Beryllium Deposits 

of the Mount Antero 

Region, Chaffee 

County, Colorado

By JOHN W. ADAMS

A CONTRIBUTION TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN 982-D

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1953
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

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

Page

Abstract-.-..____--_--------_------------------------------------- 95

Introduction. _______________ _______--___-_______-_-------_-__--- 95

General geology___ __--___________---_---_---__-------------------- 98

Beryllium deposits of the Mount Antero region__________-_-_---____--- 98

Pegmatites __________________--___-------_-------_------------ 98

Veins,.___----_---_------------------------------------------ 100

Greisen and granite.-_______________-________-_---_---_---_---- 101

The beryllium-bearing vein at the California mine.-___-_-----_-._-- 101

Location and history..._________________----_---_--_-__---- 101

Workings.. _ ______________--___-__-_.--------------------- 103

Pomeroy quartz monzonite of Crawford.___-_-_---_-_---.---- 103

. The California vein_______________.______---------__--.---_ 104

Mineralogy._ ____________-__---------__-----------_--_---- 105

 Paragenesis.__________________-___-____--_--------_-__---- 111

Temperature of formation_______-_______--_---_--___------- 112

Beryllium resources._______________________________------______---- 113

Beryllium-bearing quartz veins of other areas-_____-___-_---_-_-___--- 114

Index of refraction of beryl from nonpegmatite deposits_---___-___-__--_ 117

Literature cited.___-___-__-____------__----_---------------------- 117

Index. _____________--__--_____--_--__-- --------------~ -- 119

ILLUSTKATIONS

Page 

FIGURE 26. Index map of Colorado showing location of Mount Antero

area_______________-________-__----_--------------- 96

27. Part of the Garfield quadrangle, Colorado and contiguous

unmapped area_______--__--__----_---_------------~-- 97

28. Aerial photograph of area surrounding the California mine _ _ _ _ 102

29. South slope of Carbonate Mountain, looking northwest______ 104

30. Molybdenite in beryl, California mine.____________________ 107

TABLES

TABLE 1. Indices of refraction of beryl from several localities.__________ 108

2. Spectrographic analyses of minor elements in beryl from Chaffee

County, Colo_-.-__ -_-------_------ - -- 109

m

A CONTRIBUTION TO ECONOMIC GEOLOGY

BERYLLIUM DEPOSITS OF THE MOUNT ANTERO 

REGION, CHAFFEE COUNTY, COLORADO

By JOHN W. ADAMS

ABSTRACT

Pegmatite and quartz veins that contain beryllium minerals occur in Tertiary 

granite in the vicinity of Mount Antero and White Mountain, Chaffee County, 

Colo. The pegmatites, which generally do not exceed a few feet in maximum 

dimension, are found throughout a main granite stock, in outlying granite masses, 

ar.cl in greisonixed granite. Miarolitic pegmatites, from which fine specimens of 

aquamarine, phenakite, and bertrandite have been obtained, appear to be confined to the granite forming the upper part of the main stock.

A beryl-bearing quartz vein, once mined for molybdenite, occurs in quartz 

monzonite at the California mine southwest of Mount Antero. Mineralogical 

study shows that some of the beryl was formed during the deposition of molybdenite. Brannerite, an oxide of titanium and uranium, was identified in material collected from the mine dump. The vein at the California mine is 1% to 

3 feet thick where exposed, is nearly vertical, strikes N. 72°-75° E., and is 

thought to extend for at least 1,000 feet along the strike to the northeast.

Beryl-bearing quartz veins similar to this vein are of world-wide distribution. 

They contain molybdenum, tin, tungsten, and bismuth and are believed to be 

transitional between pegmatites and hydrothermal veins. The beryl from some 

tungsten-bearing deposits has a high index of refraction (u) compared to beryl 

from tin- and molybdenum-bearing veins.

INTRODUCTION

Mount Antero and White Mountain, in Chaffee County, Colo., have 

been known for many years as a source of crystals of the beryllium 

minerals beryl, phenakite, and bertrandite. Their occurrence in small 

pegmatites of the area was described by Switzer (1939). Beryl is 

found also in a quartz vein that was once mined for molybdenite 

(Worcester, 1919, pp. 34-38; Landes, 1934). It is known as the California vein and was studied in detail to determine the possibilities 

for commercial development.

Mount Antero and White Mountain are prominent peaks of the 

Sawatch Range of central Colorado, on the west side of the Arkansas 

River valley about 15 miles northwest of Salida and 100 miles south95
96 A CONTRIBUTION TO ECONOMIC GEOLOGY

FIGURE 26. Index map of Colorado showing location of Mount Antero area.

west of Denver (fig. 26). Mount Antero has an altitude of 14,245 feet 

and is a few hundred feet higher than White Mountain, 11/4 miles 

to the south. The beryllium deposits are in the immediate vicinity 

of these peaks (fig. 27). The area, which is above timberline, consists 

of steep talus-covered slopes, boulder fields, and broad grassy flats. 

Access to the region is limited to the summer months, and even then 

the weather around the peaks is apt to be severe and unpredictable. 

Violent electrical storms, often accompanied by hail, are common, 

and snow and high winds may be expected at any time. The weather 

conditions, the altitude, and the generally steep and hazardous terrain 

make work in the area physically difficult.

The area may be reached by the Baldwin Gulch, Little Browns 

Creek, or Browns Creek trails. The Baldwin Gulch trail, shown in 

figure 27, starts about a mile west of New Alpine on the Chalk Creek 

road (State Highway 162) and offers an approach from the north. 

The other trails start from the Arkansas River valley and enter the 

mountains from the east. The Little Browns Creek route is most 

generally used to approach Mount Antero and White Mountain. Although the trails and connecting roads are shown on the San Isabel 

National Forest Map of the U. S. Forest Service, local inquiry regarding the trails is advisable. Aerial photographs are available, and partial topographic coverage is afforded by the Garfield quadrangle sheet 

(scale, 1: 62,500). (See fig. 27.)
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 97 

80 W. R.79 W. 106° 15'

R.6E. 106° 15'

FIGURE 27. Part of the Garfleld quadrangle, Colorado and contiguous unmapped area, 

showing location of the California mine and approximate positions of Mount Antero and 

White Mountain. Area within dashed lines shows approximate location of figure 28.
98

The writer, assisted in the field by A. F. Trites, Jr., made a brief 

reconnaissance examination of the beryllium deposits of the Mount 

Antero region between June 24-and July 1, 1948, as part of the beryllium investigations being conducted by the U. S. Geological Survey on 

the behalf of the Atomic Energy Commission. In the summer of 1951, 

M. C. Dings, C. S. Eobinson, and M. R. Brock completed a geologic 

map of part of the Mount Antero region as part of their mapping of 

the Garfield quadrangle, a cooperative project of the U. S. Geological 

Survey and the State of Colorado. This map was available to the 

writer during the final stage of manuscript preparation. The area 

was revisited for one day in September 1951 by the writer, C. S. 

Eobinson, and G. R. Scott of the Geological Survey.

