GEOLOGICAL SURVEY CIRCULAR 553 

Silver in Veins of 

Hypogene Manganese 

Oxides 

Silver in Veins of 

Hypogene Manganese 

Oxides 

By D. F. Hewett 

G E 0 L 0 G I C A L S U R V E Y C I R C U L A R 553 

Washington 1968 
United States Department of the Interior 

STEWART L. UDALL, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
CONTENTS 

Page 

Abstract --------------------------------- 1 

Introduction------------------------------

Hypogene veins of manganese oxides in the 

Southwestern United States--------------- 1 

Recent development of manganese deposits in 

Nova Scotia and New Brunswick----------- 3 

Comparison of the veins of the Maritime 

Provinces of Canada with those of the 

Southwestern United States --------------- 4 

Areas in the United States attractive for 

exploration----------------------------- 5 

Areas in the United States attractive for 

exploration -Continued 

Little Florida Mountains, Luna County, New 

Page 

Mexico--------------------------------- 5 

Luis Lopez district, Socorro County, New 

Mexico--------------------------------- 7 

Arlington district, Riverside County, 

California ------------------------------ 7 

Aguila district, Maricopa County, Arizona -- 7 

Conclusions ------------------------------ 8 

References cited--------------------------- 8 

ILLUSTRATION 

Page 

Figure 1. -Map showing distribution of explored veins of hypogene oxides of manganese in the Southwestern United States and northern Mexico------------------------------------------ 6 

TABLES 

Page 

Table 1. Spectrographic analyses of hypogene manganese oxides from New Mexico and 

California------------------------------------------------------------------------- 2 

2. Spectrographic analyses of manganese oxides from the Maritime Provinces of Canada ------ 3 

3. Spectrographic analyses of hollandite from the Black Canyon (Gianera) shaft, Luis Lopez 

district, New Mexico --------------------------------------------------------------- 4 

III 

Silver 1n Veins of Hypogene Manganese Oxides 

By D. F. Hewett 

ABSTRACT 

During the First and Second World Wars, a great shortage of 

manganese ore in the United States led to an intensive search for 

deposits. One result of this search was the discovery in the Southwestern United States of numerous veins of high-grade manganese 

oxides whose mode of origin was the subject of much speculation. 

Studies of these veins during recent years indicate that the manganese in the oxide minerals was derived from great depth, that 

the explored veins were formed near the original surface, and that, 

if explored in depth, they might be succeeded by deposits of barite, 

fluorite, and sulfide minerals of zinc, lead, and copper that are 

generally mined for their content of silver and gold and that make 

up a group commonly known as epithermal. 

Recent explorations of a manganese-bearing vein of barite in 

Nova Scotia fortify these speculations. In ordertotest this speculation, it will be necessary to drill holes that would cut the veinzones 500 to 1,000 feet below the present level of explorations. 

INTRODUCTION 

Since the theory announced by Lindgren about 60 

years ago, it is now widely believed that ore deposits 

with hydrothermal affiliations may be classified into 

five zonal groups: ( 1) epithermal deposits formed within the temperature range of 50° to 200°C at moderate 

pressures, (2) mesothermal deposits formed within 

the temperature range of 200° to 300°C at high pressure, ( 3) hypothermal deposits formed within the ternperature range 300° to 500°C at very high pressure, 

( 4) pyrometasomatic deposits formed within the ter.tperature range 500° to 800°C at very high pressure, 

and ( 5) magmatic deposits proper formed within the 

temperature range 700° to 1,500°C at very high pressures. Other geologists have recognized several other 

groups such as leptothermal, telethermal, and xenothermal. Recent work has indicated modifications of 

the temperatures and pressures stated by Lindgren 

for some of the groups, but the concepts presented 

here would not .be materially affected. 

As one result of recent studies of hydrothermal 

deposits that contain manganese minerals, it seems 

possible to recognize five mineral groups (Hewett, 

1964). Of these, the deepest has been called the basemetal group (Burbank, 1933), to which many veins in 

the San Juan Mountains, Colo., and elsewhere in the 

Southwest are assigned. The mined shoots of ore contain 10 to 35 percent of base-metal sulfides and noteworthy amounts of silver and gold. Characteristic 

gangue miner a 1 s include quartz, ·barite, fluorite, 

rhodonite, rhodochrosite, and huebnerite. The next 

higher group, precious metal (gold-silver) (Nolan, 

1933), is characterized by the same assemblage of 

base-metal sulfides, but these occur in lesser amounts 

than in the base-metal group. This group also contains the same assortment of gangue minerals, but 

chalcedony is the abundant form of silica, and rhodochrosite is more abundant than rhodonite. 

Overlying these two groups are two other groups 

with abundant fluorite and barite whose limits are 

only rarely sharp and distinct. Of the veins with abundant fluorite, only a few wholly lack barite, and other 

veins exploited for barite rarely lack some fluorite. 

Some veins explored for either fluorite or barite have 

local shoots of base-metal sulfide minerals large 

enough to warrant mining. Rhodochrosite is rare in 

these veins, but some contain veins of black calcite, 

which is calcite containing several percent of dispersed 

black manganese oxides. Some of these black calcites 

contain noteworthy amounts of silver (Hewett, 

Fleischer, and Conklin, 1963; Hewett, 1964). 

