Mineral Resources of the Morongc

Wilderness Study Area,

San Bernardino County, California

U.S. GEOLOGICAL SURVEY BULLETIN 1710-B

 v^.tirr- -i

Chapter B

Mineral Resources of the 

Morongo Wilderness Study Area, 

San Bernardino County, California

By JONATHAN C. MATTI, SCOTT E. CARSON, JAMES E. KILBURN, 

ANDREW GRISCOM, and DOUGLAS V. PROSE 

U.S. Geological Survey

LUCIA KUIZON 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1710

MINERAL RESOURCES OF WILDERNESS STUDY AREAS:

SOUTH-CENTRAL CALIFORNIA DESERT CONSERVATION AREA, CALIFORNIA
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 Morongo Wilderness Study Area, 

San Bernardino County, California.

U.S. Geological Survey Bulletin 1710-B

Bibliography

Supt. of Docs. No.: I 19.3:1710-6

1. Mines and mineral resources Morongo Wilderness. 2.

Morongo Wilderness (Calif.) I. Matti, Jonathan C. II. Series.

QE75.B9 No. 1710-B 557.3 s

[553'.09794'95]

87-600295
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness 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 part of the 

Morongo Wilderness Study Area (CDCA-218), California Desert Conservation Area, San 

Bernardino County, California.

CONTENTS

Summary Bl

Abstract 1

Character and setting 1

Mineral resources and mineral resource potential 1 

Introduction 2 

Appraisal of identified resources 3

Methods and scope of investigation 3

Mining activity 3

Mineral occurrences 3

Sampling results 4 

Assessment of mineral resource potential 4

Geology 4

Geochemical studies 5

Geophysical studies 6

Mineral resources 6 

References cited 7 

Appendixes

Definitions of levels of mineral resource potential and certainty of assessment 11

Resource/reserve classification 12

Geologic time chart 13

FIGURES

1. Index map showing location of the Morongo Wilderness Study Area, San Bernardino 

County, California B2

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

Wilderness Study Area, San Bernardino County, California 4

MINERAL RESOURCES OF WILDERNESS STUDY AREAS:

SOUTH-CENTRAL CALIFORNIA DESERT CONSERVATION AREA, CALIFORNIA

Mineral Resources of the 

Morongo Wilderness Study Area, 

San Bernardino County, California

By Jonathan C. Matti, Scott E. Carson, James E. Kilburn, 

Andrew Griscom,a/7Gf Douglas V. Prose 

U.S. Geological Survey

Lucia Kuizon

U.S. Bureau of Mines

SUMMARY

Abstract

At the request of the Bureau of Land 

Management, studies were conducted on 6,400 acres of 

the Morongo Wilderness Study Area (CDCA-Z18) in the 

southeastern San Bernardino Mountains of southern 

California. The U.S. Bureau of Mines and the U.S. 

Geological Survey conducted geological, geophysical, 

and geochemical surveys during 1983 and 1984 to 

assess the mineral resources (known) and mineral 

resource potential (undiscovered) of the study area. 

The study area has no identified resources, although a 

small body of marble in the western part of the study 

area is a possible source of lime for cement and 

crushed rock for construction materials. On the basis 

of current information, marble within the study area 

does not constitute an identified resource. In the 

northern and eastern part of the study area, a unit of 

undif ferentiated plutonic rocks has moderate potential 

for silver, lead, tin, and tungsten resources in 

scattered small-scale quartz veins. The remainder of 

the area studied has low potential for silver, lead, tin, 

and tungsten resources. The entire study area has low 

potential for thorium, rare-earth elements, uranium, 

geothermal, oil and gas, sand and gravel, and marble 

resources.

Character and Setting

The part of the Morongo Wilderness Study Area 

studied comprises 6,400 acres about 20 mi north of 

Desert Hot Springs and 30 mi west of Twentynine 

Palms, Calif, (fig. 1). The area is characterized by 

mountainous terrain that is underlain mainly by

crystalline rocks, including undeformed plutonic 

igneous rocks of granitic composition that have 

intruded older igneous rocks. Sedimentary rocks in the 

study area were deformed and metamorphosed into 

granitic gneiss, marble, and /netaquartzite. Stream 

canyons contain thin deposits of sand and gravel. 

There are no active mines, prospects, leases, or mining 

claims in the study area.

