< Jasperoids of the 

Lake Valley Mining 

: District, New Mexico

By E. J. YOUNG and T. G. LOVERING

CONTRIBUTIONS TO ECONOMIC GEOLOGY

j GEOLOGICAL SURVEY BULLETIN 1222-D

i

A .Application of criteria for recognition 

of ore-associated jasperoids has revealed 

a new potentially mineralized area in a 

famous silver mining district

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C., 20402 - Price 15 cents (paper cover)
CONTENTS

Page 

Abstract__-_______---__--____-____---------------------------_-_- Dl

Introduction.________-______________-_----__--_----._--_--__----i_ 1

History and production_.________.__-_-___-_-______-___------______ 3

Geology and ore deposits-___-_---_-__----_-------_----------------- 4

Method of classification of jasperoid samples.-_____--_-___--_.________ 8

Jasperoid bodies in the Lake Valley district.._________________________ 11

Unfavorable jasperoid in Montoya Dolomite._____________________ 11

Bedded chert in the Lake Valley Limestone____.____----__---_-. 11

Favorable jasperoid in Fusselman Dolomite near the Berenda fault. _ 14 

Favorable jasperoid in Fusselman Dolomite 1,500 feet from the Berenda fault.._ _______________________________________________ 18

Favorable jasperoid from the mined area _________________________ 18

Physical-chemical relations in traverses across jasperoid-Fusselman Dolomite contact.________-___________--_--___-__---__-__-___-_-_-__. 19

Comparison of Lake Valley jasperoid samples with those from nearby 

districts.^_--___--_-__---_-_-_--_--_-------------------------__- 21

Interpretation__ _ ________________________________________________ 24

Conclusions. _ _ __.______________________---_-___-_____-_____________ 26

References cited._____________.______--____-___--_____-_____-__-__. 26

ILLUSTKATIONS

Page 

FIGURE 1. Index map of part of southwestern New Mexico.------------ D2

2. Generalized geologic map of Lake Valley district, showing location of jasperoid outcrops.. - ____________________________ 5

3. Maps showing areas in which outcrops of jasperoid and chert

bodies were sampled, and sample sites..__________________ 12

4. Photograph of unfavorable jasperoid in Montoya Dolomite... 14

5. Photographs of favorable jasperoid body in Fusselman Dolomite adjacent to Berenda fault.________ ________________ 17

6. Photograph of favorable jasperoid body in Fu&selman Dolomite

1,500 feet from Berenda fault---_---------_------__-____ 18

in
IV CONTENTS

TABLES

Page 

TABLE 1. Generalized stratigraphic section of rocks exposed in the Lake

Valley mining district.-__-_-____________---___--_-_____- D6

2. Criteria used in classifying jasperoid samples as favorable or unfavorable __-__-_________________-____-__ __________-__ 10

3. Significant features and tabulated scores of jasperoid samples

from the Lake Valley mining district._____________________ 15

4. Spectrographic analy&es of samples taken in two traverses across

jasperoid-Fusselman Dolomite contacts.__ __---._______ 20

5. Classification and tabulated scores of jasperoid samples from

mining districts near Lake Valley.________________________ 22
CONTRIBUTIONS TO ECONOMIC GEOLOGY

JASPEROIDS OF THE LAKE VALLEY MINING DISTRICT

NEW MEXICO

BY E. J. YOUNG and T. G. LOVERING

ABSTRACT

A study in the Lake Valley mining district, New Mexico, of selected bodies 

of Jasperoid involved the application of criteria for distinguishing between 

jasperoid which is favorable for association with silver and base metal mineralization and that which is not. The study revealed some favorable bodies in an 

unprospected area more than half a mile from known silver and manganese ore.

Three jasperoid bodies and one bedded chert in the unprospected part of the 

Lake Valley district were studied, mapped, and sampled in detail. Representative samples of jasperoid were also collected from within the mined area 

in the district, as well as from the nearby mining districts of Hadley, Cooks 

Peak, Jose, Kingston, Hillsboro, and Organ. Comparisons were made between 

host rock and jasperoid along two traverses, and changes within the contact 

zone were investigated by petrographic and spectrographic analyses. The 

samples showed more iron, titanium, aluminum, and barium in the jasperoid 

than in the host dolomite. They also showed more calcium and magnesium on 

the jasperoid side of the contact and correspondingly more silica on the dolomite side, which indicates that major elements are diffused in both directions 

from the contact.

The presence of favorable jasperoid in Fusselman Dolomite at some distance 

from known ore bodies in the Lake Valley district, in conjunction with other 

evidence, suggests the possibility that sulfide minerals associated with, jasperoid 

may be present in the Fusselman Dolomite near the Berenda fault.

INTRODUCTION

The field study that formed the basis of this report was undertaken 

to investigate the chemical composition, texture, mineralogy, and 

appearance of several jasperoid (silicified carbonate rock) bodies and 

to relate the characteristics to structure, stratigraphy, lithology, and 

composition of the host rocks, and to proximity of silver and manganese ore deposits. All samples were classified as either favorable 

type (probably related to ore mineralization) or unfavorable type 

(probably unrelated to mineralization) in the hope that the distribuDl
D2 CONTRIBUTIONS TO ECONOMIC GEOLOGY

tion of favorable type jasperoid samples might furnish a guide for 

future exploration for ore in the district.

The Lake Valley district is in the southwestern part of Sierra 

County, N. Mex. (fig. 1), near the center of T. 18 S., R. 7 W. It is 

about 40 miles by road north-northeast of the town of Deming and 

about 15 miles west of the Rio Grande. The district was famous 

during the 1880's for silver mining; during World Wars I and II, it 

also produced some manganese ore. However, the bonanza silver ore 

bodies have long been mined out, and the manganese deposits are too 

siliceous for profitable exploitation under current market conditions.

Representative jasperoid bodies were mapped by use of planetable 

and alidade, and samples were collected by Young during March and 

April 1962. In addition, small suites of representative jasperoid 

samples were collected for comparative purposes from several other 

districts in the same region, but the bodies from which these samples 

were taken were not mapped.

Semiquantitative spectrographic analyses of the samples were made 

by J. C. Hamilton. Maps, photographs, and field descriptions were 

prepared by Young; petrographic studies of the samples were made

Hillsboro

» 

Kingston

SIERRA

m Lake Valley

Jose* Cooks Peak 

*Hadley

LUNA COUNTY

o

Deming

DONA AlN A COUNTY

^

Las Cruces

10

I

20

I

30 

I

40 MILES

I

FIGUBE 1. Part of southwestern New Mexico showing outline of Lake Valley 

Mining district (fig. 2), and location of adjacent mining districts (black 

dots).
JASPEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D3

by both Young and Levering; and the resume of the history and geology of the district and the statistical studies of the sample data were 

done by Lovering.

HISTORY AND PRODUCTION

Ore in the Lake Valley mining district was discovered in 1878 by 

G. W. Lufkin, and the major part of the district was soon claimed by 

three mining companies the Sierra Grande, the Sierra Bella, and 

the Sierra Apache. The silver boom that followed reached its peak 

in the early 1880's after the discovery and exploitation of the famous 

Bridal Chamber ore body, which yielded 2% million ounces of silver. 

By 1893 the depletion of most of the high-grade ore bodies, coupled 

with a decline in the price of silver, caused the virtual abandonment 

of mining in the area. During the brief 15-year period of mining 

activity (1878-93), the district produced 5 million ounces of silver. 

From 1893 to 1964 approximately 800,000 ounces of silver was produced. Thus, by 1964 the Lake Valley district had produced a total 

of approximately 5.8 million ounces of silver, of which about 40 percent had come from one ore body in the Lake Valley Limestone.

