Hydrothermal Alteration Associated with 

Beryllium Deposits at Spar Mountain, Utah 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 818-A 

Hydrothermal Alteration Associated with 

Beryllium Deposits at Spor Mountain, Utah 

By DAVID A. LINDSEY, HAROLD GANOW, and WAYNE MOUNTJOY 

BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 818-A 

A description of the mineral and chemical 

composition of beryllium-bearing tuff 

at Spor Mountain, western Utah 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Di1·ector 

Library of Congress catalog-card No. 73-600204 

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

Washington, D.C. 20402 - Price 75 cents (paper cover) 

Stock Number 2401-02401 
CONTENTS 

Page Page 

Abstract-------------------------------- A1 Alteration nodules in tuff ---------------------- A12 

Introduction _____________________________ _ 1 

1 

4 

4 

5 

7 

9 

9 

Calcite-silica-fluorite nodules _________ --------- 12 

Geologic setting ___________________________ _ Fluorite-clay-manganese oxide nodules _ _ _ _ _ _ _ _ _ _ _ _ 12 

Previous mineralogical and geochemical work __________ _ Discussion and conclusions _____________ -------- 14 

Alteration of the water-laid tuff __________________ _ Alteration processes_______________________ 14 

Petrography of unmineralized tuff ______________ _ Chemical transport and precipitation mechanisms _ _ _ _ _ _ 17 

Petrography of mineralized tuff _______________ _ Origin of the Spar Mountain beryllium deposits ______ ~ 18 

Chemical composition _____________________ _ References cited _____________________ --- --- 19 

Alteration patterns at the Roadside ore deposit _________ _ 

FIGURE I. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

ILLUSTRATIONS 

Map showing location of Spar Mountain, other geographic features, and mineral occurrences mentioned in text ______ _ 

Map showing geologic setting, beryllium deposits, and sample localities in water-laid tuff at Spar Mountain and the Thomas 

Range ------------------------------------------------------------

Whole-rock X-ray diffractograms of water-laid tuff at Spar Mountain and the Thomas Range _______ ---------

Photographs of specimens and thin sections illustrating features of argillic alteration in water-laid tuff at Spar Mountain --

Photographs of specimens and thin sections illustrating features of feldspathic alteration in water-laid tuff at Spar Mountain 

Sections and graphs showing alteration patterns in the water-laid tuff at the Roadside beryllium deposit _______ ----

Photographs of calcite-silica-fluorite nodules from the Roadside beryllium deposit, selected to show progressive stages of 

alteration ____________________________________________________ -------

Photographs of fluorite-clay-manganese oxide nodules from the Roadside and Rainbow beryllium deposits __ -------

TABLES 

TABLE I. Comparison of the density, porosity, mineral composition and chemical composition of unmineralized and mineralized waterlaid tuff, Spar Mountain and the Thomas Range, Utah ________________________________ _ 

2. Distribution of elements with respect to gross mineralogy in 12 calcite-silica-fluorite nodules from the Roadside beryllium 

deposit _____________________________________________________________ _ 

3. Major chemical gains and losses per I ,000 cc of rock as shown by alteration of water-laid tuff and carbonate clasts in tuff, 

Spar Mountain and the Thomas Range, Utah ______________________________________ _ 

III 

Page 

A2 

3 

6 

9 

10 

11 

12 

15 

Page 

A5 

14 

16 

BERYLLIUM--BEARING TUFFS IN WESTERN UTAH 

HYDR01THERMAL ALTERATION 

ASSOCIATED WITH BERYLLIUM DEPOSITS AT 

SPOR MOUNTAIN, UTAH 

By DAVID A. LINDSEY, HAROLD GANOW, and WAYNE MouNTJOY 

ABSTRACT 

The beryllium deposits at Spor Mountain occur in waterlaid tuff that 

contains carbonate clasts. Vitric and zeolitic tuffs are present outside the 

mineralized area whereas argillic and feldspathic tuffs are present within 

the mineralized area. Early alteration of tuff was characterized by argillization and addition of Si, AI, Fe, Hp, F, Be, Li and many trace elements; 

advanced alteration was marked by feldspathization, fluorite-silica replacement of carbonate clasts, continued addition of many trace elements, and 

loss of water. As shown by potassium-feldspar and fluorite abundance, the 

alteration intensity at the Roadside beryllium deposit decreases with depth 

but shows a minor increase near the base of the tuff. The beryllium ore 

body and associated fluorite are near the top of the tuff and are underlain 

by a thick zone containing lithium-bearing trioctahedral montmorillonoid 

clay and associated calcite. Beryllium (as bertrandite), lithium, uranium, 

and other elements are concentrated in fluorite-rich nodules, and 

magnesium, lithium, and zinc are concentrated in trioctahedral montmorillonoid clay nodules. Most of the nodules are believed to be altered 

domomite clasts. Manganese oxide minerals occur as nodule coatings and 

fissure fillings. 

The elements concentrated at Spor Mountain are tentatively believed to 

have been derived from a buried granitic pluton by fluorine-rich hydrothermal solutions. These solutions ascended into the overlying tuff where they 

reacted with carbonate clasts, releasing carbonate ions whose hydrolysis 

turned the solutions alkaline. Decreasing temperature probably caused 

precipitation of silica minerals and fluorite, producing and accompanying 

decrease in fluorine concentration. Increasing pH triggered potassium fixation and resulted in widespread feldspathization of the tuffs. Increasing pH, 

decreasing temperature, and decreasing fluorine concentration were 

variously responsible for the breakdown of stable metal fluoride complex 

ions and for the precipitation of minerals of beryllium, uranium, and other 

elements. 

INTRODUCTION 

Large beryllium deposits in western Utah are a significant 

part of the world's known beryllium resources (Griffitts, 

1964 ). These deposits occupy a belt that extends west from 

the Sheeprock Mountains of Utah into Nevada (fig. I) 

(Cohenour, l963a). The deposits in Utah consist of beryl in 

granite of the Sheeprock Mountains (Cohenour, 1963b), 

bertrandite in tuff at Spor Mountain (Staatz and Griffitts, 

1961), beryllium in tuff at the Honeycomb Hills (Montoya 

and others, 1964 ), beryl in pegmatites at Granite Peak 

(Fowkes, 1964), bertrandite in veins at Rodenhouse Wash 

(Griffitts, 1965), and beryl in veins and pegmatites in many 

places in the southern Deep Creek Mountains (Griffitts, 

1964). The Spor Mountain deposits, discovered in 1959, 

contain large reserves of ore averaging less than 1 percent 

BeO. These ores are economically competitive with imported beryl because they are accessible by open-pit mining 

and the beryllium can be extracted by acid leaching. Brush 

WelLman Inc., began production in 1971 at their mill east of 

Delta, Utah, and the Spor Mountain deposits can be expected to provide a major source for beryllium in the future. 

