Mineral Resources of the Honeycombs 

Wilderness Study Area, 

Malheur County, Oregon

U.S. GEOLOGICAL SURVEY BULLETIN 1741-A

Chapter A

Mineral Resources of the Honeycombs 

Wilderness Study Area, 

Malheur County, Oregon

By DEAN B. VANDER MEULEN, J.J. RYTUBA, H.D. KING, 

and D. PLOUFF

U.S. Geological Survey

DOUGLAS F. SCOTT 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1741

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: EAST-CENTRAL OREGON
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 Honeycombs Wilderness 

Study Area, Malheur County, Oregon.

U.S. Geological Survey Bulletin 1741-A

Includes bibliography

Supt. of Docs. No.: I 19.3:1741-A

1. Mines and mineral resources Oregon Honeycombs

Wilderness. 2. Geology Oregon Honeycombs

Wilderness. 3. Honeycombs Wilderness (Or.) I. Vander

Meulen, Dean B. II. Series.

QE75.B9 No. 1741-A 557.3 s 86-600350

[TN24.07] [553'.09795'97]
STUDIES RELATED TO WILDERNESS 

Bureau of Land Management Study Areas

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 on 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 a part of the 

Honeycombs Wilderness Study Area (OR-003-77A), Malheur County, Oregon.

CONTENTS

Summary Al

Abstract 1

Character and setting 1

Identified resources 3

Mineral resource potential 3 

Introduction 3

Area description 3

Previous and present investigations 3

Acknowledgments 6 

Appraisal of identified resources 6

History and production 6

Mines, prospects, claims, and mineralized areas 6

Appraisal of mineral resources 6

Recommendations for further work 7 

Assessment of mineral resource potential 7

Geology 7

Geochemical studies 8

Geophysical studies 9 

Conclusions 9 

References cited 10 

Appendix 1. Definition of levels of mineral resource potential and certainty of assessment 14

FIGURES

1. Index map showing location of the Honeycombs Wilderness Study Area, Malheur County, Oregon A2

2. Map showing geology and mineral resource potential of the Honeycombs Wilderness Study Area, Malheur 

County, Oregon 4

3. Major elements of mineral resource potential/certainty classification 14

TABLE

1. Mines, prospects, claims, and mineralized areas in and adjacent to the Honeycombs Wilderness Study Area, 

Malheur County, Oregon A12

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: EAST-CENTRAL OREGON

Mineral Resources of the Honeycombs Wilderness 

Study Area, Malheur County, Oregon

By Dean B. Vander Meulen, J.J. Rytuba, H.D. King, and D. Plouff 

U.S. Geological Survey

Douglas F. Scott 

U.S. Bureau of Mines

SUMMARY

Abstract

The Honeycombs Wilderness Study Area (OR003-77A) encompasses approximately 39,000 acres 

adjacent to the Owyhee Reservoir in eastern Oregon. 

Field work was conducted by the U.S. Geological 

Survey during 1983 and 1984, and by the U.S. Bureau of 

Mines during 1984, to evaluate the mineral resources 

and the mineral resource potential of the study area. 

At the request of the Bureau of Land Management 

(BLM), the U.S. Geological Survey and the U.S. Bureau 

of Mines conducted field studies of 36,284 acres, of 

the 39,000 acre Honeycombs Wilderness Study Area. 

No mineral resources were identified in the study 

area. However, the study indicates moderate potential 

for uranium, thorium, and lithium resources in 

sedimentary and volcanic rocks, moderate potential 

for arsenic, lead, mercury, molybdenum, and zinc 

resources in caldera moat-fill sedimentary rocks and 

quartz veins, and moderate potential for arsenic and 

mercury resources in hydrothermal vein systems. The 

study area has moderate potential for zeolite 

resources in air-fall tuff beds and tuffaceous

sedimentary rocks, moderate potential for geothermal 

resources, and low potential for zinc resources in 

volcanic rocks. The study area has low potential for 

fluorite resources in lacustrine deposits, low potential 

for tin and copper resources in hydrothermal vein 

systems, and low potential for petroleum and natural 

gas resources in sedimentary rocks. The eastern part 

of the study area has identified resources of "picture 

jasper." In this report, the area studied is referred to 

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

area."

Character and Setting

The study area is located in the northern Basin 

and Range physiographic province approximately 50 mi 

west of Boise, Idaho, and 40 mi north of Jordan Valley, 

Oregon (fig. 1). Topography and drainage are 

dominated by north-trending ridges and valleys, deeply 

eroded east-trending canyons, and the north-trending 

Owyhee River canyon (Owyhee Reservoir). These 

features generally reflect local fault patterns. The 

northern topographic margin of the Mahogany 

Mountain caldera extends east-west across the 

southern third of the study area (fig. 2). The caldera

Al
43 30 -

43" 15-

Graded 

Gravel / 

Road \

PART OF THE j 

HONEYCOMBS WILDERNESS j 

STUDY AREA (OR-003-77AV

Figure 1. Index map showing location of the Honeycombs Wilderness Study Area, Malheur County, Oregon,

A2
collapse structure forms a topographic low south of 

the caldera margin. Rhyolitic flows and volcaniclastic 

rocks of Miocene age (5 to 24 million years before 

present, or Ma; see Geologic Time Chart, last page of 

this report) form a thick basal section and are the 

oldest rocks in the region. The rhyolitic flows are 

overlain by sedimentary rocks interbedded with ashflow and air-fall tuffs. Dikes, plugs, and sills of 

basalt, andesite, and rhyolite intrude the entire 

sequence. Basalt flows of Pliocene and Pleistocene 

age cap the stratigraphic section.

Identified Resources

No mineral resources were identified in the study 

area.

Mineral Resource Potential

The north-central and southern parts of the study 

area have moderate potential for uranium and thorium 

resources. High anomalous concentrations of these 

elements occur in rhyolite tuff, rhyolite intrusions, and 

tuffaceous sedimentary rocks. The mineral resource 

potential rating is based on anomalous aerial gammaray values and anomalous concentrations of uranium 

and thorium in rock samples.

The north-central and southern parts of the study 

area have moderate potential for strata-bound lithium 

resources, and low potential for volcanogenic 

disseminated-zinc resources.

Areas adjacent to the Mahogany Mountain 

caldera topographic margin (fig. 2, stipple pattern) 

have moderate potential for mercury and arsenic 

resources. Rocks exposed along fault and fracture 

zones parallel to the caldera wall are locally 

hydrothermally altered and silicified. Geochemical 

analyses indicate anomalous concentrations of mercury 

and arsenic in these altered rocks. Although no gold 

was detected in the samples analyzed, mercury and 

arsenic are good pathfinder elements for gold 

resources.

An area south of the caldera topographic margin 

has moderate potential for arsenic, molybdenum, lead, 

and zinc resources. Anomalous concentrations of 

these elements are found in silicified and pyritized 

moat-fill sedimentary rocks (fig. 2, unit Ts south of 

the caldera margin). Potential mineral resources 

associated with post-caldera ring-fracture volcanism, 

and caldera-related hydrothermal activity are depicted 

as a single area of resource potential on figure 2 

(stipple pattern).

Numerous high-silica rhyolite intrusions (fig. 2, 

unit Tr) located in the southern and central parts of 

the study area have moderate potential for arsenic, 

mercury, and zinc resources. The rhyolite intrusions 

are locally brecciated and cut by quartz veins. 