In 1928 and 1929 the lower beds of the Lake Valley Limestone were 

explored by drilling, but the contact with the underlying Percha 

Shale was barren of ore, and the project was abandoned. Harley 

(1934, p. 179) reported that one drill hole "near the old Virginia 

Shaft" penetrated through the Percha Shale into a thin bed of brecciated and partly silicified limestone, which was also barren. This 

record of exploration below the Percha is the only one published for 

the district, and the site of this exploration cannot be found because 

the Virginia shaft is not shown on published maps of the district.

During World War I the district yielded nearly 8,000 tons of manganese ore. During World War II, in 1942 and 1943, over 37,000 

tons of manganese ore, averaging 20.8 percent manganese, was shipped 

from the Lake Valley district to the U.S. Government stockpile at 

Deming. In 1953 the Haile Mines Co. built a 200-ton-per-day concentrating plant in the district to beneficiate siliceous manganese ore 

mined from opencuts; this work terminated prior to 1960.

Although much of the rich silver ore was associated with cerussite, 

the amount of lead produced as a byproduct of silver was not recorded.

The main mineralized area of the district was about a mile long 

from southwest to northeast, and half a mile wide; it was most intensely mineralized adjacent to the Berenda fault at the southwest 

end and least mineralized at the northeast. Mines in this area (fig. 2) 

were designated as belonging to three groups: the Grande Group at 

the southwest the richest which included the Boiler shaft, Office
D4

shaft, Twenty-five-cut, Thirty stope, and Bridal Chamber workings; 

the Bella Group in the center, which included the Emporia incline, 

Bunkhouse, Strieby, Harrison, and Bella Chute workings; and the 

Apache Group at the northeast, which was made up of small mines 

whose principal yield was iron flux (Harley, 1934; Creasey and 

Granger, 1953). All the mine workings were shallow. The deepest 

in the district was the Emporia incline, which penetrated 150 feet 

beneath the surface.

GEOLOGY AND ORE DEPOSITS

/

The map of the district (fig. 2) was modified from Jicha's map 

(1954). The district is in a tilted fault block of sedimentary rocks 

of Paleozoic age (Ordovician to Mississippian (table 1)), which is 

surrounded by volcanic rocks of .Tertiary age. The strata within the 

block strike northeast and dip 15°-20° SE. The block is cut off on 

the west by the Berenda fault and on the southwest by a northwesttrending fault, which was shown by Jicha (1954, pi. 1) as a continuation of the Berenda fault, but which was called the Lake Valley fault 

by Creasey and Granger (1953). We refer to both faults as the 

Berenda fault.

The exposed sedimentary rocks include approximately 800 feet of 

limestone, dolomite, and shale (table 1). The volcanic rocks surrounding the block are predominantly andesite in the> lower and 

middle parts of the volcanic rock series and rhyolite in the upper part.

Most ore bodies in the district were irregular replacements in the 

Alamogordo and the Nunn Members of the Lake Valley Limestone. 

In some places the top of the Andrecito Member, was also replaced by 

ore (Lindgren and others, 1910, p. 280). Hypogene mineralizing solutions which circulated along faults and fractures produced vein 

deposits locally; the ore was thoroughly oxidized and secondarily enriched by ground water. Ore deposits were localized stratigraphically 

by favorable limestone .beds in the Alamogordo Member and structurally by small faults and fractures, by a drag zone along the major 

southwest boundary fault, and by small warps and open folds in the 

beds on the dip slope of the Berenda fault block.

The two types of ore mined in the district were spatially related, 

but separate. Silver ore was more restricted in distribution than 

manganese ore and was confined largely to the southern part of the 

district. Most of the bonanza silver ore (>50 oz per ton) was not 

highly manganiferous, and manganese ore was poor in silver. Where 

the two types were associated, manganese ore commonly formed a 

floor beneath the silver-ore bodies. The silver-ore bodies of the 

Grande Group were highly siliceous, rich in silver, and relatively poor 

in manganese. Those of the Bella Group were less siliceous and con-
J

JASPEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D5

EXPLANATION

Contact

_ _ _ _ Doubly plunging syncline

Fault

Dashed where approximately 

located

 f. 

Anticline

FIGURE 2. Generalized geology of the Lake Valley district, Sierra County, 

N. Mex. (Modified from Jicha, 1954.) Dotted pattern indicates jasperoid outcrops, which were sampled in A, B, C, and D areas (shown in detail in fig. 3). 

General location of the three mine groups is shown. Y-61 and Y-62 are 

jasperoid sample sites. Quaternary alluvium (Qal); Tertiary volcanics, tuffs, 

and flows (Tv); Mississippian Lake Valley Limestone (Ml); Devonian Percha 

Shale (Dp); Silurian Fusselman Dolomite (Sf); Ordovician Montoya Dolomite 

(Om); and El Paso Limestone (Oep).
D6 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 1. Generalized stratigraphic section of rocks exposed m the Lake Valley

mining district

System

.2

£

1

o. 

.&*OT

.2

.2

^

c

a

1

o>

Q

.2

3

CO

0

 o

O

Stratigraphic unit

VolcanicTlows and tuffs

Unconformity

Lake Valley LimeCaballero Formation 2

Percha Shale

Fusselman Dolomite

Montoya Dolomite

El Paso Limestone

Tierra Blanca Member

Nunn Member

Alamogordo Member

Andrecito Member

Cutter Member

Aleman Chert

Member

Upham Member

Cable Canyon Sandstone Member

Thickness i (feet)

55±

110±

25±

55db

35±

200±

215±

75±

40±

55±

30±

200±

Character

Limestone, containing white chert.

Limestone, blue-gray.

Limestone, blue-gray.

Limestone, containing black chert

nodules.

Shale and very sandy limestone.

Black and greenish-gray shale.

Dolomite, medium-grained.

Dolomite, sublithographic.

Dolomitic limestone, fln§-graipedi

Dolomite, medium-grained.

Sandstone, dolomitic matrix.

Limestone and dolomite.

' Jicha(1954).

2 Laudon and Bowsher (1941).

tained more manganese and more calcite and gypsum. In the northeastern and central parts of the district, a prominent "chert" (or 

jasperoid) layer at the top of the Alamogordo Member formed the 

footwall of the replacement deposits. In the southwestern part of 

the district, where beds had been dragged and fractured close to the 

Berenda fault, this layer was brecciated and then cemented by younger
JASPEROmS, LAKE VALLEY DISTRICT, NEW ^MEXICO D7

jasperoid moderately rich in silver and rich in iron and manganese. 

In this area, stringers and small pockets of manganese oxides occurred 

in massive red, green, yellow, and white jasperoid, which filled fractures in the older chert. According to Clark (1895, p. 148) this jasperoid ore averaged 65 percent Si02 ,12 percent MnO, 6 percent FeO, 

and 20 ounces of silver per ton. In the central part of the district, 

the ore generally averaged about 8 percent SiO2 , 24 percent MnO,' 12 

percent FeO, and 20-30 ounces of silver per ton, and the remainder 

was limestone and gypsum. The following vertical section through 

the famous Bridal Chamber ore body has been modified from Jicha 

(1954, p. 72) :

Surface. Feet

Detritus_________________-__ - - : 4

Iron- and manganese-stained limestone-- 20

Silver ore (40 oz per ton)___ ____ 5

Silver ore (60 oz per ton) __________ 3

Silver ore (150 oz per ton) _____: _ 4

Open cavity___________-_____ _ 1%

Oerargyrite (15,900 oz per ton)_______ 4

Oerussite sand (40 percent lea'd, 500 oz silver per ton)__ 5

Iron- and manganese-stained decomposed limestone___ _ 3

According to Silliman (in Lindgren and others, 1910, p. 279) ore 

and gangue minerals from the Lake Valley district consist of ankerite, 

apatite, calcite, cerargyrite, cerussite (argentiferous), embolite, galena (argentiferous), hematite, limonite, manganite, native silver, 

psilomelane, pyrolusite, quartz, and vanadinite. Creasey and Granger 

(1953) reported that manganese ore from the district consists largely 

of manganite and pyrolusite but includes subordinate psilomelane 

and minor braunite and cryptomelane.

