Geochemistry and 

Mineralogy of the 

Colorado Plateau 

Uranium Ores

Compiled by ROBERT M. GARRELS and ESPER S. LARSEN 3 D

GEOLOGICAL SURVEY PROFESSIONAL PAPER 320

A summary of the results of field and laboratory 

studies concerned with the nature of the ores and 

the alteration processes affecting them. 

This report concerns work done partly on behalf 

of the U.S. Atomic Energy Commission and is 

published with the permission of the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
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 32.00 (paper cover)
FOREWORD

The urgency and magnitude of the uranium resources program have provided an unequaled opportunity to 

investigate the Colorado Plateau uranium ores. This volume summarizes the results of field and laboratory 

studies concerned with the nature of the ores and the alteration processes affecting them. Thirty scientists have 

contributed directly; they include specialists in structural geology, sedimentation, sedimentary petrology, groundwater geology, mineralogy, nuclear geology, crystal chemistry, structural crystallography, physical chemistry, 

and analytical chemistry. The studies are aimed at understanding the ores from these varied points of view.

With such a diversity of effort at work, speculation becomes more and more restricted by the empirical and 

experimental facts that are developed. Thus the facts, combined with only modest speculation, have led the 

writers of this volume to a number of important conclusions, not all new, but certainly better founded than heretofore, concerning the Plateau ores. Among the most important are: (1) the carnotite and similar ores that 

have yielded the great bulk of the production up to now are the weathering products of a different sort of primary 

ore; and (2) the primary ores are a lower valence assemblage, the predominant type consisting of vanadium clay 

minerals together with uraninite, coffinite, and montroseite present in rocks containing organic remains chiefly 

of wood. The geologic environment and the chemical course of the weathering process are now well understood 

in general outline, although much detail is still lacking.

The data and conclusions presented should prove helpful in future exploration for uranium on the Plateau, 

particularly in exploration at greater depth and in primary ores. For example, in districts in which abundant 

vanadium is associated with uranium, the stratigraphic and structural controls, the size, and the tenor of primary 

ore bodies should be comparable to the weathered ore bodies; where vanadium is scarce, the primary ore body 

may be smaller but richer than its weathered counterpart.

In addition many of the data have direct application to other types of uranium deposits than those represented on the Colorado Plateau. The general patterns of the oxidation of uranium (and of vanadium) are sufficiently determined so that they apply to any natural environment, although the details of structure and chemistry 

may vary widely.

Perhaps the greatest value, in the long run, is the establishment of the nature and environment of the primary 

ores. Knowing their habitat and their nature, we can speculate upon their origin: the source of the uranium 

and associated elements, the nature and course of the fluids that carried them, and the environmental changes 

that caused their precipitation. We are proceeding now to collect data that will give limits to our speculation.

EARL INGERSON 

September 6, 1956 Chief, Geochemistry and Petrology Branch

C. A. ANDERSON 

Chief, Mineral Deposits Branch

m

CONTENTS

Foreword. __ 

Introduction.

Part 1. Geologic setting of the Colorado Plateau ores, by 

Alice D. Weeks and R. M. Garrels________

2. Characteristics of the host rock, by Robert A. 

Cadigan _________________________________

3. Elemental composition of the sandstone-type 

deposits, by E. M. Shoemaker, A. T. Miesch, 

W. L. Newman, and L. B. Riley_-__-____.

4. Occurrence and chemical character of ground 

water in the Morrison formation, by David A. 

Phoenix _________________________________

5. Summary of the ore mineralogy, by Alice D. 

Weeks, Robert G. Coleman, and Mary E. 

Thompson _______________________________

6. Behavior of uranium minerals during oxidation, 

by R. M. Garrels and C. L. Christ.______

7. The crystal chemistry and mineralogy of vanadium, by Howard T. Evans, Jr_____________

8. Synthesis of calcium vanadate minerals and 

related compounds, by Richard Marvin and 

George B. Magin, Jr______________________

9. Clay minerals in the mudstones of the ore-bearing formations, by W. D. Keller.___-_______

10. Chemical study of the mineralized clays, by 

Margaret D. Foster.______________________

11. Mixed-layered structures in vanadium clays, by 

John C. Hathaway______________________

Page 

III

1

3

13

25

55

65

81

91

103

113

121

133

Paere

Part 12. Association of uranium with carbonaceous materials, with special reference to the Temple 

Mountain region, by Irving A. Breger and 

Maurice Deul____--_-_---_----___________ 139

13. Radium-uranium equilibrium and radium-uranium ages of some secondary minerals, by 

T. W. Stern and L. R. Stieff_.._.___.______ 151

14. Some quantitative aspects of the oxidation and 

reduction of the ores, by R. M. Garrels and 

A. M. Pommer_-_.____-------_________. 157

15. Detailed chemical and mineralogical relations in 

two vanadium-uranium ores, by R. M. Garrels, 

E. S. Larsen, 3d, A. M. Pommer, and R. G. 

Coleman__ _ ____________________________ 165

16. Mineralogy of the uranium deposit at the Happy 

Jack mine, San Juan County, Utah, by Albert 

F. Trites, Jr., Randall T. Chew III, and Tom 

G. Levering _____________________________ 185

17. Sedimentary structures and localization and oxidation of ore at the Peanut mine, Montrose 

County, Colorado, by Carl H. Roach and 

Mary E. Thompson_.____ __________ 197

18. Geology and mineralogy of the J. J. mine, Montrose County, Colorado, by Donald P. Elston 

and Theodore Botinelly______________ 203

19. Mineralogy and geology of the Rifle and Garfield 

mines, Garfield County, Colorado, by Theodore Botinelly and R. P. Fischer__________ 213

20. Vanadium and uranium in rocks and ore deposits,

by R. P. Fischer_____________ __ _ 219

21. The known and unknown____________________ 231
GEOCHEMISTRY AND MINERALOGY OF THE COLORADO PLATEAU URANIUM ORES

Compiled by EGBERT M. GAKRELS and ESPER S. LARSEN 3d

INTRODUCTION

The uranium ores on the Colorado Plateau, which 

covers parts of Colorado, Utah, Arizona, and New 

Mexico, are the principal domestic source of uranium. 

A very great effort has been devoted to unraveling the 

geologic relations of the ores to the enclosing rocks, 

and a great effort has gone into geochemical investigations of the ores.

Until very recently, most of the uranium came from 

ores in which uranium was in its highest valence state 

U(VI), such as carnotite and was commonly associated with minerals containing vanadium in its highest 

valence state V(V). These are the typical carnotite 

ores. In the past few years, an increasingly large part 

of the uranium has come from ores in which the uranium is present in uraninite and coffinite; that is, the 

uranium is in part at least in its lowest stable valence 

state, U(IV), and the minerals accompanying it are 

low-valence vanadium oxides or hydrated oxides, 

pyrite, marcasite, and other base-metal sulfides. These 

are the typical "black ores." In recent years, too, the 

carnotite-type ores have been found to grade downward in a number of deposits, through a zone of minerals of intermediate valence state, into the typical 

"black ores." Many workers were convinced, on the 

basis of the geologic relations in the field and the mineralogic character of the ores, that the "black ores" 

were the primary materials from which the highvalence (carnotite-type) ores were derived by oxidation during weathering. This concept is now widely 

accepted.

The studies reported here have been aimed at (1) 

testing this oxidation concept, (2) developing a knowledge of the stability relations of vanadium and uranium 

minerals under varying conditions of pH and oxidation-reduction potentials (Eh), and (3) defining the 

nature and equilibrium conditions of the "primary" 

(low-valent) ores. The origin of the primary ores is 

not specifically considered in these reports.

The parts that follow are summary reports of more 

extensive studies, many of which are still in progress. 

The first 5 parts present topical data of general application to the Colorado Plateau deposits; parts 6

through 15 cover the results of theoretical, experimental, or empirical studies relating to the chemical and 

physical nature of the ores and their oxidation; in parts 

16 through 19 are described the geological relationships 

between oxidized and unoxidized ore in several ore deposits on the Plateau; part 20 concerns the broad geochemical relationships of vanadium and uranium 

throughout the world. The final part summarizes conclusions and particularly emphasizes the salient problems requiring further study.

Part 1 contains no new or original data; it presents 

a background for the work reported on and a brief summary of the geology of the Colorado Plateau to serve 

as a setting for the parts that follow. No authorship 

is given for "The Known and the Unknown," which 

represents the conclusions of a large number of collaborators, a good many of whom are not authors of parts 

of this paper; it would be impossible to credit individuals with most of the ideas presented.

Semiquantitative spectrographic data are presented 

in several parts of this volume. Table 1 shows the 

limits of sensitivity of the method for the elements 

determined. These values are only approximate, as the

TABLE 1. Limits of sensitivity for elements determined by the 

Semiquantitative spectrographic method

Element

Si... .... ...

Al........ .....

Fe ... . ...

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

Ca.. . .........

Na.... .....

K_.. - .....

Ti..... _. ...

P.... . .

Mn.. .........

Atr

As......... ....

Au. ..... ...

B-. ...........

Ba....... .....

Be... ......

Bi.............

Cd.. ..........

Co.. .......

Co.. ..........

Cr..... .

Cs....... ......

Cu . ........

Dy............

Er .. .....

Percent

0.005

.0001

.0008

.00003

.01

.01

.1

.0005

.07

.0007

.00001

.01

.001

.005

.0005

.00005

.005

.005

.03

.001

.0006

.8

.00005

.006

.003

Element

F ...... ... ..

Ga...... ..... .

Gd-. -

Ge_. .. . -

Hf_...... 

Hg____ 

Ho 

In...... .......

Ir.. .......... .

La.... 

LL. ........ ...

Lu.. ........ ..

Mo... 

Nb .

Nd...... ..... .

Ni....... ......

Os..._. - .

Pb........ .... Pd 

Pr...... .... 

Pt...... ... ... .

Rb . ~

Re-.... 

Rh. .......

Percent

0.003

ns

.001

.006

.001

.007

.08

.001 nnfU

.03

.003

.01

.005

.0005

.001

.006

.001

.1

.001 ntvi

.01

.003

7

.04

.004

Element

Ru 

Sb. 

So 

Sn. ..... ....

Sr.... .........

Ta..._ .... .

Tb.. ...

To

Th_ - ... ....

Tl._._ ...... ...

Tm... 

U...... .......

V.. . ..........

w........ ... ..

Y.. ...........

Yb.. .......

Zn... . ... -

Zr...... ... ....

Percent

0.008

.01

.0005

.001

.001

.008

.1

.01

.08

.05

fU

.001

.08

.001

.05

.001

.0001

.008

.0008
GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

data reported have been collected at two laboratories 

over a period of years, during which the method has 

been refined and modified.

The major part of the work represented by this publication was sponsored by the Division of Raw Materials 

of the U. S. Atomic Energy Commission; smaller segments of the work were supported by the Division of 

Research of the Atomic Energy Commission and by 

the Geological Survey.

Many geologists of both the Atomic Energy Commission (including their contractors) and the Geological Survey have contributed ideas, materials, and 

courtesies without which the studies reported herein 

could not have been undertaken. Particular appreciation must be expressed to the staff of many of the 

mines. Their continuing cooperation permitted many 

and repeated mine examinations and extensive mineral 

collecting.
Part 1. GEOLOGIC SETTING OF THE COLORADO PLATEAU ORES

By ALICE D. WEEKS and R. M. GARRELS

CONTENTS

Geology of the uranium-ore region__-_-___- 

Topography and climate______--------

Sedimentary rocks___________________

Igneous rocks______________________

Structure __._______-__________-__--.

General description of the uranium deposits. 

Stratigraphic distribution-_--_--______

Page 

3 

3 

5 

5

5

6

6

General description of the uranium deposits Continued 

Distribution of the principal metals_______________

Characteristics of the ore_-_-____----_-__-_-_____

Age of the deposits___________________.._---_-__

Conditions at the time of ore deposition ___________

History and statement of the oxidation problem. _______

Literature cited...__________________________________

ILLUSTRATION

FIGURE 1. Map showing physiographic sections of the Colorado Plateaus province.

TABLE

TABLE 1. Generalized section of upper Paleozoic to lower Tertiary strata in southwestern Colorado and adjoining parts of 

Utah, Arizona, and New Mexico__-___----------______________________________________________________

Page

7

7

8

8

9

10

Page 

4

Page

GEOLOGY OF THE URANIUM-ORE REGION

Many reports on the geomorphology, stratigraphy, 

structure, and regional geology of the Colorado Plateau 

or various parts of it are available. Extensive bibliographies are given in many of these reports (Fenneman, 1931; Gregory, 1917, and 1938; Gillully and 

Reeside, 1928; Craig and others, 1955; Kelley, 1955a; 

Hunt and others, 1953, and Hunt, 1956). Most of the 

uranium deposits are in the east-central part of the 

Colorado Plateau and, therefore, the description which 

follows will be limited generally to a broad belt 

trending northwestward through the "Four Corners" 

area, the common corner of Colorado, Utah, Arizona, 

and New Mexico, and extending from the San Rafael 

Swell in Utah to the Grants district in New Mexico.

Figure 1 shows the general location of the uraniumbearing region of the Colorado Plateau (the Colorado 

Plateaus province of Fenneman) and its relation to 

the principal physiographic divisions and structural 

features of the Plateau. It also serves as a location 

map for places or mines receiving significant mention 

in the text; many place names used in the text are not

468652 59 2

shown, but they can be found on more detailed maps 

such as those of Finch (1955) and Kelley (1955) and 

on the geologic quadrangle maps * recently published 

by the U. S. Geological Survey. Other maps, including 

photogeologic maps, are listed in Wallace and Smith 

(1955).

TOPOGRAPHY AND CLIMATE

The uranium region occupies most of the Canyon 

Lands, and a part of the Navajo and Datil sections of 

the Colorado Plateaus province (Fenneman, 1931). 

The Canyon Lands consist of young to mature 

canyoned plateaus of high relief. The area is deeply 

dissected by the Colorado River and its tributaries 

which rise in the mountains bordering the plateaus. 

Most of the Canyon Lands lie between 5,000 and 7,500

1 These include the following quadrangles of western Colorado : Gateway, Map GQ55 ; Pine Mountain, Map GQ60 ; Juanita Arch, Map GQS1; 

Calamity Mesa, Map GQ61; Roc Creek, Map GQ83 ; Red Canyon, Map 

GQ58; Atkinson Creek, Map GQ57; Paradox, Map GQ72; Davis Mesa, 

Map GQ71'; Uravan, Map GQ78; Anderson Mesa, Map GQ77:; Bull 

Canyon, Map GQ33; Naturita N. W., Map GQG5 ; Horse Range Mesa, 

Map GQ64; Hamm Canyon, Map GQ69;. Gypsum Gap, Map GQ5&; 

Egnar, Map GQ68|;, andl Joe Davis Hill, Map- GQ66'.
GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

113° 111

109' 107° 105"

41*

Mines described in detail in this report

1 Rifle 4 J. J. and Mineral Joe

2 Garfield 5 Peanut

3 Virgin 6 Happy Jack

33 C

113" 111° 109° 107°

FIGURE 1. Map showing the physiographic sections of the Colorado Plateaus province (after Fenneman, 1931) and the principal structural 

features (largely after Kelley, 1955). Principal places mentioned in the text are also shown.
GEOLOGIC SETTING OF THE COLORADO PLATEAU ORES

feet above sea level and little of the area is below 5,000 

feet except the canyon bottoms. Stocks and laccolithic 

mountains rise several thousand feet above the surrounding plateaus and the highest point is in the LaSal 

Mountains, more than 13,000 feet above sea level. The 

climate is arid in the western and southern parts of 

the Canyon Lands (about 5 inches average annual rainfall at Hanksville, Emery County, Utah) and the vegetation is mainly bunch grass, saltbush, cactus, and sage. 

The higher mesas and plateaus receive more precipitation and support a growth of pinon and juniper. 

In the uranium region of western Colorado the average 

annual precipitation ranges between approximately 11 

inches at Paradox, Montrose County, and 16 inches at 

Norwood, San Miguel County. The highest mountains 

and plateaus have 20 inches or more average annual 

precipitation and a forest cover of spruce, pine, or 

aspen.

The northeastern part of Arizona and northwestern 

part of New Mexico in the Navajo section of the 

Colorado Plateaus province (Fenneman, 1931) is a 

dry country not as deeply dissected as the Canyon 

Lands because it has no large stream except the San 

Juan Kiver along the northern border of the Navajo 

country. Bedrock consists mainly of sandstone and 

shale strata having gentle dip. A few large volcanic 

plugs and many small plugs and dikes intrude the 

sedimentary rocks and are conspicuous in the topography; buttes, mesas, and hogback ridges are also 

common land forms.

The northern part of the Datil section in New Mexico 

is characterized by extensive lava flows in addition to 

the gently dipping sedimentary rocks.

The topography, climate, and vegetation of the 

Henry Mountains region, Utah, are described by Hunt 

and others (1953); that of the Navajo country and 

the San Juan country by Gregory (1917 and 1938).

SEDIMENTARY ROCKS

The rocks of the Colorado Plateau, and particularly 

the uranium ore region of the Plateau, are predominantly sedimentary, ranging in age from Precambrian 

to Tertiary. Precambrian metamorphic rocks are exposed along the Grand Canyon of the Colorado River, 

in the Central portion of the Zuni uplift, in valleys eroded in the Uncompahgre Plateau, and in the Black 

Canyon of the Gunnison River. Sedimentary rocks of 

Paleozoic age are exposed in the central part of the San 

Rafael, Monument, Kaibab, Defiance, and Zuni uplifts 

and in the salt anticline region (Wengerd and Strickland, 1954). Sedimentary rocks of Mesozoic age, the 

chief host rocks of the uranium and vanadium deposits, 

are exposed over large areas on the flanks of the uplifts 

and on the structural platforms and in some of the

basins between uplifts (McKee, 1951 and 1954; Stokes, 

1950; Baker, Dane, and Reeside, 1936; Craig and others, 

1955; and Young, 1955). Tertiary sedimentary rocks 

occur in considerable thickness in the San Juan, the 

Uinta, and the Piceance basins (the last two are chiefly 

outside the uranium region) and in lesser thickness in 

the Chuska Mountains, capping an unconformity on 

the Defiance monocline. The Mesozoic sedimentary 

rocks (table 1) include strata of fluviatile, lacustrine, 

eolian, volcanic, and marine origin and range from 

conglomerate, through sandstone, siltstone, and shale 

to limestone.

IGNEOUS ROCKS

Precambrian intrusive rocks are exposed in the Uncompahgre uplift, in the Black Canyon of the Gunnison River, and along the Grand Canyon of the Colorado 

River. In the central part of the Plateau are many 

small areas of younger intrusives. These include the 

stocks and laccoliths of the LaSal, Aba jo, and Henry 

Mountains in Utah, the Ute Mountains in Colorado, 

and the Carrizo Mountains in Arizona. They are composed mostly of diorite porphyry and range in composition from diorite to syenite (Gould, 1927; Hunt 

and others, 1953; Waters, 1955, p. 715-716); the age is 

probably early Tertiary. The Navajo country has many 

volcanic plugs, dikes, diatremes, and lava-capped mesas 

(Williams, 1936; Hack, 1942). Many of these are alkaline basalts, including chiefly minette in the Monument 

Valley and Shiprock areas and limburgite, monchiquite, 

and other unusual rock types in the Hopi Buttes volcanic field, and are probably younger than the stocks 

and laccoliths. Extensive Tertiary and Quaternary 

lava flows occur chiefly in the areas outside the principal 

uranium-producing districts, except those occurring 

near ore in the Mount Taylor region of New Mexico 

(Hunt, 1938).

STRUCTURE

The Colorado Plateau has about one-third of its total 

area occupied by basins ranging in structural relief 

from 700 to 14,000 feet, about one-fifth the area occupied 

by uplifts ranging in structural relief from 500 to 

5,000 feet, and nearly one-half the area is occupied by 

platforms, benches, gently dipping slopes, saddles, 

arches, sags (Kelley, 195 5a). The strata of the Plateau 

as a whole dip eastward and northeastward toward 

the deep basins that were filled during the Tertiary.

The chief structural features of the uranium-producing area are the Uncompahgre Plateau on the northeast of the salt anticline region (Dane, 1935; Cater and 

McKay, 1955; and Stokes, 1948), and the broad upwarps known as the San Rafael Swell, Circle Cliffs, 

Monument, Defiance, and Zuni uplifts each bordered
TABLE 1. Generalized section of upper Paleozoic to lower Tertiary strata in southwestern Colorado and adjoining parts of Utah, Arizona,

and New Mexico

System

Eocene

Cretaceous

Jurassic 

 ? 

Jurassic(?)

Triassic

Permian

 1 

Pennsylvanian

Group, formation, or member

Wasatch formation

Mesaverde group

Mancos shale

Dakota sandstone

Burro Canyon formation

Morrison formation

Summerville formation

Curtis formation

Entrada sandstone

Carmel formation

Navajo sandstone

Kayenta formation

Wingate sandstone

Chinle formation 

Shinarump member

Moenkopi formation

Cutler and Rico formations

Hermosa formation 

(Paradox member)

Thickness (feet)

3, 000+

1, 000±

2, 000-5, 000

50-200

50-250

300-500 

20(MOO

50-400

0-250

50-1, 000

0-600

0-2, 000

0-300

0-400

100-500 

0-100

0-1,000

0-6, 000

0-10, 000

Character and distribution

Varicolored shale, sandstone, and limestone; widespread.

Light-colored sandstone and gray shale; coal bearing; cliff forming; widespread.

Gray shale; forms valleys and steep slopes; widespread.

Gray and brown sandstone and shale; mesa capping; widespread.

Light-colored conglomeratic sandstone and green and maroon mudstone; mesa 

capping.

Brushy Basin shale member: varicolored shale (or mudstone), some sandstone 

lenses; forms slopes; widespread. 

Salt Wash sandstone member: light-colored sandstone and red mudstone; forms 

cliffs and benches; widespread.

Red and gray shale, thin sandstone; forms slopes; thickens westward.

Glauconitic sandstone, greenish shale, gypsum; present only in central Utah. 

Todilto limestone in New Mexico.

Light-colored massive cliff-forming sandstone in Colorado and eastern Utah; 

thickens westward and becomes red earthy sandstone.

Red earthy sandstone in Colorado and eastern Utah; thickens westward and 

becomes gray and red shale, limestone, and gypsum.

Light-colored massive sandstone; cliff forming; generally absent in Colorado, 

thickens westward.

Red sandstone, irregularly bedded; bench forming; absent in eastern part of 

region.

Red massive sandstone; cliff forming, absent in eastern part of region.

Red shale and sandstone; forms slopes; widespread (called Dolores in Colorado) .

Light-colored conglomeratic sandstone and shale; bench forming; absent in 

Colorado.

Red-brown shale and sandstone; forms slopes; absent in eastern part of region.

Red and gray shale, arkose, and conglomerate; thickest in Colorado though 

absent in places; thins gradually westward.

Gray limestone, black shale, salt, dolomite, anhydrite, gypsum; coarse clastic 

facies near Uncompahgre front in Colorado.

by a sharp monocline (Kelley, 1955b). Stocks and 

laccolithic intrusions (the LaSal, Abajo, Ute, Carrizo, 

La Plata, and Henry Mountains) dome the sediments 

around them. These stocks and laccoliths all intrude 

platform or basin areas and may have been controlled 

by lines of weakness adjacent to sunken sedimentary 

blocks. Kelley (1955a) notes the locations of these intrusives along three northwest lines parallel to the 

strike of the salt anticlines, the Uncompahgre uplift, 

and the lineaments of the Rocky Mountains.

GENERAL DESCRIPTION OF THE URANIUM DEPOSITS 

STEATIGEAPHIC DISTRIBUTION

Uranium deposits have been recognized in nearly 

all the sedimentary formations from Pennsylvanian to 

Tertiary age in the Colorado Plateau (Finch, 1955;

Isachsen, Mitchum, and Wood, 1955), but the major 

uranium and vanadium production has come from strata 

of Triassic age, especially the Shinarump member and 

other beds in the lower part of the Chinle formation, 

and from Jurassic rocks, particularly the Entrada sandstone, Todilto limestone, and Morrison formation.

Although many occurrences of uranium were known 

in Triassic formations in Utah long ago (Hess, 1914 

and 1925; and Butler, Loughlin, and Heikes, 1920) the 

chief production was from the Salt Wash member of 

the Morrison formation in southwestern Colorado (Coffin, 1921; Fischer, 1942) until after World War II. 

During the period 1948-53 several large mines the 

Monument No. 2 mine, Apache County, Ariz.; the 

Happy Jack and the MiVida mines, San Juan County; 

and the Delta (Hidden Splendor) mine, Emery County,
GEOLOGIC SETTING OF THE COLOEADO PLATEAU OEES

Utah and many smaller mines were opened in Triassic 

formations. Several large deposits have been found 

recently in the Morrison formation in New Mexico, one 

at the Jackpile mine in Valencia County and the others 

in the Ambrosia Lake area, McKinley County. All 

deposits in the Todilto limestone are in McKinley and 

Valencia Counties, New Mex., and all have been found 

since 1950. Deposits in the Entrada sandstone along 

the west side of the San Juan Mountains, southwestern 

Colorado, and in the Wingate(?) and Entrada sandstones near Kifle, Garfield County, Colo., are moderately 

large, but they are low in uranium and valuable mainly 

for their vanadium content.

In the Maybell-Lay area, Rio Blanco County, Colo., 

just north of the Colorado Plateau, deposits have been 

recently found in the Browns Park formations of late 

Tertiary age.

In some areas the principal deposits are restricted to 

one favorable stratigraphic zone, sandstone lens, or 

channel filling; in other areas ore is found at more than 

one horizon; in still others it crosses stratigraphic 

boundaries at a low angle. In the Uravan and Gateway districts, Colo. (McKay, 1955), all the large 

mines of the two districts are in the upper sandstone 

lens of the Salt Wash member of the Morrison formation, but small mines have been developed in the lower 

part of the Salt Wash member, or in the base of the 

overlying Brushy Basin member of the Morrison formation. In the Slick Rock district, San Miguel 

County, Colo., ore is mined from more than one horizon in the Salt Wash member, but almost all of it has 

come from the uppermost sandstone. In the Big 

Indian-Lisbon Valley area ore is mined from the Cutler formation (Permian), the Chinle (Triassic), and 

the Morrison (Jurassic). In the Grants-Laguna area 

in New Mexico, ore is mined from the Todilto limestone, the Morrison formation (chiefly Brushy Basin 

member) of Jurassic age and the Dakota sandstone 

(Cretaceous). At the Rifle vanadium mine, Garfield 

County, Colo., the ore dips more steeply than the sedimentary host rocks and crosses two formation boundaries.

DISTRIBUTION OF THE PRINCIPAL METALS

The relative abundance of uranium, vanadium, and 

copper in the ores varies both geographically and 

stratigraphically. More detailed information is given 

in the parts that follow, particularly in Part 3; also 

in Fischer (1955). In general, the Entrada sandstone 

on the eastern margin of the Plateau has deposits of 

vanadium with little uranium. The Morrison formation, particularly the Salt Wash member, has vanadium-uranium deposits with the V: U ratio commonly

between 5:1 and 10:1 in the Uravan mineral belt of 

western Colorado. The vanadium-uranium ratio is 

slightly lower in the Green River and the Henry 

Mountains districts in Utah, and is much lower toward 

the south in New Mexico. The deposits in the Shinarump member and other parts of the Chinle formation 

have a much wider range in composition than those in 

the Entrada and Morrison formations. Vanadiferous 

uranium deposits with a V: U ratio between 5:1 and 

1:1 occur at Monument Valley, Ariz.; Big Indian 

Valley, San Juan County, and Temple Mountain, 

Emery County, Utah. Copper-uranium deposits occur in the White Canyon area on the west flank of 

the Monument uplift in Utah, and uranium deposits 

with traces of other metals in many mines of the San 

Rafael Swell, Circle Cliffs uplift, Monument uplift, 

and in the Interriver district north of Moab, Utah. 

The Todilto limestone in the Grants-Laguna area of 

New Mexico has uranium ore with the V: U ratio 

about 1:2. Although traces of silver occur in several 

districts the only commercial silver deposits in the 

Plateau were those of the Silver Reef district, Washington County, Utah, where small amounts of uranium, 

vanadium, and copper were associated with the silver; 

and at the Cashin copper mine on LaSal Creek, Montrose County, Colo., where little or no uranium or 

vanadium is known. However, galena from the 

Cashin mine contains abnormal amounts of radiogenic 

lead and the lead is similar in isotopic composition to 

that in galena samples from the uranium-vanadium 

deposits.

CHARACTERISTICS OF THE ORE

The commonest type of host rock is the lenticular 

sandstone and mudstone facies of fluviatile sediments. 

Conglomerate, massive sandstone, limestone, and shale 

also contain ore in some areas. Volcanic debris, now 

largely altered to clay minerals, is associated with the 

principal ore zones; it is abundant in certain zones in 

the Chinle formation close above the basal Shinarump 

member and in the Brushy Basin shale member above 

the Salt Wash sandstone member of the Morrison formation, and lesser amounts are present within the orebearing sandstones. These relationships were studied 

by Waters and Granger (1953) who suggested the possible bearing of the volcanic material on the origin 

and precipitation of uranium.

The deposits are tabular, elongate, or podlike, in 

general parallel to the bedding but commonly with 

a gently undulant surface, or locally the ore boundary 

crosses the bedding in steep curved surfaces referred to 

as "rolls" by the miners. In length the ore bodies 

range from a few feet to thousands of feet, and in
8 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

thickness they range generally from a few inches to 10 

or 15 feet, rarely more than 50 feet. The ore may 

follow the bottom of a channel or sandstone lens or the 

top of a lens or sedimentary structure (as in a petroleum trap) or may appear to "float" midway in a permeable layer. A single deposit may range in grade 

from weakly mineralized rock below 0.10 percent U3O8 

(the lower grade of ores at present purchased by the 

Atomic Energy Commission) to strongly mineralized 

massive or disseminated ore. Locally high-grade ore 

consists of or is associated with richly mineralized 

fossil wood fragments or logs. The logs may be 75 

feet or more in length and contain small pockets of ore 

with 50 percent U3O8. The ore boundary ranges from 

a sharp distinct cutoff within a fraction of an inch to 

a broad transition zone grading into rock below ore 

grade.

Guides to ore in the Uravan mineral belt are organic 

matter, lenticular sandstone and mudstone strata, lightbrown sandstone and thick gray mudstone (altered 

from red to gray) under the ore-bearing sandstone 

(Fischer, 3950, and Weir, 1952). McKay (1955) 

shows that coincidence of lenticularity, favorable color 

of sandstone, and continuous gray mudstone underlying 

the sandstone are necessary for large deposits; and that 

lenticularity without the other characteristics (or vice 

versa) is unfavorable in the Gateway-Uravan district 

in Colorado. At the surface the favorable sandstone is 

buff with scattered brown speckles and at depth it is 

white or light gray with disseminated pyrite grains, in 

contrast to the average red sandstone of the Salt Wash 

member of the Morrison. Further description of the 

Morrison stratigraphy and guides to carnotite deposits 

in western Colorado are given by Craig and others 

(1955).

In the Shinarump member and other basal sandstones 

of the Chinle formation most of the uranium deposits 

are found in channels cut into the underlying formations near irregular pinch outs of the formation (Finch, 

1955). Carbonized wood fragments or logs, "altered" 

gray mudstone, and lenticular sandstone and mudstone 

in the channel filling indicate a favorable environment. 

Copper and iron stain, altered clay, and alunite and 

jarosite are common at the surface of the sulfide-rich 

deposits. Those uranium deposits low in vanadium or 

copper, aiid in sulfide minerals are more difficult to 

prospect than are either vanadium-uranium or copperuranium deposits, because recognizable secondary minerals are sparse.

Ore minerals are typically fine grained and fill the 

pore space of the sandstone, impregnate clay pellets and 

fossil wood, or replace the cell walls of the wood. Commonly, interstitial clay has been replaced or recrystallized and locally quartz grains have been corroded. 

Some zones of sandstone have an overgrowth of silica 

on the quartz grains that ranges from a thin coating 

giving the grains a crystal outline to a complete filling 

of the interstices with silica. Calcite is probably the 

commonest cementing material in the sandstones except near the salt anticlines where gypsum is locally 

predominant.

Sedimentary control of mineralization is common, 

and vein filling or fracture control is rare except in 

mines such as the Cashin or Big Indian copper mines. 

Secondary minerals coating joints should not be confused with primary fracture control. There is no indication that the temperature during ore deposition 

was significantly higher than that expected from the 

normal geothermal gradient at a depth of several thousand feet.

AGE OF THE DEPOSITS

Although many questions arise in making age determinations of these uranium ores, the problem has been 

approached from several angles, including a thorough 

isotopic study of all the major types of ore and the associated lead minerals and study of the various aspects 

of differential leaching or enrichment. These lines of 

evidence indicate that the ores were deposited not 

earlier than the Late Cretaceous or the early Tertiary 

(Stieff, Girhard, and Stern, 1950; Stieff and Stern, 

1952; Stieff, Stern, and Milkey, 1953). Oxidation of 

ores above the zone of saturation has taken place 

during Quaternary time (see Part 13), and those .ores 

that have remained below the zone of oxidation (saturated with water) are still relatively unoxidized.

CONDITIONS AT THE TIME OF ORE DEPOSITION

Assuming that the deposits were formed in Late Cretaceous time, estimates of the approximate thickness of 

cover of the ore zones were made, based on isopach maps 

of the Mesozoic formations (McKee, 1951, pis. 2 and 

3). Although the thickness of the different formations 

varies considerably across the broad expanse of the 

uranium region the cover of the Shinarump member 

and lower part of the Chinle formation was probably 

6,500 to 10,000 feet thick, and the cover of the Salt 

Wash member of the Morrison formation was probably 

5,000 to 8,000 feet thick. Levorsen (1954, p. 401) gives 

the average geothermal gradient in sedimentary rocks 

as 1.11° C. per 100 feet, abnormally high gradients 

about twice as great, and abnormally low gradients 

about one-third the average. At a depth of 5,000 feet 

the average temperature would be at 71° C with a possible range from 35° to 127° C, and at 10,000 feet depth 

the average temperature would be 127° C. with a possible range from 53° to 238° C.
GEOLOGIC SETTING OP THE COLORADO PLATEAU ORES 9

Another important condition at the time of deposition was the composition of the pore water in the 

various formations. Although we cannot determine 

specifically the composition in Late Cretaceous time, it 

seems fairly certain however, that the composition of 

the water differed considerably from one formation to 

another, as has been demonstrated in an extensive study 

of oil-field waters from Paleozoic and Mesozoic formations in Wyoming (Crawford, 1940). The assemblage of lithologic types in the uranium region of the 

Colorado Plateau includes limestones, dolomites, evaporites interbedded with black shales, fluvial deposits, 

volcanic ash, coal, and marine shales and sandstones. 

Such a wide variety of environments of deposition suggests a wide range in composition of formation waters. 

The Paradox member of the Hermosa formation of 

Pennsylvanian age contains salt, gypsum, anhydrite, 

and pyritic black shale (Wengerd and Strickland, 

1954), and recent wells drilled into this member in the 

Boundary Butte oil field on the Arizona-Utah border 

have found black sulfur water. Springs emerging from 

an intrusive plug of evaporite and black shale strata of 

the Paradox member at Onion Creek in T. 24 S., R. 

24 E. between Fisher Valley and the Colorado River, 

Grand County, Utah (Dane, 1935, pi. 1), are highly 

saline and contain H2S gas that is effectively bleaching 

the red color of shale pebbles along Onion Creek. In 

other areas, H2S gas is associated typically with salt 

intrusions (Dobbin, 1935, p. 1069), and with limestones, 

such as the Madison limestone (Mississippian) of Wyoming, and. in large quantity with the Rundle limestone 

in the Pincher Creek gas field in southwestern Alberta.

By Late Cretaceous time the volcanic ash in the 

Chinle and Morrison formations was probably devitrified and altered to bentonite. The waters in and near 

the bentonitic beds may have contained sodium bicarbonate derived by base exchange as Crawford (1940) 

postulated for the bentonitic beds in Cretaceous formations in Wyoming. Water bearing sodium bicarbonate 

is an effective solvent and carrier of uranium. The 

water in the fluvial deposits probably contained little, 

if any, H2S gas and was less saline than that in the 

typical marine deposits, which, in turn, was less saline 

than the water in the evaporite series.

During the Cretaceous period the waters of the 

deeper formations probably reached equilibrium with 

their environments, but as regional deformation began 

in Late Cretaceous time this equilibrium was disturbed 

by migration of oil and gas toward structural highs and 

by displacement and movement of water. Reaction 

would take place between clays and water of changing 

salinity as water moved through a formation or especially along the borders of the Paradox salt intrusions

where waters of quite different composition would come 

in contact. Zones of reducing environment favorable 

for ore deposition were present in the vicinity of carbonized logs and accumulations of plant fragments 

referred to in the field as "trash piles." They also may 

have been produced by H2S gas from the Hermosa or 

other formations, or along paths of migrating oil and 

gas. That oil and gas may have migrated through 

these rocks is suggested by the fact that the Morrison 

formation, Entrada sandstone, Shinarump member of 

the Chinle, and Hermosa formation all produce oil 

and gas (or either) in areas of Colorado and Utah 

where these strata are less strongly deformed than the 

salt anticline area and the steep monoclines (Grand 

Hogback, Comb Ridge, or San Rafael Reef) of the 

uranium region.

Work in progress in 1956 on the age of the stocks 

and laccoliths has not yet established their age relative 

to that of the uranium deposits. The importance of 

these intrusions as a factor influencing the deposition 

of the uranium ores has been considered but awaits 

proper evaluation.

HISTORY AND STATEMENT OF THE OXIDATION 

PROBLEM

The earliest workers on the Colorado Plateau (Hillebrand and Ransome, 1905, p. 17) recognized the possibility that the carnotite might represent the secondary 

product of some "material already existent in the sandstone" and that its deposition was determined by proximity to the surface, and was probably partly dependent 

upon a semiarid climate. Hess (1914 and 1933) thought 

that solutions were reduced on contact with vegetation 

in the sediment, and that later, upon the raising, draining, and oxidation of the rocks the minerals now found 

were formed. Butler and others (1920, p. 120) regarded all the deposits in the sandstone of the Plateau 

as of one type, whether mined for silver, copper, 

uranium, or vanadium. They believed the deposits 

were formed by circulating waters that collected the 

metals disseminated through the sedimentary rocks and 

deposited them on contact with carbonaceous matter or 

earlier sulfides, or other precipitating agents; and that 

most of the minerals at present exposed are the products 

of alteration of the original minerals by surface solutions. In White Canyon and in Capitol Reef, Utah, 

Hess (1925) and Butler and others (1920) observed 

uranium sulfate associated with copper sulfates that 

were forming around chalcopyrite and, although pitchblende was not identified, they concluded that the 

uranyl sulfates were developing from some primary 

uranium mineral.

In the years that followed, many geologists whose in-
10 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

vestigations were concentrated in western Colorado described vanadium silicates, carnotite, and tyuyamunite 

as the predominant minerals in the shallow deposits. 

Fischer (1950) and Stokes (1952) did not interpret 

the carnotite deposits as secondary, or the oxidation 

product of low-valent primary ores because so little 

low-valent or "black ore" was known at that time. 

Many mines were less than 50 feet beneath the surface 

of the ground and few were as much as 100 feet deep. 

Detailed field work on carnotite and roscoelite ores in 

the late 1930's and 1940's demonstrated the remarkable 

dependence of ore occurrence on sedimentary structures, and its apparent independence of larger structural features (Fischer 1942), except perhaps on a regional basis. A widely held concept in the late 1940's 

was that the ores were contemporaneous, or nearly so, 

with the enclosing sediments, and that carnotite and 

tyuyamunite were primary minerals.

In the early 1950's, when many new mines were developed during the prospecting boom encouraged by 

the government exploration program, new occurrences 

of black (unoxidized) ore began to appear. Uraninite 

was found in vanadium-uranium ore (Rasor, 1952) and 

copper-uranium ore. Montroseite [VO(OH)] and 

coffinite [U(SiO4 )i-x (OH) 4x] were also found to be 

typical of unoxidized ore.

The age-determination studies of the early 1950's indicating a Late Cretaceous or early Tertiary age, the 

finding of many uraninite occurrences, and the development of the uraninite-copper sulfide deposit at the 

Happy Jack mine, San Juan County, Utah, suggested 

to some geologists a hydrothermal origin and a deep 

source for the metals, but such an origin for typical 

carnotite deposits was untenable to many geologists.

In the controversy over a hydrothermal origin versus 

a primary sedimentary or ground-water origin the 

problem of oxidation soon was recognized as a hurdle 

to be overcome before the problem of origin could be 

satisfactorily discussed and attacked. The contrast between the chemical behavior and mineralogical character (Part 5) of vanadium-uranium ores and those of 

copper-uranium ores confused the discussion of origin.

Actually, it is quite possible that all the ore existed 

in a reduced state before oxidation during the Quaternary, quite independently of origin. The ores could 

have been (1) reduced at the time of primary sedimentary deposition, (2) deposited as a reduced-mineral 

suite at a later time by ground waters, or (3) deposited 

by ascending hydrothermal fluids. Thus it appeared 

that the problem of oxidation could be attacked without regard to these controversial issues.

If a reduced-ore stage preceded Quaternary oxidation, predictions can be made concerning mineralogic, 

chemical, and geologic relations.

1. Ores protected from air should contain an equilibrium mineral assemblage under reducing conditions.

2. As a deposit is followed from the surface to places 

of more and more limited access of air, the assemblage should converge toward the original reduced assemblage.

3. High-valent minerals should be clearly related to 

post-ore features, such as jointing; high-valent 

minerals should always be later in the sequence 

than reduced ones.

4. The texture and composition of some high-valent 

ores should resemble those clearly developed from 

reduced ores.

If there were two kinds of ore, a primary low-valent 

suite, and a primary high-valent suite, it might well be 

expected that oxidation of the low-valent suite would 

produce ore with textural character and mineralogic 

or elemental composition different from that of primary 

high-valent ore.

With such tests in mind, many investigators worked 

on various aspects of the problem. Studies were made 

of predicted versus observed sequences of minerals, assuming that all ore was once reduced. Minerals were 

synthesized to see if their conditions of formation corresponded to those expected in an oxidizing environment superimposed on the original ore suite. In general the attack was based on the premise that all ore 

originally was a reduced suite, and the hypothesis was 

tested by its ability or inability to explain field and 

laboratory observations. The following parts of this, 

volume are devoted to many facets of the oxidation 

problem.

LITERATURE CITED

Baker, A. A., Dane, C. H., and Reeside, J. B., Jr., 1936, Correlations of the Jurassic formations of part of Utah, Arizona, 

New Mexico, and Colorado: U. S. Geol. Survey Prof. Paper 

183, 66 p.

Butler, B. S., Loughlin, G. F., and Heikes, V. C., 1920, The ore 

deposits of Utah: U. S. Geol. Survey Prof. Paper 111.

Cater, F. W., Jr., and McKay, E. J., 1955, Geology of the Davis 

Mesa quadrangle, Colorado: U. S. Geol. Survey Geol. Quadrangle Map GQ-71.

Coffin, R. C., 1921, Radium, uranium, and vanadium deposits of 

southwestern Colorado: Colorado Geol. Survey Bull. 16, 

186 p.

Craig, L. C., and others, 1955, Stratigraphy of the Morrison and 

related formations, Colorado Plateau region, a preliminary 

report: U. S. Geol. Survey Bull. 1009-E, p. 125-168.

Crawford, J. G., 1940, Oil-field waters of Wyoming and their relations to geologic formations: Am. Assoc. Petroleum Geologists Bull., v. 24, p. 1214-1329.
GEOLOGIC SETTING OF THE COLORADO PLATEAU ORES 11

Dane, C. H., 1935, Geology of the Salt Valley anticline and adjacent areas, Grand County, Utah: U. S. Geol. Survey Bull. 

863, 184 p.

Dobbin, C. E., 1935, Geology of natural gases rich in helium, 

nitrogen, carbon dioxide, and hydrogen sulfide, in Geology of 

Natural Gas: Ani. Assoc. Petroleum Geologists, Tulsa, Okla., 

p. 1053-1064.

Fenneman, N. M., 1931, Physiography of the western United 

States, New York, McGraw-Hill Book Co., 534 p.

Finch, W. I., 1955, Preliminary geologic map showing the distribution of uranium deposits and principal ore-bearing 

formation of the Colorado Plateau region: U. S. Geol. 

Survey Mineral Inv. Field Studies Map MF-16.

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah: 

U. S. Geol. Survey Bull. 936-P, p. 363-394.

 1950, Uranium-bearing sandstone deposits of the Colorado 

Plateau: Econ. Geology, v. 45, p. 1-11.

 1956, Uraniuin-vauadium-copper deposits on the Colorado Plateau, in Page, L. R., Stocking, H. E., and Smith, 

H. B., compilers, Contributions to the geology of uranium 

and thorium by the United States Geological Survey and 

Atomic Energy Commission for the United Nations International Conference on Peaceful Uses of Atomic Energy, 

Geneva, Switzerland, 1955: U. S. Geol. Survey Prof. Paper 

300, p. 143-154.

Gilluly, James, and Reeside, J. B., Jr., 1928, Sedimentary rocks 

of the San Rafael Swell and some adjacent areas in eastern 

Utah: U. S. Geol. Survey Prof. Paper 150-D, p. 61-110.

Gould, L. M., 1927, The Geology of the LaSal Mountains of Utah: 

Michigan Acad. Sci. Papers, v. 7, p. 55-106.

Gregory, H. E., 1938, The San Juan Country: U. S. Geol. Survey 

Prof. Paper 188.

 1917, Geology of the Navajo country a reconnaissance

of part of Arizona, New Mexico, and Utah: U. S. Geol.

Survey Prof. Paper 93. 

Hack, J. T., 1942, Sedimentation and volcanism in the Hop!

Buttes, Arizona: Geol. Soc. America Bull., v. 53, p. 335-372. 

Hess, F. L., 1914, A hypothesis for the origin of the carnotite of

Colorado and Utah: Econ. Geology, v. 9, p. 675-688.

 1925, New and known minerals from the Utah-Colorado carnotite region: U. S. Geol. Survey Bull. 750, p. 63-78.

 1933, Uranium, vanadium, radium, gold, silver, and molybdenum sedimentary deposits, in Ore Deposits of the

Western States, the Lindgren volume, p. 450-481. 

Hillebrand, W. F., and Ransome, F. L., 1905, Carnotite and associated vanadiferous minerals in western Colorado: U. S.

Geol. Survey Bull. 262, p. 9-31. 

Hunt, C. B., 1938, Igneous geology and structure of the Mount

Taylor volcanic field, New Mexico: U. S. Geol. Survey Prof.

Paper 189-B, p. 51-80. 

 1956, Cenozoic geology of the Colorado Plateau: U. S.

Geol. Survey Prof. Paper 279. 

Hunt, C. B., Averitt, Paul, and Miller, R. L., 1953, Geology and

geography of the Henry Mountains Region, Utah: U. S.

Geol. Survey Prof. Paper 228, 234 p. 

Isachsen, Y. W., Mitchum, T. W., and Wood, H. B., 1955, Age and

sedimentary environments of uranium host rocks, Colorado

Plateau: Econ. Geology, v. 50, p. 127-134.

Kelley, V. C., 1955a, Regional tectonics of the Colorado Plateau 

and relationship to the origin and distribution of uranium: 

Univ. New Mexico Publications in Geology no. 5, Albuquerque, New Mexico, 120 p.

 1955b, Monoclines of the Colorado Plateau: Geol. Soc. 

America Bull., v. 66, p. 789-804.

Levorsen, A. I., 1954, Geology of petroleum, San Francisco, W. 

H. Freeman and Co., 703 p.

McKay, E. J., 1955, Criteria for outlining areas favorable for 

uranium deposits in parts of Colorado and Utah: U. S. 

Geol. Survey Bull. 1009-J, p. 265-282.

McKee, E. D., 1951, Sedimentary basins of Arizona and adjoining areas: Geol. Soc. America Bull., v. 62, p. 481-506.

 1954, Stratigraphy and history of the Moenkopi formations of Triassic age: Geol. Soc. America Mem. 61, p. 133.

Rasor, C.A., 1952, Uraninite from the Grey Dawn mine, San 

Juan County, Utah: Science, v. 116, p. 89-90.

Stieff, L. R., Girhard, M. N., and Stern, T. W., 1950, A preliminary report on methods of determining the age of Colorado 

Plateau carnotite: U. S. Geol. Survey, Trace Elements Inv. 

Rept. 108 (unpublished).

Stieff, L. R., and Stern, T. W., 1952, Identification and leaduranium ages of massive uraninites from the Shinarump 

conglomerate, Utah: Science, v. 115, p. 706-708.

Stieff, L. R., Stern, T. W., and Milkey, R. G., 1953, A preliminary determination of the age of some uranium ores of 

the Colorado Plateau by the lead-uranium method: U. S. 

Geol. Survey Circ. 271,19 p.

Stokes, W. L., 1948, Geology of the Utah-Colorado salt dome 

region with emphasis on Gypsum Valley, Colorado: Utah 

Geol. Soc., Guidebook to the Geology of Utah, no. 3, 50 p.

 1950, Pediment origin applied to Shinarump and similar 

conglomerates: Geol. Soc. America Bull., v. 61, p. 91-98.

 1952, Uranium-vanadium deposits of the Thompson area,

Grand County, Utah, with emphasis on the origin of carnotite ores: Utah Geol. and Mineralogical Survey Bull. 46.

Wallace, J. H., and Smith, H. B., 1955, Bibliography of U. S. 

Geological Survey trace elements and related reports to 

June 1, 1954: U. S. Geol. Survey Bull. 1019-B, p. 63-144.

Waters, A. C., 1955, Volcanic rocks and the tectonic cycle: Geol. 

Soc. America, Special Paper 62, Crust of the earth, a 

symposium, p. 703-722.

Waters, A. C., and Granger, H. C., 1953, Volcanic debris in 

uraniferous sandstones, and its possible bearing on the 

origin and precipitation of uranium: U. S. Geol. Survey 

Circ. 224, 26 p.

Weir, D. B., 1952, Geologic guides to prospecting for carnotite 

deposits on the Colorado Plateau: U. S. Geol. Survey Bull. 

988-B, p. 15-27.

Wengerd, S. A., and Strickland, J. W., 1954, Pennsylvanian 

stratigraphy of Paradox salt basin, Four Corners region, 

Colorado and Utah: Am. Assoc. Petroleum Geologists Bull., 

v. 38, p. 2157-2199.

Williams, Howel, 1936, Pliocene volcanoes of the Navajo-Hopi 

country: Geol. Soc. America Bull., v. 47, p. 111-172.

Young, R. G., 1955, Sedimentary facies and intertonguing in 

the upper Cretaceous of the Book Cliffs, Utah-Colorado: 

Geol. Soc. America Bull., v. 66, p. 177-202.

Part 2. CHARACTERISTICS OF THE HOST ROCK

BY ROBERT A. CADIGAN

CONTENTS

Abstract.__________________________________________

Stratigraphic location of major uranium-ore deposits.___ 

Methods and definitions....____.--.---------.-_.

Triassic host rocks._________________________________

Shinarump member of the Chinle formation........

Sandstones in the lower part of the Chinle formation. 

Jurassic host rocks______-_-_________________________

Entrada sandstone._-_-_______---____--_-___--__

Todilto limestone.___--_-___-___-__-_-_--_______

Morrison formation _____________________________

Salt Wash member of the Morrison formation __ 

Recapture member of the Morrison formation __

Page

13

14

14

15

15

16

18

18

18

19

19

20

Jurassic host rocks Continued Paee 

Morrison formation Continued

Westwater Canyon member of the Morrison formation __________________________________ 21

Brushy Basin member of the Morrison formation 21 

Miscellaneous features of the major uranium-producing

host rocks-.___-________________________________ 22

Detrital minerals_______________________________ 22

Summary of lithologic characteristics._____________ 23

Interpretation of environment which produced the

host rocks.____________________________________ 23

Conclusions._______________________________________ 23

Literature cited___________________________________ 24

ILLUSTRATION

FIGURE 2. Regional occurrence of uranium ore deposits of 1,000 tons or more in the major and minor producing formations 

of the Colorado Plateau.___--_------__-______-_--__-_-_____-___-_---_______________________________

Page

14

TABLE

TABLE 1. The petrologic classification of detrital sedimentary rocks.

Page 

15

ABSTRACT

Uranium deposits in the sedimentary rocks of the Colorado 

Plateau are distributed throughout most of the lithologic units 

which make up the regional stratigraphic column. The Morrison formation of Jurassic age and the Shinarump member and 

sandstones in the lower part of the Chinle formation of Triassic 

age yield at least 90 percent of current uranium ore production. 

The Todilto limestone and Entrada sandstone of Jurassic age 

together yield about 5 percent of current production.

The host rocks of the Morrison and Chinle formations are 

noted for ledge-forming lenticular fine- to coarse-grained, crossstratified sandstone bodies which occupy trough-shaped erosional 

features known as channels. Associated with the channel sandstones, particularly in the lower parts, are green clay strata 

and pellets; petrified, carbonized, and coalified plant material; 

bone; and pebbles derived from nietarnorphic, igneous, and sedimentary rocks. Interbedded with the sandstones are red, green, 

or variegated siltstone and claystone strata.

The sandstones vary regionally in composition and can usually 

be classified as arkose, sedimentary tuff, or orthoquartzite depending on the location. The clay minerals of the sandstones 

as well as those of the siltstones and claystones belong to the 

hydromica, montmorillonite, and kaolinite groups. The kaolinitic 

clays are mostly of detrital origin. The montmorillonite and 

hydromica clays were mostly derived from volcanic ash.

The Todilto limestone is a 10- to 30-foot-thick moderately 

pure limestone unit, extending throughout the southeastern 

part of the Colorado Plateau. The Entrada sandstone, typically 

a 50- to 300-f oot-thick massive partly cross-stratified, fine-grained 

sandstone varies regionally in composition, but in western Colorado it is an orthoquartzite or a feldspathic orthoquartzite.

Generally, ore deposition in the Morrison formation, Shinarump member, and sandstones of the lower part of the Chinle 

formation appears to be influenced locally by the sedimentary 

structures, plant material, bone, clay, and certain textural zones 

in certain parts of the sandstone strata. Ore deposition appears

13
14 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

to be favored regionally in the Salt Wash member of the 

Morrison formation by certain lithofacies characteristics.

Ore deposition in the Entrada sandstone appears to be related 

to the Dolores-Entrada and Entrada-Pony Express contacts. 

Ore deposition in the Todilto shows a relationship to joints and 

fractures.

STRATIGRAPHIC LOCATION OF MAJOR URANIUM-ORE 

DEPOSITS

The uranium deposits in the sedimentary rocks of the 

Colorado Plateau region are distributed throughout 

most of the lithologic units which make up the regional 

stratigraphic column. At this time (1955) the major 

part, at least 90 percent, of the production of ore is 

from the Morrison formation of Jurassic age, and the

Shinarump member and sandstones in the lower part 

of the Chinle formation of Triassic age. An additional 

5 percent of the production is from the Todilto limestone and underlying Entrada sandstone of Jurassic 

age (Fischer, R. P., 1955, oral communication). Figure 

2 illustrates the regional distribution of ore deposits 

in excess of 1,000 tons for each of the stratigraphic 

units named above.

METHODS AND DEFINITIONS

The petrographic study of the uranium ore-producing formations has been carried on by means of thin 

section study, grain-size analyses and the field examination of sedimentary structures. Most of the work has

EXPLANATION

 

Morrison formation (Jurassic)

1 

Entrada sandstone (Jurassic)

x 

Todilto limestone (Jurassic)

A

Shinarump conglomerate and 

Chinle formation (Triassic)

Other formations

L

! NEW MEXICO

50 100 MILES

FIGURE 2. Regional occurrence of uranium-ore deposits of 1,000 tons or more in the major and minor producing formations of the Colorado Plateau. .(Prepared by R. P. Fischer, R. T. Chew III, and H. S. Johnson for the paper, "Uraniumvanadium-copper deposits on the Colorado Plateau," International Conference on Peaceful Uses of Atomic Energy, 

Geneva, Switzerland, 1955, from a map by W. I. Finch.)
CHARACTERISTICS OF THE HOST ROCK 15

been done on the major producing formations and lithologic types.

TABLE 1. The petrologic classification of detrital sedimentary 

rocks

[After Pottljohn, 1949, and Krynine, personal communication, 1952; exclusive of the 

treatment of tuff']

Classification

Foldspathic orthoquartzlto.. 

Graywacke.-.-. ____ .

Quartz plus tuff ' 

(percent)

Limits

70-100 

55-90 

0-70 

15-80 0-75

Typical

85 

75 

50 

CO 

50

Feldspar plus 

kaolin 

(percent)

Limits

0-10 

10-25 

10-80 

0-10 

25-100

Typical

5 

15 

20 

5 

40

Micas 

(percent)

Limits

0-20 

0-20 

20-75 

20-75 0-20

Typical

10 

10 

30 

35 

10

1 The amount of tuff present affects the rock classification in the following manner:

1. If there is loss than 10 percent tuff, the rock classification is not affected.

2. If there is 10 to 25 percent tuff, the rock name is modified by the word "tuffacoous" that is, tuffaceous arkoso.

3. If there is 25 to 75 percent tuff, the rock name designates a variety of toff that 

Is, graywacko tuff.

4. If there Is 75 percent or more of tuff, the rock is an unmodified tuff.

Classification of the rocks generally follows the system proposed by Krynine (1948) but was modified as 

illustrated by table 1. The rocks studied represent various intermixtures of three end products: arkoses, orthoquartzites, and tuffs. Some sandstone strata of restricted occurrence could be classified as graywackes on 

the basis of their hydromica content, but due to a lack 

of other essential components such as basic rock fragments and alkalic-calcic feldspars, these rocks are not 

considered as true graywackes.

The classification of sandstones in specific stratigraphic units was based on point count analyses of an 

aggregate of 119 thin sections, including 66 for the Morrison formation, 28 for the Shinarump member, and 25 

for the lower sandstones of the Chinle formation. The 

Entrada composition studies were restricted to the 

examination of a few thin sections supported by loose 

grain studies including mineral grain counts on 15 

samples. The Todilto limestone and the correlative 

Pony Express member of the Wanakah formation composition studies were restricted to examination of a few 

thin sections and insoluble residue studies of two 

samples (one each).

The data on clay minerals in the formation studied 

was obtained from the thin section studies; from X-ray 

diffraction analyses of clay and silt separates; and from 

unpublished work of, and informal communications 

with, Alice Weeks, W. D. Keller, and others of the 

U. S. Geological Survey, and J. C. Griffiths of the 

Pennsylvania State University. Further data on the 

unmineralized clay minerals are given by Keller in 

Part 9.

Microscopic arrangements of the grains, matrix, and 

cement of the sandstones as they appear in thin section were termed the microstructure of the rock. If

the detrital grains are in contact with each other to a 

maximum extent, with a minimum of interstitial cement and matrix, the microstructure is classified as homogeneous. If the detrital grains are suspended in 

matrix and cement, with some grains in contact, but 

most separated from other grains by intervals of 

varying widths, the microstructure is classified as 

heterogeneous.

The ore-producing formations were studied on the 

outcrop to determine small-scale lithologic relationships, to obtain information pertinent to stratigraphic 

problems, and to collect representative samples for laboratory investigations. The conspicuous bedding features and forms produced by the sedimentation processes of cyclic deposition which included intervals of 

erosion, are referred to by the general all-inclusive term 

"sedimentary structures." The erosional features are 

referred to in this paper as erosion surfaces, cuts, or 

channels in ascending order of magnitude of relief. 

The writer was fortunate to be associated with a number of geologists who have done detailed studies of 

sedimentary structures and their orientations. These 

include L. C. Craig, G. W. Weir, G. A. Williams, and 

O. B. Eaup, all of the U. S. Geological Survey.

This part of the present report is aimed at describing the petrographic framework of the ore deposits. 

That the ore is stratigraphically controlled is quite obvious ; rocks of the favored strata are therefore referred 

to as host rocks whether or not they contain ore.

In the following pages, the stratigraphic and lithologic units defined above as host rocks are described so 

as to emphasize the more general or average characteristics. No attempt is made to give the detailed 

petrography, or sedimentary structure characteristics 

of any unit in these descriptions. The general outline 

to which all the descriptions are fitted seeks to bring 

out the following points for each unit: (1) Stratigraphic relations, (2) textural types present and their 

arrangement, (3) structural features of erosion and 

deposition, (4) rock composition and classification, 

and (5) microscopic arrangement of constituents. 

These are variations of the three main properties of 

rocks: composition, texture, and structure.

TRIASSIC HOST ROCKS

SHINARUMP MEMBER, OP THE CHINLE FORMATION

[Uranium-production rank, third]

Stratigraphic relations. The white to pale-brown 

Shinarump member of the Chinle formation of Late 

Triassic age occupies a position in the stratigraphic 

column of the Colorado Plateau at the base of the 

Chinle formation and above the Moenkopi formation 

of Triassic age. The Shinarump is restricted in occur-
16

rence to the southern half of the Colorado Plateau 

region (Stewart and Williams, 1954). The lower contact of the Shinarump is an erosional disconformity; 

the upper contact is conformable at most places but is 

disconformable or undefinable at a few places.

Textural types and their arrangement. The Shinarump member is in most places a medium-grained sandstone unit with persistent and conspicuous zones of 

very coarse grained sandstone, pebbly sandstone, and 

pebble conglomerate. The sandstones and conglomerates are usually moderately to poorly sorted. This 

general texture is characteristic throughout the whole 

area in which the formation is present. Green claystone or mudstone strata are above, below, and within 

the sandstone strata. In many places in the southern 

and central parts of the Plateau, as the result of a 

lateral f acies change, the Shinarump is represented by 

green claystone strata containing a 1- to 3-foot clay 

and pebble zone. Where the sandstone f acies is locally 

absent the greenish kaolin mudstone (part 9 of this volume) equivalent will, in most instances, contain coarse 

sand grains and granules dispersed throughout the 

mud. The sandstone f acies and siltstone f acies contain 

the same mineral components, but in different 

proportions.

A variegated red, purple, and white mudstone f acies 

is found in the upper part of the Shinarump in many 

areas of the northern part of the Plateau including 

the Moab, White Canyon, and San Rafael Swell areas 

in Utah. Beyond the range of the sandstone facies it 

may be a regional equivalent of the Shinarump member. However, this coarse-sand-filled kaolinitic mudstone stratum is referred to as the "purple-white zone" 

(Finch, 1953) in areas where it separates the Chinle 

and the Moenkopi formations, and is usually assigned 

to the Chinle.

Structural features of erosion and deposition. The 

sandstone strata of the Shinarump tend to form a 

single composite ledge-forming sandstone bed which 

extends many square miles laterally, but which is elongated in the direction parallel to the channel trends in 

the area. The broad areal extent is the result of the 

junction or coalescence of adjacent channel fills to 

form a uniform upper surface for the single conspicuous 

ledge. The channel fills of the Shinarump may have 

an average cross-sectional area in the order of 2,500 to 

10,000 square yards. The deeper channels contain 

abundant petrified, coalified and crushed logs, and disseminated plant material (Witkind, 1954).

Rock composition and classification. The Shinarump member may be classified typically as an arkose, 

although in some areas it grades into orthoquartzites 

and tuffs. The common detrital components are grains

of quartz, potash feldspar, plagioclase, altered tuff, and 

quartzite; the kaolinite, hydromica, and montmorillonite groups of clays; and included pebbles of quartz, 

quartzite, feldspar, chert, granite, and silicic-alkalic 

volcanic rocks (Stewart, J. H., and Albee, H. F., 1955, 

oral communication).

The chief interstitial clay minerals are of the 

kaolinite group with minor amounts of hydromica. 

Where there is a significant increase in the proportion 

of tuff, the chief clay minerals are of the montmorillonite group. Much of the bedded clays in the 

Shinarump are of the hydromica group.

The clay minerals in the sandstone are well crystallized. The kaolinite clays appear as detrital clay in 

white interstitial wads and as decomposition products 

in the cleavage cracks of weathered feldspar grains.

The main cementing materials of the Shinarump 

consist, in order of importance, of silica in the form 

of overgrowths on quartz grains, iron oxides, and 

calcite and other carbonates. The rocks are, on the 

average, only moderately indurated. Other nondetrital 

components include ore and gangue minerals and 

authigenic silica present in the altered tuff.

The major regional change in composition occurs in 

the southwestern part of the Colorado Plateau, in 

north-central Arizona and south-central Utah, where 

the sandstones can be classified as tuffaceous arkoses 

or tuffs. The rocks contain enough potash feldspar 

to support a hypothesis that they were derived from 

silicic-alkalic igneous rocks. Regional variations in 

feldspar content are also present with recognized high 

feldspar areas in the southeastern and northern parts 

of the Plateau.

Microstructure. The sandstones of the Shinarump 

contain both heterogeneous and homogeneous microstructures. The kaolin-mud matrix comprises about 

10 percent of the moderately sorted sandstones and 

about 30 percent of the poorly sorted sandstones. The 

mud is distributed throughout the rock in interstitial 

films or in wads of about 1 millimeter in size.

SANDSTONES IN THE LOWER PART OF THE CHINLE 

FORMATION

[Uranium-production rank, second]

Stratigraphic relations. The light-colored sandstones of the lower part of the Chinle formation occupy 

a position in the stratigraphic column immediately 

above the Shinarump member. They are easily confused with the Shinarump member where it is absent. 

The sandstones are found in the Monitor Butte, and 

the overlying Moss Back (Stewart and Smith, 1954) 

members of the Chinle formation. The peculiar sandstones considered to be typical of the respective units 

are not confined within the member boundaries. Thus
CHAEACTERISTICS OF THE HOST ROCK 17

the Moss Back-type sandstones are frequently found 

in the Monitor Butte member and vice versa. For this 

reason the lower sandstones of the Chinle will be referred to as the Monitor Butte-type and the Moss Backtype sandstones.

The Monitor Butte type of sandstone is similar in 

composition to the Shinarump type sandstone, but 

differs greatly in texture and structure. The Monitor 

Butte type is pale green to gray fine grained to very 

fine grained, and is tightly cemented with calcite or 

silica. The greenish beds are in most cases only a few 

feet thick, and are evenly bedded with parallel ripple 

laminations in which thin laminae of well-sorted sand 

are separated by laminae of greenish chloritic or hydromica clay. On weathering, the beds are much subjected to jointing, slumping, and separating along their 

laminae, as in beds of shale. Penecontemporaneous 

slumping is abundant; however, the general bedding 

and depositional structures are commonly preserved. 

The sandstones of the Monitor Butte are associated with 

hydromica or bentonitic claystone strata.

The white to pale-brown Moss Back-type sandstone 

of the lower part of the Chinle more nearly resembles 

the Shinarump and is almost exclusively the host rock 

for ore deposits in the lower part of the Chinle. The 

Moss Back type is the host rock in those areas in the 

northern and northwestern parts of the Colorado Plateau where the sandstone and conglomerate f acies of the 

Shinarump is absent.

Textural types and their arrangement. The Moss 

Back-type sandstones are fine grained with pebbly and 

conglomeratic zones. They contain claystone and mudstone seams, lenses, and fragments. Individual samples 

show predominantly moderate sorting with poor sorting in the coarse-grained sands.

Structural features of erosion and deposition. The 

erosional and depositional structures of the sandstones 

of the lower part of the Chinle are generally of the 

same scale and frequency as those of the sandstones of 

the Shinarump. The sandstone strata of the Moss 

Back member tend to form a single thick composite 

ledge-forming sandstone bed or a closely spaced sequence of beds, averaging about 50 feet thick. The 

unit extends over an area of about 9,000 square miles 

(Stewart and Williams, 1954). The unit fills erosion 

channels which, in extreme cases, increases the thickness of the sandstone strata to 100 to 150 feet. Thickbedded ledge-forming channel-filling sandstone strata 

of the Moss Back type are frequently found below and 

separated by thick mudstone strata from the prominent sandstone unit of the Moss Back member.

Lithified, mineralized, or coalified logs and wood 

fragments may be found in the bottoms of channels in

the same manner as those found in the Shinarump, or 

scattered throughout bedded gray claystones or mudstones associated with the channel deposits.

Rock composition and classification. The Moss 

Back-type sandstone is an arkose but shows enough 

variation in composition to be classified as a f eldspathic 

orthoquartzite in some locations. The common detrital 

components are grains of quartz, potash feldspar, plagioclase feldspar, altered tuff, quartzite fragments, and 

clays of the kaolinite, montmorillonite, and hydromica 

groups. Pebbles of chert, quartz, and quartzite are also 

present. The Moss Back-type sandstone shows an increase in feldspar to the north or northwest.

The chief interstitial clay minerals in the sandstones 

are of the kaolinite group with minor amounts of hydromica and montmorillonite. Montmorillonite clays 

increase with the amount of tuff. The bedded clays 

in and around Moss Back-type sandstones are hydromicas, montmorillonites, and mixed layer clays. The 

clay minerals in the sandstones are well crystallized. 

The kaolinite clays appear as detrital clay in white interstitial wads and as decomposition products in the 

cleavage cracks of weathered feldspar grains. The 

"purple-white" mudstone zone underlies the Moss Back 

member in the absence of the Monitor Butte member 

and the sandstone-conglomerate facies of the Shinarump.

The suite of clay minerals present in the lower part 

of the Chinle lithologic units is influenced by larger 

amounts of altered alkalic-silicic volcanic ash in the 

southern and western part of the Colorado Plateau and 

becomes dominantly montmorillonite.

The cementing material of the Moss Back type of 

sandstone consists, in order of importance, of silica in 

the form of overgrowths on quartz grains, calcite and 

other carbonates, and iron oxides. The sandstones 

range from highly indurated to poorly indurated. 

Other nondetrital components include ore and gangue 

minerals.

Microstructure. The microscopic arrangement of 

the Moss Back-type sandstones is heterogeneous, becoming more so in the coarse-grained sandstones and 

conglomerates.

General comparison of ore-bearing sandstone of 

the Shinarump member and lower part of the Chinle. 

Sandstones of the Shinarump and Moss Back members 

of the Chinle formation are similar in average composition. Pebble assemblages of the two show a significantly higher percentage of quartz for the Shinarump 

(Albee, H. F., oral communication). The main differences in appearance between the two types of sandstone are due to the finer texture of the Moss Back 

type and the multiple ledges in the lower part of the
18 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Chinle formation where the Monitor Butte member is 

present as compared with the single composite ledge 

commonly observed in the Shinarump member.

JURASSIC HOST ROCKS

ENTBADA SANDSTONE

[Uranium-production rank, eighth]

Stratigraphic relations. The Entrada sandstone, a 

formation in the San Rafael group of Jurassic age, 

extends with various f acies changes over almost the entire Colorado Plateau. It immediately underlies the 

Todilto limestone, in the southeast; the Curtis formation of Jurassic age, in the north; the Cow Springs 

formation of Jurassic age, in the south; and the Summerville formation of Jurassic age, in much of the rest 

of the Plateau. In western Colorado, where uranium 

ore is produced from the Entrada, it overlies the Dolores 

formation of Triassic age (Fischer, 1942), which is 

equivalent at least in part to the Chinle formation. 

Elsewhere it overlies the Carmel formation of Jurassic 

age conformably where this unit is present, or it forms 

the base of the San Kafael group of Jurassic age and 

disconformably overlies the Glen Canyon group of Triassic and Jurassic age.

Texturdl types and their arrangement. The sandstone units that make up the Entrada are well to moderately sorted and range from fine- to very fine-grained. 

Some strata contain medium and coarse well-rounded 

grains of chert, quartz, and potash feldspar. These 

coarse grains are concentrated along laminations or disseminated throughout the sandstone in some parts of 

the formation. In west-central Colorado, east of the 

Plateau, the basal part of the Entrada is medium to 

coarse grained, similar to the underlying Pennsylvanian 

sedimentary rocks.

Structural features of erosion and deposition. The 

Entrada sandstone consists of a number of very thick 

to thin cross-stratified and horizontally stratified sandstone beds separated by what may be referred to as 

horizontal truncation planes or partings. In most areas 

the formation weathers on exposure to form a white, 

gray or pale-brown to orange massive convex sandstone 

ledge 50 to 300 feet thick which is colloquially called 

the "slick rim." Cross-stratification in some of the beds 

is of the dimensions associated with eolian deposition.

Rock composition and classification. In the northeastern part of the Plateau where the Entrada is a 

host rock for uranium deposits, it may be classified as 

an orthoquartzite or a feldspathic orthoquartzite. It is 

composed of quartz, chert, potash and sodic feldspar, 

and a heavy-mineral suite consisting of zircon, tourmaline, rutile, anatase, muscovite, epidote, ilmenite, magnetite, and leucoxene. The Entrada is highly feldspathic in west-central Colorado, where it appears to 

contain material derived from underlying arkoses and 

possibly Precambrian granites. The feldspathic Entrada contains clays formed of ground-up mica and 

hydromica. In southwestern Colorado the Entrada contains much less feldspar and more clays formed of recrystallized hydromica and possibly some chlorite. 

Nondetrital minerals include calcite and barite, and 

euhedral anatase crystals probably of authigenic origin. 

Microstructure. The microstructure of the sandstones is nearly all of the homogeneous type. The clay 

matrix is interstitial especially when the rock is rich 

in ground-up mica, but also forms authigenic rims 

around the quartz and feldspar grains. Grains of 

feldspar, particularly albite, are speckled with calcite 

and hydromica which may be accepted as evidence of 

replacement of the detrital grains by carbonates and 

authigenic clay minerals. Some unidentified hydromica 

clay minerals occupy positions which strongly suggest 

ghosts of detrital grains. The rock is only moderately 

well cemented by carbonates and clay matrix.

TODILTO LIMESTONE

[Uranium-production rank, seventh]

Stratigraphic relations. The Todilto limestone, a 

formation in the San Rafael group of Jurassic age, is 

restricted in extent to the southeastern part of the Colorado Plateau region. It is conformable with underlying Entrada sandstone and may be separated from the 

Summerville by a disconformity. The Pony Express 

limestone member of the Wanakah formation of southwestern Colorado is probably equivalent to the Todilto 

and has generally the same stratigraphic relations.

Textural and structural features. The Todilto is 

characterized in outcrop by a 10- to 30-foot limestone 

ledge and has a gypsiferous facies in some localities. 

The depositional structures are dominantly flat bedded. 

The flat-bedded features may be emphasized by a 

banded appearance; the horizontal parallel bands are 

in the order of magnitude of 1 to 4 inches or less thick. 

Parallel distorted bands may be seen in the upper part 

of the limestone unit. The formation exhibits typical 

limestone jointing influenced by the closely spaced bedding and degree of local structural activity. The 

Todilto limestone contains crystalline textures ranging 

from microcrystalline to macrocrystalline. Ore deposits in the Todilto show some relation to structure 

and jointing (Bucher, 1953).

Rock composition and classification. The Todilto 

limestone a'nd the Pony Express limestone member are 

composed of an acid-soluble carbonate fraction, which 

constitutes about 90 percent of the rock, and an insoluble fraction. The insoluble fraction consists of authigenic quartz crystals with many bubblelike inclusions,
CHARACTERISTICS OF THE HOST ROCK 19

allogeiiic grains of quartz, orthoclase, microcline, chert, 

and in very small proportions barite, tourmaline, apatite, biotite, muscovite, rutile, and others. Considering 

the heavy minerals as index minerals, the proportion of 

apatite is higher in the Todilto and the Pony Express 

than in adjacent rocks. The color of the limestone 

facies changes from dark gray in Colorado to paleyellowish gray in New Mexico. The color probably is 

related to the amount of fine carbon disseminated in the 

rock. A gypsum facies assigned to the Todilto makes 

up most of the unit in parts of northwestern and northcentral New Mexico.

Microstructure. Microscopic examination shows 

that the banded appearance results from layers of 

macrocrystalline mosaic-structured euhedral calcite 

crystals separated by bands of microcrystalline anhedral sutured calcite crystals. Scattered within the 

microcrystalline bands are parallel-oriented lenses of 

mesocrystalline to macrocrystalline subhedral calcite 

crystals in mosaic arrangement. Detrital grains are 

scattered throughout but are more plentiful in the 

microcrystalline bands.

MORRISON FORMATION

Stratigraphic relations. The Morrison formation of 

Jurassic age is made up of light-colored, lens-shaped, 

cross-stratified sandstones and reddish, greenish-gray, 

and variegated claystones, siltstones, and mudstones. 

On the Colorado Plateau, the Morrison is divisable into 

four members. The uppermost member, the Brushy 

Basin, is composed dominantly of variegated, red, 

green, and purple bentonitic mudstone strata and lesser 

amounts of pebbly sandstone. The basal member, 

which lies just below the Brushy Basin member in the 

northern half of the Plateau, is the Salt Wash member. 

The Salt Wash is characterized by light-gray and lightbrown ledge-forming sandstones interbedded with red 

and green siltstone and mudstone strata; the Salt Wash 

is the chief uranium ore-producing member of the Morrison formation.

In the southeastern part of the Plateau, the Westwater Canyon and underlying Recapture members 

tongue in between the Brushy Basin and the Salt Wash 

members and replace the Salt Wash member and the 

lower part of the Brushy Basin member (Craig and 

others, 1955). The Westwater Canyon member is characterized by moderately lensing, moderately cross-stratified pale-yellow ledge-forming sandstones and brown 

and brownish-gray siltstone and bentonitic mudstone 

strata.

Fades changes. Facies changes of both local and 

regional scale are the rule in members of the Morrison 

formation. The host rock favored by uranium ore deposits in the Salt Wash member of the Morrison formation in southwestern Colorado and southeastern Utah 

seems closely related to certain local lithologic facies 

characteristics (Mullens and Freeman, 1952). Significant facies characteristics include: an optimum ratio of 

sandstone to mudstone in a vertical sequence (about 50 

percent), an optimum thickness "stream deposit-type" 

to "nonstream deposit-type" sedimentary units (90 to 

200 feet), and an optimum degree of average size and 

continuity of sandstone strata.

In localities in an area from south to southwest of the 

Four Corners area (juncture of Colorado, Utah, Arizona, and New Mexico, see fig. 2), the Morrison consists 

of a sequence of convex weathering, massive sandstones 

of the Westwater Canyon and Recapture members separated by silty sandstone partings. This sandy facies 

apparently is not a favorable host rock for uranium ore 

in the Morrison formation. The favorable facies appears to be the sequence of lenticular ledge-forming 

sandstone units interstratified with mudstone, siltstone, 

and claystone units to the west, north, and southeast of 

the Four Corners area.

SALT WASH MEMBER OF THE MORRISON FORMATION

[Uranium-production rank, first]

Stratigraphic relations. The Salt Wash member is 

the basal member of the Morrison formation in the central, northern, and western part of the Plateau.

Textural types and their arrangement. The Salt 

Wash member, like the Brushy Basin member, is composed of mudstone strata and ledge-forming sandstone 

beds; however, in most localities there is much more 

sandstone in proportion to mudstone than is observed 

in the Brushy Basin member. Volumetrically, the Salt 

Wash contains more sandstone than any other member 

(Freeman, V. L., oral communication).

The sandstones of the Salt Wash member are, on the 

average, fine grained and well to moderately sorted. 

The basal or lower parts of the "channel" sandstones are 

of coarse sand; moderately to poorly sorted; contain 

green clay chip conglomerates, quartzite, silicified tuff, 

chert, and silicified limestone pebbles, wood, and bone.

Structural features of erosion and deposition. The 

ledge-forming sandstone beds are lenticular composite 

cross-stratified units. The Salt Wash in any ore locality 

commonly has from 3 to 6 ledge-forming sandstone 

units separated by silty sandstone or mudstone. The 

larger resistant beds form composite ledges that are less 

continuous than the single composite ledge of the Shinarump and are of smaller dimensions with an average 

cross-sectional area in the order of 1,000 to 5,000 square 

yards.
20 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Rock composition and classification. The sandstone 

strata of the Salt Wash vary in classification over the 

Plateau region, and include orthoquartzites, tuffs, and 

arkoses, together with all possible modifications. The 

sandstones are composed of quartz, potash feldspar, 

sodic feldspar, silicified and altered tuff, chert, metamorphic rock fragments, and rhyolitelike igneous rock 

fragments and hydromica, montmorillonite, and kaolinite clay minerals. The dominant clay minerals in 

both the mudstone and in the sandstone strata are of the 

hydromica group, but with a high proportion of mixedlayer clays which were possibly derived from montmorillonite or volcanic ash. Analyses of the tuff suggest a silicic-alkalic igneous source. Heavy minerals 

represent less than 0.5 percent, by weight, of the average 

sandstone, and consist largely of varieties of zircon, 

tourmaline, garnet, staurolite, epidote, rutile, apatite, 

magnetite-ilmenite, miscellaneous titanium minerals, 

and minor amounts of biotite. This general assemblage 

is common for all sandstones of the Morrison formation 

but with regional variations in proportions.

The composition of sandstones of the Salt Wash 

varies over the region similarly to the sandstones of the 

Brushy Basin member, with high feldspar content to the 

southeast and high tuff content to the northwest.

Wood in the form of petrified, mineralized, or coalified logs or fragments is present at the base of channels. 

Bone in various degrees of alteration or replacement is 

present in the Salt Wash mudstone and sandstone 

strata.

Nondetrital components are calcite, dolomite, and 

other carbonates, iron oxides, silica, and gangue and ore 

minerals. Calcite is the dominant cement but much 

silica cement is present as overgrowths on the quartz 

grains. Iron oxides are not significant as cements.

Microstructure. The arrangement of components as 

observed under the microscope shows the sandstone to 

have microstructures of two general types, the heterogeneous type where a significant amount of clay matrix and little cement is present and a homogeneous 

type where the sandstone is made up of grains and 

cement with a minimum of matrix. The heterogeneous type appears to be the microstructure in which 

primary uranium ore mineralization is more often 

found.

RECAPTURE MEMBER OF THE MORRISON FORMATION

[Uranium-production rank, sixth]

Stratigraphic relations. The Recapture member 

intertongues with the Salt Wash member in the Four 

Corners area of the Plateau and replaces it to become

the basal member of the Morrison formation in the 

south and southeast. In contrast to the pale yellow 

of the overlying Westwater Canyon member, the Recapture member is characterized by browns and whites 

in both claystone and sandstone facies.

Textural types and their arrangement. The sandstones of the Recapture member are, on the average, 

moderately sorted and very fine grained but contain 

some medium- and fine-grained sands with granules 

and small pebbles of quartz, feldspar, granite, and 

chert. In general it is finer textured than the overlying Westwater Canyon member and contains a much 

higher proportion of bedded mudstone, siltstone, and 

claystone. Nondetrital components include calcite and 

other carbonates, secondary silica, and iron oxides.

Structural features of erosion and deposition. 

Structures of erosion and deposition in the Recapture 

member are similar to those of the Salt Wash member, 

particularly in the Four Corners area, with similar 

debris-filled, deep channels, and lenticular ledge-forming sandstone units. Although the size and shape of 

individual sandstone units are similar to those of the 

Salt Wash, there are fewer of them in the average 

vertical sequence of Recapture member strata, and they 

show less resistance to weathering.

Rock composition and classification. The sandstones of the Recapture member may be classified as 

feldspathic orthoquartzites and arkoses with the feldspar and kaolin content increasing to the southeast. 

They contain detrital grains of quartz, potash feldspar, plagioclase, silicified altered tuff, igneous rock, 

quartzite, and heavy minerals. The clay minerals 

present are of the hydromica, montmorillonite, and 

kaolinite groups, with the hydromica group dominant. 

Most of the sandstones contain the mixed layer clays 

common to many of the sandstone units described as 

host rocks. The bedded mudstones, siltstones, and 

claystones in the Recapture member contain these same 

clay minerals. In many localities the Recapture is 

characterized by thick strata of montmorillonite-rich 

swelling grayish-green and brown mudstone. Woody 

debris is present particularly in the Four Corners area.

Microstructure. The sandstones of the Recapture 

member show both homogeneous and heterogeneous 

microstructure. The detrital grains are associated with 

different amounts of hydromica and montmorillonite 

clays which form the matrix, and are cemented by 

varying amounts of carbonate minerals, iron oxide, and 

silica in the form of secondary overgrowths on quartz 

grains. Kaolinite is present chiefly as the alteration 

product of weathered feldspar grains.
CHARACTEKISTICS OF THE HOST ROCK 21

WESTWATER CANYON MEMBER OP THE MORRISON 

FORMATION

[Uranium-production rank including arkoses of the Brushy Basin 

member, fourth]

Stratigraphic relation. The Westwater Canyon 

member is an arkosic f acies of the Morrison formation 

and underlies and is interbedded with the Brushy Basin 

member in the southeastern part of the Colorado Plateau region. The ore-bearing Jackpile sandstone, although assigned to the Brushy Basin member, is essentially the same facies as the Westwater Canyon 

member.

Textural types and arrangement. The sandstones 

of the Westwater Canyon member are, on the average, 

moderately sorted, medium-grained and contain zones 

of granule conglomerate and pebbly sandstone which 

are characterized by fresh-looking cleavage fragments 

of pink feldspar. Like other members of the Morrison, 

the sandstone units are associated with bedded mudstone, siltstone, and claystone strata.

Structures of erosion and deposition. Erosional and 

depositional structures in the sandstones are similar to 

those of the thick ledges of the Shinarump and Brushy 

Basin, but show less scouring and are less lenticular. 

The channels are few and inconspicuous, and contain 

little woody material in the Four Corners area, but become more prominent and more "trashy" to the southeast. The erosional and depositional structures of the 

ore-bearing Jackpile sandstone resemble those of the 

Salt Wash member of the central part of the Plateau 

region in that they are highly lenticular and show more 

erosion and truncation surfaces.

In much of the Westwater Canyon outcrop, the sandstone beds form composite ledges which pile up in closely spaced vertical sequence to form a single massive 

bed or a thick sandstone interval of 2 or 3 ledges separated by thin yellowish-green and rare red mudstone 

strata. These thick composite sandstone strata appear 

in continuous exposures over wide areas.

Rock composition and classification. The yellowish 

sandstones of the Westwater Canyon member may be 

classified as arkoses and are composed of detrital grains 

of quartz, potash feldspar, altered and silicified tuff, 

plagioclase, igneous rock, quartzite, heavy minerals, and 

clay minerals of the kaolinite, montmorillonite, and hydromica groups. Much coarse material is present as 

pebble-sized fragments of quartz, potash feldspar, 

granite, quartzite, and chert. Nondetrital components 

include calcite and other carbonates, silica in the form 

of overgrowths on quartz grains, and in silicified tuff.

Although hydromica or mixed-layer clays are probably dominant, kaolin forms the matrix of many sandstone units and in this respect the sandstones of the

Westwater Canyon differ in composition from the other 

sandstones of the Morrison formation.

Microstructure. The sandstones of the Westwater 

Canyon member have both homogeneous and heterogeneous microstructures. The sandstones of heterogeneous texture, which are in the minority, are characterized by abundant kaolin in the matrix. Sandstones with the more homogeneous structures have 

much less matrix which is in most cases dominantly hydromica with some montmorillonite and kaolin.

BRUSHY BASIN MEMBER OF THE MORRISON 

FORMATION

[Uranium-production rank exclusive of arkose beds, fifth]

Stratigraphic relations. The Brushy Basin member 

is the most regionally extensive Stratigraphic unit within the Morrison formation and forms the top of the formation except in areas where pre-Dakota erosion has 

removed it.

Textural types and their arrangement. The texture 

of the sandstones of the Brushy Basin is generally fineto medium-grained with coarse to conglomeratic zones 

in the basal parts; thick lenses of sandy coarse conglomerate are common in many localities. The bedded mudstone which is the dominant lithologic type in the 

average exposure of the Brushy Basin member, characteristically contains granules and coarse sand grains of 

red chert or silicified tuff scattered throughout.

Structural features of erosion and deposition. The 

resistant sandstone beds are ledge-forming and were 

deposited in erosional scours. One or two of these sandstone units are commonly present in the lower third of 

the member. The basal contacts show erosion surfaces. 

Petrified wood, bone, mud and clay lenses, disturbed 

bedding, and conglomerates are characteristic of the 

first sediments deposited above the eroded surfaces. 

The bedded mudstone contains some thinner, evenly 

bedded very fine grained limy sandstones which are 

seldom of the ledge-forming type except in the southeastern part of the Plateau region. In northeastern and 

central New Mexico, thick lenses of medium-grained 

kaolin-rich arkose are present in the middle and upper 

parts of the Brushy Basin. The ore-bearing Jackpile 

sandstone (Hilpert, L. S., and Freeman, V. L., 1955, 

written communication), in New Mexico is a ledgeforming composite arkosic sandstone unit that was deposited in close association with the mudstone strata 

occurring in the middle of the Brushy Basin member.

Rock composition and classification. The Brushy 

Basin is a tuffaceous unit composed chiefly of montmorillonite-rich mudstones, fragments or grains of 

silicified altered tuff, and lesser amounts of thick lensing ledge-forming pebbly sandstone and conglomerate
22 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

beds. The sandstone strata vary over the Colorado 

Plateau region from arkose to orthoquartzite to tuff 

with many gradations and modifications. From the 

center of the Plateau the tuffaceous material increases 

northwestward, and the arkosic material increases 

southeastward.

The sandstone units are composed of detrital grains 

of quartz, altered tuff, potash feldspar, plagioclase, 

quartzite, and a volumetrically insignificant amount of 

heavy minerals. Clay minerals include hydromica, 

montmorillonite, and mixed layer clays; some kaolinite 

clays are present in the southeastern part of the Plateau 

region. The nondetrital constituents include secondary 

silica in the form of overgrowths on quartz grains, 

zoned interstitial chalcedony, calcite and other carbonates, localized occurrences of gypsum, and iron oxides 

in the form of interstitial cement and staining on grains. 

The white angular sand grains observed in hand specimens in the central, northern, and western parts of the 

Plateau are probably silicified tuff; they are generally 

slightly coarser than accompanying quartz grains. Red 

and green pebbles of chert, which also are probably derived from material of volcanic origin, dominate the 

pebble assemblage which includes also fragments of 

quartzite, silicified limestone, and silicified metamorphosed shale. Bones and bone fragments are common 

in both mudstone, sandstone, and conglomerate units.

Micro structure. The sandstones of the Brushy 

Basin contain both homogeneous and heterogeneous 

microstructures.

MISCELLANEOUS FEATURES OF THE MAJOR 

URANIUM-PRODUCING HOST ROCKS

DETRITAL MINERALS

Quartz, the principal detritial mineral, is of two main 

types; igneous and metamorphic. The grains are 

usually rounded to subrounded, but the shape is 

changed in most samples by euhedral overgrowths 

which form perfect terminations on many grains. The 

original rounded quartz grains show moderate to slight 

replacement by calcite; however, the quartz overgrowths on the original grains are replaced readily.

The feldspar varieties are, in order of quantity, orthoclase, albite, oligoclase, microcline, andesine, and 

sanidine. The feldspars show various degrees of alteration and weathering, but albite appears as the most 

weathered of the varieties. In many calcite-bearing 

sandstones albite grains are commonly replaced in part 

or wholly by calcite leaving peculiarly oriented ghosts.

The three major varieties of tuff are present, including vitric, crystal, and lithic tuffs, each in various degrees of alteration and silicification. The typical vitric 

tuff grain contains a mixture of amorphous and slightly hydrous silica, spherical microgranular crystals of 

quartz, and voids. The outside surfaces of the angular 

grains are, in most instances, white and soft, like chalk. 

Variation in the proportions of the mixture mentioned 

above results in variation of the index of refraction 

from that of opal to that of quartz. The more highly 

silicified vitric tuff may be highly colored and may 

comprise the red or green "chert" pebbles and granules 

found in the Morrison formation.

The crystal tuff grains differ from the vitric only in 

that they include a fourth component which consists 

of microphenocrysts of potash feldspar, biotite, quartz, 

and other minerals.

The lithic tuffs are the most difficult to recognize; 

they resemble very fine grained rhyolite, or at worst, a 

practically unclassifiable rock fragment.

The heavy-mineral suites present are moderately 

large; however, they constitute only 0.1 to 1.0 percent 

of the rock. Exclusive of unique occurrences of unusual 

minerals, the suites are composed of varieties of the 

nonopaque minerals zircon, tourmaline, staurolite, 

epidote, apatite, rutile, anatase, brookite, garnet, biotite, muscovite, and spinel, and the opaque minerals 

magnetite, ilmenite, leucoxene, magnetite-ilmenite, and 

ilmenite-leucoxene-anatase intermixtures.

Clay minerals include the hydromica, montmorillonite, and kaolinite groups. The term hydromica is 

used broadly to include sericite, in part, and chlorite, 

in part. In addition to the conventional groups, there 

are also mixed-layer clays and other undefined clay 

minerals which suggest instability in many of the clays. 

The clays occur in both well-crystallized and poorly 

crystallized form. The hydromica clays are well crystallized when they form the borders around detrital 

grains of quartz. The kaolinite clays that occur in isolated interstitial wads are usually well crystallized. 

Some kaolinite crystals occur in well-developed accordion-shaped systems in the matrix. Montmorillonite is 

usually poorly crystallized.

The evidence suggests that recrystallization of some 

clays has occurred or is occurring. The well-crystallized detrital kaolinite in the interstitial wads may be 

allogenic and not due to recrystallization; however, the 

accordion-shaped crystals in the matrix appear to be 

the result of recrystallization. The hydromica clays 

are probably nearly all authigenic.

Aside from the kaolinite composing parts of weathered feldspar grains, the clays are nearly all a part of, 

or were derived from the matrix. At the time the host 

rocks were deposited it is conceivable that the matrix 

consisted of a mixture of detrital clays, fine volcanic 

ash, and ground-up feldspar, quartz, and igneous and 

metamorphic rock fragments.
CHAEACTERISTICS OF THE HOST ROCK 23

The nondetrital components of the host rocks include much material which acts as a cement and some 

that does not. Isolated euhedral calcite crystals commonly seen in the matrix or in grains of albite, exert 

little influence as a cement; when calcite is an effective cement it forms continuous bands or zones which 

fill the interstices and extend through the rock. Siderite, dolomite, barite, gypsum, and the iron oxides are 

volumetrically less important than calcite, but also have 

respectively similar roles as isolated crystals and cement. Silica cement takes two forms: as overgrowths 

on quartz grains and as zoned interstitial chalcedony. 

The ore and gangue minerals in the uranium-ore deposits are also among the nondetrital minerals.

SUMMARY OF LITHOLOGIC CHARACTERISTICS

The lens-shaped cross-stratified sandstone units of 

the Chinle and Morrison formations characteristically 

weather to form conspicuous ledges which contrast with 

the less resistant siltier strata above, below, and lateral 

to them. The associated red and green claystone and 

mudstone strata, where sufficiently thick, form variegated, slightly concave slopes. If the fine-textured 

strata contain bentonite the slopes are slightly convex. 

Mostly the ledge-forming sandstones have an erosional 

disconformity at the base but are conformable with the 

sediments above; however, the upper contact may be 

a disconformity if overlying conformable siltstones 

have been removed by subsequent erosion prior to another depositional cycle.

Most of the ledge-forming sandstones are a composite of many smaller cross-stratified units which 

are nearly all separated from each other by erosional 

truncations. The bottom of a typical ledge-forming 

unit is coarse textured and poorly sorted and may 

contain a conglomerate zone of clay galls and chips, 

and pebbles of sedimentary, metamorphic, and igneous 

rocks. Pebbly zones may be observed also along some 

truncation planes within the major unit. Other accumulated material found in the basal part of many 

of the units includes disturbed claystone strata, petrified wood, and various kinds of carbonaceous material 

either concentrated in pockets or disseminated in the 

accompanying nonorganic sediments.

The dimensions of each of these major sandstone 

lenses are a function of the dimensions of the respective 

erosional cut or cuts which they occupy. The cuts resemble erosional features such as are produced by 

present-day water currents, and for this reason the 

deeper parts of the erosional cuts are referred to as 

"channels." The size of single continuous ledge-forming sandstone units ranges in order of magnitude from

several miles to 100 feet or less in breadth and from 

1 foot to 200 feet in thickness.

Any single major unit may include a large number 

of complex sedimentary and erosional structures or 

may consist entirely of a single cross-stratified set. 

The average size of the units and average scale of 

structures of deposition and erosion vary from formation to formation and within formations vary from 

area to area.

INTERPRETATION OF ENVIRONMENT WHICH 

PRODUCED THE HOST ROCKS

The majority of geologists who have worked in the 

Plateau region believe that the rocks discussed above 

were derived from sediment deposited in an alluvial 

environmental complex in a broad continental basin 

(see Mook, 1916; Longwell, 1924; Baker, 1936; Craig 

and others, 1955). This hypothesis is supported by evidence of contemporaneous deposition and erosion, the 

widespread extent of the dominant facies, the nature 

of the interbedding of mudstone strata with lenses of 

sandstone strata, the high degree of cross-stratification in the sandstone units, the plant remains in the 

bottoms of channels, and the overall resemblance to 

present-day stream deposits of the sedimentary deposits 

which form the Morrison formation, the Shinarump 

member and lower sandstone units of the Chinle formation.

CONCLUSIONS

The sedimentary rocks which rank as the major producers of uranium ore have certain characteristics 

which probably are related to the occurrence of uranium 

ore.

Unique characteristics of composition are (1) a combination of potash and sodic feldspar-rich sands; (2) 

large quantities of silicic-alkalic tuff and ash, wood, 

vegetable material, and bone, all of which produce a 

wide variety of chemical environments and the resulting variety of clay minerals and other alteration 

products; and (3) an apparent restriction of the mineralization to the sandstone and mudstone strata containing hydromica and kaolinite as the dominant clay mineral groups to the exclusion of the montmorillonite 

clays.

Unique characteristics of combined composition and 

structure are (1) the presence of channels; (2) sedimentary traps and confined aquifers; (3) the presence 

of clays, vegetable material, and conglomerates concentrated in the bottoms of channels, and (4) the region-wide association of restricted permeable sandstones with impermeable claystone strata, containing 

a trace to moderate amounts of slightly to very soluble 

salts and compounds.
24 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Critical features of the minor producing formations 

are less apparent. Uranium production from the Entrada sandstone and Todilto limestone is restricted to 

a narrow 60-foot zone in the stratigraphic column which 

straddles the Entrada-Todilto contact, and to a 20- to 

30-foot zone above the Entrada-Dolores contact 

(Fischer, 1942). The special characteristics of these 

zones include jointed limestone, well-sorted sandstone, 

and evaporite lithologic types. The Entrada-Todilto 

contact, though inconspicuous, is wide in extent and 

represents an important stratigraphic reference plane 

in the southeastern part of the Colorado Plateau region. 

All, some, or none of these factors may be related to 

the deposition of uranium in these two formations.

The stratigraphic units of Triassic and Jurassic age 

described are not in their entirety classifiable as host 

rocks, but they do contain the particular facies which 

favor the occurrence of deposits of uranium ore.

LITERATURE CITED

Baker, A. A., 1936, Geology of the Monument Valley Navajo

Mountain region, San Juan County, Utah: U. S. Geol.

Survey Bull. 865. 

Bucher, W. H., 1953, Fracture studies in the Zuni and Lucero

uplifts, New Mexico: U. S. Atomic Energy Comm. RME3042, p. 8. 

Craig, L. C., Holmes, C. N., Cadigan, R. A., Freeman, V. L., and

others, 1955, Stratigraphy of the Morrison and related

formations of the Colorado Plateau region, a preliminary

report: U S. Geol. Survey Bull. 1009-E. 

Finch, W. I., 1953, Distribution of uranium deposits in the

Shinarump conglomerate of the Colorado Plateau (abs.) :

Geol. Soc. America Bull., v. 64, p. 1422.

Finch, W. I., 1955, Preliminary geologic map showing the distribution of uranium deposits and principal ore-bearing 

formations of the Colorado Plateau region: U. S. Geol. 

Survey Mineral Inv. Field Studies Map MF 16.

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah, 

a preliminary report: U. S. Geol. Survey Bull. 936-P.

Krynine, P. D., 1948, The megascopic study and field classification of sedimentary rocks: Jour. Geology, v. 56, p. 130- 

165.

Longwell, C. R., Miser, H. D., Moore, R. C., Bryan, Kirk, and 

Paige, Sidney, 1923, Rock formations in the Colorado 

Plateau of southeastern Utah and northern Arizona: U. S. 

Geol. Survey Prof. Paper 132.

Mook, C. C., 1916, A study of the Morrison formation: New 

York Acad. Sci. Annals, v. 27, p. 39-191.

Mullens, T. E., and Freeman, V. L., 1952, Lithofacies study of 

the Salt Wash sandstone member of the Morrison formation (abs.) : Geol. Soc. America Bull., v. 63, p. 1340-1341.

Pettijohn, F. J., 1949, Sedimentary rocks: New York, Harper 

and Brothers.

Stewart, J. H., and Williams, G. A., 1954, Stratigraphic relations 

of the Triassic Shinarump conglomerate and a prominent 

sandstone unit of the Chinle formation in southeastern 

Utah (abs.) : Geol. Soc. America Bull., v. 65, p. 1387.

Stewart, J. H., and Smith, J. F., 1954, Triassic rocks in the San 

Rafael Swell, Capitol Reef, and adjoining parts of southeastern Utah in Geology of portions of the High Plateaus 

and adjacent Canyon lands central and south-central 

Utah: Intermountain Assoc. of Petroleum Geologists, Fifth 

Annual Field Conference.

Witkind, I. J., 1954, Localization of uranium minerals in channel 

sediments at the base of the Shinarump conglomerate, 

Monument Valley, Arizona (abs.) : Geol. Soc. America 

Bull., v. 65, p. 1327.
Part 3. ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS

By E. M. SHOEMAKER, A. T. MIESCH, W. L. NEWMAN, and L. B. RILEY

CONTENTS

Page 

Abstract.._ __-_----__-__--_-______-___________.____ 26

Introduction _______________________________________ 26

Methods of sampling and sample preparation_____ 26

Analytical methods..__________________________ 27

Mathematical treatment of analyses_____________ 27

Composition of sandstones of the Colorado Plateau and 

sandstone-type uranium ores.__-___-____-___----___ 29

Composition of unmineralized sandstone from the 

principal uranium ore-producing strata. _________ 29

Composition of sandstone-type uranium ores from 

Upper Triassic rocks and from the Morrison formation ______________________________________ 31

Classification of elements in sandstone-type uranium 

deposits____________________________________ 33

General features--___---___----___-_-__--___ 33

Dominantly intrinsic elements._______________ 36

Silicon________________________ 36

Aluminum _____________________________ 36

Potassium..... _________________________ 38

Iron_.________________________ 38

Magnesium. ___________________________ 39

Titanium and zirconium.________________ 40

Composition of sandstones, etc. Continued 

Classification of elements, etc. Continued

Dominantly intrinsic elements Continued 

Barium, strontium, and chromium. ___.

Beryllium. .____________-_---_-_-

Scandium, lanthanum, and gallium. 

Antimony _ ____________________

Silver and zinc.-.--..------------

Calcium, sodium, and manganese. _

Ore elements. ___________-__-_-_-_---

Uranium and vanadium....___ ____

Accessory extrinsic elements. . _________

Copper and lead__-_-_-----------

Nickel, cobalt, and molybdenum.._ 

Yttrium and ytterbium.. _ _-__.___ 

Selenium __ ____________________

Arsenic. _______________-----____

Elements not detected-..-------------

Summary______- ____________________________

Literature cited _ _-__________________-__---_

Page

40

41

41

43

43

43

43

45

45

47

48

48

50

50

51

51

52

53

ILLUSTRATIONS

Page

FIGURE 3. Map of the Colorado Plateau showing localities from which samples were obtained.--..____________________ 30

4. Correlation of elements in uranium ores and unmineralized sandstones from the Morrison formation (Jurassic)_ 34

5. Frequency distribution of the dominantly intrinsic elements of uranium ores (aluminum through boron)__.____. 37

6. Frequency distribution of the dominantly intrinsic elements of uranium (beryllium through manganese)________ 42

7. Frequency distribution of UsOs in uranium ores from the Morrison formation (Jurassic)....___________-___.___ 45

8. Frequency distribution of vanadium__________________________________________________________________ 46

9. Frequency distribution of the dominantly accessory extrinsic elements of uranium ores______________________ 49

25
26 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLES

TABLE 1. Average chemical composition of Colorado Plateau sandstones and sandstones from the principal uranium orebearing strata._____________________________________________________________________________________

2. Average composition of uranium ores and unmineralized sandstones of the principal uranium ore-bearing formations 

on the Colorado Plateau.____________________________________________________________________________

3. Comparison of weighted arithmetic mean grade of vanadium pentoxide in ores produced in 1953 and 1954 and in 

ores represented by samples studied______________-__-________________.________________________________

4. Elements looked for but not detected in pulp samples of ores from 249 uranium deposits and in 128 grab samples 

of unmineralized sandstones from the Upper Triassic rocks and the Morrison formation..____________________

5. Classification of elements in sandstone-type uranium deposits from Upper Triassic rocks and from the Morrison 

formation._ ________________________________________________________________________________________

6. Extrinsic elemental components of average uranium ore from the Morrison formation in their estimated order 

of abundance.._____________________________________________________________________________________

Page

31

32

47

51

52

53

ABSTRACT

The chemical composition of sandstone-type uranium ores 

and unmineralized sandstones from the Colorado Plateau has 

been determined chiefly by spectrographic analysis. More than 

400 samples of ore and nearly 300 samples of unmineralized 

sandstone were analysed for about 60 elements by a rapid semiquantitative technique, and more restricted suites of samples 

were analysed for 5 elements by chemical techniques. The 

spectrographic and chemical analyses were treated by conventional mathematical methods for grouped data.

The average chemical composition of sandstones from the 

principal host rocks of Colorado Plateau uranium deposits 

the Shinarump and Moss Back .members of the Chinle formation, both of Late Triassic age, and the Salt Wash member of 

the Morrison formation, of Late Jurassic age differ only moderately from the average composition of sandstones from most 

of the formations of Paleozoic and Mesozoic age on the Colorado Plateau. Average sandstones of the Shinarump and Moss 

Back members appear to contain significantly more aluminum, 

iron, titanium, zirconium, vanadium, chromium, copper, and 

probably more cobalt and nickel than average Colorado Plateau 

sandstones and less magnesium, calcium, barium, and probably 

less potassium.. Average sandstones of the Salt Wash contain 

significantly more calcium, manganese, and copper than average 

Colorado Plateau sandstones and significantly less iron and 

probably less potassium, boron, cobalt, nickel, and yttrium.

A sandstone-type uranium deposit may be considered as composed of two fundamental parts: an indigenous part, and a 

foreign part which was added to the indigenous part to form 

the deposit. The indigenous part comprises all elements that 

would have occupied the space of the uranium deposit had 

uranium mineralization never occurred; these elemental components are called intrinsic. The foreign part comprises all 

elements that were added to the indigenous part by the processes of mineralization; these elemental components are called 

extrinsic. Almost all elements in sandstone-type uranium deposits are probably partly intrinsic and partly extrinsic, but 

each element may be classified according to the dominant role 

it plays in a majority of the deposits.

Elements detected by the analyses used in this study that 

are interpreted as dominantly intrinsic in the uranium deposits 

of both Upper Triassic rocks and the Morrison formation include silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, zirconium, barium, strontium, manganese, 

beryllium, boron, scandium, chromium, zinc, gallium, silver, 

lanthanum, and antimony. Dominantly extrinsic elements in

the deposits of both the Morrison formation and the Upper 

Triassic rocks include uranium, vanadium, cobalt, nickel, copper, arsenic, molybdenum, and lead. Two elements, selenium 

and yttrium, are interpreted as dominantly extrinsic iri the 

deposits of the Morrison formation, but dominantly intrinsic 

in the deposits of the Upper Triassic rocks. Other elements 

not determined in the analyses used in this study, but known' 

from other work which may be extrinsic components of some 

of the sandstone-type uranium ores on the Colorado Plateau 

include sulfur, phosphorus, ytterbium, tin, cadmium, tellurium* 

and thallium.

INTRODUCTION

A regional study of the distribution of elements in 

the rocks and ores of the Colorado Plateau was begun 

in 1951 to provide information on the geochemical 

environment of the uranium deposits. Study of the 

gross elemental composition of the uranium ores provides a broad basis, and for some problems a starting 

point, for more detailed geochemical and mineralogical investigations. This paper summarizes information obtained to date on the gross elemental composition of the uranium deposits and the role or roles 

played by each element in the history and composition 

of the ore. The investigation is still in progress and 

all histograms and averages given are subject to minor 

revision.

Two general types of samples have been used in the 

study of the composition of the rocks and ores. Most 

samples of unmineralized sandstones from formations 

under study were collected from outcrops during detailed stratigraphic investigations (Craig and others, 

1955; Williams, 1954, p. 33-35) and were supplied by 

R,. A. Cadigan of the U. S. Geological Survey. Some 

samples were collected by the writers from drill core 

and from outcrops. Samples of uranium ore were obtained from mechanical splits of ores shipped to mills 

and buying stations.
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 27

The samples of unmineralized sandstones are essentially grab samples selected to be representative of 

randomly distributed individual sandstone strata or 

parts of strata. Samples were taken without regard 

to proximity to known uranium deposits, but no samples that were visibly mineralized or found to have 

a radioactivity greater than 0.005 percent eU were incorporated in this study of unmineralized rocks. Two 

to five pounds of rock, as fresh as could be obtained, 

were originally collected, from which about 250 grams 

of fragments were picked out by hand. Where further crushing before grinding was necessary, the samples were crushed in a jaw crusher with iron jaws, and 

all samples were ground to minus 80-mesh in a disk 

grinder with ceramic plates (Barnett and others, 1955).

The samples of uranium ores obtained from mills 

and buying stations are pulverized quarters of splits 

or pulps that were assayed to determine payment to the 

shippers. Most of the samples studied were obtained 

from the U. S. Atomic Energy Commission's Monticello plant, operated by the American Smelting and 

Refining Co. (For description of sampling process 

see Colorado School of Mines Research Foundation, 

1954, p. 46-49.) The pulps were ultimately ground to 

minus 120-mesh in cast-iron disk grinders. Nearly all 

the pulps are probably contaminated slightly with 

tramp iron. The average introduced amount of iron 

is estimated to be about 0.1 percent by weight. If the 

composition of the tramp iron is similar to that analyzed by Myers and Barnett (1953, table 2), the 

amounts of spectrographically detectable minor elements introduced with the iron are probably below or 

near the spectrographic limit of sensitivity.

Samples representing individual shipments or suites 

of shipments were combined, according to weight of 

ore represented, into composite samples for each mine. 

Final samples submitted for analysis consisted of 100- 

to 250-gram splits of the composite pulps. Samples 

from some mines were divided into two or more groups, 

and two or more composite pulps were prepared, representing different grades of ore or ore shipped from 

different parts of the mine. The amount of ore represented by the samples from each mine ranges from 

1 to more than 5,000 tons and averages about 250 tons.

The term "ore" in this report refers to mineralized 

rock mined and shipped to the mills for payment. A 

surprising proportion, about 20 percent, of the shipments studied contained less than 0.10 percent U3O8 , 

the minimum grade for ore established by the U. S. 

Atomic Energy Commission (1948). Not all of the 

material mined and classed as ore in this report, therefore, is of ore grade under present economic conditions.

46S652 59 3

ANALYTICAL METHODS

Most of the analyses were done by a rapid semiquantitative spectrographic method in the Denver spectrographic laboratory of the U. S. Geological Survey. 

R. G. Havens was the principal analyst, but large 

numbers of analyses were made by P. R. Barnett, 

G. W. Boyes, Jr., and P. J. Dunton; 428 samples of 

ore pulps and 289 samples of unmineralized sandstones 

were analyzed spectrographically.

Sixty elements are detectable with one exposure by 

the spectrographic method employed for this study. 

Of these elements, 22 are present in more than 65 percent of the ores in concentrations a above the spectrographic limits of sensitivity, and 9 elements are present 

in less than half of the ores in concentrations above the 

limits of sensitivity. The remaining 29 elements looked 

for were not detected in either the ores or the unmineralized sandstones. Study of the composition of the 

ores by the rapid spectrographic method is thus limited 

to about 30 elements.

The limits of sensitivity for each element are in general those listed by Myers (1954, p. 195). As the 

analytical work has extended over a period of 3 years 

and some changes were made in the details of the 

technique during this time, and as the individual 

analysts followed slightly different practices in reporting elements near the limit of sensitivity, the limit of 

sensitivity actually attained or reported for each element has varied slightly. Histograms given in figures 

5 to 9 are cut off at the highest limits of sensitivity reported, but averages given in tables 1 and 2 and the correlation coefficients shown in figure 4 incorporate some 

determinations below the highest limit used. A majority of the statistics are subject to minor revision, 

pending review of some analyses and incorporation of 

additional samples.

Spectrographic data on arsenic, antimony, and zinc 

have been supplemented by colorimetric analyses 

(Lakin, Almond, and Ward, 1952, p. 14-16; Ward and 

Lakin, written communication, 1953; Almond, written 

communication, 1953) because these elements are generally present in the sandstones and ores in concentrations below the spectrographic limit of sensitivity. 

Selenium analyses were done by colorimetric methods 

(Lovering, and others, 1955). The colorimetric 

analyses were done by H. E. Crow, J. H. McCarthy, 

A. P. Marranzino, J. Meadows, and J. L. Silverly under the supervision of H. W. Lakin and L. F. Rader.

MATHEMATICAL TREATMENT OF ANALYSES

The concentrations of the elements, as determined by 

semiquantitative spectrographic analysis in this study,

3 The term "concentration" Is used throughout this chapter In the conventional sense of fractional weight contained.
28 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

are reported in a series of 15 equal logarithmic classes 

that span the range from 0.0001 to 10 percent. Concentrations greater than 10 percent or less than 0.0001 

percent are generally beyond the range of sensitivity of 

the spectrographic technique employed and are noted 

but not classified. Each class interval is equal to 0.3333 

in log values, and the class limits form a geometric 

series that may be generated by integral powers of the 

cube root of 10 (2.154). After log transformation the 

analytical data may be treated with conventional mathematical methods for grouped data described in elementary statistics texts (see, for example, Waugh, 

1943, p. 81-154, 372-430; Snedecor, 1946, p. 31-74, 

137-168; or Hoel, 1947, p. 3-20, 78-92,128-166).

The formulas used are as follows:

where £ = mean log,

n= total number of samples,

X{= class midpoint of the ith class in logs,

/,-= frequency of ith class.

where

where

s=log standard deviation.

(2)

(3)

r=linear correlation coefficient between x and y, which 

are the logs of the concentration of two elements.

The number of significant figures that may be retained for x and s is a function of the number of samples 

and the magnitude of s up to a limit determined by the 

precision with which the standards used in the analysis 

were prepared. No assumptions or judgments on the 

precision or accuracy of the analyses or on the frequency 

distribution of the analytical results are involved in the 

statistical theory of the formulae employed. The computed values of x and s may be assigned some probability determined by the precision and accuracy of the 

analyses. If an analyst can assign the correct class to 

an element in 60 percent of the determinations (a conservative estimate), the minimum probability for the 

computed value of x recorded to the maximum number 

of allowable significant figures is 60 percent. By dropping one significant figure the probability of x and s is 

greatly increased.

Statistical comparison of some of the semiquantitative 

spectrographic determinations with chemical analyses 

of the same material indicates the absolute error of the 

spectrographic analysis is proportional to the concentration, over the range of sensitivity, and analysis of

replicate spectrographic determinations shows that deviations from the geometric mean are approximately 

lognormally distributed. The frequency distribution of 

most elements that lie above the spectrographic limit 

of sensitivity in the various groups of samples studied 

has been found by chi-square test to be approximately 

lognormal both in unmineralized sandstones and in the 

uranium ores. Thus the statistical theory for normal 

or Gaussian distribution may be applied to the spectrographic data with the least bias after log transformation. This transformation is based on the results obtained from the samples and is not concerned with the 

underlying causes of the form of the distribution.

If some determinations fall below the spectrographic 

limit of sensitivity the population mean log and log 

standard deviation can be estimated with least bias from 

the probability function for the truncated normal distribution (Fisher, 1931, p. xxxiii).

2<r dx

where <r= population standard deviation 

m= population mean

£= difference between m and limit of sensitivity in a 

values, limit of sensivity = m+<r £

and the Io function has the form

1

Hald (1952, p. 62-63) gives tables derived from this 

probability function for estimating the sample mean 

and log standard deviation as well as tables for the onesided censored normal distribution with which account 

may be taken of the number of analyses below the limit 

of sensitivity. Though the use of these table (for the 

truncated or censored normal distribution) introduces 

the least bias in the calculation of mean log and log 

standard deviation, several other methods of approximate calculation give closely comparable results. Where 

a majority of analyses are below the limit of sensitivity 

a rough estimate of the mean log may be obtained 

from the percent above the limit of sensitivity by use of 

the area tables for the normal curve and by assuming 

an average value for the log standard deviation. The 

means obtained by use of the area tables and an assumed 

standard deviation should be considered only as indicating the probable order of magnitude of the mean 

of the samples analyzed.

The simplest and generally most useful measure of 

central tendency that may be computed from the spectrographic analyses is the arithmetic mean of the logs, 

the antilog of which is the geometric mean. For a lognormal distribution the geometric mean is an estimate
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 29

of the population median or true median. The most 

efficient (Fisher, 1921, p. 309-310) estimate of the true 

or population arithmetic mean may also be obtained 

from the geometric mean by methods given by Sichel 

(1952, p. 265-285). For purposes of comparison the 

geometric mean is generally the most satisfactory 

measure of central tendency for lognormal or approximately lognormal distributions, because the logarithmic 

variance of geometric means of small sets of samples 

drawn from a lognormally distributed population is less 

than the logarithmic variance of the arithmetic means 

(the geometric mean is a more efficient or more stable 

statistic). All means given in this paper are geometric 

except where otherwise noted.

It must be emphasized that the geometric means given 

in this paper should not be compared directly with 

published estimates of element abundance which are reported as arithmetic means. The geometric means for 

all the elements reported are invariably less than the 

estimated true arithmetic means by an amount that is 

a function of the log standard deviation (see footnote 

table 2). For a majority of distributions studied the 

arithmetic mean is 2 to 3 times greater than the geometric mean.

COMPOSITION OF SANDSTONES OF THE COLORADO 

PLATEAU AND SANDSTONE-TYPE URANIUM ORES

Uranium deposits have been found on the Colorado 

Plateau in most of the principal formations of Permian through Tertiary age and in three kinds of sedimentary rocks: limestone, mudstone, and sandstone. 

Some uranium deposits are also known in igneous rocks 

of Tertiary and possible Cretaceous age. More than 

85 percent of the known uranium deposits are in sandstone and conglomeratic sandstone strata of the Shinarump and Moss Back members of the Chinle formation 

of Late Triassic age and of the Morrison formation of 

Late Jurassic age. Most of the ore produced from the 

Morrison formation has come from the Salt Wash member, and most of the known uranium deposits are in the 

central part of the Colorado Plateau where the Salt 

Wash member is well exposed.

COMPOSITION OF UNMINERALIZED SANDSTONE FROM 

THE PRINCIPAL URANIUM ORE-PRODUCING 

STRATA

Two principal uranium ore-producing groups of 

strata are distinguished for purposes of discussion. 

