Mineral Resources of the Little High Rock 

Canyon Wilderness Study Area, Humboldt 

and Washoe Counties, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1707-C

Chapter C

Mineral Resources of the

Little High Rock Canyon

Wilderness Study Area,

Humboldt and Washoe Counties, Nevada

By WILLIAM J. KEITH, ROBERT L. TURNER, 

and DONALD PLOUFF 

U.S. Geological Survey

THOMAS J. PETERS 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1707

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

NORTHWESTERN NEVADA
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center, Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Mineral resources of the Little High Rock Canyon 

Wilderness Study Area, Humboldt and Washoe Counties, 

Nevada.

U.S. Geological Survey Bulletin 1707-C

Bibliography

Supt. of Docs. No.: I 19.3:1707-C

1. Mines and mineral resources Nevada Little High Rock

Canyon Wilderness. 2. Little High Rock Canyon Wilderness

(Nev.) I. Keith, William, J., 1933 . II. Series.

QE75.B9 No. 1707-C 557.3s 87-600344 

[TN24.N3] [553'.09793'54]
STUDIES RELATED TO WILDERNESS 

Bureau of Land Management Wilderness Study Area

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) 

requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral 

surveys of certain areas to determine the mineral values, if any, that may be present. 

Results must be made available to the public and be submitted to the President and the 

Congress. This report presents the results of a mineral survey of part of the Little High 

Rock Canyon Wilderness Study Area (CA-020-913/NV-020-008), Humboldt and Washoe 

Counties, Nevada.

CONTENTS

Summary Cl

Abstract 1

Character and setting 1

Identified resources 1

Mineral resource potential 1 

Introduction 3

Area description 3

Previous and present investigations 3

Acknowledgments 3 

Appraisal of identified resources 5

Mining and exploration history 5

Mines, prospects, claims, and mineralized areas 5 

Prospects for epithermal gold and silver 5 

Industrial minerals and energy-related occurrences 6

Mineral economics 6 

Assessment of potential for undiscovered resources 7

Geological studies 7

Geochemical studies 7

Geophysical studies 8

Mineral and energy resources 8 

References cited 9 

Appendixes

Definition of levels of mineral potential and certainty of 

assessment 13

Resource/reserve classification 14

Geologic time chart 15

FIGURES

1. Index map showing location of the Little High Rock Canyon Wilderness 

Study Area, Humboldt and Washoe Counties, Nevada C2

2. Map showing mineral resource potential and generalized geology of the

Little High Rock Canyon Wilderness Study Area, Humboldt and Washoe Counties, 

Nevada 4

TABLE

1. Descriptions of prospects, claims, and mineralized areas in the Little 

High Rock Canyon Wilderness Study Area C16

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: 

NORTHWESTERN NEVADA

Mineral Resources of the

Little High Rock Canyon

Wilderness Study Area,

Humboldt and Washoe Counties, Nevada

By William J. Keith, Robert L. Turner, and Donald Plouff 

U.S. Geological Survey

Thomas J. Peters 

U.S. Bureau of Mines

SUMMARY 

Abstract

At the request of the U.S. Bureau of Land 

Management, 17,320 acres of the Little High Rock 

Canyon Wilderness Study Area (CA-020-913/NV-020- 

008) were studied. In this report, the area studied is 

referred to as "the wilderness study area," or simply 

"the study area." The study area is in the west-central 

Calico Mountains in Humboldt and Washoe counties, 

Nevada. Geological, geochemical, geophysical, and 

mineral surveys were conducted by the U.S. Geological 

Survey and the U.S. Bureau of Mines in 1985 to assess 

the mineral resources (known) and mineral resource 

potential (undiscovered) of the study area. No 

resources were identified in the study area, but the 

results of these surveys indicate three areas with 

moderate resource potential for gold and silver in 

epithermal deposits in the northwestern, central, and 

southern parts of the area. Elsewhere within the study 

area, the potential for these resources is low. Two 

small areas in the southeastern part of the study area 

have low potential for uranium resources; one small 

area has low potential for pozzolan resources, and one 

area has low potential for perlite resources. Potential 

for geothermal resources is low in the entire study 

area.

Character and Setting

The study area is in the west-central Calico 

Mountains, about 45 mi southeast of Vya, Nev. (fig. 

1). The topography is typical of deeply dissected

plateaus. Relief in the area is moderate; elevations 

range from 5,000 ft at the east end of Little High 

Rock Canyon to 6,474 ft 0.25 mi north of McConnel 

Canyon (fig. 2). The study area is underlain by a 

sequence of lava ilows and pyroclastic deposits that 

overlie and interfinger with lake and stream 

sediments; all are of Miocene age (see appendixes for 

geologic time chart). These volcanic and sedimentary 

rocks are faulted and locally altered.

Identified Resources

No prospects or mineralized areas with identified 

resources were found within the study area. Small 

pozzolan (additive to aid in underwater hardening of 

cement), perlite (light-weight aggregate used in the 

plaster industry), and uranium occurrences are present, 

but are distant from transportation centers or 

anticipated markets.

Mineral Resource Potential

Three parts of the study area have moderate 

resource potential for gold and silver in epithermal 

deposits of hot-spring origin, and three small areas 

have low potential for pozzolan, perlite, or uranium 

resources. The rest of the study area has low resource 

potential for gold and silver in epithermal deposits and 

geothermal energy.

The three areas that have moderate resource 

potential for gold and silver of hot-spring origin (fig. 2) 

contain anomalous concentrations of arsenic, 

antimony, bismuth, cadmium, mercury, tellurium, and

C1
1 1 9°00'

42°00'

SOLDIER MEADOW

APPROXIMATE BOUNDARY ,

OF

LITTLE HIGH ROCK CANYON

WILDERNESS STUDY AREA

(CA-020-913/NV-020-008)

Demo Ranch 

diatomite prospect

Section 24 deposit

/

West deposit

AREA OF AAAP

(______I

Rgurc 1. Index map showing the location of the Little High Rock Canyon Wilderness Study Area, Humboldt and Washoe Counties, 

Nevada.

C2
silver (U.S. Geological Survey, unpub. data, 1986). 