The purpose of this report is twofold: (1) to describe the 

mineralogy and chemical composition of the host tuff of the 

beryllium deposits at Spor Mountain, and (2) to define the 

principal alteration processes responsible for deposition of 

beryllium in tuff. This report, first in a series of reports on 

beryllium-bearing tuffs in western Utah, provides a basis for 

the recognition of alteration associated with beryllium 

deposits in tuff. 

This report was written by the senior author, who is 

responsible for the observations and conclusions presented. 

Data on mineralogy and chemical composition used in 

preparing this report are available from the U.S. Department of Commerce National Technical Information Service, Springfield, Va. 22151 (Lindsey and others, 1973). 

We thank the employees of Brush Wellman Inc., at Delta, 

Utah, for their cooperation and hospitality duFing 

fieldwork. W. R. Griffitts, U.S. Geological Survey, 

provided drill-hole samples obtained by him from the Vitro 

Minerals Corp. Kurt Buzard assisted the senior author in 

mineralogical studies and other laboratory work, and G. S. 

Bhatnagar, India Atomic Energy Commission, also participated in mineralogical studies for 2 weeks. Many other 

U.S. Geological Survey colleagues performed chemical 

analyses, and their help is acknowledged at appropriate 

places in the text. 

GEOLOGIC SETTING 

The Spor Mountain beryllium deposits are in the Basin 

and Range province in Juab County, Utah, on the east, 

south, and southwest sides of Spor Mountain (figs. l and 2). 

Al 
A2 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

I 

I 

I 

I 

I 

114" 

GREAT SALT LAKE 

DESERT 

r-------------M:~L:inc co- I 

I 

I 

I 

I 

I 

I 

I 

0 

I 

0 

I 

UTAH 

10 MILES 

I 

10 KILOMETERS 

WHITE 

VALLEY 

113" 

EXPLANATION 

'X' Be 

Mineral occurrence 

SEVIER DESERT 

FIGURE I. -Map showing location of Spor Mountain, other geographic features, and mineral occurrences mentioned in text. 

Spor Mountain itself is an oval-shaped block of northwestdipping Paleozoic rocks bounded on the east by a Basinand-Range-type fault. East and northeast of Spor Mountain, and across a narrow valley termed "The Dell," is the 

Thomas Range. The Thomas Range, which includes Topaz 

Mountain and Antelope Ridge and adjoins the Dugway 

Range to the north and the Drum Mountains to the south, 

consists almost entirely of Tertiary volcanic rocks. Fish 

Springs Flat is west of the Thomas Range and Spor Mountain; the south end of Dugway Valley is to the east. Fish 

Springs Flat and Dugway Valley are underlain mainly by 

Lake Bonneville beds and alluvium. 

The major rock units of concern in this report are, in 

ascending order, Paleozoic sedimentary rocks, the older 

volcanic rocks of Miocene(?) and older(?) age, and the 

younger volcanic rocks of Miocene(?) and Pliocene(?) age 

(fig. 2). The Paleozoic rocks, which crop out mainly on Spor 

Mountain and directly south of Topaz Mountain, are Early 

Ordovician to Late Devonian in age (Staatz and Carr, 1964, 

p. 31-53). The 3,950-foot-thick Paleozoic section at Spor 

Mountain consists mostly of dolomite, but it also contains 

some quartzite, shale, and limestone (Staatz, 1963, p. M9). 

Numerous faults of diverse orientation cut the Paleozoic 

rocks on Spor Mountain. The older volcanic rocks crop out 

mainly in The Dell and in valleys in the eastern part of the 

Thomas Range. They correspond to Shawe's ( 1972) "middle assemblage of igneous rocks" and contain labradorite 

rhyodacite, rhyodacite, porphyritic rhyolite, quartz-sanidine 

crystal tuff, vitric tuff, and intrusive breccia (Staatz, 1963, 

p. Ml2-M18; Staatz and Carr, 1964, p. 75-86). Some of 

these rocks have been reinterpreted as ash-flow tuffs 

(Shawe, 1972). Minor amounts of tuffaceous sandstone and 

conglomerate are interbedded with the older volcanic rocks 

in The Dell. The younger volcanic rocks (younger 

assemblage of Shawe, 1972) consist of five sequences, each 

consisting, in ascending order, of vitric tuff (termed "waterlaid" by Shawe, 1968, table 1), volcanic breccia, and topaz 

rhyolite (Staatz and Carr, 1964, p. 86-102). These sequences 

overlap one another, and the various sequences rest unconformably on the older volcanic rocks and on Paleozoic rocks 
113°15' 

T. 

12 

s. 

39° 

45' 

T. 

13 

s. 

HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH 

0 2 3 4 5 KILOMETERS 

EXPLANATION 

ALLUVIUM 

YOUNGER VOLCANIC ROCKS 

WATER-LAID TUFF BEDS.- Locally 

beryllium bearing 

~~~ ~NL:~~S~~EL~:!~~~:OCKS ~MARINE CARBONATE AND CLASTIC 

ROCKS 

--CONTACT 

-- FAULT. -Dotted where concealed 

- BERYLLIUM DEPOSIT. -Area underlain 

by beryllium-bearing tuff. Approximately 

located 

0 SAMPLE LOCALITY 

QUATERNARY 

TERTIARY 

PALEOZOIC 

A3 

FIGURE 2.- Geologic setting, beryllium deposits, and sample localities in 

Miocene(?) and Pliocene(?) water-laid tuff at Spor Mountain and the 

Thomas Range. Map slightly modified from Shawe (1968, fig. l ). 

Beryllium deposits shown on the map are North End (N), Tauras (T), 

Monitor (M), Roadside (Rd), Rainbow (Ra), Blue Chalk (B), Hogsback 

(H), and Claybank (C). 
A4 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

in some places. The younger volcanic rocks make up most 

of the Thomas Range and also crop out in parts of The Dell 

and southwest of Spor Mountain. The older volcanic rocks 

were deposited prior to formation of the Thomas caldera; 

the younger volcanic rocks postdate collapse of the caldera 

(Shawe, 1972). 

The beryllium deposits occur mostly in the water-laid 

vitric tuffs of the younger group, although at least one 

deposit (Claybank) is known to occur in vitric tuff in the 

older group, and traces of mineralization are present in the 

Paleozoic dolomites (Staatz, 1963, p. M25). The vitric tuff 

of the younger group exceeds 300 feet in thickness in only a. 

few places and may be entirely missing at some locations 

(Williams, 1963, p. 48; Staatz and Carr, 1964, p. 86-87). 

The tuff is termed "water-laid" because stratification and 

sorting of clasts characterize most outcrops. The tuff consists mostly of volcanic detritus or its alteration products, 

but at the base of Topaz Mountain it contains some 

limestone clasts, and southwest of Spor Mountain, abundant dolomite clasts that are commonly altered to calcite, 

silica minerals, fluorite, and clay. In the area of beryllium 

mineralization southwest of Spor Mountai'l, Williams 

(1963, p. 50-51) divided the tuff into three members. (I) The 

lower member comprises about two-thirds of the total 

thickness and is characterized by abundant dolomite clasts, 

(2) the middle member is present locally and is marked by 

welding, and (3) the upper member comprises one-third of 

the total thickness and is marked by much-altered carbonate clasts and by volcanic rock fragments that are more 

abundant than in the lower member. As will be shown later, 

the upper and lower members in part are characterized by 

differing degrees of alteration. 

Mineralization also may have been controlled by faults 

which cut the younger volcanic rocks in a few places, 

notably southwest of Spor Mountain and along the east side 

of The Dell. Southwest of Spor Mountain, southwesttrending faults can be projected from the Paleozoic rocks 

into the younger volcanic rocks (fig. 2), where they are 

believed to have controlled the orientation of tuff-filled 

paleovalleys and to have served also as conduits for 

mineralizing fluids (Williams, 1963, p. 4 7; Griffitts, 1964, p. 

73-74; Shawe, 1968, p. 1160). East of Spor Mountain, the 

Claybank and Hogsback prospects reveal zones of 

beryllium mineralization along a prominent north-trending 

fault (Staatz, 1963, p. M27). 

The beryllium deposits are closely related spatially, and 

probably genetically, to fluorite, uranium, and manganese 

deposits (fig. 1 ). All these deposits occur around the 

periphery of the Thomas caldera (Shawe, 1972, fig. 2). 

Fluorite in commercial quantities occurs in pipes and in a 

few veins on Spor Mountain (Thurston and others, 1954, p. 

24-45 ); uranium is present in some of the pipes (Staatz and 

Carr, 1964, p. 135-139). A uranium deposit of commercial 

significance (Yellow Chief) occurs in tuffaceous sandstone 

and conglomerate in The Dell (Staatz and Carr, 1964, p. 

148-157). Sizable manganese deposits are present in the 

Drum Mountains to the south (Crittenden and others, 

1961). 

PREVIOUS MINERALOGICAL AND GEOCHEMICAL 

WORK 

Most of the previous mineralogical and geochemical 

work has been limited in extent and has been directed 

toward identifying the various mineral phases in the tuff and 

beryllium ore. Staatz and Griffitts (1961 ), Staatz (1963), 

and Shawe (1968) described the mineralogy of both fresh 

and altered tuff; they noted that the altered tuff consists 

mainly of clay, silica minerals, fluorite, and feldspar. The 

occurrence of much of the beryllium as bertrandite 

(Be4Si20 7(0H) 2) or some closely related mineral was 

recognized by Staatz and Griffitts (1961, p. 947) .• They and 

Montoya, Havens, and Bridges (1962) found that bertrandite is concentrated in fluorite-silica nodules as well as being 

dispersed in the tuff. The only quantitative mineralogical· 

work is that of Montoya, Havens, and Bridges (1962), who 

reported abundant well-crystallized cristobalite, feldspar, 

and saponite in the altered tuff, and who independently discovered the presence of bertrandite. 

Early chemical studies showed the association ofF, U, 

and Mn with beryllium (Staatz and Griffitts, 1961 ). 

Fluorine was shown to accompany beryllium closely in three 

drill holes through the beryllium ore body (Griffitts and 

Rader, 1963). Unusually large amounts of lithium were 

found to be more widespread than beryllium in the altered 

tuff (Shawe and others, 1964; Shawe, 1968, p. 1156). At the 

Roadside deposit, Shawe (1968) found that MgO, F, B, Cr, 

and Tl are more abundant in beryllium-rich tuff than in 

beryllium-poor tuff. In samples from a section in the Rainbow deposit and in samples obtained from four widely 

scattered drill holes southwest of Spor Mountain, beryllium 

was found to be abundant in the upper part of the tuff and 

was accompanied by anomalous Pb, Zn, Cd, Mn, As, F, and 

U (Park, 1968, p. 30-41 ). 

ALTERATION OF THE WATER-LAID TUFF 

To acquire some idea of the total range of mineral and 

chemical composition of the tuff, we selected 14 samples 

from seven unmineralized localities in the Thomas Range 

(at Antelope Ridge, Topaz Mountain, and The Dell) and 16 

samples from eight mineralized localities representing the 

following beryllium prospects southwest of Spor Mountain: 

The Blue Chalk, an unnamed prospect south of the Blue 

Chalk, the Rainbow, the Roadside (three localities), the 

Taurus, and the North End. Samples from the Monitor 

prospect were also studied petrographically, but were not 

analyzed. Two samples were collected from each locality, 

one each from the lower and upper parts of the tuff bed or 

from opposite ends of the prospect. No attempt was made to 

sample beryllium deposits of ore grade at this stage in the 

study. A part of each sample was reserved for a reference 