The first group comprises the Shinarump and the Moss 

Back members of the Chinle formation. Nearly all the 

uranium ores from Upper Triassic rocks included in 

this study are from these two units. The second group 

of strata, which make up the Salt Wash member of the 

Morrison formation, contain most of the ore deposits in

the Morrison formation included in this study. Only 

32 samples of sandstones from the Shinarump and 

Moss Back members from the central part of the Colorado Plateau (fig. 3) are included in the study and 

averages calculated for this group of samples should 

be considered preliminary. The statistics for sandstones from the Salt Wash member, on the other hand, 

are based on 96 samples from localities distributed over 

the area occupied by the Salt Wash member. At many 

of the sample localities in the Morrison formation unmineralized sandstone samples were taken from several 

different sandstone strata in the Salt Wash member, 

and, in general, the samples of the several sandstone 

units taken from a single stratigraphic section are 

similar in major and minor element composition. The 

samples taken from the Salt Wash are thought to be 

fairly representative of the sandstones of this member. 

The chemical composition of the principal ore-bearing strata differs moderately from the average chemical 

composition of Colorado Plateau sandstones (table 1). 

The average sandstones from the Shinarump and Moss 

Back members appear to contain significantly 3 more 

aluminum, iron, titanium, zirconium, vanadium, chromium, copper, and probably more cobalt and nickel 

than the average Colorado Plateau sandstones. Aluminum in the unmineralized sandstones is contained 

chiefly in feldspar and clay minerals (for description 

of mineralogy see Part 2), and the greater content of 

aluminum in the sandstones of the Shinarump and 

Moss Back members indicates a greater content of 

feldspar and clay than is found in average sandstones 

of the Colorado Plateau (Part 2). Iron, titanium, and 

zirconium have a moderate-to-high correlation and 

vanadium, chromium, and copper a low-to-moderate 

correlation with aluminum in unmineralized Salt Wash 

sandstone (fig. 4) and probably have similar correlations in the sandstones of the Shinarump and Moss 

Back. The above-average amounts of iron, titanium, 

and zirconium and perhaps also of cobalt and nickel in 

the sandstones of the Shinarump and Moss Back members probably is in part a reflection of the above-average 

content of feldspar and clay. The concentration of

8 For large sample sets drawn from normal populations the standard 

deviation of the difference between two means may be approximated 

without serious bias from the equation

and the significance of x y may be determined from ordinate tables 

for the normal curve of error. The precise determination of significance 

of the difference between two means for small sample sets, in the general case that the variances are not equal, is mathematically more 

complex. In this paper, for purposes of simplicity, a difference is 

judged significant if one mean lies outside the 99 percent confidence 

interval of another mean. (See table 2 for confidence intervals of 

the means.)
ARIZONA NEW 

MEXICO

SAMPLE LOCALITY FOR UNMINERALIZED 

SANDSTONE IN THE MORRISON FORMATION 

(JURASSIC)

URANIUM DEPOSIT IN MORRISON FORMATION 

FROM WHICH A SAMPLE OR SAMPLES WERE 

OBTAINED

D SAMPLE LOCALITY FOR UNMINERALIZED 

SANDSTONE IN UPPER TR1ASS1C ROCKS

 URANIUM DEPOSIT IN UPPER TRIASSIC ROCKS 

FROM WHICH SAMPLES WERE OBTAINED

FIGURE 3. Map of the Colorado Plateau showing localities for samples of unminerallzed sandstone and uranium deposits from which

samples were obtained.
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 31

copper in the average of sandstones of the Shinarump 

and Moss Back members, which is more than 10 times, 

is noteworthy. Visible traces of copper carbonates 

are widespread in Shinarump and Moss Back members.

Magnesium, calcium, barium, and probably potassium 

appear to be significantly lower in sandstones of the 

Shinarump and Moss Back than in average Plateau 

sandstones. The low concentration of magnesium and 

calcium reflects a less-than-average content of carbonate 

in sandstones of the Shinarump and Moss Back 

members.

Average sandstones of the Salt Wash contain significantly more calcium, manganese, and copper than 

average Colorado Plateau sandstones. Calcium and 

manganese have a high correlation (fig. 4) and are 

contained mainly in carbonates, which are the principal 

cements of the sandstone of the Salt Wash (according 

to Cadigan in Part 2). Sandstones of the Salt Wash 

are significantly lower than average in iron and probably lower in potassium, boron, cobalt, nickel, and 

yttrium.

TABLE 1. Average chemical composition of Colorado Plateau 

sandstones and sandstones from the principal uranium orebearing strata

[Composition shown In parts per million]

.Element

81....... .............

Al........ ............

Fo.... . ............

Mff

Oa.... ._ ...........

Na.. ...... ...........

K.. ..................

Tl...... ...........

Zr....... .............

Mn...... .............

Ba......... .... .......

Sr.. ..................

B... - ............ ..

V... ..................

Cr.. __ ....

Co..... ......... ...

Nl...... ... ...........

Ou... .... ....... ..

Y..... ......... ... ....

U..... .......... ...

Sandstones of

Paleozoic and 

Mesozolc age 

from the Colorado Plateau '

> 100, 000

10, 000

3,700

2,700

12,000

690

4,300

580

88

140

280

45

16

11

7

1

2

0

4

Unmlnerallzed sa

Shinarump and 

Moss Back 

members of the 

Chlnle formation >

> 100, 000

33,000

12,000

1,300

2,500

900

«2,000

1,800

250

120

520

60

ss 16

30

14

«5

ssO

100

' 16

indstones of the 

Salt Wash member 

of the Morrlson 

formation '

>100, 000

11,900

.2. 400

2,300

33,000

890

w3,000

510

103

220

340

49

«8

10

6.6

s».5

«.5

13

ss2

« «1

i Geometric moan of the geometric-mean composition of sandstones hi each of 24 

formations on the Colorado Pleateau ranging in age from Cambrian through Cretaceous (289 samples, averaged by formations).

> Geometric moan composition (32 samples).

' Geometric moan composition (96 samples).

« Geometric mean of 23 samples analysed by fluorimetric method (Grlmaldl, May, 

and Flotcher, 1952).

Sandstones of the Salt Wash, in general, are more like 

the average Colorado Plateau sandstones than are the 

sandstones of the Shinarump and Moss Back members. 

Only two elements show a similar significant departure 

from the Colorado Plateau sandstone average in both 

major groups of ore-bearing strata. Copper is significantly higher in both the sandstones of the Salt Wash

and the sandstones of the Shinarump and Moss Back 

than in the average Plateau sandstones, and potassium 

appears to be significantly lower in both. In comparing 

sandstones of the important ore-bearing formations 

with other sandstones it should be noted that the estimates of geometric-mean concentrations of each of the 

elements in unmineralized sandstones of the Salt Wash 

would fall within the confidence interval of the mean 

(table 2) for all elements, if the elements contained in 

all the ore estimated to have been present in the Morrison formation were dispersed in sandstones. In other 

words, the estimate of average concentration of elements in the sandstones of a given formation is not 

significantly changed if the ore deposits are included 

with the unmineralized sandstones, even in the most intensely mineralized formation.

COMPOSITION OF SANDSTONE-TYPE URANIUM ORES 

FROM UPPER TRIASSIC ROCKS AND FROM THE 

MORRISON FORMATION

Most of the uranium deposits of the Colorado Plateau 

consist of sandstone and minor amounts of mudstone 

impregnated with and partly replaced by minerals of 

uranium, vanadium, and in some cases by copper or 

other heavy metals. To this kind of deposit the name 

sandstone type uranium deposit has been applied. The 

discussion of uranium deposits in this paper is restricted 

to sandstone-type deposits in Upper Triassic rocks and 

in the Morrison formation.

All the deposits studied in the Morrison formation 

are in the Salt Wash member except for a small number that are in sandstone lenses near the base of the 

overlying Brushy Basin member. More than 200 deposits, or approximately 10 percent of the known deposits, in the Morrison formation and about 40,000 tons 

of ore from the Morrison formation are represented by 

the samples studied. The arithmetic-mean grade of 

uranium and vanadium in 211 deposits, averaged by 

tonnage, is very close to the weighted-arithmetic-mean 

grade for all ore produced from the Morrison formation for successive 6 months periods in 1953 and 1954 

(see section "Uranium and vanadium"). The samples 

of ores from the Morrison are therefore considered representative of producing deposits in uranium and vanadium content and are thought to be probably representative in their content of most other elements as well.

All but two of the sampled deposits in Upper Triassic 

rocks are in the Shinarump or Moss Back members of 

the Chinle formation, and the remainder are in other 

members of the Chinle formation. Only 38 deposits in 

Upper Triassic rocks, about 6 percent of the known deposits in these rocks, have been studied, and these may 

not be fully representative of the deposits now producing ore from the Chinle formation. A disproportionate
32 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

number of deposits in Upper Triassic rocks studied are 

in one relatively small area at Temple Mountain, in central Utah.

The average composition of sandstone-type uranium 

ores from the Chinle formation and from the Morrison 

formation is given in table 2 along with the average 

composition of the unmineralized sandstones. The frequency distributions on which these averages are based 

are shown in figures 5 to 9. Class intervals used in the 

histograms for spectrographic analyses are the same 

as the class intervals by which the analyses were reported, and the class intervals used in the histograms 

for colorimetric analyses are approximately the same 

as those used for the spectrographic analyses.

TABLE 2. Average composition of uranium ores and unmineralized sandstones of the principal uranium ore-bearing formations on the

Colorado Plateau

[All elements except Zn, As, Se, and Sb were determined by semlquantltatlve spectrographic analyses, thus: (1) 211 deposits, (2) 96 samples, (3) 38 deposits, (4) 32 samples

Element

Al . ...............

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

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

Ca.. ................

Na..................

K..... ..............

Tl...... ....... ......

Zr...................

Mn.. ...............

Ba.. ................

Sr-.. ...............

Be.. ................ 

B. ..................

Sc ................

V.. .................

Or..................

Co.. ................

NL. ................

Ou........ ..........

Zn *..... ............

Oa.................. 

As*.................

Se ........ ..........

Y............. ......

Mo.................

Ag.. ................

8b «._........._..__.

La..................

Yb........ ..........

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

Morrison formation Chiefly Salt Wash member

Uranium ores 

(1)

Range of geometric 

mean

Geometric 

mean

2.48 

.90 

.68 

1.97 

.091

.104 

.0237 

.031 

.084 

.0122 

<.0001

w.0016

<.001

.49 

.00169

.00104

.00084

.0086 

.0116

<-0005

.0168 

.00118

.00129 

«. 0013

f <.0001 

\»«. 00005 

ss. 0001

<.002

.0088

2 Confidence 

Interval '

1.14 

1.12 

1.19 

1.22 

1.23

1.13 

1.14 

1.15 

1.16 

1.13

1.15 

1.14

1.27

1.28

1.30 

1.44

1.42 

1.48

1.21

}...........

............

1.29

Geometric 

deviation 8

2.03 

1.89 

2.60 

3.07 

3.19

1.95 

2.11 

2.17 

2.32 

2.00

2.14 

2.03

3.77

4.02

4.34 

2.58

2.48 

4.45

2.86

............

4.10

Unmineralized sandstones 

(2)

Range of geometric 

mean

Geometric 

mean

1.2 

.24 

.23 

3.3 

.089 

f .37 

\«».3 

.051 

.0103 

.022 

.034 

.0049 

<.0001 

f <-001 

l'ss.0008

<.001

.0010 

.00066 

f <.0002 

t'ss.0005 

f <.0002 

\»«. 00005 

.0013 

.0053

<.0005

<.001 

<.0002 

f <.0005 

1 » =3.0002

<.0005

I <.0001 

l'as.00003 

«. 0002

<.002

f <.0001 

\'s=s. 00003 

<.0001

^Confidence 

Interval '

1.18 

1.19 

1.33 

1.40 

1.42

1.20 

1.27 

1.33 

1.34 

1.28

}:::::::::::

1.32 

1.25

1

1.28 

1.53

}.._._._.

}..__.....

jr.:::::

Geometric 

deviation '

1.89 

1.91 

2.85 

3.47 

3.73

1.96 

2.40 

2. 89 

3.00 

2.50

2.81 

2.27

2.49 

2.09

............

Upper Triassic rocks Chiefly Shlnarump and Moss Back members of 

the Chinle formation

Uranium ores 

(3)

Range of geometric 

mean

Geometric 

mean

2.2 

1.5 

.17

.7 

.08

as. 48

.13 

.018 

.024 

.07 

.014 

«ss. 00007

.0014

f <.001 

X >ss. 0006 

.063 

.0030

.0025

.0025

.030 

.031 

( <.0005 

\ 'ss. 0002 

.020 

fa. 0006

.0017 

«. 0017

f <,0001 

1 ««. 00004 

». 0002

f <.002 

\ »ss. 001

.0064

^Confidence 

Interval '

1.42 

1.33 

1.61 

1.87 

1.63

1.43 

1.36 

.1.58 

1.67 

1.52

}...........

1.92 

1.56

2.00

1.67

2.76 

3.11

1.85

1.76

}.... .....

}...........

1.66

Geometric 

deviation '

2.21 

1.90 

2.99 

4.14 

3.04

2.26 

2.03 

2.85 

3.22 

2.59

4.40 

2.74

4.16

3.22

10.10 

4.16

2.16

3.61

3.16

Unmineralized sandstones 

(4)

Range of geometric 

mean

Geometric 

mean

3.3 

1.2 

.13 

.25 

w.l 

f .15 

\««.2 

.18 

.025 

.012 

.05 

.006 

 C0001

». 0016

f <.001 

l'ss.0004 

.0030 

.0014

Rs.0005

as. 0009 

.010

f <.0005 

l'ss.0001

ss. 0003

.0016

/ <.0005 

\ 'ss.0002

 C0001

f <.002 

l'ss.0008

.00024 

'ss. 001

XConfldence 

Interval '

1.66 

1.81 

2.12 

2.60

}....

1. oo 

1.81 

3.05 

1.97 

2.21

}...........

2.08 

1.54

1.79

}...._.....

1.50

}...........

}...........

1.68

Geometric 

deviation

2.85 

3.40 

4.72 

7.19

2.50 

3.39 

10.00 

4.06 

5.13

4.52 

2.44

3.33

2.31

2.42

1 The 99 percent confidence Interval for the population geometric mean: the limits 

of the confidence Interval are determined from Student's t distribution (Fisher and 

Yates, 1953, p. 1 and 40) where t is the deviation (or range of the population mean), In 

units of estimated standard error. For a normal distribution

confidence Interval of the moan=±< 

or for a lognormal distribution

confidence interval of GM=* antllog t r(1°L°.D) l

* Lv^ 1

The most efficient estimate of the arithmetic mean of a lognormal population may 

be obtained from the following equation if n is large:

logio estimated arithmetic mean=logio GM+1.1513 (logn GD)»

In table 2 a factor is given for each mean that lies 

above the analytical limits of sensitivity which defines 

the limits of the 99-percent confidence interval for the 

true geometric mean of the type of rock from which 

the samples were taken. For the elements that lie

a Geometric deviation or antilog of the log standard deviation.

s Estimated geometric mean. Estimated by assuming the part of the frequency 

distribution below the limit of sensitivity conforms to part of a lognormal distribution. 

Where a majority of analyses are below the limit of sensitivity the geometric mean is 

estimated from the frequency above the limit of sensitivity by assuming a lognormal 

distribution for the total frequency and by assuming for the element in question an 

average log-standard deviation computed for elements In the type of rock or ore 

analyzed.

4 Colorimetric analyses (1) 49 deposits, (2) 23 samples, (3) 14 deposits.

 Colorimetric analyses (1) 102 deposits, (2) 8 samples, (3) 30 deposits, (4) 30 

samples.

mainly or entirely above the analytical limits of sensitivity, a measure of the dispersion or variation of concentration of each element in the ores and rocks (the 

geometric deviation) is also given. The geometric deviation is the antilog of the logarithmic standard devi-
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 33

ation and is a measure of dispersion that is independent 

of the order of magnitude of the mean concentration. 

If the frequency distribution of an element is approximately lognormal the range of concentration between 

the limits defined by the geometric mean divided by 

the geometric deviation and the geometric mean multiplied by the geometric deviation will include about 68 

percent of the analyses.

As an example, the table may be read for aluminum 

as follows: the geometric-mean concentration of aluminum in 211 sandstone-type uranium ores from the Morrison formation is 2.48 percent. Assuming the selection 

of deposits studied to be representative and the spectrographic analyses unbiased, then the true geometric 

mean of the aluminum concentration in all uranium 

deposits in the Salt Wash member and overlying parts 

of the Brushy Basin member of the Morrison formation, of which there are about 2,000 known at the 

present time, would lie (with 99 percent confidence) 

betwen 2.83 percent (2.48X1.14) and 2.18 percent 

(2.48-H 1.14). About 68 percent of the deposits may be 

expected to have an aluminum concentration between 

5.0 percent (2.48X2.03) and 1.22 percent (2.48-^2.03). 

The calculated geometric-mean concentration of aluminum in 96 samples of the unmineralized sandstone host 

rocks in the Salt Wash member of the Morrison formation is 1.2 percent, and, if the samples are representative, the geometric mean of all sandstone of the 

Salt Wash lies between the limits of 1.40 percent and 

1.01 percent at 99 percent probability. About 68 percent of the sandstone of the Salt Wash member may 

be expected to have between 0.63 percent and 2.25 percent aluminum. The estimated geometric mean or 

median concentration of aluminum in uranium deposits 

of the Morrison formation is 2.08 times as great as the 

estimated median concentration in unmineralized sandstone of the Salt Wash member, and the median concentration of aluminum in all Morrison uranium deposits may be expected (with about 99 percent 

confidence) to be between 1.77 and 2.46 times as great 

as the median concentration in sandstone of the Salt 

Wash.

The correlation of elements in unmineralized sandstones of the Salt Wash member of the Morrison formation and in sandstone-type uranium deposits of the 

Morrison formation is given in chart form in figure 4. 

Each number on the chart is a linear correlation coefficient between the logs of the concentration of two 

elements. The distribution of the logs of most pairs 

of elements in the samples studied approximates a normal correlation surface. The pair of elements for 

which each correlation coefficient stands is determined, 

as in a mileage chart, by the headings of the column 

and row in which the coefficient is found. In figure

4 the correlation between pairs of elements is given 

for all elements that occur above the spectrographic 

limit of sensitivity in more than 63 percent of the 211 

uranium deposits of the Morrison studied.

The correlation coefficient may be taken as a measure 

of the geochemical coherence (Rankama and Sahama, 

1950, p. 48) between two elements in a given type of 

rock. The coefficients may range in value from minus 

one to plus one. Values near either plus or minus one 

indicate a nearly linear relation or proportional variation between the concentration logs of two elements, a 

positive linear relation or direct proportionality if the 

coefficient is positive and a negative linear relation or 

inverse proportionality if the coefficient is negative. A 

coefficient near zero indicates there is no linear relation 

between two elements (that the covariation is essentially 

random). In general terms the correlation coefficients 

on the chart show which elements vary sympathetically, 

which elements vary antipathetically, and which elements show no significant correlation. The lowest significant value for the correlation coefficient for a normal 

correlation surface is a function of the number of 

samples and may be determined from tables (Fisher and 

Yates, 1953, p. 54) for a given probability.

Study of figure 4 will reveal the general degrees of 

association or coherence of the elements in Morrison 

uranium deposits and unmineralized sandstones of the 

Salt Wash member. No negative correlation coefficients 

that are significant at 99 percent confidence were found. 

All significant correlations are positive and the correlation of most elements with aluminum in both the ores 

and the unmineralized rocks is significant or nearly 

significant. The causes of some of the element associations are fairly well understood at the present time; for 

others they are largely unknown. Interpretation of 

some of the correlations is given in the discussion that 

follows. For purposes of discussion a significant correlation below 0.35 will be spoken of as low, from 0.35 

to 0.49 as moderate, from 0.50 to 0.74 as high, and above 

0.74 it will be spoken of as very high. These designations are purely relative and are used merely to distinguish the ranges of correlation observed on the chart.

CLASSIFICATION OF ELEMENTS IN SANDSTONE-TYPE 

XJEANItrM DEPOSITS 

GENERAL, FEATURES

For convenience of discussion the following classification has been adopted for the elemental components 

of the sandstone-type uranium deposits.

Intrinsic elemental 

components

Syngenetic components 

Epigenetic (diagenetic) components

Extrinsic elemental jOre components 

components [Accessory components
34 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

CORRELATION OF ELEMENTS IN URANIUM DEPOSITS

CO

LU~Z.

oHco

CO

a

LU 

N

LU

CO

LU

S 

LU

-I 

LU

LL 

O

g

<

_j

LU

O 

(J

V

Ni

Cu

Pb

Mo

Cr

Y

Ti

Zr

B

Mn

Bo

Sr

K

No

Co

Mg

Fe

Al

U

V

V

+.06

+.38

+.17

+.28

+.16

+.11

-.04

+.04

+.08

+.30

+.20

+.24

Ni

+.07

Ni

Cu

+.23

+.08

Cu

.00

+.28

+.01

+.22

-.08

+.39

-.22

+.26

+.20

+.32

+.35

Pb

+.35

+.14

+.56

Pb

Mo

+.07

+.49

+.16

+.14

Mo

Cr

+.22

+.10

+.30

+.33

+.25

Cr

+.21

+.42

+.24

+.20

+.15

+ .26

+.22

+ .16

+.29

+.25

Y

+.26

+.27

+.04

+.07

+.24

+.12

Y

Ti

+.15

+.14

+.27

+.21

+.04

+.22

+.25

Ti

+.50

+.02

+ .08

+.31

+.35

-.12

+ .09

+.30

+ .60

Zr

+.37

+.08

+.29

+.25

+.22

+.20

+.39

+.41

Zr

-.05

+.16

+.05

+.14

-.12

+.14

+.20

+.40

B

+.27

+.12

+.23

+.15

-.09

+.32

+.39

+.22

+.26

B

Mn

+.07

.00

+.26

+.26

.00

+.21

+.05

+.37

+.35

+.10

Mn

-.03

+ .34

+ .47

+ .83

+ .22

+.21

+.12

Ba

+ .34

+.02

+.15

+.14

+.01

+.20

+.25

+.26

+.25

+.21

+.19

Ba

+ .34

-.09

-.05

+.19

+.19

+ .23

Sr

+.34

+.08

+.31

+.23

+.13

+.25

+.11

+.34

+.14

+.17

+.28

+.37

Sr

+.31

+ .41

+.07

+.16

+.24

K

+ .15

+ .03

+.27

+.29

+.14

+.38

+.08

+.44

+.19

+.28

+.37

+.27

+.42

K

Na

+.09

+.05

+.26

+.21

+.10

+.21

+.15

+.39

+.43

+.21

+ .56

+.19

+.26

+.34

Na

+.39

+.19

+ .27

+.30

Ca

+ .03

-.04

+.32

+.23

+.04

+.20

-.04

+.35

+.39

+.13

+.75

+.11

+.36

+.45

+.56

Ca

+.17

+.05

+.04

Mg

+.36

-.06

+.36

+.39

.00

+.27

+.11

+.25

+.38

+.23

+.30

+.15

+.19

+.22

+.45

+.48

Mg

+.44

+.16

Fe

+.28

+.37

+.07

+.25

+.34

+.20

+.31

+.17

+.31

+.16

+.20

+.15

+.10

+.02

+.37

+ .12

+.34

Fe

+.48

Al

+.50

+.11

+.36

+.49

-.13

+ .36

+.22

+.50

+.46

+.35

+.47

+.28

+.40

+.45

+.47

+.46

+.58

+.30

Al

U

+.32

+.10

-.04

+.11

+.06

+.10

+.18

+.19

+.15

+ .11

-.09

+.05

+.10

+.06

+.08

-.14

+.11

+.23

+.14'

U

COH

CO

O 

Q_ 

LU

CO

LU~S. 

LU 

_J 

LU

O

2 

O

_J 

LU 

Of 

C£ 

O 

U

CORRELATION OF ELEMENTS IN UNMINERALIZED SANDSTONES

NUMBERS ARE LINEAR CORRELATION COEFFICIENTS CALCULATED AFTER LOG 

TRANSFORMATION.

LOWEST SIGNIFICANT VALUE AT 99 PERCENT CONFIDENCE IS 0.19 FOR CORRELATION OF ELEMENTS IN URANIUM DEPOSITS AND 0.26 FOR CORRELATION OF 

ELEMENTS IN UNMINERALIZED SANDSTONES.

FIGURE 4. Correlation of elements in uranium ores and in unmineralized sandstones from the Salt Wash member of the Morrison formation

(Jurassic).

This classification applies and has meaning only for 

ore or mineralized rock. The purpose of the classification is to provide a simple framework of concepts with 

which the role of each element in the mineralogy and 

history of the ore deposits may be discussed.

Two basic assumptions are involved in this classification system.

1. The minerals that contain the bulk of the elements 

of economic importance, the ore elements, are assumed 

to be epigenetic components of the ores, in the strict 

sense of the term epigenetic (Lindgren, 1933, p. 154) 

that the minerals are introduced or formed in a preexisting rock or sediment. Because the distribution of 

ore minerals does not follow in detail the lamination of
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 35

the sedimentary rocks in which the ore is contained, the 

emplacement of the ore minerals probably was later 

than the deposition of the individual laminae in which 

the ore minerals are now found. This interpretation 

has been explicitly stated by Lindgren (1911, p. 568), 

Coffin (1921, p. 159 and 176), and Fischer (1937, p. 

943). The ore deposits are thus conceived as composed 

of two fundamental parts: (1) a mass of sediment or 

rock formed prior to emplacement of the ore minerals 

and (2) minerals carrying the bulk of the ore elements 

and other associated minerals introduced or formed in 

the mass of sediment or rock that today constitutes the 

ore deposit. The first part may be thought of as the 

indigenous or intrinsic part of the ore deposits, corresponding approximately in composition to the rocks 

that would have occupied the space of the ore deposits 

had mineralization never occurred; the second part may 

be thought of as foreign or extrinsic to the individual 

rock masses that constitute the deposits. The concepts 

of intrinsic and extrinsic, as here defined, are restricted 

in their application to mineral deposits of epigenetic 

origin.

2. It is assumed that the processes by which the minerals carrying the bulk of ore elements were emplaced 

in the ore deposit are distinct and can be distinguished 

from other processes which induced postdepositional 

changes in the sedimentary beds in which the ore deposits are located, processes that are commonly lumped 

under the broad ill-defined category of diagenesis. 

Empirically, the distinction between uranium mineralization and diagenesis is largely based on the spatial distribution of the products of the two processes; the 

uranium deposits are localized whereas diagenetic minerals such as calcite and authigenic quartz are widely 

distributed in the sediments, apparently irrespective of 

the distribution of uranium deposits. Such products 

are in both cases epigenetic. It is entirely possible, and 

even likely, that the processes of uranium mineralization may have affected rocks away from the uranium 

deposits and produced minerals indistinguishable from 

the minerals formed by unrelated diagenetic processes, 

but the distinction between intrinsic and extrinsic components applies only to rock that is recognizably mineralized with uranium.

Intrinsic elements are defined as the elements whose 

presence in the ore is unrelated to processes of uranium 

mineralization. Empirically, they are defined as elements found in the ores in amounts comparable to the 

amounts found in the unmineralized parts of the strata 

that contain the ore deposits. The intrinsic elements 

fall into two broad groups, (1) the syngenetic elements, 

or those elements contained originally in the clastic 

components and the elements contained originally in

precipitates in the mineralized rock that were strictly 

simultaneous in deposition with the clastic components 

and, (2) epigenetic elements or elements introduced 

(during diagenesis) into the locus of the ore deposit 

after deposition of the ore-bearing strata by processes 

unrelated to uranium mineralization. Both syngenetic 

and epigenetic intrinsic elements may have been partly 

rearranged during uranium mineralization and incorporated in ore minerals or other minerals formed during mineralization.

Depending upon the stage in the history of the mineralized rock that the uranium was introduced into the 

deposits, the introduction of epigenetic intrinsic elements may have either preceded or followed the introduction of uranium. Calcium, for example, which is 

contained largely in the abundant calcite cement of the 

sandstones of the Salt Wash may have been introduced 

and precipitated in the individual bodies of ore or mineralized rock early in the history of the rock, prior to 

the introduction of extrinsic uranium (Waters and 

Granger, 1953, p. 15-20), but may also have been partly introduced, rearranged, or leached away after uranium mineralization.

The extrinsic elements of a uranium deposit are elements that have been introduced by processes of or related to uranium mineralization into the body of sediment or rock that became the uranium deposit. The 

extrinsic elements are contained largely in minerals 

formed or crystallized in place, though some may be 

merely adsorbed on or absorbed in preexisting minerals. 

No sources for the extrinsic elements are implied by this 

definition nor does it imply that all the extrinsic elements had the same source as the uranium. In particular, no implication is intended that the extrinsic elements were derived either from the beds that enclose 

the uranium deposits or from sources external to these 

beds. Neither is it implied that all the extrinsic elements were necessarily introduced into the uranium deposit at the same tune, though the simultaneous introduction of extrinsic elements into most of the uranium 

deposits seems likely. The extrinsic elements are further subdivided for discussion into ore elements and 

accessory elements on the somewhat arbitrary basis of 

whether a given element contributes to the economic 

value of the ore.

The extrinsic elements are empirically defined as 

those elements that are more abundant in the uranium 

ores than in the equivalent unmineralized rocks. Because of selectivity of uranium mineralization for certain parts of the host strata the average intrinsic composition of mineralized rock in the sandstone-type 

uranium deposits differs somewhat from the average 

composition of unmineralized sandstone. Uranium ore

468652 59 4
36 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

in the Morrison formation contains, on the average, 

twice as much aluminum as the unmineralized sandstones of the Morrison, probably because the ore is localized in sandstone units that initially contained on 

the average twice as much clay or mudstone. All other 

intrinsic elements in the ore that correlate positively 

with aluminum in the unmineralized sandstones are, as 

may be expected, higher in the average ore than in the 

average unmineralized sandstone.

Probably no single chemical element in the sandstonetype uranium ores belongs exclusively to either the intrinsic or extrinsic components of any given ore, as 

each element is present in some concentration, however 

small, in the detrital minerals of the sandstone and a 

certain amount, however small, was probably carried 

in the solutions that introduced the uranium. The 

problem of classification, therefore, is to assess the relative importance of the roles played by each element in 

the ores. An element is here tentatively considered 

dominantly of one classification or another if the major 

part of the element is believed to fall in a given classification in a majority of the deposits studied. The 

classification of individual elements in the following 

discussion is based mainly on the comparison of the 

averages given in table 2.

No consideration has been given in this investigation 

to the radioactive daughter products of uranium that 

are present in the sandstone-type uranium ores. Paired 

radiometric and fluorimetric uranium analyses of thousands of samples of the sandstone-type ores from the 

Morrison formation indicate that the great majority 

of the ores are nearly in equilibrium on a hand-specimen scale. The content of radioactive daughter elements, therefore, tends to be proportional to the content 

of uranium in the ores. In the theoretical terms of 

the proposed classification of elements the radioactive 

daughter elements are neither intrinsic nor extrinsic. 

They are neither an indigenous part of the uranium deposits, nor were they introduced by the processes of 

mineralization, but were generated in place. They 

could be spoken of as authigenic elements in the prime 

sense of the word.

DOMINANTLY INTRINSIC ELEMENTS

SILICON

Silicon and oxygen occur mainly in the various mineral forms of silica and constitute the large bulk of the 

sandstone-type uranium deposits as well as the unmineralized rocks that enclose the deposits. The concentration of silicon in both the ores and unmineralized 

rocks is too high to be estimated by semiquantitative 

spectrographic analysis, but an approximation of the 

arithmetic mean concentration of silica may be obtained

by subtraction of the oxide equivalents of the arithmetic means of all other elemental constituents from 

100 percent. If carbonate is assigned to all the calcium 

a fair estimate of the arithmetic-mean silicon concentration in unmineralized Salt Wash sandstone may be 

obtained by this method, and it has been found to be 

approximately 36 percent (77 percent SiO2 ). No account of sulfate, sulfide, phosphate, carbonates other 

than calcium carbonate, or organic carbon is taken in 

such an estimate, but since the estimated arithmeticmean concentration of only two spectrographically detectable elements (Al and Ca) other than silicon are 

greater than 1 percent, the estimate for silicon is probably correct to within 1 or 2 percent silicon.

The concentrations of nearly all elements other than 

silicon and oxygen tend to be higher in ores from the 

Morrison than in the unmineralized sandstones of the 

Salt Wash member, but calcium, the second most abundant metallic element in the sandstones, is less abundant in the average ores. Because of the uncertainties 

involved in'the estimations by subtraction it cannot be 

definitely said whether the silicon content of the ores is 

significantly different from that of the unmineralized 

sandstones of the Salt Wash. In any event the difference is probably very small in proportion to the total 

silicon content and the great bulk of silicon is intrinsic 

in the ore deposits.

Fischer (1942, p. 380) and Waters and Granger 

(1953, p. 15-20) have shown that quartz has been dissolved and locally removed in apparently significant 

amounts in parts of some Morrison ore deposits, probably during mineralization. These observations suggest that some loss of total silica from the sandstonetype uranium deposits may have commonly taken place 

during mineralization. Differences in silicon content 

between host rocks and ores in Triassic formations are 

expected to be similar to the relations observed in the 

deposits in the Morrison.

ALUMINUM

Aluminum (figs. 4 and 5) in the unmineralized sedimentary rocks and in the uranium deposits is contained 

largely in various kinds of clay and claylike micaceous 

minerals (Parts 2 and 10) and in detrital feldspars 

(Part 2). Rough estimates of the distribution of aluminum between the clay and feldspar components of 

unmineralized sandstones of the Salt Wash, based on 

size and mineralogical analyses by R. A. Cadigan (unpublished data), suggest that about one-third to onehalf of the aluminum is generally contained in the 

clay-silt size fraction and the remainder is contained 

largely in sand size detrital feldspar. The twofold difference between the concentration of aluminum in the
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 37

Type of sample

Aluminum 

(spectrographic)

Titanium 

(spectrographic)

24 , 

percent|

less | 

than 

2200 ppm

I

53 I

percent I 

less I 

than !

2200ppm

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back members of the 

Chinle formation)

Unmineralized sandstones from 

the Shinarump and Moss Back 

members of the Chinle formation

ioH

211

70' 

60-

5^50 

a> 0)40' 

ST&30- 

£ 20 

10

96*

50'

&S 40- 

a) a>

rfc

10

log 10 concentration (ppm) 345 4 5 1 2 4 5 345 234

Type of sample

Boron 

(spectrographic)

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back members of the 

Chinle formation)

Unmineralized sandstones from 

the Shinarump and Moss Back 

members of the Chinle formation

log,, concentration (ppm) 1234 1 2

 Number of uranium deposits or number of samples of sandstone

FIODRB 5. Frequency distribution of the dominantly intrinsic elements (aluminum through boron) of uranium ores, contained 

in uranium ores and in Unmineralized sandstones of the Colorado Plateau.
38

Morrison ores and the concentration in unmineralized 

sandstones of the Salt Wash is probably due almost 

entirely to the presence of higher initial amounts of 

mudstone in the ores, mainly in the form of interstitial 

clay and silt, mudstone pebbles, and thin mudstone 

beds. Selective mineralization of mudstone-bearing 

parts of the sandstone strata in the Morrison formation 

has been recognized for some time (Fischer, 1942, p. 

380-381; Waters and Granger, 1953, p. 10).

Aluminum is an essential constituent of some of the 

major vanadium-ore minerals, which include clays and 

micaceous claylike minerals (Fischer, 1942, p. 370). 

(See Parts 5 and 10.) Some of the vanadium in the 

ore appears to have been taken up in preore clay minerals, but some is also present in more coarsely crystalline claylike or micacous minerals that appear to have 

crystallized in the ore (Hess, 1933, fig. 2; Fischer, 1942, 

p. 377 and fig. 54A; Waters and Granger, 1953, p. 12- 

20). Even though aluminum is an essential constituent 

of some of the major vanadium-ore minerals, most or 

nearly all of the aluminum in the ores probably was 

contained originally in the detrital components of the 

host sandstones, because the ratio of aluminum in ore 

to aluminum in unmineralized sandstone is closely comparable to similar ratios for titanium and zirconium, 

elements that are not known to be significant constituents of the ore minerals crystallized in place. (See section on titanium and zirconium in this chapter.)

The average concentration of aluminum in 38 ores 

from Triassic rocks is lower than the average obtained 

for unmineralized sandstones of the Shinarump and 

Moss Back members. As in the deposits of the Morrison this difference may be interpreted as due to selective mineralization, but in these rocks the selectivity 

would be for parts of the ore-bearing strata that contain less than average amounts of aluminum. The difference in aluminum concentration between the ores and 

the unmineralized sandstones is close to the limit of significance at 99 percent probability. The average aluminum content of the ores from Upper Triassic rocks 

is closely comparable to the average of the ores from 

the Morrison.

POTASSIUM

Potassium (figs. 4 and 5), like aluminum, is contained 

chiefly in feldspars and clay minerals, both in unmineralized sandstones and in the uranium ores. The distribution of potassium between the clay and feldspar 

components of unmineralized sandstones of the Salt 

Wash is estimated to be closely similar to the distribution of aluminum, approximately one-fourth to onethird in the clay fraction and the remainder mainly in 

the feldspars. Unlike aluminum, however, potassium 

appears to have nearly the same concentration in the

ores as in the unmineralized rocks. Some factor such 

as selectivity of mineralization for potassium-lean but 

clay-bearing rocks or leaching of potassium by mineralizing solutions may be required to explain the observed 

differences in the potassium-aluminum ratios between 

ores from the Morrison and unmineralized rocks. Part 

of the observed difference between the potassium-aluminum ratio in the ore and the ratio in the unmineraldzed sandstones is probably due to the fact that most of 

the ores studied are from the uppermost sandstone 

strata of the Salt Wash member of the Morrison formation which appear to contain less potassium on the 

average than the remainder of sandstones of the Salt 

Wash.

The reverse differences between the potassium-aluminum ratios are represented in the ores and unmineralized sandstones from Upper Triassic rocks; the average 

of the samples studied suggests the ores contain slightly 

less aluminum whereas potassium appears to be higher 

in the ores than in the unmineralized sandstones. In 

a majority of the sandstones potassium is below the 

limit of sensitivity, however, and the apparent reversal 

of the aluminum-potassium relations in the Triassic 

rocks compared with the relations in the Morrison formation may be partly due to uncertainties of estimation 

or inadequate sampling of the ores and unmineralized 

rocks from the Upper Triassic. Potassium is considered to be almost entirely an intrinsic component of 

the ores in both the Upper Triassic rocks and the Morrison formation.

IRON

Iron (figs. 4 and 5) in unmineralized sandstones of 

the Salt Wash is contained largely in clay minerals and 

oxides physically inseparable from clay minerals, in 

detrital heavy minerals, and in authigenic sulfides, oxides, and carbonates. The average iron content of 14 

chemically analysed claystones from the Salt Wash 

(Weeks, 1951, table 2) is 2.4 percent (arithmetic mean 

of average for 6 gray clays and average for 8 red 

clays). If the arithmetic-mean content of silt and clay 

(corresponding approximately to claystone or mudstone in composition) in the sandstones of the Salt 

Wash is about 6.5 percent (R. A. Cadigan, unpublished data), the arithmetic-mean content of iron attributable to the clay would be about 0.15 percent. The 

estimated arithmetic-mean content of iron in sandstones of the Salt Wash calculated from table 2 is 0.30 

percent (see footnote 1, table 2). Iron directly associated with clay may thus account for about one-half of 

the total iron in sandstones of the Salt Wash, and this 

association is brought out by the moderately high ironaluminum correlation (fig. 2). Part of the iron with 

the clay is contained in the clay-mineral lattices and
ELEMENTAL COMPOSITION OP THE SANDSTONE-TYPE DEPOSITS 39

part in the red clays as an extremely finely divided pigment, possibly hematite, which evidently imparts the 

red color (Weeks, 1951, p. 11-12). Perhaps one-fourth 

to one-third of the remaining iron may be attributable 

to opaque detrital heavy minerals and the rest mainly 

to authigenic iron minerals pyrite, marcasite, hematite, goethite, and ferriferous carbonates.

Iron is nearly four times as abundant 4 in the samples of ores from the Morrison as in the unmineralized 

sandstones of the Salt Wash. Roughly a twofold difference would be expected from the correlation of iron 

with aluminum, leaving about half of the iron in the 

ores or about 0.4 percent in the median case to be accounted for. On the order of 0.1 percent of this "excess" iron is estimated to be tramp iron introduced into 

the samples during grinding. The proportions of 

tramp iron might vary considerably but the majority 

of "excess" iron appears to represent a real difference 

between the ores and equivalent unmineralized rocks 

and is considered an extrinsic component of the ores. 

If about 0.3 percent iron in the average ore is extrinsic 

and about 0.4 percent intrinsic, the bulk of the iron 

would be intrinsic but the extrinsic part of the iron 

would be the second most abundant extrinsic component of the Morrison ores. In many ore deposits from 

the Morrison iron may be dominantly extrinsic.

The estimated mean concentration of iron in the ores 

from Triassic rocks is greater than the estimated mean 

concentration in the unmineralized sandstones, but the 

difference is within the limits of confidence at 99 percent probability. It is possible that about the same 

quantity of iron is extrinsic in the average ore from 

Triassic rocks as in the average deposit from the Morrison, but the bulk of iron in ores from Triassic rocks 

is clearly intrinsic.

MAGNESIUM

The distribution of magnesium (figs. 4 and 5) among 

the mineral components of unmineralized sandstone of 

the Salt Wash is probably similar in some respects to 

the distribution of iron, with which magnesium has a 

moderate correlation. If two clays of the Salt Wash 

for which chemical analyses are available (Weeks, 

1951, table 1) may be considered typical, about onethird of the magnesium in the average sandstone of 

the Salt Wash could be directly associated with the 

clay. About the same proportion is obtained if the

4 The term "abundance" is generally reserved for the arithmetic-mean, 

concentration in conventional geochemical usage. In this report relative abundances or abundance ratios are computed from the geometric 

means because the abundance ratios are sensitive to small errors of 

estimation and the geometric mean is a more stable statistic than the 

arithmetic mean. If the log-standard deviation is the same for two 

distributions for which an abundance ratio is calculated, then the same 

ratio is obtained for the geometric means as would be found for the 

arithmetic means. The standard deviations for most pairs of distributions compared in this report are closely similar.

geometric mean concentration of spectrographically 

determined magnesium in 32 mudstones (Newman, 

1954, p. 44) is used as a basis of estimation. Part of 

this magnesium is in the clay lattice, but part may 

also be commonly present as very fine grained dolomite (Weeks, 1951, p. 8). The association of magnesium with clay, however, is much less strong than that 

of iron with clay, as is brought out by the subsignificant magnesium-aluminum correlation coefficient. The 

greater part of the magnesium in a majority of the 

sandstones is probably contained in dolomite independent of the clay, perhaps some of detrital origin but 

most of it probably in authigenic form. The lack of 

significant correlation (fig. 4) between magnesium and 

calcium, which is the principal cation associated with 

carbonate in sandstones of the Salt Wash, indicates 

that the amount of magnesium is largely independent 

of the total carbonate content of the rocks. The magnesium-calcium scatter diagram (not illustrated) reveals that the concentration of magnesium never exceeds the concentration of calcium, and the bulk of 

magnesium in any sample could, therefore, be contained in dolomite. If all the magnesium and calcium 

in the median unmineralized sandstone of the Salt 

Wash were calculated as dolomite and calcite the proportion of dolomite to calcite would be about 1 to 4. 

The moderate correlation of magesium with iron suggests that much of the dolomite may be ankeritic. 

Magnesium is three times as abundant in the average 

of the ores from the Morrison as in the sandstones of 

the Salt Wash, and in the ores it has a high correlation with aluminum and a moderate correlation with 

calcium. Part of the observed difference may be due 

to selective mineralization of rocks with above-average 

magnesium content. The studies of Waters and Granger (1953, p. 14-15) suggest a possible selectivity of 

mineralization for rocks rich in the magnesian group of 

clays, the montmorillonites and chlorites, and the high 

correlation of magnesium with aluminum in the ores 

might be considered as suggestive that a major part 

of the magnesium in the ores was contained originally 

as an essential component of the original clays. On 

the other hand, Keller (Part 9) does not find an association of mineralized rock with montmorillonite, and 

three other elements calcium, manganese, and sodium thought to be contained or associated largely with 

carbonates also have a moderately high correlation with 

aluminum in ores from the Morrison. The bulk of the 

magnesium in a majority of ores from the Morrison is 

considered to be present as a carbonate, probably in 

the mineral form dolomite, as suggested by the moderately high magnesium-calcium correlation in the ores. 

The reason that magnesium has a moderately high cor-
40 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

relation with calcium in the ores from the Morrison 

and not in the unmineralized sandstones of the Salt 

Wash is probably because a much higher fraction of 

calcium is present in dolomite in the ores than in the 

unmineralized sandstone. If all the magnesium and 

calcium in the median ore were calculated as dolomite 

and calcite the proportion of dolomite to calcite would 

be greater than 2 to 1, as contrasted with 1 to 4 in the 

unmineralized sandstones. Because of the threefold 

higher concentration of magnesium in the ores it seems 

likely that a considerable part of the magnesium is extrinsic, though how much cannot at present be estimated. As in the case of iron, probably less than half 

of the magnesium in the average ore is extrinsic.

The difference in magnesium concentration between 

ores and unmineralized sandstones in Upper Triassic 

rocks is well within the 99 percent confidence interval 

of the means, and magnesium may be considered a 

dominantly intrinsic element in the majority of these 

ores with reasonable confidence.

TITANIUM AND ZIRCONIUM

Titanium and zirconium (figs. 4 and 5) exhibit high 

and moderate correlation in the unmineralized sandstones of the Salt Wash and in the ores from the Morrison respectively, and their manner of occurrence in 

both sandstones and ores is probably similar. Titanium 

has a high correlation and zirconium a moderate correlation with aluminum in both the ores and unmineralized sandstones, and the ratio of abundance of each 

element in the ores to the abundance in the sandstones 

is essentially the same as the ratio for aluminum in 

both the Upper Triassic rocks and the Morrison formation. This high degree of coherence suggests that 

the factors controlling the distribution of titanium and 

zirconium are essentially the same as those controlling 

aluminum, and both titanium and zirconium as well as 

aluminum are considered to be almost entirely intrinsic in the sandstone-type ores. Neither titanium 

nor zirconium are known to be essential or major constituents of any of the ore minerals in the sandstonetype uranium deposits and only rarely are they reported even as trace constituents in qualitative 

spectrographic analysis of the ore minerals (Weeks 

and Thompson, 1954).

Titanium in the unmineralized sandstones is associated closely with the clay component. The arithmeticmean titanium content of 14 chemically analyzed claystones and siltstones from the Salt Wash (Weeks, 1951, 

table 2) is 0.32 percent, and the geometric-mean titanium content of 32 mudstones of the Salt Wash analyzed 

"by semiquantitative spectrographic methods (Newman, 

1954) is 0.1 percent. On this basis about one-fifth to

one-fourth of the titanium in average unmineralized 

sandstones of the Salt Wash would be contained in the 

clay-silt component of sandstones. Whether any of 

this titanium is present in the clay lattice or whether 

most of it is present as a minutely divided titania polymorph, perhaps anatase, is not clear (Grim 1953, p. 49), 

but titania in amounts found in claystones of the Salt 

Wash are commonly found in kaolin group clays (Ross 

and Kerr, 1931, p. 163). The bulk of the remainder of 

the titanium is probably present in detrital heavy minerals such as ilmenite, ilmenomagnetite and ilmenohematite, and rutile, or in alteration products of these heavy 

minerals, mainly leucoxene and anatase. The high correlation of titanium with aluminum suggests that perhaps a major part of these heavy minerals is contained 

in the fine-grained fraction of the sandstones along 

with the clays.

Some zirconium is closely associated with the clay 

fraction of the sandstones, perhaps partly as a trace 

constituent of the clay minerals, but the bulk of the zirconium is evidently contained as zircon, about half of 

which can be separated as sand-sized detrital grains. 

As with the titanium heavy minerals, probably much 

of the rest of the zircon present in the sandstones is in 

the fine fraction, which may partly account for the correlation of zircon with aluminum; but some zircon could 

also be enclosed as minute inclusions in the light sandsized mineral fractions, perhaps in feldspars.

BARIUM, STRONTIUM, AND CHROMIUM

The distribution of barium, strontium, and chromium 

(figs. 4 and 5) in the sandstones of the Salt Wash has 

been partially evaluated from analyses of the clay-siltand sand-sized fractions and of heavy mineral separates. An appreciable part of the barium is in the fine 

fraction of the sandstones, though the bulk is evidently 

contained in coarser-grained interstitial barite, a large 

part of which is recovered in heavy mineral separates 

(R. A. Cadigan, personal communication). About onethird part of the strontium may commonly be associated 

with the fine fraction of the sandstones and the bulk of 

the remainder possibly substitutes as a trace constituent 

for calcium in the abundant calcite cement and for 

barium in the interstitial barite, as suggested by moderate strontium-calcium and strontium-barium correlation coefficients in the standstones of the Salt Wash 

member and the ores from the Morrison formation. 

Chromium occurs in such low concentrations in the unmineralized sandstones that its distribution is difficult to 

account for. Analyses of heavy minerals indicate that 

perhaps one-fifth to one-third of the chromium is in 

the heavy mineral fraction, which probably accounts 

for the moderate chromium-zirconium correlation in
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 41

sandstones of the Salt Wash, and another part of the 

chromium, perhaps one-tenth to one-fifth is in the claysilt fraction. The remainder of the chromium is dispersed in an unknown way in the sandstones.

Barium, strontium, and chromium each have a correlation with aluminum in unmineralized sandstones of 

the Salt Wash that is close to the lowest significant 

value at 99 percent confidence, and each element has a 

low to moderate correlation with aluminum in the Morrison ores. The ratio of abundance of the barium, 

strontium, and chromium, in the unmineralized sandstones of the Salt Wash to their abundance in the ores 

from the Morrison is nearly the same for each element 

and is somewhat greater than the ratio for aluminum. 

In the Triassic rocks all three elements are more abundant in the ores than in the unmineralized sandstones in 

contrast to aluminum, which is lower in the ores, though 

the difference in barium concentration between ore and 

unmineralized sandstone is within the confidence intervals of the means. A part of the barium, strontium, 

and chromium, in both the ores from the Morrison 

formation and Triassic rocks is interpreted as extrinsic, 

though the bulk of these elements in the majority of 

ores is probably intrinsic.

In a few sandstone-type uranium deposits in the Triassic rocks and the Morrison formation any one of the 

three elements, barium, strontium, or chromium may 

possibly be a major extrinsic component of the ores. 

Barium has been found to be a major extrinsic element 

in uraniferous and nonuraniferous deposits along 

faults in sandstones of Jurassic age and in the Brushy 

Basin member of the Morrison formation north of the 

Ute Mountains, Colorado, and Garrels and others (Part 

15) have found barium to be locally enriched within a 

uranium deposit in the Salt Wash. Similarly, strontium has been found to be a major constituent of a uraniferous vein deposit in the vicinity of sandstone-type 

uranium deposits in the Morrison formation, and has 

been found to be locally enriched within a ore deposit 

in the Salt Wash (Part 15). Sandstone with more than 

average chromium is closely associated with vanadiumuranium deposits in the Entrada sandstone of Jurassic 

age on the eastern margin of the Colorado Plateau 5 

(Fischer, Haff, and Rominger, 1947, p. 125 and plate 1; 

Part 19). In Sinbad Valley, in westernmost Colorado, 

chromium-rich sandstone has been found in an unidentified formation (Hillebrand and Ransome, 1905, p. 21), 

probably the Wingate sandstone of Triassic age, in the 

vicinity of uranium and- copper deposits. Chromium 

has also been found in a conspicuous concentration associated with uranium deposits in the Wingate sandstone of Temple Mountain, in central Utah, and near

"Bush, A. L., and Bryner, Lenoid, written communication, 1953.

uranium deposits in the Morrison formation in the 

vicinity of Grants in northwestern New Mexico ( L. S. 

Hilpert, personal communication).

BORON

On the basis of spectrographic analysis of heavymineral and clay-fraction separates and of mudstones, 

about half or more of the boron (figs. 4 and 5) in sandstones of the Salt Wash is estimated to be contained in 

the heavy-mineral fraction of the sandstones and a significant part of the remainder in the fine fraction. 

Probably the bulk of the boron is carried in tourmaline, 

which is the only detrital mineral identified in the sandstones of the Salt Wash that contains boron as an essential constituent (see part 2 for commonly occurring 

heavy minerals). Some of the boron associated with 

the fine fraction is probably present in soluble borates 

(A. D. Weeks, personal communication). In ores from 

the Morrison boron has a moderate correlation with 

aluminum and a low to moderate correlation with a 

number of other elements that are associated with 

aluminum probably because of association of detrital 

heavy minerals and soluble salts with the clay-silt fraction of the rocks. The estimated mean boron content of 

the ores is about twice the estimated mean boron content of the unmineralized sandstones, a difference that 

could be attributed to the higher mudstone content of 

the ores. The boron content of ores from Upper Triassic rocks is estimated to be essentially the same as the 

content of the unmineralized sandstones. In ores from 

both Upper Triassic rocks and the Morrison formation 

boron is considered almost entirely intrinsic.

BERYLLIUM

The distribution of beryllium (fig. 6) in the unmineralized sandstone can be inferred only from indirect evidence. Beryllium has not been detected by 

spectrographic methods in the sandstones of the Salt 

Wash and only rarely in sandstones of the Shinarump 

and Moss Back, but it has been detected in many mudstones of the Salt Wash. The bulk of the beryllium 

may be contained in the clay fraction of the unmineralized rocks. A few ores from the Morrison and about 

one-third of the ores from Upper Triassic rocks contain 

beryllium in detectable concentrations. The occurrence 

of detectable beryllium in the few ores from the Morrison can probably be attributed to high mudstone content of the ores in which beryllium is detected. About 

75 percent of the ores from Triassic rocks which contain 

detectable beryllium have more than average concentrations of aluminum. The bulk of beryllium may be intrinsic in ores both from Triassic rocks and from the 

Morrison, but a significant part of the beryllium in ores 

from Triassic rocks could also be extrinsic.
42 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Type of sample

Scandium 

(spec.)

Antimony 

(colorimetric)

Beryllium 

(spec.)

Lanthanum 

(spec.)

211* 

94.5

percent 

less 

than

10 ppm

211

99

percent

less

than

22 ppm

211 

95 I

percent j

211* I

67 I

percent

less I

than

1 ppm

96* 

90 I

percent 

less I 

than!

1 ppm

96*

100 

percent

less

than 

22 ppm

96*

99 I

percent I

less

than

4.6 ppm I

96*

100 

percent

less I

than) 

1 ppm I

96* 

100

percent 

less 

than

10 ppm

percent) 

less 

than 

1 ppm

38<

73 

percent

less | 

than! 

1 ppm

32* i

100 ' 

percent 

less \ 

than 

1 ppm

38*

64 ' 

percen

less!

than 

1 ppm 32*1

38*

69 

percent

less

than 

10 ppm

3

75

percent 

less 

than

10 ppm

38

69

percent 

less 

than

22 ppm

38*

76 , 

percentj

less |

than 

4.6 ppm

32* I 

84 

percent 1 

less

14*

29

percent 

less 

than 

1 ppm

o~30 

§820

78 

percent,

less

than > 

22 ppm

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back members of the 

Chinle formation)

Unmineralized sandstones from 

the Shinarump and Moss Back 

members of the Chinle formation

log 10 concentration (ppm) 0 1 1 2 1 2 0 0.9 0 1 2

Type of sample

Zinc 

(colorimetric)

Manganese 

(spectrographic)

Sodium 

(spectrographic)

Calcium 

(spectrographic)

211*

7.5 

percent

less

than

220 ppm

16 ,

percent ,

less 

than I

220 ppm I

38*

8

percent

less

than 

220 ppm

32*

12.5 

percent i

less

than 

220 oprn

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back members of the 

Chinle formation)

Unmineralized sandstones from 

the Shinarump and Moss Back 

members of the Chinle formation

>, 40- <_>*- 

§030 30"

10-

60-

t?~ 50' 

g§40-

^ 20- 

10-

40H

10-

o-soil 8 20.

cr

Iog 10 concentration (ppm) 1.9 2.8 3.7 234

 Number of uranium deposits or number of samples of sandstone

FIGURE 6. Frequency distribution of the dominantly intrinsic elements of uranium ores that are contained In uranium ores and in unmlneralized sandstones of the Colorado Plateau (beryllium through manganese).
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 43

SCANDIUM, LANTHANUM, AND GALLIUM

Scandium and lanthanum have not been detected and 

gallium only rarely detected in unmineralized sandstones of the Salt Wash (fig. 4). Although each of 

these elements occurs in concentrations above the spectrographic limits of sensitivity in only a few of the ores 

from the Morrison studied, gallium was detected in 

trace amounts (less than 4.6 parts per million (ppm)) 

in more than 50 percent of the ores; hence its median 

concentration is essentially at the limit of sensitivity. 

The mean content of scandium and gallium of 32 mudstones from the Salt Wash, on the other hand, is above 

the spectrographic limit of sensitivity (Newman, 1954, 

p. 44); lanthanum has been detected in many mudstones 

and has been found in concentrations considerably 

above the limit of sensitivity in heavy-mineral separates. Most of the scandium, lanthanum, and gallium 

may be contained in the fine fraction of the sandstones, 

either in clays or associated heavy minerals. These elements occur in concentrations above the spectrographic 

limit of sensitivity mainly in the more aluminous Morrison ores in which their infrequent occurrence is probably accounted for by above-average mudstone content.

In Upper Triassic rocks scandium, lanthanum, and 

gallium occur in concentrations above the spectrographic limit of sensitivity in 15 to 25 percent of the 

sandstones studied and are found in the ores with somewhat greater frequency. Lanthanum and gallium are 

high mainly in high-aluminum ores and scandium appears to have a moderate tendency to accompany highaluminum ores. The abundance of these elements is 

probably related to the initial mudstone content of the 

ores. All three elements are considered mainly intrinsic in ores both from Upper Triassic rocks and 

from the Morrison formation.

ANTIMONY

The distribution of antimony (fig. 6) has been 

studied by colorimetric analyses of about one-fourth 

of the samples of ores and of sandstones of the Salt 

Wash member; no analyses have been completed for 

unmineralized sandstones of the Shinarump and Moss 

Back members. The estimated mean concentration of 

antimony in 49 ores from the Morrison is about half 

the estimated mean for 23 samples of sandstone of the 

Salt Wash and the estimated mean for 14 ores from 

Upper Triassic rocks is about the same as the mean 

for sandstones of the Salt Wash. These data, though 

incomplete, strongly suggest that antimony is almost 

entirely intrinsic in the ores.

SILVER AND ZINC

The distribution of silver and zinc (fig. 6) in the 

unmineralized sandstones is largely unknown. Silver

has been reported in concentrations above the spectrographic limits of sensitivity in a few percent of the 

unmineralized sandstones of the Salt Wash, but most 

of the analyses in which silver was detected may be 

slightly biased. Zinc has not been detected by spectrographic methods in the unmineralized sandstones and 

the statistics on zinc are based entirely on colorimetric 

analyses of a limited suite of samples. Rankama and 

Sahama (1950, p. 713) reported concentrations of zinc 

in clays and shales that are considerably higher than 

the estimated arithmetic-mean zinc content of 24 sandstones of the Salt Wash (calculated from table 2). 

An appreciable part of the zinc in the sandstones may 

be in the clay fraction, though zinc does not appear 

to correlate with aluminum in the samples studied. 

Eankama and Sahama (1950, p. 706), also, reported 

that silver is enriched in some argillaceous rocks, and 

clays could be the dominant carriers of silver in the 

sandstones of the Salt Wash member.

The estimated mean concentration of silver in 211 

ores and the mean concentration of zinc in 49 ores from 

the Morrison formation are each about twice as great 

as the corresponding means for unmineralized sandstones of the Salt Wash, though little confidence 

should be attached to the ratio for silver. If silver 

and zinc are contained largely in the clay fraction of 

the sandstones this difference could be largely due to 

selective mineralization of mudstone-bearing sandstone. On the other hand, the higher concentrations 

of both silver and zinc in the ores from the Morrison 

tend to occur with high concentrations of copper and 

lead, elements which are interpreted as mainly extrinsic, and silver occurs locally in concentrations from 

10 to more than 100 times higher than the spectrographic limit of sensitivity. In a majority of ores 

from the Morrison silver and zinc may be mainly 

intrinsic but in those deposits that contain high concentrations of silver and zinc both elements are probably mainly extrinsic. The ratios of abundance of 

silver and zinc in ores from Upper Triassic rocks to 

their abundance in the unmineralized sandstones is unknown, but both elements could be mainly extrinsic in 

these ores. Silver has been the principal ore element 

in sandstone-type uranium deposits in the Chinle formation at Leeds in southwestern Utah (Hess, 1933, 

p. 452-455; Proctor, 1953, p. 78-96).

CALCIUM, SODIUM, AND MANGANESE

Calcium and manganese are contained principally as 

carbonates and sodium, partly as a bicarbonate in the 

unmineralized sandstones of the Salt Wash (figs. 4 and 

6). Calcium, the second most abundant element in 

the sandstones, occurs mainly in calcite, which is the 

dominant cement of the sandstones in the Salt Wash
44 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

(Part 2), but a significant part is also contained in 

dolomite. Locally, in the vicinity of salt structures, 

a major part of the calcium is also present as the sulf ate, gypsum. Traces of calcium are present in soluble 

bicarbonate form, in plagioclase, and in other detrital 

minerals. Most of the calcite in the sandstones forms 

a relatively coarse grained interstitial cement, but some 

is also fine grained and associated with the clay 

(Weeks, 1951, p. 8-10; 1953, table 1). On the order 

of one-tenth to one-fifth of the calcium may be contained in the fine fraction of the sandstones.

Manganese has a very high correlation with calcium 

both in the unmineralized sandstones and in the ores 

from the Morrison and is probably contained largely 

in calcite which it enters readily in solid solution. 

The proportion of manganese to calcium in the sandstones is so low that if all the calcium and manganese 

were calculated as carbonate less than 1 percent of the 

combined carbonate would be rhodocrosite in the average sandstone. A minor proportion of the manganese 

is probably present in the oxide form, perhaps mainly 

as pyrolusite, and a trace of manganese is contained in 

heavy minerals. Locally the Morrison formation 

contains ore-grade deposits of manganese oxides in 

the sandstones (Baker, Duncan, and Hunt, 1952, p. 

66-68).

Sodium is contained principally in plagioclase feldspars and in nonsilicate sodium salts in the sandstones 

of the Salt Wash. Flame photometric analyses of the 

sand-sized fraction of 14 sandstones of the Salt Wash 

(R. A. Cadigan, written communication) suggest that 

the sodium in the feldspars represents about half of 

the total sodium in the sandstones of the Salt Wash. 

The remainder of the sodium is thought to be contained 

mainly in soluble salts, principally sodium bicarbonate. 

Extraction of salts by water at 100° C. from a core of 

carnotite ore in the sandstone of the Salt Wash yielded 

28,900 ppm soluble solids per unit volume of pore 

water, of which 1,330 ppm, or about 0.006 percent by 

weight of the total rock was sodium (calculated from 

data by Manger, 1954a, p. 62 and 63). The principal 

anion was bicarbonate, but carbonate, sulfate and a 

trace of chloride were also present. Similar quantities 

of soluble solids were extracted from other segments 

of sandstone core, both mineralized and unmineralized 

(Manger, 1954b, p. 92). Weeks (1953, table 1) reports 

extracting burkeite, Na(CO3 ) (SO4 ) 2 ; Thenardite. 

Na2S04 ; halite; and soda niter, NaNO3 , from clays 

of the Salt Wash. The present ground waters in the 

Salt Wash member are principally bicarbonate solutions (Part 4), and it is likely that the bulk of the 

soluble sodium is combined with bicarbonate. A 

moderate correlation of sodium with calcium and with

manganese in the sandstones and a high correlation in 

the ores suggest that the bulk of the sodium (as bicarbonate) is physically associated with the carbonates. 

Some of the soluble sodium may also be contained in 

montmorillonite clays (Weeks, 1953, p. 10). Probably 

only a fraction of the soluble sodium is extracted by 

a hot-water leach if the bulk of the sodium salts is 

intimately mixed with the carbonate cement of the 

sandstones.

The ratio of abundance in the Morrison ores to the 

abundance in unmineralized sandstones of the Salt 

Wash is about 0.6 for calcium, approximately 1.0 for 

sodium, and 1.4 for manganese. Calcium is the only 

element that is lower in the ores from the Morrison 

than in the unmineralized sandstones. Among the 

various factors that have contributed to the apparent 

"deficiency" of calcium in the ores, two are probably 

the most important. It is possible that the present 

milling practice on the Colorado Plateau, which has 

resulted in a penalty for high-lime ores from which 

vanadium is extracted (U. S. Atomic Energy Commission, 1948), has caused ore producers to mine and 

ship ore preferentially from deposits with low calcium 

content, and has introduced bias into the sampling of 

ore deposits with respect to calcium and closely associated elements. The effect of this bias is thought to 

be negligible. The principal factor contributing to the 

apparent "deficiency" is probably selective mineralization of sandstones with low content of carbonate 

cement. The samples studied of unmineralized sandstone from the uppermost sandstone strata of the Salt 

Wash, the principal host of the producing ore deposits, 

have an average calcium content only half as great 

as the average for the remainder of sandstones of the 

Salt Wash. Another likely significant factor may have 

been actual leaching of calcite from the ore deposits 

either during or after mineralization. Leaching of the 

calcite cement during intermediate stages of oxidation 

of the ores, owing to low-pH conditions produced by 

alteration of sulfides, has been suggested by Weeks and 

Coleman (personal communication) and in Part 14. 

Most of the ores studied from the Morrison are at 

least partially oxidized and many are nearly completely 

oxidized. In the ores, but not in the unmineralized 

sandstones, calcium and manganese have a moderate 

correlation with titanium, zirconium, potassium, and 

aluminum, elements associated with the clay-silt fraction, suggesting that a significant part of the carbonate 

left in the ores is contained in the mudstone component 

where it would be the least subject to leaching.

Despite the fact that calcium content is lower in the 

Morrison ores than in the unmineralized sandstones, 

manganese, which has a very high correlation with
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 45

calcium in both the ores and sandstones, has a higher 

value in the ores. The explanation for this apparently 

anomalous relation may lie partly in the redistribution 

of calcium and manganese during oxidation. Calcium 

may tend to be flushed out of the deposits by acid 

oxidizing solutions, whereas, the manganese originally 

contained in carbonate probably would tend to reprecipitate as the relatively insoluble tetravalent oxide. 

Some of the manganese may also be extrinsic. However, the bulk of manganese, as well as calcium and 

sodium, is considered intrinsic in the Morrison ores.

In the ores from Upper Triassic rocks calcium and 

manganese are 3 and 2 times respectively more abundant 

than they are in the unmineralized sandstones. 

Whether this indicates introduction of carbonate into 

the ores or perhaps selective mineralization of carbonate-rich sandstones is not clear. It should be noted 

that the confidence interval of the mean is fairly high 

for calcium in the ores and exceptionally high for 

manganese in the sandstones. Though the observed 

differences are probably significant, too great a weight 

should not be placed on the calculated abundance ratios.

OKE ELEMENTS

Uranium contributes the bulk of the value to the ores 

now mined on the Colorado Plateau, though in a few

ores, vanadium, which is also extracted, may be the 

principal ore element in terms of its contribution to 

the price of the ore. In all ores produced from the 

Morrison formation vanadium as well as uranium is an 

ore element. Copper is paid for by uranium ore buyers 

in a few uranium ores produced from the Shinarump 

member in southeastern Utah. Selenium has been considered as a possible byproduct of some ores, but to date 

it has not been extracted. In a few sandstone-type ores 

mainly from Triassic beds, and in limestone ores from 

northwestern New Mexico uranium is the only element 

that contributes to the value of the ore.

URANIUM AND VANADIUM

Uranium and vanadium (figs. 4, 7, and 8) are 

not only the principal ore elements but are also the 

elements that have the highest ratios of abundance in 

the ores to their abundance in unmineralized sandstones 

in both Upper Triassic rocks and the Morrison formation. The minimum acceptable grade established by 

U. S. Atomic Energy Commission (1948) is about 1,000 

times as great as the mean concentration of uranium in 

23 samples of unmineralized sandstone of the Salt Wash 

(table 1). The ratio of the mean for vanadium in ores 

and in unmineralized sandstones is about 500 in the 

samples from the Morrison formation and about 20 in

i

Frequency distribution by tonnage 

in 197 deposits

Frequency distribution by tonnage 

in ore produced 

from July 1,1954, 

to December 31, 

1954 (exclusive 

of Grants district, 

New Mexico)

Log concentration of 1)3 Oa 

Arbitrary scale

60

50

40

30

20

10

{frequency distribution by tonnage 

in 197 deposits

Frequency distribution by deposits 

in 209 deposits

Log concentration of U 3 08 

Arbitrary scale

FIGURE 7. Frequency distribution of U.O., as determined by fluorlmetrlc analysis, In uranium ores from the Morrison formation.
46 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

50 - 

40 

30- 

20- 

10 -

Uranium ores from 

the Morrison formation (chiefly the 

Salt Wash member)

Unmineralized sandstones from the Salt 

Wash member of the 

Morrison formation

1 2 3

Log 10 concentration (ppm)

Uranium ores from 

Upper Triassic rocks 

(chiefly the Shinarump 

and Moss Back members 

of the Chinle formation)

Unmineralized sandstones 

from the Shinarump and 

Moss Back members of the 

Chinle formation

123 

Log 10 concentration (ppm)

FIGURE 8. Frequency distribution of vanadium, as determined by spectrographic analysis, in uranium ores and unmineralized sandstones of the Colorado Plateau.

the Upper Triassic rocks. Though the ratio is less for 

vanadium than for uranium, vanadium is the most 

abundant extrinsic element in the Morrison ores.

Some comparisons can be drawn between the uranium 

content of the samples studied and the uranium content of the ore produced over a considerable period without specifying arithmetic-mean concentrations, which 

are withheld for security reasons. The arithmetic-mean 

concentration of uranium, weighted according to tonnage, in all ore represented by the samples for which 

tonnage data are available from 197 deposits in the 

Morrison formation, is identical (to two significant figures) to the arithmetic-mean concentration of uranium 

in all ore produced from the Morrison formation for 

each of four 6-month periods in 1953 and 1954 exclusive of ore produced from the Grants district of New 

Mexico, for the period July 1 to December 31, 1954. 

The frequency distribution of U3O8 by tonnage calculated from total tonnage and weighted-average uranium 

content of ore from each deposit for the 197 deposits 

is closely similar to the frequency distribution by tonnage of all ore produced from the Morrison formation, 

exclusive of the Grants district calculated from total 

tonnage and weighted average uranium content of ore 

produced from each deposit per month or semimonthly 

settlement for the period July 1 to December 31,1954 

(fig. 7).

The arithmetic-mean concentration of uranium, 

weighted according to tonnage, in all ore represented 

by the samples from 38 deposits in Upper Triassic rocks 

is 12 percent less than the arithmetic-mean concentration of uranium in all ore produced from the Chinle 

formation in 1953 and 1954, but it is identical (to two 

significant figures) to the arithmetic-mean concentration of uranium in all ore produced from the Chinle 

formation in the latter half of 1954.

The frequency distribution of U3O8 by tonnage in 

the 197 deposits from the Morrison formation may be 

compared in figure 7 with the frequency distribution 

of U3O8 by deposits in 209 of the deposits studied for 

which fluorimetric assays are available. The first distribution weights the frequency heavily in favor of 

large producers; whereas, in the second distribution 

each of the 209 deposits is given equal weight, whether 

the amount of ore represented is large or small. It is 

the second type of distribution that is represented by 

all the histograms given for spectrographic and colorimetric analyses. The two types of distributions provide estimates of two entirely different parameters of 

the uranium distribution which should be carefully distinguished : the arithmetic mean of the distribution by 

tonnage, when multiplied by the total tonnage, gives the 

total quantity of U3O8 produced, whereas the geometric 

mean of the distribution by deposits gives an estimate
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 47

of the median grade of uranium in randomly selected 

deposits. It is of interest that, though the modes of the 

two types of distribution are significantly displaced, the 

estimated arithmetic-mean concentration of U3O8 calculated from the distribution by deposits is only 15 percent less than the estimated arithmetic mean calculated 

from distribution of tonnage.

Concentrations of most elements in the ores from the 

Morrison formation are virtually independent of the 

grade of uranium. Only vanadium, iron, and titanium 

correlate significantly with uranium, and all three of 

the correlations are low, that of titanium at the limit of 

significance. Even though deposition of the uranium 

ore appears to have been selective with respect to mudstone content and other lithologic features of the host 

sandstone strata, and although several accessory elements appear to have been introduced by the mineralizing processes, uranium exhibits no strong affinities in 

its grade distribution among deposits either for detectable intrinsic elements or for accessory extrinsic elements. The distribution of uranium may, however, 

have been strongly influenced by the distribution of 

organic carbon (Parts 5,12, and 14), analyses for which

are not yet available. The mineral forms taken by 

uranium in the deposits are listed in Part 5.

The arithmetic mean grade of V2O5 , weighted according to tonnage, for the samples of Morrison ores studied 

is 6 percent less than the mean of all the ore from the 

Morrison (exclusive of ore from the Grants district) 

produced in 1953 and 1954 (table 3). This small difference may be due to weight given among the samples 

studied to deposits in the Slick Rock district of southwestern Colorado. The weighted mean for the samples 

from 38 deposits in Upper Triassic strata is significantly 

lower than the mean of ore produced from Upper 

Triassic rocks in 1953 and 1954. Ore produced from 

the Upper Triassic during this period is heavily 

weighted toward one large mine in the Shinarump member, whereas more than half of the tonnage represented 

by the samples studied is from mines in a small area 

around Temple Mountain in central Utah, all producing from the Moss Back member of the Chinle formation. The mean for the samples studied from deposits 

in the Upper Triassic is nearly the same as the mean 

for ore produced from the Chinle formation in the 

latter half of 1954, both for V2O5 and U3O8 .

TABLE 3. Comparison of weighted arithmetic-mean grade of vanadium pentoxide in ores produced in 1958 and 1954 and in ores represented by samples studied

[Arithmetic-mean grade of VjOj weighted according to tonnage; based on chemical assays by ore buyers]

Formation from which ore is produced

1953, to Doc. 31. 1954... 

Weighted moan for samples from 38 deposits

6-month period ending 

June 30,1953

Jan. 1, 1954

July 1, 1954 

Dec. 31,1954 Jan. 1, 1954

July 1, 1954 

Dec. 31,1954

VaOs (percent)

1.08

1.25

1.07 

.92

97

.72 

.58

0.85

.59

Formation from which ore is produced

Weighted mean for Morrison formation ' Jan. 

1, 1953 to Dec. 31, 1954....... .............

6-month period ending 

June 30,1953

Jan. 1, 1954

July 1, 1954 

Dec. 31,1954

VjOs (percent)

1.65

1.66

1.64 

1.67

1.65

1.55

1 Exclusive of ores produced from Grants district, in New Mexico, during period ending December 31,1954.

The frequency distribution of vanadium in the ores 

and unmineralized sandstones, based on semiquantitative spectrographic analyses, is given in figure 8. Histograms given for the ores are for frequency by 

deposits, not by tonnage, and as with uranium, neither 

these histograms nor the means computed from them 

given in table 2 can be compared directly with production data. In the histograms for deposits given in 

figure 8 equal weight is given to all deposits, whether 

large or small, whereas the great bulk of production 

from deposits in Upper Triassic rocks, in particular, is 

from only a small percentage of the mines producing 

at present.

Vanadium in the ores from the Morrison formation 

has a high correlation with aluminum, a moderate correlation with lead, zirconium, magnesium, and uranium,

and a low correlation with many other elements including several that tend to correlate with aluminum. The 

high correlation with aluminum illustrates a strong 

tendency for vanadium to be more abundant in the more 

aluminous ores of the Morrison formation, a relation 

interpreted as due to selective precipitation of vanadium by clay minerals in the rocks that received the ore 

elements. The minerals in which vanadium is primarily contained in the deposits are given in part 5. In 

the oxidized deposits the bulk of the vanadium is contained in micaceous or claylike silicates.

ACCESSORY EXTRINSIC ELEMENTS

Most of the accessory extrinsic elements in the sandstone-type uranium ores of the Colorado Plateau were 

recognized more than 30 years ago. With reference to
48 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

the Colorado Plateau uranium-vanadium deposits 

Lindgren wrote (1923, p. 440-441):

The ores are later than the beds which they follow, and are 

characterized by a very strange assortment of elements among 

which, besides the two already mentioned, are copper, lead, 

silver, barium, chromium, nickel, molybdenum, and selenium.

To this list can be added only three other elements, cobalt, arsenic, and possibly yttrium, which can be shown 

from the present study to be characteristic extrinsic 

elements in the sandstone-type uranium ores. The principal elements detectable by the spectrographic method 

that are extrinsic in a large majority of ores from both 

the Upper Triassic rocks and the Morrison formations 

are uranium, vanadium, cobalt, nickel, copper, arsenic, 

molybdenum, and lead.

COFFER AND LEAD

The abundance of copper (figs. 4 and 9) is about 7 

times greater in Morrison ores than in unmineralized 

sandstones of the Salt Wash and about 3 times greater 

in ores from Upper Triassic rocks than in unmineralized sandstones of the Shinarump and Moss Back. 

Lead is more than 9 times as abundant in ores from the 

Morrison as in the unmineralized sandstones and about 

6 times as abundant in the ores as in the sandstones in 

Upper Triassic rocks. Though the ratio of abundances 

for copper is lower for ores and rocks from the Triassic 

than for the Morrison formation, because of the unusually high concentration of copper in the unmineralized sandstones of Triassic age, the amount of 

copper that has probably been introduced into the average ore in the Triassic strata is more than twice as great 

as the amount probably introduced into average 

Morrison ores.

Lead (figs. 4 and 9) in the sandstone-type uranium 

ores is of at least three origins: (1) intrinsic lead contained in the rocks just prior to mineralization, (2) 

extrinsic lead introduced into the deposits, probably 

at the time of initial uranium mineralization, and (3) 

radiogenic lead derived in the deposits by decay of the 

uranium in the deposits since initial mineralization. 

Isotopic analyses of lead extracted from some of the 

pulp samples included in this study (Stieff, Stern, and 

Milkey, 1953, p. 19, samples GS-40, 41, 42, 47, 48, and 

49) indicate that the proportion of radiogenic lead 

derived in place, in bulk samples of ore from the 

Morrison, ranges from about 5 to more than 80 percent 

of the total lead. The content of radiogenic lead derived in place tends to be proportional to the uranium 

content of the ores, and the highest proportions of 

radiogenic lead derived in place generally are found 

in ores that have the lowest concentrations of total lead. 

On the basis of the analyses given by Stieff, Stern, and

Milkey (1953, p. 18( and 19) it is estimated that less than 

half of the lead in ores from the Upper Triassic rocks 

and the Morrison formation with average grade and 

average lead content is derived by decay of uranium 

at the locus of the present deposits.

In the ores from the Morrison formation copper and 

lead are closely related, as is shown by a high correlation. Both copper and lead have low to moderate correlation with the elements associated with carbonates 

in the ores. A moderate correlation of copper and lead 

with aluminum, and low to moderate correlation of copper with some elements associated with aluminum and 

calcium in the unmineralized sandstones of the Salt 

Wash also suggests some affinity of copper and lead both 

for the aluminous or clay-silt fraction of the rocks and 

for the carbonate cement. The distribution of lead in 

the unmineralized sandstones is largely unknown, but 

lead is generally present in detectable concentrations in 

mudstones of the Salt Wash (Newman, 1954, p. 44) 

even though rarely reported in sandstones of the Salt 

Wash, suggesting that much of it may be contained in 

the clay-silt fraction. Higher frequency of detectable 

lead in the sandstones of the Shinarump and Moss Back 

members may be due to higher average content of clay. 

In the low-valent ores extrinsic copper and lead are 

probably contained primarily as sulfides (Part 5).

Copper and lead correspond closely in their regional 

distribution in the ores. Both elements have greater 

frequency of high concentration in uranium deposits, 

mainly in the Morrison formation, in an area partially 

coincident with a region of salt structures that lies 

athwart the Colorado-Utah State line (Shoemaker, 

1954, p. 71 and 76). Both elements also have a greater 

frequency of high concentrations in uranium deposits, 

mainly in Upper Triassic strata, in an area between the 

San Juan and Colorado Rivers in southeastern Utah 

and in an area on the San Raf ael Swell in central Utah. 

The regional distribution of above average concentrations of silver (Shoemaker, 1954, p. 77) and zinc in the 

ores resembles that of copper and lead.

NICKEL, COBALT, AND MOLYBDENUM

Nickel arid cobalt (figs. 4 and 9) are estimated to be 

about 20 times as abundant in ores from the Morrison 

formation as in unmineralized sandstones of the Salt 

Wash, though so few samples of the sandstones contain 

detectable concentrations of nickel and cobalt that these 

estimates should be regarded only as indicating the 

order of magnitude of the ratio. Molybdenum (figs 4 

and 9) is more than three times as abundant in the ores 

from the Morrison as in the sandstones and the ratio 

of abundance for molybdenum is probably as large as 

the ratios for nickel and cobalt. In the Upper Triassic
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 49

Cobalt 

(spectrographic)

Copper 

(spectrographic)

Nickel 

(spectrographic)

Lead 

(spectrographic)

211' I

3

percent I 

less I 

than

10 ppm 

96

211* 

12 , 

percent)

less

than 

2.2

96*

184* 

8.5

percent | 

less 

than

2.2

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

98

percent j

less |

94

percent 

less 

than

2.2 ppm

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

3

percent 

less 

than

2.2 ppm

3

percent 

less 

than

2.2 ppm

56 ' 

percent

less

than 

10 ppm

22

percent 

less 

than

2.2 ppm

22

percent I 

less I 

than

2.2 ppm

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back rnembers of the 

Chinle formation)

Unmineralized sandstones from 

the Shinarump and Moss Back 

rnembers of the Chinle formation

logic concentration (ppm) 012345 1234 1 2 3 1 2 3

Type bf sample

Molybdenum 

(spectrographic)

Arsenic . 

(colorimetric)

I

13 I

percent

less {

than!

4.6 ppm

Uranium ores from the Morrison 

formation (chiefly the Salt Wash 

member)

Unmineralized sandstones from 

the Salt Wash member of the 

Morrison formation

50-

f&aw

10-

211*

01 i

percent!

less ,

than |

4-6 ppm |

98 , 

percent" 

less 

than

Uranium ores from Upper Triassic 

rocks (chiefly the Shinarump 

and Moss Back members of the 

Chinle formation)

g S30

3 U

10-

26 , 

percent!

less 1

than 

4.6 ppm

Unmineralized sandstones from 

the Shinarump and Moss Back 

members of the Chinle formation

50- 

£-40-

10

84

percent! 

less I 

than I

4.6 ppm |

I

log 10 concentration (ppm) 123 123 01 1.92.83.7 1 1.92.83.7 

 Number of uranium deposits or number of samples of sandstone 

tSpectrographic analysis of ytterbium in uranium ore is interfered with by vanadium

FIOURB 9. .Frequency distribution of the domlnantly accessory extrinsic elements of uranium ores contained In uranium ores and In

Unmineralized sandstones on the Colorado Plateau.
50 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

rocks the estimated ratios of abundance between ores 

and unmineralized sandstones are about 3 for nickel, 

5 for cobalt, and 9 for molybdenum. Again, the estimated ratio for molybdenum should be regarded as indicating only the order of magnitude. The ratios of 

abundance for nickel and cobalt are low in the Triassic 

rocks because of the much higher concentrations of these 

two elements in unmineralized sandstones of the Shinarump and Moss Back members as compared with sandstones of the Salt Wash.

Nickel and molybdenum have a moderately high correlation in Morrison ores. Like uranium and unlike 

all other elements for which the correlation in the ores 

has been calculated, nickel and molybdenum show no 

significant correlation with aluminum. Both nickel and 

molybdenum exhibit a moderate correlation with iron 

and low correlation with yttrium; molybdenum has 

a significant but low correlation with chromium and 

zirconium as well. The correlation of cobalt has not 

been calculated because of interference by uranium in 

some of the cobalt analyses, but cobalt is known to correlate highly with nickel and probably has associations 

similar to those of nickel in the ores. The correlation of 

nickel with iron probably reflects an association with 

iron sulfides, which commonly contain appreciable concentrations of nickel and cobalt (Hegemann, 1942, p. 

125-138) and which are known to contain relatively 

high concentrations of nickel and cobalt in some of the 

sandstone-type uranium deposits of the Colorado 

Plateau (Part 5). The bulk of nickel and cobalt in the 

low-valent ores may be contained in bravoite or nickeliferous and cobaltian pyrite. Molybdenum may enter 

the iron sulfides to some extent but the molybdenum sulfides molybdenite and jordisite have also been found 

(Part 5).

The concentration of nickel and cobalt in the uranium 

deposits tends to be broadly zoned across the central 

part of the Colorado Plateau. Nickel and cobalt tend 

to be higher in ores from both the Upper Triassic rocks 

and the Morrison formation toward the west or northwest part of the region and lower toward the east or 

southeast (Shoemaker, 1954, p. 75). Molybdenum appears to follow a similar pattern in deposits in the Morrison formation but is more erratically distributed in 

the deposits in Upper Triassic rocks (Shoemaker, 1954, 

p. 74).

YTTBITTM AND YTTEBBIUM

Yttrium (figs. 4 and 9) is tentatively considered a 

dominantly extrinsic element in the ores from the Morrison formation. It is estimated to be about eight times 

more abundant in the ores than in unmineralized sandstones of the Salt Wash. This estimate is subject to 

large uncertainties because the large majority of sandstones analyzed did not contain detectable yttrium and 

because some variation exists in the limit of sensitivity 

as estimated by individual analysts. In the ores yttrium has a moderate correlation with iron, nickel, 

molybdenum, vanadium, titanium, barium, and aluminum. The correlations with zirconium, boron, and titanium suggest that a part of the yttrium in the ores is 

in detrital heavy minerals, which spectrographic analyses show to be the principal carriers of yttrium in 

the unmineralized Salt Wash sandstones. The correlations with iron, nickel, and molybdenum suggest some 

affinity of yttrium with the nickel-cobalt-molybdenum 

group of extrinsic elements. As in the case of iron, 

about half of the yttrium in Morrison ores may be intrinsic and about half extrinsic. In Upper Triassic 

rocks the concentration of yttrium in ores and in unmineralized sandstones is practically identical, and yttrium is considered largely intrinsic in the ores. The 

regional distribution of yttrium in all ores is similar to 

the distribution of nickel, cobalt, and molybdenum, but 

is more erratic (Shoemaker, 1954, p. 72).

Spectrographic analyses of ytterbium (figs. 4 and 9) 

in the ores has been prevented by interference from 

high concentrations of vanadium. Ytterbium has a 

very high correlation with yttrium in heavy-mineral 

separates from sandstones of the Salt Wash and is a 

member of the yttrium group of rare earths which 

are generally associated in nature (Rankama and 

Sahama, 1950, p. 517). Ytterbium may, like yttrium, 

be partly extrinsic in ores in the Morrison formation.

SELENIUM

Selenium (fig. 9) is more than six times as abundant 

in the average of the ores from the Morrison as in the 

unmineralized sandstones of the Salt Wash and about 

twice as abundant in the average of ores from Upper 

Triassic rocks as in the unmineralized sandstones of 

the Shinarump and Moss Back members. Unlike the 

distribution of all other elements investigated, the distribution of selenium in the ores studied from Triassic 

rocks is bimodal. One mode corresponds with the probable modal concentration in the unmineralized sandstones and the other mode is about 50 times higher. 

This unusual distribution is due to the high proportion 

of deposits represented from one small area, at Temple 

Mountain in central Utah, where the uranium deposits 

are unusually rich in selenium. Nearly all other ores 

studied from Triassic rocks are comparable in selenium 

content to the unmineralized sandstones. The distribution of selenium in Morrison ores is more nearly lognormal. Selenium is considered dominantly extrinsic in 

Morrison ores and in ores from Upper Triassic strata at 

Temple Mountain but dominantly intrinsic in most 

other ores from Upper Triassic rocks.
ELEMENTAL COMPOSITION OP THE SANDSTONE-TYPE DEPOSITS 51

The regional distribution of selenium in ores of the 

Morrison formation (Shoemaker, 1954, p. 73) is similar 

to the regional distribution of nickel, cobalt, and molybdenum. A majority of the more richly seleniferous ores 

are found northwest of the Colorado River. The association of selenium with elements that may be contained mainly in sulfides in low-valent ores is an expectable one. Iron sulfides, into which selenium will 

enter by substitution for sulfur (Williams and Byers, 

1934), locally contain as much as 1 percent selenium 

in the Colorado Plateau ores (Part 5) and appear to be 

the most likely hosts for the bulk of extrinsic selenium 

in low-valent ores. Some ores also contain traces of 

such selenides as eucairite (CuAgSe) and clausthalite 

(PbSe) and also native selenium (Part 5).

ARSENIC

Arsenic (fig. 9), as determined by colorimetric analyses of a limited suite of samples, is more than IT times 

as abundant in ores from the Morrison formation as in 

the unmineralized sandstones of the Salt Wash member. 

The content of arsenic in ores from Upper Triassic rocks 

appears to be similar to the content in ores from the 

Morrison, but no data are yet available on the arsenic 

content of unmineralized sandstones of the Shinarump 

and Moss Back members. In terms of abundance ratio, 

arsenic may be the third or fourth most important extrinsic element in the sandstone-type uranium ores, and 

in terms of actual amount or quantity contained it is 

the fifth most important extrinsic element, among those 

studied, in Morrison ores.

The manner in which arsenic is contained in the 

ores is not fully known. In low-valent ores the arsenides domeykite and arsenopyrite and realgar, as 

well as, native arsenic have been reported (Part 5) but 

appear to be rare. Arsenic has been found associated 

with coffinite, one of the major uranium minerals in 

low-valent ores, but apparently it is not an essential 

constituent of the mineral (Stieff, Stern, and Sherwood, 1955, p. 609). In oxidized ores arsenic occurs 

in the arsenates zeunerite and metazeunerite and in 

rare occurrences in abernathyite, novacekite, and conichalcite (Part 5; Weeks and Thompson, 1954, p. 59); 

it also enters into such phosphates as autunite and torbernite (Weeks and Thompson, 1954, p. 24 and 36) and 

into vanadates similar to calciovolborthite. Most of 

these minerals are extremely rare in vanadiferous ores, 

however, and the bulk of arsenic in oxidized ore may be 

contained as a minor constituent in some of the common vanadates.

The regional distribution of arsenic in the ores appears to be nearly or essentially random, in contrast to 

the relatively systematic distribution of most other accessory extrinsic elements. Probably the distribution

of arsenic is more closely related to the distribution of 

uranium than any other extrinsic element.

ELEMENTS NOT DETECTED

Table 4 gives the spectrographic limits of sensitivity 

for 29 elements that, with the exceptions of neodymium 

and niobium, have not been detected in samples representing more than 1 ton of ore from sandstone-type 

uranium deposits in the Upper Triassic rocks and the 

Morrison formation or in whole samples of unmineralized sandstones from these formations. Traces of 

niobium have been detected in the ores of 8 and neodymium in the ores of 1 of 211 deposits from the Morrison formation, but neither element has been detected 

in unmineralized sandstones of the Salt Wash or in ore 

or unmineralized sandstone in Upper Triassic rocks.

TABLE 4. Elements looked for but not detected in pulp samples 

of ores from 249 uranium deposits and in 128 grab samples of 

unmineralized sandstones from the Upper Triassic rocks and 

the Morrison formation

Element

Au -- 

Bi.. .....................

Cd....... ................

Ce . ................. ..

Dy_. ....... .............

Er.. ..-.-.-.-.-.-.-..-...

Gd...... -.-.---.---....

Ge . . ...

Hf.. ... .........

Hg.......................

In. _____ . __ ......

Ir.. ------.--....

Li .

Nbi..... ................

Nd >. ... ........

Spectrographic 

limit of 

sensitivity 

(percent)

0. 005

.001

.005

.05

.05

.005

.05

.0005

1.0

.001

.005

.01

.001

.01

Element

r>«

P

Pd . . ...............

Pt.---. ...............

Re.. ......... .........

Rh..... ...............

Ru ... ........ ......

Sm... _ .. __ . _ ....

Sn. ...................

Ta............. .......

Te.. ......... .........

Th... ................ .

Tl..... ....... .........

W...._ ................

Spectrographic 

limit of 

sensitivity 

(percent)

0.005

.5

.0005

.005

.005

.005

.005

.01

.001

.05

.5

.05

.05

.01

1 Traces found in ores from 8 uranium deposits in the Morrison formation. 

8 Trace found in ore from 1 uranium deposit in the Morrison formation.

A number of the elements not detected in pulp 

samples of the ores or in whole samples of the sandstones have been found in detectable quantities in heavy 

minerals or in clay fractions of the sandstones. These 

include cerium, erbium, hafnium, tin, and phosphorous 

in the heavy minerals and lithium in the clay fractions. 

Bismuth has been detected in samples of gypsum from 

salt intrusions in southwestern Colorado and has been 

found in gypsif erous sandstones of the Salt Wash and 

in gypsum from the sandstones in places where the Salt 

Wash sandstone member is adjacent to the salt intrusions. Indium has also been detected in gypsiferous 

Salt Wash sandstones and mudstones associated with 

the bismuth. Any of these elements might be detected 

spectrographically in small samples and perhaps even 

in pulp samples of the uranium ores. Some of these and 

other elements are probably partly extrinsic in a number or perhaps even in most of the sandstone-type 

uranium deposits. Tin occurs locally in moderate concentration in the uranium ore at the Peanut mine, in
52 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

southwestern Colorado (Koach and Thompson, written 

communication, 1955), and phosphorous may be a 

significant constituent of some sandstone-type uranium 

deposits where it forms phosphates in the oxidized ore 

(Part 5). Cadmium has been noted in the mineral 

greenockite (Part 5) and may be widespread in the ores 

in concentrations slightly below the spectrographic 

limit of sensitivity. Mercury has been reported from 

shales in the Chinle formation in northern Arizona 

(Lausen, 1936) and could possibly be an extrinsic component in the uranium ores. Tellurium has been reported from highly vanadiferous and seleniferous "alluvium" overlying ore in the Morrison formation at 

Thompson in southeastern Utah, by Beath (1943, p. 701 

and 704). Thallium was detected spectrographically 

in a grab sample of uranium ore from the Navajo sandstone of Jurassic and Jurassic (?) age in northern 

Arizona (Shoemaker, 1955), and might also be an extrinsic component of ores in the Morrison and Upper 

Triassic rocks.

SUMMARY

A sandstone-type uranium deposit may be considered 

as composed of two fundamental parts: an indigenous 

part and a foreign part which was added to the indigenous part to form the deposit. The indigenous part 

consists of all elements that would have occupied the 

space of the uranium deposit had uranium mineralization never occurred; these elements of the uranium deposit are called intrinsic. The foreign part consists of 

all elements that were added to the indigenous part by 

processes of mineralization; these elemental components are called extrinsic. Nearly all elements in 

sandstone-type uranium deposits are probably in part 

intrinsic and in part extrinsic, but each element may be 

classified according to the dominant role it plays in a 

majority of the deposits.

The classification of elements studied in this investigation in the uranium deposits of the Morrison formation and the Chinle formation is given in table 5.

TABLE 5. Classification of elements in sandstone-type uranium deposits from Upper 

Triassic rocks and from the Morrison formation

Abundance ratio '

Element

Morrison formationUpper Triassic 

rocks

Dominantly 

intrinsic.

Dominantly 

extrinsic.

Dominantly

epigenetic.

Si.. .

Al______._

Fe ---

K__ ______

Ti_.---_._

Zr.. ......

Be..---_-

B . _ _

Sc___ .

Cr_... ....

Zn___-.__-

Ga____.__

Ac

Sb ----.

La.. ______

Mg._ 

Ca.__._...

Mn_______

Sr. -------

V. .......

V- ....--.

Co........

Nidi-.. 

As____..__

Se 

¥.____._.

Mo 

Yb... 

Pb. 

«1

2. 1

3. 7

2.0

2. 3

«2

__ 2.6

2.2

«2 (?) ...

«0. 5 ...

3.0

0.6

1.4

2.4

2.5

>1000

500

«20

«20

7

>6

>3

>9

«1

. 7

1. 3

.7

.7

«1

«2

2. 1

«2

1

csl

1.3

3

2

1.4

2

20

««3

3

«2

«9

«6

1 Ratio of estimated geometric-mean concentration In uranium ores to estimated .geometric-mean concentration 

In unminerallzed sandstones.
ELEMENTAL COMPOSITION OF THE SANDSTONE-TYPE DEPOSITS 53

Dominantly intrinsic elements are further subdivided 

according to whether they are contained principally 

in syngenetic minerals in the uranium deposits or 

whether they are contained principally in authigenic 

minerals formed after the deposition of the sediments 

that ultimately were transformed into uranium deposits. Dominantly extrinsic elements are subdivided 

according to their economic importance into ore elements and accessory elements. The classification of elements as intrinsic or extrinsic rests primarily on the 

ratios of their abundance in unmineralized sandstones 

to their abundance in the uranium deposits. Because 

of selectivity of mineralization, account must be taken 

of the fact that the average intrinsic composition of the 

rocks or sediments mineralized is not equivalent to the 

average composition of unmineralized sandstones. In 

uranium deposits in-the Morrison formation most of the 

dominantly intrinsic elements are more abundant than 

they are in the unmineralized sandstones.

Several elements not detected by the spectrographic 

method in the sandstone-type uranium ores are probably present as dominantly extrinsic elemental components of the ores. Two of possible importance in 

the composition of the ores are sulfur and phosphorous. 

Iron, though dominantly intrinsic, is also present as 

one of the most abundant extrinsic elemental components of the ores, and the extrinsic iron is probably contained mainly in the sulfides pyrite and marcasite in 

low-valent ores. Much of the sulfur combined with 

extrinsic iron in the sulfides may have been introduced 

into the ores with the iron. On oxidation the sulfur 

may tend to be lost from the ore, but some is retained 

as sulfate. Phosphorous is identified in some ores in 

various phosphorous minerals. Among other elements 

that could be dominantly extrinsic in the ores but are 

below the spectrographic limit of sensitivity in bulk 

samples are tin, cadmium, tellurium, and thallium.

Though all elements were probably carried in some 

concentration, however small, in the solutions that introduced uranium into the ores, only a limited suite of 

elements form the recognizable extrinsic components of 

the ores. Those elements that are now thought to be 

or are likely to prove to be identifiable members of the 

extrinsic suite of elements are listed in table 6 in the 

estimated order of abundance of their extrinsic fraction 

in the average ore from the Morrison formation. No 

great weight should be placed on the exact position of 

each element in the order given; in particular, the positions of sulfur and phosphorus, which have been estimated for relatively oxidized ore mainly from indirect 

lines of mineralogical evidence, are in considerable 

doubt. The list of possible extrinsic elements whose 

concentrations are below the spectrographic limit of

sensitivity shows only those elements suggested by some 

specific analytical or mineralogical evidence and should 

not be considered inclusive.

TABLE 6. Extrinsic elemental components of average uranium ore 

from the Morrison formation, in their estimated order of abundance

Component 

Vanadium 

Iron

Magnesium 

Uranium 

Sulfur

Probably extrinsic in more than half of 

the uranium deposits.__________.__..

Probably extrinsic in less than half of the 

uranium deposits__________----___..

Possibly extrinsic in the uranium deposits 

but not detected spectrographically in 

bulk samples of the ores._____-_____.

Arsenic 

Phosphorous 

Copper 

Lead

Molybdenum 

Selenium 

Cobalt 

Nickel 

Yttrium 

(Barium) 

(Strontium) 

(Zinc)

(Chromium) 

^(Silver) 

' Ytterbium (?)

Cadmium (?) 

Tellurium (?) 

Thallium(?)

LITERATURE CITED

Baker, A. A., Duncan, D. 0., and Hunt, C. B., 1952, Manganese 

deposits of southeastern Utah: U. S. Geol. Survey Bull. 

979-B, p. 63-157.

Barnett, P. R., Huleatt, W. P., Rader, L. F., and Myers, A. T., 

1955, Spectrographic determination of contamination of rock 

samples after grinding with alumina ceramic: Am. Jour. 

Sci., v 253, p. 121-124.

Beath, O. A., 1943, Toxic vegetation growing on the Salt Wash 

sandstone member of the Morrison formation: Am. Jour. 

Bot, v. 30, p. 648-707.

Coffin, R. G., 1921, Radium, uranium, and vanadium deposits 

of southwestern Colorado: Colorado Geol. Survey Bull. 16.

Colorado School of Mines Research Foundation, 1954, A review 

and inspection of sampling processes at various main orebuying stations In the Colorado Plateau, Grants, New 

Mexico, and Edgmont, South Dakota areas: Colorado 

School of Mines Research Foundation, Golden, Colo.

Cralg, L. G., Holmes, G. N., Cadigan, R. A., Freeman, V. L., and 

others, 1955, Stratigraphy of the Morrison and related 

formations, Colorado Plateau region, a preliminary report: 

U. S. Geol. Survey Bull. 1009-E, p. 125-168.

Fischer, R. P., 1937, Sedimentary deposits of copper, vanadiumuranium, and silver in southwestern United States: Econ. 

Geol., v. 32, p. 906-951.

 1942, Vanadium deposits of Colorado and Utah, a preliminary report: U. S. Geol. Survey Bull. 936-P, p. 363- 

394.

Fischer, R. P., Haff, J. C., and Romlnger, J. F., 1947, Vanadium 

deposits near Placervllle, San Miguel County, Colorado: 

Colorado Scl. Soc. Proc., v. 15, p. 117-134.
54

Fisher, R. A., 1921, On the mathematical foundations of theoretical statistics: Philos. Trans. of the Royal Soc. of London, ser. A., v. 222, p. 309-368.

 1931, The sampling error of estimated deviates, together 

with other illustrations of the properties and applications 

of the integrals and derivatives of the normal error function: Mathematical tables, British Assoc. for the Av. of 

Sci., v. 1.

Fisher, R. A., and Yates, Frank, 1953, Statistical tables for 

biological, agricultural, and medical research: New York, 

Hafner Publishing Co., Inc.

Grim, R. E., 1953, Clay mineralogy: New York, McGraw-Hill 

Book Co., Inc.

Grimaldi, F. S., May, Irving, and Fletcher, M. H., 1952, U. S. 

Geological Survey fluorimetric methods of uranium analysis: U. S. Geol. Survey Circ. 199.

Hald, A., 1952, Statistical tables and formulas: New York, 

John Wiley and Sons, Inc.

Hegemann, F., 1942, Die geochemishe Bedeutung von Kobalt und 

Nickel in pyrit: Zeitschrift fiir angewandte Mineralogie, 

Band 4, p. 121-239.

Hess, F. L., 1933, Uranium, vanadium, radium, gold, silver, 

and molybdenum sedimentary deposits, in Ore deposits of 

the western states (Lindgren volume) : Am. Inst. Min. 

Metallurgy Eng., p. 450-481.

Hillebrand, W. F., and Ransome, F. L., 1905, On carnotite and 

associated vanadiferous minerals in western Colorado: 

U. S. Geol. Survey Bull. 262, p. 9-31.

Hoel, P. G., 1947, Introduction to mathematical statistics: New 

York, John Wiley and Sons, Inc.

Lakin, H. W., Almond, Hy, and Ward, F. N., 1952, Compilation 

of field methods used in geochemical prospecting by the 

U. S. Geological Survey: U. S. Geol. Survey Circ. 161.

Lausen, Carl, 1936, The occurrence of minute quantities of 

mercury in the Chinle shales at Lees Ferry, Arizona: Econ. 

Geology, v. 31, p. 610-617.

Lindgren, Waldemar, 1911, Copper, silver, lead, vanadium, and 

uranium ores in sandstone and shale: Econ. Geology, v. 6, 

p. 568-581.

 1923, Concentration and circulation of the elements 

from the standpoint of economic geology: Econ. Geology, 

v. 18, p. 419-442.

 1933, Mineral deposits: New York, McGraw-Hill Book

Co., Inc.

Levering, T. S., Canney, F. C., Lakin, H. W., and Ward, F. N., 

1955, The use of geochemical techniques and methods in 

prospecting for uranium: International Conference on 

Peaceful Uses of Atomic Energy, Geneva, Switzerland, 

August 8-20, 1955.

Manger, G. E., 1954a, Original-state core studies, in Geologic 

investigations of radioactive deposits, semiannual progress 

report, December 1, 1953 to May 31, 1954: U. S. Geol. 

Survey Trace Elements Inv. Rept. 440, U. S. Atomic Energy 

Comm., Tech. Inf. Service, Oak Ridge, Tenn., p. 55-63.

 1954b, Original-state core studies, in Geologic investigations of radioactive deposits, semiannual progress report, 

June 1 to November 30, 1954: U. S. Geol. Survey Trace 

Elements Inv. Rept. 490, U. S. Atomic Energy Comm. 

Tech. Inf. Service, Oak Ridge, Tenn., p. 92-99.

Myers, A. T., 1954, Spectrographic methods, Denver, in Geologic 

investigations of radioactive deposits, semiannual progress 

report, December 1,1953 to May 31,1954: U. S. Geol. Survey 

Trace Elements Inv. Rept. 440, U. S. Atomic Energy 

Comm. Tech. Inf. Service, Oak Ridge, Tenn., p. 194-195.

Myers, A. T., and Barnett, P. R., 1953. Contamination of rock 

samples during grinding as determined spectrographically: 

Am. Jour. Sci., v. 251, p. 814-830.

Newman, W. L., 1954, Distribution of elements, in Geologic investigations of radioactive deposits, semiannual progress 

report, December 1,1953 to May 31,1954: U. S. Geol. Survey 

Trace Elements Inv. Rept. 440, U. S. Atomic Energy Comm. 

Tech. Inf. Service, Oak Ridge, Tenn., p. 42^5.

Proctor, P. D., 1953, Geology of the Silver Reef (Harrisburg) 

mining district: Utah Geol. and Mineralogy Survey Bull. 44.

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press.

Ross, C. S., and Kerr, P. F., 1931, The kaolin minerals: U. S. 

Geol. Survey Prof. Paper 165-E, p. 151-176.

Shoemaker, E. M., 1954, Distribution of elements, in Geologic 

investigations of radioactive deposits, semiannual progress 

report, June 1 to November 30, 1954: U. S. Geol. Survey 

Trace Elements Inv. Rept. 490, U. S. Atomic Energy Comm. 

Tech. Inf. Service, Oak Ridge, Tenn., p. 58-78.

 1955, Occurrence of uranium in diatremes on the Navajo and Hopi Reservations, Arizona, New Mexico, and 

Utah: International Conference on Peaceful Uses of 

Atomic Energy, Geneva, Switzerland, August 8-20, 1955.

Sichel, H. S., 1952, New methods in the statistical evaluation of 

mine sampling data: Inst. Mining and Metallurgy Trans., 

v. 61, p. 261-288.

Snedecor, G. W., 1946, Statistical Methods: Ames, Iowa, Iowa 

State College Press.

Stieff, L. R., Stern, T. W., and Milkey, R. G., 1953, A preliminary 

determination of the age of some uranium ores of the 

Colorado Plateaus by the lead-uranium method : U. S. Geol. 

Survey Circ. 271.

Stieff, L. R., Stern, T. W., and Sherwood, A. M., 1955, Preliminary description of coffinite a new uranium mineral: 

Science, v. 121, p. 608-609.

U. S. Atomic Energy Commission, 1948, Guaranteed three year 

minimum price for uranium-bearing carnotite-type or 

roscoelite-type ores of the Colorado Plateau area: U. S. 

Atomic Energy Comm., Domestic Uranium Program, Circ. 3.

Waters, A. C., and Granger, H. C., 1953, Volcanic debris in 

uraniferous sandstones and its possible bearing on the 

origin and precipitation of uranium: U. S. Geol. Survey 

Circ. 224.

Waugh, A. E., 1943, Elements of statistical method: New York, 

McGraw-Hill Book Co., Inc.

Weeks, A. D., 1951, Red and gray clay underlying ore-bearing 

sandstone of the Morrison formation in western Colorado: 

U. S. Geol. Survey Trace Elements Memo. Rept. 251, U. S. 

Atomic Energy Comm. Tech. Inf. Service, Oak Ridge, Tenn.

 1953, Mineralogie study of some Jurassic and Cretaceous 

claystones and siltstones from western Colorado and eastern 

Utah: U. S. Geol. Survey Trace Elements Inv. Rept. 285, 

U. S. Atomic Energy Comm. Tech. Inf. Service, Oak Ridge, 

Tenn.

Weeks, A. D., and Thompson, M. E., 1954, Identification and 

occurrence of uranium and vanadium minerals from the 

Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B, p. 

13-62.

Williams, G. A., 1954, Stratigraphic studies, in Geologic investigations of radioactive deposits, semiannual progress report, 

December 1, 1953 to May 31, 1954: U. S. Geol. Survey Trace 

Elements Inv. Rept. 440, U. S. Atomic Energy Comm. Tech. 

Inf. Service, Oak Ridge, Tenn., p. 30-35.

Williams, K. T., and Byers, H. G., 1934, Occurrence of selenium 

in pyrites: Indus, and Eng. Chemistry, Anal., v. 6, p. 296-297.
Part 4. OCCURRENCE AND CHEMICAL CHARACTER OF GROUND WATER

IN THE MORRISON FORMATION

BY DAVID A. PHOENIX

CONTENTS

Abstract. ___._____. 

Introduction .._.__. 

Climate. _ ____.___. 

Morrison formation.

Page 

55 

55 

57 

57

Ground water in the area. 

Occurrence_ _ ______

Chemical character __

Conclusions. ________._-.

Literature cited._________

ILLUSTRATIONS

FIGURE 10. Index map of southwestern Colorado and southeastern Utah.____________

11. Hydrographs of water-level measurements in 10 diamond-drill holes___--_-

12. Bar graph showing analyses of ground water from the Morrison formation.

Page 

57 

57 

59 

64 

64

Page 

56 

59 

62

TABLES

TABLE 1. Average monthly and annual precipitation, in inches, at eight climatological stations in southwestern Colorado 

and southeastern Utah.__________________________-----.----------------------------------._--------_-_

2. Chemical analyses of ground water from wells, springs, and mines in the Morrison formation _______________

Page

57

60

ABSTRACT

Ground water in the Morrison formation of Late Jurassic 

age is in juxtaposition with deposits of uranium-vanadium 

ore minerals. This water is under water-table conditions in 

most of the region, but locally it is confined by impermeable 

clay strata. It is mostly derived from the infiltration of precipitation and surface runoff. Some water is contained in pore 

spaces in sandstone but most is in joints. Movement of this 

water is, at first, downward from the land surface, but bedding 

planes, mudstone seams, and other places where the rocks have 

a low permeability act as barriers and divert its path usually 

toward the direction of regional dip. Under water-table conditions the permeable sediments are usually saturated for a few 

inches to a few feet above each extensive barrier; under artesian 

conditions the ore-bearing sandstone is entirely saturated. The 

amount of water contained in the rocks is not great and its 

movement is slow. Evaporation from the land surface and 

transpiration by plants is sufficiently high to dispose of most 

of the discharge, but discharge is great enough to form springs 

and seeps locally.

Samples of ground water from the Salt Wash and Brushy 

Basin members of the Morrison formation have been analyzed 

to determine their chemical character and metal content. The 

ground water in the Salt Wash member is largely a bicarbonate 

solution with variable amounts of calcium and magnesium ions;

the ground water in the Brushy Basin member is either a 

sulfate or bicarbonate solution with sodium. The ground water 

from the Salt Wash and Brushy Basin members is generally 

weakly alkaline. In most samples uranium, vanadium, copper, 

lead, and selenium are present in amounts less than 1 ppm 

(part per million).

It is concluded that if ground water was responsible for introduction of the uranium and vanadium metals into the Salt 

Wash and if it was comparable to present ground water, it 

contained very small concentrations of the metal ions.

INTRODUCTION

This paper is concerned with the occurrence and 

chemical composition of ground water in the uraniumvanadium-bearing Morrison formation in southwestern Colorado and southeastern Utah (fig. 10). The 

study was undertaken to determine the influence similar ground water might have had on genesis of the 

ore deposits. Water-level measurements in numerous 

boreholes have been used to determine the mode of 

occurrence of ground water in ore-bearing sandstone 

of the Morrison formation. Chemical analyses of 

ground water from 23 sample points in the Morrison

55
56 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

38

CALAMITY MESA

Water-sample location and 

analysis number (shown 

on figure

FIGURE 10. Index map of southwestern Colorado and southeastern Utah, showing water-sample locations.
OCCURRENCE AND CHEMICAL CHARACTER OF GROUND WATER, MORRISON FORMATION 57

formation established its chemical characteristics and 

metal-ion content.

The number assigned to a well or spring in this report is both an identification and location number. It 

is based on the base and meridian system of the General Land Office. A typical number consists of three 

units. The first unit is the number of the township 

north or south of the base line. The second unit, 

separated from the first by a slant, is the number of 

the range east or west of the meridian. The third unit, 

separated from the other two units by a dash, lists 

the number of the section and is followed by a letter 

designating the quarter section, and finally a number to 

show the order in which the well or spring was recorded 

within the subdivision. The letters A, B, C, and D 

designate, respectively, the northeast, northwest, southwest, and southeast quarters of the section. On figure 

10, owing to space limitation, only that part of the 

number designating the subdivision of the section and 

the order in which the well or spring was recorded in 

that subdivision is shown.

CLIMATE

The climate of the region is semiarid, but the average 

annual precipitation differs from place to place. The 

average monthly and annual precipitation in different 

geographic and topographic localities is summarized 

in table 1. In Colorado the Norwood and Northdale 

stations are on upland mesas, the Paradox and Gateway 

stations are in the bottoms of steep-walled canyons. 

The station at Monticello, Utah, is on the east flank 

of the Abajo Mountains, and precipitation here is prob^ 

ably duplicated on the upland mesas east of the La Sal 

Mountains. Thompson, Utah, is on the eastern edge 

of the Green River desert; this region receives less 

rainfall than most areas in southwestern Colorado and 

southeastern Utah. The average annual precipitation 

in the area of detailed ground-water study (fig. 10) is 

probably not as great as that at the Norwood or Northdale stations or as little as that at the Gateway station.

The average precipitation in the area of detailed 

ground-water study is probably about 12 inches a year.

MORRISON FORMATION

The Morrison formation of Late Jurassic age is divided into two members: a lower member, the Salt 

Wash, and an upper member, the Brushy Basin. The 

Salt Wash member is composed of lenticular strata of 

sandstone and mudstone. Near the top of this member 

the strata of sandstone give the appearance of a persistent layer because the strata overlap. In detail, 

however, they are separated by beds of mudstone or 

local disconformities. The Brushy Basin member is 

varicolored bentonitic shale and mudstone interbedded 

with lenticular strata of sandstone and conglomeratic 

sandstone. Discrete strata of conglomeratic sandstone 

occur sporadically near the base of the member. The 

uranium-vanadium ore deposits are largely confined to 

the uppermost sandstone strata of the Salt Wash 

member.

Erosion has dissected the Morrison formation so 

that it now forms the midslopes of many mesas in 

southwestern Colorado and southeastern Utah. Outcrops of the Brushy Basin member are sparse except 

in the most arid regions. The beds are usually covered 

by landslide debris or talus blocks of more resistant 

and younger formations. Outcrops of sandstone in the 

Salt Wash member are resistant and they usually form 

cliffs and broad benches. Because the Morrison formation has been dissected by erosion and also broadly 

folded, outcrops of the ore-bearing sandstone of the 

Salt Wash member differ in altitude from area to area, 

so that the opportunity for ground-water recharge in 

the member depends on local structural and topographic features as well as on the average annual 

rainfall.

GROUND WATER IN THE AREA

OCCURRENCE

The main aquifer in the Morrison formation is composed of lenticular sandstone strata near the top of the

TABLE 1. Average monthly and annual precipitation, in inches, at eight climatological stations in southwestern Colorado and

southeastern Utah

[Data from U. 8. Department of Commerce, Weather Bureau. Record from establishment of station to 1954, Inclusive. Altitude In feet; precipitation In Inches]

Station

Moab, Utah. .............................

Paradox, Colo., 1 2ml. HE. ________

Gateway, Colo.,1 4 ml. NE _____ .

Altitude

6,036

7,066

4,125

5,150

7,017

6,842

5,300

4,903

Number of 

years

46

32

61

30

26

24

13

7

Jan.

1.05

1.25

.73

.59

1.00

1.10

.74

.93

Feb.

1.20

1.44

.69

.56

1.27

1.16

.53

.61

Mar.

1.08

1.57

.88

.73

1.45

1.31

.59

.67

Apr.

0.94

1.09

.73

.67

1.56

1.18

.74

.87

May

0.76

.87

.72

.51

1.10

.82

.57

' .82

June

0.68

.72

.43

.51

.96

.63

.64

.48

July

0.99

1.51

.81

.85

1.78

1.15

1.09

.90

Aug.

1.24

1.88

.79

.90

1.97

1.45

1.04

1.29

Sept.

1.47

1.62

.98

.97

1.52

1.91

.66

.89

Oct.

1.29

1.86

.99

1.10

1.32

1.52

1.14

1.33

Nov.

0.82

1.09

.65

.49

.82

1.35

.75

.59

Dec.

1.35

1.36

.86

.72

1.11

1 1Q

.82

.54

Average 

annual

12.77

16.26

9.26

8.60

15.86

14.20

8.71

9.57

 Averages based on Incomplete record, 1942-54, Inclusive. ' Averages based on incomplete record, 1947-54, Inclusive.
58 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Salt Wash member. This aquifer is locally called the 

ore-bearing sandstone because it contains most of the 

uranium-vanadium deposits in the Morrison formation. 

From a distance its appearance is often that of a continuous layer. Other strata of sandstone lower in the 

Salt Wash member as well as strata of conglomeratic 

sandstone at the base of the Brushy Basin member 

sometimes contain ground water, but generally they do 

not yield water to wells or springs.

Although ground water in the ore-bearing sandstone 

is confined in some areas, it is unconfmed in most of the 

region. It has been studied in the Calamity Mesa area, 

Mesa County, Colo. (fig. 10) in an area where the orebearing sandstone is exposed for about 2 square miles 

and where it has been explored by mine workings and 

cut by several hundred diamond-drill holes. Several 

months after drilling had stopped the depth to water 

was measured in 246 uncased diamond-drill holes. 

These drill holes are distributed throughout the Calamity Mesa area and they penetrate the ore-bearing sandstone as well as several feet of mudstone below. Water 

was encountered in all but 20 of the diamond-drill 

holes. In drill holes near the central part of the mesa, 

water levels, in places, stand 20 or 30 feet above the 

base of the ore-bearing sandstone; in drill holes nearer 

the edge of the mesa, water levels are only 2 or 3 feet 

above the base of the ore-bearing sandstone, and those 

that do not contain water are along the edge of Calamity Mesa where the ore-bearing sandstone is exposed 

as a cliff and where it is jointed.

Confined ground water has been found in synclinal 

structures where erosion has not destroyed the nearly 

impermeable cover of the Brushy Basin member. Diamond-drill holes to the ore-bearing sandstone have encountered water under sufficient hydrostatic pressure 

to flow at the land surface near Uravan, Montrose 

County, Colo., near Slick Rock, Montrose County, 

Colo., near La Sal, San Juan County, Utah, and 6 

miles west of Blanding, San Juan County, Utah. In 

these places the lenticular ore-bearing sandstone is 

probably saturated, and the lenses are sufficiently connected hydraulically to be capable of transmitting 

ground water to drill holes for at least 2 or 3 miles from 

the nearest recharge area. Flows of 30 gpm at the land 

surface and pressures sufficient to raise water levels 

20 feet above the land surface have been recorded in 

the La Sal Creek and Uravan areas. However, the 

amount of ground water flowing from these drill holes 

and the hydraulic pressure usually has decreased substantially within a few months after the hole was 

drilled. This indicates that the beds are not very permeable and, hence, that movement of water from the 

outcrop to the drill holes is slow.