This, combined with the occurrence of permissive rock 

types, faults to act as fluid conduits, and the presence 

of a similar deposit within 5 mi of the study area 

(Section 24 and West prospects, fig. 1) indicate 

moderate potential for gold and silver in epithermal 

hot-spring type deposits, similar to the Round 

Mountain deposit in Nye County, Nev., 250 mi 

southeast of the study area. The deposit would 

probably be similar in size or smaller than the Section 

24 and West prospects (known hereafter as the Hog 

Ranch deposit). The rest of the study area has low 

potential for these same commodities in epithermal 

deposits. Although the rest of the study area does not 

have the anomalous concentrations of indicator 

elements, it has numerous occurrences of arsenicbearing opal that also suggest the possible presence of 

hot-spring type gold/silver deposits.

The study area has relatively high heat flow and 

nearby low-temperature hot-springs (Soldier Meadow, 

fig. 1). This suggests a low potential for lowtemperature (less than 90 °C) geothermal energy 

resources.

Small occurrences of pozzolan-bearing 

sediments, perlite, and uranium are present in the 

southeastern part of the study area. The resource 

potential for these commodities is low due to poor 

quality and small aerial extent.

INTRODUCTION

This mineral survey was requested by the U.S. 

Bureau of Land Management (BLM) and is a joint 

effort by the U.S. Geological Survey and the U.S. 

Bureau of Mines. An introduction to the wilderness 

review process, mineral survey methods, and agency 

responsibilities were provided by Beikman and others, 

(1983). The U.S. Bureau of Mines (USBM) evaluates 

identified resources at individual mines and known 

mineralized areas by collecting data on current and 

past mining activities and through field examination of 

mines, prospects, claims, and mineralized areas. 

Identified resources are classified according to the 

system described by U.S. Bureau of Mines and U.S. 

Geological Survey (1980). Studies by the U.S. 

Geological Survey (USGS) are designed to provide a 

reasonable scientific basis for assessing the potential 

for undiscovered mineral resources by determining 

geologic units and structures, possible environments of 

mineral deposition, presence of geochemical and 

geophysical anomalies, and applicable ore-deposit 

models. Mineral assessment methodology and 

terminology as they apply to these surveys were 

discussed by Goudarzi (1984). See the appendix for the 

definition of levels of' mineral resource potential, 

certainty of assessment, and classification of 

identified resources.

Area Description

At the request of the U.S. Bureau of Land 

Management, 17,320 acres of the Little High Rock 

Canyon Wilderness Study Area (CA-020-913/NV-020- 

008) were studied. In this report, the area studied is

referred to as "the wilderness study area," or simply 

"the study area." The study area is located in western 

Humboldt and eastern Washoe Counties, Nev. (fig. 1), 

and consists of sparsely vegetated, plateau-type 

terrane. It is in the west-central part of the Calico 

Mountains and the south, east, and west margins are 

accessible by gravel roads. With the exception of two 

short jeep roads, the interior is accessible only by 

helicopter, horseback, or on foot. Elevations range 

from 5,000 ft at the east end of Little High Rock 

Canyon to 6,474 ft 0.25 mile north of McConnel 

Canyon (fig. 2).

Previous and Present Investigations

A geologic map of the study area, prepared by 

the U.S. Geological Survey in 1986 (fig. 2), provides a 

base for the interpretation of geochemical, 

geophysical, and mining claim data. The reports and 

maps by Bonham (1969), Willden (1964), and Greene 

(1984) also provided geologic data for this report.

Geochemical data were obtained from a 

geochemical-geostatistical study done for the U.S. 

Bureau of Land Management by Barringer Resources, 

Inc. (1982), and from analyses of stream sediment and 

rock samples collected by the U.S. Geological Survey 

(unpub data, 1986).

Earlier geophysical studies, which consisted of a 

regional gamma-ray survey (Geodata International, 

Inc., 1978) and an aeromagnetic survey (U.S. 

Geological Survey, 1972), were supplemented in 1984 

and 1985 with a gravity survey by the U.S. Geological 

Survey.

The U.S. Bureau of Mines studied the known 

prospects, claims, and mineralized areas within and 

adjacent to the study area as a means of predicting the 

tonnage and grade of resources that might be present 

in the study area (Peters and others, 1987). Available 

information on the geology and mineral resources of 

the Little High Rock Canyon Wilderness Study Area, 

including BLM and Washoe County mining records, and 

the USBM MILS (Mineral Industry Location System) 

files, was reviewed prior to field work. Field 

examinations included mapping and sampling of 

prospects and mineralized areas. A total of 269 

samples, including 117 rock, 106 soil, and 46 placer 

samples, were taken in or adjacent to the study area. 

Detailed analytical procedures and sample results are 

given in Peters and others (1987). Additional 

information is available from the U.S. Bureau of 

Mines, Western Field Operations Center, E. 360 Third 

avenue, Spokane, WA 99202.

Acknowledgments

The U.S. Geological Survey and the U.S. Bureau 

of Mines received assistance from the following: 

Joseph McFarland and Richard Wessman, U.S. Bureau 

of Land Management geologists, provided information 

and logistical support; Ralph Barnard and Siegfried 

Holso of Ferret Exploration, Paul Glavinovich and Carl 

Herring of Noranda Exploration, and Fred Saunders and 

Jeffrey Wilson of Tenneco Minerals provided 

permission to examine their company's gold deposits as

C3
\ I

M/C 

Ag, Au

[.1]

APPROXIMATE BOUNDARY

OF

LITTLE HIGH ROCK CANYON

WILDERNESS STUDY AREA

(CA-020-913/NV-020-008)

2 MILES 

J

Figure 2. Mineral resource potential and generalized geology of the Little Rock Canyon Wilderness Study Area, Humboldt and 

Washoe Counties, Nevada.

C4
EXPLANATION

Area with low mineral and geothermal resource potential 

Area with moderate mineral resource potential

See appendixes for definition of levels of mineral resource potential and 

certainty of assessment

Ag

Au

Geo

Pe

Po

U

Commodities

Silver

Gold

Geothermal

Perlite

Pozzolan

Uranium

[ ] Types of deposits or occurrences

1 Epithermal hot-spring low-grade bulk-mineable

2 Tuffaceous sediments

3 Basal vitrophere

Correlation of Map Units 

Qal I T Holocene

Thr

Tht

fhf

-Miocene

J- QUATERNARY

h TERTIARY

well as technical advice on disseminated gold deposits; 

Robert Swinney of Lassenite Industries provided 

information on natural pozzolan; James Canwell of the 

U.S. Bureau of Mines assisted in the laboratory work.