hand specimen and thin section; the 30 samples were then 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A5 

placed in random order prior to mineralogical and chemical 

analysis. 

All 30 samples are from the younger volcanic group, but 

the unmineralized tuffs were selected from three different 

tuff units. The mineralized tuff southwest of Spar Mountain 

represents a fourth tuff unit and differs from the unmineralized tuff in that it contains dolomite clasts and their 

alteration products calcite and fluorite. Nevertheless, the 

matrix of the mineralized tuff probably was very similar to 

that of the unmineralized tuff, and the latter is the best 

available rock from which to infer the original mineralogy 

and trace-element content of the water-laid tuffs. 

PETROGRAPHY OF UNMINERALIZED TUFF 

Fourteen samples from three different unmineralized tuff 

units were studied in hand specimen, in thin section, and by 

whole-rock X-ray diffraction. Most of the tuff contains 1-14 

percent pyrogenic crystals, as much as 80 percent pumice 

fragments, 2-26 percent volcanic rock fragments, sparse 

chert, quartzite, and sandstone, and, locally, a small percentage of obsidian and limestone fragments in a vitric or 

zeolitic matrix. Pyrogenic crystals consist of 1-14 percent 

quartz, 0-5 percent sanidine, 0-2 percent plagioclase, 0-1 

percent biotite, and trace amounts of magnetite, ilmenite, 

topaz, sphene, and zircon. Quartz and sanidine occur 

mainly as euhedral grains, many of which have ·resorbed 

outlines and are broken. X-ray diffraction (method of 

Wright, 1968, fig. ~) indicates that the sanidine is cryptoperthitic and has a structure near that of low sanidine. 

Measurement of 2V suggests an overall composition near 

Or 70 • Measurement of albite twin extinction angles by the 

Michel-Levy method indicates that some plagioclase is 

oligoclase, but that a more calcic zoned plagioclase is also 

present. Biotite and plagioclase are commonly euhedral, but 

broken plagioclase crystals are common. Biotite is brown, 

pleochroic, and typically fresh. Volcanic rock fragments 

contain varying amounts of quartz, sanidine, zoned 

plagioclase (some of which is andesine), and lesser amounts 

of biotite, amphibole, and opaque minerals scattered about 

in a fine-grained, locally spherulitic matrix which, as shown 

by X-ray diffraction, consists of potassium feldspar and d..-

cristobalite. 

The unmineralized samples that were examined are vitric 

and zeolitic tuffs (fig .. 3A and B; table 1). Fresh vitric tuffs 

are present at the south end of The Dell, where they are 

composed mainly of glassy, vesicular pumice fragments as 

large as several inches across. Lesser quantities of volcanic 

rock fragments and obsidian, a few crystals, and a matrix of 

undeformed glass shards accompany the pumice. Volcanic 

rock fragments have a devitrified matrix, whereas accomTABLE I. - Comparison of the density, porosity, mineral composition, and chemical composition of unmineralized and mineralized water-laid 

tuff, Spor Mountain and the Thomas Range, Utah 

[All values are medians (50th percentiles); where the median falls below the limit of detection, or 

where large variation is present, the maximum value (in parentheses) is recorded also. Mineralogy 

is by X-ray diffraction. Analytical methods and analysts are as follows: Si02 and Al 20 3 determined by fusion X-ray fluorescence by J. S. Wahlberg and M. W. Solt; Fet03, MgO, CaO, Li, 

and Rb determined by atomic absorption by Johnnie Gardner and Violet Merritt; Cs determined 

by atomic absorption by Wayne Mountjoy; In and Tl determined by atomic absorption by A. i. Hubert; Na,O and K,O determined by flame photometer by Johnnie Gardner and Violet Merritt; 

Unmineralized tuff Mineralized tuff 

Vitric Zeoli tic Number of Argillic Feldspathic 

samples ____ _ 10 

Density (grams per cubic centimeter) and porosity (percent) 

Powder density 2.41 2.43 2.47 2.52 Bulk density ____ 1.47 1.73 1.85 1.82 Porosity ------ 39.0 28.8 24.7 27.8 

Mineral composition (weight percent) 

Montmorillonoid' _ ------- <I (5) 66 9 Mica' ------- ------- 2 I <I Clinoptilolite 14 65 <I (40) -------- Quartz _______ 4 95 5 9 o1.. -cristobalite-' -- 3 4 5 25 Potassium feldspar' _____ II 18 18 52 Calcite _______ I (12) <I I (23) --------

Dolomite ----- ------- ------- I (5) --------

Fluorite ------ <I I 3 4 Halite ------- <I ------- <I I Glass' ------- 66 <I <I --------

Chemical composition (weight percent) 

SiO, -------- 69 68 64 64 

AI,O-' -------- 10 10 II II 

Fe tO, -------- 1.06 1.06 1.28 1.30 MgO ------- .74 .52 1.98 1.42 CaO -------- UD (9.00) 2.05 2.46 (14.00) 2.90 Na,O ------- 2.78 1.99 2.40 2.39 K,O -------- 4.22 4.34 2.69 5.10 LOI' 5.8 8.1 8.6 5.5 co. --------- .50 (6.11) .30 .45 (9.91) .06 

'Dio.:tah~dral montmorillonoid clay; quantity determined by difference. 

'Pyrogenic biotit~ plus s~condary sericite. 

'lndude' 'orne opal. 

'Pyrogenic 'anid1n~ plus secondary pota,sium feld~par. 

LOI determined by drying at 900°C for I hour by R. L. Rahill; C02 determined gasometrically by I. C. Frost; Cl determined nephelometrically with mercuric nitrate by H. H. Lipp; F determined 

volumetrically by Johnnie Gardner; and eU determined by Beta scaler by E. J. Fennelly. All 

elements from B through Zr determined by direct reader spectrograph by R. G. Havens. Elements 

looked for but not found, and their detection limits, in parts per million, are Ag, 4; Au, 20; Bi, 20; 

Cd, 100; Co, 8; Ge, 100; Mo, 20; Pd, 10; Re, 70; Sb 300; and W, 500] 

Unmineralized tuff Mineralized tuff 

Vitric Zeoli tic Argillic Feldspathic 

Number of samples ____ _ 10 

Chemical composition (weight percent) - Continued 

H,O' ________ 4.60 7.51 7.36 5.53 

Cl --------- .22 (0.94) .07 (0.57) .45 (1.15) .31 (1.75) 

F ---------- .17 .II 1.22 1.82 

Chemical composition (parts per million) 

Cs ---------- 20 10 89 38 

In ---------- <.2 <.2 <.2 (1.5) <.2 (18.4) 

Li ---------- 75 55 230 315 

Rb 305 295 395 620 --------- Tl ---------- 2.5 2.4 3.5 (19.9) 6.1 (54.0) 

eU --------- 45 45 65 85 

B ---------- 34 <30 (39) 60 60 

Ba 160 205 120 70 ---------

Be --------- 7 7 105 14 (250) 

Cr --------- 9 8 5 <5 

Cu --------- 3 3 3 3 (43) 

Fe --------- 8,700 7,350 9,100 10,500 

Ga 28 27 44 50 

La -------- 53 25 70 76 Mn _________ 700 310 510 (3.400) 805 (8,000) 

Nb ----- 30 25 66 71 

Ni <7 (7) <7 <7 (7) <7 

Pb 34 30 37 42 

Sc <10 <10 <10 (14) <10 (30) 

Sn <20 (20) <20 34 52 

Sr 195 230 210 145 

Ti 585 565 350 315 

v 14 13 17 II 

y- 29 30' 75 120 

Zn <300 <300 <300 (340) 150 (1,600) 

Zr 67 69 73 78 

'()uantity dderrnin~d by diff~r~nce. 

'Tutal Fe'" F~,o,. 

'Lo" on ignition (LOI) at 900°C for I hour. 

"LOI minu' CO,. 
A6 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

A 

B 

c 

D 

fl 

QZ 

ksp 

ca 

30 

DEGREES 28 

fl 

QZ 

ksp 

fl 

cr 

ksp qz 

ksp ksp qz 

cl 