Mineral Resources and Mineral Resource Potential

Our investigations of historic mining and 

prospecting activity indicate that no mineral 

production has come from the wilderness study area. 

A small body of marble in the western part of the 

study area is a possible source for building stone and 

crushed and quarried aggregate for construction 

applications; the marble also could be a source of lime 

and magnesium for Portland cement and industrial 

applications, however, the marble does not currently 

constitute an identified resource. Sand and gravel in 

the study area are suitable for construction uses, but 

are of very limited extent. Similar, larger deposits 

outside the study area are closer to markets. There is 

low potential for sand, gravel, and marble resources 

within the study area.

Geologic and geochemical studies indicate that a 

unit of undifferentiated plutonic rocks in the 

northeastern part of the area has moderate potential 

for silver, lead, tin, and tungsten resources (fig. 2). 

Minor geochemical anomalies for these and associated 

metallic elements in hydrothermal-vein settings were 

detected in panned-concentrate samples of alluvium 

from three drainages that dissect the undifferentiated 

plutonic rock unit. Heavy-mineral suites from the 

samples included ore and ore-related minerals similar 

to those reported at the Pierce Ranch prospect, such

B1
MORONGO WILDERNESS 

STUDY AREA (CDCA-218)

^ j> __

 ~~^"

Figure 1. Index map showing location of the Morongo Wilderness Study Area, San Bernardino County, California.

as hematite, limonite, and minor chalcopyrite and 

azurite (Marcus, 1982). The rest of the Morongo 

Wilderness Study Area has low potential for silver, 

lead, tin, and tungsten resources. Geologic, 

geochemical, and geophysical investigations indicate 

that there is low potential for uranium, thorium, rareearth elements, geothermal, and oil and gas resources 

within the study area.

INTRODUCTION

This mineral resource study is a joint effort by 

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

Mines. The history and philosophy of such joint 

mineral surveys of U.S. Bureau of Land Management 

Wilderness Study Areas were discussed by Beikman and 

others (1983). Mineral assessment methodology and 

terminology were discussed by Goudarzi (1984). 

Identified resources are classified according to the 

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

Geological Survey (1980). See appendix for the 

definition of levels of mineral resource potential,

certainty of assessment, and classification of 

identified resources. Studies by the U.S. Geological 

Survey 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. The 

U.S. Bureau of Mines 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.

The part of the Morongo Wilderness Study Area 

(CDCA-218) studied encompasses about 6,400 acres in 

the southeastern part of the San Bernardino Mountains, 

about 20 mi north of Palm Springs and about 30 mi 

west of Twentynine Palms, Calif. The study area 

flanks the north margin of Morongo Valley, an 

alluviated valley situated between the San Bernardino 

and Little San Bernardino Mountains. The study area 

consists of rugged mountainous terrain that supports a 

flora of desert scrub and pinyon-juniper woodland.

B2
Topographic relief ranges from about 3,000 ft to 6,305 

ft. Watercourses form steep-sided canyons, and 

consist of ephemeral streams that drain southeast into 

Morongo Valley; two of these, Big and Little Morongo 

Creeks, occupy major canyons that form the west and 

east boundaries of the study area. The study area is 

accessible by numerous unpaved roads that lead north 

from California Highway 62.

The U.S. Bureau of Mines researched the history 

of prospecting, mineral claims, mining, and production 

within and near the study area, and assessed the 

identified mineral resources where possible. This 

study involved a literature search, field examination of 

workings and mineralized areas, and laboratory 

analysis of samples collected in the field (Kuizon, 

1984). Reports containing information on mining and 

production within and near the area include those by 

DeGroot (1888), Hill (1912), Cloudman and others 

(1919), Wright and others (1953), Oesterling and Spurck 

(1964), Dibblee (1967), and Proctor (1968).

The U.S. Geological Survey assessed the mineral 

resource potential of the study area by integrating and 

interpreting geologic, geochemical, and geophysical 

data from existing sources and from new 

investigations. Field mapping conducted in 1984 

provided most of the geologic information, and 

regional mapping by Dibblee (1967) provided 

supplementary geologic data. A reconnaissance 

stream-sediment sampling survey conducted in 1984 

provided geochemical data (Detra and Kilburn, 1985). 

Existing aeromagnetic data (U.S. Geological Survey, 

1979, 1982) provided a basis for geophysical 

interpretations. Aerial gamma-ray investigations (U.S. 