Geochemical analyses indicate that the brecciated 

rhyolite contains anomalous concentrations of these 

elements.

The study area has low potential for copper, tin,

and fluorite resources. Anomalous concentrations of 

copper are probably associated with fracture fillings in 

mafic and intermediate intrusions. The anomalously 

high tin concentrations seem to be spatially associated 

with rhyolite intrusions. Anomalous fluorite 

concentrations are probably associated with diagenetic 

fluorite in lacustrine deposits.

The study area has moderate potential for 

zeolite resources. Although zeolite concentrations are 

highest in air-fall tuff layers, they occur in various 

rock types throughout the study area.

The study area has moderate potential for 

geothermal energy resources. Numerous thermal 

springs and wells occur north of the study area. One 

area near the northern boundary is underlain by a 

thermal water reservoir less than 1,000 m from the 

surface (Oregon Department of Geology and Mineral 

Industries, 1982).

Sedimentary rocks in the northern and central 

parts of the study area have low potential for 

petroleum and natural gas resources. A seismic study 

and drilling program are needed to help determine 

their resource potential.

Prospects and claims located near the eastern 

boundary of the study area (fig. 2) contain identified 

resources of "picture jasper." "Picture jasper" is a 

locally derived name for cryptocrystalline, nearly 

opaque, variegated silica containing as much as 1 

percent disseminated pyrite (Scott, 1986). Picture 

jasper commonly occurs along known fault and 

fracture zones.

INTRODUCTION

Area Description

The Honeycombs Wilderness Study Area (OR003-77A) consists of approximately 39,000 acres in the 

north-central Basin and Range physiographic province 

of eastern Oregon. The area is located adjacent to the 

Owyhee Reservoir, approximately 30 mi west of the 

Idaho state line and 40 mi north of Jordan Valley, 

Oregon (fig. 1). The study area is accessible from U.S. 

Highway 95 via an improved gravel road paralleling 

Succor Creek and several unimproved gravel roads and 

jeep trails. Westward-draining creeks have eroded 

deep gulches in the pyroclastic deposits. Normal pool 

elevation of the Owyhee Reservoir is 2,655 ft. The 

maximum elevation in the study area is about 5,000 ft 

along Bannock Ridge. The climate is semiarid; 

vegetation is sparse with sage brush and grasses 

dominant at all elevations. Juniper trees are found 

along creek bottoms and in protected gulches.

Previous and Present Investigations

A reconnaissance geologic map of the Owyhee 

region by Kittleman and others (1967) was used, in 

part, as a basis for preliminary investigations. In 

addition, the U.S. Geological Survey conducted a

A3
43°20

M/C Ll, Th, U

L/B Zn

APPROXIMATE BOUNDARY 

OF

PART OF THE

HONEYCOMBS WILDERNESS STUDY 

AREA (OR-003-77A)

M/C As, Hg, Pb, Mo, Zn

Tt

1 2 MILES

Figure 2. Map showing geology and mineral resource potential of the Honeycombs 

Wilderness Study Area, Malheur County, Oregon.

A4
ERRATA FOR U.S. GEOLOGICAL SURVEY BULLETIN 1741-A

Several commodities and their resource potential were inadvertently omitted from 

figure 2 (pages A4-A5). The corrections are as follows:

1. The entire study area has moderate potential for undiscovered zeolite 

and geothermal resources, with level C certainty.

2. The entire study area has low potential for undiscovered copper, tin, 

and fluorite resources, with level B certainty.

3. The Tertiary age sedimentary rocks (unit Ts) in the northern and

central parts of the study area have low potential for undiscovered 

petroleum and natural gas resources, with level B certainty.

4. Several mines, claims, and prospects within the study area (map

numbers 1-3, 5-10, 12-14, and 17) have low potential for undiscovered 

picture jasper resources, with level D certainty. (Also, this sentence 

should replace the entire last paragraph of the text on page A10 

regarding picture jasper.)

EXPLANATION

AREA WITH MODERATE MINERAL RESOURCE POTENTAIL-Lithium, thorium, and uranium. 

See appendix 1 and figure 3 for definition of mineral resource potential and certainty of 

assessment.

AREA WITH MODERATE MINERAL RESOURCE POTENTIAL-Arsenic, mercury, molybdenum, 

lead, and zinc.

COMMODITIES

As

Hg

Li

Mo

Pb

Th

U

Zn

Arsenic

Mercury

Lithium

Molybdenum

Lead

Thorium

Uranium

Zinc

MINES, PROSPECTS, AND CLAIMS

1. Painted Rock Canyon No. 1 claim 10.

2. Pinto claim 11.

3. unnamed prospect 12.

4. Wild Horse mine 13.

5. unnamed prospect 14.

6. Madonna No. 3 claim 15.

7. Betty No. 1 and Thunder Ridge claims 16. 

3. unnamed prospect 17. 

9. unnamed prospect

unnamed prospect

Desert Queen No. 2 claim

Owyhee Green Streak claim

Big 4 and More No. 1 and 2 claims

Lucky Sunday prospect

Jackpot No. 2 and JB. No. 1 claims

OE.T. 1-4 claims

Hobnob claim

CORRELATION OF MAP UNITS

"V QUATERNARY

"T- QUATERNARY AND TERTIARY

l_-T-ITO-T-IAOV/ h TERTIARY

GEOLOGIC MAP UNITS

Qs SURFICIAL DEPOSITS (QUATERNARY)

QTb BASALT FLOWS, DIKES, AND SILLS (QUATERNARY AND TERTIARY)

Ts SEDIMENTARY ROCKS (TERTIARY)

Tr RHYOLJTE FLOWS, DOMES, AND DIKES (TERTIARY)

Tth TUFF OF HONEYCOMBS VOLCANIC CENTER (TERTIARY)

Tt TUFF (TERTIARY)

MAP SYMBOLS

 CONTACT

 * FAULT-Bar and ball on downthrown side; dashed where uncertain

V CALDERA TOPOGRAPHIC MARGIN-Teeth on downthrown side (Mahogany Mountain caldera)

X MINE

X PROSPECT OR CLAIM

Figure 2. Continued.

A5
combined geological (Vander Meulen and others, 1986a, 

b, c), geochemical, and geophysical study of the area 

during the 1984 and 1985 field seasons. The U.S. 

Bureau of Mines examined all mines, prospects, and 

claims in or near the study area (Scott, 1986).

Acknowledgments

The authors gratefully acknowledge the help of 

Mike (Gruby) Grubensky, Kathy Tegtmeyer, Carol 

Goeldner, and Scott Minor of the U.S. Geological 

Survey, and Mitch Linne, Dick Winters, Andy 

Leszcykowski, Dale Avery, John Benham, Nick 

Winslow, and Brian Ballou of the U.S. Bureau of Mines, 

during fieldwork of this study.

APPRAISAL OF IDENTIFIED RESOURCES

By Douglas F. Scott, U.S. Bureau of Mines

History and Production

Gold placer claims were located south of Leslie 

Gulch (fig. 1) as early as 1906. Potash exploration 

began in 1915, but ended abruptly. Gemstone 

exploration for picture jasper may have started as 

early as 1932; however, most gemstone exploration 

began in the late 1960's and continues. Several mining 

exploration companies have been prospecting in and 

near the study area for disseminated silver and gold 

deposits.

