Prepared in cooperation with the Nevada Bureau of Mines and 

Geology and the University of Nevada, Las Vegas

Scientific Investigations Report 2006–5197

U.S. Department of the Interior

U.S. Geological Survey

Mineral Resource Assessment of Selected Areas in 

Clark and Nye Counties, Nevada

Edited by Steve Ludington
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reproduce any copyrighted materials contained within this report.

This report and any updates to it are available online at

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U.S. Geological Survey, Reston, Virginia: 2006

U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

Cataloging-in-publication data are on file with the Library of Congress (URL http://www.loc.gov/).

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement of the U.S. Government.

Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, August 2, 2006

Text edited by Peter H. Stauffer, and James W. Hendley II

Layout and design by Susan Mayfield

Cover photograph: View of the Newberry Mountains southeast of Searchlight, Nevada. The rugged dark peaks are 

composed of Miocene trachyandesite and trachydacite of the lower unit of the volcanics of the Highland Range.
iii

Contents

Chapter A. Introduction..............................................................................................................................A1

By Steve Ludington

Chapter B. Mineral Resource Potential of the Piute-Eldorado Tortoise, Crescent Townsite, 

and Keyhole Canyon Areas of Critical Environmental Concern, Clark County, Nevada .......B1

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, Kathryn S. Flynn, and 

James E. Faulds

Chapter C. Mineral Resource Potential of the Gold Butte A, Gold Butte B, Virgin Mountain 

(Gold Butte C), Whitney Pocket, Red Rock Spring, Devil’s Throat, and Gold Butte 

Townsite Areas of Critical Environmental Concern, Clark County, Nevada ........................C1

By Steve Ludington, Gordon B. Haxel, Stephen B. Castor, Brett T. McLaurin, 

and Kathryn S. Flynn

Chapter D. Mineral Resource Potential of the Mormon Mesa Tortoise, Arrow Canyon, and 

Coyote Springs Areas of Critical Environmental Concern, Clark County, Nevada .............D1

By Kathryn S. Flynn, Stephen B. Castor, Steve Ludington, and Brett T. McLaurin

Chapter E. Mineral Resource Potential of the Arden, Bird Spring, and Sloan Rock Art Areas of 

Critical Environmental Concern, Clark County, Nevada ............................................................ E1

By Stephen B. Castor, Brett T. McLaurin, Kathryn S. Flynn, and Steve Ludington

Chapter F. Mineral Resource Potential of the Ash Meadows and Amargosa Mesquite Trees 

Areas of Critical Environmental Concern, Nye County, Nevada ............................................F1

By Stephen B. Castor, Brett T. McLaurin, Steve Ludington, and Kathryn S. Flynn

Chapter G. Mineral Resource Potential of the virgin River Area of Critical Environmental 

Concern, Clark County, Nevada ..................................................................................................G1

By Brett T. McLaurin, Steve Ludington, Stephen B. Castor, and Kathryn S. Flynn

Chapter H. Mineral Resource Potential of the Hidden Valley Area of Critical Environmental 

Concern, Clark County, Nevada ..................................................................................................H1

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, and Kathryn S. Flynn

Chapter I. Mineral Resource Potential of the Rainbow Gardens Area of Critical Environmental 

Concern, Clark County, Nevada ....................................................................................................I1

By Stephen B. Castor, Steve Ludington, Brett T. McLaurin, and Kathryn S. Flynn

Chapter J. Mineral Resource Potential of the River Mountains Area of Critical Environmental 

concern, Clark County, Nevada .................................................................................................... J1

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, and Kathryn S. Flynn

Chapter K. Mineral Resource Potential of the Stump Spring Area of Critical Environmental 

Concern, Clark County, Nevada ..................................................................................................K1

By Kathryn S. Flynn, Steve Ludington, Brett T. McLaurin, and Stephen B. Castor

Chapter L. Mineral Resource Potential of the Big Dune Area of Critical Environmental Concern, 

Nye County, Nevada .......................................................................................................................L1

By Stephen B. Castor, Brett T. McLaurin, Steve Ludington, and Kathryn S. Flynn

Appendix 1. Definitions of Levels of Mineral Resource Potential and Certainty of Assessment .... 1–1

Appendix 2. Legal Descriptions of Areas of Critical Environmental Concern, Clark and Nye 

Counties, Nevada ........................................................................................................................ 2–1
Chapter A. Introduction

By Steve Ludington

Mining has been a part of the economy in southern 

Nevada since before Nevada became a state. Miners in the 

late 19th century found evidence that miners from New Spain 

and Mexico and perhaps Native Americans, had recovered 

gold and turquoise here for centuries. However, southern 

Nevada has not been as comprehensively studied by professional economic geologists as the northern part of the state. 

There are only a few important studies of mineral resources 

that describe the areas we assessed (Ransome, 1907; Hill, 

1916; Hewett and others, 1936; Vanderburg, 1937; Callaghan, 1939; Hewett, 1956; Longwell and others, 1965), 

and no significant studies of the mineral deposits have been 

published for the past 40 years.

During 2004—2006, the U.S. Geological Survey 

(USGS) conducted a mineral resource assessment of selected 

areas administered by the Bureau of Land Management 

(BLM) in Clark and Nye Counties, Nevada. The purpose of 

this study is to provide the BLM with information for land 

planning and management and, specifically, to determine 

mineral resource potential in accordance with regulations in 

43 CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural 

Resources Act of 2002 (Public Law 107-282) temporarily 

withdraws a group of areas designated as Areas of Critical 

Environmental Concern (ACECs) from mineral entry, pending final approval of an application for permanent withdrawal by the BLM. This study provides information about 

mineral resource potential of the ACECs.

Existing information was compiled about the ACECs, 

including geology, geophysics, geochemistry, and mineraldeposit information. Field examinations of selected areas 

and mineral occurrences were conducted to determine their 

geologic setting and mineral potential.

In February of 2004, USGS and BLM officials met in Las 

Vegas, Nevada, to determine the appropriate format of reports 

that would best meet the needs of BLM. It was determined that 

reports should be in a format similar to BLM’s own mineral 

assessment reports and should use subjective assessment methods. In addition, all the reports have been technically reviewed 

by BLM staff.

Partners

The assessment was conducted in partnership with the 

Nevada Bureau of Mines and Geology (NBMG), a part of 

Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

the University of Nevada, Reno (UNR), and the University of 

Nevada, Las Vegas (UNLV).

Dr. Stephen B. Castor of the NBMG provided expertise 

in the field of industrial mineral deposits, which account for 

the bulk of the mineral resources produced in Clark County. 

His wide experience, coupled with the results of his field and 

laboratory investigations, has made the completion of this 

study possible.

Two postdoctoral research scholars at the University of 

Nevada, Las Vegas contributed materially to this study. Dr. 

Brett T. McLaurin, supervised by Dr. Andrew D. Hanson, 

studied the composition and stratigraphy of alluvial fans to 

help constrain the timing of mineralizing events and to elucidate the geologic history of the area. This information contributed to the assessment of the ACECs for aggregate materials, 

and Dr. McLaurin conducted that part of the assessment. Dr. 

Haroldo L. Lledó, supervised by Dr. Jean S. Cline, is studying 

the interaction between magmatic and hydrothermal processes 

during the formation of the gold deposits of the Searchlight 

mining district. Although his tenure began too late to permit 

him to contribute to the writing of the reports, his insights in 

the field have contributed materially to our understanding of 

the area during the latter stages of the project.

Areas Studied

A total of 24 Areas of Critical Environmental Concern 

(ACECs) were identified by the BLM as the object of this 

study. They range in area from less than 1 km2

 to more than 

1,000 km2. The majority of these areas are not adjacent to 

or near known mineral deposits and required a minimum of 

extended study and field examination. What follows here is a 

brief description and summary of the assessment for each area. 

The locations of the study areas are shown on figure 1.

Piute-Eldorado Tortoise ACEC (Chap. B)

The Piute-Eldorado Tortoise ACEC is the largest in the 

study (about 1,330 km2) and is an area where the complex 

geology and the unusual nature of the mineral deposits are 

still not well understood. The area consists primarily of Piute 

and Eldorado Valleys, which are both relatively thinly covered 

with surficial sediments; bedrock is less than 1,000 m below 

the surface in most of the ACEC. There are two large excluded 
A2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 1. Locations of Areas of Critical Environmental Concern (ACECs; shaded in green), Clark and Nye Counties, Nevada.

Washington

County

Lincoln

County

Nye

County

Inyo

County

San Bernardino

County

Mohave

County

Clark

County

CALIFORNIA

NEVADA

ARIZONA

UT

US 95

US 95

US 93

NV 164

NV 160

Mormon Mesa Tortoise

 Arrow

Canyon

Coyote

Springs

Tortoise

Virgin

River

Virgin

Mountain Gold

Butte A Whitney

Pocket

Gold

Butte B

Hidden

Valley

Rainbow

Gardens

River

 Mountains

Sloan

Rock Art

Arden

Bird Spring Stump Spring

Amargosa

Mesquite Trees

Ash

Meadows

Keyhole

Canyon

Crescent

Townsite Piute-Eldorado

Tortoise

Red Rock

Spring Devil’s

Throat

Gold Butte

Townsite

Big

Dune

116° W 115° W 114° W

35°N

36° N

37°N

Kilometers

0 15 30 60 90 120

Las Vegas

Boulder City

Searchlight

Interstate

15

areas, one for the northern part of the Highland Range, and 

one that contains the town of Searchlight and much of the 

historic Searchlight mining district. An important question is 

whether the mineralized system at Searchlight extends beneath 

a thin veneer of surficial deposits into the surrounding PiuteEldorado Tortoise ACEC. Other gold-bearing vein deposits 

occur throughout the area, particularly in the western part of 

the ACEC in the Crescent mining district. There is potential 

for undiscovered gold deposits within the ACEC, in both the 

Searchlight and Crescent mining districts. 

Crescent Townsite ACEC (Chap. B)

The Crescent Townsite ACEC covers less than 2 km2. It 

is within the Crescent mining district, and has potential for 

undiscovered gold deposits.

Keyhole Canyon ACEC (Chap. B)

The Keyhole Canyon ACEC is small (less than 1 km2) 

and is located in the Eldorado Mountains about 55 km 
Introduction A3

southeast of Las Vegas. This ACEC contains no known 

mineral deposits.

Gold Butte ACEC (parts A and B) and Virgin 

Mountain ACEC (Chap. C)

These three ACECs are contiguous and have a combined 

area about as large as the Piute-Eldorado Tortoise ACEC. 

Gold Butte part A is about 750 km2 in area; Gold Butte part 

B is about 490 km2; and Virgin Mountain is about 145 km2. 

The northern part of the area, in Gold Butte part A, includes 

some unusual Proterozoic mineral deposits that contain substantial amounts of platinum group elements (PGE). Nearby, 

a group of beryllium-bearing pegmatites is found within the 

Virgin Mountain ACEC. In the southern part of the area, in 

both Gold Butte parts A and B, a series of copper deposits 

hosted in Paleozoic carbonate rocks are classified as Kipushi 

type and resemble much larger deposits elsewhere in the 

world. These deposits may contain important amounts of the 

strategic metals gallium and germanium. In Gold Butte part 

B, low-sulfide gold-quartz vein deposits that have not been 

previously studied thoroughly occur over a wide area. Also 

in Gold Butte part B, vermiculite was mined in the past, and 

a major mining company is evaluating these deposits for 

renewed production. These ACECs may contain undiscovered Ni-Cu-Au-PGE deposits, beryllium-bearing pegmatite 

deposits, Kipushi-type copper deposits, low-sulfide goldquartz vein deposits, and vermiculite deposits.

Red Rock Springs ACEC, Whitney Pocket ACEC, 

and Devil’s Throat ACEC (Chap. C)

These three very small ACECs (each is less than 3 km2) 

are all surrounded by Gold Butte part A. In the Devil’s Throat 

ACEC, a remarkable vertically walled sinkhole in the alluvium 

poses a natural hazard. None of the three areas contains important mineral deposits.

Gold Butte Townsite ACEC (Chap. C)

This very small area (less than 1 km2) is entirely surrounded by Gold Butte part B. It contains low-sulfide goldquartz veins similar to those found in Gold Butte part B.

Mormon Mesa Tortoise ACEC, Coyote Springs 

Tortoise ACEC, and Arrow Canyon ACEC 

(Chap. D)

These three areas are contiguous, and are located in 

the northeast part of Clark County, north of Interstate 15. 

Mormon Mesa Tortoise is about 610 km2 in area; Coyote 

Springs Tortoise is about 210 km2; and Arrow Canyon is 

about 8 km2. The three areas are underlain primarily by 

Paleozoic limestones, and limestone is the most important 

mineral commodity.

Arden ACEC (Chap. E)

The Arden ACEC, about 6 km2 in extent, is on the southern edge of Las Vegas. Silica was mined in the ACEC in the 

past and there may be undiscovered silica deposits.

Bird Spring ACEC (Chap. E)

The Bird Spring ACEC, a small area of less than one 

km2, is southwest of Las Vegas. The ACEC contains no known 

mineral deposits.

Sloan Rock Art ACEC (Chap. E)

A small area of less than 2 km2, this ACEC is within the 

North McCulloch Wilderness area, and is underlain by Miocene volcanic rocks. The ACEC contains no known mineral 

deposits.

Ash Meadows ACEC and Amargosa Mesquite 

ACEC (Chap. F)

These two areas in Nye County contain unique biological habitats that support rare fish, bird, and plant species. Ash 

Meadows ACEC is about 150 km2 in area, and Amargosa 

Mesquite ACEC is about 27 km2.Clays and zeolite minerals 

been mined there in the past, and additional deposits of this 

type may exist.

Virgin River ACEC (Chap. G)

The Virgin River ACEC is about 30 km2 in area, is 

located along the Virgin River, south of Interstate 15 in northeastern Clark County, and exposes primarily recent sedimentary deposits. Sand and gravel aggregate is the most important 

commodity found in the ACEC.

Hidden Valley ACEC (Chap. H)

The Hidden Valley ACEC is in the Muddy Mountains, 

about 40 km northeast of Las Vegas, and has an area of about 

14 km2. Small amounts of building stone were mined from 

this ACEC in the past, but undiscovered high-quality stone 

deposits are unlikely.

Rainbow Gardens ACEC (Chap. I)

Rainbow Gardens ACEC is an area of about 160 km2 and 

is located immediately east of the city of Las Vegas. A very 
A4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

large gypsum mine is adjacent to the area, and gypsum has 

been mined within the ACEC in the past. Some areas within 

the ACEC may contain undiscovered gypsum deposits.

River Mountains ACEC (Chap. J)

River Mountains ACEC is an area of about 45 km2 on the 

southeast edge of the Las Vegas urban area, near Boulder City. 

The area is underlain by Miocene volcanic rocks. In the past, 

manganese was mined adjacent to the north end of the ACEC, 

but there is little potential for undiscovered manganese deposits. There may be undiscovered perlite deposits in the ACEC.

Stump Spring ACEC (Chap. K)

Stump Spring is a small area (less than 3 km2) near the 

California border, west of Las Vegas. The ACEC contains no 

known mineral deposits.

Big Dune ACEC (Chap. L)

The sand dunes in this area of about 8 km2 in Nye County 

do not host any important mineral deposits.

Assessment Methods

At the request of the BLM, an assessment methodology 

is used in this report that relies on subjective assessment. 

Areas are assigned high, medium, and low mineral resource 

potential according to the degree of likelihood that geologic 

processes operated in an area in such a way as to permit 

accumulation of resources. The definitions of these levels 

of resource potential are given in Goudarzi (1984). A 

useful way to interpret the levels might be that most mining 

companies would be willing to risk exploration dollars in an 

area with high potential, whereas very few would be willing 

to take a risk on a low potential area, even though a deposit 

might possibly exist. An area of medium potential might 

be attractive to some optimistic investors, but not to more 

conservative ones.

For most locatable and leasable minerals, the 

designation of an area as having high potential does not 

necessarily imply that deposits that might be discovered 

there could be developed and operated successfully. When 

information is available about resource quality that might 

bear on the economic viability of deposits, it is presented 

separately from the potential designation. However, for 

some industrial commodities, most notably crushed rock and 

sand and gravel aggregate, resource quality and location are 

essential parts of the definition of a deposit. For aggregate 

deposits, and for some other industrial mineral deposits, we 

therefore took resource quality and potential exploitation 

costs into account in designation of levels of mineral 

resource potential. In most cases, we also assigned a high, 

moderate, or low level of certainty to the designations of 

mineral resource potential, using the terminology defined in 

Goudarzi (1984).

Acknowledgments

Any geologic study rests on the shoulders of those 

who have gone before. In the present study, we have been 

fortunate enough to have personal interactions with some of 

the most important experts in Clark County geology. Special 

thanks for teaching us the geology of the region go to Dr. 

Calvin Miller of Vanderbilt University, Dr. Jonathan Miller 

of San José State University, Dr. James Faulds of the Nevada 

Bureau of Mines and Geology, and L. Sue Beard, Tracey 

J. Felger, and Keith A. Howard of the U.S. Geological 

Survey. Drs. Jean S. Cline, Andrew D. Hanson, and Eugene 

I. Smith, of the University of Nevada, Las Vegas, gave 

valuable advice in the field and in the office. Joe Tingley of 

the Nevada Bureau of Mines and Geology offered his vast 

experience with Nevada mineral deposits and helped us 

collect information on active mining claims. Gary Johnson, 

information systems specialist at the Nevada Bureau of 

Mines and Geology, helped with digital cartography. Joyce 

Lum, of the Water Resources office of the U.S. Geological 

Survey in Henderson, Nevada, and Mary Hinson, Assistant 

Superintendent of Lake Mead National Recreation Area, 

provided extra administrative support. Melanie J. Hopkins, 

now of the University of Chicago, gave important support in 

the field and office in the early stages of the project.

Various parts of the reports have been reviewed and 

improved by Ted McKee, Alan Wallace, Peter Vikre, and 

Keith Howard, of the U.S. Geological Survey, by Dr. Calvin F. 

Miller of Vanderbilt University, and by Haroldo Lledó of the 

University of Nevada, Las Vegas.

References Cited

Callaghan, E., 1939, Geology of the Searchlight district, Clark 

County, Nevada: U.S. Geological Survey Bulletin 906-D, p. 

135–188.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-file Report 84-0787, 41 p.

Hewett, D.F., 1956, Geology and mineral deposits of the Ivanpah Quadrangle, California and Nevada: U.S. Geological 

Survey Professional Paper 275, 172 p.

Hewett, D.F., Callaghan, E., Moore, B.N., Nolan, T.B., Rubey, 

W.W., and Schaller, W.T., 1936, Mineral resources of the 

region around Boulder Dam: U.S. Geological Survey Bulletin 871, 197 p.
Introduction A5

Hill, J.M.,1916, Notes on some mining districts in eastern 

Nevada: U.S. Geological Survey Bulletin 648, 214 p.

Longwell, C.R., Pampeyan, E.H., Bowyer, B., and Roberts, 

R.J., 1965, Geology and mineral deposits of Clark County, 

Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 

218 p.

Ransome, F.L., 1907, Preliminary account of Goldfield, Bullfrog, and other mining districts in southern Nevada: U.S. 

Geological Survey Bulletin 303, 98 p.

Vanderburg, W.O., 1937, Reconnaissance of mining districts 

in Clark County, Nevada: U.S. Bureau of Mines Information 

Circular 6964, 81 p.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter B. Mineral Resource Potential of the Piute-Eldorado 

Tortoise, Crescent Townsite, and Keyhole Canyon Areas of 

Critical Environmental Concern, Clark County, Nevada

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, Kathryn S. Flynn, and James E. Faulds

Summary and Conclusions

The Piute-Eldorado Tortoise Area of Critical Environmental Concern (ACEC) contains areas related to the Searchlight mining district with both high and moderate potential 

for Searchlight-type gold-bearing vein deposits. Also related 

to the Searchlight mining district are areas with moderate and 

low potential for porphyry copper deposits. The ACEC also 

contains areas related to the Crescent mining district with high 

potential for gold-bearing polymetallic vein deposits and also 

additional moderate potential for detachment-fault-related 

gold deposits. A large area in the Piute-Eldorado Tortoise 

ACEC has moderate potential for perlite deposits; a very small 

area has high potential for perlite deposits. Potential for other 

deposits of locatable or leasable minerals is low.

The Piute-Eldorado Tortoise ACEC contains areas that 

have high, moderate, and low potential for crushed-stone 

aggregate deposits. It has large areas that have high potential 

for sand and gravel aggregate deposits, as well as smaller areas 

with moderate potential.

The Crescent Townsite ACEC has high mineral resource 

potential for gold-bearing polymetallic veins, and part of it 

has additional moderate potential for detachment-fault-related 

gold deposits. The ACEC has moderate potential for crushedstone aggregate deposits, and high potential for sand and 

gravel aggregate deposits.

The Keyhole Canyon ACEC has low potential for locatable or leasable mineral deposits. The ACEC contains areas 

with both high and moderate mineral resource potential for 

crushed-stone aggregate deposits. It has high potential for sand 

and gravel aggregate deposits.

All three areas will likely see continued production of 

decorative stone from private inholdings within the ACECs.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

on these lands.

The Piute-Eldorado Tortoise, Crescent Townsite, and 

Keyhole Canyon Areas of Critical Environmental Concern 

(ACECs) were studied in the field for several months to 

confirm descriptions of the geology that are published in the 

scientific literature. Reconnaissance mapping was conducted 

in the many areas that had not yet been geologically mapped at 

scales appropriate to this assessment. More than 200 samples 

were collected and analyzed (Ludington and others, 2005), 

and representatives of companies with mining and mineral 

exploration operations in and near the areas were contacted.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

This report describes three areas of critical environmental 

concern (ACECs), the Piute-Eldorado Tortoise, the Crescent Townsite, and the Keyhole Canyon. The small Crescent 

Townsite ACEC is near the western part of the Piute-Eldorado Tortoise ACEC, a few hundred meters away from the 

boundary. The Keyhole Canyon ACEC is about 4 km north 

of the north boundary of the Piute-Eldorado Tortoise ACEC. 

Together, these three ACECs will be referred to in this report 

as the Piute-Eldorado ACECs (fig. 1). A legal description of 

these lands is included in appendix 2.

The Piute-Eldorado Tortoise ACEC consists primarily of 

the valley floors of Eldorado and Piute Valleys that drain north 

and south, respectively, from a drainage divide near the town 

of Searchlight (fig. 1). A small part of Ivanpah Valley is also 

included, adjacent to the California border west of Crescent 

townsite. Two large islands of land are excluded from the 

Piute-Eldorado Tortoise ACEC, one in the northwest part to 
B2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 1. Index map, showing boundaries of Areas of Critical Environmental Concern (ACEC; outlined in pink), wilderness areas 

(outlined in turquoise), and access roads throughout the Piute-Eldorado ACECs. The boundary of the Lake Mead National Recreation 

Area is shown as a broken green line.

MCCULLOUGH RANGE

LUCY GREY MOUNTAINS

HIGHLAND RANGE

EL

DO

RADO MOUNTAINS

COLORA

D

O RIVER

NEWBERRY MOUNTAINS

DEAD

MTS.

PIUT

E RANGE

NEW YORK MOUNTAINS

CASTLE MOUNTAINS

PIUTE

VALLEY

CHIQUITA

HILLS

LANFAIR

VALLEY

ELDORADO

VALLEY

NEVADA

NEVADA

ARI

ZONA

CALIFORNIA

Nelson

Cal-Nev-Ari

Searchlight

South McCullough

Wilderness Ireteba Peaks

Wilderness

Spirit Mountain

Wilderness

Nellis Wash

Wilderness

Bridge

Canyon

Wilderness

Wee Thump

Joshua Tree

Wilderness

Eldorado Wilderness

PIUTE-ELDORADO

TORTOISE

ACEC

KEYHOLE CANYON

ACEC

Lake Mead

National

Recreation

Area

Lake Mead

National

Recreation

Area

CRESCENT TOWNSITE

ACEC

U.S. 95

U.S. 95

NV 164

NV 165

NV 163

115°15'0"W 115°0'0"W 114°45'0"W

35°15'0"N

35°30'0"N

35°45'0"N

0 5 10 15 20 2.5

Kilometers
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B3

exclude the rugged peaks of the northern Highland Range, and 

one in the east-central part to exclude the town of Searchlight 

and some parts of the Searchlight mining district. The ACEC 

has an area of about 1,316 km2

. It is bisected in a north-south 

direction by U.S. Highway 95 and in an east-west direction 

by Nevada State Highway 164. Access is via an extensive 

network of secondary roads that lead to various parts of the 

ACEC from these highways (fig. 1).

The Keyhole Canyon ACEC has an area of slightly less 

than 1 km2

 and includes the mouth of Keyhole Canyon, on 

the west margin of the Eldorado Mountains, and a part of 

Eldorado Valley. It is accessed by secondary roads from U.S. 

Highway 95, about 3 km to the west.

The Crescent Townsite ACEC has an area of about 1.8 

km2 and is near the head of Big Tiger Wash, a tributary valley 

to Ivanpah Valley. It is apparently intended to preserve the 

historic site of the mining town of Crescent, although existing 

maps indicate that the townsite is mostly north of the ACEC, 

probably on private land. The ACEC is accessed by a secondary road off Nevada State Highway 164.

The Piute-Eldorado Tortoise ACEC is bordered on the 

east by the Lake Mead National Recreation Area. It also 

includes all or part of three existing wilderness areas and borders three more (fig. 1).

Along the northwest boundary of the ACEC, small parcels 

of land that are part of the South McCullough Wilderness are 

included within the ACEC. The U.S. Geological Survey and 

U.S. Bureau of Mines studied this area in the late 1980s (Close, 

1987; Barton and Day, 1988; DeWitt and others, 1989).

Along the northeast boundary of the ACEC, several 

square kilometers of land that are part of the Ireteba Peaks 

Wilderness are included within the ACEC. The U.S. Geological Survey and the U.S. Bureau of Mines also studied this area 

in the late 1980s (Causey, 1988a,b; McHugh and others, 1989; 

Conrad and others, 1991).

In the western part of the ACEC, the Wee Thump Joshua 

Tree Wilderness was designated in 2002, without study for 

mineral resources.

The ACEC is bordered on the east by the Nellis Wash 

Wilderness, the Spirit Mountain Wilderness, and the Bridge 

Canyon Wilderness, all designated in 2002 without study for 

mineral resources. These three Wilderness Areas are within 

the Lake Mead National Recreation Area.

Physiographic Description

Elevations in the Piute-Eldorado ACECs range from 

about 550 m to more than 1,600 m. The lowest areas are along 

the east margin of the Piute-Eldorado Tortoise ACEC, on the 

alluvial fan that drops from the Newberry Mountains down 

to the Colorado River (about 550 m) and on the north end of 

Eldorado Valley and the south end of Piute Valley (about 750 

m). The highest areas are the crests of the Ireteba Peaks (about 

1,500 m) in the northeast part of Piute-Eldorado Tortoise 

ACEC and on the east flank of the McCullough Range northeast of Crescent townsite (more than 1,600 m).

The majority of the area is occupied by the Eldorado 

Valley that drains to the north and the Piute Valley that drains 

to the south. The climate is extremely dry and subject to 

extreme temperature variations; there are no perennial streams. 

The sediments that fill both the Eldorado and Piute Valleys 

are relatively thin compared to other valleys in the Basin and 

Range physiographic province (Jachens and Moring, 1990). 

These valleys are not grabens, and the alluvial fill in the Piute 

Valley is no deeper than about 700 m. The northern part of 

the Eldorado Valley (outside the ACEC) is somewhat deeper, 

but large parts of the east margin of the valley are covered by 

less than 1,000 m of alluvium. Pediments are relatively wide, 

especially on the west flank of the Eldorado and Newberry 

Mountains, and in Big Tiger Wash (fig. 2). In the south half 

of the ACEC, most of the Piute Valley is covered by less than 

500 m of deposits.

The vegetation is strongly zoned according to altitude, 

and the lower parts of the area are typical of much of the 

desert southwest of the United States. Some details about the 

vegetation can be found in Longwell and others (1965).

Geologic Setting

The areas studied are located in the northern Colorado 

River extensional corridor, a term first used by Faulds and 

others (2001). The corridor is characterized by closely spaced 

normal faults that originally formed as near-vertical tensile 

fractures and then rotated to low angles during progressive 

extension. This region occupies the area between the tecFigure 2. View of McCullough Range from the west, looking toward Big Tiger Wash, showing subdued 

topography and pediment surface.
B4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

tonically stable Colorado Plateaus region to the east and the 

Mojave Desert province to the west, which is bounded by two 

large strike-slip fault zones, the Garlock and the San Andreas. 

The rocks exposed in the Piute-Eldorado area include large 

areas of Proterozoic metamorphic and igneous rocks that are 

overlain by varied late Tertiary volcanic and sedimentary 

rocks. Cretaceous granitoid rocks were emplaced into the Proterozoic rocks and Miocene intrusions cut both the Proterozoic 

and Tertiary rocks.

Geology

Rocks and mineral deposits in the Piute-Eldorado ACECs 

range in age from Early Proterozoic to Recent. Proterozoic sedimentary and volcanic rocks were probably deposited between 

about 1.7 and 1.8 Ga and then deformed and metamorphosed 

between about 1.76 and 1.68 Ga (Wooden and Miller, 1990; 

Howard and others, 2003; Hook and others, 2005). Although 

no Paleozoic rocks are exposed in the area, it is likely that they 

were present but stripped off by erosion from early Eocene to 

middle Miocene time, when the area was uplifted as a broad 

arch (Bohannon, 1984). Tertiary volcanic rocks (and minor sedimentary rocks) range in age from the 18.5 Ma Peach Springs 

tuff (Nielson and others, 1990) to about 11 Ma (mafic rocks of 

the Mt. Davis volcanics; Faulds, 1995).

Proterozoic Rocks

Proterozoic rocks, mostly schists, gneisses, and granitoid 

rocks, are exposed in the McCullough Range and the northern 

New York Mountains, on the west margin of the Piute-Eldorado 

Tortoise ACEC, and in the Eldorado and Newberry Mountains, 

on the east margin of the ACEC. On the basis of sparse regional 

isotopic ages, Volborth (1973) speculated that the schists and 

gneisses in the Piute-Eldorado area formed at 1.7 Ga, but he 

also reported younger isotopic ages that he believed were reset 

during recrystallization in Cretaceous and Tertiary time. Volborth described the schists and gneisses in the Eldorado, Newberry, and Dead Mountains as granulite facies rocks containing 

almandine, sillimanite, cordierite, feldspar, quartz, and some 

pyroxene and biotite. He further noted the presence of numerous 

small gabbroic and ultramafic intrusions, as well as abundant 

pegmatite and aplite masses in some areas.

Anderson and others (1985) mapped and described Early 

Proterozoic metamorphic rocks in the McCullough Range 

as low-pressure granulite-facies paragneisses with garnet, 

sillimanite, and cordierite. The gneiss also includes abundant 

coarse leucogranite bodies and local masses of amphibolite 

and meta-ultramafic rock that is reportedly similar to that in 

the Virgin Peak-Gold Butte area. It is intruded by Proterozoic granitic to dioritic rocks that were emplaced late in the 

metamorphic history of the region. Regional research in the 

eastern Mojave Desert (Wooden and Miller, 1990), which 

included sampling in the McCullough Mountains, has shown 

that the oldest supracrustal Proterozoic rocks give minimum 

ages of 1.9 to 2.3 Ga, and these were intruded by 1.72 to 1.76 

Ga plutons. The metamorphism and deformation were named 

the Ivanpah orogeny by Wooden and Miller (1990, 1991), 

who also reported age data for 1.63- to 1.69-Ga postorogenic 

intrusive rocks in the region. Mapping of these Proterozoic 

rocks in the New York Mountains and the south end of the 

McCullough Mountains (Miller and Wooden, 1993) showed 

that Early Proterozoic gneiss exposed along the west border 

of the Piute-Eldorado Tortoise ACEC is complexly mixed 

with postorogenic intrusive rock along the eastern border of 

an extensive area of plutonic rocks. Miller and Wooden (1993) 

subdivided these postorogenic rocks, which are mostly composed of granodiorite and leucocratic granite, into the 1.68- to 

1.69-Ga New York Mountain complex in California and the 

subcircular 1.66- to 1.68-Ga Big Tiger Wash complex in the 

Crescent region.

Large areas of porphyritic Precambrian granitic rocks 

(hornblende-biotite monzogranite and syenogranite), commonly partially crushed and recrystallized, were mapped in 

the Eldorado and Newberry Mountains by Volborth (1973) and 

correlated with the Gold Butte Granite 70 km to the northeast. 

Volborth referred to these rocks as “pseudo rapakivi” granites, 

on the basis of their resemblance to similar Precambrian rocks 

in Finland. Bingler and Bonham (1973) mapped a large mass 

of similar rock, which they called augen gneiss, in the north 

part of the Lucy Gray Mountains. Kwok (1983) and Anderson 

and Bender (1989) studied some of the porphyritic granites in 

the Newberry and Dead Mountains, confirming Volborth’s correlation. They proposed that the hornblende-biotite granitoids 

in the Newberry, Dead, and Lucy Gray Mountains, along with 

the Gold Butte granite, were part of a transcontinental 1.45-

Ga zone of anorogenic granitic plutonism. They also included 

Figure 3. Proterozoic gneiss outcrop in Eldorado Mountains. abundant occurrences of similar granitic rock in nearby 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B5

southeastern California and western Arizona in this zone. The 

Eldorado Mountains also contain some strongly foliated felsic 

gneisses that appear to be the host rock for the porphyritic 

granites (fig. 3) and can be presumed to be older than 1.4 Ga.

Cretaceous Plutonic Rocks

Three Cretaceous plutons occur in or near the PiuteEldorado ACECs: the White Rock Wash pluton, the Ireteba 

pluton, and an unnamed intrusion in the Crescent mining 

district (fig. 4).

Figure 4. Index map showing named plutons exposed in Piute-Eldorado Areas of Critical Environmental Concern (ACECs; outlined in 

pink). Miocene plutons are in red, Cretaceous plutons are in orange.

White Rock Wash Pluton

The White Rock Wash pluton is located on the east flank 

of the Newberry Mountains, along the Colorado River a few 

kilometers east of the Piute-Eldorado ACEC (fig. 4). It has 

been dated by Rb-Sr methods at about 65 Ma (Haapala and 

others, 2005) and by U-Pb methods at 68.5 Ma (Miller and 

others, 1997), and its age may actually span the CretaceousPaleocene time boundary. It is a medium- to coarse-grained 

two-mica granite, consisting of plagioclase more abundant 

than orthoclase, quartz, biotite, and muscovite. Accessory 

Tertiary intrusive rocks

Tertiary volcanic and 

 sedimentary rocks

Cretaceous intrusive rocks

Proterozoic rocks undivided

Avi pluton

Spirit

Mountain

batholith

Searchlight

pluton

Aztec

 Wash

 pluton

Nelson

 pluton

Keyhole

 Canyon

 pluton

Crescent Peak

intrusion

Ireteba

pluton

(2-mica)

White Rock

Wash pluton

(2-mica)

0 8 16 24 32 4

Kilometers

35°0'0"N

35°15'0"N

35°30'0"N

35°45'0"N

115°15'0"W 115°0'0"W 114°45'0"W 114°30'0"W

KEYHOLE CANYON 

ACEC

CRESCENT TOWNSITE 

ACEC

PIUTE-ELDORADO

TORTOISE 

ACEC
B6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

minerals include magnetite, apatite, zircon, and rare garnet. 

Both neodymium and strontium isotopic studies indicate the 

pluton formed from melting of Proterozoic crustal rocks (Haapala and others, 2005). It is part of a suite of peraluminous 

granites of latest Cretaceous age found throughout the Cordillera that show a strong crustal isotopic signature and probably 

formed by melting of the crust at depths greater than 35 km 

(Miller and Bradfish, 1980; Miller and Barton, 1987; Miller 

and others, 2003).

Ireteba Pluton

The Ireteba pluton is located north of Searchlight, where 

it occupies the crest of the Eldorado Mountains, intruding 

Proterozoic metamorphic rocks (fig. 4). Dates obtained by 

U-Pb methods constrain the age of the pluton to be 69 to 64 

Ma, nearly the same as the White Rock Wash pluton (Kapp 

and others, 2002). Most of the rock is granite, between about 

72 and 77 percent SiO2

. The major minerals of the granite are 

plagioclase, quartz, K-feldspar, biotite, primary muscovite, 

and garnet. Accessory minerals include magnetite±ilmenite, 

apatite, zircon, and monazite. In the southeastern part of the 

pluton, abundant mafic dikes and inclusions indicate a zone 

of extensive interaction with mafic magmas. Neodymium and 

strontium isotope studies show the same crustal signature as 

the White Rock Wash pluton (Kapp and others, 2002).

Granodiorite in Crescent Mining District

A medium-gray equigranular biotite granodiorite that is 

exposed in limited outcrops in the Crescent mining district 

(fig. 4) has a hypabyssal texture, and it may be related to 

the porphyry copper prospect at Crescent Peak. Biotite from 

this rock was dated by conventional K-Ar methods at about 

94 Ma (Miller and Wooden, 1993), but little more is known 

about this rock.

Tertiary Volcanic and Sedimentary Rocks

The stratigraphy of the northern Colorado River extensional corridor is characterized by thick sections (generally 

>3 km) of Tertiary volcanic and sedimentary strata that rest 

directly on Proterozoic and Late Cretaceous metamorphic 

and plutonic rock. Although preserved to the north, east, and 

west of the region, Paleozoic and Mesozoic strata are missing 

from all but the northernmost part of the corridor. Wherever 

Tertiary rocks can be observed in contact with Proterozoic 

basement, they are separated by a profound nonconformity 

that reflects a relatively subdued topography that had been 

created by Miocene time. Tertiary sections in the bulk of the 

northern Colorado River extensional corridor are dominated 

by Miocene volcanic rocks, including felsic to mafic lavas, 

volcanic breccia, and ash-flow tuffs, which are interlayered 

with lesser amounts of clastic sedimentary rocks and rock 

avalanche deposits.

Conglomerate (Pre-Peach Springs Tuff)

The oldest Tertiary rocks in the area consist of a thin 

layer of poorly sorted arkosic conglomerate that is found 

sporadically throughout the area (Faulds and others, 2001). 

This unit varies in thickness from 0 to no more than about 100 

m. Its age is bracketed between about 24 and 18.3 Ma (Beard, 

1996; Faulds and others, 1995, 2001). Nearby, in other parts 

of the Colorado River Extensional Corridor, there are prePeach Springs Tuff mafic and intermediate-composition lavas 

(Faulds and others, 2001), but none of these crop out within 

the Piute-Eldorado ACECs.

Peach Springs Tuff

The 18.5 Ma Peach Springs Tuff is widely distributed 

throughout western Arizona and the eastern part of the Mojave 

Desert (Glazner and others, 1986; Nielson and others, 1990). 

It is a massive moderately welded rhyolitic ash-flow tuff 

characterized by abundant large sanidine phenocrysts that 

commonly exhibit blue adularescence. In the study area, it is 

a distal outflow facies tuff whose source, although a matter 

of much discussion, is still unknown. The source was interpreted to be in the Colorado River trough near the south tip of 

Nevada by Glazner and others (1986), on the basis of systematic variations in thickness. A study of magmatic anisotropy 

as an indicator of flow direction in the tuff reached the same 

conclusion (Hillhouse and Wells, 1991). It is an important 

marker bed because of its wide distribution.

Volcanics of the Highland Range

A volcanic and sedimentary sequence of early to middle 

Miocene rocks as thick as 4 km makes up the Highland Range 

in the northern part of the Piute-Eldorado Tortoise ACEC. 

These rocks have been mapped and studied extensively by 

Faulds and others (2002a, b). They mark the site of the Miocene Searchlight volcanic center, and host the important gold 

deposits of the Searchlight district.

Lower Intermediate-Composition Unit.—Lying directly 

on Peach Springs Tuff or Proterozoic basement rocks is a 

1.5-km-thick sequence of trachydacite and trachyandesite 

lavas that range in age from 18.5 to about 16.3 Ma (Faulds and 

others, 2002a,b). The rocks range from about 55 percent to 

about 67 percent SiO2

 (Faulds and others, 2002a; Ludington 

and others, 2005) and straddle the boundary between alkaline 

and subalkaline compositions. Grain size ranges from coarse 

to fine (fig. 5); some, but not all, of the rocks are porphyritic, 

most commonly with phenocrysts of plagioclase, with some 

phenocrysts of hornblende. It is seldom possible to map 

individual flows more than about 100 m, but scattered measurements of layering indicate that the attitudes are consistent 

within any one area.

Middle Felsic Unit.—Above the intermediate-composition rocks is a sequence of rhyolite flows, tuffs, and tuffaceous 

sediments, as much as 1 km thick. The unit also contains 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B7

some subvolcanic intrusions. The silica content of these rocks 

ranges from about 67 percent to more than 77 percent SiO2

, 

with most analyses between 73 and 77 percent (Ludington and 

others, 2005; Faulds and others, 2002a). Age dates obtained 

by 40Ar/39Ar methods (Faulds and others, 2002b) indicate the 

unit was emplaced between about 16.3 and 16.0 Ma, whereas 

more recent U-Pb dates (Dodge and others, 2005) are as young 

as 15.9 Ma. North of the Searchlight district, some outcrops 

of glassy rhyolite vitrophyre occur, but most of the rhyolite is 

crystalline (fig. 5). In the hills immediately west of the Searchlight district, most of the rhyolite has been hydrothermally 

altered to quartz and alunite (figs. 6, 7).

Figure 5. Unaltered trachyandesite, coarsely porphyritic on the left (sample 5-

061106); finer-grained on the right (sample 5-061108). Images are approximately 

actual size.

Figure 6. Rhyolite, unaltered flow on the left (sample 4-050511); alunite-altered 

breccia on the right (sample 4-043006). Images are approximately actual size.

Figure 8. Basaltic trachyandesite of upper part of the volcanics 

of the Highland Range overlying rhyolite of the middle part, 

directly north of the Searchlight district, within the Piute-Eldorado 

Tortoise Area of Critical Environmental Concern (ACEC).

Figure 7. Rhyolite outcrops on hills in the western part of the 

Searchlight district. Most of these rocks bear abundant alunite.

Upper Mafic Unit.—Overlying the felsic unit is a unit 

that is as much as 1.2 km thick, composed mostly of basaltic 

trachyandesite flows (fig. 8). The unit thickens northwestward 

toward the central part of the Highland Range where apparent 

remnants of a small stratovolcano that was the source of these 

flows are exposed. These rocks generally contain between 

about 56 and 60 percent SiO2 and have ages between about 

16.0 and 15.2 Ma (Faulds and others, 2002a,b).

Patsy Mine Volcanics

Originally defined by Longwell (1963), this sequence 

of rocks is correlative with the volcanics of the Highland 

Range, with dates ranging from 18.5 to 15.3 Ma (Gans and 

Bohrson, 1998). The name, Patsy Mine Volcanics, was originally applied to the volcanic rocks exposed in the northern 

Eldorado Mountains, on the north side of the Nelson mining 
B8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

district. Within the Piute Eldorado ACECs, these rocks are 

found in the McCullough Range south of McCullough Pass. 

There are also exposures about 3 km beyond the northeast 

margin of the Piute-Eldorado Tortoise ACEC and about 4 

km northeast of the Keyhole Canyon ACEC. These rocks 

were divided by Hansen (1962) and Anderson (1971) into 

three informal parts, the lower, middle, and upper. The lower 

part is up to about 2,700 m thick and consists of andesite 

and basaltic andesite lava flows, flow breccias, and explosion breccias. The middle part is predominantly rhyolite lava 

flows and is about 300 to 800 m thick. The upper part is relatively thin (about 500 m) and consists mostly of dark basaltic 

andesite flows (Anderson, 1971).

The petrology and age of these rocks are similar to that 

of the volcanics of the Highland Range, and whereas the lower 

part of the sequence probably had a local source, possibly the 

Nelson pluton, the uppermost part of both sequences may have 

had some of the same source areas in the central Highland 

Range (Faulds and others, 2002a).

Tuff of Bridge Spring and Tuff of Mount Davis

The 15.2 Ma tuff of Bridge Spring and the 15.0 Ma tuff 

of Mount Davis are compositionally similar, regionally extensive ash-flow tuffs that are exposed in the northwestern part of 

the Piute-Eldorado Tortoise ACEC. The tuff of Bridge Spring 

was first distinguished and described by Anderson (1971), 

whereas the tuff of Mount Davis was not described until the 

report of Faulds (1995). The two tuffs are both rhyolitic in 

composition and can be confused in the field, because the tuff 

of Mount Davis commonly lies directly on the tuff of Bridge 

Spring. Together, they form an important marker horizon in 

the area. The source of the tuff of Bridge Spring is interpreted 

to be a caldera in the northwestern part of the Eldorado Mountains, about 15 km northwest of Nelson (Gans and others, 

Figure 9. Tuff of Bridge Spring on McCullough Pass road, near 

the northwest corner of the Piute-Eldorado Tortoise Area of 

Critical Environmental Concern (ACEC). Note prominent large (up 

to 10 cm) fiamme (flattened pumice fragments) on rock face.

1994). The source of the tuff of Mount Davis is unknown, but 

it may have been erupted from the same caldera (Faulds and 

others, 2002a,b). Both tuffs are rhyolitic in composition, and 

some outcrops of the tuff of Bridge Spring exhibit distinctive 

fiamme (flattened pumice fragments) (fig. 9).

Conglomerate, Megabreccia, and Sandstone

Megabreccias (landslide deposits) that commonly contain 

abundant clasts derived from Proterozoic rocks are found 

throughout the synextensional part of the volcanic section. 

Such rocks are found directly beneath the tuff of Bridge 

Spring, between the tuff of Bridge Spring and the tuff of 

Mount Davis, and within a thick unit of conglomerate and 

sandstone that overlies the tuff of Mount Davis. Conglomerate 

and sandstone in the Highland Range appear to be the distal 

part of a large fanglomerate sheet that was partly derived from 

the southern McCullough Range.

Younger Volcanic Rocks

The Mount Davis Volcanics were first described by 

Anderson (1971) and consist of synextensional and late 

extensional basalt and basaltic andesite flows interbedded 

with minor amounts of sedimentary rocks (sandstones and 

conglomerates). They are exposed just east of the northeastern part of the Piute-Eldorado ACECs in the northern 

part of the McCullough Range and in a few localities in the 

central and northern Highland Range. Their age is bracketed 

between 15.2 and 12.8 Ma (Faulds, 1995; Faulds and others, 

1995; 2002a,b).

In the surrounding area, younger volcanic rocks include 

tholeiitic basalts with ages between 11.9 and 8.9 Ma, basaltic 

andesites with ages between 10.6 and 8.0 Ma, and alkalic 

basalts with ages between 6.0 and 4.5 Ma (Faulds and others, 2001). These young rocks do not crop out within the 

Piute-Eldorado ACECs, but an 11-Ma basalt flow is exposed 

directly to the east on the east flank of the southern Eldorado 

Mountains.

Tertiary Intrusive Rocks

A series of Miocene intrusive bodies are emplaced into 

the Proterozoic basement and Miocene volcanic rocks in the 

Black, Newberry, and Eldorado Mountains. From south to 

north, they are designated the Avi pluton, the Spirit Mountain 

batholith, the Searchlight pluton, the Aztec Wash pluton, the 

Keyhole Canyon pluton, and the Nelson pluton (fig 4).

Avi Pluton

This pluton is located just to the south of the Piute-Eldorado Tortoise ACEC (fig. 4), and it has not been studied in 

detail, nor dated. We took one sample (4-101201) that has 

a silica content of about 67 percent (Ludington and others, 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B9

2005) and is classified as a quartz monzonite. We infer that 

it is about the same age as the Spirit Mountain batholith, or 

slightly older. No apparent mineralization was associated with 

the emplacement of this pluton.

Spirit Mountain Batholith

The Spirit Mountain batholith has an outcrop area of 

about 250 km2 (figs. 10, 11) and consists of Miocene intrusive 

rocks that were emplaced over a 2 million-year time span 

(17.4 to 15.3 Ma) (Walker and others, 2005; Walker, 2006). 

Rämö and others (1999) determined a whole-rock Rb-Sr age 

of about 20 Ma for the granite. The compositions range from 

high-silica granite (about 77 percent SiO2) near the roof of the 

body (fig. 12) to quartz monzonite (about 63 percent SiO2) in 

the interior. Most of the batholith is composed of granite that 

was emplaced in a somewhat more restricted time interval 

between about 17.0 and 16.0 Ma (Walker, 2006). Fine- to 

medium-grained diorite is common in the eastern part of 

the batholith, occurring as dikes and pod-like intrusions. No 

hydrothermal mineralization can be directly attributed to the 

emplacement of the Spirit Mountain batholith.

Figure 12. Granite from near the roof of the Spirit 

Mountain batholith. Sample 4-101103 has about 76 

percent SiO2

 (Ludington and others, 2005). Image is 

approximately actual size.

At about 15.3 Ma, numerous granitic dikes were injected 

into the Spirit Mountain batholith. These have been called the 

Newberry Mountains dike swarm, and they represent the last 

pulse of the magmatic system that formed the Spirit Mountain 

batholith (George and others, 2005). These dikes all strike 

nearly north, and dip east at 40 to 60 degrees. They have been 

rotated westward 30 to 50 degrees from their original near-vertical attitude. This rotation has been documented using paleomagnetic techniques by Faulds and others (1992). Because 

tectonic tilting in the region is documented to have begun 

as early as 16 Ma (Faulds and others, 2001), the Newberry 

Mountains dike swarm may have been emplaced very rapidly 

during the tectonic extension.

Searchlight Pluton

The Searchlight pluton has a surface outcrop area of 

about 80 km2 in the southern Eldorado and northern Newberry Mountains (fig. 4) and consists of Miocene intrusive 

rocks that were emplaced over a period of at least 1 million 

years (16.9 to 15.7 Ma) (Cates and others, 2003). The pluton 

has been classified into three lithologically distinct units by 

Bachl and others (2001).

Upper Quartz Monzonite Unit.—The uppermost unit 

is primarily relatively fine-grained quartz monzonite (fig. 

13) that generally contains about 64 to 68 percent SiO2

 but 

ranges from a low of about 58 percent to a high of about 70 

percent (Ludington and others, 2005). This unit intrudes the 

lower intermediate-composition unit of the volcanics of the 

Highland Range and lies in all cases just below the productive precious-metal veins of the Searchlight district. The 

major minerals are plagioclase, potassium feldspar, quartz, 

biotite, and hornblende. Accessory minerals include titanomagnetite, sphene, apatite, allanite, and zircon (Bachl and 

others, 2001).

In the roof zone of the upper unit, porphyritic rocks 

with a very fine-grained groundmass are common (fig. 14). 

Figure 10. Outcrops of massive granite of Spirit Mountain 

batholith, near the southernmost tip of the Piute-Eldorado Tortoise 

Area of Critical Environmental Concern (ACEC).

Figure 11. Spirit Mountain, at the north end of the Spirit 

Mountain batholith.
B10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Outcrops are generally poor in this region, and it is usually 

impossible to observe crosscutting relationships. However, a 

few contacts were observed, and this fine-grained rock appears 

to always be cut by the phaneritic quartz monzonite and to 

intrude the volcanic rocks of the roof. This earliest intrusive 

phase of the Searchlight pluton may be representative of the 

composition of the original magma.

Middle Granitic Unit.—Structurally below the quartz 

monzonite is a coherent unit of granite that contains about 70 

to 77 percent SiO2

. Much of this granite formed as a cumulate and it exhibits a weak magmatic foliation in some exposures (fig. 15). The major minerals are potassium feldspar, 

plagioclase, quartz, and biotite. Accessory minerals include 

titanomagnetite, sphene, apatite, zircon, and allanite (Bachl 

and others, 2001).

Figure 13. Quartz monzonite from very near the roof of 

the upper unit of the Searchlight pluton. This is sample 4-

031004, which contains about 64 percent SiO2

 (Ludington 

and others, 2005). Note the faint green color of some of 

the plagioclase crystals, indicating mild hydrothermal 

alteration to illite and/or clay minerals. Image is 

approximately actual size.

Figure 14. Fine-grained porphyritic phase 

of upper unit of the Searchlight pluton. 

Sample 4-033102 contains about 58 percent 

SiO2

 (Ludington and others, 2005). Image is 

approximately actual size.

Lower Unit.—The lowermost unit of the Searchlight pluton 

crops out in the eastern part of the Piute-Eldorado Tortoise 

ACEC, and consists primarily of coarse-grained mafic quartz 

monzonite that contains the same mineral assemblage as the 

upper unit but in different proportions. Hornblende is commonly 

as abundant as biotite, and large euhedral sphene crystals are 

particularly prominent and abundant. The lower unit is characterized by a magmatic planar fabric defined by subparallel arrangement of all elongate minerals (Bachl and others, 2001), which is 

overprinted by a subsolidus, mylonitic fabric. Pods of mafic rock 

(mostly diorite) are present throughout the unit, commonly with 

dimensions of meters to hundreds of meters. The field evidence, 

coupled with paleomagnetic studies (Faulds and others, 1998) 

and hornblende geobarometry clearly indicate that the entire 

plutonic complex is steeply tilted to the west, and that the rocks 

in the lower mafic unit represent the floor of the pluton at a 

paleodepths of about 13 km (Bachl and others, 2001).

The overall composition of the pluton is closely similar in 

composition to the lower intermediate-composition and middle 

rhyolitic parts of the volcanics of the Highland Range, and the 

various parts of the pluton appear to represent the preserved 

subvolcanic magma bodies that fed the volcanic rocks. However, only limited parts of the pluton were fluid and erupting 

at any one time. The overall time span exhibited by the rocks 

is more than 2 million years, and the complex pluton and the 

various layers of volcanic rock are the end result of a long 

series of individual magmatic events.

Faulds (1999) and Faulds and others (2002a) suggested 

that the altered and mineralized rocks of the Searchlight mining 

district represent the hydrothermal halo around the roof of the 

Searchlight pluton within a stratovolcano complex. The middle 

and lower units, in general, were not affected by hydrothermal 

alteration, but the upper parts of the upper unit, near the roof, 

commonly exhibit varying degrees of alteration, primarily of the 

feldspars to illite and clay minerals, and of the mafic minerals 

to chlorite and epidote (fig. 13). All the rocks of the pluton have 

been tilted steeply to the west during extension.

Aztec Wash Pluton

The Aztec Wash pluton has a surface outcrop area of 

about 50 km2 in the northern Eldorado Mountains (fig. 4) and 

consists of Miocene intrusive rocks that were emplaced and 

crystallized over a somewhat shorter time period than the two 

large plutons to the south (about 15.8 to 15.5 Ma) (Cates and 

others, 2003; Koteas and others, 2003). Although there are a 

multitude of rock types in this pluton, it is convenient to divide 

it into three units (Falkner and others, 1995).

About 30 percent of the pluton is composed of the main 

granite, a medium-grained granite that is mostly between 

about 70 and 74 percent SiO2

. The major minerals are sodic 

plagioclase, quartz, potassium feldspar, and biotite. Accessory 

minerals include sphene, apatite, allanite, zircon, and opaque 

oxide minerals. Small miarolitic cavities characterize the unit, 

and they are most common at the pluton margins (Falkner and 

others, 1995).
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B11

Figure 15. Foliated outcrops of the granitic middle unit of the 

Searchlight pluton. The sample taken here (4-100802) contains 

about 73 percent SiO2

 (Ludington and others, 2005).

The heterogeneous zone constitutes nearly 70 percent 

of the pluton and is composed of diverse rocks that range in 

composition from mafic gabbros to felsic granites. These different rock types are interspersed on centimeter to 100-meter 

scales, and they locally grade into each other. The unit appears 

to have formed by the deposition of prograding tongues of 

mafic material into partially solidified granite. It occupies the 

interior of the pluton and is largely enclosed in older granite 

(Harper and others, 2005).

A third lithologic type is present as a north-trending 

dike swarm that is most prominent in the eastern part of the 

pluton. These dikes were described by Falkner and others 

(1995) to be bimodal in composition, but most are granitic 

and may be originally horizontal sheets that have been tilted 

into a steep attitude.

The Aztec Wash pluton contains the trace of the Black 

Mountain accommodation zone as delineated by Faulds and 

others (2002b). The pluton is divided into two parts by the 

Tule Wash Fault of Volborth (1973); the northeastern part of 

the pluton has been tilted to the east during Miocene extension, whereas the southwest part of the pluton has been tilted 

to the west (Falkner and others, 1995). The only mineral 

deposit that may be related to the Aztec Wash pluton is the 

silver-rich breccia zone at the Bmb No. 1 claim (see below), 

which appears to have been localized by the Tule Wash Fault.

Nelson Pluton

The Nelson pluton is an elongate intrusion that is mostly 

quartz monzonite in composition. It is located about 1 to 2 

km north of the northeast boundary of the Piute-Eldorado 

Tortoise ACEC (fig. 4). The elongate outcrop pattern of the 

pluton is due to repetition by west-dipping low-angle faults 

that have rotated it and the volcanic section on its north side to 

near-vertical attitudes. This pluton is the host for many of the 

epithermal precious-metal deposits in the Eldorado district and 

may be the source of the metals (Hansen, 1962). The age of 

the Nelson pluton has not been studied extensively by modern 

radiometric methods, although Faulds and others (1992) determined a conventional K-Ar age of 16.9 Ma on biotite, and Lee 

and others (1995) report an age of 16.3 Ma. The pluton is older 

than the Aztec Wash pluton on the basis of intrusive relationships. It appears to intrude a volcanic section that includes the 

upper parts of the Patsy Mine Volcanics, which may be as young 

as 15.3 Ma (Gans and Bohrson, 1998); however, these may be 

mostly fault contacts. It seems likely that the Nelson pluton was 

emplaced during the time interval between about 17 and 15 Ma, 

nearly contemporaneous with the Searchlight pluton.

Keyhole Canyon Pluton

The Keyhole Canyon pluton has been studied petrologically only by Hansen (1962). It is a relatively homogenous leucocratic granite that consists of orthoclase (commonly greater 

than 50 percent by volume), quartz, and plagioclase. Biotite is 

commonly no more than 1 percent of the rock, therefore qualifying as an accessory mineral along with magnetite and sphene. 

This pluton is tilted to the east. The western (lower) part of the 

pluton is less leucocratic and has more biotite. The upper (eastern) part of the pluton is characterized, like parts of the granitic 

unit of the Aztec Wash pluton, by abundant miarolitic cavities. 

It intrudes the Nelson pluton, and two samples were dated with 

conventional K-Ar methods by Armstrong (1970) at 15.4 and 

14.9 Ma. The Keyhole Canyon ACEC includes the northernmost tip of this pluton (fig. 16), which is not associated with any 

known hydrothermal mineral deposits.

Dike Swarms

Three voluminous swarms of Miocene dikes generally 

postdate all of the plutonic rocks described above. These dike 

swarms represent continued magma production and intrusion 

during brittle extension.

Figure 16. Massive outcrops of granite of the Keyhole Canyon 

pluton in the Keyhole Canyon Area of Critical Environmental 

Concern. Note geologist (sitting, with red shirt) in the center of 

photograph for scale.
B12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

A swarm of dozens of mostly felsic dikes, termed the 

Eldorado dike swarm by Steinwinder and others (2004), 

extends from the Aztec Wash pluton nearly 20 km south, 

where the dikes cut the Searchlight pluton (fig. 17). These 

dikes trend a few degrees west of north and are typically 2 

to 5 m thick. Individual dikes can be traced for at least a few 

kilometers. Most of these dikes, particularly in the north, are 

nearly vertical and have not been tilted significantly. Farther 

south, near the Searchlight pluton, some of the dikes have 

been rotated westward at least 45 to 55 degrees, as evidenced 

by paleomagnetic studies (Faulds and others, 1992; 1998). 

Many of these dikes are granitic in composition (about 73 percent SiO2

), but some are as mafic as diorite (see Steinwinder 

and others, 2004; and analyses in Ludington and others, 2005). 

A single U-Pb date of 15.5 Ma has been reported by Cates and 

others (2003). This dike swarm is almost entirely within the 

northeast part of the Piute-Eldorado Tortoise ACEC.

A contrasting swarm of generally west-trending dikes is 

found in the upper part of the Searchlight pluton and the lower 

intermediate-composition unit of the volcanics of the Highland 

Range, southeast of the town of Searchlight, in the eastern part 

of the Piute-Eldorado Tortoise ACEC (Ruppert, 1999; Ruppert 

and Faulds, 1998). These consist of both trachydacite porphyry 

dikes dated at about 16.6 Ma and rhyolite dikes dated at about 

16.0 Ma (Hodge and others, 2006). Analyses in Ludington and 

others (2005) show that the rhyolite dikes range in composition 

from about 68 to 77 percent SiO2

 and have compositions similar 

to the middle granitic unit of the Searchlight pluton. These dikes 

record a short period prior to the major east-west extension 

when the least principal stress in the region was oriented northsouth during the emplacement history of the Searchlight pluton. 

The rhyolite dikes were emplaced at about the same time that 

the gold mineralization at Searchlight was occurring, that is, just 

before major east-west extension.

To the south, the Newberry Mountains dike swarm that 

cuts mostly rocks of the Spirit Mountain batholith has been 

Figure 17. Granite porphyry dike from the Eldorado 

swarm that cuts the middle unit of the Searchlight 

pluton. Sample 4-043007 contains about 73 percent SiO2

(Ludington and others, 2005). Image is approximately 

actual size.

described by George and others (2005) as synextensional granite (about 73 percent SiO2

) dikes that are commonly rotated 

westward about 30 to 50 degrees. This swarm was emplaced 

at about 15.3 Ma. Some of these dikes extend into the Proterozoic metamorphic rocks as much as 5 km north of the Spirit 

Mountain batholith.

Structure

The Piute-Eldorado ACECs are mostly within the northern Colorado River extensional corridor, a 70- to 100-km-wide 

region of moderately to highly extended crust along the eastern 

margin of the Basin and Range Province in southern Nevada 

and northwestern Arizona. The Colorado River extensional corridor was first recognized by Howard and John (1987), and the 

distinct nature of the northern part, which extends from about 

the latitude of the south tip of Nevada to the Lake Mead area, 

was first highlighted by Faulds and others (1990). Recent and 

ongoing research on the structural and magmatic history of the 

region now permits a major reinterpretation of the mid-Miocene 

hydrothermal mineralization and its structural framework in 

the study area. The discussion that follows is based largely on a 

summary of the Cenozoic evolution of the region by Faulds and 

others (2001), as well as incorporation of ongoing work in the 

area. Figure 18 illustrates the structural setting of the area.

Magmatism swept northward through the Piute-Eldorado area beginning before 18 Ma (for example, the Avi 

pluton) in the south and at about 13 to 15 Ma (for example, 

the Boulder City pluton and volcanic rocks in the River 

Mountains-Hoover Dam area) in the north. Much of the area 

experienced simultaneous and nearly continuous igneous 

activity between about 17.5 Ma and about 15 Ma (Spirit 

Mountain batholith, Searchlight pluton, Aztec Wash pluton, 

Nelson pluton, Keyhole Canyon pluton, volcanics of the 

Highland Range, and Patsy Mine Volcanics). As evidenced 

by the east-west orientation of several early Miocene dike 

swarms and mineralized veins, much of the early magmatism 

coincided with mild north-south extension.

Major east-west extension followed the inception of 

magmatism by 1 to 4 million years, beginning at the south 

tip of Nevada at about 19 Ma, at about 16 Ma in the vicinity 

of Searchlight, and at about 14 Ma in the Boulder City area, 

north of the Piute-Eldorado ACECs. Throughout the region, 

the extension has resulted in the steep tilting of Miocene 

volcanic and sedimentary strata (commonly as much as 90 

degrees, sometimes overturned) (Faulds and others, 2001). 

In much of the southern part of the area, rocks older than 16 

Ma dip steeply west. The Black Mountains accommodation 

zone extends across the northern part of the Piute-Eldorado 

ACEC, dividing west-dipping rocks to the south from east-dipping rocks to the north. Here, oppositely dipping normal fault 

systems and their resulting tilt-block domains terminate in a 

belt of overlapping fault tips and extensional anticlines and 

synclines. The area north of the Black Mountains accommodation zone is termed the Lake Mead domain and the area to the 

south is termed the Whipple domain.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B13

Figure 18. Map showing structural blocks and Black Mountains accommodation zone in relation to generalized geology in PiuteEldorado Areas of Crical Environmental Concern (ACECs).

McCullough Range Fault

Dupont Mountain Fault

Lake Mead structural domain

(east-dipping beds)

Whipple structural domain

(west-dipping beds)

Mojave Desert block

Searchlight block

Fourth of July block

Pinto block

Bill Gays

block

Ireteba block

EXPLANATION

Boundary of structural block

Black Mountain accomodation zone

Fault, dashed where inferred

Proterozoic rocks

Cretaceous plutonic rocks

Miocene volcanic and sedimentary rocks

Miocene plutonic rocks

Black Mountains

accommodation zone

unassigned

structural

blocks

boundary of

Northern Colorado

extensional corridor

115°15'0"W 115°0'0"W 114°45'0"W

35°15'0"N

35°30'0"N

35°45'0"N

0 5 10 15 20 2.5

Kilometers
B14 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Because major east-west extension and associated tilting 

postdated emplacement of most of the plutons, the plutons in 

the Piute-Eldorado ACECs are also appreciably tilted. They are 

exposed from top, where they generally have intruded their own 

volcanic ejecta, to bottom, where they are exposed at paleodepths 

of 10 km or more, in what was the ductile middle crust.

The McCullough Range Fault is a poorly exposed eastdipping fault zone that essentially bounds the extensional 

corridor on the west. South of the study area, it links with a 

major breakaway zone that forms the west boundary of the 

extensional corridor in California (Spencer, 1985). To the west 

of this fault, the rocks are not steeply tilted; the southern Eldorado and Newberry Mountains and part of the Highland Range 

are the upthrown eastern parts of west-tilted fault blocks in the 

hanging wall of the McCullough Range Fault.

For convenience in discussing structural features of the 

study area, we have informally named a number of structural 

blocks, shown on figure 18. In the southern part of the area, in 

the Whipple domain, the boundaries of these blocks are eastdipping normal faults. These faults separate the uppermost 

crust of the area into discrete west-dipping structural entities. 

From west to east, they are here referred to as the Searchlight 

block, the Fourth of July block, the Pinto block, and the Bill 

Gays block. In the order named, each block is structurally 

higher than the previous one. The Searchlight, Fourth of July, 

and Pinto blocks each expose the upper contact of the Searchlight pluton in cross section, with each section having been 

east of the other prior to extension. Many additional east-dipping faults have been mapped by Faulds and others (2002a) 

in the Searchlight block; each of these is downthrown on the 

east and locally repeats parts of the stratigraphic section. Two 

of these are portrayed in dashed blue lines on figure 18; their 

northern and southern extensions pass under alluvial cover 

and the entire boundaries of the blocks they bound cannot be 

reconstructed, but they played an important role in increasing 

the number of exposures of the mineralized rocks above the 

Searchlight pluton in the Searchlight mining district.

Mining History

The history of mining within and near the Piute-Eldorado 

ACEC extends as much as 700 years into the past and includes 

prehistoric Native American activity and Spanish (or Mexican) 

mining that likely predated the 19th century. Except for Native 

American mining, the earliest mining was focused on deposits 

near the Colorado River, the most well traveled route at the 

time. The history of each of the five mining districts in this 

large area is given separately below in order of discovery.

Crescent District

The earliest activity in this district was prehistoric 

mining of turquoise by Native Americans. Turquoise is the 

most important commodity that has been produced in the 

district, and Morrissey (1968) estimated that its total value 

(excluding prehistoric mining) may have been in excess of 

$1 million. Although gold, silver, lead, and copper were 

mined here between 1894 and 1941, the total recorded value 

of metal production is small, at about $62,000 (Longwell 

and others, 1965).

In more modern times, turquoise was discovered in 1889 

or 1890 on the south flank of Crescent Peak (about 3 km 

southeast of the Piute-Eldorado ACEC) by George Simmons 

who picked up blue rock fragments but discarded them after 

they failed to give strong indications of copper (Morrissey, 

1968). However, following a visit to a turquoise mine in 

New Mexico, Simmons recognized the value of his find and 

returned for more thorough prospecting. He found that the 

turquoise source was a vein in an abandoned prehistoric mine, 

complete with stone tools and a primitive lapidary shop. Later 

work by archeologists put the date of abandonment at about 

A.D. 1300 (Morrissey, 1968). Most of the turquoise produced 

at Crescent Peak was mined from this property (known as the 

Toltec or Simmons Mine) between 1894 and 1906. In 1906, 

a 320-carat stone valued at $2,600 was found (Vanderburg, 

1937). In later years, mining became sporadic because of rising mining costs and lower turquoise prices and ceased as a 

commercial enterprise in the 1960s. The Morgan (Iron Door) 

Mine, which is inside the Crescent Townsite ACEC, was 

worked around 1906, but produced much smaller amounts of 

turquoise than the Toltec Mine (Morrissey, 1968).

Early metal mining in the Crescent district took place 

sporadically between 1894 and 1932, followed by more 

consistent production between 1934 and 1941 (Longwell and 

others, 1965). Early metals production, between 1905 and 

1907, was mostly from the Nippeno, Big Tiger, Calavada 

(Lily), and Double Standard Mines (Vanderburg, 1937). 

However, Ransome (1907), who visited the district in the 

winter of 1905-06, described only the Big Tiger and Calavada properties, and reported the presence of the “little settlement of Crescent, consisting of a dozen tents and wooden 

buildings...7 miles southeast of Nipton, on the road to 

Searchlight.” During the 1930s, the Nippeno, Budget, Double 

Standard, and Colonel Sellers Mines were active (Vanderburg, 1937). Vanderburg reported that mining at the relatively 

remote Double Standard Mine was done by hand methods 

in the 1930s and the ore was packed, at the rate of three tons 

per day, for a mile down a steep mountain by burros and then 

trucked to Searchlight for treatment. On the basis of data 

in Longwell and others (1965), the Nippeno was the largest 

Crescent district producer at about $20,000, followed by the 

Double Standard at an estimated $15,000, and the Budget at 

about $10,000. However, Vanderburg (1937) reported that 

“production from the Nippeno property is said to have been 

about $40,000, mostly in shipping ore.” 

Two major mining companies explored the area near 

Crescent Peak in search of porphyry copper deposits in the late 

1950s and early 1960s, and they drilled at least 6 core holes 

(Archbold and Santos, 1962). Prospecting for gold during the 

1980s and 1990s included exploration programs for detach-
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B15

ment-fault-related gold deposits by major mining companies, 

but that work has yielded no important discoveries despite the 

report of platinum-group elements (PGEs) by Lechler (1988).

Several former gold mines are now being exploited for 

decorative stone for landscaping. Current or recently active 

operations include those at the Lucky Dutchman, Modoc, and 

Nipton Red Mines and in Big Tiger Wash.

Eldorado District

Based on recorded production, about 2.3 million ounces 

of silver and 100,000 ounces of gold were produced from 

mines in the Eldorado district, mainly between 1915 and 

1920 and again between 1926 and 1943 (Hansen, 1962; 

Longwell and others, 1965). Total value of this production 

was about $4.6 million, including minor copper, lead, and 

zinc credits. Ransome (1907) estimated production from the 

19th century to the time of his visit in 1906 at $2 million 

to $5 million, and Vanderburg (1937) believed that most of 

this mining took place between 1864 and 1900. Vanderburg further noted that, based on a compilation by Yeoman 

Briggs, of Nelson, Nevada, production from the area was 

about $10 million. However, Vanderburg warned that “Briggs 

obtained his data from many sources, and due allowances 

must be made for old production figures, which have a way 

of increasing with time.” The same caution might be applied 

to Ransome’s (1907) estimate.

Old arrastras and prospect holes found in the 1860s 

were reported as evidence that the Spanish were mining in 

the Eldorado district prior to the recorded discovery of precious metals in 1857 at the Honest Miner claim. A mining 

district was organized in 1861, and the most important property, the Techatticup Mine, opened in 1863 and had produced 

an estimated $3.5 million by the mid 1930s (Vanderburg, 

1937; Hansen, 1962). Mining continued there until 1942, 

but production records for the property are not available 

(Longwell and others, 1965). Longwell and others (1965) 

reported two other significant properties in the district, the 

Wall Street and Eldorado Rand Mines, with estimated productions of $1.75 million and $1.0 million, respectively. Vanderburg (1937) reported at least 12 other mines or prospects 

in the district and cited a production figure encompassing 11 

mines in 1935. In addition, 1:24,000-scale topographic maps 

show several hundred workings scattered over an area of 

more than 100 km2

 in the district.

The Eldorado district is centered on the small village of 

Nelson, which was once an active mining town with a reputation for lawlessness. The town and most of the productive 

gold mining sites in the district are in Eldorado Canyon, a 

steep-sided canyon that empties eastward into the Colorado 

River. As noted by Ransome (1907), “It is a little surprising 

that a district once alive with activity should have attracted 

so little outside notice. This, however, is partly accounted 

for by the overshadowing performance of...other districts 

noted in the early history of mining in Nevada and by the 

isolation of Eldorado Canyon.” Ransome also noted that rich 

ore was shipped down the Colorado River by boat during 

the district’s early days, and that even by 1906 there were no 

regular means of communication with the district except for 

a road from Searchlight. Prior to the turn of the century, the 

Eldorado district was dominated by the Southwestern Mining 

Company, which owned nearly all of the productive properties (including the Techatticup and Wall Street Mines), along 

with several mills, and operated its own fleet of river boats 

(Vanderburg, 1937).

According to Smith and Tingley (1983) the Eldorado 

district was actively explored during the “1981 gold rush;” 

however, these authors saw no major exploration activity in 

the area in late 1982. Reports by the Nevada Bureau of Mines 

and Geology (Nevada Mineral Industry) show that the area 

was subject to local speculation and development during the 

1980s and 1990s, but no gold production has was reported 

in that period, or since. Exploration during that period was 

carried out by Intermountain Exploration, Amselco, Exxon, 

Weaco, Homestake, Zephyr Resources, and Alta Gold (Robinson, 1996). In 1993, a bulk-mineable deposit with a resource 

of about 1.2 million short tons at a grade of 0.044 opt (troy 

ounces/short ton) was drilled out near the sites of the old Wall 

Street and Black Hawk Mines, but the deposit was not developed (Robinson, 1996).

Newberry District

The Newberry district is larger and less focused than any 

of the other districts in the Piute-Eldorado ACEC area. The 

history of mining in the area has been sketchily recorded, but 

1:24,000-scale topographic maps show several widely spaced 

areas that contain concentrations of two to 20 individual workings. Longwell and others (1965) included some mines northeast of Searchlight in the district, but Tingley (1992) assigned 

these properties to the Searchlight or Eldorado districts and 

constrained the Newberry district to the area southeast of 

Searchlight. Production was estimated by Vanderburg (1937) 

at about $170,000, with $150,000 coming from mines of the 

Homestake group. This figure is based entirely on hearsay and 

is probably generous.

The mines of the Homestake group, which are on the east 

slope of the Newberry Mountains, 32 km southeast of Searchlight, were reported by Vanderburg (1937) to have been discovered and worked in the early 1860s by soldiers from Fort 

Mohave, Arizona. The mines were later active intermittently 

on a small scale between 1910 and 1937. The mines at Camp 

Thurman were discovered in 1906. Mines in the Roman Mine 

area were active in the 1930s. The history of other properties, 

such as the Juniper and Cottonwood Mines and the extensively 

prospected Superfluous-Gibraltar area in the Chiquita Hills, 

are not known.

The Roman Mine is being operated at present as a source 

of decorative stone, although the claims were apparently originally located primarily for silver.
B16 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Searchlight District

On the basis of recorded production, the Searchlight 

district was the second leading precious-metal mining district 

in Clark County (behind the Goodsprings district) with total 

production of about 250,000 ounces of gold (table 1). However, the Eldorado district may have been more productive if 

estimates of unrecorded early production of gold and silver are 

correct, as discussed above. Silver, copper, and lead were also 

produced at Searchlight, but they were relatively insignificant 

in terms of value. Longwell and others (1965) reported total 

recorded production for Searchlight at about $7 million.

In a U.S. Geological Survey bulletin on the Searchlight 

district, Callaghan (1939) reported production from 12 mines 

in the main part of the Searchlight district (which he mapped 

at a scale of 1:24,000) and in its extension as much as 8 km 

to the east. Callaghan provided detailed descriptions of many 

of the mines along with the carefully executed plan maps and 

cross sections typical of mining district publications of the 

era; consequently, Searchlight district gold deposits are the 

most thoroughly documented deposits in and near the PiuteEldorado ACEC. Reid (1998) wrote a detailed history of the 

Searchlight area, with information on mining activity to nearly 

the present time.

The Searchlight district was discovered relatively late in 

the mining history of Clark County. According to Ransome 

(1907), who visited the district in 1906, ore was discovered 

in 1898 at the site of the Duplex Mine, but Callaghan (1939) 

reported 1897 as the discovery year. Reid (1998) noted that 

early settlers and their descendants claim discovery took 

place in 1896. The original discoverer of Searchlight ore was 

apparently J.C. Swickard, who was grubstaked by F. Dunn of 

Needles, California (Reid, 1998). The first recorded production in the Searchlight district was in 1902 (Longwell and others, 1965). However, Ransome (1907) reported that the Duplex 

Mine was the first to ship ore, although the Quartette Mine had 

opened in 1898. In 1902, the Quartette erected a stamp mill on 

the Colorado River that was shortly thereafter connected to the 

mine by 15 miles of narrow-gauge railway. In 1903, water was 

encountered in the mine workings and a new mill constructed 

near the mine, leading to abandonment of the riverside mill 

and of the railroad, which operated for less than 2 years. During his visit in 1906, Ransome reported production from the 

Quartette, Duplex, and Blossom Mines, and noted the presence of several other mines in various stages of exploration or 

development.

This was the era of maximum growth in the district, and 

activity was intense, even in mines whose names and locations 

have not survived. The population of Searchlight probably 

peaked prior to the 1910 census when it held 613 souls, and 

figures as high as 1,500 were reported in 1906 (Reid, 1998). 

The following quotations, from “The Mining World” (Anonymous, 1906) give an indication of the emotional state of the 

district at the time. “During the past week sinking in the main 

shaft of the Searchlight Treasurer has disclosed definite walls, 

the shaft being all in ore. This shaft, which was started at a 

45-degree dip, following the ledge, is materially straightening 

up. Considerable copper stained sugar quartz has been struck 

at 50 feet, which runs $42 per ton... The shaft of the Venus 

is all in ore, and tracts have been let to sink to the 400-foot 

level. Stations are to be cut at the usual intervals, and a 15-h.p. 

hoist will supplant the whim now in use. Drifting both east 

and west will be continued on the 100-foot level, to determine 

the length of the ore body.” The identity of the Searchlight 

Treasurer and the Venus are unknown.

The Quartette Mine was the largest producer in the 

Searchlight district, particularly of gold and copper, and 

Callaghan (1939) estimated the total at $2.8 million, mainly 

between 1903 and 1910, the boom years of the district. Relatively low production came from the Quartette after 1910, and 

leasers operated the mine after 1917. Except for relatively high 

production in 1917 and the late 1930s (the latter increase was 

likely due to the higher gold price), annual district production 

never approached that attained during the district’s heyday 

years. According to Callaghan (1939), the Duplex Mine was 

the district’s second leading producer (gold, silver, and lead) at 

about $1 million, mostly during the early 20th century boom 

period. The Blossom Mine was probably the third leading 

district producer at a reported $325,000, mostly before 1906, 

and the Big Casino and Good Hope Mines had significant but 

lesser production (Longwell and others, 1965).

During the mining resurgence in the 1930s, a custom mill 

was built in Searchlight for the treatment of ore from mines 

in Searchlight and elsewhere in the region. In addition, a new 

cyanide plant was erected to treat tailings from the Quartette 

Mine (Vanderburg, 1937). There is little information about 

productivity of individual mines during this period, but ore 

was mined from the Quartette, Duplex, and Blossom Mines 

on the basis of information from Vanderburg (1937) and Callaghan (1939), with minor production from other mines.

Searchlight district production declined during the goldmining ban of World War II (WW II) and rebounded weakly 

between 1948 and 1952. Little or no metal mining has taken 

place in the district since then. Longwell and others (1965) 

reported small but unspecified amounts of gold production until 

1962, most likely from the Quartette Mine where Reid (1998) 

reported production until the 1960s. More recently, there was 

exploration by at least one major company and some minor 

activity by local individuals and at least one small company. 

During 1979–82, Felmont Oil (later Homestake Mining Company) conducted an exploration program designed to locate a 

large low-grade gold deposit in the western part of the Searchlight district. No gold resource was found, but the results led 

Homestake to suspect that a porphyry copper deposit might 

lie under the western part of the district. This target was not 

pursued at the time. Also in the late 1970s and early 1980s, a 

surge in development and exploration activity by private owners 

and independent operators took place, particularly at or near the 

Duplex, Blossom, Good Hope, and Big Casino Mines, but no 

production resulted (Smith and Tingley, 1983).

During the 1990s, development work was conducted 

on several claims (Blossom Consolidated, Whist, John, and 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B17

Year Ore (short 

tons) Gold (ounces) Silver (ounces) Copper (pounds) Lead (pounds)

1902 10,910 6,147 1,175 0 0

1903 19,522 19,275 27,691 0 0

1904 16,750 18,400 13,498 0 0

1905 38,069 19,329 28,528 22,808 12,064

1906 45,668 25,145 11,543 11,182 9,655

1907 45,921 23,441 7,494 37,063 38,113

1908 52,193 13,137 10,883 14,954 44,857

1909 68,931 16,237 13,544 22,916 36,209

1910 27,331 10,406 11,489 93,848 45,847

1911 1,850 966 2,136 12,095 7,659

1912 4,158 2,237 2,562 10,126 10,032

1913 5,989 6,654 5,903 53,971 61,006

1914 3,057 3,999 2,855 5,556 21,919

1915 7,766 4,985 3,546 20,970 35,562

1916 6,322 3,903 4,340 24,392 9,951

1917 12,866 3,445 9,073 98,923 59,453

1918 1,700 2,649 8,395 44,477 77,863

1919 6,980 2,854 5,502 18,074 39,307

1920 2,131 3,432 5,275 44,941 91,436

1921 1,182 3,601 9,877 31,128 98,048

1922 1,441 1,661 5,024 12,847 44,375

1923 1,142 1,007 2,708 22,150 47,651

1924 850 830 1,267 5,801 46,050

1925 2,833 3,314 2,586 14,974 86,768

1926 1,881 1,879 1,720 7,430 81,977

1927 106 335 306 1,429 10,415

1928 77 224 252 2,968 9,464

1929 184 105 58 654 2,743

1930 124 19 27 0 0

1931 20,855 3,276 5,826 6,022 274,687

1932 2,973 2,018 4,853 4,353 355,458

1933 2,996 913 1,182 2,261 12,040

1934 6,701 1,746 8,478 2,237 4,951

1935 29,617 3,829 12,317 9,195 72,271

1936 16,705 6,403 36,116 5,580 53,857

1937 5,692 5,456 28,688 500 12,600

1938 4,646 4,066 6,871 3,000 9,400

1939 2,035 1,471 1,682 9,400 14,200

1940 3,565 3,815 6,462 18,000 14,000

1941 4,092 3,908 4,524 2,100 5,000

1942 1,017 897 2,205 0 200

1943 117 139 1,454 3,000 4,100

1944 52 21 308 5,200 2,100

1945 401 852 5,708 2,000 1,200

1946 393 785 5,937 6,000 4,000

1947 405 737 2,768 20,300 7,500

1948 13,436 1,582 1,487 7,800 100

1949 16,399 1,007 4,109 700 4,500

1950 18,967 1,620 4,152 1,700 600

1951 24,850 2,041 5,352 4,800 800

1952 14,466 667 2,405 5,800 2,400

Table 1. Recorded production from the Searchlight district (reproduced from Callaghan, 1939).
B18 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Sanford) near the Blossom Mine by Coyote Mines, Inc., which 

is controlled by the descendants of William S. Shuler, who 

bought the claims in 1906. A resource of nearly 100,000 short 

tons was estimated, with a gold content of about 13,000 oz 

(400 kg) of gold and about 19,000 oz (590 kg) of silver. Small 

amounts of this material were produced from 2 underground 

levels at that time, but the mine is currently inactive.

Perlite was discovered north of Searchlight about 1946 

by B.L. Tanner, who operated a mine and a small perlite plant 

under the name Searchlight Insulation Products until the early 

1960s. Perlite was also mined from 1948 to 1954 at the NuLite Mine just outside the Piute-Eldorado Tortoise ACEC near 

the California border.

More recently, a number of mining claims that were 

patented for precious-metals are being exploited for decorative 

stone, which is sold for landscaping in metropolitan Las Vegas. 

A relatively large operation is conducted at the north end of the 

district, at the site of the Pompeii Mine, by Startel, Inc.

Sunset District

According to Smith and Tingley (1983) The Sunset district was established in 1897, when the Lucy Gray Mine, the 

only productive property in the district, was opened. However, 

Hewett (1956) reported discovery of the Lucy Gray in 1903, 

and Vanderburg (1937) reported it in 1905. Several other 

workings and prospects are shown in the area on the 7.5-minute topographic map, but information on their history could 

not be found.

Production for the district was estimated at about $50,000 

(Vanderburg, 1937). Hewett (1956) reported that the mine was 

active between 1905 and 1918. Recorded production from 

1911 to 1941 was about $13,000 (Longwell and others, 1965). 

According to Smith and others (1983), a small cyanide-leaching plant was operating by 1912 and production continued 

until 1919. Minor, intermittent operation took place between 

1919 and 1941. Some exploration at the property took place in 

the early 1980s (Smith and Tingley, 1983), and again in 1991 

by Golden Sunset Mining Co., but the property remains idle.

Hart District, California

Recent large-scale gold mining took place in the Hart 

district in California, about 8 km southwest of the Piute-Eldorado Tortoise ACEC. Gold was discovered in the Hart district 

in 1907 during the heyday of Searchlight mining, and mining 

continued until 1913, producing an estimated $10,000 (Hewett 

and others, 1936). Clay was mined from the district beginning 

in the 1920s; and, as at Searchlight, gold mining resumed in 

the 1930s and ended during WW II.

In the 1980s, the Hart district was explored extensively, 

and the Viceroy Gold Mine commenced production in 1992 

(Reid, 1998). Announced reserves by the Viceroy Gold Corp. 

were about 2 million ounces of gold in about 34 million metric 

tons of ore in a cluster of six deposits (Crowe and others, 

1996). The mine operated for 10 years, and it was California’s 

largest gold producer for several years, producing a total of 

about 1.2 million ounces. The mine has been inactive for 

several years, and closure obligations are expected to be met in 

2006 (Quest Capital Corp., 2005).

Mountain Pass District, California

Since 1954, rare-earth minerals and chemicals have been 

produced from Molycorp’s Mountain Pass Mine and plant, 

which is about 25 km west of the Piute-Eldorado ACECs 

(Castor and Nason, 2004). Rare-earth minerals were discovered in the district in 1949 by uranium prospectors in samples 

from the small Sulphide Queen Gold Mine, which had been 

worked on a small scale in the 1930s (Olson and others, 1954). 

In terms of value, the Mountain Pass operation has been the 

most important mineral producer in the region. For at least 30 

years, Mountain Pass was the world’s leading supplier of rareearth elements, which were mined from a unique Proterozoic 

carbonatite orebody. However, mining ceased in 2001 because 

of environmental problems and competition from China, and 

only minor amounts of rare earths are currently being sold 

from stockpile. The company, now a subsidiary of Chevron 

Corporation, may reopen the mine in the future.

Mineral Deposits

There are numerous mineral deposits within and near 

the three ACECs. The area contains part or all of 5 Nevada 

mining districts as defined by Tingley (1992), the Searchlight, 

Eldorado, Newberry, Crescent, and Sunset districts. In addition, there are a number of deposits that are not within defined 

districts, and a number of deposits of leasable and salable 

minerals that are unrelated to established mining districts.

Classification of Deposits

The area contains several different types of metallic 

mineral deposits. Because specification of deposit models is 

important in mineral potential assessment, we discuss a number of pertinent mineral-deposit models below.

Porphyry Copper Deposits

The generalized porphyry copper deposit model includes 

various subtypes, all of which contain chalcopyrite in stockwork veinlets in hydrothermally altered porphyritic intrusions and adjacent country rock. Copper is generally the most 

important commodity produced, but the deposits may contain 

important amounts of Mo, Au, Ag, Pb, and Zn. The deposits 

are associated with high-level intermediate-composition and 

felsic intrusions or cupolas of batholiths contemporaneous 

with volcanism along convergent plate boundaries. Surficial 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B19

exposures in the southwestern United States are generally 

leached to barren hematite/limonite outcrops that may locally 

contain copper carbonates or silicates and secondary copper 

sulfide minerals, such as covellite and chalcocite. Hydrothermal alteration patterns associated with porphyry copper deposits commonly exhibit zoning outward from sodic or potassic 

alteration (feldspar and biotite) through phyllic (sericite and 

pyrite) zones to distal propylitic alteration.

