Distribution and Properties of 

Clinoptilolite-B earing Tuffs in the 

Upper Jurassic Morrison Formation on the 

Ute Mountain Ute Reservation, Southwestern 

Colorado and Northwestern New Mexico

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Distribution and Properties of 

Clinoptilolite-B earing Tuffs in the 

Upper Jurassic Morrison Formation on the 

Ute Mountain Ute Reservation, Southwestern 

Colorado and Northwestern New Mexico

By PAULA L. HANSLEY and RICHARD A. SHEPPARD

GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION 

U.S. GEOLOGICAL SURVEY BULLETIN 2061-A

Prepared in cooperation with the 

Ute Mountain Ute Tribe and the 

U.S. Bureau of Indian Affairs

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1993
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

For sale by

USGS Map Distribution

Box 25286, Building 810

Denver Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

Hansley, Paula L.,

Distribution and properties of clinoptilolite-bearing tuffs in the Upper Jurassic Morrison 

Formation on the Ute Mountain Ute Reservation, southwestern Colorado and northwestern 

New Mexico / by Paula L. Hansley and Richard A. Sheppard. 

p. cm. (U.S. Geological Survey bulletin ; 2061-A)

Includes bibliographical references.

Supt. of Docs. no.: 119.3:2061-A

1. Clinoptilolite Ute Mountain Indian Reservation. 2. Morrison Formation. 

I. Sheppard, Richard A. II. Titie. ni. Series. 

QE75.B9 no. 2061-A 

[TN948.C6] 

557.3 s dc20

[549'.68] 93-11143

CIP
CONTENTS

Abstract................................................................................................................................ Al

Introduction.......................................................................................................................... 1

Geologic Setting.................................................................................................................. 3

Methods of Study................................................................................................................. 3

Sample Descriptions............................................................................................................ 4

General Descriptions................................................................................................. 4

Petrographic Descriptions of Selected Samples........................................................ 4

Clinoptilolite........................................................................................................................ 6

Description and Identification................................................................................... 6

Chemical Composition.............................................................................................. 8

NH4+-Exchange Capacity.......................................................................................... 9

Economic Potential of Clinoptilolite-Bearing Tuffs on the Ute Mountain Ute

Reservation...................................................................................................................... 10

References Cited.................................................................................................................. 10

FIGURES

1. Index map showing Ute Mountain Ute Reservation and sample localities.................................................................... A2

2. Photomicrograph of clinoptilolite pseudomorph of a glass shard.................................................................................. 7

3. Scanning electron micrograph of clinoptilolite crystals filling a vug in a smectitic matrix........................................... 7

4. Photomicrograph of clinoptilolite in a calcite-filled vug................................................................................................ 8

TABLES

1. Localities and descriptions of samples........................................................................................................................... A5

2. Mineralogical composition of tuffaceous samples......................................................................................................... 6

3. Mean index of refraction for selected clinoptilolite crystals.......................................................................................... 8

4. Chemical analyses of three clinoptilolite-rich tuffs........................................................................................................ 9

5. Semiquantitative analyses of clinoptilolite crystals........................................................................................................ 9

6. NH4+-exchange capacity of three clinoptilolite-bearing tuffs........................................................................................ 10

m

DISTRIBUTION AND PROPERTIES OF

CLINOPTILOLITE-BEARING TUFFS IN THE

UPPER JURASSIC MORRISON FORMATION ON THE

UTE MOUNTAIN UTE RESERVATION, SOUTHWESTERN

COLORADO AND NORTHWESTERN NEW MEXICO

By Paula L. Hansley and Richard A. Sheppard

ABSTRACT

The distribution, purity, chemistry, and ammonium 

(NH4+)-exchange capacity of clinoptilolite on the Ute 

Mountain Ute Reservation were evaluated to determine the 

economic potential of this area for this commercially important zeolite. Altered volcanic ash beds in the Brushy Basin 

Member of the Morrison Formation (Upper Jurassic), which 

crop out at many locations on the Reservation, contain significant amounts of clinoptilolite. Clinoptilolite-bearing 

units are easily recognized by their distinctive salmonorange color. The Brushy Basin Member is believed to be 

the oldest sedimentary unit in the United States to host clinoptilolite. Clinoptilolite constitutes as much as 55 percent 

of some tuffs, but most beds contain far less. The NH4+- 

exchange capacity, 0.33-0.51 milliequivalents per gram 

(meq/g), of the clinoptilolite-bearing tuffs is relatively low. 

Where the clinoptilolite occurs, the Morrison Formation is 

covered by a thick overburden of post-Jurassic rocks. 

Removal of the overburden to mine the zeolitic beds, separation of clinoptilolite from these impure units, and extraction 

of ferric oxide from the clinoptilolite would be prohibitively 

expensive. As a result, this clinoptilolite could not compete 

in the marketplace with zeolitic beds of higher purity and 

greater accessibility. Commercial development of the clinoptilolite-bearing tuffs on the Ute Mountain Ute Reservation, therefore, is not economically feasible at the present 

time. No other formations containing zeolitic beds are 

known to occur on the Reservation.

INTRODUCTION

The purpose of this study was to investigate the occurrence and economic potential of zeolites on the Ute

Mountain Ute Reservation in southwestern Colorado and 

northwestern New Mexico (fig. 1). Zeolites are an important 

group of minerals that are used in a wide variety of industrial 

and agricultural applications including sewage-effluent 

treatment, fertilizers, dietary supplements for livestock, and 

radioactive waste treatment (Mumpton, 1981b). These 

applications take advantage of the unique crystal structures 

and chemical and physical properties that enable zeolites to 

exhibit reversible dehydration, cation exchange, adsorption, 

and acid and thermal stability. Zeolites are crystalline 

hydrated aluminosilicates with open structures characterized 

by an infinitely extended framework of SiC>4 and A1C>4 tetrahedra enclosing interconnected cavities occupied by relatively large water molecules and various exchangeable alkali 

and alkaline-earth cations. When placed in a strong ionic 

solution, zeolites release loosely bound cations and incorporate cations from the solution with a high degree of efficiency. Each zeolite species has cavities and entry channels 

of unique diameters that afford zeolites, as a group, the capability of accepting or excluding many different sizes of cations and molecules. Because of this adsorption of molecules 

based on size, zeolites are termed "molecular sieves." 

