia, it is the

1 Structural relations of ore deposits: Trails. Ani. Inst. Min. Eng., Vol. XVI, 1888, pp. 833-834.

2 On the peculiar features of the Bassick mine: Trans. Am. Inst. Min. Eng., Vol. XI, 1882,p. 110.

3 The iniues of Custer County, Colu.: Seventeenth Ann. Rept. U. S. Geol. Survey, Pt. II, 

1890, p. 430.

4 S. F. Emmons, loc. cit., p. 438.

6 Emnions. loc. cit., p. 445. '

'Emmons, loc. cit., p. 446
108 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

normal andesitic breccia of the Silvertoii formation, which covers hundreds of square miles of the San Juan region, and is in no sense an 

agglomerate filling a A^olcanic neck.

Another common explanation is that the Red Mountain stocks 

occupy the throats of extinct geysers and hot springs. The supposition that the ascending heated waters which were primarily instrumental in forming ore bodies may have issued as hot springs, or even 

geysers, from a former surface, is of course perfectly tenable and 

difficult to disprove. But to argue that the knolls of silicified and 

impregnated andesitic breccia conspicuous in the topography of to-day 

are really mounds of siliceous sinter is to be carried away by an 

analogy of the most unessential and superficial kind. The knolls 

exist merely because the bleached and altered rock of which they are 

cqmposed resists erosion better than the crumbling, more easily 

weathered breccia, which has been less affected by the mineralizing 

solutions and is more readily disintegrated and carried away \)y rains 

and streams.

It seems most reasonable to regard the ore spaces of the Red 

Mountain district as a local modification of the general Assuring of 

the region. It is possible, however, that much of the minor, very 

irregular fissuring which is characteristic of this region may be due 

to contraction within the rock mass consequent upon the prevalent 

alteration of the volcanic rocks to aggregates of quartz, kaolin, and 

pyrite, with the removal of certain constituents, -as more fully discussed on pages 114-131. Not only Avas the fissuring locally complex, 

but the ascending thermal waters had more chemical and probably 

more physical activity than elsewhere within the quadrangle, whereby 

solution played an important part in enlarging zones or aggregations 

of fractures into ore spaces and in metamorphosing the country rock

to an extent not elsewhere observed in this region. The cause of

this local intensity of chemical and physical activity is not known, 

although it is probable that the circulating intratelluric waters were 

here hotter and more copious than elsewhere. Some indication of 

the latter is afforded by the abundant strongly mineralized springs 

which issue from the surface in this district at the present day. 

There is, moreover, some geological grounds for believing that the 

Red Mountain region may have been formerly a local center of 

volcanic activity.

There has probably been fracturing of the rocks, or at least movement along preexisting fissures, since the ore bodies were formed, but 

there are not at present facilities for studying the relation of the 

older to the later fissures. It may even be considered doubtful 

whether the so-called fault found below the seventh level in the 

Guston and the sixth level in the Yankee Girl is entirely a postmineral dislocation, or whether it is in part a fracture antedating 

the deposition of the ore.
RANSOM E.] THE STOCKS OB MASSES. 109 

CHARACTER AND STRUCTURE OF THE ORE.

It is very difficult, on account of the present condition of the mines, 

to give a satisfactory account of the mineralogy and structure of the 

ores occurring in the stocks. The chief difference between these ores 

and those occurring- in the lodes seems to have been the fact that the 

former occurred in nearly solid masses, with very little gangue. The 

occurrence of enargite, moreover, is apparently peculiar to the stock 

deposits in this region, the mineral not being known in the lodes. It 

does not, however, occur in all of the stocks. The more common ore 

minerals of the latter are galena, sphalerite, tetrahedrite, enargite, 

chalcocite (stromeyerite), bornite, chalcopyrite, and pyrite. While 

the galena ore of the upper levels was argentiferous, the highest 

silver values occurred in connection with the copper-bearing minerals, 

especially the chalcocite, bornite, and chalcopyrite. These three ore 

minerals were almost invariably accompanied by pyrite. In the

richer portions of the ore bodies the pyrite was subordinate, and 

appears to have been found chiefly in the peripheral portions of the 

stocks. But in the poorer ores the argentiferous copper minerals 

occurred as nodular bunches in masses of low-grade iron pyrite carrying up to o per cent of copper and a little silver, usually less than 

10 ounces per ton, and a .fraction of an ounce of gold. The pyrite 

usually forms a rather fine-grained and sometimes crumbling aggregate, but in the Zuni mine occurs in beautifully sharp octaheclra 

embedded in white kaolin. Bismuthiferous ores of silver and lead 

occurred in some of the ore bodies, notably in the Silver Bell and 

Genesee-Vaiiderbilt. Specimens from the latter mine contain a 

bright lead-gray mineral having the physical properties of cosalite, 

which chemical tests show to be slightly argentiferous sulphobismuthite of lead containing a little copper. Cosalite occurred also in 

the Yankee Girl. The rare mineral, kobellite, a sulphantimonite of 

lead with bismuth partly replacing the antimony, was found in the 

Silver Bell mine, 1 carrying from 3 to 4 per cent of silver. The 

only other known occurrence of this mineral is at Hvena, Sweden. 

The rich silver ores proustite and polybasite occurred in the Yankee 

Girl, Genesee-Vanderbilt, and probably other mines of this district. 

Tennantite is reported to have occurred in the National Belle mine. 

Zinkenite has been described by Hillebrand 2 from the Brobdignag 

claim, a now abandoned prospect in the Red Mountain Range near 

Chattanooga. Guitermanite and zunyite occur in the Zuni ore body 

and in a few prospects close to the latter, the. zunyite as small sparkling, colorless tetrahedrons embedded in the massive, bluish leadgray guiternianite. Barite is apparently always present in the ores 

of the stock deposits. It often occurred as isolated crystals or crystalline masses embedded in the argentiferous bornite of the Guston

' H. F. Keller: Zeitschrift Mr Krystallographie, Vol. XVII, 1890, pp. 67-7-3. 

"Proc. Colo. Sci. Soc., Vol. I, 1883-84, p. 127.
110 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

and Yankee Girl mines, and these inclosed masses occasionally carried 

free gold. In the Zuni it is intimately associated with pyrite and 

kaolin. The latter mineral is found associated with the ores of all 

the Red Mountain mines, sometimes occurring in the ore or serving 

as a matrix to pyrite, as in the Zimi, but more abundantly in fissures 

in the wall rock and as a direct product of the alteration of the latter.

Although the common structure of the principal ore bodies was 

that of a solid and massive aggregate, yet there is evidence that vugs 

or cavities sometimes occurred in the unoxidized ores. Stalactites of 

pyrite, having the radial structure usually considered as characteristic of marcasite, were seen, which were said to have come from caves 

in the Genesee-Vanderbilt. Specimens of enargite from the National 

Belle mine, preserved in various cabinets, show a free development 

of clusters of radial prisms of enargite, such as could only have formed 

in open spaces. The well-crystallized specimens of polybasite which 

have come from the Red Mountain district were also probably formed 

in vugs.

The large caves, however, such as were a feature in the upper workings of the National Belle mine, appear to have occurred above the 

ground-water surface. A few of the smaller of these caves only could 

be seen in 1899, and we are dependent upon the description of T. E. 

Schwarz 1 for knowledge of the occurrence of the oxidized or secondary ores. According to him, they occurred "above a former water 

line, either attached to walls ofo caves as broken detached masses, or 

as a bed of clayey mud or sand, more or less completely filling the 

cave." The ores are said to have been mainly "carbonates of lead 

and iron, with iron oxides, lead sulphate, and arsenates." KaoUnite 

and zinc blende were common, and galena occurred as residual kernels. "Such are the ores of the National Belle, Grand Prize, and 

Vanderbilt mines. Other mines omit lead minerals and carry oxide

and sulphide of bismuth." Several hundred pounds Of this metal are 

said to have been reduced in Durango. These caves are stated to 

have ramified through the knolls of silicified andesite, such as that 

described at the National Belle mine, whicli " are cut up by cross 

fractures." The following general conclusions are cited from Mr. 

Schwarz's paper:

1. The secondaiy ores are richer than the sulphide ores occurring 

below them.

2. The ores of adjoining or connecting caves are sometimes greatly 

different in grade.

3. In some cases the formation of the caves along fracture or cleavage planes is evident, but in others all traces of such planes are quite 

obliterated.

4. The cave walls are a porous sandy quartz (see description of

iTrans. Am. Inst. Min. Eng., Vol. XVIII, 1890, pp. 139-145.
UANSOME.] THE STOCKS OR MASSES. Ill

National Belle mine, p. 231), the sand from the disintegration of which 

forms part of the cave filling.

o. The line of change from oxidized to unoxidized ores, or the former water level, is very marked. It varies as much as 100 feet in. elevation in properties within 1,000 feet of each other, rising to the south 

and west. The quartz outcrop rarely rises more than 200 feet above it.

6. In isolated cases may be found masses of the unoxidized ore, the 

enargite, 1 above the line of change, in the vicinity of the secondary 

ores.

Mr. Schwarz considered the caves and secondary ores to have been 

due to surface waters, which dissolved the sulphide ores and country 

rock as they moved along fracture planes. It appears unlikely, however, that the surface waters exercised much solvent action upon the 

country rock. Their function was probably limited to the oxidation 

of the ore and to the removal of some of its constituents.

CHANGES IN THE ORE WITH DEPTH.

As indicated in the preceding section, the ores of some of the stocks 

were partially oxidized down to the ground-water surface. This secondary alteration was particularly noticeable in the National Belle 

mine, and to some extent in the Vanderbilt mine, but was a much 

less conspicuous feature in the Yankee Girl, Gnston, and other mines, 

the ore bodies of which outcropped nearer the bottom of the valley of. 

Red Creek. The oxidation apparently presented no unusual features, and seems to have consisted chiefly of the transformation of 

galena to carbonate and sulphate of lead, with removal of more soluble constituents, reduction in the bulk of the ores, and the consequent 

formation of caves. Even when, as in the case of the National Belle, 

the ore of the deeper workings was chiefly enargite, the oxidized ores 

nearer the surface were evidently largely composed of lead compounds, as no reference is found to the occurrence of copper carbonates. This result is probably less a consequence of any peculiar 

process of oxidation than of the relative disposition of the sulphide 

or unoxidized ores prior to superficial weathering. It is with the 

changes in these latter ores relative to depth,that this section has 

chiefly to do. .

In spite of the diversity shown by the different ore bodies, there is 

after all remarkable uniformity to be found in the change at very 

moderate depths usually less than 300 feet from an ore consisting 

chiefly of argentiferous galena to highly argentiferous silver-copper 

ores, and then a gradual diminution of value downward through the 

increasing proportion of low-grade pyrite in the ore bodies. These 

changes are best recorded in the Yankee Girl, Guston, and Silver Bell

'It is evident that in this description Mr. Schwarz has the National Belle deposit most in 

mind.
112 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 192.

mines. There are certain exceptions to what may be regarded as the 

normal"or complete sequence. Thus the Congress mine appears to 

have had an ore consisting chiefly of enargite, with some bunches of 

galena, from the croppings downward. That the enargite at greater 

depth will gradually give place to iron pyrite, with diminishing 

amounts of chalcopyrite, can scarcely be doubted m the light of what 

is known of other deposits of this district. In the National Belle, 

enargite in this case low grade was encountered near the surface, 

but the oxidized ore in the siliceous knoll which forms the croppings 

appears to have been derived chiefly from galena, while below the 

third level (fig. 20) practically no pay ore was found. Explorations 

on the fourth level resulted only in the finding of small bunches of 

good ore and masses of crumbling iron pyrite carrying less than 0.1 

ounce of gold and about 5 ounces of silver per ton, with from 1 to 

3 per cent of copper.

Chalcopyrite appears to have been usually good ore. It carries, 

theoretically, 34.5 per cent of copper, and in the Red Mountain district ran well in silver and gold; but its appearance in great quantity 

was apparently a precursor of the ultimate change to ores carrying 

chiefly the low-grade iron pyrite.

Although there was on the whole a general change from argentiferous lead ores to argentiferous and auriferous copper ores, and 

finally to slightly argentiferous and auriferous iron sulphide (pyrite), 

yet the progression was an overlapping and irregular one in detail. 

Iron pyrite and chalcopyrite occurred at practically all depths, while 

galena in small bunches was sometimes found far below the point at 

which it had ceased to be the principal ore.

VALUE OF THE ORES.

The ores of the stocks, like those of the lodes, vary widely in value. 

In 1883, 3,000 tons of ore extracted from the Yankee Girl averaged 

nearly $150 per ton. A lot of 10 tons from the richest stopes of the 

same mine carried 3,270 ounces of silver per ton and 29 per cent of 

copper, corresponding to an average value per ton of about $3,000. 

Much richer ore than this occurred in small quantities in the Yankee 

Girl and Guston. The average sales value per ton of the ore of the 

latter mine has been given in the table on p. 222 as $91.81 for a period 

of eight years. The highest annual average was $363.25 per ton, and 

the lowest $10.70. These, it should be borne in mind, are the prices 

for which the ore was actually sold to the smelters. Values based 

directly upon metallic contents, without reference to cost of treatment, would be higher. The highest annual average represents the 

ore from the rich stopes above the seventh level. The lowest corresponds to the low-grade pyritic ore of the deeper levels. The richest 

ore recorded from this district was some taken in 1891 from the Guston at a depth of 378 feet, which carried 15,000 ounces of silver and
RANSOME.] ASSOCIATED M1NEEAL WATEBS. 113

3 ounces of gold per ton, worth, at the then current price of silver, 

$14,880.

The ore of the Genesee-Vanderbilt was of much lower grade than 

that of the Yankee Girl, Guston, and Silver Bell. Its gross value for 

any one year probably never averaged more than $40 per ton. No 

records, however, are available for the ore taken out prior to 1893, 

when the price of silver stood higher. The ore of the National 

Belle Avas also low grade, but its average value is not known.

MINERAL WATERS ASSOCIATED WITH THE ORE DEPOSITS.

Probably all the waters met with in the mines of the Silverton 

quadrangle now accessible are meteoric waters variously modified by 

the materials though which they have passed in their more or less 

direct descent from the surface. The abundance of these waters 

varies much in different mines, and fluctuates with the seasons. In 

the Gold King mine scarcely a drop of water readies the lower levels. 

Many other mines, such as the Silver Peak and Iowa, which are 

moderately wet in summer, become nearly dry in winter, owing to the 

freezing of the ground near the surface. In no case was any noticeable spring or ascending mineralized water encountered in the ore 

deposits now being worked. The descent of the meteoric water through 

masses of pyrite and other ore minerals is, however, often sufficient 

to give it a strong acid reaction and render it highly ferruginous.

In the Red Mountain district the troublesome acid character of the 

mine waters was notorious. In spite of their strong mineral nature 

and abundance, however, it is not improbable that these, too, were 

meteoric waters which had become strongly charged with sulphuric 

acid by their oxidizing passage through the adjacent bodies of pyrite 

and through the masses of altered pyritized country rock which surround the latter.

Strongly ferruginous springs are abundant within the drainage of 

Cement Creek and in the upper basin of Red Creek. As their waters 

are brought in contact with the atmosphere the iron in solution is 

oxidized and deposited near the spring as a mound or apron of limonite, or accumulates as bog iron in the swampy ground along these 

creeks. Such springs, with there accompanying deposits, may be 

well seen near Burro Bridge, also just below Chattanooga, and near 

the village of Red Mountain. A spring of the same general character issues from the hillside about 150 feet above the Gustou mine, 

and has deposited a large apron of limonite. At present the water 

issues from a tunnel which was run into the limonite mass, and has 

cemented the dump of the tunnel into a firm, ferruginous mass. 

Some of this water was collected for analysis. As it issues from the 

tunnel it is clear, moderately cold, and noneffervescing, and has an 

astringent acid taste. When received in the laboratory at Washington

Bull. 182 01 8
114 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BUI.L.J82.

the water gave a strongly acid reaction, and a deposit of ferric 

hydroxide or basic ferric sulphate, together with some silica, had settled in the bottom of the bottle. The total contents of sample were 

subjected to partial qualitative tests by Dr. Hillebrand, with the following results:

Partial analysis of water from spring above the Guston mine.

Constituent.

S03 .. ..............

Cl.... .............

A12O8 . .............

Fe.. ...............

Ca. ................

Na ................

K...... ............

SiO... ..............

Remarks.

Do.

Do.

Constituent.

Zn. . .......... ....

Mn. ...........

Ni. ....... ........

Co.. ..............

Cu ...............

Pb. ...............

Mo...............

As ...............

Ag. ..............

P»Or,.. ............

Remarks.

A little.

Absent.

Not tested for.

It appeared from these preliminary tests that the water of this spring 

carried no appreciable amounts of the important ore-forming metals, 

and it was not considered advisable to devote time and labor to further 

chemical work upon it. It was at first hoped that its analysis might 

throw some light upon the nature of the solutions which originally 

deposited the Red Mountain ores.. But the preliminary tests indicate 

no characters that might not be expected in ordinary meteoric waters 

after passing for some distance through the mineralized and altered 

rocks of the immediate vicinity. There is, so far as known, no definite evidence connecting the ferruginous springs of this region directly 

with the original processes of ore deposition, nor is it necessary to

assume that the waters issuing from them have come from deep-seated

sources. The mine waters of the Yankee Girl and Guston are said to 

have carried much copper in acid solution. This is to be expected 

wherever surface waters carrying oxygen pass downward for any distance through pyrite and chalcopyrite. The presence of considerable 

alumina has an important bearing on the question of the metasomatic 

alteration of the country rock, as will be later shown.

METAMORPHISM OF THE COUNTRY ROCK IN CONNECTION WITH

ORE DEPOSITION.

The metamorphism or change which has been effected through the 

agency of the mineral-bearing solutions (hydrothermal metamorphism) in the rocks adjacent to the ore bodies differs very markedly 

in degree, and to a less extent in character, in different portions of 

the quadrangle.

The mode of alteration is in general by metasomatism (literally 

change of body), by which is meant the process by which a mineral,
KA.NSQMK.], METAMOEPHISM OF THE COUNTEY EOCK. 115

through chemical reactions, undergoes a partial or complete change 

in its chemical constitution. Rocks or aggregates of minerals are 

"inetasomatic" if any or all of the constituent minerals have undergone such changes. 1

In Silver Lake .Basin the simple-fissure veins which there predominate, carrying galena, sphalerite, chalcopyrite, pyrite, and sometimes 

tetrahedrite, in a gangue of quartz with frequently some barite, are not 

accompanied by any very evident or striking alteration of the immediate wallrock.

As elsewhere pointed out, the rocks of Silver Lake .Basin belong to 

the Silverton series. No attempt will be made in this report to give 

the petrographical characteristics of the series as a whole (for which 

the reader is referred to the forthconii-ng report of Mr. Whitman 

Cross); it is enough to say that the prevailing rock of the basin, and 

the one which constitutes the greater part of the country rock met with 

in the workings of the Silver Lake and Iowa mines, is a firmly consolidated, homogeneous, andesitic breccia. This differs from the older 

San Juan breccia in its greater homogeneity and in the frequent 

occurrence of more or less orthoclase. Indeed, it is not unlikely that 

the whole should be referred rather to the latites than to the andesites proper. With the breccia are associated massive andesites and 

latites. The breccia is in general somewhat altered, even when not 

close to an ore-bearing lode, a result that is to be expected when the 

thorough fissuring Avhich the rocks have undergone and the extent to 

which they must have been permeated by ore-bearing solutions are 

taken into account.

A specimen of this rock taken on the trail from Arrastra Gulch up 

to the basin, at an elevation of about 11,800 feet, may be regarded as 

representative of the relatively unaltered facies. It is a tough, 

greenish-gray rock with pale lilac-gray mottlings, and, although showing a few feldspar phenocrysts, is generally of rather compact texture. 

The breccia structure, not very apparent on fresh fracture, owing to 

the homogeneity of the component fragments, becomes visible when 

the rock is breathed upon or has been slightly weathered. Under the 

microscope its clastic structure is evident. Fragments of general 

andesitic character lie in the matrix of fine andesitic detritus, which 

is not always easily separable from the larger fragments. This clastic 

matrix contains broken phenocrysts of andesine or labradorite, and 

an occasional somewhat rounded grain of quartz, in a fine feldspathic 

and obscure groundmass. There is some magnetite present, but ferromagnesian constituents are lacking. If formerly present, they have 

been destroyed by secondary alteration. The feldspars are largely 

changed to sericite (with perhaps some kaolinite) and to calcite, while 

bunches of calcite and flecks of chlorite are thickly disseminated 

through the rock. Some epidote is frequently present, although not

1 Lindgren; Trans. Am. Inst. Min. Eng., Vol. XXX, 1900, p. 580.
116 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 18:.'.

seen in this particular slide. Such of the massive andesites and 

latites as were examined in thin section show a similar development 

of secondary chlorite, calcite, and sericite, indicating an alteration 

that is essentially propylitic in character.

Within the Silver Lake and Iowa mines the amount of alteration in 

the country rock which can properly be referred to the action of orebearing solutions moving along any given fissure is slight. The 

breccia usually preserves its greenish color and general appearance 

close up to the fissure walls. In the Iowa mine specimens were taken 

in the main crosscut on the fourth level at various distances from 

the Iowa vein, for the purpose of studying the alteration of the 

country rock dependent upon the formation of this lode. All of these 

specimens are pale greenish-gray rocks of one kind a breccia of the 

type already described.

At points 150 feet east of the lode the country rock is fine grained 

and faintly mottled, showing only a few pale, minute phenocrysts of 

feldspar and an occasional tiny grain of quartz. Under the microscope the rock reveals the character of a much-altered andesitic tuff 

or fine breccia. The feldspars have been completely altered to aggregates of sericite and calcite, while areas of calcite and chlorite probably represent former phenocrysts of augite. The groundmass is a 

rather indistinct aggregate of secondary quartz, sericite, and chlorite, 

with a little apatite and rutile. The rock is thus practically wholly 

recrystallized into a secondary aggregate while retaining the grosser 

structure of the original.

At a distance of 100 feet from the vein the country rock is megascopically like that just described. Under the microscope it shows 

.less alteration than the preceding. Chlorite and calcite are abundant, but much of the plagioclase is still recognizable. Sericite and 

quartz are not such prominent constituents as in the other rock.

At places 50 feet from the vein the country rock is still of the same 

general appearance as that already described. In thin section under 

the microscope it shows a general andesitic structure, but is almost 

wholly recrystallized. The feldspar phenocrysts have been changed 

to aggregates of calcite and sericite, while areas of chlorite and calcite, with sometimes rutile, are all that remain of the phenocrysts of 

augite or biotite. The groundmass, also, while preserving the outlines and in small part the substance of former lath-shaped feldspars, 

is now an aggregate consisting chiefly of quartz, chlorite, sericite, 

and a little rutile and apatite. The thin section does not show 

clastic structure, and is probably from a fragment in the breccia.

At a distance of 2 feet from the vein the only megascopical change 

in the country rock consists of the' presence of an occasional speck of 

galena. . Rather curiously, finely disseminated pyrite, which is a common feature of most country rock near a productive lode, does not in 

this case accompany the galena as a megascopical constituent. Under
KANSOJIE.] METAMOEPHISM OF THE COUNTRY ROCK. 117

the microscope it is seen that the alteration has been more thorough 

than in the specimens previously studied. The forms of some of the 

phenocrysts are preserved by pseudomorphous aggregates sericite, 

with some chlorite, calcite, and rutile, apparently after biotite, and 

calcite, quartz, sericite, and chlorite in varying proportions after augite 

and plagioclase. The groundmass is entirely recrystallized as a fine 

aggregate composed chiefly of quartz and sericite, with less chlorite. 

Occasional larger grains of quartz with rounded and embayed outlines 

are probably original phenocrysts. A little apatite and a few minute 

grains of pyrite occur in the groundmass. The dominant minerals of 

the rock are quartz and sericite. A specimen taken from the same 

crosscut at a distance of only 10 inches from the west wall of the vein 

resembles the others closely. It does not, however, show breccia 

structure, and is sparingly sprinkled with small crystals of pyrite. 

Under the microscope the rock is seen to be essentially an aggregate 

of sericite, quartz, calcite, and chlorite, named in the order of relative 

abundance. The former feldspar phenocrysts are now pseudomorphs 

of sericite, calcite, and quartz, and biotite has been altered to chlorite, 

sericite, and rutile. The groundmass consists chiefly of quartz, chlorite, calcite, and sericite. Although this facies is nearer the vein than 

the preceding, the character of its metamorphism is perhaps even less 

differentiated from the more general kind of propylitic alteration 

which the country rock in the mine, even at a distance of several hundred feet from the principal lodes, has undergone. Lastly, a specimen 

was taken from the east wall of the Iowa vein in the main stope above 

the fourth level. At this point the vein contained good ore, and the 

absence of gouge allowed the specimen to be taken immediately in 

contact with the ore. It differs from those thus far described in its 

light-gray color and more evident alteration. It is sprinkled with 

pyrite and a little galena, and is traversed by minute veinlets of 

quartz. Its breccia structure is still discernible in the hand specimen. 

Microscopically examined, the rock, while retaining traces of clastic 

origin, is wholly recrystallized. The former phenocrysts of feldspar 

are replaced by pseudomorphous aggregates of quartz and sericite. 

The quartz in such cases is often rather coarsely crystalline (grains 

up to 0.5 millimeter in diameter), the sericite being included as minute 

wisps, or gathered into bunches in the interstices between the allotrioniorphic quartz grains. Crystals of pyrite are sometimes inclosed in 

the quartz. Of augite no -trace remains, but some sericite inclosing 

rutile is apparently pseudomorphous after biotite. The groundmass 

is a finely crystalline mosaic of quartz and sericite. The notable feature of this wall rock is the absence of calcite and chlorite.

The alteration studied in the foregoing set of specimens, collected 

for that purpose in the Iowa mine, has been traced with similar 

results in collections "from the neighboring Silver Lake mine. Calcite and chlorite are as a rule prominent constituents of the altered
\

118 ECONOMIC GEOLOGY OF SILVERTON QUADKANGLE. [suLL.182.

country rock to within a few inches of the productive lodes. Frequentby, but not always, the rock in contact with the ore, or occurring 

as small horses in the veins, is free from chlorite and calcite and 

consists mainly of quartz and sericite, with some disseminated ore 

minerals. The latter, however, are not limited to the immediate 

walls of the fissure, but specks of galena and crystals of pyrite may 

occur 25 feet or more from the nearest lode, in rock carrying much 

calcite and chlorite. As an example of the extreme alteration which 

the country rock has undergone in the formation of these ore bodies 

may be described a specimen from the third level of the Silver Lake 

mine, taken from the wedge of country rock between the Stelzner and 

Royal veins at their junction. The usual breccia is here bleached 

almost white, and shows a fine, even-granular texture to the naked 

eye, but as a whole is shattered, full of quartz stringers, and contains 

flakes of galena. Under the microscope, pseudomorphs of sericite 

after feldspar and biotite preserve the only remnants of original 

structure. The grounduiass is a very finely crystalline aggregate of 

quartz and sericite traversed by microscopic quartz veinlets. As 

usual, there is a little rutile present, and some crystals of pyrite.

To sum up briefly, the rocks in which the ore deposits of Silver 

Lake Basin occur are chiefly andesitic or latitic breccias. In the 

neighborhood of the mines these breccias have been generally altered 

to an unknown depth. The alteration involves the change of feldspar to sericite, calcite, and quartz; of augite to calcite and chlorite; 

and of biotite to chlorite, sericite, and rutile. Although this metamorphis.m is probably connected with the ore deposition, it is so generally prevalent that it can not in any case be recognized as being 

connected with the deposition of ore in any given fissure. It appears 

to have been effected through the agency of water charged with carbon dioxide or carbonates. The change involved in the rocks is propylitic in nature, and, as Liiidgren1 justly maintains, should be distinguished from ordinary weathering, with which it is often confused. 

Close to the veins, usually within a few inches, and in small horses 

of country rock within the veins, metamorphism of a different kind frequently occurs. Here calcite and chlorite have diminished in amount 

or are wholly absent, and quartz and sericite constitute the bulk of 

the rock. This alteration, which plainly emanates from the individual fissure, differs from the more general metamorphism less in 

kind than in the relative proportions of calcite and chlorite on the 

one side and of quartz and sericite on the other. This usually inconspicuous and very local alteration of the wall rock to quartz and sericite is rather common within the quadrangle, especially near lodes in 

the andesitic rocks of the Silverton or San Juan series. It occurs 

in somewhat pronounced degree in the Ridgway mine, which pro1 Metasomatic processes in fissure veins: Trans. Am. Iiist. Min. Eng., Vol. XXX, 1900, p. 645.
HANSOME.] METAMOEPHI8M OF THE COUNTRY EOCK. 119

duces an .argentite ore. It is the usual alteration seen in the mines 

of Savage Basin, Sultan Mountain (in monzonite), and in many other 

lodes where metamorphism of the country rock other than that of propylitic nature is not a conspicuous phenomenon, and where no special 

microscopical study of wall rock was made.

.The alteration of the country rock in Silver Lake Basin may be 

accounted for on the assumption that the solutions which filled the fissures contained alkaline carbonates. But that the alkaline carbonates were present in small amount seems to be indicated by the uniform presence of chlorite (except in the actual walls of the vein, where 

it as well as calcite may be absent); for, as Lindgren l lias pointed 

out, it is probable that chlorite can not exist under the action of 

strong solutions of. alkaline carbonates. The immediate wall rock of 

the fissures, being more exposed to the action of solutions, has in. 

most cases suffered the removal or further alteration of the chlorite

and carbonates which were probably first formed. Connected with 

this later stage is the accumulation of the insoluble sericite, derived 

from labradorite, biotite, and probably other minerals, and very likely 

the direct addition of quart/, in place of the removed calcite. Although 

no chemical analyses have been made of these Avail rocks, it is jrrobable that the abundance of sericite (derived in great part from limesoda feldspars), which is common in the rock in contact with the vein 

filling, indicates a direct addition of potash to the substance of the 

t'ock, as was found by Lindgren 2 to be the case in the Grass Valley 

and Nevada City veins. Kaolinite Avas not certainly identified in the 

altered Avail rocks of Silver Lake Basin, but in the Dives mine (on the 

North Star lode) it apparently occurs Avith sericite and quartz, as seen 

in an altered andesitic horse in the lode. Metamorphism in connection Avith the Dives ore body is similar to that just described in detail, 

for the Silver Lake mines; but in its greater intensity, in the presence 

of kaolinite, and in the more evident silicification of portions of the 

Avail rock it is intermediate in character between that metamorphism 

and the kind next to be described.

Of a someAvhat different kind from that Avhich has just been discussed is the metamorphism observed in connection Avith the ore 

deposits of Engineer Mountain and of the Red Mountain district. As 

the ore of Engineer Mountain occurs in lodes, Avhile that of the Red 

Mountain district is prevailingly in stocks, and as the metamorphism 

presents some phases of difference in the two modes of occurrence, 

they will be separately treated.

The Polar Star lode, which has produced some rich silver ore carrying argentite and proustite, may be considered as a type of the Engineer Mountain deposits. Unfortunately, its Avorkings are no longer

i Trans. Am. Inst. Min. Eug., Vol XXX, 1900, p. 610.

3 The gold-quartz veins of Nevada City, etc.: Seventeenth Ann. Kept. U. S. Geol. Survey, 

Pt. II, 1806, p. 148.
120 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE.

accessible, but the metamorphic processes connected with ore deposition may be studied to considerable advantage from surface exposures 

and the material of the dumps. The country rock of the Polar Star 

is a dark-gray rock of andesitic appearance, carrying abundant glistening phenociysts of plagioclase up to 7 or 3 millimeters in length. 

In thin section, under the microscope, the plagioclase is seen to be chiefly 

labradorite (abt an t ) which is almost perfectly fresh. Phenocrysts 

of a pale augite or diopside are almost wholly altered to calcite and 

chlorite, and some bastite pseudomorphs indicate the former presence 

of phenociysts of an orthorhombic pyroxene. Quartz, and probably 

some orthoclase, are present in the groundmass. The chemical analysis of this rock is given in Column I, page 122. This analysis 

differs from that of a normal andesite in its rather high alkalies and 

relatively high potash. It might be classed as a latite. Owing to its 

somewhat weathered condition and lack of knowledge as to the accurate chemical constituents of the resulting chloritic and serpentinous 

products, an attempt to calculate the mineralogical composition from 

a chemical and microscopical analysis is not entirely satisfactory.

Calculating the carbon dioxide as calcite, the soda as labradorite 

(abt ani), the phosphoric anhydride as apatite, the residual lime as 

diopside, all the potash as orthoclase, and dividing up the other constituents between chlorite, serpentine, magnetite, etc., the followingapproximate mineralogical composition was obtained.

Mineralogical composition of andesitic rock (latite?) from Engineer Mountain.

Constituent.

Chlorite (H4o(FeMg)23AlHSii3O9o)-----

Peicent, by 

weight.

33.9

22 4

14

4.7

3

2.8

Constituent.

Hematite ..............................

Peicent, by 

weight.

2.6

2.3

3.8

1

1.4

98.9

There still remains about 1 per cent of alumina not accounted for 

in the above calculation. Combined with part of the ferrous iron 

here calculated as magnetite and chloride, and with some of the silica, 

reckoned as quartz, it may enter into the composition of the pyroxene, which probably does not correspond exactly to the theoretical 

diopside molecule. The percentage of kaolinite is rather higher than 

the microscopical investigation would indicate. The specific gravity 

as calculated from the foregoing mineralogical composition, ignoring 

porosity, is about 2.8. The foregoing specimen was taken a few hundred feet west of the mine, and, although fresher rock occurs in the 

vicinity, this was selected for chemical analysis as being undoubtedly 

the particular facies in which the Polar Star lode was formed.

The dumps of the Polar Star mine are made up largely of a locally
RANSOMK.] METAMOEPHISM OF THE COUNTRY ROCK. 121

altered form of the foregoing latite. The original porphyritic structure is perfectly preserved, but the rock is bleached to a very lightgray tint, and the feldspars are completely kaolinized. Small crystals 

of pyrite are abundant, occurring both in the altered phenocrysts and 

in the ground mass. This is evidently the country rock which immediately incloses the ore, although it is not known how far this pronounced alteration extended on either side of the ore-bearing fissure 

zone. Under the microscope the rock appears as a fine-granular 

aggregate, consisting chiefly of quartz, kaolin, and diaspore, with 

considerable disseminated pyrite. The porphyritic structure is partially lost between crossed nicols, although the abundance of diaspore 

in some of the altered phenocrysts differentiates them from the 

groundmass. The diaspore occurs in irregular grains up to about 0.5 

millimeter in diameter. The relatively high refractive index, strong 

double refraction with consequent brilliant polarization colors, and 

the conspicuous cleavage render the mineral very noticeable in thin 

section. It is biaxial, with dispersion red less than blue.

In order to confirm the microscopical determination, a portion of 

the rock was powdered and treated with hydrofluoric acid by Dr. 

Hillebrand. The resulting residue proved, on microscopical examination, to consist of grains of the supposed diaspore, with a few 

particles of pyrite and a little amorphous material. A rough quantitative analysis showed that the residue consisted of about 84.4 percent of alumina and 15.2 per cent of water, thus placing the identification of the mineral as diaspore beyond question.

A chemical analysis of this altered rock is given in Column II on 

page 122. The two analyses of fresh and altered rock, as they stand 

side by side, represent a comparison of unit weights, and therefore 

are not, in all probability, directly comparable for the purpose of ascertaining the actual change that lias taken place in a unit volume of the 

original rock. It may, however, be tentatively assumed Nthat the 

alumina has remained constant. An analysis of the altered rock 

recalculated on this basis gives the result shown in Column Ha. A 

comparison between Column Ha and Column I shows that, under the 

assumption made, the altered rock has suffered a total loss of substance 

of over 14 per cent. A little silica, 3.15 per cent of water, and some 

sulphur have been introduced, while magnesia and carbon dioxide 

have been Avholly, and lime-soda potash almost entirely, removed. 

Of the original iron present in the rock, a little more than one-half 

remains combined with sulphur to form pyrite. It will be noted that 

in the recalculated analysis the phosphoric and titanic acids are very 

nearly the same as in the fresh rock, which lends some support to the 

assumption previously made that the alumina has remained practically constant in the process of metamorphism. It seems at first sight 

probable that the loss of substance in the altered rock may be accompanied by an increase of porosity without actual shrinkage of the rock 

as a whole. If this be so, the specific gravities of the unaltered and
122 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

altered rock, as determined on considerable fragments, should be to 

each other approximately as 100 is to 86 (i. e., to 100 less the loss of 

substance due to metainorphism). The specific gravities as actually 

determined are 2.764 and 2.734, and their ratio is as 100 to 99. This 

result does not accord with the idea that the loss of substance has 

resulted in corresponding increase of porosity with retention of initial 

volume. In so far as the laboratory determinations of specific gravity 

may be relied upon in drawing conclusions as to the mass as a whole, 

they indicate that the loss of substance has been followed by diminution of volume, presumably associated with actual cracking or fissuring and not with increased porosity.

Analyses and recalculations of rocks of Polar Star mine, Engineer Mountain.

Constituent.

SiOs ----- ........................

A12O3 . ..... . ....... -.---- 

Fe2O3 ----- - ---------- ----- --

FeO-. .... . .. ....--. .....

MgO .....- '---

CaO. ........ .........-.-..--.-. 

Na20 ...... -.---....-.. ......

KoO.. ......... .. . .- .. 

HoO- .......... - ;.-. .

H2 0 + ................ . ....

TiO2 ............. .................

C02 . .... ....... .... .. ......

P»06 . ......... ...-. ........

0

CrA ............. ............

NiO.-... --.... ....... . ........ ....

MnO.. ... . ................ . 

BaO ............ ...... ............

SrO. ..............................

Li20 ..............................

FeS2 . .......... ...................

Total........ -. --.-.

Sp. gr ............................

I. .

Per cent. 

55.61 

16.40 

5.44 

2.37 

3.25 

5.85 

2.61 

3.77 

.-16 

1.51 

1.10 

1.33 

.45 

Trace.

None.

.09

.03 

.05 

Trace.

100.32

2.764

II.

Per cent. 

64. 79 

18.93 

None. 

None. 

None. 

.43 

.15 

.24 

.50 

5.39 

1.21 

None. 

.51

None.

.06 

Trace. 

Str.tr. 

7.19

99.40

II«.

Per cent. 

56.13 

16.40 

None. 

None. 

None. 

.37 

.13 

.20 

.43 

4.66 

1.04

.44

.05

J. 734 at 19

Loss or gain 

of each constituent in 

percentage 

of the whole 

original 

rock.

Per cent. 

+0.52 

0 

-5.44 

-2. 37 

-3.25 

-5.48 

. -2.48 

-3.57 

-'.03 

+3.15 

- .06 

-1.33 

- .01

 .09 

+ .02 

- .05

+6.22

-14.25 

° C. (W. P.

116.

Percent. 

64.14 

18.74 

None. 

None. 

None. 

.42 

.14 

.23 

.49 

5.33 

1.19

.50

.06

7.12

Hillebran

Loss or gain 

of each constituent in 

percentage 

of the whole 

original 

rock.

Per cent. 

+8. 53 

+2.34- 

-5. 44

-2.37 

-3.25 

-5.43

-2.4" 

--3.54 

' + .03 

+3.82 

+ ,0'J 

-1.H3 

+ .05

- .09 

+ .03 

- .05

+ 7.12

-1.96

a.)

I. Latite. Country rock of the Polar Star mine, Engineer Mountain. Analysis by H. N. 

Stokes.

II. Metasornatically altered latite. Wall rock of Polar Star mine, Engineer Mountain. Analysis by H. N. Stokes.

Ha. Recalculation of II on basis of constant alumina. 

116. Recalculation of II on basis of constant volume.

It will be remembered that the preceding discussion rests upon the 

initial assumption that the alumina has remained constant during the 

metamorphism. This assumption may not be correct, and it will 

further the inquiry, as well as illustrate <the complexity of the problem,
HANSOME.] METAMOEPHISM OF THE COUNTEY EOCK.

to trace the results growing out of another probable premise. If it be 

assumed that during the metamorphic processes the volume of any 

given mass of the rock has remained constant, then the analysis of: 

 the altered rock may be recalculated on this basis, using for this purpose the determined specific gravities, and be then compared with 

that of the unaltered rock. The result of this comparison is shown in 

Column 116

It appears from this total that under the assumption of constant 

volume the rock has lost only about 2 per cent of its substance through 

metasomatism. Moreover, there has been an addition, of 8.5 per cent 

of silica and 2.3 per cent of alumina. In other respects the alteration 

is not significantly different from that deduced upon the hypothesis 

of constant alumina.

It is, of course, possible that neither the hypothesis of constant 

alumina nor that of constant volume is strictly true; but it is believed

that the latter is a closer approximation to the truth than the former. 

The altered rock is not notably porous, nor does it, in the field, show 

evidence of contraction in bulk. Moreover, the very obvious introduction of quartz into some facies of it and the occurrence of diaspora 

point to that assumption involving the introduction of silica and 

alumina as being nearest the truth.

In order to further test this point a special examination was made 

of the spring water issuing above the Guston mine (see p. 114) to determine whether it carried alumina in solution. It was found to be 

present to the extent of about 214 parts per million, thus proving that 

the alumina in the rocks can not be regarded as a constant constituent 

during metasoniatic alteration, in this region.

The mineralogical composition of the altered rock may be roughly 

calculated from Analysis II as follows, the soda being considered as. 

accompanying the potash in sericite:

Mineralogical composition of metasomatically altered wall rock of Polar Star 

mine, Engineer Mountain.

Mineral.

Percentage by 

weight.

48.8

30.3

6

/j

7.2

3.9

Mineral.

Percentage by 

weight.

1.2

98.7

The specific gravity of the rock, as derived from the foregoing mineral composition and excluding pore spaces, is about 2.9, as compared 

with 2.8 similarly obtained for the unaltered rock. This rough calculation is thus in agreement with the general rule that near fissure 

veins the replacing minerals are as a whole denser than those replaced. L

Undgren: Trans. Am. Inst. Min. Eng., Vol. XXX, 1900, p. 594.
124- ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL.MB.

Although the altered facies just described appears to indicate only 

slight silicification or actual addition of silica to the rock, this process 

has taken place to a greater extent in the immediate walls of the fissures and in fragments of country rock included within the vein 

quartz. Such facies show little or no diaspore, but more sericite. 

The secondary quartz in such rocks is often more coarsely granular, 

and in thin section can be distinguished from the quartz which fills 

veinlets only through its association with nests of sericite, kaolinite, 

and a little diaspore. All original structure of the latite disappears 

between crossed riicols.

Summing up briefly, the characteristic features of the Polar Star 

metamorphism are (1) its restriction to the immediate vicinity of the 

lode, (2) the removal of at least 2 per cent of the substance of the 

rock, including all of the magnesia and carbon dioxide, nearly all of 

the alkalies and lime, and much of the iron, (3) the addition of silica, 

water, alumina, and sulphur, and (4) the formation of a secondary 

aggregate chiefly of quartz, kaolinite, pyrite, diaspore, and sericite.

The depth to which the alteration of the character extends is not 

known. The specimens studied evidently came from the deepest 

workings, probably over 500 feet from the surface.

It is not probable that the metamorphism described can have been 

effected by solutions in which alkaline carbonates were the principal 

constituents. It is more likely that the effective agent was acid 

water. If, however, the water contained sulphuric or hydrochloric 

acids it is, at first thought, rather difficult to understand the formation of kaolinite and diaspore. But as these minerals themselves are 

not soluble in acids, they may be capable of forming, under certain 

conditions, even in the presence of such a solvent for alumina as free 

sulphuric acid. Acid waters containing sulphuric acid circulate 

through the rocks of the Red Mountain region at the present day and 

have not prevented the formation of kaolinite nor effected its 

removal. In fact, they have probably in some cases aided directly in 

its formation by serving as solvents from which the alumina has been 

precipitated as kaolinite or diaspore under favorable conditions. The 

formation of diaspore instead of kaolinite in the presence of abundant silica indicates a very moderate hydration.

The metasomatic alteration of the rocks of the Red Mountain Range 

has frequently been referred to in this report. It is not limited to 

the immediate vicinity of known ore bodies, but is so widespread and 

noticeable a feature as to become an important problem in the general geology of the region and a serious embarrassment- to the geologist intent upon unraveling the structure and relationships of the 

various igneous rocks involved.

As a rule, the metamorphosed rocks, where not superficially stained 

by iron oxide, are nearly white. Frequently traces of original structure, such as outlines of feldspar phenocrysts or of breccia fragments,.
RANSOME.] METAMORPHISM OF THE COUNTRY ROCK. 125

can be recognized, but not uncominonlythese, too, have vanished, and 

the rock has become a white granular aggregate resembling a finegrained quartzite. Of such origin, and character is most of the 

so-called "quartz" of the Red Mountain mines, which forms the siliceous knobs in which many of the ore bodies outcrop.

The mound at the White Cloud mine may be taken as a typical 

example of such a knob or knoll. It is elliptical in plan and about 

50 feet long, trending N. 10° E. It rises about 30 or 40 feet above the 

general slope of the hill, and is composed of bleached siliceous rock 

which occasionally shows traces of breccia structure and which is 

evidently an altered form of the Silverton ande'sitic breccia. It contains considerable very finely disseminated pyrite.

A thin section of this rock shows a finely crystalline, rather turbid 

aggregate of quartz, kaolin, pyrite, rutile, and some minute indeterminable minerals. Some outlines of former phenocrysts are recognizable in ordinary light, but these disappear between crossed

nicols. The quartz grains are very irregular in outline and intricately 

interlocked. They are full of minute inclusions of kaolinite, rutile, 

pyrite, and other minerals too small for determination. The kaolin 

occurs in bunches showing the characteristic foliated aggregation of 

the individual scales, and the usual low double refraction.

A chemical analysis of this rock, from a specimen taken in a short 

tunnel in the knoll, is here given:

Analysis of altered andesitic breccia from White Cloud mine. 

[George Steiger, analyst.]

Constituent.

SiOa- .................................

A12 08 .. .................................

Fe^Oy. ...................................

FeO. ............................... .....

MgO. ...... ....... ................ ......

CaO... .....- ...... ------- ...........

NaoO .........................;.........

KoO.--. .-... ........................

HoO-....-. ........... ................

H:jO+ ..................................

Per cent.

85.49

5.4!)

93

.25

None.

27

.46

3. 07

Constituent.

TiO3 ...... .............................

CO,, ....................................

Po05 - ............................ ....

S03 . ....................................

MnO. .....^. ...........................

BaO. ...................................

FeS2 ....... .............................

Per cent.

.6:}

.or

.<m

.07

3.43

99.92

No analysis of unaltered rock is here available for comparison, and 

it is not possible to 'determine accurately the additions and subtractions to the original rock which have resulted in the metamorphosed 

facies. It is evident, however, that either the alumina has been 

very greatly reduced or the silica has been enormously increased. In 

all probability there has been some removal of alumina and a large 

addition of silica. Ferric and ferrous iron have been partly removed 

and the residue has been changed to pyrite. Lime has been almost 

all carried away and soda and potash have been wholly removed. Car-
126 ECONOMIC GEOLOGY OF SILVERTON- QUADRANGLE. fuuLL.182.

bon dioxide is absent. The little sulphuric anhydride present is probably combined with baryta as barite. -

The mineralogical composition, of the altered rock may be roughly 

calculated as follows:

MinercUngical composition of altered andesitic breccia from White Cloud .mine.

Mineral.

Kaolin............ .................. ........................... ...............................

Per cent.

78.5

13.8

3.4

.6

96.3

About 1 per cent of water is not accounted for, as there are no alkalies or alumina to combine with it. It may exist as chalcedony or 

opal, or as some hydrated compound of iron. No attempt has been 

made to calculate the small amounts of ferric and ferrous iron, lime, 

phosphoric acid, sulphuric acid, and baryta, which probably correspond to a little barite, apatite, and other minerals present in minute 

quantities in the rock. The total absence of sericiteis rather remarkable. The character of the alteration points to acid waters as the 

cause of metamorphism.

Of the same general character as the foregoing is the metamorphism 

which has transformed andesitic tuffs or breccias of the Silverton series 

into the highly siliceous rock forming the greater part of the picturesque knob in which the National Belle mine lies, at the village of 

Red Mountain. The resulting rock is nearly white and decidedly 

porous. Examined with a lens, it appears to consist wholly of quartz 

with a little pyrite, and is full ot minute cavities sparkling with

quartz crystals. Locally this porous structure may be so pronounced 

as to give the rock a pumiceous appearance.

Under the microscope, in ordinary light, the remnants of porphyritic 

structure are easily recognizable. Relatively clear areas having the 

shape of feldspar phenocrysts and dark areas containing much finely 

divided pyrite and other opaque particles, clearly pseudomorphs after 

some phenocrysts probably ferromagnesian constituents lie in a 

grouudmass somewhat turbid with minute dark particles. With the 

nicols crossed, however, this structure practically vanishes, and the 

whole appears as a finely crystalline granular aggregate of quartz. 

The space formerly occupied by the phenocrysts of feldspar is now 

filled with quartz, somewhat more coarsely crystalline than in the 

groundmass. Frequently the quartz does not quite fill the space, but 

has left a microscopic vug in the center. The quartz making up the 

rock is not pure, being crowded with indeterminable inclusions. But
BANSOME.] METAMORPHISM OF THE COUNTRY ROOK. 127

the rock in all probability contains over 00 per cent of silica, and the 

evidence of thorough silicification, with removal of nearly all of the 

bases save a little iron to form pyrite, is unquestionable. It shows 

that under certain conditions even the alumina may be removed, and 

that the assumption as to the constancy of this constituent in unaltered and altered rock must be used Avith caution.

An intrusive porphyry, belonging with the monzonite-latite group 

of rocks, is fairly abundant in the Red Mountain region, where it 

forms relatively small masses of circular or elliptical plan. It has 

been intruded in the form of plugs or bosses into the volcanic rocks, 

and, like the latter, has undergone metasomatic alteration. Where 

not greatly altered as, for example, at an exposure by the roadside a 

few hundred yards south of the Yankee Girl mine the rock is conspicuously porphyritic, showing phenocrysts of pink orthoclase up to 

three-quarters of an inch in length, smaller crystals of white plagioclase, and anhedrons (crystalline grains) of quartz, all lying' in a 

compact, greenish-gray groundmass.

Under the microscope the rock shows considerable decomposition. 

The orthoclase is fairly fresh, but the plagioclase (apparently in part 

acid oligoclase) is partly sericitized. Areas of calcite and chlorite 

with a little pyrite are apparently pseudomorphous after augite or 

diopside. The groundmass is a rather cloudy, fine-granular aggregate which seems to consist chiefly of quartz and orthoclase, but contains considerable calcite and chlorite, with some apatite, a good deal 

of finely disseminated pyrite, and some titanic iron altering to leucoxene. A chemical analysis of this rock is given in Column I in the 

folioving table:

Analyses of monzonitic'porphyry.

[H-. N. Stokes, analyst.]

Constituent.

SiO2 .... ....................

AloOs... .................

Fe2O3 ...... .................

FeO. .......................

MgO. ............... .......

CaO. ............ ............

Na20.. .....................

K2O ........................

HoO--.. ..................

TiO2 ... ...-----.... ..---.---

C02 .. ...... .................

I.

Per cent. 

58.78

13. 62

1.70

2.27

3.29

4.31

3.24

4.06

.99

3.49

II.

Per cent. 

73.61

13. 97

.31

.04

.06

.58

.60

Constituent.

PoOf, ................... ....

SOS .... .................... -

CroO3 ......................

NiO .......................

MnO. ......................

BaO .......................

SrO. ................... ....

LioO. ......................

FeSa ............ ...........

I.

Per cent.

. 53

12

.05

1.56

99.73

II.

Per cent. 

.33

Notdet.

.04

5.62

99.34

I. Monzonitic porphyry, from near Yankee Girl mine.

II. Metasomatically altered facies of foregoing, from near National Belle mine.
128 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL.182.

From this analysis and the microscopical study the mineralogical 

composition may be calculated as follows:

Mineralogical composition of monzonite-porphyry.

Constituent. Per cent.

27.4

21.3

21.2

11

7.8

4

Constituent. Per "cent.

1 4.2

1.5

1.2

9!1. ft

All the lime shown in the analysis is required to form calcite with 

the carbon dioxide, so that the plagioclase, whatever its original composition, must at present contain very little lime and is calculated as 

albite. The appearance of the thin section indicates that the chemical determination of the pyrite may be a little low and that a portion 

of the iron, here calculated as titanic iron ore, should really be estimated 

as pyrite.

On the north side of the National Belle knob a mass of this same 

porphyry has been altered by metasoinatic processes to a very lightgray rock in which the feldspars are transformed to dull kaolin-like 

aggregates while the quartz phenocrysts are apparently unchanged. 

A few minute veinlets, filled with kaolin, occur in the hand specimen. 

The groundmass is gray in color, compact in texture, and abundantly 

sprinkled with minute crystals of pyrite. This alteration is evidently 

directly connected with the deposition of the National Belle ore bodies, 

and is merely one phase of the metamorphism which has given rise 

to the siliceous mass in which the ore occurs.

