Selenium in Some 

Epithermal Deposits 

of Antimony, Mercury 

and Silver and Gold

GEOLOGICAL SURVEY BULLETIN 11 12-A

Selenium in Some 

Epithermal Deposits 

of Antimony, Mercury 

and Silver and Gold

By D. F. DAVIDSON

V

CONTRIBUTIONS TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN 1112-A

Deposits of silver and antimony are commonly highly seleniferous in contrast to 

similar deposits of gold and mercury

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D.C. - Price 15 cents (paper cover)
CONTENTS

Abstract__ ___________________________________________

Introduction-___________________________________________

Acknowledgments __________________________________

Selenium mineralogy in epithermal deposits._______________

Field testing for selenium______________________________

Epithermal deposits of silver and gold,__________________

Selenium in epithermal deposits of silver and gold______

Results of field tests for selenium at a silver-gold deposit . 

Epithermal mercury deposits___________________________

Selenium in mercury deposits._______________________

Results of field tests for selenium at mercury deposits. __ 

Epithermal antimony deposits__________________________

Seleniferous epithermal antimony deposits_____________

Results of field tests for selenium at antimony deposits. _ 

Discussion_ ___________________________________________

Literature cited ________________________________________

Index_ _______________________________________________

Page 

1

1

2

2

3

4

5

6

6

10

12

13

14

17

ILLUSTRATIONS

FIGURE 1. Map of the Western United States (exclusive of Alaska and 

Hawaii) showing the location of mercury, antimony, and silver deposits sampled for selenium_______________________

2. Map of the Western United States (exclusive of Alaska and 

Hawaii) showing location of seleniferous antimony deposits.

Page

10

TABLES

TABLE 1. Selenium-bearing minerals and their selenium content______

2. Some seleniferous epithermal deposits of silver and gold described in geologic literature.___________________________

3. Results of field tests for selenium of grab samples from silver 

deposits__-___________________________________________

4. Results of field tests for selenium of grab samples from mercury 

deposits.-_ ___________________________________________

5. Selenium and antimony content of selected antimony ore samples from the Western United States_____________________

6. Results of field tests for selenium of samples from antimony 

deposits and a mill.___-_-_______-____-______-_--------

Page 

3

11

13

CONTRIBUTIONS TO ECONOMIC GEOLOGY

SELENIUM IN SOME EPITHERMAL DEPOSITS OF 

ANTIMONY, MERCURY, AND SILVER AND GOLD

By D. F. DAVIDSON

ABSTRACT

The presence of selenium in some epithermal ores of silver, gold, and mercury 

has long been known. Recent work indicates that epithermal silver and antimony 

deposits are commonly highly seleniferous, and that gold and mercury deposits 

are only rarely so.

Selenium in silver and antimony deposits is associated with these metals in 

ore minerals and is not found in other minerals of the deposits. This relation 

with ore minerals also occurs in the few gold and mercury deposits which contain selenium.

Most published reports suggest that silver and antimony deposits are related 

genetically to crystalline igneous rocks. Selenium in silver and antimony deposits may have been liberated from crystallizing magma as a part of the process 

of crystallization and thus have been made available for deposition with the 

ore metals.

INTRODUCTION

Epitliermal deposits have been described by Lindgren (1933, p. 444) 

as "metalliferous deposits formed near the surface by ascending 

thermal waters and in genetic connection with igneous rocks." They 

are commonly in the form of jBssure veins, and generally occur in 

igneous flow rocks, particularly in andesite, latite, trachyte, or rhyolite, but rarely in basalt. They are usually in regions of late igneous 

activity, near Tertiary intrusive masses and, are for the most part 

of simple sulfide mineralogy. These epithermal deposits constitute 

the source of a large part of the world's production of gold, silver, and 

quicksilver. Most of the bonanzas of the cordilleran region, for example, Virginia City, Cripple Creek, Pachuca, and Guanajuato, are 

epithermal ore deposits.

Discussed in this report is the selenium content of some epithermal 

deposits of precious metals, antimony, and mercury. Similar deposits 

are well described in Lindgren's (1933), and Emmons' (1940) texts 

on mineral deposits.

The presence of selenium in many epithermal ores has long been 

known. At a few deposits, such as the DeLamar mine at Silver City, 

Idaho, the ore minerals are selenides. Typically, however, the sele-
2 CONTRIBUTIONS TO ECONOMIC GEOLOGY

nium is in either sparsely disseminated selenide minerals, or in some 

form in which it is not easily recognized.

Epithermal deposits, on the basis of present knowledge, contain 

higher concentrations of selenium than most other types of hydrothermal deposits, although the total selenium content of any given deposit 

is not large.