At least 329 potash claims were located within 

the area studied during 1915; they appear to have been 

abandoned within one year of discovery. Since 1932, 

an estimated 21 claims within the present study area, 

and 122 claims within 2 mi of the east edge of the 

study area, have been located for picture jasper. 

Seven of these are current mining claims according to 

1983 Bureau of Land Management records. At least 74 

workings (pits, bulldozer cuts, and open cuts) are in or 

adjacent to the study area. Of these, 22 are located in 

the study area.

Approximately 13 placer claims are south of 

Leslie Gulch, and one placer claim is in the study 

area. Oil and gas leases occupy 6,560 acres in the 

northern half of the study area, according to 1983 

Bureau of Land Management records.

Several tons of picture jasper have been 

produced in and adjacent to the study area; however, 

no production records are available. Value of the 

picture jasper varies; most of the material averages at 

least $2.50 per pound ($5,000 per short ton). A zeolite 

mineral (clinoptilolite) is mined by Teague Minerals 

near Adrian, Oregon, about 15 mi north of the study 

area. A zeolite mill, also owned by Teague Minerals, 

is located about 2 mi south of Adrian, Oregon and 

processes about 400 tons of zeolites per month (Glen 

Teague, personal commun., 1985). Silver and gold are 

produced from veins, fracture fillings, and veinlets in a 

caldera-related porphyritic rhyolite at the DeLamar

mine, about 30 mi east of the study area.

Mines, Prospects, Claims, and Mineralized Areas

Picture jasper is present in small quantities at 

each of the 6 prospects, 10 claim groups, and 1 mine 

that were mapped and sampled (fig. 2). Gemstone 

collectors work some of these deposits on a seasonal 

basis. The largest deposit, the Wild Horse mine (fig. 2, 

no. 4), is adjacent to the east boundary of the study 

area and is worked from June to November. Most of 

the surface area of the mine is overlain by at least 35 

ft of ash-flow tuff of the Leslie Gulch Tuff Member of 

the Sucker Creek Formation (Kittleman and others, 

1965; Kittleman, 1973).

Zeolites are present in air-fall tuff layers in the 

Sucker Creek Formation. Seventy-five samples of tuff 

collected at 67 locations were analyzed for zeolites. 

Twenty-four samples contained at least 50 percent 

zeolites. Zeolite composition ranged from 6 to 72 

percent clinoptilolite and 15 to 55 percent mordenite. 

Samples with total zeolite composition greater than 50 

percent (clinoptilolite and mordenite percentages 

combined) were tested for ammonia cation exchange 

capacity (CEC). CEC's ranged from 0.02 to 1.6. 

Erratic zeolite (CEC) values and (or) the intermittent 

nature of exposures of zeolite-bearing rock preclude 

estimation of grade, tonnage, and areal extent of any 

zeolite resource.

Although most of the study area was claimed in 

1915 for potash, no potash occurrences were found. 

Seventy-four samples analyzed for potassium ranged 

from 0.99 to 5.4 percent potassium, values typical of 

unmineralized rock.

One sample of clayey, volcaniclastic material 

from Craig Gulch in the southern part of the area was 

evaluated for its possible use as a structural clay 

product (construction-grade brick fired at 1,000 to 

1,050 °C). The sample came from a zone 2 to 3 in. 

thick and limited to about 100 ft of exposure; 

therefore, a clay resource is not apparent.

A 50-ft-long, 0.5-ft-thick carbonaceous zone 

exists in air-fall tuff layers in the northern part of the 

study area. The zone contained no detectable gold, 

uranium oxide, or thorium oxide.

No detectable gold was found in one placer 

sample collected near Mud Spring, in the southern part 

of the study area.

Appraisal of Mineral Resources

No significant mineral resources were identified 

in or adjacent to the study area.

Small amounts of picture jasper are removed 

annually from prospects in and adjacent to the study 

area.

Zeolites are found in tuff and volcanic 

sedimentary rocks throughout the study area; however, 

exposures contain erratic concentrations and are 

limited in size. Twenty-four samples contained zeolite 

concentrations greater than 50 percent. Of these,

A6
eight contain CEC's of 1.5 or more. If deposits of 

material approaching this grade are delimited by 

detailed mapping, mining companies may become 

interested in the area. Zeolites of this grade can be 

used for absorbent material.

Sand and gravel are present throughout the study 

area. There are adequate and more accessible deposits 

of sand and gravel outside the study area.

Recommendations for Further Work

Ash-flow tuff in and adjacent to the study area 

was sampled for the presence of zeolites. Twenty-four 

of 75 samples meet industry requirements for 

commercial zeolites. Based on these samples,detailed 

sampling and mapping of zeolite-bearing tuff in an 

area north of Leslie Gulch may reveal accumulations 

of zeolites.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By Dean B. Vander Meulen, James J. Rytuba, 

Harley D. King, and Donald Plouff 

U.S. Geological Survey

Geology

The Honeycombs Wilderness Study Area is 

underlain by rhyolite flows, air-fall and ash-flow tuffs, 

interbedded arkosic and tuffaceous sedimentary rocks, 

basalt flows, and silicic, intermediate, and mafic 

intrusions. All rocks in the area are of Miocene or 

younger age. The volcanic and sedimentary rocks were 

deposited in a broad,north-plunging lacustrine basin 

that evolved in eastern Oregon and western Idaho 

beginning in late Miocene time (Gray and others, 

1983).

Peralkaline rhyolite ash-flow and air-fall tuffs 

are the dominant rock type within the study area. Two 

major air-fall tuffs and four separate ash-flow tuffs 

are distinguishable. They are mapped together as units 

Tt and Tth (fig. 2). The ash-flow sheet with the 

greatest volume and areal extent in the study area is 

the Leslie Gulch Tuff Member. The tuff is divided into 

outflow facies, air-fall facies, and intracaldera 

facies. Eruption of the tuff resulted in the formation 

of the Mahogany Mountain caldera (Rytuba, 1985). A 

potassium-argon (K-Ar) age obtained from the tuff is 

15.510.5 Ma. The southern third of the study area 

includes part of the caldera collapse structure. The 

intracaldera facies of the Leslie Gulch Tuff Member is 

the lowest exposed stratigraphic unit within the 

collapse structure. Overlying and interbedded with the 

intracaldera facies is the air-fall facies of the Leslie 

Gulch Tuff Member, both of which were erupted from 

a vent in the center of the caldera. Outflow facies of 

the Leslie Gulch Tuff Member overlie bedded 

tuffaceous siltstone, mudstone, and fine- to mediumgrained arkosic sandstone. Sedimentary rocks are 

exposed along the northern topographic margin of the 

caldera and are the oldest rocks in the study area. 

Fine- to coarse-grained arkosic sandstone and

interbedded tuffaceous siltstone overlie the outflow 

facies of the tuff. Stratigraphically above these 

sedimentary rocks is the ash-flow tuff of Spring 

Creek.

The tuff of Spring Creek and sedimentary rocks 

thicken to the north and east. The thickest sections of 

the tuff of Spring Creek are localized within the moat 

of the Mahogany Mountain caldera and along the eastcentral margin of the study area. Moat-fill 

sedimentary rocks (confined to the subsided part of the 

caldera collapse structure) overlie the tuff of Spring 

Creek and the Leslie Gulch air-fall deposit. The moatfill sedimentary rocks are thin-bedded, fine-grained 

sandstone, siltstone, and shale locally altered and 

mineralized.