In the United States, mostoftheexploredepithermal 

veins contain the milieral assemblages characteristic 

of one of the five groups; a few show the mineral characteristics of two groups, and only a few are known 

that show elements of three groups. It is obviously 

a speculative venture to explore any vein to depths as 

great as several thousand feet in order to determine 

whether it contains three or more of the mineral 

groups. 

HYPOGENE VEINS OF MANGANESE OXIDES IN THE 

SOUTHWESTERN UNITED STATES 

Recent work on numerous veins of manganese oxide 

minerals in the Southwestern States indicates that they 

may be regarded as having formed near the original 

surface in the epithermal environment (Hewett, 1964). 

Several mineral associations as well as chemical composition indicate an affiliation with the veins of fluorite · 

and barite. The most abundant m an ganes e oxide 
minerals are the barium m an g an ate s, psilomelane 

and hollandite, but small amounts of barite and fluorite 

are also present in many of the veins. The common 

form of silica is chalcedony, and the wallrocks show 

alteration to adularia, which is also common in the 

deeper sulfide mineral zones. Spectrographic analyses 

of more than 125 samples from many veins show that 

the manganese oxide minerals commonly contain noteworthy zinc, copper, and especially lead; tungsten and 

arsenic are also commonly present in amounts that 

range as high as 1. 5 percent. Table 1 shows spectrographic analyses of seven samples from four veins in 

New Mexico and California. 

The available record at four localities-Manganese 

Valley, Luna, and Black Canyon mines, New Mexico, 

and Terrenates, Chihuahua, Mexico-shows that veins 

con tai ni n g shoots of manganese oxide minerals, 

ranging in manganese content from 20 to 30 percent 

near the surface, become progressively smaller and 

lower in grade at 450 to 500 feet below the existing 

surface. Recently, at the Tower mine, near Socorro, 

N. Mex., a drill hole 1,425 feet long cut the vein zone 

1,000 feet below the surface. At the surface the vein 

contained only abundant manganese oxides with some 

fluorite and barite, but 1,000 feet lower it contained 

only fragments of rhodochrosite in a wide zone in 

which the country rock was altered to chalcedony, clay, 

and adularia. Sparse barite veinlets were found from 

place to place through the entire length of the drill 

hole. The minerals in the vein indicate that it may be 

regarded as representing the precious-metal group. 

None of the manganese-bearing veins in the Southwestern United States has been explored more than a 

few hundred feet below the outcrop; the deepest exploration, at the Luna mine in the Little Florida Mountains of southwestern New Mexico, is only .510 feet; 

but a drill hole, at the previously mentioned Tower 

mine, reaches a depth of 1,000 feet. Thus, in this region 

the possibility that such veins may be succeeded downward by one or more of the mineral groups discussed 

above has not been adequately tested. Such a test has, 

however, been made recently in Nova Scotia, and the 

results are believed to be significant enough to warrant careful attention. 

Table 1.~-Spectrographic analyses of 

hypogene manganese oxides, in percent, from 

New Mexico and California 

[M indicates major constituent] 

New Mexico 

Mine-----

Field No. 

Lab.No.--

Tower Manganese Valley 

207 

63M-24 63M-25 64M-2006 

Mineral-- Psilomel3ne Coronadite 

Collector Hewett Hewett 

Si------- 0.07 0.1 

Al------- .5 . 5 

Fe------- .03 .03 

Mg------- .02 .005 

ca·------- .2 .07 

Na------- .l .03 

K-------- .7 (I 

Ti------- .01 .007 

Mn------- M .J.!. 

Ag------- .0002 0 

As------- . 5 .7 

Ba------- 15.0 7.0 

Be------- .0015 .003 

Co------- .03 .01 

Cr------- .003 .007 

Cu------- .07 .02 

Ga------- .007 .005 

Ge------- 0 0 

Mo------- .07 .03 

Nb------- .003 .003 

Ni------- .003 .003 

Pb------- 3.0 15.0 

Sb------- .2 .3 

Sc------- .0015 .002 

Sr------- .7 .15 

Tl------- .2 .l 

V-------- .03 .02 

W-------- .05 .15 

Y-------- .002 .002 

Yb------- .0003 .0002 

Zn------- .7 .7 

Zr------- .0007 .0005 

Pyrolusite 

Unknown 

0.5 

.15 

.03 

.02 

.l 

.02 

0 

.007 

M 

0 

0 

.7 

.003 

.0015 

.0007 

.07 

.001 

.05 

.003 

.02 

0 

0 

.001 

.l 

.05 

.01 

0 

.007 

.0005 

.05 

0 

2 

297 

Ml038ll 

California 

Black Jack 

298 

Ml03812 280288 

'l'olbard 

271064 

Psilomelane Pyrolusite Psilomelane Psilomelane 

Hewett Hewett Hewett Hadley 

0.1 0.5 

.05 .3 .15 -1 

.003 .07 .07 .015 

.01 .03 .07 .03 

.7 .3 .3 .3 

.l .07 

0 0 0 0 

0 .005 .007 0 

M M M M 

0 0 0 0 

.7 .7 .3 0 

M(20.) 7.0 7.0 M 

0 .001 0 .003 

.001 .001 .005 .0015 

0 0 .0007 .0007 

.02 .07 .02 .007 

0 0 0 0 

0 0 0 .015 

.15 .07 .15 .003 

0 0 0 .003 

0 .0007 0 0 

0 .03 .007 -.01 

0 0 0 0 

0 0 0 

.7 .3 1.50 .7 

.015 .02 .03 0 

.003 .003 .007 .07 

.03 .15 0 .3" 