Despite the fact that many synthetic species of zeolite are 

now produced, natural zeolites remain an important commodity because of their low cost and unique properties.

Although zeolites occur in many different rock types 

and geologic settings, economic concentrations are commonly found in Cenozoic saline, alkaline lake deposits 

where zeolites formed as alteration products of volcanic ash 

in a hydrologically closed basin environment (Hay, 1966; 

Mumpton, 198la). The zeolites commonly compose more 

than 90 percent of the altered ash beds. Sedimentary zeolite 

beds in closed-basin deposits are commonly thick, flat lying, 

extensive, and exposed at the surface, making them economically attractive targets for mining operations. The thickness

Al
A2 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

109°

DOLORES COUNTY

MONTEZUMA 

COUNTY

SAN JUAN 

COUNTY

MESA VERDE / 

NATT PARK X

XiftWttfXftttfA

lUTE MOUNTAIN UTE RESERVATIONl

*££££

CORNERS

UTAHX 

ARIZONA NEW MEXICO

APACHE 

COUNTY

SANJUAN 

COUNTY

10 KILOMETERS

EXPLANATION 

1 Sample collection site

Figure 1. Location of the Ute Mountain Ute Reservation in southwestern Colorado and northwestern 

New Mexico, showing sample-collection sites for this study. From Irwin (1966, fig. 1).

of the beds ranges from less than a centimeter to several 

meters, with many beds thicker than 0.5 m. Clinoptilolite is 

a common zeolite in these lake deposits (Sheppard and 

Gude, 1982). Examples of ancient saline, alkaline lake 

deposits are from Pleistocene Lake Tecopa (Sheppard and 

Gude, 1968) and the Miocene Barstow Formation in southern California (Sheppard and Gude, 1969), the upper 

Miocene and lower Pliocene Big Sandy Formation in 

western Arizona (Sheppard and Gude, 1973), and the Eocene 

Green River Formation in Wyoming (Surdam and Parker, 

1972).

In the closed-basin lacustrine environment, volcanic 

ash reacted with interstitial waters and altered to various 

authigenic clay minerals, zeolites, feldspars, and silica

minerals during early diagenesis. The types of authigenic 

minerals that formed depended on the chemistry of the pore 

waters, including the salinity, the pH, and the proportion of 

ions (Hay, 1966). Lake waters commonly increased in salinity and alkalinity basinward, and corresponding trends in 

sediment pore waters resulted in the formation of laterally 

concentric diagenetic alteration patterns, which overlap in 

most areas. Nearest the lake margins, where waters were 

freshest because of stream recharge, ash remains unaltered in 

the most recent deposits; farther basinward, ash altered 

largely to smectite; still farther out, to clinoptilolite and other 

zeolites; and finally, in the most saline and alkaline waters 

near the basin center, to analcime and potassium feldspar. 

Analcime and potassium feldspar did not form directly from
CLINOPTILOLITE ON UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO A3

volcanic ash but crystallized slightly later from precursor 

zeolites (Surdam, 1981).

Clinoptilolite, one of the most commercially important 

natural zeolites, is found locally in the San Juan basin occurring in the Brushy Basin Member, the uppermost member of 

the Upper Jurassic Morrison Formation (Santos, 1975; Bell, 

1983,1986). This is probably the oldest known host rock for 

Clinoptilolite in sedimentary deposits of the United States 

(Sheppard, 1971). Brushy Basin sediments were deposited in 

a large saline, alkaline lake system that extended over 

present-day northwestern New Mexico, northeastern Arizona, southeastern Utah, and southwestern Colorado (Bell, 

1983, 1986; Turner-Peterson, 1985). Voluminous amounts 

of volcanic ash fell into the lake and associated streams during deposition of the Morrison, as evidenced by the presence 

of altered ash beds more than a meter thick. During earliest 

diagenesis, tuffaceous Brushy Basin sediments were altered 

to (listed from basin margin to center) smectite, Clinoptilolite, analcime, potassium feldspar, and albite, which occur in 

wide, interfingering alteration bands roughly parallel to 

former lake margins (Turner-Peterson, 1985; Turner and 

Fishman, 1991).

Much of the commercial value of Clinoptilolite hinges 

on its ability to accommodate large cations such as ammonium, heavy metals, cesium, and strontium (Flanigen and 

Mumpton, 1981). This enables it to remove ammonium ions 

(NH4+) from sewage effluent (Ames, 1967; Mercer, 1969), 

and radioactive cesium (Cs137) and strontium (Sr90) from 

wastewaters of nuclear power plants (Ames, 1959; Brown, 

1962). Natural zeolites such as Clinoptilolite are preferred for 

water purification because they are far less expensive and 

more stable in the presence of nuclear-particle bombardment 

than synthetic organic ion-exchange resins (Mumpton, 

198 Ib). Clinoptilolite is also used in paper fillings, fertilizers, and pet litter; as building-stone aggregate; and in processes such as dehydration of liquids and gases and 

separation of gases (Gottardi and Galli, 1985).

GEOLOGIC SETTING

The Morrison Formation crops out at many locations on 

the Ute Mountain Ute Reservation and in surrounding areas, 

including exposures on the southern and northern sides of 

McElmo Canyon, on the southern flanks of Sleeping Ute 

Mountain, on cliffs in the San Juan River valley, and in Coyote Gulch near the Colorado-Utah border (Irwin, 1966). 