FIGURE 3. - Whole-rock X-ray diffractograms of water-laid tuff at Spor Mountain and the Thomas Range: 

A, Vitric tuff. B, Zeolitic tuff. C, Argillic tuff. D, Feldspathic tuff. Abbreviations: ca, calcite; Cl, clinoptilolite; cr, cristobalite; fl. fluorite; ksp, potassium feldspar; M, montmorillonoid; qz, quartz. 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A7 

panying obsidian, pumice, and shards are composed of fresh 

glass. Some vitric tuff samples also contain fine-grained 

calcite in the matrix and sparse microcrystalline to coarsely 

crystalline limestone fragments. The matrix calcite is concentrated generally in zones around pumice fragments. 

Zeolitic tuff is recognizable by whole-rock X-ray diffraction (fig. 3B) and is characterized in thin section by the 

almost complete destruction of glass and vesicular pumice. 

Relict pumice vesicles are common, however, and are outlined by clea r to light-brown , birefringent montmorillonoid 

clay flakes. Fuzzy brown material of very fine grain size is 

also common and is probably clay. Much of the matrix is 

composed of very small low-birefringence gra ins shown by 

X-ray diffraction to be a lmost entirely clinoptilolite. Identification as clinoptilolite was confirmed by heating samples 

(method of Mumpton, 1960); no destruction or change in 

structure was observed. Some zeolitic tuff contains abundant calcite, both as limestone pebbles and smaller clasts 

and as redistributed coarsely crystalline cement. Calcite is 

particularly abundant on the east side of Topaz Mountain, 

where some limestone pebbles were seen in outcrops. 

PETROGRAPHY OF MI NERALIZED TUFF 

Sixteen samples from the mineralized tuff southwest of 

Spor M ountain were studied in hand specimen, thin section, 

and by whole-rock X-ray diffraction; these observations 

were supplemented by examination of some additional 

samples. The mineralized tuff contains about 8-21 percent 

pyrogenic crystals accompanied by variable amounts of 

pumice, volcanic rock, and altered dolomite pebbles in a 

matrix which varies from brown to pink to cream. The 

pyrogenic crystals include 1-5 percent quartz, 2-11 percent 

sanidine, 0-2 percent plagioclase, and 0-1 percent biotite. 

Many grains are quite fresh and unaltered, with crystal form 

and composition similar to those of unmineralized tuff. 

Biotite in the mineralized tuff, in contrast to that in unmineralized tuff, is commonly black and appears oxidized. 

Pumice, volcanic rock, and dolomite fragments exhibit a 

wide variation in degree of alteration. Clay which swells 

upon weathering to produce popcornlike texture similar to 

bentonite is ubiquitous, and veinlets and void fillings of 

calcite, opal, and manganese oxides are common locally. 

Argillic and feldspathic alteration characterize the 

mineralized tuffs (fig. 3C and D; table 1). Much of the 

argillic alteration was incomplete, with vitric and zeolitic 

components commonly abundant. The feldspathic alteration is regarded as a more advanced stage, inasmuch as it 

was generally accompanied by complete destruction of unstable prealteration components. It must be stressed that 

these facies represent end members; all the samples studied 

were designated argi llic or feldspathic tuff, but some clearly 

show attributes of both . Assessment of the degree of alteration is best made by whole-rock X-ray diffraction, but 

examination of thin sections is often necessary to detect una ltered glass. 

Argillic tuff can be readily identified by X-ray diffraction 

(fig. 3C). It is characterized by as much as 80 percent montmorillonoid clay and 1-5 percent fluorite, by the presence of 

dolomite, calcite, and clinoptilolite in some samples, and by 

not more feldspar than the 20 percent or less which was 

probably present prior to mineralization (comparable to unmineralized tuff potassium feldspar content). The clay is a 

dioctahedral montmorillonoid similar to montmorillonite 

(Ross and Hendricks, 1945, table I); it swells when 

saturated with glycerol, collapses upon heating to 300°C, 

and has an 060 d-spacing of 1.495 A. A trioctahedral montmorillonoid clay (060= 1.515 A), which has a chemical composition similar to that of hectorite (Ames and others, 1958) 

but which also contains as much as 1 percent zinc, is also 

present locally but was not identified in the samples under 

discussion. Argillic tuff, as seen under the microscope, 

retains many fragments of fresh glassy pumice, volcanic 

rock, and carbonate rock. The glass is generally too sparse 

to be detected by X-ray diffraction . Clay, sericite, opal, and 

fine-grained (0.01-0.05 mm) anhedral fluorite are common 

and have replaced both matrix and pumice fragments. 

Euhedral halite was identified in a few samples and 

probably accounts for anomalous chlorine detected in some 

samples. Hand specimens show a wide range of dolomite 

clast alteration, from snow-white bleached calcite to complete replacement by quartz, opal, purple fluorite, and clay 

(fig. 4A , and B). Clay commonly rims the calcite fragments, 

but in the same sample other pebbles may be completely 

replaced by opal, fl uorite, and clay. The bleached calcite is 

ma inly microcrystalline, and locally it contains reflict invertebra te fossil fragments. Layered void fillings of clay, 

calcite spar, and opal (passing toward void center), more 

complex filli ngs of the same minera ls, and calcite veinlets 

indicate that redistribution of calcite was widespread . (fig. 

4C). Othe r feat ures are concentrations of fine-grai ned 

sparry calcite and sericite a round rock fragments (fig. 4D), 

voids filled with euhedral fluorite and anhedral 

microcrystalline quartz (fig. 4£), clay and fibrous 

chalcedony(?) filling pumice vesicles, and fluorite filling 

fresh glassy pumice vesicles (fig. 4F). Manganese oxides, in 

crosscutting veinlets, appear to be among the last minerals 

formed. 

Feldspathic tuff can also be readily identified by X-ray 

diffraction by the appearance of abundant potassium 

fe ldspa r (:::::20 percent) and, in some samples, 10-30 percent 

c:t-cristobalite (fig. 3D). Cristobalite is arbitrarily distinguished from opal in this report by the sharp X-ray diffraction peaks as shown in figure 3D; the peaks are very 

broad fo r opal, although gradations between sharp and 

broad are common. Similar gradational series have been 

produced by heating opal (Eitel, 1957, fig . 15; Franks and 

Swineford, 1959, p. 190-193). Montmorillonoid clay (as 

much as 40 percent) and fluorite (1-8 percent) a re abundant 

whereas glass, clinoptilolite, (lnd calcite usually are not, 
AS BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A9 

though remnant calcite may persist in altered clasts. Hand 

specimens appear to be intensely altered because former 

dolomite pebbles are replaced by quartz, opal, and purple 

fluorite or by clay, fluorite , and manganese oxides (fig. SA, 