0 0 0 0 

0 0 0 0 

0 .07 0 0 

0 0 0 0 
RECENT DEVELOPMENT OF MANGANESE 

DEPOSITS IN NOV A SCOTIA AND NEW BRUNSWICK 

Manganese deposits have been known and explored 

in Nova Scotia since 1865 (Hanson, 1932; Johnstonand 

McCartney, 1965). The most productive epoch extended 

from 1870 to 1890, but since then periods of activity 

have been only intermittent and brief until recent years. 

The greatest production of ore from one deposit (23,000 

tons) was derived from that at Markhamville, New 

Brunswick, between 1868 and 1891, but the most extensive and deepest workings are at the New Ross 

mine, Lunenberg County, Nova Scotia; here one shaft 

is 265 feet deep and another 196 feet deep (Kramm, 

1912; Fearing, 1923; Weeks, 1945). Numerous deposits 

have been explored in a belt along the northwest coast, 

adjacent to the Bay of Fundy. Since 1941 there has 

been a spec t a c u 1 a r record of development at the 

Magnet Cove mine near Walton in this belt. 

According to Boyle (1963), in the Walton-Cheverie 

map area (about 9 by 12 miles), 14 manganese-bearing 

deposits have been recorded, as well as others in the 

adjoining area northeast as far as Tennycape. From 

this area, there had been modest development and 

production during the period 1875-1900. In 1941 an 

outcropping body of manganese-bearing barite 

attracted attention, and later development revealed at 

the Magnet Cove mine the most productive barite deposit known in Canada; to 1960, about 2, 700,000 tons 

of barite had been shipped. About 1956, when the barite 

deposit had been developed by an opencut to a depth of 

about 300 feet and by underground workings to about 

600 feet, a program of diamond drilling was begun. 

Soon thereafter, drilling revealed a lenticular body of 

silver-bearing sulfide minerals underlying the veinof 

barite. Recently, this and other similar bodies ofsulfide minerals, as well as the barite body, have been 

developed to a vertical depth of I ,200 feet below the 

surface. Later exploration on the vein of sulfide minerals showed that it extended upward but pinched out 

about 250 feet below the surface. 

In addition to the study of the mine and the local area, 

a detailed study of minerals present in the sulfide assemblage has been made by Boyle and Jambor (1966). 

The ore contains at least 1 0 sulfide minerals of base 

metals and silver which are considered to have been 

deposited by low-temperature solutions (epithermal?). 

Curiously, unless some manganese is present in the 

siderite, no manganese minerals have been observed in 

the sulfide body. Specimens from the upper part of 

the barite body now exposed in the opencut submitted 

to the writer show hausmannite in process of replacement by pyrolusite. Information available to this writer 

concerning the minerals at the Magnet Cove deposit 

Table 2.--Spectrographic analyses of manganese oxides, in percent, 

from the Maritime Provinces of Canada 

[JM indicates major constituent] 

Mine----- Stephens l Stephens 2 Macumber l Macumber 2 New Ross Markham ville 

Field No. 286 287 288 289 2;!1 293 295 296 285 294 

Lab. No.- Ml03778 Ml03779 Ml03780 Ml0378l Ml03783 Ml03784 Ml03809 Ml03810 Ml03808 

Mineral-- Manganite Manganite Manganite Manganite Pyrolusite Manganite Manganite Manganite Manganite Braunite 