Porphyry copper deposits can be very large and productive; there are nearly 100 in the United States. The majority of 

them are Laramide (late Cretaceous and Paleocene) in age, but 

a few, including the giant Bingham Canyon deposit in Utah, 

are middle Tertiary. The nearest deposits to the Piute-Eldorado 

area are the modest Mineral Park (about 1,360 metric tons of 

copper production per year) and large Bagdad (about 91,000 

metric tons per year) deposits (both of Laramide age) about 50 

km east and 150 km southeast of the Piute-Eldorado ACECs, 

respectively. The closest Tertiary-age deposits are the Oligocene Copper Canyon deposit and a few Oligocene porphyry 

copper prospects, about 600 km north of the Piute-Eldorado 

ACECs, in northern Nevada.

Epithermal Precious-Metal Deposits

Epithermal precious-metal deposits are veins or groups 

of veins that formed near the surface of the Earth, contain 

significant amounts of gold and silver, and occur primarily in 

volcanic rocks. They are extremely common throughout the 

Basin and Range Province, where they formed from about 40 

Ma to the present. These deposits are commonly subdivided 

into several types. The most widely agreed upon subdivision 

of epithermal deposit types is into low sulfidation (quartzadularia) and high-sulfidation (quartz-alunite) types. Low-sulfidation deposits are typified by the presence of quartz fissure 

veins that may exhibit banded and crustiform textures, commonly with carbonate or lamellar quartz after carbonate, and 

K-feldspar (adularia) as an alteration product in wall rock or as 

a vein mineral. Alteration may also include clay minerals and 

propylitic mineral assemblages. Ore minerals include electrum 

and acanthite, with variable amounts of base-metal sulfides 

with or without silver sulfosalts. Pyrite may be common or 

sparse, but it is generally present. In addition to gold, silver, 

and base metals, low-sulfidation epithermal deposits may have 

elevated concentrations of As, Sb, Hg, Tl, Mo, W, Bi, and Te.

High-sulfidation epithermal deposits may contain quartz 

fissure veins, but they are generally typified by resistant 

“ledges” of country rock replaced by quartz. Carbonate is not 

present in main-stage mineral assemblages. Primary sulfate 

minerals, such as barite and alunite-group minerals, are typically present, and other vein and alteration phases may include 

pyrophyllite, diaspore, andalusite, and topaz. Clay mineral 

alteration is typified by the presence of kaolinite and dickite, 

and widespread propylitic alteration is generally present. Ore 

minerals include gold, enargite-group minerals, silver sulfosalts, telluride minerals, and base-metal sulfides. Pyrite is 

generally abundant. Some deposits, such as Goldfield, Nevada, 

have low silver contents; others, such as Paradise Peak, 

Nevada, are high in silver. In addition to gold and silver, highsulfidation deposits typically have elevated concentrations of 

Cu, Pb, Zn, As, Sb, Bi, Te, and Sn.

The vein deposits in the Searchlight district have been 

termed epithermal in the past, but several characteristics of 

these deposits are significantly to somewhat different than 

classic epithermal deposits. Veins at Searchlight (1) contain 

more base metals than many epithermal deposits, (2) have 

higher gold to silver ratios than many epithermal deposits, 

(3) are closely related spatially to the Searchlight pluton, and 

(4) are characterized by hematite as the chief iron-bearing 

mineral, rather than pyrite. For these reasons, in this report, we 

classify the Searchlight veins as gold-rich polymetallic veins, 

even though we are quite certain that they formed relatively 

close to the surface.

Adularia (an important indicator of low-sulfidation 

epithermal deposits) was reported in the veins in the northern 

part of the district by Callaghan (1939). We have determined 

that there is abundant secondary K-feldspar and albite in the 

wall rocks of these veins, and that minor amounts of adularia 

are also present in some of the veins. Studies are underway to 

determine the age of this adularia by the 40Ar/39Ar method.

The vein deposits in the Eldorado district near Nelson 

are much closer to the classic definition of epithermal precious-metal deposits, being relatively silver-rich and basemetal-poor. We consider them to be low-sulfidation epithermal 

deposits. On the basis of production records, the mines at Nelson produced similar amounts of ore to Searchlight, but only 

about half as much gold, nearly ten times as much silver, and 

less than one-tenth the amount of copper and lead. They are, 

however, closely associated spatially with the Nelson pluton.

Other nearby epithermal precious-metal deposits include 

the Katherine Mine (Lausen, 1931), about 15 km east of 

the Piute-Eldorado Tortoise ACEC, and the Oatman district 

(DeWitt and others, 1991), about 20 km to the southeast.

The large Mesquite deposit, about 230 km south of the 

Piute-Eldorado ACECs, near the Salton Sea in California, produced nearly 3 million ounces of gold (about 90 metric tons). 

At one time, it was thought to be a detachment-fault-related 

deposit (see below), but it is now considered an epithermal 

deposit that formed during strike-slip faulting (Willis and 

Tosdal, 1992). It consists of Oligocene quartz-adularia and 

carbonate veins in metamorphic and granitic rocks. It contains 

native Au associated with rutile, hematite, arsenopyrite, magnetite, pyrite, and chalcopyrite (Frost and Watowich, 1989; 

Mine Development Associates, 2004). Available data indicate 

deposition from boiling, low-salinity fluids largely controlled 

by moderately to steeply dipping faults that were later cut by 

shallowly dipping faults (Frost and Watowich, 1989).

Gold-Bearing Polymetallic Vein Deposits

Polymetallic vein deposits consist of quartz or quartz-carbonate veins with gold and silver and associated base metals 

(Cox, 1986). They occur in sedimentary and metamorphic rocks 
B20 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

and are commonly associated with hypabyssal igneous intrusions. Many small vein-type precious-metal and base-metal 

deposits have been assigned to this group, which has become 

a convenient catch-all model for vein type deposits of varied 

mineralogy, geochemistry, and geologic setting. The model was 

defined on the basis of many small deposits (maximum size 

about 5 million tons) in the western United States and Canada 

(Bliss and Cox, 1986), and there appear to be two subtypes, one 

with significant precious-metal values and one without. Vein 

mineralogy includes gold (or electrum) with pyrite and sphalerite; other base-metal sulfides, hematite, acanthite, and silver sulfosalts may be present. Vein textures suggest that some polymetallic veins are of epithermal origin, but associated deposit types 

may include porphyry deposits and other pluton-related deposits. 

Alteration generally consists of widespread propylitic alteration 

and restricted near-vein envelopes of sericite and clay alteration.

Detachment-Fault-Related Gold Deposits

Gold deposits related to detachment faults were mined in 

California and Arizona, mainly during the 1980s and 1990s. 

The best-known deposits assigned to this model are probably 

Picacho (0.6 million oz gold), which is about 280 km south 

of the Piute-Eldorado area, and Copperstone (0.5 million oz 

gold, 270 km southeast), both in Arizona. A number of smaller 

deposits occur in the Whipple Mountains of California, about 

190 km south. The Mesquite Mine, near the Salton Sea in California, produced nearly 3 million oz of gold and at one time 

was widely believed to be related to extension, but this relationship has now been largely discredited (Willis and Tosdal, 

1992). Information on detachment-fault-related deposits used 

in the following discussion comes primarily from Drobeck and 

others (1986), Spencer and Welty (1986), Mine Development 

Associates (2000, 2004) and Losh and others (2005). The state 

of knowledge at the time was summarized by Long (1992), 

but the model remains controversial, and questions have been 

raised about the classification of many examples of the type.

The deposit model is mostly based on descriptions of small 

(less than 1 million short tons of ore) base- and precious-metal 

deposits in California and Arizona that generally contain specular or earthy hematite, copper oxide minerals such as chrysocolla, native gold or electrum, and manganese oxides (Wilkins 

and Heidrick, 1982; Long, 1992). Copper, lead, and zinc sulfide 

minerals may be present, generally in chlorite-altered rocks 

beneath the fault surfaces. Upper-plate rocks are typically 

affected by potassium metasomatism and oxidized, yielding the 

characteristic red color. Oxide minerals such as specular hematite are considered primary. The deposits generally have nearly 

equal amounts of gold and silver, but otherwise have variable 

mineralogy and trace element chemistry. Fluid inclusion data 

indicate variable fluid temperatures (110° to 350°C) and salinities (1 to 23 equivalent weight percent NaCl).

At Copperstone, the gold occurs in quartz-hematite veins 

and in breccias containing quartz, hematite, magnetite, barite, 

calcite, and chrysocolla (Durning and Hillemeyer, 1986). In 

addition, calcite, siderite, manganese oxides, adularia, sericite, 

and fluorite were reported, as well as banded open-space 

fillings of quartz + specular hematite (Mine Development 

Associates, 2000). The Copperstone Fault, which dips 25 to 45 

degrees, was the main ore control, but steep faults in its hanging wall may also have controlled mineralization.

The Picacho Mine exploited four orebodies in metamorphic rocks and granite associated with a regional detachment 

fault (Drobeck and others, 1986). The ore mineral is goldbearing pyrite and the deposit is characterized by high Sb, Hg, 

and As, with low Cu and base metals (Losh and others, 2005). 

Fluid-inclusion data indicate that it was formed by low-salinity 

fluids somewhat different from those reported for the model. 

However, like most of the detachment-fault-related deposits, it 

does contain primary specular hematite.

The model for gold deposits related to detachment faults 

was developed primarily during exploration in the 1970s and 

onward. Geologists noted the association of some gold deposits 

with detachment faults with shallow dips in the desert regions of 

southern California and Arizona and formulated an exploration 

model that was vigorously pursued for about a decade. More 

recently, the failure to find many large economic deposits of this 

type has cooled interest, but many smaller low-grade deposits 

were found in the last 20 years. Deposits of this type are presently being explored in the Dead Mountains in California, about 

50 km south of the Piute-Eldorado Tortoise ACEC.

Deposits in the Eldorado District

Most of the mineral deposits in the Eldorado district are 

from 1 to 10 km north of the Piute-Eldorado Tortoise ACEC 

and 3 to 15 km east of the Keyhole Canyon ACEC. The geology of the district is dominated by the late Miocene Eldorado 

pluton, which is composed primarily of quartz monzonite and 

granodiorite. On the north side of the pluton, the wall rocks 

are primarily Miocene volcanic rocks, whereas Proterozoic 

igneous and metamorphic rocks make up the south wall of the 

pluton. This area is north of the Black Mountains accommodation zone (Faulds and others, 1990), and the rocks have been 

tilted steeply to the east, so that the deepest exposures in the 

district are at the west end and the shallowest at the east. The 

deposits here are emplaced in Proterozoic metamorphic rocks, 

Miocene volcanic rocks, and, most commonly, in the Eldorado 

pluton. Craw and McKeag (1995) studied some veins in the 

district and suggested that meteoric waters were the source of 

the mineralizing fluids, but the fluid inclusions they studied 

were all secondary, and this inference is not reliable.

Deposits in the Southern Eldorado Mountains 

Between Aztec Wash and Searchlight

Mines in this area were mostly located in the early part of 

the 20th century, and most have no recorded production. Those 

in the northernmost part of the area are usually considered 

to be part of the Eldorado district, while those farther south 

have been described as belonging to either the Searchlight or 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B21

Newberry districts. The St. Louis Mine (fig. 19) produced a 

few thousand troy ounces of gold between 1921 and 1948, and 

mines in the Camp Dupont area may have produced similar 

small, but unrecorded, amounts of gold (Causey, 1988a). 

The northern part of the area consists of Proterozoic gneiss 

intruded by the Miocene Aztec Wash pluton, whereas the 

south part consists of Proterozoic gneiss intruded by the Miocene Searchlight pluton. A large part of the center is occupied 

by the Cretaceous peraluminous granite of the Ireteba pluton. 

Qa

Kip

Qa

Qa

Taw

Tsll

Tsll

Qa

Tv

pCu

Tslm

pCu

pCu

Tsll

pCu Tv

unk

pCu

Tsll

pCu

Aj No. 1

H and E

Claims

Crystal

Lode

Cobalt

claims

St. Louis Mine

St. Louis

Mine

area

Bmb No. 1 Claim

Holsak

claims Rockefeller

mine

unnamed

prospect

Five Spot claims

Sazarac

claims unnamed

prospects

Piute-Eldorado

Tortoise

ACEC

114°52'30"W 114°45'0"W

35°37'30"N

01234 0.5

Kilometers

Deposits in this area are primarily of two types, gold-bearing 

polymetallic veins (St. Louis Mine area) and detachment-faultrelated gold deposits (Sazarac and Cobalt claims).

Four entries in the MRDS (Mineral Resource Data System) database (U.S. Geological Survey, undated) (Eldorado 

Mine, Eldorado project, West We Go, and Willoro project) 

have reported locations on the floor of Eldorado Valley, near 

U.S. Highway 95. Cactus Gold Corp. (see section on mineral 

exploration) maintains a facility near some of these locations, 

Figure 19. Mineral deposits in and near the Piute-Eldorado ACECs between the Eldorado and Searchlight mining 

districts. Geology compiled for this report: pCu—undivided Proterozoic rocks; Kip—Cretaceous granite of the Ireteba 

pluton; Taw—Miocene Aztec Wash pluton; Tslm—Miocene Searchlight pluton, middle unit; Tsll—Miocene Searchlight 

pluton, lower unit; Tv—Miocene mafic volcanic rocks; Qa—Quaternary alluvium.
B22 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

but we do not know if all of the database records refer to this 

installation. All were compiled from the Directories of Mine 

Operations for 1987, 1988, and 1991 produced by the Nevada 

Division of Mine Inspection.

Bmb No. 1 Claim

This mineral deposit is on the northeastern border of the 

Piute-Eldorado Tortoise ACEC. It also appears to be within the 

Ireteba Peaks Wilderness. On the 1:24,000-scale topographic 

map, it is designated the Belmont-Phoenix Mine, but it appears 

certain that the Belmont-Phoenix (formerly the Oro Plata) is 

about 2.5 km north, in the Eldorado mining district. The Bmb 

No. 1 is at the head of the deep canyon that drains southeastward from Tule Spring, and consists of a breccia zone in 

granite of the Aztec Wash pluton, cemented by quartz and 

calcite. During study of the Ireteba Peaks Wilderness, Causey 

(1988b) collected samples that contained as much as 665 ppm 

(parts per million) silver, as well as large amounts of lead and 

zinc, and low, but anomalous, amounts of gold. He inferred 

that subeconomic resources of silver are present on the claim. 

The high silver to gold ratio at this deposit suggests it is more 

closely related to the Eldorado district to the north than to the 

Searchlight district. However, the fact that the mineralized 

rock is hosted in fault breccias related to the Tule Wash Fault 

suggests that it formed after major extension and thus may not 

be directly related to the Eldorado district deposits.

H and E Claims

This area consists of a number of small pods of copperand gold-bearing quartz that both cut and are concordant with 

the metamorphic foliation of the Proterozoic gneiss. Malachite 

and chrysocolla are visible, along with iron-oxide minerals. Many of the grab samples reported by Causey (1988a) 

contained more than 1 percent copper, and several contained 

anomalous molybdenum (> 60 ppm). One sample contained 

1.4 ppm gold. The mineralized rock is exposed over an area of 

about 250 m by 30 m, elongate in a north-south direction and 

parallel to the foliation of the metamorphic host rock.

Unnamed Prospect

About 3 km south of the H and E claim block, a small 

unnamed prospect at the range front is hosted in granite of the 

Ireteba pluton. No description exists, and we did not visit it, 

but Causey (1988a) collected samples that contained as much 

as 400 ppm copper and 500 ppm zinc, though no significant 

gold or silver was detected.

St. Louis Mine Area

The St. Louis Mine (fig. 20) is on the west side of the 

Eldorado Mountains, about 12 km northeast of Searchlight 

and about 4 km southwest of the high point of the Ireteba 

Peaks (fig. 19). Patented claims cover the specific site, which 

is excluded from the Piute-Eldorado Tortoise ACEC, but mine 

workings extend north along the range front for more than 2 

km and include the Holsak claims of Causey (1988a). At the 

St. Louis Mine, Causey reported a quartz vein with hematite 

pseudomorphs after pyrite and minor malachite that trends 

N35W. We suspect this is a transcription error, as we measured 

the 1.5-m-wide vein’s strike at N35E. Causey’s two samples 

contained as much as 13 ppm gold, with abundant copper and 

lead. Our sample of the vein (4-030901) contained 1.6 ppm 

gold and 3 ppm silver and about 1,000 ppm copper, 2,000 

ppm lead, and 1,700 ppm zinc (Ludington and others, 2005). 

A sample collected by Tingley (1998) about 200 m north of 

the mine contained 1.6 ppm gold, 1,500 ppm copper, 2,000 

ppm lead, and 400 ppm zinc. Samples collected on the Holsak 

claims about 1,600 m north of the St. Louis Mine contained 

as much as 0.4 ppm gold, 5 ppm silver, and 1,200 ppm copper 

(Causey, 1988a). Samples collected by Causey (1988a) at the 

AJ No. 1 claim, about 1,200 m northeast of the Holsak claims, 

contained no more that 0.07 ppm gold.

The country rock is Proterozoic gneiss, intruded by 

numerous dike-like bodies of granite that probably correspond 

to the middle part of the Searchlight pluton. The veins here are 

not associated with a detachment fault, and they are probably 

best characterized as polymetallic veins. The vein we observed 

Figure 20. Portal of St. Louis Mine.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B23

at the St. Louis Mine strikes northeast and is near-vertical, 

although the host rocks appear to have been tilted at least 45 

degrees to the west since the beginning of extension; thus, this 

vein may be younger than the veins in the Searchlight district.

Sazarac Claims

The Sazarac block of patented claims includes the Rockefeller Mine; the area is about 17 km northeast of Searchlight, 

along the northeast boundary of the Piute-Eldorado Tortoise 

ACEC and the south boundary of the Ireteba Peaks Wilderness (fig. 19). Longwell and others (1965) refer to the entire 

area, including the Cobalt claims and the 5 Spot claim, as 

the Camp Dupont group. Thirty-five short tons of ore were 

produced in 1935. The seven claims were patented in 1913 

and have been the subject of sporadic exploration since that 

time. During study of the Ireteba Peaks Wilderness, Causey 

(1988a) collected samples that contained as much as 7.6 opt 

(260 ppm) gold in a 9-ft chip sample, but only weakly anomalous amounts of silver, copper, molybdenum, copper, lead, 

and zinc. Tingley (1998) reported 21 ppm gold from a sample 

about 100 m west of the area. Causey described the area as 

containing many small veins and iron-oxide stained faults and 

fractures, filled primarily with quartz and some barite. Chrysocolla and malachite are common, and free gold was noted. The 

area is within the Dupont Mountain detachment fault zone, 

and the geology has not been mapped in detail, but the veins 

seem to occur in both the hanging wall (Miocene mafic and 

intermediate-composition volcanic rocks) and the footwall 

(granite of the Ireteba pluton and lower part of the Searchlight 

pluton). Most veins, however, are cut by the detachment fault. 

The geochemical signature (high gold to silver ratio, low base 

metals other than copper) and the structural setting suggest 

that the appropriate mineral deposit model for much of this 

area may be detachment-fault-related deposits.

Cobalt Claims

About a kilometer west of the Rockefeller Mine area, 

a number of precious- and base-metal-bearing quartz and 

quartz-barite veins crop out over an area of less than 1 km2. A 

large claim block was established here in 1983 and an exploration program carried out during the 1980s. When the U.S. 

Bureau of Mines studied the mineral resources of the area, 

Causey (1988a) collected samples that contained as much as 

6.6 ppm gold, 7 ppm silver, as well as anomalous amounts 

of lead and zinc, and copper. The principal vein, hosted in 

granodiorite and diorite of the lower Searchlight pluton, trends 

about N40W and extends for about 500 m.

5 Spot Claim

This area adjoins the Sazarac claim block on the northwest. Causey (1998a) found only low gold values in the 

samples he took.

Crystal Lode Claim

About 700 m northwest of the Sazarac claim block, the 

Crystal Lode claim area is within the granite of the Ireteba 

pluton, and Causey (1988a) did not find high gold values in 

the samples he took.

Searchlight District

Mineral deposits in the Searchlight mining district are 

a group of Au-bearing veins that are hosted primarily in 

Miocene volcanic rocks. These veins occur in zones that are 

draped over the top of the Searchlight pluton. The most important mines in the main part of the district occur in a narrow 

band about 6 km long from north to south, just to the west of 

U.S. Highway 95 (fig. 21).

The productive parts of almost all known veins are in the 

lower intermediate-composition part of the volcanics of the 

Highland Range, within a few hundred meters above the upper 

contact with the Searchlight pluton (fig. 22). The J.E.T. vein, 

in the northern part of the district, is in the upper part of the 

Searchlight pluton, and small veins and stockwork zones are 

common within the upper part of the Searchlight pluton, but 

none of them produced important amounts of gold.

Major Mines of the Searchlight District

At Searchlight, the most important mine by far was the 

Quartette, which produced nearly half the gold from the entire 

district. The Duplex and the Blossom were the other productive mines. As far as is known, other mines shown on figure 21 

produced relatively minor amounts of ore, and most are now 

in disrepair (fig. 23). However, individual mine production 

records are almost nonexistent.

Of the mines distant from the main part of the Searchlight district, in the Fourth of July and Pinto structural blocks, 

only the Big Casino is known to have had substantial production. Although our samples show that it apparently contains 

substantial gold, the Chief of the Hills is not recorded to have 

produced much ore. Many of the mines received a large initial 

investment and then closed when the first excavations failed to 

yield profitable ore.

Although detailed production records for most individual 

mines have not been preserved, relationships among the various metals produced vary widely, both between the various 

mines and within individual mines. For example, ore from the 

Quartette commonly contained 3 times as much gold as silver, 

but these relationships were reversed for ore from some parts 

of the mine (Callaghan, 1939). Only the Quartette, Duplex, 

Good Hope, and Big Casino produced considerable lead and 

copper. Copper predominated in the Quartette, whereas lead 

was dominant in the Duplex. Further details are in Callaghan 

(1939). The results of sampling during this study (Ludington 

and others, 2005) are discussed below, in the section on geochemical zoning.
B24 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 21. Location map of major mines of the Searchlight district. Piute-Eldorado Tortoise Area of Critical Environmental Concern 

(ACEC; boundary outlined in pink). Boundaries of structural blocks are in heavy teal broken lines. The traces of productive veins, 

modified from the map of Callaghan (1939), are shown as heavy red lines.

Searchlight

structural block

Fourth of July

structural block Pinto

structural

block

Duplex

Sheba Queen Boston

Rambler

Blossom

Berlock

Pompeii

Mammoth

New Era mines

Oakland

 group

PIUTE-ELDORADO

ACEC

PIUTE-ELDORADO

ACEC

Santa Fe

Good Hope

Bay City Group

Quartette

Swickard

Pittsburg

Big Casino

Cyrus Noble

Coyote mine & mill

Southern Nevada

Chief of

the Hill

Searchlight M. & M.

Searchlight Parallel

Searchlight Insulation

Products (perlite)

J.E.T. Red Bird

114°52'30"W

35°30'0"N

01234 0.5

Kilometers
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B25

Figure 22. Generalized geology of the Searchlight district, compiled for this report. Units as follows: pCu—undivided Proterozoic 

schist, gneiss, and metaplutonic rocks; Tv1—lower intermediate-composition unit of volcanics of the Highland Range; Tv2—middle 

felsic unit of volcanics of the Highland Range; Tir—intrusive rhyolite; Tv3—upper mafic unit of volcanics of the Highland Range; Tslu—

upper part of Searchlight pluton; Tslm—middle part of Searchlight pluton; Tsll—lower part of Searchlight pluton; Tmaf—mafic pod in 

Searchlight pluton. Qa—Quaternary alluvium. Heavy black lines are faults, dashed where concealed.

Qa

Tv1

Tslu

Tslm

Tslu

Tv1

Tv1

pCu

Qa

Tv2

Tv1 pCu

Tsll

Tv3

Tv1

Tv2

Tv2

Tmaf

Tv2

Tslu

Tv2

Tv1

Tv2

Tv3

Tv2

Tmaf

Tv1

Tv1

Tv2

Tv3

Tv3

Tv2

Tir

Tv1

pCu

Tslu

Tv3

Tv1

Tv2

114°52'30"W

35°30'0"N

01234 0.5

Kilometers

PIUTE-ELDORADO

ACEC

PIUTE-ELDORADO

ACEC
B26 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Vein Mineralogy and Structure

An excellent description of the veins, one that is still 

valid for most of the veins in the Searchlight district, was 

given by Ransome (1907), “The lodes contain very little solid 

quartz and do not outcrop prominently. Toward the west they 

either pinch out or pass beneath alluvium. They are essentially 

mineralized fault zones in which the original character of the 

mineralization has been obscured by repeated movement and 

by oxidation. The lode material is generally a soft mass of 

shattered or crushed country rock colored by chrysocolla and 

oxides of iron and carrying free gold as its valuable constituent. Quartz is common in vugs, druses, and veinlets.”

According to Ransome (1907), cerussite was a characteristic constituent of the ore and was associated with wulfenite, 

cuprodescloizite, and leadhillite. Other lode minerals are 

specular hematite, malachite, azurite, and calcite. The only 

sulfides noted at that time were chalcocite, galena, and pyrite, 

which are present only in small quantities.

Visible copper minerals, primarily chrysocolla, were 

important guides to gold ore, and copper grades of several 

percent and lead and zinc grades near one percent were common in some parts of the veins. Today, virtually no base-metal 

sulfide minerals are present at the surface; we observed only 

pyrite and galena macroscopically, and have identified sphalerite and covellite microscopically. These sulfides were found at 

only three sites in the entire district. The most common gangue 

is quartz and specular hematite (fig. 24), sometimes accompanied by epidote. Historic published accounts of the vein mineralogy are cursory, as no geologist appears to have studied the 

mines between Ransome’s short visit in 1906 and Eugene 

Callaghan’s equally brief visits in 1931 and 1934. Callaghan 

(1939) prepared a summary of all earlier work and listed 17 

ore minerals, including gold, chrysocolla, cuprite, chalcocite, 

leadhillite, wulfenite, vanadinite, and rarely, galena. It appears 

that sulfides were rare, not just at the surface, but to depths as 

great as 260 m below the present ground surface.

Figure 23. Remains of mining equipment at Southern Nevada 

Mine.

On the basis of petrographic studies of thin sections 

and analysis with a scanning electron microscope (SEM) 

using energy-dispersive X-ray analysis (EDX), we identified 

galena, anglesite (PbSO4), cerussite (PbCO3), plumbogummite 

(PbAl3[(OH)5|(PO4)2]•H2O), pyromorphite (Pb5[Cl(PO4)3]), and 

covellite in partially oxidized ore from the Quartette Mine. We 

also found small (<50 microns) blebs of chalcopyrite adjacent 

to primary specular hematite in quartz veins in samples from 

the Quartette Mine (fig. 25), as well as galena and sphalerite 

blebs as much as 100 microns across.

The deposits in the northern part of the Searchlight 

district, including the Blossom and Searchlight M&M areas, 

differ from those in the Quartette Mine area. They contain thin 

quartz veins that consist mostly of granular to comb quartz 

and often occur in stockworks. Ransome (1907) stated that 

the Blossom Mine ore, which was mostly mined from a nearly 

horizontal blanket of stockwork veins, was generally not 

visibly mineralized but that the best ore contained free gold 

associated with limonite and specularite. Copper minerals are 

rare, although we found small amounts of blue secondary copper minerals at the Blossom Mine, and sparse chalcopyrite in 

quartz veins from dumps at the Searchlight M&M Mine.

During SEM examination, we noted that pyrite is partially to wholly replaced by hematite, galena, and electrum in 

a sample from the Blossom Mine. The electrum, which has 

weight percent Au:Ag of about 60:40 on the basis of semiquantitative SEM/EDX analysis, seems to have been deposited 

late as irregular grains and flakes along quartz grain boundaries and fractures (fig. 26).

As noted by Callaghan (1939), adularia is an abundant 

alteration product in the wall rock near veins in the north part 

of the Searchlight district, and poorly formed overgrowths of 

Figure 24. Sample of ore from dump of Rambler Mine, 

demonstrating abundant bright greenish-blue chrysocolla. 

Note also specular hematite and quartz in upper central part of 

photograph. Sample is about 8 cm across.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B27

Figure 25. Top: 

Plane-polarized 

photomicrograph 

of specularite (pale 

red to black) blades 

and chalcopyrite 

(rounded opaque 

mineral in center of 

photo) in a quartz 

vein sample from 

the Quartette Mine. 

4Right: Backscattered electron 

scanning electron 

clear adularia occur in some veins and veinlets (fig. 27). However, on the basis of our samples, adularia occurs only rarely 

within the veins from the north part of the Searchlight district 

as sharp rhomb-shaped crystals as much as 0.5 mm across 

(fig. 28). Callaghan reported lamellar calcite in the Searchlight 

Wall rock

chl

cpy

hem

0.5 mm

Figure 26. Secondary-electron SEM image of relatively coarse 

electrum in a quartz vein from the Blossom Mine (Sample AP254A). The electrum occurs as irregular grains along grain 

boundaries and cracks in comb quartz.

Figure 28. Plane-polarized photomicrograph of relatively clear 

rhombs of adularia in inclusion-crowded comb quartz near the 

border of a quartz vein from an unnamed prospect about 1 km 

west of the main part of the Searchlight district (sample 4-050601). 

The large adularia rhomb on the right is about 0.4 mm long; the 

tiny rhomb to the left of it is about 30 microns long. Vein border is 

at upper left.

Figure 27. Plane polarized photomicrograph of a quartz-adularia 

veinlet from the Blossom Mine (sample 5-031601). Overgrowths 

of clear adularia as much as 200 microns across occur along the 

border of the quartz vein, and the wall rock contains large amounts 

of secondary K-feldspar. The quartz-adularia vein is cut by a brown 

limonitized fracture. Horizontal field of view is about 0.6 mm.

microscope image of the same specimen showing specularite 

(hem), chalcopyrite (cpy), and chlorite (chl) in quartz vein 

adjacent to wall rock.

M&M and Blossom veins, but we did not see it there. However, we did observe ghost blade texture (quartz after bladed 

calcite) in a sample from the Chief of the Hills Mine, about 

5 km east of the main part of the Searchlight district, in the 

Fourth of July structural block.
B28 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

The fact that the veins have the same spatial relationship to the upper contact of the Searchlight pluton, no matter 

which structural block they are in, suggests strongly that the 

extension-related low-angle faults that separate the structural 

blocks were active after the mineralized veins were formed, in 

other words, that the district was dismembered after it formed 

and that mineralization largely preceded extension (Faulds 

and others, 2002a). Most veins strike west or slightly north of 

west and have varying but fairly steep dips. This is probably 

not their original attitude. All the rocks in the district appear 

to have been tilted steeply to the west as a result of middle 

Miocene extension. The result of this rotation is that the eastwest elongate surface exposures of the veins in the district are 

tilted cross sections, with tops to the west. The veins, which 

in map view appear to be peripheral to the Searchlight pluton, 

actually occur in a zone that arcs above its roof. The exposures 

in the Fourth of July block (Big Casino, Chief of the Hills, and 

Swickard) may simply be the eastern part of the Duplex, Good 

Hope, and Quartette mineralized structures, and the New Era 

Mines may be the eastern fringe of these same structures. The 

nearly horizontal mineralized zone at the Blossom Mine would 

have been a vertical, north-striking structure. These relations 

suggest that the Searchlight district provides a cross-sectional 

view of a hydrothermal system that is genetically related to 

the Searchlight pluton, as originally surmised by Faulds and 

others (2002a).

Sympathetic movements during this extensional faulting 

appear to have reactivated the mineralized structures and contributed to their crushed and disrupted state. Callaghan (1939), 

although not cognizant of the rotation, emphasized the brecciation of the veins by post-mineral movements, particularly in 

the mines in the southern part of the district.

Callaghan (1939) noted a difference in mineralization 

style between the deposits north and south of State Highway 

164. The mines south of the highway, particularly the Quartette, Cyrus Noble, Good Hope, and Duplex, are characterized 

by significant amounts of the base metals copper, lead, and 

zinc, whereas the mines to the north of the highway did not 

produce important amounts of these metals. The mines in the 

south were the main source of the base-metal oxide minerals 

described above.

Hydrothermal Alteration

Three principal types of hydrothermal alteration are 

present in the district—(1) propylitic alteration and hornfels 

formation adjacent to the Searchlight pluton, (2) hydrothermal 

alteration peripheral to the gold-bearing veins, and (3) supergene alteration and oxidation.

Within a few hundred meters of the contact with the 

Searchlight pluton, the volcanic rocks have been recrystallized 

into a rock that can be termed hornfels. The original minerals in the andesite and dacite have largely been converted to 

quartz, epidote, magnetite, biotite, and chlorite, and much of 

the original texture of the rock has been destroyed. Callaghan 

(1939) has an extended discussion of this alteration type.

Superimposed on this metamorphic imprint is a hydrothermal alteration assemblage associated with the gold-bearing 

veins. Although Callaghan (1939) did not map hydrothermal 

alteration zones in detail, he noted that alteration was negligible in the southern part of the district, specifically at the 

Quartette Mine, whereas adularia was a significant alteration 

mineral in the northern mines. He also stated that propylitic 

alteration (chlorite + albite + epidote + pyrite) is found in a 

few places in the north half but is difficult to separate megascopically from the metamorphism adjacent to the pluton. He 

also noted that pyrite is unusually rare in the altered rocks of 

the district.

We studied the distribution of hydrothermally altered 

rock with ASTER (Advanced Spaceborne Thermal Emission 

and Reflectance), which is a 14-band multispectral satellite imaging system (Rowan and others, 2003). Figure 29 

shows an image of the district that shows the areas containing 

alteration minerals that can be detected with ASTER. The 

areas enclosed with dashed lines are interpreted to be hydrothermally altered rock, and samples from these areas were 

analyzed by X-ray diffraction (XRD) and portable infrared 

mineral analysis (PIMA) to confirm the nature of the alteration. Table 2 summarizes the spectral characteristics of each of 

the areas designated on figure 29, and tabulates their alteration 

characteristics. Petrographic studies are continuing in order to 

characterize the various alteration zones in more detail. The 

figure clearly shows abundant hydrothermal alteration in the 

north half of the main part of the district, and almost none in 

the southern part.

The bright pink colors indicate the areas characterized 

by alunite-bearing assemblages. This large area of quartzalunite alteration was previously unreported in the geologic 

literature and occurs in an area as much as 1.5 km wide and 

3 km long in the western part of the Searchlight district, as 

well as in a smaller area to the east of Searchlight. On the 

basis of XRD and PIMA, this alteration is characterized by 

the presence of alunite and kaolinite-group clay minerals 

(including dickite), along with locally strong quartz flooding 

and locally abundant topaz and pyrophyllite. The altered rock 

is typified by bleached white to orange and red colors, with 

the latter colors due to the presence of abundant jarosite and 

hematite. Alunite separates prepared from three samples have 

sulfur isotope (34S) ratios of 14.6 to 15.9 per mil, which 

is consistent with a magmatic-hydrothermal or magmatic 

steam origin. These alunites will be dated using 40Ar/39Ar to 

determine the age relationship between the high-sulfidation 

quartz-alunite alteration and low-sulfidation quartz-adularia 

mineralization to the east.

The turquoise color indicates the style of alteration 

characteristic of the productive veins in the north half of the 

main part of the district. For the purposes of this assessment, 

areas 1 and 2 are particularly significant, as they show that the 

alteration type that is characteristic of productive veins has 

been repeated by normal faulting and is exposed to the west 

of the alunite-bearing rhyolite hills, within the Piute-Eldorado 

Tortoise ACEC (fig. 30).
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B29

Figure 29. Advanced Spaceborne Thermal Emission and Reflectance (ASTER) image of the Searchlight district using bands 7 (red), 5 

(green), and 4 (blue). The numbered areas outlined in yellow dashed lines are discrete hydrothermally altered areas described in table 

2. Heavy gray dashed lines are structural block boundaries—see figures 18 and 21. Medium-weight red lines are trace of productive 

veins, modified from the map of Callaghan (1939). Yellow overprint indicates areas covered by Quaternary alluvium. Fuschia line is the 

boundary of the Piute-Eldorado Tortoise Area of Critical Environmental Concern. Image covers same area as figures 21 and 22.

3

9

7

2

22

10

5

9

3

12

13

3 1

3

14

15

6

11

4

8

8

114°52'30"W

35°30'0"N

01234 0.5

Kilometers
B30 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Geochemical Zoning

As noted above, we and others have drawn a contrast 

between the northern and southern parts of the Searchlight 

district, based on vein mineralogy and the nature and intensity 

Area Description Spectral Character

1 Two samples characterized by PIMA and XRD to have smectite and illite

Strong adsorption in bands 6, 8, and 9

2 Two samples characterized by PIMA and XRD to have smectite and illiteStrong adsorption in band 8; moderate adsorption in 

band 6

3 Multiple samples characterized by PIMA and XRD to have 

smectite and illite

Strong adsorption in band 8; moderate adsorption in 

bands 6 and 9

4 No samples; spectral similarity to area 9 suggests advanced 

argillic alteration with alunite

Strong adsorption in bands 5 and 6

5 Two samples characterized by PIMA and XRD to have smectite and illiteStrong adsorption in bands 6, 8, and 9

6 No samples; possibly mostly smectite Moderately strong adsorption in bands 7 and 8

7 No samples; possibly mostly smectite Strong adsorption in bands 7 and 8

8 No samples; possibly advanced argillic alteration without 

alunite

Strong adsorption in band 5; moderate adsorption in 

band 6

9 Multiple samples characterized by PIMA and XRD to contain 

abundant alunite

Strong adsorption in bands 5, 6, and 8

10 No samples; spectral similarity to area 9 suggests advanced 

argillic alteration with alunite

Strong adsorption in bands 6 and 8; moderately 

strong adsorption in band 5

11 No samples; spectrum is unlike any others Strong adsorption in bands 6; moderately strong 

adsorption in bands 7 and 8

12 No samples; spectrum is unlike any others and may represent 

unaltered rhyolite (?)

Moderately strong adsorption in band 9; moderate 

adsorption in band 8

13 No samples; spectrum is unlike any others and may represent 

unaltered rhyolite (?)

Moderately strong adsorption in band 9; moderate 

adsorption in band 8

14 No samples; spectrum is unlike any others and may represent 

unaltered rhyolite (?)

Moderately strong adsorption in band 9; moderate 

adsorption in band 8

Table 2. Description of hydrothermally altered areas mapped in figure 25.

[PIMA is portable infrared mineral analysis; XRD is X-ray diffraction.]

Figure 30. View of alunite-bearing rhyolite hills from the west. Altered rocks of lower intermediatecomposition unit of volcanics of Highland Range in foreground.

of associated hydrothermal alteration. The geochemistry of 

altered and mineralized rocks reflects these and other distinctions. Table 3 records some simple statistics for geographic 

subgroups of mineralized samples from the district. Figure 31 

shows the location of these subgroups.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B31

Ag Au Cu Pb Zn Bi Cd Mo As Sb SO3 Cu+Pb+Zn Au/Au+Ag

Bill Gays structural block (n=1)

<0.5 0.01 8 21 10 <0.05 <0.1 1.6 5.0 0.3 1.70 39 ND

Fourth of July structural block (n=6)

Median 23 3.3 420 23 63 0.14 1.30 7.6 9.5 3.1 0.07 466 0.22

Mean 17.3 5.4 650 340 130 0.14 1.30 14.3 16.2 5.4 0.17 1,110 0.19

SD 14.4 7.1 740 490 200 0.08 1.27 20 17.8 6.0 0.27 1,310 0.17

Max 28 15 1,730 1070 540 0.25 2.2 51 52 14.3 0.72 2900 0.35

Min 1 0.01 20 13 4 0.04 0.40 0.3 5 0.5 0.02 108 0.01

Pinto structural block (n=3)

Median NA 0.00 23 27 49 0.83 NA 2.0 15 1.8 0.17 96 NA

Mean NA 0.01 24 27 47 0.83 NA 1.9 15.3 1.8 0.36 98 NA

SD NA 0.00 5 3 16 0.51 NA 0.6 3.5 0.2 0.41 12.5 NA

Max NA 0.01 30 30 62 1.19 NA 2.4 19 2.0 0.82 112 NA

Min NA 0 20 23 31 0.47 NA 1.3 1 1.7 0.07 88 NA

Northern Searchlight district (n=36)

Median 4.2 0.45 61 85 123 0.13 0.58 1.6 10 2.3 0.10 300 0.28

Mean 15.1 12.3 104 250 340 0.54 2.8 3.0 11 3.6 0.49 690 0.31

SD 30 25 128 300 430 0.89 5.6 3.8 7 4.7 0.74 750 0.26

Max 150 95 570 950 1,560 2.9 26 16.4 29 23.5 2.3 2,700 0.79

Min 1 0 4 6 4 0.02 0.10 0.3 2 0.1 0.01 31 0.00

Searchlight pluton (n=7)

Median 5 0.02 48 80 105 0.53 0.50 1.1 11 4 0.02 230 NA

Mean 15.3 0.07 320 2,700 430 4.4 0.70 7.6 12.9 6.5 0.05 3,400 NA

SD 21 0.13 630 6,700 690 9.1 0.72 11.3 6.7 6.8 0.05 7,400 NA

Max 39 0.34 1,740 17,800 1,950 25 1.90 30 23 20 0.15 20,000 0.01

Min 2 0 1 11 36 0.05 0.10 0.5 3 1.1 0.01 48 NA

Rhyolite of Searchlight district (n=22)

Median NA 0.00 26 30 9 0.53 0.15 3.4 9.5 0.8 5.4 77 NA

Mean NA 0.01 29 33 33 1.54 0.20 6.2 18 1.2 7.4 92 NA

SD NA 0.01 21 23 40 2.9 0.14 9.6 23 1.3 7.4 60 NA

Max NA 0.02 80 110 112 13.2 0.40 47 93 6.9 24 230 NA

Min NA 0.00 5 2 1 0.04 0.10 0.8 3 0.4 0.12 17 NA

Southern Searchlight district (n=13)

Median 6 0.18 670 290 161 2.6 4 11.6 8.5 1.0 0.62 1,260 0.02

Mean 53 0.43 8,300 11,400 1,320 24 5.9 28 8.5 7.0 3.0 21,000 0.06

SD 63 0.60 19,900 24,000 2,600 39 6.7 37 4.7 15.8 3.9 32,000 0.08

Max 150 1.63 73,000 79,000 8,400 119 20 119 15.0 57 9.8 83,000 0.18

Min 0.90 0.00 13 12 14 0.05 0.50 1.1 1.7 0.2 0.02 44 0.00

Western Searchlight district (n=16)

Median 2.0 0 46 23 68 0.24 0.20 2.5 14.0 1.2 0.15 176 NA

Mean 3.3 0.02 1,310 25 69 0.73 0.19 3.6 18.9 2.5 0.70 1,400 NA

SD 3.2 0.06 4,900 10 58 0.97 0.08 3.4 16.9 4.3 1.57 4,900 NA

Max 7.0 0.22 19,700 45 179 3.5 0.30 12.5 59 18.3 6.3 19,800 NA

Min 1.00 0.00 5 8 1 0.04 0.10 0.6 3 0.8 0.01 19.5 NA

Table 3. Summary statistics for mineralized samples from main part of Searchlight district.

[All data in parts per million (ppm). Complete data is in Ludington and others (2005). All values rounded to 2 (or 3) significant figures.]
B32 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

The data from the northern Searchlight district are dominated by a number of gold-rich vein samples from the Blossom 

Mine. These samples have the highest gold and some of the 

highest silver values in the district but relatively low amounts of 

the minor elements molybdenum and bismuth. The Au:Au+Ag 

ratio in strongly mineralized samples ranges from about 0.4 to 

0.8. The combined base-metal content (Cu+Pb+Zn) is also low, 

generally less than 2,000 ppm. Samples in this area also contain 

Searchlight

west

 Fourth

 of 

July

Searchlight

 rhyolite

Searchlight

 north

Searchlight

 south

Pinto

 Searchlight

pluton

Searchlight

 pluton

114°52'30"W

35°30'0"N

01234 0.5

Kilometers

Figure 31. Location of samples summarized in table 3 and used to construct figure 32.

somewhat more potassium than the less-altered samples in the 

southern part of the district, probably reflecting the adularia 

present in many of the samples.

The southern Searchlight district data include only 13 

samples, and 7 of them are from the Quartette Mine and its 

eastern extension, the Rambler. These samples are characterized by higher silver values and much higher base-metal 

contents than samples from the other parts of the district. The 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B33

combined base-metal contents of many of the mine samples 

is in excess of 2 percent. They also contain distinctly more 

bismuth, molybdenum, and cadmium, and they are also modestly enriched in arsenic, antimony, tellurium, and tungsten. 

The Au:Au+Ag ratio in strongly mineralized samples is much 

lower than in the north, ranging up to only about 0.2. Four 

samples from the western part of this area have between 4 

and 9 percent SO3

, and apparently represent the southernmost 

exposures of the alunite-altered rocks to the north. Three of 

these rocks were determined to contain alunite by PIMA.

The data for rhyolites show much different patterns 

than either of the areas related to the productive veins. These 

samples come from the large area of alunite alteration west of 

the northern Searchlight district. Silver was not detected in any 

of the samples, and gold does not exceed 0.02 ppm. Combined 

base-metal values are almost all less than 200 ppm. The sulfate 

contents are, however, quite high, with many samples containg 

more than 10 percent SO3. The presence of abundant alunite 

also results in generally elevated K2

O contents. Phosphorous 

is elevated in these rocks, being generally higher than 1,000 

ppm, and iron is locally high due to the presence of hematite, 

limonite, and jarosite. Rubidium was strongly depleted during 

the hydrothermal alteration.

The western Searchlight district data are important 

because they demonstrate that alteration and mineralization 

typical of the productive part of the district are found to the 

west of the alunite area. It is possible that these rocks are in a 

lower, as-yet undelineated structural block. Two samples have 

2 ppm silver or more, and two samples have more than 0.01 

ppm gold. Except for one sample, all these rocks have low 

base metals and trace metals.

The data for samples from the Searchlight pluton and 

related dike rocks are quite varied, although most have elevated gold contents greater than 0.02 ppm. Two samples have 

high total base metals, and several have elevated trace metals, 

with bismuth contents as high as 25 ppm and molybdenum as 

high as 30 ppm.

The data for samples from the Fourth of July structural 

block are highlighted by two samples from the Chief of 

the Hills Mine that are quartz-rich vein material with very 

high gold contents and relatively high Au:Au+Ag. They are 

geochemically quite similar to the samples from the Blossom 

Mine, except that they have high molybdenum contents (13 

and 51 ppm) and moderate bismuth contents (about 0.2 ppm).

The data for the three samples from the Pinto structural 

block (all taken near the New Era Mines) are only weakly 

mineralized, with both precious and base metal contents being 

relatively low. One sample does contain nearly 1 percent SO3

. 

These samples are of hydrothermally altered material but were 

not taken from mine dumps.

The single sample from the Bill Gays structural block is 

from an oxidized rhyolite breccia. It appears to be significantly 

enriched only in sulfur.

A study by Al-Shaieb (1969) yields additional information about the differing alteration and mineralization styles 

in various parts of the district. The study was designed to 

examine the distribution of ore and trace elements in the wall 

rocks of veins from the district, but because the samples were 

collected from underground exposures that are no longer 

accessible, the research provides important information 

about the geochemistry of the veins. Traverses were made, 

collecting samples from the veins and at regular intervals 

away from the veins. Samples were analyzed for gold, silver, 

copper, lead, and zinc.

The Al-Shaieb samples were collected from underground 

at both the Chief of the Hills and Duplex Mines. The samples 

from the vein at Chief of the Hills had compositions closely 

similar to the ones we collected at the surface, with total 

base-metal contents of a few hundred ppm, gold contents of 

10 to 30 ppm, and Au:Au+Ag of 0.3 to 0.5. The Duplex Mine 

samples had total base-metal contents of 1 to 5 percent, gold 

contents of 1 to 10 ppm, and Au:Au+Ag of 0.1 to 0.4, compositions similar to those we report for the Quartette-Rambler 

vein system.

In summary, as shown in figure 32, the veins in the northern part of the Searchlight district have low base metals, high 

gold contents, and high Au:Au+Ag; their wall rocks are generally altered to adularia and, farther from the vein, to smectiteillite assemblages. The veins in the southern part of the district 

have high base metals, moderate gold contents, and low to 

moderate Au:Au+Ag; their wall rocks are not strongly altered. 

Our geochemical results generally confirm the descriptions 

made by Callaghan (1939), except for the low gold contents 

and metal ratios of our Quartette and Rambler samples. Much 

of the ore mined from the Quartette had extremely high gold 

contents, and Callaghan (1939) reports that “the product of the 

Quartette Mine was highly variable but mostly contained three 

times as much gold as silver by weight.”

A possible implication of this contrast between the two 

areas might be that there are several hydrothermal systems 

present at Searchlight, each of a different age and mineralization style. Based on limited evidence, Callaghan (1939) 

discarded this idea, saying that “there appears to be a gradual 

transition from one to the other.” More detailed mapping 

and radiometric dating will be necessary to determine if a 

single hydrothermal system was responsible for mineralization in the Searchlight district. If the transition from south to 

north represents simple zoning, it is decidedly eccentric with 

respect to the upper contact of the Searchlight pluton. It is 

possible that the northern and southern parts of the district 

are also in two structural blocks. It is also possible that the 

deposits in the northern part of the district may be more 

intensely weathered. This could account for the enhanced 

Au:Au+Ag, but the absence of visible supergene minerals 

and the presence of unoxidized pyrite south of the Blossom 

Mine argue against this.

The north-to-south variations discussed above are important because they are related to the metallogeny of gold-bearing veins. More important to understanding the hydrothermal 

system as a whole is the east-to-west (originally bottom-totop) zoning. In the uppermost part of the Searchlight pluton 

and in the first few hundred meters above the pluton, alteration 
B34 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 32. Plot showing contrast in metallogenic character of samples from different areas of the Searchlight district. Size of symbols 

is proportional to the logarithm of the gold content of samples, in parts per billion.

Searchlight district, Clark County, Nevada

0.00

0.20

0.40

0.60

0.80

1.00

10 100 1,000 10,000 100,000

Cu+Pb+Zn (ppm)

Au/Au+Ag

Searchlight north

Fourth of July

Searchlight south

Searchlight pluton

Searchlight west

is primarily to illite and other clay minerals, and sulfur-bearing 

minerals are not abundant, although small amounts of jarosite 

are common. About 700 to 1,500 m higher in the section, 

and coinciding with the appearance of rhyolitic lithologies, 

the alteration assemblage changes abruptly to one characterized by alunite, and sulfur contents of these rocks are several 

percent (Ludington and others, 2005). This upper alteration 

zone is characteristic of high-sulfidation epithermal deposits, 

but the scarcity of pyrite in the lower clay-illite zone is not. 

Overall, the distribution and amount of hydrothermal alteration is similar to that in large pluton-related mineral deposits 

such as porphyry copper deposits, but the specific mineral 

assemblages present at Searchlight do not correspond well to 

any accepted deposit models. Nevertheless, it seems clear that 

the gold-bearing veins are the result or hydrothermal fluids 

derived from the cooling Searchlight pluton.

Our interpretation of the original geometry of and 

zoning patterns in the Searchlight district, while critical to 

an assessment of the possibilities for new discoveries, is 

far from settled. Additional work is underway that should 

lead to a great improvement in our picture of this enigmatic 

mineral district.

Newberry District

The deposits grouped into the Newberry district are probably unrelated. Most of them can be classified as polymetallic 

vein deposits, although quartz veins do not occur at all sites. 

They are structurally controlled, primarily by steep west-trending shear zones and faults. The absolute age of the deposits is 

unknown, as most of them cut only Proterozoic rocks, but we 

presume that they are of Miocene age and generally contemporaneous with the deposits in the Searchlight district. The 

hydrothermal alteration assemblage associated with the deposits is most commonly quartz, specular hematite, and illite. In 

at least 2 of the locations, the alteration and mineralization 

persists over strike lengths of several kilometers. Viewed in 

the context of the structural tilting that characterizes this area, 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B35

the suggestion is that some of these structures exhibit mineralized rock over a vertical range of at least 3 km.

The Rare Metals Corporation mill (fig. 33) was reportedly located on the floor of Piute Valley about 12 km southeast 

of Searchlight (Nevada Division of Mine Inspection, 1990), 

but there is neither any trace of any activity at the site, nor the 

remains of any road construction near this area.

Figure 33. Mineral deposits in and near the Piute-Eldorado Areas of Critical Environmental Concern (ACECs; boundaries in pink) that 

are assigned to the Newberry mining district. Geology compiled for this report: pCu—undivided Proterozoic rocks; Kwr—Cretaceous

granite of White Rock Wash pluton; Tv1—Miocene intermediate-composition volcanic rocks; Tv3—Miocene mafic volcanic rocks.

Goldenrod Mine

The Goldenrod Mine is located at the point where Nellis Wash issues from the Eldorado Mountains, and it is in an 

inholding of private land within the Piute-Eldorado Tortoise 

ACEC (fig. 33). Longwell and others (1965) mislocated this 

mine, putting it at the site of the Roman Mine (see below). 

Qa

Tsm

Qa

pCu

Tv3

Kwr

Tv1

pCu

pCu

pCu

pCu

Jetco Mill

Roman Mine

Empire Mine

Camp

Thurman

area

Stewart

mine

Juniper

mine

Yarmouth

mine

Jackdaw group,

Jetco claims

New Deal mine

Goldenrod Mine

Cottonwood mine

White Rock mine

Rare Metals Corp. Mill

Piute-Eldorado

Tortoise

ACEC

114°45'0"W

35°15'0"N

35°22'30"N

01234 0.5

Kilometers
B36 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Vanderburg (1937) described two shafts and stated that a “small 

amount” of ore had been mined and treated locally. He also 

described a near-vertical quartz vein that cuts Proterozoic granite, strikes N60E, and is about 10 to 40 cm wide. We did not 

see this vein, but we sampled some 1-cm wide quartz veins that 

appeared to have oxidized casts of former sulfide minerals. This 

sample (5-061003; Ludington and others, 2005) did not yield 

anomalous values of precious or base metals. Another small private inholding is about 2 km southwest of the Goldenrod Mine, 

but we saw no evidence of mineralized or altered rock there.

Camp Thurman

The area called Camp Thurman on topographic maps 

is shown on 1:24,000-scale topographic maps to contain the 

workings of the Potential Mine (fig. 33). Claims in this area 

were designated by Longwell and others (1965) to be the Jackdaw Group of claims, which were described by Vanderburg 

(1937). However, Vanderburg clearly stated that the Jackdaw 

Group was formerly known as the Old Roman Mine, which 

is likely to be the Roman Mine shown 2.5 km to the south on 

topographic maps. Thus, the only description of mines at this 

location seems to be that of Lawrence (1963), who describes 

the New Deal (or Polyanna) Mine and the Yarmouth Mine 

at this location. The mines were reportedly located 18 miles 

southeast of Searchlight and 2 miles northeast of Newberry 

Peak in sec. 21(?), T30S, R65E. This questionable legal location puts the property in the Camp Thurman area; however, the 

other location data suggest that it might be a few kilometers 

southwest of Camp Thurman. The workings at Camp Thurman 

consist of three shafts that were driven down a near vertical 

vein that strikes N65E and has been segmented by displacement along vertical faults that strike N25W. The deposits are 

described as being last worked in 1933, for silver, lead, antimony, and probably zinc. The antimony is described as occurring in tetrahedrite. We took two samples at this site, AP-047 

(a 65-cm chip sample) and 4-050304 (Ludington and others, 

2005). AP-047 contained only weakly anomalous values of 

precious or base metals, but 4-050304 contained 9.1 ppm gold, 

3 ppm silver, and about 1,700 ppm lead (table 4). We also visited the Empire Mine, about 1 km to the east, but saw no signs 

of significant mineralized rock.

On ASTER images, there is a linear feature that extends 

about N70W from the Camp Thurman area to the range front 

in Piute Valley (fig. 34). The signature is similar to the illiteand smectite-bearing rocks in the Searchlight district, and this 

alteration style was confirmed by PIMA analysis. The country 

rock here is Proterozoic gneiss, and there is abundant limonite. Three samples were taken within this area (5-103002, 

5-103003, 5-103004; Ludington and others, 2005). Sample 

5-103003 contains visible pyrite and is weakly anomalous in 

barium, lithium, molybdenum, and zinc, whereas 5-103004, 

which contains small quartz-specular hematite veins, is mildly 

anomalous in phosphorous, tin, and yttrium. All of these 

samples have low gold and silver contents; 5-103004 contains 

3 ppb (parts per billion) palladium.

Roman Mine Area

About 2.5 km to the south of Camp Thurman, but outside 

the Piute-Eldorado Tortoise ACEC, the Roman Mine (also 

known as the Jetco claims and the Jackdaw group) is presently 

being worked for decorative stone instead of precious metals. The Jackdaw group was described by Vanderburg (1937), 

who reported a quartz vein with malachite and azurite. At that 

time, the mine was being worked on a small scale and recent 

production was estimated at $15,000.

Samples from the Roman Mine area have elevated gold, 

as well as the highest silver, copper, and base-metal values in 

the Newberry district. A quartz vein sample with malachite 

and azurite from the Roman Mine was reported by Smith and 

Tingley (1983) to contain high Au, Ag, Cu, Pb, Zn, As, and Sb 

(sample 1342, table 4). We did not sample this site.

The Roman Mine is near the eastern part of another area 

of hydrothermal alteration inferred from ASTER imagery (fig. 

34) that extends to the west and northwest from the mine area 

to the range front, inside the Piute-Eldorado Tortoise ACEC.

About one kilometer south and southwest of the Roman 

Mine are unnamed prospects shown as a shaft and tunnel on 

the 1:24,000-scale topographic map. Smith and Tingley (1983) 

collected three samples in this area (samples 1338, 1339, and 

1341, table 4), and reported values as high as 11 ppm gold, 

with high silver, copper, lead, and zinc. The shaft is about 300 

m east of the altered area.

Cottonwood Mine Area

Longwell and others (1965) described the Cottonwood 

Mine as being located in section 18 of T31S, R65E, and as 

being hosted by Proterozoic gneisses. No Proterozoic rocks 

crop out in section 18, and there are no workings at the 

location indicated. On the basis of the geologic description, 

we believe the area referred to is in section 9, where Smith 

(1982a) described the Christmas Tree Pass workings as exploring a steeply dipping west-trending shear zone in Proterozoic 

gneiss with small quartz veins and oxidized sulfide minerals. The Yellow Stone Mine is shown on the 1:24,000 scale 

topographic map about a kilometer to the northwest. Samples 

from the Cottonwood Mine area and about 2 km to the west 

contain 2.5 and 3.4 ppm gold, respectively, with high silver, 

molybdenum, and lead (Smith and Tingley, 1983; table 4). 

Like the Roman Mine area, this area is also outside the ACEC 

boundary (fig. 33).

Stewart Mine

This mine is referred to in the literature only by a listing in Nevada Division of Mine Inspection (1977), where it is 

reported to have been a silver deposit, with minor lead. A small 

pit in the uppermost part of the Spirit Mountain pluton exposes 

granite that is pervasively stained with manganese oxides in an 

area about 100 m across. Our sample of this material (4-030703, 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B37

Sample no. Location Ag As Au Bi Cu Mo Pb Sb Zn Description

5-061003 Goldenrod Mine <1 1 0.00 0.0 4 1 6 0.3 13 Quartz vein

AP-047 Camp Thurman <1 2 0.03 0.3 30 1 68 0.3 19 Quartz vein, 65-cm chip

AP-048 Camp Thurman 1 3 <.01 0.1 24 0 66 0.7 44 Pegmatite, grab

1343 Camp Thurman 2 <10 0.30 <10 70 <5 100 4.0 20 Quartz vein with Fe-oxide 

after pyrite and Mn-oxide

4-050304 Camp Thurman 3 2 9.09 0.3 134 16 1732 0.5 41 Quartz vein with pyrite

5-103002 West of Camp 

Thurman

<1 1 0.00 0.0 4 0 27 0.4 14 Quartz veins

5-103003 West of Camp 

Thurman

<1 2 0.00 0.1 8 15 22 0.8 161 Quartz veins

5-103004 West of Camp 

Thurman

<1 2 0.01 0.2 8 2 10 0.2 54 quartz-hematite vein

1342 Roman Mine 200 110 0.90 <10 1000 <5 5000 840 250 Quartz vein with Cu-oxide

1338 South of Roman 

Mine

10 <10 0.55 <10 15000 10 1000 5.0 600 Sheared intrusive with FeMn-oxide and Cu-oxide

1341 South of Roman 

Mine

200 <10 11.0 15.0 5000 <5 15000 3.0 >2000 Quartz vein with py, cpy, ga, 

and Cu-oxide

1339 South of Roman 

Mine

<1 <10 <.05 <10 200 <5 70 2.0 10 Quartz vein with sulfides 

and Mn-oxide

1336 Cottonwood Mine 

area

15 <10 2.50 <10 30 5 500 4.0 40 Quartz vein and sheared 

rock with pyrite and 

chalcopyrite

1337 West of Cottonwood Mine3 <10 3.40 <10 20 500 70 4.0 35 Silicic rock with pyrite and 

quartz vein

1340 Yellow Stone Mine <1 <10 <.05 <10 10 <5 50 nd nd Quartz vein and sheared 

rock with limonite

4-030703 Stewart Mine 2 <1 0.12 2.6 322 5 2160 0.1 9990 Granite with Mn-oxide

5-050703 North of Juniper 

Mine

<1 1 0.01 0.1 31 3 11 0.5 35 Quartz vein stockwork

AP-049 Juniper Mine East 

shaft

<1 <1 1.07 <.04 14 1 18 0.2 35 Quartz vein, grab

AP-050 Juniper Mine ore 

pile

<1 <1 0.18 0.4 31 47 32 0.3 94 Quartz vein in altered 

gneiss, ore pile grab

4-030704 Juniper Mine <1 3 0.01 0.5 1 1 134 1.0 136 Granite with Fe-oxide

1335A Juniper Mine 70 <10 60.0 <10 7 <5 20 3.0 45 Quartz vein with oxidized 

pyrite

1335B Juniper Mine 1 <10 0.20 <10 200 <5 200 3.0 60 Siliceous dike with oxidized 

pyrite

4-030701 Prospect southeast 

of Juniper Mine

<1 1 0.28 0.1 7 2 136 0.3 32 Aplite with Fe-oxide

1334 Superfluous claims 1 <10 10.0 <10 70 <5 200 3.0 80 Quartz vein and sheared 

rock with specular hematite, Mn-oxide

AP-051 Gibraltar claims 1 25 0.92 0.2 42 14 166 5.9 191 Hematized shear zone in 

granite, 1-m chip

1333 Gibraltar claims 7 90 6.60 <10 30 70 1000 4.0 130 Siliceous dike with Fe-Mnoxide

4-033103 Unknown 2 14 0.03 3.0 73 50 20 0.2 6 Quartz veins

Table 4. Precious- and base-metal contents of mineralized samples from the Newberry district.

[Analyses of samples 1333 through 1343 are from Smith and Tingley, 1983; Ag, Ba, Bi, Cu, Mo, and Pb by semi-quantitative emission spectroscopy; As, Au, 

Sb, and Zn by atomic absorption. Other analyses are from Ludington and others, 2005. All analytical data are in ppm, nd = no data.]

table 4) contains high Ag, Au, Bi, Cu, Pb, and Zn, as well as 

elevated beryllium, cadmium, and nearly 6 percent manganese 

(Ludington and others, 2005). The style of mineralization is 

enigmatic; no structures were observed, and the association of 

beryllium with precious metals is uncommon.

Juniper Mine

The Juniper Mine is about 12 km south of Camp Thurman on the west flank of the Newberry Mountains (fig. 33), 

and consists of two shafts along a west-trending structure that 
B38 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

apparently dips steeply north. The west shaft is 30 m deep or 

more. Some minor veins with similar orientations are exposed 

in shallow surface diggings between the shafts. The veins cut 

Proterozoic granite and fine-grained metamorphic rock. Grab 

samples of loose vein material contain as much as 1 ppm 

Au (sample AP-049; Ludington and others, 2005). A sample 

collected by Smith and Tingley (1983) from the dump of the 

Juniper Mine contains 60 ppm gold and 70 ppm silver, and a 

second sample has moderately elevated gold, copper, and lead 

(samples 1335A and 1335B, table 4).

Figure 34. Map showing location of hydrothermally altered rocks identified by Advanced Spaceborne Thermal Emission and 

Reflectance (ASTER) imagery near Camp Thurman and Roman Mine areas (red cross hatch). Analyzed samples shown by 

yellow circles.

Roman Mine area,

Jackdaw and Jetco

claim groups

Empire

Mine

Yarmouth mine

New Deal Mine

Potential

Mine

5-103004

5-103003 5-103002

5-061005

4-050304

4-032903

Camp Thurman

Piute Valley

114°45'0"W

35°17'30"N

0 0.5 1 1.5 2 0.25

Kilometers

White Rock Mine

The White Rock Mine is shown on both 1:100,000 and 

1:24,000-scale topographic maps, about 2 km southeast of 

the Camp Thurman area, outside the Piute-Eldorado Tortoise 

ACEC, and inside Lake Mead National Recreation Area. The 

USGS’s MRDS database (U.S. Geological Survey, undated) 

lists the major commodities as copper, gold, and silver. This 

database also gives Volborth (1973) as a reference, but there 

is no mention of the mine in that report. It seems likely that 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B39

this is the site described by Vanderburg (1937) as the Homestake Group, 9 miles north of Hiko Springs. Vanderburg 

reported that there were 3 east-west veins, the largest being 

as wide as 6 m, dipping about 50 degrees to the north, and 

that the major commodities were gold, with small amounts of 

silver (no mention of copper). He also reported that the mine 

had been worked intermittently from 1910 until the middle 

1930s. We did not visit the White Rock Mine.

Figure 35. Map showing location of Superfluous and Gibraltar claims in the Chiquita Hills. Analyzed samples shown by 

yellow circles. Geology compiled and mapped for this study: pCu—undifferentiated Proterozoic metamorphic and igneous 

rocks; Ti—porphyritic granite dikes; Qa—Quaternary alluvium.

Superfluous and Gibraltar Claims

The Superfouous and Gibraltar claims are in the Chiquita 

Hills, immediately east of U.S. Highway 95 at the junction with 

Nevada State Highway 163 (fig. 35). Both sites are characterized by gold-bearing vein deposits similar to others in the Newberry district, and both contain shear zones in Proterozoic gneiss 

with hematite. They are briefly described by Smith (1982b,c).

Qa

Qa

pCu

pCu

Ti

pCu

pCu

Gibraltar claims

Superfluous No. 1 claim

AP-051

4-101204

Piute-Eldorado

Tortoise

ACEC

114°50'0"W

35°10'0"N

0 0.5 1 1.5 2 0.25

Kilometers
B40 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

The Superfluous claims may have been originally prospected for uranium (Garside, 1973), but Smith and Tingley 

(1983) reported a sample with 10 ppm gold and moderately 

elevated silver and lead (sample 1334, table 4) from a steeply 

northeast-dipping, quartz-cemented shear zone with calcite, 

sulfides, and hematite.

The Gibraltar claims were staked just inside California, 

but workings extend into Nevada. In Nevada, the property 

is marked by several closely spaced shafts according to the 

1:24,000-scale topographic map. Our examination disclosed 

an open pit about 20 m long that exposes old adits along a 

fault in Proterozoic gneiss and granite that strikes N70E. 

In the pit, the fault dips to the north about 45 to 75 degrees 

(fig. 36), but about 50 m to the west, the fault dips only 25 

degrees to the north. The granite is cut by a fine-grained rhyolite dike that dips gently to the north, and both the granite 

and rhyolite contain abundant hematite adjacent to the fault. 

Sample AP-051, a 1-m chip across the sheared and altered 

rock along the fault, contains about 1 ppm each of gold and 

silver, along with slightly elevated molybdenum, lead, and 

zinc (sample AP-051, table 4; Ludington and others, 2005). 

A sample reported in Smith and Tingley (1983) from the 

same area has 6.6 ppm gold, along with high lead, zinc, 

and molybdenum (table 4). In addition to the workings, the 

Gibraltar site has the remains of a small but fairly modern 

mill in a vigorous state of disrepair (fig. 37).

To the north, the Superfluous area exposes mineralized 

rock of similar appearance but containing carbonate, specular hematite, and drusy quartz. We took no samples here, but 

Smith and Tingley (1983) reported a sample from this area 

with 10 ppm gold and moderately high silver and lead (sample 

1334, table 4).

Figure 36. Small open-pit mine with old underground working 

along north-dipping fault. Sample AP-051 was collected from the 

shattered zone below the hammer.

Figure 37. Remains of a mill near the site of sample AP-051. The 

small blue shaking table at right suggests that gravity recovery of 

gold was planned. The mill appears abandoned, but the presence 

of modern excavation equipment indicates recent activity.

Crescent District

The Crescent district was originally exploited for 

turquoise, but gold was discovered in 1905, and there was 

considerable activity until 1942. There has been only limited geologic study of the area, and, for many of the deposits 

that are briefly described in the literature, the locations are 

uncertain. The country rock in the region is primarily Proterozoic schist, gneiss, and meta-igneous rocks (Longwell 

and others, 1965; Miller and Wooden, 1993). The east half of 

the district is dominated by the north end of a large pluton of 

Proterozoic biotite leucocratic granite with an age of about 

1672 Ma (Miller and Wooden, 1993). A few small plutons and 

dikes of Cretaceous granodiorite occur. One large altered area 

that encompasses Crescent Peak was explored as a porphyry 

copper prospect during the 1960s, and it probably is related 

to the Cretaceous igneous rocks (Archbold and Santos, 1962). 

Miocene volcanic rocks are found at the southwest end of the 

district, primarily in California, and at the extreme east end 

of the district, where the volcanic rocks lie unconformably on 

the Proterozoic gneisses. Miocene structure, which is probably 

key to understanding the geology of the mineral deposits, is 

poorly understood in the Crescent district.

There are many mines in the district, and most of them 

are outside the Piute-Eldorado Tortoise and Crescent Townsite 

ACECs. We describe only some of the principal ones and the 

ones we visited and sampled (see fig. 38, table 5). At least 

four types of mineral deposit exist in the district: (1) porphyry 

copper deposit (Crescent Peak), (2) metal-bearing fluorspar 

veins (Blue Crystal), (3) gold-rich polymetallic veins (Peyton, 

Sundog, Double Standard, Nippeno, Cumberland), and (4) 

detachment-fault-related deposits (Silver Bell, Big Tiger-Rest, 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B41

Figure 38. Mines and prospects in the Crescent district. Yellow circles are analyzed samples listed in table 5. Geology is 

modified from Stewart and Carlson (1978): pCu—Proterozoic metamorphic and igneous rocks; Kgr— Cretaceous granite; 

Tv—Miocene mafic volcanic rocks; Qa—Quaternary alluvium. Red cross-hatch indicates areas of hydrothermal alteration 

identified with Advanced Spaceborne Thermal Emission and Reflectance (ASTER) imagery. Boundaries of Areas of Critical 

Environmental Concern (ACECs) shown in pink.

Rest

mine

Calavada area

(White Horse,

Lily, B.T.)

Gingerload prospect

(PGE)

Morgan mine

Sundog mine

Peyton mine

Silver Bell mine

Thor claims

Double

Standard

mine

unnamed prospects

Bullion claim

unnamed shaft

unnamed prospects

Nippeno and

Cumberland

claim groups

Red Star group

unnamed

prospect

unnamed

prospect

Blue Crystal

claim group

(Ag + fluorspar)

Thorium

prospect

Last Chance claim

Big Tiger prospect

Lucky Dutchman

and Modoc mines

Prospectors

U claim

Oversight Mica mine

Yeager mine

Tiger Lily mine

Simmons, Toltec, &

Smithson Phillips mines

(turquoise)

Crescent Peak

porphyry copper

prospect

AP-042

AP-041

AP-039, 040

AP-026

AP-025

AP-024

AP-023

AP-022

AP-015 -019,

5-030901

5-030701

Qa

Qa

Qa

Qa

Tv3

Tv3

Tv3

Kgr

pCu

pCu

pCu

Tcgl

115°10'0"W 115°5'0"W

35°25'0"N

35°30'0"N

01234 0.5

Kilometers

Piute-Eldorado

Tortoise

ACEC

Crescent

Townsite

ACEC
B42 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Calvada, Lucky Dutchman). Several of the deposits are difficult to classify because of the limited information available, 

and they may be either gold-rich polymetallic veins or detachment-fault-related deposits.

Silver Bell Mine

The Silver Bell Mine is located within the Piute-Eldorado 

Tortoise ACEC, adjacent to Nevada State Highway 164 (fig. 

38). Although it is shown on both 1:24,000 and 1:100,000-

scale topographic maps, it is not mentioned in the geologic literature. It is possible that this is because it was discovered and 

developed subsequent to 1937, when the last primary geologic 

investigations in the area were carried out (Vanderburg, 1937).

The mine workings at the Silver Bell expose northeaststriking veins and shear zones with shallow northwest dips 

that consist mainly of bleached and silicified rock. Abundant 

quartz and manganese oxide were identified in hand specimen, 

along with local galena and secondary copper minerals. The 

samples have high gold (as much as 18 ppm), silver (as much 

as 12 ppm), copper, lead, and zinc along with moderately high 

molybdenum and antimony (table 5). This mineralized rock 

occurs along a N30E- to N65E-striking structure that is nearly 

horizontal in places and dips as much as 35 degrees northwest 

elsewhere (figs. 39, 40). The mineralized structure cuts Proterozoic gneiss and barren quartz veins (for example, sample 

AP-015Q, table 5). To the southwest and northeast, and 

approximately along strike with the Silver Bell structure, are 

occurrences of similar rock along structures that are horizontal 

or dip 40 degrees to the northwest. Some samples of this material (AP-022 through AP-024C, table 5) have elevated metal 

values similar to those of the Silver Bell samples. Sample AP024C is of interest because it is an ore grade chip sample (with 

about 4 ppm Au, or 0.1 troy ounce per ton) across 1.2 m of 

sheared and altered rock from a near-horizontal zone adjacent 

to an old open stope (fig. 40).

On the basis of petrographic and SEM/EDX studies, 

samples from the Silver Bell Mine contain several manganese 

oxide phases, including an iron and manganese mineral (fig. 

41), a manganese and lead mineral (coronadite?) (fig. 42), an 

unknown phase containing manganese, potassium, and lead, 

and a rare mineral that contains manganese, lead, and antimony. Other secondary phases include an iron oxide mineral 

and hemimorphite (Zn4

[(OH)2|Si2O7] · H2O) (figs. 43, 44). 

Primary sulfides include galena, pyrite, sphalerite, and chalcopyrite, along with rare acanthite and imiterite (Ag2

HgS2). 

Although galena is present in some samples, late vein- and 

breccia-filling manganese-oxide phases may be the only leadbearing minerals in others (fig. 45). Barite is present in minor 

amounts. Electrum was found as grains as much as 60 μ across 

in one sample (fig. 44).

Peyton and Sundog Mines

The Peyton and Sundog Mines are in the northeast end 

of the Crescent district, about 3 km east of the Silver Bell and 

about 1 and 2 km respectively south of the Piute-Eldorado 

Figure 40. Shallowly-dipping sheared, altered, and mineralized 

zone southwest of the Silver Bell Mine. AP-024C is a chip sample 

taken from the hammer (right of opening) downward 1.2 m across 

the sheared and limonitic rock to the top of unoxidized greenish 

gneiss below.

Figure 39. Shallowly northwest-dipping sheared, altered, and 

silicified gold-bearing zone (behind hammer) in an adit at the 

Silver Bell Mine. Site of samples AP-015 and AP-015C.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B43

SAMPLE LOCATION Au Ag Mo Cu Pb Zn As Sb

AP-015 Silver Bell Mine 6.0 4.2 13 133 2,500 570 34 3.2

AP-015C Silver Bell Mine 0.20 1.0 10.8 35 1,430 480 7 0.6

AP-015Q Silver Bell Mine 0.01 0.1 0.5 2.3 14.9 12 0.6 0.2

AP-019 Silver Bell Mine 18.1 12.7 28.2 1,150 >10,000 7,800 8.9 34

5-030901 Silver Bell Mine 0.002 <0.5 2.5 19 16 49 2 0.6

AP-022 unnamed adit 0.26 14.8 28.7 >10,000 580 149 126 52

AP-022B unnamed adit 0.00 <0.1 3 23 16.7 70 <0.5 0.1

AP-023 unnamed adit 1.52 2.9 74.3 89 3745.9 1830 4.1 2.4

AP-024 unnamed stope 4.1 6.5 17.6 200 >10,000 5300 21 7.0

AP-024C unnamed stope 1.25 7.5 29 370 8,100 >10,000 22 4.1

AP-039 Lucky Dutchman Mine 0.04 0.1 0.5 48 34 17 1.2 0.5

AP-040 Lucky Dutchman Mine 0.00 0.1 0.4 95 14.7 13 2.8 0.4

AP-041 Double Standard Mine 11.6 154 219 1,780 >10,000 5,700 1,300 43

5-030701 Dump east of Double 

Standard Mine 0.26 <0.5 3.7 10 9 7 9 0.7

AP-042 unnamed shaft 4.8 64 11.3 30 500 180 194 4.1

Figure 41. Back-scattered electron image of barite (bright) 

interlayered with a manganese-oxide mineral (dark gray) that is 

intergrown with an iron and manganese oxide mineral (light gray) 

that replaced an unknown crystalline phase. Dark background is 

mostly quartz. Sample AP-015, Silver Bell Mine.

Figure 42. Back-scattered electron image of galena (bright) 

partially replaced by lead-bearing manganese-oxide mineral, 

possibly coronadite (gray). Dark background is mostly quartz. 

Sample AP-019, Silver Bell Mine.

Table 5. Samples from vein and shear zone deposits and occurrences in the Crescent district.

[All values in ppm, rounded to 2 or 3 significant figures.]

Tortoise ACEC (fig. 38). The Peyton Mine explores a quartzgalena-chalcopyrite vein that strikes north and dips 45 degrees 

to the west (Hewett, 1956). It has no recorded production. 

The Sundog Mine exploited quartz veins that contain bornite, 

chalcopyrite, and copper-oxide minerals, and it probably had a 

small amount of production, though none was recorded (Longwell and others, 1965).

Big Tiger Prospect and Rest Mine

A linear band of enigmatic hydrothermal quartz-flooded 

rock extends from the Big Tiger prospect just east of the Crescent Townsite ACEC, slightly south of west a total of nearly 

4 km to just west of the Nipton Red decorative stone quarry 

(fig. 46). This quarry occupies the site of a small gold opera-
B44 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

tion that was apparently active in the late 1970s, the Rest Mine 

(Nevada Division of Mine Inspection, 1977). In 1982, Crescent Mining Ltd. was conducting a small cyanide heap leach 

operation less than a kilometer away (Gese, 1984), but we 

have no direct information that it was treating material from 

the Rest Mine.

The Big Tiger prospect was the chief area of interest in 

1905-6, when Crescent was visited by Ransome (1907). He 

interpreted the mineralized rocks to be a “mass of shattered 

Figure 43. Cross-polarized photomicrograph of hemimorphite 

(mostly birefringent in orange and red colors) with opaque 

manganese oxide minerals in comb quartz, sample AP-019, Silver 

Bell Mine. Horizontal field of view is about 3 mm.

Figure 44. Backscattered electron image showing electrum 

grains in lower right and a gray mass of hemimorphite with bright 

inclusions of acanthite and silver and mercury sulfide (imiterite?) 

in upper left. Quartz (black) contains some tiny bright grains of Febearing sphalerite near the hemimorphite mass. Sample AP-019, 

Silver Bell Mine.

Figure 45. Secondary electron image of manganese-oxide 

minerals in sample AP-024. Dark gray area is mostly quartz, the 

late medium gray mineral is an unknown manganese-oxide phase 

with lead and potassium, and the bright mineral is a lead-bearing 

manganese-oxide phase, possibly coronadite.

Figure 46. The Nipton Red decorative stone quarry, the 

apparent site of the Rest Mine in 1979. This is the west end of the 

band of silica-rich alteration that extends eastward to the Big 

Tiger prospect. Note abundant red hematite alteration.

quartzite that has been recemented by quartz and carries more 

or less gold and silver.” He reported that assays indicated 

values as high as $12 per short ton (corresponding to about 

0.6 opt or 20.5 ppm gold at the 1907 price). There is abundant hematite and rare malachite in the matrix of this breccia. Ransome also reported similar material at the Calavada 

property, which is described as being “3 miles southwest of 

Crescent, on the other side of a gneiss ridge.” This description 

would put the location well into California, in an area where 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B45

only Tertiary mafic volcanic rocks crop out. If he meant road 

miles, the location is likely the same as what is now known 

as the Lily Mine, the White Horse Mine, and the B.T. prospect (U.S. Bureau of Mines, 1990). Rocks at these deposits 

were described as silicified breccias by Gese (1984) and U.S. 

Bureau of Mines (1990) and yielded gold values as high as 

0.48 opt (about 16 ppm) gold in select samples. This area was 

probably the focus of the large exploration program by Newmont Exploration, Inc., in the early 1990s, in sections 31 and 

32 of T28S, R61E and section 6 of T29S, R61E.

Lucky Dutchman Mine

Today the Lucky Dutchman Mine is being exploited for 

decorative stone, but it was exploited prior to 1927 for gold 

(Hewett, 1956). It is about 3 km northwest of Crescent (fig. 

38), and it exposes altered and silicified gneiss with abundant 

hematite that contains moderately southward-dipping calcite-, 

barite-, and fluorite-bearing veins. Two samples analyzed by 

Tingley (1998) contain about 11 and 5 ppm gold, with relatively low silver and base metal contents. Our samples (table 

5) of barite-quartz and barite-fluorite veins have low preciousand base-metal contents.

Double Standard Mine

The Double Standard Mine is about 1.5 km northwest of 

the Lucky Dutchman (fig. 38) and within the Piute-Eldorado 

Tortoise ACEC. A sample there (AP-041, table 5) from a 

steeply north-dipping bleached and limonite-stained structure 

cutting gneiss contains 11.5 ppm gold, 154 ppm silver, and 

nearly 1,300 ppm arsenic. An unnamed small dump about 400 

m east of the Double Standard yielded a sample (5-030701, 

table 5) that contains 1.6 ppm gold but low silver and arsenic. 

About a kilometer north of the Double Standard, an unnamed 

prospect yielded a sample (AP-042, table 5) that contains 4.8 

ppm gold, 150 ppm silver, 500 ppm lead, 194 ppm arsenic, 

and 14 ppm antimony.

Red Star Group and Last Chance Claim

These two prospects are located about 4 km east of the 

Double Standard, within the Piute-Eldorado Tortoise ACEC 

(fig. 38). The Red Star is described by Longwell and others 

(1965) as a quartz vein in Proterozoic rocks. We did not visit 

either of these areas.

Nippeno and Cumberland Claim Groups

These two vein deposits are in close proximity about 

a kilometer southeast of the Piute-Eldorado Tortoise ACEC 

boundary and about 2 km east of the Crescent Townsite 

ACEC, between Nevada State Highway 164 and Crescent 

Peak (fig. 38). The Nippeno was a small producer in the 

1930s, with a total production for that period of 538 oz of 

gold and 294 oz of silver (Longwell and others, 1965; Hewett, 

1956). The Cumberland had a very small production of about 

$1,000 (Vanderburg, 1937). Both deposits are gold-rich quartz 

veins with moderate amounts of base-metal sulfides.

Crescent Peak Porphyry Copper Prospect

During both the 1950s and 1960s, the area centered on 

Crescent Peak was explored as a porphyry copper prospect 

(fig. 38). Most of our information about this prospect is from 

Archbold and Santos (1962). A large area about a kilometer 

in diameter is characterized by coarse sericitic hydrothermal 

alteration in a medium- to coarse-grained granite that is probably Proterozoic in age. In the center of the altered area is a 

zone of argillic alteration where clay minerals occur along 

with fine-grained sericite. Milky quartz veins 5 to 30 cm thick 

occur throughout the area as well. Boxwork casts of former 

sulfides are found throughout this altered area, and traces 

of copper-oxide minerals are found in a few places. Surface 

sampling yielded scattered values of copper in the hundreds of 

parts per million and molybdenum in the tens of parts per million. The age of this mineralized system has not been directly 

determined, but it is likely that it is related to the Cretaceous 

granodiorite intrusions dated by Miller and Wooden (1993) at 

94.4 Ma using conventional K-Ar methods.

Six diamond drill holes in the system penetrated to depths 

of as much as 300 m. Individual 10-ft intervals contained as 

much as 0.11 percent copper, but values of a few hundred parts 

per million were most common. Similarly molybdenum values 

as high as 0.12 percent were encountered, but most intervals 

contained between 50 and 150 ppm.

On the north side of the porphyry system, the Gingerload 

prospect appears to explore a polymetallic vein rich in gold 

and platinum-group elements (PGE) that is peripheral to the 

porphyry system. The determination by Lechler (1988) of 

values of as much as 650 ppb platinum in samples from the 

Gingerload resulted in a flurry of interest in the area, but no 

PGE resources have been discovered.

Fluorspar and Silver Deposits Southwest of 

Crescent

At the southwest margin of the district, primarily in 

California, there are a number of small (most less than 3 cm 

wide) fluorspar veins that cut the Proterozoic gneiss, strike 

about N80E, and dip nearly vertically (Gese, 1984). Most are 

unnamed but have been known collectively as the Mc Dermott 

fluorspar deposit, the Blue Crystal prospect, and the Nipton 

prospect. The Blue Crystal block of 67 claims was active in 

1982, but no mining was underway. The veins contain copperoxide and carbonate minerals, and some veins contain as much 

as about 1 ppm gold and 1,000 ppm copper (Gese, 1984). The 

age of these veins relative to the gold deposits in silicified and 

brecciated gneiss is not known.
B46 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Sunset District

 This district contains only one major deposit, the Lucy 

Gray, which is about 2 km outside the boundary of the PiuteEldorado Tortoise ACEC. The Lucy Gray is a polymetallic vein deposit of unknown age that has received repeated 

attention in the second half of the 20th century. Most recently, 

the Wild Bill Nos. 1, 6, and 7 were located by William Fuller 

in 1995 and are still active in 2005. These claims are at least 

partly within the Piute-Eldorado Tortoise ACEC. The Lucy 

Gray itself, although showing some promise during earlier 

exploration efforts, is too far from the ACEC boundary to 

impact potential resources in the ACEC.

Hart District

The Hart district is mostly in California, but several of the 

deposits are quite near the west boundary of the Piute-Eldorado 

Tortoise ACEC and the host rocks for the deposits in the district 

are exposed in the Castle Mountains, immediately adjacent to 

the ACEC, in the western part of the region. Although there was 

minor gold mining in the district in the early part of the 20th century, the Viceroy Mine was the most important producer. Mining 

at the Viceroy Mine from 1992 until 2001 recovered about 1.2 

million troy ounces of gold. The deposit can be classified as a 

low-sulfidation epithermal deposit and consisted of several discrete orebodies, with gold in quartz stockwork veins. The deposit 

was briefly described by Linder (1989), and the geologic setting 

of the district was described by Capps and Moore (1997).

Other Deposits of Locatable Minerals

A number of minor metal prospects were described by 

Close (1987) in the McCullough Range, mostly several kilometers west of the Piute-Eldorado Tortoise ACEC. The War 

Lord prospect, the nearest one (1 km) to the ACEC boundary, 

was described as a northeast-striking quartz vein in Proterozoic gneiss containing small amounts of malachite and scheelite. The Hacienda prospect, which is adjacent to the northeastern part of the Piute-Eldorado Tortoise ACEC, appears to be 

an oxidized gold-rich polymetallic vein that strikes northwest 

in Proterozoic gneiss and was traceable for about 200 m.

The Mammoth Mine, located about 9 km southeast of 

the town of Searchlight, is a small shaft located at the contact 

between Proterozoic gneiss and overlying Peach Springs Tuff. 

The mine is known only from its presence on the 1:24,000-

scale topographic map. We saw no evidence of mineralized 

rock on the small dump, and a sample of Peach Springs Tuff 

taken nearby showed no anomalous metals.

