Mineral Resources of the La Madre 

Mountains Wilderness Study Area, 

Clark County, Nevada

U.S. GEOLOGICAL SURVEY BULLETIN 1730-A

Chapter A

Mineral Resources of the La Madre 

Mountains Wilderness Study Area, 

Clark County, Nevada

By JAMES E. CONRAD and HARLAN N. BARTON 

U.S. Geological Survey

DAVID A. LIPTON 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1730-A

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHERN NEVADA
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1986

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

Conrad, James E.

Mineral resources of the La Madre Mountains Wilderness

Study Area, Clark County, Nevada.

U.S. Geological Survey Bulletin 1730-A

Bibliography: p. 9

Supt. of Docs. No.: I 19.3:1730-A

1. Mines and mineral resources Nevada La Madre

Mountains Wilderness. 2. Geology Nevada La Madre

Mountains Wilderness. 3. La Madre Mountains Wilderness

(Nev.) I. Barton, Harlan N. II. Lipton, David A. (David

Abraham), 1954- . III. Title. IV. Series.

QE75.B9 No. 1730-A 557.3 s 86-600162

[TN424.N3] [553'.0979'13]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Area

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

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct 

mineral surveys 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 the La Madre 

Mountains Wilderness Study Area (NV-050-412). Clark County, Nevada.

CONTENTS

Summary Al

Abstract 1

Character and setting 1

Mineral resource potential 1 

Introduction 3

Appraisal of identified resources 3 

Assessment of mineral resource potential 6

Geology 6

Geochemical studies 6 

Conclusions 6 

References cited 7 

Appendix 1. Definitions of levels of mineral resource potential and certainty of assessment 8

FIGURES

1. Index map showing location of the La Madre Mountains Wilderness Study Area, Clark County, Nevada A2

2. Map showing mineral resource potential of the La Madre Mountains Wilderness Study Area, Clark County, 

Nevada 4

3. Major elements of mineral resource potential/certainty classification 8

TABLE

1. Mines and prospects in and adjacent to the La Madre Mountains Wilderness Study Area A9

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHERN NEVADA

Mineral Resources of the La Madre Mountains 

Wilderness Study Area, Clark County, Nevada

By James E. Conrad and Harlan N. Barton 

U.S. Geological Survey

David A. Lipton

U.S. Bureau of Mines

SUMMARY

Abstract

The La Madre Mountains Wilderness Study Area 

(NV-050-41Z) encompasses 34,010 acres on the east 

side of the Spring Mountains, Clark County, Nev. 

Fieldwork for this report was carried out in 1984. No 

mineral or energy resources were identified within the 

study area. Two prospects were located and examined 

within the study area; these have traces of copper, and 

sporadic, high grade blebs containing silver, lead, and 

zinc. These prospects and the surrounding area have 

low mineral resource potential for silver, lead, and 

zinc.

Character and setting

The La Madre Mountains Wilderness Study Area 

is located in the eastern part of the Spring Mountains 

12 mi west of Las Vegas, Nev. (fig. 1). The terrain is 

rugged, with relief as much as 3,500 ft. Spectacular 

cliffs and steep canyons are present along the southern 

and eastern parts of the study area; these give way to 

less rugged terrain in the higher, northwest part of the 

study area. The area is underlain by a sequence of 

marine limestones and dolomites of Cambrian to 

Permian age (570-240 million years before present), 

and mostly subaerial sandstone and siltstone deposits 

of Triassic and Jurassic age (240-138 million years 

before present). Northwest-trending high-angle faults, 

large-scale thrust faults, and associated folds have 

greatly disrupted these strata, placing Cambrian (570- 

500 million years before present) dolomite on top of 

Jurassic (205-138 million years before present) 

sandstone in some places.

Mining activity in the Spring Mountains began in 

1857 with the discovery of lead ore in the Goodsprings 

district, about 12 mi south of the wilderness study area

(Longwell and others, 1965). Peak production in this 

area occurred during World War I, but by 1964 these 

mines were mostly dormant. Small quantities of lead 

and zinc ore were mined from the Charleston district, 

about 10 mi north of the study area, but there has been 

no production since 1956. The major mineral resource 

presently mined in the Spring Mountains is gypsum 

from the Blue Diamond mine, located about 7 mi 

southeast of the wilderness study area. Ten mining 

claims have been located within the study area, but in 

1984 there were no active claims.

