Bulletin No. 308 . f A, Economic Geology, 90- 

benes \ B, Descriptive Geology, 111

DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

CHAKLES I). VVALCOTT, DIRECTOR

GEOLOGIC RECONNAISSANCE

SOUTHWESTERN NEVADA AND 

EASTERN CALIFORNIA

SYDNEY H. BALL

WASHINGTON

GOVERNMENT PRINTING OFFICE

1907

CONTENTS.

Page.

Introduction ___ ___ 13

Field work and acknowledgments______ _ _ 13

Location and area_.____ __ ______ 14

Literature _____ ____ 15

The Great Basin______ _____ 16

Topography . _ 36

Climate __________- _ - 17

Hydrology _ . ' IS

General statement_________..__ _ 18

Streams __________________.__ . 18

Springs __ _______ - 19

Hot or warm springs____________-_______- - 19

Cold springs_______:_ _____ ___ __ 20

Tanks __________________^___ _.___-__________ 21

Wells ________________._______-_____-_____:__ 21

Snow _______________________________-________ 22

Signs of water_______________________ ________ 22

Animal life___-__________________________________ 23

Vegetation __ ______ _ ___ ._ '23

Culture ______________________ _______________- 24

Industries ___________________________-____ 24

Towns _______________________________________ 25

Railroads and stages________________________ _ 26

Roads and trails_____________________________. __ 26

Stratigraphic geology___________________________ 26

Pre-Cambrian_____________________________ 26

Cambrian ____________________________________ 28

Ordovician and Silnrian___________________________ 28

Devonian_________:__________________________ 29

Carboniferous ___________________ ____________ 30

Post-Jurassic and pre-Tertiary igneous rocks____________ 30

Tertiary. ___________________________________ 31

Pleistocene and Recent_________________________ 35

Travertine__________:______________________ 35

Desert gravels___________________.______ 35

Playa deposits____________________________ 36

Sand dunes______________._________________1_ 36

Definitions of igneous rocks______________________ 37

Geologic history___________________________________ 38
4 CONTENTS.

*" Page.

Economic geology ______ . _________i________________ 42

History of mining development..--_________ r________ 42

Economic conditions____________-___________ 48'

General character of the ore deposits____________________ 44

Post-Jurassic and pre-Tertiary deposits_____-_______ 44

Deposits in granite___________________ 44

Deposits in Palezoic sedimentary rocks, predominantly limestone________-__ _________________ 44

Tertiary deposits________________________^___ 46

Gold deposits in silicified mouzonite porphyry and related

rocks_______ _ ___________ ____ _ 46

Deposits in rhyolite__ _ _________________ 46

Aids to prospecting______ _ _ _______________ 49

Descriptive geology________________:_________________ 50

Region about Goldh'eld_______________________ 50

Lone Mountain foothills_ __________________:._______ 51

Topography and geography ___________________ 51

General geology___________1_______________ 51

Sedimentary rocks __________________ 51

Cambrian ___________________1 51

Older alluvium._____________ _..____ 52

Igneous rocks___ _ - - 52

Granite-_____________-_____________ 52

Diorite and diorite porphyry__________ 53

Structure ____-_ __ ______________ 54

Economic geology ___ _________.___ _ ________ 54

Northeastern extension of the Silver Peak Range._________ 55

Topography and geography _________ _____ ____ 55

General geology________ _____________ ____ _ 56

Sedimentary rocks____________________ 56

Cambrian_______________________- 56

Siebert lake beds ___________________._ 57

Travertine _.________________________ 58

Igneous rocks __ __________________ 58 

Post-Jurassic granite, granite porphyry, and quartzrnonzonite porphyry _______________ 58

White quartz-monzonite porphyry_____________ 60

Diorite porphyry_______________-_ 60

Andesite _____________________ 61

Rhyolites and dacites_________________ 61

Later rhyolite _ ____ _ _ _ _ _ 62

Basalt _.____ _______________________________ 62

Structure _._________ ___________________ 62

Economic geology__________-__________ 63

Montezuma district_______________ ________ 63

Lida_._______________:________________________ 64

Other mineralized areas __________________ 65

Lime________________________________ 65

Lida-Goldfleld Valley.. __________________________ 65

Mount Jackson and the hills to the northeast__________ 66

Topography and geography._ ____ _ 66
CONTENTS.

Descriptive geology Continued. ' 

.Region about Golclfielcl Continued.

Mount Jackson and the hills to the northeast Continued.

General geology.._______________________ 66

Sedimentary rocks __________ --___- __ 66

Cambrian ______________________ 66

Siebert lake beds.__________.___.____ 67

Igneous rocks_______________________ 67

Diorite porphyry _____________________ 67

Rhyolite _._________________________ 67

Basalt ____________________________________ 68

Structure ..._____________________,_________ 68

Economic geology _____ _ __ _ _ 69

Valley north of Slate Ridge.__________.____________ 71

Goldfleld hills _______________________________ 71

Topography and geography __________ _______ 71

General geology ____ _________ _______ 72

Sedimentary rocks ___________'.__________ 72

Siebert lake beds__-_-_____________ 72

Later tuffs __________________________________ 72

Igneous rocks _._______________ ___ ____ 73

Post-Jurassic granite _._______ ________ 73

Andesite and dacite _._______________i__ 73

Quartz latite and rhyolite.________________ 73

Quartz basalt _.i_____________________ 74

jater rhyolite____________________ 74

Basalt _._____________________,_____ 75

Structure _._____________________________ 76

Economic geology_________.__________________ 76

Alkali Spring Flat_____________________________ 76

Southern Klondike hills________________________ 77

Topography and geography____________________ 77

General geology_____________ L. ________________ 77

Sedimentary-rocks_______________________ 77

Cambrian _______________________ 77

Siebert lake beds___________________ 78

Older alluvium________.___________ 78

Igneous rocks__________^_________-_____ 78

Post-Jurassic granite________________ 78

Earlier rhyolite_____________________ 78

Earlier quartz latite__________-______ 79

Basalt-.:.___________________________ 79

Later rhyolite._____________________ 80

Later quartz latite_____________________ 80

Structure _.________________________________ 80

Economic geology.__________________________ 81

Gold and silver.________________________ 81

Iron ores.________________________ 82

Ralston Valley...______________________________ 83

Stonewall Flat_____________._____________________ 83

Stonewall Mountain.________________________ 83

Topography and geography _ _ _ _ _ _ 83

General geology.___________________________ 84
6 CONTENTS.

Descriptive geology Continued. ' Page. 

Region about Goldfield Continued. 

Stonewall Mountain Continued. 

General geology Continued.

Sedimentary rocks_____________________ 84

Cambrian __________________ _ 84

Siebert lake beds___.______.___..________ 84

Igneous rocks_________________________ 84

Post-Jurassic granite and granite porphyry____ 84

Earlier rhyolite________________'______ 85

Quartz syenite and quartz-monzonite porphyry___ 85

Later rhyolite_______:_________ 80

Basalt ___,___.._______.________-___ 87

Structure _._____________________________ 87

Economic geology________________________-__ 88

Ranges north of Pahute Mesa._______________,___ 89

Cactus Range__________________________ 89'

Topography and geography.______.._'____._______ . 89

General geology_________.._______________ 89

Sedimentary rocks_----_______________ __ 89

Pogonip limestone.:_____________ _ __ 89

Eureka quartzite__________:__________ 90

Weber conglomerate_________________ 90

Igneous rocks___________________________ 90

Post-Jurassic granite porphyry and granite_____ 90

Pre-Tertiary cliorite porphyry___________ 91

Hornblende-biotite Jatite___________ 91

Earlier rhyolite___________________ 92

Biotite andesite__________________.____ 93

Augite andesite____________ _.________ 94

Later rhyolite (?) _.____________________ 94

Basalt _._____________.____________ 94

Structure________________________________ 94

Economic geology.___________- _________________ 95

Hills bet\Ar een the Cactus and Kawich ranges____________ 90

Topography and geography____________________ 90

General geology________________________________ 90

Sedimentary rocks _______________,______ 90

Eureka.( ?) quartzite__________________ 90

Igneous rocks___'________________________ 90

Rhyolite_____________________________ 90

Biotite andesite____:________'.____ 90

Basalt -___________________________ 90

Monitor Hills.____._____________________________ 97

General geology_______________________ 97

Sedimentary rocks________________________ 97

Siebert lake beds_____________________ 97

Igneous rocks.____________________________ 97

Granite..__________________________ 97

Rhyolite-__________________________ 97

Basalt..__________________________ 97

Structure________________________________ 98

Cactus Flat-_____________________________:_ 98

Gold Plat____________________-_____________ 98
CONTENTS. 7

Descriptive geology Continued. Page. 

Ranges north of Paliutc Mesa Continued.

Kawich Range ______________ ______________ 99

Topography and geography__^___ __._____.______ 99

General geology:_____________________________ 100

Sedimentary rocks_____-________________ 100

Pogouip limestone and Eureka quartzite________ i.OO

Lone Mountain limestone _____^______________ 102

Siebert lake beds (?)____________________ 1.02

Igneous rocks __________'_________._____ 1.08

Post-Jurassic granite ________.__________ 103

Diorite porphyry ____________._________ 103

Morizonite porphyry _________________ 103

Earlier rhyolite._________________1___ 104

Earlier basalt______________________ 105

Biotite andesite _____________________ 106

Dacite___.______.____________________ 106

Later rhyolite ____________________ 107

Later basalt and associated andesites__ ^ _______ 107

Structure ____________________ _________. 1.08

Economic geology ______^_________________1:_ 108

Silverbow ________________________ _ 109

Slakes Camp _________________________ 1.10

Eden ____________.___________ ______ 110

Kawich .____________________________ 111

Southern Kawich ____________:____________ 113

Areas favorable to prospecting_______________ 113

Reveille Valley _______________________._______ 114

Kawich Valley ______________ ________________ 114

Reveille Range _____________________________ 114

Topography and geography_________._________ 114

General geology _________________________ 115

Sedimentary rocks _______________________ 115

Weber conglomerate- __________________ 115

Pennsylvania!! limestone ______________ 115

Ig'neous rocks____________,.___.__.________ 116

Rhyolite__________________:______ 116

Basalt_______________.__________ 116

Structure_____:_________________________ 117

Economic geology____________________._____ 117

Railroad Valley_________________-____________ 118

Belted Range________________________________ 118

Topography and geography___ _ ____________ u 118

General geology___________________________ 1.19

Sedimentary rocks__________.__.________ 119

Pogonip limestone___________-_________ 119

Weber conglomerate________:__._______ 120

Pennsylvanian limestone________________ 121

Siebert lake beds__________-______________ 122

Igneous rocks____________._____________ 123

Mouzouite_________________________ 123

Granite___1_____________.__________ 123

Andesite______________.__________ 125
8 CONTENTS.

Descriptive geology Continued. rage. 

Ranges north of Pahute Mesa Continued. 

Belted Range Continued.

General geology Continued. 

Igneous rocks Continued.

Earlier rhyolite_________________._____ 125

Later rhyolite_____^_____.___.______ 127

Basalt____________.______________ 127

Structure,_______________.______ _ _____________ 128

Economic geology_______________________ 128.

Oak Spring____________________________ 128

Other areas_____________.___________ 130

Pahute Mesa_________________________________ 131

Topography and geography____________________ 131

General geology_______________________ 131

Metamorphic rocks_________-__-_________ 132

Mica schists________________________ 132

Sedimentary rocks___________________ 132

Paleozoic quartette__________-______ 182

Siebert lake beds____________________ 132

Later tuffs__________________________- 132

Recent desert gravels_____________________ 133

Igneous rocks______________________. 133

Pre-grauite monzonite_______________ 133

Post-Jurassic granite_____._____________ 133

Earliest rhyolite____________. _____.__ 135

Biotite andesite_____________________ 135

Middle rhyolite__________'_______________. 130

Latest rhyolite_____________________ 130

Basalt __________________________________ 137

Structure ________________._____________ 137

Economic geology_________________________. 137

Trappmans Camp___________________ 138

Wilsons Camp____._______,_______________. 139

Gold Crater ..-_______________________.__. 139

Other areas______________________*______ 140

Tolicha Peak and Quartz Mountain___________________ 141

Topography and geography_____ _.,_____________ 141

General geology___________________________ 141

Sedimentary rocks__________________________ 141

Cambrian ( ?) schist______.___________. 141.

Igneous rocks______________________ 141

Structure _______________________________ 142

Economic geology_________________________ 142

Mountains southeast of Pahute Mesa____________________ 142

Shoshone and Skull mountains and the hills in the vicinity___ 142

Topography and geography._________________ 142

General geology___________________ _________ 143

Sedimentary rocks_____________________ 143

Pennsylvanian limestone________________ - 143

Siebert lake beds____________________ 143

Igneous rocks__'._____________________ 144

Quartz-monzonite porphyry ______________ 144

Earlier rhyolite__________________- 145
CONTENTS. 9

Descriptive geology Continued. Page. 

Mountains southeast of Pahute Mesa Continued.

Shoshone and Skull mountains and the hills in the vicinity Con. 

General geology Continued. 

Igneous rocks Continued.

Later rhyolite_________________________ 145

Basalt ________._______________'____ 146

Structure ________________________ 147

Economic geology_________________________ 147

Specter Range and Skeleton Hills__:______________ 147

Topography and geography______________ 147

General geology.. _______________'_______ 148

Sedimentary rocks____________________ 148

Prospect Mountain quarteite______________ 148

Prospect Mountain limestone-_____________ .1.48

Igneous rocks_________________^_______ 149

Structure_______________________________._ 149

Economic geology_._______________________ 150

Yucca Mountain_______ ._______________ 150

Topography and geography_____________________ 150

General geology___________________________ 150

Post-Jurassic pegmatite__________________ 151

Rhyolite and latite___________________ 151

Basalt _.__________________________ 151

Structure ________________________________ 152

Economic geology___________________________ 152

Timber Mountain.___________________________ 153

Topography and geography_____________________ 153

Geology _______________________________ 153

Rhyolite _.________________.________ 153

Basalt_._________________________ 153

Bare Mountain_____________________________ 153

Topography and geography_____________________ 153

General geology__________________________ 154

Paleozoic sedimentary rocks_____ _ _ 154

Igneous rocks_______________________ ____ 155

Post-Jurassic pegmatites_________________ 155

Diorite porphyry____________ _ _ _ 156

Tertiary rhyolite and-basalt____ _ _ _ 156

Structure___-____________________________ 156

Economic geology_____________________ __. 15o

Sarcobatus Flat________________________________ 157

Amargosa Desert_________________________ _____ 158

Amargosa mountain system_______________ ..___ 1.60

Amargosa Range___________________i~_ _ 160

Topography and geography _ _ . _ __ 160

General geology________________ _ 162

Sedimentary rocks______________ _ 162

Prospect Mountain quartzite (?)___-___ 162

Pogonip limestone-______ _ .. 164

Eureka quarteite________ 165

Lone Mountain limestone ________ _ - 165

Siebert lake beds and contemporaneous deposits 165

Older alluvium_________ 166
10 . CONTENTS.

Descriptive geology Continued. Page. 

Amargosa Mountain system Continued. 

Amargosa Range Continued. 

General geology Continued.

Igneous rocks______________________ 1.G7

Granite porphyry ___________________ 167

Diorite porphyry_____________________ 107

Biotite andesite____________________ 107

Earlier rhyolite______________________ 168

Earlier basalt_______________________ 170

Later rhyolite and biotite latite_-_________ 170

Later basalt_______^_______________ 171

Structure________________________________ 172

Economic geology ____________._____________ 173

Happy Hooligan mine_____ . ______________ 173

Chloride Cliff___________________________ 173

Lee's Camp__________________________.___ 175

Areas favorable for prospecting______________ 175

Bullfrog Hills ________________________________ 176

Topography and geography____________________ 176

General geology________ __ _ _ ___ _____ 176

Sedimentary rocks___________.__________ 177

Pre-Silurian schist_____________________ 177

Eureka quartzite_^.____________________ 177

Lone Mountain limestone._______________ 178

Siebert lake beds_____________________ 178

Older alluvium______________________ 178

Igneous rocks ______________________ 178

Post-Jurassic pegmatite and alaskite_________ 178

Pre-Tertiary diorite porphyry______..^____ 179

Biotite andesite_____________________ 179

Rhyolite-____________________.._______.___ ISOEarlier basalt.______________________ 181

Later basalt______________________________ 181

Structure ______________________.__.______ 181

Economic geology ___________________________ 182

Gold Mountain ridge and the hills to the north of Grapevine

Canyon _._____________________._______________ 182

Topography and geography._____________________ 182

General geology.________________-_ _ _ 183

Sedimentary rocks_______________________ 183

Cambrian _________________________ 183

Igneous rocks__________________ __ 184

Quartx-monzonite porphyry_____ 181

Post-Jurassic granite___________________ 184

Diorite porphyry- - 186

Rhyolite_______-_____-_ __ 186

Basalt -_______-___-____ __ _ 186

Structure _________________________-____ 187

Economic geology _'__ ___ _ _ 187

Old Camp ___..__..____..___-____________ 188

Tokop _____ ______!-..__..- _ _ . 189

Oriental Wash ..,._..-_.... _ _______________ 190
CONTENTS. 11

Descriptive, geology Continued. . p 

Auiargosa Mountain system Continued.

Slate Ridge. ___.______.__.._________.__.________ 191

Topography and geography______________ __ _ 191

General geology._______________ ______; _ 191

Sedimentary rocks_________________ 191

Cambrian _______________________ 191

Later tuffs________________________. 192

Igneous rocks.____.________________ 192

Post-Jurassic granite________________ 192

Pre-Tertiary quartz-nionzonite porphyry._____ 193

Pre-Tertiary diorite porphyry.__________ 193

Earlier rhyolite_________________________ 193

Later rhyolite. __ _____ ___ __- 193

Basalt __________________________ _! . 194

Structure ___________1__________________. 194

 Economic geology___________________________ 194

Death Valley._____._______________^._____-_______-____. 195

Topography and geography_____________________ 195

General geology__________________________ 197

Sediments _____________________________ 197

General statement._________________ 197

Tertiary lake beds (including Siebert lake beds)__ :i98

Older alluvium______________________ 199

Geologic history_________^________________ 200

Economic geology..__ __. _.___ ---_______ 201

Panamint Range_____ .___ ___________ 201

Topography and geography_____________________ 201

General geology- ______ ___ _____________, 202

Sedimentary rocks_____________________ 202

Prospect Mountain (?) quartzite____________ 202

Pogonip limestone _______. _________ 202

Pennsylvania!! limestone_______________ 203

Older alluvium________________.______: 204

Recent alluvium_ ___________________ 204

Igneous rocks _ _ _ . _ 205

.Earlier quartz-monzouite porphyry_________ 205

Quart/ monzonite--___________-______ 205

Soda syenite__,________________ _,_ 207

Granite ___________________________ 208

Later quartz-mouzonite porphyry_________ 208

Diorite porphyry________...___________ 208

Basalt _____________. -__________ 209

Structure ______,_____________-___________ 210

Economic geology________________________ 211

Index__________..__________-______________________ 213
ILLUSTRATIONS.

Page. 

PLATE I. Geologic map of an area in southwestern Nevada and. eastern

California ________.._______:________________ 26 

II. A, Pahute Mesa, showing benches determined by resistant flows 

of basalt; B, Death Valley, showing sand dunes protected by 

desert shrubbery (inesquite and creosote bush)__________ 36

III. Marble Canyon, Panamint Range, showing metamorphosed

Pogonip limestone near quartz-niouzonite batholith_______ 200 

FIG. 1. Index map showing location of area in southwestern Nevada and

eastern California_________________________ 14 

2. Profile across Sarcobatus Flat and Amargosa Desert, showing

relation of ground-water level to surface______________ 21 

8. Columnar section of rocks of southwestern Nevada and eastern

California _________r_____________________.___ 27

4. Economic map showing areas of altered Tertiary rocks______ 43

5. Flow folds in rhyolite (hill 10 miles east of north of Mount Jackson), showing thickening of more glassy rhyolite (white) on 

crests and troughs of folds and cross fractures in more lithoidal 

rhyolite on limbs of folds_________i_____________ 68

6. East-west section across Mount Jackson hills 1 mile south of

halfway station____________________________ 68

7. Section across north face of Stonewall Mountain through Stonewall Spring__________________________________ 88

8. East-west section across Kawich Range, 2$ miles north of Kawich- 10S

9. Section across north end of Reveille Valley, showing an inclosed

valley partially underlain by basalt_________________ 114

10. East-west section across Reveille Range at northern boundary of

area surveyed_______ _ ____ __^________ 117

11. East-west profile across Belted Range 3 miles north of Wheelbarrow Peak, showing nature, character, and present eastward 

tilt of Pliocene surface________________________ 119

12. East-west section across Belted Range through- Belted Peak___ 126

13. North-south section through Oak Spring Butte, Belted Range___ 127

14. Second and third systems of quartz veins in granite at Trappmans

Camp, as exposed on face of incline_________________ 138

15. Northwest-southeast section through Specter Range_______ 149 

 16. Northwest-southeast section across Slate and Gold Mountain

ridges _____,___________________________ 187 

17. East-west section across Death Valley 6 miles north of boundary

of area mapped____________________________ 198 

12
A GEOLOGIC RECONNAISSANCE IN SOUTHWESTERN 

NKVADA AND EASTERN CALIFORNIA. .

By SYDNEY H. BALL.

INTRODUCTION.

FIELD WORK AND ACKNOWLEDGMENTS.

The field work on which this bulletin is based covered a period 

lasting from June to December, inclusive, 1905. The geologic work 

was under the general supervision of Mr. F. L. Ransome, and was 

carried on simultaneously with the mapping of the topographic base 

by Messrs. R. H. Chapman and B. D. Stewart.

The writer is fully conscious of the many inaccuracies of the 

geologic map herewith presented, but trusts that it may prove not 

only an aid to the prospector and miner, but a contribution to the 

geology of an intensely interesting region. Each day approximately 

45 square miles was mapped in an area of by no means simple geology, and in many localities the geologic mapping of necessity preceded the topographic. No other region in the United States is so 

favorable to-rapid mapping, since the exposures are unexcelled and 

the scant vegetation masks scarcely a geologic detail. The geology 

of the Paleozoic rocks is, however, difficult, partly on account of the 

lithologic similarity of many of the formations, but largely because 

these older rocks are in part hidden by mantles of Tertiary lavas and 

Recent gravels. In the text it has been the endeavor to distinguish 

clearly between observations made at close range and inferences 

drawn with the aid of the field glass. The mapping of the outer 

Goldfield hills and of the Pahute Mesa are particularly unsatisfactory.

To Mr. F. L. Ransome the writer desires to express his appreciation for general oversight and helpful criticism. Messrs. J4 E. 

Spurr, F. B. Weeks, W. H. Emmons, and G. H. Garrey have been 

freely consulted on various points of Nevada geology. Messrs. R. H. 

Chapman and B. D. Stewart and their assistants, Messrs. T. C. 

Spaulding, E. A. Childers, and S. G. Benedict, aided the Avork by 

collecting in the field specimens of rocks from many points not visited by the writer. Mr. Spaulding also furnished some photographs 

and determined the species of the desert flora. To Messrs. W. F. Hil13
14 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

lebrand, George Steiger, and Waldemar T. Schaller the writer is indebted for mineralogical determinations, and to Messrs. E. O. Ulrich, 

G. H. Girty, Edward M. Kindle, and F. H. Knowlton for paleontologic data. The helpful interest and kindly hospitality of the Nevada pioneers is also gratefully acknowledged.

LOCATION AND AREA.

The area surveyed (see fig. 1) is situated in the south-central portion of the Great Basin and includes portions of Esmeralda and Nye

FIG. 1. Index map showing location of area in southwestern Nevada and eastern

California.

counties, Nev., and Inyo County, Cal. The topographic map is on a 

scale of 1: 253,440 (approximately 4 miles to the inch), with contour 

intervals of 100 feet, and covers the area lying between 36° 30' and 

38° north latitude, and 116° 00' an,d 117° 30' west longitude. This 

area, embracing within its limits 8,550 square miles, is the equivalent of nine of the usual 30-minute quadrangles of the Geologic 

Atlas of the United States.
INTRODUCTION. 15- 

LITERATURE.

The literature dealing with this portion of Nevada and California is scanty. In 1871 Mr. G. K. Gilbert visited the Reveille 

Range and later the Oasis Valley and crossed the Grapevine Range. 

In 1899 Mr. J. E. Spun- went from Lida to Stonewall Spring and 

thence across the Cactus, Ktiwich, and Reveille ranges. He also 

crossed Death Valley and the Funeral and Panamint ranges to the 

south of the area included in the present map. Since that time he 

has made extended studies in the neighboring districts of Tonopah 

and Silver Peak. In 1899-1900 Mr. H. W. Turner surveyed geologically the Silver Peak area, a thirty-minute quadrangle, which 

adjoins on the northwest the area mapped in this report. In 19cO 

Mr. M. R. Campbell made a reconnaissance to the south of the area 

here described. In 1905 Messrs. F. L. Ransome, G. H. Garrey, and 

W. H. Emmons made detailed studies of the geology and ore deposits of Goldfield and Bullfrog, and a preliminary account of the 

results of their work appears in Bulletin No. 303 of the United 

States Geological Survey. Since the discovery of the veins of Tonopah in 1900 the technical journals have contained numerous references to the mines in this portion of Nevada and California, but these 

have not been included in the following bibliography, since, with a 

few exceptions, they contain nothing of permanent value:

GILBERT, G. K. Report on the geology of portions of Nevada, Utah, California, 

and Arizona examined in the years 1871 and 1872. IJ. S. Geog. and Geol. 

. Surveys West of the One Hundredth Meridian, vol. 3, Geology, 1875, pp. 

21-387.

Describes the Reveille and Arnargosa (Grapevine) ranges and Bare 

Mountain, also the structure of the Basin Range.

HAGUE, ARNOLD. Geology of the Eureka district, Nevada, with on atlas. Mon. 

U. S. Geol. Survey, vol. 20, 1892.

Describes the geology and ore deposits of Eureka, Nev. The Paleozoic 

section will be used as the type section in the present report. 

SPURR, J. E. Descriptive geology of Nevada south of the fortieth parallel and 

adjacent portions of California. Bull. U. S. Geol. Survey No. 208, 1903.

Describes the geology and contains a general geologic map, scale 15 miles 

to the inch. 

TURNER, H. W. Silver Peak folio ; unpublished.

Describes general and economic geology of Silver Peak (Nev.) quadrangle. 

SPURR, J. E. The succession and relation of lavas of the Great Basin region.

Jour. Geol., voL 8, 1900, pp. 621-646. 

SPURR, J. E. Origin and structure of the Basin Ranges. Bull. Geol. Soc.

America, vol. 12, 1901, pp. 217-270. ^

CAMPBELL, M. R, Reconnaissance of the borax deposits of Death Valley and 

. Mohave Desert. Bull. U. S. Geol. Survey No. 200, 1902.

Treats particularly of the borax deposits and of Tertiary lake beds. 

SPURR, J. E. Geology of the Tonopah mining district, Nevada. Prof. Paper 

U. S. Geol. Survey No. 42, 1905.
16 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

SPURK, J. E. The ore deposits of the Silver Peak (Nevada) quadrangle. Prof. 

Paper U. S. Geol. Survey No. 55, 1906.

BALL, SYDNEY H.^ Notes on the ore deposits of southwestern Nevada and 

eastern California. Bull. U. S. Geol. Survey No. 285, 1906, pp. 53-73.

RANSOM E, F. L. A preliminary account of Goldfield, Bullfrog, and other mining districts in southern Nevada; with notes on the Manhattan district 

by W. H. Enimous and G. H. Garrey. Bull. U. S. Geol. Survey No. 303, 

1906.

THE GREAT BASIN.

The Great Basin is an elevated region in Nevada and contiguous 

portions of Oregon, California, and Utah, containing approximately 

208,500 square miles. None of its streams flow to the ocean, and in 

this it differs from all other provinces of the United States. The 

region is arid, the precipitation being less than 20 inches a year. 

The scenery, were it not for the grotesque form and bizarre coloring 

of many of the mountains and hills, would be depressingly dreary.

The mountain ranges of the region for the most part trend north 

and south and are characteristically rugged and bare, although the 

crests of some of the higher ranges are covered by a scant growth of 

timber. The mountains are cut by deep caityons, and in a few of 

these streams flow, only to sink in the desert gravels. Associated 

with the ranges are low hill groups and mesas, many of which also 

have a north and south elongation. Between the mountains and hills 

are broad, gently sloping, inclosed valleys, which send branches into 

and in places across the mountains. The lowest portion of most of 

the valleys is occupied by either a lake or a playa, which during the 

greater part of the year is a level waste of hard clay, but after heavy 

rains is covered by a thin sheet of water.

TOPOGRAPHY.

The area- under discussion, a typical portion of the Great Basin, is 

one of mountain ranges and mesas with wide valleys of gentle slope 

between. To the north of the broad Pahute Mesa lie mountain ranges 

with a general north-south trend. Southeast of the mesa the mountains are small groups whose crest lines run in various directions. 

The Grapevine and Panamint ranges, southwest of the mesa, extend 

from northwest to southeast and are in consequence parallel to the 

Sierra Nevada. The relief of the area is great; Kawich Peak is 

0,500 feet above sea level and the part of Death Valley within the area 

 lies 280 feet below sea level. Few of the ranges, however, rise more 

than 3,000 feet above the flat valley, although the mountain front 

on either side of Death Valley reaches an elevation of 7,000 feet 

within a distance of 12 miles. Between mountains with distinct 

crests, such as the Kawich Range, and the small hillocks in the desert
INTRODUCTION, CLIMATE. 17

valleys there is every gradation. The mountains are cut by gorges 

which in the more elevated ranges are deep canyons. The streams 

descend from the mountains to the flat valleys on alluvial fans and 

commonly even the stream channel disappears before the playa in 

the .center of the valley is reached.

The valleys are inclosed basins which slope rather steeply next to the 

mountains, but decrease in grade rapidly, the central portion being 

a flat in which the eye can see no differences in relief. This level 

bottom is in most cases a playa. The borders of any given valley 

are, as a rule, approximately equal in elevation, although the desert 

gravels extend to greater elevations on the higher inclosing mountains. In such cases, while the slopes are of approximately equal 

descent, that from the higher mountains is much longer, and in consequence the playa is nearer the lower hills. Near the mountains 

the alluvial slopes are scored by numerous drainage lines, and hills 

protrude through their surface. The inclosed basins send bays and 

arms of detrital wash into the mountains and in places two opposed 

arms meet and form a strait of alluvial material. Every hill within 

the area furnishes each year material with which it is slowly beingoverridden by the constantly growing flat valleys. These valleys at 

one time may have been united to one another so that they formed a 

single drainage system, flowing to the south. Whether this was the 

case or not, it is evident that they are formed in three ways by the 

union across a valley of opposed alluvial fans, as is exemplified by 

the small inclosed valleys of Grapevine Canyon; by the outflow of a 

lava barrier, such as that between Sarcobatus Flat and the inclosed 

valley to the north; or by erogenic movements, of which the Bullfrog 

Hills between Sarcobatus Flat and the Amargosa Desert are, in part 

at least, an example.

CLIMATE.

The area has an arid climate, Avith hot, dry summers and, except in 

the higher mountains, mild winters. The temperature in summer 

often rises above 100° F., the intensity of the heat, however, being 

mollified by the dryness of the atmosphere. Records kept at Hawthorne, Sodaville, and Palmetto, Nev., and quoted by Turner" show 

that the average annual precipitation to the north of the area varies 

from 3-J inches in the valleys to 15 inches on the highest mountains. 

These figures are probably both somewhat high for the area under 

consideration. The precipitation is largely concentrated in cloudbursts and 4 or 5 inches of rain may pour down in a few hours.

0 Turner, H. W., Silver Peak folio; unpublished, 

Bull. 308 07 M 2
18 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

HYDROLOGY.

GENERAL STATEMENT.

The water resources of this area consist of streams, springs, tanks, 

wells, and snow. Data concerning the local water resources are given 

 n the descriptions of the mountain ranges and valleys. While sufficient water is available or can.be developed at a number of points for 

villages, mills, small ranches, and truck gardening, it is probable that 

the present supply of the area will never be greatly increased.

STREAMS.

Well-developed drainage systems exist in the hills and mountains, 

but nearly all the channels, except in times of cloud-bursts, are dry. 

Only in the higher mountains where heavy snows fall are perennial 

streams found, and the longest of these has a length of less than 4 

miles. While the streams are small, a few, notably the Amargosa, 

furnish sufficient water for concentrating mills.

The so-called Amargosa River heads well up in Pahute Mesa, 

and the stream channel can be traced through the Amargosa Desert 

into Death Valley. Water comes to the surface only in that portion 

known as Oasis Valley, where numerous springs burst forth and give 

rise to small streams from 200 feet to one-half mile in length. Above 

Indian Camp the channel of .the Amargosa occupies a canyon 500 feet 

deep, while between this point and Beatty the valley, from 200 yards 

to 1 mile wide, is bordered by low hills. The valley floor is here 

formed of fine clay, which, where not covered by drifting sand, supports a fair growth of salt grass. In places many acres are covered 

with an incrustation of white alkali. Between Beatty and Gold Center the valley contracts to a gorge. In the Amargosa Desert the channel is from 4 to 15 feet deep and 100 feet wide. In addition to the 

recent channel there are several older channel remnants. This shallow, sinuous channel, lined by heaps of angular bowlders and banks 

of sand, strongly resembles the deserted river beds of the Great 

Plains.

Four small streams are situated in Kawich Range. Breen Creek 

has its origin in a large number of springs rising from a marshy 

area on the Breen ranch. The stream in summer is from 1 to 3 feet 

wide and 2 to 4 inches deep. Early in the morning it flows to Silver'bow, a distance of 3^ miles, but by night the lower 2 miles are 

dry. The water at sunset is warm, Avhile in the morning it is cold. 

The daily variation in size and temperature is characteristic of 

all the streams of this region and is due to the great heat of midday, 

which warms the water and induces evaporation. The large spring 

1| miles below the Longstreet ranch yields a streanr of water 1 foot 

wide and 3 or 4 inches deep, which sinks in the valley gravel onehalf mile from its source. The underflow rises to the surface three,
HYDEOLOGY, SPRINGS. 19

times in the course of the tortuous Little Mill Creek Canyon, on the 

oast side of the Kawich Range above Eden. The largest of these 

streams is 1^ feet wide and flows 1^ miles. A streamlet 200 yards 

long flows from the large spring commonly called " Georges Water," 

on the east side of the Kawich Range.

Salt Creek, 15 feet wide, rises in Death Valley, flows 2 miles, and 

then sinks. The water is heavily charged with sodium chloride 

and other salts. In the Salt Flat of Death Valley are, many gently 

flowing small streams and pools of salt water. Small streams flow 

from the Staininger ranch and from Grapevine Springs, in the Amargosa Range, but each sinks Avithin 1 mile of its head. Cottomvood 

Creek, in the Panamint Range, is 4 feet wide at its spring head, but 

sinks in gravel within 2 miles. Cottonwood and willow trees and 

grapevines line its banks, and water cress groAvs luxuriantly in the 

Avater. A short distance below the sink of this stream Avater again 

runs in the canyon for 100 yards. In the Stonewall Mountains Avater 

rises in the bed of a gulch one-fourth mile north of StoneAvall Spring. 

The streamlet, 1 foot \vide and 3 inches deep, sinks in the gravel 100 

feet from its source.

SPRINGS.

The springs are of tAvo kinds hot or Avarm and cold. The hot 

springs appear to be vents of deeply circulating Avaters; the cold 

springs evidently come from shallow depths.

HOT OR AVARM -SPRINGS.

Alkali Spring is located 11 miles northAvest of Goldfield. The 

waters originally rose at a number of small seeps, but recently the 

Combination Mines Company, of Goldfield, drove a tunnel into the 

gentle slope, concentrating the floAV in a single channel. According 

to Mr. Edgar A. Collins, of this company, about 85,000 gallons of Avater per day floAvs from the spring and is pumped to the Combination 

mill at Goldfield. The \vater is clear, slightly alkaline in taste, and 

smells of hydrogen sulphide. An analysis by Abbot A. Hanks, kindly 

furnished by Mr. Collins, is as follows:

Analysis of ivater from Alkali Spring..

Grains per wine gallon.

Silica, insoluble ___________.________________________ 2. 449 

Iron oxides and alumina.. _____ _ _ ___ .314 

Calcium carbonate __ ________:______ :___* _______ 6. 764 

Sodium chloride____________________________________ 6.122 

Sodium sulphate_________ _____ __ ___ 43. 341

58. 990

At the mouth of the 40-foot tunnel the temperature of the Avater is 

about 120° F., and at the breast it is at least 140° F. The stream 

flows from residual bowlders and soil of the later rhyolite, and the
20 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

bowlders are badly decomposed and crumble readily in the hand. 

One hundred yards north of the pumping station is a low dome of 

grayish-brown travertine, probably an abandoned vent of the spring.

Hicks Hot Springs, situated at the base of a low hillof silicified 

rhyolite on the east bank of Amargosa River about 7 miles above 

Beatty, are five in number. The hottest spring, which supplies the 

bath house, is said to have a temperature of 110° F. and to furnish 

65,000 gallons per day. The springs in the vicinity which flow from 

the gravels of Oasis Valley are cool, and it is possible that the warm 

waters are genetically connected Avith the silicification of the rhyolite.

Water rises at the Staininger ranch, in the Amargosa Range, at several places in the canyon gravel, the total flow approximating 600,000 

gallons a day. The water in December had a temperature of 75° F., 

while that of the air was but 49°. The surrounding hills are formed 

of Siebert lake beds and Pliocene-Pleistocene basalt flows. The 

Grapevine Springs flow from shallow depressions and valleys in the 

older alluvium and from the contact of that formation and the 

Pogonip limestone. Much of this water is tepid. Pliocene-Pleistocene basalt flows occur in this vicinity. At Ash Meadows, in the 

Amargosa Desert, 1 mile south of the area mapped, springs are associated with the older alluvium. The temperature of the larger 

springs is reported to be 76° F.; that of one of the smaller springs is 

94° F.

These hot or warm springs are characterized by a rather large and 

constant flow of water. They 'are without much doubt the vents of 

deeply circulating waters, and their association in many places with 

recent volcanic rocks suggests that they may in part owe their heat 

to volcanism, if, indeed, they are not magmatic waters.

COLD SPRINGS.

Cold springs and seeps are situated either at the contact of alluvial 

deposits and the mountain bed rock or in the gravels of mountain 

canyons. In the latter case the surface waters appear to seep through 

the valley gravel and to rise where the bed rock forms a bar across the 

channel. The spring from which Cottonwood Creek flows may be 

cited as an example. Springs of this class are common in the large 

quartz-monzonite area of the Panamint Range. In the granite of 

Gold Mountain and the Cambrian rocks of the Montezuma district a 

water zone occurs at the contact of the solid rock and the residual and 

detrital soil. In other cases surface water has seeped into the more 

pervious strata, particularly the Siebert lake beds, the older alluvium, 

and altered varieties of rhyolite, and many springs are situated where 

these beds either outcrop or are covered by a veneer of detrital or residual material.. Springs are located sporadically throughout the area 

surveyed, but seem to be more abundant around the bases of the 

higher mountains, especially of those which are covered with forests.
HYDROLOGY, TANKS AND WELLS. 21

$

6 Monta'na .Station 

*^Sutnmerville 

oMill in

§'To'nopah Weii 

"Scan** Well

The precipitation both in winter and summer is greater on such 

mountains, and forested areas retard the run-off and permit the water 

to sink into the rocks. The flow is subject to 

seasonal changes, and during August and September many springs are dry or greatly diminished. Heavy rains also cause fluctuations. 

The water is cool, sometimes even cold, and is 

usually palatable, though a few of the springs 

are slightly saline, and some contain other salts. 

From the direct dependence of the flow of 

the cold springs on seasonal rotation and on unusually heavy rains it is evident that these 

springs are in greater part, at least, the vents 

of shallow circulating waters.

TANKS.

Tanks are natural depressions in an impervious stratum, in which rain or snow water collects and is preserved the greater portion of 

the year. In the area studied the principal 

formations upon which tanks occur are the 

playa clay and the more compact layers of the ' 

basalt. The water in tanks decreases in volume and becomes poorer in quality as summer 

progresses; by August some are dry, and the 

water of others is scarcely drinkable.

WELLS. <

Wells have been sunk at a number of places 

in the gravels of either the flats or the gulches. 

Wells sunk in gulches where there -are signs 

of water have almost without exception proved ' 

successful; wells in the flats have been almost 

as uniformly successful. In the inclosed valleys the water table near the mountains, where i 

the desert gravels are very permeable to water, 

seems to lie at considerable depths below the ' 

surface, but at the playas the two planes ap- ' 

proach each other. In Death Valley water \ 

stands upon the surface, while in Sarcobatus i 

Flat the water table is but 2 feet below the surface (fig. 2). In other flats the depth is considerably greater, but by analogy wells located 

near playas should encounter water at less 

depths than those on alluvial slopes. The supply seems sufficient for 

stock, but insufficient for extensive irrigation.

-Mud Spring

'u Amargosa Mine 

u (Dry)

Rose's Well

= Miller No.,1

Miller No.2
22 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The prospect of developing flowing wells in the area is slight. The 

Paleozoic rocks and the Tertiary volcanics are too much faulted to 

present extensive and continuous water-bearing strata. In the flat 

valleys beds of sand and gravel and layers of clay may be locally so 

superimposed upon one another as to furnish artesian conditions. 

Flowing wells, however, would be encountered only by the merest 

chance and would probably be weak.

In Turkestan and in the arid regions of southern California gently 

ascending tunnels have been driven into alluvial fans and water 

so obtained has been used for irrigation. The construction and 

maintenance of such tunnels are expensive, and in the area studied 

they would meet with success in few if any of the larger fans in which 

strong springs sink.

SNOW.

During the winter snow lies on many of the higher ranges and 

forms a valuable water supply to the prospector and traveler.

SIGNS OF WATER.

For the benefit of those unused to desert conditions it will perhaps be of value to describe the signs which indicate the presence of water in southwestern Nevada. Vegetation near springs 

or tanks is noticeably luxuriant, and in consequence patches of vivid 

green are worthy of investigation. The desert shrubbery attains an 

unusual size around springs, and a number of bushes and flowers not 

elsewhere seen are abundant. The willow, wild rose, elderberry, and 

gooseberry, the red honeysuckle and the poppy, and the " water bush," 

or tonopah of the Indians, are unknown except in the vicinity of 

water. The " water bush " is a shrub 2 to 3 feet high, with grayishgreen leaves set on a white stalk thickly covered with spikes 1 inch 

long. Mesquite grows in Death Valley and the Amargosa Desert, 

and water may usually be obtained at slight depths near its roots. 

Where rye grass and the cane grow there is water at the surface or 

at. moderate depths.

Rabbits, coyotes, and birds are particularly abundant near water. 

Mourning doves at sunset often flock around water holes. It is more 

than unfortunate that in the last two years the shotgun and trap have 

greatly diminished the numbers of this bird, one of the surest of water 

guides. Stock trails usually lead to water, and the point at which 

several trails converge is in most cases a spring. Since the animals go 

directly to water from the flats and on leaving the spring spread over 

the surrounding country as they feed, the trail becomes perceptibly 

plainer as it nears the spring. Many such trails, however, are winter 

trails, and in consequence the recency of tracks should be noted in 

searching for water.

Wagon roads and trails are constructed from one spring or tank to
ANIMAL LIFE VEGETATION. 23

another arid unwatered stretches of more than 40 miles are uncommon. The Indians, except when gathering pinon nuts, camp at 

water, and old Indian camping grounds, numerous fragments of 

stone implements, smoke-stained rocks, and carvings on rock may be 

valuable water indicators. Perhaps the best water signs are stone 

monuments built by the Indians and early white explorers either on 

high points on each side of the trail at water or close together on a 

'commanding point above the water. These monuments are from 2 

to 8 feet in height and resemble mineral monuments, except that they 

bear -no location notices. From some of them flat stones set on edge 

point toward the water.; at others a sharpened stick lying in a forked 

one is the indicator.

ANIMAL LIFE.

Animals are nowhere abundant in the area under consideration, 

and Death Valley appears to be without resident animals, with the 

exception of a few coyotes. The lack of food and the scarcity of 

water render the area as a whole unfit for large animals. Bands of 

wild horses roam the lowlands around the Cactus and Kawich 

ranges, however, and a few antelope feed in the valleys on either 

side of the Kawich Range and on Pahute Mesa. Mountain sheep 

are reported from the Lone Mountain country and old trails were 

noted on the higher peaks of the Stonewall Mountains. A few 

mountain sheep still live in the Panamint Range and in the south 

end of the Amargosa Mountains. Coyotes and rabbits are often 

seen, particularly in the vicinity of springs. Animals allied to 

gophers seem less dependent on known water holes.

Hawks, ravens, magpies, sparrows, and owls fly long distances 

from water. Mourning doves, on the other hand, flock around the 

springs and a few coveys of California quail live in the better 

watered portions of the Panamint and Amargosa ranges. Ducks 

in their annual migrations stop ito rest and feed at the springs in the 

Oasis Valley and at Ash Meadows and the Furnace Creek ranch.

Various species of lizards, including the horned toad, are common 

in the valleys. Rattlesnakes, both the ordinary variety and the 

peculiar sidewinder, are sometimes seen, but are by no means as 

common as report would lead one to believe. The same is true of 

the scorpion and tarantula. Ants are common, and brilliantly colored butterflies are unexpectedly numerous. Mosquitoes and similar 

pests occur only near a few of the larger water holes.

VEGETATION.

Open forests of pinon (Pinus monophylla) and juniper (Juniper 

utahensis] occur above the dry timber line,0 which approximates an 

elevation of 6,500 feet. The wood of both trees, particularly the

a Russell, I. C., Bull. Geol. Soc. America, vol. 14, 1904, pp. 556-557.
24 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. .

pifion, is good fuel. Only exceptionally are the trunks large enough 

for mining timbers other than lagging. The cones of the pinon incase delicious nuts, which are carefully gathered by the Indians for 

winter food. The vividly green mountain mahogany (Cerocarpus 

ledifolius) is associated with these trees on the highest peaks.

The most striking plant of the area is the yucca (Yucca arborescens) , commonly called the " Joshua tree." It grows in open groves 

on the upper alluvial slopes and the lower lava mesas. Stiff spiny 

leaves are thickly set on the peculiarly branching stalk, which 

reaches a maximum height of 30 feet. Associated with the yucca are 

various species of cacti, including the prickly pear, the barrel cactus, 

and several branching forms. The sagebrush is widely distributed 

in the mountains, while the " creosote brush " (Larrea tridentata] 

and related shrubs occupy the lower alluvial slopes. In April and 

May the red geranium, the yellow dandelion, the purple horsemint, 

and the white primrose enliven the monotonous greenish gray of the 

desert shrubbery.

Grateful spots of green mark the springs. Here the gooseberry, 

wild rose, poppy, honeysuckle, wild rye grass, and cane thrive, while 

willow bushes and oak shrubs grow in thickets around some of the 

springs. At Poison Spring, in the Amargosa Eange, the rocks are covered by the dainty maidenhair fern. In Cottonwood Canyon and at 

the ranches in Oasis Valley willow and cottonwood trees grow to a 

height of 40 feet.

Sufficient grass for scant forage grows on the upper alluvial slopes 

and in some valleys in the mountains. Burros will live almost anywhere in the area, but horses do poorly on the best of feed. The most 

nutritious grass grows in small bunches and is commonly called " sand 

grass." The sun's heat cures it in summer and in consequence a 

scant supply is available throughout the year. The grass around the 

springs, usually called "salt grass"- (Distichlis spirata], is of little 

value to work horses. The white sage (Eurotia lanata] grows in the 

southern half of the area. Sheep are said to thrive on it and horses 

eat it with apparent relish.

cui/ruRE.

INDUSTRIES.

Prospecting and mining are practically the only industries, and 

nearly every person within the area surveyed is dependent directly or 

indirectly on these pursuits. The miners are segregated in the towns 

and camps; the prospectors range from one group of hills to another. At the Longstreet and Breen ranches in the Kawich Range, 

the Staininger and Indian ranches in the Armagosa Range, and at 

several of the springs in Oasis Valley small acreages are irrigated and 

hay, melons, potatoes, and other farm products are raised. The 

finer detrital material of the valleys is an excellent soil, but water for
CULTURE, TOWNS. 25

irrigation is lacking. A few cattle pasture in the Kawich Range, 

and while small herds might possibly live at other localities, the beef 

required by the mining camps will for the most part be shipped in by 

rail or driven across from California.

TOWNS.

The towns of this desert mining territory typify both the push and 

energy of the western pioneer and the unstable conditions of new.gold 

fields. With the report of a rich discovery a town of 100 tents rises 

in a day, only to disappear almost as rapidly if the new find falls short 

of expectations. The population of all the towns fluctuates greatly.

Tonopah, with a population of about 8,000, lies 4 miles north of the 

area and is the county seat of Nye County, Nev. It has a number of 

prosperous mines and is the shipping point for some of the northern 

and northeastern mining camps of the area under discussion. Tonopah is the terminus of a railroad and has electric light, city water, 

telephones, newspapers, both daily and weekly, banks, churches, and 

schools.

Goldfield, with a population of about 9,000, has valuable gold mines 

and is the present terminus of the Tonopah and Goldfield Railroad. 

Like Tonopah, it has most of the essentials of city life, and the number of substantial buildings is surprising in consideration of the fact 

that the first tent was pitched here in January, 1904. Columbia, a 

rival town, adjoins Goldfield'and has its own post-office. Goldfield 

and Columbia are supply points for the prospectors and miners in the 

central portion of the territory here described.

Rhyolite, Bullfrog, and Beatty are rival towns of the Bullfrog mining district. Rhyolite and Bullfrog, whose main streets meet, have a 

total population of approximately 2,500. Each has its own postoffice, water system, and newspapers, .and the two have common telegraph and telephone systems. The towns were founded in January, 

1905, and already contain a number of substantial stone, Avood, and 

adobe buildings. Beatty, 4 miles east of Rhyolite, is situated on 

Amargosa River and has a population of TOO. It has about the same 

improvements as Bullfrog and Rhyolite. These three toAvns are the 

supply points for the southern portion of the area. Gold Center, a 

tent toAvn of 40 inhabitants, is situated 2 miles beloAv Beatty, on 

Amargosa River.

SilverboAv, on the east side of the KaAvich Range, has a post-office 

and a Aveekly neAvspaper. KaAvich is a mining camp and post-office 

on the Avest side of the KaAvich Range. The number of inhabitants 

fluctuates and has varied from 50 to 400. Lida is a mining camp of 

the seventies reAdved. At present it has a population of 200. Thorp, 

more commonly knoAvn as Montana Station, is a post-office and stage 

station. Travelers can find accommodations for man and beast at
26 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

Ramsey Well, Klondike Well, Cactus Spring, Tokop, Cuprite, Currie 

Well, Miller Well No. 1, and Ash Meadows.

RAILROADS AND STAGES.

The Tonopah and Goldfield Railroad is a broad-gage line, connecting with the Union Pacific Railroad at Hazen, Nev. The Carson and Colorado Railroad in Owens Valley is from 25 to 45 miles 

west of the western border of the area. The San Pedro, Los Angeles 

and Salt Lake Railroad, commonly called the Clark road, is from 40 

to 75 miles east of the area. A railroad has been surveyed from 

Goldfield to Bullfrog and two branches are projected from the Clark 

road to the same point. The position of the railroads is shown on 

the sketch map (fig. 1). A daily stage runs from Goldfield and 

another from Las Vegas to the towns of the Bullfrog district. The 

trip from Goldfield takes about fourteen hours, from Las Vegas 

thirty-two hours. Daily or semidaily automobiles make the run from 

Goldfield to Bullfrog in four to six hours. Lida and Goldfield. 

Kawich and Tonopah, and Silverbow and Tonopah are connected by 

daily stages.

ROADS AND TRAILS.

Good roads and trails cross the area in all directions and few countries so sparsely populated are so accessible. The road gradient is 

low, although in the mountains short stretches are steep. Teaming is 

heavy in the sand surrounding the playas and in some of the stream 

gravels. Roads on playa clays are smooth and hard except after 

heavy rains, when wagons sink hub' deep in the sticky clay. Roads 

and trails are shown on the geologic map (PL I). Few places are 

impassable to a pack train, and a wagon can go anywhere in the lower 

hills and mountains.

STRATIGRAPIIIC GEOLOGY.

It is proposed in this section to describe briefly the formations of 

southwestern Nevada and eastern California (fig. 3) and to outline 

the general distribution of each. They are described in detail under 

each geographic subdivision in the section on descriptive geology. It 

will be convenient to take the formations up in order, from the oldest 

to the youngest, irrespective of their sedimentary or igneous origin. 

Owing to the lack of continuity and the complex structure of the Paleozoic rocks, their description is less accurate than that of the younger 

formations. The stratigraphic units of the Eureka" (Nev.) section 

are used as type formations for the Paleozoic rocks.

PRE-CAMBRIAN.

The presence of pre-Cambrian rocks was not definitely determined. 

The Prospect Mountain quartzite (Lower Cambrian) of the Specter

a Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, p. 13.
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PRE-TERTIARY TERTIARY QUATERNARY CAMBRIAN ORDOVICIAN SI LURIAN CARBONIFEROUS TERTIARY QUATERNARY
COLUMNAR SECTION. 27

Range contains pebbles of quartzite, jasperoid, and vein or pegmatitic 

quartz derived from pre-Cambrian formations. The mica schist of 

the Bullfrog Hills is pre-Ordovician, and although considered of CamUnconformity.

Unconformity.

Unconformity.

Second rhyolite, with minor basalt Hows.

looo feet

FIG. 3. Columnar section of rocks of southwestern Nevada and eastern California.

brian age, it may be pre-Cambrian. The schist at Trappmans Camp 

and the series in the south end of Amargosa and Panamint ranges 

are also probably Cambrian, although possibly pre-Cambrian.

a Rocks below this are cut by granite, which in turn is cut by monzonite porphyry, and this in turn 

by diorite porphyry.
28 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

CAMBRIAN.

In the Specter Range from 2,000 to 3,000 feet of quartzite and conglomeratic quartzite conformably underlie limestone containing Cambrian fossils. The rather impure quartzite, which grades into minor 

beds of slaty shale, is probably the equivalent of the Prospect Mountain quartzite a described by Hague, from the Eureka district. Less 

certainly to be correlated with this formation is the quartzite with 

intercalated schist and marble beds of the Amargosa and Panamint 

ranges, a rock series which may possibly be of pre-Cambrian age.

Conformably overlying the Prospect Mountain quartzite in the 

Specter Range is a limestone apparently from 5,000 to 6,000 feet thick, 

which is probably to be correlated with the Prospect Mountain limestone ° of Hague. The limestone is dark gray, compact, fine grained, 

and crystalline. Black chert occurs at certain horizons. In the Silver Peak Range, Stonewall Mountain, the Goldfield, Southern Klondike, Lone Mountain, and Mount Jackson hills, and Slate and Gold 

Mountain ridges occur rocks that are in part at least of Lower Cambrian age. The predominant member is a dense dark-gray limestone 

of finely crystalline texture. As a rule it is massively bedded. In a 

number of places this limestone has been silicified to a banded gray 

and black jasperoid. Interbedded with the limestone are layers of 

green slaty shale, usually finely laminated. In the Silver Peak Range 

and the Lone Mountain foothills the shale reaches a thickness of 

1,000 feet. These rocks, in part at least, are the equivalent of the 

Prospect Mountain limestone, although lithologically rather distinct 

from that formation in. the type locality.

Of less certain Cambrian age are the mica schists of the Bullfrog 

Hills, Tolicha Peak, and Trappmans Camp. The Secret Canyon shale 

and the Hamburg limestone* and shale were not recognized, and the 

Cambrian limestones appear to pass upward without distinct lithologic break into the Pogonip limestone.

ORDOVICIAN AND SILURIAN.

The Pogonip limestone as described by Hague b is 2,700 feet thick 

and contains Upper Cambrian fossils at its base and Ordovician fossils in its middle and upper portions. At Eureka it overlies the 

Hamburg shale" conformably, while in southwestern Nevada it seems 

to succeed the Cambrian limestone without marked lithologic change. 

The Pogonip limestone is well exposed in the Belted, Amargosa,

0 Present usage of the Survey does not sanction the double use of formation names, as 

Prospect Mountain quartzite and Prospect Mountain limestone, hut as this reconnaissance paper is not the place to propose new names, they are retained as used by Hague.

6 Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, pp. 48-54.
OBDOVICIAN DEVONIAN. 29

and Panamint ranges and in Bare Mountain, while transitional beds 

between it and the Eureka quartzite occur in the Kawich Eange and 

a small area of what is probably the Pogonip limestone is situated 

in the Cactus Range. The limestone is dark gray, fine to medium 

grained, and dense. It is distinguished from the Cambrian limestones, already described, by a somewhat lighter color, a slightly 

coarser and less crystalline texture, and rather more massive bedding. Near the center of the section, which ranges in thickness from 

2,000 to 4,000 feet, is about 100 feet of white or pinkish quartzite. 

The transitional rocks from the Pogonip to the overlying Eureka 

quartzite are an interbedded series of limestone, shale, and quartzite.

The Eureka (Ordovician) quartzite described by Hague as overlying conformably and Avithout transitional beds the Pogonip limestone was recognized on stratigraphic grounds in the Amargosa 

and Kawich ranges, in the Bullfrog Hills, and on Bare Mountain, 

while in the Cactus Range and the hills betAA^een it and the Kawich 

Range quartzite areas isolated in Tertiary or.Recent rocks are considered its equivalent. The Eureka quartzite in south AA7 estern Nevada 

is a typically Avhite or pink, fine to medium grained, pure metamorphosed quartzose sediment. Some beds, hoAvever, are conglomeratic 

quartzites, Avhile others are argillaceous and grade into thin, interbeaded sheets of dark-colored slaty shale. It varies from the quartzite of Hague chiefly in tAvo characteristics first, its greater thickness, reaching 1,200 to 1,500 feet in the KaAA'ich Range, and, second, 

in being underlain by interbedded quartzites, shales, and limestones, 

transitional beds from the Pogonip limestone.

Hague 0 gave to the uppermost division of the Ordovician and 

Silurian rocks at Eureka the name " Lone Mountain limestone." This 

formation lies unconformably upon the Eureka quartzite and is 

1,800 feet thick. It consists of black, gritty limestones at the base, 

which pass upAA^ard into light-gray, siliceous limestones. Its fossils include both Trenton and Niagara faunas. In the Amargosa 

and KaAvich ranges and the Bullfrog Hills the Lone Mountain limestone ts a gray, dense rock, of AA'hich about 400 feet is exposed.

DEVONIAN.

No Devonian formations Avere found in the course of the present 

Avork, and while such rocks may have been overlooked or may lie 

buried beneath Tertiary lavas it is tentatively believed that this 

portion of Nevada Avas a land mass during at least the greater part 

of Devonian time. The alternate hypothesis is that the Devonian 

beds were eroded away during post-Mississippi an and pre-Pennsylvanian time, a period of important erosion in many portions of 

the West.

a Hague, Arnold, MOD. U. S. Geol. Survey, vol. 20, 1892, pp. 57-59.
30 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

CARBONIFEROUS.

Hague ° describes the Weber conglomerate at Eureka as consisting 

of 2,000 feet of coarse and fine conglomerate containing angular and 

rounded fragments of chert, interbedded with reddish-yellow sandstones, and lying conformably between the limestones of the lower 

and the upper " Coal Measures." Iii the Belted Kange the Pennsylvanian limestone is underlain by 300 to 500 feet of shale, which in 

turn overlies 800 to 1,000 feet of sandstone. The shales are thin 

bedded and of green, gray, or brown color. The sandstone is in 

part a rather pure quartzose rock and in part an arkose. Interbedded conglomerates contain well-rounded pebbles of limestone, 

quartzite, flint, and jasperoid, evidently derived from early Paleozoic rocks. Lithologically similar beds occur in the Cactus Range. 

These rocks are probably the equivalent of the Weber conglomerate 

at Eureka.

Pennsylvania!! limestone also occurs in the Panamint and Reveille 

ranges and forms a small area on Shoshone Mountain. This limestone 

is dense, dark gray or black, and fine to medium grained. Specimens 

from many beds emit a fetid odor when hit with the hammer. Nodules of black flint are characteristic at many horizons. The limestone 

in the Belted Range, 2,500 feet thick, has near its center 55 feet of 

limestone conglomerate.

POST-JURASSIC AND PRE-TERTIARY IGNEOUS ROCKS.

The granite and associated rocks of the Belted and Panamint 

ranges, of Pahute Mesa, and of the Gold Mountain ridge contain 

fragments of gra}^ fine-grained monzonite and quartz-monzonite 

porphyry. These fragments, while clearly somewhat older than the 

rocks in which they occur, are massive and possibly represent an 

earlier solidification of the magma, from which the granitic rocks were 

afterwards differentiated. These rocks include types ranging on 

the oneliand from alaskite through muscovite, muscovite-biotite, and 

biotite granites to a quartz monzonite approaching granodiorite, 

and on the other hand from a soda-rich granite to soda syenite. 

While the granitoid rocks in the areas shown on the map are of 

rather constant composition, transitions occur in a single area. In 

the Gold Mountain ridge, for example, of two ledges separated by 

less than 10 feet, one is a microcline-granite porphyry and the other 

a hornblende - bearing quartz - monzonite porphyry. Porphyritic 

types of the granitoid rocks occur, as well as aplites and pegmatites, 

later differentiations of the same magma.

These granitoid rocks are widely distributed over the region under 

consideration, although they cover larger areas in the western portion.

"Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, pp. 91-92.
PEE-TEKTIAKY AND TERTIARY IGNEOUS ROCKS. 31

Similar rocks are the predominant formation from longitude 117° 

30', the border of the region, westward to the Sierra Nevada. 0

From the uniform amount of mashing which these rocks have suffered it is evident that all are approximately of the same age. They 

intrude the Paleozoic rocks where the two are in contact, and fragments of them are included in Tertiary lavas. The yo\mgest of the 

Paleozoic rocks is of Pennsylvanian age and the earliest lava is probably Eocene; in consequence the granites are of post-Carboniferous 

and pre-Eocene age. It is shown in the section on geologic history 

(p. 39) that the close folding of the Paleozoic rocks occurred in postJurassic time and the granite intrusion is believed to have been a relatively late event in this period of deformation, an inference supported 

by the comparatively unmashed condition of the granites. Their postJurassic age is thus probable, a conclusion in accord with that of 

Spurr for the granites of Silver Peak 6 and Goldfield 6' and that of 

Louderback (/ for those of the Humbolt region. This would make 

these granitoid rocks essentially contemporaneous with tlie granodiorite of the Sierra Nevada.

Dikes and sheets of a ferromagnesian-poor quartz-monzonite porphyry intrude Paleozoic sedimentary rocks and granite of the Silver 

Peak and Panamint ranges and of Slate Ridge. This rock near 

Lida is apparently cut by the diorite porphyry described in the next 

paragraph. It is presumably a second intrusion of the granitic 

magma.

Dikes of diorite porphyry and fewer intrusive masses of diorite 

occur in the Silver Peak, Panamint, Amargosa, and Cactus ranges, 

the Gold Mountain and Slate ridges, and the Bullfrog, Mount Jackson, and Lone Mountain hills. These rocks typically contain brown 

hornblende. They are younger than the Paleozoic rocks and the 

igneous rocks already described and nowhere were they observed 

cutting Tertiary lavas. Pebbles of diorite porphyry occur in the 

Siebert lake beds (Miocene) and the rock is probably of postJurassic and pre-Tertiary age. Its intrusion was the last event in 

the pre-Tertiary igneous activity.

TERTIARY.

The Tertiary rocks include a number of igneous rocks, lava flows 

and fewer intrusive masses, and sediments laid down in lakes. The 

accompanying table presents correlations of the Tertiary rocks of 

the various ranges

« Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 1903, PI. I.

6 Spurr, J. E., Bimonthly Bull. Am. Inst. Min. Eng., 1905, No. 5, p. 955.

c Spurr, J. E., Bull. U. S.. Geol. Survey No. 260, 1905, p. 133.

« Louderback, G. D., Bull. Geol. Socr America, vol. 15, 1904, p. 336.
32 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The oldest of the Tertiary rocks is a rhyolite which occurs in 

Stonewall Mountain. This occupies a similar stratigraphic position with rhyolites in the Panamint Eange, in the Eandsburg district, and near Daggett in the Mohave Desert, which, according to 

Spurr,0 lie beneath " lake beds which are probably, in part at least, 

Upper Eocene." This rhyolite in Stonewall Mountain is cut by 

dikes of quartz-monzonite porphyry and quartz syenite, which are 

probably contemporaneous with monzonite porphyry, quartz-mony.onite porphyry, hornblende-biotite latite, and biotite andesite of 

other ranges. These rocks are in part intrusive masses and in part 

flows. Prior to the succeeding extrusion of rhyolite the'se rocks of 

siliceous andesitic and monzonitic composition were eroded, unconformities being observed in the KaAA'ich, Amargosa, and Cactus 

ranges, in the Bullfrog Hills, and in Shoshone and Skull mountains. 

Then followed an extrusion of rhyolite, with minor siliceous latites 

and dacites, which was attended by insignificant basalt flows. This 

period of extrusion of rhyolitic lavas, the most important in this 

portion of the Great Basin, was. not, however, strictly contemporaneous over the whole area; it is believed, for example, that the 

earlier rhyolite of Goldfield represents only the base of the rhyolite 

series of the Bullfrog IJills, and that the upper portions of the Bullfrog mass may have been extravasated while the andesites and 

dacites of Goldfield were solidifying. This rhyolite is everywhere 

separated from the Siebert lake beds by a marked erosional unconformity, and in the Kawich and possibly in the Cactus Range it is 

separated by an erosional unconformity from the succeeding andesites. The next younger igneous rocks, which 'are confined to the 

northern half of the area mapped, are basic andesites and dacites. 

These-two rocks were found in contact only in the area covered by 

the Goldfield special map, and here Mr. F. L. Ransome 6 found the 

dacites intrusive into the andesites. The succeeding igneous rocks 

are rhyolites and siliceous latites and dacites which occur only'in 

the Goldfield and Southern Klondike hills and the Silver Peak 

Range. In the latter two localities at least these rocks are interbedded with the Siebert lake beds without erosional unconformity.

Thick masses of sediments occur in the majority of the ranges of 

the area, and on lithologic and stratigraphic grounds are correlated 

with the Siebert lake beds of -Miocene age at Tonopah described by 

Spurr. 0' These tuffaceous sandstones and conglomerates, largely composed of rhyolitic material, reach an observed maximum thickness (in 

the Amargosa Range) of 1,150 feet.

a Spurr, J. E., Jour. Geol., vol. 8, 1900, p. 633.

6 Oral communication. *

f Spurr, J. E., Prof. Paper U, S. Geol. Survey No. 42, .1905, pp. 51-55,' 69-70,
CORRELATION OF TERTIARY FORMATIONS. 33

^'S.po'^OoSP'CgpSOS.Of&i^^POtspj'Clg'pQg'

g : : : : : sr: : : : ; : : : p : £=: ;:;::: 

g: ::::::::::::: *:::::::::

: : : : : x ;:::::::: ::::;::::

Erosional inconformity, Kawich, Amargosa, 

Bullfrog, Cactus Shoshone.

xxx x xxxxxxx x : xx x x

: : : ; : : : : x x x : : : : : :::::::::

Erosion between rhyolite and Siebert lake beds, 

and locally erosional unconformity between 

early Miocene rhyolite and Mioeene andesite 

and dacite.