and B), but X-ray study is necessary to verify feldspathic 

alteration. Ragged matrix-carrying feldspar overgrowths on 

sanidine are commonplace (fig. 5C and D), and clay, 

potassium feldspar, cristobalite, sericite(?), and fine-grained 

anhedral fluorite replace both relict pumice and matrix. In 

some samples, the potassium feldspar and cristobalite occur 

as spherulites and fibrous masses that have replaced pumice 

and matrix alike. These closely resemble the devitrified textures of potassium feldspar and cristobalite noted in 

volcanic rock fragments of unmineralized tuff and welded 

tuffs from other areas (Ross and Smith, 1961, p. 26-38). 

Relict pumice texture is still visible in some samples of the 

feldspathic tuff, and concentric rims of fibrous 

chalcedony(?) and clay enclose pumice vesicle fillings of 

microcrystalline quartz and sericite (fig. 5£). Sericite (identified by X-ray as well as optically) rims volcanic rock 

fragments (fig. SF) and opaque grains, and a similar 

micaceous mineral, probably also sericite, rims fine-grained 

fluorite in the matrix. Everywhere, manganese oxides in 

veinlets crosscutting matrix appear to be among the last 

minerals formed . 

CHEMICAL COMPOSITION 

Caution must be used in comparing the composition of 

mineralized tuff with that of unmineralized tuff, as shown in 

table I, because only the mineralized tuff originally contained abundant dolomite clasts. Consequently, the proportion of major components, especially Si02, is somewhat 

diluted by the presence of locally abundant CaO, MgO, 

C02, and F, all due to dolomite or its alteration products 

calcite and fluorite. The most striking chemical differences 

appear in the trace-element content, however, and these are 

not due to dilution because the mineralized tuffs are considerably enriched in many trace elements. The elements Cs, 

Li, Rb, Tl, eU, B, Be, Ga, La, Mn, Nb, Sc, Sn, Y, and Zn 

show a concentration of about twofold or more in 

mineralized tuff over unmineralized tuff; Ba, Cr, and Ti are 

less ab1:1ndant. 

FIGURE 4. - Features of argillic alteration in water-laid tuff at Spor 

Mountain. A, Specimen showing angular fragments bleached to whitt> 

calcite (ca) and scattered pumice and volcanic rock fragments (vol, 

Matrix is mainly glass and montmorillonoid clay. B, Specimen showing 

nodules (nod) with opal-fluorite rind and dioctahedral montmorillonoid 

clay interiors crosscut by pyrolusite (py). Unaltered volcanic cobble (vol) 

also present. Matrix is mainly clinoptilolite. C, Photomicrograph showing montmorillonoid clay rinds (M) on bleached calcite clasts (ca) accompanied by void fillings of opal (op), montmorillonoid clay (M\ and 

sparry calcite (sp). D, Photomicrograph showing volcanic rock fra,,ment 

(vol) rimmed by sericite (s) and fine-grained sparry calcite (sp). E, Void 

fillings of euhedral fluorite (fl) and anhedral microcrystalline quartz (qz). 

F, Fine-grained fluorite (fl) filling glassy pumice vesicles. A and C are 

from Monitor pit; B is from Roadside pit; D, E, and Fare from small pit 

south of Blue Chalk prospect. C, D, and £ under crossed pol~rs : Funder 

plain light. 

Argillic and feldspathic tuffs differ in important respects 

and reflect the mineralogical differences which formed the 

basis of their classification. As alteration progressed from 

the argillic to the feldspathic stage, C02 was removed and F 

added as dolomite and calcite were converted to fluorite, 

and K20 shows a large increase from less than 3 to more 

than 5 percent as glass, zeolite, and clay were converted to 

potassium feldspar. Also noteworthy is the decrease in H20 

content of feldspathic tuff. 

Further comparison of the chemistry of the argillic and 

feldspathic tuffs shows that additional concentration of 

many trace elements occurred as alteration proceeded 

toward complete feldspathization. Li, Rb, Tl, eU, Mn, Sn, 

Y, Zn, and perhaps Ga, La, and Nb continued to be concentrated, although the differences are not as marked as those 

between unmineralized and mineralized tuff. The trace 

elements Cs, Ba, Sr, and perhaps Be, Cr, and Ti declined in 

abundance as alteration proceeded. Beryllium abundance 

appears to be extremely variable; analyses of individual 

samples show that it may be concentrated in either the 

argillic or the feldspathic stages of alteration. 

ALTERATION PATTERNS AT THE 

ROADSIDE ORE DEPOSIT 

In order to examine possible alteration patterns in 

mineralized tuff, drill cuttings from holes I and 2 at the 

Roadside deposit (Griffitts and Rader, 1963, fig . I) were 

studied by X,ray diffraction . No thin-section observations 

were possible owing to the finely ground condition of the 

cuttings. Griffitts and Rader showed the extent of beryllium 

ore cut by the drill holes and demonstrated the close 

association of beryllium with fluorine in the upper part of 

the tuff. Alteration patterns, details of the X-ray 

mineralogy, and the beryllium-abundance data of Griffitts 

and Rader are presented in figure 6. 

Both mineralogy and beryllium content are to a large extent stratigraphically controlled (fig. 6A and B). Primary 

stratigraphic features are evident in the ratio of volcanic to 

dolomite detritus present (fig. 6C, and D). Both holes reveal 

that the original tuff contained an upper, dolomite-poor interval of about 50 feet in thickness and a lower, dolomiterich interval comprising the remainder. Within the 

dolomite-rich interval, several horizons of maximum 

dolomite clast content are clearly discernible and correlative 

between holes. 

The ensuing alteration of the tuff was also concordant to 

the stratigraphy. Intensity of alteration of the dolomite 

clasts progresses upward in the tuff, passing from unaltered 

dolomite to calcite to fluorite. Small amounts of fluorite 

also occur near the bottom of the tuff. Alteration of the 

volcanic fraction was most intense in the upper 60 feet and 

the lower 30 feet of the tuff, where potassium feldspar is 

most abundant. Abundant lithium-bearing trioctahedral 

montmorillonoid clay (060= 1.515 A) coincides with abundant calcite over an interval exceeding 60 feet in thickness 
AlO BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

Fi GU RE 5. - Features of feldspathic alteration in water-laid tuff at Spor 

Mountain . A, Specimen with light-pink nodules (nod) composed ofdioctahedral montmorillonoid clay, opal, and fluorite in dark matrix of clay, 

cristobalite, quartz, and potassium feldspar. Light nodules on left contain as much as 3,000 ppm (parts per million) Be. B, Specimen with light-

~olored nodules (nod) composed of dioctahedral montmorillonoid clay, 

opal, and fluorite in light-colored matrix of same minerals plus quartz, 

abundant potassium feldspar, and mica. Dark nodules are chalcophanite 

(ch). Both light and dark nodules contain as much as 5,000 ppm Be. C 

and D, Photomicrographs of pyrogenic sanidine crystals (san) with 