Mineral Resource Potential

The Spring Mountains lie within a province 

characterized by hydrothermal deposits of silver, lead, 

and zinc. In this region, these base and precious 

metals occur in veins or bedded replacement bodies in 

carbonate rocks, and are generally associated with 

thrust faults and high-angle, northwest-trending, 

normal faults that served as pathways for metalbearing solutions.

Two prospects were identified and examined 

within the wilderness study area: the Emerald and the 

Mountain View prospects (fig. 2, nos. 4 and 5). These 

are located in Red Rock Canyon near the Keystone 

thrust and the La Madre (high-angle) fault. Samples 

from these prospects contain small amounts of copper 

and sporadic, high-grade blebs of silver, lead, and 

zinc. Geochemical sampling of stream sediments in 

this area delineates a zone of slight silver, lead, and 

zinc anomalies. The prospects and adjacent areas 

along the Keystone thrust are judged to have low 

mineral resource potential for silver, lead, and zinc 

(fig. 2).

The White Beauty mine, located about 1 mi north 

of the wilderness study area, contains gypsum 

interbeaded with limestone of the Pennsylvanian and 

Permian (330-240 million years before present) Bird

Al
1 16°00'

36°30'

36°00'

35°45'

1150 30' 115°00'

LA MADRE 

MOUNTAINS 

WILDERNESS 

STUDY AREA 

(NV-050-412)

1 CALIF\ J

"^ '

AREA OF MAP

figure I. Index map showing location of the La Madre Mountains Wilderness Study Area, Clark County, Nevada.

A2
Spring Formation. The gypsum pinches out before it 

reaches the study area, and there are no known 

deposits within the study area.

The wilderness study area has a low potential for 

petroleum resources (Sandberg. 1983).

INTRODUCTION

The La IVladre Mountains Wilderness Study Area 

(NV-050-412) comprises 34,010 acres in the Spring 

Mountains of southwestern Nevada, approximately 12 

mi west of Las Vegas (fig. 1). The terrain is rugged 

with elevations ranging from about 4,600 ft in 

Brownstone Basin to 8,154 ft at La IViadre Mountain. 

The climate is arid to serniarid and vegetation is 

sparse, with yucca, agave, sage, desert willow, prickly 

pear, barrel cactus, cholla, and hedgehog cactus at 

lower elevations, and pinon pine, juniper, and scrub oak 

above about 5,500 ft. There are several intermittent 

springs in the area, but no permanent streams.

All parts of the wilderness study area are easily 

accessible. Numerous graded dirt roads branching off 

of State Route 157 provide access along the north edge 

of the study area. Along the southeast part of the 

study area, numerous dirt roads and jeep trails lead 

from State Koute 159 to Red Rock Canyon, Calico 

Basin, and Brownstone Basin. The Red Rock Canyon 

jeep trail, which separates the La Madre Mountains 

Wilderness Study Area from the Pine Creek Wilderness 

Study Area to the south, is passable by four-wheel 

drive vehicles, although it is subject to periodic 

washout. Access to the west part of the study area is 

from the Lovell Canyon Road, which branches off 

State Route 160.

The La Madre Mountains Wilderness Study Area 

and adjacent areas in the Spring Mountains have been 

studied by many workers. Early work by Spurr (1903), 

Longwell (1926), Clock (1929), and Hewett (1931) 

formed the basis for modern understanding of the 

geology of the region, including studies by Davis 

(1973), dans (1974). Burchfiel and others (1974), and 

Axen (1984). Information on mineral deposits in Clark 

County is in Longwell and others (1965). A mineral 

resource potential report on the Pine Creek Wilderness 

Study Area, which adjoins the La Madre Mountains 

Wilderness Study Area to the south, was written by 

Bohannon and Morris (1983).

The U.S. Geological Survey carried out field 

investigations in the wilderness study area in 1984. 

The work included field checking of existing maps, new 

mapping where necessary, and geochernical sampling. 

Heavy-mineral concentrates from stream sediments 

and selected rock samples were collected; the 

analytical data are given in Day and Barton (1986).

The U.S. Bureau of Mines conducted a library 

search for information on mines and prospects within 

the wilderness study area. This data was supplemented 

by information from claim owners and Clark County 

and U.S. Bureau of Land Management claim records. 

Field studies by U.S. Bureau of Mines personnel were 

conducted in 1984. Twenty-one samples were 

collected from mines, prospects, and mineralized areas 

to help appraise the mineral resources of the 

wilderness study area (Lipton, 1985). Samples were 

analyzed by fire-assay, atomic-absorption, and

inductively coupled argon-plasma spectrophotometric 

methods. Complete analytical data are on file at the 

U.S. Bureau of Mines, Western Field Operations 

Center, E. 360 3rd Avenue, Spokane, Wash., 99202.