Most epithermal deposits of the United States are in, or near the 

Cordillera, and most seleniferous rocks described by workers with 

seleniferous soils and plants occur in this same area. However the 

rocks, which have been the parent materials for the seleniferous soils, 

are with few exceptions Cretaceous in age, and deposits of the type 

described in this report are usually Tertiary; thus there can be no 

direct relation. Still the juxtaposition of these areas is suggestive.

In the course of a continuing study of the geology and geochemistry 

of selenium, examinations of ores, rocks, and minerals from several 

epithermal deposits have been made, and it is desirable to report the 

new data at this time. Some published data concerning the occurrence of selenium in epithermal deposits are also presented here in 

tabular form.

ACKNOWLEDGMENTS

The information in table 5 has been contributed by Fred H. Dakin, 

Burlingame, Calif., and the writer is grateful to Mr. Dakin for permitting its publication. The writer was aided in the field by T. J. 

Mosher.

SELENIUM MINERALOGY IN EPITHERMAL DEPOSITS

Epithermal deposits as a class are noted for their simple mineralogy, and the deposits discussed in this report, of precious metals, 

antimony, and mercury, are not exceptions. Table 1 lists the minerals 

sometimes present in such deposits which contain appreciable amounts 

of selenium. Descriptions of the minerals can be found in any 

standard textbook of mineralogy.

Two groups, of three minerals each, listed in table 1 are of particular interest in a discussion of selenium mineralogy, because they may 

indicate isomorphous substitution of selenium for sulfur in sulfide 

minerals of silver and mercury. They are the naumannite-aguilariteargentite group, and the tiemannite-metacinnabar-cinnabar group.

Diadochic substitution of selenium for sulfur takes place readily 

because selenium and sulfur have like valence ( 2), and because the 

difference between the ionic and covalent radii is so small. Coleman 

and Delevaux (1957, p. 522) suggested the possibility that the isomorphous series FeS2-FeSe2 may be complete at moderately high 

temperatures and pressures. Earley (1950, p. 356) has synthesized
SELENIUM IN EPITHERMAL DEPOSITS

TABLE I. Selenium-bearing minerals and their selenium content 1

Type of deposit (grouped according 

to principal product)

Silver and gold deposits:

Naumannite(Ag2Se< )__________.___..__.__.____--__.___-----.-_ 30. 2

Aguaarite(Ag4SeS)--_--_--_--- -_. - - -- 14. 8

Argentite(AgoS)___ ---.-- - ------- - .0010

BerzelianiteCCuaSe) _____--____-____-_----__----------_--_-- 40. 0

Eucairite(CuAgSe).______-_---_._.-__-._-__-. _ - 32. 5

Umangite (Cu3Se2 ) _______-___--.._-__--_---------------------- 45. 1

Clausthalite(PbSe)_______-_-_---__-__-------------.----------- 31. 4

Klockmannite(CuSe)_____-__-._______________________________ 2 55. 4

Guanajuatite(Bi2Se3)__-_____..-. __________-________-__-_---- 2 34. 33

Paraguanajuatite(Bi2Se3)____ ...____________-_-___------__-_ 2 36. 2

Mercury deposits:

Ti<snannite(HgSe)-___-__-__-_--_--__-_--_------------------- 29.2

Metacinnabar, var. onofrite(Hg(S,Se))_______-_------_--------- 8.4

^CinnabarCHgS)-------.------. ------------------------------- - 0001

Antimony deposits:

Stibnite(Sb2S3 )----------^----------------------------------- 3 -0009

1 Modified from Michael Fleischer (written communication, 1956).

2 Theoretical maximums, meaningful values from natural material not available.

3 Selenium contents, in excess of 1.00 percent are given on p. 12.

the series PbS-PbSe, and Coleman (1958, p. 1679) lias demonstrated 

the natural occurrence of the series. There is little reason a similar 

system may not exist for silver, and it has been demonstrated that 

such a system exists for mercury (Earley, 1950, p. 358-360; Nikolskaya and Regal, 1956). Bethke (1956) has shown that metacinnabar, 

"onofrite'' (seleiiiaii metacinnabar) and tiemannite form a complete 

series in samples from Marys vale, Utah, but he suggested that the 

structure of cinnabar is such that only trace amounts of selenium 

may substitute for sulfur in the mineral.

Stibnite containing more than 1.00 percent selenium is reported 

in table 5 of this report, although the highest selenium content in 

stibnite reported by Fleischer (table 1) is only 0.0009 percent. Further 

work is being done with this material, and it seems probable that 

selenium is substituting for sulfur in stibnite in a partial series: 

Sb2S3-Sb2 (S2Se).

FIELD TESTING FOR SELENIUM

Qualitative field tests for selenium were used in fieldwork and were 

found very helpful in determining the distribution of selenium in 

ores and rocks. The methods used were primarily those described 

by Peterson, Jensen, and Anderson (1957).