Some of the characteristics of ground-water occurrence were determined from a contour map of the water 

table based on the measured water levels referred to a 

sea-level datum. The contour map indicates that 

ground water in the ore-bearing sandstone is perched 

on mudstone at the base of the ore-bearing sandstone 

and that the water table has a general slope of about 

3° SW., approximately the same as the dip of the rocks. 

However, the contact between the ore-bearing sandstone and the mudstone below is an irregular surface 

with locally as much as 6 feet of relief. The water-table 

map is in places a subdued replica of a map of this 

surface. The direction and rate of ground-water movement probably are controlled in part by irregularities 

in the contact. The "lows" in the contact may act as 

"channelways" along which the greater amount of the 

present day ground water moves.

The measurement of water levels was sometimes 

hindered by the presence of moisture on the walls of the 

diamond-drill holes. This moisture persisted throughout the 21 months of observation and probably is 

ground water. Where it was detected, the upper level 

of moisture always was above a lenticular stratum of 

mudstone or above some similar impermeable zone contained within the ore-bearing sandstone. It is difficult 

to evaluate the influence that leakage from these local 

zones of saturated rocks may have had on water-level 

measurements in the diamond-drill holes, for the rate of 

leakage could not be determined.

The movement of water into the rocks is at first downward from the surface. A large part of this water gains 

entry to the ore-bearing sandstone through joints, but 

some probably moves through the intergranular interstices in the more permeable places. The portion of this 

water that exceeds soil-moisture requirements is free 

to percolate to the water table and migrate laterally in 

the direction of the hydraulic gradient as ground water. 

The path of ground-water movement generally follows 

the direction of regional dip, but in detail it is devious, 

for the ore-bearing sandstone contains numerous barriers in the form of lenticular clay strata, local disconformities, and bedding planes. The ore-bearing sandstone may thus be saturated above each impermeable 

zone for a few inches or even a few feet and in more 

than one place. It is believed that ground water 

"cascades" from the extremity of each lenticular barrier to eventually reach the impermeable mudstone at 

the base of the ore-bearing sandstone.

The water levels in 22 of the holes were measured at 

monthly intervals from late in 1949 through July 1951. 

The monthly measurements of 10 of these holes are 

plotted on figure 11 to show the water-level fluctuations. 

Although the water levels in some of the holes, notably 

CA-125, CA-501, CA-505, and CA-678, show fluctuations through the period of observation, water in other
OCCURRENCE AND CHEMICAL CHARACTER OF GROUND WATER, MORRISON FORMATION 59

CA-678

CA-658

CA-505

CA-527

DIAMOND-DRIU\

HOLE CA-501 \

\

CA-165

CA-164

CA-125

CA-225

CA-550

\

\

Plugged

Piomuo lil. Hydrographs of water-level measurements in 10 diamonddrill holes, Calamity Mesa area, Mesa County, Colo., November 1949 

to July 1051.

holes shows little or no fluctuation. These data suggest 

that the water in the sandstone strata is being recharged 

locally by the infiltration of surface water and precipitation, probably introduced into the sandstone through 

fractures that are open to the surface. The lack of response of the water level in other holes to seasonal 

variations in precipitation suggests that sandstone in 

the immediate vicinity of these holes is not fractured 

and has a relatively low permeability; in places pore 

spaces in the ore-bearing sandstone may be plugged 

with drill mud.

Discharge of ground water from the ore-bearing 

sandstone is by springs or seeps, by evaporation, and by 

transpiration. The fact that some drill holes in the 

ore-bearing sandstone are "breathing" air suggests that 

locally there is atmospheric circulation in the rocks; 

therefore, some ground water is probably lost by evaporation Avithin the rocks. In places, the roots of juniper 

and pinon and probably the roots of other plants as 

well reach several tens of feet into the rocks and these 

plants act as miniature pumps to discharge ground 

water. Along the edge of Calamity Mesa plant roots 

penetrate joints to depths of about 20 feet below the

468652 58 5

top of the ore-bearing sandstone, but mine workings in 

the interior of the mesa have encountered roots along 

prominent joints to a depth of about 50 feet. The 

amount of ground water discharged from within the 

ore-bearing sandstone by plant transpiration is probably small, except near the outcrop or where the rocks 

are jointed and plant roots can easily penetrate to the 

zone of saturation or to its capillary fringe. Groundwater discharge is most active along the downdip or 

southwest edge of the mesa where the base of the orebearing sandstone is exposed. The total amount of 

ground water discharged from the Calamity Mesa area 

cannot be measured but it is probably only a small 

fraction of the average annual rainfall.

CHEMICAL CHARACTER

The chemical analyses of 23 samples of ground water 

from the Morrison formation are shown in table 2. 

These samples were collected from mines, springs, and 

wells in the Salt Wash and Brushy Basin members of 

the Morrison formation. All samples from the Salt 

Wash member were collected near ground known to 

contain uranium-bearing minerals. Samples from the 

overlying Brushy Basin member presumably had not 

percolated through or near rocks containing these 

minerals.

The milligram equivalents, or reacting values (Palmer, 1911, p. 5) called equivalents per million (epm) 

in this report of the soluble ions, have been computed 

for all the analyzed samples. The equivalents per million for 22 of the samples are shown graphically on 

figure 12 and indicate the chemical character of the 

water from each locality at the time the water was 

sampled for analysis. Of the 22 samples, 12 are classed 

as calcium, magnesium bicarbonate water; 3 as calcium, 

magnesium sulfate water; 3 as sodium sulfate water; 

and 4 as sodium bicarbonate water. These differences 

in character are probably determined in part by the 

duration of time the ground water has been in contact 

with the rocks, by the composition and physical properties of the rocks, by the presence or absence of soluble 

salts in the paths of ground-water movement, and by the 

degree to which the solution has been concentrated by 

evaporation and plant transpiration. For sample 50/ 

18W-9A (table 2), the total iron, sum of total dissolved 

solids, and tons per acre-foot appear to be questionable 

determinations and their application should be used 

with reservation. The sample was turbid when collected and the iron probably includes that from ferruginous sediments. Although total iron should include iron both in solution and precipitated, it is based 

on the premise of a clear sample at the time of collection. This, however, does not disqualify it as a calcium, 

magnesium sulfate water.
60 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 2. Chemical analyses, in parts per million, of ground water 

[Analyses for U, V, Cu, Pb, and Se, and of sediment, by George J. Petretlo or Lewis F. Rader, Jr., U. 8. Geol. Survey.

Field data (U. S. G. S.)

Field location No. i

Salt 

Lake

City

lab. No.

Denver

lab. No.

Source of sample

Date of 

collection

Silica

(SiOs)

Iron (Fe)

In

solution

Iron 

(Fe)

total

Calcium

(Ca)

Magnesium

(Mg)

Sodium

(Na)

Potassium

(K)

Manganese 

(Mn)

Bicar- bonate 

(HCOs)

Sulfate

(S04)

Chloride

(Cl)

Samples from the Brnshey

60/18W-9Di

49/17W-6Di

47/17W-27Ai

44/18W-33C1

43/19W-32Ci

42/18W-6Ai

<un9

6322

6317

6318

6319

6320

4/51

3/51.. 

1/51 

Spring.

4/9/51

3/31/51

3/23/51

3/24/51

3/24/51

3/24/51

15

9.6

15

9.9

16

20

0.01

.07

.03

.04

.05

.07

0.18

.07

41

5.8

97

41

88

98

36

12

104

13

34

103

123

847

318

360

203

118

9.6

11.0

16.0

8.8

4.4

6.6

0.00

.00

.00

.00

.00

.29

«509

'1,900

354

528

506

554

63

296

798

435

212

158

24

55

171

61

113

198

Samples from the

50/17W-19Di

60/18W-9Ai

50/18W-9Ci

60/18W-llCi

60/18W-12Ci

60/18W-12Di

49/17W-6B!

47/17W-15Bi

47/17W-27Di

47/17W-29Ai

47/17W-29Aj

43/18W-29Ci

37/21E-10Bi

36/21E-26Bi

28/23E-3Ai

23/22E-6Bj

22/22E-33Ai

3812

3811

3810

4536

3813

4537

6321

4686

4685

4687

4688

4733

4735

4734

477Q 'xl I V

4777

4778

Threshold of detection.

B-2

B-410

B-17 »

B-3

B-5

B-l

B-6

2/51

B-8

B-7

B-10

B-9

B-ll

B-13

B-12

B-16

B-15

B-14

Outlaw Mesa; dug well.

Maverick mines area, Matchless mine; sump.

Maverick mines area; spring.

Calamity Mesa; spring.

Outlaw Mesa; spring.

Outlaw Mesa; Ronnie No. 1

mine; underground spring.

Blue Mesa; spring.

Long Park area; spring.

Long Park, Long Park No. 10

mine; ore chute.

Long Park, Henry Clay mine;

underground spring.

Long Park, Henry Clay mine;

sump.

Spud Patch, May Day mine;

sump.

Blanding mines area, East

Bank mine; sump.

Blanding mines area; AEC

diamond-drill hole No.

BA-6. Yellow Circle mine area;

spring.

Yellow Cat mines area, Telluride No. 18 mine; sump.

Yellow Cat mines area, Cactus

Rat mine; 20 foot adit.

11/15/49

11/16/49

7/29/50

11/16/49

4/18/50

11/16/49

4/19/50

3/31/51

5/28/50

5/28/50

5/27/50

5/27/50

6/26/50

6/24/50

6/24/50

6/28/50

6/29/50

6/29/50

23

1222

15

16

20

13

11

12

13

14

10

17

13

13

12

11

10

0.10

.07

.05

.03

.05

.03

.02

.07

.82

.09

.11

.04

.11

.02

.03

.20

.03

0.16

99

.12

.04

.06

.19

1.24

.15

.26

.25

84

624

66

62

82

62

30

50

62

86

59

64

116

77

38

89

101

88

389

50

57

49

35

37

67

33

43

43

16

114

53

59

20

15

65

58

129

33

32

11

68

92

17

19

20

27

179

128

10

129

343

7.6

13.0

4.8

4.2

3.0

8.0

8.7

3.2

5.9

6.1

4.8

10.0

6.4

4.6

6.1

3.4

0.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00

620

479

483

408

417

344

"391

425

245

406

317

226

480

378

18351

202

205

105

2,310

119

65

59

23

32

192

77

43

48

42

631

353

28

388

806

64

165

69

40

36

14

18

33

18

34

37

30

91

27

24

13

47

> Field No., example: 50/17W-19D, indicates T. 50 N., R. 17 W., sec. 19, and 

the quarter section (A, B, C, or D, lettered counterclockwise from the NEH).

' Method of determination: Fluorimetric.

« Method of determination: Colorimetric.

< Noncarbonate hardness or "permanent" hardness refers to hardness exceeding 

the equivalence with carbonate and bicarbonate. The two hardnesses are, by 

common practice, expressed as "Hardness as CaCOj."

 Percent sodium: Obtained by dividing the milligram equivalents of sodium 

by total milligram equivalents of cations and multiplying by 100.

aIncludes 8 ppm CO».

i gpm: Gallons per minute.

8 Includes 311 ppm COs.

« See following table for analyses, in percent:

Lab. No.

B-1........ ...

B-2 ...

B-3... 

B-4 . 

Precipitate

(ppm)

5.4

2.2

7.7

39.5

UOs

0.05

.11

.1

6.4

VzOs

1.7

1.4

1.8

14.4

FejOs*

4.9

9.4

1.7

3.9

CaO**

1.0

5.6

.2

.2

K2 0**

1.4

2.5

.5

1.3

 Method of determination: Colorimetric.

 'Method of determination: Flame photometric.
OCCURRENCE AND CHEMICAL CHARACTER OF GROUND WATER, MORRISON FORMATION 61

from wells, springs, and mines in the Morrison formation

Analyses for other constituents by E. L. Singleton, W. M. Webster, and E. F. Williams, U. S. Oeol. Survey]

Fluorlde

(F)

Nitrate

(NO.)

Boron

(B)

Uranium (U)»

Vanadium (V)» Copper

(du>

Lead

(Pb)»

Selenium

(Se)

Dissolved

solids

Residue

on 

evaporation

at 180°

C.

(ppm)

Tons 

per

acreft

Hardness <

as CaCOi

Calcium

magnesium

Noncarbonate

Other data

Specific

conductance

(Micromhos

at 25°

0.)

Percent

sodi- um'

(?aboratory)

Remarks

Baaln shale member

0.7 

2.6

.7

1.0

.3 

.3

3.3 

3.8

.2

.3

.1 

14.0

0.03 

.40

.06

.07

.09 

.03

0.05 

.06

.02

0.09 

.30

.12

0.00 

.05

.00

0.00 

.00

.00

0.05 

<.05

<.05

566 

2,180

1,690

1,190

920 

989

0.77 

2.96

2.30

1.62

1.25 

1.35

250 

64

670

156

360 

668

0 

0

380

0

0 

214

908 

3,270

2,360

1,730

1,420 

1,610

50 

96

50

82

55 

27

8.1 

9.4

8.0

8.1

7.9 

7.7

Basal conglomerate of Brushy Basinmember. Yield<l gpm.' Temp. 54° F. 

Sandstone of the Brushy Basin member. Yield <1 gpm. Temp. 43° F. 

Field pH 9.

her. Temp. 38° F. Field pH 6-7.

her. Field pH 7. Temp. 42° F. 

Basal conglomerate of Brushy Basin 

member. Field pH 7. Temp. 43° F.

Brushy Basin (?) member. Field 

pH7.

Salt Wash sandstone member

0.7

.9

.6

.5

.5

.3

.4

.2

.4

.3

.3

.4

.4

.2

.4

.4

.3

0.2

('»)

.9

4.7

5.6

4.1

4.1

1.2

16.0

6.1

6.2

1.7

1.9

.2

5.4

2.6

6.8

0.04

(")

.08

.06

.02

.04

.03

.02

.00

.01

.02

.04

.00

.02

.04

.02

0.0

18.0

.82

.1

.3

.2

.0

.02

.6

.3

.2

.6

< !

8.7

<1

.2

.8

.2

.01

<0.1

95.0

11.8

<.l

<.l

<.l

.1

.16

<.l

1.2

<.l

<.l

<1

22.8

.1

<-l

<.l

< !

.01

0.06

.01

.00

.03

.00

.07

.00

.00

.00

.00

.00

.00

.00

.00

.00

.00.

.00

.00

.01

0.03

.03

.00

.17

.00

.06

.00

.00

.00

.00

.00

.00

.33

« nn \j\j

.00

.50

.04

.02

.01

0.00

12.50

3.13

.00

.00

.00

.00

<.05

.00

.00

.00

.00

.00

.00

.00

.00

1.00

7.87

.05

743

3,700

690

484

494

335

401

666

360

451

386

314

1,400

844

361

759

1,430

1.01

5.03

.94

.66

.67

.46

.55

.91

.49

.61

.52

.43

1.90

1.15

.49

1.03

1.94

572

2,910

345

389

406

298

227

400

290

392

324

226

758

410

338

304

314

64

2,510

0

54

64

16

0

62

89

59

64

40

364

100

38

138

146

1,230

4,410

1,100

820

807

584

669

1,030

576

740

655

623

1,990

1,250

647

1,100

2,030

20

4

44

15

14

7

38

33

11

9

12

20

34

40

6

47

70

7.5

6.8

8.0

7.5

7.7

7.9

8.1

7.9

7.7

7.7

7.7

7.7

7.4

7.7

8.3

7.9

7.9

Ore-bearing sandstone, 30 feet downdip from mined ore body. Sediment

analyzed. 0

Seep from mineralized sandstone. B-4

sediment analyzed.6

Ore-bearing sandstone(?). Sediment

analyzed.'

Base of ore-bearing sandstone. Yield

1 gpm. Temp. 50° F.

Ore-bearing sandstone 100 feet downdip from mined ore body. Sediment

analyzed.'

Top of ore-bearing sandstone. Yield

100 gpd. 1 ' Temp. 50° F.

Ore-bearing sandstone, 2,000 feet downdip from nearest known ore body.

Yield <1 gpm. Field pH 6."

Base of ore-bearing sandstone. Yield

84 gpd. Temp. 52° F.

Ore-bearing sandstone. Yield <25

gpd. Temp. 63^° F.

M ineralized sandstone. Yield 120 gpd.

Temp. 45^° F.

Mine sump.

Mineralized sandstone. Temp. 44° F.

Field pH 6. Mine sump. Temp. 47° F. Field

pH 7.

Ore-bearing sandstone. Yield 15 gpm.

Temp. 56° F. Field pH 6.5.

Mineralized sandstone. Yield 50 gpd.

Temp. 58° F.

Mineralized sandstone. Yield 300 gpd.

Temp. 50° F.

Ore-bearing sandstone, 60 feet below

mineralized sandstone. Temp. 56° F.

Field pH 6.5-7.

10 Sample collected from sludge pit In drift. Water contaminated by drill 

sludge. Source: Underground seep from face of ore.

11 Sample collected from flooded winze. Water uncontamlnated by drill sludge. 

Source: Underground seep from face of ore.

" On addition of HC1, yellow color developed, but faded after standing. 

M Deep-blue color developed on addition of phenodlsulfonic acid to evaporated

sample. Color disappears with addition of HjO. Deep yellow developed with

» Unable to detect green-yellow color of boron. 

" gpd: Gallons per day.

16 Contains 14 ppm COs.

17 All field pH determinations were by "Hydrion" paper. 

" Contains 7 ppm COs.
62 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

CALCIUM

MAGNESIUM 47/17,,- 

BICARBONATE 

WATER

'4T/I7W-!

WATER BEARING MEMBER OF 

THE MORRISON FORMATION

TRACE ELEMENTS (PARTS PER MILLION) 

\) V Cu Pb SO

pH

EXPLANATION

Blcorbonatt Sulfote

SALT WASH

a

Sodium SALT WASH

43/I8W-29C,

BRUSHY BAS1N

9/23E-3A,

*£SM ' 50/I8W-9A, 

WATER

NOT DETERMINED

i>sSm??,£,yA!ffSS*ss???^J^&9^ .

'///////y//////////////^^^^

Compiled from analyses by C. S. Howard, 

0. J. Petretie, and L. F. Rader

FIGURE 12. Bar graph showing analyses of ground water from the Morrison formation in equivalents per million and the concentration of

trace elements in parts per million. Sample locations shown on figure 10.

Water from the Brushy Basin member has a high copper, and lead at the threshold of detection is about

concentration of sodium ions, whereas, water from Salt 0.01 ppm, whereas, the concentration of selenium at

Wash sandstone has a high calcium- and magnesium- the threshold of detection is 0.05 ppm. Where 0.00 ppm

ion concentration. This difference in chemical quality is reported for selenium, it indicates less than 0.05 ppm;

probably is due largely to gross differences in mineral- for the other metals 0.00 ppm indicates a concentration

ogic composition between the Salt Wash and Brushy of less than 0.01 ppm. As a general rule, these metals

Basin sedimentary rocks. were found in amounts of less than 1 ppm, and some

The uranium, vanadium, copper, lead, and selenium are present in such small amounts that they are just

content of 19 of the 22 water samples is also shown on above the threshold of detection as determined by quanfigure 12. The concentration of uranium, vanadium, titative methods used at the time these solutions were
OCCURRENCE AND CHEMICAL CHARACTER OF GROUND WATER, MORRISON FORMATION 63

analyzed. Although the concentration of these metals 

differed within these limits, the amounts present do not 

seem to correspond to the variations of total dissolved 

solids in the ground waters.

Lead was detected in trace amounts in some of the 

samples collected from the ore-bearing sandstone. At 

the localities from which these waters were collected 

this metal is known to occur in minor amounts in the 

uranium-vanadium ore.

Selenium and copper, common in many ore deposits 

in the Salt Wash member, were detected in water from 

the Brushy Basin member, even though this member 

contains very few ore deposits.

Fluoride in ground water from ore-bearing sandstone 

in the Salt Wash member is usually present in amounts 

ranging from 0.20 ppm to 0.90 ppm. However, samples 49/lTW-GDi and 44/18W-33Ci, collected from the 

Brushy Basin member, have 2.60 ppm and 1.00 ppm 

fluoricle, respectively. The significance of these differences cannot be determined from the few analyses 

available.

Detectable amounts of boron are present in most of 

the ground waters sampled for analysis. The average 

concentration of boron in all the samples analyzed is 

0.05 ppm.

Uranium and vanadium were detected in all the water 

samples that were analyzed for these metals. The 

greatest amount of uranium and vanadium was detected in ground water from mine sumps (samples 50/ 

ISW-OAi and 37/21E-10BO- Either the metals in 

these samples were present as colloids or else the ore 

minerals from these mines were more soluble in this 

ground water than elsewhere. It might be significant 

that these water samples have a higher magnesium-ion 

and hydrogen-ion concentration than those from any 

other locality. It is also suggested that the oxidation 

potential of these waters might differ from the ordinary 

ground-water solution from the Salt Wash member. 

In the remaining 17 samples, none contained uranium 

or vanadium in amounts greater than 1.20 ppm, and 

the median amount of uranium or vanadium in the normal ground water is about 0.10 ppm. As observed by 

Phoenix and reported by Judson and Osmond (1955), 

these amounts are appreciably higher than can be expected from nonmineralized areas.

Observed secondary uranium and vanadium minerals 

on fractures suggest that the concentration of the uranium and vanadium ions in the ground water might bear 

some spatial relationship to the ore deposits. To test 

this, sample 49/17W-6B]. was collected at a spring issuing from ore-bearing sandstone of the Salt Wash at a 

point approximately 2,000 feet downdip from the nearest ore body, and sample 47/17W-29A! was collected

from a mine stope in the immediate vicinity of sandstone that contained carnotite ore. The first sample 

contained 0.02 ppm uranium and 0.16 ppm vanadium, 

whereas, the second contained 0.20 ppm uranium and 

<0.10 ppm vanadium. The higher concentration of the 

uranium ions in the sample of ground water collected 

near an ore body suggests a difference that may be directly related to the proximity of the deposits.

It was expected that there might be a major difference 

in the uranium and vanadium content between the 

waters collected from the Salt Wash member and those 

collected from the overlying Brushy Basin member, as 

the Salt Wash contains practically all the ore deposits 

found in the Morrison formation. Differences, however, 

are not too striking. Three water samples from the 

Brushy Basin average 0.04 ppm uranium and 0.17 ppm 

vanadium. Samples of ground water from the Salt 

Wash and from the Brushy Basin together, excluding 

samples reported from ore or from mine sumps, and exclusive of those for which a "less than" value is given, 

have the following average content: 0.24 ppm uranium 

in 5 samples (50/18W-9d 50/18W-11C1? 50/18W12d, 49/17W-6Bl5 and 47/17W-27DO, and 0.45 ppm 

vanadium in 4 samples (49/17W-6B1? 47/l7W-27D1? 

49/17W-6Di, and 43/19W-32d).

The relation of metal concentration to the hydrogenion concentration in the ground-water solutions cannot 

be determined with certainty from the few analyses 

available. Within the determined limits of hydrogenion concentration that is, a pH of 6.8 to 9.4 uranium 

concentrations are between 18.9 ppm for the most acid 

solution to 0.06 ppm for those that are most alkaline; 

whereas, vanadium concentrations are between 95 ppm 

for the most acid solutions to 0.3 ppm for the most 

alkaline. These data would suggest a rather direct correlation with pH and the solubility of the uranium and 

vanadium. However, as Garrels (1953; 1954, written 

communication) has shown, the stability of uranium 

and vanadium in aqueous solutions is not only dependent upon the pH of the solution, but upon the Eh 

of the solution and upon the oxidation state of the uranium and vanadium compounds as well. Unfortunately, it has not been possible to measure Eh in natural 

solutions with consistent results, and thus no direct correlation between the amount of the uranium and vanadium in the ground-water solution and pH alone should 

be made until more data become available. The water 

samples that contain high concentrations of uranium 

and vanadium were collected from places where ores are 

undergoing active oxidation, thus giving maximum opportunity for solution of unstable phases formed during the oxidation process.

The efflorescent coatings of bicarbonate and sulfate
64 GEOCHEMISTKY AND MINERALOGY, COLOKADO PLATEAU URANIUM ORES

salts around the rims of springs or seep outlets distant 

from known ore deposits are not radioactive. There is 

thus no indication that carnotite, or some similar uranium mineral, is being precipitated from the normal 

ground water at these places. On the other hand, the 

carnotite observed coating many fracture surfaces in 

the ore-bearing sandstone near the ore deposits above 

the present water table, as well as the efflorescent coatings-of uranium and vanadium salts on mine walls, 

show that uranium and vanadium are migrating. Uranium minerals coating fractures may have formed from 

earlier ground water. It also seems likely that capillary 

water in the zone of aeration dissolves previously deposited minerals and carries uranium and vanadium 

only a short distance before precipitating them as salts 

on the mine walls.

CONCLUSIONS

Ground water is contained in sandstone strata of the 

Morrison formation that are ore bearing. This water 

is usually perched on mudstone and is free to fluctuate 

with seasonal variations in precipitation. Locally, 

where structural conditions prevent drainage, ground 

water is confined and the sandstone strata are saturated. 

The occurrence and chemical character of ground water 

in the Morrison formation are thus dependent upon a 

number of factors including variation in climate, the 

geomorphic history of the region, and upon the structure and composition of the rocks.

The analyses of the samples of ground water collected 

from the Salt Wash and Brushy Basin members of

the Morrison formation probably represent the chemical 

character of the ground water contained in these rocks. 

The ground water in the Salt Wash is a weakly alkaline bicarbonate solution with variable amounts of calcium and magnesium ions; the ground water in the 

Brushy Basin is likewise weakly alkaline but is either 

a sulfate or bicarbonate solution with sodium.

The ground water in the Salt Wash, regardless of 

its chemical character, generally contains less than 1 

ppm of uranium, vanadium, copper, lead, and selenium 

ions. Uranium, vanadium, and selenium ions, in 

amounts of less than 1 ppm, probably are also typical 

constituents of ground water in the Brushy Basin. The 

significance of the amounts of these ions present in 

ground water in both Salt Wash and Brushy Basin 

members in regard to spatial relationships to the ore 

bodies cannot be determined with certainty from the 

number of samples analyzed, but significant differences 

may exist. If the fluid responsible for introduction of 

the uranium and vanadium metals into the Salt Wash 

was comparable to the recent ground water, it contained 

very small amounts of the metal ions.

LITERATURE CITED

Garrels, R. M., 1953, Some thermodynamic relations among the 

vanadium oxides and their relation to the oxidation states 

of the uranium ores of the Colorado Plateau: Am. Mineralogist, v. 38, p. 1251-1265.

Judson, Sheldon, and Osmond, J. K., 1955, Radioactivity in 

ground and surface waters: Am. Jour. Sci., v. 253, p. 104-116.

Palmer, Chase, 1911, The geochemical interpretation of water 

analyses: U. S. Geol. Survey Bull. 479.
Part 5. SUMMARY OF THE ORE MINERALOGY

By ALICE D. WEEKS, ROBERT G. COLEMAN, and MARY E. THOMPSON

CONTENTS

Abstract_ ________________________________________

Introduction _______________________________________

Classification _ ____________________________________

Mineralogy of the primary unoxidized ores_____________

Vanadiferous ores.______________________________

Vanadium-uranium ratio greater than 15:1__

Vanadium-uranium ratio between 15:1 and 1:1_

Nonvanadif erous ores ___________________________

Oxidation sequence and mineralogy of vanadiferous uranium ores__________---____--_--__--_-------_---_-

Early stage of oxidation__-_-_____-_____-_____-_-

Corvusite ore, partly oxidized.__________-___---__

Carnotite ore, highly oxidized.____-____--__--_-__

Mineralogy of oxidized nonvanadiferous uranium ores___ 

Uranium minerals________________-----___---_-

Secondary minerals of copper and other metals.____

66

66

66

68

68

68

69

70

71

7 1

71

72

73

73

74

Page

Mineralogy of oxidized nonvanadiferous uranium ores 

Continued

Associated minerals. ____________________________ 74

Relation of oxidation to water saturation of ore. _______ 74

Unoxidized ore in wet mines at or close to the water

table _ __ _______ ____ __ ___--_-_---___-._ 75

Partly oxidized deposits, above main water table but

in protected locations where some moisture is held. 75 

Dry mines with oxidized vanadif erous ore _ _______ 75

Oxidation in place__-_--__-__-______-_--____ 75

Modification during oxidation ________________ 76

Ore sandstone directly at the surface of mesas__ 77 

Relative stability and size of oxidized deposits _ _______ 77

Secondary enrichment__--__---_--____---_-___------- 77

Time and depth of oxidation. ________________________ 78

References ____ _ ____ .___ __ ___--__--__-_-__-_- 78

ILLUSTRATIONS

PLATE 1. A, Primary vanadiferous ore, Fall Creek mine, Placerville, Colo. B, Primary vanadiferous ore, Garfield mine, Rifle, 

Colo. C, Primary vanadium-uranium ore, Mi Vida mine, Utah. D, Pyrite associated with primary ore, Marshbank Canyon mine, Temple Mountain, Emery County, Utah____________________________________________

2. A, Partly oxidized uranium-vanadium ore, Mi Vida mine, Utah. B, Primary uranium-vanadium ore, Oversight 

mine, Montrose County, Colo. C, Primary uranium-vanadium ore, Mi Vida mine, Utah. D, Primary nonvanadiferous ore, Delta mine, Emery County, Utah__________.___________________________________ ____

Page

74

75

TABLES

TABLE 1. Uranium minerals found on the Colorado Plateau___________________________________________

2. Vanadium minerals found on the Colorado Plateau____-_____-__-___________---_-_---____.___

3. Sulfides, arsenides, selenides, and other accessory metallic minerals found on the Colorado Plateau.

4. Chemical analyses of roscoelite----_---_--_--_--_____-_____-________________-______________

5. Analyses of uraninites___---_-----_------_-____--______________________---_____________.

65

Pacre

67

68

68

69

69
66 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ABSTRACT

In the Colorado Plateau uranium has been produced chiefly 

from very shallow mines in carnotite ores (oxidized vanadiferous uranium ores). Recent deeper mining has penetrated 

black unoxidized ores in water-saturated rocks, and extensive 

exploration has discovered many deposits of low vanadiferous 

to nonvanadiferous ores. The uranium ores include a wide 

range from highly vanadiferous to nonvanadiferous and from 

as much as 1 percent to a trace of copper, and they contain a 

small amount of iron and traces of lead, zinc, molybdenum, cobalt, nickel, silver, manganese, and other metals.

Recent investigation indicates that the carnotite ores have 

been derived by progressive oxidation of primary (unoxidized) 

black ores that contain low-valent uranium and vanadium oxides 

and silicates. The uranium minerals uraninite and coffinite are 

associated with coalified wood or other carbonaceous material. 

The vanadium minerals, chiefly montroseite, roscoelite, and 

other vanadium silicates, occur in the interstices of the sandstone and in siltstone and clay pellets as well as associated with 

fossil wood. Calcite, dolomite, barite and minor amounts of 

sulfides, arsenides, and selenides occur in the unoxidized ore.

Partly oxidized vanadiferous ore is blue black, purplish 

brown, or greenish black in contrast to the black or dark-gray 

unoxidized ore. Vanadium combines with uranium to form 

rauvite. The excess vanadium is present in corvusite, f ernandinite, melanovanadite and many other quadrivalent and quinquevalent vanadium minerals as well as in vanadium silicates. 

Pyrite and part or all of the calcite are replaced by iron oxides 

and gypsum.

In oxidized vanadiferous uranium ores the uranium is fixed 

in the relatively insoluble minerals carnotite and tyuyamunite, 

and the excess vanadium commonly combines with one or more 

of the following: Calcium, sodium, potassium, magnesium, aluminum, iron, copper, manganese, strontium, or barium, or rarely 

it forms the hydrated pentoxide. The relatively stable vanadium silicates are little affected by oxidation.

The unoxidized nonvanadiferous ores contain uraninite and 

coffinite in close association with coalified wood and iron and 

copper sulfides, and traces of many other sulfides, arsenides and 

selenides. The oxidized nonvanadiferous ores differ from the 

vanadiferous ores because, in the absence of vanadium to form 

a uranyl vanadate complex, a great variety of secondary yellow 

and greenish-yellow uranyl minerals are formed. The uranyl 

sulfates and carbonates are more common than the oxides, phosphates, arsenates, and silicates. Because the sulfates and carbonates are much less stable than carnotite, the oxidized nonvanadiferous ores occur only as halos around cores of unoxidized ore and do not form large oxidized deposits close to the 

surface of the ground as do carnotite ores.

Oxidation has taken place since the lowering of the water 

table in the present erosion cycle. Because of local structures 

and the highly lenticular character of the fluviatile host rocks 

perched water tables and water-saturated lenses of sandstone 

are common high above the regional water table. Unoxidized 

ore has been preserved in these water-saturated rocks and the 

boundary between oxidized and unoxidized ore is very irregular.

INTRODUCTION

Vanadiferous uranium ores were discovered in sandstones in western Colorado in 1898 and carnotite, a 

yellow secondary uranyl vanadate mineral, was named 

the following year (Friedel and Cumenge, 1899) 5 At

first the ores were mined chiefly for radium, later for 

vanadium, and recently for uranium (Coffin, 1921; 

Fischer, 1942; Fischer, 1950). For many years the production was from oxidized ore in shallow mines, and 

the Colorado Plateau ores became characterized as 

carnotite ores (Hillebrand and Ransome, 1905; Hess, 

1933). Recent extensive exploration and deeper 

mining, in many places in the Colorado Plateau, have 

penetrated black unoxidized vanadiferous ore below 

perched water tables or close to the main water table. 

Also nonvanadiferous ores, both oxidized and unoxidized, have been found. Much of the present 

uranium produced in the Plateau is from relatively unoxidized, or primary, ore. The deposits are now generally referred to as sandstone-type uranium deposits 

rather than carnotite deposits.

The chief uranium-producing beds in the Colorado 

Plateau are in the Morrison formation of Late Jurassic 

age and contain vanadiferous uranium ore. Important 

production also comes from the Shinarump member 

and other basal sandstones of the Chinle formation of 

Late Triassic age. These contain vanadiferous uranium 

ore in Monument Valley, Ariz.; Big Indian Valley, 

San Juan County, and the Temple Mountain area, 

Emery County, Utah; copper-uranium ore in the White 

Canyon and Red Canyon areas of San Juan County, 

Utah; and uranium ore in other areas of Utah and 

Arizona. The Todilto limestone of Late Jurassic age 

on the northeast and east of the Zuni uplift in New 

Mexico contains uranium and a little vanadium. The 

Entrada formation of Late Jurassic age along the 

eastern margin of the Plateau in Colorado contains 

vanadium ore with low uranium content. Both a geographic and stratigraphic variation in metal ratios 

occurs in the Plateau ores (Part 3 of this volume).

Thanks are due many of our colleagues on the Geological Survey especially the authors of the other 

parts of this volume who have advised or participated in this study. Chemists, spectrographers, and 

X-ray crystallographers have done much analytical 

work, and many field geologists, both of the U. S. Geological Survey and the U. S. Atomic Energy Commission, and mining company employees have aided 

us in this study. References to the geology and 

mineralogy of various uranium deposits on the 

Colorado Plateau by J. W. Gruner, P. F. Kerr, and 

many others have been compiled by Cooper (1953, 

1954).

CLASSIFICATION

The Plateau uranium ores are classified on the basis 

of whether or not a significant amount of vanadium is 

associated with the uranium (Weeks and Thompson, 

1954). The presence of vanadium has an important
SUMMARY OF THE QBE MINERALOGY 67

chemical and mineralogic control on the uranium during 

the oxidation of the ore. Vanadiferous uranium ore 

ranges in V: U ratio (weight percent) from more than 

15:1 to 1:1 and contains traces of copper and other 

metals, but in general the copper content is less than 

in nonvanadiferous ores. The uranium ores referred 

to in this report as nonvanadiferous may contain traces 

of vanadium and commonly contain minor amounts of 

copper and other metals, locally as much as 1 percent of 

copper. The two main types may be subdivided 

according to the degree of oxidation that has taken 

place. Mineralogically the types differ greatly because 

the affinity of vanadium for uranium tends to make 

the uranyl vanadates carnotite and tyuyamunite the 

chief uranium minerals in oxidized vanadiferous ore, 

whereas the oxidation of uraninite in nonvanadiferous 

ore produces a greater variety of secondary yellow and 

greenish-yellow uranyl minerals such as hydrated 

oxides, carbonates, sulf ates, phosphates, arsenates, and 

silicates (tables 1 and 2). Subdivision of the nonvanadiferous uranium ores on the basis of copper content (Finch, 1954) is unnecessary because the copper 

is unimportant commercially and it does not control 

the uranium during oxidation by complexing as does 

vanadium. The uranium ore at Temple Mountain in 

the eastern part of the San Rafael Swell in Utah has 

been referred to as asphaltite ore (Hess, 1922) because 

of the abundance of asphaltic or other carbonaceous 

material. However, higher-than-average carbon content does not prevent classifying this ore on the basis 

of mineral assemblage with the other vanadiferous 

uranium ores. All the Plateau uranium deposits have 

associated carbonaceous material, and the Temple 

Mountain ores differ more in degree than in kind.

Much more vanadiferous than nonvanadiferous 

uranium ore has been mined on the Colorado Plateau. 

This is due to the influence of intensive mining of 

vanadium just prior to the recent interest in uranium 

mining. Seven of the nine processing plants on the 

Plateau in 1955 handled vanadiferous ore and recovered 

both vanadium and uranium (Bitter, 1955). Recently 

the production of low vanadiferous and nonvanadiferous ores has increased rapidly. The sandstone-type 

uranium deposits on the south and west flanks of the 

Black Hills, in South Dakota and Wyoming, are 

moderately vanadiferous and resemble the carnotite 

ores of the Colorado Plateau. However, the sandstonetype uranium deposits in the Ambrosia Lake district 

of McKinley County, New Mexico and in the Powder 

River basin of Wyoming seem to be low vanadiferous 

and those in the Wind River basin of Wyoming and

in Karnes County, Tex., many contain more uranyl 

phosphates and arsenates than uranyl vanadates.

TABLE 1. Uranium minerals found on the Colorado Plateau 

Oxides:

Uraninite, UO2+ 

Becquerelite, 2U03 -3H2 0 

Schoepite, UO2 (OH) 2 .H2 0 

Fourmarierite, PbU4 0,3 -7H2O (?)

Gummite (fine-grained mixture consisting in part of hydrated oxides)

Carbonates:

Rutherfordine, (U02 ) (C03)

Schroeckingerite, NaCa3 (U02) (C03) 3 (S04 )F.10H2 0

Bayleyite, Mg2 (U02)(C03) 3 -18H2 0

Swartzite, CaMg(UO2)(CO3)3-12H20

Andersonite, Na2Ca(U02) (C03) 3 -6H2O

Liebigite, Ca2 (U02) (C03 ) 3 -10-11H2 0

Rabbittite, Ca3 Mg3 (U02) 2 (C03) 6 (OH) 4 .18H2 0

Sulfates:

Uranopilite, (U02 ) 6 (S04)(OH)i 0 -12H2O

Johannite, Cu(UO2) 2 (SO4) 2 (OH) 2-6H2 0

Zippeite, K4 (U02) 8 (S04 ) 3 (OH)i 0 -H2O *

Zippeite-like minerals containing Na; Co, Ni, Fe, or Mg

Phosphates:

Autunite, Ca(U02) 2 (P04 ) 2 -10-12H2O 

Torbernite, Cu(U02) 2 (PO4 ) 2 -12H2 O 

Bassetite, Fe(U02 ) 2 (P04 ) 2 -8H2 0 

Meta-autunite, Ca(U02 ) 2 (PO4 ) 2 -8H2O 

Metatorbernite, Cu(UO2 ) 2 (P04 ) 2 -8H2 0 

Phosphuranylite, Ca(U02) 4 (P04) 2 (OH)4.7H20 

Sabugalite, HA1(U02 ) 4 (PO4 ) 4 .16H2O 

Sal<§eite, Mg(U02) 2 (P04 ) 2 -8H2 0

Arsenates:

Zeunerite, Cu(U02) 2 (As04 ) 2 - 10-12H2 0 

Abernathyite, K2 (U02 ) 2 (As04) 2 -8H2 0 

Metazeunerite, Cu(U02) 2 (As04) 2-8H2 0 

Novacekite, Mg(U02) 2 (As04 ) 2 -8- 10H2 0

Silicates:

Coffinite, U(SiO4 ) 1 -I(OH)4x 

Uranophane,2 Ca(H3 0) 2 (U02) 2 (Si04 ) 2 -3H2 0 

Beta-uranophane, Ca(H3 0) 2 (U02) 2 (Si04) 2 -3H2O 

Boltwoodite, K2 (U02) 2 (Si03) 2 (OH) 2.5H2 0 

Cuprosklodowskite, Cu(U02 ) 2 (Si03 ) 2 (OH) 2 -5H2O 

Sklodowskite, Mg(U02 ) 2 (Si03 ) 2 (OH) 2 .6H2O 

Soddyite, (UO2) 6 (SiO4) 2 (OH) 2 -5H2 0

Vanadates:

Carnotite,3 K2 (U02) 2V2 08 -1-3H2O 

Tyuyamunite, Ca(UO2)V2O8-5-8HH20 

Metatyuyamunite, Ca(UO2 ) 2 V2 08 -3-5H2 0 

Rauvite, CaO-2U03 -5V2 06 -16H2 0 

Uvanite, 2U03 -3V2 05 -15H2 0

Unknowns: Several carbonates, sulfates, phosphates, and silicates

1 Written communication, Clifford Frondel.

a Structural formula, Smith, Gruner, and Lipscomb, 1957.

8 Structural formula, Appleman and Evans, 1857.

468652 59-
68 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 2. Vanadium minerals found on the Colorado Plateau

Oxides:

Montroseite, VO(OH)

Haggite, V202 (OH) 8

Paramontroseite, V02

Doloresite, 3V2O4 -4H2 0

Duttonite, VO(OH) 2

Navajoite, V2O6 -3H2O 

Phosphates:

Sincosite, CaV2 02 (PO4) 2-5H2O 

Vanadite:

Simplotite, CaV4 0»-5H2 0 

Vanadyl vanadates:

Melanovanadite, 2CaO-2V2 04 -3V2 05 -H2O (?)

Sherwoodite, Ca3V8O22 -15H2O

Fernandinite, CaO-V2 04 -5V2 05 -14H2 0

Corvusite, V2 0*-6V2 08 -nH2O

Corvusite-like mineral, V2O4 -5V2O5 -12H2O

New calcium vanadyl vanadate

New sodium calcium vanadyl vanadate

New potassium iron vanadyl vanadate 

Vanadates:

Descloisite, (Zn, Cu) Pb (VO4) (OH)

Santafeite, Na2O-3Mn02 -6(Mn,Ca,Sr)O-3(V,As) 2 06 -8H2O

Tangeite, CuCa(VO4) (OH)

V<5signie"ite, Cu3Ba(V04) 2-(OH) 2

Volborthite, Cu3 (VO4) 2 -3H2 0

Vanadinite, Pbs(V04 ) 8Cl

Carnotite, 1 K2 (U02) 2V2 08 -3H2 0

Tyuyamunite, Ca(UO2) 2V2 08 -5-8KH,0

Metatyuyamunite, Ca (U02) 2V2 08 - 3-5H2O

Fervanite, Fe2 (V04) 2 -2KH2 0

Steigerite, A12 (V04) 2 -6^H2O

Brackebuschite, Pb4 MnFe (VO4) 4 - 2H2O

New vanadate, SrO-CaO-V2 05 -3H2O

Rossite, CaV2 06-4H2 0

Metarossite, CaV2Oe-2H2O

Pascoite, Ca3Vio028-16H2O

Hummerite, K2 Mg2Vi0O28 -16H2 0

Uvanite, 2UO3 -3V2 05 -15H2 0 (?)

Rauvite, CaO-2U02 -6Vz05-20H2 0 (?)

Hewettite, CaV6Ois-9H2O

Metahewettite,2 CaV8Oi 8 -3H2 0

Barnesite, Na2V6Oi6-3H2O 

Silicates:

Roscoelite, K(Al,V) 2 (Al,Si,)0,0 (OH,F) 2

Vanadium-bearing hydrous mica

Vanadium-bearing chlorite

1 Appleman and Evans, 1957. 

a Barnes, 1955.

MINERALOGY OF THE PRIMARY (UNOXIDIZED) ORES 

VANADIFEROUS ORES

The primary vanadium-uranium ores are characterized in general by their black color and by the presence 

of low-valent uranium and vanadium oxides and silicates, and by copper, iron, lead, and zinc sulfides, arsenides, and selenides (table 3). These ores should not 

be confused with the blue-black or corvusite ores which 

represent an intermediate stage of oxidation. The ores 

have a wide range of vanadium content and for convenience in description they have been divided into 

groups on the basis of their vanadium-uranium ratios.

TABLE 3. Sulfides, arsenides, selenides, and other accessory 

metallic minerals found on the Colorado Plateau

Elements:

Native arsenic 

Native selenium

Sulfides:

Pyrite, FeS2

Cobaltian pyrite (Fe,Co)S2 . As much as 1 percent Co.

Selenian pyrite, Fe(S,Se) 2 . As much as 5 percent Se.

Marcasite, FeS2

Selenian marcasite, Fe(S,Se) 2 . As much as 1 percent Se.

Galena, PbS.

Sphalerite, ZnS

Chalcocite, Cu2S

Digenite, Cu2- xS

Bornite, Cu5FeS4

Chalcopyrite, CuFeS2

Greenockite, CdS

Covellite, CuS

Molybdenite, MoS2

Jordisite, 1 Mo sulfide (?)

Realgar, AsS

Tennantite (Cu,Fe) J2As4Si3

Arsenides:

Domeykite, Cu3As 

Selenides:

Clausthalite, PbSe

Eucairite, CuAgSe

Ferroselite, FeSe2 

1 Gruner and Gardiner (1952).

VANADIUM-URANIUM RATIO GREATER THAN 15 : 1

Vanadiferous ores with low uranium content are 

characterized by the dominance of vanadium silicates 

over vanadium oxides and by the general lack of fossil wood. The unoxidized ores in the Entrada sandstone (Jurassic) of the Kifle and Placerville districts 

in western Colorado are repesentative of this group 

and appear to have a monotonous and simple mineralogic composition (pi. 1). At Placerville roscoelite is 

the dominant vanadium mineral occupying the intergranular areas as fine-grained micaceous aggregates, 

and at Rifle it is accompanied by some vanadium-bearing chlorite and mixed layer mica-montmorillonite (or 

so-called, hydrous mica). No vanadium hydrous mica 

is present in the primary roscoelite ore at Placerville. 

The chemical analyses of Placerville samples (table 4) 

indicate that vanadium substitutes for aluminum; the 

high potassium and low water content are characteristic of roscoelite and not of vanadium hydromica. In 

roscoelite-rich thin layers either concordant with or 

cutting across bedding planes the quartz is strongly 

corroded and microstylolites (Fischer, 1942, p. 380) develop where the quartz grains are in juxtaposition.
SUMMARY OF THE ORE MINERALOGY 69

TABLE 4. Chemical analyses of roscoelite

1 t Metal atoms

TABLE 5. Analyses of uraninites

SlOj............ ......

T108 .. ...............

AliOs.. 

V,03.. 

FeO..... - ........

MgO. _-..- 

KsO

NajO.... - ..

H8 0+..... ..... 

H9 0--. ..........

CaO..... .......

00».. ..... .....

CnOs..... ........ .

MnO........ ........ .

LlOn....... ...........

F ....................

P,0e ..... . ......

........... 44.81

........... .56

-. .. 18.42

..... 20.41

........... 1.58

........... .83

... .. 8.28

..... ... .07

........... 3.87

..... .53

20

..... .02

....... . .01

.... ___ None

........... .15

.-. .01

40.40

.20

18.31

17.57

1.69

.61

.83

11.26

3.54

.40

3. 10 \r

2.42 /u

<0.10

3.045 1

.011

1.626 { °;|j|4.

1.061

.092

.039

.093

1.081

h 4.000

1. 967

1.081

Loss 0-F...

99.75

0.06

99.69

100.33

1. Roscoollto from Placerville, Colo. (Fischer, Haff, and Romlnger, 1947, p. 124). 

Analyst, V. North.

2. Roscoolite from Fall Creek mine, Placerville, Colo., collected by A. L. Bush. 

Analyst, H. Levlne.

Montroseite (Weeks, Cisney, and Sherwood, 1953) is 

interleaved with the roscoelite aggregates as small discrete crystalline rosettes. Paramontroseite (Evans and 

Mrose, 1955) may locally supersede montroseite where 

oxidation has commenced. Calcite or dolomite commonly accompanies the montroseite and roscoelite and 

appears to be contemporaneous with the vanadium 

mineralization. Minor but persistent galena-clausthalite (selenium and sulfur in solid solution) and chalcopyrite are accompanied by sparse pyrite and marcasite. 

Small amounts of uranium are present, but its mineralogic occurrence has not been determined completely. 

The deposits at Rifle, Colo., are more fully described in 

Part 19 of this volume.

VANADIUM-UBANIUM RATIO BETWEEN 15:1 AND 1:1

Ores with vanadium-uranium ratios ranging between 

15:1 and 1:1 occur extensively in the Salt Wash sandstone member of the Morrison formation (Late Jurassic) and to a lesser extent in the Shinarump member 

and other basal sandstones of the Chinle formation 

(Triassic) and in other formations.

The uranium occurs in uraninite and coffinite (Stieff, 

Stern, and Sherwood, 1956) in the primary ore and almost without exception is associated with coalified wood 

or other carbonaceous material and with pyrite or other 

sulfides. Thorium and rare earths are conspicuously 

absent in analyzed uraninites (table 5) from the Colorado Plateau and the U(IV) is found to be in excess of 

U(VI). Various stages of uranium saturation of the 

coalified wood have been observed. An ordinary X-ray 

diffraction powder photograph of mineralized wood 

may not detect uraninite or coffinite unless several percent uranium is present.

Uraninite preferentially replaces the cell walls of 

the wood structure (pi. 1C). Commonly the cell

\J03 ............ ...........................................

UOt .- . . --. 

Th02 ...._. ................. .. .. ..-. . ..- ..

PbO.. .......... ..........................................

CuO. .....................................................

NinOs-. .. 

CojOs. ..._..._. . ....... ....................

FesOs-.-. __ ... __ ..--- ___ - ___ .-.--..... __ . _ .

TiOj. --- - 

AhOs .. . ..... ... -..... 

ZnO........ .............................................. .

MnO. ....................................................

SiOj........ ........................................... ....

CaO_... ............................. ....................

BaO......... ........ . ................... .....

SrO. .....................................................

HjO+........ .............................................

HjO-...._............ ....................................

VjOs.... ........................................ ......

S....... .-........_..._. -- .................

As. .......................................................

SQ........................ .................................

F._ .......................................................

0 for F.................. ..................................

Total...... __ ......... _ . _ .... ________ ..

Specific gravity _ .... . ___________________

Unit cell.. ^... ................ ............................

1

31.08 

52.28 

nil 

.74 

2. 90

1.21

.30

2.87 

2.22 } . 

.99 

.28 

.54 

1.70 

.005 

nil 

.21

97.54 

.11

97.43 

9.1 

ae=5.43

2

20.58 

42.49

1.48

.40 

.64 

1.93 

.29 

1.18 

4.09 

1 .22 

4.35 

2.40 

f 5.21 

\ .34 

1.17 

.70 

.22 

4.35 

.013 

.003 

.28

92.34 

.12

92.22 

8.6 

ao=5. 43

1 Analyst: Glen Edglngton, U. S. Geological Survey.

3 Ago determinations on these uraninites have been published by Stieff and Stern 

(1952).

1. Happy Jack mine, White Canyon, Utah. Probably contains quartz, pyrlte 

chalcocite, and chalcopyrite as minor impurities.

2. Shinarump No. 1 mine, Seven Mile Canyon, Grand County, Utah. Probably 

contains pyrite, quartz, calcite, and barite as minor impurities.

lumens (cavities) are filled by sulfides (pi. 1#), but 

if the lumens are vacant the uraninite also forms in 

this area. Where the original wood structure was 

collapsed or vitrainized or both during diagenesis, the 

uraninite intimately impregnates or replaces the coal 

and faithfully retains the coaly structures. Uraninite 

deposited in the sandstone bordering fossil wood may 

show replacement of earlier sulfides, or detrital quartz, 

or be intimately intergrown with calcite or dolomite. 

Coffinite is found within coalified wood where it fills 

the cell cavities. Most of the occurrences of coffinite 

are in vanadiferous ores, and many of these are in the 

Salt Wash sandstone member of the Morrison formation in the Uravan mineral belt of western Colorado 

(Fischer and Hilpert, 1952).

Detailed study of polished sections of mineralized 

carbonaceous material indicates that much of the socalled asphaltite ore is sandstone containing many 

small detrital fragments of coalified wood with some 

interstitial insoluble carbonaceous matter that is anisotropic and does not show any cell structure. The 

quartz grains in the impregnated sandstone bordering 

the wood are commonly corroded. Particularly in the 

Temple Mountain area this type of ore is further impregnated or coated along joint surfaces with thick 

brown crude oil. The chemical character of these 

carbonaceous materials is discussed in Part 12 of this 

volume.

In the primary ores of this group vanadium oxides 

appear to be more abundant locally than vanadium
70 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

silicates. The chief primary oxide, montroseite 

VO(OH), is easily oxidized to the more commonly 

observed paramontroseite. Another primary vanadium oxide haggite V2O2 (OH) 3 has been identified 

from near Carlile, Wyo. (Evans and Mrose, 1958) and 

from several mines in McKinley and Valencia Counties, N. Mex. In places montroseite impregnates the 

fossil wood by filling cell cavities, but the growth of its 

elongate crystals soon obscures the wood structure. 

Typically its strong crystallinity causes the formation 

of rosettes and bands of intricate and sinuous nature 

either on contraction fractures in fossil wood (pi. 

2J., B) or in interstitial areas of the sandstone (Weeks, 

Cisney, and Sherwood, 1953, p. 1237).

Associated with the montroseite and paramontroseite in the intergranular matrix are vanadium silicate 

minerals. Vanadium-bearing chlorite may be one of 

the most important vanadium silicates in the primary 

ores. Intensive study of a small number of samples 

by Hathaway (Part 11 of this volume) indicates that 

roscoelite is not an important mineral in this group, 

but that vanadium hydromica, characterized as a mixed 

layer mica-montmorillonite clay, is commonly present 

and may contain considerable amounts of vanadium. 

The vanadium silicates impart a deep greenish or 

brownish color to the rock and in thin section show 

a moderate birefringence and a marked pleochroism. 

Kaolinite is common in the ores of the Grants district 

in New Mexico but only a small amount is present locally in the Uravan district of Colorado. Kaolinite 

does not contain substituted vanadium.

Pyrite and marcasite are the most common sulfides 

associated with the primary ores and two distinct 

generations of iron sulfides have been recognized. 

Sulfides formed during diagenesis impregnate or form 

pseudomorphs of wood or occur as nodules and are 

considered pre-ore. Euhedral and massive pyrite associated with uraninite and galena are considered 

penecontemporaneous with the mineralization (pi. 

26'). Detailed study of the iron sulfides shows that 

those associated with mineralization have been enriched in cobalt and nickel relative to the diagenetic 

sulfides. Galena is commonly present within the 

uraninite and as later vein material cutting uraninite, 

indicating two generations. Chalcopyrite, chalcocite, 

digenite, sphalerite, molybdenite, greenockite, native 

arsenic, and realgar occur sparingly in the primary 

vanadiferous ores.

Minor amounts of selenides including clausthalite, 

eucairite, and ferroselite are found along ore boundaries 

or associated with coalified logs in the Salt Wash member of the Morrison formation. Selenian marcasite, 

pyrite, and chalcocite are also common in the Salt

Wash and may contain as much as 5 percent selenium 

substituting for sulfur. Although selenium has been 

detected in many ore bodies from other stratigraphic 

horizons, the only primary selenide identified as yet in 

the Chinle formation is ferroselite from a mine at 

Temple Mountain, Emery County, Utah. Ferroselite 

is a new mineral named by Buryanova and Komkov (1955) from Tuvinsk Autonomous Territory.

In addition to galena and clausthalite, lead occurs in 

small quantity in several unusual minerals. The rare 

lead vanadates descloizite, vanadinite, and brackebuschite form thin bands along ore borders in several 

mines in the Uravan district (Weeks, Truesdell, and 

Haffty, 1957). Also in this district the lead molybdate, 

wulfenite, was found in a mineralized log.

Calcite and dolomite or either with a smaller amount 

of barite make up a large part of the gangue. The primary ore from some mines contains less than 6 percent 

CaCO3 , the limit allowed in the mill processing of 

low-lime ores, but some primary ore contains much 

more calcite. At Mi Vida mine, San Juan County, 

Utah, coarsely crystalline white calcite is intimately associated with both montroseite and uraninite and fills 

spaces originally occupied by flattened branches and 

twigs of fossil wood. Small remnants of coalified wood 

as well as the shape of the calcite masses indicate that 

wood was replaced by calcite. The outer border of the 

calcite mass is commonly penetrated by montroseite 

needles forming a thing black shell. Gross (1956) estimates that the calcite content of Mi Vida ore averages 

16 percent or higher and that the calcite content of the 

host rock (Chinle formation) averages between 22 and 

28 percent. Samples of barren Salt Wash sandstone 

from drill core at depths of several hundred feet have 

a wide range of calcite content (oral communication, 

N. Archbold, 1955). Locally the sandstone host rock is 

cemented with pre-ore gypsum as in the Jo Dandy area 

on the faulted margin of the Paradox salt anticline, 

Montrose County, Colo. Detailed descriptions of ores 

from the J. J. and Mineral Joe mines in the Jo Dandy 

area are given in Parts 18 and 15 of this volume.

NONVANADIFEROUS ORES

Deposits in which vanadium is negligible and uranium is the only metal of importance except where copper may be locally of commercial value occur chiefly in the Shinarump member and other basal sandstones in the Chinle formation (Triassic). The ore is 

found mainly in channels that contain carbonaceous 

material and mudstone beds; these channels are along 

the thin edge (pinch-out) of the formation where 

conglomerate and sandstone beds fill cuts in the underlying formation (Finch, 1955). The Happy Jack mine, 

San Juan County, and the Delta (Hidden Splendor)
SUMMARY OF THE ORE MINERALOGY 71

mine, Emery County, Utah, are good examples of nonvanadif erous ore.

In general these primary ores are lighter in color 

than the vanadif erous ores because the black vanadium 

oxide, montroseite, is lacking, but a few ores with high 

sulfide content are dark colored. Uranium is contained 

chiefly in uraninite, and coffinite is scarce or lacking. 

Coalified wood and diagenetic sulfides are the main controls of uraninite deposition, and the wood is replaced 

in the same manner as described above.

Abundant sulfides are associated with uraninite in 

some of these ores for example, the Happy Jack 

mine, in Utah and a more complicated mineralization 

sequence is evidenced by ambiguous relations between 

the uraninite and the sulfides. Two generations of 

pyrite have been established in these primary ores with 

the pyrite in the uraninite showing rims of unidentified 

nickel and cobalt minerals further evidence of nickelcobalt enrichment accompanying the uranium mineralization (pi. 2D). Copper sulfides, including chalcopyrite, bornite, chalcocite, and covellite are dominant in 

some mines and lead, zinc, and iron sulfides dominate 

in others. Galena is commonly associated with uraninite either as early euhedral cubes or as late vein material. Sphalerite is very light colored with a low iron 

content (as at Happy Jack and Delta mines), indicating a temperature of formation below 138° C according 

to the method of Kullerud (1953). Molybdenum sulfide (?) in trace amount commonly occurs in mineralized wood. Silver has been noted in spectrographic 

analyses of sulfide concentrates, but no silver minerals other than those previously known at Silver 

Reef, Washington County, Utah, and the eucairite at 

Cougar mine, San Miguel County, Colo. have been 

identified. Some uraninite ores have very little accompanying sulfide; these ores are difficult to recognize in 

the field and must be prospected by careful search with 

a Geiger or scintillation counter.

Calcite content is high in some mines as at Sevenmile Canyon, north of Moab, Utah. Barite is present 

in small quantity in some nonvanadiferous ore, as at 

Dirty Devil No. 6 mine, Emery County, Utah, and 

seems to be less common than in the vanadiferous ores 

of the Morrison formation.

OXIDATION SEQUENCE AND MINERALOGY OF 

VANADIFEROUS URANIUM ORES

EABLY STAGE OF OXIDATION

The primary ores are stable in reducing environments after emplacement and generally retain their 

original minerals and textures if they are not exposed 

to oxidizing conditions. Those ores which have remained below the zone of oxidation (water table) retain their primary character. In the Colorado Plateau 

various stages of oxidation may be found superimposed 

on the primary ores because the deposits occur in many 

different situations with respect to the water table and 

also because of variable water-retention capacities of 

the pore space of the ore sandstones.

The numerous nonsilicate vanadium minerals are 

very sensitive to changes in oxidation potential and 

pH. Most of them have small fields of stability (Garrels, 1953; also Parts 6 and 7 of this volume) and therefore serve as convenient indicators of the degree of oxidation and the pH of the environment during oxidation. 

Montroseite, VO(OH), oxidizes readily to paramontroseite, VO2 , (Evans and Mrose, 1955) when exposed 

to air, as evidenced by the fact that montroseite specimens in the laboratory commonly alter to VO2 in a few 

months' time. Other new vanadium (IV) minerals 

doloresite, duttonite, and simplotite are possibly all 

alteration products of montroseite (Stern and others, 

1957, and Thompson, Roach, and Meyrowitz, 1958). 

Detailed study of these minerals has been made at the 

Peanut mine, Montrose County, Colo. (Part 17 of 

this volume).

Uraninite is altered, uranium (IV) oxidizing to uranium (VI), without producing any megascopically observable change. Coffinite seems to be slightly more 

resistant to oxidation than uraninite. The early oxidation of the primary uranium minerals apparently disperses the uranium into a black amorphous colloidal 

phase, an intermediate step between uraninite or coffinite and the yellow uranyl minerals. No X-ray pattern 

of any uranium minerals can be obtained from slightly 

oxidized ore. Considerable oxidation of vanadium 

takes place between the time of alteration of uraninite 

and coffinite and the appearance of uranyl vanadates in 

corvusite ore. The sulfides are still fresh and unaltered 

after oxidation of uraninite and montroseite has begun.

CORVUSITE ORE, PARTLY OXIDIZED

Further oxidation of the ores causes a change in color 

from black to blue black in ores of the corvusite stage. 

Some greenish-black and brown also appear at this 

stage. As soon as all the vanadium (III) has oxidized 

to vanadium (IV), the vanadium (IV) minerals alter 

to a group of compounds containing various proportions of vanadium (IV) and (V) with some calcium, 

iron, sodium, or potassium.

Available vanadium (V) combines with uranium 

(VI) to form the widespread but ill-defined and sometimes inconspicuous mineral rauvite (Hess, 1925) which 

may be dispersed in microscopic grains in massive corvusite or form glassy or gel-like coatings on quartz 

grains, pebbles, or contraction fractures in mineralized
72 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

wood. Rauvite ranges in color from purplish black 

and brownish red in the gell-like varieties to orange 

red in the powdery aggregates. Its chemical formula 

is uncertain because samples giving the same X-ray 

powder pattern have slightly different chemical compositions. The calcium content may not be essential 

but all rauvite samples have a higher V: U ratio than 

carnotite and tyuyamunite. The rare and even less 

well known mineral uvanite is intermediate in V:U 

ratio between rauvite and carnotite and was found 

with rauvite at Temple Mountain, Utah, by Hess 

(1925).

Small amounts of several uranyl minerals including 

meta-autunite, phosphuranglite, saleeite, novacekite, 

uranophane, and boltwoodite, have been found in corvusite ore. These minerals form locally where uranyl ions 

are present and where the vanadium has not reached 

the quinquevalent state or where the pH is too low for 

formation of carnotite.

The best crystallized of the vanadium (IV-V) minerals is melanovanadite, for many years known only 

from the type locality in Peru and now recognized in 

a number of mines in the Plateau. A new calcium 

vanadyl vanadate from the J. J. mine, Montrose County, Colo., and from Eastside Carrizo mines, San Juan 

County, N. Mex., occurs in black bladed microscopic 

crystals and is under investigation. Microscopic tetragonal crystals of a bluish-black to greenish-black vanadate sherwoodite (Thompson, Roach, and Meyrowitz, 

1958) have been noted in many mines. Most of the 

vanadium (IV-V) material, however, is poorly crystallized and shows a very complex and intimate mixture 

of minerals quite similar in appearance and generally 

referred to in the field as "corvusite" or fernandinite. 

A common feature associated with the growth of corvusite between quartz sand grains is microscopic fracturing of the quartz parallel to the corvusite-rich band 

or normal to the columnarlike aggregates of corvusite; 

this was noted especially in corvusite-rich nodules at 

the Monument No. 2 mine, Apache County, Ariz., and 

in many mines in the Uravan mineral belt of western 

Colorado. The molecular ratio of vanadium (V) to 

(IV) ranges from 6 in the corvusite originally described (Henderson and Hess, 1933) to somewhat lower 

values in other corvusitelike minerals (analyzed by 

A. M. Sherwood and K. Meyrowitz, 1954). The vanadium (V) to (IV) ratio decreases in this group of minerals as the calcium content increases, with a possible 

series from corvusite (6) through fernandinite (5) to 

melanovanadite (l1/^), somewhat like the navajoitehewettite-pascoite-rossite series described below. A 

new vanadium (IV) and (V) mineral containing some 

iron and potassium occurs in the Hummer, Van, and

Peanut mines, all in Montrose County, Colo. It is a 

dark-red fibrous mineral similar in appearance to hewettite and is being studied. A new sodium calcium 

vanadyl vanadate found in the Section 33 mine near 

Grants, N. Mex. and in the Bowen and LaSalle mines 

near Uravan, Colo., occurs in thin seams of dark green 

fibrous or bladed microscopic crystals.

By the time the corvusite stage is reached, some of 

the associated minerals begin also to show a response 

to the oxidizing conditions. The sulfides alter to oxides 

and sulf ates, and the selenides alter either directly or 

indirectly to native selenium. Occurrences of native 

selenium have been described from South Dakota, 

Colorado, and Utah (Thompson, Roach, and Braddock, 

1956) and many additional occurrences in Wyoming, 

Utah, New Mexico, and Colorado are known. Depending on the relative abundance of calcite with respect to 

pyrite in the primary ore, a wide range of pH is possible when the pyrite oxidizes during the corvusite stage 

and the oxidizing solutions may remain acid or be 

neutralized by calcite. Part or all of the calcite gangue 

and cement in the sandstone may be dissolved and the 

sandstone may be partly recemented by gypsum and 

iron oxides. (The possible addition of calcium carbonate as recent caliche is noted below.)

CARNOTITE ORE, HIGHLY OXIDIZED

As oxidation progresses, carnotite and tyuyamunite 

develop chiefly from rauvite, and some may form in 

other ways (investigation in progress). Once crystallized, the carnotite is remarkably stable and fixes the 

uranium very effectively. The minerals containing vanadium (IV) and (V) of the corvusite stage oxidize 

to form vanadium (V) minerals. The specific ones 

formed depend closely on pH conditions (see Parts 6, 

7, and 8 of this volume), on the presence of certain 

cations to combine with vanadium, and on several other 

factors. Vanadium fixes all available uranium in uranyl vanadates, and the excess vanadium may form 

the hydrated pentoxide, navajoite (Weeks, Thompson, 

and Sherwood, 1955), or much more commonly it combines with other elements these include calcium to 

form hewettite and pascoite (Hillebrand, Merwin, and 

Wright, 1914) and rossite (Foshag and Hess, 1927), potassium and magnesium to form hummerite (Weeks 

and Thompson, 1954), sodium for sodium vanadate 

(Weeks and Thompson, 1954), aluminum for steigerite 

(Henderson, 1935), iron for fervanite (Hess and Henderson, 1931), copper for volborthite and tangeite 

(formerly known as calciovolborthite), or barium and 

copper for vesignieite (Guillemin, 1955). These 

vanadates range in color from brown through red, 

orange, yellow, and green to nearly colorless. Hewett-
SUMMARY OF THE ORE MINERALOGY 73

ite readily dehydrates to metahewettite (Barnes, 1955) 

and rossite dehydrates to metarossite. Other new 

vanadates include santafeite, a manganese vanadate 

(Sun and Weber, 1957), and a strontium calcium 

vanadate being studied by M. E. Thompson.

Although the presence of tyuyamunite in the "carnotite ores" of the Colorado Plateau has been known for 

many years (Hillebrand, 1913 and 1924), the relative 

abundance of the two minerals is not known quantitatively. Neither is it known how much tyuyamunite 

has been converted to carnotite (or vice versa) by cation 

exchange (Hillebrand, 1913, 1924; Murata, Cisney, 

Stieff, and Zworykin, 1951). The common assumption 

that carnotite is more abundant than tyuyamunite in 

the Uravan mineral belt of Colorado is difficult to evaluate in this mineralogic study, because more identifications have been made of mineral specimens from joint 

coatings and mineralized logs than of average ore sandstone with fine-grained uranyl vanadates disseminated 

interstitially between the quartz grains and impregnated in clay. Most of the yellow coatings on joints 

and some of the richly mineralized logs (such as those 

found in 1950 in the Charles-T No. 2 mine in the Slickrock district, San Miguel County, Colo.) are tyuyamunite, but these account for a small part of the total 

uranium that has been mined from oxidized ore, and 

carnotite may be the dominant mineral in the Uravan 

belt. However, in the Lukachukai group of mines, 

Apache County, Ariz., and especially in the mines in 

Todilto limestone in the Grants district, McKinley and 

Valencia Counties, N. Mex., tyuyamunite seems to be 

more abundant than carnotite. The recent formation 

of tyuyamunite on joints and fractures is related to the 

calcium content and alkaline nature of the ground water 

caused by the present semiarid climate and to the high 

calcite content of the country rock (as at Mi Vida 

mine, p. YO). Phoenix (Part 4 of this volume) classed 

most of the ground-water samples from the Salt Wash 

sandstone member of the Morrison as calcium bicarbonate waters. He found these water samples were 

alkaline as did R. F. Marvin during field work in 1954 

and 1955 with the senior author.

Although in the laboratory, tyuyamunite is readily 

base-exchanged to carnotite in the presence of potassium-bearing solutions, evidence is lacking that the bulk 

of Plateau carnotite has undergone exchange. A general rule for the Plateau is that carnotite is typically 

finer grained than tyuyamunite although some exceptions to this rule are known. If much of the carnotite 

had formed by exchange, one would expect the grain 

size and habit to be similar to that of tyuyamunite. 

Carnotite apparently occurs where potassium is available in the interstitial hydrous mica of the sandstone,

and tyuyamunite forms where calcium is available from 

the host rock or ground water. Tyuyamunite contains 

more water than carnotite, and when tyuyamunite ores 

are mined, the mineral readily dehydrates to metatyuyamunite (Stern, Stieff, Girhard, and Meyrowitz, 

1956).

In the oxidized ores of the Uravan belt carnotite, 

tyuyamunite, and the various brightly colored vanadates are locally abundant but in the bulk of the 

ore are actually less abundant than the fine-grained 

greenish-gray and light-brown vanadium silicates that 

contributed much of the vanadium mined in the 

Plateau (Fischer, 1942) previous to World War II. 

Mineralogic and chemical study of these vanadium silicates by the Geological Survey, is in progress and 

therefore the present description of these minerals is 

tentative. The outcrop of ore sandstone is commonly 

gray with little or none of the brightly colored minerals. The probable leaching of the vanadates from the 

outcrop is discussed below. These gray sandstone ores 

have commonly been termed roscoelite ores in contrast 

to carnotite ores, but preliminary study suggests that 

true roscoelite is common only in the Rifle and Placerville districts of Colorado. In the Uravan belt 

vanadium-bearing chlorite, and hydrous mica or mixedlayer clays seem to be more abundant than true roscoelite. Some of the vanadium silicate interstitial in the 

sandstone probably has persisted practically unchanged 

from the unoxidized ore, whereas some clay may have 

become impregnated with vanadium solutions migrating during oxidation.

At the Rifle mine near Rifle, Colo., where the vanadium silicate ore is affected very little by oxidation, 

small amounts of the uranyl carbonates bayleyite and 

swartzite form efflorescences on the mine walls. Here 

probably little or no soluble vanadium is available to 

combine with the uranium.

In areas where the vanadium-uranium ratio is low 

or the vanadium is moderately low and irregularly distributed, small amounts of other uranium minerals may 

occur, as uranophane near Grants, N. Mex., and autunite, andersonite, schroeckingerite, and zippeite in the 

Thompsons district, Grand County, Utah. Study is in 

progress on the uranium deposits in the Morrison formation and in the Todilto limestone of the Grants and 

Laguna areas in New Mexico which range from low to 

nonvanadiferous.

MINERALOGY OF OXIDIZED NONVANADIFEROUS 

URANIUM ORES

URANIUM MINERALS

The nonvanadiferous uranium ores differ notably 

from the vanadiferous because oxidation of uraninite
74 GEOCHEMISTRY AND MINERALOGY, COLORADO .PLATEAU URANIUM ORES

in the absence of a significant amount of vanadium produces a greater variety of secondary uranium minerals. 

These include hydrated oxides, carbonates, sulfates, 

phosphates, arsenates, and silicates. They are microcrystalline or massive and range in color from orange 

through yellow, and greenish yellow to green. They fill 

pore spaces or minute fractures in sandstone, conglomerate, or fossil wood and coat joint surfaces and mine 

walls. Among these minerals none is as predominant 

as carnotite and tyuyamunite are in the oxidized vanadiferous ore (Weeks and Thompson, 1954). In general 

these secondary minerals form irregular rims around 

unoxidized remnants of the primary minerals. They 

develop next to the core of unoxidized minerals and are 

removed from the outside of the rim until the source is 

gone. These secondary uranium minerals generally do 

not form large deposits of completely oxidized ore as 

does carnotite, because their relative solubilities are 

much greater than that of carnotite.

The hydrated uranium oxides are small in quantity 

and found in only a few mines because sulfate, carbonate, or some other anion is usually present to combine with uranium. Small amounts of becquerelite, 

schoepite, and fourmarierite are closely associated with 

oxidizing uraninite.

In the oxidation of sulfide-rich uraninite ore the most 

abundant secondary uranium minerals are the uranyl 

sulfates: johannite, uranopilite, zippeite, and other unidentified zippeitelike minerals. These green, yellowish-green, and deep-yellow minerals are beautifully 

developed by evaporation on the walls of Happy Jack 

mine in White Canyon, San Juan County, Utah (Part 

16 of this volume; and Trites and Chew, 1955).

The uranyl carbonates are commonly developed 

wherever the sulfide content of the ore is low and host 

rock, or gangue, contains sufficient carbonate, as at 

Shinarump No. 1 mine, Utah (Finch, 1954), or where 

the ground water is carbonate rich. Seven uranyl carbonates have been identified on the Colorado Plateau, 

including rutherfordine (rare), liebigite, and schroeckingerite; and four new carbonates andersonite (Axelrod and others, 1951), bayleyite (Axelrod and others, 

1951; Stern and Weeks, 1952), rabbittite (Thompson, 

Weeks, and Sherwood, 1955), and swartzite (Axelrod 

and others, 1951). Two additional uranyl carbonates 

were unidentified. Small amounts of rutherfordine are 

found associated directly with uraninite. All the uranyl 

carbonates except rutherfordine form on mine walls 

and on fracture surfaces by evaporation of uranyl carbonate solutions. Only because of the semiarid climate 

on the Plateau are these carbonates temporarily preserved. Occasional heavy rains wash away the carbonates, such as bayleyite at Hideout mine and andersonite at the Atomic King mine in San Juan County, 

Utah, and then they gradually accumulate again during 

a dry season.

The uranyl phosphates are rare in the Plateau, because the sandstone host rock is low in phosphate except 

very locally where fossil bones are preserved. Small 

amounts of autunite, meta-autunite, phosphuranylite 

(possibly an alteration product of autunite), torbernite, metatorbernite, and bassetite have been found. 

Small amounts of uranyl arsenates are present: metazeunerite at a number of localities in White Canyon 

and in the San Eafael Swell, in Utah; and novacekite 

(Stern and Annell, 1954), abernathyite (Thompson, 

Ingram, and Gross, 1956), and zeunerite at one locality 

each. The uranyl silicates uranophane, boltwoodite 

(Frondel and Ito, 1956) sklodowskite, and cuprosklodowskite are not abundant in the Plateau. The unknown sulfates, phosphates, and silicates that are being 

studied probably include several new minerals.

( SECONDARY MINERALS OP COPPER AND 

OTHER METALS

Copper, the chief associated metal in some of the nonvanadiferous ore as well as in some of the vanadiferous 

deposits, occurs in many secondary minerals, commonly 

as malachite, azurite, chalcanthite, antlerite, brochantite, and chyrsocolla, and rarely as conichalcite, chalcoalumite, and volborthite. Several other metals differ 

in abundance from one mine to another: iron and manganese in limonite and wad; cobalt in bieberite (commonly dehydrated), cobaltocalcite, cobaltomenite, 

erythrite, or cobaltoan pickeringite; molybdenum in 

ilsemannite, powellite, or ferrimolybdite; and traces of 

lead, zinc, nickel, and silver.

The presence of brightly colored copper, cobalt, and 

molybdenum secondary minerals on the rock outcrop or 

on joint surfaces within a few feet of the cliff face is 

helpful to the prospector, but many small copper deposits on the Plateau do not contain commercial quantities of uranium.

ASSOCIATED MINERALS

Clay lenses in the ore and mudstone or shale.underlying ore are commonly bleached. During oxidation, 

especially of the sulfide-rich ores, the clays are altered 

further by development of one or more of the following: Kaolinite, jarosite, alunite, or gibbsite. Fluorescent uraniferous opal and allophane coat some joint 

surfaces and serve as prospecting guides.

RELATION OF OXIDATION TO WATER SATURATION 

OF ORE

Second only in importance to the range of primary 

composition of the Colorado Plateau uranium ores is
GEOLOGICAL SUEVEY PROFESSIONAL PAPER 320 PLATE 1

A. PRIMARY VANADIFEKOUS ORE, 1,700 FT IN FROM THK PORTAL, FALL 

CREEK MINE, PLACERVILLE, COLO.

The irregular white areas are strongly corroded quartz-saml grains. The gray groundmass is roscoelile and the black opaque areas are montroseite, some showing 

radiating bladed crystals. Thin section.

II. PRIMARY VANAUIFEROUS ORE, 7,000 FT IN FROM THE PORTAL, GARFIELD 

MINE, RIFLE, COLO.

The irregular white areas are quartz grains showing some corrosion. The gray 

intergranular areas are roscoelite and the black opaque grains are montroseite. 

Thin section.

C. PRIMARY VANADIUM-URANIUM ORE, Ml VIDA MINE, SAN JUAN COUNTY,

UTAH.

Uraninite (light gray) replaced cell walls of coalified wood and partially infilled

the lumens. Calcite (dark gray) filled the remainder of the lumens and fractures

along the wood rays. Polished section.

D. PYRITE ASSOCIATED WITH PRIMARY ORE, MARSHBANK CANYON MINE, 

TEMPLE MOUNTAIN, EMERY COUNTY, UTAH.

Pyrite (white) replaced the cell walls of coalified wood and impregnated the lumens. 

The dark particles are quartz. Polished section.
GEOLOGICAL SURVEY PEOFESSIONAL PAPER 320 PLATE 2

A. PARTLY OXIDIZED URANIUM-VANADIUM ORE, MI VIDA MINE, SAN JUAN 

COUNTY, UTAH.

Light-colored needlelike paramontroseite crystals replaced by dark-gray massive 

doloresile. Polished section.

B. PRIMARY URANIUM-VANADIUM ORE, OVERSIGHT MINE, MONTROSE 

COUNTY, COLO.

Banded aggregates of montroseite fractured and healed later by calcile (dark gray). 

The medium-gray patch along the bottom is coalified wood. Polished section.

C. PRIMARY URANIUM-VANADIUM ORE, MI VIDA MINE, SAN JUAN COUNTY,

UTAH.

The mottled dark-gray groundmass is an intimate mixture of uraninite and coffin He. 

Zoned crystals of pyrite show selective replacement by galena, nraninite, and 

cofnnite. Two well-developed crystals of galena are in the lower left of the 

picture. The light irregular patches also are pyrite, and they show strong corrosion 

by the uranium minerals. Polished section.

D. PRIMARY NOXVANADIFEROUS ORE, DELTA MINE, EMERY COUNTY, UTAH.

Detrital quartz (qtz) and massive pyrite (py) replaced by calcite (cc). The lightcolored zone crystals in the uraninite (u) are second generation cobalt-rich pyrite. 

A band of sphalerite (sp) is along the right-hand border of the picture. Polished 

section.
SUMMARY OP THE ORE MINERALOGY 75

their range in degree and depth of oxidation. Oxidation depends on access of air to the ore, as in exposed 

rocks with no soil cover and where evaporation is high, 

in relatively continuous permeable sandstone beds above 

the water table, and in strata truncated downdip by a 

canyon. Oxidation has been prevented or retarded 

where water is held in the pore space of the ore sandstone, as in strata protected by thick soil cover, in 

lenticular sandstone beds surrounded by clay, in strata 

below a perched water table or the main water table, 

and in strata that dip away from the valley wall.

TJNOXIDIZED ORE IN WET MINES AT OR CLOSE TO 

THE WATER TABLE

A good example of wet unoxidized ore is at the School 

Section No. 36 mine, T. 30 S., R. 25 E., near the south 

end of the floor of Lisbon Valley, San Juan County, 

Utah. At a depth of about 70 feet a relatively sharp 

boundary occurs between partly oxidized ore and wet 

unoxidized ore containing fossil wood replaced by 

uraninite and calcite. The mine is at the foot of a long 

northward-facing slope that rises nearly 2,000 feet to 

the Monticello Plateau; the slope is covered with vegetation and holds considerable moisture.

The Basin No. 1 mine on the east side of Cottonwood 

Creek, west of Blanding, San Juan County, Utah, is wet 

because it is below the level of the creek bed. The mine 

is in a blanket-type deposit and the wettest and least 

oxidized ore is spotted, cemented with calcite, and contains small coalified wood fragments. Updip, above the 

west side of the creek, are many old mines in more oxidized ore.

The unoxidized ore at the Peanut mine, Montrose 

County, Colo., is described in Part 17 of this volume. 

During mining operations at the Peanut mine, the 

School Section No. 36, and many other mines in unoxidized ore, considerable water was released from saturated sandstone lenses that contained unoxidized ore.

PARTLY OXIDIZED DEPOSITS, ABOVE THE MAIN 

WATER TABLE BUT IN PROTECTED LOCATIONS 

WHERE SOME MOISTURE IS HELD

The Corvusite mine on Beaver Mesa, Grand County, 

Utah, is a good example of partly oxidized ore with 

small remnants of unoxidized ore. The deposit was 

mined intermittently for more than 40 years and was 

the type locality for the mineral corvusite (Henderson 

and Hess, 1933). The mine is located on the updip side 

of the mesa toward the La Sal Mountains, and the ore 

is in richly mineralized fossil trees and relatively small 

sandstone lenses interbedded with thick clay so that the 

ore remains saturated with water. The mesa is more 

than 7,500 feet above sea level, has considerable soil

cover and vegetation, cool temperature, low evaporation, 

and possibly more rainfall than the lower parts of the 

Plateau. These factors all contribute to the continued 

dampness of the ore and they have prevented more than 

partial oxidation although the mine is high above the 

main regional water table.

At the Bitter Creek mine on the north side of Paradox 

Valley, Montrose County, Colo., the Salt Wash sandstone member of the Morrison formation dips 15° to the 

northeast, away from Paradox Valley. These strata 

are truncated by the San Miguel River some distance to 

the north, and water in the mine drains slowly downdip. At Bitter Creek the ore at the surface of the 

ground is oxidized, is lower than average grade in both 

vanadium and uranium, and contains gypsum. Mining 

has progressed several hundred feet downdip through 

a thick transition zone of partly oxidized ore consisting 

chiefly of corvusite and rauvite with remnants of unoxidized montroseite or paramontroseite and pyrite. 

The water-soluble efflorescence, pascoite, forms on the 

moist corvusite-rich layers. At depth, gypsum and iron 

oxides are absent and the barren rock is gray rather 

than buff. Partly oxidized rich ore pockets commonly 

contain a small amount of radioactive barite. This indicates that recent oxidation of the primary uranium 

minerals separated trace amounts of radium which, 

probably as sulfate, formed a coating on the crystals of 

barite in the gangue. Inasmuch as radium has a halflife of about 1,500 years, the radioactive coating on the 

barite would lose more than 99 percent of its radioactivity in 15,000 years. Possibly the radioactive coating was formed considerably less than 15,000 years ago. 

The lower grade of the ore in the old open-pit workings 

is probably due to leaching at the outcrop rather than 

to dissemination or spreading of small high-grade ore 

bodies as proposed by Heyl (1956).

The J. J. mine, Montrose County, Colo., described in 

Part 18 of this volume, shows the transition from unoxidized to oxidized ore at a perched water table.

DRY MINES WITH OXIDIZED VANADIFEROUS ORE

The dry mines with highly oxidized ore may be classified in three groups. Many carnotite deposits apparently have been oxidized in place with practically 

no movement of material. Some have been modified 

during an intermediate stage of oxidation by downdip 

migration of vanadium and possibly of uranium. Ore 

sandstone directly at the surface of the ground probably has been leached of some uranium and vanadium 

by alkaline surface and ground water.

OXIDATION IN PLACE

Where there is little or no catchment area to supply 

ground water to the ore sandstone, moist-air oxidation
76 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

takes place without significant migration of vanadium 

and uranium. The supply of ground water is small 

or negligible in isolated knolls, in small fault blocks 

along the borders of the collapsed salt anticlines, or 

where strata dip away from a valley wall. Examples 

of mines situated thus are the Rattlesnake mine in the 

north end of Lisbon Valley, San Juan County, Utah; 

several mines in the Jo Dandy group along Paradox 

Valley; and the Dolores group of mines on the bench of 

Atkinson Mesa above the Dolores River, Montrose 

County, Colo.

The Rattlesnake mine in Lisbon Valley had (in 1954) 

highly oxidized ore in dry friable sandstone. The yellow and brown ore had spotted and banded textures 

resembling those in unoxidized ore and giving the appearance of oxidation with little or no movement of 

material. Hewettite, the red calcium vanadate, seems 

to be more abundant in the ores of the Jo Dandy and 

Dolores groups of mines than in the ores of the Club 

group (see below) of mines through which oxidizing 

solutions probably have migrated. In general, if the 

vanadium-uranium ratio is high, ores that have been 

oxidized in place by moist air have more of the brightly 

colored vanadates than other ores.

The carnotite- and tyuyamunite-rich logs found in 

various mines appear to be the oxidized product of 

fossil wood partly replaced with uraninite and impregnated with montroseite. Some of these have been oxidized with very little spreading or dissemination of 

uranium and vanadium. The detailed wood cell structure so commonly observed in polished sections of uraninite (pi. 1C) is destroyed by volume changes during 

oxidation, and carnotite logs show only the gross feature of the wood. Only one instance of wood cell structure preserved in secondary minerals has been noted 

that of a narrow rim of becquerelite around uraninitereplaced fossil wood at Monument No. 2 mine, Apache 

County, Ariz. (oral communication, D. H. Johnson).

MODIFICATION DUHING OXIDATION

Ores in strata that have a ground-water catchment 

area updip and that are truncated downdip by a canyon 

may have been modified during oxidation by migration 

of water-soluble vanadium and possibly selenium and 

other constituents, especially if the strata are moderately permeable. Vanadium is readily leached from 

partly oxidized ore by water; 50-g samples of blueblack ore (from the Bitter Creek mine, Montrose 

County, Colo., and the Corvusite mine, Grand County, 

Utah) in 500 ml of distilled water yielded solutions 

with pH below 2 which contained uranium as well as 

vanadium. Oxidizing ground water moving downdip 

through ore would leach vanadium from the vanadyl 

vanadates more easily than from the vanadium silicates.

The water would be acid until neutralized by solution 

of carbonate cement.

The Club group of mines (Fischer, 1942, p. 386) on 

the bench formed by the Salt Wash sandstone member 

of the Morrison formation above the San Miguel Canyon at Uravan, Montrose County, Colo., are dry with 

chiefly oxidized ore and the ore rolls have "breakaway 

surfaces." The strata dip toward the canyon allowing 

water to drain through the more permeable sandstone 

beds. Higher on Club Mesa the Lasalle Mining Co.'s 

260-foot shaft mine also is dry and has well-developed 

rolls in oxidized ore; a little corvusite ore and radioactive barite in mineralized logs; and some blanketlike 

spotted ore with calcite cement in the deepest, least 

oxidized part of the mine. The barite is coated with 

radioactive daughter products, probably radium sulfate, precipitated from recently oxidized primary ore 

minerals. Evaporation of moisture on certain beds of 

sandstone along the mine walls forms pascoite. Still 

higher on Club Mesa the Shattuck Denn Co.'s 500-foot 

shaft mine is moderately dry although certain horizons 

in the Brushy Basin shale member of the Morrison 

formation had considerable water when the operators 

were sinking the mine shaft. The ore is partly oxidized with a few remnants of coffinite and montroseite 

and a trace of secondary yellow appearing on the joint 

surfaces. The ore has an undulating surface but no 

typical "breakaway roll surfaces."

The Cougar mine in the Lower Group at Slickrock, 

San Miguel County, Colo., is on a bench of sandstone 

of the Salt Wash that dips toward the Dolores River 

canyon and has the same structural situation as the 

Club mines. Around the rim of the bench are many 

old adits and on top of the bench old open-pit workings 

which show mined-out rolls with "breakaway surfaces." The underground workings have numerous 

rolls in several sandstone lenses separated by thin clay 

beds. Away from the surface and cliff face some lessoxidized patches of ore persist and locally copper sulfides and copper, lead, and silver selenides occur, and 

the vanadiferous ore is in the corvusite stage. Up the 

hill a few hundred yards from the Cougar mine is the 

Little Muriel shaft about 35 or 40 feet deep. In the 

summer of 1954 after the mine had been abandoned 

for a time, about a foot of water had accumulated and 

seepage from a layer of corvusite ore had formed a 

thick coating of pascoite on the mine wall. Also, alteration of selenides had produced a pink efflorescence, the 

unstable monoclinic form of native selenium. Here is 

indication that water seeping through a partly oxidized 

deposit can transport vanadium, selenium, and 

probably other constituents.

Both the Cougar and Club mines are on the downdip
SUMMAEY OF THE OBE MINEEALOGY 77

side of areas that would feed water intermittently 

through them, spreading the vanadium and modifying 

its distribution. Vanadium silicate ore seems to predominate over vanadate ore in these mines probably 

because of leaching of corvusite. The ore rolls have 

well-developed "breakaway surfaces" that have been 

accentuated during oxidation by one or more of the 

following processes: solution of pyrite, the vanadates, 

and some of the carbonate cement, and volume changes 

due to oxidation and changes in hydration. These 

mines illustrate the gradation from oxidized ore near 

the surface to less oxidized ore back from the outcrop.

ORE SANDSTONE DIRECTLY AT THE SURFACE OF MESAS

Where small dry mesas are capped by ore sandstone 

as at the Eastside Carrizo mines, west of Shiprock, 

N. Mex., the chief vanadium mineral is vanadium chlorite, hydromica, or other vanadium silicate mineral. 

The uniformly light-gray ore is low in uranium, which 

is present in thinly disseminated yellow grains of tyuyamunite in the sandstone or as a coating of tyuyamunite 

on the joint surfaces below a thick calichelike crust. 

Uranium seems to have been leached from these surface deposits probably by recent alkaline ground water. 

Hewettite, also, probably has been leached from the 

surface by alkaline ground water; only a few remnants 

of hewettite and vanadyl vanadates occur under a hard 

cemented sandstone bed in the deepest part of one of 

the abandoned mines in the Eastside Carrizo group.

Other areas having vanadium silicates with very 

little carnotite or other vanadium minerals in ore exposed on top of mesas or broad benches include Flat 

Top Mesa in the middle of the syncline south of Gateway, Colo., and another Flat Top Mesa (also called 

Shinarump Mesa), west-southwest of Temple Mountain, Emery County, Utah.

A salt crust consisting principally of sodium sulf ate, 

with some carbonate and other salts, accumulates near 

the foot of the Brushy Basin shale outcrops at the 

Cactus Rat mines in the Thompsons district, Utah. 

The surface water saturated with these salts has affected 

the recent oxidation of the ore in this area, causing the 

development of sodium vanadate, schroeckingerite, 

andersonite, zippeite, and other minerals not typical 

in vanadif erous ores.

The highly alkaline condition of the ground water 

and the thick salt crusts probably has affected the ore 

since Altithermal time in the Recent epoch a warm 

dry period of great caliche formation from Wyoming 

(Leopold and Miller, 1954) south to Texas and Mexico 

(A. W. Weeks, 1945). In some areas as in Monument 

Valley, Arizona and Utah arid conditions were 

present in pre-Wisconsin time.

RELATIVE STABILITY AND SIZE OF OXIDIZED 

DEPOSITS

Because of the stability of carnotite, large oxidized 

deposits of carnotite have developed at shallow depth 

in the Colorado Plateau. In the progressive alteration of the black low-valent ores, the corvusite stage is 

the critical stage when the minerals are rather unstable and vanadium or uranium or both could be 

leached if water moved through. As soon as the carnotite stage is reached the deposit becomes relatively stable 

under shallow-depth conditions and little happens to it 

until, uncovered by erosion, it reaches the caliche zone 

at or close to the outcrop. Then in the alkaline environment carnotite appears to be slowly leached.

During oxidation of nonvanadiferous uranium ores 

on the Plateau, uranyl carbonates and sulf ates seem to 

be more common than hydrated uranyl oxides, phosphates, arsenates, and silicates. The carbonates and sulf ates are the least stable of the secondary uranium minerals (Garrels and Christ, Part 6 of this volume) and 

do not accumulate to form large oxidized deposits in 

place as does carnotite. The secondary minerals form 

around oxidizing uraninite and spread into joint fractures or along bedding planes but do not remain if 

water moves through the fractures.

Preservation of nonvanadiferous deposits in a dissected plateau such as the Canyon Lands of Utah depends on local structural and sedimentary features. 

Ore in a channel that is parallel to the regional strike 

has a better chance of preservation than ore in a channel parallel to the dip, especially if the channel is in 

strata that dip away from a canyon wall rather than 

toward the canyon. In addition to conditions favoring 

original deposition of ore, the prospector should consider the favorable conditions for preservation of nonvanadiferous ore. The Happy Jack mine on the southwest side of White Canyon is in a much more favorable 

situation for preservation of ore than are some of the 

mines 011 the southwest end of Deer Flats where there 

is less cover and the strata dip toward the canyon; 

these are on the west flank of the Monument Uplift in 

San Juan County, Utah. The ore of the Delta (Hidden 

Splendor) mine is protected in its location under the 

steeply dipping Wingate sandstone of Triassic age along 

the monocline of the southeast side of the San Rafael 

Swell in Utah.

SECONDARY ENRICHMENT

Secondary enrichment is unlikely in most of the vanadif erous uranium ore bodies for the following reasons: 

(1) the ore bodies are small tabular or podlike bodies
78 GEOCHEMISTEY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

with their long dimension parallel to the bedding; (2) 

the thickness is rarely more than 25 feet and commonly 

less than 10 feet; (3) in moist-air oxidation little if any 

migration takes place; (4) oxidation of the small ore 

bodies is rapid; (5) carnotite, the chief oxidized-uranium mineral has very low solubility; and (6) the sulfide content of vanadiferous ore generally is low.

Only a few nonvanadiferous uranium ore bodies in 

the Plateau, such as that at Happy Jack mine, Utah, 

(see Part 16 of this volume) have abundant sulfides 

and a favorable structure for migration of solutions 

from oxidized into unoxidized ore where sooty pitchblende, chalcocite, and covellite are deposited to form 

a zone of secondary enrichment. The chief oxidized 

products of nonvanadiferous uranium ore are much 

more soluble than carnotite and are generally washed 

away rather than redeposited.

TIME AND DEPTH OF OXIDATION

The oxidation of the Colorado Plateau uranium ores 

took place since the water table was lowered following 

the canyon cutting of the present erosion cycle. As the 

regional water table dropped, water was retained in 

the pore spaces of many rocks high above the main 

water table. This is particularly true in the fluvialtype sediments that are the common host rocks of the 

Plateau uranium ores. Tolman (1937, p. 156-157) 

states that the so-called capillary fringe zone may be 

much thicker above a sinking water table than above 

a rising water table.

Detailed study in the Uravan mineral belt shows that 

interbedding of shales, shaly sandstones, and lenticular 

sands together with a folded and faulted structure allows many varied situations with respect to perched 

water tables, retention of moisture, and the location of 

preserved unoxidized ore. The depth to unoxidized ore 

ranges from a few feet to many hundreds of feet. Because of the moderately low rainfall and the wide range 

of permeability of the sediments some deposits have had 

almost no water moving through and others have had 

enough to modify the deposit appreciably.

Bateman (1950, p. 265-269) states that submerged 

oxidized zones are common in western United States. 

Possibly when more detailed knowledge of the oxidation pattern of the Colorado Plateau ores is obtained, a 

history of fluctuating water tables may be found, but 

as yet no submerged oxidized zones have been recognized in Plateau ores. The irregular boundary of oxidation high above the regional water table more closely 

fits his description of stranded oxidized zones (Bateman, 1950, p. 265), "If the water table is depressed 

rapidly, oxidation may not be able to keep pace with it 

and the bottom of oxidation may become stranded above

the water table." The oxidation history of the Plateau 

ores appears to be a one-way process following a lowered water table.

The small amount of radioactive barite found in several mines near Thompsons, Utah, and between Uravan 

and Paradox Valley in Colorado indicates that some of 

the oxidation is Recent. Studies of the Ra-U equilibrium of several high-grade carnotite and tyuyamunite samples by Stieff and Stern (Part 13 of this volume) indicate that in some mines oxidation occurred 

during the Pleistocene.

REFERENCES

Appleman, D. E., and Evans, H. T., Jr., 1957, The crystal structure of carnotite: Acta Cryst, v. 10, p. 765.

Axelrod, J. M., Grimaldi, F. S., Milton, Charles, and Murata, 

K. J., 1951, The uranium minerals from the Hillside mine, 

Yavapai County, Arizona: Am. Mineralogist, v. 36, p. 1-22.

Barnes, W. H., 1955, Hewettite and metahewettite: Am. Mineralogist, v. 40, p. 689-691.

Bateman, A. M., 1950, Economic mineral deposits: New York, 

John Wiley and Sons, Inc., 916 p.

Buryanova, E. Z., and Komkov, A. I., 1955, A new mineral 

ferroselite: Doklady Akad. Nauk S. S. S. R., v. 105, p. 

812-813.

Coffin, R. C, 1921, Radium, uranium, and vanadium deposits of 

southwestern Colorado: Colorado Geol. Survey Bull. 16.

Cooper, Margaret, 1953, Bibliography and index of literature on 

uranium and thorium occurrences in the United States, Part 

1, Arizona, Nevada, and New Mexico: Geol. Soc. America 

Bull., v. 64, p. 197-234.

 , 1954, Bibliography and index of literature on uranium 

and thorium occurrences in the United States, Part 3, 

Colorado and Utah: Geol. Soc. America Bull., v. 65, p. 467- 

590.

Evans, H. T., Jr., and Mrose, M. E., 1955, A crystal chemical 

study of montroseite and paramontroseite: Am. Mineralogist, v. 40, p. 861-875.

 , 1958, The crystal structures of three new vanadium

oxide minerals: Acta Cryst., v. 11, p. 56. 

Finch, W. I., 1954, Geology of the Shinarump No. 1 mine, Seven

Mile Canyon area, Grand County, Utah: U. S. Geol. Survey

Circ. 336.

 , 1955, Preliminary geologic map showing the distribution 

of uranium deposits and principal ore-bearing formations 

of the Colorado Plateau region: U. S. Geol. Survey Mineral 

Inv. Field Studies Map MF 16.

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah: 

U. S. Geol. Survey Bull. 936-P, p. 363-394.

 , 1950, Uranium-bearing sandstone deposits of the Colorado Plateau: Econ. Geology, v. 45, p. 1-11. 

Fischer, R. P., Haff, J. C., and Rominger, J. F., 1947, Vanadium

deposits near Placerville, San Miguel County, Colorado:

Colorado Sci. Soc. Proc., v. 15, p. 115-134. 

Fischer, R. P., and Hilpert, L. S., 1952, Geology of the Uravan

mineral belt: U. S. Geol. Survey Bull. 988-A, p. 1-13. 

Foshag, W. F., and Hess, F. L., 1927, Rossite and metarossite,

two new vanadates from Colorado: U. S. Nat. Mus. Proc.,

v. 72, p. 1-12. 

Friedel, C., and Cumenge, E., 1899, Sur une nouvelle espdce

minerale, la carnotite: Comptes rendus 128, p. 532.
SUMMARY OF THE OEE MINERALOGY 79

Frondel, Clifford, and Ito, Jun, 1956, Boltwoodite, a new uranium silicate: Science, v. 124, p. 931.

Garrels, R. M., 1953, Some thermodynamic relations among 

the vanadium oxides and their relations to the oxidation 

state of the uranium ores of the Colorado Plateaus: Am. 

Mineralogist, v. 38, p. 1251-1265.

Gross, E. B., 1956, Mineralogy and paragenesis of the uranium 

ore, Mi Vida mine, San Juan County, Utah: Econ. Geology, 

v. 51, p. 632-648.

Gruner, J. W., and Gardiner, L., 1952, Mineral associations in 

the uranium deposits of the Colorado Plateau and adjacent 

regions with special emphasis on those in the Shinarump 

formation, Part III. Annual Report, July 1, 1951 to June 

30,1952: Atomic Energy Commission, RMO-566.

Guillemin, M. C., 1955, Une nouvelle espfice minerale: la v6signielte CuaBa(VO4)2(OH) a : Comptes Rendus, v. 240, no. 24, 

p. 2331-2333.

Henderson, E. P., 1935, Steigerite, a new vanadium mineral: 

Am. Mineralogist, v. 20, p. 769-772.

Henderson, E. P., and Hess, F. L., 1933, Corvusite and rilandite, 

new minerals from the Utah-Colorado carnotite region: Am. 

Mineralogist, v. 18, p. 195-205.

Hess, F. L., 1922, Uranium-bearing asphaltite sediments of 

Utah : Eng. and Mining Jour., v. 114, p. 274.

 , 1925, New and known minerals from the Utah-Colorado 

carnotite region: U. S. Geol. Survey Bull. 750, p. 63-78.

 , 1933, in Ore deposits of the western states (Lindgren

volume), p. 459, Am. Inst. Mining Met. Eng.

Hess, F. L., and Henderson, E. P., 1931, Fervanite, a hydrous 

ferric vanadate: Am. Mineralogist, v. 16, p. 273-277.

Heyl, A. V., 1956, Zoning of the Bitter Creek vanadium-uranium 

deposit near Uravan, Colo.: U. S. Geol. Survey Bull. 1042-F, 

p. 187-201.

Hillebrand, W. F., 1913, A danger to be guarded against in making mineral separations by means of heavy solutions: Am. 

Jour. Sci., 4th ser., v. 35, p. 439-440.

 , 1924, Carnotite and tyuyamunite and their ores in Colorado and Utah: Am. Jour. Sci., 5th ser., v. 8, p. 201-216.

Hillebrand, W. F., Merwin, H. E., and Wright, F. E., 1914, 

Hewettite, metahewettite, and pascoite, hydrous calcium 

vanadates: Am. Philos. Soc. Proc., v. 53, p. 31-54.

Hillebrand, W. F., and Ransome, F. L., 1905, On carnotite and 

associated vanadiferous minerals in western Colorado : U. S. 

Geol. Survey Bull. 262, p. 9-31.

Kullerud, Guunar, 1953, The FeS-ZnS system, a geological thermometer : Norsk geol. tidsskr., v. 32, p. 61-147.

Leopold, L. B., and Miller, J. P., 1954, A postglacial chronology 

for some alluvial valleys in Wyoming: U. S. Geol. Survey 

Water-supply Paper 1261, 90 p.

Murata, K. J., Cisney, E. A., Stieff, L. R, and Zworykin, E. V., 

1951, Hydration and base exchange properties of carnotite, 

tyuyamunite and related compounds (abs.) : Am. Mineralogist, v. 36, p. 323.

Ritter, G. C., 1955, Ore procurement program: The Mines Mag., 

v. 45, p. 102.

Smith, D. K., Gruner, J. W., and Lipscomb, W. H., 1957, The 

crystal structure of uranophane

[Ca(H,O) a ](UO2 )2(SiO4)2-3H2O: 

Am. Mineralogist, v. 42, p. 594-619.

Stern, T. W., and Annell, C. S., 1954, A second locality of novacekite: Am. Mineralogist, v. 39, p. 675-676.

Stern, T. W., Stieff, L. R., Evans, H. T., Jr., and Sherwood, 

A. M., 1957, Doloresite, a new vanadium oxide mineral from 

the Colorado Plateau: Am. Mineralogist, v. 42, p. 587-593.

Stern, T. W., Stieff, L. R., Girhard, M. N., and Meyrowitz, Robert, 1956, The occurrence and properties of metatyuyamunite, Ca(UO2 ) 2 (VO4) 3 -3-5H2O: Am. Mineralogist, v. 41, p. 

187-201.

Stern, T. W., and Weeks, A. D., 1952, Second occurrence of bayleyite in the United States: Am. Mineralogist, v. 37, p. 1058- 

1060.

Stieff, L. R., and Stern, T. W., 1952, Identification and lead-uranium ages of massive uraninites from the Shinarump conglomerate, Utah : Science, v. 115, p. 706-708.

Stieff, L. R. Stern, T. W., and Sherwood, A. M., 1956, Coffinite, 

a uranous silicate with hydroxyl substitution: a new mineral : Am. Mineralogist, v. 41, p. 675-688.

Sun, Ming-Shan, and Weber, R. H., 1957, Santafeite, a new hydrated vanadate from New Mexico: Geol. Soc. America 

Bull., v. 68, p. 1802.

Thompson, M. E., Ingram, Blanche, and Gross, E. B., 1956, Abernathyite, a new uranium mineral of the inetatorbernite 

group: Am. Mineralogist, v. 41, p. 82-90.

Thompson, M. E., Roach, Carl, and Braddock, William, 1956, 

New occurrences of native selenium: Am. Mineralogist, v. 

41, p. 156-157.

Thompson, M. E., Roach, C. H., and Meyrowitz, Robert, 1958, 

Simplotite, a new quadrivalent vanadium mineral from the 

Colorado Plateau: Am. Mineralogist, v. 43, p. 16-24.

Thompson, M. E., Roach, C. H., and Meyrowitz, Robert, 1958, 

Sherwoodite, a mixed vanadium (IV)-vanadium (V) mineral from the Colorado Plateau: Am. Mineralogist, v. 43, 

p. 749-755.

Thompson, M. E., Weeks, A. D., and Sherwood, A. M., 1955, Rabbittite, a new uranyl carbonate from Utah: Am. Mineralogist, v. 40, p. 201-206.

Tolinan, C. F., 1937, Ground water, New York, McGraw-Hill 

Book Co., 593 p.

Trites, A. F., Jr., and Chew, R. T., 3d, 1955, Geology of the 

Happy Jack mine, White Canyon area, San Juan County, 

Utah: U. S. Geol. Survey Bull. 1009-H.

Weeks, A. D., Cisney, E. A., and Sherwood, A. M., 1953, Montroseite, a new vanadium oxide from the Colorado Plateaus : Am. Mineralogist, v. 38, p. 1235-1241.

Weeks, A. D., and Thompson, M. E., 1954, Identification and 

occurrence of uranium and vanadium minerals from the 

Colorado Plateau: U. S. Geol. Survey Bull. 1009-B.

Weeks, A. D., Thompson, M. E., and Sherwood, A. M., 1955, 

Navajoite, a new vanadium oxide from Arizona: Am. Mineralogist, v. 40, p. 207-212.

Weeks, A. D., Truesdell, A. H., and Haffty, Joseph, 1957, The 

nature of the ore boundary and its relation to diagenesis 

and mineralization: Geol. Soc. America Bull., v. 68, p. 

1810-1811.

Weeks, A. W., 1945, Quaternary deposits of Texas Coastal Plain 

between Brazos River and Rio Grande: Am. Assoc. Petroleum Geologists Bull., v. 29, p. 1693-1720.

Part 6. BEHAVIOR OF URANIUM MINERALS DURING OXIDATION

By R. M. GARRELS and C. L. CHRIST

CONTENTS

Abstract. ___________________________________________

Introduction _______________________________________

Uraninite. _________________________________________

Coffinite__ _________ _ __ __ __ __ __. _ ______ __ _

Reaction of uraninite with ground water without oxidaReactions of UOs with ground water. _________________

UOs hydrates and related compounds. ____... . ..___

UOs carbonate complexes____________________ _ _

Page 

81 

81 

84

84

85

85

85

85

Reactions of UOs with ground water Continued

Uranylsulfates.________________________________

Summary of the oxidation-reduction relations in 

uranium ores low in vanadium, phosphorus, or 

arsenic ______________________________________

The uranium layer compounds vanadates, phosphates, 

and arsenates.___________________________________

Summary, _________________________________________

Literature cited.__________________________________

Page

86

87

87

89

89

ILLUSTRATIONS

FIGURE 13. Reactions and products in the weathering of uraninite and cofBnite. 

14. Some structures involved in oxidation of uraninite _______________

Page

82

83

ABSTRACT

Uranium occurs as U(VI) and U(IV) in minerals of the 

Colorado Plateau ores. The number of species containing 

U(VI) is large, but only two U(IV) minerals are known from 

the Plateau: uraninite, an oxide, and coffinite, a hydroxy-silicate. These oxidize to yield U(VI) before reacting significantly with other mineral constituents. Crystal-structure 

analysis has shown that U(VI) invariably occurs as uranyl 

ion, UO.+a. Uranyl ion may form complex carbonate or sulfate 

ions with resulting soluble compounds, but only in the absence 

of pentavalent vanadium, arsenic, or phosphorus. In the presence of these elements In the +5 valence state, the uranyl ion 

is fixed in insoluble layer compounds formed by union of uranyl 

ion with orthovanadate, orthophosphate, or orthoarsenate. Under favorable conditions UOa+a may react to form the relatively 

insoluble rutherfordine, UO.COa, or hydrated uranyl hydroxides. 

These are rarely found on the Colorado Plateau as opposed to 

their excellent development in other areas, a condition which 

is apparently related to the semiarid climate and low water 

table of the Plateau. Uranium may also be flxed~as-uranyl 

silicate, but little is known about minerals of this kind. In 

the present study, emphasis has been placed on a detailing 

of the chemical and crystal-structure changes which occur in 

the oxidation paragenetic sequence.

INTRODUCTION

Uranium occurs in two valence states in minerals 

from the Colorado Plateau uranium ores: as U(VI) 

and U (IV). The number of species containing U (VI) 

is large, but only two minerals containing U(IV) have 

been isolated and characterized. They are uraninite, 

an oxide, and coffinite, a silicate or hydroxy-silicate. 

As has been documented in other parts of this volume 

(see especially Parts 5, 14 and 15), the occurrences of 

uranium minerals are quite consistent with the view 

that these two minerals are the progenitors of all the 

U(VI) phases. That interpretation will be accepted 

for the purposes of this discussion, and emphasis will 

be on a detailing of the chemical and structural 

changes that result in the production of many-hued 

and chemically diversified later generations from these 

two parent materials. These relations are shown in 

figures 13 and 14; the text is best followed by continuous reference to them.

81
82 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES 

INSOLUBLE OXIDATION PRODUCTS

VAN£P>TTES

FIGURE 13. Reactions and products in the weathering of uraninlte and cofflnite. Data on minerals from Weeks and Thompson (1954),

Gruner (1954), and Weeks (oral communication).
BEHAVIOR OF URANIUM MINERALS DURING OXIDATION 83

+ 2

. ,

Mg

D

ZP (As0 4)~ H,0

(Illustrated by autunite Ca(U0 2). 2 (P04) 2 . n H20, 

after Beintema, 1938)

INSOLUBLE OXIDATION PRODUCTS

Phosphates and arsenates 

(Vanadates are similar but see Part 7)

SULFATES

Silicon Uranium

SILICATES

[(UO 2).2(5104)3]" Sheet structure in uranophane, 

according to Smith, Gruner, and Lipscomb, 1957

* [(U0. 2)(C0 3) 2(H 2 0)]'

CARBONATE COMPLEX IONS 

(U02T 2 ion normal to plane)

(OH)'

U0. 2(OH) 2

URANYL HYDROXIDES 

2 ion normal to plane

u

+ 4

URANINITE U0 2 

FIOTJEB 14. Some structures Involved in oxidation of uraninite.
84

URANINITE

Uraninite from Plateau deposits is fine grained. 

Analysis of carefully purified materials invariably 

shows UO2 and UO3 in various ratios, with a tendency 

for the maximum ratio to occur in massive specimens 

collected from sites protected from the atmosphere 

until mining operations took place. Presumably the 

material originally precipitated was largely UO2, and 

most of the UO3 reported is a product of the radioactive 

decay of uranium to lead, plus that from oxidation by 

the atmosphere (Palache and others, 1944).

Synthetic preparations of UO2 give sharp X-ray diffraction powder patterns (Kerr and others, 1954) corresponding to the fluorite structure (fig. 14). Uraninite 

samples from the Plateau give essentially the same 

powder patterns, but the definition of the patterns 

varies widely. The diffuseness of the patterns increases 

with increasing UO3. The reasons for this have been 

studied by many investigators (Brooker and Nuffield, 

1952; Kerr and others, 1954). Apparently, the loss of 

definition in the patterns results from a variety of causes 

including a reduction in crystallite size of the UO2 and 

nonunif orm oxidation throughout the sample. No pattern corresponding to a TJ(VI) compound is found; 

presumably the U( VI) exists as UO3 in the amorphous 

state.

During radioactive decay, uranium atoms disintegrate through a series of daughter products to lead, leaving an excess of oxygen atoms relative to uranium 

atoms; hence chemical analysis reports UO2, UO3 , and 

PbO. As an equation (for 50 percent disintegration) :

2UO2 >PbO+UO3

Plateau uraninites are not older than 60 to 70 million 

years (Stieff and Stern, 1952); the analytical UO3 content from development of lead in that time span would 

be about 2 percent by weight. The least altered uraninite so far analyzed for UO2 and UO3 has a 

UO8 content of about 30 percent (Stern, T. W., oral 

communication) showing that no entirely fresh material 

has been obtained.

The structural pattern of uraninite can still be discerned in X-ray powder photographs of material containing as much as 80 percent UO3 (Brooker and Nuffield, 1952, p. 366), and no trace of a UO3 pattern can 

be seen.

The development of UO3 by atmospheric oxidation is 

clearly as pseudomorphic process; the original grain 

shapes of UO2 are retained, and there are no characteristic changes in color or texture. However, U03 percentage of a given specimen does agree with position 

relative to access to oxygen; cores of massive specimens 

are lower in UO3 content than the rims.

Thus the first stage of supergene oxidation of uraninite is essentially a solid-state phenomenon and gives 

rise to material that analyzes as UO3 but that still resembles the parent UO2 , megascopically. This new material is amorphous under X-rays.

The probable reaction is :

UO UO3 AF = - 36 .4 kcal

The free-energy change probably is somewhat less 

negative than that calculated here for the crystalline 

materials because the UO3 is amorphous.

Solution of UO2 without oxidation is not an important process because of the extremely low solubility of 

U02 in deaerated water. Instead, it oxidizes much more 

rapidly and effectively in the solid state.

COFFINITE

The new mineral, coffinite (Stieff and Stern, 1955), 

is not well characterized, but is a U(IV) silicate, with 

some hydroxyl substitution for the silicate ion. Presumably its formula ranges between U2 (SiO4 ) 2 and 

U2 ( OH ) 4 ( SiO4 ) . It occurs typically as a replacement 

of woody material, or in intimate association with carbonaceous material, mostly of woody origin (Part 5). 

Very serious problems have arisen in attempting to 

separate a pure phase from the environment, owing to 

many causes such as the usual extreme fineness of grain 

and the intimate intergrowth with other materials. 

However, X-ray, infrared, and electron-diffraction 

studies show it to be an analogue of zircon and thorite, 

with the same kind of transition to an hydroxy-substituted species. It is probably a primary mineral, although Weeks and Coleman (oral communication) suspect that it is nearly always late in the paragenetic 

sequence, and may result from complex reactions among 

uranium in solution, woody material, and silica released 

into solution by the action 'of the ore fluid on sand 

grains.

Its intimate intergrowth with uraninite indicates 

similar very low solubility relations in a reducing environment, and there is a suggestion that it is somewhat 

more resistant to oxidation than uraninite. Nevertheless, it probably oxidizes much more rapidly than it 

dissolves, so that, as in the case of uraninite, mineralogic 

changes involving a quadrivalent uranium ion in solution are an unimportant aspect of its postdepositional 

history.

The importance of coffinite as an ore mineral is difficult to assess, chiefly because of the short time that 

has elapsed since its recognition ; the number of occurrences already recorded, however (Gruner and Smith, 

1954, p. 8 ; Stieff and Stern, oral communication) , sug-
BEHAVIOR OF URANIUM MINERALS DURING OXIDATION 85

gests that it makes up a significant proportion of the 

uranium content of many primary Plateau ores.

In summary, the uranium of coffinite, like that of 

uraninite, alters rapidly to U(VI) in the presence of 

air; the mineral structure is destroyed and the greater 

part of the postdepositional history involves U(VI).

REACTION OF URANINITE WITH GROUND WATER 

WITHOUT OXIDATION

One of the major questions concerning the postdepositional history of the Plateau ores is the possibility 

of migration of uranium by solution and redeposition 

as a result of the action of moving ground water. Inasmuch as ground waters below the water table are 

usually reducing and slightly alkaline, the problem in 

that environment appears to be related to direct solubility of uraninite and coffinite in such media rather 

than to transport by a combined oxidation-transportreduction process.

Uraninite is so extremely stable, in terms of giving 

up U(IV) to water solutions, that it appears doubtful 

if much movement can take place without oxidation. 

The same is probably true of coffinite. No good data 

are available on the solubility of UO2 in water, although 

some work has been done on U(OH) 4, the less stable 

hydroxide (Leider, 1954). Values reported for the 

solubility of the hydroxide in water and NaOH solutions range around 10~6 moles per liter at average 

ground water pH values (7-9). There is, however, a 

strong likelihood that this measured value is that of 

TJ(VI), rather than U(IV), inasmuch as oxidation 

occurs very easily, and the amount of soluble uranium involved is so small. Also, Leider's results 

(1954) for the solubility of UO3 -H2O and U(OH) 4 

are strikingly similar, both in acid and alkaline solution. UO2 is notably difficult to dissolve even in very 

strong nonoxidizing acids. According to Phair and 

Levine (1953, p. 367),

The results of these investigations show that unaltered pitchblende is itself relatively insoluble in even the most concentrated 

solutions of H2SO4 at room temperature. Once, however, it 

has become partly oxidized by contact with oxygen * * *.