APPRAISAL OF IDENTIFIED RESOURCES

By David A. Lipton, U.S. Bureau of Mines

There were no active mines or prospects within 

the wilderness study area in 1984. The nearest active 

mine, the Blue Diamond mine 7 mi to the southeast, 

produces gypsum from several open pits. Several sand 

and gravel operations also were producing from pits 

located 4 mi east of the study area.

An examination of Clark County records 

indicates that 10 claims have been located within the 

wilderness study area. In April 1984, there were no 

active claims. The White Beauty patented claim lies 

about 1 mi north of the study area. Current oil and 

gas leases cover the entire study area.

There has been no recorded mineral production 

from within the wilderness study area; however, the 

White Beauty mine (fig. 2, no. 1) produced gypsum 

from 1972 to 1975 (Boyd, unpub. report, 1983).

Exposures of Triassic(?) and Jurassic Aztec 

Sandstone 0.25 mi south of the wilderness study area 

were quarried for building stone during the early 

1900's. Another attempt at commercial building-stone 

production was made in the early 196O's, but was 

discontinued after a few months (Fisher, unpub. report, 

1967).

In the late 1920's, mines in the Charleston 

district a few miles northwest of the wilderness study 

area produced $5,000 worth of oxidized lead-zinc ore 

from replacement deposits in dolornitized limestones 

(Longwell and others, 1965). Eleven oz of silver and 

18,300 Ibs of lead valued at $2,574 were produced in 

1953 and 1954 (Longwell and others, 1965). No mining 

activity has been reported since 1956.

The Goodsprings (Potosi) district, 12 mi south of 

the wilderness study area, was one of the first leadzinc districts to be developed in Nevada (about 1857). 

The Potosi mine, regarded as the oldest in the district, 

produced over 44,000,000 Ibs of zinc and just under 

3,000,000 Ibs of lead from 72,500 tons of ore from 

replacement deposits in limestone and dolomite 

between 1905 and 1927 (Butner, 1942).

Sites examined for this study are shown on figure 

2 and listed in table 1 (Lipton. 1985). Only two 

properties, the Emerald and Mountain View prospects 

(fig. 2, nos. 4 and 5), were found inside the wilderness 

study area, the 10 claims filed in the study area being 

either multiple claims on these two properties, or were 

not developed. Three other claims outside the study 

area were examined to determine their characteristics 

and the possibility of extension into the study area.

The Emerald and Mountain View prospects 

contain blebs and zones with anomalously high silver, 

lead, and zinc contents (table 1). They are situated in 

an area of abundant north-striking faults northwest of 

the Keystone thrust. These prospects contain no 

identified resources.

The gypsum deposit at the White Beauty mine

A3
115°35' 1 1 5°30 115°25'

36°15'

36° 10'

APPROXIMATE BOUNDARY OF 

LA MADRE MOUNTAINS 

WILDERNESS STUDY AREA 

(NV-050-412)

0 1 2 3 MILES 

I______I_____I______I

Figure 2. Map showing mineral resource potential of the La Madre Mountains Wilderness 

Study Area, Clark County, Nevada.

A4
EXPLANATION

Area with low resource potential; see Appendix 1 for explanation 

of resource potential and certainty levels

X Mine with identified resources; number refers to Table 1

o

X Prospect; number refers to Table 1

COMMODITIES

Ag silver

Pb lead

Zn zinc

MINES AND PROSPECTS

1. White Beauty mine

2. Karen Placer prospect

3. Iron Age prospect

4. Emerald prospect

5. Mountain View prospect

CORRELATION OF MAP UNITS

J- CENOZOIC

Jurassic to

Permian 

Permian to 

Cambrian

- MESOZOIC

- PALEOZOIC

GEOLOGIC MAP UNITS

Qa Alluvium (Quaternary)

JPs Sandstone, siltstone, and minor limestone (Jurassic to Permian)

P I Limestone, dolomite, and cherty dolomite (Permian to Cambrian)

MAP SYMBOLS

 CONTACT

 FAULT-Dotted where concealed

 * KEYSTONE THRUST FAULT-Sawteeth on upper plate; 

dotted where concealed

 RED SPRING THRUST FAULT-Boxes on upper plate; 

dotted where concealed

Figure 2. Continued.