: : : x : : : x : : x x x x x :::::::::

x : : : : : x : : x x x x : : : ::,:::;: x 

Orogenic movement.

; : x : : x x : : : : x x : : :::::::::

Mature land surface, probably here, at least, 

prebasaltic.

: : : : : : : : :::: :

: : : : : : : x : : x : : : : ; :::::::::

X X X X X X X X X X X X X X X X X XXXXXXX

pa

or)

Rhyolite. 

Mouzonite and biotite

Rhyolite, dacite, and latite.

Basalt, contemporaneous 

with rhyolite of preAridesite and dacite. 

Rhyolite and biotite latite. 

Siebert lake beds. 

Rhyolite and latite

folded with Siebert 

lake beds.

Later rhyolite in places 

containing augite, not 

folded with Siebert lake

Later tuffs passing into 

older alluvium.

Basic andesites.

Basalts in large part contemporaneous with upper part of older alluvium, but ranging from 

M iocene to Pleistocene.

or ear Eocene 

£

Miocene.

*o

iocene.

2

part. ocene i 

Bull. 308 07 M-
34 SOUTH WESTERN NEVADA AND EASTERN CALIFORNIA.

Before the deposition of the Siebert lake beds ceased rhyolites and 

siliceous latites and dacites outflowed. In some of the ranges these 

are folded 'with the lake beds; in others they lie upon the tilted 

and eroded surfaces of the sediments. During and immediately after 

the extrusion of these siliceous rocks tuffaceous sediments Avere 

deposited in several of the ranges in the northwestern part of the 

area, and these are in part probably equivalent to the Humboldt 

series, the deposits of the Shoshone Lake (late Pliocene) of King.0 

The older alluvium, so widely distributed, particularly in the inclosed 

valleys, represents ancient play a deposits and alluvial slopes of what 

was probably the Pleistocene residuum of this lake. The early stages 

of Shoshone Lake were followed immediately by basalt flows which 

cover wide areas in southwestern Nevada and eastern California. 

In several of the ranges these basalts were preceded by basic pyroxene andesites. While the basalt is thus largely of late Pliocene 

age, its extrusion began during the deposition of the Siebert lake 

beds, basalt flows occurring near the top of these sediments in the 

Amargosa Range and the Goldfield hills,6 and probably in the Monitor Hills. Some of the basalt cones are remarkably fresh and are 

certainly of Pleistocene age, and it is by no means impossible that 

volcanism has not ceased in this portion of the Basin Range.

The succession of the lavas of the Great Basin has recently been 

treated at length by Spurr.c His succession for the petrographic 

province of the Great Basin and that of the writer for the portion of 

that province here treated are practically identical. Both assign 

the first rhyolite to the end of Cretaceous and to Eocene time. It is 

believed, however, from the length of time indicated by the complex 

history of extrusion and erosion intervening between this rhyolite and 

the deposition of the Siebert lake beds, that the monzonites and acidic 

andesites may well also be in part Eocene, while the second rhyolite is 

believed to be largely of early Miocene age. The andesite and dacite 

are also of comparatively early Miocene age, while the third rhyolite 

covers the middle and late Miocene and early Pliocene. The basalts 

range in age from late Miocene to Pleistocene, the major extrusions 

occurring in late Pliocene and Pleistocene time. As to the genetic, 

relations of the magmas, the writer is wholly in accord with the views 

of Spurr in the article already cited. He believes that the Tertiary 

lavas of the Great Basin are the representatives of two complete 

cycles of the differentiation of a magma of medium composition into 

acidic and basic lavas and that probably the end of a still earlier cycle 

is also represented.

« King, Clarence, U. S. Geol. Explor. 40th Par., vol. 1, 1878, pp. 434, 456.

6 Oral communication from Mr. F. L. Ransome.

« Spurr, J. E., Jour. Geol., vol. 8, 1900, pp. 621-646.
STRATIGRAPHIC GEOLOGY. 35 

PLEISTOCENE AND RECENT. 

TRAVERTINE.

At Alkali Spring, 11 miles northwest of Goldfield, is a low dome 

200 feet long formed of platy masses of grayish-brown travertine. 

This was the vent of the spring probably in late Pleistocene time.

DESERT GRAVELS.

The desert gravels cover the surface of the broad valleys above the 

play as and fill valleys of erosion in the mountains. They extend over 

about 45 per cent of the area mapped. These detrital deposits are 

composed of bowlders, pebbles, and sand. Many of the angular or 

subangular bowlders near the mountains are 6 feet in diameter; near 

the playas the bowlders grade into pebbles, measuring one-half inch 

or less. Some bowlders of quartzite show small crescentic fractures, 

and some of fine-grained limestones show white crushed spots; these 

are due to the impact of one bowlder against another during rapid 

transportation such as is characteristic of cloudbursts. Near the 

mountains the gravels are but slightly stratified, and here crossbedding and slight erosional unconformities are common. Qn the 

border of playas layers of small pebbles and sand are regularly interbedded with lamina? of playa clay. The material of these detrital 

deposits is undecomposed, and if consolidated would form a secondary 

rock of practically the same chemical composition as the rock from 

the debris of which it was derived. Calcium carbonate is a common 

cement particularly adjacent to limestone and basalt outcrops. In a 

number of the arroyos shelves along the sides and tiny scarps in the 

channels mark lime-cemented conglomerates. Gypsum and silica also 

occur as cements at a few places.

The thickness of the desert gravels is unknown. In some of the inclosed valleys lava floAvs and older alluvium are exposed here and 

there and probably underlie the valley at no great depth. In other 

valleys, however, the gravels probably reach a thickness of hundreds 

and possibly thousands of feet. The Amargosa mine at Bullfrog, 

which is situated about five-sixteenths of a mile from the rhyolite 

ridges, has been sunk 330 feet in detrital deposits. Wells have been 

put down in other valleys to depths of 75 to 275 feet, and, while the 

records are very imperfect, it is apparent that they have not passed 

through the desert gravels.

These gravels in large part make up alluvial fans and the contiguous alluvial slopes; in minor part they form cliff taluses. Where no 

playa exists there is a zone in the center of the valley in which the 

material is derived from the mountains on both sides, since cloudbursts, first from one range and then from the other, push the debris 

across the median drainage line.
36 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

I The desert gravels on the surface are without question still accumulating and are in part of Kecent age. Their deposition, however, 

is slow, and from their thickness it is probable that the lower portions 

of the formation are of Pleistocene age. The length of time required for their accumulation is indicated not only by the present infrequency of cloudbursts. Embedded in the gravels are pebbles 

deeply scored by wind erosion on the exposed side, while the under 

surface is untouched. Such pebbles must have been stationary for 

long periods. The alluvial fans, with the exception of a single channel, are superficially stained by the black " desert varnish," a process 

also requiring a considerable period.

PLAYA DEPOSITS.

Playa deposits composed of light-gray or white fine clay, in many 

places arenaceous, occupy the bottoms of nearly all the inclosed valleys. Grotesque concretions of calcium carbonate from 1 inch to 8 

inches in length are locally embedded in the clay, while some strata 

are lime cemented. Salt Flat and other areas mapped as playa deposits in Death Valley differ from those just described in the fact 

that some water continually stands in depressions and that considerable amounts of saline material are being deposited. For convenience 

several areas in Oasis Valley have been mapped as playa deposits. 

These areas are occupied by clays, loams, and sands of complex origin, 

partly playa deposits, partly stream alluvium, and partly winddeposited sand. The thickness of the playa deposits is unknown, 

although from their mode of origin it is believed that they are thinner 

than the desert gravels in the same basin.

i During periods of unusual precipitation the playas are wholly or 

partially covered by water, and at such periods some fine detrital 

material is washed into them. More or less wind-blown sand becomes 

mixed with the clay, and on desiccation of the temporary lakes chemical deposits are formed. The playa deposits are of late Pleistocene 

and Recent age.

SAND DUNES. °

Large sand dunes are confined to the southern portion of the area 

mapped, although smaller dunes border all the playas. Big Dune, in 

the Amargosa Desert, is 300 feet high, and lower ones, similarly perfect in contour, occur in Death Valley. These are said to retain their 

general position from year to year, their situation apparently being 

determined by wind eddies. Some of the smaller dunes are directly 

dependent on the desert shrubbery for their existence (PL II. Z>), 

while the position of those on higher ground is evidently determined 

by the protecting influence of surrounding hills.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 308 PL.

PAHUTE MESA 

Showing benches determined by resistant flows of basalt.

Jl. DEATH VALLEY. 

Showing sand dunes protected by desert shrubbery (mesquite and creosote bush).
STBATIGRAPHIC GEOLOGY. 37 

DEFINITIONS OF IGNEOUS ROCKS.

The various igneous rocks which occur in the area under discussion 

are simply defined below for the benefit of the nontechnical reader.

Alaskite is a granular rock of white or light-gray color. It is composed almost entirely of quartz and orthoclase.* It is a granite lacking mica and hornblende.

Andesite is a porphyritic rock; that is, it has visible crystals 

(phenocrysts) embedded in a finer-grained, often glassy groundmass. 

The most conspicuous features are the phenocrysts of hornblende or 

biotite or augite and plagioclase.

Aplite is here applied to a finely granular rock which usually occurs in dikes cutting, for example, a granite. The aplite, which as a 

rule is more siliceous than the granite, in many instances has solidified 

from a portion of the granite mass that is still liquid at great depths.

Basalt is a black or dark-gray rock which is often porous through 

the presence of steam holes. Crystals of olivine, plagioclase, and 

pyroxene may or may not be visible in the dense or finely granular 

groundmass.

Dacite may be briefly defined as a quartz-bearing andesite. The 

more basic dacites closely resemble andesites, while siliceous dacites 

are closely connected by transition rocks to rhyolite and might be confused with rhyolite were it not for the presence of plagioclase crystals. , . '

Diorite is a gray granular rock which is composed essentially of 

plagioclase and hornblende, while biotite or augite may also be present. " Diorite and andesite are similar chemically, but differ texturally.

Diorite porphyry is a rock of the composition of diorite with abundant crystals of plagioclase, hornblende, and biotite. The groundmass is finely granular.

Granite is a granular rock of pink or gray color. It is composed of 

orthoclase, quartz, and either muscovite, biotite, or hornblende.

Granite porphyry is a rock of porphyritic habit having the same 

composition as granite. Quartz and orthoclase are the more common 

phenocrysts, and these are embedded in a finely granular groundmass.

Latite is a porphvritic rock with more or less glassy groundmass. 

Phenocrysts of orthoclase and plagioclase are present in equal 

amounts, while either hornblende, augite, biotite, or olivine is usually 

also present. Chemically, latite is the equivalent of monzonite.

Monzonite is a granular rock resembling both granite and diorite, 

but containing orthoclase and plagioclase in approximately equal

a Orthoclase (alkali feldspar) is unstrlated; plagioclase (soda-lime feldspar) is striated and when light strikes it alternate tiny parallel bands reflect the light simultaneously.
38 SOUTHWESTERN NEVADA AND EASTERN CALlfOHNIA.

amounts. If quartz is present, the rock is called a quartz monzonite. 

It is usually of a gray color.

Monzonite porphyry bears the same relation to monzonite as granite 

porphyry to granite.

Pegmatite is here applied to a coarsely crystalline rock which occurs as dikes in some other rock granite, for example with which 

it practically coincides in composition. Such rocks are probably 

formed by segregations from the original molten mass of the inclosing igneous rock.

Rhyolite is a porphyritic rock with glassy base. It has the same 

chemical composition as granite. The most abundant phenocrysts are 

orthoclase and quartz, although biotite, augite, and hornblende also 

occur.

Syenite is a granular rock usually of gray color. The component 

minerals are orthoclase and hornblende or mica. If quartz is present, the rock is called u quartz syenite, and with increase in this constituent quartz syenite passes into granite. Where the component 

minerals are rich in soda, the rock is a soda syenite.

GEOLOGIC HISTORY.

As has been stated, no pre-Cambrian formations have been found" 

in the area studied, but the Prospect Mountain quartzite in the 

Specter Range contains pebbles which are in part derived from sedimentary rocks and in part from granite. It may be inferred, therefore, that pre-Cambrian rocks, both sedimentary and igneous, at 

one time covered areas in southwestern Nevada and eastern California.

In Cambrian and Ordovician time this portion of the Great Basin 

was part of a sea bottom upon which sandstones and then limestone 

and finally sandstones were laid down. The sinking of the sea bottom progressed step by step with the' deposition of the sediments. 

King a has shown that the eastern border of the land surface from 

which the sediments were derived was, in the latitude of the fortieth 

parallel, near 117° 30' west longitude, while the shore line farther 

south appears from Spurr's map B to have been at about 118° 15'. 

The early Paleozoic rocks of the area studied contain a greater proportion of sandy sediments, and the limestones are more impure than 

those described by Hague at Eureka, Nev., facts in harmony with the 

closer proximity of this area to the old continental shore line. The 

presence in the lower Paleozoic rocks of ripple marks, cross-bedding, 

intraformational conglomerates, and oolitic limestones indicates that 

the sea was for the greater portion of the time shallow, and locally, 

as evidenced by sun cracks, the deposits Avere even raised above sea

"King, Clarence, U. S. Geol. Explor. 40th Par., vol. 1, 1878, p. 247. 

"Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 1903, PI. I.
GEOLOGIC HISTOBY. 39

level. The area under consideration was, indeed, so near the ancient 

shore line, naturally a zone of greatest differential uplift, that islands 

may have stood at times above the surface of the sea.

Hague 0 has found in the Eureka district a marked unconformity between the Eureka quartzite and the Lone Mountain limestone, arid according to his description younger formations overlap 

the Eureka quartzite. Such an unconformity was not definitely 

recognized in the area surveyed, but it probably exists. The apparent absence of Devonian rocks has been already mentioned, and the 

alternative hypotheses are presented that the area was a land mass 

during the greater portion of Devonian time, or that Devonian rocks 

were deposited and later eroded. Spurr found Devonian rocks 18 

miles south-southeast of Ash Meadows 6 and 5 miles east of Point 

of Rocks," and his map shows large Devonian areas from 30 to 40 

miles east of the area here considered. Whichever of these hypotheses may be true, it is evident that at some time between the deposition 

of the Lone Mountain limestone and the Weber conglomerate a land 

mass existed over a portion at least of southwestern Nevada and 

eastern California. Not only were the Cambrian, Ordovician, and 

Silurian rocks uplifted and eroded, but the limestones were cut by 

calcite veins and in part silicified to jasperoid, and the sandstones 

were cemented to quartzites prior to their inclusion as pebbles in the 

Weber conglomerate. Cementation is evident not alone from the 

presence of these pebbles, but also from the fact that the early Paleozoic quartzites are thoroughly indurated, while the Pennsylvanian 

sandstones are of more open texture. The earliest Carboniferous 

rocks exposed in the area studied are of Pennsylvanian age, and it is 

evident that during that period the area again formed the bottom of a 

sea, which, however, during the deposition of the Weber conglomerate could not have been far from a land mass, while a conglomerate 

in the Pennsylvanian limestone- also indicates shallow-water conditions. After the deposition of this limestone the area was probably lifted above the sea and never sank beneath it again. The 

period of Paleozoic sedimentation thus concluded was unattended 

by volcanism, with the possible exception of that which produced 

the metamorphosed basic igneous rocks of the Amargosa Range.

King d believed that contemporaneously with the emergence of 

this portion of the Great Basin above the sea the old land mass to 

the west subsided and that upon it were deposited Triassic and 

Jurassic rocks. He further believed e that the ranges of western 

Nevada were formed at the same time as the Sierra Nevada, or at

« Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, p. 57.

6 Spurr, ,T. E., Bull. U. S. Geol. Survey No. 208, 1903, pp. 197-198.

c Op. clt.v p. 161.

" King, -Clarence, U. S. Geol. Explor. 40th Par., vol. 1, 1878, p. 759.

' Op. cit, p. 747.
40 SOUTHWESTERN" NEVADA AND EASTEBN CALIFORNIA.

the close of the Jurassic. This seems very probable from the general 

parallelism of the Nevada ranges with the Sierra Nevada crest line, 

particularly since some of the ranges west of the area surveyed are 

composed of folded Triassic and Jurassic rocks. At this time the 

Paleozoic rocks were complexly folded, the larger proportion of the 

flexures striking west of north. The folding in some places is close 

and in others open, being particularly intense in the ranges nearer the 

Sierra, such as the Panamint and Amargosa ranges. It was accompanied by reverse faulting. These post-Jurassic structural lines have 

ever since their formation proved to be lines of weakness, of which 

advantage has been taken by later deformation.

After considerable folding had taken place, and probably before 

the end of the deformation, granitoid rocks were intruded into the 

Paleozoic strata. That the granite intrusion was a late event in the 

deformation is indicated by the massive character of that rock. The 

intrusion was accompanied by local buckling of strata, by contact 

metamorphism, and somewhat less directly by ore deposition. It 

was followed by the intrusion of a quartz-monzonite porphyry, and 

later of diorite porphyry and diorite.

A long period of erosion, extending at least to Eocene time, followed the post-Jurassic folding and consequent mountain building. 

This period was probably one of heavy rainfall and large rivers. 

No estimate cart be formed of the amount of erosion, but it was 

sufficient to remove from the granite the covering beneath which it 

solidified. Notwithstanding the length of this erosion period no 

peneplain was formed; from this it is inferred that the area was subjected to successive uplifts while being eroded. Where exposed beneath the oldest Tertiary formation the Palezoic rocks appear to have 

been eroded into mountain ranges, many of which have a northRouth extension. Some of these mountains of Paleozoic rocks 

for example, the Kawich Range were fully as high and rugged as 

the present ranges.

The Eocene inaugurated the Tertiary period of volcanism and lake 

sedimentation processes, accompanied by important deformation, 

erosion, and ore deposition. The Tertiary igneous rocks, being 

largely in, flows, in contradistinction to the intrusive post-Jurassic 

rocks, produced but little contact metamorphism. The permanency of 

the structural lines, initiated probably in early Cretaceous time, has 

already been mentioned. Along these lines the Tertiary deformation occurred, while many of the main lava extrusions burst from 

north-south vencs along pre-Tertiary mountain ridges. The first 

lava to outflow was a rhyolite, which was followed by monzonites and 

acidic andesites, in part intrusive bodies. Next there was an important and probably long erosional interval, followed by a mighty 

extrusion of rhyolite, which equals or exceeds in bulk the basalt out-
GEOLOGIC HISTORY. 41

flow of late Pliocene and early Pleistocene time. The rhyolite in 

turn was followed by andesites and dacites, and these by unimportant 

rhyolites, immediately preceding the deposition of the Siebert lake 

beds in the Pahute Lake. It was probably during this general period 

that the most important ore deposits in the Tertiary rocks were 

formed, presumably by waters heated by the still-hot magmas. 

Between the outflow of the rhyolite and the formation of the Pahute 

Lake erosion was probably continuous, partially accounting for the 

formation of the lake basin which in the main, however, originated 

through erogenic sinking that was possibly, in part, consequent on 

adjustments due to the extrusion of immense masses of lava, a hypothesis suggested by Spurr.0 The Pahute Lake covered practically the 

whole area surveyed, although the presence of coarse conglomerates in 

the Kawich and Amargosa ranges and the Bullfrog Hills indicates 

that rugged islands rose above the surface of the lake. Wherever theformer shores of the-lake are now seen it is evident that the surface 

of the older rocks was uneven and that each island was surrounded 

by islets. The climate must have been moist and the presence of fossilized wood in the lake beds shows that trees flourished near its 

shores. While the lake was thus for the most part fresh, periods of 

aridity alternated with those of comparative humidity, and the lake 

or portions of it were partially desiccated, permitting the local precipitation of limestone, gypsum, and boron minerals. Volcanic .flows 

and explosive eruptions of rhyolitic material occurred at various 

times during the existence of the lake. The Pahute Lake was 

destroyed in part by the increasing.aridity of the climate and in part 

by deformation, which was accompanied and immediately followed 

by the extrusion of rhyolite; By this deformation the whole area 

was uplifted with attendant southward tilting, which accounts for 

the relatively low altitudes occupied by the Siebert lake beds in the 

southern portion of southwestern Nevada. Furthermore, the deformation, by differential uplift, blocked out the mountain ranges as they 

now appear and formed many of the inclosed valleys by broad folding or warping. Death Valley was at this time first outlined, though 

it was depressed later, probably in the late Pliocene or early Pleistocene time, by block faulting.

Extensive erosion followed and before the end of Pliocene time it 

had reduced the surface to mature and comparatively gentle topography. In restricted areas the Pliocene-Pleistocene basalt appears to 

have flowed upon a local peneplain. In late Pliocene time the climate was moist and a shallow lake probably covered a considerable 

area in the vicinity of Goldfield. The older alluvium, a formation 

widely distributed over the area, may be considered as deposits of the 

waning stages of this lake period in the inclosed valleys. Toward the

« Spurr, J. E., Prof. Paper TJ. S. Geol. Survey No. 42, 1905, pp. 52-53.
42 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

end of this period the basalt extrusion reached its. climax. Uplift 

accompanied by normal faulting and folding followed the deposition of the older alluvium, and at this time erosion appears to have 

been very active.

In Recent time the erosion characteristic of arid lands has partially 

filled the inclosed valleys with bowlders, gravels, and sands debris 

from the wasting mountains and the process is still going on.

The ranges of this portion of the Great Basin were delineated by 

post-Jurassic folding and Cretaceous erosion. Later uplift, coupled 

with volcanic outbursts along these same structural lines, has added 

much to their height, and the effect of these processes has been emphasized by the deepening of the intermontane valleys by erosion. 

In Death Valley alone does faulting appear to have been the dominant 

process in blocking out the existing topographic forms. The unimportance of faulting* in the topographic evolution elsewhere is well 

exhibited in the northeast quarter of the area surveyed. The Paleozoic rocks of the Kawich and the Belted and Reveille ranges are folded 

in a syncline with its trough in the Kawich and Reveille valleys. The 

presence of early Miocene rhyolites in the Cactus, Kawich, Reveille, 

and Belted ranges at approximately equal elevations further proves 

that, unless compensating faults are hidden in the intervening inclosed valleys, faults have been of little moment. The projection of 

minor transverse ridges from the main ranges into the desert valleys 

and the frequently observed gradation from small erosional buttes to 

groups of rounded hills, such as the Monitor Hills, and from these to 

such elevations as the Cactus Range, are also opposed to the view that 

the principal mountain masses have been bodily uplifted by great 

faults. The ascendency of erosion over faulting is further indicated 

by the broad and rounded detrital embayments which notch many of 

the ranges.

ECONOMIC GEOLOGY. 

HISTORY OF MINING DEVELOPMENT.

Two waves of activity in prospecting and mining have passed over 

the portions of Nevada and California under consideration. The 

first started in the late sixties, reached its maximum height in the 

seventies, and died out before 1890. The hardy prospector and miner 

in these years confined his attention to the Paleozoic limestones and 

the post-Jurassic granites. Lida, Old Camp, and Montezuma were 

flourishing mining centers. Mining in the area studied was dormant 

in the nineties, but with the discovery of Tonopah's phenomenal 

veins in 1900 the desert region was attacked with new ardor. The 

Tertiary eruptives have been more especially the chosen field of the 

prospector, although the limestones and granites have been by no 

means neglected.
ECONOMIC GEOLOGY. 

ECONOMIC CONDITIONS.

43

The various camps herein described are connected with supply 

points by wagon, roads, most of them surprisingly good considering 

the fact that many are less than a year old. Some mines have a small 

but for the present sufficient water supply near at hand. Other

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FIG. 4. Economic map showing areas of altered Tertiary rocks.

camps are compelled to haul their water from springs or seeps 20 

miles distant. Pinon and juniper are rarely of sufficient size for 

mine timbers, other than stalls, but pinon makes an excellent fuel. 

The power question will probably be solved at the other successful 

camps, as it has been at Goldfield, by the transmission of electricity
44 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

generated on the swift streams of the Sierra Nevada. The heat-of 

July and August renders surface work in those months almost impossible in the more southern camps.

GENERAL CHARACTER OF THE ORE DEPOSITS.

The ore deposits herein described are apparently the work of two 

distinct main periods of mineralization, one post-Jurassic and preTertiary, the other Tertiary. The veins at Chloride Cliff may, indeed, be pre-Jurassic, but their resemblance to the post-Jurassic veins 

renders this questionable.

POST-JURASSIC AND PRE-TERTIARY DEPOSITS. 

(A) DEPOSITS IK GRANITE.

1. Pegmatitic dikes: Dikes of pegmatite at Oak Spring are reported to carry gold and silver values. These, so far, have proved 

unimportant.

2. Reopened pegmatitic dikes: The quartz, itself of pegmatitic 

origin, has been crushed, and the veins are probably due to the same 

period of mineralization as that which formed the deposits described 

in the next paragraph. The deposits of Lime Point and some of 

those at Trappmans Camp are of this origin.

3. Massive quartz veins in fissures, joints, and irregular zones of 

brecciation: The quartz is not crustified. The chief sulphide is pyrite, 

although galena, chalcopyrite, and sphalerite occur locally. The 

deposits are usually gold bearing, but with the introduction of galena silver values may predominate. The ores were deposited by 

water, which may have been remotely connected with the granitic 

intrusion. The sharp contact with the comparatively unaltered wall 

rock indicates that these veins filled open fissures. Such appear to 

be the deposits at Old Camp and some of those at Trappmans Camp, 

Oak Spring, and Southern Klondike. The deposits of Goldbelt are 

in quartz monzonite. In the past the veins at Old Camp have been 

large producers.

4. Impregnation of pyrite along joints: This is a'n unimportant 

form of deposit seen only at Trappmans Camp.

(B) DEPOSITS IN PALEOZOIC SEDIMENTARY ROCKS, PREDOMINANTLY LIMESTONE.

1. Quartz veins and irregular masses occupying faults^ joints, 

bedding planes, and brecciated zones, as a rule in the neighborhood 

of granitic intrusions: Rarely a little calcite is associated with the 

quartz. The original sulphides deposited in the quartz, include 

chalcopyrite, galena, pyrite, and sphalerite, while telluride was 

probably originally present in some deposits. In the veins in limestone the predominant sulphides are chalcopyrite and galena and the
GENERAL CHARACTER OF THE ORE DEPOSITS. 45

values largely silver. In quartzite and schist, in metamorphosed 

limestones composed of quartz, garnet, epidote, and calcite, and in 

limestone zones in Avhich silification extended beyond the quartz 

vein pyrite is the predominant sulphide, with gold values alone or 

in excess of silver. It is probable that the relate abundance and 

variety of sulphides were determined by the wall rock, the more 

siliceous rock tending to precipitate from the waters auriferous 

pyrite and the calcareous rock precipitating argentiferous galena 

and chalcopyrite. The secondary ores of this subdivision include 

malachite, azurite, chrysocolla, native copper, brochantite, cerussite, 

emmonsite (or durdenite), native gold, and horn silver, while chlorobrornides of silver are reported. Chalcocite is probably of secondary 

origin. Two or more of these ores are associated with hematite and 

limonite or with a heavily stained jaspery quartz with conchoidal 

fracture. Gypsum, and at one place sulphur, are secondary gangues 

of less wide distribution. The secondary minerals replace the 

wall rock and in part fill open fissures. In many places cavities in 

the secondary ores are frosted by later quartz crystals. The Tokop 

veins belong to this subdivision and their similarity to veins 

in the granite of Old Camp and their reported extension into the 

granite beneath indicate that the quartz veins in the granite and 

limestone are contemporaneous in age and of like origin, a conclusion entirely in accord with the character of both the gangues and 

ores of types A 3 and B 1. The quartz veins in the granite (A 3) 

are not demonstrably of pegmatitic origin and yet their form, 

here lenslike, there sigmoid and independent of apparent faulting, is, in many instances, more closely allied to that of a 

pegmatite dike than to that of a water-deposited vein. In the 

Paleozoic rocks surrounding granite masses these quartz veins are 

abundant, a fact exemplified by the clustering of mining camps 

around the post-Jurassic intrusive masses. At a distance from the 

granite the veins decrease in number and in size, and finally the 

same ores replacing the limestone occur without quartz, as at 

Cuprite. It is probable that the quartz veins in granite and limestone 

were deposited by heated waters, in part at least the magmatic 

waters of the granite, but much mWe remotely connected with the 

magma than those which formed the pegmatite dikes. The resemblance between the ores of these veins and those of the veins 

along contacts (B 3) is striking. The latter deposits may have been 

laid down by waters from portions of the granite deeply buried and 

still molten, or by waters from the white quartz-monzonite porphyry, 

an igneous rock probably genetically related to the granite.

The Lida, Bare Mountain,, and Oriental Wash deposits, and some 

of those of Chloride Cliff, Montezuma, Oak Spring, and Southern
46 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

Klondike, are of this type. These deposits were the most important 

source of ore in the seventies and eighties.

2. Replacement deposits: In the Cuprite mining district and to a 

less extent in the General Thomas mine, in the Lone Mountain foothills, the sulphides appear to replace the limestone in irregular masses. 

The Cuprite deposits are at a considerable distance from granite, and 

in these quartz is lacking. The same ores are found here as in other 

deposits in the sedimentary rocks, and it is believed that the ore deposits of Cuprite were formed contemporaneously with those of the 

type B 1 by similar waters, which, however, had deposited their silica 

before journeying so far from the granite mass.

3. Veins along contacts: Deposits along contacts occur in the limestone along dikes and sheets of monzonite and diorite porphyry in 

the northwestern part of the area mapped, and along a mass of hornblende schist at Chloride Cliff. The porphyries are almost certainly 

pre-Tertiary and the mineral association is so similar to that in the 

deposits already described (B 1 and 2) that there can be but small 

doubt of at least a remote genetic relation in the origin of the two. 

The General Thomas and some of the Montezuma prospects are of 

this type.

TERTIARY DEPOSITS. 

(C) GOLD DEPOSITS IN SIIICIFIED MONZONITE PORPHYRY AND RELATED ROCKS.

Gold occurs at Kawich and Gold Crater, respectively, in silicifiecl 

and kaolinized monzonite porphyry and biotite andesite. When the 

igneous rock was silicified pyrite was deposited in open fissures in it 

and probably partially replaced it. Disseminated pyrite occurs beyond the silicified zone. Copper sulphide is unimportant, and galena 

is apparently not present. Kaolinization is probably a later process. 

During the surface alteration of the pyrite free gold lodged in the 

cavities of the altered rock and at Gold Crater was deposited along 

joints in the surrounding iron-stained andesite. The quartz-monzonite porphyry of Shoshone and Skull mountains is similarly silicified. The ores of KaAvich and Gold Crater Avere deposited by ascending hot waters carrying silica in solution, and while the waters were 

similar chemically, it by no means follows that the deposits are contemporaneous, since the country rock in the one case was probably 

of Eocene and in the other of Miocene age.

(D) DEPOSITS IN RHYOLITE.

1. Silver- and gold-bearing quartz veins in silicified and kaolinized rhyolite: At Silverbow, Eden, Cactus Spring, Wilsons Camp, 

Stonewall Mountain, and Wellington vuggy quartz veins, many of 

them with crustification well developed, fill fault fissures, joint 

planes; and cavities of brecciation and solution. These veins grade 

along their strike into zones of silicified rhyolite carrying gold and
GENERAL CHARACTER OF THE ORE DEPOSITS. 47

silver values. The ore deposits of these camps, if not demonstrably 

of contemporaneous origin, were formed by physically similar 

waters. The original sulphides include stephanite, iron pyrites, 

and chalcopyrite. Pyrargyrite, also noted, may be secondary. 

From the primary ores free gold, horn silver, malachite, azurite, 

.limonite, and hematite are derived. The relative abundance of 

silver sulphides or of pyrite determines whether the veins carry predominant silver or gold values. In the same camp structurally 

similar veins may carry either gold or silver and in various parts of 

the same vein the proportion of the two metals differs greatly. A 

little calcite is associated with quartz in some veins, and at Silverbow and Eden quartz bodies suggestive of the crystal form of calcite probably indicate its former presence. Irregular zones or areas 

surrounding these veins are either siliciiied or kaolinized, the former 

process having been contemporaneous with ore deposition, the latter,

in certain cases at least, subsequent to it. The contact with the vein 

quartz is in some cases transitional, in others sharp. In all the 

camps these zones of altered rock are much more extensive than the 

' ore deposits, and ore deposition unaccompanied by either silicificatibn or kaolinization has apparently not occurred. The silicified 

rhyolite is white in color, flinty in texture, and without prominent 

phenocrysts, although careful inspection shows the presence of quartz 

phenocrysts, while weathered surfaces show feldspar casts. In 

some instances the slightly smoky quartz phenocrysts alone retain their identity. Some of the altered rhyolite is so dense that the 

Indians have used it in making arrowheads. During the deformation of the rocks after silicification the brittleness resulting from the 

density of this conchoidally fracturing rock was an important factor 

in the production of numerous cracks which furnished channels to 

surface oxidizing waters. Cavities of solution and the interstices 

of brecciated zones are lined with clear quartz crystals or filled with 

quartz masses. The alteration has taken place along joints and 

faults and in bands between joints. The silicified rhyolite, being 

much more resistant to weathering than the unaltered rock, stands 

up in rugged Avails and knobs whose extent is coincident with that of 

the silicification. The peculiar topography resulting is well seen in 

the domical hills three-fourths of a mile east of north of Silverbow. 

Here there are rugged walls from 1 to 5 feet high, while cross walls 

show that silicification has also occurred along minor fractures between the main joints.

Under the microscope the silicified rhyolite shows a mosaic of 

quartz or chalcedony notably uneven in grain, while coarser mosaics 

or limonite-lined cavities represent the biotite and feldspar phenocrysts, although in some specimens biotite is replaced by muscovite 

and limonite. The silicified rhyolite of the Cactus Range, south of the
48 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

Goldfield-Cactus Spring road, presents features of considerable interest. The groundmass is composed in part of secondary interlocking 

plates of orthoclase micropoikilitically inclosing quartz blebs and jn 

part of a secondary microgranitic mosaic of quartz and orthoclase varying greatly in grain throughout the rock. Alunite in grains is scattered through the groundmass. A few orthoclase phenocrysts are 

unaltered, but most of them are changed to an aggregate of alunite 

crystals and quartz granules. The rock appears to have suffered 

through recrystallization, with the introduction of sulphurous or a 

related acid and probably some silica. A thin section of the altered 

rhyolite from the Calico Hills, near Shoshone and Skull mountains, 

is somewhat different. The original rock was a glass containing numerous tabular orthoclase crystals and deeply embayed quartz grains. 

Chalcedonic quartz has replaced some of the feldspar phenocrysts, 

and with it, forming pseudomorphs after other feldspar phenocrysts 

and occurring scattered throughout the groundmass, are tiny irregular specks and granular aggregates of a mineral too small for satisfactory determination, probably scapolite. It is evidently contemporaneous with the chalcedonic quartz, -and its even distribution 

throughout the rock shows that the solutions which deposited it must 

have saturated the whole rhyolite mass. The kaolinized rhyolite is a 

white, chalky, rather incoherent rock. The feldspar phenocrysts 

pass to a white unctuous substance and are finally completely removed, forming casts, and the biotite changes to^a silvery micaceous 

mineral.

These quartz veins, the fillings of open fissures, and the attendant 

silicification of the country rock are evidently due to ascending heated 

waters which carried, in addition to metallic salts, notable quantities of 

silica, while locally they contained salts of calcium as well as fluorine, 

sulphurous acid and chlorine. The presence of the fluorine is indicated by the alteration of biotite to muscovite; sulphurous acid is a 

constituent of alunite and chlorine of scapolite. The waters in part, 

then, were of magmatic origin and contained gases typical of waning 

volcanism. These ore deposits, except those in the rhyolite of Stonewall Mountain and that to the north of Cuprite and some of .those in 

the Southern Klondike hills, occur in the early Miocene rhyolite. 

But at Wellington and Wilsons Camp silicification appears to affect 

not alone this rhyolite, but the succeeding formation, the biotite 

andesite. This shows that at these places either the silicifipation was 

dependent on the magmatic waters derived from andesite or it 

occurred long after the extrusion of the rhyolite, probably through 

waters ascending from warm or hot portions of the rhyolite buried 

at considerable depths. The presence of silicified reefs in the Siebert 

lake beds in the Silver Peak Range and on Shoshone Mountain is a 

phenomenon probably of later origin.
AIDS TO PKOSPECTING. 49

Ore deposits of this type are now being extensively worked throughout southwestern Nevada and eastern California. As they have 

many analogies with those of Goldfielcl and Bullfrog, other important camps will without doubt be developed.

2. Gold ores in fault *oi^ey: At Blakes Camp free gold has been 

panned from crushed rhyolite along a fault. The iron pyrite Avas 

probably originally disseminated in the crushed zone.

3. Gold ores along contacts-of Tertiary lavas and Paleozoic limestone : A quartz vein at Southern Klondike is situated along the contact of rhyolite with Cambrian limestone. At the Happy Hooligan 

mine free gold occurs in decomposed rock at the contact of basalt with 

Pogonip limestone.

AIDS TO PROSPECTING.

Ore deposits in the area under consideration appear to be confined 

to the Paleozoic rocks, the post-Jurassic granitoid rocks, and the older 

Tertiary lavas. Of the Paleozoic rocks the limestones have so far 

been and probably in the future will be the most favorable country 

rocks. As an exception to the above, however, it should be stated that 

the Cambrian quartzite-schist-limestone series in the southern Amargosa and Panamint ranges contains strong quartz veins. Of the postJurassic granitoid rocks the granites appear to be more favorable to 

ore deposits than the quartz monzonites. Of the Tertiary rocks the 

first and second rhyelites and the andesitic rocks immediately preceding and succeeding the second rhyolite have alone up to the present 

.time proved productive. The rhyolites younger than the Siebert lake 

beds have, however, in two known instances been silicified and 

slightly mineralized.

The various formations recognized in southwestern Nevada and 

eastern California are represented by appropriate colors and patterns 

on the geologic map (PI. I), from which the approximate distribution 

of the various rocks may be determined.

In prospecting in the Paleozoic rocks the limestones should be given 

preference. Mining experience in this region indicates that the most 

favorable portions of the limestone are those nearest igneous rocks, not 

only the larger intrusive masses, but the dikes as well. Such dikes are 

common in the Cambrian rocks from Lida to the General Thomas 

Camp. The abundance of ore deposits appears to depend almost 

directly on proximity to igneous rocks, and to this Cuprite alone seems 

an exception. Most of the ore deposits in the Paleozoic rocks are 

found in well-defined quartz veins, but some deposits are marked by 

heavy "gossans" (hydrated masses of spongy iron ores of red or 

brown color).

Bull. 308 07 M 4
50 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The map (PL I) shows the areas in which the older Tertiary lavas 

are known to occur, and, while many areas have doubtless been missed 

in the present rapid survey, it is believed that the larger ones have 

been mapped. The ore deposits within these older rhyolites and 

andesites, so far as is at present known, a£e contained in the silicified 

and kaolinized portions. These are shown in fig. 4. although it is certain that many others exist which were not encountered in the course 

of the present work. In searching for such areas of altered rock, the 

peculiar rugged topography with its walls (commonly called " dikes " 

by prospectors) and pinnacles (see p. 47) will be helpful in many instances. The compact, flinty texture of the silicified rocks, already described (see p. 47), is very characteristic. In the Kawich Range, 

Paleozoic quartzite has been mistaken by some for silicified rhyolite. 

The quartzite, however, can be distinguished by its more glassy appearance as well as by the presence in it of rounded sand grains or 

pebbles. In both the silicified rhyolite and the monzonitic and 

andesitic rocks veins occupy fault fissures, and prospect trenches 

and pits located on such faults often bring good results. Within the 

silicified rhyolite in particular quartz veins should be carefully assayed, as in this quartz the values in the rhyolite camps usually lie. 

Further, a yellow scaly coating similar to that from Goldfield, .determined by Dr. W. F. Hillebrand a as a basic ferric-alkali sulphate, 

appears to be confined to joints in the immediate vicinity of ore 

deposits in rhyolite.

DESCRIPTIVE GEOLOGY.

In this section the different localities are described in the following 

order: The mountain ranges and valleys in the vicinity of Goldfield; 

those to the north of Pahute Mesa; the mesa itself; the mountain 

ranges to the1 south of Pahute Mesa; the Amargosa Mountain system; 

Death Valley; and the Panamint Range.

REGION ABOUT GOLDFIELD.

In the northwest quarter of the area shown on the map, in the 

vicinity of Goldfield, are the Lone Mountain foothills, the Silver 

Peak Range, the Mount Jackson, Goldfield, and Southern Klondike 

hills, and Stonewall Mountain. The hills are characterized by a 

north-south extension, the trend verging toward northeast in several 

instances. Geologically they are marked by important developments of the Cambrian rocks and the Siebert lake beds.

"Bull. U. S. Geol. Survey No. 260, 1905, p. 137.
DESCEIPTIVE GEOLOGY, REGION ABOUT GOLDFIELD. 51

LONE MOUNTAIN FOOTHILLS. 

TOPOGRAPHY AND GEOGRAPHY.

Lone Mountain is a prominent craggy peak 9,121 feet high, situated 

immediately north of the11 northwest corner of the area mapped. 

While this mountain and its foothills are cut off from the Silver 

Peak Range to the southwest by the detritus-filled pass 7 miles northwest of Montezuma, the two mountain .masses are geologically and 

topographically closely related. For convenience, the long ridge in 

which General Thomas Camp is situated will also be described here.

The'Lone Mountain foothills reach a maximum elevation of 7,600 

feet. They have rather steep slopes and show a tendency to elongation parallel to the strike of the Paleozoic rocks. The eastern ridge 

has a serrated crest Hue, due to the alternation of steeply dipping 

resistant limestones and soft shales. The Lone Mountain foothills 

are bare of timber and without water, although both are present on 

the, mountain itself.

GENERAL GEOLOGY.

Lone Mountain is a batholith of granite Avhich intrudes Cambrian 

sedimentary rocks, the predominant rocks of the foothills. The 

formations are as follows, the oldest being named first: Cambrian 

sedimentary rocks, post-Jurassic granite, pre-Tertiary diorite and 

diorite porphyry and associated serpentine, and older alluvium.

C SEDIMENTARY ROCKS.

Cambrian. The predominant formation of these hills is a series of 

limestones and shales which appears to consist of a lower shale member, at least 1,000 feet thick, and an upper limestone, several thousand 

feet thick, which in turn is probably overlain by a second shale 

member.

The limestone is compact and rather fine grained. It is dark gray or 

bluish gray in color, although in places weathered surfaces are stained 

yellow or brown by limonite. It is for the most part probably dolornitic, since an analysis of a limestone from the westward extension 

of the area, in the Silver Peak quadrangle,0 showed 19 per cent of 

magnesia. Layers of black flint, from a few inches to 2 feet thick, 

are interbedded with the limestones near General Thomas Camp. 

In the same vicinity the limestone has been altered to a white cherty 

quartz and all gradations exist between this and the unsilicified limestones. White calcite veins traverse the limestone in all directions, 

while quartz veins are less common. These veins are not folded, and 

are doubtless younger than the folding.

0 Turner, H. W., Silver Peak folio; unpublished.
52 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA. 

The shale is fine grained and thin bedded. It is in most places 

olive green, although locally brilliant rose or purplish pink, while red 

is imparted to weathered exposures by iron stains. Arenaceous f acies 

are rare. Rather commonly the shale breaks down into pencils which 

are produced by the intersection of two closely spaced joint systems 

and bedding planes. Veins in the shale are usually quartz.

No fossils were found in these beds, but on lithologic grounds they 

are probably Lower Cambrian. Turner a so considers the extension 

of these rocks in the adjoining Silver Peak quadrangle.

Older alluvium. The road from Alkali Spring to Lone Mountain 

passes through a gap in the ridge south of the General Thomas mine. 

The saddle and the low hills on either side are composed of fragmental 

material lithologically like the Recent alluvium deposits, except that 

it is somewhat weathered. Erosion has cut it into a number of low 

hills. This deposit is the remnant of an old alluvial slope, and is 

tentatively correlated with the older alluvium of Pliocene-Pleistocene 

age in Death Valley.

IGNEOUS KOCKS.

Granite. Lone Mountain is a batholith of granite which has 

pushed up the Cambrian rocks on its border, and into these apophyses extend. The batholith covers about 14 square miles at the northwest corner of the area mapped.

The granite is light gray in color and of either medium or coarse, 

grain. The constituents, which in coarse-grained types reach a 

maximum diameter of one-half inch, are white feldspar, smoky 

quartz, and biotite. Phenocrystic feldspars 2 inches long and onehalf inch wide are locally present. In some exposures the constituents possess a parallel arrangement, probably original. Epidote 

films are developed along some joint surfaces, while on others 

flattened, distorted cubes of limonite after pyrite occur. Muscovite 

films cover planes of movement.

An excellent sheeting, the joints being from 1 to 3 feet apart, 

cuts the granite and imparts to many portions of Lone Mountain a 

sedimentary aspect. The granite weathers into rounded slablike 

joint blocks stained by limonite, and in consequence the mountain 

mass is yellowish white in color. The mountain itself has a very 

rugged topography characterized by knife-edge divides and deepcut, steep valleys. The foothills and inliers in the wash have strong 

tendencies to dome form.

Under the microscope the granite is seen to be uneven grained 

and rather poor in both biotite and quartz. With orthoclase and 

microcline is a little oligoclase. Titanite rhomboids are very abundant, and the other accessory minerals are magnetite, apatite, and

« Op. cit.
LOttE MOUNTAIN FOOTHILLS. 53

zircon. Quartz shows rather strong imdulatory extinction. The 

rock is somewhat altered, biotite changing to chlorite, orthoclase 

n,nd microcline to muscovite, and oligoclase to zoisite.

The granite is cut by aplite and grades into pegmatite. The 

aplite is a white, fine-grained rock composed of white feldspar and 

some quartz. It forms dikes from one-half inch to 2 inches wide, 

which weather in relief. The constituent minerals of the pegmatite 

reach a maximum diameter of 1 inch. Some veins of pegmatitlc 

quartz are also present, as is graphic granite, with characters onefourth inch in length.

At the contact the Cambrian rocks are rather highly metamorphosed. The impure limestone is altered to a quartz-epidote rock 

in which brown garnet occurs locally. The microscope shows that 

magnetite and pyrite are also present. The shale is metamorphosed

to a silvery knotted schist, In thin section it is found to be a

chlorite-epidote schist in which chlorite, quartz, and orthoclase form 

an interlocking mosaic. Epidote with a little- zoisite is equally 

abundant, although less evenly distributed. Magnetite grains and a 

few fibrous scapolite aggregates are also present. Veinlets and lenses 

of coarser.quartz, epidote, and zoisite appear to form the "knots."

The granite cuts Cambrian rocks and is itself cut by dikes of 

diorite porphyry. It is presumably one of the post-Jurassic granites.

Diorite and diorite porphyry. A small intrusive mass of diorite 

cuts the granite and another the Cambrian rocks northwest of General Thomas Camp. The diorite appears to be a granitoid rock composed of feldspar and hornblende. The microscope shows that the 

feldspar is a rather basic labradorite in crystals, with some orthoclase. The hornblende is rudely idiomorphic. Some quartz and 

magnetite are present, the rock approaching a granodiorite. Epidote 

and chlorite are secondary to plagioclase and hornblende.

The granite of Lone Mountain is also cut.by dikes of a greenishgray diorite porphyry, which breaks into angular joint blocks with 

a slight tendency to spheroidal weathering. The dikes, which are 

from 2 to 20 feet wide, weather in troughs beneath the surface of the 

granite.

Under the microscope the groundmass appears as small plagioclase 

laths, between which are some orthoclase grains. The phenocrysts 

include hornblende, plagioclase (labradorite-anclesine), and titanite. 

Many of the simple plagioclase crystals, which are more or less 

altered to sericite, calcite, and chlorite, are twinned according to the 

Carlsbad law. The brown hornblende phenocrysts are partially 

altered to calcite., chlorite, and iron ores. Apatite and magnetite are 

accessories.

Sheets and dikes of diorite porphyry, with abundant phenocrysts 

of striated feldspar and fewer of hornblende, occur in the vicinity
54 SOUTHWESTERN NEVADA. AND EASTERN CALIFORNIA.

of General Thomas Camp, their strike coinciding with that of the 

Cambrian rocks. The largest masses reach a thickness of 25 feet. 

Similar dikes cut Cambrian rocks north of the summit on the road 

from Alkali Spring to Silver Peak.

Pieces of greenish-black serpentine are common on the hills formed 

of the older alluvium, although the rock'was not seen in place. Under^ 

the microscope the magnetite and hematite masses associated with the 

serpentine are seen to be lacking in certain areas, and the texture 

rather suggests that of an igneous rock. In the Silver Peak quadrangle Turner" found a small mass of serpentine in the Lone 

Mountain foothills. The original rock of each of these occurrences 

was probably a pyroxenite, genetically related to the diorite.

The diorite and diorite porphyry are probably of post-Jurassic 

and pre-Tertiary age.

S1RTTCTTTRE.

The Cambrian rocks are strongly and complexly folded. The 

axes of the main folds course east of north; those of the minor folds, 

east and west. The folding is particularly intense along the border 

of the area here discussed. Fan folds and isoclinals are common, and 

in many places these are arranged en echelon. Numerous minor faults 

and zones of brecciation occur in the Cambrian rocks, but faults of 

large throw were not noted. The injection of the Lone Mountain 

batholith has induced in the near-lying sediments a strike parallel to 

its boundary.

While it is probable that the Cambrian rocks were somewhat folded 

prior to the intrusion of the granite, the major folding can probably 

be referred to that intrusion. The position of the older alluvium, 

300 feet above the Recent alluvium deposits, shows that the range 

was considerably uplifted in Pleistocene time.

ECONOMIC GEOLOGY.

The location of the General Thomas mine, the property of the 

Tonopah-Belcher Mining Company, is shoAvn on the map. When 

visited by the writer (June, 1905) the mine was closed down. Several inclines follow the steeply dipping beds of limestone and shale, 

into which in the vicinity are injected sheets of diorite porphyry. 

Cerussite, malachite, azurite, and chrysocolla in limestone, heavily 

stained by limonite, lie on the dump. The gypsum associated with 

the ore was evidently formed simultaneously with these secondary 

minerals. Galena and pyrite in calcite were the only original sulphides seen, but some copper sulphide must also occur. Lakes 6 states 

that lenticular bodies of " sand " carbonate of lead, containing nodules 

of unaltered galena, lay along the contact of porphyry and lime0 Turner, H. W., Silver Peak folio; unpublished.

"Lakes, Arthur, Min. and Sci..Press, vol. 88, 1904, p. 246.
SILVER PEAK RANGE, NORTHEASTERN EXTENSION. 55

stone as well as in the limestone itself. The ore is said to carry 

high silver values, a carload shipment in January," 1904, having 

netted $4,300. At that time the shaft was 150 feet deep. The resemblance of this deposit to some of those at Montezuma may be noted. 

The surrounding hills are bare of timber; and water is scarce. Tonopah and Goldfteld are the supply points of these prospects.

The hills near General Thomas Camp have already been located. 

An abandoned tunnel 150 feet long has been driven into the diorite 

mass 1 mile northwest of the General Thomas. The tunnel was not 

visited, but ore collected by Messrs. Chapman and Spaulding consists of galena, azurite, malachite, and limonite, which appear to fill 

cavities in the diorite. In the older alluvium the writer found 

limonite float heavily stained by malachite. This doubtless comes 

from the hills to the north or south of the road.

NORTHEASTERN EXTENSION OF THE SILVER PEAK RANGE. 

TOPOGRAPHY AND GEOGBAPHY.

The mountains north of Lida and south of the valley in which the 

Klondike Well is situated form the northeast tip of the crescentic 

Silver Peak Range, which lies mainly to the west of the area surA^eyed. These mountains are cut off from the Lone Mountain foothills by the detritus-covered pass 7 miles northwest of Montezuma; 

they are separated from Mount Jackson by a similar gap, and a basalt 

mesa bridges the interval between them and the Goldfield hills. 

There are three main ridges, which course N. 30° E/, parallel to the 

predominant strike of the Cambrian rocks. The crest lines average 

7,500 feet in height, although Montezuma Peak reaches 8,426 feet. 

The ridges are, for the most part, rather smooth, although where the 

strike of the Cambrian rocks crosses them rugged squared hills and 

pinnacles are common. The hills formed of the Siebert lake beds are 

conical peaks and gentle domes with broad valleys between. The 

north-south valley southwest of Montezuma Peak follows approximately the crushed zone along a fault of considerable displacement. 

Lida Valley is an interesting example of stream capture. The traveler 

going up the valley from the flat north of Slate Ridge first encounters a narrow canyon. One-eighth of a mile east of Lida the gulch 

suddenly opens into a gently sloping valley 1 mile wide. The youth 

of the canyon and the maturity of the valley suggest stream capture, 

and Spurr, who followed the road westward, believes that the upper 

broader portion originally drained westward to Fish Lake Valley.

The mountains are covered with piiiori and juniper above an altitude which varies from 6,500 feet at Lida to 6,800 feet on the east side 

of Montezuma Peak. A little grass grows on the upper alluvial 

slopes and the inter-ridge valleys-. An abandoned shaft at Monte-
56 SOUTHWE'STERN NEVADA AND EASTERN CALIFORNIA.

zuma is filled with good water, and a tunnel near by furnishes a little 

stock water tainted with ferrous sulphate. Alkali Spring has already 

been described (p. 19). Springs flow from the mountain slopes near 

Licla, and the water table in the canyon below the village is in many 

places but 30 to 100 feet below the surface.

GENERAL GEOLOGY.

The formations exposed in these mountains, from the oldest to the 

youngest, include: Cambrian sedimentary rocks, post-Jurassic granite and gray quartz-monzonite porphyry, white quartz-monzonite 

porphyry, diorite porphyry, andesite, older rhyelite and dacite, 

Slebert lake beds, younger rhyolite, and basalt.

SEDIMENTARY ROCKS.

Cambrian. The dominant rocks of these mountains are limestones, 

shales, and quartzites, in part at least of Cambrian age, and in the 

series no break in the process of sedimentation is apparent. West of 

Montezuma Peal? these rocks consist of 1,000 feet of limestone with 

some shale beds near its top, overlain by 1,000 to 1,200 feet of shale 

with some interbedded limestone layers. A bed of white quartzite 

of fine to medium grain, 40 feet thick, occurs near the middle of the 

upper shale member. Neither bottom nor top of this series is exposed. 

Quartzite is more prominent in the hills southwest of Alkali Spring, 

where it is as abundant as shale.

The limestone is dark graj^, compact, and fine grained. The weathered rock is medium gray in color, except in mineralized portions, 

where the reds, yellows, and browns of iron stains are characteristic. 

Much of it is siliceous and grades into a black, dense secondary jasperoid of conchoidal fracture. The limestone is massively bedded, except Avhere interlaminated with shale, where it is usually in rather 

thin beds. Gray lenses and nodules of flint form one-third of the 

limestone mass 6 miles north of west of Montezuma Peak. By the 

addition of clay the limestone passes into calcareous shale and finally 

into shale.

The thin-bedded slaty shales are of fine, even grain and of gray or 

olive-green color. In many places muscovite plates are present upon 

bedding planes, and semischistose facies are developed by further 

formation of muscovite. Where joint planes are closely spaced the 

shale breaks into pencil-like fragments. Locally Aveathered surfaces 

are stained red or brown by iron compounds. With increase in size of 

grain and in content of quartz the shales pass into dense argillaceous 

quartzites of greenish-gray to black color and fine to medium grain. 

Cross-bedding is in places well developed.

The character of the rocks and the series of alternations of various 

rocks across the bedding planes in'dicate that the Cambrian rocks were
SILVER PEAK RANGE, NORTHEASTERN' EXTENSION. 57

laid down in comparatively shallow water in which conditions favor- 

. ing mechanical sedimentation on the one hand and organic and perhaps chemical sedimentation on the other hand alternated.

Spun"1 found fossils southwest of Lida which were determined 

by Mr. C. D. Walcott to be of Lower Cambrian age. The limestone 4 

miles west-northwest of Montezuma Peak contains closely concentrically laminated balls averaging one-half inch in diameter. Mr. E. 

O. Ulrich states that these resemble Girvanella, a calcareous alga, and 

are probably of Cambrian age. On the evidence of these fossils and 

the resemblance of the series to that at Cuprite the rocks are believed 

to be, in the main at least, of Lower Cambrian age. Turner J> maps 

Ordovician rocks at one place near the border of the Silver Peak 

quadrangle, but such rocks, if they exist, were not differentiated 

during the present reconnaissance.

Siebert lake beds. Prior to the deposition of the Siebert lake beds 

the Cambrian rocks had a rugged topography. These beds, IT miles 

north of Lida, are coarsely conglomeratic and inliers of limestone protrude through them and outliers of lake beds occur on the Cambrian 

rocks: The lake beds cover a considerable area on the western border 

of the region under consideration, a somewhat-smaller area near Montezuma Peak, and a small area 5 miles south of Alkali Spring. The 

northern boundary of the largest area is approximately correct as 

mapped. The southern boundary is less accurately drawn and some 

Tertiary igneous rocks may lie between the Cambrian rocks and the 

lake beds.

These beds, which are composed largely of rhyolitic material, consist of typically incoherent, unevenly granular, Avell-bedded sandstones. When unstained by iron, they are white in color, but brilliant 

reds and yellows are characteristic of many areas. Fine-grained beds 

alternate with conglomeratic layers containing pebbles of Cambrian 

rocks, quartz-monzonite porphyry, diorite porphyry, rhyolite, and 

igneous rocks of andesitic and basaltic affinities. The pebbles are well 

rounded or semiangular. Microscopic examination of several slides 

shows the presence of quartz and orthoclase crystals in ii pyroclastic 

matrix.

Locally the Siebert lake beds have been indurated by silicification 

along joints and in irregular bodies. Quartz, chalcedony, and opal 

fill cavities. The silicified portions weather into wall-like masses 

along joints and into grotesque topographic forms where silicification 

has been less regular.

Rhyolitic and dacitic flows are interbedded throughout the sediments, although they increase toward the bottom of the formation 

and dacite appears to underlie it.

"Turner, H. W., Silver Peak folio; unpublished.

"Spun-, .1. E., Bull. U. S. Geol. Survey No. 20S, 1903, p. 18G.
58 SOUTHWESTERN NEVADA AND EASTEKN CALIFORNIA.

The lake beds at Montezuma Peak are about 1,100 feet thick. On 

the western border of the area mapped they are probably 200 or 300 

feet thicker. The formation was for the most part deposited in an 

inland lake, although some portions were possibly laid down subaerially by explosive volcanic action. 4

Mr. E. H. Chapman found a piece of silicified wood at a point 4 

miles west of Montezuma Peak. Mr. F. H. Knowlton, who kindly 

examined it, states that it is wood of a deciduous tree not older than 

the Tertiary. These sandstones are correlated with the Siebert lake 

beds of Tonopah, described by Spnrr.a

Travertine. A small area of travertine at Alkali Spring, presum- 

-ably of Pleistocene age, has already been described (p. 35).

IGNEOUS ROCKS.

Post-Jurassic granite, granite porphyry, and quartz-mon&onite porphyry. The dikes and small irregular intrusive masses of white finegrained alaskite and granite porphyry 2 miles southwest of Alkali 

Spring are usually injected parallel to the bedding of the upturned 

Cambrian rocks, but here and there cut across it. The porphyritic 

habit is better developed at the contact and next to the border phenocrysts are in flow orientation. The rock breaks down into angular 

joint blocks, many of which are stained by limonite. A single thin 

section under the microscope proves to be a granite porphyry with 

microgranitic groundmass of quartz and orthoclase. Coronas of micropegmatitic quartz and orthoclase surround the abundant phenocrysts of dominant quartz and orthoclase and subordinate biotite and 

plagioclase (oligoclase). Some phenocrysts are composed of quartz 

and feldspar in a graphic-granite intergrowth. The phenocrysts all 

show undulatory extinction, and in consequence the rock has suffered 

some deformation. Biotite has been completely altered to muscovite 

shreds, rutile and an iron ore forming simultaneously.

The dikes on the east slope of this hill are composed of mediumgrained gray biotite granite. On weathering the granite breaks 

down into spheroidal masses. It includes numerous small Cambrian 

fragments, while basic segregations of biotite and probably hornblende are present. This rock proves on microscopic examination to 

have a granular, hypidiomorphic texture, plagioclase individuals being of columnar habit. The orthoclase,'much of which is microperthitic, is usually twinned according to the Carlsbad law. The feldspars are partially replaced by kaolin and sericite and the biotite by 

chlorite. Zircon and magnetite are accessories. Fine-grained pink 

aplitic dikes, from 1 inch to 4- inches wide, cut the granite and locally 

fault the Cambrian inclusions. These more acidic dikes are probably 

genetically related to the main granitic intrusion.

"Spnrr, .T. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, pp. 51-55.
SILVER PEAK RANGE, tfORTHEASTEKN EXTENSION. 59

Dikes in the Cambrian rocks, 6 miles west of south of Alkali Spring, 

are composed of a dense white granite porphyry with rather numerous 

small phenocrysts. These dikes are too small to show on a map of 

the scale employed in this report. Under the microscope the groundmass appears as a mosaic of quartz and orthoclase which are in micropegmatitic intergrowth over small areas. A little plagioclase is also 

present. The phenocrysts include orthoclase, usually microperthitic, 

quartz deeply embayed, and plagioclase. In some specimens rutile 

rods are so grouped as to simulate somewhat rudely biotite crystals, 

and it may be that biotite phenocrysts present in the magma were absorbed prior to its solidification. Magnetite is an accessory.

The mass of quartz-monzonite porphyry 4 miles west of south of 

Alkali" Spring and the dikes extending from it into the Cambrian 

rocks to the northeast are composed of a gray rock of porphyritic 

habit in which numerous medium-sized phenocrysts lie in a finely 

granular groundmass. The constituents in the order of their abundance are feldspar, both striated and unstriated, biotite, and hornblende. The rock weathers into rounded blocks. Inclusions of Cambrian rocks are common, as are basic segregations. Microscopic 

examination shows a microgranitic groundmass, composed of plagioclase laths, orthoclase tablets, and quartz grains. The phenocrysts 

consist of plagioclase; orthoclase, much of which shows excellent 

zonal growths; ragged biotite tablets, and hornblende columns. Magnetite and apatite are accessory minerals. The quartz-monzonite porphyry is cut by dikes of diorite porphyry and white quartz-monzonite 

porphyry. It is believed that this rock is a variant of the granitic magma intruded contemporaneously with the granites of the" 

vicinity. .

The Cambrian limestone in contact with the quartz-monzonite porphyry just described has been metamorphosed to a white, mediumgrained marble in which epidote and other lime silicates are developed. The shales near the granitic rocks 2 miles southwest of Alkali 

Spring have been metamorphosed to slates. A dense, greenish -gray 

slate shows under the microscope as a mosaic of quartz and orthoclase 

in which are shreds of sericite and chlorite. Locally the sericite 

and chlorite form large skeleton growths containing numerous quartz 

and feldspar individuals. Another facies is a dense, black slate of 

conchoidal fracture. In thin section this is formed of large, rounded 

areas of orthoclase lying in a ramifying network of orthoclase 

grains intimately cut by biotite and muscovite shreds. Imperfect andalusite crystals are scattered throughout the rock, and some of these 

have the black centers characteristic of the variety called chiastolite. 

- These igneous rocks intrude Cambrian rocks and occur as pebbles 

in the rhyolite and Siebert lake beds. They are believed to be members of the post-Jurassic granite series.
60 SOUTHWESTERN NEVADA AND EASTEKN CALIFOENIA.

White quartz-monzonite porphyry. In the vicinity of Lida dikes 

and feAver sheets of white quartz-monzonite porphyry are common. 

The three areas shown on the map include both sheets and complex 

intrusive masses filled with inclusions of Cambrian rocks, while 

many other areas are too small to be mapped on the scale employed 

here. The dike which cuts the gray quartz-monzonite porphyry 

4 miles west of south of Alkali Spring has already been mentioned.

This quartz-monzonite porphyry is a dense, white or locally greenish rock, with rather abundant medium-sized phenocrysts, consisting 

of somewhat altered whitish feldspars, some striated and others unstriated, silvery mica, and rarely a quartz crystal. The central portions of the dikes and intrusive masses are more coarsely crystalline 

than the borders, and in certain instances approach a granitoid 

texture.

The rocks break into sharp joint blocks, which in many places are 

stained by limonite. Limestone in the vicinity of this rock is here and 

there silicified and indurated, although the metamorphisrn is slight.

Microscopic examination proves the medium-grained microgranitic groundmass to consist of orthoclase grains, plagioclase 

]aths, and a few quartz anhedra. The phenocrysts of orthoclase 

slightly predominate over those of plagioclase (oligoclase-andesine). 

Kaolin and*sericite are the alteration products. Biotite phenocrysts 

altered to muscovite or chlorite, with an iron ore and rutile in rods 

or sagenitic webs, are constantly present, while quartz phenocrysts, 

much corroded, appear in some thin sections.

The white quartz-monzonite porphyry is younger than the granite which it cuts in the area 4 miles west of south of Alkali Spring. 

Pebbles of the porphyry are included in the Siebert lake beds. It is 

believed that it is genetically related to the granite and is a later 

intrusion of the same magma.

Diorite porphyry. Dikes of quartz-diorite porphyry cut the gray 

quartz-monzonite porphyry 4 miles west of south of Alkali Spring, 

and many dikes of diorite porphyry, probably of contemporaneous 

age, intrude Cambrian rocks near Lida. The quartz-diorite porphyry is a- dark, rather fine-grained holocrystalline rock. Under the 

microscope the presence of biotite is revealed. Ophitic texture is 

well developed, plagioclase laths (some andesine and more basic) 

lying in a mesostasis of hornblende, biotite, and a little quartz. The 

rock weathers into sharply jointed blocks of dark color. The diorite 

porphyry is a greenish-gray rock of porphyritic habit, both hornblende and striated feldspars occurring as phenocrysts. Epidote' is 

developed in the rock and forms crystalline felts along joint planes. 

Spheroidal weathering is characteristic.

The contact of the white quartz-monzonite porphyry and the 

diorite porphyry is poorly exposed 1- mile northeast of Lida, and the
SILVER PEAK RANGE, NORTHEASTERN EXTENSION. 61

latter rock is apparently younger than the former. Pebbles of the 

diorite porphyry occur in the Siebert lake beds -a fact, which leads 

to the belief that these dikes were intruded in post-Jurassic and preMiocene time.

Andesite. The andesite masses 4 miles north of Lida were seen 

by the writer only at a distance, but Turner,0 who mapped their 

western extension, believes the andesite to be of " early Neocene " age, 

and it is probably older than the formation described in the following paragraphs.

Rhyalites and dacites. Thin flows of rhyolite are interbedded with 

the lower portions of the Siebert lake beds of Montezuma Peak and 

of the area 4 miles north of it. The lake beds seem to lie on a siliceous effusive igneous rock which forms a narrow north-south band to 

the east of Montezuma Peak. Small areas of rhyolite are exposed 

by the erosion of the overlying basalt mesa 3^ miles east and 4 and 5 

miles southeast of Montezuma Peak. A small poorly exposed mass 

of rhyolite possibly a dike, to judge from the disturbed condition 

of the surrounding limestone lies 5 miles north of west of Mon- O

tezuma Peak. Rhyolite is also exposed 3^ miles north of Lida.