Department of Energy, 1980) conducted under the 

National Uranium Resource Evaluation (NURE) 

program provided the basis for evaluating the uranium 

resource potential of the area. Our evaluation of 

mineral resources within the study area benefitted 

from resource evaluations of nearby public lands: Cox 

and others (1983); Matti and others (1983); Powell and 

others (1983); and Matti and others (1982).

APPRAISAL OF IDENTIFIED RESOURCES

By Lucia Kuizon 

U.S. Bureau of Mines

Methods and Scope of Investigation

Studies of the U.S. Bureau of Mines of the 

Morongo Wilderness Study Area entailed literature 

searches and review of mining-claim records. Field 

studies were conducted in 1983 and included 

examination of mines, claims, and prospects, and 

mapping and sampling of mineralized properties. Six 

rock samples and three alluvial samples were collected 

in and near the study area and checked for 

fluorescence and radioactivity. The rock samples were 

fire assayed for gold and silver content and analyzed 

by semiquantitative spectrography for 40 elements. 

The three alluvial samples were concentrated and 

checked microscopically for gold and other heavy 

minerals. Complete analytical data are included in 

Kuizon (1984).

Mining Activity

In 1983, there were no mining claims, prospects, 

or any other evidence of mining activity within the 

study area. Eight prospects and one patented group of 

mining claims and millsites are within 3 mi of the 

study area. The Pierce Ranch prospect (fig. 2) is about 

0.5 mi northeast of the study area. A hematite and 

limonite vein containing gold, silver, and copper is 

exposed in a 100-ft adit (Oesterling and Spurck, 1964).

Mining activity near the study area in 1983 

consisted of a sand and gravel operation in Yucca 

Valley 6 mi to the east and quarrying of limestone for 

cement in the Cushenberry quarry 20 mi to the 

northwest. The Morongo mining district lies north of 

the study area and may extend into it (Hill, 1912). 

Other mining districts nearby include the Black Hawk, 

Holcomb, Bear Valley, Ruby, and Twentynine Palms 

(DeGroot, 1888). Prospecting began in the San 

Bernardino Mountains in 1859, and gold placers were 

mined in 1860 in Bear and Holcomb Valleys, 20 mi 

northwest of the study area (Cloudman and others, 

1919).

Mineral Occurrences

A small body of marble in the western part of 

the study area was mapped by the USGS during this 

study (Matti and others, this report, fig. 2). Other 

similar marble deposits in the San Bernardino 

Mountains are sources of (1) lime for cement and 

chemicals, (2) crushed aggregate for roofing granules, 

road bases, and decorative stone, (3) rip rap and 

building stone for construction purposes, and (4) 

calcium and magnesium carbonate for industrial and 

manufacturing applications (Gray, 1982; Joseph, 1982; 

Miller and Morton, 1982; Brown, 1982; and Fife and 

Brown, 1982). The quality and quantity of the 

carbonate rock present in the marble body in the study 

area was not assessed. However, because of the small 

surface outcrop, limited accessibility, and availability 

of large marble bodies elsewhere in the San Bernardino 

Mountains area that are more likely to be developed, 

the marble body is considered an occurrence.

Deposits of sand and gravel in the study area 

may provide possible sources of aggregate for 

construction uses. Larger gravel in creek bottoms may 

be a possible source for rip rap. However, stream 

deposits in the study area are thin and limited in areal 

extent. Larger, more easily accessible deposits are 

present in Morongo and Coachella Valleys (fig. 1), and 

some are being mined. Therefore, stream deposits 

within the study area are considered occurrences, not 

resources.

Granitic rocks in the study area may provide 

possible sources of crushed stone, decomposed 

aggregate, and rip rap. However, granitic rocks of 

equal quality and better accessibility are widespread in 

the San Bernardino Mountains area. Therefore, 

granitic rocks in the study area are occurrences, not 

resources.

B3
116° 37'30

M/C Ag,Pb,Sn, W

Ag, Pb, Sn, W

7 Pierce 

Ranch 

prospect

Sn, W (all units exclusive 

ofMzu)

RE, OG

L/C geo V entire study

L/D mar, SG

APPROXIMATE BOUNDARY OF

MORONGO WILDERNESS 

STUDY AREA (CDCA-218)

Figure 2. Mineral resource potential and generalized geology of the Morongo Wilderness Study Area, San Bemardino County, California.