A5
(fig. 2, no. 1) pinches out before it reaches the 

wilderness study area boundary. The larger and more 

accessible gypsum deposit at the active Blue Diamond 

mine nearby serves existing markets.

Sand and gravel and limestone suitable for 

construction materials are abundant in the wilderness 

study area, but. because similar materials are 

available closer to major markets, occurrences in the 

study area are not classified as resources.

Folds in the area are either small, 

intraformational folds of various orientations or largeamplitude, long-wavelength structures that trend 

northeast and are probably associated with the thrust 

faults (Burchfiel and others, 1974). high-angle faults 

trend north to northwest in the wilderness study area. 

Right-lateral movement on the Las Vegas shear zone 

in Las Vegas Valley has rotated the eastern part of the 

study area clockwise.

ASSESSMENT OF MINERAL RESOURCE POTENTIAL

By James E. Conrad and Harlan N. Barton. U.S. 

Geological Survey

Geology

The La Madre Mountains Wilderness Study Area 

is underlain by a sequence of Paleozoic marine 

sedimentary rocks and Mesozoic marine and 

continental deposits about 10,700 ft thick. Structure 

in the region is dominated by large, east-directed 

thrust faults and related folds of Mesozoic age. The 

study area lies in the northeast part of the Spring 

Mountains, a coherent block that has been relatively 

undisturbed by basin and range faulting.

The wilderness study area is on the eastern edge 

of a westward-thickening sequence of rniogeosynclinal 

strata that can be considered to be transitional 

between more rniogeosynclinal rocks to the west and 

cratonal rocks to the east (Axen. 1980). Rocks older 

than Devonian are primarily dolomite, whereas postDevonian rocks are mainly limestone. Terrigenous 

sediments are minor in rocks older than the 

Carboniferous, but they increase up section to form a 

major part of the Pennsylvanian and Permian strata. 

This includes the Pennsylvanian and Permian Bird 

Spring Formation, a thick sequence of limestone and 

siltstone that underlies most of the northwest part of 

the study area.

In early Mesozoic time, a transition from marine 

deposition to continental deposition occurred. About 

4,200 ft of mostly terrigenous clastic and aeolian rocks 

of Middle Triassic and younger age include the 

massive, crossbedded, Aztec Sandstone. Deposition of 

these rocks terminated with large-scale thrust faulting 

and associated deformation after Early Jurassic time.

The wilderness study area is located on the 

eastern edge of a major Mesozoic thrust belt that can 

be traced from southern Nevada to Canada. Seven 

major thrust faults are found in the Spring Mountains, 

and two of these, the Keystone and Red Spring thrusts, 

are exposed in the study area. The Red Spring thrust 

is the older and structurally lower of the two and 

places the Middle and Upper Cambrian Bonanza King 

Formation on the Aztec Sandstone. This fault is 

dramatically exposed at the top of the sandstone cliffs 

just south of the study area. The Keystone thrust has 

less stratigraphic displacement, placing the Bonanza 

King Formation above rocks of Late Cambrian to 

Mississippian age. The combined minimum horizontal 

displacement on these faults is about 19 rni (Axen, 

1984).

Geochemical Studies

For the geochemical survey, heavy-mineral 

concentrates taken from stream sediments were 

augmented by selected rock samples. Details on 

sample preparation and analysis, along with the 

presentation of data and sample sites, are found in Day 

and Barton (1986). Heavy-mineral concentrates and 

rock samples were analyzed for 31 elements by the 

semiquantitative emission-spectrographic method of 

Grimes and Marranzino (1968). Rock samples were 

also analyzed for antimony, arsenic, bismuth, 

cadmium, and zinc by atomic-absorption spectroscopy 

(Ward and others. 1969). Heavy-mineral concentrate 

samples were collected from 58 streambed sites within 

or peripheral to the wilderness study area, giving a 

sampling density of approximately one sample/mi .

The most anomalous of the sites sampled are 

outside the wilderness study area in the vicinity of the 

Iron Age prospect (fig. 2., no. 3). reported to contain 

small quantities of lead and zinc ore in dolomitized 

limestone (Longwell and others, 1965). A heavymineral concentrate sample from near the prospect 

contains the following element concentrations in parts 

per million (pprn): antimony 2.000, bismuth 100. 

copper 700, lead 50,000, silver 5, and tin 100. A 

nearby rock sample contained the following 

concentrations in ppm: arsenic 290. bismuth 4. 

cadmium 6.7, copper 1,000. lead 200. molybdenum 70, 

silver 10. tin 15, and zinc 6.