Two north-striking rhyolite dike systems intrude 

the floor of the Mahogany Mountain caldera. The 

rhyolite dikes are exposed in the southernmost part of 

the study area (fig. 2), parallelling both sides of a 

graben in the resurgent dome of the Mahogany 

Mountain caldera. Potassium-argon ages obtained 

from the rhyolite dikes are 14.7±0.4 Ma and 14.9±0.4 

Ma. The caldera margin within the study area is 

intruded by one rhyolite dome and several rhyolite 

plugs and dikes. A K-Ar age obtained from one of the 

rhyolite plugs is 14.910.4 Ma. Rhyolite domes and 

plugs are common along the southeastern boundary of 

the study area. Rhyolite intrusions are locally 

brecciated, silicified, and cut by quartz veins.

The Honeycombs volcanic center (Vander Meulen 

and others, 1986b), located in the north-central part of 

the study area, contains voluminous air-fall tuff and 

several rhyolite dikes and plugs. Near-vent air-fall 

deposits form coalescing pumice cones armored with 

rhyolite agglutinate. Distal vent deposits are wellbedded pumice lapilli air-fall tuff. The tuff and 

pumice cones were subsequently intruded by rhyolite 

dikes and plugs, all with a similar high-silica rhyolite 

composition. Geochemical and stratigraphic relations 

suggest that the tuff erupted from the Honeycombs 

volcanic center is younger than the tuff erupted from 

the Mahogany Mountain caldera.

North-dipping volcaniclastic and arkosic 

sedimentary rocks onlap the air-fall tuff in the 

northern part of the Honeycombs volcanic center. An 

intermediate-to-mafic, lithic-rich palagonite ash-flow 

tuff is interbedded with the sedimentary rocks. The 

sequence of volcanic and sedimentary rocks is intruded 

by numerous dikes and sills of pyroxene andesite. 

Pyroxene andesite is exposed in large sills (2 to 3 mi 

long) that intrude tuffs of the Honeycombs volcanic 

center, and in north-trending dikes cutting 

sedimentary rocks immediately north and west of the 

Honeycombs volcanic center. Basalt flows, dikes, and 

sills cap and (or) intrude the entire sequence of 

sedimentary rocks in the northern part of the study 

area. The basaltic rocks are the youngest volcanic 

rocks in the study area.

Stream-bed and alluvial-fan deposits form the 

thickest accumulations of Quaternary sediment in the 

study area. Lag gravels and colluvium form extensive 

veneer deposits on low-angle slopes and terraces.

The study area is located within the Basin and 

Range physiographic province, a region characterized 

by extensional tectonism. Volcanic and sedimentary 

rocks of Miocene age within the study area are broken

A7
by several north- to north-northwest-trending horst 

and graben stuctures; the resulting fault blocks form 

the dominant structural pattern in the study area. The 

central part of the Owyhee reservoir is located within 

a north-trending graben, which is the largest fault 

block in the study area. Normal faults along the west 

side of the Owyhee reservior (fig. 2) help delineate the 

graben. Poorly exposed, northwest-trending faults 

cross the northern and central part of the study area. 

These faults control tributary drainage and truncate 

north-trending normal faults. Faults in the southern 

part of the study area reflect both east-west extension 

and collapse along an east-west-trending caldera ring 

fracture. The topographic margin of the Mahogany 

Mountain caldera is, in part, controlled by northtrending normal faults, indicating caldera collapse may 

have occurred along preexisting north-trending normal 

faults.

Geochemical Studies

In 1984, the U.S. Geological Survey conducted a 

geochemical study of the Honeycombs Wilderness 

Study Area based on the analysis of stream sediments, 

stream-sediment heavy-mineral concentrates, and rock 

samples. Geochemical data obtained from streamsediment analyses represents the composite chemistry 

of rock units in a particular drainage basin. Drainage 

basins within the study area range from 0.5 to several 

square miles in size.

Fifty-three stream-sediment samples, 49 heavymineral-concentrate samples, and 12 rock samples 

were analyzed for 31 elements by six-step 

semiquantitative emission-spectrographic methods 

(Myers and others, 1961; Grimes and Marranzino, 

1968). Several samples were analyzed by inductively 

coupled argon plasma atomic-emission spectroscopy 

(ICAP-AES) (Crock and others, 1983) using a 

modification of the O'Leary and Viets digestion 

method (1986). Atomic-absorption and cold-vapor 

atomic-absorption methods were used to determine 

concentrations of gold and mercury (Thompson and 

others, 1968; Koirtyohann and Khalil, 1976).

Peralkaline rhyolite tuffs and intrusions, which 

comprise the Honeycombs volcanic center (unit Tth, 

fig. 2), have the highest uranium (12 parts per million, 

or ppm) and thorium (20 ppm) concentration in the 

study area. Tuffaceous sedimentary rocks derived 

from the Honeycombs volcanic center also have high 

uranium and thorium contents. Aerial gamma-ray 

surveys (EG and G geoMetrics, 1979), which cover part 

of the Honeycombs volcanic center, revealed uranium 

and thorium anomalies over the volcanic center 

approaching five times one standard deviation from 

the mean uranium and thorium concentrations for 

rocks in the Boise 2° quadrangle. The anomalies 

closely correspond to the distribution of rock types 

within the Honeycombs volcanic center and associated 

tuffaceous sedimentary rocks. The anomalies most 

likely reflect high magmatic concentrations of the 

elements dispersed throughout the strata, rather than 

local high-grade concentrations of uranium and 

thorium. Although no zones of hydrothermal 

alteration were noted in or adjacent to intrusive rocks 

within the Honeycombs volcanic center, vein-type

uranium deposits typically associated with peralkaline 

may be present at depth.

Peralkaline rhyolite tuffs and intrusions 

associated with the Mahogany Mountain caldera have 

high uranium (8 ppm) and thorium (18 ppm) contents. 

Aerial gamma-ray surveys (EG and G geoMetrics, 

1979), which cover part of the caldera, show uranium 

anomalies over the caldera. The anomalies likely 

reflect the high concentrations of uranium 

present in the Leslie Gulch Tuff Member and rhyolite 

intrusions associated with the Mahogany Mountain 

caldera. Hydrothermal alteration associated with 

rocks intruded by rhyolite along the margin of the 

caldera, as well as geochemical anomalies of arsenic, 

mercury, molybdenum and zinc, indicate that local 

high-grade concentrations of uranium and thorium may 

be present. Vein-type uranium deposits in the 

McDermitt caldera complex (Rytuba and Glanzman, 

1979) are associated with peralkaline rhyolite 

intrusions and may be present within the Mahogany 

Mountain caldera complex. Sedimentary rocks that fill 

the moat of the caldera have been zeolitized, 

silicified, and pyritized. Geochemical anomalies of 

arsenic, mercury, zinc, and molybdenum in these rocks 

indicate the possible existence of stratiform uranium 

deposits similar to those associated with the 

peralkaline calderas in the McDermitt volcanic field 

(Rytuba, 1981).