GENERAL GEOLOGY

The rocks of the Mount Antero region are granite, andesite, Prmceton quartz monzonite, and Pomeroy quartz monzonite all of which are 

parts of a large intrusive complex known as the Princeton batholith. 

These rocks were first named and described by R. D. Crawford (1913), 

and are believed by him to be probably of Tertiary age. He concluded 

that Pomeroy quartz monzonite is older than Princeton quartz monzonite and that both rocks were intruded by the granite. Crawford 

was unable to establish.definitely the relative age of the andesite, but 

considered it to be the youngest rock. This is now questionable, inasmuch as beryl-bearing quartz veins, presumably derived from the 

granite, occur in an andesite body (C. S. Robinson, personal communication) on the ridge between Baldwin Gulch and Browns Gulch.

Most of the beryllium-bearing pegmatites and veins, except the 

California vein, are in the main granite stock that is several miles in 

extent, and underlies a large part of Mount Antero and White Mountain. A much smaller body of the same granite crops out about threefourths of a mile west of the main stock and is separated from it by 

andesite and Crawford's Pomeroy quartz monzonite. The California 

vein, in the vicinity of the mine workings, is in Pomeroy quartz 

monzonite, but probably extends into granite and possibly andesite.

PEGMATITES

The pegmatites of the Mount Antero region are described by Switzer 

(1939, p. 793) as being "uniformly small in size, seldom exceeding 

three feet in width and extending laterally for only a few feet." 

Where the pegmatites could be completely excavated, they were found 

to be "roughly disk-shaped or cylindrical bodies of limited extent in all
BERYLLIUM DEPOSITS, MOUNT ANTEBO REGION, COLORADO 99

directions." On the basis of mineralogy Switzer classified them as 

follows:

1. Beryl pegmatites: Beryl-smoky quartz.

2. Phenakite pegmatites : Phenakite-colorless quartz. Phenakite-smoky quartz.

3. Beryl - phenakite - bertranclite pegmatites : Beryl - pbenakite - bertranclite. 

Beryl-phenakite-bertrandite-fluorite.

4. Topaz pegmatites.

Pegmatites containing large miarolitic cavities occur near the top of 

the granitic stock. Almost all the pegmatites seen by the writer, however, were little more than relatively coarse-grained schlieren a few 

inches wide and at most a few feet long that grade imperceptibly into 

the enclosing granite. These pegmatites rarely contain the welldeveloped miarolitic cavities in which gem minerals occur and except 

for small crystal-lined voids less than an inch across are composed 

entirely of interlocked anhedral to subhedral grains. This schlieren 

type of pegmatite commonly so rich in beryl as to be almost monomineralic, is widely, though sparsely, distributed throughout a vertical 

range of at least 2,500 feet in the granite of the main stock. This type 

is present also in the smaller body of granite and greisen to the west.

The pegmatites characterized by large miarolitic cavities, which may 

be as much as 4 feet in diameter, are found in granite on the higher 

slopes of Mount Antero and White Mountain. This granite most 

probably formed the upper few hundred feet of the stock. Switzer 

(1939, p. 800) says that all the pegmatites and quartz veins which he 

studied were in a zone 500 feet thick. The upper limit of this zone is 

probably the top of the stock, which is only a short distance below the 

summit of Mount Antero, as shown by an essentially horizontal contact of granite with overlying Princeton quartz monzonite at an altitude of about 14,000 feet (C. S. Robinson, personal communication).

Pegmatites from any part of the stock may contain small voids, thus 

the miarolitic pegmatite zone must be defined as a zone in which the 

cavity development is most pronounced. Undoubtedly the size of the 

cavities increases in general with elevation, but the size of any individual cavity is probably the result of local pressure conditions, the 

volume of material, and the concentration of volatiles.

The mineralogy of the miarolitic pegmatites and the more common 

schlieren type is fundamentally the same. The dominant minerals of 

both types are smoky quartz, perthitic microcline, albite, beryl, muscovite, and fluorite. Accessory minerals include phenakite, topaz, garnet, apatite, bertrandite, calcite, biotite, magnetite, limonite, and sulfur. Some of the rarer minerals, such as topaz, may locally become 

dominant in an individual pegmatite. Bertrandite is probably restricted to pegmatites of the miarolitic type, as it is apparently the 

product of reaction of late-stage fluids or gases on beryl exposed in

227163 53 2
100 A CONTRIBUTION TO ECONOMIC GEOLOGY

open cavities. A description and analysis of cyrtolite from Mount 

Antero has been given by Genth and Penfield (1892, p. 387), but no 

subsequent discoveries of the mineral have been reported. Limonite 

forms pseudpmorphs after pyrite crystals, and the sulfur probably is 

derived also from pyrite (Montgomery, 1938, p. 368). A black, 

strongly radioactive mineral that occurs sparsely in the pegmatites is 

probably brannerite. No lithium minerals have been identified from 

the pegmatites.

VEINS

Quartz veins containing beryllium minerals are present in the 

Mount Antero area. They differ from the pegmatites in that they are 

much richer in quartz, contain little or no feldspars, and appear to be 

more nearly continuous.

Two such veins in the granite of the southwest face of Mount Antero 

were described by Switzer (1939, pp. 797-800) as (1) a muscovitequartz vein containing phenakite, and (2) a phenakite-quartz-fluorite 

vein. A third vein, containing beryl and molybdenite lies outside the 

main granite stock and has been previously described by Landes (1934. 

pp. 697-702). It is discussed in this paper under "The berylliumbearing vein at the California mine." (See page 101.)

In general the mineralogy of the veins is quite similar to that of the 

pegmatites with the notable exceptions of perthitic microcline, which 

has not been found in the veins, and of molybdenite, hiibnerite and 

the sanadine variety of orthoclase which have not been noted in the 

pegmatites. Quartz, fluorite, muscovite, beryl, phenakite, albite, 

pyrite, and probably brannerite occur in both types of deposits and 

suggest that a close relationship, if not a complete gradational 

sequence, exists between the pegmatites and the veins. Switzer (1939, 

p. 801) believes that the veins in the granite represent the lowertemperature or late-stage mineralization phase of the pegmatites, a 

phase which followed the crystallization of beryl and microcline. As 

phenakite was the only beryllium mineral found in the veins in the 

granite, and as it followed beryl in the paragenetic sequence of the 

pegmatite minerals, Switzer concluded that phenakite was stable at a 

lower temperature than beryl and might be present under conditions 

unfavorable for beryl crystallization.

The relationship between phenakite and beryl, while apparently 

applicable to the deposits in the main granite stock of Mount Antero 

and White Mountain, does not always exist. This fact is shown by 

the beryl-bearing vein at the California mine, and by the world-wide 

occurrence of beryl in quartz veins further discussed under "Berylbearing quartz veins of other areas." (See page 114). It is more probable that the formation of phenakite instead of beryl is a result of
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 101

differences in the chemical environment, not lower-temperature 

conditions.

GREISEN AND GRANITE

Two areas of greisenized granite were sampled for possible beryllium 

content. The first of these areas is about a mile northeast of the 

California mine and consists of a large boulder field of greisen (fig. 28, 

locality B). The greisen has a coarse, granular texture and contains 

small vugs lined with quartz crystals which generally range from 

1 to 2 millimeters in length. Microscopically, the rock consists almost 

entirely of interlocking quartz grains with some interstitial finegrained muscovite or sericite and scattered flakes of molybdenite. 