Most exposures are partial sections of the upper part of the 

formation. In this region, the Morrison Formation is 

150-200 m thick and is composed of five members (in 

ascending order): the Tidwell (Fred Peterson, written commun., 1986), Salt Wash, Recapture, Westwater Canyon, and 

Brushy Basin (Ekren and Houser, 1959; 1965). The Morrison is underlain conformably by the Jurassic Junction Creek

Sandstone or equivalent rocks and is overlain by the Lower 

Cretaceous Burro Canyon Formation. The Brushy BasinBurro Canyon contact is generally indistinct, lying in a graygreen to gray-red zone of hackly, nonbentonitic mudstone 

and siltstone.

The Tidwell Member consists of interbedded mudstone, siltstone, and sandstone deposited on a floodplain. 

The next three members of the Morrison Formation are composed of lenticular, light-gray sandstone interbedded with 

red and green siltstone and claystone that were deposited by 

an aggrading system of braided streams (Craig and Dickey, 

1956) flowing from source areas located to the west and 

southwest of the Colorado Plateau. The Brushy Basin Member consists of 50-90 m (Irwin, 1966) of variegated, darkreddish to purplish-brown and light-greenish-gray bentonitic 

and zeolitic claystones and mudstones in the Ute Mountains 

area. Locally, it contains interbeds of silicified siltstone and 

sandstone and discontinuous beds of limestone and altered 

tuff. Weathered surfaces of fine-grained Brushy Basin sediments have a characteristic "popcorn" appearance as a result 

of wetting (and subsequent swelling) and drying of the bentonitic clays. The Brushy Basin Member intertongues with 

the upper part of the underlying Westwater Canyon Member. 

The fine-grained, flat-bedded character of the sedimentary 

units and the regional-facies patterns indicate that the Brushy 

Basin Member was deposited near the center of a large 

saline, alkaline lake system that existed in the vicinity of the 

present-day Ute Mountain Ute Reservation (TurnerPeterson, 1985).

METHODS OF STUDY

Tuffaceous, fine-grained samples suspected of containing Clinoptilolite were collected from six localities in and 

adjacent to the Ute Mountain Ute Reservation (fig. 1). 

Because of their distinct salmon-orange to red-orange color, 

clinoptilolite-bearing beds in the Brushy Basin Member are 

easy to recognize (Bell, 1983). Petrographic thin sections of 

selected samples were impregnated with blue-dyed epoxy 

and stained with Alizarin-red S for calcite detection. These 

sections were examined closely to obtain textural, compositional, and paragenetic data. X-ray diffractograms of 

packed-powder mounts of all samples were made with a 

Picker diffractometer to estimate mineralogical composition. The major-element-oxide chemistry of bulk samples 

containing significant amounts of Clinoptilolite was determined by x-ray fluorescence; this technique gave only an 

approximation of the composition of the Clinoptilolite. A 

better indication of the composition was provided by analyses of Clinoptilolite in gold-coated, polished petrographic 

thin sections with a Tracor Northern Semiquantitative Analysis System (SSQ), an energy-dispersive x-ray system 

attached to a Cambridge 250 Mark 2 scanning electron
A4 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

microscope (SEM). The analyses were corrected for atomic 

number, absorption, and fluorescence. Standards in the SSQ 

program are pure elements that were not analyzed at the 

same time under the same conditions as the unknowns; 

therefore, the results are considered to be semiquantitative 

because of unknown matrix effects and differences in operating conditions between the analyses of standards and analyses of unknowns.

The NH4+-exchange capacities of the three samples 

containing the highest amounts of clinoptilolite as determined from x-ray diffractograms were measured following 

the method of Busenberg and Clemency (1973). One hundred milligrams of each sample was saturated overnight with 

NH4+ using a 1 N ammonium-acetate solution (pH 7) and 

then leached with 1 N ammonium chloride. Each sample 

was washed with methanol and water to remove excess 

ammonium salts, air dried, and placed in a beaker to which 

deionized distilled water was added. An ammonia electrode 

was inserted into the beaker, and drops of 10 M sodium 

hydroxide were added slowly to displace the NH4+ ions and 

convert them to ammonia. After equilibrium was reached, 

the ammonia potential of each sample was recorded. The 

NH4+-exchange capacity was then determined by comparison with standard solutions of ammonium chloride.

SAMPLE DESCRIPTIONS

GENERAL DESCRIPTIONS

General descriptions of hand specimens, and results of 

x-ray diffractometer analyses of all samples collected from 

the Brushy Basin Member are presented in tables 1 and 2, 

respectively. Petrographic examination of selected samples 

revealed well-preserved vitroclastic textures and variable 

amounts of altered glass shards, lava, and other lithic fragments, along with detrital or pyrogenic grains of quartz and 

feldspars, in a fine-grained matrix. Accretionary lapilli and 

originally vitric shards are well preserved in the tuffs. Detrital, rounded quartz grains are present throughout the finegrained matrix, and authigenic microcrystalline quartz and 

chalcedony are locally abundant. Feldspars include sodic 

plagioclase and potassium feldspars sanidine, orthoclase, 

and (rarely) microcline. X-ray diffractograms of UT-85-5b 

and UT-85-5c revealed significant amounts of potassic 

sanidine, which may be present in small amounts in other 

samples as well. Some of the sodic plagioclase may be albite 

that formed during burial diagenesis of the tuffaceous material. However, recent studies suggest that the authigenic 

albite may have formed during early diagenesis of volcanic 

ash (Fishman and others, in press). Authigenic albite has 

been found in Brushy Basin sediments at other locations on 

the Colorado Plateau (Fishman and others, in press; Hansley, 

1984). Clay minerals are chiefly smectitic (expandable 

smectite/illite), but small, variable amounts of illite,

kaolinite, and chlorite(?) are also present. Vermiculite is the 

dominant clay mineral in samples UT-85-3c and 

UT-85-3e. All samples contain some calcite as a replacement of the smectitic matrix and clinoptilolite. Gypsum was 

detected in UT-85-2a and was also noted during SEM 

examination of UT-85-4a and UT-85-5a. Analcime was 

identified in only one sample, UT-85-5d.