potassium feldspar overgrowths enclosing remnants of tuff matrix. E, 

Photomicrograph of relict pumice vesicles with concentric rims of fibrous 

chalcedony(?) (ch) and clay (M) and fillings of microcrystalline quartz (qz) 

md sericite. F, Photomicrograph of volcanic rock fragment (vol) rimmed 

.Jy clay (M) and sericite (S). Dark band in middle of sericite is unidentified 

opaque mineral (op). A - D and Fare from the Roadside pit; E is from the 

Blue Chalk prospect. All photomicrographs under crossed or partly 

crossed polars. 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH All 

indicating that the clay formed in response to dedolomitization of the clasts. Quartz shows no concentration or trend, 

but cristobalite is clearly most abundant in the lower half 

and in the extreme upper 20 feet of the tuff, where it roughly 

parallels but does not coincide exactly with the distribution 

of secondary potassium feldspar. Remnant clinoptilolite is 

present locally. 

Beryllium is most closely associated with the distribution 

of fluorite (fig. 6A and B), as demonstrated by Griffitts and 

Rader ( 1963). Beryllium is mainly concentrated in the upper 

Clasts mainly tl 

fluorite _ ~ 

Clasts '; u 

mainly +"' Q) 

calcite ~ .~ ~ E ~ 0 

~0 

"'" 100 

~:E 

B 

Hole 1 

=-- - - -·---'-'"'Percent > 20 Percent 

Potassium feldspar 

Kaolinite Trioct.:hedral 

montmorillinoid 

c 

100 

0 

80 

20 

HOLE 1 

D 

100 

0 

Upper 

flu o rite-bearing zone 

- - --

Middl e fl uoritebearing zo ne 

---

Ca lcit e-rich zone 

Volcanic detritus 

and alteratio n products 

Dolomite clast s 

and alteration products 

EXPLANATION 

T, Trioctahedral montmorillinoid clay 

K, 7-A clay- probably kaolinite 

Possible correlation based 

on dolomite clast alteration 

Hole 2 . Hole 3 

Beryllium, in parts per million 

80 

20 

HOLE 2 

PERCENT 

60 40 

40 60 

Volcanic detritus 

and alteration products 

20 

80 

60 

Dolomite clasts 

and alteration products 

FIGURE 6. - Alteration patterns in the water-laid tuff at the Roadside 

beryllium deposit. A , Summary of the distribution of alteration 

minerals. 8 , Distribution of beryllium from Griffitts and Rader (1963 , 

fig. I). C, Profile of mineralogy cut by drill hole I. D, Profile of mineralogy 

cut by drill hole 2. Mineralogy determined by X-ray diffraction . 
Al2 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

part of a zone of feldspathic alteration and is directly above 

most of the lithiuin-bearing trioctahedral montmorillonoid 

clay and calcite zone. The lower zone of feldspathic alteration, which does not show extensive alteration of dolomite 

clasts, contains no large concentration of beryllium. 

Contrary to the relationships shown by other minerals, a 

7-A clay mineral thought to be kaolinite does not show a 

concordant distribution. The kaolinite zone clearly transects , 

the calcite-dolomite boundary and is more nearly parallel to 

the topographic surface than to the zones of other minerals. 

It evidently reflects a later stage in alteration, possibly 

related to supergene processes. 

ALTERATION NODULES IN TUFF 

CALCITE-SILICA-FLUORITE NODULES 

Subspherical nodules as much as 1 foot in diameter are 

commonplace and are characteristic of the altered tuff at 

the Roadside and other beryllium deposits at Spor Mountain . Figure 7 illustrates a sequence of typical nodules 

representing progressive stages of alteration, with details of 

mineralogy and chemistry. Some nodules exhibit complex 

alteration patterns, but many consist of concentric zones of 

calcite, microcrystalline quartz (chalcedony), opal, and 

fluorite, passing from core to rim. All the minerals are fine 

grained, and the fluorite ranges from purple to colorless. 

Numerous small nodules that consist only of alternating 

opal- and fluorite-rich zones are inferred to represent more 

advanced alteration. Relict bedding, invertebrate fossil 

fragments, and carbonate rock textures are seen in thin sections of the calcite cores of some nodules, confirming the 

earlier statement that the nodules are mainly the result of 

replacement of the original dolomite clasts. Twelve nodules 

from the Roadside beryllium deposit were selected for 

detailed mineralogical and chemical study in order to assess 

a lteration patterns independently. The nodules were sawed 

into slabs, and 89 small samples of 1-2 grams each were cut 

from the various layers in the nodules. Each sample was 

studied by X-ray diffraction and ana lyzed by semiquantitative spectrographic methods. 

The mineralogy and chemical composition of the Roadside nodules are summarized in table 2. The 89 sample 

analyses were grouped according to major mineralogy; 

those having 10 percent or more calcite were compiled into 

one group, those having 10 percent or more quartz were 

compiled into another group, and so on. By necessity, this 

resulted in some samples being included in more than one 

group, but for the most part the groups adequately represent 

the four mineral zones of calcite, quartz, opal, and fluorite, 

passing from core to rim in the idealized nodule. Median 

values (50th percentiles) were then computed for each element in each group. The median mineral content for each 

group as tabulated in table 2 reveals that the calcite- quartzrich samples are nearly pure, containing only I 0-20 percent 

other minerals. The opal and fluorite zones are less effecFIGURE 7 (facing page). - Calcite-silica-fluorite nodules from the 

Roadside beryllium deposit, selected to show progressive stages of 

alteration. Mineral zones in nodules are labeled as follows: ca, calcite; 

qz, quartz; op, opal; fl, fluorite; op-fl, opal with lesser fluorite; fl-op, 

fluorite with lesser opal; op-qz-fl, opal, quartz, and fluorite, in decreasing 

order of abundance. A, Nodule with calcite core (200 ppm Be), dark 

quartz zone (300 ppm Be), and outer light opal zone (as much as 2,000 

ppm Be, 200 ppm Li) with minor fluorite. B, Nodule with white calcite 

core (as much as 500 ppm Be, 700 ppm Li, and 2,000 ppm Zn), gray 

quartz zone (as much as 500 ppm Be, 50 ppm Li, and 700 ppm Zn), and 

outer white zone of opal with as much as 15 percent fluorite (7,000 ppm 

Be, 1,000 ppm Li, and 10,000 ppm Zn). Nodule is crosscut by spongespicule-bearing chert concretion with manganese oxide fracture fillings 

containing as much as 70 ppm Be and 70 ppm Ag. C, Nodule with large 

gray quartz core ( 1,000 ppm Be) and outer light zone of opal with as 

much as 15 percent fluorite at the margin (as much as 5,000 ppm Be and 

150 ppm Li). Dark spots are manganese oxides. D, Nodule with dark 

core of opal, quartz, and fluorite (I 0,000 ppm Be), brown and light 

patchy zone of opal and fluorite (as much as 10,000 ppm Be, 1,000 ppm 

U, and I ,000 ppm Mn), and outer light-purple rim of opal and fluorite 

(20,000 ppm Be, 150 ppm Li, and 1,500 ppm Mn locally).£, Left nodule 