Further indirect evidence on the solubility of U02 

comes from the tendency of U(IV) in solution to behave as a moderately strong basic cation with little 

tendency to form stable soluble complexes. In other 

words, it is quite certain the U02 will not dissolve 

appreciably without oxidation unless very stable complexes exist. We are always in the quandary of not 

being sure of the composition of ancient ground waters, 

but at least there is no current reason to expect that 

they contained any effective U(IV) complexing agents.

REACTIONS OF U08 WITH GROUND WATER

TJ08 HYDBATES AND BELATED COMPOUNDS

As shown before, the first stage of alteration of 

uraninite is to amorphous UOg, apparently by an essentially solid state reaction, without the intervention of 

a solution step. UO3 is unstable relative to uranyl hydroxide hydrate in water solution (Garrels, 1955), and 

the reaction

UO3 +2H20-VU02 (OH) 2 .H2O AF=-13 kcal

takes places in a pure water solution.

There is a family of uranyl hydroxide hydrates, including UO2 (OH) 2 -H2 0, UO2 (OH) 2 -i/2H2O, and 

UO2 (OH) 2 (Katz and Rabinowitch, 1951, p. 281-294), 

but they are not common minerals on the Colorado 

Plateau. They differ from each other by small increments of free energy, which probably explains their 

coexistence. It appears that the hydroxide monohydrate (U02 (OH) 2 -H2O) is in fact the stable species 

in water at 25° C and atmospheric pressure (Bullwinkel, 1954, p. 8).

The sparsity of uranyl hydroxide hydrates on the 

Plateau, as opposed to their abundance and striking 

development in other areas, perhaps is related to the 

semiarid climate and low water table of the Plateau. 

Oxidation takes place in thin films of water on the 

mineral grains after the water table has dropped, and 

concentration of ions is high in these films, so that 

compounds other than the oxides develop. The uranyl 

hydroxide hydrates probably form and persist only in 

the virtual absence of carbonate species.

Structurally the uranyl hydroxide hydrates are members of the more general class of compounds represented 

by the formula xMeOyUO3 -zH2O where Me is Pb or 

Ba, and perhaps Ca (Christ and Clark, 1955). Among 

the minerals included in this class are becquerelite, 

schoepite, billietite, masuyite, fourmarierite, and vandendriesscheite. The structure common to all these 

minerals is shown in figure 14. It consists of a pseudohexagonal arrangement of linear vertical uranyl ions 

linked together into infinite horizontal sheets by the 

hydroxyl ions, with the sheets held together in the 

crystal in the vertical direction by water molecules or 

by metal ions and hydroxyl ions. Thus, the formula 

xMeO-yUOS 'zH2O should be written as

xMe(OH) 2 -yUO2 (OH) 2 - (z-x-y)H2O

UO, CABBONATE COMPLEXES

Uranyl ions form soluble complexes with carbonate 

ions. In many ores calcite is an abundant constituent
86 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

of the rocks, and during oxidation of accompanying 

pyrite the calcite is dissolved to give a solution high in 

HCCVion. Unless there is an excess of pyrite relative 

to calcite, the resultant solution eventually reaches a 

pH between 6 and 8, representing ideal conditions for 

the formation of uranyl carbonate complexes (Bullwinkel, 1954).

The following discussion of the carbonate complexes 

in water is based largely on the work of Bullwinkel 

(1954).

Both a di- and a tri-carbonate complex are formed:

and

U02+++3COr2-»[U02 (C03) 3]-4 

UO2+++2COr2 +2H2O^[UO2 (CO3)2 (H2O) 2]-2

These complexes are most effective in the intermediate pH range because they are destroyed both by H+ 

and OH~. Addition of H* to the tricarbonate complex 

in solution gives successively the dicarbonate complex 

and the uranyl ion:

[U02 (C03 ) 3]-4+2H20+H-'-->[U02 (C03 ) 2 (H20)2]-2

+HCO-3 

[U02 (CO3 ) 2 (H20) 2]-2+2H+-VUO2++ + 2H2O + 2HCOr

Further acid addition will form H2CO3 .

Addition of OH" to the tricarbonate complex tends 

to form insoluble metal uranates with available cations:

[U02 (C03) 3]-4 +40H-+Me++- »MeUO4+2H2O

+ 3CO3-2

Thus either acid or alkaline conditions tend to break 

up the carbonate complexes and reduce the solubility 

of uranium in solution. Evaporation, on the other 

hand, tends to precipitate the solid uranyl carbonates. 

Five of these are known from the Plateau: liebigite, 

schroeckingerite, bayleyite, andersonite, and rabbittite. 

Their compositions are shown in figure 13. The particular species formed depends chiefly on the relative 

abundance of Na+, Ca+f, or Mg1"1".

All these carbonates are hydrated. The crystals contain the complex carbonate ions (fig. 14) as discrete 

units and, accordingly, are all easily soluble in water; 

their geologic behavior reflects this high solubility. 

The minerals form as efflorescences on mine walls and in 

the zone of evaporation near the ground surface. Their 

existence is transitory even by human standards. 

Changes in the distribution of the carbonates can be 

observed almost from day to day. With the exception 

of an occurrence in the Thompsons district, Utah 

(Weeks, A. D., oral communication) uranyl carbonates 

are known only from nonvanadiferous ores.

Anhydrous uranyl carbonate UO2CO3 (rutherfordine) is very rare on the Plateau, although it is relatively abundant in other uraniferous terranes. Some 

insight into the reason for its rarity can be interpreted 

from Bullwinkel's observations (1954, p. 35) on the 

conversion of UO2 (OH) 2 H2O to UO2 CO3 by bubbling 

of air through a water suspension of the hydrated oxide. 

The small amount of CO2 in air is sufficient to cause 

the change. On the other hand, if excess carbonate or 

bicarbonate is added to the solution (as Na2C03 or 

NaHCO3 ) rutherfordine dissolves as uranyl carbonate 

complexes are formed. Although the experiment has 

not been performed, it appears likely that evaporation 

would yield hydrated compounds with a UO2++ : CO3= 

of 1 : 3, like those observed on the Plateau. Thus rutherfordine probably forms under humid climatic conditions, where relatively pure water is draining through 

the zone of oxidation; whether it or uranyl hydroxide 

hydrates forms depends on the partial pressure of CO2 

in the atmosphere. On the Plateau, where the ground 

waters contain much carbonate and bicarbonate, rutherfordine, if formed, would dissolve, and the only carbonates are those formed by evaporation, which record 

their genesis from the soluble carbonate complex by the 

universal UO2++ : CO3= of 1 : 3, as opposed to the 1 : 1 in 

rutherfordine. Furthermore the structure of rutherfordine is similar to that of the uranyl hydroxide hydrates, rather than to the hydrated uranyl carbonates 

(Christ, Clark, and Evans, 1955) .

URANYL SULFATES

When pitchblende or coffinite oxidizes in the presence 

of iron sulfides or copper-iron sulfides, or both, and in 

the absence of appreciable amounts of vanadium, phosphorus, or arsenic, small amounts of the sulfates 

uranopilite, johannite, and zippeite may form. The 

genesis of the sulfates is similar to that of the carbonates. Oxidation of accompanying sulfides yields 

sulf ate ion in acid solution. Sulf ate, like carbonate, 

forms a complex with the uranyl ion. The sulf ate complexes are not nearly so stable as the carbonate but are 

sufficiently stable to increase the solubility of U(VI) 

markedly. According to Brown (Brown and others, 

1954) the "complex" is undissociated UO2SO4 . The 

dissociation constant of the reaction

is approximately 7 x 10~4 at room temperature, indicating that uranyl sulf ate dissolved in water would have 

a few percent of its uranium available as uranyl ion. In 

the presence of excess sulf ate, as in the oxidation of an 

ore containing sulfide, the fraction of uranium tied up 

would be much greater.
BEHAVIOR OF URANIUM MINERALS DURING OXIDATION 87

Like the carbonates, solid uranyl sulfates apparently 

form only by evaporation of ground water. The resultant compounds are poorly characterized. They 

form crystals of appreciable size only with great difficulty; in most occurrences they form colloform precipitates. They are somewhat analogous to the basic 

copper sulfates, such as brochantite, for the originally 

precipitated material is essentially a gel of indefinite 

composition. Upon aging, composition changes progressively with water loss, and continuous recrystallization of a whole series of solid phases takes place. It 

is likely then that the compositions given in figure 13 

are not truly representative of most natural uranyl sulfates inasmuch as they have been determined from the 

best crystallized minerals available. The natural materials found as crusts 'and efflorescences are probably 

more hydrated than the selected materials studied in the 

laboratory. Only the structure of johannite is known 

(D. Appleman, oral communication). A sketch of the 

structure is shown in figure 14.

SUMMARY OF THE OXIDATION-REDUCTION RELATIONS IN URANIUM ORES LOW IN VANADIUM, 

PHOSPHORUS, OR ARSENIC

As indicated in figure 13 oxidation of primary 

uranium ores in the absence of vanadium, phosphorus, 

and arsenic may well result in rapid loss of uranium to 

ground water. The absence of any "fixing elements", 

plus complexing of the uranyl ion by sulfate or carbonate ion, provides optimum conditions for retaining 

uranium in solution. If the primary association is 

uraninite plus pyrite in a noncarbonate gangue, oxidation produces a strongly acid sulfate solution in which 

UO3 dissolves as fast as it is formed by solid-state oxidation of the original UO2 . Unless evaporation essentially to dryness takes place the dissolved uranium is 

carried away.

Uranium is even more soluble in the presence of carbonates. The hydrogen ion developed by oxidation of 

the sulfides is neutralized by reaction with the calcite of 

the gangue and a neutral or slightly alkaline solution 

high in sulfate, bicarbonate, and carbonate is formed 

under these conditions. The complexing action of the 

carbonate ion is added to that of the sulfate ion producing conditions of maximum uranium solubility.

In the presence of reactive silica, uranium can be 

fixed into the relatively insoluble silicates. Unfortunately, little is known of the environment in which they 

can form, or even concerning their stability after crystallization. Locally, however, they are important factors in the fixation of uranium in nonvanadiferous 

ores.

In nonvanadiferous ores, then, there is commonly 

abundant evidence of the migration of uranium in the

zone of oxidation. For example, the outcrop itself may 

be almost entirely free of uranium, and its former 

presence may be suggested only by traces of oxidized 

copper minerals. Behind the outcrop, a zone measured usually in a few feet or a few tens of feet may 

be found in which uranyl sulfates and carbonates are 

intermixed with iron oxides and oxidized copper minerals. In this zone chemical uranium values may differ markedly and erratically from equivalent uranium, 

inasmuch as the daughter products of radioactive disintegration are generally less soluble and uranium tends 

to move differentially. At the margin of oxidation a 

rather abrupt change to essentially unaltered pitchblende-sulfide ore may take place. The extent and effects of oxidation differ markedly, of course, from place 

to place, depending upon the details of the- geology, 

but movement, redistribution, and loss of uranium are 

characteristic. Loss of uranium is retarded by adsorption of uranyl ion on hydrous ferric oxides, and similar 

colloidal materials, but the efficiency of the process is 

incompletely understood (Lovering, 1955).

THE URANIUM LAYER COMPOUNDS VANADATES, 

PHOSPHATES, AND ARSENATES

In the upper part of figure 13 a large number of 

mineral species are listed under the headings of vanadates, phosphates, and arsenates. There is, however, a 

single structural theme that unifies them so that their 

genesis can be discussed almost as if they were but a 

single mineral. Inspection of their formulas and of 

their basic structure, as shown in figure 14, shows that 

they are composed of sheets made up by a combination 

of uranyl ion with vanadate, phosphate, or arsenate ion 

and that various metal ions and (or) water are rather 

loosely bound between the sheets. The vanadate, arsenate, and phosphate ions are coordinated around the 

uranium of the uranyl ion in similar manner, except 

that in the arsenates and phosphates the ortho-ion, 

(X04 )~3, is the coordinating unit, whereas in the vanadates the metavanadate ion, (V2O8 )~6, is the coordinating unit (Daniel Appleman, oral communication). The 

(V2O8 )~6 ion has essentially the same structure as a 

segment of the vanadium-oxygen chain found in 

KVO3 -H2O (Christ, Clark, and Evans, 1954). The 

bonds within a layer are very strong. In addition, as 

can be seen from figure 14, the planar structure can be 

extended essentially indefinitely. This possibility of 

a development of "infinite" sheets explains why the 

vanadates, phosphates, and arsenates are so slightly soluble, whereas the carbonates and sulfates, which contain 

finite groups, are so soluble.

The picture emerges that primary uranium minerals 

oxidize to UO3 . UO3 in turn reacts with water to pro-
88 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

vide a certain amount of uranyl ion. As soon as uranyl 

ion encounters pentavalent vanadium, phosphorus, or 

arsenic in solution, there is a tendency to build up the 

claylike sheets which are held together loosely by whatever cations happen to be in solution and by water molecules. Neither phosphorus nor arsenic occurs in important amounts in the Plateau deposits except locally. 

Therefore, the reactions of uranium with vanadium will 

be discussed at length and the corresponding phosphates 

and arsenates will be treated only by implied analogy.

The two major uranium vanadates are carnotite and 

tyuyamunite or metatyuyamunite, which has a lower 

degree of hydration. The vanadium in these compounds 

is 5-valent vanadium. Because the primary oxidizable 

vanadium mineral apparently is montroseite, V(III) 

oxide, neither carnotite nor tyuyamunite can form until 

uranium has achieved a +6 valence and vanadium has 

gone all the way from +3 to +5. Various studies (see 

Part 5) have shown that pitchblende and coffinite are 

among the first minerals to oxidize. Usually uranium 

reaches +6 valence before all the vanadium has been 

oxidized to vanadium (IV). Consequently there is a 

stage during the oxidation of a given uranium-vanadium deposit in which the uranium occurs as uranium 

(VI) but in which there is no vanadium (V) with which 

it can combine. Little is known concerning the solid 

phase in which uranium occurs at this stage. Some 

specimens have been examined that contain several percent uranium as (VI) but in which there is no identifiable uranium mineral. It is conceivable that at this 

stage the uranium exists as amorphous black UO3 , although it is difficult to understand why some hydration 

to give brightly colored UO3 hydrates has not occurred, 

but they seem to be absent. Also, at this stage the uranium is readily leachable in very dilute acid solution 

if precautions are taken to prevent any oxidation of 

vanadium to vanadium (V). Numerous speculations 

could be made concerning the phases containing uranium at this stage, but so little real evidence is available 

that these probably should be deferred.

In studies of the system involving UO3 , V2 05 , K2O, 

and H2O a uranyl vanadate with a higher vanadiumuranium ratio than carnotite or tyuyamunite has a 

rather wide field of stability (see Part 8). It is possible, therefore, that carnotite and tyuyamunite do not 

precipitate directly at pH below about 6, but are preceded by a solid phase of different composition which 

reconstitutes by a decomposition reaction. The presumed intermediary compound is shown in figure 13 as 

rauvite. The necessity for such an intermediary, together with the extreme insolubility of the minerals, 

may explain the extreme fineness of grain of most natural carnotite and tyuyamunite.

The solubility of carnotite in normal ground waters 

is very small, perhaps even in the presence of appreciable carbonate. The solubility of tyuyamunite is considerably greater although no quantitative values are 

available. This difference can be attributed to the excellent "fit" of potassium ion into the positions between 

the uranyl vanadate sheets. The calcium ion is smaller 

than the potassium ion and even though it is doubly 

charged it does not bind the sheets together with equal 

effectiveness. A good parallel can be drawn between 

the uranyl vanadates, phosphates, and arsenates and 

the ordinary clay minerals. The cations are held in 

exchange positions. As in the clays, potassium and 

calcium are held very firmly, whereas sodium and magnesium are more easily exchanged.

Therefore, even in the presence of abundant calcium 

and sodium a small amount of potassium ion in solution is preferentially taken up in the interlayer positions to form carnotite, so that carnotite is a widespread 

and extremely important ore mineral even in environments in which calcium ion is more concentrated than 

potassium in the ground waters. On the other hand, a 

great deal of yellow powdery material probably has 

been called carnotite that is in fact tyuyamunite.

The very low solubility of carnotite under most earthsurface conditions is shown by the presence of equilibrium between uranium and daughter products in 

most bulk samples of carnotite-bearing ores. If there 

were substantial active leaching, relative movement of 

uranium and daughter products should have disrupted 

this equilibrium. Furthermore, lead-uranium ages of 

many carnotite-bearing samples are in good agreement 

with those containing pitchblende, showing oxidation 

in place without migration. On the other hand, near 

the outcrop, or more generally in the zone in which 

there is active entrance of water into and evaporation 

from uranium-vanadium ores, it appears possible that 

considerable movement of uranium may occur. The 

thin soils in most of the Plateau area are very high in 

carbonates, attesting the continuous upward migration 

of carbonates by a capillary process. Under these optimum conditions for the formation of soluble uranyl 

carbonate complexes uranium may be leached even from 

carnotite.

Oxidation of a primary uraninite-montroseite (or 

coffinite-montroseite) ore probably follows these steps: 

First, uranium minerals oxidize to uranium (VI). The 

solid species of this stage are unknown. At a slower 

rate the vanadium oxidizes to vanadium (IV) and then 

to vanadium (V). As soon as any vanadium (V) is 

available it unites with uranyl ion to form a uranyl 

vanadate. The nature of original uranyl vanadate 

formed is not well defined and perhaps is best described
BEHAVIOR OF URANIUM MINERALS DURING OXIDATION 89

under the general term of rauvite. Then, through decomposition, typical uranyl metavanadate sheet structure develops and available ions in the solution take up 

interlayer positions. If there is any appreciable potassium, it is taken up preferentially and binds the sheets 

together into the very insoluble carnotite. After potassium is essentially used up in forming carnotite, tyuyamunite is formed. Carnotite or tyuyamunite, once 

formed, tend to be stable under the semiarid conditions 

of the Colorado Plateau, although local movement and 

recrystallization along cracks and fractures is observed 

commonly, and it is not unlikely that there is considerable movement at or near the present ground surface. 

This near-surface movement undoubtedly is promoted 

chiefly by the presence of carbonates.

No quantitative data are available on the relative 

solubilities of the uranyl vanadates, arsenates, and 

phosphates, although from their general geologic behavior the sequence as given probably is in order of 

increasing solubility.

SUMMARY

In summary, primary uranium minerals are essentially insoluble under reducing conditions. As soon as 

oxygen is added to the system, however, direct oxidation of the solid uranium (IV) phases apparently takes 

place to give amorphous UO3 . In the absence of vanadium, phosphorus, or arsenic the U03 dissolves very 

easily in ground waters, especially those containing 

carbonate or sulfate. Deposition of the dissolved uranium takes place only as a result of evaporation of the 

ground water to form crusts and efflorescences of uranyl 

carbonates or basic uranyl sulfates, or locally by reaction with dissolved silica to form uranyl silicates. 

Uranium (VI) is fixed by arsenic and phosphorus and 

especially by vanadium. It apparently becomes fixed as 

a uranyl vanadate of transitory existence by reaction 

with almost any anionic species containing vanadium 

(V). Decomposition of this intermediate, plus reaction with potassium or calcium produces insoluble 

carnotite or tyuyamunite. Once precipitated these 

minerals persist except where exposed at the outcrop.

LITERATURE CITED

Beintema, J., 1938, On the composition and the crystallography 

of autunite and the meta-autunites: Rec. travaux chim. 

Pays-Bas, v. 57, p. 155-175.

Brooker, E. J., and Nuffield, E. W., 1952, Studies of radioactive 

compounds: IV Pitchblende from Lake Athabaska, Canada : Am. Mineralogist, v. 87, p. 363-385.

Brown, R. D., Bunger, W. B., Marshall, W. L., and Secoy, O. H., 

1954, The electrical conductivity of uranyl sulfate in aqueous solution: Am. Chem. Soc. Jour., v. 76, p. 1532-1535.

Bullwinkel, E. P., 1954, The chemistry of uranium in carbonate 

solutions: U. S. Atomic Energy Comm., RMO-2614.

Christ, 0. L., and Clark, J. R., 1955, Crystal chemical studies of 

uranium oxide hydrates (abstract) : Geol. Soc. America 

Bull., v. 66, p. 1542.

Christ, 0. L., Clark J. R., and Evans, H. T. Jr., 1954, Crystal 

structure of potassium metavanadate monohydrate, KVO«* 

HaO: Acta Cryst., v. 7, p. 801-807.

 1955, Crystal structure of rutherfordine, UO2COa: Science, v. 121, p. 472-473.

Garrels, R. M., 1955, Some thermodynamic relations among the 

uranium oxides and their relation to the oxidation states 

of the uranium ores of the Colorado Plateaus: Am. Mineralogist, v. 40, p. 1004-1021.

Gruner, J. W., 1954, The uranium mineralogy of the Colorado 

Plateau and adjacent regions: Guidebook no. 9, Utah Geol. 

Soc., and Utah Geol. and Mineral. Survey, Salt Lake City, 

Utah.

Gruner, J. W., and Smith, D. K., Jr., 1954, Ninth progress report for period April 1 to Oct. 1,1954: U. S. Atomic Energy 

Comm., RME-3103.

Eatz, J. J., and Rabinowitch, Eugene, 1951, The chemistry of 

uranium. Pt. I, The element, its binary and related compounds, New York, McGraw-Hill Book Co., Inc.

Kerr, P. F., Croft, W. J., Miller, L. J., and Sciacca, T. P., Jr., 

1954, Annual report June 30, 1953, to April 1, 1954, Pt. II: 

U. S. Atomic Energy Comm., RME-3096.

Leider, Herman, 1954, Equilibria of thorium hydroxide, uranium (IV) hydroxide, and uranium trioxide monohydrate 

in acidic and alkaline media at 25° C.; Ph. D. thesis, Department of Chemistry, Wayne University, Detroit, Mich.

Levering, T. G., 1955, Progress in radioactive iron oxides investigations : Econ. Geology, v. 50, p. 186-195.

Palache, Charles, Berman, Harry, and Frondel, Clifford, 1944, 

Dana's system of mineralogy, v. 1, p. 614, New York, John 

Wiley and Sons, Inc.

Phair, George, and Levine, Harry, 1953, Notes on the differential 

leaching of uranium, radium, and lead from pitchblende 

in H2 SO4 solutions: Econ. Geology, v. 48, p. 358-369.

Stieff, L. R., and Stern, T. W., 1952, Identification and leaduranium ages of massive uraninites from the Shinarump 

conglomerate, Utah: Science, v. 115, p. 706-708.

 1955, Preliminary description of coffinite a new uranium 

mineral: Science, v. 121, p. 608-609.

Weeks, A. D., and Thompson, M. E., 1954, Identification and occurrence of uranium and vanadium minerals from the Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B.

Part 7. THE CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM

BY HOWARD T. EVANS, JR.

CONTENTS

Abstract.______------_--_--------___--_--_---------

Introduction _______-__-_----_--_-_____-__----_---_-

Electrochemistry of vanadium.-. ______ _______________

Reduced forms of vanadium~_---______-_--_-_________

Vanadium (II)-----_-_-------__----_-----------

Vanadium (III) and vanadium (IV): the montroseite group.____-__-_-_-_----_______--_------_

Oxidized forms of vanadium._________________________

Oxidation of quadrivalent vanadium. ______ _______

pH dispersion of vanadium (V) complexes in solution. ._________---___-_--____----_----_-__-__

Orthovanadates and pyrovanadates-_-_-__________

.Page . Page

91 Oxidized forms of vanadium Continued

91 Meta vanadates _ _ _______________________________

92 Poly vanadates: the pascoite group________-__--__-

93 Hewettite group____-__________________-________

93 Mixed vanadium (IV) and vanadium (V): the corvu-

	site group__________________________________ 100

93 Metavanadate layer complexes: carnotite, tyuya95 munite, and rauvite___________________________ 100

95 General characteristics of vanadium (V)___________ 101

	Summary and.conclusions__________________________ 101

96 References-__-_-_---------__---__---_------_---_--_ 102

97 .

ILLUSTRATIONS

	Page 

_--_____.___ 92

______-___.- 93

____________ 94

____-___-.__ 94

____________ 95

__.__--____- 96

____________ 98

____________ 98

____________ 98

___-.___-__-_ 98

25. Sheet structure of carnotite showing linkage of uranyl and divanadate groups._____________________________ 100

26. .Portion of .the oxidation potential pH phase diagram of fig. 15. __ __^-____--_-_---_______-_-___-___-_____ 101

FIGUKE 15. Oxidation potential pH phase diagram for vanadium in aqueous solutions. ___-______--___

16. Pictorial view of montroseite structure_______________________________________________

17. Projections along the c-axis of the crystal structure of montroseite and paramontroseite__-_-

18. Pictorial view of artificial V.04 structure_----_--__-____-___-_-_-_________--_-__________

19. Pictorial view of duttonite _ _ ^-_________------__---_--_______-_________-_-__--________

20. Dispersion of vanadate phases with pH________________________________________________

21. Pictorial view of KV03 . _-.->-___________________ _ -. ______________________

22. Pictorial view of :KV03:H2Q_--______--____________________________________________

23. Projections along the c-axis of KVOa.H2O and V2Oj_______________----_--_-_-_____--_-

24. Possible mechanism for'transformation from 5-fold to 4-fold coordinated metavanadate chain.

 ' :. . '..' '.' : ."' '"' ABSTRACT

Many recent crystal structure investigations on vanadium 

oxides and compounds are reviewed in terms of the over-all 

chemistry and mineralogy of the element. The structure studies 

are compared with the oxidation potential-pH phase diagram 

 which is constructed from the best available thermodynamic 

data for the element. From these correlative studies, an alteration sequence is derived for the weathering process of the vanadium ores of the Colorado Plateau. Accordingly, montroseite [VO(OH)] is treated as the primary vanadium mineral. 

During weathering, montroseite is converted to various insoluble tetravalent and pentavalent oxide minerals, including 

parampntroseite and "corvusite." Final oxidation of "corvusite" 

yields soluble polyvanadate complexes from which crystallize 

pascoite, hummerite, .hewettite, and other pentavalent vanadate 

minerals. Under more alkaline environments, duttonite 

£VO(OH) a ] is formed, from which may be derived simplotite,

melanovanadite, and rossite. If uranium is present these are 

converted to rauvite, tyuyamunite, and carnotite. Generally 

speaking, in its lower valence states vanadium Is similar to 

manganese in behavior, but in the higher states of oxidation It 

resembles phosphorus (in strongly alkaline media) and molybdenum and tungsten (in acid media).

INTRODUCTION

Until recently, vanadium had played a minor role 

in mineralogy. Lately, interest in vanadium mineralogy has been increased because vanadium plays a 

key role in the paragenetic relationships in the sandstone-type uranium deposits, such as those of the Colorado Plateau. Recent geologic studies have raised many 

questions concerning the time, mechanism, and mode
92 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

of deposition of the uranium and vanadium ores in the 

sandstones, shales, and conglomerates, and their subsequent weathering and transport. Extensive recent 

studies on the chemistry and crystallography of vanadium compounds and minerals in various laboratories has 

led to a greater understanding of the behavior of vanadium under varying conditions of oxidation potential and pH, which give promise to provide valuable 

clues to the solution of these problems.

An important vanadium ore mineral (at Globe, Ariz., 

for example) is vanadinite, a member of the apatite 

group of minerals. A second important type is vanadium silicate, as mica, as clay minerals, and as chlorites. Vanadium forms a host of other minerals, many 

of which are as yet undescribed or poorly characterized. They are listed in a miscellaneous group in 

Dana's System of Mineralogy (Palache, Berman, and 

Frondel, 1951, p. 1042) and also in a U. S. Geological 

Survey publication by Weeks and Thompson (1954). 

Phases involving oxygen are numerous and very complex, mainly because of the variability of the valence 

state of vanadium.

A fair amount of information concerning the chemical and mineralogical behavior of vanadium is available 

in a widely dispersed and somewhat conflicting literature. In addition, recent work in X-ray crystallography by members of the U. S. Geological Survey has 

revealed new and significant structural relationships 

among vanadium compounds and those of other elements. It is the purpose of this report to review briefly 

present knowledge of the behavior of vanadium in Qie 

solid state.

The emphasis in this paper will be on the structure 

and nature of the known minerals as they are found 

in nature, in relation to each other and to artificial 

solid compounds, and to the solution studies of Garrels 

(1953), Ducret (1951), Jander and Jahr (1933), and 

others. While the methods of electrometric and pH 

titration have proved to be the most informative in the 

study of the solution phases, the most powerful approach to the problem, of the constitution of the solids 

has been through the medium of X-ray diffraction and 

crystal-structure analysis. As the body of information on structure increases, it is often possible to infer 

the nature of the solution components through various 

interrelationships and characteristic physical properties of the solids. . .

The ideas and information presented in this paper 

have resulted from the concerted efforts of many workers at the U. S. Geological Survey, some of whom are 

mentioned in the text, as well as many other independent workers outside the Survey. Especial thanks are 

due to K. M. Garrels, of the Geological Survey, who

has continuously urged and encouraged the compilation of this report on vanadium chemistry and mineralogy and who has contributed in no small way 

directly to its makeup. Finally, the author wishes to 

express his gratitude to W. H. Barnes and his colleagues, of the National Research Council of Canada, 

who in personal discussions from time to time have 

provided much valuable information.

ELECTROCHEMISTRY OF VANADIUM

Before entering upon a discussion of the various minerals containing vanadium, let us review briefly the 

equilibrium behavior of vanadium under various conditions of pH and oxidation potential as it has been 

revealed in recent studies by Souchet and Carpeni 

(1946), Ducret (1951), Garrels (1953), and others. 

The best thermodynamic information available to us 

is summarized in figure 15, in the manner described by 

Pourbaix (1949). The tabulated data of Latimer 

(1952) have been used in the construction of the 

diagram.

-VzOs (brown)

--.,. Potyvanadate

Metavanadate

V4012-4

(colorless)

2-VALENT 

r- Vanadium metal, V*

4 5 6 .7 8 9 10 11 

Hydrogen-Ion concentration, pH units

12 13 14

FIGURE 15. Oxidation potential pH phase diagram for vanadium in 

 aqueous solutions. Stippled fields represent solids (solubility of 

V<0.01 mol.. per 1.). Phases may be hydrated or hydrogenated to 

an unknown degree.

In the diagram of figure 15, all conditions of pH 

(hydrogen-ion concentration) and Eh (oxidation potential) are represented. The diagram is divided into 

regions which are labeled with the species that predominates in that region. Two sloping dashed lines 

are shown: the lower one represents the limit below 

which hydrogen ion is reduced to hydrogen, a condition which ordinarily does not occur in nature; the
CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM 93

upper line is the limit above which water or hydroxyl 

ion is oxidized to oxygen, and toward which all systems 

below the line trend under terrestrial weathering 

conditions.

The areas between the heavy lines represent the four 

valence states of vanadium. They correspond roughly 

to the regions of stability of V(OH) 8, VO(OH) 2 and 

V2 05 -nH2O as determined by Garrels (1953). The 

slope of these heavy lines is determined by the way in 

which H+ ions are involved in the oxidation reaction. 

Thus, the oxidation potential required to convert V+2 

to V+3 is independent of pH since no H+ ions are involved in the oxidation reaction; but when V+2 is converted to V2O3 , H> is liberated in the reaction, and the 

potential boundary falls with increasing pH. When 

no oxidation or reduction takes place, changes in pH 

will effect profound changes in the constitution of the 

vanadium-bearing ion or solid; these changes are 

marked by vertical lines on the diagram. The formula 

species indicated may actually be replaced by hydrates, 

without changing the phase boundaries significantly. 

The presence of hydrogenated ions such as HV2O7"3 

may affect the boundary distributions to a small degree.

In the following discussion, reference will be made 

to figure 15 to clarify relationships among minerals 

and artificial compounds under consideration. Thus, 

the diagram will serve as a "road map" in our survey 

of the. mineralogy and chemistry of vanadium.

REDUCED FORMS OF VANADIUM 

VANADIUM (II)

Bivalent vanadium is unstable and releases hydrogen 

from water. This behavior is consistent with the diagram of figure 15, which shows that the conditions 

under which V*2 ions are stable are well below the 

limit below which water decomposes. The artificial 

compound VO is known; like MnO, it has the rocksalt structure. Thermodynamic considerations have 

shown that bivalent vanadium probably does not occur 

in nature (Garrels. 1953, p. 1263).

VANADIUM (III) AND VANADIUM (IV) : THE 

MONTBOSEITE GROUP

Trivalent vanadium is also relatively unstable, and 

has a short life in the presence of air. Unlike the 

bivalent ion, V+3 is stable in oxygen-free acid water 

solution, from which, characteristically, vanadium 

alums may be crystallized for example, CsV(SO4 ) 2 - 

12H2 0. V203 has the corundum type of structure but 

is not yet known in nature. VO(OH) is the mineral 

monotroseite (Weeks, Cisney, and Sherwood, 1953), 

which occurs as steel-black prismatic lath-shaped crystals, or as a brittle, crystalline, jet black mass. Paramontroseite, V2O4, is a common alteration product resulting from the atmospheric alteration of montroseite.

Another distinct oxide species (Weeks and Thompson, 

1954, p. 54), now designated doloresite, which is 

closely associated with paramontroseite, forms dark 

brown, nonmetallic crystalline masses when pure and 

is probably a quadrivalent hydrous oxide. Still another quadrivalent oxide species, duttonite, has been 

identified recently, occurring as pale brown flaky crystals, but it is found in more alkaline environments. 

The oxide minerals have proved to be difficult to separate and characterize by the usual chemical and mineralogical methods, but their interrelationships and 

essential constitution have been revealed by the methods of X-ray diffraction and crystal structure 

analysis.

Montroseite and paramontroseite both have the diaspore (A12O3 -H2O) structure. The details of these 

structures have been given by Evans and Block (1953), 

and Evans and Mrose (1954)i The structure contains 

double chains of VO6 octahedra sharing edges, the 

chains being linked to each other by sharing octahedron corners (see the pictorial view in fig. 16).

Q .... 5

Angstrom units

 V OO O-O H bond

PIGUHE 16. Pictorial view of montroseite structure (dlaspore type).

Evans and Mrose found that montroseite single crystals give multiple diffraction patterns showing the 

presence of two intimately mixed phases, but whose 

crystal structures are similar and are in parallel position throughout the crystal mass. By means of 

Fourier analyses of the electron density distribution 

in each of the two phases separately, they were able
94 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

to show conclusively that hydrogen is present in one 

and absent in the other. These two structures, which 

are montroseite and paramontroseite, respectively, are 

illustrated in figure 17, projected along the chain axis. 

The chains are visible in end view in both drawings. 

Comparison of the two structures leads unequivocally 

to the conclusion that the original host mineral is 

montroseite (VO(OH)) and that the paramontrosite 

(V2O4 or VO2 ) has originated by the solid state oxidation of montroseite. The oxidation process has taken 

place by the diffusion of hydrogen out of the structure 

without breaking the vanadium-oxygen bonds or disrupting the hexagonal close-packed oxygen framework. 

Artificial vanadium dioxide, V2O4, has a slightly 

distorted rutile type of structure (Andersson, 1953). 

This structure is characterized by straight octahedron 

chains as shown in the pictorial view of figure 18. It 

is very probable that the diasporelike form of V2O4, 

paramontroseite, is entirely metastable and can only

O

o

Angstrom units

FIGUBB 17. Projections along the c-axis of the crystal structure of 

(a), montroseite and (b) paramontroseite. Large circles are oxygen 

atoms, dark circles vanadium, small open circles hydrogen. Note. 

absence of hydrogen bond in paramontroseite.

FIGURE 18. Pictorial view of V2O* structure (distorted rutile type). 

Large circles are oxygen atoms, small circles vanadium.

be formed through the low-temperature alteration 

mechanism just described, controlled by the original 

montroseite structure. Similar alteration mechanisms 

have been observed for certain of the iron oxides 

(Evans and Mrose, 1954). Montroseite is a highly 

insoluble stable mineral under reduced conditions, but 

by its conversion to the metastable paramontroseite, 

it becomes readily decomposable and subject to further 

oxidation.

Paramontroseite (pseudomorph after montroseite) is 

sometimes intimately mixed with another vanadium 

oxide mineral, doloresite. Petrographic studies (Coleman, oral communication) indicate that doloresite replaces montroseite or paramontroseite. Since any remnant montroseite is oxidized to paramontroseite on atmospheric exposure, the mixture probably rep resents, a 

close association of stable and a metastable form of the 

tetravalent oxide. Crystalline fragments of doloresite 

give exceedingly poor single crystal diffraction patterns, but it has been possible to index them on an orthorhombic lattice .which is obviously related to montroseite 

and artificial V2O4. These oxides all share a fiber axis 

spacing of 3.0 A, which is characteristic of the octahedron chain. .
CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM 95

All evidence indicates that montroseite is probably 

the chief primary vanadium mineral, aside from the 

vanadium silicates, of the Colorado Plateau sandstone 

deposits. The conditions of formation are not known, 

but possibly they are hydrothermal in type. Figure 15 

shows that a portion of the V2O3 field extends above the 

water decomposition line in the vicinity of pH 3-5. 

While the room temperature conditions represented by 

the diagram will be altered somewhat at elevated temperatures, montroseite may be considered to have 

formed somewhere in this region.

Kecently, the new mineral duttonite (Thompson, 

Eoach, and Meyrowitz, 1956b) has been found at the 

Peanut mine, Bull Canyon, Montrose County, Colo., 

where more alkaline conditions prevail. Crystal structure studies have shown that it is the dioxide hydrate, 

V2 04 2H2 0. The structure consists of strings of VO6 

octahedra linked vertically by their apices to form 

sheets, which are then tied together with hydrogen 

bonds (fig. 19). An unusual feature of the structure 

is the close approach of the vanadium atom to the apical 

oxygen atom to form a strong V-O bond, corresponding to a VO2 ion. Since this ion is well known from 

chemical studies, its appearance in the solid is not sur0

Angstrom units

FIGURE 19. Pictorial view of duttonite. Large circles are oxygen 

atoms, small circles vanadium, and dashed lines are hydrogen bonds.

prising. In fact, it is probably present in the artificial 

V2O4 structure, in which the ideal tetragonal cell is 

doubled in volume and reduced to monoclinic symmetry. If the octahedron chains (vertically arranged 

in fig. 18) contain the VO+2 bond pointing in alternate 

directions as in duttonite, such a distortion would 

readily be accounted for.

In its valence states three and four, vanadium is similar to manganese in its behavior. Single and double 

and even triple octahedron chains have been found in 

several manganese oxide minerals for example, pyrolusite, coronadite, hollandite, and psilomelane (Wilson, Structure Reports, 1949, 1950). Indeed, groutite, 

Mn2O3 -H2O, and ramsdellite, Mn2O4 (Wilson, Structure Reports, 1949, 1950), are completely analogous to 

montroseite and paramontroseite, respectively. Unfortunately, very little work has been done on the phase 

relations of manganese oxide minerals in the natural 

environment, so that we are not at present able to compare any similarities there may be to vanadium systems. 

On the other hand, the tendency of vanadium to form 

asymmetric oxygen bonds in its coordination environment when it attains the quadrivalent or higher state 

is in contrast to manganese.

OXIDIZED FORMS OF VANADIUM 

OXIDATION OF QUADRIVALENT VANADIUM

Weathering action ultimately raises vanadium oxide 

minerals to the highest oxidation state -that is, +5. 

This oxidation process is evident from the sequence of 

minerals in the Colorado Plateau region, and is also 

predicted by the thermodynamic studies which are summarized in figure 15. The oxidation process is very 

complex, passing through numerous intermediate stages. 

Many take place in the solid state, like the conversion 

of montroseite, to paramontroseite described in the previous section. When vanadium passes above the tetravalent state, its oxides are still relatively insoluble 

(above pH 3), but the oxide structures are completely 

reconstituted.

A number of phases, changing one into another, probably exist between V2O4 nH2O and V2O6 nH2O. These 

phases are the principal constituents of the so-called 

"blue-black ore." None of these phases has been isolated and uniquely characterized as yet. "Corvusite" is 

a name associated with a fibrous vanadium oxide hydrate which yields a blue-black powder on scratching 

or crushing. Its essential constitution and nature are 

unknown (it may be a mixture) and "corvusite" cannot 

yet be regarded as a well-established species. Other 

oxide phases in this range have a green streak and all
96 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

are commonly coated with an almost iridescent blue 

tarnish.

During oxidation the pH of the environment tends 

to drop, especially if much pyrite is present. The 

vanadium then becomes relatively soluble and is leached 

out of the oxide bodies as V0+2 and Vi0O28-6 ions as 

would be expected by reference to figure 15. As soon 

as the solutions reach the surrounding rock, they become 

diluted and react with the calcium carbonate cement. 

The pH is thus raised sharply again, causing the remaining VO2 ions to be completely oxidized by atmospheric action.

Complete oxidation of vanadium to vanadium (V) is 

marked by a distinct color change from the blue-black 

associated with the vanadium (IV)-(V) complexes to 

brown, red, or orange shades associated with derivatives 

of V2O5 . The presence of uranium introduces yellow 

and yellow-green phases in this oxidized zone.

pH DISPERSION OF VANADIUM (V) COMPLEXES 

IN SOLUTION

Vanadium pentoxide is strongly amphoteric, dissolving readily to form cations in strong acid solutions, 

and anions in weakly acid and alkaline solutions. In 

these solutions, vanadium forms a great variety of oxygen ion complexes. The relative concentrations of the 

various complexes depend critically upon the acidity 

and concentration of the solution, the presence of other 

complexing ions (UO2+2 or PO4"3 ), and, because of the 

slow rate of many of the reactions, the history of the 

solution. Some insight into the constitution of V2O5 

solutions as a function of pH has been gained by Jander 

and Jahr (1933) by means of diffusion-rate studies. In 

figure 20 is shown their plot of diffusion rate of vanadium in solution (corrected for viscosity) against pH. 

The presence of plateaus in this curve suggests that at 

certain critical pH values the ions present in the solution react to form other more complex ions (with decreasing pH), but that between these critical values, the 

solutions are relatively stable. Assuming very approximately that ion molecular weight is proportional to the 

square of the diffusion rate, Jander and Jahr suggested 

that above pH 12.6 only VO4~3 ions are present; in the 

range pH 9.6 to 12.6, V2O7~4 ions are present; in the 

range pH 6.7 to 9.6 ions like V4013~6 exist; and between 

pH 6 and the oxide precipitation point at pH 2.2 ions 

similar to V5Oi6~r predominate. A study of solutions 

in the system K2O-V2O5-H2O by R. Marvin (Part 8 of 

this volume), of the U. S. Geological Survey, has 

produced a large number of crystallized products. 

Crystal structure studies of these products suggest that 

the constitution of all solutions of pH below 12 are

i 2

Hydrogen-ion concentration, pH

FIGURE 20. Dispersion of vanadium phases with pH. Upper diagram, 

titration curve for sodium vanadate solution after Ducret (1951). 

Lower diagram, diffusion rate curve for sodium vanadate solution 

after Jander and Jahr (1933).

somewhat more complex than is suggested by Jander 

and Jahr's diffusion studies.

Similar plateaus are also observed on titration curves 

of pH versus added acid. Such a curve is shown in the 

upper half of figure 20 as measured by Ducret (1951). 

The breaks in such curves between plateaus correspond 

to the vertical boundaries in the quinquevalent field at 

the top of figure 15. Souchet and Carpeni (1946) and 

previous workers have associated the indicated stability 

fields with complexes similar to those proposed by 

Jander and Jahr, but Ducret, basing his conclusions on 

the shape of the titration curves in the vicinity of the 

breaks, repudiates the idea of successive condensation 

to higher molecular-weight groups. Only in the orange 

"polyvanadate" region does he postulate the existence of 

a H3V2O7 - ion; in the "meta-" and "pyro-" regions the 

ions H2VO4~ and HV04~2, respectively, are supposed 

to predominate. Nevertheless, all the structures that 

have been worked out related to this system show that 

there is a powerful tendency for the orthovanadate ion 

to condense into complex groups, and it seems very 

likely that such complexes are important constituents 

of the solutions.
CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM 97

In view of all the evidence that is now available, we 

may propose the following reactions as taking place 

over the whole pH range :

At 

PH12.6: 2VO4-3 +2H+-^V2Or4 +H2O 

pH9.6: 2V2O7-*+4H+-»V4O12-4 +2H2O

(or H2V4013-4+H20)

pH 6.7 : 5V4O12-4+8H+-»2V10O28-fl+4H2O 

pH 2.2: V10 028-6 + 6H+-»5V2 05 +3H2O 

pH 0.8 : V2OB + 2H+-»2 VO2+ + H2O

All the vanadium groups written in these equations may 

be for the most part hydrated. Some of the ions may 

also form hydrogenated ions like HV2O7~3 or H2V2Or2. 

These reactions are based primarily on the concept of 

condensation, that is, the linking together of small coordination groups to form larger ones, by splitting out 

H2O. The behavior of quinquevalent vanadium , with 

respect to the stepwise formation of more condensed 

complexes with increasing coordination as pH decreases greatly resembles that of molybdenum and 

tungsten.

ORTHOVANADATES AND PYROVANADATES

At pH levels above 12.6, the tetrahedral orthovanadate ion V04~8 appears to be stable in solution. Although no crystal structures of orthovanadates prepared from such solutions have been studied in detail 

a number of highly soluble, deliquescent salts have been 

obtained which are clearly isostructural with the corresponding phosphates and arsenates. Thus, H. Baker 

(1885) demonstrated by crystallographic and optical 

means the following isomorphous groups:

Hexagonal :

Na3VO4 -12H2O

Na3PO4 -12H2O

Na3AsO4 -12H2O 

Cubic:

Na3V04 -10H2O

Na3PO4 -10H20

Na3AsO4 -10H2O 

Orthorhombic:

Na3V04 -8H2O

Na3P04 -8H2O

Na3As04 -8H20 

Cubic:

2Na3VO4 -NaF.19H20

2Na3PO4 -NaF.19H2O

2Na3As04 -NaF-19H2O

This strong evidence by analogy for the prevalence of 

the VO4~3 ion in solution is in direct contradiction to

Ducret's conclusion (1951) that this ion cannot exist 

in the presence of water.

Several orthovanadate mineral types are well known: 

vanadinite, isostructural with apatite. These minerals 

are usually characterized by the presence of a complexing amphoteric element such as Pb, Zn or Bi, and are 

formed under hydrothermal conditions. Truly ionic 

compounds such as the sodium salts mentioned above 

are not known in nature, as is to be expected from their 

strong basic character and high solubility.

The properties of V2O5 solutions in the range of pH 

9.6 to 12.6 suggest that a pyrovanadate ion, V2O7~4 may 

be stable. No crystal structure evidence is available to 

establish its existence definitely, although colorless 

crystalline salts such as Ca2V2O7 -2H2O are readily 

formed in this pH range.

METAVANADATES

The range from pH 6.7 to pH 9.6 represents a stability field corresponding to the so-called metavanadates. The crystal structures of the colorless compounds 

KVO3 (Evans and Block, 1953) and KVO3 -H2O 

(Christ, Clark, and Evans, 1954), which readily crystallize in this range of pH, have been worked out. These 

crystals both have chain structures, which means that 

the actual ion present in the solution is still unknown. 

In the pyrovanadate range we see the tendency for 

the single VO4~3 tetrahedra to condense into coordination complexes, containing several vanadium atoms, as 

the pH is lowered. In KVO3 (fig. 21), tetrahedra link 

into endless zigzag chains of composition (VO3 ) n~n, by 

sharing corners. These chains are very similar to the 

silicate chains in diopside, CaMg(SiO3 )2; indeed, the 

compound NaVO3 appears to be isostructural with diopside.

At low temperatures, prisms of KVO3 -H2O are also 

formed, and these have an entirely different structure 

(fig. 22). In the monohydrate, the vanadium is in strict 

fivefold coordination with oxygen, forming a trigonal 

bipyramid configuration which links into endless chains 

of composition (VO3 ) n~n by sharing edges. A similar 

type of chain has been confirmed for V2O5 by Bystrom, 

Wilhelmi, and Brotzen (1950), but the chains are linked 

laterally to form sheets, and the vanadium coordination 

is distorted so that it approaches sixfold. The two 

structures are compared in figure 23, in which the end 

views of the chain elements are projected on the (001) 

planes. In this compound, vanadium shows the tendency to increase its oxygen coordination as the pH is 

lowered. Although the two types of chain appear to be 

completely different, it is not hard to imagine that the 

fivefold chain could be formed by an accofdionlike 

pleating of the fourfold chain along its length, while
98

OEOCHEMISTKY AND M.NEKALOOY, COLORADO PLATEAU URANIUM OBES

wil, convert it partly to KVO3 (Christ, Clark, and

KVa 8 has a prism axis (chain direction) spacing of3.70 A. This spacing is the fundamental five- 

£fd chain link unit length, and is a charade^feaoften easily recognized as a fibre spacing, of many

vironment of low temperature which is -- - 

I present day Colorado Plateau deposits Apparently,

hiffivlfold chain in one or -another modification isa 

common fundamental structure motif of such

compounds.

0

Angstrom units

K

21._Pictorial view of the crystal structure of artificial KVO,

circles K+ ions.

Angstrom units 

K ©HoO O; 0

atoms, small circles vanadium
CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM 99

Minerals which - correspond to the metavanadate 

range are rare, the only ones likely to belong, here being 

rossite Ca(VO3 ) 2 -4H2O and metarossite Ca(VO3 ) 2 * 

2H2O. Their true character is not certain because their 

structures are not yet known.

Regarding the nature of the ion which is stable in the 

metavanadate solutions, it seems reasonable to suppose 

that it consists of either a trivanadate, V3Oi0~5 , or a 

tetravanadate, V4Oi3~6, or probably both in addition to 

others. These would be threefold and fourfold links 

from the KVO3 chain. Analogous phosphate complexes are known to exist in solution, in equilibrium 

with the HPOr2 and H2PO.r ions, but apparently 

HVO4~2 and H2VO4" ions are much less stable than the 

corresponding acid phosphate ions.

POLYVANADATES: THE PASCOITE GROUP

If a V2O5 solution is acidified below pH 6'.7, the solution suddenly turns orange, and it enters a new stability 

field covering the range from pH 6.7 to 2.2, corresponding to the so-called polyvanadates. These solutions 

yield a variety of different orange and red crystalline 

products of complex composition. Marvin (Part 8) has 

prepared, among others, the following compounds, 

which have been characterized crystallographically 

(Evans, Mrose, and Marvin, 1955) :

I. K0VioO28 10H2O, triclinic (pseudomonoclinic).

II. K0Vi0O28 9H2O, monoclinic.

III. Ca3Vi0O28 16H2O (pascoite), monoclinic.6

IV. K2Mg2VioO28 16H2O (hummerite), triclinic. 

, V. KV3O8, monoclinic.

The appearance of the tenfold group Vi0028"6 in the 

first four compounds strongly indicates, since the compounds are quite soluble, that such a polycomplex is an 

important component of the solution. The strong inference from the crystal structure studies that poly-ions 

of high molecular weight are stable in these solutions 

supports generally the views of Jander and Jahr 

(1933), Souchet and Carpeni (1946) and most other 

chemical workers, but stands opposed to the hypotheses 

of Ducret (1951) who maintains that the orange solutions contain mostly H3V2 07~ ions.

Neither the crystals nor the solutions are stable for 

any length of time. The crystals tend to dehydrate, 

falling to a yellow powder after some weeks at ordinary 

temperatures. The potassium polyvanadate solutions 

after some weeks at room temperature, or rapidly at 

higher temperatures, deposit light orange insoluble 

crystals of KV3 08 while any crystals of KeVi0O28 9H2 0

0 Pascoite has been incorrectly described as triclinic and having the 

composition CaaVoOwllHoO in Dana's System of Mineralogy (Palache, 

Berinan, and Frondel, 1951).

.present in the solution disappear. Ky3O8 is apparently 

a stable end product of a series of competitive condensation reactions going on in the solution. In the same 

way, hewettite, CaV6Oi6 9H2O, is formed from solur 

tions of pascoite.

A recent structure determination of KV3O8 (Block, 

1954) indicates that it contains chains built of segments 

of the fivefold chain of KVO3 -H2O. These bent chains 

are linked laterally to form sheets of composition 

(V3O8 ).n~n which are interleaved with K+ ions. The 

interesting thing about this structure is that two out of 

three vanadium atoms in the sheet have fivefold coordination while the third approaches sixfold. The 

structure of the decavanadate complex ion is not yet 

known, but it also probably consists of some linkage 

based on the fivefold chain, and acts as an intermediate 

step in the formation of the more highly condensed 

phases such as KV3O8 , hewettite, and others which are 

referred to below.

The minerals hummerite (Weeks and Thompson, 

1954; and Marvin and Magin, Part 8 of this volume) 

and pascoite (Palache, Berman, and Frondel, 1951; 

and Marvin and Magin, Part 8) are true representatives of the polyvanadate stability field. When the 

vanadium oxides reach the highest valence state, the 

acid ground waters dissolve them as the polyvanadate, 

in which form the vanadium moves into the surrounding rock. The brilliant orange crusts of pascoite that 

form on the blue-black vanadium oxide .pockets in the 

Colorado mines make a striking underground display 

under the miner's lamp.

HEWETTITE GROUP

When the vanadate solutions are brought to a pH 

below 3, the vanadium is almost entirely precipitated 

as brown and red-brown solids. These products have 

a constitution that has not been revealed in detail, but 

they undoubtedly correspond to the natural minerals 

hewettite and navajoite. The complexes containing 

large cations like hewettite are apparently stable with 

respect to the decavanadate ion, and may be formed 

at somewhat higher pH than that allowed for the pure 

oxide (navajoite). These minerals are fibrous, with 

the fiber axis invariably exhibiting the characteristic 

3.7 A spacing. Recent structure studies by Barnes and 

his coworkers (Barnes and Qurashi, 1952; Barnes, written communication) have revealed the fivefold chains 

tied together by oxygen links to form sheets of composition (VO3 ) n~n. The details of these structures have not 

yet been described, but apparently the vanadium atoms 

are more nearly sixfold in coordination than fivefold. 

The sheets are loosely held together by Ca+2 ions (in 

hewettite), Na* ions (in a new undescribed mineral)

468052 5S 8
100 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

or H+ ions (in navajoite), and varying amounts of 

water. The variety of discrete phases that readily 

transform from one to another by base exchange or 

change in vapor pressure has made the study of this 

group of minerals and compounds especially involved.

MIXED VANADIUM (IV) AND VANADIUM (V) : 

THE CORVUSITE GROUP

The picture is made even more confusing at lower 

oxidation potentials. This brings us again to the group 

of minerals now designated loosely and collectively as 

"corvusite." No distinct species has yet been isolated 

from these dark green or blue-black mixtures. Kecently, specimens have been found in which a good 

fibrous development is apparent, and such fibrous samples always show a fiber spacing of 3.7 A by X-ray diffraction. The close relation between the "corvusite" 

and hewettite groups is further emphasized by the 

existence of specimens showing the fibrous seams of 

blue-black "corvusite" partly altered to navajoite, the 

fibrous structure being maintained from one phase to 

the other. Artificial compounds which possibly are related to the "corvusite" group are: 2V2O4 -V2O5 ; 

Na2O V2O4 5V2O5 ; Na,O V2O4 11V2O5 . All these are 

prismatic or fibrous in habit, and have a 3.7 A fiber spacing. The last two, described by Flood and S0rum 

(1943), illustrate the way in which a relatively small 

amount of alkali can play an essential stoichiometric 

role to balance corresponding amounts of reduced 

vanadium in V2O5 -like structures. "Corvusite" usually 

contains small but appreciable amounts of calcium. 

2V2O4 -V2O5 actually has a V2O5 structure with certain 

oxygen atoms removed (Aebi, 1948). All these observations indicate that the .valence range four to five in 

vanadium is represented in the "corvusite" group by 

many structures based on the fivefold chain of 

KVO3 -H2O in generally condensed lateral linkages, all 

retaining the characteristic 3.7-A fiber habit of the 

chain. The complexity of the group is increased by the 

incorporation of alkali and alkaline-earth ions and 

water into these structures. These phases grade into 

the fully oxidized species of the hewettite group. The 

fact that the transition from vanadium (IV) to vanadium (V) takes place with little change in structure 

accounts in part for the fact that the natural vanadates 

frequently contain 1 or 2 percent V2O4 . Some specimens of pascoite have been found which are dark green 

because of a relatively high V2O4 content.

Another mixed quadrivalent and quinquevalent oxide 

is the mineral melanovanadite. Its structural constitution is unknown at present, but it is apparently unrelated to "corvusite." Its mineralogical associations 

suggest that possibly it represents an intervalent complex phase adjacent to the metavanadate field, analogous to the "corvusite" phase which is adjacent to 

the poly vanadate field.

METAVANADATE LAYER COMPLEXES: CARNOTITE, 

TYUYAMUNITE, AND RAUVITE

The uranyl vanadate complexes carnotite, 

K 2 (UO 2 ) 2 V 2 O 8 -fl'H2O, and tyuyamunite, 

Ca(U02 ) 2V2O8'7iH2O, play u special role in the vanadate systems into which uranium is introduced. A tentative structure for anhydrous carnotite (KUO2VO4 ) 

has been proposed by Sundberg and Sillen (1949), but 

recent crystal structure studies (Appleman and Evans, 

1957) have shown this structure to be incorrect. The 

sheet complex does not contain discrete ortho vanadate 

VO4~3 groups, but is made up of double V2O8~6 groups 

linked to the uranyl UO2+2 groups, so that the latter 

have a uniform fivefold coordination about their equators (fig. 25). The vanadium atoms are in fivefold 

coordination with oxygen, and the V2O8~6 group corresponds closely to two links in the five-coordinated 

metavanadate chain found in KVO3 H2O. The strong 

layer structure is common to the autunite and carnotite 

groups of minerals, and accounts for their outstanding 

hydration-dehydration and base exchange properties.

Kecent chemical studies (Paul Barton, written communication) indicate that carnotite is formed most 

readily in the pH range 7 to 9, but precipitates slugU02 + 2 V2 08

-6

FIGURE 25. Sheet structure of carnotite (after Daniel Appleman) showing linkage of uranyl and divanadate groups (interlayer K+ ions not 

shown).
CRYSTAL CHEMISTRY AND MINERALOGY OF VANADIUM 101

gishly from more acid solutions. This observation confirms the close relationship of carnotite to the metavanadate series indicated by its crystal structure. The 

solubility of carnotite is very low and removes practically all vanadium or uranium (whichever is less) 

from the solution.

Rauvite is a red to reddish-brown resinous mineral 

of variable composition which may be represented by 

the formula ajUOs'yV^CVflHaO, with y usually somewhat greater than oo. While calcium is frequently present in natural rauvite, it is apparently not an essential 

constituent. It gives a characteristic powder X-ray 

diffraction pattern, but instead of sharp lines, the pattern consists of a number of bands. These bands are 

characteristic of partial crystalline order, such as 

would be found for a layer structure in which the stacking and orientation of the layers is completely random. 

Mineralogic associations suggest that rauvite may be a 

precursor to the formation of carnotite under very acid 

conditions. Rauvite can be prepared artificially from 

acid potassium vanadate solutions, especially when the 

relative potassium ion concentration is low. Much 

work needs to be done in order to determine the relation between rauvite and carnotite and the mechanism 

of their formation.

The special characteristics of these layer structures 

has been further emphasized by the recent new green 

calcium vanadite mineral, simplotite (Thompson, 

Roach, and Meyrowitz, 1956a). Preliminary single 

crystal work on this species has brought out an unusual 

crystal chemical relationship among the following 

series of minerals:

Mineral Formula 

Meta-autunite_____. CaU2P2Oi2 -4H2O 

Metatyuyamunite___ CaU2V2O12 -3-4H2O 

Sincosite (Peru)___. CaV2P2Oio-5H2O 

Simplotite________ CaV2V209 5H2O

V valence

5

4

4

These minerals all have the basic layer structure referred to above, and form yellow or green plates with 

a micaceous cleavage and a pseudotetragonal aspect. 

Apparently, in addition to its similarity to phosphorus, 

vanadium can also play a role similar to that of uranium in these layer complexes. The implied relationship between the VO2 and U(V2 ions will be clearer 

when detailed crystal structure analyses of these minerals become available.

GENERAL CHARACTERISTICS OF VANADIUM (V)

In retrospect, we see that the behavior of vanadium 

(V) varies markedly with conditions of acidity. In 

basic media, it resembles phosphorus and forms phosphatelike structures for example, vanadinite, isostructural with apatite. In acid media, vanadium (V) increases its oxygen coordination to five, tending toward 

six, and the vanadate groups show a strong tendency 

to polymerize. In this respect, vanadium is very similar to molybdenum and tungsten. Vanadium is most 

soluble in the pH ranges 2.2 to 6.7, and below 0.8 

(where the vanadyl ion VO2+ is formed), with a gap 

near the isoelectric point near pH 1.5 where V2O5 hydrates precipitate even from moderately dilute 

solutions.

Since the lower valence vanadium minerals are generally insoluble, we may conclude that vanadium is 

transported during weathering in the Colorado sandstones only in the fully oxidized poly vanadate or metavanadate form under acid or weakly alkaline conditions. Some vanadium (IV) may also be released by 

the acid waters, but this will be quickly oxidized by 

atmospheric action. If uranium and vanadium are oxidized in the same environment, carnotite or tyuyamunite will be precipitated until the uranium or vanadium 

is used up. No uranium-vanadium complexes are 

known at lower valence states; apparently these elements interact only in the fully oxidized state. Excess 

vanadium in the form of polyvanadate may be temporarily deposited as pascoite-type or hewettite-type minerals, or be taken up in a silicate hydromica or clay 

structure, or be washed away altogether.

SUMMARY AND CONCLUSIONS

Referring once more to figure 15, it is useful to indicate on the Eh-pH diagram the regions in which the 

various minerals which have been discussed are stable.

1.0 

0.8 

0.6-

I 0.4.

>

s

S 0.2

I

-0.2

-0.4

-0.6

vcr*

16H2(T- 

(Carnotite) 

(Rauvite) (Tyuyamunite

5-VALENT 

Corvusite >

Paramont- \ 

roseite V02)

Ooloresite

CaV206.4H20 

(Carnotite) 

^. (Tyuyamunite

2-VALENT

1 2 34 56 7 8 10

Hydrogen-Ion concentration, pH units

FIGURE) 26. Portion of the Eh-pB phase diagram of figure 15, showing 

positions of various vanadium mineral species and probable alteration sequences.
102 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

This has been done in figure 26, in which the direction 

of alteration is also suggested by means of arrows. 

.The focal point is montroseite, the most reduced state 

of vanadium oxide. minerals. The alteration under 

weathering then moves upward on the diagram, with 

.excursions to higher or lower pH conditions, depending 

upon mineral associations and environment. In the 

region of complete oxidation, the presence of uranium 

causes the various complex fields above the shaded 

boundary to be completely replaced by carnotite.

Broadly speaking, the following generalizations may 

be made in conclusion:

1. Trivalent vanadium is represented by the primary 

mineral montroseite (VO(OH)), and is readily 

oxidized by the atmosphere to the quadrivalent 

form. Vanadium is similar in its crystal chemistry 

to manganese in the three- and four-valent state.

2. Mixed vanadium (IV) and (V) oxides comprise the 

"blue-black ores," and probably are derived to a 

considerable extent from oxidation of montroseite.

3. Vanadium (V) oxide and its derivatives form the 

final stage of oxidation. In alkaline media, vanadates behave structurally like phosphates; in acid 

media, vanadates condense successively to form 

colorless and orange-red soluble complexes, and 

finally slightly soluble red or brown fibrous 

hewettite-type compounds. Vanadium (V) is 

similar to molybdenum and tungsten in behavior 

with regard to the tendency to polymerize with 

decreasing pH.

4. An important structural property of pentavalent 

vanadium is the formation of the five-coordinated 

chain which appears between pH 2 and 8. This 

structure motif appears to play an important role 

in the formation of the mixed vanadium (IV) and 

vanadium (V) oxides and hydrates.

5. Carnotite covers a wide pH range of stability for 

vanadium (V). Pentavalent vanadium will precipitate any uranium present as carnotite or 

tyuyamunite. Excess vanadium may be temporarily deposited as hewettite or pascoite, or bound 

up in a silicate mica or clay.

REFERENCES

Aebi, F., 1948, Phase studies in the system vanadium-oxygen,, and 

the crystal structure of VriOze: Helvetica Chimica Acta, v. 

31, p. 8-21.

Andersson, G., 1953, X-ray studies on vanadium oxides: Research, v. 6, p. 45S-46S.

Appleman, D. E., and Evans, H. T., Jr., 1957, Crystal structure 

of carnotite: Acta Cryst. v. 10, p. 765.

Baker, H., 1885, The orthovanadates of sodium and their analogs: Chem. Soc. London Jour., v. 47, p. 353-361.

Barnes, W. H., and Qurashi, M. M., 1952, Unit cell and space 

group data for certain vanadium minerals: Am. Mineralogist, v. 37, p. 407-422.

Beintema, J., 1938, On the composition and the crystallography 

of autunite and the meta-autunites: Rec. travaux Chim. 

Pays-Bas, v. 57, p. 155-157.

Block, S., 1954, Crystal structure of K-VoOw: Ph. D. Thesis, The 

Johns Hopkins University, Baltimore.

Bystrom, A., Wilhelmi, K. A., and Brotzen, O., 1950, Vanadium 

pentoxide a compound with five-coordinated vanadium 

ato'ms: Acta Chemica Scandinavica, v. 4, p. 1119-1130.

Christ, C. L., Clark, J. R., and Evans, H. T., Jr., 1954, The crystal structure of potassium metavanadate monohydrate,

.." KVO3 -H2O: Acta Crystallographica, v. 7, p. 801-807.

Ducret, L. P.,. 1951, Contributions to the study of penta- and 

tetravalent vanadium ions: Annales de Chemie, v. 6, p. 

705-773.

Evans, H. T., Jr., and Block, S., 1953, The crystal structure of 

KVO3 (abs.) : Geol. Soc. America Bull., v. 64, p. 1419.

Evans, H. T., Jr., and Mrose, M. E., 1954, A crystal chemical 

study of montroseite and paramontroseite: Am. Mineralogist, 

v. 40, p. 861-875.

Evans, H. T., Jr., Mrose, M. E., and Marvin, R., 1955, The constitution of the natural and artificial decavanadates (abs.) : 

Am. Mineralogist, v. 40, p. 314-315.

Flood, H., and S0rum, H., 1943, Vanadyl vanadate. A new type 

of semi-conductor. The system Na2O-V2O5 : Tidsskr. Kjemi, 

Bergvesen Metallurgi, v. 3, p. 55-59.

Garrels, R. M., 1953, Some thermodynamic relations among the 

vanadium oxides, and their relation to the oxidation state 

of uranium ores of the Colorado Plateaus: Am. Mineralogist, 

v. 38, p. 1251-1265.

Jander, G., and Jahr, K. F., 1933, Formation and decomposition 

of high molecular weight compounds in solution as illustrated by vanadic acid, polyvanadates and vanadate salts: 

Zeitschr. anorg. Chemie, v. 212, p. 1-20.

Latimer, W. M., 1952, Oxidation states of the elements and their 

potentials, New York, Prentice-Hall, Inc.

Palache, C., Berman, H., and Frondel, C., 1951, Dana's system 

of mineralogy, v. 2, New York, John Wiley and Sons, Inc.

Pourbaix, M. J. N., 1949, Thermodynamics of dilute aqueous solutions, London, Edward Arnold and Co.

Souchet, P., and Carpeni, G., 1946, On the constitution of the 

vanadates in aqueous solution: Soc. chim. France Bull., v. 

13, p. 160-168.

Sundgren, I., and Sill6n, L. G., 1949, On the crystal structure 

of KUO2VO4 (synthetic anhydrous carnotite) : Arkiv for 

Kerni, v. 1, p. 337-351.

Thompson, M. E., Roach, C. H., and Meyrowitz, Robert, 1956a, 

Simplotite, a new calcium tetravanadite from Colorado 

Plateau: Science, v. 123, p. 1078.

 1956b, Duttonite, a new vanadium mineral from the 

Peanut mine, Montrose County, Colo.: Science, v. 123, p. 990.

Weeks, A. D., Cisney, E., and Sherwood, A. M., 1953, Montroseite, 

a new vanadium oxide from the Colorado Plateaus: Am. 

Mineralogist, v. 38, p. 1235-1241.

Weeks, A. D., and Thompson, M. E., 1954, Identification and 

occurrence of uranium and vanadium minerals from the 

Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B.

Wilson, A. J. C., editor, 1949, 1950, Structure reports, International Union of Crystallography, v. 12 [1952] ; v. 13 [1954], 

Utrecht, A. Oosthoek Uitgevers Mij.
Part 8. SYNTHESIS OF CALCIUM VANADATE MINERALS AND RELATED COMPOUNDS

By RICHARD MARVIN and GEORGE B. MAGIN, JR.

CONTENTS

Page 

Abstract...__...........___.._.... _'__.i.._.____.. 103

Introduction. __-__--_--_-__-_---------_----------.- 103

Calcium vanadates.-------.------------------------- 103

Uranium-containing vanadates......------------------ 107

Miscellaneous vanadates. 

Con elusions. ________ _: _ __

References. _ ______---__

Page

109

110

111

ILLUSTRATIONS

. Page 

FIGURE 27. Sections of the CaO-V2 05-H20 system..___________________________________________.____l____-__-__--___ 105

28. Diagram showing the relationship of calcium vanadates to pH and temperature..----------------.--.------- 106

29. Section of the KOH-V2 O8-U02(N03)2 aqueous solution phase diagram...______-______-_-_-_-______-_--__-__ 108

TABLE

TABLE 1. The preparation and handling of,two runs used in construction of parts of CaO-VaOs-HaO phase diagram.

Page 

104

ABSTRACT

Synthesis of natural vanadates shows that most of them are 

stable in an acid environment. Phase studies of a portion of the 

system CaO-VsOo-HsO indicate that calcium vanadates are 

an indicator of environmental pH conditions. Some minerals 

such as pascoite indicate rapid evaporation of vanadate solutions ; other minerals such as hewettite show that slow 

evaporation took place. Cursory examination of systems 

KaO-UO3 (NOa)ir-VaOB and .CaO-UO2 (NO3)2-V2O5 , both in 

aqueous solution, has yielded information on the relationships 

among carnotite, tyuyamunite, and rauvite.

INTRODUCTION

The weathering of primary vanadium and uranium 

minerals leads to the formation of many secondary minerals, some containing both uranium and vanadium. 

Synthesis of some of the secondary minerals was undertaken to obtain knowledge of the environment of formation. The synthesis of vanadium minerals containing 

only fully oxidized vanadium (V) was first undertaken. 

Then uranium (VI) was added to solutions to obtain 

uranium-containing vanadates. In this way, the pH 

range, temperature, and saturation conditions under

which some of these minerals can be synthesized are 

now known.

Since these minerals presumably result from the attack of ground water and air on primary uranium and 

vanadium minerals, resulting in their oxidation and 

solution, synthesis was attempted from aqueous solutions containing the desired ions at temperatures between 20° and 90° C. The pH of a solution was varied 

by adding either acetic or nitric acid. The solid phases 

were identified by X-ray diffraction patterns and, when 

possible, by optical methods. The fine-grained habit of 

some precipitates made optical identification unreliable.

The authors acknowledge the help and advice of 

many of their colleagues in the U. S. Geological Survey, 

especially that of Daphne R. Ross, who made the X-ray 

identifications, and Robert Meyrowitz, who performed; 

the chemical analyses.

CALCIUM VANADATES

One- to two-liter stock solutions containing calcium 

and vanadate ions were prepared from dry reagents, 

CaO and V2OS (containing a small amount of V2O4 ), 

in the following way. The V2O5 was powdered and

103
104 GEOCHEMISTKY AND MINERALOGY. COLORADO PLATEAU URANIUM ORES

stirred into a liter of water containing 100 ml of 30 percent H2O2 which increased the solubility of V2O5 and 

oxidized any V (IV) to V (V). The powdered CaO 

was then added. The mixture was agitated and slowly 

heated to boiling to rid the solution of excess H2O2 . 

Care was taken in boiling the solution, as the release of 

O2 from the H2O2 was very rapid and as the solution 

was violently agitated. The ratio of V2OS to CaO 

should not be smaller than 3:1 by weight unless the 

solution is very dilute, as a fairly insoluble hydrated 

pyrovanadate will precipitate when the solution is 

heated. After the excess H2O2 was destroyed, the solution was cooled, filtered, and analyzed. A useful stock 

solution has a concentration of 0.04M CaO and 0.08M 

V2O5 . More concentrated solutions are saturated at 

room temperature.

After the stock solution was prepared and analyzed, 

an aliquot was taken (generally not less than 20 ml). 

The pH was adjusted to the desired value by adding 

dilute (1:10) nitric acid, drop wise (dilute acetic acid 

was sometimes used). The solution was then placed in 

an oven set at the desired temperature, and evaporated 

until a solid phase or phases separated out. Table 1 

illustrates the actual handling of two aliquots (runs).

TABLE 1. The preparation and handling of two runs (aliquots) 

used in construction of parts of CaO-V^Os-HzO phase diagram

OaO-ViO» solution i.ml

i . ' :d

Run Ca-17-18

20 

5.15

5.0

4.95

4.85

Run Ca-17-19

20 

4.0

3.9

3.9

. Remarks

Dilute HNOi added to each run to 

adjust to initial pH.

glasses and placed in oven at 56° C.

Hewettite recovered from solution

Ca-17-19. 

Hewettite plus a few pascoite crystals

recovered from solution Ca-17-18. 

Phases were separated from the 

mother liquor in a Buchner funnel, 

washed with water and acetone or 

alcohol, and air dried.

i 8.4 g/1 CaO+27.9 g/1 VaOj.

As can be seen from samples in table 1, the pH of 

a solution varies with time. Such variations are probably the result of ionic adjustments or changes in volume, and, if precipitation occurs, changes in concentration. The direction of change in pH may be erratic, 

but generally solutions having pH values above 3.0 

have a pH drift towards the pH value representing 

the phase boundary between the polyvanadates and 

metavanadates. Solutions having a pH value below 

3.0 tend to become more acid. Highly alkaline solutions absorb atmospheric CO2 ; this lowers the pH and 

causes calcite crystals to form.

Since stock solutions with a pH value greater than 

8 necessarily have a very low concentration of V2O8 

and CaO to prevent precipitation during preparation, 

large aliquots must be taken to provide sufficient solid 

phase for proper identification. To facilitate matters 

an aliquot of a more concentrated stock solution (pH 

less than 7.5) was placed in a beaker and diluted sufficiently with H2O to prevent immediate precipitation 

of a solid phase at the basic pH which was to be 

explored. The electrodes of the pH meter were then 

placed in the diluted aliquot and the pH raised to the 

desired value by adding freshly prepared Ca(OH) 2 

solution or 100 to 200 mg of powdered CaO. In the 

latter case, the solution was vigorously stirred until the 

pH rose to the desired value; the solution was then filtered to remove excess solid CaO and then evaporated 

at the desired temperature.

The addition of CaO or Ca(OH) 2 changed the 

known V2Os/CaO ratio. Since it was impractical to 

analyze each solution prepared in the above manner, 

the approximate ratio was determined as a function 

of the pH. From the analyses of stock solutions and 

their pH values, a graph of pH plotted against 

V2O5/CaO ratio was constructed. Then the approximate ratio in a solution can be determined from its 

pH by using this graph if the solutions are approximately the same dilution. Knowledge of the exact 

ratio is not necessary as it has been found that the 

phase boundaries are not sensitive to this variable.

Figure 27 shows three sections of the 

CaO-V2O6-H2O system; pH is plotted on the ordinate 

axis, V2OB /CaO ratio in grams on the abscissa. The 

pH and the temperature determine the solid phase to 

be formed. The V2O5/CaO ratio seems relatively unimportant. The phase boundaries are primarily controlled by pH and secondarily by temperature; this 

can be seen in Figure 28.

As mentioned before, HNO3 was added to solutions 

so as to explore the system at lower pH values than 

could be obtained with dissolved CaO-V2O5 alone. 

As solutions with a V2O5/CaO ratio of four or greater 

are acid, the alkaline region could not be explored without adding a soluble base, the cation of which might 

form new solid phases, further complicating the phase 

diagram. Therefore this area has been left blank 

although it seems reasonable to assume that the phase 

boundaries would remain the same if extended to the 

right.

Figure 28 shows the five stability areas found in 

the examined portion of the CaO-V2O6-H2O system. 

No phase boundary is shown for the Ca3 (V04 ) 2 - 

Ca(OH) 2 ; its formation is dependent on the concentration of CaO and V2O8 in solution but not their ratio.
SYNTHESIS OF CALCIUM VANADATE MINERALS AND RELATED COMPOUNDS 

Pyrovanadates

Metavanadate

PH

Polyvanadates

20°-30°C

105

2H20

10

Pyrovanadates.

*

I

 

__.____ :

Metavanadate

PH

Polyvanadates

456 

V2Os/CaO by weight

10

 Experimental solution and solid phase .

55°-60°C

2H2O

10 -

2,

Pyrovanadates

456 

V205/CaO by weight

Metavanadate

pH Polyvanadates . { 

85°-90°C

V205 ..2H20

10 11

34567

V205/CaO by weight 

FIOURH 27. Sections of the CaO-VaOir-HaO system.

10 11
106 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

12

11

10

9

e

7

pH 6 

5 

4 

3 

2 

1

Ca3(V04)2 Ca(OH)2

Pyrovanadates

Pascoite Hewettite 

Polyvanadates

V20s 2H20

20 30 40 50 60 70 80 90

Temperature °C

FIOUIIB 28. Diagram showing the relationship of calcium vanadates to 

pH and temperature.

If the solution is nearly saturated, Ca3 (VO4 ) 2 < 

Ca(OH) 2 may precipitate in the metavanadate region; 

while in a dilute solution, precipitation may not occur 

until the pH approaches 11. This basic salt precipitates very rapidly as a flocculent, white material which 

if heated to boiling or left at room temperature for a 

few days, may become crystalline or revert to a 

pyrovanadate.

Under the Ca3 (VO4 )2-Ca(OH)2 precipitation region and sometimes covered by it, is the stability 

area for pyrovanadates ; no orthovanadates were 

discovered. Two pyrovanadates, Ca2V2O7 > 2H2O and 

Ca2V2O7 , were found. Neither has been established 

as a mineral although Hess and Schaller (1914) reported a mineral which they called pintadoite 

(Ca2V2(V9H2O), a hydrated pyrovanadate. Neither 

of the synthetic pyrovanadates agrees with the description of pintadoite.

At room temperature, the metavanadate stability 

area which adjoins the pyrovanadate area is mostly 

in an alkaline environment but at higher temperatures 

gradually shifts toward the acid side. The hydrated 

metavanadate, CaV2O6 -4H2O, corresponding to the 

mineral rossite, is stable up to 85° C. The stable 

phase then is anhydrous calcium metavanadate, 

CaV2O6 . The high temperature metavanadate is not 

known to occur in nature.

The next stability area contains the hydrated polyvanadates, Ca3V10O28 16H2O and CaV6Oi6 9H2O, corresponding respectively to pascoite and hewettite. 

Their formation depends not only on pH and temperature but also on the rate of evaporation. A calcium vanadate solution at 40° C with a pH value 

between 5.9 and 3.0 produces pascoite if rapidly evaporated and hewettite if very slowly evaporated. Increasing the temperature of the solution favors the 

crystallization of hewettite. Sometimes hewettite will 

start crystallizing, then pascoite crystals will also appear, and the two will grow simultaneously.

Potassium polyvanadates, like the calcium polyvanadates, are dependent on temperature and rate of evaporation, Various evaporation rates at room temperatures 

will cause metastable polyvanadates of composition 

K2V4On 7H2 0, K6V10O28 10H2O, and K6V10O28 8H2O 

to crystallize. Then if further evaporation is prevented, the existing polyvanadates will redissolve as the 

stable phase K2V6Oi6 or K2 (OH) 2V6Oi5 crystallizes. 

By analogy, pascoite, Ca3Vi0O28 16H2O, is considered 

the metastable phase and hewettite, CaV6O16 9H2O, the 

stable phase, although pascoite cannot be redissolved 

and hewettite crystallized in its place merely by stoppering the solution, as is possible with potassium vanadate 

solutions.

Solutions having a low pH, below 3, are thought to be 

in the stability area for V2O5 2H2O. The phase boundary between the V2O5 -2H2O and the polyvanadates is 

dotted to show uncertainty. Generally, V2O5 -2H2O 

will crystallize below this boundary but occasionally it 

will be above it. Similarly, the polyvanadates will occur above this boundary but pascoite has occasionally 

formed at pH 2.2. Furthermore, another phase which 

is similar to hewettite in appearance and composition 

may possibly be present in this pH region.

No V2O5 < 3H2O, corresponding to the mineral navajoite, has been found in the study of this system.

Synthetic rossite and pascoite are identical to the 

natural minerals in physical properties and appearance, 

but the synthetic materials are better crystallized. Synthetic hewettite is like the natural hewettite in fibrous 

habit, silky luster, and hardness, but differs in color. 

Natural hewettite is a vivid deep red; synthetic hewettite is a light to dark brown. Like their natural 

counterparts, synthetic rossite and hewettite dehydrate 

on exposure to the atmosphere to metarossite and metahewettite, respectively.

Below are the optical properties determined for synthetic rossite and pascoite using phosphorus-sulfurmethylene iodide index liquids with white light. 

SYNTHETIC ROSSITE (CaV2O6 4H2O)

Optical properties

a= 1.720 ±0.003 at 28° C 

0= 1.783 ±0.003 

7=1.842±0.003

triclinic 1 

biaxial negative 

2V=85° (calc.) 

colorless, nonpleochroic 

r<v (?) dispersion^faint

Found. 

Calc_.

Chemical analysis 

[Analyst, George B. Magin, Jr.]

CaO VtOs 

........ 18.58 58.43

......_. 18.09 58.67

H,0 Total

22.89 99.90

23.24 100.00
SYNTHESIS OF CALCIUM VANADATE MINERALS AND RELATED COMPOUNDS 107

SYNTHETIC PASCOITE (Ca3Vi0028 16H2 0)

Optical properties

a= 1.771 ±0.003 at 27° C monoclinic 2 

/3= 1.824±0.003 biaxial negative 

7 =1.826 ±0.003 2V=30° (calc.)

pleochroic

X light cadmium yellow 

Y=orange 

Z = cadmium yellow 

. ' absorption X<Z<Y

r>v dispersion, very strong

Found. 

Calc..

Chemical analysis 

[Analyst, George B. Magin, Jr.] 

CaO VaOj

...--... 12.56 65.23 

.-.---.. 12.32 66.58

HiO Total

22.23 100.02

21.10 100.00

i As reported by Weeks and Thompson, 1954.

' As reported by Evans, Mrose, and Marvin, 1954.

Pascoite has been heretofore listed as 

Ca2V6O17 -llH2O

(Hillebrand, Merwin, and Wright, 1914; Palache, Berman, and Frondel, 1951), but crystallographic and 

density studies (Evans, Mrose, and Marvin, 1954) on 

synthetic pascoite plus chemical analyses show that its 

formula should be Ca3V10028 16-17H2O. The formula 

as determined from the chemical analysis alone requires 

IT molecules of water, but 16 molecules of water to agree 

best with density measurements (Evans, Mrose, and 

Marvin, 1954). The exact amount of water will not be 

known until the crystal structure has been determined. 

The extra water revealed by chemical analysis may be 

due to included water in rapidly formed crystals.

Synthetic hewettite was not identified optically because of its fine fibrous habit, its high indices of refraction (above 2.0), and its reaction with high-index 

oils which changed the color of the fibers from a yellow 

or red to a dark green or black. Nonreacting index oils 

show that the fibers have a yellow to red color, parallel 

extinction, and are nonpleochroic. Identification was 

made by X-ray powder diffraction films.

The V2 05 '2H2O phase is usually very fine grained, 

occasionally fibrous. It is dark reddish brown in the 

mother liquor but changes on washing and drying to 

a dull brown or green. Solutions with pH values less 

than 1 sometimes produce a black, hydrated vanadium 

pentoxide. The V2 05-2H2O is soft with a dull, sometimes velvetine, luster. Examination with a petrographic microscope reveals an anisotropic, yellowish 

green material with indices of refraction greater than 

1.9; high index oils react with the material. Identification is made by X-ray powder diffraction patterns 

and chemical analyses.

The solubilities of synthetic rossite, pascoite, hewettite, and V2O5'2H2 0 as determined in doubly distilled 

water at 30° C are as follows:

Rossite____ _ 4.55 g/1, pH of solution 6.8

Pascoite___1__ More than 20 g/1, pH of solution 6.1 

Hewettite-^-__- 0.03 g/1, pH of solution 4.5 

V2O5 -2H2O___. 0.03 g/1, pH of solution 4.1

The solubility figure of the pascoite is approximate. 

Hewettite crystallized within a short time from the 

nearly saturated or saturated pascoite solution and 

changed the ratio and concentration of dissolved 

CaO-V2O5 .

To apply the information of the phase diagram to 

field conditions, one must understand what happens 

during the attack by air and ground water on the primary mineral assemblage. Thus, the breakdown of sulfides, predominantly pyrite, produces acid conditions. 

The acid conditions and available oxygen facilitate the 

solution and oxidation of vanadium. The pH of such 

a solution is affected by the solution of vanadium minerals and associated calcite, dilution by other ground 

waters which may be slightly basic, and movement 

through the sediments. When the solution is saturated, 

rossite will crystallize if the pH is above 6.2, assuming 

the temperature is near 30° C. It is doubtful if the 

pH ever rises much above 8, as no indisputable evidence 

of natural pyrovanadates has been found. Hewettite 

will develop if the pH value is below 6.2 and concentration is very slow. The necessity of very slow concentration in the formation of hewettite is shown by the 

fact that it does not form as an efflorescence on mine 

walls or surface exposure where evaporation is rapid, 

as does pascoite. Hewettite is found in porous or fractured sediments where evaporation is greatly retarded.

If the ground water is quite acid, below pH 3.0, hydrated vanadium pentoxide should form. It is possible that if only a very minor amount of calcium ions 

or other cations were present in the ground water, hydrated V2O5 would also form at higher pH values, since 

hydrated V2O5 has formed at pH values up to 4 in the 

laboratory.

The presence of rossite in a deposit may indicate a 

maximum temperature limit as rossite is not formed 

above 90° C.

URANIUM-CONTAINING VANADATES

In an attempt to learn about the formation of 

carnotite, K2 (UO2 ) 2 (VO4 ) 2 -1-3H2O, and .tyuyamunite, Ca(UO) 2 (VO4 ) 2 -7-10.5H2O, exploration of the 

systems

K2O-UO2 (NO3 ) 2 -V2O5 and CaO-UO2 (NO3 ) 2-V2O5 , 

both in aqueous solution, was started.

The method of exploration was much the same 

as in the CaO-V205-H2O system. Thus, in the 

K2 0-U02 (NO3 ) 2 -V2O5 system, stock solutions were prepared from the dry reagents, KOH, V2 0S (containing 

some V2O4 ), and UO2 (NO3 ) 2 6H2O. Since KOH and
108 GEOCHEMISTEY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

UO2 (NO3 ) 2 -6H2O are readily soluble in water, stock 

solutions of 5.5M KOH and 0.127M UO2 (NO3 ) 2 were 

easily prepared. A colloidal solution of V2O5 (0.0015M) 

was prepared by dissolving V2O8 in water containing 

H2O2 . A KOH-V2O5 stock solution was prepared by 

dissolving KOH in a liter of H2O, adding powdered 

V2O(5 and 50 ml of 30 percent H2O2 , and heating to 

"boiling to rid the solution of excess H2O2. The solution 

was then cooled, filtered, and analyzed. Concentrations 

ranged between 0.18 to 0.32M KOH and 0.23 to 0.62M 

T206 .

Solutions for evaporation are prepared from aliquots 

of the stock solutions. These aliquots have to be diluted approximately 100 fold to prevent instant precipitation on mixing. The KOH-V2O5 aliquot is first 

diluted, then any additional KOH or V2O5 which is 

needed to obtain the desired ratio is added from the 

prepared stock solutions. The UO2 (NO3 ) 2 aliquot is 

put in another beaker and diluted. The two solutions 

are then mixed by pouring the uranium nitrate into the 

KOH-V2 05 solution. The reverse procedure results in 

initially cloudy solutions. The pH is adjusted by 

adding HNO3 (1:10). Solutions are evaporated at 

room temperature (24° to 30°C) or on a hot plate at 

«0°C.

The precipitated phases are usually so finegrained 

that identification is made by X-ray powder diffraction 

patterns, rather than by optical methods.

Figure 29 shows a section containing the KOH axis 

and midpoint of the opposite side of the triangular 

phase diagram of the KOH-V2O5 -UO2 (NO3 ) 2 system. 

This section shows the tentative relationship between

 carnotite, rauvite, and hydrated vanadium pentoxide. 

Phase boundaries are dependent on pH and concentration of reacting ions; temperature has no appreciable

 effect on these phase boundaries. The dashed line 

across the top of the diagram indicates the limits of

 exploration. No experimental solution had an initial 

pH above the dashed line. The area below the line 

was explored by depressing the pH of a solution with 

HN03 .

The yellow synthetic carnotite, as identified by X-ray 

diffraction patterns, has a fairly large area of stability. 

The only noticeable difference between carnotite formed 

in the basic environment as against that formed in an 

acid environment, is in the degree of crystallinity. The 

carnotite formed in the basic region is of finer grain, 

giving broad, diffuse X-ray diffraction lines. No 

chemical analyses are available as yet on these synthetic carnotites. A solubility study on synthetic

 carnotite has indicated that its solubility is near 0.15 

ppm in distilled water and increases to 4 ppm at pH 

3.3 (NOr present).

pH

14

1.3

12

11

10

9

8.

7

6

5

4

3o

2

1 

1(

 ^

\x

X

X

X

X

X

\ \

\

\

\

\

\

\

\

Carnotite \

\

\

\

\

\

\*

\

Rauvite

V2 05-2H20

ft 80 60 40 20 0

KOH Percent bv weight ^20$ .rercent oy weignt U02 (N03 )2

(1 to 1 by weight)

FIGURE 29. Section of the KOH-V2OB-U02 (NO3 )2 aqueous solution phase 

diagram showing the relative positions of the initial phases formed 

upon evaporation of solutions.

Synthetic rauvite or rauvite-like material forms 

under acid conditions as a bright yellow precipitate 

which dries to a dull yellow, orange, or brown material. 

The bright yellow color usually returns when the material is returned to water. The X-ray diffraction 

pattern of this material is distinctive, but the lines are 

broad and diffuse, due to very fine grain size, and 

possibly to a disordered structure. Malcolm Eoss, of 

the Geological Survey, after examining natural rauvite 

with the electron microscope, suggests that it has a 

platy or claylike character. His examination of synthetic rauvite showed it to consist of very fine crystalline aggregates.

Although natural rauvite has been listed as 

CaO-2UO3 -5V2O5 -16H2O(?) (Weeks and Thompson, 

1954), some doubt remains as to its real composition. No 

analysis on rauvite or rauvite-like material precipitated 

from solutions containing potassium ion is available. 

But synthetic rauvite, as identified by X-ray powder 

diffraction pattern, was precipitated as a bright yellow 

material from a solution containing only UO2 (NO3 ) 2 

and V2O5 , no calcium or potassium ions present. A
SYNTHESIS OF CALCIUM VANADATE MINERALS AND BELATED COMPOUNDS 109

chemical analysis of this material, by George B. Magin, 

Jr., gave the following composition (in percent):

UOt

47.08

ViOt

37.72

HjO

15.49

Total

100.29

This composition gives the tentative formula, 

UO8 -V2CV5H2O.

When a solution is prepared containing relatively 

high concentrations of uranium and vanadium ions, 

rauvite is sometimes precipitated in the stability region 

of carnotite. This action suggests that rauvite may 

form as a metastable phase and later convert to the 

stable phase, carnotite.

Results of solubility runs with synthetic rauvite are 

not available, but its solubility is thought to be comparable to carnotite.

Solutions with pH values less than 1 precipitate dark 

brown to black V2O5 -2H2O, as identified by X-ray 

methods. Precipitation of the V2O5 -2H2O continues 

until the vanadium pentoxide in solution is depleted. 

Then green crystals of UO2 (NO3 ) 2 '#H2O crystallize if 

the solution is at room temperature. At 80° C a finegrained yellow material forms, tentatively identified by 

X-ray powder diffraction patterns as a hydrated uranium oxide. The last material to come out of solution 

is KNO3 , colorless crystals. As the solutions increase 

in KOH and V206 concentration, golden crystals of 

K2V0Oi6 may form after the precipitation of the carnotite or rauvite at 80° C.

Examination of the CaO-UO2 (NO3 ) 2 -V2O5 system 

in aqueous solution has been started but not enough data 

have been collected to delineate phase boundaries. 

From what data are known, the phase diagram will 

probably be similar to that of the K2O-UO2 (NO3 ) 2- 

V2O6 system in aqueous solution, with tyuyamunite 

appearing in place of carnotite.

Preparation of stock solutions of CaO-V2O5 , V2O8 , 

and U02 (NO3 ) 2 used in this study has been described 

above. Small aliquots of CaO-V2O6 and UO2 (NO3 ) 2 

stock solutions are placed in separate beakers and diluted with water. The diluted CaO-V2O6 is brought 

to the desired ratio by adding the necessary milliliters 

of V2O8 stock solution or freshly prepared Ca(OH) 2 

solution (approx. 0.015M). Then the diluted 

UO2 (NO3 ) 2 is poured into the CaO-V2O5 solution. As 

mentioned before, this method of mixing prevents immediate precipitation. The pH of a solution is adjusted 

with HNO3 . Solutions are then evaporated at 30°, 

55°, or 90° Gin ovens.

The phases so far encountered are tyuyamunite, 

Ca (UOa ) 2 (V04 ) 2 5-10.5H2 0, rauvite, and V2O6 2H2O.

They are fine grained and identification is made by Xray methods. The tyuyamunite phase corresponds 

to the carnotite phase of the K2O-UO2 (NO3) 2-V2OB 

system. The synthetic rauvite and V2O6 2H20 are similar to previously synthesized phases. However, in one 

case, the rauvite remained quite yellow in color instead 

of changing to a dull orange or brownish color.

Again pH, concentration of reacting ions, and temperature are factors affecting stability of the solid phase. 

Thus far, no tyuyamunite has been synthesized below 

90°C at the few points explored on the phase diagram. 

It may be possible that at lower temperatures rauvite 

forms as a metastable phase which will slowly convert 

to tyuyamunite. Most of the rauvite was precipitated 

under conditions similar to its formation shown by the 

K2O-UO2 (NO3 ) 2-V2O5 phase diagram.- The same also applies to V2O6 -2H2O. Again, as in the above system, the exact relationship of rauvite to tyuyamunite 

(or carnotite) is not known. Rauvite may be either a 

metastable or a stable phase, depending on the pH of 

the environment.

The study of synthetic carnotite and tyuyamunite 

shows that carnotite and probably also tyuyamunite 

can be formed under either acid or basic conditions. 

However, the attack on the primary mineral assemblage, as previously related, presumably took place in 

an acid environment, oxidizing and dissolving both 

uranium and vanadium. Since uranium-containing 

vanadates are quite insoluble above pH 3 and precipitate quite readily, they should form in preference to 

other vanadates if the fully oxidized uranium and 

vanadium ions came together in solution. Highly acid 

conditions, pH 1 or below, would prevent the formation 

of uranium vanadates and redissolve those already 

formed. Hydrated V2 06 would probably be the first 

phase to appear under such conditions.

MISCELLANEOUS VANADATES

Some of the rarer vanadates found on the Colorado 

Plateau have been synthesized.

The sodium analog of hewettite, Na2V6Oie -3H2O, 

which has recently been found in nature (A. D. Weeks, 

oral communication), can be synthesized either by direct precipitation or by base exchange. At 55° C, 

Na2V6Oi6 '3H20 formed directly from slowly evaporated NaOH-V2O5 solutions (0.22M NaOH, 0.11M 

V2O6 ) with pH values between 3.0 and 6.0, adjusted with 

glacial acetic acid. Na2V6Oi8 3H2O was identified by 

X-ray diffraction patterns and chemical analyses. It 

would probably form at 20° C if the solution were 

evaporated very slowly; more rapid evaporation would 

produce a metastable polyvanadate analogous to 

K6V10O28 -9H2O and Ca3Vi0O28 -16H2O (pascoite). In 

forming Na2V6Oi6 3H2O by base exchange, hewettite
110 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

(CaV6Oi6 '9H2O) or one of its lower hydrates is placed 

in a sodium-bearing solution with a pH between 3.0 and 

6.0 for an appropriate length of time. Several grams 

of synthetic hewettite were converted to the sodium 

analog in Na2SO4 solutions (Na2SO4 concentration 

varied from 0.1N to 0.7N) in three weeks. Identifica-. 

tion was made by X-ray diffraction patterns. Natural 

Na2V6Oi6 3H2O could have formed in either way.

Hummerite, K2Mg2V10O28-16H2O, is easily crystallized from solutions containing stoichiometric amounts 

of potassium,. magnesium, and vanadium at pH 5 by 

rapid evaporation at room temperatures. Variation in 

the relative ratios of potassium, magnesium, and vanadium concentrations, if not extreme, does not prohibit 

hummerite formation. A KOH-V2O5 solution 

0.00676M KOH, 0.0165M V2O5 ) was made by dissolving dry KOH and V2O5 in water. H2O2 was used to 

dissolve, the V2O5 ; excess H2O2 was boiled off. One 

tenth of a gram of Mg(]SrO3 ) 2 was then dissolved in 100 

ml of KOH-V2O5 solution. The pH was raised to the 

desired pH by adding concentrated KOH solution. The 

solution was placed in an open, shallow evaporating 

dish, and; crystals soon formed. Synthetic hummeritecrystals are sensitive to heat, dehydrating readily.

Volborthite, Cu3V2O8 3H2O, will slowly crystallize 

out of a solution having a pH between 2.0 and 4.7. 

Above pH 4.7, it becomes very insoluble and precipitates as a flocculent material which will crystallize if 

the solution is boiled for a few minutes. In synthesizing volborthite, 20 ml of 0.0855M NH^VOs solution 

were added to 200 ml of H2O. The pH was adjusted 

to 2 with concentrated HNO3 to prevent an immediate 

precipitation from forming on addition of 2 ml of 2.5M 

Cu(NO3 ) 2 . The solution was stirred and NH4OH 

(1:10) added to raise the pH to the desired value. 

Heating the solution before the addition of the NH4OH 

increases the grain size of volborthite if precipitated at 

a pH value above 4.7. Identification of the volborthite 

was made by X-ray diffraction pattern and chemical 

analysis. Chemical analysis was done by Robert Meyrowitz, U. S. Geological Survey, by microchemical techniques.

Several attempts were made to synthesize calciovolborthite, (Cu,Ca) 2VO4OH, by adding various amounts 

of 1.25M Cu(NO3 ) 2 to 40 ml portions of CaO-V2Os 

solution (0.0365M CaO, 0.0412M V2O5 ). HNO3 (1:50) 

was added to the CaO-V2 05 solutions before the 

Cu(NO3 ) 2 to lower the pH to 5, then again after the 

addition of the Cu(NO3 ) 2 to give a pH value between 

4.5 and 4.0. No calciovolborthite was formed; dark 

brown crystalline aggregates of volborthite appeared.

To determine if calciovolborthite was stable at high 

pH values, the Cu(NO3 ) 2 solution was diluted to approximately 0.005M and then made ammoniacal with 

NH4OH. This solution was added to 100 ml of CaOV2O5 (approximately 0.0035M CaO, 0.0005M V2O5 ) 

solution and placed in an oven at 90° C. A light green, 

fine-grained precipitate formed which gave an X-ray 

powder diffraction pattern tentatively identified as 

tangeite (calciovolborthite, Guillemin, 1956) by Daphne 

Boss (written communication). Chemical analyses of 

three precipitates by George B. Magin, Jr., reveal calcium, copper, and vanadium present in major amounts. 

Samples were apparently not pure tangeite as the analyses did not agree with the theoretical composition. 

Both copper and calcium are thought to be essential 

components of the material as it is not formed if either 

copper or calcium ions are absent. Heating the precipitate in its mother liquor for several days at an elevated temperature also seems to be required to crystallize the tangeite. It formed at pH values between 8.5 

and 10. Volborthite was sometimes present as a contaminant in precipitates formed near pH 8.5.

Several attempts have been made to synthesize fervanite, Fe4 (VO4 ) -5H2O, and steigerite, 

Al2 (VO4 ) 2 t 6.5H2O. The procedure is similar to the 

synthesis of volborthite except Fe(NO3 ) 3 or A1(N03 ) S 

were substituted for Cu(NO3 ) 2 . A very insoluble, 

brown, flocculent iron vanadate precipitated near pH 

1.6; an insoluble, yellow, flocculent aluminum vanadate 

precipitated near pH 4. Even though the flocculent 

materials were boiled for several minutes or precipitated 

from near-boiling solutions or precipitated by very 

slowly increasing the pH of the solution (urea, 

CO,(NH2 ) 2 , was added; then the solution was heated 

to cause decomposition of urea and formation of 

NHtOH); no indication of crystallinity was detected 

by X-ray powder diffraction. Chemical analyses by 

Robert Meyrowitz, U. S. Geological Survey, using 

microchemical techniques, give the following empirical 

formulas: Fe2 (VO4 ) 2 -5H2O and A1VO4 -4H2O.

CONCLUSIONS

Synthesis of many of the vanadates found on the Colorado Plateau, study of the system CaO-V2OB -H2O, and 

cursory examination of systems K2O-UO2 (NO3 ) 2 -V2O5 

and CaO-UO2 (NO3 ) 2 -V2O5 , both in aqueous solution, show that the natural vanadates can form over a 

wide range of pH conditions. The best pH indicators 

are the calcium vanadates; rossite forms under slightly 

alkaline or acid conditions, depending on the temperature; pascoite and hewettite crystallize in a weak to
SYNTHESIS OF CALCIUM VANADATE MINERALS AND BELATED COMPOUNDS 111

moderate acid environment. Carnotite indicates pH 

values above 2.2; rauvite and navajoite indicate acid 

conditions. While it has not been possible to duplicate 

actual natural conditions, especially the presence of 

other ions and their influence on vanadium (V) concentration and precipitation, the presence of pascoite 

seems to indicate rapid evaporation of ground water 

carrying vanadate ions; hewettite and probably Nahewettite seem to indicate slow evaporation.

REFERENCES

Evans, H. T., Jr., Mro'se, Mary E.( and Marvin, Richard, 1954, 

The constitution of the natural and artificial decavanadates: 

Geol. Soc. America Bull., v. 65, p. 1249, (Abstract).

Guillemin, C., 1956, Contribution a la mine'ralogie des ars6niates, 

phosphates et vanadates de cuivre, II. Phosphates et 

vanadates de cuivre: Soc. franchise Mine'ralogie et Cristallographie Bull., tome 79, p. 219-275.

Hess, F. L., and Schaller, W. T., 1914, Pintadoite and uranite, 

two new vanadium minerals from Utah, a preliminary note : Washington Acad. Sci. Jour., v. 4, p. 576-579.

Hillebrand, W. F., Merwin, H. E., and Wright, F. E., 1914, 

Hewettite, metahewettite, and pascoite, hydrous calcium 

vanadates: Am. Phil. Soc. Proc., v. 53, p. 31-54.

Palache, Charles, Berman, Harry, and Frondel, Clifford, 1951, 

Dana's system of mineralogy, 7th ed., v. 2, New York, John 

Wiley and Sons, Inc.

Weeks, A. D., and Thompson, M. E., 1954, Identification and occurrence of uranium and vanadium minerals from the 

Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B.

Part 9. CLAY MINERALS IN THE MUDSTONES OF THE ORE-BEARING FORMATIONS

BY W. D. KELLER

CONTENTS

Page Page

Abstract_________________________________________ 113 Clay minerals in representative samples of mudIntroduction _______________________________________ 114 stone Continued

Acknowledgments____--____________-_-_-_----____. 114 Clay minerals in the Salt Wash member of the Morrison

The problem of clay minerals in red-green mudstones__ 114 formation from productive and barren localities 118

Field and laboratory work___________________________ 114 Red-green mudstone along faults__.__________-_-_ 118

Clay minerals in representative samples of mudstone. __. 116 Alunitization at the Oyler mine, Capitol Reef NaClay minerals in red-green mudstone samples____ 116 tional Monument-_____-_-______----__-_ ___ 119

	Literature cited___________________________________ 11$

ILLUSTRATIONS

Pag*

FIGURE 30. X-ray powder diffractograms of red mudstone of the Moenkopi (formation (No. 235) and a green counterpart

(No. 234). Diffractogram 225 is of an alunitized seam in bleached Moenkopi.___________________________ 116

31. X-ray powder diffractograms of purple (No. 519) and white (No. 520) Shinarump member of the Chinle formation. 117

32. X-ray powder diffractograms of green (No. 6) and red (No. 5) mudstone___-______--_-_-____--_-_---------- 117

TABLES

Page 

Table 1. Clay minerals in mudstone samples from selected formations___________________________-_---__________-----_ 116

2. Chemical composition of purple (No. 519) and white (No. 520) silty mudstones from Dille Butte, north end of San

Rafael Swell, Utah_________________________________________________________ 117

3. Clay minerals in selected productive and nonproductive samples of the Salt Wash member of the Morrison formation

from the Colorado Plateau________________________-______-__-__-_-_________-____--_____-__-_---_---- 118

4. Clay minerals in mudstone samples from mineralized faults and nearby barren rocks in the Kane Springs district,

Utah_________-_______________________________________________________________-_-_---_---_---.___--_ 119

5. Samples collected at the Oyler mine, Capitol Reef National Monument, Utah________-_____-_____-__---_- __ 119

ABSTRACT

Mudstone samples were collected from uranium-vanadium orebearing sedimentary formations on the Colorado Plateau to determine if differences could be detected in the gross clay mineralogy between red- and green-colored mudstones which are 

otherwise stratigraphically equivalent, between ore-bearing and 

barren mudstone, and within other relationships referred to in 

the conclusions below. Clay mineral identifications, which were 

made by the use of X-ray powder diffraction patterns, differential thermal analyses, and petrographic examinations, lead to 

the following conclusions concerning the gross clay mineralogy 

of the mudstones.

Red and green (also purple and white) counterparts of mudstone do not show a significant difference in gross clay mineralogy in the Rico formation of Pennsylvanian and Permian (?) 

age, the Cutler formation of Permian age, the Moenkopi, and 

Chinle formations of Triassic age, and the Salt Wash and

Brushy Basin members of the Morrison formation of Jurassic 

age. Clay minerals within all the common clay mineral groups 

may be constituents of red and green mudstone without regard 

to color. No difference was detected in the gross clay mineralogy of red-green counterparts whether the green color was developed along mineralized fault planes which transected the 

red beds long after lithification or in isolated spots within 

thick, relatively impermeable mudstones whose color change 

may have occurred during diagenesis.

Mudstones may be ore bearing or barren without necessary 

difference in their clay mineral components.

Alunitization of red mudstone of the Moenkopi formation at 

the Oyler mine in Capitol Reef National Monument was preceded by bleaching of the red ferric oxide pigment, mobilization 

of the iron as sulphate and the formation of jarosite, removal 

of calcite, and formation of some gypsum.

113
114 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

It is difficult to find unequivocal evidence of effects on the 

rocks from the solutions which carried uranium-vanadium ore 

minerals apart from the ore minerals themselves.

INTRODUCTION

Mudstones, of which clay minerals are major components, constitute an integral part of the sequence of 

sedimentary rocks which contain uranium and vanadium ore on the Colorado Plateau. It is probable that 

the mudstones have played an essential role, one way 

or another, in the precipitation, localization, and concentration of many of the ore deposits. For example, 

the bulk properties of mudstones, especially low permeability, have made them important as barriers, traps, 

and guides for ore-bearing solutions.7 The chemical 

and mineralogical properties of the clay minerals, on 

the other hand, are probably more important where replacements by ore minerals occur. The color of the 

mudstones also has been of special interest because it 

has been observed that a high ratio of green to red 

mudstone and sandstone can be successfully used as an 

indicator of favorable ground (Weir, 1952) on the 

Plateau.

In consequence of the close association of mudstone 

with ore deposits, and of the red-green (similarly, 

purple-white) color relationship to ore-bearing ground, 

at least two major questions have arisen regarding their 

mineralogic composition. Does the clay mineralogy 

of mudstones in localities productive of ore differ from 

that in barren country, and does the clay mineralogy 

of the green mudstone differ from that of the red which 

is stratigraphically equivalent?

This report is concerned with the above questions. 

It does not include consideration of the clay minerals 

finely disseminated in the sandstones or of the vanadiferous clay minerals which are ore minerals.

ACKNOWLEDGMENTS

The writer is most grateful for the courteous and 

unstinted help given him by geologists of the U. S. 

Geological Survey and the U. S. Atomic Energy Commission during the collection of the samples. Floyd 

Twenter, Earle McBride, and Henry Ott assisted the 

writer in the field and laboratory.

THE PROBLEM OF CLAY MINERALS IN RED AND 

GREEN MUDSTONES

To answer the question whether the clay minerals in 

red and green stratigraphically equivalent mudstones 

are different, it is relatively simple to collect specimens 

from red and green counterparts at one locality and 

analyze them mineralogically. An analysis from a

7 Mullens, T. B., and Freeman, V. L., Lithofacies of the Salt Wash 

member of the Morrison formation. (Written communication.)

single locality merely opens up the geologic problem, 

however, because green and red clay-bearing rocks occur in contact over a wide variety of geologic conditions which bear on the deposition and concentration 

of ore.

For example, although the ratio of green to red mudstones and sandstones is higher in favorable ground, 

it is also recognized that apparently similar green-red 

pairs, except for ratios of green to red, occur in red 

beds far removed from localities in which uraniumvanadium mineralization occurs. The problem enlarges thereby: are red-green counterparts from within 

ore deposits different from those in barren ground? 

Next, where green mudstones are mineralized, were the 

ore-transporting solutions responsible for the green 

color within red beds, or were the chemical and mineral 

environments within the green rock the causes for deposition of the ore minerals? Hence, a single question 

is immediately doubled or tripled.

Green spots may occur isolated within the interior 

of relatively impermeable thick mudstone layers indicating color differentiation probably during diagenesis that is, early in the history of the rock, but in 

contrast to this relationship elsewhere, green zones 

occur alongside joints and fault planes which clearly 

transect the primary stratification structures in red 

beds. Some of the fault and joint planes are mineralized, others are not. Was the mineralization the 

the cause or the effect of the secondarily developed green 

color, and what clay minerals are present across the 

color contact in these red-green rocks ?

In a similar way, it may be asked if the clay minerals, 

and possibly other minerals except the iron-oxide 

minerals, differ in red-green counterparts in rocks of 

different geologic ages, in those deposited under different sedimentational environments, in those composed 

of different clay mineral groups, in occurrences where 

the uranium-vanadium ore minerals are dark and low 

in oxidation state as against those higher in oxidation 

state, and in various other combinations. With the 

introduction of each new variable to the problem the 

number of questions increases geometrically to the point 

where it becomes impossible practically to collect redgreen pairs for analysis in such a way as to eliminate 

all variables except color in the many combinations 

referred to above. Specimens were collected and 

analyzed, however, from the relationships encountered 

most commonly in field work and these will be described subsequently.

FIELD AND LABORATORY WORK

Approximately 400 samples of mudstone and clayey 

sandstone were collected from localities on the Colorado
CLAY MINEARLS IN THE MUDSTONES OF THE ORE-BEARING FORMATIONS 115

Plateau during parts of the summers of 1953 and 1954. 

Where red and green counterparts were taken, they 

were always obtained from the same stratigraphic level 

and within a few inches apart across the color contact, 

unless otherwise stated. The clay minerals were identified mainly from X-ray powder diffraction patterns, 

but differential thermal analysis and the petrographic 

microscope were also used.

The clay fraction was extracted from sandstones by 

gently disaggregating in distilled water by rolling (not 

grinding) in a ball mill, and then recovering from 

sedimentation the particles having settling velocities 

equivalent to and less than 2-micron spheres according 

to Stoke's Law. Some muds rich in gypsum or other 

soluble flocculating salts required repeated stirring 

with distilled water, settling, and decantation before 

the clay remained in a dispersed state, but no dispersing 

chemical, other than very dilute NH4OH, was added.

During the first stages of the laboratory work all 

samples were dispersed and only minus 2-micron fractions analyzed, some in random orientation and others 

as oriented aggregates (clay films). The orientedaggregate technique greatly enhances the X-ray reflections from the basal planes of platy minerals, making it 

possible to detect small amounts of platy clay minerals 

which might otherwise be missed, particularly mixedlayer types which characteristically give weak reflections.

After comparing the diffraction patterns of those 

minus 2-micron fractions from mudstones with patterns 

from the bulk or entire mudstone it was concluded that 

more or less mineral segregation and concentration occurred during sedimentation. Minerals heavier than 

the clay minerals, like iron oxides, iron sulfides, and 

some uranium-vanadium ore minerals, were removed to 

a significant degree from the minus 2-micron fraction 

of clay minerals owing to the more rapid settling of the 

heavier minerals, and, therefore, the minus 2-micron 

fraction was not always representative of the original 

rock.

It is obvious that geologic conclusions based on 

mineral identifications of nonrepresentative fractions 

of a rock may be dangerously erroneous. It was necessary then to choose in this study between sacrificing 

either some sensitivity in clay mineral identification or 

of fidelity in representation of the outcrop by the specimen. Because the first objective of the problem was to 

look for possible differences between the red and green 

counterparts of mudstones which might be utilized in 

geologic interpretation or as a guide to ore, it seemed 

of paramount importance that the sample which was 

analyzed must represent the rock.

Therefore, the considered decision was made to

identify primarily the dominant clay mineral constituents in the whole mudstones that is, the bulk 

samples, although it is possible that small amounts of 

some clay minerals detectible only by more refined 

methods, may have remained unreported. Many 

samples were still fractionated, however, to check observations on the bulk samples. A truly refined clay 

mineral analysis requires determinations of ion exchange and perhaps even chemical analysis, which become so costly in terms of both time and money that the 

limit of diminishing returns is quickly reached in a geologic study where many clay samples are involved, as in 

this one.

Physical methods of clay mineral analysis, as were 

used, rarely permit recognition, at our present stage of 

knowledge, of the nature of cationic population in the 

octahedral, tetrahedral, and interlayers of the clay minerals. It is possible that chemical differences of this 

type occur between clay minerals, but which would 

escape detection by the physical analytical techniques 

employed. This reservation must be made on the conclusions to be reached later in this report.

For the purposes of identification by X-ray, a 001 interplanar spacing of approximately 7A in the clay mineral was taken to indicate a member of the kaolin group. 

The reflections of kaolin-type minerals were regularly 

more characteristic of the "fire-clay type of kaolinite," 

one with layers stacked partially at random, than of 

well-crystallized kaolinite (Grim, 1953). The fire-clay 

type of kaolin is commonly developed in argillaceous 

sedimentary rocks whose source material is not previously well-crystallized kaolinite.

Hydrous mica, which has also been called illite, is 

identified by an interplanar spacing of approximately 

10A. This is commonly a broader (platykurtic) peak 

than the sharper one provided by clastic muscovite. 

Some diffraction patterns showed broad 10A bases 

which abruptly narrowed to a sharp peak, as if pierced 

by a sharp 10A shaft. Such patterns were interpreted 

as coming from both hydrous mica clay and clastic 

muscovite flakes. The presence of muscovite in mudstones showing this type of pattern was confirmed by 

microscopic examination.

Chloritic minerals were identified by a spacing of approximately 14A. Because chlorite peaks persisted 

regularly after heating several of these clays to 500° C. 

for 6 hours, which destroys the structure of kaolinite, 

it was assumed that the ancient sediments under study 

did not contain chlorite whose structure is destroyed at 

a lower temperature than that which wrecks kaolinite. 

This assumption may be incorrect because chlorite 

which was destroyed below 500° C. has been found in 

ore clays (Part 11) from the Colorado Plateau. Even
116 GEOCHEMISTRY AND MINERALOGY ; COLORADO PLATEAU URANIUM ORES

if this assumption should prove to be incorrect, it does 

not invalidate the results obtained by comparing red 

and green counterparts, because the samples of both 

colors were treated the same.

Montmorillonite minerals were identified by swelling 

along the c axis to approximately 17A upon solvating 

with ethylene glycol.

These criteria for clay mineral identification, using 

the 001 spacings, are in general use currently, although 

they are vulnerable to criticism (Weaver, 1953). The 

060 peaks of clay minerals also were regularly checked. 

X-ray equipment used was a North American Philips 

unit at the University of Missouri. A wide-range 

Geiger-Muller goniometer and nickel-filtered copper 

K« radiation were employed.

CLAY MINERALS IN REPRESENTATIVE SAMPLES 

OF MUDSTONE

Mineral analyses of representative mudstone samples 

have been organized in terms of stratigraphic sequence, 

productive (uranium-vanadium ore) and nonproductive 

localities, occurrence along faults, and a deposit where 

bleaching and alteration to alunite (the Oyler mine) 

has occurred. Many more mineral analyses were run 

than reported on herein, but these described will represent the data which have lead to the final conclusions.

CLAY MINERALS IN RED-GREEN MUDSTONE 

SAMPLES

A tabulated record of representative red and green 

stratigraphically equivalent samples of mudstones 

from red-bed ore-bearing formations on the Colorado 

Plateau is given in table 1.

Many samples were collected and analyzed from the 

Moenkopi formation of Triassic age, especially near its 

contact with the Shinarump member of the Chinle formation of Triassic age (or other overlying sandstone) 

primarily at mining localities from Monument Valley, 

Arizona, to the north end of the San Rafael Swell in 

Utah. Hydrous mica and muscovite characterize this 

zone in the Moenkopi, and kaolinite may, or may not, 

be present in it.

In figure 30 are shown X-ray diffractograms of 

stratigraphically equivalent green (No. 234) and red 

(No. 235) Moenkopi from a mineralized zone near the 

Oyler mine, Capitol Keef National Monument, Utah. 

Hydrous mica, muscovite, kaolinite, quartz, and probably calcite are represented in the diffractograms. No 

significant difference is found between the patterns of 

the clay minerals in the red and green counterparts.

The Shinarump member of the Chinle formation exposed on Dille Butte in the San Kaf ael Swell, which is 

the source of samples Nos. 519 and 520 described herein,

TABLE 1. Clay minerals in mudstone samples from selected 

formations

Sample 

No.

451 R..~ ...

451 G. ...

270 R. ......

270 G.. -

519.. .......

520.... -.

273 R. ...

273 G. ......

15 R..... 

15 G.. 

5 R. ...... ..

6 G. ...... ..

Formation or member and 

locality

Rico formation, Hercules

mine, Kane Springs district, Utah. 

Rico formation, Hercules

mine, Kane Springs district, Utah.

Roef Nat. Monument.

Reef Nat. Monument.

Chinle formation, Dille 

Butte, N. end San Rafael 

Swell.

Chinle formation, Dille 

Butte, N. end San Rafael 

Swell.

mine, San Rafael Swell.

mine, San Rafael Swell. 

Salt Wash member of Morrison formation, Uravan. Colo.

son formation, Uravan, Colo. 

See table 3, for other Salt 

Wash samples.

Morrison formation, Uravan, Colo.

Morrison formation, Uravan, Colo.

Color, 

red (R) 

or 

green (G)

R

G

R

G

White

R

G

R

G

R

G

Clay-size minerals

quartz, calcite, hematite. 

Hydrous mica, muscovite,

quartz, calcite.

dolomite.

dolomite.

kaolinite, quartz, hematite.

kaolinite, quartz.

mica (?).

mica (?).