Chip samples taken from a number of representative specimens of 

greisen showed only a trace of beryllium by spectrographic analysis 

(Saratoga Laboratories, Inc.).

The second area of greisen (fig. 28, locality C) was found in the 

small mass of granite west of the main granite stock. A sample of 

this greisen, collected by C. S. Robinson contained 0.0008 percent BeO 

(spectrographic analysis by U. S. Geological Survey).

During the writer's examination of the Mount Antero region several small chip samples were collected from the granite on the north 

slope of White Mountain. These samples were believed to be representative of the granite and contained no megascopic beryl. A composite of these samples contained 0.018 percent BeO (spectrographic 

analysis by Saratoga Laboratories, Inc.). Because of the high percentage of BeO in this sample, additional samples of granite were 

collected by C. S. Robinson and M. R. Brock from 12 widely separated exposures of the main stock and outlying masses. The highest BeO content found in these additional samples was 0.0016 percent; 

and all were consistently much lower than the original composite sample (spectrographic analysis, U. S. Geological Survey). Although 

beryl-bearing pegmatities are relatively abundant on White Mountain, it is doubtful that the granite from this part of the main stock 

actually contains more BeO than the small quantities found in the 

12 samples from other exposures. Until verified by check samples, the anomalous BeO content of the White Mountain samples 

should be questioned, and it is probable that neither the granite nor 

greisen contains appreciable amounts of beryllium.

THE BERYLLIUM-BEARING VEIN AT THE CALIFORNIA MINE 

LOCATION AND HISTORY

The California mine is about 2 miles southwest of the crest of 

Mount Antero, on the south slope of the divide between the basins of 

Browns Creek and Baldwin Gulch (figs. 27, 28), at an altitude of 

approximately 12,500 feet.
102 A CONTRIBUTION TO ECONOMIC GEOLOGY
Although some earlier work had been done, most of the development 

of the mine was done during World War I by the Molybdenum Mines 

Co., of Denver. No production is recorded, but when the property 

was visited by P. G. Worcester in 1917, small lots of hand-cobbed ore 

were being shipped to Denver for experimental treatment. At that 

time the company held four claims, the California, California No. 2, 

Nevada, and Nevada No. 2. The mine has not been operated since 

1918. Ownership of the property, known as the California group, 

Patent 19,925, is claimed by Mr. G. G. Furman, Farmington, N. Mex.

WORKINGS'

Worcester (1919, p. 35) described the workings as follows: . All the development work, with the exception of some shallow surface cuts and 

location shafts, has been done on the California claim. In the summer of 1917 

the workings consisted of: an open cut with a 50-fool drift on the vein; an 

inclined shaft "»0 feet deep, near the open cut, but apparently not on the vein; 

a cross-cut tunnel, that was started 50 feet vertically below the open cut and 

was run 98 feet to the vein; and drifts from this tunnel, one 30 feet westerly 

on the vein and another 126 feet to the east. Small stopes, only 2 or 3 feet 

above the normal roof of the tunnel, have been run for 75 feet, on the east drift. 

Mr. W. B. Lowry reported in June 1918, that since July 1917 the drift has been 

continued on to the east 15 feet to a fault, and 130 feet beyond, where the vein 

was recovered. '

All underground workings are now inaccessible, but as recently as 

1938 the lower adit and part of the main drift were open but in a 

dangerous condition (Over, Edwin, personal communication). The 

portal of the adit now is buried under slide rock, but the rails leading 

from it into the sorting shed still can be seen. The inclined shaft and 

upper adit have been completely obscured by caving and by the slumping of the walls of the open cut.

POMEROY QUARTZ MONZONITE OF CRAWFORD

The country rock in the vicinity of the mine, identified by Crawford (1913, p. 279) as the Pomeroy quartz monzonite, is part of 

a large stock, as shown on his geologic map of the Monarch and 

Tomichi mining districts. The California mine is about half a mile 

north of the area shown on this map.

In the vicinity of the mine the rock has a light-gray groundmass 

of plagioclase, orthoclase, and quartz, with numerous irregular dark 

aggregates of finely intergrown biotite, chlorite, and magnetite. 

Phenocrysts of purplish-gray plagioclase are present in some places.

Wall-rock alteration apparently is related to the intensity of vein 

mineralization. Where the vein is essentially barren of molybdenite 

and beryl the quartz monzonite is unaltered except for an inch or less 

of siliceous material along the contact. The rich beryl and molyb-
104 A CONTRIBUTION TO ECONOMIC GEOLOGY

denite vein-filling on the dump, however, is associated with a sericitequartz rock that probably represents altered country rock adjacent to 

the highly mineralized parts of the vein. This type of rock is also 

present locally in walls of the open-cut where it was probably adjacent to the ore. The sericite-quartz rock contains abundant molybdenite and molds of cubic pyrite crystals.

THE CALIFORNIA VEIN

The part of the California vein that was mined is a quartz vein 

containing molybdenite, beryl, muscovite, molybdite, and minor 

amounts of other minerals. Worcester (1919, p. 36), who saw the 

vein exposed in the workings, describes it as follows:

The vein varies from 18 inches to 3 feet in width. Its average dip is 80° N. 

18° W., but it straightens up in many places to almost 90°. It seems to be a 

strong vein. It holds its course well and according to Mr. W. W. Rogers, superintendent at the mine, it has been followed by float on the surface for a mile or 

more. Work done since the writer's visit to the property in 1917 shows that at 

a distance of 141 feet from the cross-cut the vein is faulted, and that the east 

side is displaced 30 feet to the north.

The observations obtained by the writer from the present limited 

outcrop indicate a strike of N. 75° E.

The length of the vein is problematical. Outcrops are rare along 

the steep hillside (fig. 29) where grassy patches alternate with wide 

talus areas. A large block projecting through the talus about 1,000

FIGURE 29. South slope of Carbonate Mountain, looking northwest. The California urine 

 . .. In the left foreground ; portal of lower adit is just behind building. ..
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 105

feet east-northeast of the mine may be an outcrop of the vein. This 

exposure consists of a quartz vein about 1 foot wide that contains about 

2 percent beryl but no visible molybdenite. Limonitic material is interstitial to crystals of beryl and quartz. The block may not be in 

place, but is probably part of the California vein.

Numerous fragments of coarsely crystallized vein quartz and 

oxidized pyritic wall rock were found in a prospect pit (fig. 28, locality D) in andesite near the crest of the ridge and about half a mile 

northeast of the California mine. A single specimen of beryl and a 

few small crystals of hiibnerite were found in the quartz at this locality. Eeexamination of the pit in September 1951 failed to disclose additional beryl, but a beryl-bearing quartz vein in andesite was 

seen in a small excavation a few hundred feet southwest of the pit. 

This vein was about 1 foot wide and had a selvage zone of small blue 

beryl crystals. While there is little supporting evidence, these findings may represent the easternmost extension of the California vein. 