Sampling Results

One alluvial sample from three placer claims 

immediately west of the study area along Big Morongo 

Creek (fig. 2) contained 2.0 mg/yd (milligrams per 

cubic yard) flour gold. Two other alluvial samples 

taken from intermittent streams within the study area 

contained 2.25 mg/yd 3 and 6.5 mg/yd3 of gold. Six 

rock samples were taken from altered rock outcrops 

within the study area. Two samples of iron-oxidestained granitic rock from the southwestern and 

eastern parts of the study area contained 0.4 and 0.8 

oz/ton silver. No other significant mineral values 

were found in the study area.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By Jonathan C. Matti, Scott E. Carson, James E. 

Kilburn, Andrew Griscom,and Douglas V. Prose 

U.S. Geological Survey

Geology

The Morongo Wilderness Study Area is underlain 

mainly by crystalline rocks that form three distinct 

suites: (1) an older suite of prebatholithic sedimentary 

rocks that were metamorphosed to marble and 

metaquartzite; (2) a suite of granitoid rocks that

B4
EXPLANATION

Area with moderate mineral resource 

potential

Area with low mineral resource potential

See appendix for definition of levels of mineral resource 

potential and certainty of assessment

Commodities

Ag Silver

Pb Lead

Sn Tin

W Tungsten

U Uranium

Th Thorium

RE Rare-earths

OG Oil and gas

SG Sand and gravel

geo Geothermal

mar Marble

Geologic map units

Qa Alluvium (Quaternary)

Qoa Older alluvium (Quaternary)

Mzup Monzogranite and granodiorite of undeformed

plutonic suite (Mesozoic) 

Mzu Undifferentiated unit of deformed and undeformed

plutonic suite (Mesozoic) 

Mzdp Granitic gneiss of deformed plutonic suite

(Mesozoic)

Pzm Marble (Paleozoic) 

Pzpb Prebatholithic metasedimentary rocks (Paleozoic)

- Contact Dashed where approximately located

 Fault Dashed where approximately located; dotted 

where concealed. Arrows show direction of 

relative movement

Landslide deposit Arrows show direction of 

movement

Geochemical sample site

Figure 2. Continued.

intruded the prebatholithic suite and subsequently was 

deformed into well-foliated and layered granitic 

gneiss; and (3) a suite of undeformed plutonic rocks of 

granitic composition that intruded the two older suites 

in late Mesozoic time (see appendix for geologic time 

chart). These rocks are dissected by stream canyons 

that contain alluvial sand and gravel. The study area 

is cut by several northwest-trending, high-angle faults. 

The Pinto Mountain fault, a major left-lateral strikeslip fault that had more than 9 mi of displacement 

during late Cenozoic time (Dibblee, 1968), is present 

just south of the study area.

The prebatholithic rocks in the western part of 

the study area consist of a small body of marble and 

associated layers of metaquartzite. These rocks 

represent ancient accumulations of calcareous 

sediment and quartz-rich sand that originally were 

deposited in the sea, probably during late Precambrian 

or early Paleozoic time. During Mesozoic time the 

lithified sediments were intruded by large granitic 

magma bodies that metamorphosed the sedimentary 

rock to metaquartzite and marble. Within the study 

area, the granitic intrusions engulfed and assimilated 

most of the sedimentary rocks; however, a few miles 

to the west, the sedimentary rocks escaped total 

assimilation and formed extensive outcrops of 

metaquartzite and subordinate marble (Dibblee, 

1967). Prebatholithic metasedimentary rocks in the 

study area represent discontinuous extensions of the 

adjacent metasedimentary belt.

The deformed plutonic suite (terminology of 

Matti and others, 1982) in the study area is an 

assemblage of granitic gneiss and foliated granitoid 

rock. It consists of light- to dark-colored granitic 

gneiss that is well foliated or that has compositionally 

layered fabrics in which the layering is well defined to 

streaky and diffuse. The gneiss is predominantly 

granodioritic in composition, but includes rock that is 

tonalitic. Textural features indicate a plutonic origin 

for the gneisses, although their original plutonic aspect 

has been obscured by subsequent deformation that 

created the foliated and layered fabrics. Dibblee 

(1967) concluded that the granitic gneiss in the study 

area and vicinity is older than the prebatholithic 

metasedimentary rocks, and he tentatively inferred a 

Precambrian age for the gneiss. We conclude that the 

granitic gneiss intruded the metasedimentary rocks 

and is early Mesozoic(?) in age (Matti and others, 

1982).