Clark (1895, p. 165-167) thought that silver was originally disseminated in the Tertiary volcanic rocks that once covered the area, 

and was leached by ground water during subsequent erosion to be 

precipitated and concentrated at favorable sites in the underlying 

limestone. Subsequent investigators, however, attributed the primary mineralization to hydrothermal solutions that rose along faults 

and subsidiary fractures, later to spread laterally along favorable 

zones in the Lake Valley Limestone. According to Harley (1934, p. 

177), the early primary solutions were rich in silica and contained 

minor amounts of manganese, iron, and silver; these solutions formed 

the chert layer, at the base of the ore bodies and also a few siliceous 

low-grade silver deposits. Later solutions preceded or accompanied 

by renewed movement on some of the faults were richer in lime, 

silver, and manganese and poorer in silica; they deposited ankerite, 

manganiferous calcite, ruby silver, argentiferous galena, and a little
D8

pyrite along cracks and fractures in the older siliceous replacement 

bodies. The mined ore bodies had been subject to supergene enrichment caused by oxidizing solutions migrating down the dipslope of 

the major fault block, over and through the "chert layer." Where 

this layer was fractured the ores were siliceous, but where it was 

undisturbed the overlying ore bodies were calcareous but relatively 

poor in silica.

Harley (1934, p. 173-177) recognized three distinct types of epigenetic silica in the district: the early "chert layer" at the top of the 

"Blue Limestone" (Alamogordo Member of the Lake Valley Limestone) ; the variegated silver-bearing silica that fills fractures in this 

layer in the southwestern part of the district; and brecciated siliceous 

replacement bodies in the Fusselman Dolomite west of the mineralized area. He described the jasperoid bodies in the Fusselman Dolomite as milky colored and granular, resembling quartzite, and as 

highly brecciated and cemented by vuggy late quartz. These bodies 

are most abundant near the Berenda fault, but some are as much as 

a mile distant. They form prominent rough, craggy outcrops that 

are surrounded by a talus of angular blocks and fragments. Clark 

(1934, p. 148) also mentioned the late silver-bearing "flint" ores from 

the workings in the Grande Group. He described the ore from the 

Thirty stope as consisting principally of gray, brown, chocolate, 

pearl, and green flint, brecciated, and cemented by veins of transparent 

quartz. He reported that the green flint was much richer in silver 

than were the other types of flint.

The proximity of favorable and supposedly unfavorable jasperoid 

bodies in the Fusselman Dolomite and the presence of ore-bearing 

jasperoid bodies in the Lake Valley Limestone, as described by Harley, 

prompted the choice of the Lake Valley district for this study. The 

original intent was to map and sample representative jasperoid bodies 

and their adjacent host rocks, both in the Lake Valley Limestone 

within the main mineralized area and in the Fusselman Dolomite at 

a distance from it, so that the two types of jasperoid bodies could be 

compared in detail. Unfortunately, only the outcrops in the Fusselman Dolomite were amenable to study; those in the Lake Valley 

Limestone had been either mined out or covered by mine dumps, so 

that only small scattered outcrops of jasperoid remained.

METHOD OF CLASSIFICATION OF JASPEROID SAMPLES

Classification of jasperoid samples from this area as favorable or 

as unfavorable was based on the statistical comparison of various 

properties, or criteria, such as color, texture, mineralogy, and chemical composition. Large groups of samples representing more than 

20 mining districts were first classified, on the basis of their field rela-
JA8PEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D9

tions, into two groups: those closely associated with ore bodies (favorable) , and those not associated with ore bodies (unfavorable). The 

distribution of the various properties between these groups was then 

compared by the Chi Square test and the Kolmogorov-Smirnov twosample test (Siegel, 1956, p. 104-111, 127-135; Lovering and Hamilton, 1962). Those properties whose distributions showed a statistically significant difference between the two groups were then given 

point scores that corresponded to the level of significance obtained: 

one, for the 90-percent level; two, for the 95-percent level; and three, 

for the 99-percent level. For the chemical elements the significance 

test was applied at the concentration which showed the greatest difference between the cumulative distributions for the two groups. If 

the difference was significant at. this level, one scoring point was added 

for each order of magnitude of increase in the concentration of the 

element. Thus, for silver, the greatest difference in the cumulative 

distributions between unfavorable and favorable samples occurred at 

0.0001 percent silver, and this difference was statistically significant 

at the 99-percent level. Points were assigned to samples containing 

more than 0.0001 percent silver on the following basis: Three points, 

if content was more than 0.0001 percent silver; four points, if more 

than 0.001 percent silver; and five points, if more than 0.01 percent 

silver. Plus scores were assigned to characteristics that were more 

common in jasperoids associated with ore; minus scores, to those more 

common in japeroids not associated with ore.

The scores for each sample in both groups were then totaled algebraically, and the resulting distribution of scores was compared with 

the original classification of the samples to arrive at a cutoff score 

between unfavorable and favorable that would result in misclassification of the fewest possible samples in both groups. This point was 

found to be +5. About 90 percent of the samples originally classified as favorable gave scores of + 5, and about 80 percent of those 

originally classified as unfavorable gave scores of ^ + 5. The classification system was further refined by grouping the scores in increments of five as indicative of unfavorable, probably unfavorable, 

possibly favorable, favorable, and highly favorable jasperoid samples. 

Table 2 lists the characteristics used as criteria, the scoring points 

awarded to each, and the classifications as based on the total scores.

All jasperoid samples collected in the Lake Valley mining district, 

as well as those taken from other mining districts in the region, were 

classified on the basis of their total scores; their proximity to known 

ore was disregarded. All samples of jasperoids known to be associated with ore bodies gave favorable scores; several samples from 

jasperoid bodies some distance from any known ore in the Lake Valley 

district also gave favorable scores.
CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 2. Criteria used in classifying jasperoid samples 

as favorable or unfavorable

'Criterion

Color ' 

Pale red 5Riy-z _ __ __ -__-_____-__ 

4 5 Moderate red 5R-:- * - --- --- ----------- -

4-D

fi Light brown 5 YR-j - ----------------------

Dark brown 5YR^~ -7---- - ------------ __

Phaneritic _ -___ _---_--_____-____ _

Vuggy. ____-----___ _---__--_____---._-_

Ratio of largest quartz grain diameter to 

smallest quartz grain diameter > 10_______

Reticulated_-_- -------- ------ __ _____

"Jigsaw puzzle".. -___ ___ __________ __

Hypogene minerals

Pyrite ___ ___ _ __________ ____________'_

Sericite or hydromica____ __ ______ -___

Supergene minerals 

Calcite_-_-_--------_-__ _ . _ ___. ___

Goethite____ --__-__ ____ __-____- ___

Jarosite_ ____-------_ _____ ________ ___

Yellow-orange limonite _ _ _ _ ____.__--____

Element and concentration (percent)

Me > 01

Cu_________----_-_. >.002 _____---__.

Pb._._ _ ._ >.001 ____--_--_.

Mo--_------------_- >. 0005_-__-------

Zn _______ >.01 _-__ _

Cu_____-__-__------ >.02 ____------.