Collector Boyle Boyle Boyle Boyle Eakins Eakins Nowlan Nowlan u.s. Eakins 

Museum 

Si------- 0.15 0.1 0.1 0.15 0.05 0.07 0.2 0.15 0.1 2.0 

Al------- • 5 .15 . 5 .5 .15 .15 .3 .15 .2 . 3 

Fe------- .15 .l .02 .l .01 .2 .15 .05 .007 .2 

Mg------- .015 .01 .01 ,02 .007 .02 .03 .03 .007 .02 

Ca------- .3 .3 .07 .7 .15 .05 .15 .05 .5 2.0 

Na------- 0 0 0 0 .2 0 0 0 0 0 

K-------- 0 0 0 0 1.5 0 0 0 0 0 

Ti------- .02 .003 ,002 <,001 0 0 .005 <,001 0 ,007 

Mn------- M M M M M M M M M M 

Ag------- 0 0 0 0 0 0 0 0 .0007 0 

B-------- 0 0 0 0 0 0 0 0 .l .03 

Ba------- .03 1.5 .2 .2 3.0 .05 .02 .015 .l .03 

Be------- .0007 .0015 .001 .001 .005 .007 .007 .005 0 .0003 

Bi------- 0 0 0 0 0 .001 0 0 0 0 

Co------- .02 .015 .015 .03 0 0 0 0 .007 .02 

Cr------- .005 ,002 .002 .001 .0002 .0007 .0007 .0005 0 .001 

Cu------- .07 .07 .07 .05 .05 .15 .15 .15 .l .l 

Mo------- .003 .01 .002 .005 .003 .002 .003 .003 .01 .0015 

Ni------- .015 .015 .01 .015 (I .001 .0007 .001 .002 .0007 

Pb------- 0 0 0 0 1.0 .03 .03 .03 .05 .07 

Sr------- .005 .05 .01 .Ol . 5 .01 .01 .007 .007 .002 

Tl------- .007 .007 .01 ,007 .15 .007 .01 .01 .015 .005 

V-------- .005 .015 .005 .007 .01 .003 .005 .005 .03 .01 

W-------- 0 0 0 (I .007 0 .005 .003 0 0 

Y-------- 0 0 0 0 .003 .003 .005 .003 0 0 

Yb------- 0 0 0 0 .0002 .0001 .00015 ,0001 0 0 

Zn------- .l .07 .l .15 0 .03 .02 .03 .03 .7 

Zr------- 0 .001 0 0 0 0 0 0 0 0 

3 
indicates that hausmannite and probably some of the 

pyrolusite are hypogene; some pyrolusite may be 

supergene. 

The Magnet Cove deposit reveals characteristic 

minerals of three groups that are considered to belong 

to the epithermal zone (Hewett, 1964). The hausmannite 

and pyrolusite represeht the uppermost group; the barite, the next group downward; and the shoot of silverbearing sulfide miner a 1 s represents the preciousmetal(gold-silver)group defined by Nolan(1933). The 

fluorite group, which might be expected to lie between 

the barite and precious-metal groups, is not reported. 

Through the kindness ofR. W. Boyle of the Geological 

Survey of Canada, Don LeHeup of the Magnet Cove 

Barium Co., and J. P. Nowlan of the Department of 

M in e s of Nova Scotia, the writer has been able to 

examine specimens of the minerals from the Macumber, Magnet Cove, Stephens, and New Ross mines in 

Nova Scotia, and the Markham ville mine in New Brunswick (Sidwell, 1952). In table 2, there appear spectrographic analyses of manganese oxides from I 0 of these 

specimens. In these specimens, manganite is the most 

widely dispersed and abundant mineral; hausmannite is 

common in the Magnet Cove deposit; braunite and manganite are present in the Markham ville deposit. To the 

writer, familiar with the modes ofoccurrenceofthese 

minerals in the United States and Cuba, the manganite, 

hausmannite, and braunite in the specimens from Nova 

Scotia and New Brunswick are definitely hypogene; the 

pyrolusite is in part hypogene and in part supergene 

(Smitheringale, 1929). 

COMPARISON OF THE VEINS OF THE MARITIME 

P R 0 VINCE S OF CANADA WITH THOSE OF THE 

SOUTHWESTERN UNITED STATES 

The deposits in the Southwestern States resemble 

those in the Maritime Provinces in Canada, but there 

are some differences. The manganese minerals in both 

regions are oxides, but abundant species in the ores 

from Nova Scotia are absent in the veins in the Southwestern United States. The characteristic oxides in the 

Maritime Provinces include manganite, hausmannite, 

and braunite, with some pyrolusite; in the Southwestern 

States, the most widespread and abundant oxides are 

psilomelane, hollandite, and cryptomelane, with some 

pyrolusite and coronadite. Barite is a persistent gangue 

mineral in both regions but is apparently more abundant 

in the Canadian districts than in the United States. 

Quartz is present in some Canadian deposits, whereas 

chalcedony, which is widespread in the United States, 

is not recorded. In Canada, most of the deposits are 

Table 3.--Spectrographic analyses of hollandite specimens, in percent, from the 

Black Canyon (Gianera) shaft, Luis Lopez district, New Mexico 

[M indicates major constituent] 

Veins--------- 210 211 212 213 262 263 264 265 266 267 

Depth (ft)---- Surface 150 250 400 150 250 300 350 4oo 450 

Collector----- Radtke Radtke Radtke Radtke Bluege Bluege Bluege Bluege Bluege Bluege 

Si------------ 0.7 0.2 0.15 0.15 O.l 0.05 O.l 0.07 0.05 0.15 

Al------------ .7 .3 .15 .2 • 5 . 5 .2 .3 .2 .3 

Fe------------ .l ,015 .005 .007 ,015 .003 .003 .005 .003 .03 

Mg------------ .02 ,02 .01 .015 .01 ,005 .007 .007 .01 .015 

Ca------------ .3 .l .15 .15 .2 .l .15 .15 .l .2 

Na------------ .02 .15 .07 .07 .15 .07 .15 .l .l .07 

K------------- 0 l.O l.O .7 l.O .7 .7 l.O l.O .5 

Ti------------ .01 .0005 .0005 .0003 .0007 .003 .0005 .0007 .0003 ,005 

Mn------------ M M M M M M M M M M 

As------------ .15 .15 .3 .3 • 5 . 5 .3 .3 .2 .5 

Ba------------ M M M M M M M M M M 

Be------------ .0015 .001 .002 .003 .002 .001 .0015 .0015 .001 .005 

Co------------ .01 .02 .01 .03 .015 .015 .007 .02 .015 .03 

Cr------------ .Ol .002 .003 .01 .002 .002 .001 .002 .005 .015 

Cu------------ .02 .03 .03 .l .03 .l .05 .l .07 .15 

Ga------------ .0015 .0015 .0015 .0015 

Ge------------ 0 0 0 0 .002 .003 .003 .003 .003 .003 

Mo------------ .02 .05 .05 .07 .02 .l .05 .07 .07 .07 

Nb------------ .003 .002 .002 .003 .0015 .0015 .0015 .0015 .0015 .om; 