The rhyolite flows in the Siebert lake beds are dense gray or pink 

rocks, in which are sparse and small phenocrysts of quartz, orthoclase, 

and biotite. Black glasses are also present. Flow banding is "highly 

developed, and spherulites form freely in cavities and impinge against 

one another in the more dense facies. The spherulites, some of which 

are simple and others compound, are of radial structure. The larger 

ones are 2 inches in diameter. Lithophj^sai occur in the area 4 miles 

north of Montezuma Peak. Under the microscope the glassy groundmass appears somewhat devitrified. The flows here contain numerous 

pebbles of Cambrian jasperoid and quartz-monzonite porphyry.

The siliceous eruptive rock east of the Siebert lake beds of Montezuma Peak is a red semivitreous rock in which some small phenocrysts of striated feldspar and fewer of unstriated feldspar and 

quartz are sparsely distributed. The microscope shows numerous 

plagioclase microlites in the glassy groundmass, and orthoclase is so 

subordinate that the rock is a siliceous dacite.

The rhyolite of the other areas mentioned has abundant phenocrysts of quartz, orthoclase, and biotite in a light-colored groundmass 

which under the microscope appears as a glass somewhat devitrified, 

showing flow banding and spherulites. In one slide a few plagioclase phenocrysts are present with those already mentioned. Zircon 

and magnetite are accessories. This rhyolite grades into a white 

waxy glass without phenocrysts in the area 4 miles east of Montezuma 

Peak.

"Turner, H. W., Silver Peak folio; unpublished.
62 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The siliceous igneous rocks are probably all portions of a single 

series that is .older, for the most part, than the Siebert lake beds, 

They are probably contemporaneous with the Tonopah rhyolite-dacite 

described by Spurr * as presumably of Miocene age.

Later rhyolite. Lying upon the eroded surface of the Cambrian 

rocks and protruding from the Kecent alluvial deposits in the vicinity 

of Alkali Spring are small exposures of a lavender lithoidal igneous 

rock, with fairly numerous glassy feldspar phenocrysts of medium 

size. These rocks closely resemble the later rhyolite underlying the 

basalt flows at Goldfield and are tentatively correlated with it.

Basalt, A basalt mesa lies between the spurs of the Silver Peak 

Range and the Goldfield hills. For convenience its description is 

given Avith that of the hill group (p. 75). A basalt dike 50 feet wide - 

cuts the Cambrian limestone near its contact with the Siebert lake 

beds on the Montezuma-Goldfield road. The basalt is a dense black 

rock containing medium-sized glassy olivine grains and small striated 

feldspars and black augites. Under the microscope the rock is seen 

to be a holocrystalline olivine basalt. The plagioclase is partially 

altered to calcite and the olivine to serpentine. Basalt also covers a 

considerable area 1-J miles southeast of Lida. This is evidently a flow, 

the red or black rock being full of vesicles and much of it having a 

ropy surface. This rock is contemporaneous with the basalt of Mount 

Jackson and Goldfield, and the dike near Montezuma is probably of 

the same age.

Five miles northeast of Lida a flow of andesite or basalt lies upon 

the eroded surface of the Cambrian limestone. It has a gray lithoidal groundmass in which large striated feldspar phenocrysts are 

prominent. Lithologically the rock resembles certain members 

of the basalt flow south of Goldfield, but the mature .topographic 

form of its surface may more nearly ally it to the older andesite 

already described.

STRUCTURE.

The Cambrian rocks are for the most part in rather open folds 

with north or northeast axes, which are crossed by minor folds. The 

amount of dip as a rule is not great, although at many points in the 

isolated hill southwest of Alkali Spring the rocks are on edge and 

the folding appears close. Locally small isoclinal folds are present, 

particularly near intrusions of granite, and the northwest strike of 

the Cambrian 5 miles north of Montezuma Peak is probably due 

to the intrusion of the quartz-monzonite porphyry. The gentle 

character of the folding of much of the Silver Peak Range is in 

marked contrast with that of the Amargosa Range and Bare Mountain to the south and southwest. The folding, in part at least, preceded the intrusion of the granite, since this rock is intruded along

0 Spurr, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, pp. 41-43.
SILVEE PEAK RANGE, MONTEZTJMA DISTRICT. 63

vertical bedding planes southwest of Alkali Spring. Small faults, 

usually reverse, are common in the Cambrian rocks, while zones of 

brecciation in the limestone indicate that differential movement has 

occurred at many places. The Siebert lake beds are approximately 

horizontal, although flexures and normal faults occur. The .normal 

north-south fault west of Montezuma Peak has a throw probably 

amounting to several thousand^ feet. The uplift of this range since 

Miocene time has been great, since the Siebert lake beds, once beneath a lake, have been elevated and eroded into mountains.

ECONOMIC GEOLOGY.

Two mining camps, Montezuma and Lida, are located in this spur 

of the Silver Peak Range.

MONTEZUMA DISTRICT.

The Montezuma-mining district was organized in 1867, and soon 

afterwards several mines were opened in the country Avest of Montezuma Peak. In 1886 a mill was erected in the gulch to the northwest of the mountain. Active work ceased in 1887, but at present 

a number of prospectors are reopening old properties and locating 

neAv claims. The district product, estimated at $500,000, was 

freighted in wagons to Belmont, 65 miles away. At present only a 

few shallow prospect holes and the dumps of the old mines are accessible for examination. The mineralized area lies to the west of 

Montezuma Peak,*in Cambrian rocks.

In the old mines the chief gangue is quartz, with rarely a little 

calcite and kaolinitic material. Vugs filled with quartz crystals 

occur in the quartz. The ores at the surface are cerussite, malachite, 

azurite, manganese dioxide, and limonite, and associated with these 

and replacing them in depth are galena, chalcocite, and pyrite. The 

values are largely in silver, the gold values being uniformly low. 

Chlorobromides of silver are reported, but were not seen.

A prospect hole exposes a quartz vein having white quartz-monzonite porphyry as the hanging Avail and limestone as the foot Avail. 

Chalcopyrite is the original sulphide, and malachite with less limonite, azurite, and a little native copper are the secondary ores. The 

natiA'e copper forms thin sheets in cracks and small nodules in the 

A7 ein. Malachite partially replacing limestone Avas noted at a number of other places.

At Montezuma copper and lead sulphides Avith quartz fill open fissures in limestone. Some, probably all, of the deposition followed 

the pre-Tertiary dike injection. Later the veins Avere crushed, and 

surface Avaters altered the sulphides to carbonates, oxides, native 

metals, and probably haloid salts. This chemical breakcloAvn of the 

sulphides continues to the present day, as is shoAvn by the fact that
64 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

the water flowing from an abandoned tunnel southwest of the mill at 

Montezuma deposits considerable limonite and is so charged with 

ferrous sulphate that animals will scarcely drink it.

In several of the older mines and prospects water, both good and 

bad, was encountered at a depth of 30 feet. The mines will probably require pumps, but abundant fuel surrounds them. Goldfield, 

the railroad terminus, is 9 miles distant, the road being fairly good.

The Lida mining district was organized August 28, 1871, and in 

the succeeding decade some rich surface pockets of horn silver and 

silver-bearing galena were removed. The ore, probably picked, ran 

from $500 to $1,000 per ton. It is said that the values decreased at 

depths of 200 to 300 feet. In the latter part-of 1904 and the early 

part of 1905, the attention of mining men having been turned to 

southwestern Nevada, old mines were reopened and new locations 

made. Unfortunately, at the time of the writer's visit (December, 

1905). the principal prospects were closed through litigation, and in 

many cases pumps and ladders had been removed. The prospects 

are situated partly outside the area surveyed and partly on the east 

slope of Mount Macgruder to the south and southeast of the village.

The Florida-Goldfield Mining Company's shaft is near the mouth 

of a gulch which joins the Lida Valley about one-half mile beloAV 

ihe village. When visited, the shaft, 150 feet deep, was filled Avith 

Avater within 80 feet of the surface. The ore on the dump includes 

Cambrian limestone rather heavily-impregnated Avith iron pyrites 

and pyrite inclosed in veins of coarsely crystalline Avhite calcite and 

in Avhite quartz veinlets. In some specimens galena and lightbrown zinc blende are associated with the quartz veinlets carrying 

pyrite. Chalcopyrite, an apparently still more uncommon sulphide, 

is in places superficially altered to malachite and azurite. The 

limestone cut by the quartz vein has been more or less silicified. An 

old open cut above this shaft shoAvs a zone of brecciated limestone 4 

feet in Avidth healed by innumerable connecting quartz veinlets in 

which the ores mentioned occur. On the dump of the Thanksgiving mine quartz masses and veinlets cutting similar limestone Avere 

examined. The quartz contains much pyrite and less chalcopyrite.

The sulphides of the Lida deposits are in part fissure fillings and in 

part impregnations of the country rock, Avhile the oxidized ores appear 

to be largely replacements of limestone. The oxidized zone is, for a 

desert country, very shalloAv.

In the early daj^s of mining in this district considerable bunches 

of oxidized ore were hauled to Austin and Belmont. It is scarcely 

probable that all these pockets have been found, and Avith the 

improved transportation facilities such deposits should pay well.
SILVER PEAK RANGE, LIDA-GOLDFIELD VALLEY. 65

Some of the ore mined from the newly located prospects is reported 

to rim from $100 to $500 per ton in gold and silver. Such assay returns, however, in at least the majority, of cases, were obtained from 

picked samples and are of no value in estimating the economic possibilities of a prospect. The water level, to judge from the development work so far carried on in the Lida district, is comparatively near 

the surface. Much of the ore already taken out is refractory and 

would require milling and smelting. In this respect the Lida district 

is at a disadvantage in comparison with the surrounding districts, but 

on the hills surrounding the mines there is a fair growth of pin on 

and juniper, which will furnish, for a time at least, satisfactory fuel 

and some mining timber. Water, sufficient for mining and domestic 

purposes, flows from springs in and above the village and can be 

obtained in the Lida Valley at slight depths. A daily stage runs 

from Lida to the railroad at Goldfield.

OTHER MINEKAL1EEU AUEAS.

Quartz veinlets are abundant in the Cambrian quartzite and shale 

and are locally present in the limestone, although calcite veins are 

more characteristic of the limestone. The quartz and calcite veins 

were evidently formed at several periods, since in many places one set 

faults .another and in turn has itself been faulted'. Strong quartz 

veins occur in limestone heavily stained by limonite and hematite 5 

miles north of west of Montezuma Peak. Quartz veins also occur in 

the limestone area 6 miles north of Montezuma Peak. Thin sheets 

of malachite replace limestone along joint planes 3 miles north of 

Montezuma Peak.

. LIME.

A kiln 2|- miles west of south of Montezuma Peak burns Cambrian 

limestone. The lime, which is sold in Goldh'eld, is reported to be of 

good quality.

LIDA-GOLbiriELD VALLEY.

The Lida-Goldfield Valle}^ lies between Mount Jackson and the 

Goldfield hills on one side and the Silver Peak Range on the other. 

A low detrital divide west of Mount Jackson separates it from the 

valley north of Slate Ridge. The lowest part of the valley lies at an 

elevation of 5,100 feet, and from a distance appears to be occupied by 

two small playas. On the east side of the valley, north of Mount 

Jackson, some intensely dissected hills, 50 to 150 feet above the valley 

bottom, appear at a distance to be formed of playa deposits of the 

older alluvium. It is also possible that the apparent playas are in 

reality eroded exposures of the same formation. 

Bull. 308 07 M 5
66 SOUTHWESTERN NEVADA AND EASTEKN CALIFORNIA.

MOUNT JACKSON AND.THE HILLS TO THE NORTHEAST. 

TOPOGRAPHY AND GEOGRAPHY.

Mount Jackson is a prominent butte which rises 800 feet above its 

alluvial base. Northeastward from it extends a ridge on which are 

superimposed buttes of the Mount Jackson type, capped by resistant lava flows. At its north end this ridge is divided by a valley into 

two parts. These hills are separated .from the Goldfield hills to the 

north by basalt lava flows. For convenience the mesa-capped hill east 

of Cuprite and the isolated hills 10 miles east of north of Mount Jackson will be described here.

Water is unknoAvn in these hills, and with the exception of scattered groves of the tree yucca they are bare. Grass is fairly abundant 

on the upper portions of the encircling alluvial slopes.

GENERAL GEOLOGY.

The formations exposed in these hills, named from the base upward, are Cambrian sedimentary rocks, diorite porphyry, Siebert lake 

beds, rhyelite, and basalt.

SEDIMENTARY ROCKS.

Cambrian. An area in the southern ridge and another at the north 

end of the northern ridge are occupied by Cambrian sedimentary 

rocks, and the same rocks also in part form the isolated hills in the 

valley traversed by the Goldfield-Lida road.

A compact fine-grained black or dark-gray limestone, locally silicified to a black jasperoid of conchoidal fracture, is the dominant member of the Cambrian series. Both rocks are intricately cut by white 

calcite veinlets. Laj^ers of thin-bedded green slaty shale, in places 

schistose, are interbedded with the limestone, as are smaller amounts 

of Avhite medium-grained quartzite. A total thickness of 3,000 to 

3.500 feet of Cambrian rock is exposed. These sediments form gentle 

hills elongated in the direction of strike, the shales being characterized by few, the limestone and quartzite by many exposures.

Mr. E. 0. Ulrich determined the following fossils collected by the 

writer near the Goldfield-Midway-Bullfrog mining camp, 2 miles south 

of west of Cuprite: Olenellus, near 0. gilberti; Hyolithes, closely 

related to or identical with H. americanus; undetermined orthoid 

shell.

He states: " So far as this imperfect material will permit of determining age, it points to a Lower Cambrian horizon." Girvanella-like 

forms similar to those from the Silver Peak Range were also found 

in these Cambrian rocks. The Lower Cambrian age of portions of the 

series is thus demonstrated, although other portions may be somewhat 

younger. The rocks are correlated with those of the north spur of the 

Silver Peak Range and of the Lone Mountain foothills,.
MOUNT JACKSON AND HILLS NORTHEAST. .67

Siebert lake beds. White, finely bedded tuffaceous sandstones 

.and clays, 200 to 300 feet thick, underlie the rhyolite of Mount Jackson and that of the isolated butte 10 miles east of north of it. Small 

areas of the same formation, not shown on the map, occur with the 

rhyolite northeast of Mount Jackson. Rhyolite pebbles occur in 

these sediments. At the more northerly butte they contain also 

thin rhyolite flows and lie unconformably upon the folded Cambrian 

rocks, which were evidently low hillocks in the lake bottom on which 

the sandstones were deposited. On lithologic and structural grounds 

these sandstones are correlated with the Siebert lake tuffs at Tonopah, 

described by Spurr.a

IGNEOUS BOCKS.

Diorite porphyry. A dike of dark greenish-gray diorite porphyry 

cuts the Cambrian limestone one-fifth of a mile northwest of the 

Goldfield-Midway-Bullfrog mining camp already mentioned. The 

dike is 20 feet wide and courses N. 35° E. The dike rock, much 

altered, weathers into iron-stained spheroidal masses. The limestone 

at the contact is slightly indurated, approaching a hornfels. Macroscopically this dike rock resembles pre-Tertiary diorite prophyry of 

the Silver Peak Range.

Rhyolite. Rhyolite flows cover a large portion of these hills. 

The rhyolite contains small and scarce phenocrysts of quartz, glassy 

feldspar, and biotite, which however, in some facies are lacking. 

The groundmass ranges from pumiceous to compact glasses of conchoidal fracture and varies in color from white through gray to black. 

Perlitic cracks traverse the glass in all directions and reddish-brown 

spherulites are common. The smaller spherulites show both radiate 

and concentric structure, while the larger, Avhich reach a diameter 

of 8 inches, are traversed by fine w"avy lines parallel to a diameter, 

although they break1 into sectors of a sphere. Some of the spherulites 

are simple, although as a rule two or more are linked together. Chalcedony is abundantly developed in joint cracks. Thin sections under 

the microscope show spherulites, cavities filled with gas, perlitic 

cracks which may extend through the phenocrysts, flow lines, and 

other phenomena typical of rhyolites.

The flow beds are from 2 inches to 50 feet thick, the upper surface 

being in some instances corrugated like the ropy surface of basaltflows. The maximum determined thickness of the rhyolite flows 

is 400 feet, although the total thickness may be somewhat greater. 

Small isoclinal folds were formed during the' outflow of the lava, 

which must have been rather viscous-and which on meeting an obstruction was crumpled. In one case a glassy facies folded with thin 

bands of semiglassy phenocryst-bearing rhyolite exhibits interesting

"Spurr, J. E., Prof. Paper U, S. Geol. Survey No. 42, 1905, pp. 51-55.
feet.

DO SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

features. (See fig. 5.) The more crystalline rhyolite was sheared 

and fractured °along the limbs of the fold, while the glassy facies 

thickened at the troughs and crestsT The thinner flows weather somewhat like a horizontal sedimentary rock, while the thicker show the 

rounded topographic forms of granite.

Minor rhyolitic effusions started Avhile the Siebert lake beds were

being deposited, although the major outflow was later. The rhyolite is probably to be correlated 

with the younger rhyolite of the 

Amargosa Range and is of late 

Miocene or early Pliocene age.

Basalt. Slightly eroded benches 

of basalt flank Mount Jackson on 

the south and a small basalt area 

is located 5 miles to the east. The 

FIG. 5,-Fiow folds in rhyolite (hili 10 miles east, basalt is a dense black vesicular

of north of Mount Jackson), showing thicken- . .

ing of more glassy rhyolite (white) on crests HOW 1'OClv Wilich lYllCI'OSCOplC

and troughs of folds and cross fractures in ination proves' to be an Ordinary 

more hthoidal rhyolite on limbs of folds. . . A - -

ohvine basalt. As Spurr states,"

erosion carved Mount Jackson approximately to its present form 

prior to the outflow of basalt. At the north end of the ridge 

east of Cuprite and in several small, areas west of the GoldfieldBullfrog road is basalt which is an extension of the younger basalt 

of -the Goldfield hills. (See p. 75.) It is probable that small areas 

of younger rlryolite and late tuffs of these hills are here mapped 

with the basalt. The basalt northeast of Cuprite clearly- overlies 

and is younger than the rhyolite, being probably of late Pliocene or 

early Pleistocene age.

STRUCTURE.

The Cambrian rocks are in rather open folds of northeast-southwest axes (fig. G). The angle of dip rarely exceeds 30°, although

Fiu. G. East-west section across Mount Jackson hills 1 mile south of. Halfway Station.

4 miles west of Cuprite isoclinal folds occur. The highest hills of 

the two main ridges are situated on the axes of synclines. The rocks 

on the south face of the hills toward the valley north of Slate Ridge 

dip gently to the .west. Faults, usually normal and across the strike

«Spurr, J. E., Bull. U. S. Geol. Survey No. 208. 1903, p. 1S3.
MOUNT. JACKSON AND HILLS NOBTHEAST. . 69

of the rocks, occur but do nof seem to be of large throw. The Siebert 

lake beds and the later lavas are practically horizontal, their elevation being attended only by minor flexing and faulting.

ECONOMIC GEOLOGY.

The prospects of the Cuprite mining district, in which the first 

locations were made early in 1905, lie in a belt 1 mile wide which 

extends from a point 17 miles south of Golclfield westward to Mount 

Jackson. The mines are from 2 to 9 miles west of the stage and 

automobile road between Golclfield and Bullfrog.

The properties of the Goldfield-Midway-Bullfrog Mining Company and the Tri-Metallic Mining Company may be taken as types 

of the Cuprite mining district. The Copper Bell shaft of the firstnamed company, 85 f^et deep, is located on the side of a gentle valley 

in Cambrian sedimentary rocks 2 miles south of west of Cuprite. 

The shaft is being sunk to encounter a vein which strikes N. GO 0 E. 

and dips from 80° to 85° NW. This vein has been traced by means 

of prospect holes at least 1,000 feet. At one prospect hole the vein 

is capped by a gossan of spongy limonite 9 feet thick. At this depth 

malachite and less azurite .are associated Avith the limonite and at 

the bottom of the hole, 9 feet deeper, the vein is reported to have run 

12 per cent copper, with 14 ounces of silver and $1.20 in gold per 

ton. The vein is from 2 to 5 feet wide and on its borders shows a 

gradual passage from totally unaltered limestone to pure limonite. 

The limonite, on the border of the vein at least, is a replacement of 

the limestone. The same company has an incline 65 feet deep situated 

on a shear zone which strikes 1ST. 85° E. and dips GO 0 S., cutting practically horizontal limestone. A streak of ore 1-J to 2-| feet wide, traceable more or-less continuously for 900 feet, occupies the shear zone. 

The ore consists of malachite, azurite,-and limonite associated with 

heavily limonite-stained chalcedony of conchoidal fracture. The sulphides are chalcocite and less chalcopyrite and pyrite. The two latter 

are undoubtedly original. A number of assays of the ore are said 

to have averaged between 9 and 10 per cent of copper, while the 

silver values are variable, reaching as high as 400 ounces per ton. 

Evidently the silver is intimately associated with the copper minerals, the iron compounds giving no silver returns. The aA^erage ore 

runs about 1 ounce of sih^er per ton to 1 per cent of copper, while 

gold is present in traces only. Another prospect on this property 

is in limestone much stained by limonite. Malachite and less azurite, 

with an intensely limonite-stained chalcedonic quartz, occur in small 

kidneys throughout the limestone and in narroAv seams along joint 

planes. Chalcopyrite is reported from the surface here, but is not 

abundant. In another prospect irregular lenses of the same ores and 

ffangues lie in a narroAA7 shear zone in the limestone. Small bunches o o

of chalcopyrite are sporadically distributed in the dark chalcedony.
70 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The property of the Tri-Metallic Mining Company lies one-half 

mile Avest of that last described. The Cambrian limestone, although 

gently flexed, is approximately horizontal. Intense staining by 

limonite is characteristic of limestone in the vicinity of the ore. A 

shipment of picked ore which netted $236 per. ton (averaging 7 

ounces gold, 230 ounces silver, and 19 per cent copper) was recently 

made from a surface pocket of ore. Chalcopyrite is the only original sulphide present. Chalcocite, malachite, and azurite with darkbrown chalcedony are secondary, and these are partially at least 

replacements of limestone. A few masses of native copper, presumably of secondary origin, are also reported, but they were not 

seen by the writer. Apparently chalcopyrite was originally distributed in the limestone in masses which, so far as known, do not exceed 

one-half inch in diameter. Later these scattered particles were concentrated, the secondary copper minerals apparently being, replacements of limestone. In the main shaft bunches of chalcopyrite lie 

in the limestone in association with coarse calcite much stained by 

limonite. In some cases the chalcopyrite has been brecciated and the 

narrow interstices filled with iron-stained chalcedony. The ore in 

this shaft is said to have been in " kidneys," some of which were 

connected with others by narrow seams. From one of these masses 

1,900 pounds of ore were removed. This lens of ore, 9 feet long, was 

4 feet in diameter at the center and tapered to a point at each end.

Ore examined from a claim owned by E. Oldt showed similar 

characteristics, a little galena and white quartz of apparently equal 

age being associated with the sulphides. Transparent drusy quartz 

crystals contemporaneous Avith or later than the copper and lead 

carbonates and broAvn chalcedony are also characteristic. The Aralues 

in this ore are said to be in silver and copper.

In the Cuprite district chalcop}7 rite and less pyrite, galena, calcite, 

and quartz appear to have been deposited as sporadic masses in the 

limestone as seams along joints and as lens-shaped bodies along 

shear zones. Later these ores Averc altered by aqueous solutions to 

chalcocite, carbonates, and oxides, the secondary ores in large part 

replacing limestone. At many points faulting accompanied or preceded the change. Contemporaneously a much iron-stained chalcedony Avas deposited in intimate association with the oxidized ores. 

Later, in some instances, drusy quartz Avas deposited upon the copper carbonates. The deA^elopment is altogether too slight to determine AA7 hat part of the secondary copper ores haA^e been concentrated 

from sulJDhides originally lying in limestone HOAV remoA^ed by erosion. It is probable, hoAvever, that a considerable proportion is of 

such origin and that when the oxidized ores are worked out the copper content will decrease. It may well be, however, that the water 

at Cuprite is deep.
GOLDFIELD HILLS. 71

In the rhyolite north of the east end of the copper belt are some 

prospects. The values reported are gold, and these deposits are undoubtedly late Tertiary veins.

Water is hauled from Stonewall Spring, 17 miles distant. Wood, 

except the almost valueless yucca, is equally distant. The Cuprite 

mines, however, are only 18 to 25 miles from the railroad at Goldfield, 

and ore may be shipped from the district at a comparatively low cost.

Sulphur of good quality, said to occur in a vein in the rhyolite 

about three-fourths of a mile northeast of Cuprite, was examined.

VALLEY NORTH OF SLATE RIDGE.

The valley north of Slate Ridge is connected by two narrow arms 

of gravels with Sarcobatus Flat and by a single similar arm with 

Stonewall Flat. The valley has an east-west extension and is of moderate grade. Playas are situated in its eastern portion at elevations 

between 4,500 and 4,600 feet above sea level. Buttes of late Tertiary, 

lavas are scattered over the lower portions of the valley. South of 

Mount Jackson a number of low white domes and dissected mesas of 

the older alluvium protrude from the Recent gravels, and the position 

of the more important of these is shown on the map. The exposures, 

where examined, consist of stratified clay beds lying horizontally. 

The area immediately south of Mount Jackson is 300 feet above the 

lowest deposits in the valley, and this may be taken as the minimum 

thickness of the formation, which is evidently a playa deposit of the 

older alluvium.' The Recent gravels are probably thin throughout the 

valley. Some water lies most of the year in a tank at Forks Station.

GOLDFIELD HILLS." 

TOPOGRAPHY AND GEOGRAPHY.

The Goldfield hills are separated from the northeastern spur of 

the Silver Peak Range and the Mount Jackson hills by low mesas of 

basalt and from the Southern Klondike hills and the Cactus Range 

by low ridges of desert gravels. Most of the low hills and ridges 

around Goldfield have a north-south trend, but some run. east and 

west. The highest summits are less than 7,000 feet above sea level. 

Except for the usual desert shrubbery the Goldfield hills are bare. 

Several springs occur in the eastern portion of the hills, and a spring

0 The ore deposits and geology of the Goldfield special area have already been described by Mr. F. L. Ransome (Bull. 0. S. Geol. Survey No. 303). The map made by 

Mr. Ransome and his assistants, Messrs. G. 1-1. Garrey and Wm. II. Emmons, has been 

generalized and incorporated in PI. I, and the writer is indebted to these gentlemen for 

many suggestions as to the stratigraphy in these hills. The description here given 

applies mainly to the Goldfield' hills beyond the area shown on the special map. The 

geology of these outer hills was studied practically without a topographic base, a fact in 

part accounting for the shoi'tcomings of the map.
72 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

is located near Goldfield. Wells at Goldfield, in the Siebert lake beds, 

have struck water, but the main water supply is piped from distant 

points.

GENERAL GEOLOGY.

In the detailed survey of the special area Mr. Ransome and his 

assistants recognize the following formations, named from the oldest 

to the youngest:-Cambrian (?) jasperoid; post-Jurassic granite; first 

andesite; earlier rhyolite; andesite and dacite, the latter formation 

probably being slightly younger; quartz latite and rhyolite; Siebert 

lake beds, with associated quartz-basalt and rhyolite flows; later 

rhyolite; later tuffs, and basalt.

Of these formations the Cambrian jasperoid and the first andesite 

and rhyolite appear to be confined to the special area and are described 

in another bulletin of the Survey." The rhyolite flow breccia occurs 

only in thin flows and, because of the small scale employed, is mapped 

with the basalt.

.SEDIMENTARY ROCKS.

Siebert lake beds. The Siebert lake beds cover considerable areas 

in the central and southern portions of the Goldfield hills and form 

a band between the basalt and the Recent desert gravels. The actual 

distribution of the formation is greater than that shown on the map, 

since small areas lie on the eroded surfaces of the andesite and the 

latite and rhyolite in many places. These lake beds are gray, yellow, 

or reddish sandstones, shales, grits, and conglomerates, composed predominantly of material derived from the Tertiaiy lava flows, but 

subordinately of Paleozoic sedimentary rocks and post-Jurassic granular igneous rocks. The larger bowlders are 2 feet in diameter. 

Sections on the mesa scarp, in which the base is not exposed, show a 

vertical exposure of 240 feet. The Siebert lake beds were folded and 

the edges of the beds truncated by erosion prior to the outflow of the 

later rhyolite. The formation closely resembles the Siebert lake beds 

of Tonopah & and is presumably of Miocene age.

Later tuffs. On the mesa scarp to the west and northwest of Goldfield 10 to 20 feet of tuffaceous sandstone lie above the later rhyolite 

and beneath the basalt. These sediments, probably deposited under 

Avater, are characterized by many bowlders of a silvery-gray pumice, 

presumably derived from the erosion of the surface of the underlying 

rhyolite. The position of these tuft's beneath the basalt with no 

marked erosional interval indicates that they are probably to be correlated roughly with the lower portion of the Pliocene-Pleistocene 

older alluvium occurring elseAvhere in the area studied, although they 

were probably deposited in a lake, the predecessor of the older playas.

" Ransouie, F. L., Preliminary account of Goldfield, Bullfrog, and other mining districts 

in southern Nevada, etc. : Bull. D. S. Geol. Survey No 303, 1907, 98 pp., 5 pis. 

6 Spun-, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 51.
GOLDPIELD HILLS, GENERAL GEOLOGY. 73

IGNEOUS ROCKS.

Post-Jurassic granite. In addition to the granite mapped by Ransome in the special area, pebbles of alaskite and a somewhat less 

siliceous rock, probably to be correlated with the darker monzoriite 

porphyry of the northeast spur of the Silver Peak Range, occur in 

the Siebert lake beds.

Andesite and dacite. Ransome found that andesite flows and 

dacite intrusions, the latter probably being slightly younger, followed 

the extrusion of the earlier rhyolite. These formations have been 

separated in the detailed study of the Goldfield special area, but since 

the andesite is by far the more abundant rock, the dacite is here 

grouped with it. It is the most widely distributed formation in the 

Goldfield hills and appears from a distance to cover a large area in 

their northeast portion. The later andesite is a rather dark-gray to 

light-pinkish rock 'with dense lithoidal groundmass. Phenocrysts, 

which equal the groundmass in bulk," consist of feldspar and hornblende, augite, and biotite, one of these latter being present in many 

cases to the almost total exclusion of the others. The dacite, which 

covers considerable areas within the district shown on the special 

map, extends eastward beyond its borders, is usually slightly lighter 

in color than the andesite and contains a few quartz phenocrysts.

The andesite and dacite are younger than the earlier rhyolite and 

older than the biotite latite and rhyolite. The later andesite is similar in many ways to the later andesite of Tonopah a and the two formations may be roughly contemporaneous. The dacite is correlated 

with that of the Kawich Range. These rocks are probably of early 

or middle Miocene age.

Quartz latite and rhyolite. Several outcrops of quartz latite and 

rhyolite occur in the hills surrounding the Goldfield special area. 

While some of these may belong to the earlier rhyolite, the majority 

should certainly be assigned to the quartz latite and rhyolite. Quartz 

latite outcrops 2 miles south of Preble Mountain. The rock here has 

a white stony groundmass, slightly exceeded in bulk by the mediumsized phenocrysts of which black mica is most conspicuous, while 

glassy feldspar striated or unstriated and slightly smoky quartz also 

occur. Many small ellipsoidal areas of pumiceous latite are present, indicating that the rock was in part a flow breccia. Under the 

microscope the quartz latite is seen to have a turbid glassy groundmass, with many eddying flow lines. The larger feldspar phenocrysts are andesine and in total bulk the plagioclase phenocrysts 

slightly exceed those of orthoclase.. Orthoclase in particular is 

zonally built. Quartz has been greatly and biotite slightly corroded 

by the magma. The magma must have been very viscous prior to the

« Spurr, J. B., Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 33.
74 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA,

cessation of movement in it, since the phendcrysts are typically broken 

fragments. Apatite is an accessory mineral.

Rhyolitic glasses that outcrop 3 miles, south of east of Diamondfielcl 

probably belong to the biotite-latite-rhyolite series. These gray perlitic glasses are poor in phenocrysts, although biotite and less, commonly feldspar and quartz are locally present. Flow banding is evidenced by slight alterations in the color and texture of various bands. 

The perlitic glass grades into spherulitic and dense pinkish-gray 

glassy rhyolites. The perlitic facies breaks readily into globular 

fragments along the perlitic parting. The clear glass in some thin 

sections contains sparse phenocrysts of orthoclase, quartz, and biotite, 

while in others the phenocrysts are more abundant and oligoclase is 

also present.

The rhyolite in the southeast corner of the Goldfield hills has 

highly developed flow banding, and in consequence the rock has a 

platy structure which wraps knotlike around the phenocrysts. 

Blackish glasses with numerous phenocrysts also occur. Microscopic 

examination shows this glass to be in reality a latite with phenocrysts of oligoclase, orthoclase, biotite, quartz, and hornblende.

On the east side of the Goldfield-Lida road, 2-| miles south of Goldfield, is a poorly exposed area of rhyolite. The .white lithoidal 

groundmass, much of it brown or red through iron stains, somewhat 

exceeds in bulk the abundant phenocrysts. The latter include glassy 

unstriated feldspar, someAvhat less quartz, and a few black mica tablets. Fragments of a pumiceous rhyolite are present. Under the microscope the groundmass appears as a- turbid, slightly devitrified 

glass, showing flow lines and spherulites. A few rather large oligoclase phenocrysts are associated with those of orthoclase, quartz, and 

biotite. The phenocrysts are all somewhat embayed by magmatic 

corrosion and were broken into fragments during the flow of the nearly 

viscous lava. This rhyolite probably belongs to the series under consideration, although it may be one of the later rhyolites. One mile 

farther south a similar rhyolite outcrops, and this clearly belongs with 

the quartz latite and rhyolite series, since it was a low boss when the 

mesa basalt was extruded and that formation flowed in a gentle arch 

over its surface.

The quartz latite and associated rhyolite are older than the Siebert 

lake beds and younger than the andesite.

Quartz l>asalt. The basalt to the east of the Lida road and 2 miles 

south of Goldfield is probably a portion of the quartz-basalt flow 

which Kansome found interbedded with the Siebert lake beds in the 

special area.

Later rhyolite. Lying for the most part in a horizontal position 

upon the eroded Siebert lake beds is a rhyolite flow, which is separated from the overlying basalt by the Pliocene tuffs. This formation
GOLDFIELD HILLS, IGNEOUS BOCKS. 75

is too thin to be shown on the map, but it forms a narrow band from 

50 to 100 feet thick beneath the basalt capping of the mesa and occurs 

also to the south of Goldfield in the area here mapped as Siebert lake 

beds.

The later rhyolite includes a number of facies of acidic flow rocks. 

On the Goldfield-Bullfrog road, 3 miles east of south of Goldfield, 

the formation is 50 feet thick and consists of 4 feet of black glass, 

above which is 20 feet of faded brick-red dense rhyolite and above 

this 25 feet of lavender lithoidal rhyolite. The black glass has an excellent flow parting. The middle rhyolite carries rather numerous 

glass}^ feldspar phenocrysts, which are, however, subordinate in bulk 

to the groundmass. It contains many vesicles elongated parallel to 

the flow, and in these spherulites are developed. The spherulites 

in some instances form shelf-like partitions in the cavities. Vertical columnar parting is fairly well developed in this portion of the 

flow. Under the microscope the groundmass, which has many eddying flow lines, shows as a slightly devitrified turbid glass. The phenocrysts are orthoclase, with which are associated a few of plagioclase and bluish-green aug-ite. The presence of considerable quartz 

in the devitrified glass probably justifies the use of the name rhyolite. The upper member is a flow breccia with lithophysse here and 

there throughout its mass. The phenocrysts in the glassy base are 

seen under the microscope to be orthoclase, bluish-green augite, and 

quartz. A rhyolite similar to the middle member of this section is 

exposed H miles southwest of the type locality and north of the Goldfield-Cactus Spring road, 1 mile west of the edge of the alluvial slope. 

Similar rocks occur beneath the basalt of the mesa west of Goldfield. One facies from this mesa is similar to the upper portion of the 

flow at the type locality, although phenocrysts, particularly quartz, 

are more abundant. Apatite is also microscopically visible. Such 

facies locally include fragments of quartz basalt and the Cambrian 

jasperoid.

The extrusion of this rhyolite occurred after the folding and erosion of the Siebert lake beds. It is presumably of Pliocene age. Similar rocks occur in the Silver Peak Range, in Slate Ridge, and beneath 

the basalt of Pahute Mesa.

Basalt. The youngest formation of the Goldfield hills is the basalt 

which forms the mesa west of Goldfield, with which the basalt 

to the northwest of Diamondfield is probably contemporaneous. At 

one time basalt covered the greater portion of the Goldfield hills.

The basalt is for the most part a dense, compact, dark-gray or black 

rock, in some instances with phenocrysts equal to the groundmass in 

bulk and in others without phenocrysts. The phenocrysts, which 

reach a maximum length of one-fourth inch, include glassy striated 

laths of feldspar, stocky black columns'of augite, and rounded grains
76 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

of iron-stained glassy olivine. Vesicular facies occur at the top and 

bottom of the two main flows that compose the 350 feet of basalt. 

With the introduction of vesicles much of the rock takes on a 

magenta-red color. The vesicles, which reach a maximum length of 

2 inches, are usually elongated parallel to the flow bedding. Some 

of them are filled by white granular calcite and others by chalcedony. 

 Certain bands contain in a basalt matrix many fragments of basalt, 

indicating that some portions of the rock solidified before cessation of 

movement in the magma. Surfaces of flows are often ropy.

Under the microscope the groundmass is usually seen to be holocrystalline and composed of plagioclase laths, augite columns, and 

magnetite grains. Rarely a little dark glass is also present, and in 

other thin sections large areas of augite inclose plagioclase laths in 

the manner of the ophitic texture. A reddish-brown serpentine is 

developed at the expense of olivine, and a little calcite is formed from 

plagioclase.

The basalt forms a typical mesa, and buttes isolated in the desert 

gravels have been carved from it by erosion. This rock is to be correlated with other basic flows widely distributed throughout the area 

surveyed, which are presumably of late Pliocene or early Pleistocene age.

STRUCTURE.

As Ransome has shown, the Goldfield hills have a domical structure, the oldest formations being confined to the central portion of 

the hills. He further shows a that the older Tertiary rocks have 

been subjected to considerable folding and some faulting. The Siebert lake beds usually clip away from the central portion of the 

Goldfield hills. Even the later basalt has been subjected to tilting, in 

the main away from the center of the dome, and also to some normal 

faulting. These faults have usually an east-west or north-south 

strike.

ECONOMIC GEOLOGY.

The ore deposits of GoldfiSld have been treated at some length in 

the bulletin already mentioned. 6 Outside of the special area few prospects exist. The andesite and rhyolite 3 miles southeast of Preble 

Mountain have been altered similarly to those of the productive 

territory in Goldfield, and the area has been located by prospectors.

ALKALI SPRING FLAT.

The broad valley north of Montezuma Peak is separated from Big 

Smoky Valley by a gravel-covered divide. The valley has gently 

sloping sides, except on the west, where it rises rather steeply to the 

Lone Mountain foothills. The lowest portion, 4,850 feet above sea

"Ransome, F. L., Bull. U. S. Geol. Survey No. 303, p. 21. & Idem, pp. 22-39.
SOUTHERN KLONDIKE HILLS. 77

level, is occupied by a playa, situated considerably west of the center 

of the valley. Inliers of rock do not occur at a distance from the encircling hills, and the recent alluvial deposits are probably deep. 

The Ramsey and Klondike wells struck water at 240 and 140 feet, 

respectively. The Ramsey Well is 100 feet higher than the Klondike, 

and water could probably be obtained near the playa at shallower 

depths.

SOUTHERN KLONDIKE HILLS. 

TOPOGRAPHY AND GEOGRAPHY.

Between Ralston Valley and the flat east of General Thomas Camp 

are two groups of conical hills and ridges joined by a broad sag 

formed of Siebert lake beds. These hills are separated from the 

Goldfield hills by a depression filled with Recent alluvial deposits. 

The highest peak in the northern part of the hills reaches an altitude 

of 7,000 feet. The east slope of the group is comparatively gentle, 

while the Avest slope is steep. The hills are bare, of timber and without Avater.

GENERA! GEOLOGY.

The formations of the Southern Klondike hills, named in order 

from the oldest to the youngest, include Cambrian sedimentary rocks, 

post-Jurassic granite, earlier rhyolite, Siebert lake beds, earlier 

quartz latite, basalt, later rhyolite, later quartz latite, and earlier 

alluvium. The mapping to the south of the area of Siebert lake 

beds is approximately correct, \vhile that to the north is less accurate.

SEDIMENTAKY KOCKS.

Cambrian. Cambrian rocks cover a considerable area in the 

southern part of these hills. They consist of an interbedded series 

of limestones, jasperoids, and shales, named in the order of their 

abundance. Neither the top nor the bottom of the series is exposed, 

but it is many hundreds of feet thick. The limestone, by far the 

predominant member of the series, is dark gray or blue black, fine 

grained, compact, and crystalline. Bedding planes are from 2 to 3 

feet apart. Weathered surfaces are blackish gray in color and 

smooth in contour, although minor irregularities are produced by the 

varying hardness of the rock. The limestone grades into a silicified 

facies, best styled a jasperoid. This is ordinarily a dense-banded 

rock of black and gray color, the laminae of Avhich are in many cases 

but one-fourth inch in thickness. It breaks Avith a conchoidal fracture. The slaty shale is rather fine grained and of dark-gray or 

greenish-gray color. Even minor lenses and thin parting bands of 

of fine-grained sandstone are rather unusual. The sediments form 

hills of moderate slope AAath numerous exposures. No fossils Avere 

found, but the lithology of the series is similar to that of the Lone'
78 SOUTHWESTERN NEVADA AND EASTEEN CALIFORNIA.

Mountain hills to the west, and in consequence the rocks are almost 

certainly Cambrian.

Siebert lal-e beds. The intensely dissected gap between the two 

groups of hills is composed" of white or yellow, well-bedded tufaceous' sandstones, conglomerates, and clays, slightly consolidated. 

About 400 feet of this formation is exposed. Thin sheets of rhyolite appear to be interbedded with the sediments at the south end of 

the exposures. These soft horizontal beds are eroded into numberless low rounded hills and gullies. Veins of white calcite from onefourth inch to 1 foot thick cut the sediments and stand in relief on 

weathering. These beds are similar lithologically to the Siebert 

lake beds of Tonopah," and like them have thin sheets of the Tonopah rhyolite near their top.

Older alluvium. North of the large isolated latite cone on the west 

side of the hills occur small exposures of white sandstones and conglomerates. The pebbles and bowlders consist of latite and biotitehornblende andesite. . These beds are perhaps to be correlated Avi^h 

the older alluvium, probably of late Pliocene or early Pleistocene age.

IGNEOUS KOCKS.

Post-Jurassic granite. Three small areas of granitoid rocks lie 

near Southern Klondike. Three-fourths of a mile northwest of the 

village a granite sheet 250 feet thick, which courses northeast, injects 

the Cambrian rocks parallel to their bedding. This is a fine-grained 

rock, although minor portions are of medium to coarse grain. Under 

the microscope it shows as a rather fresh muscovite granite in which 

some oligoclase occurs with orthoclase. The quartz shows gentle 

undulose extinction, but the deformation indicated is not great. A 

little sericite and less kaolinitic material has been developed in the 

feldspars. This granite weathers into small rounded bowlders, and 

exposures are scarce. It is complexly cut bj joints 6 inches apart, 

and in those parallel to the bedding of the surrounding sediments 

quartz veins occur. A small area of a similar muscovite granite of 

medium grain is exposed one-fourth mile west of Southern Klondike. 

An aplitic sheet of the same rock injects the limestone in a mining 

tunnel at the village. The sedimentary rocks are more or less metamorphosed in the vicinity of the granite, the shale in particular being 

altered to a knotted silvery schist. Granite cuts the Cambrian rocks 

and occurs as pebbles in the Siebert lake beds. It is believed to be 

of post-Jurassic age.

Earlier rhyolite. Prior to the eruption of the earlier rhyolite 

which occurs near Southern Klondike the Cambrian rocks and the 

granite were eroded into a group of hills of .slightly greater relief

0 Spurr, J. E., 1'rof. Paper U. S. Geol. Survey No. 42, 190y, pp. 51-55,
SOUTHERN KLONDIKE HILLS, IGNEOUS BOCKS. 79

than the present Southern Klondike hills. Since that extrusion 

erosion lias removed considerable masses of the once more extensive 

rhyolite and partially exhumed the sedimentary rocks. The rhyolite at the northern boundary of the area mapped, on the west side of 

the hills, is also probably the earlier rhyolite. It occurs in flows and 

dikes, the flows overlying the Cambrian rocks!, the dikes clearly cutting them. The white or pinkish or lilac-white lithoidal groundmass predominates in bulk over the small phenocrysts, among which 

feldspar is more abundant than quartz. Narrow wavy flow bands 

wrap around the phenocrysts. One-half mile north of Southern 

Klondike a resin-colored glassy facies was noted. Rhyolite tuffs and 

flow breccias are associated with the normal igneous rock near the 

boundary of the area.

The rhyolite is cut by two sets of joints from 2 to 5 inches apart, 

and the flow parting constitutes a third plane of weakness. In consequence the residual fragments' are rectangular or platy. Weathered fragments are characterized by small pits, the casts of feldspar 

phenocrysts. The rhyolite forms yellowish or slightly pinkish-white 

conical hills or low areas. The single slide examined 'has a brown 

devitrified groundmass showing flow lines and spherulites. Quartz 

and orthoclase predominate in the groundmass, while the rather 

sparse phenocrysts are orthoclase, quartz, and plagioclase. The rock 

is a rhyolite tending toward latite. The earlier rhyolite is tentatively 

correlated with the Miocene Tonopah rhyolite-dacite a of Tonopah, a 

correlation already suggested by Spurr & for the northern mass.

Earlier quartz latite. In the northwest "portion of the hills, near 

the areal boundary, is an outcrop of quartz latite of dull-lilac or 

medium-gray color, which, however, as mapped, may include some 

basalt. The dense groundmass contains numerous crystals of Avhite 

striated and unstriated feldspar reaching a maximum length of 

one-eighth inch, and black mica. Under the microscope the predominant groundmass shows as a devitrifiecl glass containing considerable quartz. Plagioclase and orthoclase are equally abundant 

phenocrysts, while biotite is in some specimens surrounded by a reaction rim of magnetite. Magnetite, apatite, and zircon are accessories. The latite flow overlies the Siebert lake beds. The rock 

is rather similar to the later rhyolite of the Goldfield hills, although 

less siliceous, and the two are perhaps contemporaneous. The Goldfield rhyolite underlies and is older than the basalt.

Basalt. The large mass of volcanic rock capping the Siebert 

lake beds northeast of Southern Klondike appears to be an eroded 

basalt flow, as are the hills between this mass and the large playa 

crossed by the road from Tonopah to Cactus Spring. It is probable

" Spurr, J. E., Prof. Paper U. S, G<?ol. Suvvey NO, 42, 1905, pp. 51-55. 

"Op. cit., p. 99. '
80 SOUTHWESTERN NEVADA AND EASTERN" CALIFORNIA.

that this basalt is to be correlated with that of Tonopah and the 

Monitor Hills and that it is of Pliocene age.

Later rhyolite. The eastern side of the hills on the boundary of 

the area is formed of rhyolite in flows. The groundmass, much of 

which is glassy, when fresh is white or light gray, but in places it 

is stained pink, yellow, or brown by iron oxides. Medium-sized feldspar phenocrysts are more abundant than those of quartz and biotite. 

This rock is perhaps contemporaneous with the Oddie rhyolite ° of 

Tonopah, which is younger than the Siebert lake beds.

Later quartz latite. The, prominent isolated cone between the 

roads 4 miles west of north of Southern Klondike, several small exposures east of this cone, and a considerable portion of the northern 

part of the hills east of the Tonopah-Goldfield road are composed of 

a lilac-gray igneous rock. A black glassy facies occurs on the east 

side of the cone. As phenocrysts, fresh and altered, feldspars are 

more abundant than quartz grains-, biotite tablets, and hornblende 

columns. Under the microscope the groundmass appears as a spherulitic glass in which considerable calcite is developed. Orthoclase 

predominates over plagioclase, which proved in one determination to 

be an acidic labradorite. Apatite, magnetite, and zircon occur as 

accessories.

The latite is characterized by vertical flow lines, particularly near 

the contact with the rhyolite, and the mass is probably a volcanic 

neck. It is very similar to the Brougher dacite & of Tonopah, although somewhat richer in hornblende, and the two are presumably 

contemporaneous and of rMiocene age.

STRUCTURE.

The Cambrian rocks have been complexly folded, the chief structural feature being an anticline with a northeast-southwest axis. 

Superimposed upon this anticline are numerous lesser anticlines and 

synclines, and at many points the beds are intensely crenulated. The 

rocks are horizontal or dip at varying angles up to 90°, those of 45° 

predominating. The folding probably immediately preceded and 

accompanied the granite intrusion.. Faults of small displacement 

occur, and brecciation is common. The sediments are cut in every 

direction by veins of calcite and less commonly by those of quartz. 

The veins are not folded, and hence fracturing occurred after the 

folding of the series and was probably connected with the granitic 

intrusions. Faulting and some tilting have occurred since the formation of the Tertiary rocks, although it is not known whether the tilting 

is dependent on faulting or is clue to flexing without rupture. On the 

southern edge of the hills dikes of earlier rhyolite are faulted, but

0 Spun-, J. E., Prof. Paper U; S. Geol. Survey No, 42, 1905, pp. 49-50. 

" Ibid., pp. 44-48,
SOUTHERN KLONDIKE HILLS, ECONOMIC GEOLOGY. 81

lack of time did not permit their being mapped. Some faulting also 

occurred after the formation of the ore deposits in the northern part 

of the hills. The basalt northeast of Southern Klondike dips to the 

south.

.ECONOMIC GEOLOGY. 

GOLD ANIJ SILVEH.

Gold and silver ores were discovered in the Cambrian rocks at Southern Klondike in March, 1899, by J. G. Court and T. J. Bell. Since 

that time the prospects have been worked" more or less continuously. 

It was while on a trip to these prospects in 1900 that J. L. Butler discovered the veins at Tonopah. From one group of claims shipments 

of ore ranging in value from $200 to $284 per ton and aggregating 

$50,000 are reported. Several thousand feet of tunnels, shafts, and 

inclines have been driven. In June, 1905, eight men were at work in 

the camp.

The ore deposits are of three kinds first, quartz veins a which are 

parallel to the bedding of the Cambrian rocks, and which carry predominant silver values; second, veins along the contact of the sedimentary rocks and rhyolite dikes, the values, about $45 per ton, being 

predominantly gold, and third, thin veins of quartz carrying silverbearing galena and cerussite in granite along joint fractures parallel 

to the bedding of the surrounding Cambrian rocks. The veins along 

contacts apparently show post-mineral faulting.

The quartz veins parallel to the bedding planes, which occur at and 

1 mile east of the village of Southern Klondike, are of greatest value 

and interest. These are tabular lenses of quartz, from a few inches to 

a foot or more in thickness. Horses of limestone are included. Adjacent veins connected by cross veins of quartz or completely separated 

by thin bands of limestone form in some instances mineralized zones 

14 feet thick. Quartz appears to have filled a fissure in the limestone, 

brecciation of the limestone having accompanied the fissuring. The 

contact betAveen the limestone and quartz is sharp, and important silicification of the limestone has not occurred. Vugs lined with acicular 

quartz crystals are rather characteristic.

The original sulphides deposited simultaneously Avith the quartz and 

disseminated in small masses in it are, in the order of their abundance, 

galena, copper sulphide,2* and iron pyrites. The secondary ores include cerargyrite, chrysocolla Avith less malachite and azurite, specular 

hematite, and cerussite in broAvnish -granular masses and to a less 

extent in crystals. These secondary minerals surround the sulphides

« For a detailed description of this type see Spurr, J. E., Economic Geology, vol. 1, 1906, 

pp. 309-382.

6 Stetefeldtite, according to .T. K. Spurr, Trans. Am. Inst. Min. Eng., 1905, p. 961.

° Bull. 308 07 M 6
82 SOUTHWESTERN NEVADA AND EASTEEN CALIFORNIA.

and fill cavities and cracks in the quartz. Some calcite and gypsum^ 

accompanied by sulphur, are secondary gangue minerals. Sulphur in 

places forms masses 3 inches in diameter. Assays did not detect the 

presence of gold at the surface, although gold values are encountered 

50 feet below the surface in one tunnel. One small aplite dike was 

noted near a quartz vein, and masses of quartz rhyolite are not far 

distant, although their proximity has not apparently determined an 

unusual abundance of quartz veins. The prospects are yet Avell 

above water level.

In Southern Klondike fissures and brecciated zones were opened 

in the Cambrian sediments along bedding planes. Water filled these 

cavities with silica and lead, copper, and iron sulphides carrying silver 

and less gold. The quartz veins have since been fractured and faulted, 

and surface waters have developed a number of secondary minerals. 

In this district the presence of quartz veins at the contact of rhyolite 

and limestone shows the gold veins to be of late Tertiary age, but the 

more important silver veins are presumably of post-Jurassic and 

pre-Tertiary age.

Water is obtained at the Klondike Well, 4 miles distant. The 

Southern Klondike hills are bare of timber. When the district was 

visited Tono'pah was the supply and shipping point.

The earlier rhyolite northwest of the Tonopah-Goldfield road near 

the boundary of the area mapped has locally been silicified and kaolinized by mineralizing waters, and in it some quartz veins occur. The 

reported values are in gold with less silver. The Kankakee .Mining 

Company has a 100-foot shaft, which passes through rhyolite, tuffs, 

and breccia. Dense quartz fills the interstices of breccia and also 

occurs in veins. The ore is free milling and is said to run about $30 

in gold and silver per ton, although assay returns have reached $317. 

Spurr a says, concerning these veins: " Through these rhyolites run 

strong and persistent veins of quartz and delicately colored chalcedony 

veins, sometimes containing pyrite. In some parts of some of these 

veins, especially in the oxidized portions, rich assays have been obtained." In his report on Tonopah Spurr correlates these veins with 

those of the Tonopah rhyolite-dacite^

IKON ORES.

A several places northwest of Southern Klondike lenses of porous 

hematite occur in limestone. These masses occupy joints in the limestone and are from 5- to 10 feet wide and from 50 to 100 feet long. 

The hematite appears to be partially a replacement of limestone and 

partially a cavity filling. Cubes of pyrite are present in the neighboring limestone. These masses of iron ore are probably gossan and 

with depth will pass into pyrite veins.

" Spurr, .T. E., Bull. TJ. S. Gcol. Survey No. 213, 1903, p. 87. 

6 Spurr, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 99.
EEGION ABOUT GOLDFIELD. 83 

RALSTON VALLEY.

The south end of Ralston .Valley is within the area surveyed and 

lies between the Monitor, Goldfield, w and Southern Klondike hills and 

the Cactus Range. Hills surrounded by gravels extend from the 

Cactus Range northeastward toward the Kawich Range and separate 

Ralston Valley from Cactus Flat, and on the divide the Recent gravel 

deposits are probably but a few Hundred feet thick. Ralston Valley is very shallow, the rim of hills being in many places but 200 

feet above the playa (elevation, 5,270 feet). Low sand dunes lie on 

the northeast- of the playa. A Avell sunk in the playa struck water 

at a depth of 240 feet.

STONEWALL FLAT.

Stonewall Flat, of northeast-southwest trend, is inclosed by the 

Cactus Range, Stonewall Mountain,1 the Goldfield hills, and the 

Mount Jackson hills. A gently, sloping detrital divide with rock 

inliers separates it from Ralston Valley to the north, while the 

detrital barrier between it and the valley north of Slate Ridge is 

less than 100 feet high. Several small playas, between 4,700 and 

4,800°feet above sea level^ occupy minor depressions in the valley. 

The playas nearest the Cactus Range are encircled by low sand dunes. 

A well on the Goldfield-Gold Crater road, 2 miles east of the largest 

playa, struck water at a depth of about 110 feet. The water contains small amountsx of salt and probably sodium carbonate. On 

the west side of the largest playa are low dissected bosses of dazzling 

white older alluvium, the highest of which are 25 feet above the present playa. Massive beds of white or cream-colored clay of fine 

texture, with thin interbedded layers of white limestone, are exposed. 

A number of compact lenticular lime-carbonate concretions, with 

hackly surface, which reach a maximum length of 6 inches, are embedded in the clay. These beds resemble those of Gold Flat and the 

valley north of Slate Ridge and have suffered about tlie same amount 

of erosion. They were evidently deposited in an ancient playa, 

possibly of late Pliocene, but probably of early Pleistocene, age.

STONEWALL MOUNTAIN. 

TOPOGRAPHY AND GEOGRAPHY.

Stonewall Mountain rises from the northwest border of Pahute 

Mesa. It was named, according to some, from Gen. Stonewall Jackson, but by others the name is said to have been derived from the 

precipitous, wall-like northern face of the mountain. The rugged 

mountain group, 9 miles in diameter, is formed of sharp peaks and 

steep ridges culminating in a summit 8,3.90 feet high. Stonewall 

Mountain is an excellent example of the symmetrical erosion of a 

homogeneous mass of an approximately circular horizontal plan. Deep
84 SOUTHWESTERN NEVADA AND 'EASTERN CALIFORNIA.

canyons radiate from the central peak, ending at the alluvial slopes 

2,500 to 3,000 feet below. The most striking feature of the mountain is the fault scarp at Stonewall Spring, a sheer wall 800 to 1,000 

feet high. Erosion has cut partially through this scarp, forming a 

narrow V-shaped gap, the lowest, point of which is at least 100 feet 

above the stream bed to the south. Behind this wall the valley is 

broad and U-shaped, regaining its.V shape some distance back in the 

mountains. Other streams near by are characterized by narrow canyons, which open upstream into more mature'valleys.

The mountains above an elevation of G,100 feet are clothed with a 

sparse although locally heavy growth of juniper, pinon, and mountain 

mahogamr. Excellent, pasturage covers the higher peaks and valleys. 

Groves of the tree 37 ucca occur on alluvial slopes to the west and on 

Pahute Mesa to the southeast. Stonewall Spring yields daily about 

3,000 gallons of pure cold water. A stream 100 }^ards long flows 

from a spring in the gulch one-half mile east of Stonewall Spring. 

Another spring is located 1 mile west of the culminating peak of the 

range.

GENERAL GEOLOGY.

The formations of Stonewall Mountain are, in ascending order, 

Cambrian limestone, post-Jurassic granitoid igneous rocks, earlier 

rhyelite, quartz syenite and .quartz-monzonite porphyry, Siebert lake 

beds, later rhyolite, and basalt. 

SEDIMENTARY ROCKS.

Cambrian. Three small masses of dark-gray crystalline limestone, 

cut by many white calcite veinlets, protrude from the igneous rocks 

near the north edge of the mountain. Angular inclusions of limestone and jaspilite are embedded in the older rhyolite, the monzonite 

porphyry, and the basalt. The limestone is similar lithologically to 

that of the Cuprite mining district, and, like it, is probably of Cambrian age. In contact with quartz-monzonite porphyry, near the 

northwest boundary of the mountain mass it has been metamorphosed 

to a white marble containing epidote.

Siebert lak°. beds. Incoherent, Avell-bedded tuffaceous sandstones 

and conglomerates of red, yellow, white, and greenish-white color 

cover a small area oast of Stonewall Spring. The bowlders, which 

are well rounded to semiangular, are largely of the earlier rhyolite. 

A thickness of about 500 feet is exposed. These beds are without 

much doubt the equivalent of the Siebert lake beds.

IGNEOUS ROCKS.

Post-Jurassic granite and granite porphyry. A few inclusions of 

granite occur in the earlier rhyolite and prior to the extrusion of 

that rock granite may have been exposed in these mountains, A nar-
 ' STONEWALL MOUNTAIN. -85

row dike of granite porphyry cuts the easternmost limestone. This 

rock has a finely granular yellowish groundmass in which are inclosed 

medium-sized quartz and feldspar phenocrysts. In the field this resembles the granite porphyry near Alkali Spring in the Silver Peak 

Range and it may be genetically related to the post-Jurassic granites. 

 Angular fragments of a gray monzouite porphyry occur in the earlier 

rhyolite near the summit of the group and these may be correlated 

with similar rocks of the Silver Peak Range that are also related in 

origin to the post-Jurassic granites. '

Earlier rhyolite. The most widely .distributed formation of Stonewall Mountain is a rhyolite characterized by many small colorless 

and glassy or white and opaque un stria ted feldspar phenocrysts. 

Near Stonewall Spring the rhyolite is medium gray and compact; 

that of the highest peak is also compact and of a faded red color; 

the rhyolite of the small hill in the detrital apron on the southwest 

side of the mountain is' a gray lithoidal rock. The rhyolite from 

the last two localities contains biotite phenocrysts.

An indistinct original banding is locally present and some facies 

are a flow breccia. The rhyolite is probably a flow, although the 

vertical position of the banding in places and the texture of some 

facies indicate that the rock may possibly be an intrusive mass. The 

rhyolite as exposed at present is several thousand feet thick, and the 

granitoid habit of the quartz syenite which injects it suggests that 

it was probably once much thicker. The rhyolite has well-developed 

joints over large areas which express themselves in the topography 

as straight elements. Where the joints are less closely spaced the 

rhyolite weathers in rounded forms like a granite.

Microscopic examination shows the rhyolite to have either a 

devitrified glassy or a microgranitic groundmass composed of predominant orthoclase with fewer quartz grains and many small magnetite cubes. The groundmass varies widely in grain from one part 

of the thin section to another, but is everywhere rather fine grained. 

Orthoclase phenocrysts, many of them microperthitic, with ragged 

borders which inclose some of the groundmass anhedra, are abundant. 

Rarely plagioclase laths, well-formed biotites, very ragged hornblende, and in some thin sections one or more quartz phenocrysts 

are associated. Zircon and apatite are accessories.

The mature topography of Stonewall Mountain shows tha^ the 

rhyolite is old, and pebbles of it occur in the Siebert lake beds. It. 

is believed to be older than the rhyolite of the Kawich Range, with 

which it has no lithologic affinities, and is probably of early Eocene 

or even late Cretaceous age. 

Quartz syenite and quartz-monzonite porphyry. Dikes and elongated masses of quartz syenite and quartz-monzonite porphyry, 

which grade into one another and are hence contemporaneous, intrude
86 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

the earlier rhyolite at widely separated localities in the mountain. 

Dikes of quartz syenite less than 200 feet Avide intrude the earlier 

rhyolite on the fault scarp just east of Stonewall Spring. The 

quartz syenite is a grayish-white, medium-grained granitoid rock 

composed of unstriated feldspar with a little biotite. Microscopic 

examination shows the presence of a few small wedges of quartz 

betAveen the feldspar grains and the biotite tablets. Ilmenite, apatite, and zircon are accessories. The granitoid habit of these small 

masses indicates that its magma solidified beneath a considerable 

depth of rhyolite now removed by erosion.

The quartz-monzonite porphyry is typically porphyritic in habit, 

with a gray and black speckled holocry stall ine groundmass. The 

phenocrysts, which predominate over the groundmass, include white 

or gray glassy feldspar, striated or unstriated, and. black or bronzebrown biotite. The largest phenocrysts are one-fourth inch in 

length. The contact facies of the dike three-fourths of a mile 

southeast of the summit of Stonewall Mountain is of slightly finer 

grain and includes many fragments of the earlier rhyolite. The 

rock weathers into rounded bosses and disintegrates into spheroidal 

bowlders stained brown or reddish by iron oxides. The microscope 

shows that the microgranitic groundmass is composed of orthoclase grains,.many of them twinned according to the Carlsbad law, 

with a few associated quartz wedges and biotite shreds. The phenocrysts include both plagioclase, in large complex individuals, and 

orthoclase. Phenocrysts of biotite and smaller ones of light-green 

augite.are also present. Magnetite, apatite, and zircon are the accessory minerals. Calcite, sericite, and kaolin are present as alteration 

products of the feldspars.

One and three-fourths miles upstream from the easternmost area of 

Cambrian liriiestone a poorly exposed black glass with rather numerous feldspar phenocrysts apparently, cuts the earlier rhyolite. The 

exposure is too small to map. Under the microscope this proves to 

be a glass with orthoclase and a few bluish-green augite phenocrysts. 

It may welUbe a glassy form of the quartz syenite. A small fragment of hornblende andesite, unlike any rock exposed in the mountain, is included in the thin section.

The quartz syenite and quartz-monzonite porphyry of Stonewall 

Mountain intrude the earlier rhyolite, and pebbles are embedded in 

the Siebert lake beds. They most closely resemble the post-Jurassic 

monzonite porphyry of the Silver Peak Range (see p. 59), although 

they are not very different from the monzonite porphyry of the 

Kawich Range and their correlation with the latter is more nearly 

correct. The rocks are believed to be of late Eocene age.

Later rhyolite. The later rhyolite forms the low, massive brown 

and gray domes of the eastern part of Stonewall Mountain. Two
STONEWALL MOUNTAIN. 87

outlying hills on Pahute Mesa to the south are of the same formation. 

The later rhyolite has a dense gray stony to glassy groundmass. In 

it are numerous medium-sized glassy imstriatecl. feldspar and fewer 

rounded quartz phenocrysts. The feldspar crystals often exhibit 

beautiful plays of color, purples and blues being refracted from numerous cracks. The glassy facies locally show well-developed flow 

lines and spherulites, while slightly vesicular facies also occur. The 

later rhyolite breaks into platy fragments and in places a granitelike weathering is developed. The rhyolite flow, as now exposed, 

1,200 feet thick, is in broad, gentle flexures which may be due in part 

to the slightly uneven surface upon which it flowed. Microscopic 

examination shows a turbid glass in which orthoclase and quartz and 

fewer acidic plagioclase phenocrysts are associated. A little magnetite is also present.

For a distance of 2 miles west of the rhyolite, pebbles of blackglassy obsidian are common upon the surface of Stonewall Mountain. 

These pebbles may indicate that the rhyolite once extended some distance farther west, although similar rocks were not noted in the later 

rhyolite section.

The later rhyolite overlies and is in consequence younger than the 

Siebert lake beds. The contact between the rhyolite and the basalt 

which forms the top of Pahute Mesa at the northeast corner of Stonewall Mountain was examined at one point. The contact is slightly 

undulating, and the base of the overlying rhyolite for 5 to G feet is a 

flow breccia of massive blocks of vesicular rhyolite. This apparently 

indicates that the rhyolite is younger than the basalt beneath it. The 

topography of the rhyolite, however, is so much more mature than 

that of -the Pahute Mesa basalt that it is believed that the rock here 

underlying the rhyolite is a portion of an older basalt which extended from Stonewall Mountain as a shelf and which happened 

to be on a level with Pahute Mesa. The later rhyolite is probably to 

be approximately correlated with the later rhyolite of the Southern 

Klondike hills.

Basalt. A small mass of a gra}ash-black basalt outcrops 1 mile east 

of south of Stonewall Spring. Basalt breccias indicate that it is a 

flow. The age of this rock is unknown, but from the apparent 

absence of its bowlders in the Siebert lake beds it is probably to be 

correlated with the later basalt of the Goldfield hills.

STRTJCTTJRE.

The Cambrian limestone is practically horizontal, the folding being 

broad and open like that of the hills of the Cuprite mining district. 

In restricted areas, however, the rock is closely folded. Prior to the 

extrusion of the earlier rhyolite the Paleozoic rocks appear to havehad a gently accentuated topography. The most striking structural
SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

and topographic feature of StoneAvall Mountain is the fault on thefront of the mountain group, near Stonewall Spring. This fault 

strikes N. 65° E. and dips 70° N. Minor faults 

and sheeting parallel to the main fault occur for 

a distance of one-half mile south of the mountain 

front. The Siebert lake beds strike east and 

Avest and dip 5° to 50° N. This fact probably 

indicates that Stonewall Mountain is on the upthrown side of the fault. The fault fissure Avas 

healed by a quartz vein and has been reopened 

several times and again healed. (See p.. 88.) 