PETROGRAPHIC DESCRIPTIONS OF 

SELECTED SAMPLES

Sample UT-85-3d, a well-indurated tuff, was collected 

on Cannon Ball Mesa, located on the north side of McElmo 

Canyon just north of the Reservation. It contains altered 

shards embedded in a smectitic matrix. Most shards have 

altered to smectite, although irregular red areas and some 

shard pseudomorphs have been replaced by chalcedony and 

(or) calcite. Locally, both smectite and chalcedony have 

been replaced by calcite. Sparse, angular quartz and feldspar 

occur throughout the microcrystalline, quartz-rich, smectitic 

matrix. Clinoptilolite was not detected in this sample.

Sample UT-85-4a was collected on the eastern edge of 

the clinoptilolite-bearing facies of the Brushy Basin Member 

in McElmo Canyon. The sample has a well-preserved vitroclastic texture, and clinoptilolite forms pseudomorphs of the 

originally vitric shards (fig. 2) and of the rare pumice fragments. The largest (about 170 jam long) clinoptilolite crystals occur in vugs and are commonly rimmed by chalcedony. 

Calcite locally has replaced chalcedony and clinoptilolite. 

Some shards are replaced by smectite and rimmed by chalcedony. Sparse, angular quartz, plagioclase, and rock fragments are scattered throughout the smectitic matrix.

Samples UT-85-5, UT-85-5c, UT-85-5g, and 

UT-85-5h were collected from the Brushy Basin Member in 

the San Juan River valley on the extreme southwestern part 

of the Reservation. Sample UT-85-5 is a mixture of red and 

green sandy tuff. The reddish portion contains abundant clinoptilolite, but the greenish portion has only a trace. Both red 

and green parts contain detrital grains of quartz, feldspar, 

rock fragments, rare pyroxene, and traces of calcite and 

pyrogenic biotite; red areas contain significantly more plagioclase than green areas. Sample UT-85-5g is a sandy 

altered tuff that is predominantly smectite with abundant 

detrital quartz and feldspar and traces of clinoptilolite. Samples UT-85-5c and UT-85-5h are vitric tuffs that have 

altered chiefly to clinoptilolite. Sample UT-85-5c has a 

spectacular vitroclastic texture characterized by clinoptilolite pseudomorphs of originally vitric shards. Sample 

UT-85-5h has more quartz, smectite, plagioclase, biotite, 

and calcite than UT-85-5c, with many shards altered to 

smectite or to clinoptilolite with a smectitic border.

Sample UT-85-6 is an altered vitric tuff that was collected from a roadcut adjacent to the Four Corners Monument. Clinoptilolite has replaced originally vitric shards that
CLINOPTILOLITE ON UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO 

Table 1. Localities and descriptions of samples collected from the Brushy Basin Member of the Morrison Formation.

A5

Sample1 Locality Color2 Description

UT-85-la 

UT-85-lb

UT-85-lc

South side of Sleeping Ute Mountain,

sec. 10,T.33'/2N.,R. 18 W., 

lat37°1030"N., long 108°4735"W.

Dusky yellow (5Y 6/4) 

Pale olive (10Y 6/2)

Pale olive (10Y 6/2)

Siliciiied tuff; base of exposed Brushy Basin Member 

Silicified tuff; irregular patches of dark-green

chalcedony; 0.5 m above la 

Altered tuff; 1 m above Ib

UT-85-2a Coyote Wash, west edge of Reservation, Light greenish-gray (5GY 8/1) Sandy tuff; base of exposed Brushy Basin Member

UT-85-2b SE1/isec.33,T.34N.,R.20W., Grayish yellow-green (5GY 7/2) Sandy tuff, red veinlets; base of exposed Brushy Basin

lat 37°15-N., long 109°00'W. Member

UT-85-3a 

UT-85-3b 

UT-85-3c 

UT-85-3d 

UT-85-3e 

UT-85-3f

McElmo Canyon, southeast side of

Cannon Ball Mesa,

SEl/4 sec. 29, T. 36 N., R. 19 W.,

lat37°20'50"N., long 108°56'10"W.

Pinkish gray (SYR 8/1) 

Greenish gray (5GY 6/1) 

Dusky green (5G 3/2) 

Light greenish-gray (5GY 8/1) 

Grayish olive-green (5GY 3/2) 

Pale olive (10Y 6/2)

Lowest altered tuff, reddish-brown streaks

Tuff; irregular red areas

Dense nodule in tuff; 3 m above 3b

Altered tuff; well-indurated; sparse irregular red streaks

Altered tuff; well-indurated

Altered tuff; highest tuff

UT-85-4a West end, north side of McElmo Canyon, 

UT-85^»b SEVi sec. 31, T. 36 N., R. 20 W., 

lat 37°207^., long 108°5T50"W.

Dark reddish-brown (10R 3/4) 

Pale reddish-brown (10R 5/4)

Clinoptilolite-richtuff; well-indurated 

Clinoptilolite-rich tuff

UT-85-5gn

UT-85-5rd

UT-85-5a

SJ-85-2a

UT-85-5aa

UT-85-5b 

UT-85-5c 

UT-85-5d 

UT-85-5e 

UT-85-5f 

UT-85-5g 

UT-85-5h

Reentrant, north side of San Juan River

valley,

NEW sec. 22, T. 32 N., R. 20 W., 

lat37°00'05"N., long 109C«2'40"W.