In the present report the methods have been called simply "pyrosulfate," "caustic fusion," and "heated tube." The pyrosulfate and 

caustic fusion tests are based upon the facts that selenium occurs 

in nature as selenides, elemental selenium, selenites, and selenates, 

and that these compounds can be oxidized, or reduced, to form ele-
4 CONTRIBUTIONS TO ECONOMIC GEOLOGY

mental selenium, which can in turn be volatilized, and condensed, 

to form a visible elemental selenium mirror.

The pyrosulfate test consists of heating a finely ground sample 

in a test tube with potassium pyrosulfate and tartaric acid. Selenium, 

if present, will coat the tube walls. The caustic fusion method, used 

for samples containing much carbon or sulfur, comprises heating a 

ground sample with sodium peroxide, and sodium hydroxide, then 

heating the product of this reaction with potassium pyrosulfate, and 

tartaric acid. As in the pyrosulfate test, selenium, if present, will 

form a mirror. In the writer's experience, these methods are simple 

and reasonably fast and reliable, although selenium often will not 

be detected if present in concentrations below 50 ppm (parts per 

million).

If selenium is in selenide or elemental form, it is possible to test for 

it by simply heating a ground sample and watching for formation 

of a selenium mirror, or testing for odor (heated tube test). However, this method of testing is somewhat unreliable.

EPITHERMAL DEPOSITS OF SILVER AND GOLD

No attempt is made to refer to all of the geologic literature describing epithermal deposits of silver and gold for such completeness is 

not needed to serve the purpose of this report.

Nolan (1933), however, has presented a useful summary of the 

characteristics of epithermal silver and gold deposits and much of 

the following information is taken from his compilation. He indicates that epithermal deposits of precious metals in the Western United 

States are a part of a great circum-Pacific zone characterized by the 

occurrence of these deposits, and that they are found in regions of 

Tertiary volcanism.

Nolan discusses a classification of precious metal epithermal deposits 

proposed by Ferguson (1929) by which these deposits are divided 

into two types according to the ratio by weight, of gold to silver in 

hypogene ore. The first class, called the silver-gold class includes 

deposits in which silver equals or exceeds gold, and the second class, 

gold-silver, comprises deposits in which gold exceeds silver.

Silver-gold deposits are commonly found in well-defined fault 

fissures that may extend for long distances both horizontally and 

vertically. In most localities the faults seem to be of tectonic origin, 

cut the volcanic country rock, and have no direct connection with the 

extrusion of the volcanics. Silver-gold deposits probably are derived 

from large deep-seated igneous sources, and they commonly contain 

selenium, but little tellurium.

Unlike silver-gold deposits, gold-silver deposits are commonly
SELENIUM IN EPITHERMAL DEPOSITS

localized by fractures which in many places seem to be genetically 

related to the emplacement of the igneous rocks with which they are 

associated. These fractures are generally discontinuous, and rarely 

have measurable displacements. Gold-silver deposits are probably 

derived from small shallow, rapidly cooling (thus probably finegrained) igneous sources, and commonly contain tellurium, but little 

selenium.

SELENIUM IN EPITHERMAL DEPOSITS OF SILVER AND GOLD

Seleniferous epithermal deposits of silver and gold are widespread, 

and well known. Lindgren (1933) and Nolan (1933) have published 

short descriptions of some of them and the listing of deposits composing table 2 is compiled from these descriptions. There are other such 

deposits.

Of the 12 deposits listed, 11 are silver-gold deposits. At only 1 

deposit, in the Hauraki district of New Zealand, does gold content of 

ore exceed silver.

TABLE 2. Some seleniferous epithermal deposits of silver and gold described in

geologic literature

Geographic 

location

United States:

Utah.. 

District

hee County. 

Yankee Fork, Custer Countv. 

Jarbidge, Elko

County.

Esmeralda Counties.

Aurora, Mineral

County.

Piute and Sevier 

Counties.

Principal 

product

.. do.... 

 -do.... 

- do.......

 do.......

 -do.... 

 -do.......

 -do.......

 .. do........

Gold--.-. 

Mode of selenium occurrence

Up to 2 percent selenium in 

silver concentrates.

mineral.

Up to 2 percent selenium reported in ore.

lite, berzelianite"zorgite" 

(a mixture of clausthalite 

and umanpite) .

thalite eucairite, klockmannite.

aguilarite, guanajuatite, 

paraguanajuatite.

Up to 4.35 percent selenium 

reported in bullion.

Reference

485, 496; Xolan, 

1933, p. 624, 626, 

633. 

Nolan, 1933, p. 633.

Lindgren, 1933, p.

485; Nolan, 1933, 

p. 635.

488, 496. 

Nolan, 1933, p. 624, 

625, 634. 

Nolan, 1933, p. 635.

Nolan, 1933, p. 639.

Thompson, 1954.

497. 

Nolan, 1933, p. 625, 

640. 

Lindgren, 1933, p.

496. 

Do.

Doi

Lindgren, 1933, p.

481, 496. 