APPRAISAL OF IDENTIFIED RESOURCES

By Thomas J. Peters 

U.S. Bureau of Mines

Mining and Exploration History

No mineral production has taken place within the 

study area. The only historical mineral production 

near the study area is from the Leadville district 

(Bonham, 1969, p. 67-69), which lies 6 mi south of the 

study area. The Leadville mine produced over 1.3 

million troy ounces (oz) silver and 4.9 million pounds 

(Ib) lead from 1910 through 1927.

The Denio Ranch diatomite prospect is west of 

the study area (fig. 1). Several perlite claims were 

located in 1951 within and contiguous to the southeast 

corner of the study area (fig. 2, No. 5). Work began in 

September 1954 on the Big Doubt group (fig. 2, No. 3), 

which also straddles the study area boundary. An 

additional area of uranium prospect pits lies southwest 

of the study area along both sides of route 34 (fig. 1, 

unnamed) and was noted by Garside (1973, p. 98, 

locality No. 7).

Two active claim blocks cover disseminated 

epithermal gold prospects west of the study area and 

are being explored by mining companies. The Jabo 

claim block (fig. 1), owned by Tenneco Minerals, is 

adjacent to the study area. Directly west of the Jabo 

group is the Hog Ranch deposit, originally a uranium 

prospect, which is owned by Ferret Exploration. The 

Hog Ranch group includes the Section 24 and West 

prospects (fig. 1). Ferret Exploration is initially 

developing the Section 24 deposit and plans to begin 

processing ore in 1987.

There are no active or patented mining claims 

within the study area.

Geologic map units

Qal Alluvium (Holocene)

High Rock Sequence of Bonham (1969) (Miocene) 

Thr Rhyolite of Little High Rock Canyon 

Tht Tuff of Little High Rock Canyon 

Thf Fluviolacustrine sediments-Locally includes

air-fall tuffs

Tsm Soldier Meadow Tuff (Miocene) 

Tcr Canon Rhyolite of'Merriam (1910) (Miocene) 

Tsl Summit Lake Tuff (Miocene) 

Ta Andesite lava flows (Miocene)-Rocks equivalent to

the Steens Basalt

 Contact-Dashed where approximately located

 Fault-Dashed where approximately located. Bar and ball

2 on downthrown side

X Prospect or mineralized area-See table 1 for description

"**- Fissure

Figure 2. Continued.

Mines, Prospects, Claims, and Mineralized areas

There are no mines in the study area, but, three 

mineralized areas have been identified (fig. 2, Nos. 1, 

2, and 6). These include the west end of Little High 

Rock Canyon, the central part of the study area, and 

an area near the southwest corner. Three prospects 

for disseminated epithermal gold near the study area 

(fig. 1, Jabo, West, and Section 24 prospects) are being 

explored and are similar to the mineralized areas 

within the study area. In addition, uranium, pozzolanbearing tuffaceous sediment, and perlite are also 

present in the study area (fig. 2, Nos. 3-5). A summary 

of available data from each occurrence within the 

study area is given in table 1.

Prospects for Epithermal Gold and Silver

The Section 24 prospect, West prospect, Jabo 

prospect (fig. 1), and Jabo extension (fig 2, No. 6)

C5
occur along a northeast-trending lineament and 

although the geology is different at each locality, they 

share some common features.

The Section 24 prospect rs exposed in two 

trenches. Mineralization occurred near the base of a 

kaolinized and silicified tuffaceous sediment bed and 

in an underlying silicified rhyolite flow (north trench), 

and near the top of a tuffaceous bed and in an 

overlying silicified rhyolite flow (south trench). The 

northeast-trending lineament is represented by a fault 

that bisects the deposit between the trenches.

The West prospect is not yet as well 

understood. Characteristics include white silicified 

outcrops and anomalous concentrations of the 

pathfinder elements arsenic, antimony, and mercury in 

rock and soil.

The Jabo prospect (fig. 1) contains siliceous 

sinter, deposited within and over rhyolite flows and 

tuffaceous sediments. It is intruded by a diapiric 

breccia that contains clasts of sinter, rhyolite, and 

andesite. Both the sinter and the diapiric breccia are 

gold bearing (Fred Saunders, Tenneco Minerals, oral 

commun., 1985). Anomalous pathfinder elements in 

rock and soil include arsenic, antimony, and mercury.

At the Jabo extension area (fig. 2 and table 1, 

No. 6), silicification appears to follow a northeasttrending volcanic vent. Arsenic anomalies are found in 

rock and soil samples, but antimony and mercury 

anomalies are absent (Peters and others, 1987). A 

vertical volcanic fissure is as much as 40 ft wide and 

strikes N. 57° E. (fig. 2). It is filled with flow-banded, 

vesicular, partially devitrified and argillized obsidian, 

which contains cobble- and boulder-size rhyolite 

clasts.

In summary, these four sites, although 

geologically varied, define a northeast-trending 

lineament and show similar alteration. The complete 

alteration sequence, not all elements of which are 

present at each prospect, includes a silicified core 

area, an increase in argillization peripherally, and 

concentration of arsenic. Siegfried Holso (Ferret 

Exploration, oral commun., 1985) also noted an outer 

zone of opalization peripheral to argillization at the 

Section 24 and West prospects.

mainly as relatively inert feldspar minerals and would 

not affect pozzolan suitability.

Three representative samples were subjected to 

a 28-day Pozzolan Activity Index with Portland 

Cement test (No. 4, table 1) One sample exceeded the 

required compressive strength of 75 percent of the 

4,870 psi (pounds per square inch) control cube 

strength. None of the samples were within the 

maximum allowable water requirement of 115 percent 

of the control cube requirement (T.S. Poole, Cement 

and Pozzolan Unit, Army Corps of Engineers, written 

commun., 1985) High water requirements of the 

samples are probably caused by the montmorillonite 

clay content (R.R. Swinney, Lassenite Industries, oral 

commun. 1986).