Grayish olive-green (5GY 3/2) 

Pale reddish-brown (10R 5/4) 

Light brown (SYR 6/4) 

Grayish orange-pink (SYR 7/2) 

Pale red (10R 6/2)

Grayish green (10GY 5/2) 

Pale reddish-brown (10R 5/4) 

Grayish green (10GY 5/2) 

Grayish orange-pink (SYR 7/2) 

Grayish orange-pink (5YR 7/2) 

Grayish orange-pink (5YR 7/2) 

Moderate orange-pink 

(10R 7/4)

Multicolored altered tuff just above Westwater Canyon

Member

Clinoptilolite-bearing tuff; 6 m above 5rd 

Tuffaceous sandstone; 7 m above 5a 

Clinoptilolite bands in gray shale above organic-rich

zone

Well-indurated tuff, red streaks 

Clinoptilolite-bearing tuff; 6 m above 5b 

Sandy altered tuff; 3 m above 5c 

Altered tuff, chalky 

Altered tuff 

Altered tuff 

Altered tuff, just below contact with Cretaceous rocks;

1 m above 5g

UT-85-6 Roadcut at entrance to Four Comers

Monument,

T. 32 N., R. 21 W.,

lat 37«00'02"N., long 109C«2I36"N.

Moderate reddish-brown 

(10R 4/6)

Clinoptilolite-rich tuff

Number in third term denotes sample-collection site indicated in figure 1. 

2Colors are from the rock-color chart (Goddard, 1948).
A6 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Table 2. Mineralogical composition of tuffaceous samples of the Brushy Basin Member of the Morrison Formation, 

as estimated from x-ray diffractograms of bulk samples.

[Ni-filtered CuKa radiation. Numbers are 2-theta peak heights in chart units for the peaks in brackets; n.d., not detected]

Sample

UT-85-la

UT-85-lb

UT-85-lc

UT-85-2a

UT-85-2b

UT-85-3a

UT-85-3b

UT-85-3c

UT-85-3d

UT-85-3e 

UT-85-3f

UT-85-4a

UT_85-4b

UT-85-5gn

UT-85-5rd

UT-85-5a

UT-85-5aa

UT-85-5b

UT-85-5c 

UT-85-5d

UT-85-5e

UT-85-5f

UT-85-5g

UT-85-5h

UT-85-^

Clinoptilolite 

[020]

n.d.

n.d.

n.d.

n.d.

n.d.

3

22

n.d.

n.d.

n.d. 

n.d.

36

34

2

48

68

13

5

25 

2

9

14

5

38

50

Quartz 

[100]

40

54

90+

58

78

76

45

90+

51

90+ 

90+

77

42

48

58

39

33

89

39

90+

31

81

38

68

42

Clay Minerals1 

[001]

6

4

7

21

32

21

7

4

12

3 

2

4

7

3

4

23

11

3

6 

10

21

26

18

24

4

Plagioclase 

[202]

11

10

34

55

38

39

19

37

14

34 

10

38

23

17

27

73

40

trace

17 

77

20

40

28

83

16

Other2

n.d.

n.d.

n.d.

Gypsum (4,[020])

n.d.

n.d.

n.d.

Vermiculite(7,[001])

n.d.

Vermiculite(3,[001]) 

Illite (7,[001]); kaolinite (7,[001])3

n.d.

n.d.

Kaolinite (9,[001])3

n.d.

n.d.

n.d.

Authigenic sanidine (59,[220])

Authigenic sanidine (18,[220]) 

Analcime (19,[400]); kaolinite (10,[001])3

n.d.

n.d.

n.d.

n.d.

n.d.

'Unknown mixture of 10-14A naked-layer clay minerals. 

Potassium feldspar and calcite occur in all samples. 

3May include [002] 14A clay mineral.

are embedded in a smectitic matrix containing volcanic(?) 

lithic fragments and biotite. Isolated patches of calcite have 

replaced the smectite.

CLINOPTILOLITE

DESCRIPTION AND IDENTIFICATION

Clinoptilolite is monoclinic and is a member of the heulandite structural group (Gottardi and Galli, 1985). It is distinguished from heulandite by a higher Si:Al ratio (>4.0)

(Boles, 1972), a higher Na+K:Na+K+Ca+Mg ratio (>0.6) 

(Mason and Sand, 1960), a lower mean index of refraction 

(< 1.485) (Mason and Sand, 1960), and thermal stability 

above 450°C (Mumpton, 1960). Clinoptilolite is generally 

stable up to 700°C, whereas heulandite either decomposes or 

converts to a different structure at 450°C (Alberti, 1975). 

Many clinoptilolite-heulandite minerals exhibit intermediate 

chemical and physical properties and thermal behavior 

(Alietti, 1972); the Brushy Basin samples are no exception.

Chemical and physical data collected during this study 

indicate that the heulandite-group zeolite in the Brushy
CLINOPTILOLITE ON UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO A7

Figure 2. Clinoptilolite pseudomorph of a glass shard in a smectitic matrix of altered tuff. Sample 

UT-85-4a from the Brushy Basin Member of the Morrison Formation. Plane-polarized light.

Basin Member is clinoptilolite. The average Si:Al ratio of 

eight zeolite crystals in sample UT-85-4a is 4.3 based on 

measurements of eight crystals; values ranged from 4.1 to 

4.8. Samples UT-85-4a and UT-85-5a retained their structures after heating for 15.75 hours at 450°C, although 

UT-85-5a showed a 40 percent loss in intensity of the [020] 

reflection. SEM examination of samples revealed crystal 

forms dominated by [010] lamellae characteristic of clinoptilolite (Gottardi and Galli, 1985) (fig. 3). On the other hand, 

the mean indices of refraction of representative samples of 

Brushy Basin clinoptilolite crystals are relatively high, ranging from 1.484 to 1.492 (table 3), which may be due in part 

to the presence of ferric oxide and a high calcium content. A 

high index of refraction in heulandite-group minerals is generally attributed to calcium substitution for potassium and 

sodium (Shepard and Starkey, 1966) or to a lower SirAl ratio 

(Boles, 1972). The cation ratios could not be used for identification because of the impurity of the samples.