FIGURE 30. X-ray powder diffractograms of red mudstone of the 

Moenkopi formation .Triassic) (No. 235) collected about 600 feet 

west of the entrance to the Oyler mine in Capitol Reef National 

Monument, Utah, and a green counterpart (No. 234), stratigraphically 

equivalent 6 inches from sample 235. Diffractogram 225 is of an 

alunitized seam in bleached Moenkopi at what appears to be the same 

stratigraphic zone as that of samples 234 and 235.
CLAY MINERALS IN THE MUDSTONES OP THE ORE-BEARING FORMATIONS 117

exhibits a purple-white mudstone zone which is probably representative of other purple-white occurrences, 

presumably parallels in color relationship the red-green 

pairs of red beds.

The X-ray pattern (fig. 31) of the white Shinarump mudstone (No. 520) shows peaks of kaolinite

pies 519 and 520 support the clay-mineral analysis as 

given above.

The samples from the Chinle contained hydrous mica 

and kaolinite, except that tuffaceous portions of the 

Chinle contained montmorillonite. The Brushy Basin 

member of the Morrison formation of Jurassic age contains montmorillonitic zones (fig. 32), and zones in

FIGURE 81. X-ray powder diffractograms of purple (No. 519) and 

white (No. 520) Shlnarump member of the Chinle formation (Triassic) 

from Dille Butte, north end of San Rafael Swell, Utah. North 

American Philips wide-range goniometer, Ni-flltered Cu-Ko radiation. 

Degrees 26 are shown along base lines of diffractograms.

and quartz while that of the purple counterpart (No. 

519) shows hematite in addition to kaolinite and quartz. 

The hematite pattern of the purple sample is more 

nearly complete for hematite than are those of the 

hematite-red rocks of the red beds. The purple color 

(very dusky red purple 5KP 2/2; Goddard, and others, 

1948) is reminiscent of certain specular hematite, but 

when the rock is finely pulverized for analysis it becomes red (pale reddish brown, 10R 5/4; Goddard and 

others, 1948) that is typical of red-bed sedimentary 

hematite. Because the X-ray patterns of the purple 

and white counterparts of the mudstone of the Shinarump member are practically superimposable, except 

for the additional hematite peaks in the purple sample, 

it is concluded that the clay mineral in the purple and 

white counterparts is the same.

The mineral composition of No. 520 was computed 

from its chemical composition (table 2) to be approximately, as follows:

FIGURE 32. X-ray powder diffractograms of green (No. 6) and red 

mudstone (No. 5) stratigraphically equivalent to the Brushy Basin 

member of the Morrison formation (Jurassic) from near Uravan, 

Colo.

which hydrous mica is dominant. The diffractograms 

of the montmorillonite in the red (No. 5) and green 

(No. 6) counterparts of the Brushy Basin samples are 

as nearly alike as are duplicate runs of the same sample. 

It is concluded, therefore, that the gross clay mineralogy 

of the two samples is the same.

The data in table 1 may be summarized in the following conclusions. No significant difference was found between the clay minerals in stratigraphically equivalent 

red and green counterparts of mudstones collected from

TABLE 2.^Chemical composition of purple (no. 519) and white 

(no. 520) silly mudstones from Dille Butte, north end of San 

Rafael Swell, Utah

[Analyst,,Lols Trumbull, U. S. Geological Survey.]

Percent

Kaolinite _________ 37 

Quartz ________ 51

Percent

Hematite _____1____ 10 

TiOa (rutile, anatase?)__ 2

100

Extended studies with the microscope and differential thermal analysis of bulk and fine fractions of samSiOj....... ....... .-. .-.. ........................

A1.0,.. ...............................................

FeaOs--- ......... ...... ......... ................ ...

FeO__... ....._.........-. -_........................

MgO........ .. .. ...... .............. ............

CaO.. ................. ...............................

NajO.. I. ....................................

KjO ..... ... : .... ......... ........

HiO-........ .. ... ...... ... ...............

H,0+........... :- ..............

TlOi--.- ... ... ....................................

C08 ........... ...... .................................

P8 0... ........... .....................................

MnO. -...-...-..-. ........... ..................

Sample 519

68.03

14.31

10.29

.10

.04

.06

.06

.16

.55

5.09

1.06

.02

.04

.01

99.82

Sample 520

78.75

13.42

1.14

.04

.05

.05

.01

.15

.44

4.62

1.03

.02

.03

.00

99.75
118 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

the Rico, Cutler, Moenkopi, and Chinle formations, 

and the Salt Wash and Brushy Basin members of the 

Morrison formation, or within clay mineral groups including the kaolin group, the hydrous micas, the montmorillonites, and probably chlorite. The red color of 

mudstone red beds disappears with removal or absence 

of the ferric oxide; it need not, and ordinarily does not 

involve a change in the clay minerals.

CLAY MINERALS IN THE SALT WASH MEMBER OF 

THE MORRISON FORMATION FROM PRODUCTIVE 

AND BARREN LOCALITIES

Mudstone samples from the Salt Wash member of 

the Morrison formation were collected to study the following relationships of clay minerals to ore mineralization: productive mudstone, which was enriched with 

uranium-vanadium minerals of ore grade, taken from 

generally favorable districts (Club group, Uravan, 

Colo.; Lower group, Slick Rock, Colo.); nonproductive 

mudstone from generally favorable districts (Uravan, 

Slick Rock, and Long Park, Colo.); productive mudstone from a less favorable to generally unfavorable district (Yellow Cat, Utah) ; and nonproductive mudstone 

from a generally unfavorable district (Salt Wash member type section, Emery Co., Utah). Red and green 

counterparts were collected from the nonproductive localities, but the productive mudstone was found in only 

green or gray colors. The results of the clay mineral 

analyses are shown in table 3.

TABLE 3. Clay minerals in selected productive and nonproductive samples of the Salt Wash member of the Morrison formation from

the Colorado Plateau

Sample No.

10 

15R.. .. --.-.... .

15G . 

25..................

28G . ............

29R-. 

LP-954G. ....... ..

LP-954R.. ........

47.... ..............

52R ...

63G. ..........

54R.. ..............

55G. ... .......

Locality

Yellow Cat, Utah... ____ ._._.:.. ___ ....

County, Utah.

Country, Utah.

County, Utah.

County, Utah.

Productive clay

X

X

X

Nonproductive 

clay

X

X

X

X

X

X

X

X

X

X

Favorable 

district

X

X

X

X

X

Unfavorable 

district

X

X

X

Red

X

X

Green or 

gray

X

Clay minerals

It is concluded from this study that the clay minerals 

are not significantly different between the productive 

and nonproductive mudstones, with one possible reservation. Productive mudstones are usually more likely 

to contain kaolinite and (or) chlorite(?) in addition to 

hydrous mica, than are nonproductive mudstone. It 

is doubted, however, that kaolinite per se, is responsible 

for deposition of ore minerals, because the same kaolinite-containing beds elsewhere along the strike may be 

nonproductive. It appears, therefore, that kaolinitecontaining mudstones represent a set of physical, chemical, or stratigraphic environments which are more likely 

to favor deposition of uranium-vanadium ore minerals 

than those in which hydrous mica alone, of the clay 

minerals, was deposited.

No significant difference was noted between the clay 

minerals in green and red mudstone counterparts examined in the foregoing study. Hydrous mica is the 

common clay mineral in the Salt Wash member, as was 

found also by Weeks (1953).

RED-GREEN MUDSTONE ALONG FAULTS

Mudstone samples were collected from red-green 

counterparts along faults in the Kane Springs district, 

Utah, in the Cutler formation of Pennsylvanian and 

Permian (?) age (Atomic King No. 2 mine), the Rico 

formation of Permian age (Hercules mine), and the 

Moenkopi formation of Triassic age (supplied by Otis 

McRae); the faults are now mineralized by oxidizedtype minerals. The green zone along the fault plane 

ranges from a few inches to 2 feet wide on each side. 

Clay mineral identifications are shown in table 4.

No significant differences were noted between the clay 

minerals in bleached mineralized zones along the fault 

planes, in their red counterparts, and in control samples 

collected nearby from barren rocks in the same stratigraphic beds as those containing ore minerals. From 

this lack of difference it is inferred that solutions which 

carried oxidized-type minerals did not necessarily 

bleach the red beds, and that they did not necessarily 

modify the gross clay mineralogy of the mudstones.
CLAY MINERALS IN THE MUDSTONES OF THE ORE-BEARING FORMATIONS 119

It is possible, however, for solutions to react with and 

modify clay minerals in association with uranium-vanadium ore deposits.

TABLE 4. Clay minerals in mudstone samples from mineralized 

faults and nearby barren rocks in the Kane Springs district, 

Utah

Sample No.

448 O. .......

449 R........

451 G-......

451 R........

447...........

446...........

C30-4... ......

630-1... ......

Locality

Rico formation mineralized. 

Counterpart of 448 Q- ...

for 448 Q.

Atomic King No. 2

mine, fault In Cutler 

formation, mineralized.

collected 60 feet away.

Moenkopi along fault.

foot from altered zone 

(No. 530-4).

Red

X

X

X

Green 

or gray

X

X

X

X

X

Clay-size minerals

vite, quartz, calcite, 

dolomite. 

Hydrous mica, muscovite, quartz. 

Hydrous mica, muscovite, quartz, calcite.

vite, quartz, calcite, 

hematite. 

Mixed layer hydrous

mica and montmorillonite.

Mixed layer hydrous

mica and montmorillonite. 

Hydrous mica, kaolinito

quartz.

quartz.

ALUNITIZATION AT THE 0YLEB MINE, CAPITOL BEEF 

NATIONAL MONUMENT

A sequence of four samples of mudstone of the Moenkopi formation collected at the Oyler mine in Capitol 

Beef National Monument, Utah, illustrate the effect of 

sulf ate reaction on the clay and carbonate minerals in 

the mudstone (table 5)^ Red, barren Moenkopi (No. 

235) occurring 600 feet west of the mine, contains hydrous mica, muscovite, kaolinite, quartz, calcite, and 

hematite. The same stratigraphic zone at the entrance 

to the mine is bleached of iron oxide but contains gypsum. A mineralized seam in the mine contains alunite 

and metatorbernite (fig. 1, diffractogram 225). The 

metatorbernite peak is marked "Me."

It is inferred from this sequence that sulfate-bearing 

solutions, probably acidic, at the Oyler mine locality 

reacted with the ferric oxide in the red mudstone of the 

Moenkopi formation to bleach the pigment. Jarosite 

has been found at the mine and it is probable that the 

iron was moved, and partially removed, as iron sulfate. The sulf ate reaction converted the calcite (and

dolomite?) to gypsum. Further reaction of sulf ate 

with aluminous clay minerals resulted in the development of alunite.

TABLE 5. Samples collected at the Oyler mine, Capitol Reef 

National Monument, Utah

Sample No.

225......... 

227............

229... .........

235.... ........

Description

mudstone, Oyler mine entrance.

tains metatorbernite, Oyler mine 

entrance.

minerals, Oyler mine entrance.

Oyler mine entrance. Essentially 

equivalent stratigraphically to 

above samples, as nearly as can 

be observed.

Minerals present

quartz, alunite, metatorbernite.

quartz.

quartz, dolomite, gypsum.

kaolinite, quartz, calcite, 

hematite.

The presence of metatorbernite in the bleached portion of the Moenkopi and in the alunite-rich seams may 

be interpreted as follows: (1) that the sulf ate solutions 

also carried in the metatorbernite, or alternatively, that 

(2) metatorbernite-bearing solutions followed the same 

avenues previously traversed by sulfate solutions. 

Spatial association of the minerals is permissive toward 

the first alternative, but the writer has not found compelling evidence that alunite and metatorbernite were 

genetically associated. It is difficult to find unequivocal 

evidence of effects from the solutions which carried the 

ore minerals apart from the ore minerals themselves.

LITERATURE CITED

Goddard, E. N. (chin.), and others, 1948, Rock-color chart:

Washington, D. C., National Research Council. (Republished by Geol. Soc. America, 1951.) 

Grim, R. E., 1953, Clay mineralogy: New York, McGraw-Hill

Book Co. 

Weaver, C. E., 1953, A classification of the 2:1 clay minerals:

Am. Mineralogist, v. 38, p. 698-706. 

Weeks, A. D., 1953, Mineralogic study of some Jurassic and

Cretaceous claystones and siltstones from western Colorado

and eastern Utah. U. S. Geol. Survey Trace Elements Inv.

Kept. 285, U. S. Atomic Energy Comrn., Tech. Inf. Service,

Oak Ridge, Tenn. 

Weir, D. B., 1952, Geologic guides to prospecting for carnotite

deposits on the Colorado Plateau: U. S. Geol. Survey Bull.

988-B.

Part 10. CHEMICAL STUDY OF THE MINERALIZED CLAYS

By MARGARET D. FOSTER

CONTENTS

Page 

Abstract.._ __---___--____---__---____--_-------_--_ 121

Introduction _-___________-----__-___-____--.--_--__ 122

Composition and character of the vanadiferous clays..__ 122 

Chemical analyses._ .__-__-____________--_-_-_-_ 122

Comparative composition of mineralized and unmineralized clays.._-___----_______-_____-__-___-_ 124

Minor elements_-_-.-_-_-_-____--___------_--_ 125

Stages of oxidation._____-__--_-__---__-__---__-_ 125

Page 

Composition'and character of the vandiferous^clays Con.

X-ray diffraction studieS-_____-__-----_-__-_-__-_ 126

Differential-solution analysis______-__---_-_-__-__--_- 126

Octahedral-tetrahedral ion differentiation __________ 126

Formulas and their interpretation--____-____ ________ 127

Discussion and conclusions.__________________________ 131

-_____---___----__---_____------_-_-__- 132

ILLUSTRATIONS

Page 

FIGURE 33. Relation between V2 04 and (SiOa plus A1.08) in mineralized and unmineralized clays.______ ___-_-__.____ 125

34. Differential solution analysis of AW-144-52___________________________________________________________ 127

TABLES

Page

TABLE 1. Unadjusted chemical analyses of vanadium clays---_------------------__----------------_---------_--_---_ 122

2. Adjusted chemical analyses of vanadium clays---________--_____-_----_____-___---_-_-_-____---_-_---_____ 124

3. Quantitative spectrographic analyses of vanadium clays for minor elements____________________________________ 125

4. Calculation of structural formula of G-29M-53___--_____-_____-__--___________.__-_-_____-__-_--___-_-__ 128

5. Structural formulas for vanadium clays..________________________________________________________________ 129

6. Formulas for Colorado roscoelites___-----_-_---_-----_----------------------_-----_-----_---------__---_ 130

7. V+8 substituted for V+« in formulas for vanadium clays ______---___--_-_-_-_-_-----__-_-__-__-__---_-_-___ 131

ABSTRACT

In the vanadium-bearing sandstones on the Colorado Plateau 

the principal vanadium mineral is a clay, which coats and replaces sand grains and partly or completely fills the pore spaces 

of the sandstone and imparts a dark color to it, the depth of 

color being deeper the greater the vanadium content.

Of the eight samples used in studying the composition and 

character of the mineralized clays and their relation to the unmineralized clays, three were mineralized clay pellets, two 

pairs were clay fractions from adjacent mineralized and unmineralized (dark and light) zones in sandstone, and one was 

an unmineralized clay fraction from a light-colored zone in 

sandstone. All were from the Salt Wash member of the Morrison formation.

Chemical analyses show that the samples are similar in composition except for vanadium content, and that increase in 

vanadium content is accompanied by decrease in alumina and

silica content, the content of the other constituents remaining 

relatively constant throughout. In composition the samples are 

similar to hydrous micas, but X-ray diffraction studies show 

that they are mixtures principally of mica and interlayered 

mica-montmorillonite, with usually a small amount of chlorite 

and quartz. Vanadium is present in all the phases making up 

the clays, except quartz, as is shown by differential solution 

studies.

The samples differ in degree of oxidation. In the least oxidized sample some vanadium is present in the trivalent state, 

and all the iron is present as divalent iron; in the most highly 

oxidized sample there is some free V2O5 and all the iron is trivalent. In the other six samples all vanadium is present as 

V2O4 and the iron is present in different proportions as ferrous 

and ferric.

Structural formulas derived from the analyses show that 

seven of the samples form a suite in which the sum of the octa121
122 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

hedral positions occupied by Al and V+4 and the sum of the 

positions occupied by Fe and Mg are remarkably constant. Increase in the number of positions occupied by V is accompanied by decrease in Al positions, the number of positions occupied by Fe and Mg remaining constant throughout. As substitution of V+4 for A1+3 decreases the negative charge on the 

octahedral layer, increase in V+4 content and consequent decrease in octahedral charge is accompanied by increase in tetra-" 

liedral charge; the total charge and the potassium content remain fairly constant.

The chemical and mineralogical similarity of the mineralized 

And unmineralized clays suggest that the unmineralized clays 

became mineralized simply by the replacement of some of the 

octahedral aluminum by quadrivalent vanadium, with the necessary charge adjustments in the tetrahedral layer. However, 

other deposits are known where the vanadium clay was deposited by the mineralizing solutions.

INTRODUCTION

Deposits of vanadium-bearing sandstone, widely 

distributed on the, Colorado Plateau,, have been the 

principal domestic source of vanadium and uranium. 

As described by Fischer (p. 377, 1942), the ore occurs 

mainly as an impregnation of the sandstone, coating 

and replacing the sand grains and partly or completely 

filling the pore spaces of the sandstone. The principal.. 

yanadium mineral is micaceous and was thought to be 

roscoelite until X-ray studies by S. B. Hendricks (as

 cited by Fischer, 1942) showed that in some formations as in the Morrison of Jurassic age the principal vanadium mineral is a clay mineral of the hy-

 drous mica group. The mineral imparts a dark color 

to the sandstone, the depth of color being greater theliigher the vanadium content. Kichly mineralized 

clay pellets, which occur in some places, are black and 

brittle.

This study of the vanadium-bearing clays was undertaken to determine whether vanadium is present as

a superficial impregnation of the clay or whether it is 

in the clay structure, and if so, its position and valence.

CHEMICAL ANALYSES

Of the suite of eight samples used in this study, 

three (AW-22-52, AW-144-52, and AW-146-52) are 

clay pellets collected by A. D. Weeks, and five are 

clays separated from sandstone collected by Robert M. 

.Garrels. Samples G-43M-53 and G-43UM-53, and 

G-29M-53 and G-29UM-53, are paired samples representing mineralized and relatively unmineralized 

clay from dark and light colored zones in the same 

specimen. Sample G-27UM-53 is a relatively unmineralized clay from a light colored zone in sandstone. 

The suite of samples studied, therefore, includes five 

mineralized and three relatively unmineralized samples. The three latter were included in order to study 

the differences in composition brought about in the 

clay by mineralization. For this purpose the two 

pairs of samples, G-43UM-53 and G-43M-53, and 

G-29UM-53 and G-29M-53, are of particular interest. 

All samples are from the Salt Wash member of the 

Morrison formation of Jurassic age. Chemical analyses of these samples, together with their locality, are 

given in table 1. The chemical analyses were made 

by the writer according to the usual methods of rock 

analysis as described by Hillebrand and Lundell (1929) 

except for sodium and potassium, which were determined with the flame photometer by Paul Elmore, of 

the U. S. Geological Survey, and vanadium. In this 

study the state or states of valence in which vanadium 

is present was of especial interest. For this determination, the following procedure was used:

TABLE 1. Unadjusted chemical analyses of vanadium clays 

[M. D. Foster, analyst. KaO and NajO determined by Paul Elmore by flame photometer]

SiOj. 

AlaOi. 

FeO

Va05 . ......... 

V,04~~ -- 

 ViOi... ..... ......... ....... ..... ....... ...... ..... ....

TiOa .... . ....... ...

 CaO . 

MgO ~ ... ............ : .....

Na2 0.. . - 

KjO.-, 

MnO ~ 

H2 0. 

Total............ 

G-27UM-53

52.78

20.48

2.06

2.32

.00

.75

.00

.90

.62

4.61

.31

6.30

.03

8.43

99. 59

G-43UM-53

52.22

20.96

1.19

2.56

.00

1.02

.00

.92

.48

4. 00

.23

6.18

.02

9.86

99.64

G-29UM-53

53.36

20.44

1.90

1.85

.00

1.16

.00

.82

.64

4.47

.25

5.94

.02

8.92

 99. 77

O-29M-53

50. 24

17.38

.00

3.58

.00

8.38

.00

.46

.48

4.43

.27

5.86

9.12

100. 20

G-43M-53

47.32

19.36

.00

3.49

.00

7.60

1.34

.52

.62

5.01

.23

5.40

.02

9.14

100.05

AW-146-52

48.10

17.62

2.61

1.03

.00

12.36

.00

.52

.74

4.09

.30

: 4. 96

.01

7.92

100.26

AW-22-52

45.46

16.02

2.93

2.00

.00

16.07

.00

.64

.62

2.13

.24

6.58

.02

8.00

100.71

AW-144-52

43.68

15. 32

7.70

.00

2.39

10.55

.00

.32

1.60

3.75

.30

4.67

.05

9.96

100. 29

 G-27UM-53. Mineral Joe Mine, Jo Dandy group, Paradox Valley, Montrose Co., 

'Colorado.

G-29UM-53, G-29M-53. Mineral Joe Mine, Jo Dandy group, Paradox Valley, 

(Montrose Co:, Colorado. . . . ~:G-43UM-53, G-43M-53. Virgin Mine, Long Park area, Montrose Co., Colorado.

AW-146-52. Cougar Mine, Slick Rock, San Miguel Co., Colorado. 

AW-144-52. Sunnyside Mine, east side of Carrizo Mountains, San Juan Co., New 

Mexico. 

. AW-22-52. Little Peter Claim, La Sal Creek, San Juan Co., Utah.
CHEMICAL STUDY OF THE MINERALIZED CLAYS 123

Example 1:

15 ml of 1-2 H2SO4 was added to 0.50 g of the sample 

in a 50-ml Erlenmeyer flask, the air in the flask was 

then displaced with C02 and the flask was stoppered. 

This mixture was digested on a steam bath (at about 

95° C) for a week or ten days that is, until the clay 

appeared to have been decomposed and all the Fe and 

V extracted. After transferring the mixture to a 500- 

ml Erlenmeyer flask, it was diluted to 250 ml with distilled water, heated to 80° C, and titrated to the first 

permanent pink with 0.05 KMnO4 solution. The 

mixture was then filtered to remove the undissolved 

residue (quartz and silica released from the clay on 

decomposition). A second 500-ml Erlenmeyer flask 

containing the filtrate was placed on an electric radiator 

and SO 2 gas was passed through the solution for 10 minutes. Still keeping the solution hot, a rapid stream 

of CO2 was passed through the solution until it was 

free of S02 , as tested by bubbling the exit gases from 

the flask through a hot, very dilute solution of KMnO4 . 

Lack of fading of the permanganate indicates the absence of SO2 . When the solution was free of S02 and 

had cooled to about 80° C it was again titrated to a 

pink end-point with KMnO4. The amount of iron in 

solution was then determined. From the relationships 

between the first and second titrations and the KMnO4 

equivalent of the iron present, the amounts of V2O3, 

V2O4 , V2 0B , FeO, and Fe2O3 can be calculated as 

follows:

1. If the second titration is the same as the first titration, all the vanadium was originally present in 

the solution as V(IV) and all the iron as Fe(II). 

The KMn04 equivalent of the iron present is 

subtracted from the first titration (or second titration, as they are the same) to obtain the KMnO4 

equivalent of the V(IV) present.

Example:

KMnO< usedBlank........

1st id Iron

titration titration titrction

(ml) (ml) (ml)

13.10

.10

13.10

.10

6.35 

.10

6. 25

Reduced by SOa -- __ _ . __ 13.00 

Originally reduced......................... 13. 00 >13.00

FoO ........ ...... . ......... 6.25<

Originally oxidized..... ________ ... ____ .00 ... - __ 

Vj04.-~- - ----- 6.75 .. .........

NOTE. No VaOs or FejOs because 1st titration equals 2d titration.

2. If the 2d titration is greater than the 1st titration 

some or all of the Fe and V were present in the 

original solution as Fe (III) and V (V) depending 

on the relations between the 1st, 2d, and iron 

titrations.

ist ed

titration titration

(ml) (ml)

Iron

titration

(ml)

KMn04Used . . . 6.20 12.50 3.45

Blank_.______._________....__ .10 .10 .10

Reduced by SOa... .......... ............ ..... 12.40 .........

Originally reduced (=VjOO~ ----- -- 6.10 >6.10

Originally oxidized (=Fea03+VaO6)--.~ _- ... 6.30 ..... . 

Total iron (=FeaOs).________________ --__-- 3.35< 3.35

VjOj-. -. .- .................. ..... 2.95 .........

NOTE. No FeO or VjOs because VaOs is present.

Example 2:

1st 8d Iron

titration titration titration

(ml) (ml) (ml)

KMn04Used ............... . ._.. 8.20 9.85 2.35

Blank...................... ............ .10 .10 .10

Reduced by SOa___________________ ____ 9.75 .........

Originally reduced____.___..______ 8.10 >8.10

Total iron....._____..____________... __.... ........ 2.25

Originally oxidized (=Fea03).____.__....- .._... 1.65 >1.65

FeO. - ..... ... . .60< .60

VaOi---_-__. _ 7.50. 

NOTE. No VjOs because FeO is present; no VjOs because 2d titration is 

larger than 1st titration.

Example 3 :

1st 8d Iron

titration titration titration

(ml) (ml) (ml)

KMn04 used .............. . ...... 0.10 8.30 3.80

Blank.___.._..........__.___........ .10 .10 .10

Originally oxidized....... ..._...-____ __.... 8.20 ... _

Originally reduced__________________ .00 >.00

FeaOs+VaOs .... ............. ........ 8.20 ..... .

Total iron (=Fea03)---___-_____-__._ ____ 3. 70< 3.70

VaOj.._ _ ........ 4.50 .........

NOTE. No FeO, Va04, or VaOs because 1st titration is zero.

3. If the 2d titration is less than the 1st titration some 

or all of the V was originally present as V (III); 

if only part of the Vwas present as V (III), the 

rest was present as V (IV). Either way, all the 

Fe was present originally as Fe (II). In the 1st 

titration, therefore, some or all of the V had to be 

oxidized from V (III) to V (IV) to V (V), resulting 

in a higher 1st than 2d titration.

Example:

1st Sd Iron

tilration titration tilration

(ml) (ml) (ml)

KMnO< usedBlank........

17.70

.10

15.90

.10

4.40 

.10

Originally reduced__________________ 17.60 ........

Reduced by SOj ..___----___...____ 15.80< 15.80

Va03 . 1.80 >1.80

Va04+FeO._......__....._....____..... ..._.. 14.00 .

Total iron (=FeO).._._.__...___......_ ....._ 4. 30<- 4.30

9.70

NOTE. No VS 0» or FeaOs because 1st titration exceeds 2d titration.

X-ray powder patterns by F. A. Hildebrand, of the 

U. S. Geological Survey, showed that all the samples 

contained quartz. It was also possible that part of the

468652 59 9
124 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

A12O3 , Fe2O3 , V2O4, and V2O5 found on analysis was 

not in the clay structure. Consequently to determine 

as nearly as possible the composition of the clay itself, 

it was necessary, in addition to the usual chemical 

analysis, to make use of several special tests. The 

amount of quartz present was determined by digesting 

the residue from the vanadium-iron acid extraction 

with 0.5N NaOH, which dissolves silica freshly released 

by the decomposition of the clay but leaves the quartz 

present untouched. Soluble silica and alumina were 

determined by digestion with NaOH, as described by 

Foster (1953, p. 151), using a separate portion of each 

sample. V2O4 , V2O5 , FeO, and Fe2O3 not in the clay 

structure were determined by digesting another portion 

of each sample in 1-2 H2SO4 (1 part of H2SO4 to 2 

parts of distilled water) for 1 hour at room temperature, filtering, and determining the amounts of these 

constituents that had gone into solution in that time. 

Preliminary studies had shown that the clay materials 

making up these samples are very stable under acid 

treatment and that in a 1-hour digestion period there is 

little or no attack on the clay structure, whereas the 

vanadium and iron compounds present but not in the 

clay structure are dissolved. This treatment also effects solution of any "free" alumina present, providing 

a check on "free" alumina determined by digestion 

with NaOH.

All the samples were found to contain some quartz, 

"free" alumina, "free" iron oxide, and vanadium oxide,

either V2O4 or V2O5 , that apparently did not belong in 

the clay structure. However, it is of particular interest 

in this study that the amount of "free" vanadium oxide 

present, especially in the mineralized clays, was small in 

comparison with the amount that seemed to belong in 

the clay structure.

Adjusted analyses of the clays, after making allowances for quartz, and for aluminum, vanadium, and 

iron compounds not in the clay structure, are shown in 

table 2. TiO2 was also deducted in adjusting the 

analyses as X-ray studies indicated TiO2 to be present 

as anatase.

It should be pointed out that the procedure used for 

determining the valence states of vanadium and iron 

apply rigorously only to the valence states of the ions 

present in solution, and not in the original clay minerals. At the low pH used, vanadium (V) will be reduced to vanadium (IV) by any ferrous iron going into 

solution, and the iron thus oxidizing to ferric. However, inspection of table 2 indicates that the analyses 

must approximate closely the composition of the clays. 

Sample G-27UM-53 contains very little vanadium, but 

contains a significant amount of ferric iron. Thus ferric iron must be present in the clay. Similarly, samples 

G-29M-53 and G-43M-53 contain no ferric iron but 

abundant vanadium (IV); thus neither ferric iron nor 

vanadium (V) were present in the clay and the analysis 

must be correct as stated. In the other samples, no 

large deviations from the reported values seem likely.

TABLE 2. Adjusted chemical analyses of vanadium clays 

[M. D. Foster, analyst. KjO and NajO determined by Paul Elmore]

SlOi ........ ........ ........ ...............

AljOn... .... _ .-.- .-.- ..- .- 

FejO». . . . ...

FeO.-.........-.- .................................

Vl04 ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...

ViO«.......... .........................................

CaO

MgO....... ................ _ ........................

NajO .... ...........-.................. ..........

K»O.. ............... .......... ....... ..............

HiO.......... ...... ............. ..-... ..........

Total.. _______ .. __ .... . .........

G-27UM-53

53.26

20.74

2.12

1.76

.51

.00

.65

4.82

.32

6.59

8.82

99.59

Q-43UM-53

52.36

21.40

1.23

2.04

1.06

.00

.50

4.15

.24

6.42

10.24

99.64

G-29UM-53

52.46

21.15

1.95

1.95

.99

.00

.67

4.71

.26

6.25

9.39

99.78

G-29M-53

49.12

17.62

.00

3.54

8.52

.00

.50

4.66

.28

6.16

9.59

99.99

G-43M-53

46.94

19.84

.00

3.23

7.36

1.40

.67

5.23

.24

5.63

9.54

100. 08

AW-146-52

47.39

18.51

2.41

.91

11.73

.00

.79

4.38

.32

5.32

8.49

100.25

AW-22-52

44.87

16.84

2.65

1.10

16.03

.00

.68

2.33

.27

7.19

8.74

100. 70

AW-144-52

45.86

15.40

5.80

.00

10. 15

.00

1.36

4.35

.35

5.42

11.56

100. 25

COMPARATIVE COMPOSITION OF MINERALIZED AND 

UNMINERALIZED CLAYS

The principal differences in the chemical composition 

of the clays studied are in their content of SiO2 , A12O3 , 

and V2O4 . Their content of all other constituents is remarkably uniform. The three (relatively) unmineralized clays (G-27UM-53, G-29UM-53, and G-43UM5.3) have essentially the same content of SiO2 (52.37 to 

53.26 percent) and of A12O3 (20.74 to 21.41 percent). 

In the mineralized clays greater V2O4 content is accompanied by lower SiO2 and A12O3 content, as shown in 

figure 33. Comparison of the adjusted analyses for 

G-29UM-53 and G-29M-53 (table 2), which represent 

light and dark layers of the same specimen, shows that 

an increase of 7.53 percent in V2O4 content is accompanied by a decrease of 3.31 percent in SiO2 content and 

3.54 percent in A12O3 content; the content of all other 

constituents remains essentially the same. In terms of 

molecular ratios this amounts to a loss of 0.43 in SiO2 

plus A12O3 and a gain of 0.36 in V2O4. The fact that
CHEMICAL STUDY OF THE MINEEALIZED CLAYS 125

20.0 r

16.0

12.0

8.0

4.0

0.0

X Refers to samples in Table 1

O Magnetic black sand separated from G-43M-53

62.0 66.0 70.0 74.0

Percent (SiOz+AI 2 03 ).

FIGURE 83. Relation between VaO« and (SiOu plus A1208 ) In mineralized 

and unminerallzed clays.

increase in V2O4 content is accompanied by a proportionate decrease in the content of these two constituents 

only, without altering the content of any of the other 

constituents, suggests that V2O4 has not simply impregnated the clay as such, but that it is actually a part of 

the clay structure; thus V44 affects both Si and Al but 

not other cations in the structure.

MINOR ELEMENTS

Quantitative spectrographic analyses for minor elements in these clays, by K. J. Murata, of the U. S. 

Geological Survey, are given in table 3. The most important of the minor elements are uranium and lead. 

Two of the unmineralized samples, G-27UM-53 and 

G-29UM-53, and one mineralized sample, AW-146-52, 

contained no uranium. All the other samples contained from 0.1 to 0.2 percent of uranium except for 

AW-144r-52, which contained 0.6 percent. All of the 

samples contained lead, the amount present ranging 

from 0.06 to 0.3 percent, but there was no correlation 

between the amount of lead and the amount of uranium 

present nor was there any correlation between the 

amount of vanadium and the amount of uranium or 

lead present. Other minor elements are present in the 

low hundredths or thousandths of a percent except for 

0.1 percent of Ba in G-43UM-53 and AW-144-52, and 

0.1 percent of Zr in the latter sample.

TABLE 3. Quantitative spectrographic analyses of vanadium clays for minor elements 

[K. J. Murata, analyst. Looked for but not found: Au, Pd, Ft, W, Ge, As, Sb, Bi, Cd, Tl, In, Th, Nb, P]

Ou.... .. _ ._

AK

Mo... _. . -- . ._ . .

Sn.... ... .... .

Pb..... . .. . ._ _. 

Zn . . . _ . .

Co.... . _ .. ._. _

Nl . . . 

Or . . ... . . ..

So.........-........... ... ..........................

Y. ... .... .-..._.-_-_._.. _-........-_._._._ 

La........................ ..... ...... ..................

ZT.. ...................................................

U ................... . .-... . .... 

Be.............. . ...................... .....

BT.. ...................................................

Ba...... . ..-....................... . ..

B ... ........ ... 

O-27UM-53

0.003

finr>4

0

0

.06

0

.002

.003

.005

.004

0

0

.03

0

.0005

.02

.009

.009

G-43UM-53

0.002

0

0

0

.07

0

.005

.002

.01

.002

0

.01

.02

.1

.0004

.03

.1

.008

Q-29UM-53

0.005

0

0

0

.1

0

.004

.003

.007

.003

0

0

.03

0

.0005

.04

.02

.007

G-29M-53

0.005

0

0

0

.08

0

.008

.005

.004

.001

.009

0

.02

.1

.0005

.02

.01

.005

Q-43M-53

0.003

.0004

0

0

.08

0

.005

.004

.007

.001

.008

0

.01

.2

.0004

.01

.01

.004

AW-144-52

0.009

0

.003

0

.2

0

.002

.002

.005

.001

0

0

.01

.6

.0003

.1

.1

.002

AW-146-52

0.2

.0005

0

0

.06

0

.001

.003

.01

.002

.008

0

.01

0

.0004

.01

.02

.003

AW-22-52

0.06

.004

0

0

.3

.04

.01

.005

.006

.001

0

0

.009

.2

.0005

.05

.07

. . .004

STAGES OF OXIDATION

At the time of analysis all vanadium in the structure 

of the clays was present as V2O4 , except for 1.40 percent of V2O3 in G-43M-52. All the samples had had 

opportunity for oxidation, as they had been collected 

from mine walls, and had been exposed to the air. In 

many mines the assemblage of minerals indicates that 

oxidation had taken place before the mine was opened. 

If all vanadium had been originally present as V*3, all 

iron must have been present as Fe+2. The first step in

the oxidation of such a mixture is oxidation of V+8 to 

V+4. The V+3-V+4-Fe+2 relationship of G-43M-52 and 

of G-29M-52 indicates that, if all the vanadium had 

once been present as V+s, the former is now near the 

end of this stage of oxidation and the latter has completed it but has not yet progressed to the second stage 

of oxidation of Fe+2 to Fe+3 . All the other samples, 

except for AW-144-52, are in this second stage of oxidation. AW-22-52, in which two-thirds of the iron is 

present as Fe+2, has progressed least in this stage and
126 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

AW-146-52, in which two-thirds of the iron is present 

as Fe+s, has progressed farthest. The Fe+2-Fe+3 relationship of the three (relatively) unmineralized samples falls between these two samples in degree of 

oxidation. In AW-144-52 all the iron is present as 

Fe+3. The final stage in the oxidation process is oxidation of V+4 to V+5. The presence of 2.39 percent of 

free V2O5 in AW-144-52 (table 1) may indicate that 

some of the vanadium originally in this clay has been 

oxidized to the pentavalent stage and has been ejected 

from the structure because V+5 does not take octahedral 

coordination.

X-RAY DIFFRACTION STUDIES

X-ray diffraction studies of the suite of vanadium 

clays under consideration were made by John Hathaway, of the U. S. Geological Survey, and his methods 

and data are presented in Part 11. Part of his data 

are summarized here.

All the samples gave diffraction patterns showing 

lines in the 10A region that broaden and shift on treatment with ethylene glycol and shift again on heating 

to 500° C. This is interpreted as an indication of the 

presence of montmorillonitic layers randomly interstratified with mica layers.

All the samples except AW-22-52 contain chlorite in 

various amounts with some mixed-layered chloritemontmorillonite exhibited by sample G-29UM-53. 

The fine-grained material in these samples contains 

less chlorite than the coarser material.

The composition of each sample is tabulated below 

with quantitative estimates given as parts in ten. Inasmuch as these estimates are derived from the intensities of the diffracted lines and many factors in addition 

to quantity of a mineral affect diffraction intensity, 

these estimates are not intended to give more than a 

general indication of the relative amounts of the various minerals present.

l/'Mica

Field No.

AW-146-52........

AW-144-52........

AW-22-52.........

G-27UM-53.. ._

G-29UM-53.......

G-29M-53.. ....

G-43UM-53.......

G-43M-53... ...

Minerals present

Mica and mixed-layered mica-montmorillonite ..

Chlorite .........................................

Mica and mixed-layered mica-montmorillonite...

Mica and mixed-layered mica-montmorillonite ..

Mica and mixed-layered mica-montmorillonite.-

Mica and mixed-layered mica-montmorillonite- .

Chlorite ________________________

Chlorite _________ . ____________

Quantitative 

estimates 

(parts in 10)

9

Tr.

Tr.

8

1

Tr.

9

Tr.

9

<1

8

1

<1

8

2

Tr.

9

Tr.

6

3

AW-22-52

G-43M-53 

G-43UM-53

Increasing mixed-layering

G-29M-53 

G-29UM-53

G-27UM-53

AW-146-52

AW-144-52

2. Mica

AW-144-52 

AW-22-52

G-13UM-53

G-27UM-53

AW-146-52

Increasing chlorite content

G-29UM-53 

G-29M-53

G-43M-53

Chlorite decomposition temperature (loss of 14A lire) : 

Below 500° C

G-29UM-53 fine 

G-29M-53 fine 

G-43UM-53 coarse 

G-43UM-53 fine 

G-43M-53 fine

Above 500° C 

G-27UM-53 coarse 

G-27UM-53 One 

G-29UM-53 coarse 

G-29M-53 coarse

G-43M-53 coarse 

AW-146-52 (whole sample)

All of the samples except AW-22-52 showed approximately the same intensity relationships among the 001 

reflections with a 002 reflection of greater intensity 

than that exhibited by roscoelite. This suggests a lesser 

degree of substitution in these samples of V for Al than 

that encountered in roscoelite. Sample AW-22-52 on 

the other hand shows a very weak 002 reflection suggesting that this material approaches roscoelite in octahedral composition.

DIFFERENTIAL-SOLUTION ANALYSIS

NOTE. The above samples might be grouped as follows:

In the foregoing discussion it has been assumed that 

V+4 proxies for octahedral aluminum in the mineralized 

clays. In order to determine definitely the position of 

vanadium in these clays a modification of Brindley's 

(1951) procedure for determining tetrahedral and octahedral aluminum in silicates was used. Separate 0.50 

gram samples of a given clay were digested in 1-2 

H2SO4 on a magnetic stirrer for different periods of 

time at room temperature; the residue was then filtered 

off and the solution was analyzed for A12O3 , MgO, vanadium oxides, and iron oxides. For each specimen a few 

widely separated time runs were first made; additional 

runs were then made to establish critical points in the 

curve more definitely. The amount (in percent) of 

A12O3 , V2O4 , Fe2O3 , and MgO extracted from AW-144- 

52 plotted against time is shown in figure 34. The curve 

for V2O4 has the same shape as those for Fe2O3 and 

MgO, known to be octahedral constituents. Like the 

curves for these constituents, the V2O4 curve flattens 

after 20 hours of acid treatment, when extraction of
CHEMICAL STUDY OF THE MINERALIZED CLAYS 127

Total

25 30 35 40 45 50 55

Length of time of treatment-hours 

FIGURE 34. Differential-solution analysis of AW-144-52.

65 75 80 82

octahedral ions is essentially complete. The similarity 

between the Fe2O3 , MgO, and V2O4 curves suggests very 

strongly that V2O4 is, like Fe2 0s and MgO, an octahedral constituent.

For as long as 20 hours of treatment the A12O3 curve 

has the same shape as the other curves, but instead of 

flattening out at this point, it swings upward. Complete extraction of A12O3 required 62 more hours of 

treatment. The shape of the curve suggests that octahedral A12O3 is extracted first, with the other octahedral 

constituents, and that only when extraction of octahedral constituents is complete, or nearly so, does extraction of tetrahedral constituents begin. This stepwise extraction permits differentiation of octahedral 

and tetrahedral ions, particularly of A12O3 , as well as 

that of "free" constituents such as Fe2O3 and A12O3 

that are not in the clay structure and that dissolve very 

quickly compared with ions that are in the clay or mica 

structure.

AW-144-52 broke down much more rapidly on acid 

treatment than any of the other clays in this study. 

That it is also the most highly oxidized and that its 

formula is deficient in octahedral positions occupied 

(see table 4) all suggest that the structure is under considerable strain and may be to some extent disorganized.

FORMULAS AND THEIR INTERPRETATION

As shown by Foster (1955) mixtures of dioctahedral 

micas and montmorillonites are similar in composition 

to materials that have been called hydrous micas and 

illites and rational formulas may be derived from analyses. This is to be expected, as dioctahedral micas, dioctahedral hydrous micas, and montmorillonites have

the same 2:1 layer structure, in which only two positions are occupied in the octahedral layer and in which 

the charge induced on the structure by the proxying 

of lower valence cations for higher valence cations is 

balanced by large cations, such as K, Ca, Mg, or Na, located between the composite layers. Structural formulas may, therefore, be derived for materials like these 

vanadium clays that are composed predominantly of interlayered mica and montmorillonite, as if they were 

hydrous micas.

The formulas for the clays studied were derived by 

the method devised by Marshall (1949, p. 58) and modified by Foster (1951, p. 728). The calculations involved 

in deriving a formula for G-29M-53 are shown in detail 

in table 4. The gram-equivalents of cationic constituents in the structure are obtained by dividing the 

percent of each constituent present by a factor obtained 

by dividing the molecular weight of that constituent by 

the number of cationic valencies in its formula. Thus 

for SiO2 the factor to be used is the molecular weight of 

SiO2 , 60.06, divided by 4, which is 15.015; for A12O3 it 

is 101.96, divided by 6, or 16.993.

In the idealized unit of 2:1 layer structures there are 

20 oxygen ions and 4 hydroxyl ions, which together 

carry 44 anionic or negative charges, and which are 

neutralized by the same number of cationic or positive 

charges. In order to convert the gram-equivalents of 

the cationic constituents to cationic valencies present in 

the unit cell, they are, therefore, divided by a factor obtained by dividing the sum of the gram-equivalents by 

44. The resulting value is divided by the valence of 

each cation to obtain the number of cations of that constituent in the unit cell.
128 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 4. Calculation of structural formula of G-S9M-5S

SiO,.. .........................................................

AlaOs . ............... ............... ...... ...

FeO....-. ......... .....-....... . 

Vs04 ........... ...... ..-..-.-. - . .-. ..

MgO... ............ .................-.-.. ...... ........ 

MgO. .........................................................

CaO ....... ................. .... ................ 

NtuO.. . -..-..-....-... --. 

KtO. ..........................................................

Percent

49.12

17.62

3.54

8.52

4. 16 

.50

.50 

.28

6.16

Calculation

* (60. 06*4) =

* (101. 96*6) =

-5- (71. 85*2) =

* (165. 90*8) =

* (40. 32*2) = 

* (40. 32*2) =

* (56. 08*2) = 

* (62. 00*2) =

* (94. 20*2) =

Gram 

equivalent 

of cationic 

constituents

3.271

1.037

.099

.411

.iUo 

.025

.018 

.009

.131

5.207

Calculation

i *0. 1183=

* .1183=

-i. 1 1 JW 

* .1183=

* .1183- 

* .1183=

* .1183- 

* .1183=

* .1183=

Cationic 

value per 

total of 44

27. 650

8.766

QQ7

3.474

1.741 

.211

.152 

.076

1.107

44.014

Calculation

*4=

*3-

 O 

*4=

*2= 

*2=

*2- 

*1 =

*1 =

Cations per unit 

cell

6.912

1.088 

8.000 

» 2. 922 1. 834

4.1ft

.869

.870 

3.991 

.106

.076 

.076

1.107

1.365

Charge

} -1.088

 . 476

-1.564

i 5.207+44=0. 1183. 

» 2.922=1.088+1.834.

Note : Structural formula (half-cell) :

-.24 -.54

(Si3.«Al.M)010 (OH) 2X.78

2.01

The aluminum cations are divided between the 

tetrahedral and octahedral layers, allotting enough to 

the tetrahedral layer to bring, with silicon, the total 

cations in that layer to 8.00, and assigning the remainder to the octahedral group. The sum of the cations in the octahedral group should be close to the 

theoretical 4.00. A total of less than 4.00 may indicate 

(1) excess silica, (2) unoccupied octahedral positions, 

or (3) a faulty analysis. A total in excess of 4.00 commonly indicates that some of the magnesium is present 

as an interlayer exchangeable cation (Foster, 1951). 

Sufficient magnesium is then withdrawn from the octahedral group to bring the sum of the octahedral ions to 

4.00±.04, and is added to the interlayer cations.

The charge on the tetrahedral group is equivalent to 

the aluminum assigned to that group because aluminum, 

being trivalent, carries one less charge than an equivalent amount of silicon, which is quadrivalent, and leaves 

unsatisfied anionic charges equivalent to the amount of 

aluminum added. The charge on the octahedral group 

is equivalent to the sum of the cations in that group 

multiplied by their respective valencies subtracted from 

12.00, the number of octahedral anionic valencies. The 

sum of the tetrahedral and octahedral charges represents the total charge on the structural layers and should 

agree closely with the sum of the external cations. In 

the vanadium clays studied the sum of the external 

cations was usually somewhat higher than the total 

charge, probably owing to the small amount of chlorite 

in most of them.

Formulas for 2:1. layer minerals are usually stated 

in terms of the half -cell ; the values for ions per unit 

cell of the constituents in each group are therefore divided by 2 to obtain the amounts of each ion to be used 

in writing the formula.

Structural formulas for the vanadium clays studied, 

calculated as described above from the adjusted analyses 

(table 2) are given in table 5. Seven of the eight clays 

form a suite in which the sum of the positions occupied 

by Al and V, and the number of positions occupied by 

Fe and Mg is remarkably constant ranging from 

1.37 to 1.43 positions for Al plus V, from 0.18 to 0.21 

for Fe and from 0.39 to 0.44 for Mg. In table 5 the 

formulas for these seven clays are arranged in order 

of increasing vanadium content, with the formula for 

the odd clay (AW-144-52) at the end of the table. In 

general, the formulas show that increase in vanadium 

is accompanied by (1) decrease in octahedral aluminum, 

(2) increase in tetrahedral aluminum, (3) decrease in 

total aluminum, and (4) decrease in silicon. The 

proxying of increasing amounts of quadrivalent vanadium for trivalent aluminum causes an equivalent decrease in octahedral charge, which is, in most of the 

samples, compensated by increase in tetrahedral charge, 

due to increased proxying of aluminum for silicon. 

Thus, introduction of V+4 into the octahedral layer of 

the clay structure, and consequent decrease in octahedral 

charge necessitates readjustment in the tetrahedral layers to maintain a relatively constant total charge. 

Throughout these adjustments, however, the sum of the 

octahedral aluminum and vanadium and the sum of the 

iron and magnesium remain essentially constant. These 

relationships support the conclusions drawn from the 

analyses; that increase in vanadium content is accompanied by decrease in aluminum and silicon content, but 

does not affect the content of any of the other constituents iron, magnesium, calcium, sodium, and potassium.
CHEMICAL STUDY OF THE MINERALIZED CLAYS 129

TABLE 5. Structural formulas for vanadium days

Sample No.

-.47

Formula

-.34

G-27UM-53.. .._.. _... (Ali .MV .^) (Si3 .e6A1.34)010 (OH)2X.81 _

L37 .64

-.44 -.37

G-43UM-53 ..__._.---.-_--.. (Ah .ssV^Fe^Fe^lMg^) (Sis.MAl.s7) 010 (OH)2X.81 .

1.43 .57

-.46 -.39

G-29UM-53-.......--...---. (Ah.32V^!Fe+ioFe+nMg.42) (Si8.«Al.s«)Oio(OH)3X.M1.37 .63

-.24 -.54

G-29M-53 -.-...._--_...._ (Al.fl2V+4|Fe^?Mg.44) (Si3 .46Al.s4)0,o(OH)2X.78 _

G-43M-53.

1.36 .65

-.19 -.69

Mg.40) (Si3 .31 Al.eo) do(OH)2X.88 .

1.42 .59

+.13 -.71

AW-146-52... ......__..._... (Al.8oV+s|Fe+iiFe^Mg.43) (Si3 .29A1.7,)010 (OH) 2X.68 .

1.39 .61

+.04 -.83

A W-22-52---... -...--.. .....f,(Al.s7V^|Fe4i4Fe^6Mg.25) (Si3 .i7Al.83)010 (OH)2X.79 .

AW-144-52.

1.39 .45

-.16 -.70

Ll.eiVimJFejjaMg^) (Si3 .aoAl.70)Oio(OH)2X.86-

External cations 

K Others

0. 58 0. 23

.57 .24

.55 .30

.55 .13

.51 .37

.47 .13

.65 .14

.50 .36

1.14 .79

The amount of V+4 that can be admitted into the 

clay structure without producing a positive charge on 

the octahedral layer is determined by the bivalent ion 

content. In the formulas for the clays separated from 

sandstone (the "G" samples), bivalent ions, or ions 

like Fe+3, which probably were present originally as 

bivalent ions, occupy from 0.57 to 0.65 octahedral positions. None of these samples contain more than 0.44 V 

ions, and in their formulas the octahedral groups all 

have a negative charge.

In the formula for AW-146-52 the octahedral group 

has a positive charge of 0.13, exactly equivalent to the 

Fe+3 present. If it is assumed that all the iron was 

originally present as Fe+2, the V+4 present would have 

been almost exactly equivalent to the sum of the Fe*2 

plus Mg (0.59 and 0.61 respectively), and would represent the maximum amount of V+4 that could be accepted 

into the structure without inducing a positive charge 

on the octahedral layer.

The V+4 content of these six samples does not exceed 

the original bivalent ion content, assuming Fe to have 

been present originally as Fe+2. In AW-22-52, however, V+4 is greatly in excess of Fe and Mg, occupying 

0.82 positions, whereas Fe and Mg occupy only 0.45 

positions. This excess of V+4 over bivalent ions does 

not lead to a positive charge on the group, as would be 

expected, because of the deficiency of octahedral positions occupied 1.84 of the theoretical 2.00.

It has been pointed out that in the formulas for this

suite of seven samples the sum of the positions occupied 

by octahedral Al and V*4 is remarkably constant, as 

is also the number of positions occupied by Fe and by 

Mg^ In the formula for AW-22-52 the number of 

positions occupied by Al plus V*4 and by total Fe fall 

within the range of the number of positions occupied by 

these ions in the other members of the suite, but the 

number of positions occupied by Mg is lower by approximately the same number of positions (0.16) as 

the octahedral group is deficient of the theoretical 2.00. 

This deficiency in Mg and in octahedral positions suggests that if V+4 in excess of the bivalent ion content 

enters the structure of a clay similar to G-29UM-52, 

electrical balance is achieved and a positive octahedral 

charge is avoided by vacating bivalent positions, Mg in 

this case, equivalent to the excess of V+4.

AW-144^52 differs from the other clays studied in 

having a lower Al plus V*4 content (1.14 positions) 

and a higher Fe (0.32 positions) content. The Mg 

content (0.47 positions) is only slightly higher than 

the highest number of positions occupied by Mg in the 

other clays (0.44). At the time of analysis oxidation 

had proceeded farther in this sample than in any of 

the others, and all the iron was present as ferric iron. 

In the unadjusted analysis of this sample some 

vanadium was found to be present as V2O5 (2.39 percent) . As this V2O5 was found to be free of the clay 

structure, it was not included in the adjusted analysis. 

However, it may have been present originally in the clay
130 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

structure as V+4 and have been expelled from the structure on oxidation to V (V), with perhaps some Fe 

(III), thus accounting for the deficiency of octahedral 

positions occupied. The ease with which this sample is 

broken down by acid treatment suggests that the structure is under considerable strain and perhaps disorganization. If iron is considered to have once been 

present as Fe+2, the original bivalent ion content of 

this sample was considerably higher than that of the 

samples that have been considered 0.75 as compared 

with an average of 0.61. It had, consequently, a correspondingly greater capacity for the acceptance of V+4 

into the structure without inducing a positive charge

on the octahedral group. The V+4 content of the sample 

is, however, considerably lower (0.54) than the maximum that could have been accepted by neutralization 

of the bivalent ion content (0.75).

X-ray diffraction studies showed that the vanadium 

clays studied are composed predominantly of mica 

(roscoelite) and mixed-layered mica (roscoelite) and 

montmorillomte. As vanadium is present in roscoelite 

as V+3, it might be postulated that vanadium was 

originally present in these clays as V+3. Three of the 

formulas shown in table 6 are rewritten below on this 

assumption, with the further necessary assumption that 

Fe was present originally as Fe+2.

Sample No.

-.62

Formula 

-.39

G-29UM-53....- ___.._..._.. (Al,.32Vi

1.37 .63 

-.62

G-29M-53.

-.54

;.44) (Si3 .48Al.B4)01o(OH) 2X1 . 14 .

1.36 .65

-.59 -.71

AW-146-52. ........._. ._ ._ (Al.goViSFeilMg.43) (Si3.2flAl.71) 0,0 (OH) 2X1 .30....

K

0. 55

.55

.47

El

0.56

.59 

.83

1.39 .61

Most significant in these formulas is the high charge 

or external cation value (X value), especially in the 

formulas of the mineralized clays. In clays like these, 

made up predominantly of mica and interlayered mica 

and montmorillonite, the X-value or charge would be 

expected to be less than that of a mica (1.00) but more 

than that of a montmorillonite (0.30 to 0.50). The K 

equivalent (average 0.55) indicates that they are made 

up of approximately 55 percent mica (including interlayered mica), and 45 percent montmorillonite (interlayered with mica), and consequently, should have a 

charge or X value of 0.70 to 0.80. In these formulas, 

however, the charge increases from 1.01 to 1.30, as V+s 

increases from 0.05 to 0.59.

When V+4 proxies for Al+3 in a 2:1 layer structure

the charge on the octahedral layer decreases with increase in V"1"4 content, and becomes zero when V"1"4 is 

equivalent to the bivalent ions (Fe+2 and Mg) present. 

To maintain a constant charge on the structure, such 

decrease in octahedral charge must be accompanied by 

increase in tetrahedral charge that is, increased proxying of Al for Si. On the other hand, when V+s proxies 

for octahedral Al, it causes no change in the octahedral 

charge and there is no need for adjustment and increase 

in charge on the tetrahedral layers with increase in vanadium content. In the formulas for Colorado roscoelites shown in table 6, in which the numbers of octahedral positions occupied by V+3 ranges from 0.73 to 

1.16, there is no correlation between V+3 content and 

tetrahedral charge.

Sample No. and Location

TABLE 6. Formulas for Colorado roscoelites

Formula 

-.08 -.95 

1. Paradox Valley_.._............__..__._. ___ (Al.88vi|Fe+i§Mg.o4) (Sis.osAl.gs)Oi0 (OH) aXi M

1.87 .14 K.90

-.18

2. PlacervUle.

1.85

3. Placerville.. ..._..____. _ __.__._._._____.__ ( Al .

.14 

-.10

-.75

(Sis.MAl.78)Oio(OH) 8X.93

K.79 

-.94

1.85

V Fe Mg .09) (Si3 .o8Al.94)O10 (OH) 2X1 .o4

.13 Ki.09

-.04 -.81

4. PlacerviUe _.__........._._____._ ___.._._ (Al.73ViigFe+o|Mg.o4 ) (Si8.iBAl.g1 )O10 (OH) 8X.M,

1.89 K.80

1. Wells, R. C., and Brannock, W. W., 1945, Composition of roscoelite: U. S. Geol. 

Survey Bull. 950, p. 123.

2. Hillebrand, W. F., and Ransome, F. L., 1900, On carnotite and associated 

vanadiferous minerals in western Colorado: Am. Jour. Sci., 4th ser., v. 10, p. 133.

.13

3. A. L. Bush, analyst; calculated from an unpublished analysis, U.S. Geological 

Survey.

4. V. North, analyst; calculated from an unpublished analysis, U. S. Geological 

Survey.
CHEMICAL STUDY OF THE MINERALIZED CLAYS 131

As (1) the analyses of the clays show that increase in 

vanadium content is accompanied by decrease in silica

and alumina content, (2) formulas derived from the

, T . . ' *?,, , , , , . analyses show increase in V+4 content and decrease in

octahedral charge and maintainance of a relatively constant total charge, that is, (X) value, and (3) substitution of V+3 for V+4 in the formulas leads to abnormal X

values (see table Y ) , whereas the X values obtained with

T7,, , , , . , .,, ,, . , V+4 are reasonable and in accord with the mineralogytoj

of the clays> ^ may be concluded that vanadium entered 

the clays as V+4 and not as V+s.

TABLE 7. V+3 substituted for V+* in formulas for vanadium clays 

Sample No. Formula

-.60 -.34

G-27UM-53. ................ (Al 1 .34V.o33Fe.ti2Mg.43) (Si3.66Al.34)Oio(OH) 2X.94.-. ...._..........

1.37 .64

-.54 -.37

G-43UM-53. ....... ......... (Alh38V.l3Fe.t|Mg.39) (Si3 .63A1.37)Oio(OH).X.01 .- ...... -. 

1.43 .57

-.62 -.39

G-29UM-53. ................ (Al,.32V.o53Fe.ti2 Mg.42) (Si8.M Al.8o)Oio(OH) 8Xi.oi------- - --.

r_7 .63

-.62 -.54

G-29M-53..... ...... ........ (Al.MV.t48Fe.tia Mg.«4).(Si8.46A1.54)Oio(OH) 2Xi. 14 ------. ------.--.

1.37 .65

-.57 -.69

G-43M-53... .-..-.-.---.-.-- (% A^,aV^Fe^Mg;1!0,(Si8.8iAl.M)O,o(OH) 8X1 .8«... --------------

1.42 .59

-.59 -.71

3

(Al.8oV.t93Fe.tMg.43) (Si8.2»Al.7 i)Oio(OH).Xi.8oU9 .61

-.92 -.83

*AW-22-52...... ............ (Al.57V.823Fe.to2 Mg..5) (Sia .i7Al.8g)01 o(OH).X1 . 75

1.39 .45 

-.79 -.70

K Ex

0.58 0.36

.57 .34

.55 .56

.55 .68

.51 .85

.47 .83

.65 1.15

.50 .99

1.14 .79

*The discrepancy between the charge (0.92) on the octahedral group and the charge resulting from divalent-ion substitution (0.45) is due to 0.16 unoccupied position, which 

leaves 0.48 anlonic charge unneutralized, and which adds that much to the charge induced by divalent ions.

DISCUSSION AND CONCLUSIONS

The eight clays from the Salt Wash member of the 

Morrison formation in the Colorado Plateau that have 

been studied are mineralogical mixtures, consisting predominantly of mica and interlayered mica and montmorillonite, with minor amounts of chlorite and quartz, 

There is little difference, mineralogically, between the 

mineralized and unmineralized clays. Their potassium 

content indicates that mica (including the mica interlayered with montmorillonite) makes up about 50 percent of the clays. Vanadium is present, in the tetravalent state, in all the mineralogical phases making up 

the mineralized clays.

In chemical composition the mineralized and unmineralized clays are also very similar. The most significant feature of difference is the progressive decrease in Si02 and A12O3 with increase in V204 content, 

the other constituents remaining relatively the same, 

Vanadium is present in the structure of the mineralized 

clays as an octahedral cation, replacing aluminum ion 

for ion. Substitution of tetravalent vanadium for trivalent aluminum causes an equivalent decrease in the 

octahedral charge. This is compensated for by increased replacement of silicon by aluminum, with consequent increased tetrahedral charge, so that the total 

charge remains relatively constant. In the unmineralized clays the octahedral charge is slightly greater 

than the tetrahedral charge. With increase in V+4 content the octahedral charge progressively increases, until 

in the most highly mineralized there is no negative 

charge on the octahedral layer all negative charge is 

on the tetrahedral layer. These relationships are refleeted in the chemical composition as decrease in SiO2 

and A12O3 content with increase in V204 content.

The increase in tetrahedral charge with decrease in 

octahedral charge which accompanies increase in V2O4 

content suggests that vanadium entered the structures 

of the mineralogical phases making up the clays in the 

tetravalent state, and not in the trivalent state as in 

roscoelite. If vanadium had originally entered these 

structures in the trivalent state, substituting for aluminum, it would have caused no change in the octahedral

4686,52 5.9 10
132 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

charge and there would have been no need for adjustment and increase in charge in the tetrahedral layers 

with increase in V content, as is observed.

It is worthy of note that the vanadium clays studied, 

in which vanadium is present in the tetravalent state, 

occur in clay-bearing sands (the Salt Wash member of 

the Morrison formation), whereas roscoelite, a mica containing trivalent vanadium, is found in the Colorado 

Plateau in sand formations with low clay content. This 

difference in environment suggests that the minerals 

deposited, and the state of valence of the vanadium 

in them, is in some way related to the presence or absence 

of clay in the sands. In the absence of clay, roscoelite 

containing trivalent vanadium was deposited by the 

invading solutions; in the presence of clay, there was 

interaction between the clay and the invading solutions, 

which resulted in (tetravalent) vanadium-bearing clays 

similar to the non-vanadium-bearing clays in 

mineralogy and in chemical composition except for 

greater or less replacement of octahedral (trivalent) 

aluminum by tetravalent vanadium and additional replacement of silicon by aluminum sufficient to maintain the total charge at a relatively constant value. On 

the other hand, cases are known (for instance, at the 

Mineral Joe mine, see Part 15) where vanadium hydromicas have been introduced as part of the mineralization process.

REFERENCES

Brindley, G. W., and Touell, R. F., 1951, A chemical determination of "tetrahedral" and "octahedral" aluminum ions in a 

silicate: Acta Crystallographica, v. 4, p. 495-496.

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah, 

a preliminary report: U. S. Geol. Survey Bull. 936-P, p. 

363-394.

Foster, M. D., 1951, The importance of the exchangeable magnesium and cation-exchange capacity in the study of 

montmorillonite clays: Am. Mineralogist, v. 36, p. 717-730.

Foster, M. D., 1953, Geochemical studies of clay minerals, III, 

The determination of free silica and free alumina in 

montmorillonites: Geochimica et Cosmochimica Acta, v. 3, 

p. 143-154.

Foster, M. D., 1955, The classification and correlation of dioctahedral potassium micas: U. S. Geol. Survey Bull. 1036-D, 

p. 57-67.

Hillebrand, W. F., and Lundell, G. B. F., 1953, Applied inorganic 

analysis: New York, John Wiley and Sons.
Part 11. MIXED-LAYERED STRUCTURES IN VANADIUM CLAYS

By JOHN C. HATHAWAY

CONTENTS

Abstract _ ______________________

Introduction ._.__.__.___________.

Materials. . ______________________

Procedure. __ ___________________

Page 

.....___-_.-..-__-. 133

_...-_-.._.-.-.--- 133

_._-.....---..--.. 133

._.._--..____-_--- 134

Results. ___---____--_______--_-_-._______----_---._

Literature cited __ ____-_._____-_ _________________

Page 

134 

138 

138

ILLUSTRATIONS

Page 

FIGURE 35. X-ray diffraction patterns of two roscoelite samples..____-_______-__-_----_---__-_----__---_------------ 134

36. Comparison of X-ray diffraction patterns of oriented aggregates of roscoelite and glauconite________________ 135

37. X-ray diffraction patterns of oriented aggregates of five Colorado Plateau samples in which mica is the principal

constituent _________________________________________-________-_-____---__----__-_-_-___-_----___- 136

38. X-ray diffraction patterns showing expansion of vanadium silicates treated with ethylene glycol._____________ 136

39. X-ray diffraction patterns of AW-67-51 (a mixture of two or more minerals) showing shift in peaks caused by

treating with ethylene glycol and by heating________________--___-_______-_____________ ___________ 137

40. X-ray diffraction patterns of sample G 53-53 untreated, after ethylene glycol treatment, and after heating.___ 137

41. X-ray diffraction patterns of oriented aggregates of two samples from the Mineral Joe mine, Montrose County,

Colo. _____________________________________________.______________--_.___ 138

ABSTRACT

A group of claylike silicates containing vanadium have been 

examined by X-ray diffraction methods to determine their mineraloglc composition. The results indicate that mica and chlorite are the principal minerals. The micas resemble roscoelite 

but depart from it in two different ways, by interstratification 

with montmorillonitic layers and by variation in octahedral substitution. Some of the chlorites also exhibit mixed-layered 

expanding structures, but no interstratification of mica and 

chlorite layers has yet been noted. The chlorites show some 

variation in the temperature of decomposition, presumably because of differences in composition and degree of crystallinity.

INTRODUCTION

Identification of the claylike materials occurring in 

zones of vanadium mineralization in the sandstone type 

deposits of the Colorado Plateau is often hampered by 

the fine particle size and poor crystallinity of these 

materials, although mica-type minerals have been recognized through usual X-ray diffraction methods and 

have been variously reported as roscoelite or vanadium 

hydromica. In this investigation, X-ray diffraction 

procedures commonly used in the study of clay minerals have been applied to the problem of differentiating these poorly crystalline materials. The chemistry 

of some of these samples used is discussed in Part 10 

of this volume.

MATERIALS

[The American Museum of Natural History supplied sample 

AMNH-13565]

The samples 

AMNH-13565. 

ALB-34-54_

AW-207-54A_ 

AW-207-54B. 

AW-146-52___ 

AW-1M-52_

AW-67-51.

studied were as follows:

. Koscoelite, Coloma, .Calif.

 Roscoelite, Fall Creek mine, Placerville, San Miguel County, Colo.

 Vanadium silicate from oxidized 

ore, Rifle, Garfield County, Colo.

___. Vanadium silicate from unoxidized 

ore, Rifle, Garfield County, Colo.

 Vanadium silicate from Cougar 

mine, San Miguel County, Colo.

 Vanadium silicate from Sunnyside 

mine, east of Carrizo Mountains, 

San Juan County, N. Mex.

_ Vanadium silicate, Little Pittsburg 

No. 5 mine, Thompson district, 

Grand County, Utah.

133
134

G-53-53 _____ Vanadium silicate, Bitter Creek 

mine, Montrose County, Colo.

P-l-M-53____. Mineral Joe mine, Jo Dandy group, 

Montrose County, Colo.

P-l-P-53_____ Mineral Joe mine, Jo Dandy group, 

Montrose County, Colo.

PROCEDURE

AU of the samples except AMNH 13565, P-l-M-53, 

and P-l-P-53 were purified by water elutriation, bromoform separation, or both. Sample AMNH 13565 

consisted of a group of fairly pure roscoelite crystals 

and therefore did not require further separation. A 

portion of these crystals was crushed in a mullite mortar to pass a 230-mesh sieve. This material as well as 

a portion of each of the other purified samples were 

placed in plastic test tubes and dispersed in distilled 

water using a motor-driven brush. A small amount of 

sodium metaphosphate was added to each sample as a 

dispersing agent. Oriented aggregates were prepared 

by pipetting portions of each suspension onto each of 

three glass slides. The suspension remaining in the test 

tube was allowed to stand about four hours and the 

material still in suspension at the end of this time was 

pipetted on three additional slides. The material 

placed on these two groups of slides will hereinafter 

be referred to as coarse and fine, respectively.

Samples P-l-M-53 and P-l-P-53 8 were dispersed 

in distilled water, wet sieved to remove particles larger 

than 62/A, further dispersed using an end-over-end 

shaker, and centrifuged repeatedly to separate the silt 

(2-62/i) and clay (<2/*) fraction. Excess water was 

removed from the clay fraction using porcelain filter 

candles under vacuum and portions of the resulting 

concentrated suspensions were pipetted onto glass 

slides. The remaining suspensions were dried at room 

temperature and the clay removed and crushed.

X-ray diffractometer patterns were made for each 

sample as follows:

Oriented aggregates:

1. Untreated.

2. Treated with ethylene glycol.

3. Heated to 400° C.

4. Heated to 500° C.

5. Treated with hot concentrated MCI (samples 

AMNH 13565, AW-67-51, G-53-53, P-l-M53, and P-l-P-53 only).

Randomly oriented powder (samples AMNH 13565, 

ALB-34-54, P-l-M-53, and P-l-P-53, only).

RESULTS

In figure 35 a comparison is shown between the X-ray 

diffractometer patterns of minerals which have been 

identified by chemical and optical methods as roscoelite. 

Most of the apparent differences in the randomly

50 40 20 

CU Kct RADIATION

FIGURE 35. X-ray diffraction patterns of two roscoelite samples.

30 

DEGREES 26

8 These two samples are further considered in Part 15 of this volume, 

and there are identified as samples M and P, respectively.

oriented powder patterns are the result of the much 

higher degree of preferred orientation that occurred in 

the preparation of the mount for sample AMNH 13565. 

Otherwise both samples exhibit similar patterns except 

that the peak marked "A" at 33.4° 20 in the randomly 

oriented powder pattern for sample AMNH 13565 is 

not evident in ALB-34-54 and calcite is present in 

ALB-34-54. Inasmuch as the spacing of peak "A" is 

not part of the integral series of higher orders for the 

001 spacing, its presence is probably not due to the 

preferred orientation of the roscoelite flakes but more 

probably represents a separate unidentified phase. Further evidence for this suggestion is the appearance of a 

peak with a spacing of 6.9A in the pattern for an 

oriented aggregate of sample AMNH 13565 heated to
MIXED-LAYERED STRUCTURES IN VANADIUM CLAYS 135

500° C. The same peak appears with considerable intensity at the same temperature in the acid-treated 

sample suggesting that this separate phase is acid insoluble. Elimination of lines apparently due to separate phases leaves a pattern with a distribution of hkl 

lines that closely resembles a one-layer monoclinic 

muscovite. This is in agreement with the proposal of 

Heinrich and coworkers (1953) that roscoelite is 

characterized by a one-layer monoclinic structure. An 

important departure from the muscovite pattern may 

be seen in the distribution of intensities of the OOZ lines 

shown in the oriented aggregate patterns in figure 35. 

Whereas the 001 and 003 reflections show strong and 

medium intensities, respectively, the 002 and 004 reflections are almost absent. Muscovites, on the other 

hand, show a second-order reflection of considerably 

greater intensity relative to the first- and third-order 

reflection. A weak second-order basal reflection is 

usually, but not always, a characteristic of the biotites. 

The spacings of the 060 reflections (not shown in fig. 35) 

for samples AMNH 13565 and ALB-34-54 are 1.525A 

and 1.515A, respectively, which places them within the 

overlap of the ranges usually associated with the dioctahedral and trioctahedral micas. It does not seem 

likely, however, that a trioctahedral mica would form 

with vanadium occupying the octahedral positions. 

Calculations of the octahedral layer population by the 

Marshall method (1949, p. 58) for ALB-34-54 and for 

a roscoelite from Placerville, Colo., from the analysis 

quoted in Weeks and Thompson (1954, p. 55) give sums 

of 1.969 and 2.069 atoms per half-unit cell, respectively. 

It seems probable then that these micas are dioctahedral 

and that the moderately large b0 dimensions shown by 

the 060 spacings are due to the replacement of aluminum by vanadium in the octahedral layer. Such substitutions would also account for the low intensities of 

the second order OOZ reflections. G. Brown (1951, p. 

162) has calculated the effect on 001 intensities of substitution of Fe+3 for Al+s in the dioctahedral mica structure and has demonstrated that a high-iron mica should 

exhibit an extremely weak 002 reflection. As the atomic 

scattering curve for vanadium closely follows that of 

iron (Klug and Alexander, 1954, p. 138), a similar distribution of OOZ intensities should occur for both a 

roscoelite and a high-iron dioctahedral mica such as a 

glauconite, and figure 36 shows the similarity of the 

X-ray patterns for oriented aggregates of the two 

minerals. Conversely a lesser amount of vanadium substitution should be revealed by an increase in intensity 

of the 002 reflection relative to the 001 and 003 reflections.

Figure 37 shows the X-ray patterns given by oriented 

aggregates for five Colorado Plateau samples in which

30 20 

DEGREES 26

10 

CU Koc RADIATION

FIGURE 36. Comparison of X-ray diflEraction patterns of oriented aggregates of roscoelite and glauconite.

mica is the principal constituent. All show a weak 002 

reflection although in samples AW-207-54A and AW146-52 this line is relatively stronger than in the other 

samples suggesting a lesser amount of octahedral vanadium in these two samples. The patterns are arranged 

in order of decreasing degree of crystal perfection 

toward the bottom of the diagram, although the first 

three patterns show approximately equal crystallinity. 

Accompanying this decrease is an increase in the 001 

spacing as tabulated below:

Sample No. 001 spacing in A 

ALB-34-54_________ 10.1 

AW-207-54B__._____ 10.1 

AW-207-54A__._____ 10.1

All the samples in figure 37 except ALB-34-54 contain impurities as indicated on the diagram by G for 

chlorite and T for metatyuyamunite. Ethylene glycol 

treatment had little effect on samples ALB-34-54, 

AW-207-54B, and AW-207-54A, but some expansion 

took place in samples AW-146-52 and AW-144-52 as 

is shown in figure 38. The extreme loss in intensity sufSample No. 001 spacing in A 

AW-146-52________ 10. 3 

AW-144-52________ 10. 5
136

40 

DEGREES 28

30 30 

CU Kcc RADIATION

FIGUBB 37. Xray diffraction patterns of oriented aggregates of five 

Colorado Plateau samples in which mica is the principal constituent.

fered by the 001 reflection in these samples sometimes 

occurs through physical disruption of the surface of the 

oriented aggregate on glycol treatment. Such disruption did not occur with samples AW-146-52 and 

AW-144-52 therefore it is suggested that the loss of 

intensity is entirely the result of the expansion of montmorillonitic layers randomly interstratified with layers 

of roscoelite. These two samples might justifiably be 

called vanadium hydromicas in the sense that they are 

micaceous and contain vanadium and would show a 

high proportion of water in a chemical analysis; however, they might better be identified as mixed-layered 

mica-montmorillonite minerals which would acknowledge their expandable properties.

A slightly different type of material is shown in 

figure 39 by sample AW-67-51. This sample is a mixture of at least two minerals, both of which expand 

slightly on ethylene glycol treatment. The shift of a

ORIENTED AGGREGATES

TREATED WITH ETHYLENE GLYCOL

I I 

T- METATYUYAMUNITE

40 30

DEGREES 29

20 10 

CU Kcc RADIATION

FIGURE 38. X-ray diffraction patterns showing expansion of vanadium 

' silicates treated with ethylene glycol.

peak at 12.9 A to 13.8 A is suggestive of a vermiculitic 

mineral, whereas the behavior of the other major component with a reflection at 10.6 A suggests a mixedlayered mineral similar to samples AW-144-52 and 

AW-146-52. Heat treatment however indicates that 

both of these minerals are less durable than either vermiculite or the mixed-layered minerals discussed above. 

At 400° C both AW-144-52 and AW-146-52 collapsed 

to structures closely resembling roscoelite and at 500° C 

still give lines of strong intensity. AW-67-51, on the 

other hand, gives evidence of destruction of the crystal 

lattice at 400° C, and at 500° C a new unidentified phase 

has appeared. Treatment of this sample with hot concentrated HC1 leaves a residue which gives an X-ray 

pattern similar to that of roscoelite except that its structure is apparently destroyed between 400° and 500° C.

Sample G-53-53 (fig. 40) is an example of a mixture 

of chlorite and a mica which shows only a minor amount 

of interstratification with more highly hydrated layers 

as ethylene glycol and heat treatment affect the shape 

and position of the mica 00? reflection only slightly. 

The intensity of the 002 reflection after heat treatment 

at 500 °C suggests that the mica is roscoelite with less 

substitution of vanadium for aluminum than in sample 

ALB-34-54. The chlorite in sample G-53-53 is characterized by the almost equal intensity of the first four 

00.7 reflections and by the accentuation of the first order 

reflection with loss of the higher orders after heat 

treatment at 500°C, a reaction that occurs in most wellcrystalized chlorites. It should be noted that the chlo-
MIXED-LAYERED STRUCTURES IN VANADIUM CLAYS 137

AW-67-51

ORIENTED AGGREGATES G-53-53

ORIENTED AGGREGATES

40 30 20 10 

DEGREES 29 CU- Kof RADIATION

FIOURB 89. X-ray diffraction patterns of AW-67-51 (a mixture of 2 or 

more minerals) showing shift in peaks caused by treating with 

ethylene glycol and by heating.

rites in samples AW-207-54A and AW-146-52 behave 

similarly, whereas in AW-207-54B the increase in intensity of the 001 line fails to take place at elevated 

temperature, the chlorite lines disappearing and the 

lines of an unidentified new phase appearing at 400°C 

instead. At 500°C still another unidentified phase appears replacing the one occurring at 400°C. No experiments have been carried out as yet to determine if 

these phases are at equilibrium at the given temperatures. Inasmuch as sample AW-207-54B comes from 

unoxidized ore whereas AW-207-54A represents an oxidized zone, it seems possible that the oxidation state of 

the vanadium in the chlorite affects the stability of the 

mineral. The relationship, however, may be difficult to 

visualize when it is considered that the normal chlorite

4O 30 20

DEGREES 20 CU Koc RADIATION

FIGURE 40. X-ray diffraction patterns of sample (3-53-58 untreated, 

after ethylene glycol treatment, and after heating.

usually contains bivalent elements in both the octahedral 

layer and the interlayer brucite sheet. The manner in 

which vanadium (III), (IV), or (V) atoms are contained in a chlorite structure remains as a further problem of investigation.

Samples P-l-M-53 and P-l-P-53 from a channel 

sample taken at the Mineral Joe mine, Montrose County, Colo. (Part 15), were examined without purification other than size fractionation to concentrate the 

clay size particles. The X-ray patterns for oriented 

aggregates of the < 2^ fraction of these samples are 

given in figure 41. Mica, chlorite, and carnotite are 

the principal constituents of the clay fraction of sample 

P-l-M-53. The mica and chlorite 001 reflections show 

slight shifts on treatment with ethylene glycol suggesting that they have montmorillonitic layers interstratified with them. Their behavior on heat treatment lends 

support to the supposition that the mica and chlorite 

are mixed-layered minerals, as a distinct shift toward 

lower spacings occurs after heating of the sample to 

400°C. The characteristics of the first-order chlorite 

reflection after heating is suggestive of a vermiculitic 

mineral except that the higher order OOZ reflections of 

the untreated material show intensities greater than 

those expected from a vermiculite.
138 GEOCHEMISTEY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ORIENTED AGGREGATES 

UNTREATED

C - CHLORITE

M- MICA

T - NieTATYUYAMUNITE

CN- CARNOTITE

40 20 10 

CU Koc RADIATION

F.IGUBE 41. X-ray diffraction patterns of oriented aggregates of two 

samples from the Mineral Joe mine, Montrose County, Colo.

Sample P-l-P-53 differs from the previous sample 

in that metatyuyamunite is present as a major constituent. Further differences are a higher degree of 

mixed layering in the mica and a chlorite which shows 

greater thermal stability closely resembling the chlorite 

of sample G-53-53. The mica in turn shows characteristics on ethylene glycol treatment similar to the mica 

of sample AW-144-52.

CONCLUSIONS

The vanadium silicates examined contain mica that 

varies from roscoelite (AMNH 13565) to highly mixed 

layered mica-montmorillonite (AW-144-52) in which 

the mica layers are probably roscoelite-like in octahedral composition but of very poor crystallinity. Chlorites are present in most of the samples and vary from 

types of high thermal stability and good crystallinity 

(G-53-53) to mixed-layered chlorite-montmorillonite 

aggregates (P-l-M-53) and chlorites of poor thermal 

stability (AW-207-54B).

The samples might be grouped according to the 

character of each of their mineral components as follows:

Mica:

Roscoelite >

AMHN 13565

ALB-34-54

AW-207-54A

AW-207-54B

G-53-53

P-l-M-53

AW-146-52

AW-67-51

P-l-P-53

AW-144-52

Increasing mixed layering

Roscoelite:

AMNH-13565 

ALB-34-54 

AW-207-54B 

AW-144-52

AW-67-51

AW-207-54A

AW-146-52

G-53-53

P-l-M-53

P-l-P-53

Decreasing octahedral substitution of V for Al (based 

on relative 002 intensity)

Chlorite 

G-53-53

P-l-P-53

AW-207-54A

AW-207-54B

AW-146-52

-» Increasing mixed layering

P-l-M-53

AW-67-51 (vermiculite?)

Chlorite 

G-53-53

P-l-P-53

AW-207-54A

AW-146-52A

 * Decreasing thermal stability

P-l-M-53

AW-67-51 (vermiculite?) 

AW-207-54B

LITERATURE CITED

Brown, G., 1951, The mica clay minerals, in X-ray identification 

and crystal structures of clay minerals: London, The Mineralogical Society, p. 162.

Heinrich, E. W., Levinson, A. A., Levandowski, D. W., and 

Hewitt, C. H., 1953, Studies in the natural history of micas: 

Michigan Univ., Eng. Research Inst. Proj. M-978, p. 212-215.

Klug, H. P., and Alexander, L. E., 1954, X-ray diffraction procedures for polycrystalline and amorphous materials: New 

York, John Wiley and Sons, Inc., p. 138.

Marshall, C. E., 1949, The colloid chemistry of the silicate minerals : Am. Soc. Agronomy, Mon. Ser. 1, New York, Academic 

Press, Inc., p. 58.

Weeks, A. D., and Thompson, M. E., 1954, Identification and occurrence of uranium and vanadium minerals from the Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B, p. 55.
Part 12. ASSOCIATION OF URANIUM WITH CARBONACEOUS MATERIALS, WITH SPECIAL

REFERENCE TO TEMPLE MOUNTAIN REGION

By IRVING A. BREGER and MAURICE DEUL

CONTENTS

	Page 

Abstract_____-_-__-__-__-----_-__-____-_.__-_____ 140

Introduction _______________________________________ 140

Crude oils___-_________--_-____-----___________--_- 140

Experimental and analytical data_________________ 140

Oils as transporting agents for uranium ____________ 141

Carbonaceous sandstone.____________________________ 142

Experimental and analytical data_________________ 142

Origin of carbonaceous material in sandstone ores___ 142

Carbonaceous pellets._______-_____-___-__-__-.__--__ 145

Experimental and analytical data_________________ 145

Origin of carbonaceous pellets.___________________ 145

Carbonaceous shale.________________________________

Experimental and analytical data_________________

Significance of uranium-organic association in carbonaceous shale.__._____________---_-_-___-__

Coalified wood.________________--______---__-_-----

Experimental and analytical data.__________----_-

Role of coalified wood in uranium fixation. _ _______

Summary and conclusions__________________________

Literature cited___________________________________

Page 

146

146

147

147

147

148

148

149

ILLUSTRATIONS

FIGURE 42. Vacuum differential thermal analysis of carbonaceous material from pellets and ore__________

43. Vacuum differential thermal analysis of asphaltites and related substances.__________________

44. Infrared absorption analysis___________-___________________-_-____----___-_---_--__-___.

45. Infrared absorption analysis_-___-_____________-__-_-___---_-__-__--__---_-----_--------

46. Plot of analyses of carbonaceous materials from the Colorado Plateau on a standard coal curve.

Page

143

144

144

144

146

TABLES

Page 

TABLE 1. Oils collected from mines in the Temple Mountain region, Emery County, Utah______________________________ 140

2. Analysis of asphaltenes from oils of the Temple Mountain area.____________________________________________ 141

3. Distribution of uranium in the oils from the Temple Mountain area_________._-___---________--___-_________ 141

4. Analysis of fractions from carbonaceous sandstone ore_________--__-_-----------------------------------___ 142

5. Semiquantitative spectrographic analyses of ashes from carbonaceous sandstone ore and separates._____________ 142

6. Analytical data for carbonaceous pellets from the Temple Mountain region, Emery County, Utah.____________ 145

7. Semiquantitative spectrographic analysis of ash from carbonaceous pellet from Rex No. 2 mine_________________ 145

8. Analysis of carbonaceous shale collected from Dakota sandstone in Zuni uplift area, New Mexico, and of separates

from shale_________________________________________________________________________________________ 146

9. Semiquantitative spectrographic analyses of ash of original shale sample from Dakota sandstone formation and of

ash of separates_____-_______________-__---________-_-__--_______--__-____-__-_-_______-_-__________ 147

10. Analysis of coalified wood from Rex No. 1 mine. _________________________________________________________ 147

11. Semiquantitative spectrographic analysis of ash from vitrain from the Rex No. 1 mine ________________________ 148

12. Analysis of coalified wood fragment from Corvusite mine, Grand County, Utah_____________________________ 148

13. Analysis of coalified wood from Corvusite mine, Grand County, Utah_______________________________________ 148

139
140 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ABSTRACT

On the Colorado Plateau uranium Is associated with coalifled 

wood, crude oil, carbonaceous shale, and carbonaceous matter of unknown origin. Investigations have shown that crude 

oil plays no role in the emplacement of uranium, although its 

ability to pick up small quantities of uranium while migrating 

through uraniferous zones may make oils an aid to general 

prospecting. Carbonaceous matter with no cellular structure 

occurs as impregnations in sandstones or as pellets, and has 

been chemically related to coal. Tar acid yields, infrared spectra, and differential thermal analyses, as well as ultimate analyses, all indicate that these substances are derived from coal 

or coal extracts. The reduction to U(IV) of uranium associated with coalifled wood may take place after absorption 

of the uranyl ion. Study of a terrestrial shale shows that the 

uranium is associated with carbonaceous material similar to 

lignite in chemical composition. From these studies it is concluded that the fundamental association of uranium with carbonaceous material on the Colorado Plateau is with coalified 

wood and allied chemical substances.

INTRODUCTION

Coalified plant debris is the most common type of carbonaceous material occurring on the Colorado Plateau. 

Coal beds are absent in uraniferous zones, but ore-bearing rocks may contain several kinds of carbonaceous 

matter. Some of these carbonaceous materials are comparable to coals and as such vary in rank from lignite 

to bituminous. Emplacements and impregnations of 

fossil wood by uranium minerals and by sulfide minerals, as well as by silica and calcium carbonate, are 

common, and it is not at all surprising that we have 

found evidence for the migration of extracts of organic 

material.

An unusual and perhaps unique situation exists in 

the Temple Mountain area, Emery County, Utah. 

There, in addition to an association with coalified wood, 

uranium is associated with crude oil and with carbonaceous substances apparently derived as extracts from 

coaly material. Because these various kinds of organic 

matter occur within the same or neighboring mines in 

the same formation, samples were collected from this 

area for detailed study to determine the relationship of 

the uranium to the different carbonaceous materials.

Uranium-bearing carbonaceous shale occurs within 

the Colorado Plateau near Gallup, New Mexico, and a 

sample of this shale, which occurs in the Dakota sandstone of Cretaceous age in the Zuni uplift area, was 

studied in detail.

The carbonaceous substances studied have at various 

times been known by different names. Some of these 

names, although applied to substances of then unknown origins, have genetic connotations. "Asphalt" 

and "asphaltite" are two such terms that have been 

used to describe hard black impregnations in sandstone, rounded black pellets, viscous crude oil, and

even coalified fragments of wood. Use of these terms 

to describe materials from the Colorado Plateau is 

misleading, hence thiy nomenclature has not been applied to such substances in this paper.

Soluble or extractable organic substances are amenable to study by standard physical and chemical techniques such as chromatography, fractional distillation, 

infrared and ultraviolet absorption analysis, and functional group ( OH, hydroxyl; CHO, aldehyde; 

etc.) analysis. When organic material is found to 

be insoluble in any common solvent, physical and 

chemical methods of analysis become less effective and 

interpretation of results less reliable. Furthermore, 

fine-grained mineral matter is often intimately associated with insoluble carbonaceous material and a 

problem arises in attempting to separate the organic 

material by mechanical techniques that result in only 

minor changes, if any, to its chemical structure and 

composition.

Of the various carbonaceous materials collected, 

only the crude oils, occurring as seeps or as impregnations in sandstone, are readily soluble. Because of 

the relative ease of working with oils they were studied 

first to determine the relationship of uranium to them 

and the manner by which uranium is retained by them.

CRUDE OILS

EXPERIMENTAL AND ANALYTICAL DATA

Samples containing crude oil were collected from 

four operating uranium mines in the Temple Mountain area (table 1). One sample was an oil-impregnated sandstone exposed during mining operations. 

The other samples were collected from seeps by scraping the oils from mine walls or by chipping portions 

of the rock through which they were flowing. The 

viscosity of these oils varied greatly, the most viscous 

having a taffylike consistency.

TABLE 1. Oils collected from mines in the Temple Mountain 

region, Emery County, Utah

Source

AEG No. 8 mine ..........

Marsh Bank Canyon mine. 

AEC No. 5 mine ..........

Description

Consistency of taffy. 

Seep through uraniferous zone. ....

Collectors

L. R. Stleft and

T. W. Stern. 

A. D. Weeks.

M. Deul.

M. Deul.

In the laboratory each oil was first dissolved in 

benzene to free it from mineral matter. Multiple 

filtrations of the benzene solution were carried out to 

make certain that suspended mineral matter was removed from the oil. Benzene was removed from filtered 

oils by distillation at room temperature and then by
ASSOCIATION OF URANIUM WITH CARBONACEOUS MATERIALS 141

freeze-drying. Small samples (approximately 5 g) of 

the oils were redissolved in 25 to 30 ml of benzene and 

pure pentane was added to the solutions in the ratio of 

40 volumes of pentane per volume of benzene. This 

mixture was stored overnight at approximately 5° C to 

precipitate asphaltenes. The chilled solutions were 

filtered, and the asphaltenes were thoroughly washed 

with pentane. The filtrate and washings from the 

asphaltenes were mixed and diluted with pentane to 

assure complete precipitation of asphaltenes from the 

oil.

The asphaltenes were vacuum dried for two hours 

at room temperature and then analyzed for carbon 

and hydrogen by standard microcombustion techniques. 

Ash from each analysis was weighed and analyzed for 

uranium (Grimaldi and others, 1954). Nitrogen and 

sulfur were determined by combustion analysis. Analytical data for the asphaltenes are shown in table 2. 

Table 3 summarizes data showing the distribution of 

uranium in the oils.

TABLE 2. Analysis, in percent, of asphaltenes from oils of the 

Temple Mountain area

f. Analysts: B. T. Moore and E. B. Brittln, U. S. Geological Survey. Asphaltenes 

Isolated by H. M. Ezeklel, U. S. Geological Survey]

Ash..............................

AECNo.4 

mine

0.34

.000147

82.21

7.92

.08

5.7

3.2

AECNo.5 

mine

0.28

.0221

82.84

8.44

1.07

5.1

2.5

Marsh 

Bank 

Canyon 

mine

1.83

.0386

82.71

8.24

.40

6.7

3.0

AEG No. 8 

mine

1.07

.0922

83.31

9.44

1.0

6.3

TABLE 3. Distribution of uranium in the oils from the Temple 

Mountain area

[All data are In percent]

Original oil:

Asphaltenes:

Ash............................

Uranium In ash. ...............

Uranium in original oil held by

AEC No. 4

mine

0.0000438

22.7

.000147

.34

.0432

76.2

.00020

AEC No. 6

mine

0.00445

16.2

.0221

.28

7.89

80.5

Marsh

Bank

Canyon

mine

0.0137

22.5

.0386

1.83

2.11

63.4

AEO No. 8

mine

0.0310

27.8

.0922

1.07

8.62

82.6

OILS AS TBANSPOBTING AGENTS FOB UBANIUM

The uranium content of crude oils from nonuraniferous provinces is known to be low. Unkovskaya 

(1940) has reported from 0.0001 to 0.001 ppm of ura- 

:nium in naphthenic base oils from Russia and, although 

tfchese results may be low, an increase by one or even by

two orders of magnitude will not make them geochemically significant. Erickson, Myers, and Horr (1954) 

have also shown that oils from nonuraniferous provinces contain very small quantities of uranium 

0.00001 to 0.064 ppm. Because crude oils normally contain extremely small percentages of uranium, it is 

reasonable to surmise that the oils collected from operating uranium mines on the Colorado Plateau have absorbed uranium during their migration through uraniferous zones.

Variations of from 45 to 310 ppm of uranium in the 

three oils collected from seeps probably reflect the migratory history of each oil. The uranium content of 

the oil extracted from impregnated sandstone from 

the AEC No. 4 mine is somewhat lower than might be 

anticipated considering the proximity of the oil to 

the uranium. Here the oil-impregnated sandstone occurs 

below the ore horizon, and the uranium in the oil (0.44 

ppm) may represent only that which came into contact 

with it through a medium such as ground water. It 

is possible that the oil in this sandstone was already in 

place before the introduction of the uranium in the 

region and has remained static. If this is so, then oil 

in this sandstone might represent oil that migrated 

into the Temple Mountain area before the introduction 

of uranium into the region. Oil collected from seeps 

would then represent the same oil that had migrated 

by various paths within the area following introduction 

of the uranium.

Asphaltenes from crude oils range in sulfur content from 0 to as much as 11 percent (Sachanen, 1945; 

Mariani, 1951); the asphaltenes isolated from the oils 

that have been studied in this work contain from 5.1 to 

6.3 percent sulfur. This narrow range of variation in 

sulfur contents suggests that these oils are from the 

same source.

In the oils that have been studied, 63.4 to 82.6 percent of the uranium is retained in the asphaltenes. Infrared studies of the asphaltenes indicate the existence 

of functional oxygen-containing groups that may be 

responsible for the retention of the uranium.

From these results, it is suggested that reconnaissance 

for uranium might be carried out in uraniferous provinces, such as the Colorado Plateau, by analyzing oils 

that may occur. Oils found to contain appreciable percentages of uranium might then be used as guides to 

uranium ore. A factor that must be considered is the 

unknown migratory course a crude oil may take. Use 

of an oil as an ore guide would, therefore, be based on 

the assumption of very limited movement of the oil or 

other geologic evidence that would indicate the course 

of migration.
142 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

CARBONACEOUS SANDSTONE 

EXPERIMENTAL AND ANALYTICAL DATA

The ore-grade sample of carbonaceous sandstone 

used in this study was collected from the AEC No. 9 

mine, Temple Mountain area, Emery County, Utah, by 

L. E. Stieff and T. W. Stern of the U. S. Geological 

Survey. The sample was taken from the Moss Back 

member of the Chinle formation (Triassic). By means 

of lead-uranium isotope analysis, Stieff and Stern (oral 

communication) have shown the age of the uranium in 

an equivalent sample to be not older than 60 million 

years. In hand specimen the material is black and 

very dense and yields a faint X-ray powder pattern 

for uraninite; on being struck, the material emits a 

petroliferous odor which may have led to its being 

called an "asphaltite." In thin section the sandstone 

consists of clean rounded quartz grains. Voids between 

the grains are filled with black, carbonaceous material. 

Abraham (1945) describes similar material that, on the 

basis of physical tests, has been classified as glance 

pitch.

Soxhlet extraction of 80-mesh carbonaceous sandstone with 1:1 benzene-alcohol dissolved 0.09 percent 

by weight of the sample. Further treatment of the 

sample with pyridine, aniline, 6N hydrochloric acid, 

5 percent sodium hydroxide, or a pyridine-acetic acid 

mixture resulted in no further extraction.

Because of the difficulty in performing accurate organic microanalyses on a sample containing 72 percent 

ash (table 4), it was first necessary to concentrate the

TABLE 4. Analysis of fractions from carbonaceous sandstone ore 

[Analysts: O. Johnson, A. Sweeney, and E. Brittin, U. S. Geological Survey]

TABLE 5. Semiquantitative spectrographic analyses of ashes from 

carbonaceous sandstone ore and separates

[Analyst: C. S. Annell, U. S. Geological Survey]

Inorganic separate .... 

Ash (percent)

72.46

18.01

95.35

83.16

88.38

Carbon 

(percent)

20.49

62.63

1.92

12.69

9.05

Hydrogen 

(percent)

1.53

4.01

.35

1.24

1.22

Uranium 

(percent)

2.4

1.1

.63

1.1

4.9

organic material. This separation was accomplished by 

using a technique (Deul, 1956) developed during 

studies of carbonaceous shales, namely, by ballmill grinding with a mixture of kerosene and water. 

Under these conditions organic substances concentrate 

in the kerosene phase. As shown in table 4, an organic 

separate containing only 18.01 percent ash was isolated 

from the carbonaceous sandstone. Each separate was 

analyzed for ash, carbon, hydrogen, and uranium. 

Semiquantitative spectrographic analyses of the ashes 

obtained from the samples are given in table 5 (Waring 

and Annell, 1953).

U in ash 2 (percent) ..

Range (percent): 

>10 ............

5-10 __ ...... ....

1-5 

0.5-1- . .

0.1-0.5.. .

0.05-0.1.. 

0.01-0.05. ..

0.005-0.01...... ....

0.001-0.005.. 

0.0005-0.001........

0.0001-0.0005... 

Original 

sandstone

72.46

3.2

Si

U, Al, Fe,

V

Mn. B,

Pb, Ti, 

Zn

Ni

Sr, Cu,

Zr, Y,

Sn

Or, Ag, 

Be

Organic 

separate

18.01

6.1

Si

U.Fe, Al,

V 

Ca

Mg

Zn 

Pb, Mn,

B, Ti, 

Ni, Zr, 

Cu

Sr, Y

Ag, Or, 

Be

Mineral 

separate

85.35

.66

Si

Fe, Al, V

U

Ba

Na, Ti,

Mn, B, 

Pb, Zn

Ni

Sn, Y, Sr,

Cu

Cr, Ag

Organic 

middlings

83.16

1.3

Si

Fe, Al, U,

V

Mg, Na, 

Zr 

Ba

Zn, Pb,

Mn, Ti, 

B

Ni, Sn

Sr, Cu, Y

Ag, Cr, 

Be

Mineral 

middlings

88.38

5.5

Si

Al, U, Ca,

Fe, V

Ba, As

Zr, Mn,

B, Pb, 

Ti, Zn,

Ni 

Sn

Sr, Cu, Y

Cr, Ag, 

Be

1 Data from table 4.

2 Calculated from data of table 4. Katio of percent II in each fraction to percent 

ash in corresponding fraction.

ORIGIN OF CARBONACEOUS MATERIAL IN 

SANDSTONE ORES

The black, carbonaceous ore bodies of the Temple 

Mountain region have been known by several names 

since their discovery, and the terms used have implied 

genesis from crude oils. Because of the conclusions 

reached with regard to the association of uranium with 

crude oil, it was necessary to establish the composition 

and structure of these carbonaceous materials and their 

relationship to the oils.

From autoradiographic studies (Stieff and Stern, 

1952) to investigate the relationship of uranium to the 

mineral and organic constituents of the sandstone, the 

following observations were made:

1. There is no concentration of alpha-particle tracks at 

boundaries between the carbonaceous material and 

mineral fragments indicating that uranium is not 

present in the ore as a coating on the mineral 

grains.

2. Alpha-particle tracks are dispersed throughout the 

carbonaceous material with some areas containing 

greater or lesser concentrations of tracks.

3. Quartz and pyrite grains are practically devoid of 

tracks. Vanadium minerals show some tracks but 

not nearly as many as appear in the carbonaceous 

material.

Because permeable sandstones permit the flow of 

aqueous solutions, gases, petroleum, or other fluids, it 

is possible that uranium entered the interstices of the 

sandstone before the introduction of the organic matter. 

If this were true, there should be a concentration of
ASSOCIATION OF URANIUM WITH CARBONACEOUS MATERIALS 143

uranium on the surfaces of the quartz and other mineral 

particles. Such evidence is lacking. On the contrary, 

the dispersion of uranium throughout the organic 

matter and the fact that the quartz grains are practically devoid of alpha-particle tracks suggest that the 

uranium and carbonaceous matter entered the sandstone in solution or as a nearly homogeneous suspension. 

The separation of uranium from the organic matter 

by fine grinding (table 4) indicates that most of the 

uranium is not now chemically associated with the 

organic matter. Had a chemical combination existed, 

separation has since taken place, perhaps as a result 

of bond cleavage by the alpha particles.

Recalculation to a moisture- and ash-free basis of 

the composition of the organic matter isolated by ballmill grinding shows that the organic matter contains 

76.5 percent carbon, 4.9 percent hydrogen, and, by difference, 18.6 percent oxygen, nitrogen, and sulfur. 

This composition is indistinguishable from that of 

lignite and suggests that the organic impregnation in 

the sandstone is derived from a low-rank coal.

The data of table 5 show that the organic separate 

from the carbonaceous sandstone, as compared to the 

mineral separate, has been enriched in uranium, tin, 

copper, beryllium, and possibly arsenic. The same elements are also enriched in the ashes of organic separates from coal as compared to ash of minerals separated from coal (Deul, 1955). The organic separate 

from the sandstone contains a higher percentage of 

uranium than does the mineral separate, but both are 

lower in uranium content than the original sandstone 

ore.

Vacuum differential thermal analysis (Whitehead 

and Breger, 1950) provides further evidence that the 

impregnating organic material is related to coal. Carbonaceous material separated from the sandstone gives 

a decomposition curve similar to those obtained for 

low-rank coals (fig. 42) but different from those for 

such substances as gilsonite, wurtzilite, etc. (fig. 43). 

As can be seen from figure 42, the shape of the exothermic curves for carbonaceous material from the pellet 

and from the ore are similar to the shape of the curve 

for coals between 300° and 500° C (Breger and Whitehead, 1951). The small exothermic peaks at 300° C 

are superimposed on the general curve and are of unknown origin. The small endothermic peak on the 

curve for the carbonaceous material from the ore at 

about 425° C is similarly superimposed on the general 

curve and is of unknown origin. It is possible that 

mineral matter may be the source of these small peaks.

tr

UJ

x 

o

X

UJ

o

cr

UJ1 ho 

o

2 

UJ

SUBBITUMINOUS 

COAL

200 400 600 800

TEMPERATURE (°C)

FIGURE 42. Vacuum differential thermal analysis of carbonaceous material from Utah pellets and ore. The curve for a subbltumlnous coal 

is shown for comparison. Small peaks at 575° C are caused by 

quartz used as an Internal standard.

The curves of figure 43 for wurtzilite, gilsonite, and 

other asphaltites are quite different from the curves for 

coal.

In figure 44 infrared absorption curves, obtained by 

R. G. Milkey, are shown for the asphaltenes isolated 

from an oil of the Temple Mountain region (curve A), 

for the residual oil following removal of the asphaltenes 

(curve B), and for the extract isolated from the carbonaceous sandstone by means of Soxhlet extraction 

(curve C).

In curves A and B the large absorption indicative of 

saturated carbon-hydrogen bonding (3.4,6.9, and 7.3 /*.) 

with respect to absorption from aromatic structures 

(6.3 /A) is important. Curve C, in contrast, shows practically no saturated carbon-hydrogen bonding; the extract has strong absorption in the OH region (2.9 /A) 

and is practically wholly aromatic in structure. From 

this evidence it can only be concluded that the extract 

from the carbonaceous sandstone cannot be related to 

petroleum.
144 GEOCHEMISTRY AND MINERALOGY, COLORADO iPLATEATJ TJRANITJM^ORES

SUBBITUMINOUS COAL (COLORADO)

GRAHAMITE (WASHINGTON CO., 

PENNSYLVANIA)

GILSONITE (UINTAH CO., UTAH)

ASPHALTITE (ARGENTINA)

200 400 600 800 1000 

TEMPERATURE (°C)

1200

FIGURE 43. Vacuum differential thermal analysis of asphaltites and 

related substances. The curve for a subbituminous coal is shown for 

comparison. Small peaks at 575° C are caused by quartz used as an 

internal standard. Curves by S. Rubinstein, U. S. Geological Survey.

4 5 6 7 8 9 10 

.WAVE LENGTH, IN MICRONS

12-13 14 15

FIGURE 44. Infrared absorption analysis. Curve A, asphaltenes isolated from a crude oil; curve B, crude oil after removal of asphaltenes ; curve C, extract from carbonaceous sandstone. All spectra 

obtained with material compressed in potassium bromide pellets.

Curve D of figure 45 is the infrared absorption curve 

for an organic extract obtained from a uranium-bearing lignite (Breger, Deul, and Rubinstein, 1955). The

80_

40 _ 

20I

60_ 

40 _

WURTZILITE (DUCHESNE CO, UTAH) 5 20 j

H - 

£ o60

40

20

0

60 

40 

20 _

567 8 9 10 II 

WAVE LENGTH, IN MICRONS

12 13

FIGURE 45. Infrared absorption analysis. Curve D, extract from lignite from South Dakota ; curve E, organic separate from carbonaceous 

sandstone; curves F and G, pellets from Temple Mountain area, 

Emery County, Utah. All spectra obtained with sample compressed 

in potassium bromide pellets.

strong OH absorption, strong aromatic absorption, 

and absence of appreciable saturated carbon-hydrogen 

structure are all significant features. Curve E of figure 

45 was obtained for the organic isolate from the carbonaceous sandstone. Absorptions in the OH and 

aromatic regions, and absence of appreciable absorption 

in the saturated carbon-hydrogen region provide further strong evidence that the isolate is not related to 

crude oil but, rather, to coal.

Attempts have been made to establish the origin of 

the carbonaceous impregnation in the sandstone by 

other techniques. It has long been known that coals 

derived from vascular plants have aromatic and phenolic structures that lead to the formation of relatively 

high percentages of phenolic products (tar acids) on 

distillation. Other types of coal, such as boghead coal 

which is mainly derived from algae, have long-chain 

fatty acid skeletal structures that lead to the formation of much tar but not of much tar acid. The great 

bulk of carbonaceous substances is derived either from 

higher plants or from algae, and it is possible to use 

the composition of tar produced as a clue to the origin 

of such materials. The technique followed consisted 

of retorting 3-g samples using a modification of the 

technique described by Cuttitta (1953) collecting the 

total distillate, and extracting, purifying, and weighing the tar acids. Because tar formation is dependent 

on rank, the criterion for evaluation is not the total
ASSOCIATION OF TJEANIUM WITH CARBONACEOUS MATERIALS 145

tar acid produced but the percentage of tar acids in 

the tar. Data obtained are tabulated below:

Sample

Lignite.

Average.

Boghead coal.

Average.

Organic isolate from ore from AEC No. 9 

mine._ _--_-_-.______________--___

Tar 

(percent)

2.33

2.35

3.80

2.83

25.76

26.58

24. 77

25.70

0.41 

.34

Tar acids 

(percent)

17.33

16.15

20.50

17.99

2.87

1. 57

1.85

2. 10

86. 10

42.60

Stadnikoff (1930) suggested that coals such as lignite should yield 15 to 50 percent of tar acids, while 

bogheads and other substances mainly of algal origin 

should yield less than 5 percent of tar acids. The experimental data for the lignite and boghead coal fit the 

pattern suggested by Stadnikoff. The yields of tar 

acids from the isolate from the carbonaceous sandstone 

are high, indicating that this material was derived from 

vascular plants. Considering the small amounts of 

sample available for this work and the low yields of tar, 

better check data for tar acids are not to be expected.

Based on the analytical data, a possible explanation 

for the accumulation of uranium in the carbonaceous 

sandstones of the Temple Mountain region is that aqueous solutions carrying organic material extracted from 

low-rank coals in the region, along with uranium and 

vanadium, may have saturated the pores of the sandstone. Eventually the organic matter was devolatilized 

and converted to its present insoluble state, perhaps 

radiochemically.

CARBONACEOUS PELLETS

EXPERIMENTAL AND ANALYTICAL DATA

Pellets of black carbonaceous material, ranging from 

several millimeters to several centimeters in diameter, 

occur in certain strata of a sandstone unit (the Moss 

Back member) of the Chinle formation at Temple 

Mountain. In places these rounded masses merge with 

the carbonaceous material that impregnates sandstone. 

Gruner (oral communication) and Stieff and Stern 

(oral communication) have reported that some of the 

carbonaceous material replaces clay balls imbedded in 

sandstone. The carbonaceous material of the pellets 

also corrodes some of the quartz grains with which it 

comes into contact.

Pellets for this study were collected at three sites: the 

Rex No. 2 mine, the AEC No. 4 mine, and the AEC No. 

8 mine, all in the Temple Mountain region, Emery 

County, Utah. Because many of the pellets were extremely small and weighed less than 100 mg each, detailed work on individual pellets has been limited.

Six pellets from a suite collected in the AEC No. 4- 

mine were selected on the basis of their specific gravities, 

which ranged from 1.29 to 1.56. One pellet from the 

AEC No. 8 mine was chosen because of its rather large 

size and its relatively high specific gravity. The specific gravity of the pellet from the Rex No. 2 mine was 

determined to be 1.38±0.02. Analyses of these pellets 

are given in table 6.

Spectrographic analysis of ash (6.94 percent) from 

the pellet from the Rex No. 2 mine is shown in table 7.

TABLE 6. Analytical data, in percent, for carbonaceous pellets 

from the Temple Mountain region, Emery County, Utah

[Carbon, hydrogen, oxygen, nitrogen, and sulfur determined on a moisture- and 

ash-free basis]

Mine

AEO No. 4_ _

Rex No. 2 > ...

AEO No. 8 > ..

Specific

gravity

1.29

1.34

1.38

1.43

1.57

1.56

1.38

1.63

Ash

6.61

9.13

10.77

15.88

19.15

8.26

6.94

9.72

Carbon

80.2

80.8

81.4

79.7

78.7

77.7

76.1

76.3

Hydrogen

7.54

6.52

5.18

6.12

6.08

6.20

4.93

5.53

Oxygen,

nitrogen,

and sulfur

12.26

12.68

13.42

14.20

15.22

16.10

18.97

18.17

Uranium

In original

pellet

0.038

2.54

2.96

2.44

2.51

1.67

2.77

1.68

i Collected by L. R. Stleff and T. W. Stern. U. S. Geological Survey. 

» Collected by T. Botinelly, U. S. Geological Survey.

TABLE 7. Semiquantitative spectrographic. analysis of ash from 

carbonaceous pellet from Rex No. & mine

[Analyst: Helen Worthing, U. S. Geological Survey]

Percent Elements 

>10.............. U

5-10._-._---_-.... Si

l-5__..__....__ Al, Fe, V, Ca

0.5-1____...._ As, Pb

0.1-0.5......_.._._ P, Mg, Y, Ba, Ti

0.05-0.1._____.. B, Ce. Sr, Nd

0.01-0.05-.___... Zn, Mn, Ni, Pr, Dy, Er, Yb, Gd, Cr, Co

0.005-0.01_. ____ . Zr, La, Cu, Sn

0.001-0.005.....__ Sc, Ho, Lu

0.0005-0.001....... Be

ORIGIN OE CARBONACEOUS PELLETS

The origin of carbonaceous pellets occurring in the 

Temple Mountain region has been a subject for speculation for some time. Abraham (1945) states, "The 

asphaltite is characterized by the fact that it carries 

uranium and vanadium, which are assumed to have been 

incorporated in it during its migration from the underlying strata, thereby hardening the asphaltite and "fixing" it in the present associated rocks." Others have 

since extended the hypothesis that the material has 

been derived from petroleum.
146 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

With obvious exceptions, examination of the data of 

table 7 reveals certain trends: (1) ash rises with specific 

gravity; (2) carbon and hydrogen both decrease with 

specific gravity; and (3) the total of oxygen, nitrogen, 

and sulfur rises regularly with specific gravity. There 

does not appear to be any specific relationship between 

uranium and any of the other components or properties 

of the pellets.

In figure 46 data have been plotted for a number of

0+N*S

95 90 85 80 0+N +

 CARBONACEOUS MATERIAL FROM SANDSTONE ORE (TABLE 4)

 CARBONACEOUS PELLETS (TABLE 7)

A VITRAIN FROM REX NO. I MINE (TABLE II)

T VITRAIN FROM CORVUSITE MINE (TABLE 14)

(D BROWN VITRAIN FROM CORVUSITE MINE (TABLE 13)

® INTERMEDIATE VITRAIN FROM CORVUSITE MINE (TABLE 13)

® BLACK MINERALIZED VITRAIN FROM CORVUSITE MINE (TABLE 13)

FIGURE 46. Plot of analyses of carbonaceous materials from the 

Colorado Plateau on a standard coal curve. All analyses on moistureand ash-free basis. Dashed lines enclose average analyses of most 

mined coals.

carbonaceous pellets and other substances collected from 

the Colorado Plateau. Represented are analyses of 

pellets (table 6), analysis of the carbonaceous material 

isolated from the carbonaceous sandstone (table 4), 

analysis of vitrain (table 10), and analyses of four samples of vitrain from the Corvusite mine, Grand County, 

Utah (tables 12 and 13). The dashed lines enclose an 

area in which most normal mined coals occur (Lowry, 

1945). The deviation from this area for a coal that has 

been subjected to mineralization is clearly shown. 

Analyses for the pellets all fall close to or within the 

normal coal curve strongly suggesting that these materials are related to coal in origin. This conclusion

has been confirmed by the differential thermal analysis of one pellet from the region (fig. 42). Infrared 

curves F and G of figure 45, moreover, show the material to be related structurally to coal and not to have 

the characteristics generally found in crude petroleum 

or its fractions. The evidence points to the materials 

as being coaly in nature.

The occurrence of pyrite in the pellets indicates that 

they have not been subjected to appreciable oxidation. 

In view of this fact, it is not believed that the relatively high oxygen content of the pellets can be explained 

as resulting from oxidation of carbonaceous material 

of petroliferous origin.

Spectrographic analysis of the ash from the pellet 

from the Rex No. 2 mine (table 7) has shown the presence of 10 of the 15 rare earths. This is in contrast to 

analyses of petroleum ash (Erickson, Myers, and Horr, 

1954) which normally show the presence of only the 

more abundant and more easily detectable rare earths. 

Sodium, on the other hand, should appear in the analysis of the ash if the pellet were derived from petroleum 

(Erickson, Myers, and Horr, 1954). These data may 

be interpreted as signifying a nonmarine and therefore, a nonpetroliferous origin for the pellets.

CARBONACEOUS SHALE

EXPERIMENTAL AND ANALYTICAL DATA

Although uranium-bearing carbonaceous shales are 

quantitatively unimportant on the Colorado Plateau, 

a shale from the Zuni uplift area of New Mexico was 

studied to determine the relationship of the uranium to 

the carbonaceous material. The section of the Dakota 

sandstone containing the carbonaceous shale is reported 

to have been deposited marginal to the sea. In contrast 

to marine shales, these stream and lagunal sediments are 

essentially terrestrial, exhibiting braided stream deposits and paleostream channels (Mirsky, 1953). Shale 

for this study was collected by T. W. Stern. Mineral 

and organic fractions were separated and concentrated 

by the ball-mill technique that has already been mentioned.

Table 8 gives the analytical data for carbon, hydrogen, ash, and uranium for the original shale and for

TABLE 8. Analysis, in percent, of carbonaceous shale collected 

from Dakota sandstone in Zuni uplift area, New Mexico, and 

of separates from shale

[Analysts: H. Levine and R. T. Moore, U. S. Geological Survey]

Ash

76.22

30.21

89.68

67.85

Carbon

12.97

48.47

.81

13.90

Hydrogen

1.62

12.98

'1.60

12.25

Uranium

0.091

.41

.0051

.12

High hydrogen values caused by hydration of shales during milling.
ASSOCIATION OF URANIUM WITH CARBONACEOUS MATERIALS 147

the separates. The results of the spectrographic analyses of the ashes of the same samples are shown in 

table 9.

TABLE 9. Semiquantitative spectrographic analyses of ash of 

orignial shale sample from Dakota sandstone and of ash of 

separates

[Analysts: Mona Franck and K. Valentine, U. S. Geological Survey]

Ash i. ...................

U In ash ». ___ . .......

Kange: 

>10....................

5-10 

1-5. 

0.5-1..... ..........

0.1-0.6-.- 

0.05-0.1 

0.01-0.05- 

0.006-0.01---- - 

0.001-0.005.- 

0.0005-0.001 .. ...

0.0001-0.0005.... ..

0.00005-0.0001..........

0.00001-0.00005.........

Original

sample

76.22

.12

Al, Si

Ti, K

Fe, Ca, Mg

Na, Ba, V

B, Pb, Zr,

Co, Sr 

Cu, Ni, Or,

La. Y

Mo 

Sc, Be, Yb

Ag

concentrate

30.21

1.35

Al, Si

Ca

Fe, K, Ti,

Mg 

Ba, Na

Pb

Zr, V, Zn,

B, Co, 

Mn, Or, 

La, Ni, Y 

Ga

Sc, Sn, Yb,

Ag, Mo 

Be

concentrate

89.68

.0057

Al, Si

K

Ca, Fe, Mg,

Ti, Na

Sr, B, Zn

Or, Ni, V

Y, Ga, Pb,

Cu, Mn, 

Mo, Co, 

Sc

Yb, Ag, Be

Middlings

67.85

.18

Al, Si

Ca, K, Fe

Mg

Ti, Na

Pb, B. Cu,

Cr, Mn

Ga, Ni, V,

Y, Co, Mo

Yb

Be, Ag

1 Data from table 8.

8 Calculated from data of table 8. (Ratio of percent U in each fraction to percent 

ash in corresponding fraction.)

SIGNIFICANCE OP URANIUM-ORGANIC ASSOCIATION 

IN CARBONACEOUS SHALE

The shale from the Dakota sandstone yielded a mineral fraction which contained only about 1 percent 

organic matter, whereas the organic concentrate showed 

a fourfold enrichment of carbonaceaus material (table 

8). The direct association of uranium with organic material is shown in the analyses for uranium where the 

organic concentrate has a fourfold enrichment of 

uranium over that in the original sample and an eightyfold enrichment of uranium over that in the mineral 

concentrate. It is not at all unlikely that most of the 

uranium in the mineral fraction is associated with 

organic matter remaining with the mineral matter.

Spectrographic analyses of the fractions (table 9) 

show that the organic concentrate, with respect to 

the original shale, is enriched in uranium, cerium, tin, 

copper, manganese, silver, and ytterbium. In addition, 

the organic concentrate, as compared with the mineral 

separate, is enriched in lanthanum, cobalt, lead, and 

calcium. With the exceptions of calcium and silver, 

it has been shown that the minor and trace elements 

concentrated in the organic fraction are similar to the 

elements concentrated in organic separates from coal 

(Deul, 1955).