Since the fissure filling erosion has uncovered the 

fault and a secondary fault scarp, Avhose position 

is determined by the resistant quartz vein, has 

been formed. The topographic form of the valley 

of the StoneAvall Spring drainage line (see p. 84) 

indicates that in comparatively recent time the 

mountains behind the fault line have been uplifted. Fig. 7 is a section through the north side 

of StoneAvall Mountain.

ECONOMIC GEOIOGY.

Quartz A'eins and stringers filling faults, joints, 

and the cavities of brecciation are very abundant 

in the earlier rhyolite, quartz-monzonite porphyry, and quartz syenite near StoneAvall Spring. 

The most prominent vein folloAvs the fault scarp 

immediately south of the spring. The quartz 

vein is in some places simple and 40 feet Avide; 

in others it is complex and composed of many 

parallel veins. This vein or other A^eins of approximately similar strike extend 2 miles Avest 

and 1 .mile east of the spring. The quartz is 

Avhite or colorless, rarely greenish yelloAv, and 

is beautifully crustified. Vugs Avith quartz crystals or mammillary quartz are common. Movement reoccurred along this fault and the quartz 

has locally been fractured and slightly displaced, 

later quartz filling the cavities. Heavy stains 

of limonite and slight stains of azurite Avere 

noted in the quartz, and pyrite is locally developed. Prospectors report from a trace to $6 

in gold per ton at a number of places on this 

a "" vein. Similar but smaller quartz veins occur

throughout the areas of earlier rhyolite and quartz-monzonite

porphyry. ...
RANGES NORTH OF PAHUTE MESA. 89

A prospect is located in the Cambrian limestone area 2 miles east of 

Stonewall Spring. A thin vein of quartz cuts a granite-porphyry 

dike, which here intrudes limestone. The quartz is slightly limonite 

stained and said to carry from $2 to $56 in gold per ton.

* RANGES NORTH OF PAHUTE MESA.

To the north of Pahnte Mesa, which occupies the central portion of 

the area, surveyed, lie the Cactus, Kawich, Reveille, and Belted 

ranges. These, with the exception of the Cactus Range, trend north 

and south. They have as their predominant formation a rhyolite of 

early Miocene age.

CACTUS RANGE. 

TOPOGRAPHY AND GEOGRAPHY.

The Cactus Range lies between Stonewall and Cactus flats. To the 

north its outlying hills are separated from the Monitor Hills by Ralston Valley; its low southern portion is buried beneath lava flows of 

Pahute Mesa. The range as defined is 22 miles long and has a crest 

line coursing northwest. The low central part is almost cut in two 

by gently sloping valleys filled with alluvial material. To the north 

of this median line the range culminates in Cactus Peak, a symmetrical cone 7,550 feet high and a landmark visible for many miles. 

The highest peak of the range south of the center line is a black massive mountain 7,600 feet high.

Pinon and juniper grow sparsely on the higher parts of the range 

south of the median line, and the tree yucca abounds on the lower 

hills and upper alluvial slopes. Good grazing is found on the alluvial slopes next to the mountains and in some of the valleys. Cactus 

Spring has a daily flow of about 500 gallons of clear cold water. The 

water of Alkali Spring is cool, but slightly saline.. Several other 

small water holes are reported to the west and north of Alkali Spring. 

Antelope Spring flows from 300 to 400-gallons of cool palatable 

water daily, and two smaller evanescent springs are situated in 

gulches to the south within one-half mile of Antelope Spring.

GENERAL GEOLOGY.

The succession of formations exposed in this range, from the* base 

u.p, is as follows: Pogonip limestone, Eureka quartzite, Weber conglomerate, granite, diorite porphyry, hornblende-biotite latite, earlier 

rlryolite, biotite andesite, augite andesite, later tuffs (?), later rhyolite (?), and basalt.

SEDIMENTARY KOCKS.

~, ogonip limestone. A small exposure of dark-gray fine-grained 

limestone, surrounded by alluvial deposits, occurs in the broad valley 

3 miles south of the Goldfield-Cactus Spring road. This limestone is
90 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA,

cut by numerous small white calcite veins. On lithologic grounds it is 

probably the Pogonip limestone of Ordovician age. Bowlders of similar limestone are embedded in rhyolitic tuffs near by and fragments 

of limestone and jasperoid are inclosed in the rhyolite at several 

places and in a granite porphyry in the northern part of the range. 

These fragments were probably derived from Ordovician or Cambrian limestones.

Eureka quartzite. Two miles southwest of Antelope Spring an 

area of quartzite lies unconformably below the surrounding rhyolite. 

This is a fine- to medium-grained quartzite of white, yellow, or red 

color and is cut by small stringers of white quartz. From its lithologic character it is considered to be the Eureka quartzite (Ordovician).

Weber conglomerate. Three miles west of south of Cactus Spring 

a mass of rusty-looking sedimentary rocks, one-half mile in diameter, 

protrudes through rhyolite. About 150 feet of conglomeratic beds, 

with the matrix of sand and small pebbles thoroughly cemented, are 

exposed. Embedded in this matrix are many beautifully rounded 

pebbles of green and black flint and jasperoid, white quartzite, and 

black limestone. The rounclness of the pebbles, the largest of which 

are 4 inches in diameter, indicates a long period of attrition and the 

conglomerate is probably of marine origin. Prior to their inclusion 

in the conglomerates the pebbles, probably derived from Cambrian, 

Ordovician, and Silurian rocks, were cut by quartz and calcite 

veinlets and the limestone silicified to jasperoid. The conglomerate 

is thus much younger than the Pogonip limestone, but since it contains no granite or diorite pebbles it is believed that it is of Carboniferous age'and that it is to be correlated with the Weber conglomerate of the Belted Range.

IGNEOUS ROCKS.

Post-Jurassic granite porphyry and granite. Midway between 

Cactus Peak and Cactus Spring is a small area of granite porphyry 

that is poorly exposed, but litholqgically distinct from the surrounding rhyolite. The pinkish-graj^ rock is of well-developed porphyritic .habit, with a finery crystalline groundmass. The phenocrysts, 

which exceed the groundmass in bulk, are pink glassy feldspar 

tablets up to three-fourths of an inch in length, a few smaller quartz 

grains, and fairly abundant biotite flakes. In it are fragments of 

Paleozoic sedimentary rocks. Under the microscope the groundmass 

is seen to be a microgranitic mosaic of orthoclase and quartz with 

here and there a little plagioclase and biotite. The orthoclase phenocrysts, many of which have zonal structure, are in places twinned 

according to the Carlsbad law. Quartz, biotite, and a few plagioclase phenocrysts are associated. Magnetite and zircon occur as
CACTUS RANGE; IGNEOUS ROCKS. 91

accessory minerals. Both quartz and orthoclase phenocrysts show 

undulose extinction, which in certain instances is rather strongly 

developed. The plagioclase phenocrysts and the feldspars of the 

groundmass are turbid through kaolinization. This granite porphyry 

closely resembles some of those of post-Jurassic age. Inclusions of 

a siliceous granite occur in rhyolite at a number of places.

Pre-Tertiary diorite porphyry. TAVO miles north of Antelope 

Spring is a small area of greenish-gray diorite porphyry. The rock 

has a well-developed porph.yri.tic texture; small gray striated feldspars, grayish-green altered hornblendes, and much smaller black 

micas lie in a fine-grained gray groundmass. Under the microscope 

the groundmass appears as a fine microgranitic mosaic of plagioclase 

and some orthoclase. Of the phenocrysts already mentioned both 

plagioclase and hornblende are much altered, the plagioclase being 

sprinkled with epidote, calcite, and zoisite, and the hornblende being 

more or less completely replaced by epidote, chlorite (ripidolite, in 

part), and calcite. Ilmenite and apatite are accessory minerals. 

TKis rock is practically identical with the older pre-Tertiary diorite 

porphyry of the Lone Mountain foothills.

Hornblende-Motite latite, On the west side of the Cactus Range, 

north of Wellington and south of the median line of the range, low 

rounded bosses of a much altered greenish-gray rock protrude from 

beneath the younger rhj^olitc. The dull groundmass contains biotite 

plates, white or pale-green areas, apparently altered feldspar, and 

dark-green areas, probably altered hornblende, while the weathered 

surfaces show numerous casts of these phenocrysts. The rock contains many well-rounded pebbles, some of grayish-white quartzite 

(Eureka?), others .of the diorite porphyry last described. The 

largest pebbles are 3 inches in diameter. The latite appears to have 

flowed out upon an old erosional surface covered by well-rounded 

pebbles. Under the microscope the groundmass shows as a glass, now, 

however, much altered and composed of epidote, calcite, quartz, and 

orthoclase. The plagioclase phenocrysts are almost completely 

altered to epidote and calcite, with less chlorite, quartz, and zoisite. 

The hornblende phenocrysts are altered to the same minerals, although 

zoisite is as a rule absent. Biotite is replaced by chlorite in association with sagenitic webs of rutile.. The phenocrysts and groundmass 

have thus been altered similarly, although the secondary minerals of 

the phenocrysts are coarser in grain, than those of the groundmass.

Wherever the contact with the rhyolite was seen the latite appears 

to be the older, a view supported by the absence of rhyolite pebbles 

in it and by the intense alteration and deformation which it has suffered. Petrographically the latite is rather similar to the later andesite of Tonopah,0 but mineralogically it is more closely allied to the

"Spurr, J. E., Prof. Paper TJ. S. Geol. Survey No. 42, 1905, p. 33.
92 SOUTHWESTERN NEVADA AND EASTEEN CALIFORNIA.

monzonite porphyry of the Kawich Range; it is therefore tentatively 

considered the effusive equivalent of that formation'and is thus 

probably of Eocene age.

Earlier rhyolite. TliQ most widespread formation of the Cactus 

Range is a rhyolite which occurs in flows. Throughout the range it 

appears to bear similar relations to the other Tertiary rocks and in 

the main probabty represents a single period of rhyolitic vblcanism. 

More detailed work may, however, prove that some of the rhyolites 

near Cactus Peak are younger than those of the central and southern 

portions of the range.

The rhyolites vary among themselves in color, in character of 

groundmass, and in the relative abundance of the various phenocrysts. 

The predominant type is a Avhite or gray rock of lithoidal or glassy 

groundmass, in which are embedded abundant medium-sized, slightly 

smoky quartz and glassy orthoclase phenocrysts; biotite phenocrysts 

are small and inconspicuous or absent. Other phases of the rhyolite 

are black, purple, or red in color. The phenocrysts of quartz are 

typically corroded grains, although some exhibit the dihexagonal. 

pyramid and prism. Wavy flow bands of slightly different color 

traverse the groundmass. In many beds irregular fragments of rhyolite are inclosed in a matrix of similar rhyolite, showing that portions 

of the magma were solidified prior to cessation of movement in the 

flow. The presence of Avell-roimded pebbles of Paleozoic rocks in the 

basal portions of the rhyolite indicates that the surface upon which 

the lava flowed was covered by such pebbles.

Microscopic examination of several thin sections shows these rocks 

to be normal rhyolites. The groundmass is a brown glass, and many 

of the phenocrysts are fractured by flow. One or two acidic plagioclase phenocrysts are present in some sections. Biotite in some instances is altered to chlorite and epidote or muscovite. Accessories 

are rare, although apatite and ilmenite occur.

On weathering the feldspar phenocrysts are removed and the quartz 

protrudes slightly. In some portions of the range the rock has the 

smooth contours of weathered granite, but in the vicinity of Cactus 

Peak the greater resistance to erosion of certain bands gives a bedded 

aspect to the series.

Vertical columnar parting is well developed through cooling on 

Cactus Peak, while on the Goldfield-Cactus Spring, road, horizontal 

hexagonal joints occur. The rhyolite is so similar to that of the 

Kawich, Reveille, and Belted ranges that it is considered to be also 

of early Miocene age.

Four areas of slightly consolidated rhyolitic sandstones and conglomerates occur in the-Cactus Range. Two are on the northwest 

border of the range near the Cactus Spring-Tonopah road, a third is 

situated 2 miles southwest of Cactus Spring, and in a fourth area
CACTUS' RANGE, IGNEOUS KOCKS. 93

these rocks underlie the augite andesite on the east side of the range. 

The tuffaceous sandstone, which is well bedded and white or greenish 

in color, is but slightly consolidated and breaks down readily into a 

deep sandy soil. Interbedded with the sandstones are conglomerates 

which, in the area southwest of Cactus Spring, contain bowlders of 

Paleozoic limestone 3 or 4 feet in diameter. These beds are tentatively 

considered rhyolitic tuffs deposited in local basins during the rhyolitic 

extrusion. It is recognized, however, that these sediments may in 

reality be the Siebert lake, beds, in which case the earlier rhyolite of 

Cactus Range is of late Miocene age and is to be correlated with the 

later.rhyolite of the Belted Range.

Biotite andesite. Dikes and flows of biotite andesite are Avidely 

distributed in the southern part of the Cactus Range, but do not 

appear to extend far north of the Goldfield-Cactus Spring road. In 

dikes' and irregular intrusive masses and possibly in flows this rock 

covers considerable areas southeast- of Cactus Spring, apparent dikes 

cut the rhyolite at Wellington, and an andesite flow caps the highest 

mountain in the southern half of the range. Other areas of biotite 

andesite occur northeast of Antelope Springs, and a traverse from 

Wellington to Antelope Springs crossed numerous areas of this rock 

too small to show on the present map. Dikes of biotite andesite occur 

on both sides of the Goldfield-Cactus Spring road, but these also are 

too small to indicate on the map.

The biotite andesite is everywhere more or less altered. The freshest rocks have a dark-gray groundmass in which are embedded abundant medium-sized phenociysts. Striated feldspars of white color and 

in many cases of zonal growth are more conspicuous than the altered 

grayish-green biotite and hornblendelike mineral. More altered 

facies are greenish gray or purplish red in color. The andesite 

breaks into sharp joint blocks which on further alteration develop 

spheroidal weathering. Under the microscope this rock appears to 

have had originally a pilotaxitic groundmass. Plagioclase phenocrysts are common and grade in size into the laths of the groundmass. 

One or more orthoclase phenociysts are present in the majority of 

slides. Biotite is now a pseudomorph of chlorite, calcite, epidote, 

quartz, and sagenitic rutile. Aggregates of chlorite, epidote, calcite, 

and quartz surrounded by reaction rims of magnetite appear in some 

cases to have the form of a pjamene and in others that'of an am phibole. Probably both minerals were originally present. These pseudomorphs, like the plagioclase phenocrysts, grade into groundmass 

microlites of similar form. Magnetite is a "common accessory.

The biotite andesite cuts the rhyolite in dikes and caps it in flows; 

inclusions of rhyolite occur in the andesite, and near some of the 

rhyolite masses the phenocrysts of the andesite become smaller. The 

andesite, then, is younger than the rhyolite, and from its altered con-
94 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

dition it is believed to be older than the augite andesite and basalt. It 

closely resembles the andesite of the Goldfield hills and may be contemporaneous with it. If so, it is probably of early or middle Miocene age.

Augite andesite. A flow of dark-gray andesitic rock overlies the 

tuffaceous facies of the earlier rhyolite 2 miles north of Antelope 

Springs. In the dense gronndmass are blackish-green pyroxene and 

amphibole columns which reach a maximum length of one-eighth 

inch. The rock breaks into sharply jointed blocks, in the interstices 

of which some epidote has developed. Microscopic examination 

shows that this is an augite andesite with glassy groundmass in which 

are numerous plagioclase laths, pyroxene crystals, and magnetite 

grains. Augite. phenocrysts with slight zonal structure and twins 

parallel to the orthopinacoid are abundant. The augite is remarkably 

fresh, although a little secondary epidote and chlorite is locally 

present. A few brown hornblende phenocrysts. some of them outlined by a reaction rim of magnetite, also occur. Apatite and magnetite are present as accessory minerals.

The augite andesite forms a flow which is apparently younger than 

the rhyolite and, to judge from its fresh coridition, is probably also 

younger than the biotite andesite. In the Great Basin the pyroxene 

andesites are of late Pliocene-Pleistocene age,a and their formation 

usually immediately preceded that of the later basalts.

Later rhyolite ( ?). One mile northeast of Cactus Peak are some 

low hills of purplish-gray rock with rather large feldspar crystals. 

Tuffaceous beds underlie the igneous rock, and the two rocks are probably to be correlated with the younger tuff and the youngest rhyolite 

of the Goldfield hills. It is by no means impossible that the same 

series underlies the basalt in the west slope of the range.

Basalt. The hill 3 miles southeast of Antelope Springs is composed of rhyolite apparently overlain by basalt, and several hills along 

the edge of the range on the Cactus Spring-Silverbow road are composed of a similar rock. The dissected mesa slopes on the west side 

of the range north of Wellington appear from a distance to be a northward extension of the basaltic rocks of Pahute Mesa. Probably to be 

correlated with the basalt is a reddish-brown vesicular rock which 

caps a low dome 1-| miles north of Cactus Peak. These basalts appear to overlie the rhyolite and they are probably of late Pliocene or 

earty Pleistocene age.

STRUCTURE.

The Cactus Range is predominantly formed of Tertiarjr rocks unconformably overlying Paleozoic sedimentary rocks and granites and 

diorite porphyries probably of post-Jurassic age. The small areas of

0 Spurr, ,1. E., Trans. Am. Ingt, Min. Eng., vol. 33, 1903, p. 333,
CACTUS KANGE, ECONOMIC GEOLOGY. 95

Paleozoic sedimentary rocks are gently folded in a manner comparable 

probably with the folding of the Stonewall Mountain Paleozoic rocks. 

Minor normal faults were observed in all the Tertiary lavas, although 

they are much more abundant in the rhyolite and other older formations than in the younger. The rhyolite in places is tilted at an angle 

of 30°, but it was not determined whether the tilting is due to faulting or to actual folding.

ECONOMIC GEOLOGY,

Wellington, formerly called O'Briens Camp, ^ is situated on IOAV 

rounded hills in the southwestern portion of the range, 11 miles 

south of Cactus Spring. Claims were first located in August, 1904, 

and when visited (July, 1905) several men were doing development 

work.

The country rock, the earlier rhyolite, is considerably kaolinized 

and silicified in the vicinity of the veins and is heavily stained by 

limonite. The rhyolite is apparently cut by dikes of altered biotite 

andesite of purple color. Both rocks along a zone striking N. 70° E. 

are cut by quartz veins, many of which strike parallel to the extension of the zone and dip northward. The larger veins are from 

2 to 4 feet in width. Connecting these are numerous quartz stringers, 

which course in all directions, in many places cementing crushed portions of the rock. The quartz is semitransparent, crystalline, and for 

the most part white, although locally intensely stained by limonite and 

manganese dioxide. Vugs with small quartz crystals are very common, as is also erustification. Minor veins of calcite'were observed. 

Differential movement has occurred parallel to some of the veins, 

and much* of the quartz is intensely brecciated, while minor faulting 

across the strike was noted in several places. Microscopic examination shows that the brecciated fragments were first rimmed by fringes 

of quartz, the interstices being later filled by calcite and limonite. 

The values reported are largely gold, silver constituting but onetwentieth of the assay value. The ore is free-milling and the gold 

is in close association with limonite. The quartz and the contained 

ores were deposited in joints in the interstices of breccia and along 

small and possibly large fault fissures. The veins have been faulted 

and the quartz crushed. Only ores oxidized by surface waters have 

as yet been encountered.

The Cactus Mining Company has a shaft in silicified rhyolite 

three-fourths of a mile south of Cactus Spring. Coarsely crystalline white quartz veins, with many vugs, cut the rhyolite. and 

these on surface outcrops are heavily stained by iron compounds. 

Pyrite and chalcopyrite are sparingly present in the quartz and 

to a less degree impregnate the. surrounding rhyolite. Free gold is 

reported. Both fissure filling and replacement of the country rock
96 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

have occurred. To the north of Alkali Spring some quartz veins cut 

iron-stained kaolinized and silicified rhyolite. Prospectors report 

that the quartz carries low-grade values.

Over a considerable area south of the Goldfield-Cactus Spring 

road, beneath the north end of the andesite flow, which caps the high 

mountain south of the median line, and in several smaller areas the 

rhyolite has been silicified and kaolinized. (See fig. 4, p. 43.) Quartz 

veinlets occur in some of these areas. Masses of hematite and limonite outcropping 2 miles S. 60° E. of Cactus Spring may be the 

gossan of a pyrite vein. Malachite stains occur on joint surfaces in 

the biotite andesite one-half mile southeast of Cactus Spring.

HILLS BETWEEN THE CACTUS AND KAWICH RANGES. 

TOPOGRAPHY AND GEOGRAPHY.

Lying between the Cactus and Kawich ranges is a rather broad 

ridge of north-south trend, from which low doiries arise. The southern part of the ridge is a mesa sloping gently southward, evidently 

once a portion of Pahute mesa, but now separated from it as a result 

of erosion. The hills are bare of timber. A small seep, dry in summer, is located in the northern part of the ridge.

GENERAL GEOLOGY.

The formations of these hills, from the oldest to the youngest, are 

the following: Eureka quartzite, rhyolite, biotite andesite, and 

basalt.

SEDIMENTARY ROCKS.

Eureka (f) quartzite. Mr. T. C. Spaukling states that a small hill 

on the north of the range is composed of lilac-gray quartzite. The 

quartzite is rather coarse grained and contains some tiny pebbles of 

kaolinized feldspar and red jasperoid. The similarity of this rock 

to that of Quartzite Mountain in the Kawich Range indicates that it 

is probably the Eureka quartzite.

IGNEOUS KOCKS. °

Rhyolite. The rhyolites are similar to those of the Cactus Range 

and are presumably contemporaneous. Slightly vesicular facies are, 

however, present.

Biotite andesite. Masses of dark-gray biotite andesite identical 

with that of the Cactus Range intrude the rhyolite in the northwestern portion of the hills. . 

Basalt. The greater portion of these hills is composed of black 

basalt with dense groundmass. The -phenocrysts are striated feldspar, black pyroxene, and pellucid olivine, the feldspar and pyroxene 

showing a rude flow alignment. Vertical columnar jointing is well
MONITOR HILLS; GENERAL GEOLOGY. 97

developed in much of the rock. Some tuffaceous sediments with perfect feldspar crystals lie below the basalt on the west side of the area, 

and it is not improbable that the younger tuffs, as well as the later 

rhyqlite of Goldfield, are here associated with the basalt. This rock 

is probably of late Pliocene or early Pleistocene age.

MONITOR HILLS.

The Monitor Hills are situated in the north-central part of the area 

surveyed. They are of gentle grade and rise 1,000 feet above the 

surrounding alluvial slopes.

GENERAL GEOLOGY.

The rocks of the Monitor Hills, the oldest being named first, are 

granite, Siebert lake beds, rhyolite, and basalt.

SEDIMENTARY ROCKS.

Siebert lake beds. These hills are in greater portion formed of 

sandy slopes, from, the disintegration of well-bedded tuffaceous sandstones. These are light gray or white in color and usually rather 

fine-grained, although some facies are conglomeratic. The rounded 

pebbles are of light-grayish glassy rhyolite. The tuffaceous sandstones show an apparent exposure of 800 feet. These beds are lithologically similar to and are here correlated with the Siebert lake beds 

of Tonopah, situated 16 miles north of west of the Monitor Hills. 

These Spurr 0 considers of Miocene age.

IGNEOUS SOCKS.

Granite. Angular fragments of a medium-grained siliceous granite occur in the basalt described below, indicating that the basalt in 

its ascent to the surface passed through a mass of granite.

Rhyolite. Two isolated hillocks to the south of the main hills 

appear from a distance to be an igneous rock that is lighter in color 

than basalt, and that is probably rhyolite.

Basalt. A number of basalt areas are scattered over the Monitor 

Hills, and this rock caps the summit of the group. The compact 

facies has a dense blue-black groundmass which is locally spotted 

with gray blotches one-fourth inch in diameter. The phenocrysts 

include light-gray glassy feldspar from one-sixteenth to one-half 

inch in length. Columns of a dark pyroxene and rounded grains of a 

glassy black substance, presumably olivine, occur. Under the microscope this rock proves to be a holocrystalline olivine basalt. The 

black color of the olivine in hand specimens is due to its "partial alter-

°.Spurr, J. E., Prof. Paper U. S. Geol. Survey No, 42, 19Q§, p. 69. 

Bull. 308 07 M 7
98 SOUTHWESTERN" NEVADA AND EASTERN CALIFORNIA.

ation to a blood-red serpentine. Vesicular facies of the basalt are 

usually reddish brown and scoriaceous facies are brick red. In some 

beds angular fragments of basalt are embedded in a matrix of similar 

basalt, forming a flow breccia and showing that motion continued in 

the lava after some portions had solidified. The more dense facies 

show spheroidal weathering well developed. Vesicular basalt bounds 

a central sheet of dense basalt and a ropy surface. The original flow 

surface is seen at places; this indicates that the larger portion of the 

basalt is without doubt a flow. The largest mass, however, is probably the site of the vent from which the flows occurred.

Where the contact between the basalt and the Siebert lake beds is 

exposed the basalt is seen to lie upon the eroded surface of the sandstone. While it is possible that some masses of basalt on the lower 

hill slopes are flows contemporaneous with the Siebert lake beds or1 

are later sheets, they are more probably portions of the flow which 

owe their position partly to the uneven surface of the tuffs and 

partly to later deformation. The basalt, on structural and lithologic 

grounds, is believed to be contemporaneous with that of Tonopah, 

which Spurr a believes to be of late Miocene or early Pliocene age.

STRUCTURE.

The Siebert lake beds and the basalt flows are in a broad way horizontal, although they have been tilted slightly to the northeast. The 

relative distribution of the basalt and the lake beds is such as to suggest that they are cut into a number of blocks by intersecting systems 

of normal faults.

CACTUS FLAT.

Cactus Flat lies between the Cactus and Kawich ranges. Its 

center is occupied by a series of playas with north-south trend, 

which during very exceptional rains merge into one another. They 

are from 5,330 to 5,350 feet above sea level, and are surrounded by 

low sand dunes. In this valley the Recent detrital deposits may be 

thick. The valley from the Cactus to the Kawich Range across 

Cactus and Gold flats, illustrates the steeper slope of valleys near 

large and high mountain masses and the gentler grade near small 

and low hills.

GOLD FLAT.

Gold Flat lies between Pahute Mesa and the Cactus and Kawich 

ranges. Its lowest point, 5,035 feet above sea level, is occupied by 

a playa, 4 miles west of which, in a small inclosed basin, is another 

playa. North of the larger playa, at an elevation of 20 to 100 feet 

above its surface, are a number of round intensely dissected hillocks.

« Spurr, J, E., Prof. Paper U. S. Geol, Survey No, 42, 1000, p. 09.
KAWICH RANGE. 99

These hills show a total thickness of 100 feet of white, well-stratified 

clay, to be correlated with similar play a deposits of the older alluvium in the Stonewall Flat. * Presumably this playa deposit and 

its associated alluvial slope deposits underlie the Recent gravels of 

Gold Flat at no considerable depth.

KAAVICH RANGE. 

TOPOGRAPHY AND GEOGRAPHY.

The Kawich Range was named after Chief Kawich, an Indian 

who lived at the spring at the head of Breen Creek. The range is 

a southward continuation of the Hot Creek Range, from which it 

is separated by a narrow transverse valley.0 From this gap it 

extends 50 miles southward to a point where it sinks beneath the lava 

flows of Pahute Mesa. The range has a well-developed .crest line 

with north-south trend. It is deeply indented by valleys at Rose 

Spring and at Kawich, while 8 miles north of Kawich the Recent 

alluvial deposits completely arch the range.

In the rugged northern part of the range the sinuous crest line 

is in many places a knife-edge flanked by high cliffs; south of Rose 

Spring the topography is much less rugged. From the main crest 

line subordinate divides of similar character extend at right angles. 

The crest line at the north edge of the area mapped has an elevation 

of 9,000 feet, while in the south end of the range it rarely rises 

above 7,000 feet. Kawich Peak, with an elevation of 9,500 feet, is 

the highest summit. Quartzite Motintain, a beautiful symmetrical 

dome southwest of the village of Kawich, is 7,900 feet high.

The Kawich Range is intensely dissected by many stream channels. 

The drainage line of Little Mill Canyon, which alone is abnormal, 

courses east 2 miles, bends sharply to the north j and 1 mile beloAv 

again turns at right angles and resumes its easterly course to the 

Reveille Valley. A low divide separates the first segment of the 

stream from a prominent east-west valley in alignment with it south 

of the mountain southwest of the town of Eden, and it is probable 

that Little Mill Creek has captured the upper part of its valley.

On the crest line, near the northern boundary of the region shown 

in the map, are areas of an older and more mature mountain topography, with gentle slopes, in strong contrast with the rugged character of the surrounding ridges and cliffs. Exposures of rock are few 

and nowhere conspicuous; the surface is covered with soil and supports some grass. This old topography is in advanced maturity or in 

old age, but the hills existing on its rolling surface are too numerous 

to call it a peneplain. Remnants of a similar surface are preserved 

in the Belted, Amargosa, and Panamint ranges, and in the Panamint

"Spurr, J. E., Bull, U. S. Geol. Survey No. 208, 1903, p. .181.
100 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

the surface was developed prior to the outflow of the PliocenePleistocene (?) basalt. This less accentuated surface, which probably extended completely over the area surveyed, is perhaps of early 

Pliocene age.

The Kawich Range is rather heavily timbered at its north end 

above an elevation of 6,500 feet. The timber line becomes higher to 

the south and neither pin on nor juniper grows south of the. detrituscovered gap 8 miles north of the village of Kawich. In consequence of its height and of its rather heavy growth of timber, the 

Kawich is the best watered range within the area surveyed. The 

streams of this range have already been described (p. 18). The 

springs south of the timbered areas are small and some become dry 

during the summer. The following are rough estimates of the flow 

of the larger springs in gallons per day: Longstreets Ranch Spring, 

3,000 gallons; Stinking Spring, 2,000 gallons; Heenan Water, 1,500 

to 2,000 gallons; Rose (sometimes called Wild Horse) Spring, 2,000 

gallons; Sumner Spring, 1,500 gallons; Corral Spring, 1,500 gallons; Jarboe Spring, 500 gallons. At Silverbow and Stephanite 

wells have been sunk in stream gravels and water encountered at 

depths of 10 to 45 feet.

GENERAL GEOLOGY.

The formations of the Kawich Range, in ascending order, are: 

Pogonip limestone, Eureka limestone, Lone Mountain limestone, 

granite, diorite, monzonite porphyry, earlier rhyolite with minor 

contemporaneous latite and dacite and basalt flows, biotite andesite, 

dacite, Siebert lake beds (?), later rhyolite, and later basalt and 

associated andesites.

SEDIMENTARY ROCKS.

Pogonip limestone and Eureka guartzite. Quartzite Mountain is 

composed of Paleozoic rocks and from it an arm extends north on the 

west side of the range and another south on the east side of the range. 

Small inliers of Paleozoic rocks also occur 2 miles east of Rose 

Spring, 6 miles west of north of the same point, and 3 miles north of 

west of Silverbow. Angular fragments of Paleozoic jasperoid, 

quartzite, and schistose shale are widety distributed in rhyolite, and the 

vent through which the rhyolites were extruded passed through Paleozoic rocks. Inclusions of Paleozoic rocks also occur in the andesites 

southeast of Quartzite Mountain.

The sedimentary rocks exposed on Quartzite Mountain consist of 

1,200 to 1,500 feet of quartzite underlain by 400 to 600 feet of interbedded quartzites, slaty shales, and limestones. The quartzites of 

Quartzite Mountain are typically light in color, usually being either 

white, pinkish white, or gray, although some of the more feldspathic
KAWICH KANGE, SEDIMENTABY EOCKS. ' 101

varieties are greenish on account of the development of secondary 

sericite. Rarely thin lamina? of dark gray or black alternate with the 

white bands. Pure quartzose facies are more abundant than feldspathic, although well-characterized arkoses also occur. While these 

rocks are largely quartzites some beds are better defined as indurated 

sandstones. The rock is typically fine to medium grained, but conglomerates with well-rounded pebbles one-half inch in diameter also 

occur. The pebbles include smoky or pinkish quartz, probably of 

granitic origin, pink feldspar, compact red jaspilite, and fine-grained 

biotite schist with phenocrystic muscovite crystals one-eighth inch 

long. These pebbles can not be certainly referred to any Paleozoic 

rocks seen in the area surveyed, although they may possibly be derived 

in part from the Cambrian or from a pre-Cambrian series. The 

quartzite is medium to heavily bedded. Cross-bedding is common and 

ripple marks are locally well developed, while sun cracks are rare and 

confined to the finer grained arkoses. The quartzite is well cemented 

and both pebbles and matrix are cut by numerous quartz veinlets. 

The presence of two intersecting systems of quartz veins at an angle 

of 45° to the bedding planes, one set short and rather wide in the plane 

of stretching, the other thin, more numerous, and of greater length 

in the plane of compression, indicates that the quartzite beds have 

suffered considerable shearing. Muscovite films have been developed 

on some parting planes. Minor faults occur in the quartzite mass and 

in some cases cut the quartz veins. Joints are well developed and in 

consequence the rock fragments are angular blocks,.

The rugged inlier of quartzite 3 miles north of east of Silverbow is 

surrounded by rhyolite. It is similar lithologically to the purer 

white or pinkish-white quartzites of Quartzite Mountain. Thin 

quartz veins with viigs and a few seams of pyrite cut it. The quartzite area 6 miles west of north of Rose Spring exposes 400 feet of 

similar quartzite. Conglomeratic bands with white. quartz pebbles 

one-half inch in diameter are interbedded with the fine-grained bands.

The slaty shale of Quartzite Mountain grades on the one hand into 

argillaceous sandstone and on the other into clayey limestone. The 

shale is fine grained and olive green or dark gray in color, although in 

rare instances bright-green facies occur through the development of 

chlorite. Secondary mica films are common on the shale parting 

planes.

The limestone of the Quartzite Mountain section is a siliceous, 

compact, well-bedded rock of medium grain. In color it is yellow or 

reddish j^ellow. Some beds are oolitic, with white calcite cement 

which over areas one-half inch in diameter is of common orientation 

and. reflects light like a single cleavage face. The texture is the 

poikilitic of igneous rocks. Suture joints occur, but are not characteristic. In the small area of sedimentary rocks 2 miles east of
102 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

Eose Spring finely banded, dark-colored silicified limestone similar 

to that of the Southern Klondike hills outcrops, and this, while 

probably Ordovician, may possibly be a Cambrian inlier.

The rocks of Quartzite Mountain appear to have been laid down 

in a shallow sea. At some periods during the deposition of the lower 

portion the sea received fragmental material, both fine and medium 

grained; at others it received but little, in consequence permitting 

the deposition of limestone. The presence of sun cracks indicates 

that at times the deposits were even above sea level. The main 

quartzite mass was deposited in a shallow sea to which medium to 

coarse fragmental material was rather constantly supplied.

The rocks beneath the quartzite of Quartzite Mountain resemble 

the interbedded quartzites, slaty shales, and limestones which overlie 

the Pogonip limestone of the Belted Kange. In consequence the 

lower rocks of Quartzite Mountain are probably the transitional 

beds of the Pogonip limestone, while the quartzite, notwithstanding 

its unusual thickness, is the Eureka quartzite.

Lone Mountain limestone. A small limestone hill protrudes from 

the Recent detrital deposits 7£ miles south of east of Rose Spring. 

Mr. T. C. Spaulding collected a specimen which proves to be a gray 

crystalline limestone with numerous calcite veins. If the structure 

of the Paleozoic rocks extending northward from Quartzite Mountain 

beneath the rhyolite of the Kawich Range continues its easterly dip, 

this limestone lies above the Eureka quartzite and is probably the 

Lone Mountain limestone of the Eureka section, described by Hague.

Siebert lake beds (?). Lying unconformably upon the earlier 

rhyolite and in one case apparently unconformably below the later 

rhyolite are a number of small exposures of rhyolitic sandstone, 

usually conglomeratic. These slightly consolidated sandstones are 

white, gray, or greenish in color and are distinctly bedded. The 

well-rounded pebbles and bowlders, the larger of .which are 1 foot in 

diameter, include Paleozoic quartzites and jasperoids, granites, diorite porphyry, monzonite porphyry, and the earlier rhyolite. Quartz, 

feldspar, and biotite crystals are characteristic, and either explosive 

eruptions of rhyolite occurred during the deposition of these sandstones or the crystals were derived from rhyolites with incoherent 

groundmasses. The more easterly of the two masses mapped 3 miles 

north of Kawich. is a bedded conglomerate cemented by chalcedony. 

The conglomerate is better assorted than that of the rhyolitic sandstone and resembles the well-rounded conglomerates of the Amargosa 

Range. It is certainly younger than the earlier rhyolite, since it 

carries rhyolite bowlders and is perhaps contemporaneous with the 

Siebert lake beds.

Spurr" found similar rhyolitic sandstone?; 600 feet thick at the

« Spun-, J. E., Bull. U. S. Geol. Survey No. 208, 1903, p. 163.
KAWICH RANGE, IGNEOUS EOCKS. 103

north end of the ,Reveille Range. If the correlation of the earlier 

rhyolite with the Tonopah rhyolite-dacite is correct, these beds are 

probably the Siebert lake beds, of Miocene age. The last-mentioned 

exposure may, like the conglomerates of the Grapevine Range, be a 

shore deposit of this lake.

IGNEOUS ROCKS.

Post-Jurassic granite. One mile west of Sumner Spring is an outcrop of gray granite porphyry with a dense groundmass containing 

many phenocrysts of feldspar three-fourths of an inch in length and 

rounded quartz individuals one-fourth inch in diameter. Under the 

microscope the groundmass shows as a fine mosaic of quartz and orthoclase with a little plagioclase. With the phenocrysts of orthoclase 

and embayed quartz are some of plagioclase and very small tablets 

of biotite altered to muscovite and a'rutilelike substance. Apatite, 

zircon, and magnetite are accessory minerals. The relations of this 

mass to the earlier rhyolite are poorly exposed, but on lithologic 

grounds it is considered a post-Jurassic granite porphyry.

Granite inclusions in rhyolite were observed at five widely separated localities. The varieties include fine- or medium-grained biotite 

granites, coarse-grained muscovite granite, pegmatitic quartz, and 

biotite granite with .porphyritic feldspar crystals similar to the granite of Lone Mountain. Large bowlders of medium-grained biotite 

granite are so abundant in the Siebert lake beds 4 miles east of north 

of Silverbow that a granite outcrop was probably near at hand when 

the sandstone was deposited.

Diorite porphyry. Bowlders of diorite porphyry are associated 

with those of granite in the area of Siebert lake beds just mentioned. 

The rock has a white, finely crystalline groundmass, in which are 

embedded numerous white striated feldspar phenocrysts with a maximum length of one-fourth inch and smaller biotite phenocrysts. The 

rock is similar to the diorite porphyry'of the Lone Mountain foothills 

and is probably a later manifestation of the post-Jurassic granite 

intrusion.

Monzonitc porphyry. Monzonite porphyry occupies an area 4 

miles long and 3 miles wide west of Kawich. It has a fine-grained C? O

dark or medium-gray groundmass, in which are embedded abundant 

phenocrysts, many one-fourth inch, a few one-half inch long, of white 

or greenish -white striated feldspar, brown biotite, and altered hornblende. While both hornblende and biotite are usually present the 

relative porportion of the two varies widely throughout the area. 

Oxidation of the iron of the rock produces pink and purple varieties, 

while kaolinization gives a white color.

Microscopic examination shows the groundmass to be a mediumgrained interlocking mosaic of orthoclase and plagioclase. Plagio-
104 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

clase phenocrysts, which are more abundant than those of hornblende 

or biotite, are usually complex crystals showing albite and, less commonly, Carlsbad and pericline twinning. Zonal growth is rather 

common. The plagioclase is slightly altered to calcite, zoisite, sericite, 

and chlorite. Biotite is altered to chlorite, calcite, magnetite, titanite, 

and epidote. Areas of chlorite, epidote, calcite, and quartz rudely 

preserve hornblende forms, while a little fresh brown hornblende is 

present.

Dikes of monzonite porphyry cut the Paleozoic sediments and the 

main mass is probably an eroded stack. The outcrops of monzonite 

porphyry are cut by rather closely spaced joints and in consequence 

break down into angular blocks. Spheroidal weathering is here and 

there poorly developed.

The monzonite porphyry in places appears to lie upon the eroded 

edges of the Paleozoic sedimentary rocks and inclusions of monzonite porphyry occur in the rhyolite on its northern border. This 

rock is rather similar to the biotite-hornblende latite of the Cactus 

Range and more closely resembles the quartz-monzonite porphyry of 

Stonewall, Shoshone, and Skull mountains. These rocks are in a 

broad way contemporaneous and of late Eocene age.

Earlier rhyolite. Earlier rhyolite with associated latite and dacite 

forms most of the mountain range north of an east-west line 2 miles 

north of KaAvich. Small areas occur south of this line, and in the 

Reveille Valley. The rhyolite south of Rose Spring and on the flanks 

of the range north of this point is unquestionably a flow. The crest 

of the range north of Rose Spring is composed of compact rhyolite, 

in which flow bedding is absent or very obscure. It is probable that 

the crest in part or as a whole lies upon the fissure from which the 

rock was extruded. Some of the masses of rhyolite in the vicinity of 

Kawich- are perhaps dikes intruded in the monzonite porphyry, and 

the poorly exposed rr^olite in the Paleozoic quartzite 6-| miles west 

of north of Rose Spring may also be a dike.

These acidic rocks include many f acies. Perhaps the predominant 

type is a reddish rhyolite with compact flinty groundmass, containing 

abundant medium-sized phenocrysts of glassy orthoclase and slightly 

smoky quartz, with fewer and smaller phenocrysts of black mica, which 

in some instances are absent. The quartz phenocrysts are, as a rule, 

rounded crystals and only a few show the dihexagonal pyramid and 

prism. Other rhyolites are gray or brown in color, while some black 

glasses with the normal phenocrysts also occur. In the more glassy 

types flow lines, spherulites, and perlitic parting are common. The 

microscope shows the groundmass of the rhyolite to be of turbid 

brown glass, in which flow lines and spherulites are well developed 

locally. The phenocrj^sts are in some instances well formed and in 

others are angular fragments, showing that flow continued while the
KAWICH RANGE, IGNEOUS EOCKS. 105

lava was very viscous. Biotite is fairly abundant in some slides, 

while in others it is represented by ill-defined pseudomorphs.

Quartz latites are widely interbedded with the rhyolites, being particularly well exposed at Stinking Spring. They are characterized 

in the hand specimen by the presence of phenocrysts of both striated 

and unstriated feldspar and a hornblende-like mineral which reaches 

a maximum length of one-fourth inch. Microscopic examination 

shoAvs a glassy groimdmass containing as phenocrysts quartz, orthoclase, plagioclase, and hornblende or augite. Both feldspars are 

often zonally built. Magnetite and apatite are common accessories.

Brown glassy dacites are less widely distributed. Microscopic 

examination shows a rock similar to the quartz latite, except that 

plagioclase is present to the almost total exclusion of orthoclase, and 

ilmenite accompanies magnetite.

Many beds of the acidic series are flow breccias, including angular

fragments of texturally similar or dissimilar acidic rocks, indicating 

that portions of the flow solidified prior to the cessation of movement 

in other parts. White, slightly porous pieces of rhyolitic glass, 

elongated in the direction of flow, are common in certain areas. Similar inclusions characterize the earlier rhyolite of Goldfield and the 

rlryolite of Bullfrog. *

About 1% miles east of Rose Spring is an area of consolidated white 

phaly sandstones and coarse, well-bedded sandstones. The microscope shows that the rock is a typical tuffaceous sandstone of rhyolitic composition. It was probably deposited in a small body of water 

contemporaneous with the outflow of the earlier rhyolite.

The acidic series imparts to the Kawich Range a white, yellow, or 

red color, and in places all these are distributed in broad bands 

either horizontally or slightly tilted. Spires are developed on canyon 

walls in jointed rhyolite, the same rock forming rounded bosses in the 

broader, more mature valleys. South of the detrital gap in the range 

the hills have a marked northwest-southeast alignment parallel to the 

strike of resistant rhyolite flow bands.

The earlier rhyolite of the Kawich Range lies below supposed Sie-' 

bert lake beds and is similar to and probably contemporaneous with 

the rhyolite of the Belted, Cactus, and Reveille ranges and the Bullfrog Hills. In a general way the series is comparable with the preSiebert rhyolites and dacites of the Tonopah district/1 which are 

probably of early Miocene age.

Earlier basalt. Minor flows of basalt were extruded contemporaneously with the earlier rhyolite. The small mass of dense blade 

basalt with sparse, medium-sized, glassy feldspar phenocrysts threefourths of a mile east of Silverbow is probably such flow. This 

rock on microscopic examination proves to be a holocrystalline

< Spun-, J. E., I'rof. Paper U. S. Geol. Survey No. 42, 1905, pp. 37-43.
106 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

olivine- and augite-bearing basalt, somewhat altered. Orthoclase 

phenocrysts are also present. Small inclusions of vesicular basalt 

occur in rhyolite 1^ miles north of Silverbow. Basaltic flows contemporaneous with rhyolite also occur in the Amargosa Range and 

the Bullfrog Hills.

Biotite andesite. One mile northwest of Silverbow a small hill 

surrounded by alluvium is composed of a fine-grained dense andesite 

of gray color. The small phenocrysts, which are in rude flow orientation, consist of white striated feldspars and more numerous smaller 

biotites. Southeast of Blakes Camp is a poorly exposed mass of a 

greenish-gray andesitic rock, considerably altered. Biotite and striated feldspars one-eighth inch long are equally abundant. Under the 

microscope the glassy groundmass is seen to be subordinate to the 

phenocrysts, which consist of medium-sized simple crystals of plagioclase, biotite, and a few deeply embayed orthoclase individuals. The 

plagioclase is considerably altered to calcite,. and the sericite and the 

biotite to chlorite. It is probable that these two exposures are to 

be correlated with one another and with the biotite-andesite intrusive 

in the rhyolite of the Cactus Range.

Dacite. In the vicinity of Rose Spring are five small areas of 

dacite. Another small mass lies 1 mile east of Stinking Spring and 

a rather similar rock is exposed 3 miles south of Georges Water. 

The dacite has a compact aphanitic groundmass of medium to darkgray or brown color. The phenocrysts equal the groundmass in bulk, 

and consist of medium-sized glassy striated feldspars, hornblende, 

mica, and quartz. The quartz, while not abundant, is constantly 

present. A few well-formed crystals of striated feldspar, evidently 

of a later origin than those just mentioned, are from three-fourths of 

an inch to 1J inches long. These are white or gray in color and 

include tiny biotite plates and hornblende columns. Weathering 

brings out clearly the zonal structure, while Carlsbad twins are 

sometimes seen. The phenocrysts near contacts with older rocks 

possess a parallel flow orientation. Microscopic examination shows 

the rock to have a felty groundmass of plagioclase laths with a few 

orthoclase and quartz grains. Many of the smaller plagioclase 

phenocrysts, which are usually compound and slightly rounded by 

magmatic corrosion, show beautiful zonal growth. Plagioclase is 

ordinarily fresh, although calcite is locally developed from it. One 

or more quartz phenocrysts deeply embayed are present in most of 

the thin sections. Biotite, usually surrounded by a magnetite reaction rim, is abundant. Forms characteristic of hornblende and 

heavily rimmed by magnetite grains are completely altered, calcite. 

in places accompanied by serpentine, and magnetite being the alteration products. Magnetite and apatite are accessory minerals. The 

dacite occurs in dikes and irregular intrusive masses which cut the 

earlier rhyolite 2 miles southwest of Sumner Spring. The mass ! £
KAWiGH RANGE, IGNEOUS ROCKS. 107

miles east of Rose Spring is intrusive in shaly sediments that are 

probably interbedcled with the earlier rhyolite. This dacite is lithologically identical with the dacite of the Goldfield hills and the two 

are probably contemporaneous and of middle Miocene age.

Later rhyolite. Forming the gently sloping flanks of the range 

west of Silverbow and capping some of the hills to the south of the 

same village is a brown, dense, and in many places glassy rhyolite 

characteristically poor in biotite and rich in quartz phenocrysts. 

Vesicles, elongated parallel to the flow banding, and vertical joints 

of cooling occur. In some places this rhyolite apparently 1 lies upon 

the slightly eroded surface of the earlier rhyolite, and 5 miles south 

of Blakes Camp it appears, at a distance, to overlie the Siebert lake 

beds. The later rock has suffered much less erosion than the earlier 

rhyolite. The rock, so far as seen, was not altered by the mineralizing waters which formed the ore deposits. This rhyolite is younger 

than the supposed Siebert lake beds and is.perhaps about contemporaneous with the later rhyolite of the Belted Range.

Later basalt and associated andesites. Basalt caps the Kawich 

Range south of Quartzite Mountain. A number of basalt hills outcrop 

m the Reveille Valley, and on the east side -of the range are a number of 

low buttes partly of the same rock. The basalt of the south end of 

the range is black, dense, and more or less vesicular. The cone on the 

east flank of the mountains 10 miles east of north of Kawich is composed of a similar rock, in which a few small feldspar laths are the 

only conspicuous phenocrysts. Olivine basalts occur in the Reveille 

Valley. Basalt also forms a mesa 5 miles west of Silverbow. Andesite 

is associated with some of the basalt. The andesitic rocks of the 

Reveille Valley have a dense mottled reddish-gray or lilac-gray 

grounclmass, Avhich is locally vesicular. The medium-sized phenocrysts, which equal the base in mass, include glassy striated feldspar 

laths, many of which are twinned according to the Carlsbad law; 

fewer biotite plates, and hornblende or pyroxene columns. Spheroidal weathering is rather characteristic. Flow breccias occur in 

bands, and the rock appears to be closely related to the associated 

basalts, each partially burying the small earlier rhyolite outcrop. A 

similar rock, although practically lacking biotite, forms a number of 

IOAV, flat-topped hills 6 miles south of Kawich. Phenocrysts are 

abundant in some facies and in others lacking. The rock occurs in 

flows which dip to the east. The hill 6 miles N. 30° E. of Kawich is 

capped by vesicular basalt beneath which are gray andesitic rocks 

with glassy striated feldspar phenocrysts up to one-fourth inch in 

diameter.

The basalt is similar to that of the Belted and Reveille ranges arid 

is probably of late Pliocene or early'Pleistocene age. The andesites 

are doubtless earlier manifestations of the same periods of volcanism.
108 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

STRUCTURE.

The Paleozoic rocks are complexly folded (see fig. 8). The Quartzite Mountain section is a north-south monocline with dips of 10° to 

30° E. The Paleozoic rocks on the west side of the Belted Range 

dip to the east, and the Kawich Valley probably overlies a gentle 

syncline, although the structure may be much more complex. The vertical strata of the inlier 3 miles north of east of Silverbow strike east 

and west. The quartzite 6 miles west of north of Rose Spring strikes 

N. 75° W. and dips 45° S. Zones of brecciation, indicating that this 

pre-Tertiaiy folding was accompanied with some faulting, are not unusual. The presence in the volcanic rocks of Paleozoic inliers proves 

that prior to the inauguration of the Tertiary volcanism the Paleozoic rocks of the Kawich Range had a diversified topography. , The 

mountain range then may have been as rugged as now, since the valleys 'on either side were doubtless at lower levels than at present.

It is unknown whether or not the normal faults in the monzonite 

porphyry at Kawich, which are in part older and in part younger 

than the ore deposits, were formed prior to the outflow of the rhyolite.

Desert gravels 

550O

Monzonite

Desert ___^

_x/ x '' r ' ' s 7/v ' v-' x '/ x \ ,V,' v '^' 

T>^V: '^' ' Rhyolite

_gmiles 

FIG. S. East-west section across Kawich Range 2| miles north of Kawich.

The rhyolite series north of Rose Spring is a monocline with northsouth strike and low easterly clip. Minor folds of similar strike are 

superimposed upon the monocline. At the detrital gap the strike 

changes to northwest with a dip of 10° to 20° NE. This uplift 

occurred after the deposition of the Siebert lake beds, since they lie 

on the very crest of the range. Joints were developed in the.rhyolite 

contemporaneously with the folding. Sheeting parallel to the folds 

is rather characteristic, although cross joints occur. After the outflow of the basalt the range was uplifted, as is shown by the fact that 

the flows southeast of Quartzite Mountain have a decided dip to the 

east. An undetermined amount of normal faulting accompanied the 

post-rhyolitic elevation, and in certain areas, notably in the shales 

associated with the rhyolite l-£ miles east of Rose Spring, the faulting 

is very complex.

ECONOMIC GEOLOGY.

Mining activity in the Kawich Range centers in three major 

camps Silverbow, Kawich, and Eden and in two minor camps 

Blakes Camp and Southern Kawich.
KAWICH RANGE, ECONOMIC GEOLOGY. 109

SILVERBOW.

Silverbow is situated in the canyon of Breen Creek, on the west 

side of Kawich Range, 43 miles north of east of Goldfield. The 

principal prospects are within 3 miles to the east, northeast, and 

northwest of the village. The first locations were made in November, 1904. When visited by the \vriter (July 20, 1905) Silverbow' 

was the supply center for several hundred men, and a number of 

shallow prospect holes had been sunk.

The ore deposits lie in rhyolite^ which in the vicinity of veins is 

either kaolinized or silicified, the silicification being perhaps more 

common. (See p. 47.) Either type may be intensely stained red, 

brown, or yellow by iron oxides.

The more important prospects are located on parallel quartz veins 

or lenses, which widen, thin, and in places give out, forming mineralized bands whose strike in the district is in many cases north of west. 

The individual quartz veins vary in width from a fraction of an inch 

to 5 feet, and many of these are connected by minor cross veins. 

While in some instances the quartz was deposited along premineral 

faults, in others it occurs along joints, \vhich locally form intersecting systems. Quartz likewise fills many of the spaces caused by 

brecciation and forms in solution cavities in the rhyolite. The 

quartz is, as a rule, white and translucent or colorless and transparent, although in the Blazier tunnel a single vein of amethystpurple color was noted. -A thin section of quartz from the Wheaton 

and McGonagill prospects is a quartz mosaic of very uneven grain. 

In the mosaic are zonally grown crystals of quartz, and finely 

divided silver sulphides dust some of the bands of growth. The 

borders of these quartz crystals appear to be formed of quartz fibers, 

radiating from the center. Crystal-lined vugs are common in this 

vein quartz, and crustification is beautifully developed in many 

specimens, fortification, agate, and mammillary forms being common.

The quartz is more or less stained by iron salts, rarely by malachite. In the quartz specks of stephanite, ruby silver, silver chloride, and probably other silver ores occur. The silver chloride is at 

least a secondary mineral and to a limited extent is disseminated in 

the country rock. Gold occurs free. Silver is the predominant 

metal, and $1 in gold to $3" in silver is perhaps an average for the 

whole camp, although in some prospects the silver values are 20 times 

those of gold. The ore runs from $6 to $250 per ton, though soma 

reports give higher values. Since the writer's visit strikes in which 

gold, predominates over silver have been reported. Rarely values 

occur in limonite stringers in the country rock, while in several prospects a greasy crushed rhyolite constitutes the ore.

The striking similarity between the ore deposits of Silverbow and 

certain of those of Goldfield is worthy of note. Ascending water
110 SOUTHWESTERN NEVADA AND EASTEKN CALIFORNIA.

carrying silica and metallic salts in solution appears to have deposited its' burden largely in preexisting cavities. Simultaneously 

waters wandering from the main channels silicified contiguous portions of the rhyolite. Kaolinization is presumably a later phenomenon. Movement has occurred in the veins since silicification, and 

they have been more or less faulted and brecciated. Surface waters 

have altered silver sulphides, pyrite, and probably less amounts of 

chalcopyrite to the corresponding chloride, oxides, and carbonates, 

while secondary sulphides have also been formed. Gold, probably 

originally in pyrite, was simultaneously set free.

Timber and water are abundant near the mines. Gol'dfield is 

about 50 miles distant by road.

BLARES CAMP.

Blakes Camp is located on one of the earlier rhyolite inliers which 

protrude from the " wash " 12 miles northwest of Silverbow. The 

prospect was discovered late in June, 1905. A fault with well-defined walls coursing N. 80° E. cuts the rhyolite, and in its immediate 

vicinity the country rock is silicified. Along this fault for a distance of 600 feet a zone from 18 to 24 inches Avide is crushed to a fine 

clay, in which are embedded slickensided fragments. The groundup rhyolite is white or stained by hematite or limonite and to a less 

extent by manganese dioxide. This material is said to pan about $15 

per ton of free gold. Quartz veins in rhyolite north and east of 

Blakes Camp are said to carry both gold and silver.

The mining camp of Eden is situated near the mouth of Little 

Mill Creek Canyon, on the east side of the Kawich Range. The first 

locations were made February 20,1905, by John Adams.

Three distinct vertical zones of mineralization cross Little Mill 

Creek from north-northeast to south-southwest, respectively, onefourth, one-half, and five-eighths mile above the old mill at the road 

forks. The country rock is rhyolite, which in many places is intensely silicified parallel to. the mineralized zones. While the contact between the silicified and the unsilicified rhyolite is as a rule 

rather sharp, in some places there is transition. The quartz and silicified rhyolite stand out in distinct walls, aptly called by 'the miners 

" dikes," which follow the mineralized zones.

The central zone has been more developed than the others and was 

studied in more detail. This zone is situated along a line of faulting 

and brecciation and the rhyolite near the zone is mashed. The mineralized zone varies from a vein of quartz 3 feet wide with a few rhyolite horses to a band of silicified rhyolite 8 feet wide, intensely netted 

by quartz stringers. Parallel quartz veins more or less continuous
KAWICH BANGE, ECONOMIC GEOLOGY. Ill

and connected by cross veins are transitional between the two forms 

along the strike. The quartz, much of it crustified, is white and more 

or less iron stained. Finely divided sulphides impart a blue tinge to 

some of the quartz, and the parallel position in thin bands of the 

white and blue quartz shows clearly the contemporaneous origin of 

the quartz and sulphides. Vugs, usually elongated, parallel to the 

walls of the veins, are characteristic. Colorless quartz crystals are 

common in these vugs, while botryoidal quartz walls are less common. 

The vein in some portions is composed of clusters of quartz plates 

an inch in length set at right angles to the vein walls. These suggest 

that the quartz in parts is a replacement of calcite. The normal 

crystalline quartz grades into a compact white flinty variety, which 

is said to be a good carrier of gold.. Under the microscope this 

appears as a cryptocrystalline mosaic of quartz with a little sericite.

This central zone is a silver bearer, the gold values being one-tenth

those of silver. As silver ores, ruby, and native silver are reported 

intimately associated, secondary silver chloride in knobs and wirelike masses is widely distributed in the vugs, and the silicified rhyo- 

]ite itself carries values. Iron sulphide was noted in a few small 

specks in quartz vein.

The upper zone of mineralization is said to be very similar to the 

central zone. The lower zone is also similar to the central, although 

there is perhaps less parallelism and constancy of the quartz veins. 

The strike is more northerly. Pyrite locally impregnates the rhyolite. The flinty quartz already mentioned is abundant in this ledge, 

and the values are largely gold. The resemblance of the Eden deposits to those of Silverbow is striking, and the genesis was doubtless 

similar and contemporaneous.

Water and fuel are abundant. Tonopah, the supply depot, is TO 

miles distant.

KAWICH.

Kawich, in the Gold Reed mining district, lies in a detrital embayment on the east side of the Kawich Range. The town is 54 miles 

south of east of Goldfield. The first locations were made in December, 1904, and early in the spring of 1905 several hundred men rushed 

to the camp. When visited (August 4, 1905) 10 miners were at work. 

Two shafts have been sunk 150 feet and several thousand feet of 

drifts have been driven. The mines are situated on a gently sloping 

area of washj from which protrude numerous small rugged knobs of 

monzonite porphyry and smooth domes of rhyolite. The monzonite 

porphyry has so far been the ore bearer.

The first locations were made on the property of the Gold Reed 

Mining Company. Here a rugged outcrop of intensely silicified monzonite porphyry, dark brown on weathered surfaces, contains in the 

limonite-stained casts of its many phenocrysts plates of hackly gold,
112 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

some of which are an inch in diameter. This altered rock has a conchoidal fracture. The microscope shows the rock to be composed of 

interlocking quartz grains in which there is some finely divided material, possibly of a clayey nature. The areas once occupied by feldspar 

phenocrysts contain a slightly higher percentage of this turbid substance, while some sagenitic.webs of rutile indicate the former presence of biotite. Associated with the silicified porphyry are white 

kaolinized facies which are locally stained red or purplish by iron 

oxides. Numerous other areas of silicified porphyry have been located 

by prospectors, but at none was gold Adsible to the eye, although many 

panned gold. The boundary between the silicified and unsilicified 

porphyry is usually sharp. Strong iron stains and some dendrites of 

manganese dioxide are associated with the gold. The iron stains 

probably point to pyrite as the original source of the ore, an inference 

strengthened by the presence of gypsum. This mineral is rather 

closely associated with the ore, in some places filling cavities in it and 

in others filling joint and fracture planes in the country rock. The 

gjrpsum occurring in the country rock is fibrous, the fibers being set 

at right angles to the walls. The residual soil near ore deposits is 

locally cemented by gypsum. Gypsum was probably formed by the 

interaction of iron sulphate, set free by the-oxidation of pyrite, and 

of calcium-bearing solutions derived from the decomposition of the 

plagioclase of the monzonite porphyry. Quartz veinlets cut the silicified porphyry, but these are reported to carry no values. Certain 

clear phenocryst-like quartz areas indicate that silicification continued after the removal of the phenocrysts usual in monzonite porphyry. 

In the deepest shafts the silicified porphyry holds its width, although 

up to the time of this examination the values were low except at the 

surface. At the Gold Reed mine good values have been obtained in a 

kaolinitic substance found in the cavities of the silicified porphyry at 

the 100-foot level.

Iron pyrite has been encountered on the 150-foot level at the Gold 

Reed mine, disseminated in unsilicified monzonite porphyry. Its 

assay value is low. Several thin veins of pyrite occur on the lower 

levels of the Diamond No. 2. These veins are banded and vugs occur 

here and there in the center. This pyrite is said to assay $35 in gold 

per ton.

The silicified monzonite porphyry has been considerably faulted 

and slickensides and breccias are common. At the Gold Reed mine 

the faulting has been very complex, and wedge-shaped cavities, 

which reach a maximum length of 5 feet, appear to be due to faulting. At the Chief Kawich mine the faults strike N. 50° W., parallelto the silicified-porphyry boundary, and dip 80° SW. At the Diamond N.o. 2 the faults dip 45° E. The step-like offsets in the silici- 

^ porphyry on which the Chief Kawich and the Gold Reed mines
KAWICH KANGE, ECONOMIC GEOLOGY. 113

are situated are rather suggestive of faulting, although the effect may 

be due to a chance distribution of several small masses of silicified 

porphyry.

The resemblance between the Kawich and Gold Crater deposits is 

close. It is probable that waters bearing silica, in solution arose 

along joint and fault planes and that silica more or less completely 

replaced the rock contiguous to the fractures. Pyrite was probably 

simultaneously deposited, partly in the country rock and partly in 

open fissures. Since the silicification the veins have been faulted. 

The kaolinization of. certain portions of the porphyry was probably 

contemporaneous with the surface alteration of the original sulphides. From the lean character of, the pyrite so "far encountered it 

is probable that the rich surface gold deposits have been concentrated from the pyrite .contained in many feet of porphyry which 

have been removed by erosion, but it is by no means impossible that 

rich pockets of gold may be found from time to time near the surface.

Water is obtained at Cliff Spring, 12 miles east of the settlement, 

and pinon .grows on the Kawich Kange 8 miles to the north. Tonopah is 70 miles distant by road. . »

SOUTHERN KAWICH.

In the blue-black Pogonip limestone on the northwest slope of 

Twin Peaks, 6 miles south of Kawich, prospects are located on a 

quartz vein 1£ feet thick. The quartz is strongly stained by limonite 

and is said to carry free gold.

AREAS FAVORABLE TO PROSPECTING.

The areas noted in the progress of work in which occur altered 

rocks of the same character as those Avhich accompany the ore deposits at the camps already described are shown in fig. 4. Other 

areas of similarly altered rock doubtless exist, although it is believed 

that the largest are mapped. Of the rhyolite areas shown those 

near Silverbow and Eden and east of Blakes Camp contain an unusual mimber of quartz veins. The monzonite porphyry in which 

the ore deposits of Kawich occur is confined to the immediate vicinity 

of the town. The areas of altered monzonite porphyry have already 

been located and the future of .this form of ore deposits depends 

on the development of these areas.

Quartz veins occur in the Paleozoic sedimentary rocks, particularly in quartzite. So far as seen these veins are narrow and of no 

great length, and with the exception of the Southern Kawich Veins 

the quartz is apparently barren. .Quartz A^eins, probably barren, on 

the western side of Quartzite Mountain contain tablets of specular 

hematite.

Bull. 308 07 M 8 - 
114 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

REVEILLE VALLEY.

Reveille Valley lies between the Kawich and" Reveille ranges. 

The depression is separated into two parts by a low gravel divide 

north of its center, the northern portion draining northward and 

the southern portion draining southeastward into Railroad Valley. 

The Recent gravels are probably nowhere thick in Reveille Valley. 

Basalt flows underlie much of the area and form hills in the valleys 

and scarps along the drain line. 'Fig. 9 is a section across the 

valley, drawn north of west to the Kawich Range from a point on 

the Reveille Range 6 miles north of Reveille Peak. A single mass zj O

of early Miocene rhyolite is exposed beneath the basalt northeast 

of Sumner Spring.

KAWICH VALLEY.

The Kawich Valley lies between the Kawich and Belted ranges. 

It is separated from Railroad Valley to the northeast by a low gravel 

divide and from Reveille Valley to the north by hills of basalt. 

Kawich Valley is notable for its even grade, since the mountains on 

either side have approximately an equal elevation and mass. Its

E

c

Kawich Range .2

^Rhyolite ' ' V '"'"

O 1 Z 3.4

Basalt

srniles

L

Reveille Range

Rhyolite

FIG. 9. Section across north end of Reveille Valley, showing an inclosed valley partially

underlain by basalt.

playas lie at an elevation of .about 5,300 feet above sea level.. A few 

rounded exposures of older alluvium lie 20 feet above the small 

play a on the road from Kawich to Indian Spring. These are similar 

to those of Gold Flat.

REVEILLE RANGE. 

TOPOGRAPHY AND GEOGRAPHY,

The Reveille Range is separated from the Pancake Rangfe on the 

north by a narrow transverse gap and from the Belted Range on 

the south by Railroad Valley. In former descriptions and in the 

parlance of prospectors the Reveille and the Belted ranges are 

merged into one, the name Reveille being applied not only to that 

range itself but also to the north end of the Belted Range. As 

here defined, each range is a unit, separated by a transverse valley 

from 2,500 to 3,000 feet below the crest line of the ranges. These 

two north-south ranges are, however, aligned, and the structure of 

the Paleozoic rocks indicates that, prior to the long period of erosion 

which preceded the Tertiary volcanisin they were connected.
REVEILLE RANGE, SEDIMENTARY ROCKS. 115

The Reveille is a narrow, rugged mountain range with a crest 

line of rather sharp peaks culminating near its south end in Reveille 

Peak, 8,900 feet high. The eastern slope, descending to the deep 

Railroad Valley, is the more precipitous. The crest line against 

which deep, narrow canyons head, is in places a knife-edge flanked 

on either side by cliffs hundreds of feet high. The more profound 

of these canyons are 1,000 feet deep and are notable for the forests 

of rhyelite spires which cover their precipitous sides. The rhyolite 

is everywhere characterized by a rugged topography. Fang Ridge 

is a prominent part of the range from which protrude fantastic 

domes and spires strikingly like the fangs and molar teeth of an 

ancient monster. The " teeth " are from 200 to 300 feet high. The 

smooth slopes and shallow, straight-walled canyons of the flanking 

masses of basalt, which in some cases almost bridge over the range, 

are in strong contrast Avith the intensely dissected rhyolite.