Texturally massive to slightly foliated late 

Mesozoic plutonic rocks comprise the undeformed 

plutonic suite (terminology of Matti and others, 1982) 

in the study area. This suite consists of light-colored, 

biotite-bearing monzogranite and granodiorite that 

locally contain muscovite and garnet. All units of the 

undeformed plutonic suite intrude granitic gneiss of 

the deformed plutonic suite. In the eastern part of the 

study area, the two suites are mixed together so 

intimately that we mapped them together as 

undifferentiated plutonic rocks. Quartz veins and 

siliceous dikes cut these granitic rocks.

Two types of alluvial sand and gravel are present 

in the study area: relatively undissected alluvium that 

accumulated during late Quaternary time and older 

dissected alluvium that accumulated in earlier 

Quaternary time. Both of these types were deposited 

by streams and floods.

Geochemical Studies

A reconnaissance geochemical survey of alluvial 

sediment in the Morongo Wilderness Study Area was 

conducted for 30 elements. Detra and Kilburn (1985) 

describe sample collection and processing procedures. 

Nonmagnetic heavy- mineral panned concentrates 

from the sediments were analyzed by a six-step

B5
semiquantitative emission-spectrographic method 

described by Grimes and Marranzino (1968).

Three panned-concentrate samples from the 

northeastern part of the study area contain metallic 

sulfides that indicate a metallic-element suite that 

includes silver, lead, tin, bismuth, and tungsten. 

Several concentrates from the southwestern part of 

the study area contain barite and scheelite and have 

anomalous concentrations of barium and tungsten, and 

one sample contained pyrite. These occurrences 

probably are similar to a mineralized quartz vein at 

the Pierce Ranch prospect (fig. 2) described by 

Oesterling and Spurck (1964), who reported assay 

values of 5.4 oz silver, 0.08 oz gold, 1.3 percent 

copper, and the ore-related minerals hematite, 

limonite, and minor chalcopyrite and azurite (cited in 

Marcus, 1982).

The silver-lead-bismuth association is typical of 

hydrothermal veins, and tungsten can be present in 

veins even though it typically is a skarn mineral. 

Except for tungsten, the metallic association may 

result partly from contamination by lead shot. 

Analysis of shot removed from one of the concentrates 

revealed an elemental suite (silver, bismuth, cadmium, 

copper, lead, and antimony) that is also commonly 

associated with hydrothermal mineralization (Detra 

and Kilburn, 1985).

Barium and tungsten from several samples in the 

southwestern part of the study area may have two 

possible sources: (1) scheelite in skarns associated 

with the small body of marble and stringers of 

metaquartzite that are intruded by granitic gneiss of 

the deformed plutonic suite; and (2) scheelite-bearing 

quartz-barite hydrothermal veins within the deformed 

plutonic suite.

Anomalous concentrations of titanium and 

zirconium are present in virtually all of the sediment 

samples. We attribute these to abundant sphene, 

rutile, and zircon present in all of the samples; these 

minerals are common accessory minerals in granitic 

rocks. Similarly, locally elevated values for lanthanum 

probably represent lanthanum substituting for calcium 

in sphene. Reconnaissance geochemical studies 

conducted in the Morongo and adjacent Bighorn 

Mountains Wilderness Study Areas (Matti and others, 

1982) suggest that the eastern San Bernardino 

Mountains may have high background levels for 

titanium, zirconium, and rare-earth elements and 

transition metals.

Geophysical Studies

The Morongo Wilderness Study Area is covered 

by two aeromagnetic maps (U.S. Geological Survey, 

1979, 1982). The aeromagnetic data were collected 

along parallel north-trending flightlines spaced 0.5 mi 

apart with a nominal altitude of 1,000 ft above ground.

In general, variations in the Earth's magnetic 

field as depicted on a residual map are caused by 

variations in the amounts of magnetic minerals of 

different rock units, magnetite being the common 

magnetic mineral in this area. Magnetic minerals, 

where locally either concentrated or absent, may 

cause magnetic anomalies that can be guides to 

mineral occurrences or deposits.