Perlite is commonly found at the base of rhyolite 

flows, especially where flows have been extruded over 

wet sediments, but most deposits large enough to be 

commercial formed over rhyolite domes (Kadey, 1983, 

p. 987) The largest perlite occurrence (fig. 2 and table 

1, No. 5) is south of the pozzolan occurrence. Four 

samples from the perlite prospect had refractive 

indices of 1.496 (± 0.004), similar to commercial 

perlite (Kadey, 1963, p. 334). Approximately 2 million 

tons of perlite is present at this locality; it is in a 

north- to northwest-trending, 2,600-ft-long by 200- to 

400-ft-wide belt along the northeast-facing slope of a 

rhyolite mesa. The perlite is capped by rhyolite to the 

southwest and removed by erosion to the northeast. 

The perlite has a high expanded density, making it 

unsuitable to "lighter weight" uses such as filter aid or 

cryogenics. However, high compaction resistance 

(table 1, No. 5) would make the product excellent for 

building and construction product end uses such as 

lightweight aggregate in plaster or concrete (J.M. 

Baker and J.S. Hingtgen, New Mexico Bureau of Mines 

and Mineral Resources, written commun., 1985).

Uranium is present at the Big Doubt prospect 

(fig. 2 and table 1, No. 3) in scattered petrified tree 

parts in the upper part of the pozzolanic deposits. 

Uranium concentrations are low; all samples contained 

less than 0.2 Ib per ton. Uranium is also present in 

petrified wood (Garside, 1973, p. 98) southwest of the 

study area (fig. 1, unnamed prospect).

Industrial Minerals and Energy-related Occurrences

Pozzolan is a siliceous volcanic ash, or artificial 

substance resembling the ash, used to produce 

hydraulic cement. Tuffaceous sediments with 

pozzolanic qualities (U.S. Bureau of Mines, 1969, p.l) 

are present in many parts of the study area. A 130- 

acre area southeast of McConnell Canyon (fig. 2. and 

table 1, No. 4) includes approximately 28 million tons 

of montmorillonitic tuffaceous fluviolacustrine 

sediments. Chemically, silica and alumina and iron 

oxide exceed 70 percent and magnesium oxide was less 

than 5 percent in all samples. Loss on ignition is less 

than 10 percent for most samples (table 1, No. 4), 

indicating the sediments are within the range of 

natural pozzolans. The alkali-metal oxides (potassium 

oxide and sodium oxide) exceed the 1.5 percent 

maximum in all samples (American Society for Testing 

and materials, 1985); however, the alkalies are not 

available to the pozzolan reaction because they occur

Mineral Economics

There are no prospects or mineralized areas with 

identified resources (U.S. Bureau of Mines and U.S. 

Geological Survey, 1980) within the study area.

Three occurrences in the study area are of 

interest (fig. 2, Nos. 1, 2, and 6) because the rhyolite 

has been epithermally altered, mainly by silicification 

and the introduction of arsenic, a pathfinder element 

that commonly indicates disseminated gold in the 

vicinity. The USBM did not find significant gold at 

prospects in the study area, even within a favorable 

fissure structure at the Jabo extension (fig. 2 and table 

1, Nos. 1, 2, and 6). Disseminated gold may be present 

at depth, but a low-grade disseminated deposit that is 

not at, or near, the surface cannot be economically 

mined. Pathfinder element concentrations do not 

indicate the presence of an economic gold deposit at 

the prospects, but the possibility of such an occurrence 

cannot be ruled out.

C6
The pozzolan-bearing sediment occurrence (fig. 2 

and table 1, No. 4) contains 28 million tons of 

pozzolanic material. Most pozzolan used in the United 

States is fly ash, a byproduct of coal-fired furnaces. 

The only known producing domestic natural pozzolan 

deposit, Lassenite Industries mine at Doyle, Calif., is 

located at a railhead. The Lassenite product is 

calcined (roasted) to ensure a low-water requirement, 

but calcining alone would probably not produce a 

suitable product from pozzolanic material in the study 

area; montmorillonite clay would also need to be 

removed. Remoteness and expensive processing make 

exploitation of the deposit unlikely.

The perlite occurrence (fig. 2 and table 1, No. 5) 

contains approximately 2 million tons of material, 

which is considerably less than typical economic 

deposits, which generally exceed 10 million tons. More 

importantly, however, the occurrence is 45 mi from 

the nearest railhead at Gerlach, Nev. In addition, the 

perlite is only suitable for aggregate, a high bulk-low 

value end use. Alternate materials can be substituted 

for all uses of perlite, if necessary (U.S. Bureau of 

Mines, 1986, p. 115).

Mining of perlitic and pozzolanic materials from 

the study area could be feasible if a major local 

construction project were required by a government 

agency such as the U.S. Bureau of Reclamation, 

Department of Defense, or Department of Energy. 

Product quality and remoteness, however, preclude the 

usefulness of these materials to the general economy 

for the foreseeable future.

Uranium occurrences at the Big Doubt prospect 

(fig. 2 and table 1, No. 3) are too low in grade and too 

scattered to be of economic interest. The best 

material found, 0.2 Ib per ton uranium oxide is worth 

only $3.45 per ton at a price of $17.25 per Ib 

(Engineering and Mining Journal, 1986, p. 9).

ASSESSMENT OF POTENTIAL FOR UNDISCOVERED 

RESOURCES

By William J. Keith, Robert L. Turner, and

Donald Plouff

U.S. Geological Survey

Geological Studies

The study area is in the west-central part of the 

Calico Mountains, a poorly defined group of mountains 

in the transition zone between the Basin and Range 

and the Columbia Plateau physiographic provinces. It 

consists of interfingering pyroclastic deposits, mafic 

and silicic lava flows, and fluviolacustrine sediments. 

All of these rocks are of Miocene age (5 to 24 million 

years before present, or Ma; see appendixes for 

,geologic time chart).

The oldest unit in the study area is a series of 

aphanitic andesite lava flows equivalent in age to the 

Steens Basalt (lavas of Steens age, Noble and others, 

1973, p. 1396). Most flows do not contain visible 

phenocrysts but a few contain large (0.5 in) thin 

plagioclase phenocrysts, a distinctive feature of the 

Steens Basalt. The unit interfingers with the 

fluviolacustrine sediments of the High Rock sequence 

of Bonham (1969).

The Summit Lake Tuff (Noble and others, 1970), 

which overlies the andesite, is a brown to reddishbrown, generally quartz-poor, densely welded ash-flow 

tuff. The tuff typically displays fiamme and contains 

phenocrysts of anorthoclase and minor biotite, 

clinopyroxene, and amphibole. It has an approximate 

potassium-argon age of 15.5 Ma (Noble and others, 

1970, p. D27).