Lindgren, 1933, p.

498.

529250 6C
6 CONTRIBUTIONS TO ECONOMIC GEOLOGY

EESULTS OF FIELD TESTS FOB SELENIUM AT A SILVEB-GOLD

DEPOSIT

Field tests for selenium were made during the summer of 1957 at 

two mines of the Silver City district, Owyhee County, Idaho. This 

district is one of the few in the United States at which selenium minerals comprised a substantial part of the ore. At the DeLamar mine, 

virtually all silver was recovered from silver selenide (naumannite), 

and K. G. Coleman (written communication, 1957) reports that 1 

sample of pure pyrite from DeLamar may contain 0.90 percent 

selenium. The district has long been dormant and sampling for 

selenium was restricted to material on mine dumps. Location of the 

district is shown on figure 1 (locality 9). Table 3 presents the results 

of field testing for selenium six samples from the dumps of the Trade 

Dollar mine at Silver City, and one sample from the DeLamar millsite, at DeLamar. None of the samples contained detectable amounts 

of selenium. Four samples from the Trade Dollar mine were of vein 

material, and two of mineralized wallrock. Selenium may have accompanied only silver in the veins for the dumps represent material 

from which silver minerals have been carefully removed.

The dumps of the DeLamar mine have been remilled in recent 

years and no samples of seleniferous silver ore could be found on the 

property.

TABLE 3. Results of field tests for selenium of grab samples from silver deposits

Locality

Idaho: 

SilTer City district, Owyhee County

DO :,

Do 

Do 

Do. 

Do 

DeLamar mine

No. 

(fig. 1)

9

Sample description

tite (?).

pyrite.

mill.

Test method

C austic fusion. 

 do...... 

 .do...... 

 -do...... ~

Caustic fusion... - 

 . .do. .......

Caustic fusion.. .-

Result of 

test*

Do. 

Do.

Do.

Do.

Do.

Do. 

Do.

Do.

Do.

' Negative result indicates selenium content less than 50 ppm.

EPITHERMAL. MERCURY DEPOSITS

A useful compilation by Boss (1933) of information relating to 

epithermal mercury deposits indicates that the deposits are widespread in the Western United States and that only two, in Arkansas 

and Texas, are known outside the cordilleran region. Most deposits 

are probably related to volcanic rocks, or hot springs of Tertiary or 

later age. Some deposits, not obviously related to late volcanism, are
SELENIUM IN EPITHERMAL DEPOSITS 7

classified with the others because of their structural relations and 

mineralogy. Eoss does not, in most of his district descriptions, attempt to relate mercury deposits to source materials from which the 

mercury was derived. Where Ross has drawn this relation, for example in the Copper Basin district near Prescott, Ariz., mercury 

deposits probably occur in association with fine-grained intrusive 

rocks.

7"T 

MONTANA

EXPLANATION

O2 

Mercury deposit

C8

Antimony deposit

Silver deposit

__..__.. . 4--- --~

FIGURE 1. Map of the Western United States (exclusive of Alaska and Hawaii) showing 

the location of mercury, antimony, and silver deposits sampled for selenium. Numbers 

refer to locality and sample descriptions in table 4 (mercury), table 6 (antimony), and 

table 3 (silver).
8 CONTRIBUTIONS TO ECONOMIC GEOLOGY

SELENIUM IN MEBCUBY DEPOSITS

Selenium has long been known in mercury deposits, and selenium 

minerals have been reported from many mercury mines in the United 

States. For example, Becker (1888, p. 375) mentions seleniferous 

mercury deposits in California, Eoberts (1940), and Lindgren (1915) 

in Nevada, and Butler and others (1920, p. 551-552), have described 

the Lucky Boy mine near Marysvale, Utah, at which the ore was 

principally mercury selenide. In spite of this widespread occurrence 

of selenium minerals in mercury deposits, highly seleniferous mercury 

ores are rare, and the Lucky Boy mine is the only deposit of its kind 

in the United States. Tiemannite is probably the most common 

selenium mineral in the mercury deposits.

RESULTS OF FIELD TEST FOE SELENIUM AT MEBCUBY DEPOSITS

During the summer of 1957, six mercury deposits were visited by 

the writer and 38 field tests for selenium were made of a total of 24 

samples. Sample localities and descriptions, and results of field tests 

are reported in table 4. Locations of the deposits are shown on figure 1. Selenium was recognized only in samples from the Lucky Boy 

mine, Piute County, Utah. Selenium, if present in any of the samples 

tested at other localities, was in concentrations too low to be recognized 

by field testing and it is concluded that neither cinnabar nor the other 

sulfide minerals tested at these properties contain much selenium.

Field tests at the Lucky Boy mine indicate, within the limitation of 

the test, that selenium is present only in the mercury-bearing minerals, for samples of limestone in direct contact with masses of 

tiemannite contain no identifiable selenium.