The crest line of the range is covered by a fair growth of pinon and 

juniper, which at the northern border of the area surveyed on the 

west side descend to the alluvial slopes. Several large springs are 

located at Old Reveille, 11- miles north of the boundar}^ of this area, 

and a pipe line extends from these to New Reveille.

GENERAL GEOLOGY.

The formations of the Reveille Range include, in ascending order, 

the Weber conglomerate, Pennsylvania!! limestone, rhyolite,- and 

basalt.

SEDIMENTARY ROCKS.

Weber conglomerate. North of the area mapped from Old Reveille 

to the summit, betAveen that town and New Reveille, the predominant 

formation is a white massive quartzite, of which from 1,000 to 2,000 

feet is exposed. If, as is apparently the case, this quartzite underlies 

the Penn.sylvan.ian limestone it is the Weber conglomerate, although 

lithologically it is more nearly related to the Prospect Mountain 

(Cambrian) or Eureka (Silurian) quartzite.

Pennsylvanian limestone. Overlying this quartzite, apparently 

conformably on the west side of the range near Reveille, is 2,000 feet 

or more of dark-gray to black compact, massively bedded limestone. 

With it are associated bands of black flint and thin beds of argillaceous limestone. The limestone is cut in every direction by veinlets of 

calcite. The formation is similar to the Pennsylvanian limestone of 

the Belted Range, and poorly preserved fossils from a bowlder near 

New Reveille are considered by Dr. George H. Girty to be probably 

of Pennsylvanian age. Inclusions of flint are common in the rhyolite, 

described in the following paragraphs, near its contact with the Paleozoic rocks,
116 SOUTHWESTERN NEVADA AND EASTEKN CALIFORNIA.

IGNEOUS ROCKS.

Rhyolite. The major portion of the Keveille Kange is composed 

of rhyolite, which has a flinty, glassy groundmass, flow banding 

being common. Gray and pink are the predominant colors, although, 

red, black, and brown are not unusual. Phenocrysts are abundant 

and equal the base in mass. Colorless or smoky quartz and glassy 

feldspar phenocrysts of medium size predominate over the smaller 

individuals of biotite. Weathered surfaces show feldspar whitened 

or represented by casts, biotite flush with the surface, and quartz in 

relief. Thin sections under the microscope present a brown, glassy 

groundmass, exhibiting well-defined flow flexures, and over small 

areas a spherulitic structure. A small portion of the feldspar is an 

acidic plagioclase, while many of the biotite phenocrysts were bent 

prior to the solidification of the lava. Magnetite, zircon, and apatite 

are also present.

The rhyolite is a series of flows, and in consequence over large areas 

it Aveathers like a well-bedded sedimentary rock, a resemblance magnified by the presence of a north-south sheeting. Vertical joints are 

locally-present, and where flow banding is not prominent the rhyolite 

weathers into spires from 30 to 150 feet high and from 5 to 25 feet in 

diameter. In places these are single and spring from a common base. 

Where no parting planes are prominent the rhyolite displaj^s the wellrounded domes and bosses characteristic of a granite country.

The rhyolite of the Reveille Range is similar lithologically to that 

of the Kawich Range and has suffered equal deformation and erosion. 

The two are doubtless contemporaneous in age and are probably early 

Miocene.

Basalt. Lying upon the rhyolite are basalt flows which usually 

occur flanking the range, but in one case extend from the eastern base 

across the crest line. The flows were once much more extensive and 

perhaps completely covered the range 4 miles north of Reveille 

Peak. Basalt also forms isolated hills in the alluvial deposits. . As 

shown in fig. 9, these are probably connected with flows on the 

flanks of the range. The basalt varies from a dense black rock to a 

vesicular slag of red color. The vesicles reach a maximum diameter

o

of 1 inch and are elongated in the plane of flow. The phenocrysts 

are subordinate in bulk to the groundmass, and include conspicuous 

gray or white striated feldspar laths up to three-fourths of an inch 

long, rather obscure yellow altered olivines, and black pyroxene columns. Weathered basalt breaks down into spheroidal masses surrounded by thin concentric shells.

On microscopic examination the rock proves to be an augite-olivine 

basalt with glassy base. Abundant plagioclase laths, fewer augite 

crystals, rounded olivines, and magnetites are the phenocrysts,
EEVEILLE KANGE, ECONOMIC GEOLOGY. 117

The basalt is similar lithologically to the later basalt and is probably of Pliocene age, since the amount of erosion suffered renders its 

effusion in Pleistocene time improbable.

STRUCTURE.

The Paleozoic rocks are folded into a monocline striking north and 

south and dipping 15° to 30° W., but a corresponding eastward 

dipping arm of an anticline may be covered by the rhyolite of the 

eastern side of the range. Minor faults are present. Prior to the 

effusion of the rhyolite the rocks formed a rugged mountain range. 

(See fig. 10.) After the outflow of the rhyolite the range was subjected to erogenic movements, the compress!ve force acting from the 

east or the west, and the mountains were again uplifted, the rhyolite 

was slightly crumpled, and a north-south sheeting was produced. 

When the basalt flowed out the range was rugged and probably approximately as high as at present. The small peak of rhyolite surrounded by basalt 6 miles west of north of Reveille Peak was probably never completely covered by basalt. A decided thickening of 

the basalt occurs at the base of the mountains, but the dip of the flow

Pennsylvanian limestone

Rhyolite - porphyry Webe^-3*^ 7 -' ~' N ^^K/X V/1 

dikes conglomerate_________ Rhyolite

3 miles

FIG. 10. East-west section across Reveille Range at northern boundary of area surveyed.

surface, in places 15° to 18°, is probably in part due to recent uplifts 

of the range. The vent from which the basalt was extruded was 

probably near the crest of the range 7 miles north of Reveille Peak.

ECONOMIC GEOIOGY.

The abandoned mining camp of Old Reveille lies 1-| miles north of 

the area surveyed. The Gila mine, one of the best known of those 

extensively operated thirty years ago, is situated in Paleozoic limestones and quartzites near the rhyolite contact. The ore occurs in 

quartz veins and stringers ramifying through brecciated zones in the 

Paleozoic rocks. The ores on the dump include malachite, azurite, 

cerussite, and galena, with quartz and gypsum as gangues. Malachite here and there coats the surface of the dump and has doubtless 

been deposited since the mines were abandoned. Recently considerable work has been done on similar deposits at New Reveille." The 

rhyolite of the Reveille Range, where examined, has not suffered the 

alterations which usually accompany ore deposits.

. ° During the field work, New Reveille was believed by the topographers to be outside 

the boundary of-the area mapped, but more accurate computations have placed it within. 

In the pressure of reconnaissance work the mines were not examined.
118 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

RAILROAD VALLEY

Railroad Valley is a long depression between the Pancake and Reveille ranges on the west and the Grant and Quinn Canyon ranges on 

the east. Its south end lies in the northeast corner of the area 

mapped and is of interest because it has two well-developed northsouth drainage lines. The play a is 5,106 feet above sea level.

BELTED RANGE. 

TOPOGRAPHY AND GEOGRAPHY.

The north end of the mountain range east of Kawich Valley is 

called b}^ prospectors the Reveille Range, while the south end is 

known as the Belted Range. The undesirability of using two names 

for a single mountain range is patent, and as the range immediately 

north has long been called the Reveille Range the name Belted will 

here be used for the whole-range east of Kawich Valley. Thus defined, the Belted Range extends from the junction of Reveille, Kawich, and Railroad valleys southward 49 miles to Shoshone Mountain, which trends east and west. From the north end of the range 

the crest courses southward to Wheelbarrow Peak, where it turns to 

the south-southwest. The range in the latitude of Oak Spring is 

13 miles wide. The crest line has an average elevation of 7,000 to 

8,000 feet and lies in a median position, except in the central portion 

of the range, where the long eastward-sloping basalt mesas throw it 

nearer the western base. Wheelbarrow Peak and- a dome 3 miles 

north of it reach an elevation of 8,600 feet; Belted Peak is 8,340 feet 

high.

A gentle valley separates the Pogonip limestone from the rhyolite 

at the north end of the range and a parallel detrital embayment lies 

west of Cliff Spring. The Pogonip limestone forms hills and ridges 

elongated parallel to their strike. The Pennsylvanian limestone where 

metamorphosed by granite forms rugged ridges, but elsewhere its 

topography is much less accentuated, the ridges being comparatively 

low and smooth. Minor dip-slope elements are present in all the 

limestone formations, as Avell as in the earlier rhyolite near Cliff 

Spring. The Weber conglomerate forms broad domelike ridges of 

gentle slope. The earlier rhyolite forms domes and cone-shaped hills 

with which cliffs are combined near the crest line. Vertical joints 

are less prominent in the earlier rhyolite of the Belted Range than in 

that of the Reveille Range, and in consequence spires are uncommon 

except to the north of Wheelbarrow Peak. The later rhyolite caps 

prominent buttes, like Oak Spring Butte, whose sides are formed by 

the soft Siebert lake beds. The basalt mesa country is characterized 

by level slopes deeply cut by straight-walled canyons.
BELTED RANGE, GENERAL GEOLOGY. *. 119

Remnants of a more mature mountain surface surrounded^by recent 

cliffs and rugged hills oecur on Wheelbarrow Peak, on the high peak 

3 miles north of it, and in the rhyolite area 5 miles west of south of 

Wheelbarrow Peak. The old land surface extends 2 miles east of the 

first-named points. The smooth and gentle slope of this surface is 

shown on the map, although it is somewhat obscured by the use of 100- 

foot contours on so small a scale as 1 inch to 4 miles. These mature 

.areas are characterized by few and inconspicuous rock outcrops and 

a deep soil covered by grass and trees. The contrast between this 

topography and the sharp ridges and cliffs, practically all a single 

rock exposure, of the younger topography is very great. Since this 

old mountain surface developed the Belted Range has been tilted to 

the east and the older surface has been completely removed from the 

west versant of the range. (See fig. 11.)

The range north of Belted Peak is bare, but south of this point 

there is a fair growth of pinon and juniper above 6,500 feet, although 

the southern quartzite and slate hills are as a rule without timber. A 

few oak shrubs grow in moist places. The tree yucca and the Spanish bayonet are common on the upper alluvial slopes in the vicinity

.OLD TOPOGRAPHY__

FIG. 11. East-west profile across Belted Range 3 miles north of Wheelbarrow Peak, 

showing mature character and present eastward tilt of Pliocene surface.

of Oak Spring. Cliff and Indian springs each flow about 500 gallons of water per day; Wheelbarrow Spring is weak and is probably 

dry during a part of the summer. Oak, Whiterock, and Captain 

Jack springs all flow from the Siebert lake beds. Oak and Whiterock springs each flow from 1,500 to 3,000 gallons a day; Captain 

Jack Spring is considerably smaller.

GENERAL GEOIOGY.

The formations of the Belted Range, from the oldest to the young-. 

est, are as follows: Pogonip limestone, Weber conglomerate, Pennsylvanian limestone, monzonite, post-Jurassic granite, andesite, 

earlier rhyolite, Siebert lake beds, later rhyolite, and basalt.

SEDIMENTARY ROCKS.

Pogonip limestone. The Pogonip limestone forms low hogback 

hills on the Avestern border of the Belted Range from a point 1 mile 

north of the Kawich-Indian Spring road to the north end of the 

range. Inclusions of the same rocks occur in the rhyolite and are 

particularly abundant near its contact with the limestone. A thick-
SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

ness of 4,000 feet of stratified rocks is exposed from a point 2 miles 

southwest of Belted Peak westward to the detrital deposits mantling 

the range. The section contains no important stratigraphic break, 

and while shales and quartzites are interbedded, limestone is the predominant rock. The limestone is typically fine grained, crystalline, 

and dark gray or black in color. The bedding planes are as a rule 

massive. Thinner beds of a yellow or brown, more coarsely crystalline limestone are also present, and a single stratum of oolitic lime-, 

stone was observed. Intraformational conglomerates and cross-bedding, each an indication of shallow-water deposition, occur throughout the section. Nodules and fewer lenses of black chert are present 

in places. The nodules are in part original, but since the bedding 

planes in certain instances cut them, they are also in part secondary. 

A related phenomenon is the silicification of certain beds of limestone to a compact, conchoidally fracturing black jasperoid. The 

limestones are cut in all directions by veinlets of coarsely crystalline 

Avhite calcite, and these were evidently formed at several distinct 

periods, since they cut and, in places, fault one another.

Quartzite forms a prominent bed near the middle of the Pogonip 

limestone, and in many places shale- and quartzite beds are laminated 

with limestone near the top of the series. The quartzite is usually 

light in color and fine grained, although some beds are stained red by 

hematite and others are medium grained. Quartz veinlets with 

crystal-lined vugs cut the quartzite. Much of the quartzite is argillaceous and grades into slaty shales, which are thin bedded, fine 

grained, and, as a rule, olive green in color, although locally black or 

brown. Muscovite films are developed on the parting planes of both 

the shales and the more argillaceous quartzites.

This sedimentary series was evidently laid down in a sea of moderate depth which at times was shallow. The conditions were on the 

whole favorable to the deposition of limestone, although at intervals 

fine fragmental material was carried into that portion of the ancient 

sea now occupied by the Belted Kange. This limestone closely resembles the Pogonip limestone of the Panamint Range, although from 

its great thickness it may extend well down into the Cambrian. Mr. 

E. O. Ulrich identified, from material collected by the writer, Girvanella-likQ forms of smaller size and denser structure than those 

collected from the Cambrian limestone of the Silver Peak Range. 

lie considers these probably of Ordovician age.

Weber conglomerate. The Weber conglomerate forms the crest 

and eastern slope of the Belted Range south of Whiterock Spring, 

as well as broad ridges west of Oak Spring and north of Whiterock 

Spring. The formation includes a sandstone from 800 to 1,000 feet 

thick and an overlying shale from 300 to 500 feet thick. While 

sandstone predominates in one member and shale in the other, some
BELTED RANGE, SEDIMENTARY ROCKS. 121

bands of shale are included in the sandstone, as well as sandstone in 

the shale member.

The reddish or brownish sandstone is either a quartzose rock or an 

arkose of medium grain. It is somewhat indurated, but when crushed 

fracture occurs around the grains rather than through them, as in 

quartzite. The indurated sandstone grades into conglomeratic bands 

which contain well-rounded pebbles up to 4 inches in diameter. These 

pebbles are smoky quartz of vein or pegmatitic origin, gray banded 

flint, pinkish or white quartzite, and black jasperoid seamed with 

quartz veinlets. The quartzite and jasperoid closely resemble the 

Cambrian rocks of other portions of the area, and if such is their age, 

it indicates that between the deposition of the Cambrian and the Carboniferous sediments a. period of deformation intervened. The metamorphism of these supposed Cambrian pebbles is such that the beds 

from which they were derived must have been folded and eroded prior 

to'the deposition of the Carboniferous strata. The arkose grades into 

thin-bedded shale of olive-green, brown, purple, or light-gray color.

The Weber conglomerate appears to lie conformably beneath the 

Pennsylvanian limestone, and hence occupies a position similar to that 

of the Weber conglomerate at Eureka, Nev., as described by Hague.0 

Near Whiterock Spring some peculiar f ucoid-like markings occur on 

a light-gray shale. Mr. E. 0. Ulrich states that these resemble 

Palceodictyon and are probably of Carboniferous age.

Pennsylvanian limestone. Pennsylvanian limestone forms the 

prominent ridges north of Oak Spring and the low ridges south of the 

ifame point. It also covers considerable areas too the east and northeast 

of Tippipah Spring. Approximately 2,500 feet of this limestone is 

exposed in the Belted Range, although the top of the formation is not 

present. It is a fine- to medium-grained gray limestone of dense texture. Certain layers in fineness of grain and density resemble lithographic limestone. Much of it is magnesian, and other portions 

when struck Avith the hammer smell oily. Small black flint nodules 

occur in some beds, and white calcite veinlets are locally abundant. 

The limestone is for the most part rather heavily bedded, although 

inter bedded shaly layers are fine bedded.

Intraformational conglomerates occur at several horizons, and near 

the center of the section as exposed is 55 feet of limestone conglomerate. 

The included pebbles, which reach a maximum diameter of 4 inches, 

are jasperoid and quartzite, probably of Cambrian age, and limestone, 

probably from the lower part of the Pennsylvanian section. It seems 

likely that this conglomerate merely indicates shallow-water conditions and not an important stratigraphic break, since Pennsylvanian 

fossils occur above and below it. Above this bed numerous thin layers, 

of similar conglomerate and shale are interbedded with the limestone.

0 Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, pp. 91-92.
122 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The Pennsylvania]! limestone appears to overlie the Weber conglomerate conformably. The formation is fossiliferous, and collections 

were made 4 miles south of Oak Spring and at several horizons 

northeast of Tippipah Spring. Dr. George H. Girty kindly made 

the following determinations of Pennsylvania!! fossils, the first four 

lots being found beneath the limestone conglomerate and the-fifth 

above it.

Fossils from Pennsylvania.!!, limestone 'in Belted Range. 

LOT 1.

Fenestella sp. Froductus sp. 

Rhombopora sp. Avicullpecten? sp. 

Chonetes sp. Phillipsia sp. 

Productus cora?

LOT 2

Fiisulina sp. . . Marginifera? sp. 

Rhombopora sp. Serninula sp. 

Archaiocidras sp. Aviculipecten sp. 

Derbya? sp.

LOT 3.

Chonetes sp. art. C. permianus. Leda? sp. 

Seminula sp.

LCT 4.

Zaphrentis sp. Marginifera? sp.

Rhombopora sp. Amboccelia? sp.

Stenopora sp. cf. S. carbonarla. Derbya? sp.

LOT 5.

Rhombopora sp. Productus sp. cf. P. semireticulatus. 

Stenopora? n. sp. Productus nevadensis ?

Siebert lake beds. Siebert lake beds cover considerable areas north 

of Oak and.Whiterock springs, and a .number of small outliers occur 

on the Carboniferous rocks near by, indicating that the lake beds 

were at one time continuous with those of Pahute Mesa. Another 

outcrop lies south of Wheelbarrow Peak, and to the east there are 

smaller areas not mapped.

A section at Oak Spring is as follows:

Section at Oak Spring.

Feet. 

Later rhyolite______________________________________ __ 250

Well-bedded, incoherent sandstones and conglomerates; white with some 

dark gray, bands. Many of the layers, which are from 2 to 4 feet thick, 

show cross-bedding. Crystals of glassy feldspar, quartz, and biotite are 

abundant in some beds and lacking in others. The pebbles in the conglomerate for the most part are small, but some of them reach 6 inches 

in diameter__________________________________________ 200

Later rhyolite__-____________ ..__ _ _ ________ _ 40

White sediments as above_______________________________ 100

Later rhyolite_-__-_-_-______:__________________________ 60

Salmon pink, white, and yellow sediments as above___________'______ 280
BELTED BAttGE, IGNEOUS KOCKS.

Chalcedonic quartz, in considerable quantities, is deposited in the 

cavities of the sediments in this vicinity. The conglomerate near 

Wheelbarrow Peak incloses many bowlders of earlier rhyolite from 

3 to 4 feet in diameter. Such bowlders protect the softer sandstone 

immediately beneath from erosion, and in consequence they form 

in places the caps of columns 20 feet high.

These beds appear to be contemporaneous with those of Pahute 

Mesa and Shoshone Mountain, and like them are considered the 

equivalent of the Siebert lake beds/1 of Miocene age, at Tonopah.

IGNEOUS ROCKS.

Monzonite. Included in the granite near Oak Spring are fragments of a fine-grained, dark-gray, granular igneous rock. On microscopic examination this proves to be a hornblende-biotite monzonite. 

Titanite and magnetite are accessory minerals.

Granite. A stock of granite, approximately three-fourths of a mile 

in diameter, cuts the Pennsylvania!! limestone 24* miles south of Oak 

Spring and sends many apophyses into it. The granite, forming a 

dome, set with many exposures in blocklike masses, rises above the 

near-lying limestone. In the eastern portion of the area it has a 

sheeting clipping eastward, parallel to the limestone contact. The 

granite tends to weather into spheroidal masses, although some of the 

joint blocks have their corners but slightly blunted.

This rock is a light-gray porphyritic granite, characterized by 

unusually large feldspar and quartz phenocrysts, which lie in 

a medium- to coarse-grained matrix of white feldspar and biotite. 

Quartz is an unimportant constituent of the groundmass, the silica 

having largely separated out in the older crystals. Phenocrysts of 

pale-pink feldspar, of perfect outline, reaching a maximum length 

of 4 inches, are the most prominent, in places forming one-third of the 

rock surface. The feldspar phenocrysts inclose minute blades of biotite zonally arranged. The slightly smoky quartz phenocrysts are 

perhaps more numerous, though smaller than those of feldspar, their 

maximum diameter being one-half inch. Phenocrysts of mica 1 inch 

in diameter are rare. Both feldspar and quartz phenocrysts protrude on weathering and finally drop out. The granite is in places 

deeply weathered. The smaller feldspars are more kaolinized than 

the large crystals, while the biotites are bronze-brown in color and are 

surrounded by hematitic stain which has separated from them. Under the microscope this rock-proves to be a biotite-hornblende granite, containing considerable plagioclase and hence leaning toward 

quartz monzonite. The texture is granular and hypidiomorphic, on 

account of the presence of plagioclase laths in the groundmass and of

0 Spun-, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 51.
124 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

the large zonally built orthoclase phenocrysts. The accessory minerals include titanite, zircon, and apatite.

The granite is cut by dikes of aplite rather poor in biotite. Pegmatite dikes are common. The coarsely granular pegmatite is composed of feldspar and quartz anhedra which reach a maximum diameter of 12 inches. Limonite pseudomorphs after pyrite are inclosed in 

both quartz and feldspar grains. Graphic granite, with letters onefourth inch across, is a less common variety of pegmatite. A third 

facies is an aggregate of coarse feldspar individuals with a few quart/, 

anhedra. Embedded in the feldspar are numerous biotite blades from 

one-half to 1 inch long. Under the microscope this rock is seen to 

 be composed of large plates of microperthitic orthoclase intergrown 

with quartz in the manner characteristic of graphic granite. Between these large areas is a granular mosaic of orthoclase and quartz.' 

A few needle-like blades of biotite and grains of magnetite are also 

present.

Next to the limestone the granite becomes fine grained, although the 

phenocrysts retain their size and in consequence probably solidified 

prior to the intrusion of the magma into the limestone. Limonite 

cubes after original pyrite are particularly common near the contact. 

The limestone near the contact is metamorphosed to a fine-grained 

marble of white color, which in some localities contains lenses of 

pale-gray marble. In less pure layers fibrous tremolite, locally in 

globular masses, is developed. Other layers are colored greenish yellow by serpentine and chlorite. The more impure layers are changed 

to grdssular garnet-, forming a heavy dark-brown rock. This garnet 

in cavities occurs as beautiful citron-yellow crystals. A heavy rock 

of deep-green color also proves, on microscopic examination, to be 

composed of gar-net, which even in thin section has a decided green 

tinge and which is associated with calcite, staurolite, tremolite, quartz, 

zoisite, titanite, and iron ore. Another thin section of altered limestone proves to be a finely granular marble, between the calcite grains 

of Avhich are tremolite and colorless garnet grains and a few irregular areas of chlorite. Still another thin section is composed of large 

plates of calcite and quartz, in which chlorite, tremolite, and colorless garnet are micropoikilitically inclosed. The shale of the Weber 

conglomerate is metamorphosed to a slaty shale, in which nests of 

tiny muscovite tablets are developed. Other facies contain numerous 

pyrite crystals. The most interesting metamorphosed shale is a black 

argillite, in which are many rectangular white columns with black 

cores. Under the microscope these columns embedded in the carbonaceous argillite are seen to be chiastolite, a variety of andalusite. 

On its edges this mineral is somewhat altered to muscovite.

This coarse granite porphyry, characterized by two generations of 

mineral solidification and associated with aplitic and pegmatitic
BELTED RANGE. IGNEOUS ROCKS. 125

fades, clearly bridges the interval between granite and granite 

porphyry. The granite cuts Pennsylvania!! limestone and is doubtless 

one of the post-Jurassic series. It rather strikingly resembles the 

granite outcropping 5 miles north of Ammonia Tanks.

Several smaller masses of similar granite occur near the main 

stock. The mass 1-i miles east of south of Oak Spring lacks phenocrysts, and, since it is only 200 yard's in diameter, is very similar in 

other respects to the contact facies of the main mass. It is medium 

grained or-in a few places medium coarse grained. The granite is 

more altered than that of the main mass, and the mica is usually 

muscovite, apparently secondary to biotite. The granite grades into 

a coarse pegmatite, which in turn grades into pegmatitic quartz, 

each of which contains pyrite altered to limonite. The larger of the 

limonite cubes are one-half inch in diameter, and the pj^rite was 

undoubtedly an original constituent of the pegmatite. The pegmatite 

has some miarolitic cavities into which quartz and feldspar crystals 

1 inch long project. A third mass of granite lies between the two 

already described, and two small outcrops isolated in the alluvial 

deposits appear to have been separated from the largest mass by 

erosion.

Andesite. About 2-| miles west of Wheelbarrow Peak is an exposure of andesite partially covered by the earlier rhyolite flows. 

The rock has a dense reddish-black groundmass, in which are embedded many medium-sized striated feldspar phenocrysts, Avhich are 

either glass}7 and colorless or cloudy and white. Hand specimens 

suggest the presence of hornblende. Under the microscope the 

groundmass appears as a glass containing many tiny laths of plagioclase. The phenocrysts are plagioclase (labradorite), brown hornblende, with a reaction rim of magnetite, which, in some instances 

completely replaces the hornblende, and a little augite. The plagioclase phenocrysts, some of which are complex crystals, are somewhat 

rounded by magmatic corrosion and, as a rule, show beautiful zonal 

groAvth. Inclusions of a greenish-gray andesite, rather similar, altho 

with smaller feldspar phenocrysts, occur in rhyolite near Cliff Spring. 

In the gravels of the valley 1-| miles west of Wheelbarrow Peak are 

bowlders of a greenish-gray andesite. Phenocrysts of altered 

greenish-white feldspar are abundant, and associated with these are 

biotite and either hornblende or pyroxene phenocrysts. The source 

of this andesite is unknown. It strikingly resembles the postrhyolitic andesite of the Kawich Range and may perhaps be younger 

than the earlier rhyolite of the Belted Range. Certainly in this 

range andesite older than the rhyolites occurs, while andesitic eruptions may also have followed the rhyolitic effusion.

Earlier rhyolite. The earlier rhyolite is the predominant rock 

of the northern part of Belted Range, and. from its rather striking
126 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

bands of red, purple, gray, and brown, the name of the range is 

derived. Of the many rhyolitic f acies' perhaps the most common 

has a rather dense reddish groundmass, in which are embedded 

medium-sized phenocrysts which equal or exceed it in bulk. The description of the phenocrysts of the earlier rhyolite of the Kawich 

Range applies almost equally well to those of this formation. Biotite, 

however, is the predominant plienocryst in a facies outcropping 1.! 

miles northwest of Cliff Spring. Hornblende phenocrysts are very 

rare. The rhyolite varies in color from white, gray, brown, or purple to black. In texture the groundmass varies from glassy with 

^yell-developed flow lines, perlitic cracks, and spherulites through 

pumiceous to lithoidal. The rhyolites in the vicinity of Wheelbarrow 

Peak are more glassy and appear to be poorer in phenocrysts, particularly quartz. Chalcedony is abundart on joint planes, and throughout 

the area surveyed a-n unusually great development of this form of 

secondary quartz is associated with the more glassy facies. The only 

thin section examined proved to be a normal rhyolite with partially 

devitrifled brown glassy groundmass.

Fui. 1:!. Kast-west section across Belted Range through Belted 1'eak.

Near Cliff Spring the red rhyolite of the cliffs has been bleached 

to a yellowish white by surface waters along joints-and irregular 

cracks. The contact between the bleached and unbleached portions 

ifi unusually sharp. The joints are often offset regularly, and the 

bleaching follows such offsets. Microscopic examination shows that 

the bleaching is due to the removal of the hematite coloring matter 

of the somewhat devitrified glass. It is probable* in consequence, 

that considerable portions of the white chalky rhyolite of the range 

have been produced by similar bleaching.

Columnar jointing, due to contraction during cooling of the lava, 

is particularly well developed on a hill isolated in the wash, 1-| miles 

west of Cliff Spring, to the north of the road. The columns are from 

6 to 12 inches in diameter and vary in position from vertical to 

horizontal, intermediate directions being common.

The rhyolite as seen on either flank of the range is clearly a flow, 

which in places is over 2,000 feet thick. Belted Peak has some of the 

characteristics of a vent (fig. 12), although the rhyolite may have been 

extruded from a long fissure near and parallel to the crest line, a suggestion which, however, requires for proof more careful field observa-
BELTED RANGE, IGNEOUS ROCKS. 127

tion than was possible in the present reconnaissance. The relations 

between the small rhyolite mass 2 miles south of west of Belted Peak 

and the Paleozoic rocks are poorly exposed, but the rhyolite probably 

represents the lower portion of the rhyolite flow rather than a dike, 

since no dikes were observed in sedimentary rocks to the west.

The earlier rhyolite is similar lithologically to that of the Ivawich 

 and Reveille ranges, and like them lies beneath the Siebert lake beds. 

' All three are practically of the same age, probably'early Miocene.

Later rhyolite. Later rhyolite caps Oak Spring Butte (see fig. 13) 

and forms a lower bench on the same butte and a similar bench on the 

ridge north of Whiterock Spring. It also covers large areas to the 

west, on Pahute Mesa. The predominant facies is a resinous or glassy 

rhyolite composed of light-gray and black flow bands and lenses. 

Peiiitic parting is locally present. Medium-sized phenocrysts equal 

the groundmass in bulk and in the hand specimen consist of unstriated feldspar, often showing beautiful - color plays, and colorless 

quartz in rounded grains or dihexagonal pyramid and prism crystals. 

The microscope shows the presence also of smaller phenocrysts of

FIG. 1'*. North-south section through Oak Spring Butte, Belted Range.

deep-green augite and biotite. Another facies is a reddish-gray 

aphanitic rock with a fe\v phenocrysts of feldspar and black mica. 

Some quartz and plagioclase phenocrysts are also visible under the 

microscope in the devitrified-glass groundmass.

The later rhyolite is a flow, in part contemporaneous with the Siebert lake beds, but mostly younger. It is therefore of middle and 

possibly late Miocene age. It is contemporaneous with the rhyolite of Shoshone Mountain and Pahute Mesa, and probably with the 

later rhyolite of the Kawich Range and of Stonewall Mountain and 

with the later rhyolite and biotite latite of the Amargosa Range.

Basalt. Basalt covers considerable areas near the middle of the 

Belted Range. The low hills at the north end of the range also 

appear from a distance to be basalt. The basalt, where examined, is 

lithologically similar to and probably contemporaneous with that of 

the Reveille Range, and, like it, overlies the eroded earlier rhyolite. 

It is probably of late Pliocene age. The surface of the Belted Range 

was, however, probably less rugged than that of the Reveille Range 

at the time of the basalt effusion.
128 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

STRUCTURE.

The Pogonip limestone, as exposed in the Belted Range, lies in a 

monocline which strikes north and dips 20° to 30° W. next Kawich 

Valley and TO 0 W. southwest of Belted Peak. Superimposed upon 

the main fold arc a few minor isoclinal folds of similar strike, as well 

as gentle cross folds. This is probably the eastern limb of a broad 

syncline which underlies Kawich Valley and which has for its western limb the eastward-dipping monocline of Quartzite Mountain. 

A number of dip faults of east-west strike cut the Pogonip limestone, 

Avith a uniform offset of the beds on the north side of the faults to the 

east. The lateral displacement of the largest faults shown on the 

map is 100 feet.

The Carboniferous rocks are bent into rather open folds, which 

near Oak Spring have north-south axes and to the north of Tippipah 

Spring, as a rule, course northeast and southwest. Small isoclinal 

folds passing into overthrust faults occur, particularly in the shale. 

The intrusion of the granite considerably disturbed the strata on its 

north side, Avhile the beds on the other sides Avere but little affected. 

The folding was evidently in part prior to the granite intrusion, in 

part due to it, and in part later, since the granite in places has a 

sheeting parallel to the bedding planes of the limestone. Since the 

folding of the strata some normal faults have been formed.

Prior to the extrusion of the earlier rhyolite in the northern part 

of the.range the Pogonip limestone formed a mountain range possibly someAvhat loAA^er than the present Belted Range, with its crest 3 

miles AA7 est of the present crest line. In the southern part of the range 

prior to the deposition of the Siebert lake beds the Carboniferous 

rocks had at least a gently accentuated surface, since numerous hillocks of the older rocks protrude through the younger sediments north 

of Tippipah Spring. The Siebert lake beds at Oak Spring have been 

uplifted without important flexure. After this uplift erosion developed a mature mountain surface, Avhich prior to the extrusion of 

the basalt was tilted to the east. The basalt floAvs on the east side of 

the range dip to the east at the rate of 500 feet to the mile, possibly 

indicating that the eastward tilting continued after the outfloAV of the 

basic lava.

ECONOMIC GEOLOGY.

OAK SPRING.

 At Oak Spring a number of prospects are being developed. In 

granite 1-| miles nearly due south of Oak Spring quartz veins of 

.pegmatitic origin, from 1 to 3 feet wide, striking N. 30° E. and dipping 15° NW., have been staked. The quartz is Avhite and slightly 

sugary and contains vugs Avith small quartz crystals. Some of it is 

intensely 'brecciated, the cracks being stained by hematite and limo.n-
BELTED KANGE, ECONOMIC GEOLOGY. 129

ite; Sulphides are sparingly present and consist of pyrite, chalcopyrite, galena, and zinc blende, named in the order of their abundance. From these hematite, limonite, malachite, azurite, and cerussite are derived as secondary minerals. A coating of an unctuous 

mineral in silvery tablelo frosts some of the cavities. The values in 

this locality are said to be gold with less silver. The deposits are 

genetically similar to the mineralized pegmatite veins of Lime Point, 

in Slate Ridge, and the sulphides were probably introduced into the 

pegmatitic quartz after its solidification.

The pegmatitic quartz veins abundant in a small granite mass 

three-fourths of a mile east of south of Oak Spring contain pyrite 

crystals, as do the less acidic pegmatites and the surrounding and 

genetically related granite. The quartz is said to carry good gold 

and silver values, presumably in the pyrite.

About 300 yards southwest of Oak Spring and down the same ridge 

is a 25-foot shaft in Pennsylvanian limestone, here locally horizontal. 

A vein 2 feet wide, which strikes N. 35° E. and dips 70° NW., cuts 

the limestone. The vein is formed of malachite, chrysocolla, and a 

jaspery quartz, which is deeply stained by blotches of manganese 

dioxide and limestone. Striking vugs in malachite lined with later 

azurite which in turn is covered with clear quartz crystals resemble 

copper-sulphate crystals. Massive yellowish-gray cerussite (lead carbonate) is also present. A yellowish-green, finely scaly coating on 

fractures was determined by Mr. Waldemar T. Schaller to be either 

emmonsite or durdenite, hydrated ferric tellurites. The presence 

of the compound of tellurium is of considerable interest, since it indicates the presence of a telluride among the original minerals of the 

post-Jurassic ore deposits. Emmonsite is one of the last secondary 

minerals to form and coats both jaspery quartz and chrysocolla. 

Postmineral faulting has occurred. The secondary minerals, which 

alone are seen, partly replace the limestone and partly fill preexisting cavities.

The so-called turquoise mine at Oak Spring is a small cut in the 

nietamorphic Pennsylvanian limestone 1-| miles south of the spring 

and three-fourths of a mile from .the granite contact. Two veins 

strike north and south and dip 65° W., apparently parallel to the 

bedding of the limestone, which is here partially marmorized and 

silicified. The wider vein varies in width from. 2 inches to 1 foot and 

can be traced several hundred feet. Four feet away is a parallel 

vein, the two being connected by a few chrysocolla stringers. The 

veins are composed of a mottled mosaic of chrysocolla and a dark 

compact jaspery quartz, stained in some places by limonite and in 

others by manganese dioxide. The chrysocolla is usually verdigris 

green, although picked pieces are a beautiful robin's-egg blue, The 

Bull. 308 07 M 9
130 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

substance'is usually opaque, but some is slightly translucent. The 

chrysocolla is commonly massive, locally with a botryoidal structure, 

and in some massive phases an occasional cleavage face is seen. It 

is cut by veinlets of manganese dioxide and"white calcite or quartz. 

Chrysocolla veinlets of slightty different color cut one another, 

showing that the formation of this mineral extended over a considerable period. Associated with it is a crystalline, bottle-green, semitransparent mineral whose cleavage faces reach a length of one-half \ 

inch. A radial structure is observed in places. This mineral is "^ 

embedded in the chrysocolla or cuts it in veins and is of practically 

contemporaneous age. It is probably brochantite, a hydrous sulphate of copper. Both the chrysocolla and the brochantite were 

determined by Mr. Waldemar T. Schaller. Postmineral faults cut the 

veins and parallel them. Pieces of blue chrysocolla closely resemble 

turquoise, and several hundred pounds of the material have been sold 

for this gem. The mineral takes an excellent polish. The largest 

piece of pure chrysocolla seen was 6 by 3 by 2 inches.

In these copper deposits the minerals exposed are all secondary. 

Malachite, chrysocolla, brochantite, cerussite, a jaspery quartz, and 

limonite seem practically contemporaneous. There is considerable 

evidence that the" formation of the copper minerals and the jaspery 

quartz extended over a considerable period, during which some fracturing occurred and in consequence the relations between these minerals are complex. They partly replace the limestone and partly fill 

fissures. Azurite, emmonsite, quartz, and calcite are of later origin.

.Narrow seams and veins of quartz are rather widely distributed in 

the Pennsylvania!! rocks, particularly near granite intrusions. In 

the slaty shales and quartzites throughout the southern portion, of the 

.range such veins occur. A quartz vein 2 inches thick which carries 

some pyrite cuts the shale one-half mile south of Whiterock Spring. 

Specimens of quartzite, which evidently came from the quartzite to 

the north, were found at Tippipah Spring. These were rather 

strongly stained by malachite and hematite.

Oak Spring .furnishes sufficient good water for domestic purposes, 

iind there are several other springs in the general vicinity. Oak 

Spring Butte is timbered to some extent. Calientes, on the San 

Pedro, Los Angeles and Salt Lake Railroad, is the natural shipping 

point.

OTHER AREAS. <

\

Prospects are located on either side of the road from Kawich to 

Cliff Spring, near the eastern border of the Pogonip limestone. Thesupposed ore is in part a fine-grained quartzite and in part vein 

quartz, in which are small disseminated iron-pyrite cubes and thin 

stringers of pyrite. The veins where examined are thin.
PAHUTE MESA. 131

Eeefs of silicified rhyolite similar to that of the Kawich Range 

occur south of Belted Peak. The alteration of the rhyolite is strikingly like that at Silverbow, Eden, and other mining camps situated 

in rhyolite, and the groun.d is worthy of prospecting. Over a considerable area east and southeast of Belted Peak; near the boundary 

of the area mapped, the rhyolite appears in a distant view from its 

color and topography to be much altered.

PAHUTE MESA. 

TOPOGRAPHY AND GEOGRAPHY,

The name Pahute Mesa is applied to the lava-capped table-land 

stretching from Stonewall Mountain on the northwest to the Belted 

Range on the southeast, a distance of 48 miles. The mesa is 12 miles 

wide except near its center, Avhere Tolicha Peak cuts it into two portions. Notwithstanding this break ^these divisions are so similar, 

both topographically and geologically, that it is convenient to describe them under a single name.

Pahute Mesa consists of a series of benches one above another, the 

surfaces of which are determined by resistant flows of lava (PI. II, 

A ). These level benches are trenched deeply by canyons, while hills 

of older rocks and cones, the vents of the lavas, rise from their surfaces. Southeast of Stonewall Mountain the mesa has an average 

elevation of 5,500 feet. It gains in altitude to the southeast and near 

the Belted Range the highest mesa bench is 7,500 feet high. The 

southward-facing scarp is 1,500 feet high.

The western portion of the mesa is without vegetation other than 

sage and related shrubbery and the yucca. The higher portions of 

the eastern edge are, on the other hand, covered with a fairly heavy 

growth of pinon and juniper, and grass grows luxuriantly in the 

higher valleys, making this portion of Pahute Mesa the best winter 

range in the area mapped. The mesa has no large springs, Pillar 

Spring containing less than 50 gallons of water. A well sunk in a 

canyon 3 miles north of east of Gold Center yields about 300 gallons 

of water a day. It is 90 feet deep and passes through Recent gravels 

into tuffaceous sediments beneath the basalt. Tanks are common 

on the surface of the mesa, but in summer, with one probable exception, these are dry. A little bad water can be procured, probably 

throughout the year, by digging in the gravels at Ammonia Tanks. 

On account of the lack of water Pahute Mesa is more dangerous in 

summer than Death Valley.

GENERA! GEOLOGY.

On account of its inaccessibility and the comparative simplicity of 

its geology, but little time was devoted to the mapping of this region. 

While many inaccuracies exist in the geologic boundaries as here laid
132 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

down, they broadly represent the main features. The latest rhyolite 

and later tuffs beneath the basalt in the northwestern portion of the 

mesa are not differentiated from the basalt, while the separation of 

the Siebert lake beds and the middle rhyolite near the Belted Range 

is only approximate.

The list of the formations of Pahute Mesa, from the oldest to the 

youngest, is as follows: Mica schist, pre-granite monzonite, postJurassic granite, earliest rhyolite, biotite andesite, Siebert lake beds, 

middle rhyolite, latest rhyolite, later tuffs, and basalt.

METAMOIU'HIO ROCKS.

schists. At Trappinans Camp the granite contains fragments 

of mica schist, and an outcrop several hundred yards in diameter, 1 

mile east of Trappmans Camp, may extend eastward a considerable 

distance beneath the Tertiary lavas. These rocks are crenulated and 

foliated schists. One facies is a dark-brown schist apparently composed of tiny plates of biotite and muscovite well arranged in the 

plane of foliation. The microscope shows that the two micas are distributed in rather distinct bands parallel to one another. Andalusite, 

sillimanite, and finely divided magnetite are present as accessories. 

Another facies is a silvery schist composed of muscovite, Avith here 

and there an ellipsoidal aggregate of deep-green chlorite. Under the 

microscope this proves to be a schist composed of the essential constituents, muscovite, chlorite, and quartz, and the accessory constituents, sillimanite, zircon, andalusite, and rutile. Nothing is known 

concerning the age of these intensely metamorphosed rocks beyond the 

fact that they are much older than a granite of supposed post-Jurassic 

age. They are perhaps of Cambrian age, since they somewhat resemble the more metamorphosed Cambrian schists near granite at Gold 

Mountain.

SEDIMENTARY ROCKS.

Paleozoic quartzite. Prospectors report that quartzite occurs on 

the north slope of Mount Helen, but the locality was not visited by 

the writer.

Siebert lake beds. The Siebert lake beds west of the Belted Range 

are similar to those described in the vicinity of Oak Spring. (See p. 

122.) The beds are either horizontal or tilted up to angles of 30°. 

Probably to be correlated AN7 ith these are the white conglomeratic 

sandstone 10 miles north of Tolicha Peak, and green tuffaceous sediments 7 miles southwest of Trappmans Camp. From the tuffaceous 

beds, which contain quartz, feldspar, and biotite crystals, Mr. B. I). 

Stewart collected pieces of silicified wood which Dr. F. H. Knowlton 

states belonged to a deciduous tree.not older than the Tertiary.

Later tuffs. Beneath the basalt of Pahute Mesa east of Stonewall 

Mountain are tuffs and rhyolite flows which appear to be similar to
PAHtJTE MESA, IGNEOUS EOCKS. 133

the later rhyolite and later tuft's of the Goldfield hills. (See pp. 72, 74.) 

'Similar beds outcrop at many points where, erosion has removed the 

basalt, and it is probable that these beds underlie the greater portion 

of the basalt. No attempt has been made to separate them from 

basalt on the map. A section east of Stonewall Mountain is as 

follows:

Section east of Stonewall Mountain.

Basalt. ' . . Fee t. 

Rhyolite _____________________________________________ 5

Gray tuff with small pebbles.__________ _______ 15

Rhyolite __________________________________________ 7 

Yellow tuff, very rich in pebbles of pumice, which reach a maximum diameter of 1 inch__________________________;___________ 20 

Gray, rather incoherent, conglomeratic tuffaceous sediments. The pebbles, 

which reach a maximum diameter of G inches and become smaller toward 

the top, are formed of rhyolitic pumice, a quartz-poor rhyolite like the 

later rhyolite of Goldfield, and basalt. Tiny crystals of feldspar, similar 

to the phenocrysts of the rhyolite of Goldfield, are present_______ 55

Yellow tuffs, like above__________________»________ 10

From this section and that at Goldfield it may be inferred that a 

lake covered considerable territory in the northern part of the area 

under discussion, probably in late Pliocene time. The deposits of this 

lake are separated from those of the Pahute Lake (Siebert lake beds) 

by an erosional unconformity, and are probably older than the playa 

deposits of the older alluvium in Stonewall Flat. Between the Pliocene lake beds and the older playa deposits there is little relation, 

although the deposits laid down in playas probably represent the last 

stages of the drying up of the lake in which the lake beds were 

formed. Spurr ft found deposits of a late Pliocene lake widely distributed in Nevada, and it is possible that this lake and the one here 

described are broadly contemporaneous.

Recent desert c/ravels. Recent desert gravels mask the bed rock 

over a considerable area east of Fortymile Canyon and extend some distance up the main canyons.

IGNEOUS ROCKS.

The igneous rocks of Pahute Mesa include pre-Tertiary granular 

rocks and Tertiary dikes and lava flows.

Pre-cjranite monzonite. In the granite 5 miles north of west of 

Whiterock Spring are inclusions of a gray fine-grained granular rock. 

Both striated and unstriatecl feldspars are present with quartz and 

biotite, and the rock is similar to the monzonite included in the postJurassic granitoid rocks of Gold Mountain and the Belted and Panamint ranges.

Post-Jurassic granite, Granite forms the hills at Trappmans Camp 

and also outcrops 5 miles north of west, of Whiterock Spring. The

"Spun-, .1. E., Bull U. S. Geol. Survey No. 20S, 1!)<W, pp. .124-125, 200-210, etc.
134 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

rock at Trappmans Camp is a light-gray fine- to medium-grained 

biotite-rnuscovite granite. It forms low, rounded hills and shallow 

valleys, and outcrops are inconspicuous. The granite is cut by several 

systems of intersecting joints and by faults and zones of brecciation. 

In consequence the residual masses are squared blocks, more or less 

rounded. Under the microscope the granite shows as an allotriomorphic, granular rock, composed of orthoclase, quartz, plagioclase, 

biotite, muscovite, and zircon. The muscovite is in part original and 

in part an alteration product of feldspar. The rock has been considerably mashed, and quartz and muscovite have been deposited in the 

fractures of feldspar and quartz.

The granite grades into and is cut by irregular masses and dikes of 

pegmatite, composed of feldspar and quartz anhedra up ta 1 inch in 

diameter. Quartz stringers and veins of pegmatitic origin, some of 

which are several hundred feet long and 40 feet wide, are common. 

The quartz on portions of the borders of the larger masses contains 

fragments of granite and sends well-defined veins into the granite. 

At other places single individuals of quartz on the contact seem common to both pegmatitic quartz and granite, and arms of feldspar 

extend from the granite into the quartz. Evidently the quartz solidified contemporaneously with some portions of the granite and subsequently to other portions. A few thin dikes of fine-grained aplite, 

which stand in relief on weathering, cut the granite.

A granite mass 1 mile long occurs iii the midst of the Siebert lake 

beds 5 miles north of west of Whiterock Spring. It is low and covered by a yellowish granite soil from which protrude low, rounded 

granite domes. Near its center is a rugged hill, set with sharp pinnacles, whose forms are controlled by the well-developed joints. The 

granite is coarse grained and is composed of pink feldspar, white 

semitransparent quartz, and biotite. Feldspar and quartz reach a 

maximum length of three-fourths of an inch. Under the microscope 

the granite shows as a hypidiomorphic granular rock formed predominantly of large orthoclase plates poikilitically inclosing quartz 

anhedra and plagioclase laths. A little biotite is also present, and 

this, since it occurs along fractures in orthoclase, has been considerably recrystallized. The accessory minerals are titanite, apatite, and 

magnetite, the last probably titaniferous, since it is surrounded by 

secondary titanite.

.The granite is cut by narrow dikes of pink aplite, practically lacking biotite. These dikes weather in relief. In the granite are ellipsoidal masses of quartz-feldspar pegmatite from 4 inches to 5 feet in 

diameter, the contact between the granite and pegmatite being in 

some instances sharp, in others gradational. Feldspar and quartz 

individuals with a maximum diameter of 6 inches, together with a 

few biotite plates, compose the pegmatite. This rock grades into
PAHTJTE MESA, IGNEOUS BOCKS. 135

pegmatitic quartz. The ellipsoidal form and the absence of channels 

from one mass to another in the place of observation suggest that 

the pegmatite formed in place from the local residual fluids of the 

.granitic magma.

The granite of Trappmans Camp contains inclusions of the schist 

already described and of a black Paleozoic quartzite. It is cut by 

dikes of the earlier rhyolite, and the later tuffs overlap it. It resenir 

bles the granite of Lone Mountain. The granite near Whiterock 

Spring is much older than the Siebert lake beds and closely resembles that near Oak Spring in the Belted Range. Each granite is 

probably of post-Jurassic and pre-Tertiary age.

Earliest rhyolite. The earliest rhyolite protrudes from the basalt 

in a number of hills in the northwestern portion of the mesa. It evidently occurs for the most part as a flow, although dikes of rhyolite 

cut granite at Trappmans Camp. These dikes reach an observed maximum width of 40 feet. They are formed of a lithoidal, brownishgray rhyolite with conchoidal fracture. The feldspar, quartz, and 

biotite phenocrysts rarely exceed a length of one-tenth of an inch and 

are exceeded in bulk by the groundmass. The flow at Wilsons Camp 

is composed of a white phenocryst-rich rhyolite, in which biotite is 

present in some places and absent in others. The rock of the inlier, 

9£ miles northwest of Tolicha Peak, is a semipumiceous, brownishgray rhyolitic glass, with a few small phenocrysts. Pebbles of black 

obsidian occur on the mesa near by. Other hills in the vicinity were 

not visited, but on the basis of their color and the report of prospectors some are mapped as rhyolite. Beyond the fact that the rhyolite of this vicinity is younger than the granite and older than the 

basalt, its age is unknown. It is believed, however, that the different masses are portions of the rhyolite of the Cactus Range buried by 

later lava flows, and are in consequence of early Miocene age.

Biotite andesite. Biotite andesite forms the inlier'of Gold Crater 

and several smaller inliers near by, and also occurs as dikes cutting 

the rhyolite at Wilsons Camp and the granite at Trappmans Camp.

The biotite andesite at Gold Crater forms a group of low hills 

which protrude above the basalt, later rhyolite, and later tuffs. It is 

evident that the andesite flow was eroded into hills prior to the formation of the younger rocks, and it is probable that the younger rocks 

never completely covered the summits of these hills, although liquid 

lava dammed up against their sides. The biotite andesite here is for 

the most part intensely altered, but appears to have been originally a 

dense gray rock with phenocrysts equaling the groundmass in bulk. 

The phenocrysts are medium sized and consist of predominant feldspar in laths, biotite, and locally hornblende. Flow banding and 

flow breccias are present. Under the microscope the microfelsitic 

groundmass is rather ill defined, but seems to be composed predomi-
136 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

nantly of plagioclase and orthoclase. The phenocrysts include sericitized feldspars, Avhich Avere at least mainly plagioclase, biotites 

altered to milscovite and magnetite, and some hornblende-like forms of 

serpentine and limomte.

The biotite andesite at Wilsons Camp is a highly altered, finely 

granular rock of pale-greenish color, containing many phenocrysts 

of white altered feldspar and some of bronze biotite. Probably to be 

correlated with this rock is a much altered greenish-gray, finely granular rock which occurs in dikes at Trappmans Camp. Laths of altered 

feldspar, columns of hornblende, and tiny tablets of biotite are determinable in the hand specimen. The microscope shoAVS that the 

much altered groundmass Avas probably originally a glass Avith a feAv 

plagioclase laths (hyalopilitic). The only phenocrysts recognizable 

are large calcitized plagioclase and chloritized biotite and a feAv 

small, fresh orthoclase tablets. Aggregates of secondary minerals 

suggest the presence of hornblende or pyroxene. Apatite and magnetite, probably titaniferous, are accessory minerals.

The andesite at Wilsons Camp bears the same relation to the rhyolite 

as the biotite andesite of the Cactus Range, and the tAA7 o are doubtless contemporaneous and of middle Miocene age. The andesite of 

Gold Crater is much older than the latest rhyolite. Lithologically it 

is not very different from the biotite andesite and is provisionally correlated A\7 ith it. It is, hoAvever, possible that it is the flow equivalent 

of the monzonite porphyry of the Ka\A7 ich Range.

Middle rhyolite. The middle rhyolite, evidently a floAv, is the predominant formation of Pahute Mesa east of Thirsty Canyon. The 

most Avidely distributed type is a gray or pink lithoidal rhyolite, in 

which the groundmass is exceeded in bulk by the medium-sized phenocrysts. The latter include glassy orthoclase, colorless or slightly 

smoky quartz, and, usually, biotite. This variety in many places 

contains small fragments of a AA'hite pumiceous rhyolite and in consequence is a floAv breccia, Other facies include dense rocks of red, 

broAvnish, or gray color, Avith feAv phenocrysts. FloAV banding, spherulites, and perlitic parting accompany the denser groundmass in 

much of the rock. Black glasses Avith feldspar phenocrysts occur 

near Ammonia Tanks, and gray semipumiceous glasses Avith abundant 

feldspar and quartz phenocrysts are found on the east side of Silent 

Canyon, 4'miles south of its mouth. This rhyolite for the most part 

lies upon the Siebert lake beds and it is to be correlated with the later 

rhyolite of the Belted Range. It is presumably of late Miocene or 

early Pliocene age.

Latest rhyolite. The latest rhyolite occurs1 below the basalt in the 

A'icinity of StoneAA^all Mountain and probably outcrops in many other 

places on the border of the mesa that are shown on the map as basalt. 

It is interbedded Avith and overlies the later tuffs. A section already
PAHUTE MESA, STRUCTURE. 137

described (see p. 133) shows that there are two thin flows of this rhyolite. The lower flow is a dense grayish-purple rock containing a 

vast number of small phenocrysts. Under the microscope the groundmass is seen to be a glass with highly developed flow lines. The phenocrysts all appear to be orthoclase. The upper rhyolite is similar to 

the lower, although it contains slightly larger orthoclase phenocrysts, 

and in addition a few tiny biotite and quartz phenocrysts are visible. 

The younger rhyolite of Pahute Mesa and that of Goldfield hills 

are similar lithologic units occupying like stratigraphic positions, 

and without doubt are contemporaneous and probably of late Pliocene 

-age.

Basalt, Flows of basalt cover Pahute Mesa northwest of Tolicha 

Peak, similar flows extend eastward from Quartz Mountain to 

Thirsty Canyon, and a third area of considerable size lies west of 

Timber Mountain. The last-named mass appears from a distance 

to have flowed from two cones, one 5 miles northeast and the other 

8 miles southeast of Timber Mountain. Black Mountain, from a distance, also resembles a volcanic cone, and the north peak of Mount 

Helen may have been an ancient vent.

The basalt of Pahute Mesa includes vesicular and nonvesicular 

facies, the former red, the latter black. In some of the basalt white 

striated feldspars, reddish altered olivines, and black pyroxenes are 

prominent, while in other portions these phenocrysts are inconspicuous. Stratigraphically the basalts of Pahute Mesa and of the Goldfield hills have identical positions and they are considered of late 

Pliocene age.

x STRUCTURE.

Pahute Mesa northwest of Tolicha Peak is capped by lava flows, 

which dip gently in all directions from a center 5 miles southwest of 

Mount Helen. The only structural feature of interest in this portion 

of the mesa is the slight rise of the lava sheets as they approach the 

older hill groups, well seen at Gold Crater and on the southeastern 

face of Stonewall Mountain. A similar gentle dome is present in the 

mesa between Quartz Mountain and Thirsty Canyon, but eastward 

from the canyon the mesa gradually rises, owing probably to comparatively recent uplifts of the Ivawich and Belted ranges. In this portion of the mesa normal faults with north-south strike, few of which 

have a displacement of over 50 feet, are common. Although of late 

Tertiary age, these faults do not exhibit fault scarps, since erosion has 

planed down the upthrown side. In some instances, however, the 

downthrown side, being more resistant, is now a scarp.

ECONOMIC GEOLOGY.

Three mining camps are situated in Pahute Mesa Trappmans 

Camp, Wilsons Camp, and Gold Crater.
138 . . SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

TKAIM'MANS CAMP.

Trappmans Camp lies 34 miles south of east of Goldfield. The. 

veins were discovered by Hermann Trappman and John Gabbard in 

June, 1904, and at the time of the writer's visit a year later five men 

were opening up the veins, the chief development being a shaft 50 

feet deep. t

The prospects are in granite, and three distinct periods of vein 

formation were noted first, quartz lenses probably -of jpegmatitic 

origin; second, quartz veins of distinctly later formation, which in 

one place are said to cut a rhyolite dike; and, third, quartz veins of a 

third generation which cut the second. (See fig. 14.) The latest 

veins are in places well crustified.

The pegmatitic quartz forms bodies varying from minute stringers 

in the granite to lenses one-fourth mile long and 40 feet wide. The 

quartz is hard and whitish, and in some places it is intensely

.8 feet

Later quartz veins Iron-stained fractures

FIG. 14. Second and third systems of quartz veins in granite at Trappmans Camp, ap

exposed on face of incline.

brecciated and stained by limonite. It is said to carry silver and gold 

values.

The quartz veins of the second class have sharp contacts with the 

granite. These veins are exceedingly common in the vicinity of 

Trappmans Camp and vary widely in strike and dip. In limited 

areas they tend to form series of veins along parallel joint planes in 

the granite. In width the veins vary from an inch or less to a foot 

or more, and some of the parallel series are a number of feet thick. 

Locally these veins are faulted, as indicated by the presence of breccias, while the surrounding granite shows considerable differential 

movement. The quartz is slightly bluish, but is usually heavily 

stained red or brown by hematite and limonite. Vugs elongated 

parallel to the direction of the veins are sometimes seen. On encountering the pegmatitic lenses, in the one instance noted, these 

veins are deflected downward.

The veins of the third class are of later origin than those of the
MESA, ECONOMIC GEOLOGY. . 139

second, which they cut. As a rule they are more narrow and less 

continuous and dip more steeply than the veins of the second class. 

In places they curve sharply. The quartz in them is similar to that 

in the second group. .

In the vicinity of the vein the granite is cut by partings stained by 

limonite and manganese dioxide, which are parallel to or join the 

quartz veins at low angles, and the surrounding kaolinized granite 

is said to carry values. The granite near the veins is in places thickly 

peppered with cubes of pyrite altered to limonite.

The ore of the two younger sets of A7 eins so far encountered is 

practically alloxidized, although a little original galena remains. The 

predominant original sulphide was pyrite, and limonite cubes after 

pyrite are common in the quartz. Assays show the values to be in 

the proportion of one of gold to four of silver. Some silver chloride 

was noted, while secondary native silver is reported. In one prospect calcite is associated as a gangue with quartz.

While the quartz of the first set of veins is of pegmatitic origin, 

its mineralization is probably later and genetically connected with, 

the filling of the fissures of the second set, probably in Tertiary time. 

After the veins of the second system were fractured another period 

of mineralization followed, perhaps in late Tertiary time. Later the 

veins were crushed and surface waters have more or less completely 

oxidized the sulphides.

Wood and water are hauled from Antelope Springs, about 9 miles 

away. Trappmans Camp is 40 miles by road from Goldfield.

WILSONS CAMP.

Wilsons Camp is 2 miles north of Trappmans Camp and was discovered in May, 1904. Five miners were employed in July, 1905, 

and at that time several shallow shafts and short tunnels were open. 

The country rocks, white altered rhyolite and biotite andesite, are 

cut by rather steeply dipping quartz veins, the majority of which 

strike northeast, although some strike east. The quartz veins, many of 

which are crustified, are characterized by quartz-lined vugs. Since 

its formation the quartz has in some instances been crushed. 

Limonite and less commonly malachite stain the quartz. The reported assay values run from $110 to $180 per ton and average one 

of gold to five or six of silver. These quartz veins are to be correlated with the veins of Silverbow. The economic conditions at 

Wilsons Camp are similar to those at Trappmans.

GOLD CRATER.

The mining camp of Gold Crater is situated 10 miles east of the 

summit of Stonewall Mountain. The first locations were made in
140 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

May, 1904. In the fall of 1904 several hundred people rushed to 

the camp, but few remained long. At the time of the writer's visit 

(July 7, 1905) a number of lessees were at work. The country rock, 

silicified and kaolinized biotite andesite, has been fractured and in 

many places faulted and brecciated.. The intensely silicified andesite is a white or gray rock with conchoidal fracture. ^ In some 

instances it is porous through the removal of the phenocrysts and in 

others the casts have been filled by milky quartz. The iron-stained 

outcrops are very rugged, since silicification and consequently the 

resistance of the rock to erosion are very irregular throughout the 

mass. Under the microscope this silicified facies is seen to be a 

medium to very fine mosaic of quartz and some chalcedony, with here 

and there a blotch of limonite. No phenocrysts remain, although a 

few sagenitic webs of rutile suggest the former presence of biotite-. 

By kaolinization the rock is reduced to a chalky mass, in which biotite 

phenocrysts, altered to a silvery mica, alone are visible. It is intensely stained by limonite and hematite, especially along fractures, 

and from such places rich gold pannings are obtained. A little 

chrysocolla was observed along some joints, while a thin coating of 

hyalite has been deposited since the oxidation of the sulphides. The 

ore is said to run from $40 to $240 in gold per ton.

Waters carrying silica and metallic salts in solution appear to have 

ascended along faults, brecciated zones, and joints in the country rock 

and to have deposited silica, pyrite, and some copper sulphide. Later 

surface waters oxidized the sulphides and set the gold free. The 

original deposition was without much doubt an impregnation of the 

country rock, as is the case with the secondary minerals. There is a 

notable resemblance between these deposits and those of Kawich and 

certain of those of Goldfield.

Gold Crater derives its water supply from tanks on the basalt mesa 

and from two wells, 3 and 9 miles distant. Fuel for mining purposes 

is obtainable from Stonewall Mountain. Goldfield is 27 miles distant.

OTHER AREAS.

Some of the pegmatitic quartz in the granite 5 miles north of west 

of Whiterpck Spring is stained by limonite, but no other indication of 

mineralization was noted. It is probable that some of the masses of 

the older Tertiary volcanic rocks protruding through the later lava 

flow are worthy of prospecting, but such were not observed in the 

course of the present work. Prospecting in Pahute Mesa can be most 

advantageously pursued in the winter or early spring, when water 

can be obtained from snow or the tanks.
DESCRIPTIVE GEOLOGY. 141 

TOLICHA PEAK AND QUARTZ MOUNTAIN.

TOPOGRAPHY AND GEOGRAPHY.

Tolicha Peak, a striking cone rising from Pahute Mesa, is a landmark for miles. Quart//, Mountain, a somewhat lower east-west 

. ridge, extends eastward from Tolicha Peak. The hills are bare, except 

for a sparse growth of desert shrubbery. Monte Cristo Springs, on 

the western slope, furnish sufficient water for 15 to 20 head of stock.

GENERAL GEOLOGY.

The formations of these-mountains from the base up are Cambrian (?) schist, post-Jurassic granite, Tertiary rhyolite, and Tertiary basalt.

SEDIMENTARY ROCKS.

Cambrian (?} schist. The hill 2^ miles southeast of Tolicha Peak 

appears greenish gray in color at a distance, and is probably formed 

of a bluish-gray schistose rock which occurs abundantly in the desert 

gravels to the south of this hill. The rock is very fine grained, except' 

for some small crystals of biotite and hornblende. White, ellipsoidal 

areas 1 inch long spot the blue-gray rock. Under the microscope the 

grounclmass appears as an exceedingly fine aggregate of quartz and 

feldspar, in which are embedded small areas of quartz, orthoclase, 

ragged hornblende, and biotite. The rock is probably a metamorphosed Paleozoic shale, possibly of Cambrian age.

IGNEOUS ROCKS.

A specimen of rhyolite from Tolicha Peak collected by Mr. S. G. 

Benedict contains an inclusion of gray granite of medium grain. 

Post-Jurassic granite probably underlies this peak.

Rhyolite form's Tolicha Peak and the east side of Quartz Mountain. The predominant type is a dense flinty rock of reddish color 

with a few small phenocrysts of glassy feldspar, quartz, and biotite. 

Flow lines, perlitic parting, and spherulites are well developed. 

Gray glassy facies, transparent in thin flakes, are interbedded with 

this type, as are white or light-gray incoherent facies in which the' 

phenocrysts are abundant and equal the groundmass in bulk. Flow 

breccias are rather common. This rhyolite is probably about contemporaneous with the earlier rhyolite of the Kawich Range and is 

presumably of early Miocene age.

Prior to the extrusion of the basalt which covers Pahute Mesa 

(see p. 137) Tolicha Peak was eroded into a rugged mountain. The 

valley between Tolicha Peak and Obsidian Butte is upon the contact 

between the rhyolite and basalt.
142 SOUTHWESTERN NEVADA AND EASTEEN CALIFOKNIA.

STRUCTURE.

The rhyolite of Tolicha Peak is complexly cut by normal faults 

with displacements of 10 to 50 feet. These faults in some places 

are less than 100 yards apart. The rhyolite is also intensely jointed.

ECONOMIC GEOLOGY.

The rhyolite around Monte Cristo Springs is kaolinized or silicified. Prospect holes are located on quartz veins in altered rhyolite, 

the ore being quartz and silicified rhyolite stained by limonite. 

Quartz Mountain Camp, on the northern slope of Quartz Mountain, 

was not visited, but the conditions, according to the reports of prospectors, are similar to those at Monte Cristo Springs. The altered 

masses, which resemble those of Silverbow and are faulted like those 

of Bullfrog, are outlined on the economic map (fig. 4, p. 43).

MOUNTAINS SOUTHEAST OF PAHUTE MESA.

Southeast of P.ahute Mesa are a number of small groups of mountains with crest lines of varying trend, although a number have an 

eastward extension. These include Shoshone, Skull, Yucca, Timber, 

and Bare mountains and the Specter Range. Geologically they are 

characterized by the important development of the early Miocene 

rhyolite.

SHOSHONE AND SKULL MOUNTAINS AND THE HILLS IN THE VICINITY. 

TOPOGRAPHY AND GEOGRAPHY.