The Canon Rhyolite (Merriam, 1910) consists of a 

series of laminated rhyolite flows. The flow 

laminations usually appear as pink, red, or gray color 

bands separated by thin bands of quartz. Much of the 

unit is spherulitic, with spherulites as much as 5 cm in 

diameter (Bonham, 1969). Three potassium-argon ages 

are available for this unit: 13.7±1.4 Ma on glass, 

16.3±1.3Ma on sanidine, and 22.3±1.8 Ma on alkali 

feldspar. The 22.3 Ma age is considered unreasonable 

in light of stratigraphic and structural relations and 

dates of other units (McKee and Marvin, 1974, p. 3).

The Soldier Meadow Tuff (Noble and others, 

1970) overlies the Summit Lake Tuff in this area and 

is a bluish gray, partly to densely welded ash-flow 

sheet composed of many individual flows (Korringa, 

1973, p. 3856). Phenocrysts consist largely of smokey 

quartz and sodic sanidine, minor arfvedsonite, and 

iron-rich clinopyroxene. The sanidine is locally 

chatoyant. The Soldier Meadow Tuff has an 

approximate potassium-argon age of 15 Ma (Noble and 

others, 1970, p. D29).

The High Rock sequence of Bonham (1969) 

consists of a sequence of ash-flow and air-fall tuffs, 

silicic lava flows, and tuffaceous fluviolacustrine 

deposits that both interfinger with and overlie the rock 

units described above.

The oldest unit in the High Rock sequence 

consists of white to buff to gray fluviolacustrine 

sediments that grade upward into air-fall tuffs and 

tuffaceous fluviolacustrine sediments. This unit 

interfingers with the andesite.

Overlying the fluviolacustrine sediments is the 

tuff of Little High Rock Canyon. This tuff is pink to 

bluish red and shows abundant fiamme near the base. 

Sparse sanidine crystals are the only phenocrysts.

The uppermost unit of the High Rock sequence, 

the rhyolite of Little High Rock Canyon, is a pink to 

buff to gray rhyolite lava flow petrographically similar 

to the Canon Rhyolite. Phenocrysts consist of glassy 

feldspar, quartz (some of which are amethyst), and 

biotite. The unit has more vapor phase material and 

more phenocrysts than the Canon Rhyolite.

Geochemical Studies

Geochemical data were obtained from a regional 

geochemical reconnaissance study (Barringer, 1982) 

and rock and stream sediment samples collected by the 

U.S. Geological Survey in 1985 (unpub. data).

Three localities within the study area contain 

anomalous concentrations of several precious-metal 

indicator elements: the northwestern part, a small 

area in the center of the study area, and McConnel 

Canyon.

The northwestern part of the study area has 

anomalous concentrations of arsenic, antimony, and 

silver, which may indicate epithermal precious-metal 

mineralization. Anomalous concentrations of zinc,

C7
cadmium, and lead also are found in this area. The 

highest concentrations are found in the Canon 

Rhyolite. Anomalous concentrations of arsenic, 

antimony, and zinc are found in and near Little High 

Rock Canyon in the High Rock sequence.

The small area in the center of the study area 

contains anomalous concentrations of arsenic, 

antimony, bismuth, cadmium, silver, tin, and zinc. 

Mineralization is probably controlled by north-trending 

fault systems.

Samples from the McConnel Canyon area contain 

anomalous concentrations of antimony, arsenic, 

bismuth, cadmium, chromium, mercury, nickel, 

tellurium, tin, and zinc. The nickel and chromium 

anomalies represent concentrations of the elements 

from the nearby mafic andesite. The tin is probably 

concentrated from the Canon Rhyolite upstream; the 

other anomalous concentrations probably represent a 

hot-spring type deposit. This conclusion is also 

supported by the nearby occurrence of siliceous sinter.

Anomalous concentrations of tin and arsenic are 

present sporadically throughout the study area. Small 

areas (2 to 20 ft ) of opal containing anomalous 

concentrations of arsenic are also found throughout 

the area. These opalized areas are present at various 

stratigraphic levels in the silicic rocks. The tin 

anomalies found in the heavy mineral concentrates are 

probably derived from the silicic rocks.

Geophysical Studies

Geophysical evaluation of the mineral resources 

of the study area was based on interpretations of three 

kinds of geophysical data: aerial gamma-ray, 

aeromagnetic, and gravity surveys.

Radiometric data were compiled by Geodata 

International, Inc. (1978), for the National Uranium 

Resource Evaluation (NURE) program of the 

Department of Energy. Two east-west flightlines 

totalling about 8 mi in length and separated by about 3 

mi recorded gamma-ray flux from radioactive isotopes 

of uranium, thorium, and potassium. Flight altitudes 

varied from 300 to 700 ft above the ground. The 

northern flightline recorded no anomalies in the study 

area. The southern flightline, which nearly overlies 

McConnel spring, has conspicuously low radioactive 

levels for all three records of radioactive flux. The 

lows occur over a one-mile segment near the east edge 

of the study area. The values of the minima are 

approximately the same as the background level over 

sediments in other parts of the region. The location of 

the minima does not correlate with a flight-altitude 

high (topographic low) nor an area of marked surface 

rock alteration. Inasmuch as a layer with a thickness 

of 1 ft at the surface would be sufficient to mask the 

radioactivity of underlying rocks (Duval and others, 

1971), only a small thickness of sediments or 

nonradioactive rocks could cause the observed low.

An aeromagnetic survey (U.S. Geological Survey, 

1985) was flown over the study area at an elevation of 

approximately 1,000 ft above the mean ground surface 

elevation. Flightlines were flown north-south at a line 

spacing of 0.5 mi. The most conspicuous feature of 

the aeromagnetic map is a north-trending elongate 

cluster of magnetic lows in an area of about 2.5 by 6

mi in the southern part of the area. Inverse 

correlation of magnetic anomalies with topography 

indicates that the source rocks for the magnetic lows 

are reversely magnetized and are near the ground 

surface. Steep magnetic gradients with magnetic 

intensities increasing outward, especially along the 

west edge of the cluster of anomalies, suggest that the 

source rocks are part of a larger underlying body. The 

reversely magnetized source rocks probably consist of 

rhyolite that caps the mesas, underlying rocks that are 

equivalent in age and composition to the Steens Basalt, 

and older flows. An aeromagnetic map of the region 

(U.S. Geological Survey, 1972) includes many magnetic 

lows over the Steens Basalt and its equivalent rocks. 