Lithium concentration in peralkaline volcanic 

and volcaniclastic rocks associated with the 

Honeycombs volcanic center and the Mahogany 

Mountain caldera is the highest known for peralkaline 

rocks ( 200 ppm). High initial concentrations of 

lithium in the volcanic rocks, as well as widespread 

occurrences of zeolites in these rocks, suggest that 

stratiform lithium deposits, similar to occurrences in 

peralkaline rhyolite of the McDermitt caldera (Rytuba, 

1981), may be present in the study area.

The peralkaline rhyolite associated with the 

Honeycombs volcanic center and the Mahogany 

Mountain caldera has the highest zinc concentration 

for peralkaline rocks known to the authors. The high 

zinc content of the peralkaline rhyolite is attributed to 

chlorine enrichment of the magma (Rytuba, 1981). 

Fifty rock samples of ash-flow and air-fall tuff were 

analyzed for zinc by X-ray fluorescence (kevex). 

Concentrations typically ranged from 200 to 500 ppm, 

with some values as high as 700 ppm (T. L. Vercoutere, 

written commun., 1986).

Various rock types along the Mahogany Mountain 

caldera ring fracture are hydrothermally altered and 

silicified. Samples of intracaldera tuff collected from 

a silicified fracture, which trends parallel to the 

northern caldera margin, contain anomalous 

concentrations of arsenic (120 ppm) and mercury (0.7 

ppm). Samples of silicified and pyritized moat-fill 

sedimentary rock collected a little south of the 

topographic wall of the caldera contain anomalous 

concentrations of arsenic (140 ppm), lead (126 ppm), 

molybdenum (65 ppm), and zinc (90 ppm). The 

northern margin of the caldera is intruded by several 

high-silica rhyolite plugs and dikes. Locally, rhyolite 

intrusions are cut by quartz veins. Samples of the 

fractured rhyolite and quartz veins contain anomalous 

concentrations of arsenic (30 ppm), mercury (2.8 ppm), 

and zinc (250 ppm). The high zinc content probably

A8
reflects normal magmatic enrichment and (or) 

concentrations derived from hydrothermal systems 

active during the close of the caldera cycle. No gold 

was detected in these samples.

Several stream-sediment samples collected in 

the study area contain anomalous concentrations of 

copper (300 to 3,000 ppm), tin (799 to 1,000 ppm), and 

fluorine (600 to 850 ppm) (Gray and others, 1983; 

Erickson and others, 1986). Samples containing 

anomalous concentrations of copper are restricted to 

the northern part of the study area and seem to be 

associated with intrusions of basalt and andesite. The 

distribution of samples containing anomalous 

concentrations of tin seem to correlate with rhyolite 

plugs and dikes in the Honeycombs volcanic center, 

and with dikes in the southern part of the study area. 

Potential tin resources in the study area may have 

formed in an environment similar to the tin deposits 

found in Tertiary rhyolite of the Black Range (Lufkin, 

1976) in southwestern New Mexico. Stream-sediment 

samples collected in the central part of the study area 

contain microscopic grains of fluorite (H.D. King, 

written commun., 1986). Authigenic fluorite in 

lacustrine and tuffaceous sedimentary rocks is 

reported by Sheppard and Gude (1969) 30 mi southeast 

of the study area. Diagenetic fluorite in lacustrine 

and tuffaceous sedimentary rocks may occur in the 

study area.

Near the eastern boundary of the study area, 

identified resources of picture jasper are mined from 

silicified and pyritized tuffaceous and sedimentary 

rocks. The pattern of alteration in the rocks roughly 

corresponds with known fault zones.

Geophysical Studies

The U.S. Geological Survey established 11 

gravity stations in and near the study area to 

supplement gravity data obtained from the National 

Geophysics Data Center (1984). Other gravity data 

were obtained by Couch and Baker (1977). A 

preliminary Bouguer gravity-anomaly map of the study 

area (Plouff, 1985, unpublished map) is dominated by a 

north-south-elongated, 8- by 20-mi gravity low with an 

amplitude of about 20 mGal. The gravity low probably 

reflects the presence of a subsided wedge of 

tuffaceous sediments of relatively low density within a 

caldera. The steep gravity gradients at the edges of 

the anomaly (9 mGal/mi near the south and southwest 

edges of the study area) indicate that the wall of the 

caldera is steep and the top of the intracaldera fill is 

buried at a shallow depth. Furthermore, the 

intracaldera fill is thickest where the gravity low has a 

minimum value, about 4 mi north of the south edge of 

the study area. Spatial associations indicate that the 

caldera may have subsided in response to depletion of 

an underlying magma chamber aher extrusion of the 

Leslie Gulch Tuff Member.

An aeromagnetic survey of the region was flown 

at a barometric elevation of 9,000 ft above sea level 

with east-west flightlines spaced at 2-mi intervals 

(U.S. Geological Survey, 1972). The aeromagnetic map 

is dominated by a north-south-elongated, 6- by 10-mi 

magnetic high centered over the Owyhee reservoir. 

The only other magnetic anomaly in the study area is a

small magnetic low located in its northwest corner. 

The magnetic low probably is a normal polarization 

effect of the large magnetic high. A small gravity 

high with an amplitude of less than 3 mGal nearly 

coincides with the crest of the large magnetic high. 

The axis of the magnetic high is located along the west 

edge of the gravity low. Therefore, although the two 

geophysical anomalies are roughly the same size, the 

lack of coincidence suggests a separate source for the 

magnetic anomaly. The magnetic high may reflect a 

large intrusive body with moderate to high magnetization centered beneath the west wall of the caldera.

CONCLUSIONS

Geologic and geochemical investigations indicate 

that there are several levels of mineral resource 

potential in the Honeycombs Wilderness Study Area.

Areas within the Honeycombs volcanic center 

and Mahogany Mountain caldera (fig. 2) have moderate 

potential for lithium, thorium, and uranium mineral 

resources with level C certainty. The mineral 

resource potential rating is based on anomalous 

concentrations of these elements in rock samples, and 

anomalous aerial gamma-ray values for thorium and 

uranium. The level of certainty rating is based on the 

preceeding data, and genetic models presented in 

previous sections that describe possible resourceforming processes. See appendix 1 and figure 3 for 

definitions of levels of mineral resource potential and 

certainty.

Large volumes of peralkaline rhyolite tuff 

associated with the Honeycombs volcanic center and 

Mahogany Mountain caldera have extraordinarily high 

zinc concentrations. Volcanogenic disseminated-zinc 

resources of this type were previously unrecognized; 

therefore, low potential for zinc resources is assigned 

to areas underlain by the rhyolite tuff, with level B 

certainty.

Rocks present along the northern margin of the 

Mahogany Mountain caldera contain anomalous 

concentrations of arsenic, lead, mercury, molybdenum, 

and zinc. Hydrothermal systems active during the 

close of the caldera cycle likely concentrated these 

elements; therefore, areas adjacent to the caldera 

margin (fig. 2, stipple pattern) have moderate 

potential for arsenic, lead, mercury, molybdenum, and 

zinc resources, with level C certainty.

The study area has low potential for copper, tin 

and fluorite resources, with level B certainty. The 

mineral resource potential rating is based on 

anomalous concentrations of these elements in soil 

samples.

The study area has moderate potential for 

zeolite resources, with level C certainty. Zeolite 

minerals occur in various rock types throughout the 

study area, with the highest concentrations occurring 

in air-fall tuff beds.

Resource potential for geothermal energy in the 

study area is moderate, certainty level C. An 

unnamed hot spring is located along a north-trending 

normal fault 3 mi southwest of the study area. 