Under the microscope rounded and embayed phenocrysts of quartz

containing minute fluid inclusions, and pseudomorphous aggregates 

after feldspar, are seen to lie in a finely crystalline, granular groundmass. The feldspar phenocrysts have been changed to pseudomorphs 

of kaolin, diaspore, and quartz. The diaspore is intimately associated 

with the kaolin, in which it often occurs embedded in ragged, shredlike areas. Near it there is sometimes a small amount of a colorless 

isotropic mineral with a fairly high refractive index, which has thus 

far defied identification. The groundmass is a finely crystalline mosaic 

of quartz and kaolin with small scattered crystals of pyrite and occasional crystals of rutile and apatite. Sericite was not noted, but is 

perhaps not entirely absent.

A chemical analysis of this rock is given under II, on page 127, and 

although the two rocks are not from the same mass, there can be little 

doubt that they were both originally of the same character.

It may be that the nearly identical contents in alumina shown by 

the two analyses is merely a coincidence, but it is probable that it
HANSOM E.] METAMOEPHISM OF THE COUNTRY BOCK. 129

denotes practical constancy of the alumina during the change which 

has taken place in the rock.

The notable features of the alteration are the introduction of silica, 

water, and sulphur, the total removal of iron (except that combined 

with sulphur to form pyrite), magnesia, and carbon dioxide, and the 

'almost entire abstraction of lime and alkalies. The formation of 

diaspore brings this alteration close to that described at the Polar Star 

mine, the original rocks in both cases being of similar chemical composition, while the addition of silica and the formation of kaolin, 

usually without sericite, is characteristic of"the Red Mountain mines.

Ignoring the small amount of the unknown isotropic mineral, the 

mineralogical composition of the altered rock may be roughly calculated from the chemical and microscopical data as follows:

Mineralogical composition of altered monzonitic porphyry from National Belle

mine,

Constituent.

Kaolinito....... ..........................

Per cent.

00.9

26.3

5.6

a 3. 8

.6

Constituent.

Rutile.... ..............................

Percent.

.6

.6

98.4

a The diaspore of this rock was also isolated with hydrofluoric acid. It appeared to be fully as 

abundant in the residue as in the similar residue from the Polar Star rock, described on page 

121, and the above calculation may below.

This is a very different alteration from that normally brought about 

by waters carrying alkaline carbonates, which, as Lindffren J has shown, 

tend to form sericite and carbonates in the wall rock. It is believed 

to be due to the action of acid waters.

It is unfortunate that the study of the metarnorphism connected 

with the Bed Mountain ore bodies is at the present time practically 

confined to the surface. However, as far as can be judged from the 

mine dumps, metamorphism of the character described accompanied 

the ore bodies to the greatest depth explored.

On Anvil Mountain, which forms the southern end of what has been 

called for convenience the Red Mountain Range, the bleached rocks, 

when critically examined, are found to present some variations in 

composition. Thus the country rock of the Brobdignag claim, probably originally andesitic, is converted into a fine-granular aggregate 

of quartz and barite, with a little sericite. It is impregnated with 

pyrite and is traversed by some veinlets of sericite or kaolin. At the 

Zuiii mine the country rock, which was evidently an andesiteor Jatite, 

has been recrystallized near the ore body to a mass of quartz, sericite, 

kaolin, and barite, with a little epidote in small grains. Some rutile

1 The gold-quartz veins of Nevada City and Grass Valley districts, California: Seventeentu 

Ann. Kept. U. S. Geol. Survey, Pt. II. Ib9f>, p. 172.

Bull. 182 01 9
130 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [Bur,L.182.

and some undetermined minerals in minute grains are also present. 

At the Mysteiy claim, on the summit of Anvil Mountain, the rock 

(rhyolite?) has been changed to a nearly white, rather porous mass 

showing no traces of original igneous structure. Under the microscope il shows faint outlines of former phenocrysts, which become 

nearly invisible between crossed nicols. The rock consists chiefly of 

quartz and alunite in a fine-granular aggregate, with a little kaolin 

and rutile. At John Roland's tunnel, about 1-^- miles southeast of the 

Mystery claim, an opportunity was presented for studying some of 

the steps of alteration. About 150 feet from its mouth the tunnel cuts 

through a very irregular vein-like mass of kaolin and continues beyond 

it for 200 feet or more. Near the breast the rock, although altered, can 

be recognized as an andesite, or closely related rock. It is greenish 

gray in color and shows outlines of small feldspar phenocrysts. 

Under the microscope, although the original porpkyritic structure is 

partly preserved, the rock is seen to be completely altered. The phenocrysts of plagioclase are changed to sericite and quartz, while the 

augite and perhaps other dark constituents are represented by pseudomorphs of chlorite and calcite. At about 150 feet from the fissure 

the country rock is already bleached to a light greenish-gray tint and 

the original texture partly obliterated. Under the microscope it is 

seen to be a secondary aggregate, consisting chiefly of sericite, quartz, 

and calcite, retaining, hoAvever, outlines of the original porphyritic 

structure. About 45 feet from the fissure the rock is- nearly white 

and shows very faint traces of original texture. In general appearance it is identical with most of the bleached and metamorphosed rock 

of the Red Mountain Range. Microscopically examined, the outlines 

of former phenocrysts are distinctly visible, but the whole rock is 

recrystallized to a very fine aggregate of quartz and sericite with some 

leiicoxene (rutile). The former feldstoar phenocrysts are now nearly 

pure sevicite. Lastly, a specimen taken from the wall of the fissure 

is a nearly white, compact rock in which close scrutiny fails to detect 

any vestige of primary structure. Under the microscope the rock 

appears as a finely crystalline aggregate consisting of quartz and sericite, with a little brownish isotropic material occurring in minute veinlets. Recrystallization in this case has not only been complete, but 

there has been such thorough rearrangement of the crystallizing material as to obliterate all traces of primary structure. The alteration 

has plainly been accompanied by removal of iron, lime, magnesia, and 

probably other constituents. Whether alumina has been removed is 

an open question, but the fact that the fissure from whence the metamorphosing solutions penetrated the inclosing rock is itself filled with 

a vein-like deposit of kaolin shows that at some depth both potash and 

alumina have been removed from the country rock and concentrated 

as kaolinite within the fissure walls.

The conspicuous metamorphism of the Red Mountain region has
RANSOME.1 PAEAGENESIS OF LODE AND STOCK ORES. 131

undoubtedly involved rocks of various kinds, reducing them all to 

light-colored secondaiy aggregates of similar appearance. Andesites, 

latites, monzonite-porphyry, and rhyolite have been altered to products which often give little indication of the nature of the original 

rock. But in many portions of the quadrangle the rhyolitic rocks 

show certain characteristic phases of metamorphism in connection 

with ore deposition which seem to merit some special notice. This 

rock, when acted upon by ore-bearing solutions, is particularly susceptible to recrystallization into secondary aggregates of quartz and 

sericite, quartz and kaolin, or quartz, sericite, and kaolin. As a 

general rule such metasomatic alteration is accompanied by more or 

less replacement of the rock by ore, as may be seen in the Tom Moore 

or Silver Ledge mines.

No favorable opportunity was presented for studying in detail the 

metasomatic processes which accompanied the deposition of ore in the

monzonitic stocks, such as Sultan Mountain. But so far as observed 

the alteration is not conspicuous.

PARAGENESIS OF THE LODE AND STOCK ORES.

By paragenesis is here meant the association of the various ore and 

gangue minerals with special reference to the order and mode of their 

formation.

Beyond the common and well-known derivation of certain secondary minerals in the zone of oxidation, as, for example, anglesite or 

lead sulphate from galena, the directly observable paragenesis of the 

ores offers few points which can be embodied in any general statement 

of regular association. As a general rule the ore minerals which arc 

found together in any one deposit, have formed contemporaneously, 

and cases are rare in Avhich a definite and constant succession of different ore minerals can be recognized. In the Tom Moore lode, 

chalcopyrite appears to have formed later than tetrahedrite. The 

same relation was observed in the .Dives lode, where masses of tetrahedrite are surrounded by an- envelope of chalcopyrite from which 

radiate still younger quartz crystals. But in many other lodes these 

two minerals occur in such irregular relations as to point to practical ly 

contemporaneous crystallization. In the .Empire-Victoria lode, on 

Sultan Mountain, hiibnerite and fluorite have been formed since the 

ore was deposited. Native copper, wherever seen, was plainly of 

later origin than the sulphide ores with which it was associated. 

Native silver was seen only in detached specimens of ore, but it occurs 

characteristically in the upper.portions of the deposits and is undoubtedly of secondary origin. Quartz of at least two generations is common, as shown by the relatively barren stringers of this mineral, 

which can be found traversing the ore in many of the deposits.

Free gold occurs usually embedded in quartz and associated with 

pyrite or chalcopyrite. In the Sunnyside, Sunnyside Extension, and
132 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. I BULL. 182.

Camp Bird mines it is also associated with pale-yellow sphalerite and 

fluorite. Some specimens were .seen from the Sunnyside Extension 

mine in which the gold occurred as implanted crystals on quartz and 

was therefore of later age than the latter.

Unfortunately there are at present few opportunities for studying 

the occurrence of proustite and argcntite in the Silverton quadrangle. 

In the Ridgwaj7 mine much of the ai'gentite occurs implanted on, or 

wedged between, the quartz crystals of small vugs, and was the last 

mineral to crystallize. It has been the universal experience in the 

Silverton district that argentite, proustite, and polybasite are not 

found below a very moderate depth. The data at hand do not permit 

of a definite statement as to the depth at which these rich argentiferous minerals change to low-grade ore, but the indications are that it 

is less than 1,000 feet, although it is well known that in other regions 

some of these minerals extend to greater depths. It is probable, 

although not at present demonstrable, that in the Silverton region 

proustite, argentite, and polybasite are of secondary origin and indicate a zone of enrichment of the kind to which Emmons 1 and Weed 2 

have recently called attention.

The downward change from galena through richly argentiferous copper ores to chalcopyrite and pyrite, which was found to be a character- 

. isticfeature of many of the Red Mountain mines, is a case of paragenesis 

on a large scale, which will be discussed in the following section on 

the origin of ores. The origin of the rhodonite, which is so abundant 

in many of the lodes of the northern half of the quadrangle, and its 

exact relation to the quartz and ore which accompany it constitute a 

puzzling problem, for which no satisfactory solution has been found. 

Such a solution must account for the presence of large lenticular or 

partition-like masses of rhodonite, carrying a few specks of low-grade 

ore, and dividing the ore bodies longitudinally into two or more parts, 

arid for the presence of patches and stringers of rhodonite. In the 

Saratoga mine rhodonite has formed by metasomatic replacement of 

limestone. It is possible that in such lodes, as the Sunnyside the large, 

solid masses of rhodonite within the vein may represent metasoniatically altered horses of country rock. This, however, is merely a 

hypothesis, which requires confirmation before acceptance. It has 

undoubtedly been deposited also in open fissures as a true vein 

inineral.

ORIGIN OF THE LODE AND STOCK ORES.

That the ores of the Silverton quadrangle were deposited from 

aqueous solution is a proposition which, in the light of present knowledge, needs no special demonstration. They were precipitated partly

irThe secondary enrichment of ore deposits: Trans. Am. Inst. Min. Eng.. Vol. XXX, 1900, 

pp. 177-217.

- Enrichment of mineral veins by later metallic sulphides: Bull. Geol. Soc. Am., Vol. XI, 1900. 

pp. 179-206.
RANSOME.] ORIGIN OF THE LODE AND STOCK ORES. 133

in open spaces, to which the solutions had access, and partly as 

replacements of various rocks through metasomatic action. Their 

deposition was accompanied by chemical and raineralogical changes 

in the immediately adjacent country rock, producing effects which in 

the majority of cases diminish rapidly in intensity with increasing 

distance from the fissure walls. As far as is known, the deposition of 

ore within the fissures was not affected by differences in character of 

the wall rock. It is believed that the facts presented in the descriptive portions of this report all indicate an initial primary deposition 

by ascending mineralized waters. It is probable, as pointed out by 

Lindgren 1 and Van Hise, 2 that these waters were originally .meteoric 

waters, which gained their heat and collected their mineral contents 

during slow downward and lateral percolation through the rocks, and 

were subsequently gathered as ascending currents into the main 

fissures. It is not known from what particular rocks they extracted 

their metalliferous burden, nor at what depth most of the solution took 

place.

That the entire process of ore deposition was directly connected 

with volcanism can scarcely be doubted. The most obvious aspects 

of this connection are threefold: (1) The mechanical formation of the 

fissures; (2) the accession of heat, whereby the chemical actiAnty of 

underground water was intensified; and (3) the accumulation of vast 

masses of igneous rock from wThich, at some depth, the constituents 

of the ore minerals were probably derived. - It is possible that there 

should be included here also the evolution of carbon dioxide, sulphydric acid, arid probably other volatile substances, as active solvent 

and chemical agents.

Very different views are held by various investigators in regard to 

the extent to which pueumatolytic processes, due to the emanation of 

highly heated gases and vapors from solidifying igneous rocks, are 

responsible for ore deposition. Van Hise, in his suggestive paper 

just cited, practically ignores pneumatolysis as a factor in the formation of ore bodies. Kenip, 3 on the other hand, considers that meteoric 

waters have little or 110 efficiency in the original concentration and 

deposition of ores, and that the waters of ore-bearing solutions, 

together with their dissolved mineral constituents, are of intratelluric 

origin, and are given off at high temperatures by masses of igneous 

rock in process of congelation. Various intermediate views are held 

by many European geologists and writers on ore deposits, notably by 

Beck, Vogt, and Du Launay. The evident connection between ore 

deposition and volcanism, or at least the products of volcaiiism, the

1 The gold-quartz veins of Nevada City and Grass Valley districts, California: Seventeenth 

Ann. Rept. U. S. Geol. Survey, Pt. II, 1896, p. 176.

"Some principles controlling the deposition of ores: Trans. Am. Inst. Miri. Eng., Vol. XXX, 

1900, p. 47.

3 The role of the igneous rocks in the formation of veins: Trans. Am. Inst. Mining Eng., Richmond meeting, 1901.
134 ECONOMIC GEOLOGY OF SILVEKTON QUADBANGLE. [BULL. 188.

presence of fluorite and hiibnerite in some of the lodes of the Silverton region, and the occurrence of alunite and diaspore, in connection 

with metasomatic alteration of the country rock apparently brought 

about by acid waters and locally very pronounced in character, are 

all to some extent indicative of pneumatolytic processes. But, as 

Lindgren 1 remarks, fluorine and boron compounds are found in some 

deposits which are certainly not of pneumatolytic origin, nor even 

formed at high temperature. The Silverton lodes, as a whole, possess 

neither the distribution nor the mineralogical characters of those 

deposits to which in the light of present knowledge an essentially 

pneumatolytic origin can be most safely assigned. The known igneous masses had certainly solidified and probably had lost much of 

their heat before the lode fissures were formed. It is most probable 

that the transportation and concentration of the Silvertou ores was 

effected chiefly by meteoric waters, which derived their chemical and 

mechanical energy mainly from the heat connected with volcanism 

and from pressure, but possibly in some minor part, also, to g-ises and 

vapors giv^en off at high temperature by solidifying igneous rocks and 

taken into the deeper meteoric circulation.

It is difficult to determine the exact character of the solutions which 

deposited the ore of the Silverton quadrangle. Many natural solvents 

'are known for the common gangue minerals, for sulphide minerals, 

and for gold. According to Doelter's 2 experiments, pyrite, sphalerite, 

galena, stibnite, chalcopyrite, arsenopyrite, and bournonite are all 

appreciably soluble in pure water under the influence of moderate 

heat (80° C.) and pressure. Galena and pyrite are soluble in water 

containing carbon dioxide, and gold and copper are soluble in solutions 

of sodium carbonate. 3

Solutions of sulphydric acid' or sodium sulphide are relatively active 

solvents of gold, as well as of pyrite, chalcopyrite, bournonite, arsenopyrite, galena, and sphalerite, according to the investigations of 

Becker 4 and Doelter. 5 The experiments of Doelter in particular 

indicate that heat and probably pressure increase the solvent action, 

although the law of this increase of the different minerals is unknown. 

Solution is also favored by a great preponderance in the mass of the 

solvent and by the long contact of solvent and solid under favorable 

conditions of heat and pressure. Obviously these latter conditions 

are those common in nature, but which can be only very imperfectly 

realized in the laboratory. It appears, therefore, that nearly all 

aqueous solutions that occur in nature may, under suitable conditions of heat and pressure, act as solvents and carriers of the heavy

1 Metasomatic processes in fissure veins: Trans. Am. Inst. Min. Eng., Vol. XXX, 1900, p. 644.

2 Chemische Mineralogie, Leipzig, 1890, p. 188.

3 Doelter, loc. cit., pp. 190-191.

4 Natural solutions of cinnabar, gold,and associated sulphides: Am. Jour. Sci., Vol. XXX, 1887, 

pp. 199-210. Also Mon. U. S. Geol. Survey, Vol. XIII, 1888, pp. 432-433.' 

6 Loc. cit., p. 192.
RJV.NSOME.] ORIGIN OF THE LODE AND STOCK ORES. 135

metals and their sulphides. Some solutions are undoubtedly more 

efficient than others under like conditions, but where so many unknown 

elements, such as degree of heat, amount of pressure, relative mass 

of solvent and solute, and duration of the process, enter into the 

problem, it is rarely possible to arrive at even approximate quantitative 

results.

As the lode and stock ores were deposited from solutions, it follows 

that the chemical action of these solutions on the wall rocks offers a 

very important mode of attacking the problem of their chemical character. The nature of this metasomatic alteration has been discussed 

at some length on. pages 114-151 of this report. It is concluded that 

the solutions producing it were chemically different in different portions of the quadrangle. The very slight development of carbonates 

in connection with some lodes, and their entire absence in others, indicate that carbon dioxide or alkaline carbonates were not abundant 

in the mineralizing waters, although probably not wholly absent in 

the case of deposits such as those of Silver Lake Basin. The silicification observed in connection with the Red Mountain deposits, with 

the removal of most of the bases, including in some cases part of the 

alumina and the addition of sulphur and water, indicate the action of 

acid waters, probably containing free sulphuric acid. But here 

another element, which can not be ignored, enters the problem. 

Water containing sulphuric acid and ferric sulphate is known in the 

Red Mountain region to-day: not as ascending thermal water, but as 

(in part at least) descending water, which owes its acidity to the 

oxidation of previously deposited iron pyrite. The capacity of this 

water to effect some changes in the country rock is beyond doubt. It 

is not unlikely, therefore, that much of the alteration visible in the 

Red Mountain region is the result of complex processes involving the 

action of solutions of different characters and origin and acting upon 

any given mass of the rock at different times.

Writers on the genesis of ore deposits very commonly speak of 

the "circulation," "currents," or "flow" of the ore-bearing solutions 

within the fissures. Although the use of these terms is convenient 

and can not be regarded as entirely incorrect, yet it is believed that 

it has tended to give artificial or false conceptions in regard to the 

actual processes of ore deposition in many veins, particularly in large 

veins. Ore deposited by solutions having obvious movement through 

a fissure should exhibit the phenomenon called by Posepuy crustification i. e., it should be deposited in successive layers or coatings upon 

the walls of the fissure. J But this structure, formerly so much insisted 

upon as evidence of deposition in open fissures, is, as a matter of 

fact, of comparatively rare occurrence even in veins which on other 

evidence are demonstrably simple fissure fillings. In most of the

1 It is perhaps hardly needful to point out that the converse of this proposition is not necessarily true.
136 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

important lodes of the Silverton quadrangle no crustifieation can be 

detected. The fissures are filled by coarsely crystalline allotriomorphic aggregates of ore and gangue (massive structure), and there is 

no evidence to show that such a structure could result from successive 

deposition upon the walls of the fissure until the whole was finally 

filled. On the contrary, crystallization has proceeded simultaneously 

from many points within the solution. Quartz, galena, pyrite, sphalerite, chalcopyrite, and other minerals have formed practically contemporaneously about local centers of crystallization scattered irregularly through the solidifying mass. It is difficult to conceive all the 

details of a process which results in the formation from aqueous solution of an irregular allotriomorphic aggregate of minerals differing so 

widely in specific gravity. But reasoning from analogy with similar 

structures met with in petrology and in the arts, it is fair to assume 

that this structure in veins is the result of the undisturbed crystallization of a nearly motionless saturated solution. In other words, it 

was the crystallization of a reservoir so large, in comparison with the 

current 01- currents which circulated through it, as to have been itself 

free from megascopic motion. The conditions which induced crystallization were present throughout the mass of material which filled 

the fissure, and solidification, instead of proceeding gradually from 

the walls inward, took plaoe almost simultaneously, although not necessarily with rapidity, throughout the mass. Obviously this massive 

structure and crustifieation may be present in the same vein. In such 

cases deposition appears to have begun by crustifieation next the 

walls, passing at a later stage into the more general mode of crystallization indicated by what has been described as massive structure.

Attention has been strongly drawn of late, through the writings of 

De Launay, 1 Van Hise, 2 Weed, 3 and Ernmons, 4 to the important part 

played by secondary sulphide enrichment in the formation of many 

ore bodies, particularly those carrying copper and silver. As a probable example of such an enriched deposit, Mr. Eramons 5 has cited the 

Yankee Girl ore body. Unfortunately, at the time Mr. Emmons visited the mine, in 1888, but little attention had been given to the subject of secondary sulphide enrichment, while at the present day the 

state of the workings is such as to render impossible the verification 

by direct observation of this application of the theory. However, 

there are many facts which point strongty toward secondary enrichment as the true mode in which the rich ore bodies, not only of the 

Yankee Girl, but of the Guston, Silver Bell, and other mines, were 

formed. To have the important facos fresh in mind, it will be well to

1 Contribution & 1'etude des gites metalliferes: Ann. des Mines, Vol. XII, 1897, pp. 119-228. 

" 2 Some principles controlling deposition of ores: Trans. Am. Inst. Min. Eng., Vol. XXX, 1900. 

pp. 27-177.

3 Enrichment of mineral veins by later metallic sulphides: Bull. Geol. Soc. Am., Vol. XI, 1900, 

pp. 179-206.

4 The secondary enrichment of ore deposits: Trans. Am. Inst. Min. Eng., Vol. XXX, 1900, pp. 

177-217. 

D Loc. cit., p. 19.
BAKSOME.] OEIGIN OF THE LODE AND STOCK OEES. 137

review briefly the characteristic features of these ore bodies which 

bear upon this question.

The ore first struck, in some cases actually at the surface, consisted 

chiefly of argentiferous galena. At a depth which varied somewhat 

in different mines, but which appears to have been usually less than 

200 feet, this galena changed to an ore consisting chiefly of highly 

argentiferous stromeyerite. At a still greater depth usually about 

500 feet the stromeyerite changed to argentiferous bornite, still 

deeper to chalcopyrite and pyrite, and finally to low-grade aurifer- 

.ous and argentiferous pyrite. These changes were more or less irregular and overlapping. Thus pyrite was found at nearly all levels, and 

bunches of galena were met with far below the levels at which it ceased 

to be the dominant ore. Small rich streaks of bornite were also found, 

with chalcopyrite and pyrite, below the levels where it occurred in 

large masses. According to Schwarz, 1 who opened and worked many

of the ore bodies of the Red Mountain district, the rich portions of 

the ore bodies were always associated with open water-bearing fissures, and he apparently regarded the entire deposits as formed primarily by deposition from the water entering1 through these fractures. 

It seems to be a well attested fact that at a depth of about 500 feet 

there was encountered in the Yankee Girl and Gruston mines a fault 

or "slip plane" with low westerly dip, and, further, that the richest 

ore occurred just above this seam, which was filled with clay-like 

gouge. Moreover, most of the water entering the mines came in at or 

above this fault. The acid character of this water was well known, 

and it carried in solution large amounts of the sulphates of iron and 

copper. Lastly, the mines are situated within a valley of erosion, 

within which the ore bodies outcrop at different levels. It is not 

known what thickness of material has been removed in the shaping of 

the present topography, but it probably exceeds 2,000 feet. It is 

hardly conceivable that the observed relation between the vertical 

variations in the ore bodies and the present topographic surface is a 

haphazard one. It is without much doubt genetic.

Ore deposits wrhich show a fairly orderly vertical succession from 

rich sulphides near the ground-water level down to poor sulphides at 

greater depth are in nearly all cases regarded as the product of two 

concentrations a concentration by ascending waters and a further 

concentration by descending waters. 2 By the former are deposited 

lean ores, found in the deepest workings, which are enriched to a 

greater or less depth by the downward-moving solutions. As "Van 

Hise has pointed out, these two processes may go on at the same 

time, or they may have operated successively on any given vertical 

section of the ore body. The facts obtainable in the Red' Mountain 

region point to the original deposition of bodies consisting chiefly of

1 Trans. Am. Inst. Min. Eng., Vol. XVIII, 1890, p. 144. 

8 Van Hise, op. cit., p. 101.
138 ECONOMIC GEOLOGY OF SILVEKTON QUADBANGLE. [BULL. 183.

pyrite carrying a little gold, silver, and copper. The lead may have 

originally been sparingly deposited as galena with the pyrite. It is 

into such low-grade auriferous and argentiferous pyrite, carrying 2 or 

3 per cent of copper and containing an occasional bunch of galena, 

that the rich ore bodies passed in the Guston, National Belle, Silver 

Bell, Hudson, and Yankee Girl mines when the ore became too poor 

to work.

Subsequently, as the surface of the region was reduced by erosion, 

descending waters, which found ready passage through the fissured 

and mineralized rocks of the region and through the upper portions of 

the lean primary ore bodies, effected a second concentration, which 

produced the rich ore formerly mined. The penetration of this water 

into the primary pyritic ore must have been aided by the porous, 

crumbling character of much of the latter. These waters are known 

to have been heavily laden with the sulphates of iron and copper and 

other salts, resulting from oxidation of the upper portions of the ore 

bodies. As these solutions penetrated downward they probably acted 

upon the low-grade pyritic ore, replacing part of the iron sulphide by 

sulphides of copper and silver. Apparently much experimental work 

remains to be done before all the details of the chemical processes 

involved will be actually known, but the probability of the transformations outlined ,is shown by the following chemical equations taken 

from \ran Hise's suggestive paper. 1

By taking solutions containing merely the sulphates of copper the 

production of chalcopyrite from iron sulphides may be written as 

follows:

Cupric sulphate+ferrous sulphide=chalcopyrite+ferrous sulphate.

CuS04 + 2 FeS = CuFeS2 + FeS04 

Or,

Cupric sulphate+ pyrite +oxygen = chalcopyrite+£errous sulphate+sulphurous anhydride.

CuS04 + 2 FeS2 + 0, = CuFeS2 + FeS04 + 2 S02 

Bornite may be produced as follows:

Cuprous sulphate + cupric sulphate + ferrous sulphide = bornite + ferrous sulphate.

Cu2S04 + CuS04 + 3 FeS =Cu3FeS3 + 2 FeSO4 

Or,

Cuprous sulphate + cupric sulphate + pyrite + oxygen = bornite + ferrous sulphate +

Cu2SO4 + CuS04 + 3FeS2 + 6O =Cu8FeS3+ 2 FeSQ4 +

sulphurous anhydride.

- 3S02

But bornite may also be formed by direct action of the copper sulphates on chalcopyrite, as follows:

Chalcopyrite+cupric sulphate+oxygen= bornite +ferrous sulphate+sulphurous anhydride.

2 CuFeS2 + CuS04 + 02 =Cu3FeS3+ FeS04 + S02

1 Some principles controlling the deposition of ores: Trans. Am. Inst. Min. Eng., Vol. XXX, 

1900, pp. 111-112.
RANSOME.] ORIGIN OF THE LODE AND STOCK OEES. 139

Chalcocite may be produced from pyrite, chalcopyrite, or bornite, 

as follows:

Cupr.ms sulphate + pyrite + oxygen = chalcocite + cuprous sulphate + sulphurous anhydride.

CuoSO,, +FeS3 + 02 = CnaS 4- FeS04 + S02

Cupric sulphate+chalcopyrite+oxygen=chalcocite+cuprous sulphate-f sulphurous anhydride.

CuSo4 + CuFeSa + 02 = Cu2S + FeS04 -;- S02

Cupric sulphate + bornite +oxygen = chalcocite + ferrous sulphate+sulphurous anhydride.

CuS04 +Cii8 FeS8 4- 02 = 2Cu2S + FeS04 + S02

Of course it is understood that these sulphides overlap one another. Before the 

iron sulphide has wholly been replaced by chalcopyrite bornite may appear. At 

the place where bornite has become reasonably abundant chalcocite may be found. 

However, certain general statements may be made. If the dominating material is 

iron sulphide, the copper mineral which is present is likely to be chalcopyrite 

rather than the richer sulphurets. Chalcopyrite, on the one hand, is likely to 

be associated with the pyrites, and on the other hand with bornite, or even chalcocite. Bornite and chalcocite are likely to be associated with each other and with 

chalcopyrite, but with the first two compounds iron sulphide is likely to be subordinate or absent.'

When the sequence of formation, deduced largely on theoretical 

grounds by Van Hise, is compared with the facts of occurrence in the 

Yankee Girl and Guston mines, the close correspondence affords 

striking confirmation, not only of the probable truth of the theory of 

secondary sulphide enrichment, but also of its applicability to these 

deposits. As far as the cupriferous sulphides and pyrite are concerned, the relations are exactly those which might be expected as a 

result'of the downward percolation of solutions of copper sulphates 

through a body of low-grade pyritic ores.

The iron sulphates, of course, can not act directly, as do the copper 

sulphates, in enriching the ore. Their role is limited to an attack upon 

the previously formed sulphides, which converts them into sulphates 

and redeposits them in part as sulphides below the zone of oxidation. 2 

They thus aid, although in a different manner, the copper sulphates in 

effecting a secondary concentration of the ores. It is probable that, 

owing to the slight solubility of its sulphate, the lead is deposited as 

sulphide at an early stage in the downward movement of. the solutions, and that, through a constant and prolonged continuance of this 

process, as the outcrop of the ore body is lowered by erosion, there 

have resulted the masses of nearly pure galena ore which occurred 

above the chalcocite or stromeyerite.

The application of the theory of secondary sulphide enrichment to 

any ore body naturally presupposes the existence of small amounts 

of the valuable metals in the low-grade ore of primary deposition. 

But this fact is not always easily determined, as mining operations are 

not often pushed very far beyond the depth at which the ore ceases to

1 Van Hise, op. cit., p. 112.

2 The secondary enrichment of ore deposits, by S. P. Emmons: Trans. Am. Inst. Min. Eng., 

Vol. XXX, 1900, p. 210.
140 ECONOMIC GEOLOGY OF SILVEKTON QUADKANGLE. .[BULL. 188.

pay, and it is not always possible to determine the actual downward 

limit of the enrichment. But the numerous assays made of the 

unworkable pyrite in the deepest levels of the Guston, Silver Bell, and 

National Belle mines all show the presence of a fraction of an ounce 

of gold and a few ounces of silver. Lead has not been determined. 

It is probable that in the assays made for practical purposes no 

attempt was made to determine its presence in small amounts. It 

should further be borne in mind that the enrichment in question is 

not of necessity due solely to waters which have descended from the 

upper portion of the selfsame ore deposit. The descriptions of the 

mines indicate that some of the second concentration -was effected by 

waters which may have traveled laterally, from some distance, through 

rocks which are themselves mineralized and may contain considerable 

bodies of ore as yet undiscovered.

The theory of secondary enrichment, which is regarded as giving 

the most probable and satisfactory explanation of some of the peculiar features of the Red Mountain deposits, has, if its application is 

correct, certain very important and practical consequences. It indicates that the rich ores formerly mined have a working lower limit 

which is probably less than 1,000.feet in depth. While small bodies 

of rich ore may occur deeper than this, it is probabty not worth while 

prospecting for them when once the depth has been reached at which 

the ore is practical!}7 all low-grade pyrite. On the other hand, as 

some pyrite occurs at all depths, and as the vertical limits of the 

zones of enrichment, are necessarily irregular and overlapping, it is 

unwise to suspend operations too quickly, merely because the ore falls 

off locally in value and becomes pyritic.

Passing from the Red Mountain stock deposits to the lodes occurring in other portions of the quadrangle, the evidence of secondary 

enrichment is less easily road. It seems very probable that the rich 

silver minerals, such as polybasite, proustite, and argeutite, are the 

result of secondary enrichment similar to that described by Weed 1 

in the Neihart district in Montana. In the San Juan region, however, 

the actual steps of the alteration of lower-grade ores into those rich 

in silver can not be traced. The evidence for a secondary origin consists in the fact that these rich minerals occur largely in vugs, and 

that in several cases they pass at moderate depths into low-grade ores. 

These features, however, do not in themselves preclude the idea that 

the minerals are primary, and resulted from original deposition in a 

zone where ascending and descending waters mingled.

In the Tomboy mine the undoubted association of the richest gold 

ore with shattering and movement in the lode, accompanied by some 

oxidation far below the level of general weathering, is suggestive of 

secondary enrichment, but it is hardly safe to assume that this process

1 Geology of the Little Belt Mountains, Montana: Twentieth Ann. Bept. U. S. Geol. Survey, 

Pt. Ill, 1900, pp. 421-122.
RANSOME.] THE GROUND WATER. 141

lias actually been effective. Both in this mine and in the Silver Lake 

mine it is stated by those-in charge that rich bunches of ore are commonly associated with secondary or "post-mineral" fissuring, which, 

if true, is significant of some secondary enrichment below the zone of 

oxidation.

THE GROUND WATER.

In many mhiing'regions the level at which the ground water stands, 

or, more accurately, the shape of its surface and the relation/ of the 

latter to the topography, is a matter of much importance, as by it are 

frequently determined questions of mine drainage and the depths at 

which oxidized ore changes to unoxidized ore. In the Silverton region, 

however, erosion has proceeded Avith such celerity relative to processes 

of oxidation and weathering that the change in question is largely 

independent of the depth of the ground water, arid the latter is

accordingly of less moment to the miner.

In most regions of considerable relief the upper surface of the 

ground water corresponds to a very subdued copy of the topographic 

relief. In the exceedingly rugged and much fissured Silverton area, 

however, the ground-water surface is very much less accentuated than 

the topography. Not only is the water tapped and drained away by 

the deeply cut ravines, but its level is often modified by the tunnels 

run into the mountains, sometimes several thousand feet below the 

crests of the ridges. Under these conditions it is often practically 

impossible to predict at what depth the ground-water surface will be 

encountered in mining operations.

Tunnels driven in from the floors of the high basin do not, as a rule, 

encounter permanent ground water. Those run below the basins, 

such as the Unity tunnel, or from the bottoms of the deeper ravines, 

such as the Highland Mary tunnel in Cimningham Gulch, the Bonanza 

tunnel near Animas Forks, the Old Lout tunnel in Poughkeepsie 

Gulch, the Revenue tunnel, the North Star tunnel on Sultan Mountain, 

and the Empire tunnel near Silverton, usually tap the ground water 

and artificially lower its surface within the overlying rock masses. 

In the shafts of the Red Mountain district permanent water is encountered at depths varying from 50 to 200 feet below the surface, dependent upon the location of the shaft and the seasonal fluctuations of the 

ground-water surface, which sometimes exceed 50 feet. In the Red 

Mountain district the ground-water surface is nearest the topographic 

surface in spring or early summer.

REPLACEMENT DEPOSITS.

Between certain replacement deposits and the metasomatic impregnations frequently accompanying fissure veins or ore stocks no sharp 

distinction can be made. Whether the deposit shall be classed as a 

vein or as a replacement deposit may depend simply upon the quantitative relation between the ore found within the walls of the fissure
142 ECONOMIC GEOLOGY OP SILVEKTON QUADKANGLE. [BULL. 182.

and that occurring in disseminated particles or in larger masses inthe metasomatic country rock. The Red Mountain stocks undoubtedty owe their form partly to metasomatic replacement, and might 

almost as well be described under this head. Ore-bearing fissures 

traversing rhyolite rocks are in this region frequently accompanied 

bj7 notable replacement of the wall rock by ore. But there are a few 

deposits where replacement is so conspicuous a feature and where so 

small a part of the ore occurs within distinct fissure Avails that but 

little doubt need arise as to their proper classification. They are, 

however, neither abundant nor relatively important in the Silverton 

quadrangle.

Direct replacement of limestone by ore occurs on the eastern side 

of Iron ton Park, where, for some distance, a'thick bed of white 

crystalline limestone, probably of Devonian age, is exposed beneath 

Tertiary volcanic rocks. At the Saratoga mine the ore, consisting in 

its unoxidized state of pyrite, chalcopyrite, and galena, with perhaps 

a little argentite, has replaced the upper portions of this limestone 

to a varying depth. The ore-bearing solutions have been chiefly 

active along the contact between the limestone and an overlying 

andesitic breccia or tuff belonging to the Silverton series. A little 

Telluride conglomerate, consisting largely of limestone pebbles, 

occurs near the adit of the mine, between the limestone and the overlying volcanic series. It has been silicified and probably partly 

replaced by ore, but was not recognized as present in 'the main workings. The ore is sometimes associated with rhodonite, which has 

also replaced the limestone and frequently incloses residual kernels 

of the latter. The ore was probably deposited by solutions rising 

through one or more northeast-southwest fissures, although no direct 

connection of the ore with any of the fissures could be made out. In 

the Baltic mine a similar but lower-grade ore occurs, also as a replacement of the upper portion of the same bed of limestone. This ore, 

however, is directly connected with an ore body filling a fault fissure 

(the Mono vein). In the Maud S. claim, which is part of the Baltic 

group, some argentiferous copper ore occurred in bunches in the same 

limestone alongside of a fault fissure. The direct connection between 

the replacement ore bodies of the Baltic group and a system of northeast-southwest fault fissures strongty suggests that a similar connection does or did formerly exist in the case of the Saratoga ore body.

In the southern portion of the quadrangle the Devonian limestone 

at the east base of Sultan Mountain carries disseminated particles of 

native silver on the Fairview claim, while in an unknown prospect 

near the King mine a body of chalcopyrite occurs partly in a fissure 

and partly as a replacement of the limestone near the fissure. The 

ore in this case makes largely at the underside of the limestone, where 

it rests upon quartzite.
RANSOME.] MISCELLANEOUS MINEEAL EESOUECES. 143

The facility with which the rhyolitic rocks of this region become 

to a greater or less extent metasomatically replaced by ore has 

already been noted. In most-cases such replacement is a minor 

accompaniment of the deposition of ore in fissures. But at the Silver 

Ledge mine replacement is the dominant mode of occurrence. The 

ore, consisting of galena and sphalerite, occurs metasomatically, 

replacing rhyolite in the vicinity of a zone of fracturing and faulting 

trending about N. 20° E. These fractures contain crushed country 

rock and ore, and there has evidently been movement along them 

since the ore was deposited. The principal ore bodies, however, are 

not found within the fissures, but as irregular replacements of the 

rhyolite which forms their walls. In spine instances bodies of ore have 

been followed into the country rock for 30 or 40 feet from the main 

fissures. The replacement is sometimes complete, resulting in solid 

masses of ore. More often it takes the form commonly described as 

impregnation; i. e., the ore is more or less thickly scattered through 

the rhyolite in specks and small bunches. In'this case there is no 

definite boundary to the ore body, and only so much of it is removed 

as can be profitably worked.

The deposition of the ore has been accompanied by metasomatic 

change and a complete reciystallization of the rhyolite. The resulting material, which forms the gangne of the ore, is a nearly white, 

minutely crystalline aggregate of sericite, kaolin, and quartz, with 

generally a little rutile and occasionally a small amount of calcite. 

The proportions of the three principal constituents vary, some facies 

of the rock consisting chiefly of sericite and kaolin, while others are 

largely sericite and quartz.

MISCELLANEOUS MINERAL RESOURCES.

Compared with the extraction of gold, silver, copper, and lead, all 

other mineral productions of the quadrangle are insignificant. At 

present no deposit is being worked for zinc, but sphalerite ores are 

abundant. As a rule, ore bodies showing much sphalerite with little 

galena have been little prospected, on account of the smelter penalty 

attaching to an excess of zinc in ores smelted for other metals. But 

with the increasing demand for'zinc ores it is not unlikely that some 

of the sphalerite lodes may ultimately be worked for this metal. 

This, however, may be some years hence, owing to the natural disadvantages under which mining is carried on in so elevated a region.

The occurrence of hubnerite on Cement Creek has aroused expectations of the profitable exploitation of the deposits. The mineral is 

easily concentrated from its gangue, but it is very doubtful whether 

it occurs in deposits of sufficient size or constancy to justify extensive 

operations.
144 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Bog iron ore occurs in the swampy ground along Mineral Creek and 

in Ironton Park as a deposit from iron-bearing springs. It was formerly used to some extent in Silverton as a flux for smelting, but 

has at present no market.

Limestone suitable for making lime occurs at .several points in the 

peripheral portions of the quadrangle, and has been burned for lime 

just below Silverton to supply local demand.

Building stone is not in much request. Good stone might undoubtedly be quarried from the monzonite of Sultan Mountain were there 

any demand for a building material involving so much labor in its 

production.
PART II, DETAILED DESCRIPTIONS OF SPECIAL AREAS AND INDIVIDUAL

INTRODUCTION.

The following descriptions are arranged in general conformity to 

a geographical plan. The mines in the Silver Lake Basin, in the 

southeastern part of the quadrangle, are first described. Proceeding 

northward, other groups are taken up, in the eastern and northeastern portions of the area. Then follow, successively, accounts of 

mines in the northern, northwestern, western, and southern districts, 

and, finally, descriptions of the Cement Creek ore deposits in the 

southwest-central part of the quadrangle.

LODES OF SILVER LAKE BASIN.

General features. The basin in which Silver Lake lies is a typical 

high cirque of a kind common in the San Juan Mountains. Its rocky, 

hummocky floor, with an altitude between 12,000 and 12,500 feet, is 

inclosed on three sides by cliffs and precipitous slopes culminating 

in Kendall and Little Giant peaks, which attain altitudes of over 

13,400 feet. The basin opens to the north-northwest, and its sloping 

floor is terminated, at an altitude of about 12,000 feet, by precipices 

which plunge down to the talus-covered bottom of Arrastra Gulch. 

Silver Lake, 1 a characteristic mountain tarn, occupies a depression of 

considerable depth, excavated by glacial erosion in the softer rock 

behind the sheet of massive andesite at the northern end of the lake, 

over which the present drainage escapes to Arrastra Gulch. The 

marks of glacial scoring are still plainly visible on this resistant sill, 

through which the clear water escaping from the post-Glacial lake has 

been unable to cut. The original beauty of this little sheet of water 

has been marred by mining operations, particularly by a partial filling with tailings from the Silver Lake mill. The basin is well above 

timber line, and the mine buildings are sometimes seriously damaged 

by snow slides. Mine timbers are packed in from Deer Park by 

burros, over the coi or saddle at the southern end of the basin. 

The main communication with the mines, however, is by the trail and 

the wire-rope tramways running up Arrastra Gulch.

The rocks in which the basin has been carved, and which form the

1 Formerly known as Arrastra Lake, and still so designated on the maps of the Generaljjand 

Office. This is also the name of the post-office at the Silver Lake mine.

Bull. 182 01 10 145
146 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

country rock of the mines to the depth now worked, belong to the 

Silverton series and illustrate its typical development. They are prevailingly breccias, in which the angular fragments and the interstitial 

matrix are composed of the same materials, with practically no admixture of foreign particles. The induration of these breccias has produced rocks which can with difficulty be distinguished from massive 

lavas. A careful inspection of weathered surfaces, or a microscopical 

examination, will, however, usually reveal their true clastic nature. 

The general character of these breccias is andesitic. But they differ 

from normal andesite, such as occurs in the San Juan formation, by 

the presence of occasional porphyritic crystals or phenocrysts of 

orthoclase and quartz, and in the occurrence of orthoclase in the 

groundmass. The abundance of the phenocrysts of orthoclase feldspar 

and quartz varies in different varieties or facies of the breccia. As a 

whole these.rocks appear to be most closely related to the latitic group 

of intermediate rocks. Associated with the breccia are massive rocks 

of the same general type as the breccias, which have been intruded 

as sheets and dikes, and possibly in part as contemporaneous lava 

flows. As examples of these may be cited the masses forming the 

summit of Bound Mountain and the hard sill that holds up the waters 

of the lake at its northern end. The latter, a dark-gray rock of splintery fracture, shows abundant fresh-looking phenocrysts up to about 

a centimeter in length, and smaller crystals of hornblende, lying in a 

compact groundmass. A thin section shows, under the microscope, 

phenocrysts of labradorite feldspar, brown hornblende, and palegreenish augite, in a feldspathic groundmass. The augite is partly 

decomposed to calcite and chlorite, and certain areas of chlorite appear 

to represent former phenocrysts of biotite. The groundmass, while 

somewhat obscured by calcite, chlorite, and other products of alteration, appears to consist chiefly of plagioclase, orthoclase, and glass. 

The accessory minerals are magnetite and apatite. The rock from 

the summit of»Round Mountain is very similar, but the presence of 

orthoclase in the groundmass is more clearly shown and the augite is 

fresher and more abundant.

The lodes of Silver Lake Basin are large and prominent, and on 

this account were discovered and located at an early stage of the 

mining development of the region. But it was not until the erection 

of the Silver Lake mill, about 1890, that they were worked on the 

scale necessary for the profitable and permanent extraction of lowgrade ore. They are nearly all fissure veins of comparatively simple 

form, and have clearly denned walls. The wall rock has been chemically altered by the solutions traversing the fissures and, to a slight 

degree, impregnated with ore minerals, but it is not regarded as ore 

and is always readily distinguished from the vein filling.

The lodes wholly or partly within the basin may be divided into two 

groups. The first group comprises at least two very strong and per-
U. S. GEOLOGICAL SUKVEY BUIiLETTN" W0.182 PL. XTH

PLAT

Of THE

PRINCIPAL MINING CLAIMS 

or

SILVER LAKE BASItfAND YTCDsTlTY 

COLORADO

CompilccUi'Oin General T^ond Office Surveys 

., Scale

 fr______-Mi;______(f

NAM ES O F 

MINING C LA IMS

2. KING SOLOMON

3 JURA

4 NIGHT BIRO

6 HIGHLAND CH1E

7 IONS TOM

8 BLACK CROOK

93 UNITY 

95 EL PASO

M GRETCHEN

IUMBER 3 

HGHLAND MARY

56 ROYAL TIGER

57 HOMESTAKE

1« LOOKOUT

16 MOUNTAINEER

16 SHENANDOAH

17 BIG PINE

18 QUEEN

19 SHENANDOAH

21 DIVES

22 CREMORNE

60 DIAMOND L

61 DUMP

62 GRIP

63 BLACK DIAMOND

64 J. W. COLLINS

65 IOWA

66 STAG

67 CABO

68 DANON

69 AMERICAN BOY

LUCY

03 ORIENTAL

04 TOM PAINE

05 TOLEDO

06 GREY EAGLE

07 EZRA R

08 MOTH

10 PROSPECTOR

11 ASPEN

12 SUSQUEHANNA

13 MAC GRECOR

14 LEGAL TENDEf

15 SILVER STAR

24 NORTH STAR

25 NORTH STAR EXTE

26 POTOMAC

27 TERRIBLE

28 SLIDE

29 MAYFLOWER

30 ARGENTINE

ISION 71 BUCKEYE NO. 2

72 BUCKEYE

73 PROFESSOR ZEUNER

FREE COI 

LAST CHA

75 LAST CHANCE

76 CAIRO

32 MOUNTAIN QUAIL

33 BIG GIANT

34 BLACK PRINCE

35 ESMERELDA

36 SILVER CROWN

37 JESS

38 EMMA S

39 PEERLESS

40 GOLDEN FLEECE

41 LITTLE GIANT

42 IRON MASK

43 LITTLE SHAVER

44 CROSS CUT

78 ALGIERS

79 SMYRNA

81 ROCHESTER

82 LENA ALLEN

83 ROUND MOUNTAII

84 NEW YORK CITY

85 ROYAL

86 RIVINGTON ST.

87 ESSEX ST.

I GALENA

I LAST CHANCE

3 IDAHO NO.

4 BOWERY

5 SAL CUSTER

26 POMPEII

27 PYRAMID

3 TITUSVILL 

SOLSTICE 

5 PANOCO
RANSOMB.] LODES OF SILVER LAKE BASIN. 147

sistent lodes, which may be referred to as the Silver Lake and Titusville lodes. The general,course of the fissures of this group is nearly 

northwest and southeast. The second group embraces a number of 

shorter lodes, having a general average course about.N. 25° W., and 

lying between the two chief lodes of the first group. The members of 

the second group are locally spoken of as " north-and-south veins" 

an obviously inaccurate expression.

The general dip of all the productive lodes in the basin is northeasterly, although some of them are nearly vertical and often dip locally 

to the southwest. Those of the first group frequently have a much 

natter dip than those of the second group, and the ore is generally of 

lower grade and more irregular in its occurrence. Large bunches of 

ore are separated by relatively barren portions of the lode. As a rule 

the product is a lead-silver ore, consisting chiefly of galena accompanied by sphalerite, chalcopyrite, pyrite, and sometimes tetrahedrite. 

In some cases the silver may be so low as to be subordinate in importance to the lead. The lodes of the second group have a much steeper 

dip, the ayerage being probably near 80°. Their ore bodies are usually more regular and of higher grade. Galena is still the most prominent ore mineral, but chalcopyrite and pyrite are generally more 

abundant, and the ore may carry several ounces of gold per ton. 

These lodes have been best explored toward the north, where some of 

them form junctions with the Silver Lake lode. Several of them 

pinch and die out in a few small, irregular stringers before reaching 

this fissure. Others, such as the New York City and Royal veins, 

reach and connect with the master lode. The general relations of the 

lodes of the two groups can perhaps be best understood from fig. 2, 

page 51, which is a generalized and diagrammatic sketch of the plan 

of the principal fissures exploited in the Silver Lake and Iowa mines, 

on the west side of Silver Lake. The Silver Lake lode is fully as long 

again as shown. It has been exploited on the northwest through the 

old Nevada mine and is known to extend into the head of Blair Gulch. 

Toward the southeast it passes under the lake and is probably continuous with the lode of the Royal Tiger mine. Just before crossing the southeast rim of the basin, the Tiger lode divides into two 

branches, neither of which has been traced far beyond the point of 

divergence. A plat of the principal claims of Silver Lake Basin and 

vicinity is shown in PI. XIII.

As the lodes of the second group approach the junction with the 

Silver Lake vein they become poor. Their courses are also deflected 

toward the west, as indicated in the sketch. The country rock in the 

V near the junction is usually shattered and traversed by numerous 

quartz stringers. Some of these are irregular, but there is often 

noticeable a radiation of the stringers outward from the angle of junction. In some instances a breccia has resulted, the fragments being 

cemented by quartz and themselves altered into aggregates of quartz,
148 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

sericite, and other secondary products by the action of the vein solutions. A close study of all exposures of such conjugations of the 

veins of the two groups failed to show any evidence of different age. 

The filling of both sets of veins is continuous, as it would be in synchronously filled branches of a single fissure, or is separated by a 

clay gouge due to subsequent movement. As far as is known, there 

is no continuation of the lodes of the second group north of the Silver 

Lake lode. A single small vein (the Jim Owen), shown in fig. 2, 

has been, prospected for a short distance northward from the Silver 

Lake lode, but it is very improbable that this represents the continuation of any of the productive lodes south of the latter. If the Silver 

Lake lode were, as is supposed by the miners,,younger than the lodes 

of the second group, the absence of the latter on the northern side of 

the intersecting lode could be accounted for only on the assumption 

that the Silver Lake fissure is a fault of at least 2,500 feet throw. 

The entire evidence of the region, however, as is elsewhere shown, 

indicates that the fissures now occupied by productive ore bodies 

were not formed by large faults, but on the contrary often reveal no 

appreciable displacement of their walls.

The relation of the lodes of the second group to the great Titusville 

lode on the south are not so well known as in the case of the Silver 

Lake lode on the north. The lodes in this portion of the basin are 

imperfectly exposed and have received very little underground 

exploration.

The ore bodies of the lodes of Group II have not been worked in 

such a manner as to give any very definite data as to their dimensions 

and shapes. ' In nearly every slope considerable masses remain which 

are regarded as pay ore. The pay shoots are supposed to pitch northward, but it is by no means certain that there is any regularity in 

their pitch.

In addition to the main lodes a great number of smaller fissures

traverse the country rock, particularly west of the lake. The strike 

of these minor veins ranges from 20° to 40° west of north. They are 

nearly vertical, but one group of them sometimes exhibits a steep 

northeasterly dip, while another group dips southwesterly. The latter 

case appears to be more common. They are often so closely spaced, 

a few-feet apart, as to produce a conspicuous sheeting of the country 

rock. This spacing does not exhibit any regularity or recognizable 

rhythm in its occurrence. Many of these fissures are ore bearing, 

and it is not uncommon to see on a clean exposure of rock a stringer, 

an inch or so wide, consisting of quartz next the walls and solid galena 

in the medial portion. Such mineralized stringers can be seen to 

branch or to wedge out completely in the rock and be succeeded by 

an overlapping stringer a short distance to one side. On a small 

scale they repeat the phenomena to be observed underground in the 

larger veins of the second group. They are believed to belong to the 

same system and to have been formed at the same time as the latter.
RANSOME.] SILVEE LAKE MINE. 149

Although the lodes of the Silver Lake Basin have been classified in 

two groups, it should be borne in mind that the distinctions upon 

Avhich the grouping is based are quantitative rather than qualitative. 