Sample measurements of reversed magnetization made 

over extensive areas of the Steens Basalt and 

equivalent basalt in Oregon, Nevada, and Idaho 

indicate that these rocks are both normally and 

reversely magnetized (E.A. Mankinen, written 

commun., 1986).

The only conspicuous anomaly on the preliminary 

Bouguer gravity anomaly map (Plouff, unpub. data) is 

shown by north-trending gravity contours along the 

east edge of the north half of the study area. The 

contours outline a 5-milligal (mGal) gravity high and a 

magnetic high centered about 0.5 to 1 mi east of the 

study area. Inasmuch as Cenozoic rocks of relatively 

low density crop out within the gravity high, the 

source of the anomaly must be a body of relatively 

dense rocks concealed at shallow depth. These rocks 

probably are basement rocks similar to pre-Cenozoic 

rocks (Stewart and Carlson, 1974) that crop out in the 

study area and reveal the source of a 10- by 25-mi, 40- 

mGal gravity high (Plouff, unpub. data) located 5 to 30 

mi south-southwest of the study area.

Mineral and Energy Resources

Three parts of the study area have moderate 

potential for gold and silver in epithermal deposits. 

The rest of the area has low potential for gold and 

silver in epithermal deposits. In addition, the study 

area also has low potential for geothermal resources 

and small areas have low resource potential for 

pozzolan, perlite, or uranium.

Three parts of the study area (fig. 2) have 

moderate resource potential with a certainty level of 

C for gold and silver. These resources would probably 

be of a low-grade bulk-minable hot-spring type 

similar to the Round Mountain deposit in northern Nye 

county (Berger, 1986) and the Hog Ranch deposit 

(Harvey and others, 1986) 5 mi southwest of the study 

area. The size of these deposits would probably be 

similar to, or smaller than the Hog Ranch deposit. The 

geochemical anomalies, permissive rock types and 

ages, and faulting all support this classification.

Small (2 to 20 ft 2) outcrops of opalized rock 

scattered throughout the study area contain anomalous 

concentrations of arsenic, which is a precious-metal 

indicator. Outcrops of opal are described by Berger 

(1986) as one of the characteristics of hot-spring goldsilver deposits. Opalized outcrops are also found in 

and near the Hog Ranch deposit. This evidence would 

place the rest of the study area in a low resource 

potential for gold and silver category with a certainty 

level of C.

C8
Although the study area contains no active hotsprings, the presence of a low temperature (less than 

90 °C) system in nearby Soldier Meadow (Reed, 1983) 

and the relatively high heat flow (approximately 100 

milliwatts/m2) in the area (Muffler, 1979) suggests a 

geothermal resource classification of low with a C 

certainty level.

Deposits of pozzolanic tuffaceous sediments, 

perlite, and uranium are present in the southeastern 

part of the study area and have low resource potential, 

certainty level D. The quality of these commodities is 

low which limits their usefulness and the areal extent 

of their respective host areas is small.

REFERENCES CITED

American Society for Testing and Materials, 1985, 

Concrete and mineral aggregates (ASTM C 618- 

85): Annual Book of ASTM Standards, v. 04.02.

Barringer Resources, Inc., 1982, Geochemical and 

geostatistical evaluation of wilderness study 

areas, Winnemucca district, northwest Nevada, 5 

v.: Golden, Colo. (available from NTIS, U.S. 

Department of Commerce, Springfield, VA 22161, 

or call Information Center and Bookstore (202) 

377-0365).

Beikman, H.M., Hincle, M.E., Frieders, Twila, Marcus, 

S.M., and Edward, J.R., 1983, Mineral surveys by 

the Geological Survey and the Bureau of Mines of 

Bureau of Land Management Wilderness Study 

Areas: U.S. Geological Survey Circular 901, 28 p.

Berger, B.R., 1986, Descriptive model of hot-spring 

Au-Ag, in_ Mineral Deposit models, Cox, D.P., and 

Singer, D.A., eds.: U.S. Geological Survey 

Bulletin 1693, 379 p.

Bonham, H.F., 1969, Geology and mineral deposits of 

Washoe and Storey Counties, Nevada, with a 

section on Industrial mineral deposits by K.G. 

Papke: Nevada Bureau of Mines and Geology 

Bulletin 70, 140 p.

Duval, J.S., Cook, B., and Adams, J.A.S., 1971, Circle 

of investigation of an airborne gamma-ray 

spectrometer: Journal of Geophysical Research, 

v. 76, p. 8466-8470.

Engineering and Mining Journal, 1986, E & MJ 

markets: Engineering and Mining Journal, v. 187, 

no. 5, p. 9-13.

Garside, L.J., 1973, Radioactive mineral occurrences 

in Nevada: Nevada Bureau of Mines and Geology 

Bulletin 81,

Geodata International, Inc., 1978, Aerial radiometric 

and magnetic survey, Vya national topographic 

map, Nevada: U.S. Department of Energy OpenFile Report GJBX-136 (79), v. 2, 73 p., scale 

1:500,000.

Goudarzi, G.H., 1984, Guide to preparation of mineral 

survey reports on public lands: U.S. Geological 

Survey Open-File Report 84-787, 51 p.

Greene, R.C., 1984, Geologic appraisal of the Charles 

Sheldon Wilderness Study Area, Nevada and 

Oregon: U.S. Geological Survey Bulletin 1538-A, 

p. 15-37.

Harvey, D.S., Noble, D.C., and McKee, E.H., 1986, Hog 

Ranch gold property, northwestern Nevada: Age 

and genetic relation of hydrothermal

mineralization to coeval peralkaline silicic and 

associated basaltic magmatism: Isochron/West, 

no. 47, p. 9-11.

Kadey, F.L., 1963, Petrographic techniques in perlite 

evaluation: American Institute of Mining and 

Metallurgical Engineers Transactions, v. 22, p. 

332-336.

___1983, Perlite, in_Lefond, S.J., ed., Industrial rocks 

and minerals, (5th ed.): American Institute of 

Mining and Metallurgical Engineers, p. 997-1015.