Ag____---__--------- >.001 ____-------

Mo--------------__- >.005 ____------_

Zn...... ............ >.l -___-------

Mg__ .. -___ >1.5 __-_-_.----

Cu____--_--------_- >.2 ____-----__

Pb.. ------------- >. 1 -----------

Mo-----_-_-_------- >.05 ____------_

Score

-1

-2

+ 1

4-1

+ 2

+ 2

+ 2

+ 2

-2

-1

-1

-1

+ 2

+ 2

-1

4-2

+ 3

+ 3

+ 3

4-3

4-3

-2

+ 4

+ 4

+ 4

+4

+ 4

-3

+ 5

4-5

-1-5

+ 5

4-5

' Rock colors are from the National Research Council "Rock-Color Chart" (Goddard 

and others. 1948).
JASPEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO Dll

TABLE 2. Criteria used m classifying jasperoid samples as favorable or unfavorable Continued

Total score

< + l._._-_

+ lto < + 5. _-_-.-

+ 5 to <-fl(L_-____

+ 10to < + 15----.--

> + 15-__---.

Clsssification

Probabfy unfavorable jUnfavorable 

Possibly favorable 1 

Probably favorable [Favorable 

Highly favorable J

JASPEROID BODIES IN THE LAKE VALLEY DISTRICT

Two of the four bodies mapped are jasperoid in the Silurian Fusselman Dolomite; these show favorable characteristics. The third, a 

jasperoid in the Ordovician Montoya Dolomite, shows unfavorable 

characteristics, as does the fourth, a bedded chert in the Mississippian 

Lake Valley Limestone. These bodies, as well as five favorable jasperoid samples that were taken from the "Blue Limestone" in the 

mined area apparently from the Alamogordo and Nunn Members 

of the Lake Valley Limestone will be discussed next.

UNFAVORABLE JASPEROID IN MONTOYA DOLOMITE

An elongate body of jasperoid about 170 feet long is present in the 

Ordovician Montoya Dolomite in the NW^SW1^ sec. 20, adjacent 

to the Berenda fault (fig. 3J. ) . The jasperoid in this body is mottled 

red and gray and seemingly has two textures : brecciated and massive, 

It is massive only by contrast, however, for brecciation can be seen 

on close inspection (fig. 4). The Montoya Dolomite is light olive 

gray to light brownish gray and is lithographic ; it is presumably the 

Cutter Member. Rhyolite of Tertiary age crops out south of the 

Berenda fault.

Five samples were taken from the jasperoid body, and all were 

found to be unfavorable. (See table 3.) Proximity to the Berenda 

fault apparently had no positive mineralizing effect on the Montoya 

Dolomite, because the jasperoid shows no characteristics indicative 

of association with ore.

BEDDED CHERT IN THE LAKE VALLEY LIMESTONE

A small knob in the SW^NE^ sec. 20 was mapped by, Jicha 

(1954) as jasperoid, but the knob is actually underlain by a doublyplunging syncline of Lake Valley Limestone that contains chert. 

The knob, according to Jicha, is surrounded by Quaternary alluvium ; 

however, field evidence suggests that the base of the knob is underlain 

by Percha Shale of Devonian age. Figure 2 has been modified accordingly. ' ( See also fig. 35. )
D12 CONTRIBUTIONS TO ECONOMIC GEOLOGY

\ \ \ % 

Nl \xv ,. ^'l^jS'w- \.---v/;;<s.;;:;s«;> -: X. /\ >C8:©'-'. : ^SCLeoV>:.!:::;;::::;>:':

50 FEET 

\

\

A. Unfavorable jasperoid body (dotted) in Montoya Dolomite

B. Bedded chert body (dotted) in Lake Valley Limestone (Mississippian)

A

FIGURE 3. Areas in which outcrops of jasperoid
JASPEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D13

\ f

\ ^^i^^'.f-^M^Wf^itevL^^^B

V '^-'^^t-^'''^^ '? :'*:%; ^'': *$'^'':&:::-:^^ 

^XJ-SJ^S^LJ- ^:-,^ *. :?-/"?-.:'*-:--*:':*^*-!?.^:!^^::S^:':'-::-:^:^:-;^:::S^:':;^:':::::':::x-:v:; »I v . \^-^^-^^^.y^^^9\^-^--t^^^^^y-'^^'^^-^-^:''y-:^^^^^^

N \^S^1^I^^^^J 

100FE EVv

Nx^li||||||||[i

C. Favorable jasperoid body (dotted) in Fusselman Dolomite adjacent to Berenda fault.

EXPLANATION

Contact 

Dashed where inferred

Fault 

Dashed where approximately located

Doubly plunging syncline 

 5575 

Topographic contour 

Interval 25 feet

Strike and dip of 

sedimentary beds

55

Strike and dip of joints

40*37

Strike and dip of slickensided 

surface and plunge of striations

 Y-48 

Sample site

D. Favorable jasperoid body (dotted) in Fusselman Dolomite 1,500 feet from Berenda fault.

and chert bodies were sampled, and sample sites.
D14 CONTRIBUTIONS TO ECONOMIC GEOLOGY

FIGTJBB 4. Unfavorable jasperoid in Ordovician Montoya Dolomite, showing 

brecciated and seemingly massive textures.

Three chert samples were taken from this knob for comparison with 

the jasperoid samples; samples Y-57 and Y-60 are from the Alamogordo Member, and sample Y-59 is a black chert from the Andrecito Member. All samples were classified as unfavorable. (See table 

3 for significant features of the chert samples and their scores.)

FAVORABLE JASPEROID IN FUSSELMAN DOLOMITE NEAR THE 

BERENDA FAULT

A jasperoid body, irregular in form and about 200 feet wide, lies 

in the SW^SE1^ sec. 20 and is very near the Berenda fault (figs. 2, 

3, 5A) ; there is a small outlier 100 feet to the north. The larger 

jasperoid body is very similar to that in the Montoya Dolomite previously described. A small part of the outlier has milky-white fragments of jasperoid in a dark-reddish-black hematitic matrix. (See 

fig. 5B.)
JA8PEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D15

TABLE 3. Significant features and tabulated scores of jasperoid samples from

the Lake Valley minvng district (flff.S) 

[Numbers in parentheses (+2) indicate scores. Analyst: J. C. Hamilton]

Sample 

Criteria

Megascopic 

examination

Microscopic 

examination

Spectrographic 

analyses

Total 

score Classification

JASPEROID BODY IN ORDOVICIAN MONTOYA DOLOMITE

[Average, +1; probably unfavorable]

Y-31 

Y-32

Y-33

Y-34 

Y-35

Vuggy.... ..(+2)

Vuggy........ .(+2)

"Jigsaw puzzle"

Calcite... -.(-1)

"Jigsaw puzzle"

IGoethite +2)

Calcite.... . -1)

"Jigsaw puzzle"

Mg 0.1 ... (-1)

JMg.. . .1 ... (-1)

Mg.... .. .3 (-2) 

Zn...... .05 (+4)

/Mg.... .. .1 (-1)

\Zn._-_ .05 (+4) 

Mg. .. .03 ... (-1)

-1 

-4

} +' 

}+,

Unfavorable. 

Do.

Probably unfavorable.

Do. 

Unfavorable.