The vein could not be traced southwest of the mine. 

To project the California vein with certainty beyond the known 

limits of the workings cannot be justified from the surface indications 

seen during the brief examination by the writer. The occurrence of 

beryl-bearing quartz at several points to the northeast is, however, 

encouraging.

MINERALOGY

The mineralogy of the California vein has been discussed previously 

by Landes (1934, pp. 697-702). He reports that the following minerals are present: quartz, beryl, molybdenite, molybdite, mica (muscovite and sericite), and tourmaline. Three additional vein minerals 

were collected by the writer from the dump above the portal of the 

lower adit: these are fluorite, rutile, and brannerite.

Quartz is the most abundant mineral, and although generally massive, some of it occurs in well-formed crystals that, according to 

Worcester (1919, p. 36) are as much as 12 inches in length. It ranges 

in color from clear and colorless to dark smoky, but generally it is 

milky white. The surface exposures of the vein near the mine are 

almost entirely quartz.

The beryl in the vein is variable in form, transparency, and color. 

Although the color differences may be ascribed to slight compositional 

variations, form and transparency are probably closely related to 

constantly changing physical conditions during the period of beryl 

growth. From a study of the material collected, the beryl apparently 

falls into the following three types which reflect different growth 

environments:

(1) The greater part of the beryl occurs as crystals embedded in
106 .. A CONTRIBUTION TO ECONOMIC GEOLOGY

quartz. These crystals, which undoubtedly were the first .to-form, are 

generally less than 2 inches in length and rarely exceed one-half inch 

in diameter. The color ranges from pale green or blue to almost white. 

Clear and glassy areas are rare, and the crystals generally are fractured. The beryl generally tends to be in columnar aggregates; individual crystals are poorly formed.

(2) Beryl crystals that form vuggy intergrowths with quartz are 

less abundant. These crystals apparently were formed on the walls 

of open channels, near the end of the period of deposition of beryl 

and quartz when there was less mutual interference and possibly a 

slower growth rate. Some individual crystals have excellent crystal 

form. Although commonly more transparent than the embedded 

crystals, these are rarely of gem quality. ;

(3) Beryl that formed as isolated crystals in vugs is comparatively 

rare. These crystals rarely exceed an inch in length, but they are 

commonly of gem quality. Simple combinations of prism and pinacoid forms predominate, but some of the crystals have first and second 

order pyramids as well. The crystals may be light bluish green, pale 

straw yellow, or colorless. Several of the crystals collected are 

markedly zoned. They are bluish in color for most of their length, 

but near their terminal end they are almost colorless (fig. 30). The 

colorless parts are more transparent than the bluish parts, owing to 

the presence of fewer minute fluid cavities. Some crystals have fine 

flakes of mica coating one or more prism faces, and both mica and 

molybdenite may be enclosed in the beryl (fig. 30). In the crystal 

shown in figure 30 (collected by Edwin Over, 1938), the almost colorless terminal end appears dark in the photograph in contrast to the 

bluish cloudy part. This is the result of the scattering of light by 

clouds of bubbles in the colored part of the crystal and the almost 

complete transmission of light through the clear terminal end. The 

molybdenite inclusion consists of a cluster of several brilliant crystal 

plates.

The manner of occurrence of these isolated crystals is shown by a 

large fragment of vein quartz found on the dump. The specimen contains a vug lined with milky quartz crystals from which projects a 

transparent straw-yellow beryl crystal about 7 millimeters long. 

Small muscovite crystals are implanted on the quartz lining the vug 

and grow against the lower part of the beryl crystal. Molybdite, presumably derived from molybdenite, is interspersed with the mica.

The order in which the three types of beryl have been described does 

not imply a strict genetic sequence, although probably the more abundant beryl of the first type was of early origin. It is possible that conditions prevailed that permitted the simultaneous development of all 

three types at different points in the vein.
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 107

Colorless beryl

Blue, cloudy beryl

Molybdenite

I MILLIMETER

FIGURE 30. Molybdenite in beryl, California mine. A, Zoned beryl crystal enclosing molybdenite. B, Sketch of crystal to show zoning and position of molybdenite inclusion.

The beryl varies considerably in color and appearance, but only 

slight differences in the index of refraction can be noted, and from 

this it may be assumed that differences in composition are slight. Observed values for the slow ray range from 1.572 to 1.575, and almost 

all the values approach the higher figure. The lower indices were

227163 53 3
108 A CONTRIBUTION TO ECONOMIC GEOLOGY

obtained from almost colorless crystals (table 1). From an unpublished curve prepared by W. T. Schaller of the U. S. Geological Survey, the average index of refraction of the beryl would indicate that 

it contains approximately 13.5 percent BeO. Further mention (p. 117) 

will be made of the index of refraction of beryl from quartz veins inasmuch as a relationship appears to exist between this property and 

the metals present in the veins.

TABLE 1. Indices of refraction of beryl from several localities

Locality

son quadrangle, Ariz.

district, Mineral County, 

Nev.

County, N. Mex. 

Do^ ... . 

Lakeview mine Pershins

County, Nev.

ana, Nev. 

Irish Creek, Va.._. ._------.

S. Dak.i

S. Dak.i 

Do.'....... ........

County, Colo. 

Do..... . - 

Do..--....--...--.... .

Do.... ...... .............

sion California vein.

Type of 

deposit

 do... 

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

 do. .

morphic(?). 

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

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

.... .do.. ___

 do.. 

.....do .

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

 .do. 

 do 

..-..do .....

Associated metallic 

minerals

lite. 

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

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

Cassiterite, minor

wolframite, bismuto-plagionite.

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

...._do . ...... .

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

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

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

Types of beryl

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

matic. 

Minute greenish crystals....

ing MoS 2.

matic.

(NU) 

Index of refraction

1.591

1 fiftR

1.573

1.574

1.590

1.587

1.577

1.568

1.570

1.572

1.572

1.575

1.575

1.574

' Data, including indices, from Page, L. E., and others, 1953, Pegmatite investigations, 1942-45, Black 

Hills, S. Dak.: U. S. Geol. Survey Prof. Paper 247. [In press].

Spectrographic analyses (table 2), made in the laboratory of the 

Geological Survey, of beryl from the California mine and from White 

Mountain indicate that there is a close similarity in the type and 

amounts of the minor constituents in the beryl from both the vein and 

the pegmatites. Blue beryl from both localities contained approximately the same percentage of the alkali elements (Na, K, Li, and Cs). 

This similarity in composition, suggesting a common origin, is further 

shown by the almost identical values for the omega index of refraction 

(close to 1.575) that is given by the California mine beryl and both gem 

and common blue beryl from the pegmatites in the granite.