Shoshone and Skull mountains lie to the north of the Specter Range 

and the Skeleton Hills and to the east of Fortymile Canyon. Shoshone Mountain is joined to the Belted Range by a.low gap, but from 

its east-west trend it more properly belongs with the other ridges in 

the vicinity. Shoshone (7,540 feet) and Skull (6,100. feet) mountains 

are each capped by horizontal lava flows, and in consequence from a 

distance appear as mesas. The other hills and ridges vary in form 

from the jagged ridges of Carboniferous rocks to the smooth depressed domes of the Siebert lake beds. The various ridges and hills 

are in many instances separated from one another by opposed valleys 

which are filled with desert gravels.

A fairly heavy growth of juniper and pinon is found on the north 

slope of Shoshone Mountain above Tippipah Spring, but other portions of this mountain and the other ridges are bare except for sparse 

groves of the tree yucca and here and there a Spanish bayonet (Yucca 

aloifolia?}. Scarcely a spear of grass grows throughout these hills. 

Of the four springs in these hills, Cane Spring flows about 1,500 gallons a day; Tippipah contains from 50 to 100 gallons of standing 

water; Topopah (or Blackrock) floAvs from 15 to 25 gallons a da}^
SHOSHONE AND SKULL MOUNTAINS AND HILLS NBAK BY. 143

and the fourth, which lies 4 .miles south of Cane Spring, is small and 

is dry in summer.

GENERAL GEOLOGY.

The formations of these hills, from the oldest to the youngest, are 

the following: Carboniferous (Pennsylvanian)- sedimentary rocks, 

quartz-monzonite porphyry, earlier rhyolite, Siebert lake beds, later 

rhyolite, and basalt.

SEDIMENTARY KOCKS.

Pennsylvanian limestone. Pennsylvanian limestone forms the ridge 

to the northeast of Tippipah Spring and the northern face of the 

ridge northwest of Yucca Pass. A third area of limestone, 6 miles 

south of Tippipah Spring, outcrops between the desert gravels below 

and the later rhyolite above. Limestone pebbles are abundant in the 

Siebert lake beds, and small inclusions occur in the quartz-monzonite 

porphyry and the earlier rhyolite. This limestone is similar to that 

of the Belted Range. (See p. 121.)

Siebert lake beds. Siebert lake beds form the northern and northeastern faces of Shoshone Mountain, rim the southern edge of Skull 

Mountain, and cover areas 4 miles southeast of Tippipah Spring 

and 4 miles south of Cane Spring. Somewhat over 1,000 feet of lake 

beds are exposed on the north side of Shoshone Mountain, a section 

being as follows:

Section on north side of Shoshone Mountain.

Feet.

White (locally yellow through iron stains), fine-grained, incoherent, impure sandstone.' Bedding planes near the base 100 feet apart. Crystals 

of biotite, glassy feldspar, and quartz occur in upper 200 feet. Some 

bands contain pebbles of glassy rhyolite less than 3 inches in diameter. 650

Same, but without the small crystals. Some pink layers. Bedding 

planes well developed from 40 feet to 1 foot or less apart. Pebbles of 

glassy rhyolite up to 3 inches in diameter occur in certain beds____ 100

Same, with pebbles of Carboniferous limestones and quartzites onefourth inch in diameter_____________________ 200

Same, with abundant crystals of biotite, glassy feldspar, and quartz. 

Pebbles up to 4 inches in diameter, largely of glassy or semipumiceous rhyolite__________________________________ 100

In other areas these sediments are more brilliantly -colored, pinks 

and reds not being unusual. The bowlders of the conglomeratic 

beds in some instances reach a diameter of 5 feet. In addition to 

the pebbles already mentioned, others are present of quartz-monzonite 

porphyry, the earlier rhyolite, and a vesicular basalt. The basalt 

was not seen in place, but is perhaps contemporaneous with the 

earlier rhyolite and corresponds to the earlier basalt of the Amargosa Range. The Siebert lake beds, which characteristically form 

depressed domes, break down readily into a sand. Huge globular 

cavities, due in part to exfoliation and in part to wind erosion, and
144 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

pillars capped and protected by huge bowlders add fantastic elements to many hills. Joints affect only the minor topographic features. In certain instances silicification has followed joints and 

chalcedony has been deposited in their fractures. Such joints, being 

resistant, weather in relief.

The Siebert lake beds appear to have been deposited in a lake of 

some depth, to which much fragmental material was carried. The 

size of the material varied considerably from time to time, the variation in coarseness being an expression in part of the depth of the 

lake and in part of the topography of the lake shores. Much of the 

material was derived from disintegrating rhyolite, but at times there 

were apparently also explosive rhyolitic eruptions, which threw into 

the lake many small crystals of biotite, feldspar, and quartz. The 

sediments on Shoshone Mountain overlie the quartz-monzonite porphyry and earlier rhyolite unconformably and are overlain apparently conformably by later rhyolite; while on Skull Mountain the 

basalt overlies them unconformably. They are without much doubt 

to be correlated with the Siebert lake beds at Tonopah a of Miocene 

age.

IGNEOUS ROCKS. .

Quartz-monzonite porphyry. Quartz-monzonite porphyry is the 

predominant formation in the hills to the east, north, and northeast 

of Cane Spring. The texture of the rock indicates that it was probably intruded in older rocks, which are, however, not at present 

exposed.

The quartz-monzonite porphyry has a gray or greenish-gray, finely 

crystallized or lithoidal groundmass, which is somewhat subordinate 

in bulk to the phenocrysts. The latter include feldspar, usually 

altered but in rare instances fresh and then clearly striated; biotite, 

fresh to altered, and serpentinized hornblende. In many cases hornblende is very subordinate to biotite. The feldspars reach a maximum length of one-fourth inch; the other phenocrysts are slightly 

smaller. The microscope shows that the rock is a quartz-monzonite 

porphyry almost approaching granodiorite porphyry. The groundmass consists usually of a microgranitic, but over small areas micropegmatitic mosaic of orthoclase, quartz, and a little plagioclase. The 

plagioclase phenocrysts, complex crystals, are usually twinned according to the Carlsbad law and many of them are zonally built. One 

determination proved this mineral to be basic andesine. A few phenocrysts of quartz, deeply embayed by magmatic corrosion, and of 

orthoclase are also present, in addition to the phenocrysts microscopically determined. Magnetite, zircon, and apatite are present as 

accessory minerals. The secondary minerals include kaolin and epi0 Spun-, J. E., Prof. Paper U. S. Geol. Survey No. 42, 1905, p. 54.
SHOSHONE AND SKULL MOUNTAINS, IGNEOUS ROCKS. 145

dote after the feldspars, chlorite and epidote after biotite, and pseudomorphs of serpentine after hornblende or possibly augite.

The rock resembles lithologically and in its stratigraphic position 

the monzonite porphyry of the Kawich Range, and the two rocks 

are doubtless approximately contemporaneous. Each is strikingly 

similar to the quartz-monzonite porphyry of Stonewall Mountain. 

The porphyry of Skull Mountain and that of the Kawich Range are 

older than a rhyolite, which is supposed to be of early Miocene age. 

The quartz-monzonite porphyry also closely resembles rocks which 

on the Avestern border of the area surveyed appear to be a variant of 

the post-Jurassic granite magma. While it is possible that they are 

pre-Tertiary in age they are here tentatively assigned to the late 

Eocene.

Earlier rhyolite. The earlier rhyolite and its kaolinized and ironstained alteration products form the Calico Hills, remarkable for 

their brilliant pink, red, and Avhite coloring. A number of smaller 

areas lie in the group of hills in which the Horn Silver mine is situated, and some of the rhyolite to the west of Yucca Pass may possibly belong to the earlier series.

The earlier rhyolite includes a number of facies, most of Avhich 

are characterized by abundant phenocrysts that equal or exceed the 

groundmass in bulk. The groundmass is AA^hite or gray in color 

and is usually dense. The phenocrysts are of medium size. Tabular crystals of glassy unstriated feldspar and rounded grains of 

slightly smoky quartz 'are much more abundant than the someAvhat 

smaller hexagonal plates of black mica. Other facies are black 

glasses Avith perlitic parting, but Avithout phenocrysts, and gray 

glasses Avith a few quartz phenocrysts. The rock is fa floAAr , since certain beds shoAv distinct floAv banding and others contain many fragments of rhyolites and are evidently floAA7 breccias.

The earlier rhyolite appears to lie upon the uneven surface of 

the quartz-monzonite porphyry. The later rhyolite apparently overlies the earlier, Avhile pebbles of the earlier rhyolite are contained in 

the Siebert lake beds. The same relations exist in the KaAvich Range, 

and the earlier rhyolites of the tAvp ranges are doubtless approximately contemporaneous and of early Miocene age.

Later rhyolite. The later rhyolite floAv. overlies the Siebert lake 

beds on Shoshone Mountain, Avhile seAreral small masses to the south 

of Cane Spring cap the same formation. In the latter locality the 

former extension of the rhyolite Avas much greater and the southAvard-dipping floAv of the Shoshone Mountain may at one time haA'e 

been connected Avith it. The rhyolites AA'est of Yucca Pass are, from 

their lithologic character and relation to the Siebert lake beds, probably to be correlated Avith the later rhyolite. 

Bull. 308 07 M 10
146 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

Southwest of Tippipah Spring 275 feet of the later rhyolite overlies the Siebert lake beds, while near the center of Shoshone Mountain about 1,500 feet of rhyolite is exposed. At the first locality the 

lower 250 feet is a dense brownish-pink rock with sparse and small 

phenocrysts of glassy feldspar, biotite, and quartz. Some flow bands 

are purple or gray in color, others are vesicular, and still others 

carry numerous small inclusions of rhyolite, and are in consequence 

flow breccias. Vertical columnar joints, originating during the cooling 

of the magma, are not unusual. The broadest columns are 4 feet in 

diameter. Above this is 15 feet of a black glass, in which the phenocrysts exceed the groundmass in bulk. This in turn is overlain by 10 

 feet of rhyolite like that first described, except that the phenocrysts 

are larger and more numerous. In it are thin bands of the black 

glassy variety. At the south end of Shoshone Mountain similar facies 

occur, and in some of these the flow banding is strongly developed, 

the flow lines, as a rule, being straight, although in places wavy.

The later rhyolite south of Cane Spring is a yellowish-brown rock 

Avith lithoidal or challry groundmass, which is equal in bulk to the 

phenocrysts. These include medium-sized glassy unstriated feldspar 

and slightly smoky quartz, together with abundant but tiny biotitephenocrysts. The rhyolites west of Yucca Pass are waxy-lustered 

glasses and well-banded, phenocryst-rich flow breccias of purplish 

color. In the latter gray spherulites occur.

The later rhyolite ordinarily forms buttes and mesas, since the 

various flow bands vary considerably in resistance to erosion. Like 

the later rhyolite of the Kawich Range, the later rh}^olite of these hills 

overlies the Siebert lake beds. The two, which are rather similar 

lithologicaly, are probably about contemporaneous and are of late 

Miocene or early Pliocene age.

Basalt. A basalt floAv caps Skull Mountain, a number of small 

areas occur to the east of the Calico Hills and to the west of the Horn 

Silver mine, while three small hills lie 4 miles east of the iron tank 

in Fortymile Canyon. Basalt also occurs between Fortymile Canyon-and Shoshone Mountain. It is a dense black or dark-gray rock 

with sparse phenocrysts of glassy striated feldspar and slightly 

altered glassy olivine. Both the vesicular and nonvesicular facies 

previously described in other ranges occur. The nonvesicular basalt 

weathers into spheroidal masses, while the vesicular facies usually 

break down into slabs which are elongated parallel to the flow banding. A single thin section of a dense, slightly vesicular facies proved 

on microscopic examination to be composed of dark glass containing 

many laths of a calcic plagioclase and grains and partial crystals of 

olivine more or less altered to reddish-brown serpentine.

On Skull Mountain the basalt lies upon the eroded surface of the 

Siebert lake beds, while in' the low isolated hills 4 miles east of the
SHOSHONE AND SKULL MOUNTAINS, ECONOMIC GEOLOGY. 147

iron tank it appears to overlie the later rhyolite. It is without doubt 

the youngest formation of these hills, and is probably of late Pliocene 

or early Pleistocene age.

STRUCTURE.

The Pennsylvania!! limestone is folded into rather open folds, the 

dips of which rarely exceed 45°. The predominant axes trend from 

northeast to southwest, although minor folds with east-west axes also 

occur. The ridge to the northeast of Tippipah Spring is synclinal 

in structure. The Pennsylvania!! rocks appear to have had a rather 

uneven surface prior to the deposition of the Siebert lake beds. Not 

only do many of the lake beds contain large bowlders of limestone, but 

west of Tippipah Spring a number of hillocks of the older limestone 

protrude through the Tertiary sediments.

In a broad way the Siebert lake beds and the later rhyolite are 

slightly flexed and the beds on Shoshone Mountain dip gently to the 

south. Normal faults of 50 feet displacement are not unusual in the 

tuffs. The latest deformation is that of the basalt. On Skull Mountain it dips gently to the south, while on the ridge to the east it dips 

with a similar angle to the north, the two blocks being separated by 

a north-south fault.

ECONOMIC GEOLOGY.

The quartz-monzonite porphyry and the earlier rhyolite have been 

silicified and kaolinized in restricted areas, the silicification being 

comparable to the alterations in the vicinity of Kawich and the kaolinization to those of Silverbow. These areas, which are worthy of prospecting are delineated in fig. 4 (p. 43). The quartz-monzonite porphyry near the Horn Silver mine has not only been altered to a spongy 

mass of brownish-gray silicified porphyry like that of Kawich, but it 

is cut bj quartz stringers with associated gypsum. Other veins and 

irregular cavities are partially filled with chalcedony, which in turn 

is incrusted by quartz crystals. The rhyolite of the Calico Hills has 

been in places intensely silicified. The silicified rhyolite 2 miles north 

of the Horn Silver mine is cut by thin quartz seams. A similar yellow stain (a basic ferric-alkali sulphate?) to that noted near the 

prospects at Silverbow is present on joint surfaces.

SPECTER RANGE AND SKELETON HILLS. 

TOPOGRAPHY AND GEOGRAPHY.

The hills in the southeast corner of the area surveyed may be considered as the westward extension of the irregular Spring Mountain 

Range. They consist of a number of mountains and hills now isolated from one another by narrow canyons and broad valleys filled 

with desert gravels. The ridges and hills are rugged and sharp and 

are crowned by many peaks. The highest point (5,800 feet above
148 SOUTHWESTERN NEVADA AND. EASTERN CALIFORNIA.

sea level) is in the southeast corner of the area. The presence of 

many inlying hills near; by indicates that those portions of the old 

 mountain mass partially buried by desert gravels possessed an equally 

dissected topography. A majority of the hills are elongated parallel 

to the strike of the Paleozoic rocks. West of the road between Cane 

Spring and Ash Meadows ridges Avith northeasterly trend predominate, and east of the road lie irregular massive groups of hills. The 

hills stop abruptly along a north-south line east of Fortymile Can3'on, and prior to the inwash of detrital material this canyon must 

nave been a strikingly prominent topographic feature. The hills are 

bare of timber and destitute of springs.

GENERAL GEOLOGY,

The formations of these hills, from the oldest to the youngest, are 

Prospect Mountain quartzite, Prospect Mountain limestone," and 

basalt.

SEDIMENTARY ROCKS.

Prospect Mountain quartette. Two areas of quartzite, one large 

and the other small, cover 20 square miles near Point qf Rocks. The 

formation, 2,000 to 3,000 feet thick, underlies the Prospect Mountain 

limestone conformably, with transitional beds between the two. The 

rock, either a quartzite or an indurated sandstone, varies in color 

from gray to purplish red and in grain from fine quartzite to conglomerates, with pebbles one-fourth inch in diameter. The pebbles include white qnartzite, red and brown jasperoid, and white, 

smoky, or opalescent quartz of vein or pegmatitic origin. The rocks 

are rather constantly impure and grade through arkoses into minor 

beds of red and green slaty shale. The coarse-grained arkose resembles granite on first sight. The quartzite is usually considerably 

jointed.

This rock appears to have been deposited in a comparatively shallow sea, to which much fragmental material was carried. From its 

position, conformably beneath Cambrian limestone, this quartzite is 

undoubtedly to be correlated Avith the Prospect Mountain quartzite,6 

of loAver Cambrian age.

Prospect Mountain limestone. The Prospect Mountain limestone 

is the predominant rock of the Specter Range and the Skeleton Hills. 

It is typically light to dark gray, compact, crystalline, and fine 

grained. Some beds have a conchoidal fracture and are almost as compact and fine grained as lithographic limestone. Pinkish gray varieties of medium grain also occur, but are rather unusual. Cross-bedding is observed in places. The beds are typically massive, although 

certain horizons are thin bedded. On Aveathering the various beds

" See note, p. 2S.

6 Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, p. 35.
SPECTER RANGE AND SKELETON HILLS. 149

assume red, yellow, and gray colors of A^arying tints, rendering the 

mountain structure legible at great distances. Near the middle of the 

section, as exposed, are a fe\v layers of black chert, AA^hile a bed of. 

quartzose sandstone, 20 to 30 feet thick, occupies a similar position 

in the more northerly hills east of Fortymile Canyon; This rock, 

locally a quartzite, is Avhite or pinkish Avhite and fine grained.

The formation appears to be betAveen 5,000 and 6,000 feet thick. 

It Avas deposited in a sea of medium or shalloAv depth, in which 

depression of the sea bottom kept pace Avith deposition and into 

which little detrital material was introduced. A feAV poorly preserved fossils AVere collected north of the Skeleton Hills. Mr. E. O. 

Ill rich reports that these consist of trilobite fragments and a valve 

of a brachiopod, probably, refer able to the genus Billingsella. He 

believes that they are of Cambrian age. The limestone is without, 

much doubt the Prospect Mountain (Cambrian) limestone of Eureka, 

Nev.,a although the upper portions may belong more properly Avith the 

Pogonip limestone.

IGNEOUS ROQKS.

In no other-equal area surveyed during this reconnaissance do 

igneous rocks cover so little territory. The Avriter saAv no indications

j

/ Desert gravels.

3 miles

FIG. 15'. Northwest-southeast section through Specter' Range.

of granite or other intrusions, an observation verified by statements 

of several prospectors who have examined the .hills in considerable 

detail. A single small butte of vesicular basalt similar to that of 

the mesa south of Cane Spring protrudes from the desert gravels 

northeast of Point of Rocks. This butte is probably an erosional 

remnant of a flow which extended from this mesa southward.

STRUCTURE.

The Cambrian rocks are folded in a complex manner. Two sets 

of folds are present in almost equal development, the axes of one 

striking northeast, those of the other striking east and west. Zones 

of brecciation and normaj faults occur at a number of places, but 

few of the faults show a displacement of more than 30 feet. The 

fault 2 miles north of west of Point of Rocks'is normal and has a 

displacement of 100 feet. It trends N. 30° E. and the western side 

is downthrown. A sag in the hills coincides with the fault, the 

doAvnthrowri side being slightly higher than the upthrown. Fig. 15 

is a section passing through the hills from northwest to southeast.

"Hague, Arnold, Mon. U. S. Oeol. Survey; vol. '20, 1892, pp. 36-38.
150 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

ECONOMIC GEOLOGY.

Although the Cambrian rocks are cut by thin veins of white crystalline or banded calcite and by thin quartz veins, apparently barren, 

they appear to offer slight attractions to the prospector. The Johnnie mine, where strong quartz veins occur, lies 2 miles south of the 

area surveyed. From information furnished by prospectors it is 

'probably in the Prospect Mountain quartzite.

YUCCA MOUNTAIN. 

TOPOGRAPHY AND GEOGRAPHY.

Yucca Mountain is so called from the groves of the tree yucca 

which cover its lower slopes. The group lies between Fortymile Canyon on the east, Beatty Wash on the north, Oasis Valley and Crater 

Flat on the west, and the Amargosa Desert on the south. The 

mountains of the main east-west ridge are gently sloping domes with 

rugged summits, the highest of which is 6,700 feet above sea level. 

The ridge drops rather suddenly to Fortymile Canyon on the east, but 

on the west it descends gently and merges with Bare Mountain. 

From the main east-west ridge mesa tongues extend southward to 

the Amargosa Desert, rhyolite being the predominant rock. Yucca 

Mountain is colored dull tones of gray, brown, red, and yellow. Near 

the summits the varying resistances to erosion of the rhyolite flow beds 

are expressed in cliffs and gentle slopes. Spires tend to form where 

vertical joints are well developed. The mesa tongues to the south 

become lower toward the south-southeast, the surface being determined by resistant lava flows. The eastern side of these mesa 

tongues passes beneath the Recent alluvial deposits, while the western 

face is, as a rule, a scarp. The magenta-red basaltic cone 4 miles east 

of Rose's Well is a prominent landmark. Other volcanic cones are 

located in Crater Flat and for convenience will be described with 

Yucca Mountain.

The wide and open character of Beatty Wash between Timber and 

Yucca mountains is noteAvorthy. Alluvial deposits cover the depression for a width of 2 miles, although many hills of solid rock protrude 

from them. The narrowness of the canyon farther downstream is due 

partly to the more resistant character of the rhyolite to the west, 

while the. width of the upper valley is probably due to the rapid 

waste of the adjoining high mountain masses on either side.

No water is known in Yucca Mountain. A few junipers 'and 

pinons grow on the highest summits of the main ridge.

GENERAL GEOLOGY.

This mountain is composed entirely of igneous rocks, which include 

the following, beginning with the oldest: Post-Jurassic pegmatite, 

rhyolite and latite. and basalt.
YTJCCA MOUNTAIN, IGNEOUS ROCKS.

Post-Jurassic 'pegmatite. A single fragment of quartz-feldspar 

pegmatite-was noted in the basalt of the cone 8 miles north of Rose's 

Well. The basalt in its passage to the surface evidently passed 

through a mass of pegmatite.

Rhyolite and latite. The mountain mass, with the exception of a 

number of rather small basalt areas, is composed wholly of rhyolite 

and latite. The series includes siliceous volcanic rocks of varying 

aspect. The brown groundrnass in many instances is dense., aphanitic, 

and o.paque, and from the presence of flow banding, perlitic parting, 

spherulites, and lithophysa?, is evidently of a glassy nature. Gray 

and black semitransparent glasses also occur. The more altered f acies 

have a gray or white dull lithoidal groundmass and the microscope 

proves that this also was once a glass that is now devitrified. The 

phenocrysts are medium sized and usually subordinate to the groundmass; in certain instances they are practically lacking. Slightly 

smoky rounded quartz individuals and glassy unstriated feldspar 

crystals are present in equal development; smaller black or bronze 

biotite crystals are less abundant. In some f acies the phenocrysts are 

all orthoclase, but microscopic examination shows enough quartz in 

the groundmass to determine their rhyolite nature.

Latites 0 are interbedded with the rhyolites. They are slightly 

darker in color and contain both striated and unstriated feldspar 

phenocrysts in approximately equal development. The single specimen examined microscopically proves to be a clear glass, the brownish color of the hand specimen being due to abundant curved 

trichites radiating from a common center. Perlitic parting is beautifully developed. Phenocrysts of orthoclase and plagioclase- of 

medium composition are each more abundant than biotite. Wedgeshaped titanite crystals, magnetite, and a little hornblende are also 

present.

Interbedded with the rhyolite and latite flows are porous semi- 

.tutfaceous f acies. Flow breccias also occur, the inclusions being of 

a slightly different rhyolite than that of* the main mass. The central portion of the main east-west ridge is probably the site of a 

vent from which siliceous volcanic rocks flowed. The flows, which 

extended particularly to the south and west, reach a minimum thickness of' 1,000 feet. The series is a continuation of similar rocks of 

the Bare Mountain group. Presumably it is to be correlated with 

the rhyolites of the Bullfrog Hills and the Kawich, Belted, and 

Reveille ranges, and is probably of early Miocene age.

Basalt. In Crater Flat are two large and one small volcanic cone 

and a number of low mesa ridges of basalt. A fourth cone is situated

0 The use of the term latite is here tentative, since no chemical analyses of the rocks.

0 ;

have been made.
152 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

4 miles east of Rose's Well. The basalt of the cones is vesicular and 

. dull brick-red or black in color,, while in the flow pediment around 

the cones are dense black facies with a few greenish glassy grains 

of olivirie.

The cones are gently depressed and are usually superimposed 

upon circular basalt flows. The flows present ropy surfaces, cross 

fractures produced during the flow of the almost solid mass, and 

caverns formed by the onflow of the liquid interior after the surface 

had hardened into a crust, each a characteristic phenomenon of surface lavas which have been but little eroded. The cones themselves 

are formed in part of flows, but largely of vesicular lapilli, scoriae, 

and volcanic bombs. The intimate mixture of these red and black 

fragments imparts to the cones their magenta-red color. The cone 

4 miles east of Rose's Well has on its summit a crater, 300 feet.in 

diameter, which is depressed from 15 to 75 feet below its rim. Sulphur coats the volcanic breccia in the crater. The crater of the cone 

7 miles north of Rose's Well has been largely destroyed by erosion, 

the throat displaying a "rubble of vesicular basalt fragments. Beds 

of fragmental material dip inward toward a common center at the 

crater of the cone \\ miles farther north.

Since the eruption of the basalt the cones have been somewhat 

eroded, calcium carbonate has been deposited in the vesicles, shrubbery has taken root on the lava flows, and a sand' dune has been superimposed upon the cone 4 miles east of Rose's Well. The basalt is 

probably of very late Pliocene or early Pleistocene age.

STRUCTURE.

The rhyolite-latite series has been subjected to mountain-building 

forces acting in an east-west direction. Joint sheeting and normal 

faults striking north and south are developed in the mass, while m\nor 

joints of east-west strike are also present. The series had been carved 

into forms approximating those of the present day when basalt eruptions occurred.

ECONOMIC GEOLOGY.

Two small masses of rhyolite whose location is shown on the map 

(fig. 4, p. 43) are kaolinized and silicified in a similar manner to the 

rhyolite in the vicinity of ore deposits. Silicification has occurred 

along joints and in irregular forms, and these resistant masses form 

the topographic details peculiar to silicified areas of rhyolite. Tunnels 

have been driven in the larger of the two areas, the ore extracted being a silicified rhyolite slightly stained by limonite. The ore, in part 

free milling and in part refractory, is said to carry gold with minor 

silver values. Quartz does not seem abundant in either area.
MOUNTAINS SOUTHEAST OF PAHUTE MESA. 153

TIMBER MOUNTAIN. 

TOPOGRAPHY AND GEOGRAPHY.

Timber Mountain, named on account of its heavily forested summits, is bounded on the east and northeast by Fortymile Canyon, on 

the northwest and west by Oasis Valley, and on the south by Beatty 

Wash. A low divide connects it with Pahute Mesa to the north. The 

massive mountain has two peaks, each 7,500 feet high, which are separated by a col. The western slope to Oasis Valley is somewhat more 

gentle than that on the east to Fortymile Canyon. The heaviest 

forest growth in the area surveyed covers this mountain above an elevation of 6,300 feet. Some of the trees are of sufficient size to be 

of value as timber.

GEOLOGY.

Timber Mountain appears to be wholly composed of Tertiary rhyolite and basalt, the rhyolite being the older.

Rhyolite. The mountain peaks and the north and west slopes are 

formed of rhyolite, which imparts to the mountain a red tone. The 

most abundant variety is a dense brown or red rock in which the phenocrysts, medium-sized glassy orthoclase and slightly smoky quartz 

with fewer bronze biotite, equal or exceed the groundmass in bulk. 

The rjiyolite is but an extension of that of Yucca Mountain, and the 

various facies there noted probably also exist on Timber Mountain. 

The rhyolite is presumably of early Miocene age. *

Basalt. The rhyolite of Timber Mountain had been eroded into 

practically its present form when ba'salt was extruded, filling depressions in the rhyolite and forming level reaches here and there on the 

mountain. Basalt flanks Timber Mountain on the east, forms the 

prominent black dome 8 miles east of south of the more northerly of 

the two peaks, and occurs in several areas on the western slope of the 

range. The basalt is a dense black or dark-gray rock in which striated feldspar and olivine phenocrysts are prominent. Much of the 

basalt is vesicular, and the rounded cavities, locally filled by zeolites, 

vary greatly in size across the flow banding. The basalt flow reaches 

a thickness of over 1,000 feet. The basalt of Timber Mountain is 

much younger than the rhyolite, and from the amount of erosion 

which it has suffered it is believed to be one of the late Pliocene or 

early Pleistocene basalts.

BARE MOUNTAIN. 

TOPOGRAPHY AND GEOGRAPHY.

Bare Mountain, so named on account of its almost total lack of 

verdure, lies south of Oasis Valley and Beatty Wash, between the 

Amargosa Desert and Crater Flat. The mountain mass is triangular 

in form, the apex being at the south end. It is 15£ miles long from
154 SOUTH WESTERN NEVADA AND EASTERN CALIFORNIA.

north to south -.and 8 miles wide at the north, its broadest portion. 

The Bare Mountain hills are comparable to the most rugged portions 

of the Amargosa and Panamint ranges, the valleys being deep Vshaped troughs and many of the ridges between being knife-edges. 

Throughout the range the south sides of the gulches are somewhat 

less steep than the north sides, owing to the prevalent dip to the 

northeast. The highest point of Bare Mountain, 6,235 feet above sea 

level, is but 2 miles from the detrital pediment 3,000 feet below. The 

strongly folded Paleozoic rocks band the mountain with dark and 

light gray, yellow, white, and red. No water is known in these bare 

hills. . GENERAL GEOLOGY.

The formations exposed in Bare Mountain, from the oldest to the 

youngest, are as follows: Pogonip limestone, Eureka quartzite, pegmatite, monzonite porphyry, rhyolite-, and basalt.

PALEOZOIC SEDIMENTARY ROCKS.

Bare Mountain is composed largely of Paleozoic sedimentary rocks 

so strongly folded and faulted that a satisfactory section could not be 

made in the time at the writer's disposal. The series presented from 

the top down is probably as follows:

Probable sect-ion in, Bare Mountain.

Feet.

Schist '___________J___________-t_____________ 200 

Qnartzite with some schist and limestone_______________ 1,000

Limestone containing near its top a considerable number of beds

of schist____________________________________ 3, 000-4, 000 

Quartzite and schist______________________________ 100-200

At the top of the series the schist, limestone, and quartzite repeatedly replace one another within a thickness of 100 feet. These 

rocks, particularly at the north end, have been metamorphosed, the 

original limestone, shale, and sandstone being altered, respectively, to 

marble, schist, and quartzite.

The limestone in the central part of the range is dark gray to blueblack in color, fine grained, compact, and rather crystalline. Anastomosing veinlets of calcite are characteristic. Much of the limestone 

is thinly laminated. At the north end of the mountain the limestone 

is changed to a white or light-colored marble, for the most part 

rather coarse grained. Weathered surfaces are yellow or brownish 

in color. Muscovite films are developed on parting planes. The 

upper and lower quartzites consist of a white or light-gray metamorphosed quartzose sandstone of fine or medium grain and conchoidal 

fracture. Cross-bedding is common and ripple marks are present in 

places. In transition to schist the quartzite becomes darker in color, 

finer in grain, and less pure, some muscovite being present. The
BARE MOUNTAIN, IGNEOUS BOCKS. . 155

original shale of the series, now a silvery or greenish-gray mica schist, 

is well exposed near Gold Center. The schist is a fine-grained, 

foliated, and locally crenulated rock composed of micaceous minerals 

with some quartz and feldspar. Small magnetite and pyrite crystals 

are common in certain bands and are evidently contemporaneous with 

the other metamorphic constituents. The planes of schistosity are 

usually parallel to the bedding planes, which are in places ripple 

marked, although in certain instances the foliated structure crosses 

the original bedding at right angles. Weathered outcrops have a 

typical rusty appearance. A single thin section under'the microscope 

showed a thoroughly recrystallized rock lacking all traces of original 

structure. The rather well oriented micaceous minerals are muscovite, biotite, and limonite-stained chlorite, and grains of quartz and 

orthoclase lie between their blades. Tiny magnetite crystals and 

grains are abundant.

The lower limestone member of the series was deposited in a sea 

of medium depth, into which for a long period little or no fragmental 

material was carried. The upper portion of the series, on the other 

hand, was deposited in a shallow sea which at times received fragmental material of varying grain. The quartzites and schists mark 

periods in which the deposition of fragmental material exceeded 

organic and chemical sedimentation, while the interbedded limestones 

indicate a reversal of the dominant process. A few poorly preserved 

fossils (one of which is identified by Mr. E. 0. Ulrich as a gasteropod 

suggesting Eccyliopterus or some other euomphaloid genus) were 

obtained from Bare Mountain, and although by no means diagnostic 

of the age of the series, they are probably younger than the Cambrian 

and older than the Carboniferous. The basal quartzite may be an 

intercalated bed in the Pogonip limestone or possibly may represent 

the Hamburg shale of the Eureka section. The thick limestone on 

lithologic grounds is correlated with the Pogonip (Ordovician) limestone, while the overlying quartzite is probabty the Eureka (Ordovician) quartzite of Hague.'1 This upper quartzite and schist rather 

closely resemble the Eureka quartzite of the Kawich Range. The 

area covered by the two formations is roughly indicated on the map 

(PL I), but future work will prove the distribution much more, 

complex.

IGNEOUS ROCKS.

Post-Jurassic pegmatites. Pegmatitic dikes from 2 inches to 4 

feet thick are common in the northern part of the range. The most 

widely distributed type .is composed of white or very light pink feldspar, with some "colorless quartz and'muscovite. None of the individuals exceed a diameter of one-half inch. A less common variety

" Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1802, pp. 54-57. 
156 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

is a glassy quartz in which are many biotite flakes one-eighth inch in 

diameter. A few black tourmaline rods up to one-fourth inch long 

occur in a quartz-rich muscovite pegmatite. While some of the 

tourmaline occurs in nests of clustered rods, some also forms along 

minute cracks and appears to be of pneumatolitic origin. Pegmatitic quartz veins with small quantities of feldspar and muscovite are 

very common, and it is probable that many of the older quartz veins 

were deposited by waters from the granite magma. The pegmatite 

dikes cut Paleozoic rocks and are included in the Tertiary volcanic 

rocks, and are probably post-Jurassic in age. They closely resemble 

the pegmatites west of Bullfrog.

Diorite porphyry. Bowlders of the biotite-monzonite porphyiy 

or diorite porphyry occur on an alluvial fan at the northwest edge of 

Bare Mountain. Dikes of this rock, possibly of pre-Tertiary age, 

probably cut the Paleozoic rocks.

Tertiary rhyolite and basalt. Flows of rhyolite and basalt form 

the north end of the Bare Mountain hills. These are similar lithologically to the rhyolite and later basalt of the Bullfrog Hills. (See 

pp. 180-181.)

STRTJCTTJKE.

The Paleozoic rocks of Bare Mountain form a faulted monocline, 

the beds of which strike from north of west to northwest and dip 

from 15° to 80° NE. Superimposed upon the monocline are minor 

cross folds. The schist and in a less degree the limestone are closely 

crenulated and small isoclinals and overturned folds are common. 

The folding was so intense that schist bands between limestone and 

quartzite are severed on the limbs of the folds and greatly thickened 

at the crests and troughs. At least two profound normal faults of 

over 1,000 feet displacement cut the Paleozoic rocks, and other faults 

of almost equal magnitude exist. Small faults, both normal and 

reverse, are common. Joints traverse all the formations, but are 

particularly developed in the quartzite, which in consequence breaks 

down into squared blocks.

Prior to the extrusion of the Tertiary rhyolite the range stood out 

boldly and was probably as high or almost as high as at present. The 

clifferential movement which has occurred at the contact of the Paleozoic and Tertiary rocks is unimportant.

ECONOMIC GEOLOGY.

Quartz veins are common in the north end of the range, and mineral locations were made on some of them early in 1905. Older veins, 

which were folded with the Paleozoic rocks, are cut. and faulted by 

a younger set. All the quartz veins are characterized by rather 

abrupt variations in width.

The Decillion claim is located in the northwestern portion of the
BABE MOUNTAIN SAECOBATUS FLAT. 157

range near the mouth of a deep canyon. The principal development 

work is a 50-foot shaft. Quartz veins and stringers reaching.a maximum thickness of 1 foot cut limestone and schist. Some of the veins 

strike east and west and dip 45° S. Chalcopyrite in grains up to onehalf inch in diameter is disseminated through the quartz. Malachite 

and a little azurite stain the quartz around the sulphide and have 

been deposited in cavities in the quartz. The quartz vein since its 

deposition has been faulted and crushed, the fragments being in places 

cemented by granular gypsum, while gypsum crystals line some cavities. The ore of this mine is said to run high in silver, with low gold 

values.

The two 50-foot shafts 'of the Kismet Mining Company, better 

known as the Lonsway property, are situated on the crest of a high 

ridge 1| miles southwest of Beatty. The country rock here, a quartzite, strikes N. 35° W. and dips 15° NE. The quartz vein, which is 

traceable for several hundred feet, is from 1£ to 2 feet wide and strikes 

N. 85° W. and dips 55° S. The quartz has a sparry texture arid is 

white except at the surface, where it is heavily stained by limonite 

and hematite. This vein is said to have been locally, charged with 

gold, probably derived from pyrite which occurs with limonite in 

quartz at the bottom of the shaft. The quartzite near the vein is 

sheeted. Silver ores with purple-fluorite gangue occur at the Lige 

Harris prospect. In other portions of the. range the quartz veins contain galena cubes.

The quartz and associated sulphides were deposited in open eastwest fissures, possibly by granite magmatic waters. Later the veins 

were faulted and crushed, and surface waters have more or less completely altered the sulphides to oxides and carbonates, forming freemilling ores.

The mines on Bare Mountain are controlled by practically the same 

economic conditions as those of the Bullfrog district. Good water can 

be obtained in the springs of Amargosa Eiver one-half mile away. 

The most accessible wood is that of the Amargosa Mountains', 25 

miles distant. The mines are 1 to 8 miles from the proposed railroad to the Bullfrog district.'

SARCOBATUS FLAT.

Sarcobatus Flat lies west of Pahute Mesa and'east of the Amargosa Range and Slate Ridge., It is one of the largest valleys in the 

area surveyed, .being 32 miles long and having an average width of 

10 miles. It has very gently graded slopes. Near its center, at an 

elevation of 3,950 feet, is a large playa, and two small play as lie in 

the arm of the valley south of Tolicha Peak. The surface of the 

larger playa is slightly roughened by erosion, but the total difference 

of altitude over the entire" flat is probably less than 20 feet. A few
158 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

lime-carbonate concretions of rude cylindrical form are embedded in 

the playa clay. Similar concretions occur in the playa clay of the 

Alkali Spring flat.

Adobe bricks have been made from the playa clay at several places, 

and it is probable that the clay of all the playas is well adapted to 

their manufacture. Borax is said to have been leached from the 

clay of this flat 3 miles south of east of Montana Station. The industry was never extensive, and until the rich bedded deposits of 

borax minerals are exhausted these playa deposits will be commercially unimportant. A number of wells, sunk in or near the large 

playa, have uniformly obtained water. In the center of the playa the 

surface and the water table are practically at the same level (see fig. 

2, p. 21). The coyotes scratch holes from 2 to 3 feet deep in the clay 

and get water. The water is adequate for domestic and stock purposes and for the most part pure, although some is brackish and that 

in one well is unfit for use. Water was obtained at the following 

depths in the various wells: Forks of Goldfield-Bullfrog and Goldfield-Beatty roads, 180-190 feet; Farmer Station, 8-10 feet; Thorp's 

mill, 30 feet; Montana Station, 18 feet; Summerville, 1 mile south 

of Montana Station, 8-9 feet; Tonopah Well, 10-12 feet, and Seattle 

Well, 40-50 feet. Mr. E. L. Eickard reports that the water at Montana station occurs in a layer of quicksand.

AMARGOSA DESERT.

The Amargosa Desert is one of the most extensive depressions in 

the Great Basin. The main valley heads against the Amargosa 

Range and Bullfrog Hills, south of Sarcobatus Flat, with which it is 

connected by a thin ribbon of Recent gravels, and trends southeast to 

Ash Meadows, and thence south 60 miles to a point where it swings 

around the Funeral Mountains to join Death Valley. Within the area 

mapped the valley is about 10 miles Avide at the north end, contracts 

in the middle, and expands to a width of 21 miles at the southern 

border of the area. The valley sends branches well into the surrounding mountains. From the summit south of Currie Well the valley 

descends 1,600 feet in 10 miles and but-500 feet in the next 20 miles. 

The cross section of the valley is comparatively flat except in the 

northern part. The lowest portion within the area shown on the map 

lies at an elevation of 2,500 feet. The channels of the so-called Amargosa River and of Forty mile Canyon, each characterized by bowlders 

and coarse gravel, are slightly depressed beneath the surface of the 

valley. The valley is without grass, but is covered with a sparse 

growth of creosote bush and other shrubbery, while mesquite trees 

grow north and east of Ash Meadows.

The Recent detrital deposits in the southern portion of the valley 

are fine grained, and the wind has heaped these into dunes, The most
AMAEGOSA DESERT. 159

important group of sand dunes, 3 miles south of Rose's Well, is shown 

on the map. .The Amargosa mine at Rhyolite has been sunk 330 feet 

in Recent gravel, and in some portions of the valley the Recent alluvial deposits are probably 500 or more feet deep. Inliers of Tertiary 

and Paleozoic rocks are, however, common. Many hills and ridges of 

Paleozoic limestone protrude from the gravel in the southeast corner 

of the area. The line of Paleozoic inliers northwest of the sand dunes 

is probably the crest of a ridge formerly connected with the Amargosa Range, but now separated from it by a mantle of detrital 

material.

The springs at Ash,Meadows have already been described (p. 20). 

Water has been obtained at the following depths in three wells in the 

valley: Rose's Well, 208 feet; Miller Well No. 1, 183 feet; Miller 

Well No. 2, 70 feet. The water in all cases is good, although that of 

Rose's Well has a slight saline taste. The log of Miller Well No. 1, as 

reported by Mr. W. F. Miller, is as follows:

Lay of Miller Well No. .1, Amuryosu, Desert.

Feet. 

Gravel _____________________________________________________ 2

"Cement," indurated gravels_____________________'________ 70

Gravel __________________________________________ 4-6

" Cement " _i_____________'. ____________________________ 10-12

Sand _________________'. ______________________ 0-7

" Cement " _____________________________________ 78

Gravel (water stratum)___________________-__________ 11

Playa and alluvial slope deposits of the older alluvium outcrop in a 

number of places in the Amargosa Desert, and these beds probably 

underlie at no great distance the south end of the valley.. The hills 

in the desert 8 miles south of Bullfrog are composed of angular and 

subangular bowlders and sand derived from the surrounding hills, 

and among other rocks basalt occurs. The material closely resembles 

that of the present alluvial slopes. It has been eroded into hills, and 

its bowlders are somewhat weathered. It is without doubt an alluvial 

slope contemporaneous with the playa deposits next, described. South 

of Rose's Well exposures of ancient playa deposits are common, and 

the northern border of the old playa appears to have been north of 

this well. At the southern border of the area surveyed this playa 

was probably 20 miles wide. The deposits now occur as IOAV, white 

domes and dissected mesas, which are particularly abundant southeast and east of Miller Well No. 2. Six miles,west of the Big Dune 

the deposits consist of fine-grained clay, in which are embedded many 

grotesque lime-carbonate concretions. Bedding planes are rare, but 

appear to be horizontal. The small deposit 1 mile north of Rose's 

Well is similar except that a-few small, well-rounded pebbles occur 

in the clay and that a 1-foot layer of white porous limestone is inter-
160 SOUTHWESTERN NEVADA. AND EASTEEN CALIFORNIA.

bedded Avith it. These becls at Ash Meadows form white limestonecapped mesas and buttes, which are landmarks for miles. A section 

of the bluff north of Ash Meadows is as follows:

Section of 'bluff north of Ash Meadows.

Feet.

1. White, carious, dense limestone, with ninny lenticular openings parallel to 

the bedding. The limestone is finely banded parallel to these openings 

and has the characteristics of chemically precipitated limestone___ 10

2. White, tine-grained clay, massive, inclosing small crystal aggregates of 

selenite_______-_________-________________________ 40

3. Limestone like No. 1____________________________ 1

4. Clay like No. 2_.-_-________.__.____________________ ___ 20

5. Limestone like No. l___.-___________________________ . £

6. Clay like No. 2_____________________________________ 30

These beds lie horizontal, although Campbell a states that farther 

south they dip to the west. The playa deposits and gravels are 

without doubt members of the older alluvium, which is considered 

in part of late Pliocene and in part of Pleistocene age.

AMARGOSA MOUNTAIN SYSTEM.

The Amargosa Mountain system, including the Amargosa Range, 

Gold Mountain, Slate Ridge, and the Bullfrog Hills, is the most 

important uplift in the area under discussion. The mountain mass, 

which has a northwesterly trend, lies between Death Valley on the 

west and Sarcobatus Flat and the Amargosa Desert on the east. 

Geologically this mountain system is characterized by the widespread 

distribution of early Paleozoic rocks and in its northern portion by 

the presence of granite.

AMARGOSA KANGE. 

TOPOGRAPHY AND GEOGRAPHY.

The mountain range between Sarcobatus Flat and the Amargosa 

Desert on the east and Death Valley on the west is designated the 

Amargosa Range by the United States Geographic Board, which 

also calls that portion of the range north of Boundary Canyon the 

Grapevine Mountains and that south of the canyon the Funeral 

Mountains. The mountain range as a Avhole is a unit, the most 

natural division on physiographic and geologic grounds being at 

Furnace Creek, south of the area surveyed", as suggested by Spurr.'J 

The range here changes its trend; moreover, to the south of Furnace 

Creek it is composed principally of Tertiary sedimentary .rocks and 

to the north of much older rocks.

The sinuous crest line of the Amargosa Range trends N. 40° W. 

and roughly coincides with the California-Nevada boundary line.

" Campbell, M. R., Bull. T.T. S. Oeol. Survey No. 200, 1002, p. 14. 

"Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 1903, p. 187.
AMARGOSA RANGE. 161

The northeastern side of the range is not impressive, the crest line 

rising only 2,000 to 4,000 feet above the Amargosa Desert and 

Sarcobatus Flat. On the other hand, the crest is from 5,000 to 7,000 

feet above Death Valley, and in consequence the southwestern slope is 

steep, deeply cut by canyons, and set with numerous rugged peaks 

and pinnacles. The ridge culminates near its north end in Grapevine Peak, 8,705 feet above sea level. Wahguyhe Peak, with an elevation of 8,590 feet, is a magnificent truncated cone.

The Amargosa Eange from Death Valley presents a somber appearance, the grays and blacks of the Paleozoic rocks predominating. 

The northern and middle portions of the range, as seen from the 

Amargosa Desert and Sarcobatus Flat, are colored by the rather 

brilliant reds, yellows, white, and grays of rhyolite flows.

The valleys heading in the range from the east are wide and gently 

sloping, and in some places, as at Indian Pass, broad detritus-filled 

embayments extend almost to the range crest. The stream channels 

on the southwestern side of the range are deep canyons, which, near 

the higher peaks, are sunk 3,000 feet beneath the sharp ridges on 

either side. The tortuous stream bed of Titus Canyon is only 40 

feet wide, and from it the rocks rise sheer 200 feet, while the slope 

to the ridges 2,000 feet above is very steep. The canyon walls to a 

height of 40 feet are water polished, and cloudbursts have recently 

lodged bowlders 50 feet above the stream bed. The smoother reaches 

of the stream gradient are separated by transverse rock walls from 

10 to 100 feet high. These barriers, Avhich in most regions would 

cause waterfalls, are formed of resistant rock strata.

The eastern side of the range, from Chloride Cliff southward to 

the boundary of the area here discussed, is topographically older than 

the rest of the range, being a land surface to be correlated with similar tracts in the Panamint, Belted, and Kawich ranges. (See pp. 99, 

119, 202.) A smaller area of this older topography is situated north 

of Thimble Peak. These portions of the range are characterized by 

dome-like mountains, shallow and gently sloping valleys, deep soil, 

and comparatively few and inconspicuous rock exposures. The area 

north of Thimble Peak is surrounded, by deep-cut canyons, and the 

drainage lines pass precipitously'from the mature upland to the young 

gulches. This mature topographic surface at one time extended over 

the whole mountain range, but is now preserved only where advantageously situated. Since it forms the eastern slope of the range south 

of Chloride Cliff and is npt present on the western slope, it may be 

inferred that the grade of the streams on the west has been greatly 

increased by a rather recent depression of Death Valley. This depression occurred probably in early Pleistocene time, since a similar 

Bull, 308 07 M 11
162 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

surface in the Panamint Range was developed before the outflow of 

late Pliqcene or early Pleistocene basalt. (See p. 202.)

The crest of the Amargosa Range above 6,000 feet, at a distance of 8 

miles northwest and southeast of Grapevine Peak, is partly covered by 

a sparse growth of pinon and juniper. The largest trees are 1-| feet 

through and from 20 to 25 feet high. The Paleozoic rocks to the west 

of the crest line are bare even above an elevation of 6,000 feet. Some 

grass grows in the higher valleys on the northeastern slopes of the 

range. South of Chloride Cliff the Grapevine Mountains have but 

few springs, and the largest of these is said to be poisonous and is 

shunned by the Indians. North of Chloride Cliff springs are comparatively abundant. The largest of these, Keane Spring, flows 

about 1,350 gallons per day; the two Willow springs and Daylight 

Spring, from 500 to 1,000 gallons each. The other springs are 

smaller, Hole in the Rock, when full, containing only about 10 

gallons.

GENERAL GEOLOGY.

The formations exposed in the Amargosa Range, from the oldest 

to the youngest, are as follows: Prospect Mountain quartzite (?), 

PogonifT limestone, Eureka quartzite, Lone Mountain limestone, postJurassic granite, pre-Tertiary diorite porphyry, biotite andesite, 

earlier rhyolite and contemporaneous- basalt, Siebert lake beds, later 

rhyolite and biotite latite, and basalt.

SEDIMENTARY BOCKS.

Prospect Mountain quartzite (f}. The Amargosa Range south of 

a line somewhat north of Chloride Cliff is formed of a series of 

quartzite beds with intercalated schists and garble. The large hill 

group north-northeast of Lee's Camp and the small boss-like hills 

northwest of the Big Dune are of the same formation. This series, 

which includes several thousand feet of sedimentary rocks, is considerably metamorphosed, the alteration being more evident in the 

schists and the quartzites than in the marble.

The quartzites are usually white, pink, or gra}^ in color, although on 

the one hand a cement of specula.r hematite and on the other much 

clayey matter in the quartzite change the color to black. The normal, 

rather pure quartzose rock is fine to medium grained, and is in many 

places thin bedded. Cross-bedding and ripple marks are locally 

present. The quartzite passes into conglomerate with well-rounded 

pebbles, which reach a maximum diameter of one-half inch. The 

pebbles are of quartz, of vein or pegmatitic origin, .white quartzite, 

black jasperoid, and schist. The development of sericite, particularly 

in the conglomeratic facies of the quartzite, imparts a greenish tinge 

to the rock. On microscopic examination this sericite proves to be
AMAEGOSA BANGE, SEDIMENTARY KOCKS. 163

contemporaneous with the quartz cement, which secondarily enlarges 

the clastic grains of quartz. Mashing, besides developing sericite, 

has locally elongated the pebbles of the conglomerate, forming a 

schistose conglomerate.

The more impure quartzite grades into slaty shales and schists. 

The shales are fine grained and of a greenish or dark-gray color, with 

laminae from one-sixteenth to one-half inch thick. The slaty shale has 

usually a few muscovite plates on its parting, planes and passes, with 

gradations, into fine-grained bluish or greenish-gray sericite schists. 

The schistosity is usually parallel to the original bedding of the rock, 

but in- places cuts it at all angles. In the schist deep-red garnets, 

small tabular hexagonal greenish plates (ottrelite), greenish-gray 

micaceous aggregates (chlorite), or grayish prisms (andalusite) are 

developed. Under the microscope these schists appear without original structures. Fine shreds of sericite, with chlorite, in some thin 

sections are well aligned parallel to the schistosity, and between such 

bands are fine mosaics of quartz and a little orthoclase. Among the 

phenocrystic minerals of the series, clearly of later origin than the 

groundmass, are staurolite, andalusite, ottrelite, biotite, chlorite, garnet, ilmenite, and magnetite. Zircon, graphite, and rutile are present 

locally. Small crystals of tourmaline, cutting the* schistosity in all 

directions, are present in most of the thin sections. The occurrence 

of this mineral 10 miles or more from the nearest granitic outcrop 

possibly indicates the presence of .a considerable body of granite beneath the Amargosa Range. The interbedded marbles are fine- to 

medium-grained rather dense rocks, of buff, pink, purple, gray, or 

white color. Much of the marble is finely laminated. The presence 

of clastic grains and small pebbles of quartz and of cross-bedding 

indicates that the original limestone was deposited in shallow water. 

Through metamorphism not only has the 'rock been thoroughly recrystallized and locally somewhat silicified, but muscovite has been 

developed on the parting planes, and calcite veins, cutting it in all 

directions, have been formed.

Interbedded with and sending short arms out into the schist at 

Poison Spring are thin discontinuous sheets of hornblende gneiss, 

composed of a fine mosaic of quartz and feldspar, with much fibrous 

greenish-black hornblende and in certain bands red garnet. Under 

the microscope the mosaic is seen to be composed of quartz, orthoclase, and plagioclase. In the mosaic are large skeletons of hornblende, garnet, zoisite, and titanite. Apatite and magnetite are present as accessory minerals. Chlorite is secondary to hornblende, 

sericite, or kaolin, and calcite to the feldspars, and zoisite to the mutual alteration product of hornblende and plagioclase. A sheet of 

hornblende schist cuts across the bedding planes of marble and schist 

at a low angle 200 yards west of the Chloride Cliff camp, near the
164 SOUTHWESTERN NEVADA AND EASTEEN CALIFOKNIA.

head of a gulch. The sheet is over 200 feet thick and is at least onefourth mile long. This schistose rock is composed largely of hornblende, with some quartz and feldspar. Eed garnets which reach 

a maximum diameter of one-half inch are abundant in some portions 

of it and are also present in the adjacent sericite schist. The hornblende schist is composed of the following minerals, named in the order of their abundance: Hornblende, quartz, biotite, plagioclase 

(oligoclase in part), orthoclase, garnet, magnetite, and apatite. The 

rock has the form of a sheet injected in the Cambrian rocks. This 

schist and the gneiss above described, each of which is probably a 

mashed basic igneous rock, are the oldest igneous rocks known- in the 

nrea surveyed. The hornblende rocks are older than the post-Jurassic granite, which is everywhere massive, and since they have suffered 

approximately the same metamorphism as the rocks which they inject they, are probably of Paleozoic age.

The sedimentary rocks of this series were laid down in a shallow 

sea in which the conditions of deposition were constantly and rapidly 

changing. Fragmental material was carried into the sea even during 

the deposition of limestone, since clastic quartz grains are common 

in it.

The series is identical with that of Tucki Mountain, in the Panamint Range. Its age was not definitely determined, since unfortunately the contact with the Ordovician and Silurian rocks lies 

between two traverses made across the range. Lithologically it 

more closely resembles the Prospect Mountain quartzite (Cambrian) 

of the Specter Range than any other formation. The two are both 

quartzites, with shale and conglomeratic facies containing similar 

pebbles. Limestone was, however, not noted in the quartzite of the 

Specter Range. While tentatively considered Cambrian, these sedimentary rocks may in reality be of pre-Cambrian age. The severe 

metamorphism of the series indicates that the rocks have undergone 

folding not suffered by the Ordovician rocks farther north, and that 

they are hence of pre-Ordovician age.

1 Pogonip limestone. The Pogonip limestone extends from Keane 

Springs northwestward to Grapevine Canyon. It also covers a large 

area north of Grapevine Springs and smaller areas in the vicinity 

of and north of the Staininger ranch, east of Cave Rock Spring, and 

4 miles east of boundary post No. 94. In the large area north- of 

Keane Spring from 2,000 to 3,000 feet of limestone is exposed. "It 

is a fine- to medium-grained dense rock, most of it dark gray or black 

in color, though some beds are light gray. The laminae are as a rule 

from one-sixteenth to one-fourth inch thick, while the bedding planes 

are from 4 inches to 40 feet apart, heavy bedding being rather 

characteristic. Calcite veinlets anastomose throughout the limestone mass, and in Titus Canyon areas of coarse white calcite blotch
AMAKGOSA RANGE, SEDIMENTARY ROCKS. 165

the limestone. A thin bed of white quartzite is interbedded with 

the limestone in the lower part of the series at Cave Rock Spring. 

Similar quartzite and black 'flint occur in the limestone north of 

Grapevine Springs.

The Pogonip limestone is rather fossiliferous, the fossils being of 

Ordovician age. From the limestone north of Grapevine Springs 

poorly preserved fossils were collected, which Mr. E. O. Ulrich 

identified as Orthocerds olorus and 0. perroti, other Orthoceras 

fragments, and a fragment of a pelecypod probably of the genus 

Clionychia. These fossils indicate a middle Ordovician horizon. 

Mr. F. B. Weeks a collected Ordovician fossils from the main Paleozoic area, 5 miles southeast of the Staininger ranch, and Mr. G. K. 

Gilbert ** collected fossils in Boundary Canyon which he considered 

early Silurian or Cambrian.

«/ -o <y

Eureka quartzite. Overlying the Pogonip limestone near Boundary Canyon is about 800 feet of quartzite. It is well exposed at 

Daylight Spring and is a pink, rather pure quartz rock of medium 

grain. The bedding planes, which are rather massive, are emphasized by many fine laminae varying slightly in color and in size 

of the constituent grains. Conglomeratic bands containing wellrounded pebbles one-half inch in diameter occur. Some of the pebbles are of quartzite, possibly derived from Cambrian rocks. Thin 

layers of black fine-grained argillaceous quartzite and of olivegreen or brown slaty shales are also interbedded with the normal 

quartzite. This rock is correlated, with considerable confidence, 

with the Eureka quartzite (Ordovican).

Lone Mountain limestone. Overlying the supposed Eureka 

quartzite in the vicinity of Keane, Daylight, and Willow springs 

is about 300 feet of limestone which resembles the Pogonip closely, 

although less distinctly bedded. This is probably the Lone Mountain 

limestone ° of the Eureka section. The inlier 4 miles north of the 

Staininger ranch is composed of fine-grained dark-gray limestone, 

with interbedded black flint, white or pink quartzite, and limy 

shales. Imperfect silicified fossils, one of which Mr. E. O. Ulrich 

considers a late Silurian coral' (genus Cladopora] , were collected 

by the writer from this locality. Other small inliers in this vicinity 

may in realty be the Lone Mountain limestone rather than the 

Prdgonip.

^Siebert lake -beds and contemporaneous deposits. The rather large 

mass of later, rhyolite and biotite latitS to the southeast of Stainingers Ranch has between its flows layers of white or light-colored in-

« Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 1903, p. 188.

"Gilbert, G. K., U. S. Geog. Survey W. 100th Mer., vol. 3, 1875, pp. 34, 169, 181.

<= Hague, Arnold, Mon. U. S. Geol. Survey, vol. 20, 1892, pp. 57-59.
166 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

coherent tuffaceous sandstone, which readily breaks down into sand. 

The section at this point is as follows:

Section southeast of Stainingers Ranch.

Feet

Lava, largely biotite latite____________________________ 375 

Rhyolite flows and some tuffiaceous sandstone-__________________ 100 

Tuffaceous sandstone and thin rhyolite flows________________ 375

Rhyolite flows ___________^______________________^____ 75 

Tuffaceous sandstone.___ _________________________ 225

Between the lava and the sediments are minor erosional gaps, but 

these are probably current erosional unconformities, and the series is 

approximately all of one age. Bedding planes from 2 inches to 20 

feet apart are well developed at some places.

Locally the tuffaceous sandstone lies unconformably upon folded 

Pogonip limestone. It is closely similar to that of the Mount Jackson hills and, like it, is overlain by siliceous lavas. This formation is, 

without much doubt, the Siebert lake beds.

A number of small areas of conglomerate occur on the eastern slope 

of the Amargosa Eange, east of boundary post No. 94, southeast of 

Daylight Spring and north of Willow Spring. The rocks, varying 

from loosely to rather strongly consolidated material, consist of conglomerates and arkoses with a little shale. They range in color from 

green to red, yell'ow, or brown. Bedding planes, which are from 1 

inch to 2 feet apart, are well developed. The pebbles in the conglomerate, which are-very well rounded and many of them highly polished, 

reach a maximum diameter of 4 inches. They are derived principally 

from the Paleozoic rocks near by, with here and there a pebble of fineto medium-grained granite, and in the area east of boundary post No. 

94 some of earlier rhyolite. These rocks appear to be the shore deposits of a lake in which waves swept with considerable force. Material was transported from considerable distances, since granite does 

not now outcrop in the vicinity. Since the conglomerate contains 

pebbles of rhyolite and none of basalt, the deposits are younger than 

the rhyolite (early Miocene) and older than the basalt (PliocenePleistocene), and in consequence of middle or late Tertiary age, presumably Miocene. They are approximately contemporaneous with 

the lake in which the Siebert lake beds were. deposited, and it is believed that they are shore deposits of that lake. The conglomeratic 

lake beds of the Funeral Mountains, south of the area mapped, are 

to be correlated \vith these conglomerates. >v

Older alluvium. From a point 8 miles north of Surveyors Well to 

a point 3 miles north of Mesquite Spring the western flank of the 

Amargosa Eange is formed of older alluvium, and the same formation covers a considerable area west of boundary post No. 85. This 

deposit consists of clays and bowlder beds similar to those of Death
AMAEGOSA RANGE, IGNEOUS ROCKS. 167

Valley and the Panamint Range and, like them, is considered in part 

of Pliocene and in part of Pleistocene age.

Probably representing stream gravels contemporaneous with the 

older alluvium are small areas of conglomerates in Boundary Canyon 

and in the gulch in which Poison Spring is situated. In Boundary 

Canyon, near Hole in the Rock Spring, reddish conglomerate lies 

upon the eroded surface of the Paleozoic rocks, from which the bowlders have been derived. These bowlders reach a maximum diameter of 3 feet. The stream bed of the Poison Spring gulch is largely 

cut in caicite-cemented conglomerates. At the mouth of the gulch 

these beds are 40 feet above the stream, but 2 miles above Poison 

"Spring they are at stream level, indicating that the present grade is 

steeper than that of the stream which deposited these gravels. Calcite 

veins, many of which are banded, fill joint fissures in the conglomerates. In a few places narrow seams of limonite indicate that some 

pyrite. was deposited with the calcite.

IGNEOUS ROCKS.

In addition to the hornblende gneiss and schist already described 

(p. 163), the igneous rocks of the Amargosa Range include postJurassic granite, pre-Tertiary diorite porphyry, and several Tertiary 

lavas.

Granite porphyry. Dikes of granite porphyry cut the Pogonip 

limestone 6 miles northwest of the Staininger ranch. The rock has a 

grayish-pink fine-grained groimdmass, which is exceeded in bulk by 

the phenocrysts. Unstriated pinkish-gray feldspars, which reach 

a maximum length of one-fourth inch, are more abundant than small 

rounded quartz phenocrysts. Rarely a little chlorite stained by iron 

suggests the former presence of biotite. Under the microscope the 

groimdmass appears as a microgranitic aggregate of quartz, orthoclase, and a little plagioclase. With the phenocrysts of orthoclas.§ 

and quartz are some of biotite altered to chlorite and calcite and a 

few of plagioclase. This granite porphyry is probably one of the 

post-Jurassic granites.

Diorite porphyry. Fragments of a greenish-gray much-altered 

igneous rock occur in the desert gravels on the eastern slope of the 

range west of Rose's Well, and dikes of this rock probably cut the 

Cambrian sediments. The rock is apparently the pre-Tertiary diorite porphyry.

Biotite andesite. The oldest of tl^e Tertiary lavas is a biotite andesite, which occurs in a number of small areas between Grapevine 

Canyon and Willow Spring, being particularly abundant near Mexican Camp. The biotite andesite is a ttense lithoidal or semiglassy 

rock, which is gray, green, brick red, or purplish red, the last color 

evidently being due in many cases to alteration. Phenocrysts are
168 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

usually somewhat subordinate in bulk.to the groundmass. Biotite 

and lath-shaped feldspars, many of them considerably altered, are 

as a rule equally abundant. The feldspar phenocrysts are slightly 

larger than those of biotite, but they are nowhere over one-fourth 

inch long and are in most places much smaller. Flow lines are present in the groundmass and many of the phenocrysts show flow orientation. Much of the rock is vesicular. The vesicles reach a maximum length of 1|- inches and are more or less completely filled by 

chalcedony and chlorite. Hyalite, chalcedony, and quartz occur 

along joint planes.

One thin section shows under the microscope as a biotite andesite 

with a groundmass composed of plagioclase laths in a rather illdefined gently birefringent substance. The phenocrysts include 

plagioclase, biotite rimmed by beads of magnitite, orthoclase, and 

magnetite. The small plagioclase phenocrysts are simple and the 

large ones complex aggregates. Zircon is a rare accessory mineral. 

Another thin section,, although clearly from the same magma, is somewhat more acidic, having affinities with latite. Quartz and orthoclase are present in the microfelsitic groundmass and orthoclase 

phenocrysts are as abundant as those of plagioclase.

The biotite andesite occurs in flows which were eroded prior to the 

outflow of the earlier rhyolite. On the range crest "4 miles south of 

Wahguyhe Peak the rhyolite contains small fragments of andesite. 

The andesite is in consequence younger than rhyolite and is probably 

of late Eocene age. The more acidic facies of the rock are mineralogically rather like the monzonite porphyry of the Kawich Range, 

which is older than the earlier rhyolite of that range, but which is 

probably contemporaneous with the earlier rhyolite of the Amargosa 

Range. The andesite and monzonite porphyry are probably, in a 

broad way, contemporaneous.

t Earlier rhyolite. Rhyolite forms the crest and eastern slope of 

the Amargosa Range from Thorp's mill to a point 2 miles northwest 

of Willow Spring, and thence to a point 2-| miles southeast of Daylight Spring it forms the eastern slope of the range. East-southeast 

of this point several small rhyolite areas occur.

The rhyolite series comprises a considerable number of siliceous 

volcanic rocks, which lie in well-defined flow beds. The predominant facies is a lilac, gray, white, or pink rhyolite, with lithoidal 

groundmass and medium-sized phenocrysts of equal volume. Of the 

phenocrysts, colorless or slightlyc smoky quartz and glassy, unstriated 

feldspar are, as a rule, equally abundant, although the feldspar may 

predominate. Biotite phenocrysts are usually sparse and of smaller 

size. Other facies are gray glasses without phenocrysts, but with 

highly developed perlitic parting, and black glass, with feldspar and 

fewer quartz phenocrysts. Similar rocks from other ranges prove, on
AMARGOSA RANGE, IGNEOUS ROCKS. 169

microscopic examination, to be latite, and the series probably includes 

latite and siliceous dacite in addition to rhyolite. Compact aphanitic 

red facies of rhyolite are-also common, arid in these flow banding, 

lithophysse, and spherulites are well developed. The rhyolite of 

Shale Peak (elevation, 7,370 feet), 4 miles southeast of Wahguyhe 

Peak, is a faded brick-red rock banded with pink lines. Exfoliation 

breaks this rock, which is rather poor in phenocrysts, along the flow 

lines into numberless platy fragments, which caused the members of 

a United States Coast and Geodetic Survey party to give the peak 

its expressive name. Many angular inclusions of rhyolite of 

slightly different character occur in the lava, forming flow breccias. 

The rhyolite is in some places kaolinized and in others silicified. 