Korringa, M.K., 1973, Linear vent area of the Soldier 

Meadow Tuff, an ash-flow sheet in northwestern 

Nevada: Geological Society of America Bulletin, 

v. 84, p. 3848-3866.

McKee, E.H., and Marvin, R.F., 1974, Summary of 

radiometric ages of Tertiary volcanic rocks in 

Nevada; Part IV., Northwestern Nevada: 

Isochron/West, v. 10, p. 1-6.

Merriam, J.C., 1910, Tertiary mammal beds of Virgin 

Valley and Thousand Creek, in northwestern 

Nevada; Part I, Geologic history: California 

University, Department of Geology Bulletin, v. 6, 

no. 2, p. 21-53.

Muffler, L.J.P., ed., 1979, Assessment of geothermal 

resources of the United States-1978: U.S. 

Geological Survey Circular 790, 163 p.

Noble, D.C., Hedge, C.E., McKee, E.H., and Korringa, 

M.K., 1973, Reconnaissance study of the 

strontium isotopic composition of Cenozoic 

volcanic rocks in the northwestern Great Basin: 

Geological Society of America Bulletin, v. 84, p. 

1393-1406.

Noble, D.C., McKee, E.H., Smith, J.G., and Korringa, 

M.K., 1970, Stratigraphy and geochronology of 

Miocene volcanic rocks in northwestern Nevada, 

in Geological Survey Research, 1970: U.S. 

Geological Survey Professional Paper 700-D, p. 

D23-D32.

Peters, T.J., Munts, S.R., and Miller, M.S., 1987, 

Mineral resources of the Little High Rock Canyon 

study area, Humbolt and Washoe Counties, 

Nevada: U.S. Bureau of Mines Open-File Report 

MLA 16-87, 39 p.

Reed, M.J., ed., 1983, Assessment of low-temperature 

geothermal resources of the United States-1982: 

U.S. Geological Survey Circular 892, 73p.

Stewart, J.H., and Carlson, J.E., 1974, Preliminary 

geologic map of Nevada: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-609, 4 sheets, 

scale 1:500,000.

U.S. Bureau of Land Management, 1984, Eagle 

Lake/Cederville study areas draft environmental 

impact statement: U.S. Bureau of Land 

Management, Susanville (CA) District Office, 340

PU.S. Bureau of Mines, 1969, Pozzolanic raw materials

resources in central and western United States:

U.S. Bureau of Mines Information Circular 8421,

117 p. 

__ 1986, Mineral commodity summaries: U.S. Bureau

of Mines, 187 p. 

U.S. Bureau of Mines and U. S. Geological Survey,

1980, Principles of a resource/reserve

classification for minerals: U.S. Geological

Survey Circular 831, 5 p. 

U.S. Geological Survey, 1972, Aeromagnetic map of

C9
the Vya and part of the McDermitt 1° by 2° Survey Open-File Report 85-751, 1 sheet, scale

quadrangles, Nevada: U.S. Geological Survey 1:62,500

Open-File Report 72-393, 1 sheet, scale 1:250,000. Willden, R., 1964, Geology and mineral deposits of

_ 1985, Aeromagnetic map of the High Rock Lake Humboldt County, Nevada: Nevada Bureau of

area, northwestern Nevada: U.S. Geological Mines Bulletin 59, 154 p.

C10
APPENDIXES

DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

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 

broad category embraces areas with dispersed but insignificantly mineralized rock as well as areas with 

few or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate 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.

HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurence, where interpretations of 

data indicate a high degree of likelihood for resource accumulation, where data supports mineral-deposit 

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.

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.

Levels of Certainty

o

a.

cc

O 1/5

LU

ac

UJ

>

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

B C 

LEVEL OF CERTAINTY

A. Available information is not adequate for determination of the level of mineral resource potential.

B. Available information suggests the level of mineral resource potential.

C. Available information gives a good indication of the level of mineral resource potential.

D. Available information clearly defines the level of mineral resource potential.

Abstracted with minor modifications from:

Taylor, R. B., and Steven, T. A., 1983. Definition of mineral resource potential: Economic Geology,

v. 78, no. 6, p. 1268-1270. 

Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential

of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p.

40-42. 

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

Geological Survey Open-File Report 84-0787, p. 7, 8.

C13
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

I 

I

Reserves

I

 | _

I

Marginal 

Reserves

I

I

Demonstrated

Subeconomic 

Resources

I

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical

__ _

Speculative

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from U.S. Bureau of Mines 

and U.S. Geological Survey, 1980, Principles of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, p. 5.
GEOLOGIC TIME CHART 

Terms and boundary ages used by the U.S. Geological Survey in this report

EON

Phanerozoic

Proterozoic

Archean 

pre- Ar

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

:hean 2

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 -(3800?)- -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

 _

AGE ESTIMATES 

OF BOUNDARIES 

'(in Ma)

- 0.010

- 1.7

- 5\j

*"l A

- 'Sfi

\J*J

_ cc

- 96

 1*?R

_ one

- -240

t-\j\J

oou

*J\J\J

- 410

A *"il- - 435

- 500

+J / \J

&\j\j

1 df\n

 ounn /9UU

- 3000

O"rUU

'Rocks older than 570 Ma also called Precambrian, a time term without specific rank. 

Informal time term without specific rank.

C15
o

_l 

O)

TABLE 1. Prospects, claims, and mineralized areas in and near the Little High Rock Canyon Wilderness Study Area, Humbo

Counties, Nevada

[*, prospect straddles study area boundary]

Map No. Name Summary Workings and production Sample and resourc

Unnamed 

mineralized 

area

3*

Unnamed 

mineralized 

area

Big Doubt 

prospect

4* Pozzolanic 

sediment 

occurrence 

(unnamed)

A 5- to 30-ft-thick sill-like zone 

of limonite-colored and black 

chalcedony and opal extends for 

approximately 0.5 mi along north 

wall of Little High Rock Canyon. 

Similar irregular void fillings 

and veins, 0.5 to 2 ft thick, are 

fairly common in west and central 

parts of study area north of 

canyon.

An approximately 60-acre area of 

intensely silicified and commonly 

brecciated gray rhyolite along a 

north-northwest-trending ridge. 