The analysis of this sample for carbon and hydrogen, 

when calculated on an ash-free basis (carbon, 69.5 percent ; hydrogen, 4.3 percent), shows that, although too 

low in carbon content to fall on the coal curve as plotted 

in figure 46, the composition of the material is in the 

proper range for a lignite. The data, when considered 

in the light of the geologic interpretation for this deposit as given by Mirsky (1953), provide strong 

evidence that the uranium in the shale is associated 

with carbonaceous material similar to coal in composition. Observation of plant casts in the shale during 

recent field studies has confirmed this conclusion.

COALIFIED WOOD

EXPERIMENTAL AND ANALYTICAL DATA

The association of uranium with coalified wood on 

the Colorado Plateau is universally recognized. Extensive studies conducted on uraniferous coals from 

other regions (Breger, Deul, and Rubinstein, 1955) 

have demonstrated the nature of the association of 

uranium with the coal substance. It was felt that our 

present studies could best be directed toward carbonaceous substances about which little was known, hence 

only few samples of coalified wood have been studied.

Although coalified wood from the Colorado Plateau 

has not yet been investigated in detail, hand-picked 

vitrain from a coalified log taken from the Rex No. 1 

mine, Temple Mountain region, Emery County, Utah, 

was submitted to the U. S. Bureau of Mines for 

standard coal analysis. On the basis of data shown in 

table 10, the equivalent rank of this coal is subbituminous C. The uranium content of the coal is 7.54 percent, and X-ray diffraction patterns have weak lines 

indicating the presence of uraninite. Table 11 gives the 

semiquantitative spectrographic analysis of the ash 

from the vitrain. The radioactivity of fusain in contact with the vitrain is extremely low.

A small sample of coalified wood was collected in 

1952 from the Corvusite mine, Grand County, Utah, 

by Alice D. Weeks of the U. S. Geological Survey.

TABLE 10. Analysis of coalified wood from Rex No. 1 mine 

[Analyses by U. S. Bureau of Mines, Lab. No. E-61765, Jan. 26,1955]

Proximate analysis (percent) :

Ash. . .-

Ultimate analysis (percent) :

Ash. ....... .............

Forms of sulfur (percent) : 

Sulfate...... ___ .................

Pyrltic.. . . .

As received

2.6

24.^

50.9

22.3

3.3

56.8

.1

8.9

8.6

22.3

.07

1.04

7.45

10, 210

Moisture free

24.8

52.3

22.9

3.1

58.3

.1

6.8

8.8

22.9

.07

1.07

7.65

10, 480

Moisture and 

ash free

32.2

67.8

4.0

75.6

.2

8.8

11.4

.09

1.39

9.92

13,600
148 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 11. Semiquantitative spectrographic analysis of ash from 

vitrain from the Rex No. 1 mine

[Analyst: Mona Franck, Ui S. Geological Survey]

Percent Elements 

................................ U, V

l-5_______________________________..__ Si, Pb, Ca

0.5-1._________________________________ Al, Fe

0.1-0.5._______________________________ Zn

0.05-0.1_______________________________ Ba, Nd, La, Cu

0.01-0.05.______________________________ B, Ti, Y, Mg, Mn

0.005-0.01. ____________________________ Sr, Co, Dy

0.001-0.005.._--...__._..__.-.._.._.._. Cr, Ag, Sc, Zr 

0.0005-0.001 __..-............._...._... ______

0.0001-0.0005.------_------_--__-_---.- Be

Note. Na obscured by high Zn; K obscured by high U; Yb obscured by high V.

This sample of vitrain, about 2 inches long, graded 

longitudinally from brown at one end to black at the 

other end. The black end was highly mineralized. 

Analytical data for this sample are given in table 12.

TABLE 12. Analysis, in percent, of coalified wood fragment from 

Corvusite mine, Grand County, Utah.

[Analysis on dry basis. Analysts: Jesse J. Warr, Jr., and Robert Meyrowitz, 

U. 8. Geological Survey]

Description

Black, highly mineralized

Ash

3.01

.64

22.46

Carbon '

82.7

81.3

83.0

Hydrogen '

7.7

6.7

4.2

Uranium

0.067

.0018

6.63

Atomic 

ratio 

(0:H)

0.90

1.00

1.64

1 Ash-free basis.

Another sample of coalified wood from the Corvusite 

mine consisted of vitrain and fusain, analyses for which 

are given in table 13.

TABLE 13. Analysis, in percent, of coalified wood from Corvusite 

mine, Grand County, Utah

[Analysis on dry basis. Analysts: Jesse J. Warr, Jr., and Robert Meyrowitz, 

U. S. Geological Survey]

Description

Vltrain..........................

Ash

13.06

2.04

Carbon '

80.1

94.4

Hydrogen >

5.8

2.8

Uranium

2.28

.0038

' Ash-free basis.

BOLE OP COALIFIED WOOD IN URANIUM FIXATION

The samples studied probably represent in rank most 

of the coalified wood in the region. The hand-picked 

vitrain from the Kex No. 1 mine has an extremely high 

content of organic sulfur for which no explanation can 

as yet be made. The presence of a very high concentration of zinc, of high copper, of cobalt in concentrations 

greater than nickel (table 11), and the unusually high 

sulfur content of the coal are undoubtedly related to 

the mineralization of the sample.

Examination of the analytical data shows that where 

vitrain is in contact with fusain, the vitrain contains 

the uranium. Fusain mineral charcoal is chemically 

inert and would not, therefore, be expected to contain

chemically bound uranium. Vitrain, on the other hand, 

is chemically reactive because it contains functional 

groups which are capable of combining with uranium. 

The data of table 12 illustrate variations in carbonhydrogen ratios that exist within a single specimen of 

vitrain. When the data for vitrain shown in tables 10, 

11, and 12 are plotted in figure 46, only one of the points 

falls within the normal coal range as defined on the 

graph. This coal range is based on analyses of coals 

composed of vitrain, fusain, and other coal ingredients. 

Vitrain normally contains more hydrogen than do other 

major coal ingredients, while fusain contains less. It is 

not possible to determine from the few data available 

whether there is a direct relationship between increasing uranium content and decreasing hydrogen content 

in vitrains, but we suspect that this is so.

A hypothesis has been proposed that ground-water 

solutions bearing alkaline or alkaline-earth uranyl carbonates introduced uranium into coals; in acid environment below a pH of 4.5 such complex compounds decompose and release uranyl ions (UOa"1"1") which are 

made available for the formation of ionic uranyl organic compounds, insoluble above a pH of about 2.2 

(Breger, Deul, and Meyrowitz, 1955).

It is not known whether the uranium associated with 

coalified wood on the Colorado Plateau was introduced 

as the uranous ion, which was directly absorbed, or 

whether the uranyl ion was reduced by the carbonaceous 

material upon or subsequent to absorption. Both degraded wood and subbituminous coal can reduce the 

uranyl ion to uraninite under laboratory conditions 

(Breger and Moore, written communication, 1955). 

Mechanisms are known that would permit the retention 

of uranium by coal, coalified wood, or related substances regardless of the state of oxidation of the 

uranium in the ore solution.

SUMMARY AND CONCLUSIONS

Studies of the carbonaceous materials from the 

Colorado Plateau lead to several conclusions:

1. The crude oil that occurs in seeps in the operating 

mines seems to have no effective role in the emplacement of uranium. The association of uranium with oil results from the ability of oil to 

pick up and carry small quantities of the element. 

The association of crude oil with the other carbonaceous substances in the Temple Mountain region is fortuitous the result of geological conditions which permit the flow of crude oil through 

strata containing uranium and vanadium. The 

ability of crude petroleum to pick up small quantities of uranium may make oils an aid to geochemical prospecting.
ASSOCIATION OF UKANIUM WITH CARBONACEOUS MATERIALS 149

2. The carbonaceous material associated with the 

sandstone ore that we have studied is apparently 

derived from plant material that has been coalified, or from the low-rank coals of the region. It 

is possible that uranium- and vanadium-bearing 

solutions extracted organic matter from degraded 

plant debris in the sediments and that the mixture 

of carbonaceous material, uranium, and vanadium 

was subsequently deposited in porous sandstones. 

The present insolubility of the carbonaceous matter may be the result of cross-linkage of coal 

molecules caused by irradiation by the alpha particles from the uranium and its daughter products.

3. The carbonaceous pellets are believed to have much 

the same origin as the carbonaceous material that 

is impregnating the sandstone ore. Some samples 

of sandstone ore show impregnations of carbonaceous material that appear to coalesce into pelletal groups replacing sandstone, and the rank of 

the materials, as reflected by their composition, is 

similar. Discussion of the mechanics of such replacements is beyond the scope of this paper.

The carbonaceous pellets are by no means uniform and it is not at all surprising that this is so. 

Plant materials and coals vary in composition 

and type, and migrating solutions or dispersions 

of colloidal material derived from coal could not 

be expected to be uniform in composition. Analyses have shown that coals from the Colorado 

Plateau can deviate more from the normal coal 

curve than do the carbonaceous pellets. This is 

illustrated in figure 46.

4. The direct association of uranium with carbonaceous 

material separated from the shale from the Dakota 

sandstone is further evidence of the potency of 

certain kinds of carbonaceous material for the 

fixation of uranium. That this particular shale is 

of terrestrial rather than of marine origin supports 

the conclusion that the organic material separated 

from the shale is related to lignite.

5. Coalified fragments of wood and coalified logs are 

the most abundant carbonaceous materials on the 

Colorado Plateau. We have shown that many 

of the carbonaceous materials that are of unknown 

origin or that have been considered to be of 

petroliferous origin have probably been derived 

from woody or coaly material. Insofar as carbonaceous materials are concerned, on the Colorado Plateau as well as in the Dakotas, in the Ked 

Desert area of Wyoming, and in the Fall Creek

area of Idaho (Vine and Moore, 1952), coal and 

humic materials related to coal are the major controls for the fixation of uranium. 

Based on available evidence, it appears that the 

fundamental association of uranium with carbonaceous 

materials on the Colorado Plateau is with coalified 

plant debris and allied chemical substances.

LITERATURE CITED

Abraham, H., 1945, Asphalts and allied substances: 5th ed., 

v. 1, p. 264, New York, D. van Nostrand Co.

Breger, I. A., Deul, M., and Meyrowitz, R., 1955, Geochemistry 

and mineralogy of a uraniferous subbituminous coal: Econ. 

Geology, v. 50, p. 610-624.

Breger, I. A., Deul, M., and Rubinstein, S., 1955, Geochemistry 

and mineralogy of a uraniferous lignite: Econ. Geology, v. 

50, p. 206-226.

Breger, I. A., and Whitehead, W. L., 1951, Thermographic study 

of the role of lignin in coal genesis: Fuel, v. 30, p. 247-253.

Cuttitta, F., 1953, A photometric method for the estimation of 

the oil yield of oil shale: U. S. Geol. Survey Bull. 992, 

p. 15-31.

Deul, M., 1956, Colloidal method for the concentration of carbonaceous matter from rocks: Am. Assoc. Petroleum Geologists Bull., v. 40, p. 909-917.

Erickson, R. L., Myers, A. T., and Horr, C. A., 1954, Association of uranium and other metals with crude oil, asphalt, 

and petroliferous rock: Am. Assoc. Petroleum Geologists 

Bull., v. 28, p. 2200-2218.

Grimaldi, F. S., May, Irving, Fletcher, M. H., and Titcomb, 

Jane, 1954, Collected papers on methods of analysis for 

uranium and thorium: U. S. Geol. Survey Bull. 1006.

Lowry, H. H., 1945, Chemistry of coal utilization: v. 1, p. 44, 

New York, John Wiley and Sons.

Mariani, E., 1951, Researches on the constitution of natural 

asphalts: Third World Petroleum Congress, Section 6, preprint 23, p. 1-9.

Mirsky, A., 1953, Preliminary report on uranium mineralization 

in the Dakota sandstone, Zuni uplift, New Mexico: U. S. 

Atomic Energy Comm., RME-47, p. 1-21.

Sachanen, A. N., 1945, The chemical constituents of petroleum: 

p. 400-403, New York, Reinhold Publishing Corp.

Stadnikoff, G., 1930, The origin of coal and oil: p. 1-254, Stuttgart, Enke Press.

Stieff, L. R., and Stern, T. W., 1952, Preparation of nucleartrack plates and stripping films for the study of radioactive 

minerals: Am. Mineralogist, v. 37, p. 184-196.

Unkovskaya, V., 1940, Determination of small quantities of 

uranium by the fluorescence technique: Compt. rend. acad. 

sci. U. R. S. S., v. 29, p. 380-383.

Vine, J. D., and Moore, G. W., 1952, Uranium-bearing coal and 

carbonaceous rocks in the Fall Creek area, Bonneville 

County, Idaho: U. S. Geol. Survey Circ. 212, p. 1-10.

Waring, C. L., and Annell, C. S., 1953, Semiquantitative spectrographic method for analysis of minerals, rocks, and ores: 

Anal. Chemistry, v. 25, p. 1174-1179.

Whitehead, W. L., and Breger, I. A., 1950, Vacuum differential 

thermal analysis: Science, v. Ill, p. 279-281.

Part 13. RADIUM-URANIUM EQUILIBRIUM AND RADIUM-URANIUM AGES OF SOME

SECONDARY MINERALS

By T. W. STERN and L. K. STIEPP

CONTENTS

Page 

Abstract.._________________________________________ 151

Introduction. ______________________________________ 151

Occurrence of carnotite, tyuyamunite, and metatyuyamunite____________________________ _ 152 

Radium-uranium equilibrium_______________________ 152

Conditions for equilibrium_______________________ 152

Previous work__________________________________ 153

Radium content of unoxidized uranium ores____.__. 153

Pas-e 

Radium-uranium equilibrium Continued

Radium content of oxidized uranium ores__________ 153

Radiocolloids_ _ _______________________________ 154

Radium content and radium-uranium ages of secondary uranium minerals. _____________________ 154

Summary. _________________________________________ 155

References._--_---_-____-_____________-__-_________ 155

ILLUSTKATION

FIGURE 47. Age in years as a function of percent radium-uranium equilibrium.

TABLES

Page 

153

Page

TABLE 1. Radium-uranium content of some high-grade lead-bearing carnotite and metatyuyamunite samples__________ 154

2. Radium-uranium content and radium-uranium ages of some high-grade carnotite and metatyuyamunite samples

containing less than 0.01 percent lead_----____---_____________________________________________________ 155

ABSTRACT

Ten samples of carnotite and metatyuyamunite ore that contain more than 0.1 percent lead have been analyzed for uranium, 

Ra228, and lead. Seven contain less than the equilibrium amount 

of Ra:2a for the uranium present, and three are in radioactive 

equilibrium within the limits of experimental error. Radioactive equilibrium between U238 and Th230 is effectively established in 500,000 years, therefore the seven radium-deficient 

minerals have been altered within that time span. The remaining three samples have not lost Th230 by alteration within 

the last 500,000 years or Ra220 within the last 15,000 years. An 

approximate lead-uranium age can be determined from these 

lead-bearing minerals if they have not been significantly 

leached of lead or uranium.

Carnotite and metatyuyamunite that have formed on joints 

and fractures are low in lead (less than 0.01 percent) and 

appear from field relations to be of recent origin. These coatings are local concentrations formed after the water table was 

lowered and the deposits were oxidized. If these minerals are 

not now in radium-uranium equilibrium, did not contain Th230 

and Ra220 at the time of their deposition, and have not been 

further altered by selective leaching or enrichment of radium, 

Th230, or uranium, their time of formation can be established. 

Radium-uranium ages determined on five Colorado Plateau secondary minerals range from approximately 10,000 to 120,000 

years.

Radiocolloids, local concentrations of radium and its daughter 

products, which persist for only about 15,000 years, are present 

in some oxidized ores.

INTRODUCTION

The primary vanadiferous uranium ores of the 

Colorado Plateau are characterized by their black 

color. Low-valence vanadium and uranium minerals 

as well as iron, copper, lead, and zinc sulfides, arsenides 

and selenides are present. Uraninite and coffinite are 

associated with carbonaceous materials; vanadium is 

present in montroseite and in vanadium silicates. 

Pyrite and marcasite are abundant.

Oxidation of the uranium deposits probably took 

place when the water table was lowered. Ores exposed 

to the air oxidize rapidly and a highly variable and 

complex mineral suite results (Part 5 of this volume). 

Vanadium minerals oxidize from vanadium (III) to 

vanadium (IV) and (V) minerals and uranium

151
152 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

minerals oxidize from uranium (IV) to (VI). When 

the uranium is in the sexivalent form it is relatively 

soluble and free to migrate unless precipitated by complexing with vanadium. Many samples of ore containing carnotite and tyuyamunite (or metatyuyamunite) which were formed in place give Pb206/U238 

ages comparable to the unoxidized ores because there 

was no opportunity for the uranium or the elements derived from the decay of the uranium to become separated. Some deposits, however, have been leached both 

during and after oxidation, the uranium and vanadium 

having migrated relative to Th230, Ka226, and radiogenic 

lead. A criterion of such movement of uranium and 

vanadium would be the redeposition of carnotite or 

metatyuyamunite on joints and fractures containing 

essentially no radiogenic lead. In other cases, daughter 

products may be moved and the uranium and the radiogenic lead remain in place. Presence of radiumuranium disequilibrium in ores oxidized in place is 

another measure of migration of radioactive daughter 

products during the past 500,000 years.

A. M. Sherwood and R. G. Milkey of the U. S. Geological Survey made the chemical analyses for uranium 

and lead. E. G. Rice and W. A. Peavy, Jr., of the National Bureau of Standards, and John Rosholt of the 

Geological Survey measured the radium content of our 

samples.

OCCURRENCE OF CARNOTITE, TYUYAMUNITE, AND 

METATYUYAMUNITE

Several distinct occurrences of carnotite, tyuyamunite, and metatyuyamunite can be observed in the field 

and laboratory. These occurrences are:

1. Secondary uranyl vanadates locally replace woody 

material such as branches and trunks of trees and 

"trash piles" of organic material. Some of these 

occurrences are very rich in uranium and samples 

with as much as 35 percent uranium may be obtained 

with little purification. Cellular structure of these 

woody materials is no longer visible in thin sections 

although in the field the general treelike shape is still 

evident. Age determinations by the lead-uranium 

method of this type of occurrence of carnotite, tyuyamunite, and metatyuyamunite as a rule give Tertiary 

ages but not Quaternary ages.

2. Some of the secondary uranium minerals from the 

Colorado Plateau impregnate clay pebbles of various 

sizes and shapes. These clay pebbles are of varying 

uranium content and some are very high grade. 

These occurrences, in general, give lead-uranium ages 

no older than Late Cretaceous but not as young as 

Quaternary.

3. A large portion of the secondary ore is disseminated 

in sandstone. These ores are believed to be the result

of oxidation essentially in place accompanied or followed by some leaching. The lead-uranium ages of 

these samples are variable.

4. Coatings of carnotite and tyuyamunite or metatyuyamunite on joints and fractures are relatively rare and 

make up a very minor amount of the secondary uranium ores of the Plateau. The geologic evidence indicates they are of Quaternary age.

RADIUM-URANIUM EQUILIBRIUM 

CONDITIONS FOB, EQUILIBRIUM

Radium-uranium equilibrium is established when the 

rates of radium formation and decay are equal. Ninetynine percent of radium-uranium equilibrium is attained 

in approximately 500,000 years (Knopf, 1931, p. 110) 

assuming Th230 was not present at the time of deposition. The isotopes of uranium, U235 and U238, decay 

through two series of radioactive nuclides to the radium isotopes, Ra223 and Ra226, respectively, which in 

turn decay through a number of radioactive nuclides 

to the stable end products Pb207 and Pb206, respectively. 

The contribution of the actinium series (U236 ) to the 

radium content in the samples is negligible and therefore, this series will not be considered in the discussion 

that follows. Figure 1 is a curve of the age in years 

plotted against percent Ra226 and U238 equilibrium 

for the range 10,000 to 500,000 years.

If a uranium mineral contains less radium than required by the equilibrium ratio 3.32 X 10~T g Ra^Vg 

U238, two explanations are possible:

1. The mineral has been unaltered since deposition, and 

its age is less than 500,000 years.

2. The mineral has been influenced by selective leaching of Ra228 , Th290, or enrichment of uranium, or all 

three, and the radium-uranium age of the mineral is 

indeterminate but the leaching or enrichment has 

taken place within 500,000 years. 

Only those samples with essentially no radiogenic 

lead can be given meaningful radium-uranium ages, for 

the absence of such lead is the clue that uranium in 

these samples has migrated away from its former location. In addition it must be assumed that all the Th230 

and Ra226 present has been produced since the redeposition of the uranium. Finally, the geologic evidence 

for lack of post-mineral leaching must be established. 

In pyritic environments uranium ores can also depart 

from equilibrium in the direction of a large excess of 

radium caused by preferential leaching of uranium 

(Phair and Levine, 1953, p. 358). However, to the 

authors' knowledge large excesses of radium are uncommon in the various occurrences of secondary minerals 

from the Plateau, suggesting that this type of alteration is unusual.
RADIUM-URANIUM EQUILIBRIUM AND RADIUM-URANIUM AGES, SECONDARY MINERALS 153

600,000 - 

500.000 -

400,000 - 

300.000

200,000

<*

100.000

90.000

80.000

70.000

60.000

50.000

40,000

30,000

20,000

10,000

10 20 30 40 50 60 70 80 90 100

Radium-uranium equilibrium,in percent

FIOOBE 47. Age in years as a function of percent radium-uranium 

equilibrium.

PBEVIOI7S WOBK

In the study of the variation of the radium-uranium 

ratio in minerals other than pitchblende, Boltwood 

(1904, 1908) and McCoy (1904, 1905) found that carnotite did not show any abnormalities. Mile. Gleditsch (1911) and Marckwald and Kussell (1911a, p. 

771; 1911b) found, however, that small samples of 

carnotite were appreciably deficient in radium.

Lind and Whittemore (1915) have published the only 

detailed study of the radium-uranium ratio in Colorado 

Plateau carnotite. They found that in samples of a 

few hundred pounds to several tons the ratio was in 

agreement with that of pitchblende, whereas small samples of a few pounds or less exhibited abnormal ratios. 

In one small sample the ratio was 25 percent deficient 

and in another 39 percent in excess of the normal ratio 

for pitchblende. The fact that abnormal radiumuranium ratios, both high and low, occurred in samples

representative of small quantities of ores, and that all 

samples from bulk specimens of ores showed normal 

radium-uranium ratios, was interpreted as an indication of local reconcentration of radium within the ore 

body rather than removal of the radium by leaching.

BADIUM CONTENT OF UNOXIDIZBD URANIUM ORBS

It is reasonable to expect that samples of massive, unleached uraninite would be essentially in radiumuranium equilibrium. At the present time, however, 

only two samples of unoxidized Colorado Plateau 

uraninite have been examined indirectly for their 

radium-uranium ratio. Senftle, Stieff, Cuttitta, and 

Kuroda (1957) have determined that the Ra^yRa226 

activity ratio for samples of uraninite from the Happy 

Jack mine and Mi Vida mines, San Juan Co., Utah to 

be 0.048. This agrees with the value of 0.048 for the 

Ra223/Ra22C activity ratio determined by Kuroda for 

Great Bear Lake uraninite which is in radioactive 

equilibrium. For samples of secondary minerals from 

the Colorado Plateau, Kuroda (1954, p. 10) determined 

Ra223/Ra226 activity ratios of from 0.0441 to 0.131. He 

interpreted this variation as a variation in the U235/U238 

ratio. However, mass spectrometric analyses of the 

uranium present in a selected group of secondary 

Colorado Plateau samples do not show any 

variation greater than 0.8 percent in the TJ235/U238 

ratio (Senftle, Stieff, Cuttitta, and Kuroda, 1957). 

The variation in the Ra223/Ra226 activity ratio is here 

interpreted to be the result of recent preferential leaching of daughter elements during oxidation and is a 

consequence of the relatively shorter time required for 

Ra223 compared to Ra226 to return to radioactive 

equilibrium.

BADIUM CONTENT OF OXIDIZED URANIUM OBE

Of the 10 samples of oxidized uranium ore tabulated 

in table 1 containing more than 0.1 percent lead, 7 are 

deficient in radium when compared with the equilibrium amount. Three of the samples are in equilibrium 

within experimental error. As these 10 samples contain 

radiogenic lead they should not be dated by the radiumuranium method. These radium analyses are consistent 

with those reported for small samples by Lind and 

Whittemore (1915) and those reported by Gleditsch 

(1911).

As a rule, the near-surface occurrences of metatyuyamunite and carnotite have the greatest radium deficiencies. However, even samples collected from underground occurrences may show large radium deficiencies. 

For example, samples from the Club mine (Nos. 61, 62, 

and 63) were collected within 30 feet of each other and 

have essentially the same Pb206/U238 age of about 70
154 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 1. Radium-uranium content of some high-grade lead-bearing carnotite and metatyuyamunite samples

Sample No.

9...................

13.. ...... .......

19. ......... . .......

20...... .........

25. .......

28..... ... ...... ....

61..... .............

62....... ...........

63. .............

64........ ..........

Type of 

occurrence l

2,3,4

2

2,3

2,3

2

2

2

1

2

2,3

Locality

.....do... ._..-.... . ... . ..

__ do __ _________________________

 do... ____ . ...

Mineral

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

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

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

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

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

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

Average 

U 

(percent)

37.9

31.1

21.7

32.6

32.5

36.0

32.2

14.8

25.4

34.6

Theoretical 

gRa/g 

sample » 

(XlO-s)

12.6

10.3

7.20

10.8

10.8

12.0

10.7

4.91

8.43

11.5

Experimental 

gRa/g 

sample * 

(XlO-s)

7.62

8.53

7.36

11.3

10.6

11.1

8.64

1.78

7.19

8.45

Percent radiumuranium 

equilibrium

60

83

2

excess 

5

excess 

98

92

81

36

85

73

1 These numbers refer to the numbers given under the heading "Occurrence of 

carnotite, tyuyamunite, and metatyuyamunite" on p. 152.

2 Computed from g Ra/g U in equOibrium=3.32X10-' g Ra/g TJ. 

s Prepared for analysis by R. G. Rice and counted under direction of L. S, Stockman, National Bureau of Standards.

Sample 9. Shinarump member of the Chinle formation. The sample was collected from a freshly blasted face of the open cut. The tyuyamunite and metatyuyamunite are found as coatings on the joints and fractures, as disseminated material 

in the sandstone and conglomerate, in thin veins of very pure material, and as 

tyuyamunite and metatyuyamunite replacements of clay pebbles. The sample was 

covered by a minimum of 6 to 10 feet of sandstone and probably was protected from 

extreme weathering.

Sample 13. Salt Wash sandstone member of the Morrison formation. Sample 13 

was taken from a small pocket of very high grade carnotite with corvusite approximately 140 feet inside the portal of the lower haulage adit. The field relations of 

sample 13 strongly suggest that the mineralizing solutions were controlled by a small 

joint. In comparison to the Jo Dandy mine sample given in table 2, this sample is 

well protected from the effects of weathering.

Samples 19 and 20. Salt Wash sandstone member of the Morrison formation. 

Sample 19 was collected from a pillar at the mine portal and should be representative 

of the effects of moderate weathering. The metatyuyamunite occurs as a clayey seam

million years. Their radium-uranium equilibrium 

ranges from 36 to 85 percent. Such deficiencies are believed to be the result of preferential leaching processes 

which have removed either radium or its longer halflived radioactive parent, Th230. The differences in 

radium deficiency may reflect relative accessibility of 

the samples to the leaching solutions.

In summary, the radium-uranium equilibrium of carnotite and metatyuyamunite, which occur as replacements of woody material or as impregnations of clay 

or as disseminations in sandstone, is variable and is 

probably related to the habit and to local geologic factors such as distance from the surface of the ground 

and porosity and permeability of the surrounding rock. 

On the other hand, the deposition of crystalline carnotite and metatyuyamunite on joints and fractures is 

recent and the lack of radioactive equilibrium may be 

a result of the short time that has elapsed since the 

formation of the minerals.

In recent work Garrels and others (Part 15 of this 

volume) give a comparison of the uranium and equivalent uranium determinations for specimens from a channel sample from the Mineral Joe mine. These measurements show general agreement for each sample 

indicating that the channel sample is in radioactive 

equilibrium in spite of marked differences in extent of 

oxidation from sample to sample. This is evidence 

supporting the conclusion that uranium or radium has 

not been leached from the channel sample.

as much as 1 inch thick and also as disseminated material. The carnotite in sample 20 

was taken from a pillar approximately 100 feet inside the portal where the carnotite 

occurs both in small pockets and as disseminated material. This sample was overlain by approximately 30 feet of sandstone.

Samples 25 and 28. Salt Wash sandstone member of the Morrison formation. The 

deposit is reached by an incline. Sample 25 was collected from a clayey seam of 

carnotite in the back of a small drift approximately 25 feet from the foot of the incline. 

Sample 28 was taken from another clayey seam in the back of a stope approximately 

160 feet from sample 25.

Samples 61, 62, and 63. Salt Wash sandstone member of the Morrison formation. 

All three samples were collected from a small stope approximately 200 feet from the 

entrance to the upper workings of the mine. Samples 61 and 63 were collected from 

a clayey seam near the back and on the opposite sides of the stope. Sample 61 was 

collected slightly lower in the formation than sample 63. Sample 62 was collected 

from the back near the middle of the stope. This sample seemed to be a carnotite 

replacement of a crushed log.

Sample 64. Salt Wash sandstone member of the Morrison formation. The deposit 

has been developed by an incline. The sample was obtained from the first drift 

to the left down the incline. Close to the sample location, the deposit was overlain 

by about 10 to 15 feet of sandstone. The sample was taken from a rich pocket of 

clayey carnotite and corvusite. The carnotite is disseminated or occurs in thin 

clayey seams.

RADIOCOLLOIDS

If recent movement of radium within the ore body 

has occurred, the Plateau deposits might be expected 

to contain radium-bearing barite, (Ba,Ra)SO4, and, 

in fact, they do. This highly radioactive mineral is 

formed by the coprecipitation of radium and barium 

sulf ate. It is possible that the radium would exchange 

with the barium in barite as it moved through the 

sandstone in the ground waters so that these radiocolloids might actually be formed more or less continuously. Unless continuously deposited, radiocolloids 

local concentrations of radium would be apparent for 

only about 15,000 years after formation because of the 

relatively short half-life of radium226 (1,620 years). 

These radiocolloids are additional evidence, therefore, 

of a recent alteration of the radioactive equilibrium.

RADIUM CONTENT AND RADIUM-URANIUM AGES OF 

SECONDARY URANIUM MINERALS

The calculated radium-uranium ages for four samples of carnotite and metatyuyamunite from the Colorado Plateau containing less than 0.01 percent Pb determined by the Geological Survey together with the 

earlier result of Hess and Foshag are given in table 2. 

These samples are carnotite or metatyuyamunite. 

Their ages range from 10,000 to 120,000 years. The 

spread in ages from 10,000 to 120,000 years is real providing that there has been no postmineralization leaching and no Th230 or Ea226 was deposited with the sam-
RADIUM-URANIUM EQUILIBRIUM AND RADIUM-URANIUM AGES, SECONDARY MINERALS 155

TABLE 2. Radium-uranium content and radium-uranium ages of some high-grade carnotite and metalyuyamunite containing less

than 0.01 percent lead

Locality Mineral

__ do _ . _______________

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

U

(percent)

"27.2

'20.0

852.0

» 56. 6

54.6

Theoretical, 

gRa/g 

sample (XlO-s)

9.03

6 64

. 0. 184

0.186

Experimental, 

gRa/g 

sample (X10-8)

'2.60

3.461

« . 108'

« . 0333

/ . 1244

\ .1269'

Percent radiumuranium 

equilibrium

 90

7

62

18.

\ R7

/ 67

Ra/U age

40, 000

10,000

105, 000

24, 000

120, 000

' Average of four determinations: two by L. R. Sttoff, M. N. Oirhard, and T. W. 

Stern. U. S. Geological Survey, and two by W. A. Peavey, Jr., National Bureau of 

Standards.

» Analyst: R. O. Rice, National Bureau of Standards.

«Analyst: A. M. Sherwood, U. S. Geological Survey.

* Analyst: John Rosholt, U. S. Geological Survey.

« Hess, P. L., and Foshag, W. P., 1927, Crystalline carnotlto from Utah: U. S. Nat. 

Mus. Proc., v. 72, art. 12, p. 1-6.

Parco mine. Salt Wash sandstone member of the Morrlson. formation. The 

sample was collected from coatings of carnotlto found on the surface of joint blocks 

at the entrance to the mine and from blocks of sandstone found on the mine dump.

Jo Dandy mine. Salt Wash sandstone member of the Morrlson formation. This 

sample was taken from a completely unprotected outcrop of very friable mineralized

pies. If uranium has been leached from these carnotite 

and metatyuyamunite samples, the measured radiumuranium age would be older than the actual age of the 

mineral. Hess and Foshag (1927) found that crystalline carnotite from the Bridger Jack Flat, Cane 

Springs Pass, Utah, is 32 percent deficient in radium. 

The radium-uranium age of this material, using the 

currently accepted time required to reach radiumuranium equilibrium is approximately 120,000 years. 

The young ages are apparently a result of Quaternary 

deposition of carnotite and metatyuyamunite after the 

water table was lowered and the deposits oxidized. The 

field relations also strongly indicate that these joint 

and fracture coatings have been recently deposited and 

are related to the present erosion surface. The source 

of the metals in those secondary coatings was the unoxidized vanadium and uranium ores whose age is 

thought to be not greater than 75 million years (Stieff, 

Stern and Milkey, 1953, p. 1; Stieff and Stern, 1952). 

These Quaternary ages give the approximate time for 

the oxidation of the particular deposits.

These Quaternary ages were determined on local reconcentrations of carnotite and metatyuyamunite which 

formed after the water table was lowered and the deposits were oxidized; the ages give a minimum time for 

oxidation of the particular deposits.

SUMMARY

Methods of determining the time of Quaternary alteration of the oxidized Colorado Plateau uranium ores 

are here suggested. First, there is a group of uranium 

ores which appear to have been oxidized in place. These 

ore samples contain significant amounts of radiogenic 

lead yet they are not in radium-uranium equilibrium. 

It is assumed that these samples were in radiumuranium equilibrium until oxidation and Quaternary

468,052 59 11

sandstone In an open cut leading to the lower haulage adit of the mine.

May Day mine. Salt Wash member of the Morrison formation. The sample was 

taken from a joint surface at the portal of the mine. This metatyuyamunite formed 

on gypsum and was coarsely crystalline.

Small Spot mine. Salt Wash sandstone member of the Morrison formation. This 

sample of coarsely crystalline metatyuyamunite had formed on gypsutn which filled 

a fracture in the sandstone. The sample was found In the ore bin and no Information 

concerning Its exact location within the mine Is available.

Bridger Jack Flat. Salt Wash sandstone member of the Morrison formation. 

Hess and Foshag (1927) describe this sample, thus: "The mineral formed compact 

crusts one to two millimeters thick and 15 to 20 centimeters broad on the walls of 

narrow cracks. Where the crusts did not entirely fill the cracks the exposed surface 

had a dull greenish color and showed indistinct crystal terminations."

leaching selectively removed some of the radium or 

thorium230 present. The time at which the selective 

leaching took place cannot be calculated from the 

radium deficiency. However, the fact that radiumuranium equilibrium has not been reestablished sets an 

upper limit of approximately 500,000 years for this 

leaching process. This disequilibrium can also be explained by the recent addition of uranium but this explanation in the case of the Plateau ores is not believed 

likely.

Secondly, uranium essentially stripped of its daughter products has been redeposited on joints and fractures 

as coatings of metatyuyamunite and carnotite. These 

coatings contain only trace amounts of lead and are not 

in radium-uranium equilibrium. Assuming that the 

Th230 and Ra228 present have been produced since the 

formation of the minerals, the radium-uranium ages 

calculated from their disequilibrium range from 10,000 

to 120,000 years. These ages indicate that some Quaternary redistribution of the uranium in the Colorado 

Plateau deposits has occurred after their oxidation. 

Finally, local concentrations of radium sulfate coprecipitated with barium sulfate are present in some oxidized deposits. These concentrations of radium are apparent for only about 15,000 years after their formation 

because of the relatively short half-life, 1,620 years, of 

radium226 and are another indication of Quaternary 

alteration of the uranium deposits.

REFERENCES

Boltwood, B. B., 1904, On the ratio of radium to uranium in some

minerals: Am. Jour. Sci., 4th ser., v. 18, p. 97-103. 

 1908, On the radioactivity of uranium minerals: Am.

Jour. Sci., 4th ser., v. 25, p. 269-298. 

Gleditsch, Ellen, 1911, Sur le rapport entre 1'uranium et le

radium dans les mineraux actifs: Le radium, tome 8, p.

256-273.
156 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Hess, F. L., and Foshag, W. F., 1927, Crystalline carhotite from

Utah: U. S. Nat. Mus. Proc., v. 72, art. 12, p. 1-6. 

Knopf, Adolph (Chairman), 1931, Physics of the earth. IV. The

age of the earth: Nat. Research Council Bull. 80. 

Kuroda, P. K., 1954, On the isotopic constitution of radium

(Ra223/Ra226 ) in uranium minerals, and recent problems of

geochronology: Univ. of Arkansas, Dept. of Chemistry,

unpublished report. 

Lind, S. C., and Whittemore, C. F., 1915, The radium-uranium

ratio in carnotite: U. S. Bur. Mines Tech. Paper 88. p. 1-28. 

Marckwald, W., and Russell, A. S., 1911a, Uber den Radiumgehalt einiger Uraherze: Deutsche chem. Gesell. Ber., Jahrg.

44, Band 1, p. 771. 

 1911b,. Tiber den Radiumgehalt von Uranerzen: .Tahrb.

Radioakt. Elektronik, Band 8, p. 457. 

McCoy, H. N., 1904, Uber das Entstehen des Radiums: Deutsche

chem. Gesell. Ber., Jahrg. 37, Band 4, p. 2641-2656.

 1905, Radioactivity as an atomic property: Am. Chem. 

Soc. Jour., v. 27, p. 391.

Phair, George, and Levine, Harry, 1953, Notes oh the differential leaching of uranium, radium, and lead from pitchblende 

in H2SO« solutions: Econ. Geology, v. 88, p. 358-369.

Senftle, F. E., Stieff, Lorin, Cuttitta, Frank, and Kuroda, P. K., 

1957, Comparison of the isotopic abundance of U235 and U238 

and the radium activity ratio in Colorado Plateau uranium 

ores: Geochim. et Cosmochim. Acta, v. 11, p. 189.

Stieff, L. R., and Stern, T. W., 1952, Lead-uranium ages of some 

uraninites from Triassic and Jurassic sedimentary rocks of 

the Colorado Plateau (Abstract) : Geol. Soc. America Bull., 

v. 63, p. 1299.

Stieff, L. R., Stern, T. W., and Milkey, R. G., 1953, A preliminary 

determination of the age of some uranium ores of the Colorado Plateau by the lead-uranium method: U. S. Geol. 

Survey Circ. 271.
PART 14. SOME QUANTITATIVE ASPECTS OF THE OXIDATION AND REDUCTION

OF THE ORES

By R. M. GARRELS and A. M. POMMER

CONTENTS

Page 

Abstract....-----------.--.-.---------------------- 157

Introduction ____________________--------__-__-__-__ 157

Oxidation of uranium ores.--.---------------------.-- 157

Pyrite_____-----.....-.--.-------------_---- 158

Chalcopyrite.....________.__-_-__.________.____ 158

Montroseite..__.______...____________.________. 158

Vanadium mica, vanadium hydromica, and vanadium chlorite_______________________________ 160

Summary of oxygen requirements.-.______---___._ 160

Oxidation of uranium ores Continued

Oxidation of a typical uranium-vanadium ore_... 

Reducing effect of woody materials__-___.__--_-_--.

Some aspects of wood chemistry.____-___--__.-..

Experimental determination of reducing capacities.

Amount of reducing agent required ___._.____.

Some typical reduction equations_____-_-______-.

Summary and geologic application_._.__---_-_______.

References. ___________________________--_-_---__-.

Page

160

161 162'

162

163

164

164

164

TABLES

Page 

TABLE 1. Summary of maximum oxygen demand for oxidation of some typical Plateau minerals_______--__-_----------__ 160

2. Reducing capacity of wood and lignite_____-_--_--__-__________________--___________------------------_ 162

3. Amount of reducing material required for the deposition of some reduced minerals from oxidized solutions. ______ 164

ABSTRACT

Equations illustrating the oxidation of many minerals of the 

ores are presented, and the "oxygen demand" for complete oxidation of a representative uraninite-montroseite-pyrite-vanadium clay ore Is calculated. Approximately 100 to 150 pounds of 

oxygen are required per ton of ore. From considerations of the 

rate at which oxygen can be supplied by ground water as opposed to that from air circulation in unsaturated rocks, it is concluded that significant oxidation below the water table is not 

likely.

Experiments on the reduction of qulnquevalent vanadium 

solutions by fresh Norway spruce and a North Dakota lignite at 

120° to 150° 0 show that both materials are effective reducing 

agents. Their experimentally determined reducing capacity in 

runs lasting a few days is approximately half the theoretical 

reducing capacity calculated on the assumption of complete oxidation to COa and H2O. The conclusion is reached that about 

0.5 weight percent of lignite is sufficient to form a typical 

uranium-vanadium ore by reduction of uranium (VI) and vanadium (V) or (IV) in solution to uraninite and montroseite, 

respectively. Subbitumlnous or higher rank coals may be expected to behave in a similar fashion.

INTRODUCTION

The mineralogic and chemical changes during oxidation of the Colorado Plateau uranium deposits are now 

known in considerable detail. The primary ore minerals are chiefly low-valence uranium, vanadium, iron 

and copper compounds. In the first part of this paper 

the probable chemical reactions that occur during oxidation are assembled, and estimates are made of the 

quantitative oxygen requirements for maximum alteration of a typical ore. The latter part is devoted to 

study of a process that may have been important in ore 

deposition, namely, the reducing effect of woody materials.

We are grateful to G. J. Jansen who worked with 

us on the high-temperature experiments; to C. A. 

Kinser for his help with the glass blowing; to I. A. 

Breger who gave us samples of wood and lignite as well 

as chemical advice; to R. G. Milkey for infrared spectroscopy; and to J. C. Chandler for his capable assistance in the laboratory.

OXIDATION OF URANIUM ORES

Oxidation of uranium ores involves chiefly the oxidation of pitchblende (UO2 ), montroseite (VOOH), 

vanadiferous chlorite, vanadiferous hydromica, pyrite 

(FeS2 ), and chalcopyrite (CuFeS.). Many other minerals are present in small amounts from mine to mine, 

but oxidation of the six chosen probably constitutes

157
158 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

more than 90 percent of the oxygen demand. They 

serve also as examples for the other compounds. The 

oxidation equations, plus some of the subsequent reactions with wall-rock constituents, are given in sequence 

for the individual minerals. A few notes on the environment of oxidation are included.

PYRITE

Pyrite usually oxidizes to produce ferric oxide or hydrated ferric oxide. Jarosite is important locally: 

From the reaction :

2FeS2 +15/2 O2 +4H2O >Fe2O3 1 +8H++4SO4=

it is evident that every mol of pyrite produces 4 mols 

of hydrogen ion. If calcite is present, as is common, 

it is dissolved to give bicarbonate ion and calcium ion 

in solution :

8H+ + 8CaCO3 + 8Ca++

Some of the Ca++ commonly reacts with SO4~to give 

gypsum :

4Ca+++4SOr+8H2O >4(CaSO4 -2H2O).

Reaction with calcite tends, then, to give gypsum 

and a neutral or slightly alkaline solution with residual 

dissolved Ca**. If calcite is absent or sparse, the hydrogen ions may attack clay or feldspar. Little is known 

of the process in Plateau deposits, although it may be 

an important reaction.

The reaction to form jarosite requires K+ from the 

environment:

2K++6FeS2 +45/2O2 +15H2O »2KFe3 (OH) 6 (SO4) 2 +

Free acid is formed, as in the oxidation of pyrite to 

Fe2O3 , but each mol of pyrite produces 3 mols of hydrogen ion. It is probably necessary to use up most of 

the acid produced by reaction with minerals such as 

calcite, if jarosite is formed as a stable solid.

CHALCOPYRITE

In the oxidation of chalcopyrite, iron and copper are 

released when sulfide goes to sulfate. Iron is usually 

precipitated as ferric oxide or hydrated ferric oxide, 

whereas copper reacts with carbonate and hydroxyl ions 

to form, malachite or azurite. For chalcopyrite:

The Fe^ oxidizes to Fe+++ and hydrolyzes to ferric 

oxide:

2Fe+++l/2O2 +2H2O >Fe2

Cupric ion reacts with water and carbonate ion in solution to form malachite:

2Cu+++CO; +2H2O *Cu2 (OH)2CO3 +2H+. 

The overall reaction is:

2CuFeS2 +17/2O2 +CO 3 +4H2O -*Fe203 -|-

Cu2 (OH)2CO3 +4SO; +6H+.

MONTROSEITE

Montroseite oxidizes in a complex manner. Figure 

26, page 101, shows the minerals formed and some of 

the possible pathways. Here many of the individual 

reactions are given. They then can be used for calculation of oxygen demand for a given stage of oxidation 

along a desired pathway.

Montroseite to paramontroseite. As shown by Evans 

and Mrose (1955, p. 872), montroseite alters pseudomorphously to paramontroseite by loss of hydrogen 

from the structure :

2VOOH+ 1/2 O2-^2VO2 +H2O.

Montroseite to simplotite. Under slightly alkaline 

conditions montroseite may oxidize to the calcium vanadite simplotite, for at a pH of about 8 vanadium (IV) 

behaves as an anion. Direct oxidation is not likely; 

paramontroseite probably precedes formation of other 

vanadium (IV) species.

Paramontroseite may dissolve under slightly alkaline 

conditions and reconstitute to simplotite by combining 

with Ca++ :

4VOOH+O2 *4VO2 +2H2O 

4VO2 +2OH-+Ca++

Montroseite to duttonite. Duttonite, a vanadium 

(IV) hydroxide, has been recognized. It may form by 

solution of paramontroseite under either alkaline or 

acid conditions, with reprecipitation by neutralization. 

Paramontroseite may dissolve under the influence of 

acid from pyrite:

VO2 +2H+-^VO+++H2O.

Then reprecipitation by increase in pH would give : 

VO++ +2OH-^VO(OH)2 (duttonite).

Alternatively, simplotite might be converted to duttonite by decrease in pH:

CaV409+2H+ +3H2O-^4VO(OH)2 +Ca++.

Paramontroseite to mixed vanadium (IV) and (V) 

oxides. It appears that paramontroseite is the most
SOME QUANTITATIVE ASPECTS OF OXIDATION AND REDUCTION OF ORES 159

common first oxidation product of montroseite and that 

further oxidation reactions probably involve paramontroseite more frequently than duttonite or simplotite. 

Under neutral or acid conditions part of the vanadium 

(IV) apparently oxidizes to vanadium (V) containing 

anions, which react with the vanadyl ion (VO++) to 

form vanadyl vanadates. The formation of many compounds is possible, and many actually do form as indicated by the complex corvusite group of mixed vanadium (IV) and (V) oxides. The summary equation of 

a typical reaction might be:

12VO2 -!-H20+5/2 O2-^V204-5V205 -H2O.

According to the postulated mechanism the reaction 

takes place in two steps. First, some of the paramontroseite is oxidized to a vanadate ion:

10V02 +3H2O+5/202-^H2V10O28 -4 -f4H+.

The reaction of some of the remaining paramontroseite with water produces some vanadyl ions:

2VO2 +2H2O >2VO++ +4OH-.

Then the vanadyl ion combines with the vanadate ion 

to form vanadyl vanadate (a member of the corvusite 

group):

2VO++ +H2V10028 -4- »(VO)2 (H2V10028) or 

V2 04 -5V2O6 -H2 0.

The great variety of species possible becomes evident 

when it is considered that VO+ ion might react with 

H2V1002 8"4 as indicated, or with H3VioO28~2 , as well as 

with such vanadate ions as V4Oi2~4, HV4Oi2~3 , or 

H2V4Oi2~2, to mention but a few (see Part 7 for discussion of vanadate ion relations). However, most 

combinations in the neutral or acid range would be expected to produce compounds with a V2O5 /V2O4 ratio 

of 3 or higher, the ratio increasing with decreasing pH.

Paramontroseite to 'metal vanadite-vanadates. The 

reactions to form mixed vanadium (IV) and (V) compounds so far discussed involve reaction between V"4 

as a cation (V0++ ) and vanadate ions. Inasmuch as 

vanadium (IV) also occurs as anions in such minerals 

as simplotite (CaV4O9 ), there is a possibility of 

forming compounds by reaction among metal ions, 

vanadite ions (V4 09~2 or HV4O8~1 ), and vanadate ions. 

Again the probable complexity is apparent. However, a typical reaction might be described in steps. 

First, paramontroseite could react with hydroxyl ions 

to form vanadite ions:

4V02 +OH-->V4(V2 +H+.

Also, paramontroseite could be oxidized to a vanadate 

ion:

6VO2 +3/2 O2 +3H2O-^2H2V3O9- 1 +2H+.

The metal ions, such as calcium, could combine with 

the vanadite and vanadate ions to form a mineral such 

as melanovanadite :

2Ca+++V409-2 +2H2V309- 1 -^Ca2 (V409 )(H2V3Ofl) 2 . 

This also can be written as

2CaO 2V2O4 3 V2O5 2H2O.

In general, such metal vanadite-vanadates have a 

lower ratio of V2O5/V2O4 than the vanadyl vanadates 

and probably form at higher pH (Part 7).

Paramontroseite to metal vanadates. With sufficient 

oxygen available, the complex of mixed vanadium 

(IV) and (V) compounds is oxidized completely to 

metal vanadates, such as hewettite, hummerite, 

pascoite, and rossite. Overall reactions are presented 

for the oxidation of paramontroseite to some of the 

chief metal vanadates. 

For paramontroseite to hewettite :

6VO2 +Ca++ +3/2O2 +10H2O-^CaV6O16 .9H2O+2H+. 

For paramontroseite to hummerite:

10VO2 +2K++2Mg+++5/2

K2Mg2V10O28 - 16H20 + 6H+.

Montroseite to metal vanadates. The overall reaction from montroseite to metal vanadates shows the 

total oxygen demand. The change to hewettite is 

typical :

6VOOH+3O2 +7H2O+Ca++->CaV6O16 .9H2O+2H+ .

Pitchblende and montroseite to carnotite. The overall reaction from original pitchblende and montroseite 

to carnotite is :

K+H-UOz+VOOH+Oa+a to

K(U02 )(V04)-(1 to 3)H2O+H+.

One mol of pitchblende and one mol of montroseite 

thus require one mol of oxygen to form one mol of 

carnotite.

, Uraninite to uranyl carbonate, sulfate, or silicate. 

In the presence of excess vanadium, oxidation of pitchblende yields only carnotite or tyuyamunite. If 

vanadium is absent, uranyl carbonates, silicates, or 

sulfates may form. For all such uranyl compounds,
160 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

 the oxygen demand is ^ Mol 02 for each mol of pitchblende. A typical reaction is the oxidation of pitchblende to form bayleyite:

UO2 +l/2 O_+2Mg+++3CO3 °-f 19H20-> 

Mg2 (UO2 )(CO3 ) 3 -18H2O+2OH-.

VANADIUM MICA, VANADIUM HYDROMICA, AND 

VANADIUM CHLORITE

Details of oxidation of the vanadium silicates are 

not known, but some inferences can be drawn from the 

chemical analyses (Part 10). Vanadium mica 

(roscoelite) contains vanadium (III) and apparently 

is not altered at a finite rate by ordinary oxidation 

processes. Vanadium chlorite and vanadium hydrous 

mica are found by analysis to contain vanadium (IV) 

and a mixture of iron (III) and iron (II). According 

to Foster's interpretation (Part 10), the vanadium entered the structure as V (IV), in which case only 

enough oxygen would be used to change iron from 

Fe (II) to Fe (III). If, on the other hand, the iron 

and vanadium originally were Fe (II) and V (HI), 

the maximum oxygen demand would be that necessary 

to change the vanadium to V (IV) and the iron to 

Fe(III).

 The chemical formulas of the vanadium hydrous 

micas are complex, but the analyses (Part 10) can be 

approximated by:

[Al,Mg) 1 . 4 (V^Fe+2)o. 6 .][Si3. 5Alo. 5]0Jo(OH) 2 .

Thus the maximum oxygen requirement would be 

that necessary to change the (V+3, Fe+2 ) 0. 6 to 

(V+4, Fe+3 ) 0.e or about 0.15 mols O2. "Therefore, the 

oxygen demand ranges somewhere between zero and 

0.15 mols per mol of vanadium hydromicas. That for 

the vanadium chlorites is presumably about the same.

SUMMARY OF OXYGEN REQUIREMENTS

The amount of oxygen required for maximum oxidation of the various primary minerals of the Plateau 

ores is given in table 1.

Table 1. Summary of maximum oxygen demand for oxidation 

of some typical Plateau minerals.

Mineral

Pyrlte...... .................

Vanadium hydrous mlca...-

Oxidatlon products

FejOsand SO'.. ... ....- _ .

bonate.

Oxidized vanadium mica. .....

Mols Oz/per mol 

mineral

3W

4H

reactants).

M (approximately). 

0

OXIDATION OF A TYPICAL URANIUM-VANADIUM ORE

Consider the oxidation of an ore containing pitchblende 0.5 percent, montroseite 4 percent, vanadium hydromica 6 percent, and pyrite 6 percent by weight, with 

the remainder chiefly quartz and other unreactive 

detrital minerals. Each ton of ore contains 16.8 mols 

of pitchblende, 433 mols of montroseite, 456 mols of 

pyrite, and 146 mols of vanadium silicate. This figure 

must be considered a rough approximation because of 

the variability of the vanadium and iron content of 

the silicates.

The final result of natural oxidation might convert 

the iron of pyrite to ferric oxide, and the sulfide to 

sulfate; montroseite and pitchblende would oxidize 

to carnotite and the excess montroseite to hewettite. 

Assuming original V+3 and Fe+2 in the structure of the 

hydrous mica, the vanadium would be changed from 

trivalent to quadrivalent, and the iron from bivalent 

to trivalent.

The oxygen requirements can be determined from 

table 1.

Mols Oa required

17 mols pitchblende+17 mols montroseite______ 17 

416 (433-17) mols montroseite_________________ 208 

456 mols pyrite_______________________ 1710 

146 mols vanadium hydromica__ 21

Total mols Oa per ton of ore_______________ 1956

Total pounds 02 per ton of ore_______ 137

It is of interest to assess the two chief mechanisms by 

which oxidation can occur in terms of this oxygen requirement. Oxidation can be accomplished either by 

air moving in and out of damp rock or by oxygenated 

ground waters flowing through the ore. In the former 

case, oxidation would take place in a thin film of adsorbed water on the rock grains. In the latter, oxidation would take place below the water table, in the 

former above it.

Air is 21 percent by weight oxygen; thus it would 

require about 137/0.21 = 650 pounds of air for complete 

oxidation by a "breathing" or "moist air" process. At 

earth-surface conditions, 650 pounds of air occupy about 

250,000 liters, or about 8,800 cubic feet. A ton of ore 

occupies about 15 cubic feet; with 10 percent porosity 

it could accommodate about 1.5 cubic feet of air. Thus, 

for final oxidation the air in a given volume of ore 

would have to be changed 8800/1.5 = 5850, or about 

6,000 times.

On the other hand, if oxidation occurs below the 

water table through the agency of air-saturated water, 

about 8,000,000 liters of water would be required per 

ton of ore, for the solubility of air in water is only 

about 20 milliliters per liter, and its oxygen content is 

about 6 milliliters per liter.
161

In other words, about 280,000 cubic feet of water 

would have to pass through each ton of ore. Assuming 

10 percent porosity- and ideal permeability, this would 

mean refilling of the volume occupied by 1 ton 185,000 

times.

From these considerations it appears that "moist 

air" oxidation above the water table could be far more 

rapid than oxidation by air-saturated water below it. 

For example, if an ore layer 3 feet thick, of the composition assumed, occurred just below the water table, 

so that oxidation had to take place by air dissolved 

in the ground water draining downward through the 

ore, 56,000 cubic feet of water would have to drain 

through each square foot of surface to oxidize the ore 

completely (as illustrated below). The source of water, 

under the condition shown, would be rain.

Surface

::::::: :r Zone of aeration

Inasmuch as the amount of water now being added 

to the zone of saturation by rain is probably negligible 

because of loss by evaporation and transpiration, oxidation by such a mechanism is undoubtedly much slower 

than by circulating air.

Large volumes of water and long time intervals are 

involved if it is assumed that oxidation is by aerated 

water moving laterally through an ore-bearing layer. 

Under these circumstances the ore would have to be 

oxidized sequentially in the direction of water movement. Each linear foot of ore oxidized would require 

about 185,000 linear feet of water flow. At common 

rates of ground-water movement of a few feet per year 

in moderately permeable media, several million years 

would be required to oxidize an ore body a hundred feet 

long, even if the entering water were fully aerated.

Inasmuch as the reducing capacity of rocks is such 

that the oxygen content of ground water disappears at 

or near the water table, and as a result conditions below 

the water table are reducing, oxidation of ores beneath 

the water table must be extremely slow or lacking under 

all but unusual conditions of very rapid circulation.

In summary, oxidation of the Colorado Plateau 

uranium ores probably has taken place after the water 

table dropped below the ore zones.

Important, perhaps, is the demonstration of the difficulty of moving deposits by lateral migration of

ground water during the geologic past, when the rocks 

were saturated with water. If uranium and vanadium 

were moved, it appears unlikely that the process involved was an oxidation-transportation-reduction and 

deposition cycle, where laterally moving phreatic 

waters act as both oxidizing and transporting agents. 

The oxygen (or equivalent) demand for large-scale 

oxidation in water-saturated rocks is large, and ground 

waters are characteristically anaerobic.

The conclusion drawn is not new; long ago Spencer 

(1917) deduced that oxidation of copper ores under 

semiarid conditions takes place above the water table 

in a film of moisture on the mineral grains. Describing 

the copper deposits at Ely, Nevada, he says (p. 80-81):

By considering the'amount of oxygen that water can absorb by 

contact with the air under atmospheric pressure at 7,000 feet 

elevation and at the present mean annual temperature of the 

region, it is found that, even if precipitation in the past has 

been 25 percent greater than at present, and that as much as 

60 percent of the rainfall could have penetrated to the ore 

body, the oxygen required to oxidize 500 feet of ore like that now 

existing would require the contributions of rainfall during a 

period longer than physicists and geologists are willing to allow 

for the age of the earth. [Spencer assumed 60 million years 

at that time.] Although all the assumptions made tend to a 

minimum, the time required, as calculated in this way, is still 

so immoderately great as to demand a different hypothesis in 

regard to the manner in which oxygen has been delivered to 

the place of sulfide decomposition. It is thought, therefore, 

that a large part of the oxygen must have been derived from 

air that circulated through the oxidizing capping. * * * It would 

seem, then, that the greater part of the oxidization must take 

place when the sulfides are moist rather than when they are 

flooded. * * *

REDUCING EFFECT OF WOODY MATERIALS 9

It is well known that many reduced uranium ores are 

associated with woody material; impregnation and replacement of woody material by pitchblende, coffinite, 

montroseite, and pyrite in ore-bearing material are 

quite common. Is it possible that such ores were deposited by the reducing action of woody material upon 

oxidized mineralizing solutions carrying vanadium (V) 

and uranium (VI) ions?

Because interest here is in a quantitative appraisal of 

the reduction requirement, it becomes necessary to determine the reducing capacity of woody material, so 

that the amount of woody material necessary to produce 

a typical ore can be calculated. To do this it is first 

necessary to consider some aspects of the chemistry of 

woody material; as no experimental values of reducing 

capacity of woody material in solutions containing 

uranium (VI) and (or) vanadium (V) have been 

found in the literature, it was necessary to determine 

this factor experimentally, using conditions approach8 Extracted from a dissertation presented by A. M. Pommer to Georgetown University In partial fulfillment of the requirements for the degree 

of Doctor of Philosophy.
162 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ing the geological environment within the limits of the 

laboratory.

SOME ASPECTS OF WOOD CHEMISTRY

Wood usually contains moisture ranging up to 10 percent and a fraction of a percent ash (Lange, 1949). 

The dry matter contains 40-50 percent cellulose, 10-30 

percent hemicellulose, and 20-30 percent lignin. Cellulose and hemicellulose are polymers of glucose or its 

isomers. Some sugars of slightly different composition, 

such as xylose, are present, but they do not change the 

calculated results significantly and may be treated as 

glucose.

In the presence of a strong oxidizing agent glucose 

is decomposed according to the following reaction:

C6H12O6 +6O2-»6CO2 +6H2O

One mol (180 g) of glucose then requires 24 equivalents 

to oxidize it completely; it has an equivalent weight of 

7.5.

The cellulose monomer is C6H10O5 with a molecular 

weight of 162. For complete oxidation:

C6H10O5 +6O2->6CO2 + 5H2O

Thus cellulose or its monomer, assuming complete oxidation to CO2 and H2O, also requires 24 equivalents 

and its equivalent weight is 6.75. In other words 100 

grams of cellulose has a theoretical reducing capacity 

of 14.8 equivalents, or 14,800 milliequivalents.

The oxidation of ligniri is much more complicated. 

Klason (1920) postulated lignin to be a polymer of 

coniferyl alcohol or coniferyl aldehyde

OH

1OCH3

CH=CH CHO

and this belief is currently accepted by many (Gortner, 

1949). Assuming complete oxidation of the coniferyl 

aldehyde monomer to CO2 and H2O gives an equivalent 

weight of 4.05 and a reducing capacity of 24,700 milliequivalents per 100 g, almost twice that of cellulose, according to the reaction:

C10H10O3 +23/2O2-»10CO2 + 6H2O

If a formula for lignin proposed by Russell (1948) 

is used, the summary equation is:

C10H8O3 +21/2O2-»10CO2 +4H2O

The equivalent weight is 4.03 and the reducing capacity 

of 24,900 meq/100 g. These two examples illustrate 

that different proposed lignin structures do not differ 

greatly in reducing capacity.

We,have no assurance, of course, that cellulose or 

lignin are completely oxidized.

A series of experiments was carried out to determine 

the reducing capacity of wood. When wood is placed 

in an acidified solution of ammonium vanadate at room 

temperature and pressure, a green color is observed 

after a few days, indicating partial reduction of V(V) 

to V(IV). It also was possible to reduce V(IV) solutions to V(III) with wood at elevated temperatures. 

However, to simulate conditions in nature, experiments 

were run at 150° C, a temperature representing a consensus of several of our coworkers of the temperature 

of formation of the ores. Determinations of reducing 

capacity were carried out according to the following 

procedure: a 10-mg sample was placed together with 

10 ml 0.1 formal (VO2 ) 2SO4 solution containing an excess of free sulfuric acid and some Na2SO4 in a Pyrex 

tube, sealed, and heated at 150° C at an estimated pressure of 70 psi (ignoring the boiling-point elevation of 

the solution by the added electrolytes) for three days; 

at the end of the run the reduced vanadium was titrated 

potentiometrically. Any remaining sample was recovered, washed, dried, and weighed. (See table 2.) 

From the data two sets of reducing capacity values 

were obtained. The first set is the milliequivalents of 

vanadium reduced per 100 grams of original sample, 

the second set is the milliequivalents of vanadium reduced per 100 grams of wood or lignite decomposed 

(wood decomposed equals original sample minus solid 

residue).

TABLE 2. Reducing capacity of wood and lignite

Calculated reducing capacity 3 __ 

Experimental reducing capacity

Average experimental reducing capacity__

Experimental reducing capacity corrected

for insoluble constituents 5 ____-_____-

Average corrected reducing capacity 6 _ _ _ _ 

Average corrected reducing capacity expressed as percentage of calculated reducing capacity _________________

Wood ' Lignite '

(meg/100 g) (meg/100 g)

15800 14600

10300 5600

5100 6800

9700 8200

8400 6900

11300 8600

7100 8400

9200 8500

58 58

1 Fresh spruce (Picea excelsa Lk) containing 58 percent cellulose and 29 percent 

lignin (Varossieau and Breger, 1951).

' Lignite from the Beulah-Zap bed, Dakota Star mine, Mercer County, N. Dak., 

containing 41.2 percent moisture and ash (Analyst, E. T. Moore, U. S. Geological 

Survey).

' For details of calculation see text.

4 All reducing capacities were determined by potentiometric titration of the product obtained by heating a 10-mg sample with 10 ml of a 0.1-formal vanadium (V) solution acidified to a pH of 0.7 in a sealed Pyrex tube for 3 days at 150° C. All values 

were corrected for a blank (0.15 ml).

8 The undecomposed residue was isolated, washed, dried, and weighed, and the 

reducing capacity of the decomposed portion calculated. This was done on duplicate 

samples only owing to experimental difficulties on the triplicate run.

 This value was rounded off to 9000 in both samples for use in table 3.
SOME QUANTITATIVE ASPECTS OF OXIDATION AND REDUCTION OF ORES 163

As the experimental results were 58 percent of the 

calculated results, an attempt was made to obtain reducing capacities closer to the calculated value by extending the time of the run to 12 days. This attempt 

was not successful. Although it was possible to increase the reducing capacity of glucose under parallel 

conditions from 8900 meq per 100 g to an apparent 

10,000 meq per 100 g by increasing the heating time 

from 3 to 12 days, the reducing capacities of wood and 

lignite samples were of the same order of magnitude in 

the 3 day runs and in the 12 to 13 day runs, with some 

of the long runs giving slightly lower reducing capacities. There are two possible explanations for this 

phenomenon, both probably contributing simultaner 

ously: it was noted in the blank runs that the vanadate 

solution on heating gave a brown precipitate, which 

gave an X-ray pattern of V2O5 -H2O. If we consider 

that we have two competing reactions, one the precipitation of the vanadium (V) oxide which removes it 

from the reaction, and the other the reduction of the 

VO2+ ion by the slowly decomposing polymers of the 

woody material, it can be seen that relatively soon a 

point is reached where the concentration of vanadium 

(V) ions in the solution is so low that reduction becomes very slow and in effect ceases. The other reaction is the formation of high-carbon polycyclic compounds by partial degradation of the wood which loses 

hydrogen and oxygen atoms during oxidation and results in reaction products becoming increasingly more 

resistant to attack. In the case of glucose this phenomenon does not take place.

The calculated reducing capacities used in table 2 

were obtained as follows: The theoretical reducing capacity of a fresh spruce of the given composition is 

computed, assuming complete oxidation to CO2 and 

H2 0 and using the Russell formula for lignin. A 100-g 

sample contains 58 g cellulose with a reducing capacity 

of (0.58 x 14,800) 8600 milliequivalent (meq) per 

100 g; it also contains 29 g lignin with a reducing 

capacity of (0.29 x 24,800) 6700 meq per 100 g, giving 

a total reducing capacity of 15,300 meq per 100 g. The 

experimental value at pH 0.7 corrected for undecomposed matter is 9200 meq per 100 g, or 58 percent of 

the theoretical maximum value.

The reducing capacity of the lignite used is substantially that of wood; this was an unexpected result. The 

chemistry of lignite is little known, but Breger (1951) 

has presented evidence based on infrared spectra that 

the skeletal structures of humic acid and lignin are related and has suggested that they may even be identical. 

Let us now assume that the reducing capacities of 

lignin and humic acid are the same. Let us next assume that lignite consists of moisture, ash, and humic

acid only; we know that this is not quite correct, but 

this assumption would leave us with the same carbon 

content for lignite as for lignin. The carbon content 

of Russell lignin is 66 percent and its carbon-hydrogen 

ratio is 100: 7.4; both values are not markedly different 

from typical lignite values and our assumption may not 

be far off. Because our lignite has a moisture and ash 

content of 41.2 percent, it now is assumed to contain 

58.8 percent humic acid (reducing capacity 24,800 meq 

per. 100 g) and its reducing capacity assuming total 

oxidation is (0.588 x 24,800) 14,600 meq per 100 g. The 

experimental value of 8500 meq per 100 g then indicates 

either incomplete oxidation or the transition of some 

of the humic acid to fixed carbon, which is not too unlikely in a lignite. To investigate whether the oxidation of cellulose, lignin, wood, and lignite by vanadium (V) solutions proceeds to CO2 and H2O at least 

in part or whether it does not proceed at all beyond 

some intermediate state, the reaction products of these 

substances with vanadium (V) solutions were examined 

by infrared spectroscopy; carbon dioxide was identified in all samples (R. G. Milkey, analyst, written 

communication).

AMOUNT OF REDUCING AGENT REQUIRED

If primary ore was deposited by the reduction of solutions carrying quinquevalent vanadium and sexivalent 

uranium ions, it may now be possible to make rough 

estimates of the concentration of wood or lignite necessary for precipitation of a typical ore. Unfortunately, 

the requirement in terms of equivalents of reducing 

agent is not necessarily the same as equivalents of oxygen necessary to oxidize low-valent ore minerals as 

shown in table 1.

For oxidation the primary mineral assemblage is reasonably well known as are the oxidation products. It 

is not necessary to distinguish between minerals already 

present in the rock before ore deposition and those 

superimposed during mineralization. Any pyrite present in an ore body becomes oxidized eventually, whether 

it is syngenetic, diagenetic, or epigenetic.

Therefore, it may be instructive to calculate the 

weight percent of fresh spruce or lignite necessary to 

precipitate each ore mineral from aqueous solution by 

reduction from a specified ion.

In this connection it must be noted that it is impossible to make an intelligent allowance for pyrite. In 

the first place, it is impossible to make a valid correction 

for syngenetic or diagenetic pyrite, which must be deducted from the total pyrite in the ore. Also no accurate correction can be made for other sulfides or sulfur 

compounds in the organic matter available for the reduction of possible ferric iron carried in a mineralizing 

solution. Finally, in the absence of sulfide made avail408,652 58 -12
164 GEOCHEMISTRY AND MINEEALOGY, COLORADO PLATEAU URANIUM ORES

able by the woody material and free hydrogen sulfide 

fortuitously present in the system which of course also 

would reduce vanadium and uranium ions any pyrite 

sulfur must be produced by reduction of sulfate ions. 

Under 200° C, reduction of sulfate ions to sulfide or 

polysulfide in nature is known only in the presence of 

certain microorganisms for example, /Sporovibrio.

Table 3 is a compilation of data which, it is hoped, 

will enable its user to compute the amount of woody 

material required to precipitate an ore containing a 

given amount of montroseite, pitchblende, and vanadium clay. He can then judge whether the amount of 

carbonaceous material expected in the formation under 

consideration is sufficient to make this process probable.

It can be seen from the calculations that woody material 

can easily be present in sufficient amounts to deposit 

typical ore concentrations from oxidized solutions by 

reduction, but, of course, this does not hold in every case. 

Subbituminous and higher rank coals may be expected 

to behave like lignite.

SOME TYPICAL REDUCTION EQUATIONS

Finally, it may be of interest to demonstrate some possible reducing reactions by writing down some speculative equations showing the reduction of uranyl and 

vanadate ions by cellulose (represented by CeHioOs, its 

monomer). Of course, it is also possible to write similar 

reactions for lignin.

TABLE 3. Amount of reducing material required for the deposition of some reduced minerals from oxidized solutions

Mineral species formed

Pitchblende _________ ... .

V-chlorlte. ..... .... .... ...

 Formula

UOa 

VOOH

|.

Oxidized 

species in 

solution

uo*1-*-

VOi+ 

VOa+

Concentration of mineral species in sediment

ll Ib-ton of mineral.. . ______ ___ .........

U Ib/ton of U.. ..................................

1 wt percent of mineral _________ ..........

1 Ib/ton of mineral. -. ________ __ ........

lib/ton of V. -...... .........................

lib/ton of V... ... _. .

Fresh spruce or lignite required

Theoretical

Wt percent

0.048 

.002 

.055 

.002 

.15 

.008 

.25 

.013 

.034 

.002 

.25 

.013

Lb/ton

0.96 

.048 

1.10 

.055 

3.1 

.15 

5.1 

.25 

.68 

.034 

5.1 

.25

Percent 

C

0.022 

.001 

.025 

.001 

.69 

.004 

.11 

.006 

.015 

.003 

.11 

.006

Experimental

Wt percent

0.082 

.004 

.092 

.005 

.26 

.013 

.44 

.022 

.060 

.003 

.44 

.022

Lb/ton

1.6 

.082 

1.8 

.092 

5.3 

.26 

8.8 

.44 

1.2 

.060 

8.8 

.44

Percent 

C

0.037 

.002 

.040 

.002 

.12 

.006 

.20 

.010 

.027 

.005 

.20 

.010

i Molecular weight, 373.

NOTES. Values used in construction of table: "Theoretical" equivalent weight of 

wood or lignite, 6.5: this weight was obtained by averaging the equivalent weight for 

wood (6.3) and lignite (6.8) obtained from the calculated reducing capacities given 

in the text by the conversion formula; equivalent weight (in g) = 100000 .-reducing 

capacity (in meq/100 g). The "experimental" value was obtained from the rounded 

off reducing capacity of 9000 meq/100 g. Both the wood and the lignite contained 

about 45 percent C (actual values: wood 46 percent, lignite 42 percent). 1 percent 

V»0j=0.56 percent V; 1 percent U«Os=0.85 percent U.

Reduction of vanadium (V) ion to montroseite 

12 V02+ +C6H10O5 +7 H2O >12 VOOH.+ 12 H++6 CO2

Reduction of vanadium (V) ion to duttonite 

24 V02++31 H20-fC6H1005 *

6 CO2 +24 H++24 VO(OH) 2 .

Reduction of uranyl ion to pitchblende 

12 U02++ +CaH10O5+7 H2O * 12 U02+6 C02 +24 H+.

SUMMARY AND GEOLOGIC APPLICATION

It has been assumed that uranium and vanadium ores 

of the Colorado Plateau originally were in a reduced 

form and have been oxidized subsequently. This oxidation was carried on by moist air above the water table. 

The reduced ore may have been deposited either from 

reduced or oxidized solutions. In the latter case woody 

materials are a likely precipitating agent, and it is 

possible to appraise their sufficiency in a given environment from reducing capacities.

Sample calculation:

1. An ore contains 50 Ib/ton montroseite, and 100 Ib/ton pitchblende. 

What is the theoretical amount of lignite required for deposition? Answer: 50X 

0.15+100X0.048=12.3 Ib/ton or about 0.6 wt percent lignite.

2. Ore content: 2 percent VsO» and 0.5 percent TJsOs. Lignite required: 2X 

0.56X0.25+0.5X0.85X0.055=0.5 wt percent.

REFERENCES

Breger, I. A., 1951, Chemical and structural relationship of 

lignin to humic substances: Fuel, v. 30, p. 204-208.

Evans, H. T., Jr., and Mrose, Mary E., 1955, A crystal chemical 

study of montroseite and paramontroseite: Am. Mineralogist, v. 40, p. 861-876.

Gortner, R. A., 1949, Outlines of biochemistry: 3d .ed., New York, 

John Wiley and Sons, p. 742.

Klason, P., 1920, Beitrag zur Kenntnis der Konstitution des 

Fichtenholz-Lignins: Ber. deutsche chem. Gesell., v. 53B, 

p. 1864-1873; Uber Lignin und Lignin Reaktionen: Ber., 

v. 53A, p. 706-711.

Lange, N. A., editor, 1949, Handbook of chemistry: 7th ed., 

Sandusky, Handbook Publishers, p. 792.

Russell, Alfred, 1948, Interpretation of lignin. I. The synthesis 

of gymnosperm lignin: Am. Chem. Soc. Jour., v. 70, p. 

1060-1064.

Spencer, A. C., 1917, The geology and ore deposits of Ely, Nev.: 

U. S. Geol. Survey Prof. Paper 96, p. 80-81.

Varossieau, W. W., and Breger, I. A., 1951, Chemical studies on 

ancient buried wood and the origin of humus: Extrait 

du Compte Rendu, 3e Congres de Strat et de G6ol. du 

Carbonifere, Heerlen, p. 637-646.
Part 15. DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO

VANADIUM-URANIUM ORES 10

By R. M. GARBELS, ESPEE S. LARSEN 3o, A. M. POMMEB, AND R. G. COLEMAN

Abstract.__________________________________________

Introduction _______________--____________----__---_

Mineral Joe No. 1 mine channel sample.______________

Sampling. _____________________________________

Geology and gross appearance of the ore__---_-____

Mineralogy of the channel sample.____---__-_-_.

Chemistry of the channel sample.________________

Preparation of the samples___________________

Major constituents___-_-_-______----______

Uranium and equivalent-uranium relations.-... 

Trace-element relations..____________________

States of oxidation of the specimens._.__.---____._

Salient features of the Mineral Joe No. 1 mine 

channel sample._____--_-___-________--__-___

Page 

166

166

167

167

168

168

170

170

171

171

171

174

177

Page

Virgin No. 3 mine channel sample.___________________ 177

Location and geology__________________________ 177

Preparation of the sample___-_-__-___________- 177

Mineralogy of the channel sample.________________ 178

Weakly mineralized rock.__________________ 178

Strongly mineralized rock____________________ 179

Chemistry of the channel sample.________________ 181

State of oxidation of the channel sample__________- 181

Salient features of the Virgin No. 3 mine channel

sample ______________________________________ 183

Summary and conclusions_________-___-___._-_____- 183

References._______________-____-_--_--__-_---_._-_- 184

ILLUSTRATIONS

	Page 

PLATE 3. Photograph of channel sample from Virgin No. 3 mine.--_-_____________-__-__-_________-------_---_---__- 178

FIGURE 48. Sketch of the upper stopes of the Mineral Joe No. 1 mine._______________________________________________ 167

49. Sketch of the Mineral Joe No. 1 mine wall___________________-_____________-___________-_______________ 167

50. Graph showing distribution of several elements across the Mineral Joe No. 1 mine channel sample.___________ 172

51. Distribution of uranium, vanadium, and organic carbon.________________________________________________ 173

52. Plot of log U against log equivalent U_--__-_______------_-__--_--___-___-__________----------_-_-__-__ 174

53. Semiquantitative spectrographic analyses._____________________________________________________________ 175

54. Sketch of the workings of the Virgin No. 3 mine--__-_---____________-______________-_--_------________- 178

55. Mineralogic composition of specimens of the Virgin No. 3 mine channel sample.___________--_-_--________-- 179

56. Semiquantitative spectrographic analyses-____________---____-______--_-_-----___-_-_---------____-___- 182

TABLES

Page 

TABLE 1. Chemical analyses of specimens of the Mineral Joe No. 1 mine channel sample.______________________________ 171

2. Reducing capacities and vanadium and iron content of acid extracts of specimens from the Mineral Joe No. 1 mine

channel sample.--._________________________________________________________________________________ 176

3. Analyses of specimens from the Virgin No. 3 mine channel sample_________.________________________________ 181

4. Reducing capacities and vanadium, iron, and uranium content of acid extracts of specimens from the Virgin No. 3

mine channel sample_____________________________ _______________________________________________ 183

10 Dosed in part on a dissertation presented by A. M. Pommer to Georgetown University in partial fulfillment of the requirements for the degree of Doctor of 

Philosophy.

165
166 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ABSTRACT

Channel samples from two mines on the Colorado Plateau 

have been studied in detail both mineralogically and chemically.

A channel sample from the Mineral Joe No. 1 mine, Montrose 

County, Colo;, extends from unmineralized rock on one side, 

through a zone of variable mineralization, into only weakly 

mineralized rock. The unmineralized rock is a fairly clean 

quartz sand cemented with gypsum, and contains only minor 

amounts of clay minerals. One boundary between unmineralized and mineralized rock is quite' sharp and is nearly at right 

angles to the bedding. Vanadium clay minerals, chiefly mixed 

layer mica-montmorillonite and chlorite-montmorillonite, 

are abundant throughout the mineralized zone. Except in the 

dark "eye" of the channel sample, the vanadium clay minerals 

are accompanied by hewettite, carnotite, tyuyamunite, and probably unidentified vanadates. In the dark "eye," paramontroseite, pyrite, and marcasite are abundant, and are bordered 

on each side by a zone containing abundant corvusite. No recognizable uranium minerals were seen in the paramontroseite zone 

although uranium is abundant there. Coaly material is recognizable throughout all of the channel, but is most abundant in 

and near the dark "eye." Detailed chemical studies show a general increase in Fe, Al, U, and V, and a decrease in SO*= toward 

the "eye" of the channel. Reducing-capacity studies indicate 

that V(IV) and Fe(II) are present in the clay minerals 

throughout the channel, but only in and near the "eye" are other 

V(IV) minerals present (paramontroseite and corvusite). The 

uranium is everywhere sexivalent, although its state of combination is conjectural where it is associated with paramontroseite. 

Where the ore boundary is sharp, the boundary of introduced 

trace elements is equally sharp. Textural and chemical relations leave no doubt that the "eye" is a partially oxidized 

remnant of a former lower-valence ore, and the remainder of 

the channel is a much more fully oxidized remnant.

A channel sample from the Virgin No. 3 mine, Montrose 

County, Colorado, extends from weakly mineralized sandstone 

on both sides through a strongly mineralized central zone. 

The weakly mineralized zone is a poorly sorted sandstone with 

common detrital clay partings; chlorite and mixed layer micamontmorillonite are abundant interstitial to the quartz grains. 

No distinct vanadium or uranium minerals are recognizable, 

although the clay minerals are vanadium-bearing. Euhedral 

pyrite grains and selenian galena are present but rare. The 

strongly mineralized rock is separated from the weakly mineralized rock by a narrow transition zone which only approximates the bedding planes. It contains abundant vanadiumbearing clay minerals (predominantly chlorite) interstitial to 

the quartz grains, and apparently replacing them. Paramontroseite is common and is intergrown with the clay minerals. 

Pyrite and marcasite are present, chiefly in or near the abundant blebs and fragments of carbonaceous material. Selenian 

galena is rarely present, and generally in or near carbonaceous 

material. Coffinite is the only uranium mineral identified; it is 

extremely fine-grained and was identified only in X-ray diffraction patterns of heavy separates. Distribution of trace 

elements is not clear; some are consistently high in the strongly 

mineralized rock, and some are consistently low. The trace 

element composition of the unmineralized rock is not known. 

Chemical studies show a very abrupt rise in the total U, V, 

and Fe from the weakly mineralized to strongly mineralized 

rock. Reducing capacity studies indicate that most of the 

vanadium is present as V(IV), but some is present as V(V) ;

that iron is present as both Fe(II) and Fe(III), the latter 

believed to have been present in the primary clays of the unmineralized rock; and that some of the uranium is present as 

U(VI) in addition to the U(IV) in the coffinite. All evidence 

points to weak oxidation of an ore once having a somewhat 

lower valence state.

The channel samples from both the Mineral Joe No. 1 mine 

and the Virgin No. 3 mine are believed to have been essentially 

identical in mineralogy prior to oxidation by weathering: 

vanadium was present as V(III) in montroseite and V(IV) in 

the vanadium clays; uranium was present largely as U(IV) in 

coffinite and/or uraninite. The Mineral Joe No. 1 mine channel 

sample is now more fully oxidized.

Vanadium clays are unquestionably formed abundantly during the primary mineralization, and they persist with a minimum of alteration during much of the weathering. They suggest that the vanadium is carried as V(IV) in the ore-forming 

fluids; it seems likely too that the uranium is carried as a 

U(VI) ion.

INTRODUCTION

Until the last few years the uranium-vanadium ores 

in the developed "sandstone type" deposits of the Colorado Plateau contained chiefly carnotite (or tyuyamunite) and vanadium clays together with a host of minor 

uranium and vanadium minerals. Except in the clays, 

the uranium and vanadium were usually present in 

their highest oxidation state U(VI) and V(V). For 

lack of reason to think otherwise, these were commonly 

considered "primary" ores and ideas of their genesis 

were based on this concept. Recently, many so-called 

"black ore" deposits, both large and small, have been 

discovered and developed; these share many common 

geologic characteristics with the carnotite-bearing ores 

and differ primarily in the oxidation state of the contained uranium, iron, and vanadium. In some deposits, 

the carnotite ores grade at depth into the "black ores," 

and in others the two occur together. In the "black 

ores" U(IV) is common as uraninite and coffinite, and 

V(IV) and V(III) are common in hydrated oxides 

and hydroxides as well as clays.

These deposits containing lower-valence metals are 

now thought to be the "primary" ore from which the 

carnotite deposits were derived by oxidation during 

weathering (Garrels, 1955). Since some single deposits 

commonly contain high-valence ores that grade into 

low-valence ores, we felt it would be fruitful to study 

in detail the nature of the changes in the mineralogy, 

element distribution, valence state, and relation of host 

rock to mineralization in a channel sample crossing from 

one type of ore to the other. Moreover, since much less 

is known about the low-valence ores and their relation 

to host rock, we felt it desirable to study these in the 

same way, but less intensively. It was hoped that these 

studies might lead to a more specific knowledge of the
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 167

nature of the alteration of the ores, at least for the 

deposits studied. Results of the study of two channel 

samples are reported below.

We are indebted to John C. Hathaway, Jr., and 

Margaret D. Foster, for discussions on the character of 

the vanadium-bearing clay minerals. Howard T. 

Evans, Jr., and A. E. Flint assisted Garrels in selecting and collecting the channel sample from the Mineral 

Joe No. 1 mine. John C. Chandler assisted with the 

chemical laboratory work. Lillie B. Jenkins was of 

great help in selecting a consistent and reliable method 

for the determination of reducing capacity.

MINERAL JOE NO. 1 MINE CHANNEL SAMPLE

SAMPLING

After a reconnaissance of a number of mines an ore 

occurrence at the Mineral Joe No. 1 mine, Jo Dandy 

group, Montrose County, Colo., was selected for detailed work. The location of the sampling site is shown 

in figure 48, and a sketch of the ore occurrence, together with the sampling pattern, in figure 49. The site 

was chosen because it appeared possible to collect a 

continuous channel sample from unmineralized sandstone through a heavily mineralized zone that exhibited 

a variety of brown, yellow, and black colors presumably

^038

OCI

OMJI7

FIGURE 48. Sketch of the upper stopes of the Mineral Joe No. 1 mine; 

x indicates the site of the channel sample taken.

Barren sandstone

Mineralized sandstone 

Gypsum veins

Shale bed

Channel specimens

FIGURE 49. Sketch of Mineral Joe mine wall showing relation of channel sample to ore. The letters refer to the separate specimens which

made up the channel sample.
168 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

representing differences in oxidation state. It was not At the sampling site in the Mineral Joe No. 1 mine a

possible to get a continuous set of samples that crossed mineralized zone cuts across the flat-lying sandstone at

from unmineralized rock on one side of the mineralized a steep angle. The sandstone is overlain by a greenish

zone to unmineralized rock on the other side, but field shale bed which is irregularly mineralized. Figure 49

observation suggested that one end of the channel shows the general appearance of the ore in relation to

sample was in unmineralized rock, and the other end the channel taken. The following is a description of

of the channel was in weakly mineralized ground prob- the specimens along the channel: 

ably low in vanadium and uranium, but that all of the.

I'-ii . T i -i-i-i- XT r. Specimen Description more highly mineralized zone was included in the chan- nel. It was hoped that detailed study of the min- A- -- fUzseadndstone; fairly wel1 cemented ' unmin'

eralogy, oxidation state, and distribution of major and B _.__..... Weakly cemented sandstone; tan with brownish

minor elements all in relation to the host rock, would speckles; unmineralized.

provide more concrete data with which to consider the C_.--.____-_ Same as B, but with thin carbonaceous seams at

geochemical history of the ore. Before collecting the ^ kase of specimen,

. ,1 , i <? 11 -j.1 D_________ Similar to B; speckles less prominent. specimens, the entire working face was cleaned with a E Do

wire brush. No marked difference was seen between the F._______.__ Edge of mineralized zone; half of specimen is

exposed surface of the sample area after wire brushing light-buff sandstone; other half is dark yellowand the face freshly exposed by channeling. Most of ish brown; boundary is quite sharp,

the specimens were obtained as unbroken rock units; G - - Yellowish-brown sandstone; heavily mineralized;

f r i i , i T contains reddish-brown patches, probably

a few were broken into several pieces during sampling. hewettite

Only specimen I had to be collected as an incoherent H_________ Same as specimen G; cut by 8-mm seam of

mass. It is estimated that the specimens are essen- coarsely crystalline gypsum.

tially as satisfactory as a single unbroken piece of I---- Soft, largely incoherent yellow-brown sand.

i J_._________ Mottled yellowish to reddish brown coherent ore.

', ,. . .,.., . K_________ Strongly fractured zone; mottled yellow and

In the laboratory, the individual specimens were brown . surrounded and impregnated by gypsawn in two along a horizontal plane parallel to the sum. 

line of the channel. One half of each sepcimen was re- L ____ Friable yellow ore; considerable organic matter

tained for mineralogic work, the other for chemical alonS bedding planes; few seams of hewettite.

tests. No water was used in any of the processing steps M- M^ ore; brown, yellow, with small nodular

_, i 1*1* DlfliCK H1&SS6S. such as sawing, grinding, or polishing. N___________ Black dense ore forming coarse irregular masses

	in brownish matrix. 

GEOLOGY AND GROSS APPEARANCE OP THE ORE Q______._ Black ore, apparently corvusite, forming small

mi » * T T j/i T T\ j irregular masses in bleached-looking sandstone. The Mineral Joe mine is in the Jo Dandy group, Bougnded sharply by nam)w gypgum geam

which has been described briefly in an unpublished re- p......._._. Friable bleached carbonaceous sandstone; carries

port by E. M. Shoemaker in 1950. The Jo Dandy group some yellow minerals near gypsum band.

lies on the south side of Paradox Valley, a structural Numerous coaly seams.

valley developed in the crest of a salt anticline. Nar- Q - Light colored, friable, carbonaceous sandstone;

P i, u-i i j T- j.i ^ j.- T- -j not evidently mineralized. 

row fault blocks, caused by the solution or subsidence

of salt and gypsum of the underlying Paradox member MINERALOGY or THE CHANNEL SAMPLE 

of the Hermosa formation of Pennsylvanian age, form

the south side of the Valley; many of the deposits are Essentially unmineralized sandstone is represented in 

faulted, but the beds remain essentially flat-lying. The the channel sample by specimens A through E (fig. 49). 

deposits occupy the uppermost sandstone lenses of the The rock is made up of subangular to poorly rounded 

Salt Wash member of the Morrison formation of Juras- quartz grains, very minor amounts of microcline, and 

sic age. Thin lenses of mudstone are interbedded with rare green tourmaline; varying but small amounts of 

the sandstone, and mudstone pebbles and pockets of clay aggregates both as tiny pellets and as stringers are 

plant remains are scattered through it. Certain un- common. The quartz carries euhedral overgrowths hi 

usual features characterize the deposits in the Jo Dandy small patches. Limonitic grains probably representing 

area, particularly the abundance of gypsum which im- the oxidation remnants of authigenic pyrite crystals appregnates the sandstone and fills fractures; the almost pear as widely scattered dark spots on some of the 

continuous extent of the deposit along 3,000 feet of specimens. Gypsum occupies almost the entire interoutcrop ; and the relatively great abundance of pyrite stitial space between the granular minerals; it also 

and lower-valence vanadium minerals. occupies small veinlets where it is later than the matrix
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 169

gypsum. Calcite is present only as very rare grains and 

not at all as matrix. Patches and seams of coalified 

wood can be seen in some sections. Evidence of extremely weak mineralization is in flakes of "vanadium 

clay" which can be seen wrapping around quartz grains; 

this material has a variable reddish brown color, mean 

index of refraction near 1.61, and high birefrigence 

typical of the clays in the mineralized portion of the 

channel. Evidence of weak mineralization is also shown 

by the faint yellowish stain which developed on the surface of the samples after they were originally collected 

and air dried. A few tiny patches of carnotite are present on some of the specimens.

Evidence of mineralization begins abruptly in the 

channel in specimen F. Part of this sample is typical 

of the unmineralized rock, made up largely of detrital 

quartz and interstitial gypsum, with a very minor 

amount of reddish brown clay forming coatings around 

some of the quartz grains. Very abruptly, along a line 

nearly at right angles to the general bedding, reddishbrown vanadium clay becomes abundant as an interstitial component. In one thin section cut across this 

boundary, the gradational zone between essentially unmineralized rock and that more or less typically mineralized rock is only 0.2 to 0.3 mm across. The vanadium clay forms rims on many of the quartz grains and 

has clearly replaced and encroached on the interstitial 

gypsum, and to a much lesser extent corrodes the quartz 

grains. The clay is erratically distributed, being absent 

in parts of some slides, forming thin films around quartz 

grains, or occupying the entire interstitial volume between the detrital grains. Isolated ragged plates of the 

clay are commonly scattered through the gypsum. The 

sedimentary clay aggregates are only slightly replaced 

by shreds of the vanadium clay. Limonitic aggregates 

(presumably goethite) are considerably more abundant 

in the clay-mineralized portions; they are highly irregular in outline and it can be only a guess that they are 

derived from oxidation of pyrite.

' This generally typifies the channel sample between 

specimens F and J. Carnotite first is seen as more than 

traces in specimen H. It is erratically distributed as 

small patches or very fine grained aggregates apparently replacing the clays and gypsum.

An unidentified mineral, perhaps a vanadate, is common, but not abundant, in most of the mineralized section of the channel; it is in tiny lath-shaped grains, 

light yellowish brown across the length and dark brown 

to nearly opaque parallel to the length; it has a relatively ;high index of refraction and a strong birefringence. It appears to replace both interstitial gypsum and the vanadium clays. We have so far been 

unable to isolate the mineral for further .study.

Carnotite becomes abundant in specimen K. It is 

quite erratically distributed, some parts of the rock 

being essentially unmineralized and showing strong development of quartz overgrowths and others showing 

marked corrosion of the quartz grains accompanied by carnotite. The carnotite commonly hugs the 

quartz grains, and appears to replace the clay irregularly; it also spreads into areas of sandstone where 

clays are absent. It forms small haloes around many 

of the isolated grains of coaly material present. The 

irregularly mineralized patches are in places bounded 

by a thin band of a very fine grained opaque mineral, 

which seems to be largely replace4 by carnotite; the 

mineral is unknown. Gypsum, abundant in the unmineralized areas, continues as an important interstitial 

component in the strongly mineralized patches. Hewettite and metahewettite form a few thin seams in 

narrow fractures across the rock; they appear to be 

definitely later than all of the other minerals.

Specimen L is basically similar, but has carnotite 

more uniformly distributed through the matrix.

Corvusite and small amounts of pyrite, marcasite, and 

paramontroseite appear in specimen M. The corvusite 

is in irregular patches, in places completely filling the 

matrix between the quartz grains; Elsewhere it irregularly replaces vanadium clay minerals and penetrates 

along gypsum cleavages as long fingers. Carnotite is 

abundant in'areas bordering corvusite, and in one place 

a microscopic veinlet of carnotite cuts corvusite. Hewettite and metahewettite are rare as fillings in late fractures, in one place bordering a late gypsum veinlet. Pyrite and marcasite grains, mostly small and anhedral 

but including a few larger euhedral crystals, are locally rather abundant and are limited to areas where 

corvusite is absent. A few of the pyrite grains are corroded remnants of larger grains, and are surrounded by 

goethite (?), but most show no evidence of corrosion. 

The pyrite and marcasite clearly were introduced at the 

time of mineralization. Paramontroseite is very sparingly present as prisms radiating from quartz grains 

and as minute rosettes; it is present in areas near 

pyrite and away from corvusite.

Specimen N comprises the black heavily mineralized 

"eye" of the ore zone. Parts of the sample contain 

abundant corvusite, similar to specimen M. Most of 

the sample has abundant euhedral pyrite and marcasite 

crystals, mostly in the interstitial space between quartz 

grains, and commonly replacing parts of quartz grains. 

The two sulfides occur side -by side, with pyrite somewhat in excess of marcasite. Where they occur near 

corvusite the crystals show evidence of corrosion and 

limonitic material is present. Associated with the pyrite and marcasite is abundant paramontroseite; it
170 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

forms prisms and massive areas between the quartz 

grains, growing into both clay and gypsum; paramontroseite too is absent near corvusite areas. Carnotite 

is abundant where pyrite and paramontroseite are absent. No uraninite or coffinite have been found. Carnotite does not seem sufficiently abundant to account 

for the amount of uranium in the sample, and it seems 

likely that uranium is distributed colloidally in the 

matrix material containing the pyrite and paramontroseite. It seems likely, also, by comparison with occurrences in other mines, that uraninite was originally 

present.

Specimen O is heavily mineralized with corvusite and 

carnotite, and in this Way is similar to specimen M on 

the opposite side of the "eye" of the channel. In irregular areas, corvusite forms nearly all of the matrix between the quartz grains, and the quartz grains are 

rounded and corroded. Elsewhere the corvusite clearly 

replaces parts of the gypsum and vanadium clay matrix. 

Some areas show only minor mineralization and strong 

euhedral overgrowths of quartz so that little interstitial 

volume remains. A small amount of pyrite, in what 

appears to be remnants of larger grains, and very small 

marcasite grains, are present in the protected quartz 

areas, and only rarely are near corvusite. Carnotite 

and metatyuyamunite (the latter predominating) are 

abundant and widespread; they replace corvusite, and 

commonly form a band between the corvusite areas and 

the less mineralized areas.

Carnotite, metatyuyamunite, and vanadium clay are 

abundant in specimen P. Mineralized clay is abundant, 

replacing gypsum. In addition, primary clay is common as pellets and less so as thin clay seams and stringers ; this clay has a much lower index of refraction and 

low absorption as compared to the vanadium clay, and 

is of sedimentary origin. The carnotitelike minerals 

are spottily distributed, and are abundant in large 

patches; they appear to replace chiefly the clay minerals. The quartz grains are largely embayed and corroded. Coalified organic remains are abundant and 

form thin streaks that emphasize the bedding. The 

mineralization does not seem to have been influenced in 

detail by the organic material. An unidentified reddish 

brown mineral, perhaps goethite, appears as irregular 

streaks and bands associated with strong carnotite mineralization.

Evidence of mineralization is weak in specimen Q. 

Carnotite is limited to a few small specks seen in hand 

specimen. Gypsum comprises most of the matrix material. Vanadium clays form thin films around many of 

the quartz grains, and in patches fill the interstices. 

Fairly large sedimentary clay pellets are present but 

not abundant. Microscopic clay seams of sedimentary

origin are present and commonly accompany microscopic seams of coalified organic material. The quartz 

grains show little corrosion.

A small amount of organic matter (coalified wood) 

is present in nearly all of the specimens. Most of it 

forms microscopic rounded or worm-shaped grains; 

under crossed nicols in polished section the material 

ranges from isotropic to that showing a grating structure similar to microcline; no cellular woody structures 

were seen. Only in specimens P and Q are continuous 

seams of coaly material common; these were not studied 

in polished section.

The clay fractions from specimens M and P have 

been studied by John C. Hathaway and are considered 

in detail in Part II.11 These clays appear to have been 

introduced during mineralization. Briefly, the clays 

in each sample are chiefly mixed layered mica-montmorillonite and chlorite-montmorillonite, and are similar to vanadium clays in other deposits.

Summary of the mineral sequence. The rock prior 

to mineralization was a fairly clean quartz sand with 

relatively little clay, a very small amount of coaly 

material, and was cemented with gypsum; specimens 

P and Q contained more abundant clay and organic 

material. Prior to mineralization, euhedral overgrowths developed on a portion of the quartz grains. 

Mineralization commenced with the introduction of 

vanadiferous clays, which replaced gypsum and in part 

quartz. Perhaps simultaneous with the clay, but probably later, was the deposition of pyrite, marcasite, and 

montroseite; the relative ages of these latter three minerals are not clear, but they appear to be nearly contemporaneous. The montroseite has since oxidized 

pseudomorphously to paramontroseite (Evans and 

Mrose, 1955). The clay minerals were widespread in 

the channel sample, but the others were largely limited 

to the areas in the vicinity of the dark eye of the channel sample.

The corvusitelike minerals are distinctly later; they 

replace clays, gypsum and the other matrix minerals 

and apparently were simultaneous with or later than 

the oxidation of pyrite and marcasite. Widespread development of carnotite and metatyuyamunite followed 

corvusite. Even later was the formation of hewettite 

and metahewettite, with gypsum, in open cracks.

CHEMISTRY OF THE CHANNEL SAMPLE

Preparation of samples. The specimens were hand 

crushed to 40 mesh, with special care taken to avoid 

loss of material and contamination. About 1 percent 

of each specimen was lost during crushing, most of this

11 Specimens M and P are coded by Hathaway as P 1 M 53 and 

P-l-P-53, respectively.
DETAILED CHEMICAL AND MINEEALOGICAL EELATIONS IN TWO VANADIUM-URANIUM ORES 171

due to discarded material contaminated during the 

labeling of the samples. For most of the chemical 

work %-gram samples were prepared by careful hand 

splitting. Duplicate samples checked well during various determinations, indicating that the sampling procedure and sample size apparently were satisfactory. 

Major constituents. A sample of each specimen in 

the channel was analyzed for Ca, Al, Fe, V, U, total S,

and SO4 ; the results are shown in table 1 and plotted 

in figure 50. In figure 50, instead of showing values as 

percent by weight of each element in the specimen they 

are shown as millimoles of each element per 100 grams 

(except U, which is shown as millimoles per 1,000 

grams). Thus, each plotted value is proportional to 

the number of atoms of each element present, rather 

than to the weight of each element.

TABLE 1. Chemical analyses of specimens of the Mineral Joe mine channe sample

[In percent by weight]

Specimen

A.. . .-........--_-

B...-......... 

O. .......... ........

D........... ........

E. ............ .. .

F-. .................

G. ........ ..........

H...................

I.............. 

J... ....... ..........

K.... ............. ..

L.. .................

M......... ..........

N........ ...........

0. ..................

P...................

TJi

0.003

.003

.005

.003

.003

.005

.060

.25

.47

.36

1.22

.85

1.26

1.13

1.90

1.74

.009

eU>

0.003

.003

.006

.005

.004

.007

.065

.23

.53

.34

1.0

.82

1.3

1.0

1.6

1.2

.012

Acid i insoluble U

0. 00005

. 00002

.00004

. 00004

. 00006

.00005

.0010

.0014

.0020

.0022

.0095

.0027

.0050

.0112

.0113

.0042

.0015

Total « 

Fe

0.22

.12

.11

.10

.11

.81

.64

.66

.93

.91

.56

1.18

1.60

4.40

' .68

.83

.38

Acid* 

soluble Fe

0.17

.13

.08

.08

.12

.76

.64

.40

.84

.99

.61

1.07

1.55

2.45

.68

.76

.35

Acid « insoluble Fe

.011

1.78

.018

Total s 

V

0.11

.13

.08

.10

.10

1.09

1.41

1.19

1.88

2.06

1.64

2.10

3.14

4.15

4.82

2.19

.47

Total «

S

3.57

4.16

4.00

3.90

3.90

2.62

2.46

5.44

1.53

2.50

2.38

1.41

1.93

6.31

1.84

1.20

2.47

Acid « insoluble S

3.43

Sulfate «

S

3.50

4.20

4.02

3.90

3.83

2.57

2.21

5.38

1.50

2.43

2.30

1.38

1.95

2.23

1.68

1.09

2.43

Oa<

4.37

4.97

4.72

4.37

4.55

3.27

2.91

6.55

2.00

3.27

2.88

1.97

2.69

2.36

2.36

1.65

3.17

Al»

2.2

1.1

1.9

2.2

1.2

4.3

5.9

2.8

4.1

2.7

4.1

4.7

5.0

2.0

3.3

8.9

8.1

1 Analyst: Carmen Johnson, U. S. Geological Survey. Acid Insoluble U determined after leaching sample 24 hours in cold 1 N HiSOi. 

 Analyst: B. A. McCall, U. S. Geological Survey. 

«Analyst: W. B. Tucker, U. S. Geological Survey.

The data clearly reflect the mineralogy. The plots 

for Ca and S coincide, within the limit of determinative error, except in samples M and N, and represent 

gypsum; in specimen N the excess sulfur is present as 

pyrite and marcasite and is accompanied by an appropriate increase in total Fe. The values for SO4 , as 

distinct from total S, were not plotted because they so 

nearly coincide with Ca throughout. The unusually 

high Ca and S values for specimen H reflect an 8 mm 

thick gypsum seam in the specimen; this depresses the 

values of most of the other elements for that specimen. 

The Al value is a proportionate measure of the "clay" 

minerals present; it is roughly complementary to the 

Ca values, representing gypsum. The unusually high 

Al content in specimens P and Q reflects abundant 

sedimentary clay.

Clay and gypsum comprise the bulk of the material 

interstitial to the detrital grains except in specimens 

M, N, and O, where pyrite, marcasite, and vanadium 

oxides bulk large. Uranium (which is exaggerated by 

a factor of 10 in figure 50) is everywhere far subordinate to V, with which it combines in a 1:1 ratio to form 

carnotite or metatyuyamunite or both. The excess of 

V above that combined with uranium in carnotite largely follows the Al in the clay minerals, but in samples 

M, 1ST, and O it occurs also as separate vanadium oxide 

minerals (corvusite and paramontroseite). The iron

4 Analyst: L. B. Jenkins, IT. S. Geological Survey. Acid-soluble and acid-Insoluble 

values determined after leaching sample 5 days in hot 33^4 percent HjSO4.

4 Analyst: C. S. Annell, U. S. Geological Survey. Quantitative spectographic 

determinations.

in small part forms limonitic material and in larger 

part is combined in the clays; in specimen N, and to a 

much lesser extent to M, it is abundant as pyrite and 

marcasite.

Organic carbon, a measure of the coalified wood 

present, is plotted for some of the specimens in weight 

percent in figure 51; total uranium and vanadium are 

also shown for comparison. Uranium and vanadium 

are highest in and near the organic-rich part of the 

channel.

The analytical data reflect the sharp boundaries of 

mineralization. Clearly U, V, Fe, and Al have been 

introduced, and Ca and S (as SO4 ) have been removed.

Uranium and equivalent-uranium relations. The 

analytical results for U and equivalent U are plotted 

in figure 52. Inspection shows differences only of the 

order of magnitude of the expected determinative error. 

The ore is essentially in radioactive equilibrium, and it 

can be concluded that there has been no appreciable migration of the uranium for many thousands of years; 

in all probability none during Quaternary weathering. 

(See Stieff and Stern, Part 13, p. 152.) The only explanation of the observed relations, if recent migration 

had taken place, would be that the transporting medium 

had exactly the same solvent capacity both for uranium 

and for its daughter products a most unlikely coincidence.
172

o 

Zi

z

UJ to (J

GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

SPECIMEN

230

210-

190 -

170-

150 -

130 -J

110-

90-

70 -

50-

30-

10-

BC DEF GH I J

ii -iii__i i___i i

CM N

Straight portion 

of channel 

sample

[^Offset portion of 

channel about 2 in. 

higher

340

-320

-300

-280

-260

r240

220

16 20 24 28 32 36 40 44 484042 46 50 54 ,58

INCHES FROM LEFT (NORTHWEST) EDGE OF CHANNEL SAMPLE

FIGURE 50. rGraph showing distribution of several elements across the Mineral Joe 'No. 1 mine channel sample. Values are 

in millimoles per 100 grams of sample, except uranium which is in millimoles per 1,000 grams of sample. Data derived 

from, table 1. . . - . 
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 173

2.0-1

1.5-

it*

.2

O 

.CO

V i.o

:x 

o

'CO

0.5-

f\

/ I

/ I

EXPLANATION 

 Carbon ? Carbon not determined

 X Uranium 

..... A Vanadium

Q

SPECIMEN 

FIOUHB 51. Distribution of uranium, vanadium, and organic carbon In specimens across the Mineral Joe No. 1 mine channel.

Trace-element relations. Semiquantitative spectregraphic analyses of the specimens were obtained, and 

the results are plotted in figure 53. These data, plus the 

 data in table 1, show definite strong anomalies 

for uranium, lead, vanadium, and iron; probable 

anomalies for barium, strontium, aluminum, and molybdenum ; and a doubtful anomaly for copper. The definite and probable anomalies, with the exception of that 

for barium, appear initially in specimen F and are 

maintained across the profile; that for barium occurs 

initially in specimen G. The first five specimens, classified as "unmineralized" in the field, are remarkably uniform in trace-element content, and they approach closely

the barren sandstone of the Salt Wash member of the 

Morrison formation except for small uranium and vanadium anomalies (see Part 3, p. 32). Furthermore, the 

anomalies are all positive; there is no indication of removal of any minor element during the mineralization 

process.

The channel sample selected is a representative one 

in its minor element content; the unmineralized sandstone is uniform, and typical of barren sandstone of 

the Salt Wash member; the mineralized zone contains 

additions of the elements that are enriched in "average 

ore," as determined from many ore pulps (see Part 3, 

p. 32). The most remarkable features of the minerali-
174 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

2

z

O

o

OE

OD

-3 -2 -I 0

LOG EQUIVALENT URANIUM

FIGURE 52. Plot of log U against log equivalent U of specimens from the Mineral Joe No. 1 mine channel sample.

+ 1

zation are: (1) the abrupt cut-off of all introduced 

elements at a zone no more than a few inches wide, and 

perhaps only a few tenths of an inch wide if the mineralized clay is an indicator; and (2) the lack of any 

negative trace element anomalies in the mineralized 

zone, suggesting that no minor constituents have been 

removed during or after mineralization.

STATES OF OXIDATION OF THE SPECIMENS

It is desirable to know the proportion of each element present in each of its oxidation (valence) states. 

Of the elements likely to be present in unknown valence 

states, spectrographic and chemical data show that only

iron, uranium, vanadium, and sulfur are present in any 

sample in amounts exceeding 0.05 percent. Sulfur is 

present as sulfide and as sulfate; these can be readily 

separated by their relative solubilities, and are reported 

separately in table 1. Gypsum, and probably a minor 

amount of barite, represent the sulfate; pyrite and 

marcasite, the sulfide.

Uranium can be present both as U(IV) and as 

U(VI). Of the U(IV) minerals, uraninite is essentially insoluable in cold \N H2SO4, but coffinite is appreciably soluble. In the channel sample specimens 

practically all of the uranium is readily soluble (see 

table 1). Neither coffinite nor uraninite could be
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 175

0.1-0.5

Ba 0.05-0.1 

0.01-0.05

Zr 0.001-0.005

0.0005-0.001

A B C D E F G H'J K L M N° P Q

ACEG IKMOQ ACEGI KMOQ

A C E G

Cr 0.001-0.005

0.0005-0.001

A C IKMOQ

Mg

0.5-1 

0.1-0.5

ACEGIKMOQ

Cu 0.001-0.005 

0.0005-0.001

ACEGI K M O O

Na

Sr

0.1-0.5 

0.05-0.1

0.01-0.05

ACEG I KMOQ

ACEGI KMOQ

Ni

0.005-0.01

0.01-0.05 

Mo 0.005-0.01 

0.001-0.005

ACEG IKMOQ

ACEGilKMOQ

Ti 0.05-0.1

0.01-0.05

ACEGI KMOQ

Pb

FIGURE 53. Semiquantitative spectrographic analyses of specimens from the Mineral Joe mine channel sample. 

Ranges are in percent. Horizontal letters deisgnate specimens. Analyst, C. A. Annell.

found mineralogically, and the abundance of oxidized 

mineral species in all samples suggests (by analogy 

with other deposits) that any TJ(IV) minerals would 

not have persisted. It is therefore assumed that the 

uranium is present entirely as TJ(VI).

The valence states in which vanadium and iron are 

present cannot be directly determined, and yet these 

largely control the variable oxidation state of the ore. 

From the mineralogy, it is known that vanadium is 

present as V(IV) and V(V), and that the iron is 

present as both Fe (II) and Fe (III), at least in some

parts of the channel sample. If such an assemblage 

of redox-active 12 elements is taken into solution in airfree sulfuric acid (where no over-all oxidation or reduction will take place), the vanadium and iron ions 

formed will promptly reach an equilibrium state in 

which the valences of the ions are a function of both 

the pH of the solution and the cumulative interactions 

of all the redox-active elements present. Thus, the 

valences of the metals in solution need not be the same

u Redox-active elements are those that change their valence state 

with natural changes in reducing or oxidizing environment.
176 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

as they were in the minerals dissolved. However, the 

reducing capacity of the solution should be the same.

The reducing capacity of a sample refers to the 

amount of oxidant the sample can reduce, and can be 

expressed in milliequivalents per 100-gram sample. 

The reducing capacity expressed in this unit is given 

by the number of ml of a 1 N solution of oxidant 

(KMnO4 in this case) reduced by a 100-gram sample. 

For direct comparison, it is convenient to state composition of the sample in milliequivalents per 100 grams. 

If the equivalent weight of the oxidant is defined as the 

amount necessary to oxidize one mole of any ion by 

removal of a single electron, one milliequivalent of an 

element is equal to one millimole of that element.

To determine the reducing capacity of each part of 

the channel sample, about 100 mg of each was digested 

for five days in hot 33.3 percent H2SO4 in a carbon 

dioxide atmosphere. Quantitative tests showed that 

essentially all of the redox-active elements, except iron 

in the sulfides, were taken into solution. The solution 

was then titrated with 1 N KMnO4. The reducing 

capacity of each specimen, together with the concentration of vanadium and iron in solution, expressed in 

milliequivalents as defined above, are given in table 2.

Pyrite and marcasite are insoluble under the treatment noted above. Therefore, the sulfur present as 

sulfide and the iron combined with the sulfide are not 

reflected in the value of the reducing capacity obtained. 

Sulfides were present in chemically significant amounts 

only in sample N.

The coaly material contained in the specimens may 

have reduced some of the redox-active elements during 

digestion (see Part 14, p. 162); we have no measure of 

the amount of such reduction, but we feel it was not 

great enough to distort the conclusions appreciably.

TABLE 2. Reducing capacities and vanadium and iron content of 

acid extracts l of specimens from the Mineral Joe No. 1 mine 

channel sample.

[All values are In milliequivalents per 100 grams of sample]

Specimen

A.. 

B.. 

O.......... 

D.. ... ..................... .- ...

E... 

F-. . .

G. _ 

H_--_-...-.__... -...- . - .

I. . ___._._._....._.. ..

J.. -.. ._._ 

K.. . ...... 

L... 

M..-i ._ .-._

N_.__._ . -- ... ... ...

O . 

P . 

Q

Vanadium, 

acid soluble a 

(meq/lOOg)

. 2.2

2.6

1.5

2.0

2.0

21.4

27.7

23.5

36.9

40.4

32.5

39.5

61.6

81.4

94.6

34.3

9.2

Iron, acid 

soluble J 

(meq/lOOg)

3.0

2.3

1.4

1.4

2.1

13.6

11.4

7.1

15.0

17.7

9.1

19.1

27.7

43.8

12.1

13.6

6.3

Reducing 

. capacity,* 

acid soluble 

(meq/lOOg)

1.9

1.9

2.1

1.8

1.6

19.5

29.1

17.6

21.1

19.9

20.2

26.3

29.6

102.0

59.4

30.1

15.4

i Extracted In 33.3 percent HtSOt.

* All the vanadium present is acid soluble; figures, given were recalculated from 

table 1. . . «Determined by L. B. Jenklns.

In the unmineralized portion of the channel (specimens A through E), the reducing capacity is low but 

ranges between about % and % of the sum of vanadium* 

plus iron; this is the amount of vanadium or iron, or 

both, which is in a reduced state that is, 'V(IV) or 

Fe(II); the remainder must be V(V) or Fe(III) or 

both. It has been shown mineralogically that small 

amounts of carnotite (or tyuyamunite) and ferric hydroxides are present, accounting for part of the V(V) 

and the Fe(III). The reduced vanadium and ironi 

must be present in the clays.

The reducing capacity rises abruptly at the boundary 

of mineralization (specimen F) and continues at 

roughly the same level through specimen L. Basing 

interpretation on the mineralogy, the bulk of the reducing capacity is due to the vanadium (IV) and the 

ferrous iron contained in the clay minerals; this conforms to the chemical study of vanadium clays by 

Foster, reported in Part 10 of this volume. The clays 

may also contain a small amount of vanadium (V) and 

considerable iron (III). The iron staining observable 

in the samples may account for some iron (III). It 

seems likely that more vanadium (V) is present than 

can be accounted for by the carnotite and hewettite reported mineralogically; probably other vanadates not 

identified under the microscope are dispersed through 

the fine-grained matrix.

The reducing capacity of specimen M, which contains a small amount of lower-valence oxides, appears 

to result largely from the vanadium (IV) and iron 

(II) in the clays and to a much smaller degree to the 

paramontroseite and corvusite. The increase in acid 

soluble iron probably reflects the oxidation products 

of pyrite and marcasite. The large amount of vanadium (V) is present chiefly in hewettite, metahewettite,. 

carnotite, and perhaps other unidentified vanadate 

minerals, as well as corvusite.

In specimen N, the black "eye" of the channel sample, 

the reducing capacity is very high and approaches the 

sum of the vanadium plus iron in milliequivalents, so 

that most of both the iron and vanadium must be 

present in reduced minerals as V(IV) and Fe(II). 

This conforms with the mineralogy, in that vanadium 

clays and paramontroseite are the dominant vanadium 

minerals, with smaller amounts of corvusite. The fully 

oxidized elements present in minor amounts, make up 

carnotite, perhaps unidentified vanadates, and corvusite ; iron (III) is present in oxidation products of pyrite and marcasite.

Specimen O is nearly as heavily mineralized as specimen N, but has only half the latter's reducing capacity. 

Here paramontroseite is lacking, but considerable vanadium (IV) is present in the corvusite as well as in 

the clays. Carnotite, corvusite, and perhaps unidenti^
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-UBANIUM ORES 177

fied vanadates account for the abundant vanadium (V). 

A small amount of iron (III) may be present as a result of alteration of pyrite and marcasite; the remaining iron, mostly as iron (II), is in the clays.

Specimen P is comparable to specimens on the opposite side of the black "eye" of the channel sample. 

The reducing capacity appears to result wholly from 

the abundant vanadium clays present. Some iron (III) 

may be present as goethite; vanadium (V) is present 

in uranyl vanadates, and probably in other unidentified 

vanadates.

The reducing capacity of specimen Q nearly equals 

the sum of iron plus vanadium (in milliequivalents 

per 100 g), so that most of these metals must be present 

as vanadium (IV) and iron (II); they are doubtless 

contained in the clay structures. Judging from the 

petrographic study of this sample, these elements were 

likely introduced into existing sedimentary clays.

To summarize, the entire reducing capacity, except 

in the very highly mineralized "eye" of the channel 

sample, can be accounted for by the vanadium (IV) 

and iron (II) held structurally in the clay minerals. 

The remaining iron taken into solution as Fe(III), can 

be accounted for by the clays in part and the rest by 

hydrated ferric oxides. The remaining vanadium, as 

V(V), is present in the form of vanadates, some of 

them probably unidentified mineralogically. Only in 

specimen N, and to a much smaller extent in the adjacent specimens M and 0, does the reducing capacity 

result from the presence of vanadium oxides containing 

vanadium (IV) (chiefly paramontroseite). In these 

same samples, the low-valence iron sulfides (pyrite and 

marcasite) are also present, but these are insoluble and 

do not affect the measured reducing capacity. There 

is no evidence, either from the reducing capacities or 

from the mineralogy, that vanadium (III) or uranium 

(IV) are present in any part of the channel sample.