(See p. 47.) It is probable that much of the rhyolite that is now, 

through kaolinization, white or light gray in color, was formerly 

brick-red, since at certain places bleaching has occurred along joint 

fractures and irregular- cracks, forming mottled fantastic patterns 

in reds and whites.

Beds and lenses of red, white, and greenish-white incoherent sandy 

rlryolitic tuffs, containing feldspar, quartz, and biotite crystals, are 

interbedded with the lavas. In these tuffs pebbles of rhyolite, which 

in rare instances reach a diameter of 1 foot, are abundant. All 

gradations exist between the normal igneous rock and these sediments deposited in small lakes or subaerial basins.

The earlier rhyolite of the Amargosa Range occurs in flows from 

10 to 300 feet thick, superimposed one upon another, which impart 

to the eastern side of the range its varicolored banding. The thickness of the series is unknown, although it reaches at least 3,000 feet. 

The greater portion outflowed as lava, but at various times during the 

extrusion rhyolitic material was deposited in local sheets of water 

and at others dust from explosive eruptions formed subaerial accumulations. The vents from which the rhyolite flowed are probably 

situated near the crest line, but their position was not determined 

in the course of the present work. Where the rhyolite flows vary 

considerably in hardness the more resistant beds form benches and 

the softer beds are covered by talus, a method of weathering well 

developed on the eastern side of the north end of the range. Where 

vertical systems of joints are prominently developed, outcrops are 

bounded by vertical planes and rock pinnacles form. If the rhyolite 

flows are of approximately equal hardness and joints are not prominent, rounded bosses and smooth domelike hills result. Such forms 

are well seen near Shale Peak. Perhaps the most common topographic forms are cones, a mean between the pinnacles of the welljointed rhyolite and the domelike hills of the more massive facies.

The earlier rhyolite lies upon the eroded surface of the Paleozoic 

rocks and the biotite andesite and near contacts contains numerous
170 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

pebbles of these rocks. The later basalt lies upon the eroded surface 

of the rhyolite. This rhyolite is practically continuous with that of 

the Bullfrog Hills and is of similar lithologic character. It is 

roughly to be correlated with the earlier rhyolite of the Kawich, 

Belted, and Reveille ranges, probably of early Miocene age. 

x Earlier basalt. Basalt fragments are locally contained in the 

rhyolite flow breccias, and at several places thin lenses of basalt, too 

small to-show on the map, are interbedded with the rhyolite. The 

best example is at the Happy Hooligan mine, 12 miles south of west 

of Rhyolite. . Mr. F. L. Ransome a states that recent mining development has here exposed a basalt bed from 25 to 50 feet thick between 

the rhyolite and the Pogonip limestone. The rhyolite of the Bullfrog Hills and the Kawich Range also contains minor flows of basalt, a fact further indicating the contemporaneity of the two rocks.

Later rhyolite and biotite latite. To the southeast of the Staininger ranch is an area covering about 12 square miles of rhyelites and 

latites interbedded with the Siebert lake beds. The rhyelites are the 

older of these lavas and the latites the younger.

The rhyolites are semitransparent to opaque, glassy or semiglassy 

rocks, with few quartz, feldspar, and biotite phenocrysts. In color 

they range from light gray, through red, to black. Flow breccias are 

common. Perlitic parting, which causes the rock to disintegrate into 

pebble-like masses, is well developed in many of .the flows. Flow 

folding, with overturned isoclinals, in places with horizontal axes, 

is not unusual. The spherulites, which are very abundant in some 

flows, making up at least one-third of the rock, are similar to those 

already described from the Mount Jackson hills (p. 67). In some 

c-ases large spherulites, rudely globular and from ,3 inches to 1 foot in 

diameter, inclose smaller ones. The large spherulites are cut by 

horizontal flow lines, while the smaller have the typical radiate structure. Lithophysse also occur.

The latites are white semipumiceous rocks with myriad bronzebrown hexagonal plates of mica and less conspicuous phenocrysts of 

feldspar. In some instances the biotite plates have an excellent orientation in the place of flow and the rock breaks into platy masses 

along the flow banding. A single thin section examined under the 

microscope showed the rock to be a biotite latite, with groundmass 

of a vesicular colorless glass. The phenocrysts exceed the groundmass in bulk, and orthoclase and biotite are more abundant than 

plagioclase. Apatite is present as an accessory mineral.

The later rhyolite is similar lithologically to the rhyolite associated with the Siebert lake beds of the Mount Jackson hills, and the 

two series are probably approximately contemporaneous. In the

a Oral communication.
- AMARGOSA RANGE, IGNEOUS ROCKS. 171

upper portion of the series a few basalt flows are apparently interbedded with the rhyolite. At another place the basalt clearly cuts 

the Siebert lake beds and the rhyolite. (See p. 171.) This shows 

that while toward the end of the period of rhyolite extrusion some 

basalt probably outflowed, for the most part the basalt is younger. 

The rhyolite and latite are probably of late Miocene and early Pliocene age.

Later basalt. Basalt is the youngest of the igneous rocks. Its flows 

cover a considerable area at the north end of the range, and a number 

of smaller areas occur on eitheV side of Grapevine Canyon. A dike 

of basalt 4 feet thick cuts the younger rhyolite and Siebert lake beds 

2 miles north of the Staininger ranch. This was probably one of the 

vents through which the lava outflowed, while a small, red, conical hill 

to the south of the Staininger ranch-Thorp road, 5 miles from the 

ranch, appears from a distance to be a volcanic cone. The two small 

buttes in Sarcobatus Flat, north and northeast of Currie Well, seen only 

from a distance, are probably basalt. Remnants of flows cap rhyolite 

hills southeast of Daylight Spring, and at one locality a dike of basalt 

cuts the Pogonip limestone. This dike may be the ancient vent from 

which the basalt in this vicinity flowed. The basalt of the dike is 

reddish brown in color and much altered, but on microscopic examination appears to hlive been originally an olivine basalt. The basalt 

from the flows in the vicinity is black, vesicular, and without prominent phenocrysts. The basalt of Grapevine Canj^on is for the most 

part black and dense, although basal portions of the flows (in many 

places flow breccias) are vesicular and red. The more vesicular rocks 

are locally covered by a layer of basalt banded horizontally by 

flow lines, and this in turn by more massive beds which show spheroidal weathering. Phenocrysts, while usually small, are abundant 

in many outcrops and include glassy lathjS of plagioclase and rounded 

grains of olivine, either fresh and glassy or iron stained. Granular 

calcite, probably derived from the alteration of the basalt, fills vesicles in the basalt and veins cutting it. A thin section cut from basalt 

from the low mesas 4 miles east-northeast of the Staininger ranch 

proves to be a quartz-bearing olivine basalt with holocrystalline 

groundmass. The quartz is deeply embayed and surrounded by a 

corona of augite columns of the groundmass.

The basalt from the south end of the Amargosa Range overlies 

the Siebert lake-bed conglomerates, and from its lithologic character is considered to be one of the Pliocene-Pleistocene basalts. The 

basalt in the vicinity of Grapevine Canyon is probably in part contemporaneous with the upper part of the later rhyolite and Siebert 

lake beds, but is for the most part younger and of late Pliocene or 

early Pleistocene age.
172 SOUTHWESTEEN NEVADA AND EASTEEN CALEFOENIA.

STRTTCTTJRE.

The Amargosa Range has been subjected to two main periods of 

folding and uplift, the earlier in pre-Tertiary and presumably postJurassic time, the later probably in late Miocene time, after the deposition of the Siebert lake beds. In the northern part of the range this 

later folding was somewhat earlier than in the southern part and appears to have succeeded the outflow of the earlier rhyolite and preceded the deposition of the Siebert lake beds. North of Wahguyhe 

Peak the Paleozoic rocks and the earlier rhyolite are so folded 

together that the differentiation of the two periods of folding is difficult. Even here, however, the Paleozoic rocks are more profoundly 

folded. The earlier.folding was accompanied by reversed faulting 

and probably in the last stages by normal faulting; the later folding 

was accompanied by normal faulting.

The major direction of the early folds was parallel to the trend of 

the range, but accompanying them are cross folds, which west of 

Grapevine Peak equal in importance and south of Indian Pass predominate over the northwest-southeast folds. In the vicinity of 

Grapevine Peak these cross folds were intensified by later folding. 

In the central portion of the range there is an anticlinorium with 

northwest-southeast axis, composed of two main ^anticlines with a 

syncline between. The syncline at Keane Spring is comparatively 

narrow; at Boundary Canyon it is broader and more open; and in 

the canyon in which Tule Spring is situated it is represented by two 

minor synclines and an intervening anticline. At Chloride Cliff the 

syncline is broken by a normal fault. Many of the minor folds are 

closely appressed isoclinals or fan folds, which in some instances 

have horizontal axes. The passage from isoclinal folds to reverse 

faults is by no means unusual. South of Indian Pass the structure 

is that of an anticlinorium with northeast-southwest axis, of which the 

long northwest limb dips rather gently to the southeast, while the 

shorter southeast limb dips somewhat more steeply to the northwest. 

Superimposed upon the main folds are minor folds, many of which 

are rather steep. The Pogonip limestone north of Grapevine Springs 

is folded into a gentle arch with east-west axis.

Before the later folding was inaugurated the range was worn 

down to an inconspicuous ridge, and the eastern slope and the whole 

range south of the area mapped formed the bottom of the Miocene lake. 

It is to the later folding and succeeding minor uplifts that the range 

owes its height. South of Daylight Spring the rhyolites dip at angles 

of 20° to 40° away from the range, while the Siebert lake conglomerates in this vicinity have a dip away from the range which in some 

instances reaches 70°. North of Daylight Spring the earlier rhyolite 

is folded into a synclinorium whose axis strikes N. 70° E., with its 

trough situated about 4 miles north of Grapevine Peak. Normal
AMARGOSA RANGE, ECONOMIC GEOLOGY. 173

strike faults having the same strike are common in the vicinity of 

Thorp's mill and form numerous fault scarps. The Siebert lake beds 

south of the Staininger ranch have been flexed and are broken by 

small normal faults of north-south strike.

Unimportant folding and faulting are recorded in the basalt and 

older alluvium areas. The basalt below the Staininger ranch dips toward Death Valley and has apparently been tilted westward along a 

north-south axis. Normal faults of 4 to 5 feet displacement, usually 

with north-south trend, cut the basalt in the vicinity of Grapevine 

Caiiyon. The older alluvium at Hole in the Rock Spring for the most 

part dips toward Death Valley, although northeasterly dips here and 

there indicate that since the deposition of the conglomerate the range 

has not only been uplifted, but also somewhat folded.

ECONOMIC GEOLOGY.

Active mining operation's are being caried on at three points in the 

Amargosa Range within the area mapped at the Happy Hooligan 

mine, at Chloride Cliff, and at Lee's Camp.

HAPPY HOOLIGAN MINE.

The Happy Hooligan mine is situated at the eastern base of the 

Grapevine Mountains, 9 miles northwest of Bullfrog. A number of 

test pits have been sunk at the contact of the eroded surface of the 

Pogonip limestone, with its interbedded quartzite and the Tertiary 

lava flows. The predominant lava is a kaolinized rhyolite, from 

which the feldspar phenocrysts have been largely removed by 

weathering. This is underlain by a flow of basalt which rests upon 

the limestone. At the contact with the limestone the basalt is reddened 

by hematite and altered to a greasy substance, which pans fine free 

gold, as does the limestone when decomposed. Gold values also 

occur where the lava, comes in contact with the quartzite. The contact has been traced several hundred feet and values are reported 

from all the test pits. The ore is free milling, and no sulphides were 

observed. It is said to run $40 in gold per ton, the values appearing 

to be closely associated with limonite and hematite. Several springs 

are situated near the mine and fuel can be obtained within 6 miles. 

The road to Bullfrog is rather heavy.

CHLORIDE CLIFF.

Chloride Cliff is situated in Inyo County, Cal., on the crest of the 

Amargosa Range, 15 miles south of Bullfrog. At this point the 

Cambrian limestone strikes N. 15° W. and dips 30° E. A steeply 

inclined fault trendmg N. 50° W. cuts the limestone. The limestone 

along the fault is silicified and in it are disseminated galena and
174 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

some chalcopyrite. The secondary ore is a porous yellowish lead 

carbonate with some malachite stains. The surface outcroppings are 

heavily stained by limonite. At another place a 4-foot vein of quartz 

lies between the gently dipping hornblende schist and the sericite 

schist and altered limestone above it. The quartz is free milling and 

heavily iron stained, and the crushed portions have been recemented 

by limonite. The writer traced tne vein 200 feet, but it extends much 

farther. It is reported that one sampling across the vein gave 

values in gold averaging $1,500 per ton. At a third prospect a 

reversed fault cuts the schist member of the series, which here strikes 

N. 60° W. and dips 15° NE. A quartz vein 2 to 3 feet wide occupies 

the fissure. The quartz is stained by limonite, and pyrite is the only 

original sulphide seen. Small nodules of native copper are, in rare 

instances, associated with the limonite stains. The ore is said to 

assay from $13 to $500 per ton in free gold. The values are associated with limonite.

The prospects at Chloride Cliff are either fissure fillings or deposits 

along contacts. In some gases the quartz and accompanying sulphides probably filled open fissures; in others the limestone was 

metasomatically replaced. There is a distinct tenden'cy for galena to 

be the predominant sulphide in limestone, and pyrite in the other 

country rocks. Since the deposition of the quartz the veins have been 

crushed and surface waters have produced from the original sulphides native gold, copper, cerussite, malachite, and limonite. The 

deposits are structurally similar to those which hold their values well 

with depth, and if surface enrichment has not been out of all proportion to the original sulphide values, further development is well 

justified.

Water is at present packed on burros from Keane Spring, 4 miles 

distant. Wood suitable for fuel occurs on the Amargosa Range, 10 

miles north of the prospects, but at present must be teamed by way of 

Bullfrog. A fair road connects the prospects with Bullfrog, the 

shipping and supply point.

Ores from a number of mines in the Cambrian rocks in the vicinity 

of Chloride Cliff were examined, but the mines themselves were not 

visited. At the Keane Wonder mine a blanket vein of quartz, dipping gently westward, is said to lie along the bedding planes of the 

Cambrian rocks. The gold ore is quartz heavily stained by limonite 

and is said to be free-milling. The Trio mine, in the next gulch south 

of the Keane Wonder, is said also to. be on a quartz vein in the Cambrian rocks. The ore is a limonite-stained quartz containing chalcopyrite and galena and some cerussite: Free gold is reported to 

occur in schist arid limestone along a fault fissure down the gulch 

from Keane Spring. The ore of this deposit closely resembles that 

from the metasomatic replacement deposits of Chloride Cliff. The
AMAKGOSA KANGE, ECONOMIC GEOLOGY. 175

Bismuth mine is situated on the road to Bullfrog, somewhat below the, 

Chloride Cliff mine. The quartz, which is heavily stained by limonite, contains finely granular galena. The presence of some malachite 

probably indicates the former presence of chalcopyrite with the pyrite 

and galena.

LEE'S CAMP.

Lee's Camp is situated in the Cambrian rocks, 10 miles southwest 

of Rose's Well. The camp was not visited by the writer, but strong 

veins of quartz are said to exist there. The ore, which is said to mill 

free gold, is quartz and either dolomite or siderite, each heavily 

stained by limonite.

AEEAS FAVOBABLE FOB PBOSPECTING.

Quartz veins are common in the metamorphosed Cambrian sedimentary rocks. They occupy joint and bedding planes and fault 

fissures, and in the latter case may contain angular fragments of the 

Cambrian rocks. In size they vary from mere stringers to veins 6 

feet or more across, which can be traced for hundreds of yards. In 

the vicinity of Poison Spring these are particularly strong, and over 

restricted areas make up almost one-third 'of the rock. The quartz 

in most instances is white and semitransparent and appears barren. 

In others it has been faulted and brecciated and is stained by limonite, 

while pj^rite and specular hematite are disseminated in it here and 

there. The mines of Echo Canyon, to the south of the area surveyed, 

are reported to be situated on similar quartz veins. Pyrite and 

hematite also occur in quartz veins on the small Cambrian hills to 

the northwest Oof the Big Dune, and these minerals and malachite are 

found in the quartz veins of the big Cambrian inlier to the southwest 

of the Big Dune. 

In the Pogonip limestone of the central and northern portion of 

the Amargosa Range quartz veins are of minor importance. The 

veins, some of which contain pyrite and specular hematite, appear to 

be comparatively small. About 6 miles south of the Staininger ranch 

prospectors sunk a shaft 10 feet deep on a quartz vein stained with 

malachite. At this depth the vein divided into several stringers and 

the shaft was abandoned. The ore carried low gold and silver values. 

With the change of the country rock from the siliceous deposits of the 

Cambrian area to the calcareous rocks of the Silurian and Ordovician, 

calcite veins, probably in part contemporaneous with the quartz veins, 

become predominant. These are extremely abundant, but as a rule 

are less persistent and less mineralized than the quartz veins in the 

Cambrian. At Titus Canyon the calcite veins are of two ages. The 

older are formed of white crystalline calcite, much of which is very 

coarsely granular, The younger veins, of banded yellow or brown
176 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

calcite, are still forming. River bowlders are here and there inclosed 

"in these veins, and stalactitic calcite hangs from them in some canyon 

walls. The bands are either parallel to the walls or at right angles to 

them, while in certain places the borders of the veins are vertically 

banded and the centers horizontally banded. Many of the later veins 

fault the older.

Areas of silicified ana kaolinized rhyolite in the Amargosa Range 

are shown on the map (fig. 4, p. 43). The rhyolite 8 miles southeast 

of Daylight Spring has been silicified, and small quartz veins cut it. 

The area has been located, but no information is at hand as to the 

value of the ore. Silicified rhyolite, with many small quartz Veins, 

outcrops at several places east of Mexican Camp and 1 mile north of 

McDonald Spring. At the latter locality small quartz veins also 

occur in the biotite andesite. The quartz in this portion of the range 

is largely white or gray and compact. At Currie Well bowlders of 

silicified rhyolite, said to pan gold, occur as float, but the original position of the rock is not known. Silicified rhyolite stained by the yellow basic ferric-alkali sulphate (?) already mentioned .(p. 50) covers 

a considerable area to the south of Grapevine Canyon. This rhyolite 

is doubtless worthy of careful prospecting.

BULLFROG HILLS.8 

TOPOGRAPHY AND GEOGRAPHY.

The Bullfrog Hills lie west of Oasis Valley, between the Amargosa 

Desert and Sarcobatus Flat. They form a spur of the Amargosa 

Range and have an east-west crest line, from which an eroded 

mesa extends northward and rather sharp ridges stretch out to the 

south. The highest peak in the hills reaches an elevation of 6,035 

feet. The Bullfrog Hills are bare of timber and are only sparsely 

covered with desert shrubs and cacti. The towns in these hills obtain water from Amargosa River (see p. 18) and from a number of 

springs in Oasis Valley and in the hills themselves. Among the latter may be mentioned Indian (30,000 to 40,000 gallons per day), 

Crystal, and Mud springs. Hicks Hot Springs, in Oasis Valley, have 

already been described (p. 20).

GENERAL GEOLOGY.

The formations exposed in the Bullfrog Hills include the following, the oldest being named first: Pre-Silurian schist, Eureka 

quartzite, Lone Mountain limestone, post-Jurassic pegmatite, pre0 The geology and ore deposits of the Bullfrog district will be described in detail by 

Messrs. P. L. Ransome, W. H. Emmons, and G. H. Garrey in a forthcoming Professional 

Taper, and the geology of the area shown on the Bullfrog special sheet has been generalized from their map. The description here given refers more particularly to the 

area outside that covered by the special map.
BULLFROG HILLS, SEDIMENTARY ROCKS. 177

Tertiary diorite porphyry, andesite, rhyolite, earlier basalt contemporaneous with rhyolite, Siebert lake beds (?), and later basalt.

SEDIMENTARY ROCKS.

Pre-Silurian schist. Three miles Avest of Bullfrog is a low ridge 

of post-Jurassic pegmatite containing a vast number of schist inclusions. The rocks are present in practically equal amounts, and the 

area could as Avell be described as an area of schist intensely injected 

by pegmatite. The pegmatite, however, is more resistant to erosion 

and hence gives its white color to the low rounded ridge. 

The schist varies from a finely foliated biotite schist to an " eye " 

schist, containing many lenses of pegmatitic feldspar from onesixteenth inch to 2 inches long. These eyes are elongated parallel to 

the schistosity, the shortest diameter usually being one-fourth the 

length of the longest. Some of the schist is composed of minute 

scales of biotite of common orientation, while other portions also contain quartz, a little feldspar, and the large feldspar lenses already 

mentioned. The planes of schistosity dip at considerable angles, but 

are rarely minutely crenulated. A single thin section of the " eye " 

schist under the microscope proves to be a schist in which shreds of 

biotite and a little muscovite are arranged in folia. Between these 

is a fine-grained mosaic of orthoclase and quartz, with here and there 

a partial crystal of apatite or zircon. The pegmatitic " eyes," which 

are usually acidic plagioclase and in only a few cases quartz or orthoclase, are closely encircled by the biotite films.

The schists are presumably metamorphosed sedimentary rocks, but 

they may possibly be mashed igneous rocks. Mr. G. H. Garrey," 

who examined the relations between the schist and the Pogonip limestone on the western border of the Bullfrog special area, states that 

the contact between the two rocks is not exposed, but that outcrops 

of limestone adjacent to the schist are comparatively unmetamorphosed and that the schist in consequence is presumably pre-Silurian. 

Lithologically this rock resembles Cambrian schists near Tokop, and 

although possibly of pre-Cambrian age it is tentatively correlated 

with the Cambrian.

Eureka quartzite. A hillock rising from the rhyolite to the 

southeast of the limestone last described and a hill 2 miles south of 

Indian ranch are formed of quartzite interbedded with shale. Fragments of similar shale are included in Tertiary rhyolite 3£ miles 

northeast of Bullfrog. The Eureka quartzite of Bare Mountain 

extends across Amargosa River northwest of Gold Center. The 

quartzite of the hills first mentioned is gray, pink, or white in color, 

and of fine to medium grain. It appears to be a practically pure

a Oral communication. 

Bull. 308 07 M 12
178 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

quartzose rock, many portions of which are finely laminated. Associated with it are minor bands of brown, greenish, or purplish-gray 

shale, the laminae of which are in places paper thin. The quartzite 

apparently underlies the limestone south of Indian ranch and lithologically resembles the Eureka quartzite (Ordovician).

Lone Mountain limestone. Small bodies of limestone, in part, at 

least, of Silurian age, protrude from the Tertiary lavas and Recent 

gravels at four points 3 miles west of Bullfrog, three-fourths mile 

southwest of the Gold Bar mine, and 1£ miles south and 2£ miles 

southeast of Indian ranch. The limestone is dark gray, dense, and 

of medium grain. Finer grained facies closely resemble lithographic limestone. Interbedded with the normal type are layers 

of intraformational conglomerate. Thin seams of calcite locally 

cut the limestone in all directions. The limestone 1£ miles south of 

Indian ranch clearly overlies a quartzite which is probably the 

Eureka quartzite; if so this is the Lone Mountain limestone. Moreover, Mr. G. H. Garrey collected from the limestone inlier 4 miles 

northwest of Bullfrog a number of fossils which Mr. E. 0. Ulrich 

states are of Silurian age.

iSiebert lake beds. One mile north of Crystal Spring is a small 

outcrop of an arkose conglomerate. The well-rounded pebbles, 

which reach a diameter of 1 foot, consist of quartzite, jasperoid, 

limestone, and medium-grained biotite granite. The first three are 

derived from Paleozoic rocks, while the granite resembles many 

post-Jurassic granites. The conglomerate is lithologically similar to 

the more conglomeratic of the Siebert lake beds of the Amargosa 

Range, and may well be contemporaneous with it. If such is the 

case the shore line of the lake must have been near Bullfrog. The 

relative ages of the rhyolite and the lake beds are unknown.

Older alluvium. On the northeastern face of the Bullfrog Hills 

and across Amargosa River to the east are hills and terraces dissected by the present streams. These hills and terraces are 

formed of detrital material similar to that now being deposited in 

stream beds and on the alluvial slopes. The deposits were made 

while Amargosa River was at a higher level and presumably are 

alluvial slope deposits of the older alluvium. Basalt bowlders (presumably of Pliocene-Pleistocene age) are contained in the upper 

portion of the beds.

IGNEOUS ROCKS.

Post-Jurassic pegmatite and alaskite. Pegmatite with alaskite 

occurs with the pre-Silurian schist west of Bullfrog and dikes of pegmatite cut the Eureka quartzite near Gold Center. (See p. 155.) West 

of Bullfrog the pegmatite grades into alaskite, but the former rock is
BULLFROG HILLS, IGNEOUS ROCKS. 179

predominant. The most widely distributed facies of pegmatite is 

formed of white feldspar, less muscovite, still less smoky quartz, 

and a little pyrite. The largest feldspar individuals reach a diameter of 4 inches, while muscovite is in aggregates of plates from onefourth to 1 inch across. Quartz veins of pegmatitic origin are also 

present and similar veins, probably of the same origin, cut the more 

feldspathic pegmatite. From this it is probable that a rock of 

- granitic composition separated from the magma and at a later period 

a more quartzose rock Avas deposited from the residual liquid in 

fractures in the older pegmatite. Lens-like veins of practically pure 

white feldspar grade on the one hand into normal pegmatite, and 

on the other into the eyelike areas of the schist already mentioned.

The associated alaskite is a white, medium-grained rock composed 

of quartz and feldspar, with muscovite and a little altered biotite. 

The quartz and orthoclase grains are micropegmatitically intergrown along their borders and the biotite shreds are largely chloritized. Accessory minerals are not abundant, but include apatite, 

zircon, and magnetite, and apparently tourmaline. In the hand 

specimen the rock is considerably mashed and the microscope shows 

phenomena of granulation and recrystallization, including the deposition of muscovite, derived from feldspar, in fractures.

The pegmatite and alaskite inject the schist bed by bed, although 

in rare instances the planes of schistosity are. crossed. The wider pegmatitic bands are 100 or more feet thick, while the thinner pegmatitic laj'ers are but onex-fourth inch wide, and many of them are separated only by an equal thickness of schist. The pegmatite cuts 

schists probably of pre-Silurian age and is older than the unmashed 

rhyolite of Tertiary age. On lithologic grounds its age is provisionally believed to be post-Jurassic and pre-Tertiary.

Pre-Tertiary diorite porphyry. A few narrow dikes of diorite 

porphyry cut the pegmatite and schist 3 miles west of Bullfrog.' The 

diorite porphyry is a dark grayish-green rock speckled with tiny 

white areas, and is evidently composed predominantly of a ferromagnesian mineral and feldspar. The rock has a medium-grained 

microgranitic groundmass of plagioclase, orthoclase, and some 

quartz. Columns of brown hornblende are very numerous, while 

larger phenociysts of sericitized plagioclase are fewer. The accessory minerals, titanite, apatite, and magnetite, are very abundant. 

Epidote and chlorite are developed from hornblende or from hornblende and plagioclase. This rock is, without much doubt, to be 

correlated with the pre-Tertiary diorite porphyry widely distributed 

in the mountains on the western border of the area surveyed. (See 

p. 31.)

Biotite andesite. A hill 2 miles northwest of Howell ranch and 

a small knob rising from the older alluvium three-fourths of a mile
180 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

south of Indian ranch are of biotite andesite. This is a dense, flinty 

or lithoidal rock of medium, pinkish, or purplish gray color. 

Black glassy facies are less common. The small phenocrysts, feldspar laths, with slightly fewer black mica plates are subordinate to 

the groundmass in bulk. The feldspars are usually altered, but in 

?ome instances they are glassy and twinning striations are visible.. 

From the bedded disposition of the various textural facies and the 

flow orientation, visible in many of the phenocrysts, the biotite andesite is probably a flow considerably eroded and masked by coverings 

of later formations. The groundmass under the microscope is seen 

to consist of a felt of plagioclase laths in a somewhat devitrified 

glass (hyalopilitic). Besides the simple laths of plagioclase, usually showing Carlsbad twinning, and the slightly bleached biotites, 

a rare orthoclase phenocryst is present, while certain ill-defined 

pseudomorphs, largely of serpentine, have the crystal outlines of 

hornblende. Ilmenite and apatite are present as accessory minerals.

On the west side of the hill northwest of Howell ranch muchaltered pebbles and fragments of andesite are included in a tuffaceous member of the rhyolite series, and between the outflows of the 

two lavas there was apparently an erosion interval. The andesite is 

probably of late Eocene age, and is similar to and probably contemporaneous with the biotite andesite of the Amargosa Range.

Rhyolite. The predominant formation of the Bullfrog Hills is a 

series of rhyolite flows. The most widely distributed facies is a 

lithoidal rhyolite of gray, pink, or purple color. The mediumsized phenocrysts, which cusually exceed the groundmass in bulk, 

consist of glassy unstriated feldspar, slightly smoky quartz, and in 

many places biotite. Hornblende is also locally present. Less 

widely distributed types include aphanitic rocks with varicolored 

flow banding, resembling slaty shales; brown or greenish glasses, 

with or without phenocrysts, and -gray glasses with perlitic parting 

well developed. Interbedded with the other members of the rhyo-. 

lite series are rhyolitic sandstones and conglomerates, while Messrs. 

Ransome, Emmons, and Garrey found a thin limestone lens in the 

series. Through metamorphism, kaolinized and silicified facies arise. 

(See p. 47.)

The rhyolite is a series of igneous flows, with minor intercalated 

beds of sedimentary rocks, in part deposited under water and in part 

subaerially. Where the flows are thick the rhyolite in places 

weathers into bosses and IOAV domes, but for the most part the varying resistances of the different flows to erosion give a bench and cliff 

character to the topography.

This rhyolite, which contains fragments of Paleozoic rocks and 

biotite andesite, on lithologic and structural grounds is correlated 

with the earlier rhyolite of the Amargosa and Kawich ranges. It is 

probably of early Miocene age.
BULLFBOG HILLS, STRUCTUKE. 181

Earlier basalt. Interbedded with the rhyolite series in the Bullfrog district are several thin flows of basalt, and the latest of these 

is also found in the surrounding hills near the boundary of the special 

area. Dacite usually lies on the basalt and is evidently a later flow of 

a practically continuous period of extrusion. The basalt is a darkgray or blue-black dense rock containing numerous laths of glassy 

striated feldspar and here and there a suggestion of an olivine or 

pyroxene phenocryst. Vesicular facies are common, and with the 

introduction of vesicles much of the rock takes on a red tinge. A 

single thin section examined proved to be an olivine basalt, with 

plagioclase, augite, and olivine phenocrysts in a groundmass composed of glass and tiny crystals of plagioclase, pyroxene, and iron 

ore (hyalopilitic).

Dacite is well exposed 1 mile southwest of Indian Spring. It is a 

purplish-gray rock, with dense groundmass and abundant phenocrysts, including glassy striated feldspar, black mica, and quartz. 

The feldspars very in size from one-sixteenth to 1 inch, the larger 

ones usually showing well-developed zonal growth. The quartz 

crystals reach a maximum diameter of one-fourth inch. Under the 

microscope the groundmass is seen to be a glass containing many tiny 

plagioclase laths (hyalopilitic). Besides the phenocrysts already 

mentioned, augite is present, while aggregates of heavily iron-stained 

serpentine may possibly be altered olivine.

Later basalt. Large areas of later basalt cap the rhyolite in the 

northern portion of the hills and pass into northeastward-dipping 

mesas, which extend toward Pahute Mesa. The basalt, which is a 

dense black rock, locally vesicular, lies upon the eroded surface of 

the early Miocene rhyolite. It is similar lithologicalty to and appears to be an extension of the Pahute mesa basalt, and is, in consequence, probably of late Pliocene age.

STRUCTURE.

The isolated inliers of Ordovician-Silurian rocks are gently folded 

and somewhat faulted. Upon the major folds minor flexures,in some 

cases overturned isoclinals, are superimposed. The folding of the 

Paleozoic rocks probably occurred largely prior to Tertiary time, 

although the supposed Siebert lake beds appear to be conformable in 

clip with the Lone Mountain limestone. The rhyolite throughout the 

Bullfrog Hills is a mosaic intersected by numerous normal faults. 

These faults have been worked out in detail by Messrs. Emmons and 

Garrey in the area covered by the Bullfrog special map. The work 

carried on under the direction of Mr. F. L. Eansome shows that the 

predominant faults trend northeast, while a second set trends north 

and south. The later basalt is slightly tilted to the northeast.
182 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA* '

ECONOMIC GEOLOGY.

The ore deposits of Bullfrog have recently been described by 

Ransomed He shows that the ore occurs in and along fault fissures 

in silicified or kaolinized rhyolite. Silicification and kaolinization 

have been important processes of metamorphism throughout the 

Bullfrog Hills. The areas outside of the region shown on the Bullfrog special map so altered are delineated in' fig. 4 (p. 43). Both 

the rhyolite and the andesite of the two domelike hills northwest of 

Howell ranch are silicified, and in addition seams of chalcedonic 

quartz fill solution cavities and fault and joint fractures. Other 

areas of silicified rhyolite are situated northwest of Crystal Spring, 

west of Indian Springs, and 4 miles south of east of Currie Well.

GOLD MOUNTAIN RIDGE AND THE HILLS TO THE NORTH OF GRAPEVINE

CANYON.

TOPOGRAPHY AND GEOGRAPHY.

Gold Mountain, with an elevation of 8,145 feet, is situated on a 

ridge which parallels Slate Kidge. North of Tokop the two ridges 

are connected by low hills. The Gold Mountain ridge lies to the south 

of Oriental Wash and to the east of Death Valley. In the vicinity of 

Gold Mountain the ridge is rugged and steep, being formed of sharp 

peaks and V-shaped valleys. Strikingly distinct from the other 

summits is the basalt-capped butte northeast of Old Camp. A number of northeast-southwest ridges northwest of Grapevine Canyon 

are joined to Gold Mountain on the south or are isolated in the desert 

gravels near by. These ridges, which parallel the trend of the Gold 

Mountain ridge, are here included in its description. On the other 

hand, the mountain front north of Grapevine Canyon, northeast of 

Death Valley, and southwest of the California-Nevada line is structurally an extension of the Amargosa Range.

The distributive drainage characteristic of arid regions is Avell exemplified in these hills. Fragmental material from the Gold Mountain ridge near the Rattlesnake mine has reached loAver levels by three 

distinct channels. A portion of the gravels moved to the southeast 

and found lodgment either around the playa in Grapevine Canyon 

or Avas Avashed out into Sarcobatus Flat near Thorp's mill. A second 

portion traveled south 4 miles, north of east 2 miles, and then south 

around the hill at the junction of the county line and parallel 37° 15'. 

The material eventual^ mingled Avith that Avhich took the more direct 

route already described. A third portion did not SAving around the 

hill just mentioned, t>ut continued north of east into Sarcobatus Flat. 

Probably at any one time but a single channel Avas used, but in comparatively recent times all three have been used.

0 Ransome, F. L., Bull. U. S. Geol. Survey No.'303 (in press).
GOLD MOUNTAIN RIDGE AND HILLS NEAR BY. 183

Juniper and pifion cover the crest of the Gold Mountain ridge, the 

timber line being on the 6,200-foot contour on the south and on the 

6,700-foot contour on the north side of the ridge. Yucca groves are 

sporadically distributed over the rhyolite and basalt flows to the 

south of the main ridge, .while a fair growth of grass covers Gold 

Mountain and the surrounding hills. The main ridge on which 

Gold Mountain is situated is Avell watered. Tunnels and wells in the 

vicinity of Old Camp strike water at depths varying from 50 to 75 

feet. The water in some cases appears to flow from crevices in granite and in others to seep from the overlying soil. Two wells located 

in Cambrian sedimentary rocks 1 mile east and northeast of Tokop 

are about 20 feet deep. The water is said to come from rock crevices. 

The water of Sand Spring, west of the boundary of the area here 

discussed, in Death Valley, is rather strongly impregnated with sulphur, but is nevertheless usable.

GENERAL GEOLOGY.

The formations exposed in the Gold Mountain ridge and the adjacent hills, from the base up, are as follows: Cambrian sedimentary 

rocks, quartz-monzonite porphyry, post-Jurassic granite, pre-Tertiary 

diorite porphyry, rhyolite, and basalt.

SEDIMENTARY ROCKS.

Cambrian. Cambrian rocks form the rugged ridge northeast of 

Tokop and the western front of the ridge facing Death Valley. A 

thin band of Cambrian rocks rims the southern border of the granite batholith which forms the central portion of the main ridge. 

These narrow Cambrian masses between the granite and the Tertiary 

rhyolite are due to the fact that resistance to late Mesozoic and early 

Tertiary erosion was greater in the granite and the adjacent metamorphosed Cambrian rocks than in the immetamorphosed Cambrian 

rocks. Large inclusions of Cambrian schist and metamorphosed 

limestone are sporadically distributed in the granite, while small 

fragments are widely distributed in both granite and rhyolite.

The Cambrian rocks of the Gold Mountain ridge include interbedded metamorphosed shales and impure limestones and calcareous 

sediments. The amount of metamorphism suffered by these rocks 

decreases with increase of distance from the granite batholith. Argillaceous rocks are widely distributed, although they do not appear to 

be present at the extreme west end of the range. They include finegrained, well-banded slates of black to light-gray color and biotite 

schists both with and without knotlike aggregates of biotite.

Limestone and calcareous sediments are represented by white and 

gray marbles of medium to coarse grain and by lime-silicate rocks 

in which brown garnet, vesuvianite, epidote, tremolite, chlorite, and
184 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

serpentine are developed. These rocks are usually well banded. 

One of the striking types is composed of layers of brown garnet and 

white quartz, alternating with fine-grained bands of quartz, epidote, 

.and other silicate minerals in which large crystals of brown garnet 

are locally embedded. Garnet also occurs in veins cutting the rocks, 

indicating a second recrystallization of that mineral. A single specimen of the banded rock examined under the microscope proved to be 

an uneven-grained, banded rock. The contemporaneous constituents 

of recrystallization include slightly brownish garnets, quartz, epidote, 

zoisite, tremolite, calcite, orthoclase, and plagioclase (oligoclase and 

andesine), in places showing Carlsbad twinning. Apatite and titanite are present as accessories and sericite and chlorite as secondary 

minerals derived from the feldspars. At the west end .of the Gold 

Mountain ridge bands and lenses of brown garnet rock up to 30 feet 

in thickness are interbedded with white and canary-yellow marble. 

Crystals of garnet also occur in the numerous interstices of the 

weathered surface.

These metamorphosed sedimentary rocks are similar to those 

of Slate Ridge, which grade into less metamorphosed facies, probably 

of Lower Cambrian age.

IGNEOUS BOCKS.

Quartz-monzonite porphyry. The granite, particularly near Old 

Camp, contains inclusions up to 1 foot in diameter of a fine-grained, 

medium-gray igneous rock, formed of biotite and white feldspar, in 

which are rather sparse phenocrysts of pink orthoclase reaching a 

maximum length of one-half inch, smoky quartz grains one-fourth 

inch' in diameter, and smaller biotite plates. Under the microscope 

the groundmass is seen to be hypidiomorphic granular and to consist 

of grains of orthoclase and partial crystals of plagioclase (oligoclase) 

and biotite, with a little quartz. Magnetite, titanite, zircon, and 

apatite are abundant accessory minerals. The phenocrysts are orthoclase, much of it zonally grown, quartz, biotite, and more rarely 

plagioclase. Similar inclusions occur in a number of the postJurassic granular rocks'in other portions of the area, but beyond the 

fact that the quartz-monzonite porphyry is older than the granite, 

its age is unknown.

Post-Jurassic granite. The central portion of the 'Gold Mountain, 

ridge is a mass of granite which prior to the formation of Oriental 

Wash was probably connected with the granite batholith at the west 

end of Slate Ridge. The smaller area of granite 8 miles west of Gold 

Mountain was also perhaps at one time connected with the Slate 

Ridge batholith. Dikes and apophyses extend from the main mass 

into the Cambrian rocks. .
GOLD MOUNTAIN KIDGE AND NEAR-BY HILLS, IGNEOUS ROCKS. 185

The predominant type in the vicinity of Gold Mountain is an 

uneven-grained, coarse, pink biotite granite. The constituents are 

pink feldspar, locally in good crystals one-half inch long which show 

Carlsbad twinning, slightly smoky quartz, and black biotite. Microscopic examination shows this granite to be formed of quartz, microcline, microperthitic orthoclase (in some specimens), oligoclase, biotite, and magnetite. Quartz shows strong undulose extinction. Sericite and kaolin are alteration products of the feldspars. The granite 

at the west end of the ridge is more variable in character, the most 

abundant type being a fine- to medium-grained gray biotite granite. 

This is composed of quartz, orthoclase, plagioclase, and biotite, with 

titanite, magnetite, muscovite, zircon, and apatite as accessory minerals. Plagioclase (oligoclase) occurs in rude laths. The coarse pink 

variety of Gold Mountain is also present, and it grades into a gray 

granite porphyry, with fine-grained groundmass of quartz, biotite, 

and feldspar. The phenocrysts, which reach a maximum length of 

one-half inch, are tabular gray feldspars rimmed by white bands, 

some of them Carlsbad tAvinned; rounded, strongly smoky quartz, and 

hexagonal biotite. The microscope shows that this granite porphyry 

has a hypidiomorphic groundmass, composed of orthoclase, quartz, 

biotite, and plagioclase, with magnetite, apatite, and titanite as accessory minerals. Quartz in this granite is notably variable, being abundant in some outcrops and inconspicuous in others. With decrease in 

quartz the normal granite porphyry grades into a quartz-poor hornblende-bearing porphyry in which some pink feldspar phenocrysts 

are 1 inch long. Under the microscope this proves to be a quartzmonzonite porphyry, with rare tabular microcline and orthoclase and 

lath-shaped plagioclase phenocrysts. The groundmass, -which is 

allotriomorphic granular, is composed of quartz, biotite, hornblende, 

orthoclase, and plagioclase. The accessory minerals are titanite, 

apatite, zircon, and magnetite. A little epidote is secondary to hornblende and biotite.

Both areas of granite are cut by dikes of a fine-grained pink apatite, 

in some places as rich in biotite as the granite and in others poor in 

this mineral. The granite is also cut by coarse pegmatite dikes and 

grades into similar pegmatitic masses. Graphic granite is not uncommon and at many points is the transition facies between granite 

and coarsely crystalline pegmatite. The aplite is, as a rule, older 

than the pegmatite, although in one case an aplitic dike passes along 

its strike into a dike with narrow aplitic border and pegmatitic center.

The yellowish outcrops of granite, at the base of the ridge are discontinuous, being, as a rule, mere heaps of bowlders partially buried 

in granite soil. The outcrops near the crest are much more continuous. The granite intrudes Cambrian sediments, and rhyolite flows
186 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

of Miocene age lie upon its eroded surface. Its age is in consequence 

post-Cambrian and pre-Tertiary. The granite is also cut by dikes of 

diorite porphyry presumably of pre-Tertiary age. It is probably of 

post-Jurassic age.

Diorite ^porphyry. Dikes of diorite porphyry reaching a maximum 

observed width of 40 feet cut the Cambrian rocks and the granite of 

the Gold Mountain ridge. The rock is greenish in color, contains 

abundant phenocrysts of white altered feldspar, and tends to weather 

into spheroidal bowlders. It is probably of pre-Tertiary age.

Rhyotite. The hills to the southwest of Gold Mountain, the ridge 

east of the Rattlesnake mine, a number of isolated hills and ridges to 

the east, south, and southwest of the latter ridge, and a small area 

northwest of the granite at the west end of the Gold Mountain ridge 

are composed of rhyolite. The presence of a small outlier of rhyolite 

on granite, three-fourths of a mile southeast of Tokop, indicates that 

erosion has removed considerable portions of. a once more extensive 

rhyolite flow.

The most widely distributed type is a lilac-gray rock of lithoidal, 

in places rather incoherent, groundmass. The medium-sized pheno- 

'crysts, which in bulk usually equal the groundmass, are tabular crystals of glassy, unstriated feldspars, often showing blue and purple 

color plays, and rounded grains of colorless quartz. Smaller plates 

of biotite are locally present. Pink, purple, and red facies also occur. 

Black glassy types in which feldspar greatly predominates over 

quartz, to judge from the hand specimen, may be more properly called 

latite.

Many of the rhyolite flows are flow breccias, containing abundant 

inclusions of rhyolite of different colors and textures. Vesicular 

facies showing flow lines are unusual. Interbedded with the rhyolites 

are sandy beds which contain normal feldspar and quartz crystals 

and rounded rhyolite pebbles. These are contemporaneous tuffs of 

either aqueous or subaerial origin. It is probable that minor flows 

of basalt were contemporaneous with those of rhyolite, since vesicular 

basalt fragments are in places included in rhyolite.

The rhyolite occurs in mesa-like ridges whose top is often coincident with the surface 'of a resistant rhyolite flow. This rock lies 

unconformably upon granite and Cambrian limestone, and upon its 

slightly eroded surface basalt flows rest in turn. The rhyolite is to 

be correlated with that of the Amargosa and Kawich ranges and the 

Bullfrog Hills and is probably of early Miocene age.

Basalt. Basalt covers the butte between Old Camp and Tokop and 

occurs in two small areas to the west of the butte and in a number of 

small areas 11 miles south of Gold Mountain, resting upon the slightly 

eroded rhyolite surface. The basalt of the butte just mentioned is 

a dense dark-gray flow rock, which is vesicular along some bands.
GOLD MOUNTAIN RIDGE AND HILLS NEAE BY. 187

ECONOMIC GEOLOGY. ^

o

The Gold Mountain mining district, organ- § 

ized January 25, 1868, embraces within its lim- 5- 

its the Gold Mountain and Slate ridges. Mines ~ 

have been worked in the district intermittently 1 

since that time, and several mills have been 

built, none of Avhich are now in operation. Old 

residents estimate the total product of the distrist as $500,000, the concentrates being hauled 

by wagons to Belmont and Austin, Nev. The 

mines and prospects lie in the more highly metamorphosed Cambrian rocks and in granite,, 

and these rocks in this vicinity are probably 

most favorable for prospecting. The contact ° 

of the rhyolite and granite 9 miles south of west of Gold Mountain is 

in places altered to an iron-stained, incoherent mass, cemented by 

chalcedonic quartz, and this contact is perhaps worthy of examination.

This rock, like some of the basalt of the Panamint Range, is spotted 

by areas of lighter color. The phenocrysts, which are small and 

fairly abundant, include striated feldspar, a 

glassy green olivine, and blackish-green pyroxene. The basalt breaks down into rounded 

bowlders heavily stained by iron oxide. It is 

later than the rhyolite and is probably contemporaneous with the basalt of Slate Ridge and 

Mount Jackson and of late Pliocene or early 

Pleistocene age.

STRUCTURE.

.

The Cambrian rocks dip steeply away.from i 

the granite batholith, and near-by faults and ! 

brecciation, isoclinal folds, and buckled strata 

are developed. (See fig. 16.) At a distance 

from the granite the dips become less pronounced, but the mass of granite is so large and 

the Cambrian masses so small that rather high i 

dips are characteristic throughout them. The 

granite is cut by fault and joint planes. Prior 

to the outflow of the rhyolite and basalt the 

granite and Cambrian rocks had a topography 

somewhat less rugged than at present, but the 

Gold Mountain ridge appears to have existed. 

Blocks of rhyolite north of Grapevine Canyon 

are tilted in different directions by normal 

faults, the majority of which strike northeast 

and southwest.

Slate 

Ridge

\Go\d Mtn. 

Ridge
188 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

OLD CAMP.

The almost deserted village of Old Camp, near Gold Mountain, 

is situated 30 miles west of south of Goldfield and 20 miles 'southeast 

of Lida. Abandoned mines and prospects are numerous in the vicinity and a number of prospects are being developed 2 or 3 miles south 

of the village.

The Central mine, which supplied the ore used in the mill at Old 

Camp, may be taken as a type of ore deposits in the granite of this 

region. This mine is situated on the side of a deep gulch 1^ miles 

north of east of the mill. Five tunnels, with an average length of 

300 feet, pierce the granite and all are situated on a single vein or 

system of connecting veins. The feldspars of the granite within 20 

feet of the vein are considerably kaolinized and the biotite is bleached 

or altered to a sericitic mineral. The quartz vein, or rather zone, 

within which the numerous connecting quartz veinlets and stringers 

occur, is from 1-| to 6 feet wide, the proportional amount of quartz 

increasing with the narrowing of the zone. The ordinary veinlets 

are from 2 to 5 inches wide. The zone also contains many ellipsoidal 

and globular areas of quartz which, at least in the plane of observation, are independent masses. The quartz zone in some places changes 

its direction 90° within 100 feet. While minor postmineral faults 

are common, the displacement ranging from 6 inches to 7 feet, the 

major changes in strike and dip are evidently parts of the original 

structure.

The quartz is white and translucent or slightly smoky, with a 

strong vitreous luster. Vugs with inch-long crystals are rather 

rare. In places the clear quartz seems to grade into a gray chalcedonic form, the deposition of which by ordinary waters can scarcely 

be doubted. Isolated crystals of pyrite, with very rare crystals of 

chalcopyrite and galena, are embedded in the quartz, while the former 

abundance of pyrite in particular is shown by numerous iron-stained 

cavities of cubical form. Both hematite and limonite occur in the 

porous quartz, and where these are abundant gold values rise. An 

occasional malachite stain and a cerussite coating are- also present. 

Dendrites of manganese dioxide occur in the granite, and are probably 

derived from the alteration of the granite rather than from a decomposing gangue mineral. Horn silver is reported to be present in 

small amounts, but was not seen. The ore is free-milling, the arrastres, now abandoned, having saved about 75 per cent of the assay 

value. Films of a bluish-white chalcedony were noted at a number of 

places. Some of it was deposited prior to the oxidation of the pyrite 

and some was deposited after partial or complete oxidation.

While the quartz is rather similar to the quartz of pegmatitic 

origin in the district, and the form of the ore deposit rather suggests 

that of a pegmatitic dike, the apparent gradation into chalcedony indi-
GOLD MOUNTAIN RIDGE AND HILLS NEAR BY. 189

cates a less close connection with waters of the granitic magma. 

Water appears to have filled a most complex zone of fracture with 

quartz and sulphides, the gold p'robably being originally contained in 

pyrite. Later oxidizing waters attacked the sulphides and altered 

them to oxides and carbonates, setting the gold free. These waters 

apparently carried some silica in solution, which was deposited as 

chalcedony.

The mines in the vicinity of Old Camp are situated near water 

sufficient for mining and milling purposes. Timber for fuel and 

mining use is standing within 2 or 3 miles. The railroad terminus 

at Goldfield is 35 miles distant.

TOKOP.

Tokop is 4 miles in an air line northeast of Old Camp and 25 miles 

by road west of south of Goldfield. The properties of the Gold Crest 

Mining Company, situated three-fourths of a mile south of Tokop, 

were examined in some detail. On the Ouida claim a vertical vein 

cuts the Cambrian garnet-quartz-epidote rock, which strikes N. 10° 

E. and dips 20° W. This vein is 1$ feet wide and strikes N. 80° W. 

The. quartz of the vein, which is white and semitransparent, has been 

intensely crushed, and the fragments have been cemented by hematite and limonite. Dendrites of manganese oxide also occur. Some 

portions of the quartz are compact, with here and there an ironpyrite cube unaltered, while other portions have a few vugs lined with 

quartz crystals or are honeycombed .with iron-pyrite casts. From 

the fact that the compact varieties are refractory and the honeycombed varieties are free-milling, it is evident that the gold was set 

free by the alteration of the pyrite. A mashed greasy phase of the 

garnet-quartz-epidote rock on one side of the vein is said to pan, but 

whether pyrite originally occurred in the metamorphosed limestone 

or whether the values were derived from the surface alteration of 

the quartz vein is unknown.

Angular fragments of altered limestone and shale are common 

near the borders of some veins. In such places silicification has extended into the limestone, and these belts, like the quartz veins, 

weather in relief. Such veins grade into sheared and .brecciated 

zones of silicified limestone, and these again are reported to carry 

values.

Another vein is similar to the vertical vein first described, but the 

shattered quartz is cemented by a gray chalcedonic quartz. Still 

another, at first sight, appears crustified, but close inspection shows, 

that the appearance is due to a longitudinal fracturing of the vein 

and subsequent filling by limonite and chalcedonic quartz. Both 

forms of quartz are said to assay, but the earlier quartz appears to 

carry both the sulphides already mentioned and slight amounts of
190 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

galena as noted in other veins. It may be that the chalcedonic quartz 

appears to carry values simply because sufficient care has not been 

taken to eliminate the older quartz from samples.

Limonite, hematite, cerussite, free gold, and a little malachite were 

observed as secondary minerals. Probably some chalcopyrite exists 

at greater depths. One of the last changes which these ore deposits, 

like those of Old Camp, have undergone is the local deposition of a 

thin film of bluish-white chalcedony.

The contact of the granite and limestone here probably has locally 

a rather gentle dip, and deep mines in limestone near the contact may 

encounter granite. Mr. Joseph Mackedon, the manager of the Gold 

Crest Mining Company, states that in several prospect holes the 

quartz veins have past from metamorphosed limestone to granite 

without diminution in size or value. From the striking resemblance 

of these veins to those of Old Camp this is to be expected.

Similar veins of iron-stained quartz carrying gold values occur at a 

number of places in metamorphosed Cambrian rocks around Tokop.

Waters carding silica and metallic salts in solution appear to have 

deposited these substances in strong fractures which extend, in some 

cases, at least, into the granite. The country rock was to a less extent 

impregnated. The quartz veins were subsequently crushed and iron 

oxide and chalcedonic silica were deposited in the fractures. Simultaneously, probably, iron pyrite was dissolved and the gold set free.

Water and wood for mining and domestic purposes are near at 

hand, and the distance to the railroad at Goldfield is 25 miles. The 

Rattlesnake mine, near the properties described, appears to be in the 

same rock formation, and its ore deposits and those of Tokop are said 

to be similar. Eight or ten years ago the Rattlesnake produced 

$150,000, and recently it has been reopened. The veins of Tokop, like 

those of Old Camp, seem strong and will probably be permanent to 

such depths as mining is possible. With depth, however, the ore will 

become refractory and may become leaner.

ORIENTAL WASH.

Several prospects, now abandoned, are located in the altered limestone West of the granite area at the west end of the Gold Mountain 

ridge. At one prospect a thin quartz vein cuts the limestone. Malachite, azurite, chrysocolla, and limonite-stained chalcedonic quartz 

occur in irregular patches and veinlets through the quartz. Vugs 

occur in the secondary minerals, and the azurite and malachite are in 

places covered with numerous quartz crystals. A little chalcopyrite 

is embedded in the oldest quartz and cores of chalcopyrite are surrounded by the secondary copper minerals. A vein of malachite 1 

inch in width, apparently replacing the limestone, is exposed in 

another prospect. At still another prospect, in association with mal-
SLATE BIDGE, SEDIMENTABY BOOKS. 191

achite, azurite, and coral-red opaline quartz, heavily stained by 

manganese dioxide, is a streak from 1^ to 2 inches wide of a canaryyellow granular mineral which appears to replace limestone. Dr. 

W. F. Hillebrand determined this mineral to be chloropal, a hydrous 

iron silicate. The general resemblance in structural relations and 

mineralogic composition of these deposits to those near the granite of 

the Belted Range at-Oak Spring is worthy of note. The nearest 

water to these prospects is at Sand Spring, 6 miles away, and fuel 

can be obtained from Gold Mountain within 10 miles. By road the 

prospects are 45 miles from the railroad terminus at Goldfiejd.

SLATE RIDGE. 

TOPOGRAPHY AND GEOGRAPHY.

Slate Ridge lies between the valley south of Mount Jackson on the 

north and Oriental.Wash and an opposed westAvard-reaching arm 

of Sarcobatus Flat on-the south. The ridge trends a little north of 

east, and near its middle is almost severed by opposed-gravel-filled 

valleys. West of the Stateline Mill the ridge is formed of a number 

of low domelike granite hills, which reach a maximum elevation of 

0,500 feet. The hills are rather gently sloping and Avithout prominent rock exposures. From a distance they are yellowish gray in 

color. East of the Stateline Mill the rocks are largely of sedimentary origin and there is a sharp crest line. The east end of Slate 

Ridge is a mesa of lava flows.which have been considerably dissected. The range is covered by a sparse growth of tree yucca and 

a little grass grows throughout its extent.

GENERAL GEOLOGY.

The formations exposed in Slate Ridge, from the oldest to the 

youngest, are the following: Cambrian sedimentary rocks^ postJurassic granite, pre-Tertiary quartz-morizonite porphyry, pre-Tertiary diorite porphyry, earlier rhyolite, later rhyolite, and basalt.

SEDIMENTABY BOCKS.

Cambrian. Cambrian rocks form the central part of Slate Ridge 

and occur in numerous areas isolated in the granite in its west end. 

Of the latter some are clearly inclusions buoyed up by the granite 

inagma, while others may perhaps be connected with larger masses 

beneath the surface. Small Cambrian fragments are abundantly 

included in granite and the earlier rhyolite, particularly near the 

contact of these rocks with the sediments.

The Cambrian rocks of Slate Ridge are little metamorphosed on 

the road between Tokop and Goldfield. Here the interbedded series 

consists of paper-thin olive-green shales, gray limestones, or mag-
192 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

nesian limestones, usually rather thin bedded, and some impure medium-grained quartzites of purple, gray, or white color. Rounded 

hills of gentle slope are developed in these slightly metamorphosed 

rocks. The Cambrian rocks are intensely metamorphosed near 

granite, and these facies have been described in the section on the 

Gold Mountain ridge (p. 183), along which they are more extensively 

developed.

No fossils were found in these rocks, but from their lithologic similarity to the rocks in the vicinity of Lida and Cuprite they are without" much, doubt of Lower Cambrian age.

Later tuffs. Beneath the later rhyolite at several places is exposed 

a thin band of white tuffaceous sandstones, possibly to be correlated 

with the later tuffs of the Goldfield hills and Pahute Mesa.

IGNEOUS ROCKS.

Post-Jurassic granite. Granite forms a considerable batholith on 

the west end of Slate Ridge and smaller intrusive masses and dikes 

occur in the Cambrian rocks. This rock is a coarse-grained biotite 

granite of pinkish tone. The pink or white feldspar and slightly 

smoky quartz individuals reach a maximum diameter of one-half 

inch, while the black biotite plates are smaller. The granite tends to 

weather into spherical masses. The surface of these bowlders appears to undergo a kind of cementation, and on further weathering 

the hardened surface protrudes beyond the soft interior, forming 

mushroom-like forms. The granite breaks down into a soil of the 

constituent minerals and mechanical disintegration is so rapid that 

recent detrital deposits extend as broad basins well up into the hills. 

The granite is cut by parallel sheeting in certain localities and on 

weathering assumes the appearance of a sedimentary rock. Microscopic examination shows the texture to be allotriomorphic. The 

feldspar is orthoclase, considerably kaolinized and sericitized. Zircon and magnetite are present as accessory minerals.

Dikes of fine-grained biotite aplite, rather more siliceous than the 

granite, cut it, and these on weathering protrude from the granite 

mass. The granite is also cut by dikes and in turn grades into irregular masses of coarse-grained pegmatite. Some quartz veins are evidently of pegmatitic origin, since they grade into less siliceous pegmatites. In some instances microscopic examination shows quartz 

individuals at the contact of granite and pegmatite to be common to 

both rocks. At the Bullfrog-George mine fluorite and molybdenite 

occur in a quartz vein which is without much doubt of pegmatitic 

origin. Molybdenite occurs sporadically in small tablets and irregular areas in\ and between the quartz individuals. A bright-yellow 

mineral in minute crystals and tufted aggregates, apparently secondary to molybdenite, was determined by Dr. Waldemar T. Schaller
SLATE RIDGE, IGNEOUS ROCKS. 193

to be molybdite (molybdenum trioxide). Purple fluorite occurs in 

crevices in the quartz, and fluorite cubes one-fourth inch in diameter 

also line vugs in the quartz. Microscopic examination shows that the 

quartz individuals in contact with fluorite possess sharp outlines, 

showing that they were but little corroded by the introduction of the 

fluorite, which is probably of pneumatolitic origin.

The granite is similar lithologically to that of Gold Mountain and 

has like relations to the Cambrian rocks and the Tertiary rhyolite. 

It is probably of post-Jurassic age.

Pre-Tertiary quartz-monzonite porphyry, The Cambrian sedimentary rocks on the road from Tokop to Goldfield are cut by dikes 

which reach a maximum width of 40 feet. The rock is white and 

dense and contains a few feldspar phenocrysts. It is similar to the 

quartz-monzonite porphyry already described from the vicinity of 

Lida and, like it, is probably genetically related to the granite.

Pre-T ertiary diorite porphyry. The Cambrian rocks and the granite are cut by narrow dikes of a greenish-gray much-altered rock 

in which some of the prominent kaolinized feldspar phenocrysts are 

one-half inch long; This is probably the pre-Tertiary diorite porphyry.

Earlier rhyolite. The earlier rhyolite forms a considerable portion 

of the east end of Slate Ridge, and small areas of it occur, widely distributed over the central and western portions. In some places east of 

the Bullfrog-Goldfield road it appears from a distance to protrude 

from the later rhyolite. The earlier rhyolite is a flow rock of purple, 

gray, or white color. The grouhdmass, which is usually lithoidal, is 

equaled in bulk by the medium-sized phenocrysts of glassy unstriated 

feldspar, quartz, .and biotite. Semituffaceous layers are interbedded 

with the flows northeast of Tokop. The earlier rhyolite lies upon 

the eroded surface of the Cambrian rocks and the granites, and in 

turn is overlain by basalt and the younger rhyolite. It is similar to 

that of the Amargosa Range and is probably of earlier Miocene age.

Later rhyolite. The dissected mesa at the east end of Slate Ridge 

and a number of outliers in the recent gravels east of it are formed 

of flows of rhyolitic rocks. This later rhyolite has a dense groundmass of deep-brown color, in which are abundant glassy feldspar 

phenocrysts; in some facies very small and in others medium sized. 

Microscopic examination proves the groundmass to be a brown glass 

with well-developed flow lines. The phenocrysts are orthoclase, somewhat corroded, rare and small greenish augite crystals, and very 

rare quartz grains. While this rock is tentatively here called a rhyq,- 

lite, chemical analysis might prove it to be of less acidic composition.

Beneath this rhyolite are tuffaceous sandstones in which are rhyolite pebbles. This is probably the later tuff (Pliocene) of the Gold/.

Bull. 308 07 M 13
194 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

field hills. The rhyolite immediately above the sandstone is in many 

places vesicular and is a flow breccia.

This rhyolite is similar, lithologically to the later rhyolite of the 

Goldfield hills, and the two have suffered equal deformation. They 

are without much doubt contemporaneous lava flows of Pliocene age.

BasaU.^Black vesicular basalt occurs in a number of small outlier? 

upon the Cambrian rocks, the granite, and the earlier rhyolite and a? 

small buttes on the border of Slate Ridge. The basalt is similar 

lithologically to that of Mount Jackson and, like it, is probably of 

"Pliocene or early Pleistocene age.

STRUCTURE.

The Cambrian rocks at a distance from granitic intrusions lie in 

gentle folds many of whose axes trend northeast. The folding is 

comparable in intensity with that at Cuprite and Lida. On the other 

hand, they dip steeply away from the granite batholith and in its 

vicinity are buckled and minor isoclinal folds are common. (See fig. 

16, p. 187.) It is evident that in this region the Cambrian rocks .were 

folded prior to the intrusion of the granite, a process which superimposed upon the gentle folds complex elements. The granite is cut 

by normal faults. Since the Tertiary rocks were formed the ridge 

has suffered domical uplift, centering 4 or 5 miles east of the Stateline Mill.

ECONOMIC GEOLOGY.

Quartz veins, some of which are of pegmatitic origin, cut granite 

and the more metamorphosed Cambrian rocks. The best prospecting 

ground is the granite and the metamorphosed limesjtone and shales in 

its vicinity. In the late sixties mines were opened on Slate Ridge and 

considerable ore bodies were removed. The ledge at the Stateline 

Mill, now abandoned, is said to have been 20 feet wide, the ore averaging $40 per ton in gold. Recently a number of claims have been 

located in Slate Ridge and development work is now being done.

The Bullfrog-George prospect is situated on the side of a domical 

granite hill, near the Lida-Old Camp road. The surrounding hills 

are cut by quartz veins which weather in relief and can be traced for 

long distances. Some of these contain feldspar and others grade into 

pegmatite dikes. The Bullfrog-George claims are situated on a 

quartz vein from 4 to 9 feet wide, which is traceable for about a quarter of a mile. The vein is vertical and strikes N. 70° "W. The contact with the granite is in some places gradational, the white translucent quartz of the granite passing into that of the vein without 

break. In other places the granite appears to have been shattered 

prior to the deposition of the quartz, which now fills linked cavities 

in the granite. The feldspars of the granite within 4 feet of the vein 

are locally much kaolinized. Apparently isolated in the quartz are
DEATH VALLEY. 195

small areas of- pyrite and chalcopyrite, with less galena and chalcocite or a related sulphide. The quartz in many portions is intensely 

crushed, this crushing perhaps being contemporaneous with faults 

which cut the diorite-porphyry dikes of the vicinity. The crushed 

fragments have been recemented by limonite or a chalcedonic quartz 

intensely stained by limonite. With these knife-edges of limonite 

and in limonite-stained cavities malachite, cerussite, and traces of 

azurite occur. Such quartz pans free gold, and coarse pannings were 

examined from the heavily iron-stained contact of the granite and 

quartz. At the east end of the quartz veins less shattering was noted. 

Vugs lined with quartz crystals are common, and here the fluorite 

and molybdenite already described (see p. 192) occur.

The quartz vein itself appears to be a pegmatite which crystallized 

while portions of the granite were still viscous and other portions 

were comparatively solid. Later, faulting occurred and the vein 

was crushed. Since then limonite and chalcedonic quartz have recemented the quartz fragments. The period at which the sulphide 

mineralization occurred is unknown. The molybdenite and fluorite 

are probably of pegmatitic origin, while the sulphides were doubtless 

deposited later. Similar quartz from other prospects on'the ridge 

was examined. AVhere iron stained it is said to carry free gold.

Water is at present hauled from a pipe line on the Lida-Old 

Camp road, 9 miles distant. The nearest timber grows in the vicinity of Old Camp. The prospect is 30 miles from the railroad terminus at Goldfield.

DEATH VALLEY. 

TOPOGRAPHY AND GEOGRAPHY.

Death Valley is a deep depression lying between the Panamint 

Range on the west and the Amargosa Range on the east. The valley, 

which has a length of 120 miles and a width varying from 3 to 10 

miles, unites with the Amargosa Desert at the south end of the 

Funeral Mountains. In the fifties a band of eighty emigrants are 

said to have perished here and the valley received its name from this 

tragedy. In the Pahute language the valley is called Tomesha, 

meaning "ground afire." Many fantastic stories, most of them 

Avholly without foundation, center in Death Valley. Lives have 

been lost from year to year, but the majority of such sacrifices have 

been clue to ignorance of desert conditions. In July and August 

the temperature is reported, apparently on good authority, to reach 

136° F., and in summer none but the most desert-hardened men 

should enter the valley. In winter and fall the climate is delightful. 

In those portions of the valley which lie. beneath sea level the dry 

air seems heavy and the brightest days are sultry. In the lower
196 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

s

portions of the valley no animals other than a few coyotes live, and 

the oppressive silence is unbroken. Much of the valley is absolutely 

without vegetation and the adjacent mountain slopes are equally 

bare. Mesquite grows on the sand area west of Surveyors and 

Stovepipe wells and at Mesquite Spring. The upper portions of 

the alluvial slopes have here and there a sparse growth of creosote 

bush and white sage, and salt grass covers restricted areas around 

the wells.