The difference in direction, sufficiently marked and definite on the 

west side of the lake, becomes less so on the east side, where the Silver 

Lake lode appears to begin splitting up into its ultimate ramifications. 

Moreover, as will appear when the separate mines are described, the 

general difference in the ores of the two groups is a difference in value 

rather than in mineralogical type, and is neither constant nor without 

exceptions.

It is fairly certain that the original formation of the fissures of Silver Lake Basin was unaccompanied by any considerable faulting. A 

careful study of all the available underground workings and of the 

surface geology and topography of the basin has failed to reveal the 

existence of any extensive tangential movement (faulting) along the 

vein fissures. Moreover, if the mutual relationship of the lodes has 

been correctly interpreted, it would seem that the conception, very commonly held, that vein-filled fissures are produced essentially by faulting involving considerable tangential movement, and usually by thrust 

faults, is inapplicable as an explanation in the present case. The 

more general aspects of this subject are discussed under the head of 

"The lode fissures," on pages 43-63.

Silver Lake mine. This, the most extensively developed mine 

within the quadrangle, is situated at an altitude of about 12,300 feet, 

with its principal adit near the western edge of Silver Lake. As is 

frequently the case, it includes a number of individual claims, some 

of which, such as the Whale, were separately worked in former days 

and produced considerable ore. Prior to 1881, the Whale, Silver Lake, 

Round Mountain, and other claims now embraced in the Silver Lake 

mine had attracted but slight attention. In 1882 a little ore was produced, which is said to have carried 50 ounces of silver and 60 per 

cent of lead. In 1883, 72 tons of ore, containing 28 ounces of silver per 

ton and 55 per cent of lead, were shipped to Sweet's Sampling Works in 

Silverton, and the Silver Lake claim, with its 55 feet of drifting, was 

regarded as a promising prospect. Since then its development has 

progressed with rapid strides. In 1891 the mine was credited in the 

Mint reports with a product of $254,908.

At least six distinct lodes have been worked, and the vertical distance from the uppermost to the lowermost stopes is somewhat over 

1,000 feet. The main adit is a crosscut for about 250 feet. It then 

follows the Silver Lake lode northwesterly for about 1,000 feet. 

Thence a crosscut to the southwest, some 900 feet in length, gives 

.access to the various lodes of the second group, viz, the L. A. S., 

E. G. S., Royal, Stelzner, and New York City lodes. A northwesterly 

drift along the New York City lode for about 1,250 feet again comes 

into the Silver Lake lode, and from this junction a drift of about 400 

feet runs out to the surface in Whale Basin, on the west side of
150 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Round Mountain. In addition, the U"ntty tunnel, run in from the 

southwest side of Arrastra Gulch, cuts the Silver Lake and New York 

City lodes 700 feet below the present main adit level (No. 1). Still a 

third tunnel is being run in a southeasterly direction from a point 

near the Animas River, at the mouth of Blair Gulch, which will, if 

carried through, ultimately tap the Silver Lake lodes at the lowest 

practicable point, over 2,500 feet below the No. 1 level.

There are no abandoned workings, and the character and relationships of the lodes may be studied under more than usually advantageous circumstances.

The Silver Lake lode as exposed in the mine has a general strike 

of N. 53° W. Its dip is to the northeast and varies from 50° to 70° 

the natter dip being more common in the upper workings. The average dip is probably a little over 60°. Its croppings are conspicuous 

as a rust-colored zone of oxidation running up the declivity west of 

the lake and passing through the col just south of Round Mountain. 

At this point they have an apparent width of about 40 feet of stained 

and cellular quartz carrying galena, as well as the carbonate and 

sulphate of lead. Northwestward from this saddle the lode, different 

portions of which are known as the Round Mountain, Lowville, and 

Nevada lodes, crosses Whale Basin just above the cliffs of Arrastra 

Gulch, and passes through another saddle into the head of Blair 

Gulch. In its productive portions the Silver Lake lode is from 6 to 20 

feet in width. Elsewhere it may be represented by a strong clay 

seam or gouge, or less commonly a small tight vein. The filling of 

the fissure is quartz, carrying variable amounts of galena, sphalerite, 

chalcopyrite, and pyrite. No regular arrangement of the ore minerals 

within the quartz could be detected. They occur in irregular bunches 

in all portions of the vein, and appear to be the result of a single 

uninterrupted process of deposition. The ore bodies, also, although

often of considerable size, are without any known regularity in their 

distribution through the lode. The best ore is usually found in the 

more solid portions of the lode, a soft lode with abundant gouge being 

regarded as less favorable. The ore is nearly always separated from 

the walls by more or less gouge. A sheeting of the walls parallel 

with the main fissure is not infrequent, and where it occurs careful 

prospecting is necessary to avoid overlooking considerable masses of 

ore which may be lying behind what appears at the time to be the 

outer wall of the lode. On levels 1 and A the most productive portion of the Silver Lake lode is1 divided into two branches by a large 

horse of country rock traversed by stringers of quartz.

In the levels above No. 1, particularly in level 4, the Silver Lake 

vein is frequently a soft yellowish mass of more or less broken quartz, 

decomposed country rock, clay, cerussite, and other products of alteration. This portion of the lode thus shows considerable oxidation, 

particularly where there is evidence, in the form of clay seams and 

crushing of the quartz, of movement since the deposition of the ore.
RANSOME,] SILVER LAKE MINE. 151

Anglesite and cerussite were found associated with the 'galena in 

these upper levels, but never formed a very large proportion of the 

ore, of which the important bodies, even in these upper workings, 

were chiefly galena.

Movements within the Silver Lake lode subsequent to the deposition of the ore may be conveniently divided into four classes, (1) 

faults cutting the lode obliquely and 'at a considerable angle with the 

horizontal; (2) strike faults essentially parallel with the lode; (3) 

strike faults making a considerable angle with the plane of the lode, 

and (4) irregular fracturing. Those of class 1 will first be described.

(1) A close inspection of the southwest or foot wall of the Silver Lake 

vei-n shows that it is cut at frequent although irregular intervals by fissures, usually of small width. It is seldom possible in such cases to 

determine accurately the general course of these fissures. Fissures are 

never geometrical planes, and an observation made on a fissure exposed 

in the walls of a drift may give figures differing very much from the 

general or average course of the dislocation. The observed courses of 

these fissures give directions varying from north and south to 1ST. 55° W. 

In general, they appear to form a system essentially parallel with the 

productive lodes of Group II, such as the New York City and Royal. 

Their dip is usually to the southwest at a high angle (over 70°), but 

there are a few notable exceptions. The fissures vary from narrow 

cracks up to openings a foot wide. Jn a few cases they are filled with 

solid quartz, carrying a little ore. These last are not known to cut 

the Silver Lake lode. They are probably of the same age as the bitter and are comparable, in all respects save size, with such A~eins as 

the E. G. S. and L. A. S. of Group II. Most of these fissures, however, are filled with a clay seam or gouge of varying thickness, sometimes containing broken vein quartz. These fissures cut through the 

Silver Lake lode and are therefore younger. They record disturbance 

subsequent to it s formation. They have not influenced the product! veness of the latter to any known extent, but are well knoAvn and carefully watched by the miners on account of their misleading tendency. 

Experience has shown that a miner, on running upon one of these cross 

seams, is very likely to follow it into the hanging wall, leaving, 

unknowingly, the main lode on his left. The presence of broken 

quartz mixed with the gouge of these seams shows that in some cases 

they record fresh movement along preexisting fissures which had 

become filled with quartz. The actual result of movement along these 

post-mineral fractures is present as gouge, but the net displacement 

seems to have been always small. It is usually impossible to detect any 

actual faulting of the main lode where crossed by these later fissures.

On Level A, southeast drift, a set of fissures occurs which, while 

apparent^ belonging to this system, are of unusually flat dip, in one 

case as low as 20°. The direction of dip is easterly. The vein itself 

is very irregular southeast of the first of these faults and is chiefly a 

breccia of country rock cemented by quartz and low-grade ore. It is
152 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

such an irregularity as might be expected near the lower edge of the 

large horse which divides the lode on this level and the one above.

(2) Strike faults, essentially parallel witli the -lode, are more conspicuous in the case of the Silver Lake than in the other lodes of the 

mine. They are indicated by gouges, often of considerable thickness, 

on foot or hanging-wall, and by sheeting of the country rock when 

accompanied by soft gouge. Their effect upon the lode is well seen 

near the northwest end of level 2, where there is a pronounced strike 

fault on the hanging-wall side of the vein associated with approximately parallel slips within the country rock of the hanging wall. 

The lode here is crushed and contains much clayey gouge. The character and amount of the movement could not be determined in any 

case. It is believed, however, to have been in the main oscillatory, 

with but little net displacement. Had it been otherwise it would be 

very difficult to account for the present relation of the Silver Lake

? Faufr,

Fro. 11. Sketch section across the Silver Lake lode between levels 1 and 2, showing probable 

faulting of the lode by a flat strike fault.

lode to the lodes of Group II and for the absence of gouge or other evidence of recent movement in certain portions of the former lode.

(3) Strike faults making a considerable angle with the plane of the 

lode are not common on the Silver Lake lode. The best example of 

this form of dislocation was noted in a large stope between levels 1 

and 2. The fault here is nearly horizontal and cuts both branches of 

the Silver Lake lode near the apex of the horse which divides them. 

The dislocation is a thrust fault with about 12 feet throw. The 

character of the fault and its result upon the ore body are shown by the 

accompanying sketch section across the stope (fig. 11). This fault 

appears to die out within a comparatively short distance to the southwest, as it was not noted on the stopes of the Royal and Stelzner lodes.

(4) Irregular fracturing of the lode includes those minor dislocations which it has not been found possible to group according to any 

prevailing regularity of direction. They are often directly connected 

with the more regular fissures and are of small importance.
KANSOME.] SILVEB LAKE MINE. 153

The ore of the Silver Lake lode is low grade, canning very little 

gold. Although it has been extensively stoped in the past, the main 

output of the mine is from the lodes of the second group.

The New York City vein (or Whale-Rochester vein) is the most 

important of these, from the extent, regularity, and comparatively 

high grade of its ore body. Its general strike is about N. 20° W., 

and its average dip is about 80° to the northeast. As to the WhaleRochester vein, its upper portions were formerly extensively worked 

through an adit in Whale Basin. In the Silver Lake mine it has been 

worked through levels 1 and C, 300 feet apart, and by means of an 

intermediate level halfway between them. This lode is generally 

smaller than the Silver Lake, and has been less disturbed by postmineral movement. The ore is generally fast, or frozen, to the walls, 

and is usually solid and unoxidized. In common with the other lodes 

Of Group II the New York sometimes pinches to a very narrow and 

tight seam. This is well illustrated at the 'point where it is intersected by the crosscut on level 0. It is here a. stringer less than 

an inch in width, showing little indication of being part of a great 

productive vein. The chief value of the New York City vein has 

been found to lie northwest of the points where it is pierced by the 

crosscuts on levels 1 and C. In this direction it is stoped practically continuously up to the Silver Lake lode. A typical section of 

the lode from the stope above level 1 is shown in fig. 3, page 67. As 

it approaches the Silver Lake lode it becomes smaller and more irregular, and bends westward. It is also somewhat oxidized and stained. 

At the junction it passes into the Silver Lake with no other lines of 

separation than those due to later movement, and is usually denned 

by seams of gouge. From the point of junction westward the ore of 

the Silver Lake vein contains more chalcopyrite than is usual elsewhere, and thus resembles somewhat the ore of the New York City 

vein. The productive portion of the New York City vein is cut by a 

fault about 750 feet south of its junction with the Silver Lake vein. 

The strike of this fault is apparently about N. 73° E., and it hades 

northerly about 15°. It has thrown the northern portion of the lode 

from 12 to 15 feet to the west. This fault was best seen in the stope 

above the midway level. Here the vein is cut off abruptly by a 

breccia zone about 6 feet wide which crosses the stope. The breccia 

is composed of sharply angular fragments of country rock cemented 

by quartz, which carries a little ore, but is of too low grade to pay. 

Within the breccia zone are two or three fairly regular quartz stringers. This occurrence is of special interest as showing that the deposition of quartz and ore was not confined to the period within which 

the important lodes were filled, but also took place at a later time. 

On the other hand, it seems very probable that this fault is older 

than the faults usually filled with soft, moist gouge, which have been 

described in connection with the Silver Lake vein. South of the
154 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

"crosscuts the New York City lode has proved of little value. This 

portion of it has obviously been subjected to strong disturbance connected with a pronounced zone of post-mineral faulting. This fault 

appears to have a general north-and-south strike, and hades to the 

east about 20°. Where it is cut by the crosscut on level 1, about 

140 feet east of the New York vein, it shows a zone of broken and 

disturbed country rock about 12 feet wide, with a strong gouge on 

the hanging wall. This zone of disturbance appears to intersect the 

New Yor'k City lode about 200 feet south of the crosscut. The lode 

and the adjacent country rock have been broken up, and the value 

of the former has been destroyed. The country rock is traversed by 

seams of soft, moist gouge, in general parallel with the line of the 

fault, but often showing considerable irregularity. Small bunches 

and stringers of ore are found, but they are not continuous. On 

level C what is supposed to be the same fault crosses the crosscut 

about 330 feet east of the New York lode. It is here less than 6 feet 

wide, and is composed of broken, decomposed country rock and wet 

clay gouge. As on level 1, the New York lode has so far proved 

worthless south of the crosscut. The New York lode, probably 

originally somewhat irregular south of the crosscut, has been dislocated by a fault cutting it at a small angle and thus producing 

somewhat the effect of a strike fault parallel with the vein. The 

direction and amount of movement along this fault are not known. 

Some light may be thrown on it when the Silver Lake lode, which it 

should cut, is more thoroughly opened up. If any undisturbed ore 

bodies exist in the southern part of the New York lode they probably 

lie east of the present south drift on level 1.

In the autumn of 1899 the crosscut driven to cut the New York lode 

from the Unity tunnel, 400 feet below level C, had overshot its objective, and upon searching back the New York was found at the beginning of the crosscut near the Silver Lake lode. This was opened by 

a shorj drift and found to carry a body of excellent ore similar to 

that of the upper levels.

The ore of the New York Cit}7 lode consists of galena, sphalerite, 

chalcopyrite, and pyrite in a quartz gangne. Some of the richest ore 

occurs in a rather friable stringer near the foot wall, which contains 

black oxide of copper (melaconite), with considerable chalcopyrite and 

pyrite. This may carr}* several ounces in gold, although free gold is 

very rarely seen. It is worth noting that the melaconite is^found in 

the deepest workings, level C, at least 700 feet below the surface.

The Stelzuer and Royal veins resemble in their general characters 

the New York City. The course of the Stelzner is rather curving and 

irregular, but may be generalized as about N. 20° W. That of the 

Royal is about N. 35° W. It thus nearly bisects the angle between 

the Stelzner and Silver Lake and illustrates the essentially radial 

character of the whole group of lodes. This feature is still further
HANSOME.] . SILVER LAKE MINE. 155

brought out by the fact that the Stelzner and the Royal with its two 

branches, called the right-hand and left-hand Royals, are, in the lower 

levels, all ramifications of a single vein, which in turn is a branch of 

the Silver Lake lode. Both the Royal and the Stelzner veins dip to 

the northeast. The Royal is very nearly vertical, while the Stelzuer 

has an average dip of 75° to 80°. Consequently the line in which the 

two lodes join pitches southeastward. On the other hand, the much 

flatter dip of the Silver Lake lode causes the lines of junction between 

it and the veins of Group II to pitch to the northwest. As a result of 

these conditions the Stelzner and Royal join'the Silver Lake on level 4 

as separate veins. On level 3 the Stelzner, Royal, and Silver Lake 

lodes all come together at about the same point. On level 1, however, 

the two veins unite about.200 feet before they join the Silver Lake lode 

as a single vein. The junction of the Royal-Stelzner vein with the 

Silver Lake is similar to that described in the case of the New York 

lode. On level 2, at the point where the two veins come together, no 

clay seam could be seen separating them, although a little farther 

northwest the Silver Lake lode shows well-marked seams of soft, wet 

gouge on foot and hanging walls. At the junction there is much 

brecciated country rock, cemented by quartz which is full of small 

vugs. '

On level B, north drift, the combined Royal-Stelzher vein has been 

stoped for about 400 feet, to a point where the lode diminishes to a small 

stringer. A short crosscut to the west, however, discovered the continuation of the lode. There is apparently no fault at this point. 

The lode has merely pinched out and is succeeded by a slightly overlapping parallel fissure in the manner already described.

The productive portions of the Stelzner vein are sometimes 10 or 12 

feet in width. The Royal is usually somewhat narrower. The ore in 

both veins is usually solid and not accompanied by any considerable 

gouge. Post-mineral movement along the fissures is not, however, 

wholly lacking, and is best seen where the veins pinch to very narrow 

dimensions. As usual, in this mine the country rock near the veins 

has not undergone any alteration which can be recognized by the eye 

as evident and characteristic. The ore of the Stelzner and Royal 

veins consists of abundant-galena, with sphalerite, chalcopyrite, and 

P37 rite in a gaugue of quartz. A little dolomite occurs in the vein, 

usually associated with included fragments of country rock. The 

quartz also shows greenish patches of chlorite, which are regarded as 

an indication of good ore. Chalcopyrite is less abundant than in the 

New York vein. The ore may carry 2 or 3 ounces of gold and is of 

higher grade than that of the Silver Lake lode, although somewhat 

inferior as a whole to the ore of the New York vein.

The E. G. S. is a small vein approximately parallel with the Royal 

and lying about 60 feet to the northeast of it. In its general character it resembles the Stelzuer and Royal, but is smaller. Its junction
156 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

with the Silver Lake can be seen on level 2. At the junction the 

quartz of the two lodes is separated by a narrow seam of gouge. 

Together they constitute a solid vein of low-grade ore about 10 feet 

wide. The E. G. S. has contained some of the richest pockets of ore 

encountered in the mine, but its value falls off, like the other veins of 

Group II, as it approaches the Silver Lake. The L. A. S. is another similar small vein, which was not worth working until level B was reached. 

It illustrates the fact, thus far exemplified in this mine, that the small 

veins of Group II may prove more valuable and have longer ore 

bodies as they are worked downward and as their junctions with the 

Silver Lake are carried farther and farther to the northeast on account 

of the relatively flat dip of the latter lode.

The Silver Lake mine is worked by overhand stoping, the ore being 

broken down onto canvas, and the stopes are filled with waste as the 

work is carried up. Siemens and Halske electric drills are used in most 

of the stopes. They are portable and convenient, but somewhat too 

lightly constructed for the work required of them. The ore from the 

various levels is all dumped into bins at the central station on level 1, 

that from the lower levels being raised through a vertical shaft by a 

.cage and an electric hoist. From the central station the ore is drawn 

out in trains of cars by mules to the mill at the mouth of the adit.

At the mill it is sorted, the larger and heavier pieces of nearly solid 

ore being sent down the tramway as crude, or shipping, ore. The 

equipment of the mill is 2 Blake crushers, 50 stamps, 4 sets of rolls, 10 

Wilfley tables, 8 Hartz jigs, 8 Woodbury tables, and 18 "end-shake" 

slime tables. Power is furnished by three 100-horsepower boilers and 

a, 150-horsepower engine, and the mill has a daily capacity of about 

200 tons. The water for milling is pumped from the lake, into which 

the tailings are allowed to run at another point. A new mill is now 

in progress of erection on the Animas River, at the lower terminal of 

the tramway.

As already stated, the ore of the mine is low grade. Ore running 

$10 a ton can be worked, but even $8 ore is often run through the 

mill with the better grades. About half the total value of the output 

is in gold, the rest being in silver, lead, and copper. Free gold is 

very rarely seen, and no attempt is made at amalgamation. The concentrates are said to average about 145 per ton. The crude ore and 

concentrates are carried down from the mill on a substantially 

constructed Bleichert tramway to a large terminal station near the 

mouth of Arrastra Gulch, furnished with capacious bins. From 

these bins the ore is loaded directly onto the railroad cars. A second 

tramway from the Unity tunnel was completed in October, 1900, and 

will soon handle the bulk of the ore.

Power for hoisting, pumping, and lighting the mine and buildings 

is generated by dynamos run by two Pelton water-wheels located on 

the Animas opposite the mouth of Boulder Gulch, the water for this
RANSOM E.] IOWA MINE. 157

purpose being taken from the Animas River just below Howardsville. 

In 1900 a substantial plant was also being installed at the same place 

for generating power by steam.

loiua mine. The Iowa mine also lies on the west side of Silver 

Lake and joins the Silver Lake property on the south. A prospect 

in 1881, its growth has, in a general way, followed that of its larger 

neighbor. The principal development has been on the Iowa, East 

Iowa, Stelzner, and Melville lodes. The last is probably continuous 

Avith the Black Diamond-Royal lode, but has not proved profitable in 

the Iowa mine, as it has in the Silver Lake ground. Practically all of 

the stoping has been on the Iowa, East Iowa, and Stelzner lodes. The 

relation of these three lodes, as shown in fig. 2 (p. 51), illustrates admirably the arrangement of veins en echelon, as observed in the small 

ore-bearing stringers on the surface. The Stelzner lode becomes 

small and poor at its southern end and is succeeded on the west by 

the Overlapping East Iowa lode, which in turn is similarly succeeded 

by the Iowa lode. The Iowa and East Iowa lodes can be seen to die 

out in a few small stringers toward the north. That they actually 

terminate as individual lodes and do not open out again still farther 

northwest is shown by the fact that no lodes corresponding to them 

have been found in the two long crosscuts to the New York vein in 

the Silver Lake mine. Similarly, any southeasterly extension of the 

Stelzner and East Iowa should have been noted in the crosscuts of 

the Iowa workings. A lode, plan such as is here described is not 

consistent with any extensive faulting along the lines of the fissures.

The Iowa has been worked on four levels, connecting with the surface by adit tunnels. They are numbered from above clown. Work 

at present is confined to levels 3 and 4. The distance between levels 

is not uniform. Thus from level 1 to level 2.is 100 feet; from level 2 

to level 3, 200 feet; and from level 3 to level 4, 130 feet.

The best ore in the mine occurs in the Stelzner vein and is identical 

with that already described in the Silver Lake workings. It may 

carry 2 or 3 ounces of gold. The ore of the loAva and East Iowa lodes 

is a heavy lead ore carrying little gold, and resembling the ore of the 

Silver Lake lode more than is usual in the veins of the second group.

The main Iowa vein varies in width in its productive portions up 

to 15 feet. It is commonly between 2 and 5 feet wide. It dips steeply 

to the northeast, the average angle being near 80°. It is a generally 

simple and regular fissure vein, with well-defined walls. At its best 

it consists of nearly solid galena, with some quartz, chalcopyrite, 

sphalerite, pyrite, and chlorite. Comb structure is occasionally 

shoAvn in the quartzose portions of the vein, and irregular vugs occur 

lined Avith crystals of quartz and galena. The galena sometimes 

occurs chiefly in the middle portion of the A^ein, as if it Avere of later 

crystallization than the quartz. In many cases, hoAvever, it is scattered through the vein in bunches Avithout any apparent regularity.
158 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. LBULL.IS?.

The vein filling is solid and shows very little trace of movement subsequent to the deposition of the ore. It generally lies close against 

the walls of the fissure, with little or no gouge. As in the Silver Lake 

mine, the wall rock does not, as a rule, exhibit any very marked alteration close to the vein. The microscope shows, however, in the rock 

alongside the vein a thorough recrystallization of the original rock 

constituents into aggregates of quartz and sericite, with some calcite 

and specks of pyrite. A specimen 10 inches from the vein shows 

similar alterations, but with more calcite and abundant chlorite. The 

same general character of alteration is found 2 feet from the vein. At 

50 feet from the vein quartz, chlorite, and calcite make up most of 

the rock, in which traces of the original structure remain, and the 

sericite is confined chiefly to the altered feldspar phenocrysts.

The Stelzner lode presents the same characteristics in the Iowa mine 

as in the Silver Lake. It is a nearly solid, simple vein, showing as 

much as 8 feet of excellent ore in the stopes. There is usually no 

gouge between the vein filling and the walls.

The East Iowa vein has not proved of very great importance. It 

has been stoped for a distance of over 100 feet, but presents no features 

of special interest.

The Melville lode is chiefly notable from the fact that in its southern portion it dips to the southwest at from 70° to 75°. It carries 

galena, sphalerite, chalcopyrite, and pyrite in a gangue of quartz, 

with a little barite. It varies in width, being in some places as much 

as 4 feet wide. The ore is too poor to work. Northward this vein 

becomes irregular and in places is a nearly vertical fissure containing 

some gouge, but no quartz. It finally dies out in a few barren stringers. Although in general line with the Black Diamond-Royal lode, it 

is by no means certain that it occupies the same fissure. The low 

grade of its ore and its westerly dip, contrasted with the good ore and 

steep easterly dip of the Royal, seem rather to indicate that it is an

overlapping fissure, bearing a similar relation to the Royal that the 

East Iowa does to the Stelzner.

Regular parallel fissuring of the country rock, the fissures being 

usually filled bjr stringers of quartz and ore, is even more conspicuous 

in the Iowa than in the Silver Lake mine. As in the latter mine, 

these fissures are apparently minor results of the same forces that 

produced the productive veins of Group II, seeming, in fact, to belong 

to that group., In the Iowa these fissures usually dip very steeply to 

the southwest.

Generally the lodes in the Iowa are very regular in their productive 

portions, having comparatively few horses. The ore is confined 

within the fissure walls. The disturbance and movement which has 

taken place since the veins were formed is scarcely appreciable. 

Tetrahedrite is reported as occurring in the Iowa workings, but none 

was seen at the time of visit.
HANSOMB.] EOYAL TIGEE MINE. 159

The Iowa ore is carried on a Bleichert tramway, built in 1897, doAvn 

to a mill situated in Arrastra Gulch, about a mile from its mouth. In 

1899 an additional tramway was built from the mill to the railroad, 

on the Animas River. As a whole the ore is of low grade, averaging 

from $10 to $14 a ton, and carrying a large proportion of lead. The 

mill is equipped with 1 9 by 15 Blake crusher, 2 sets 14 by 27 rolls, 7 

3-compartment jigs, 2 5-foot Huntingtons, 1 5-foot Chilian mill, and 

5'Wilfley and 8 Cammett tables. The power is steam, and the daily 

capacity of the mill is given as from 175 to 200 tons of crude ore.

Royal Tiger mine. This property, which is in the early stages of 

development, is on the east side of Silver Lake, and is supposed to be 

on the continuation of the Silver Lake lode. This, indeed, seems 

probable, although it is by no means certain, as there are too many 

nearly parallel veins in this vicinity to permit offhand correlation 

across the width of the lake. The Tiger lode, moreover, presents 

several characters foreign to the Silver Lake lode as exploited on. the 

west side of the lake, and may fill an overlapping fissure nearly in line 

with the latter. The main adit is a crosscut at an elevation of 135 

feet above the lake, and the levels are numbered from this upward. 

A little stoping has been done on level 4, but the bulk of the work 

has been on levels 2 and 3.

The lode dips steeply northeast, the average being nearly 80°. 

Locally, however, it may sometimes have a steep southwesterly dip, 

as on level 2, about 400 feet from the entrance of the tunnel. The 

Avidth of the' lode varies up to about 10 feet. It is usually fairly 

regular, but sometimes pinches for considerable distances, showing 

crushed rock accompanied by gouge, but very little ore. Near the 

entrance to level 2 the lode is divided by a horse 30 or 40 feet in width. 

Both branches of the lode come together in the stope above this level, 

where the lode shows about 19 feet of low-grade milling ore. It here 

takes on the character of a stringer lead, consisting of a network of 

stringers with much shattered country rock. The lode in this stope 

shows no.gouge and no regular Avails, the stringers running out irregularly into the country rock. Some of the ore-bearing stringers Avere 

faulted by later stringers of barren quartz. Small vr.gs, lined Avith 

quartz crystals, are frequent. The Tiger lode is frequently free from 

gouge and often without Avell-defined Avails. In such cases the country rock near the lode is intersected by stringers and may carry 

bunches of ore. In other places there may be clay gouge 011 foot or 

hanging Avail, or both, and even Avithin the lode itself. Thus, movement1 subsequent to deposition of the ore has affected some portions 

of the lode, but not others.

The mine produces essentially a lead ore carrying from 20 to 60 per 

cent lead, rarely more than 12 ounces of silver, and occasionally a 

little gold up to half an ounce. One specimen of free gold has been 

found. The gold usually occurs associated Avith sphalerite and
160 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

chalcopyrite. The chief ore mineral is galena, which is accompanied 

by sphalerite and a little tetrahedrite and chalcopyrite. The tetrahedrite was in ost abundant in level 6, near the top of the ridge. It occurs 

in the lower levels, but less abundantly. The gangue of the ore is 

quartz with some barite. The quartz and galena are crystallized 

together irregularly in the larger stringers and in the main lode. A 

little native copper lias been found on level 3. The alteration of the 

wall rock adjacent to the lode is somewhat more noticeable in the 

Tiger than in the other mines of the Silver Lake Basin. A specimen 

from the south wall of level 3, about 3 feet from the main ore body, 

is a compact, light greenish-gray rock, showing indistinct traces of 

former porphyritic structure. It is traversed by numerous veinlets. 

The largest of these, about one-fourth inch wide, carries quartz, galena, 

and sphalerite. This veinlet shows comb structure, and the ore minerals tend to crystallize along the medial line. Smaller veinlets consist of galena without quartz. The rock itself is thickly speckled with 

minute crystals of pyrite. Under the microscope the rock shows the 

general structure of an andesite, but no remnant of the original minerals remains. The feldspars are changed to aggregates of quartz 

and sericite, and the same minerals, very finely crystalline, seem to 

compose the entire mass of the rock, exclusive of the thickly sprinkled 

pyrite.

In the breast of the drift, level 4, the lode, which is about 4 feet, 

wide, contains a dark horse-like mass. This is said to have been 4 

feet wide in places and to carry 1 to 2 ounces in gold. This material 

shows numerous white spots, which suggest altered feldspathic phenocrysts, lying in a dark-gray groundmass. The whole is mineralized, 

and contains specks of galena, sphalerite, chalcopyrite, and finely 

crystalline pyrite. Under the microscope fragments showing the 

structure of an andesitic rock are seen embedded in a matrix of quartz 

and a very finely crystalline material, which is apparently kaolin, 

although there seems to be some sericite present also. The andesite 

fragments are altered to aggregates of these same minerals, but preserve their original porphyritic structure. The material is a much 

altered and mineralized -breccia, but whether an original tuff-breccia 

or a breccia formed during the formation of the fissure it is impossible 

to say. The lode at this point shows indications of some brecciation 

of the ore and subsequent cementation by barren white quartz.

The Royal Tiger mine has not yet a separate mill. It is connected 

with the Iowa mine by a wire tram across the lake, and the ore is sent 

down to the Iowa mill. Although extensive work had barely begun 

in 1899, in 1900 the Royal Tiger was producing more ore than the 

Iowa.

. Buckeye mine. This mine, situated about one-third of a mile south 

of the lake, is on the Titusville lode. Work on it was abandoned 

some years ago, but the old tunnels were being cleaned out and
BANSOME.] LODES OF HAZELTON MOUNTAIN. 161

reopened in 1899. The ore is chiefly galena, with some tetrahedrite, 

the latter being more abundant in the upper tunnel. There is no 

mill at this mine, and the ore was formerly packed out on burros.

Titusville mine, at the head of Kendall Gailch, although not in Silver Lake Basin, may be most appropriately mentioned here as being on 

the same great lode as the Buckeye. This mine was first worked about 

1886. A small mill was subsequently erected in Kendall Gulch, and 

the ore was carried down on a lightly constructed Huson tramway 

about 8,000 feet in length. The mine ceased operating in 1893. It 

was developed on four levels, aggregating about 1,150 feet of drifts. 

The lode is about 30 feet wide. Its general dip is to the northeast at 

about 80°, although it is locally vertical. It consists of chalcopjrrite, 

galena, sphalerite, and pyrite, in a gangue of quartz and rhodochrosite. Chalcopyrite is the most abundant ore mineral. The ore is generally of low grade, that containing abundant chalcopyrite running 

about $6 per ton. There is a richer streak, liowe'ver, usually about 14 

inches wide, which may run as high as $30 per ton. Some of this 

richer ore contains very finely crystalline galena scattered through 

the quartz in minute particles. Where this occurs the ore may carry 

from 1 to 3 ounces of gold and 60 to 100 ounces of silver per ton, 

the value being associated with the presence of the galena. The 

product of the Titusville mine in 1888 was $51,300.

From this mine the lode can be traced over" the slope to the summit 

of Kendall Mountain, where it appears to divide. It has been prospected along this distance on the Seymour, Emma, Pyramid, Pompeii, 

and Sal Ouster claims, and some ore has been taken out, chiefly 

galena. On the west slope of Kendall Mountain, the Idaho prospect, 

in Silverton Gulch, is apparently on the same fissure or fissure zone, 

although it is here very different in character. The country rock at 

this point is monzonite, part of the great stock of Sultan Mountain. 

The vein here is usually without gouge and narrow 18 inches or less. 

It dips southwesterly about 80°. The ore is mostly chalcopyrite and 

pyrite, with pockets of galena in a quartz gangue. The galena nsualty occurs in the middle of the vein, with quartz, chalcopyrite, and 

pyrite on the sides. This prospect has been worked intermittently 

for twenty years and has produced some ore. The development consists of two tunnels and some small stopes.

LODES OF HAZEL/TON MOUNTAIN.

G-eneral. Hazelton Mountain, as the spur separating Blair and 

Arrastra gulches is called, was the scene of some of the earliest mining in the quadrangle. In 1874 work was already in progress on the 

Aspen, Prospector, Susquehanna, Mammoth, and other claims, most of 

which were afterwards consolidated as the Aspen mine.

Aspen mine. The workings of this mine, which are extensive, are 

shown in plan and longitudinal section in fig. 12.° As early as 1875,

Bull. 182 01= 11
162 ECONOMIC GEOLOGY OF SILVERTON QU ABE ANGLE. [BULL. 183.

the Susquelianna and Aspen claims were being worked at a profit, 

while in 1876 the Prospector lode was developed by two shafts, 100 

and 130 feet deep, connected by a drift 100 feet long. The product 

of the group up to 1880 has been estimated at over $200,000. In 1882 

the Aspen group, embracing the Aspen, Susquelianna, Mammoth, 

Legal Tender, Matchless, and McGregor claims, was one of the best 

developed properties in the district and had over 5,000 feet of workings. During this year its operators contracted to furnish Sweet & Co., 

in Silverton, with 3,000 tons 'of ore, which were crushed, sampled, and 

sent to the new smelter in Durango. In 1893 the Mint reports credit 

the mine with a product of $75,000, and in. 1897, $78,000. In 1892 the 

output, according to the same authority, was $50,916. In all, 11,423 

tons of ore have been produced since January 1, 1884.

PIG. 12. Plan and longitudinal section of the workings of the Aspen mine, Hazelton Mountain.

As the mine has been idle for several years, it was impracticable ill 

1899 to make a satisfactory study of its underground workings. In 

1900, however, some progress had been made toward opening or retimbering the Amy tunnel, connecting with the 800-foot level. Access 

to a small portion of the lode was obtained through the Legal Tender 

tunnel. The vein at the point cut by the tunnel strikes N. 50° W. and 

dips southwest at about 80°. It is small at this place, accompanied 

by soft gouge and disturbed by som e cross faulting. The Legal Tender 

tunnel shows the country rock to be traversed by several other veins 

running generally parallel to the Aspen.

The Aspen workings are in rocks belonging to the Silverton series, 

exhibiting chiefly the characteristic breccia structure already described and containing much rock of rhyolitic character. The lowest
BAHSOME.] NORTH STAR GROUP OF LODES. 163

tunnel, Avhicli, judging from the dump, has not cut the lode, is in 

massive andesite.

According to information received from W. H. Thomas, there were 

several small veins near the surface, which came together in the 

deeper \\sorkings. The plan of the workings (fig. 12) indicates that 

the lode is of rather irregular character and that the general dip is 

northeasterly, at angles varying from 40° to vertical. It is often 

 assumed that the Aspen lode is the northwestern continuation of that 

branch of the North Star lode upon which are located the Slide and 

Mayflower claims. But, as elsewhere pointed out, it is more likely 

that they are distinct.

The ore of the Aspen is chiefly a heavy lead-silver ore, consisting 

of galena, sphalerite, chalcopyrite, pyrite, tetrahedrite, and a little 

native silver in the upper workings. The gangue is quartz, with considerable green fluorite. The tetrahedrite is said to have occurred in 

pockets or bunches in the other ore minerals. One trial lot of ore, 

consisting of 1,000 tons, is reported to have run 110 ounces of silver 

and 60 per cent of lead, no returns being made for gold. The Aspen 

ore Avas smelted in. the old Greene smelter, north of Silverton, as long 

as that pioneer plant was in operation.

It is commonly stated that the Aspen ceased working on account of 

the poverty of the ore in the lowest workings. It is probable, however, that good bodies of ore will yet be found, and that the mine will 

again become productive.

NORTH STAR 1 (KING SOLOMON) GROUP OF LODES.

General. The prominent North Star lode crosses Little Giant Peak, 

northeast of Silver Lake Basin, very near its summit. Its general 

course is a little more northerly than that of the Silver Lake vein, or 

about N. 48° W. The dip is northeasterly, but nearly vertical. 

Northwest of the peak the lode continues through the Terrible, Slide, 

Mayflower, and Argentine claims, down into Arrastra Gulch. It is 

often supposed that the Grey Eagle-Aspen lode, on the south side of 

Arrastra Gulch, is part of the North Star lode. But the connection, 

if it exists, which is doubtful, is concealed by the talus in the gulch. 

It seems more probable that the Aspen is a distinct, essentially parallel, overlapping lode. Southeast of Little Giant Peak the North 

Star lode continues through the Dives, Shenandoah, Mountaineer, 

and Lookout claims into Mountaineer Gulch.

North Star (King Solomon) mine. This mine was first regularly 

worked in 1883, although it had been exploited intermittently for 

three or four years previous to that time. Since then it has been producing steadily up to a year or two ago. The total product since 1883

1 There are two North Star mines within the quadrangle one on Little Giant Peak, commonly spoken of as "The North Star of King Solomon," and the other on the north base of 

Sultan Mountain. The former will be referred to in this report as " The North Star (King 

Solomon) mine."
164 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

has been $1,200,000. The lode 011 the North Star property is a strongstringer lead, consisting of a zone of country rock traversed irregularly by ore-bearing stringers. At the croppings, near the summit of 

Little Giant Peak, this zone is about 100 feet wide. The vein as a 

whole has no Avails, and the stringers are usually not accompanied by 

gouge. The country rock is that found in the Silver Lake Basin, and 

belongs to the Silverton series. The hard, massive sheets of anclesite 

are found to be less favorable for the deposition of ore than the softer 

breccias. The character of the lode makes it very difficult to Avork. 

Ore-bearing stringers may be encountered anywhere \vithin the zone 

of fissured country rock, and frequent crosscutting is a necessity. 

The reduced horizontal projection of the levels, shown in fig. 13, will 

give some idea of the irregular character of the Avorkings. The pay

Exit in C//ffs

9 100 200 300 400 300 600)

FIG. 13. Sketch plan of underground workings of the North Star (King Solomon) mine.

shoot as a Avhole pitches to the southeast, apparently at an angle of 

about 45°. The upper 200 feet, near the surface, Avas largely sulphate 

of lead (anglesite) not carrying much silver. This changed in depth 

to galena, which was associated Avith increasing amounts of tetrahedrite as the ore Avas f olloAved doAvnward. In the loAver levels the galena 

Avas subordinate to the gray copper. This Avas the most valuable ore 

mineral in the mine, being a highly argentiferous tetrahedrite, or the 

variety of gray copper known as freibergite. BeloAv the fifth leArel 

the pay shoot failed, although the fissure continues. No serious prospecting has yet been undertaken to determine Avhether there may not 

be other ore bodies beneath the pay shoot. That there are such ore 

bodies is rendered probable by the fact that ore similar in character 

to that of the North Star mine occurs at a lower level in the DiA^es 

mine, Avhich adjoins the former on the southeast. The gangue of the 

North Star ore was quartz. Some gold occurred occasionally in the
BAKSOME.] DIVES MINE. 165

ore of the lower levels, assays of 6 ounces to the ton having been 

obtained. This metal, however, formed an exceedingly small proportion of the whole output, which was chiefly in silver.

Owing to the cessation of mining and the accumulation of ice and 

mud in the abandoned workings, it was impossible to make any satisfactory study of the detailed structure of the lode. Small stringers 

and gouge seams are said to come in from the foot wall (southwest), as 

in the Silver Lake lode.

The ore from the North Star was sorted and packed on burros down 

to the road in Big Giant Gulch. From this point wagons carried it 

down to the Crooke mill, near the mouth of Boulder Gulch. Built to 

treat ore from the Polar Star mine, on Engineer Mountain, this mill 

was originally equipped with a modification of the Augustin leaching 

process. Its present plant consists of 1 7 by 10 Blake crusher; 10 

1,000-pound stamps, dropping 5 inches at 90 to the minute; 5 Harz 

jig'S, 1 Wilfley table, 3 Frue vanners, and 6 canvas tables. Power is 

furnished by a 60-horsepower engine and boiler. The capacity of the 

mill is about 50 tons. It is evident that ore so irregularly mined, and 

milled under such disadvantages, must have been high grade to have 

paid for extraction and treatment. Much ore that might have been 

profitably milled in .a better-equipped mine has undoubtedly gone on 

the dump or remained in the stopes.

Dives mine. This claim joins the North Star (King Solomon) on 

the southeast and is on the same lode. The workings here are not 

extensive and the mine has not yet produced much ore. It contains 

two stopes, one on the Dives,and the other on the Shenandoah claim. 

The general character of the lode resembles that describe'd in the 

North Star. It is an irregular stringer lead, without gouge and without regular walls. The ore is argentiferous gray copper (perhaps not 

a normal tetrahedrite, as it carries some lead), galena, chalcopyrite, 

and pyrite, in a gangue of quartz and barite. Small vugs lined with 

quartz crystals are common. Much of the vein matter is merely 

filtered country rock, in which the outlines of former porphyritic crystals of feldspar are still recognizable. The ore-bearing stringers are 

distinctly cut by one, and possibly two, sets of later stringers of 

quartz, generally parallel to the course of the lode. These later 

stringers, as far as observed, are small, and are usually barren, 

though some carry a little ore. Comb structure is particularly common in them. A well-marked spherulitic structure was noted in some 

of the ore. More or less rounded, irregular lumps of tetrahedrite 

were surrounded by a skin of chalcopyrite, from which, as a foundation, the quartz had crystallized radially outward (see PI. XI, C). The 

high-grade ore may run about 200 ounces of silver. On the Dives 

claim there is a solid vein of barite, 6 to 7 feet wide, on the hanging 

wall of the productive lode. Its relation to the latter was not determined. Its presence and the occurrence of barite within the ore body
166 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

are perhaps connected with the Potomac lode, which is known to 

carry barite, and should join the North Star lode from the north at 

about this point. Barite was not recognized in the ore of the North 

Star mine.

The country rock of the Dives is that of the North Star. It shows 

some alteration close to the ore bodies, being bleached in color, traversed by veinlets of quartz, and full of minute cubical crystals of 

pyrite and occasionally specks of galena. The microscope shows that 

it has undergone entire metasomatics recrystallization and consists 

chiefly of quartz, sericite, and pyrite.

The Dives was worked on a lease in 1899, the ore being treated in 

the North Star (Crooke) mill. In 1900 it was idle.

The Mountaineer and Lookout mines have not proved steadily productive claims, although in the Mint report for 1891 the Lookout is 

credited with a production of $27,152. Both are now idle. The tunnel of the latter is run in Algonkian schists, just beneath their contact with the overlying volcanic rocks of the San Juan series. The 

schists are shattered and 'decomposed, and the deposit appears to be 

very bunchy and irregular. The ore shows galena, chalcopyrite, and 

pyrite. The Mountaineer is said to have been located by prospectors 

from New Mexico in 1870. At least three veins can be seen cropping 

in the steep bluffs of San Juan breccia above the Lookout tunnel, and 

apparently converging just south of the tunnel mouth in what is 

locally termed a '' blow-out." This is a mass of shattered limestone" 

(probably the Ouray limestone (Devonian), which overlies unconformably the Algonkian schists south of the Highland Mary mine) and 

fragments of schist and andesite, cemented by comminuted andesitic 

material. Some of the limestone fragments are surrounded by envelopes of hematite. The whole mass is somewhat mineralized and is 

traversed by quartz stringers. The origin of this area of local disturbance is not certainly known. The original shattering may have 

been due to the movements which formed the veins that converge at 

this point. There has, however, been some recent movement of a landslip character, which has tended to obscure the original relationships.

Big Giant lode and others. In Big Giant Gulch are several lodes 

which may be conveniently described in connection with the North 

Star lode. The most important of these is the one on which the 

Potomac claim is located. Some work has been done on this claim, . 

and also on the Big Giant, which appears to be on the same lode. 

On the latter claim the lode is apparently a stringer lead, without 

any considerable gouge and carrying much chalcopyrite in its ore. 

It dips southwest at from 75° to 80°. A small mill was erected on 

this claim, but the. mine was not successful, and was idle in 1899. 

Toward the southeast this lode passes over the northern shoulder of 

Big Giant Peak and is supposed to join the North Star vein in the 

Dives claim. There are other lodes in'this gulch, two of which are 

shown on the map, but they have not proved to possess any value.
HANSOMB.] LODES OF CUNNINGHAM GULCH. 167

Little Giant lode. This lode, which lies between Big Giant and 

Arrastra gulches, has not been worked for many years, and its chief 

interest at present is a historical one. Discovered by Miles. T. Johnson in 187.1, it was the first mine to be opened in the district, and, in 

contrast with the present mines in the vicinity, produced a gold ore. 

Such portions of this ore as were not shipped to Pueblo in the crude 

state were originally treated in arrastras. About 27 tons were treated 

in this way and yielded $150 per ton. In 1872 the Little Giant Company was formed in Chicago to work the mine, and in the following 

year the company erected a mill equipped with a Dodge crusher, ball 

pulverizer, and 5 stamps. Power Avas supplied by a 12-horsepower 

engine. The mill was constructed 1,000 feet below the mine opening 

and the ore was brought down by the pioneer wire-rope tramway of 

the region. About 100 tons of ore were milled this year, producing 

about $14,500. The saving is said to have been about 65 per cent of 

the assay value. The mine became involved in litigation, and this, 

coupled with the diminution of the pay shoot, led to its abandonment.

The strike of the vein is N. 40° W., and its dip southwest. The pay 

streak is said to have been about 8 inches wide.

LODES OF CUNNINGHAM GULCH.

General. Cunningham Gulch, named from one of the pioneers of 

Baker's company, is the largest of the various side gulches which 

open on the Animas River above Silverton. At an early date it was 

the scene of mining activity, and then gave promise of a development Avhich has not yet been fulfilled. In 1899 and 1900 a little A\7ork 

Avas in progress on the Pride of the West, but otherwise the gulch 

above its junction Avith Stony Gulch contained no Avorking mines. 

AboA'e the Green Mountain mine the bottom of the gulch is excaAbated 

in the Algonkian schists, Avhich immediate!)7 underlie considerable 

areas of the volcanic rocks of the quadrangle, but are seldom exposed 

in its central portion. The San Juan and SiNerton formations lie 

upon the characteristically uneven erosion surface of the older schists. 

The lodes traverse both the schists and the overlying volcanic rocks, 

and thus afford opportunity for studying the changes, if any, that 

take place in the lodes Avhen they pass from the older to the much 

younger formations. This investigation, however, is unfortunately 

seriously handicapped by the abandonment of most of the old Avorkings, which has rendered many of them inaccessible.. The general 

course of most of the lodes in Cunningham Gulch is between ~N. 30° W. 

and N. 40° W. The Highland Mary vein, hoAvever, is about N. 62° W., 

and still other lodes run more nearly north and south.

Highland Mary mine. This mine has it-Avorkings in the ancient 

schists at the point Avhere Cunningham Gulch, rising by an abrupt 

ascent to a higher level, loses its narroAv linear character. The schists 

Avhich compose the country rock A^ary someAvhat in mineralogical composition, but the most common facies is an ordinary hornblende-schist
168 ECONOMIC GEOLOGY OF SIIA/EKTOJST QUADKANGLE. [BULL.182.

consisting essentially of green hornblende and quartz. The strike of 

the schistosity is here about N. 48° E. The vein has a strike of N. 

62° W., and is practically vertical. Its average width is from 2 to 3 

feet, and it is a simple quartz-filled fissure, the vein being adherent, 

or "frozen," to the schist walls. Several tunnels have been run into 

the vein, but none of them were accessible in 1899. The only ore 

minerals seen on the dump were chalcopyrite and pyrite. According 

to Endlich, 1 of the Hayden Survey, who visited the mine in 1874, the 

width of the vein is from 4 to 5 feet, and galena and tetrahedrite formed 

the main ore, accompanied by pyrite, chalcopyrite, and sphalerite. 

The lower tunnel has a somewhat devious westerly course, and was 

designed by Edward Innis, its projector, to tap the Royal Tiger and 

other lodes of the. Silver Lake Basin. It was started about 1875 and 

had reached a length of about 3,000 feet when work was abandoned 

in 1884. Several veins are said to have been cut in this tunnel, but 

none were prospected. An inspection of the dump shows that the 

whole of the tunnel is in schist. The total product of the mine was 

about $50,000:

Toward the northwest the Highland Mary vein passes upward from 

the schists into the volcanics of the San Juan and Silverton series. 

As examined at a point 1,500 feet above the mine buildings, the lode 

in the volcanics is somewhat larger than in the schists below, having 

a width of about 12 feet. It is here composed of apparently barren 

quartz. The lode probably joins the North Star vein on the Shenandoah claim.

Green Mountain mine. This mine, which is credited with a production of about 1100,000, was being opened when visited by the officers 

of the Hayden Survey in 1874. In 1883 it is said to have produced 

about 300 tons of ore, averaging 38 ounces of silver and 45 per cent of 

lead per ton, valued at about 125,000. It was idle in 1899, and evidently had not been worked for several years. The mine was Opened 

through four tunnels, entering on or near the course of the lode. The 

country rock of the three lower tunnels is a rhyolitic flow-breccia. 

The upper tunnel is in Algonkian schist. The schist of course underlies the rhyolite, and the fact that it is encountered in the upper 

instead of the lower Avorkings of the mine is due to the irregularity of 

the contact between it and the younger volcanic rocks, and to the 

course of the fissure, which makes an angle with the contact. The 

strike of the lode is N. 38° W., and the general dip nearly vertical, or 

at a high angle to the northeast. In the rhyolite the vein is generally 

about 3 feet wide and is destitute of gouge. It is a simple fissure filling, containing a few small horses of altered country rock. The ore 

contains abundant sphalerite and galena, with some chalcopyrite and 

pyrite, in a quartz gangue. In the schists the vein is from 3 to 4 feet 

wide and fills a clean-cut fissure. The quartz and ore are "frozen"

1 Report on the San Juan region: Hayden Survey, 1874, p. 234.
RANSOME.] PRIDE OF THE WEST MINE. 169

to the cleanly fractured edges of the schists. The latter are slightly 

impregnated with pyrite, but show less alteration than the rhyolite 

breccia. The differences in the country rocks have not affected the 

vein or ore in any way recognizable by the eye. Pay ore was evidently 

stoped in both. From a scientific point of view it is much to be 

regretted that this mine is not now in operation aiid open to inspection.

Pride of the West mine. This was one of the earliest mines in the 

district to ship .out ore. The first lot was token out by pack animals 

to Del Norte, on the Rio Grande, and there sold, in 1874. It was 

from.the upper workings, and is said to have contained handsome 

masses of wire silver. The total product of the mine lias probably 

been near $100,000. In the Mint.report for 1884 the mine is credited 

with a total product from the upper tunnel (level 3) of 1,500 tons, 

with an average value of $65. This would give a total of $97,500 up 

to the end of 1884. The product since that time has probably not 

been large. Work of a desultory character only was in progress in 

1899. The general course of the Pride of the West lode is K 32° W. 

The general dip appears to be to the southwest at about 80°. Local 

variations, however, are common. The country rock is a greenish, 

indurated tuff, belonging to the Silverton series, and probably latitic 

in character. The upper and older workings are situated some 500 

feet above Cunninghain Creek, near the croppings of the vein, which 

are here from 20 to 25 feet wide. A crosscut tunnel of about 80 feet 

gives access to the lode, which has a threefold character. Next the 

hanging Avail, where cut by the crosscut, lies about 3 feet of apparently fair milling ore, upon which no stoping has been done. This 

is succeeded on the northeast by 15 feet of quartz, carrying abundant 

pyrite and chalcopyrite. A division plane, carrying a little gouge, 

separates these two portions t>f the lode. Northeast of this wide mass 

of quartz, and next the foot wall, is the main "pay streak" of the 

mine. This ore body is a stringer lead. Its thickness, where stoped, 

was apparently about 15 feet at the most, and usually considerably 

less. There are no true walls. Stringers from the lode penetrate the 

foot wall irregularly. For a distance of several feet the latter is 

traversed by stringers generally parallel to the lode. The lode has 

been stoped from the main level, and from a level 60 feet beloAv, 

reached through a winze.