Ni------------ .0015 .003 .002 .007 .003 .002 .003 .005 .003 ,007 

Pb------------ 2,0 0 .2 2.0 .7 1.5 1.5 .3 .l.§) 2,0 

Sb------------ .2 .15 .15 .l .15 .15 .15 .l .07 .15 

Sc------------ .0015 .007 .0005 .0007 .001 .002 .001 .0015 .001 .0015 

Sr------------ .2 .5 .5 . 5 • 5 .15 .2 .3 .2 .3 

Tl------------ .15 .2 .3 .5 .l .03 .1 .15 .2 .05 

V------------- .07 .l .05 .2 .05 .2 .07 .2 .3 .15 

w ------------- .2 .07 .03 .15 .15 .15 .15 .l .07 .2 

Y------------- 0 0 0 0 0 0 0 0 0 ,002 

Yb------------ ,00015 .00015 .0001 .0003 0 0 0 0 0 .0002 

Zn------------ .15 .3 • 5 .7 .2 .15 .2 .l .15 .5 

4 
in Paleozoic carbonate host rocks, but one important 

deposit (New Ross) is in granite. In the United States, 

most of the veins are in layered volcanic rocks that 

are widely altered to adularia, but some are in Precambrian crystalline rocks. 

Minor elements in the manganese oxides of the two 

regions show similarities as well as some distinct 

differences (tables 1, 2, and 3). Noteworthy amounts 

of lead, arsenic, copper, and tungstenarepersistently 

present in the manganese oxides in the veins of the 

Southwest: lead, 0.5 to 4 percent; arsenic, 0.2 to 1.5 

percent; copper, 0.1 to 0.5 percent; and tungsten, 0.1 

to 1. 5 percent (Hewett, 1964 ). In the Canadian manganese oxides, zinc and copper are persistently low, 

rarely in excess of 0.15 percent; small amounts of 

tungsten are sporadic, and arsenic has not been found. 

Small amounts of thallium, generally 0.01 to 0.1 percent, are persistently present in the manganese oxides 

of both regions. Alteration of the host rocks to adularia 

is common in the United States but is not recorded in 

Canada. 

Most of those who have studied the Canadian deposits 

have concluded that the manganese oxide vein minerals 

are supergene, whereas those who have studied the 

vein deposits in the United States in recent years conclude that most of the oxides are hypogene. 

AREAS IN THE UNITED STATES ATTRACTIVE 

FOR EXPLORATION 

As the result of widespread search for manganese 

deposits during the two World Wars, many veins of 

manganese oxides were found in the Southwestern 

United States. Most of the explored deposits lie in a 

broad arc that extends from southern Colorado and 

southwestern New Mexico across southern Arizona into 

southeastern California. Only a few are known in Utah 

and Nevada, and only one is known in Oregon. About 

250 veins are known in the Southwest; the location of 

the principal districts is shown in figure 1. 

There follow brief descriptions offive veins in three 

districts in New Mexico and California and a de scription of a fourth district in Arizona that are worthy of 

attention as sites for exploration in depth to test the 

vertical distribution of the mineral groups considered 

to belong to the epithermal zone. 

Little Florida Mountains, Luna County, New Mexico 

Within an area of about 1 square mile at the south 

end of the Little Florida Mountains, Luna County, 

N. Mex., there are the deepest shaft on a vein of manganese oxides (Luna mine, 510 ft) and the greatest 

explored length of a vein (Manganese Valley, about 

2, 700 ft) in the entire Southwest. The production of 

crude ore and concentrate shipped is ·32, 704long tons, 

exceeded only by the Black Jack mine in the McCoy 

Mountains, Calif., (about 71,000 tons). Within thearea 

of the Little Florida Mountains, numerous other veins 

have been less extensively explored-Manganese Valley No. 13 and Killion, for example. 

The mines were first examined by the writer in 1924 

and were reexamined several times in the following 

5 

6 years. In 1938 Lasky and Thayer mapped the geology 

of the Little Florida district and examined the mines 

(Lasky, 1940); in 1941-42 the U.S. Bureau of Mines 

drilled 13 holes below the existing workings (Evans, 

1949) and thoroughly sampled the accessible workings. 

About 1960, in connection with a review of the manganese deposits of the State, the workings were reexamined (Farnham, 1961). Aspartofareviewof veins 

of manganese oxides in the Southwest, the writer has 

recently made spectrographic and X-ray-diffraction 

analyses of several specimens. 