Molybdenite occurs sparsely in small veinlets in the massive quartz 

outcrop of the vein; material can be found on the dump, however, 

that is representative of the molybdenite-rich parts of the vein seen 

by Worcester when the mine was in operation. He has described 

these rich parts as follows: (Worcester, P. G., 1919, p. 36).
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 109

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110 A CONTRIBUTION TO ECONOMIC GEOLOGY

Molybdenite is found everywhere that the vein has been opened. The richest ore 

is near the walls, but there are rich streaks and vugs scattered all through the 

vein. In these rich streaks, and along the walls, chunks of solid molybdenite 

from 1 to 2 inches thick, and from 6 inches to 2 feet in length, are of common 

occurrence. The molybdenite is entirely crystalline, the flakes being as a rule, 

one-eighth to one-half of an inch in diameter. The intimate association of pure 

white quartz crystals, some of which are 12 inches long, with opaque or clear 

beryl (aquamarine) crystals, and molybdenite is an interesting phase of the occurrence of this ore. Much of the richest ore is found with beautiful specimens 

of beryl. In many places pockets are found between masses of beryl and 

quartz crystals from which it is possible to dig out with a. candlestick 20 to 

30 pounds of practically pure molybdenite and molybdite. While the vein as 

a whole is strong, there are rich and lean streaks all through it.

The molybdenite, in the specimens collected by the writer, is concentrated along surfaces that presumably represent the walls of open 

channelways or vugs. Away from such surfaces, it is in isolated 

flakes that in many places project into small voids between beryl and 

quartz crystals. Because the molybdenite' commonly is partly embedded in beryl or quartz and may be completely enclosed in transparent beryl, it is reasonable to assume that the molybdenite formed 

in part contemporaneously with beryl and quartz. The occurrence 

of the large masses of molybdenite interstitial to beryl and quartz 

crystals as described by Worcester (1919, p. 36) indicate, however, 

that these masses were deposited after beryl and quartz.

Muscovite is relatively abundant in the vein as scattered flakes, 

scales, and crystals, none of which are more than 3 millimeters in maximum dimension. Like molybdenite, with which it is associated in 

places, muscovite coats the walls of vugs and may be on, or enclosed in, 

crystals of beryl. Specimens of altered and mineralized wall rock on 

the dump consists largely of fine-grained sericitic mica. The crystallization of muscovite probably began and ended during the early stage 

of molybdenite formation.

A single broken crystal of a black submetallic mineral, found on 

the dump, was identified as impure rutile by X-ray and other tests 

made by the Geological Survey laboratory. The crystal was embedded in milky quartz associated with beryl and molybdenite.

Several fragments of colorless to dark-purple fluorite were found 

on the dump and in minute crystals and grains in altered wall rock.

Worcester (1919, p. 36) noted considerably more pyrite in the 

mineralized wall rock than in the vein; however, no pyrite was seen 

in any of the vein material collected in this investigation, and probably the mineral was not a common constituent of the vein where 

mined. Chalcopyrite was reported by Hess (1920, p. 912'), and Landes 

(1934, p. 698) reports finding "a few very small fragments of black 

tourmaline."

Minute fibrous lemon-yellow crystals of molybdite form powdery 

films or felty aggregates and are in close association with molybdenite. 

Molybdite commonly fills the voids between other minerals and oc-
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO HI

curs with jarosite in pyrite molds in altered wall rock. Worcester 

(1919, p. 36) has noted that although molybdite is more abundant 

in the upper workings, it is found in considerable quantities in the 

main tunnel level. Molybdite from the California mine was studied 

and analyzed by Schaller (19ll, pp. 84-92) as part of an investigation 

which found the mineral to be hydrated ferric molybdatc (Fe2 03 . 

SMoOs.T^^O), rather than molybdenum trioxide as was previously 

believed.

An incomplete crystal of a radioactive mineral was found on the 

dump above the portal of the lower adit. The crystal, showing only 

what appear to be prism faces, is roughly square in cross section and 

about 5 millimeters in length. The exterior of the crystal has a 

brownish-yellow coating resulting from alteration, but freshly broken 

surfaces are black and have a submetallic luster. Quantitative spectrographic analyses and X-ray powder patterns made by the Geological 

Survey laboratory show the mineral to be brannerite, essentially an 

oxide of titanium and uranium. The brannerite is metamict, being 

isotropic and giving an X-ray powder pattern only after ignition. 

This species has previously been reported from only one locality 

(Hess and Wells, 1920, pp. 225-237, 779-780), a gold placer in Ouster 

County, Idaho.

PAEAGENESIS

The limited information obtained from surface exposures and dump 

material makes it difficult to reconstruct the history of the vein. Some 

conclusions involving the individual minerals can be drawn, however, 

together with generalizations regarding the deposit.

(1) Quartz makes up the bulk of the vein and appears to have been 

deposited almost continuously throughout the period of vein formation. Locally, accessory minerals are either abundant or sparse. 

Feldspars appear to be absent.

(2) Beryl is concentrated along the outer edges of the vein, where 

most of it is embedded in quartz. The deposition of beryl probably 

began at the same time as that of quartz, but terminated earlier.

(3) A minor amount of beryl forms a vuggy intergrowth with 

quartz. This beryl is thought to be generally of later formation than 

the beryl completely enclosed in quartz. The quartz in the vuggy 

intergrowths is commonly smoky or colorless in contrast to the more 

abundant milky quartz.

(4) Molybdenite is partly embedded in the quartz and beryl of 

the vuggy intergrowths, and it projects into voids between the crystals. 

Molybdenite deposition may have begun early in the period of vein 

development but most of the molybdenite formed later along open 

fissures resulting from incomplete filling of vein space by quartz 

and beryl.
112 A CONTRIBUTION TO ECONOMIC GEOLOGY

(5) The deposition of muscovite began about the same time as 

molybdenite but probably was of shorter duration.

(6) Pyrite probably formed about the same time as molybdenite 

largely from the reaction of sulfide-rich solutions on the iron-bearing 

minerals in the wall rocks.

(7) The formation of vugs began early in the history of the vein 

by channelways being progressively sealed off leaving voids in which 

solutions of varying composition were trapped. The solution present 

in any particular void is believed to represent a fraction of the vein 

fluids passing through the channel way just prior to entrapment, and 

the minerals deposited on the walls of this void will be those representative of that particular stage of mineralization. For example a 

vug such as described on page 106 probably enclosed fluids of the 

period when molybdenite deposition began. The vug contained the 

early minerals, quartz, and beryl, a minor amount of muscovite, and 

some molybdenite as indicated by secondary molybdite. The clear 

transparent beryl of the vug suggests growth in an undisturbed 

environment.

(8) Late vugs or open fissures have the same mineral assemblage, 

with abundant molybdenite coating all other minerals. The beryl is 

"opaque" or cloudy.

(9) A change in the nature of the solutions sometime after molybdenite deposition resulted in corrosion of the vein. This action probably was very limited as most of the fissures had been sealed off. Both 

beryl and quartz were attacked, leaving molybdenite flakes standing 

out in relief from the etched surface.

(10) Oxidation of the pyrite and molybdenite followed corrosion 

of the vein. Pyrite has been oxidized to a much greater extent than 

molybdenite and has left numerous cubic molds in the wall rock that 

are now filled wholly or partly with light-buff powdery jarosite and 

yellow needles of molybdite.

TEMPERATURE OF FORMATION

Tests were made to determine the temperature of crystallization 

of beryl and fluorite from the California vein. These tests, based 

on the temperature of disappearance of the vapor phase of fluid 

inclusions, wero made by Earl Ingerson of the Geological Survey.