Perlite

Nevada has large perlite resources and several deposits 

that were mined extensively in the past. The Hollinger Mine 

near Pioche in Lincoln County was the largest producer, 

with production of as much as 40,000 short tons per year in 

the 1950s. However, current Nevada perlite production is 

restricted to relatively small-scale mining of two deposits. 

In Lincoln County, Wilkin Mining and Trucking, Inc., mines 

perlite from the Tenacity (Mackie) Mine and has a small plant 

that produces relatively coarse expanded perlite useful in 

horticultural applications. It currently produces about 1,500 

to 2,000 short tons of expanded perlite per year. Eagle-Picher 

Minerals, Inc., produces expanded perlite that is marketed as 

filter aid from perlite mined in northern Nevada. The plant 

capacity is reportedly about 8,000 tons per year (Castor, 

2005a). By contrast, the largest domestic perlite producer is 

a mine at No Agua Peaks in New Mexico that yields about 

200,000 short tons per year. Other mines in New Mexico, 

Oregon, and Utah produce more than 20,000 short tons per 

year (Barker and Santini, 2006).

Two perlite deposits are in or near the Piute-Eldorado 

Tortoise ACEC. Both are in rhyolite flows or domes in Miocene (15 to 16 Ma) volcanic rock sequences. Neither is being 

mined currently, but each has had production in the past.

The Searchlight Insulation Products (Perlite Ridge) Mine, 

which is about 5 km north of the town of Searchlight, is in 

a small inholding of private land within the Piute-Eldorado 

Tortoise ACEC (fig. 21). It produced 300 to 600 short tons 

of crude perlite annually in the 1950s, and consists of three 

small open pits (fig. 47). The largest is the north pit, which is 

about 30 m long, 10 m wide, and 5 m deep. Most of the perlite 

here is hard, gray, granular rock that occurs as clasts in friable 

white perlite. It contains trace amounts of purplish devitrified material in small masses and discontinuous veinlets. The 

north pit is near the northeast end of a mass of perlite that 

is bounded on the northwest by a near-vertical fault. About 

300 m to the southwest is a 35 m x 10 m x 3 m pit in similar 

perlite that appears to be part of the same mass. A smaller pit 

Figure 47. Aerial photograph of Searchlight Insulation Products 

property, showing north and south pits.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B47

containing nearly pure granular perlite lies between the two 

pits. On the basis of our field examination, the perlite mass 

that contains these pits is about 600 m long and 100 m wide. It 

extends south-southwest into the ACEC. It is likely a rhyolitic 

flow that dips steeply to the northwest. We estimate reserves at 

about 1.2 million short tons to a depth of 10 m with little waste 

removal. Cochran (1951) estimated indicated reserves of good 

quality, granular perlite at about 10 million short tons, but 

reported that the deposit consisted of two masses, one 1,500 ft 

x 240 ft x 21 ft and a second 2,600 ft x 500 ft x 100 ft.

Perlite that we collected from the Searchlight Insulation 

Products deposit (AP-301 and AP-302, table 6) is light-gray 

granular rock with sparse feldspar and biotite phenocrysts, 

silica contents (72.6 to 74.0 percent) typical of rhyolite, and 

LOI (loss on ignition) of 3.6 to 5.1 percent. In these samples, 

LOI values mostly represent combined water contents, and 

perlite is defined as having 2 to 5 percent combined water 

(Barker and Santini, 2006). Our samples from the Searchlight 

deposit have high expanded density when compared with perlite from the large No Agua perlite deposit in New Mexico and 

with other Nevada perlites (table 6). Sinks (unexpanded material) for Searchlight perlite are moderate to high and coarse 

expanded perlite sizes are low. Brightness is low relative to the 

No Agua perlite, but comparable to other Nevada perlites. The 

results do not show that perlite from the deposit is noncommercial, but they suggest that it would find limited markets. 

For example, it would likely not be usable in horticultural 

or loose-fill insulation applications, which require relatively 

Sample SiO2 LOI Furnace 

Yield

Expanded 

Density

Avg. 

Bright Sinks

Percent Expanded Retained (Tyler Mesh)

(%) (%) (%) (lbs/ft3) (%) (%) +20 +30 +50 +70 +100 +140 -140

AP-10A 73.6 4.0 77 1.94 52.1 22.2 1.0 9.4 30.5 14.2 10.8 11.4 22.7

AP-10B 71.0 5.1 88 2.27 55.5 9.6 1.9 17.9 41.1 10.5 7.4 6.8 12.4

AP-45 73.3 4.3 68 1.97 60.1 8.4 0.6 6.0 29.9 17.2 12.5 13.0 20.8

AP-119 72.3 3.8 92 2.06 52.5 4.8 20.1 34.0 33.7 5.6 2.5 1.3 2.8

AP-120 72.8 3.4 96 2.05 50.8 9.0 1.0 8.4 33.1 16.8 12.0 10.3 18.4

AP-121 74.1 3.8 86 2.04 52.8 12.0 2.4 16.7 34.5 16.1 9.8 2.1 17.4

AP-122 73.1 4.0 85 2.52 57.2 7.0 16.2 27.4 38.7 7.5 35.0 1.9 4.8

AP-124 72.1 4.0 96 3.05 42.4 0.6 8.1 42.1 42.9 3.2 1.1 5.0 2.1

AP-186 70.8 5.1 95 2.26 57.2 10.2 16.8 33.3 36.0 8.4 3.3 2.1 3.1

AP-301 72.6 5.1 84 3.03 56.0 26.2 1.0 12.1 35.9 16.5 11.7 7.7 15.1

AP-302 74.0 3.6 90 2.80 59.2 11.4 2.8 12.5 35.1 16.5 10.3 9.5 13.3

AP-303 73.3 3.7 90 3.79 62.3 14.2 1.6 21.8 52.0 11.4 4.0 3.0 6.2

Std. 99 1.87 72.4 6.8 9.9 41.0 37.4 2.9 2.1 4.0 2.7

Std. 99 1.54 70.6 2.4 19.4 42.5 30.7 3.2 1.9 1.5 0.8

Sample locations and descriptions:

AP-10A—grab sample, friable perlite, Nu-Lite Mine, Clark County, Nevada

AP-10B—5-m chip, friable perlite, Nu-Lite Mine, Clark County, Nevada

AP-45—select grab sample, granular perlite, NW, Searchlight Perlite Mine, Clark County, Nevada

AP-119—grab sample, granular perlite, Tenacity pit, Mackie Mine, Lincoln County, Nevada

AP-120—select grab sample, onionskin perlite, Mackie Mine underground, Lincoln County, Nevada

AP-121—grab sample, granular perlite, main pit, Hollinger Mine, Lincoln County, Nevada

AP-122—grab sample, granular perlite, east pit, Hollinger Mine, Lincoln County, Nevada

AP-124—grab sample, granular perlite with obsidian cores, Lovelock perlite pit, Pershing County, Nevada

AP-186—select grab sample, granular perlite with phenocrysts, River Mountains, Clark County, Nevada

AP-301—grab sample, granular perlite, north pit, Searchlight Perlite Mine, Clark County, Nevada

AP-302—grab sample, granular perlite, south pit, Searchlight Perlite Mine, Clark County, Nevada

AP-303—grab sample, granular perlite, outcrop east of north pit, Searchlight Perlite Mine, Clark County, Nevada

Std.—perlite from two No Agua, New Mexico, deposits

Table 6. Physical and chemical properties of perlite samples.

[Test data are for perlite expanded at 1300°F without preheat using -50+100 mesh samples. Sieve analyses of expanded perlite are reported as 

percent of sample retained at each mesh size. Testing by New Mexico Bureau of Geology and Mineral Resources. The testing parameters (for 

example, temperature, sizing) are optimized for testing perlite from No Agua; somewhat different results might be obtained using a modified 

methodology.]
B48 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

coarse perlite (Barker and Santini, 2006). It would not be 

useful in most construction applications, which require perlite 

with expanded densities of less than 2.5 lbs/ft3

 (M. Houseman, oral commun., 2006). Perlite from this deposit could find 

applications in uses that do not require low expanded density 

and large particle size, such as in filter aids. It might find 

markets in uses that require fine perlite, but its low brightness 

might preclude its use in some products.

Perlite at the Searchlight deposit occurs in a rhyolite 

flow of the middle rhyolitic unit of the volcanics of the Highland Range (Faulds and others, 2002a). Our reconnaissance 

of these rocks revealed that perlite is locally abundant, but 

most of the perlite that we found was moderate to dark-gray 

rock with relatively high phenocryst contents. A sample 

from a 30- to 60-m-wide perlite zone about 0.5 km northwest of the Searchlight deposit (AP-45, table 6) had similar 

brightness and expanded size distribution to perlite from the 

Searchlight deposit but considerably lower expanded density. 

However, this sample was selected to represent the purest 

material available, and much of the perlite in this mass contains variable amounts of non-glassy rock, particularly in the 

form of spherulites (fig. 48) that would decrease its value as 

commercial perlite.

The Nu-Lite Perlite Mine is on the east flank of the 

Castle Mountains about 17 km southwest of Searchlight near 

the California State line. It is about 200 to 300 m outside 

the Piute-Eldorado Tortoise ACEC. The deposit was mined 

between 1948 and 1954 by Nu-Lite Insulated Homes, Inc., 

and produced as much as 600 short tons of crude perlite 

annually. The mine consists of a shallow open pit about 20 m 

in diameter in a west-northwest striking and shallowly north 

dipping, possibly intrusive mass that is nearly 1 km long 

and 100 m wide. Other small open cuts occur in this zone. 

In addition, perlite occurs as a shallowly dipping rhyolite 

flow as much as 50 m thick that occurs in places atop a 

thick sequence of light colored bedded tuffs and beneath a 

sequence of devitrified rhyolite flows and domes. Capps and 

Moore (1997) reported ages of about 15 Ma for these rhyolites. They have mapped the perlite within a unit of rhyolite 

autoclastic breccias, block and ash flows, and pumice flows. 

The perlite-bearing unit has been locally prospected both in 

Nevada and California, in places by underground workings. 

Neither our mapping or that of Capps and Moore (1997) 

shows any nearby exposures within the Piute-Eldorado 

Tortoise ACEC, although these same rhyolites crop out in the 

ACEC about 3 km to the northeast.

We collected two samples of perlite from the small 

Nu-Lite pit. Both are of friable, light-gray to white perlite 

that ranges from breccia (fig. 49) to nicely flow-banded rock 

(fig. 50). Testing of these samples yielded expanded density 

approaching that of the No Agua perlite; but the Nu-Lite 

perlite has similar expanded size distribution to, and lower 

brightness than, expanded Searchlight Insulation Products 

perlite (table 6). These data suggest that it would face some 

Figure 48. Spherulites in perlite near the Searchlight perlite 

deposit.

Figure 49. Perlite breccia, Nu-lite Mine. Fragments of light-gray, 

moderately resistant perlite in white friable perlite.

Figure 50. Pure, friable, flow-banded perlite, Nu-lite Mine.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B49

of the same marketing challenges faced by the Searchlight 

perlite, but its low expanded density indicates that it could be 

used in construction applications.

Stone

Crushed stone is mined from several deposits in private 

inholdings within and areas adjacent to the Piute-Eldorado 

ACECs. The stone is used as decorative landscape rock in 

Las Vegas where the market is relatively large because Clark 

County imposed a ban on grass front lawns for newly constructed residences in 2003. This has resulted in a substantial 

market for crushed stone in the Las Vegas metropolitan area. 

Colored decorative aggregate from quarry locations as distant 

as Searchlight now commands a price of $8/short ton or more 

(depending on color) at quarry sites, and selected boulders sell 

for as much as $30/short ton (Castor, 2005b). Prices are higher 

for material delivered in Las Vegas where single decorative 

boulders sell for as much as $400.

The largest decorative crushed stone producers in the 

Las Vegas region are the El Dorado operation of Rinker 

Materials at Railroad Pass and the Rainbow Quarries of Las 

Vegas Rock north of Goodsprings. Exact tonnages of decorative stone produced at these operations are not known, but 

we estimate them to be on the order of 200,000 short tons per 

year. In addition to use in residential and commercial landscaping projects, crushed stone from these operations is used 

along newly constructed highways in the Las Vegas area. The 

operations are commonly on old patented gold mining claims 

and thus on lands under private ownership. They include 

moderate sized operations at the Roman Mine in the Newberry Mountains, which is on unpatented claims about 2 km 

from the boundary of the Piute-Eldorado Tortoise ACEC (fig. 

34), and at the Pompeii Mine directly north of Searchlight, 

which is about 100 m south of the ACEC boundary (figs. 

21, 51). The rock from these operations is of various colors, 

including gray, light yellowish gray, and pale red. Smaller 

operations include at least three producers in the Crescent 

district—the John Yeager operation; the Lucky Dutchman 

Mine (figs. 38, 52); and the Modoc Mine (fig. 38). These 

operations are apparently all within the boundaries of old 

mining claims that were patented as gold claims. In addition, 

there is an inactive operation on private land just south of the 

Crescent townsite. Most of the rock from these producers is 

pale red, light pink, and purplish gray, colors that apparently 

bring premium prices in Las Vegas and are due to the presence of hematite in altered Proterozoic rocks.

Turquoise 

Turquoise was mined extensively from the Simmons 

(Toltec) Mine on the south side of Crescent Peak about 3 km 

outside the Piute-Eldorado ACEC beginning in the late 1890s 

(fig. 38). According to Morrissey (1968), the total value of 

turquoise taken from this mine may have exceeded $1 million, and the deposit showed evidence of prehistoric Native 

American mining.

A less-productive turquoise mine, the Morgan (Iron 

Door) Mine is within the Crescent Townsite ACEC (fig. 38). 

Our examination disclosed a small open pit and an adit (fig. 

53). The turquoise, which is light blue to greenish blue, occurs 

as irregular veins as much as 5 mm thick in white to brown 

altered and limonitized granitic rock (fig. 54). Several hundred 

pounds of gem-quality turquoise were produced from the mine 

in 1906 (Morissey, 1968). Turquoise such as that shown in 

figure 54 can still be found on the dumps at this site.

Figure 51. Quarries and access roads at a decorative stone 

operation north of Searchlight. The Piute-Eldorado Tortoise Area 

of Critical Environmental Concern lies just to the north of the 

northern pit.

Figure 52. Crushing and screening equipment with light pink to 

purplish-gray decorative stone stockpiled at the Lucky Dutchman 

Mine, Crescent district.
B50 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 53. Portal of the Iron Door (Morgan) Turquoise Mine in 

the Crescent Townsite ACEC. A small open pit is out of the picture 

on the upper right.

Figure 54. Turquoise vein in altered and limonitized granitic rock, 

Iron Door Mine, Crescent Townsite ACEC. Horizontal field of view 

about 5 cm.

Mineral Exploration and Development

Although most metal mining activity has been greatly 

reduced since World War II, the Piute-Eldorado ACECs have 

been the site of a number of mineral exploration programs 

since that time, and they are still the focus of some mineral 

exploration today. There are a number of current and recently 

current mining claims in the area. Our information was gathered in the Spring of 2006.

Crescent District

Most of the mineral exploration and development in this 

area appears to have taken place since the visit of Vanderburg 

(1937), as he did not mention most of the patented claims now 

present in the district.

A prominent area of hydrothermally altered rocks centered on Crescent Peak was explored during the 1950s and 

early 1960s as a porphyry copper prospect. Drilling of at least 

seven holes to depths of more than 300 m was conducted at 

that time by Bear Creek Mining Company and Homestake 

Mining Company. No ore-grade material was found, but sporadic occurrences of copper values >1,000 ppm and molybdenum values >300 ppm in the analyzed drill core seems to 

confirm the existence of a large mineralized body that can be 

characterized as a porphyry copper deposit. Although analyses for precious metals were made only on 50-foot composite 

samples, the precious-metal content of the rock appears to be 

low. Widespread phyllic alteration and some anomalous copper concentrations in surface samples were the basis for the 

exploration effort. Curiously, the age of this mineralization is 

still completely unknown. No radiometric age determinations 

have been made, and the geologists working in the area at that 

time were unable to map a post-Proterozoic intrusion within 

the altered area. Miller and Wooden (1993) mapped and dated 

a Cretaceous granodiorite about 4 km to the west, and they 

tentatively suggested that this rock may be present within the 

mineralized area at Crescent Peak.

Most of this area is about 3 km outside the boundaries of 

the Piute-Eldorado Tortoise and Crescent Townsite ACECs. 

Subsequently, Houston International Minerals held claims 

in this area from 1983 to 1993, but we have found no documentation of their exploration activity or findings. A small 

company proposed mining gold ore from the surface just 

north of Crescent Peak in the early 1980s, but they apparently 

never conducted the operation. The 1988 publication that 

platinum-group elements were present in mineralized rock 

from the Gingerload Mine (Lechler, 1988), on the north flank 

of Crescent Peak, sparked renewed activity. In section 23 of 

T28S, R61E, near the Sundog Mine on the northeast flank of 

Crescent Peak, about 2 km outside the Piute-Eldorado Tortoise 

ACEC, drilling was conducted in 1989 by Francis Friestad and 

Mark Davis, with unknown results. In 1991, Westland Mineral 

Exploration Company drilled two holes just west of Crescent Peak, between the Gingerload and Nippeno Mines, with 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B51

unknown results. Subsequent attempts to organize mining and 

exploration ventures at Crescent Peak have been unsuccessful.

In the early 1990s, Newmont Exploration Ltd., in conjunction with Westland Minerals Exploration Co. and Stena 

Resources, conducted exploration on a large claim block about 

4 km southwest of Crescent townsite, near the California 

border. The results of the work are unknown, but the exploration was probably for gold in the area described by Ransome 

(1907) as the Calavada claims. In 1992, a resource of 390,000 

short tons at 0.05 opt gold, or 3.3 million short tons at 0.022 

opt gold was reported by Westland Minerals Exploration Co. 

for their Crescent properties, but we do not know exactly to 

what deposit(s) they referred (Nevada Bureau of Mines and 

Geology, 1994).

At about the same time, a company called Nevada Noble 

Metals explored the Susie Q claim block that is partly within 

the Piute-Eldorado Tortoise ACEC, about 2 km north of the 

Silver Bell Mine in sections 9 and 10 of T28S, R61E. Immediately to the west, Eldorado Mining Co. explored the Silver 

Lady claims, as well as an area between the Silver Bell and 

Nippeno Mines. Also within the Piute-Eldorado Tortoise 

ACEC, Houston International Minerals conducted exploration 

on the alluvium-covered area between the Lucky Dutchman 

Mine and the Crescent townsite in 1983. We have no information on the nature of the target or of the results for any of these 

exploration programs.

In 2005, there were 43 current lode claims and 3 current millsite claims along the corridor where Nevada State 

Highway 164 crosses the south end of the McCullough Range. 

Many of these are at least partially within the Piute-Eldorado 

Tortoise and Crescent Townsite ACECs. At the east end of 

the district, in sections 10, 15, 16, and 21 of T28S, R61E, the 

Rainbow’s End group of 31 claims is owned by Stanley Pierce, 

Michael Sean, Katherine Pierce Denos, and Diana Kirtley; 

these have been maintained for nearly 15 years, and we presume their target is gold. In addition, in section 25 of T28S, 

R60E, the Silver Crescent millsite claim has been maintained 

since 1994 by Norma Pierce Oppenheimer. In section 20 of 

T28S, R62E, two millsite claims have been maintained by 

James Skidmore since 1983. A single claim in section 10 of 

T28S, R61E has been maintained by Saylor Dean since 2001. 

Two claims in section 21 of T28S, R61E have been maintained 

by Fuller Gulliosa since 2001. The Gold Nos.11, 14, and 15 

have been maintained in section 30 of T28S, R61E by John 

and Sally Denton since 1984. At the west end of the district, at 

the south end of the Lucy Gray Mountains in sections 10 and 

16 of T28S, R60E, 3 claims (the Wild Bill group) have been 

maintained by William Fuller since 1995.

Searchlight District

Interest in the Searchlight district has never totally disappeared, and there are a number of active mining claims in 

the area, some of them reflecting the interests of mining and 

exploration companies, and others the interests of individual 

prospectors. Two areas on the margins of the Searchlight district within the Piute-Eldorado Tortoise ACEC are the objects 

of active exploration programs by mining companies.

A large block of more than 100 claims (45 in our database) was located in 2003–2005 by Desert Pacific Resources, 

Inc., in sections 15, 16, 17, 20, and 29 of T28S, R63E. This 

claim block (the ‘VES’ group) is partly within the PiuteEldorado Tortoise ACEC, immediately north and west of the 

Searchlight district, and it is known as the Copper Hill project. 

The claims are presently (spring, 2006) under option to Great 

Western Minerals Group Ltd., and are being actively explored.

A group of 20 claims were located in 2004 by William 

R. Stanley, within the Piute-Eldorado Tortoise ACEC, directly 

north of the Searchlight district, in sections 14 and 15 of T28S, 

R63E. This claim block (the Searchlight Bonanza group) is 

being explored by Atna Resources Ltd. In addition, Coyote 

Mines, Inc., has held 1 claim nearby in sections 14 and 15 of 

T28S, R63E since 1994.

A major exploration program was mounted by Southwestern Exploration Associates, Inc., on behalf of the Felmont 

Oil Corporation in 1979–81. Homestake Mining Company 

acquired Felmont Oil during this effort. A large area west 

of the historic part of the Searchlight district was mapped at 

1:6,000 scale, several hundred surface geochemical samples 

were collected and analyzed, and a total of 29 holes were 

drilled using reverse circulation methods. Only sporadic 

gold anomalies were encountered in these holes, which were 

designed specifically to test the possibility for disseminated 

low-grade precious-metal ore. A more surprising result was 

elevated levels of copper in several of the holes, at depths of 

about 100 m. Intervals containing in excess of 200 ppm copper 

were encountered in 6 of the holes, compared to background 

values of less than 50 ppm.

Areas North of Searchlight

Two claims (Canaan), located by Pete Baldonado and 

Richard H. Culmer, near the north end of the Highland Range, 

in sections 26 and 27 of T26S, R62E, have been current since 

1985. A claim located by Joan Sullivan in the Eldorado Mountains near the Rockefeller Mine and Cobalt claims, in section 

25 of T27S, R64E, has been current since 2003. A placer claim, 

located by Robert Anderson and Douglas E. Noland, near 

Nevada State Highway 164 west of the Searchlight district, in 

section 29 of T28S, R63E, has been current since 1994. Doris 

Atchison and a group of four other individuals hold a placer 

claim in section 7 of T28S, R 64E that was newly located in 

2005. The claim is within the Piute-Eldorado Tortoise ACEC, 

about 10 km northeast of the town of Searchlight.

Areas South of Searchlight

Three placer claims located by James E. Tinnell are near 

the Roman Mine in the Newberry Mountains, in section 21 

of T30S, R65E. They have been current since 2003. A placer 
B52 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

claim and a millsite claim, located by Thomas E. Smigel, near 

Hiko Spring, in the southeasternmost part of the Piute-Eldorado Tortoise ACEC, have been current since 1997. The claims 

are in section 12 of T32S, R65 SE.

A group of 10 claims (the Big John group), located by 

Misra Shruti, along the west flank of the Newberry Mountains about 2 km north of the Juniper Mine, has been current 

since 1999. The claims are in section 24 of T31S, R64E. We 

took a single sample here of quartz-veined Proterozoic gneiss 

(5-050703) that did not contain anomalous metals (Ludington 

and others, 2005).

Four claims (the Search group) were located by four 

individuals in 1980 and were still current in 2005. These 

claims are in section 6 of T31S, R65E, on the pediment along 

the front of the Newberry Mountains about 2 km northwest of 

Christmas Tree Pass. We noticed some small pits in the areas 

but saw no evidence of hydrothermal mineralization. Two 

claims (the Blue Cloud group) were located in 2001 by Leslie 

W. Hopper, in section 32 of T31S, R65E. These claims are in 

granite of the Spirit Mountain batholith about 2 km southeast 

of the Juniper Mine.

A group of 9 claims (the Treasure Trove group) were 

located by Michael Steven and Stanley Pierce in 1981 and 

1998, in sections 9, 10, and 16 of T32S, R64E. These claims 

are 2 to 3 km southeast of the junction of U.S. Highway 95 

and Nevada State Highway 163 in the Chiquita Hills. They 

are, at least in part, within the Piute-Eldorado Tortoise ACEC 

and remained current in 2005.

Placer Claims in Piute and Eldorado Valleys

In addition, most of the surface of Piute and Eldorado Valleys in the Piute-Eldorado Tortoise ACEC is covered by a group 

of hundreds of association placer claims staked in 1986, 1989, 

1990, 1993, 1994, 1996, 1997, 1999, and 2000 under a variety 

of names. The claims appear to be all controlled by a group 

known as Cactus Gold Corp., of Surrey, British Columbia. The 

intention of this group is to recover precious metals that might 

occur in late Tertiary and Quaternary sediments. Their activities 

and exploration model came to our attention after field and laboratory studies for this assessment were complete.

Mineral Resource Potential

Locatable minerals in Piute-Eldorado Tortoise 

ACEC

The complex structural environment of the Piute-Eldorado Tortoise ACEC means that relating inferences about the 

size and shape of the original preextension mineral deposits is 

difficult and subject to different interpretations. The mineral 

resource potential tracts described in this section are subject 

to this caveat. Furthermore, because of suspected low-angle 

faults with large displacements in the subsurface, these tracts 

are valid to depths of no more than a few hundred meters. As 

structural interpretations improve, it may become possible to 

identify tracts at greater depths. The tracts were delineated in 

the context of the entire mineralized system; those that are not 

within the ACECs are identified as such.

Searchlight-Type Gold-Bearing Vein Deposits 

(Searchlight Area)

Many of the mines in the Searchlight District were 

abandoned because of changing economic conditions, and it is 

likely that modern exploration methods could find significant 

quantities of additional ore in the known part of the district. 

However, reassessment of the district in the light of our present understanding of the structural context for these veins, 

combined with the geochemical sampling we conducted, leads 

to the identification of additional areas that have the potential 

for the discovery of gold ore. Figure 55 shows areas that have 

potential for Searchlight-type gold-bearing vein deposits, as 

well as some other types of deposits.

Tract PEV01 includes the mines that were productive in 

the 20th century, but it also includes areas to the west, originally above the roof of the Searchlight pluton. The tract has 

high potential for undiscovered Searchlight-type gold-bearing vein deposits, with a moderate level of certainty, and it 

includes all the environments where gold might have been 

deposited, based on studies of hydrothermal alteration (fig. 

29) and geochemistry (fig. 31). Most of the area is outside the 

Piute-Eldorado Tortoise ACEC, but much of the outer parts 

of the tract are within the ACEC. The tract includes the hills 

underlain by alunite-bearing rhyolite west of the main part of 

the Searchlight district, and, although we found no significant 

amounts of precious metals in this altered rock, the rocks of 

the lower intermediate-composition unit of the volcanics of the 

Highland Range, which commonly host gold veins in the district, may underlie these hills at shallow depths. The position 

of the western limit of the tract is guided by the hydrothermal 

alteration west of the rhyolite hills and by the presence of 

>0.2 ppm gold in sample 5-110201 (Ludington and others, 

2005). To the south, the identified rocks pass under Quaternary 

alluvium, and we lack any subsurface information that would 

allow the delineation of the southern limits of the tract. Further 

geochemical sampling near the margins of this tract would be 

required to raise the certainty level.

Tract PEV02 (fig. 55), which is centered on the Fourth 

of July Mountain area, is our interpretation of where this 

same environment is located in the Fourth of July structural 

block. It has high potential for undiscovered Searchlight-type 

gold-bearing vein deposits, with a moderate level of certainty. 

The samples taken at the Chief of the Hills Mine (5-031702 

and 5-031703; Ludington and others, 2005) contain some of 

the highest gold values we obtained in this study, >15 ppm 

and 6.5 ppm, respectively. The area to the west of this mine 

is characterized by intense hydrothermal alteration, both illite 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B53

Figure 55. Mineral resource potential tracts for gold-bearing deposits in the Searchlight area (Piute-Eldorado Tortoise Area of Critical 

Environmental Concern (ACEC)).

PEV01

PEV02

PEV08

PEV07

PEV04

PEV05

PEV06

PEV03

114°55'0"W 114°50'0"W 114°45'0"W

35°20'0"N

35°25'0"N

35°30'0"N

02468 1

Kilometers

Piute-Eldorado Tortoise

ACEC Tract ID Deposit Type Potential Level Certainty Level

PEV03 High Moderate

Searchlight

Au vein Moderate Low

PEV05

Searchlight

Au vein

Low Moderate

PEV06

unspecified

Moderate Low

PEV07

Searchlight

Au vein

Moderate Low

PEV08

Searchlight

Au vein

Moderate Moderate

PEV04

High

High Searchlight

Au vein

Searchlight

Au vein PEV01

PEV02

Polymetallic

vein

Moderate

Moderate

High mineral

resource potential

Moderate mineral

resource potential

Low mineral

resource potential

and quartz-alunite (fig. 29), and the limits of the tract are 

delineated primarily on the basis of this alteration, the high 

gold values obtained, and the structural setting just above 

the contact with the Searchlight Pluton. This tract is entirely 

outside the Piute-Eldorado Tortoise ACEC, but the south end 

is within 150 m of the ACEC boundary. Further geochemical 

sampling could help modify the boundaries and increase the 

certainty level of this tract.

Tract PEV03 (fig. 55), about 2 km east of Fourth of July 

Mountain, includes the New Era Mines, delimits the analogous environment in the Pinto structural block, and has high 

potential for undiscovered Searchlight-type gold-bearing vein 
B54 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

deposits, with a moderate level of certainty. The volcanic 

rocks just above the quartz monzonite in the upper member 

of the Searchlight Pluton are altered to smectite clays, and the 

tract is delineated primarily on the basis of this alteration and 

the structural setting just above the contact with the Searchlight Pluton. None of the samples we took contained substantial amounts of precious or base metals, but they are variously 

anomalous in arsenic, antimony, and tellurium (Ludington 

and others, 2005). Interestingly enough, all the samples in this 

tract contained detectable platinum or palladium, although at 

levels less than 2 ppb. This tract is entirely outside the PiuteEldorado Tortoise ACEC, but the south end is within 100 m 

of the ACEC boundary. Sampling in this area was sparse, and 

further geochemical samples could change the boundaries and 

certainty level for this tract.

Two areas in the Fourth of July structural block have 

moderate potential for undiscovered Searchlight-type gold-bearing vein deposits, with a low level of certainty (tracts PEV04 

and PEV06, fig. 55). The northern one, PEV04, is about 2 km 

east of the Searchlight airport, and its boundaries are delineated 

primarily on the basis of inferred hydrothermal alteration, based 

on ASTER imagery (fig. 29). We did not sample this area. The 

other one (PEV06) is about 3 km further south, just to the south 

of Tip Top Well. The boundaries of this tract are similarly delineated using inferred hydrothermal alteration based on ASTER 

imagery, and passes to the south under the sediment that fills 

Piute Valley. Neither of these tracts is within the Piute-Eldorado 

Tortoise ACEC. These areas have been little studied, and field 

visits and geochemical sampling could help modify the tract 

boundaries and raise the certainty level.

Tract PEV05 (fig. 55) is also delineated on the basis of 

ASTER imagery, as well as petrographic studies. Rocks in 

this area seem to have abundant, but very fine-grained drusy 

quartz filling myriad internal fractures, but are otherwise little 

altered. One sample, 5-061103 contains only mildly anomalous precious-metal values (1 ppm silver and 0.01 ppm gold; 

Ludington and others, 2005). We designate the tract based on 

the coherent area of silica addition but have difficulty assigning a mineral deposit model. The tract has low potential with 

a moderate level of certainty; it is also not within the PiuteEldorado Tortoise ACEC.

Tract PEV07 (fig. 55) also has moderate potential for 

undiscovered Searchlight-type gold-bearing vein deposits, but 

with a low level of certainty. It lies partially within the Pinto 

structural block and partially within the Bill Gays structural 

block. It is delineated on the basis of inferred hydrothermal 

alteration based on ASTER imagery, on the structural setting, 

and on some curious geochemistry in the only sample we 

took from the area (5-060702, Ludington and others, 2005). 

This sample is a brecciated rhyolite that has been subjected 

to strong argillic alteration. Kaolinite is the chief alteration 

mineral. The sample contains 0.68 percent sulfur and 24 

ppm tungsten. The area is mostly within the Piute-Eldorado 

Tortoise ACEC and partly within the Lake Mead National 

Recreation Area and Nellis Wash Wilderness. Further study of 

this remote area is necessary to refine the assessment.

Gold-Bearing Vein Deposits North and South of 

Searchlight

Tract PEV08 (fig. 55) also has moderate potential for 

undiscovered gold-rich polymetallic vein deposits with a 

moderate level of certainty. This tract is well to the southeast (20 km) of Searchlight, and it is entirely in Proterozoic granitic and metamorphic rocks. It contains the area 

surrounding Camp Thurman, where the mines are known 

variously as the Potential Mine, the Yarmouth Mine, and 

the New Deal Mine. A sample from the dumps in this area 

contained 9 ppm gold and 3 ppm silver (4-050304; table 4 

and Ludington and others, 2005). ASTER imagery shows a 

linear band of hydrothermal alteration extending from Camp 

Thurman west to the range front, an area about 3.5 km long 

and about 800 m wide. Two areas farther south, near the 

Roman Mine, show similar ASTER signatures. Our field 

examination and PIMA studies of these areas confirmed that 

the rocks are altered to clays and illite and stained with iron 

oxide. Chemical analyses of rocks from these areas show 

only weakly anomalous Ba, Li, Mo, Zn, P, Sn, and Y. None 

of the samples (aside from one from the Potential dump) 

showed elevated precious metals. Many areas within the 

tract show scattered quartz veining. Parts of all three areas 

delineated as tract PEV08 extend into the Piute-Eldorado 

Tortoise ACEC. The parts within the ACEC were not sampled, and further study could help refine the tract boundaries 

and raise the certainty level.

Although the area has been prospected to a moderate 

degree in the past, the deposits at the Sazarac patented claim 

group (Rockefeller Mine) and the Cobalt claims (figs. 19, 56) 

have yielded gold values that merit the designation of mineral resource potential for the area. Tract PEV19 (fig. 56) has 

moderate potential for detachment-fault-related gold deposits, 

with a moderate level of certainty. The tract is partially within 

the Piute-Eldorado Tortoise ACEC and partly within the Lake 

Mead National Recreation Area. More detailed geochemical 

sampling could help refine the boundaries of this tract and 

increase the certainty level.

Significant gold values are also present in samples from 

the Juniper Mine (fig. 33), and from the Superfluous and 

Gibraltar claims (fig. 35), and these areas definitely have 

potential for the development of additional resources. Tract 

PEV18 (fig. 57) has moderate potential for gold-bearing 

polymetallic vein deposits, with a low level of certainty. The 

low level of certainty applies to the spatial accuracy of the 

delineation; this is because no large area of hydrothermally 

altered rock is associated with these deposits, and we can identify no other features to guide the delineation of tracts.

Porphyry Copper Deposits (Searchlight Area)

Evaluation of the possibility for existence of a porphyry 

copper deposit beneath the Searchlight mining district is based 

primarily on results of the exploration program carried out by 

Felmont Oil Corporation and Homestake Mining Company 
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B55

Figure 56. Mineral resource potential tract for detachment-fault-related gold deposits near the Rockefeller Mine, in the northern part 

of the Piute-Eldorado Tortoise Area of Critical Environmental Concern ACEC). Boundary of ACEC is in pink.

in 1979–81. They conducted an extensive surface sampling 

program to complement the 41 shallow drill holes. The surface 

sampling and the drill holes yielded disappointing results for 

gold and silver, as no indications of low-grade disseminated 

deposits were found. However, several of the drill holes intersected zones of copper mineralization, and one in particular 

revealed more than 30 m with greater than 1,000 ppm copper 

and a corresponding increase in sodium and decrease in potassium. Drill logs suggest that the copper-rich zone is in a rhyolite breccia altered to a quartz-alunite-topaz assemblage. Pyrite 

is found in this lower zone, instead of hematite. Although it is 

critical to the structural interpretation, it is not clear whether 

this breccia is intrusive and post-tilting or not. We interpret 

the mineralization to be pre-tilting like the gold mineralization, and therefore, any porphyry deposit would be rotated 90 

degrees and lying on its side.

PEV19

Crystal Lode

Cobalt

claims

Rockefeller mine

(Sazarac claims)

Five Spot claims

114°45'0"W

35°35'0"N

0 0.5 1 1.5 2 0.25

Kilometers

Tract ID Deposit Type Potential Level Certainty Level

Moderate Detachment-faultrelated Au PEV19 Low

Moderate mineral

resource potential
B56 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 57. Mineral resource potential tract for gold-bearing polymetallic vein deposits in the southern part of the Piute-Eldorado 

Tortoise Area of Critical Environmental Concern (ACEC). Boundary of ACEC is in pink.

The copper mineralization encountered in these drill 

holes leads us to designate three tracts in the area with 

potential for porphyry copper deposits, albeit with a low 

level of certainty. Tract PEV10 (fig. 58) has moderate 

potential with a low degree of certainty and represents our 

interpretation of where porphyry copper mineralization 

may be found in the subsurface in the main part of the 

Searchlight district, in the Searchlight structural block. It 

includes a small area within the Piute-Eldorado Tortoise 

ACEC west of the rhyolite hills on the north side of Nevada 

State Highway 164. Additional drilling and petrographic 

study of subsurface rocks, more radiometric dating, and 

detailed structural studies would be necessary to further 

refine this assessment.

PEV18

PEV18

Stewart mine

Juniper mine

Gibraltar claims

Superfluous No. 1 claim

114°50'0"W

35°10'0"N

0 0.5 1 1.5 2 0.25

Kilometers

US 95

Tract ID Deposit Type Potential Level Certainty Level

Moderate Gold-rich

polymetallic vein PEV18 Low

Moderate mineral

resource potential
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B57

Tracts PEV11 and PEV12 (fig. 58) have low potential 

with low certainty. They represent where the analogous 

porphyry environment may occur in the Fourth of July and 

Pinto structural blocks. PEV12 includes a small part of 

the Piute-Eldorado Tortoise ACEC south of Nevada State 

Highway 164, east of the town of Searchlight. In addition, 

we designate a more generalized tract, PEV13 (fig. 58), 

also with low potential and low certainty, to reflect the 

uncertainty in the structural interpretation of the area; it 

simply encloses all areas where a possible porphyry copper 

deposit might underlie the area. Tracts PEV11, 12, and 

13 lack any direct evidence for copper mineralization and 

are based on extrapolation from porphyry copper deposit 

models.

Figure 58. Mineral resource potential tracts for porphyry copper deposits in Searchlight area (Piute-Eldorado Tortoise Area of Critical 

Environmental Concern(ACEC)).

PEV13

PEV10

PEV11 PEV12

114°55'0"W 114°50'0"W

35°25'0"N

35°30'0"N

01234 0.5

Kilometers

Piute-Eldorado Tortoise

ACEC

Moderate mineral

resource potential

Low mineral

resource potential

Tract ID Deposit Type Potential Level Certainty Level

PEV12 Low

Porphyry

copper

Low Low

Porphyry

copper

PEV13

Moderate

Porphyry Low

copper

Porphyry

copper

PEV10

PEV11

Low

Low

Low
B58 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Gold-Bearing Polymetallic Vein Deposits 

(Crescent Area)

A number of deposits that contain significant amounts of 

gold in both veins and shear zones are found in the Crescent 

district. Because we are uncertain of the classification of many 

of these deposits, we designate two tracts to represent the mineral potential of these deposits, one (PEV09) for gold-bearing 

polymetallic veins and one (PEV14) for detachment-faultrelated gold deposits (fig. 59).

Figure 59. Map showing mineral resource potential tracts for gold-bearing polymetallic veins, detachment-fault-related gold deposits, 

and porphyry copper deposits in the Crescent area of the Piute-Eldorado Tortoise and Crescent Townsite Areas of Critical Environmental 

Concern (ACECs). Red cross hatch indicates areas of hydrothermal alteration identified with Advanced Spaceborne Thermal Emission 

and Reflectance (ASTER) imagery. Boundaries of ACECs are in pink.

PEV09

PEV14

PEV15

115°10'0"W 115°5'0"W

35°25'0"N

35°30'0"N

01234 0.5

Kilometers

Piute-Eldorado Tortoise

ACEC

Crescent Townsite

ACEC

High mineral

resource potential

Moderate mineral

resource potential

Low mineral

resource potential

Tract ID Deposit Type Potential Level Certainty Level

PEV15 Porphyry copper Low High

High

Moderate Detachment faultrelated deposits

Au-bearing PEV09 polymetallic veins

PEV14

High

Moderate
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B59

Tract PEV09 includes all the gold-bearing deposits in 

the Crescent area, so we designate it as high potential, with 

a high level of certainty for gold-bearing polymetallic veins. 

A remarkable proportion of the samples we took in this area 

contained significant gold values. The tract includes a large 

area on both sides of Nevada State Highway 164, and it also 

extends both eastward and westward under cover of Quaternary alluvium; we do not have information to delimit the western and eastern limits of this tract. Large areas of the tract are 

within the Piute-Eldorado Tortoise ACEC, and the Crescent 

Townsite ACEC is entirely within the tract. More exhaustive 

geochemical sampling of rocks within the ACEC could help 

refine the boundaries of the tract; petrographic studies of these 

samples could help refine the deposit classification.

Detachment-Fault-Related Gold Deposits 

(Crescent Area)

Tract PEV14 (fig. 59) is designed to represent the 

potential area for deposits we interpret to be detachmentfault-related gold deposits. It is entirely enclosed within tract 

PEV09, and has moderate potential with moderate certainty. 

Note that this is not meant to represent an area with lower 

potential within tract PEV09. Deposits within this tract could 

also be gold-bearing polymetallic veins; the designation of 

this tract reflects our lower confidence in the classification 

of some of the deposits, not overall lower mineral potential. 

The boundaries of this tract are guided by the distribution of 

silicified rocks related to low-angle faulting and by the mapping of Miller and Wooden (1993). Most of this tract is not 

within either the Piute-Eldorado Tortoise or Crescent Townsite 

ACEC. Detailed structural mapping of this area could help 

raise the level of certainty for application of the detachmentfault-related model.

Porphyry Copper Deposits (Crescent Area)

Tract PEV15 (fig. 59) has low potential with a high 

degree of certainty for porphyry copper deposits. The exploration of the deposit at Crescent Peak was done nearly 50 years 

ago. However, the drilling showed that some areas do not contain significant mineralization, and, unless there are important 

structural complications related to low-angle faulting, there is 

little room left in the prospective area to contain a porphyry 

copper deposit. The tract does not impinge on the Piute-Eldorado Tortoise or Crescent Townsite ACECs.

Perlite

Two tracts in the Piute-Eldorado Tortoise ACEC have 

potential for perlite deposits. A small area (Tract PEV16, fig. 

60) that includes the Searchlight Insulation Products perlite 

mine has high potential, with a moderate level of certainty. 

Perlite was produced in small amounts from this area in the 

1950s, and significant reserves remain. However, it is not 

clear that perlite from this property would be competitive in 

current markets. Part of the high potential area is in a private 

inholding, but the perlite mass that was mined and the tract we 

designated both extend into the ACEC.

A much larger tract (PEV17, fig. 60) has moderate potential for perlite deposits, with a moderate level of certainty. This 

tract includes areas mapped as middle Miocene rhyolite lavas 

(Faulds and others, 2002), which is the same rock unit that 

contains perlite in the high potential perlite area. On the basis 

of our field examination, this unit contains local exposures of 

perlite that might have commercial potential. None of the perlite occurrences that we examined outside Tract PEV16 were 

as large or as pure as the perlite in the Searchlight Insulation 

Products deposit, but undiscovered deposits may exist.

Perlite deposits that had past production, including the 

Nu-Lite Mine, are in the Castle Mountains just west of the 

Piute-Eldorado Tortoise ACEC. However, no perlite occurs 

within the Piute-Eldorado Tortoise ACEC, and we do not 

designate any potential tracts in this area.

Leasable Minerals in Piute-Eldorado Tortoise 

ACEC

None of the Piute-Eldorado Tortoise ACEC is within the 

region considered by the BLM to be moderately favorable for 

oil and gas (Smith and Gere, 1983). There is no indication of 

potential for brine or evaporite deposits of sodium or potassium. The Piute-Eldorado Tortoise ACEC contains no known 

deposits of other leasable minerals, and the potential for their 

occurrence is low.

Salable Minerals in Piute-Eldorado Tortoise 

ACEC

Crushed Stone.—High quality crushed stone resources 

occur mostly in the northern and eastern parts of the ACEC 

in parts of the Highland Range, Eldorado Mountains, and 

Newberry Mountains. Tract APET01 (fig. 61) has high 

potential for crushed rock aggregate resources, with a 

moderate level of certainty. Isolated areas of high potential 

resources are also scattered along the northeast flank of the 

New York Mountains on the southwest side of Piute Valley. 

The rock types that were used to define high potential areas 

include Miocene basaltic andesite and basalt in the Highland 

Range, northern McCullough Range, northeastern New York 

Mountains, and parts of the Newberry Mountains, as well as 

Miocene and Cretaceous granites within the Searchlight and 

Ireteba plutons.

Most of the rock outcrops in the ACEC were designated to have moderate potential for crushed-stone aggregate 

deposits, with a moderate level of certainty (Tract APET02, 

fig. 61). Volcanic rocks with moderate potential are so 

designated primarily based on the occurrence of volcanic 

glass. Although the glassy intervals may be interbedded with 
B60 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 60. Mineral resource potential tracts for perlite deposits in the Piute-Eldorado Tortoise Area of Critical Environmental Concern 

(ACEC). ACEC boundary is in pink.

PEV17

PEV17

PEV17

PEV16

115°0'0"W 114°55'0"W

35°30'0"N

35°35'0"N

01234 0.5

Kilometers

Piute-Eldorado Tortoise

ACEC

High mineral

resource potential

Moderate mineral

resource potential

Tract ID Deposit Type Potential Level Certainty Level

High

Perlite Moderate

PEV16 Perlite

PEV17 Moderate

Moderate

higher-quality volcanics, selective mining in such a case 

would probably not be feasible. Other volcanic units, particularly hydrothermally altered, intermediate-composition 

units of volcanics of the Highland Range are also considered to have moderate potential. Plutonic rocks classified as 

moderate aggregate potential include most of the Newberry 

Mountains, along with parts of the Eldorado Mountains and 

McCullough Range. Many of these granitic rocks commonly 

weather to gruss, and the porphyritic nature of these granitic rocks can result in rapid mechanical breakdown of the 

aggregate, which would be considered deleterious for many 

aggregate applications.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B61

Figure 61. Mineral resource potential tracts for crushed-stone and sand and gravel aggregate in the Piute-Eldorado Tortoise, Keyhole 

Canyon, and Crescent Townsite Areas of Critical Environmental Concern (ACECs). ACEC boundaries are in pink.

APET04

APET05

APET04

APET02

APET02

APET04

APET01

APET04

APET02

APET01

APET02

APET01

APET02

APET02

APET01

APET01

APET02

APET02

APET02

ACT01

APET02

APET02

APET01

APET02

APET01

APET01

APET03

AKCY03 AKCY02

AKCY01

APET02

APET02

ACT02

APET02

APET02

APET01

APET04

APET01

APET01

APET02

Aggregate

Potential

Crushed stone,

high

Crushed stone,

moderate

Sand and gravel,

high

Crushed stone,

low

Sand and gravel,

moderate

APET01 Crushed stone moderate

APET02 moderate

APET03 moderate

APET04 high

APET05 high

AKCY01 moderate

Crushed stone

Crushed stone

Sand and gravel

Sand and gravel

Crushed stone

high

moderate

low

high

moderate

high

Tract ID Deposit Type Potential Level Certainty Level

AKCY02

AKCY03

ACTS01

ACTS02

Crushed stone

Sand and gravel

Crushed stone

Sand and gravel

moderate moderate

high high

moderate moderate

high high

115°15'0"W 115°0'0"W 114°45'0"W

35°15'0"N

35°30'0"N

0 4 8 12 16 2

Kilometers

The lowest quality rocks in the area occur in the southern 

Highland Range to the northwest of Searchlight (Tract 

APET03, fig. 61). These rocks are felsic volcanics that are 

both unsound and commonly contain abundant glass, which 

would severely limit their use in aggregate applications. 

Tract APET03 has low potential for crushed-stone aggregate 

deposits, with a moderate level of certainty.

Sand and Gravel.—High quality sand and gravel deposits 

occur on the alluvial fans and washes along the margins of 

both Eldorado and Piute Valleys. Farther down slope, rock 
B62 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

materials are commonly broken into smaller and smaller 

fragments, eventually to mostly coarse sand with only minor 

amounts of material coarser than 4.75 mm, which is the 

necessary size for most aggregate applications. The width of 

the zone of high quality deposits is controlled by composition 

and mechanical properties of the source rock. Coarse, 

porphyritic-type granites and granite gneisses are distinctly 

more rapidly affected by mechanical breakdown than basalts, 

thus the transition from coarse- to fine-grained deposits is 

closer to the mountain front for the porphyritic and micaceous 

rocks, whereas large basalt clasts can be found many 

kilometers from their source. Tract APET04 (fig. 61) has high 

potential for sand and gravel aggregate deposits with a high 

level of certainty. Tract APET05 (fig. 61), which occupies the 

central parts of Piute Valley, has moderate potential for sand 

and gravel aggregate deposits, with a high certainty level.

Decorative Stone.—Decorative stone is generally considered a saleable commodity and is a subset of the crushedstone category. The Las Vegas metropolitan area is an 

excellent decorative stone market. Decorative stone, which 

is mostly used for landscaping, does not need to meet standards for high-quality construction aggregate, such as concrete or asphalt aggregate. Therefore, almost any rock type 

has potential as decorative stone, and it is difficult to assess 

its suitability on the basis of physical properties. However, it 

should be relatively sound and resistant to weathering, and 

it is generally sold on the basis of appearance. Pink or pale 

red stone seems to be the most marketable material in Las 

Vegas, but yellow, gray, white, brown, and black stone are 

also used. Therefore, marketability of decorative stone is 

based on the customer’s personal taste. Sandstone, granitic 

rock, volcanic rock, carbonate rock, and metamorphic rock 

are all utilized. Hydrothermally altered rock that contains 

hematite and (or) limonite is also suitable, providing that it 

is relatively sound.

With the exception of the Roman Mine, which is on 

unpatented mining claims directly east of the ACEC, decorative stone mines active in the vicinity of the Piute-Eldorado 

Tortoise ACEC are on patented mining claims. Mining on fee 

land obviates the necessity for BLM contracting and oversight, and reduces cost to the producer. Because it is difficult 

to assess the suitability of any rock unit or rock type for 

decorative stone, we have not delineated potential areas for 

these deposits.

Locatable Minerals in Crescent Townsite ACEC

All of the Crescent Townsite ACEC is within tract 

PEV09 (fig. 59), which has high potential, with a high level 

of certainty for gold-bearing polymetallic veins. A remarkable proportion of the samples we took in this area contained 

significant gold values. The northern part of the ACEC is also 

within tract PEV14 (fig. 59), which has additional moderate 

potential with moderate certainty for detachment-fault-related 

gold deposits.

Leasable Minerals in Crescent Townsite ACEC

None of the Crescent Townsite ACEC is within the region 

considered by the BLM to be moderately favorable for oil and 

gas (Smith and Gere, 1983). There is no indication of potential 

for brine or evaporite deposits of sodium or potassium. The 

Crescent Townsite ACEC contains no known deposits of other 

leasable minerals, and the potential for their occurrence is low.

Salable Minerals in Crescent Townsite ACEC

Crushed Stone.—Bedrock areas within this ACEC have 

moderate potential for crushed-stone aggregate deposits, 

with a moderate certainty level (tract ACTS01, fig. 61). 

Although much of the southern part of the ACEC is granodiorite, there are zones of hydrothermal alteration and 

shearing, both of which reduce the quality of any potential 

crushed-stone deposits.

Sand and Gravel.—The northern part of the ACEC has 

high potential for sand and gravel aggregate deposits with high 

certainty in Big Tiger Wash (tract ACTS02, fig. 61). Although 

relatively thin, the sand and gravel deposits contain abundant 

coarse clasts of resistant metamorphic and igneous rocks.

Decorative Stone.—Decorative stone is generally considered a saleable commodity and is a subset of the crushed-stone 

category. The Las Vegas metropolitan area is an excellent 

decorative stone market. Decorative stone, which is mostly 

used for landscaping, does not need to meet quality standards 

for high-quality construction aggregate, such as concrete or 

asphalt aggregate. Therefore, almost any rock type has potential as decorative stone, and it is difficult to assess its suitability on the basis of physical properties. However, it should be 

relatively sound and resistant to weathering, and it is generally 

sold on the basis of appearance. Pink or pale red stone seems 

to be the most marketable material in Las Vegas, but yellow, 

gray, white, brown, and black stone are also used. Therefore, 

marketability of decorative stone is based on the customer’s 

personal taste. Sandstone, granitic rock, volcanic rock, carbonate rock, and metamorphic rock are all utilized. Hydrothermally altered rock that contains hematite and (or) limonite is 

also suitable, providing that it is relatively sound.

Decorative stone mines active in the vicinity of the Crescent Townsite ACEC are on patented mining claims. Mining 

on fee land obviates the necessity for BLM contracting and 

oversight, and reduces cost to the producer. Because it is difficult to assess the suitability of any rock unit or rock type for 

decorative stone, we have not delineated potential areas for 

these deposits.

Locatable Minerals in Keyhole Canyon ACEC

Although it is relatively close to the Eldorado mining 

district, the Keyhole Canyon ACEC has no areas with high or 

moderate potential for metallic mineral deposits or any other 

locatable minerals.
Piute-Eldorado Tortoise, Crescent Townsite, and Keyhole Canyon ACECs B63

Leasable Minerals in Keyhole Canyon ACEC

None of the Keyhole Canyon ACEC is within the region 

considered by the BLM to be moderately favorable for oil and 

gas (Smith and Gere, 1983). There is no indication of potential 

for brine or evaporite deposits of sodium or potassium. The 

Keyhole Canyon ACEC contains no known deposits of other 

leasable minerals, and the potential for their occurrence is low.

Salable Minerals in Keyhole Canyon ACEC

Crushed Stone.—The granite in the north end of the Keyhole Canyon pluton is quite competent and has high potential 

for crushed-stone aggregate deposits, with a moderate level of 

certainty (tract AKCY01, fig. 61). The Proterozoic gneiss and 

schist north of the granite has moderate potential for crushedstone aggregate deposits with a moderate level of certainty 

(tract AKCY01, fig. 61).

Sand and Gravel.—Deposits of high quality sand and 

gravel aggregate in the alluvial fan that empties Keyhole 

Canyon constitute tract AKCY03 (fig. 61), which has high 

potential for sand and gravel aggregate, with a high certainty 

level. These deposits are a mixture of Keyhole Canyon granite 

and Proterozoic metamorphic rocks.

Decorative Stone.—Decorative stone is generally 

considered a saleable commodity, and is a subset of the 

crushed-stone category. The Las Vegas metropolitan area is 

an excellent decorative stone market. Decorative stone, which 

is mostly used for landscaping, does not need to meet quality standards for high-quality construction aggregate, such as 

concrete or asphalt aggregate. Therefore, almost any rock type 

has potential as decorative stone, and it is difficult to assess 

its suitability on the basis of physical properties. However, it 

should be relatively sound and resistant to weathering, and it 

is generally sold on the basis of appearance. Pink or pale red 

stone seems to be the most marketable material in Las Vegas, 

but yellow, gray, white, brown, and black stone area also used. 

Therefore, marketability of decorative stone is based on the 

customer’s personal taste. Sandstone, granitic rock, volcanic 

rock, carbonate rock, and metamorphic rock are all utilized. 

Hydrothermally altered rock that contains hematite and (or) 

limonite is also suitable, providing that it is relatively sound.

Decorative stone mines active in the vicinity of the Keyhole Canyon ACEC are on patented mining claims. Mining on 

fee land obviates the necessity for BLM contracting and oversight, and reduces cost to the producer. Because it is difficult to 

assess the suitability of any rock unit or rock type for decorative 

stone, we have not delineated potential areas for these deposits.

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Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter C. Mineral Resource Potential of the Gold Butte A, 

Gold Butte B, Virgin Mountain (Gold Butte C), Whitney 

Pocket, Red Rock Spring, Devil’s Throat, and Gold Butte 

Townsite Areas of Critical Environmental Concern, Clark 

County, Nevada

By Steve Ludington, Gordon B. Haxel, Stephen B. Castor, Brett T. McLaurin, and Kathryn S. Flynn 

Summary and Conclusions

The Gold Butte A Area of Critical Environmental 

Concern (ACEC) contains areas with high potential for the 

occurrence of nickel-copper-platinum group element (PGE) 

deposits and Kipushi-type sedimentary-rock-hosted copper 

deposits. Exploration in the Bunkerville district could reveal a 

significant resource of nickel, copper, gold, and PGE. Exploration for Kipushi-type sedimentary-rock-hosted copper deposits 

could reveal significant amounts of the strategic metals gallium and germanium. Technological developments to improve 

recovery could transform these small copper deposits into 

important sources of germanium and gallium. There are also 

areas with moderate potential for Kipushi-type sedimentaryrock-hosted copper deposits, for uranium deposits in sedimentary rocks, and for gypsum deposits. The potential for other 

undiscovered deposits of locatable or leasable mineral deposits 

is low. The Gold Butte A ACEC contains regions with high, 

medium, and low potential for crushed-rock aggregate deposits and areas with high, medium, and low potential for sand 

and gravel aggregate deposits.

The Gold Butte B ACEC has areas with high potential 

for low-sulfide gold-quartz vein deposits, high and moderate 

potential for Kipushi-type sedimentary-rock-hosted copper 

deposits, high and moderate potential for vermiculite deposits, moderate potential for nickel-copper-PGE deposits, and 

moderate potential for uranium deposits in sedimentary rocks. 

Exploration of small gold-bearing veins might reveal deposits 

that could be mined successfully. Exploration for Kipushi-type 

deposits could reveal significant amounts of the strategic metals gallium and germanium. Technological developments to 

improve recovery could transform these small copper deposits 

into important sources of germanium and gallium. The potential for other undiscovered deposits of locatable or leasable 

mineral deposits is low. The Gold Butte B ACEC contains 

regions with high, medium, and low potential for crushedrock aggregate deposits and areas with high, medium, and low 

potential for sand and gravel aggregate deposits.

The Virgin Mountain ACEC has areas with high potential for the occurrence of nickel-copper-PGE deposits and for 

beryllium-bearing pegmatite deposits. Additional exploration 

in the Bunkerville district could reveal a significant resource 

of nickel, copper, gold, and PGE. There are also regions with 

moderate potential for mica deposits. The potential for other 

undiscovered deposits of locatable or leasable mineral deposits 

is low. The Virgin Mountain ACEC contains areas with high, 

medium, and low potential for crushed-rock aggregate deposits and small areas with high potential for sand and gravel 

aggregate deposits.

The Whitney Pocket ACEC contains no mineral deposits, 

and the potential for undiscovered deposits of locatable or 

leasable mineral deposits is low. This ACEC contains areas 

with moderate and low potential for crushed-rock aggregate 

deposits and areas with high potential for sand and gravel 

aggregate deposits.

The Red Rock Spring ACEC contains no mineral deposits, and the potential for undiscovered deposits of locatable 

or leasable mineral deposits is low. This ACEC contains 

areas with low potential for crushed-rock aggregate deposits 

and areas with high and low potential for sand and gravel 

aggregate deposits.

The Devil’s Throat ACEC contains no mineral deposits, 

and the potential for undiscovered deposits of locatable or leasable mineral deposits is low. This ACEC contains areas with 

low potential for crushed-rock aggregate deposits and areas with 

high potential for sand and gravel aggregate deposits.

Most of the Gold Butte Townsite ACEC has high 

potential for gold vein deposits. A small part of it has moderate potential for Kipushi-type copper deposits. There are 

regions with medium potential for crushed-rock aggregate 

deposits and areas with high potential for sand and gravel 

aggregate deposits.
C2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management and, specifically, to determine mineral 

resource potential in accordance with regulations at 43 CFR 

2310, which governs the withdrawal of public lands. The Clark 

County Conservation of Public Land and Natural Resources Act 

of 2002 temporarily withdraws the lands described herein from 

mineral entry, pending final approval of an application for permanent withdrawal by the BLM. This report provides information about mineral resource potential on these lands.

Several months of field examinations were conducted 

in the area, with a special focus on the nickel and platinumgroup-element (PGE) deposits in the Bunkerville district (Virgin Mountain ACEC) and on the gold-bearing vein deposits 

in the Gold Butte district (Gold Butte B ACEC). A number of 

samples were collected and analyzed. Individuals with mining 

interests and representatives of companies with mining operations in and near the areas were contacted.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

This report describes a total of seven areas of critical environmental concern (ACECs) that are all contiguous. They are 

Gold Butte part A, Gold Butte part B, Virgin Mountain, Whitney Pocket, Red Rock Spring, Devil’s Throat, and Gold Butte 

Townsite. Collectively, we refer to them as the Gold Butte–Virgin 

Mountain ACECs (fig. 1). These areas collectively cover about 

1,394 km2 south of Interstate 15, east of the Virgin River, and 

west of the Arizona-Nevada border. A secondary road that leads 

south from Interstate 15 near Riverside townsite accesses all 

areas. The exit is about 120 km (75 mi) northeast of Las Vegas. A 

legal description of these lands is included in appendix 2.

Gold Butte A (749 km2

) and Gold Butte B (493 km2) are 

the largest of these ACECs, and they enclose Devil’s Throat, 

Whitney Pocket, Red Rock Spring, and Gold Butte Townsite 

ACECs. 

The Virgin Mountain ACEC (145 km2

) encompasses the 

highest elevations in the area, more than 2,400 m. It is south 

of the town of Mesquite, Nevada, and adjoins Gold Butte A 

ACEC.

The Whitney Pocket ACEC covers an area of less than 

1 km2 and occurs within Gold Butte A ACEC, immediately 

south of the Virgin Mountains.

The Red Rock Spring ACEC, with an area of 2.6 km2, 

contains a perennial spring. When visited in November of 

2004, the southwest-trending wash was flowing for several 

hundred meters downstream from the spring.

The Devil’s Throat ACEC, with an area of 2.6 km2

, is a 

very small rectangular area that is nearly flat, except for the 

Devil’s Throat sinkhole in its center. This sinkhole is about 25 

m in diameter and about 60 m deep.

The Gold Butte Townsite ACEC is also less than 1 km2

and is apparently meant to include the remains of the town of 

Gold Butte, which thrived briefly in the early part of the 20th

century. Curiously, most of the original townsite, including 

the site of the Post Office, is several hundred meters outside 

(south of) the ACEC.

These areas incorporate two existing wilderness areas, the 

Lime Canyon Wilderness, in the northwest part of Gold Butte 

B, and the Jumbo Spring Wilderness in the southeast part of 

Gold Butte B (fig. 1). Lime Canyon was studied extensively 

by the U.S. Geological Survey (Winters, 1988; McHugh 

and Nowlan, 1989; McHugh and others, 1989; Bullock and 

others, 1990; and Evans and others, 1990). The Jumbo Spring 

Wilderness was designated in 2002, and its mineral resources 

were not studied at that time.

In addition, two areas were studied for possible 

wilderness designation, the Million Hills Wilderness Study 

Area (Causey, 1988; McHugh and Nowlan, 1989; McHugh 

and others, 1989; Moyle and Buehler, 1990; and Bergquist 

and others, 1994) in the southern part of Gold Butte A and 

the eastern part of Gold Butte B ACECs, and the Virgin 

Mountains Instant Study Area (Hose, 1980; Carlson and 

Cooley, 1981; and Hose and others, 1981) in the central part 

of the Virgin Mountain ACEC (fig. 1).

Physiographic Data

The Gold Butte–Virgin Mountain ACECs range in 

elevation from about 500 m to more than 2,460 m. The low 

areas are on the west boundary of Gold Butte B, just above 

the shoreline of Lake Mead and on the northwest boundary 

of Gold Butte A, along the Virgin River (fig. 2). The high 

point is the summit of Virgin Peak (about 2,460 m), in the 

Virgin Mountain ACEC. Many of the valley floors, including 

the broad flat area in the southern part of Gold Butte A that 

includes Red Rock Spring and Devil’s Throat, lie between 

about 700 and 800 m elevation.

Because of the dry climate and the temperature 

extremes prevalent here, the physiography of the mountain 

ranges commonly reflects the composition of the bedrock. 

Limestones form rugged, linear ridges, whereas sandstone, 

shale, and tuffaceous rocks form less regular and more 

subdued shapes. The crystalline rocks in the Virgin 

Mountains and in parts of the Gold Butte B area are resistant, 

irregularly dissected, and form massive mountains (fig. 3).

Most of the area drains southwest, west, and northwest, 

into the Virgin River or its extension, the Overton Arm of 

Lake Mead, but there are few perennial streams other than 

the Virgin River.

Geologic Setting

These seven ACECs are on the western margin of the 

tectonically stable Colorado Plateaus region, and at the eastern 

margin of the Basin and Range Physiographic Province, a region 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C3

Figure 1. Index map, showing boundaries of Areas of Critical Environmental Concern (ACECs; outlined in pink), wilderness areas (bluegreen), wilderness study areas (yellow-green), and mining districts (teal).

Bunkerville

mining district

Gold Butte

mining district

Pinto Valley

Wilderness

Jimbilnan

Wilderness

Lime Canyon

Wilderness

Jumbo Spring

Wilderness

Million Hills

Wilderness

Study Area

Virgin Mountains

Instant Study Area

GOLD BUTTE, PART A

ACEC

GOLD BUTTE, PART B

ACEC

MORMON MESA

ACEC

VIRGIN MOUNTAIN

ACEC

VIRGIN RIVER

ACEC

DEVIL'S THROAT

ACEC

RED ROCK SPRING

ACEC

WHITNEY

POCKET ACEC

GOLD BUTTE

TOWNSITE ACEC

Overton

Mesquite

Riverside

Glendale

NV 168

NV 169

I-15

NV 170

ARIZONA

NEVADA

Lake Mead

114°30'0"W 114°15'0"W 114°0'0"W

36°15'0"N

36°30'0"N

36°45'0"N

GoldButeACE

Scale1:24,0

0 8 16 24 32 4

Kilometers
C4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 2. View north from high in the Virgin Mountains, showing 

the town of Mesquite and the Virgin River.

Figure 3. View of Virgin Mountains from northwest. Highest 

point on skyline (right) is Virgin Peak. Light area in middleground is 

workings of the Key West Mine.

characterized by extensive Tertiary deformation. Much of the 

bedrock in the area is composed of unmetamorphosed Paleozoic and Mesozoic sedimentary rocks, but there are two large 

areas of Proterozoic metamorphic rock—one in the north, in 

the Gold Butte A and Virgin Mountain ACECs, and one in the 

south, in Gold Butte B. A third, smaller area of Proterozoic rock 

is exposed in the Gold Butte B ACEC. There are also extensive 

exposures of Tertiary rocks in the Gold Butte A ACEC.

Geology

Rocks and mineral deposits in the Gold Butte–Virgin 

Mountain ACECs range in age from Early Proterozoic to 

Recent. Early deformation and metamorphism took place in 

the Proterozoic before about 1.6 Ga. The front of the Sevier 

thrust belt, which was active in late Mesozoic time, lies to the 

west and north, and therefore only minor Mesozoic deformation is recorded in the rocks of the area. The Paleozoic to 

Cenozoic rocks were mainly deformed after 16 Ma during a 

period of large-scale regional extension (primarily east-west) 

(Duebendorfer and others, 1998). Major faults active during 

this period subdivided the bedrock areas into several major 

structural blocks that are the first evidence of Basin-andRange-style extensional faulting west of the Colorado Plateaus 

(fig. 4). From north to south, the blocks are referred to as Bunkerville Ridge, Virgin Peak, Lime Ridge, Tramp Ridge, and 

Gold Butte (Beard, 1996; Deubendorfer and others, 1998).

The direction of movement along some of these major 

faults is a matter of debate. The Hen Spring and Bitter Ridge 

Faults on the north (fig. 4) are considered left-lateral faults 

that merge with the Lake Mead Fault Zone (Anderson, 1973; 

Beard, 1996). The Lime Ridge and Gold Butte Faults to the 

south, also interpreted as left-lateral faults (Beard, 1996), may 

be more complex features that also accommodated right lateral 

and (or) normal movements (Fryxell and others, 1992; Brady 

and others, 2000).

Proterozoic Rocks

Proterozoic metamorphic and igneous rocks are exposed 

in three principal areas. They form the core of the northeasttrending northern part of the Virgin Mountains and are also 

exposed in a small area in the southernmost part of the Virgin 

Mountains. They are exposed in two areas near Lime Ridge, 

one at the south end of the ridge and one in the valley to the 

east, between Lime and Tramp Ridges. Further south, all but 

the extreme east margin of the Gold Butte block is made up 

of Proterozoic rocks. These crystalline rocks record a prolonged Proterozoic history of multiple phases of metamorphism, ductile deformation, and granitic magmatism. They 

are depositionally and tectonically overlain by deformed 

but unmetamorphosed Paleozoic strata of continental shelf 

facies. The postmetamorphic brittle deformation of the 

basement and the Paleozoic and Mesozoic strata is probably 

mostly Tertiary in age.

In the Bunkerville Ridge and Virgin Peak blocks, the 

rocks exposed are quartzofeldspathic and granitic gneiss, 

pegmatite, and lesser amounts of schist and amphibolite (Beal, 

1965; Beard, 1993; Williams and others, 1997; Quigley and 

others, 2002). North and west of the Hen Spring Fault (fig. 5), 

the rocks are relatively leucocratic and consist of biotite- and 

garnet-bearing gneisses. South and east of the fault, the rocks 

are much more mafic and consist of mostly dark granodiorite 

gneiss with abundant amphibolite. Quigley and others (2002) 

describe the Virgin Mountains shear zone (fig. 5), a northeasttrending deformation zone that is exposed throughout most of 

the length of the northern Virgin Mountains. This zone was 

active primarily during the waning stages of the Early Proterozoic high-grade metamorphic episode in the Virgin Mountains.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C5

Figure 4. Structural blocks of the Virgin Mountains and areas to the south, southeastern Nevada and northwestern Arizona. Geology 

modified from Stewart and Carlson (1978) after Beard (1996).

Bunkerville Ridge block

Virgin Peak block

Lime Ridge block

Tramp Ridge block

Gold Butte block

Gold Butte Fault

Hen Spring Fault

Lime Ridge Fault

Bitter Ridge fault

Cabin Canyon Fault

Wheeler Fault

Black Ridge

Lime Ridge

Tramp Ridge

Azure Ridge

Bunkerville Ridge

Quaternary unconsolidated

 sediments

Cenozoic sedimentary and

 volcanic rocks

Mesozoic sedimentary

 rocks

Paleozoic sedimentary

 rocks

Proterozoic igneous and

 metamorphic rocks

EXPLANATION

114°30'0"W 114°15'0"W 114°0'0"W

36°15'0"N

36°30'0"N

36°45'0"N

Gold Butte ACEC

0 6 12 18 24 30 3

Kilometers

Mesquite

Overton

Lake Mead

Virgin River
C6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

The rocks in the Proterozoic outcrops south and east of 

Lime Ridge are granitic gneisses intruded by the biotite-hornblende granite of Lime Wash. In the Gold Butte block, there 

are four main types of metamorphic rock: (1) a garnet-bearing 

cordierite-sillimanite paragneiss, (2) a charnockitic gneiss that 

contains hypersthene and clinopyroxene in addition to quartz, 

feldspar, and biotite, (3) syntectonic foliated metagranitoid 

rocks, and (4) ultramafic intrusive rocks (Fryxell and others, 

1992). Radiometric dating of similar rocks in surrounding 

areas of Arizona and the Mojave Desert in California suggest 

that the age of the protoliths for these rocks is about 1.8 to 1.7 

Ga (Hook and others, 2005). The age of prograde metamorphism and polyphase deformation is about 1.76 to 1.68 Ga 

(Hook and others, 2005; Howard and others, 2003).

The metamorphic rocks are cut by a series of early and 

middle Proterozoic plutons, some of considerable size. The 

Gold Butte Granite, which makes up a large part of the Gold 

Butte block, is conspicuous for its large potassium feldspar 

phenocrysts and rapakivi texture (Volborth, 1962). It is about 

1.45 Ga in age (Anderson and Bender, 1989; Howard and 

others, 2003) and is representative of the anorogenic granites 

of that age that are widely distributed in the Western U.S. 

Cordillera (Anderson, 1983). The youngest Proterozoic rocks 

are a series of mafic intrusions composed of diabase, diorite, 

and gabbro that are found as both plutons and dikes (Volborth, 1962).

Proterozoic pegmatite and aplite dikes and sills occur 

widely in the gneissic rocks and are locally abundant. Volborth 

(1962) recognized three generations of aplite-pegmatite in the 

Gold Butte block—early, conformable, lens-like bodies and 

two younger generations of crosscutting dikes. Rubidiumstrontium ages of 1.70 and 1.63 Ga were reported on muscovite and potassium feldspar from large lens-shaped pegmatites (Volborth, 1962). In the Virgin Peak block, Beal (1965) 

described small, concordant lit-par-lit pegmatites; larger, concordant, lens-shaped pegmatites; and massive, tabular pegmatites that “may or may not be concordant with the host rocks.” 

A minimum K-Ar age for muscovite from a massive pegmatite 

at the Taglo Mine in the Virgin peak block was reported as 

1.37 Ga (Beal, 1965). Howard and others (2003) speculated 

that aplite dikes cutting the Gold Butte Granite might have 

been emplaced in the Mesozoic.

Figure 5. Geologic relations in part of the Virgin Peak and Bunkerville Ridge blocks, showing relations between mafic and felsic 

gneisses, Hen Spring Fault, and Virgin Mountains shear zone. Proterozoic rocks are portrayed with Advanced Spaceborne Thermal 

Emission and Reflection Radiometer (ASTER) imagery (Hook and others, 2005), using bands 4, 6, and 8. Reddish colors are silica-rich 

rocks. Pink line is boundary between Gold Butte A (left) and Virgin Mountain (right) Areas of Critical Environmental Concern (ACECs).

Area of Figure 6 Hen Spring Fault

Strands of Virgin

Mountains Shear

Zone

Paleozoic sedimentary rocks

Cenozoic and Quaternary

cover

Felsic gneisses

Key West

Mine

Great Eastern

Mine

Mafic gneisses

012345 0.5

Kilometers

36°37'30" N

114°7'30" W
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C7

Proterozoic mafic and ultramafic intrusive rocks occur in 

the gneisses in the Bunkerville Ridge, Virgin Peak, and Gold 

Butte blocks. The largest of the intrusive bodies is an irregular 

mass of ultramafic rock north of Mica Peak in the Gold Butte 

block that averages about 600 m wide and is about 1,800 

m long. It is mainly composed of mica-bearing peridotite, 

hornblendite, and pyroxenite that have been partially altered to 

serpentine and vermiculite (Leighton, 1967). Volborth (1962) 

mapped 20 relatively large lens-like bodies of this rock type 

in the Gold Butte block, and presented evidence indicating 

that they were emplaced before intrusion of the Gold Butte 

Granite. He also noted many smaller mica-bearing bodies 

with lamprophyric appearance, which he interpreted to be 

originally diabase dikes. Beal (1965) mapped several large 

masses of hornblendite as much as 90 m wide and 300 m 

long in the Bunkerville district, and noted that many smaller 

masses, some with gneissic textures, were also present in the 

area, generally in association with pegmatite. In addition, parts 

of the granodiorite gneiss found in the Virgin Peak block are 

distinctly rich in hornblende and at least as mafic as diorite.

Because of their relevance to nickel-copper-PGE deposits in the Bunkerville district, we studied Proterozoic mafic 

and ultramafic dikes in the Virgin Mountains extensively. The 

Bunkerville district features a regionally uncommon type of 

mineralization—nickel and platinum group elements (PGE) in 

pyrrhotite-bearing ultramafic dikes. The district includes two 

small deposits at the Key West and Great Eastern Mines, as 

well as a few surrounding prospects (fig. 6).

Pyrrhotite mineralization in the Bunkerville district 

is associated with a swarm of Paleoproterozoic mafic to 

ultramafic dikes. Within the variably metamorphosed dikes of 

this swarm we have identified four major protolith rock types: 

(1) augite-hornblende gabbro; (2) gabbro-related hornblendite 

(GRH); (3) olivine hornblendite (OHB); and (4) altered olivine 

hornblendite, some of which is pyrrhotite-rich. Gabbro and 

GRH are far more abundant than OHB. At one place we 

observed these different types of dike in contact; there, OHB 

intrudes gabbro and GRH.

Gabbro Dikes

Gabbro and GRH dikes are largely metamorphosed to 

amphibolite and extensively intruded by leucogranite and pegmatite. They form boudins within the regional gneissic foliation. Bodies of amphibolite or relict gabbro and GRH range in 

size from a decimeter thick and a few meters long to several 

hundred meters in largest surface dimension. Their shapes and 

sizes are partially inherited from original intrusive forms, but 

they more directly represent the cumulative effects of several 

episodes of deformation.

GRH is a minor phase or facies of a few gabbroic dikes 

and presumably formed by local crystal accumulation. Mesocratic gabbro grades into hornblendite through melanocratic 

gabbro and feldspathic hornblendite. Gabbro-GRH dikes only 

locally contain accessory or vein phlogopite. GRH typically is 

coarse grained and characterized by euhedral, lath-shaped hornblende. It does not contain olivine. In gabbro and GRH, wholerock concentrations of Ni, Pd, and Pt are broadly basaltic (table 

1, fig. 7). Gabbro and GRH lack primary pyrrhotite, only locally 

contain secondary pyrrhotite, and evidently are only indirectly 

or incidentally associated with mineralization. Data for all analyzed elements is reported in Ludington and others (2005).

Olivine Hornblendite Dikes

Olivine hornblendite (OHB) is common or dominant on 

mine dumps and in many prospects, but uncommon in natural 

exposures. This dike rock is distinctive in appearance, especially on weathered surfaces of outcrops and loose cobbles. 

Typically, differential weathering of olivine and hornblende 

produces a rough or pitted surface with a finely mottled dark 

green and brown appearance (fig. 8).

Petrographically, OHB dikes are mostly fine- to mediumgrained olivine hornblendite, olivine-clinopyroxene hornblendite, or clinopyroxene hornblendite; subordinate varieties 

include phlogopite hornblendite and hornblende clinopyroxenite. Virtually all OHB dikes have primary accessory pyrrhotite, and most have accessory phlogopite. Phlogopite may 

be uniformly distributed or concentrated in diffuse veins or 

patches. Hornblende generally is equant and subhedral, as well 

as lighter colored and less strongly pleochroic (presumably 

more magnesian) than the hornblende in gabbro and GRH. 

These dikes are not foliated.

Altered Olivine Hornblendite Dikes

Altered OHB is characterized by the presence of substantial phlogopite, along with various combinations and 

proportions of serpentine, secondary amphibole, and carbonate. Some, but not all, of these altered rocks contain a few to 

as much as about 20 percent pyrrhotite, plus other subordinate 

sulfide minerals, particularly chalcopyrite (fig. 8). Pyrrhotite 

and other sulfides form veinlets and diffuse patches or clusters, 

intergrown with phlogopite, amphiboles, and serpentine. 

Phlogopite alteration and pyrrhotite mineralization are almost 

entirely restricted to OHB dikes; rarely do they occur in gabbro-GRH dikes or country rocks.

Geochemistry

Most samples of unaltered and altered OHB (excluding 

pyrrhotite-rich OHB) contain approximately 44 percent SiO2, 

22 percent MgO, 0.1 to 0.7 percent S, 900 ppm (parts per million) Ni, and 10 to 200 ppb (parts per billion) Pd and Pt (table 

1 and fig. 6; Ludington and others, 2005). Palladium and platinum are considerably more variable than nickel. Median concentrations of palladium and platinum slightly to significantly 

exceed global averages for several major types of ultramafic 

rocks. Overall, Pt/Pd is slightly below average. Nickel is less 

abundant in unaltered OHB than in many or most ultramafic 

rocks; consequently, OHB has unusually high Pd/Ni.
C8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Hen Spring Fault

C a b i n Can y o n F a u l t Z o n e

North Key

West Spring

South

Key

West

Spring

Nickel Creek

Great

Eastern

Mine

Key West

Mine

Explanation

Metamorphic and igneous rocks [Paleoproterozoic]

Olivine hornblendite dike (locality)

Amphibolite, gabbro, hornblendite

Gneiss, pegmatite,

Attitude of gneissic foliation:

inclined, vertical

Fault

Adit, open-pit mine

?

0 2 1

km

N

Figure 6. Geologic sketch map of part of the Bunkerville district in the Virgin 

Mountains (see figure 5 for location). Olivine hornblendite dikes, typically only 

a few meters wide, are too small to map at this scale; localities are indicated 

by red dots. The dikes and other intrusions mapped in blue are predominantly 

medium-grained amphibolite, but also include medium- to coarse-grained 

mesogabbro, melanogabbro, hornblendite, feldspathic hornblendite, metagabbro, metahornblendite, and rare microgabbro. The gneiss and pegmatite unit 

comprises chiefly granitic and granodioritic gneiss, quartzofeldspathic gneiss 

and schist, pelitic or aluminous gneiss and schist, and fine-grained amphibolite. All of these metamorphic rocks are intruded by abundant pegmatite and 

leucogranite, and minor granite, mostly foliated but locally unfoliated. Only a 

small fraction of the many hundreds of bodies of amphibolite or gabbro and 

related rocks within the map area are shown. Dip of foliation is steep to locally 

moderate. Elevations range from about 1,050 m in the northwest part of the map 

area to about 1,600 m along a ridge between the Great Eastern Mine and Nickel 

Creek and near the southeast corner of the map area. Sources: Needham and 

others, 1950; Beal, 1965; Beard, 1993; Williams and others, 1997; and minor 

remapping by G.B. Haxel in 2004 and 2005.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C9

Ni (ppm) Pd (ppb) Pt (ppb) (Pd/Ni)×10 Pt/Pd References

Bunkerville district, medians

Gabbro and related hornblendite (n = 5) 340 3 9 8.8 2.0

OHB, unaltered and altered (n=11) 950 25 37 25 0.89

OHB, unaltered (n=5) 880 13 13 22 0.93

OHB, altered (n=6) 990 49 46 40 0.81

OHB, altered, pyrrhotite-rich (n=4) 3,100 690 620 280 0.91

Mafic and ultramafic rocks, global averages Crockett, 2002; Mungall, 

2005

MORB 140 0.46 0.41 3.3 0.89

MORB 110 0.26 0.30 2.5 1.1

OIB 370 4.6 4.3 12 0.93

OIB, alkalic 150 0.75 0.95 5.1 1.3

OIB, tholeitic 190 2.4 3.6 13 1.5

OIB, picritic – 7.3 5.9 – 0.81

Continental flood basalt 85 8.8 6.2 10 0.70

Island arc picrites and boninites ~400 ~3–10 ~3–10 ? ?

Boninite 520 4.5 5.7 11 1.3

Island arc picrite – 2.4 3.0 – 1.2

Island arc andesite – 0.38 0.95 – 2.5

Basalt associated with komatiite 330 12 15 36 1.2

Komatiite 1,200 10 10 8.3 1.0

Alpine lherzolite 2,100 7.4 10 3.5 1.4

Alpine harzburgite 2,400 3.8 5.1 1.6 1.3

Ophiolitic harzburgite 2,200 6.0 8.3 2.7 1.4

Spinel lherzolite nodules 2,100 2.8 4.4 1.3 1.6

Harzburgite nodules 2,400 2.0 5.6 0.83 2.8

CI carbonaceous chondrites 11,000 560 990 51 1.8 Anders and Grevesse, 1989

Bulk silicate Earth 2,000 3.9 7.1 2.0 1.8 McDonough and Sun, 1995

Primitive mantle 1,900 3.3 6.6 1.8 2.0 Palme and O’Neill, 2004

Continental crust Rudnick and Gao, 2004

Bulk 59 1.5 1.5 25 1.0

Lower 88 2.8 2.7 32 0.96

Middle 34 0.76 0.85 22 1.1

Upper 47 0.52 0.51 11 0.98 Peucker-Ehbrink and Jahn, 

2001

56 0.4 0.4 7.1 1.0 Wedepohl, 1995

Table 1. Median concentrations of Ni, Pd, and Pt, and median Pd/Ni and Pt/Pd, in dike rocks of the Bunkerville district compared with 

global averages for basaltic and ultramafic rocks, CI carbonaceous chondrites, and several earth reservoirs.

[Values rounded to two significant figures. MORB is mid-ocean ridge basalt; OIB is oceanic island basalt; OHB is olivine hornblendite.]

Four samples of pyrrhotite-rich altered OHB contain 

about 400 to 1,000 ppb palladium and platinum. Concentrations of nickel are about 3,000 ppm. Palladium and platinum 

are enriched over their abundances in average upper continental crust by factors of about 103, but nickel by only a 

factor of about 50.

Figure 9 demonstrates the progressive enrichment of Pd 

and Pt in altered OHB and pyrrhotite-rich altered OHB, relative to unaltered OHB. As already noted, enhancement of Ni 

is considerably less pronounced. Progressive enrichment in 

Cu, Au, and (surprisingly) Bi mimics that of Pd and Pt. The 

other 10 metals plotted in figure 9 show little or no systematic 

variation. The unaltered OHB compositions are similar to midocean ridge basalt (MORB) and perhaps typical of ultramafic 

rocks worldwide, except for slight enrichment in the chalcophile elements nickel, copper, platinum, palladium, and gold. 

Dikes of this composition are not common in the Proterozoic 

rocks of North America.

Paleozoic Rocks

Lying unconformably on the Proterozoic rocks is a series 

of marine sedimentary rocks of Cambrian through Permian 

age. These are primarily carbonate rocks, including both limestone and dolomite, with lesser amounts of siliciclastic rocks. 

The Paleozoic rocks are exposed primarily in a series of elongate, north-northeast-trending ridges in the Lime Ridge and 

Tramp Ridge blocks (fig. 4). They also crop out on the north 

side of the Bunkerville Ridge block, in the Virgin Peak block, 

and along the eastern edge of the Gold Butte block. Some 

Paleozoic units in the Gold Butte–Virgin Mountain ACECs 

have been assigned different names depending on whether 

they are correlated with the Grand Canyon or southern Great 

Basin stratigraphic section (table 2).

Basal Paleozoic (lower and middle Cambrian) rocks are 

primarily shale and sandstone. A Cambrian carbonate rock 

section overlies these. Ordovician and Silurian rocks are 
C10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Pt/Pd = 1.0

2.0

0.5

100

101

102

103

104

Pt

(ng/g)

100 101 102 103 104

Pd (ng/g)

10

1000

 100

100

101

102

103

104

Pd

(ng/g)

101 102 103 104 105

Ni (μg/g)

A

B

Gabbro and related hornblendite

Olivine hornblendite

unaltered

altered

pyrrhotite-rich

Figure 7. Covariation of nickel with palladium (A) and platinum 

(B) in Neoproterozoic gabbroic and olivine hornblendite 

(OHB) dikes in the Bunkerville district. Light gray indicates the 

approximate composition fields of common ultramafic, mafic and 

intermediate igneous rock types, based upon the data summarized 

in table 1. Because palladium and platinum are geochemically 

much alike and have subequal mantle and crustal abundances 

(table 1), concentrations of the two elements will be similar in 

most rocks. In B, the two dotted lines indicate deviations of a 

factor of two from a Pt/Pd ratio of unity (thin solid line). Nearly all 

of the Bunkerville samples plot within these limits.

Figure 8. Hand specimens of olivine hornblendite (OHB) from 

the Bunkerville district. A, Weathered surface of typical finegrained OHB, from a prospect near the Key West Mine (sample 

V42). Darker, slightly raised areas are chiefly hornblende; 

lighter colored, slightly depressed areas are partially altered 

or weathered olivine. B, C, Pyrrhotite-rich altered olivine 

hornblendite, upper dump, Great Eastern Mine (B, sample V83; C, 

sample V40).
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C11

Figure 9. Median abundances of 16 metals in gabbroic dikes and olivine hornblendite (OHB) dikes in the Bunkerville district, compared 

with average mid-ocean ridge basalt (MORB) (Sun and McDonough, 1989) and average upper continental crust (McLennan, 2001). 

Concentrations are normalized to those in Earth’s primitive mantle (McDonough and Sun, 1995). Elements are arranged (left to right) in 

order of increasing compatibility in partitioning between the present upper continental crust and the primitive mantle as indicated by the 

ratio of concentrations in these two reservoirs (Hofmann, 1988).