The Little Florida Mountains are carved from a 

block of layered fragmental volcanic rocks separable 

into two units; the lower unit is interbedded flows, 

tuffs, and breccias about 3,000 feet thick; and the upper, 

also layered fragmental volcanic rock about l,OOOfeet 

thick, is considered a fanglomerate. Both are well 

indurated; the layering dips eastward at a low angle. 

The veins form an echeloned system that lies along 

the eastern slope of the Little Florida Mountains. As 

regional geologic mapping shows that there are only 

slight changes in the rocks for several thousand feet 

below the mine workings, the veins should persist 

downward at least that distance. The manganese minerals consist of several oxides in veins that have a 

strike length ol500 to 3,000 feet; underground workings 

prove that several extend more than 500 feet below 

the local surface (Manganese Valley, Luna). 

Manganese Valley mine.-The stopes and sampling 

records of the Manganese Valley mine workings indicate that the manganese oxides are concentrated in at 

least three distinct shoots (Evans, 1949), the greatest 

lengths of which were found in the upper levels; also 

that the lengths as well as percent of contained manganese minerals in the veins decrease downward. Of 

the 13 drill holes, only one attained a depth of as much 

as 200 feet below the existing stopes (middle shoot). 

On the lower level, 19 samples ina distance of 100 feet 

showed the vein to have an average width of 5 feet and 

a manganese content of 25 percent; 240 feet lower the 

vein zone was 13 feet widebutcontainedonly about 1.5 

percent manganese as oxide. 

The oxides from the Manganese Valley vein (No. 12) 

have not been thoroughly analyzed for minor elements. 

Mill concentrate of the oxides mined in 1924 from the 

northern shoot, upper level, contained 75 to 77 percent 

manganese oxide, 0.468 to 0.558 percent lead, 0.068to 

0.077 percent copper, and 0.028 to0.032percentarsenic. One spectographic analysis of a specimen from the 

lower level of the middle shoot appears in table 1. 

Luna mine.-About 2,500 feet northwest of theManganese Valley mine, the Luna vein, trending northwest, 

crops out for 2,500 feet and is explored by a shaft to 

a depth of 510 feet; it is also explored by drifts at five 

levels whose aggregate length is about 1, 700 feet. There 

is one major shoot of manganese oxides; the greatest 

horizontal length, about 200 feet, is on the upper three 

levels, whereas the proved length on the lower two 

levels is less than 100 feet and the manganese content 

is uniformly less than 5 percent. About 1941-42, the 

U.S. Bureau of Mines thoroughly sampled the vein zone 
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r-- LA CANDELA& 

OBREGON& 

100 200 MILES L_ ________ _L _____ ~ 

Figure 1,-Map showing distribution of explored veins of hypogene oxides of manganese in the Southwestern 

United States and northern Mexico. 

6 
to the lowest level of the shaft, 500 feet, and drilled 

four holes, of which the deepest, 540 feet, cut the vein 

zone (Evans, 1949). Near the bottom, one hole cut veinlets of manganese oxides over a distance of 33 feet; the 

central part of the zone, 18 feet thick, contained 5 to 

7 percent of manganese as oxides. As the vein on the 

second level largely ranged from 3 to 6 feet in width 

and, sampled over a distance of about 275 feet, 

contained 10 to 35 percent manganese, it is clear that 

the manganese content decreased considerably in the 

explored depth of 500 feet. No samples of manganese 

oxides from the Luna vein have been examined by X-ray 

diffraction or spectrographic analysis; so the minerals 

and content of minor elements have not been determined. Chemical analyses of a specimen of oxides 

from the Killion vein, halfway between the Luna shaft 

and the Manganese Valley adit, appear in Hewett and 

Fleischer, table 6 ( 1960) and Hewett, Fleischer, and 

Conklin, table 3 (1963). 

Luis Lopez district, Socorro County, New Mexico 

More manganese oxide veins have been explored and 

the production of high-grade oxides has been greater 

in the Luis Lopez district, Socorro County, N.Mex., 

than in any other in the Southwest. Most of the explored 

veins lie within an area about 15 miles in diameter, 

5 to 10 miles southwest of Socorro. The production of 

high-grade concentrate to 1957 was about 77,000tons, 

of which about 26,295 tons was derived from the Red 

Hill group, 10,613 tons from the Tower (Lucky Strike 

No. 2), and 16,060 tons from the B 1 a c k Canyon 

(Gianera); the remainder was derived from numerous 

other mines (Jicha, 1956; Miesch, 1956;Farnham, 

1961). 

Tower (Lucky Strike No.2) mine.-At this mine an 

opencut 1,600 feet long and about 30 to 40 feet wide 

explores a zone of oxide veins to a depth that ranges 

from 80 to about 150 feet. As this is one of the most 

persistent veins known in New Mexico, the vein and its 

minerals have been closely studied by the writer. 

Here and at most of the other productive veins of this 

district, the host rock is rhyolite, but near the veins 

the feldspars are widely altered to adularia. At this 

mine, most of the veins of manganese oxideminerals 

are confined to zones 5 feet or more thick adjacent to 

the walls. The veins are made up of layers of manganese oxides as much as several inches thick that 

cement angular fragments of altered host rock; probably psilomelane is the most abundant oxide, but hol1 landite and coronadite are persistently present. 