Determinations were made on two specimens, a crystal of glassy 

straw-yellow beryl and a cleavage fragment of very pale purple 

fluorite, both showing several fluid inclusions. The results, unconnected 

for pressure, are given below:

Mineral Temp, range °C Inclusions tested 

Beryl _______________250-255_______________ .8 

Fluorite ___._________265-272_______________ . 7 ,
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 113

The depth at which the California vein formed is not known, but 

according to Ingerson (1947, p. 383) the pressure correction to be 

added would be only about 65° C assuming a depth of 10 kilometers. 

Applying this correction would bring the temperature of the beryl 

crystallization to about 315° C, or close to the lower limit of the 

hypothermal range as defined by Lindgren (1933, p. 212). The 

particular beryl crystal tested was of the late-stage type that developed in vugs, hence its temperature of crystallization probably was 

somewhat lower than that at which vein deposition began but is 

higher than the temperature range existing during the period of 

maximum molybdenite deposition.

BERYLLIUM RESOURCES

In the brief reconnaissance of the granitic area of Mount Antero 

and White Mountain nothing was seen that could be considered a 

commercial deposit of beryllium minerals. The pegmatites, although 

unusually rich in beryl, are generally so small and so widely scattered 

that they are valueless except as a source of gems and specimen 

material.

On the basis of the analysis of a composite of chip samples collected 

from White Mountain, it was first thought that the granite might 

contain appreciable beryllium. A composite sample of small granite 

fragments collected from several exposures on the north slope of 

White Mountain had a BeO content of 0.018 percent (spectrographic analysis by Saratoga Laboratories, Inc.). The fragments 

making up the sample were taken at some distance from pegmatites 

and showed no megascopic beryl. The results of additional samples 

taken in 1951, however, tend to disprove this and indicate the beryllium content of the granite of the main stock and outlying masses 

to be insignificant.

Little information could be obtained regarding the possible beryl 

resources of the California vein. As previously stated, there is 

reason to believe that the vein continues for 1,000 feet to the northeast, 

and possibly the mineralized vein material exposed in the prospect pit 

(fig. 28, locality D) represents the extension of the vein more than 

a half mile from the mine.

Examination of the dump of the California mine suggests that as 

much as 10 percent beryl may have been present in molybdenite-rich 

parts of the vein. As exposed on the surface in the vicinity of the 

mine workings, the vein shows little beryl or molybdenite, and in part 

is apparently barren. A channel sample taken across an outcrop 

contained 0.016 percent beryllium oxide (spectographic analysis by 

Saratoga Laboratories, Inc.), the equivalent of a little over 0.1 percent beryl; the vein as exposed may average less.
114 A CONTRIBUTION TO ECONOMIC GEOLOGY

Although most of the beryl is readily recognizable, the general 

size of the crystals is too small for efficient hand sorting. From 

Worcester's observations it would be expected that any beryl-rich 

parts of the vein that might be developed also would contain considerable molybdenite, and for the economic exploitation of the vein 

it would be almost imperative to utilize some method of milling 

that would recover both minerals efficiently. Any successful operation of the deposit certainly would depend on the extension or recurrence of rich ore, factors than cannot be predicted with the limited 

geologic information now available.

Undoubtedly much could be learned about the vein by reopening 

the underground workings. To do this, at least a ton of slide rock 

would have to be removed from the portal before even the condition 

of the adit coulcl be determined. Surface sampling has been limited 

to a few small outcrops. Additional exposures could be obtained 

only by much difficult trenching through slide rock that may be as 

much as 10 feet in depth. Exploration by core-drilling probably 

would yield good structural information, but the presumably spotty 

distribution of the valuable minerals in a narrow vein would make 

sampling by this method unreliable.

BERYLLIUM-BEARING QUARTZ VEINS OF 

OTHER AREAS

Beryl has .been reported from several metalliferous veins throughout 

the world, and probably this mineral is present, but has been overlooked in many other deposits. These occurrences of beryl are all in 

quartz veins that in many places contain tungsten, tin, molybdenum, 

or bismuth in economic quantities. These metallic elements are not 

uncommon in granite pegmatites but, unlike beryllium, they are rarely 

sufficiently abundant to be of economic interest.

The mineralogy of several of the reported vein occurrences of beryl 

is given for comparative purposes:

Wolframite veins in the Torrington district, New South Wales 

(Runner and Hartman, 1918, p. 32) contain beryl associated with 

native bismuth, molybdenite, chalcopyrite, arsenopyrite, cassiterite, 

ilmenite, monazite, fluorite, topaz, smaltite, and lithia mica.

At the La Corne molybdenite deposit, Quebec, described by Norman 

(1945, pp. 1-17) quartz veins with margins of plagioclase or muscovite contain molybdenite with minor amounts of pyrite, and less 

commonly, native bismuth, bismuthinite, chalcopyrite, and columbite. 

Norman (1945, p. 15) states that "conspicuous amounts of tourmaline 

and beryl are present in some veins, and a little scheelite occurs rarely."

In describing the mineralogy at the San Antonio mine in Argentina, 

Smith and Gonzales (1947, p. 31) state:
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 115

Practically the only minerals in the tungsten veins are wolframite and quartz. 

The presence of sparse grains of sulphides is suggested by spots of secondary 

copper and arsenic (?) minerals, but no sulphides were seen. A few crystals 

of beryl were found in one vein.

Beryl occurs in the tungsten veins at Boreana, Ariz,, (Hobbs, 

1944, p. 254) where it is associated with wolframite, scheelite, and 

chalcopyrite in a quartz gangue. Other minerals in the tungsten 

veins are fluorite, pyrite. arsenopyrite, molybdenite, a little calcite, 

and small stringers of microcline.

At Irish Creek, Virginia (Koschman, Glass, and Vhay, 1942) beryl 

is found in the tin lodes as minute crystals that are most abundant at 

the edges of the quartz veins, but also are scattered throughout the 

bordering greisen. The veins contain cassiterite, muscovite, fluorite, 

phenakite, carbonates, minor wolframite, and sparse sulfides including 

bismutoplagionite (5PbS.4Bi2 S3 ).

Reid (1919, p. 70) mentions beryl at the S and M Syndicate mine 

in Tasmania. The major economic minerals of the vein are wolframite, cassiterite, bismutite, and bismuthinite, and the subordinate 

minerals are native bismuth, molybdenite, scheelite, gold, chalcopyrite, 

pyrite, arsenopyrite. galena, monazite, and limonite. The gangue 

is largely quartz, with lesser amounts of fluorite, topaz, pinite, and 

beryl. The other minerals noted were calcite, satin spar and 

laumontite.

Occurrences of beryl in quartz veins in Kazakhstan S. S. R., are 

described briefly by Sinegub (1943, pp. 129-157). The usual association is with tin and tungsten, but two veins in granite near the 

Karagaila River contained beryl, molybdenite, and bismuthinite. 