SALIENT FEATURES OF THE MINERAL JOE NO. 1 

MINE CHANNEL SAMPLE

I* One boundary between mineralized and unmineralized rock is nearly pencil-sharp, and cuts across 

the bedding at right angles. The boundary bears 

no relation to sedimentary or other structures, or 

to changes in lithology. The unmineralized rock 

contains appreciably more uranium and vanadium 

than typical unmineralized sandstone of the Salt 

Wash member.

2. Vanadium-bearing clay minerals are abundant 

throughout the mineralized part of the channel 

sample. A large part of the vanadium in the clays 

has a valence of 4. The vanadium clays are mostly 

newly constituted minerals, and are not simply 

"vanadated" sedimentary clays.

3. Except in the dark "eye" of the channel sample 

(specimen N and parts of M and O), the vanadium 

clays are associated with vanadates, uranyl 

vanadates, and traces of ferric oxides, and represent an assemblage largely in equilibrium under 

oxidizing conditions.

4. In the dark central "eye" of the channel sample 

(specimen N and parts of M and O) the vanadium 

clays are associated in part with vanadates, uranyl 

vanadates, and traces of ferric oxides; and in addition, grading inward to the center of the dark 

"eye," with vanadyl vanadates, and ultimately with 

iron sulfides and a vanadium (IV) oxide (paramontroseite) . This gradational zone represents a 

mineral assemblage out of equilibrium; part of the 

assemblage is in equilibrium under oxidizing conditions, and part is in equilibrium under mildly 

reducing conditions.

5. The relatively high percentage of vanadium and 

uranium in the dark core of the channel coincides 

with the relatively high organic content of the 

rock in that part of the channel. The presence of 

iron sulfides and of vanadium (IV) oxides also 

coincides with this high organic content.

VIRGIN NO. 3. MINE CHANNEL SAMPLE

LOCATION AND GEOLOGY

The Virgin No. 3 mine is in the Long Park area, 

Montrose County, Colo. The channel sample used for 

this study was collected by T. W. Stern. The site 

of the sampling and a sketch of the ore occurrence is 

shown in figure 54. The sample was removed as one 

large piece as shown by the shaded area in the sketch. 

No precautions were taken to prevent air oxidation 

after sampling.

The locality sampled in the Virgin No. 3 mine is 

approximately 300 feet below the surface. The mineralized zone occurs in the Salt Wash member of the 

Morrison formation. The mine generally shows little 

megascopic evidence of oxidation and the gross appearance of the mineralized sandstone at the sampling 

site suggests no alteration of the primary features. It 

can be assumed that the position of the mineralized 

lens is essentially the same as it was just after mineralization and that the sample is fairly representative of rich primary ore in the Salt Wash member in 

that area.

PREPARATION OF THE SAMPLE

The general shape and appearance of the channel 

sample is shown in plate 3. The sample was cut in 

half vertically as marked and divided into ten parts 

based on the lithologic variations. The ten segments
178 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

. "TOP . '

Buff massive sandstone

Pyrite nodule 

*

Carbonaceous 

fragments

-Mineralized 

sandstone

-Vanadium - 

stained 

sandstone

BOTTOM

V Foot

FIGURE 54. Sketch of the workings of the Virgin No. 3 mine showing location of sampling site, and sketch of sampling site showing relation 

of channel sample to ore and sedimentary features. Channel sample is the shaded area.

on the left side of the channel sample were ground to 

pass through an 80-mesh sieve. These pulverized portions were used for chemical and spectrographic analysis. A second slab, 1 inch thick, was cut from the 

right-hand portion of the channel sample and also 

divided into 10 parts equivalent to the left-hand portion. These parts in turn were cut in half and a thin 

section and polished section were made of each along 

the mutually cut planes. The sections were ground 

and polished without using water to retain any watersoluble minerals that might be present. The specimen 

numbers henceforth refer to those shown in plate 3.

MINERALOGY OF THE CHANNEL SAMPLE

The discussion of the mineralogy is divided into two 

parts: weakly mineralized and strongly mineralized 

rock. This division is based on the chemical and mineralogical results. A point-count analysis was made on 

each thin section to determine the relative abundance 

of the constituent minerals, and the results were plotted 

in figure 55. A sharp change is noted between specimens 3 and 4 and a lesser one at specimen 10; specimens 

1, 2, 3, and 10 are here considered as weakly mineralized 

rock and specimens 4 through 9 as strongly mineralized 

rock. The strongly mineralized zone is highly irregular and mineralogical continuity is lacking because of 

discontinuous horizontal zones. The channel sample

exhibits marked color changes from weakly mineralized 

rock into strongly mineralized rock. The weakly mineralized portion is dark gray with a banding derived 

from minor mineralization by vanadium clay minerals. 

The strongly mineralized zone is dark green to black 

and contains many irregular patches of light-gray recrystallized quartz; small black carbonaceous fragments 

are randomly distributed throughout the zone.

WEAKLY MINERALIZED BOCK

The weakly mineralized rock contains no recognizable 

uranium or vanadium minerals, although minor 

amounts of vanadium are present within the clay minerals shown in plate 3. The detrital quartz is poorly 

sorted and authigenic overgrowths produce a mosaic 

texture. Clastic feldspar, both microcline and plagioclase, is present but never in excess of 2 percent. Clastic 

mudstone partings that roughly parallel the bedding 

are common in specimens 2 and 3. These partings have 

been contorted by compaction, and along the upper and 

lower surfaces strong pressure solution of the quartz 

is apparent from the corroded grains and development 

of microstylolites. The mudstone partings retain their 

original particle orientation and contain mostly mixed 

layer mica-montmorillonite, sericite, and quartz with 

minor pyrite and marcasite showing framboidal textures. Wisps of carbonaceous fragments are commonly
GEOLOGICAL SURVEY PROFESSIONAL PAPKll 320 PLATE 3

PHOTOGRAPH OF CHANNEL SAMPLE FROM VIRGIN NO. 3 MINE, SHOWING DIVISION OF SAMPLE INTO SPECIMENS

REFERRED TO IN TEXT
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 179

W

lOO-i 

90-

80- 

70- 

60- 

50- 

40- 

30- 

20- 

10-

0-

\

\

\

/

\

\ / 

\ /

.A-

\ nQuartz /

\

\

\ / Vanadium oxides

Carbonaceous material

1

T . 

3

i 

4 5

.,. , , 

6 7 8

i 

9

i 

10

SPECIMEN NUMBERS

FIGURE 55. Mineralogical composition, based on point-count analysis, of specimens from the Virgin No. 3 mine channel sample. 

Nos. are distributed along the horizontal base in proportion to the thickness of each segment in the channel sample.

Specimen

present in the clastic mudstone partings. The intergranular areas of the sandstone contain mixed layer 

mica-montmorillonite, chlorite, and kaolinite accompanied by calcite and minor barite. Clear calcite forms 

anhedral patches replacing the quartz and it appears to 

truncate the quartz overgrowth boundaries. Honeyyellow barite with weak pleochroism also forms anhedral patches which usually show a prominent inclusion band near the outer boundary. In specimen 10, 

euhedral pyrite forms inclusion bands in the barite. 

Possible evidence of weak oxidation of the sulfides is 

observed in the polished sections along with limonitic 

stains around the outer boundaries of the clastic mudstone partings. Several anhedral grains of galenaclausthalite were identified in specimen 3. The X-ray 

patterns of this mineral suggest that there is more 

selenium present than sulfur. Heavy mineral separations of the weakly mineralized rock samples contain

tourmaline, zircon, and apatite in decreasing order of 

abundance.

STRONGLY MINERALIZED ROCK

The boundary of strong mineralization is reflected by 

an abrupt change in gross mineralogy of the rock. The 

upper boundary is marked visually by a dark-greenish 

coloration which cuts across the bedding planes and in 

the lower boundary there is a narrow transition zone 

from black to gray. Within the mineralized zone the 

coloration is variegated and roughly follows the trend 

of the bedding. Quartz, clay minerals, vanadium oxides, and carbonaceous material comprise the bulk of 

the rock. The relative abundance of these is shown in 

figure 55; the color banding is due only to different 

proportions of minerals.

The quartz no longer maintains its detrital outline 

within the mineralized zone and is strongly corroded
180 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

into cuspate forms. The corrosion appears to have been 

greatest normal to the bedding and the cuspate quartz 

grains show elongation in the directions of the bedding 

planes. Microstylolites are commonly developed where 

the quartz grains are in juxtaposition. Isolated elongate patches of quartz grains within the mineralized 

zone, particularly in specimen 5, have not been corroded 

but rather show strong secondary overgrowths on the 

detrital quartz grains. Clastic feldspar grains are also 

scarce in the mineralized zone, although the feldspar 

appears to be much more stable than the quartz and 

little or no corrosion of the feldspars was noted. Most 

of the feldspars are orthoclase and microcline.

Associated with the corroded quartz are green to 

brown vanadium clay minerals that fill the matrix 

around the quartz. It appears that the clay minerals 

have replaced the quartz and may have derived their 

silica from the breakdown of the quartz. The vanadium 

clay minerals form extremely fine aggregates with 

moderate birefringence and marked pleochroism. In 

areas rich in vanadium clays, the clays have an aggregate structure with a strong preferred orientation 

parallel to the bedding producing a "pseudo-flow 

structure."

The fine clay aggregates have a mean index of refraction near 1.61; it was not possible to identify the clay 

minerals optically. X-ray diffraction studies, carried 

out by John C. Hathaway, indicate that chlorite is the 

most abundant vanadium silicate and it is assumed 

from previous chemical work that the chlorite contains 

appreciable amounts of vanadium. Accompanying the 

chlorite is a mixed-layered vanadium mica-montmorillonite. Kaolinite also has been identified although it 

apparently does not contain vanadium.

Chlorite increases from the barren rock into the mineralized zone with concomitant decrease in the mixed 

layer mica-montmorillonite; kaolinite does not present 

any definite trend from barren to mineralized rock. As 

indicated above, it is not possible to distinguish the clay 

minerals optically, although strong color variations 

were noted. The clay matrix is a reddish brown near 

carbonaceous fragments and a strong greenish color 

where associated with vanadium oxides. The greatest 

corrosion of the detrital quartz takes place in the 

vanadium clay rich layers, but in those isolated stringers carrying quartz overgrowths, vanadium clay is 

absent.

Paramontroseite is intimately interleaved with the 

vanadium clay minerals and forms opaque elongate 

crystals in minute rosettes. The abundance of paramontroseite roughly parallels that of vanadium clay. 

X-ray determinations have indicated only paramontroseite, but. the poor quality of the X-ray patterns was 

such that montroseite could be present in small amounts

and not be identified. No other vanadium-bearing 

minerals were found in the channel sample.

Carbonaceous material is common within the mineralized zone and forms elongate stringers characterized by a pitchy luster and subconchoidal fracture. 

Two distinct types of carbonaceous material can be 

distinguished in thin and polished sections: (1) fragments showing well preserved cell structure of woody 

material. These particles conform to, or wrap around 

contiguous detrital quartz grains and are translucent 

in thin section. (2) Kidney-shaped, opaque, carbonaceous blebs that cross-cut the bedding and replace the 

detrital and recrystallized quartz overgrowths. There 

is no recognizable wood structure present within these 

blebs, although in polished section under polarized 

light, strong anisotropy is observed. This anisotropy 

is similar to the grid-iron twinning observed in 

microcline.

These kidney-shaped blebs appear to have formed 

from the detrital coalified wood of the first type, although as yet the relationship is not clear. Autoradiographs show that these carbonaceous fragments contain 

a large part of the uranium, although no distinct uranium minerals have been identified within the carbonaceous material.

Coffinite is the only uranium mineral identified from 

the channel sample. Coffinite could not be identified in 

polished section and was determined only by X-ray 

analysis of a heavy residue. Coffinite was also identified in the clay-size fraction during the study of the 

clay minerals. From the autoradiograph and X-ray 

analysis the coffinite is probably dispersed as colloidal 

size particles. Uraninite may be present also as colloidal size particles but neither X-ray nor polished section studies revealed its presence. The chemical studies 

show that there is little or no acid insoluble uranium 

(in IN H2SO4 ) and since uraninite is considered insoluble (Phair and Levine, 1953) it can be concluded 

from the chemistry that most of the crystallized uranium is contained within the coffinite which is appreciably soluble in IN H2SO4.

.Calcite is common in the barren sandstone and also 

in the mineralized zone within the recrystallized quartz 

lenses. No calcite was found in the mineralized zone 

associated with vanadium clays and corroded detrital 

quartz. Honey yellow barite (beta=1.63±.01) is 

common in specimen 5 in the recrystallized quartz 

lenses. The irregularity shown in the quartz content, 

figure 55, results from the fact that specimen 5 has more 

quartz overgrowths than the other specimens.

Pyrite and marcasite are irregularly distributed in 

the mineralized zone and are closely associated with the 

carbonaceous fragments. The iron sulfides form near 

the fragments and in some cases impregnate the wood
DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 181

cell cavities. The iron sulfides in specimen 7 form a 

marked stringer parallel to the bedding and coincide 

with a'high concentration of uranium. Marcasite and 

pyrite are commonly intergrown in framboidal clots. 

Euhedral cubes of pyrite are common particularly in 

specimen Y. Sphalerite was identified in the recrystallized quartz lenses and appears to be a late mineral; it 

truncates the quartz overgrowths. Patches of a solid 

solution mixture of galena-clausthalite are common in 

and around the carbonaceous fragments and in one isolated spot sphalerite was seen to have replaced this lead 

selenium mineral. The scattered nature of the sulfide 

minerals precludes the establishment of a complete 

paragenetic sequence.

The heavy detrital minerals remain the same in the 

strongly mineralized zone except for apatite. The absence of apatite suggests the possibility of leaching by 

the ore solutions. In polished sections, strong corrosion 

was observed on zircon. The negative anomalies in 

some of the minor elements (fig. 56) suggest the possibility of differential leaching of heavy detrital minerals 

during mineralization.

CHEMISTRY OF THE CHANNEL SAMPLE

A portion of each specimen of the channel sample was 

analyzed for uranium, vanadium, and total iron. The 

results are given in table 3 in percent by weight. The 

relatively sharp boundaries of mineralization types are 

apparent. The high vanadium content of specimen 5 

suggests that the percent of paramontroseite, and perhaps vanadium clays (fig. 55), was not representative 

in the thin section studied. Abundant carbonaceous 

material coincides with the strong mineralization.

Chemical uranium and equivalent uranium shown in 

table 3 appear to be close to radioactive equilibrium, 

although there is some suggestion of differential movement of daughter products. Equivalent uranium deterTABLB 3. Analyses of specimens from the Virgin No. 3 mine 

channel sample

[In weight percent]

Specimen

\. ...................

2........... ......

3... .................

4. ...................

6...... ..............

6...... ......... .....

7....................

8....................

9....................

10....... ............

Percent U 

Total »

0.003

.003

.095

1.0

5.0

4.0

4.8

4.2

1.2

.13

Percent 

Equlv. U 

Total »

0.005

.02

.2

1.0

2.9

2.8

2.8

2.9

.98

.16

Percent U 

Insol. »

<0. 001

<.001

.001

.003

.003

.004

.004

.004

.002

<.001

Percent Fe 

Total'

0.38

.54

1.31

1.75

1.30

1.42

1.29

1.75

1.57

.74

Percent V 

Total <

0.10

.30

1.08

6.65

5.98

6.80

4.16

1.24

1.24

.33

' Analyst: Roosevelt Moore, U. S. Geological Survey. Acid-Insoluble U determined after leaching sample 24 hours In cold 1 JVHjS04. 

» Analyst: B. A. McCall, U. S. Geological Survey. 

« Analysts: L. B. Jenklns and M. H. Delevaux, U. S. Geological Survey. 

VAnalyst: L. B. Jonklns, U. 8. Geological Survey.

minations at values as high as most of these are not 

usually considered accurate. There is no other evidence 

of movement of elements after mineralization.

Semiquantitative spectrographic analyses of minor 

and trace elements were made, and the results are shown 

in figure 56. Al, Sr, Zr, Be, Pb, and Mg show a slight 

to marked increase from weakly mineralized rock into 

strongly mineralized rock. These anomalies for the 

most part maintain a remarkably uniform level across 

the strongly mineralized zone. Ba shows no ordered 

trend across the channel sample and appears to concentrate in the areas of strong quartz overgrowths. Ca 

maintains a constant level across the channel. Negative 

anomalies coinciding with the mineralized zone are apparent for K, Na, Mn, Cu, and Ni. Sn and Cr show 

no trend. The potassium anomaly in specimens 3 and 

4 and the lack of alkali metals in the strongly mineralized zone suggests a selective removal during mineralization. Truly unmineralized rock was not 

available for analysis.

The positive anomalies for Fe, U, V, and Pb can be 

construed as definite additions. Although there is 

evidence of extensive movement of silica in the strongly 

mineralized zone, and we have no adequate data on 

the silica balance, it is not likely that sufficient silica 

was removed to account for the other positive anomalies 

by residual enrichment. Some of the anomalies, however, may be due in part to irregular placer concentrations of heavy minerals and not related to 

mineralization.

The minor element composition of the weakly mineralized portion of the channel sample is not similar to 

typical unmineralized Salt Wash sandstone (see Part 

3 of this volume). The most striking feature of the 

minor element distribution is the sharp boundary, coinciding with the boundary of strong mineralization, of 

the positive and negative anomalies.

STATE OF OXIDATION OF THE CHANNEL SAMPLE

The valence states of the specimens from the channel 

sample were studied as in the Mineral Joe No. 1 mine 

channel sample, described previously. The reducing 

capacity of the acid-soluble fraction of each sample, 

and the acid-soluble Fe, V, and U (the only soluble 

' redox-active species present in significant amounts), 

all expressed in milliequivalents per 100 grams, is given 

in table 4. Essentially all of the V, U, and nonsulfide 

Fe are acid soluble.

Milliequivalents of vanadium and iron are used in 

the sense that one milliequivalent equals one millimole; 

for uranium, two milliequivalents equal one millimole, 

because two electrons must be removed to oxidize 

uranium from U(IV) to TJ(VI).
182

Si

GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Ti

m ' Ni

-10.0

1.0-10.0

Al

1 3 5. 7 9

2468 10

1 3 5, 7 !9

Ca

13579

Mg

13 5 7 '9

13579

1-3579

1 .3 5 79

2 4 6 8 10

135 79"

Pb

0.01-0.05 

0.005-0.01 

0.001-0.005

1 35 7 9

Cr

13579

Ga

Mo

0.001-0.005

13579

0.01-0.05 

0.005-0.01 

0.001-0.005

Ag

0.00005-0.0001 1 

0.00001-0.00005

13579

13579

13579

FIGURE 56. Semlquantltative spectrographlc analyses of specimens from the Virgin No. 3 mine channel sample. Ranges are 

in percent. Horizontal figures designate specimens. Joseph Haffty, analyst.

From the mineralogical character of vanadium, it is 

known that it occurs in the clay minerals, probably as 

vanadium (IV), and in paramontroseite as vanadium 

(IV); it is not certain that montroseite is absent, so 

that some vanadium (III) may be present. The acid 

soluble iron is believed to be entirely present in the 

clay minerals, and in this assemblage of low valences 

is probably present as Fe(II). At least part of the 

uranium is present in coffinite, as uranium (IV) ; the 

valence state of any additional uranium may be (IV) 

or (VI).

Garrels (1955, p. 1014-1019, particularly his figure 

7) discusses the theoretical (and partly hypothetical) 

pH-Eh stability fields of some major minerals and 

mineral assemblages from the Colorado Plateau. The 

strongly mineralized portion of the channel Bample 

corresponds mineralogically to his "Field 2" in that it 

contains paramontroseite, pyrite, and sphalerite; coffinite is also present and probably has a stability field 

near that of uraninite. The stability relations of the 

vanadium-bearing clays are not known, but work by 

Foster (Part 10 of this volume) suggests that in this
DETAILED CHFMICAL AND MINERALOGICAL RELATIONS IN TWO VANADIUM-URANIUM ORES 183

TABLK 4. Reducing capacities and vanadium, iron and uranium 

content of acid extracts l of specimens from the Virgin No. 3 

mine channel sample

[All values are In mllllequlvalents per lOOg of sample]

Specimen

1. ..............

2..................

3..................

4..................

8- ..............

0.. .............

7..................

8..................

9..................

10.................

Vanadium * 

(moq/lOOg)

1.90

6.97

19.0

130.5

117.0

133.5

81.0

24.3

24.3

6.47

Iron.s acid 

soluble 

(moq/lOOg)

6.6

8.8

17.4

27.0

22.9

25.1

22.0

15.4

12.3

10.0

Uranium > 

(meq/lOOg)

0.03

.03

.78

8.4

42.0

33.6

40.2

35.2

10.1

1.10

V+Fe+U 

(meq/lOOg)

8.6

14.8

37.8

165.9

181.9

192.2

143.8

74.9

46.7

17.6

Reducing 

capacity,4 

acid soluble 

(meq/lOOg)

3.4

9.6

37.6

168.4

149.6

158.7

117.8

65.0

46.2

16.6

' Extracted for 5 days on steam bath In 33 M» percent HjSO«. 

1 Essentially nil V and U wcro soluble In the extraction; values given are total V 

and total U recalculated from table 3, In this paper. 

» Analyst: M. H. Dolovaux, U. S. Geological Survey. 

'Analyst: L. B. Jonklns, U. S. Geological Survey.

mineral association, the vanadium contained in the 

clays should all be V(IV) and the iron largely Fe(II). 

If it is assumed that all of the uranium is U(IV), all 

of the vanadium is V(IV), and all of the acid-soluble 

iron is Fe (II), then the measured reducing capacities 

should equal the sum of (U+V+Fe), all expressed in 

milliequivalents.

The measured reducing capacities of the specimens 

from the channel sample are significantly less than the 

sum of (U+V+Fe), with the exception of samples 3, 

4, and 9. These latter samples appear to fall ideally 

in Garrels' "Field 2". In the remaining samples, the 

deficiency in reducing capacity is believed to be due 

to the presence of Fe (III) (and possibly some V(V)) 

in the clays and to some U(VI). Specimens 1 and 2, 

the weakly mineralized part of the channel sample, 

must contain a considerable amount of Fe(III), probably in the sedimentary clays of the original unmineralized rock; such sedimentary clays probably persist to 

some extent throughout the channel sample. A considerable part of the uranium is believed to be present 

as TJ(VI); this assumption is based on analogy with 

uraninite, which invariably contains considerable 

amounts of U(VI). Although analyses of coffinite do 

not show any appreciable U(VI) (Stieff and others, 

1956), coffinite is believed to oxidize early and through 

much the same course as uraninite (Part 6 of this 

volume). The belief that much of the uranium is present as U(VI) is consistent with the mineralogy of the 

channel sample in that coffinite was identified only in 

a few concentrates, and yet uranium values are relatively high. The uranium is probably dispersed as 

amorphous UO3 .

SALIENT FEATURES OF THE VIRGIN NO. 3 MINE 

CHANNEL SAMPLE

1. The boundary between weakly mineralized and 

strongly mineralized rock is sharp. This boundary roughly follows a sedimentary boundary.

2. The zone of intense mineralization coincides with 

the presence of abundant organic matter in the 

rock.

3. Vanadium - bearing clay minerals are present 

throughout the channel sample. In the more 

strongly mineralized portions, the vanadium-bearing clays clearly replace clastic quartz grains.

4. Paramontroseite, coffinite, pyrite, marcasite, and 

vanadium clay minerals characterize the strongly 

mineralized portion of the channel sample. Much 

of the uranium is probably present as amorphous 

U03 . These minerals constitute an assemblage in 

equilibrium under mildly reducing conditions.

SUMMARY AND CONCLUSIONS

The two channel samples reported on support a number of generalizations concerning the nature of the 

primary ore and its course of alteration. Most of the 

generalizations have been recognized previously by 

other workers.

1. The boundary between mineralized rock and unmineralized rock can be sharp and independent of 

any observable sedimentary or other structures 

and of any changes in original lithologic character. The Mineral Joe No. 1 mine channel sample 

demonstrates this clearly.

2. The mineralized rock is enriched by a somewhat 

variable suite of minor and trace elements. The 

most important added elements are U, V, Fe, Pb, 

Ba, and Sr. Most of the trace elements originally 

present in the unmineralized rock have not been 

removed by the mineralizing process.

3. Vanadium-bearing clay minerals have been introduced in the mineralized portions of the Mineral 

Joe No. 1 mine channel sample. Sedimentary 

clay minerals in the Virgin No. 3 mine channel 

sample have been recrystallized, and vanadium 

introduced into their structures; additional vanadium-bearing clay minerals have been introduced.

4. The principal vanadium clays are mixed-layered 

mica-montmorillonite and chlorite-montmorillonite. The vanadium is present largely in a valence 

of (IV). The vanadium clays persist without 

evident alteration during weathering.

5. The Mineral Joe No. 1 mine channel sample represents a section through an ore ranging from dominantly vanadates, uranyl vanadates, and vanadium clays to a dark core of paramontroseite, 

pyrite and marcasite, and vanadium clays; the 

state of combination of much of the uranium is not 

known. This dark core is actively oxidizing, with 

destruction of the sulfide and the formation of 

vanadium (IV)-(V) minerals, vanadates, and
184 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

uranyl vanadates. The paramontroseite indicates 

that montroseite was originally present (Evans 

and Mrose, 1955, and Part 7 of this volume) and 

that much of the vanadium must have been present previously as vanadium (III). The present 

assemblage is markedly out of chemical equilibrium and must be moving toward a higher'state 

of oxidation. The primary assemblage, assuming 

equilibrium, must have contained montroseite, vanadium clays, a uranium (IV) mineral (uraninite 

or coffinite), and pyrite and marcasite.

6. The Virgin No. 3 mine channel sample is in a lower 

state of oxidation than the Mineral Joe No. 1 mine 

channel sample. It comprises an equilibrium assemblage of paramontroseite, coffinite (and additional uranium as amorphous UO3 ), pyrite and 

 marcasite, and vanadium clays in which the vanadium is present largely as vanadium (IV). 

Montroseite must have been the precursor of paramontroseite. Thus the original ore must have been 

a more reduced assemblage consisting of montroseite, coffinite (and perhaps uraninite), pyrite 

and marcasite, and vanadium clays. This is essentially identical to the original assemblage proposed 

for the Mineral Joe No. 1 mine channel sample.

7. Both channels studied show unequivocal evidence of 

partial oxidation of an original low-valence assemblage.

The vanadium clay minerals are not yet completely 

defined and the role in them of vanadium in its various 

valence states is still somewhat uncertain. Little is 

known of their fields of stability under varying EhpH conditions, except that they are resistant to oxidation. And yet they are the dominant carrier of vanadium in many of the so-called "primary" ores on the

Colorado Plateau. The Mineral Joe No. 1 mine channel sample typifies many such deposits. In the "primary" ore, the great bulk of vanadium was in. the clays, 

with the vanadium at valence (IV) ; accompanying it 

was a small but commercially important content of 

uranium, probably present as uraninite or coffinite, or 

both, and probably predominantly located in or near 

scattered coalified wood fragments. Actually, montroseite (or paramontroseite) is rare in most ore of this 

type. Only where the organic matter is abnormally 

abundant do the rich patches of montroseite ore develop, but even here the vanadium clay minerals are 

abundant. It seems probable that the nature of the orebearing fluids may be better defined by the vanadium 

clays than by the vanadium oxides. Speculation at this 

stage leads to the guess that the vanadium was originally carried as a V(IV) ion and precipitated with the 

clays without the need of a markedly reducing environment; the uranium may well have been carried as a 

U(VI) ion (probably complexed) and precipitated 

locally where reducing conditions were adequate such 

as near coaly remains.

REFERENCES

Evans, H. T., Jr., and Mrose, M. E., 1955, A crystal chemical 

study of montroseite and paramontroseite: Am. Mineralogist, v. 40, p. 861-875.

Garrels, R. M., 1955, Some thermodynamic relations among the 

uranium oxides and their relation to the oxidation states 

of the uranium ores of the Colorado Plateaus: Am. Mineralogist, v. 40, p.1004-1021.

Phair, George, and Levine, Harry, 1953, Notes on the differential leaching of uranium, radium, and lead from pitchblende in H2 SO4 solutions: Econ. Geology, v. 48, p. 358- 

369.

Stieff, L. R., Stern, T. W., and Sherwood, A. M., 1956, CofBnite, 

a uranous silicate with hydroxyl substitution: a new .mineral : Am. Mineralogist, v. 41, p. 675-688.
Part 16. MINERALOGY OF THE URANIUM DEPOSIT AT THE HAPPY JACK MINE, SAN

JUAN COUNTY, UTAH

By ALBERT F. TBITES, JR., RANDALL T. CHEW III, and TOM G. LOVERING

CONTENTS

	Page 

Abstract__._--______----___-__--__-___________-__ 186

Introduction.______________________________________ 186

General geology____________________________________ 186

Structure.___--___-__-_-______-_-_-___-_---_.____ 187

Mineralogy ___-_____-_-_--_____----_-_-___--___--_- 187

Ore deposit.____-_______--___--_---___-__----__-.__ 188

Ores of the sulfide zone.____-_-_-______--_-______ 188

Uraninite___________-_--_--_-_---_-________ 188

Pyrite________________________._ 189

Chalcopyrite. _._-_____-_________-_______-_. 190

Other sulfide minerals.______________________ 190

Nonmetallic gangue minerals.________________ 191

Page 

Ore deposit Continued

Ores of the sulfide zone Continued

Statistical interpretation of assay data___ T ____- 191

Paragenesis and origin_____________________ 193

Ores of the transition zone_______________________ 193

Mineralogy ________________________________ 194

Statistical interpretation of assay data.________ 194

Ores of the oxidized zone__ ______________________ 194

Statistical interpretation of assay data_________ 194

Summary. _________________________________________ 195

Literature cited__________-_---______________________ 195

ILLUSTRATIONS

Page

PLATE 4. A, Photomicrograph of a cross section of a wood fragment partly replaced by uraninite and chalcopyrite. B, Photomicrograph of uraninite intergrown with pyrite, replacing fine-grained organic material. C, Photomicrograph 

of uraninite partly filling spaces between quartz grains and filling fractures cutting the grains. D, Photomicrograph of complex-zoned pyrite crystals and a skeletal pyrite crystal.______________________________________ 194

5. A, Photomicrograph of pyrite rimming quartz and chalcopyrite filling spaces between the grains of the sandstone.

B, Photomicrograph of marcasite rimming a cavity in wood that has been replaced by pyrite________________ 195

FIGURE 57. Frequency-distribution histograms of uranium, copper, manganese, iron, and calcium carbonate, sulfide zone____ 191

58. Frequency-distribution histograms of uranium, copper, manganese, iron, and calcium carbonate, transition zone. _ 192

59. Chart showing paragenesis of uraninite and sulfide minerals-_____-------__--___--__--_--__--_-_____--____ 193

TABLES

Page 

TABLE 1. Geometric means and geometric deviations of various elements and calcium carbonate at the Happy Jack mine,

White Canyon district, San Juan County, Utah___------_---_--_----------_-_------_-__--_--_------_-__ 192

2. Correlation coefficients between uranium and various other elements and calcium carbonate at the Happy Jack

mine, White Canyon district, San Juan County, Utah_____________________________.__________________.__ 192

185
186 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ABSTRACT

The large uranium deposit at the Happy Jack mine occurs 

in beds of the Shinarump member of the Chinle formation of 

Triassic age that fill a channel cut into the underlying 

Moenkopi formation of Triassic age. The deposit has been 

divided on the basis of mineralogy into a sulfide zone, a transition zone, and an oxidized zone. Three types of ore are recognized in all these zones: replacements of woody "trash" accumulations, replacements of larger wood fragments, and bedded 

ores.

Ores of the sulfide zone consist of uraninite associated with 

pyrite, chalcopyrite, sphalerite, bornite, and galena. These primary sulfide ores appear to have been localized in the more 

permeable beds containing concentrations of coalified vegetal 

material and siltstone. Uranium and copper show evidence of 

secondary enrichment in the sulfide zone and the inner part 

of the transition zone.

Ores of the transition zone contain relict concentrations of 

uraninite and sulfide minerals and large amounts of goethite 

and jarosite. The ores of the oxidized zone contain abundant 

iron oxides but no sulfide minerals. Some uranium, copper, and 

iron have been retained during the weathering process, but 

most of the manganese, zinc, and lead are believed to have been 

removed by oxidation.

INTRODUCTION

The Happy. Jack is the largest uranium mine in the 

White Canyon district, San-Juan County, Utah. It is 

about 75 miles west of Blanding, Utah, in a deep reentrant in the southwest rim above White Canyon. 

Uranium ore was first shipped from the mine in 1948, 

and constant production has been maintained since 1951.

This study, begun in 1952, was to determine the mode 

of occurrence of the uranium minerals, to find structural and lithologic features that may be used as ore 

guides, and to obtain information on the geochemistry 

of the emplacement and oxidation of the ore deposit.

The walls of approximately 900 feet of drifts in the 

northeast part of the mine have been mapped on a scale 

of 1 inch equals 5 feet. About 750 feet of these drifts 

were mapped by Trites and Chew between August 7 

and October 2, 1952; the remainder was mapped by 

Trites, assisted by E. J. Ostling, on August 19 and 20, 

1954. The mineralogical study was made by Trites who 

examined about 30 polished sections and 50 thin sections of rock specimens from the mine. X-ray identification of some of the minerals was made by W. F. 

Outerbridge of the U. S. Geological Survey. Statistical 

analyses of assays from 103 chip samples from the mine 

have been made by Levering and Chew.

Four main adits, connected by crosscuts, have been 

driven into the Shinarump. The main workings were 

all on one level and consisted of slightly more than 

3,000 feet of drifts and crosscuts when the study was 

made.

The writers wish to thank W. P. Walker, of the 

photographic laboratory of the Geological Survey, for

his careful preparation of the photomicrographs used 

in this paper.

GENERAL GEOLOGY

The rocks exposed in the area are sedimentary beds 

of continental origin that range in age from Permian 

to Jurassic. They have a total thickness of more than 

4,000 feet and are predominantly sandstone and siltstone. The nearest exposures of igneous rocks are in 

the Henry Mountains about 17 miles west of the Happy 

Jack mine.

The uranium deposit at the Happy Jack mine is in 

the Shinarump member of Late Triassic age. The 

member is from 16 to 40 feet thick at the Happy Jack 

mine; it pinches out half a mile northwest and 1% 

miles southeast of the mine. The lower part of the 

formation fills a discontinuous channel cut into siltstone 

and sandstone of the underlying Moenkopi formation 

of Early and Middle (?) Triassic age. The channel 

trends about due east and is more than 750 feet wide 

and 10 feet deep in the area of the mine workings. 

Diamond drilling by the U. S. Atomic Energy Commission has suggested that the channel bends rather 

abruptly toward, the. southwest near the southwestern 

limit of the mine workings.

The Shinarump' is overlain conformably by the 

Chinle formation of Late Triassic age. This younger 

formation is composed principally of beds of siltstone 

and sandstone, and is gradational with the Shinarump 

member. A prominent sandstone member of the Chinle 

formation is about 175 feet above the top of the 

Shinarump, from which it is separated by siltstone and 

small lenses of sandstone.

The Shinarump member is composed of about 80 percent coarse- to fine-grained sandstone, 15 percent conglomerate, 8 percent siltstone, and 2 percent claystone. 

Gradation is common between beds of coarse-grained 

sandstone and conglomerate and between beds of finegrained sandstone and siltstone. The sandstone beds 

are lenticular in shape and range from 1 to 100 feet in 

length and from a few inches to 4 feet in thickness. 

Cross-stratification is common in the sandstone beds; 

the cross-strata dip from less than 10° to more than 

20° toward the northwest. Planar cross-stratification 

(McKee and Weir, 1953) is common in fine-grained 

sandstone and in coarse-grained conglomeratic sandstone containing abundant interstitial clay and silt. 

Small-scale slump features and current lineation also 

have been noted in the Shinarump conglomerate.

The sandstone is composed predominantly of colorless, angular to subangular, quartz grains; it also contains from a trace to 5 percent of microcline, and a 

trace of tourmaline and zircon (?). Authigenic quartz 

overgrowths have been added to many of the quartz
MINERALOGY OF URANIUM DEPOSIT AT HAPPY JACK MINE 187

could be found between the uranium deposits and the 

larger fractures that were mapped.

MINERALOGY

grains before the deposition of the metallic minerals. 

Granules and pebbles of quartz, quartzite, siltstone, and 

claystone comprise from 1 to more than 10 percent of 

many of the sandstone beds; siltstone and claystone

pebbles are especially abundant in the lower parts of The minerals listed below have been observed at the

the sandstone beds. In general, conglomerate beds Happy Jack mine by J. W. Gruner, Lynn Gardiner,

grade laterally into beds of coarse-grained sandstone, and D. K. Smith, Jr. (written communication), who reSiltstone and claystone are present throughout the ported them officially to the Atomic Energy CommisShinarump conglomerate at the Happy Jack mine. sion. They have not been observed by the present

They occur in beds ranging from 10 to 100 feet in writers and are not discussed in this paper.

length and from 1 to 4 feet in thickness; they also occur ., Mine'al _ A , , ^ ^T'* _

. f, . , . . . , _ . ' . , ,, , Cyanotnchite. _____________ Cu4Al 2 (SOO(OH),j.2HjO in thin layers ranging from 1 to 6 feet in length and Gersdorffite________________ NiAsS

from one-eighth to one-half inch in thickness. Sabugalite (Al-autunite).._._ HAl(UOO«(PO04-l6H,0

_,,..?,, , . , ,, ,. , Schoepite-_-_---_-________- U03-2HjO (approximately) Most of the beds contain carbonaceous matter which SiderotiL--__-_--______-_-_ FeSO«-5H 3O(?)

ranges in size from finely comminuted organic material §)llfu.'---7,--j-,-v"""""""' ?n T^C^ ^ TT ^

_ to , P , i /, i . T Not described before._______ (Co.Fe)SO4-4H»0

to logs as much as 3 feet long and 6 inches in diameter. Not described before._______ MgSCh-GHaO

Accumulations of smaller fragments have been termed Bright-yellow. _____________ Unknown uranium mineral

. . ° Waxy yellow.._____________ Unknown uranium mineral

"trash deposits (Trites and Chew, 1955), a term that Yellow....._________..__.. Unknown uranium mineral

is in general use on the Colorado Plateau. These trash The alphabetical list of minerals given below includes

accumulations are commonly present near the bottom those observed by the senior author at the Happy Jack

of the sandstone beds and at the contacts between sand- mine; many of these minerals are discussed in this

stone beds. paper. The formulas are from Dana's Textbook of

STRUCTURE Mineralogy (1932) unless otherwise stated.

Mineral Formula

The White Canyon district is on the west flank of Allophane (silicate)..__.___._. AljSi05 -nHaO

HIP. MftmimpTif- imwarn n hroad srmrh-nliinp-in^ anti- Antlerite (sulfate) ________ Cu3 (SO4)(OH)«' tne Monument, upwarp, a oroaa sout-n pmnging anti Azurite (carbonate)___________ Cu3 (OH)2(003)2'

cline that extends northward from 30 miles south of Barite (sulfate)__.___.___.---. BaSCh 1

*}m ^in Tnnn TJivnr fn TT!llr "Rirlo-P 3fl milpc: north of Bieberite (sulfate) ____________ CoS04-7H2O

tne &an Juan niver to &IK. itiage, 6V nines norm 01 Bornite (suifide)______________ Cu5FeS4 2

the river (Gregory, 1938, p. 85-88). The Monument Brochantite (sulfate)

upwarp has a steeply dipping east flank in which dips ^^^(^

exceed 50°; and a gently dipping west flank in which Chalcocite (suifide)__

dips range from hall a degree to 3°. cSSS^^

The rocks in the ^Vliite Canyon district strike region- Erythrite (arsenate) _______ (Co,Ni) 3 (As04)j-8H20 :

ally from north to northwest and dip 2° to 3° west to GoeTniteToS)"---"-"""!!-!- Hl^eO, 2

southwest. Small folds occur locally and their axes are Gypsum (sulfate)_____________ CaS04-2HaO 1

generally parallel to subparallel to the axis of the Mon- ^ro^^o^(smc^"::"" K!a3Al2O3 .6Si02 .2HaO

ument upwarp. Normal faults with displacements as Ilsemannite (sulfate)?.__.___-_ MoOs-SOa-SHsO 1

i IAA x j. _ _i u j .1 A. . j Jarosite (sulfate)____--_'_______ KFe 3 (S04)2(OH) 6 1 much as 100 teet cut the beds in the northwestern and Johannite (sulfate)_____..____- Cu(UO,),(SOO.(OH),.6H,O»

southwestern part of the area. Magnetite (oxide)_________.--_ FeFe 2C>4 2

, , ,T T , - -, , XT Malachite (carbonate)___------ Cui(OH)i(COi) l

Ihe rocks at the Happy Jack mine strike about JST . Marcasite (sulfide)__-_--_-_-_- FeSs 2

20° W. and dip 3° SW. These rocks have been cut by Metatorbemite (phosphate).... Cu(UOOj(POO.-nH.O

four sets of steeply dipping fractures that have the Metazeunerite (arsenate)------ Cu(UO2)s(As04)2-8H2 0 3

 fnllnwino- cfrilrpe! licsrprl in ni-rlpr nf Hppi-piqino- nrnmi- Microcline (silicate)______.-_-. KaO-AhOs-GSiOs loiiowing sciiKes iistea in oiaei or aecieasing promi psa0melane(?) (oxide).....--.. BaMn2 Mn<8O16 (OH)4 2

nence: N. 65° W., N. 60° E., N. 85° E., and due north. Pyrite (suifide)_______________ FeS, 2

Only one small fault was noted in the mine, about 30 j^^^-"::::""_"_ fMgO.3SiO,2HsO

feet from the portal. This fault strikes N. 69° W., Sphalerite (suifide) ______ ZnS 2

dips almost vertically, and has had horizontal movement ^^f^_i:::::::::::"_"" Wetjl

of less than 2 feet but no vertical movement. Minor Uranopilite"(sulfate)__________ (U02) 8 (S04)(OH)io-12Ha0 3

bedding-pkne movement is suggested by clay seams that 

have been thickened by movement along lithologic conJ oo i (Palachc, and others, 1951).

tactS. 2 (Palache, and others, 1944).

	s (Frondel and Fleischer, 1955). Although uraninite and suifide minerals have filled 4 (weeks and Thompson, 1954).

rvii^./%CT ^/^-rx;^ li«nnfii-»nct 4,-> fVi/^- wri/iVo virv r.^1 nfi^^oV>i^ NOTE. Pitchblende has been omitted from the above list as being a variety of miCrOSCOplC fractures in ttl6 rOCKS, no relationship uraninite. However, the term "sooty pitchblende" is retained as a generic term.

468652 59 18
188 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ORE DEPOSIT

The ore deposit at the Happy Jack mine may be divided on the basis of mineralogy into a sulfide zone, 

a transition zone, and an oxidized zone. The sulfide 

zone is exposed in those parts of the mine farthest from 

the surface; the outer edge of this zone is about 200 

feet horizontally from the outcrop of the Shinarump 

member and is roughly parallel to the outcrop. The 

transition zone.extends from the sulfide zone to within 

10 to 60 feet of the Shinarump rim in the part of the 

mine studied. The oxidized zone extends outward from 

the transition zone and includes the leached outcrop. 

The contacts between these zones are gradational.

The sulfide zone contains uraninite and sulfide minerals with no appreciable amounts of goethite. The 

transition zone contains abundant goethite and jarosite 

and locally it contains relict concentrations of uraninite 

and sulfide minerals. The oxidized zone contains abundant goethite, little jarosite, and insignificant amounts 

ofsulfides.

About 15 percent (approximately 325 feet) of the 

mine workings in the sulfide zone were mapped and 

studied in detail in 1952. Most of the workings examined extend in a line across the Shinarump channel. 

The farthest part of the mine studied is about 475 feet 

from the rim. . The uranium ore in the sulfide zone occurs mainly in sandstone and conglomerate. Three 

types of ores are recognized: replacements of "trash" 

accumulations, bedded deposits, and replacements of 

larger wood fragments.

Emplacements of. "trash" accumulations constitute 

most of the high-grade uranium deposits and, although 

the rock has not been mined selectively, these probably 

have yielded the greatest tonnages of ore from this zone. 

Ore bodies of this type are widely distributed in the 

mine in sandstone beds containing carbonaceous material. They range from 50 to 150 feet in length, from 

25 to 50 feet in width, and from a fraction of an inch to 

3 feet in thickness in the part of the mine studied.

Bedded ore bodies contain less carbonaceous material, 

are much smaller, and of slightly lower grade than the 

ores resulting from the replacements of "trash" accumulations; they have supplied less than 10 percent of 

the ore produced from the sulfide zone. Bedded ore 

bodies range from 1 to 25 feet in length, from 6 inches 

to 10 feet in width, and from a knife-edge to slightly 

more than 1 foot in thickness. They are localized at 

contacts between two sandstone beds and commonly replace siltstone seams at the contacts.

Large wood fragments, sparsely disseminated in the 

mine, are commonly replaced by ore minerals in or near

the two other types of uraniferous ores. These replacement ores are extremely variable in grade and conr 

tribute only a small part of the ore.. .

Local concentrations of uraninite, pyrite, chalcopyrite, sphalerite, and galena have been noted, but no 

definite zoning of these minerals has been found in the 

sulfide zone. Most of the uraninite apparently has been 

localized by sedimentary features; localization by faults 

and fractures has not been shown. The most .highly 

mineralized beds appear to be semipermeable sandstone 

and conglomerate, in the lower part of the Shinarump, 

which commonly overlie siltstone. They contain from 

1 to 5 percent carbonized wood, from 5 to 25 percent 

siltstone or claystone seams, and from 10 to 20 percent 

siltstone or claystone matrix. ... . A microscopic study was made of 13 polished sections 

from the-sulfide zone. The .modes of occurrence of the 

uraninite and the primary sulfide minerals are .discussed 

below; the sulfides are given in descending order of 

abundance.

 " ': . " TJRANINITE '' ' . . ... ' .

Uraninite (ideally UO2 ) is the principal uranium 

mineral in the sulfide zone. The term "uraninite" is 

here reserved for the massive, nearly metallic variety 

and "sooty pitchblende" is reserved for the finely divided npnmetallic variety. Coffinite, the newly described uranous silicate (Stieff, Stern, and Sherwood, 

1955), which has been identified in more than 15 

uranium mines in the Colorado Plateau, has not been 

found at the Happy Jack mine.

The uraninite replaces carbonized wood, is disseminated in sandstone where it replaces quartz grains and 

microcline grains along cleavage planes, and fills 

microscopic veinlets cutting sandstone adjacent to 

fossil wood fragments. The suites of sulfide minerals, 

with which the uraninite is associated, appear to vary 

with the mode of occurrence of the uraninite. In 

wood and other organic matter the uraninite is most 

commonly associated with pyrite, chalcopyrite, sphalerite, bornite, galena covellite, and marcasite; in sandstone containing no appreciable amounts of organic 

debris, uraninite is associated mainly with pyrite and 

sphalerite.

The uraninite is of two distinct colors in polished 

section: most of the uraninite is gray but some of that 

which occurs with chalcopyrite and covellite in wood 

is brownish gray. The reason for this color difference 

is not known. The variation in color may reflect a 

difference in age of the uraninite or may be caused 

by admixed copper minerals. Uraninite with crystal 

outlines has not been observed except where the 

uraninite is intergrown with pyrite by replacement of 

organic material.
MINERALOGY OF URANIUM DEPOSIT AT HAPPY JACK MINE 189

Many wood fragments have been replaced by chalcopyrite and uraninite; a few have been replaced by 

uraninite and sphalerite. In general, the uraninite has 

replaced the cell walls and chalcopyrite has either replaced or filled the cell cores (pi. 4A). Even in wood 

containing little or no chalcopyrite the Uraninite 

shows a preference toward cell wall replacement as 

shown in plate 4A. Nearly complete replacement of 

wood by uraninite is not uncommon, but sufficient unreplaced cell core material commonly remains to preserve the woody structure.

Uraninite is more concentrated in the centers of the 

wood fragments and is commonly surrounded by chalcopyrite which has in part replaced the edge of the 

wood and in part nearly completely impregnated the 

sandstone adjacent to the wood. Uraninite extends outward into the sandstone surrounding the wood fragments, partly filling interstices between the grains of 

the sandstone, coating some of the quartz grains, and 

filling cavities in chalcopyrite. The uraninite seems to 

be especially abundant in the sandstone at the ends of 

wood fragments, suggesting a "streaming out" of the 

uraninite from the wood which was the locus of deposition. Further study of the relative amounts of 

uraninite deposited in the sandstone at each of the 

ends of the pieces of uraninite-replaced wood may suggest a direction of flow of the uranium-bearing 

solutions.

Some of the uraninite in the sandstone near wood 

seems to have a cell structure suggesting that smaller 

bits of organic matter have been replaced. Three 

specimens of sandstone containing uraninite without 

recognizable organic material were studied. In each 

of these specimens the uraninite was gray in color and 

was associated either with pyrite or with pyrite and 

sphalerite. Uraninite has embayed and replaced 

quartz grains, has replaced feldspar grains along the 

cleavages, has formed a thin rim around many grains 

of quartz, and has lined cavities. Some of the uraninite 

appears to be intergrown with the pyrite, and has 

crystal outlines (pi. 4J3). The uraninite is believed to 

be younger than the pyrite and to have replaced either 

organic material or a gangue mineral which was not 

completely replaced by the pyrite.

Locally uraninite has partly filled microscopic veinlets cutting individual quartz grains in the sandstone

(pi. 4:0).

PYBITB

Pyrite is a widespread mineral at the Happy Jack 

mine; it is the most abundant sulfide mineral in the 

sulfide zone although it was subordinate to chalcopyrite 

in the polished sections studied. It occurs as a partial 

to nearly complete wood replacement, as a replacement

468,652 59 1A

of finely divided organic material, as disseminations in 

sandstone, and as partial fillings in fractures cutting the 

quartz grains in the sandstone. The pyrite is commonly 

associated with chalcopyrite, uraninite, sphalerite, marcasite, galena, and bornite in many places in the sulfide 

zone.

A few pieces of wood have been replaced mainly by 

pyrite with subordinate sphalerite or chalcopyrite. In 

the pieces of wood replaced by pyrite and sphalerite, 

the pyrite has replaced both the cell cores and walls, 

retaining a large part of the cell structure. Stringers 

of sphalerite grains cut the pyrite-replaced wood and 

replace the pyrite. In pieces of wood replaced by pyrite 

and chalcopyrite the cell structure has been destroyed 

and the pyrite is in the form of irregular masses that 

have been embayed and replaced by chalcopyrite.

Pyrite replaces wood which apparently acted as a 

nucleus of deposition. Both individual cells, and entire 

fragments of wood as much as 5 inches long and 3 

inches wide have been replaced. Pyrite that has been 

deposited in larger areas in the wood commonly occupies the centers of cells whose walls remain unmineralized or have been replaced by pyrite or uraninite. 

Most of the pyrite in the center of the cells is separated 

from the pyrite or uraninite in the cell walls by unreplaced organic material.

Some of the pyrite in the sandstone has replaced 

small bits of disseminated organic material. Study of 

this occurrence of pyrite under high magnification has 

shown that the pyrite has surrounded the organic material in thin crenulated subround bands and has 

formed small blebs within the organic mass.

Pyrite has been deposited between the grains of the 

sandstone, especially near pieces of wood that contain 

abundant pyrite. Some of the pyrite has been concentrated along the edges of the quartz grains, incompletely filling the interstices between the grains (pi. 

5A) and embaying and replacing the edges of the 

grains.

A small amount of the pyrite is in microscopic crystals ; both cubes and pyritohedrons have been observed 

under the microscope. Four different types of pyrite 

crystals have been observed: simple homogeneous crystals ; crystals with a core of unreplaced coalified wood; 

crystals with a core of pyrite separated from a rim of 

pyrite by a layer of unreplaced coalified wood or uraninite ; and zoned crystals of alternating pink and yellow 

layers.

The simple homogeneous pyrite crystals are the most 

widespread and abundant. These simple crystals have 

been deposited in the sandstone as well as in the wood, 

and have mainly cubic forms.

Some pyrite crystals that have grown around plant
190 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

cells have a core of organic material. The skeletal crystal of pyrite in plate 4Z> is believed to have been formed 

in this manner. A more complex type of selective replacement of the cell by pyrite has produced the 

crystals with cores and rims of pyrite separated by 

unreplaced organic material. Later replacement of the 

unaffected part of the cell by uraninite has produced 

zonal intergrowths made up of pyrite and uraninite 

(pi. 45). Both cubic and pyritohedral forms are found 

in pyrite crystals of these types.

The zoned pyrite crystals are of many types. The 

most simple type of zoned pyrite crystal is that of normal yellow pyritohedral pyrite crystals having pinkish 

cores. More complex zoned crystals have many alternating zones as shown in plate 4Z>. Square, pentagonal, 

and triangular outlines have been noted on these crystals, suggesting that the crystals have cubic and pyritohedral forms. In general, the inner zones have crystal 

forms similar to the outer boundaries of the pyrite 

crystals. Many of the inner zones are rotated with 

respect to the outer faces of the crystals so that the 

edges of the inner zones are not parallel to the outer 

edges of the crystals.

The reason for the pyrite zoning has not been determined, but the difference in color may be differences in 

the trace amounts of cobalt, nickel, or selenium in the 

layers.

CHAI.COPYRITB

Although chalcopyrite is overwhelmingly the most 

abundant sulfide in specimens studied from the sulfide 

zone, the gross aspects of the deposit suggest that it is 

less abundant than pyrite. The chalcopyrite has formed 

disseminations in the sandstone, conglomerate, and siltstone ; it has replaced fragments of wood and stringers 

of carbonaceous siltstone; and it has filled small fractures cutting the sandstone. In most places the chalcopyrite is associated with pyrite and locally it is 

associated with uraninite, sphalerite, bornite, and galena 

in the sulfide zone.

The amount of chalcopyrite in the beds varies from 

a few scattered masses to complete fillings between 

grains. Chalcopyrite is most abundant in sandstone 

and conglomerate that contain coalified wood. Rims 

of concentrated chalcopyrite as much as one centimeter 

wide surround many wood fragments that have been 

replaced by uraninite and sulfide minerals. The concentrated chalcopyrite grades outward from the rims 

into more widely scattered masses in the sandstone. The 

chalcopyrite has embayed and apparently has replaced 

many of the quartz grains; complete replacement of 

quartz grains is uncommon in specimens studied from 

the mine. Most of the chalcopyrite in the Sandstone

is massive, although many small crystals have been 

observed.

Many fragments of coalified wood have been partly 

replaced by chalcopyrite. The amount of chalcopyrite 

in these wood fragments ranges from an occasional 

"eye" or lens of chalcopyrite in the center of the cells 

(pi. 4A) to nearly complete replacement of both cell 

cores and walls. The initial deposition of chalcopyrite 

in the wood seems to have been a filling or replacement of the core of the cells. Subsequent replacement 

of the cell walls took place only where there was a 

superabundance of chalcopyrite. In its preference to 

fill cavities, the chalcopyrite is similar to that in the 

porphyry copper deposit at A jo, Ariz. (Gilluly, 1946, 

p. 87.)

Small subround masses of chalcopyrite in the sandstone have a pattern that suggests the replacement of 

seeds, pollen, or finely divided organic material with 

a very small cell structure. Ghalcopyrite in carbonaceous siltstone has also been concentrated in fragments 

of wood and in finely divided organic matter.

Megascopic veins and fracture fillings of chalcopyrite 

have been observed at several places in the Happy Jack 

mine. Veinlets of chalcopyrite, less than 6 inches long 

and one-fourth inch across, cut siltstone lenses southwest of the part of the mine mapped, and small concentrations of chalcopyrite were observed in the sandstone adjacent to a vertical fracture in the eastern part 

of the mine workings.

OTHER SUUFtDE MINERALS

Sphalerite is the third most abundant sulfide mineral 

in the sulfide zone; it is about one-tenth as abundant as 

chalcopyrite. Most of the sphalerite occurs as minute 

fracture fillings and linings of cavities; as replacements 

in wood that was previously replaced by pyrite, chalcopyrite, and uraninite and as disseminations in sandstone. The sphalerite is light gray in polished section 

and nearly free of iron; it forms crystals and anhedral 

masses that display yellow internal reflections.

Bornite is found in trace quantities replacing wood 

and chalcopyrite in the sulfide and transition zones. 

Some of the bornite forms a eutectoid intergrowth with 

rods of chalcopyrite. Bornite has also been deposited 

as rims between chalcopyrite and grains of sphalerite; 

locally the bornite has been deposited in veinlets cutting chalcopyrite. All of the bornite is of microscopic 

size and most patches of it are less than 0.05 mm across.

Galena occurs in trace quantities as microscopic crystals and irregular masses that have been deposited 

locally in the wood and sandstone. The galena is surrounded and veined by chalcopyrite and covellite.

Covellite and chalcocite are present in the sulfide 

zone and the inner part of the transition zone. Covel-
MINERALOGY OF URANIUM DEPOSIT AT HAPPY JACK MINE 191

lite occurs as bladed crystals cutting chalcopyrite and 

chalcocite and as rims surrounding many grains of 

chalcopyrite, pyrite, and galena; the covellite is the 

youngest of the sulfide minerals. The chalcocite occurs 

as feathery masses along fractures cutting chalcopyrite 

and as replacement rims around grains of chalcopyrite 

and bornite. The covellite and chalcocite are believed 

to be of supergene origin because they appear to be 

localized near the boundary between the sulfide and 

transition zones.

Marcasite is present locally in microscopic veinlets 

cutting and replacing the uraninite, pyrite, and chalcopyrite (pi. 5B) in fragments of replaced wood. A 

small amount of wood cell texture has been preserved 

by marcasite but most of the woody texture has been 

destroyed. The marcasite occurs in the sulfide zone 

and in the inner part of the transition zone and is associated with either covellite or chalcocite in all but one 

of the specimens examined. Most marcasite found in 

nature is in surface or near-surface deposits where it is 

considered to have been formed at low temperatures 

and from acid solutions (Palache and others, 1944, p. 

313). The origin of the marcasite at the Happy Jack 

mine is not clearly shown, but its association with 

covellite and chalcocite suggests that it also may be a 

supergene mineral.

NONMETAJLLIC GANGT7E MINERALS

The nonmetallic gangue minerals in the sulfide zone 

are mainly quartz, microcline, and clay minerals 

(mostly hydrous mica and kaolinite) typical of the 

Shinarump conglomerate. Quartz is present as grains 

and locally as authigenic overgrowths on quartz grains. 

The most abundant quartz overgrowths appear to be in 

areas surrounding abundant uraninite and sulfide minerals; although microscopically, a few overgrowths 

occur with the uraninite and sulfides and have been embayed by these minerals. The association of minor 

amounts of quartz overgrowths with uraninite and sulfide minerals and the embayment of the authigenic 

quartz by these minerals suggests that silica was leached 

from the quartz grains of the sandstone by the mineralizing solutions and redeposited in the beds nearby. 

Silica was thereby moved, as a front, ahead of the orebearing solution; and as deposition of sulfide minerals 

advanced, the authigenic quartz previously deposited 

was moved further outward from the deposit. The 

more intense silicification that Waters and Granger 

(1953, p. 15) observed surrounding ore bodies on the 

Colorado Plateau could possibly be explained by this 

process.

Barite has been introduced locally into the sulfide 

zone and is particularly associated with sphalerite.

The barite rims cavities that are filled with sphalerite, 

and is believed to be older than the sphalerite. Its age, 

relative to the other sulfide minerals, has not been 

determined.

Jarosite, apparently one of the earliest secondary 

minerals formed by the oxidation of sulfide minerals in 

the mine, is common throughout the part of the sulfide 

zone studied.

STATISTICAL INTERPRETATION OF ASSAY DATA

Preliminary studies suggest an approximately lognormal distribution of certain elements in the samples 

(figs. 57 and 58). No histogram is shown for the oxidized zone because of the low number of samples. A 

statistical study based on the assumption of log-normal 

distribution of these elements in the deposit was made 

of chemical analyses of 68 samples from the sulfide zone,

15

.2 5-

URANIUM 15-1

2 5;

COPPER

to O «H lO i-»c\«i-i

. i-l CM «* O -« VO 

O O O -« CM M-O JVO

ri ci cJ rf d c> * « e>i *t o

Percent

I I I I I I I I !

Percent

45 

40- 

35- 

30-

15-

10-

5-

MANGANESE 45- 

40- 

35-

30-

>>

£25- 

o>

cr

£20

u.

15

10

IRON CALCIUM 

CARBONATE

35- 

30- 

25-

£20- 

o>

115-

Percent

O rH VO t-i cJ ^- 

Percent

S 2 S 5? o 

o o' o cS --i

Percent

FIGDRB 57. Frequency-distribution histograms of uranium, copper, 

iron, manganese, and calcium carbonate, sulflcle zone, Happy Jack 

mine, San Juan County, Utah (logarithmic class intervals ; 68 

samples).
192 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

10- 

o c

C 

0)

3

§" 4- 

ul

2-

U RANILJM

Frequency

5 ro^ cc» cr>

 cc)PF'ER 10-

8-

c 6- 

o>

u. n 

1 n

MM*Gl\N ESE

n

9 o 1-4 u>

»-H O 1 CM ^ 

0 -< 0 0 O 0 rM

d o ^ o 1 °1 dcicicic)

lIlT1 O »-< O O> rH ID ' 

O .-1 1 1 1 1 CM 3 O >-4 UJ 

O O * O*-* ' OOOOO

cJcJcJ--! o c> >-i o cio'cScDo'

TABLE 1. Geometric means and geometric deviations of various 

elements and calcium carbonate at the Happy Jack mine, San 

Juan County, Utah

Percent Percent Percent

IRON 141

12-i

10-

>, 8-

0

c

(U

= 6-

CT

O)

* 4-

2-

12-

10-

>, 8-

u

c

* ^

= 6-

CT

0)

"- 4-

1 1 ^"

CALCIUM

CARBONATE

0- u rrfl n o >-< <o -i cvj ^F o ^H vo

rn 10 rt o c> . c> t-J oi «* o

CM' <*' o CNI Jj ' ' ' ' ' '

OI-<»OQ Ot-'CVJ'TO'-'^D

Percent Percent

FIGUKB 58. Frequency-distribution histograms of uranium, copper, 

manganese, iron, and calcium carbonate, transition zone, Happy 

Jack mine, San Juan County, Utah (logarithmic class intervals; 

22 samples).

22 samples from the transition zone, and 10 samples 

from the oxidized zone. The results of this study are 

shown in tables 1 and 2. The geometric means (M) and 

the geometric deviations (GD) of samples from each 

of the three zones are shown in table 1; the correlation 

coefficients of copper, manganese, iron, and calcium carbonate 13 with respect to uranium in each of the three 

zones are shown in table 2.

The geometric deviations (GD) suggest that copper 

(GD = 10.02) and uranium (GD=7.62) have the greatest deviation, and therefore, the greatest dispersion in 

the sulfide zone. Dispersion means the amount of scat13 This refers to the determination as made for metallurgical purposes. Although this Is an empirical method that measures calcium 

taken into solution by an acetic acid leach, It generally gives a good 

approximation of the calcium carbonate actually present in most 

sandstone-type ores. The weakness of this method is that It measures 

any acetic acid soluble calcium salt Including some, but not necessarily 

all, of calcium carbonate. All the calcium found in the leach is expressed as calcium carbonate.

Element

TTranHiTn..... ^^ ^ ^

Geometric 

mean (M),

in percent; 

geometric 

deviation 

(GD)

M

GD

M

GD

M

GD

M

GD

M

GD

Sulfide 

(68 samples)

0. 31 X 1. 43

* 7.62 

0. 20 X 1. 76

^"10.02 

0. 014 X 1. 16

*1.83 

3. 09 X 1. 15

* l.W

0

17X1 on

"5"2.25

Zones

Transition 

(22 samples)

0. 28 X 2. 42

T 7. 10 

0. 39 X 5. 35

^41. 12 

0.0133X 1.50

~2.47

3 on X - 0 _

1.95 

0 26 X i R9

~3.79

Oxidized 

(10 samples)

0. 021 X 2. 72

"*" 3.85 

0. 54 X 4. 38 " "7.30 

0. 0018 X 3. 95

+ 6.35

2

K1 X » on

*1.88

O

ia X o 79

*3.84

TABLE 2. Correlation coefficients between uranium and various 

other elements and calcium carbonate at the Happy Jack mine, 

San Juan County, Utah

Elements correlated 

with uranium

Iron. ____ . .......

Calcium carbonate.......

Correlation

coefficient 

(r) Sulflde 

(68 samples) 

r.=0.23

+0.12 -.07

+.69

+.09

Zones '

Transition 

(22 samples) 

r.=0.42

+0.25 -.12

+.22 -.38

Oxidized 

(10 samples) 

r.=0.63

+0.45

+.52

+.44

+.11

1 r»=significant value of correlation coefficient that is, that value, which if exceeded, 

yields a 95-percent probability that the two variables being correlated are not independent.

ter of the values about a mean. This high dispersion 

of uranium and copper assays is in accordance with 

the observed non-uniform high-grade concentrations of 

uraninite and chalcopyrite in the mine. The dispersion of calcium carbonate (GD=2.25), manganese 

(GD=1.83) and iron (GD=1.67) is lower than that 

of copper and uranium suggesting that distribution of 

these elements is more uniform in the part of the sulfide zone studied.

The arithmetic mean of iron was calculated to be 

3.43 percent hi samples in the sulfide zone. This indicates that considerably more iron is present than that 

which is chemically combined with copper (arithmetic 

mean Cu 1.51 percent) in chalcopyrite. Most of this 

iron is contained in pyrite.

The uranium appears to correlate significantly with 

iron, but does not show significant correlation with 

copper, manganese, or calcium carbonate in the sulfide zone (table 2). The relatively high correlation 

of uranium with respect to iron suggests that sites in 

the sulfide zone which favored the deposition of pyrite 

also favored the deposition of uraninite. Since the 

principal mode of occurrence of both uraninite and pyrite is the replacement of coalified wood, it is believed
MINERALOGY OF URANIUM DEPOSIT AT HAPPY JACK MINE 193

that these sites of deposition consisted of wood and 

other organic matter in sandstone, conglomerate, and 

siltstone. The pyrite was both earlier and more abundant than the uraninite, consequently its distribution 

is more uniform than the uraninite.

PABAGENESIS AND ORIGIN

The general paragenetic sequence of the formation 

of the uraninite and sulfide minerals in the sulfide zone 

is shown in figure 59. Secondary silica was added to

URANINITE'AND 

PRIMARY SULFIDE MINERALS

Pyrite

Goleno

(Sooty pitchblende)

Cholcopyrito\

Bomitci

Uraninite

Sphoforito

Marcasite

Chalcaclte

Covellite

FIOORB 59. Chart showing paragenesis of uraninite and sulfide 

minerals, Happy Jack mine, San Juan County, Utah.

the sandstones prior to the deposition of these metallic 

minerals which have embayed and replaced the authigenic quartz. Significant wall-rock alteration apparently did not accompany the deposition of the metallic minerals. The solutions which deposited the 

minerals in the sulfide zones are believed to have contained large amounts of iron and abnormal amounts of 

zinc, lead, and other metallic ions.

Levering (1949, p. 56) believed that the abundance 

of barite and the absence of alunite suggested precipitation from bicarbonate solution in late barren stage 

alteration of East Tintic, Utah. Iron and zinc are 

known to be soluble in a bicarbonate solution under

SOOTY PITCHBLENDE

AND;SUPERGENE 

SULFIDE MINERALS

pressure (Levering, T. S., oral communication, 1955). 

With a release of pressure and in the presence of available hydrogen sulfide the sulfides of iron and zinc are 

precipitated. Copper and lead are considerably less 

soluble than iron or zinc in bicarbonate solution and 

may not have been carried in such a solution. Both iron 

sulfide and zinc sulfide will be reacted on by such solutions as that of lead chloride to precipitate lead sulfide, 

the iron and zinc ions returning to solution during the 

process. Such processes as these may have taken place 

during the deposition of the uranium deposits. Pyrite 

was apparently the earliest of the sulfide minerals 

formed and could have been derived from iron carried 

in bicarbonate solution under pressure and precipitated 

in the presence of hydrogen sulfide, extracted perhaps 

from organic matter. If solutions carrying copper and 

lead were passed over the pyrite, the sulfur could have 

been removed from combination with the iron to recombine with these cations. Sulfur could unite with the 

lead to form the galena, and sulfur and iron could combine with the copper to form chalcopyrite and bornite. 

The role of uranium and zinc in this sequence of reactions is not known. Uranium apparently has a greater 

affinity for oxygen than for sulfur and has been deposited as the oxide instead of the sulfide. Sphalerite 

was apparently deposited later than the pyrite, galena, 

and uraninite; its replacement of pyrite suggests that 

it may have been deposited similarly to the manner suggested for the galena, by solution of the pyrite and combining of the zinc with sulfur. Much of the pyrite has 

been etched by the later sulfide minerals, suggesting 

that solution of the pyrite took place as these minerals 

were being deposited.

The average ratio of equivalent uranium to uranium 

(eU percent/U percent) is less than 1.0 in samples from 

the sulfide zone, greater than 1.0 in samples from the 

transition zone, and considerably greater than 1.0 in 

samples from the oxidized zone. Dodd (1950) has previously described these differences between radiometric 

count and percent uranium and attributed them to 

leaching (see also Part 13 of this volume). These data 

suggest that uranium has been leached from the oxidized and transition zones and some of it redeposited 

in the sulfide zone. Uranium is thus apparently being 

secondarily enriched in the sulfide zone. An alternative, 

believed to be less likely, is that daughter products of 

uranium have been enriched by deposition in the oxidized and transition zones.

ORES OF THE TRANSITION ZONE

The transition zone has been defined as a zone containing abundant geothite and relict concentrations of 

primary sulfide minerals. The three types of uranium
194 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ores (replacements of "trash" accumulations, bedded 

ores, and replacements of large wood fragments) found 

in the sulfide zone are also recognized in the transition 

zone. In general, the grade of the ores of each type is 

lower in the transition zone than in the sulfide zone. 

The relict concentrations of uraninite and sulfide minerals are believed to remain in the transition zone because the oxidizing solutions did not penetrate the rock 

everywhere and local concentrations of carbonaceous 

matter may have retained reducing conditions.

MINERALOGY

The uranium ore in the transition zone consists of 

relict uraninite and primary sulfide minerals, secondary 

uranium and copper minerals, and possibly uranif erous 

iron oxides. Secondary uranium minerals include the 

oxide sooty pitchblende (Kerr, 1951, p. 91-92), the sulf ates, uranopilite and a zippeite-like mineral, and the 

silicate uranophane. The secondary copper minerals 

are the sulfates chalcanthite, brochantite, and antlerite(?) and the carbonates malachite and azurite. Secondary uranium-copper minerals include the sulfate, 

johannite; the phosphate, metatorbernite; and the 

arsenate, metazeunerite. Most of these secondary minerals have formed disseminations in the sandstone, conglomerate, and siltstone, and are associated with gypsum, goethite, and hematite as fracture coatings. Some 

of the sulfates, especially the zippeite-like mineral, 

johannite, uranopilite, siderotil, bieberite, and chalcanthite, and the arsenate erythrite have formed efflorescent coatings on the walls in moist parts of the mine.

Goethite, hematite, jarosite, and gypsum are abundant in the transition zone. The goethite has impregnated sandstone and conglomerate, coated fractures, and 

replaced pieces of wood that were formerly replaced by 

sulfide minerals. Locally the goethite appears to be an 

alteration product of hematite and jarosite, and some 

of the goethite is colored red by hematite.

Jarosite is believed to be the first product formed 

during the oxidation of the deposit. It is present in 

greatest amounts in the inner part of the transition 

zone and in the sulfide zone. Only small amounts of 

the mineral are found in the oxide zone and in the 

outer part of the transition zone. Oxidation in arid 

rather than humid climate is believed to favor the deposition of jarosite (Locke, 1926, p. 107).

Gypsum is common throughout the transition zone. 

It has formed disseminations in the sandstone and conglomerate and has coated the surfaces of fractures*

STATISTICAL INTERPRETATION OF ASSAY DATA

A statistical study was made of 22 samples from the 

transition zone. The results (table 1) suggest that the 

only statistical values which are significantly different

from the values of the sulfide zone are the geometric 

deviations of copper, manganese, and calcium 

carbonate. The geometric deviation of copper 

(GD=41.12) in the transition zone is much higher than 

that of copper (GD = 10.42) in the sulfide zone. Large 

amounts of secondary copper minerals, mainly the 

sulfates, have formed local concentrations in the transition zone and probably account for the greater dispersion of copper assays. Secondary copper minerals 

are present in local concentrations similar to those 

found in zones of secondary enrichment in many 

porphyry copper deposits and vein copper deposits 

elsewhere. Chalcocite and covellite have been deposited 

in some of the relict sulfide bodies in the transition 

zone where they commonly replace chalcopyrite and 

bornite.

Manganese is present in about the same amount in 

the transition zone (M=0.013) as in the sulfide zone 

(M=0.014), although the manganese assays show a 

greater dispersion in the transition zone (GD=2.47). 

Some of the manganese apparently has been moved 

about in the transition zone, but apparently no significant amounts have been removed from or added to the 

zone.

The distribution of calcium carbonate is also more 

variable in the transition zone (GD=3.79) than in the 

sulfide zone (GD=2.76). The calcium carbonate may 

be more variable in the transition zone because it is 

being removed near the oxidizing sulfides. Calcium 

carbonate is present in such extremely small amounts 

that it cannot be recognized in the mine.

Uranium shows no significant correlation with 

copper, iron, manganese, or calcium carbonate in the 

transition zone.

ORES OF THE OXIDIZED ZONE

The uranium ores in the oxidized zone are similar in 

type to those in.the transition zone but the average 

grade of the deposits in the oxidized zone is only about 

one-tenth of those in the transition zone. Copper, however, shows a slight increase in the oxidized zone over 

the transition zone. All the uraninite has been leached 

from the oxidized zone and nearly all of the sulfide 

minerals have been removed by oxidation. In general, 

the secondary uranium and copper minerals are similar 

to those in the transition zone, although efflorescent deposits of secondary uranium minerals are not common 

on the mine walls and jarosite is sparse in the oxidized 

zone.

STATISTICAL INTERPRETATION OF ASSAY DATA

A statistical analysis was made on 10 samples from 

the oxidized zone (table 1). The number of samples 

is admittedly small and may be insufficient for the
GEOLOGICAL SUBVEY 

A. PHOTOMICROGRAPH OF A CROSS SECTION OF A WOOD FRAGMENT PARTLY REPLACED BY

URANINITE AND CHALCOPYRITE.

Uranir.itc has replaced the cell walls, and chalcopyrite has filled or replaced part of the cell cores: IL, uraninite; 

c, chalcopyrite; w, unreplaced wood, x 145.

B. PHOTOMICROGRAPH OF URANINITE INTERGROWN WITH PYRITE, REPLACING FINE-GRAINED 

ORGANIC MATERIAL IN SANDSTONE.

u, Uraninite; p, pyrite. x 710.

C. PHOTOMICROGRAPH OF URANINITE PARTLY FILLING THE SPACES BETWEEN QUARTZ GRAINS 

AND FILLING FRACTURES CUTTING THE GRAINS.

u, Uraninite; q, quartz grains, x 145.

D. PHOTOMICROGRAPH OF COMPLEX ZONED PYRITE CRYSTALS AND A SKELETAL PYRITE CRYSTAL.

x 710.
GEOLOGICAL SUBVEY PROFESSIONAL PAPER 320 PLATE 5

A. PHOTOMICROGRAPH OF PYKITE RIMMING QUARTZ GRAINS AND CHALCOPYRITE 

FILLING THE SPACES BETWEEN THE GRAINS OF THE SANDSTONE.

p, Pyrite; c, chalcopyrite; g, quartz grains. Blue filter, x 145.

B. I'HOTOMICKUGK.M'H oh MM:(.\>III HIMMING A CAVITY IN WOOD THAT HAS 

BEEN REPLACED BY PYRITE.

m, Marcasite; p, pyrite. x 145.
MINERALOGY OF URANIUM DEPOSIT AT HAPPY JACK MINE 195

drawing of valid conclusions. The data suggest, however, that the amount of uranium is significantly less 

in the oxidized zone (M=0.021) than in the transition 

zone (M=0.28) or the sulfide zone (M=0.34) although 

its distribution is more uniform in the oxidized zone 

(GD=3.85) than in the transition (GD=7.10) and 

sulfide zones (GD=8.40). Complete oxidation of concentrations of uraninite with the formation of dispersed 

secondary minerals probably accounts for the greater 

uniformity of uranium distribution.

The amount of manganese is considerably smaller 

and the assay values show more dispersion in the 

oxidized zone (M=0.0018; GD = 6.35) relative to both 

the transition (M=0.013; GD=2.47) and the sulfide 

zones (M=0.014; GD=1.80). Manganese has apparently been leached from the deposit near the outcrop and a large part of it is believed to have migrated 

along fractures. The deposition of manganese oxide 

along many of the fractures is believed to account for 

part of its variability in the oxidized zones. The correlation of uranium with copper, manganese, iron, and 

calcium carbonate is not significant in the oxidized 

zone.

SUMMARY

The uranium deposits at the Happy Jack mine are in 

the Shinarump member of the Chinle formation which 

have filled a channel cut into the underlying Moenkopi 

formation. The deposits are believed to have been 

localized principally in the more permeable beds containing large amounts of coalified wood and claystone 

or siltstone seams. Secondary silica was added to the 

quartz grains prior to the deposition of the uraninite 

and sulfide minerals. Iron, copper, uranium, zinc, lead, 

barium, manganese, and other metallic elements apparently were deposited by solutions which removed a 

large part of the secondary quartz. The acidity of the 

solution is not known, but it is believed that bicarbonate 

solution could have removed part of the quartz and 

deposited some of the metallic minerals. Pyrite, galena, 

chalcopyrite, bornite, uraninite, and sphalerite were deposited from the solution by replacement of wood and 

of portions of sandstone and deposition in the pores 

of the sandstone.

Oxidation of the sulfide ore body by oxygen-bearing 

acid sulfate waters has penetrated to about 200 feet 

behind the cliff face. With oxidation of the sulfide 

ore body, movement of metallic ions has been both, outward to be lost to surface waters, and inward to increase 

the concentration of elements. Although large amounts 

of copper and uranium have been lost by oxidation and 

removed at the surface, small amounts of uranium and 

significant amounts of copper have migrated inward

from the rim and have been redeposited as supergene 

minerals. The uranium apparently has migrated 

farther than the copper to form sooty pitchblende in 

the outer part of the primary sulfide zone. Copper has 

been enriched as chalcocite and covellite principally in 

the transition zone and as sulf ates in the transition and 

oxidized zone. Some of the iron has been redeposited 

as jarosite and possibly as marcasite in the transition 

zones and the outer part of the sulfide zone; a large part 

of the iron has been deposited as goethite and hematite 

in the transition and oxidized zones. Most of the manganese, zinc, and lead, are believed to have been removed by oxidation. In general, the oxidation and 

supergene enrichment has tended to decrease the size 

of the ore body, although slightly enriching it.

LITERATURE CITED

Dana, B. S., 1932, A textbook of mineralogy, with an extended 

treatise on crystallography and physical mineralogy: 4th 

ed. revised and enlarged by W. E. Ford, New York, John 

Wiley and Sons.

Dodd, P. H., 1950, Happy Jack mine, White Canyon, Utah: U. S. 

Atomic Energy Comm., RMO-660, Tech. Inf. Service, Oak 

Ridge, Tenn.

Frondel, J. W., and Flelscher, Michael, 1955, Glossary of uranium- and thorium-bearing minerals: U. S. Geol. Survey Bull. 

1009-F.

Gilluly, James, 1946, The Ajo mining district, Arizona: U. S. 

Geol. Survey Prof. Paper 209.

Gregory, H. E., 1938, The San Juan country: U. S. Geol. Survey 

Prof. Paper 188.

Kerr, P. F., 1951, Natural black uranium powder: Science, v. 

114, p. 91-92.

Locke, Augustus, 1926, Leached outcrops as guides to copper 

ore: Baltimore, Md., The Williams and Wilkins Co.

Lovering, T. S., 1949, Rock alteration as a guide to ore East 

Tintlc district, Utah: Econ. Geology Mon. 1., 65 p.

McKee, B. D., and Weir, G. W., 1953, Terminology for stratification and cross-stratification in sedimentary rocks: Geol. 

Soc. America Bull., v. 64, p. 381-390.

Palache, Charles, Berman, Harry, and Frondel, Clifford, 1944, 

The system of mineralogy of James Dwight Dana and 

Edward Salisbury Dana, Yale University 1837-1892: v. 1., 

New York, John Wiley and Sons, Inc.

 1951, The system of mineralogy of James Dwight Dana 

and Edward Salisbury Dana, Yale University 1837-1892: 

v. 2. New York, John Wiley and Sons, Inc.

Stieff, L. R., Stern, T. W., and Sherwood, A. M., 1955, Preliminary description of cofflnite a new uranium mineral: 

Science, v. 121, p. 608-609.

Trites, A. F., Jr., and Chew, R. T., Ill, 1955, Geology of the 

Happy Jack mine, White Canyon area, San Juan County, 

Utah: U. S. Geol. Survey Bull. 1009-H, p. 235-248.

Waters, A. G., and Granger, H. C., 1953, Volcanic debris in 

uraniferous sandstones, and its possible bearing on the 

origin and precipitation of uranium: U. S. Geol. Survey 

Clrc. 224.

Weeks, A. D.f and Thompson, M. E., 1954, Identification and 

occurrence of uranium and vanadium minerals from the 

Colorado Plateaus: U. S. Geol. Survey Bull. 1009-B.

Part 17. SEDIMENTARY STRUCTURES AND LOCALIZATION AND OXIDATION OF ORE AT 

THE PEANUT MINE, MONTROSE COUNTY, COLORADO

By CARL H. ROACH and MARY E. THOMPSON

CONTENTS

Page

Abstract__________._______...___-..._ 197 

Introduction and acknowledgments.__________________ 197

Structure and stratigraphy____________-____--_-_.____ 198

Ore bodies._____._._________._._____-._. 199

Page 

Mineralogy and paragenesis__________________________ 201

Conclusions. ____________________________________ 202

Literature cited__________________________________ 202

ILLUSTRATIONS

Page 

FIGURE 60. Diagrammatic sketch of a festoon solid.. -.. _.__----__-.___-___--_____ 198

61. Various types of festoon solids and their relation to ore bodies___________________-__---______--____._ 200

62. Pattern of oxidation of a typical ore body in the Peanut mine, Montrose County, Colo______________________ 200

ABSTRACT

At the Peanut mine in the Bull Canyon mining district, 

Montrose County, Colo., vanadium-uranium ore is mined from 

the Salt Wash member of the Morrison formation of Late 

Jurassic age. All of the ore bodies occur in the upper orebearing sandstone zone of the Salt Wash member. Ore bodies 

are relatively small and occur in clusters on the flanks of 

channels cut into a mudstone zone below. Most ore bodies conform in shape to the outlines of festoon "solids"; smaller ore 

bodies are restricted to the upper parts of festoon "solids." 

The upper parts of individual ore bodies are more oxidized than 

lower parts. The festoon surfaces are relatively impermeable to 

ground water; many of the ore bodies are saturated with water 

perched above the basal surfaces of festoons.

The principal ore minerals are uraninite, coffinite, montroseite, 

and vanadiferous clays. Four unidentified and probably new 

vanadium minerals occur in the ore. Molybdenite, digenite, and 

native selenium are present in addition to the normal suite 

of metallic minerals.

The hypothesis is offered that the less permeable festoon surfaces "trap" the ore and inhibit draining of ground water, thus 

protecting the lower parts of ore bodies from oxidation.

INTRODUCTION AND ACKNOWLEDGMENTS

The Peanut mine is in the Bull Canyon mining district, Montrose County, Colo., about 15 miles west of 

Naturita, Colo.

A detailed study of the geology of the Peanut mine 

was begun in February 1954, for the primary purpose 

of determining the trace element composition of the ore 

deposit. Secondary objectives were to determine ,(1) 

if trace element dispersion patterns are present that 

might be used as guides to ore, (2) possible structural 

controls of the ore bodies, and (3) the paragenesis of 

the ore minerals.

The study of the mine included detailed mapping and* 

extensive sampling of the ore and adjacent rock, as 

mining progressed. The mine was visited almost every 

day during the first year of the study. Thin sections 

and polished sections were obtained for many of the 

samples. Preliminary results of the study reported 

in this paper indicate a definite relation between sedimentary structures of the host rock and the localization and oxidation of the ore bodies.

Mining on the Peanut claims was begun early in 1954 

by the J. R. Simplot Mining Co. of Boise, Idaho. In 

September 1954, the mine was sold to the Camoose 

Mines of America, Incorporated, of New York. The 

managements of both these companies were very cooperative in permitting the extensive studies of the mine.

197
198 GEOCHEMISTRY AND MINEEALOGY, COLORADO PLATEAU URANIUM ORES

Thanks are due to the chemists and spectrographers 

at the Denver and the Washington laboratories of the 

U. S. Geological Survey, who analyzed samples from 

the Peanut mine, and to D. A. Jobin, U. S. Geological 

Survey, who made permeability measurements of a 

number of samples.

STRUCTURE AND STRATIGRAPHY

The Peanut mine is located along the axis of the Dry 

Creek Basin syncline which lies between the Paradox 

Valley and the Gypsum Valley salt anticlines (Cater, 

1954). The rock strata are essentially horizontal in 

the vicinity of the mine.

The dissection of Bull Canyon has caused the regional water table to lower to a position several hundred 

feet below the ore horizon. This dissection, according 

to Fenneman (1931, p. 325), began at, or soon after, the 

beginning of the Pleistocene. Water now present in 

the Peanut mine is in small perched water tables.

Sedimentary rocks exposed in the vicinity of the 

mine range in age from Late Jurassic to Late Cretaceous. The formations in ascending order of age are 

the Entrada sandstone, the Summerville formation, and 

Morrison formation of Jurassic age and the Burro 

Canyon formation and Dakota sandstone of Cretaceous 

age. The Morrison formation of Late Jurassic age 

is composed of two members, the lower, the Salt Wash 

member, and the upper, the Brushy Basin member.

The Brushy Basin member consists of varicolored 

mudstones with a few interstratified layers of sandstone and conglomerate. It is about 400 feet thick in 

the vicinity of the Peanut mine, and has an indistinct 

contact with the underlying Salt Wash member.

The Salt Wash member is about 350 feet thick near 

the Peanut mine. It consists of a series of sandstone 

layers separated by red and green mudstone beds. 

Regionally, the sandstone layers pinch out or coalesce 

with other sandstone units. The top 40 to 60 feet of 

the Salt Wash member consists of a series of broad discontinuous sandstone lenses and thin discontinuous 

layers of red and green mudstone. All of the ore bodies 

at the Peanut mine occur in this stratigraphic zone, 

which is commonly referred to as the ore-bearing sandstone. The ore-bearing sandstone is underlain by a 

mudstone layer from 20 to 40 feet in thickness. 

Throughout most of the area the ore-bearing sandstone 

has a nearly uniform thickness of about 40 feet. Locally, it thickens abruptly to 60 feet or more where 

channels are cut into the underlying mudstone. Much 

of the ore-bearing sandstone is flat bedded or gently 

crossbedded, but in the vicinity of a channel the crossbedding is more complex. On the flanks of the channels 

a particular type of crossbedding, known as festoon 

cross-lamination, is especially well developed.

According to Knight (1929; 1930), festoons are the 

results of (1) the erosion of plunging troughs having 

the shape of a quadrant, or segment,14 of an elongate 

ellipsoid; (2) the filling of the troughs by clastic sediments, commonly in thin laminae which generally conform to the shape of the trough floors; and (3) the 

partial destruction, in differing degrees, of the filling 

laminae by subsequent erosion, producing younger 

troughs which intersect the older troughs.

Knight believes the force that created the festoons 

to have been oscillating currents in comparatively shallow water. Probably the same stream that cut the channel into the mudstone layer, at a later stage in its history and after some aggradation, created the festoon 

cross-laminations.

The geometric features produced by the intersections 

of groups of festoons are many and complex. The feature shown diagrammatically on figure 60 is produced 

by the intersection of three festoons and is more common than any other. Festoon 1 has been intersected by 

the later formation of festoon 2 and both have been 

intersected and partially destroyed by the formation 

of festoon 3.

For convenience in discussion, this physical feature 

as shown in figure 60, will be referred to as a festoon 

solid, i. e., a solid bounded by three festoon surfaces. 

The lower erosion surface, or trough floor, of the festoon solid will be called a basal festoon surface, and 

the mass of sandstone above the basal festoon surface 

and terminated by the upper festoon surfaces will be 

called the festoon fill. Less prominent cross-laminaFIOURB 60. Diagrammatic sketch of a festoon solid, showing festoon 

surfaces under which ore occurs. Numbers indicate order of formation of surfaces. Shaded areas represent roof of festoon solid under 

which ore occurs.

M The word "segment" was added by the authors.
SEDIMENTARY STRUCTURES, LOCALIZATION AND OXIDATION OF ORE, PEANUT MINE 199

tions occur in the festoon fill. They are related to the 

basal festoon surface, and will be referred to as secondorder festoon surfaces.

The festoon surfaces are relatively impermeable. 

Water perched above a basal festoon surface will drain 

only after the festoon surface is punctured by mining 

activities. A number of permeability measurements 

were made on samples taken from an unmineralized 

festoon solid. Samples from the center of the festoon 

solid showed relatively small differences in permeability measured parallel to and normal to the bedding 

planes. Samples taken from close to the festoon surface showed marked differences in permeability in the 

two directions; some samples were more than 100 times 

more permeable parallel to the bedding than normal 

to it. A thin clay seam is commonly present along the 

festoon surface; this clay is seldom retained when the 

core is prepared for the permeability measurement; 

therefore, the relative impermeability may actually be 

much greater through the festoon surface than measurements indicate on available samples.

ORE BODIES

Most of the ore bodies at the Peanut mine occur as 

clusters in the lower part of the ore-bearing sandstone 

zone, but small bodies of mineralized rock also occur in 

a zone 5 to 15 feet above the principal ore-bearing zone.

The ore bodies are lenticular in shape and tend to 

pinch out rapidly. Some closely spaced lenticular 

masses of ore coalesce into a single ore body. The 

average ore body is about 50 feet long, 20 feet wide, 

and varies in thickness from a few inches at the edges 

to 6 or more feet at the thickest part. Contacts between mineralized rock and barren rock are very sharp, 

and in general correspond to the major changes of direction of bedding, i. e., the cross-laminated festoon 

surfaces.

A few ore bodies in the mine have the shape of rolls 

(Fischer, 1942); the contact between mineralized and 

barren rock curves across the bedding. The contact is 

well defined and may be mapped as a continuous surface for a distance of 20 feet or more. Rolls trend 

about S. 70° to 80° E., and conform to the trend of 

rolls mapped in other mines in the district.

The average vanadium-uranium ratio of the ore 

bodies is about 9 to 1. Assays of a number of drill 

cores of ore bodies show an average grade of 0.5 percent U and 4.5 percent V. The average vanadiumuranium ratio of the smaller bodies of mineralized rock 

that occupy a stratigraphically higher position is about 

4 to 1. Assays of a few drill cores of these bodies show 

about 1 percent U and about 4 percent V. The grade 

of ore within one ore body does not appear to vary significantly, except where oxidation along fractures may 

have leached the ore. Local concentrations of higher 

grade uranium-bearing material are associated with 

organic matter. Sulfide minerals accompanying the 

ore tend to concentrate at the base of ore bodies.

The shapes of all ore bodies, except those few that 

make rolls, conform to the shapes of festoon solids 

whose surfaces mark the boundaries of the ore. Larger 

ore bodies nearly fill a festoon solid, but most of the 

ore bodies are smaller and are restricted to the upper 

parts of the structure.

The upper contacts of ore with barren rock almost 

invariably correspond to festoon surfaces the few exceptions are the ore bodies in the shape of rolls. Ore 

bodies are restricted to those festoon solids, or parts of 

festoon solids, whose upper surfaces have structural 

closure. The lenticular shape of the ore body is determined by the shape of the festoon solid in which it 

occurs and the amount of structural closure formed by 

the upper surfaces of the festoon solid. The simple 

lenticular shape of an ore body may be complicated by 

the presence of "splits" of barren rock penetrating the 

ore body. These "splits" correspond to second-order 

festoon surfaces.

Many variations of the symmetrical festoon solid are 

present in the mine. Some of the most common of 

these are shown in figure 61. Figure 61A shows a cross 

section of a symmetrical festoon solid, with mineralized 

rock in the upper part. Figure 61B shows a longitudinal section of the same festoon solid. The mineralized rock extends downward no further than the 

structural closure of the upper festoon surfaces. Figure 61B also shows the festoon solid as completely 

closed to the right, whereas to the left the festoon surfaces gradually flatten in dip, and either lose definition, 

or are truncated by other festoon surfaces.

Smaller bodies of mineralized rock that occur stratigraphically 5 to 15 feet above the ore zone commonly 

show a "satellite" relation to larger bodies of ore that 

are enclosed (in part) under the same through-going 

festoon surface. Such a relation is shown in figure 61C.

Some festoon solids are skewed rather than symmetrical, but in those too, the ore extends downward 

only as far as the festoon solid has closure, as shown in 

figure 61D.

Figure 61E shows a generalized cross section of a 

cluster of closely spaced or coalescing ore bodies contained in a complex group of interpenetrating festoon 

solids. It can be seen from this figure that prediction of 

the location and extent of ore bodies is difficult or impossible without recognition of the relation of ore 

bodies to the festoon surfaces. A positive result of this 

study has been the adaptation of mining methods to the
200 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

A. SYMMETRICAL FESTOON SOLID 

CROSS SECTION

B. SYMMETRICAL FESTOON SOLID 

LONGITUDINAL SECTION

C. ORE BODY IN FESTOON SOL ID 

WITH "SATELLITE"

CROSS SECTION

D. SKEWED FESTOON SOLID

CROSS SECTION

E. COALESCING FESTOONS; COMPOUND ORE BODIES

CROSS SECTION

EXPLANATION

Barren sandstone Mudstone

10 Feet

FIOUBB 61. Various types of festoon solids and tbeir relation to 

ore bodies.

controlling influences of the festoon surfaces, and a 

number of ore bodies have been discovered that might 

otherwise have been missed.

The position of ore bodies under relatively impermeable surfaces is similar to petroleum occurrences in 

anticlinal reservoirs under impermeable cap rocks, and 

also resembles certain types of hydrothermal mineral 

deposits where the ascending ore solutions are considered to have been impounded by an overlying impervious cover. A density stratification of the ore solutions with the ground water may have been responsible 

for this relation, or perhaps a hydrostatic head forced 

the solutions up into areas where under the influence 

of gravity alone they would not travel.

It is difficult to understand how the parts of festoons 

having closure, which would have been areas of relative 

stagnation, should have become loci of deposition. Presumably the solutions were dilute, though perhaps not 

far from saturation, and a large body of solution passing through the incipient ore body would seemingly 

be required. It is probably important that the festoon 

surfaces were only relatively impermeable.

It has been suggested, with, certain types of hydrothermal ore deposits (Mackay, 1946), that the impounding rocks were not entirely impermeable to the ore solutions, and by a process of "hypofiltration" permitted the 

water to pass through, leaving the minerals behind.

Much of Mackay's theory seems applicable to localization of vanadium-uranium ore. One of the physical 

features of ore deposits which he cites as evidence for 

his argument is the frequently observed presence of 

smaller ore bodies or weakly mineralized areas above 

the major ore body and localized under another "impermeable" layer. But the ore solutions must have 

passed through the lower "impermeable" rock! The 

"satellite" ore bodies observed in the Peanut mine are 

very similar in physical arrangement to the secondary 

ore bodies discussed by Mackay. The particular suite 

of metals that compose these vanadium-uranium deposits may be explained by a careful investigation into 

the penetrative power of the ions involved.

This discussion of the localization and method of deposition of the ore does not lead one inevitably to the 

conclusion that the ore solutions were hydrothermal. 

Circulating ground waters would most likely have been 

subjected to the same controls as low-temperature hydrothermal solutions.

Most of the ore bodies at the Peanut mine are unoxidized. Some oxidation has taken place, but is commonly restricted to zones along fractures, or to the 

upper parts of ore bodies. One partly oxidized ore 

body was sampled in detail. The pattern of oxidation 

is shown in figure 62. The lower part of the ore is unoxidized, and contains montroseite, vanadiferous clays,

BARREN SANDSTONE BARREN SANDSTONE 

OPEN FRACTURE

WATER

LEVEL

CROSS SECTION

EXPLANATION

5 Feet

Limonite stains

Tyuyamunite and pascoite

V(IV) Minerals, and native selenium

Unoxidized ore

V(IV) - V(V) Minerals Level of water before mining

FIOUBB 62. Pattern of oxidation of a typical ore body in the Peanut 

mine, Montrose County, Colo.
SEDIMENTARY STRUCTURES, LOCALIZATION AND OXIDATION OF ORE, PEANUT MINE 201

uraninite, and coffinite. Doloresite and other vanadium 

(IV) minerals occur as fracture coatings in the montroseite-bearing sandstone and at the top of the unoxidized ore. Abundant crystals of native selenium are 

also present in the fractures. Melanovanadite and 

other vanadyl vanadates occur slightly higher in the 

ore body than the vanadium (IV) minerals. At the 

top of the ore body are tyuyamunite and pascoite. The 

unmineralized sandstone around the most oxidized part 

of the ore body is stained by limonite.

The approximate level of the water perched above 

the basal festoon surface is indicated in figure 62. 

Montroseite containing essentially all vanadium (III) 

was collected from beneath the water level in one ore 

body, and after a few months in the laboratory, the 

material had oxidized almost completely to vanadium 

(IV), indicating that the presence of standing water 

in the festoon solid prevented oxidation of the montroseite in place.

The controlling influence of the festoon cross-laminations on the oxidation of the ore is indirect. After the 

lowering of the regional water table, the relative impermeability of the basal festoon surfaces caused the 

formation of perched water tables. The standing water 

saturating the ore bodies prevented their oxidation or 

restricted the oxidation that took place to the upper 

parts of the ore bodies.

MINERALOGY AND PARAGENESIS

Ore minerals impregnate sandstone and replace 

coalified wood. The highest grade uranium-bearing 

samples are associated with coalified wood. The chief 

uranium minerals are uraninite and coffinite; the most 

abundant vanadium minerals are montroseite and vanadium silicates.

Vanadiferous silicates occur as ill-defined masses interstitial to the quartz grains in the sandstone, and 

montroseite occurs as euhedral, lath-shaped crystals radiating from quartz grains. Commonly, the montroseite 

crystals are partly or completely surrounded by secondary quartz overgrowths. Montroseite associated with 

wood occurs both as masses of loosely coherent lathshaped crystals and as more solid botryoidal aggregates. 

In sandstone ore, uraninite and coffinite are finely divided and are not generally visible as discrete minerals. 

Polished section studies show that uraninite and coffinite 

in coalified wood replace cell walls and cell interiors 

selectively.

Montroseite in coalified wood is commonly associated 

with pyrite and yellow barite. Sulfide minerals found 

in small amounts with the unoxidized ore are pyrite, 

marcasite, chalcopyrite, chalcocite, molybdenite, galena, 

and sphalerite. Studies of polished sections show that

a small amount of digenite is associated with the chalcocite. Molybdenite and chalcocite commonly occur as 

thin layers along bedding planes at the base of an ore 

body, or at the base of a festoon solid whose upper part 

contains an ore body.

Doloresite is found intermixed with paramontroseite, 

but occurs more commonly as thin massive coatings on 

fractures. Thin coatings of doloresite are velvety 

black. In polished section extremely small terminated 

crystals are seen along the outer edges of the doloresite 

coating. In immersion the doloresite is brown and anisotropic. Simplotite (Thompson, Roach, and Meyrowitz, 1956a), a new calcium tetravanadite, and duttonite 

(Thompson, Eoach, and Meyrowitz, 1956b), a new oxide 

of tetravalent vanadium, form on the coatings of doloresite. Associated with the new minerals are felted 

masses of native selenium crystals.

Simplotite, CaV4O9 '5H2O, occurs as hemispherical 

aggregates of dark-green platy crystals. Duttonite, 

VO(OH) 2, occurs as crusts of randomly oriented platy 

crystals, light brown in color. Although simplotite, 

duttonite, and native selenium typically occur together 

on the earlier coating of doloresite, they are not intermixed, but instead each mineral occupies a separate 

though generally contiguous area.

The best samples of duttonite are associated with 

thicker layers of doloresite, which appears gray and 

submetallic. In these samples the doloresite partly or 

completely recements the fractures. Crusts of duttonite 

crystals are found in open spaces in the fractures, apparently altering from the doloresite.

Melanovanadite is the next formed vanadium mineral. It is abundant at the Peanut mine and a number 

of excellent specimens have been collected. It is found 

associated with duttonite and simplotite, as well as 

alone, and with two undescribed vanadium minerals that 

are considered to be vanadyl vanadates. On samples 

of coalified wood that has been replaced in part by 

uraninite and coffinite, melanovanadite occurs with the 

two undescribed vanadyl vanadates and tyuyamunite. 

In this type of occurrence, however, it apparently forms 

earlier than the other secondary minerals, because, while 

they occur as surface coatings, the crystals of melanovanadite penetrate the wood.

There is little oxidized ore as such at the Peanut mine 

although minerals typical of oxidized ore are present 

in small amounts that is, tyuyamunite, corvusite, and 

efflorescences of pascoite. Oxidation of the ore apparently results in the movement of some ions because 

limonite typically stains the unmineralized sandstone 

around the oxidized parts of ore bodies. Small amounts 

of malachite are found with the limonite. There is 

some indication that during oxidation vanadium moves
202 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

out into previously unmineralized sandstone and combines with silicates in place to form the light-gray lowgrade "vanadium clay" typical of oxidized ore.

No selenides have been found at the Peanut mine 

although clausthallite is present in a mine not far away. 

Detailed studies of the selenium content and association 

of pyrite and marcasite at the Peanut mine have not 

been made, but there is probably enough selenium in 

pyrite and marcasite to account for all of the native 

selenium found. Native selenium occurs relatively early 

in the oxidation sequence, with the last formed quadrivalent vanadium minerals, duttonite and simplotite, but 

pyrite occurs with more oxidized vanadium minerals. 

It is probable that marcasite alters before pyrite and 

yields the first formed native selenium.

In summary, the primary ore minerals are uraninite, 

coffinite, montroseite, and vanadiferous silicates. Associated with the primary minerals are small amounts 

of a number of sulfides and barite.

Montroseite alters in place to paramontroseite, but 

doloresite most commonly forms secondary coatings. 

Two new quadrivalent vanadium minerals form in the 

doloresite and are associated with native selenium. 

Melanovanadite forms next, then two undescribed 

vanadyl vanadates, and lastly corvusite, tyuyamunite, 

pascoite, and probably "vanadium clay." Limonite and 

malachite are associated with the last formed vanadium 

minerals.

CONCLUSIONS

Ore bodies are concentrated on the flanks of channels, 

where festoon cross-laminations are best developed. 

Contacts between mineralized and barren rock are 

sharp, and in all ore bodies, except rolls, they correspond to festoon surfaces. Ore bodies are contained

within festoon solids and are found only in the part of 

the festoon solid having structural closure. This fact 

is verified by observation of many separate ore bodies 

in the Peanut mine, and the same relationship has been 

observed in other mines in the area. Permeability 

measurements and the presence of perched water tables 

indicate that the festoon surfaces are relatively impermeable. Oxidation of the ore bodies has been inhibited by the presence of the perched water tables and 

most of the ore at the Peanut mine is unoxidized even 

though the regional water table is several hundred 

feet below the ore-bearing sandstone.

The sedimentary structures of the host rock, in particular the festoon cross-laminations, have exerted a 

controlling influence on the localization of the ore, and 

have determined the pattern of oxidation of individual 

ore bodies.

LITERATURE CITED

Cater, F. W., 1954, Geologic map of the Bull Canyon quadrangle:

U. S. Geol. Survey Geol. Quad. Map Series, GQ 33. 

Fenneman, N. M., 1931, Physiography of western United States:

New York, McGraw-Hill Book Co., 534 p. 

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah:

U. S. Geol, Survey Bull. 936-P, p. 363-394. 

Knight, S. H., 1929, The Fountain and Casper formations of the

Laramie Basin: Wyoming Univ. Pub. Sci., Geol., v. 1,

p. 1-82.

 1930, Festoon cross-lamination (abs.) : Geol. Soc. 

America Bull., v. 41, p. 86.

Mackay, R. A., 1946, The control of impounding structures on 

ore deposition: Econ. Geology, v. 41, p. 13-46.

Thompson, M. E., Roach, C. H., and Meyrowltz, Robert, 1956a, 

Simplotite, a new calcium tetravanadite from the Colorado Plateau: Science, v. 123, p. 1078.

 1956b, Duttonite, a new vanadium mineral from the 

Peanut mine, Montrose County, Colo.: Science, v. 123, 

p. 990.
Part 18. GEOLOGY AND MINERALOGY OF THE J. J. MINE, MONTROSE COUNTY, COLORADO

By DONALD P. ELSTON and THEODORE BOTINELLT

CONTENTS

Page

Abstract.........___.-_-----_._----------------__-_ 203

Introduction.______________________________________ 203

General geology...._________________________________ 204

Stratigraphy______________.-______---_--_-__-__ 204

Structure.. ___._.----.-___.---._...--_.--___-. 205

Description of ore body..____________________________ 205

Habits of the ore..---__-_-_-----_.--.._._....... 206

Ore controls__--__________----___-_-___--__-_- 206

Rolls-..-...---.--.-........-.-..---.-..------. 208

	Page 

Mineralogy....______-___.._-__-____-___.-____.-..__ 208

Unoxidized ore _________________________________ 208

Partly oxidized ore--___-____-------________---__ 210

Oxidized ore_________-__-__-----__._-._-_.-___ 210

Paragenesis--__.___..________-__-___________.__ 210

Oxidation of ore._______________________________ 210

Conclusions._______________________________________ 211

Literature cited___.______._____-_-__--.___________ 211

ILLUSTRATIONS

Page 

PLATE 6. A, Ore minerals deflected into a diffuse S-roll. B, Diffuse S-rolls. C, C-roll in black ore. D, Ore minerals with

a double C-roll configuration--______--__________________-.____________________________________________ 210

7. A, Corroded quartz grains (dark gray) surrounded by clay (gray) with montroseite crystals (white). B, Montroseite 

crystals (white) penetrating quartz overgrowths (gray). C, Montroseite (white) in organic material (gray) 

with comnite (dark gray)...__________________________________________________________________________ 211

FIGURE 63. Measured sections near the J. J. mine_____________._-----_______-__-_-_-__-______.____________________ 205

64. Geologic sections and outline map of the J. J. mine ___________________________________________________ 206

65. Outline map showing trends of paleostreams...___-_----------__-_-_-_____-_____-__--_-_________________ 207

66. Outline map showing location of ore types and water table_----_----_-__----______--_-___-__-__--____._._ 209

TABLES

Page 

TABLE 1. Generalized description of Paleozoic and Mesozoic strata, southwest side of Paradox Valley.__________________ 204

2. Paragenesis of the ore and gangue minerals in the J. J. mine.---_-__________________________________________ 210

ABSTRACT

Vanadium-uranium ore is mined at the J. J. mine in the Jo 

Dandy area, Montrose County, Colo. The ore is in the upper 

sandstone layer of the Salt Wash member of the Morrison 

formation of Jurassic age. Permeability and variations in 

permeability in cross-stratified sandstone units within the sandstone layer have influenced the gross distribution and, in many 

places, controlled the detailed configuration of ore. Carbonized 

wood apparently has been influential in localization of ore minerals where sedimentary structures have allowed ore solutions 

access to the wood. The J. J. mine intersects the ground water 

table; above the water table the ore and enclosing sandstone 

are oxidized, and carnotite and "vanadium clay" are the major

ore minerals. Below the water table the ore is unoxidized, 

and montroseite, uraninite, and comnite are the major ore 

minerals. An intermediate oxidized zone composed of hydrous 

vanadium oxides with intermediate valences is thin and poorly 

defined. The configuration and distribution of ore are little 

changed by oxidation. The ore minerals were emplaced by 

mineralizing fluids which moved laterally through the sandstone and which deposited low-valent minerals.

INTRODUCTION

Detailed geologic mine mapping and sampling of 

the J. J. mine in the Jo Dandy area, Montrose County, 

Colo., were undertaken to study a vanadium-uranium

203
204 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

ore body in terms of the physical relationships of ore 

to host rock, the paragenetic sequence of ore minerals, 

and the sequential development of an oxidized suite of 

ore minerals from unoxidized ore.

The J. J. mine is in the southwest part of the Jo 

Dandy area in the Bull Canyon mining district, and is 

about 8 miles due west of Naturita, Montrose County, 

Colo. The Jo Dandy area is an elongate strip of land, 

about 4 miles in length, bounded on the northeast by 

the floor of Paradox Valley (elevation 5,600 feet) and 

on the southwest by the rim of Monogram Mesa (elevation 7,100 feet).

Early in 1955, eight mines were active in the Jo 

Dandy area; in addition many mines and prospects 

were abandoned or inactive. The J. J. mine is the 

easternmost mine in the area. Production from the 

mine since 1949 has been in excess of 10,000 short tons.

Detailed mine mapping was begun in December 1953 

and completed by March 1954. Since that time periodic 

mapping has kept the outline of workings and geology 

up to date.

Permission to map and sample the J. J. mine was 

given by Mr. Everett M. Paris of the U. S. Vanadium 

Co. X-ray analyses were made by M. E. Thompson, 

U. S. Geological Survey.

GENERAL GEOLOGY 

STRATIGRAPHY

Kocks exposed in the area range from Pennsylvanian 

to Early Cretaceous in age (table 1). All the Mesozoic 

strata present in the area are exposed in faulted blocks 

along the south margin of Paradox Valley. Triassic 

and Lower Jurassic sedimentary rocks thin and pinch

out toward the axis of the Paradox Valley anticline to 

the north; the Morrison formation of Jurassic age and 

the Cretaceous formations were deposited across the 

anticline (Cater, 1954).

The mines are in the upper sandstone layer of the 

Salt Wash member of the Morrison formation of Jurassic age. Locally this sandstone is called the "ore-bearing sandstone." In the vicinity of the J. J. mine, the 

ore-bearing sandstone is subdivided into two sandstone 

strata separated by green or green and red mudstone 

(fig. 63, section A}. At the mine the ore-bearing sandstone is about 50 feet thick; the upper sandstone stratum 

ranges from 20 to 30 feet in thickness and contains the 

principal reserves of the area. The ore body in the J. J. 

mine is in the lower and middle parts of the upper 

sandstone stratum.

The ore-bearing sandstone is generally light to dark 

brown, medium to fine grained, and may be stained or 

speckled by limonite derived from the oxidation of 

pyrite. Light- to bright-red hematite staining has been 

observed locally. In areas where the pyrito has not 

been oxidized the sandstone is light gray. The sandstone is composed largely of subangular, clear and 

frosted grains of quartz and, in places, contains, apparently reworked, rounded to subrounded grains of 

quartz. Minor amounts of feldspar, biotite, red and 

green chert, and opaque minerals are present. Silica 

and calcite are the most common cementing agents. 

Where the rock is highly fractured and the pyrite well 

oxidized, little cementing material remains and the 

sandstone is friable. Seams of gypsum occur along 

many fractures above the water table, and in many 

places within the J. J. mine gypsum is currently being

TABLE 1. Generalized description of Paleozoic and Mesozoic strata, southwest side of Paradox Valley, Jo Dandy area,

Montrose County, Colo.

[Data are In part from an unpublished report on the Jo Dandy area by E. M. Shoemaker, 1950]

Era

Mesozoic

Paleozoic

System

Cretaceous

Jurassic

Jurassic(?)

Triassic

Pennsylvanian

Group

-Unconform

San 

Bafael 

group

-Unconform 

Glen 

Canyon 

group

-Unconform

Formation

Burro Canyon formation

ty 

Morrison formation

Summerville formation

Entrada sandstone

Ity 

Kayenta formation

Wlngate sandstone

Chinle formation ity 

Hermosa formation

Thickness 

(feet)

175-250

375-425

205-400

50- 70

0-95

0-200

0-300

0-80+

10,000+ 

locally

Character

Conglomeratic sandstone with Interbedded green mudstone; minor red 

mudstone near top. Vanadium-uranium bearing locally.

Brushy Basin member; red and green mudstone; some sandstone lenses; 

locally conglomeratic. Vanadium-uranium bearing locally.

Salt Wash member; red and green mudstone, light-colored sandstone layers 

persistent near top and base; lenticular strata between. Locally rests on 

Paradox member of Hermosa formation. Vanadium-uranium bearing.

Red with minor green mudstone; light-brown sandstone bed with ripple 

marks near top.

Yellow to light-red very fine-grained to fine-grained sandstone with subordinate medium-fine rounded quartz grains; locally large-scale crossbedding; red silt in basal part equivalent to the Carmel (?) formation.

Lavender micaceous sandstone, light brown locally; thin maroon mudstone 

beds.

Red massive sandstone, white locally; Irregularly bedded.

Dark- to light-red mudstone and sandstone; thin bedded; micaceous locally.

Paradox member; gypsum and black to dark-gray contorted shale and limestone; dark colored where overlain by Morrison formation, light colored 

where overlain by landslide debris.
GEOLOGY AND MINERALOGY OF THE J.J. MINE 205

precipitated as hairlike coverings on the mine walls. 

Soft, white subangular grains, resembling chert fragments altered to clay, occur both in barren and mineralized rock. X-ray patterns of samples of this material 

collected in the Jo Dandy area from the Salt Wash

Located hear the pbrtals of the thunderbolt, 

mine, about 300 to 500 feet northwest of the 

J.J.mine .

FEET ?-3-^-2

21.0 

8.3

0-

50-

100-

35.0

18.0

5.0. 6.0'

16.0

14.4 

5.0

Located 1,000 feet 

rjorth of the J. J

mne

sandstone

150-J 

.Scale in feet

EXPLANATION

Mineralized, rock

. FEET

ing

e" 52.0

- ___ _

52.0

2.0

15.0

15.0

10.0

22.0

5.0

42.0

15.0

3.5

18.0

8.0 

4.0

2.4' 

7.0

17.6

4.3

'.'. ' ' ' '.

"ir^S^

rt_r-L^_-

. . .

IJ-^Tt-T:

^_ !_~^_~

E- E~

n^injT

, j " _

i~-^~-^"-^"

^J^.

 _^ 

^F?f?

_ . _

 _rTLr-=_-;

~-T~iS~JT-

~^~. "= '

_rr_=-^rJ!fc<

s. 

u

*

4-

C

U

\

L

 z.

o

1-

<

2

cc 

0

u_

 z.

8

» o: 

a CE:

: O 

: s

5

^

-»

3

f }

j 1'

^

dO

="!- 

V

00 

(0

o.

I/I

«J

3 

 )

0

'

0)

30

0}

O

SUMMER FORMA of Jurass

FIODKB 63. Measured sections near the J. J. mine, Jo Dandy area, 

Montrose County, Colo.

sandstone member of the Morrison formation and Burro 

Canyon formation show quartz (Outerbridge, William 

F., written communication).

The ore-bearing sandstone is composed of an interbedded sequence of cross-stratified units similar to the 

^simple,: planar^ and trough cross-stratified units described by McKee and Weir (1952). Discontinuous, 

interbedded seams of gray-green mudstone, scattered 

mudpebble layers and carbonaceous zones and trash 

pockets are common. Cross-stratification ranges from 

laminations a few inches in length, within an individual 

bed, to trough cr6ss:stratified beds tens of feet in length 

which crosscut earlier sediments. The trough crossstratified beds are similar to "festoons" as described by 

Knight (1929), Stokes (1953), and Roach and Thompson (Part 17, p. 198).

STRUCTURE

The J. J. mine is adjacent to faulted strata on the 

southwest flank of the Paradox Valley anticline. In 

general the beds strike N. 64° W. and dip 10° to 14° SW. 

Fractures in the mine generally parallel the long axis 

of Paradox Valley. The dominant fracture set in the 

J. J. mine strikes N. 30° to 70° W. and has an average 

dip of 85° NE. A minor fracture set strikes about N. 

30° E. and dips either southeast or northwest. Most 

fractures show no displacement; a few show displacements of a few inches. In the Jo Dandy area faults displace both the ore and the enclosing sandstone and no 

fault or fracture set has been found that clearly predates 

the ore.

DESCRIPTION OF ORE BODY

The ore body is composed of interconnecting and 

overlapping layers of mineralized rock which coalesce 

locally to form minable rock as much as 19 feet thick. 

Ore minerals are distributed as mineralized spots, 

streaks, and disseminations, and in many places follow 

bedding laminae within larger sandstone units. Ore is 

distributed irregularly through cross-stratified sandstone units and generally is bounded top and bottom by 

less permeable mudstones and sandstones. In places 

the lower edge of mineralized rock may be 2 to 5 feet 

above the gray-green mudstone that separates the upper 

stratum of the ore-bearing sandstone from the lower. 

In other places the ore is in contact with or penetrates 

the upper few inches of this mudstone. The upper edge 

of mineralized rock coincides in places with mudstone 

seams and mudstone pebble layers (fig. 64, sections 

A-A' and B-B'}. Individual ore layers are more 

persistent and continuous along rather than across the 

trend of the sedimentary structures (compare figs. 64 

and 65). The trend of the main part of the ore body
206

EXPLANATION

Geology by 0. P. El.ton and 0. D. Hoym

FIGURE 64. Geologic sections and outline map of the J. J. mine, Jo Dandy area, Montrose County, Colo.

follows these sedimentary structures and crosscuts, at a 

low angle, the dominant fracture set of the area.

HABITS OF THE ORE

Although the boundaries of mineralized rock in many 

places cut across sedimentary structures, the sedimentary structures seem to control the location of ore both 

on a broad scale and in detail.

On outcrop at the portal of the J. J. mine (fig. 64, 

section A-A') two layers of sandstone, that are less 

massive and more intensely cross-stratified than overlying and underlying beds, are mineralized. The lower 

mineralized layer is more prominently crossbedded and 

this layer is extensively mineralized throughout the 

mine. Near the portal of the mine a flat-layered thinbedded mineralized sandstone contains a single tabular 

layer of ore. The upper and lower limits of ore are 

gently undulating; in detail they cross the bedding at a 

low angle, but in general parallel the bedding. Ore 

minerals follow minor cross-laminae within the sandstone layer.

In places in the J. J. mine the distribution of mineralized layers is erratic, and abrupt variations in thickness and sharp crosscutting relationships are prominent 

(fig. 64, sees. A-A', B-B', D-D'}. These configurations are associated in part with trough cross-stratification. The ore minerals follow bedding laminations in 

detail, but the ore minerals may pinch out against intersecting structures.

In mineralized zones, pods of very rich ore are found 

associated with carbonaceous material. Essentially similar carbonaceous material in barren zones is barren.

ORE CONTROLS

The relations described above indicate that the varying permeability of the different sedimentary structures 

controls the detailed shape of the ore body. The permeability is high, but irregular in sandstones that show 

trough crossbedding, and in these beds the ore layers 

and mineralized zones are very irregular. In the sandstones where simple and planar crossbedding is dominant, and where the permeability is less variable, the 

ore layers are tabular and less irregular in shape.

Carbonaceous material has caused, probably by chem-
GEOLOGY AND MINERALOGY OF THE J.J. MINE 207

EXPLANATION

Trend of axis of roll showing geometric, 

configuration of the mineralized rock, 

roll open to the northeast

Trend of "S°-shaped roll

Trend of axis of cross-stratified trough 

in sandstone showing direction of 

flow of depositing stream, based 

on measurements of dips of crossbedding.