The granitic gneiss in the southwestern part of 

the study area is relatively magnetic; the local 

topographic highs there produce magnetic anomalies as 

high as 400 gammas in amplitude. Granitic rocks in 

the northern part of the study area are only weakly 

magnetic; the topographic highs produce a few 

magnetic highs with values of less than about 50 

gammas. A steep magnetic gradient sloping down to 

the northeast and trending northwest across the center 

of the study area (U.S. Geological Survey, 1979) is the 

magnetic expression of a boundary between magnetic 

gneiss to the southwest and weakly magnetic granitic 

rocks to the northeast.

Geophysical investigations 15 mi to the north in 

the Bighorn Mountains Wilderness Study Area (Matti 

and others, 1982) indicate that some magnetic highs 

are associated with mineralized zones and that 

magnetic lows are associated with metallic prospects 

and altered zones where hydrothermal rock alteration 

has apparently destroyed the magnetite. No magnetic 

lows of this sort are identified in the Morongo 

Wilderness Study Area. The major isolated magnetic 

high in the northeastern part of the study area is most 

likely caused by granitic gneiss in the undifferentiated 

plutonic rocks unit, although occurrences of 

hornblende diorite mapped by Dibblee (1967) in this 

vicinity also could account for this isolated high.

Gravity data for the study area (Oliver and 

others, 1980; Roberts and others, 1981) are too sparse 

to permit making any local interpretations. An 

airborne gamma-ray spectrometer survey is available 

for the San Bernardino Mountains (U.S. Department of 

Energy, 1980) and includes one helicopter traverse at a 

flight altitude of 400 ft eastward across the study area 

at approximately lat 34°06f N. No uranium or thorium 

anomalies, which may indicate possible uranium 

resources, were recognized within the study area in 

the results of the aeroradiometric survey.

Mineral Resources

Geochemical anomalies for silver, lead, tin, and 

tungsten were detected in three alluvial samples from 

separate tributaries of Little Morongo Creek, in the 

northeastern part of the study area. The origin of the 

metallic anomalies is unknown, and they in part may 

reflect contamination by lead shot, which yields a 

similar geochemical signature. However, three factors 

suggest a high likelihood that mineralization has 

occurred: (1) mineralized quartz veins containing gold, 

silver, and copper are present in the same geologic 

setting just outside the study area at the Pierce Ranch 

prospect, (2) galena, cerussite, and pyrite are present 

in one of the samples and scheelite is in all three, and 

(3) a bedrock sample collected from the 

undifferentiated plutonic rock unit that is drained by 

the three tributaries contained silver. Thus, we have 

assigned moderate mineral resource potential, 

certainty level C, for silver, lead, tin, and tungsten in 

the undifferentiated plutonic rocks unit. However, 

there is no indication that undiscovered occurrences 

are larger in scale than those at the Pierce Ranch 

prospect, a deposit that has no known reserves, no 

production, and resources that presumably are 

subeconomic (resource terminology from U.S. Bureau 

of Mines and U.S. Geological Survey, 1980).

B6
Elsewhere in the study area, generalized geologic 

environments exist that may include potential sites for 

localized deposits of silver and associated preciousand base-metals. Thus, we assign low potential, 

certainty level C, for silver, lead, tin, and tungsten 

resources in the part of the study area not underlain by 

the unit of undifferentiated plutonic rocks.

Geophysical and geochemical studies indicate 

that the wilderness study area has low potential, 

certainty level D, for uranium, thorium, and rare-earth 

element resources. An airborne gamma-ray 

spectrometer study of the region (U.S. Department of 

Energy, 1980) showed that uranium and thorium levels 

in the wilderness study area are low by comparison 

with locally elevated gamma-ray signals for these 

elements elsewhere in the eastern San Bernardino 

Mountains. Our geochemical survey showed that 

values for thorium and for rare-earth element and 

transition metals like lanthanum, yttrium, and niobium 

are within background levels for the study area.

Although the study area is adjacent to a region 

of known geothermal resources near Desert Hot 

Springs, no hot springs or hot-water wells were 

identified. Thus, the study area has low potential for 

geothermal resources, with a certainty level of C.

The Morongo Wilderness Study Area has low 

potential for oil and gas resources, with a certainty of 

D. Scott (1983) states that the region including this 

area is not likely to have any potential for oil and 

gas7 However, no known exploration has been 

conducted in or near the Morongo Wilderness Study 

Area, and there is a slight possibility that faulting 

adjacent to the study area could have produced 

pockets that contain oil or gas. There are no known 

source rocks in or near the study area.