Sinegub states:

In the first vein, in addition to beryl, which occurs along its entire length, 

there are also large druses of molybdenite and bismuth glance; in the second, 

besides beryl, bismuth glance occurs chiefly. There is some muscovite in the 

structure of the vein. Tourmaline is entirely absent. The beryl is distributed 

in the veins more or less evenly ; it also occurs in the form of schliers segregations 

in the granite together with schliers of amazon stone.

In the vicinity of Sherlovoi Gore (Schorl Mount), (Sinegub, 1943; 

Fersman, 1940, pp. 120-122) in the Agin Buryat Mongolian National 

District of eastern Siberia, beryl occurs in veins cutting a granite 

laccolith. The veins generally are symmetrically,zoned as follows:

1. Greisen layer along walls contains quartz, green topaz, and 

fluorite.

2. Smoky quartz, in places in well formed crystals.

3. Ferberite (wolframite^), basobismutite (Frondel, 1943, p. 531), 

topaz, and other minerals.

4. A central core of greenish-blue beryl.
116 A CONTRIBUTION TO ECONOMIC GEOLOGY

In addition to the minerals mentioned above, Fersman states that 

the following occur in the veins: Native bismuth, gold, molybdenite, 

cassiterite, arsenopyrite, pyrite, chalcopyrite, sphalerite, bismuthinite, 

scheelite, molybdite, torbernite, monazite, scorodite, malachite, goethite and hematite, biotite, potassium and lithium micas, potash 

feldspar, tourmaline, kaolinite, and siderite (?). -

Holser 1 reports a quartz vein in the Victorio Mountains, Luna 

County, N. Mex., that contains beryl, hiibnerite, and scheelite. The 

beryl occurs irregularly in a hanging-wall quartz-mica selvage, as 

crystals up to 5 millimeters in diameter and 5 centimeters in length. 

The vein is in dolomitic limestone.

At Winslow, Maine (Hess, 1905, p. 163) beryl occurs in quartz veins 

in schist, associated with cassiterite, lepidolite, fluorite, and arsenopyrite.

Beryl is present in several of the tin-bearing quartz veins of Hill 

City district, Pennington County, S. Dak. (Page and others, 1953). 

These deposits contain "primarily milky-white vein quartz, clots and 

streaks of fine-grained muscovite, and clots or masses of white beryl." 

Attempts have been made to mine these veins for cassiterite.

The writer has been unable to find any reported occurrence of beryl 

in base-metal deposits, although beryllium is known to occur in a few 

such deposits as a constituent of other minerals, notably helvite (Burbank, 1933, pp. 513-517; Hewett, 1937, pp. 803-804; Weissenborn, 1948, 

pp. 648-649).

In the several beryl-bearing veins described above, copper commonly 

is present in small amounts, but lead and zinc are uncommon or absent. 

Conversely, topaz, cassiterite, tourmaline, monazite, and wolframite, 

generally considered to be high-temperature minerals, may be present 

in conspicuous amounts.

In his description of the California vein, Landes (1934, p. 702) 

concludes:

The relationship between beryl and pegmatites is so close that one is justified 

in assuming that beryl-containing deposits have been formed by peginatitic solutions. The quartz-molybdenite-beryl vein of Chaft'ee County, Colorado, which 

occurs in a region of granite and pegmatite intrusion, is thought to have been 

deposited by hydrothermal solutions escaping from a deeper solidifying pegmatite. 

If these conclusions are correct, quartz veins containing beryl may be looked upon 

as a link connecting pegmatites with normal quartz veins.

In a later paper (Landes, 1937, p. 559) devoted to the relationship 

between pegmatites and hydrothermal veins, Landes states:

Granitic magmas produce pegmatites and these in turn produce hydrothermal 

solutions which may precipitate ores of tin, tungsten, and molybdenum both in 

the pegmatite and in veins in the country rock adjacent to and for indefinite 

distances above the pegmatite.

1 Holser, W. T., 1952, Beryl and helvite in the Victorio Mountains. New Mexico : U. S. 

Geol. Survey Trace Elements Inv. Kept. 166. [Unpublished.]
BERYLLIUM DEPOSITS, MOUNT ANTERO REGION, COLORADO 117

The writer is in agreement with Lancles' statement that the presence 

of beryl appears to link the quartz veins and the pegmatites, but he 

cannot wholly subscribe to a pegmatitic origin for all these veins. 

From the mineralogy of the examples cited above, it seems apparent 

that some of the deposits, for example, the La Corne, Quebec, molybdenite veins, closely resemble pegmatites; but others, like the Tasmanian occurrence, are richer in heavy metals, contain little or no feldspar, and may be considered to have a closer kinship to hydrothermal 

veins. It would seem reasonable to assume an essentially continuous 

sequence of deposits having a common magmatic source and ranging 

from pegmatites through the high-temperature quartz veins to the 

normal heavy-metal veins. In the transition from pegmatite to metalliferous vein, conditions highly favorable for beryl development may 

change to those in which beryl cannot form and in which any remaining beryllium must be precipitated as some other compound.

INDEX OF REFRACTION OF BERYL FROM 

NONPEGMATITE DEPOSITS

The study of beryl from the California mine and from some of the 

localities discussed in the preceding section indicates that the index 

of refraction (w) of beryl from the various deposits varies within the 

same range as the beryl from granite pegmatites (Page, L. R., and 

others, 1953). Beryl from simple pegmatites or from outer zones 

of complex ones generally has an index between 1.57 and 1.58. Indices 

higher than 1.58 characterize beryl from inner zones or late fracture 

fillings of lithia-bearing pegmatites. The increase of the index of 

refraction of pegmatite beryl is accompanied by a decrease in the BeO 

content through the substitution of certain alkalies, notably Cs2O, 

Li2O, and Na2 0 for BeO.

Although beryl from only 9 localities was studied by the writer, it 

is believed that the data (table 1) indicate that the beryl in veins containing molybdenum or tin has a low or intermediate index compared 

to beryl associated with tungsten. The anomalous occurrence of lowindex beryl in the tungsten vein at the Victoria Mountains, New 

Mexico, (table 1) indicates that the relationship needs to be qualified, 

and it is not known to the* writer whether the index variations of 

beryl from nonpegmatitic deposits are accompanied by the same 

compositional changes found in pegmatite beryl.

LITERATURE CITED

Burbank, W. S., 1933, The manganese minerals of the Sunnyside veins, Eureka

Gulch, Colorado : Am. Mineralogist, vol. 18, pp. 513-527 

Crawford, II. D., 1913, Geology and ore deposits of the Monarch and Tomichi

districts, Colorado : Colorado Geol. Survey Bull. 4, 317 pp.
118 A CONTRIBUTION TO ECONOMIC GEOLOGY

Fersrnan, A. E., 1940, Pegmatites, vol. 1, Granite pegmatites, 3d ed.: Acad.

Sci. U. S. S. R. (Akad. Nauk), 712 pp. 

Frondel, (Clifford, 1943, The oxides and carbonates of bismuth: Am. Mineralogist,

vol. 28, pp. 521-535. 

Genth, F. A., and Penfield, S. L., 1892, Contributions to mineralogy, no. 54: Am.

Jour. Sci., 3d ser., vol. 44, p. 387.