Clinoptilolite is characteristic of low-temperature, 

near-surface, silicic tuffaceous sedimentary deposits, 

whereas heulandite occurs chiefly in hydrothermal or deeply 

buried deposits (Gottardi and Galli, 1985) and commonly in 

mafic volcanic rocks, regardless of burial depth. Based on 

Si:Al and cation ratios, Bell (1983) identified all heulanditegroup zeolite species (with the exception of one sample) collected from the Brushy Basin Member in the southeastern 

part of the San Juan basin as clinoptilolite.

In the present study, the largest prismatic clinoptilolite 

crystals (up to 170 |im in length) have parallel extinction and 

are length slow (fig. 4). The tips of these cloudy, orange-red

Figure 3. Scanning electron micrograph of clinoptilolite (cl) 

crystals filling a vug in the smectitic (s) matrix of altered tuff. Sample UT-85-4a from the Brushy Basin Member of the Morrison Formation.

crystals are commonly clear. The salmon-orange to redorange colors of clinoptilolite-bearing beds in the Brushy 

Basin Member (as opposed to the white-gray colors of most
A8 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Table 3. Mean index of refraction for selected samples of clinoptilolite in the Brushy Basin Member of the Morrison Formation. All crystals are length slow.

Sample Mean index of refraction

SJ-85-2a

UT-85-^a

UT-85-5a

UT-85-5c

UT-85-6

1.485

1.492

1.484

1.490

1.489

clinoptilolite-rich beds) are due to the presence of ferric 

oxide. Hydrothermal clinoptilolite that has a similar red 

color and contains 0.75 weight percent structural ferric oxide 

has been reported from Italy (Alberti, 1975; Gottardi and 

Galli, 1985). In the Brushy Basin samples, it is unknown 

whether ferric iron has substituted for aluminum in the clinoptilolite structure or whether the iron is present as submicroscopic inclusions that exsolved from original structural 

positions in the zeolite. Examination of large crystals in 

transmitted plane-polarized light under high magnification, 

however, did not reveal a separate ferric-oxide phase.

CHEMICAL COMPOSITION

The chemical composition of clinoptilolite 

[Cax(Na,K)6.2x(Al6Si3oOv2)'24H2O] is approximated by

bulk analyses of samples containing the most clinoptilolite 

(table 4). Estimates of the amount of clinoptilolite in these 

samples can best be obtained by using the water content as a 

guide, because clinoptilolite averages 14 percent water (Gottardi and Galli, 1985). Assuming that all the water is in the 

clinoptilolite, sample UT-85-4a contains 49 percent clinoptilolite, and sample UT-85-6 contains 55 percent. However, 

the amount of clinoptilolite in sample UT-85-5a cannot be 

determined in this manner because of its high clay content. 

High silica contents in all three samples reflect the proportions of detrital and authigenic quartz. Sodium is the dominant cation in sample UT-85-5a but calcium is dominant in 

the others. Not all of the sodium and calcium are contained 

in the clinoptilolite; some sodium is in plagioclase and some 

calcium is in calcite. Sample UT-85-5a is higher in A^C^ 

because of a higher clay mineral content. Fe2C>3 contents of 

these samples are higher than for most clinoptilolites (or 

heulandites) inasmuch as the highest Fe2O3 content in clinoptilolite reported by Gottardi and Galli (1985) is only 1.75 

weight percent.

A comparison of the chemical analysis of sample 

UT-85-4a with the SSQ analysis of clinoptilolite crystals 

from the same sample (table 5) gives a clearer picture of the 

composition of clinoptilolite. Although the normalized analytical totals are anhydrous, the relative amounts of oxides 

are meaningful. SSQ results show that the Fe2O3 content is 

consistently less than 1 percent, suggesting that some iron in 

the bulk sample is contained in clay minerals or iron oxides. 

Al2C>3 values are 13-16 percent, typical of clinoptilolite. 

MgO is 0.4-3.8 percent; clinoptilolite crystals having the

Figure 4. Clinoptilolite (cl) crystals lining a calcite-filled (Ca) vug in altered tuff. Sample 

UT-85-4a from the Brushy Basin Member of the Morrison Formation. Note transparent tips of 

cloudy clinoptilolite crystals. Plane-polarized light.
CLINOPTILOLITE ON UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO A9

Table 4. Chemical analyses of three clinoptilolite-rich tuffs in the 

Brushy Basin Member of the Morrison Formation.

[Numbers represent composition in weight percent. X-ray fluorescence analyses by 

AJ. Bartel, K. Stewart, and J. Taggart, analysts]

Sample

Major 

oxide

SiO2

A1203

Fe2O3

MgO

CaO

Na20

K20

Ti02

P2O5

MnO

LOI1

OT*4.

76.5

8.82

1.76

0.51

1.98

1.52

1.46

0.24

O.05

0.07

6.89

UT-85-5a

66.8

14.3

2.29

1.24

1.22

2.56

1.97

0.28

<0.05

0.02

8.89

UT-85-6

74.1

10.0

1.87

0.74

1.73

1.33

1.53

0.1

<0.05

0.04

7.67

Total 99.80 99.62 99.16

'LOI: Loss on ignition (HjO) at 900°C.

highest MgO contents have the lowest Si:Al ratios. K2O is 

0.9-2.56 percent, and Na2O is 0.46-1.9 percent. Low Na2O 

values are probably due to absorption. The CaO contents of 

the analyzed crystals in sample UT-85-4a are consistently 

high, ranging from 5.16 to 5.59 percent; thus, this clinoptilolite is calcium rich inasmuch as most clinoptilolites average 

only 1-3 percent CaO (Gottardi and Galli, 1985).