The lowest point of Death Valley within the area mapped is 

about 280 feet below the sea level, but 15 miles farther south the 

depression is at least 125 feet deeper. The mountain ranges on 

either side of the valley are from 6,000 to 8,900 feet high, and in 

consequence of this great difference in elevation the slopes are steep 

and wide alluvial cones sweep up to the mouths of the deeply scored 

canyons. The floor of the valley is diversified by numerous hills 

and low ridges of Tertiary sediments. The part of the valley lying 

north of a low ridge at the head of Salt Creek is sometimes called 

Mesquite Flat.

A large sand dune occupies the bottom of Mesquite Flat. Most of 

the larger sand dunes are without vegetation, while some of the 

smaller ones (20 feet high and 100 feet in diameter) owe their existence chiefly to the protecting influence of mesquite and similar 

vegetation (PI. II, B}. Death Valley is the only portion of the area 

surveyed in which sand storms endanger life. The area mapped 

as sand contains within its limits many small areas of clay and is 

\vithout doubt partially under water in times of excessive floods. In 

like manner the playa deposits mapped to the south, north, and 

east of the sand are studded with minor sand dunes.

South of Salt Creek the center of the valley is a loamy flat covered 

with salt grass. This passes gradually southward into a salt marsh, 

4 miles wide, which, according to Campbell," extends about 25 miles 

south of the area mapped. It is a dirt-brown flat, containing numerous channels and ponds of stagnant or gently flowing salt water. 

The soil itself is heavily impregnated with salts, and by fractional 

recrystallization the margins of the water bodies are coated with 

glittering white salt deposits. The salt-cemented soil stands up in 

rugged pinnacles and hummocks from 6 -to 18 inches high. Campbell 6 states that a specimen of this material from a point south of 

Furnace Creek has the following composition:

0 Campbell, M. R., Bull. U. S. Geol. Survey No. 200, 1902, p. 18. 

6 Loc. cit.
DEATH VALLEY, GENERAL GEOLOGY. 197

Analysis of soil from Death Valley.

Per cent. 

Chloride of sodium_________________^_____. 94.54

Chloride of potassium_______i_____________________________ .31

Sulphate of sodium_________________________ 3. 53

Sulphate of calcium (hydrous) _______ _____ _ ____ _ .79

Moisture ___________ _ ____ _____ 14

Undissolved residue (gypsum and clay)_________ ____ _____ .50

99. 81

This large supply of salt, while at present, as Campbell states, too 

impure to be of commercial value, may in the future be economically 

important. From 1883 to 1887 an extensive plant extracted borax 

from the salts of this marsh, but on the discovery of extensive 

colemanite deposits in the Tertiary lake beds on Furnace Creek it 

was closed down. Borax is also reported in the clay of the plava 

2 miles east of south of Surveyors Well.

Death Valley is one of the best watered areas within the limits 

of the area here discussed, and the water for the most part is good. 

Salt Creek and the warm Indian Springs have already been described 

(pp. 19, 20). At Stovepipe Wells, Surveyors Well, Ruiz Well, Salt 

Creek Wells, and the water hole on the Furnace Creek road, 1 mile 

' north of the boundary of this area, water stands in shallow holes dug 

in the sand and clay. The water of the last-named hole is too salt for 

man's use, although animals will drink it. Mesquite Spring is a small 

spring in Recent gravels, while the water of Cow Creek and Triangle 

Spring flows from Tertiary lake beds.

GENERAL GEOLOGY. 

SEDIMENTS.

General statement. Two sedimentary series much later in age than 

the Paleozoic rocks of the Amargosa and Panamint ranges outcrop 

in Death Valley. The one is composed of coarser fragmental material, well rounded, and appears to have been deposited in a waveswept lake, while the material of the other is angular or subangular 

and evidently analogous in origin to the present alluvial slopes and 

fans. Associated with each are finer grained clays and limestones - 

those of the one series, lake deposits; those of the other, playa deposits. The delineation of these finer deposits on the map is in many 

cases probably inaccurate. The lake deposits are clearly older than 

those of the playa and are better cemented and in general more 

deformed. The two formations, while less extensively developed, 

are much more easily differentiated on the east side of the Amargosa 

Range and in the adjoining portions of the Amargosa Desert, where 

the detrital and playa deposits are uncemented angular gravels, clays, 

and chemically precipitated limestones, which are particularly unde-
198 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

O

coc 1%

E E

informed, Avhile the older lake beds are sandstones and well-rounded 

conglomerates which dip at high angles. BeIOAV Ash MeadoAvs, in the Amargosa Desert, 

Campbell ° found evidence that the detrital 

deposits Avere laid doAvn after the folding and 

elevation of the lake beds into the Funeral 

Mountains. The time gap betAveen the two is 

considerable, and the older beds are tentatively 

considered by Campbell v Eocene 'and the others 

Pliocene. It is believed, hoAvever, from evidence obtained in the Amargosa Range, that 

the older beds are probably largely as late as 

the Miocene and that they may be the shore 

deposits of Siebert Lake, Avhile the presence of 

basalt, contemporaneous Avith the upper portion 

of the younger beds, indicates that their deposition probably extended into the Pleistocene. 

The later beds are evidently the equivalent of 

the older alluvium.

Territory lake .beds (including the /Siebert 

lake beds). The Tertiary lake beds, which are 

a northwesterly extension of the folded Tertiary sediments extending across the Funeral 

Mountains soutlrwest of Furnace Creek ranch, 

are confined, in the area surveyed, to the east 

side of Death Valley near the boundary. Numerous hills of these beds rise above the Recent 

gravels, and the scale of the map permits only 

 an approximate representation of their complex distribution.

The Tertiary lake beds consist of AA7 hite, 

yelloAv, and green consolidated clays, friable 

sandstones Avith ironstone concretions, rounded 

and subangular gravels, and thin limestone 

lenses. Much of the clay shows sun cracks 

and ripple marks, indicating that the lake Avas 

at times shallow and eA^en dry. The subangular 

form of certain of the gravels indicates that 

cloudbursts at times spread sheets of detrital 

deposits over the lake beds. Colemanite and 

other chemical precipitates interbedded Avith the 

other deposits were laid down during periods 

of unusual evaporation. The more northerly

hills to the Avest of the Daylight Spring-Furnace Creek road Avere

.ego>E

>5fl

i' t

" Campbell, M. R., Bull. U. S. Geol. Survey No. 200, 1902, p. 16. 

"Loc. clt.
DEATH VALLEY SEDIMENTS. 199

not visited by the writer, but specimens collected by Mr. K. H. 

Chapman are reddish-brown conglomerates and conglomeratic sandstones with rounded pebbles. The pebbles, which reach a maximum 

diameter of 2-| inches, are limestone, quartzite, and schist derived 

from the Amargosa Kange. They are probably members of the 

lake-bed series.

The Tertiary lake beds are folded into open folds, usually with 

northwest axes. (See fig. 17.) Joints from 4 to 5 feet apart are 

developed.

Older alluvium. Hills of the older alluvium diversify the surface 

of Death Valley, at two places extend a considerable distance up the 

Amargosa Range, and form the north end of the Panamint Range. 

In the large sand area north of Salt Creek a few hillocks of slightly 

consolidated clay'occur, and these probably indicate the former extension of these deposits across the valley.

The road from Daylight Spring to Stovepipe Wells passes through 

a desiccated ridge from 200 to 400 feet high; which trends northwest 

and southeast and is cut by antecedent drainage lines. Next to the 

Amargosa Range the hills are composed of slightly consolidated beds 

of angular or subangular bowlders and bands of gravel and sand. 

Cross-bedding and local unconformities are common. Well-developed 

joints form buttresses on the main cliffs, and larfk bowlders crown 

many of the high pinnacles. Within one-half mile of the western 

edge of the hills the sand beds are replaced along their strike by clay, 

and clay layers wedge in between the bowlder beds. At the western 

edge of the hills the base of the series is clay and the top bowlder beds. 

A section measured 2 miles south of east of Stovepipe Wells is as 

folknvs:

Sect-ion in Death Valley near .Stovepipe Wells.

Feet.

Angular bowlder beds, similar to those of the present alluvial slopes___ 150-f 

Clay and bowlder beds in equal development_________________ 110 

Salmon-pink clay beds, from 3 inches to 3 feet thick; a few layers of angular bowlders interbedded ______ ___ 1___________ 100

At Triangle Spring fine-grained, dirty-brown cellular limestone 

is interbedded with the .clays. The limestone shows desiccation cracks. 

Compact, fine-grained, light-colored limestone and caramel-brown 

mammillary gypsum also occur here. The beds exposed at Salt Creek 

include yellow, white, and green clays, with here and there a thin 

bed of white limestone. Brownish beds of angular bowlders constitute a considerable portion of the upper part of the section. The long 

ribbon of these deposits near the Grapevine Mountains northeast of 

Surveyors Well consists of tawny-yellow clays and thin beds of cellular limestone. At Grapevine Springs the deposits consist of limestones and fine clays. The cl&y contained crystal aggregates of selenite. The limestone is white or gray in color and is partly compact
200 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

and very finely laminated and partly porous. The areas in the middle of the valley northwest of these springs are of interest, since flows 

of the supposed Pleistocene basalt are interbedded with the clay, 

while other layers contain bowlders of basalt. In some places the 

clay beneath the basalt has been reddened and slightly baked. These 

clay beds, which are well up in the section, are broadly contemporaneous with basalt eruption.

About 2,500 feet of-the older alluvium is exposed in the Amargosa 

Range, and it is probable that the series was originally over 3,000 

feet thick. The beds are gently flexed, and dips from the mountains 

to the valley axis predominate, particularly in the northern part of 

the valley. The sediments have, been jointed, the principal system 

striking N. 25° W., and along some of these joints occur normal faults 

with from 2 to 4 feet displacement.

GEOLOGIC HISTORY.

In Tertiary, probably early and middle Miocene time, Death Valley did not exist, Amargosa and Panamint ranges were low, and their 

southern portions a at least were covered by a lake which extended well 

into the present Death Valley south of Salt Creek. This lake was at 

least partly contemporaneous and may have been connected with that 

in which the Siebert lake beds were deposited, and which probably 

at one time covered almost the entire area surveyed. In late Pliocene 

time, however, Death Valley was probably a closed basin, occupied 

by a sheet of water, which appears to have been a playa. This 

playa varied widely from tinie to time in extent and was bordered by 

the uplifted Panamint and Amargosa ranges. Before the deposition 

of the older alluvium ceased the inwash of material from the 

mountains raised the center of the valley hundreds of feet above the 

present level. Alluvial slopes, much like those of to-day, extended 

well up on the Panamint and Amargosa ranges. In the playa great 

thicknesses of clay were deposited, and at periods of unusual desiccation limestone and gypsum were precipitated. Unusual floods from 

time to time throughout the period of deposition spread thin layers 

of bowlders over the playa. Basalt outflows accompanied the deposition of the upper playa deposits.

Death Valley is believed to have been roughly blocked out in late 

Miocene and early Pliocene-time, through erosion and deformation, 

including faulting and possibly folding. The folding of-the Amargosa and Panamint ranges does not alone account for the valley, and 

it appears to be a block dropped down between the bounding ranges 

by faults. The earliest structural lines, probably of late Miocene age, 

trend northwest and southeast and include the fault 6 on the north-

« Spurr, J. E., Bull. U. S. Geol. Survey No. 208, 1903, pp. 189, 202. 

"Campbell, M. R., Bull. U. S. Geol. Survey No. 200, 1902, p. 16.
U. S. GEOLOGICAL SURVEY BULLETIN NO. 303 PL.

MARBLE CANYON, PANAMINT RANGE. 

Showing metamorphosed Pogonip limestone near quartz-monzonite batholith.
PANAMINT RANGE. '201

east side of the lake beds in the Funeral Mountains and normal faults 

in the Panamint Range. In early Pleistocene time the lines of disturbance were north-northwest, and normal faults, with a strike 

parallel-to the valley axis, occur in the older alluvium east of Stovepipe Wells. In the Panamint Range 22 miles beyond the boundary 

of the area mapped and in line with Death Valley a narrow block, 

apparently faulted into the older rocks, has, at a distance of 15 miles, 

the appearance of the older alluvium. The fronts of the Panamint 

and Amargosa ranges facing Death Valley are very steep and may be 

due to the erosional shifting of a fault scarp. The absence of Paleozoic inliers in the valley indicates the steep grade with which these 

rocks descend beneath the valley gravels. That the drainage lines 

of the Panamint and Amargosa ranges flowing into Death Valley 

have been revived in comparatively late geologic time is indicated 

by the intense dissection of the prebasaltic mature topography of 

the Panamint and Amargosa ranges. (See pp. 202 and 161.) The 

history of Death Valley has been complex, and the solution of the 

problem requires more detailed work than was possible in the present 

reconnaissance.

ECONOMIC GEOIOGY.

Extensive deposits of colemanite and other borax minerals occur in 

the Tertiary lake beds near Furnace Creek, and the extension of these 

beds in the area mapped is worthy of careful prospecting. " Marsh " 

borax has been found 2 miles south of Surveyors Well, and it is probable that this has been leached from the older alluvium near by. The 

clays and limestone of this formation may contain important colemanite deposits.

PANAMINT RANGE. 

TOPOGRAPHY AND GEOGRAPHY.

The Panamint Range is 130 miles long and trends north-northwest 

parallel to the Sierra Nevada. At its north end lava mesas unite it 

with the Amargosa Range; its south end passes into low hills of 

Tertiary sediments and lavas capped by later basic volcanics.0 The 

ascent from Death Valley on the east ranges from 6,000 to 11,000 

feet, while that from Panamint and Termination valleys on the west 

is almost as great. The range culminates 20 miles south of the area 

here mapped in Telescope Peak, which the Wheeler survey determined to be 10,938 feet high. Within the area the highest point is Tin 

Mountain, whose elevation is 8,900 feet. The range crest is somewhat 

west of the center, and the western slope seems a succession of cliffs 

and declivities. The range is scored by deep canyons, some of which 

are comparable with the most famous gorges of the Rocky Mountains. 

Marble Canyon (PI. Ill) is particularly impressive. The sharply

0 Spun-, ,T. E., Bull. U. S. Geol. Survey No. 208, 1903, p. 201.
202 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

curving inner canyon, which is but 10 feet wide, is overhung.by walls 

200 feet high, and many portions of the stream channel are in perpetual shadow. The walls are beautifully smoothed and rounded 

by erosion.75 feet above the stream bed. Rock cliffs 10 to 100 feet 

high, which in other regions would form waterfalls, break the more 

gentle grades of gravel. The brilliant yellows, reds, whites,, and. 

blacks of the limestone enhance the beauty due to form.

The crest of the range is characterized by an older, more mature 

topograph}^ with well-graded stream channels and gently rounded 

peaks and slopes. Near the southern boundary of the area mapped 

and for a distance of 4 miles south of Tin Mountain this belt is 3 

miles wide, while the intermediate belt along the crest line is but 1 

mile wide. Remnants occur in favorable positions on the middle 

slopes of the mountain range above an elevation of 5,000 feet. On 

the southern border of the area the basalt covers a portion of this surface a fact which indicates that the surface was probably developed 

in Pliocene time. The older alluvium, in part, is formed of remnants 

of the alluvial slopes, the gravel pediment of this subdued mountain 

range. .

Sparse growths of pirion and juniper cover the southwest corner of 

the area and the northeastern and southern slopes of Tin Mountain, while cottonwood and willow grow along Cottonwood Creek. 

Grass is found around the small playa northwest of Goldbelt Spring 

and in the valleys in the higher portion of the range. The Panamint 

Range, because of its elevation, has a heavier annual precipitation 

than most of the other ranges. One or more springs rise in nearly 

all the main gulches tributary to Cottonwood and Marble Canyon 

creeks. Several springs lie south of Tin Mountain. Emigrant 

Spring, to the south of the area mapped, flows 1,100 gallons of water 

per day.

GENERAL GEOLOGY.

The formations of the Panamint Range, from the oldest to the 

youngest, are as follows: Prospect Mountain quartzite (?), Pogonip 

limestone, Pennsjdvanian limestone, earlier quartz-monzonite porphyry, post-Jurassic granitoid rocks (quartz monzonite, soda syenite, 

and granite), later quartz-monzonite porphyry, older alluvium, basalt, 

and Recent alluvium.

SEDIMENTARY EOCKS.

Prospect Mountain quartzite (?). Tucki Mountain is formed of 

metamorphosed sediments identified with the supposed Prospect 

Mountain quartzite of the Amargosa Range. (See p. 162.)

Pogonip limestone. The most widely distributed formation of the 

Panamint Range is the Pogonip limestone, of which at least 3,000 feet 

is exposed. The limestone, which is compact and fine grained, ranges
PANAMINT RANGE, SEDIMENTARY BOCKS. 203

in color from dark gray to black. The dark color is, at least in part, 

due to carbonaceous matter, since some beds are fetid, and when 

heated exude a tarry substance. The bedding is, as a rule, massive, 

although some slightly argillaceous facies are thin bedded. Crossbedding was noted in several places. Near the top of the section 

occur layers and lenses of black, semitranslucent flint from one-half 

inch to 3 inches thick, separated by bands of limestone from 1 to 18 

inches thick. In other beds globular and ellipsoidal flint concretions 

from one-fourth inch, to 3 inches in diameter are abundant. A quartzite layer interbedded with the limestone occurs rather well up in the 

formation. The rugged exposures of this white or pinkish-white finegrained quartzite outcrop on the western side of the play a 4 miles 

north of Goldbelt Spring: The bed of quartzite is 100 feet thick and 

has thin bands of limestone interbedded near its base, and especially 

near its top. Four miles south of Tin Mountain Mr. T. C. Spaulding 

noted interbedded in the limestone a 30-foot band of muscovite schist. 

The schist is less metamorphosed than that of Tucki Mountain.

At one locality the writer collected fragmentary fossils which Mr. 

E. 0. Ulrich states include a shell belonging either to Maclurea or 

some related genus and a fragment of a pelecypod. These indicate 

undoubtedly Ordovician and probably Stones River age. Near the 

playa to the north of Goldbelt Spring Messrs. Chapman and Spaulding collected fossils of which the gasteropods, Mr. Ulrich states, 

remind one of Baltic Ordovician species and indicate a lower Ordovician horizon. The fossils include a very large Helicotoma-l\kQ 

shell; Eccyliopterus sp. unclet., of large size and with contiguous 

.whorls; Receptaculites sp. nov., obconical, with thick walls and small, 

crowded stolons. Not only in its organic remains, but also in its 

lithologic-character, this limestone resembles the Pogonip limestone 

present in many of the ranges in the area surveyed. It .was deposited 

in water of shallow or medium depth, a conclusion .indicated by the 

presence here and there of cross-bedding and abundant organic remains. With the accumulation of the limy sediments the sea bottom 

must have been depressed step by step, an inference drawn from the 

great uniformity and thickness of the limestone.

Pennsylvanian limestone. The Pennsylvanian limestone forms a 

narrow band along the east front of the Panamint Range. It is 

separated from the Pogonip limestone to the west by a fault of several 

thousand feet displacement. This limestone, of which probably some 

1,500 feet is exposed, is fine grained and gray or dark gray in color. 

Some of the darker limestone when struck with a hammer gives off a 

fetid odor. Lenses and ellipsoid masses of black flint occur in some 

beds. To the west of the soda-syenite area is a bed 75 feet thick of 

white, fine-grained quartzose sandstone. This sandstone, as well as 

some beds of limestone, is cross-bedded.
204 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

From one locality the following Pennsylvanian fossils, determined 

by Dr. George H. Girty, were collected:

Fusulina sp. Small indeterminable gasteropod. 

Crinoidal fragments. Indeterminable fragments. 

Fenestella sp.

Fragmentary fossils were collected from two other localities, and 

concerning these Doctor Girty states that while they are undoubtedly 

Carboniferous, they indicate nothing further.

Older alluvium. On either side of Emigrant Wash and at the 

north end of the Panamint Range are a number of areas of the older 

alluvium. The deposit east of Emigrant Wash forms intensely dissected hills which are continuations of the ridges of Tucki Mountain. 

The two large areas across the valley to the northwest are eastwardsloping plains cut by erosion into low hills, and each is separated from 

Death Valley by a low ridge of Paleozoic limestone. A few small 

outliers occur higher up in the mountains at a maximum altitude of 

5,000 feet.

These deposits are composed of beds of angular bowlders and wellstratified sand. These are locally so well cemented by calcium carbonate that caves 25 feet high exist in them. Around Emigrant Spring, 

in the southern extension of the area west of Tucki Mountain and in 

the area at the north end of the Panamint Range, Avhite and pink clay 

similar to that of the present playa deposits is interbedded with the 

boAvlder beds. At the north end of the range the series has an exposed 

thickness of 2,500 feet.

Recent desert gravels unconformably overlie the older alluvium, 

which in turn lies upon the eroded surface of the quartz-monzonite 

and Paleozoic rocks. The upper portion of the series and the basalt 

are contemporaneous, and in consequence the older alluvium is probably of Pliocene and early Pleistocene age. In Pliocene-Pleistocene 

time, when Death Valley was occupied by an extensive playa, the 

Panamint Range was comparatively low and insignificant. The older 

alluvium areas are the remnants of alluvial slopes which once fringed 

its borders. These alluvial slopes near Goldbelt Spring reached an 

elevation of 5,000 feet, while to the north of Tin Mountain no remnants remain above 4,000 feet. Considerable portions of the Tin and 

Tucki mountain deposits are formed of playa clays, showing that 

during periods of exceptional rainfall the playa of Death Valley extended well up on the Panamint Range.

Recent alluvium. The valley above the head of Cottonwood Creek 

is covered with coarse soil and loam. A more resistant portion, of the 

quartz monzonite has narrowed and partially dammed the valley, and 

behind this barrier the material washed from the surrounding hills 

has accumulated. Four miles north of Goldbelt Spring is a basin 

whose bottom in depressed 275 feet below the inclosing rim of hills.
PANAMINT RANGE,, IGNEOUS ROCKS. 205

The basin is in Pogonip limestone and is probably the site of an 

ancient sink hole formed when the climate was less arid. Later the 

channel became obstructed by the inwash of debris from the surrounding hills, and eventually alluvial slopes and a playa were formed.

IGNEOUS ROCKS.

Earlier guartz-monzonite porphyry. A few small fragments of a 

fine-grained, medium-gray igneous rock are included in the quartz 

monzonite in the southwest corner of the area mapped. Similar 

inclusions in the granite of Gold Mountain prove, on microscopic 

examination, to be quartz-monzonite porphyry.

Quartz monzonite. A batholith of quartz monzonite underlies 75 

square miles in the southwest corner of the area surveyed. The rock 

is light to medium gray in color, rarely pinkish gray. The minerals 

visible to the unaided eye are predominant gray feldspar, a greenishblack mineral, either amphibole or pyroxene, bronze-brown biotite, 

and pink feldspar, while small individuals of magnetite and sealbrown titanite are also visible in places. As a whole biotite is almost 

as abundant as hornblende, but it appears to be totally lacking over 

restricted masses. The diameter of the component minerals varies 

throughout the mass from one-fourth to one thirty-second of an inch. 

In many places the gray feldspars occur as well-developed tablets up 

to three-fourths of an inch in length and impart to the rock a por.phyritic aspect. Green epidote in granules replaces the hornblende and 

biotite more or less completely, while veins of epidote cut the rock, and 

felts of this mineral are common on joint surfaces. Calcite veins are 

less common. The monzonite is cut by joint planes from 1 foot to 5 

feet apart. In weathering the joint blocks become slightly rounded 

and finally disintegrate into soil. The monzonite forms rugged 

ridges. The outcrops are usually low bosses or bowlderlike masses, 

and many of the hills have the appearance of moraines, upon which 

large bowlders are prominent.

Under the microscope the rock shows an allotriomorphic granular 

texture, although some of the smaller plagioclase individuals form 

laths. The essential constituents, in order of abundance, are plagioclase, orthoclase, piotite, quartz, hornblende, and ugite. The accessory 

minerals are apatite, magnetite, and titanite. Disks of micropegmatite lie between the other constituents and are inclosed in the feldspars. Some hornblende is secondary to augite, while kaolin, sericite, 

and epidote form at the expense of the feldspars. .The rock is on the 

border line between quartz monzonite and granodiorite.

The monzonite is cut by thin dikes of a fine-grained pink aplite 

composed of feldspar and some hornblende. Quartz is sometimes 

seen in the rock, which then appears to be of granitic composition. 

The dikes are usually simple. Under the microscope this rock shows
206 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

the composition of an acidic quartz monzonite, containing a little 

biotite altered to chlorite. The accessory minerals are the same as 

those of the quartz monzonite. Some of the aplite is blotched by 

globular aggregates of coarser hornblende from 1 inch to 4 inches in 

diameter. These aggregates are formed by the segregation of hornblende from the surrounding ro'ck and are rimmed by halos of almost 

pure feldspar in individuals from one-half to 1 inch Avide. The 

aplite is probably but a later differentiation product of the monzonitic 

magma.

Scattered throughout the monzonite are segregations of hornblende 

from 2 to 3 inches in diameter. These represent a threefold enrichment in hornblende by magmatic differentiation.

The monzonite is cut by and grades into thin dikes of coarser 

grained rock, localty having the same composition as the monzonite, 

but usually of more acidic constitution. The individuals of these 

pegmatite dikes reach a maximum diameter of 2 inches. Some of 

the dikes have basic borders composed of almost pure hornblende, 

with a median band of feldspar. While the boundary planes are 

rather distinct, individual crystals extend from the monzonite into 

the basic bands and from these into the acidic center. The more 

acidic portion of this pegmatite shows under the microscope the 

composition of a soda syenite, containing orthoclase, anorthoclase, 

augite, hornblende, biotite, quartz, titanite, magnetite, apatite, and 

zircon. The augite probably contains a little of the aegirite molecule. 

Other forms of the pegmatite are composed of quartz, pinkish-gray 

feldspar, and hornblende, named in the order of abundance and the 

reverse order of solidification. Some limonite pseudomorphs after 

pyrite occur in the pegmatite, but the original character of the 

P3^rite was not determined beyond doubt. In other pegmatites partial crystals of ferromagnesian minerals are inclosed in a coarse 

crystalline aggregate .of feldspar. Microscopic examination showed 

that orthoclase and microperthite are so predominant over plagioclase in this rock that it has the composition and texture of a syenite 

porphyry. The ferromagnesian minerals include augite, olivine, 

broAvn hornblende, and biotite. Apatite occurs in unusually large 

crystals and magnetite in grains. Miarolitic openings occur in this 

pegmatite and crystals of the constituent minerals protrude into 

them. The pegmatite therefore consolidated under less pressure 

than the monzonite, which lacks such cavities, or its composition Avas 

more favorable to their production. The pegmatite is evidently 

but a late intrusion of the monzonite-magma residuum. Not only 

is the pegmatite more acidic than the quartz monzonite, but it has 

undergone an enrichment in soda, linking the quartz monzonite to the 

soda syenite next to be described.

The batholith sends thin dikes into the Pogonip limestone. At the
PANAMINT BANGE, IGNEOUS ROCKS. 207

contact the limestone' is considerably disturbed and dips sharply, 

usually away from the monzonite mass. The small limestone area 

inclosed by monzonite on the southern border of the area appears to 

have been buoyed up on the surface of the molten rock. Smaller 

inclusions are common. An aureole of limestone from one-fourth 

to 1 mile wide is metamorphosed to a rather coarse-grained gray marble. In this marble are bands, lenses, and irregular bodies of white 

marble. Large brown garnets, epidote, serpentine, and tremolite are 

present in the metamorphosed limestone. The two latter minerals 

occur in veins as well as in sporadic masses through the limestone.

The quartz monzonite intrudes Pogonip limestone and is cut by 

pre-Tertiary diorite porphyry. It is presumably contemporaneous 

with the post-Jurassic granite, since intermediate facies between it 

and the granite, described on page 208, appear to exist. It is rather 

similar in mineralogic composition to the post-Jurassic granodiorites 

of the Sierra Nevada.

Soda syenite. About 114* miles southeast of Tin Mountain there is 

a very irregular mass of soda syenite and soda-syenite porphyry, 300 

feet long and 200 feet wide. It intrudes the Pennsylvania!! limestone 

and sends into it many straight-walled dikes and ramifying veins of 

varying width. Prior to recent erosion the limestone appears to 

have covered the syenite. Bowlders of similar rock occur in the 

gulch due west of this area, but 'the masses from which these were 

derived were not located. Similar rock appears from a distance to 

form a small area 4 miles west of Lost Wagons. The soda syenite is 

characterized by abrupt and great changes in granularity and in the 

relative abundance of the constituent minerals. The predominant 

form is a coarse- to medium-grained rock of gray color, composed of 

predominant gray with some pink feldspar, subordinate greenishblack amphibole or pyroxene, and black mica. Many of the feldspars 

have good crystal outlines and in the more porphyritic facies the 

abundant feldspar laths have a length of 1^ inches and are aligned in 

flow orientation. The rock next to the limestone is very fine grained. 

Epidote has developed at the expense of the hornblende and biotite in 

all facies. Under the miscroscope this rod?: proves to be a soda 

syenite or nordmarkite of hypidiomorphic and uneven granular texture. The predominant constituents are alkali feldspars, including 

the species orthoclase, microperthite, and anorthoclase. With these 

is a little oligoclase. The alkali feldspars form rude tabular crystals, 

many of which are twinned according to the Carlsbad law. Between 

these tabular forms are anhedra of augite, quartz, biotite, and yellowish-brown garnet. The augite verges toward segirite-augite. -The 

accessory minerals are titanite, magnetite, apatite, and fluorite. The 

fluorite flecks the alkali feldspar and may be original or introduced 

by magmatic gases.
208 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

The soda syenite is cut by dikes of compact greenish-gray aplitic 

rocks. Pink feldspar is associated with the gray feldspar and pyroxene and it alone forms some veins. The aplite under the microscope 

has a very uneven-grained allotriomorphic texture. The feldspars 

include microperthite, orthoclase, and some anorthoclase. A little 

quartz is also present. While the rock is not rich in ferromagnesian 

minerals, there are many small grains and partial crystals of eegiriteaugite. This mineral shows the usual zonal structure, with deeper 

green bands on the border. Irregular grains of a light-yellow garnet 

are rather abundant. The accessories are titanite and apatite. 

Fluorite occurs in small blebs, surrounded by a mesh of sericite 

shreds, which were probably formed by the same gases that deposited 

the fluorite. Calcite is also present and its contacts with other minerals are so sharp that it was probably deposited in miarolitic openings. The contact between the aplite and the syenite is in some cases 

sharp, in others gradational. In one instance a dike of syenite 

porphyry is faulted by an aplitic dike, but there can be little doubt 

that the two are genetically related. Narrow pegmatitic dikes, the 

feldspar and pyroxene of which reach a diameter of 1 inch, occur.

The limestone immediately adjoining the igneous mass is metamorphosed to a coarse- or fine-grained white marble, through which 

small plates and veinlets of tremolite are scattered.

The soda syenite intrudes Pennsylvanian limestone and has suffered 

practically the same deformation as the quartz monzonite, and it may 

well be, as indicated by the monzonite-pegmatite, a later variant of 

the same magna.

Granite.* A. considerable area of biotite granite occurs to the east 

of the Emigrant Wash, 3 miles south of the area surveyed. Dikes 

of muscovite granite, genetically related to the biotite granite, were 

observed cutting the Cambrian rocks 1 mile south of Tucki Mountain, and a few probably occur in the area surveyed. This granite 

is probably of post-Jurassic age.

Later quartz-monzonite porphyry. Four miles south of Tin Mountain is an area of siliceous quartz-monzonite porphyry, probably intrusive in the Pogonip limestone. This area was not seen by the 

writer, but specimens collected by Mr. R. H. Chapman closely resemble the white quartz-monzonite porphyry of the Silver Peak Range, 

and, like it, this rock is probably genetically related to the intrusion 

of the post-Jurassic granitoid rocks. Under the microscope the 

phenocrysts of quartz, orthoclase, plagioclase, and biotite are seen 

to be embedded in the finely granular groundmass of microcline, 

plagioclase, quartz, and biotite. The accessory minerals are magnetite, titanite. and apatite.

Diorite porphyry. Dikes of diorite porphyry from 2 to 6 feet 

wide cut the quartz-monzonite batholith in the southwest corner of
PANAMINT RANGE, IGNEOUS ROCKS. 209

the area surveyed. The rock is light greenish gray in color and has 

prominent white feldspar phenocrysts from one-eighth to one-fourth 

inch in length, which are in parallel alignment through flow. The 

rock has suffered considerable epidotization. Under the microscope it 

proves to be a much-altered diorite porphjTy with a groundmass of 

plagioclase laths and a little orthoclase. Aggregates of epidote, 

zoisite, and chlorite and a smaller amount of calcite are evidently 

pseudomorphs of plagioclase and hornblende phenocrysts. This 

rock is evidently the pre-Tertiary diorite porphyry.

Basalt. Six small masses of basalt occur in the southern portion 

of the Panamint Range, and the same rock caps a considerable area 

at the north end of the range, where it occurs in several flows, each 

500 or more feet thick, interbedded with the older alluvium. The 

small basalt mass If miles south of west of the head of Cottonwood 

Creek is a north-south dike 250 feet wide. The basalt on the borders 

of this dike is vesicular and includes numerous quartz-monzonite 

fragments. The outcrop on the. Cottonwood Canyon trail threefourths of a mile above its entrance into the mountains may also be 

a dike cutting the Carboniferous limestone. The other masses are 

erosional remnants of a single flow or of contemporaneous flows. 

The prebasaltic mature- Panamint Range in consequence must have 

been cut deeply by canyons on its borders, while the old surface to the 

south and southwest of the area mapped was but little dissected when 

the basalt was extruded. The flow on the east side of Emigrant 

Wash forms a black bluff 200 feet high, which is a prominent landmark for many miles. The flow 4 miles east of the dike is 400 feet 

thick and forms a mesa.

The basalt has a dense dark-gray groundmass mottled by lightgray areas. It is more or less vesicular, the largest cavities being 2 

inclies long and usually elongated parallel to the direction of flow. 

Calcite, quartz, and zeolites, fill the vesicles more or less completely. 

The phenocrysts, which are usually subordinate to the groundmass, 

include blebs of olivine, more or less altered, and striated feldspars 

up to one-fourth inch in length, some of them showing zonal growth. 

Greenish-black augite is less commonly present. Under the microscope the basalt shows a dark, greasy groundmass, in which are 

^microlitic laths of basic plagioclase and pyroxene columns. The 

phenocrysts include laths of basic plagioclase; rounded grains of 

olivine, usually fresh, although in places altered to iron-stained serpentine, and columns of grayish pyroxene, much of it twinned. The 

basalt is usually well jointed and weathers into 'spheroidal masses.

The basalt east of Emigrant Wash and the flow on the Cottonwood 

Canyon trail lie unconformably below the older alluvium. The 

Bull. 308 07 M 14
210 . SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

flows at the north end of the range and others near Emigrant Spring 

are interbedded with the same formation. The deposition of the 

upper-part .of the older alluvium and the effusion of the basalt were 

therefore contemporaneous, although the latter process continued 

after the former had ceased. The basalt is probably of the late Pliocene and early Pleistocene age.

STRUCTURE.

The structural history of the Panamint Range has doubtless been 

as complex as that of the Amargosa Range, but the absence of 

Miocene formations removes the means by which the pre-Tertiary 

and middle Tertiary folding can be differentiated. It is, however, 

evident that the Paleozoic rocks were folded prior to the intrusion 

of the post-Jurassic igneous rocks.

Tucki Mountain appears to be the northward-pitching end of a 

north-south canoe, the western side of which is buried beneath 

Emigrant Wash or has been faulted off. The Cambrian rocks show 

well the differential folding suffered by-a heterogeneous rock series. 

The schist is typically closely folded and even crenulated; the 

limestone bands are less strongly folded while the folds of the 

quartzite are open. The lithologic character of the series renders 

the detection of the many faults difficult. The folding of the Pogonip and Pennsylvanian limestones is complex, although in its minor 

details less intense than that of the Amargosa Range, since overturned folds and isoclinals are unusual. The major fold is an anticline, the axis of which is situated near the western border of the 

area and trends a little west of north. The eastern arm of the fold 

is long and dips gently eastward. Superimposed upon it are many 

minor parallel folds, while cross folds with east-west axes cross it. 

This fold appears to die out a short distance south of Tin Mountain 

and here the strata are approximately horizontal. The earlier folding was apparently accompanied by reverse strike faulting. The 

intrusion of the quartz monzonite in the southwest corner of the 

area mapped considerably disturbed the limestones in its immediate 

vicinity. They are buckled and dip steeply, usually away from the 

batholith. Faulting has occured at the contact, as well as in the 

quartz-monzonite mass itself.

The fault between the Pogonip and Pennsylvanian limestones is 

presumably a normal fault and is certainly of several thousand feet 

displacement. Its position is only approximately shown on the 

map. Small normal faults of northwesterly strike are common in 

the Pennsylvanian limestone near Death Valley, and these were 

probably formed when the valley originated. Similar faults with 

2 to 4 feet displacement occur in the older alluvium, and this formation has been uplifted and tilted toward Death Valley in places as 

much as 15°.
PANAMINT EANGE. 211 

ECONOMIC GEOLOGY.

No mining camp exists in the portion of the Panamint Range included in the area under consideration. Harrisburg lies near the 

Emigrant Spring-Ballarat road, about 6 miles south of the boundary. 

Assays reported by prospectors indicate that gold-bearing copper ores 

occur in the quartz monzonite and silver-bearing galena ores in the 

limestone areas. . ^

Goldbelt, a deserted camp, is situated at the Goldbelt Spring, near 

the contact of the Pogonip limestone, here marmorized, and the quartz 

monzonite. A number of men are said to have rushed to this camp 

in the spring of 1905, but little work was done. The more important 

development work was on certain thin veins or lenses in the quartz 

niQiizonite. The 'ore contains a little chalcopyrite, probably a portion 

of the original sulphide unaltered. Of later origin are malachite, 

chrysocolla, and a dark-brown or black, iron-stained, flinty chalcedony, of approximately contemporaneous age. These minerals are 

coated with small quartz crystals. This ore is said to have panned 

free gold. Similar ore is reported from other localities in this monzonite area. A specimen from a vein near the source of Cottonwood 

Creek consists of dark limonite-stained jasperoid and chrysocolla, in 

which occur radial crystals of bottle-green brocharftite. This also is 

reported to pan gold. In the soda-syenite mass 6| miles southeast of 

Tin Mountain thin veins of limonite, presumably after iron sulphide, 

occur.

The areas most favorable to prospecting for precious metals are 

the Cambrian rocks of Tucki Mountain and the Pogonip limestone 

in the vicinity of the quartz-monzonite mass. Quartz veins, usually 

of lenslike form, are common on Tucki Mountain. They reach an observed maximum width of 3 feet and usually appear barren, although 

in some instances they have been crushed and are heavily stained by 

limonite and hematite. It is said that an old lead mine was at one time 

'worked on this mountain, and several promising camps in the Amargosa Range are situated on similar veins in the same rocks. Veins 

of two ages in the Pogonip limestone are formed of barren-looking 

calcite. Some occupy overthrust fault fissures, and these are faulted 

by other veins. The older veins are composed of massive crystalline 

calcite; the younger are often beautifully crustified. On the Cottonwood Canyon trail magnificent calcite veins 4 feet wide occupy fault 

fissures. The crustified calcite curves around included fragments 

of limestone in concentric bands. Near the quartz-monzonite masses 

a few small quartz veins occur and some of these contain pyrite. In 

other portions of the area surveyed ore-bearing veins have been found 

in limestone near granite contacts, and by analogy they probably 

also exist near the related monzonite. At a number of places in the
212 SOUTHWESTERN NEVADA AND EASTERN CALIFORNIA.

limestone the rock is heavily stained by hematite and limonite. In 

some cases at least these appear to be gossan deposits and the determination of the underlying sulphides might prove profitable.'

The older alluvium is contemporaneous with rocks of Death Valley in which some borax minerals have been found. With the possible exception, however, of the area north of Tin Mountain and one 

up Emigrant Wash beyond the boundary, the Panamint Range is 

not worth prospecting for borax.
INDEX.

A - Page. 

Acknowledgments to those aiding.......... 13-14

Adams, John, discoveries by............. 110

Alaskite, definition of.................... 37

occurrence and character of....... 58,178-179

Alkali Spring, description of............. 19-20,89

rocks near..................... 57-59,02-63,96

water of, analysis of.................... 19

Alkali Spring Flat, description of............ 76-77

Alluvium, occurrence and character of..... 52,

78,166-107,178,190,204-205 

Ainargosa Desert, depth to water in....... 159

description of......................... 158-160

geology of......................... 36,158-160

section across, figure showing.......... 21

sections in............................. 159,160

Amargosa mine, rocks in................... 35

Amargosa Mountain system, descriptive

geology of................... 160 195

Amargosa Range, economic geology of... 173-176 

geologic history of...................... 200

geology of.. 27-29,31-34,41,106,162-172,199-200 

prospecting in........................ 175-176

structure of........................... 172-179

topography of........................ 160-162

Amargosa River, description of............ 18

springs in............................... 157

Amboccelia sp., occurrence of............... 122

Ammonia tanks, rocks near................ 136

water in................................ 131

Andesito,°definition of...................... 37

occurrence and character of............ 32,

01,72,73,94-95,96,125,135-136,167-168,179-180 

Animals, abundancy of..................... 23

Antelope Spring, description of............ 89

rocks near........................ 90-91,93-94

water from............................. 138

Aplite, definition of......................... 37

Archgeocidras sp., occurrence of............ 122

Area of district......... v ................... 14

Ash Meadows, section in................... 100

springs at...'........................... 20

wells in................................. 159

section of........................... 159

Aviculipecten sp., occurrence of............. 122

B.

Bare Mountain, economic geology of.. 45,156-157 

geology of............................ 154-156

section of............................... 154

structure of............................. 156

topography of........................ 153-154

Basalt, definition of........................ 37

occurrence and character of......... 32,33,62,

68, 74,75-76,79-80,87,95,96-97,98-99, 

105-107, 116,127,146-147,151-152,153 

156, 170-171, 181, 186-187,194,209-210

Page. 

Basalt, topography due to, view of......... 36

Beatty description of...................... 25

Bell, T J., discoveries by................... 81

Belted Peak, altitude of.................... 118

section through, figure showing........ 126

Belted Range, economic geology of....... 128-131

geojogy of.. 28-29,30,32,42,105,107,115,119-127 

location of............................... 118

section across........................... 122

figures showing............... 119,120,127

structure of............................. 128

topography of........................ 118-119

Benedict, S. G., work of................... 13,141

Bibliography of region..................... 15-16

Big Dune, rocks near....................... 175

Billingsella, occurrence of.................. 149

Bismuth mine, ore.deposits of.............. 175

Blakes Camp, ore deposits at.............. 49,110

rocks near............................ 106,107

Borax, occurrence of................. 197,201,212

Boundary Canyon, fossils from............ 165

rocks in................................. 167

Breen Creek, description of................ 18-19

ore deposits on......................... 109

Bullfrog, description of..................... 25

rocks at and near...................... 35,178

Bullfrog-George prospect ore deposits of. 194-195 

Bullfrog Hills, economic geology ol......... 182

geology of...... 27-29,32,33,41,105,106,176-181

structure of............................. 181

topography of.......................... 176

Butler, J. L., discoveries by................ 81

Cactus and Kawich ranges, hills between,

geology of...................... 90-97

topography of.......................... 96

Cactus Flat, description of..:.............. 98

Cactus Mining Company, property of.....". 95

.Cactus Range, economic geology of......... 95-90

geology of.... 2*9-33,42,47-48,89-94,104,105,106

structure of............................. 84-85

topography of.......................... 89

Cactus Spring, description of............... 89

Ore deposits at.......................... 46

rocks near......................... 92-93,95,96

Calico Hills, rocks in.................. 48,140 147

Cambrian rocks, deposition of.............. 39-40

occurrence and character of... 28,51-52,56-57, 

59,66,72,77-78,84,141,164,183-184,191-192 

ores in.................................. 81,82

structure of............................. 54,

62-63,68-69,80-81,87-88,149,187,194 

Campbell, M. R., on Death Valley.......... 196

work of................................. 15

Cane Spring, flow of... '. .................... 142

213
214 INDEX.

Page. 

Cane Spring, rocks near.............. 143-146,149

Captain Jack Spring, flow of................ 119

Carboniferous rocks, occurrence and character of............'......./.... 30

Cave Rock Spring, rocks near............. 164-165

Central mine, description of................ 188

Chapman, R. H., work of.................. 13,58

Chief Kawich mine, description of........ 112-113

Childers, E. A., work of.................... 13

Chloride Cliff, ore deposits at....... 45,46,173-175

rocks near............................ 161,162

springs near............................ 162

Chonetes permianus, occurrence of......... 122

sp., occurrence of....................... 122

Cladopora, occurrence of................... 165

Cliff Spring, rocks near..................... 126

water from........................... 113,119

Climate, description of...'.................. 17

Colemanite, occurrence of................ 197,201

Columnar section of rocks of area......... 27

Combination Mines Company, water supply of................. ................... 19

Contact veins, ore deposits in........ 46,49,81-82

Copper, occurrence of....................... 130

Corral Spring, flow of...................... 100

Cottonwood Creek, description of.......... 19

rocks on.............................. 209,211

Court, J. G., discoveries by................. 81

Cow Creek, water of........................ 197

Crinoids, occurrence of..................... 204

Crystal Spring, flow of..................... " 176

4 rocks near.............................. 182

Culture, description of...................... 24-26

Cuprite district, ore deposits in......... 46,69-71

Currie Well, rocks near............... 171,176,182

D. 

Dacite, definition of ........................ 37

occurrence and character of............. 32,

34,61-62,73,106-107,181 

Daggett, rocks near........................ 33

Daylight Spring, flow of.................... 162

rocks near................. 165-168,171,172,176

Death Valley, depth to water In............ 21

economic geology of.................... 201

elevation of............................ 16,196

formation of............................ 41

geologic history of............ ; ....... 200-201

geology of...................... 32, 36,197-200

section of............................... 199

figure showing...................... 198

soil from, analysis of................... 197

topography of........................ 195-197

view in................................. 36

Decillion claim, description of............ 150-157

Derbya sp., occurrence of.................. 122

Devonian rocks, occurrence of.............. 294

Devonian time, history in.................. 39

Dikes, occurrence and character of......... 31,

33,52-54,58-59 

Diorite, definition of........................ 37

occurrence and character of......... 31,53-54

Diorite porphyry, definition of............. 37

occurrence and character of... 53-54,60-61,67,

91,103,156,167,179,186,193,208-209

Drainage, description of.............. 16,17,18-19

^ E: Page. 

Eccyliopterus sp., occurrence of.......... 155,203

Echo Canyon, mines of..................... 175

Economic conditions, description of........ 43-44

Economic geology, description of.......... 42-50,

54-55,63-65,69-71,76,81-83,88-89 

Eden, ore deposits at.................. 46,110-111

Electricity, use of.......................... 43-44

Emigrant Spring, flow of................... 202

rocks near.............................. 204

Emigrant Wash, rocks near.............. 204,209

Emmons, W. H.. work of.............. 15,71,181

Erosion, history of...................... 40,41-42

Eureka district, Nev., rocks of............. 28-29

Eureka quartzite, occurrence and character

of........ 29,90,96,100-102,155,177-178

F.

Fault zones, ore deposits in................ 49

Faulting, occurrence of..................... 39-42

Fenestella sp., occurrence of.............. 122,204

Florida-Goldfield Mining Company, property of.... ...................... 64

Fortymile Canyon, rocks near.............. 133

Funeral Mountains, location of............. 160

rocks of................................. 116

Furnace Creek, rocks on.................... 160

soil near, analysis of.................... 197

Fusulina sp., occurrence of............... 122,204

G. 

Gabhard, John, discovery by............... 138

Ganey, G. H., work of...'........... 15,71,177,181

General Thomas Camp, rocks at........... 51-55

General Thomas mine, ores of........... 46,54-55

Geography. See Topography.

Geologic history, account of................ 38-42

Geologic map of altered Tertiary rocks..... 43

of southwestern Missouri and eastern

California....................... 26

Geology, description of..................... 26-42

Geology, economic, account of............. 42-50,

54-55, 63-65, 69-71, 76, 81-83, 88-89, 

94-95, 108-113, 117, 128-131, 137-140, 

142, 147, 150, 152, 156-157, 173-176, 

182, 187-191, 194-195, 201, 211-212 

Geology, descriptive, by districts, account

.......................... 50-212

Georges Water, ocation of................. 19

Gila mine, description of................... 117

Gilbert, G. K., fossils determined by....... 165

reconnaissance by % ..................... 15

Girty, G. H., fossils determined by... 115,122.204 

Girvanella, occurrence of............... 57,66,120

Gold Bar mine, rocks near................. 178

Gold Center, location of.................... 25

water near.............................. 131

rocks near.................:............ 178

Gold Crater, ore deposits at....... 46,113,139-140

rocks at................................ 135

Gold Crest Mining Company, property of. 189-190 

Gold Flat, description of................... 98-99

Gold Mountain, economic geology of..... 187-191

geology of................... 28,30-32,183-187

structure of............................. 187

topography of........................ 182-183

Gold Mountain mining district, development in......................... 187
INDEX. 215

Gold Reed Mining Company, property of. 111-112 

Goldbelt, ore deposits at.................. 44,211

Goldbelt Spring, recks near.............. 203,204

Goldfleld, ancient lake near................. 41

description of........................... 25

region near, descriptive geology, of..... 50-89

wells at................................. 72

Goldfleld hills, economic geology of........ 76

geology of................. 28,32-34,72-76,107

structure of............................. 76

topography of.......................... 71-72

Goldfield-Mid way-Bullfrog Mining Company, properties of............. 69

Gossan, occurrence of...................... 49

Granite, definition of....................... 37

occurrence and character of........... 30-31,

52-53, 58-59, 73, 78, 98, 103, 123,

125, 133-135, 184-186, 192-193, 208

ore deposits in................. 44,84-85,90-91

veins in, figure showing................ 138

Granite porphyry, definition of............ 37

occurrence and character of........... 58-59,

84-85,90-91,124-125,167 

Grapevine Canyon, rocks in and near... . 171,176

Grapevine Range, location of............... 160

rocks of............................... 103,199

Grapevine Springs., description of.......... 20

rocks near........................ 164,165,199

Gravels, occurrence and character of.... 35-36,133

Great Basin, location and character of..... 16

Ground water, leyel of...................... 21-22

level of, section showing................ 21

H.

Hague, Arnold, on Eureka district... 28-30,38-39 

Halfway Station, section near, figure showing............................... 68

Hamburg limestone and shale, nonoccurrence of......................... 28

Hanks, A. A., analysis by.................. 19

Happy Hooligan mine, ore deposits in.... 49,173

rocks at................................ 170

Harrisburg, ore deposits at................ 211

Heenan water, flow of...................... 100

Helicoma, occurrence of..................... 203

Hicks Hot Springs, description of.......... 20

Hillebrand,.\V. F., mineral determined by.. 191 

History, geologic, account of............... 38-42

Hole in the Rock, rocks near............... 107

water of................................ 162

Horn Silver mine, rocks near............... 147

Hot Springs, description of................. 19-20

Howell ranch, rocks near................. 180,182

Humboldt series, correlation of............ 34

Hydrology, account of..................... 18-23

Hyolithes americanus, occurrence of....... 66

I.

Igneous rocks, definitions of................ 37-38

intrusion of............................. 40-41

figure showing...................... 27

occurrence and character of........... 30-34,

52-54, 58-62, 67-68, 73-76, 78-80, 

84-87, 90-94, 96-98, 103-108, 116- 

117,123-127,133-137,141,144-147, 

149,151-152,153,155-156,167-171, 

178-181,. 184-187,192-194, 206-210

Page. 

Indian Pass, rocks at....................... 161

Indian ranch, rocks near................... 178

Indian Spring, flow of............'........ 119,176

rocks near.............................. 181

Industries, character of.................... 24-25

Iron ores, character and distribution of.... 82

J.

Jackson, Mount, economic geology of...... 69-71

geology of........................ 28,31,66-68

section across, figure showing.......... 68

structure of............................. 68-69

section showing.................... 68

topography of.......................... 66

Jarboe Spring, flow of...................... 100

Johnnie mine, character of................. 150

Kankakee Mining Company, property of... 82 

Kawich, character of...................... 25

ore deposits at..................... 46,111-113

rocks near.:...................... 102-104,108

section near, figure showing............ 108

Kawich and Cactus ranges, hills between. 

See Cactus and Kawich ranges. 

Kawich Peak, elevation of.................. 16

Kawich Range, economic geology of...... 108-113

geology of............................... 29,

32,33,41,42,50,100-107,116 

prospecting on.......................... 113

section across, figure showing.......... 108

structure of............................. 108

timber on............................... 100

topography of...................... 16,99-100

Kawich Valley, rocks in.................. 108,114

Keane Spring, flow of....................... 162

rocks near............................ 164-165

water from............................. 174

Keane Wonder mine, ore deposits of....... 174

King, Clarence, on geology of region.... 38,39-40

Kismet Mining Company, property of...... 157

Klondike well, description of............... 77,82

Knowlton, F. H., fossils determined by... 58,132

L. 

Latite, definition of........................ 37

occurrence and character of............ 32,

34,73-74,79,80,91-92,105,151,170-171 

Leda sp., occurrence of..................... 122

Lee's Camp, ore deposits of................. 175

rocks near.............................. 162

Lida, character of..'....-.................... 25

ore deposits at....................... 45,64-65

rocks near........................ 31,57,60.62

Lida-Goldfield Valley, description of....... 65

Lige Harris prospect, description of........ 157

Lime, occurrence and character of.......... 65

Lime Point, ore deposits at................ 44

Limestone, ore deposits in............... 4-1-46,81

Literature, list of........................... 15-16

Little Mill Creek, description of............ 99

ore deposits on......................... 110

Location of district, map showing......... 14"

Lone Mountain foothills, economic geology

Of............................... 54-55

geology of........................ 28,31,51-54

ore deposits on......................... 46

structure of............................. 54
216 INDEX.

Page. 

Lone Mountain foothills,topography of.... 51

Lone Mountain limestone, occurrence and

character of............ 29,102,165,178

Longstreets Ranch Spring, flow of......... 100

Lost Wagons, rocks near................... 207

M.

McDonald Spring, rocks near............... 176

Map, geologic, of altered Tertiary rocks.... 43

of southwestern ^Nevada and eastern

California....................... 26

accuracy of......................... 13

Map, index, showing area described........ 14

Map, topographic, description of........... 14

Marble Canyon, description of............ 201-202

view of.................................. 200

Marglnifera sp., occurrence of.............. 122

Mesquite Flat, location of.................. 196

Mesquite Spring, water of ................. ' 197

Metamorphic rocks, occurrence and character of........................... 132

Mexican Camp, rocks near................ 167,176

Mica schists, occurrence and character of... 132 

Mining, development of.................... 42

Mohave Desert, rocks of.................... 33

Monitor Hills, geology of............. 33,34,97-98

structure of............................. 98

Monte Cristo Springs, rocks near........... 142

water of................................ 141

Montezunia district, ore deposits of.. 45,40,63-64 

Montezuma Peak, rocks of ........... 55-58,61-65

Monzonite, definition of...........1....'.... 37-38

limestone near, view of................. 200

occurrence and description of........... 32,

123,133,205-207 

Monzonite porphyry, definition of.......... 38

occurrence and character of............ 58-60,

85,103-104,144-145,184,193,205,208

ore deposits in.......................... 46

Mud Spring, flow of......................... 176

N.

New Reveille, location of................... 117

ore deposits and rocks at............. 315,117'

0. 

Oak Spring, flow of....................... 119,130

ore deposits at.................. 44,45,128-130

rocks near.................... 122,123,125,128

section at............................... 122

Oak Spring Butte, rocks of............... 118,127

section through, figure showing........ 127

Oasis Valley, rocks in...................... 36

O'Briens Camp. See Wellington.

Old Camp, ore deposits at............. 44,188-189

Olenellus gilberti, occurrence of............ 66

Ordovician rocks, deposition of............ 38-39

occurrence and character of............ 28-29

Ore deposits, character of.................. 44-49

Oriental Wash, ore deposits at........ 45,190-191

Orthoceras olorus.......................... 165

perroti.................................. 165

Orthoclase, description of.................. 37

Ouida claim, ore deposits of................ 189

P.

Pahute Lake, deposition in................. 41

Pahute Mesa, economic geology of........ 137-140

Page.

Pahute Mesa, geology of....... 30,32,123,131-137

ranges north of, descriptive geology of.. 89-131 

ranges southeast of, descriptive geology of........................ 142-157

structure of............................. 137

topography of.......................... 131

view of................................. 36

Palteodictyon, occurrence of°................ 121

Paleozoic sediments, ore deposits in........ 44-46

Panamint Range, economic geology of.... 211-212

geologic history of....................*.. 200

geology of............... 27,29-33,120,202-210

structure of............................. 210

topography of........................ 201-202

Pegmatite, definition of..................... 38

dikes of, ore in.......................... 44

occurrence and charactor of............ 151,

155-150,178-179 

Ponnsylvahian limestone, fossils from...... 122

occurrence and character of............ 115,

118,121-122,143,203-204 

Phillipsia sp., occurrence of...... I.!....... 122

Pillar Spring, water of..................... 131

Plagioclascj description of.................. 37

Playa deposits, occurrence and character of. 36 

Pleistocene rocks, occurrence and character

of............................... 35-36

Pogonip limestone, occurrence and character of.................... 28-29,89-90,

100-102,118-120,155,164-165,202-203 

structure of............................. 128

view of................................. 200

Point of Rocks, rocks near............... 148,149 .

Poison Spring, rocks near............ 163,167,175

Preble Mountain, rocks near............... 76

Precipitation, records of.................... 17

Productus'cora, occurrence of....."......... 122

nevadensis, occurrence of............... 122

semireticulatus, occurrence of.......... 122

sp., occurrence of....................... 122

Prospect Mountain limestone, occurrence

and description of......... 28,148-149

Prospect Mountain quartzite, correlation of 28 

occurrence and description of.......... 25-26,

38,148,162-164,202 

Prospecting, aids to........................ 49-50

Quartz Mountain, economic geology of..... 142

geology of............................ 137,141

structure of............................. 142

topography of........................... 141

Quartz Mountain Camp, rocks at.......... 142

Quartz veins, ore deposits in..... 44-45,66,81,138

ore deposits in, figure showing......... 138

Quartzite, occurrence of.................... 132

Quartzite Mountain, elevation of........... 99

rocks on.......................... 100-102,113

section of............................... 108

R. 

Railroads, access by........................ 26

Ralston Valley, description of.............. 83

Ramsay well, description of................ 77

Randsburg district, rocks of............... 33

Ransome, F. L., on Happy Hooligan mine. 170 

work of.......................... 13,15,71,181
INDEX. 217

Page 

Rattlesnake mine, rocks near..'............ 186

Recent rocks, occurrence and character of.. 33,71 

Recent time, erosion in..................... 42

Receptaculites sp., occurrence of............ 203

Relief, description of....................... 16-17

Replacement deposits, occurrence and character of.......................... 46

Reveille, ore deposits and rocks at........ 115,117

Reveille Peak, altitude of...:............... 115

rocks near............................. 116-117

Reveille Range, economic geology of........ 117

geology of............ 30,32,42,103,105,115-117'

section across, figure showing.......... 117

structure of............................. 117

topography of........................ 114-115

Reveille Valley, description of.............. 114

rocks in............................... 104,114

section across, figure showing.......... 114

Rhombopora sp., occurrence of............. 122

Rhyolite, definition of...................... 38

flow folds in, figure showing............ 68

occurrence and description of.... 25,32-33,61-

62,67-68,72,73-76,78-79,80,85-87, 

92-94,98,104-105,.107,116,125-127, 

131, 135-137,141, 145-146,150,151, 

153, 156, 168-171, 180, 186,193-194 

ore deposits in.......................... 46-49

 Roads, character of........................ 26

Rose Spring, flow of......................... 100

rocks near........................ 102,104-108

Rose's Well, rocks near.................... 152

Ruiz Well, water of....................... 197

S.

Salt Creek, description of................... 19

rocks on................................ 199

soil near................................ 196

Salt Creek Wells, water of.................. 197

Sand dunes, occurrence and character of... 36 

Sand Spring, water of....................... 183

Sarcobatus Flat, depth to water on....... 21,158

description of......................... 157-158

economic geology of.................... 158

section across, figure showing.......... 21

Schaller, Waldemar, minerals determined

by............................ 129-130

Schists, occurrence and character of........ 177

Secret Canyon shale, nonoccurrence of.-..... 28

Sedimentary rocks, columnar section showing.............................. 27

occurrence and character of............ 26,35,

«l-52, 56-58, 66-67, 72, 77-78, 84, 89-90, 

96,97,100-103,115,119-123,132-133, 141, 

143-144, 148-149, 154-155, 162-167, 177- 

178, 183-184, 191-192, 197-200, 202-205 

Seminula sp., occurrence of................. 122

Shale Peak, rocks of......................... 169

Shoshone Mountain, economic geology of... 147 

geology of......... 30,32,33,48,104,123,143-147

section on.............................. 143

structure of............................. 147

topography of........................ 142-143

Siebert lake beds, correlation of............ 33

deposition of........................... 41

occurrence and character of............ 31-33,

48,57-58,67, 72,77,78,84,98,102-103, 

122-123,132,143,165-166,178,198-199

Silent Canyon, rocks of..................... 136

Silurian rocks, occurrence and character of. 28-29 

Silver Peak quadrangle, rocks of........... 51

Silver Peak Range, northeast extension of,

economic geology of............ 63-65

northeast extension of, geology of...... 28,

31-33,48,56-62,120 

 structure of............................. 62-63

topography of.......................... 55-56

Silverbow, character of...................... 25

ore deposits at..................... 46,109-110

rocks near......................... 47,103,106

Skeleton Hills, economic geology of........ 150

geology of............................ 148-149

structure of............................. 149

topography of......................... 147-148

Skull Mountain, economic geology of....... 147

geology of.................. 32,33,104,143-147

structure of............................. 147

topography of........................ 142-143

Slate Ridge, economic geology of......... 194-195

geology of.................... 28,31,32,191-194

structure of............................. 194

topography of......................... % 191

valley near, description of.............. 71

Snow, occurrence of........................ 22

Southern Klondike, ore deposits at...... 44-46,49

Southern Klondike hills, economic geology

of............................... 81-82

geology of..................... 28,32,33,48,77

ores of, value of........................ 81

structure of............................. 80-81

topography of.......................... 77

Spaulding, T. C., on geology of region..... 9(5,102

work of................................ 13,203

Specter Range^ economic geology of........ 150

geology in..:............. 26-28,32,38,148-149

section of, figure showing............... 149

structure of............................. 149

topography of........................ 147-148

Spring Mountain Range, extension of...... 147

Springs, occurrence and description of...... 18,

19-21,56 

Spurr, J. E., on geology of region.......... 33,

34,39,57,68,82,102-103 

work of................................. 15

Stage lines, access by....................... 26

Staininger ranch, ore deposits near ........ 175

rocks at and near................. 164-165,170

section at............................... 166

springs On.............................. 19.20

Stateline Mill, rocks near................. 191,194

Stenopora carbonaria, occurrence of....... 122

sp., occurrence of....................... 122

Stewart, B. D., work of................... 13,132

Stinking Spring, flow of ............... v ... 100

rocks at................................ 105

Stonewall Flat, description of.............. 83

Stonewall Mountain, economic geology of. 40-47,

geology of.......... 28,32,33,48,84-87,104,136

section across........................... 133

figure showing...................... 88

structure of............................. 87-88

topography of.......................... 83-84

Stonewall Spring, section through, figure

showing......................... 88
218 INDEX.

Page. 

Stonewall Spring, water from.............. 71

Stovepipe Wells, section near.............. 199

water of................................ 197

Stratigraphy, columnar section showing.... 27

description of........................... 2&-3S

Streams, description of..................... 18-19

Structure. See particular districts.

Sulphur, occurrence and character of....... 71

Sumner Spring, flow of......-................ 100

rocks near........................ 103,106,114

Surveyors Well, rocks near............... 166,199

water of................................ 197

Syenite, definition of....................... 38

occurrence and character of..... 85-86,207-208

T.

Tanks, character of......................... 21

Telescope Peak, altitude of................. 201

Temperature, records of.................... 17

Tertiary rocks, areas of, economic map

showing........................ 43

occurrence and character of............ 31-34

ore deposits in................;......... 46

Tertiary time, history in................... 40-41

Thimble Peak, rocks of..................... 161

Thirsty Canyon, rocks near.............. 136,137

Thorp, character of......................... 25

Timber, character and distribution of...... 23-24,

100,119,162,183,202 

Timber Mountain, geology of.......... 32,137,153

topography of.......................... 153

Tin Mountain, altitude of.................. 201

rocks near. ....................... 202,204,207

Tippipah Spring, flow of................... 142

rocks near................ 121,122,143,146-147

Titus Canyon, rocks of................... 164,175

Tokop, ore deposits at.................... 189-190

wells near............................... 183

Tolicha Peak, economic geology of......... 142

geology of.............. 28,32/132,135,137,141

structure of............................. 142

topography of..............:........... 141

Tonopah, description of.................... 25

Topography, description of................ 16-17

See also particular districts. 

Topopah Spring, flow of.................... 142

Towns, character of........................ 25-26

Trails, character of......................... 26

Trappman, Hermann, discoveries by....... 138

Trapprnans Camp, ore deposits at.....44,138-139

ore deposits at, figure showing. 138

rocks at and near........... 27,28,132,133-135

Travertine, occurrence and character of.... 58

Triangle Spring, rocks near................. .199

Triangle Spring, water of.................. 197

Tri-Metallic Mining Company, properties of. 69-70 

Trio mine, ore deposits of.................. 174

Tucki Mountain, ore deposits of............ 211

rocks near.............................. 204

Tuft's, occurrence and character of.......... 32,

72,132-133,192 

Turner, H. W., on climate of district....... 17

on geology of district................ 5i-52,57

work of................................. 15

Turquoise, occurrence of................. 129-130

Twin Peaks, rocks on...................... 113

U.

Ulrich, E. O., fossils determined by ....... . 57,

66,120,121,149,155,165,203 

on geology of region.................... 66

V. 

Valleys, formation of....................... 17

Vegetation, character of.................... 23-24

W.

Wahguyhe Peak, altitude of................ 161

rocks of............................... 168-169

Walcott, C. D., fossils determined by....... 57

Water, occurrence of, signs of.............. 22-23

Weber conglomerate, correlation of........ 30

occurrence and character of. 30,90,118,120-121 

Weeks, F. B., fossils determined by........ 165

Wellington, ore deposits at................. 46,95

rocks at............................... 48

Wells, occurrence and character of......... 21-22

Wheelbarrow Peak, altitude of............. 118

rocks on and near................ 119,122,125

section near, figure showing............ 119

Wheelbarrow Spring, flow of............... 119

Whiterock Spring, flow of.................. 119

rocks near................ 122,127,133-134,140

Wild Horse Spring, flow of................. 100

Willow Springs, flow of..................... 162

rocks near............................ 165-168

Wilsons Camp, ore deposits at............ 46,139

rocks at........................... 48,135-136

Yucca Mountain, economic geology of...... 152

geology of......................... 32,150-152

structure of............................. 152

topography of.. ....................... 150

Yucca Pass, rocks near................... 145-146

Zaphrentis sp., occurrence of...........

0

si