Recorded temperature of the spring water is 50° C 

(Bliss, 1983). Several thermal springs and wells are

A9
located about 10 mi north of the study area (Oregon 

Department of Geology and Mineral Industries, 1982). 

One area, less than 3 mi north of the northwest 

boundary of the study area, may be underlain at 

shallow depth (less than 1,000 m) by thermal water of 

sufficient temperature for direct heat applications 

(Oregon Department of Geology and Mineral 

Industries, 1982).

Sedimentary rocks in the northern and central 

parts of the study area have low potential for 

petroleum and natural gas resources, with level B 

certainty. The sedimentary rocks are intruded and 

interbedded with volcanic rocks. Heat which 

accompanied the volcanic intrusions likely destroyed 

nearby petroleum and natural gas reservoirs. A 

drilling program in conjunction with seismic studies is 

needed to test the sedimentary rocks for the presence 

of hydrocarbons.

Several prospects and claims, and one mine near 

the eastern boundary of the study area contain 

identified resources of picture jasper, with level D 

certainty. The deposits are small, commonly 

restricted to silicified and pyritized fault and fracture 

zones. Because of the small and confined nature of 

the deposits, the economic value of the picture jasper 

is considered low.

REFERENCES CITED

Bliss, J.D., 1983, Oregon; basic data for thermal 

springs and wells as recorded in Geotherm: U.S. 

Geological Survey Open-File Report 83-435, 247

P'

Couch, R.W., and Baker, B., 1977, Geophysical 

investigations of the Vale-Owyhee Geothermal 

Region, Malheur County, Oregon: Oregon State 

University Technical Report No. 2 to the 

Geothermal Research Program of the U.S. 

Geological Survey, 52 p.

Crock, J.G., Lichte, F.E., and Briggs, P.H., 1983, 

Determination of elements in National Bureau of 

Standards' Geological Reference Materials 

SRM278 Obsidian and SRM688 Basalt by Inductively Coupled Argon Plasma-Atomic Emission 

Spectrometry: Geostandards Newsletter, v. 7, p. 

335-340.

EG and G geoMetrics, 1979, Aerial gamma ray and 

magnetic survey - Idaho project, Hailey, Idaho 

Falls, Elk City quadrangles of Idaho/Montana and 

Boise quadrangle, Oregon/Idaho, (contract DEAC13-76GJ01664, subcontract no. 79-323-5): U.S. 

Department of Energy Open-File Report GJBX-10 

(80), Available through U.S. Geological Survey 

Branch of Open File Services, Denver, CO , 114 p.

Erickson, M.S., Malcolm, M.J., Hoffman, J.D., and 

King, H.D., 1986, Analytical results and sample 

locality maps of stream-sediment and heavymineral-concentrate samples from the 

Honeycombs (OR-003-77A) and the Owyhee 

Canyon (OR-003-195) Bureau of Land Management 

Wilderness Study Areas, Malheur County, 

Oregon: U.S. Geological Survey Open-File Report 

in press .

Gray, J.J., Peterson, J.C., Clayton, J., and Baxter, G.,

1983, Geology and mineral resources of 18 BLM 

Wilderness Study Areas, Harney and Malheur 

Counties, Oregon: Oregon Department of Geology 

and Mineral Industries, Open-File Report 0-83-2, 

106 p.

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

survey reports on public lands: U.S. Geological 

Survey Open-File Report 84-787, 25 p.

Grimes, D.J., and Marranzino, A.P., 1968, Directcurrent arc and alternating-current spark emission 

spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

U.S. Geological Survey Circular 591, 6 p.

Kittleman, L.R., 1973, Guide to the Geology of the 

Owyhee Region of Oregon: University of Oregon 

Museum of Natural History Bulletin 21, 61 p.

Kittleman, L.R., Green, A.R., Hagood, A.R., Johnson, 

A.M., McMurray, J.M., Russell, R.A., and Weeden, 

D.A., 1965, Cenozoic stratigraphy of the Owyhee 

Region, southeastern Oregon: University of 

Oregon Museum of Natural History Bulletin 1, 45

PKittleman, L.R., Green, A.R., Hagood, A.R., Johnson, 

A.M., McMurray, J.M., Russell, R.A., and Weeden, 

D.A., 1967, Geologic map of the Owyhee Region, 

Malheur County, Oregon: University of Oregon 

Museum of Natural History Bulletin 8, scale 

1:125,000.

Koirtyohann, S.R., and Khalil, Moheb, 1976, Variables 

in the determination of mercury by cold vapor 

atomic absorption: Analytical Chemistry, v. 48, 

no. 1, p. 136-139.

Lufkin, J.L., 1976, Oxide minerals in miarolitic 

rhyolite, Black Rock Range, New Mexico: 

American Mineralogist, v. 61, p. 425-430.

Myers, A.T., Haven, R.G., and Dunton, P.J., 1961, a 

spectrochemical method for the semiquantitative 

analysis of rocks, minerals, and ores: U.S. 

Geological Survey Bulletin 1084-1, p. 207-229.

National Geophysical Data Center, 1984, DMA gravity 

file of the U.S.: National Oceanic and 

Atmospheric Administration, Boulder, Colo., 

2 magnetic tapes.

O'Leary, R.M., and Viets, J.G., 1986, Determination of 

antimony, arsenic, bismuth, cadmium, copper, 

lead, molybdenum, silver, and zinc in geological 

materials by atomic absorption Spectrometry 

using a hydrochloric acid-hydrogen peroxide 

digestion: Atomic Spectroscopy, v. 7, no. 1, p. 

4-8.

Oregon Department of Geology and Mineral Industries, 

1982, Geothermal resources of Oregon Available 

through Oregon Department of Mineral Industries, 

1005 State Office Building, Portland, OR, 97201 , 

scale 1:500,000.

Plouff, Donald, 1985, Unpublished Bouguer gravityanomaly map of part of the Honeycombs 

Wilderness Study Area, scale 1:65,000.

Rytuba, J.J., 1981, Relation of calderas to ore deposits 

in the western United States, in Dickinson, W. R., 

and Payne, W. D., eds., Relation of tectonics to 

ore deposits in the Southern Cordillera: Arizona 

Geological Society Digest, v. 14, p. 227-236.

Rytuba, J.J., and Glanzman, R.K., 1979, Relation of 

mercury, uranium, and lithium deposits to the 

McDermitt caldera complex, Nevada-Oregon:

MO
Nevada Bureau of Mines and Geology, Report 33, 

Fifth International Association on the Genesis of 

Ore Deposits Quadrennial Symposium, p. 109-117.

Rytuba, J.J., Vander Meulen, D.B., Plouff, Donald, and 

Minor, S.A., 1985, Geology of the Mahogany 

Mountain caldera, Oregon abs. : Geological 

Society of America Abstracts with Programs, v. 

17, no. 4, p. 70.

Scott, D.F., 1986, Mineral resources of the 

Honeycombs Study Area, Malheur County, 

Oregon: U.S. Bureau of Mines Open-File Report, 

MLA 30-86, 26 p.

Sheppard, R.A., and Gude, A.J. 3d, 1969, Authigenic 

fluorite in Pliocene lacustrine rocks near Rome, 

Malheur County, Oregon: U.S. Geological Survey 

Professional Paper 650-D, p. D69-D74.