BEDDED CHERT IN MISSISSIPPIAN ALAMOOORDO AND ANDRECITO MEMBERS OF 

LAKE VALLEY LIMESTONE

[Average, %; unfavorable]

Y-57 

Y-59 

Y-60

Vuggy........ .(+2)

Light brown (SYR 

6/4) > (+1)

F

uggy......... (+2)

rayish orange 

pink (5YR 

7/2). b (+1)

"Jigsaw puzzle" 

texture ____ ( 2)

{

"Jigsaw puzzle" 

texture... ...... (-2)

Late calcite .-.(-1)

1

" Jigsaw puzzle"

Mg.. . 0.03 (-1)

Mg.... .. .15 (-2) 

Cu _ . .005.. .(+3)

Mg.... .. .07 ... (-1)

-1

} -'

0

Unfavorable. 

Do.

Do.

JASPEROID BODY IN SILURIAN FUSSELMAN DOLOMITE CLOSE TO BERENDA FAULT

[Average, +12; favorable]

Y-47 

Y-48

Y-49A

Y-49B 

Y-49C

Y-52A

Y-52B 

Y-53

Vuggy... . .(+2)

.....do.. ...... (+2)

.....do........(+2)

Vuggy... .....(+2) 

.....do.. ...... (+2)

[....do.. ...... (+2)

< Brown (YR 

I 3/4)b.......(+i)

Size range >10 c -(+2)

Size range >10°.(+2)

Size range >10°.(+2) 

Reticulated texture... . (+2)

Grain size >0.1 

mm...... . .(+2)

Montmorillonite... .,(-!)

Size range >10°.(+2) 

Grain size >0.1 

mm. .......... (+2)

"Jigsaw puzzle"

Size range >10 °.(+2) 

Giain size >0.1

Size range >10 °-(+2) 

Grain size >0.1 

mm.... __ ...(+2)

Jarosite.... .(+2)

"Jigsaw puzzle"

Size range >10 °.(+2) 

Goethite.... .(+2)

"Jigsaw puzzle"

Size range >10°.(+2) 

Grain size >0.1 

mm. .......... (+2)

Pb .. 0.002. .(+3)

Fe...... 5.0 -(+2) 

Ag...... .003.. (+4) 

Mo..... .003.. (+3) 

Pb... ... .07 ..(+4) 

Zn.. . .05 ..(+3)

Mg..... .05 -.(-1) 

Pb ... .002.. (+3)

Fe--- 5.0 -.(+2) 

Pb .02 ..(+4)

Mg..... .1 ..(-1) 

Fe_. . 3.0 ..(+2) 

Pb .. .015. .(+4)

Pb .. .015.. (+4) 

Mo..... .007.. (+4) 

Ag... ... .002.. (+4)

Fe._ 2.0 ..(+2) 

Pb .015.. (+4 

Mo..... .003. .(+3 

Ag...... .003. .(+4

Mg..... .05 ..(-1)

+7 

 +20

} +'

} * 

}«.

} +20

+17 

+6

Possibly favorable.

Highly favorable.

Possibly favorable.

Do. 

Do.

Highly favorable.

Do.

Possibly favorable.

See footnotes at end of table.
DIG CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 3. Significant features and tabulated scores of jasperoid samples from 

the Lake Valley mining district (fig. 3) Continued

Sample 

Criteria

Megascopic 

examination

Microscopic 

examination

Spectrographic 

analyses

Total 

score Classification

JASPEROID BODY IN PUSSELMAN DOLOMITE AWAY FROM BERENDA FAULT

[Average, +7fi; possibly favorable]

Y-63

Y-64 

Y-65 

Y-68

Y-69

Vuggy. - (+2)

f . do...... (+2)

\ Pale red (-1) 

I (5«6/2)b.

Vuggy.- ....(+2)

.....do......... (+2)

Size range>10° _(+2) 

Grain size >0.1 (+2) 

mm. 

"Jigsaw puzzle" ( 2) 

texture. 

Yellow-orange (-1) 

limonite. 

Size range >1<K~ (+2) 

Grain size >0.1 (+2) 

mm. 

/Size range >10<=___(+2) 

ISupergene calcite.( 1) 

fSizerange >1<K- (+2) 

i Grain size >0.1 (+2) 

1 mm. 

[Size range >10° (+2) 

\ Grain size >0.1 (+2) 

I mm.

Mg.._ 0.05 .... (-1) 

Pb..- .005 ---(+3)

Zn..._ .07 ---(+3) 

Mo .002 ...-(+3)

Mg .02 ....(-I) 

Pb.... .01 ...-(+3)

Mg_... 1.5 . (-2) 

Pb.... .003 --(+3) 

Mg-.- .03 .... (-1) 

Pb.-.- .007 ---(+3)

(Mg-.._ .07 .... (-1) 

^Pb..._ .005 .(+3) 

lZn___. .07 . (+3)

+11

} +'

} +*

} «

} +u

Probably 

favorable.

Possibly 

favorable.

Probably 

unfavorable. 

Possibly 

favorable.

Probably 

favorable.

JASPEROID FROM THE MINED AREA IN THE LAKE VALLEY DISTRICT

[Average, +RH; possibly favorable] 

Green and gray jasperoid

Y-61A 

Y-61B 

Y-61C

f Vuggy.... ... -(+2)

\ Light brown (+1) 

[ (5YR 6/4). b

"Jigsaw puzzle" ( 2) 

texture. 

[Reticulated (+2) 

< texture. 

(Late caleite __.(-l)

/Ag_... 0.03 ....(+5) 

\Pb .003 ..-(+3) 

(Mg.... .02 .... (-1) 

{Pb_._. .003 .(+3) 

Ug...-. .01 . (+4) 

Mg.... .2 ....(-2)

Ag.... .0007.. ..(+3)

} * 1 +7

} +4

Possibly 

favorable.

Do.

Probably unfavorable.

Redjasperoid

Y-62A

Y-62B

Vuggy.. ....... (+2)

texture.

Mg.... 0.02 ..-(-1) 

Fe..... 7.0 ....(+2) 

Pb.... .03 ....(+4)

Ag.... .005 ....(+4) 

Zn___. .05 . (+3) 

Mg.._. .05 .... (-1) 

Fe..... 7.0 (+2) 

Zn_._. .1 (+3)

Pb.... .05 - (+4) 

Ag.._. .005 (+4)

1 10

+12

favorable. 

Do.

» A, B, or C suffix denotes a variant of a sample.

b Rock colors are from the National Research Council "Rock-Color Chart" (Goddard and others, 1948).

c Ratio of largest quartz-grain diameter to smallest quartz-grain diameter >10.

Eight samples were taken from the jasperoid body and its outlier; 

one sample from the outlier (fig. 5B) yielded a +20 score. Significant features and tabulated scores of the samples, as shown in table 3, 

indicate the average of the samples to be "favorable."
JASPEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D17

FIGURE 5. Favorable jasperoid body (mapped in fig. 3G) in Fusselman Dolomite adjacent to Berenda fault. A, Prominent jasperoid outcrops. B, Angular white jasperoid-breccia fragments in a dark siliceous hematite matrix
D18 CONTRIBUTIONS TO ECONOMIC GEOLOGY

FAVORABLE JASPEBOID IN FTJSSELMAN DOLOMITE 1,500 FEET 

FROM THE BERENDA FAULT

An outcrop of jasperoid about 150 feet wide (fig. 3Z>) is in Fusselman Dolomite in the center of sec. 20, about a quarter of a mile north 

of the jasperoid body in Fusselman Dolomite near the Berenda fault. 

This jasperoid has the same appearance as that in jasperoid bodies 

in other areas. A part of the smaller arcuate body in figure 3Z> is 

shown in figure 6, which also shows the fretted surface-weathering 

characteristic common to the Fusselman Dolomite in other areas.

Five samples were taken from this body, and they have an average 

score of +7% (table 3), which classes them as "possibly favorable."