0.01

0.1

1

10

100

1000

Rock-type average / primitive mantle

Pb

Pb

W

W

Bi

Bi

Mo

Mo

Nb

Nb

Sn

Sn

Au

Au

Zn

Zn

V

V

Cu

Cu

Sc

Sc

Co

Co

Pd

Pd

Pt

Pt

Cr

Cr

Ni

Ni

Gabbro and related hornblendite

Olivine hornblendite

unaltered

altered

pyrrhotite-rich

MORB

Upper continental crust

missing, and the Cambrian rocks are overlain by Devonian 

to Permian carbonate and siliciclastic units. Above these is 

a thick Permian redbed section, and marine carbonate rocks 

overlie the redbeds. Chert is common throughout much of the 

Paleozoic section and is especially prominent in the Mississippian, Pennsylvanian, and Permian carbonate rocks.

Mesozoic Rocks

Mesozoic rocks mainly crop out in the Lime Ridge and 

Tramp Ridge structural blocks. The Bunkerville Ridge and 

Virgin Peak blocks contain only minor areas of Mesozoic rock 

exposures. The Mesozoic rocks are dominated by the thick 

Triassic Moenkopi Formation, a varied unit of carbonate rock, 

shale, and sandstone, locally gypsiferous. Rocks in this unit 

record the transition from a marine environment to a continental one. The Moenkopi is overlain by sandstone and siltstone 

of the Moenave and Kayenta Formations. Capping the Triassic 

succession is the colorful eolian sandstone of the Jurassic 

Aztec Formation.

Cenozoic Rocks

Late Oligocene to Middle Miocene rocks of the Horse 

Spring Formation lie with slight angular unconformity on 

the Mesozoic rocks (Beard, 1996). In contrast to the Muddy 

Mountains and Rainbow Gardens areas to the west, the Virgin 

Mountain–Gold Butte area contains only the two lowest units 

in this formation, the Rainbow Gardens and Thumb Members 

(Bohannon, 1984). The Rainbow Gardens Member includes a 

basal conglomerate and overlying carbonate rocks with some 

sandstone and minor tuff, and the Thumb Member is domi-
C12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Age Formation Grand Canyon 

correlate

Great Basin 

correlate Lithology

Cretaceous Baseline 

Sandstone — — Sandstone, conglomerate, siltstone

Early Cretaceous Willow tank 

Formation — — Claystone, siltstone, carbonaceous shale, sandstone, conglomerate

Early Jurassic Aztec Sandstone Navajo Sandstone — Eolian sandstone

Early Jurassic

Kayenta and 

Moenave 

Formations

— — Gypsiferous sandstone, siltstone, claystone, and conglomerate

Late Triassic Chinle Formation — — Mudstone, fine-grained sandstone, limestone, conglomerate

Early and Middle Triassic Moenkopi 

Formation — — Mudstone, siltstone, sandstone, limestone, dolomite

Early Permian Kaibab 

Formation — — Limestone dolomite, gypsum, siltstone, 

chert

Early Permian Toroweap 

Formation Coconino Sandstone — Calcareous siltstone and sandstone, gypsum, limestone and dolomite, chert

Early Permian Hermit Formation — — Sandstone, siltstone

Early Permian Esplanade 

Formation — Queantoweap Sandstone Sandstone, mudstone, siltstone

Pennsylvanian and 

Permian

Pakoon 

Limestone Supai Group Bird Spring Group Dolomite, gypsum, chert

Pennsylvanian and 

Permian 

Calville 

Formation Supai Group Bird Spring Group, Illipah Formation

Limestone, calcareous sandstone, dolomite, chert

Mississippian Redwall 

Limestone —

Monte Cristo 

Limestone, Rogers 

Spring Limestone

Limestone, dolomite, chert

Devonian

Temple Butte 

Limestone 

(Sultan)

—

Sultan Limestone, 

Muddy Peak 

Limestone, 

Guilmette 

Limestone

Limestone, dolomite, chert

Late Cambrian Nopah Formation — — Shale, siltstone, dolomite

Late Cambrian Muav Formation —

Frenchman 

Mountain Dolomite, 

Bonanza King 

Formation

Limestone, dolomite

Early and Middle 

Cambrian

Bright Angel 

Shale —

Chisolm Shale, 

Lyndon Limestone, 

Pioche Shale

Shale, sandstone

Early and Middle 

Cambrian

Tapeats 

Sandstone — — Sandstone

Table 2. Stratigraphic correlation chart for Paleozoic and Mesozoic sedimentary rocks in the Gold Butte–Virgin Mountain ACECs.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C13

nantly sandstone and conglomerate with some gypsum-rich 

sequences and some carbonate rocks near the base. Beard 

(1996) proposed that the Thumb Member was deposited in 

two basins, one corresponding with the present Wechech 

Basin in the northeast part of the Lime Ridge structural block, 

and another in the Horse Spring–Garden Spring area in the 

northeast part of the Tramp Ridge structural block. Deposition 

of the Thumb Member was, at least in part, synchronous with 

Miocene extension (Beard, 1996; Brady and others, 2000).

Mining History

The Virgin Mountain–Gold Butte group of ACECs is 

the site of two large mining districts. The Gold Butte district, 

organized in 1873, occupies most of the Gold Butte B ACEC 

and extends into the south part of the Gold Butte A ACEC 

(Tingley, 1992). The Bunkerville district (also known as the 

Key West or Copper King district) includes almost all of the 

Virgin Mountain ACEC and a large area in the north part of 

the Gold Butte A ACEC. A statement by Beal (1965) in a 

report on the Bunkerville district is applicable to all of these 

seven ACECs: “the mining history of the district is characterized by much development and exploration but little production.” Beal went on to note that only limited amounts of 

copper, nickel, cobalt, platinum, tungsten, mica, and beryllium 

were produced in the Bunkerville district. Minor amounts of 

gold, silver, copper, lead, zinc, and mica were produced in the 

Gold Butte district (Longwell and others, 1965).

Copper was discovered in the Bunkerville district around 

1900 at the site of the Key West Mine, which produced a little 

more than 3,000 short tons of copper-nickel-cobalt-platinum 

ore sporadically between 1908 and 1929 (Beal, 1965). According to Hewett and others (1936), recorded metal production for 

the Bunkerville district up to 1935 was about 128,000 pounds 

of copper, 1,700 pounds of nickel, 982 troy ounces of silver, 

52 troy ounces of gold, 10 troy ounces of platinum, and 177 

troy ounces of palladium. Unsuccessful attempts were made 

to put the Key West Mine into production again in the 1930s 

and 1950s. There is no recorded production from the nearby 

Great Eastern Mine, which was located and opened between 

1910 and 1920. From 1939 to 1941, the U.S. Bureau of Mines 

conducted underground exploration (sampling, drifting, and 

drilling) for nickel at the Great Eastern (Needham and others, 1950). All underground workings in both mines are now 

flooded and inaccessible.

Between 1900 and 1919, the average grade of ore 

produced in the Bunkerville district was reported to be 2.55 

percent copper, 3.29 percent nickel, and 0.183 opt (troy ounces 

per short ton) platinum (Tingley and LaPointe, 2001). Exploration by Falconbridge Exploration U.S., Inc., and Superior 

Oil, Minerals Division, in the 1980s resulted in an estimate 

for surface and underground resources of 226,000 t at average 

grades of 1.5 percent copper, 1.1 percent nickel, 0.4 percent 

cobalt, 0.06 opt platinum, 0.68 opt palladium, 0.01 opt gold, 

and 0.34 opt silver (Tingley and LaPointe, 1999).

Around 1999–2000, Freeport Resources Canada, Inc., in 

cooperation with Royal Standard and Falconbridge, planned to 

further explore the district based on new targets resulting from 

detailed geophysics provided by Falconbridge, but the work 

was never carried out. Trend Mining Co., of Coeur d’Alene, 

Idaho, was also active at the time, holding claims northeast 

and southwest of the Key West and Great Eastern Mines, on 

the trend of the dikes. Their last claims lapsed in 2004.

Tungsten was found in 1947 east of the Key West Mine 

area at what became the Walker (or Silver Leaf) Mine. In 1953 

Tri-State Metals Inc. erected a small mill near the Virgin River 

and operated the Walker Mine until 1956. Recorded production 

was reported to be only 27 units of WO3

 (equivalent to about 7 

kg of tungsten metal) in 1953 and 1954, and an additional 7 units 

produced in 1953 was probably from the same area (Longwell 

and others, 1965). At least 150 units of WO3 reportedly were 

produced in the Bunkerville district as a whole (Beal, 1965).

Metal mining began in the Gold Butte district when gold 

was discovered in 1905 and copper in 1907 (fig. 10). Recorded 

production of gold through 1965 was 1,669 troy ounces, 

mostly between 1935 and 1941 from the Lakeshore Mine 

about 1 km south of the Gold Butte B ACEC (Longwell and 

Figure 10. Gold Butte Post Office, March, 1907. Image courtesy of Utah State Historical Society.
C14 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

others, 1965). Recorded copper production from the district, 

about 150,000 pounds, was mostly before 1932 from the 

Azure Ridge, Lincoln, and Tramp Mines.

The Treasure Hawk Mine has a long history, although 

the actual year of discovery is not known. By 1913, when Hill 

(1916) visited the area, the mine, then known as the New Era 

group of claims, consisted of one shaft about 35 m deep and 

numerous smaller workings. In 1937, when it was known as 

the Webster group, the shaft had been deepened, and about 

150 short tons of ore had been produced, with an average 

grade of about 1 opt (Vanderburg, 1937). In the 1980s, Dexter 

and others (1983) reported that the mine had been operated 

for 10 years by Eddie Bounsall, who had used heap leaching 

methods to recover gold from alluvium and from crushed lodevein material that commonly contained from 0.5 to 0.75 opt 

of gold. The property was purchased from Bounsall’s heirs in 

the late 1990s and has been rehabilitated by Cutthroat Mining 

Corporation (Lear, 2000, 2004); production was scheduled to 

begin again in March of 2006.

The Lakeshore Mine, just outside the south boundary of 

Gold Butte B ACEC, was worked from 1934 to 1937, producing about 1,800 short tons of ore that contained approximately 

1,000 troy ounces of gold. Much of this ore was shipped by 

barge across Lake Mead, where it was loaded into railroad cars 

for shipment to a smelter (Vanderburg, 1937).

Pegmatites were explored in the Virgin Mountains and 

Gold Butte areas in the late 1800s. Muscovite-bearing pegmatites were found near Gold Butte in 1873 (Volborth, 1962). 

According to Longwell and others (1965), a few shipments of 

mica were made from mines in pegmatite in the “South Virgin 

Mountains” (Gold Butte B ACEC) in the 1890s and early 

1900s. According to Beal (1965), sheet mica was reportedly 

mined from “pegmatites several miles northeast of Virgin Peak” 

(probably in the Taglo Mine area), and a minor amount of beryl 

ore was produced from the Mica Notch area in 1935. The Taglo 

Mine (or Santa Cruz Mine), which was developed in the 1950s, 

reportedly consisted of three adits with about 500 ft (150 m) of 

underground workings and several shallow open cuts (Longwell 

and others, 1965). Mica was also produced from the Mica 

Notch area in the Virgin Mountain ACEC, and in 1958 a small 

mica separation plant was erected at the town of Riverside along 

the Virgin River to the north. One trial carload of mica from this 

plant was shipped to Los Angeles (Beal, 1965).

In 1960, Beryllium Associates of Salt Lake City leased 

claims in the Mica Notch area and evaluated them extensively 

by surface and underground methods (Beal, 1965). Development work consisted of two adits totaling 250 m and a number 

of trenches and pits. The only recorded production was about 

410 kg of beryl ore (Beal, 1965). The U.S. Bureau of Mines 

also investigated the Mica Notch beryllium deposits in the early 

1960s (Holmes, 1963). These deposits were explored actively in 

the 1960s, until the beryllium mine at Spor Mountain, Utah, was 

opened in 1970. Spor Mountain has remained the largest source 

of beryllium in the United States since that time (Lindsey, 1998).

Vermiculite was mined near Mica Peak in the Gold Butte 

ACEC in the 1940s, and several carloads of unprocessed 

vermiculite were shipped beginning in 1942. A 25-ton-per 

day mill was completed in 1945; however, the production rate 

was no more than 5 short tons per day, and the operation soon 

ceased (Leighton, 1967). A small open pit remains, along 

with several bulldozed trenches, but we noted no sign of the 

mill in 2005 (fig. 11). The size of the pit and tailings indicates 

that no more than a few hundred tons of vermiculite concentrate was produced (Hindman, 1995). In the 1980s, the area 

was examined for vermiculite by the Oglebay Norton Co. In 

2000, International Vermiculite LLC, a joint venture between 

Nevada Vermiculite and Stansbury Holdings Corp., announced 

plans to drill a deposit near Mica Peak (Castor, 2001). In 2001, 

Stansbury Holdings decided to abandon the Mica Peak project 

to concentrate on vermiculite in Montana. In 2004, IBI Corporation signed an option to acquire the claims (IBI Corporation, 

2004). In April of 2006, IBI signed a letter of agreement with 

Rio Tinto America Industrial Minerals Inc. that grants Rio 

Tinto an option to acquire a 100 percent interest in the claims. 

Mark Whitmore of Las Vegas currently holds the vermiculite 

deposits in the Mica Peak area under claim.

The Bauer magnesite prospect was located in 1922 in 

the Gold Butte A ACEC, but has had no recorded production (Longwell and others, 1965). Gypsum was prospected by 

trenching and pitting in two areas in the Gold Butte A ACEC, 

but there has been no production (Papke, 1987), and it is not 

known when this prospecting took place.

Mineral Deposits

A wide variety of mineral deposits and occurrences are 

within and near the seven ACECs addressed in this report. 

Many of the deposits are uncommon and do not lend themselves easily to standard mineral-deposit models. We have 

grouped the deposits into a number of categories based on 

commodities and formation processes, and we describe them 

according to these categories. The locations of the mines and 

prospects discussed below are shown on figure 12.

Figure 11. View of trenches and a small open-cut pit at the Gold 

Butte Vermiculite Mine (the western wall of the pit is in the right 

middle ground at the base of the hill). The vehicle is parked at the 

approximate site of the old vermiculite mill.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C15

Figure 12. Locations of mines and prospects in Gold Butte–Virgin Mountain Areas of Critical Environmental Concern (ACECs; 

boundaries in pink). Commodity sought or mined is in parentheses under each name (gyp=gypsum, verm=vermiculite). Red crosses are 

exploratory oil wells.

MORMON MESA TORTOISE

ACEC

VIRGIN RIVER

ACEC

GOLD BUTTE A

ACEC

GOLD

BUTTE B

ACEC

GOLD BUTTE

TOWNSITE

ACEC

RED ROCK SPRING

ACEC

DEVILS THROAT

ACEC

WHITNEY 

POCKET

ACEC

VIRGIN MOUNTAIN

ACEC

114°30'0"W 114°15'0"W 114°0'0"W

36°15'0"N

36°30'0"N

36°45'0"N

0 4 8 12 16 20 2

Kilometers

Taglo Mine

(Be)

Po' Boy

(Au mill)

Red Dot

(Cu)

Key West

(Ni-Cu-PGE)

Ole

(Au)

Pink Lady

(Cu)

Blue Chip

(U)

Blue Bell

(Cu)

Hen Spring

(gyp)

Ranch View (Cu)

Union (Au)

Tramp (Cu)

Eureka (Au)

Yellow Queen (U) Quartz Claim (Mn-Co) Lincoln Mine

Winona (Au)

Hilltop (U)

Green Monster

(Cu)

Bachmann (mica)

Lead (Pb-Zn) Jacob's Ranch

(U)

Windmill (Au)

Whitney Ridge

(Ti)

Great Eastern

(NI-Cu-PGE)

Lakeview Mine

(Cu)

Anderson

(Au)

Gudice Claims

St. Thomas Gap

(gyp)

Lakeshore Mine

(Au)

Jumbo (Au)

Bauer

(magnesite)

Legion Nos. 1-2

(gyp)

Atomic (U)

Black Jack (Cu) Boulder Nos. 1-2

(gyp)

Nevada Mica

(mica)

Azure Ridge (Cu)

Lookout

(Au)

Lime Kiln Canyon

(W)

Hummingbird (Be)

Whitmore (Au)

Roadside Prospect (Cu)

Leeway Nos. 3-4-5

(gyp)

Mica Mountain (mica)

Long Shot (U)

Mica Queen (mica)

Albert Nay (Au)

Virgin River Project

(Au mill)

Blackrock No. 1 (Be)

Black Ridge

(Cu-Au)

Thanksgiving

(NI-Cu-PGE)

Walker Tri-State

(W)

Gold Crown (Au)

South Valley No. 4

(U)

Marron (W)

Kim Ball

(magnesite)

Thomas Gap Fed JP-1

(oil well)

Gold Butte KPS Fed 1

(oil well)

Virgin Mtns. Be Deposits Hodges Whorton

(W)

Gethell (Au)

Blue Bird (verm)

First Chance (U) Treasure Hawk Mine

(Au)

Blue Ridge Nos. 1-2

(gyp)

Gold Butte (Au)

Snowflake (mica)

Horseshoe Mine (verm)

Old Dad and Uranium No. 1 Claims

Horse Springs (U)

Lucky Bart (U)

South Valley No. 2 (U)

Gold Butte

(Au)

Virgin Mts.

(gyp)

Western Beryl (Be) United Nickel Group

(NI-Cu-PGE)

Blue Beetle No. 1

(fluorspar)

North Star

(mica)

East Nos. 51-57

(NI-Cu-PGE)

+

+
C16 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Platinum-Bearing Ni-Cu Deposits

The most important mineral deposits in the area are 

Ni-Cu-Au-PGE deposits in the Bunkerville (or Copper King) 

district, in the Gold Butte A and Virgin Mountain ACECs. The 

Key West (fig. 13) and Great Eastern Mines contain significant 

amounts of platinum-group elements (PGE), which continue 

to create interest in the deposits.

The deposits were discovered in the late 1890s as copper 

deposits; their nickel and PGE contents were noticed later. 

Episodic production between 1908 and 1935 yielded about 

128,000 pounds of copper, 1,700 pounds of nickel, 982 troy 

ounces of silver, 52 troy ounces of gold, 10 troy ounces of 

platinum, and 177 troy ounces of palladium (Bancroft, 1910; 

Knopf, 1915, Longwell and others, 1965).

The deposits are hosted in Paleoproterozoic schist and 

gneiss, primarily the dark granodiorite gneiss that is found 

southeast of the Hen Spring Fault (figs. 5, 6). The ore at the 

Figure 13. View of Key West Mine area, looking southwest; 

Black Ridge in middle distance.

Key West and Great Eastern deposits consists of pods, disseminations, and veinlets of pyrrhotite and other sulfide minerals that occur within and in close association with the olivine 

hornblendite (OHB) dikes that characterize the deposits. These 

dikes, and the other mafic dikes that are not directly associated 

with mineralized zones, trend about N60°E, generally parallel 

with the trace of metamorphic foliation. The OHB dikes and 

the mineral deposits are also confined to the area northwest of 

the main strand of the Virgin Mountains shear zone (see fig. 

5), as mapped by Quigley and others (2002).

At the Great Eastern deposit, all of the principal adits and 

shafts are associated with OHB dikes, and a large majority of 

the rocks in the mine dumps are OHB, altered OHB, or pyrrhotite-bearing altered OHB. Variably altered OHB dikes at the 

Key West Mine are almost invariably associated with pyrrhotite. 

Throughout the district, most of the larger prospects and many 

of the smaller prospects target OHB or altered OHB. Altered 

OHB is the only significant host for pyrrhotite mineralization. 

From these facts, we infer that OHB dikes are the principal or 

sole agent or antecedent of pyrrhotite mineralization. Other 

geologists, some of whom had access to the deposits during 

exploration or small-scale mining, previously reached similar 

conclusions (Bancroft, 1910; Lindgren and Davy, 1924; Needham and others, 1950; Longwell and others, 1965).

Alteration of OHB and pyrrhotite mineralization of 

altered OHB are related but, to some extent, independent. Evidence pertaining to the origin of altered OHB can be observed 

in several prospects and at the Key West Mine. In these 

exposures, phlogopitized OHB forms a shell that envelops 

OHB and separates it from granitic country rock (fig. 14A). In 

another revealing exposure, a small pegmatite dike intruding 

OHB is surrounded by a sheath of phlogopitite (a rock comFigure 14. Phlogopotized olivine hornblendite (OHB) dikes in a prospect pit about 0.6 km southwest of the Great Eastern Mine. Hammer 

for scale is 35 cm long. A, OHB dike intruding gneiss, gneissic leucogranite and pegmatite. The dike consists of an outer zone of strongly 

phlogopitized OHB and a core of less altered OHB. B, Small pegmatite dike intruding OHB. The pegmatite dike is surrounded by a sheath 

of phlogopitite, which grades outward into phlogopitized OHB, which in turn grades (abruptly) into minimally altered OHB. Weathering 

and light Fe-oxide staining accentuate the color contrasts between these three zones.

gneiss

and

pegmatite

gneiss

olivine hornblendite (OHB) rubble

phlogopitized OHB

olivine hornblendite (OHB)

phlogopotized

OHB leucogranite

and

pegmatite pegmatite dike

phlogopitite

coarse-grained

phlogopite selvage

A B
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C17

posed almost entirely of phlogopite mica), grading outward 

into phlogopitized OHB (fig 14B). From these observations, 

we infer that altered OHB was produced by metasomatic reactions between the ultramafic OHB dikes and the quartzofeldspathic rocks that enclose or intrude them.

Pyrrhotite-rich altered OHB is observed only in mine 

dumps; the process by which this mineralized rock formed 

apparently is not visible at the surface, in either natural or 

artificial exposures. We suspect (but cannot demonstrate) that 

formation of large quantities of pyrrhotite in some altered 

OHB also was caused by thermal and chemical interaction of 

ultramafic magma with silicic country rock (Gianfagna and 

Tuzi, 1988; Li and Naldrett, 2000).

Relations of OHB and pegmatite are somewhat perplexing. In general, OHB dikes are unfoliated, apparently 

unmetamorphosed, and not intruded by leucogranite or 

pegmatite. Locally, the situation is more complicated. On the 

ridge east of the Great Eastern Mine, gabbro and amphibolite 

are, as usual, abundantly intruded by multiple generations 

of foliated and unfoliated pegmatite and leucogranite dikes. 

In contrast, OHB there is completely free of such intrusions, 

suggesting that it postdates all granitic magmatism associated with regional metamorphism. However, in exposures 

around adits at the Great Eastern Mine, OHB is intruded by 

at least two small nonfoliated pegmatite dikes (similar to the 

one shown in figure 14B). During underground exploration at 

the Great Eastern Mine, Needham and others (1950) noted an 

apparent association of pegmatite dikes with OHB: “Numerous granite pegmatite dikes converge with the main [hornblendite] dike at various angles and ... places.” Beal (1965) 

noted the same relationship. Did intrusion of ultramafic OHB 

magma cause local melting, now manifest as small pegmatite 

dikes? This possibility, though seemingly improbable, must 

be considered.

The relation between gabbro, gabbro-related hornblendite 

(GRH), and OHB is important in assessing PGE-Ni potential. 

Despite the fact that gabbro and GRH are much more abundant than OHB, all the mafic to ultramafic rocks clearly appear 

to belong to the same dike swarm. Though typical GRH and 

typical OHB are petrographically distinct, there are several 

dikes that seem to be texturally and geochemically intermediate. Gabbro, GRH, and unaltered OHB have generally similar 

abundance patterns for both ore and other metals and incompatible elements (fig. 9). Thus, gabbro, GRH, and OHB probably are petrogenetically related. However, all other information suggests that gabbro and GRH are not responsible for nor 

directly involved in pyrrhotite mineralization. Only OHB is 

closely associated with sulfide minerals.

The distribution of OHB, shown on figure 6, appears to 

form an east-northeast-trending belt that passes through the 

Key West and Great Eastern Mines. The dikes are conspicuous and weather to a distinctive dark soil, so it is reasonable 

to expect that we have identified all the surface expressions. 

However, dikes of this lithology that do not intersect the present erosion surface may be present at shallow depths, as well 

as a possible larger gabbro body.

Detailed magnetic and electromagnetic data indicated to 

industry geologists that “a structural zone is the locus for several large, altered dikes and a source pluton which could host a 

Sudbury-type offset dike environment for magmatic and remobilized hydrothermal Cu-Ni-PGE mineralization” (Freewest 

Resources Canada, Inc., 1999). This deposit type is described 

by Rickard and Watkinson (2001) and Lightfoot and Farrow 

(2002) and is dependent on local concentration of sulfides 

by flow differentiation. We concur that this deposit model is 

applicable to the Bunkerville deposits. Less-detailed regional 

geophysical data (Langenheim and others, 2000) show positive 

features beneath the Bunkerville area for both isostatic gravity 

and magnetism.

The ultramafic intrusions in the Gold Butte block are 

not known to contain copper, nickel, and PGE ore. However, 

Volborth (1962) reported copper and tungsten mineralization 

in the contact zone of a large body of pyroxene hornblendite at 

the Blue Bird Mine in the southeastern part of the Gold Butte 

B ACEC. Some of the Gold Butte block ultramafic rocks have 

nickel contents similar to those in unaltered OHB. Olivinepyroxene hornblendite sampled at the Blue Bird Mine contains 

as much as 870 ppm nickel and 0.02 ppm gold, and similar rock 

collected 1.5 km to the northeast has as much as 1,025 ppm 

Ni (Dexter and others, 1983). Rock samples from both localities contain <0.01 ppm palladium and <0.05 ppm platinum. In 

addition, samples of olivine- and pyroxene-bearing rock from 

the large body north of Mica Peak contain about 950 ppm nickel 

(samples AP-192 and AP-195A, Ludington and others, 2005).

Beryllium-Bearing Pegmatite Deposits

Beryllium deposits have been identified and evaluated in 

the Virgin Mountain ACEC (fig. 15). The beryllium mostly 

occurs as beryl and chrysoberyl in pegmatite dikes or sills as 

much as 20 m thick, but it has also been reported as disseminated chrysoberyl in schist with small pegmatite stringers 

(G.W. Hansen, written commun., 2005). The most extensively 

studied area is the Mica Notch area, also known as the Virgin 

Mountain chrysoberyl property, which was the site of 41 

unpatented mining claims in the 1960s (Holmes, 1964). In this 

area, beryllium-bearing pegmatites occur as sills, dikes, and 

irregularly shaped bodies that cut garnet-mica-quartz feldspar 

schist and locally cut amphibolite. Most of the pegmatite 

bodies appear to be steeply dipping, but some have shallowly 

dipping contacts with the host rocks (fig. 16). In addition to 

beryl and chrysoberyl, the pegmatites contain quartz, microcline, sodic plagioclase, muscovite, garnet, and tourmaline. 

Greenish-yellow chrysoberyl locally makes up as much as 10 

percent of the rock, and light-green to nearly colorless beryl 

crystals as much as 10 cm in diameter are also present (Beal, 

1965). The pegmatite bodies are mainly elongate bodies and 

sills, concordant with structure in the surrounding schist, that 

strike northeast, dip steeply to the southwest, and occur in a 

northeast-trending zone 1,800 m by 750 m (Holmes, 1964). 

Strike lengths of individual pegmatites are as much as 150 m 

and widths as much as 8 m.
C18 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 15. Beryllium-bearing pegmatites in the Virgin Mountain Area of Critical Environmental Concern (ACEC; boundary in 

pink), showing sample locations. Geology modified from Stewart and Carlson (1978).

Xm

Xm

Xm

Xm

Xm

JTRs

lPzc

lPzc

lPzc

lPzc

uPzc

lPzs

uPzc

uPzc

lPzc

lPzs

lPzs

lPzs

lPzc

lPzc

lPzs

uPzs

uPzc uPzs

Taglo mine

(Be)

Walker Tri-State mine

(W)

AP-062

AP-331

5-121502

AP-330

AP-057–061

JTRs

uPzc

lPzs

lPzc

Metamorphic rocks (Paleoproterozoic)—Undivided metasedimentary, metavolcanic, and gneissic rocks,

including locally abundant amphibolite, and pegmatite. May also include Paleoproterozoic 

granitoid rocks

Carbonate rocks (Mississippian to Permian)—Limestone, dolomite, and some shale. May include Kaibab,

Callville, Monte Cristo, Pakoon, and Redwall Limestones

Dolomite and Limestone (Cambrian to Devonian)—Dolomite, limestone, and minor amounts of sandstone,

shale, and siltstone. May include Temple Butte and Sultan Limestones, Frenchman Mountain Dolomite,

Bonanza King Formation

Sedimentary rocks (Triassic and Jurassic)—Shale, mudstone, siltstone, sandstone, and carbonate rock; 

some sparse volcanic rock. Includes Lower Jurassic Glen Canyon Group and Chinle and Moenkopi Formations

Sedimentary rock (Cambrian)—Sandstone, shale, and limestone. May include Pioche Shale, Tapeats Sandstone,

Bright Angel Shale, and Bonanza King, Muav, and Nopah Formations.

Xm

contact

fault

mine or prospect

sample location, with sample number AP-001

EXPLANATION

beryllium-bearing pegmatite

114°7'30"W

36°37'30"N

0 0.8 1.6 2.4 3.2 4 0.4

Kilometers
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C19

The U.S. Bureau of Mines collected 95 samples by 

percussion drilling and blasting or by outcrop chip sampling. 

Sample widths were as much as 3 m, and BeO contents 

ranged between 0 and 2.98 percent (Holmes, 1964), averaging (weighted by width) about 0.28 percent. Samples that we 

collected in the area contained as much as 0.115 percent BeO 

(table 3; Ludington and others, 2005). Beal (1965) reported 

that Beryllium Associates estimated a resource of 7,700 short 

tons of chrysoberyl ore averaging more than 1 percent BeO or 

190,000 short tons averaging 0.35 percent BeO in an area of 

about 800 m by 300 m. This resource amounts to a total BeO 

content of about 665 short tons.

Figure 16. Shallowly dipping upper contact of a berylliumbearing pegmatite in the Mica Notch area. Sample 5-121502 was 

taken in the core of the pegmatite, which is about 20 m thick here.

The Taglo Mine area (fig. 17) is about 1 km northeast 

of the Mica Notch area and is likely an extension of the same 

pegmatite zone. This area consisted of 20 unpatented claims 

in the 1960s (Holmes, 1964). Here, minor amounts of beryl, 

chrysoberyl, and possibly phenakite occur in steeply dipping, 

northeasterly trending pegmatite dikes. The pegmatites are 

mainly composed of quartz and K-feldspar and are as much 

as 2 m thick. Some outer zones contain abundant muscovite in 

books as much as 5 cm across (fig. 18). Pinkish-red to brown 

garnet and black tourmaline occurs locally. We found chrysoberyl as yellow-green plates as much as 1.4 cm across and 

0.2 cm thick (fig. 19), mainly in inner zones of white feldspar 

Sample Description Sample type Be (ppm} BeO (%)

AP-057 Taglo Mine, pegmatite dike, no Be minerals noted grab 89 0.025

AP-057A Taglo Mine, thin quartz-tourmaline vein grab 1 0.000

AP-058 Taglo Mine, 1.5-m wide dike, chrysoberyl + beryl 1-m chip 121 0.034

AP-059 Taglo Mine, 2-m wide dike with chrysoberyl 1.5-m chip 61 0.017

AP-330 Mica Notch, 10-m wide pegmatite dike with beryl 0.5-m chip 415 0.115

AP-331 Mica Notch, 7-m wide dike with chrysoberyl 1-m chip 56 0.016

5-121502 Mica Notch, 20-m thick sill with chrysoberyl chip 99 0.028

Table 3. Beryllium contents of samples from the Taglo Mine and Mica Notch areas, Virgin Mountain ACEC.

[BeO percent calculated as 2.78 x (Be ppm)/10,000.]

Figure 17. View looking southwest from the Taglo Mine area. 

The main pegmatite is in the immediate foreground, and a possible 

extension of this steeply dipping pegmatite is on the next hill to the 

southwest. The Mica Notch pegmatite area is on the vegetated 

ridge behind this that extends to the skyline.
C20 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

+ quartz rock. We also found minor amounts of light-gray to 

pale bluish-gray beryl. According to Beal (1965) pale-bluishgreen to green beryl crystals as much as 2 cm in diameter are 

present. The amount of beryl and chrysoberyl in Taglo Mine 

Figure 19. Platy crystals of yellow-green chrysoberyl in feldsparrich pegmatite from the Taglo Mine at sample site AP-058. The 

largest crystal in this image is about 1.4 cm across.

Figure 18. Detail of 1.5-m-wide pegmatite at sample site AP-058, 

Taglo Mine, showing coarse muscovite books in the border zone 

of the dike (bright areas at top of view).

pegmatites was estimated at 0.25 percent or less (Beal, 1965). 

Grab and chip samples that we collected from pegmatites and 

veins in the area contain only 1 to 121 ppm beryllium (table 

3; Ludington and others, 2005). The average BeO content of 

22 samples collected by the U.S. Bureau of Mines was 0.10 

percent, and the range was 0 to 0.62 percent (Holmes, 1964). 

No estimate is available for the amount of beryllium-bearing 

rock in the Taglo Mine area.

The area also contains pegmatites as much as 4 m thick 

that contain garnet and tourmaline, but they do not seem to 

contain beryllium minerals. In addition, the area contains 

quartz-tourmaline veins without visible beryllium minerals.

Other areas of Be-bearing pegmatites are along trend 

with the Mica Notch prospects and the Taglo Mine and extend 

northeastward several kilometers into Arizona. A sample that 

came from the Walker-Condie claims between the Mica Notch 

and Taglo areas is a 5-m chip sample that contains about 

0.07 percent BeO (Holmes, 1964). Beal (1965) showed many 

occurrences scattered over an area of about 1.3 x 2.8 km in the 

Nevada portion of this pegmatite belt.

Other Pegmatite Deposits

Radioactive pegmatite occurrences in the Gold Butte 

B ACEC were studied and sampled by Dexter and others 

(1983) during the National Uranium Resource Evaluation 

(NURE) program. They concluded that, although several 

occurrences had elevated contents of uranium, thorium, tantalum, and niobium, they were unlikely to be of sufficiently 

high grade or large size to be significant sources of uranium 

or rare metals.

The Hilltop Mine is probably the best known radioactive pegmatite occurrence in the area and reportedly yielded 

14 kg of samarskite (niobium oxide with variable amounts 

of uranium, tantalum, iron, and rare earth elements) from an 

underground location (Longwell and others, 1965). Dexter and 

others (1983) were unable to verify the presence of samarskite, 

but did report the rare-earth minerals allanite and monazite. 

Our examination showed that the Hilltop Mine pegmatite, a 

moderately east dipping dike at least 60 m long and as much 

as 14 m wide, has locally high radioactivity (as much as 35 

times background). The high radioactivity corresponds with 

concentrations of a greenish gray to black vitreous mineral 

that occurs sparsely in a 1.5- to 3-m-thick zone near the footwall of the dike. Based on analyses reported by Dexter and 

others (1983), the Hilltop Mine pegmatite has high thorium 

and tantalum contents, moderate uranium (about 100 ppm), 

and relatively low niobium.

Tungsten Deposits

Several small tungsten-bearing deposits and prospects 

occur in and near the Gold Butte–Virgin Mountain ACECs 

(fig. 12). All of them are hosted in Proterozoic metamorphic 

rocks. Two of them, the Walker Tri-State Mine and the Lime 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C21

Kiln Canyon prospect (which is outside the Virgin Mountain 

ACEC in Arizona), are located in the same rock unit that 

contains the beryllium pegmatites described above. These 

two tungsten deposits contain scheelite in quartz veins. The 

Walker Tri-State Mine was worked from 1953 to 1957, but 

production of only 34 units (245 kg) of tungsten trioxide was 

recorded (Longwell and others, 1965). The Hodges-Wharton 

prospect, also in the Virgin Mountains, is in the silica-rich 

gneisses north and west of the Virgin Mountain shear zone. No 

production has been recorded, and our examination showed no 

evidence for large amounts of mineralized rock. We took no 

samples at any of these tungsten occurrences.

The Marron tungsten prospect is in the southeast part of 

the Gold Butte block, about 4 km from the boundary of the 

Gold Butte B ACEC. Here, scheelite and powellite occur in 

joints and fractures in the Proterozoic gneiss and are spatially 

associated with concentrations of granitic dikes related to the 

Gold Butte pluton. No production has been recorded.

Gold-Bearing Vein Deposits

In the Gold Butte block, a number of northeast-trending 

quartz veins cut the Gold Butte granite and its wall rocks on 

the west side of its outcrop. Figure 20 shows the locations of 

mines and prospects that explore these veins and the relationship of the veins to the granite of the Gold Butte pluton. 

From north to south, the deposits are the Gold Crown, Gold 

Butte, Treasure Hawk, Ole, Lookout, Anderson, Winona, 

Gethell, Windmill, and Whitmore, all within the Gold Butte 

B ACEC, and the Lakeshore, Union, Jumbo, Eureka, and 

Joker, all within a few kilometers of the south boundary of 

the ACEC.

These deposits have been described briefly by Hill 

(1916), Lincoln (1923), Vanderburg (1937), and Longwell and 

others (1965). All of the prospects we visited consist of milkywhite quartz veins, from a few centimeters to nearly a meter 

in thickness. In some cases the veins are spatially related to, or 

grade into, tabular pegmatites.

The Gold Butte Mine was among the first gold discoveries in the Gold Butte district, and was explored as early as 

1905 (see fig. 10). Here, small quartz veins strike north and 

northeast and cut Proterozoic Gold Butte Granite (Hill, 1916).

Dexter and others (1983) sampled an adit in the Golden 

claim group, which was staked near or over the Gold Butte 

Mine, and reported a high-grade quartz vein sample containing 14.2 ppm gold and 8 ppm silver. A second quartz vein 

sample of questionable origin from the dump of the same 

adit was reported to have 9.4 ppm gold and 137 ppm silver 

with high copper, lead, and bismuth, and to contain abundant 

sulfide minerals, including galena and chalcopyrite. Samples 

from an area about a kilometer south of the Gold Butte Mine 

had gold values of 0.38, 0.59, and 4.26 ppm. Winters (1988) 

reported five samples from the Golden claim group, on the 

northwest side of the road, about a kilometer northwest of 

the Gold Butte Mine, with gold values of 0.06, 0.095, 0.23, 

0.43, and >10 ppm.

The nearby Gold Crown Mine and mill were reportedly 

active in the 1970s (Nevada Department of Industrial Relations, 1975) but are not mentioned in earlier reports, so the 

origin of any ore processed there is unknown.

The vein at the currently active Treasure Hawk Mine 

trends N85°E, and is exposed for a length of nearly 2 km 

(Longwell and others, 1965). The area has been described in 

the past under the names Radio Crystal Mine and Webster 

Mine. These are simply names for two different workings on 

the same vein. The width of the vein varies, but is commonly 

less than 1 m; the vein dips steeply to the south. It is primarily composed of quartz, but pyrite, galena, and fluorite have 

also been identified (Dexter and others, 1983). A grab sample 

from this vein (sample 5-020403, Ludington and others, 

2005) contained 0.73 ppm gold, 1.4 ppm tellurium, and 28.5 

ppm molybdenum; silver was not detected. Dexter and others 

(1983) reported samples from the Treasure Hawk Mine with 

1.01 to 10.5 ppm gold, undetectable (<3 ppm) to 4 ppm silver, 

and variably high copper, lead, and fluorine.

The Ole Mine (fig. 21) was originally called the Big 

Thing Tunnel, which was driven by Olli Rosson before 1913 

(Hill, 1916). Longwell and others (1965) reported that the tunnel had been lengthened, but no production had been recorded. 

This vein is also less than 1 m wide and trends N35°E to 

N45°E. Sulfide minerals in the vein are pyrite, chalcopyrite, 

galena, and sphalerite. A grab sample (4-110202) from the 

mouth of the tunnel yielded values of greater than 5 ppm gold, 

55 ppm silver, 2,600 ppm lead, about 45 ppm molybdenum, 

and about 36 ppm tellurium (Ludington and others, 2005).

The Lookout prospect is about 1 km south of the Ole 

Mine. There, a small quartz vein trends northeast and dips to 

the southeast; no production was recorded (Longwell and others, 1965).

The Anderson Mine is a vertical quartz vein with unreported strike; it contains pyrite, chalcopyrite, bornite, azurite, 

and chrysocolla (Longwell and others, 1965). There was 

apparently no production. We were unable to find any evidence for this deposit at the indicated location.

The Winona group of claims were on a quartz vein 

apparently seen only by Hill (1916). He observed a quartz 

vein striking N65°E, with sparse pyrite and chalcopyrite. We 

visited this site, but found no evidence of workings, only white 

quartz and pegmatitic material.

The Windmill Mine, known in 1913 as the Finance group 

of claims, exposes veinlets of white quartz striking N35°E. 

Hill (1916) noted pyrite, chalcopyrite, galena, and sphalerite. 

There has been no recorded production. Dexter and others 

(1983) reported gold values of 0.96, 3.01, and 3.82 ppm for 

samples they took from this mine.

The Whitmore property, also called the Greenhorn Mine, 

is a quartz vein with unknown strike that carries pyrite, chalcopyrite, bornite, and chrysocolla (Longwell and others, 1965). 

There is no recorded production.

The Lakeshore Mine, less than 1 km south of the Gold 

Butte B ACEC, was the largest producer of this entire group; 

between 1934 and early 1937, more than 2,500 short tons of 
C22 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 20. Mines and prospects on gold-bearing quartz veins in the Gold Butte block. Pre-Gold Butte granite metamorphic rocks are 

shown in gray, Gold Butte granite is dark pink, Paleozoic carbonate rocks are blue, Tertiary sedimentary rocks are gold, and Quaternary 

alluvium is pale yellow.

Ole aaaaaaaaMine

Joker Mine

Union Mine

Eureka Mine

Winona Group

Windmill Mine

Anderson Mine

Lakeshore Mine

Jumbo prospect

Gold Butte Mine

Lookout prospect

Whitmore

property

Gold Crown

Mine & Mill

Treasure Hawk

Mine

GOLD BUTTE B

ACEC

GOLD BUTTE TOWNSITE

ACEC

114°15'0"W

36°15'0"N

3

GoldButeACE

Scale1:24,0

0 2.5 5 7.5 10 1.25

Kilometers
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C23

gold ore were produced here (Vanderburg, 1937). Ore was 

trucked to the shore of Lake Mead, loaded on barges, and 

towed to the docks near Saddle Island, where it was again 

shoveled into trucks for a 6-mile trip to the railroad at Boulder City. One shipment of about 60 short tons averaged about 

1.55 opt gold and 0.78 opt silver. The vein is notable because 

it dips only about 8°. The Union, Jumbo, Eureka, and Joker 

Mines explored similar gold-bearing quartz veins, beginning 

before 1913, but they are located 3 to 7 km south of the ACEC 

boundary. Only the Eureka and Joker produced ore, and only 

in very small quantities.

The characteristics of these deposits are suggestive of a 

type of mineral deposit termed low-sulfide gold-quartz veins, 

characterized by gold in massive, persistent quartz veins 

in shear zones in regionally metamorphosed volcanic and 

sedimentary rocks (Berger, 1986; Drew, 2003). The typical 

mineral assemblage is quartz, pyrite, galena, sphalerite, and 

chalcopyrite, along with native gold. The most prominent 

examples in North America are the Mesozoic quartz veins of 

the Mother Lode in California, but these deposits are common in Proterozoic metamorphic rocks throughout the western 

United States. These veins typically persist over large vertical 

ranges, forming most commonly at paleodepths ranging from 

4 to 12 km (Drew, 2003).

Because the entire Gold Butte block is dipping to the east 

at about 45°, it presents a singular continuous exposure of an 

intact Proterozoic through Miocene crustal section that reaches 

paleodepths of about 15 km at the western edge (Fryxell and 

others, 1992; Fitzgerald and others, 1991; Reiners and others, 

2000). From this perspective, the distribution of the low-sulfide gold-quartz vein deposits in the Gold Butte block (fig. 20) 

makes an understandable pattern. The deposits are all within 

about 5 to 13 km southwest of the exposed unconformity 

Figure 21. Mouth of adit at Ole Mine. The sample (4-110202) 

containing >5 ppm gold was selected from the pile in the 

foreground.

between Proterozoic and Paleozoic rocks. Corrected for dip, 

this means they occur at paleodepths of 3 to 8 km below the 

unconformity. Adding about 2 km of crust that was eroded 

between 1.4 Ga (the approximate age of formation of the 

veins) and 600 Ma (the beginning of Paleozoic deposition) 

results in an inferred depth interval at the time of formation of 

5 to 10 km.

The style and inferred genesis of these gold-bearing veins 

indicates that, though relatively small, they are best classified 

as low-sulfide gold-quartz veins. Trace-element signatures of 

the samples we took from the Ole Mine and from the Treasure 

Hawk Mine were both anomalous in molybdenum and tellurium, also typical of the deposit type (Drew, 2003).

There are two reported gold deposits in the Gold Butte–

Virgin Mountain ACECs that are not spatially related to the 

Gold Butte pluton—the Albert Nay prospect and the Gold 

Butte prospect, both of which are in Paleozoic sedimentary 

rocks about 2 km north of the Whitney Pocket ACEC (fig. 

12). Both are reported only by Hose and others (1981), and 

it is possible that they have been mislocated; examination of 

detailed aerial photography of the areas shows no sign of any 

surface disturbance.

Copper Deposits in Sedimentary Rocks

A number of copper mines and prospects are located 

within the Gold Butte–Virgin Mountain ACECs, and about 

150,000 pounds of copper was produced from mines in the 

Gold Butte district between 1907 and 1956. The most important mines were the Tramp, Lincoln, Bennett, and Black Jack, 

all in the Tramp Ridge block, along with the Azure Ridge 

Mine (Bonella properties), in the Gold Butte block (fig. 22).

These deposits are all hosted in Paleozoic limestone 

and consist primarily of small concentrations of hematite, 

limonite, base-metal oxides, and base-metal carbonates. Copper minerals noted in the various mines include malachite, 

azurite, cuprite, chalcocite, chalcopyrite, and bornite. Other 

minerals noted include smithsonite (ZnCO3), aurichalcite 

((Zn,Cu)5

[(OH) 3|CO3]2), and cerussite (PbCO3). The distribution of the mineralized rock in all of these deposits is structurally controlled.

These deposits appear to form a continuum between two 

end-member structural styles. One end member, displayed at 

the Black Jack Mine, consists of chalcocite veins in slightly 

brecciated limestone. The other end member, the Tramp 

Mine, is characterized by limestone breccia cemented and 

mineralized by base-metal carbonate minerals. The deposits 

we observed at the Azure Ridge Mine, though dominated by 

chalcocite veins, display more brecciation of the host limestone than do those at the Black Jack Mine. The Lincoln Mine 

is intermediate in character between the Black Jack and Azure 

Ridge and the Tramp.

Stratigraphically, the Tramp, Lincoln, Black Jack, and 

Bennett Mines are situated near the contact between the Devonian Temple Butte Formation and the overlying Mississippian 
C24 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 22. Locations of copper deposits in Gold Butte A and B Areas of Critical Environmental Concern (ACECs; outlined in pink). 

Generalized geology from Stewart and Carlson (1978).

Pzs

Mzs

Ts

Paleoproterozoic igneous and metamorphic rocks, undivided

Paleozoic carbonate and silicilastic rocks

Tertiary sedimentary rocks

Xm

mine or prospect

EXPLANATION

Mesozoic sedimentary rocks

Qu Quaternary sediments, undivided

Red Dot prospect

Pink Lady

Tramp Mine

Bennett Mine

Quartz claim

Lincoln Mine

Green Monster

Gudice claims

Black Jack Mine

unnamed prospect

unnamed prospect

Azure Ridge Mine

Qu

Ts

Pzs

Xm

Xm

Pzs

Qu

Xm

Pzs

Pzs

Pzs

Pzs

Mzs

Mzs

Ts

Mzs

Mzs

Ts

GOLD BUTTE A ACEC

GOLD BUTTE B ACEC

GOLD BUTTE TOWNSITE

ACEC

GoldButeACE

Scale1:24,0

01234 0.5

Kilometers

36°22'30"N

114°15'0"W 114°07'30"W
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C25

Redwall Limestone, primarily in the Redwall. The Azure Ridge 

Mine workings we visited are in limestone of the Cambrian 

Muav Formation, but other workings are in the Temple Butte 

Formation and Redwall Limestone. We visited and sampled the 

Tramp, Lincoln, Black Jack, and Azure Ridge Mines.

Tramp Mine

The orebody at the Tramp Mine is steep to subvertical, cuts across bedding, and appears to be pipelike. The ore 

consists of brecciated limestone impregnated or cemented with 

copper-carbonate minerals, chiefly malachite, and iron-oxide 

minerals. Stringers and irregular pockets of mineralized rock 

appear to be controlled by fractures, and they occur over a 

width of 1 to 2 m and a vertical distance of at least 100 m. A 

nearby minor, steep fault apparently is unrelated to the ore 

body. In contrast to the Black Jack and Azure Ridge Mines, 

mineralization at the Tramp Mine has no veinlike aspect, and 

chalcocite is rare to absent. Hill (1916) described the mineralogy of the deposit (called the Tramp Miner property at that 

time) as limonitic, with minor cuprite and malachite. A select 

grab sample that we analyzed contains about 220 ppm silver, 

0.96 percent copper, 5.7 percent lead, and 0.96 percent zinc.

Lincoln Mine

Many of the underground workings at the Lincoln Mine 

are difficult to locate with certainty, and all are now inaccessible. The dumps and piles of rock at the mine are dominated by 

three types of material: fine-grained, homogeneous, noncherty 

limestone; medium-grained, marble-like, recrystallized limestone; and limestone breccia, derived mostly from recrystallized 

limestone but also in part from fine-grained limestone. Much 

of the breccia contains malachite, some poorly crystalline and 

some filmy or powdery. Some pieces of recrystallized limestone 

and fine-grained limestone have malachite coatings on fractures. 

Chalcocite ore and derivative gossan are minor constituents 

of the dump material. Scattered shallow diggings (but no adits 

or shafts) north of the Lincoln Mine proper are in distinctive, 

light-yellowish brecciated limestone and fault gouge (or other 

clayey material), in part gypsum-bearing. Hill (1916), who had 

access to the underground workings, describes a stratiform ore 

body in pinkish-gray crystalline limestone below chert-rich gray 

limestone. He also described chalcocite replacing small amounts 

of bornite and chalcopyrite.

Black Jack Mine

The well-exposed chalcocite veins of the Black Jack 

Mine are subvertical and about 0.5 m to as much as 2 m thick. 

These veins are at a high angle to the gently dipping beds of 

the host limestone. Veins typically are bordered by a zone, a 

few meters wide, of slightly to moderately brecciated limestone, grading outward into unbrecciated limestone. This 

marginal breccia zone is cut by chalcocite veins and veinlets, 

a few tens of centimeters to 1 m thick. Some veins contain 

minor sphalerite. Weathering of the chalcocite veins has 

produced gossan. Dump materials include both chalcocite and 

subordinate copper-carbonate–bearing breccia.

Azure Ridge Mine

Originally called the Bonella claims (Hill, 1916), the 

chief workings are at the northern end of Azure Ridge, 

immediately adjacent to Garden Wash (fig. 22), although other 

workings exist a kilometer or more south along strike. Hill 

(1916) described the ore as irregular replacement lenses of 

limonite in massive limestone. We observed that some of the 

mineralized rock at the Azure Ridge forms veins and veinlets 

similar in style and size to those at the Black Jack Mine. These 

are accompanied by veinlike bodies of chalcocite-bearing 

breccia, some of which have been altered or weathered to copper-carbonate–bearing breccia. Both chalcocite and mineralized breccia are prominent in the dumps.

During the study of the Million Hills Wilderness Study 

Area, a detailed sampling program was conducted at the Azure 

Ridge Mine by Bergquist and others (1994). They reported small 

pods of mineralized rock along bedding-plane faults over an area 

5,000 ft (>1,500 m) long. Along with concentrations in excess of 

1 percent for copper, lead, and zinc, they found values of cobalt 

as high as 471 ppm, gold as high as 3.3 ppm, germanium as high 

as 150 ppm, and gallium as high as 75 ppm. Although many of 

these samples were carefully selected and are not representative 

of average compositions, the high values obtained for cobalt, 

gold, germanium, and gallium may be significant.

Our samples from the Azure Ridge, Black Jack, Tramp, and 

Lincoln Mines (Ludington and others, 2005), do not show significantly elevated gallium contents. The highest value obtained 

was 14 ppm. Our samples do have elevated cobalt (as much as 

279 ppm), indium (as much as 39 ppm), and gold (as much as 

0.9 ppm). We analyzed only 4 samples for germanium, and two 

of them contained 22 to 26 ppm, which is anomalous, but not as 

high as the samples reported by Bergquist and others (1994).

Mineral Deposit Model

All these mines show similarities in host rock, mineralogy, 

and geochemistry, although they exhibit a variety of structural 

styles. From our reconnaissance observations and sketchy previous descriptions, their mode of origin remains unclear, and the 

relative importance of structure and stratigraphy is indeterminate. We compare the deposits with three well-known types of 

deposits in nearby northern Arizona and southwestern Utah.

Solution-collapse breccia pipes of the southern Colorado 

Plateau

These deposits are subvertical pipelike bodies of breccia 

formed by collapse of Pennsylvanian and Permian strata into 

paleokarst cavities in the underlying Mississippian Redwall 

Limestone (Wenrich, 1985). Several thousand breccia pipes 
C26 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

have been identified in northern Arizona; only a few are mineralized. Primary mineralization has two aspects or phases: 

(1) younger uraninite mineralization and (2) older Mississippi Valley–like base metal sulfide mineralization, which 

evidently acted as a reductant that caused later deposition 

of uranium. Breccia pipe deposits have produced copper, in 

the late 1800s and early 1900s, and uranium, over the past 

several decades. In addition, some mineralized breccia pipes 

also contain anomalous levels of a variable suite of other 

metals and metalloids, including Ag, As, Au, Ba, Cd, Co, 

Hg, Mo, Ni, Pb, Sb, Se, Sr, V, W, Zn, and rare earth elements 

(Wenrich and Silberman, 1984).

Although the breccia in the deposits in the Gold Butte 

district suggests some affinity to the solution-collapse breccia pipes, the Gold Butte deposits occur in rocks stratigraphically lower than typical breccia pipes of the Colorado Plateau. Chalcocite, the dominant sulfide mineral at the Black 

Jack and Azure Ridge Mines, is found in some Colorado 

Plateau breccia pipes.

Stratabound Copper Deposits in the Kaibab Formation

These small deposits occur in the Harrisburg Member of 

the Kaibab Formation at several places in the Grand Canyon 

region (Tainter, 1947; Gibbons, 1952; Keith and others, 1983; 

Sorauf and Billingsley, 1991). These deposits contain disseminated and fracture-controlled malachite, azurite, and less commonly chalcopyrite and chalcocite in flat-lying sedimentary 

chert breccias. Mineralized zones are sporadic and generally 

less than a meter thick. Small-scale mining with hand sorting, 

conducted intermittently from the early 1900s through the 

early 1960s, produced some copper, along with minor silver 

and gold. Genesis of these small copper deposits is unclear. 

Apparent associations with high-angle fault zones may or may 

not be important. Possible genetic relations to the solution-collapse breccia pipes have yet to be investigated. Bliss and Pierson (1993) suggest that the presence of gypsum, as a source of 

sulfur, within the Harrisburg Member of the Kaibab Formation 

may be an important factor.

The Nevada deposits do have some similarities in lithology and mineralogy to the stratabound copper deposits in the 

Kaibab Formation in Arizona. However, the Nevada deposits 

have significant lead and zinc contents, have no evidence of 

being stratigraphically controlled on scales of meters or ten of 

meters, and do not have any apparent association with chert or 

chert breccia. Furthermore, the Black Jack and Azure Ridge 

Mines contain important steeply inclined veins.

The Apex Mine, Southwest Utah

This extraordinary mine is located about 90 km to the 

northeast of Gold Butte, in the Tutsagubet District near St. 

George, Utah. It was the first mine in the world devoted 

primarily to production of gallium and germanium (Bernstein, 

1986; Petersen and others, 1989). Gallium and germanium are 

strategic materials with a variety of high-technology applications, particularly in semiconductors (Orton, 2004). Most gallium and germanium demand is met from recycling and from 

production as byproducts from the processing of aluminum 

and zinc ores, respectively. The Apex Mine was active from 

the mid 1980s until 1991. A reserve of about 272,000 short 

tons averaging 1.9 percent copper, 1.8 percent zinc, 60 ppm 

silver, 370 ppm gallium, and 1,000 ppm germanium had been 

delineated just before mining began in 1986 (Petersen and 

others, 1989). A yearly production goal of 9,000 kg of gallium 

and 19,000 kg of germanium was set, but we have been unable 

to determine the actual production figures. The mine apparently closed because of complications in the recovery process. 

After closure, the property was apparently sold to a partnership of Preussag AG and Teck Cominco Ltd., both major 

producers of germanium from zinc ores.

Apex Mine ore occurs in breccia, gouge, and fissures in 

steeply dipping fault zones in Pennsylvanian Callville Limestone. The ore consists of copper and iron oxides, carbonates, 

arsenates, and sulfates. Principal host minerals for gallium and 

germanium are, respectively, jarosite and goethite (Dutrizac 

and others, 1986). Owing to thorough oxidation of the ore, 

few remnants of primary, sulfide ore have been found. Primary 

minerals include pyrite, marcasite, galena, chalcopyrite, 

bornite, sphalerite, anhydrite, quartz, and goyazite (SrAl3

[(O

H)5|(PO4)

2

]•H2O) (Mahin, 1990). Although jarosite commonly 

occurs as a secondary mineral, and the fine grain of the Apex 

material makes textural interpretations difficult, at least part of 

the gallium-bearing jarosite has been interpreted to be hypogene, not secondary. This jarosite yielded late Miocene K-Ar 

ages (Bowling, 1988), corresponding to the timing of tectonic 

extension, both at Apex and in the Gold Butte–Virgin Mountain ACECs.

Because of the high value of germanium and gallium, 

mineralized rock from these deposits could be more valuable 

for germanium and (or) gallium than for the base metals. The 

germanium price has fallen recently, but has typically been in 

excess of $1,000/kg since the early 1980s. Gallium prices have 

hovered near $500/kg over the same time period.

Wenrich and others (1987) consider the Apex deposit to 

be a variety of solution-collapse breccia pipe. However the U.S. 

Geological Survey (Cox and Bernstein, 1986) and the British 

Columbia Geological Survey (Trueman, 1998) classify Apex as 

a Kipushi-type carbonate-hosted Cu±Pb±Zn deposit. The namesake deposits for the Kipushi type are in the Democratic Republic of the Congo, Africa. The African deposits are distinctly 

larger but have a similar structural and stratigraphic setting and 

have produced both gallium and germanium (De Magnée and 

Francois, 1988). Other examples of this deposit type are found 

in Canada, Alaska, Ireland, Namibia, Australia, and China 

(Trueman, 1998; Cox and Bernstein, 1986). The similar (and 

uncommon) geochemistry suggests that the Apex Mine and the 

Nevada deposits are genetically similar to the African ones.

The source of sulfur in most genetic models for the 

Kipushi-type deposits is evaporites at depth. In the Gold Butte 

district, there is abundant gypsum in the stratigraphic section, 

but it is all at higher stratigraphic levels than those occupied 

by the copper deposits. Exposures in the Gold Butte district 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C27

are not extensive enough to evaluate the relative importance of 

stratabound karst breccias versus throughgoing steep structures 

in localization of the mineralizing process. The Nevada mines 

are all lower in the regional stratigraphic section than the Apex 

Mine, Whether or not stratigraphic setting is an essential aspect 

of the genesis of the Apex deposit is unknown. The primary 

sulfide minerals recognized at Apex do not include chalcocite, 

though a little secondary chalcocite is present.

Other Copper Deposits

In addition to the deposits on Tramp and Azure ridges, 

Winters (1988) studied several copper prospects (Green 

Monster and Pink Lady claims, fig. 12) in Permian sandstone 

and conglomerate (Toroweap Formation?) and another nearby 

unnamed prospect in limestone of the Permian Kaibab Formation. Samples from the prospects in sandstone and conglomerate 

are anomalous in copper and silver, but not lead or zinc, and 

may represent traditional redbed copper deposits. The unnamed 

prospect in limestone has anomalous lead and zinc concentrations, as well copper and silver, and may represent another 

Kipushi-like prospect. The claims are no longer current.

Winters (1988) noted two other prospects to the south of 

the Green Monster and Pink Lady claims. The Red Dot claim 

and an unnamed prospect about 800 m northeast of the Red 

Dot also have anomalous copper, silver, lead, and zinc contents, and could be Kipushi-like occurrences. These prospects 

are apparently mislocated, as their reported coordinates plot in 

Proterozoic rocks, yet they are described as being in Paleozoic 

limestone. Examination of aerial photography in the region 

revealed a likely location for the Red Dot, but no surface 

disturbance could be seen to the northeast. These possible 

locations still do not correspond with carbonate bedrock; it is 

possible that the prospects might be in large blocks of Paleozoic rock in the Tertiary conglomerates.

Uranium Deposits in Sedimentary Rocks

A low-grade, stratiform uranium deposit (Long Shot 

deposit, also known as the Blue Chip prospect) is exposed 

along the west side of a ridge that is in part of the Gold Butte 

A and Gold Butte B ACECs (fig. 12). The deposit occurs in 

the Thumb Member of the Tertiary Horse Spring Formation. 

Anomalously radioactive rock composed predominantly of 

calcite, with locally abundant dolomite, gypsum, and iron 

oxide, occurs near the base of a section of resistant limestone 

with bedding that dips shallowly east. According to Johnson 

and Glynn (1982), rock with U3

O8 contents of as much as 240 

ppm and local carnotite (K2

(UO2)2[VO4]2•3H2O) on fractures 

occur in a 1-m-thick body as much as 5,000 m long. Gypsiferous bedding planes are the primary ore control and organic 

matter is rare, although sparse fossil twig casts were noted by 

Johnson and Glynn (1982). The radioactive zone was explored 

by numerous pits, nine drill holes, and an 11-m-long adit, most 

along a 4-km access road.

Prospects in the area include those known as the Long 

Shot Mine, Lucky Bart prospect, Atomic prospect, and South 

Valley No. 2 claim, among others (Johnson and Glynn, 1982; 

U.S. Geological Survey, undated; fig. 12). In addition to the 

radioactive zone in this area, we noted carnotite in white 

dolomitic limestone of the same rock unit in a prospect 

near Horse Spring at the north end of the ridge containing 

the Long Shot Mine. We have no information on uranium 

content of carnotite-bearing rock in the Horse Spring area, 

but dolomitic limestone collected there contains about 12 

ppm U, which is weakly anomalous (sample AP-072A, 

Ludington and others, 2005). The U.S. Geological Survey’s 

MRDS (Mineral Resource Database System; U.S. Geological 

Survey, undated) database also lists uranium occurrences at 

the Atomic prospect 0.8 km south of Horse Spring, the South 

Valley #2 claim 1.5 km southeast of Horse Spring, and the 

Blue Chip prospect about 1.5 km north of Horse Spring. We 

did not examine these locations, which are all in exposures 

of the Horse Spring Formation.

Our examination of the Long Shot Mine area showed 

local radioactive areas as high as 16 times background (2,500 

counts per second (cps) with a background of 150 cps) and 

extensive radioactivity at 3 or more times background. The 

highest radioactivity is generally associated with yellow 

carnotite on fractures (fig. 23). Interestingly, some of the most 

radioactive material was not carbonate rock, but clay-altered 

tuff near a caved adit at the Long Shot Mine (fig. 24). Uranium contents of samples taken here verify those reported 

by Johnson and Glynn (1982), with a high value of 181 ppm 

(Ludington and others, 2005). In addition to uranium, our 

analyses show scattered anomalous amounts of As, Bi, Co, 

Cu, Li, Mo, Ni, Sb, Sr, Tl, V, and Zn (table 4). With the exception of vanadium and copper, this is not the usual suite of trace 

element enrichment that accompanies uranium in sedimentaryrock-hosted deposits.

Figure 23. Yellow carnotite crusts on fractures in limestone, 

Long Shot Mine (also called Blue Chip), Gold Butte B Area of 

Critical Environmental Concern (ACEC).
C28 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

We examined several samples with the scanning electron microscope (SEM), using energy-dispersive analysis 

(EDX). The only uranium-bearing mineral we identified was 

carnotite (K2

(UO2)2V2O8·3H2O), which explains the strong 

correlation between uranium and vanadium seen in table 4. 

In addition to carnotite, sample AP-204, which is hematiterich brecciated limestone with high contents of many trace 

metals (table 4), was found to contain pyrite framboids that 

are wholly replaced by iron oxide (fig. 25). The framboids 

mainly occur in the breccia matrix and are only sparsely 

distributed in limestone clasts. The sample also contains late 

veinlets of strontianite and tiny crystals of chromian spinel 

(fig. 25), which may be the source of the anomalously high 

nickel and cobalt contents.

The limestone-hosted uranium in the Long Shot Mine 

area in the Horse Spring Formation is unusual. Possible 

analogue deposits are those in the Grants Uranium Belt of 

New Mexico, where about 3 million kg of U3O8 were mined 

from small deposits in the Todilto Limestone with 0.2 to 

0.5 percent U3O8 (McLemore, 2002). The uranium mineral 

assemblage in the Todilto deposits includes pitchblende 

(UO2), coffinite ((U,Th)[(OH)4x|(SiO4)1-x]), and tyuyaminite 

(Ca(UO2)2[VO4]

2

•8H2O, the calcium analog of carnotite), 

along with several vanadium minerals, fluorite, barite, hematite, pyrite, and galena (Berglof and McLemore, 1996). Data 

on trace elements in the Todilto deposits are not available, but 

the mineral assemblage does not suggest a trace-element suite 

similar to that associated with uranium in the Horse Spring 

deposit. In addition, pyrite framboids have not been reported 

in the Todilto deposits, which occur in a “marine-influenced 

salina/playa” setting (Armstrong, 1995).

Element AP-204 AP-206 AP-207 AP-208 AP-209

U 139 181 128 40 12

Th 6.4 4.0 7.1 0.2 0.9

As 2,100 116 206 22 40

Bi 1.1 0.2 0.2 0.1 <0.1

Co 158 2.3 4.7 0.7 2.8

Cs 40 4.8 26 0.8 4.0

Cu 134 15 14 4.5 3.3

Li 460 86 150 10 nd

Mo 7.4 25 6.8 1.0 1.5

Ni 1,820 28 17 5.6 22

Sb 0.7 2.4 1.1 0.1 0.1

Sr 804 2,230 800 1,200 523

Tl 14 3.6 1.5 0.4 0.3

V 571 172 109 22 9

Zn 178 137 288 38 8

Radioactivity 650 cps 2,500 cps 500 cps 450 cps 150 cps

Table 4. Selected element concentrations (in ppm) in samples from Long Shot prospect. 

[Complete results are in Ludington and others (2005). nd = not detected; cps = counts per second.]

Figure 24. Radioactive clay-altered tuff (in dug-out area) 

beneath limestone, Long Shot Mine. Scintillometer, about 25 cm 

long, for scale.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C29

Figure 25. Photomicrographs in reflected light of minerals in sample AP-204, Long Shot Mine. Left, a hematitized framboid about 30 

microns in diameter. Right, a chromian spinel crystal about 50 microns across in a cavity. On the basis of SEM/EDX spectra, the spinel 

has chromium>iron>aluminum>magnesium.

The mineralogy, chemistry, and geologic setting of the 

Long Shot Mine are generally similar to those of many highly 

productive sandstone-hosted uranium deposits in the southwestern United States. These deposits commonly contain carnotite as a secondary uranium mineral, and have anomalously 

high vanadium, molybdenum, and selenium, with locally high 

copper and silver (Turner-Peterson and Hodges, 1986). They 

occur most commonly in continental sedimentary rocks of 

Mesozoic age.

The uranium in the Horse Spring Formation in the Long 

Shot Mine area may have been derived from weathering of 

the Proterozoic rocks to the south, including the Gold Butte 

granite (Johnson and Glynn, 1982; Dexter and others, 1983), 

although the latter authors noted that the Gold Butte granite 

has few characteristics associated with “fertile” uraniumenriched granites. The unusual trace-metal suite in our 

sample AP-204 may have been derived from detrital material 

from the Proterozoic rocks. The accumulation of framboids 

and spinel in that sample may reflect the concentration of 

residual material during the dissolution of limestone by 

the fluids that originally transported uranium. Johnson and 

Glynn (1982) also suggested tuffs within the Horse Spring 

Formation as a possible source for the uranium. Extraction 

of uranium from volcanic glass by ground water or hydrothermal fluids is a well-documented process (Zielinski, 1978; 

George-Aniel and Leroy, 1988).

A uranium occurrence has also been described in Mesozoic sedimentary rock near the Bitter Ridge Fault in the Gold 

Butte A ACEC (fig. 12). It is about 20 km north-northwest 

of the Long Shot Mine. The occurrence, which has yielded 

samples with as much as 193 ppm U3

O8, was described as ferruginous claystone in a 1-m-thick gouge zone along a high-angle 

fault (Johnson and Glynn, 1982). The occurrence bears some 

resemblance in its chemistry to the Long Shot prospect, because 

samples have anomalously high Cd, Co, Cu, Mo, Ni, Sn, W, V, 

and Zn (Johnson and Glynn, 1982). The Bitter Ridge uranium 

occurrence was not visited during our field reconnaissance, nor 

were several other uranium prospects shown on figure 12.

Titanium-Bearing Placer Deposits

Beal (1963) studied titanium-bearing pegmatite and 

placer deposits in a 25-km2 area north and west of the Windmill Mine in the south part of the Gold Butte B ACEC. He 

reported TiO2

 contents as high as 3.5 percent in pegmatite 

samples and 5.8 percent in placer samples. He also reported 

that the pegmatites associated with granitic plutons contain 

ilmenite and Ti-magnetite as plates or blebs, but that the 

titanium mineral content does not exceed 7 percent in any 

pegmatite and the pegmatites constitute less than 15 percent 

of the exposed rock. This would indicate grades of less than 

1 percent TiO2 for any large amounts of rock. Beal stated that 

the area contains millions of tons of placer material containing 

2 to 5 percent TiO2

. The Ti-bearing minerals in placers in the 

area reportedly include both Ti-magnetite and ilmenite, but Timagnetite was the only mineral noted in samples investigated 

petrographically (Beal, 1963).

Dexter and others (1983) also discussed titanium placer 

potential in the Gold Butte area, and they reported TiO2

 contents 

of stream-sediment samples to be between 0.5 and 6.2 percent 

and to average about 2 percent. They noted that sphene, Timagnetite, ilmenite, and leucoxene occur in Proterozoic rocks 

in the Gold Butte area. According to Dexter and others, the 

titanium placers in the area represent a low-grade, subeconomic 

resource. Nonetheless, they assigned low to moderate potential for titanium placers in major drainages in the northern and 

western parts of Gold Butte B ACEC. Of 41 stream sediment 

samples collected by Dexter and others (1983), five were found 

to have 2 percent or more TiO2. The largest area that Dexter and 

others delineated as having titanium potential is a large area of 
C30 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Quaternary alluvium as much as 1 km wide that extends 5 km 

southeastward from near the Gold Crown Mine (fig. 12) into 

Cedar Basin. However, only one stream sediment sample with 

1.8 percent TiO2

 was collected from a tributary to this drainage. 

All stream sediment samples with 2 percent or more TiO2 were 

taken from relatively small drainages with minor amounts of 

potential placer reserves.

Mica Deposits

Mica was mined on a small scale in the Virgin Mountain 

and Gold Butte B ACECs. During the 1950s, mica schist in the 

Virgin Mountains was mined in the Mica Notch area, screened 

nearby (Tingley, 1989), and further processed in a separation 

plant at Riverside (Beal, 1965). According to Beal, one trial 

carload of this mica was shipped to Los Angeles in 1959, but 

transportation cost reportedly prevented further economic 

development. In addition, book mica was mined from pegmatite in the Gold Butte area in the 1890s and early 1900s and 

probably from pegmatite at the Taglo Mine. We examined 

mica occurrences in all three areas during this study.

The Mica Notch deposit, which is in the same area as the 

Mica Notch beryllium deposits, consists of friable to moderately indurated mica schist that contains quartz, feldspar, garnet, 

muscovite, and biotite. The mica deposit was investigated by the 

Union Pacific Railroad Company and described in a short report 

as a band of mica schist “600–800 feet in width throughout a 

length of 3,000 feet... that appears to consist almost entirely of 

biotite mica” (Union Pacific Railroad Company Oil Development Department, 1959). However, a map accompanying the 

report shows a larger area of mica schist about 1,800 m long and 

as much as 750 m wide. According to a Beryllium Associates 

company report (Hansen and others, 1961) the best grades are in 

“an area of 2,000 feet by 4,000 feet and, as exposed in the canyon bottoms, at least 1,000 feet deep.” Beal (1965) reported that 

large amounts of clean mica schist could be mined at low cost 

from the area. Our reconnaissance examination showed that this 

material occurs in a large, poorly exposed area that also contains 

pegmatite and amphibolite.

On the basis of thin-section examination of two samples 

from the Mica Notch area, we found that the rock contains 

about 40 percent mica by volume. The mica consists of 

approximately equal amounts of biotite and muscovite (fig. 

26). In general it occurs in grains that average about 1 mm 

across and 0.1 mm thick, but in one sample a significant 

amount was found to occur as extremely fine grains. Finegrained quartz and plagioclase make up most of the rest of 

the rock. As much as 10 percent garnet, in grains about 1 mm 

across, is also present.

Beryllium Associates evaluated the Mica Notch mica 

schist deposit in conjunction with work on beryllium deposits 

in the area. According to G.W. Hansen (written commun., 

2006), the mica was concentrated by air tabling methods and 

a pure muscovite separate was produced from this concentrate 

by electromagnetic separation. Mr. Hansen further stated that 

he calculated that the Mica Notch schist contains about 30 percent muscovite that could be processed into paint-grade flake 

muscovite by wet grinding methods.

Longwell and others (1965) noted that sheet mica was 

mined from pegmatite in the “South Virgin Mountains” 

(that is, in the Gold Butte B ACEC) in the 1890s, and 1,800 

pounds were reportedly mined at that time (Beal, 1965). The 

Snowflake Mine, about 2 km north of Mica Peak, is one of 

two mica localities known in the area. We visited the site in 

2005 (fig. 27) and found a small pit and adit driven into an 

irregular pegmatite mass that contains a few percent mica in 

surface exposures. Sheets of biotite and muscovite as much as 

10 cm in diameter were noted on the Snowflake Mine waste 

dump. We also found sheet mica in books as much as 5 cm 

across to be abundant in 1-m-wide border zones in pegmaFigure 26. Photomicrograph of mica schist that contains about 40 percent mica, by volume, from Mica Notch. Left, in cross-polarized 

light, horizontal field of view about 3 mm. The mica shows bright birefringent colors; white to black grains are quartz and feldspar. Right, 

same view in plane-polarized light, showing that the mica is a mixture of brown to black biotite and white muscovite.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C31

Figure 27. Snowflake sheet-mica deposit in pegmatite on Mica 

Peak.

tite at the Taglo Mine (fig. 17). The Mica Queen prospect is 

reported near the eastern boundary of the Virgin Mountain 

ACEC, about 5 km north of Whitney Ranch (fig. 12), but we 

did not visit this location. The Bachmann mica prospect is 

northeast of the Taglo Mine in Arizona. Other pegmatite mica 

prospects that we did not visit include the Nevada Mica and 

Mica Mountain mines in the Gold Butte B ACEC to the south 

of Gold Butte (fig. 12). Longwell and others (1965) reported 

muscovite at the former to be of poor quality and less than 2.5 

cm in diameter.

Vermiculite Deposits

Several vermiculite deposits are in the Gold Butte B ACEC 

in the vicinity of Mica Peak. The vermiculite occurs in Proterozoic ultramafic rocks that intrude gneisses and schists. The host 

gneisses are of high metamorphic grade (granulite facies) on 

the basis of the local presence of hypersthene and sillimanite in 

quartz- and feldspar-rich rocks with biotite and garnet (Volborth, 1962). The protoliths of the gneisses are thought to have 

been Early Proterozoic (1.9–1.7 Ga) strata dated elsewhere in 

the region (Wooden and Miller, 1990). The ultramafic rocks are 

mainly pyroxenite and amphibolite, but include some peridotite. 

Volborth (1962) mapped many small (<100 m wide) lenses and 

five larger bodies of such rocks in the Gold Butte Proterozoic 

terrain, mostly east and southeast of Gold Butte (fig. 28). The 

Horseshoe claim (Gold Butte) vermiculite deposits, which are 

north of Mica Peak, were described by Leighton (1967). The 

Cascade and Summit deposits, on the south flank of Mica Peak, 

have not been described in detail in the literature, but current 

(2005) claim blocks covering these deposits appear to correspond with relatively large ultramafic rock bodies mapped by 

Volborth (1962).

On the basis of detailed mapping by Leighton (1967), the 

vermiculite in the deposits on the Horseshoe claims occurs in 

an area 300 m by 600 m and in two smaller areas of altered 

ultramafic rock. These are part of an irregular ultramafic 

body exposed over an area 1.5 km by as much as 0.75 km. 

The vermiculitized rock is not resistant and rarely forms good 

outcrops, but it is exposed in an open pit 100 m by 25 m that is 

about 3 m deep and in several trenches and road cuts in a lowlying area about 250 m in diameter (fig. 11). The vermiculite 

occurs in variable amounts in friable pyroxene-rich ultramafic 

rock, and masses of more resistant vermiculite-poor amphibolite and peridotite are also present. According to Leighton 

(1967), mixtures of vermiculite and biotite are present in the 

deposit, including two types that display marked exfoliation 

on heating—“vermiculite-hydrobiotite” and “biotite-hydrobiotite.” Biotite that does not exfoliate is also present. Chemical analyses reported by Leighton show that both expandable 

types have MgO/(FeO +Fe2

O3) of nearly 3:1 (by weight), 

indicating highly magnesian compositions that may be termed 

phlogopite. X-ray diffraction (XRD) analyses indicate that the 

expandable mica in the Gold Butte deposits is more than one 

mineral. Leighton (1967) reported basal spacings of 12.48 Å, 

10.75 Å, and 10.27 Å, with the last essentially a biotite spacing. Spectra on samples that we collected have XRD peaks at 

14.25 Å, 11.8 Å, and 10.1 Å. The first is typical of vermiculite and the last of phlogopite or biotite. The peak at 11.8 Å 

is unusual but near the 12-Å peak common for commercial 

vermiculites (Hindman, 2006). Hindman (1995) reported 

prominent XRD reflections at 14.6 Å, 12.2 Å, and 10.1 Å 

for vermiculite from Mica Peak and noted that the presence 

of a 12-Å phase is common in the highest quality exfoliating 

vermiculites.

Information on the quality of the Gold Butte area vermiculite suggests that it has commercial potential. Leighton 

(1967) reported expanded specific volumes of Gold Butte 

vermiculite to be from 11 to 20 cm3

/g for 14-, 8-, and 3-mesh 

screened samples. For comparison, average volumes for 

commercial exfoliated vermiculite from Libby, Montana, are 

12–16 cm3/g. Hindman (1995) reported expanded volumes 

of 10–14 cm3/g for Mica Peak samples and noted that this 

compared favorably with published measurements of commercial vermiculite concentrates. According to Leighton (1967), 

the Gold Butte vermiculite is generally present in small flakes, 

but it also occurs in books as much as 12 cm across. Hindman 

(1995) reported that the vermiculite ore in the Mica Peak area 

contains a significant amount of vermiculite in excess of 2 mm 

grain size and that concentrates of material as large as grade 

number 1 (ca. 3–6 mm; Hindman, 2006) could be produced. 

On the basis of crude propane-torch testing and sieving of four 

samples that we collected, 49-85 percent of the expanded vermiculite is less than 0.85 mm (-20 mesh Tyler), 15-44 percent 

is 0.85-1.7 mm (10–20 mesh Tyler), 1-8 percent is 1.7–3.35 

mm (6-10 mesh Tyler), and amounts of larger material are 

negligible (table 5). Vermiculite books as large as 3 by 10 mm 

were produced from our samples by this testing (fig. 29).

Data on the grade of the deposits is limited. Leighton 

(1967) reported that the vermiculite content (probably by 

volume) of altered ultramafic rock was 40 percent but that 
C32 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 28. Mafic and ultramafic rocks in the Mica Peak area, showing location of mineral deposits. Basic geology generalized from 

L.S. Beard (written commun., 2005); outlines of ultramafic rock bodies modified from Volborth (1962), and our unpublished mapping. 

Boundaries of Areas of Critical Environmental Concern (ACECs) in pink.

Blue Bird Mine

Snowflake Mine

Unnamed Prospect

Treasure Hawk Mine & Mill

Horseshoe Vermiculite Deposit

Qu Qu

Qu

Qu

Pzs

Pzs

Xm

Xum

Xum

Xum

Xum

Xum Xum

Paleoproterozoic igneous and metamorphic rocks, undivided

Paleoproterozoic mafic and ultramfic metamorphic rocks

Xm

mine or prospect

EXPLANATION

Qu Quaternary sediments, undivided

Pzs

Xum

Paleozoic carbonate and silicilastic rocks

114°7'30"W

36°15'0"N

GoldButeACE

Scale1:24,0

01234 0.5

Kilometers

GOLD BUTTE B

ACEC

GOLD BUTTE A

ACEC
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C33

vermiculite made up 60 percent of a narrow zone. Hindman 

(1995) reported that the northern (Horseshoe claim) area generally had 20-25 percent vermiculite, whereas exposures to the 

south (Summit and Cascade claims) contained 30-35 percent 

vermiculite. Expandable vermiculite makes up 2.5 to 17.2 percent of the sampled material from the Horseshoe claim block 

that we tested (table 5).

We have no information on the size of the Gold Butte 

area vermiculite deposits. Hindman (1995) speculated that no 

more than a few hundred tons of vermiculite concentrate could 

have been produced, judging from the size of the old workings. However, the large extent of the surface exposures of 

potentially exploitable vermiculite-bearing rock suggests that 

the resource may be significant.

Borate Mineral Deposits

Colemanite (Ca2B6O11•5H2O) has been mined from bedded deposits in the Horse Spring Formation in two areas in 

the Muddy Mountains west of the Gold Butte–Virgin MounSample Total weight 

(g)

Expanded 

weight (g)

Calc. % vermiculite6 mesh 

(%)

6-10 mesh 

(%)

10-20 

mesh (%)

20 mesh 

(%)

AP-193 79.3 2.0 2.5 0 5 10 85

AP-194 66.4 11.4 17.2 1 8 43 48

AP-196 83.4 8.7 10.4 0 1 35 64

AP-201 40.0 2.0 5.0 0 5 20 75

Figure 29. Coarse expanded vermiculite grains produced from 

sample AP-194 by heating with a propane torch. Most of the 

expanded vermiculite from this sample was finer-grained than that 

shown in the photograph.

Table 5. Data on vermiculite samples from the Horseshoe claims, Gold Butte ACEC. 

[Total weight = sum of expanded and nonexpanded material weights. Expanded weight = weight of material separated by flotation 

on water subsequent to exfoliation.]

tain ACECs, and it has been speculated that the Horse Spring 

Formation in the Lime Ridge and Tramp Ridge structural 

blocks may have potential for such deposits (F. Johnson, oral 

commun., 2004). In the Muddy Mountains, the colemanite 

is restricted to the upper part of the Bitter Ridge Limestone 

Member (Castor, 1993). Geologic maps by Beard (1993) 

and Beard and Campagna (1991) suggest that Bitter Ridge 

Limestone is not present in the Gold Butte–Virgin Mountain 

ACECs. During reconnaissance examination of the Horse 

Spring Formation section in the Horse Spring and Gardens 

Spring area in the Gold Butte A ACEC, we found no occurrences of borate minerals. However, we did not collect samples in the area to test for high boron contents or for pathfinder 

elements, such as lithium and strontium, that might suggest the 

presence of borate minerals.

Gypsum Deposits

Four areas in the Gold Butte–Virgin Mountain ACECs 

have identified gypsum resources, but there is no record of 

gypsum production from the ACECs. Three of these areas 

include inholdings of mining claims, presumably for gypsum, 

within the ACEC boundaries.

Gypsum deposits have been described in the Toroweap 

Formation along the north flank of the Virgin Mountains. The 

Hen Spring deposit (fig. 12), described by Papke (1987) as 

the Bunkerville Ridge deposit, consists of a 15-m-thick lower 

gypsum unit and a 10-m-thick upper gypsum unit separated 

by about 5 m of dolomite. The bedding in these units dips 

50° to 60° northwest, and outcrops of carbonate rocks to the 

southwest suggest that the gypsum beds are terminated by a 

fault in that direction. The gypsum is reportedly white, massive, friable, and relatively pure except for dolomite interbeds. 

Exploration has been by trenching and one open cut. According to Beal (1965), gypsum deposits as much as 3 m thick are 

exposed by shallow excavations a short distance to the east.

The Virgin Mountains deposit (fig. 12) is on the south 

slope of Virgin Peak about 2 km north of Whitney Pocket. 

Papke (1987) described it as poorly exposed, massive, white, 

fine-grained gypsum with dolomite in the Pakoon Formation. On the basis of small-scale geologic mapping (Longwell 

and others, 1965), the deposit is in the Toroweap Forma-
C34 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

tion. According to Papke, the deposit dips 30° to 40° to the 

southwest and has a thickness of about 20 m. It contains an 

unknown proportion of dolomite interbeds.

The St. Thomas Gap deposits, in the Wechech Basin in 

the Gold Butte A ACEC (fig. 12), which occur in the Thumb 

Member of the Horse Spring Formation, crop out along northnortheast-trending ridges (fig. 30), and are traceable for a total 

distance of about 4 km (Papke, 1987). The gypsum occurs in 

four principal units ranging from 10 to 30 m thick that dip 10° 

to 45° east according to Papke; however, our reconnaissance 

in this area disclosed gypsite units ranging from 5 to 10 m 

thick that dip 15° to 35° to the southeast. The gypsite is impure 

because of interbedded and intermixed quartz, clay, and carbonate (Papke, 1987). Chip samples that we collected from this area 

contain only 80 to 82 percent gypsum on the basis of chemical 

analyses (table 6; Ludington and others, 2005), but analysis of 

a grab sample indicates gypsum content as high as 93 percent 

(Papke, 1987). There is no evidence of past gypsum mining in 

this area, but gypsum was mined from the Thumb Member of 

the Horse Spring Formation in the Rainbow Gardens area, near 

Las Vegas (Castor, 1989; Castor and others, 2000).

Gypsum occurs in the upper part of the Toroweap Formation in two areas along the west side of Gold Butte Wash, and 

these areas include three blocks of claims that form inholdings within the Gold Butte A and B ACECs. The northern area 

(Legion Nos. 1–2 and Leeway Nos. 3–5, fig. 12) contains poorly 

exposed gypsum-bearing sequences as much as 10 m thick that 

dip about 30° east beneath yellowish-gray cherty limestone. 

The gypsum is underlain by pale yellow to white sandstone and 

cherty limestone that probably belong to the Esplanade Formation. There are no prospects or mine workings, and the gypsum 

is relatively impure. The deposits in the southern area (Boulder 

Nos. 1–2, Blue Ridge Nos. 1–2; fig. 12), which are about 4 km 

northwest of the Gold Butte townsite, appear to be in approximately the same stratigraphic interval.

Limestone Deposits

Relatively pure limestone suitable for lime or cement 

has not been reported in the Gold Butte–Virgin Mountain 

ACECs. The Paleozoic carbonate rocks in the Bunkerville area 

are mostly described as variably dolomitic, sandy, shaly, or 

containing abundant chert (Beal, 1965). Devonian limestone, 

mined for lime production at Apex northeast of Las Vegas 

and under development as a source of cement limestone in the 

Sample----------- AP-065 AP-066 AP-064 — —

Location---------- Wechech Basin Wechech Basin Wechech Basin Apex (PABCO) Blue Diamond

Unit--------------- Horse Spring Horse Spring Horse Spring Muddy Creek Kaibab

Sample type----- 5-m chip 4.5-m chip grab grab grab

SiO2 7.53 5.44 5.35 9.43 0.33

Al2

O3 0.97 0.74 0.63 3.94 0.03

Fe2

O3 0.24 0.26 0.16 0.22 0.01

MgO 0.93 1.39 0.77 5.47 0.03

CaO 26.90 27.91 30.50 27.70 33.40

Na2

O 0.06 0.05 0.18 0.69 0.02

K2

O 0.27 0.22 0.45 0.68 0.02

LOI 20.60 21.30 17.77 13.2 18.3

CO2 1.06 1.32 0.62 9.20 0.02

SO3 37.38 38.15 43.20 29.40 48.10

Gypsum (calc.) 80.21 81.87 92.71 63.09 103.22

Table 6. Composition of gypsum samples from the Wechech Basin, Gold Butte A ACEC, compared with high-grade 

gypsum ore from the Blue Diamond Mine and low-grade gypsum ore from the PABCO Mine.