Thompson, C.E., Nakagawa, H.M., and VanSickle, G.H., 

1968, Rapid analysis for gold in geologic 

materials, in Geological Survey Research 1968: 

U.S. Geological Survey Professional Paper 600-B, 

p. B130-B132.

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

the Adel and parts of the Burns, Boise, and Jordan 

Valley 1 by 2 degree quadrangles, Oregon: U.S. 

Geological Survey Open-File Report, 1 pi., scale 

1:250,000.

Vander Meulen, D.B., Rytuba, J.J., Grubensky, M.J., 

and Goeldner, C.A., 1986a, Geologic map of the 

Bannock Ridge 7.5' quadrangle, Malheur County, 

Oregon: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1903A, scale 1:24,000.

Vander Meulen, D.B., Rytuba, J.J., Grubensky, M.J., 

Vercoutere, T.L., and Minor S.A., 1986b, Geologic 

map of Pelican Point 7.5' quadrangle, Malheur 

County, Oregon: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1904B, scale 

1:24,000.

Vander Meulen, D.B., Rytuba, J.J., Vercoutere, T.L., 

and Minor, S.A., 1986c, Geologic map of the 

Rooster comb 7.5" quadrangle, Malheur County, 

Oregon: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1902C, scale 1:24,000.

All
Table 1. Mines, claims, and prospects in and adjacent to the Honeycombs Wilderness 

Study Area [ (*) indicates outside study area ]

Map No.

1

Name Geology

Painted Rock Canyon Tabular outcrop of 

No. 1 claim vitrophyre exposed 

in Sucker Creek Fm. 

Mafic rocks capped by 

zone of red oxidized 

mafic rocks and volcanic detritus.

Workings / Produc t ion

No workings; no known 

production; claim 

prospected for 

picture jasper.

Sample Data

Four samples: 2 chip samples 

from mafic sill, one grab sample 

of sill rock contained no gold 

or silver; 1 chip and 1 grab 

sample contain <5.7 percent iron 

oxide; 1 grab sample of oxidized zone contains no gold, silver 

or iron oxide.

Pinto claim

Unnamed prospect

Wild Horse mine

Unnamed prospect

Madonna No. 3 

claim

Betty No. 1 and 

Thunder Ridge 

claims

Unnamed prospect

Unnamed prospect

Fractures in Leslie 

Gulch Tuff Member 

are filled with green 

limonite-stained 

cryptocrystalline 

silica.

Gray to white, clayey, 

poorly consolidated 

volcaniclastic rock.

5-ft-thick fracture 

zone in Leslie Tuff 

Member filled with 

limonite-stained 

brown to blue cryptocrystalline silica; 

fault adjacent to 

fracture strikes N. 

37°-5V W. and dips 

/;7°-75° SW; fau] t contains brecciated 

cryptocrystalline silica with <1 percent 

disseminated pyrite.

1 trench 125 ft long, 

12 ft wide, and 3 ft 

deep prospected for 

picture jasper; no 

known production.

3 shallow pits, each 

< 25 ft long and 12 

ft wide, were prospected for picture 

jasper; no known 

production.

1 open cut about 300 

ft long, 40 ft wide, 

and 20 ft deep, 1 

trench 60 ft long by 

20 ft and 3 ft deep, 

and 3 shallow trenches 

<50 ft long and 12 ft 

wide were mined in 

1984 for picture jasper; no known production.

A 2-A-ft-thick fracture 

zone striking N. 44° E. 

and dipping 80° NW. in 

Leslie Gulch Tuff 

Member is filled with 

limonite- and manganese-stained blue to 

brown cryptocrystalline 

silica.

Frature zone 22 ft thick 

striking N. 25° W. and 

dipping 70° NE. in 

Leslie Gulch Tuff 

Member is filled with 

blue to brown cryptocrystalline silica.

1-2-ft-thick fracture 

zone in Leslie Gulch Tuff 

Member is filled with 

blue to green limonitestained cryptocrystalline silica; vitrophyre 

caps the tuff.

2 pits <A ft in diameter 

and < 3 ft deep were 

prospected for picture 

jasper; no known production.

1 select sample of silica contained no gold or silver.

2 chip samples of volcaniclastic rock contained no diatoms, and from 2.3 to 3.3 percent potassium, 0.03 percent 

chlorine, and 0.14 to 0.26 

percent sulfate.

10 samples: 4 chips of silica, 

2 chip and 4 grab samples of 

tuff; of 9 samples analyzed, 

none contained gold, 1 contained 0.2 oz/ton silver, 1 

contained 6 ppm antimony, 5 

contained 4.0-8.3 ppm arsenic, 

1 contained low concentrations 

of mercury and thallium, and 

1 contained 8,900 ppm fluorine; 

of 8 samples analyzed for magnesium, all contained >150 ppm; 

1 grab sample of tuff contained 15 percent mordenite, a zeolite mineral.

2 samples (1 select, 1 chip) 

of the silica contained no 

gold or silver.

Prospected for picture 

jasper; no known production.

Trench 50 ft long, 12 

ft wide, and <3 ft deep, 

was prospected for 

picture jasper; no known 

production.

A 5-ft-thick fracture Pit <6 ft in diameter 

zone in Leslie Gulch Tuff and < 3 ft deep was 

Member is filled with prospected for picture 

gray cryptocrystalline jasper; no known prosilica, duction.

Fracture zone 2.5 ft 

thick in Leslie Gulch 

Tuff Member filled with 

buff to green cryptocrvstalline silica.

2 trenches <50 ft long, 

12 ft wide, and 3 ft 

deep were prospected 

for picture jasper; no 

known production.

1 chip sample of silica contained no gold, silver, antimony, mercury, or thallium, 

5 ppm arsenic, 82 ppm fluorine, 

and 150 ppm magnesium; 1 grab 

sample of tuff contained no 

gold or silver.

4 samples (3 chip of silica, 

1 chip of tuff) collected; 

none contained gold or silver; 

of 2 samples analyzed for 

antimony, mercury, and thallium, none contained detectable 

amounts; 2 analvzed for 

arsenic contained 7 and 11.9 

ppm; 1 contained >150 ppm 

magnesium.

1 chip sample of gray silica 

contained no gold, silver, 

antimony, mercury, thallium, 

or sulfate, 11 ppm arsenic, 

0.004 percent chlorine, 76 

ppm fluorine, 480 ppm magnesium, and 3.2 percent potassium.

2 chip samples of silica 

contained no gold or silver; 

1 chip sample contained no 

antimony, mercury, or thallium, 

15 ppm arsenic and 819 ppm 

magnesium.

A12
Table 1. Mines, claims , and prospects in and adjacent to the Honeycombs Wilderness Study Area Continued

Map No. Name Geology Worki ngs/Product ion Sample Oata

10 Unnamed prospect

11* Desert Queen 

No. 2 claim

12

13

Owyhee Green 

Streak claim

Big A and More 

claims 1 and 2

1A Lucky Sunday 

prospect

15* Jackpot No. 2 and 

J.B. No. 1 claims

16* O.R.T 1-A 

claims

17 Hobnob claim

Fracture in the Leslie 

Gulch Tuff Member is 

filled with blue to 

green cryptocrystalline 

silica with <1 percent 

disseminated pyrite.

Buff to brown tuff of 

the Leslie Gulch Tuff 

Member.