Only very minor anomalous concentrations of 

certain elements are found within the wilderness study 

area. Four of these are from sites located along the 

southeast boundary of the study area. Of these four 

samples, two contain 2,000 ppm lead without 

anomalies in any other elements, one contains 1,000 

pprn lead with 1.000 ppm zinc, and one 300 ppm lead 

with 3 pprn silver.

Five heavy-mineral concentrate samples from 

widely scattered sites in Paleozoic carbonate rocks in 

the western half of the wilderness study area contain 

500 to 700 pprn zinc. No other anomalies are 

associated with these low zinc anomalies.

CONCLUSIONS

Geologic studies, geochemical sampling, 

examination of mines and prospects, and review of 

mine production and ore types indicate that the La 

Madre Mountains Wilderness Study Area lies within a 

province characterized by hydrothermal deposits 

containing silver, lead, and zinc in veins or bedded 

replacement bodies in carbonate rocks. These deposits 

are mainly associated with thrust faults and major

A6
northwest-trending, high-angle faults that cut the 

Spring Mountains.

The two prospects in the wilderness study area, 

the Emerald and Mountain View prospects, are located 

in Red Rock Canyon near the Keystone thrust and the 

La Madre fault. These faults may have served as 

conduits for metal-bearing solutions that mineralized 

the area. Although no resources were identified in 

these prospects, samples from both contained small 

amounts of silver, lead, and zinc in sporadic, highgrade blebs, and traces of copper. Geochernical 

sampling of the surrounding area showed slightly 

anomalous amounts of silver, lead, and zinc. In 

general, hydrothermal activity in the area appears to 

have been slight. There are no igneous bodies in or 

near the study area, and the geochemical anomalies 

associated with the mineralization are small. The Red 

Rock Canyon area northwest of the Keystone thrust 

fault (fig. 2) has a low potential for silver, lead, and 

zinc resources with a certainty of C (see appendix 1 

and figure 3 for definition of certainty levels).

The principal nonmetallic mineral mined in the 

region, gypsum, occurs in deposits interbedded with 

limestone of Permian to Triassic age. There are no 

known gypsum deposits in the wilderness study area, 

and discovery of any significant near-surface deposits 

is unlikely.

Current oil and gas leases cover the entire 

wilderness study area, but there are no producing wells 

in the Spring Mountains. The potential for petroleum 

resources is low (Sandberg, 1983).

REFERENCES CITED

Axen, G.J., 1980, Geology of the La Madre Mountain 

area, Spring Mountains, southern Nevada: 

Cambridge, Massachusetts Institute of 

Technology, M.S. thesis, 170 p.

____1984, Thrusts in the eastern Spring Mountains, 

Nevada: Geometry and mechanical implications: 

Geological Society of America Bulletin, v. 95, no. 

10, p. 1202-1207.

Bohannan, R.G., and Morris, R.W., 1983, Geology and 

mineral resources of the Red Rocks Escarpment 

Instant Study Area, Clark County, Nevada: U.S. 

Geological Survey Miscellaneous Field Studies 

Map MF-1522, scale 1:62,500.

Boyd, F.S., Jr., August 11, 1983, Mineral Report-- 

Mineral patent application of B. J. Londo, et al 

for the White Beauty Nos. 1-10 placer mining 

claims: U.S. Bureau of Land Management, 

Nevada, ser. no. N-27611 3860-A.

Burchfiel, B.C., Fleck, R.J., Secor, D.T., Vincelette, 

R.R., and Davis, G.A., 1974, Geology of the Spring 

Mountains, Nevada: Geological Society of

America Bulletin, v. 85, no. 7, p. 1013-1022.

Butner, D.W., 1942, Potosi Mine dumps Clark County, 

Nevada: U.S. Bureau of Mines, War Minerals 

Memorandum, Nev. 74, 4 p.

Davis, G.A., 1973, Relations between the Keystone and 

Red Spring Thrust Faults, eastern Spring 

Mountains, Nevada: Geological Society of 

America Bulletin, v. 84, no. 11, p. 3709-3716.

Day, G.W., and Barton, H.N., 1986, Analytical results 

and sample locality map for heavy-mineralconcentrate samples from the La Madre Mountain 

Wilderness Study Area (NV-050-0412), Clark 

County, Nevada: U.S. Geological Survey OpenFile Report 86-195.