EPITHERMAL ANTIMONY DEPOSITS

F. C. Schrader (1933) in a summary of the distribution and geology 

of epithermal antimony deposits has written that the principal (and 

primary) ore mineral of antimony is the sulfide, stibnite, and that 

the mineral occurs chiefly in quartz veins, which in turn are found 

in many kinds of rocks. He suggests (p. 659) that the deposits were 

formedjnear the surface, at low temperatures by "hot hypogene solutions emanating from rocks ranging from diorite to granite." Nearly 

all of the deposits described in his report are supposedly genetically 

related to crystalline (by this is meant relatively coarse-grained) 

igneous rocks. Thus in Nevada, deposits in Pershing and Humboldt 

Counties are probably genetically connected with "granular intrusives of Cretaceous age;" and in Lander County, deposits are probably 

connected with Late Cretaceous granitic intrusives.

According to Schrader (1933, p. 662), antimony deposits in Idaho 

are "genetically connected with later Cretaceous or Tertiary 

granites * * * and * * * are mostly associated with gold and sil-
SELENIUM IN EPITHERMAL DEPOSITS

TABLE 4. Results of field tests for selenium, of grab samples from mercury

deposits

Locality

 California: 

Corona mine, Mayacmas 

district, Lake County.

Guadalupe mine, New 

Alamaden district, Santa 

Clara County.

Nevada:

district Humboldt 

County.

Utah:

district, Piute County.

No. 

(flg.l)

1

2

4

Sample description

Highly pyritiferous cinnabar, 

- .do..... ___ 

Millerite- _ _ _ _ _ 

Arseiiopyrite and pyrite _ 

 . do... 

. .do. ....... 

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

 . do- - ___

 do... 

 -do 

.. do ....... ..-.- . 

_ . do. _.__ . 

site

Limestone coated with tiemannite crystals at retort 

site.

tiemannite.

 -do 

Test method

Caustic fusion.. ... 

 _do 

 --do.... ....... -

 -do.... ... 

 ..do .

Pyrosulfate.-.- - 

Caustic fusion _

---do. ... 

 do 

...-do... ........ ..

 -do....... ...

Caustic fusion. ....

Caustic fusion _ __

Caustic fusion _ _

Caustic fusion _ .. 

Heated tube... 

 -.do.. ------

 ..do... ..-- -----

___-.do __---

Results of field 

test'

Negative. 

Do.

Do.

Do.

Do.

Do.

Do. 

Do.

Do.

Do.

DC

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do. 

Do.

Do.

Do.

Negative.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

tive. 

Do.

Do. 

Do.

Do.

Do.

Do.

1 Negative result indicates selenium content less than 50 ppm.

ver," but D. E. White (written communication, 1958) states that the 

deposits are probably related to Tertiary volcanics. Deposits in California are not so thoroughly described, and Schrader states only that 

stibnite, cinnabar, and sometimes gold, and silver occur in quartz veins 

in different kinds of rocks. In the Stayton district, San Benito and 

Merced Counties, antimony deposits may be related to Tertiary andesite; in other districts, in Kern County for example, deposits may 

be related to granites.

Deposits in Utah are probably related to eruptive andesitic rocks. 

The deposits of Montana are not described, but those of Oregon and 

Washington are probably related to late Mesozoic and Tertiary 

granitic intrusive rocks.
10 CONTRIBUTIONS TO ECONOMIC GEOLOGY

SELENIFEROTJS EPITHERMAL ANTIMONY DEPOSITS

Little published information is available on the selenium content 

of epithermal antimony deposits. This is somewhat surprising because selenium is widespread in these deposits, and in relatively large 

concentrations as is shown by the data in table 5. The table lists the 

selenium and antimony contents, and sample localities of 79 selected 

samples of antimony ores from the Western United States. These 

data were collected by F. H. Dakin of Burlingame, Calif. Sample 

localities are shown on figure 2.

EXPLANATION

 2

MONTANA Location of seleniferous 

\ antimony deposit

k.._.^ J . ?

I COLORADO

L ------i---- ""1

AHiZONA NEW MEXiCO

FIGURE 2. Map of the Western United States (exclusive of Alaska and Hawaii) showing 

location of seleniferous antimony deposits. Numbers refer to descriptions in table 5.
SELENIUM IN EPITHERMAL DEPOSITS 11

Selenium content of the sample ranges from a trace to 1.06 percent, 

and antimony content ranges from 14.8 to 81.7 percent. Selenium and 

antimony contents in these ores are not correlative. The ore samples 

listed in table 5 are part of a group of 298 from British Columbia (1), 

Honduras (4), Japan (1), Mexico (5), United States, including 

Alaska (285), and the Yukon. Territory (2). Only 1 sample containing detectable selenium is not listed in table 5; it is from the 

vicinity of Nome, Alaska, and contains a "trace." Two hundred five 

samples from the United States contain no detectable selenium, and 

among these are samples from the following states not listed in table 5: 

Alaska (7), Arkansas (1), Arizona (4), Montana (18), Oregon (14) 

and Washington (12).