FAVORABLE JASPEROID FROM THE MINED AREA

Five samples of "favorable" jasperoid were taken from the mined 

area at points 61 and 62 shown in figure 2. The three green and 

gray samples are relatively less "favorable" than the two red samples, 

as is indicated in table 3.

FIGURE 6. Favorable jasperoid body in Fusselman Dolomite 1,500 feet from 

Berenda fault; note contact between jasperoid and dolomite in foreground. 

Synclinal body of Lake Valley Limestone containing mapped body of chert 

is in middle distance.
JA8PEROIDS, LAKE VALLEY DISTRICT, NEW MEXICO D19

PHYSICAL-CHEMICAL RELATIONS IN TRAVERSES 

ACROSS JASPEROID-FUSSELMAN DOLOMITE CONTACT

Samples were collected from two jasperoid bodies along two traverses that extended from jasperoid into apparently fresh dolomite 

(fig. 3Z>). These samples were analyzed to evaluate the physical, 

chemical, and mineralogical changes that accompany replacement of 

dolomite by jasperoid.

The contact between the larger body of jasperoid and the fresh 

dolomite (fig. 3Z>, traverse 1) is very irregular and exhibits a transitional contact zone, whereas the contact between the smaller, arcuate 

body of jasperoid and the dolomite (fig. 3Z>, traverse 2) is abrupt.

Both bodies show increases in calcium and magnesium in the jasperoid as the dolomite contact is approached and a corresponding 

increase in silica in the dolomite as the jasperoid is approached. The 

jasperoid in both traverses also contains more iron, aluminum, titanium, and barium than does the dolomite (table 4).

The contact zone crossed in traverse 1 has little iron, vanadium, 

chromium, and lead; whereas in traverse 2, across the arcuate body, 

the jasperoid near the contact zone contains considerable iron, vanadium, and manganese. This fact is probably a reflection, however, 

of the hematite-rich jasperoid near the contact. Considerable diffusion of certain elements appears to have occurred across the contact.

Megascopic and microscopic descriptions of the samples collected 

along the two traverses are given in table 4.

The older, original jasperoid in traverse 1 preserves in large measure the color and texture of the dolomite it replaces. Changes in 

texture of the dolomite outward from the contact suggest that brecciation and partial recrystallization occurred prior to silicification. The 

fact that the abundance of disseminated epigenetic quartz grains in 

the dolomite gradually diminishes away from the contact also suggests that the older jasperoid was formed by expansion and coalescence 

of isolated centers of quartz precipitation rather than by a wave of 

silicifioation that advanced from the feeding channels. Veinlets of 

younger, coarse grained clean quartz, which cut both the older jasperoid and the host rock, probably represent direct precipitation in 

these channels by late-stage silica-bearing solutions that were more 

nearly in chemical equilibrium with the host rock and, thus, were unable to replace it.

Chemically, the contact zone seems to contain less iron, vanadium, 

chromium, and lead than do either the jasperoid or the dolomite. 

Strontium increases in abundance from the jasperoid to the dolomite. 

Copper content decreases slightly from the jasperoid to the dolomite,
CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 4. Characteristics of samples taken in two traverses across jasperoidFusselma/n Dolomite contacts (fig. 3D) 

[Elements in percent; M, >10 percent. Analyst: J. C. Hamilton]

Distance from

Traverse 1

Y-64 

Jasperoid

12

Y-65 

Jasperold

1

Y-65A 

Slicifled 

dolomite

Q

Y-66 

Dolomite

1

Y-67 

Dolomite

25

Traverse 2

Y-68 

Jasperoid

5

Y-69 

Jasperoid

<1

Y-70 

Dolomite

<1

Y-71 

Dolomite

15

Determinations by spectrographic analyses

Si.. 

Al

Fe.. ... ... ... ...

Mg....... .... .....

Ca ----- 

fj&.. ........... ...

Ti.. ... 

Mn .. -

B.__ ............

Ba .. . 

Ce 

Cr.... ... .

Cu-. 

Mo. ... - ....

NL .

Pb. ... ... .... ...

Sr_ ... ... .....

V.....,...... ...

Zn... ..............

ZT-. ...............

M 

0.15 

1.5 

.02 

.15

0 

.005 

.03 

0 

.01

0 

.0007 

.002 

0 

0

.01 

0 

.005 

0 

0

M 

0.07 

.16 

1.5

5

0 

.001 

.03 

0 

.002

0 

.0003 

.0015 

0 

0

.003 

.002 

.001 

0 

0

7.0 

.07 

.2

M 

M

0 

.002 

.02 

0 

.001

0 

.0005 

.0015 

0 

0

.003 

.003 

.0015 

0 

0

1.5 

.015 

.3 ' M 

M

0 

<.001 

.15 

0 

.0005

<.05 

.0007 

^ .0007 

0 

0

.003 

.003 

.002 

0 

0

0.3 

.03 

.5 

M 

M

0 

.0015 

.02 

0 

.0005

<.05 

.0007 

.0007 

0 

0

.01 

.005 

.003 

0 

0

M 

0.15 

.3 

.03 

.1

0 

.015 

.005 

0 

.007

0 

0 

.001 

0 

0

.007 

.003 

.001 

0 

0

M 

0.15 

1.5 

.07 

.15

0 

.007 

.03 

0 

.005

0 

.0003 

.0007 

0 

.0007

.005 

.001 

.002 

.07 

0

0.7 

.015 

.15 

7 

M

.05 

<.001 

.01 

0 

.0003

<.05 

.0003 

.0007 

0 

0

.0015 

.003 

.001 

0 

0

0.07 

.015 

.2 

M 

M

.05 

<.001 

.05 

0 

.0003

<.05 

.0003 

.0005 

0 

0

.002 

.002 

.001 

0 

0

Determinations by megascopic and microscopic examination

Y-64. Jasperoid, massive, mottled light-gray and red (5R 8/2 and 5R 6/2), vuggy. Two generations. 

Older is heterogeneous and xenomorphic and has a range in grain size of 0.005to0.2 mm; it contain s 

sparse carbonate dust, abundant red-hematite dust, and, locally, abundant microvugs. It has 

been brecciated and cemented by a younger coarser relatively homogeneous quartz, which has an 

average grain size of 0.15 mm and forms prominent zonal overgrowths outlining pyramidal forms.

Y-es. Jasperoid, pinkish-gray (&YR 8/1); contains some carbonate; a few vugs, Equal amounts ef 

jasperoid and dolomite. The dolomite is fine grained and contains local coarse grains and aggregates of coarse grains, all of which are very irregularly replaced by heterogeneous xenomorphic jasperoid. Veinlets of clean xenomorphic quartz, younger than- the jasperoid, are 

cut by still younger veinlets of calcite.

Y-65A. Silicifled dolomite; grayish orange pink (5YR 7/2) on weathered surface. Heterogeneous coarseand fine-grained dolomite, partly replaced by coarse- and fine-grained xenomorphic quartz. 

The rock is brecciated and filled with younger clean coarse homogeneous xenomorphic quartz 

that contains numerous vugs.

Y-66. Dolomite, light-brownish-gray (5YR 6/1), bioclastic, fine- to medium-grained. Heterogeneous 

coarse- and fine-grained dolomite cut by thin irregular and discontinuous veinlets of heterogeneous xenomorphic quartz (avg grain size, 0.15 mm), which show incipient replacement along 

the walls. The dolomite between the veinlets also contains sparse disseminated interstitial 

quartz grains.

Y-67. Dolomite, grayish-orange-pink (5YR 7/2), very fine grained. Fine-grained homogeneous dolomite locally contains coarse grains of dolomite and aggregates of coarse-grained dolomite and 

very sparse tiny interstitial grains of quartz.