The ore is chiefly galena, occurring in stringers and bunches, with 

more or less quartz gangue. Pyrite, chalcopyrite, and sphalerite are 

also present. The richer pockets, however, carried rich tetrahedrite 

(freibergite), and sometimes wire silver.

A tunnel has been run at a point on th,e road about 100 feet above 

Cunning-ham Creek, for the purpose of cutting the Pride of the 

West lode at a greater depth and at a more convenient point for working. Many hundred feet of crosscut and drift were run, without, 

however, finding any pay ore. Much of this rock was on the Silver
170 ECONOMIC GEOLOGY OF SILVERTON QUADBANGLE. [BULL. 182.

Fountain lode, which runs southwest of and approximately parallel 

with the Pride of the West lode. Its general course is N". 42° W 

The crosscuts show that between this and the Pride of the West lode, 

which appears never to have been reached in these lower workings, 

are several other generally parallel lodes, none of which carry pay ore, 

as far as prospected.

The ore from the upper workings of the Pride of the West is brought 

down to the road by a small wire-rope tramway, and is thence hauled 

to the railroad at Howardsville in wagons.

Pliiladelpliia mine. This is a small mine higher up the slope and 

apparently on the same lode as the Pride of the West. Work on it 

began in 1875, and it is said to have contained a single pocket of ore, 

chiefly freibergite with a little galena, which afforded about 100,000 

ounces of silver. It has been idle for years.

Oilier lodes. There are several other lodes on Green Mountain 

between Stony and Cunningham gulches. Several of these have produced small pockets of ore, but have never been extensively mined. 

The stronger lodes run approximately northwest and southeast. One 

of .these is prominent along the crest of the mountains. Some large 

masses of barren-looking white quartz outcrop along the course of 

the lode, but often the rock (andesite) is bleached and full of small 

quartz stringers for a width of about 30 feet. About a quarter of a mile 

northwest of the summit of Green Mountain this lode cuts an older 

vein of solid white quartz, about 10 feet wide, accompanied by some 

parallel stringers. This older vein strikes N. 60° E. and dips southeast.at 80°-8o°. The lode along the ridge at this point dips southwest. 

On the northern spur of Green Mountain the veins form a complex 

network. A few only of the better-defined ones are shown on the 

map. As far as could be determined they are all of the same age. 

As a rule they show small indications of "mineralization. I Avas 

informed, however, by the owner of one of the claims that ore 

occurred in scattered pockets, from one of which he had taken out a 

carload running 3 ounces of gold per ton.

North of the Pride of the West is a lode running generally parallel 

to the road. There are several prospects upon it, but it has never 

produced pay ore. In one of these prospects, the Osceola, just north 

of the Pride of the West, occurs a very curious banded ore, described 

more fully in the general section*on the ores. Owing to the caved 

state of the tunnel this banded ore could not be studied in place.

LODES OF GALENA MOUNTAIN AND VICINITY.

General. Under this heading there will be described not only tho 

fissure deposits on Galena Mountain itself, but those of Maggie, Porcupine, and Stony gulches. Galena Mountain is an exceedingly 

precipitous peak, the upper part of which is composed chiefly of 

andesite, both massive and fragmental (tuff-breccias), belonging to
BANSOME.] LODES OF GALENA MOUNTAIN AND VICINITY. 171

the Silverton series. In its lower portions occur some rhyolite and 

intrusive masses of rnonzonite. The mass of the mountain is traversed by very numerous lodes, in great part true veins, many of which 

are prominent on the surface. Only a few of the more conspicuous 

ones could be platted on the map, and those with merely approximate 

accuracy. The number, prominence, and rough parallelism of certain 

sets of these lodes suggest their division into at least four groups.

(1) N. 4-5° E. lodes. Lodes having a nearly northeast and southwest strike are not so numerous on Galena Mountain as they become 

farther north. The best example in this portion of the quadrangle is 

the Ridgway lode, the general course of which is about N. 40° E., 

with local variations. Thus, in the Ridgway mine the strike, as 

observed in the drifts, is aboutN. 65° W. The lode dips southeast 

at from 75° to 80°. The Ridgway lode is faulted by the Alaska lode, 

with a strike of 1ST. 40° W.

(2) N.-S. lodes. In this group are included a number of rather

short lodes, of which the Veta Madre may be taken as an example. 

They usually dip to the east at an angle of about 80°. No important 

ore bodies have been found 011 any of them, nor was any work on them 

in progress in 1899. The larger of these N.-S. lodes are often accompanied by parallel nssuring and veining of the country rock.

(3) N. 25° W. lodes. Lodes of this group are very well seen on the 

south declivity of the mountain in the vicinity of the Veta Madre 

mine. The massive andesite is here traversed by a very prominent 

set of fissures running N. 25° W. and generally nearly vertical. The 

fissures are closely spaced, a foot or less apart, and are usually occupied by rather small stringers, which are sometimes mineralized. In 

the Veta Madre tunnel the N.-S. lode is cut by a vein belonging to 

this group (N. 25° W.), which was followed for about 300 feet, and 

carried galena with chalcopyrite and probably sphalerite and pyrite. 

The veins of this group are thus, in part at least, younger than the 

N.-S. veins of group 2.

(4) N. 65° W. lodes. Lodes whose courses are within a few degrees 

of N. 65° W. are generally larger and more prominent than the other 

lodes of Galena Mountain. Just southwest of the summit of the peak 

a prominent lode of this group has been extensively prospected. The 

lode at this point is a large one, striking N. 60° W. and dipping 75° 

to the northeast. The ore is chiefly chalcopyrite and galena in a 

quartz gangue. The Neigold mine is also working one of these strong 

lodes (N. 75° W.), in this case practically vertical. The ore shows 

galena, chalcopyrite, a finely disseminated sulphobismuthite of lead, 

specularite, and pyrite, in a quartz gangue. A gray prismatic mineral of brilliant metallic luster, determined as probably bismuthinite, 

is also present. The veins of this group cut the N. 25° W. veins of 

group 3, and in one case were observed to cut a vein striking about N. 

30° E. They are thus, as far as is known, the youngest veins on the 

mountain.
172 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

Although Galena Mountain has been prospected at many points and 

has produced some ore, no important ore bodies have yet been developed. The veins in general contain milk-white quartz and some 

barite and are apparently not heavily mineralized.

Antiperiodic mine. This is a small property on the east side of 

JRocky Gulch. The lode has a general strike of about 1ST. 38° W. and 

dips southwest about 75°. It is irregular and the ore occurs in pockets. 

The country rock is andesite. The ore consists of galena, with cerus- 

 site and wire silver near the surface. Tetrahedrite, chalcopyrite, 

pyrite, and sphalerite are also present. The total product of this 

little mine during the twenty years it has been worked amounts to 

.about $12,000. The ore is often of high grade, carrying sometimes 

1,100 ounces of silver and 5 ounces of gold, but it is difficult to find 

and variable in tenor.

Ridgway mine. This mine is situated on a spur which runs out 

northeast from Galena Mountain to Maggie Gulch. It was first worked 

in the summer of 1896 and has paid continuously. The strike of the 

lode is N. 40° E. and the dip southeast at 75°. The workings consist 

of two tunnels, with drifts and stope on the upper level. The lower 

tunnel has just cut the lode, and a winze is being sunk from the upper 

level to meet it. The countiy rock of the two main levels is massive 

andesite. The stope, however, is partly in well-bedded andesitic tuff 

about 200 feet thick, resting upon an uneven surface of the massive 

andesite. The tuff is in turn capped by an andesitic flow. The lode 

in the stope shows a maximum width of 7 feet, nearly all ore. The 

vein is "frozen" to the walls, the rock of which exhibits considerable 

alteration-. The microscope shows that the andesite near the ore has 

been changed into an aggregate of quartz and. sericite. The gangue 

of the ore is chiefly quartz, with a little calcite. Vugs are common, 

usually lined with crystals of quartz, which are sometimes faintly

amethystine. Toward the northeast the vein, as followed in the stope, 

becomes a barren stringer lode. Toward the southwest the ore body 

is sharply terminated by the Alaska vein, which faults the main ]ode, 

apparently offsetting its southwestern continuation to the southeast. 

No ore has yet been found south of the fault, although the vein continues beyond the offset.

The valuable constituent of the ore consists chiefly of a dark-gray 

or black, sectile, argentiferous mineral, which contains neither arsenic 

nor antimony and is, without much doubt, argentine. Curiously, this 

mineral, with sectility as its most characteristic physical property, is 

called "brittle silver" by the miners. It occurs finely disseminated 

through the quartz (PI. X, A) and as small irregular crystals, with 

quartz, in the vugs. A little ruby silver is reported. There is very 

little galena in the ore, and the product of the mine is wholly in gold 

and silver. The ore shipped averages $110 per ton and carries about 

3 ounces of gold. Some of it runs much higher. In 1898, 300 tons of
RANSOME.] LODES OF GALENA MOUNTAIN AND VICINITY. 173

ore were shipped, and in 1899 ab.out 150 tons. Ore under $20 in valueis thrown on the dump. The crude ore is taken down on pack animals to Middleton and shipped to Durango by rail. It costs $6 per 

ton to transport it to the smelter, The total product of the mine has 

been about $60,000.

Gold Nugget claim. In Maggie Gulch are numerous lodes and 

veins, nearly all of which have been superficially prospected. The 

Gold Nugget is one of the oldest of these prospects and has produced 

about $10,000, chiefly from a single rich pocket near the surface. The 

value is in gold and silver, and the ore is the so-called "brittle silver," probably in this case argentite. The strike of this vein is N. 10° 

E. and its dip about 60° to the east. It is a strong, solid, white veiny 

containing some calcite and barite with the quartz. The country 

rock is andesite.

Little Maud claim. This is on a strong vein about 12 feet wide, 

Striking N. 20° E. and dipping southeast about 77°. The vein is 

frozen to the walls. The country rock is andesite. The ore is similar 

in character to that of the Ridgway, consisting of the so-called 

"brittle silver" with pyrite in a quartz gangue. It has thus far been 

found near the hanging wall, but the pay streak appeared to be 

changing to the footwall. About 40 sacks of high-grade ore had 

been taken out in 1899, but none shipped.

As a whole the veins in Maggie Gulch, including the Ridgwayr 

differ markedly in the character of their ores from those hitherto 

described in Silver Lake Basin, Cunningham Gulch, and on Galena 

Mountain. They do not. contain noticeable quantities of galena, and 

are mined for gold and silver only. The important ore mineral is. 

the so-called "brittle silver," which usually is finely disseminated 

through the quartz. As usual, it is not brittle silver (stephanite) at 

all, but either an argentiferous galena or a mixture of galena and. 

argentite. Common pyrite is also usually an abundant constituent. 

As far as observed, veins carrying ore of this character all strike east 

of north. The value of the ore is about equally distributed between 

gold and silver. The ore is usually of a high grade, but has not 

been found in large bodies. It is generally in irregular bunches and 

streaks in prominent, generally barren lodes. Except the Ridgway 

mine, there are no workings in the gulch which can be regarded as 

anything more than prospects.

Hamlet mine. This mine, about three-fourths of a mile south of 

Middleton, although hardly in Maggie Gulch, may be conveniently 

referred to. in this place. This is a silver-lead-coppsr mine, which 

was worked intermittently from 1883 to 1887. Most of the work was 

done during the last two years, when the mine shipped several hundred tons of chalcopyrite and galena ore. The strike of the \ 

is N. 50° W. and the dip 80° to 85° to the northeast. The ore is 

galena, sphalerite, and chalcopyrite in quartz. The country rock is a
174 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

fine-grained monzonite, and the vein is a simple fissure filling, with little 

or no gouge. The workings are rather extensive, embracing three adit 

tunnels, with drifts, stopes, and crosscuts. The ore was taken down 

to the railroad on pack animals, and it is remarkable that so much 

work was done on an ore deposit of this character without more effective means of handling and concentrating the ore.

Other lodes. Just north of Howardsyille the precipitous slopes of 

Dome Peak are traversed by several prominent lodes. There are two 

sets of these, one with a course of about N. 63° W., and the other 

about IsL 25° E. They are not distinct fissures, such as would result 

from decisive faulting, but are veins showing considerable regularity 

for some distance, then branching, anastomosing with other veins or 

dyilTg out in networks of irregular stringers. There is a tunnel, the 

name of which was not ascertained, about half a mile north of Howardsville, at the junction of two of the most prominent veins. In it 

much fruitless work was done, but no extensive ore body was ever 

discovered and the mine, was abandoned. The lodes, so prominent 

in the cliffs above, seemed to be pinched, barren, and irregular when 

followed under ground.

LODES OF BURNS GULCH.

General. Although the lodes in this gulch were prospected at an 

early date in the history of the region and have produced some ore, 

none of them have proved permanently productive.

Tom Moore lode. This lode, reported to have been located in 1870, 

was being worked in 1881, and then produced a massive galena said to 

carry about 70 ounces of silver. But its development has been slow 

and intermittent. Its strike is N. 53° E. and its dip NW. 68°. The 

country rock is a rhyolitic flow breccia, part of the Silverton series. 

This, when examined at some distance from the lode, is a light-gray 

rock showing very conspicuous mottling, due to the brecciation which 

its material has undergone. Both the fragments and the matrix are 

essentially of rhyolitic character, although an occasional andesitic 

particle occurs. The rock is usually streaked and spotted with little 

nests of epidote. The microscope shows that the original glassy base 

of the rock has been largely devitrified and is now a fine-grained 

granular aggregate in which quartz is the outy recognizable constituent. Phenocrysts of orthoclase and plagioclase are abundant and are 

usually partly altered to sericite. Other phenocrysts, presumably 

ferromagnesian silicates, have been changed to aggregates of quartz 

and epidote. Areas of chlorite represent what were probably former 

phenocrysts of biotite. There is also a little calcite present. The 

accp^sory constituents noted are allanite and titanite. The lower 

tumiel, near the Animas River, shows an irregular stringer lead with 

a well-defined gouge slip along the foot wall. The ore shows chiefly 

galena, with sphalerite, chalcopyrite, pyrite, and sometimes tetrahe-
IIANSOME.] LODES OF BURNS GULCH. 175

drite, in a quartz gangue. A little rhodochrosite occurs in vugs. The 

country rock alongside the lode is impregnated \vithpyrite and specks 

of galena to a greater extent than is usually observed in this region. 

When examined in thin section under the microscope, it is seen to be 

altered to an. aggregate of quartz, sericite, and ore, traversed by veinlets of quartz. The original brecciated structure and the outlines of 

many of the feldspar phenocrysts have been preserved in spite of 

complete recrystallization. The feldspars have usually been altered 

to aggregates of sericite.

A second tunnel, .several hundred feet above the lowest opening, 

was not accessible. The dump, however, showed that this portion of 

the lode was originally a breccia zone in the rhyolite which became 

filled with ore, accompanied by considerable impregnation and 

replacement of the country rock. This ore deposit was itself shattered and veined with white quartz, carrying little or no ore.

The upper tunnel, 200 feet above the last, was being worked on a 

small scale in 1898. The ore streak here is frozen to the walls and 

carries no quartz save in some small later stringers, often accompanied by kaolin, which cut the ore, and in a few drusy vugs, where 

it. is sometimes accompanied by a little pale-lilac fluorite. The ore 

is chiefly tetrahedrite, with some chalcopyrite and galena. Sphalerite was not seen. There is said to be some bismuth present, probably 

as a sulphobismuthite of lead, and the occurrence of hiibnerite was 

noted in small crystals in the later quartz stringers. The width of 

the lode is usually from 3 to 6 feet, and it is in part a replacement of 

the rhyolitic walls. The chalcopyrite occurs chiefly in the middle 

portions of the ore stringers. The tetrahedrite on each side of io is 

solid for a short distance and then fades off into the altered country 

rock as minute veinlets and specks associated with chalcopyrite or 

pyrite. Such gangne as is present with the ore is altered rhyolitic 

flow breccia, consisting chiefly of finely crystalline quartz and sericite. 

The lode is thus not sharply differentiated from the country rock on 

each side of it. The tetrahedrite is not highly argentiferous. The 

first-class ore runs about $60 to the ton and the second-class about 

'148. The chief value is in copper, but there is some silver and a little gold, the last sometimes in visible particles. Free copper is not 

uncommon in these upper workings, but is confined, as far as is known, 

to the small stringers of younger white quartz which cut the ore. 

These sometimes show comb structure, and the copper occurs along 

with the medial suture of the stringers.

The middle tunnel is said to have furnished ore carrying more 

galena and higher in silver, with subordinate amounts of tetrahedrite, 

while in the lowest tunnel tetrahedrite was rare.

Silver Wing mine. This property comprises several lodes, of which 

one is the northeast extension of the Tom Moore. Some development 

of these lodes was in progress as early as 1880, but they have never
176 ECONOMIC GEOLOGY OF SILVEETON QUADRANGLE. [BULL. 182.

been successfully worked. An extensive tunnel has been run in from 

the Animas River near the month of Burns Gulch, and a costly mill 

has been erected to treat the ore when it should be found. The property became involved in legal difficulties, and in 1899 all work had 

ceased before ore had been discovered in paying quantities.

LODES OF SUNNYSIDE BASIN.

General. Although the Sunnyside mine is the only one in. the 

basin now producing, there are several other large lodes which have 

in the past produced ore from superficial workings. In the general 

character of their ores they show much similarity. They are all of 

prevailingly low grade, although the Sunnyside contains masses of 

richer ore carrying free gold. The lodes are unusually massive, in 

some cases over 50 feet wide, and all carry abundant rhodonite. The 

ore minerals are galena, sphalerite, chalcopyrite, pyrite, and sometimes tetrahedrite and free gold. The ore minerals are usually rather 

evenly scattered through a quartz gangue, and the ores are more siliceous and the galena is more finely crystalline than in those of the 

Silver Lake Basin. The large veins at the head of Lake Emma are 

curved and show abrupt changes in their courses. The cause of these 

irregularities is nob apparent.

Sunny side mine. Situated in the basin at the head of Eureka Gulch, 

this mine enjoys the distinction of having been an almost continuous 

producer from the first discovery of the region. It is to-day one of 

the few mines in the quadrangle that are actively working on a considerable scale. The deposit, like man}7 another prominent lode in 

the district, was located in 1873, while the land Avas still held by the 

Indians, and afterwards relocated when the San Juan country was 

thrown open to settlement in 1874. It was worked as a prospect in 

1875, and about four years later produced considerable ore. Thompson Brothers worked the mine for several years, during one of which 

they are said to have taken out $385,000. The rich gold ore which 

made the early exploitation profitable finally gave out. A 10-stamp 

mill was erected at the outlet of the lake and an attempt was made 

to concentrate the lower-grade ore. The effort resulted in failure. 

Finally, about 1890, J. H. Terry put up the present mill in Eureka 

Gulch and operated it successfully. About 1896 this mill was connected with the mine by a wire-rope tramway. In 1899 a second mill 

was completed at Eureka, designed to relieve the work of the upper 

mill by concentrating the lower grades of ore which do not require 

amalgamation. A tramway was also constructed connecting the two 

mills.

The Sunnyside lode is very large 30 to 50 feet in width. Its general strike is about 1ST. 50° E. and it dips to the southeast at 65° or 70°. 

Toward the northeast it passes through a saddle, where it is known 

as the Sunnyside Extension lode, and continues down Placer Gulch..
BANSOME.] LODES OF SUNNYSIDE BASIN. 177

Southwest of the Sunnyside the lode becomes the Belle Creole, curves 

sharply westward, and is concealed by alluvium at the head of Lake 

Emma. A short distance northeast of the Sunnyside lode, and nearly 

parallel to it, is the No Name lode, dipping 75° to the southeast, and 

joining the Sunnyside in the Sunnyside Extension ground. Between 

this lode and the Sunnyside are at least three other veins, making in 

all a very large body of low-grade ore. The Sunnyside vein is frozen 

to the walls, and gouge is usually absent. The ore minerals of the 

vein are galena, sphalerite, chalcopyrite, pyrite, tetrahedrite, and free 

gold, in a gangue of quartz and rhodonite. The ore streaks occur 

irregularly in the vein, between partitions of rhodonite. As a rule 

the ore occurs near the Avails, and when an ore shoot pinches on one 

wall it usually thickens on the other. The best ore, carrying free 

gold, occurs in irregular lenses parallel with the plane of the lode and 

sometimes 30 or 40 feet in diameter. It is usually [tssociated with

rosin-colored sphalerite and small amounts of lilac fluorite. These 

are regarded as-useful indications, but are not invariably accompanied \>y free gold. The ore has been brecciated to some extent since 

its original deposition and is sometimes traversed by a network of 

veinlets. These are usually filled with quartz carrying a little chalcopyrite. But where the veinlets traverse rhodonite they are often 

filled with that mineral instead of quartz. The exact relation of the 

rhodonite "partitions" to the ore is not always clear. In some cases 

the rhodonite appears to form the mass of the vein, in which the ore 

occurs as lenticular bodies, and sometimes lenses of rhodonite are surrounded by ore. The large masses of rhodonite, or "pink," as the 

miners term it, are never regarded as ore, although they are not destitute of the ore minerals. The material is rose-pink in color on fresh 

fracture, very compact, and exceedingly tough to work. It always 

contains a little quartz, calcite, and fhodochrosite. The rhodonite 

sometimes occurs as distinct stringers cutting the quartz and ore, 

while in other places it may be seen intimately and irregularly intercrystallized with them. As far as observed, neither the rhodonite nor 

the ore shows any regular megascopic structure, such as banding, 

crustification, or comb structure, other than tb.e general relationship 

already indicated.

The No Name lode has not yet been commercially worked. Where 

seen it showed about 6 feet of quartz and ore on the foot wall and 

about 4 feet on the hanging wall, the two streaks being separated by 

10 feet of rhodonite (fig. 7, p. 88). The ore is chiefly galena.

The Sunnyside is worked through a main adit tunnel about 100 feet 

above the lake. There are two other important levels above the present adit. Underhand stoping is employed, resulting in empty stopes 

of great height. Fortunately the nature of the country rock is such 

that the men working in the bottoms of these stopes are fairly safe 

from falling material. There are no stopes as yet below the main adit

Bull. 182 01 12
178 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182'.

level. As is too^ often tke case in the mines of this region adequate 

maps, showing the underground workings and the shapes of the ore 

bodies as developed up to date, are lacking.

The chief product of the mine is in gold and lead, the silver averaging not much more than 11 ounces per ton. Occasional streaks of 

tetrahedrite may, however, carry as much as 400 ounces. The ore is 

carried ou a Finlayson wire-rope tramway down to the mill in Eureka 

Gulch. This mill is equipped with 1 Blake crusher, 15 stamps of 650 

to 700 pounds weight, dropping 55 to 60 times a minute, 3. Bartlett 

tables, 2 Wilfleys, and 2 canvas tables. The power is water. The 

batteries are provided with one amalgamated copper plate each. The 

capacity of the mill is 30 to 35 tons daily. In 1900 this mill was not 

in use, and all the ore was sent down on a Finlayson tramway to the 

new mill at Eureka, originally designed for a concentrating mill and 

furnished with rolls. The equipment of this mill is at present one 11 

by 15 Blake crusher, 20 stamps, 3 Wilfley tables, and 5 Bartlett tables. 

Power is supplied by 2 Pelton water wheels.

La Belle Creole. This claim is on the main Sunnyside lode, which 

has here turned so as to strike east and west, dipping south 75°. The 

croppings are very prominent and have been worked by open cuts 

and through a small tunnel. Several pockets of good ore have been 

taken out near the surface.

The Lake claim is on a prominent lode just north of Lake Emma. 

This has also produced some good ore and has been worked by an 

open cut and small shaft. The strike of the fissure is N. 74° W., and 

the dip practically vertical. The continuation of this lode toward 

the east is lost beneath the talus. On the west it appears to be connected with the George Washington lode, although the two are not in 

line.

The George Washington is a strong lode, striking east and west

and dipping south 70°. It also has been superficially worked by'an 

open cut and a shallow shaft. In 1900 a new prospecting shaft had 

been sunk south of the vein and a crosscut driven across the latter, 

here over 100 feet wide. About 20 feet of very compact rhodonite 

was cut through about in the middle of the vein, and alongside the 

rhodonite, on the north, is about 5 feet of ore, carrying in places as 

much as 9 ounces of gold. Most of the vein, however, is of low grade. 

The relation of the rhodonite to the ore is similar to that described in 

the Sunnyside mine. The George Washington vein shows no gouge 

and no regular walls. The ore resembles that of the Sunnyside in 

general mineralogical character, but perhaps carries more galena. 

The lode apparently curves and passes through the saddle into Ross 

Basin, down which it is easily followed by its remarkably prominent 

croppings.

Ben Franklin mine. This is an enormous lode of low-grade ore, 

in places over 100 feet in width, which crosses Eureka Gulch about
BAHSOME.] PLACEE GULCH AND TREASURE MOUNTAIN LODES. 179

half a mile below Lake Emma. Its strike is IsT. 43° E., and it dips 

northwest from 45° to 60°. This mine caused considerable excitement in 1883. Two tunnels, 20 and 80 feet in length, had been run 

and some 300 tons of ore averaging $36 per ton had been taken from 

the longer tunnel. An. inclined shaft was -also sunk for a short distance on the lode. The ore consists of sphalerite, galena, chalcopyrite, and pyrite, in a gangue of quartz and rhodonite. Masses of 

richer ore, carrying tetrahedrite and native silver, are said to have 

occurred in caves within the lode. A road was built up Eureka 

Gulch to the mine, but the latter did not fulfill expectations and was 

abandoned.

PLACER GULCH AND TREASURE MOUNTAIN GROUP OF LODES.

General. As may be seen by reference to the map, on which only 

a few of the most prominent viens are shown, the veins of'this area!

group form a complex network in which certain dominant directions 

of fissuring are plainly recognizable. There is a series of strong, continuous lodes, represented by the Sunnyside and Scotia veins, having 

a general course of about N. 40° E. The dip of these is southeasterly 

at a high angle. The Scotia lode appears to be a very persistent one. 

There is good reason to suppose it to be continuous with a lode which 

passes up Cinnamon Creek and over Wood Mountain to the Lake 

Fork of the Gunnison. A second system of shorter, less conspicuous 

veins crosses the first series almost at right angles, with a course 

approximately N. 55° W. These are nearly vertical, but the majority 

of them dip southwest at high angles. Whether they are older or 

younger than the dominant northeast veins could not be satisfactorily 

determined with the exposures at hand, although some of them appear 

to cut the Scotia lode. A third system of transverse veins, represented by the Golden Fleece, has a course about N. 75° E., with 

usually steep southerly dip. Besides the three systems already noted, 

there is a very prominent set exposed at the head of Placer Gulch, 

which have an average trend of about N". 25° E. Their dip is usually 

steep and easterly. They resemble in character the great Suunyside 

lode, and in most cases are branches of the latter, forming with it a 

fan-like group somewhat similar to that previously described in Silver 

Lake Basin.

There are several other lodes in this area which do not strictly 

belong with any of the systems noted. Several of them have a nearly 

east-and-west strike and might "perhaps be grouped together, or possibly included with veins of the Golden Fleece system.

The country rock of all these lodes is in the main the Silverton 

series, with a few masses of intrusive rhyolite.

The Sunnyside Extension lode and those just described as its 

branches resemble very closely those in the Sunnyside Basin. They 

are for the most part strong, heavy lodes with bold outcrops, to which
180 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

the abundant rhodonite, by oxidation, generally gives a black color. 

Underground it is seen that these lodes are as a rule composed of 

alternating bands or streaks of ore and barren pink rhodonite. The 

ore bodies may vary from a few inches up to 30 feet in width. They 

are sometimes continuous for long distances, but are elsewhere plainly 

lenticular. The miner has sometimes followed a single ore streak for 

a considerable distance without suspecting that another ore body lay 

close alongside, separated from him by a partition of rhodonite. The 

ore streaks frequently show irregular banding, by deposition, and 

often contain small vugs. The ore minerals are sphalerite, galena, 

pyrite, chalcopyrite, free gold, sulphobismuthites of lead and silver, 

and sometimes small amounts of tetrahedrite, molybdenite, native silver, and native copper. The sphalerite varies from dark brown to 

rosin-yellow in color, and usually about equals the galena in amount, 

and exceeds the other ore constituents. The light-colored zinc blende 

often accompanies ore rich in free gold. The gangue is quartz, rhodonite, aud locally a little nuorite and calcite. The rhodonite, which 

forms the "partitions of pink" between the ore bodies, is tough and 

compact, and varies from light pink to rose-red in color. It is always 

poor in ore minerals when it occurs in large masses, but small amounts 

of rhodonite may be embedded in the richest ore. '

In spite of the banding on a large scale shown by the veins, they 

are as a rule simple, thick plates of vein filling, frozen to the walls 

and containing very few horses of country rock. Of low grade as a 

whole, they have hitherto been mined for the richer portions, carrying 

free gold.

Sunny side Extension mine. This property joins the Sunny side on 

the northeast, and is on the same lode. The main lode dips southeast 

about 75°. Just northwest of it is a second lode, nearly parallel and 

bearing to it a relation similar to that which the No Name bears to 

the Sunnyside. This second lode also dips southeasterly, but in 

places it is as flat as 40°. It probably joins the Sunnyside vein in 

depth.

The Sunnyside Extension mine was first extensively worked in 1886, 

when $3,965 worth of ore was shipped. It was worked steadily until 

1892, producing in all $337,687. After a short intermission it wasagain worked up to about 1897, but the output for this period is not 

known. The mine is now (1900) being again reopened. The ore 

resembles in general character and occurrence that of the Sunnyside 

mine, but is more irregular in its distribution. There are three main 

levels, all connecting with the surface by adit tunnels. Above level 

2 is a sfcope about 30 feet wide, 200 feet long and 125 feet high, which 

is said to have been practically all ore. Some very rich ore has been 

taken from this mine, carload lots running as high as 74 ounces of 

gold per ton, together with silver and lead. The gold occurred very 

largely free, and, as in the Sunnyside, was limited to certain pockets
RANSOJIE.] PLACEE GULCH AND TBEASUEE MOUNTAIN LODES. 181

or bunches within the mass of the otherwise low-grade vein. Specimens of this ore in the possession of Mr. Rasmus Hansori, of Eureka, 

showed the gold scattered through masses of friable spongy quartz, 

and also as implanted crystals on the quartz crystals of drusy cavities or vugs. It also occurs embedded in a dark-gray mineral locally 

termed "graphite," but which in reality is molybdenite, 1 in a sulphobismuthite of lead and silver not specifically determined, and also in 

light-yellow zinc blende. A little native silver sometimes occurs with 

the gold, and some native copper was in the upper workings. The 

general mineralogy of the vein is identical with that of the Sunnyside. 

The Sunnyside Extension (lianson's) mill, erected in 1889 near the 

head of Placer Gulch, is equipped with a Blake crusher, 20 750-pound 

stamps, dropping 9 inches at 64 to the minute, 4 Gilpin County shaking tables, and 2 Woodbury tables. The mill was driven by steam 

and has a capacity of 47 tons per day. Ore was brought down to the

mill on a Huson tramway 2,300 feet in length, with 61 buckets and a 

daily capacity of 175 tons.

The Mastodon is on the same lode as the Sunnyside Extension mine, 

and lies just northeast of the latter. This claim has never been extensively developed. It is known to contain some rich silver ore, but 

this is irregularly distributed through the large low-grade lode. A 

mass of this ore, consisting chiefly of an argentiferous sulphobismuthite of lead in a fine aggregate of quartz and barite, was 

assayed by Mr. Hanson and found to carry 400 ounces of silver. The 

sulphobismuthite occurs as a bright lead-gray mineral, finely disseminated through the quartz and barite, or in minute ragged prismatic 

crystals. It is not practicable to obtain the mineral in sufficient 

purity and quantity to warrant quantitative chemical analysis, by 

which alone the mineral species could be determined.

The Mastodon mill was one of the earliest to be constructed in the 

district. In 1899 it had been repaired and was working on ore from 

the Silver Queen mine. Its present equipment is a Blake crusher, 

2 sets of rolls, I Huntington, 1 double compartment .jig, 2 sets of 

revolving screens, 1 large Bartlett table, 2 "double-deck" Wilfleys, 

and 4 slime tables. Its capacity was said to be 35 tons.

Silver Queen. This is a small mine at the head of Placer Gulch 

and about one-fourth mile east of the Sunnyside Extension. The lode 

is somewhat irregular, but appears to strike about N. 10° W. Its dip 

is to the west and unusually flat for this region, being near 40°. Considerable work has been done, but in a most unsystematic manner. 

The ore seen showed galena, pyrite, chalcopyrite, tetrahedrite, and 

sphalerite, in a gangue of quartz and rhodonite, with a little rhodochrosite. It is also said to carry some free gold. This mine has produced 

some good ore, but how much is not known. The silver is said to

1 T. A. Rickard has erroneously referred to this as graphite, supposing that it aided in precipitating the ore. See The Enterprise mine, Rico, Colorado: Trans. Am. Inst. Min. Eng.,Vol. XXVI, 

1897, pp. 976-977.
182 ECONOMIC GEOLOGY OF S1LVEETON QUADRANGLE. [BULL. 182.

have occurred largely in combination with bismuth, probably as 

a sulphobismuthite of lead and silver. In 1899 a crosscut was 

being driven to cut the extension of the Sound Democrat lode to the 

eastward.

Hidden Treasure, Pride of the Rockies, etc. These claims are 

located on lodes lying radially in the angle between the Silver Queen 

and the Sunnyside Extension. They have been prospected in a small 

way and have produced inconsiderable amounts of ore. According 

to Mr. Rasmus Hanson, ore from the Hidden Treasure vein has assayed 

300 ounces of silver and 4 ounces of gold per ton: In their general 

character these lodes resemble the others of this group already 

described. The lodes at the head of Placer Gulch are exceedingly 

numerous, and those named or those indicated on the map comprise 

merely a few of the more prominent ones.

Sound Democrat. This also is a small mine which was being developed in 1899. The principal lode strikes N. 20° E. and dips northwest 

about 68°. The portion of the lode now being worked is very irregular, the ore occurring in bunches, as if the lode had been broken up 

and the parts displaced. Much of the irregularity is apparently due 

to the fact that two or more transverse or intersecting lodes occur in 

the workings. Owing to the absence of maps and the small scale of 

the present workings, it was impossible to make a satisfactory study 

of the ore bodies. In its general mineralogical character the lode 

resembles the Sunuyside. The ore shows pyrite, sphalerite, galena, 

chalcopyrite, and free gold, in a gangue of quartz and rhodonite, and 

a little rhodochrosite. A gray metallic mineral occurring in minute 

particles in some of the ore is probably one of the sulphobisniuthites 

of lead. Gold is the most important constituent, and occurs free in 

fine particles in the quartz and in .the pyrite. Chalcopyrite is not

abundant, and when present is regarded as an indication of the presence of gold. The galena in the best ore occurs in such fine particles 

as to make its recognition difficult. Quartz is the principal gangue 

mineral, and often shows small vugs. In 1899 the ore of the Sound 

Democrat was beiug packed on burros to the upper Sunnyside mill 

in Eureka Gulch and there treated.

Scotia lode. This is a very prominent lode, which outcrops along 

the southeast slope of Treasure Mountain. It is probable that the 

same fissure or fissure zone crosses the Animas River and extends up 

Cinnamon Gulch and over the southeast shoulder of Wood Mountain. 

Its strike on Treasure Mountain is N. 43° E. and its dip about 75° to 

the southeast. It is occupied by a large low-grade lode, with a more 

or less black outcrop, owing to the oxidation of the rhodonite of which 

it is partly-composed. Although prospected at many points, it has 

not been profitably worked. The Scotia claim has produced some 

high-grade ore, but it has come from a small transverse vein, the 

Golden Fleece.
UANSOME.] PLACER GULCH AND TREASURE MOUNTAIN LODES. 183

Golden Fleece vein. This is a very small and tight vein which has 

produced some rich free-gold ore. The strike of the vein is 1ST. 75° E. 

and its dip about 75° to the south. Its width varies from a fraction 

of an inch to 0 inches, and it is unaccompanied by gouge. Although 

so small, the vein is remarkably regular and has been extensively 

stoped. As it approaches the Scotia lode it breaks up into stringers 

and grows poor. This splitting up of the vein into string.ers as it 

approaches the Scotia lode is at least an indication that the latter is 

older. 1 Toward the east it bends southward and joins the Golden 

Fleece extension, a low-grade lode approximately parallel with the 

Scotia. The ore of the Golden Fleece is free gold, which occurs in 

beautiful dendritic forms made up of thin branching plates of gold 

embedded in a gangue of quartz with some pale-pink rhodochrosite. 

The quartz near the gold is usually dark' colored, and this darker 

shade is apparently due to the presence of extremely minute particles 

of pyrite, galena, and sphalerite, and possibly other ore minerals. 

 The gold occurs both in the quartz and in the rhodochrosite. Some 

beautiful specimens of rich gold ore from this little vein were seen in 

the possession of.Mr. Hanson, of Eureka, who worked the vein for 

years. The product was all sorted and shipped as crude ore. There 

was no work in progress in 1899 when I visited the mine, but a resumption of mining was reported in 1900.

San Juan Queen. This is a prospect in Picayune Gulch just southeast of the Scotia and Golden Fleece mines. The lode strikes N. 83° E. 

and dips south about 80°. Its average width is from 3 to 4 feet. The 

ore consists of pyrite, galena, sphalerite, and a little free silver, in a 

gangue of quartz with some rhodonite. Much of the galena is very 

finely crystalline, giving a dark-gray tint to the quartz. The prospect 

'has been developing for about seven years, and has shipped about 10 

tons of ore. The best-grade ore is said to carry about 5£ ounces of 

gold and 180 ounces of silver.

Toltec lode. This is a prominent lode on the ridge east of the upper 

part of Picayune Gulch. Its course, N. 40° E., is nearly parallel 

with that of theSunnyside and the Scotia. It dips northwest at from 

50° to 60°. It has not been worked on any extensive scale and is low 

grade. In the Toltec claim the vein is in places about 60 feet wide, 

of solid quartz carrying finely disseminated pyrite, with a more heavily mineralized streak carrying galena, sphalerite, and chalcopyrite 

near the hanging wall. An upper tunnel on this claim has afforded 

some coarsely crystalline galena resembling more the ores of the Silver Lake Basin than those usually found in this vicinity. The Toltec 

was idle in 1899, and has never emerged from the condition of a prospect. Farther southwest the vein carries abundant tetrahedrite, probably in. bunches.

Mountain Queen mine.- Situated at the head of California Gulch,

1 See von Cotta: Erzlagerstatten, Freiberg, 1859, p. Ho.
184 ECONOMIC GEOLOGY OF SILVERTON QUADEANGLE. [BOLL. 183.

under Hurricane Peak, this mine may be conveniently described with 

those of Placer Gulch. It is one of the oldest workings in the 

district, and in 1877 shipped 370 tons of ore to Lake City. This ore 

was carried by pack animals to Rose's Cabin at $3 per ton, and is 

said to have contained 30 ounces of silver and 64 per cent of lead. 

The mine was most active from 1878 to 1880, and during one of these 

years is reported to have shipped $60,000 worth of ore. It was still 

shipping ore in 1882. It was worked by an open cut and through a 

vertical shaft. There are at least two large lodes, and the shaft is 

sunk at or near their junction. The largest strikes N. 80° E. and 

dips south 75° to 80°. Its croppings are very prominent and in 

places over 200 feet wide. It is quite likely the same lode as that on 

which the Custer claim is located, but is not worked in the Mountain 

Queen. The lode exploited in this mine appeai-s to strike about N. 

42° E. and to dip southeast at nearly 85°. It apparently curves somewhat and passes through a saddle east of Hurricane Peak, but the 

abundant talus and numerous intersecting veins obscure the course 

of the main fissure. As seen in one of the old levels, 60 feet below 

the surface, the vein is wide and adherent to its walls. The galena 

occurs as rather irregular bunches in the quartz near the footwall. 

At the present time work is carried on by a few leasers in a shallow 

shaft south of the old works. The ore as sorted for shipping is 

nearly solid galena. It is associated in the vein with chalcopyrite, 

pyrite, sphalerite, and sometimes tetrahedrite, in a quartz gangue. 

No rhodonite or rhodochrosite was seen. Fluorite was observed with 

some galena ore in a prospect about 100 feet north of the old workings, but may possibly not be on the same vein. The country rock 

of the Mountain Queen belongs to the Silverton series.-

Other lodes. Several other lodes than those mentioned have been 

worked to a small extent in Placer Gulch and on California Mountain. 

The Evening Star, on the west side of Placer Gulch, has shipped some 

ore, consisting of galena and tetrahedrite with pyrite, sphalerite, and 

chalcopyrite, in a quartz gangue. The Custer is a large lode which 

crosses California Mountain just north of the northern peak. Its 

strike is N. 81° E., and it is supposed to dip south. It is possibly the 

same lode as that upon which the Mountain Queen mine is located in 

California Gulch. The ore of this prospect resembles the Ridgway ore, 

save in the presence of rhodonite. It carries chiefly an argentiferous 

lead sulphobismuthite, wrongly called " brittle silver" by the miners, 

and pyrite. The workings are of a most superficial character. The 

Black Diamond prospect is on a strong lode striking N. 56° E. and 

dipping 80° NW., on the eastern slope of California Mountain. It is 

crossed by another lode striking N. 81° E. and dipping 80° NW., 

which passes through the saddle between the two summits of the 

mountain. The ore in this lode is chiefly a gray copper, carrying 

both antimony and arsenic, with lead and a little silver replacing part 

of the copper.
BANSOME.] DESCBIPTIONS OF INDIVIDUAL MINES. 185 

LODES OF MINERAL POINT.

General. There is probably no area within the quadrangle where 

outcrop so numerous and such conspicuous lodes and veins as in that 

immediately surrounding Mineral Point, at the headwaters of the 

Animas and Uncompahgre rivers. The general trend of these lodes 

is roughly northeast and southwest, but they are not all parallel. A 

radial disposition of the fissures is plainly discernible south of Mineral Point, recalling the similar arrangement at the head of Placer 

Gulch and in Silver Lake Basin. From the knob south of the deserted 

town (from which the latter takes its name) the croppings of many of 

the lodes can be followed with the eye for long distances to the northeast and southwest. Unlike large quartz veins in some other regions, 

the prominent veins here do not stand up uniformly as topographic 

ridges, but they are, nevertheless, often easily tracea'ble as long white 

lines stretching away over the uneven country. The summit of Mineral Point knob is formed by a heavy vein of nearly solid white 

quartz at least 60 feet Avide, which dips about 75° to the southeast. 

Toward the northeast this vein divides into three. The middle branch 

is that upon which the San Juan Chief is located, while the Bill Young 

mine is on the eastern branch. . Toward the southwest this vein passes 

over the eastern spur of Tuttle Mountain. The triangle between 

Houghton and Tuttle mountains and Mineral Point is occupied by a 

most complicated network of fissure veins. Only the more prominent 

ones can be shown 011 the map, and their representation on a map of 

this scale and character is necessarily somewhat diagrammatic. Some 

of them follow curved courses, as is well shown by a large vein which 

crosses the road just west of Mineral Point town arid extends southwest toward Lake Como.

Although so numerous and persistent, the lodes in the vicinity of 

Mineral Point have been productive of more disappointment than 

profit. Excluding the Old Lout, which will be described with the 

Poughkeepsie Gulch mines, there has not been a mine in this vicinity 

which can be said to have yielded a substantial profit over and above 

its total cost. The Polar Star, on Engineer Mountain, was formerly 

extensively worked, and produced some rich silver ore; but the ore 

shoots apparently had little depth, and the net profit of this mine was 

probably not large when it was finally compelled to close. In 1899 

and 1900 the work in this vicinity was practically limited to prospecting or the extraction of small amounts of ore from shallow Avorkings.

The prevailing country rock of the Mineral Point area is andesite, 

belonging in the Silverton series. There are also considerable bodies 

of rhyolite, which are intrusive in the aiidesite, and some latite.

Red Cloud mine. This claim was first worked about 1874, and in 

1881 is reported to have had about 1,200 feet of drifting and to have 

taken out some 800 tons of gray copper and galena ore in the progress 

of development. . The present workings consist of three shafts, a
186 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

lower adit tunnel, and an unknown extent of drifts. The mine never 

proved successful, and has been idle for ten or fifteen years. No 

examination of the underground workings was possible in 1899.

The Red Cloud lode is a very strong one. It passes through the 

saddle just east of Tuttle Mountain, where its individuality is somewhat obscured by a multitude of intersecting veins. It appears, however, to continue along the southeast slope of Tuttle Mountain and 

to form, one member of the remarkable plexus of veins about Lake 

Como. Toward the northeast it passes through the Ben Butler claim, 

and over., the dividing ridge between the Animas River and Henson 

Creek drainage. At the Red Cloud mine the lode is split into several 

members, of which the three most prominent are indicated, on the 

map. The mine is located on the western or main fissure.

Inspection of the dumps shows that much of the ore originally filled 

a brecciated zone in rhyolite. The ore contains galena, often disseminated in minute particles through the quartz, sphalerite, chalcopyrite, and pyrite, in a quartz and rhodonite gangue. Some of the pyrite 

has the radial structure usually taken as indicative of marcasite. 

(See p. 77; also PI. XI (7.) Ruby silver (proustite) is also reported. 

The crude ore is said to have contained about $40 and the concentrates about $15 per ton. The process of ore deposition was attended 

by much alteration, impregnation, and possibly some replacement of 

the country rock. Subsequently the ore was brecciated by renewed 

movement along the fissure and recemented by quartz carrying small 

amounts of .sphalerite and galena.

Ben Butler mine. This is a prospect on the same lode as the Red 

Cloud. The lode dips southeast about 75°. It is less evidently 

brecciated than in the Red Cloud. The country rock is andesite. 

The ore shows much sphalerite, with galena, pyrite, and ruby silver

(proustite), in a quartz gangue. The different ore minerals are not

uniformly distributed through the lode, but are more or less concentrated into zones or bands. The best ore is the very finely crystallized 

galena and ruby silver in a quartz gangue. This galena, minutely 

disseminated through the quartz, is called "brittle silver" by the 

miners, but chemical examination shows that this name is erroneously 

applied. These two minerals are practically confined to two streaks 

4 to 8 inches wide. The lode is a large one, and the walls are not 

exposed in the workings. The latter are 100 feet in depth and opened 

through an inclined shaft. The shipping ore is said to run about 40 

ounces of silver, 40 per cent of lead, and a little gold, which sometimes amounts to 4 ounces per ton. Work on this property was in 

progress in a small way in 1899 and 1900,, and a tunnel was being run 

to cut the lode at greater depth.

Uncompahgre Chief claim. This prospect, about a quarter of a 

mile southwest of the Ben Butler, on an approximately parallel lode, 

had a shaft 50 feet deep in 1899. The vein is in two main branches,
HANSOME.] LODES OF MINERAL POINT. 187

25 feet apart, and dips southwesterly at about 75°. The ore near the 

surface consisted of tetrahedrite, presumably argentiferous, and a 

little galena, in a quartz gangue. The tetrahedrite is erroneously 

termed "brittle silver" by the prospectors. Another mineral of 

bright metallic luster and gray color occurs near the surface. It is 

usually in small, more or less radially grouped prisms in the quartz 

and is locally termed "star silver." It proves to be a sulphobismnthite of lead and copper, probably argentiferous. The ore in the 

bottom of the shaft is pyrite in a quartz gangue. A little chalco^- 

pyrite and rhodocrosite in small vugs were also observed.

Bill Young mine. This mine, just east of the dismantled town of 

Mineral Point, is on the easternmost of the three lodes which join on 

the summit of Mineral Point knob. It produced some ore about 1876 

and was worked to a considerable extent, but it has been idle for 

many years and few data concerning it could be secured.

San Jiian Chief mine. This mine is on a very prominent lode 

striking N. 40° E. and dipping southeast at about 75°. It- is crossed 

by a second lode striking about N. 60° E., also dipping steeply southeast. The present developments consist of a shaft '300 feet deep, 

sunk at the intersection of the two lodes, and a crosscut and drift at 

the 300-foot level. The work has been unsystematically done and 

without accurate surveys or maps. No ore has yet been found in 

these workings, and it is highly probable that the drifting has all been 

done on the barren intersecting lode and not on the San Juan Chief 

lode at all. 1 .The latter has produced in all nearly $75,000 from open 

cuts and shallow shafts. The ore from these is very siliceous and 

consists of quartz and pyrite with a little tetrahedrite. The British 

Queen claim, which joins the San Juan Chief on the northeast, has 

produced some gold ore from an open cut, the gold occurring in finely 

disseminated pyrite in quartz/

In spite of its small output and the fact that no ore body has yet 

been systematically developed in depth, this mine has been equipped 

with substantial buildings and expensive machinery. The present 

mill is the second one that has been erected and has never worked on 

pay ore from the San Juan Chief. In 1899 it was supplied with two 

roasting furnaces, a Blake crusher, rolls, 15 stamps, and lixiviation 

vats. In 1900 the vats had been removed and 3 Cammett tables and 

a canvas plant substituted. These were running on ore from the Ben 

Butler. The power is steam.

Polar Star mine. This property, situated on Engineer Mountain, 

has been more thoroughly exploited than any other in the vicinity. 

The average strike of the lode is about N. 25° E., with a dip of about 

75° to the southeast. The croppings on the Polar Star claim show

1 The mine was closed in 1900, but I was informed that the main lode had been found by crosscutting on the 310-foot level. The ore, however, ran only $8 or $10 per'ton.- It is reported to 

.be 30 -feet wide. . . ....
188 ECONOMIC GEOLOGY OF SILVERTON QUADEANGLE. [BULL. 183.

very little solid quartz, and the ore occurs in a breccia zone in a latitic 

andesite. The mine was worked in the late seventies and early 

eighties, and was idle in 1899. The workings were then blocked with 

ice and inaccessible.

From the material on the dump it is evident that the ore, after filling the interstices in the brecciated zone of country rock, was itself 

shattered by later movement and cemented by white quartz. The lode 

in the lower workings was apparently not accompanied by much gouge 

and did not possess regular walls. The ore is said to have consisted 

chiefly of ruby silver and argentite in the upper workings, It was 

practically free from lead, although a little galena occurs in the vein 

and some specimens of galena ore were seen from near the southwest 

end of the claim,'next to the Mammoth. The ruby silver occurred in 

pockets in the lode. In the lower workings the high-grade silver ore 

is said to have changed abruptly to an ore consisting chiefly of pyrite 

in quartz, carrying about 12 ounces of silver per ton, with no gold. A 

similar change is said to have been experienced in all the mines on 

Engineer Mountain.

The country rock immediately alongside of and included in the 

Polar Star lode has been bleached and altered by the ore-bearing solutions and transformed to a mixture of quartz, kaolin, and pyrite. 

The nature of this alteration is discussed on pages 120-124.

The ore from the Polar Star was hauled in wagons down to the 

Crooke mill on the Animas, near the mouth of Boulder Gulch, and 

there treated by the Augustine process. It seems to have been well 

adapted to this treatment, a saving ot about 95 per cent being reported.

Other mines. The Mammoth, Syracuse Pride, and Annie Wood 

are all mines on the southern slope of Engineer Mountain upon which 

considerable work has been .expended but which are now idle. The

Mammoth is on a branch of the Polar Star lode, which here shows

croppings of solid quartz nearly 12 feet in width, dipping southeast 

at 70°. The lode material as seen on the dump is generally similar to 

that of the Polar Star. This mine is reported to have yielded about 

$30,000 in silver and gold. The Mint reports give its total product 

for 1891 and 1892 as $25,655. According to the reports of the Tenth 

Census, stephanite (true brittle silver) occurred in the Annie Wood 

and Mammoth mines, together with freibergite, ruby silver, and sulphide of bismuth. It is quite possible, however, that this is an error, 

due to the very loose use of the term "brittle silver" by the miners. 

The Mammoth and Polar Star are often asserted to be on the San Juan 

Chief lode. As may be seen by reference to the map, where the lodes 

are plotted as accurately as the scale and topography will allow, this 

assertion is improbable. They are probably overlapping fissures. 

The Syracuse Pride shipped ore to Crooke & Co., in Lake City, during 187(5, and is credited with a product of $10,000 in 1890, but the 

mine was never successful. Some ore was found in the upper work-
KANSOME.] LODES OF HENSON CREEK. 189

ings and a shaft sunk to cut the lode at depth, but no ore was found, 

and there is some doubt whether the ore-bearing A^ein was ever cut in 

the lower workings.

The Black Silver, on the crest of Engineer Mountain, east of the summit, was developed by a shaft and several tunnels run in on the north 

slope of the mountain. The lode strikes N. 38° E., and dips northwest at about 75°. It is 18 inches to 2 feet in width, and in general 

character closely resembles the Polar Star. Some very rich silver ore 

was formerly extracted near the surface.