[All data in weight percent. Gypsum calculated = 2.146 x SO3. Data on Wechech Basin grab, Apex, and Blue Diamond samples are from 

Papke, 1987.]

Figure 30. Ridge-forming gypsite in the Wechech Basin at 

sample site AP-066. Gypsite is as much as 10 m thick here and 

dips 15° to 35° to the east.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C35

Moapa area, is represented in the Virgin Mountain–Gold Butte 

area by the Muddy Peak Limestone or Temple Butte Limestone. According to McNair (1951), the Muddy Peak Limestone is about 550 ft (170 m) thick and consists of dolomitic 

limestone with interbedded limestone. Such material would 

likely not be suitable for high-calcium lime or cement.

Tertiary limestone in the Horse Spring Formation may 

have potential as cement limestone. A chip sample of relatively pure limestone taken by us from the Thumb Member 

of the formation in the Garden Spring area contains high 

SiO2, high MgO, and marginally low CaCO3 for lime (table 

7). The sample is sufficiently high in CaO for cement rock, 

but Na2O+K2O is marginally excessive. A grab sample of 

hard, white carbonate from the Kim Ball prospect has less 

Na2O+K2O but is from a relatively small mass (10 m by 20 

m) of rock.

Element AP-069 AP-070 AP-071 AP-072A AP-209 Portland cement 

ore specification

High-Ca lime ore

specification

SiO2 5.81 0.50 3.15 8.08 4.96 <1

Al2

O3 0.03 0.07 0.39 0.54 0.79

Fe2

O3 0.04 0.12 0.18 0.21 0.35

MgO 0.23 22.06 20.46 14.31 1.55 <1

CaO 53.22 30.29 29.45 33.40 52.49 ca. 50

Na2

O+K2O 0.05 0.09 0.43 0.55 0.57 <0.4

P2

O5 0.02 0.01 0.02 0.01 0.02

LOI 40.6 46.7 45.8 42.8 39.2

CaCO3 94.73 53.92 52.42 59.45 94.43 >95

MgCO3 0.48 46.11 42.76 29.91 3.23

Total carbonate 95.21 100.02 95.18 89.36 97.66

Table 7. Comparison of some major element analyses of carbonate rock samples from the Horse Spring Formation in 

the Gold Butte A and Gold Butte B ACECs with Portland cement and high-Ca lime ore specifications.

[All figures are weight percents. AP-069 and AP-070 are grab samples from the Kim Ball prospect area; AP-071 is a 5-m chip sample from 

Horse Spring prospect; AP-072A is a 2-m chip from the Horse Spring prospect; AP-209 is a 10-m chip sample from the Garden Spring area. 

CaCO3 percent calculated using CaO x 1.78; MgCO3 percent using MgO x 2.09. Portland cement specifications from Ames and others (1994). 

High-Ca lime ore specification from Stanley T. Krukowski (oral commun., 2005).] 

Magnesite Deposits

Magnesite deposits have been reported in the Horse 

Spring Formation (Hewett and others, 1936; Longwell and 

others, 1965). The best-known magnesite deposit in the area, 

the Bauer prospect, has been reported to be at different locations by different authors. Longwell and others (1965) located 

it about 11 km northeast of the Gold Butte townsite near Horse 

Spring (fig. 12). We found carbonate from prospects in that 

area to be mainly dolomite rather than magnesite (samples 

AP-071 and AP-072A; table 7; Ludington and others, 2005). 

Hewett and others (1936) reported the Bauer prospect to consist of two exploratory tunnels about 14 km north of the Gold 

Butte post office, and gave analytical results of 20.2 to 41.3 

percent MgO and 3.1 to 23.8 percent CaO for samples from 

the tunnels and surface outcrops. The highest MgO content 

was for a bed of hard white rock only 0.4 ft (12 cm) thick. 

The samples were described as “lump” samples of relatively 

resistant rock from the lower 6 m of a shallowly east dipping 

unit of soft white dolomite, magnesite, and clay as much as 25 

m thick. They reported that the unit crops out for more than 1 

km along strike and estimated a reserve of about 500,000 short 

tons, assuming an average thickness of 6 m. We did not examine this location and cannot comment on this size estimate. 

Another deposit, the Kim Ball Magnesite deposit, is located 

about 18 km north-northeast of the Gold Butte townsite (fig. 

12). Our reconnaissance in that area disclosed some small 

masses of white carbonate with chemistry that ranged from 

nearly pure calcite to dolomite (samples AP-069 and AP-071; 

table 7; Ludington and others, 2005).

At present, the only magnesite deposit mined in the 

United States is in the Paradise Range at Gabbs, Nevada, 

where magnesium minerals have been mined since 1935 

(Castor, 2004). By contrast to the Bauer prospect, analyses 

of typical magnesite ore from Gabbs range from 39.9 to 46.8 

percent MgO and 1.3 to 8.9 percent CaO (Hewett and others, 

1936; Dixon, 1961). Reserves are unspecified but said to 

exceed 50 years at the present mining rate (L. Johnson, oral 

commun., 2003).

Silica Deposits

The Aztec Sandstone is exposed in many places in the 

Gold Butte A ACEC and also in the Whitney Pocket and Red 

Rock Spring ACECs. Rocks of this unit have been prospected 

regionally as a source of silica but have not been extensively 

mined (Longwell and others, 1965). The unit is generally 
C36 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

composed of moderately indurated, reddish-orange to pink, 

coarsely cross-bedded eolian sandstone that forms cavernous 

outcrops (figs. 31, 32). In some places the unit contains thick 

beds of nearly white to pale-yellow sandstone. Hewett and 

others (1936) reported that a few carloads of Aztec Sandstone 

were shipped from the Wyatt Mine in the Muddy Mountains 

to the west of the Virgin Mountain–Gold Butte area. MurMineral Exploration and Development

There is no known currently active mineral exploration by large mining companies in any of the ACECs that 

are the subject of this report. However, the copper-nickelPGE deposits in the Bunkerville district were the subject of 

considerable exploration and promotion during the 1980s 

and late 1990s, and that work extended outside the private 

inholding at the Key West Mine into the Gold Butte A and 

Virgin Mountain ACECs.

Element AP-063

20-m chip

Simplot 

Silica Mine

Simplot 

Silica Plant

Container glass 

specification

SiO2 88.89 97.25 98.93 98.5 min

Al2O3 2.47 1.38 0.65 0.5 max

Fe2

O3 0.45 0.19 0.03 0.035 max

MgO+CaO 3.93 0.27 0.05 0.2 max

TiO2 0.08 0.08 0.03 0.03 max

Cr2

O3 0.025 0.00 nd 0.001 max

Table 8. Composition of white Aztec Sandstone from the Whitney Pocket ACEC 

compared with commercial silica sand and container glass specifications.

[All figures are weight percents; Simplot Silica Plant data are from Murphy (1954); container glass data 

are from Zdunczyk and Linkous (1994).]

phy (1954) reported the Aztec Sandstone to be marginal as 

a source of silica sand, but he noted that its potential might 

be enhanced if iron-free beds were found. We analyzed a 

20-m chip sample of nearly white Aztec Sandstone from the 

Whitney Pocket ACEC. The results (sample AP-063, table 8; 

Ludington and others, 2005) show that the sandstone is unsuitable for container glass.

Figure 31. Excavation in pink Aztec Sandstone in the Whitney 

Pocket ACEC. Partially walled excavation is about 1.5 m high.

Figure 32. White to pale-pink Aztec Sandstone just west of 

Whitney Pocket. Site of sample AP-063.

Coneva Holdings Ltd. LLC, of St. George, Utah, plans to 

remove and process stockpiles of ore from the Key West Mine, 

and they have a valid use permit from Clark County that was 

recently extended until 2010. The company acquired a second 

use permit to maintain an extraction plant for copper, nickel, 

and platinum that involves a chemical leaching process at a 

site 22 miles (35 km) to the northwest of the Key West Mine.

A group of nine locators, including American Gold 

Corporation, holds four eight-member placer claims on the 

northwest flank of Bunkerville Ridge in the Gold Butte A 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C37

ACEC. The same locators have placer claims in the Virgin 

River ACEC to the northwest.

The Western Mining Association of Eight holds four 

eight-member association placer claims north and west of the 

Key West Mine that have been active for five years. In 2004, 

both Trend Mining and Mountain Gold Exploration Inc. held 

claims in the same region, but these were not listed as active in 

November 2005.

The Leavitt family has held as many as 40 claims for 

beryllium, mica, and tungsten in the Mica Notch area in the 

Virgin Mountain ACEC, some of them for over 50 years. 

In November of 2005, only a single claim, the Blue Bell # 

10, was still listed with Don and Eldred Leavitt as locators. 

Peeples Inc. holds seven claims east of Whitney Pocket in the 

Virgin Mountain ACEC near the Roadside prospect, described 

by Tingley (1989) as a copper and silver(?) prospect.

Current claim holdings in the Gold Butte B ACEC are 

more numerous. At least 100 lode and millsite claims are held 

jointly by Mark Whitmore and the Whitmore Family Trust 

in three groups in a northwest-trending swath that covers 

vermiculite discoveries around Mica Peak. These claims were 

originally staked from 1993 through 1998, and all were current in 2005. Minor amounts of vermiculite were mined from 

a deposit north of Mica Peak in the 1940s. This area is within 

Whitmore’s Horseshoe group of claims. Since the 1980s, at 

least three companies have evaluated the area for vermiculite. 

Most recently, work has focused on Whitmore’s Cascade and 

Summit groups south of Mica Peak (IBI Corporation, 2004; J. 

Hindman, oral commun., 2005).

James Harlow holds 10 lode claims in the Gold Butte 

B ACEC that possibly extend into the Gold Butte Townsite 

ACEC. The claims were filed in 1991 and 1993 and were 

probably staked for gold, because the locations are quite near 

the Gold Butte Mine.

There is one known active mining and milling operation 

in the Gold Butte B ACEC. This is the small-scale, privately 

held Treasure Hawk Mine, owned by John Lear. It operated 

in a sporadic manner until at least 1987 and is again active 

as of spring 2006. Joanna Dill holds two placer claims near 

the Treasure Hawk Mine that were originally staked in 1981. 

Cutthroat Mining Corp. holds two lode claims and a millsite 

claim in the same area; these were staked in 2004. Rhonda 

McCauley holds three lode claims near Summit Pass in the 

east part of the Gold Butte B ACEC that were located in 2003 

for unknown commodities.

Two areas that cover parts of the Gold Butte A and Gold 

Butte B ACECs were the subject of mineral resource assessments by the U.S. Geological Survey and the U.S. Bureau of 

Mines. They are the Lime Canyon Wilderness, in the northern 

part of Gold Butte B and the southwestern margin of Gold 

Butte A (Winters, 1988; Evans and others, 1990), and the 

Million Hills Wilderness Study Area (Causey, 1988; Moyle 

and Buehler, 1990) in the southernmost part of Gold Butte A 

and the eastern margin of Gold Butte B. The studies of both 

these areas included geochemical analyses of stream-sediment, 

panned concentrate, and spring and well water samples (Bullock and others, 1990; McHugh and others, 1989; McHugh and 

Nowlan, 1989).

At one time, parts of the Gold Butte A ACEC were under 

lease or lease application for oil and gas. Two shallow exploratory wells were drilled there in the 1980s.

Mineral Resource Potential

Locatable Minerals in Gold Butte A ACEC

Ni-Cu-Au-PGE Deposits

The potential for discovery of additional Ni-Cu-PGE 

deposits like those studied here (Key West and Great Eastern Mines) is high, with a moderate level of certainty. Any 

undiscovered deposits would be related to unexposed olivine 

hornblendite dikes or a larger subsurface intrusion, so the most 

prospective areas are the regions between the two mines and 

the extensions of that trend, both to the northeast and to the 

southwest, where the trend passes under alluvial cover. This 

area is delineated on figure 33 as tract GBV04. Factors used 

to delineate this tract include the known deposits, the observed 

occurrences of olivine hornblendite, the aeromagnetic data 

of Falconbridge (Theodore A. DeMatties, written commun., 

2006), and the aeromagnetic high described by Langenheim 

and others (2000). Hose and others (1981) also identified this 

as an area of mineral resource potential. The tract includes 

some areas covered by a thin layer of alluvium.

Whereas the probability that undiscovered deposits like 

those at the Key West and Great Eastern Mines exist is high, 

deposits with either higher grade or larger tonnage would be 

necessary for further development to be likely. This is not 

impossible, as commercial deposits related to mafic dikes 

(Lightfoot and Farrow, 2002) are commonly not exposed at the 

surface. Deep exploration in the Bunkerville district has been 

proposed several times in the past, but has never been carried 

out. A significant Cu-Ni-Au-PGE resource may be present.

Kipushi-Type Copper Deposits

The small base-metal deposits in Paleozoic limestone in 

the Tramp Ridge and Gold Butte blocks are unlikely to ever 

be important sources of copper, lead, zinc, or silver. However, 

they may contain potentially significant concentrations of two 

unusual high-value metals, gallium and germanium, as well 

as cobalt. The characteristics of these deposits indicate clearly 

that they can be considered to be Kipushi-type deposits. The 

deposits in the ACECs have not been explored seriously 

for more than 70 years, and no modern methods have been 

employed. The genesis of this deposit type is not well enough 

understood to know for certain if the age or detailed stratigraphic variations in lithology of the host rocks are important 

factors controlling their occurrence, but all the deposits in 

the Gold Butte A and B ACECs are restricted to the Muav 
C38 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 33. Mineral resource potential tracts for Ni-Cu-Au-PGE deposits, Be-bearing pegmatite deposits, and mica deposits in the Gold 

Butte A and Virgin Mountain Areas of Critical Environmental Concern (ACECs; outlined in pink).

VMT01

Be pegmatites

VMT02

mica

GBV04

Ni-Cu-Au-PGE

GOLD BUTTE A

ACEC

VIRGIN MOUNTAIN

ACEC

WHITNEY POCKET

ACEC

High mineral

resource potential

Moderate mineral

resource potential

Tract ID Deposit Type Potential Level Certainty Level

GBV04 PGE High Moderate

VMT01 Be peg High Moderate

VMT02 Mica Moderate Moderate

114°7'30"W

36°37'30"N

GoldButeACE

Scale1:24,0

0123456 0.5

Kilometers
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C39

Formation, Temple Butte Formation, and Redwall Limestone. 

We have used stratigraphy to outline a tract (GBV03, fig. 34) 

that has moderate potential for the occurrence of undiscovered 

deposits, with a low level of certainty. Because exploration 

of the known deposits could reveal important amounts of 

germanium and gallium, we designate three small areas (tract 

GBV02, fig. 34) within tract GBV03 to have high potential, 

Figure 34. Mineral resource potential tracts for Kipushi-type Cu (Ge-Ga) deposits, uranium deposits in sedimentary rocks, 

vermiculite deposits, and Ni-Cu-Au-PGE deposits in the Gold Butte A and Gold Butte B Areas of Critical Environmental Concern 

(ACECs; outlined in pink).

with a moderate level of certainty. In their study of the Million 

Hills Wilderness Study Area, Bergquist and others (1994) 

designated this area to have high potential for Kipushi-type 

deposits. Technological developments to improve recovery of 

germanium and gallium could transform these small copper 

deposits into significant sources of the strategic metals gallium 

and germanium.

High mineral

resource potential

Moderate mineral

resource potential

Tract ID Deposit Type Potential

Level

Certainty

Level

GBV02 Kipushi Cu High Moderate

GBV03 Kipushi Cu Moderate Low

GBV05 U in seds Moderate Moderate

GBV08 Vermiculite High High

GBV09 Vermiculite Moderate Moderate

GBV09 Ni-Cu-Au-PGE Moderate Low

GBV05

U in sedimentary rocks

GBV01

low-sulfide Au-qtz

GBV03

Kipushi Cu

GBV09

vermiculite,

Ni-Cu-Au-PGE

GBV03 GBV02

Kipushi Cu

GBV02

GBV08

vermiculite

GBV02

GOLD BUTTE B

ACEC

GOLD BUTTE A

ACEC

DEVILS THROAT

ACEC

GOLD BUTTE

TOWNSITE

ACEC

114°15'0"W 114°7'30"W 114°0'0"W

36°15'0"N

36°22'30"N

GoldButeACE

Scale1:24,0

0 3 6 9 12 1.5

Kilometers
C40 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Uranium Deposits in Sedimentary Rocks

A laterally extensive low-grade uranium deposit straddles 

the boundary of the Gold Butte A and B ACECs, extending northeast from the Long Shot Mine area. The deposit is in limestone 

of the Horse Spring Formation. According to Johnson and Glynn 

(1982), an area of 5 km by 17 km underlain by the Horse Spring 

Formation in the Tramp Ridge block in both ACECs is favorable 

for uranium. Although surficial uranium contents only range as 

high as 0.02 percent U3O8, we consider the same approximate 

area to have moderate potential, with a moderate level of certainty 

(tract GBV05, fig. 34) for sandstone- or limestone-hosted uranium deposits. We have expanded the potential area of Johnson 

and Glynn to the east to include Horse Spring Formation rocks 

that fill the Tertiary basin in the east part of the Tramp Ridge 

block, including those buried beneath younger deposits. Beard 

(1996) proposed that this basin was separate from the Wechech 

Basin to the north, where no uranium occurrences are known, so 

we do not include the Wechech basin in the tract.

Borate Mineral Deposits

The Horse Spring Formation contains borate deposits 

to the west, in the Muddy Mountains. However, in the Gold 

Butte A ACEC the formation lacks the stratigraphic unit that 

contains borate minerals, and hence potential for undiscovered 

deposits is low.

Gypsum Deposits

Parts of the Gold Butte A ACEC in Wechech Basin have 

moderate potential for deposits of gypsum in the Horse Spring 

Formation, with a high certainty level (tract GBV06, fig. 35). 

Gypsite units as much as 10 m thick in the area contain about 80 

percent gypsum, a higher grade than ore at the PABCO Mine. 

However, the commercial PABCO gypsite is in a thick, flatlying deposit with little or no overburden, whereas the Wechech 

Basin gypsite dips shallowly east and extraction of commercial amounts would require removal of overburden. Permian 

rock units in the ACEC contain gypsum on the north flank of 

Bunkerville Ridge and in private inholdings in the Lime Canyon 

Wilderness Area, but these deposits have low commercial potential because they are thin, dip moderately, and would require 

substantial stripping of resistant Permian carbonate overburden.

Limestone Deposits

Relatively pure limestone suitable for lime or cement has 

not been reported in the Gold Butte A ACEC. Paleozoic carbonate rocks in the area are generally impure. Devonian limestone, mined for lime and under development as a source of 

cement limestone elsewhere in the region, has been described 

as dolomitic in the ACEC, and such material would likely not 

be suitable for high-calcium lime or cement. Our chip sample 

of Tertiary limestone from the Horse Spring Formation in the 

Garden Spring area in the Gold Butte B ACEC to the south 

indicates that this limestone is also chemically unsuitable for 

lime production. It is sufficiently high in CaO for cement rock, 

but alkali contents are slightly high. Relatively pure Tertiary 

limestone is present, but only in small amounts. It is possible 

that the ACEC contains large unexamined deposits of limestone that are suitable for cement or lime production; however, 

based on the available information the potential is low.

Magnesite Deposits

Magnesite occurs in the basal part of the Horse Spring 

Formation. Hewett and others (1936) reported that magnesitebearing beds contain a reserve of about 500,000 short tons. 

We did not examine the deposit and cannot comment on this 

size estimate. However, the deposit is relatively small and low 

grade when compared with the magnesite deposits at Gabbs, 

Nevada; therefore we consider the potential for commercial 

magnesite in the Gold Butte A ACEC to be low.

Silica Deposits

The Aztec Sandstone, which is exposed extensively in the 

Gold Butte A ACEC, has been proposed as a potential source 

of silica, but the unit typically has a chemical composition that 

makes it unsuitable for silica sand, and the potential for silica 

deposits is low.

There is no evidence for other types of metallic mineral 

deposits in the ACEC, and the potential for other types of 

locatable mineral deposits is low.

Leasable Minerals in Gold Butte A ACEC

The northern and southern parts of the area are within the 

region considered by the BLM to be moderately favorable for 

oil and gas (Smith and Gere, 1983). Two shallow exploratory 

oil wells were drilled within the ACEC (fig. 12). Gold Butte 

KPS Fed. No. 1 was drilled to a depth of 705 m about 2 km 

northwest of Horse Spring by Redi Corp. in 1986. There is no 

information on the rocks encountered, and Garside and others 

(1988) show it as a dry hole with no oil or gas shows. Thomas 

Gap Federal No. JP-1 was drilled by Ruby Drilling Co. to a 

depth of 619 m about 6 km to the north in 1987. Information 

in the files of the Nevada Bureau of Mines and Geology Information Office indicate that this hole was drilled into Permian 

rock; it was a dry hole but had a “slight oil show” between 

depths of 288 m and 326 m. A deep exploratory well, Virgin 

River U.S.A. No. 1-A was drilled to a depth of nearly 6,000 m 

on Mormon Mesa about 7 km west of the ACEC. It was a dry 

hole with no oil shows that was collared in the Muddy Creek 

Formation, intersected Mesozoic and upper Paleozoic rocks, 

and bottomed in granitic basement (Garside and others, 1988).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. This ACEC contains no 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C41

Figure 35. Mineral resource potential tract for gypsum deposits in the Gold Butte A Area of Critical Environmental Concern (ACEC; 

outlined in pink).

Moderate mineral

resource potential

Tract ID Deposit Type Potential Level Certainty Level

GBV06 Gypsum Moderate High

GBV05

uranium in

sedimentary

rocks

GBV06

gypsum

GOLD BUTTE A

ACEC

VIRGIN MOUNTAIN

ACEC

DEVIL’S THROAT

ACEC

RED ROCK SPRING

ACEC

WHITNEY POCKET

ACEC

GOLD BUTTE B

ACEC

114°7'30"W

36°30'0"N

Gold Butte ACEC

Scale 1:24,000

01234 0.5

Kilometers

known deposits of other leasable minerals, and the potential 

for their occurrence is low.

Salable Minerals in Gold Butte A ACEC

Crushed Stone.—The highest quality stone for crushedstone aggregate production in the Gold Butte A ACEC is 

Proterozoic granite, quartz monzonite, and granodiorite 

gneiss, as mapped by Beal (1965). Other high quality units 

include Devonian Muddy Peak Limestone and Cambrian 

Prospect Mountain Quartzite. The Muddy Peak Limestone 

is relatively free of chert and thus not subject to alkali-silica 

reactivity, which can degrade concrete. Together, these lithologic units constitute tract AGBV01 (fig. 36), which has high 

potential for crushed-stone aggregate deposits. This tract has 

only a moderate level of certainty, because the distribution 

of different Proterozoic lithologies has not been mapped in 

detail throughout this ACEC.
Figure 36. Mineral resource potential tracts for aggregate resources in the Gold Butte A (A,B,C), Gold Butte B (B,C), Virgin Mountain 

(A,B), Whitney Pocket (B), Red Rock Spring (B), Devil’s Throat (B), and Gold Butte Townsite (C) Areas of Critical Environmental Concern 

(ACECs; outlined in pink).

AGBV04

AGBV04

AGBV02

A

AGBV02

AGBV02

AGBV02

AGBV01

AGBV03

AGBV02

AGBV01

AGBV01

AGBV01

AGBV03

GOLD BUTTE A

ACEC

VIRGIN MOUNTAIN

ACEC

Aggregate

Potential

crushed stone,highcrushed stone,moderatesand and gravel,highsand and gravel,lowcrushed stone,lowsand and gravel,moderate

AGBV01 crushed stone moderate

AGBV02 moderateAGBV03 moderate

AGBV04 high

AGBV05 low

AGBV06 low

crushed stonecrushed stonesand and gravelsand and gravelsand and gravel

high

moderate

low

high

moderate

low

Tract ID Deposit Type Potential Level Certainty Level

A

114°22'30"W 114°15'0"W 114°7'30"W

36°37'30"N

36°45'0"N

012345

Kilometers
Figure 36.—Continued. AGBV04 AGBV04 

AGBV02 AGBV02 AG

AGBV03 AGBV05 AGBV04 AGBV03 AGBV02 AGBV02 AGBV02AGBV06 AGBV03 AGBV03 AGBV03 AGBV03 GOLD BUTTE A ACEC GOLD BUTTE B ACEC VIRGIN 

DEVIL’S THROAT ACEC RED ROCK SPRING ACEC WHITNEY POCKET ACEC 

AGBV01 AGBV01 Aggregate Potential crushed stone, high crushed stone, moderate sand and gravel, high sand and gravel, lowcrushed stone, lowsand and gravel, moderate AGBV01 crushed stone moderate AGBV02 moderate AGBV03 moderate AGBV04 high AGBV05 low AGBV06 low crushed stone crushed stone sand and gravel sand and gravel sand and gravel high moderate lowhigh moderate low Tract ID Deposit Type Potential Level Certainty Level 114°22'30"W 114°15'0"W 114°7'30"W 36°22'30"N 36°30'0"N 012345 0.5 Kilometers B
Figure 36.—Continued.

AGBV02

AGBV04

AGBV04

AGBV02

AGBV01

AGBV01

AGBV02

AGBV02

AGBV03

AGBV03

GOLD BUTTE B

ACEC

GOLD BUTTE A ACEC

GOLD BUTTE 

TOWNSITE ACEC

AGBV01

AGBV03

A

AGBV01 crushed stone 

AGBV02 AGBV03 

AGBV04 

AGBV05 

AGBV06 

crushed stonecrushed stonesand and gravelsand and gravelsand and gravel

high

modera

low

high

moder

low

Tract ID Deposit Type Potential Lev

114°15'0"W 114°7'30"W 114

36°7'30"N36°15'0"N

012345 0.5

Kilometers

C
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C45

Somewhat lower quality metamorphic rocks, including 

biotite and biotite-garnet gneiss and schist, make up most of 

the Proterozoic part of the Bunkerville Ridge block. Chertbearing limestones make up most of the Paleozoic rocks in 

the Bunkerville Ridge, Virgin Peak, Lime Ridge, and Tramp 

Ridge blocks. Together, these two groups of units were used 

to delineate tract AGBV02 (fig. 36), which has moderate 

potential for crushed-stone aggregate deposits, with a moderate degree of certainty.

The Triassic sedimentary rocks in the ACEC are composed of shale, sandstone, conglomerate, limestone, and 

gypsum. Most of the sandstone, including the Jurassic Aztec 

Sandstone, is friable. The Tertiary sedimentary rocks, Miocene 

Horse Spring Formation and Miocene-Pliocene Muddy Creek 

Formation, are made up primarily of friable sandstone, shale, 

conglomerate, and gypsum. Together with the shales in the 

Paleozoic section, these units have low potential for crushedstone aggregate deposits (tract AGBV03, fig. 36), with a 

moderate degree of certainty.

Sand and Gravel.—A large area in the Gold Butte 

A ACEC is covered with alluvial fan and wash deposits, 

notably the large alluvial fan on the north flank of the Virgin 

Mountain and smaller fans in the Overton Basin south of 

Black Ridge, the Wechech Basin east of Lime Ridge, and 

to the east of Tramp Ridge. The thickness of these deposits is in general unknown, but they represent a significant 

aggregate resource. Several small sand and gravel operations exploit the fan deposits west of Bunkerville along the 

Virgin River. These deposits have high potential for sand 

and gravel aggregate deposits (tract AGBV04, fig. 36), with 

a high degree of certainty.

A large area on the west side of the ACEC, northwest of 

Bitter Ridge, has only moderate potential for sand and gravel 

aggregate deposits (tract AGBV05, fig. 36), with a moderate certainty level, because it is capped with well-cemented 

calcrete. Areas that are primarily sand dunes and sand derived 

from erosion of the Aztec Sandstone have low potential for 

sand and gravel aggregate deposits (tract AGBV06, fig. 36), 

with a moderate level of certainty.

Locatable Minerals in Gold Butte B ACEC

Low-Sulfide Gold-Quartz Vein Deposits

None of the gold-bearing quartz veins in the Gold Butte 

block have become important sources of gold, although they 

have been explored and prospected for more than a hundred 

years. Nevertheless, they conform to a recognized deposit 

type, low-sulfide gold-quartz veins (Berger, 1986; Drew, 

2003), and sampling during the present study as well as during the studies of Dexter and others (1983) and of Winters 

(1988) consistently returned values in excess of 3 ppm gold. 

These concentrations suggest that at least part of most of the 

quartz veins may contain gold at grades high enough to mine 

successfully.

Similar deposits have been developed into small, but 

profitable operations. An example would be the Keystone 

Mine, near Death Valley in California (Pray, 2001).The gold 

apparently occurs primarily as free electrum, so efficient concentration methods can be simple and relatively inexpensive. 

There is no indication of gold disseminated in the wall rocks 

of these veins, so any operations will be small. Some material could be mined from the surface, but most mining would 

eventually have to be by underground methods. Veins commonly pinch and swell, both laterally and vertically, and there 

is a high probability that a number of vein deposits exist that 

are not exposed at the surface.

The tract (GBV01) that we have outlined (fig. 37) is based 

on paleodepths estimated using the reconstructions of Fryxell 

and others (1992), Fitzgerald and others (1991), and Reiners and 

others (2000) and reflects paleodepths of about 5 to 10 km. The 

tract has high potential for the occurrence of additional low-sulfide gold-quartz vein deposits like the ones already known, with 

a high degree of certainty. Dexter and others (1983) designated 

areas within this tract to have moderate potential for small gold 

deposits, but low potential for large valuable deposits. Whether 

any particular vein can be exploited successfully is a function 

of detailed grade distribution and can only be determined by 

detailed on-site exploration.

Kipushi-Type Copper Deposits

The small base-metal deposits in Paleozoic limestone in 

the Tramp Ridge and Gold Butte blocks are unlikely to ever 

be important sources of copper, lead, zinc, or silver. However, they may contain potentially significant concentrations 

of two unusual high-value metals, gallium and germanium, 

as well as cobalt. The characteristics of these deposits indicate clearly that they can be considered to be Kipushi-type 

deposits. The deposits in the ACECs have apparently not 

been explored for more than 70 years, and no modern methods have been employed. The genesis of this deposit type is 

not well enough understood to know for certain if the age or 

detailed stratigraphic variations in lithology of the host rocks 

are important factors controlling their occurrence, but all the 

deposits in the Gold Butte A and B ACECs are restricted 

to the Muav Formation, Temple Butte Formation, and 

Redwall Limestone. We have used the occurrence of these 

stratigraphic units to outline a tract (GBV03, fig. 34) that 

has moderate potential for the occurrence of undiscovered 

Kipushi-type deposits, with a low level of certainty. Because 

exploration of the known deposits could reveal important 

amounts of germanium and gallium, we designate three small 

areas (tract GBV02, fig. 34) within tract GBV03 to have 

high potential, with a moderate level of certainty. In their 

study of the Million Hills Wilderness Study Area, Bergquist 

and others (1994) designated this area to have high potential 

for Kipushi-type deposits. Technological developments to 

improve recovery of germanium and gallium could transform 

these small copper deposits into significant sources of the 

strategic metals gallium and germanium.
C46 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Titanium Deposits

Pegmatite and placer deposits that contain as much as 3.5 

percent and 5.8 percent TiO2, respectively, have been evaluated 

as sources of titanium in the Gold Butte B ACEC (Beal, 1963; 

Dexter and others, 1983). Ilmenite and Ti-magnetite occur 

in the pegmatite deposits, but according to Beal (1963) the 

pegmatites contain 7 percent or less of combined ilmenite and 

Ti-magnetite and represent less than 15 percent of the exposed 

Figure 37. Mineral resource potential tracts for low-sulfide gold-quartz vein deposits, vermiculite deposits, and Ni-Cu-Au-PGE 

deposits in the Gold Butte A, Gold Butte B, and Gold Butte Townsite Areas of Critical Environmental Concern (ACECs; outlined in pink).

GBV01

low-sulfide

Au-qtz veins

GBV03

Kipushi Cu

GBV09

vermiculite,

Ni-Cu-Au-PGE

GBV03 GBV05

uranium

GBV02

Kipushi Cu

GBV08

vermiculite

GBV02

GOLD BUTTE B

ACEC

GOLD BUTTE A

ACEC

GOLD BUTTE

TOWNSITE ACEC

Tract ID Deposit

Type

Potential

Level

Certainty

Level

GBV01 Low-sulfide

Au-qtz veins High

High

High

High

High

Low

Moderate

Moderate

Moderate

Moderate

Moderate

Moderate

GBV03

GBV02

GBV08

GBV09

GBV09

Kipushi-type

Cu deposits

Kipushi-type

Cu deposits

Vermiculite

deposits

Vermiculite

deposits

Ni-Cu-Au-PGE

deposits

High mineral

resource potential

Moderate mineral

resource potential

114°15'0"W 114°7'30"W

36°7'30"N

36°15'0"N

GoldButeACE

Scale1:24,0

0 3 6 9 12 1.5

Kilometers

rock. By contrast, the Tellnes Mine in Norway, a 350-millionton lode titanium deposit, contains about 40 percent ilmenite, 

and other lode deposits under evaluation in Brazil contain 

similarly large reserves with TiO2 contents of 15 to 20 percent 

(Garnar and Stanaway, 1994).

Commercial placer titanium deposits can have low bulk 

TiO2 contents, but are generally very large. The huge shoreline 

and dune deposits in Australia, which extend for hundreds 

of kilometers along the country’s east and west coasts are 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C47

examples (Garnar and Stanaway, 1994). Titanium minerals 

recovered from such deposits are restricted to ilmenite, rutile, 

and leucoxene, and the deposits often produce zircon as a 

byproduct (King, 2005). The most valuable titanium placer 

deposits in the world are probably in Sierra Leone; these 

deposits have rutile contents of about 1.5 percent (Garnar and 

Stanaway, 1994). On the basis of samples collected by Beal 

(1963), titanium in the Gold Butte area placer deposits occurs 

mostly as Ti-magnetite, which is not a titanium ore mineral.

On the basis of this evidence, the potential for commercial titanium deposits in the Gold Butte area is low. The 

pegmatite deposits that contain titanium-bearing minerals 

are too small and low grade, and potential placer deposits are 

small and likely do not contain significant amounts of titanium 

ore minerals.

Uranium Deposits in Sedimentary Rocks

The Long Shot Mine area in the Gold Butte B ACEC is 

a laterally extensive low-grade uranium deposit in limestone 

of the Horse Spring Formation. We consider a large area 

that extends northward into the Gold Butte A ACEC to have 

moderate potential, with moderate certainty, for sandstone- or 

limestone-hosted uranium deposits (Tract GBV05, fig. 34). 

This tract is part of an area that was considered favorable for 

uranium deposits on the basis of an earlier study (Johnson and 

Glynn, 1982), although surficial uranium concentrations in 

this area only range as high as 0.02 percent U3O8.

Vermiculite Deposits

Bodies of ultramafic rock that contain potentially 

economic deposits of vermiculite occur in scattered areas in 

Proterozoic rocks in the Gold Butte B ACEC. Well-delineated 

areas that include ultramafic rock with known vermiculite as 

mapped by Volborth (1962) have high potential for vermiculite 

deposits with a high certainty (tract GBV08, fig. 34). These 

areas are in blocks of currently valid mining claims held for 

vermiculite. A larger area of Proterozoic rock that contains 

mapped bodies of ultramafic rock and may contain others that 

are poorly exposed has moderate potential for vermiculite 

deposits with moderate certainty (tract GBV09, fig. 34).

Ni-Cu-Au-PGE Deposits

The ultramafic rocks in the Gold Butte B ACEC do not 

occur as dikes, like those in the Bunkerville Ridge block. They 

have more complex forms and have clearly been subject to 

regional metamorphism. Nevertheless, numerous samples of 

this rock, particularly at the Blue Bird Mine and at the Marron Tungsten prospect, outside this ACEC, have anomalous 

concentrations of copper, gold, and platinum. Some of these 

samples have relatively high nickel concentrations as well. 

Although we did not study these rocks extensively, they have 

geochemical affinities with altered and mineralized rocks in 

the Bunkerville District. We designate the same tract (GBV09, 

fig. 34) that we assigned moderate potential for vermiculite 

deposits to have moderate potential for Ni-Cu-Au-PGE deposits, with a low level of certainty.

Limestone Deposits

Relatively pure limestone suitable for lime or cement has 

not been reported in the Gold Butte B ACEC. Paleozoic carbonate rocks in the area are generally impure. Devonian limestone, mined for lime and under development as a source of 

cement limestone elsewhere in the region, has been described 

as dolomitic in the Gold Butte A ACEC to the north, and these 

rocks, probably present in the Gold Butte B ACEC, would not 

be suitable for high-calcium lime or cement. Our chip sample 

of Tertiary limestone from the Horse Spring Formation near 

Garden Spring indicates that this limestone is also chemically unsuitable for lime production. It is sufficiently high in 

CaO for cement rock, but alkali contents are slightly high. It 

is possible that the ACEC contains large unexamined deposits 

of limestone that are suitable for cement or lime production; 

however, on the basis of the available information the potential 

is low. In addition, any such deposits would lie a considerable 

distance from easy access routes and would probably not be 

commercial because of high haulage costs.

There is no evidence for other types of metallic mineral 

deposits in the ACEC, and the potential for other types of 

locatable mineral deposits is low.

Leasable Minerals in Gold Butte B ACEC

Small areas in the northern part of this ACEC are within 

the region considered by the BLM to be moderately favorable 

for oil and gas (Smith and Gere, 1983). No exploratory wells 

have been drilled in the ACEC, although two shallow dry holes 

were drilled in the Gold Butte A ACEC to the north. Highly 

metamorphosed Proterozoic rocks underlie most of this ACEC 

and such rocks generally have no hydrocarbon potential.

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. The ACEC contains no 

known deposits of other leasable minerals, and the potential 

for their occurrence is low.

Salable Minerals in Gold Butte B ACEC

Crushed Stone.—The rock units that contain high-quality 

stone in the ACEC are the Paleozoic carbonate rocks that are 

relatively free of chert and some of the quartz- and feldsparrich Proterozoic granitic rocks. These units have high potential 

for crushed-stone aggregate deposits (tract AGBV01, fig. 36), 

with a moderate degree of certainty. Most of the Proterozoic 

metamorphic rocks are either relatively mica- and hornblenderich gneisses or the coarsely porphyritic Gold Butte Granite 

(Volborth, 1962). Large parts of this granite weather readily 

to a gruss, and are not suitable for high-quality crushed stone. 
C48 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

In addition, there are large areas in the Lime Ridge and Tramp 

Ridge blocks that expose chert-bearing Paleozoic carbonate 

rocks. These rocks constitute a tract (AGBV02, fig. 36) that 

has moderate potential for crushed-stone aggregate deposits, with a moderate degree of certainty. The Miocene Horse 

Spring Formation, as well as areas of Proterozoic rock characterized by easily weathered ultramafic rocks, has low potential 

for crushed-stone aggregate deposits (tract AGBV03, fig. 36), 

with a moderate level of certainty.

Sand and Gravel.—The alluvial fan deposits in this 

ACEC contain mostly Proterozoic metamorphic and 

Paleozoic carbonate rock clasts and help delineate a tract 

with high potential for sand and gravel aggregate deposits, 

with a moderate level of certainty (tract AVGB04, fig. 37). 

These deposits are far from transportation corridors and are 

unlikely to be developed in the near future. Some areas on 

the western edge of the ACEC have moderate potential for 

sand and gravel aggregate deposits (tract AGBV05, fig. 36), 

with a moderate certainty level, because the alluvium is 

capped with well-cemented calcrete. Areas with substantial 

amounts of low-quality Tertiary rocks in the Horse Spring 

and Muddy Creek Formations, as well as thin deposits 

of talus on steep slopes, have low potential for sand and 

gravel aggregate deposits, with a low certainty level (tract 

AVGB06, fig. 36). 

Locatable Minerals in Virgin Mountain ACEC

Ni-Cu-Au-PGE Deposits

The potential for discovery of additional Ni-Cu-PGE 

deposits like those studied here (Key West and Great Eastern Mines) is high, with a moderate level of certainty. Any 

undiscovered deposits would be related to unexposed olivine 

hornblendite dikes or a larger subsurface intrusion, so the 

most prospective areas are the regions between the two 

mines and the extensions of that trend, both to the northeast 

and to the southwest, where the trend passes under alluvial 

cover. This area is delineated on figure 33 as tract GBV04. 

Factors used to delineate this tract include the known 

deposits, the observed occurrences of olivine hornblendite, 

the aeromagnetic data of Falconbridge (Theodore A. DeMatties, written commun., 2006), and the aeromagnetic high 

described by Langenheim and others (2000). Hose and others (1981) also identified this as an area of mineral resource 

potential. The tract includes some areas covered by a thin 

layer of alluvium.

Whereas the probability that undiscovered deposits like 

those at the Key West and Great Eastern Mines exist is high, 

deposits with either higher grade or larger tonnage would be 

necessary for further development to be likely. This is not 

impossible, as commercial deposits related to mafic dikes 

(Lightfoot and Farrow, 2002) are commonly not exposed at the 

surface. Deep exploration in the Bunkerville district has been 

proposed several times in the past, but has never been carried 

out. A significant Cu-Ni-Au-PGE resource may be present.

Beryllium-Bearing Pegmatite Deposits

An area in the north part of the Virgin Mountain ACEC 

is considered to have high potential, with moderate certainty, 

for deposits of beryllium in pegmatite (tract VMT01, fig. 33). 

The most abundant beryllium mineral in the Virgin Mountains 

deposits is chrysoberyl, which has been effectively concentrated 

using gravity techniques (Holmes, 1964). Work by the U.S. 

Bureau of Mines in the 1960s indicated weighted average grade 

at about 0.30 percent BeO for pegmatite deposits in the Mica 

Notch area in this ACEC. This compares favorably with other 

pegmatite resources in the world, which have grades ranging 

between 0.04 percent and 0.20 percent BeO (Sabey, 2006).

The only domestic beryllium deposit that is mined at this 

time is the Spor Mountain deposit in Utah, which has an average grade of 0.7 percent BeO and a resource estimated at more 

than 70,000 short tons of BeO (Sabey, 2006). By contrast, the 

known Mica Notch BeO resource was estimated at 190,000 

short tons of rock with 0.35 percent BeO, which constitutes a 

small resource of 665 short tons of BeO. The exposed beryllium deposits in the Virgin Mountain ACEC, which were 

explored by minor excavations and shallow drilling, are small 

and unlikely to be developed at this time. However, the area 

might contain larger deposits at depth.

Limestone Deposits

Relatively pure limestone suitable for lime or cement has not 

been specifically reported in the Virgin Mountain ACEC. Paleozoic carbonate rocks in the area are generally impure. Devonian 

limestone, mined for lime and under development as a source of 

cement limestone elsewhere in the region, has been described as 

dolomitic in this ACEC, and such material would likely not be 

suitable for high-calcium lime or cement. The potential is low for 

limestone deposits in the Virgin Mountain ACEC.

Mica Deposits

Mica was mined on a small scale in the Virgin Mountain 

ACEC during the 1930s and 1950s. Sheet mica deposits in 

pegmatite in this ACEC are small, and we consider them to 

have low potential. Large amounts of mica-rich schist occur 

in the Mica Notch area, and this area has moderate potential, 

with moderate certainty, for the occurrence of flake mica 

deposits (tract VMT02, fig. 33). The schist contains about 40 

percent mica by volume, half of which is muscovite. Unpublished work on beneficiation suggests that a muscovite concentrate may be produced from the schist. Muscovite is widely 

used for industrial applications, but biotite has little commercial application at this time (Tanner, 1994). Further evaluation, 

beyond the scope of this study, would be needed to determine 

mica quality and marketability.

There is no evidence for other types of metallic mineral 

deposits in this ACEC, and the potential for other types of 

locatable mineral deposits is low.
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C49

Leasable Minerals in Virgin Mountain ACEC

A few small areas along the southwest boundary of 

this ACEC are within the region considered by the BLM to 

be moderately favorable for oil and gas (Smith and Gere, 

1983). There are no known exploratory wells. There is no 

indication of potential for brine or evaporite deposits of 

sodium or potassium. The ACEC contains no known deposits of other leasable minerals, and the potential for their 

occurrence is low.

Salable Minerals in Virgin Mountain ACEC

Crushed Stone.—The highest quality stone for crushedstone aggregate production in the Virgin Mountain ACEC is in 

Proterozoic granite, quartz monzonite, and granodiorite gneiss, 

as mapped by Beal (1965). Other high quality units include 

Devonian Muddy Peak Limestone and Cambrian Prospect 

Mountain Quartzite. The Muddy Peak is relatively free of 

chert, and thus not subject to alkali-silica reactivity, which can 

degrade concrete. Together, these lithologic units were used 

to delineate tract AGBV01 (fig. 36), which has high potential 

for crushed-stone aggregate deposits. This tract has only a 

moderate level of certainty because the distribution of different 

Proterozoic lithologies has not been mapped in detail throughout this ACEC.

Chert-bearing limestones make up most of the Paleozoic 

rocks in the Virgin Peak block, and they constitute the major 

part of tract AGBV02 (fig. 36) in this ACEC. This tract has 

moderate potential for crushed-stone aggregate deposits, with 

a moderate degree of certainty.

A large part of the Proterozoic part of the Virgin Peak 

block, south of the Virgin Mountains shear zone (see fig. 5), is 

made up of mafic gneisses with a high biotite content, which 

results in low durability. There are also few equant fragments. 

Together with the shales in the Paleozoic section, and all 

Triassic and younger sedimentary rocks, these units have low 

potential for crushed-stone aggregate deposits (tract AGBV03, 

fig. 36), with a moderate degree of certainty.

Sand and Gravel.—Most of the Virgin Mountain ACEC 

exposes bedrock; a few valleys contain alluvial material. Most 

of this alluvial material is of high quality, and these areas have 

high potential for sand and gravel aggregate deposits (tract 

AGBV04, fig. 36), with a high level of certainty.

Locatable Minerals in Whitney Pocket ACEC

Silica Deposits

The Aztec Sandstone, which makes up much of the 

bedrock in the Whitney Pocket ACEC, has been proposed as 

a potential source of silica and was mined in the past in small 

amounts elsewhere in Clark County. However, chemical analysis of white sandstone from this ACEC indicates that the unit 

has low potential as a source of silica.

There is no evidence for metallic mineral deposits in this 

ACEC, and the potential for other types of locatable mineral 

deposits is low.

Leasable Minerals in Whitney Pocket ACEC

This entire ACEC is within the region considered by the 

BLM to be moderately favorable for oil and gas (Smith and 

Gere, 1983), but there are no known exploratory wells. There 

is no indication of potential for brine or evaporite deposits of 

sodium or potassium. The ACEC contains no known deposits 

of other leasable minerals, and the potential for their occurrence is low.

Salable Minerals in Whitney Pocket ACEC

Crushed Stone.—There is a small amount of Permian 

Toroweap Formation in the northeast corner of this ACEC that 

consists of sandstone, limestone, siltstone, and interbedded 

gypsum. This area has moderate potential for crushed-stone 

aggregate deposits, with a moderate degree of certainty (tract 

AGBV02, fig. 36). The rest of the bedrock in the ACEC is either 

Triassic Moenkopi Formation or Jurassic Aztec Sandstone and 

has low potential for crushed-stone aggregate deposits, with a 

moderate degree of certainty (tract AGBV03, fig. 36).

Sand and Gravel.—The alluvial deposits surrounding the 

outcrops of Aztec Sandstone in this ACEC contain mostly clasts 

of durable carbonate rocks from the mountains to the north and 

so have high potential for sand and gravel aggregate deposits, 

with a high level of certainty (tract AGBV04, fig. 36).

Locatable Minerals in Red Rock Spring ACEC

Silica Deposits

The Aztec Sandstone, which makes up all of the bedrock 

in the Red Rock Spring ACEC, has been proposed as a potential source of silica and was mined in small amounts in the 

past elsewhere in Clark County. However, chemical analysis 

of white sandstone from the nearby Whitney Pocket ACEC 

indicates that the unit has low potential as a source of silica.

There is no evidence for metallic mineral deposits in this 

ACEC, and the potential for other types of locatable mineral 

deposits is low.

Leasable Minerals in Red Rock Spring ACEC

This entire ACEC is within the region considered by the 

BLM to be moderately favorable for oil and gas (Smith and 

Gere, 1983), but there are no known exploratory wells. There 

is no indication of potential for brine or evaporite deposits of 

sodium or potassium. The ACEC contains no known deposits 

of other leasable minerals, and the potential for their occurrence is low.
C50 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Salable Minerals in Red Rock Spring ACEC

Crushed Stone.—The outcrops within the Red Rock 

Spring ACEC are all friable Aztec Sandstone and thus have 

low potential for crushed-stone aggregate deposits, with a 

moderate level of certainty (tract AGBV03, fig. 36).

Sand and Gravel.—Much of the alluvial material in 

this ACEC is primarily fine sand derived from the Aztec 

Sandstone, with few clasts present, and has low potential for 

sand and gravel aggregate deposits, with a moderate level of 

certainty (tract AGBV06, fig. 37). Some other, slightly older 

terrace deposits contain carbonate clasts and have high potential for sand and gravel aggregate deposits (tract AGBV04, fig. 

36), with a high level of certainty.

Locatable Minerals in Devil’s Throat ACEC

Gypsum Deposits

The Devil’s Throat ACEC has low potential for commercial gypsum deposits, although it contains a sinkhole that may 

have been caused by solution collapse of subsurface gypsum 

beds. This gypsum would lie at depths in excess of 20 m, and 

mining would entail expensive removal of overburden.

There is no evidence for metallic mineral deposits in this 

ACEC, and the potential for other types of locatable mineral 

deposits is low.

Leasable Minerals in Devil’s Throat ACEC

This entire ACEC is within the region considered by the 

BLM to be moderately favorable for oil and gas (Smith and 

Gere, 1983). No exploratory drilling has been done within the 

ACEC, but two shallow dry holes were drilled nearby in the 

Gold Butte A ACEC. Thomas Gap Federal No. JP-1, which 

reportedly intersected an oil show (Garside and others, 1988), 

was about 1.5 km to the southeast of the ACEC.

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. This ACEC contains no 

known deposits of other leasable minerals, and the potential 

for their occurrence is low.

Salable Minerals in Devil’s Throat ACEC

Crushed Stone.—The only bedrock exposed in the ACEC 

is Miocene Horse Spring Formation, which consists of finegrained clastic sedimentary rocks and gypsum. This material 

has low potential for crushed-stone aggregate deposits, with a 

moderate level of certainty (tract AGBV03, fig. 36).

Sand and Gravel.—The alluvial fan deposits in this ACEC 

contain mostly carbonate rock clasts, with only minor chert, 

and have high potential for sand and gravel aggregate deposits, 

with a high degree of certainty (tract AGBV04, fig. 36). The 

Devil’s Throat sinkhole suggests a natural hazard that could 

affect exploitation of these resources. Studies of this and other 

sinkholes in the area (McLaurin and others, 2005) indicate that 

dissolution of gypsum beds beneath the alluvium is responsible 

for the karstlike features. Their study used seismic profiling to 

suggest that the alluvial deposits here are about 50 m thick.

Locatable Minerals in Gold Butte Townsite 

ACEC

Low-Sulfide Gold-Quartz Vein Deposits

The Gold Butte Townsite ACEC does not contain any 

known mineral prospects. However, currently valid lode 

claims, possibly for gold, were staked in 1991 and 1993 in the 

Gold Butte B ACEC just to the south and may extend into the 

Gold Butte Townsite ACEC. Quartz vein samples from the 

Golden claim group in this area contain as much as 14.2 ppm 

gold (Dexter and others, 1983). Almost the entire ACEC has 

high potential for low-sulfide gold-quartz vein deposits like 

the ones already known, with a high degree of certainty (tract 

GBV01, fig. 37). Whether any individual vein can be exploited 

successfully is a function of detailed grade distribution and 

can only be determined by detailed on-site exploration.

A very small part of the northwest corner of the ACEC 

has moderate potential for the occurrence of undiscovered 

Kipushi-type copper deposits, with a low level of certainty 

(tract GBT03, fig. 34).

There is no evidence for other types of metallic mineral 

deposits in the ACEC, and the potential for other types of 

locatable mineral deposits is low.

Leasable Minerals in Gold Butte Townsite ACEC

The area is not within the region considered by the BLM 

to be moderately favorable for oil and gas (Smith and Gere, 

1983), nor is it within the region considered by the BLM to 

be prospectively valuable for sodium and potassium (Wayland 

and others, 1980).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. This ACEC contains no 

known deposits of other leasable minerals, and the potential 

for their occurrence is low.

Salable Minerals in Gold Butte Townsite ACEC

Crushed Stone.—Bedrock exposures in the Gold Butte 

Townsite ACEC are either coarsely porphyritic Gold Butte 

granite or chert-bearing Paleozoic limestone. Both these units 

have moderate potential for crushed-stone aggregate deposits 

(tract AGBV02, fig. 36), with a moderate level of certainty.

Sand and Gravel.—The alluvial fan deposits in the 

ACEC, although probably quite thin, contain mostly highquality clasts, and have high potential for sand and gravel 

aggregate deposits, with a moderate level of certainty (tract 
Gold Butte A, Gold Butte B, Virgin Mountain (Gold Butte C), Red Rock Spring, Devil’s Throat, and Gold Butte Townsite ACECs C51

AGBV04, fig. 36). However, like those in the Gold Butte 

B ACEC, they are distant from transportation corridors and 

unlikely to be developed soon.

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Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter D. Mineral Resource Potential of the Mormon Mesa 

Tortoise, Arrow Canyon, and Coyote Springs Tortoise Areas 

of Critical Environmental Concern, Clark County, Nevada

By Kathryn S. Flynn, Stephen B. Castor, Steve Ludington, and Brett T. McLaurin

Summary and Conclusions

The Mormon Mesa Tortoise Area of Critical Environmental Concern (ACEC) contains areas with high potential for 

limestone deposits and areas with moderate potential for stone 

and silica deposits. The potential for undiscovered deposits of 

other locatable and leasable minerals is low. The Mormon Mesa 

Tortoise ACEC has areas with high, moderate, and low potential 

for crushed-stone aggregate deposits and areas with high and 

moderate potential for sand and gravel aggregate deposits.

The Arrow Canyon ACEC has no known mineral deposits, and the potential for undiscovered deposits of locatable 

and leasable minerals is low. Arrow Canyon ACEC has areas 

with high and moderate potential for crushed-stone aggregate 

and moderate potential for sand and gravel aggregate.

The Coyote Springs Tortoise ACEC contains known 

deposits of stone and silica, and a part of it has moderate 

potential for additional silica deposits. The ACEC also has 

areas with high potential for limestone deposits. The potential for undiscovered deposits of other locatable and leasable 

minerals is low. The Coyote Springs Tortoise ACEC has areas 

with high, moderate, and low potential for crushed-stone 

aggregate deposits and high and low potential for sand and 

gravel aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management and, specifically, to determine mineral 

resource potential in accordance with regulations at 43 CFR 

2310, which governs the withdrawal of public lands. The Clark 

County Conservation of Public Land and Natural Resources Act 

of 2002 temporarily withdraws the lands described herein from 

mineral entry, pending final approval of an application for permanent withdrawal by the BLM. This report provides information about mineral resource potential on these lands.

The Mormon Mesa Tortoise, Arrow Canyon, and Coyote 

Springs Tortoise ACECs were studied in the field to confirm descriptions of the geology that were gleaned from the 

geologic literature. Samples were collected and analyzed, and 

known mineral deposits were visited and examined wherever 

possible. Definitions of mineral resource potential and certainty levels are given in appendix 1, and are similar to those 

outlined by Goudarzi (1984).

Lands Involved

The Arrow Canyon, Coyote Springs Tortoise, and Mormon Mesa Tortoise Areas of Critical Environmental Concern 

(ACECs) are contiguous, and they are located northeast of Las 

Vegas on the northwest side of Interstate 15 (fig. 1). A legal 

description of these lands is included in appendix 2.

The Mormon Mesa Tortoise ACEC is located northwest of 

the Virgin River and adjoins the north border of Clark County, 

about 90 km northeast of Las Vegas (fig. 1). Interstate 15 forms 

the south boundary of the ACEC for about 30 km and provides 

access to the area. The ACEC includes part of the Arrow Canyon 

Wilderness. It also overlaps part of the Arrow Canyon ACEC, 

that is, some lands are included within both ACECs (fig. 1).

The Arrow Canyon ACEC straddles Pahranagat Wash (fig. 

1). The western part of the area is also included in the Mormon 

Mesa Tortoise ACEC and partially overlaps the Arrow Canyon 

Wilderness. Nevada State Highway 168 and Warm Springs 

Road both cross Pahranagat Wash to the east of the ACEC.

The Coyote Springs Tortoise ACEC adjoins the Mormon 

Mesa Tortoise ACEC on the west (fig. 1). It measures about 

52 km north to south and is 2 to 6 km wide. The south tip of 

the ACEC is about 10 km northeast of the edge of Las Vegas. 

The ACEC encompasses the southern part of Coyote Springs 

Valley and also Hidden Valley to the southwest. U.S. Highway 

93 bisects the ACEC from north to south.

Physiographic Description

Mormon Mesa forms a triangular highland between 

the Muddy and Virgin Rivers. The Mesa stands about 200 m 
Figure 1. Index map of Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise Areas of Critical Environmental Concern (ACEC; outline

and roads, wilderness areas, and wilderness study areas. Arrow Canyon ACEC boundary is shown in contrasting color (blue) to clarify the boundary Mesa Tortoise ACEC.

MORMON MESA

TORTOISE ACEC

G

COYOTE SPRINGS

TORTOISE ACEC

HIDDEN VALLEY

ACEC

ARROW CANYON

ACEC

RED RO

A

VIRGIN

RIVER

ACEC

Moapa

Overton

Glendale

Arrow Canyon

Wilderness

Meadow Valley Mountains

Wilderness Study Area

Mormon Mountains

Wilderness Study Area

I-15

US 93

NV 168

NV 169

Muddy River

Meadow Valley Wash Mormon Mountains

Virgin River

Coyote Springs Valley

Warm Springs Road

Las Vegas Range

Hidden Valley Arrow Canyon Range

Meadow Valley Mountains

Pahranaga Wash t

Mormon

Mesa

Dry Lake Valley

115°0'0"W 114°45'0"W 114°30'0"W 114°15'0"W

36°30'0"N36°45'0"N

GoldButeACE

Scale1:24,0

0 4 8 12 16 2

Kilometers
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D3

above the riverbeds. From the Meadow Valley Mountains in 

the west, the Mormon Mesa Tortoise ACEC extends 60 km 

east across the mesa to the Virgin River Valley. The Meadow 

Valley Mountains have the most relief in the ACEC, reaching 

elevations of 1,500 m. The Mormon Mountains, in the central 

part of the ACEC, are lower in elevation. Much of the ACEC 

is a flat pediment at an elevation of about 750 m, with no 

streams or gullies and an average topographic gradient of less 

than 50 feet (18 m) per mile (Gardner, 1972).

Arrow Canyon is a narrow gorge that cuts through the 

northern Arrow Canyon Range for several miles. The Arrow 

Canyon ACEC contains part of the Arrow Canyon gorge (fig. 

2) and the mouth of the Pahranagat Wash, which flows southeast (see also fig. 14). The canyon walls are about 120 m high 

in the gorge (Page and Dixon, 1997). Elevations in the ACEC 

range from about 570 m to about 840 m.

The Coyote Springs Tortoise ACEC contains most of 

southern Coyote Springs Valley and also part of Hidden Valley 

(fig. 1) to the south. The area is bounded by the Las Vegas 

Range on the west and the Arrow Canyon Range on the east. 

Perennial streams in the northern part of the ACEC flow northward into Coyote Springs Valley, where they join Pahranagat 

Wash at the north tip of the Arrow Canyon Range and flow 

east toward Arrow Canyon. The central part of the ACEC 

drains into the Hidden Valley alkali flat, and drainages in the 

south part of the ACEC drain eastward into Dry Lake Valley 

(fig. 1). The ACEC has little relief in the valleys (fig. 3) but 

it does include the western flank of the Arrow Canyon Range 

(up to 1,530 m elevation).

Geologic Setting

The three ACECs are located on the eastern edge of the 

Basin and Range Physiographic Province. The Colorado Plateaus Province lies to the east. The mountain ranges in all three 

ACECs are composed of Paleozoic sedimentary rocks (predominantly carbonates). These rocks underwent folding and thrust 

faulting during the late Cretaceous Sevier orogeny, followed by 

extensional basin and range faulting in the late Cenozoic. Large 

parts of the region are underlain by sedimentary deposits that 

blanketed low-lying areas during the late Miocene and filled 

intermontane valleys during the Quaternary. Figure 4 is a generalized geologic map of the three ACECs.

Geology

Mormon Mesa Tortoise ACEC

Mormon Mesa is mostly covered by Quaternary alluvium 

but also has large exposures of Tertiary sedimentary rocks 

and smaller outcrops of Paleozoic sedimentary rocks (fig. 4). 

The Tertiary rocks include relatively minor exposures of the 

Oligocene to middle Miocene Horse Spring Formation and 

extensive exposures of the late Miocene Muddy Creek Formation. The Meadow Valley Mountains and Mormon Mountains 

within the area are composed primarily of Paleozoic carbonate 

Figure 2. Cliffs of Paleozoic limestone at the mouth of Arrow 

Canyon.

Figure 3. Starvation Flat, at the north end of the Coyote Springs 

Tortoise Area of Critical Environmental Concern (ACEC). Looking 

west, beyond the ACEC to the Las Vegas Range.
Figure 4. Generalized geology of the Mormon Mesa Tortoise, Coyote Springs Tortoise, and Arrow Canyon ACECs. Geology modified from Stewart an

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MORMON MESA

TORTOISE ACEC

COYOTE SPRINGS

TORTOISE ACEC

ARROW CANYON

ACEC

0 4 8 12 16 2

Kilometers

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Undivided surficial deposits (Pleistocene and Holocene)—Alluvium, colluvium,lake, playa, landslide, terrace, and eolian sand depositsSedimentary rocks (Pliocene and Pleistocene)—Mostly lake and alluvial depositsYoung sedimentary rocks (middle Miocene to Pliocene)—Alluvial, lacustrine,and fluvial deposits. Locally includes minor tuff. Includes Muddy Creek FormationHorse Spring Formation (upper Oligocene and Miocene)—Clastic and tuffaceoussedimentary rocks; includes some volcanic rocks, limestone, and gypsumYoung volcanic rocks (middle and upper Miocene)—Rhyolite, andesite, and basaltlava flows, tuff, and tuffaceous sedimentsSedimentary rocks (Triassic and Jurassic)—Shale, mudstone, siltstone, sandstone, and carbosome sparse volcanic rock. Includes Lower Jurassic Glen Canyon Group and Chinle and MoeCarbonate rocks (Mississippian to Permian )—Limestone, dolomite, and some shale. May incMonte Cristo, Pakoon, and Redwall LimestonesSedimentary rocks (Mississippian to Permian)—Siltstone, sandstone, shale, and conglomeratdolomite, chert, and gypsum. May include Queantoweap and Coconino Sandstones, and HerDolomite and Limestone (Cambrian to Devonian)—Dolomite, limestone, and minor sandstonMay include Temple Butte and Sultan Limestones, Frenchman Mountain Dolomite, Bonanza Sedimentary rock (Cambrian)—Sandstone, shale, and limestone. May include Pioche Shale, Bright Angel Shale, and Bonanza King, Muav, and Nopah Formations.Metamorphic rocks (Paleoproterozoic)—Undivided metasedimentary, metavolcanic, and gnelocally abundant amphibolite, and pegmatite. May also include Paleoproterozoic granitoid 

EXPLANATION

115°0'0"W 114°45'0"W 114°30'0"W 114°15'0

36°30'0"N36°45'0"N

Gold Butte ACEC

Scale 1:24,000
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D5

rocks, but some Mesozoic siliciclastic rocks are also exposed, 

including the Triassic Moenkopi Formation and the Jurassic 

Aztec Sandstone (Page and Pampeyan, 1996; Schmidt, 1994; 

Schmidt and others, 1996). These units are cut by thrust faults 

associated with the Sevier orogeny and high-angle normal 

faults related to Cenozoic extension.

The young basin that underlies the eastern part of Mormon Mesa and areas to the east is known as the Virgin River 

Depression. Geophysical data (Langenheim and others, 2001) 

indicate that the basin is 5 to 10 km deep and filled with Tertiary and Quaternary sediments. A few Quaternary faults strike 

generally north in the central part of the basin (Langenheim 

and others, 2000).

The surface of Mormon Mesa (fig. 5) is a pediment cut 

on the Muddy Creek Formation and its reworked alluvial 

deposits (Gardner, 1972). Bedrock in the area is locally covered by caliche, an indurated layer of calcium carbonate that 

formed in the arid climate under aggrading conditions. The 

soil profile consists of a few meters of caliche, which transitions downward into the clastic parent material. This caliche 

is at least 890,000 years old, and it may be as old as 3 million 

years (Gardner, 1972).

Arrow Canyon ACEC

The walls of Arrow Canyon expose Mississippian, 

Pennsylvanian, and Permian strata. These carbonate rocks 

are especially well exposed and accessible in Arrow Canyon, 

giving it a reputation as one of the best-studied Paleozoic 

sections in the eastern Great Basin (Page and Dixon, 1997). 

Bedrock in the eastern part of the ACEC is the Permian Bird 

Spring Formation, which includes abundant marine fossils 

and a distinctive reddish marker bed near the top of the unit 

(Page and Dixon, 1997). The western part of the ACEC is 

composed of the Bird Spring Formation, the Indian Springs 

Formation, the Battleship Wash Formation, and the Monte 

Cristo Group (Page, 1992). These units are mostly limestone 

Figure 5. Mormon Mesa pediment, as seen from Meadow Valley 

Wash. Moapa Peak, just north of the ACEC, in background.

with beds of chert, except for the Bullion Dolomite member 

of the Monte Cristo Group (Page and Dixon, 1997). Continuous and extensive stratigraphic exposure has made Arrow 

Canyon a popular place to study stratigraphy. Conodont fossils from the Indian Springs Formation were used to define 

the boundary between the Mississippian and Pennsylvanian 

Periods (Brenckle and others, 1997).

Coyote Springs Tortoise ACEC

Paleozoic carbonate rocks form the bedrock of the Coyote Springs Tortoise ACEC (fig. 4), but much of it consists 

of wide valleys filled with younger sediments (Eakin, 1964). 

Ordovician, Silurian, and Devonian carbonate rocks form the 

northern part of the Arrow Canyon Range that is exposed in 

the ACEC (Page, 1998). The Las Vegas Range on the west and 

the southern part of the Arrow Canyon Range expose the same 

Permian and Mississippian rock units as Arrow Canyon. Coyote Springs Valley contains Quaternary deposits of alluvium 

and playa sediments.

Numerous large and small folds in these Paleozoic rocks 

are evidence of regional compression during the Sevier orogeny. The Battleship Wash Syncline is an open fold whose axis 

crosses Arrow Canyon in the study area, and it is visible along 

the east side of the Arrow Canyon Range (Page and Dixon, 

1997). Another major syncline is concealed by alluvium in 

Coyote Springs Valley (Page, 1992). The rocks are cut by 

thrust faults associated with the Sevier orogeny and high-angle 

normal faults related to Cenozoic extension.

Mining History

The only recorded mining activity within the boundaries 

of these three ACECs was at the Quartzite quarry (fig. 6) in 

the central part of Coyote Springs Tortoise ACEC. We found 

no information about dates or amounts of production at that 

quarry. The quartzite may have been mined as a source of 

silica or for building stone.

Quartzite was reportedly mined for several years from the 

Tiffany Minerals Co. quarry (fig. 6), which is about 2 km east 

of the Coyote Springs Tortoise ACEC (Murphy, 1954). No 

figures are available for total production, but in 1954 production was reported to be less than 2,000 short tons of quartzite 

per year. The quartzite was trucked to a mill on the Union 

Pacific Railroad, but the operation was abandoned because the 

abrasiveness of the rock caused high milling costs. In addition, building stone was mined about 10 km east of the Coyote 

Springs Tortoise ACEC.

The Apex limestone quarries and plant of Chemical Lime 

Inc. form the largest mining operation in the vicinity of the 

three ACECs. The limestone was drilled and evaluated in the 

1930s (Hewett and others, 1936), and limestone was mined 

and shipped from the area by U.S. Lime Products Corp. and 

processed elsewhere. In the early 1950s, annual production 
Figure 6. Mines and prospects in and near the Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise Areas of Critical Environmental Coutlined in pink).

Rock quarry

Silverstone

Jordan Claims

Sampson Claim

Marble quarry

June Bug

mine

Moapa Venture

Tiffany quarry

Lead King Mine

White Star

mine

Quartzite

quarry

Great Basin

mine

Nickel Creek Mill

Micron Mine & Mill

Moapa geothermal wells

Moapa #1 Mine & Mill

Micronic Metals

mine Volcanic Ash

prospect

Roaring Springs Ranch

prospect

White Star

No. 2 mine

Fry And Jeffers

prospect

Apex Limestone quarry

G

unnamed

clay prospect

115°0'0"W 114°30'0"W

36°30'0"N

0 8 16 2

4

MORMON MESA

TORTOISE ACEC

COYOTE SPRINGS 

TORTOISE ACEC

ARROW CANYON

ACEC
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D7

was given by the U.S. Bureau of Mines at more than 500,000 

short tons. In 1958, after acquisition of the operation by the 

Flintkote Co., a lime plant was constructed. In 1980 the operation was acquired by Genstar Lime and Cement Inc., which 

was succeeded by Chemstar Lime Inc. in 1986 and by Chemical Lime Inc. in 1994. The most recent production figure 

for the operation is 195,000 short tons of quicklime in 1990 

(Nevada Department of Minerals and Nevada Bureau of Mines 

and Geology, 1991).

Although we found no direct evidence of placer gold, it 

is possible that there has been some placer gold mining along 

Meadow Valley Wash, which bisects the Mormon Mesa Tortoise ACEC. There has been no other known mining within the 

boundaries of the three ACECs, although moderately extensive 

mining of silica and dimension stone has taken place a few 

kilometers east of Coyote Springs Tortoise ACEC. In addition, 

exploration drilling for geothermal energy has taken place 

immediately east of the Arrow Canyon ACEC and southeast of 

the Mormon Mesa ACEC, along the Virgin River (fig. 6).

Mineral Deposits

Mormon Mesa Tortoise ACEC

The mines database of the Nevada Department of 

Environmental Protection locates the Roaring Springs Ranch 

gold prospect within the Mormon Mesa Tortoise ACEC, on 

Meadow Valley Wash (fig. 6), but provides no further information. A field visit to the indicated site revealed no evidence 

of exploration or mining aside from a primitive road off the 

Meadow Valley Wash road (fig. 7). Another source (Nevada 

Department of Industrial Relations, 1987) indicates that the 

Moapa #1 mine and mill was under construction in 1986 by 

the Roaring Springs Ranch Company, but that the site of this 

mine and mill was 20 km to the west, in section 6 of T13S, 

R64E. There are no other references to these developments.

In the far northwestern corner of the area, the Moapa 

#1 mine and mill (gold) and the Micron mine and mill (gold) 

were reportedly in operation in the mid 1980s (Nevada Department of Industrial Relations, 1987, 1988). Given the geologic 

Figure 7. Purported site of Roaring Springs Ranch gold prospect.

Figure 8. Purported site of the Micron Mine and mill; Paleozoic 

carbonate rocks in hills on right. Looking north along former U.S. 

Highway 93.

Figure 9. Possible old claim marker in the vicinity of the 

Moapa #1 and Micron sites, Mormon Mesa ACEC.

context, these could have exploited polymetallic vein or 

replacement deposits in Paleozoic limestone. They are located 

at the south end of the Meadow Valley Mountains district (Tingley, 1989). Two visits to this area (fig. 6) yielded no evidence 

of gold mining activity (fig. 8). A shallow gravel pit was noted 

in the area, as well as some possible claim markers (fig. 9).

Clay deposits occur in the Muddy Creek Formation in the 

western part of the Mormon Mesa Tortoise ACEC. According 
D8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

to Vandenberg (1937), a bed of white bentonite about 3 feet (1 

m) thick is exposed for about 2 km in a bluff at the Volcanic 

Ash prospect (figs. 6, 10).

During field reconnaissance in this area, which is along 

Pahranagat Wash, we sampled a 1.1-m-thick, nearly flat lying 

bed of white to pale olive green expansive clay from a small 

prospect (fig. 11) along the south side of the wash (sample site 

AP-114). XRD analysis of this sample indicates the presence 

of smectite clay, possibly the sodium-rich clay beidellite, along 

with significant amounts of dolomite and minor quartz and 

feldspar. However, a chemical analysis of the sample (Ludington and others, 2005) suggests the presence of a magnesian 

smectite such as saponite, because MgO/CaO is higher than can 

be accounted for by dolomite contamination. In a road cut about 

500 m to the west is a poor exposure of low-quality clay mixed 

with calcite and glassy shard tuff at about the same stratigraphic 

level (sample AP-115). This clay occurs in a sequence of 

sandstone, gypsum, and 5.6-Ma tuff capped by limestone that is 

probably part of the Muddy Creek Formation.

A second clay prospect, about 65 m long and 10 m wide 

(fig. 12), is about 6 km north-northwest of the Volcanic Ash 

prospect (sample site AP-038). At this prospect, a bed of 

pale-olive-green to pale-brown clay occurs in shallowly west 

dipping redbeds of the Muddy Creek Formation. On the basis 

of XRD analysis, this clay is considered to be of low quality 

because it contains large amounts of impurities, mainly calcite 

and quartz with minor feldspar and dolomite. The clay mineral 

could not be determined by XRD analysis; the clay differs 

considerably from the Volcanic Ash prospect clay on the basis 

of chemical analysis (Ludington and others, 2005).

The Fry and Jeffers prospect (fig. 6) was reportedly 

explored for uranium in lower Paleozoic limestone in the 

western part of the Mormon Mesa Tortoise ACEC (Campbell, 

1987). Radioactivity at the site was about 1.6 times background, and soil samples from the area reportedly contained 

as much as 110 ppm U3

O8 (Nelson, 1954). This occurrence 

is in shallowly northeast dipping black Paleozoic limestone 

with no veins or structures and no visible uranium minerals. 

Later reconnaissance of the area showed only weakly anomalous radioactivity, and the occurrence was judged to be of no 

interest (Campbell, 1987). Examination of aerial photography 

of the region reveals no evidence of any significant surface 

disturbance.

Near Meadow Valley Wash, but outside the ACEC, four 

other gold prospects have been reported (fig. 6): the Moapa 

Venture prospect, about 5 km north of the ACEC boundAP-116

AP-115

AP-114

Volcanic Ash Prospect

Arrow Canyon Wilderness

Mormon Mesa Tortoise GoldButeACEC ACEC boundary

Scale1:24,000

0 250 500 750 1,000 125

Meters

Figure 10. Aerial view of Volcanic Ash clay prospect in the Mormon Mesa ACEC, showing wilderness (orange) and 

ACEC (pink) boundaries, and location of samples.
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D9

Figure 11. White to pale-olive-green clay in a small prospect on 

the south side of Pahranagat Wash. Sample site AP-114.

ary (Nevada Department of Industrial Relations, 1983); the 

Great Basin prospect, about 1 km south of the ACEC boundary (Nevada Department of Industrial Relations, 1987); 

the Micronic Metals mine, about 2 km south of the ACEC 

boundary (Nevada Department of Industrial Relations, 1981); 

and Silverstone, about 7 km southwest of the south tip of the 

ACEC (Nevada Department of Industrial Relations, 1983). 

These sites were reportedly in operation in the 1980s, but we 

were unable to find any further information about these locations or locate them in the field.

The Gourd Springs mining district is in the East Mormon Mountains of Lincoln County, 12 to 15 km north of the 

Mormon Mesa Tortoise ACEC. Reported lode deposits are 

either associated with Precambrian pegmatites or consist of 

manganese enrichments in Cambrian limestone (Tschanz and 

Pampeyan, 1970). Manganese ore was reportedly produced 

in 1929 from this district, but Tingley (1984) was unable to 

locate these workings.

The Mormon Mountains district contains the Whitmore 

Mine, which is about 10 km north of the ACEC. It consists 

of several adits, shallow shafts, and prospect pits along a 

moderately northwest-dipping detachment fault. Unmineralized Paleozoic limestone is in the hanging wall, and altered 

and veined granitic rock is in the footwall. Quartz, pyrite, 

chalcopyrite, and bornite occur in the veins, and a select vein 

sample contains more than 2 percent copper and 50 ppm silver 

(Tingley, 1989). In 1908, 19 short tons of ore were produced 

containing 4 troy ounces of silver and 2,621 pounds of copper.

Near the town of Mesquite, about 10 km east of the 

ACEC, three small mills reportedly operated intermittently 

in the 1980s (fig. 6): Envirochem (Nevada Department of 

Industrial Relations, 1982); White Park R.D (Nevada Department of Industrial Relations, 1991); and Aggandize Mining 

Co. (Nevada Department of Industrial Relations, 1991). None 

of these is known to be operating at present.

The White Star bedded gypsum deposit is located about 

7 km southwest of the south tip of the ACEC, near the town of 

Glendale, Nevada (figs 1, 6). The deposit, a flat-lying gypsite bed about 7 m thick in the Muddy Creek Formation, was 

mined by the White Star Plaster Co. from 1919 to 1920 to supply a nearby mill (Papke, 1987). The White Star No. 2 deposit, 

about 4 km to the southeast, was mined underground from 

1921 to 1923 to feed the same mill. The latter deposit consists 

of a shallowly west dipping gypsum unit about 8 m thick in 

the Kaibab Formation (Papke, 1987).

Federated Commercial Industries Co. is currently exploring a large area of gypsum in the upper part of the Muddy 

Creek Formation in Lincoln County, about 4 km north of the 

Mormon Mesa ACEC. Published information on gypsum in 

this area describes the Snowhite deposit as flat-lying, near-surface gypsite about 2 m thick in an area of about 7 km2

 (Papke, 

1987). The current exploration personnel of Federal Commercial Industries report that it covers a much larger area (G. W. 

Hansen, written commun., 2005).

Arrow Canyon ACEC

No mineral deposits are known in or near the Arrow Canyon ACEC. However, several wells were drilled to explore for 

geothermal energy in the Muddy Springs area about 1 to 6 km 

east of the east end of the Arrow Canyon ACEC.

Coyote Springs Tortoise ACEC

The Lead King mine, in the Dike mining district, 

exploited a polymetallic deposit in a shear zone in upper 

Paleozoic carbonate rocks. It is less than 2 km south of the 

south tip of the Coyote Springs Tortoise ACEC (fig. 6). It 

reportedly produced 2 carloads of lead ore sometime before 

the 1950s (Longwell and others, 1965). This deposit may be a 

Mississippi-Valley-type deposit of Paleozoic age.

Small quantities of ore have been produced from mines in 

the Gass Peak mining district, which is about 10 to 15 km west 

of the south end of the Coyote Springs Tortoise ACEC (fig. 

6). The bedrock in this district is Monte Cristo Limestone that 

Figure 12. Clay bed in redbeds of the Muddy Creek Formation. 

Unnamed clay prospect, sample site AP-038.
D10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

has been replaced with lead and zinc minerals (now oxidized) 

adjacent to shear zones. The June Bug Mine produced about 

1,000 short tons of ore in 1916-1917 (Longwell and others, 

1965). The Sampson claim has no recorded production. Some 

of the deposits in the Gass Peak district may be MississippiValley-type replacement deposits.

A once-active quarry in the Ordovician Eureka Quartzite 

is in the central part of the Coyote Springs Tortoise ACEC 

(fig. 6). This quarry is about 150 m long, 30 m wide, and 20 m 

deep (fig. 13). It is visible from Highway 93 near the western 

base of the Arrow Canyon Range. The quartzite is white, very 

hard, firmly cemented, and partially recrystallized. It may 

have been mined as a source of stone rather than of silica. A 

chip sample of quartzite that represents about 10 m of bedded 

thickness (sample AP-036; Ludington and others, 2005) contains more than 99 percent SiO2

. Except for slightly elevated 

Fe2O3, it is suitable for the production of container glass (table 

1). The thickness of the Eureka Quartzite in the area is given at 

40 to 50 m (Page, 1998). Reserves available at economic minFigure 13. Quartzite quarry on the Coyote Springs Tortoise ACEC 

at the west base of the Arrow Canyon Range. Sample site AP-036.

Table 1. Comparison of major element composition of Nevada silica deposits. 

[AP-036 = quartzite quarry, Coyote Springs ACEC; AP-117 = American Cement and Aggregate Corp. plant, Mercury, Nevada; AP-006C 

= Arden Quarries, Nevada. Tiffany Mine and Simplot Silica data are from Murphy (1954); container glass specification data are from 

Zdunczyk and Linkous (1994). na = data not available.]

Element AP-036 AP-117 AP-006C Tiffany 

Mine

Simplot 

Silica ore

Simplot Silica 

product

Container glass 

specification

SiO2 99.42 98.53 95.56 99.52 97.25 98.93 98.5 min

Al2

O3 0.17 0.33 0.77 0.27 1.38 0.65 0.5 max

Fe2

O3 0.16 0.25 0.4 0.01 0.19 0.03 0.035 max

MgO + CaO 0.07 0.06 1.22 0.02 0.27 0.05 0.2 max

TiO2 0.01 0.02 0.02 0.01 0.08 0.03 0.03 max

Cr2

O3 0.036 0.04 0.031 na 0.00 na 0.001 max

ing costs may be low because the bedding dips shallowly westward under increasingly thick cover. Mapping by Page (1992, 

1998) shows that the Eureka Quartzite crops out extensively in 

the Arrow Canyon Range. In the Coyote Springs ACEC it is 

mainly high on the steep western face of the range and within 

the Arrow Canyon Wilderness Area.

The quarry described above is west of the Arrow Canyon 

Range mining district as defined by Tingley (1992). This district reportedly contains several deposits of silica and building 

stone within about 10 km of the east boundary of the Coyote 

Springs Tortoise ACEC. The locations of some of these are 

in doubt because of discrepancies among published sources 

(Murphy, 1954; Tingley, 1989; Hess, 2001). The Tiffany 

Minerals Co. quarry is the only other mined deposit located by 

us or by Tingley (1989) with certainty. The Eureka Quartzite 

was mined at a rate of about 2,000 short tons per year from 

this site (Murphy, 1954), which is about 1 km east of the 

Coyote Springs Tortoise ACEC. The quarry is about 75 m 

long, 40 m wide, and 12 m deep in a dip slope on beds that dip 

at a low angle to the east (Tingley, 1989). On the basis of an 

analysis reported in Murphy (1954), the chemistry of Tiffany 

mine quartzite has very high SiO2

 and is similar to that of our 

sample AP-036. We have no information about reserves at the 

Tiffany deposit.

The Chemical Lime Corporation mines high-calcium 

limestone from the Crystal Pass Limestone Member of the 

Devonian Sultan Formation at Apex about 5 km east of the 

south end of the ACEC (fig. 6). In addition, the company 

mines dolomite from the Bullion Dolomite Member of the 

Monte Cristo Formation in the same area. Both rocks are used 

to make lime in an adjacent plant. Relatively minor amounts 

of magnesium are considered to be deleterious in high-calcium 

lime, and kiln feed that contains more than 1 percent MgCO3

(about 0.5 percent MgO) is unsuitable (S. Krukowski, personal commun., 2006). In addition, kiln feed with more than 1 

percent SiO2 is generally considered unacceptable. In southern 

Nevada, Cambrian through Middle Devonian rocks, which are 

predominantly dolomite and dolomitic limestone, generally 
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D11

Table 2. Comparison of some major element analyses of 3-m chip sample AP-324 and 25-m chip sample AP328 from the Coyote Springs Tortoise ACEC with a grab sample from the Apex quarry, with Portland cement 

specifications, and with high-Ca lime specifications.

[CaCO3 % calculated using CaO x 1.78; MgCO3 % calculated using MgO x 2.09. Apex Limestone Quarry data from Tingley and others (1992). Portland cement specifications from Ames and others (1994). High-Ca lime ore specification from Stanley T. Krukowski 

(oral commun., 2005).]

Element AP-324 AP-328 Apex Limestone 

Quarry

Portland cement 

ore specification

High-Ca lime ore

specification

SiO2 1.86 2.00 0.80 <1

Al2

O3 0.20 0.16 0.16

Fe2

O3 0.11 0.08 0.12

MgO 0.54 0.26 0.34 <0.5

CaO 54.32 56.23 54.94 ca. 50

Na2

O+K2O 0.12 0.08 0.05 <0.4

P2

O5 0.08 0.01 0.04

LOI 42.8 41.10 43.20

CaCO3 96.69 100.09 97.79 >95

MgCO3 1.13 0.54 0.71

Total carbonate 97.82 100.63 98.50

contain too much MgO and (or) other impurities (such as silica 

in the form of chert) to meet specifications. However, some 

Upper Devonian and Mississippian limestone units in southern 

Nevada generally have sufficiently low MgO contents for lime 

production. The Crystal Pass Limestone at Apex is chemically 

suitable (table 2), and it is especially attractive because its very 

fine grain size is desirable for the production of high-quality 

lump lime. More coarsely crystalline limestone decrepitates 

during calcination, producing fine-grained lime.

Mineral Exploration and Development

There are a number of current placer claims in and 

adjacent to the Mormon Mesa Tortoise ACEC. American Gold 

Corp. holds four current association placer claims on the surface of Mormon Mesa, along the south boundary of the Mormon Mesa Tortoise ACEC, near its east end. These are part of 

the same block of claims described in the Virgin River ACEC 

report (Chapter G of this report). A group of eight individuals 

hold five association placer claims in the central part of the 

Mormon Mesa Tortoise ACEC, near the northern boundary, 

along Meadow Valley Wash. These claims include the Roaring 

Springs Ranch prospect mentioned above. A different group of 

eight people holds two other placer claims further south along 

Meadow Valley Wash, just within the Mormon Mesa Tortoise 

ACEC. The Fire Corporation holds seven association placer 

claims along the south boundary of the ACEC, about 3 to 8 

km west of Meadow Valley Wash, and a third group of eight 

people holds two claims in that same vicinity. John P. Simons 

holds five placer claims in the western part of the ACEC, just 

south of the Fry and Jeffers uranium prospect.

American Cement and Aggregate Corp. holds eight 

claims near the center of the Coyote Springs Tortoise ACEC 

in the vicinity of the quartzite quarry described above. The 

company produces silica sand from the Eureka Quartzite 

near Mercury, Nevada. Nevada Aggregates Holding LLC 

holds a single claim near the south tip of the Coyote Springs 

Tortoise ACEC.

None of the claims listed above shows any signs of current exploration activity. We are not aware of any other current 

exploration activity in the three ACECs.

Geothermal Sites and Exploration

Wells drilled near the Mormon Mesa Tortoise and Arrow 

Canyon ACECs intersected thermal water (fig. 6). Warm 

springs and wells in the Muddy Springs area are within 1 km 

of the Arrow Canyon ACEC and 2 km of the Mormon Mesa 

Tortoise ACEC. On the basis of data in Garside (1994) and 

Shevenell and Garside (2005), well CSV-3, which is near 

U.S. Highway 93 along the west border of the Coyote Springs 

Tortoise ACEC, intersected hot water (41°C), and other wells 

and springs in the area produce warm water (31-36°C). Warm 

Spring, which is in the Muddy Springs geothermal area, 

produces one of the highest flows of thermal water in Nevada 

(Garside, 1994).

Despite the presence of thermal wells and springs in the 

area, the likelihood for a geothermal system with sufficiently 

high temperature (150°C) for electrical generation in the area 
D12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

is considered to fall in the “permissive” to “marginally favorable” classes in most of the three ACECs (Coolbaugh and 

others, 2005). These classes constitute the two lowest geothermal favorability classifications for the Great Basin. Relatively 

small areas in the central and northern part of the Coyote 

Springs Tortoise ACEC and the northwestern part of the Mormon Mesa Tortoise ACEC are shown by Coolbaugh and others 

as “favorable,” which is equivalent to only moderate potential 

in their classification scheme. However, potential for direct 

use applications, such as residential or aquacultural heating, is 

high in the Muddy Springs area.

Mineral Resource Potential

Locatable Minerals in Mormon Mesa Tortoise 

ACEC

Precious and Base Metals.—Although there are hydrothermal precious- and base-metal deposits in nearby areas, the 

geologic environments that host these deposits do not occur 

inside this ACEC, and the potential for their presence is low.