Coronadite is so abundant that most shipments of concentrate contained 2 to 4 percent lead. Two spectrographic analyses are shown in table 1. Amongthe nonmetallic minerals, crystals of fluorite are present 

in the early and late layers of manganese oxides, and 

small amounts of barite and chalcedony are present. 

At the Optimo prospect, 2,000 feet north of the Tower 

opencut, the principal mineral in the vein (4 ft wide) 

is coronadite. 

7 

Black Canyon (Gianera) mine.-At the Black Canyon 

mine, about 1,500feet southwest oftheTower mine, the 

shaft ex p 1 ores to a depth of 450 feet a vein that is 

parallel to that at the Tower mine; there are drifts on 

the vein at six levels. Unlike the Tower vein zone, 

manganese oxides form crusts several inches thick on 

fractures in the vein zone several feet wide. On the 

levels, the shoot is only 200 feet long, but minable ore 

persists to the lowest level. 

Table 3 presents spectrographic analyses of two 

suites of samples collected from the surface downward 

on the separate levels to the bottpm of the shaft. The 

analyses of the suite of four samples indicate an almost regular increase downward of the contents of 

copper, lead, zinc, molybdenum, arsenic, and thallium. 

Analyses of the second suite of six samples show less 

consistent trends. 

Arlington district, Riverside County, California 

ln the northwest part of the McCoy Mountains, eastern Riverside County, Calif., several groups of veins 

of manganese oxides have been extensively explored 

(Trask, 1950). The Black Jack group, not named in 

figure 1 but lying about 25 miles north of the Paymaster district, shipped ore as early as 1916, but the 

greatest development took place after the war of 1941-

45, and there was further exploration under a loan 

from the Government in 1958. The total length of underground tunn~s and drifts exceeds 6, 000 feet, and more 

than 70,000 tons of ore has been shipped to date. The 

early work explored one vein for about 600 feet, but 

later work discovered several other parallel veins; 

they trend generally north and dip about 55°W. The 

greatest depth of workings below the surface is about 

250 feet. The most abundant manganese oxide is psilomelane, but there is some pyrolusite; three spectrographic analyses appear in table 1. The contents of 

copper, lead, and zinc are less than 0.10 percent, but 

arsenic is as much as 0. 7 percent and tungsten as 

much as 0.15 percent. 

The principal vein crops out along the ridge which 

forms the north end of the McCoy Mountains; west of 

this ridge, there is a small valley from which holes 

could readily be drilled to explore the veins in depth. 

Probably a drill hole could be drilled west of the vein 

that would cut the main vein 500 feet below the main 

level within a distance of 800 feet. 

Aguila district, Maricopa County, Arizona 

The Aguila district includes an area about 15 miles 

long and 4 miles wide in west-central Arizona. The 

first discoveries were made during the first World 

War when six propertieswereexploredandabout4,000 

tons of ore was shipped. During the second World War, 

there was little activity, but by 1958 the total number 

of explored deposits was about 25, and considerable 
low-grade ore had been shipped. During the postwar 

period, the greatest production came from the opencut 

of the Black Rock mine. Most of the explored deposits 

are simple veins of manganese oxides, and the latest 

record indicates that no explorations exceeded 100 feet 

in depth. 

During a brtef examination of the district in 1963, 

F. S. Simons, of the Geological Survey, collected numerous samples of the vein oxides, and spectrographic 

analyses have been made of 17 samples of the crude 

oxides and three samples of the manganese oxide residues (insoluble in dilute HCl) from associated black 

calcites. Measurable amounts of copper are present in 

every sample of crude oxides, largely ranging from 

0.05 to 2 percent and in excess of 0.15 percent in five 

samples. Measurable amounts of lead are present in 

every sample and more than 0.2 percent in three samples; measurable zinc is present in every sample and 

in excess of 0.1 percent in seven samples. Measurable 

tungsten is present in 16 samples, attaining 1.5 percent in one sample and in excess of 0.1 percent in 

seven samples. Measurable thallium is present in 

every sample, and more than 0.1 percent in six samples. Small fractions of an ounce of silver to the ton 

are present in two samples, but 1.5 ounces to the ton 

is present in the residues from two samples of black 

calcite. 

For several reasons, it is concluded that the veins 

of man g an e s e oxide in this district are hypogene 

(Hewett and Fleischer, 1960; Hewett, Fleischer, and 

Conklin, 1963; Hewett, 1964). 

From the samples collected by Simons, 13 were 

selected for assay for silver. A black calcite sample 

from the Hatton mine, Yavapai County, contained about 

5 percent dispersed manganese oxide and contained 

0.10 ounce of silver to the ton. Of the other samples, 

eight showed traces of silver and four showed no silver. 

CONCLUSIONS 

In the modern era, with the increasing need for 

numerous minerals, many types of inquiry are being 

used in the search for new sources. In a broad way, 

the greater the number of types of data, the greater the 

chances of success in discovery. Unfortunately, however, even after exhaustive study of areas by all the 

methods available, the element of luck still plays a 

great part in discovery. 

The theory of dow n w a r d changes in epithermal 

deposits is based largely upon the kind, abundance, and 

paragenetic relations of the minerals, the chemical 

elements present in the minerals and their abundance, 

and the nature of the alterations of the wallrocks. 