The Mohawk, on the north side of Engineer Mountain, was not visited. It was not working in 1899 and 190.0.

The Sunset, on the southwest slope of. Engineer Mountain, is a small 

mine which has shipped a feAv tons of ore. The lode strikes N. 25° W., 

and dips southwest at an angle of 75° to 80°. It is 4 to 5 feet wide 

and consists of gouge, crushed decomposed rock, and bunches of quartz 

and ore. The country rock is a rather coarsely porphyritic altered 

audesite, like that of the Polar Star. The ore consists chiefly of tetrahedrite and pyrite in a gangue of quart/, with some kaolin.

The Wewissa is a small mine or prospect on the western spur of 

Engineer Mountain, and is credited with a production of about 113,000 

in 1890. It was shipping a galena and tetrahedrite ore, carrying silver, in 1899, the ore being taken by burros and wagons to Ouray. The 

lode is irregular and is not extensively worked.

The Early Bird, on the north slope of Houghton Mountain, is on a 

small and irregular vein striking N. 12° E. and dipping 75° to the 

east. The ore is tetrahedrite and a little galena in a gangue of quartz, 

which is in part a replacement of the andesitic country rock. The 

tetrahedrite carries as much as 300 ounces of silver, and gold up to 7 

ounces per ton is occasionally met with in small amounts. The prospect has produced 11 carloads of ore ranging in value from $19.to $100 

a ton. East of the Early Bird are two prominent lodes striking 

about northeast, one of which, the Denver, has produced a little ore.

The London, formerly worked through a shaft near the road, north 

of Houghton Mountain, is now abandoned. It is reported to have 

produced some ore carrying 3 ounces of gold per ton.

LODES OF HENSON CREEK.

G-eneral. In the northeast corner of the quadrangle are several old 

locations, some of which have produced ore in considerable quantity, 

but at the present time active work is limited to prospecting on a 

small scale.

Frank Hough mine. This mine, situated in American Fla^s, under 

the northern slope of Engineer Mountain, began work early in 1882 

on large and irregular bodies of argentiferous and auriferous copper 

ore. During 1882 the mine was worked through a shaft 250 feet deep, 

with drifts at 50, 80, 140, and 200 feet below the surface. The lower
190 ECONOMIC GEOLOGY OF SILVERTOTST QUADRANGLE. [BULL. 182.

drift was run nearly 60 feet in solid ore and 100 tons were extracted 

in running it. During this year some 60 tons of ore were shipped, 

carrying from 50 to 60 ounces of silver and 25 to 27 per cent copper. 

The gold varied from a trace up to about one-fourth' ounce per ton. 

A road was built to the mine and a great production was looked for. 

When the shaft had reached a depth of 350 feet the mine buildings 

were destroyed by fire and the mine has since lain idle. In all about 

2,000 tons of high-grade copper and silver ore were shipped. 1 From 

the accounts of Mr. J. S. Hough, who operated the mine, the ore body 

seems to have been an irregular impregnation or replacement deposit 

alongside a fissure. The country rock is a fine-grained, soft, tuffaceous sandstone, probably of andesitic origin. Near the ore body it 

is hardened and impregnated with pyrite. This material, when thrown 

on the dump, weathers to a soft, crumbling mass, stained with the 

carbonates of copper. The strike of the fissure is N. 23° E., and the 

dip, according to Mr. Hough, about 45° to the west.

Judging from specimens collected on the dump, the ore of the Frank 

Hough consists chiefly of chalcocite, often intimately intergrown with 

quartz, associated with a little chalcopyrite. There is possibly some 

tetrahedrite present with the chalcocite.

Palmetto 'mine. This mine, about 1 mile northeast of Engineer 

Mountain, is on the continuation of the Polar Star lode, which here 

has a strike of N. 23.° E. and a dip of 75° to the southeast. It was 

originally owned by J. S. Hough, who stated that the ore in the old 

workings, near the surface, resembled that in the Polar Star, and consisted chiefly of argentite and ruby silver. It sometimes ran as high 

as $500 per ton. Several carloads of this rich ore were shipped about 

1878. He subsequently sold the mine, and-a vertical three-compartment 

shaft was sunk east of the vein to a depth of 400 or 500 feet, with the 

intention of cutting the ore body at a depth of a few hundred feet.

The ore from this shaft contained much iron pyrite and was low 

grade. In 1882 a 15-stamp mill was erected on Henson Creek, a mile 

below the mine, and the ore treated by chlorination. The mine during 

this year was working five levels, and produced $14,840. It shortly 

afterwards closed. In the Mint report for 1891 it is credited with a 

product of $9,566, which, if true, indicates a temporary resumption of 

activity in that year. The total output is not known. The mine has 

been idle several years and the mill is dismantled.

Specimens of the ore and vein matter obtained on the dump resemble some of those from the Polar Star. It has been brecciated at least 

once and healed with comparatively barren white quartz. Small vugs 

lined wjth quartz crystals are common. The country rock is andesite, 

and is evidently considerably impregnated with pyrite and chalcopyrite near the vein.

Dolly Varden lode. This prospect, situated in Dolly Varden Gulch,

1 Oral communication from Mr. Jas. W. Abbott, a pioneer mineral surveyor of Lake City.
HANSOMS.]- LODES OF POUGHKEEPSIE GULCH. 191

.was producing copper and silver ore as early as 1878. The lode, as 

revealed on the surface, is a sheeted zone in an amygdaloidal andesite. The fissures comprising this zone contain very little quartz, and 

the only ore seen on the surface consisted of the carbonates of copper 

disseminated through the amygdaloid. Good ore, consisting of tetrahedrite with some ".brittle silver," is said to have been taken from a 

shaft sunk on the lode. A crosscut tunnel 600 to 700 feet in length 

was run lower down in the gulch, but did not reach paying ore. The 

dump of this tunnel shows some chalcopyrite deposited in a breccia 

zone in the andesite. The average strike of the Dolly Varden lode is 

nearly north and south, with an easterly dip.

Other prospects. On Copper Mountain the John J. Crooke, Big 

Horn, and other prospects have be'en worked intermittently for many 

years and have produced some ore, chiefly argentiferous bornite and 

chalcocite (strorneyerite), with a little galena and some native silver, 

in a gangue often containing considerable calcite. The strike of these 

lodes is usually a little east of north, with steep easterly dips. The 

country rock is andesite.

Other prospects have been opened in a small way in the gulches and 

.basins south of Henson Creek. These are chiefly galena ores, carrying some silver and a little gold, in andesite coiintry rock.

LODES OF POUGHKEEPSIE GULCH.

Q-eneral. There is no reason, other than that of convenience, for 

separating these veins as a whole from those about Mineral Point, of 

which they are in many cases the direct continuation. Formerly the 

scene of busy activity, the gulch, with the exception .of two or three 

prospectors, was deserted when visited in 1899. The first location was 

the Pough-keepsie claim, staked by R. J. McNutt in 1874. In 1879 mining was actively proceeding in several claims. A road was built from 

Cement Creek to the head of the gulch, and lixiviation works were 

erected at Gladstone to treat the ore. Since 1890, however, the only 

work done has been desultory prospecting on a small scale.

In general the longer fissures have trends varying from N. 30° E. 

to N. 50° E., with southeasterly dips. But they are sometimes curved 

and irregular, and near Lake Como occurs the most remarkable group 

of large, closely spaced lodes to be found in the quadrangle. An 

observer standing on the north side of the lake may count at least five 

prominent veins running down the steep slopes to the south and west 

and passing beneath the deep blue water of the tarn. At the point 

now occupied by the latter the fissures were deflected sharply eastward, and from the eastern side of the lake four prominent lodes and 

many smaller ones converge at a point on the ridge separating the 

head of Poughkeepsie from California Gulch. In addition to these, 

numerous other lodes come in through the saddle connecting with 

Boss Basin and converge toward the same point on the ridge. The
192 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE.' [BULL. 182.

result is a very interesting complex, which is represented as faithfulty 

as possible on the map.. But in addition to the lodes shown, the rocks 

in this vicinity are traversed by innumerable small veins and fissures 

which can not be indicated on so small a scale. Those shown are 

chiefly strong massive veins of white quartz, sometimes including 

considerable country rock, usually carrying a little rhodonite or rhodochrosite, and not showing much evidence of mineral wealth. They 

frequently branch and are linked together by smaller fissures.

In the saddle between Lake Como and Ross Basin the remarkably 

thorough manner in which the rock between the main fissures has 

been sheeted is beautifully shown. This minor sheeting is generally 

parallel in strike with the larger lodes. At the particular point where 

the structure was best shown, these sheeting planes dip westerly at 

about 60°. As many as 50 of them may frequently be counted within 

a width of a foot. There has been some infiltration of quartz along 

these minute planes of fracture, which causes them to stand out as 

little parallel ribs on weathered surfaces. The appearance in the 

western part of the saddle is as if a series of finely laminated cherty 

sediments had been tilted up at a high angle. The .local strike of this 

sheeting is about N. 35° E., but it is sometimes disturbed by later 

cross fractures. No regularity or rhythm could be detected in the 

spacing of these minor sheeting planes. The country rock is apparently andesite, but too altered and decomposed for certain identification. It may be rhyolitic.

Faulting was not detected along any of the fissures about Lake 

Como. Study of them was, however, necessarily confined to the 

surface.

Old Lout and Forest mines. These properties, situated a mile and 

a quarter due west of Mineral Point, being closely connected, will be 

described together. The Old Lout was located about 1876. Shortly

afterwards it sold for $10,000 and became, in the years of its activity, 

the most important mine in the gulch. It has produced between 

$300,000 and $400,000 worth of rich silver ore, containing bismuth. 

According to the Mint reports, about $200,000 of this amount was produced in 1884, in which year the mine was the largest producer in the 

county. It employed about 30 men, raising some 5 tons of ore per 

day. In 1886 it was sold to a London company for $200,000, and in 

1887 it is credited with a product of $86,654. The new owners ran a 

tunnel some 1,800 feet in length, from the bottom of the gulch, but 

never found the rich ore which had rendered the upper workings profitable, and about the year 1890 operations were abandoned. The 

tunnel house and the machinery were subsequently destroyed by fire. 

The upper workings were exploited by means of a shaft of unknown 

depth, which in 1899 was no longer safely accessible. The lower tunnel, being partly caved and filled with a strongly flowing stream of 

water, can not now be entered. The ore which came from it indicates
BANSOME.] LODES OF POUGHKEEPSIE GULCH. 193

a strong and well-mineralized lode carrying galena, sphalerite, chalcopyrite, pyrite, and a little marcasite, rather equally distributed in 

a gangue of quartz with a little barite. This ore is, presumably, low 

grade. Fragments on the dump show that a part of the lode consists of brecciated and altered country rock (rhyolite flow-breccia) 

cemented by quartz. The richest ore of the Old Lout is said to have 

been bismuth if erous, in which case it is probable that an argentiferous sulphobismuthite of lead occurred in this, as in other lodes in 

Poughkeepsie Gulch.

The Forest mine was worked through a vertical shaft only a few 

hundred feet east of the Old Lout shaft. Through this it was possible in 1899 to gain access to an upper level 200 feet below the 

surface. The Forest lode here strikes N. 70° E. and dips south at 

about 70°. It consists of stringers of ore, without much quartz, traversing altered country rock. These stringers are irregular, sometimes

expanding to 2 or 3 feet of nearly solid ore with included fragments 

of country rock, and again contracting to narrow veinlets. ' The ore 

is adherent to the country rock and the lode is without regular walls.

The ore, as seen in this drift and in the ore house, consists of tetrahedrite, pyrite, galena, sphalerite, and chalcopyrite, in a gangue of 

quartz and barite. The Forest mine was never a profitable producer.

The exact course of the Old Lout lode could not be determined on 

the ground, but it is more nearly northeast and southwest than the 

Forest. The two lodes come together southwest of the shafts, and at 

this junction occurred the rich bismuthiferous ore which made the 

Old Lout profitable. The lodes are said to have dipped toward each 

other, the Forest at a lower angle than the Old Lout. If this is true, 

the dip observed at the 200-foot level of the Forest is not the general 

dip of the lode.

The country rock of the Old Lout and Forest is a rhyolite, but so 

much altered in proximity to the ore bodies as to be scarcely recognizable. A specimen taken 7 feet from the Forest lode on the 200- 

foot level is completely recrystallized and consists of a finely crystalline aggregate of quartz and sericite impregnated with minute crystals 

of pyrite and galena. As seen in thin section under the microscope, 

the sericite (and possibly some kaolin) occurs in irregular areas without definite boundaries, and also scattered through the rock amid the 

quartz grains.

Maid of the Mist mine. This mine, which has apparently been idle 

for many years, lies a few hundred yards northeast of the Old Lout 

and Forest shafts. The workings comprise an inclined shaft of 

unknown depth and two tunnels, one, a crosscut, cutting the lode 

about 150 feet below the surface. The strike of the vein is about N. 

25° E., and it dips southeast about 65°. It has been drifted upon and 

stoped from several levels. In the northeast portion of the workings 

it is a solid vein of quartz 18 inches to 2 feet in width, containing

Bull. 182 01 13
194 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

fragments of altered rliyolitic country rock and ore which is apparently of low grade. Toward the southwest the vein has been disturbed by post-mineral movement and is accompanied by crushed 

wall rock and soft gouge. The course of the vein would carry it into 

the Old Lout shaft, and it is probable that both mines are on the same 

fissure.

Alabama mine. This mine, situated on the east side of Poughkeepsie Gulch, about half a mile south of the Old Lout tunnel, is 

commonly supposed to be on the same lode as the Old Lout, the strike 

of the Alabama lode being 1ST. 35° E. The dip is southeast at 70°, 

although locally variable. In general character the lode resembles 

that seen in the accessible portion of the Forest workings, but it is 

more irregular and shows less ore. It is essentially an irregular 

Stringer lead, passing sometimes into a breccia of country rock 

cemented by quartz and sometimes dwindling to a few narrow and 

tight stringers. The country rock is rhyolite flow-breccia. Considerable prospecting has been done by tunnels, drifts, and winzes, but 

apparently no ore was stoped. The mine has been long idle. On the 

other side of the gulch some work has been carried on upon the same 

vein, which here appears to dip about 60° to the southeast and shows 

similar ore.

The ore of the Alabama consists of galena, chalcopyrite, and pyrite, 

 in a gangue consisting of quartz and barite.

Poughlteepsie mine. This property is situated half a mile up the 

gulch from the Alabama and on the same side. It was located in 

1874 and has produced in all about $12,000. The strike of the vein is 

N. 62° E., and it is practically vertical. It is a strong and apparently 

fairly simple vein, frozen to the walls of rhyolitic flow-breccia. It 

produced a silver ore carrying bismuth. The pyrite in the vein is also 

Said to have carried good values. The tetrahedrite, on the contrary, 

. was poor ore. Argeiitite is reported x as occurring in the ore as mined 

in 1875. The mine was worked through two tunnels. It has been 

idle since 1891 and inspection was confined to the surface.

The ore in the bins showed chalcopyrite, pyrite, and tetrahedrite in 

a quartz gangue.

Amador mine. This mine, formerly worked through two tunnels, 

lies on the west side of the gulch. It was deserted in 1899 and little 

could be ascertained of its history or product. The lower tunnel was 

originally run in on a small vein striking N. 30° E., but it soon turns 

and cuts a vein of which the course is N. 80° W. This vein dips north 

about 60° and is a solid and fairly regular but not heavily mineralized mass of quartz. The lode has been stoped and a shaft sunk 

from the drift, evidently some years ago. The upper tunnel, 100 feet 

above, is run directty on the main lode, which is here nearly vertical, 

and shows from 3 to 5 feet of solid white quartz in the croppings.

1 Raymond: Mineral Resources west of the Rocky Mountains, 1875, pp. 383-386.
RANSOME.] LODES OF POUGHKEEPSIE GULCH. 195

The country rock, which is rhyolitic flow-breccia, of rather andesitic 

aspect, is sheeted and traversed by veinlets parallel to and for a distance of several feet from the large lode. A small mill, equipped with 

crusher and rolls and run by water power, was formerly operated at 

the mouth of the upper tunnel.

Saxon mine. This lode is apparently the same as that first followed 

in the lower tunnel of the Amador. Its strike is N. 30° E., with a 

steep southeast dip. The mine was working in 1879, and in 1890 is 

credited with a production of over $30,000. The workings were not 

accessible in 1899. The ore on the dump showed galena, sphalerite, 

tetrahedrite, chalcopyrite, and pyrite, in a quartz gangue.

Alaska mine. Situated about a third of a mile a little north of 

west from Lake Como, this mine is best known from the occurrence 

in it of an argentiferous galeuobismuthite named alaskaite by Koenig. 1 

The mine was working in 1879, and in 1881, when Professor Koenig 

collected his specimens, had two adits. The alaskaite occurs with 

tetrahedrite and chalcopyrite in a gangue of quartz and barite, the 

latter being abundant in the richer ore. Zinc blende and galena were 

not seen by Koenig, but they are abundant on the dump and in portions of the lode now accessible. Kaolin also was noted, intimately 

associated with the ore minerals. In 1887 the Mint reports credit the 

mine with a production of $35,658, but in 1888 it was hot producing. 

I was informed on reliable authority that about $90,000 had been produced in all, chiefly from one large pocket. The Alaska lode strikes 

about N. 75° E., with a dip of about 75° to the southeastward. At 

least three veins intersect at or near the old shaft through which the 

mine was Avorked; and another lode, the May Belle, which has been 

superficially prospected, lies just west of and nearly parallel with 

the Alaska lode. All these lodes carry some rhodonite and rhodochrosite crystallized with the quartz. The country rock is andesite.

In 1900 the mine was being reopened and it was possible to see 

something of the old workings, although still partly filled with ice. 

Like many other lodes in this region, the Alaska is less prominent 

under ground than the croppings would indicate. It contains much 

altered country rock traversed by stringers of quartz. It is in the 

soft altered country rock, near the quartz, that the richest ore, 

alaskaite, occurs as bunches of varying size. Pieces of this ore may 

carry as much as 3,000 ounces of silver per ton. The solid vein 

quartz, on the other hand, is low grade, carrying pyrite, galena, sphalerite, and some tetrahedrite, associated with rhodonite, barite, and 

rhodochrosite.

No ore was extracted from the main workings in 1900, but good 

bismuthiferous ore, in small bunches, was being taken out from a 

lower tunnel on the Acapulco claim, which joins the Alaska claim on 

the east and is under the same ownership.

1 Proc. Am. Philos. Soc., Vol. XIX, pp. 472-477; also Vol. XXII,p. 211.
196 ECONOMIC GEOLOGY OF «ILVEKTON QUADRANGLE. [BULL. 182.

Bonanza mine. In 1879 this mine was opened on the north side of 

Lake Corno, through a tunnel 250 feet in length, and is said to have 

produced an ore carrying gray copper (tetrahedrite) and barite. In 

1881 it was reported that 700 tons of tetrahedrite and galena ore had 

been extracted and piled on the dump, and in 1883 some 700 feet of 

development work had been accomplished. The lode was also 

exploited by a small shaft near the edge of Lake Como. No great 

amount was produced and the property has been idle since 1890. The 

ore seen on the dump in 1899 showed galena, sphalerite, pyrite, chalcopyrite, and tetrahedrite, in a gangue of quartz, barite, and a little 

rhodonite. The tetrahedrite appeared to be closely associated with 

the barite. The ore shipped is reported to have carried from 40 to 45 

ounces of silver. There are several other idle prospects about the 

lake, but they present no features meriting special description. A 

project was at one time set on foot to drain the lake by a tunnel, in 

order to secure the rich "float"which it was supposed would be 

found in its bottom. Fortunately for the projectors and for the lovers 

of the picturesque, this scheme fell through.

Other mines and prospects. The Red Rogers claim is on a very 

prominent lode just southwest of Lake Como and crossed by the 

trail from the lake to Cement Creek. This property, which was well 

known in the early eighties, has been idle for some years. It was 

developed by surface cuts and one or more small tunnels, and probably never produced much paying ore. The course of the lode is N. 

43° E., with nearly vertical dip. It is the most westerly of the numerous large lodes that converge from the south toward the lake. It 

does not appear to reach the latter, however, as it curves strongly 

eastward just north of the Red Rogers cabin (which is on the croppings), and joins the Seven Thirty lode. The Seven Thirty lode is 

one of the strongest and most persistent lodes of this region. Its

course is about N. 85° E. The dip is approximately vertical. Toward 

the west the lode passes over the ridge into Grey Copper Gulch.

LODES OF THE UNCOMPAHGRE CANYON.

General. The Uncomphagre River, below the mouth of Poughkeepsie Gulch, has cut the greater part of its picturesque gorge deep 

into the Algonkian schists. The San Juan andesitic breccias rest 

upon the uneven eroded surface of these schists, slates, and quartzites, and tower in lofty cliffs above the river. These cliffs are traversed by fractures and veins, which are particularly conspicuous 

when they cut the San Juan breccias. The cliff faces of the latter 

are sometimes directly due to the falling away of great masses of 

rock along one of these fracture planes. Some of the fractures carry 

ore, and have been worked with varying success.

Michael Breen mine. This mine, more familiarly known as the 

Micky Breen, is on a small, nearly east-and-west lode (N. 85° W.)
BANSOME.] LODES OF UNCOMPAHGBE CANYON. 197

dipping about 85° to the north. The mine has been quite extensively 

worked through five tunnels. Most of the pay ore has been extracted 

from the four upper tunnels. The lower one was a more ambitious 

venture, opened in connection with a mill in an attempt to work the 

property on a large scale. Although the lode has produced some 

good ore, it is doubtful whether it is sufficiently abundant, or accompanied by enough lower-grade ore, to justify an extensive plant. 

The Mint reports credit the mine with a total product of $105,751 

during the years 1890-1892. In 1899 the second and nearly third 

levels above the mill adit were being worked by Italian leasers at a 

very small profit. The country rock is the andesitic breccia of the 

San Juan formation.

, The lode filling is usually less than a foot in width and frozen to the 

walls. It is accompanied, however, by considerable parallel sheeting 

and veining of the adjacent country rock, and the lode itself contains 

thin sheet-like horses. The Assures are clean cut, regular, and quartz 

filled, carrying greater or less amounts of ore. Where stoped in the 

upper of the two tunnels worked in 1899, the lode consists of numerous small stringers, frozen to the country rock and separated by thin 

sheets of the latter. It is an excellent example of a deposit filling 

empty spaces in a sheeted zone of much regularity. The pay streak 

is usually only a few inches wide and lies on the south wall of the 

vein. It carries tetrahedrite, galena, sphalerite, pyrite, and chalcopyrite. The tetrahedrite is not rich in silver. Small vugs and comb 

structure are common, often with crystals of tetrahedrite and rhodochrosite projecting with the quartz into the open spaces. The 

country rock is impregnated with pyrite and chalcopyrite, but is 

sharply distinguishable from the vein filling. Fluorite was noted on 

the dump of the uppermost tunnel.

The Micky Breen lode is crossed by a conspicuous system of approximately parallel fissures striking about N. 20° W. and dipping east 

about 80° to 85°. These fissures usually carry small quartz veins, often 

showing comb structure. Two narrow and conspicuous zones of 

sheeting, accompanied by considerable veining, one striking N. 20° 

W. and the other N. 7° W., are indicated on the map. These converge toward the north and form the lode of the Silver Link mine, 

and possibly also the Silver Queen lode, in Bear Canyon, on the northern border of the quadrangle. The relation of these fissures to the 

east-and-west Micky Breen lode could not be determined.

The Micky Breen mill, on the Uncompahgre River, is equipped with 

a Blake crusher, 2 sets of rolls, 1 5-foot Huntington mill, trommels, 

and 7 4-foot Frue vanners. It was run by water power and steam. 

The mill had been idle some time when visited in 1899.

Happy Jack mine. This property is situated just west of the 

Micky B reen, and apparently on the same vein. It at one time shipped 

a little ore and then erected a mill, but the ore gave out. Mine and
198 ECONOMIC GEOLOGY OF SILVERTON QQADKANGLE. [BULL. 182.

mill were abandoned, and in 1899 the workings were not accessible. 

The mill is equipped with roasting furnace, crusher, two sets of rolls, 

trommels, three sets of mixing troughs, and vats. The ore was apparently treated by the Augustin or a similar process.

'Silver Link mine. This mine is situated on the east side of the 

canyon, about a mile north of the Micky Breen lode. Its principal 

adit is a crosscut tunnel 1,700 feet in length. The course of the lode 

is about 1ST. .12° W. It is nearly, vertical. This tunnel was run in the 

early eighties. According to the Mint reports, the total product of 

the mine for the years 1888, 1890, and 1891 was nearly $50,000. The 

mine had been idle since 1873, but was reopened in 1899.

The tunnel mouth is in Algonkian quartzite and schist, but the crosscut soon passes into the overlying San Juan breccia. The latter lies 

upon a clean and very uneven erosion surface, showing local variations in relief to the extent of 100 feet or more. Sometimes a breccia 

of schist and quartzite fragments mingled with andesitic material 

rests directly upon the Algonkian and grades upward, without break, 

into the typical andesitic San Juan breccia. There is no trace of 

movement or mineralization along this contact plane.

The lode is a sheeted zone, 20 feet or more in width. The ore is 

chiefly bornite and tetrahedrite, carrying silver and chalcopyrite, and 

occurs as bunches along some one of the fissures. It is found in 

quartz, which is largely silicified San Juan breccia. It contains from 

20 to 30 per cent of copper and sometimes as much as 300 ounces of 

silver per ton. The best ore is said to occur in solid quartz. There 

has been considerable post-mineral movement along the lode, resulting in soft gouge, and where the disturbance is pronounced it is 

regarded as unfavorable for ore. The ore usually occurs near the 

west (called the foot) wall, but it is far from continuous. The country rock on both sides of the lode is traversed by numerous parallel

fissures, along which there has frequently been some late movement, 

as attested by the presence of wet clay gouges.

An old shaft was sunk on the lode for 60 feet below the tunnel 

level, but apparently did not reach the bottom of the andesitic breccia. 

Thus it is impossible to gain from this occurrence any light'on the 

important question of what changes, if any, take place in an orebearing lode as it passes from the Tertiary breccia to the Algonkian 

schist. In 1900 this old shaft was being reopened, and it is possible 

it may be carried down into the schists.

The country rock in the vicinity of the Silver Link mine is intersected by numerous fissures, with a general trend of a few degrees 

west of north, and therefore approximately parallel with the Silver 

Link vein. Many of these fissures can be seen extending southward 

across the TJncompahgre to Mount Abrams. Their average strike, as 

seen on the surface, appeared to be about N. 5° W. Thejr dip is 80° 

to 85° to the east. At the mine these fissures, which do not, as a rule,
HANSOME.J LODES OF UNCOMPAHGKE CANYON. 199

carry conspicuous lodes, have cut the San Juan breccia into huge, 

.nearly vertical slabs (PI. VII), which, becoming .undermined at their 

bases, occasionally fall in chaotic ruins at the base of the cliff. A 

second and less prominent set of fissures, usually carrying quartz 

stringers, has a general strike of about N. 60° W. The relative ages 

of the two sets of fissures could not be determined.

Silver Queen mine. This is a small mine nearly a mile north of 

the Silver Link, in the canyon of Bear Creek, and on the northern 

boundary of the quadrangle. The lode, which is possibly a continu: 

ation of the Silver Link, here strikes N. 3° E., and is practically vertical. It is a breccia zone, 10 or 12 feet wide, in San Juan breccia, 

with a clay gouge on the east wall. The pay streak, from 3 to 6 

feet Avide, lies next the clay seam on the east wall. It is worked 

through a tunnel 300 feet in length and a 40-foot shaft with short 

drifts below the tunnel level.

As far as known, the ore occurs in three distinct bodies or shoots, 

pitching south. In such shoots there is practically no quartz, the 

ore, sometimes with a little barite, filling the spaces between the 

fragments of country rock, which is altered to a soft, putty-like 

material, locally called "talc," but in reality impure kaolin. The 

northern ore shoot, nearest the tunnel mouth, consists of low-grade 

copper ore, chiefly chalcopyrite, with subordinate galena and tetrahedrite. It is separated from the next ore shoot on the south by 

12 or 15 feet of solid quartz, carrying too little ore to work. This 

second ore body was rich in a bismuthiferous silver ore (argentiferous sulphobismuthite of lead), associated with galena, at the tunnel level, but changed into chalcopyrite in stoping upward. The 

third ore body, also separated from the second by a mass of relatively barren quartz, is almost wholly galena ore. South of this ore 

body the main lode is cut, but not noticeably faulted, by a younger, 

nearly east-aud-west vein, carrying galena, chalcopyrite, and zinc 

blende and assaying fairly well in gold. South of this intersecting 

vein the main lode is poor and grows smaller. It is to be noted that 

not sufficient work has been done to establish the fact that the three 

small ore bodies cut in the tunnel are really distinct and characterized throughout by different kinds of ore. The fact that the second 

one changed into chalcopyrite when followed upward would rather 

tend to negative this idea of the characteristic individuality of these 

ore bodies.

Post-mineral movement is indicated by the clay gouge along the 

east wall of the vein and by siinilar sheets of gouge within the Arein, 

generally nearly parallel to the walls. Contrary to the experience on 

the Silver Link, the best ore is said to occur in soft clayey ground.

The mine was working a small force in 1899, the ore being packed 

to the toll road on burros and thence hauled to Ouray in Avagons. 

In 1900 it Avas idle. The total output has been between $15,000 and 

$20,000.
200 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 183. 

LODES OF CANYON CREEK.

General. Under the above head it is proposed to describe the lodes 

of Iinogene, Richmond, and Silver basins, Potosi Peak, and other 

portions of the Canyon Creek drainage included within the bounds of 

the Silverton quadrangle. The only realty important mine at present 

being worked in this area is the Camp Bird. The Revenue tunnel, 

it is true, has its entrance at Porter, in the Silverton quadrangle, 

.but the lodes worked through it are within the Telluride quadrangle, 

and have been described by Purington. 1

Canyon Creek, from near Ouray to the mouth of Richmond Gulch, 

is crossed by a system of fractures conspicuously visible in the lofty 

cliffs of the San Juan breccia, and resembling those already noted on 

the Uncompahgre River. These fractures appear to have an average 

strike of about N. 35° W., and dip steeply northeastward. They 

divide the San Juan formation and the underlying sediments into 

huge, nearly vertical slabs. As far as observed there is no visible 

vertical displacement along these fissures. They sometimes carry 

quartz veins, which have been prospected in a small Avay.

Camp Bird mine. The Camp Bird lode crosses the head of Imogene Basin, with a strike of N. 80° W. and a dip of 65° to 85° to 

the south; the average is probably about 70°. Toward the west the 

lode has been traced on the surface into Marshall Basin, and identified with great probability with the Pandora lode, in the Telluride 

quadrangle. Toward the east the lode is less easily followed on the 

surface.

Considerable work had already been done in Imogene Basin prior 

to 1880. But no high-grade ore had been found, and the locality had 

fallen into disrepute. The Una and Gertrude claims, on the Camp 

Bird lode, had been worked for silver-lead ore, but in 1896 had been 

abandoned, like the other mines in the basin. The presence of highgrade gold Ore "was first discovered by Thomas F. Walsh, who for 

many years had industriously leased and prospected a great number 

of claims scattered over the entire quadrangle. The rich ore was 

first struck in the Camp Bird, then an undeveloped claim. It was 

found by Walsh on the dump of the Una and Gertrude claims, which 

were purchased by him in 1896 for $10,000. At the same time he 

secured control of practically all the lodes in the basin, much of the 

necessary surveying being accomplished in the deep snow of winter. 

The following year development was actively pushed. The substantial tramway connecting the mine with the mill at the mouth of the 

gulch, 2 miles in length, was completed in forty-nine days. In 1899 

the vein had been opened by a crosscut tunnel and about 4,000 feet 

of drifting, with stopes extending up to the old workings.

In 1900 this tunnel had already been superseded as the main adit

»Preliminary report on the mining industries of the Tellnride quadrangle, Colorado: Eighteenth Ann. Kept. U. S. Geol. Survey, Pt. Ill, 1898, pp. 830-838..
U. S. GFOLOGICAL SURVEY 

VIEW OF THE SURFACE WORKINGS OF THE CAMP B

The older workings are shown on the left; trie present main adit is on the right anil runs under the Urge lobe of taius 
RANSOME.] LODES OF CANYON CREEK. 201

by a much longer tunnel 300 feet below it. This is a crosscut about 

2,200 feet in length, driven S. 15° W-. It is furnished with a single 

well-laid track, and in October already connected with over 1,200 feet 

of drift, which length was being rapidly augmented. A view of the 

surface features of the Camp Bird mine and of the large lobe of 

"slide-rock" beneath which the main tunnel is run is shown in 

PI. XIV.

The country rock of the Camp Bird is the andesitic breccia of the 

San Juan formation. As this rock extends to the mouth of the gulch 

and some way down Canyon Creek, it is probably considerably over 

2,000 feet in thickness below the croppings of the lode. It thus insures 

practical uniformity of volcan ic country rock to a rather unusual depth, 

and is so far favorable to regular and persistent ore bodies.

Nearly all the ore produced under the present ownership has come 

from the level 300 feet above the new adit. The lode where intersected by this crosscut adit is a mere fracture, the thickness of a 

knife blade, accompanied by. a few small quartz stringers on the 

footwall side. The fissure soon widens to the east and west, and the 

lode lias an average width of 4 or 5 feet. When typically developed 

it is a sheeted zone in the rather fine San Juan breccia, made up of 

narrow stringers of gangue and ore alternating with sheets of country 

rock, and having fairly well-defined walls. The hanging (south) wall 

is the more regular, and a very thin seam of clay gouge shows that 

there has been slight movement along it since the lode was formed. 

Near the foot wall there is uniformly a streak of lead-silver ore, canying galena and sphalerite. This is sometimes contiguous with and 

apparently an integral part of the main lode. At other times the two 

are separated by a thin sheet of country rock. The vein is unusually 

adherent to a somewhat irregular foot wall, which is often traversed 

by irregular quartz stringers, or may be brecciated and cemented by 

quartz. Although the lode is a sheeted zone, the country rock, outside the recognized limits of the deposit, is not notably fissured. The 

foot-wall streak of galena ore has been partly brecciated and recemented 

by stringers of white quartz. This later quartz is not to be distinguished from the quartz of the auriferous portion of the lode and may 

be of the same period of deposition. The silver-lead foot-wall streak 

was the ore mined twenty years ago, before the high-grade ore lying 

alongside it was discovered. The richest ore occurs near the hanging 

wall, often directly against it, and the richest portion of the pay streak 

is indicated by dark, narrow, undulating lines of ore minerals. These 

lines define the course of small stringers, usually an inch or less in 

diameter, which are of later origin than the mass of the vein. The 

latter is a pale greenish-white mottled aggregate of quartz, fluorite, 

sericite, and calcite, thickly sprinkled with small crystals of pyrite, 

with some sphalerite, galena, and possibly other ore minerals in 

minute specks. It is probably in part altered country rock. The
202 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

rich stringers, although very irregular in detail, are remarkably persistent along the hanging-wall side of the main lode. They possess, 

moreover, a regular internal structure. Next their walls there is usually a thin layer of fluorite. Then follows a narrow band, from onesixteenth to one-eighth of an inch in width, of rosin-yellow sphalerite 

.and galena, with a few minute specks of chalcopyrite. The medial 

portion of the stringer is occupied by white quartz carrying a little 

sericite and calcite. The gold occurs chiefly free in this white quartz, 

especially close to the dark ore lines near the walls of the stringer. 

It is firmly embedded in the quartz and is often distinctly visible, 

although not occurring in large masses.

When the ore is crushed and panned, the concentrates contain 

abundant free gold in irregular hackly particles, averaging about 

0.25 mm. in diameter. Microscopic examination shows that the vast 

majority of these gold particles have the characteristics of original 

gold that has been embedded in vein quartz. A very few small, rodlike particles suggest a possible derivation from a telluride of gold. 

Chemical tests reveal the presence of a very small .amount of some 

telluride in the ore, but it has not been detected by the eye and is 

not present in sufficient amount to determine its mineral species. 

Microscopic and chemical investigation shows that the value of the 

ore is chiefly in free gold and not in telluride of gold.

The quartz in portions of the Camp Bird lode is often very glassy 

in appearance and shows little trace of mineralization, even when 

carrying some $20 per ton. Ore below $8 or $10 is not removed. The 

average value of all the material removed from drifts and stopes on 

the lode is probably not far from $40 per ton. The average on good 

stopes, however, may be three or four times this. According to a 

statement by Mr. J. W. Benson, manager of the Camp Bird mines, the 

material removed in merely running the main drift, waste included,

ran in places about $1,600 per linear foot. Much of the vein quartz 

on the upper level (300 feet above main adit) is shattered and stained 

with black oxide of manganese. The shattering of the brittle quartz 

does not appear, however, to be associated with any very pronounced 

post-mineral movement, nor has it any known effect on the tenor of 

the ore. A little rhodochrosite and considerable calcite occur in ihe 

lode, the latter often filling vugs or comb structure in the quartz. A 

soft, white, putty-like substance, which proves to be chiefly kaolin, is 

also common in the quartzose portions of the lode.

Not enough development has yet been reached to determine the 

shape of the pay shoots. The ore body on the west drift of the main 

level is about 1,200 feet in length. Other pay shoots occur along the 

vein, separated by pinches. They are said to be increasing in length 

as they are followed down. The ore bodies east of the crosscut are 

generally wider, but. of lower grade than the large one west of it.

About 1,700 feet west of. the crosscut tunnel on the main level the
BANSOME.] LODES OF CANYON CKEEK. 20&

lode suddenly contracts and splits into a few small stringers. Beyond 

this point the country rock on the south side of the drift is lighter 

colored than elsewhere and is full of irregular quartz stringers, some 

of which appear to strike southerly into the hanging wall. I was 

unable in the field to discover any contact or fault in the exposures 

in the drift, but microscopic study shows that the country rock at 

this point is a devitrified and altered rhyolite. It is probably an 

intrusive mass or dike cutting the San Juan breccia. It is exposed 

in the south wall of the drift for 15 or 20 feet, but has never been 

found on the north side. West of this contraction no ore was found 

on this level for nearly 900 feet. A barren stringer was followed for 

a portion of this distance, which finally led into the main lode, which 

was found to be offset into the hanging wall. The rhyolitic dike is 

older than the Camp Bird lode, but its presence has probably caused 

a local deflection of the generally straight simple fissure. The newly 

found portion of the lode has been drifted on for 600 feet, and IS 

being followed back toward the rhyolite and point of original deflection. This irregularity is apparently not due to faulting, but is an 

example of linked-vein structure. The western deflected portion of 

the lode has an average width of 9 or 10 feet of good ore. The dip is 

slightly flatter than in the eastern portion of the workings. In the 

present bottom level of the Camp Bird the galena ore, commonly 

found on the foot wall above, is less abundant and more bunchy. 

The dark, curving lines described in connection with the rich ore are 

less regular and continuous.

Power drills are used almost exclusively for drifting, crosscutting, 

and.stoping. The air compressors are run by electricity from Ames, 

in the Telluride quadrangle. The ore from the present main level 

is carrie.d on a temporary Hnson wire-rope tram to the tram house 

near the mouth of the new adit. Thence it goes over the permanent 

Bleichert tramway to the mill, situated at the mouth of the gulch, on 

Canyon Creek. This tramway is about 2 miles in length and has a 

transfer station at the turn in the gulch, in Richmond Basin. In 

1899 about 45 buckets Avere running over it, carrying about 700 

pounds of oro each. One man can dispatch 350 bucket loads in a day, 

of which the mill, then running 30 stamps, required from 325 to 330. 

All ore goes direct to the mill without sorting. The mill, as equipped 

in 1899, contained 2 Blake crushers, 40 800-ponnd stamps, dropping 

90 to the minute, and 20 Frue vanners. In 1900 20 more stamps 

were being added. The pulp from the batteries passes through a 

40-mesh screen over silvered copper plates 17 feet long. Thence it 

passes through classifiers onto the vanners. The latter are so arranged 

that all the slimes must pass over two vanners before escaping as 

tailings. The ore passing through the mill is often worth $200 per 

ton. The average, when visited in 1899, was said to be nearly $150. 

About 75 to 80 per cent of the total gold is amalgamated on the plates.
204 ECONOMIC GEOLOGY OF SILVEKTON QTJADKANGLE. [BULL. 182.

The concentrates rarely exceed $4 or $5 per ton of ore. The tailings 

from the main mill average from $3 to $5 per ton. They were formerly 

treated in a small auxiliary mill fitted with Wilfley tables. A cyanide 

plant was, however, nearly completed in 1900, and will treat the slimes 

directly from the mill. Power for the main mill is supplied by a 

Pelton water wheel or a 75-horsepower engine. The full capacity 

with 40 stamps is about 130 tons.

Hidden Treasure mine. This mine, just north of the Camp Bird, 

was opened in 1875, but, like other properties in Iniogene Basin, has 

lain idle for many years. It is now owned by Mr. Walsh, and will 

probably be again worked. It has at present about 2,000 feet of 

drift, and has produced some ore from its sbopes. It is opened by 

a crosscut tunnel about 150 feet in length. The lode strikes about 

N. 50° W. and dips northeast at approximately 60°. It is a regular 

lode, in part occupying a sheeted zone and in part a solid vein of 

quartz and ore. The country rock is San Juan breccia. There has 

been some later movement along the plane of the vein, as shown by 

thin, clay gouges. The ore formerly extracted is said .to have consisted chiefly of galena and tetrahedrite, and to have contained 100 

ounces of silver and 42 per cent of lead. The present workings show 

a low-grade milling ore consisting of galena, abundant sphalerite, 

and some chalcopyrite and pyrite.

Hancoclc mine. This property lies just east of the present Camp 

Bird workings, and is also owned by Walsh. The lode strikes 1ST. 55° 

W., and is very similar in general character to the Hidden Treasure. 

It joins the Camp Bird lode on the southeast. It has been idle many 

years, and is not now worked. In 1884 it was said to have furnished 

in all about 80 tons of ore, but has never been a large producer.

Yellow Rose mine. This is another old prospect, situated in Richmond Basin, upon which considerable work has been done. In 1881 

a '' strike " of ore, consisting chiefly of galena, with chalcopyrite, pyrite, 

tetrahedrite and sphalerite, argentite, and some native silver, was 

reported on level 2, 470 feet from the entrance to the tunnel. But the 

mine has never produced much. The vein strikes N. 47° W. and dips 

NE. 65°. The ore, as seen in 1899, is low grade and very similar in 

general mineralogical character to that of the Hidden Treasure.

U. S. Depository mine. This mine, with the Caribou, Grand Trunk, 

and other claims, is regarded as being probably on the same vein as 

the Yellow Rose. Considerable work was done on this mine years 

ago, and in 1887 it was credited with an output of nearly $18,000, but 

it never was thoroughly successful and has been idle several years. 

A tunnel some 700 feet in length was run in from the small mill, now 

dismantled, on the road up Richmond Basin. The vein, as opened at 

this level, is in part a fairly regular sheeted zone in San Juan breccia 

and in part a less regular stringer lead. Such ore as the mine produced came from upper workings, 400 or 500 feet higher up the slope,
RANSOME.] LODES OF CANYON CHEEK. 205

and was carried down to the mill on a light and primitive wire-rope 

tramway. The ore is a low-grade galena-sphalerite ore, resembling 

in general character that of the Yellow Rose. Some freibergite has 

also been reported. 1

Wheel of Fortune mine. This lode occupies a strong and persistent 

fissure, Avith nearly northeast-and-southwest strike, crossing Canyon 

Creek just east of the Revenue tunnel. It thus crosses such lodes 

as the Yellow Rose and Hidden Treasure nearly at right angles, and 

is the most prominent member of several approximately parallel lodes 

which may be seen traversing the southern slope of Potosi Peak.

The Wheel of. Fortune was located about 1877, and has produced 

some very rich ore. According to Mr. Krisher, now foreman of the 

Revenue Tunnel, the mine, prior to 1880, shipped some ore to JBlack 

Hawk containing 20 ounces of gold and 800 ounces of silver. In 1879 

the mine had about 500 feet of drift and shaft, and was said to have 

produced $20,000. Most of the work was done in the early eighties. 

During the latter six months of 1882 the mine shipped about 62 tons 

of ore, averaging 176 ounces of silver and 18 in gold per ton. 2 The 

ore appears to have been irregular or pockety in its occurrence, and 

is said to have contained freibergite and stephanite, 1 with galena and 

ruby silver. In 1899 the mine was being reopened after several years 

of idleness.

The local strike of the Wheel of Fortune lode is 1ST. 30° E., and the 

dip 65° to the northwest. The country rock is San Juan breccia. 

The lode is chiefly a stringer lead, but it grades on the one hand into 

a breccia zone and on the other into a fairly regular sheeted zone. It 

has been faulted along a nearly vertical transverse fissure, the southern portion of the lode being thrown about 15 feet to the west. There 

has also been movement along the foot wall, as shown by clay seams 

or gouges. The croppings of the lode extend strongly up into Silver 

Basin, and the. country rock for a distance of 100 feet or more southeast of the lode shows pronounced sheeting unaccompanied by perceptible faulting. There was no opportunity in 1899 for studying the 

ore in place. In 1900 the mine was reported to be shipping ore, but 

was not visited.

Bimetallist mine. This property, situated on Potosi Peak, and 

probably on the same lode as the Wheel of Fortune, has produced 

from $40,000 to $50,000 from a single rich pocket near the surface. 

The ore of this pocket ran usually about 10 ounces of silver and 1 

ounce of gold. Chemical examination of a specimen of this ore shows 

it to be a silver-copper sulphantimonic arsenite (tetrahedrite?), in 

which the gold is probably combined with the silver. Small portions, 

however, were very much richer. The workings were idle in 1899 

and were not visited.

1 Tenth Census, Vol, XIII, 1885, p.. b4. » Report of the Director of the Mint, 1882.
206 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183. 

LODES OF SAVAGE BASIN.

General. The upper portion of Savage Basin, although within the 

Silverton quadrangle, was included by Purington1 in his study of the 

lodes of the Telluride area. In 1899 two mines, the Tomboy and 

Japan, were working in the upper basin, while in 1900 some work 

was also in progress on the Argentina and the Columbia. The basin 

contains several large lodes and many smaller ones, all possessing a 

common northwesterly strike.

Tomboy mine. The character of the Tomboy 'lode was so well 

described by Purington3 in his report, written in 1897, that his 

account will be quoted almost entire, and supplemented by the observations made in 1899 and 1900. Pie says:

It is only within the past four years that the property known as the Tomboy 

has made any considerable product; especially in the last two years the output of 

the mine has surprisingly increased. The workings now on the vein comprise 

the length of two claims, very nearly, namely, the Belmont and the Tomboy, and 

several more claims have been located on the vein in its southern extension. The 

history of this mine is somewhat remarkable, considering its present large output.

The original location on the vein was the Belmont claim, made in 1880; and in 

1886 the Tomboy claim, to the south of the Belmont, was located. Since the 

original discovery of the lode, and up to the year 1892, no considerable product 

was obtained; in fact, the vein was generally regarded as of little value and 

interests in the claim were sold and resold at very low figures. The Tomboy Gold 

Mining Company, which bought the mine in 1894, had it profitably working by 

April, 1895. In that year the product was nearly §600,0,00, and in 1896 the product 

was nearly $800,000. Recently the mine has again changed hands, and it is stated 

that the present monthly output averages about §90,000.

The main adit is at 12,130 feet elevation, very near the head of Savage Basin. 

The greater portion of the work has been done on one level, consisting of a drift 

over 3,000 feet in length, with stopes extending up to a height of 200 feet above 

the drift. As indicated on the map, a second adit, 381 feet vertically below the 

upper one, is being run to cut the vein. At the time of my visit this was 1,128

feet in length. Its starting point is directly above the site of the Tomboy mill.

All the portions of the vein worked during 1896 were in the upper augite-andesite, 

although the contact of this with the top of the San Juan breccias lies not far 

below. The lower adit is certainly in the breccias, but the exact level at which 

the contact occurs it is impossible at present to state. A specimen collected in a 

winze sunk 100 feet from the main level, although it contains fragments, is of the 

normal color characteristic of the augite-andesite. and is altogether so decomposed 

that its microscopic determination is impossible. It was stated that a dike accompanies the Tomboy vein for a part of its length, as now developed. Although I 

can not say that the observations in the mine confirmed this statement, nor that 

the microscopic examination revealed any rock differ ing, from that of the country 

in general, yet in view of the limited examination which was made, it can not be 

denied that a dike may exist. 8

The peculiarities of the Tomboy vein, considered with reference to the fissure 

systems which it follows, have been described and illustrated. 4 So constantly 

does the vein shift from one to another set of fissures that it is impossible to get,

1 Preliminary report on the mining industries of the Telluride quadrangle, Colorado: Eighteenth Ann. Rept. U. S. Geol. Survey, Pt. III. 1898.

2 Op. cit., pp. 838r841.

3 No dike was seen in my own examination. F. L. R.

4 See Purington, op. cit., p. 778. '
RANSOME.] LODES OF SAVAGE BASIN. 207

at any one point in the workings, a compass reading which represents its average 

course. This is, however, as may be measured from the surveys plotted on the 

map, N. 41° WV, while the dip averages 77° to the southwest. The limits of the 

narrowly cleaved zones, which have been filled by ore, are fairly well defined, and 

it is only occasionally that stringers accompany the main lode, separated by any 

considerable amount of wall rock. Such stringers have been found, however, at 

as great a distance as 10 feet from the main vein. The width of the main lode is 

variable, but is generally from 4 to 7 feet. It sometimes attains the width of 12 

feet, and in one place pinches to less than 1 foot. This vein presents more the 

character of a solid filling between two walls than most of those seen in the district. 

The linked-vein type is very well shown in some places, but is subordinate, 

' Angular fragments of the country rock are frequent, and are especially well 

shown in the faces of the stopes and drifts on account of the whiteness of the 

surrounding quartz. Figure 73 shows such a fragment included in the quartz. 

As before stated, the angular character of these fragments is one of th6 strongest 

pieces of evidence that the ore is the filling of open spaces, unaccompanied by 

molecular replacement of the country rock.

The vein minerals are remarkably few in number, and, with the exception of

the quartz, do not appear to bear much relation to the values, which are almost 

entirely in gold. The quartz is by far the largest constituent, is white, and may 

be described as coarsely saccharoidal, with the spheroidal arrangement of crystals 

noted above. It is remarkable that much of the quartz which is commonly 

referred to as " bony," and is ordinarily barren of values, is, in the Tomboy vein, 

rich in gold, and often contains free gold visible to the unaided eye. Accompanying the quartz there is much blackish, soft material, which has been determined 

as peroxide of manganese. Although no manganese carbonate has been found in 

this vein, its general occurrence in neighboring veins makes it probable that it 

was formerly present, and the oxide is in part the result of its decomposition. 

The vein, on the whole, pi-esents an unusually decomposed appearance, as does the 

wall rock in contact with it. Much white, clay-like material, usually of a sticky 

consistency, from its saturation with water, is of universal occurrence in the 

vein. This is, indeed, present in such quantities as to give considerable difficulty 

/in the milling of the ore. It is usually known as " talc." Doubtless much of it 

is merely material residual from the trituration of the country rock along the 

fissured zones. Some is, however, of more definite composition, and chemical 

tests prove it to consist largely of finely divided sericite one of the potash micas. 

Kaolinite has been shown to occur with it, its presence being probably due to 

surface decomposition of portions of the wall rock included in the lode. The 

greater or less amount of this material in the vein does not appear to bear any 

relation to the value of the ore.

Calcite, and probably siderite, occur. The occurrence of fhiorite has already 

been described at some length. Iron pyrite is present in small amount, and the 

gold values do not appear to be associated with it to any extent. More often 

than otherwise it occurs associated with galena and zinc blende in a narrow 

streak, which crosses from one wall to the other in the vein, and is fairly continuous through the workings. Small quantities of sulphurets are,'however, 

disseminated throughout the vein. The gold is more than three-fourths free, its 

total value being about §20 to the ton. The concentrates run §40 to §45. The 

gold averages 0.735 fine. The gold has not been found in the iron pyrite except 

in small amount. Much of it is extremely finely divided, and hitherto difficulty 

has been experienced in saving it at all.

Since Purington's observations were made, the lower tunnel has 

been extended through the main lode to what is known as the "North 

vein," or Iron vein, some 300 feet beyond. The main lode was cut
208 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

through and considerable drifting clone on the low-grade North lode 

before the fact was suspected that the main lode had been overshot. 

These two veins show a very interesting relationship, which will be 

further described later on. This main adit connects, through stopes 

and raises, with the drifts of the "300 level," 140 feet below the "200 

level." A shaft has also been sunk for 300 feet below the 600 level 

(main adit level), and drifts run in both directions on the main lode 

at the 700 and 800 levels, while drifting was about to begin also on the 

900 level in 1900.

Purington states that the "vein presents more the character of a 

solid filling between two walls than most of those seen in the district." 