Y-68. Jasperoid, mottled light-gray to very light gray (N 7-N 8), vuggy; light gray to pinkish gray 

(SIT? 8/1) on weathered surface. Heterogeneous, medium grained, xenomorphic; contains 

carbonate dust inclusions, breccia fragments of older coarse xenomorphic quartz, and euhedra 1 

zonal overgrowths. It is cut by red hematite in irregular veinlets and is in irregular concentrations locally.

Y-69. Jasperoid, mottled medium-light-gray to blackish-red (N 6-5B 2/2), vuggy; light olive gray to 

blackish red (5Y 5/2-5E 2/2) on weathered surface. Similar to Y-68, but brecciation is more 

intense and rock contains more of the younger hematite; much is in large irregular opaque masses.

Y-70. Dolomite, pinkish-gray (5YR 8/1), fine- to medium-grained; grayish orange pink (5YR 7/2) on 

weathered surface. Fine- t) medium-grained homogeneous dolomite containing very sparse 

tiny interstitial quartz grains which have been introduced and are not detrital.

Y-71. Dolomite. Same as Y-70.
D21

as does titanium, except that titanium increases slightly at the contact. Manganese content remains virtually the same throughout the 

traverse, except where it unexplainedly increases in the dolomite within 

a foot of the contact. Chemical changes are shown by spectrographic 

analyses of the suite. (See table 4.)

Traverse 2 shows a much more abrupt transition across the contact 

into fresh wallrock than does traverse 1. The host dolomite adjacent 

to the contact lacks the brecciation and local recrystallization which 

characterizes that in traverse 1, nor does it contain abundant disseminated quartz. The jasperoid body sampled along traverse 2 is 

a small outlier of the one sampled along traverse 1, and it also differs 

from the larger mass by being long and narrow (figs. §D; 6)-. A 

possible explanation for the observed differences in the contact zones 

may be that the silica-bearing solutions that formed the jasperoid in 

the small outlier welled up along an open fissure which contained a 

rubble of breccia fragments. The wallrock on either side of this 

fissure was not highly fractured and was relatively impermeable; 

hence, the alteration was largely concentrated in the rubble between 

the walls of the fissure.

The larger irregular, body, sampled in traverse 1, may represent a 

zone, originally shattered by many small fractures, through which 

solutions seeped more slowly.

An estimate of the overall chemical changes brought about by the 

replacement of dolomite by jasperoid can be made by comparing the 

analyses of the two jasperoid samples taken farthest from the contact 

with the analyses of the two fresh dolomite samples taken farthest 

from the contact (table 4). Comparison indicates that, in addition 

to the silica, the jasperoid samples contain significantly larger amounts 

of aluminum, titanium, barium, and copper than do the dolomite 

samples. Cerium is the only element besides calcium and magnesium 

that is in consistently larger amounts in the dolomite samples. During the silicification process then, probably only the carbonate-forming cations were flushed out, so that many trace-element impurities in 

the dolomite remained in the replacing jasperoid, in substantially their 

original concentrations.

COMPARISON OF LAKE VALLEY JASPEROID SAMPLES 

WITH THOSE FROM NEARBY DISTRICTS

Jasperoid samples from six districts other than the Lake Valley 

district were collected, studied, and given scores. (See fig. 1.) Significant features and tabulated scores of these jasperoids are given 

in table 5.
TABLE 5. Significant features and tabulated scores of jasperoid samples from 

[Numbers in parentheses (+2) indicate scores. Spectrographic analyses by J. C

District

Organ (Dona Ana 

County).

Jose (Luna County) 

Kingston (Sierra County) .

Cooks Peak (Luna 

County).

Hillsboro (Sierra County). 

Hadley (Luna County). ..

Sample a

Y-46A

Y-39 

Y-21 

Y-18A

Y-18B 

Y-19

Y 22A

Y-22B

Y-22C 

Y-6 

Y-6A

Y-7B

Criteria

Megascopic examination

Vuggy-. ... ... ... ... ... ... (+2)

/Moderate pink (5R 7/4)« (-1) 

\Vuggy... . ..(+2)

/Medium brown (SYR 3/4)° _ (+1) 

\Vuggy... .. .(+2)

/Medium brown (SYR 3/4)« _ (+1)

\Vuggy. .(+2) 

/Brown (5F.B 4/4)<>_._. _ .....(+1)

\ Vuggy.. ................. .(+2)

VIICKTV ( \ *?\

/Moderate red (5R 5/4)°.... _ (-2)

\Vuggy.. ......(+2) 

Vuggy...-....... ..(+2)

/Light brown (5YK 6/4)<> (+1)

iVuggy.. .... ..(+2) 

Light brown (5YR 6/4)"..... .(+1)

Microscopic examination

Size range >10»> ______ (+2)

fSericite...... _ ... .... _ . _ (-1)

 {"Jigsaw puzzle" texture. __ ( 2)

(.Reticulated texture.. __ (+2)

JReticulated texture. ____ (+2)

}. .do................. . ..........

JMontmorillonite. . ______ ( 1)

/Size range >10>>-. ______ (+2)

\Yellow limonite.. ___ . __ (-1)

}._...____.__.____.

Yellow limonite.-.... .....(-1)

... ...do.... _ ._ ..

} . do.... ... ... ... .

( ..do ....- -.

<"Jigsaw puzzle" texture. __ ( 2)

ISericite.. ...... .... __ .... ..(-1)

Spect

/Mg.. _

\Cu.. _

iMg 

Mg. 

Mg 

!

Pb..

Zn __

Mg..

Pb... 

Mg..

Mg... 

Pb. _

(Mg 

JCu 

IPb 

lZn __

(Fe..

JMg 

|Pb __

lZn..

/Mg.. _ 

\Pb 

Pb... 

Fe..

I

Mg..

Cu. 

Pb 
Y-8B

Y-9

Y-10

Y-16A

Vuggy.. (+2)

r Grayish pink (5R 8/2)° (-1)

\Vuggy.. ...... ......... (+2)

Vuggy..... ...... (+2)

} ..do............................

 ... do .. ....... ... ..... .

... do 

Mg 

{Cu 

lPb _

Fe_

Mg

Cu- 

Pb _

» A, B, or C suffix denotes a variant of a sample.

t> Ratio of largest quartz-grain diameter to smallest quartz-grain diameter >10.

c Rock colors are from the National Research Council "Rock-Color Chart" (Goddard and others, 1948).

SAMPLE LOCALITY

Y-46A. 1,600 ft east of U.S. Highway 70, sec. 2, T. 22 S., R. 3 E.

Y-39. Center NE& sec. 11, T. 20 S., R. 9 W.

Y-21. Between North and South Percha Creeks, 1 mile east of Kingston.

Y-18A. Near east end of Othello fault, SW^NEJ^ sec. 24, T. 20 S., R. 9 W.

Y-18B. SameasY-18A.

Y-19. 500 ft north of Y-18A and Y-18B.

Y-22A. Top of fault scarp 1 mile east of Jlillsboro.

Y-22B. Same as Y-22A.

Y-22C. Same as Y-22A a

Y-6. Near center sec. 3

Y-6A. Same as Y-6.

Y-7B. Same as Y-6 and 

Y-8B. Center south bou

Y-9. Near SW. cor. sec

Y-10. Same as Y-9.

Y-16A. 1,000 ft north of c
D24 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Most samples were taken from jasperoid bodies that are not close 

to any known ore bodies. Only samples Y-18A and Y-18B, from 

the Cooks Peak district, represent jasperoid that is apparently related both spatially and genetically to sulfide ore. Both of these 

favorable samples from the Fusselman Dolomite are vuggy and contain anomalously high concentrations of lead characteristics also of 

most jasperoid samples taken from the Fusselman Dolomite in the 

Lake Valley area, particularly those from the jasperoid body close 

to the Berenda fault.