Uranium.—The Fry and Jeffers uranium prospect is not 

in an area that exhibits significant or widespread effects of 

mineralizing processes, and radioactivity in the area is not 

much above background levels. On the basis of this and the 

regional geology, we do not consider the ACEC to have potential for uranium deposits.

Clay. —There are clay occurrences within this ACEC, 

but the clay is of poor quality and unlikely to be present in 

large amounts. The potential for clay deposits is low.

Stone and Silica.—At least two deposits have produced 

silica and/or stone near this ACEC. However, there are no 

continuous outcrops of Eureka quartzite within the ACEC, and 

the mineral resource potential is low.

Limestone.—At Apex (fig. 6), high-calcium limestone 

is mined from the Crystal Pass Member, the uppermost unit 

in the Devonian Sultan Limestone, and this unit is known to 

contain high-calcium limestone elsewhere in southern Nevada. 

An equivalent limestone unit is included in the upper part of 

the Guilmette Formation, which crops out in the western part 

of the Mormon Mesa Tortoise ACEC (Page, 1992, 1998). 

Although we have demonstrated that the Sultan (or upper 

Guilmette) contains high-calcium limestone at one site in the 

Coyote Springs Tortoise ACEC, the potential for economic 

deposits cannot be demonstrated at the highest certainty level 

without more careful sampling. Two large areas mapped as 

Sultan Formation (Longwell and others, 1965) and upper Guilmette Formation (Page, 1992, 1998) are considered to have 

high potential, with moderate certainty, for limestone deposits 

(tract MMT01, fig. 14).

Gypsum.—There are two abandoned gypsum mines near 

the south tip of this ACEC, but the appropriate depositional 

environments are not found inside the ACEC, and the potential 

for gypsum deposits there is low.

Leasable Minerals in Mormon Mesa Tortoise 

ACEC

The entire Mormon Mesa Tortoise ACEC is within the 

region considered by the BLM to be moderately favorable for 

oil and gas (Smith and Gere, 1983). There is no indication of 

potential for brine or evaporite deposits of sodium or potassium. The Mormon Mesa Tortoise ACEC contains no known 

deposits of other leasable minerals, and the potential for their 

occurrence is low.

Salable Minerals in Mormon Mesa Tortoise 

ACEC

Crushed Stone.—The highest potential areas for crushedstone aggregate are located in the western part of this ACEC, 

where Paleozoic carbonate rocks form north-trending ridges. 

The highest quality lithologies are found in the Highland Peak 

Formation, the Nopah Formation, Eureka Quartzite, Laketown 

Dolomite, Simonson Dolomite, the Guilmette Formation, the 

Crystal Pass Limestone, Battleship Wash Formation, and various members of the Bird Springs Formation. Geologic mapping by Page (1992) indicates that the carbonate rocks in these 

units are limestone, dolomitic limestone, and dolomite and are 

relatively chert-free compared to other Paleozoic carbonate 

units. Areas underlain by these rocks constitute tract AMAC03 

(fig. 15), and have high potential for crushed-stone aggregate, 

with a high degree of certainty. High-potential areas in the 

tract are also present in the south-central part of the ACEC 

along the southern extension of the Mormon Mountains.

Siliceous beds in other carbonate units are composed of 

discontinuous chert layers that can be in intervals of as much 

as 7 m thick. Units that have shale interbeds and/or significant 

chert content were designated to have moderate potential for 

crushed-stone aggregate, with a moderate level of certainty 

(tract AMAC08, fig. 15).

Low potential units include the Muddy Creek Formation, 

which is a friable sandstone-shale sequence with conglomeratic units. The distribution of Muddy Creek Formation was 

used to designate tract AMAC05 (fig. 15), which has low 

potential for crushed-stone aggregate, with a high level of 

certainty. Some areas of Muddy Creek Formation are covered 

with varying thicknesses of Quaternary alluvial deposits; these 

areas were evaluated for sand and gravel aggregate deposits.

Sand and Gravel.—Extensive sand and gravel units occur 

across Mormon Mesa. These deposits are characterized by carbonate clasts from the Arrow Canyon Range and the Mormon 

Mountains. They constitute good-quality aggregate and are 

assigned a high potential for sand and gravel aggregate deposits, with a high level of certainty (tract AMAC10, fig. 15). 

On the mesa itself, alluvial fan deposits lie atop the Mormon 

Mesa caliche horizon, which in turn is underlain by the Muddy 

Creek Formation. In areas south of the Mormon Mountains, 

the alluvial deposits are thinner and expose the caliche horizon 

and the underlying Muddy Creek Formation.
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D13

Figure 14. Mineral resource potential tracts for limestone deposits in the Mormon Mesa Tortoise Area of Critical 

Environmental Concern (ACEC).

Tract ID Deposit Type Potential Level Certainty Level

MMT01 Limestone High Moderate

High mineral

resource potential

Mineral Potential

114°52'30"W 114°45'0"W

36°45'0"N

GoldButeACE

Scale1:24,0

0 0.8 1.6 2.4 3.2 4 0.4

Kilometers

MORMON MESA

TORTOISE ACEC

COYOTE

SPRINGS

TORTOISE

ACEC

ARROW CANYON ACEC

MMT01

Limestone

MMT01

Limestone
D14 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 15. Mineral resource potential tracts for aggregate resources in the Mormon Mesa Tortoise (B, C, D), Arrow Canyon (B), 

and Coyote Springs Tortoise (A, B) Areas of Critical Environmental Concern (ACEC).

AMAC09

AMAC11

AMAC07

AMAC07

AMAC02

AMAC07

AMAC02

AMAC07

AMAC07

AMAC02

crushed stone,

high

crushed stone,

moderate

sand and gravel,

high

sand and gravel,

low

Aggregate

Potential

Tract ID Commodity Type Potential Level Certainty Level

AMAC02 Crushed Stone High

AMAC09 Sand and Gravel High

AMAC07 Crushed Stone Moderate

Aggregate assessment

tracts

AMAC11 Sand and Gravel Low

COYOTE SPRINGS

TORTOISE ACEC

High

High

Moderate

High

115°0'0"W 114°45'0"W

36°30'0"N

0 1 2 3 4 5 Kilometers

A
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D15

Figure 15. —Continued.

AMAC09

AMAC14

AMAC14

AMAC03

AMAC08

AMAC02

AMAC08

AMAC10

AMAC03

AMAC04

AMAC03 AMAC08

AMAC08

AMAC14

AMAC08

AMAC02

AMAC07

AMAC10

AMAC04

AMAC03

AMAC05

MORMON MESA TORTOISE ACEC

COYOTE SPRINGS

TORTOISE ACEC

ARROW CANYON ACEC

Tract ID Commodity Type Potential Level Certainty Level

AMAC02 Crushed Stone High High

AMAC09 Sand and Gravel

AMAC07 Moderate Moderate

Aggregate assessment

tracts

AMAC11 Sand and Gravel Low

High

AMAC03 Crushed Stone High High

AMAC04 Crushed Stone Low High

AMAC05 Crushed Stone Low High

AMAC14

High

AMAC08

AMAC10

Crushed Stone

Crushed Stone Moderate Moderate

Sand and Gravel High High

High

Sand and Gravel Moderate Moderate

Aggregate

Potential

crushed stone,

high

crushed stone,

moderate

sand and gravel,

high

sand and gravel,

low

crushed stone,

low

sand and gravel,

moderate

0 1 2 3 4 5 Kilometers

115°0'0"W 114°45'0"W

36°45'0"N

B
D16 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 15.—Continued.

AMAC10

AMAC05

AMAC08

AMAC08

AMAC03

AMAC03

AMAC08

AMAC05

AMAC05

AMAC08

AMAC05

AMAC03

AMAC05

MORMON MESA TORTOISE ACEC

Tract ID Commodity Type Potential Level Certainty Level

Aggregate assessment

tracts

AMAC03 Crushed Stone High High

AMAC05 Crushed Stone Low High

AMAC08

AMAC10

Crushed Stone Moderate Moderate

Sand and Gravel High High

Aggregate

Potential

crushed stone,

high

crushed stone,

moderate

sand and gravel,

high

crushed stone,

low

114°30'0"W

36°45'0"N

0 1 2 3 4 5 Kilometers

C
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D17

Figure 15.—Continued.

AMAC05

AMAC05

AMAC05

AMAC05

AMAC05

AMAC05

AMAC08

AMAC08

AMAC10

MORMON MESA TORTOISE ACEC

Aggregate assessment

tracts

AMAC05 Crushed Stone Low High

AMAC08

AMAC10

Crushed Stone Moderate Moderate

Sand and Gravel High High

Tract ID Commodity Type Potential Level Certainty Level

Aggregate

Potential

crushed stone,

moderate

sand and gravel,

high

crushed stone,

low

114°15'0"W

36°45'0"N

0 1 2 3 4 5 Kilometers

D
D18 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Farther west, a thin veneer of alluvial deposits overlies 

the Muddy Creek Formation, making separating the two difficult. Together, the Muddy Creek Formation and these alluvial 

deposits were used to delineate a tract (tract AMAC14, fig. 

15) that has moderate potential for sand and gravel aggregate 

deposits, with a moderate level of certainty. Three small areas 

(tract AMAC12, fig. 15) have low sand and gravel potential, 

with a low certainty level.

Locatable Minerals in Arrow Canyon ACEC

Clay.—There are clay occurrences near the Arrow Canyon 

ACEC, but the clay is of poor quality and unlikely to be present 

inside the ACEC. The potential for clay deposits is low.

Stone and Silica.—At least two deposits have produced 

stone and (or) silica near this ACEC. However, there are no 

outcrops of the Eureka Quartzite inside the ACEC, and there is 

no potential for the occurrence of sand and (or) silica deposits.

The Arrow Canyon ACEC contains no known deposits of 

other locatable minerals.

Leasable Minerals in Arrow Canyon ACEC

The entire Arrow Canyon ACEC is within the region considered by the BLM to be moderately favorable for oil and gas 

(Smith and Gere, 1983). There is no indication of potential for 

brine or evaporite deposits of sodium or potassium. The Arrow 

Canyon ACEC contains no known deposits of other leasable 

minerals, and the potential for their occurrence is low.

Salable Minerals in Arrow Canyon ACEC

Crushed Stone.—High quality stone in Paleozoic carbonate rocks was used to define tract AMAC01 (fig. 15) in the 

eastern part of the Arrow Canyon ACEC. This tract has high 

potential for crushed-stone aggregate with a high certainty 

level. The western part of the ACEC is characterized by the 

lower quality stone in tract AMAC06 (fig. 15), which has 

moderate potential for crushed-stone aggregate deposits, with 

a moderate level of certainty.

Sand and Gravel.—Alluvial deposits and the Muddy 

Creek Formation constitute tract AMAC13, in the southwest 

and easternmost parts of this ACEC, which has moderate 

potential for sand and gravel aggregate deposits, with a moderate certainty level (fig. 15). The area of Pahranagat Wash that 

is upstream from Arrow Canyon gorge is alluvial gravels and 

has high potential for sand and gravel aggregate deposits, with 

a high certainty level (tract AMAC10, fig. 15).

Locatable Minerals in Coyote Springs Tortoise 

ACEC

Precious and Base Metals.—Although there are hydrothermal precious- and base-metal deposits in nearby areas, the 

geologic environments that host these deposits do not occur 

inside this ACEC, and the potential for their presence is low.

Silica and Stone.—At least two mines produced silicarich quartzite in and near this ACEC. Both metallurgical-grade 

silica and stone were probably produced. Small tracts that 

include outcrop areas of the Eureka Quartzite have been designated to have moderate potential for silica deposits with a high 

level of certainty. The potential for commercial silica deposits 

is not high in these tracts because the Eureka Quartzite dips 

shallowly west under large thicknesses of carbonate rock; 

therefore, development of these deposits appears unlikely. The 

potential for production of building stone from such deposits 

is considered to be low because the stone is neither unique 

nor particularly attractive. These areas (tract CST01, fig. 16) 

are all near the eastern boundary of the ACEC and near the 

western base of the Arrow Canyon Range. Part of one of the 

areas is in the Arrow Canyon Wilderness and thus closed to 

mineral entry.

Limestone.—Three small areas of Devonian limestone in 

the Coyote Springs Tortoise ACEC have been designated as 

high potential, with moderate certainty, for commercial highcalcium limestone. This designation is supported by a sample 

of high-calcium limestone in one of these areas, although 

our sample of this rock has unacceptably high SiO2

 (table 2). 

Further sampling and analysis would be required to raise the 

certainty level. These areas (tract CST02, fig. 16) are along the 

eastern boundary of the ACEC in the Arrow Canyon Range 

and along the western boundary in the Las Vegas Range. 

Leasable Minerals in Coyote Springs Tortoise 

ACEC

The entire Coyote Springs Tortoise ACEC is within the 

region considered by the BLM to be moderately favorable for 

oil and gas (Smith and Gere, 1983). There is no indication of 

potential for brine or evaporite deposits of sodium or potassium. The Coyote Springs Tortoise ACEC contains no known 

deposits of other leasable minerals, and the potential for their 

occurrence is low.

Salable Minerals in Coyote Springs Tortoise 

ACEC

Crushed Stone.—The areas with the highest potential for 

crushed-stone aggregate in the Coyote Springs Tortoise ACEC 

are in the northern half of the ACEC, at the base of the Arrow 

Canyon Range. Here, the rocks include the Nopah Formation, Ordovician dolomites and quartzites, and the Silurian 

Laketown Dolomite. Monte Cristo Limestone is found in the 

southern part of the ACEC in the Las Vegas Range. These rock 

units were used to delineate tract AMAC02 (fig. 15), which 

has high potential for crushed-stone aggregate, with a high 

certainty level.

The presence of significant amounts of chert in some 

parts of the Bird Springs Formation leads to designation of 
Mormon Mesa Tortoise, Arrow Canyon, and Coyote Springs Tortoise ACECs D19

Figure 16. Mineral resource potential tracts for silica and limestone deposits in the Coyote Springs Tortoise Area of Critical 

Environmental Concern (ACEC).

CST02

CST01

CST02

CST01

CST01

MORMON MESA

TORTOISE ACEC

COYOTE SPRINGS

TORTOISE ACEC

Tract ID Deposit Type Potential Level Certainty Level

CST01 Silica Moderate Low

CST02 Limestone High Moderate

High mineral

resource potential

Mineral Potential

Moderate mineral

resource potential

114°52'30"W

36°37'30"N

GoldButeACE

Scale1:24,0

012345 0.5

Kilometers
D20 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

the areas underlain by this rock unit to have only moderate 

potential for crushed-stone aggregate, with a moderate level of 

certainty. This tract (AMAC07, fig. 15) is mostly in the southern part of the ACEC.

In the far northeastern part of the ACEC, just west of the 

Arrow Canyon Range, some areas of Muddy Creek Formation 

that are moderately well lithified constitute tract AMAC04 

(fig. 15), which has low potential for crushed-stone aggregate, 

with a high level of certainty.

Sand and Gravel.—Most of Coyote Springs Valley is 

underlain by alluvial deposits containing primarily clasts 

of carbonate rocks from the Las Vegas and Arrow Canyon 

Ranges. These areas constitute tract AMAC09 (fig. 15), which 

has high potential for sand and gravel aggregate deposits, with 

a high level of certainty.

In the southern part of this ACEC, playa deposits extend 

some 11 km along the axis of the valley. The playa deposits are fine-grained silt and clay, and they constitute tract 

AMAC11 (fig. 15), which has low potential for sand and 

gravel aggregate deposits, with a high level of certainty.

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Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter E. Mineral Resource Potential of the Arden, Bird 

Spring, and Sloan Rock Art Areas of Critical Environmental 

Concern, Clark County, Nevada

By Stephen B. Castor, Brett T. McLaurin, Kathryn S. Flynn, and Steve Ludington

Summary and Conclusions

The Arden Area of Critical Environmental Concern 

(ACEC) contains known deposits of silica that were mined in 

the past. These deposits help define an area in the ACEC that 

has high potential for the occurrence of silica deposits. The 

Arden ACEC contains a gypsum deposit that was mined in the 

past, but the potential for the occurrence of undiscovered gypsum deposits in this area is low. Two small uranium prospects 

are near the Arden ACEC, but these imply only low potential 

for the occurrence of uranium deposits. There is no potential 

for the occurrence of other deposits of locatable or leasable 

minerals.

The Arden ACEC contains areas with both low and moderate potential for the occurrence of crushed-stone aggregate 

deposits. The ACEC also contains tracts with high potential 

for the occurrence of sand and gravel aggregate deposits.

The Bird Spring ACEC contains no known mineral 

deposits. There is no potential for the occurrence of other 

deposits of locatable or leasable minerals. The ACEC has 

areas of both moderate and low potential for the occurrence of 

crushed-stone aggregate deposits, and a tract with high potential for the occurrence of sand and gravel aggregate deposits.

The Sloan Rock Art ACEC contains no known mineral 

deposits. There is no potential for the occurrence of other 

deposits of locatable or leasable minerals. The ACEC has 

moderate potential for the occurrence of crushed-stone aggregate deposits; sand and gravel aggregate does not occur.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

on these lands.

The Arden, Bird Spring, and Sloan Rock Art Areas of 

Critical Environmental Concern (ACECs) were studied in the 

field to confirm descriptions of the geology that were gleaned 

from the scientific literature. Samples were collected and 

analyzed, and representatives of the companies with mining 

operations in and near the areas were contacted.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The Arden ACEC, Bird Spring ACEC, and the Sloan 

Rock Art ACEC are described together in this report because 

they are in close proximity. The areas are south of Las Vegas 

near Interstate 15 (fig. 1). Arden and Bird Spring can be 

accessed by various primitive roads that extend west from the 

Sloan exit on Interstate 15 or south from the Blue Diamond 

Road (Nevada Highway 160), although some access roads 

from the Blue Diamond Road are partially blocked by new 

housing developments. Sloan Rock Art ACEC is within both 

the Sloan Canyon National Conservation Area and the North 

McCullough Wilderness. It is accessed from a primitive road 

that extends east from Las Vegas Boulevard near the Sloan 

exit off I-15. A legal description of these lands is included in 

appendix 2.

Physiographic Description

The Arden ACEC consists primarily of hills that reach 

elevations of more than 1,300 m; Longwell and others (1965) 

referred to them as “hills near Sloan.” They are drained by 

alluvial fans that range between 800 and 900 m in elevation 

along north- to northeast-draining valleys. The Bird Spring 

ACEC ranges in elevation from 1,250 to 1,450 m on the 
Figure 1. Generalized geology of the Arden, Bird Spring, and Sloan Rock Art Areas of Critical Environmental Concern (ACECs; outlined in pink). See e

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S

BIRD SPRING

ACEC

ARDEN

ACEC

Chemstar

Pit

Bard deposit

(gypsum) Arden quarries

(silica)

Nevada Royale

Quarry

Uranium

prospect

Little Snake and

Purple Valentine

prospect (U)

Uranium prospect

Uranium

prospects

Uranium

prospects

Sloan limestone

quarry

Uranium

prospects

Gary Allen

Quarry

AP-007

AP-006

AP-001

115°22'30"W 115°15'0"W 

35°52'30"N

36°0'0"N

Gold Bu tte ACE C

01234 0.5

Kilometers
Arden, Bird Spring, and Sloan Rock Art ACECs E3

Figure 1.—Continued.

northeast slope of the Bird Spring Range. The Sloan Rock 

Art ACEC is an area of small hills with a valley that drains 

north on the east side of the ACEC. The area ranges in elevation from 900 to 1,150 m, and is on the west flank of the 

McCullough Range.

Geologic Setting

The area is part of the Basin and Range Physiographic 

Province, characterized by north trending mountain ranges and 

intervening valleys. The Arden and Bird Spring ACECs are in 

the southern part of the Spring Mountain structural block, an 

area mainly characterized by west- to north-dipping Paleozoic and Mesozoic sedimentary rocks that are cut by major 

Mesozoic thrust faults and Cenozoic normal faults (Burchfiel 

and others, 1974). The Sloan Canyon ACEC is in the northern 

part of the McCullough Range structural block, an area that is 

mainly underlain by west-dipping Miocene volcanic rocks.

Geology

Bedrock in the Arden ACEC consists of, from oldest to 

youngest: cherty carbonate rocks of the Pennsylvanian-Permian Bird Spring Formation; Permian redbeds; and Permian 

cherty carbonate strata of the Kaibab and Toroweap Formations. The Permian redbeds were originally correlated with the 

Supai Formation (Hewett, 1931) but later correlated with the 

Hermit Shale and placed in the Hermit Formation (Longwell 

and others, 1965). Strata in these units mostly dip gently westward; however, Longwell and others (1965) mapped northeast-trending folds south of the ACEC, and they described the 

overall structure in the hills near Sloan as an elongate dome. 

They noted that all the Paleozoic strata in the area have dips of 

less than 10°. Northwest-striking Cenozoic normal faults cut 

the bedrock.

The Bird Spring ACEC is notable for exposures of the 

Bird Spring thrust fault, which dips about 25° west. It separates the Pennsylvanian-Permian Bird Spring Formation in the 

upper plate from Mesozoic rocks (mostly Chinle and Moenkopi Formations) in the lower plate.

Rocks of the Sloan Rock Art ACEC consist of Miocene 

basalt and andesite flows. Some details of the volcanic geology of the area were studied by Bridwell (1991).

Mining History

At least seven inactive silica and gypsum open-pit mines 

are in and near the Arden ACEC, mostly in the Arden Quarries area (fig. 1). In addition, there are some inactive underground mines and several prospects. Within 10 km of the area, 

gypsum, dolomite, limestone, silica, stone, and construction 

aggregate have all been mined.

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fault, approximate

fault, concealed

thrust fault

EXPLANATION

mine or prospect

sample site, with sample number AP-001

JTRs

Undivided surficial deposits (Pleistocene and 

Holocene)—Alluvium, colluvium, lake, playa, 

landslide, terrace, and eolian sand deposits

Young volcanic rocks (middle and upper Miocene)-

Rhyolite, andesite, and basalt lava flows, tuff, and 

tuffaceous sediments

Sedimentary rocks (Triassic and Jurassic)—Shale, 

mudstone, siltstone, sandstone, and carbonate 

rock; some sparse volcanic rock. Includes Lower 

Jurassic Glen Canyon Group (Navajo Sandstone, 

Kayenta and Moenave Formations, Wingate Sandstone, Aztec Sandstone) and Chinle and Moenkopi 

Formations

Carbonate rocks (Mississippian to Permian)-

Limestone, dolomite, and some shale. May include 

Kaibab, Callville, Ely, Tippipah, Temple Butte, 

Rogers Spring, Monte Cristo, and Redwall Limestones, Toroweap Formation, Coconino Sandstone, 

and Bird Spring Formation

Sedimentary rocks (uppermost Devonian to 

Permian)—Siltstone, sandstone, shale, and conglomerate; some limestone, dolomite, chert, marble, 

and gypsum. May include Queantoweap Sandstone, 

Hermit Shale, Coconino Sandstone, Supai Group, 

Pakoon Formation, Pilot and Chainman Shales, 

Eleana and Diamond Peak Formations, and Joana, 

Narrow Canyon, and Mercury Limestones

Dolomite and Limestone (Cambrian to Devonian)-

Dolomite, limestone, and minor amounts of 

sandstone, shale, and siltstone. May include Sevy, 

Simonson, Laketown, Lone Mountain, Ely Springs 

Dolomites, Devils Gate and Muav Limestone, and 

Guilmette, Nevada, Carrara, Bonanza King, and 

Nopah Formations, Dunderberg and Pioche Shales, 

Pogonip Group, and Eureka Quartzite
E4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

The mining of limestone in the Sloan area, about 5 km 

southeast of the Arden ACEC, began in 1910 (Longwell and 

others, 1965), and dolomite mining was initiated in the same 

area in 1928 and continued until 1997. Both limestone and 

dolomite were used to produce lime at a plant in Henderson. 

Carbonate rock mining at Sloan has resumed, but the rock is 

now used in construction aggregate.

Gypsum mining in the Arden area, about 3 km north of 

the Arden ACEC, began in 1909 and continued until 1931. 

Mining in the Bard area within the Arden ACEC (fig. 1) took 

place at about the same time (Papke, 1987). In 1925, mining began at the Blue Diamond gypsum deposit, about 10 km 

northwest of the Arden ACEC. This operation, which was 

scheduled to cease in 2005 to make way for housing development, has likely produced more gypsum than any other deposit 

in Nevada.

Silica mining began in 1930 at a locality about 5 km 

north of the Arden ACEC (described by Murphy [1954] as the 

Arden operation). Foundry sand and glass sand were reportedly produced there. Steel-molding sand was shipped in 1934 

from the Bard operation, which mined silica from sites in 

the Arden ACEC and nearby areas. Building stone may also 

have been produced from these sites. Silica was also reportedly shipped as glass sand from a deposit near Jean, about 12 

km south of the Arden ACEC, although this production may 

actually have come from the Nevada Royale and Gary Allen 

Quarries, which are further north, closer to the Arden and Bird 

Spring ACECs.

There are no known mines or prospects in the Bird Spring 

ACEC. Significant amounts of base and precious metals 

were mined in the Goodsprings district, about 20 km to the 

southwest. Stone and aggregate are presently mined at the Las 

Vegas Rock Quarry 7 km to the west. Minor amounts of silica 

and stone were mined in the past, about 5 km to the east at the 

Nevada Royale and Gary Allen Quarries.

The Sloan Rock Art ACEC has no history of mining. 

Sand and gravel have been mined from alluvial fans about 

8 km to the north. Limestone, dolomite, and crushed stone 

have been mined at Sloan, about 10 km to the northwest of 

the ACEC. An abandoned mineshaft is about 2 km to the 

southwest, but no mineral deposit has been described from 

the area.

Mineral Deposits

Arden Quarries

Silica-rich sandstone is exposed in several quarries and 

underground excavations (figs. 2 and 3), now closed, along 

the west edge of the Arden ACEC. These deposits occur in a 

relatively resistant unit of white to light-pink, cross-bedded 

quartz arenite about 50 m thick that is likely correlative with 

the Coconino sandstone (fig. 4). The northernmost quarry, in 

the Arden ACEC, is a narrow pit, about 300 m long and 15 m 

wide. Chip samples from exposures just south of this quarry 

that represent about 40 m of section contain 93.19 percent to 

94.39 percent SiO2 (Ludington and others, 2005). X-ray diffraction (XRD) analysis and petrographic examination show 

that the major impurities are K-feldspar, calcite, and dolomite. 

To the south is a 250-m-long and 10-m-wide open cut that 

has a series of portals to room-and-pillar workings cut into its 

west wall. A sample of representative rock from the open cut 

contains 95.6 percent SiO2

 (Ludington and others, 2005).

The chemical analyses of the sandstone samples from the 

Arden Quarries suggest that the material will not meet specifications for glass sand (table 1; Ludington and others, 2005). In 

comparison with analyses of the Baseline Sandstone from the 

Simplot Silica operation at Overton, Nevada, which is used as 

glass sand, sandstone from the Arden Quarries area contains 

too little silica and too many impurities for glass sand, which 

requires at least 98.5 percent silica (table 1). It is possible that 

the quality can be upgraded by simple processing; however, 

examination of a thin section of the best material that we collected from the Arden Quarries showed that carbonate occurs 

as small rhombs intergrown with quartz at grain boundaries 

(fig. 5), and it is unlikely that glass sand can be produced from 

it by inexpensive processing.

Bard Gypsum Deposit

The Bard gypsum deposit is in the Arden ACEC (fig. 1),

where it is exposed in an abandoned open pit that is 75 m x 

15 m. The gypsum has a maximum exposed thickness of 5 m 

in a bed that is nearly horizontal. The gypsum is of only fair 

quality because of interbeds of clayey and silty material. X-ray 

diffraction of a sample showed small amounts of quartz, montmorillonite, and illite (Papke, 1987). The gypsum is overlain 

by about 5 m of reddish-brown sandstone and about 15 m of 

gray limestone. This sequence is capped by cherty limestone 

of the Kaibab Formation.

Figure 2. Narrow open cut at the North Arden Silica Quarry.
Arden, Bird Spring, and Sloan Rock Art ACECs E5

Table 1. Composition of sandstones from Arden Quarries. 

[Simplot Silica Plant data are from Murphy (1954); container glass specifications are from Zdunczyk and Linkous (1994).]

Element AP-001M AP-001T AP-006C Simplot 

Silica mine

Simplot 

Silica Plant

Container glass 

specification

SiO2 94.39 93.19 95.56 97.25 98.93 98.5 min

Al2

O3 1.51 1.65 0.77 1.38 0.65 0.5 max

Fe2

O3 0.31 0.37 0.4 0.19 0.03 0.035 max

MgO + CaO 1.62 2.03 1.22 0.27 0.05 0.2 max

TiO2 0.05 0.08 0.02 0.08 0.03 0.03 max

Cr2

O3 0.027 0.024 0.031 0.00 nd 0.001 max

Figure 3. Concrete-barricaded portals in Coconino Sandstone at 

the South Arden Quarry site.

Figure 4. Relatively resistant cliffs of Coconino Sandstone (red 

rocks in lower part of face), Arden Quarries area.

Figure 5. Photomicrograph, in planepolarized light, of silica-rich sandstone from 

the South Arden Quarry (sample AP-006) 

showing tiny dolomite rhombs along grain 

borders and within sand grains. Horizontal 

field of view is 1.25 mm.
E6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Uranium Prospects

Two uranium prospects are about 5 km southeast of the 

Arden ACEC. One, called the Little Snake and Purple Valentine prospect (fig. 1), was visited during this study. In a small 

pit there (fig. 6), yellow and greenish-yellow fracture coatings are present in the most radioactive part of an exposed 

shear zone, where maximum radioactivity is about 20 times 

background. A grab sample (sample AP-007, fig. 1) of the 

most radioactive rock contains 384 ppm U along with elevated 

Sr and V (Ludington and other, 2005). The occurrence does 

not correspond with any commercial uranium deposit models, although Johnson (1982) and Johnson and Glynn (1982) 

compared carnotite occurrences in the area with the potentially 

commercial Yeelirie calcrete carnotite deposit in western 

Australia. However, the Yeelirie deposit is a 6-km-long, 3-kmwide, and 8-m-thick deposit in calcrete that was deposited in a 

broad valley, which is unlike the occurrence examined.

although it was reportedly used for that purpose in the past. It 

may be suitable for commodities with less rigorous specifications, such as foundry sand, for which it was used in the past. 

The amount of silica-rich sandstone in the area is large, and we 

estimate that about 20 million short tons of resource could be 

mined by open-cut methods without removal of overlying rock 

in the area of the Arden quarries. The certainty level for this 

determination is moderate because it is unclear whether or not 

the silica product that could be produced from the sandstone is 

of sufficient quality for commercial use.

A small part of the Arden ACEC has low potential, with a 

moderate certainty level, for sedimentary gypsum deposits (tract 

ABS02, fig. 7). The potential area surrounds the Bard gypsum 

mine, where the exposed gypsum is thin and of relatively poor 

quality. The potential area extends beneath Quaternary alluvium 

in this area, where removal of overburden would be necessary. 

Potential for economically viable gypsum deposits is low here 

because mining of thin, low-grade gypsum deposits under cover 

is too expensive. The gypsum undoubtedly extends under the 

Kaibab Formation to the west; however, successful commercial 

extraction of such material is highly unlikely.

In the past, gypsum mining in the Arden area was by 

underground methods, which are not now competitive. Modern gypsum mining in Nevada is by surface mining methods 

in areas with little overburden. At the BPB operation at Blue 

Diamond, high-grade gypsum (>92 percent gypsum) was 

mined until recently from erosional remnants of gypsum 

that cap resistant limestone of the Kaibab Formation. At 

the PABCO and Pioneer Mines, low-grade (70-85 percent 

gypsum) ore is mined from very large deposits (Castor, 

2003; Papke, 1987). The PABCO ore is easily beneficiated 

by washing to a purity of 92-95 percent gypsum, which is 

suitable for wallboard and plaster. At both mines, mining and 

beneficiation costs are low. The Pioneer Mine produces lowcost gypsum for agricultural uses only.

There is no evidence for deposits of other locatable 

minerals.

Leasable Minerals in Arden ACEC

The area is within the region considered by the BLM 

to be moderately favorable for oil and gas (Smith and Gere, 

1983). The Arden Dome, a structure that lies mostly to the 

north and northeast of the area, was the site of oil exploration 

drilling between 1929 and 1944. Six wells were drilled to test 

the structure, one more than 1,100 m deep. Two of six wells 

in the area had hydrocarbon showings (Lintz, 1957). Miller 

(1945) suggested that the dome was formed during nearby 

intrusive activity rather than by compressive tectonism and 

that the chance of finding carbon dioxide exceeded that of 

finding hydrocarbons.

There is no indication of potential for brine or evaporite 

deposits of sodium and potassium. The ACEC contains no 

known deposits of leasable minerals, and the potential for their 

occurrence is low.

Figure 6. Hematitic radioactive shear zone in uranium prospect, 

hammer for scale.

Mineral Exploration and Development

The Arden, Bird Spring, and Sloan Rock Art ACECs contain no active mining claims, and there is no current exploration activity.

Mineral Resource Potential

Locatable Minerals in Arden ACEC

A part of the Arden ACEC is considered to have high 

potential for deposits of silica, with a moderate certainty level 

(tract ABS03, fig. 7). The samples that we took indicate that the 

sand is probably not pure enough for the production of glass, 
Figure 7. Mineral resource potential tracts for gypsum and silica deposits in the Arden, Bird Spring, and Sloan Rock Art Areas of Critical Environmen

outlined in pink).

ABS03

ABS02

Silica

Gypsum

S

ARDEN

ACEC

BIRD SPRING

ACEC

115°22'30"W 115°15'0"W 

35°52'30"N

36°0'0"N

Gold Bu tte ACE C

01234 0.5

K

High mineralresource potentialLow mineralresource potential

Tract ID Deposit Type Potential Level Certainty Level

ABS02 Gypsum Low Moderate

ABS03 Silica High Moderate

Legend
Figure 8. Mineral resource potential tracts for aggregate resources in the Arden, Bird Spring, and Sloan Rock Art Areas of Critical Environmental Co

outlined in pink).

crushed stone,highcrushed stone,lowcrushed stone,moderatesand and gravel,high

Aggregate

Potential

Tract ID Commodity Type Potential Level Certainty Level

AABS01 Crushed Stone High ModerateAABS02 Crushed Stone Low ModerateAABS03 Crushed Stone Low HighAABS04 Crushed Stone Moderate LowAABS05 Crushed Stone Moderate ModerateAABS06 Sand and Gravel High ModerateAABS07 Sand and Gravel High Moderate

Aggregate assessment

tracts

115°22'30"W 115°15'0"W 

35°52'30"N

36°0'0"N

Gold Bu tte ACE C

01234 0.5

K

SL

ARDEN

ACEC

BIRD SPRING

ACEC 

AABS02 AABS04

AABS06

AABS07

AABS03

AABS05
Arden, Bird Spring, and Sloan Rock Art ACECs E9

Salable Minerals in Arden ACEC

Crushed Stone.—West-dipping Coconino Sandstone, 

Toroweap Formation, and Kaibab Limestone characterize the 

western side of this ACEC. The Coconino Sandstone has been 

quarried for stone, but the friable nature of most of the unit 

means it will not make high-quality aggregate. The Coconino 

does have zones that are more strongly lithified, but overall 

the material is not suitable for high-quality aggregate. Areas 

where Coconino Sandstone crops out are assigned a low 

potential for crushed-stone aggregate deposits, with a moderate certainty level (tract AABS02, fig. 8). Cherty zones in the 

Bird Spring and Toroweap formations and the Kaibab Limestone lead to assignment of a moderate potential for crushedstone aggregate deposits, with a low certainty level (tract 

AABS04, fig. 8) in areas where these units are exposed.

Sand and Gravel.—Although friable clasts of Permian 

sandstone occur in alluvial deposits, carbonate clasts derived 

from adjacent highlands means that much of the available 

aggregate material is of high quality. Carbonate clast sources 

include the Bird Spring Formation, the Toroweap Formation, 

and the Kaibab Limestone. Most of the area that is underlain 

by alluvium has high potential for sand and gravel aggregate, 

with a moderate certainty level (tract AABS06, fig. 8).

Locatable Minerals in Bird Spring ACEC

The Bird Spring ACEC contains no known deposits of 

locatable minerals, and there is no potential for their occurrence.

Leasable Minerals in Bird Spring ACEC

There is no indication of potential for brine or evaporite 

deposits of sodium and potassium in the Bird Spring ACEC. 

The area contains no known deposits of leasable minerals, and 

the potential for their occurrence is low.

Salable Minerals in Bird Spring ACEC

Crushed Stone.—This ACEC is along the south end of 

the Bird Spring thrust fault, where Paleozoic carbonate rocks 

overlie siltstone and sandstone of the Triassic Moenkopi 

Formation. Carbonate rocks in the hanging wall that are interbedded with chert define a tract with moderate potential for 

crushed-stone aggregate deposits, with a moderate certainty 

level (tract AABS05, fig. 8). The Moenkopi Formation is a 

slope former, dominated by shale and some sandstone. This 

unit has low potential for crushed-stone aggregate deposits, 

with a high certainty level (tract AABS03, fig. 8).

Sand and Gravel.—Alluvial deposits with mostly carbonate clasts occur on the eastern side of this ACEC, covering the 

lower slopes and filling in the northward-draining wash. This 

area has high potential for sand and gravel aggregate deposits, 

with a moderate certainty level (tract AABS07, fig. 8).

Locatable Minerals in Sloan Rock Art ACEC

The Sloan Rock Art ACEC contains no known deposits of 

locatable minerals, and there is no potential for their occurrence.

Leasable Minerals in Sloan Rock Art ACEC

There is no indication of potential for brine or evaporite deposits of sodium and potassium in the Sloan Rock Art 

ACEC. The area contains no known deposits of leasable minerals, and the potential for their occurrence is low.

Salable Minerals in Sloan Rock Art ACEC

Crushed Stone.—The rocks of this ACEC are faulted and 

fractured basaltic andesites and basalt. They define an area 

of high potential for crushed-stone aggregate deposits, with a 

moderate certainty level (tract AABS01, fig. 8).

Sand and Gravel.—A canyon drains this ACEC, and the 

wash contains clasts of volcanic rocks. However, the alluvial 

deposits are too small to be significant, and the area has no 

potential for sand and gravel aggregate deposits.

References

Bridwell, H.L., 1991, The Sloan Sag—a mid-Miocene volcanotectonic depression, north-central McCullough Mountains, southern Nevada: Las Vegas, University of Nevada, 

Las Vegas, unpub. Master’s thesis, 118 p.

Burchfiel, B.C., Fleck, R.J., Secor, D.T., Vincelette, R.R., 

and Davis, G.A., 1974, Geology of the Spring Mountains, 

Nevada: Geological Society of America Bulletin, v. 85, p. 

1013-1022.

Castor, S.B., 2003, Industrial minerals and rocks in Nevada, 

in Castor, S., Papke, K., and Meeuwig, R., eds., Proceedings of the 39th forum on the geology of industrial minerals: 

Nevada Bureau of Mines and Geology Special Publication 

33, p. 57–67.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Hewett, D.F., 1931, Geology and ore deposits of the Goodsprings Quadrangle, Nevada: U.S. Geological Survey 

Professional Paper 162, 172 p.

Johnson, C.L., 1982, Correlation and origin of carnotite occurrences in the southern Nevada region: Reno, University of 

Nevada, Reno, unpub. Ph.D. dissertation, 184 p.

Johnson, C., and Glynn, J., 1982, National Uranium Resource 

Evaluation, Las Vegas Quadrangle, Nevada, Arizona, and 

California: Bendix Field Engineering Corp. Report PGJ/F121(82), 51 p.
E10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Lintz, J., Jr., 1957, Nevada oil and gas drilling data, 1906-1953: 

Nevada Bureau of Mines and Geology Bulletin 52, 80 p.

Longwell, C.R, Pampeyan, E.H., Bower, B., and Roberts, 

R.J., 1965, Geology and mineral deposits of Clark County, 

Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 

218 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Miller, J.C., 1945, Geologic reconnaissance of the Arden area, 

Clark County: U.S. Geological Survey Open-File Report 

45–107.

Murphy, T.D., 1954, Silica resources of Clark County, 

Nevada: Nevada Bureau of Mines and Geology Bulletin 

55, 33 p.

Papke, K.G., 1987, Gypsum deposits in Nevada: Nevada 

Bureau of Mines and Geology Bulletin 103, 26 p.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for 

oil and gas, Nevada: U.S. Bureau of Land Management, 

prepared by the U.S. Geological Survey, Conservation 

Division, Western Region, scale 1:500,000.

Zdunczyk, M.C., and Linkous, M.A., 1994, Industrial sand 

and sandstone, in Carr, D.D., ed., Industrial minerals and 

rocks, 6th Edition: Littleton, Colo., Society for Mining, 

Metallurgy and Exploration, p. 879–891.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter F. Mineral Resource Potential of the Ash 

Meadows and Amargosa Mesquite Trees Areas of Critical 

Environmental Concern, Nye County, Nevada

By Stephen B. Castor, Brett T. McLaurin, Steve Ludington, and Kathryn S. Flynn

Summary and Conclusions

The Ash Meadows Area of Critical Environmental 

Concern (ACEC) contains known deposits of montmorillonite 

clay and zeolite that have been mined in the past. Two areas 

in the southern part of the ACEC have high potential for the 

occurrence of zeolite deposits on the basis of field evaluation and samples collected during this study. Extensive areas 

in the northern and western parts of this ACEC have high 

potential for the occurrence of montmorillonite clay deposits. 

Important deposits of sepiolite and saponite clay are mined 

by IMV Nevada in a 4-km-wide corridor between the Ash 

Meadows and Amargosa Mesquite Trees ACECs. Three areas 

that include parts of both ACECs have high potential for the 

occurrence of such clay deposits, although IMV Nevada has 

dropped most of the claims within the ACECs.

There is no potential for the occurrence of other deposits 

of locatable or leasable minerals in either ACEC.

The Ash Meadows ACEC has areas with high, moderate, 

and low potential for the occurrence of crushed-stone aggregate deposits. There are areas of both high and low potential 

for the occurrence of sand and gravel aggregate deposits.

The Amargosa Mesquite Trees ACEC has no potential 

for the occurrence of crushed-stone deposits. There are areas 

of both high and low potential for the occurrence of sand and 

gravel aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

on these lands.

The Ash Meadows and Amargosa Mesquite Trees ACECs 

were studied in the field to confirm descriptions of the geology 

that were gleaned from the scientific literature. Samples were 

collected and analyzed, and representatives of the companies 

with mining operations in and near the areas were contacted.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1 and are similar to those outlined 

by Goudarzi (1984).

Lands Involved

The Ash Meadows ACEC and the Amargosa Mesquite 

Trees ACEC were combined in this chapter because they have 

similar geology and mineral resource potential and they are in 

close proximity. The ACECs are in Nye County, southwest of 

Highway 95 and east of Nevada State Highway 373 and the 

community of Amargosa Valley. The Ash Meadows ACEC 

surrounds the Ash Meadows National Wildlife Refuge, and 

its southwest edge lies along the Nevada-California border. A 

mineral report was prepared before the withdrawal of the wildlife refuge from mineral entry (Wallace, 1999). Ash Meadows 

ACEC also surrounds the Devils Hole area, a small satellite 

of Death Valley National Park. The ACECs can be accessed 

by various secondary and primitive roads that extend eastward from Highway 373. A legal description of these lands is 

included in appendix 2.

Physiographic Description

The Ash Meadows ACEC consists mainly of Ash Meadows, a low-lying, spring-fed wetland area that ranges between 

about 640 m and 700 m in elevation. The wetlands lie in the 

Amargosa Desert, a broad intermontane basin that drains 

southward, via the Carson Slough, into the Amargosa River 

and eventually into Death Valley. The Ash Meadows wetland 

area flanks hills that reach elevations of as much as 960 m 

within the ACEC. The Amargosa Mesquite Trees ACEC is 

at elevations of 730 m to 780 m in a transitional bajada-playa 

environment along the east side of Amargosa Flat, an alkali 
Figure 1. Generalized geology of the Amargosa Mesquite Trees and Ash Meadows Areas of Critical Environmental Concern (ACEC), showin

location of analyzed samples. Geology modified from Stewart and Carlson (1978). See explanation on page F3.

F

F

AP-105

AP-106

AP-092

AP-081

AP-031

AP-029

AP-027

AP-027B

AP-027A

Qu

Qu Qu

Qu

lPzc

Qu

lPzc

lPzc

Tsy

Tsy

Tsy

CZs

Tsy

Tsy

Tsy

lPzc

lPzc

Tsy

lPzc

Tsy

lPzc

Tsy

CLAY CAMP

PITS

AMARGOSA MINE

(IMV CLAY PLANT)

IMV SAPONITE PITS

IMV (MORETTI) SEPIOLITE

PITS

ZEOLITE PROSPECT

ASH MEADOWS

ZEOLITE MILL

CLAY PIT NO. 4

CLAY PIT NO. 2

EWING MINE

KINNEY

CLAY PITS

AMARGOSA

MESQUITE

ASH ACEC

MEADOWS

ACEC

116°22'30"W 116°15'0"W 

36°22'30"N

36°30'0"N

GoldButeACE

Scale1:24,000

02468 1

Kilometers
Ash Meadows and Amargosa Mesquite Trees ACECs F3

playa. The Amargosa Flat playa drains westward into the north 

part of the Ash Meadows wetlands.

Geologic Setting

The Ash Meadows and Amargosa Mesquite Trees ACECs 

are in the Amargosa Desert, a northwest-trending structural 

basin in the Basin and Range Physiographic Province. The 

Amargosa Desert occupies an area between the north-trending 

basin and range structures to the northeast, and northwesttrending structures of the Walker Lane belt to the southwest. 

The Walker Lane belt is a zone of diverse topography and 

strike-slip faulting caused mostly by late Tertiary to modern 

extension (Stewart, 1992). Miocene to modern extensional 

tectonism created northwest-trending ranges and valleys in the 

Death Valley region to the southwest.

Geology

Lower Paleozoic (Cambrian) rocks underlie the hills in 

and near the Ash Meadows and Amargosa Mesquite ACECs 

(fig. 1). The oldest rocks are in the Bonanza King Formation, 

which is mostly dolomite with some limestone. Parts of the 

unit contain silty to sandy layers (Cornwall, 1972). Shale and 

carbonate rocks of the Nopah Formation overlie the Bonanza 

King Formation at the north end of the hills.

Rhyolitic tuffs and sedimentary rocks of Miocene and 

Pliocene age crop out in the southern part of the Ash Meadows 

ACEC. These rocks may be part of 16- to 10-Ma volcanic 

deposits of the southwestern Nevada volcanic field (Sawyer 

and others, 1994), and may also include younger rocks. They 

are widely zeolitized, and the zeolitized tuffs are overlain 

by siltstones, limestones, and tuffs, similar to the 7- to 5-Ma 

Furnace Creek Formation (Fleck, 1970).

Most of the Ash Meadows ACEC is underlain by Pliocene lacustrine and spring silt, clay, and carbonate deposits, 

which are covered by thin Quaternary deposits. Tuffs in the 

Pliocene strata have K-Ar and fission track ages of 3.2 to 2.1 

Ma (Hay and others, 1986).

In the Amargosa Mesquite Trees ACEC, Quaternary 

deposits are the only geologic units exposed, but drilling there 

by IMV Nevada has shown that Pliocene clay and carbonate 

deposits are present at shallow depth.

Mining History

The mining history in the area of the Ash Meadows and 

Amargosa Mesquite Trees ACECs primarily involves clay 

mining in the Ash Meadows mining district. A large part of 

Nevada’s industrial clay has come from this district, and we 

estimate total clay production from the district at more than 1 

Qu

lPzc

uPzc

Contact, certain

EXPLANATION

Fault, certain

Fault, approximate

Fault, concealed

Thrust fault

Mine or prospect

Mineral processing plant

AP-001 Sample site, with sample number

CZs

Tsy

Undivided surficial deposits 

(Pleistocene and Holocene)—Alluvium,

colluvium, lake, playa, landslide, 

terrace, and eolian sand deposits

Young sedimentary rocks (middle 

Miocene to Pliocene )—Alluvial,

lacustrine,and fluvial deposits. Locally 

includes minor amounts of tuff. Includes 

Panaca, Bouse, and Muddy Creek 

Formations

Carbonate rocks (Mississippian to 

Permian)—Limestone, dolomite, and 

some shale. May include Kaibab, Callville, 

Ely, Tippipah, Temple Butte, Rogers 

Spring, Monte Cristo, and Redwall 

Limestones, Toroweap Formation, 

Coconino Sandstone, and Bird Spring 

Formation

Dolomite and Limestone (Cambrian to 

Devonian)—Dolomite, limestone, and 

minor amounts of sandstone, shale, and 

siltstone. May include Sevy, Simonson, 

Laketown, Lone Mountain, Ely Springs 

Dolomites, Devils Gate and Muav 

Limestone, and Guilmette, Nevada, 

Carrara, Bonanza King, and Nopah 

Formations, Dunderberg and Pioche 

Shales, Pogonip Group, and Eureka 

Quartzite

Sedimentary rocks (Neoproterozoic and 

Cambrian)—Quartzite, siltstone, and 

phyllite, with lesser amounts of conglomerate, limestone, and dolomite. May 

include Stirling , Zabriskie, and Prospect 

Mountain Quartzites, Wood Canyon, Deep 

Spring, Campito, Poleta, Harkless, Saline 

Valley, Wyman, and Johnnie Formations, 

and Reed Dolomite

Figure 1.—Continued.
F4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

million short tons. Clay was discovered in the district in 1917, 

and mining began in 1918 (Kral, 1951). Early clay production 

in the district was mainly of fuller’s earth used to decolorize and filter oils, but it also included some bentonite used in 

drilling mud (Papke, 1970). Most of the mining was in the 

Clay Camp area just west of the Ash Meadows ACEC (fig. 1), 

where the clay was mined by dragline excavation. It was dried, 

crushed, sized, and sacked at Clay Camp and shipped by rail. 

Recorded production through 1949 was about 180,000 short 

tons; however, this total is probably low because more than 

34,000 short tons were produced in 1929 alone (Kral, 1951). 

U.S. Bureau of Mines (USBM) records indicate that clay 

production ceased in 1954, which probably marked the end of 

clay mining in the Clay Camp area.

In the 1970s, Industrial Minerals Ventures (IMV) began 

clay mining again in the Ash Meadows district. Clay produced 

by this operation in the 1970s and 1980s was listed as fuller’s 

earth and bentonite by the USBM. Dragline trenching of 

sepiolite at the Moretti deposit (fig. 1) in the Amargosa Flat 

area was noted by Papke (1972), and both bentonite and sepiolite were being mined by 1980 (Papke, 1981). Saponite clay 

production began in the 1990s from deposits a few kilometers 

north of the sepiolite operation. In the 1990s, Rio Tinto PLC 

acquired IMV, and in 1997, the current owner, Mud Camp 

Mining Co. LLC, acquired IMV from Rio Tinto. In 2002, 

about 30,000 short tons of sepiolite, saponite, and bentonite 

were produced by IMV at a processing plant in Amargosa 

Valley (Castor, 2003). Production in 2003 and 2004 was about 

33,200 and 32,600 short tons, respectively (Driesner and 

Coyner, 2004, 2005). The company exports a variety of clay 

products worldwide and is the only producer of sepiolite and 

saponite in the United States.

In addition to clay mining, small amounts of zeolite 

have been produced from the Ash Meadows ACEC. A Union 

Carbide geologist discovered zeolite in 1960, and in 1973 a 

similar deposit was discovered a few kilometers to the south in 

California. Anaconda Minerals Co. acquired both deposits in the 

1970s, and they were subsequently leased to Zeolite International Inc., who began mining in the 1980s. A processing plant 

(fig. 1) on private land that is surrounded by the Ash Meadows ACEC has been shipping zeolite, mostly mined from the 

California deposit, since the 1980s. The current operator, Ash 

Meadows Zeolite LLC, a subsidiary of Badger Mining Corp., 

ships 1,000 to 2,000 short tons annually of zeolite used in water 

filtration, odor control, and nuclear clean-up (Castor, 2003).

Mineral Deposits

Clay Deposits

Clay deposits occur in and around the Ash Meadows 

ACEC and adjacent to the Amargosa Mesquite Trees ACEC. 

These deposits may be subdivided into montmorillonite, 

saponite, and sepiolite deposits on the basis of the main clay 

mineral commodity; however, more than one type of clay may 

be found in some of the deposits. Montmorillonite is sodium 

and (or) calcium smectite. Sodium-rich montmorillonite is 

typically a high-swelling clay that is used in drilling mud, 

scoopable cat litter, and in other applications that require high 

swelling capacities. Calcium-rich montmorillonite is generally used where swelling capacities are less important, as in 

foundry bonding clay. Saponite is magnesium-rich smectite. It 

is related to the more common montmorillonite, but is chemically and structurally distinct. Sepiolite is a rare fibrous clay 

that is used in salt-water and geothermal drilling muds, cat 

litter, and absorbent products. It is commonly included with 

palygorskite (attapulgite) in the hormite group of clay minerals (Heivilin and Murray, 1994). About 80 percent of the clay 

mined by IMV Nevada is sepiolite.

Clay Camp Deposits

Ash Meadows mining operations that produced clay 

between 1918 and 1954 mainly exploited deposits directly west 

of the Ash Meadows ACEC and north of the Clay Camp ruins 

(fig. 1). According to Kral (1951), these deposits were as much 

as 100 feet (30 m) in diameter, and were mined to a depth of 

24 feet (7 m); a high water table in this area precluded deeper 

extraction. Exposures in a number of places indicate that about 

2 m of carbonate-rich overburden overlies the useable clay. 

Excellent quality white montmorillonite is reportedly still present in one pit as a lens-shaped body 30 feet (9 m) long and 1.5 

feet (45 cm) thick that is underlain by an unknown thickness of 

fair-quality clay (Papke, 1970). Kral (1951) described the clay 

mineral from these deposits as montmorillonite and reported 

that the clay was used for both fuller’s earth and in drilling 

mud. However, on the basis of analyses by Papke (1970), clay 

sampled from this area swelled only slightly and the dominant 

clay mineral is saponite. Small pits and prospects extend east 

from the Clay Camp area into the Ash Meadows ACEC. A 

sample (AP-027) from a 2-m-thick clay bed in a small pit (fig. 

2) inside the ACEC and about 150 m from its western border 

contains saponite clay with feldspar, dolomite, and quartz as 

impurities on the basis of X-ray diffraction (XRD) analysis. 

Chemical analysis of this sample (Ludington and others, 2005) 

yields MgO/CaO of 3.7, indicating that this is a magnesiumrich clay because this ratio exceeds the MgO/CaO for dolomite.

A sample of pale-brown nonswelling clay from a small pit 1.5 

km within the Ash Meadows ACEC on a private inholding 

was found to contain saponite clay with quartz, feldspar, and 

illite impurities. This sample (AP-092) has extreme MgO/CaO 

(Ludington and others, 2005) and no dolomite, indicating that it 

contains relatively large amounts of saponite.

Saponite Pits

Smectite clay is currently mined by IMV Nevada from 

pits that lie just northeast of the Ash Meadows ACEC and just 

west of the Amargosa Mesquite Trees ACEC (fig. 1). The pits 

are shallow (fig. 3) and exploit clay-rich beds that range from 
Ash Meadows and Amargosa Mesquite Trees ACECs F5

a few centimeters to 6 m thick, occur over a wide area, and 

appear to be nearly continuous (Wahl and Papke, 2004). The 

average thickness is about 5 feet (1.5 m), and the average overburden thickness is about 7 feet (2 m). According to Wahl and 

Papke, the dominant clay mineral here is saponite. Khoury and 

others (1982) and Hay and others (1986) reported mixtures 

of stevensite (a magnesian clay mineral) and kerolite (a talc 

variety) from this area. However, their samples were not taken 

from the pits from which clay is currently mined and marketed 

as saponite. XRD analysis of samples that we collected from 

an active clay pit in this area shows significant amounts of 

dolomite and a little halite as impurities in the clay. Although 

nonglycolated XRD analysis of our samples indicates the 

presence of sepiolite and possible saponite, glycolated patterns 

give a strong response for an expansive smectite clay such as 

saponite (glycolation causes distinctive expansion of the mineral lattice in some clay minerals that is measurable by XRD; 

in sepiolite there is no lattice change, but glycolation of a 

smectite clay such as saponite causes a distinctive peak shift). 

Chemical analyses (samples AP-106 and AP-106HG; Ludington and others, 2005) show MgO/CaO of 1.1 to 1.7, indicating 

that the clay is magnesium-rich. It is beyond the scope of this 

study to make a definitive mineralogic determination, but the 

clay has been marketed as saponite for many years and most 

of our data support the saponite identification.

Sepiolite Pits

The only source of commercial sepiolite in the United 

States is on Amargosa Flat in a 2.5-mile-wide corridor 

between the Ash Meadows and Amargosa Mesquite Trees 

ACECs. Here sepiolite occurs in a nearly continuous and 

essentially horizontal bed as much as 20 feet (6 m) thick, with 

an average thickness of 6 feet (2 m). It lies below 10-25 feet 

(3–8 m) of overburden (Wahl and Papke, 2004). The sepiolite 

bed occurs within the saponite-bearing sequence described 

above. Impurities in the sepiolite clay include dolomite, calcite, quartz, feldspar, volcanic glass, and traces of other clays 

(Wahl and Papke, 2004). We took two samples of sepiolite 

from an operating pit (figs. 4 and 5). One, a 30-cm channel 

sample from a 30- to 60-cm-thick high-grade bed, was nearly 

pure sepiolite with a trace of dolomite (sample AP-105). 

Another was a grab sample of medium-grade sepiolite from 

below the high-grade bed (sample AP-105A). Samples of clayrich beds from above and below the sepiolite (AP-105B and 

AP-105C, respectively) contain minor amounts of montmorillonite clay, as does a nearby surface sample near the boundary 

of the Ash Meadows ACEC.

Kinney Mine

Clay has been mined from two pits and one underground 

operation in the Kinney Mine area (fig. 1), which is within the 

Ash Meadows ACEC. The clay occurs in a gently westward 

sloping bench that is capped by limestone. The two pits, a 

western pit (fig. 6) and an eastern pit (fig. 7), are each about 

200 m in diameter and expose a 2- to 3-m-thick bed of clay Figure 2. Location of clay channel sample AP-027 in small pit 

east of Clay Camp.

Figure 3. Shallow saponite pit 0.5 km northwest of the Ash 

Meadows ACEC.

Figure 4. Belly dump mining of overburden in an IMV Nevada 

sepiolite pit; overburden in this area is about 5 m thick.
F6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 5. Pale pinkish-gray high-grade sepiolite bed (above and 

behind hammer head, see white arrow) about 30 cm thick (sample 

AP-105), lying above light-gray medium-grade sepiolite about 1 

m thick (sample AP-105A). Greenish-gray bed (sample AP-105B) 

above sepiolite and light brownish-gray bed (sample AP-105C) 

below it are impure montmorillonite clay. IMV Nevada sepiolite pit.

that is overlain in most places by 1–4 m of bedded limestone. 

Samples of clay from these pits contain variable amounts of 

quartz, potassium feldspar, and calcite as impurities. Chemical analysis (Ludington and others, 2005) suggests that the 

clays are magnesium-rich (AP-029 and AP-031). The best 

identification for an unexpanded sample by XRD analysis 

is montmorillonite; however, the chemical analysis suggests 

that it is saponite. XRD analysis following glycolation shows 

expansion to 17 Å, which is appropriate for smectite. Papke 

(1970) described clay in this area, which he referred to as East 

Ash Meadows, as similar to clay from the Main Ash Meadows 

(Clay Camp) district. He reported that white montmorillonite 

from approximately the same location as our sample AP-031 

(fig. 8), unlike the saponite at Clay Camp, had good swelling 

ability and high plastic viscosity. Melhase (1926) described 

underground clay mining in this area, but production was 

probably small (Papke, 1970).

Ewing Mine

Montmorillonite clay has been mined by IMV Nevada 

from pits in the Ewing Mine area (fig. 1), which is about 4 

km north of the Ash Meadows ACEC. Papke (1970) called 

Figure 6. West Kinney Pit looking east. Sample AP-029 is from 

the southwest corner of the pit.

Figure 7. East Kinney Pit looking northeast. Sample AP-031 was 

taken from the east wall of the pit.

this property the K-B deposit and described the clay as 4 feet 

(1.2 m) of white clay, overlain by 2.5 feet (0.8 m) of very pale 

orange impure clay, capped by as much as 8 feet (2.4 m) of 

vuggy limestone (fig. 9). According to Papke, the white clay 

has moderate swelling ability and low viscosity, whereas the 

overlying clay has lower swelling capacity and higher viscosity. Although Papke (1970) reported that the clay in this area 

contains abundant gypsum, a sample of the white clay taken 

for this study (AP-108) was found to consist of nearly pure Ca 

bentonite on the basis of XRD and chemical analysis (sample 

AP-108; Ludington and others, 2005).

Zeolite Deposits

Nearly pure deposits of the zeolite mineral clinoptilolite 

occur in the southwestern part of the Ash Meadows ACEC. 

Pale-yellow to white clinoptilolite occurs in a large deposit 
Ash Meadows and Amargosa Mesquite Trees ACECs F7

Figure 9. White Ca-bentonite bed at least 1 m thick in the bottom 

of a pit wall in the Ewing Mine.

about 3 km south of the ACEC in California, where it is 

mined (fig. 10). The deposit reportedly extends into Nevada 

(Santini and Shapiro, 1982), where green clinoptilolite was 

mined in the past (fig. 11). The zeolite occurs in rocks that 

were mapped as a unit of Miocene or Pliocene sandstone and 

claystone (Denny and Drewes, 1965). According to ShepFigure 8. Site of sample AP-031 in the East Kinney Pit, a channel 

sample representing about 1.2 m of the 2-m thick clay bed.

pard (1986), the clinoptilolite occurs in vitric, nonwelded, 

ash-flow tuff that dips 15°-30° eastward and ranges from 

46 to 122 m thick. On the basis of XRD analysis, zeolitized 

tuffs from both the California mine site and exposures in 

Nevada are mineralogically identical and remarkably pure. 

The zeolitized rock is almost wholly composed of clinoptilolite (figs. 12 and 13), verifying Sheppard s report that the 

rock contains more than 80 percent clinoptilolite. Impurities are smectite clay, opal, and crystal and lithic fragments 

(Sheppard, 1986). Chemical analysis indicates that the green 

zeolite from Nevada (AP-081) is nearly identical in silica 

content to the California zeolite (AP-078), but has slightly 

higher amounts of potassium and lower amounts of sodium 

and calcium (table 1; Ludington and others, 2005). The zeolitized rock from both localities has considerably lower silica 

than nonzeolitized tuff collected nearby (AP-104G).

Figure 10. White clinoptilolite in an active pit in California south 

of the Ash Meadows ACEC. Pit walls are 15–30 m high.

Figure 11. Pale-green zeolitized tuff exposure in the Ash 

Meadows ACEC. Sample AP-081 was taken from the relatively 

resistant outcrop in the left foreground. The Ash Meadows Zeolite 

LLC processing plant is in the right background.
F8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 12. XRD analysis of sample AP-078, zeolite ore from Ash Meadows Zeolite pit in 

California.

Figure 13. XRD analysis of sample AP-081, zeolitized tuff from Nevada.
Ash Meadows and Amargosa Mesquite Trees ACECs F9

Sample------------ AP 078 AP 081 AP 104G

Location----------- Ash Meadows Zeolite 

mine, CA

Ash Meadows Zeolite 

prospect, NV

SW of AMZ claims, NV

Description------- White zeolitized tuff Green zeolitized tuff White glass shard tuff

SiO2

 (wt. %) 65.59 66.36 71.34

Al2

O3 (wt. %) 10.96 10.82 10.76

Fe2

O3 (wt. %) 0.79 0.68 0.85

MgO (wt. %) 0.24 0.16 0.30

CaO (wt. %) 1.41 0.99 1.27

Na2

O (wt. %) 3.96 2.79 3.73

K2

O (wt. %) 3.73 5.64 3.31

TiO2

 (wt. %) 0.09 0.09 0.09

P2

O5 (wt. %) 0.01 0.02 0.02

MnO (wt. %) 0.04 0.01 0.03

Loss on ignition 13.1 12.3 8.3

Sum 99.92 99.86 100.00

Mineral Exploration and Development

The Ash Meadows and Amargosa Mesquite Trees 

ACECs have been the site of significant exploration drilling in 

the past. An extensive shallow drilling program was undertaken in the 1990s by Rio Tinto PLC in the area of sepiolite 

and saponite mining in the northeast part of the Ash Meadows 

ACEC and in the west part of the Amargosa Mesquite Trees 

ACEC. On the basis of this drilling, a large area of claims was 

staked in the Amargosa Flat area, including claims in the Ash 

Meadows and Amargosa Mesquite Trees ACEC.

Anaconda Minerals Co. drilled for zeolite in the southeast 

part of the Ash Meadows ACEC in the 1970s. On the basis of 

data acquired during this drilling, a block of claims was staked 

in the ACEC and in an adjacent area in Nevada and California.

We found many small pits and prospects in the Ash 

Meadows ACEC. Most of these were probably dug during 

clay exploration; however, they are generally poorly preserved 

shallow excavations that do not contain good exposures of 

clay-bearing strata. A few small prospects, probably exploring 

for zeolite, are in the south part of the Ash Meadows ACEC.

There are 60 active mining claims in or near the Ash 

Meadows and Amargosa Mesquite Trees ACECs. The largest 

claim block is the 31-claim “GA” group of Ash Meadows 

Zeolite LLC in the southwestern part of the Ash Meadows 

ACEC. These claims, with 2005 as the last assessment year 

of record, are southwest of the company’s Ash Meadows 

Ranch processing plant and extend in a southwesterly direction to the California border. Mud Camp Mining LLC holds 

five “CAT” claims in the Ash Meadows ACEC, three claims 

that are about 1 mile (1.5 km) south of the Kinney mine 

clay pits in Sec. 26, T. 17 S., R. 50 E., and two claims in the 

northeast part of ACEC the near its clay mines. In addition, 

the company holds 10 CAT claims in the west part of the 

Table 1. Comparison of chemical analyses of zeolite ore from the Ash Meadows Zeolite (AMZ) 

mine in California and a prospect in Nevada with unaltered tuff.

Amargosa Mesquite Trees ACEC near its clay mines. A 12-

claim block of “BOB” claims is held by individual locators 

near the south edge of the Ash Meadows ACEC. Individuals 

hold two claims, the Tyco and Broken Pick Mine claims in 

the northeast part of the Amargosa Mesquite Trees ACEC. 

This site includes a water well and a sign proclaiming the 

presence of the Buck Mining Company.

Mineral Resource Potential 

Locatable Minerals in Ash Meadows ACEC

Metals.— There is no evidence for metallic mineral 

resource potential in the Ash Meadows ACEC.

Clay.— Areas with high potential for clay deposits with 

a high level of certainty (tracts AMA06 and AMA08, fig. 14) 

contain active IMV Nevada clay mines, are directly adjacent to 

the mines, or are currently held under claim by IMV Nevada. 

For the most part, these areas are outside the ACECs, but tract 

AMA06 covers a small part of the Ash Meadows ACEC along 

its northwest boundary.

Areas with high potential for clay deposits with a moderate certainty level (tracts AMA02, AMA03, and AMA05, fig. 

14) contain inactive clay mines that yielded samples with high 

clay contents. All these tracts cover part of the Ash Meadows 

ACEC and include areas near the Clay Camp pits and the Kinney Mine (fig. 1).

Areas with high potential for clay deposits with a low 

certainty level (tracts AMA01, AMA04, and AMA07, fig. 14) 

are defined by scattered occurrences of clay noted in Hay and 

others (1986) and (or) by favorable strata of probable Pliocene 

age. Tracts AMA01 and AMA04 cover large parts of the Ash 

Meadows ACEC.
Figure 14. Mineral resource potential tracts for locatable and leasable minerals in the Amargosa Mesquite Trees and Ash Meadows Are

Environmental Concern (ACEC).

Clay

Clay

Clay

Clay

Clay

Clay

Zeolite

Clay

Clay

Zeolite

AMA04

AMA05

AMA06

AMA07

AMA01

AMA10

AMA09

AMA02 AMA03

AMA08

02468 1

Kilometers

Tract ID Deposit Type Potential 

AMA01 Clay HigAMA02 Clay HigAMA03 Clay HigAMA04 Clay HigAMA05 Clay HigAMA06 Clay HigAMA07 Clay HigAMA08 Clay HigAMA09 Zeolite HigAMA10 Zeolite Hig

High mresourc

Mineral Poten

116°22'30"W 116°15'0"W 

36°22'30"N

36°30'0"N

GoldButeACE

Scale1:24,000

AMARGOSA

MESQUITE TRE

ACEC

ASH MEADOWS

ACEC
Ash Meadows and Amargosa Mesquite Trees ACECs F11

Zeolite.— In the southern part of the Ash Meadows 

ACEC, two areas are considered to have high potential for 

zeolite deposits (fig. 14). Tract AMA09 is a small area with 

high potential with a high certainty level, and is defined by 

exposures of strongly zeolitized tuff that are currently under 

claim by Ash Meadows Zeolite LLC. The larger tract AMA10 

has high potential with a moderate certainty level, and is 

covered by overburden; it is currently under claim by Ash 

Meadows LLC.

Leasable Minerals in Ash Meadows ACEC

The southwestern half of the Ash Meadows ACEC is 

within the region considered by the BLM to be moderately 

favorable for oil and gas (Smith and Gere, 1983). The northeastern half, and the entire Amargosa Mesquite Trees ACEC, 

are not within this region.

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium.

The Ash Meadows ACEC contains no known deposits of 

other leasable minerals, and the potential for their occurrence 

is judged to be low.

Salable Minerals in Ash Meadows ACEC

Crushed Stone.— A few areas underlain by Cambrian carbonate rocks in the eastern part of the ACEC (tract 

AAMA03, fig. 15) are designated to have moderate potential 

for crushed-stone aggregate, with a low level of certainty. The 

northernmost exposures of bedrock are mapped as Nopah 

Formation. The low chert content within this unit means that 

this area (tract AAMA01, fig. 15) has high potential, with a 

low level of certainty. In the southern part of the area, outcrops 

of the younger sediments and volcanic rocks (tract AAMA02, 

fig. 15) are soft and friable and unsuitable for crushed stone 

and are designated to have low potential, with a moderate 

certainty level.

Sand and Gravel.— A large part of the Ash Meadows 

ACEC has low potential for sand and gravel aggregate, with 

a moderate level of certainty (tract AAMA07, fig. 15); the 

materials exposed are primarily soft and fine-grained sedimentary material. High-potential sand and gravel deposits with a 

moderate certainty level occur adjacent to carbonate outcrops 

in the Devils Hole area and around the southern and western 

parts of the area (tract AAMA05, fig. 15).

Locatable Minerals in Amargosa Mesquite 

Trees ACEC

Metals.— There is no evidence for metallic mineral 

resource potential in the Amargosa Mesquite Trees ACEC.

Clay.— Areas with high potential for clay deposits with 

a moderate level of certainty (tracts AMA02, AMA03, and 

AMA05; fig. 15) contain inactive clay mines that yielded 

samples with high clay contents. Only tract AMA05 impinges 

on the Amargosa Mesquite Trees ACEC, including small areas 

along its western boundary.

Areas with high potential for clay deposits with a low 

certainty level (tracts AMA01, AMA04, and AMA07, fig. 

15) are areas defined by scattered occurrences of clay noted 

in Hay and others (1986) and (or) by favorable strata of 

probable Pliocene age. Tract AMA07 includes a substantial 

part of the northwestern part of the Amargosa Mesquite 

Trees ACEC.

Leasable Minerals in Amargosa Mesquite Trees 

ACEC

The entire Amargosa Mesquite Trees ACEC is outside 

the region considered by the BLM to be moderately favorable 

for oil and gas (Smith and Gere, 1983).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium.

The Amargosa Mesquite Trees ACEC contains no known 

deposits of other leasable minerals, and the potential for their 

occurrence is judged to be low.

Salable Minerals in Amargosa Mesquite Trees 

ACEC

Crushed Stone – There are no rock outcrops, and thus 

there is no potential for crushed-stone aggregate in the Amargosa Mesquite Trees ACEC.

Sand and Gravel - The northern part of the Amargosa 

Mesquite Trees ACEC has low potential for sand and gravel 

aggregate, with a high level of certainty (tract AAMA06, fig. 

15). This area consists of soft and fine-grained sedimentary 

material. In the southern part of the area quartzite and carbonate clasts derived from the highlands to the southeast indicate 

an area with high potential for sand and gravel aggregate, with 

a low certainty level (tract AAMA04, fig. 15).

References

Castor, S.B., 2003, Industrial minerals and rocks in Nevada, in

Castor. S., Papke, K., and Meeuwig, R., eds., Proceedings 

of the 39th Forum on the Geology of Industrial Minerals: 

Nevada Bureau of Mines and Geology Special Publication 

33, p. 57-67.

Cornwall, H.R., 1972, Geology and mineral deposits of 

southern Nye County, Nevada: Nevada Bureau of Mines and 

Geology Bulletin 77, 49 p.

Denny, C.S., and Drewes, H., 1965, Geology of the Ash 

Meadows Quadrangle, Nevada-California: U.S. Geological 

Survey Bulletin 1181-L, 56 p.
AAMA07 AAMA07

AAMA07

AAMA07

AAMA05

AAMA06

AAMA04

AAMA05

AAMA02

AAMA03 AAMA03

AAMA05

AAMA03

AAMA02

AAMA02

AAMA01

crushed stone,highcrushed stone,lowcrushed stone,moderatesand and gravel,highsand and gravel,lowsand and gravel,moderate

Aggregate

Potential

Tract ID Commodity Type Pote

AAMA01 Crushed Stone AAMA02 Crushed Stone AAMA03 Crushed Stone MAAMA04 Sand and Gravel AAMA05 Sand and Gravel AAMA06 Sand and Gravel AAMA07 Sand and Gravel 

Aggregate As

Trac

116°22'30"W 116°15'0"W 

36°22'30"N

36°30'0"N GoldButteACEC Scale 1:24,000

02468 1

Kilometers

AMARGOSA

MESQUITE TREE

ACEC

ASH MEADOWS

ACEC

Figure 15. Mineral resource potential tracts for aggregate resources in the Amargosa Mesquite Trees and Ash Meadows Areas of CriticEnvironmental Concern (ACEC).
Ash Meadows and Amargosa Mesquite Trees ACECs F13

Driesner, D., and Coyner, A., 2004, Major mines of Nevada 

2003: Nevada Bureau of Mines and Geology Special Publication P-15, 28 p.

Driesner, D., and Coyner, A., 2005, Major mines of Nevada 

2004: Nevada Bureau of Mines and Geology Special Publication P-16, 28 p.

Fleck, R.J., 1970, Age and tectonic significance of volcanic 

rocks, Death Valley area, California: Geological Society of 

America Bulletin, v. 81, p. 2807-2815.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Hay, R.L., Pexton, R.E., Teague, T.T., and Kyser, T.K., 1986, 

Spring-related carbonate rocks, Mg clays, and associated 

minerals in Pliocene deposits of the Amargosa Desert, 

Nevada and California: Geological Society of America Bulletin, v. 97, p. 1488–1503.

Heivilin, F.G., and Murray, H.H., 1994, Hormites—palygorskite (attapulgite) and sepiolite, in Carr, D.D., ed., Industrial Minerals and Rocks (6th ed.): Littleton, Colorado, 

Society for Mining, Metallurgy, and Exploration, Inc., p. 

249-254.

Khoury, H.N., Eberl, D.D., and Jones, B.F., 1982, Origin of 

magnesium clays from the Amargosa Desert, Nevada: Clays 

and Clay Minerals, v. 30, p. 327-336.

Kral, V.E., 1951, Mineral resources of Nye County, Nevada: 

Nevada Bureau of Mines and Geology Bulletin 45, 223 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Melhase, J., 1926, Mining bentonite in California: Engineering 

and Mining Journal, v. 121, p. 837-842.

Papke, K.G., 1970, Montmorillonite, bentonite, and fuller’s 

earth deposits in Nevada: Nevada Bureau of Mines and 

Geology Bulletin 76, 43 p.

Papke, K.G., 1972, A sepiolite-rich playa deposit in southern 

Nevada: Clays and Clay Minerals, v. 20, p. 211-215.

Papke, K.G., 1981, Industrial Minerals, in Schilling, J., and 

Hall, J., eds., The Nevada mineral industry 1980: Nevada 

Bureau of Mines and Geology Special Publication MI-1980, 

p. 15.

Santini, K.N., and Shapiro, A.R., 1982, Geology of the Ash 

Meadows clinoptilolite deposit, Inyo County, California, 

and Nye County, Nevada, in Austin, G.S., ed., Industrial 

minerals and rocks of the southwest: New Mexico Bureau 

of Mines and Mineral Resources Circular 182, p. 108.

Sawyer, D.A., Fleck, R.J., Lanphere, M.A., Warren, R.G., 

Broxton, D.E., and Hudson, M.R., 1994, Episodic caldera 

volcanism in the Miocene southwestern Nevada volcanic 

field—Revised stratigraphic framework, 40Ar/39Ar geochronology, and implications for magmatism and extension: Geological Society of America Bulletin, v. 106, p. 

1304–1318.

Sheppard, R.A., 1986, Death Valley Junction – Ash Meadows 

zeolite deposit, California and Nevada, in Hayes, J.B., ed., 

Clays and Zeolites, Los Angeles, California to Las Vegas, 

Nevada: International Association for the Study of Clays 

(AIPEA), p. 51-55.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, scale 1:500,000.

Stewart, J.H., 1992, Walker Lane belt, Nevada and California—An overview, in Craig, S.D., ed., Structure, tectonics 

and mineralization of the Walker Lane: Reno, Nevada, 

Geological Society of Nevada, Walker Lane Symposium 

Proceedings Volume, p. 1–16.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.

Wahl, B. and Papke K., 2004, The IMV story—sepiolite and 

saponite, in Castor, S.B., Papke, K.G., and Meeuwig, R.O., 

eds., Proceedings of the 39th Forum on the Geology of 

Industrial Minerals: Nevada Bureau of Mines and Geology 

Special Publication 33, p. 224-228.

Wallace, K.A., 1999, U.S. Fish and Wildlife Service land and 

reserved minerals withdrawal: U.S. Department of the Interior, Bureau of Land Management Mineral Report, Serial 

Number N-62752, 31 p.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter G. Mineral Resource Potential of the Virgin River 

Area of Critical Environmental Concern, Clark County, Nevada

By Brett T. McLaurin, Steve Ludington, Stephen B. Castor, and Kathryn S. Flynn

Summary and Conclusions

There are 27 current placer claims in or adjacent to the 

Virgin River Area of Critical Environmental Concern (ACEC), 

but there is insufficient information available to evaluate 

placer deposits of precious metals in the area, and the potential 

for the occurrence of gold placer deposits is unknown. There 

is no potential for the occurrence of other deposits of locatable 

or leasable minerals.

The Virgin River ACEC has potential for the occurrence 

of deposits of sand and gravel aggregate that are similar to 

currently active sand and gravel operations nearby. Two tracts 

have high potential for sand and gravel aggregate deposits 

and two have low potential. Potential for the occurrence of 

crushed-stone aggregate deposits in the area is low.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

on these lands.

The Virgin River ACEC was studied in the field to confirm descriptions of the geology that were gleaned from the 

scientific literature. No samples were collected.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The Virgin River ACEC is about 9 km southwest of 

Mesquite, Nevada, and lies just south of Interstate 15 along 

the Virgin River (fig. 1). Access to the area is by Nevada State 

Highway 170 (Riverside exit off I-15). The area includes the 

Virgin River, its floodplain and adjacent riverbanks. A legal 

description of these lands is included in appendix 2.

Physiographic Description

The Virgin River ACEC consists primarily of the floodplain of the Virgin River (fig. 2), much of which may be 

inundated during rare storm events. Elevations along the river 

range from 455 m at the upstream end to 407 m at the downstream end, and the highest elevations along the riverbank are 

about 500 m.

Geologic Setting

The Virgin River ACEC lies along the eastern margin 

of the central part of the Basin and Range Province, which 

adjoins the Grand Canyon region of the Colorado Plateaus on 

the east. The Virgin River flows along the axis of the Virgin 

River depression, a deep structural basin that marks the northern border of the South Virgin Mountains.

Geology

The central part of the area was mapped by Williams and 

others (1997) at a scale of 1:24,000 (Riverside Quadrangle), 

and they provide detailed descriptions of the rock units in the 

area. The north bank and a small portion of the south bank 

of the Virgin River expose the Pliocene and upper Miocene 

Muddy Creek Formation. All other deposits in the ACEC are 

Quaternary in age.

The area is on the divide between the Mesquite Basin 

and the Mormon Basin, which together form the Virgin 

River depression. The depth to basement in the ACEC is 

about 2 to 3 km, although the depression is considerably 

deeper both upstream and downstream (Langenheim and 

others, 2000).
Figure 1. Generalized geology of the Virgin River Area of Critical Environmental Concern (ACEC; outlined in pink). Geology modified from St

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VIRGIN RIVER

ACEC

Explanation

Qu Undivided surficial deposits (Pleisto

Alluvium, colluvium, lake, playa, laeolian sand depositsYoung sedimentary rocks (middle MAlluvial, lacustrine,and fluvial depoFormation. Locally includes minor 

Tsy

contact, certain

mine or prospect

QToa Older alluvial deposits (upper Plioce

Alluvium, with minor talus and eolia

114°15'0"W

36°45'0"N Gold ButeACEC Scale 1:24,000

01234 0.5

Kilometers
Virgin River ACEC G3

Muddy Creek Formation

The Muddy Creek Formation in the ACEC is mostly sandstone and siltstone, but it also includes some evaporite deposits 

(mostly gypsum), as well as limestone, conglomerate, and breccia. A fluvial facies of the Muddy Creek Formation that consists 

primarily of sandstone with minor conglomerate was deposited 

by an ancestral Virgin River before more recent incision.

Quaternary Deposits

Quaternary deposits in the ACEC were mostly deposited 

in floodplain, stream terrace, and alluvial fan settings. The 

floodplain and stream terrace sediments were deposited by the 

Virgin River. The alluvial fan deposits were derived from areas 

to the south and east, including Black Ridge and the South 

Virgin Mountains. All of the stream terrace and alluvial fan 

deposits may be capped by caliche horizons (as much as 2 m 

thick) in various stages of development.

Floodplain and Channel Deposits

These deposits are the topographically lowest in the 

area, and are the result of activity of the present day Virgin 

River. Williams and others (1997) mapped two units in the 

main channel area. An approximately 2-m-thick unit of fine to 

medium sand with lesser amounts of silt and gravel is characterized as bar deposits, active channel fill, and abandoned 

channel fill. The floodplain deposits are also approximately 2 

m thick and consist primarily of sand, with some gravel. The 

floodplain deposits are volumetrically the most abundant in 

the lower areas of the Virgin River Valley.

Terrace Deposits

The terrace deposits are found at higher elevations above 

the floodplain. The terraces include sediments deposited by 

both the present-day and ancestral Virgin Rivers. Terrace 

deposits closest to the modern floodplain are predominantly 

Figure 2. Floodplain of the Virgin River.

sand with lesser amounts of gravel, silt, and clay. Higher 

elevation terrace deposits are primarily gravel and can be as 

much as 50 m thick. Clast composition is variable. Deposits 

originally derived from the Virgin Mountains and Black Ridge 

may contain limestone, dolomite, gneiss, granite, pegmatite, 

quartzite, and chert, and they are found on the southeast side 

of the river. Sediments originally derived from the Mormon 

Mountains have mostly carbonate clasts and lack the igneous 

and metamorphic clasts. Terrace deposits with Mormon Mountain lithologies lie on the northwest side of the river.

Alluvial Fan and Pediment Deposits

These sediments are part of a large alluvial fan complex 

that slopes to the northwest from the flanks of the Virgin 

Mountains and Black Ridge. The distributary channels of the 

fan are upwards of 100 m wide and contain gravelly braided 

stream deposits. The depth of incision is between about 15 m 

and 30 m. The interchannel areas of the alluvial fan complex 

also contain abundant gravel and may be greater than 35 m 

thick. Clast composition of the alluvial fan deposits is consistent with their derivation from the Virgin Mountains.

Mining History

There are several active sand and gravel mining operations on the south bank of the Virgin River, near the townsite 

of Bunkerville, outside of the ACEC. No other present-day or 

historic mining operations are known.

Mineral Deposits

The sand and gravel deposits near Bunkerville are the 

only known mineral deposits of any kind within the ACEC. 

Other known mineral deposits are about 10 km to the southeast, on the northern flank of the Virgin Mountains. These 

include the Key West and Great Eastern nickel-platinum 

deposits and the Hodges-Wharton tungsten prospect.

A sand and gravel aggregate operation, operated by Sunroc Corporation, is located about 2 km east of the ACEC, and 

several other small sand and gravel pits are 2 to 3 km farther 

upstream (fig. 1).

Mineral Exploration and Development

There are 27 current placer claims within and adjacent 

to the Virgin River ACEC. All were located in 2003 and 

2004 by American Gold Corporation. We have no additional 

information about these claims, but presume they are for 

placer gold exploration. We noted no evidence of recent 

disturbances in the area.
VIRGIN RIVER ACEC AVRV01AVRV05 AVRV03 AVRV03 AVRV04 AVRV02 AVRV02 AVRV05AVRV01 Tract ID Commodity Type Potential Level Ce

AVRV01 Crushed Stone Low AVRV02 Sand and Gravel High AVRV03 Sand and Gravel High AVRV04 Sand and Gravel Low AVRV05 Sand and Gravel Low 

Aggregate assessment

tracts

crushed stone,highcrushed stone,lowcrushed stone,moderatesand and gravel,highsand and gravel,lowsand and gravel,moderate

Aggregate

Potential

114°15'0"W

36°45'0"N Gold ButeACEC 02468 1 Kilometers

Figure 3. Mineral resource potential tracts for aggregate resources in the Virgin River Area of Critical Environmental Concern (ACEC).
Virgin River ACEC G5

Mineral Resource Potential

Locatable Minerals

There are no known lode mineral deposits in the Virgin 

River ACEC. Because there is no appropriate bedrock, there 

is no potential for the existence of undiscovered deposits. The 

potential for placer gold deposits is unknown, but there are no 

known important sources of gold upstream from the ACEC.

Leasable Minerals

The entire Virgin River ACEC is within the region considered by the BLM to be moderately favorable for oil and gas 

(Smith and Gere, 1983). An exploratory oil well, Virgin River 

U.S.A. No. 1-A, was drilled by Mobil Oil Corp. to a depth 

of 5,964 m about 10 km southwest of the ACEC on Mormon 

Mesa. The well, Nevada’s deepest as of 1986, was collared in 

the Muddy Creek Formation and bottomed in granitic rock. It 

was a dry hole (Garside and others, 1988).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. Evaporite deposits in the 

Muddy Creek Formation contain primarily gypsum.

The Virgin River ACEC contains no known deposits of 

other leasable minerals, and the potential for their occurrence 

is low.

Salable Minerals

The Virgin River ACEC is favorably located for the 

development of aggregate resources. It is in close proximity to 

both I-15 and the Mesquite-Bunkerville road, which provide 

ideal transportation routes to Mesquite and to metropolitan Las 

Vegas. Figure 3 illustrates the aggregate potential for various 

areas of the ACEC.

Crushed Stone.—Most of the exposed material in the 

ACEC is alluvium. Some partially consolidated beds in the 

Muddy Creek Formation, primarily along the northwest side 

of the river, can be considered to be rock, but their friable 

nature makes them unsuitable for crushed stone. These areas 

are assigned low potential for crushed-stone aggregate deposits, with a moderate level of certainty (tract AVRV01, fig. 3).

Sand and Gravel.—Within this ACEC, the highest potential for the development of sand and gravel resources is on the 

northwest side of the river in the vicinity of Riverside, Nevada. 

This assessment is based on the apparent quality and quantity 

of the material as well as proximity to transportation routes. 

Two tracts have been designated to have high potential for 

sand and gravel aggregate, AVRV02, with a high level of certainty, and AVRV03, with a moderate certainty level (fig. 3).