To one coming to the study of this lode from the Silverton region, to 

the east "and southeast, its striking feature is the regular and narrowly spaced zone of sheeting and the fact that the lode is composed 

of a series of more or less regular plates of quartz separated by sheets. 

of country rock. In fact, this structure, combined with that characteristic of the linked-vein type, are the two most prominent structural 

features of the Tomboy lode. The peculiar intersections, at small 

angles, of various fissured zones referred to by Purington ! appears to 

be a relatively subordinate feature, and was recognized by me at only 

one place. There is one curve in the main vein which is found on all 

the levels. At this curve on the 600 level a few small stringers were 

noted running out into the walls. However, in any but ideal exposures it is manifestly a most difficult matter to distinguish the intersections described by Purington from what I have preferred to regard 

as an example of linked-vein structure.

The dip of the lode varies from 50° to 80° to the southwest usually 

about 70°. It is commonly accompanied by a wet seam of clay gouge 

along the hanging wall. Along the foot wall is a stringer, or vein, 

somewhat more, solid than the auriferous portion of the lode, carrying galena and zinc blende and '' frozen " to the wall. This foot-wall 

streak is sometimes in contact Avith the higher-grade gold-bearing 

quartz, sometimes separated by a plate of country rock. Its solidity 

and fresh appearance is often in great contrast to the rusty auriferous 

ore alongside. It has been brecciated in places, and the ore solidly 

healed with white quartz. The foot wall alongside it has been rather 

irregularly fractured and veined.' I was unable to ascertain whether 

this foot-wall streak was distinctly different in age from the auriferous portion of the lode.

The crushed and decomposed aspect of the gold-bearing part of the 

lode,, often accompanied by black oxide of manganese, kaolinite, 

sericite, and copper stains, has been referred to by Purington. That 

these portions of it have been subjected to some movement subsequent 

to the original deposition of the quartz is shown by the presence of 

clay seams traversing the ore. Subsequent fractures filled with wet

1 Op. cit, p. 778, fig. 66. .
KANSOME.] LODES OF SAVAGE BASIN. 209

200 Level

clay gouge and crushed quartz frequently enter the lode obliquely 

from the southwest. Some of the richest bunches of ore said to have 

been found were where they intersect the main lode. The best ore 

usually occurs in the steeper portions of the vein. The pay shoots 

are stated to lie flat, one above another, and to extend diagonally 

across the lode from northwest to southeast.

The richest ore is invariably found in the shattered and stained 

parts of the lode, generally alongside a soft gouge of crushed and 

decomposed andesite. The gold usually occurs free and very finely 

disseminated. When visible, it is embedded solidly in the unpromising-looking vitreous quartz, although Mr. Roscoe Wheeler, the assayer at the mine, 

informed me that he had-found one 

piece of gold in a fracture plane in the

quartz. In the more recent workings, 

below the 300 level, the vein is, as a 

whole, less shattered and stained. Even 

at the 800 level, however, portions of 

the lode exhibit the character above described, accompanied by clay seams, 

and such portions are always rich. On 

this level the vein is sometimes 10 to 12 

feet wide, with 2 to 3 feet of galena ore 

on the foot wall, the latter ore being 

more abundant here than in the upper 

levels.

The description thus far lias been of 

the main Tomboy lode. There remain 

to be described the Iron lode and its 

relation to the Tomboy. The two lodes 

are nearly parallel in strike, the Iron 

vein having a slightly more westerly 

course than the Tomboy, which is about 

N. 40° W. But the Tomboy lode dips 

to the southwest, whereas the Iron

vein dips northeast. As a consequence of this diversity of dip 

the two veins intersect, so that the Iron vein, which above the 300 

level was encountered on the northwest side of the Tomboy, on the 

lower levels is found on the northeast side. .Near the main adit this, 

intersection takes place at about the 300-foot level, but the line is not 

horizontal. The slight difference in strike of the two lodes gives their 

intersection a pitch to the northwest of about 6° from the horizontal. 

The intersection in vertical plane is shown in the accompanying cross 

sections (figs. 14 and 15), drawn from notes of surveys made by 

Mr. John Herron. The relation of these lodes is such that at each

0 10 20 30 40 SO

far.

FIG. 14. Cross section of the Tomboy 

and Iron lodes through No. 2 raise, 

between the 000-foot and 200-foot 

levels. Platted from notes of surveys by Mr. John Herron.

Bull. 182^01- -14
210 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [HUM,. 182.

Cross-cut*-

Cross -cut.

ZOO Level

300 Levet

level, if carried far enough, there should be found a place where the 

two lodes cross in a horizontal plane. The confluent portions, howevei'j must lie much farther northwest, theoretically about 950 feet 

for each additional 100 feet in depth. The workings as yet are not 

sufficiently extensive to determine whether this feature of their intersection actually holds true on all levels. The intersection of the lodes 

led to a curious error when the present main adit tunnel (600 level) 

was run. In all the old adits above the 300 level the relatively barren 

Iron vein had been cut before reaching the Tomboy lode, the two 

being 220 feet apart on the 200 level. In the 600 adit, however, the

Tomboy was first cut, and as it 

was not productive at this point, 

it was supposed by those then 

in charge of the exploitation to 

be the Iron vein reversed in dip. 

Consequently the adit tunnel 

was continued 185 feet farther 

to the Iron vein, which was 

then worked on the supposition 

that it was the Tomboy. It is 

generally barren, but on this 

level shows an ore body about 

15 feet wide and over 100 feet in 

length. It.is, however, a galena 

ore, carrying about 40 ounces of 

silver, and totally different from 

the Tomboy ore.

The exact nature of the intersection of the two'lodes is not 

determinable from present exposures. In raising from the 

600 level to the 200 level on the 

Iron vein for the purpose of 

connecting with the upper drifts 

on the Tomboy lode, it was 

found that these raises came 

out as much as 50 feet within the hanging wall of the latter lode and 

connection had to be made by crosscut/ting (figs. 14 and 15). It was 

noted that each of these raises passed at some point .through a great 

mass of somewhat shattered quartz, usually about 12 feet wide, and 

with no regular walls. This was probably the intersection of the lodes, 

as indicated by subsequent surveys. One of the best pay shoots in the 

mine occurred at a point which was afterwards discovered to be on or 

near this line of the intersection. On the 300 level, northwest drift, 

the gradual convergence of the Tomboy and Iron lodes has been 

traced by crosscutting at intervals from the former to the latter. At

eoo Level

PiG. 15. Cross section of the Tomboy and Iron 

lodes through No. 12 raise oil the Iron lode and a 

neighboring raise (projected) on the Tomboy 

lode. Platted from notes of surveys by Mr. 

. John Herron.
RANSOME.] LODES OF SAVAGE BASIN. 211

the point where the intersection probably takes place is a confused 

mass of quartz, altered country rock, and ore over 12 feet wide, with 

irregular walls. From this ore body two veins again diverge, which 

ma}7 represent the northwest continuations of the Tomboy and Iron 

lodes. They are here small and have not yet been much drifted upon. 

It is at present impossible to determine the relative ages of the Tomboy and Iron lodes. It is not unlikely that their ages are substantially 

the same.

The contact between the San Juan breccia and the overlying massive 

andesite belonging to the Silvertoii series occurs in the Tomboy at 

about the 300 level, but the two rocks are not very readily distinguished under ground. It does not appear that the change in country 

rock has effected any noticeable change in the character or quantity 

of the ore.

In the general sheeted character of the Assuring, in the vitreous

nature of most of the auriferous quartz and in its shattered and 

stained appearance, in the presence of a low-grade galena streak near 

the foot wall, and in the almost exclusively gold output, the Tomboy lode 

shows much similarity to the Camp Bird. About nine teen-twentieths 

of the Tomboy product is gold.

The Tomboy mill is equipped with 2 Union and 1 Blake crusher, 2 

sets of rolls, 8 Huntington mills, and 24 Frue vanners. The pulp from 

the Huntingtons is passed over silvered amalgamating plates, which 

retain over 75 per cent of the gold. The Huntingtons are the equivalent of about 60 stamps, and the capacity of the mill is about 200 tons 

daily. The power is electricity transmitted from Ames, 12 miles distant, to a 150-horsepower motor. A Corliss engine of 120 horsepower is held in reserve.

The water supply of the Tomboy is drawn from a small lake on the 

eastern side of the divide, in Ouray County. It is pumped to the 

mine by electric power from Ames.

The Tomboy has produced from $4,000,000 to $5,000,000.

Japan mine.'1 The Japan vein is nearly parallel with the Tomboy 

and lies to the southwest. It is recognized as crossing the main Tomboy adit tunnel at about 900 feet from its mouth, and therefore about 

835 feet southwest of the Tomboy lode. It has been drifted on for a 

.short distance, but in the Tomboy ground is too small to work. The 

workings of the Japan mine lie about one-fourth mile northwest of 

the Tomboy adit, and the two mines are not connected. Not much 

work had been done on the Japan prior to 1894.

The course of the Japan lode is about N. 47° W. The general dip 

is to the southwest at from 70° to 80°, although on level No. 1 the 

exceptionally low dip of 50° was noted.

1 Since this description was written, readjustment of the primary triangulation of the United 

States Coast and Geodetic Survey has resulted in placing the Japan and Columbia mines outside 

.of the Silverton quadrangle. The descriptions, however, are retained as originally written.
212 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

A crosscut tunnel of about 250 feet, running a little west of north, 

gives access to the vein on the No. 1 level. Below this level, at intervals of 125 feet, are levels 2 and 3, worked through a shaft from No. 

1 level. The lode as a rule is an unusually regular plate of ore, having an average width of about 18 inches and generally frozen, to the 

walls. Less frequently it is a regular sheeted zone, 3 or 4 feefwide, 

the stringers of ore and quartz showing comb and vug structure. 

Even where the lode is a simple solid vein a foot in width, the walls, 

especially the foot wall, may show conspicuous sheeting for some distance from' the ore. The hanging wall is usually smooth and regular. The country rock of the portions of the vein now worked is 

andesitic breccia of the San Juan series.

The ore consists of galena and sphalerite, with a little free gold, 

argentite, and wire silver, in a gangue of quartz, rhodochrosite, and a 

little fluorite. A banded structure is often very noticeable. Atypical section of the vein as seen in one of the stopes is shown in fig. 5 

(p. 69). In this case the stringers of barren-looking quartz next the 

walls appeared to be of later age than the banded ore between them.

The average value of the Japan ore is about $25 per ton. Nearly 

one-half of this is in gold, the other being equally divided between 

silver and lead. All the ore, except a little streak of rich lead ore, 

which often occurs in veins, is milled.

About 150 feet northeast of the Japan vein is a second parallel 

lode the Morning vein with the same general dip as the Japan. 

Where cut by the Mikado crosscut from the No. 1 level of the Japan, 

this vein is only 5 inches wide and carries galena ore, frozen to the 

walls. Elsewhere it is wider and often carries much coarsely crystalline pale-green and white fluorite. This lode is not worked:

About 750 feet northeast of the Morning vein the Mikado crosscut 

passes through a third parallel vein, here not much more than a fissure 

cariying some gouge. In all, the Mikado crosscut has been driven 

nearly 1,900 feet to the northeast in the hope of cutting the continuation of the Tomboy lode. Several small fissures, generally parallel 

with the Japan lode, have been cut, but none of them carry ore in 

commercial quantities. Apparentty the Tomboy lode does not continue so far to the northwest, or else is diminished in size and changed 

in character so as to be unrecognizable.

The Japan and Morning veins are both faulted by the Flora vein, 

with a course of N. 65° E. and a dip of 55° or 60° to the southeast. 

This is a barren quartz vein about 2 feet wide filling a fault fissure 

which has thrown the southeastern portion of the Japan and Morning 

lodes about 16 feet to the southwest. This same vein probably faults 

the Tomboy lode also, in ground not yet explored, and may be connected with the failure of the Tomboy to appear in the Mikado crosscut. The position of the Flora vein is well marked on the surface, as 

its outcrop determines the presence of a little ravine.
RANSOME.] LODES OF SAVAGE BASIN. 213

About .150 feet southwest of the Japan lode lies the Whale vein, 

striking N. 40° W., and therefore a member of the same generally 

parallel system of veins to which belong the Tomboy, Iron, Japan, 

and Morning lodes, with others jei to be described. The dip is southwest at 75°. The Whale is a small vein, seldom over 6 inches Avide, 

and consists of solid white quartz carrying some free gold. It has 

been worked near the surface and has produced some rich gold ore. 

It is cut in the Climax tunnel, an unused upper level lying east of the 

Flora A'Cin. The Climax crosscut also continues into the Japan lode 

(here called the Climax) and on to the Morning A^ein, 170 feet beyond. 

The andesitic country rock between these A^eins shoAvs pronounced 

parallel sheeting.

The Japan mill is equipped with 1 Gates crusher, 2 sets 12 by 20 

Davis rolls, 6 3-compartment Harz jigs, 1 5-foot Huntington mill, 2

6-foot Wilfley concentrators, and 2 4-foot Triumph concentrators.

 PoAver is furnished by a 50-horsepOAver Westinghouse motor supplied with electricit}7 from Anies. The capacity of the mill is about 

60 tons. The total product of the Japan has been about $600,000.

Argentina mine. This is located on a AT ery prominent lode cropping near the bed of Savage Creek, just southAvest of the Tomboy and 

Japan mines. The strike of the lode is about N. 35° W., and the dip 

75° to 80° to the southwest. The croppings, often stained black by 

oxide of manganese, may be traced over the ridge to the southeast 

into Ingram Basin and beyond the edge of the quadrangle to the 

northwest into Marshall Basin. It is one of the prominent group of 

strong, continuous, generally parallel lodes of this region, to which 

belong the Smuggler, Cimarron, Tomboy, Japan, and countless smaller 

veins. As early as 1882 and 1883 seA^eral shafts Avere sunk on the 

Argentina claim and some rich free-gold ore Avas taken out near the 

surface, but for many years the mine has been idle. In 1900, however, the Tombo3r Company took hold of the property and drove a 

tunnel on the vein. In August a length of 800 feet had been attained, 

and the Avhole width of the lode Avas being milled.

The lode nowhere shows less than 5 feet of ore, and in places is 12 

and 15 feet wide. The country rock is the San Juan andesitic breccia, 

with some massive andesite. There is no gouge and no regular Avails. 

Stringers from the main vein-filling traverse the hanging Avail irregularly, and the best ore is usually found in this mixture of stringers 

and country rock.

The ore shoAvs galena, sphalerite, chalcopyrite, pyrite, and sometimes free gold, in a gangue of quartz and rhodonite. It is Arariable 

in tenor, but as a Avhole carries about $16, chiefly in gold, with less 

important Aralues in silver and lead.

The present Avork is considered merely as prospecting, and the ore 

removed in drifting has been treated in the Tomboy mill. 1

A tramway has since been erected, connecting the Argentina with the Tomboy mill.
214 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Columbia mine. This property is also 011 a prominent lode which 

lies southwest of the Argentina, and which is the southeastern continuation of the Cimarron \7 ein in the Telluride quadrangle. The 

Columbia mine is at present not extensively or continuously worked. 

The vein as seen underground is much like the Japan, but less regular. Its strike is about N. 30° W., with.a variable dip of 60° to 75° to 

the southwest. The ore is sometimes 2 feet in width, but more often 

about 10 inches. In places it is solid, consisting of quartz, galena, 

sphalerite, and pyrite, with little or no gouge; but often it is crushed 

and pinched by post-mineral movement along the fissure. As in the 

Japan, parallel sheeting of the walls of San Juan breccia is a noticeable accompaniment of'the. vein. The stringers of quai'tz which often 

fill the fissures in the sheeted country rock are practically barren.

All the ore is concentrated. The best of it carries about 1 ounce of 

gold, 70 ounces of silver, and 30 per cent of lead.

North Chicago mine. This property, which has been idle for some 

time, lies in Savage Basin near its head, and is perhaps on the Tomboy 

lode. It was worked through a shaft.

ORE DEPOSITS OF THE RED MOUNTAIN REGION.

General. Under this head will be described the various ore deposits occurring about Ironton Park and Red Mountain. They include 

ordinary fissure lodes and replacement deposits of more than one kind. 

But the bodies of ore which gave this particular region its fame are 

of a type less commonly met with in other districts. The ore occurs 

in so-called "chimneys" i. e., nearly vertical bodies of ore roughly 

circular or elliptical in plan. Unfortunately, owing to the idleness of 

these mines, satisfactory study of the ore bodies is not at this time 

possible. In a few cases access was had to the old upper workings,

but for information in regard to the deeper portions of the deposits 

recourse must be had to a few published descriptions, the annual 

reports made by superintendents to the directors of companies, and 

to information gathered from those who were familiar with the deeper 

mines before they shut down. The latter is sometimes conflicting, 

but by judiciously weighing its various sources and by making allowances for different points of view an endeavor has been made to. 

supply as nearly as possible the unavoidable lack of observation at 

first hand.

The country rock in which the Guston, Yankee Girl, and neighboring mines lie is a part of the Silverton formation. It is an andesitic breccia, usually somewhat decomposed near the surface, and 

apparently originally of rather homogeneous character. With it are 

associated some flows of massive andesite. Locally the rock has been 

so altered by thermal action as to obliterate its original features. It 

is changed to a white or yellowish siliceous mass, in which the breccia 

structure is usually obscured or lost. Quartz is abundantly visible
BANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 215

in it as fine veinlets and irregular bunches, and the mass generally 

contains much finely disseminated pyrite. The nature of this alteration has already been fully described on pages 124-131.

The Silverton breccia is cut by numerous dikes, sills, and irregular 

intrusive masses of andesite. Intrusive plug-like masses of monxonite-porphyry, carrying conspicuous phenocrysts of orthoclase and 

quartz in a fine gray groundmass, are also common. Such a mass is 

exposed at the roadside between the Yankee Girl and Guston mines.

The general character and distribution of the typical Red Mountain 

ore deposits have already been discussed (pp. 103-104), and it is only 

necessary in this place to proceed directly to the detailed descriptions 

of the various mines.

Yankee Girl mine. The Yankee Girl ore body was discovered in 

the autumn of 1881 by John Robinson. 1 In 1882 it was being opened 

by two shafts, each about 50 feet deep. At that depth the ore is said to 

have been about 9 feet wide, consisting chiefly of galena with bunches 

of chalcopyrite, and carrying as much as 80 ounces of silver and Go 

per cent of lead. The ore body was rapidly opened up and proved 

large and rich. In 1883, with a thousand feet of drifts and-shafts, 

about 3,000 tons of ore were extracted, with an average value of nearly 

$150 per ton. The product for this year is given in the Mint report 

as $400,000, and the ore is said to have carried a high percentage of 

lead. In 1884, according to the same authority, the mine was producing about 40 tons a day, which, at $150 per ton, would be something 

over 12,000,000 for the year. This, however, is obviously an excessive 

estimate. In 1887 the output is not known, but was probably much 

less than $200,000. In 1890 it is credited with $1,352,994, the silver, 

as usual, being given at its coinage value and no return being made for 

copper or lead. In 1891 the product is given as $001,465 in gold and 

silver, and in 1892 ib had fallen to $95,445. Of this amount $5,200 

was in gold,. $48,333 in silver (coinage value), $3,632 in lead, and 

$38,280 in copper. Thus these fragmentary records show that in the 

course of ten years' working the ore changed, within a vertical distance of 1,000 feet, from one carrying chiefly galena to one rich in 

copper.

This has probably been the most widely known and most productive mine in the Red Mountain district, although closely rivaled by 

the Guston. But it was an expensive mine to operate on account of 

the irregular form of its large ore bodies, the abundance and corrosive 

activity of its waters, and the necessity of hoisting and pumping 

through deep shafts. These adverse conditions, in conjunct/ion with 

a falling off in the value of the ore and the decline in. silver, finally 

caused the mine to shut down about 1896.

The Yankee Girl ore body lies in Silverton breccia (possibly extend1 T. A. Rickard (Trans. Am. Inst. Min. Eng., Vol. XXVI, 1800, p. 942) states that the discovery 

was made in August, 1S&J, by Andrew Meldruin. This is apparently erroneous.
216 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

ing below into the San Jnan breccia), which, in the vicinity of the 

mine, is decomposed and weathered near the surface. Such croppings 

as may formerly have been visible have been covered by the shaft 

house and other mine buildings. The mine was formerly worked by 

a vertical shaft over 1,000 feet in depoh, which in 1899 was nearly full 

of water, rendering the workings wholly inaccessible.

T. E. Schwarz 1 described the Yankee Girl ore in 1883 as occurring 

"in four chimneys, three near the south side of a dike and the fourth 

near the north side of another .dike some distance away. The ore in 

each chimney is similar and often occurs in bowlder form." In 1880 

Mr. S. F. Emmons made a brief Adsit to the mine and recorded his 

observations in the following notes, not hitherto published:

The main shaft is sunk about on a level with the road, but the old tunnel runs 

in from the bottom of the valley below, which slopes here very steeply; the tunnel 

cuts the shaft about 75 feet from the surface. From the top of the shaft dovrn 

to the tunnel level the ore was lead ore, mainly galena and pyrite. From the 

tunnel level down the ore began to change, copper coming in and lead disappearing; below the third level is practically no lead. The rich ore is now a purple copper ore with stromeyerite, copper glance, copper pyrite, and some gray copper and 

barite. Outside the ore body the country rock is impregnated with fine-grained 

pyrite. In the Orphan Boy, one of the Yankee Girl claims, is some manganese 

spar, but it is not at all common.

The mine has six levels, the adit making the first. The sixth level is at a depth 

of 500 feet. The shaft has been sunk 113 feet deeper, and a station made for a 

seventh level, which has not yet been opened.

The ore is found in several cylindrical or elliptical chimneys, called, respectively, 

the Yankee Girl, Orphan Boy, North, West, and South chimneys. The main 

shaft was sunk about in the middle of one of these chimneys the Yankee Girl. 

The discovery shaft, about 50 feet north of the main shaft, was 10 feet down in 

this body when the mine was. finally purchased for §125,000. In the first and 

second levels the main shaft is still in this chimney, but below it is cut at an everincreasing distance south. The chimney is nearly cylindrical in shape, 20 to £0 

feet in diameter, and consists of white quartz rock, more or less impregnated 

with mineral. Around this is country rock, somewhat decomposed, and impregnated with pyrite a sort of transition material; be}rond this is unaltered breccia. 

Dike rock, according to Schwarz, is always within 15 feet or less of the ore shoot. 

The west drift on each level, running off as a rule a little south of the shaft, 

generally cuts through the "dike rock" and finds another chimney beyond it. 

But the shape of the dike is very irregular; in one drift it is over 100 feet wide, in 

the next below almost wanting, and comes in again in the next below. According to Schwarz it sometimes runs quite flat for a considerable distance. Herecog 

nizes two dikes running in his ground, and another running from the Guston 

into the Robinson. I observed many joint planes or cross fractures, some showing 

slickensided surfaces, and these generally form walls to the ore bodies. Although 

these have a prevailing direction northwest, there are many other directions, and 

their surfaces are sometimes curving. It is my impression that such planes have, 

admitted or given form to the ore bodies, and Schwarz admits that there is always 

a prominent one running with the longer axis of the ore body, which often tapers 

up into it when running out.

Kaolin occurs, presumably pure, but resembling Chinese talc, although not so 

translucent. Bournonite and enargite occur in the Yankee Girl; also polybasite 

in the upper part.

1 Proc. Colo.- Sci. Soc., Vol. 1,1883-84, p. 132.
RANSOME.] DEPOSITS OF EED MOUNTAIN EEGION. 217

Iii a paper published in 1888 Mr. Emmons 1 says:

In the Yankee Girl there are several chimneys in which the ore occurs. They 

are of elliptical outline, the longer axis corresponding in direction with a main 

system of fractures running through the region. Although the striated surfaces 

of these planes show that there has been movement along them, there is but little 

evidence left of actual brecciation of the country rock, the ore solutions having 

completely replaced the andesitic country rock between the fracture planes which 

gave access to them; in places a siliceous skeleton is left, the basic constituents 

being replaced by vein material; in other places a solid body of metallic minerals 

is found, while the country rock adjoining the body of pay ore is impregnated to 

a considerable distance with low-grade sulphurets.

This same year (1888) Mr. Emmons paid a second visit to the 

Yankee Girl. He found 2 that on the sixth level, 432 feet deep according to Schwarz, the Yankee Girl ore body was connected by ore with 

the Orphan Boy, a small ore '' chimney," lying in the upper levels about 

150 feet south of the Yankee Girl. On this level the Yankee Girl ore

body was elliptical in plan, 10 feet wide, and 32 feet long. At the 

fifth level it was nearly cylindrical, 8 to 10 feet in diameter, and 

nearly solid galena, passing below into '' gray copper ore." Just below 

the sixth level occurred a "floor" or horizontal fault plane. This 

varied from. 3 inches to a foot or more in thickness, of clayey 

attrition material, and frequently contained rounded masses of ore 

with rock centers. It dipped to the westward, sometimes as much as 

25°. There seemed to him to have been some movement along this 

floor to the westward or downhill toward the valley, but that the ore 

bodies had not been much displaced. A third or "west ore body"* 

lay to the westward of the Yankee Girl shoot, lenticular in shape, 

with, its longer diameter nearly north and south. On the sixth level 

this was 2 or 3 feet Avide and 8 or 10 feet long, but with rather 

poorly defined boundaries, the ore fading off into mineralized country 

rock.

Mr. Emmons records that 

Around each chimney of oi'e is an envelope of "quartz." This is a blue siliceous 

material, sometimes granular looking, sometimes compact and almost jaspery, 

and yet in the mass full of cracks, and .sometimes of vesicles which are filled 

with white kaolin. It is generally impregnated with fine-grained pyrite. The 

ore, moreover, fills little fine cracks or seams down to an eighth of an inch in 

width. These are sometimes large enough to be worth taking out in the vicinity 

of the ore body. Outside the " quartz " envelope comes the "white rock," which 

is evidently altered porphyry, which passes into a hard, compact blue rock, which 

is probably the less altered variety.

What was called quartz at that time in the mine, Mr. Emmons considers at the present time to have been a jasperoid or siliceous replacement of the country rock. He also states that replacement is very 

abundant in the volcanic breccia, the matrix being first replaced by 

ore, which finally coats the pebbles or fragments of the breccia.

1 Structural relations of ore deposits: Trans. Ain. Inst. Min. Eug., Vol. XVI, 1888, p. 834.

2 Unpublished notes.
218 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Mr. T. E. Scliwarz, for several years superintendent of this mine, 

has kindly furnished some important data in regard to the ore bodies. 

The ore in the Yankee Girl shoot, down to No. 1 level, a distance of 

75 feet, was chiefly galena, and averaged 77 ounces of silver and 36 

per cent of lead. From No. 1 level to No. 2 level, 80 feet, it averaged 

242 ounces of silver and 29 per cent of copper, lead not being given. 

The galena, however, was disappearing, and the characteristic mineral from the second to the sixth levels was stromeyerite, associated 

with chalcopyrite, pyrite, and occasional occurrences of argentite and 

other rich silver ores, some of which carried bismuth. Similar changes 

took place in the Orphan Boy shoot, although the galena continued 

to greater depth. On the sixth level (432 feet deep) these two ore 

shoots came together, a straight drift in continuous ore connecting 

them. A few feet below this occurred a heavy, strong, nearly horizontal seam or slip carrying much "talcy" material.

The rich ores of the Yankee Girl disappeared at this seam, no stromeyerite or 

other distinctive rich silver mineral being found below it. The main Yankee Girl 

ore shoot continued down through it without perceptible change of position,"and 

was large and strong from No. 6 to No. 8 levels. The character of the ore changed, 

however, and "peacock copper,'' with pyrite and chalcopyrite became its constituents. Bornite I took to be the principal ore for large masses. To show grade of 

selected ore produced from richest stopes, I may note a shipment of 10 tons which 

carried 3,270 ounces of silver and 29 per cent of copper. A smaller lot of 7,360 

pounds returned 5,301 ounces of silver and 28.75 per cent of copper. 1

1 Speaking from memory, Mr. Schwarz believes that the ore in the 

bottom levels of the Yankee Girl was low grade and carried more 

pyrite than above.

These various descriptions of the ore bodies are given at some 

length, since they are not in perfect agreement on all points, and yet 

they furnish cumulative evidence of the truth of certain important 

features.

Mr. Schwarz2 has also published a description of the ore bodies of 

which the Yankee Girl is the type. He says, in part:

The ore occurs in "chimneys," so called, having in some cases an elliptical or a 

circular cross section, but more generally long in proportion to their width. The 

greatest length of ore body so far observed has been about CO feet.

The immediate envelope of the ore chimneys is " quartz," which is sometimes of 

considerable extent, while the whole is inclosed in an area of greater or less extent 

of andesite.

The andesite is metamorphosed in proportion to its nearness to the ore chimney, 

showing more kaolin and quartz and less of its original structure. It thus merges 

into a fine-grained brown or grayish quartz, sometimes very hard and flinty, and 

again quite porous. In depth the quartz matrix becomes less characteristic.

1 Personal letter from Mr. Schwarz. It is not clear, in view of the figures just given by Mr. 

Schwarz, just what he means by saying that no rich silver ore occurred below No. 6 level. He 

probably refers merely to the inineralogical change in the ore from stromeyerite to bornite, or 

he may mean that these high-grade lots came from above level (i. The high copper percentage^ 

however, would not indicate this.

2 Notes on the ore occurrences of the Bed Mountain district: Proc. Colo. Sci. Soc., Vol. Ill, 

1888, pp. 77-85.
RAXSOME] DEPOSITS OF RED MOUNTAIN REGION. 219

In the case of six chimneys occurring on the Yankee Girl, Guston, and Silver 

Bell properties, being the only ones on which depth has been obtained, a marked 

increase in the silver content of the ores occurred irom the surface down to 300 to 

400 feet of depth.

Changes of character of ore with depth are noticeable in several chimneys, but 

notably so in the Yankee Girl chimney. In this case the distinctive minerals, in 

order of depth, have been galena, gray copper, stromeyerite, and bornite. In those 

chimneys in which enargite has been the surface ore no depth has yet been 

obtained.

The chimneys frequently change their pitch, sometimes quite suddenly. * * * 

A jump of 15 to 25 feet along some horizontal plane is not infrequent. * * *

Every chimney is connected with one or two cleavage or fracture planes, which 

bound a portion of the ore body, while on the other sides the ore merges into the 

quartz or andesite. These planes usually show strialions, slickensides, and more 

or less gouge material, but are not of great persistence laterally.

Horizontal planes occur of great strength, which have indirectly had marked 

influence on the ore bodies, changes of character occurring at such horizons.

In the Guston and Yankee Girl the increase in the amount of the copper ore 

with depth is notable, as is also the fact, that the silvei- is confined mainly to such 

ores.

Mr. Schwarz supposed the ore to have been brought in by solutions 

moving chiefly along horizontal planes, perhaps bedding planes, and 

to have been derived from the andesite of the region. His explanation is essentially that of a rather narrowly confined lateral secretion. 

The maximum length of 60 feet was probably exceeded by the ore 

bodies worked in the Yankee Girl and Guston subsequent to 1888. 

One of them is reported by one who saw it to have been 140 feet in 

length and 20 feet wide. According to Schwarz, several carloads of 

ore from the Yankee Girl carried from 1,500 to 3,000 ounces of silver 

per ton, and one lot of about 6 tons contained 5,300 ounces of silver 

per ton. Such ores carried 30 to 33 per cent of copper.

According to Mr. J. Owen, who formerly worked in the Yankee 

Girl and is at present superintendent of the Silver Lake mines, the. 

rich bodies of stromeyerite, which had been so productive prior1 to 

.1888, began to change, at about 500 feet in depth, to bornite, which, 

although lower grade, was yet good ore. At this level there was a 

fault encountered which threw the lower portion of the ore body to 

the west. Below this the deposit, according to Owen, has more the 

character of a vein 10 or 12 feet wide and running "north and 

south." It consists, near the bottom of the shaft, of large bodies of 

bornite, with some chalcocite, assaying as much as 57 per cent of copper. (As pure, nonargentiferous bornite contains only 55.5 per cent 

of copper, this assay, if correct, would indicate the presence of considerable chalcocite.) Two carloads of this ore were shipped by Owen 

from a winze 40 feet below the bottom of the present shaft, and it is 

said to be abundant at that depth. From the eleventh level ore was 

shipped worth from $500 to $700 per ton in silver and copper. The 

latter averaged about 20 per cent No large bodies of iron pyrite 

were found in the Yankee Girl, according to Owen.
220 ECONOMIC GEOLOGY OF SILVEBTON QUADRANGLE. [BULL.1S2.

At present the Yankee Girl shaft is about 3,050 feet in depth. A 

plan of the extensive levels shows an intricate maze of workings in 

which no linear system is discernible. The mass, of the Avorkings lie 

just west of the shaft, and in plan may be roughly inclosed in an irregular triangle. A smaller extent of workings lies just east of the shaft.

Inspection of the dump, as well as inquiry, shows that there was 

never much vein quartz associated with the ore. The "quartz "of 

the miners is very largely the bleached and silicified countiy rock 

adjacent to the nearly solid bodies of ore. Where vein quartz occurs 

it usually carries iron pyrite. Barite, in small masses and crystals, 

occurs embedded in the bornite. The chalcocite is generally' intimately associated with small amounts of chalcopyrite. Some specimens,.show that the ore has been fractured and recemented by veinlets 

of calcite. The ore minerals observed on the dump were galena, 

sphalerite, chalcocite (stromeyerite), bornite, chalcopyrite, and pyrite. 

Cosalite was recognized in 1884, therefore, in the upper part of the 

deposit, and was analyzed by A. H. Low, 1 as follows:

Analysis of cosalite from Yankee Girl mine.

Constituent.

Silver .................................

Per cent.

36.22

8.70

28.22

3.74

Constituent. Per cent.

<1 .IS

18.64

100. 00

Pronstite and polybasite also occurred occasionally in the Yankee 

Girl ore bodies.

All accounts of the Yankee Girl mine unite in emphasizing the 

chemical activity of the underground waters encountered in the workings. According to Schwarz 2 they contained "24 grains per gallon of 

sulphuric acid (SO3 )." Candlesticks, picks, or other iron or steel tools 

left in this water become quickly coated with copper. Iron pipes and 

rails were rapidly destroyed, and the constant replacement of the 

piping and pumps necessary to handle the abundant water was a 

large item in the working expenses. All agree in stating that the 

water entered far less abundantly below the sixth level. Some who 

worked in the mine express it as being " not so bad" below that level. 

But closer inquiry usually elicits the information that it was less abundant but as much or even more corrosive than at the upper levels.

The product of the Yankee Girl is roughly estimated at about 

$3,000,000.

Robinson mine. This mine is really a part of the Yankee Girl, 

both being Avorked together. It has produced some good ore, but

1 Proc. Colo. Sci. Soc., Vol 1,1884, p. 111.

"Trans. Am. Inst. Min. Eng., Vol.'XVIII, 1889-90, p. 139,
RANSOMK] DEPOSITS OF RED MOUNTAIN REGION. 221

little could be ascertained concerning the details of its occurrence. 

According to Mr. J. Owen, the ore changed to iron pyrite, but the 

depth at which the change took place was not stated by him. The 

shaft of the Robinson is sunk alongside one of the mounds of siliceous 

altered breccia characteristic of this region.

It is stated by Mr. Owen that a distinct vein or fissure was followed 

from the Guston into the Robinson, and was demonstrated by drifting to extend into the Genesee-Vanderbilt. The same fissure was 

cut by an east crosscut in the Yankee Girl..

Crustonmine. This ore deposit, just north of the Yankee Girl, was 

opened shortly after the latter, in 1882. The ore body as exposed at 

that time is said to have been 5 feet wide and carried 58 ounces of 

silver per ton. It was chiefly galena, with some copper mineral, probably tetraliedrite. In 1883 the mine produced, according to the Mint 

reports, $57,500. In September, 1887, steps were taken to form the

present New Guston Company, Limited, of London, England, and 

the mine was closed until June, 1888, when work was resumed with 

Mr. T. E. Schwarz as superintendent, and extensive bodies of ore 

were found on the third, fourth, and fifth levels, yielding in carload 

lots up to 450 ounces of silver per ton. The depth of the mine at this 

time was only 288 feet, while the Yankee Girl was down 1,050 feet. 

The product for 1888 was about $130,000. In 1889 ore was produced 

to the value of over $390,000, and work was carried to the sixth level, 

378 feet from the surface. Mr. James K. Harvey this year- succeeded 

Mr. Schwarz as superintendent. At the close of 1889 the mine had 

already paid dividends amounting to £56,374 (about $274,000). In 

1890 the shaft was sunk to the seventh level and extensive stoping 

carried on in the upper levels. Ore to the amount of 4,469 tons was 

sold, which realized $491,336 (£101,098), or an average of nearly $110 

per ton after deducting treatment charges. Several carloads of this 

ore carried from 600 to 1,400 ounces of silver per ton. The product 

this year was principally from the stopes of the fifth and sixth levels. 

The ore carrying most silver was encountered on the fifth level north 

of the shaft, and contained 12 per cent of copper. At this time there 

were from 200 to 300 men employed in the mine, and the small settlement of Guston had grown up in the vicinity of the shaft. The water 

pumped from the mine this year was about 35 gallons per minute, 

and is said to have been charged with sulphuric acid from oxidation 

of pyrite. The Mint reports credit the mine with a total output of 

864,768 ounces of silver and $57,500 in gold for 1890. The product in 

copper is not given. In 1891 the main shaft had reached the ninth 

level, about 678 feet below the surface, and the water had increased 

to about 50 gallons per minute, being of the same corrosive character 

as that found in the upper levels. The ore raised this year amounted 

to 11,723 tons, which realized $824,467, or an average of over $70 per 

ton, net value. The cost of mining was nearly $19 per ton, while
222 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BCLL.183.

during the preceding year it had averaged about $32 per ton. The 

decrease in the price of silver was already affecting the profits of the 

company. In 1892 the ore raised amounted to 14,291 tons, which 

realized approximately $247,232, or an average of only about $17.40 

per ton. .The cost of mining was about $13 per ton. This great 

decrease in value was due not only to general fall in the price of silver, but to a falling off in the grade of the ore. The shaft had been 

sunk to the tenth level, but no important bodies of ore were discovered in the 200 feet between the eighth and tenth levels, and the product was chiefly from the nearly worked-out stopes of the upper levels, 

from No. 3 to No. 7. In 1893 the shaft was carried down 136 feet 

T3elow the tenth level and a crosscut started on the eleventh level. 

The ore raised amounted to 7,280 tons, which sold for $18.40 per ton. 

The water now pumped from the mine amounted to 60 gallons a minute. In 1894 a large quantity of ore was extracted, chiefly from the 

ninth to the twelfth levels, of which the greater part, being low grade, 

went to the Silverton matte smelter, then beginning operations. In 

1895 the maximum tonnage for any year 14,833 tons was extracted 

from the mine, but the average value was lower than ever before. 

The annual tonnage, average sales value of the ore per ton (gross 

value less cost of treatment), average cost of mining per ton, and 

amount of dividends paid, covering the eight years in which the mine 

was in most active operation, are shown in the following table, compiled from the annual reports of the directors of the company:

Tonnage, ore values, cost of mining, and dividends of Guston mine.

Year.

1888.....-----........ ........ ....................

1889.. ........ ............................... ........

1890...... ...........................................

1891.........-.-............-.. .....---.-..-....

1892...---.-.. ....-_..--.- .....-----..

1893.. ...................... .....................

1894......................... ....... .-. -' ....

1895.....-.. .....................................

Total..... ....................................

Ore raised.

Tons.

315

3 889

4,469

11,723

. 14,291

7,280

13,334

14,833

- 69,137

Average 

sale value 

per ton.

§363.25

. 131.50

109.80

70.65

17.40

18.40

12.80

10.70

a 91. 81

Average 

cost of 

mining per 

ton.

$53. 50

32.60

32.25

18.90

13.10

17.30

9.60

10.20

a 23. 43

Amount of 

dividends 

paid.

$77, 941. 90

181,875.00

315,250.00

436, 800. 00

146,713.50

1.148,579.40

a Average.

In 1897 the mine was compelled to cease operating, the low grade of 

the ore and the decline in the value of silver having acted together 

to render further work unprofitable. The total output since 1888 has 

considerably exceeded $2,500,000, of which nearly half was distributed 

in dividends. In all, 14 levels had been worked and a depth of nearly 

1,300 feet attained. To free the mine from water at this depth the 

pumps were required to raise over 100 gallons a minute and great care
RANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 223

and constant attention was required to prevent the destruction of the 

pumps and column by corrosion.

When visited in 1899 the mine was filled with water to the second 

level, 114 feet below the surface. The level of this water fluctuates 

with the seasons, and in spring sometimes rises to the first level, 50 feet 

from the surface. As the deeper workings are wholly inaccessible, 

the following description of the ore bodies is drawn from the annual 

reports of the superintendents, Messrs. Schwarz and Harvey, and 

from personal conversation with men who worked in the mine.

In their general shape the ore bodies resembled those of the Yankee 

Girl. They were roughly ellipsoidal masses standing nearly vertical, 

and consisting of nearly solid ore with very little gangue, surrounded 

bjr altered country rock impregnated with pyrite. The actual sixes of 

these masses of ore are difficult to ascertain at the present time. Some 

of the stopes were nearly 200 feet in length and seAreral hundred feet 

in height. The width of the ore varied greatly in different bodies and 

in different portions of the same ore mass. A^7"idths of from 20 to 30 

feet appear to have been not uncommon.

The ore-body stope on the seventh level was, in 1892, 45 feet in 

length and 94 feet average height. The width of the ore for a distance 

of 20 feet was 14 feet; elsewhere less, and irregular. The ore from this 

stope carried from 20 to 80 ounces of silver and 0.3 ounce of gold per 

ton, with from 5 to 8 per cent of copper. The middle stope on the 

same level had a length of 116 feet, an average height of 87 feet, and 

an average width of ore of 22 feet. Its ore carried from 15 to 35 

ounces of silver and 0.2 ounce of gold per ton. These are given 

simply as examples of typical stopes which produced large amounts of 

rather low-grade ore.

These ore bodies usually occurred along what was termed the "ore 

break," a zone of altered, disturbed, and more or less broken country 

rock, intersected by slip planes and containing much kaolin, as well 

as soft attrition material. This ore break is said to traverse the 

Guston claim from end to end, which would give it a course of from 

20° to 30° east of north and to be, in places at least, nearly 60 feet in 

width. From levels 2 to 7, a depth of 364 feet, this ore break, dips 

steeply to the east; but just below the seventh level a slip or fault was 

encountered dipping 45° to the west, which cut off the ore entirely. 

By following the soft clay gouge which occupied this fracture plane 

the ore break was found again below, lying from 30 to 50 feet to the 

westward. It here dipped steeply westward and did not carry much 

ore. It was not until the tenth level was reached that its dip again 

became easterly and it resumed the character which it had had above 

the seventh level. The ore in this level also was better, or at least in 

larger bodies, than anything hitherto found below the seventh level.

The ellipsoidal or irregular ore bodies were nearly always found in 

connection with this ore break, but they were most irregularly placed 

and were found only by persistent and thorough prospecting, partly
224 ECONOMIC GEOLOGY OF SILVEBTON QUADKANGLE. [BULL. 182.

with the diamond drill. In general the longer axes of the ellipsoids 

appeal- to have been nearly parallel with the trend of the ore break. 

Individually, however, the ore bodies show much variation. Thus, on 

the thirteenth level a streak of ore is recorded as bearing N". 30° W. 

They were commonly found by'drifting along the "soft ground," 

presumably fracture planes associated with attrition material and 

kaolin. A plan of the underground workings of the Guston mine 

(PL X\r) shows a highly intricate and irregular maze of drifts and 

crosscuts running out in all .directions from the shaft. The map,

«00 fa

FIG. IK. Longitudinal and transverse sections through the Guston mine.

however, shows distinct evidence of a general elongation of the ore bodies, or of the ore-bearing ground, along an axis bearing about N. 20° E. 

As shown by the longitudinal section of the mine, the stopes attained 

their greatest aggregate length, about 600 feet, on the fifth level, and 

grew shorter below. Longitudinal and transverse sections of the 

"main ore body," compiled from a mine map made in 1890 and from 

the annual reports of the company, are shown in fig. 16. The transverse section was evidently intended to show the general position of 

the so-called ore break, and not of the actual ore bodies.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 182 PL. XV

MAP OF A PORTION 

OF THE

UNDERGROUND WORKINGS

OF THE

GIJSTON AND ROB INS ON MINES

Corapiledfronn.3nin.eiiiapsinadeial890 and 1895
RANSOMB.] DEPOSITS OF BED MOUNTAIN EEGION. 225

One of the most interesting and important facts in connection with 

the Gnston, as well as with other mines of this district, is the change 

in character of their ores Avith depth. The galena ore of the main ore 

body, carrying from 50 to 60 per cent of lead and from 30 to 40 ounces 

of silver, continued down to the second level, or a little beyond, Avhere 

it is said to have changed rather abruptly to high-grade stromeyerite. 

Galena, however, occurred in the mine in considerable quantities down 

to the fifth level, 288 feet in depth, and in decreasing amounts to 

greater depths. Some heavy galena, carrying from 100 to 175 ounces 

of silver, is known to have occurred at a depth of 212 feet. With 

increasing depth stromeyerite, or argentiferous chalcocite, became the 

characteristically rich ore of the mine, associated with pyrite and 

chalcopyrite. Some of this was very rich, and in 1891 some ore from 

the sixth level (378 feet) carried as much as 15,000 ounces of silver 

and 3 ounces o.f gold per ton. The lowest-grade ore in the deeper

workings was pyrite, which usually carried less than 20 ounces of silver and a fraction of an ounce of gold per ton, and from 3 to 5 per 

cent of copper, probably from admixture of chalcopyrite. The chalcopyrite was higher grade, usually carrying from 12 to 45 ounces of 

silver and a fraction of an ounce of gold per ton, and from 8 to 12 per 

cent of copper. Even in the best stopes of the fifth and sixth levels 

there was always more or less chalcopyrite and pyrite associated with 

the rich stromeyerite, the lower-grade ores apparently often prevailing on the peripheries of the larger ore masses.

Below the slip plane, which occurred just below the seventh level, 

at about 500 feet in depth, the ore was harder and more compact and 

stromeyerite was not found in any quantity, the ore down to the tenth 

level consisting chiefly of large masses of low-grade pyrite, with some 

bornite and chalcopyrite. The pyrite rarely carried as much as 20 

ounces of silver, with a little gold and copper. Some bornite found 

on the ninth level (678 feet) carried from 125 to 450 ounces of silver 

and one-fourth to one-half ounce of gold per ton, with 25 to 50 per 

cent of copper. This was associated with chalcopyrite carrying 16 to 

75 ounces of silver and gold up to 1 ounce per ton, with from 8 to 15 

per cent of copper, and with pyrite carrying up to 15 ounces of silver 

per ton, with a little gold and copper-. In both the ninth and tenth 

levels small quantities of ore were frequently met with carrying free 

gold, assays from level 9 giving as much as 29 ounces of gold per ton.

The ore of the eleventh level was similar to that of the tenth, but, 

as in all these lower levels, the rich bornite bore a smaller proportion, 

to the low-grade pyrite and chalcopyrite than did the stromeyerite and 

galena of the upper workings. The ore in the stopes connected with 

these levels varied in width from 18 inches up to 25 feet. Some free 

gold was seen in barite, associated with the bornite. On level 12 .ore 

occurred in large solid masses, one being known to be 72 feet in length,

Bull. 182 01 15
226 ECONOMIC GEOLOGY OF SILVERTON QUADBANGLE. [BULL. 182.

with a maximum width of 37 feet. But it was chiefly low-grade pyrite 

containing occasional nodules of bornite ancl. chalcopyrite, usually 

with some barite. Substantially identical ore was found on the thirteenth level.

Through the kindness of Mr. Bedford McNeill, of London, liquidator of the New Guston Company, the following notes, dated March 

13, 1900, were obtained from Capt. James K. Harvey, formerly superintendent of the mine:

Galena ore was most abundant in the superficial workings, it having been 

met with almost at surface, and continued down to the fourth level. The ore 

contained from 8 to 50 per cent lead; silver, 9 to 30 ounces; gold, trace per ton.

At the third level chalcopyrite and chalcocite were discovered, and continued 

down to where the fault was encountered, a few feet underneath the floor of the 

seventhlevel. Contents of ore: Copper, 5 to 15 per cent; silver, 25 to 700 ounces; gold, 

0.1 to 3 ounces per ton. A few cars were shipped (about 10 tons to the car) that 

ran over 1,200 ounces silver per ton, with a corresponding gold increase.

From the third to the sixth level the ore occurred in the form of a chimney, its 

dimensions being from 12 to 15 feet in length and width at the third, fourth, and 

fifth levels, to 20 to 30 in length and width at and over the sixth level. Underneath the sixth level the ore lengthened south approximately 200 feet, with a width 

of from 3 to 30 feet.

Solid bodies of iron pyrites were discovered at the sixth level, and continued to 

the deeper workings. Contents: Silver, 4 to 20 ounces; copper, 1 to 3 per cent; gold, 

trace to 0.20 ounce per ton.

Bornite was met with in quantity between the ninth and twelfth levels. Contents: Copper, 18 to 25 per cent; silver, 60 to 175 ounces; gold, one-fourth to 1| ounces 

per ton. Free gold was found occasionally with the bornite; that is to say, on the 

fluorspar ' associated with the bornite. No free gold was seen above the ninth 

level, or in any other instance.

There was but little change in the volume or character of the water. It was 

destructive to pumps and column if they were not properly protected.

Generally speaking, the inclosing porphyry was more decomposed where the 

ore was most compact and richest in its metallic contents.

From the foregoing it appears that there was first an increase in

the value of the ores down to the sixth or seventh level, and then a 

sudden falling off in value at the slip-plane below the seventh level. 

Below this occurred a diminution in the richness of the ore down to 

the bottom of the mine. The characteristic ore minerals, in the order 

of the depth at which they prevailed, were galena, stromeyerite 

(pyrite?), bornite, chalcopyrite, and pyrite. But this succession is 

true only in general terms. Sudden and perplexing changes in the 

value and mirieralogical composition of the ore occurred within the 

individual ore bodies at all levels, and the various minerals named 

overlapped in most complex fashion, although the bornite apparently 

had a definite upper limit and the stromeyerite a definite lower limit. 

Of all the ore minerals pyrite appears to have had the greatest vertical range, and it undoubtedly formed an 'increasing proportion of 

the ore Avith depth. The highest values in silver and gold were found 

in connection with high percentages of copper.

1 Barite ? (F. L. R.)
RANSOME.] DEPOSITS OF. RED MOUNTAIN REGION. 227

According to Mr. Terrill, at present in charge of the mine, good ore, 

consisting of argentiferous bornite, was struck in the fourteenth or 

bottom level, but was never extracted. Had there been any considerable body of high-grade ore revealed, however, it is hardly probable 

that the mine would have shut down, no considerable loss in its operation having been incurred and no assessments having been levied- on 

the shareholders when work ceased.

Mr. S. F. Emmons made a brief visit to the mine in 1888 and has 

recorded his observations in unpublished notes. lie visited a new 

find of ore on the third level, which had been overlooked by the former 

owners. This was a solid mass of chalcopyrite mixed with tetrahedrite and galena and carrying up to 750 ounces of silver per ton. He 

found that this ore body, with a strike of N. 30° E., and dipping from 

30° to 45° to the northwest, was limited on its foot-wall side by a distinct plane showing fault movement. According to Mr. Emmons,

the sheeted structure of the original country rock, which had been

replaced for a width of about 10 feet by ore, was still recognizable in 

the latter. The ore body, which was not more than 10 or 15 feet long, 

graded into quartz, clouded with snow-white kaolin, and this in turn 

into altered country rock or "white rock."

Q-enesee-Vanderbilt mine. The original Vauderbilt shaft was sunk 

just southwest of the Yankee Girl, in one of the characteristic siliceous 

knolls of the district. This consists of a hard, quartz-like rock, in 

which can still be detected outlines of porphyritic crystals of feldspar, 

now wholly decomposed, In some places the original rock is practically wholly replaced by quartz. In the Mint report for 1882 it is 

noted that the Genesee, then opened by two shafts 15 feet and 20 

feet deep, showed a body of galena 3 feet thick, associated with "copper," the whole carrying from 15 to 40 ounces of silver per ton. The 

"copper" was probably chalcopyrite or tetrahedrite. In 1888 the 

product of the Vaiiderbilt as derived from the same source was 

$72,672. It was subsequently found that the Vanderbilt and Genesee 

ore bodies were identical, or at least so closely associated that it was 

impracticable to work them separately, and the mines were therefore 

consolidated. The .present workings (fig. 17), begun in 1891, consist 

of a tunnel 820 feet in length, connecting with the old shaft through 

stopes, and a second shaft, 700 feet in depth, sunk near the end of the 

adit tunnel. Levels were run at 300, 400, 500, 600, and 700 feet below 

the tunnel level. In 1899 this shaft was filled with water to within a 

few feet of the collar. Although the mine has produced some good 

ore, it is said to have been on the whole unprofitable. The ore was of 

a lower grade than that in the Guston and Yankee Girl, and the profits 

accruing from the exploitation of one ore body were usually more than 

expended in searching for the next one. Work was finally suspended 

in 1896.