The three samples taken from the large jasperoid body in Fusselman Dolomite along a strong north-trending fault a mile east of 

Hillsboro show anomalously high concentrations of lead and zinc. 

No ore deposits are known to be associated with this body, however.

The seven samples from the Hadley district were taken at intervals 

along a strong north-trending silicified zone in Tertiary volcanic rock. 

No mineral deposits have been discovered in this zone, although, 

locally, its small faults and fracture zones are enriched by manganese 

oxide.

The single random grab samples from each of the three remaining 

districts (Organ, Jose, and Kingston) were collected merely to check 

the possibility of some regional similarity in jasperoid bodies in southwestern New Mexico. No such similarity was apparent; accordingly, 

no particular significance can be ascribed to these single samples.

INTERPRETATION

Replacement of carbonate rocks by jasperoid in the Lake Valley 

district was controlled structurally by faults and fracture zones and 

stratigraphically by the contact of the Fusselman Dolomite with the 

overlying Percha Shale. Exposed jasperoid bodies in all the formations except the Fusselman Dolomite are concentrated near the Berenda fault, whereas large masses of jasperoid are present in the 

upper part of the Fusselman Dolomite more than a mile from this 

fault.

Carbonate host rocks were locally brecciated, shattered, and partially recrystallized before they were silicified. Several minor elements were brought in by silicifying solutions, and many others that 

were originally present in the carbonate rocks remained in the jasperoid. Only the carbonate-forming cations calcium, magnesium, 

and cerium were largely removed during silicification.

The widespread distribution of jasperoid bodies in the Fusselman 

Dolomite exposed in the fault block at Lake Valley can possibly be 

attributed to the fact that a 200-foot-thick section of Percha Shale 

originally overlay the Fusselman and formed a relatively impermeable
D25

barrier to the upward migration of silica-bearing solutions, forcing 

them to spread out and deposit their load in the Fusselman. This 

hypothesis is supported by the conclusions of Harley (1934, p. 177) 

and of Jicha (1954, p. 70) that the early mineralizing solutions in 

the Lake Valley district were rich in silica and comparatively poor 

in calcium carbonate, but that a reverse relationship existed in the 

later mineralizing solutions that carried the lead and silver, which 

formed the primary ore. Replacement of carbonate rock in the Fusselman Dolomite by jasperoid would contribute calcium carbonate 

to the upward-moving solutions and would thus provide a logical 

source for calcium carbonate in the late ore solutions that penetrated 

the Lake Valley Limestone in the main mining district. The presence of favorable jasperoid in the Fusselman Dolomite at some distance from the center of the mined area in the Lake Valley district 

suggests the possibility that primary sulfide-ore bodies of argentiferous lead and zinc formed in association with jasperoid in the Fusselman Dolomite beneath the Percha Shale near the Berenda fault. 

This zone is the host rock for sulfide-replacement ore bodies in the 

Cooks Peak district a few miles southwest of Lake Valley and in the 

Kingston district a few miles northwest of it. The two jasperoid 

bodies at a distance from the mined area in the district which yielded 

the most favorable jasperoid samples are both in the upper part of 

the Fusselman Dolomite.

Two locations seem most favorable for exploration in the Fusselman. One is at the Fusselman-Percha contact beneath the alluvium 

adjacent to the Berenda fault about midway between the jasperoid 

body (fig, 30) and the road intersection about 1,500 feet southeast 

of the body (fig. 2). The other is in the same stratigraphic zone 

beneath the Grande group workings, close to the fault in the main 

district.

The first location has apparent potential as a possible area for 

prospecting because of three considerations:

1. It is close to the jasperoid body that yielded the samples with the 

highest scores.

2. Water moving through the alluvium along and near the buried 

Fusselman-Percha contact may have caused supergene enrichment of any ore bodies that existed in this area.

3. The contact is close to the surface at this point; hence, exploration

would be relatively inexpensive.

The second location has apparent potential because of the known 

presence of ore bodies, in part contemporaneous with late calcite, in 

the overlying Lake Valley Limestone. Late calcite was probably 

brought upward in solution by hydrothermal fluids moving along the 

Berenda fault, and'its most logical source is the Fusselman Dolomite.
D26 CONTRIBUTIONS TO ECONOMIC GEOLOGY

If the Fusselman had been dissolved, it seems quite possible that the 

sulfides and silica were precipitated simultaneously.

CONCLUSIONS

Jasperoid bodies having favorable characteristics that suggest proximity to ore deposits are present in the Lake Valley district not only 

in the Lake Valley Limestone in the mined area but also in the Fusselman Dolomite near the Berenda fault in a hitherto unexplored area. 

Thi& facfe^ together with the known presence of sulfide ore in the Fusselman Dolomite in nearby districts and the conclusion of Harley 

(1934, p. 177) that ore-stage solutions in the mined area were high 

in calcium carbonate, suggests the possible existence of sulfide-ore 

bodies in the Fusselman Dolomite beneath the Percha Shale and close 

to the Berenda fault.

Detailed examination and chemical analysis of samples taken along 

two traverses across the contact between jasperoid and dolomite show 

incipient ^silicification of the dolomite for several feet beyond the 

apparent contact. The elements aluminum, titanium, barium, and 

copper were probably introduced with silica during the replacement 

of dolomite by jasperoid; the carbonate-forming cations calcium, magnesium and cerium were probably the only ones expelled. Iron, 

manganese, chromium, lead, strontium, and vanadium, present as 

impurities in the dolomite, seem to have remained in the,jasperoid in 

substantially their original concentrations.

REFERENCES CITED

Glark, Ellis, Jr., 1895, The silver mines of Lake Valley, New Mexico: Am. Inst. 

Mining Engineers Trans., 1894, v. 24, p. 138-167.

Creasey, S. C., and Granger, A. K, 1953, Geologic map of Lake Valley manganese district, Sierra County, New Mexico: U.S. Geol. Survey Mineral Inv. 

Field Studies Map MF-9.

Goddard, E. N., chm., and others, 1948, Rock-color chart: Washington, Natl. 

Research Council.

Harley, G. T., 1934, The geology and ore deposits of Sierra County, New Mexico: 

New Mexico Bur. Mines Bull. 10, 220 p.

Jicha, H. L., Jr., 1954, Geology and mineral deposits of Lake Valley quadrangle, 

Grant, Luna, and Sierra Counties, New Mexico: New Mexico Bur. Mines 

Bull. 37, 93 p.

Kuellmer, F. J., and others, 1953, Road log from Las Cruces to Silver City, in New 

Mexico Geol. Soc. Guidebook 4th Field Conf., southwestern New Mexico, 

1953: p. 42 (map), 47, 50 (map).

Laudon, L. R., and Bowsher, A. L., 1941, Mississippian formations of Sacramento Mountains, New Mexico: Am. Assoc. Petroleum Geologists Bull., 

v. 25, no. 12, p. 2107-2160.

Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., 1910, The ore deposits 

of New Mexico: U.S. Geol. Survey Prof. Paper 68, 361 p.
D27

Levering, T. G., and Hamilton, J. C., 1962, Criteria for the recognition of jasperoid associated with sulfide ore, in Short papers in geology and hydrology: U.S. Geol. Survey Prof. Paper 450-C, p. C9-C11.

Siegel, Sidney, 1956, Nonparametric statistics for the behavioral sciences: New 

York, McGraw-Hill Book Co., 312 p.

U.S. GOVERNMENT PRINTING OFFICE : 1965 O 787-997