Chalcedony and opal locally common 

as small fracture and irregular 

void fillings.

Scattered fossil tree parts, 

partially replaced with silica and 

near top of sequence of tuffaceous 

sediments, emitted as much as 250 

cps (counts per second) gamma 

radiation (40-50 cps 

background). Coextensive with 

prospect No. 2.

A 100-ft-thick pile of poorly 

consolidated waterlain tuffaceous 

sediments with pozzolanic 

qualities occurs as partially 

dissected mesa over a 130-acre 

area east of mouth of McConnel 

Canyon. Deposit is readily 

accessible from an unimproved road 

along east side of prospect, and 

is not capped by overburden, 

except for a few local 10-ft-thick 

patches of unconsolidated 

perlite. Coextensive with 

prospect No. 1.

None

None

One 10-ft-long adit and 

at least 12 small 

prospect pits, 

approximately 15 ft by 

10 ft by 5 ft deep. No 

production recorded or 

indicated by excavations 

at site.

None

Six chip samples from sil

chip samples from dikes, 

samples taken. Gold not 

detected in two samples; 

ppm. Antimony detected i

to 5 ppm. Arsenic, detec

ranged from 4 to 170 ppm. 

found, but pathfinder ele

epitherraal mineralization

Three chip, one grab, and 

samples contained no dete

silver. Antimony detected 

ppm. Arsenic, detected i

ranged from 8 to 29.7 ppra

found in placer grab samp

found, but pathfinder ele

epithermal mineralization

Ten rock samples from fos

contained 28 to 84 ppm ur

Ib/ton uranium oxide). R

indicated because materia

insufficient grade and to

tree parts are potentiall

recreational collectors.

Ten chip samples from occ

59.1 to 71.0 percent sili

20.3 percent alumina, 1.3 

percent ferric oxide, 0.2

percent magnesium oxide, 

percent potassium oxide, 

1.8 percent sodium oxide. 

ranged from 5.51 to 10.57 

samples passed all chemic

Three samples passed all 

standards. Three samples 

day Pozzolan Activity Ind

Cement had compress!ve st

3250, and 3400 psi (pound

water requirements of 127 

percent and 122 percent w

Society for Testing Mater

Specific gravity was 2.54

respectively. Pozzolan o

28 million tons (at 12.8 

material , 14 million ton

million tons contiguous t
TABLE 1. Prospects, claims, and mineralized areas in and near the Little High Rock Canyon Wilderness Study Area, Humboldt and Washoe 

Counties, Nevada Continued

Map No. Name Summary Workings and production Sample and resource data

5* Perlite claims 

(name unknown)

Jabo extension 

mineralized area

An approximately 2,600-ft-long by 

200- to 400-ft-wide belt of darkgray perlite trends north to 

northwest along northeast facing 

slope of a rhyolite mesa. Perlite, which apparently formed 

as a chill zone at base of 

rhyolite, is approximately 50 ft 

thick along southwest margin of 

belt where it extends under the 

rhyolite; it pinches out along 

northeast margin of belt because 

of erosion; average thickness is 

25 ft.

An area of altered rhyolite 

extends over more than 320 acres near northeast-trending structural 

lineament that extends into 

southern part of study area from 

west. In study area, lineament 

appears to have been the locus of 

an elongate rhyolitic vent, marked 

by vertical or highly contorted 

flow bands. A northeast-trending fissure, 40 ft wide and over 1,000 

ft long, formed within vent. Subsequent epithermal mineralization was marked by silicification, local kaolinization, and the 

introduction of arsenic.

Four trenches, 40 ft by 

7 ft by 4 ft deep, 50 ft 

by 6 ft by 4 ft deep, 13 

ft by 2 ft by 2 ft deep, 

and 40 ft by 12 ft by 6 ft deep, spread over 

approximately 700 ft 

from north to south 

along length of deposit. No production 

indicated by excavations 

at site.None. Southwest of 

study area along the 

same structural 

lineament, two disseminated gold prospects 

are being actively explored and a third is 

undergoing preproduction development.

Four perlite chip samples had refractive 

indices of 1.496 (±0.004). Dsta from one 

sample expanded in a vertical furnace includes: expanded density, 10.7 lb/ft 3 ; 

furnace yield, 97 percent; sinkers 

(unexpended fraction, 11 percent; compacted 

density, 14 lb/ft 3 ; compaction resistance, 

280 lb/in 2 (at 1 in.) and 410 lb/in2 (at 2 

in.). Tests indicated material is unsuitable for lightweight sggregate, but 

suitable for end use such as road 

material. Occurrence contains 2 million 

tons (at 12.6 ft 3 /ton of material 1 , 

1 million tons within and 1 million tons 

contiguous to study area.

A total of 102 soil grid, 35 rock, 2 soil 

grab, and 15 placer grab samples taken. 

Four north-south soil lines, 600 ft apart and approximately 6,000 ft long, were run across northeast lineation west of No. 6 

(fig. 2) along study area boundary between 

unimproved road on south and McConnel Canyon 

on north; sample spacing was 300 ft. Gold 

was detected in 92 soil samples (0.017 to 

0.287 ppm), silver in 21 (0.35 to 23.2 ppm), mercury in 11 (2 ppm), arsenic in 63 (3 to 

15 ppm), and barium in all samples (430 to 1060 ppm); antimony was not detected (less 

than 2 ppm). Contours of arsenic and barium soil data (Peters and others, 1987, 

appendix I) show the northeast-trending 

lineament. A crosscutting north-south fault suggested by gold contours, and a N. 20° E. fault by mercury and silver contours.

Thirty-five rock and 2 soil grab samples 

were taken in and near alteration area, 

including two samples from volcanic fissure 

(fig. 2). Gold, mercury, and antimony not 

detected, and silver (1.198 ppm) found in 

only one sample. Arsenic, however, detected 

in 22 samples (3 to 100 ppm). Barium, 

detected in all samples, had wide range of 

values (14 to 1900 ppm). Placer grab 

samples taken from stream beds; six of 15 

samples contained free gold (0.003 to 0.038 

mg (milligrams)). No resources were found, 

but pathfinder elements indicate epithermal mineralization.

O

-J

The "material" is not designated "resources" because factors such as product quality and distance to markets make mining unlikely.
o

<f

m

oooCN m 

m 

I

PHo

m

oo