Fossil log

10; 0 50 Feet

Geology by D. P. Elston

FIGURE 65. Outline map showing trends of paleostreams as mapped from trough cross-stratified sandstone beds, J. J. mine, Jo Dandy area,

Montrose County, Colo.

ical rather than physical means, the precipitation of 

rich pods of ore where permeable layers have allowed 

access of solutions to this material.

The gross control for the localization of mineralized 

ground is not evident. Although the ore body is elongate in the general direction of the dominant fracture 

set, which in turn parallels the Paradox Valley anticline, the trend of the thicker or main parts of the ore

468652 5« 15

body crosscuts the fractures. The southward and southeastward extension of the ore body, as known from 

drilling, supports the mapped and observed data in the 

mine. The trend of the best ore is parallel to the stream 

trends as determined by mapping of the sedimentary 

structures (fig. 65). Lateral separation of the ore body, 

from a single mineralized layer, into two or more thinner mineralized layers is more abrupt and more pro-
208 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

nounced across rather than along the trend of the sedimentary structures. The trend of the best ore is southeastward in the northern part of the mine and swings 

to a more southerly direction in the southern part of 

the mine. The sedimentary structures do not represent 

a clearly defined channel in the ore-bearing sandstone, 

but they seem to define a composite channel trend developed at the time of deposition of the sediments. As 

such they would present a zone of greater permeability 

to laterally moving mineralizing solutions.

BOLLS

The term roll (Fischer, 1942, p. 380-384) is applied 

to mineralized rock where the edges of mineralized 

rock, or the configurations of leaner and richer material with mineralized rock, cut across bedding and 

usually described a geometric figure (e. g. C-shaped, 

S-shaped). The formation of some rolls in the J. J. 

mine can be attributed to primary sedimentary structures (pi. 6A, B). Some may be the result of localization of ore minerals around fossil trees (C-roll around 

fossil tree, fig. 65). Plate 6C and D show views of Crolls in the J. J. mine. Other rolls may be the result of 

local redistribution of vanadium (pi. QB). Still others 

are unexplained.

The axes of the roll surfaces in the J. J. mine (fig. 

65) parallel the regional structure, are normal to the 

"Uravan mineral belt" (Fischer and Hilpert, 1952), 

and parallel the long axis of the trend of mineralized 

ground in the mine which in turn generally parallels the 

trend of the sedimentary structures. One roll, which 

has an anomalous strike, contains a thin, mineralized 

tree along its axis. The tree seems to have been trapped 

and buried in sandstone at an angle to the stream flow 

of that time.

A set of S-shaped roll surfaces in oxidized sandstone (pi. 64, B) has diffuse bands of gray "vanadium clay" which in part crosscuts the bedding and obscures the remants of primary spotted and streaked disseminations similar to those in unoxidized ore. No similar S-rolls have been found in unoxidized parts of the 

mine. Several modes of formation can be postulated 

for the S-shaped rolls: (1) the rolls are primary and 

represent periods of pulsation and temporary stagnation of an edge of a mineralizing solution; (2) the rolls 

represent a pulsating movement of the mineralizing 

solutions which caused a partial redistribution of the 

ore minerals into the poorly defined S-shaped bands 

with a partial depletion of the ore minerals from the 

intervening areas; or (3) the roll surfaces are the result of a partial redistribution of ore minerals during 

oxidation and were superimposed on original spotted 

and streaked mineralized rock. In any event, the field 

relations indicate that the configuration of these S-rolls

is the result of a deflection of solutions by an overlying partly intersecting, trough crossbedded sandstone structure.

MINERALOGY

The ore in the J. J. mine ranges from oxidized ore 

in the upper part of the mine to unoxidized ore below 

the water table (fig. 66). The major uranium minerals 

are carnotite, tyuyamunite, uraninite, and coffinite. 

The major vanadium minerals are montroseite, vanadium silicates,15 and corvusite. Accessory vanadium minerals are melanovanadite, hewettite, and several unnamed vanadate minerals. Nonmetallic gangue minerals are quartz, gypsum, calcite, barite, clay minerals, 

and limonite. Carbonaceous material is widely distributed through the mine in small quantities. Metallic 

gangue minerals include pyrite, marcasite, galena, 

sphalerite, and native selenium.

The black unoxidized ore containing montroseite, 

coffinite, and uraninite occurs below the water table. 

Immediately above the water table is a thin discontinuous zone of partly oxidized ore. Above this zone 

is the zone of oxidized ore containing carnotite, tyuyamunite, and vanadium silicates. Minor exceptions to 

this distribution occur. In black ore, high-valent minerals occur close to some through-going fractures. In 

oxidized ore, pods of unoxidized or partly oxidized ore 

occur where carbonaceous material has reduced oxidizing solutions or, more likely, an impermeable area has 

prevented oxygen from reaching the ore.

UNOXIDIZED ORE

Ore minerals of the black unoxidized ores are montroseite, uraninite, coffinite, and vanadium silicates. 

Quartz, calcite, gypsum, clay minerals, and barite are 

the major gangue minerals. Pyrite and marcasite are 

prominent locally. Galena and sphalerite occur 

sparsely distributed through the ore.

Characteristic microtextures of unoxidized ore show 

montroseite in intergranular areas either by filling or 

by replacement of the clay mineral matrix. A few 

specimens show corrosion of the quartz grains (pi. fA) 

and some show montroseite crystals penetrating silica 

overgrowths on the quartz grains (pi. 7.Z?).

Montroseite occurs typically as bladed crystals in 

radial arrangement. A few crystals show terminal 

faces; typically the ends are ragged or fibrous.

Uraninite and coffinite were studied in polished sections of organic material; uraninite with montroseite 

fills cell interiors and coffinite replaces cell walls. Where 

cell textures are obscure, coffinite occurs as fine dark

15 Vanadium silicates here denote the fine-grained nonmetallic 

vanadium-bearing matrix material of the sandstone and include one or 

more of the following: vanadium mica, vanadium-bearing chlorite and 

clay minerals, and clay minerals with adsorbed vanadium.
GEOLOGY AND MINERALOGY OF THE J.J. MINE 209.

6A, 6B

EXPLANATION

Partly oxidized blue-black corvusite-montroseite 

pods and seams in oxidized limonite-stained 

sandstone which contains carnotite and gray- 

"vanadium clay* minerals; distribution .not 

shown where these overlie black montroseiteApproximate location of ground-water table 

and coincident black montroseite ore overlain 

by oxidized carnotite-type ore

Approximate location of present limit of 

montroseite ore not overlain by oxidized 

carnotite-type ore; some local oxidation is 

found adjacent to fractures which extend 

into overlying zone of oxidation

Location of photographs, 

Plate 6

- ^VSSRCW^SSS*

Geology by D. P. Elston 

Surveying by D. P. Elston and D. D. Haynes

FIGURE 66. Outline map showing location of ore types and water table, J. J. mine, Jo Dandy area, Montrose County, Colo. Numbered locations : 1, figure 4; 2, figure 5; 3, figure 6.

shreds in a lighter-colored matrix (pi. 7C). A few 

minute grains tentatively identified as uraninite were 

seen in sandstone.

All the organic material examined shows some indication of woody texture. Samples of organic material 

with low radioactivity are brownish black in color and 

contain small amounts of metallic minerals. Samples 

of organic material with high radioactivity are black,

and contain a larger amount of metallic minerals. 

Under the reflecting microscope, the brownish-black 

material is gray and isotropic; the black material is 

olive tan and strongly anisotropic.

Overgrowths on quartz grains are common, and in 

areas a few millimeters across, the rock type approaches a quartzite. Partial crystal outlines are 

common.
210 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

PABTLY OXIDIZED ORE

Partly oxidized ore as it occurs in the mine is a 

mixture of low-, intermediate-, and high-valent minerals. The chief vanadium mineral of this stage is 

corvusite which gives the ore a blue-black color. 

Uranium occurs in uraninite and coffinite as relicts of 

unoxidized ore, and in carnotite and tyuyamunite where 

oxidation has occurred. Accessory vanadium minerals 

are melanovanadite and other vanadate minerals. 

Gangue minerals are limonite, native selenium (rare), 

and gypsum. Some sulfides, such as pyrite, may remain 

from the primary ore.

Many of the textures of unoxidized ore are retained 

in the partly oxidized ore. Shreds and corroded fragments of montroseite remain in the clay matrix; carbonized wood is apparently not changed by oxidation.

TABLE 2. Paragenesis of the ore and gangue minerals 

Paragenetic stage

1. Sedimentary _

2. Diagenetic.

3. Mineralization.

4. Partly oxidized.

5. Oxidized.

Mineral 

Quartz.__---__-______

Feldspar.____________

Clay minerals.________

Carbonaceous material 

Gypsum_ _ __________

Calcite. ______________

Quartz. ______________

Pyrite______________

Montroseite. __________

Vanadium silicates. 

Uraninite. ________

Coffinite________

rCorvusite__ _ ________

Melanovanadite__ ______

New vanadate minerals.

Native selenium. ______

^Limonite _____________

Carnotite_ _ _ ________

Tyuyamunite _________

| Gypsum____________

(.Hewettite. ___________

are approximately contemporaneous; minerals of an 

early stage may persist into a later stage. No textural 

evidence was found to indicate any separation in time 

of emplacement of the low-valent uranium and vanadium minerals. Some minerals such as pyrite and gypsum may have formed in several stages.

OXIDATION OF ORE

The ore minerals were originally distributed as 

spotted and streaked disseminations in sandstone, as 

local high-grade zones or bands in sandstone, and as 

pods or irregular masses of high-grade ore associated 

with carbonaceous material.

Spotted and streaked montroseite-type ore oxidizes 

from black through varying stages of gray, to a lightand dark-gray ore faintly speckled with carnotite. 

This sequence can be observed in a vertical space of

Carnotite and tyuyamunite occur in sandstone as disseminations and seams.

OXIDIZED ORE

Carnotite and tyuyamunite are the major uranium 

minerals in oxidized ore; the major vanadium minerals 

are vanadium silicates. Common gangue minerals are 

gypsum and limonite. A small amount of hewettite 

occurs disseminated in seams.

Oxidized ore is primarily an intergranular filling. 

Seams of the bright yellow uranyl vanadates are conspicuous, but most of the ore minerals are disseminated 

through the sandstone.

PARAGENESIS

Paragenesis of the ore and gangue minerals is shown 

in outline form in table 2. The minerals of each stage

in the J. J. mine, Jo Dandy area, Montrose County, Colo. 

Mode of occurrence

fDetrital minerals, sand grains, and intergranular material.

JAs cements and intergranular material.

Overgrowths on quartz grains.

As disseminated grains, replacing wood.

As crystals in intergranular material, in cells in wood, in quartz 

overgrowths.

In intergranular area.

In carbonaceous (woody) material, in wood cells.

In carbonaceous (woody) material, in cell walls.

Disseminated and massive, replacing wood, quartz, and in intergranular space.

Disseminated, in seams, massive.

Rosettes in veins (rare).

Surrounding quartz and other vanadium minerals, in fine-grained 

irregular masses (rare).

Disseminated, banding (rare).

Disseminated, replacing pyrite or marcasite.

1 Coatings on fractures, veins, disseminated in sandstone, 

jEfflorescences, veins, disseminated in sandstone.

about 10 feet at places in the mine where stoping has 

intersected the ground water table. The gross physical 

appearance of such spotted and streaked disseminations is not changed by oxidation. 

. Blue-black corvusite ore is not megascopically apparent where disseminated ore minerals have been oxidized. If a corvusite stage does form during oxidation 

of all montroseite-type ore, it may be short lived and 

megascopically inconspicuous in places where the ore 

minerals are disseminated in sandstone.

Blue-black corvusite pods, masses, and seams are distributed through the oxidized light-gray carnotitevanadium clay part of the mine (fig. 66). The pods 

contain corvusite, montroseite, pyrite, marcasite, and 

carbonaceous material. These are the little or partly 

oxidized equivalents of black high-grade montroseite 

.pods and seams of ore which have been protected from
GEOLOGICAL SURVEY PROFESSIONAL PAPEK 320 PLATE 6

A. ORE MINERALS DEFLECTED INTO A DIFFUSE S-ROLL AT THE BASE OF 

AN OVERLYING TROUGH CROSS-STRATIFIED SANDSTONE BED.

Bed strikes into picture.

B. DIFH M >-!{(]].I >, WHICH KKH.Il.l NIK S-ROLL CONFIGURATION OF 

FIGURE I>A.

C. C-ROI.L IN BLACK ORE. 

Ore minerals are partly oxidized in upper part of roll.

D. ORE MINERALS WITH A DOUBLE C-ROLL CONFIGURATION CONNECTING 

TWO MINERALIZED LAYERS.

Ore is partly oxidized.
GEOLOGICAL SURVEY P

B.

A. CORRODED QUARTZ GRAINS 

ROUNDED BY CLAY (GRAY) 

CRYSTALS (WHITE).

Black dots are pits in section. Polish

light, green filter

B. MONTROSEITE CRYSTALS (W

QUARTZ OVERGROWTHS 

Clay and quartz are same shade of gray

section. Polished section, X 165, pla

C. MONTROSEITE (WHITE) IN ORGA

WITH COFFINITE (DAR

Black dots are pits in section. Polish

light, green filter

4fc,
GEOLOGY AND MINERALOGY OF THE J.J. MINE 211

rapid oxidation by a combination of physical and 

chemical means. Oxidation proceeds more slowly 

within these pods and the change from a black to a 

blue black is coupled with a decrease of montroseite 

and an increase of corvusite. A thin disseminated red 

to red-brown band is formed adjacent to the main mass 

of the montroseite; outside of this is a thin diffuse band 

of native selenium and outside of this a yellow zone. 

Further oxidation causes removal of the native selenium and the unidentified red band. Vestiges of these 

pods are represented by high-grade pods of carnotite 

developed when the uranium and vanadium are oxidized to U (VI) and V (V).

CONCLUSIONS

In the J. J. mine sedimentary structures have, in 

many places, influenced the detailed configuration of 

the ore and are probably the cause of the gross localization of the ore. The permeability and the variation in 

permeability are the major controlling features of the 

sedimentary structures. Fractures show no controlling 

relation to ore. Carbonized wood has caused deposition of rich ore where mineralizing solutions have had 

access to it.

The ore was deposited as low-valence oxides and silicates of uranium and vanadium. Oxidation above the 

ground water table has modified the original distribution of minerals. The carnotite assemblage is in the 

oxidized zone and the montroseite-uraninite assemblage 

is in the unoxidized zone. Oxidation has caused no 

important change in either the gross or the detailed 

configuration of the ore; however, some minor redistribution of vanadium and uranium occurs during 

oxidation.

LITERATURE CITED

Cater, F. W., 1954, Geology of the Bull Canyon quadrangle, 

Colorado: U. S. Geol. Survey Geol. Quadrangle Map GQ 33.

Fischer, R. P., 1942, Vanadium deposits of Colorado and Utah: 

U. S. Geol. Survey Bull. 936-P.

Fischer, R. P., and Hilpert, L. S., 1952, Geology of the Uravan 

mineral belt: U. S. Geol. Survey Bull. 988-A.

Knight, S. H., 1929, The Fountain and Casper formations of the 

Laramie basin: Univ. Wyo. Pub. Sci., Geol., v. 1, p. 56-74.

McKee, E. D., and Weir, G. W., 1952, Terminology for stratification and cross-stratification in sedimentary rock: Geol. Soc. 

America Bull., v. 64, p. 381-390.

Stokes, W. L., 1953, Primary sedimentary trend indicators as 

applied to ore finding in the Carrizo Mountains, Arizona 

and New Mexico: U. S. Atomic Energy Coinm. RME-3043, 

pt. 1, Tech. Inf. Service, Oak Ridge, Tenn.

Part 19. MINERALOGY AND GEOLOGY OF THE RIFLE AND GARFIELD MINES, GARFIELD

COUNTY, COLORADO

By THEODORE BOTINELLY and R. P. FISCHER

CONTENTS

	Page 

Abstract_..._.-__._..__..._.__._._____._-_-___--- 213

Introduction _______________________________________ 213

Geology......____...__...__________.__..___._____. 214

Stratigraphy ______._____________-___--_--_-_--- 214

Structure______________________________________ 214

Ore deposits___-_-__._____.__--_--______-_-____-- 215

Mineralogy ________________________________________ 216

Vanadium ore-----_____-__-__--_----___-------- 216

Mineralogy Continued

Oxidation of the vanadium ore. -___________--__.

Mineralogy of the galena-clausthalite band____-_-.

Oxidation of the galena-clausthalite band._____.-.

Mineralogy of the green (chromium-bearing) layer. 

Conclusions.______________________________________

Literature cited.-______-__--__-__-______-_.__---__.

Page

216

217

217

217

218

218

ILLUSTRATIONS

PLATE 8. A, View of No. 3 vein, Garfield mine. B, Photomicrograph of thin section of high-grade ore.

Page

216

ABSTRACT

The vanadium-uranium deposit at the Rifle and Garfield 

mines is in the Navajo(?) sandstone of Jurassic and 

Jurassic (?) age and the overlying Entrada sandstone of 

Jurassic age. Both formations are composed of clean, lightcolored, fine-grained, massive, and crossbedded sandstone.

The ore, which consists of vanadium with only a small 

uranium content, occurs in fine-grained minerals that impregnate the sandstone. It forms three partly overlapping layers, 

each of which is tabular and lies generally parallel to the 

major bedding. Each vanadium layer is bordered on one side 

by a very thin band of finely disseminated galena and clausthalite, beyond which is a thin greenish layer containing a 

chromium-bearing mineral. The galena band and the chromiumbearing layer lie above the lower and upper vanadium layers 

but below the middle vanadium layer.

Primary ore minerals of the vanadium layer are roscoelite, 

vanadium-bearing hydromica, and small amounts of vanadiumbearing chlorite and inontroseite. Base-metal sulfides are 

sparse in the ore but abundant in the galena band. The 

chromium-bearing layer is similar in appearance to that at 

Placerville, Colo., where inariposite has been described. Oxidation has not appreciably affected the roscoelite; montroseite 

and perhaps vanadium-bearing chlorite and hydromica have 

oxidized to form minor secondary vanadium minerals. A little 

carnotite is present in the oxidized parts of the deposits, but 

the primary uranium minerals have not been recognized.

The deposit is similar to vanadium-uranium deposits of the 

Plateau but is unique in the high ratio of vanadium to uranium, 

the lack of carbonaceous material, and the abundance of 

roscoelite.

INTRODUCTION

The vanadium-uranium deposit at the Rifle and 

Garfield mines is partly in the Entrada sandstone of 

Jurassic age and partly in an underlying sandstone 

that has been questionably correlated with the Navajo 

sandstone of Jurassic and Jurassic (?) age. Both formations are composed entirely of clean, fine-grained, 

massive sandstone. This deposit, like those in the Entrada near Placerville, Rico, and Durango, Colo., has 

been worked mainly for vanadium; the uranium content of the ore is so low that it has had only byproduct 

value. In addition to the low uranium content, these 

deposits in the Navajo(?) and Entrada sandstones 

differ from most of the vanadium-uranium deposits in 

other formations on the Colorado Plateau in that 

abundant shaly and carbonaceous material is lacking. 

Otherwise these deposits are quite alike, and all are 

of the same general type.

The Rifle and Garfield mines are on East Rifle 

Creek about 13 miles northeast of Rifle, Garfield 

County, Colo. The Rifle mine, on the east side of the 

creek, was worked from 1925 to 1932, during World 

War II, and again in the late forties and early fifties. 

Mine workings extend for more than 7,000 feet eastward from the outcrop along the creek. The Garfield 

mine, on the west side of the creek, was worked mainly

213
214 GEOCHEMISTRY AND MINEEALOGY, COLORADO PLATEAU URANIUM ORES

during World War II, though a small amount of 

mining was done before then and some development 

has been done since the war. The workings extend 

several hundred feet westward from the outcrop.

The deposit at the Rifle and Garfield mines presents 

an unusually good opportunity to study and interpret 

some geochemical relations that are more confusing 

elsewhere. Not only is this deposit well exposed in the 

mines and at the outcrop, so the character of the ore 

and the habits of the ore bodies can be readily observed, 

but also these features are more consistent than in many 

of the Plateau deposits. Even so, in spite of these 

advantages, the geologic factors that influenced localization of the deposit have not been recognized, and the 

genesis cannot yet be explained.

The mines and surrounding area were studied and 

mapped by the junior author, assisted by W. L. Stokes 

and L. E. Smith, in the summer of 1944. The area 

was revisited by the junior author in 1954, to bring 

the geologic map of the mine workings up to date, during which time he was assisted for intervals of several 

days each by D. C. Hedlund, E. B. Ekren, R. T. Chew 

III, H. S. Johnson, and D. D. Haynes. The present 

report is based on this field work and the samples collected at that time; these samples and thin sections from 

them were studied by the senior author. A more detailed report on the geology and ore deposits of the 

area, which will include an areal geologic map as well 

as detailed geologic maps of the mines, is being 

prepared.

GEOLOGY

The area lies on part of the Grand Hogback monocline, a fold that flanks the White River Plateau uplift 

to the north and east, and which exposes rocks ranging 

from Precambrian to Tertiary in age. Rocks in the 

immediate vicinity of the Rifle and Garfield mines consist of sedimentary formations of Triassic, Jurassic, 

and Cretaceous ages. Only the Navajo(?) sandstone 

(Jurassic and Jurassic(?)) and the Entrada sandstone 

(Jurassic), which contain the ore deposit in these mines, 

will be described in detail.

STRATIGRAPHY

The oldest rocks in the vicinity of the Rifle and Garfield mines consist of a thick sequence of red beds, and 

the upper few hundred feet of which have been correlated by Thomas, McCann, and Raman (1945) with 

the Chinle formation of Triassic age. The Chinle is 

composed of shale, siltstone, and fine-grained sandstone. 

These beds are dominantly red, but in the vicinity of 

the Rifle and Garfield mines the upper few feet of the 

formation is altered to gray.

The sandstone unit immediately above the Chinle

and beneath the Entrada sandstone is host to much of 

the ore in the Rifle mine. Several formational names 

have been applied to this unit, but on the basis of recent 

work, which is not yet published, N. Wood Bass and 

John R. Donnell (written communication, 1957) consider this unit to be equivalent to the Navajo sandstone. 

This name, with a query, will be used in this report.

The Navajo (?) is a light-brown fine-grained sandstone with large-scale crossbedding inclined southward. 

It crops out in a rough, nearly vertical cliff. As it is 

hard and brittle, it is fractured by many vertical joints, 

both at the outcrop and underground. This formation 

ranges from 30 to 70 feet in thickness in the vicinity 

of the mines, and it pinches out a few miles east of the 

mines. The Navajo( ?) contains the principal ore body 

(No. 1 vein) in the Rifle mine.

The Entrada sandstone is white to light gray and 

predominantly fine grained but with large, well-rounded 

grains scattered through it. Crossbedding is prominent; the planes are curved, but, in contrast to the 

Navajo (?), they are not inclined in a common direction. 

The formation is soft and friable and weathers to 

rounded cliffs and steep slopes; jointing is not as conspicuous as in the Navajo(?). The Entrada ranges 

from 75 to 125 feet in thickness. It contains the ore 

bodies (No. 2 and No. 3 veins) in the Garfield mine 

and several small masses of ore in the Rifle mine.

The Entrada sandstone is overlain by the Morrison 

formation of Jurassic age. The Morrison is about 500 

feet thick. The lower 150 feet consists of several lenticular sandstone strata that are gray to greenish gray, 

medium grained, and interbedded with red, green, and 

gray mudstone. The sandstone beds contain a few 

small deposits of uranium-vanadium ore, which will not 

be described in the report. The upper part of the Morrison consists of mudstone that is predominantly green 

or gray but in part varicolored, with a few thin and 

lenticular beds of sandstone, siltstone, and limestone.

The Dakota (?) sandstone of Cretaceous age overlies 

the Morrison and consists of gray and brown sandstone 

and shale. It is about 80 feet thick.

The Mancos shale, also of Cretaceous age, lies on the 

Dakota (?). It consists of several thousand feet of gray 

shale.

STRUCTURE

The rocks in the vicinity of the Rifle and Garfield 

mines generally dip southward at moderately low 

angles, but this attitude is modified locally by faults 

and minor flexures. Within the mines, beds dip southward at angles ranging from about 15° to 30°.

Three sets of faults are present; two sets dip nearly 

vertical and the third dips at low angles. Of the two 

high-angle sets, one trends generally eastward and is
MINERALOGY AND GEOLOGY OF THE RIFLE AND GARFIELD MINES 215

the stronger and apparently the older. One fault has 

been traced for several miles and has a maximum displacement of a few hundred feet; most faults of this 

set, however, are shorter and have displacements of less 

than 100 feet. The other set of high-angle faults trends 

northwestward, rarely exceeds a few tens of feet in displacement, and has not been traced for more than a 

few thousand feet. Faults of both sets are exposed in 

the mines but none of these have displacements exceeding 10 feet.

The low-angle faults are reverse faults with displacements ranging from a small fraction of an inch to as 

much as a foot. All dip southward and for the most 

part follow the bedding planes or cut across the beds at 

small angles. They are conspicuous in massive sandstone and probably resulted from bedding plane sliding 

at the time of folding. They appear to be younger than 

the high-angle fractures.

Joints are common, especially in the hard sandstone 

units, such as the Navajo(?). All the joints dip at 

high angles, and most strike easterly and northwesterly, 

parallel to the two sets of nearly vertical faults.

Below the zone of oxidation, some of the joints and 

a few of the high-angle faults contain thin, discontinuous veinlets of calcite and marcasite; where oxidized 

these fractures are iron stained. In the Chinle formation, some of the joints and faults are bordered by a 

narrow band of alteration, which has changed the color 

of the rock from red to gray, and which is similar in 

appearance to the zone of alteration that is present at 

the top of the Chinle in the vicinity of the ore deposit.

ORE DEPOSITS

The ore is sandstone impregnated with fine-grained 

vanadium and uranium minerals. These minerals color 

the rock gray, and, in general, the color darkens as vanadium increases in content. Most of the ore that has 

been mined contains between 1 and 3 percent V2O5 . No 

plant fossils or other carbonaceous material has been 

recognized in the ore-bearing sandstone, except for 

small pellets of asphaltic material that occur sparsely 

along a few joints.

The ore occurs in three layers, which the miners call 

the No. 1, No. 2, and No. 3 "veins" in ascending order. 

These layers are tabular, and they range in thickness 

from a few inches to as much as 30 feet. They lie generally parallel to the major bedding or formational 

contacts, but in detail they cross the bedding and in 

a few places even the formational contacts. The No. 

1 vein is the principal ore layer in the Eifle mine. It 

lies mostly in the Navajo( ?) sandstone, but in at least 

two places it thickens sufficiently to extend up into the 

lower part of the Entrada sandstone, and in a few

places it crosses into the upper foot of the underlying 

Chinle formation. The No. 2 vein is discontinuous. It 

forms the principal ore body in the Garfield mine and a 

few small- to moderate-sized ore bodies in the Rifle 

mine. The No. 2 vein is in the Navajo( ?) sandstone at 

the east end of the Rifle mine, where it connects with 

the No. 1 vein. All of the other known ore bodies in 

the No. 2 vein are in the Entrada and do not obviously 

connect with the No. 1 vein. The No. 3 vein is known 

only in the Garfield mine, where it forms two ore bodies 

in the Entrada. One small body has been mined at the 

outcrop, and it is about 20 feet above the No. 2 vein. 

The second ore body in the No. 3 vein lies several feet 

above the ore layer of the No. 2 vein in the main workings of the mine and the two layers join along the 

northwest edge of the mine.

Each of the layers is strikingly asymmetric vertically across the layer. Each shows the same asymmetry, 

but the middle layer (No. 2 vein) is a mirror image (or 

upside down) with respect to the lower and upper layers (No. 1 and No. 3 veins, respectively). The asymmetric characteristics of the No. 3 vein are shown and 

described in plate 8A. The No. 1 vein shows exactly 

the same characteristics, and the same vertical sequence; 

the No. 2 vein shows exactly the same characteristics 

but in a reverse vertical sequence.

The No. 1 vein in the Rifle mine forms an elongate 

ore body that has been followed by mining for about 

7,000 feet in a northeasterly direction from its outcrop 

on East Rifle Creek. The ore is generally thicker and 

lower grade on the north side of the body, and the 

limit of minable ore to the north is mainly an assay 

wall. On the south side, on the other hand, the layer 

thins gradually until it is too narrow to mine profitably, 

but the grade of the thin ore is generally higher than 

average for the deposit. In a few places along the 

south edge of the deposit, the layer passes from the 

Navajo(?) sandstone into the top foot of the altered 

zone of the underlying Chinle formation. The No. 1 

vein also is in the altered zone at the top of the Chinle 

on the west side of East Rifle Creek.

Where the ore in the Rifle mine is thick, the upper 

and lower limits of the layer usually are not well defined, and the asymmetric character of the ore layer 

is not obvious; similarly, the associated galena-clausthalite band and chromium-bearing layer are not recognizable or are poorly developed.

Although none of the ore bodies in the No. 2 vein in 

the Rifle mine have been completely explored by mining or drilling, they appear to be moderately small 

bodies that are not connected with one another by 

mineralized material. Those known to contain material 

of approximate commercial grade and thickness all lie

4*086521 6.9- -16
216 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

'Satellitic to or fringe the ore body in the No. 1 vein in 

plan projection; none have yet been found that directly 

overlie minable ore in the lower layer. Only one of 

the ore bodies in the No. 2 vein is known to be connected with.the No. 1 vein.

The altered zone at the top of the Chinle formation 

ranges from a feather edge to 8 feet in thickness. The 

contact with the unaltered rock beneath is well defined 

but uneven and crosses the bedding. Where fresh, the 

altered rock is greenish gray and contains finely disseminated cubic crystals of pyrite; at the outcrop the 

color of the altered zone is buff.

Beneath the ore body in the Rifle mine the altered 

zone ranges from 2" to 8 feet in thickness, and there is 

no obvious systematic relationship between the thickness of this zone and the thickness or grade of ore. 

Nevertheless, generally speaking, the altered zone is 

thicker beneath and near the ore body, and it decreases 

in thickness away from the deposit. On the west side 

of East Rifle Creek the altered zone thins to a vanishing 

point about 2,000 feet from the deposit and is absent 

beyond that point. Its character and habit are similar 

to the zone of altered mudstone near uranium-vanadium deposits in the Morrison formation elsewhere on the 

Plateau.

MINERALOGY

The vanadium ores at the Rifle and Garfield mines 

consist of sandstone with the interstitial volume occupied by micaceous vanadium-bearing silicates, a few 

other vanadium minerals, a few-common base metal 

sulfides, and a solid-solution mixture of galena and 

clausthalite. The Navajo (?) and Entrada sandstones, 

in which the ore occurs, are fine-grained moderately 

sorted sandstones, mainly quartz with a little feldspar 

and clay minerals.

Where mineralization was strong, the ore minerals 

uniformly impregnate the sandstone, coloring it dark 

gray, and the bedding is almost completely obscured. 

Where mineralization was weaker, the ore minerals accumulated mostly along favorable bedding planes and 

laminae, yielding a banded ore that makes bedding 

conspicuous. These two types of ore grade into one 

another.

The galena-clausthalite band, like the vanadium layer, also may cut across bedding. In detail it is made 

up of thin laminae of abundant sulfide grains parallel 

to the bedding.

VANADIUM ORE

The vanadium-bearing silicates in the ore have been 

identified by X-ray analyses as mixed-layered micamontmorillonite, chlorite, and roscoelite, according to 

John Hathaway (written communication, 1955). 

Samples from different locations in the mine show variations in mineral composition, some samples having a 

large proportion of vanadium-bearing mixed-layered 

mica-montmorillonite (hydromica) and chlorite and 

others showing principally roscoelite with only traces 

of. chlorite.

The roscoelite and vanadium-bearing clays occur as 

extremely fine grained irregular masses surrounding the 

quartz grains, and no determination of the relative 

amounts could be made in thin section. Roscoelite, according to Heinrich and Levinson (1955) is a vanadium 

mica with vanadium substituting for aluminum in the 

tetrahedral layer. It may contain as much as 17 percent V2O3 (Wells and Brannock, 1946). Roscoelite in 

thin section is brown with a faint tinge of green and has 

weak pleochroism and a high birefringence.

Montroseite occurs as very small opaque black bladed 

crystals with high luster, in radial aggregates and in 

individual crystals in the spaces between the sand 

grains (pi. 8B). It is a trivalent vanadium oxide, 

ideally VO(OH) ; iron may substitute for vanadium, 

requiring some quadrivalent vanadium to balance the 

ionic charges. Specimens of montroseite oxidize readily to paramontroseite (VO2 ) in air.

Pyrite, marcasite, galena, sphalerite, and chalcopyrite are sparsely distributed throughout the ore. They 

occur as small discrete grains disseminated among the 

ore minerals in the space between the sand grains.

No low-valence uranium minerals were found, but it 

is speculated that uranium may occur in fine-grained 

uraninite. Uranium in the unoxidized ore of other 

deposits of this type on the Plateau occurs in uraninite 

and coffinite. Uraninite may occur with or without 

organic material, whereas coffinite is known to occur 

only with organic material. As practically no organic 

material has been recognized at Rifle, it seems most 

likely that uranium occurs as uraninite rather than 

coffinite.

OXIDATION OP THE VANADIUM ORE

Oxidation apparently does not affect the vanadiumbearing silicates and produces little change in this type 

of ore. Montroseite oxidizes to melanovanadite, corvusite, and pascoite. Carnotite is present in small 

amounts coating fractures and impregnating sandstone. 

Other vanadate minerals are present in small amounts 

but could not be definitely identified. Traces of bayleyite, water-soluble magnesium uranyl carbonate, occurring as a pale-greenish-yellow efflorescence on the 

walls not far inside the portals of the Garfield and 

Rifle mines, indicate leaching of uranium near the surface of the ground. The sulfide minerals in the ore are 

destroyed by oxidation and the usual evidence of their 

former presence is a brown limonitic stain.
GKOI.OtllCAL SURVEY PKOKESS1OXAI, I'Al'KH 320 PLATE

A. PHOTOGRAPH OF NO. 3 VEIN, GARFIELD MINE, SHOWING THE MINERAL LAYERS.

The scale of the photograph is indicated by the 6-inch scale on the right side of the picture. Note 

that the galena-clausthalitc band and the vanadium layer cross the laminae with little regard for 

the bedding. Chromium-bearing layer (a), galena-clausthalite layer (6), barren or weakly mineralized 

layer (c) , and vanadium ore (d).

B. PHOTOMICROGRAPH OF THIN SECTION OF TYPICAL UNOXIDIZED HIGH-GRADE VANADIUM 

ORE OF THE NAVAJO(?) SANDSTONE.

Blark is nioittroseitc (m) ; gray is roscoelilc (r) ; white is (|iiartz (q). Plane-pnlari/eil liglit, x 250.
MINEKALOGY AND GEOLOGY OF THE RIFLE AND GARFIELD MINES 217

MINERALOGY OF THE GALENA-CLAUSTHALITE BAND

Each of the three vanadium layers is bounded on 

one side by a thin layer of disseminated sulfides, called 

the galena-clausthalite band (see p. 215 and pi. 8A). 

This band consists mostly of galena-clausthalite with 

minor amounts of marcasite, pyrite, chalcopyrite, and 

sphalerite. These sulfides form small discrete grains 

up to 0.2 mm in diameter, filling pore spaces in the sandstone rather than replacing the sandstone grains. Calcite and dolomite occupy some of the pore spaces in the 

band but are also present in the barren rock away from 

the ore.

Tables 1 and 2 (R. G. Coleman, written communication, December 1955) show the results of analyzing concentrates of galena-clausthalite, which contain only 

minor, amounts of impurities (pyrite, marcasite, and 

other heavy minerals). Selenium was determined by 

chemical analysis, and all other elements by spectrographic analysis.

X-ray studies of the galena-clausthalite concentrates 

show that the lead mineral in these concentrates is a 

solid-solution mixture of galena and clausthalite. The 

amount of clausthalite in solid solution as determined 

by X-ray in the concentrates varies from 25 to 74 weight 

percent ; the chemical analyses for Se in the concentrates 

verify the order of magnitude of these figures (table 1) .

1. X-ray and chemical analyses of galena-clausthalite 

from the Rifle and Garfield mines, Gaifield County, Colo. 1

[X-ray measurements by J. R. Houston]

Sample No. Vein

No.

Unit cell 

(In A)

PbSi PbSei So"

Percent

Oarfield mine

66-RaO-65.....-._.-... ._.-

68-RGC-55....--.-._..-.-._.-.

65-ROC-55. ...... .............

3

2

2

5.996

5.981

5. 996

69

69

31

31

8.10

7.09

8.66

Rifle mine

69-ROC-55. ...... .............

74-ROO-55-0... ..............

72-ROO-55. ...................

74-ROC-55. ................. ..

73-ROO-55. ...... .............

1

1

2

1

2

6.044

6. 048

6.033

6.099

6.048

49

47

53

26

47

51

53

74

53

14.2

15.1

11.8

17.0

18.0

1 Determined from unit-cell measurements using 5.92 A for galena and 6.162 A for 

clausthaltto.

$ Quantitative chemical analyses of concentrates estimated to be at least 95 percent 

pure galona-clausthallto. Analyst, Maryse Delevaux.

Although no physical variation in the galena-clausthalite band is apparent along the strike of the ore 

body, some of the elements in the concentrates show 

a spatial variation. The selenium content increases 

from west to east along the strike of the ore-bearing 

horizon. Silver is consistently present in amounts from 

0.001 to 0.01 percent and no spatial variation is apparent. Nickel and cobalt are erratic in their distribution showing no correlation with position or 

mineralogy. Copper is consistently present and seems 

to show a slight increase from east to west along the 

strike of the beds. Cr and V are present in all the 

concentrates and in general an increase in one is reflected by a concomitant increase in the other. Since 

the galena-clausthalite concentrates have heavy detrital 

minerals as impurities, as well as vanadium and 

chromium minerals introduced as part of the ore deposition, it is not possible to determine if the Cr and 

V are camouflaged in the sulfide structure or contained 

in these other impurities. The Zn detected in three 

of these samples probably comes from-sphalerite, whichhas been identified in polished sections. Cd, Bi, Th, 

and Te commonly reported as trace and minor elements in galenas from hydrothermal deposits were not 

detected in any of these concentrates.

Marcasite associated with calcite from a vertical 

joint within the vanadium layer and pyrite from the 

altered zone at the top of the Chinle were purified and 

analyzed in the same fashion as the galena-clausthalite 

concentrates (table 2). The selenium content in marcasite and pyrite, although much less than that of the 

galena-clausthalite, was above average for Se normally 

present in iron sulfides. Mo and Zn were not detected 

in the iron sulfides although Ni, Co, Ag, V, Cr, As, 

and Sr are present in the same relative amounts as 

found in the galena-clausthalite concentrates. Cu 

shows a 10-fold increase in the pyrite from the altered 

red beds of the Chinle compared to the galenaclausthalite.

OXIDATION OF THE GALENA-CLAUSTHALITE BAND

The galena-clausthalite band shows more rapid oxidation than does the vanadium layer. Where it is exposed near the surface, the sulfides are completely 

destroyed by oxidation. The galena-clausthalite alters 

to cerussite from the outer rim inward, and relict galena 

grains are present within the cerussite. During oxidation selenium forms monoclinic native selenium, the unstable polymorph of hexagonal native selenium, rather 

than selenates or selenites. The monoclinic native selenium remains stable underground and produces a characteristic pink bloom along the band. A limonitic stain 

is also present due to the oxidation of iron sulfides 

associated with the galena-clausthalite.

MINERALOGY OF THE GREEN (CHROMIUM-BEARING)

LAYER

Overlying the galena band in the number 1 and 3 

veins and underlying it in the number 2 vein is a 2- to 

3-foot layer that is similar in habit to the vanadium 

layer. This layer is usually green, ranging from a pale 

to an intense light green. Hess (1913, p. 148,154) has
218 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 2. Semiquantitative spectrographic and chemical analyses of sulfides from the Rifle and Garfield mines, Garfield County, Colo.

[Analyst, Joseph Haffty]

Element

Se'~- ...

m... ..........

Co....... ...

A a

oS:::::::::::::

Mo... ......

V... __. -_- 

Or.-.. .........

Zo.... ......... .

As

Sr._ .. .........

Qarfleld mine

66-RGC-55 galenaclausthalite

8.1 

. 01- 05 

. 01- 05 

. 01-. 05 

. 01- 05 

. 01- 05

. 01-. 05 

. 01- 05

. 01-. 05 

. 001- 005

67-RQO-55 

marcasite 

in fracture

0.02 

. 001-. 005 

. 005-. 01 

. 01- 05 

. 01-. 05

. 01-. 05 

. 001- 005

. 01-. 05 

. 001- 005

68-RQC-55 galenaclaust halite

7.09 

. 001-. 005

. 001- 005 

. 01-. 05 

. 001- 005 

. 01- 05 

. 005-. 05

. 005-. 01

65-RQC-55 galenaclausthalite

8.66 

. 001- 005

. 001-. 005 

. 01-. 05 

. 0005-. 001 

. 01-. 05 

. 01- 05

. 005-. 01

Rifle mine

69-RQC-55 galenaclausthalite

14.2 

. 01- 05 

. 01- 05 

. 01-. 05 

. 01- 05 

. 001- 005 

.1-.5 

.05-.! 

. 01- 05 

. 01- 05 

. 001- 005

74-RQC-55- 

C galenaclausthalite

15.1 

.01-05 

. 01-. 05 

. 01-. 05 

. 01- 05 

. 01-. 05 

. 01-. 05 

. 001-. 005 

. 01- 05 

. 01-. 05 

. 001-. 005

72-ROC-55 galenaclausthalite

11.8 

. 005-. 01 

. 001- 005 

. 01-. 05 

. 005-. 01 

. 01-. 05 

. 01- 05 

. 01-. 05 

. 01-. 05

70-ROC-55 

pyrite 

altered zone

0.14 

. 01-. 05 

. 01-. 05

.1-5

. 01-. 05 

. 01-. 05

.05-.!

. 001- 005

74-ROC-55 galenaclausthalite

17.0 

. 001-. 005 

. 001- 005 

. 001- 005 

. 001-. 005 

. 001- 005 

.05-.1 

. 01-. 05

. 005-. 01

73-RQC-55 galenaclausthalite

18.0

.001-005 

. 001- 005 

. 001-. 005 

. 001-. 005 

.001-005 

. 001-. 005

Sensitivity

0.0003 

.005 

.008 

.00001 

.00005 

.0005 

.001 

.0006 

.008 

.11 

.001

1 Samples taken along the strike of the ore; columns arranged progressiveljifrom west (at left) to east (at right). 

3 Quantitative chemical analyses; analyst, Maryse Delevaui.

described a green layer in the geologically similar vanadium deposits at Placerville, Colo., and ascribes the 

green color to the chromium-bearing mica, mariposite; 

the green layer both at Placerville and Eifle contains 

as much as O.X percent chromium. However, X-ray 

analyses of the clay-size material from this layer at 

Rifle show that the dominant mineral is mixed layered 

mica-montmorillonite with a small amount of chlorite. 

No mariposite has yet been identified.

Thin sections of samples of this layer show a small 

amount of fine-grained material surrounding the quartz 

grains that is pleochroic in shades of green; polished 

sections show no sulfides except close to the galenaclausthalite band.

Exposure of this green layer to oxidation produces 

no apparent changes.

CONCLUSIONS

From the standpoint of ore textures, ore habits, and 

the assemblage of metals, the ore at Rifle shows certain 

similarities to the uranium-vanadium deposits of other

parts of the Colorado Plateau. Certain differences are 

also obvious the ratio of vanadium to uranium is very 

high, organic material is practically absent, vanadiumbearing silicates are the predominant vanadium minerals, and secondary vanadium minerals are rare. The 

cause of the difference in primary minerals is not known 

but this difference results in only rare secondary minerals and general resistance to oxidation of these 

deposits.

LITERATURE CITED

Heinrich, E. W., and Levinson, A. A., 1955, Studies in the mica 

group; X-ray data on roscoelite and barium-muscovite: 

Am. Jour. Sci., v. 253, p. 39-43.

Hess, F. L., 1913, Notes on the vanadium deposits near Placerville, Colorado: U. S. Geol. Survey Bull. 530, p. 142-156.

Thomas, 0. R., McCann, F. T., and Raman, N. D., 1945, Mesozoic 

and Paleozoic stratigraphy in northwestern Colorado and 

northeastern Utah: U. S. Geol. Survey Oil and Gas Inv. 

Prelim. Chart 16 (2 sheets).

Wells, B. C., and Brannock, W. W., 1946, The composition of 

roscoelite, in Contributions to geochemistry, 1942-1945: 

U. S. Geol. Survey Bull. 950, p. 121-127.
Part 20. VANADIUM AND URANIUM IN ROCKS AND ORE DEPOSITS

BY R. P. FISCHER

CONTENTS

	Page 

Abstract__-_.____________.___.___.____.__._____._ 219

Introduction.______________________________________ 220

Geochemical characteristics of vanadium and uranium_ 220

In igneous rocks.________-__-__-__-__-_--__-____ 220

During weathering,_____________________________ 220

In sedimentary rocks___---------_------_------_- 220

Uranium deposits._-______._______-_-____-_____-__._ 221

Veins________________________________________ 221

Sandstone deposits of the Colorado Plateau -------- 221

Limestone deposits of Tyuya Muyan, Russia.______ 222

Witwatersrand conglomerate._____-_---_----_____ 222

Vanadium in ore deposits.______-_--____---__________ 222

Productive vanadium deposits__________________ 222

Vanadium-uranium deposits in sandstone

and limestone..-.-.----------_--_-____ 222

Page 

Vanadium in ore deposits Continued

Productive vanadium deposits Continued

Iron ores.-_.-_-------_----_--------------- 222

Vanadate ores.______-___-_____________---_- 222

Minasragra, Peru._______--____--_-__--__--- 223

Miscellaneous deposits____--_____-__-_-___-_- 223

Vanadium in other deposits._____________________ 223

Vanadium in rocks, ores, and mill and smelter

products...______.__---_-__-__._-- 223 

Vanadium in urarium-bearing veins.._________ 225

Vanadium in hot springs.---------------.------------ 229

Summary and conclusions.--------------------------- 229

Literature cited____.___-________--___--_____--__.- 230

ILLUSTRATIONS

Page 

FIGURE 67. Scatter diagram of geologic samples from uranium-bearing veins, showing the vanadium content plotted against

uranium.________________________________________________________________________________________ 226

68. Scatter diagram of uranium ore samples, showing the vanadium content plotted against uranium.____________ 227

69. Scatter diagram of samples from uranium-bearing veins, showing the vanadium content plotted against titanium. _ 228

TABLES

Page 

TABLE 1. Distribution of vanadium samples by grade classes-------------------------------------------------------- 225

2. Character and source of samples reported by Kaiser, Herring, and Rabbitt (1954) to contain 0.1 percent V.Os or

______-_-______________________._____-___-__-____________.___--____---_-._--__---------- 226

ABSTRACT

Trace amounts of vanadium and uranium are common in both 

igneous and sedimentary rocks. Vanadium is more abundant in 

mafic igneous rocks, uranium in silicic ones. Both metals tend 

to concentrate in some sedimentary rocks containing organic 

material.

Uranium accumulates in some igneous rocks, pegmatites, 

veins, sandstones, limestones, conglomerates, coals, black shales, 

and phosphorites, but the more productive deposits are those

in veins, sandstones, and conglomerates. Uranium minerals 

have been recognized in many types of hydrothermal veins.

Productive sources of vanadium include deposits with uranium in sedimentary rocks, iron ores (both magmatic and sedimentary), vanadates of base metals, asphaltic deposits, phosphate rock, and the soot or ash of some natural carbonaceous 

material. None of these deposits are clearly of hydrothermal 

origin. Accessory vanadium minerals are not generally recognized in hydrothermal deposits except titanium-bearing veins 

and gold-telluride deposits.

219
220 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

The average vanadium content of 775 samples of ores and mill 

products is less than 100 parts per million (ppm), which is less 

than the average reported for igneous rocks and shales. A 

group of 296 samples from uranium-bearing veins also shows 

less than 100 ppm vanadium.

These data suggest that vanadium does not tend to concentrate in the common hydrothermal environment, and specifically 

that it does not concentrate in most veins containing uranium 

ore. If this is true, unusual processes and conditions might be 

required to explain the origin and source of vanadium and 

uranium in deposits containing commercial amounts of both 

metals.

INTRODUCTION

Vanadium and uranium are intimately associated in 

many productive uranium deposits in sedimentary 

rocks, especially in those of the type found in sandstone. The genesis of these deposits is an unsolved 

problem and the source of the metal is also unknown. 

This study of vanadium and uranium in rocks and ore 

deposits was undertaken to see if the geochemical habits 

of these metals might focus attention on certain aspects 

of the problems of genesis and source of metals that 

need special study.

It has long been known that vanadium and uranium 

are disseminated in igneous rocks but are not closely 

associated in this environment, whereas, these two 

metals do get together in the sedimentary environment, 

especially in rocks containing organic material. On 

these aspects of the subject, this report merely summarizes information available in published literature. 

It has also long been recognized that vanadium and 

uranium do not commonly concentrate together in normal hydrothermal deposits, but heretofore, this picture 

has been based largely on negative information the 

lack of known occurrences. Some quantitative information on the amount of vanadium in ore deposits is contributed in this report.

The information in this section is summarized mainly 

from the comprehensive studies on geochemistry by 

Kankama and Sahama (1950) and by Goldschmidt 

(1954). The reader interested in more detailed information should refer to these works and the references cited in them.

IN IGNEOUS ROCKS

Vanadium is relatively abundant among the "trace 

elements" in igneous rocks. It averages 150 grams per 

metric ton (parts per million), is slightly more abundant than zinc, about twice as abundant as copper, and 

about 10 times more abundant than lead. Uranium 

averages 4 parts per million (ppm) in igneous rocks 

(Rankama and Sahama, 1950, table 2.3, p. 39 and 40).

Both vanadium and uranium are classed among the 

"lithophile" elements, those that are enriched in the 

silicate crust. Within this environment, however, the 

two metals are not intimately associated.

Vanadium is more abundant in the mafic igneous 

rocks than in the silicic ones. Vanadium does not form 

a constituent part of any common rock-forming mineral ; rather its ions replace those of iron and aluminum 

in the common ferromagnesian minerals and those of 

titanium and iron in titanium minerals and titaniferous 

iron ores.

Uranium, on the other hand, concentrates more 

abundantly in the later or more silicic part of igneous 

differentiates. In these rocks some uranium is held in 

accessory minerals, such as zircon, monazite, allanite, 

and some is in a loosely bound form in mineral interstices (McKelvey, Everhart, and Garrels, 1955). Uranium is common in pegmatites and hydrothermal veins; 

many uranium minerals are found in pegmatites and 

veins, but uraninite is the most important of these.

DURING WEATHERING

During weathering of igneous rocks, much of the 

vanadium goes into clay minerals. Some of it, and 

perhaps a large part of it, must remain with these 

minerals as they are transported to places where they 

accumulate as sedimentary rocks, for argillaceous sediments are generally richer in vanadium than sandstone 

or limestone. Some vanadium, however, goes into solution, from which it can enter the geologically temporary states of combination with heavy metals to form 

vanadates or be taken up by plants and animals. Rankama and Sahama (1950, table 6.19, p. 295) show that 

90 ppm of vanadium is supplied to sea water but that 

only 0.0003 ppm is present. Either much of the vanadium precipitates rapidly from sea water, or more 

likely, most of that supplied is associated with clay 

particles suspended in river waters rather than being 

in solution.

The habits of uranium during weathering are more 

varied. Some of the uranium-bearing minerals in 

rocks and veins are refractory, and they mainly weather 

mechanically and are distributed to clastic sediments. 

Other minerals oxidize readily to form complex secondary minerals and soluble salts; these salts are carried 

seaward, either in solution or adsorbed on hydroxide 

gels Rankama and Sahama (1950, table 6.19, p. 295) 

report that 0.0016 ppm U is present in sea water whereas 0.6 ppm is supplied to sea water.

IN SEDIMENTARY ROCKS

The average content of vanadium is <10 ppm in carbonate rocks, 20 ppm in sandstone, and 120 ppm in clays 

and shales (Rankama and Sahama, 1950, table 5.52,
VANADIUM AND URANIUM IN ROCKS AND ORE DEPOSITS 221

p. 226). Shaw (1954, table 4, p. 1170) also shows a 

120 ppm vanadium content in shales, schists, and 

gneisses. As a general rule, vanadium increases with 

the increase in argillaceous material, and especially 

with an increase in organic matter; it is richly concentrated in some coal, petroleum, and asphalt (Jost, 

1932). Uranium is more dispersed and of uniform 

grade in the three principal types of sedimentary rocks. 

Rankama and Sahama (1950, table 5.52, p. 226) give 

1.2 ppm U in sandstones, 1.2 ppm in shales, and 1.3 ppm 

in limestones. These authors show (p. 637), however, 

that uranium is significantly concentrated in some carbonaceous shales of marine origin, in certain coals, and 

in some petroleum, as is vanadium. Erickson, Myers, 

and Horr (1954) give more specific information regarding uranium and vanadium, as well as other metals, in 

crude oil, asphalt, and petroliferous rock.

URANIUM DEPOSITS

Uranium is widely distributed and its types of occurrences much varied; it is enriched in some igneous rocks, 

pegmatites, veins, sandstones, limestones, conglomerates, coals, black shales, and phosphorites (McKelvey, 

Everhart, and Garrels, 1955). Representatives of many 

of these types have yielded production, either for 

uranium itself or as a byproduct, but the deposits in 

veins, sandstones, and conglomerates have been the more 

productive.

VEINS

As Everhart and Wright (1953) have recently summarized the geologic character of typical uraniumbearing (pitchblende) veins, including the more productive deposits, only the general features of these deposits Avill be mentioned here. They recognize two 

major types of deposits. One, a nickel-cobalt-native 

silver type, has a complex mineralogy, a gangue dominantly of carbonates with lesser silica, and occurs in 

metasediments and volcanic host rocks. The second, a 

siliceous-pyrite-galena type, has a simple mineralogy, a 

gangue of silica and fluorite with lesser carbonate, and 

occurs in felsic intrusives. McKelvey, Everhart, and 

Garrels (1955) have added a third type, iron-titanium 

veins, in which uranium occurs as the mineral davidito, 

with a silica gangue, in granitic intrusives.

Intensive exploration for radioactive material during 

recent years has revealed the presence of uranium in 

many vein deposits of varied metal and mineral assemblages. Many of these deposits, however, have not 

yielded significant production, either because the uranium content is low or restricted to small ore shoots.

Generally speaking, all of these deposits have characteristics of typical veins, to which an origin of hydrothermal mineralization from a hypogene source is normally ascribed.

SANDSTONE DEPOSITS OF THE COLOBADO PLATEAU

The so-called "carnotite" deposits of the Colorado 

Plateau form a group of deposits with wide distribution 

and many common characteristics. They have yielded 

important amounts of vanadium, uranium, and radium.

Although these deposits are found in many formations, ranging from late Paleozoic to middle Tertiary in 

age, the more productive deposits are restricted to a few 

stratigraphic units of Mesozoic age. Most of the deposits are in sandstone beds of continental origin, 

though some are in limestone and a few in shale. The 

host rocks in nearly all deposits contain carbonaceous 

material, mostly fossil wood.

The early minerals in the ore consist of low-valent 

oxides and silicates of vanadium and uranium, small 

amounts of copper and iron sulfides, and traces of 

galena and sphalerite. The ore minerals alter to higher 

valent oxides of vanadium and to vanadates and other 

secondary uranium minerals. They mainly occupy pore 

spaces in the sandstone, though in part they replace sand 

grains and associated argillaceous and carbonaceous 

material. The ore bodies are tabular layers that lie 

nearly parallel to bedding but do not follow beds in detail. Most ore bodies are small, and they range from 

masses only a few feet across to those several hundred 

feet across.

It is generally agreed that the ore minerals were introduced into their present position by solutions, but the 

nature of these solutions and the source of the metals 

are not known. Some students believe the solutions 

were hypogene and that the metals were introduced 

from deep-seated sources; others favor the idea that the 

metals were originally disseminated in the ore-bearing 

and associated rocks and were transported and concentrated at favorable site by aqueous solutions or perhaps 

even petroleum. It is also generally agreed that sedimentary structures, such as lenses, had some influence on 

the migration of the ore-bearing solutions and the 

localization of many ore deposits. In addition, the regional distribution of deposits suggests to some geologists that regional deformation also influenced localization by providing pathways for the vertical movement 

of solutions to ore-bearing beds, and a few deposits show 

a close association with such vertical pathways. Igneous activity and mineralization of definite hydrothermal 

origin are not closely associated with carnotite deposits, 

except in a few places.

McKelvey, Everhart, and Garrels (1955) give a fairly 

complete list of references to reports on these deposits.
222 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Deposits similar to these on the Colorado Plateau 

are also present elsewhere; some in Wyoming and 

South Dakota have yielded significant production.

LIMESTONE DEPOSITS OF TYUYA MUYAN, RUSSIA

At Tyuya Muyan, Fergana, in central Asia, oxidized 

uranium, vanadium, and copper minerals, associated 

with barite, calcite, and quartz, occur in limestone. 

The ore bodies are peculiar pipelike structures that 

partly fill cavities and perhaps partly replace the host 

rock. The area is one of complex structure and geologic 

history, with considerable faulting and igneous 

activity.

The origin of these deposits also is in doubt. 

Pavlenko (1933) believes the ore formed from thermal 

solutions derived from diabase intrusives. According 

to Bain (1950, p. 295), Fersman considers the uranium 

and vanadium to have been leached from nearby black 

shales, which, according to Rankama and Sahama 

(1950, p. 638) contain "approximately 400 g/ton U 

and 850 g/ton V."

WITWATERSBAND CONGLOMERATE

Conglomerate beds of the Witwatersrand, South 

Africa, are yielding large quantities of uranium as well 

as gold. In addition to native gold, the ore minerals 

consist of uraninite and thucholite, a uraninite-hydrocarbon aggregate. These minerals, along with minor 

amounts of common sulfides, are mainly disseminated 

in pore spaces in lenses of coarse sandstone and conglomerate. Some gold and uranium, but apparently 

only minor amounts, occur in quartz and thucholite 

veinlets where these cross ore-bearing beds. Although 

the rocks are fractured and also invaded by igneous 

dikes, the ore bodies are not clearly localized by these 

features. A "placer" versus "hydrothermal" origin 

for the gold ores has long been debated among geologists and the same discussion continues since the discovery of uranium in these deposits. Readers interested 

in more detail regarding these deposits and the 

problem of their origin are referred to McKelvey, 

Everhart, and Garrels (1955) and the reports they list.

VANADIUM IN ORE DEPOSITS

There are but few deposits in which vanadium alone 

is sufficiently concentrated to support a profitable operation, though there are several types of deposits that 

have yielded byproduct vanadium or from which production might be economic under reasonably favorable 

conditions. These are described below under "Productive vanadium deposits." Vanadium shows little or 

no tendency to concentrate in most types of ore deposits; available information regarding the vanadium 

content of these deposits is presented below.

PRODUCTIVE VANADIUM DEPOSITS

VANADIUM-URANIUM DEPOSITS IN SANDSTONE AND 

LIMESTONE

A description of the vanadium-uranium deposits in 

sandstone on the Colorado Plateau and in limestone at 

Tyuya Muyan, Russia, has been given previously.

IRON ORES

Many iron ores contain small amounts of vanadium, 

and some have yielded byproduct vanadium. Commonly the titanif erous magnetite deposits are the most 

vanadiferous (Singewald, 1913); the vanadium content ranges from about 0.2 percent V2O5 to more than 

1 percent and probably averages between 0.4 and 0.6 

percent. In these deposits, vanadium is reported to be 

in the magnetite rather than in the titanium minerals 

(Balsley, 1943), a seemingly peculiar relation considering that most nontitaniferous magnetites contain 

less vanadium.

Many sedimentary iron ores contain 0.02 to 0.2 percent V2O5 . During World War II Germany produced 

considerable vanadium from iron ores containing about 

0.2 percent V2O5 (Fischer, 1946). Vanadium is also 

concentrated in laterites and bauxites, especially those 

derived from mafic igneous rocks.

VANADATE ORES

Vanadates of lead, zinc, and copper are found in many 

base metal deposits in southwestern United States, 

Mexico, South America, Spain, Africa, and Australia; 

some vanadium has been produced from a number of 

these deposits, but most productive are those at Broken 

Hill, Northern Rhodesia, and in the Otavi district, 

Southwest Africa. Most, though not all, of these deposits are in carbonate country rock. Typically they 

are in areas of moderately arid climate and deep oxidation; the vanadate ores are described as being in the 

oxidized parts of the deposits.

Evidence and opinions differ as to the source of the 

vanadium in these deposits. Skerl (1934) reports that 

the unoxidized ore at Broken Hill was tested chemically and spectrographically, but no trace of vanadium 

was found; Clark (1931) states that the primary ores 

in Southwest Africa contain little or no vanadium and 

believes that no reasonable amount of concentration 

from the weathering of eroded lead-zinc ore bodies 

could account for the vanadium ore. In both areas the 

vanadium is thought to have come from that originally 

disseminated in the surrounding rock. The same explanation has been offered for other deposits.

In contrast to the evidence and opinions mentioned 

above, Peterson (1938) finds that the vanadate minerals at the Mammoth-St. Anthony area, Arizona, were
VANADIUM AND URANIUM IN ROCKS AND ORE DEPOSITS 223

introduced during the last stage of hypogene mineralization and later than the base-metal sulfides.

In addition, Newhouse (1934), aided by spectroscopic 

work of Claussen (1934), tested specimens of pyrite, 

galena, and sphalerite for vanadium, and concluded 

that at least some of the vanadium in the vanadates of 

the oxidized base-metal deposits was derived from the 

trace amounts in the sulfides. Five selected samples 

each of pyrite, galena, and sphalerite were tested; 1 

sample of pyrite and 5 of galena showed O.OX O.OOX 

percent V spectrographically, and the vanadium content of the other samples was below the limit of detection. One pyrite sample showed 0.01 percent V by 

chemical analysis and the rest much less; the sphalerite 

samples showed less vanadium than the pyrite samples; 

and the chemical tests on the galena samples showed a 

few thousandths percent, confirming the spectroscopic 

results (Newhouse, 1934).

Moritz (1933) reported about 0.001 percent vanadium in the sulfide ore (tenantite, enargite, sphalerite, 

and other sulfides), as well as in calcite and dolomite, 

and as much as 0.01 percent vanadium in pyrite in the 

Tsumeb mine, Otavi district, Southwest Africa.

The problem of the origin of the vanadate ore in 

oxidized base-metal deposits, per se, is not of immediate 

concern. The source of vanadium may be the country 

rock, as some believe; or it may be the trace amounts 

disseminated in sulfides, as suggested by Newhouse; or 

it may be a separate hypogene stage, as reported by 

Peterson at the Mammoth-St. Anthony deposit. But 

two points are of immediate interest: (1) all available 

evidence shows only a very low concentration of vanadium in the primary sulfides and (2) even if the vanadate ore at the Mammoth-St. Anthony area is hypogene, as Peterson suggests, it is a phase separate from 

the normal sulfide mineralization.

MINASRAGRA, PERU

The vanadium sulfide ("patronite") deposit at Minasragra, Peru (Hewett, 1909), has been the most productive single deposit of vanadium. The ore consists 

of quisqueite (a hydrocarbon), coke, and patronite; 

bravoite, an iron-nickel sulfide, is present in small 

amounts in the patronite. These materials occupy a 

fracture and permeate the adjoining shale, forming a 

lens-shaped body up to 30 feet wide and a few hundred 

feet long. The fracture dips steeply and crosses bedding 

at a moderate angle. Country rock consists of shales 

and thin-bedded limestones of Cretaceous age. These 

rocks are invaded by several igneous dikes and cut 

by numerous faults near the deposit.

Similar vanadiferous asphaltic veins are common in 

this part of Peru; though none are nearly as rich in

vanadium as the Minasragra deposit, they do contain 

about 1 percent vanadic oxide. All the asphaltic deposits apparently are in the same group of sedimentary 

beds, which also contain vanadiferous black shales.

Although the origin of the Minasragra deposit certainly is not known, most authorities (Hewett, 1909; 

Jost, 1932; and Rankama and Sahama, 1950) relate the 

formation of this deposit to the process responsible for 

forming asphaltite and its common contamination by 

vanadium. Thermal solutions, however, may have 

played a part in transporting or altering the asphaltite 

and enriching this deposit.

MISCELLANEOUS DEPOSITS

Under peculiarly favorable conditions, vanadium has 

been, or can be, recovered as a byproduct from several 

other sources. Among these are ash or soot from crude 

oil or petroleum refinery products or from other carbonaceous material such as natural asphalt and vanadiferous coals. Byproduct vanadium has also been obtained from phosphate rock at Conda, Idaho (Argall, 

1943, p. 47 and 48); uranium is also present (McKelvey 

and Nelson, 1950, p. 41). Lovering and Goddard (1950, 

p. 234) report that in 1910 some gold-telluride ore was 

shipped for its vanadium content from the Kekionga 

claim, Boulder County, Colo. A brief discussion of 

vanadium in gold-telluride veins is given on page 225.

VANADIUM IN OTHER DEPOSITS

Not much information is available regarding the distribution and amount of many elements that occur in 

ore deposits in quantities below levels of economic value, 

especially if the elements do not form constituent parts 

of readily recognized minerals. Vanadium is one of 

these. The failure of observers and analysts to detect, 

or mention, the presence of vanadium in many hydrothermal ore deposits can be used, in a negative manner, 

to suggest a low vanadium content, as well as to indicate 

that its geochemical habits do not favor concentration 

in this particular environment. Even so, conclusions 

based on such negative information are unsatisfactory. 

In recent years, however, some quantitative information 

has become available, and perhaps this information 

can support broad generalizations.

VANADIUM IN ROCKS, ORES, AND MILL AND SMELTER 

PRODUCTS

In 1942, at the request of the "War Production Board, 

the Geological Survey began a search for certain strategic and minor elements in domestic rocks, ores, concentrates, tailings, smelter slags, and flue dusts. Several hundred samples of these materials were collected 

by geologists or furnished by mining and smelting com-
224 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

panics and were tested for 22 elements, including vanadium, by semiquantitative spectrographic analyses. 

The analytical results are published in a report by 

Kaiser, Herring, and Rabbitt (1954).

Although these samples are not completely representative of any single deposit or type of deposit, they do 

give a coverage of most types of ore deposits in the 

United States the samples are from deposits that 

yielded 85 percent or more of the 1942 domestic production of copper, lead, zinc, manganese, mercury, tin, 

tungsten, and chromium, and lesser percentages of production of aluminum, gold, silver, iron, and pegmatite 

minerals. As such, these samples have some value on 

which to base generalizations. Information regarding 

vanadium in these deposits is summarized below. Similar information regarding vanadium in veins that have 

been studied and sampled because they are uraniumbearing (or might be), is summarized in the section 

"Vanadium in uranium-bearing veins."

The semiquantitative spectrographic results for vanadium in rocks, ores, and mill and smelter products 

(Kaiser, Herring, and Rabbitt, 1954) are mostly expressed in numerical percentages and as V2O5 . For 

this study, these values were converted to percent V, 

and then grouped into the grade classes shown on figures 67, 68, and 69, and table 1 so the values would be 

more nearly comparable to the manner in which semiquantitative spectrographic results are now being reported by the U. S. Geological Survey laboratories. To 

convert the numerical values of V2O5 to V, the figures 

were multiplied by 0.5 rather than by the true conversion factor of 0.56. Obviously this introduced a 

consistent error, though one so small as to be of little 

import, and the error is lost in most cases in conversion to the X categories.

A few values of V2O5 are reported by Kaiser, Herring 

and Rabbitt (1954) as "X" to the proper decimal place. 

These were assumed to have a medial value of 5 to the 

same decimal place, and they were converted in the 

manner described above. Values reported as 0.001 percent V2O5 , and those shown as "trace" V2O5 , are grouped 

in the category of "trace" V in table 1.

The distribution by grade classes of the 775 samples 

tested for vanadium is shown in the left side of table 1. 

The samples were divided into two groups: one group 

(column 1) includes mill heads, tailings, and ore (including grab samples), as it was thought these might 

be more representative of ore deposits; the other group 

(column 2) includes concentrates, slag, and flue dust. 

There appears to be no significant difference between 

the two groups. The combined total of these two 

groups is shown in column 3. The graphic plot below 

each column shows the distribution of samples in each

grade class by percent of the total number of samples.

By inspection of the subcolumns "percent of total," 

it is obvious that at least half of the total samples 

in columns 1, 2, and 3 fall in the grade classes containing .OOX or less (0.0046 percent, or 46 ppm, V or 

less). At least half of the samples, therefore, contain 

considerably less vanadium than the figures given by 

Rankama and Sahama (1950, table 5.52, p. 226) as V 

content of igneous rock (150 ppm) or shale (120 ppm); 

on the other hand, more than half of the samples contain more than the average amount of vanadium in 

sandstone (20 ppm) and limestone (<10 ppm).

Thus, if these 775 samples should be considered representative of ore deposits in general, it appears that 

vanadium does not tend to concentrate in most deposits; 

rather, the vanadium content of most samples possibly 

represents the vanadium content of the host rock.

For those readers who may be interested in seeing 

the character and source of the higher grade vanadium 

samples reported by Kaiser, Herring, and Rabbitt 

(1954), this information is listed in table 2 for all 

samples reported to contain 0.1 percent V2O5 or more 

(about 0.056 percent V, in the .OX+ class or higher).

Table 2 shows moderate amounts of vanadium in 

iron, chromium, and manganese ores, as might be expected. It also shows moderate amounts of vanadium 

in samples of some ores of titanium and gold, a relation that seemed to the writer to be worthy of a sideline 

investigation and to justify a brief mention here.

The habit of vanadium to accumulate in magmatic 

titaniferous-magnetite deposits is well known. The 

relatively high vanadium content in brookite and rutile 

samples (see table 2, samples ARK-26-1, ARK-26-2, 

and ARK-26-3; more data regarding vanadium and 

titanium at Magnet Cove, Ark., are given by Fryklund, 

Harner, and Kaiser, 1954) suggests that the association 

of vanadium with titanium may even extend into other 

types of titanium deposits, including titanium-bearing 

hydrothermal veins. If this is true, it may explain the 

presence of vanadium in the deposit of davidite (uranium-bearing iron-titanium oxide) at Radium Hill, South 

Australia (Parkin and Glasson, 1954), as well as the 

vanadium in the lower levels of the Ace mine, Saskatchewan, Canada, where ilmenite also is reported to 

be abundant (Robinson, 1955, p. 22-23). Only field 

study will establish whether the vanadium in these two 

deposits is more intimately associated with uranium or 

titanium, or largely independent of each.

More information regarding the association of vanadium and titanium in uranium-bearing veins is given 

on page 228.

The presence of roscoelite, the vanadium mica, in 

gold-telluride veins is not infrequent and suggests a
VANADIUM AND URANIUM IN ROCKS AND ORE DEPOSITS 225

TABLE 1.-DISTRIBUTION OF VANADIUM SAMPLES BY GRADE CLASSES v

[ The limits of the grade classes are generated by integral powers of the cube root of 10 (2.154); for example, O.OX~ = 0.01 to 0.0215 percent, O.OX = 0.0215 to

0.0464 percent, and O.OX+ = 0.0464 to 0.1 percent ]

Vanadium in some rocks, ores, and mill and smelter products

Grade

percent V

Tr. .

o.ooox +....

.OOX- -

.oox---

.OOX+- 

.ox----

.ox 

.OX+ 

X

-

. x ...... ......

Totals 

Column 1

Samples of ore, 

mill heads, and tails

Number

of

samples

28 

15

87

79

80 

86

33

8

6

2 

424

Percent

of

total

 7

3

21

19

19 

20

8

2 

1

0 

100

Column 2

Samples of concentrates, flue 

dust, and slag

Number

of

samples

30

33

69

84

48

38 

31

9

 7

2 

351

Percent

of

total

9

9

20

24

14

11 

9

3 

2

1

102

Column 3

Combined total

Number

of

samples

. 58 

48

156

163

128 

124

64

17 

13

4 

775

Percent

of

total

 7

6

20

21

17 

16

8

2 

2

1 

100

Vanadium in uranium-bearing veins

Column 4

Samples containing 

0.01 percent or more U

Number

of

samples

4

3 

9

23

53

30

14

144

Percent

of

total

3

2 

6

16

37

21

6 

10

101

Column 5

Samples containing 

'0.01 percent U

Number

of

samples

2

2

21 

38

49

24

7 

9

152

Percent

of

total

1

1 

14

25

32

16

5 

6

100

Column 6

Combined total

Number

of

samples

6

5

30 

61

102

54

15 

23

296

Percent

of

total

2

2

10 

20

35

18

5 

8

100

r 40

-30

-20

- 10

-0

fl I

o I .oox .ox .x

Tr.

7fl ' ' I ' ' i 

0 I .OOX .OX 

Tr.

.OOOX" .OOOX

second type of hydrothermal deposit in which vanadium tends to concentrate.

Eckel (1949, p. 74) emphasizes the association of 

roscoelite with gold-telluride veins in the La Plata district, Colorado. Levering and Goddard (1950) mention the presence of roscoelite in several veins in the 

Colorado Front Range, all but one of which are classified as gold-telluride veins. Roscoelite is also mentioned in other reports in districts where gold-telluride 

deposits are known, but the literature available to the 

writer is not sufficiently specific to determine whether 

or not roscoelite and the telluride minerals are closely 

associated.

The specific association of vanadium with gold tellurides was noted by de Launay (1911), whereas Lindgren (1933, p. 873) generalized, stating "Roscoelite is 

found in many gold-quartz veins." This subject is introduced here merely to call this problem to the attention of geologists, in the hope that others may furnish 

a better understanding of relations.

VANADIUM IN URANIUM-BEARING VEINS

Uranium-bearing (pitchblende or uraninite) veins 

have been the source of much of the world's radium and 

uranium. The geologic characteristics of the typical 

and more productive deposits of the class have been 

summarized by Everhart and Wright (1953). This 

summary makes no mention of vanadium in any of the 

13 deposits described, and both Everhart and Wright 

have told the writer personally that they watched for 

but failed to find mention of vanadium in these de-
226 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

TABLE 2. Character and source of samples reported by Kaiser, 

Herring, and Rabbitt (1954) to contain 0.1 percent VzO$ or 

more

VsOs 

(percent)

0.1- 

0.1- 

0.2. 

0.1. 

0.1- 

0.1. 

0.68. 

0.64- 

0.2. 

0.1. 

0.1 

0.6- 

0.6- 

O.X. 

O.X 

O.X. . 

O.X-- - 

O.X.- 

0.2- - 

0.1. 

0.2. 

0.4. 

0.1. 

0.2. . 

0.2. 

0.2. 

0.2... . 

0.1. 

0.3. 

0.2. 

0.3. 

0.1-. 

0.1- 

0.1- 

0.2. 

0.1- ..

Sample No.

ARI-7-14.. 

ARI-13-13 ..

ARK-15-3-.- _

ARK-15-4-...

A T> V Ofi 1

ARK-26-2....

COL-10-12... .

COL-10-13 

MIC-7-1 

MIC-7-2 

MIC-7-3 

MIC-7-11 

MON" 10 25

"M"FV 97 19

ORE-5-2.... .

ORE-5-5.. 

ORE-5-6- __._

ORE-5-9-. 

ORE-5-10 . . 

SD-10-6 .

UT-12-2......

UT-12-3...

UT-12-5 

VA-10-1- 

V A 1 <; 1

VA-15-2. 

VA-70-1. 

WAS-5-1. 

Character and source of sample

Copper tails, Oracle, Pima County, Ariz.

moth-St. Anthony mill, Final County, Ariz.

pile, Batesville district, Arkansas.

Batesville district, Arkansas.

pile, Batesville district, Arkansas.

pile, Batesville district, Arkansas.

Cove, Ark. 

Rutile crystals, composite sample, Magnet Cove, 

Ark.

district, Colorado.

district, Colorado.

chiefly from Cripple Creek district, Colorado.

Cripple Creek district, Colorado. 

Copper concentrates, Kearsarge Amygdaloid mine,

Houghton County, Mich. (O.X TiOj).

County, Mich. (O.X TiO2).

ton County, Mich. (O.X T102). 

Copper concentrates, White Pine mine, Ontonagon 

County, Mich. (3.6 TiO2).

County, Mich. (O.X TiOa).

Phillips County, Mont.

gold tailings deposits, Coos County, Ore.

ings deposit, Coos County, Ore. 

Chromite heads, mill sample, Seven Devils mine, 

Coos County, Ore. 

Chromite concentrate, Seven Devils mine, Coos 

County, Ore.

Primary chromite concentrate, Coos County, Ore.

S. Dak.

mine, Iron County, Utah.

County, Utah.

Iron Mountain mine, Iron County, Utah.

gilina district, Virginia.

Virginia. 

Manganese concentrates, Appalachian district, 

Virginia.

Heavy sand concentrate (chromite), Cle Elum 

district, Kittitas County, Wash.

posits in the geologic reports to which they referred 

during their study.

In a similar study, Bain (1950) summarized the 

geologic characteristics of all types of uranium deposits 

that have been or might be productive. He. classifies 

the deposits as primary or hypogene, sedimentary or 

bedded, and oxidized. In the primary or hypogene 

class Bain mentions most of the deposits described by 

Everhart and Wright, as well as a few other deposits 

of this type. Again no mention is made of vanadium 

in these deposits, though vanadium is frequently mentioned in connection with the descriptions of sedimentary and oxidized deposits.

To obtain quantitative data on vanadium in uraniumbearing veins, the writer has made a search of published and unpublished material in the files of the 

Atomic Energy Commission and the Geological Survey. 

These data are presented below, grouped in two categories geologic samples and ore samples because of 

differences in the character of the samples and in the 

methods of assay.

The assay results of the group of "geologic samples" 

are plotted on the right side of table 1 and on figure 67.

xx.+

xx.

xx.-

X."1

3.x

.ox

.OX'

.oox

.oox

.OOX'

Tr

9

14

10

15

11

11

14

12

28

a

B

B

O Tr -OOOX + .OOX- -OOX .OOX + .OX~ .OX 

Percent vanadium (V)

FIGURE 67. Scatter diagram of geologic samples from uranium-bearing 

veins, showing the vanadium content plotted against uranium. The 

number of samples in each grade class is shown by the figure in the 

lower right corner of each square. The solid blocks, which are plotted 

as equivalent squares of the number of samples, also Indicate visually 

the quantitative distribution of samples.
VANADIUM AND URANIUM IN ROCKS AND ORE DEPOSITS 227

They consist of 296 samples taken by geologists of the 

Atomic Energy Commission and the Geological Survey 

during geologic study of uranium-bearing vein deposits. The samples are from 84 localities in 9 western 

states; some localities are represented by a single 

sample, others by a dozen or more samples. The localities represented were screened with care to include only 

those deposits that would be classed as hydrothermal 

veins; deposits for which there might be some reasonable doubt or argument regarding the hypogene source 

of the uranium are not represented in this group of 

samples. All available assay reports from these deposits were used. This group contains a few samples 

representing ore shipments or mill heads, but mostly 

they consist of grab or channel samples. As such, most 

individual samples cannot be considered as good 

samples of ore bodies, but collectively they may be 

broadly representative of this type of ore deposit 

uranium-bearing vein deposits of hydrothermal origin.

All assays were made in the Denver laboratory of the 

Geological Survey; only equivalent uranium determinations were made on samples having low radioactivity 

(a few thousandths percent eU), but chemical determinations for U were available for all other samples; 

all vanadium determinations were made by semiquantitative spectrographic analysis. For purposes of plotting on figure 67, the uranium assays (either eU or 

chemical U) were converted from the numerical figure 

to the grade classes used in reporting spectrographic 

results.

The frequency distribution of vanadium determinations in the several grade classes is tabulated on the 

right side of table 1. The samples are divided into two 

groups: one group consists of samples containing 0.01 

percent or more U (column 4), as it was thought that 

this group might be more representative of uraniumbearing ore bodies or ore shoots; the other group consists of samples containing less than 0.01 percent U 

(column 5). The combined totals for the two groups 

are shown in column 6. The graphic plot below each 

column shows the distribution of samples in each grade 

class by percent of the total number of samples.

The geometric means for the combined total of 

samples (column 6, table 1) is 31 ppm V, that for the 

samples containing 0.01 percent or more U (column 4) 

is 36 ppm V, and that for the samples containing less 

than 0.01 percent U (column 5) is 27 ppm V. These 

figures suggest a slight tendency for vanadium to increase with an increase in uranium content of these 

samples, but the differences in the mean figures are so 

small that they might result from chance or random 

variation in the sampling. The correlation coefficient 

between vanadium and uranium for all samples (fig.

67) is +0.12, which is below the normal level of 

significance.

The assay results of the group of 74 "ore samples" are 

plotted on figure 68. This group includes samples taken 

for settlements on ore shipments, samples of material

1.13

1.0

5

E -215

3

s

~ .10

1

£

.0464

.0215 

.010

2

13

13

^^^ M17

4

6

2

1

4

1

B

2

1

2

Samp 

35.0 p

1

1

'I

Sam

20.1

e contains 

ercent TK>

ate contain

percent TK

tK

B j Sample cc

r

4.7 perce

Sample Is Tl bearing 

but the amount Is 

not reported

,

^J 1

n tains

ntT»2

.010 .0215 .0464 .10 .215 

Percent vanadium (V)

.464 1.0

FIOUBE 68. Scatter diagram of uranium ore samples, showing the 

vanadium content plotted against uranium. The number of samples 

in each grade class is shown by the figure in the lower right corner 

of each square. The solid blocks, which are plotted as equivalent 

squares of the number of samples, also indicate visually the quantitative distribution of samples.

used for metallurgical or pilot-plant tests, and a few 

samples submitted by miners and prospectors. These 

samples are from 36 localities (deposits) in 10 western 

states and 4 foreign countries; some localities are represented by single samples, others by several samples; 

a few samples represent average assays calculated for 

numerous shipments of ore from a single mine. As 

such, most of the samples are presumably well representative of ore and the parent ore bodies, and from this 

standpoint they are better than those classed as geologic 

samples. All assays were made by chemical methods, 

mostly of the routine "commercial" type, and by several 

laboratories. With these methods the threshold of determination for vanadium is in the low hundredths percent V2O5 , and assay accuracy at this level is admittedly 

poor. Discrepancies ranging from 0.01 to 0.04 percent 

V2O5 have been noted between different laboratories and 

different standards of analyses. At this low level of vanadium content, such discrepancies, of course, are of no 

practical concern to the ore vendor, buyer, or metallurgist, but they do present problems in a study of this 

kind. Furthermore, many of the vanadium determinations in this group of samples are reported as "0.00 per-
228 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

cent V2O5" or as "<0.01 percent V2O5 ." When converted to V for plotting on figure 68, these values are all 

plotted in the vanadium grade class of "less than 0.01."

Because the accuracy of the vanadium assays for 

these ore samples is subject to question, it is difficult to 

determine whether or not the relations shown by figure 

68 have any true significance. The illustration is presented, however, so the reader can see these data and 

arrive at his own conclusions. It is obvious that the 

higher grade vanadium samples occur with some of the 

higher grade uranium samples and none of the lowgrade uranium samples contain much vanadium. Even 

so, the vanadium content of all these samples is quite 

low, except those containing abundant titanium.

Because of the vanadium-titanium relations shown on 

figure 68 and the association suggested by the study of 

the ores and mill-products samples (p. 224), a record 

was made of the spectrographic determinations of 

titanium for 172 of the 296 samples of uranium-bearing 

veins. Figure 69 is a scatter diagram showing the 

vanadium content of these 172 samples plotted against 

titanium. The correlation coefficient between vanadium 

and uranium in these samples is +0.36, which is low 

but significantly different from zero. Presumably none 

of these samples are from deposits in which titanium is

.dx

jj.ox-

(L

.OOX+

.OOX

.oox

10

13

m

12

19

 a

11

O Tr .OOOX + .OOX~ .OOX .OOX+ .OX" .OX 

Percent vanadium (V)

FIGURE 69. Scatter diagram of samples from uranium-bearing veins, 

showing the vanadium content plotted against titanium. The number of samples in each grade class is shown by the figure in the lower 

right corner of each square. The solid blocks, which are plotted as 

equivalent squares of the number of samples, also indicate'visually 

the quantitative distribution of samples.

much enriched, for the titanium content of most samples, as well as their vanadium content, is that common 

among rocks. Likely the titanium and vanadium in 

these samples is essentially the same as the content of 

these metals in the host rocks of these deposits.

Wright (1954) arrived at a similar conclusion regarding vanadium and titanium in his study of a uraninite deposit at Caribou, Colo. He tested the vein at 

three places with sets of samples from the host rock 

through the altered zones on both sides of the vein; 

spectrographic determinations showed the titanium 

content to be constant at 0.1 to 1.0 percent and the 

vanadium content at 0.01 to 0.1 percent (Wright, 1954, 

figs. 3, 4, and 5). In an unpublished report to the 

Atomic Energy Commission he states, "this distribution 

indicates that the titanium and vanadium present in the 

altered wall rock were original constituents of the 

monzonite and were not supplied by the vein; and that 

leaching of these elements by vein solutions was 

negligible."

The information plotted on figures 67 and 68, and 

tabulated on the right side of table 1, permit a few 

broad generalizations. For the deposits represented by 

the samples used in this study it appears that vanadium 

is concentrated in large amounts only in uraniumbearing veins containing abundant titanium. The average vanadium content in the other deposits is probably 

no more, and perhaps is somewhat less, than the average 

vanadium content of most rocks at the earth's crust, as 

reported by Kankama and Sahama (1950) and by 

others. This suggests that there is little or no tendency 

for vanadium to concentrate with uranium in most 

hydrothermal uranium-bearing veins. Nevertheless, the 

tabulated sample assays do show a slight tendency for 

vanadium to increase in amount with an increase in 

uranium.

In addition to the generalizations made above, a few 

more detailed observations made during the compilation of these data seem worthy of record.

The assays of several uraninite or pitchblende specimens or concentrates were found; these, however, were 

not included with the other samples, because of the 

peculiar character of the sample or the manner in which 

the assay was reported. The vanadium content of these 

samples was reported to range from zero to a few tenths 

percent V2O5 . Among these several samples there is 

a slight suggestion that the vanadium content may be 

higher in "sooty pitchblende" than in crystalline uraninite. Geologists working on uranium-bearing veins 

may be interested in checking this suggestion.

Among groups of samples from most uranium-bearing veins there is no obvious tendency for the vanadium 

content to increase with the uranium content. Excep-
VANADIUM AND UEANIUM IN .ROCKS AND ORE DEPOSITS 229

tions to this generalization were noted in samples from 

the Schwartzwalder mine, Jefferson County, Colo., and 

the Miracle mine, Kern County, Calif. In both deposits the vanadium content is moderately high (perhaps averaging 0.1 to 0.2 percent V2O5 ) 1G, and in the 

available samples from both deposits there is an obvious, though not invariable, tendency for vanadium to 

increase with uranium. The writer has no idea why 

these two deposits have a moderately abnormal vanadium content. Titanium is not obviously concentrated in 

the Schwartzwalder deposit; the writer has no data 

regarding the titanium content of the ore from the 

Miracle mine.

VANADIUM IN HOT SPRINGS

Like the geologic descriptions of most ore deposits, 

reports on hot springs and hot-spring sediments usually 

fail to mention vanadium. The assumption can be 

made that vanadium is not abundant in these thermal 

solutions and that it does not precipitate from them in 

recognizable minerals but this is negative evidence 

and weak.

Based on his studies of hot-spring waters and sediments at Steamboat Springs, Nev., and Morgan 

Springs and Wilbur Springs, Calif., D. E. White (written communication) states:

Vanadium Is not present in amounts detectable by spectrographic methods in the dissolved solids of water samples from 

Steamboat Springs, Nev., and Morgan Springs and Wilbur 

Springs, Calif. Its content in the water at Steamboat Springs 

is less than 0.2 ppm and less than 2 pprn in the highly saline 

water of Wilbur Springs.

On the other hand, several samples of sediments from these 

three springs showed O.OX percent V by spectrographic analysis, 

and two from Steamboat Springs showed 0.01 percent V2Oa 

by gravimetric analysis.

Vanadium is not being deposited within the explored depths 

of the Steamboat Springs system, and there is even some evidence pointing toward a slight leaching of vanadium from the 

wall rock by the hydrothermal solutions.

Hot springs have not yet thrown light on the origin of 

hypogene uranium deposits. Hot spring waters are lower in 

uranium content than many other types of waters.

SUMMARY AND CONCLUSIONS

Vanadium and uranium are both dispersed in igneous 

rocks, but the two metals are not intimately associated 

in this environment vanadium is more abundant in 

the mafic rocks, uranium in the silicic ones.

Both metals tend to concentrate in some sedimentary 

rocks, especially those containing organic material; in 

these rocks either metal alone may be enriched, or both 

together.

10 A composite of sample pulps representing more than 400 tons of 

ore shipped from the Schwartzwalder mine shows only O.OX percent V, spectrographically. This analysis was received after the tabulation of all the other data used in this report.

Uranium obviously enters the hydrothermal environment, and in places it concentrates sufficiently in veins 

to form commercially valuable deposits. Prospecting 

in recent years has shown that uranium is rather widely 

distributed in hydrothermal veins.

None of the productive vanadium deposits, on the 

other hand, are of undoubted hydrothermal origin, although the vanadate ores and the deposit at Minasragra 

do have some characteristics of hydrothermal deposits. 

Furthermore, except in some titanium-bearing veins 

and some gold or gold-tellur'ide deposits, vanadiumbearing minerals have not been generally recognized 

in hydrothermal deposits, suggesting a low-vanadium 

content in most hydrothermal deposits, a suggestion 

that seems to be confirmed by recently available spectrographic data. A group of 775 analyses of samples of 

ores and mill products from numerous deposits in the 

 United States shows an average of less than 100 ppm V, 

a content somewhat less than that commonly reported 

for igneous rocks and shale. A second group of 296 

samples from uranium-bearing veins also shows an 

average of less than 100 ppm V. Perhaps the vanadium 

in many of these samples is that of the wall rock rather 

than introduced vanadium.

Although these samples certainly do not give a complete coverage of ore deposits, and many individual 

samples certainly are not representative of their parent 

ore bodies, as a group they probably represent the best 

available sample of vanadium in ore deposits in general and in uranium-bearing veins in particular. They 

suggest that vanadium does not tend to concentrate in 

the common hydrothermal environment, and specifically 

that it does not concentrate in most veins containing 

uranium ore. If this is true, it appears that deposits 

containing commercial amounts of both vanadium and 

uranium, such as deposits of the sandstone type, are 

not common hydrothermal deposits.

The fact that both vanadium and uranium do accumulate in some sedimentary rocks containing organic 

material suggests that a thorough study be made of the 

geochemical processes that influence this accumulation, 

to see if in any way these processes are compatible with 

the geologic habits of the productive vanadium-uranium deposits of the sandstone type, most of which do 

contain plant fossils.

The lack of evidence that vanadium and uranium 

are enriched together in common hydrothermal deposits 

does not eliminate the possibility of a hydrothermal 

origin and a hypogene source of these metals in the 

sandstone deposits, but it would seem to require field 

evidence that unusual processes or conditions were extant in order to support the idea of a hydrothermal 

origin and a hypogene source.
230 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

LITERATURE CITED

Argall, G. O., Jr., 1943, The occurrence and production of vanadium: Colorado School of Mines Quart., v. 38, p. 1-56.

Bain, G. W., 1950, Geology of the fissionable materials: Econ. 

Geology, v. 45, p. 273-323.

Balsley, J. R., Jr., 1943, Vanadium-bearing magnetite-ilmenite 

deposits near Lake Sanford, Essex County, New York: U. 

S. Geol. Survey Bull. 940-D, p. 99-123.

Clark, A. W., 1931, The ore-deposits of the Otavi Mountains, 

South-West Africa: Mining Mag., v. 44, p. 265-272.

Claussen, G. E., 1934, Spectroscopic analysis of certain galenas, 

sphalerites, and pyrites: Am. Mineralogist, v. 19, p. 221-224.

de Launay, L., 1911, Traite" de m6tallog6nie-gites min6raux et 

metalliferes: Paris.

Eckel, E. B., 1949, Geology and ore deposits of the La Plata 

district, Colorado: U. S. Geol. Survey Prof. Paper 219.

Erickson, B. L., Myers, A. T., and Horr, C. A., 1954, Association 

of uranium and other metals with crude oil, asphalt, and 

petroliferous rock: Am. Assoc. Petroleum Geologists Bull., 

v. 38, p. 2200-2218.

Everhart, D. L., and Wright, B. J., 1953, The geologic character 

of typical pitchblende veins: Econ. Geology, v. 48, p. 77-96.

Fischer, R. P., 1946, German iron ores yield vanadium: Am. 

Inst. Min. Met. Eng. Tech. Pub. 2070.

Fryklund, V. C., Jr., Harner, B. S., and Kaiser, E. P., 1954, Niobium (columbium) and titanium at Magnet Cove and Potash Sulphur Springs, Arkansas: U. S. Geol. Survey Bull. 

1015-B.

Goldschmidt, V. M., 1954, Geochemistry: Oxford, the Clarendon 

Press.

Hewett, D. F., 1909, Vanadium deposits in Peru: Am. Inst. 

Min. Met, Eng. Trans., v. 40, p. 274-299 (1910).

Jost, Konrad, 1932, Uber den Vanadiumgehalt der Sedimentgesteine und sedimentaren Lagerstatten: Chemie der Erde, 

v. 7, p. 177-290.

Kaiser, E. P., Herring, B. F., and Babbitt, J. C., 1954, Minor 

elements in some rocks, ores, and mill and smelter products: U. S. Geol. Survey TEI-415, U. S. Atomic Energy 

Comm., Tech. Inf. Service, Oak Bidge, Tenn.

Lindgren, Waldemar, 1933, Mineral deposits: New York,

McGraw-Hill Book Co., Inc. 

Lovering, T. S., and Goddard, E. N., 1950, Geology and ore

deposits of the Front Bange, Colorado: U. S. Geol. Survey

Prof. Paper 223. 

McKelvey, V. E., and Nelson, J. M., 1950, Characteristics of

marine uranium-bearing sedimentary rocks: Econ. Geology,

v. 45, p. 35-53. 

McKelvey, V. E., Everhart, D. L., and Garrels, B. M., 1955,

Origin of uranium deposits, in Fiftieth Anniversary

Volume, Economic Geology: p. 464-533. 

Moritz, H., 1933, Die Sulfidschen Erze der Tsumeb Mine:

Neues Jahrb. der Min., Beilage-Band 67A, p. 130-134. 

Newhouse, W. H., 1934, The source of vanadium, molybdenum,

tungsten, and chromium in oxidized lead deposits: Am.

Mineralogist, v. 19, p. 209-220. 

Parkin, L. W., and Glasson, K. B., 1954, The geology of the

Badium Hill uranium mine, South Australia: Econ.

Geology, v. 49, p. 815-825. 

Pavlenko, D. M., 1933, New data on the geology and genesis of

the Tyuya Muyan deposit in Uzbekistan: Problems of

Soviet Geology, v. 4, p. 123-141, Leningrad and Moscow.

(In Bussian). 

Peterson, N. P., 1938, Geology and ore deposits of the Mammoth

mining camp area, Final County, Arizona: Arizona Bur.

Mines Bull. 144, Geol. ser. 11. 

Bankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry:

Chicago, Univ. Chicago Press.

Bobinson, S. C., 1955, Mineralogy of uranium deposits, Goldfields, Saskatchewan: Geological Survey of Canada Bull. 31. 

Shaw, D. M., 1954, Trace elements in pelitic rocks, Part II:

Geochemical relations: Geol. Soc. America Bull., v. 65, p.

1167-1182. 

Singewald, J. T., Jr., 1913, The titaniferous iron ores in the

United States: U. S. Bur. Mines Bull. 64. 

Skerl, A. C., 1934, Vanadium at the Bhodesia Broken Hill:

Mining Mag., v. 50, p. 280-383. 

Wright, H. D., 1954, Mineralogy of a uraninite deposit at

Caribou, Colorado: Econ. Geology, v. 49, p. 129-174.
Part 21. THE KNOWN AND THE UNKNOWN

CONTENTS

Page 

Summary and conclusions_________-_____-_---_-_-__ 231

Areas of ignorance._________________________________ 232

Qualitative elemental and mineral composition of 

unweathered ore.______________________________ 232

Quantitative aspects of unweatbered-ore mineralogy. 233 

Chemical and mineralogic changes during oxidation 

of ore....___.____.._______._____ 234

Page 

Areas of ignorance Continued

Oxidation rates..____________-_____-_-_-_---_--_ 235

Near-surface effects,____________________________ 235

Valedictory. __.___.__________ _________-_... 236

References cited.______,_______-______-_-----.-_---_ 236

SUMMARY AND CONCLUSIONS

The problem around which this volume has been 

compiled, as discussed in Part 1, is the deciphering of 

oxidation relations in the Colorado Plateau ores. 

Most of the workers soon became convinced of the validity of the postulate that all ores were at one time 

reduced mineral suites, and most of their effort has 

gone into documenting the case. In fact, the postulate 

was so readily accepted, and fitted so well when deposits 

were examined, that it is almost a tacit assumption of 

many of the papers presented. This perhaps questionable scientific act of faith has been justified; the abundant data now available fit without difficulty into the 

theory. There are still areas of ignorance, to be sure, 

but no contradictory relations are known, which is rare 

in the explanation of a geologic phenomenon. This 

chapter is devoted to those areas of ignorance. In exposing them a framework is provided for summarizing 

the known. Whereas it is not the intent of this report 

to speculate on the origin of the ores, definition of the 

character of the various low-valent preoxidation suites 

necessarily precedes any speculation on origin.

The major conclusion derived from the preceding 

papers is that the ores are made up of an equilibrium 

low-valence assemblage if they occur in rocks saturated 

with water. In unsaturated rocks oxidation alteration 

has taken place, ranging from barely recognizable 

changes to nearly complete reconstitution of the mineral 

suites. The degree of oxidation depends upon many 

factors, such as time since exposure, proximity to the 

land surface, permeability of the blanketing rocks, 

structural attitude of the enclosing rocks, local rainfall, 

and the specific mineralogy and occurrence of the unweathered ore.

Unoxidized ore is commonly referred to as primary; 

at the moment there seems to be little reason to suspect 

that it is not. Whereas it would be extremely difficult 

to prove that the ores now found beneath the water 

table have resided there unchanged since original emplacement, in the absence of evidence to the contrary the 

view can be entertained with appropriate reservation 

concerning the possibility of new data.

Thus the picture has emerged that the unweathered 

ores have resulted from addition of a suite of elements 

to the enclosing rocks. The elements were emplaced 

in a reducing environment (whether they brought it 

with them or encountered it) in Late Cretaceous or early 

Tertiary time before regional deformation or during 

its early stages, so that movement of the transporting 

agent and the locus of deposition were chiefly controlled 

by sedimentary structures in essentially undeformed 

rocks. The major added elements, which differ markedly in their absolute amounts and proportions from 

place to place, are vanadium, copper, and iron, in addition to the essential uranium. Minor added elements 

which vary similarly include selenium, arsenic, phosphorus, lead, zinc, cobalt, nickel, molybdenum, and 

chromium. The entire suite is one generally characterized in its geologic behavior as being strongly affected 

by biochemical processes.

In terms of compounds formed, the ore is a mixture 

of oxides, silicates, and sulfides, with oxides and silicates 

predominating in vanadium-rich material, and oxides 

and sulfides in copper-rich deposits. Unoxidized ores 

have a relatively simple mineralogy, in that few phases 

are added to the enclosing rocks. The ore forming 

process appears chiefly to have been an additive one, 

in that the ores are to a large extent pore fillings.

231
232 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

Hematite, calcite, and gypsum are the chief minerals 

reconstituted during ore formation. Quartz is attacked 

locally.

The host rock is typically nonmarine sandstone lying in the range between pure quartz sand and greywacke. In the vicinity of ore the host is almost invariably light colored, with traces to large amounts of disseminated pyrite, and with traces to large amounts of 

carbonaceous matter of woody origin. Also, the host 

is usually a sandstone that has developed from the deposits of streams moving back and forth across an aggrading plain, so that it is lenticular, with interbedded 

lenses of shale, and is generally characterized by lithologic units of small lateral extent, abundant cross bedding, and complex channeling of higher units into lower 

ones. The chief clay mineral of the sandstones and of 

the associated shales is mixed-layer mica-montmorillonite, or so-called hydrous mica.

Texturally, the ore is characterized by fineness of 

grain, controlled in part by its restricted development 

in the rock pores, but also apparently resulting from 

the conditions of deposition. The development of several ore minerals within a given interstice suggests that 

the ore might well have been fine grained, even if large 

open spaces were available to accommodate it.

In gross configuration the ore bodies are generally 

tabular, with their long dimensions parallel to the 

formational boundaries. However, in many places ore 

boundaries transgress bedding at both low and high 

angles. Where transgression is abrupt, the ore boundary 

tends to be smoothly curved, producing lobate or crescentic forms known as rolls. There is a tendency for 

ore to occupy the lower or upper parts of the containing sandstone layer, as in the deposits in the Shinarump member of the Chinle formation where it lies in 

channels in the Moenkopi formation or where it is 

formed adjacent to roof shales in the Morrison formation.

Oxidation of the ores has occurred almost entirely 

above the zone of saturation. Because over most of the 

Plateau the general water table is at an unknown depth 

at present, but certainly many hundreds of feet below 

the surface, oxidation is prevented locally by perched 

water tables, and is prevented elsewhere simply by the 

distance air must penetrate to reach ore. If, for example, an ore body is above the zone of saturation but 

is 500 feet from the nearest land surface, oxidation 

might take place at an infinitely slow rate. The result 

of the gradual encroachment of oxidation as the land 

surface approaches the ore bodies is a markedly erratic 

pattern, as air infiltrates slowly along fractures and 

along zones of bulk rock permeability. In a humid 

climate, with the water table near the surface, abrupt

mineralogic transitions parallel to the water table occur ; 

in the Plateau where the oxidation is a slowly accelerating process, air has ample opportunity to seek 

out and employ the most delicate differences in permeability, resulting in complex oxidation patterns, and 

marked disequilibrium from one part of an ore body 

to another.

Consequently oxidation has resulted in a remarkably 

complex mineral assemblage as a given body passes 

from the relatively simple low-valence mineral assemblage to the simple high-valence assemblage developed 

at or near the surface. On the other hand, the slowly 

progressive nature of the process has produced essentially all possible intermediate stages, and has permitted detailed documentation of the process.

The mineralogical behavior of uranium and vanadium during the oxidation stages is clearly summarized' 

in figure 13 of Part 6 (page 82) and figure 26 of Part 

7 (page 101).

AREAS OF IGNORANCE

QUALITATIVE ELEMENTAL AND MINERAL COMPOSITION OF UNWEATHEBED ORE

In general the elemental and mineral composition of 

unweathered ores are now known. The kinds and 

amounts of extrinsic elements have been established and 

the major minerals identified. As pointed out in Part 

2, the added elements show marked regional and 

stratigraphic differences, but the major added elements of a "composite" ore are uranium, vanadium, 

iron, aluminum, copper, and sulfur and the prominent 

minor elements are lead, zinc, molybdenum, cobalt, 

arsenic, nickel, and selenium. The major minerals are 

pitchblende, coffinite, montroseite, vanadium silicates, 

pyrite, marcasite, bornite, and chalcopyrite. Of these 

pitchblende, coffinite, and pyrite are ubiquitous whereas 

the vanadium, aluminum, and copper minerals vary 

regionally.

There are two major areas of ignorance apparent at 

the moment: the nature of some of the carbonaceous 

materials associated with ores, and the detailed mineralogy of the vanadif erous silicates. A great deal of uranium is clearly associated with coalified wood. Chemical and physical studies have demonstrated that where 

uranium occurs in intimate association with material 

from the Temple Mountain region that is not obviously 

of woody origin, the carbonaceous material is, nevertheless, derived from wood or coalified wood. Early work 

emphasized an apparent relationship between uranium 

and carbonaceous substances derived from petroleum, 

but investigations to date have shown no such relationship to exist. The final answer to this problem must 

await further study of carbonaceous substances of all 

types from various parts of the Colorado Plateau.
THE KNOWN AND THE UNKNOWN 233

The vanadiferous silicates have been among the most 

vexing mineralogic problems of the Plateau. First of 

all, as pointed out by R. P. Fischer (oral communication), there are two distinct geologic occurrences of 

such silicates. In the first the silicate is developed by 

entry of vanadium into the structure of a pre-existing 

detrital clay; in this instance vanadium apparently is 

added and silica and alumina ejected, while the cationic 

constituents and the original structures are maintained; 

even if recrystallization occurs, the structure apparently is duplicated (Part 10). In the second, the vanadiferous silicate is formed where no clay or mica 

mineral previously existed. In this second case, although evidence is far from complete, the tendency 

seems to be to form roscoelite, a true vanadium mica. 

At Rifle (Part 19) and at Placerville, in particular, 

where vanadium silicates are developed in reasonably 

clean sandstones, the major silicate is known to be 

roscoelite. The vanadium in roscoelite is trivalent, even 

in those occurrences where the mineral has been exposed 

at the surface for many years.

On the other hand the super-imposition of vanadium 

on preexisting hydrous micas yields a vanadiferous 

variety of that mineral, and it is fairly well established 

that the original valence of the vanadium is four (Part 

10). It is not known to what extent vanadiferous 

chlorite is the result of addition of vanadium to preexisting chlorite, or whether it is developed as a transformation of preexisting hydrous mica, or whether it is 

a new species in the rock. Analyzed chlorites contain 

tetravalent vanadium, and the question as to original 

valence is not settled.

There is still uncertainty concerning the possibility of 

the development of vanadiferous silicates during the 

oxidation stages of primary montroseite. Much vanadium silicate is clearly primary, but because the fate of 

primary nonsilicate vanadium is not known, it has been 

suggested that new vanadium silicates are developed 

during weathering.

QUANTITATIVE ASPECTS OF UNWEATHEBED-OBE 

MINEBALOGY

Not enough is yet known of the quantitative aspects 

of Plateau mineralogy, although the work presented in 

Part 3 (p. 32) on average elemental composition of 

unmineralized rocks versus ore has gone far toward 

making accurate reconstructions possible. The elements, unfortunately, do not tell the whole story, for 

only in a few occurrences is it known accurately how 

uranium is divided between uraninite and coffinite, or 

how much of the vanadium is distributed among montroseite, roscoelite, chlorite, and hydrous mica. Until 

more data are accumulated it will not be possible to 

determine with confidence to what extent montroseite

has a genetic relation to carbonaceous matter; if coffinite is more abundant in vanadiferous ores; or if the 

roscoelite-bearing rocks are characteristically relatively 

clean sandstones, to mention but a few relations that 

have been suggested.

The nature and amount of carbonaceous material in 

and near ore is another question that needs quantitative 

study. Carbonaceous material has been suggested as a 

requirement for precipitation of uranium, and perhaps 

for vanadium as well. Pommer, in Part 14 (p. 162), 

has established some approximate values for the reducing capacity of wood and lignite; now studies of the 

actual content of such materials in ore and adjacent 

rocks are needed to establish fully its sufficiency for one 

or both reductions.

Another study would be the silica balance in a given 

deposit. In some ore samples quartz is strongly corroded; in others grain growth has taken place. Both 

features have been observed within a given ore body. 

It should be possible to determine whether the total 

silica remains the same, with a balance reached, for 

example, between quartz solution and development of 

new silicates, or whether there is gross silica loss during mineralization. The devitrification of volcanic ash 

in horizons close to ore-bearing sandstones probably 

furnished silica for overgrowth on quartz sand grains 

and silicification of fossil wood (Murata, 1940; and 

Waters and Granger, 1953). In some samples ore 

minerals are outside the silica overgrowth; in others ore 

minerals rim the detrital quartz grains and the silica 

overgrowth apparently formed after the ore minerals 

or in a late stage of the ore process. More work is 

needed to document the history of silica deposition and 

solution. Such studies would provide further background for hypotheses of origin. Also such studies 

would help to assess the degree to which the ores are 

simply additions to the preexisting rocks and the extent 

to which rock constituents have been leached. Certainly calcite and gypsum have been removed in large 

quantities in some cases; otherwise the ore-forming 

process appears to have been an additive one. In Part 

15 (p. 171, 173), for example, element anomalies reported chemically and spectrographically are positive 

except for calcium and sulfur, indicating removal only 

of interstitial gypsum.

Also of interest in the genesis of the ores is the 

"bleaching" that accompanies ore bodies. Unweathered 

ores are found surrounded by light-colored sandstones 

or green mudstone, particularly the large ore bodies 

in the Uravan belt almost never by reddish sandstone 

or mudstone. The extent and nature of this "envelope" 

and its relation to ore has received much attention, but 

it deserves still more attention. In a stratigraphic section composed of alternations of "reduced" and "oxi-
234 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

dized" rocks that is, light-colored pyritic sandstones 

with carbonaceous material, and green shales, as opposed to hematite-stained sandstones and shales it is 

extremely difficult to distinguish between primary features and subsequent changes. Although some of the 

red and gray coloration is undoubtedly primary, some 

alteration was probably effected by one or more of 

the following: diagenetic processes; alteration due to 

sulfur-bearing waters from the salt anticlines or oil 

and gas fields; bleaching accompanying ore formation; 

postore-preweathering bleaching; and the results of 

Quaternary weathering.

In some areas a strong positive correlation has been 

established between the thickness of ore and the thickness of green mudstone directly beneath. Furthermore, 

the boundary between green and adjacent red mudstone 

transgresses bedding. Under these circumstances it appears that the change from red to green has accompanied 

the emplacement of ore. Studies to date of chemical 

changes accompanying the alteration from red to green 

have shown little but disappearance of calcite and 

hematite as mineral species, plus a slight decrease in the 

ferric-ferrous ratio. Huff (1955) found a higher basemetal content (Pb+Zn+Cu) in bleached clays than 

in adjacent unbleached clays in one deposit. Clearly 

much more work is needed.

CHEMICAL AND MINERALOGIC CHANGES DURING 

OXIDATION OF ORE

The preceding papers show that the gross changes 

that occur during weathering have been worked out 

out theoretically, experimentally, and from field 

observation.

Uraninite and coffinite oxidize rapidly when exposed 

to air above the zone of saturation. In the presence of 

excess vanadium the resultant uranyl ion is fixed as 

difficultly soluble carnotite or tyuyamunite. If vanadium is deficient a host of uranyl compounds is possible, 

ranging through phosphates, arsenates, silicates, carbonates, sulphates, and hydrated hydroxides. In general these compounds are not so stable as the vanadates. 

Thus in a semiarid climate where little or no vanadium 

is washed out by circulating water vanadium fixes 

uranium; without vanadium, migration occurs.

Although the gross changes are known, much remains 

to be done to permit satisfactory prediction of the behavior of a given ore in a given matrix under a stipulated geologic environment. Among the problems is 

isolation of enough coffinite for satisfactory chemical 

analysis. It is so extremely fine grained and so intimately intermixed with other materials that there is 

still uncertainty concerning its nature. Coffinite has 

recently been synthesized (Hoekstra and Fuchs, 1956),

so that material for analysis should soon be available. 

More needs to be learned about the mechanism of oxidation of uraninite and coffinite, as well as about their relative rates. Both alter early to dark-colored materials 

containing uranium ( VI) , but there appears to be a considerable proportion of the time involved in the weathering process during which the uranium-bearing material is not further characterized. The evidence for this 

is analyses of samples of "black ores" that show abundant V(IV) mineral species, or mixed V(III)-V(IV) 

species, but have no trace of carnotite or tyuyamunite. 

They may contain several percent uranium, present in 

the six-valent state, but there is no uranium mineral 

species identifiable. Presumably the uranium is present 

chiefly as amorphous anhydrous UO3 . The considerable duration of this oxidation stage is attested by the 

frequency of its occurrence.

Also, there must be a difference in oxidation rate between uraninite and coffinite, but so far the absence of 

free energy data on coffinite has prevented calculation 

of an oxidation potential stability boundary for it ; the 

obscurity of its mineralogy and the complexity of the 

oxidation process have prevented conclusions from 

study of natural material, and the inability to synthesize 

it, until recently, has prevented laboratory studies.

The successive stages of oxidation of the primary 

vanadium hydroxy-oxide montroseite have been worked 

out in considerable detail theoretically, experimentally, 

and from natural materials. The relations are summarized well in figures 15 (p. 92) and 26 (p. 101). Because of the number of ionic species in solution that 

contain vanadium, a long list of possible or probable 

compounds can be drawn up, many of which perhaps 

will be found eventually as minerals. Among these 

"possible" mineral groups are metal vanadites, analogous to the recently discovered calcium vanadite simplotite. Combinations of vanadite ions with the other 

cations present in the system should be looked for in 

partly oxidized ores in alkaline environments. Two 

other obvious groups are corvusite and rauvite. Socalled corvusite, the abundant "blue-black" material in 

so many ores that have been oxidized in place by dampair oxidation, is poorly characterized. Two analyses of 

apparently pure phases of "corvusite" gave

V2 04 -6V2O and V2O4 -5V2O5 (

These combinations can be regarded as vanadyl analogues of the calcium vanadates, hewettite, and pascoite. 

If so, there may be as many species in the corvusite 

groups as have been recognized among the calcium vanadates. The same possibility of uranyl analogues of 

calcium vanadates exists in the material currently called 

rauvite "a uranyl vanadate of uncertain composition."
THE KNOWN AND THE UNKNOWN 235

Still other vanadiferous species could be postulated, 

but these three perhaps suffice to show that mineralogic 

study of vanadium species has not been completed.

Oxidation studies of copper minerals have not been 

emphasized, for in general they behave as in nonuranif - 

erous copper ores, which have been much studied, with 

the obvious exception of the development of small 

amounts of oxidized copper uranium compounds such 

as johannite.

OXIDATION RATES

The small amount of information available through 

measurements of radioactivity and radium-uranium 

equilibrium (Part 13) indicates oxidation has taken 

place during the past 100,000 years at least. The data, 

although fragmentary, agree well with the conclusion 

from geologic data (Part 5, p. 78) that oxidation has 

taken place since the ores emerged above the water 

table during the Quaternary cycle of canyon cutting. 

Further indirect evidence comes from the fact that 

minerals out of chemical equilibrium occur side by side 

in many ores minerals that alter rapidly in the laboratory under simulated natural conditions.

Unweathered ores, when dumped at the surface, alter 

markedly during a few months exposure. In fact, the 

uranium ores are such sensitive indicators of oxygen 

availability that they could be used to map in detail the 

controls of air movement underground. No trace of 

oxygen can move far through an ore containing uranium and nonsilicate vanadium before being used to 

produce a new mineral species.

A remarkable aspect of ore oxidation is the apparent 

uniformity of the oxidation reaction rates. The number of oxidation stages that can be discerned shows that 

each species in the sequence has a "half-life" of the same 

order of magnitude as that of the next higher stage. 

Indeed, it is almost as if the oxidation process has been 

carried on at near-equilibrium with a continuously rising oxidation potential, which is not the case, for the 

merest trace of oxygen produces an environment of 

high potential. The oxidation process, in the beginning, is the reaction between two extremes the high 

potential of aerated water versus the low potential of 

unweathered ore. If reaction to equilibrium between 

entering air and the ore minerals took place instantaneously, there would be no intermediate phases instead, 

but two sharply delimited f acies: unweathered ore and 

fully oxidized material.

Specifically, uraninite is usually the first mineral to 

oxidize completely, followed by montroseite. Both of 

these react much more rapidly than the sulfides. If the 

vanadium hydrous micas and chlorites originally contained trivalent vanadium, which is doubtful, it oxidized very rapidly to valence four, inasmuch as all

specimens analyzed so far contain tetravalent vanadium. The oxidation of paramontroseite to corvusite 

group minerals is slower than that of montroseite to 

paramontroseite, and that of corvusite to vanadates still 

slower. Inasmuch as each is the precursor of the other, 

the total vanadium involved in each stage is the same, 

so that the relative abundance of each species throughout the Plateau is a rough index of its lifetime. More 

quantitative studies are needed, but the relative rates 

given probably will not be changed.

NEAR-SURFACE EFFECTS

When ore is exposed to air above the water table, but 

below the reach of surface processes, oxidation takes 

place in an essentially closed system. That is, oxygen 

comes in and combines with minerals, but nothing 

moves out. Also, under these conditions, oxidation apparently takes place in place, with but minor diffusional movements over distances measured in inches, or 

perhaps, in extreme cases, a few feet. Maintenance of 

radioactive equilibrium within such ores, the presence 

of abundant water-soluble materials, the clear superposition of oxidation on an unaltered primary element 

distribution these and other criteria have been advanced to document the case. From the economic standpoint, this conclusion is important, for it means that 

the weathered ore drilling target is the same as that for 

unweathered ore.

But when the descending erosion surface approaches 

ore, a series of changes set in about which little information is available. The effects of the zone of capillary water movement must be drastic, especially in a 

semiarid area, where water sinks in after each rain, 

and then evaporates back to the surface. As pointed 

out by Weeks (Part 5, p. 77) the effect must be especially great in host rocks with calcareous cement, where 

alkaline bicarbonate waters would be expected to complex and thus solubilize uranium. We can be sure the 

effects are marked, for all the "free" vanadium that 

is, not in silicates and much of the carnotite disappears somewhere between oxidized ore underground 

and oxidized ore at the surface.

How much vanadium is simply dissolved and moved 

away, and how much (if any) is fixed in hydrous micas 

and chlorites is at present a matter of conjecture. For 

vanadium at least it is known that a major change takes 

place near the surface; information concerning uranium 

is much less concrete. Study of the Happy Jack Mine 

(Part 16, p. 194) is the only one that has traced such 

changes. Nothing comparable has been done on a high 

vanadium occurrence. Furthermore, the magnitude of 

the changes in uranium content brought about by 

weathering near the surface at Happy Jack shows how
236 GEOCHEMISTRY AND MINERALOGY, COLORADO PLATEAU URANIUM ORES

misleading many outcrops may be. The persistence of 

vanadium silicates and of copper "stains" at the outcrop 

has led to the discovery of many ore properties that 

would otherwise have been missed; the relatively late 

development of low copper-low vanadium deposits in 

northwest New Mexico can be blamed on the absence, in 

part, of persistent indicator minerals.

VALEDICTORY

In concluding this report that has resulted from the 

concentrated effort of many scientists using the field and 

laboratory equipment of the atomic age, respect and 

praise are asked, not for the writers of this volume, but 

for the geologists who learned so much about the Colorado Plateau uranium ores and reasoned and speculated 

so well in the period from 1900 to 1920 Hillebrand, 

Kansome, Hess, Butler, and Coffin.

REFERENCES CITED

Hoekstra, H. R., and Fuchs, L. H., 1956, Synthesis of coffinite 

USK>4: Science, v. 123, p. 105. 

Huff, L. C., 1955, Preliminary geochemical studies in the Capitol

Reef area, Wayne County, Utah: U. S. Geol. Survey Bull.

1015-H, p. 247-256. 

Murata, K. J., 1940, Volcanic ash as a source of silica for the

silicification of wood: Am. Jour. Sci., v. 238, p. 586-596. 

Waters, A. C., and Granger, H. C., 1953, Volcanic debris in uraniferous sandstones and its possible bearing on the origin

and precipitation of uranium: U. S. Geol. Survey Circ. 224.

U.S. GOVERNMENT PRINTING OFFICE: 1959