In 1899 a little ore, consisting chiefly of galena and sphalerite, was 

being taken out by leasers above the adit level. Access was gained
228 ECONOMIC GEOLOGY OF SILVEKTON QTJADEANGLE. [BULL. 183.

to one large stope extending nearly to the surface where the original 

Vanderbilt shaft was sunk. The ore body that once filled this stope 

was evidently of lenticular form, the maximum dimension nearly vertical, and the mean diameter nearly north and south. Around the 

periphery of the lens the ore body wedged out completely. I was unable 

in the accessible portions of the stope to recognize any dominant fis- 

.sure of which the lens of ore might be considered as filling an enlarged 

portion. Nevertheless it was by following the so-called slips or gouges

PIG. 17. Plan of a portion of the underground workings of the Genesee-Vanderbilt mine.

in the country rock that the ore bodies were always discovered when 

not found by drilling (fig. 18).

Mr. T. E. Schwarz has pointed out that the principal "ore break" 

of the Genesee-Vanderbilt turned through an angle of about 140° in 

passing from the surface down to the 600 level. This is indicated in 

fig. 19, taken from Mr. Schwarz's paper. 1

According to Mr. Otto J. Schulz, of St. Louis, at present trustee of 

the Genesee-Vanderbilt mine, there were four separate pay shoots on 

the surface, only one of which was explored to the 700 level. The best 

ore occurred at a depth of about 250 feet below the collar of the main 

shaft, and extended down to within about 20 feet of the 300 level.

1 Trans. Am. Inst. Min. Eng., Vol. 26,1896, p. 1058.
BANSOME.] DEPOSITS OF BED MOUNTAIN REGION. 229

This ore was solid and contained little waste. Its value is shown in 

the following table, compiled from data furnished by Mr. Schulz:

Assay contents per ton of ore from Genesee-Vanderbilt mine.

Year.

1893a .........................................................

1894a ..................................................... ....

18956..........................................................

1896c. .........................................................

Ore.

Tons. 

1,525

2, 153

5.939

3.005

Gold.

Ounce. 

0.2

.4

.2

.07

Silver.

Ounces. 

30.4

45.9

39.8

18.1

Lead.

Per cent. 

1.0

3.3

3.9

.06

a From 300 level.

b About two-fifths from 500 level and rest from upper workings.

c From 500, 600, and 700 levels. Output for 2 months only.

It is rather difficult to account for the low percentage of lead and

the very small amount of copper in these assay returns, as the silver 

was probably associated with one or both of these metals.

FIG. 18. Plan of fourth level of the Genesee-Vanderbilt mine, showing method of prospecting 

for ore bodies with the diamond drill.

The value of the ore, never high grade as a whole, fell off with 

increase of depth below the 300 level, depreciating rapidly below the 

500 level, and changing near the 700 level to large bodies of low-grade 

pyrite.

Near the surface, in the old workings, the ore is said to have been 

oxidized and soft, changing to galena at about 100 feet in depth.
230 ECONOMIC GEOLOGY OF SILVEBTOIST QUADKANGLE. [BULL. 182.

Particulars concerning the mineralogy of the ore of the GeneseeVanderbilt are now difficult to obtain. It is said to have contained 

considerable lead from top to bottom, which statement, however, is 

not fully borne out by the records furnished by Mr. Schulz. Cosalite 

is recorded as having been an important constituent of the ore". Some" 

small caves containing stalactites of pyrite occurred in the ore 

bodies, but it is not known at what depth. Specimens of ore said to 

have come from this mine and preserved in the mine office showed 

some very argentiferous bornite, a slightly argentiferous sulphobismuthite of lead containing a little copper and corresponding in

FlG. 19. Sketch plan showing changes in position of the Genesee-Vanderbilt ore bodies, with 

depth. X-T", surface outcrop of ore break; V, <?,#, surf ace outcrop of oro bodies; Jf, 0, position 

of same ore bodies on 300-foot level; P, IV, position of same ore bodies on 600-foot level; T, R, 

ore break on 600-foot level (after T. E. Schwarz).

physical properties and appearance to cosalite, and some small crystals 

of ruby silver (proustite).

The total output under the old Vanderbilt Company of Red Mountain is not known, although the Mint reports credit the mine with 

$72,672 in 1888. The output of the Genesee-Vanderbilt Company 

from 1891 to 1896 amounted to about 12,622 tons of ore, containing 

2,884 ounces of gold, 436,675 ounces of silver, 702,183 pounds of lead, 

and 30,520 pounds of copper.

The water encountered in the Genesee-Vanderbilt was of the same 

corrosive character as that met with in the Yankee Girl and Guston.
(I. S.OEOLOGICAL SURVEY BULLETIN NO. 182 PL. XVI

P:LAN OF 

UNDERGROUND WORKINGS

OF TTTK

NATIONAL BELLE MINE

Scale of feet

O 5 10 15 2O 25 75 1OO

LEGEND

Upper north tunns! Other levels

Lower north tunnel Ore bodies on surface

No. 2 level Stopes and caves opening to surface

No. 3 level (j ,'"y'.J Ore bodies in or below levels

No. 4 level I^C^l Winzes
RANSOME.]' DEPOSITS OF RED MOUNTAIN BEGION. . 231

Alexandra mine. This is situated on the slope of Red Mountain, 

a few hundred feet above the Guston. The earlier workings are .in 

one of the siliceous mounds common in this region, this one forming 

a small, elongated ridge, striking S. 85° W. The upper workings are 

reached through a tunnel. These seem to have two or more of the 

usual lenticular, nearly vertical ore bodies. One small one, stoped 

at the tunnel level, was elliptical in plan, the longer diameter striking N. 35° W. The ore pinched at the ends, but a small fissure, 

tilled with kaolinite, can be seen continuing on into the country 

rock. The ore left in this stope is a fine-grained aggregate of pyrite, 

galena, and .sphalerite, with specks of kaolinite. The country rock 

near the ore bodies is much altered, contains much kaolinite, and 

is thickly impregnated with fine pyrite. The ore is, in part at least, 

a replacement of the andesitic country rock.

About 400 feet below this woi kings is a second tunnel, from which

issues a strong stream of highly ferruginous water. This tunnel is 

how only partly accessible. It runs through a mass of bleached and 

altered andesitic breccia, now changed in places to an aggregate of 

barite, kaolinite, and pyrite. As the mine was abandoned in 1899 

or 1900, no information could be gained concerning its output or the 

portions of the workings not now open.

Grand Prize mine. This property, a few hundred yards north "of 

and about 150 lower than the upper Alexandra tunnel, is abandonee! 

and at present wholly inaccessible. Its clump shows the usual materials common to the mines of the vicinity.

National Belle mine. 1 The croppings of the bleached and silicified 

country rock associated with this ore body form a prominent knoll, 

over 200 feet in height, on the northwestern outskirts of the settlement, of Red Mountain. The principal mine buildings, adits, and 

main shaft (490 feet deep), are on the eastern side of this knob, close 

to the railway. The mine was closed and deserted in 1897, and the 

superficial workings only were accessible. A plan of the workings, 

from a mine map made in 1890, is shown in PL XVI.

The first extensive development was in 1883, when about 980 tons 

of ore were produced, valued at nearly $70,000. This occurred chiefly 

in an oxidized form in caves, as carbonate of lead, one of which, 

occurring about 22 feet below No. 2 level (fig. 20), is known to have 

been 40 feet long, 20 feet wide, and 10 feet high. This cave ore carried from 5 to 7 ounces of silver and from 15 to 60 per cent of lead. 

For 1890 the product is given as $87,591, of which $4,500 was in gold, 

&29,091 in silver at coinage value, and $54,000 in copper. It is evident that the output for this year was chiefly from the lower workings,

1 This mine is now often called the "American Belle mine," from the name of the company 

which last operated it, but the company's reports always refer to it under its original name. 

National Belle. The attempts sometimes made to change the names of mines with change of 

ownership are usually to be deplored, especially when, as in this case, the old name is well 

known in mineralogical literature.
232 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE. [BULL. 182.

in unoxiclizecl, relatively low-grade enargite and pyrite. In 1891 the 

property came into the possession of the American Belle Mines, Limited, a London company, which operated the mines until 1897. The 

report of the Director of the Mint for 1891 credits the mine with 

a product of $145,721 in gold and silver only, with no returns 

for copper. Since the sale of ore for this year yielded the company 

111 the neighborhood of $110,000, the foregoing output probably includes both copper and lead. At this time, however, the lower-grade 

copper ores could not be handled, as the nearest point at which they 

could be smelted was Denver, 500 miles distant. It was not until 

1892 that these ores could be treated in the Standard Smelter, at 

Durango.

Mr. S. F. Emmons visited the mine in 1886, and the following facts 

in this paragraph are taken from his unpublished notes. He found

TO ft

FIG. 20. Sections through the National Belle mine, showing ore bodies stoped and natural ore

that the mine had been opened very irregularly, chiefly by tunnels 

run into the knoll, with overhead stopes. "The ore chimney was 

irregular, containing oxidized ore ("sand sulphate"), with kaolin in 

seams and vugs. The ore was confined to the quartzitic rock, the 

porphyry adjoining it being impregnated with unoxidized fine pyrite, 

as in the Yankee Girl. It seemed to follow two general fracture 

planes running at right angles to the main direction of fracturing, 

viz, N. 10° W. He suggested that the copper sulphates had been 

leached out first, leaving the relatively insoluble lead salts and open 

spaces. Mr. Emmons did not visit the lower part of the mine, which 

he was informed produced a low-grade enargite carrying chalcopyrite. 

The caves characteristic of the upper workings were said not to occur 

in the lower workings. Schwarz, ! in the paper already referred to, gives

1 The ore deposits of Red Mountain, Ouray County, Colo.: Trans. Am. Inst. Min. Eng., Vol. 

XVIII, 1889-90, pp. 139-145.
RANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 233

a description of the secondary or oxidized ores of the American Belle 

and neighboring mines. They "occur above a former water line, 

either attached to walls of caves, as broken detached masses, or as a 

bed of clayey mud or sand, more or less completely filling the cave. 

The cave formation is identified with the massive ontcroppings or 

knolls of silicified andesite ordinarily termed 'quartz.' These knolls 

* * * present a rough mass of quartz, cut up by cross fractures, 

and showing small vugs and cavities on the exposed cliff faces. The 

ore-bearing caves, which ramify throughout the mass, generally come 

to the surface along the cliff base." The caves are stated to come 

together in depth. The ores were mainly carbonates of lead and. iron, 

with iron oxide, lead sulphate, and arsenates. Kaolinite and zinc 

blends were common. Galena occurred, but usually as a residue 

core. Such were the ores of the National (American) Belle, Grand 

Prize, and VaDderbilt mines, according to Schwarz. He briefly summarizes the characteristics of these secondary ores as follows:

1. The secondary ores are richer than the sulphide ores occurring below them.

2. The ores of adjoining or connecting caves are sometimes greatly different in 

grade.

3. In some cases the formation of the caves along fracture or cleavage planes is 

evident, but in others all traces of such planes are quite obliterated.

4. The cave walls are a porous sandy quartz, the sand from the disintegration of 

which forms part of the cave filling.

5. The line of change from oxidized to unoxidized ores, or the former water 

level, is very marked. It varies as much as 100 feet in elevation in properties 

within 1.000 feet of each other, rising to the south and west. The quartz outcrop 

rarely rises more than 200 feet above it.

6. In isolated cases may be found masses of the unoxidized ore, the euargite (i. e., 

in National Belle), above the line of change, in the vicinity of the secondary ores.

Mr. Schwarz ascribes the formation of the caves-and the secondary 

ores within them to "surface waters" which "dissolved" sulphide 

ores and country rock as they moved along fracture planes.

In 1899 no thorough examination of the mine was possible, the 

croppings and an adit tunnel constituting the only accessible places 

for observation. The knob, or "blow-out," as the miners commonly 

term it, is in many places plainly an altered igneous rock, probably 

andesite or andesitic breccia. But the material in which the original 

porphyritic structure is still recognizable passes with no discoverable 

line of demarcation into a rock consisting chiefly of quartz, in the 

condition of a fine-granular crystalline aggregate. On the northwestern side of the knoll the country rock was originally a monzoniteporphyry mass of the same kind as that exposed just south of the 

Yankee Girl, or forming the cliffs just east of Summit Station. This 

intrusive rock has been altered in a similar manner to the andesitic 

breccia. The comparatively fresh facies in which the orthoclase and 

quartz phenocrysts lie in a fine greenish groundmass may be traced 

into a medium stage of alteration in which the orthoclase phenocrysts
234 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182."

are still recognizable from their outlines, although changed to kaolin 

and diaspore, and finally into a white siliceous rock in which nearly all, 

or quite all, traces of original structure are lost. The exact character 

of this alteration has already been discussed on page 126. The silicified material of the knob is most irregularly and thoroughly fissured. 

The larger fissures often expand into irregular caves, which, as far as 

could be seen with the limited opportunities for observation in 1899, 

did not run in any single dominant direction. A few of the smaller 

caverns only, near the surface, could be seen. These were lined with 

crumbling, rust-colored, oxidized ore, beneath which there was often 

unaltered galena. Sometimes these caves are lined and partly filled 

with a light, porous, pumiceous sponge of quartz. This is not the 

cellular, honeycombed quartz resulting from the removal of ore by 

oxidizing waters, but is an original spongy crystallization of minute 

quartz crystals, with some interstitial kaolin. It forms a light friable 

mass that is strongly suggestive of pumice. It is analogous to the 

"sugar quartz" occurring in vugs, with sericite, in some of the goldquartz veins of California, although not to the " sugar quartz " which 

results from a crushing of the vein.

The National Belle mine has long been noted for the abundance 

and purity of the kaolin found in its workings. 1 It occurs as a soft, 

white filling of fractures in the altered country rock, or in brecciated 

zones as a matrix inclosing fragments of the wall rock. It appeared 

to be, in part at least, of more recent origin than the sulphide ores, 

but no opportunity was available to study its occurrence in the deeper 

workings or in connection with the unoxidized ores. When dry this 

kaolin forms a pure white powder which the microscope shows to consist of crystal scales, usually hexagonal in outline and about 0.1 mm. 

in average diameter. The optical properties of these crystals have 

been described by Reusch. 2 Two chemical analyses of this material 

are here reproduced, (I) by Hillebrand 3 and (II) by Hiortdahl: 4

Analyses of kaolinite from National Belle mine.

Constituent.

SiOo. ......................................... ............... .....................

A12O3 .............................................................................

Fe2O3 ............... ................................................................

HoO.. .................... ...................................... ...... ..............

F ..................................................................................

Less O for P......................................................................

I.

46. 35

39. 59

.11

13.93

.15

100.13 

.06

100.07

II.

45.57

41 52

13. 58

100.67

1 R. C. Hills: Am. Jour. Sci., 3d series, Vol. XXVII, 1884, p. 472.

2 Neues Jahrb. fur Min., etc., 1887, Vol. II, pp. 70-72.

3 Bull. U. S. Geol. Survey No. 20,1885, p. 98. 

'Neues Jahrb. fiir Min., 1887, Vol. II, p. 70.
KANSOME.'J DEPOSITS OF BED MOUNTAIN KEGION. 235

As shown by E. B. Huiibut, 1 however, not all of the white crystalline powder found in the National Belle is kaolin, but alunite also 

occurs in nearly identical form, clearly associated with enargite. 

Hurlbut's analysis is here quoted:

Analysis of alunite from National Belle mine.

Constituent.

Si03 ........................ ....... ..

AliOa. ............................. -- 

K«0. ....................................

Na.O ...................................

Per cent.

38.93

39.03

4,20

4.41

Constituent.

0

H-O ....................................

Per cent.

13.35

.50

100.48

No study could be made in 1899 of the occurrence of the unoxidized

ore, chiefly enargite, of the deeper workings of the mine. Some of

the enargite occurred lining caves beloAV the zone of oxidation, forming beautiful radiating clusters of orthorhornbic prisms several centimeters in length. These prisms are usually covered with a thin 

moss-like film of malachite and often partly incrusted with minute 

crystals of quartz.

From reports made to the company by the superintendent, Mr. 

James K. Harvey, for the years 1891-1896, the ore appears to have 

occurred in large masses irregularly distributed in the altered country 

rock and irregular in shape. The greatest recorded length of one of 

these bodies is about 75 feet, and they commonly varied in width from 

1 to 4 feet, although occasionally as much as 60 feet wide. The greatest dimension was commonly nearly vertical, and in some cases the 

chimney-like form was pronounced (see fig. 20). The unoxidized ore 

was in part enargite, carrying at its best as much as 30 ounces of silver and 40 per cent of copper. It was associated with both copper and 

iron pyrites, some tetrahedrite, and galena in diminishing amount 

down nearly to the No. 4 level. The latter, at the second level, 

occurred as streaks in the copper and iron pyrites, and carried up to 

44 ounces of silver and 60 per cent of lead in 10-ton carload lots. In 

a winze 50 feet below the third level galena occurred in small nodules 

only. In the National Belle ore the gold rarely amounted to more 

than a tenth of an ounce per ton, and was usually much less.

Practically no paying ore "was found below the third level, explorations on the fourth level resulting only in finding small bunches of 

ore and masses of crumbling iron pyrite carrying less than one-tenth 

ounce of gold and about 5 ounces of silver per ton, with from. 1 to 3 

per cent of copper. The large north ore body, which on level 3 was 

a nearly solid mass of ore 31 feet long and 24 feet wide, carrying as a 

whole 4 to 7 ounces of silver, 4 to 6 per cent of copper, and .04 ounce 

of gold, and which had been stoped up over 100 feet above level 2, was' 

not encountered in the bottom level. On level 2 this ore body was 75

i Am. Jour. Sci., 3d series, Vol. XL VIII, 1894, pp. 130,131.
236 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL.ISS.

feet long by 60 feet wide, and carried from 7 to 25 ounces of silver per 

ton and from 7 to 20 per cent of copper. It is said to have been chiefty 

iron, pyrite, and chalcopyrite, with some galena and enargite. This 

ore was firmer and of higher grade than that at the level below. 

From the annual reports of the company it appears that masses of 

iron pyrite were not limited to the deeper workings, but occurred 

above the second level, sometimes immediately beneath the carbonate 

ore. Much- of the higher-grade ore, such as enargite, galena, and 

tetrahedrite, occurred as bunches of various sizes in the pyrite.

Owing to the decline of silver to almost half its former value, the 

general low grade of the National Belle ore, and the lack of facilities 

for its economic treatment, it was found impossible to operate at a 

profit, and the mine was closed in 1897. The ground below the fourth 

level is as yet unexplored, but the diminished value and amount of 

ore at that level deterred the company from further sinking.

The water in the National Belle mine was apparently not abundant 

or troublesome, as no mention is made of it in the superintendent's 

reports. From the location of the mine and its moderate depth (490 

feet) no great amount would be expected.

White Cloud mine. This mine, now abandoned, lies less than a 

quarter of a mile north of the Guston. It appears never to have 

struck a paying ore body. The shaft is sunk on the northern end of 

an elliptical knob of bleached and silicified San Juan breccia. The 

length of this knoll is about 50 feet and its trend about N. 10° E. It 

terminates rather abruptly, with no sign on the surface of any vein 

in the line of its major axis. The silicified material of the knob is 

impregnated with small crystals of iron pyrite.

Paymaster mine. This also is an abandoned property lying a quarter of a mile northeast of the White Cloud. About 16 carloads of ore 

are said to have been shipped from one ore body, but the mine was 

never a large producer. It is credited with an output of $14,434 in 

1890. In 1899 the shaft was filled with water to within about 200 feet 

from the surface, and the first level only was accessible. The country rock at this depth is all much altered and irregularly fissured and 

the fissures are frequently filled with seams of kaolin or talc, which 

is evidently a product of the alteration of the adjacent rock. Drifts 

and crosscuts run in all directions from the shaft, but apparently no 

ore was found on this level. The ore seen on the dump and in the 

ore bins was essentially a galena ore, associated with much pyrite.

Silver Sell mine. Lying about a quarter of a mile north of the 

Paymaster, this, at one time one of the better-known and productive 

mines of the district, is also dismantled and inaccessible. The shaft, 

about 700 feet in depth, is now filled with water to within 100 or 200 

feet from the surface. Sections through the mine are shown in fig. 21. 

According to Schwarz l this mine had, in 1888, produced large amounts 

of ore carrying from 500 to 1,000 ounces of silver per ton. This rich

i Proc. Colo. Sci. Soo., Vol. Ill, 1888, p. 84.
BANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 237

ore is said to have been bismuthiferons. The product for the three 

years that have been recorded in the Mint reports is as follows, the 

silver being quoted at coinage value and lead or copper not given:

Product of Silver Bell mine.

Year.

1887... ................ .............................. .......................

18S8. ....................................................................

1890............ .I................. ........................................

Gold.

$2, 400

1,5] 3

Silver.

§77,600

72,404

24 211

Total.

880, 000

72,404

25t 723

A specimen of the rich ore, obtained from a miner who had worked 

in the mine, proved on chemical examination to be an argentiferous 

lead sulphobismuthite. Kobellite, a sulphobismuthite of lead, in which

FIG. 21. Sections through the Silver Bell mine, showing ore bodies stoped.

part of the bismuth is replaced by antimony, has been described by 

H. F. Keller l from this mine, associated with chalcopyrite and barite. 

He gives four analyses, of which the mean is here quoted:

Mean analysis of kobellite'from Silver Bell mine.

Constituent.

Bi. .................. ..................

Sb. ...... ...........................

Pb. ...................................

A 

Ou. ...................................

Per cent.

18.39

28 40

7.55

36.16

3.31

2.59

' Constituent.

Fe..... ...............................

Zn. ...................................

Per cent.

1.50

.39

.45

98.74

i Zeitschrift fur Kryt., Vol. XVII, 1890, pp. 67-72.
238 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE.

In 1890 the Silver Bell, with other mines, came into the possession 

of the American Belle Mines, Limited, of London, and in 1891 the 

mine was worked through a vertical shaft 706 feet in depth, with ten 

levels. At this depth about 65 gallons per minute of strongly corrosive water had to be removed by the pumps. According to Superintenden t Harvey, this water was "strongly impregnated with sulphuric 

acid generated from the pyrites in the ore bodies."

The rich ore found in the upper levels changed in depth to large 

bodies of low-grade ore consisting chiefly of pyrite and carrying less 

than 20 ounces of silver. Most of the high-grade ore seems to have 

been extracted when the mine came into the possession of its new 

owners, and after some attempt to work the low-grade ores in the face 

of the falling price of silver the mine was abandoned in 1894. Details 

of the character of the ore and its changes are lacking, but the ore 

bodies seem to have been generally similar, in shape and in their 

relation to the country rock, to those of the Yankee Girl.

Congress mine. This ore body, situated about a mile south of Red 

Mountain, was located in the autumn of 1881, and sold the following 

year for $21,000. In 1883, according to the Mint reports, the mine 

produced about 2,500 tons of ore, valued at $220,000. It was worked 

through an adit tunnel and a shaft 350 feet in depth sunk from the 

tunnel. In 1899, after some years of inactivity, the mine was being 

reopened. The shaft was carried to the surface and new buildings 

and hoisting plant were in course of erection.

The old workings were not accessible in 1899, but the ore bodies 

appeared to constitute a chimney-like stock deposit of the kind characteristic of the Red Mountain mines. The ore occurs in irregular 

bunches, although there is said to be some indication of a vein running 

nearly north and south. The richest ore was found in a soft, decomposed streak near the surface'and carried from $12 to $20 in gold. 

The oi-e is chiefly enargite, but there are also bunches of galena, 

which are said to occur on the peripheries of the ore bodies. The 

enargite as seen near the surface had been partly brecciated and 

recemented by a very compact, soft aggregate apparently largely 

composed of kaolin. In 1900 the mine was again idle.

St. Paul mine. This property, lying a short distance south of the 

Congress, shows certain points of resemblance to the latter. Some 

ore was formerly extracted from a shaft 75 feet deep. The present 

workings comprise a vertical shaft 200 feet deep, with some drifts 

at the 200-foot level. The ore is low grade and consists chiefly of 

enargite with some galena,' forming a fine-grained aggregate. It 

occurs in irregular bunches in much altered andesitic breccia of the 

Silverton series, which, near the ore, is heavily impregnated with fine 

iron pyrite, associated with small knots and veinlets of kaolin. No 

definite line can be drawn between ore and country rock, the former 

being largely a replacement of the latter. The ore bodies are found
KANSOMK.] DEPOSITS OF RED MOUNTAIN REGION. 239

by following small seams of gouge or kaolin in the country rock. 

There is no regular direction to these seams, and they are themselves 

curved and irregular. The mine has not produced much, but was 

shipping ore in 1900.

Carbonate ILing mine. This property, in Corkscrew or Humboldt 

Gulch, is opened by a shaft 395 feet deep. After lying idle for some 

years, work was resumed in 1900. In some ways this deposit is a connecting link between the stock or chimney deposits of Red Mountain 

and the lodes of the rest of the quadrangle. It resembles in this regard 

the Henrietta mine, which is described on another page. The ore of 

the Carbonate King occurs in a distinct fissure, striking about N. 5° 

W. and dipping west about 50°. The lode is a zone, 4 to 5 feet wide, 

of crushed country iv ck, apparently altered andesite, in which the ore 

occurs in bunches. There is usually a soft gouge on the foot wall of 

this crushed zone. The ore is sometimes frozen to the hanging wall,

sometimes separated by gouge. Between the walls is much kaolin, 

occurring in the interstices between fragments of altered unmiiieralized 

rock. It also occurs as seams in the wall rock.

There is a second fissure of similar character which branches off from 

the main lode. It strikes N. 20° W. and dips southwest at 60° to (55°. 

It consists of'a zone of crushed rock 4 to 5 feet wide, containing abun-. 

dant kaolin, and separated by gouge from uneven walls. This branch 

fissure contains bunches of galena ore.

The ore of the main lode is an intimate mixture of pyrite, one of 

more sulphobismuthites, and probabty tetrahedrite, withbarite as the 

common gangue. No vein quartz was seen. The ore streak may vary 

from a few inches to 3 feet in width. It is often absent altogether.

The bismuthiferous varieties carry as much as 500 ounces of silver, 

Avith lead and copper. Ore worth less than $20 per ton can not be 

shipped.

Midnight mine. This mine, situated in Corkscrew Gulch, a short 

distance below the Carbonate King, has not been worked for some 

years. It contained some good ore, but its extraction was rendered 

expensive by the abundant water met with. It is wholly inaccessible 

at present.

Other mines. Many other mines, such as the Senate, Hudson, 

Charter Oak, and Humboldt, Avere all formerly active in this region, 

and have in some cases produced considerable ore. In those named 

the ore, AArhen it occurred, appears to have had the form and characteristics already described as common to the typical Red Mountain 

deposits. All these mines had been abandoned in 1899 and consequently were not accessible for study, and very little information 

regarding them could be obtained. The Hudson, oAvned by the 

American Belle Company, A\ras Avorked through a vertical shaft 253 

feet in depth. The ore does not appear to have occurred in large 

bodies. On the first level ore consisting of pyrite and chalcopyrite
240 ECONOMIC GEOLOGY OF SILVEETON QUADEANGLE. [BULL. 182.

(and probably enargite) carried from 20 to 26 ounces of silver per ton 

and 6 to 40 per cent of copper. The mine was closed in 1891. In 

1805, 20 tons of enargite ore, carrying about 20 per cent of copper, 

were collected from the dump and realized $18.77 per ton. In its 

general character the ore of this mine seems to have been very similar to the low-grade ore of the National Belle, carrying enargite and 

copper and iron pyrite.

Other mines and prospects, showing more or less ore occurring in 

typical Red Mountain form, occur at the heads of Prospect and Dry 

gulches on the eastern slope of Red Mountain. The Mineral King, in 

Prospect Gulch,has a shaft 150 feet deep, sunk to develop a "chimney" of ore which outcropped in the bed of the creek. This ore 

shoot was cylindrical in form and nearly vertical, with a diameter of 

about 6 feet. The ore was a highly argentiferous copper ore, which 

is said to have contained as much as 1,300 ounces of silver per ton. 

It was surrounded by the usual envelope of silicified andesitic breccia, 

which graded outward into less altered forms of the same rock. This 

ore body 'pitched slightly to the south, and was followed down for 110 

feet, when it pinched out. Forty feet deeper, drifts have been run in 

all directions in an endeavor to find a continuation of the pay shoot, 

but without avail. The rock at this level is traversed by numerous 

fissures, usually carrying some kaolin and accompanied by kaolinization'of the wall rock. They sometimes widen into "pockets" filled 

with soft, unctuous yellow clay. One prominent, fissure has a course 

of N. 80° W., another of S. 5° W., and still others run in various 

directions. It is probable that the original ore channel was formed 

by the intersection of two or more of these fissures. All of the andesitic breccia exposed in the artificial openings of this vicinity show 

some mineralization, with frequent small bunches of galena and other

ore, but it was apparently only under exceptionally favorable conditions of fissuring that this diffuse mineralization was concentrated 

into ore bodies of workable size.

Near the head of Prospect Gulch the Galena Queen, with a shaft 

about 300 feet deep, shows a dump of similar character to that of the 

St. Paul. It is no longer worked.

Active prospecting was in progress in 1900 in the neighborhood of 

the Galena Queen, many of the shallow openings showing some ore.

The Henrietta mine, in the lower part of the same gulch, is described 

with the Cement Creek mines, on page 257.

The Webster, at the head of Dry Gulch, is worked through an 

inclined shaft 320 feet deep. The shaft is sunk on a fissure carrying 

a little gouge, in Silverton breccia. This fracture strikes about S. 10° 

W. The dip at first is about 75° to the south, but at 200 feet it flattens to about 45°. A little argentiferous copper ore has been found 

in bunches.

Saratoga mine. On the eastern side of Ironton Park are several
BANSOME.] DEPOSITS OF BED MOUNTAIN KEGION. 241

ore deposits which are of different types from those just described. 

The conspicuous alteration which has given the rocks of Red Mountain their brilliant tints is limited on the northeast by Grey Copper 

Gulch, and it is to this area of altered rock that the peculiar chimneylike deposits of the Yankee Girl type are confined.

The Saratoga was located in 1883, and has produced in all about 

$125,000. «& far greater sum than this has been expended in development and in the erection of an expensive lixiviation plant. Considerable work was done in 1886, and in 1889 and 1890 about 100 men were 

employed. Since 1890 work has been confined to extracting pockets 

of ore with two or threje men.

The lowest formation exposed at the Saratoga mine is a massive 

quartzite, white or light buff in color, which outcrops near the mill, 

with uo recognizable bedding. Without much doubt this quartzite

represents a portion of the Algonkian series, here rising a little above

the level of Iron ton Park. Lying unconformably upon this quartzite 

is a locally neaiiy horizontal formation of limestone, sometimes thinly 

bedded, which is probably of Devonian age and to be correlated with 

the limestone occurring south of Silverton. The thickness of this 

limestone is not known, but is apparently somewhat variable, and in 

places it certainly reaches a thickness of 75 feet. ] Some thinly bedded 

portions at its top appear to have been silicified, forming a material 

resembling quartzite at first glance, but composed of vein quartz containing numerous little vugs. Above the limestone there occurs a 

thin stratum of telluride conglomerate, originally composed largely of 

limestone pebbles, but now silicified and Avith its conglomeratic character obscured. This appears to represent the rapidly thinning eastern margin of this conglomerate, for it is not recognizable a. short 

distance Avithin the hill, in the mine workings, where the volcanic 

breccias of the Silverton series, containing some massive andesite, Jie 

upon the limestone.

The ore body of the Saratoga occurs in the limestone, and probably 

in part in the telluride conglomerate, and is very irregular. Near 

the surface of the hill it is a mass of soft, rust-colored, oxidized material, easily \vorked with pick and shovel, and traversed by numerous 

irregular seams of soft clay gouge. The pay ore occurs along these 

seams or gouges and is chiefly a carbonate of lead carrying silver, 

probably as chloride. Residual kernels and masses of white crystalline limestone are of frequent occurrence, surrounded by the rusty 

decomposed material of the ore body. The best ore is found resting 

on the oxidized upper surface of a mass of iron pyrite. This pyrite 

varies greatly in thickness, and in what is knoAvn as the lower 

tunnel it is nearly 100 feet thick a mass of nearly pure, crumbling 

pyrite, resting on the quartzite, or occasionally on limestone, when 

the latter has not been Avholly replaced. This pyrite carries, according

1 According to Kedzie, loc. oit., its mean thickness is 140 feet.

Bull. 182 01 16
242 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BUM,. 182.

to Mr. W. R. Fry, part owner and former superintendent of the 

mine, from 3 to 4 ounces of silver and 0.4 to 0.5 of an ounce of 

gold, being thus too poor to work. Several tunnels have been run 

into the hill, but owing to the easterly dip of the ore they all pass 

through the ore body and, if continued far enough, come into the 

volcanic rocks of the Silverton series. This oxidized ore is not capped 

by the overlying andesite, but passes upward into the loose material 

and soil of the present surface of the hillside. When, however, the 

ore is followed far enough to the eastward it passes beneath andesitic 

breccia and changes to a sulphide ore, consisting of pyrite and a little 

chalcopyrite, with occasional bunches of partly oxidized pay ore, carrying galena and argentite. This ore is the result of a replacement of 

the limestone to varying depth along the contact between it and the

Pink yuartzite ^^ 

Vein material

Upper quartzite

FIG. 22. East-and-west section through the Saratoga mine. (After G. E. Kedzie.)

overlying andesitic breccia. It varies in thickness from a few inches 

up to 3 feet. The overlying volcanic breccia is usually much altered, 

thickly impregnated with pyrite, and traversed by veinlets of the 

same mineral. The ore is not distributed at random through the contact plane between limestone and breccia, but the bunches of ore thus 

far found lie along a line bearing about N. 30° E., as if the mineralization had been controlled by some fissure or fissures having this 

direction. As this is the dominant direction of fissuring in the vicinity, this seems not unlikely. The actual fissure which determined 

the mineralization is, however, not readily identified. It may lie to 

the westward, in which case its intersection with the ore horizon has 

been removed by erosion. It may be the large lode, presently to be 

described, which lies to the eastward, or it may be some less conspicuous fissure. A small fissure having this strike of N. 30° E. was
BANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 243

noted, which faulted the ore body, throwing down the southeast portion a few inches. This, however, appeared to be a post-mineral 

fault and is probably a late manifestation of the same faces which 

produced the earlier dominant Assuring of identical trend.

The upper tunnel of the Saratoga has been run 1,000 feet into the 

hill. It passes through the ore and limestone into a fine-grained, 

massive andesite, and about 600 feet from its mouth cuts a strong lode 

carrying pyrite, in a gangue of vnggy, white quartz. This vein is from 

2 to 3 feet wide, striking N. 30° E., and dipping southeast at about 

85°. It is too low grade to work. Beyond the lode the tunnel passes 

through about 50 feet of iron pyrite, limestone, and quartz all much 

shattered. This appears to be a mineralized fault breccia, disturbed 

by later movement. On the southeast of this shattered zone is andesitic

Andesitic xv'^'-: ' ' ' <l:'-'-.'fl''--'.-.'..-.''A':':

Tellunde conglom 

Ore, oxidized 

near surface

Xlgonkian quartzite

FIG. 23. Diagrammatic easfr-and-west section, illustrating in a general way the occurrence of

ore in the Saratoga mine.

breccia, but owing to the gas in the end of the tunnel it was found 

impossible in 1899 or 1900 to make any further observations.

It is to be noted that G. E. Kedzie T has interpreted the form of the 

Saratoga ore body in a different manner from that set forth in the 

foregoing pages. His section is herewith reproduced-(fig. 22). This 

same section is also given in Phillips and Louis's Treatise on Ore 

Deposits, although these authors remark that there seems to have 

been hardly enough work done to pronounce very.positively as to the 

character of the ore body. 2 At the time of Kedzie's visit the mine was 

more accessible throughout, but not enough ground had been exploited 

upon which to base all the details of his section. Thus his "upper

'The bedded ore deposits of Red Mountain mining district, Ouray County, Colo.: Trans. Am. 

Inst. Min. Eng., Vol. XVI, 1887-88, pp. 570-581.

2 A Treatise on Ore Deposits, J. Arthur Phillips, second ed, rewritten and enlarged by 

Henry Louis, London, 1896, p. 163.
244 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. .[BULL. 182.

qnartzite" appears to be the same as the massive quartzite here 

included in the Algonkian. His "pink quartzite" is evidently the 

silicified telluride conglomerate, while his "lower quartzite" could 

not be identified in the Saratoga workings. He states that it is penetrated by the Jackson tunnel, about 800 feet south west of the Saratoga, but this tunnel is no longer accessible. A truer representation 

of the ore body and its relations to the inclosing rocks is believed to be 

afforded by the rough diagram, fig. 23.

In 1900 a drift was being run along the ore-bearing horizon toward 

the northeast with the object of ascertaining whether any ore has 

been deposited at the intersection of this horizon by the large vein 

cut in the tunnel above. This seems an advisable piece of prospecting. Hitherto the development has been rather unsystematic, and it 

was not discovered until 1900 that the large oxidized ore bodies were 

continuous, with sulphide ores passing beneath the andesitic breccias 

to the eastward.

Baltic group. This group, comprising the Maud S., Mono, and 

other claims, is a prospect in Brooklyn Gulch, south of the Saratoga. 

The principal work at present, is in connection with the Mono lode, 

which strikes N. 43° E. and dips northeast at about 75°, and is reached 

by a tunnel through the limestone about 400 feet in length. This 

lode occupies a fault fissure of at least 100 feet throw, which drops 

the overlying andesitic breccia on the southeast until it lies against 

the limestone. The ore, consisting of nearly solid pyrite and chal- 

' copyrite, occurs as a vein in the fault fissure and as a relatively flat 

replacement deposit between the limestone and overlying andesite on 

the northwest side of the fault. Where both walls of the fissure 

are andesitic the vein is narrow; but where one wall is limestone it 

widens, evidently by replacement of the calcareous wall. There has 

been some post-mineral movement along the fault fissure, as shown 

by the presence of gouge and slickensides.

The ore is low grade, carrying at its best about 30 ounces of silver 

and 12 per cent of copper. Ore of this general character is very 

abundant both here and in the Saratoga mine, but can not at present 

be economically worked.

It is evident that the ore bodies have been only partly prospected. 

No attempt has been made to find the ore which very likely exists at 

the top of the limeston<Ton the downthrown side of the fault. This 

would seem to be an excellent opportunity to employ a diamond drill, 

provided the known ore bodies indicate that the ore on the other side 

of the fissure is worth searching for.

The Maud S. is also on a fault fissure, which crosses the gulch near 

the mouth of the Mono tunnel. Its general strike is N. 30°-40° E., 

and its dip southeast at about 85°. This also is a normal fault, letr 

ting down the andesite against the limestone on the southeast for at 

least 25 feet. Some argentiferous copper ore was formerly taken
RANSOME.] DEPOSITS OF RED MOUNTAIN REGION. 245

from this claim, the ore occurring in replacement bunches in the 

limestone alongside the fault. The ore is associated with a soft, 

black alteration product or residue of the limestone. Between the 

Maud S. and the Mono fissures is a third fault exposed on the Mono 

tunnel, of variable northeasterly strike, dipping southeast at about 

70°. Here also the andesitic tuff or breccia is brought down on the 

southeast so as to be in iuxtaposition with the'limestone. The fault 

is well shown in a long drift run on it to the southwest. . The fissure 

contains soft gouge and shows slickensides, but is about destitute 

of ore.

The Brooklyn tunnel, 200 feet below the Mono tunnel, enters in 

limestone, Avhich is probably over 200 feet thick in this gulch. The 

.tunnel has several branches, the longest about 800 feet in length. It 

cuts through at least two large masses of crumbling iron pyrite,

formed by replacement of the limestone. These masses are bounded

on the southeast by a northeast fault plane, which brings them 

against a downthrown mass of andesitic breccia. This fault is supposed to be the one already described between the Maud S. and 

Mono fissures. The only one of these pyrite masses which could be 

reached in 1900 is at least 6 feet in thickness (the height of the drift), 

and probably considerably more. Northwest of,the fault it extends 

irregularly into the limestone for over- 100 feet. Northwest of these 

masses of pyrite is a long northeast drift, which appears to follow a 

fault for most of its course. On the southeast side of the drift is 

limestone with bunches of ii-on pyrite. On the northwest side is an 

irregularly laminated and much disturbed quartzite, which may probably be the "lower qnartzite" of Kedzie. The general strike of this 

laminated quartzite, i. e., of the laminae, is about northeast. The 

general dip is northwest, but exceedingly variable. This quartzite 

belongs presumably below the limestone, but whether it is the same 

as the massive quartzite at the Saratoga Mill or is a younger quartzite 

not there seen, and perhaps of Devonian or Silurian age, is not at present known.

Jay Eye See mine. This also is a prospect situated in Parole Gulch, 

south of the Maud S. A shaft was formerly sunk on a heavy lode or 

bunch of pyrite, associated in this case with a little quartz gangue. 

No pay ore was ever found in this shaft. Subsequently a tunnel run 

in just west of the shaft cut a lode which in places carried tetrahedrite, 

pyrite, and chalcopyrite up to 4 feet in width. The ore occurred in 

lenses connected by a barren seam of clay gouge in soft decomposed 

andesitic tuff-breccia, and the mine never paid steadily. .The tetrahedrite sometimes carried 400 ounces of silver per ton. The bodies 

of pyrite cut in the original shaft are quite probably part of the Mono 

lode. But parallel fault fissures of southeasterly dip and normal 

heave are here so common, however, that identification of any single 

one is almost impossible.
246 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

Barstow mine, This mine, formerly known as the Bobtail, was the 

only mine in the Red Mountain district working and producing ore 

in 1899 and 1900 on any considerable scale. It is situated about a 

mile west of the Gnston, on a prominent lode running up Commodore 

Gulch, on which the Iranstan, Bobtail, Hector, Saratoga, and Moscow 

claims are located. The Iranstan and Bobtail were worked early in 

the eighties, but have been idle for the last few years, until work was 

resumed by the Barstow Mining and Milling Company. The mine is 

opened by an oblique crosscut tunnel and all the work is on one level.

The lode, which has a general northwest-and-southeast strike, and 

dips southwest at about 50°, is a large one, 30 to 40 feet wide, but the 

ore is confined to one or two rich streaks in its middle portion. The 

lode contains much soft, altered country rock and is traversed by clay 

gouges, making it exceedingly treacherous and difficult to work by 

overhand stoping. The mass of the lode contains pyrite, chalcopyrite, sphalerite, and some bunches of low-grade galena. The gangue 

is chiefly quartz, often cavernous and drusy, with a little.fluorite. 

The best ore is a light-gray metallic mineral called "gray copper" at 

the mine, which, when pure, assays as much as 2,000 ounces of silver 

and 25 ounces of gold per ton. The gold always accompanies and is 

proportional in amount to the silver. Chemical examination shows 

that the so-called "gray copper" is in this case an argentiferous lead 

sulphobismuthite containing almost no copper, probably the mineral 

cosalite. But the present material obtainable (sp. gr. 7.04 at 30° C.) 

proves on chemical investigation to be a mixture of the lead sulphobismuthite with pyrite and some telluride. Under these circumstances it was inadvisable to spend time in making a complete 

quantitative analysis. From his preliminary tests, however, Dr. W. F. 

Hillebrand has kindly supplied the following rough approximation

to the composition of the mixture:

Approximate composition of mixture from Barstoiv mine.

Constituent.

Pb. .......................................

Bi.--....- ... -- -.- - -

AC*

Au. .....................................

Per cent.

45.5

.23.5

6.0

.06

Constituent.

Cu. .....................................

ITo

S . .... ........... ........ ......

Per cent.

.3

3.5

14.1

1.5-2.0

The lead of cosalite is known to be sometimes partly replaced 'by 

silver and copper. In this particular case the silver is evidently 

accompanied by some gold, which is probably combined with tellurium 

and not directly with the sulphur and bismuth. The sulphobismuthite is often closely associated with chalcopyrite, which carries little 

value. The rich ore streaks are more or less lenticular in form and 

are usually separated from the mass of the lode by wet clay gouges. 

The best ore occurs nearer the footwall. As the workings are con-
RANSOME.] DEPOSITS OF BED MOUNTAIN EEGION. 247

fined within the mass of the lode, the relation, of the latter to the wall 

rock could not be studied.

Silver Ledge mine. This property, situated about half a mile north 

of Chattanooga, and operated by the Ledge Mining and Milling 

Company, is worked through a shaft about 400 feet in depth, sunk 

in the bed of Mineral Creek. Most of the work at present is on the 

fourth level, at a depth of 360 feet, and in the stopes immediately 

above it. The workings are all in rhyolite. This rhyolite forms a 

considerable area extending to the westward of the mine with a 

rather irregular boundary. Its eastern limit is very close to the mine 

workings. For more detailed accounts of this rhyolite mass the 

reader is referred to the forthcoming work of Mr. Cross. The conclusion reached by him at the present writing is that it represents an 

area of the Potosi rhyolite 1 which has been faulted down into the 

surrounding rocks. If this view is correct the rhyolite is limited in 

depth. There are no data now available for even a rough estimate 

of the thickness of this rhyolitic mass, but if mining be pushed deep 

enough it will be passed through. If, on the other hand, the rock is 

intrusive, it may extend to practically unlimited depth.

There are certain features about the rock itself which sustain Mr. 

Cross's hypothesis. It has many of the characteristics of the surficial rhyolite flows of the Potosi series, and, as far as could be seen 

in its altered condition near the mine, has not the crystalline structure 

that might naturally be looked for in an intrusive mass of such size. 

Moreover, on the 400 level of the Silver Ledge occur masses of a 

compact, slightly pinkish rock, which are soinetlines fairly distinct 

from the white altered rhyolite and sometimes appear to grade into 

it. This pinkish rock occurs as isolated patches or nodules in the 

rhyolite, aud at one point forms a considerable mass, of which the 

bottom is not yet exposed. Under the microscope this rock shows 

numerous small grains of quartz in a very minutely crystalline sericitic groundmass. It is, without very-much doubt, a devitrified glassy 

rhyolite or rhyolitic tuff. Such material could hardly occur in such 

a place if the rhyolite were intruded. It strongly suggests volQanic 

or effusive conditions. It is even possible that the appearance of 

this material indicates an approach to the bottom of the rhyolitic 

mass.

The work of Mr. Cross has established the existence along the 

eastern border of the rhyolite mass of a fault which, just southeast 

of the mill, brings the rhyolite against andesite on the east. Th.e 

line of this fault would carry it not far east of the main shaft, and it 

was thought that a crosscut which had been driven 100 feet to the 

eastward from the 400 (360 feet) level might be found passing through 

this fault fissure into andesite. About 70 feet east of the shaft the 

crosscut does pass through a strong gouge-filled fissure, but the

1 See the Telluride folio. No. 57.
248 ECONOMIC GEOLOGY OF SILVEETON QUA DE ANGLE. [BULL. 182.

rock, although all much altered, shows no change either in hand 

specimens or under the microscope. It all appears to have been 

originally rhyolite.

The ore, consisting of galena and sphalerite, occurs replacing and 

impregnating the rhyolite in the vicinity of two or more fractures, 

which have a general strike of about 1ST. 27° E. and dip southeast at 

a high angle. These fissures contain crushed country rock and ore, 

and there has evidently been late movement along them since the ore 

was deposited. They are probabty merely a portion of a pronounced 

fault zone, which here follows the general trend of the creek. The 

ore bodies are found by following these fractures, but are not confined 

within their walls. They extend irregularly into the rhyolite for 30 

or 40 feet to the west, the low-grade galena, associated Avith considerable sphalerite, sometimes forming large masses wholly replacing the 

rhyolite, but more often impregnating it thickly in small nests and 

isolated particles. There are no walls to the ore bodies, and they are 

followed into the rhyolite until the proportion of ore to gangue 

becomes too small for profitable working. Very little ore has thus 

far been found to the east of the fissures, although the workings have 

as. yet revealed 110 change of country rock in that direction. 

.. The rhyolite has been altered in connection with the ore deposition 

to a finely crystalline mass of sericite, kaolin, and quartz in varying 

proportions, serving as gangue for the ore.

The principal fractures of this mine appear to be comparable to the 

so-called ore break in the Guston mine. It is very probable that the 

zone of fractures extending up Mineral Creek and passing just east 

of Summit forms part of the fissuring found in the Lake and National 

Belle mines near Red Mountain.

The ore of the Silver Ledge, is concentrated in a small mill run by 

steam. It is equipped with 1 Gates crusher, 2 sets of wells, 4 threecompartmeut jigs, 10 stamps, and 4 double-deck and 2 single-deck 

Wilfley tables. The capacity is about 60 tons a day. The principal 

output of the mine is a low-grade galena, which is shipped in the form 

of concentrates. A little free gold, associated with a telluride supposed to be calaverite, was found on the 300 level as a thin skin on a 

slickensided fracture surface in the usual impregnated rhyolitic country rock. This was the only occurrence of free gold known in the 

mine.

The future development of this mine is likely to be of great interest. 

It is evident that if the interpretation of the rhyolite as a down-faulted 

sheet or flow be correct, then an entirely different set of conditions 

will be encountered when the bottom of the rhyolite is reached. In 

all probability the ore deposit will become a simple fissure vein or a 

series of parallel veins. Moreover, further exploration of the country 

east of the shaft may reveal ore bodies yet unknown. The crosscut 

already begun in this direction might perhaps be extended with 

advantage until the andesitic rock of the Silverton series is reached.
RANSOME.] DEPOSITS OF EED MOUNTAIN REGION. 249

Magnet mine. This, an old location, is situated on the east side of 

Mineral Creek, near Burro Bridge. It produced a little rich silver ore 

in the early eighties, but owes its interest at present to the occurrence 

of a telluride of silver, probably hessite.

The workings comprise a tunnel about 540 feet in length and a few 

superficial openings. The lode strikes N. 85° W. and dips from 60° 

to 80° to the south. It is a compact stringer lode, in places 2 feet 

wide, which contains considerable mineralized and altered andesitic 

breccia, which forms the country rock. The stringers are filled with 

quartz, "frozen" to the walls and containing bunches of ore. A 

radial structure of the quartz is common and vugs are numerous. 

The ore, consisting of argentiferous galena, a silver telluride (hessite?), a little free gold, sphalerite, chalcopyrite, and pyrite, occurs 

partly in the quartz and partly replacing the included fragments of 

breccia. The richest ore, containing the hessite, is usually associated

with the radial quartz and often occurs in the interstices between the 

outer ends of the crystals. The ore is unevenly distributed through, 

the lode and has been found only in small bunches.

Brdbdignag claim,. This abandoned prospect is of interest as the 

locality whence some zinkenite Avas formerly obtained, which, was 

described and analyzed by Dr. Hillebrand. 1 No ore was visible in 

1900. The country rock was apparently originally an andesite, but 

is altered to a white aggregate consisting chiefly of quartz and barite.

Zuni mine. This mine, well known in mineralogical literature as 

the source of guitermanite and zunyite, is situated near the summit 

of Anvil Mountain, at an elevation of about 12,000 feet. The ore 

body was worked from the surface by an open cut and a shaft and 

by two tunnels. The upper tunnel branches, the twro breasts being 

156 and 180 feet in from the surface. A second tunnel, 200 feet below 

the upper one, is 540 feet in length. There is no connection, between 

these two tunnels.

The surface ore of the Zuni, discovered in 1881, was chiefly massive 

sulphate of lead (anglesite) containing abundant small tetrahedral 

crystals of unaltered zunyite. This soon changed to un oxidized 

guitermanite in characteristic association with zunyite. This was the 

chief ore of the upper tunnel, and occurred in a mass about 60 feet 

long and 15 feet wide. Below the tunnel level this bismuthiferous 

lead ore decreased in width to about 6 feet and changed gradually to 

a copper ore, consisting chiefly of enargite, with pyrite, kaolin, and 

a little barite. The enargite carried about 216 ounces of silver and 

40 per cent of copper. In the lower tunnel the ore body, about 40 

feet long and 12 feet wide, is a soft mass of kaolin and embedded 

pyrite, with nests of enargite. The pyrite occurs chiefly in octahedra and is said to carry a very little gold. The ore at this depth contains many fragments of the immediate country rock, a much altered

' i Bull. U. S. Geol. Survey No. 30, p. 93.
250 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

porphyry, apparently originally an andesite or latite. The contact 

between the ore and these fragments is perfectly sharp, and the latter 

often have sharp, angular corners.

Small masses of similar ore, showing no apparent connection with 

the main body, were encountered at several points in the tunnel. 

They often contain small caves or vugs lined with crystals of quartz, 

barite, enargite, and pyrite. The country rock around such caves is 

brecciated and the crevices are filled with ore. The ore in the lower 

tunnel, consisting chiefly of pyrite, is too low to work. The longer 

diameter of the Zuni ore body apparently strikes about N". 15° W., 

and the dip is from 75° bo 80° to the west.