NH4+-EXCHANGE CAPACITY

The NH4+-exchange capacity of clinoptilolite-bearing 

tuffs from the Brushy Basin Member was determined 

because many commercial or potential uses of clinoptilolite 

are based on this property. The exchange capacity of a zeolite is directly related to the amount of aluminum that substitutes for silicon in the zeolite structure (Flanigen and 

Mumpton, 1981), because substitution of aluminum for silicon results in a charge deficiency that is balanced by incorporation of monovalent or divalent cations. The NH4+- 

exchange capacities of six samples from three tuffs relatively 

rich in clinoptilolite range from 0.33 to 0.51 meq/g (table 6). 

Even taking into consideration the fact that these values represent the NH4+-exchange capacities of impure bulk samples, the values are low compared to the average cationexchange capacity (2.3 meq/g) of pure clinoptilolite (Flanigen and Mumpton, 1981).

Table 5. Semiquantitative analyses of clinoptilolite crystals from sample UT-85-4a from the Brushy Basin 

Member of the Morrison Formation.

[Values are average normalized compositions in weight percent based on 3-5 analyses per crystal; totals represent anhydrous samples. Analyses 

made with the Tracor Northern Semiquantitative Analysis System (SSQ) attached to a Cambridge 250 Mark 2 scanning electron microscope: accelerating potential, 20 kV; beam diameter, l|im; count time, 30 sec; take-off angle, 56.5°; corrected for atomic number, absorption, and fluorescence; pure elemental standards used by SSQ program]

Clinoptilolite crystal number

Major 

oxide

SiO2

A12O3

Fe2O3

MgO

CaO

Na2O

K20

1

75.03

14.71

0.61

1.62

5.28

1.00

1.78

2

76.67

15.02

0.27

1.06

5.16

0.58

1.20

3

76.23

14.70

0.45

1.10

5.60

0.60

1.31

4

74.23

15.33

0.47

1.71

5.59

1.14

1.57

5

72.25

15.49

0.63

2.34

5.50

1.78

2.01

6

71.%

15.10

0.83

2.70

5.22

2.15

2.04

7

72.64

14.93

0.89

2.44

5.19

1.96

2.02

8

79.25

13.92

0.12

0.23

5.19

0.03

1.29

Total 100.30 99.96 99.99 100.04 100.00 100.00 100.07 100.03
A10 GEOLOGIC STUDIES OF THE UTE MOUNTAIN UTE INDIAN RESERVATION

Table 6. NH4+-exchange capacity of three clinoptilolite-bearing tuffs from the Brushy Basin Member of the Morrison Formation.

[Analytical method after Busenberg and Clemency (1973); D. Eberl, analyst]

uranium mineralization: Berkeley, University of California, 

Ph.D. thesis, 102 p. 

-1986, Deposition and diagenesis of the Brushy Basin

Sample NH4+-exchange capacity (meq/g)

UT-85-^a

UT-85-^a

UT-85-4a

UT-85-5a

UT-85-5a

UT-85-6

0.33

0.34

0.51

0.39

0.44

0.49

ECONOMIC POTENTIAL OF

CLINOPTILOLITE-BEARING TUFFS

ON THE UTE MOUNTAIN

UTE RESERVATION

Based on the data presented in this report, the economic 

potential of clinoptilolite-bearing tuffs in the Brushy Basin 

Member is low. Although the samples collected for analysis 

were taken from tuffs containing the most clinoptilolite, this 

zeolite constitutes no more than 55 percent of any sample. 

The other mineral phases present in these samples detract 

from the economic value of the clinoptilolite because of the 

difficulty and high costs of purification. In addition, the low 

NH4+-exchange capacity of the clinoptilolite-bearing tuffs 

and the presence of relatively thick post-Jurassic overburden 

on the Morrison Formation would render mining of clinoptilolite prohibitively expensive.

REFERENCES CITED

Alberti, Alberto, 1975, The crystal structure of two clinoptilolites: Tschermaks Mineralogische und Petrographifche 

Mitteilungen, v. 22, p. 25-37.

Alietti, Andrea, 1972, Polymorphism and crystal-chemistry of 

heulandites and clinoptilolites: American Mineralogist, v. 57, 

p. 1448-1462.

Ames, L.L., Jr., 1959, Zeolitic extraction of cesium from aqueous 

solutions: U.S. Atomic Energy Commission, Unclassified 

report Hy-62607, 23 p.

 1967, Zeolitic removal of ammonium ions from agricultural 

wastewaters, in 13th Pacific Northwest Industrial Waste 

Conference, Pullman, Wash., 1967, Proceedings: Pullman, 

Washington State University, p. 135-152.

Bell, T.E., 1983, Deposition and diagenesis of the Brushy Basin 

and upper Westwater Canyon Members of the Morrison 

Formation in northwest New Mexico and its relationship to

Member and upper part of the Westwater Canyon Member of 

the Morrison Formation, San Juan Basin, New Mexico, in 

Turner-Peterson, C.E., Santos, E.S., and Fishman, N.S., eds., A 

basin analysis case study The Morrison Formation, Grants 

uranium region, New Mexico: American Association of 

Petroleum Geologists Studies in Geology 22, p. 77-91.

Boles, J.R., 1972, Composition, optical properties, cell dimensions 

and thermal stability of some heulandite group zeolites: 

American Mineralogist, v. 57, p. 1463-1493.

Brown, R.E., 1962, The use of clinoptilolite: Ore Bin, v. 24, no. 12, 

p. 193-197.

Busenberg, E., and Clemency, C.V., 1973, Determination of the 

cation exchange capacity of clays and soils using an ammonia 

electrode: Clays and Clay Minerals, v. 21, p. 213-217.

Craig, L.C., and Dickey, D.D., 1956, Jurassic strata of southeastern 

Utah and southwestern Colorado, in 7th Annual Field 

Conference Guidebook: Intermountain Association of 

Petroleum Geologists, p. 93-104.

Ekren, E.B., and Houser, F.N., 1959, Relations of Lower 

Cretaceous and Upper Jurassic rocks, Four Corners area: 

American Association of Petroleum Geologists Bulletin, v. 43, 

p. 190-201.