The theory seems to be fortified by the recent explorations at the Magnet Cove mine, Nova Scotia. These 

explorations to the depth of 1,200 feet reveal three of 

the five groups of the epithermal zone, but one group, 

that with abundant fluorite, present in the Southwestern 

United States, is missing in the Magnet Cove mine. 

8 

In the Southwestern United States in the vein depositE 

which have been explored to the greatest depths (Manganese Valley, 500ft; Luna, 510ft; Black Canyon, 45( 

ft), the oxides lie in well-defined shoots, which are 20( 

to 500 feet long on the upper levels but narrower ir: 

the lowest levels. Explorations in depth should be sc 

placed as to cut the downward extensions of the knowr: 

shoots, not less than 500 feet and probably as much as 

1,000 feet below the lowest explorations. There is 

general agreement that the deposits of the epithermal 

zone were formed at depths offrom 3,000to 5,000 feet 

below the original surfaces; so the upper parts of the 

precious-metal group would probably lie 1,000to2,00C 

feet below those original surfaces. 

REFERENCES CITED 

Boyle, R. W., 1963, Geology of the barite, gypsum, 

manganese and lead-zinc-copper-silver deposits of 

the Walton-Cheverie area, Nova Scotia: Canada 

Geol. Survey Paper 62-25, p. 1-36. 

Boyle, R. W., and Jambor, J. L., 1966, Mineralogy, 

geochemistry, and origin of the Magnet Cove baritesulphide deposit, Walton, Nova Scotia: Canadian 

Mining and Metall. Bull., v. 59, no. 654, p. Pl209-

P1228. 

Burbank, W. S., 1933, Epithermalbase-metaldeposits, 

in Ore deposits of the Western States (Lindgren 

Volume): New York, Am. Inst. Mining Metall. Engineers, p. 641-652. 

Evans, A. M., 1949, Investigation of manganese deposits, Little Florida Mountains mining district, Luna 

County, New Mexico: U.S. Bur. Mines Rept Inv. 

4536, 11 p. 

Farnham, L. L., 1961, Manganese deposits of New 

Mexico: U.S. Bur. Mines Inf. Circ. 8030, 176 p. 

Fearing, F. C., 1923,ManganesedepositsofLunenburg 

County, Nova Scotia: Eng. and Mining Jour.-Press, 

v. 115, no. 1, p. 11-15. 

Hanson, G., 1932, Manganese deposits of Canada: 

Canada Geol. Survey Econ. Geology Ser. 12, 120p. 

Hewett, D. F., 1964, Veins of hypogene manganese 

oxide minerals in the southwestern United States: 

Econ. Geology, v. 59, no. 8, p. 1429-1472. 

Hewett, D. F., and Fleischer, Michael, 1960, Deposits 

of the manganese oxides: Econ. G eo 1 o g y, v. 55, 

no. 1, p. 1-55. 

Hewett, D. F., Fleischer, Michael, and Conklin, N., 

1963, Deposits of the manganese oxides--supplement: Econ. Geology, v. 58, no. 1, p. 1-51. 

Jicha, H. L., Jr., 1956,Manganesedepositsofthe Luis 

Lopez district, Socorro County, New Mexico, in 

Gonzalez Reyna, J., ed., Symposium on deposits 

of manganese: Internat. Geol. Cong., 20tli, Mexico 

City, 1956, v. 3, p. 231-253. 

Johnston, A. G., and McCartney, W. D., 1965, Manganese occurrences in Canada (preliminary reports 

and metallogenic map): Canada Geol. Survey Paper 

64-37, 63 p. 

Kramm, H. E., 1912, On the occurrence ofmanganese 

at New Ross in Nova Scotia: Canadian Mining Inst. 

Trans., v. 15, p. 210-217. 
Lasky, S. G., 1940, Manganese deposits in the Little 

Florida Mountains, Luna County, New Mexico: U.S. 

Geol. Survey Bull. 922-C, p. 55-73. . 

Miesch, A. T., 1956, Geology of the Luis Lopez Manganese district, Socorro County, New Mexico: New 

Mexico Bur. Mines and Mineral Resources Circ. 

38, 31 p. 

Nolan, T. B., 1933, Epithermal precious-metal 

deposits, in Ore deposits of the Western States 

(Lindgren Volume): New York, Am. Inst. Mining 

Metall. Engineers, p. 623-640. 

9 

Sidwell, K. 0. J., 1952, Manganese oreoccurrencesin 

New Brunswick: Fredericton, New Bruns w i c k 

Resources Devel. Board, 168 p. 

Smitheringale, W. V., 1929, Notes on etchingtests and 

X-ray examination of some manganese minerals: 

Econ. Geology, v. 24, no. 5, p. 481-505. 

Trask, P. D., and others, 1950, Geologic description of 

the manganese deposits of California: California 

Div. Mines Bull. 152, 378 p. 

Weeks, L. J., 1945, Manganese, New Ross, in Report on 

mines* * * 1945: Nova Scotia Dept. Mines,p.135-

166. 

U. S. GOVERNMENT PRINTING OFFICE : 1968 0- 286-135