Terrace gravels of the ancestral Virgin River are the 

primary aggregate resource in this area. Estimated thickness of 

the gravels is between 10 and 50 m. Sandy terrace sediments 

that are as much as 10 m thick cap these terrace gravels. Clast 

composition in the terrace gravels varies between the deposits 

west and east of Riverside. Deposits east of Riverside in tract 

AVRV02 contain carbonate clasts derived from the Mormon 

Mountains and thus have fewer chert and metamorphic clasts 

(Williams and others, 1997). These constitute a higher-quality aggregate resource, since the lack of silica-rich clasts can 

decrease the potential for alkali-silica reactivity (ASR) in 

concrete applications. Alluvial fan deposits south of the river, 

between the floodplain and Riverside Road, are also within 

this tract. They are about 30 m thick. Although it has high 

potential, the area between the road and the floodplain is narrow, no more than 400 m wide, and the space available for a 

possible mining operation could be problematic. These alluvial 

fan deposits are similar to those mined by Sunroc Sand and 

Gravel outside the eastern edge of the ACEC.

The other tract with high potential, AVRV03, is primarily 

west of Riverside. The alluvial fan deposits there are somewhat thinner than those in tract AVRV02, and they are not as 

accessible to I-15.

The areas within the floodplain (tract AVRV05, fig. 3) of 

the Virgin River have low potential for sand and gravel aggregate deposits, with a high level of certainty. This is because 

the aggregate material that is in the floodplain and channel bar 

deposits is of lower quality, and is subject to periodic flooding.

Areas that encompass sandy terrace deposits and the 

Muddy Creek Formation also have low potential for sand and 

gravel aggregate deposits, with a moderate level of certainty 

(tract AVRV04, fig. 3). The Muddy Creek Formation in 

the ACEC is poorly consolidated and sand-rich, with some 

conglomerate layers of limited thickness and lateral extent. 

Although this material could be utilized as a sand resource, the 

nearby terrace and alluvial fan gravels are of higher quality.

References

Garside, L.J., Hess, R.H., Fleming, K.L., and Weimer, B.S., 

1988, Oil and gas developments in Nevada: Nevada Bureau 

of Mines and Geology Bulletin 104, 136 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Langenheim, V.E., Glen, J.M., Jachens, R.C., Dixon, G.L., 

Katzer, T.C., and Morin, R.L., 2000, Geophysical Constraints 

on the Virgin River Depression, Nevada, Utah, and Arizona: 

U.S. Geological Survey Open-File Report 00-407, 28 p.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, scale 1:500,000.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.

Williams, V.S., Bohannon, R.G., and Hoover, D.L., 1997, 

Geologic map of the Riverside quadrangle, Clark County, 

Nevada: U.S. Geological Survey Geologic Quadrangle Map 

GQ-1770, scale 1:24,000.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter H. Mineral Resource Potential of the Hidden Valley 

Area of Critical Environmental Concern, Clark County, Nevada

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, and Kathryn S. Flynn

Summary and Conclusions

The Hidden Valley Area of Critical Environmental 

Concern (ACEC) contains deposits of building stone that were 

mined in the past. However, the stone is of low quality, and the 

potential for the occurrence of locatable stone or silica sand 

deposits is low. There is no potential for the occurrence of 

other deposits of locatable or leasable minerals.

The Hidden Valley ACEC contains areas with both moderate and low potential for the occurrence of crushed stone 

aggregate deposits, as well as a tract with low potential for the 

occurrence of sand and gravel aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral 

resource potential in accordance with regulations at 43 CFR 

2310, which governs the withdrawal of public lands. The Clark 

County Conservation of Public Land and Natural Resources Act 

of 2002 temporarily withdraws the lands described herein from 

mineral entry, pending final approval of an application for permanent withdrawal by the BLM. This report provides information about mineral resource potential on these lands.

The Hidden Valley ACEC was visited briefly to confirm descriptions of the geology that were gleaned from the 

scientific literature. Definitions of mineral resource potential 

and certainty levels are given in appendix 1, and are similar to 

those outlined by Goudarzi (1984).

Lands Involved

The Hidden Valley ACEC is about 40 km northeast of the 

city of Las Vegas. It is about 15 km south of the townsite of 

Crystal (exit 75 on Interstate 15), and is reached by secondary 

roads from there. A legal description of these lands is included 

in appendix 2.

Physiographic Description

The Hidden Valley ACEC consists primarily of a flat valley at an elevation of about 1,000 m, surrounded by hills and 

mountains that reach elevations of more than 1,600 m. The 

area is drained to the north by a tributary of California Wash.

Geologic Setting

The Hidden Valley ACEC is in the Basin and Range 

Physiographic Province, an area characterized by late Cenozoic tectonic extension, including numerous thrust faults. It 

lies on the western margin of the Grand Canyon region of the 

Colorado Plateaus Province. Proterozoic gneiss and schist are 

exposed in the Virgin Mountains, less than 40 km to the east. 

On the west, nonextended Pennsylvanian and Permian limestone and dolomite are exposed less than 10 km away.

Geology

The valley floor of Hidden Valley and part of its flanks 

are composed of Jurassic Aztec Sandstone (fig. 1). The Aztec 

Figure 1. Panoramic photograph of Sandstone consists of brick-red to pink, fine- to mediumHidden Valley, showing floor of Aztec 

Sandstone (pink) 

and surrounding 

hills of Paleozoic 

carbonate rocks 

(dark grey).
H2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 2. Generalized geology of the Hidden Valley Area of Critical Environmental Concern (ACEC; outlined in pink). 

Geology modified from Stewart and Carlson (1978)

COLOROCK

QUARRIES

COLOROCK QUARRY

#1 WELL

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HIDDEN VALLEY

ACEC

114°45'0"W

36°22'30"N

Scale 1:24,000

01234 0.5

Kilometers

Undivided surficial deposits (Pleistocene and Holocene)—alluvium,

colluvium, lake, playa, landslide, terrace, and eolian sand deposits

Horse Spring Formation (Upper Oligocene and Miocene)—tuffaceous

sedimentary rocks; includes some volcanic rocks, sandstone, limestone,

and gypsum

Sedimentary rocks (Triassic and Jurassic)—mostly sandstone and shale.

Includes Lower Jurassic Aztec Sandstone and Chinle and Moenkopi

Formations

Carbonate rocks (Mississippian to Permian)—limestone, dolomite, and

some shale. May include Kaibab, Callville, Temple Butte, Monte Cristo,

and Redwall Limestones, Toroweap Formation, Coconino Sandstone, and

Bird Spring Formation

Dolomite and Limestone (Cambrian to Devonian)—dolomite, limestone, and

minor amounts of sandstone, shale, and siltstone. May include Temple Butte,

Muddy Peak, and Guilmette Limestone; Nopah, Muav, and Bonanza King

Formations; Pioche Shale; and Eureka Quartzite

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EXPLANATION

oil exploration drill hole
Hidden Valley ACEC H3

grained, well-sorted, quartz-rich sandstone. It is characterized by large cross beds generally considered to be of eolian 

(wind-blown) origin (Stewart, 1980) and typically weathers 

to form high cliffs and distinctive knobby outcrops. The 

Aztec Sandstone is correlative with the Navajo Sandstone of 

the Colorado Plateaus, and it is the formation that forms distinctive red cliffs at Valley of Fire State Park and Red Rock 

Canyon in Nevada and at Zion National Park in Utah.

The hills and valleys surrounding Hidden Valley consist 

of Cambrian and Ordovician carbonate rocks. These rocks 

are massive to well bedded, light- to dark-gray dolomite and 

limestone that represent a variety of different marine carbonate depositional environments (Longwell and others, 1965).

These carbonate rocks were thrust westward over the 

Aztec Sandstone on the North Buffington back-thrust fault 

system related to the Sevier orogeny in Late Cretaceous 

time (Carpenter and Carpenter, 1994). This fault was later 

deformed and, in places, overturned by the eastward-moving Muddy Mountains thrust system in earliest Tertiary 

time (Bohannon, 1983). Fine-grained lacustrine and fluvial 

deposits of the Miocene Horse Springs Formation crop out in 

the eastern part of the area. Figure 2 is a geologic map of the 

ACEC and surrounding area. No igneous rocks occur in or 

near the area.

Mining History

Two stone quarries were developed at the northern edge 

of the Hidden Valley ACEC at an unknown date. Longwell and 

others (1965) reported that the Colorock Quarry in this area 

had small recorded production. During our reconnaissance of 

the area, two other small quarries were found about 200 m outside of the northern boundary of the ACEC. Both sites showed 

some evidence of drilling and stone splitting. Other activity 

within 20 km of the area has been restricted to small-scale 

mining of industrial minerals (silica, clay, and borates).

Mineral Deposits

The Hidden Valley ACEC contains outcrops of Aztec 

Sandstone that is variegated pale red, pale orange-pink, and 

light reddish-brown to white (fig. 3). Quarries in this rock 

have furnished small amounts of building stone. The largest quarry in the area is a cut about 30 m long, 10 m wide, 

and 2 to 3 m deep (fig. 4). It and two other quarries are 

within about 200 m of the northern boundary of the ACEC. 

The Wyatt silica mine, located about 2 km northeast of the 

ACEC, produced three or four carloads of silica sand from 

the Aztec Sandstone.

Other nearby mineral deposits and prospects are: the Vanderbilt bedded clay deposit, 10 km southwest; the Anniversary 

lacustrine borate deposit, 11 km south; the Ore Car Mine (gem 

beryl), 11 km south; the Bauer-Dollery and Virgin River manganese deposits, 25 km southeast; the White Basin lacustrine 

borate deposit, 10 km east; and the Overton bedded magnesite 

deposit, 25 km northeast.

Mineral Exploration and Development

There has been no known modern mineral exploration 

or development in this ACEC. Past development activity was 

restricted to limited quarrying of building stone at two sites 

Figure 3. Banded pale-red and white Aztec Sandstone from a 

quarry near the northern boundary of the Hidden Valley ACEC. 

GPS instrument (15 cm long) for scale.

Figure 4. Aztec Sandstone at a small quarry near the Hidden 

Valley ACEC. Note the drill hole to the left of the rock hammer.
H4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

near the north edge of the ACEC, including the Colorock 

Quarry. A small stone building in the area was likely constructed at that time.

In the past, there has been a small amount of petroleum 

exploration activity in Clark County, particularly in the 1950s 

and 1980s, and a number of deep wells have been drilled. 

However, no discoveries of exploitable petroleum have 

resulted. In 1983, Colorock Quarry # 1 well was drilled in 

the Colorock Quarry area by Chevron U.S.A. Inc. and Michel 

T. Halbouty Energy Co. (Garside and others, 1988). Another 

oil well, Frank #1, was drilled by Hall Co. in the area, but its 

exact location is not available (Garside and others, 1988).

Mineral Resource Potential

Locatable Minerals

The Hidden Valley ACEC has only low potential for the 

development of low-quality stone deposits. The Aztec Sandstone in the ACEC has been the source of a limited amount 

of stone production that was likely sold in the Las Vegas area 

as rough-hewn flagstone and ashlar. In the judgment of the 

authors, the Hidden Valley stone is of relatively poor quality 

and the area is difficult to access. The stone is too friable for 

the production of cut dimension stone. Existing producers of 

rough-hewn stone in the Las Vegas area exploit less friable 

parts of the Aztec Sandstone and other units, and there are 

large reserves of such material outside the ACEC. On the 

basis of analyses of Aztec Sandstone from other deposits in 

Clark County (Ludington and others, 2005), the Hidden Valley 

ACEC is not considered to be a good source of high-quality 

industrial sand.

There are no other known deposits of locatable minerals 

in the ACEC.

Leasable Minerals

The entire Hidden Valley ACEC is within the region 

considered by the BLM to be moderately favorable for oil and 

gas (Smith and Gere, 1983). No oil or gas shows were reported 

by Garside and others (1988) in the Colorock Quarry # 1 well, 

which was collared about 125 m north of the ACEC. It was 

drilled to a depth of 10,030 feet (3,058 m) through the Aztec 

Sandstone and underlying Mesozoic rock units. On the basis 

of the lithologic log (Nevada Bureau of Mines and Geology 

Information Office file), it probably also penetrated the Permian 

Kaibab and Toroweap Formations, and bottomed in red Permian 

sandstone. No data are available for the vaguely located Frank 

#1 well, other than a total depth of 1,005 feet (306 m).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium.

The Hidden Valley ACEC contains no known deposits of 

other leasable minerals, and the potential for their occurrence 

is low.

Salable Minerals

Crushed Stone.—Because they contain moderate amounts 

of chert, the carbonate rocks above the thrust fault are judged 

to have moderate potential for crushed-stone aggregate deposits, with a low certainty level (tract AHDV01, fig. 5). The 

areas underlain by friable Aztec Sandstone have low crushedstone aggregate potential, with a moderate level of certainty 

(tract AHDV02, fig. 5).

Sand and Gravel.—Alluvial deposits fill the valley east 

of the Aztec Sandstone outcrop area and are primarily finegrained sand. Although some coarse material from the carbonate rocks is present, the sand and gravel potential in this area is 

low, with a moderate level of certainty (tract AHDV03, fig. 5).

References

Bohannon, R.G., 1983, Mesozoic and Cenozoic tectonic development of the Muddy, North Muddy, and northern Black 

Mountains, Clark County, Nevada, in Miller, D.M., Todd, 

V.R., and Howard, K.A., eds., Tectonic and stratigraphic 

studies in the eastern Great Basin: Geological Society of 

America Memoir 157, p. 125-148.

Carpenter, D.G., and Carpenter, J.A., 1994, Fold-thrust structure, 

synorogenic rocks, and structural analysis of the North Muddy 

and Muddy Mountains, Clark County, Nevada, in Dobbs, S.W. 

and Taylor, W.J. eds., Structural and stratigraphic investigations and petroleum potential of Nevada, with special emphasis south of the Railroad Valley producing trend: Nevada 

Petroleum Society Conference Volume II, p. 65-94.

Garside, L.J., Hess, R.H., Fleming, K.L., and Weimer, B.S., 

1988, Oil and gas developments in Nevada: Nevada Bureau 

of Mines and Geology Bulletin 104, 136 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Longwell, C.R., Pampeyan, E.H., Bowyer, Ben, and Roberts, R.J., 

1965, Geology and mineral deposits of Clark County, Nevada: 

Nevada Bureau of Mines and Geology Bulletin 62, 218 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, scale 1:500,000.

Stewart, J.H., 1980, Geology of Nevada—a discussion to 

accompany the Geologic Map of Nevada: Nevada Bureau of 

Mines and Geology Special Publication 4, 136 p.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.
Hidden Valley ACEC H5

Figure 5. Mineral resource potential tracts for aggregate resources in the Hidden Valley Area of Critical 

Environmental Concern (ACEC; outlined in pink).

HIDDEN VALLEY

ACEC

AHDV01

AHDV02

AHDV03

114°45'0"W

36°22'30"N

Gold Butte ACEC

Scale 1:24,000

01234 0.5

Kilometers

Moderate potential for crushed stone aggregate

Low potential for crushed stone aggregate

EXPLANATION

Low potential for sand and gravel aggregate

Tract ID Commodity Type Potential Level Certainty Level

AHDV01 Crushed Stone Low Moderate

AHDV02 Crushed Stone Moderate Low

AHDV03 Sand and gravel Low Moderate

Aggregate Assessment

Tracts
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter I. Mineral Resource Potential of the Rainbow 

Gardens Area of Critical Environmental Concern, Clark 

County, Nevada

By Stephen B. Castor, Steve Ludington, Brett T. McLaurin, and Kathryn S. Flynn

Summary and Conclusions

The Rainbow Gardens Area of Critical Environmental Concern (ACEC) contains known deposits of gypsum, 

as well as prospects for limestone, silica, lithium, copper, 

uranium, and sand and gravel aggregate. Only gypsum has 

been mined in significant quantities, and the PABCO (Apex) 

gypsum mine, immediately adjacent to the ACEC, is a major 

gypsum source, producing more than 1,000,000 short tons of 

gypsum annually.

The ACEC contains areas of high mineral resource 

potential for gypsum deposits in the Tertiary Muddy Creek 

Formation and areas of moderate mineral resource potential 

for gypsum in the Mesozoic Moenkopi Formation. Areas with 

high potential for limestone deposits are found in the northern 

part of the ACEC. There is an area with moderate potential for 

lithium (hectorite clay) deposits. The potential for undiscovered deposits of silica, uranium, and metals is low.

The ACEC has areas with high, moderate, and low 

potential for crushed-stone aggregate deposits. Unconsolidated 

material in the ACEC has high potential for sand and gravel 

aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

of these lands.

The Rainbow Gardens ACEC was studied in the field to 

confirm descriptions of the geology that were gleaned from 

the scientific literature. Samples were collected and analyzed, 

and representatives of companies with mining operations in 

and near the areas were contacted.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The Rainbow Gardens ACEC is east of Las Vegas and 

southeast of Interstate 15 (fig. 1). The ACEC is bounded on 

the southeast and east by the Lake Mead National Recreation 

Area and on the north by Nellis Air Force Base. It is accessed 

most easily from Nevada State Highway 143 (Lake Mead 

Boulevard) and by several secondary and primitive roads 

that branch off of this highway. It may also be accessed from 

Hollywood Boulevard in southeast Las Vegas and by primitive roads in that area. A legal description of these lands is 

included in appendix 2.

Physiographic Description

The Rainbow Gardens ACEC is named for an area of 

colorful rock strata near its southeastern boundary. Near its 

western boundary, it includes Frenchman Mountain, a rugged ridge that forms the eastern backdrop for Las Vegas and 

reaches elevations of more than 1,200 m. The northwest part 

of the ACEC includes Sunrise Mountain, which is more than 

1,000 m in height. The lowest part of the ACEC is at an elevation of about 440 m along its southern boundary in Las Vegas 

Wash, which drains into Lake Mead to the east. Streams and 

washes in the Rainbow Gardens ACEC drain westward into 

Las Vegas basin and eastward into Lake Mead.

Geologic Setting

The Rainbow Gardens ACEC is in the Basin and Range 

Physiographic Province, which is characterized by north-
Frenchman Fault Gypsum prospects Abandoned sand and gravel pits Abandoned sand and gravel pits Frenchman Mill Site White Eagle gypsum mines East Rainbow Gardens gypsum mines North Rainbow Gardens gypsum mines Pioneer gypsum mine Pabco (Apex) gypsum mine and mill Sandia Rock sand and gravel pit Uranium prospect Copper prospect Qu Tsy Ths 

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AP-248

AP-247

AP-131

AP-130

AP-129

AP-128

AP-127

AP-126 AP-125

Boulevard Fault

Frenchman Fault

RAINBOW GARDENS

ACEC

Exploratory oil well

Exploratory

oil well

115°0'0"W 114°52'30"W

36°7'30"N36°15'0"N

GoldButteACEC

Scale 1:24,000

024

1

Figure 1. Generalized geology of the Rainbow Gardens Area of Critical Environmental Concern, showing mines, prospects, and locations of analyzed 

from Stewart and Carlson (1978).
Rainbow Gardens ACEC I3

trending mountain ranges and intervening valleys. However, 

the ACEC lies near the border of this province with the Colorado Plateaus Province and exposes Paleozoic and Mesozoic 

strata that are similar to those of the Colorado Plateaus. The 

geology of the region is characterized by rocks ranging in age 

from Proterozoic through Miocene that are cut by a complex 

of late Cenozoic extensional faults. Important regional structural features include the Lake Mead Fault system, the Las 

Vegas Valley shear zone, and steep to moderately dipping normal faults. The Las Vegas Valley shear zone is a major westnorthwest-striking right-lateral fault zone that extends across 

much of southern Nevada. It has accommodated as much as 

65 km of dextral displacement to the northwest of the ACEC 

(Longwell, 1974; Wernicke and others, 1988; Deubendorfer 

and Black, 1992) and is associated with large-magnitude 

clockwise rotation of adjacent rocks. The Lake Mead Fault 

system is a major east-northeast-striking left-lateral fault zone 

(Anderson, 1973) that appears to merge with the right-lateral 

Las Vegas Valley shear zone.

Geology

The Rainbow Gardens ACEC has been completely 

mapped geologically at 1:24,000 scale (Bingler, 1977; Bell 

and Smith, 1980; Matti and others, 1993; Castor and others, 

2000; Deubendorfer, 2003). Rock units range in age from 

Proterozoic through late Miocene. Proterozoic schist and 

gneiss, exposed along the western base of Frenchman Mountain (Matti and others, 1993), is overlain by relatively thin 

lower Cambrian sandstone and shale units and then by a thick 

sequence of carbonate-dominated Cambrian, Devonian, and 

Mississippian to Permian rocks. Mesozoic rocks, mainly composed of shallow marine to nonmarine Triassic and Jurassic 

redbeds, with some carbonate and gypsum beds, are capped 

by eolian sandstone. Rocks of the uppermost Oligocene to 

middle Miocene Horse Spring Formation and a red sandstone 

unit described by Bohannon (1984) are mainly composed of 

nonmarine red sandstone, with some carbonate rocks and tuff. 

The Muddy Creek Formation, which is mostly composed of 

poorly indurated sandstone and siltstone with local gypsum, 

limestone, and conglomerate units, filled late Miocene basins. 

The Paleozoic and Mesozoic strata are conformable, but the 

break between the youngest Mesozoic unit (Jurassic Aztec 

Sandstone) and the oldest Tertiary unit (basal part of the Horse 

Spring Formation) is marked by a low-angle unconformity.

The Rainbow Gardens ACEC contains six major structural elements: the Frenchman Mountain block, Sunrise 

Mountain block, Boulder Basin, Nellis Basin, Gale Hills 

block, and Las Vegas Valley. The Frenchman Mountain block 

is bounded by the Frenchman Fault and Las Vegas Valley on 

the west, the Sunrise Mountain block on the north, and the 

Boulder Basin on the east. The east-trending, left-lateral Boulevard Fault Zone separates the Frenchman Mountain block 

from the Sunrise Mountain block (Castor and others, 2000). 

Figure 1.—Continued. The Frenchman Mountain block is dominated by east-tilted 

contact, certain

fault, certain

fault, approximate

fault, concealed

thrust fault

mine or prospect

sample site, with sample nmber

exploratory oil well

AP-001

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Undivided surficial deposits (Pleistocene and 

Holocene)—Alluvial, colluvial, lake, playa, landslide, 

terrace, and eolian sand deposits

Sedimentary rocks (Pliocene and Pleistocene)—Mostly 

lake and alluvial deposits

Young sedimentary rocks (middle Miocene to 

Pliocene)—Alluvial, lacustrine, and fluvial deposits. 

Locally includes minor amounts of tuff. Includes Muddy 

Creek Formation

Horse Spring Formation (upper Oligocene and 

Miocene)—Clastic and tuffaceous sedimentary rocks; 

includes some volcanic rocks, limestone, and gypsum

Young volcanic rocks (middle and upper Miocene)-

Rhyolite, andesite, and basalt lava flows, tuff, and 

tuffaceous sediments

Intrusive rocks (Oligocene and Miocene)—Aphanitic, 

porphyritic, and coarsely crystalline rocks ranging in 

composition from gabbro to granite

Sedimentary rocks (Triassic and Jurassic)—Shale, 

mudstone, siltstone, sandstone, and carbonate rock; 

some sparse volcanic rock. Includes Lower Jurassic 

Glen Canyon Group (Kayenta and Moenave Formations, 

Aztec Sandstone) and Chinle and Moenkopi Formations

Carbonate rocks (Mississippian to Permian)— 

Limestone, dolomite, and some shale. May include 

Kaibab, Callville, Monte Cristo, and Redwall 

Limestones, Toroweap Formation, and Bird Spring 

Formation

Sedimentary rocks (uppermost Devonian to Permian) — 

Siltstone, sandstone, shale, and conglomerate; some 

limestone, dolomite, chert, and gypsum. May include 

Queantoweap Sandstone, Hermit Formation, Coconino 

Sandstone, Supai Group, and Pakoon Formation

Dolomite and Limestone (Cambrian to Devonian) — 

Dolomite, limestone, and minor amounts of 

sandstone,shale, and siltstone. May include Muav 

Limestone, Frenchman Mountain Dolomite, and 

Bonanza King ? and Nopah and Sultan Formations

Sedimentary rock (Cambrian)—Sandstone, shale, and 

limestone. May include Pioche Shale, Lyndon 

Limestone, and Chisholm Shale

Metamorphic rocks (Paleoproterozoic)—Undivided 

metasedimentary, metavolcanic, and gneissic rocks, 

including locally abundant amphibolite and pegmatite. 

May also include Paleoproterozoic granitoid rocks

EXPLANATION
I4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Paleozoic, Mesozoic, and Miocene strata and widely spaced, 

generally northwest-dipping normal faults that have produced 

three major stratigraphic repetitions.

In contrast to the Frenchman Mountain block, the Sunrise 

Mountain block is composed of many small blocks. Eastnortheast-striking, moderately southeast-dipping Paleozoic 

and Mesozoic strata are cut by closely spaced normal, oblique, 

and strike-slip faults that fragment the Sunrise Mountain 

block. The structural complexity in the Sunrise Mountain 

block increases northward toward the Munitions Fault, a major 

east-striking fault zone that dips moderately northward and 

bounds the Sunrise Mountain block on the north.

The Frenchman Fault forms the west side of the Sunrise 

Mountain and Frenchman Mountain blocks, and has a northwest-striking southern strand partly within the southwest part 

of the Rainbow Gardens ACEC that accommodated normal 

dextral (Castor and others, 2000) and reverse dextral motion 

(R.E. Anderson, oral commun., 1998). This strand merges 

northward with the central north-striking part of the Frenchman Fault, which surfaces west of the ACEC (Matti and others, 1993) and extends into the northwest part of the ACEC.

The Boulder Basin is east of the Frenchman Mountain 

block and consists primarily of Miocene sedimentary strata 

that are tilted gently to moderately eastward. The northern part 

of the Boulder Basin is complicated by an east- to northeast-trending fold belt that extends beyond the east border of 

the ACEC (Deubendorfer, 2003), suggesting that the basin, 

once a half graben or series of half grabens, was significantly 

modified by north-south shortening. The late Miocene Muddy 

Creek Formation is locally deformed in this area.

The Nellis Basin, a small late Tertiary basin north of the 

Munitions Fault, extends southeast into the ACEC. A limestone 

member of the late Miocene Muddy Creek Formation is apparently confined to this basin. The basin may have developed in a 

right step or pull-apart along the Las Vegas Valley shear zone.

Within the Rainbow Gardens ACEC, bedrock exposed in the 

Gale Hills block, which bounds the Boulder Basin on the northeast, is almost all middle Miocene sedimentary rock. However, 

east of the ACEC, the Gale Hills block includes the southeast 

extension of the Las Vegas Valley shear zone, along which Paleozoic and Mesozoic strata are exposed (Deubendorfer, 2003).

Mining History

There are seven inactive open-pit gypsum mines in the 

Rainbow Gardens ACEC; most are in or near the Rainbow 

Gardens area (fig. 2). The best known is the White Eagle mine, 

where gypsum was mined from a series of narrow pits (fig. 3) 

between 1938 and 1956 by Pabco Products, Inc. (Papke, 1987) 

and later by Fibreboard Paper Products. According to Papke, 

the nearby East Rainbow Gardens pits (figs. 4, 5) were the 

source of gypsum for Pabco Products, Inc., in the late 1950s 

after mining ceased in the White Eagle area; however, U.S. 

Bureau of Mines records show the operator as Fibreboard 

Paper Products at this time.

Gypsum mining at the North Rainbow Gardens mine (fig. 

6), about 5 km northeast of the White Eagle mine, began in the 

late 1950s (Papke, 1987). Fibreboard Paper Products was the 

operator at this mine (referred to by the U.S. Bureau of Mines 

as the “Henderson” operation). In 1959, the company switched 

its mining operations from the Rainbow Gardens area to the 

PABCO mine about 7 km to the northeast (see below). The 

North Rainbow Gardens mine was mostly idle until the late 

1980s, when it was again operated by Nevada Gypsum and 

Mining and Nevada Gypsum, Inc. The last mining activity 

recorded at the property was in 1993 (Castor, 1994).

Figure 2. View looking northeast at part of the Rainbow Gardens 

Area of Critical Environmental Concern showing the abandoned 

East Rainbow Gardens pits in white gypsum beds in the Horse 

Spring Formation (center) and the access road in the foreground. 

Lava Butte is immediately behind. The abandoned Rainbow 

Gardens pits, including the White Eagle mine, are in the left center 

along Rainbow Gardens Road. The light-colored plateau beyond 

Lava Butte is capped by gypsite that is currently being mined by 

PABCO and Pioneer Gypsum.

Figure 3. White Eagle mine, Rainbow Gardens, looking north. 

Gypsum is in moderately east-dipping red sandstone in the lower 

part of the Moenkopi Formation. Sample AP-130 was taken north 

of the white vehicle in the distance.
Rainbow Gardens ACEC I5

The PABCO Gypsum Mine, also called the Apex Mine 

(fig. 7), is located in a large inlier of private land in the 

Rainbow Gardens ACEC (fig. 1). It is one of five active 

gypsum mines in Nevada and has been the site of continuous 

mining since 1959. U.S. Bureau of Mines records show that 

it was operated by Fibreboard Paper Products in 1959 and 

by Johns Manville Products Corp. between 1968 and 1976. 

In 1976 the operation was purchased by Pacific Coast Building Products, Inc., which currently owns the property as part 

of its PABCO Gypsum subsidiary. Production from the mine 

has been more than 1,000,000 short tons annually since 

2001; however, the ore contains 70 to 80 percent gypsum, 

and production figures for beneficiated gypsum (92 percent 

or more gypsum by weight) must be adjusted downward to 

account for this factor.

The Pioneer Gypsum Mine, a subsidiary of D.L. Denman Construction of Las Vegas, began mining gypsum for 

cement manufacture and agricultural uses in 2001. The mine 

is located adjacent to the ACEC within the same inholding as 

the PABCO Gypsum mine. Production figures have not been 

published for this operation.

Although gypsum has been the main focus of mining 

in the Rainbow Gardens ACEC, the earliest mining operation was probably at the Frenchman mine, which produced 

minor amounts of copper in 1917 and 1918 (Longwell and 

others, 1965). Paul Watelet, a Belgian miner who managed 

Pacific Coast Gypsum and South Nevada Gold Mining, 

was purported to be the “Frenchman,” and these companies 

reported discoveries of gypsum and gold east of Las Vegas 

between 1905 and 1912. Clippings in the Nevada Bureau 

of Mines and Geology Las Vegas district file from 1912 to 

1914 indicate that the South Nevada Gold Mining Co. operated the Frenchman mine and report that the mill included a 

300-ton-per-day cyanide plant and that a shipment of metal 

to an assay office was made. The ruins of a mill stand on 

the site shown on topographic maps as the Frenchman mine, 

but no ore was noted there or nearby.

Figure 4. East Rainbow Gardens gypsum mine, looking south. 

Dark, resistant conglomerate of Thumb Member of Horse Spring 

Formation caps the gypsum and forms skyline. Sample AP-128 is 

from outcrop behind vehicle.

Figure 5. East Rainbow Gardens gypsum mine, looking north. 

Lava Butte is in background.

Figure 7. PABCO (Apex) Mine. Gypsite ore is conveyed to be 

washed, calcined, and made into wallboard and plaster at the 

plant in the background.

Figure 6. North Rainbow Gardens gypsum mine. The open pit 

was reclaimed in the middle 1990s after mining ceased in 1993.
I6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Mineral Deposits

Gypsum

Open-pit operations at the PABCO Gypsum mine (Apex 

mine) are within 1 km of the Rainbow Gardens ACEC in 

a large inholding in the ACEC. The gypsum forms a thick, 

relatively resistant cap on a gently south-dipping plateau. It is 

underlain by sandy redbeds of the Muddy Creek Formation. 

Drilling indicates that the thickness of the gypsum exceeds 35 

m in the vicinity of the mine (L. Ordway, PABCO mine manager, oral commun., 1997). The gypsum is generally covered 

by less than 2 m of sandy overburden and occurs in an area of 

13 km2 (Papke, 1987). Mineable reserves in this area are quite 

large, probably more than 400 million short tons. The gypsum 

ore mined by PABCO is transported from the open pit by 

conveyor belt and upgraded to gypsum suitable for plaster and 

wallboard production at a simple washing plant.

The ore mined by PABCO is generally friable and porous 

gypsite that consists of fine intergrown gypsum crystals with 

various amounts of admixed silt and sand. The gypsite is white 

to grayish orange or light greenish gray. Locally, it contains 

layers of fine-grained, sugary, compact gypsum. In places, 

relatively large selenite crystals or masses of crystals are present (Papke, 1987), and crystals as much as 20 cm long have 

been noted (Castor and others, 2000). Steeply dipping northwest-striking faults that probably have only minor amounts of 

offset are exposed in the pit.

The Pioneer Gypsum mine, also within 1 km of the 

ACEC boundary, exploits the same gypsum-bearing unit as the 

PABCO operation, and the gypsum appears to be of similar 

grade. The ore is shipped without processing for use in cement 

manufacture and agricultural applications.

Gypsum has been mined and prospected for at several 

sites within the Rainbow Gardens ACEC in the past, and gypsum prospect pits are common. The Permian-Pennsylvanian 

Pakoon Formation is the oldest unit that has been explored for 

gypsum. Other units that contain beds of relatively pure gypsum are the Toroweap, Kaibab, Moenkopi, and Horse Spring 

Formations. At the White Eagle mine, where the gypsum is in 

the lower redbed unit of the Moenkopi Formation, it is white 

to pale greenish yellow, as much as 35 m thick, and contains 

some silty interbeds. It was mined over a strike length of 

about 1,200 m from three pits, the largest of which is about 

370 m long and 60 m wide. Papke (1987) reported 78 percent 

gypsum in a sample from the White Eagle mine; however, a 

select sample taken for this study from the White Eagle mine 

contains nearly 88 percent gypsum (sample AP-131, table 1).

Gypsum was also mined from the Thumb Member of 

the Miocene Horse Spring Formation about 1 km east and 5 

km northeast of the White Eagle mine at the East Rainbow 

Gardens and North Rainbow Gardens areas (fig. 1). In the East 

Rainbow Gardens area, gypsum was mined from four pits over 

a strike length of about 1,500 m. The largest pit is about 550 m 

long and 30 m wide. A 25-m-long chip sample taken along the 

south end of the largest pit contains about 83 percent gypsum 

on the basis of chemical analysis (Sample AP–128, table 1; 

Ludington and others, 2005). In the North Rainbow Gardens 

area, site of the most recent gypsum mining within the ACEC, 

the gypsum-rich sequence is about 150 m wide and is apparently repeated by faulting and folding (Castor and others, 

2000). Gypsum mined from the North Rainbow Gardens area 

in the 1980s and 1990s was shipped crude (generally 87 to 92 

percent gypsum) for agricultural use or for use in cement. A 

select grab sample of gypsum taken from the North Rainbow 

Gardens mine for this study contains about 91 percent gypsum 

on the basis of chemical analysis (Sample AP–129, table 1; 

Ludington and others, 2005).

Mineral Resource Data System (MRDS) data (U.S. Geological Survey, undated) indicate that gypsum prospects occur 

in the Muddy Creek Formation to the north of the Rainbow 

Gardens ACEC and in the Kaibab Formation near Gypsum 

Cave. In addition, mining claim inholdings in the ACEC north 

of Gypsum Cave include gypsum prospects in the upper part 

of the Toroweap Formation. On the basis of our observations, the gypsum in the Toroweap occurs as relatively narrow, 

steeply south-dipping bodies, and only minor amounts of 

gypsum occur at Gypsum Cave.

Gypsum is abundant in the middle part of the Pakoon 

Formation, but this unit has only been the site of minor gypsum 

prospecting. Other gypsum-rich units in the area include the 

upper part of the Toroweap Formation, where resistant limestone is overlain by 10 to 30 m of gypsum, and the Harrisburg 

Member of the Kaibab Formation, which includes a gypsiferous sequence as much as 20 m thick (Castor and others, 2000). 

Harrisburg Member gypsum has been mined for many years at 

the Blue Diamond mine, about 30 km southwest of the Rainbow Gardens ACEC. In addition to gypsum in the lower redbed 

unit of the Moenkopi Formation, as at the White Eagle mine, 

abundant gypsum is also present in the Schnabkaib Member and 

upper redbed unit of the Moenkopi Formation.

Limestone

Relatively pure limestone suitable for use in Portland 

cement and possibly high-calcium lime occurs in the Rainbow 

Gardens ACEC but has not been mined. At Apex, about 9 km 

north of the ACEC, large amounts of high-calcium lime are 

produced annually from pure micritic limestone in the upper 

part of the Crystal Pass Member of the Sultan Formation. The 

fine-grained texture of this limestone is important, because 

more coarsely crystalline limestone decrepitates during 

calcination, making the production of lump lime impossible. 

Micritic carbonate is present in the unit in the Frenchman 

Mountain Quadrangle, but X-ray diffraction (XRD) analysis 

of a chip sample from this unit shows that it is dolomitic. No 

pure Paleozoic limestone is known to occur in the ACEC; the 

Paleozoic carbonate rocks there are either dolomitic, or contain interbeds of dolomite, sandy detritus, or minor to abundant chert (Castor and others, 2000).
Rainbow Gardens ACEC I7

Sample--------- AP-128 AP-129 AP-131 — — —

Location-------- Rainbow Gardens E Rainbow Gardens N White Eagle White Eagle Apex (PABCO) Blue Diamond

Unit------------- Horse Spring Horse Spring Moenkopi Moenkopi Muddy Creek Kaibab

Sample type--- chip select grab select grab grab grab grab

SiO2 5.89 0.86 0.24 1.53 9.43 0.33

Al2

O3 0.89 0.11 0.05 0.15 3.94 0.03

Fe2

O3 0.28 0.05 0.04 0.08 0.22 0.01

MgO 1.52 0.32 0.23 4.92 5.47 0.03

CaO 31.33 34.67 33.61 31.60 27.70 33.40

Na2

O 0.07 0.01 0.01 0.05 0.69 0.02

K2

O 0.39 0.04 0.04 0.15 0.68 0.02

LOI 21.2 21.2 20.4 14.8 13.2 18.3

CO2 1.46 0.22 0.62 10.40 9.20 0.02

SO3 38.48 42.23 40.98 36.50 29.40 48.10

Gypsum 82.57 90.61 87.93 78.33 63.09 103.22

Table 1. Composition of gypsum samples from the Rainbow Gardens ACEC compared with high-grade gypsum ore from the Blue 

Diamond mine and low-grade gypsum ore from the PABCO mine. 

[All data in weight percent. Gypsum = 2.146 x SO3. Data on White Eagle grab, Apex, and Blue Diamond samples are from Papke, 1987.]

The Bitter Ridge Limestone Member of the Horse Creek 

Formation may locally have potential for use as cement or highcalcium limestone. Regionally this unit contains large thicknesses of nearly pure high-calcium limestone. However, in the 

Rainbow Gardens ACEC, it is commonly interbedded with tuff, 

volcanic breccia, and sandstone (Castor and others, 2000), and 

is not as economically desirable as in other locations.

Lacustrine algal limestone in the Nellis basin in the 

northern part of the ACEC may be more desirable because it 

is relatively pure and could be easily mined. This limestone 

unit, mapped as part of the Muddy Creek Formation (unit Tml, 

Castor and others, 2000) is as much as 50 m thick in places, 

is nearly flat-lying, and is exposed over about 1.5 km2 in the 

ACEC. XRD analyses of this limestone indicate that it is nearly 

pure calcite, and the chemistry of a 35-m chip sample and a 

grab sample (samples AP-320 and AP-324, respectively, table 

2) indicates that it is suitable for Portland cement. However, its 

chemistry and the fact that it is relatively coarse grained, indicate that it is not suitable for high-calcium lime production. The 

limestone is also exposed extensively to the north of the ACEC.

Element AP-320 AP-324 Portland cement 

ore specification

High-Ca lime ore 

specification

SiO2 4.04 1.86 <1

Al2

O3 0.54 0.20

Fe2

O3 0.26 0.11

MgO 0.92 0.54 <1

CaO 52.40 54.32 ca. 50

Na2

O+K2O 0.22 0.12 <0.4

P2

O5 0.14 0.08

LOI 41.5 42.8

CaCO3 93.27 96.69 >95

MgCO3 1.92 1.13

total carbonate 95.19 97.82

Table 2. Comparison of some major element analyses of 35-m chip sample AP 320 and grab sample 

AP–324 (Rainbow Gardens ACEC) with Portland cement and high-Ca lime ore specifications.

[CaCO3 % calculated using CaO x 1.78; MgCO3 % calculated using MgO x 2.09. Portland cement specifications from 

Ames and others (1994). High-Ca lime ore specification from Stanley T. Krukowski (oral commun., 2005).]
I8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Lithium

A rise in lithium demand and consumption during 

the 1970s, driven by new uses coupled with concern about 

future availability for the production of deuterium, prompted 

significant lithium exploration by the U. S. Geological 

Survey. Exploration was mainly focused on modern playa 

deposits in Nevada and California, but deposits of older 

lithium-rich lacustrine sedimentary rocks were also studied. 

The upper part of the Lovell Wash Member of the Horse 

Spring Formation in the Frenchman Mountain quadrangle 

was found to contain a 40-m-thick section with average lithium content of 1,000 ppm (Brenner-Tourtelot and 

Glanzman, 1978; Brenner-Tourtelot, 1979). The presence 

of hectorite (Na0.3(Mg,Li)3Si4O10(F,OH)2), a trioctahedral 

lithium-rich clay mineral, was suspected.

Samples collected from the Lovell Wash Member in both 

the Frenchman Mountain and Henderson quadrangles were 

found to have lithium contents as high as 900 ppm on the 

basis of atomic absorption analyses at the Nevada Bureau of 

Mines and Geology Analytical Laboratory (Castor and others, 

2000). In addition, XRD analysis indicates that clay separates 

from one of these samples contains trioctahedral clay, and we 

concur that hectorite is probably present.

Sand and Gravel

The Sandia Aggregate sand and gravel pit (fig. 8) is in 

the northeastern part of the ACEC. It is about 2 km east of 

the PABCO Gypsum mine and is also operated by Pacific 

Coast Building Products, Inc. The pit is about 100 m by 800 

m in area and 30 m deep. The material mined is Quaternary 

alluvium that is mostly composed of pebble- to boulder-sized 

clasts of Paleozoic carbonate rock.

Silica

According to Longwell and others (1965), the Sunrise Mountain silica deposit, which is probably in the Aztec 

Sandstone, lies in or near the Rainbow Gardens ACEC. No 

production has been recorded from this deposit and its location 

is poorly known. The Sunrise Mountain silica deposits may 

be on Nellis Air Force Base to the north of the ACEC. No 

evidence of mining in Aztec Sandstone exposures were found 

during detailed mapping in the area (Castor and others, 2000). 

Analyses given in Hewett and others (1936) for Aztec Sandstone from a silica prospect in the Muddy Mountains indicate 

that the silica content, about 94 percent, is too low to meet 

specifications for glass sand. White Aztec Sandstone from 

Whitney Pocket in the Gold Butte area contains only about 89 

percent silica.

The silica-rich Coconino Sandstone occurs in places in 

the Rainbow Gardens ACEC; however, it is generally thin 

and occurs on steep slopes beneath thick Permian carbonate 

(Castor and others, 2000). One area in the ACEC contains 

Coconino Sandstone exposures as much as 70 m thick and 300 

m wide over a distance of 2 km.

Metal Mines and Prospects

Frenchman Mine.—The Frenchman Mine, the site of an 

old mill (fig. 9) at the western base of Frenchman Mountain 

near the western border of the ACEC, was credited with small 

production of oxidized copper ore in 1917 and 1918 (Longwell and others, 1965). No copper minerals were found when 

the site was visited for this study, and samples taken from 

waste piles and a limonitic breccia outcrop to the south contain 

less than 20 ppm Cu, along with low Ag, Pb, and Zn contents 

(Samples AP-126 and AP-127, Ludington and others, 2005).

Figure 8. Sandia Aggregates sand and gravel pit in the Rainbow 

Gardens Area of Environmental Concern. Pit is about 110 m wide 

and 800 m long.

Figure 9. Remains of a mill at the reported site of the Frenchman 

Mine. No sign of mining was noted here; ore was probably 

transported from a mine site to the north.
Rainbow Gardens ACEC I9

About 3 km north of the Frenchman Mine is a group of 

adits that follow a north-striking, steeply east-dipping breccia 

zone as much as 12 m wide that is cemented by carbonate, 

hematite, and copper minerals. This is the only occurrence of 

copper minerals noted during detailed mapping of the Frenchman Mountain quadrangle (Castor and others, 2000). Access 

to the adits is by pack trail from the valley floor to the west, 

and the authors suspect that these adits were the source of 

ore processed at the Frenchman mill site described above. 

The breccia zone locally forms a contact between vuggy pale 

orange dolomite and brown dolomite of the Nopah Formation. Examination of samples of this breccia by reflected light 

microscopy and scanning electron microscope (SEM) with 

energy-dispersive X-ray analysis (EDX) shows that the copper 

minerals include primary chalcopyrite, along with secondary chalcocite, covellite, cuprite, and malachite (figs. 10 and 

11). Tiny grains of a silver-bearing sulfide mineral are locally 

intergrown with the covellite and chalcocite. Samples from 

this site contain 0.7 percent to more than 1 percent copper and 

as much as 95 ppm silver, along with anomalously high Sb, 

As, Au, Hg, Mo, Ni, and Se (samples AP-345 and AP-345A, 

Ludington and others, 2005).

Uranium

A uranium prospect, the Little Hal, Steve Nos. 1 and 11 

claims, is reported near the west edge of the Rainbow Gardens 

ACEC. Garside (1973) describes the prospect as occurrences 

of anomalous radioactivity (six times background) associated 

with pegmatite dikes in Precambrian metamorphic rocks. The 

location in Precambrian host rocks puts it west of the ACEC. 

During detailed mapping (Castor and others, 2000), radioactivity as high as three times background was noted in similar 

rocks in the same general area. Interestingly, uranium contents 

as high as 139 ppm occur in copper-rich rock (sample AP345A, Ludington and others, 2005) from the adits described 

above, which are in the same general area. Uranium is associated with copper and base-metal deposits in carbonate rocks 

in the Goodsprings district about 50 km to the southwest; 

however, except for a shipment of five short tons of uranium 

ore from one mine, uranium occurrences there are very low 

grade (Garside, 1973).

Mineral Exploration and Development

The Rainbow Gardens ACEC contains 72 mining claims 

that are current as of 2005. Pacific Coast Building Products, Inc., holds 56 placer claims in sections 1, 12, and 13 

of T20S, R63E, just to the west of the company’s PABCO 

(Apex) mine. Bedded deposits of nonmetallic minerals, such 

as gypsum, are staked using placer claims. Several areas of 

claims that were presumably staked for gypsum are in the 

ACEC west of the PABCO mining area and claims. A group 

of four individuals holds three placer claims in section 14 of 

T20S, R63E, southeast of the PABCO claims near Gypsum 

Spring. Bingham’s Pride holds four placer claims in sections 

15 and 16 of T20S, R63E, west of Gypsum Spring. The Lima 

brothers hold seven placer claims in section 16 of T20S, 

R63E about 2 km west of Gypsum Spring. In addition, the 

Lima brothers hold eight claims in section 34 of T20S, R63E 

about 4 km to the south in the area of the north Rainbow 

Gardens gypsum pit.

Other small holdings within the ACEC include a single 

millsite claim held by Robert Dawson in section 2 of T20S, 

R63E, and a single claim held by J.L. Block in section 2 of 

T21S, R62E, in the east part of the ACEC near an abandoned 

sand and gravel pit.

Figure 10. Photomicrograph of chalcopyrite (pale yellow) partly 

replaced by chalcocite (bluish gray) surrounded by iron oxide, 

cuprite, and malachite. Cross-polarized light. Sample AP-345A.

Figure 11. Back-scattered scanning electron microscope 

image of sample AP-345A, showing silver-bearing sulfide (bright) 

in chalcocite (gray) with blades of covellite (darker gray). 

Surrounding dark areas are cuprite and iron oxide.
I10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Mineral Resource Potential

Locatable Minerals

Gypsum.—Parts of the Rainbow Gardens ACEC have 

high potential for gypsum deposits, with a high certainty level 

(tract RBG01, fig. 12). This tract contains extensions of the 

gypsum unit in the Muddy Creek Formation that is currently 

being mined at the PABCO and Pioneer Gypsum Mines. On 

the basis of present and past production and the existence of 

remaining gypsum resources, part of the Middle Miocene 

Thumb Member of the Horse Springs Formation has high 

potential, with moderate certainty (tract RBG02). Potential 

areas in this tract are a gypsum-rich unit mapped in the Thumb 

Member by Castor and others (2000). On the basis of past 

production and the presence of gypsum-rich beds (upper part 

of the Kaibab Formation and rocks in the lower part of the 

Moenkopi Formation), tract RBG03 has moderate potential 

with a moderate certainty level (fig. 12). The gypsum beds in 

tract RBG03 are generally lower in quality than those in tract 

RBG02, owing to the presence of silty interbeds. With the 

exception of the area including the North Rainbow Gardens 

mine (fig. 1), gypsum in tracts RBG02 and RBG03 occurs in 

relatively thin, moderately dipping deposits, and large volumes 

cannot be mined without extensive overburden removal. In 

parts of the Sunrise Mountain structural block north of the 

Boulevard Fault (fig. 1), the rock units are segmented by abundant faults into small blocks that render commercial gypsum 

mining unlikely.

Other units that have been explored, but not mined for 

gypsum in the ACEC, are the late Paleozoic Pakoon, Kaibab, and Toroweap Formations. In most of the ACEC, these 

Mesozoic and Paleozoic units are moderately dipping and 

the gypsum deposits, which are as much as 30 m thick, have 

been explored with narrow pits. More extensive mining would 

require removal of significant amounts of overburden, rendering the relatively low-value gypsum noncommercial. For 

instance, the upper part of the Toroweap Formation contains 

gypsum beds as much as 30 m thick. However, this gypsum is 

typically sandwiched between thick resistant carbonates of the 

Toroweap and the overlying Kaibab Formation, and thus only 

small amounts of gypsum could be mined by open pit methods 

without prohibitively expensive overburden removal. The three 

active gypsum mines in the Las Vegas area—PABCO (Apex), 

Blue Diamond, and Pioneer—exploit relatively flat-lying gypsum deposits that require removal of little or no overburden. 

Presumably, Fibreboard Paper Products moved its gypsum 

mining operations from the Rainbow Gardens area to the 

PABCO (Apex) location to reduce mining costs and to ensure 

long-term reserves.

Limestone.—An area underlain by limestone in the north 

part of the ACEC is considered to have high potential for the 

limestone deposits for cement production, with a moderate 

level of certainty (tract RBG04, fig. 12). Although the chemical composition of this limestone has not been directly determined, XRD analyses indicate that it is nearly pure calcium 

carbonate. Similar lacustrine limestone is mined by Nevada 

Cement Company for cement production in northern Nevada 

(Hardy and others, 2004). Other limestone units in the area are 

considered to have low potential because they are dolomitic or 

contain other impurities.

Lithium Clay.—An area underlain by lithium-rich 

sedimentary rocks in the Lovell Wash Formation is judged to 

have moderate potential as a source of lithium clay (hectorite), with a low certainty level (tract RBG05, fig. 12). 

The presence of such clay in the area has been established, 

but the size and purity of possible deposits are unknown. 

The potential for the production of lithium chemicals is 

considered to be low. Modern lithium production comes 

almost exclusively from brines pumped from beneath playas 

(Kunasz, 2005). Lithium extraction from such brine deposits 

is very inexpensive, and it is unlikely that other sources will 

be developed in the near future.

Silica.—An area in the north part of the Rainbow Mountains ACEC contains large exposures of Coconino Sandstone 

as much as 70 m thick; elsewhere in the area the unit is thinner 

(Castor and others, 2000). The sandstone is similar to that 

in the Arden ACEC; however, Coconino Sandstone deposits 

in the Rainbow Gardens ACEC constitute a much smaller 

resource and commercial potential is low. On the basis of 

analyses from other areas, potential for commercial silica 

deposits in the Aztec Sandstone in the Rainbow Gardens 

ACEC is also low.

Metals.—Although copper and silver minerals occur in 

a breccia zone on the west flank of Frenchman Mountain, the 

potential for hydrothermal base- or precious-metal deposits in 

the ACEC is low.

Detailed geologic mapping in the area did not reveal other 

occurrences of mineralized rock, and there is nothing distinctive 

about the geologic environment of the single occurrence that 

would suggest the presence of undiscovered deposits.

Although anomalous radioactivity was noted in Precambrian rocks west of the Rainbow Gardens ACEC, and anomalously high uranium occurs with copper minerals near the west 

edge of the ACEC, the area is considered to have low potential 

for uranium deposits.

Leasable Minerals

The area is not within the regions considered by the BLM 

to be prospectively valuable for oil and gas (Smith and Gere, 

1983). A single oil exploration hole, McAuley Associates 

No. 2, was drilled in 1953 to 691 m inside the ACEC near its 

western border (fig. 1). No geologic data are available, and 

it was reported as a dry hole by Garside and others (1988). 

Another dry hole, was drilled to 915 m about 1 km west of the 

ACEC. Muddy Dome No. 1 was drilled by Rosen Oil Co. in 

1965 to a depth of 1,662 m about 5 km east of the ACEC. This 

hole targeted the Gale anticline, a feature mapped in the Gale 

Hills block by Longwell and others (1965). The hole was col-
Gypsum

Gypsum

Lithium

Gypsum

Limestone

RGB01

RGB04

RGB03

RGB03

RGB03

RGB03

RGB03

RGB02

RGB02 RGB05

RAINBOW GARDENS ACEC

High mineralresource potential

Mineral Potential

Moderate mineralresource potential

Tract ID Deposit Type Potential Level 

RGB01 Gypsum High RGB02 Gypsum High 

RGB03 Gypsum Moderate 

RGB04RGB05 Lithium Moderate 

Limestone High 

115°0'0"W 114°52'30"W

36°7'30"N36°15'0"N

Scale 1:24,000

0123

0.5

Figure 12. Mineral resource potential tracts for gypsum, limestone, and lithium resources in the Rainbow Gardens Area of Critical Environmental Cooutlined in pink).
I12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

lared in Jurassic sandstone and bottomed in the Permian Supai 

Formation. No oil and gas shows were reported, but fresh- and 

salt-water zones were noted at depth.

There is no indication of potential for brine or evaporite deposits of sodium or potassium. The Rainbow Gardens 

ACEC contains no known deposits of other leasable minerals, 

and the potential for their occurrence is low.

Salable Minerals

Crushed Stone.—High quality stone is confined to the 

Cambrian Nopah Formation, the Devonian Crystal Pass 

Member of the Sultan Formation, and the Permian Pakoon 

Limestone. These units contain less chert than other Paleozoic 

carbonate rocks. Together, they constitute tract ARBG01 (fig. 

13), which has high potential for deposits of crushed-stone 

aggregate, with a moderate level of certainty.

Lower quality stone is characterized by chert-bearing 

carbonate rocks, and including the Cambrian Muav Limestone, Cambrian Frenchman Mountains Dolomite, Mississippian Redwall Limestone, and Permian Kaibab Formation. 

Portions of the Horse Spring Formation that are composed of 

conglomerate, sandstone, limestone, and volcanic rocks can 

also be considered in this category. These rocks constitute tract 

ARBG03 (fig. 13), which has moderate potential for deposits 

of crushed-stone aggregate, with a moderate level of certainty.

Triassic sedimentary rocks, Tertiary rocks of the Muddy 

Creek Formation, and gypsiferous and brecciated units of 

the Thumb Member of the Miocene Horse Spring Formation represent the lowest quality material, due to their friable 

nature, lack of thick sandstone and conglomerate units, and 

the presence of gypsum. These rocks constitute tract ARBG02 

(fig. 13), which has low potential for deposits of crushed-stone 

aggregate, with a low level of certainty.

Sand and Gravel.—All the unconsolidated material in 

the Rainbow Gardens ACEC has high potential for sand and 

gravel aggregate deposits, with a high degree of certainty (tract 

ARBG04, fig. 13). Clasts in the most extensive and highest 

quality sand and gravel deposits are mainly carbonate rocks, 

and are in the southern and eastern part of the ACEC. The 

southern deposits are alluvial fans and are ideally situated to 

provide aggregate materials to the growing Las Vegas Valley. 

These materials are mostly carbonate rocks. The sand and 

gravel in the eastern part of the ACEC is mostly eroded from 

Miocene and Triassic deposits and may not perform as well in 

construction applications as aggregate supplied from the fans 

in the south.

References

Ames, J.A., Cutcliffe, W.E., and MacFadeyn, J.D., 1994, 

Cement and cement raw materials, in Carr, D.D., ed., Industrial minerals and rocks: Littleton, Colorado, Society for 

Mining, Metallurgy and Exploration, p. 295–316.

Anderson, R.E., 1973, Large-magnitude late Tertiary strikeslip faulting north of Lake Mead, Nevada: U.S. Geological 

Survey Professional Paper 794, 18 p.

Bell, J.W., and Smith, E.I., 1980, Geologic map of the Henderson Quadrangle, Nevada: Nevada Bureau of Mines and 

Geology Map 67, scale: 1:24,000.

Bingler, E.C., 1977, Las Vegas SE folio geologic map: Nevada 

Bureau of Mines and Geology Map 3Ag, scale: 1:24,000.

Bohannon, R.G., 1984, Nonmarine sedimentary rocks of Tertiary age in the Lake Mead region, southeastern Nevada and 

northwestern Arizona: U.S. Geological Survey Professional 

Paper 1259, 72 p.

Brenner-Tourtelot, E.F., 1979, Geologic map of the lithiumbearing rocks in parts of the Frenchman Mountain and 

Henderson Quadrangles, Clark County, Nevada: U.S. Geological Survey, Miscellaneous Field Studies Map MF-1079, 

scale 1:24,000.

Brenner-Tourtelot, E.F., and Glanzman, R.K., 1978, Lithiumbearing rocks of the Horse Spring Formation, Clark County, 

Nevada: Energy, v. 3, p. 255-262.

Castor, S.B., 1994, Industrial minerals, in The Nevada Mineral 

Industry, 1993: Nevada Bureau of Mines and Geology Special Publication MI-1993, p. 31-34.

Castor, S.B., Faulds, J.E., Rowland, S.M., and dePolo, C.M., 

2000, Geologic map of the Frenchman Mountain Quadrangle, Cark County, Nevada, Nevada Bureau of Mines and 

Geology Map 127, scale 1:24,000.

Deubendorfer, E.M., 2003, Geologic map of the Government 

Wash 7.5’ Quadrangle: Nevada Bureau of Mines and Geology Map 140, scale: 1:24,000.

Deubendorfer, E.M., and Black, R.A., 1992, Kinematic role of 

transverse structures in continental extension—an example 

from the Las Vegas Valley shear zone, Nevada: Geology, v. 

20, p. 1107-1110.

Garside, L.J., 1973, Radioactive mineral occurrences in 

Nevada: Nevada Bureau of Mines and Geology, Bulletin 81, 

121 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Hardy, S., Elgby, B., and Bryan, D.P., 2004, Nevada Cement 

Company plant and raw materials, Fernley, Nevada, in S.B. 

Castor, K.G. Papke, and R.O. Meeuwig, Proceedings of the 

39th Forum on the Geology of Industrial Minerals: Nevada 

Bureau of Mines and Geology Special Publication 33, p. 

114-123.

Hewett, D.F., Callaghan, E., Moore, B.N., Nolan, T.B., Rubey, 

W.W., and Schaller, W.T., 1936, Mineral resources in the 

region around Boulder Dam: U.S. Geological Survey Bulletin 871, 197 p.
Figure 13. Mineral resource potential tracts for aggregate resources in the Rainbow Gardens Area of Critical Environmental Concern (ACEC; outline

ARBG04

ARBG03

ARBG04

ARBG02

ARBG03

ARBG04

ARBG02

ARBG02

ARBG02

ARBG02

ARBG03

ARBG03

ARBG02

ARBG03

ARBG01

ARBG04

ARBG02

ARBG04

ARBG01

Tract ID Commodity Type Potentia

ARBG01 Crushed Stone High ARBG02 Crushed Stone Low ARBG03 Crushed Stone ModARBG04 Sand and Gravel High 

Aggregate assessm

crushed stone,highcrushed stone,lowcrushed stone,moderatesand and gravel,highsand and gravel,lowsand and gravel,moderate

Aggregate

Potential

115°0'0"W 114°52'30"W

36°7'30"N

36°15'0"N

Scale 1:24,000

024

1

RAINBOW GARDENS ACEC
I14 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Kunasz, I.A., 2005, Lithium in brines, in Rhoden, H.N., 

Steininger, R.C., and Vikre, P.G., eds., Window to the 

World: Geological Society of Nevada Symposium, 2005, 

Reno, Nevada, p. 1251-1258.

Longwell, C.R., 1974, Measure and date of movement on Las 

Vegas Valley shear zone, Clark County, Nevada: Geological 

Society of America Bulletin, v. 85, p. 985-990.

Longwell, C.R, Pampeyan, E.H., Bower, B., and Roberts, 

R.J., 1965, Geology and mineral deposits of Clark County, 

Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 

218 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Matti, J.C., Castor, S.B., Bell, J.W., and Rowland, S.M., 1993, 

Geologic map of the Las Vegas NE Quadrangle: Nevada 

Bureau of Mines and Geology Map 3Cg, scale 1:24,000.

Papke, K.G., 1987, Gypsum deposits in Nevada: Nevada 

Bureau of Mines and Geology Bulletin 103, 26 p.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, scale 1:500,000.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.

U.S. Geological Survey, undated, Mineral Resources Data 

System (MRDS): [http://tin.er.usgs.gov/mrds/].

Wayland, R.G., Oberlindeerler, P., Throckmorton, M., and 

Crowby, J., 1980, Lands valuable for sodium and potassium, 

Nevada: U.S. Bureau of Land Management, prepared by the 

U.S. Geological Survey, Conservation Division, Western 

Region, map, scale 1:500,000.

Wernicke, B., Axen, G.J., and Snow, J.K., 1988, Basin and 

Range extensional tectonics at the latitude of Las Vegas, 

Nevada: Geological Society of America Bulletin, v. 100, p. 

1738-1757.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter J. Mineral Resource Potential of the River Mountains 

Area of Critical Environmental Concern, Clark County, Nevada

By Steve Ludington, Stephen B. Castor, Brett T. McLaurin, and Kathryn S. Flynn

Summary and Conclusions

The River Mountains Area of Critical Environmental 

Concern (ACEC) contains occurrences of altered and mineralized volcanic rocks that are similar to epithermal preciousmetal deposits. An area in the southern part of the ACEC, 

near Railroad Pass and Boulder City, Nevada, has moderate 

potential for the occurrence of undiscovered epithermal precious-metal deposits. The results of historical exploration 

and geochemical studies made for this report indicate that the 

exposed occurrences do not have high enough precious-metal 

concentrations to encourage development.

Until the 1960s, there was extensive mining of manganese at the north end of the ACEC. These deposits are not now 

viable, and there is only low potential for the occurrence of 

undiscovered sedimentary manganese deposits.

Potentially commercial perlite occurs in the northeast 

part of the ACEC. There are current mining claims staked for 

perlite, and a small area has high potential for the occurrence 

of perlite deposits.

There is no potential for the occurrence of other deposits 

of locatable or leasable minerals.

The River Mountains ACEC has areas of high, moderate, and low potential for the occurrence of crushed-stone 

aggregate deposits, and areas of high and low potential for the 

occurrence of sand and gravel aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

of these lands.

The River Mountains ACEC was studied in the field to 

confirm descriptions of the geology that were gleaned from 

the scientific literature. Numerous samples were collected 

and analyzed.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The River Mountains ACEC is southeast of Las Vegas, 

directly east of the city of Henderson and northwest of Boulder City. It is reached from city streets and paved roads that 

surround it, as well as by hiking and bicycle trails that enter 

the area from the Bootleg Canyon road, at the southeast corner 

of the ACEC. A loop trail, under development, will skirt the 

south and west sides of the ACEC (http://www.rivermountainstrail.com). A legal description of these lands is included in 

appendix 2.

Physiographic Description

The River Mountains consist of a series of low mountains 

whose ridgelines trend north-northwest, parallel to normal 

faults in the area. Elevations range from about 750 m at the 

foot of the mountains to a little more than 1,100 m on the 

highest peaks. 

Geologic Setting

The River Mountains are in the central Basin and Range 

Physiographic Province, generally characterized by northtrending mountain ranges and intervening valleys, and lie 

between the Sevier orogenic belt and the Colorado Plateaus. 

The area underwent large-magnitude extension in the middle 

to late Miocene, and it lies directly north of the Colorado 

River extensional corridor (Deubendorfer and others, 1998). 

The rocks exposed in the River Mountains form part of an 
J2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Tvy

Qu

Qu

Tvy

Ti

Tsy

Tsy

Qu

Tvo

Tvy

Tsy

Tvo

Ti

Qu

Ti

Tvy

Tvy

Qu

Tvy

Tsy

Tvy

Tvo

Ths

Tvy

Ti

Tvy

Tvy

Tvy

Tvy

Tvo

Ths

Ti

Tvy

Ti

Tvy

ALUNITE

MINE

GOLD

PROSPECTS

RED CHIEF

CLAIM (Mn)

THREE KIDS

MINE (Mn)

FANNIE RYAN

DEPOSIT (Mn)

area of perlite

prospects

MANGANESE

PROSPECTS

EBONY QUEEN

PROSPECT (Mn)

RAILROAD PASS DEPOSIT

AP-239

AP-235

AP-233,

233B, 233C

AP-229

AP-227

AP-225

AP-222

AP-219 AP-216

AP-215

AP-214

AP-152

AP-212

AP-182 AP-184

AP-178

AP-177

AP-168

AP-165 AP-164

AP-146

AP-138

AP-136

AP-135

AP-243A,B

AP-142B

AP-186

RIVER MOUNTAINS

ACEC

114°52'30"W

36°0'0"N

GoldButteACE

Scale1:24,00

01234 0.5

Kilometers

to Las Vegas

Figure 1. Generalized geology of the River Mountains Area of Critical Environmental Concern (ACEC), showing mines, 

prospects, and locations of analyzed samples. Geology modified from Stewart and Carlson (1978), Anderson (1977), Bell and 

Smith, (1980), and Smith (1984). See explanation on page 3.
River Mountains ACEC J3

extensive group of middle Tertiary volcanic rocks that extend 

west into the Mojave Desert of California and south into western Arizona (Smith, 1982, 1986a, b).

Geology

The rocks in the River Mountains consist of a series of 

primarily intermediate-composition volcanic and intrusive 

rocks. These rocks are portrayed on a series of three geologic 

maps (Anderson, 1977; Bell and Smith, 1980; Smith, 1984) 

Figure 1. Continued.

Qu

contact, certain

EXPLANATION

fault, certain

fault, approximate

fault, concealed

mine or prospect

sample site, with sample number AP-001

Tsy

Ths

Tvo

Tvy

Ti

Undivided surficial deposits (Pleistocene and 

Holocene)—Alluvium, colluvium, lake, playa, 

landslide, terrace, and eolian sand deposits

Young sedimentary rocks (middle Miocene to 

Pliocene)—Alluvial, lacustrine,and fluvial 

deposits. Locally includes minor amounts of 

tuff. Includes mostly Muddy Creek Formation

Horse Spring Formation (Miocene)—Tuffaceous 

sedimentary rocks; includes some volcanic 

rocks, sandstone, limestone, and gypsum

Intrusive rocks (Miocene)—Aphanitic and 

porphyritic rocks ranging in composition from 

granodiorite to granite

Young volcanic rocks (middle and upper 

Miocene)—Rhyolite, andesite, and basalt lava 

flows, tuff, and tuffaceous sediments; consists 

of volcanic rocks of Bootleg Wash, Powerline 

Road, and unnamed younger rhyolites and 

basalts

Older volcanic rocks (middle Miocene)—Rhyolite 

andesite, and basalt lava flows, volcanic 

breccias, and pyroclastic rocks; consists of

volcanic rocks of Red Mountain and volcanic 

rocks of River Mountains volcano. Both rock 

sequences are strongly altered and oxidized

that were used to help compile the simplified geologic map 

presented in figure 1.

The oldest group of rocks has been termed the volcanic rocks of River Mountains by Smith (1986a). This group 

consists of a central intrusion and a sequence of andesites that 

form the flanks of the volcano. The age of the central pluton is 

between 13.4 and 12.8 Ma. West of the main outcrop area of 

this River Mountains volcano is an area underlain by strongly 

altered and oxidized rocks. The original composition of many 

of these rocks is uncertain, but they were probably primarily dacites. These rocks, termed the volcanic rocks of Red 

Mountain by Bell and Smith (1980) and Smith (1984), may be 

the strongly altered distal equivalents of the rocks of the River 

Mountains volcano.

A second episode of volcanism produced the volcanic 

rocks of Bootleg Wash (undated), which are found only in a 

small outcrop area in the southern part of the River Mountains 

and consist primarily of andesite and dacite. Succeeding these 

rocks is a widespread sequence of dacite and andesite domes 

and flows termed the volcanic rocks of Powerline Road (also 

undated). Capping the sequence are rhyolites and alkali basalts 

dated at 12.1 Ma. Each of these four groups of rocks appears 

to be fault bounded (Smith, 1986a).

Smith and others (1990) and Metcalf and others (1993) 

studied the petrology of these volcanic rocks and found the 

andesites and dacites to contain between about 54 and 67 percent silica. They proposed that the rocks formed by mixing of 

mantle- and crustal-derived magmas, aided by crystal fractionation. They are fundamentally calc-alkaline, although some 

show elevated potassium contents that are believed to be the 

result of potassium metasomatism. Several of the rock units 

commonly contain abundant basaltic inclusions.

All these volcanic rocks are cut by an extensive series of 

north-northwest-trending normal faults that dip primarily to 

the east. In detail, the dips of the volcanic rocks are variable, 

and many of the rocks show no clear bedding features. This 

structure is thought to be the result of transport and extension 

related to the west-dipping Saddle Island detachment fault that 

underlies the River Mountains and McCullough Range (Weber 

and Smith, 1987). This fault is part of the Lake Mead Fault 

Zone, and the original position of the River Mountains was 

apparently tens of kilometers to the east-northeast (Deubendorfer and others, 1998).

The volcanic rocks of Red Mountain are very distinctive 

on satellite images. This is a result of hydrothermal alteration that has added silica, potassium, and sulfate to the rocks. 

X-ray diffraction studies of samples from this region show 

that many of the rocks have been altered to mixtures of quartz, 

sericite/illite, and alunite.

At the northern end of the ACEC, in the vicinity of the 

Three Kids Mine, a limited amount of tuffaceous sedimentary 

rock belonging to the Horse Spring Formation is found above 

and interlayered with the Miocene volcanic rocks.

All these rocks are overlain by younger sedimentary 

rocks of the Muddy Creek Formation, and by Quaternary 

deposits.
J4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Mining History

Gold and alunite were discovered by R.T. Hill at the 

southern end of the River Mountains in 1908. The hydrothermal 

alteration was recognized to be similar to that in the Goldfield 

district, and initial expectations were high for the discovery of 

important gold deposits. However, exploration failed to discover 

high-grade gold ore. Sporadic attempts to mine deposits here, 

in what became known as the Alunite (or Railroad Pass) district 

occurred into the 1930s, but the total production of gold was 

probably not much more than 1,000 ounces, and attempts to 

recover alunite also proved unsuccessful. The principal mine, 

known as the Quo Vadis, is about 9 km southwest of the ACEC. 

However, other deposits, including the Alunite Mine and the 

Railroad Pass deposit, are located within 2 km of the ACEC, 

just north of U.S. highways 93 and 95, at Railroad Pass (fig. 

1). Information about the history of the Alunite district is from 

Vanderburg (1937) and Longwell and others (1965).

Several manganese deposits were discovered in Clark 

County during World War I, when there was a rush of prospecting caused by wartime needs for manganese. The Three 

Kids Mine, which is located at the north end of the River 

Mountains ACEC (fig. 1), was active intermittently from 1917 

until 1952. Low-grade manganese ore was also produced from 

unnamed deposits immediately west of the Three Kids Mine, 

and total production until the end of mining in 1961 exceeded 

2,000,000 short tons of ore that yielded about 300,000 short 

tons of manganese. Most of the ore was mined and sold under 

contract to the U.S. General Services Administration at a price 

substantially above the world market price. The Ebony Queen 

prospect is about 1 km east of the ACEC, about 3 km west 

of Boulder City. This deposit is a vein, a few hundred meters 

long, and about 1 to 3 m in width. It was initially explored 

about 1925, but no manganese was produced. Other manganese occurrences in and near the River Mountains and south 

of Boulder City have been explored, but ore was not found. 

Information about the history of the manganese deposits is 

from Vanderburg (1937) and Longwell and others (1965).

Advanced Mining LLC submitted a plan of operations 

to the BLM for the Dawson perlite claims located east of 

Henderson in the northern part of the River Mountains ACEC 

(fig. 1) in September 2000. The plan called for taking bulk 

samples for testing, and mining at 50,000 short tons per year 

was planned if test results were positive (Castor, 2001). More 

recent information on the project has not been received, and 

no sign of mining or prospecting activity was noted when the 

area was visited in early 2005. The claims were active as of 

November 2005.

Mineral Deposits

Two important types of metallic mineral deposit occur in 

and near the River Mountains ACEC. They are the gold deposits related to quartz-alunite alteration in the Alunite (Railroad Pass) district, and the manganese deposits that occur in 

sedimentary rocks of the Horse Spring Formation and volcanic 

rocks of the River Mountains. Perlite of possible commercial 

value also occurs in the volcanic rocks of the River Mountains.

Epithermal Gold Deposits

The old workings at Railroad Pass are on the southwestern margin of a large area of altered volcanic rock that extends 

east and north from Railroad Pass. These rocks crop out 

prominently in the southeastern corner of the River Mountains 

ACEC (fig. 2). The combination of scattered high preciousmetal values, locally anomalous amounts of Bi, Te, and Sn, 

and widespread altered quartz-alunite rock suggests that this 

area can be best classified as a high-sulfidation epithermal precious-metal deposit.

The color patterns in figure 2 were generated using 

Advanced Spaceborne Thermal Emission and Reflection 

(ASTER), which is a 14-band multispectral satellite imaging system (Rowan and others, 2003). The composite color 

image uses the ratio of ASTER bands 7 (2.235–2.285 μm) and 

6 (2.185–2.225 μm). Ground-truth comparisons of the areas 

colored intense pink in the image, both here in the southern 

River Mountains and farther south, in the Searchlight district, 

suggest that this color commonly indicates pervasive quartzalunite alteration.

The altered rocks, which appear in visible light as various 

shades of red, yellow, and orange because of fine-grained ironoxide minerals (fig. 3), correspond closely with rocks mapped 

by Anderson (1977), Bell and Smith (1980) and Smith (1984) 

as intensely altered and oxidized volcanic rocks. The altered 

rocks may be part of a hydrothermal system related to the 

River Mountains volcano of Smith (1982) or to the Boulder 

City pluton, dated by Anderson and others (1972) at 13.8 Ma. 

Of 34 samples analyzed using X-ray diffraction (XRD), 12 

were found to contain sericite/illite, 10 alunite (fig. 4), two 

kaolinite/dickite, and one pyrophyllite. In places, the altered 

rock contains barite±gypsum veins (sample AP-182, fig. 3; 

fig. 5) and breccia cemented by gypsum+pyrite. Green copper 

oxide minerals occur locally. The strongest alteration generally 

occurs along faults (fig. 6) or resistant silica ledges (fig. 7).

Figures 1 and 2 show the location of rock samples collected during this study that were geochemically analyzed for 

a variety of elements related to hydrothermal mineralization 

(Ludington and others, 2005). Of 33 samples analyzed, all 

but 2 show evidence of sulfur enrichment. Twenty of the 33 

samples are at least moderately anomalous in Ag, As, Bi, Cd, 

Cu, Mo, Pb, Sb, Sn, Te, Tl, W, or Zn. Five samples are highly 

anomalous: AP-184 (Ag, Bi, Cu, Mo, Zn), AP-233B (Cu, Zn), 

AP-182 (Mo, Pb), AP-275 (Ag, Pb), and AP-282 (Cu). Only 

three samples have been analyzed for gold, and they yielded 

background values (1–7 parts per billion, ppb). One sample 

reported by Smith and Tingley (1983) from dumps at the Alunite Mine (fig. 1) contains 0.1 parts per million (ppm) Au and 

<0.5 ppm Ag, and their sample 1327 (fig. 1) contains 0.5 ppm 

Au and 1 ppm Ag. None of these anomalous samples contain 
River Mountains ACEC J5

Figure 2. ASTER image (ratio of bands 7/6) of southern part of the River Mountains Area of Critical Environmental Concern (ACEC; 

outlined in pink). Red color indicates quartz-alunite alteration. See text for details.

RIVER MOUNTAINS ACEC

ALUNITE MINE

GOLD PROSPECTS

EBONY QUEEN DEPOSIT

(Mn)

RAILROAD PASS DEPOSIT

Boulder

City

U.S. 93

U.S. 95

AP-239

AP-235

AP-233, 233B, C

AP-229AP-227,

227B

AP-225

AP-222

AP-219

AP-216

AP-215

AP-214

AP-212

AP-182 AP-184

AP-178

AP-177,

177B

AP-168

AP-165

AP-164 AP-152

AP-149

AP-146

AP-138 AP-136

AP-135

AP-243A, B

AP-142A, B

geochemical

sample,with

sample number

mine or prospect

AP-146

114°52'30"W

36°

00'

00"N

Gold Butte ACEC

Scale 1:24,000

01234 0.5

Kilometers

Figure 3. Altered and mineralized rocks within the River 

Mountains ACEC in foreground. Cascata golf course is below, and 

Boulder City is in the distance.

Figure 4. Nearly pure alunite in quartz-alunite rock (sample AP216), 1.6 km south of the River Mountains ACEC. Horizontal field 1.3 

mm. Cross-polarized light.
J6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 5. Barite + hematite vein cut by fibrous gypsum (sample 

AP-182) from a prospect 2 km south of the River Mountains ACEC. 

Horizontal field about 2.5 mm. Cross-polarized light.

Figure 7. Resistant west-trending ledge of altered rock at 

location AP-132, about 0.5 km east of the River Mountains ACEC. 

The resistant rock consists mostly of quartz, with lesser feldspar 

and jarosite.

Figure 6. Mineralized northeast-striking, northwest-dipping fault 

within the River Mountains ACEC near sample site AP-138. Altered 

rock in this area contains quartz, pyrite or limonite, feldspar, and 

minor alunite.

values indicative of commercially viable precious-metal ore; 

however sample AP-184 contains nearly 7 percent copper.

The area that is strongly altered and mineralized has an 

extent of more than 10 km2, about a third of which is within 

the River Mountains ACEC (fig. 2). Most of the highly anomalous samples come from an area between US Highway 93 and 

the ACEC boundary, in and near Boulder City. Alteration and 

mineralization produced alunite-rich rock that is well exposed 

in an abandoned railroad cut, as well as at scattered prospects 

and adits. These workings expose barite+hematite+gypsum 

veins and, locally, copper oxide minerals. This area along U.S. 

93 seems to be the most prospective for precious-metal deposits. However, the hydrothermally altered area extends northward into the ACEC, and rock with anomalous metal contents 

(sample AP-233A, fig. 1, fig. 8) occurs there in association 

with barite veins; silicified, limonitized, and locally alunitebearing structures; and a few prospect pits.

Sedimentary Manganese Deposits

The manganese deposits at the Three Kids Mine and 

nearby unnamed deposits (fig. 1) consist of local accumulations of manganese oxides in tuffaceous siltstone, sandstone, 

conglomerate, and tuff of the Miocene Horse Spring Formation. According to Longwell and others (1965), the manganese occurs primarily as wad (hydrous manganese oxides), 

but psilomelane, pyrolusite, and manganite (Mn3+O(OH)) are 

also reported. In places, the wad is opalized. The manganese 

minerals occur mixed with clastic grains and tuffaceous and 

gypsiferous material. These accumulations form lenticular 

pods that vary in size and grade and occur in a syncline that 

has been deepened by graben faulting at the north end of the 

River Mountains, adjacent to underlying (but structurally 

higher) volcanic rocks (Hewett and Weber, 1931).

More modern studies have shown that the mineralized 

rock consists of transported clasts of colloform manganese 
River Mountains ACEC J7

Figure 8. Altered and mineralized rocks at the south end of 

the River Mountains. In the background, the right half of the 

photograph shows rocks within the River Mountains ACEC.

oxide (todorokite [(Mn,Mg,Ca,Ba,K,Na)2Mn3O12•3H2O] and 

coronadite [Pb(Mn4+,Mn2+)8O16]), manganese-oxide cement 

(pyrolusite), and manganese-oxide cavity infillings (cryptomelane [K(Mn4+,Mn2+)8

O16] and coronadite) (Koski and 

others, 1988).

In addition to manganese, the rocks in the deposit contain 

trace amounts of iron, lead, copper, silver, and gold, some 

of which were occasionally recovered during ore processing 

(Longwell and others, 1965).

The characteristics of the deposits suggest that manganese minerals were deposited from oxidized, low-temperature 

fluids in contact with unconsolidated clastic sediment on and 

below the floor of stratified saline lakes. Strontium isotopic 

ratios of evaporite and limestone that are interbedded with the 

manganese deposits are consistent with a lacustrine depositional environment (Koski and others, 1988). Radiometric ages 

of interbedded tuff units range from about 14 Ma to 12.4 Ma, 

about the same age as the volcanic flow rocks adjacent to the 

south (Koski and others, 1990) and as Horse Spring Formation 

rocks in the Frenchman Mountain area to the north (Castor and 

others, 2000). The deposits are thus of syngenetic origin, and 

their ultimate source was probably hot springs related to local 

volcanic activity (Hewett and Weber, 1931; Hewett, 1933).

Perlite Deposits

Perlite occurs in a moderately to steeply northwest-dipping tabular body about 20 m wide in the northeastern part of 

the River Mountains ACEC (fig. 1). This perlite is probably 

part of the deposit that has been staked as the Dawson perlite 

claims. It contains minor amounts of feldspar, quartz, and 

biotite phenocrysts, and the upper part of the body contains 

as much as 20 percent devitrified rhyolite in the form of 

spherulites. The perlite is light gray (fig. 9) and is of rhyolitic 

composition with more than 70 percent SiO2 (sample AP-186, 

Ludington and others, 2005). It is contained within devitrified 

to glassy pumiceous rhyolitic flow rock, which is overlain to 

the northwest by basaltic andesite flows and debris flows. The 

perlite is mapped within the dacitic volcanic rocks of Powerline Road. Bell and Smith (1980) reported spherulitic and 

perlitic dacite in the area of the Dawson perlite claims.

Properties of a select grab sample of the perlite were 

measured by the New Mexico Bureau of Geology and Mineral 

Resources. The results of these tests indicate that the perlite 

sample has relatively high furnace yield, moderate expanded 

density, and on expansion yields a moderate amount of sinks 

(sample AP-186, table 1). The expanded perlite has relatively 

low brightness and large particle size. The test results indicate 

that it compares favorably with perlite from the Mackie Mine, 

which is an active operation in Lincoln County, Nevada, that 

produces expanded perlite mostly sold in horticultural markets. On the basis of the testing, perlite from the River Mountains is less suitable for many markets than perlite from the 

highly productive No Agua, New Mexico deposits. However, 

the testing procedure is specifically designed for optimum performance of the No Agua perlite, and better results might be 

obtained for perlite from the River Mountains using different 

temperature and feed particle size.

Figure 9. Perlite outcrop in the northeastern part of the River 

Mountains ACEC. Sample AP-186 was taken from this outcrop.
J8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Table 1. Test data for perlite expanded at 1300 degrees F. without preheat using material sieved to between 50 and 100 mesh.

[Sieve analyses of expanded perlite reported as percent of sample retained on each sieve at each mesh size. Testing by New Mexico Bureau of Geology and 

Mineral Resources.]

Sample Furnace 

Yield

Expanded 

Density

Average 

Brightness Sinks Percent Expanded Retained (Tyler Mesh)

% lbs/ft3 % % 20 30 50 70 100 140 Pan Sum

AP-010A 77 1.94 52.1 22.2 1.0 9.4 30.5 14.2 10.8 11.4 22.7 100.0

AP-010B 88 2.27 55.5 9.6 1.9 17.9 41.1 10.5 7.4 6.8 12.4 100.0

AP-045 68 1.97 60.1 8.4 0.6 6.0 29.9 17.2 12.5 13.0 20.8 100.0

AP-119 92 2.06 52.5 4.8 20.1 34.0 33.7 5.6 2.5 1.3 2.8 100.0

AP-120 96 2.05 50.8 9.0 1.0 8.4 33.1 16.8 12.0 10.3 18.4 100.0

AP-121 86 2.04 52.8 12.0 2.4 16.7 34.5 16.1 9.8 2.1 17.4 99.0

AP-122 85 2.52 57.2 7.0 16.2 27.4 38.7 7.5 35.0 1.9 4.8 100.0

AP-124 96 3.05 42.4 0.6 8.1 42.1 42.9 3.2 1.1 5.0 2.1 100.0

AP-186 95 2.26 57.2 10.2 16.8 33.3 36.0 8.4 3.3 2.1 3.1 100.0

AP-301 84 3.03 56.0 26.2 1.0 12.1 35.9 16.5 11.7 7.7 15.1 100.0

AP-302 90 2.80 59.2 11.4 2.8 12.5 35.1 16.5 10.3 9.5 13.3 100.0

AP-303 90 3.79 62.3 14.2 1.6 21.8 52.0 11.4 4.0 3.0 6.2 100.0

Standard 99 1.87 72.4 6.8 9.9 41.0 37.4 2.9 2.1 4.0 2.7 100.0

Standard 99 1.54 70.6 2.4 19.4 42.5 30.7 3.2 1.9 1.5 0.8 100.0

AP-010A Grab of fibrous perlite, Nu-Lite Mine, Clark Co., Nevada

AP-010B 5-m chip of fibrous perlite, Nu-Lite Mine, Clark Co., Nevada

AP-045 Select grab of granular perlite with phenocrysts, NW of Searchlight Perlite Mine, Clark Co., Nevada

AP-119 Grab of granular perlite, Pahrock Pit, Mackie Mine, Lincoln Co., Nevada

AP-120 Select grab of onion skin perlite, Mackie Mine underground, Lincoln Co., Nevada

AP-121 Grab of granular perlite, main pit, Hollinger Mine, Lincoln Co., Nevada

AP-122 Grab of granular perlite, east pit, Hollinger Mine, Lincoln Co., Nevada

AP-124 Grab of granular perlite with obsidian cores, Lovelock perlite pit, Pershing Co., Nevada

AP-186 Select grab of granular perlite with phenocrysts, River Mountains, Clark Co., Nevada

AP-301 Grab of granular perlite, main pit, Searchlight Perlite Mine, Clark Co., Nevada

AP-302 Grab of granular perlite, northeast pit, Searchlight Perlite Mine, Clark Co., Nevada

AP-303 Grab of granular perlite, outcrop east of main pit, Searchlight Perlite Mine, Clark Co., Nevada

Standard Dicaperl granular perlite, No Agua, New Mexico

Figure 10. The Bootleg Canyon 

aggregate pit, a sand and 

gravel mining operation about 

2 km southwest of the River 

Mountains ACEC.
River Mountains ACEC J9

Sand and Gravel Operations

A currently active sand and gravel aggregate mine is 

about 2 km east of the southern part of the ACEC, just west 

of Boulder City, at the mouth of Bootleg Canyon. It is called 

the Bootleg Canyon Pit, and is operated by Boulder Sand and 

Gravel (see figs. 10, 12). Three other similar operations are a 

few kilometers south of the ACEC along U.S. 95, the Eldorado 

Pit, the Gornowich Plant, and the Goldstrike Mine.

Mineral Exploration and Development

There is apparently no current exploration activity for 

precious metals in or near the River Mountains ACEC. However, there are three active placer claims in sections 25 and 36 

of T22S, R63E. In addition, there are 5 active lode claims for 

perlite in section 36 of T21S, R63E, south of the Fannie Ryan 

manganese deposit.

Mineral Resource Potential

Locatable Minerals

The southeastern part of the River Mountains ACEC 

appears to have been affected by a robust hydrothermal system 

that altered most of the rocks to mineral assemblages containing 

quartz, sericite/illite, and limonite. Alunite occurs in this altered 

rock locally, along with rare kaolinite and pyrophyllite. These 

minerals are characteristic of high-sulfidation epithermal precious-metal deposits. However, on the basis of our sampling, the 

hydrothermal system appears to have been relatively deficient 

in precious and base metals, and we have designated this area 

(tract RVM01, fig. 11) to have moderate potential for highsulfidation epithermal precious-metal deposits, with a moderate level of certainty. The discovery of significant amounts of 

mineralized rock with significantly higher metal contents could 

raise this potential estimate. This would probably require drilling to test the hydrothermal system at depth.