Buff to brown tuff of 

Leslie Gulch Tuff Member exposed here; limonite-stained blue to

green silica found in 

trenches and on dumps.

Buff to brown tuff of 

Leslie Gulch Tuff Member 

is exposed here; limonite-stained blue to 

green silica found in 

trenches and on dumps.

Fractures in Leslie 

Gulch Tuff Member filled with tan to brown 

cryptocrystalline silica

A 4-7-ft-thick fracture 

zone in Leslie Gulch Tuff 

Member filled with cryptocrystalline silica; adjacent fault zone strikes 

N. 75° E. and dips 68° 

NE. in Leslie Gulch Tuff 

Member and is filled with 

brown to blue brecciated 

cryptocrystalline silica.

Fault zone striking N. 

80° E. and dipping 80° 

SE. in Leslie Gulch 

Tuff Member is filled 

with green to blue 

cryptocrystalline 

silica.

2 shallow trenches <50 

ft long and 12 ft wide 

were prospected for 

picture jasper; no known 

production

3 pits, <20 ft in diameter, and 1 trench <50 

ft long and 12 ft wide 

were prospected for 

picture jasper; no 

known production.

2 trenches <50 ft long 

and 12 ft wide were 

prospected for picture 

jasper; no known production.

A trenches <60 ft long 

and 12 ft wide were prospected for picture 

jasper; no known production.

Trench <100 ft long 

and 12 ft wide prospected for picture 

jasper; no known 

production.

Trench <70 ft long and 

12 ft wide, and shallow 

pit <10 ft in diameter 

prospected for picture 

jasper; no known production.

2 shallow pits <20 ft 

in diameter prospected for picture jasper; 

no known production.

A 0.5-ft-thick fracture Trench <10O ft long and 

zone in Leslie Gulch Tuff 12 ft wide was prospectMember filled with blue ed for picture jasper; 

to brown cryptocrystalline no known production, 

silica.

3 chip samples of silica were 

collected; 2 contained trace 

of gold; none contained 

silver; 3 contained 31, 32, 

and 36 ppm arsenic; none 

contained mercury or thallium; 1 contained 2 ppm antimony, and 1 contained >150 

ppm magnesium.

3 samples collected; 1 grab 

sample of buff-colored tuff 

contained no gold, silver, 

antimony, mercury, or thallium, 4 ppm arsenic, 200 ppm 

fluorine, and 1,420 ppm magnesium; 2 chip samples of 

tuff contained 4 and 16 percent analcime.

Grab sample of silica contained no gold, silver, or mercury, and 5.7 ppm uranium.

thallium; 3 contained 3 ppm 

mercury; 8 contained 3-11 ppm 

arsenic and >150 nom magChip sample of silica contained no gold, silver,antimony, mercury, or thallium; 

sample contained 10.8 ppm 

arsenic, 0.03 percent chlorine, 12 ppm fluorine, 270 

ppm magnesium, 2.8 percent 

potassium, and 0.04 percent 

sulfate.

Seven chip samples of silica 

and 5 chip and one grab of 

tuff collected; of 12 analyzed 

for gold, 2 contained a trace; 

of 12 analyzed for silver, 4 

contained 0.1 oz/ton and 1 

contained 0.2 oz/ton; none 

contained antimony, mercury, 

or thallium; 5 contained 3-7 

ppm arsenic; of 9 analyzed 

for magnesium, 7 contained 

> 150 ppm; 3 chip samples of 

tuff contained A7-100 ppm 

fluorine.

3 chip samples and 1 grab 

sample of silica, and 2 chip 

samples of tuff collected; 

none contained gold; 2 contained 0.1 and 0.2 oz/ton 

silver; of 5 analyzed for 

mercury and thallium, none 

contained detectable concentrations; 1 contained 3 

ppm antimony; 5 samples contained 5-70 ppm arsenic; 

A contained >150 ppm magnesium.

2 samples of silica collected; 1 grab sample contained 

no gold or silver; one chip 

sample contained no gold, 

silver, antimony, arsenic, 

mercury, or thallium; 1 

contained 150 ppm fluorine 

and 1,020 ppm magnesium.

A13
APPENDIX 1. Definition of levels of mineral resource 

potential and certainty of assessment

Mineral resource potential is defined as the 

likelihood of the presence of mineral resources in a 

defined area; it is not a measure of the amount of 

resources or their profitability.

Mineral resources are concentrations of naturally 

occurring solid, liquid, or gaseous materials in such 

form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible.

Low mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment where 

the existence of resources is unlikely. This level of 

potential embraces areas of dispersed mineralized rock 

as well as areas having few or no indications of 

mineralization. Assignment of low potential requires 

specific positive knowledge; it is not used as a catchall 

for areas where adequate data are lacking.

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 a reasonable chance for resource 

accumulation, and where an application of genetic and 

(or) occurrence models indicates favorable ground.

High mineral resource potential is assigned to 

areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment 

favorable for resources, where interpretations of data 

indicate a high likelihood for resource accumulation, 

where data support occurrence and (or) genetic models 

indicating presence of resources, and where evidence 

indicates that mineral concentration has taken place. 

Assignment of high resource potential requires positive 

knowledge that resource-forming processes have been 

active in at least part of the area; it does not require 

that occurrences or deposits be identified.

Unknown mineral resource potential is assigned 

to areas where the level of knowledge is so inadequate 

that classification of the area as high, moderate, or

low would be misleading. The phrase "no mineral 

resource potential" applies only to a specific resource 

type in a well-defined area. This phrase is not used if 

there is the slightest possibility of resource 

occurrence; it is not appropriate as the summary 

rating for any area.

Expression of the certainty of the mineral 

resource assessment incorporates a consideration of (1) 

the adequacy of the geologic, geochemical, geophysical, and resource data base available at the time of 

the assessment, (2) the adequacy of the occurrence or 

the genetic model used as the basis for a specific 

evaluation, and (3) an evaluation of the likelihood that 

the expected mineral endowment of the area is, or 

could be, economically extractable.

Levels of certainty of assessment are denoted oy 

letters, A-D (fig. 3).

A. The available data are not adequate to 

determine the level of mineral resource potential. 

Level A is used with an assignment of unknown mineral 

resource potential.

B. The available data are adequate to suggest 

the geologic environment and the level: of mineral 

resource potential, but either evidence is insufficient 

to establish precisely the likelihood of resource occurrence, or occurrence and (or) genetic models are not 

known well enough for predictive resource assessment.

C. The available data give a good indication of 

the geologic environment and the level of mineral 

resource potential, but additional evidence is needed 

to establish precisely the likelihood of resource occurrence, the activity of resource-forming processes, or 

available occurrence and (or) genetic models are 

minimal for predictive applications.

D. The available data clearly define the geologic 

environment and the level of mineral resource 

potential, and indicate the activity of resourceforming processes. Key evidence to interpret the 

presence or absence of specified types of resources is 

available, and occurrence and (or) genetic models are 

adequate for predictive resource assessment.

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

Figure 3. Major elements of mineral resource potential/certainty classification.

A14
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

Neogene 

Subperiod

Tertiary 

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Si unan

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

- 24

aa

- 96 

_no

- 410

- 500

_ _, c~7fi1

 Qftrt

- 1600

 ocnfi

- 3000 

- 3400

 AKKfl 

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

'Informal time term without specific rank

A15
GPO 785-048/48028