There is an apparent regionalization of high selenium content, for 

the antimony ores from a block of 4 states California, Nevada, Utah, 

and Idaho are more seleniferous than those from other areas of 

the United States, or from areas outside the United States.

TABLE 5. Selenium and antimony content of selected antimony ore samples from 

the Western United States 1

Locality

California: 

Near Stayton mine, Hollister, San Benito County. 

Near Frazier Park, Kern County. .......

Colorado:

Idaho:

Near Elk City, Idaho County.. __ ... .

Near Silver City, Owyhee County--

No. 

<%. 2)

1

2

3

4

5

6

7

8

9

Sample description 2

Ore.. __ .. ___ ._--

 do 

 ..do.. _ .. .. 

 -do __... 

 -do...... 

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

 .do .... . -

..... do... -

 do 

 do... _ 

 -do ... ...

 do . . . -

do

 do _____ ... ... . _

 do .... _ ______

 .do ... ... ...

. do

 do ... ,.._. ... ....

Antimony (stibnite) concentrate. 

 do . 

 do 

 do 

 do 

 ..do 

 do 

 do - 

 do 

Selenium 

content 3 

(percent)

0.11

Trace

Trace

.15

.15

Trace

.20

.05

.07

.08

.03

.06

.04

.03

.04

.04

.05

.08 

.02

.03

.03

.04

.04

.03

.03

.05

Antimony 

content 3 

(percent)

37.4

34.7

22.7

55.8

35.1

14.8

60.7

50.6

52.5

52.7

58.8

37.0

56.6

59.7

55.8

56.6

60.6

69.0

55.9 

51.3

54.3

48.2

50.6

50.8

47.5

48.2

50.4

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

TABLE 5. Selenium and antimony content of selected, antimony ore samples from 

the Western United States 1 Continued

Locality

-Nevada:

Near TJnionville, Pershing County ___

Near Reno, Storey County ___ ._. __

Near Sparks, Storey County _______

No. 

(fig. 2)

10

11

12

10

14

15

16

17

is

10

20

21

22

23

24

25

26

27

28

29

30

31

Sample description 2

Ore-. 

 ..do... 

. do 

 do. 

 do 

 do 

 do . _ 

 do 

 do 

. _ .do . 

 do... ....... - 

.... .do ... 

 do 

 do 

..... do .. 

.....do .

... ..do 

... ..do 

.....do .. 

 .do 

 ..do ... 

 do 

 .do 

 .do . 

 ..do. ... 

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

.....do .. 

. .do. 

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

 ..do ........ - .

.....do 

 .do 

 .do 

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

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

 .do 

..... do 

 _do~. -

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

.... . do . 

.... .do -. - - 

.... .do .-

 -do .. . 

.....do ... 

 do 

 do 

 do ..- 

... ..do 

 .do 

Selenium 

content » 

(percent)

0.08

.10

Trace

.46

.08

Trace

Trace

.03

.03

.10

.08

.07

.03

.05

.07

.05

.08

.03

.05

.05

.03

.15

.10

.07

1.00

.05

Trace

Trace

Trace

.07

.80

.05

Trace

Trace

Trace

.10

Trace

Trace

1.06

.03

Trace

.05

.11

.02

Trace

.10

Trace

.08

.06

.06

Antimony 

content * 

(percent)

44.2

19.1

68.0

52.5

36.5

60.7

49.0

39.6

23.1

37.7

51.2

41.9

29.3

32.2

53.3

57.9

54.6

68.0

40.7

61.9

66.9

30.9

46.1

45.1

60.3

68.5

37.6

36.7

60.6

47.9

44.9

65.7

41.2

52.5

41.0

53.6

34.6

40.8

40.5

58.4

40.9

53.6

34.9

19.7

80.8

81.7

47.5

34.1

39.7

53.5

42.9

48.7

' Data collected by F. H. Dakin, Burlingame, Calif., published by permission. 

2 Stibnite ores unless otherwise identified. 

* Sensitivity of selenium assays not known.

EESULTS OF FIELD TESTS FOB SELENIUM AT ANTIMONY DEPOSITS

From 2 localities (1 in Idaho and 1 in Nevada) 18 samples have 

been tested by field methods for selenium content. The localities are 

shown on figure 1 and the localities, sample descriptions, and methods 

and results of field testing are listed in table 6.

Selenium in these deposits occurs in the antimony mineral (usually 

stibnite) to the exclusion of any other mineral of the antimony deposit, as shown by the results of field testing. The writer has been
SELENIUM IN EPITHERMAL DEPOSITS 13

unable to detect inclusions of selenium minerals in seleniferous stibnite under the microscope and concludes that such inclusions either 

are too small to be seen, or do not exist. Where such inclusions da 

not exist, the selenium content of the stibnite presumably is substituting for sulfur in the stibnite crystal lattice.