Although several small manganese deposits, similar to 

those exploited at the Three Kids Mine exist within and near 

the River Mountains ACEC, these deposits appear to be too 

small and too low grade to be commercially viable. Outcropping manganese deposits are relatively easy to detect, and we 

assign only a low potential for the occurrence of undiscovered 

sedimentary manganese deposits. A dramatic rise in the price 

of manganese could change this, but the large size of manganese deposits typically exploited throughout the world makes 

development of manganese deposits in the River Mountains a 

highly unlikely event in the foreseeable future.

Perlite of possible commercial quality occurs in the 

northeastern part of the River Mountains ACEC. It is not clear 

if the deposits can be mined economically; the perlite body that 

we examined is steeply dipping and would have to be mined in 

narrow pits or underground. However, more extensive deposits 

may be present in the immediate area. We assign high potential 

for perlite, with a moderate level of certainty, to a small area that 

includes the Dawson perlite claims and our sample site (tract 

RVM02, fig. 11). There is no indication from our work, previous prospecting, or detailed geologic mapping (Bell and Smith, 

1980) that there are more perlite deposits in the area.

Leasable Minerals

No part of the River Mountains ACEC is within the region 

considered by the BLM to be moderately favorable for oil and 

gas (Smith and Gere, 1983). There is no indication of potential 

for brine or evaporite deposits of sodium or potassium. The 

ACEC contains no known deposits of other leasable minerals, 

and the potential for their occurrence is judged to be low.

Salable Minerals

Crushed Stone.—We consider the fanglomerates that 

are exposed in the interior valley in the southern part of the 

ACEC to have high potential for crushed-stone aggregate, 

with a moderate certainty level (tract ARVM01, fig. 12). The 

clasts in these fanglomerates are primarily dacitic volcanic 

rocks that have been sorted for durability by abrasion during 

Pliocene fan formation. Most of the outcrop areas of volcanic 

rock are judged to have moderate potential, with a moderate 

certainty level (tract ARVM03, fig. 12). The presence of glass 

and microcrystalline quartz in these fine-grained volcanic 

rocks makes them susceptible to alkali-silica reactivity (ASR), 

which can cause rapid deterioration of concrete and reduces 

the suitability of such rocks for concrete applications. The 

material might be suitable as base rock or asphalt aggregate. 

Areas underlain by volcanic breccia and mudflow units and by 

fine-grained parts of the Muddy Creek Formation are assigned 

low crushed-stone aggregate potential, with a high level of 

certainty (tract ARVM02, fig. 12).

Sand and Gravel.—Alluvial sand and gravel deposits are 

found at the north end and in the interior valley in the southern part of the ACEC. The intermittent streams that deposited 

this alluvium drain northwest and empty onto alluvial fans 

east of the city of Henderson. Together, these areas have been 

designated to have high potential, with a high level of certainty 

(tract ARVM04, fig. 12). There are also low-potential sand and 

gravel deposits that have been backfilled into pits associated 

with the manganese mining at the Three Kids Mine site (tract 

ARVM05, fig. 12).

References

Anderson, R.E., 1977, Geologic map of the Boulder City 

15-minute quadrangle, Clark County, Nevada: U.S. Geological Survey Geologic Quadrangle Map GQ-1395, scale 

1:62,500.
J10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Figure 11. Mineral resource potential tracts for locatable and leasable minerals in the River Mountains Area of Critical 

Environmental Concern (ACEC; outlined in pink).

RIVER MOUNTAINS ACEC

RAINBOW GARDENS

ACEC

RVM02 - Perlite

RVM01 - Epithermal

precious-metals

114°52'30"W

36°0'0"N

GoldButteACE

Scale1:24,00

01234 0.5

Kilometers

High mineral

resource potential

Moderate mineral

resource potential
River Mountains ACEC J11

Figure 12. Mineral resource potential tracts for aggregate resources in the River Mountains Area of Critical Environmental 

Concern (ACEC; outlined in pink).

ARVM03

ARVM03

Bootleg Canyon

sand and gravel pit

ARVM01

ARVM04

ARVM02

ARVM04

ARVM05

ARVM02

ARVM02

ARVM02

ARVM01

ARVM04

RIVER MOUNTAINS ACEC

Tract ID Commodity Type Potential Level Certainty Level

ARVM01 Crushed Stone High Moderate

ARVM02 Crushed Stone Low High

ARVM03 Crushed Stone Moderate Moderate

ARVM04 Sand and Gravel High High

ARVM05 Sand and Gravel Low Low

crushed stone,

high

crushed stone,

low

crushed stone,

moderate

sand and gravel,

high

sand and gravel,

low

sand and gravel,

moderate

Aggregate

Potential

Aggregate Assessment

Tracts

114°52'30"W

36°0'0"N

GoldButteACE

Scale1:24,00

01234 0.5

Kilometers
J12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Anderson, R.E., Longwell, C.R., Armstrong, R.L., and Marvin, R.F., 1972, Significance of K-Ar ages of Tertiary rocks 

from the Lake Mead region, Nevada-Arizona: Geological 

Society of America Bulletin, v. 83, p. 273-288.

Bell, J.W., and Smith, E.I., 1980, Geologic Map of the Henderson quadrangle, Nevada: Nevada Bureau of Mines and 

Geology Map 67, scale 1:24,000.

Bohannon, R.G., 1983, Mesozoic and Cenozoic tectonic development of the Muddy, North Muddy, and northern Black 

Mountains, Clark County, Nevada, in Miller, D.M., Todd, 

V.R., and Howard, K.A., eds., Tectonic and stratigraphic 

studies in the eastern Great Basin: Geological Society of 

America Memoir 157, p. 125-148.

Castor, S.B., 2001, Industrial minerals, in The Nevada Mineral 

Industry, 2000: Nevada Bureau of Mines and Geology Special Publication MI-2000, p. 39–42.

Castor, S.B., Faulds, J.E., Rowland, S.M., and dePolo, C.M., 

2000, Geologic map of the Frenchman Mountain quadrangle, Clark County, Nevada: Nevada Bureau of Mines and 

Geology Map 127, 1:24,000.

Deubendorfer, E.M., Beard, L.S., and Smith, E.I., 1998, Restoration of Tertiary deformation in the Lake Mead region, 

southern Nevada; the role of strike-slip transfer faults, in

Faulds, J.F., and Stewart, J.H., eds., Accommodation zones 

and transfer zones; the regional segmentation of the Basin 

and Range Province: Geological Society of America Special 

Paper 323, p. 127–148.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Hewett, D.F., 1933, Sedimentary manganese deposits, in

Ridge, J.D., ed., Ore deposits of the Western States (Lindgren Volume): American Institute of Mining and Metallurgical Engineers, p. 488–89.

Hewett, D.F., and Weber, B.N., 1931, Bedded deposits of 

manganese oxides near Las Vegas, Nevada: University of 

Nevada Bulletin, Geology and Mining Series, v. 25, 17 p.

Koski, R.A., Bouse, R.M, Hein, J.R., and DeRosa, M.L., 1988, 

Composition and geologic setting of stratiform manganese 

deposits in the southern Basin and Range Province, Arizona and Nevada, in Schindler, K.S., ed., USGS Research 

on Mineral Resources, 1989; Program and Abstracts: U.S. 

Geological Survey Circular 1035, p. 41–42.

Koski, R.A., Hein, J.R., Bouse, R.M, Evarts, R.C., and Pickthorn, L.B., 1990, K-Ar and fission-track ages of tuff beds 

at the Three Kids Mine, Clark County, Nevada—implications for manganese mineralization: Isochron West, no. 56, 

p. 30–32.

Longwell, C.R., Pampeyan, E.H., Bowyer, Ben, and Roberts, 

R.J., 1965, Geology and mineral deposits of Clark County, 

Nevada: Nevada Bureau of Mines Bulletin 62, 218 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Metcalf, R.V., Smith, E.I., and Mills, J.G., 1993, Magma mixing and commingling in the northern Colorado River extensional corridor; constraints on the production of intermediate magmas, in Lahren, M.M., Trexler, J.H., and Spinsosa, 

C., eds., Crustal evolution of the Great Basin and the Sierra 

Nevada: Geological Society of America Guidebook, Cordilleran-Rocky Mountain Section Meeting, p. 35–55.

Rowan, L.C., Hook, S.J., Abrams, M.J., and Mars, J.C., 2003, 

Mapping hydrothermally altered rocks at Cuprite, Nevada, 

using the Advanced Spaceborne Thermal Emission and 

Reflection Radiometer (ASTER), a new satellite-imaging 

system: Economic Geology, v. 98, p. 1019–1027.

Smith, E.I., 1982, Geology and geochemistry of the volcanic 

rocks in the River Mountains, Clark County, Nevada and 

comparisons with volcanic rocks in nearby areas, in Frost, 

E.G., and Martin, D.L., eds., Mesozoic-Cenozoic tectonic 

evolution of the Colorado River region, California, Arizona, 

and Nevada: San Diego, California, Geological Society 

of America Field Trip Guide, Cordilleran Publications, p. 

41–54.

Smith, E.I., 1984, Geologic Map of the Boulder Beach quadrangle, Nevada: Nevada Bureau of Mines and Geology, Map 

81, scale 1:24,000

Smith, E.I., 1986a, Geology of the River, Eldorado, and 

McCullough Ranges, Clark County, Nevada, in Rowland, 

S.M., ed., Field guide to the geology of southern Nevada: 

Department of Geoscience, University of Nevada, Las 

Vegas, Publication No. 1, p. 23–35.

Smith, E.I., 1986b, Road log and field guide from Henderson 

to Hoover Dam via Lake Mead, in Rowland, S.M., ed., 

Field guide to the geology of southern Nevada: Department 

of Geoscience, University of Nevada, Las Vegas, Publication No. 1, p. 36–64.

Smith, E.I., Feuerbach, D.L., Naumann, T.R., and Mills, J.G., 

1990, Mid-Miocene volcanic and plutonic rocks in the 

Lake Mead area of Nevada and Arizona—production of 

intermediate igneous rocks in an extensional environment, 

in Anderson, J.L., ed., The nature and origin of Cordilleran 

magmatism: Geological Society of America Memoir 174, p. 

169–194.
River Mountains ACEC J13

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, scale 1:500,000.

Smith, P.L., and Tingley, J.V., 1983, Results of geochemical 

sampling within Esmeralda-Stateline resource area, Esmeralda, Clark, and southern Nye counties, Nevada (portions of 

Death Valley, Goldfield, Kingman, Las Vegas, Mariposa and 

Tonopah 2 degrees sheets): Nevada Bureau of Mines and 

Geology Open-File Report 83-12, unpaginated.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.

Vanderburg, W.O., 1937, Reconnaissance of mining districts 

in Clark County, Nevada: U.S. Bureau of Mines Information 

Circular 6964, 81 p.

Weber, M.E., and Smith, E.I., 1987, Structural and geochemical constraints on the reassembly of disrupted mid-Miocene 

volcanoes in the Lake Mead-Eldorado Valley area of southern Nevada: Geology, v. 15, p. 553–556.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter K. Mineral Resource Potential of the Stump 

Spring Area of Critical Environmental Concern, Clark 

County, Nevada

By Kathryn S. Flynn, Steve Ludington, Brett T. McLaurin, and Stephen B. Castor

Summary and Conclusions

The Stump Spring Area of Critical Environmental 

Concern (ACEC) exposes only unconsolidated Quaternary 

sediments. There are no known mineral deposits in the ACEC 

and no potential for the occurrence of deposits of locatable or 

leasable minerals.

Because there is no bedrock outcrop in the ACEC, there 

is no potential for the occurrence of crushed-stone aggregate 

deposits. The potential for the occurrence of sand and gravel 

aggregate deposits is low.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral 

resource potential in accordance with regulations at 43 CFR 

2310, which governs the withdrawal of public lands. The Clark 

County Conservation of Public Land and Natural Resources Act 

of 2002 temporarily withdraws the lands described herein from 

mineral entry, pending final approval of an application for permanent withdrawal by the BLM. This report provides information about mineral resource potential on these lands.

The Stump Spring ACEC was studied in the field to confirm descriptions of the geology that were gleaned from the 

scientific literature.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The Stump Spring Area of Critical Environmental Concern (ACEC) is located approximately 2 km northeast of the 

Nevada-California border in the Pahrump Valley. It is about 50 

km west of Las Vegas and about 30 km southeast of the town 

of Pahrump. The ACEC is accessible by unimproved roads 

from the Old Spanish Trail Highway. A legal description of 

these lands is included in appendix 2.

Physiographic Description

The Stump Spring ACEC is in Pahrump Valley, which 

is separated by the Spring Mountains from Las Vegas Valley to the east. The west boundary of the Pahrump Valley is 

formed by the Nopah and Kingston Ranges. The valley is 

relatively flat and as much as 25 km wide. The ACEC ranges 

from about 780 to 850 meters in elevation and contains a 

small intermittent stream that drains southwest. The ACEC is 

named for Stump Spring, which was used by early travelers 

through the area.

Geologic Setting

Pahrump Valley is on the southwest margin of the Basin 

and Range Physiographic Province. The region has experienced multiple periods of deformation, including Mesozoic 

compression followed by extension that began in Miocene 

time. The State Line Fault Zone, a zone of strike-slip faulting 

that strikes almost parallel to the Nevada-California border in 

the center of the valley, is within the Walker Lane belt, a major 

northwest zone of right-lateral faulting caused by late Tertiary 

to modern extension (Stewart, 1992). Analysis of gravity 

data indicates that the valley could have formed as a pullapart, transtensional structure along the State Line Fault Zone 

(Blakely and others, 1998).

The mountains bordering the Pahrump Valley are mostly 

composed of Late Proterozoic and Paleozoic carbonate and 

siliciclastic rocks, which probably also underlie the valley. The subsurface bedrock of Pahrump Valley is deformed 

and topographically complex (Blakely and others, 1998); it 

is covered by sedimentary deposits that are Oligocene and 

younger in age. These include Quaternary playa deposits and 

large alluvial fans on the northeast side of the valley (Sweetkind and others, 2003).
K2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Geology

The Stump Spring ACEC is located in an area of Quaternary sediments (fig. 1). Channel gravels become finer-grained 

upward, becoming mudstone near the top of the sequence. The 

mudstones are overlain by silt and thin gravel beds (Quade, 

2000). These deposits, as well as fossils found in the area, 

record a change from an environment of fluvial and lacustrine 

conditions during the most recent glacial cycle to the arid 

conditions found today.

Mining History

There has been no known mining within the study area.

Mineral Deposits

There are no known mineral deposits within the study 

area. The Beck mine, an iron skarn deposit, is about 10 km 

southwest of the ACEC in California, and some outlying 

mines of the Goodsprings polymetallic district are about 20-30 

km east-southeast of Stump Spring.

Mineral Exploration and Development

There are no active mining claims in or near the area, and 

no known mineral exploration activity.

Mineral Resource Potential

Locatable Minerals

On the basis of gravity data, the basin fill beneath the 

Stump Spring ACEC is about 1,000 m thick (Jachens and 

others, 1996). There is no known metal-mineralized rock or 

indication of other locatable mineral deposits, and there is no 

potential for locatable minerals.

Leasable Minerals

The area is within the region considered by the BLM 

to be moderately favorable for oil and gas (Smith and Gere, 

1983). The closest exploration well, Miskell-Gov’t No. 1, was 

drilled in 1959 along the west flank of the Spring Mountains 

about 18 km northeast of the ACEC. It was a dry hole, with 

minor oil shows, drilled entirely in the Permian Bird Spring 

Formation to a depth of 793 m (Garside and others, 1988).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. The Stump Spring ACEC 

contains no known deposits of other leasable minerals, and the 

potential for their occurrence is low.

Salable Minerals

Crushed Stone.—There is no bedrock outcrop in the 

ACEC, and no potential for crushed-stone aggregate deposits.

Sand and Gravel.—The surface of the ACEC is dominated by small sand dunes stabilized by sparse vegetation. 

Cobbles of limestone, chert, and sandstone are present, but 

not in enough quantity to be considered high-quality aggregate. The area has low potential for sand and gravel aggregate 

deposits, with a high certainty level (fig. 2).

References

Blakely, R.J., Morin, R.L., McKee, E.H., Schmidt, K.M., Langenheim, V.E., and Dixon, G.L., 1998, Three-dimensional 

model of Paleozoic basement beneath Amargosa Desert 

and Pahrump Valley, California and Nevada: Implications 

for tectonic evolution and water resources: U.S. Geological 

Survey Open-File Report 98-496, 29 p.

Garside, L.J., Hess, R.H., Fleming, K.L., and Weimer, B.S., 

1988, Oil and gas developments in Nevada: Nevada Bureau 

of Mines and Geology Bulletin 104, 136 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Jachens, R.C., Moring, B.C., and Schruben, P.G., 1996, Thickness of Cenozoic deposits and the isostatic residual gravity 

over basement, in Singer, D.A., ed., An analysis of Nevada’s 

metal-bearing mineral resources: Nevada Bureau of Mines 

and Geology Open-File Report 96-2, Chapter 2, p. 2-1– 2-

10 [http://www.nbmg.unr.edu/dox/ofr962/index.htm].

Quade, J., 2000, Hydrologic and geologic characteristics of 

the Yucca mountain site relevant to the performance of a 

potential repository; Day 1, Las Vegas, Nevada to Pahrump, 

Nevada; Stop 1, Southern Pahrump valley—Hidden Valley 

and Stump Springs, Great Basin and Sierra Nevada: Geological Society of America Field Guide 2, p. 386-387.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, map, scale 1:500,000.

Stewart, J.H., 1992, Walker Lane belt, Nevada and California; 

an overview, in Craig, S.D., ed., Structure, tectonics and 

mineralization of the Walker Lane USA: Reno, Nevada, 

Geological Society of Nevada, Walker Lane symposium 

proceedings volume, p. 1–16.

Sweetkind, D.S., Taylor, E., and Putnam, H., 2003, Stratigraphic inferences derived from borehole data of Tertiary 

basin-filling rocks of the Pahrump Valley basin, Nevada 

and California: U.S. Geological Survey Open-File Report 

03-051, 30 p.
Stump Spring ACEC K3

Figure 1. Generalized geology of the Stump Spring Area of Critical Environmental Concern. All materials are 

unconsolidated Quaternary deposits, including alluvium, colluvium, and playa deposits.

Figure 2. Mineral resource potential tracts for sand and gravel aggregate deposits in the Stump Spring Area of 

Critical Environmental Concern (ACEC; outlined in pink).

Qu

115°45'0"W

36°0'0"N

Stump Spring ACEC

Scal e 1:24,000 01234 0.5

Kilometers

Gold Butte ACEC

115°45'0"W

36°0'0"N

01234 0.5

Kilometers

ASSG01

Tract ASSG01 has low potential for

sand and gravel aggregate,

with a high level of certainty.

Stump Spring ACEC
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Chapter L. Mineral Resource Potential of the Big Dune Area 

of Critical Environmental Concern, Nye County, Nevada

By Stephen B. Castor, Brett T. McLaurin, Steve Ludington, and Kathryn S. Flynn

Summary and Conclusions

The Big Dune Area of Critical Environmental Concern 

(ACEC) is mostly underlain by Quaternary eolian sand. The 

sand is unsuitable as a silica source, and the sandy area has 

low potential for the occurrence of silica sand deposits. There 

is no potential for the occurrence of other deposits of locatable 

or leasable minerals.

The ACEC contains areas with both moderate and 

low potential for the occurrence of sand and gravel aggregate deposits, but there is no potential for the occurrence of 

crushed-stone aggregate deposits.

Introduction

This report was prepared for the U.S. Bureau of Land 

Management (BLM) to provide information for land planning and management, and, specifically, to determine mineral resource potential in accordance with regulations at 43 

CFR 2310, which governs the withdrawal of public lands. 

The Clark County Conservation of Public Land and Natural Resources Act of 2002 temporarily withdraws the lands 

described herein from mineral entry, pending final approval 

of an application for permanent withdrawal by the BLM. This 

report provides information about mineral resource potential 

on these lands.

The Big Dune ACEC was studied in the field to confirm 

descriptions of the geology that were gleaned from the scientific literature. One sample was collected and analyzed.

Definitions of mineral resource potential and certainty 

levels are given in appendix 1, and are similar to those outlined by Goudarzi (1984).

Lands Involved

The Big Dune ACEC is about 15 km west of the town of 

Amargosa Valley and about 3 km southwest of US Highway 

95 (fig. 1). It can be accessed most easily using unimproved 

roads from the east (U.S. 95) and south. A legal description of 

these lands is included in appendix 2.

Physiographic Description

The southwest part of the Big Dune ACEC consists of 

a cluster of shifting longitudinal and barchan dunes (fig. 2) 

that reach elevations of as much as 835 m. The dunes lie on a 

southward draining alluvial fan surface, which comprises the 

east and northeast part of the ACEC. The lowest point in the 

ACEC is at the southeastern corner at an elevation of about 

750 m on the alluvial fan surface.

Geologic Setting

The Big Dune ACEC is in the Amargosa Desert, a 

northwest-trending structural basin in the Basin and Range 

Physiographic Province. The Amargosa Desert occupies an 

area between the north-trending Basin and Range structures 

to the northeast and northwest-trending structures to the 

southwest. It lies along the possible southeastern continuation of the Walker Lane Belt, a major northwest-trending 

zone of right-lateral faulting caused by late Tertiary to modern extension (Stewart, 1992).

Geology

The Big Dune ACEC is covered by Quaternary eolian 

sand and fanglomerate. A simplified geologic map is presented 

in figure 1. The source of the sand is mostly Precambrian 

(Neoproterozoic) rocks that lie 2 to 10 km to the southwest. 

The alluvium mainly contains Precambrian metamorphic, 

Paleozoic carbonate, and Cenozoic volcanic detritus.

Mining History

There has been no known mining in the Big Dune area. 

Claims were staked on the sand dunes for silica, aluminum, 

iron, gold, and titanium (records 6461 and 14977, Nevada 

Bureau of Mines and Geology, 2001), but these claims have 

lapsed and there are now (2006) no active claims in the ACEC.
L2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Mineral Deposits

There are no known mineral deposits in the Big Dune 

ACEC. Chemical analysis of a sample (AP–110) of eolian 

sand from Big Dune (Ludington and others, 2005) shows 

that the sand contains about 73 percent SiO2 and thus is not 

suitable as a source of silica. In addition, the sand contains no 

significant metal concentrations.

The closest mineral occurrences are gold-bearing quartz 

veins in Proterozoic rocks and limonitically altered Paleozoic 

carbonate rocks. These occurrences are in the Lee mining district, about 7 km southwest of Big Dune (Ball, 1907). No gold 

production has been reported from the district (Cornwall, 1972).

Mineral Exploration and Development

There is no current exploration activity for minerals in 

or near the Big Dune ACEC. There are no active claims in the 

Big Dunes ACEC.

Mineral Resource Potential

Locatable Minerals

The Big Dunes ACEC has no potential for locatable 

mineral deposits.

Leasable Minerals

Because the chemical composition is not suitable, the 

dune area in the ACEC cannot be considered a viable silica 

sand deposit. The potential for silica sand is low.

Most of the Big Dune ACEC is within the area the region 

considered by the BLM to be moderately favorable for oil and gas 

(Smith and Gere, 1983). There are no exploration wells reported 

in Nevada within 80 km of the ACEC (Garside and others, 1988).

There is no indication of potential for brine or evaporite 

deposits of sodium or potassium. The ACEC contains no 

known deposits of other leasable minerals, and the potential 

for their occurrence is low.

Salable Minerals

Crushed Stone.—Because no rock crops out, there is no 

potential for crushed stone aggregate in the ACEC.

Sand and Gravel.—The southwest half of the ACEC is 

covered by fine-grained sand, as sheets and dunes as much as 80 

m thick (Swadley and Carr, 1987). The portion of the ACEC that 

is beneath sand has low potential for sand and gravel aggregate, 

with a high certainty level (tract ABGD03, fig. 3). However, 

clastic sediment underlies the dune; it is primarily exposed in the 

northeast half of the ACEC. This sediment consists of alluvial fan 

deposits that contain pebble- to boulder-sized clasts of Proterozoic quartzite, Paleozoic carbonate rocks, and Cenozoic volcanic 

rocks. This area has moderate potential for sand and gravel aggregate, with a moderate certainty level (tract ABGD02, fig. 3).

Figure 1. Big Dune Area of Critical Environmental Concern (ACEC; outlined in pink), showing generalized geology and 

location of analyzed sample. Geology modified from Stewart and Carlson (1978).

AP-110

01234 0.5

Kilometers

116°37'30"W 116°30'0"W

36°37'30"N

Qu

Tvy Tvy

Tvy

Czs

Czs contact, certain

fault, certain

sample locality, with

sample number

Qu

Tvy

CZs

Undivided surficial deposits (Pleistocene

and Holocene)—Alluvium, colluvium,

playa, terrace, and eolian sand deposits

Young volcanic rocks (middle and upper

Miocene)—Rhyolite, andesite, and

basalt lava flows, and tuff

Sedimentary rocks (Neoproterozoic

and Cambrian)—Quartzite, siltstone,

and phyllite, with lesser amounts of

conglomerate, limestone, and dolomite

EXPLANATION
Big Dune ACEC L3

Some of the silica-rich clasts may reduce the quality of 

this aggregate due to alkali-silica reactivity (ASR). There are 

very large amounts of similar material in the immediate surroundings of the Big Dune ACEC, as it constitutes much of 

the sediment that fills the Amargosa Valley.

Figure 2. Sand dunes in the Big Dune Area of Critical 

Environmental Concern. Photo taken toward the northwest. Note 

all-terrain vehicle tracks in the foreground.

ABGD02

ABGD03

BIG DUNE

ACEC

Sand and gravel,

moderate

Sand and gravel,

low

Tract ID Deposit Type Potential Level Certainty Level

ABGD02 sand and gravel Moderate

ABGD03 sand and gravel Low High

Moderate

116°37'30"W 116°30'0"W

36°37'30"N

01234 0.5

Kilometers

Gold Butte ACEC

Figure 3. Mineral resource potential tracts for aggregate resources in the Big Dune Area of Critical Environmental 

Concern (ACEC; outlined in pink).

Garside, L.J., Hess, R.H., Fleming, K.L., and Weimer, B.S., 

1988, Oil and gas developments in Nevada: Nevada Bureau 

of Mines and Geology Bulletin 104, 136 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787, 41 p.

Ludington, Steve, Castor, S.B., Budahn, J.R., and Flynn, 

K.S., 2005, Geochemical analyses of geologic materials 

from areas of critical environmental concern, Clark and 

Nye Counties, Nevada: U.S. Geological Survey Open-File 

Report 05-1450 [http://pubs.usgs.gov/of/2005/1450/].

Nevada Bureau of Mines and Geology, 2001, Nevada Abandoned Mines Database Compilation Update: Nevada Bureau 

of Mines and Geology Bulletin Open-File Report 01-03.

Smith, M.B., and Gere, W.C., 1983, Lands valuable for oil and 

gas, Nevada: U.S. Bureau of Land Management, prepared 

by the U.S. Geological Survey, Conservation Division, 

Western Region, map, scale 1:500,000.

Stewart, J.H., 1992, Walker Lane belt, Nevada and California: 

An overview, in Craig, S.D., ed., Structure, tectonics and mineralization of the Walker Lane: Geological Society of Nevada 

Walker Lane Symposium Proceedings Volume, p. 1–16.

Stewart, J.H., and Carlson, J.E., 1978, Geologic map of 

Nevada: U. S. Geological Survey, scale 1:500,000.

Swadley, W.C., and Carr, W.J., 1987, Geologic map of the 

Quaternary and Tertiary deposits of the Big Dune Quadrangle, Nye County, Nevada, and Inyo County, California: 

U.S. Geological Survey Miscellaneous Investigations Map 

I-1767, scale 1:48,000.

References

Ball, S.H., 1907, A geologic reconnaissance in southwestern 

Nevada and eastern California: U.S. Geological Survey Bulletin 283, 308 p.

Cornwall, H.R., 1972, Geology and mineral deposits of 

southern Nye County, Nevada: Nevada Bureau of Mines and 

Geology Bulletin 77, 49 p.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Appendix 1. Definitions of Levels of Mineral Resource Potential and Certainty 

of Assessment

Definitions of Mineral Resource Potential

HIGH mineral resource potential is assigned to areas where 

geologic, geochemical, and geophysical characteristics define 

a geologic environment favorable for resource occurrence, 

where interpretations of data indicate a high degree of likelihood for resource accumulation, where data support mineraldeposit models indicating presence of resources, and where 

evidence indicates that mineral concentration has taken place. 

Assignment of high resource potential to an area requires 

some positive knowledge that mineral-forming processes have 

been active in at least part of the area.

MODERATE mineral resource potential is assigned to areas 

where geologic, geochemical, and geophysical characteristics 

define a geologic environment favorable for resource occurrence, where interpretations of data indicate reasonable likelihood of resource accumulation, and (or) where an application 

of mineral-deposit models indicates favorable ground for the 

specified type(s) of deposits.

LOW mineral resource potential is assigned to areas where 

geologic, geochemical, and geophysical characteristics define 

a geologic environment in which the existence of resources is 

permissive. This category embraces areas with dispersed but 

insignificantly mineralized rock, as well as areas with few or 

no indications of having been mineralized.

UNKNOWN mineral resource potential is assigned to areas 

where information is inadequate to assign low, moderate, or 

high levels of resource potential.

NO mineral resource potential is a category reserved for a 

specific type of resource in a well-defined area.

Definitions of Levels of Certainty

LOW certainty level means that available information suggests 

the level of mineral resource potential.

MODERATE certainty level means that available information gives a good indication of the level of mineral resource 

potential.

HIGH certainty level means that available information clearly 

defines the level of mineral resource potential.

These definitions are adapted from those published in: 

Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey 

Open-File Report 84-0787.
Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, 

Nevada, Edited by Steve Ludington

U.S. Geological Survey Scientific Investigations Report 2006-5197

Prepared in cooperation with the Nevada Bureau of Mines and Geology and 

the University of Nevada, Las Vegas

Appendix 2. Legal Descriptions of Selected Areas of Critical 

Environmental Concern in Clark and Nye Counties, Nevada.

The chapter to which the legal descriptions apply is indicated by capital letters; for example, appendix 2E gives legal descriptions for the areas discussed in chapter E. There is no legal 

description for the introductory chapter (chapter A).
2–2 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2B. Legal Descriptions of Piute-Eldorado Tortoise, Crescent Townsite, 

and Keyhole Canyon Areas of Critical Environmental Concern, Clark County, 

Nevada

Piute-Eldorado Tortoise 

 Legal Description Part

T. 28 S., R. 60 E.,

Approx. Total Acreage = 325,271.50 sec. 2, All;

(Clark County) sec. 3, All;

(NVN 076881) sec. 10, All;

sec. 11, All;

sec. 13, W1⁄2;

secs. 14 to 17, inclusive;

secs. 21 to 23, inclusive;

sec. 24, All, Except Mineral Entry Patents;

sec. 25, N1⁄2, All, North of Right-of-Way Nev058548 (NV Hwy 164) Centerline;

sec. 26, lots 2-7, inclusive, 9, partial lots 8, 10, 11, SW1⁄4NE1⁄4, SE1⁄4NW1⁄4, NW1⁄4SE1⁄4, All, North 

of Right-of-Way Nev058548 (NV Hwy 164) Centerline;

sec. 27, All.

T. 26 S., R. 61 E.,

sec. 1, All;

sec. 2, All;

secs. 11 to 14, inclusive;

sec. 24, All;

sec. 25, All;

sec. 36, All.

T. 27 S., R. 61 E.,

sec. 1, All;

sec. 12, All;

sec. 13, All;

secs. 23 to 26, inclusive;

sec. 35, All;

sec. 36, All.

T. 28 S., R. 61 E.,

sec. 1, All;

sec. 2, All;

secs. 10 to 12, inclusive;

sec. 13, N1⁄2N1⁄2N1⁄2, All, North of Right-of-Way Nev058548 (NV Hwy 164) 

 Centerline;

 sec. 14, N1⁄2N1⁄2N1⁄2, All, North of Right-of-Way Nev058548 (NV Hwy 164) 

 Centerline;

sec. 15, N1⁄2NE1⁄4, SW1⁄4NE1⁄4, NW1⁄4, W1⁄2SW1⁄4, All, North of Right-of-Way Nev058548 (NV Hwy 

164) Centerline;

sec. 16, All;

sec. 19, lots 3, 4, partial lots 1, 2, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4,SE1⁄4, All, Except Mineral Entry 

Patents;

sec. 20, N1⁄2, N1⁄2S1⁄2, All, North of Right-of-Way Nev058548 (NV Hwy 164) Centerline and 

Excluding Mineral Survey 4916A Patent;

sec. 21, All, North of Right-of-Way Nev058548 (NV Hwy 164) Centerline;

sec. 22, All, North of Right-of-Way Nev058548 (NV Hwy 164) Centerline;

sec. 29, All ,North of Right-of-Way Nev058548 (NV Hwy 164) Centerline;
Appendix 2 2–3

sec. 30, lot 1, partial lot 2, NE1⁄4NW1⁄4, All , North of Right-of-Way Nev058548 (NV Hwy 164) 

Centerline. 

T. 29 S., R. 61 E.,

sec. 36, All.

T. 26 S., R. 62 E.,

secs. 3 to 10, inclusive;

secs. 15 to 20, inclusive;

sec. 22, E1⁄2, N1⁄2NW1⁄4;

secs. 23 to 26, inclusive;

sec. 27, NE1⁄4;

secs. 29 to 32, inclusive;

sec. 35, All;

sec. 36, All.

T. 27 S., R. 62 E.,

sec. 1, All;

secs. 5 to 8, inclusive;

sec. 12, All;

sec. 13, E1⁄2; 

secs. 17 to 20, inclusive;

sec. 24, E1⁄2; 

sec. 25, E1⁄2;

secs. 29 to 36, inclusive.

T. 28 S., R. 62 E., 

secs. 1 to 17, inclusive;

sec. 18, partial lots 5, 6, All, North of Right-of-Way Nev058548 (NV Hwy 164) Centerline;

sec. 20, All;

sec. 21, All;

sec. 22, N1⁄2, N1⁄2SW1⁄4, SE1⁄4;

secs. 23 to 26, inclusive;

sec. 27, NE1⁄4, S1⁄2NW1⁄4, S1⁄2;

sec. 28, All;

sec. 29, All;

sec. 31, lot 15, partial lots 14, N1⁄2SE1⁄4, Excluding MS 2518 Patent;

secs. 32 to 36, inclusive.

T. 29 S., R. 62 E.,

secs. 1 to 5, inclusive;

sec. 6, E1⁄2;

secs. 7 to 32, inclusive;

sec. 33, NE1⁄4NE1⁄4, NW1⁄4NW1⁄4;

secs. 34 to 36, inclusive.

T. 30 S., R. 62 E.,

sec. 1, All;

sec. 2, All;

secs. 11 to 14, inclusive.

T. 27 S., R. 621⁄2 E.,

sec. 1, All, unsurveyed;

sec. 12, All, unsurveyed;

sec. 13, All, unsurveyed;

sec. 24, All, unsurveyed;
2–4 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

sec. 25, All, unsurveyed;

sec. 36, All, unsurveyed.

T. 26 S., R. 63 E.,

sec. 19, All;

sec. 20, W1⁄2NE1⁄4, W1⁄2, W1⁄2SE1⁄4, All, West of Right-of-Way CC020733 (Interstate-95) Centerline 

and South of Powerline Right-of-Way N869 Centerline;

sec. 21, S1⁄2S1⁄2, All, South of Powerline Right-of-Way N869 Centerline;

sec. 22, S1⁄2S1⁄2S1⁄2, All, South of Powerline Right-of-Way N869 Centerline;

sec. 23, All, South of Powerline Right-of-Way N869 Centerline;

sec. 24, All, South of Powerline Right-of-Way N869 Centerline;

sec. 25, S1⁄2N1⁄2NE1⁄4NE, W1⁄2NE1⁄4, SE1⁄4NE1⁄4, W1⁄2, SE1⁄4, All, South of Powerline Right-of-Way 

N869 Centerline;

secs. 26 to 36, inclusive.

T. 27 S., R. 63 E.,

secs. 1 to 36, inclusive.

T. 28 S., R. 63 E.,

secs. 1 to 8, inclusive;

sec. 9, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, N1⁄2SW1⁄4SE1⁄4, E1⁄2SW1⁄4SW1⁄4SE1⁄4, SE1⁄4SW1⁄4SE1⁄4, SE1⁄4SE1⁄4; 

sec. 10, All;

sec. 11, All;

sec. 12, lots 1 to 8, inclusive, N1⁄2;

sec. 13, lots 1 to 3, inclusive, NW1⁄4NE1⁄4, S1⁄2NE1⁄4, NW1⁄4, N1⁄2SW1⁄4, SE1⁄4;

sec. 14, lots 1,2, N1⁄2, SW1⁄4, N1⁄2SE1⁄4;

sec. 15, lots 1, 2, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, All, Except Mineral Entry Patents; 

secs. 16 to 20, inclusive;

sec. 29, NE1⁄4, N1⁄2NW1⁄4, N1⁄2SW1⁄4NW1⁄4, SE1⁄4NW1⁄4, All, North of Right-of-Way Nev058548 (NV 

Hwy 164) Centerline;

 sec. 30, lots 1 to 4, inclusive, N1⁄2NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, W1⁄2SE1⁄4, All, Except SENE that is 

South of Right-of-Way Nev058548 (NV Hwy 164) Centerline and Except the E1⁄2SE1⁄4;

 sec. 31, All;

sec. 32, W1⁄2SW1⁄4, SE1⁄4SW1⁄4.

T. 29 S., R. 63 E.,

secs. 5 to 10, inclusive;

secs. 15 to 22, inclusive;

sec. 23, W1⁄2NE1⁄4NE1⁄4, W1⁄2NE1⁄4, W1⁄2SE1⁄4NE1⁄4, W1⁄2, SE1⁄4, All, West of Right-of-Way 

CC020845 (Interstate-95) Centerline; sec. 24, All, West of Right-of-Way CC020845 

(Interstate-95) Centerline;

sec. 25, W1⁄2W1⁄2NW1⁄4, W1⁄2SW1⁄4, All, West of Right-of-Way CC020845 (Interstate-95) 

Centerline;

secs. 26 to 36, inclusive.

T. 30 S., R. 63 E.,

secs. 1 to 24, inclusive;

sec. 25, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, SW1⁄4SE1⁄4, W1⁄2SE1⁄4SE1⁄4;

secs. 26 to 29, inclusive;

secs. 32 to 35, inclusive;

sec. 36, S1⁄2N1⁄2NE1⁄4NE1⁄4NE1⁄4, W1⁄2NE1⁄4NE1⁄4, SE1⁄4NE1⁄4NE1⁄4, E1⁄2NE1⁄4, SE1⁄4NE1⁄4, W1⁄2, SE1⁄4; 

T. 31 S., R. 63 E.,

secs. 1 to 5, inclusive;

secs. 8 to 16, inclusive;

secs. 22 to 26, inclusive;
Appendix 2 2–5

sec. 36, All.

T. 26 S., R. 64 E.,

sec. 29, S1⁄2N1⁄2, S1⁄2, All, South of Powerline Right-of-Way N869 Centerline;

sec. 30, lots 2, 3, 4, partial lot 1, S1⁄2N1⁄2NE1⁄4, S1⁄2NE1⁄4, S1⁄2N1⁄2SW1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, 

All, South of Powerline Right-of-Way N869 Centerline; 

secs. 31 to 33, inclusive.

T. 27 S., R. 64 E.,

secs. 4 to 9, inclusive;

secs. 16 to 23, inclusive;

sec. 25, All, Except Mineral Survey 4071 Patent;

sec. 26, All;

sec. 27, All;

sec. 28, All, Except Mineral Survey 3541 Patent;

sec. 29, All, Except Mineral Survey 3541 Patent; 

sec. 30, All;

sec. 31, All;

sec. 32, All, Except Mineral Survey 3541 Patent;

sec. 33, All, Except Mineral Survey 3541 Patent; 

secs. 34 to 36, inclusive.

T. 28 S., R. 64 E.,

secs. 1 to 6, inclusive;

sec. 7, lot 1, partial lots 2, 3, 4, NE1⁄4, W1⁄2SE1⁄4, All, Except Mineral Survey and Mineral Entry 

Patents;

sec. 8, All, Except Mineral Survey 3788 Patent;

secs. 9 to 16, inclusive;

sec. 17, All, Except Mineral Surveys 3755 and 3788 Patents;

sec. 18, lots 2, 4, partial lot 1, W1⁄2NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, Except Mineral Survey 

and Mineral Entry Patents;

secs. 21 to 26, inclusive;

sec. 35, All;

sec. 36, All.

T. 29 S., R. 64 E.,

secs. 1 to 3, inclusive;

secs. 9 to 16, inclusive;

secs. 21 to 28, inclusive;

secs. 31 to 36, inclusive.

T. 30 S., R. 64 E.,

secs. 1 to 29, inclusive;

sec. 31, lots 3, 4, 13 to 68, inclusive, E1⁄2NE1⁄4, E1⁄2SW1⁄4, SE1⁄4;

secs. 32 to 36, inclusive.

T. 31 S., R. 64 E.,

secs. 1 to 31, inclusive;

sec. 32, N1⁄2, SW1⁄4;

secs. 33 to 36, inclusive.

T. 32 S., R. 64 E.,

secs. 1 to 3, inclusive;

sec. 4, lots 1, 2, 5 to 24, inclusive, 34 to 47, inclusive, 59 to 82, inclusive, 84 to 128, inclusive, 

S1⁄2SE1⁄4NW1⁄4, SW1⁄4, S1⁄2NE1⁄4SE1⁄4, SE1⁄4NW1⁄4SE1⁄4, E1⁄2SW1⁄4SE1⁄4, SE1⁄4SE1⁄4;

sec. 5, lots 6 to 9, inclusive, 12, 13, 15 to 22, inclusive, 25 to 29, inclusive, 32 to 37, inclusive, 40 
2–6 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

to 45, inclusive, 47 to 78, inclusive, SW1⁄4NE1⁄4, SE1⁄4NW1⁄4, NW1⁄4SE1⁄4;

sec. 6, All;

sec. 8, All;

sec. 9, lots 1, 2, 7, 8, 10 to 21, inclusive, 27 to 30, inclusive, 38 to 41, inclusive, 48, 49, 56, 63, 75 

to 77, inclusive, 79 to 84, inclusive, SW1⁄4NE1⁄4, NW1⁄4SE1⁄4;

secs. 10 to 16, inclusive;

sec. 22 to 26, inclusive;

sec. 36, All.

T. 30 S., R. 65 E.,

secs. 4 to 6, inclusive, unsurveyed;

sec. 7, All, Except Mineral Survey 3942 Patent, unsurveyed;

sec. 8, All , Except Mineral Survey 3936 and 3942 Patents, unsurveyed;

sec. 9, All, Except Mineral Survey 3936 Patent, unsurveyed;

sec. 16, All, unsurveyed;

sec. 17, All, Except Mineral Survey 3942 Patent, unsurveyed;

sec. 18, All, Except Mineral Survey 3942 Patent, unsurveyed; 

secs. 19 to 21, inclusive, unsurveyed;

sec. 30, All, unsurveyed;

sec. 31, All, unsurveyed.

T. 31 S., R. 65 E.,

sec. 6, All, unsurveyed;

secs. 28 to 33, inclusive, unsurveyed.

T. 32 S., R. 65 E.,

secs. 2 to 8, inclusive;

sec. 9, N1⁄2, All, North of Right-of-Way CC022416 (NV Hwy 163) Centerline;

sec. 10, N1⁄2, All, North of Right-of-Way CC022416 (NV Hwy 163) Centerline;

sec. 11, N1⁄2, N1⁄2N1⁄2SW1⁄4, N1⁄2SE1⁄4, All, North of Right-of-Way CC022416 (NV Hwy 163) 

Centerline;

sec. 12, NW1⁄4, N1⁄2SW1⁄4, All, North and West of Right-of-Way CC022416 (NV Hwy 163) 

Centerline;

secs. 17 to 20, inclusive;

secs. 29 to 32, inclusive.

T. 33 S., R. 65 E.,

sec. 5, All.

Crescent Townsite 

 Legal Description Part

 T. 28 S., R.61 E., 

Approx. Total Acreage = 420.00 sec. 29, SW1⁄4, W1⁄2SE1⁄4, Except Mineral Entry Patents; 

 (Clark County) sec. 30, E1⁄2SE1⁄4;

(NVN 076872) sec. 32, W1⁄2NE1⁄4, E1⁄2NW1⁄4,.

Keyhole Canyon 

 Legal Description Part

 T. 26 S., R. 63 E.,

Total Acreage = 240.53 sec. 3, lots 6 to 8, inclusive, SW1⁄4NE1⁄4, S1⁄2NW1⁄4.

(Clark County)

(NVN 076879)
Appendix 2 2–7

Appendix 2C. Legal Descriptions of Gold Butte A, Gold Butte B, Virgin Mountain 

(Gold Butte C), Whitney Pocket, Red Rock Spring, Devil’s Throat, and Gold Butte 

Townsite Areas of Critical Environmental Concern

Gold Butte, Part A

 Legal Description Part

 T. 14 S., R. 69 E.,

Approx. Total Acreage = 185,670.52 secs. 24 to 26, inclusive;

(Clark County) secs. 34 to 36, inclusive.

(NVN 076875) 

 T. 15 S., R. 69 E.,

secs. 1 to 3, inclusive,

sec. 9, All;

sec. 10, All;

sec. 11, N1⁄2, N1⁄2SW1⁄4, SW1⁄4SW1⁄4, N1⁄2SE1⁄4, SE1⁄4SE1⁄4;

sec. 12, All;

sec. 13, All;

sec. 14, NE1⁄4NE1⁄4, S1⁄2NE1⁄4, NW1⁄4NW1⁄4, S1⁄2NW1⁄4, S1⁄2;

sec. 15, All;

sec. 16, All;

secs. 21 to 28, inclusive;

secs. 33 to 36, inclusive.

T. 16 S., R. 69 E.,

secs. 1 to 5, inclusive;

secs. 8 to 17, inclusive;

sec. 18, SE1⁄4SE1⁄4;

sec. 19, E1⁄2;

secs. 20 to 28, inclusive; 

secs. 33 to 36, inclusive.

T. 17 S., R. 69 E.,

secs. 1 to 3, inclusive;

secs. 11 to 14, inclusive;

sec. 24, All;

sec. 25, All, Except Mineral Survey 4709 Patent;

sec. 36, All, Except Mineral Surveys 4709 and 4710 Patents; 

T. 18 S., R. 69 E., 

sec. 1, lots, 1,2, partial lots 3, 4, S1⁄2NE1⁄4, S1⁄2NW1⁄4, S1⁄2, Except Mineral Survey 4710 Patent.

T. 14 S., R. 70 E.,

sec. 1, All;

secs. 10 to 36, inclusive.

T. 15 S., R. 70 E.,

secs. 2 to 11, inclusive;

secs. 15 to 20, inclusive;

sec. 21, All, Except Mineral Survey 1988 Patent;

sec. 22, All, Except Mineral Survey 1988 Patent;

secs. 28 to 33, inclusive.

T. 16 S., R. 70 E.,

secs. 4 to 11, inclusive;
2–8 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

secs. 13 to 36, inclusive.

T. 17 S., R. 70 E.,

secs. 1 to 36, inclusive.

T. 18 S., R. 70 E.,

secs. 1 to 6, inclusive, unsurveyed;

secs. 10 to 15, inclusive, unsurveyed;

secs. 22 to 27, inclusive, unsurveyed;

secs. 34 to 36, inclusive, unsurveyed.

T. 13 S., R. 71 E.,

sec. 32, All;

sec. 33, W1⁄2NE1⁄4, W1⁄2, W1⁄2SE1⁄4, All, West of Range Improvement (Fence) 0101.

T. 14 S., R. 71 E.,

sec. 4, lots 2, 3, 4, partial lot 1, SW1⁄4NE1⁄4, S1⁄2NW1⁄4, SW1⁄4, W1⁄2SE1⁄4, All, West of Range 

Improvement (Fence) 0101;

secs. 5 to 8, inclusive;

sec. 9, W1⁄2NE1⁄4, W1⁄2, W1⁄2SE1⁄4, All, West of Range Improvement (Fence) 0101;

sec. 10, W1⁄2W1⁄2, All, West of Range Improvement (Fence) 0101;

sec. 15, W1⁄2, All, West of Range Improvement (Fence) 0101;

secs. 16 to 20, inclusive;

sec. 21, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, SW1⁄4SE1⁄4, All, West of Range Improvement (Fence) 

 0101 (and CC 022455 Pipeline);

sec. 22, W1⁄2W1⁄2, All, West of Range Improvement (Fence) 0101;

sec. 28, W1⁄2NE1⁄4, W1⁄2, All, West of Range Improvement (Fence) 0101 (and CC 022455 Pipeline);

secs. 29 to 31, inclusive.

T. 16 S., R. 71 E.,

sec. 19, All;

secs. 29 to 32, inclusive.

T. 17 S., R. 71 E.,

secs. 4 to 10, inclusive, unsurveyed;

secs. 15 to 22, inclusive, unsurveyed;

secs. 27 to 34, inclusive, unsurveyed.

T. 18 S., R. 71 E.,

secs. 3 to 10, inclusive, unsurveyed;

secs. 15 to 22, inclusive, unsurveyed;

secs. 27 to 34, inclusive, unsurveyed.

T. 19 S., R. 71 E.,

sec. 3, All, unsurveyed;

sec. 4, All, unsurveyed;

sec. 9, All, unsurveyed;

sec. 10, All, unsurveyed;

sec. 15, All, unsurveyed;

sec. 16, All, unsurveyed;

sec. 21, All, unsurveyed;

sec. 22, All, unsurveyed;

sec. 27, All, unsurveyed;

sec. 28, All, unsurveyed;

sec. 33, All, unsurveyed;

sec. 34, All, unsurveyed.
Appendix 2 2–9

Gold Butte, Part B

 Legal Description Part

 T. 17 S., R. 69E.,

Approx. Total Acreage = 122,270.42 sec. 22, All;

(Clark County) sec. 23, All;

(NVN 076876) sec. 26, All, Except Mineral Survey 4709 Patent;

sec. 27, All;

sec. 34, All;

sec. 35, All, Except Mineral Survey 4709 Patent.

T 18 S., R. 69E.,

sec. 2, lots 1 to 4, inclusive, All, Except Mineral Survey 4709 Patent;

sec. 3, All;

sec. 9, All;

sec. 10, All;

sec. 11, All, Except Mineral Survey 4710 Patent;

sec. 12, All, Except Mineral Survey 4710 Patent;

sec. 13, All;

sec. 14, All, except MS 4710 patent;

secs. 15 to 17, inclusive;

secs. 20 to 29, inclusive;

secs. 32 to 36, inclusive.

T.19 S., R. 69 E.,

sec. 1, lots 1 to 4, inclusive, All, Except Mineral Survey 4707 Patent;

sec. 2, lots 1 to 4, inclusive, All, Except Mineral Survey 4707 Patent;

secs. 3 to 10, inclusive;

sec. 11, All, Except Mineral Survey 4707 Patent;

secs. 12 to 36, inclusive.

T. 20 S., R. 69 E.,

secs. 1 to 29, inclusive;

secs. 33 to 36, inclusive.

T. 18 S., R. 70 E.,

secs. 7 to 9, inclusive, unsurveyed;

secs. 16 to 21, inclusive, unsurveyed;

secs. 28 to 33, inclusive, unsurveyed.

T. 19 S., R. 70 E.,

secs. 1 to 36, inclusive, unsurveyed.

T. 20 S., R. 70 E.,

secs. 1 to 11, inclusive, unsurveyed;

secs. 14 to 22, inclusive, unsurveyed;

secs. 27 to 34, inclusive, unsurveyed.

T. 19 S., R. 71 E.,

secs. 5 to 8, inclusive, unsurveyed;

secs. 17 to 20, inclusive, unsurveyed;

secs. 29 to 32, inclusive unsurveyed.

Virgin Mountains (Gold Butte C)

 Legal Description Part

 T. 15 S., R. 70 E.,

Total Acreage = 37,090.18 sec. 1, All;
2–10 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

(Clark County) secs. 12 to 14, inclusive;

(NVN 076887) secs. 23 to 27, inclusive;

secs. 34 to 36, inclusive.

T. 16 S., 70 E.

secs. 1 to 3, inclusive;

sec. 12, All.

T. 14 S., 71 E.

secs. 32 to 34, inclusive.

T. 15 S., 71 E.

secs. 3 to 10, inclusive, unsurveyed; 

secs. 15 to 22, inclusive, unsurveyed;

secs. 27 to 34, inclusive, unsurveyed.

T. 16 S., 71 E.

secs. 3 to 10, inclusive;

secs. 15 to 18, inclusive;

sec. 20, All;

sec. 21, All;

sec. 22, lots 1,2, E1⁄2NW1⁄4, NE1⁄4SW1⁄4;

sec. 27, lots 2, 3, 4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4;

sec. 28, All;

sec. 33, All;

sec. 34, All.

T. 17 S., 71 E.

sec. 3, All, unsurveyed.

Whitney Pocket

 Legal Description Part

 T. 16 S., R. 70 E.,

Total Acreage = 160.00 sec. 23, SE1⁄4.

(Clark County)

(NVN 076889)

Red Rock Spring

 Legal Description Part

 T. 17 S., R. 70 E.,

Total Acreage = 640.00 sec. 7, SE1⁄4;

(Clark County) sec. 8, SW1⁄4;

(NVN 076883) sec. 17, NW1⁄4;

sec. 18, NE1⁄4;

Devil’s Throat

 Legal Description Part

 T. 17 S., R. 70 E.,

Total Acreage = 640.00 sec. 26, All.

(Clark County)

(NVN 076874)
Appendix 2 2–11

Gold Butte Townsite

 Legal Description Part

 T. 19 S., R. 70 E.,

Total Acreage = 160.00 sec. 17, S1⁄2NW1⁄4, N1⁄2SW1⁄4, unsurveyed.

(Clark County)

(NVN 076877)
2–12 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2D. Legal Descriptions of Mormon Mesa Tortoise, Arrow Canyon, and 

Coyote Springs Tortoise Areas of Critical Environmental Concern, Clark County, 

Nevada

Mormon Mesa Tortoise

 Legal Description Part

 T. 13 S., R. 63 E.,

Approx. Total Acreage = 146,702.28 sec. 25, SW1⁄4NW1⁄4, S1⁄2, All, South of Right-of-Way Nev065186 (NV Hwy 168) 

(Clark County) Centerline;

(NVN 076880) sec. 36, All. 

T. 131⁄2 S., R. 63 E., 

sec. 36, All, unsurveyed.

T. 14 S., R. 63 E.,

sec. 1, All, unsurveyed.

T. 13 S., R. 64 E.,

secs. 1 to 5, inclusive, unsurveyed;

sec. 6, E1⁄2, unsurveyed;

sec. 7, NE1⁄4, E1⁄2SE1⁄4, unsurveyed;

secs. 8 to 17, inclusive, unsurveyed;

secs. 20 to 29, inclusive, unsurveyed;

sec. 30, S1⁄2NE1⁄4, S1⁄2SW1⁄4NW1⁄4, SE1⁄4NW1⁄4, S1⁄2, All, South of Right-of-Way Nev065015 (NV 

Hwy 168) Centerline, unsurveyed;

secs. 31 to 36, inclusive, unsurveyed.

T. 131⁄2 S., R. 64 E.,

secs. 31 to 35, inclusive, unsurveyed;

sec. 36, W1⁄2NE1⁄4, NE1⁄4NW1⁄4, N1⁄2NW1⁄4NW1⁄4, All, North of Right-of-Way Nev060130 (NV Hwy 

168), Centerline, unsurveyed.

T. 14 S., R. 64 E.,

secs. 2 to 6, inclusive, unsurveyed;

secs. 8 to 11, inclusive, unsurveyed;

sec. 15, All, unsurveyed;

sec. 16, All, unsurveyed.

T 13 S., R. 65 E.,

sec. 1, lots 2 to 4, inclusive, SW1⁄4NE1⁄4, S1⁄2NW1⁄4, SW1⁄4, W1⁄2SE1⁄4;

secs. 2 to 24, inclusive;

sec. 26, N1⁄2;

sec. 27, N1⁄2;

sec. 28, N1⁄2, SW1⁄4;

sec. 29, All;

sec. 30, All;

sec. 31, lots 1 to 3, inclusive, partial lot 4, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, North of Right-ofWay Nev060130 (NV Hwy 168) Centerline;

sec. 32, All;

sec. 33, W1⁄2.

T. 13 S., R. 66 E.,

secs. 1 to 5, inclusive;

sec. 6, lots 1 to 4, inclusive, S1⁄2NE1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, SE1⁄4;
Appendix 2 2–13

sec. 7 to 18, inclusive; 

sec. 19, lots 1 to 4, inclusive, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, SW1⁄4SE1⁄4;

secs. 20 to 24, inclusive.

T. 13 S., R. 67 E.,

secs. 1 to 36, inclusive.

T. 14 S., R. 67 E.,

secs. 1 to 5, inclusive;

sec. 6, lots 1, 2, S1⁄2NE1⁄4, SE1⁄4;

sec. 7, NE1⁄4;

secs. 8 to 11, inclusive;

sec. 12, N1⁄2NE1⁄4, SW1⁄4NE1⁄4, NW1⁄4, N1⁄2SW1⁄4, SW1⁄4SW1⁄4, All, North of Right-of-Way Nev06475 

(Interstate-15) Centerline;

sec. 13, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 14, NW1⁄4NE1⁄4, NW1⁄4, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 15, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 16, All;

sec. 17, N1⁄2, SE1⁄4;

sec. 20, E1⁄2;

sec. 21, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 22, NW1⁄4NW1⁄4, All, North of Right-of-Way Nev06475 (Interstate-15) 

 Centerline. 

T. 13 S., R. 68 E.,

secs. 1 to 32, inclusive;

sec. 33, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, SW1⁄4SE1⁄4, All, North of Right-of-Way Nev06475 (Interstate-15) 

Centerline;

sec. 34, N1⁄2, N1⁄2SW1⁄4, All, North of Right-of-Way Nev 06475 (Interstate-15) 

 Centerline;

sec. 35, N1⁄2N1⁄2, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 36, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline.

T. 14 S., R. 68 E.,

sec. 4, partial lots 2, 3, 4, All, North of Right-of-Way Nev06475 (Interstate-15) Centerline;

sec. 5, lots 1 to 4, inclusive, SW1⁄4NW1⁄4, All, North of Right-of-Way Nev06475 (Interstate-15) 

Centerline;

sec. 6, lots 1 to 7, inclusive, S1⁄2NE1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, All, North of Right-of-Way 

Nev06475 (Interstate-15) Centerline;

sec. 7, partial lots 1, 2, All, North of Right-of-Way Nev06475 (Interstate

 15) Centerline.

T. 13 S., R. 69 E.,

secs. 1 to 24, inclusive;

sec. 25, lots 1, 3, 12, 15, partial lots 4, 6, 8, 11, 14, N1⁄2, N1⁄2SE1⁄4, All, North of Right-of-Way 

Nev06475 (Interstate 15) Centerline;

sec. 26, lots 1, 5, 8, 10, 11, 14, partial lots 2, 4, 7, 9, 12, 15, 17, N1⁄2NE1⁄4, SE1⁄4NE1⁄4, NE1⁄4NW1⁄4 

All, North of Right-of-Way Nev06475 (Interstate 15) Centerline;

sec. 27, lots 1, 3, 5, 7, 9, partial lots 2, 4, 6, 10, 12, 16, All, North of Right-of-Way Nev06475 

(Interstate 15) Centerline;

sec. 28, lots 1, 3, 5, 8, partial lots 2, 4, 6, 9, 14, 16, N1⁄2N1⁄2, All, North of Right-of-Way Nev06475 

(Interstate 15) Centerline;

sec. 29, lots 1, 5, 8, 11, 13, partial lots 2, 4, 7, 10, 12, 14, N1⁄2NE1⁄4, SW1⁄4NE1⁄4, NW1⁄4, All, North 

of Right-of-Way Nev06475 (Interstate 15) Centerline;

sec. 30, lots 5 to 10, inclusive, 12 to 16, inclusive, 18, 20, 23, 26, partial lots 11, 17, 

 19, 21, 24, 27,NE1⁄4, NW1⁄4SE1⁄4, All, North of Right-of-Way Nev06475 
2–14 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

 (Interstate 15) Centerline;

sec. 31, partial lots 8, 10, All, North of Right-of-Way Nev06475 (Interstate 15) Centerline.

T. 13 S., R. 70 E.,

sec. 4, SW1⁄4NW1⁄4, W1⁄2SW1⁄4, All, West of Boundary Line; 

sec. 5, lots 7, 8, 9, 10, partial lots 5, 6, 11, 12, S1⁄2NE1⁄4, S1⁄2NW1⁄4, S1⁄2, All, West of Boundary 

Line; 

sec. 6, All;

sec. 7, All; 

sec. 8, All, West of Boundary Line;

sec. 9, NW1⁄4NW1⁄4,NW1⁄4, SW1⁄4SW1⁄4NW1⁄4, W1⁄2NW1⁄4SW1⁄4, All, West of 

 Boundary Line; 

sec. 17, W1⁄2NE1⁄4, W1⁄2, W1⁄2SE1⁄4, All, West of Boundary Line;

sec. 18 All;

sec. 19, All; 

sec. 20, W1⁄2NE1⁄4, W1⁄2, W1⁄2SE1⁄4, All, West of Boundary Line;

sec. 29, NW1⁄4NE1⁄4, NW1⁄4, W1⁄2SW1⁄4, All West of Boundary Line; 

sec. 30, lots 5, 6, 7, 9, 12, 14, 15, 16, 17, partial lots 10, 13, NE1⁄4, E1⁄2NW1⁄4, NE1⁄4SW1⁄4, N1⁄2SE1⁄4, 

All, North of Right-of-Way Nev06475 (Interstate 15) Centerline;

sec. 31, partial lots 9, 11, All, North of Right-of-Way Nev06475 (Interstate 15) Centerline;

sec. 32, lots 6, 9, partial lots 3, 4, 7, 10, All North of Right-of-Way Nev06475 (Interstate 15) 

Centerline and Boundary Line. 

Note: The “Boundary Line” as denoted in the above legal descriptions for the Mormon Mesa ACEC refers to the Eastern Boundary line of the 

ACEC, which follows closely the edge of the Mesa and Toquop Wash. However, the line is NOT the Mesa edge, nor Toquop Wash, but follows closely between the two. The “Boundary Line” denoted for the eastern boundary edge of the ACEC is shown on the 7.5” U.S. Geological 

Survey Flat Top Mesa Topographic Map. This map is in the casefile.

Arrow Canyon 

 Legal Description Part

 T. 14 S., R. 64 E.,

Total Acreage = 2,083.68 sec. 3, NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, unsurveyed;

(Clark County) sec. 2, SW1⁄4, unsurveyed;

(NVN 076867) sec. 12, All, unsurveyed;

sec. 11, N1⁄2, SE1⁄4, unsurveyed;

sec. 10, NE1⁄4, E1⁄2NW1⁄4, unsurveyed.

T. 14 S., R. 65 E.,

sec. 7, lots 3, 4, E1⁄2SW1⁄4, SE1⁄4.

Coyote Springs Tortoise 

 Legal Description Part

 T. 13 S., R. 63 E.,

Approx. Total Acreage = 50,824.18 sec. 5, 700 Feet West of Right-of-Way Nev060729 (Hwy 93) Centerline 

(Clark County) to Fish & Wildlife (F&W) Management Boundary;

(NVN 076871) sec. 8, 700 Feet West of Right-of-Way Nev060729 (Hwy 93) Centerline to 

 F&W 

 Management Boundary;

 sec. 17, 700 Feet West of Right-of-Way Nev060729 (Hwy 93) Centerline to 

 F&W 

 Management Boundary;

 sec. 20, 700 Feet West of Right-of-Way Nev060729 (Hwy 93) Centerline and All South of Rightof-Way Nev065185 (Hwy 168) Centerline;

sec. 21, All, South of Right-of-Way Nev065185 (NV Hwy 168) Centerline;

sec. 22, All, South of Right-of-Way Nev065185 (NV Hwy 168) Centerline;

 sec. 23, All, South of Right-of-Way Nev065185 (NV Hwy 168) Centerline;
Appendix 2 2–15

 sec. 26, NW1⁄4NE1⁄4, S1⁄2NE1⁄4, W1⁄2, SE1⁄4, All, South of Right-of-Way 

 Nev065185 

 (NV Hwy 168) Centerline;

 sec. 27, All;

 sec. 28, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W Management

 Boundary;

 sec. 29, All, East of F&W Management Boundary;

 sec. 33, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W Management

 Boundary;

 sec. 34, All;

 sec. 35, All. 

T. 131⁄2 S., R. 63 E.,

sec. 33, NE1⁄4, NE1⁄4NW1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W 

 Management Boundary, unsurveyed;

sec. 34, All, unsurveyed;

sec. 35, All, unsurveyed. 

T. 14 S., R. 63.,

sec. 2, All, unsurveyed;

sec. 3, All, unsurveyed;

sec. 4, NE1⁄4, E1⁄2NW1⁄4, SE1⁄4, All, East of F&W Management Boundary, 

 unsurveyed;

sec. 9, E1⁄2, All, East of F&W Management Boundary, unsurveyed;

sec. 10, All, unsurveyed;

sec. 11, All, unsurveyed;

sec. 14, All, unsurveyed;

sec. 15, All, unsurveyed;

sec. 16, NE1⁄4,E1⁄2SE1⁄4, All, East of F&W Management Boundary, unsurveyed;

sec. 21, E1⁄2E1⁄2, All, East of F&W Management Boundary, unsurveyed;

sec. 22, All, unsurveyed;

sec. 23, All, unsurveyed;

sec. 26, All, unsurveyed;

sec. 27, All, unsurveyed;

sec. 28, E1⁄2NE1⁄4, All, East of F&W Management Boundary, unsurveyed;

sec. 33, E1⁄2E1⁄2NE1⁄4, All, East of F&W Management Boundary, unsurveyed;

sec. 34, All, unsurveyed;

sec. 35, All, unsurveyed.

T. 15 S., R. 63 E.,

sec. 2, All, unsurveyed;

sec. 3, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W Management

 Boundary, 

 unsurveyed;

sec. 4, All, East of F&W Management Boundary;

sec. 10, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W Management

 Boundary, 

 unsurveyed;

sec. 11, All, unsurveyed;

sec. 14, All, unsurveyed;

sec. 15, NE1⁄4,E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, All, East of F&W Management

 Boundary, 

 unsurveyed;

sec. 18, SW1⁄4SW1⁄4, All, South of F&W Management Boundary, unsurveyed;

sec. 19, NW1⁄4, S1⁄2, All, South of F&W Management Boundary, unsurveyed;

sec. 20, S1⁄2S1⁄2, All, South of F&W Management Boundary, unsurveyed;
2–16 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

sec. 21, S1⁄2SE1⁄4, All, South of F&W Management Boundary, unsurveyed;

 sec. 22, NE1⁄4, E1⁄2NW1⁄4, NE1⁄4SW1⁄4, SW1⁄4SW1⁄4, SE1⁄4, All, East and South of F&W Management 

Boundary, unsurveyed. 

secs. 27 to 34, inclusive, unsurveyed.

T. 16 S., R. 63 E.,

secs. 3 to 10, inclusive;

secs. 15 to 22, inclusive;

secs. 28 to 33, inclusive.

T. 17 S., R. 63 E.,

secs. 7 to 9, inclusive;

secs. 16 to 21, inclusive;

secs. 28 to 31, inclusive;

sec. 32, lots 1, 8, 9,14, 15, 16, NW1⁄4, NW1⁄4SW1⁄4, All, West of Powerline Right-of-Way N53399 

Centerline.

T. 18 S., R. 63 E.,

sec. 5, lots 4, 8, 9, 16, 17, SW1⁄4NW1⁄4, W1⁄2SW1⁄4, All, West of Powerline Right-of-Way N53399 

Centerline;

sec. 6, All;

sec. 7, All;

sec. 8, lots 3, 5, 6, 13, 14, All, West of Powerline Right-of-Way N53399 Centerline;

sec. 17, lots 4, 5, 12, All, West of Powerline Right-of-Way N53399 Centerline;

sec. 18, lots 1 to 4, inclusive, 6, 7, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, W1⁄2SE1⁄4, All, West of Powerline 

Right-of-Way N53399 Centerline;

 sec. 19, lots 1 to 4, inclusive, 6, 7, 10, 11, W1⁄2NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, W1⁄2SE1⁄4, All, West of 

Powerline Right-of-Way N53399 Centerline;

 sec. 29, lots 4, 22, All, West of Powerline Right-of-Way N53399 Centerline;

sec. 30, lots 1 to 4, inclusive, 6 to 8, inclusive, W1⁄2NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, W1⁄2SE1⁄4, All, West 

of Powerline Right-of-Way N53399 Centerline;

sec. 31, lots 7, 8, 9, 15, 18, NW1⁄4NE1⁄4, All, West of Powerline Right-of-Way N53399 Centerline.

T. 19 S., R. 63 E.,

sec. 6, lots 9, All, West of Powerline Right-of-Way N53399 Centerline.

Note: The U.S. Fish and Wildlife Service Management Boundary that parallels Right-of-Way Nev060729 (Hwy 93) is 500 feet west of the 

right-of-way boundary, or 700 feet from centerline. This land was transferred to the U.S. Fish and Wildlife Service under P.L. 107-282.
Appendix 2 2–17

Appendix 2E. Legal Descriptions of Arden, Bird Spring, and Sloan Rock Art Areas 

of Critical Environmental Concern

Arden 

 Legal Description Part

 T. 22S., R. 60 E.,

Total Acreage = 1,480.10 sec. 32, W1⁄2NE1⁄4NE1⁄4NE1⁄4, W1⁄2NE1⁄4NE1⁄4,

(Clark County) SE1⁄4NE1⁄4NE1⁄4, W1⁄2NE1⁄4,

(NVN 076866) W1⁄2NE1⁄4SE1⁄4NE1⁄4, W1⁄2SE1⁄4NE1⁄4,

W1⁄2NE1⁄4NE1⁄4NW1⁄4, S1⁄2NE1⁄4NW1⁄4,

E1⁄2NE1⁄4NW1⁄4NW1⁄4, E1⁄2SW1⁄4NW1⁄4NW1⁄4,

W1⁄2SE1⁄4NW1⁄4NW1⁄4, E1⁄2NE1⁄4SW1⁄4NW1⁄4,

W1⁄2SW1⁄4NW1⁄4, SE1⁄4SW1⁄4NW1⁄4,

W1⁄2NE1⁄4SE1⁄4NW1⁄4, W1⁄2SE1⁄4NW1⁄4,

SE1⁄4SE1⁄4NW1⁄4, S1⁄2;

 sec. 33, NE1⁄4NE1⁄4SW1⁄4, W1⁄2NW1⁄4NE1⁄4SW1⁄4,

S1⁄2NE1⁄4SW1⁄4, NW1⁄4SW1⁄4, W1⁄2NE1⁄4SW1⁄4SW1⁄4, W1⁄2SW1⁄4SW1⁄4,

SE1⁄4SW1⁄4SW1⁄4, E1⁄2NE1⁄4SE1⁄4SW1⁄4, W1⁄2SE1⁄4SW1⁄4, W1⁄2SE1⁄4SE1⁄4SW1⁄4, 

N1⁄2SE1⁄4, SW1⁄4SE1⁄4, W1⁄2NE1⁄4SE1⁄4SE1⁄4, NW1⁄4SE1⁄4SE1⁄4.

T. 23 S., R 60 E.,

sec. 4, lots 1 to 4, inclusive, S1⁄2N1⁄2;

sec. 5, lots 1 to 4, inclusive, S1⁄2N1⁄2. 

Bird Spring

 Legal Description Part

 T. 24 S., R. 59 E.,

Total Acreage = 160.77 sec. 4, lots 1, 2, S1⁄2NE1⁄4. 

(Clark County)

(NVN 076870)

Sloan Rock Art

 Legal Description Part

 T. 23 S., R. 61 E.,

Total Acreage = 319.88 sec. 35, S1⁄2S1⁄2.

(Clark County) 

(NVN 076885) T. 24 S., R. 61 E.,

 sec. 2, lots 1, 2, 3, 4.
2–18 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2F. Legal Descriptions of Ash Meadows and Amargosa Mesquite Trees 

Areas of Critical Environmental Concern

Ash Meadows

 Legal Description Part

 T. 17 S., R. 50 E.,

Total Acreage = 36,904.532 sec. 7, All;

(Nye County) sec. 8, All;

(NVN 076868) sec. 9, lots 1 to 12, inclusive;

sec. 10, lots 1 to 8, inclusive, 12;

sec. 11, All;

sec. 12, lots 1 to 15, inclusive;

sec. 13, All;

sec. 14, All;

sec. 15, lots 1 to 4, inclusive;

sec. 17, N1⁄2, SW1⁄4, W1⁄2SE1⁄4;

sec. 18, All;

sec. 19, All;

sec. 20, NW1⁄4, N1⁄2SW1⁄4;

sec. 21, lots 5, 6; 

sec. 22, lots 1 t0 5, inclusive, W1⁄2SE1⁄4, S1⁄2N1⁄2SE1⁄4SE1⁄4,S1⁄2SE1⁄4SE1⁄4;

sec. 23, lots 1 to 6, inclusive, N1⁄2SE1⁄4, E1⁄2SW1⁄4SE1⁄4,SE1⁄4SE1⁄4; 

sec. 24, All;

sec. 25, All;

sec. 26, NE1⁄4NE1⁄4, E1⁄2NW1⁄4NE1⁄4, S1⁄2NE1⁄4, SW1⁄4NW1⁄4, S1⁄2SE1⁄4NW1⁄4, S1⁄2; 

sec. 27, All;

sec. 28, E1⁄2NE1⁄4;

sec. 29, NE1⁄4NW1⁄4

sec. 30, lots 3 to 10, inclusive, E1⁄2SW1⁄4, W1⁄2SE1⁄4;

sec. 31, All;

sec. 32, NE1⁄4NE1⁄4, S1⁄2NE1⁄4, W1⁄2W1⁄2, N1⁄2SE1⁄4;

sec. 34, NE1⁄4;

sec. 35, N1⁄2NE1⁄4, SE1⁄4NE1⁄4, NE1⁄4NW1⁄4, W1⁄2W1⁄2, N1⁄2NE1⁄4SE1⁄4, NW1⁄4SE1⁄4; 

sec. 36, NE1⁄4, W1⁄2, N1⁄2SE1⁄4, SE1⁄4SE1⁄4.

T. 18 S., R. 50 E.,

sec. 1, lots 1 to 4, inclusive;

sec. 2, lots 1, 2, S1⁄2NE1⁄4, SE1⁄4;

sec. 3, SW1⁄4SW1⁄4;

sec. 5, All;

sec. 6, lots 1, 2, 8 to 12, inclusive, S1⁄2NE1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4, W1⁄2W1⁄2SE1⁄4;

sec. 7, lots 4 to 10, inclusive, S1⁄2NE1⁄4, E1⁄2NW1⁄4, NE1⁄4SW1⁄4, N1⁄2SE; sec. 8, 

All; 

sec. 9, W1⁄2NW1⁄4, SW1⁄4;

sec. 10, E1⁄2;

sec. 11, N1⁄2NW1⁄4, W1⁄2SW1⁄4;

sec. 12, W1⁄2NE1⁄4, NW1⁄4;

sec. 13, SW1⁄4NE1⁄4, SE1⁄4SW1⁄4, NW1⁄4SE1⁄4, E1⁄2SW1⁄4SE1⁄4, E1⁄2W1⁄2SW1⁄4SE1⁄4;

sec. 14, NE1⁄4, E1⁄2SW1⁄4, SE1⁄4;

sec. 15, NE1⁄4, E1⁄2SW1⁄4, SE1⁄4;

sec. 16, lot 2, W1⁄2NE1⁄4, NW1⁄4, N1⁄2SW1⁄4, SE1⁄4SW1⁄4, W1⁄2SE1⁄4;

secs. 17 to 23, inclusive;

sec. 24, N1⁄2NE1⁄4, SE1⁄4NE1⁄4, N1⁄2NW1⁄4, W1⁄2SW1⁄4;

sec. 25, S1⁄2NE1⁄4, W1⁄2NW1⁄4, SE1⁄4NW1⁄4, S1⁄2;

secs. 26 to 29, inclusive;
Appendix 2 2–19

secs. 33 to 36, inclusive.

T. 17 S., R. 51 E.,

sec. 7, All;

sec. 8, NW1⁄4NE1⁄4, W1⁄2SW1⁄4NE1⁄4, W1⁄2, W1⁄2NW1⁄4SE1⁄4;

sec. 17, S1⁄2NE1⁄4NE1⁄4, W1⁄2NE1⁄4, SE1⁄4NE1⁄4, W1⁄2, SE1⁄4;

secs. 18 to 20, inclusive;

sec. 29, All;

sec. 30, All;

sec. 31, lots 1 to 4, inclusive, NE1⁄4NE1⁄4, W1⁄2NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, W1⁄2SE1⁄4;

sec. 32, lots 1 to 4, inclusive, N1⁄2.

T. 18 S., R. 51 E.,

sec. 5, lot 1;

sec. 6, lots 2 to 6, inclusive, SW1⁄4NE1⁄4, SE1⁄4NW1⁄4, NE1⁄4SW1⁄4, SE1⁄4;

sec. 7, NE1⁄4, E1⁄2NW1⁄4;

sec. 8, NW1⁄4;

sec. 17, E1⁄2E1⁄2;

sec. 18, lots 2, 3, 4, SW1⁄4NE1⁄4, SE1⁄4NW1⁄4, E1⁄2SW1⁄4;

sec. 19, lots 1, 2, NE1⁄4, E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4;

sec. 20, All;

sec. 29, All;

sec. 30, lots 2 to 4, inclusive, NE1⁄4NE1⁄4, N1⁄2NW1⁄4NE1⁄4, N1⁄2S1⁄2NW1⁄4NE1⁄4, 

NW1⁄4NW1⁄4NE1⁄4, SW1⁄4NW1⁄4NE1⁄4, S1⁄2N1⁄2SE1⁄4NW1⁄4NE1⁄4, S1⁄2SE1⁄4NW1⁄4NE1⁄4, S1⁄2NE1⁄4, 

E1⁄2NW1⁄4, E1⁄2SW1⁄4, SE1⁄4, Excluding Patent 27-70-0091;

sec. 31, All;

sec. 32, All.

Amargosa Mesquite Trees

 Legal Description Part

 T. 16 S., R. 51 E.,

Total Acreage = 6,890.97 sec. 35, All;

(Nye County) sec. 36, SW1⁄4. 

(NVN 076865) 

 T. 17 S., R. 51 E.,

sec. 1, lots 3, 4, S1⁄2NW1⁄4, S1⁄2;

sec. 2, All;

sec. 11, E1⁄2;

sec. 12, All;

sec. 13, All;

sec. 14, E1⁄2;

sec. 23, E1⁄2;

sec. 24, All;

sec. 25, All;

sec. 26, E1⁄2;

sec. 35, All;

sec. 36, All.
2–20 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2G. Legal Description of Virgin River Area of Critical Environmental 

Concern, Clark County, Nevada

Virgin River 

 Legal Description Part

 T. 14 S., R. 69 E.,

Approx. Total Acreage = 6,312.82 sec. 11, SE1⁄4;

(Clark County) sec. 12, W1⁄2NE1⁄4, NW1⁄4, NW1⁄4SW1⁄4;

(NVN 076888) sec. 13, All Federal Land North of Gold Butte Back Country Byway Road; 

sec. 14, N1⁄2NE1⁄4, NW1⁄4, N1⁄2SW1⁄2, SE1⁄4SW1⁄4;

sec. 15, SE1⁄4;

sec. 22, NE1⁄4, S1⁄2;

sec. 23, All Federal Land North of Gold Butte Back Country Byway Road;

sec. 26, All Federal Land North of Gold Butte Back Country Byway Road;

sec. 27, All Federal Land North of Gold Butte Back Country Byway Road;

sec. 28, N1⁄2, SW1⁄4, S1⁄2SE1⁄4, All Federal Land North of Gold Butte Back 

 Country Byway Road

sec. 29, S1⁄2;

sec. 32, N1⁄2, SW1⁄4, SE1⁄4SE1⁄4;

sec. 33, All Federal Land North of Gold Butte Back Country Byway Road.

T. 13 S., R. 70 E.,

sec. 27, lots 8, 10, 17, 19, 20, 21, partial lots 7, 9, 11, 13, 16, 18, All, South of 

Right-of-Way Nev065014 (Interstate 15) Centerline; 

 sec. 33, lots 1, 11, 13, 15, 16, 17, partial lots 2, 4, 6, 8, 10, 12, 14, SW1⁄4, N1⁄2SE1⁄4, SW1⁄4SE1⁄4, All, 

South of Right-of-Way Nev065014 (Interstate 15) Centerline;

sec. 34, lots 1 to 4, inclusive, 6, 11, NW1⁄4NW1⁄4, All Federal Land South of Right-of-Way 

Nev065014 (Interstate-15) Centerline and North of Right-of-Way Nev07490 (NV Hwy 

170) Centerline.

T. 14 S., R. 70 E., 

sec. 3, partial lot 4, All, North of Right-of-Way Nev07490 (NV Hwy 170) 

 Centerline;

sec. 4, lots 2, 3, 4, partial lot 1, S1⁄2NW1⁄4, All, North of Right-of-Way 

 Nev07490 (NV Hwy 170) Centerline;

sec. 5, lots 1 to 4, inclusive, S1⁄2NE1⁄4, S1⁄2NW1⁄4, SW1⁄4, N1⁄2SE1⁄4, All, North of 

 Right-of-Way Nev07490 (NV Hwy 170) Centerline; 

 sec. 6, lots, 1, 2, 6, 7, S1⁄2NE1⁄4, E1⁄2SW1⁄4, SE1⁄4;

sec. 7, partial lot 2, 3, N1⁄2NE1⁄4, NE1⁄4NW1⁄4, All Federal Land North of Right-of-Way Nev07490 

(NV Hwy 170) Centerline and North of Gold Butte Back Country Byway Road;

sec. 8, All, North of Right-of-Way Nev07490 (NV Hwy 170) Centerline.

Note: The Gold Butte Back Country Byway is an RS2477 road authorization.
Appendix 2 2–21

Appendix 2H. Legal Description of Hidden Valley Area of Critical Environmental 

Concern

Hidden Valley

 Legal Description Part

 T. 18 S., R. 65 E.,

Total Acreage = 3,360.00 sec. 26, W1⁄2, unsurveyed;

(Clark County) sec. 27, E1⁄2, unsurveyed;

 (NVN 076878) sec. 34, All, unsurveyed;

sec. 35, All, unsurveyed.

T. 19 S., R. 65 E.,

sec. 2, W1⁄2, unsurveyed;

sec. 3, All, unsurveyed;

sec. 10, N1⁄2, unsurveyed;

sec. 11, NW1⁄4, unsurveyed.
2–22 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2I. Legal Description of Rainbow Gardens Area of Critical 

Environmental Concern, Clark County, Nevada

Rainbow Gardens 

 Legal Description Part

 T. 20 S., R. 62 E.,

Approx. Total Acreage = 38,172.03 sec. 12, All;

(Clark County) sec. 13, All;

(NVN 076882) sec. 24, All;

sec. 25, All;

sec. 35, lots 1 to 4, inclusive;

sec. 36, All.

T. 21 S., R. 62 E.,

sec. 1, All;

sec. 2, lots 5, 6, 9 to 12, inclusive, 17, 18;

sec. 11, lots 1 to 6, inclusive, 11, 12;

sec. 12, All;

sec. 13, All;

sec. 14, E1⁄2;

sec. 23, NE1⁄4NE1⁄4, E1⁄2SE1⁄4;

sec. 24, All;

sec. 25, N1⁄2NE1⁄4, NE1⁄4NW1⁄4.

T. 20 S., R. 63 E.,

sec. 1, N1⁄2, NW1⁄4NE1⁄4SW1⁄4, N1⁄2NW1⁄4SW1⁄4, 

SW1⁄4NW1⁄4SW1⁄4, SW1⁄4SW1⁄4, W1⁄2SE1⁄4SW1⁄4, unsurveyed;

sec. 2, All, unsurveyed;

sec. 3, SE1⁄4, unsurveyed;

sec. 7, All, unsurveyed;

sec. 8, W1⁄2, unsurveyed;

sec. 11, All, Except Mineral Entry Patents, unsurveyed;

sec. 12, NW1⁄4NW1⁄4, W1⁄2SW1⁄4, unsurveyed; 

sec. 13, W1⁄2NE1⁄4NW1⁄4, W1⁄2NW1⁄4, W1⁄2SE1⁄4NW1⁄4, SW1⁄4,

S1⁄2NE1⁄4SE1⁄4, W1⁄2NW1⁄4SE1⁄4, S1⁄2SE1⁄4, unsurveyed; 

secs. 14 to 34, inclusive, unsurveyed.

T. 21 S., R. 63 E.,

sec. 3, All;

sec. 4, All, Except Mineral Entry Patents;

secs. 5 to 7, inclusive; 

sec. 8, All, Except Mineral Entry Patents;

sec. 9, All, Except Mineral Entry Patents;

sec. 10, All;

sec. 16, All, Except Mineral Entry Patents;

sec. 17, All, Except Mineral Entry Patents;

sec. 18, All;

sec. 19, All;

sec. 20, All, Except Mineral Entry Patents;

sec. 21, N1⁄2, SW1⁄4, N1⁄2SE1⁄4, SW1⁄4SE1⁄4;

sec. 30, lots 1, 2, NE1⁄4, E1⁄2NW1⁄4.

T. 20 S., R. 64 E.,

sec. 4, All;

sec. 5, All;
Appendix 2 2–23

sec. 8, N1⁄2, SE1⁄2;

sec. 9, All;

sec. 16, All;

sec. 19, lots 7, 8, SE1⁄4SW1⁄4;

sec. 20, S1⁄2NE1⁄4, NE1⁄4SW1⁄4, S1⁄2SW1⁄4, SE1⁄4;

sec. 21 All;

secs. 28 to 30, inclusive.
2–24 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2J. Legal Description of River Mountains Area of Critical 

Environmental Concern, Clark County, Nevada

River Mountains 

 Legal Description Part

 T. 21 S., R. 63 E.,

Approx. Total Acreage = 10,963.31 sec. 25, NE1⁄4NW1⁄4, S1⁄2NW1⁄4NW1⁄4, S1⁄2NW1⁄4, S1⁄2, All, South of NV Hwy 147 

(Clark County) (Lake Mead Drive) Centerline;

(NVN 076884) sec. 26, partial lots 5, 14, 15, 17, 24, 25, South of NV Hwy 147 (Lake Mead 

 Drive) Centerline; sec. 35, lots 1, 6, 7, SE1⁄4SE1⁄4;

 sec. 36, All.

T. 22 S., R. 63 E.,

sec. 1, All;

sec. 2, All;

sec. 3, S1⁄2;

sec. 10, NE1⁄4, NE1⁄4NW1⁄4 , N1⁄2SE1⁄4, SE1⁄4SE1⁄4; 

secs. 11 to 13, inclusive;

sec. 14, N1⁄2, SE1⁄4;

sec. 23, E1⁄2;

sec. 24, All;

sec. 25, All;

 sec. 26, E1⁄2;

sec. 36, All.

T. 22 S., R. 631⁄2 E.,

sec. 1, All;

sec. 12, All;

sec. 13, All;

sec. 24, All;

sec. 25, All;

sec. 36, All;

T. 23S., R. 631⁄2 E.,

sec. 1, lots 1 to 7, inclusive, S1⁄2NE1⁄4.
Appendix 2 2–25

Appendix 2K. Legal Description of Stump Spring Area of Critical Environmental 

Concern, Clark County, Nevada

Stump Spring 

 Legal Description Part

 T. 22 S., R. 55 E.,

Total Acreage = 641.32 sec. 32, S1⁄2;

(Clark County)

(NVN 076886) T. 23 S., R. 55 E.,

 sec. 5, lots 1 to 4, inclusive, S1⁄2N1⁄2.
2–26 Mineral Resource Assessment of Selected Areas in Clark and Nye Counties, Nevada

Appendix 2L. Legal Description of Big Dune Area of Critical Environmental 

Concern, Nye County, Nevada

Big Dune

 Legal Description Part

 T. 15 S., R. 48 E.,

Total Acreage = 1,920.00 sec. 8, S1⁄2, unsurveyed;

(Nye County) sec. 9, S1⁄2, unsurveyed;

(NVN 076869) sec. 16, All, unsurveyed;

sec. 17, All, unsurveyed.