Hess, F. L., 1921, Molybdenum: Mineral Resources, U. S., 1917, pt. 1, pp. 907-915. 

Hess, F. L., and Graton, L. C., 1905, The occurrence and distribution of tin: U. S.

Geol. Survey, Bull. 260. 

Hess, F. L., and Wells, R. C., 1920, Brannerite, a new uranium mineral: Franklin

Inst. Jour., vol. 189, no. 2, pp. 225-237; no 6, pp. 779-780. 

Hewett, D. F., 1937, Helvite from the Butte district, Montana: Am. Minerologist,

vol. 22, pp. 803-1804. 

Hobbs, S. W., 1944, Tungsten deposits in the Boreana district and the Aquarius

Range, Mohave County, Ariz.: U. S. Geol. Survey Bull. 940-1, pp. 247-264. 

Ingerson, Earl, 1947, Liquid inclusions in geologic thermometry: Am. Mineralogist, vol. 32, pp. 375-388. 

Koschmann, A. H., and Glass, J. J., and Vhay, J. S., 1942, Tin deposits of Irish

Creek, Virginia: U. S. Geol. Survey Bull. 936-K, pp. 271-296. 

Landes, K. K.* 1934, The beryl-molybdenite deposit of Chafl'ee County, Colo.:

Econ. Geology, vol. 29, pp. 697-702. 

Landes, K. K., 1937, Pegmatites and hydrothermal veins: Am. Mineralogist, vol.

22, pp. 551-560.

Lindgren, W. S., 1933, Mineral deposits, 4th ed., McGraw-Hill Book Co., 930 pp. 

Montgomery, Arthur, 1938, Storm over Antero: Rocks and minerals, vol. 13, pp.

355-369. 

Norman, G. W. H.. 1945, Molybdenite deposits and pegmatites in the Preissac-La

Corne area, Abitibi County, Quebec: Econ. Geology, vol. 40, pp. 1-17. 

Page, L. R., and others, 1953. Pegmatite investigations, 1942-45, Black Hills,

South Dakota: U. S. Geol. Survey Prof., Paper 247. [In press.] 

Reid, A. Mclntosh, 1919, The mining fields of Moina, Mount Claude, and Lorinna:

Tasmanian Geol. Survey, Bull. 29,183 pp. 

Runner, J. J., and Hartmann, M. L., 1918, The occurrence, chemistry, metallurgy,

and uses of tungsten: South Dakota School of Mines, Bull. 12, pp. 4-159. 

Schaller, W. T., 1911, Mineralogical notes, ser. 1: U. S. Geol. Survey Bull. 490. 

Sinegub, E. S., 1943, Berill: Nematallicheskiye iskopayemye, U. S. S. R, MoscowLeningrad, vol. 2, pp. 129-157. 

Smith, W. C., and Gonzales, E. M., 1947, Tungsten investigations in the Republic

of Argentina, 1942^3; U. S. Geol. Survey Bull. 954-A, pp. 1-37. 

Switzer, George, 1939, Granite pegmatites of the Mount Antero region, Colorado :

Am. Mineralogist, vol. 24, pp. 791-809. 

Weissenborn, A. E., 1948, A new occurrence of helvite: Am. Mineralogist, vol.

33, pp. 648-649. 

Worcester, P. G., 1919, Molybdenum deposits of Colorado : Colorado Geol. Survey

Bull. 14. .
INDEX

Page 

Albite -- 99, 100

Andesite.. - -- 98,105

Apatite.....-.-........-...---..---------.--. 99,105

Arkansas River Valley...---------..--------- 95,96

Arsenopyrite.......... .. ....... 114

Baldwin Gulch._____-_ ___. 96,98,101

Bertrandite- . -- 95,99

Beryl, color..............- ....... 105-107,108; 112

growth environment... - 105-106

index of refraction. _.________. 107-108 

temperature of crystallization..- ...- 112-113 

vein occurrence.-.---- 95,98,103,104,110,115-116

Biotite............... . . 99,103

Bismuth................................... 114,113

Bismuthinite--------------------------- - 114

Boreana, Ariz., tungsten veins____----- 115

Brannerite.-- 100,105,111

Browns Creek.......-..-...--....-.-....- 9(5,101

Cassiterite...--.------------------------- 114,116

Chalcopyrite...-. .- 110,114,115

Chlorite --- ..----. ...-.... - - 103

Columbite... _ ............................. 114

Condition of underground workings..-------- 114

Cyrtolite..---------------------------------- 100

Eastern Siberia, occurrence of beryl.. 115 

Fluorite..... ..--.-- ----- 100,106,110,112 

Garnet-..--------.-- . ..---... ...... 99

Helvite --------------------------- 116

High-temperature minerals---..---.--..___ 116 

Hill district, Pennington County, S. Dak., tinbearing quartz vein_........... 116

Hiibernite 100,105,110

Ilmenite - - -- - - - ------ 114

Index of refraction.......__.............. 107-108

Irish C.eek, Virginia, beryl in tin lodes....... 115

Jarosite-... . . . -. Ill, 112 

Kazakstan S. S. R., beryl in quartz vein. .- 115

La Corne, Quebec, molybdenite deposit_... 117 

Laumontite......- ------- --. 115

Limonite.- _-__.__._____._.. 99,100

Little Browns Creek.

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96

Magnetite.-....---------..------------------. 99,103

Microcline....___..__. ...... .. ...- 100

Molybdenite.. 95, 100, 101, 103-104, 105, 108, 110,

].U, 114 

Molybdenum Mines Co., of Denver... .... 103

Monarch and Tomichi mining districts.__.. 103 

Monazite..._..__.____-______ 114,116 

Muscovite-..-...-.. ------ 99,100,104,110,112

New Alpine.

Pheaakite ....... 95,99,100

Finite....---.-------------------------------- 115

Princeton batholith........................... 98

PrincPton quartz monzonite.------------.-.- 98,99

Pyrite.. . .... 104,110-111,112,115

Rutile..- -. --. ...... 105,110

S and M Syndicate mine in Tasmania, economic minerals.-..-__------- 115

San Antonio mine in Argentina, beryl crystals

in tungsten veins.. ___. _ 114 

Sawatch Range.... ..___...- ....- 95

Scheelite. . 115,116

Schlieren........ -------- .. . -.. 99

Sericite 101,101

Sphalerite...--------------------.--.-----.- 116

Spectrographic analyses.___-... 101; 108-109

Temperature of crystallization, of beryl.-... 112-113 

of fluorite.--.---.-------------------- 112-113

Tin.... . . . . 114,115,116

Topaz..------------...--.-.-.--.-. - 99,114.115

Torberite.------------.-----------.------ 116

Torrington district, New South Wales, wolframite veins.......__-....- _ 114

Tourmaline-------....---.-.-------- 105,115.116

Tungsten.....-.-..---.----.-------.-..- - 114-115

Victoria Mountains, Luna County, N. Mex.,

quartz vein......----------- 116

Vugs, formation of .. -.- . . 112

intergrowth of--------------.-------. 106,111

Winslow, Maine, occurrence of beryl in quartz

veins-..---------------------..- 116

Wolframite. 114,115,116

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