TABLE 6.- -Results of field tests for selenium of samples from antimony deposits 

and « mitt

Locality

Idaho: 

Stibnite, Yellow Pine

district, Valley County.

Nevada:

shing County.

No.

(fig. 1)

7

8

Type

-,.do 

 do-..

 do___

 do._.

posite 

grab 

 do 

_..do-_.

 do...

 do...

-,_do...

Grab.. 

...do 

_-do__.

...do...

-_do._.

...do....

...do...

Sample

Description

Stibnite .

(slime). 

Stibnite. __ . __ ........

 do. 

..--do........- ....

 do.. . ....

duction furnace.

production unit. 

Brick, antimony reduction furnace. 

Electric furnace slag. . ....

dust.

dust.

 do.... 

Test method

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

 do.... 

 do..... 

 -do. . ...

 -do 

 -do...-... .

 ..do 

-. do .

 .do... ... 

Caustic fusion...

Pyrosulfate.-..- 

Caustic fusion ...

.. do ... ...

 -do .... .

 -do... 

Result of test !

tive.

Do.

Do.

Do.

itive.

Do.

tive.

Moderate positive. 

Negative. 

Do. 

Do.

itive. 

Do.

Do.

i Negative result indicates selenium content less than 50 ppm.

DISCUSSION

The information presented in this report suggests that selenium is 

common in epithermal silver-gold and antimony deposits, but less common in gold-silver and mercury deposits. Evidence cited from Eoss 

(1933), Nolan (1933), and Sclirader (1933) indicates that silver-gold 

and antimony deposits are genetically related to coarse-grained intrusive rocks, whereas gold-silver and mercury deposits are related 

to finer-grained intrusive rocks.

A recent study by D. F. Davidsoii and H. A. Powers (1959) of 

selenium analyses of extrusive volcanic rocks suggests that crystalline 

volcanic rocks are only rarely seleniferous, and that noncrystalline 

volcanics are more commonly seleniferous. These workers believe
14 CONTRIBUTIONS TO ECONOMIC GEOLOGY

that this distribution of selenium can be accounted for if selenium is 

lost by molten extrusive rocks during crystallization. Rocks which 

cool without crystallizing presumably retain their selenium content. 

If these presumptions are the explanation of the apparent difference in 

selenium content of the two types of volcanic rocks, the same or a 

similar mechanism may account in part for the difference in selenium 

content between silver-gold and antimony deposits, and gold-silver 

and mercury deposits.

The deep-seated magmas from which silver-gold and antimony deposits are formed crystallize slowly and in the process give up their 

selenium content. Selenium is thus available for movement to the 

site of ore deposition, along with other constituents of the magma. 

The igneous material from which gold-silver and mercury deposits are 

derived cools and crystallizes rapidly and in some way this material 

retains its selenium content. Selenium is therefore not available for 

transport and deposition with ore minerals. At the site of ore deposition the composition of the ore fluids, and pressure-temperature conditions undoubtedly affect the deposition of selenium. Conditions 

favorable for the deposition of silver-gold and antimony deposits 

probably allow selenium in the ore fluids to enter sulfide mineral 

structures readily, and those conditions favorable for the formation of 

gold-silver and mercury deposits are unfavorable for such a 

substitution of selenium for sulfur.

An alternative hypothesis which applies equally well to seleniferous 

vitrophyres, nonseleniferous crystalline volcanic rocks, seleniferous 

silver-gold and antimony deposits, and nonseleniferous gold-silver 

and mercury deposits, is that the magmas which produced the vitrophyres and silver-gold and antimony deposits were seleniferous, and 

those which produced the crystalline volcanics and the gold-silver 

and mercury deposits were not. This hypothesis lacks any known 

support, and in the writer's opinion must be discarded.

LITERATURE CITED

Becker, G. F., 1888, Geology of the quicksilver deposits of the Pacific slope: U.S.

Geol. Survey Mon. 13, 486 p. 

Bethke, P. M., 1956, Sulfo-selenides of mercury (abs.) : Geol. Soc. America Bull.,

v. 67, no. 12, p. 1671. 

Butler, B. S., Loughlin, G. F., Heikes, V. C., and others, 1920, Ore deposits of

Utah: U.S. Geol. Survey Prof. Paper 111, 672 p. 

Coleman, R. G., 1958, The natural occurrence of galena-clausthalite solid solution

series (abs.) : Geol. Soc. America Bull., v. 69, no. 12, p. 1679. 