A small body of marble in the western part of 

the study area and accumulations of sand and gravel 

that are present in narrow stream valleys that drain 

the study area could be used for industrial purposes. 

The resource content of the marble occurrence was 

not identified. Additional marble occurrences are not 

likely in the study area; our mapping has shown the 

predominant rock type to consist mainly of granite and 

gneiss. Therefore, the potential for marble resources 

is low, with a certainty level of D. No other 

occurrences of sand and gravel are present in the study 

area beyond those indicated in figure 2. Within the 

study area, the potential for sand and gravel resources 

is low, with a certainty level of D.

REFERENCES CITED

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

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

the Geological Survey and the Bureau of Mines of 

Bureau of Land Management Wilderness Study 

Areas: U.S. Geological Survey Circular 901, Z8 p. 

Brown, A.R., 198Z, Economic geology of the Smart 

Ranch limestone deposit, San Bernardino 

Mountains, California, in_ Fife, D.L, and Minch, 

J.A., eds., Geology and mineral wealth of the 

California Transverse Ranges (Mason Hill 

volume): Santa Ana, Calif., South Coast 

Geological Society, Guidebook no. 10, p. 539-549.

Cloudman, H.C., Huguenin, Emile, and Merrill, F.J.H., 

1919, San Bernardino County, California: 15th 

Report of the State Mineralogist, p. 775-899.

Cox, B.F., Matti, J.C., Oliver, H.L., and Zilka, N.T., 

1983, Mineral resource potential map of the San 

Gorgonio Wilderness, San Bernardino County, 

California: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1161-C, scale 1:62,500.

DeGroot, Henry, 1888, San Bernardino County, 

California: 7th Report of the State Mineralogist, 

p. 518-539.

Detra, D.E., and Kilburn, J.E., 1985, Analytical results 

and sample locality map of heavy-mineralconcentrate samples from the Morongo Valley 

(CDCA-218) and Mecca Hills (CDCA-343) 

Wilderness Study Areas, San Bernardino and 

Riverside Counties, California: U.S. Geological 

Survey Open-File Report 85-244.

Dibblee, T.W.,"Jr., 1967, Geologic map of the Morongo 

Valley quadrangle, San Bernardino and Riverside 

Counties, California: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map 1-517, 

scale 1:62,500.

 1968, Evidence of major lateral displacement in the 

Pinto Mountain fault, southern California: 

Geological Society of America Special Paper 115, 

p. 322.

Fife, D.L., and Brown, A.R., 1982, White Mountain 

carbonate resources, Lucerne Valley limestone 

district, San Bernardino Mountains, California, in 

Fife, D.L, and Minch, J.A., eds., Geology and 

mineral wealth of the California Transverse 

Ranges (Mason Hill volume): Santa Ana, Calif., 

South Coast Geological Society, Guidebook no. 10, 

p. 550-560.

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.

Gray, C.H., Jr., 1982, Limestone and dolomite 

resources of the Transverse Ranges, southern 

California, in Fife, D.L, and Minch, J.A., eds., 

Geology and mineral wealth of the California 

Transverse Ranges (Mason Hill volume): Santa 

Ana, Calif., South Coast Geological Society, 

Guidebook no. 10, p. 213-218.

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.

Hill, J.M., 1912, The mining districts of the western 

United States: U.S. Geological Survey Bulletin 

507, 309 p.

Joseph, S.E., 1982, Mineral land classification of the 

Pleuss-Stauffer, Inc., limestone deposit, Lucerne 

Valley, San Bernardino County, California, in Fife, 

D.L, and Minch, J.A., eds., Geology and mineral 

wealth of the California Transverse Ranges 

(Mason Hill volume): Santa Ana, Calif., South 

Coast Geological Society, Guidebook no. 10, p. 

526-531.

Kuizon, Lucia, 1984, Mineral resources of the Morongo 

Wilderness Study Area (BLM No. CDCA-218), San 

Bernardino County, California: U.S. Bureau of 

Mines Open File Report MLA 29-84, 10 p.

B7
Marcus, S.M., 1982, Preliminary mineral resources 

evaluation of the geology-energy-mineral resource 

area of the Morongo Valley, eastern Transverse 

Ranges, California, in Fife, D.L, and Minch, J.A., 

eds., Geology and mineral wealth of the California 

Transverse Ranges (Mason Hill volume): Santa 

Ana, Calif., South Coast Geological Society, 

Guidebook no. 10, p. 589-602.