Fisher, D.F., February 21, 1967, Mineral Report-- 

Validity determination of mining claims in the 

Sandstone Quarry Area: U.S. Bureau of Land 

Management, Nevada, ser. no. N-5.

Gans, W.T., 1974, Correlation and redefinition of the 

Goodsprings Dolomite, southern Nevada and 

eastern California: Geological Society of 

America Bulletin v. 85, p. 189-200.

Clock, W.S., 1929, Geology of the east-central part of 

the Spring Mountain Range, Nevada: American 

Journal of Science, 5th ser., v. 17, p. 326-341.

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

spectrographic field methods for the 

semiquantitative analysis of geologic materials: 

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

Hewett, D.F., 1931, Geology and ore deposits of the 

Goodsprings Quadrangle, Nevada: U.S. Geological 

Survey Professional Paper 162, 172 p.

Lipton, D.A., 1985, Mineral resources of the La Madre 

Mountains Study Area, Clark County, Nevada: 

U.S. Bureau of Mines Open-File Report MLA 41- 

85, 14 p.

Longwell, C.R., 1926, Structural studies in southern 

Nevada and western Arizona: Geological Society 

of America Bulletin, v. 37, p. 551-584.

Longwell, C.R., Pampeyan, E.H., Bowger, B., and 

Roberts, R.J., 1965, Geology and mineral deposits 

of Clark County, Nevada, Nevada Bureau of Mines 

and Geology Bulletin 62, 218 p.

Sandberg, C.A., 1983, Petroleum potential of 

Wilderness Lands in Nevada: U.S. Geological 

Survey Circular 902-H, p. H1-H11.

Spurr, J.E., 1903, Descriptive geology of Nevada south 

of the fortieth parallel and adjacent portions of 

California: U.S. Geological Survey Bulletin 208, 

229 p.

Ward, F.N., Nakagawa, H.M., Harms, T.M., and 

VanSickle, G.H., 1969, Atomic-absorption methods 

of analysis useful in geochemical exploration: 

U.S. Geological Survey Bulletin 1289, 45 p.

A7
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

I'D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

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

A8
Table 1. Mines and prospects in and adjacent to the La Madre Mountains Wilder

[Underlined name indicates identified mineral resources; asterisk (*) indicates outside stud

Map

no.

(fig. 2) Summary

Workings 

and production 

White Beauty Gray limestone of the Bird Spring Formation is 

mint; interbedded with white sugary gypsum. The 

gypsum trends N. 30° E. , dips about 25° NW, 

and is exposed for as much as 7,300 ft along 

its trend and 1,400 ft down dip. Thickness of 

the exposed intercalated limestone and gypsum 

is from 10 to 100 ft; it appears to be 

lenticular and pinches out on the northeast 

and southwest.

One open pit, 1,000 ft long, 

500 ft wide, and 20 ft deep, 

and several test pits. An 

unspecified amount of 

production was reported from 

1972 to 1975.

One chip 

contain 9

respectiv

quartz an

Boyd (unp

the reserv

additiona

Karen placer 

prospect

Iron Age 

prospect

Emerald 

prospect

Mountain View 

prospect

A recent alluvial bar is composed of 

limestone, sandstone, and dolomite gravel. 

Thickness of the gravel could not be 

determined.

Gray limestone contains a stockwork of 

limonite veins. They range in thickness from 

paper thin to 4 ft, are sinuous, and lengths 

range from a few inches to about 50 ft. The 

limonite contains trace amounts of malachite.

Blue-gray limestone contains isolated zones of 

iron oxide. Mineralized shear zones contain 

veins of sphalerite and trace amounts of 

malachite, galena, chalcopyrite, and 

smithsonite. The zones range from 0.6 ft to 

2.8 ft thick and are exposed for as much as 80 

ft along the northeast and northwest strikes.

Pods of limonite are randomly distributed in 

fractured gray limestone and dolomite. Blebs 

of galena and sphalerite are dispersed with 

the limonite.

No workings.

One adit, two shafts, two 

inclined shafts, and five 

pits.

Six adits which range from 8 

to 105 ft long; one shaft 72 

ft deep, one caved shaft, and 

one pit.

One pit and one inclined shaft 

20 ft deep.

A sample 

gold. Th

S350/OZ g

Two selec

percent a

0.13 perc

Fourteen 

select, a

copper, l

detected 

0.3 and 1

oz/ton. 

percent, 

Two selec

percent z

fc
687-049/48001

""*""*"

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