Coleman, R. G., and Delevaux, Maryse, 1957, Occurrence of selenium in sulfides

from some sedimentary rocks of the Western United States: Econ. Geology,

v. 52, p. 499-527.
SELENIUM IN EPITHERMAL DEPOSITS 15

Davidson, D. F., and Powers, H. A., 1959, Selenium content of some volcanic

rocks from Western United States and Hawaiian Islands: U.S. Geol. Survey

Bull. 1084-C, p. 69-81. 

Earley, J. W., 1950, Description and synthesis of the selenide minerals: Am.

Mineralogist, v. 35, p. 337-364. 

Emnions, W. H., 1940, The principles of economic geology: New York, McGrawHill Book Co., 529 p. 

Ferguson, H. G., 1929, The mining districts of Nevada: Econ. Geology, v. 24,

p. 131-141. 

Lindgren, Walderaar, 1915, Geology and mineral deposits of the National mining

district: U.S. Geol. Survey Bull. 601, 58 p.

 1933, Mineral Deposits, 4th ed.: New York, McGraw-Hill Book Co., 930 p. 

Nikolskaya, E. I., and Regal, A. R., 1956, Formation of solid solutions and the

magnetic susceptibility in the system Hg-Te-Hgse, HgTe-/3-HgS, HgSe-/3-

HgS: Chern. Abs., v. 50, p. 1391. 

Nolan, T. B., 1933, Epithermal precious metal deposits, in Ore deposits of the

Western States: Am. Inst. Mining Metall. Engineers, New York, p. 623-640. 

Peterson, H. E., Jensen, C. L., and Andersen, R. G., 1957, A field test for selenium:

U.S. Bur. Mines Rept. Inv. 5328, 7 p. 

Roberts, R. J., 1940, Quicksilver deposit at Buckskin Peak, National Mining

district, Humboldt County, Nevada: U.S. Geol. Survey Bull. 922-E,

p. 115-134. 

Ross, C. P., 1933, Quicksilver deposits, in Ore deposits of the Western States : Am.

Inst. Mining Metall. Engineers, New York, p. 652-658. 

Schrader, F. C., 1933, Epithermal antimony deposits, in Ore deposits of the

Western States: Am. Inst. Mining Metall. Engineers, New York, p. 658-665. 

Thompson, R. M., 1954, Naumannite from Republic, Washington: Am. Mineralogist, v. 39, p. 525.
INDEX

Page

Age of seleniferous rocks_______ 2, 8, 9 

Diadochic substitution________ 2, 13, 14 

Epithermal deposits:

antimony________ 2, 8, 10, 11, 12 

classification __________ 4, 5

definition and description. __ 1 

emplacement _ _ __ 1,14 

faulting, associated________ 4 

mercury_ ______________ 2, 6, 8

silver and gold 4, 5, 6, 8, 9, 13, 14 

Faults. See Epithermal deposits. 

Field tests, caustic fusion_____ 3, 4, 6, 9 

heated tube__ ________ 3, 4, 9 

pyrosulfate 3, 4, 6, 9 

results_ ___________ 6, 8, 9, 12 

Isomorphous substitution___ __ 2 

Metacinnabar______________ 3 

Minerals:

aguilarite _ __ 3, 5 

argentite _____________ 3, 6 

arsenopyrite ____ 9 

"asphalt" ______________ 9 

berzelianite______________ 3, 5 

cinnabar. _ _____ 3, 8, 9 

clausthalite _____________ 3, 5 

eucairite- ___________ 3, 5 

guanajuatite ________ 3, 5 

klockmannite ____________ 3, 5 

metacinnabar____________ 3 

naumannite _____________ 3, 5, 6 

naumannite - aguilarite-argentite

group _ _ 2 

onofrite. See Metacinnabar.

Page

Minerals Continued

paraguanajuatite 3, 5 

pyrite __________ __ 5, 6, 9 

quartz 6 

stibnite_______ 3, 8, 11, 12, 13

tiemannite______ 3, 5, 8, 9

tiemannite - metacinnabar- cinnabar group_ 2 

umangite_ 3, 5

Rocks, intrusive, fine-grained___ 5, 1, 13 

coarse-grained__ _ _ 8, 9, 13, 14

Seleniferous deposits, occurrence,

Alaska__________ 11 

Argentina- 5 

Arizona 7,11 

Arkansas_ _ _ __ _ 6,11 

British Columbia 11 

California____________ 8, 9, 11 

Colorado_ _ _ _ 11 

Honduras _ 11 

Idaho_____________ 1, 6, 11, 13 

in volcanic rocks_ _ 9, 13, 14 

Japan 11 

Mexico _ _ _ _ 5,11 

Montana_____________ 9,11 

Nevada___________ 5, 9, 11, 12, 13 

New Zealand____________ 5

Oregon _ _ _ __ 11 

Sumatra __ _ _ 5 

Texas_________________ 6 

Utah________________ 3, 5, 8, 9 

Washington___________ 5, 8, 11 

 with limestone_________ _ 8, 9

Volcanism, Tertiary_____ ___ 4, 6, 9

16