There are several smaller prospects of the general type of the Zuni 

on Anvil Mountain. These are usually small irregular bunches or 

"chimneys" of ore of small horizontal and vertical extent. They 

sometimes occur immediately at the surface, as in a claim owned by 

John Roland, where masses of galena, showing only superficial oxidation, occur at the grass roots. In some cases the surface ore is argentiferous enargite (Dewey claim). There can be little doubt that 

many undiscovered small irregular masses of ore occur within the 

altered andesites and other igneous rocks of Anvil Mountain. But 

such is their irregularity in occurrence, and so limited are they in 

extent, that small inducements are held out for extensive deep prospecting.

Meldrum and Hammond tunnels. The success of the Revenue 

tunnel has encouraged the prosecution of other extensive tunneling 

ventures in the vicinity. The Meldrum tunnel is being driven on .a 

coarse about 4° S. of W. from a point on Red Creek opposite the Silver Bell mine through to Bridal Veil Basin in the Telluride quadrangle, a distance of over 4 miles. The tunnel is 12 by 12 feet and 

had run about 900 feet in 1899. Work was also in progress at the 

western end of the tunnel line. In 1900 all work was suspended. 

The Hammond tunnel also enters from Red Creek,' nearly west of the 

Yankee Girl mine and has a course of N. 80° W. It had a length of 

about 2,000 feet in September, 1900 all in andesitic breccia. As a 

rule the rock is solid, very little timbering being required. But in the 

neighborhood of 1,000 feet from the mouth some zones of recent brecciation, dipping eastward, are cut through. These indicate faulting, 

possibly connected with the movements of landslide character revealed 

in the topography above the tunnel.

These tunnels are evidently designed to cut the continuation of the 

Tomboy lode and other less known and undeveloped lodes traversing 

the high ridge west of Red Creek. A very large outlay of capital will, 

be required to complete them. Without expressing an opinion upon 

these particular enterprises, it may be pointed out that, in so far as 

the projectors of long tunnels count upon finding richer or more 

abundant ore than is indicated near the surface, they are playing a
RANSOME.] 'MINES OF SULTAN MOUNTAIN. , 251

game of chance in which the probabilities are decidedly against them. 

But where the object is to cut a lode of proved value and continuity, 

as was the case with the Vi rginius lode tapped by the Revenue tunnel, the unertaking involves no more than the legitimate risks incident 

to most large business enterprises.

MINES OF SULTAN MOUNTAIN.

North Star mine. Situated on the northern slope of Sultan Mountain, about a mile southwest of Silverton, this mine was at one time 

one of the largest and most productive in the quadrangle. It was 

located in 1876, but not extensively worked until about 1881, when it 

became the most productive mine in Sari Juan County, some 3,000 

tons of ore having been mined. At the close of 1882 the workings 

comprised about 1,700 feet of drifts, and, according to the report of 

the Director of the Mint, over 100,000 ounces of silver and 1,500,000

pounds of lead had been extracted. The ore at that time was shipped 

to St. Louis, and is said to have carried from 70 to 80 ounces of silver 

and 35 per cent of lead, In 1883 the output is given by the Mint 

reports as $200,000, and in 1884 as 1,100 tons, value not stated. The 

same source gives the product for 1888, 1890, and 1891 as $46.522, 

$206,072, and $337,192, respectively, the silver being reckoned at its 

coinage value. The mine was finally closed about 1897, it having 

been practically worked out down to the tunnel level.

The main adit is a tunnel (No. 7) 7 feet in the clear and 2,100 feet 

in length, which has its entrance about 50 feet above Mineral Creek 

and penetrates the mountain in a southwesterly direction, cutting the 

lode nearly at right angles. The latter is a fissure vein in monzonite, 

striking nearly northwest and' southeast, but showing considerable 

variation in trend. The dip is to the southwest at from 45° to 60°. 

The monzonite near the vein- is decomposed and soft, and Avhen the 

mine was visited in 1899 it was found impossible, on account of 

caving, to reach the ends of any of the drifts or to enter the stopes. 

The vein contains much quartz, and is usually wide, the average width 

according to one account being about 8 feet. The pay streak, generally 

about a foot wide, and consisting of galena and tetrahedrite, occurs 

A^ery persistently along the footwall side of the vein. The pyrite 

occurring in the more quartzose portion of the vein is said to carry 

some gold, and small amounts of the latter have been found.free. The 

average tenor of the ore is reported to have been about a half ounce 

of gold, 40 ounces of silver, and 50 per cent of lead.

About 100 feet southwest of the North Star vein is the Crown Point 

and Wheal Alfred lode, a nearly parallel quartz vein carrying some 

gold. The dip of this lode is steeper than that of the North Star. It 

shows pyrite, chalcopyrite, and tetrahedrite, with a little specularite, 

in a quartz gangne. Barite is probably present in both lodes.
252 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

An abundant flow of water issues from the main tunnel, and proved 

troublesome when the mine was being worked on account of the 

rapidity with which it corroded rails and pipes.

The North Star mill, erected about 1890, is equipped with 2 Blake 

crushers, 3 sets of rolls, 8 three-compartment jigs, 2 four-compartment 

jigs, 20 stamps, and 3 Woodbury tables. The power is water. This 

plant was running in 1899 as a custom mill.

Belcher mine. This mine, now abandoned, is situated in the high 

basin opening to the northeast on the northeast side of Sultan. Mountain, the principal adit being at an elevation of about 11,250 feet. 

It, was located in 1876, yielded over 300 tons of ore in 1881, and in 

1882 had become a steady producer. In 1883 there were three levels 

opened by tunnels, and a product of 1,700 tons of ore is recorded, 

averaging 38 ounces of silver and 40 per cent of lead. The outputs 

for the years 1883, 1884, 1890, 1891, and 1892, as given in the Mint 

reports, were$85,000, $13,500, $8,467, $34,995 and $63,510, respectively. 

The Belcher lode is in monzonite, and is said to be very similar to the 

North Star lode and to have nearly the same strike and dip. v The 

Avorkings were wholly inaccessible in 1899, and no observations could 

be made on the lode itself. According to Mr. W. H. Thomas, at one 

time part owner of the mine, the galena ore was less abundant in the 

lower levels, its place being largely taken by sphalerite. According 

to another former owner, the lode was practically worked out down to 

the tunnel level, and there is no reason to suppose the good ore to be 

any less abundant below the bottom workings.

Fragments of ore seen on the dump of the lowest tunnel showed 

galena, sphalerite, pyrite, chalcopyrite, and tetrahedrite in a gangue 

of quartz and barite with some calcite. The ore was sorted, sacked, 

and carried on burros down a steep trail to Silverton.

Empire group. Through the present Empire tunnel it is intended 

to work a group of claims on the northeast slope of Sultan Mountain, 

overlooking Silverton and Bakers Park. The more important of 

these claims are the Empire, Little Dora, Victoria, Jennie Parker, 

Ajax, and Hercules. They cover portions of three important lodes, 

which are only roughty parallel and which have a general trend of 

about N. 20 W. The Jennie Parker and Hercules are supposed to 

form a continuation of the North Star lode.

The Empire and Jennie Parker were worked at a very early date by 

Melville & Summerfield, who in 1876 had a shaft 50 feet deep on the 

Empire lode and were erecting reduction works near the Animas 

River. They were apparently not successful, and the mine was idle 

for some years. In 1882 the Little Dora lode, which in 1881 was 

shipping ore from a shaft, was struck in an upper tunnel. This is a 

clean-cut fissure vein, usually about 2 feet wide, and, although small, 

has produced a fair amc'int of ore. The Empire at this time was 

opened by a shaft 125 feet deep and is said to have had about 18
IIANSOME.] MINES OF SULTAN MOUNTAIN.

inches of excellent ore, largely tetrahedrite, which averaged LOO 

ounces of silver and 10 per cent of copper. In 1883 the Ajax and 

Victoria were being developed by tunnels. None of these lodes has 

thus far been worked on an extensive scale.

They are all simple, nearly vertical fissure veins in monzonite. 

The ore is mineralogically similar to that found in the North Star lode, 

viz, galena, sphalerite, tetrahedrite, chalcopyrite, and pyrite, in a 

gangue consisting chiefly of quartz with some barite. "With the prevailing price of silver, the ore is, as a whole, low grade.

The Empire tunnel enters the mountain about 150 feet above the 

bed of Mineral Creek, and has a straight course of S. 35° W. It cuts 

the Little Dora vein about 1,230 feet from the tunnel mouth. About 

900 feet farther in it passes through a fissure about 10 feet wide, 

filled with crushed rock and gouge, but containing no ore. This is 

probable the Jennie Parker-Hercules lode, which it was expected to 

cut about 800 feet beyond the Little Dora. The tunnel was iso feet

beyond the large fissure in August, 1900, and still driving on in solid 

monzonite. An upper tunnel, 208 feet vertically above and about 

400 feet west of the Empire tunnel, formerly known as the Montezuma 

and used to work the little Dora, lias been relocated as the Boston 

tunnel and extended through to the Hercules lode, here found to be 

a strong vein up to 10 feet wide, dipping to the southeast at about 85°. 

It showed evidence of post-mineral movement along the fissure, particularly along the foot wall. The Empire-Victoria vein, as drifted on. 

from the Boston tunnel, is fairly regular and shows a width up to 7 

feet. Its dip is somewhat variable in places as low as 05° to the 

southwest. Hiibnerite, associated with fluorite, occurs as crystalline 

streaks and bunches next the hanging wall, and usually surrounded 

by soft gouge. It is probably of later formation than the ore.

On account of the very favorable location of the Empire tunnel it 

is expected that ore considerably below what is commonly regarded 

as the lowest grade for profitable working in this region can be here 

successfully handled.

Other mines and prospects. The Fairview is a prospect a little 

more than a mile south of Silverton, at the contact between the intrusive monzonite stock of Sultan Mountain and the Algonkian schists 

and overlying limestone. The property includes a nearly north-andsouth vein, carrying ore mineralogically similar to that of the Hercules 

lode. The Devonian limestone also, near the monzonite, has been 

mineralized and carries particles of native silver. Argentine is also 

reported. Two tunnels, one 200 and the other 600feet in length, have 

been run, but there is not enough development to allow satisfactory 

study of the deposit.

The King lode is a quartz vein in Algonkian schists in Cataract 

Gulch, and outcrops just below the basal conglomerate (Cambrian?) 

which underlies the Devonian limestone and rests unconformably
254 EGOISTOMIO GEOLOGY OF SILVERTON QUADKANGLE. [BULL. 182.

upon the edges of the schists. The strike of the vein is N. 6° W., and 

it dips westerly at 78°. It varies in width from 18 inches to 4 feet, 

and is destitute of gouge. The inclosing schists strike N. 85° E., and 

their planes of schistosity stand nearly vertical. The vein thus crosses 

the schistosity nearly at right angles. No offsetting of the schists 

could be detected on opposite sides of the fissure. The King lode is 

faulted by a small vein dipping south about 50°, and the northern portion of the lode is thrown about 12 feet to the west.

The ore of the King lode consists of galena, gray copper (probably 

tennantite), and chalcopyrite, with some sphalerite and pyrite, in a 

quartz gangue. It carries about 0.1 ounce of gold, 55 ounces of silver, 

and 15 per cent of lead.

Close to the King lode is a deposit of chalcopyrite, which occurs at 

the contact between the limestone and the underlying quartzite. 

This deposit is apparently directly connected with a fissure of rather 

flat southerly dip, which traverses both quartzite and limestone.

The Moles mine, now abandoned, is on a nearly vertical fissure 

vein, about 2 feet wide,- in limestone, chert, and shales of Devonian 

age. The vein strikes 1ST. 72° W., and occupies a fault fissure.

MINES OF CEMENT GREEK.

General. The ore deposits of Cement Creek occur in lodes, which 

in Ross Basin attain great prominence. The ores are prevailingly 

low grade, carrying silver and lead, or, as in the case of the Gold 

King mine, a large proportion of gold. The occurrence of hubnerite, 

although it is not at present worked on a commercial scale, lends 

additional interest to the ore deposits of this portion of the quadrangle. A few of the mines within the Cement Creek drainage have 

been described in connection with adjacent portions of the region, 

for, as elsewhere pointed out, the geographical grouping of the ore 

deposits of the quadrangle has no necessary significance beyond convenience of description, and is accordingly not rigidly adhered to 

when other courses seem desirable.

Gold King mine. This property, with which are included the 

Sampson and American mines, now under the same ownership, is by 

far the most important mine of the Cement Creek district. It lies on 

the western slope of Bonita Peak, with the present main adit tunnel 

at about 12,500 feet elevation. Two lodes are worked, termed, 

respectively, the Davis and Gold King. Both have a general northeast course, and on the main level are about 70 feet apart. The Gold 

King lode, which is the northwesterly one, dips southeast at about 

75° on the main level. The dip of the Davis is to the northwest, but 

nearly vertical. In the lower level, 107 feet below the adit, these 

lodes are closer together. Both are strong, typical stringer lodes without any gouge. So little have they been disturbed by post-mineral 

movements that there is practically no water in the mine. The ore
RANSOME.] MINES OF CEMENT CREEK. 255

is a network of irregular stringers, inclosing much mineralized a_ndesitic country rock. Distinct walls are lacking, and the ore is taken 

out to a width determined by its value. This is sometimes over 30 

feet.

The Gold King lode is particularly irregular, and its character led 

almost inevitably to the litigation between the Gold King and Sampson companies, which was wisely settled by the purchase of the latter 

by the former.

It shows a marked tendency to split, inclosing large, irregular horses 

of the country rock, and dividing locally into two or more apparently 

distinct lodes of varying dips and strikes. It thus, with our present 

mining laws in force, opened unending possibilities of contention, so 

long as the two mines were under separate ownership. One of the 

most remarkable instances of this tendency seems to be developing 

on the main Gold King level, about 400 feet west of the adit crosscut. Here a large, flat body of ore, continuous with the. ore of the 

main Gold King lode, has been followed out for 30 or 40 feet to 

the northwest with a very gentle northwest dip. This ore apparently 

rests upon the top of a large horse, as in the northern part of the 

stope the dip of the ore is now found to be suddenly increasing. 

Possibly a still more striking case is the relation between the Gold 

King and Davis lodes. It seems very probable that these are not distinct, but merely branches of a very large, irregular stringer lead 

separated by a large horse of country rock, in which case they may 

be expected to come together in dip and strike.

At the point where it. is reached by the adit crosscut (which runs 

nearly north) the Gold King lode is faulted by the so-called "Red 

vein," which has a northwesterly course and dips northeast about 

75°. The horizontal displacement is about 30 feet, the northeast portion of the Gold King being thrown to the northwest. A supposed 

"bend" in the Gold King lode on the level below is almost certainly 

the same fault. The Red vein contains rhodonite (hence its name), 

'which is not found in the Gold King and Davis lodes. It contains no 

ore of value, 'as far as known.

The characteristic ore of the Gold King and Davis lodes consists of 

white quartz with abundant pyrite, often showing banding by disposition. The pyrite, when massive and nearly free from quartz, is of 

little value in the Gold King lode, but carries gold in the Davis lode. 

The best ore always contains quartz, which may occasionally show, 

some free gold. Galena, usually fine granular, occurs in bunches, 

being more abundant in some portions of the lodes than in others. 

As a whole, the ore is low grade, and probably no mine in the quadrangle can set as small nether value for workable ore.

Extensive preparations are being made for the future working of 

this property. The American tunnel cuts what is thought to be the 

same lode at a vertical distance of several hundred feet below the
256 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 183.

present adit; while a second tunnel, about 700 feet in length in September, 1900, is being driven from the mill at Gladstone. This will 

eventually tap the lode about 1,500 feet below the present workings.

The ore is carried down to the mill at Gladstone on a well-built 

Bleichert wire-rope tramway, running from 300 to 400 buckets of 700 

or 800 pounds per day. A second tramway is being built to the American tunnel. The mill is equipped Avith a Gates crusher, 80 stamps, 

and 40 Frue vanners. Power is supplied by a 250-horsepower Westinghouse engine. The free gold is amalgamated, but the bulk of the 

product is in the concentrates, which are shipped to the smelter. The" 

owners of the Gold King built and control the narrow-gauge railway 

from Silverton to Gladstone. "ft

Tungsten ore deposits. The Adams claim, which has for several 

years furnished ca.binet specimens of the tungstate hiibnerite, lies on 

the western slope of Bonita Peak at an elevation of about" 11,300 feet. 

The hiibnerite occurs in a lode which strikes N. 10° E. and dips east 

about 85°. In the main it is a sheeted zone 3 or 4 feet wide, in altered 

andesite of the Silverton series, the fissures being filled with quartz 

and fluorite. The individual stringers or veinlets of the lode are 

rarely more than 6 inches wide and are adherent or "frozen" to the 

walls. The hiibnerite does not occur in all portions of the lode, but 

in isolated and irregular bunches, streaks, or nests of bronze-brown 

radial crystals embedded in quartz and fluorite. The development of 

this deposit is very superficial, consisting of a short tunnel and some 

open cuts, and the tungsten ore has never been worked on a commercial scale. The prospect was evidently opened in search of other ore, 

as the hiibnerite has been thrown with the waste on the dump.

In Dry Gulch hiibnerite occurs in a strong lode, on which have been 

located the Dawn of Day, Sunshine, and Minnesota claims. This 

lode has a course of about S. 60° E. and dips southwest at 65°. Several prospecting openings have been made on it on the south side of 

the gulch. One of these shows a solid vein of quartz 3 or 4 feet wide 

in Silverton andesite. The hiibnerite occurs in the quartz in two or 

three small streaks, from 1 to 3 inches wide, and in small isolated 

bunches. The ciystals are smaller than those in the Adams lode.

Owing to its weight (sp. gr., 7.2) and its occurrence in otherwise 

nearly barren quartz and fluorite, the hiibnerite of Cement Creek can 

be readily and cleanly concentrated. Some 5 tons of concentrates 

have been produced from the Dry Gulch claims; but whether the 

material occurs in sufficient abundance and in sufficiently continuous 

bodies to paj7 for mining is a question not yet decided.

In its occurrence the hiibnerite is purely a vein mineral, occurring 

in a quartz or quartz and fluorite gangue, as do galena, pyrite, and 

other ore minerals of the region.

Red and Bonita mine. -The adit tunnel of this mine runs in an 

easterly direction into Bonita Mountain, from a point about 100 feet 

above Cement Creek. About 3,000 feet of work has been done from
RANSOME.] MINES OF CEMENT CREEK. 257

this tunnel, but the ore could not be made to pay and the attempt 

was abandoned. The workings are no longer,accessible and the lode 

was not seen. The Red and Bonita mill is equipped with Gates 

crusher, 2 sets of rolls, jigs, 10 stamps, and 4 Frue vanners.

Queen Anne mine. This is near the month of Ross Basin, on a lode 

which here consists of two or more parallel veins close together. The 

one worked in the Queen Anne strikes N. 50° E. and dips north west at 

85°. It consists of solid banded quartz and bismuthif erous galena ore 

up to 2 feet wide, " frozen" to the walls. Toward the southwest the 

vein pinches and carries a little gouge. It could not be traced on the

.rface beyond a large northwest-southeast lode which passes up into 

toss Basin.

Columbia mine. This, one of the oldest mines of the quadrangle-, 

lies just northeast of the Queen Anne and is apparently on the same 

lode. It has been an intermittent'producer of argentiferous galena 

ore on a small scale.

Ross Basin lodes-. There is at present no mine in operation in 

Ross Basin, and none of the developments have thus far passed beyond 

the prospecting stage, but the basin is traversed by several lodes of 

unusual size with well-exposed croppings. The most prominent one 

has a nearly northwest course and dips southwest at 80°. It outcrops 

boldly along the northeast side of the basin, especially near theiead 

of the latter, where it passes over the ridge into Sunnyside Basin, and 

is apparently the same as the George Washington lode. 'Toward the 

northwest it continues probably into Grey Copper Gulch. Some ore, 

resembling in mineralogical character that found in Sunnyside Basin, 

but apparently in irregular bunches, occurs in this huge lode, which 

is often over 50 feel. wide. Several other lodes with nearly northeast 

courses come into the main lode from the southwest, but can not as a 

rule be traced on the surface to the northeast. The lodes shown on 

the map are only a few of those which traverse the floor of the basin 

in various directions, although most of them have a northeast trend. 

They are not all of great length, for one vein often, stops short at the 

junction with a second vein of different course. In one case two wellexposed, strong quartz veins, one striking southwest and the other S. 

80° W.,come together in a massive cropping of quartz, beyond which 

there is no surficial sign of the continuation of either lode. Distinct 

evidence of one lode faulting another could not be obtained. They 

are apparently all of substantially the same age. The fissure fillings 

are usually solid white quartz with a little rhodonite and bunches of 

low-grade ore. In some cases the lodes contain numerous fragments 

of altered mineralized countiy rock.

Henrietta mine. This property, in Prospect Gulch, is on a lode 

striking S. 40° W. and dipping northwest at 65°. Three tunnels on 

the south side of the gulch give access to the workings, while a fourth 

tunnel, destined to be the future main adit, is being driven to the

Bull. 182 01 17
258 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE. [BULL. 182.

westward to intersect the lode from a point about 150 feet above the 

qottom of the gulch. All the workings are in andesitic rocks, chiefly 

breccias, of the Silverton series. The ore occurs in a brecciated zone 

which is usually from 3 to 5 feet wide. The hanging and foot walls 

are well defined by planes of recent slipping, that on the hanging 

wall being especially regular and continuous. These slip planes usually contain a little soft gouge. Between these walls the ore occurs 

in stringers and bunches, partly replacing the shattered country rock 

included within the breccia zone. It consists of pyrite and chalcopyrite and occasionally a little galena. Pyrite is very abundant, occur 

ring in solid masses, which, however, are not mined unless they contain 

chalcopyrite. Next the hanging wall there is a persistent seam, sometimes a foot in width, which consists of crushed country rock with 

sometimes a little white quartz. This portion of the lode is worthless, 

although a little sphalerite and tetrahedrite are said to occur in the 

v quartz. No quartz was seen with the pay ore. The lode is not everywhere productive. There are frequent barren intervals, where the 

space between the walls is filled with broken and altered country rock 

impregnated with pyrite. The wall rock is impregnated with pyrite 

for at least 150 feet from the lode, but no ore is mined outside of the 

walls of the fissure.

The ore is low grade as a whole, containing from 0. 05 to 0.1 ounce 

of gold and 12 to 30 ounces of silver per ton, with up to 30 per cent 

of copper. In 1900 the mine was reopened after some years of idleness, and it was proposed to treat the ore in a new smelter then nearing completion at the point where Cement Creek enters Bakers Park.

The lowest tunnel, which in September, 1900, had a length of about 

550 feet and had not yet cut the lode, exhibits well the rather remarkable mineralization of the Silverton breccias in this vicinity. All the 

rock passed through is heavily impregnated with fine pyrite and frequently contains small sporadic bunches and stringers of galena and 

sphalerite. In some places the andesitic breccia has -been locally 

silicified.

The Henrietta lode is of theoretic interest from the fact that the 

ore, in its freedom from quartz, presence of kaolin, and partial replacement of country rock, as well as in mineralogical character, is similar 

to the ores occurring in the stock deposits of Red Mountain. At the 

Henrietta, however, it is found, not in stock, but in a distinct fissure.

Other mines and prospects. From Prospect Gulch southward to 

Silverton are many prospects along Cement Creek and in the side 

gulches. None of them are yet of much importance and not all were 

visited. The most ambitious of these is the Yukon tunnel of the 

Boston and Silverton Mining Company. No ore has yet been produced, but the tunnel is supplied with a new mill equipped with 

Blake crusher, rolls, jigs, 10 stamps, 2 Wilfley tables, and 4 Frue 

vanners. The power is steam.
INDEX.

}Jage. 

Abbott, J., reference to................... 99

Abrams, Mount, fissures near, course of. 50 

Adams claim, description of.............. 256

Alabama mine, description of ............ 194

Alaska mine, description of .............. 195

Alaskaite, occurrence of.................. 84

Alexandra mine, description of .......... 331

Alunite, analysis of, from National Belle

mine ........................... 235

Amador mine, description of....... ... 194-195

American Belle mine. See National Belle

mine. 

Analyses, alunite...................*_..... 235

andesitic breccia ...................... 125

cosalite................................. 220

kaolinite.........:..................... 234

kobellite.............. ................ 237

monzonitic porphyry................. 127

water ....................... ........ 114

zunyite ............_...._.......... 76

Aiidesitic breccia, analysis of ............. 126

mineral composition of ................ 126

Aiidesitic rock, mineral composition of.. 120 

Animas Forks, decline of ................. 21

Animus River, rocks exposed on ......... 35

Antiperiodic mine, description of........ 172

Anvil Mountain, country rock at...... 129-130

Arrastra Gulch, fissures in, course of.... 48-49

gold on, discovery of.................. 19

note on name of...................._ 145

rock from, character of............... 115

Area discussed, climate of................ 25-26

geographic position of ................ 14

geology of.............................. 30-39

historical sketch of.................... 19-25

location of, map showing ............. 14

maps of............................. 26,32,34

production of.......................... 25

topography of ......................... 26-29

vegetation in ........................... 26

Argall, P., cited ..............!............ 53

Argentina mine, description of .......... 213

Argentite, occurrence and character of.. 83 

Aspen mine, description of.............. 161-163

lode ores of ............................ 94

ore in, depth of........................ 98

workings of, section of................ 162

Baltic group of mines, description of .. 244-245 

Baker, J., exploration by................. 19

Bakers Park, view of ..................... 13

Bancroft, H. H., cited............ ......... 20

Banded structure of ode ores, examples

of.......................... ..... 88-91

Page. 

Barite, occurrence and character of..... 71-72

Barstow mine, description of............. 246

Bassick mine, ore body in, origin of 1..... 107

Becker, G. F., cited ................ 42,65,66,134

Belcher mine, description of.............. 252

ore in, depth of........................ 93

Ben Butler mine, description of.......... 136

Ben Franklin mine, description of ..... 178-179

Benson, J. W., reference to....... ..... 202

Bibliography ....................!......... 15-18

Big Giant lode, description of............ 166

Bill Young mine, description of .......... 187

Bimetallist mine, description of.......... 205

Bismuthinite, occurrence and character

of................................ 82

Black Diamond mine, description of..... 184

Black Silver mine,description of......... 189

Blair Gulch, fissures in, course of ........ 48-49

Bobtail mine See. Barstow mine.

Bonanza mine, descri ption of............. 196

Bonanza tunnel, work on................. 21

Bonita mine. See Red and Bonita mine. 

Bornite, occurrence and character of .... 80

Bournonite, occurrence and character of. 81 

Breccia, andesitic, analysis of ........ 126

mineral composition of ............... 126

Brecciated structure of lode ores ........ 91

British Queen claim, description of ...... 187

Brobdignag claim, description of ........ 249

Brooklyn tunnel, description of.......... 245

Brunot treaty, provisions of.............. 20

Buckeye lode, effect of depth on ......... 93

Buckeye mine, description of ........... 160-161

Bull Domingo mine, ore body in, origin

of................................ 107

Burns Gulch, lodes of^.............. .... 174-176

Calcite, occurrence and character of..... 72

California Gulch, mining in .............. 21

Camp Bird lode, section through rich ore

band in......................... 90

Camp Bird mine, banded ore ac .......... 89-90

description of......................... 200-204

ore from, plates showing............... 72,88

ore in, occurrence of ...^.............. 97

surface workings of, view of.......... 200

Canyon Creek, fissures in, course of...... 50

lodes of............................... 200-205

Carbonate King mine, description of .... 239

Cataract Gulch, fault fissure in .......... 57

Cellular structure in lode ores ........... 91

Cement Creek, fissures near............... 50

mines of.............................. 254-258

springs, ferruginoiis, near ...... ...... 113

259
INDEX.

Page.

Chalcocifce, occurrence and character of . 79 

Chalcopyrite, occurrence and character

of............................... 86

Climate of Silverton quadrangle ......... 25-26

Columbia mine (Cement Creek), description of.......................... 25?

Columbia mine (Savage Basin), description of..............-. ..-..- 214

Congress mine, description of............ 238

Copper, average annual price of.......... 24

occurrence and Character of ---------- 86

Copper, gray. See Tetrahedrite.

Copper, yellow. See Chalcopyrite.

Cosalite, analysis of .,. ....__......._.... 220

occurrence of....-.--.-.-............-. 84

Cotta,B.von,cited .............. 43,44,07,70,103

Country rock, metamorphism of, in connection with ore deposition. 114-131 

relation of fissures to.................. 53-55

relation of lode ores to................ 101

Crooke,W.,reference to .................. 99

Crosby.W. 0., cited........................ 66

Cross, W.,cited ....... .................... 60

outline of geology by.................. 29^39

photographs by........"............. 13, '18,50

reference to ............. 13,55,63,64,115,247

Cross fractures of lodes................... 59

Cunningham Gulch, description of....... 167

. lodes of ..........................'.,....167-170

ore from, plate showing structure of. 88 

Custer lode,description of................ 184

Daubree,A.,cited ......................... . 65

 reference to.._..................._ 52

Davis and Gold King lodes, description 

. of.....................,.......!......... 254-255

De Launay,.cited.....^.................... 136

Decomposition, superficial, products of.. 87 

Deer Park, lode ores of.................... 94

Deer Park Creek, faulting and assuring

at...................^........... 65

Depth, effect of, on character of lode

ores ............. ............. 98-100

Dikes, relation of fissures to.............. 55

Displacement, fissuring and relations of. 55-56 

Dives mine, description of.............. 165-166

ore frotn, plate showing structure of. 86 

Doelter, C., cited .......................... 134

Dolly Varden lode, description of...... 190-191

Dolomite, occurrence and character of.. 72 

E.G.S. vein, description of..... ...... 155-156

Early Bird mine, description of.......... 189

East Iowa vein, description of............ 158

Emmons, S. F., acknowledgments to..... 14

cited.......-..-...-....---- 66,106,132,136,139

quoted ........................... 107,P1 3,217

reference to................ 79,81,106,227,232

Eininous, S. F., and Tower, G. W., cited.. 44 

Empire group of mines, description of... 252 

Empire and Jennie Parker mines, description of.............. ............ 252

Enargite, occurrence and character of... .79

Endlich,F.M., cited................... 20,46,168

- reference to............................ 35

Engineer Mountain, andesitic rock from,

mineralogical composition of. 122 

latito.from, analysis of ................ 122

Page. 

Engineer Mountain district, country rock

in, metamorphism. of ........ 119-124

Enrichment, secondary, of ore bodies,

discussion of................. 136-141

Evening Star claim, description of ....... 184

Fan-view prospect, description of......... 253

Faulting, assuring and, relations of...... 55-56

Faults,extent and age of.................. 37

Fissures, age of ............................ 60

Fissuring, faulting as an accompaniment

of................................ 55

Fissures, intersections and relative age

of..............................J.. % 56-60

origin of............................... 63"-67

persistence of.......................... 61-62

relation of dikes to. ......-...'......... 55

relation of country rock and rock

structure to ................... 53-55

strike-fractures dipping with .._..... 59.

strike-fractures parallel with........ 59

See also Fissures, ore-bearing; Lodes. 

Fissures, lode. See Fissures, ore-bearing. 

Fissures,ore-bearing,coordination of.... 45-53

course of,diagram showing .......... 4Y

distribution of......................... 44-45

See also Fissures. 

Flora vein,'description of................. 212

Fluorite, occurrence and charactei of... 74-75 

Forest and Old Lout mines, description

of ............:................ 192-193

Frank Hough mine, description of..... 189-190

Fry, W.R., cited........................... 242

Galena, change to sphalerite.............. 100

Galena, occurrence and character of.....' 80-81

Galena Mountain,fissures on...._ ...... 45

fissures, intersections of.............. 57

course of.. ................... ....^. 49

lodes of .............................. 170-174

Galena Queen mine, description of....... 240

Galenobismuthite,occurrence of......... 84

Gangue minerals of the ores.............. 70-87

Genesee - Vanderbilt mine, description

of............................. 227-230

fourth level of,plan of ...... .......... 229

ore. bodies of, sketch plan showing

changes in...................... 230

stock ore in, value of ................... 113

underground workings of, plan of.... 228

George Washington lode, description of . 178 

Gold, occurrence and character of........ 85-86

Gold King mine, description of ......... 254-256

Gold Nugget claim,description of........ 173

Golden Fleece mine, fissures at, course of. 49 

Golden Fleece vein, description of.-.-.... 183

Grabill.L.R.,cited ........................ 107

Grand Prize mine, description of......... 231

Gray copper. See Tetrahedr&e. 

Green Mountain, fissures at, intersections of......................... 57

Green Mountain mine, description of .. 168-169 

Groddeck, A. von, cited . .................. 44,70

Ground water, discussion of.......... -141

Guitermanite, occurrence and character

of............................... 82

Gustoii mine,description of ......'... 221-227

longitudinal and transverse sections

through ...........I....... ..... 224
INDEX. 261

Page. 

Guston mine, production of ............... 223

stock ore of, value of................. 112-113

water from spring near, analysis of.. 114 

Guston ore body,discovery of ............ 22

Gnston and. Robinson mines,, underground workings of, plan of.. 224 

Hamlet mine, description of............ 173-174

Hammond. and Meldrum tunnels, description of ......--............ 250

Hancock mine, description of...... ...... 204

Handles Peak, elevation of ............... 26

Hanson, R., reference to................. 181.183

Happy Jack mine, description of........ 197-198

Harvey, J. K., notes furnished by..--.... 22C

reference to.......................... 221,235

Hazeltoii Mountain, lodes of............ 161-163

mining on.............................. 20

Hematite, occurrence and character of.. 83 

Henrietta mine, description of ......... 257-258

Henson Creek, lodes of.................. 189-191

Hermosa limestone, thickness of......... 35

Herron, J., reference to.......... .... 97,209,310

Hidden Treasure mine (Canyon Creek),

description of.................. 204

Hidden Treasure mine (Placer Gulch),

description of.................. 183

Highland Mary mine, description of... 167-168

Hillebrand,'W.F.,analysisby. 76,84,114,234,246

cited............................ 75,81,82,109

reference to ........................... 121

Hills, R. C., cited.......................... 234

Hiortdahl, T., analysis by ................ 234

Hoskins,L.M.,and Van Hise,C.R.,cited. 62 

Hough, J. S., reference to................. 190

Howardsville, lodes near ................. .174

Hiibnerite, occurrence and character

of........................... 86-87,256

Hudson mine, description of............ 239-240

Hurlbut, E.B., analysis by ................ 235

Imogene Basin, mining in................. 200

Innis,E.,reference to ...................'... 168

Iowa lode, ore from, plate showing structures of .. ..................... 86

Iowa mine, country rock near, character

of............................. 116-117

description of.......... .............. 157-159

lode ore in, value of ................... 102

Iowa vein,description of................. 157-158

Iron and Tomboy lodes, cross sections

of.................. ........... 209,210

Ironton, rise and decline of ............... 22

silver near, discovery of .............. 22

topography near ...................... 28

Ironton Park, faulting and Assuring at.. 55 

fissures in,course of................... 50

replacement of limestone by ore at _. 142 

James. J., reference to .................... 81

Japan lode, cross section of ....:.......... 69

Japan mine, description of.............. 211-213

Jay Eye See mine, description of ........ 245

Jennie Parker and Empire mines, description of........................ 252-253

Johnson, M. T., reference to .............. 167

Kaolin, occurrence of, diagram showing . 74 

Kaolinite, analysis of, from National Belle

mine ........................... 234

I'nge.

Kaolinite, occurrence and character of .. 73-74 

Kedzie.G.E.,cited ...................... 241,243

Keller.H.P.,analysis by .................. 237

cited .................................... 109

Keinp.J.F.,cited.......................... 133

KendaJl Mountain, dike and fissure at,

relation of ......... ........ 55

King lode, description of........ ..... 253-254

faulting in .............................. 57

oresof.................. ............... 94

Kobellite, analysis of, from Silver Bell

mine ..................... ...... 237

occurrence of.......................... 84

Koenig, G. A.,cited ....................... 84,195

Krisher, reference to...................... 205

La Belle Creole claim, description of..... 178

Lake City, founding of .................... 21

Lake claim, description of ................ 178

Lake Como, fissures near................... 50

lodes on,view of....................... 52

Landslides, areas affected by............. 37-39

Latite, analysis of ......................... 123

mineral composition of................ 120

Lead,average annual price of ............ 24

Lindgren..W.,cited................... 52,61,62,

63,70,92,115,118,119,123,129,133,134 

Little Giant lode, description of.......... 167

Little Giant mine,opening of............. 19

Little Maud claim, description of......... 173

Lode fissure, definition of................. 43-44

See also Fissures, ore-bearing. 

Lode ores,areal distribution of........... 04-96

banded structure in. .................. 88-91

brecciated structure in ............... 91

cellular structure in .................. 91

massive structure in ........ ...... 87-88

raegascopical features of ............. 87-93

micr oscopi cal features of............. 92-93

origin of................................ 102

relation to country rock .............. 101

secondary alteration of ....... ...... 101-102

spherulitic structure in............... 91-92

structure of............................ 87-93

value of ............ .................. 102-103

See also Lode and stock ores; Ore

deposits. 

Lode and stock ores, origin of .......... 133-141

paragenesis of ....................... 131-133

Lodes, ores of............................. 70-103

ores within, distribution of.......... 96-101

structure of ............................ 67-70

See Fissures. 

London shaft, cross section of banded

vein near ...................... 89

Lookout mine, description of............. 166

Louis, H.,and Phillips, J. A., cited. ...... 56,243

Low, A.H.,analysis by ..................... 220

Maggie Gulch, lod e ores of................ 9.">

Magnet mine, description of .............. 249

Magnolia lode, dike and fissure at........ 55

Maid of the Mist mine, description of.. 193-194 

Mammoth mine, description of ........... 188

Marcasite. character of.............. ...... 78

Masses. See Stocks.

Massive structure of lode ores, examples

of............................... 87-88
262 INDEX.

Page. 

Mastodon mine, description of............ 181

Maud S. claim, replacement of limestone

by ore at....................... 142

Matr.l S. vein, description of ............ 244-245

McNeill, B., acknowledgments to........ 14,226

McNutt.R.J.,reference to.......... ..... 191

Meldrum and Hammond tunnels, description of.......................... 250

Melville lode,description of .............. 158

Metamorphism of country rock in connection with ore deposition .... 114-13!

Meteoric water, action of, in ore deposition ........................... 133-134

Michael Breen mine,description of .... 196-197

Micky Breen mine. See Michael Breen

mine. 

Midnight mine,description of ............ 239

Mineral King mine,description of ....... 240

Mineral Point, banded vein at, cross section of...... ..................... 89

lodes of ..... ........................ 185-189

operations near........................ 22

Mineral waters associated with ore deposits ........................ 113-114

Minerals,gangue,of the ores ............. 70-87

Minerals,ore,of the lodes. -.-.....-...... 77-87

Mineralogy of ores........................ 70-87

Mining, methods of..........._.......... 39-41

Moles mine,direction and position of .... 254

faulting and flssuringat ............... 55

Molybdenite, occurrence and character

of............................... 83

Mono lode, description of............ ..... 244

M'onzonitic porphyry, analyses of........ 127

mineral composition of ............... 129

Monzonite-porphyry, mineral composition of.......................... 128

Morning vein, Jesc_ iption of ............. 212

Mountain Queen mine, description of.. 183-184 

shipments of ore from ................ 21

Mountaineer mine, description of........ 166

National Belle mine, ahmite from, analysis of........................... 235

description of ....................... 331-236

kaolinite from, analysis of ............ 234

kaolinite in ............................ 73

monzoni tic porphyry from near, analysis of.......................... 127

mineral composition of ........... 129

sections through .................._... 232

underground workings of, plan of ... 224 

New York City lode, cross section of .... 67

ore in, effect of depth on.............. 98

New York City vein, description of.... 153-154

faulting along......................... 57

No-Name lode, cross section of........... 88

description of.......................... 177

North Star (King Solomon) group of

lodes, description of......... 163-165

North Star (King Solomon) lode, ore 

from, plate showing structure 

of............................... 86

North Star (King Solomon) mine, description of.................. 163-165

sketch plan of workings of ........... 164

Page.

North Star mine (Little G-iant Mountain), ore in, distribution of .. 97 

ore in, effect of depth on.............. 98-99

North Star lode (Sultan Mountain), ores

of .............................. 94

North Star mine (Sultan Mountain), description of................... 251-253

lode ore in, value of ...... ............ 103

Osceola claim, ore from, plate showing

structure of.._............... 88

Old Lout lode, ore in, effect of depth on . 99 

Old Lout and Forest mines, description

of............. ................ 192-193

Ore, changes in, due to depth ........... 98-100

spaces filled with, origin of......... 104-109

Ores, distribution of, within lodes ...... 96-101

mineralogy of ...........'...'........... 70-37

of the lodes ........................... 70-103

plates showing structure of ......_ 86,88

treatment of, methods of ............. 41-43

See also Ores, lode; Ores, stock; Ores,

lode and stock. 

Ores, lode, areal distribution of.......... 94-96

banded structure iu.'.......-......._ 88-91

brecciated structure in ... _......... 91

cellular structure in ..............._ 91

massive structure in .................. 87-88

megoscopical features of.............. 87-92

microscopical features of... ... _ 92-93 

origin of............................... 102

relation to country rock.............. 101^

secondary alteration of............. 101-102

spherulitic structure in .............. 91-92

structure of ........................... 87-93

value of............ ...... ............ 102-103

See also Ore deposits. 

Ores, lode and stock, origin of.......... 132-141

paragenesis of ........................ 131-132

Ores, low grade, utilization of ............ 23

Ores,stock,change in, with depth...... 111-112

character an/1 structure of......... 109-111

value of.............................. 112-113

See also Ore deposits. 

Ore-bearing fissures. See Fissures, orebearing.

Ore bodies, secondary enrichment of... 136-141 

Ore breaks,definition of ................... 103

Ore deposition, metamorphism of country rock in connection with. 114-131 

Ore deposits, classification of............. 43

mineral waters associated with .... 113-114

See also Ores, lode; Ores, stock. 

Ore minerals of the lodes................. 77-67

Ouray limestone,relations of............. 35

Owen, J,, cited.--........................... 219

Paleozoic formations in Silver ton quadrangle.......................... 35-36

Palmetto mine, description of............ 190

ore in,effect of depth on.............. 99

Parageuesis of lode and stock ores..... 131-132

Paymaster mine, description of .......... 236

Philadelphia mine, description of ........ 170

Phillips, J. A., cited........................ 70

Phillips, J. A. and Louis H.. cited........ 56,243

Pile, reference to.-....._............._._.. 19
INDEX. 268

Pago. 

Placer Gulch, fissures in, course of.... 49-50,52

lode ores of............................ 95

Placer Gulch and Treasure Mountain,

lodes of ....................... 179-185

Polar Star lode, andesitic rockj from, mineral composition of............ '120

metamorphism near ................ 119-124

Polar Star mine, description of......... 187-188

latite from, analysis of............:... 122

ore in,effect of depth on .......... 99

wall rock from, mineral composition

of.............................. 123

Polybasite, occurrence and character of. 82 

Porphyry, intrusions of................... 33-34

Porphyry,monzonitic,analyses of ....... 127

mineral composition of ............... 129

Porphyry Gulch, fissures near, course of. 50 

Potosi series, extent and character of.... 32-33 j

Poughkeepsie Gulch, lode ores of ........ 95

lodes of .............................. 191-190

mining in.............................. 21

Poughkeepsie mine, description of------- 194

Pride of the Rockies mine, description of. 182 

Pride of the West mine, description of. 109-170 

Proustite, occurrence and character of.. 82 

Purington, C. W., cited................... 44,

46,54,56,70,73,91,200,208 

quoted....-......... - 03,206-207

reference to ........ - -- - 64

Pyrite, occurrence and character of..... 77-78

plate showing ......................... 86

Quartz, occurrence and character of..... 70-71

Queen Anne mine, description of ........ 257

Raymond, R. W., cited ................... 194

Red Cloud mine, description of ........ 185-186

marcasitefrom ........................ 78

ore from, plate showing structure of. _ 86 

Red Creek, view of........... ... . 38

Red Mountain.metamorphism near.... 124-131

mines at, view'of ...................... 38

rise and decline of....... ........ ........ 22

silver near, discovery of.............. 22

stocksnear ................ ........:... 104

topography near ...................... 28

Red Mountain district, mine water in,

character of ................... 113

, mining claimsin, map of.............. 105

ore deposits of....................... 214-251

Red Rogerrnclaim, description of......... 196

Replacement deposits, discussion of ... 1.41-143 

Red and Bonita mine, description of 256-257 

Reusch, H., cited .......................... 234

Revenue tunnel, ore transportation in. . 40 

Rhodochrosite, occurrence and character

of... -.-............ ....... 73

Rhodonite, occurrence and character of. 75 

Richmond Basin, fissures in, course of... 50 

Rickard, T. A., cited................. 19,181,215

Ridgway lode, course of .................. 171

ore from, plate showing .............. 72

Ridgway mine,description of .......... 172-173

fault fissure at ........................ 57-58

lode ores of ............................ 95

Rock, A.M.,aid by......................... 13

Rock structure, relation of fissures to ..'.. 53-55

Robinson, J., ore body discovered by..... 215

Robinson mine,description of .......... 3-0-221

Robinson and Guston mines,underground

workings of, plan of............. 224

Ross Basin lodes,description of .......... 257

Royal Tiger mine, description of....... 159-160

lode ores of ............................. 94

Royal vein, description of............... 154-155

Ruby silver. See Proustite.

St. Paul mine, description of............ 238-239

San Juan breccia, sheeted structure in,

view showing........j......... 50

San Juan Chief mine, description of ..... 187

fissures at, intersection of .«.._'...... 57

San Juan formation, extent and character of............. .............. 31

San Juan Queen mine, description of .... 183

San Juan region, historical sketch of..... 19-25

literature on........................... 14-18

San Juan volcanic area, extent and character of ........................ 29-30

San Miguel conglomerate, use of name .. 36 

Saratoga mine, description of .......... 240-244

replacement of limestone by ore at.. 142 

sections through .................... 242,243

Savage Basin,lodes of................... 206-214

Saxon mine, description of................ 195

Schulz,O. J.,acknowledgments to........ 14

cited ............................... ... 223

Schwarz,T.E.,acknowledgments to ..... 14

cited ... 79,80,103,110,137,216,220,228,232,236 

information furnished by............. 218

quoted........................... 218-219,233

reference to............................ 221

Scotia lode, description of................. 182

Scotia mine, fissures at. course of......... 49

Secondary enrichment of ore bodies, discussion of..................... 136-148

Seven Thirty lode,description of .... . 196

Silver, average annual price of........... 24

occurrence and character of.......... 86

Silver, ruby. See Proustite.

Silver Bellmiue,description of ........ 236-238

kobellite from,analysis of ........ .... 237

section through ......................_ 237

Silver Crown lode, sketch section of ..... 63

Silver Lake, lodes west of, projection of . 51 

Silver Lake Basin,country rock of..... 115-119

lode ores of ........... .............. 91

fissures in............................... 44-45

course of........................... 48

general features of.................. 145-146

lode ore in, value of.................... 102

lodes of .............................. 145-161

mining claims in, plat of ............... 146

Silver Lake lode, description of........ 150-153

ore distribution of..................... 97

movemen ts. within .................. 151-152

sketch section across.................. 152

Silver Lake mine, country rock near,

character of ................. 117-118

cross section of New York City lode

of........................:...... 67

description of........................ 149-157

fault fissure at........................... 57
264 INDEX.

Page. 

Silver Lake mine, lode ores of....--.-..-. 94

manner of working.-.-....---.---...-.. 156

ore of,value of ........ ........... 102,156

ore transportation at..-..-...--..---.- 40 

Silver Ledge mine, description of....-- 247-248 

Silver Link mine, description of......... 198-199

sheeted structure near, view showing. 50 

Silver Queen mine (Bear Creek), description of ..........-.---....------ 199

ore in, occurrence of.-.....-.-....---- 9"

Silver Queen mine (Placer Gulch), description of....................181-182

Silver Wing mine, description of ... ....175-176

Silverton, view of ......................... 13

.Silver ton series, extent and character of. 32 

Smelters, erection of...............;-..-.- 22-23

Sound Democrat mine, description of ... 182

Specularite. See Hematite.

Spencer, A.C.,photograph by ............ 200

reference to -...............-----...... 55,64

Sphalerite, change from galena to. -..---. 100

occurrence and character of.......... 81

Spherulitic structure in lode ores........ 91-92

Steiger.G., analysis by......--..--..------ 125

Stelzner lode, description of.............. 158

vein-quartz structure in, plate showing ............................. « 70

Stelzner vein,description of....... . ....154-155

Stibnite, occurrence and character of.... 82

Stock eruptions, extent and character of. 33 

Stock ores,change in, with depth .......111-112

character and structure of ..........109-111

value of--.............. ...............112-113

See also Stock and lode ores; Ore deposits. 

Stock andlode ores,origin of ............132-141

paragenesis of ........................131-132

Stocks, distribution of .................... 104

definition and general description of. 103-104 

Stokes, E.N., analyses by.................122,127

quoted ................................. 78

reference to............................ 77

Stress, tangential, as cause of fissures .... 64-65

Stress, torsional, as a cause of fissures ... 65-66 

Strike fractures parallel with lode, occurrence of ..._.................. 59

Stromeyerite, occurrence and character

of............................... 79

Structure of lode ores .................... 87-93

of lodes ................................ 67-70

Sulphobismuthites, occurrence and character of ... .................... 83-85

Sultan Mountain, lode ores of............. 94

mines of--....._....-__._......_...._. 251-254

Sunnyside Basin, lode ores of.............. 95

lodes of .............................. 176-179

Sunnyside Extension mine, description .

of............................. 180-181

ore from, value of ..................... 102

Sunnyside lode, description of.-..-..... 176-177

vein-qiiartz structure in, plate showing ............................. 70

Sunnyside mine, cross section of NoName lode ..................... 88

description of ....................... 176-178

Page, 

bunnyside mine, fissures at, course of.... 49

ore in,distribution of ..'..-............ 97

Sunset mine,description of.......... . 189

Syracuse Pride mine, description of.... 188-189

Tangential stress as a cause of fissures .. 64-65 

Telluride conglomerate, extent and character of ........................ 36

Telluride quadrangle, fissures in, direction of ......................... 46

fissures in,origin of .... ...... ...... 63

fissuring and faulting in .............. 56

Tellurides, occurrence and character of.. 85 

Terry, J.H.,reference to.................". 176

Tetrahedrite, occurrence and character

of............................... 78-79

Thomas, W. H., information furnished

by............................. 98,163

reference to ........................... -252

Titusville mine, description of ........... 161

Toltec lode, description of ................. 183

Tom Moore lode, description of ........ 174-175

Tomboy mine, description of........... 206-211

lode ore in, value of................. 102-103

ore in, occurrence of .................. 97-98

Tomboy and Iron lodes, cross section of 209,210 

Topography of Silverton quadrangle .... 20-29

Torsional stress as a cause of fissures.... (55-66

Tower, G. W., and Emnions, S. F.. cited.. 44 

Treasure Mountain, fissures on, course of 49 

Treasure Mountain and Placer Gulch, .

lodes of ....................... 179-185

Tungsten ore, deposits of.................. 256

U. S. Depository lode, ore in, effect of

depth on ............. ...... .... 99

U. S. Depository mine, description of... 204-205 

Uncornpahgre Canyon, lodes of ........ 196^-199

^ sheeted structure in, view showing.. 50 

Uncornpahgre Chief mine, description

of.............................. 186-187

ore in, effect of depth on.............. 99

Uucompahgre River, fissures along,

course of....................... 50

Van Hise, C. R., cited. 60,100,133,136,137, 138,139

Van Hise,C. R., and Hoskins,L. M.,cited. 62 

Vegetation in Silverton quadrangle...... 26

Vein, definition of......................... 43

Veins. See also Fissures.

Vein-quartz structure, plates showing... 72

Volcanic rocks, formations underlying .. 34-36

original thickness of ............ ...... 60-61

Volcanism, evidences of presence of...... 133

Walsh.T.F., reference to................ 200,204

Water, analysis of, from spring near Gus

ton mine ....................... 114

Water, ground, discussion of............. 141

Waters, meteoric, action of, in ore deposition ....I..................... 133-134

Webster mine, description of.............. 240

Weed, W. H., cited ................. 132,136,140

Wewissa mine, description of............ 189

Whale vein, description of................ 213

Whale-Rochester vein. See New York

City vein.

Wheel of Fortune mine, description of.. 205 

Wheeler, R., reference to................. 209
INDEX. 265

White Cloud mine, andesitic breccia Irom,

analysis of ............... .... 12(>

andesitic breccia from, mineral composition of ............ ........ 12C

description of..................:....... 230

rock near, character of....... ..... 125-126

Yankee Girl mine, cosalite from, analysis

of ..... ......................... 220

description of............ .............. 221

monzonitic porphyry from near, analysis of.-....---...----......... 127

Page.

Yankee Girl mine, stock ore in, value of.. 112 

Yankee Girl ore body, discovery of....... 22

Yellow copper. .See Chalcopyrite.

Yellow Rose mine, description of......... XQ1

Zinc blende. Cee Sphalerite.

Zinkenite, occurrence and character of.. 81

Zuiii mine, kaolinite in........ ........... 73

description of ....................... :249-250

Zunyite, analysis of....................... 7C

occurrence and character of.......... 75-77

o