Matti, J.C., Cox, B.F., Rodriguez, E.A., Obi, C.M., 

Powell, R.E., Hinkle, M.E., Griscom, Andrew, 

Sabine, Charles, and Cwick, G.J., 1982, Mineral 

resource potential of the Bighorn Mountains 

Wilderness Study Area (CDCA-217), San 

Bernardino County, California: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1493- 

A, scale 1:24,000.

Matti, J.C., Cox, B.F., and Iverson, S.R., 1983, Mineral 

resource potential map of the Raywood Flat 

Roadless Areas, San Bernardino and Riverside 

Counties, California: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1563-A, scale 

1:62,500.

Miller, R.V., and Morton, P.K., 1982, Mineral land 

classification of Pfizer, Inc., limestone deposits in 

Lucerne Valley area, San Bernardino County, 

California, in Fife, D.L, and Minch, J.A., eds., 

Geology and mineral wealth of the California 

Transverse Ranges (Mason Hill volume): Santa 

Ana, Calif., South Coast Geological Society, 

Guidebook no. 10, p. 532-538.

Oesterling, W.A., and Spurck, W.H., 1964, Eastern 

Mojave and Colorado Deserts, in Southern 

California, v. 3 o_f_ Minerals for industry; summary 

of geological survey of 1955-1961: San Francisco, 

Calif., Southern Pacific Co., p. 99-198.

Oliver, H.W., Chapman, R.H., Biehler, S., Robbins, 

S.L., Hanna, W.F., Griscom, A., Beyer, L.A., and 

Silver, E.A., 1980, Gravity map of California and 

its continental margin: California Division of 

Mines and Geology, scale 1:750,000, 2 sheets.

Powell, R.E., Matti, J.C., Cox, B.F., Oliver, H.W., 

Wagini, Alexander, and Campbell, H.W., 1983, 

Mineral resource potential of the Sugarloaf 

Roadless Area, San Bernardino County, 

California: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1606-A, scale 1:24,000.

Proctor, R.J., 1968, Geology of the Desert Hot 

Springs-upper Coachella Valley area, California: 

California Division of Mines and Geology Special 

Report 94, 50 p.

Roberts, C.W., Jachens, R.C., and Oliver, H.W., 1981, 

Preliminary isostatic residual gravity map of 

California: U.S. Geological Survey Open-File 

Report 81-573, scale 1:750,000, 5 sheets.

Scott, E.W., 1983, Petroleum potential of wilderness 

lands, California: U.S. Geological Survey 

Miscellaneous Investigations Series Map 1-1538, 

scale 1:100,000, 1 sheet plus 12 p. pamphlet.

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

PU.S. Department of Energy, 1980, Airborne gammaray-spectrometer and magnetometer survey, Los 

Angeles, San Bernardino, Santa Ana, and San 

Diego quadrangles, California: Department of 

Energy, Grand Junction, Colo., Open-File Report 

GJBX-214, 5 volumes, 640 p.

U.S. Geological Survey, 1979, Aeromagnetic map of 

the southern San Bernardino Mountains area, 

California: Open-File Report 79-1448, scale 

1:62,500.

 1982, Aeromagnetic map of the Bighorn Mountains 

area, California: Open-File Report 82,664, scale 

1:62,500.

Wright, L.A., Stewart, R.M., Gay, T.E., Jr., and 

Hazenbush, G.C., 1953, Mines and mineral 

deposits of San Bernardino County, California: 

California Journal of Mines and Geology, v. 49, 

no. 1-2, p. 9-249.

B8
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

I

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-^2. 

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.

B11
RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

Inferred Probability Range

Hypothetical Speculative

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

Reserves

I

Inferred 

Reserves

Marginal 

Reserves

I

Inferred 

Marginal 

Reserves

I

Demonstrated

Subeconomic

Resources

i

Inferred

Subeconomic

Resources

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.

B12
GEOLOGIC TIME CHART 

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

EON

Phanerozoic

Proterozoic

Archean

pre -Arc

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

u 

- 24

«3o

«JvJ

 KK

- 96

1 oo 

one

t*TV/

£.*y\j 

o^/\

 iftn

- 410

~o*j

CfWl

U / \J

- 900

- 1600

£. *J\J\J

- 3000

r vj*rww

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

2 lnformal time term without specific rank.

B13
GPO 785-048/77407