 1965, Geology and petrology of the Ute Mountains area, 

Colorado: U.S. Geological Survey Professional Paper 481, 

74 p.

Fishman, N.S., Turner-Peterson, C.E., and Brownfield, I.K., in 

press, Authigenic albite in a Jurassic saline, alkaline lake 

deposit Evidence for early diagenetic formation: U.S. 

Geological Survey Bulletin 1808-P.

Flanigen, E.M., and Mumpton, F.A., 1981, Commercial properties 

of natural zeolites, in Mumpton, F.A., ed., Mineralogy and 

geology of natural zeolites (2d ed.): Mineralogical Society of 

America, Reviews in Mineralogy, v. 4, p. 165-176.

Goddard, E.N., chairman, 1948 (reprinted 1975), Rock-color chart: 

Boulder, Colo., Geological Society of America.

Gottardi, Glauco, and Galli, Ermanno, 1985, Natural zeolites 

(Minerals and Rocks, v. 18): New York, Springer-Verlag, 

409 p.

Hansley, P.L., 1984, Feldspar alteration patterns in the Upper 

Jurassic Morrison Formation, northwestern New Mexico 

[abs.]: Society of Economic Paleontologists and Mineralogists, 

First National Midyear Meeting, Technical Program, v. 1, 

p. 37.

Hay, R.L., 1966, Zeolites and zeolitic reactions in sedimentary 

rocks: Geological Society of America Special Paper 85,130 p.

Irwin, J.H., 1966, Geology and availability of groundwater on the 

Ute Mountain Indian Reservation, Colorado and New Mexico: 

U.S. Geological Survey Water-Supply Paper 1576-G, 109 p.

Mason, Brian, and Sand, L.B., 1960, Clinoptilolite from 

Patagonia The relationship between clinoptilolite and 

heulandite: American Mineralogist, v. 45, p. 341-350.

Mercer, B.W., 1969, Clinoptilolite in water-pollution control: Ore 

Bin, v. 31, no. 11, p. 209-213.

Mumpton, F.A., 1960, Clinoptilolite redefined: American 

Mineralogist, v. 45, p. 351-369.
CLINOPTILOLITE ON UTE MOUNTAIN UTE RESERVATION, COLORADO AND NEW MEXICO All

 1981a, Natural zeolites, in Mumpton, F.A., ed., Mineralogy 

and geology of natural zeolites (2d ed.): Mineralogical Society 

of America, Reviews in Mineralogy, v. 4, p. 1-17. 

-1981b, Utilization of natural zeolites, in Mumpton, F.A.,

ed., Mineralogy and geology of natural zeolites (2d ed.): 

Mineralogical Society of America, Reviews in Mineralogy, v. 

4, p. 177-204.

Peterson, Fred, 1988, Stratigraphy and nomenclature of Middle and 

Upper Jurassic rocks, western Colorado Plateau, Utah and 

Arizona: U.S. Geological Survey Bulletin 1633-B, 

p.B17-B56.

Santos, E.S., 1975, Lithology and uranium potential of Jurassic 

formations in the San Ysidro-Cuba and Majors Ranch area, 

northwestern New Mexico: U.S. Geological Survey Bulletin 

1329,22 p.

Shepard, A.O., and Starkey, H.C., 1966, Effect of cation exchange 

on the thermal behavior of heulandite and clinoptilolite, in 

Short papers in geology and hydrology: U.S. Geological 

Survey Professional Paper 475-D, p. D89-D92.

Sheppard, R.A., 1971, Clinoptilolite of possible economic value in 

sedimentary deposits of the conterminous United States: U.S. 

Geological Survey Bulletin 1332-B, 15 p.

Sheppard, R.A., and Gude, A.J., 3d, 1968, Distribution and genesis 

of authigenic silicate minerals in tuffs of Pleistocene Lake 

Tecopa, Inyo County, California: U.S. Geological Survey 

Professional Paper 597,38 p.

 1969, Diagenesis of tuffs in the Barstow Formation, Mud 

Hills, San Bernardino County, California: U.S. Geological 

Survey Professional Paper 634,35 p.

 1973, Zeolites and associated authigenic silicate minerals in 

tuffaceous rocks of the Big Sandy Formation, Mohave County, 

Arizona: U.S. Geological Survey Professional Paper 830,36 p.

 1982, Mineralogy, chemistry, gas adsorption, and NH4+-

exchange capacity for selected zeolitic tuffs from the western 

United States: U.S. Geological Survey Open-File Report 

82-969,16 p.

Surdam, R.C., 1981, Zeolites in closed hydrology systems, in 

Mumpton, F.A., ed., Mineralogy and geology of natural 

zeolites (2d ed.): Mineralogical Society of America, Reviews 

in Mineralogy, v. 4, p. 65-92.

Surdam, R.C., and Parker, R.D., 1972, Authigenic aluminosilicate 

minerals in the tuffaceous rocks of the Green River Formation, 

Wyoming: Geological Society of America Bulletin, v. 83, 

p. 689-700.

Turner, C.E., and Fishman, N.S., 1991, Jurassic Lake 

T'oo'dichi' A large alkaline, saline lake, Morrison 

Formation, eastern Colorado Plateau: Geological Society of 

America Bulletin, v. 103, p. 538-558.

Turner-Peterson, C.E., 1985, Lacustrine-humate model for primary 

uranium ore deposits, Grants uranium region, New Mexico: 

American Association of Petroleum Geologists Bulletin, v. 69, 

p. 1999-2020.

Published in the Central Region, Denver, Colorado 

Manuscript approved for publication April 2,1993 

Edited by John Synnefakis 

Graphics prepared by Pat Wilber 

Photocomposition by Shelly Fields

. GOVERNMENT PRINTING OFFICE: 1993-774-049/66059

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