with light- purple core of .fluorite and opal (15,000 ppm Be, 200 ppm Li, 

and 500 ppm U), a dark-purple zone of nearly pure fluorite ( 10,000 ppm 

Be and 1,500 ppm U), and an opal-and-fluorite rim (10,000 ppm Be, 200 

ppm Li, and 500 ppm U). Right nodule with dark-purple core of nearly 

pure fluorite (300 ppm Be and 700 ppm U), light-purple zone of fluorite 

and opal (10,000-20,000 ppm Be and 1,000-1,500 ppm U), and outer 

dark-purple zone of nearly pure fluorite (10,000 ppm Be and 2,000 ppm 

U). F, Fluorite and opal nodule with outer lavender zone containing as 

much as 20,000 ppm Be and 200 ppm Li. Light spots in lower half are 

spherulitic silica; dark patches in upper half are manganese oxides (all 

contain more than 1,000 ppm Be). 

tively separated because of the finely intergrown nature of 

the two minerals as can be seen in thin sections. 

The fluorite- and opal-rich zones, as shown by the 

chemical data in table 2, contain at least twice as much of 

the minor elements Na, Ti, As, B, Be, La, Li, Pb, Sr, U, Y, 

Yb, and Zn as do the calcite-rich zones. The calcite-rich 

zones, on the other hand, contain more Ba, Cd, Cu, and Mn 

than do the fluorite- and opal-rich zones. The quartz zones 

are generally the most impoverished in trace-element content, with the exception of Mo and Cu. Perhaps the most 

noteworthy concentrations of elements are those of Be, Li, 

U, and, locally, Zn, in the opal and fluorite zones and of Mn 

in the calcite zones. 

Six samples containing more than I percent Be were 

selected for identification of beryllium minerals. All the 

samples were mixtures of opal and fluorite, but in each sample the fluorite content ranged from 50 to nearly 100 percent. The samples were boiled in concentrated, acidified 

AICI 3 for about 15 minutes to remove the fluorite (Stevens 

and others, 1962). The residue was washed repeatedly, 

dried, and X-rayed. All the residues contained opal and bertrandite. Attempts to identify other beryllium minerals 

which might he present in lesser amounts than bertrandite 

were unsuccessful. 

FLUORITE-CLA ¥-MANGANESE OXIDE NODULES 

Fluorite-clay-manganese oxide nodules are locally abundant in the zone of feldspathic alteration. Twelve specimens 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A13 
Al4 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

TABLE 2.- Distribution of elements with respect to gross mineralogy in 

12 calcite-silica-fluorite nodules from the Roadside beryllium deposit 

lThc four mineralogic groups correspond roughly to the four zones from core to rim of some 

nod ules. All val ue s arc medians (50th percentiles) expressed as weight percent or parts per 

million; where the median fell below the limit of detection , the maximum va lue.: (in parentheses) is recorded also. Bulk density calculated from mineral composition assum ing zero porosity. Minerul 

..:om position .. determined by X-ray diffract ion. Chemical composition determ ined by six-step 

semiquantitative spectrographic ana lysis by L. A. Bradley. Elements looked for but not found, 

and their detection limits, a re: Au, 20 ppm; II f. 100 ppm; In, 10 ppm; P. 0.2 percent; Pd. I ppm; 

Pt. 30 ppm; Re, 30 ppm; Sb, 150 ppm; Sc, 5 ppm; Ta, 200 ppm; Te, 2,000 ppm; and Th. 200 ppm] 

Zone 

(from 

core to 

rim of 

idealized 

nodule) - Major 

minentl 

(2: 10 

percent 

present) Calcite Quarll Opal Fluorite 

Number 

of 

samples _ 22 29 47 33 

Bulk 

density 

(gj cc; 

calculated 2.70 2.60 2.37 2.64 

M ineral composition (in percent) 

Calcite 90 10 <I 0 Quartz ___ 10 RO 10 <I Opal ____ < I 10 70 50 Fluorite < I < I 20 50 

Chemical composilion (weight percent) 

Si ----- 6 > 10 > 10 10 

AI - .29 .34 .39 .4 1 

Fe . 10 .06 .07 .06 Mg _____ .30 . 10 .27 .25 Ca __ > 10 1.62 > 10 > IO Na _____ .06 .05 .12 .13 K ____ __ < .7 <.7 <.7 (0.7) <.7 (0.7) 

Ti .002 .002 .004 .004 

Chemical composition (parts per million ) 

Ag <0.5 ( 1.5) < 0.5 (70) < 0. 5 (3) < 0.5 (7) 

As ----- < 1.000 < 1.000 < 1,000 (3 ,000) < 1.000 (3.000) 

B ------ <20 37 44 54 

Ba ----- 38 10 I I 12 

Be ----- 162 359 5.843 10.436 

Bi < 10 < 10 < 10 (20) < 10 (20) Cd _____ 28 <20 (70) < 20 (20) < 20 Cc _____ < 150 < 150 < 150 (300) < 150 (300) Co _____ <3 <3 < 3 (10) < 3 (10) Cr 2 I 2 I Cu _____ 7 9 4 3 

Ga ----- < 5 <5 <5 (10) <5 ( 10) Ge _____ < 10 < 10 (15) < 10 (15) <1 0 La _____ <30 <30 <30 (300) 57 Li <50 (700) <50 ( 150) 90 87 Mn _____ 1.000 1,100 88 60 Mo _____ 6 12 3 3 ( 10) Nb < 10 (20) 9 12 12 Ni <5 (7) <5 ( 10) <5 (7) <5 (5) Pb _____ 14 II 17 36 Sn < 10 < 10 (15) < 10 (30) < 10 (30) Sr 68 17 67 117 Tl <50 (300) <50 (300) <50 (300) <50 ( 150) 

u <500 < 500 <500 (2,000) 536 v <7 (10) <7 <7 (30) <7 (30) w < 100 < 100 (150) < 100 ( 150) < 100 

y ------ 13 II 37 75 Yb _____ 2 2 4 6 Zn <200 (2,000) <200 (700) <200 (10,000) <200 (10.000) Zr ----- < 10 (15) < 10 ( 15) 9 9 

of nodule-bearing tuff from the Roadside and Rainbow 

deposits were selected for X-ray diffraction and spectrographic analysis. From the 12 specimens, 74 samples of 

1-2 grams each were handpicked to represent various 

mineral zones observed in the nodules. Fluorite, clay, and 

manganese oxides were found to compose the major mineral 

components of the zones, but the zones themselves do not 

indicate a single alteration sequence. Thus some nodules 

have fluorite cores and clay rinds, others have fluorite cores 

enclosed by a clay zone and a manganese oxide rind, and 

still others have clay-fluorite cores and fluorite-potassium 

feldspar-clay rinds (fig. 8). The manganese oxides in every 

sample examined appear to have been deposited as rinds or 

fracture fillings within the nodules; hence they were the last 

formed. Manganese oxide minerals identified by X-ray diffraction and spectrographic analysis are pyrolusite, cryptomelane, chalcophanite, and todorokite(?). 

The most significant geochemical feature of the fluoriteclay-manganese oxide nodules is the high concentration of 

some elements, notably Be, Li, Mg, Mn, and Zn (fig. 8). 

Many of the cores contain dioctahedral montmorillonoid 

clay, but some also contain trioctahedral montmorillonoid 

clay with abundant Mg, Li, and Zn (fig. 8A). Beryllium, 

although it is abundant in some trioctahedral 

montmorillonoid-clay-bearing nodules, is not associated 

with all the clays, as shown by analysis of the large nodule in 

figure 8A. Generally the distribution of beryllium is not 

governed by zoning in the fluorite-clay-manganese oxide 

nodules; if it is abundant in the tuff matrix, it is abundant in 

most of the zones. Many of the manganese oxide rinds are 

chalcophanite and contain abundant zinc. Uranium (~500 

ppm) was found in only two specimens (fig. 8D), where it is 

mainly concentrated in the clay-fluorite rinds of nodules. 

DISCUSSION AND CONCLUSIONS 

ALTERATION PROCESSES 

Evaluation of chemical changes involved in the alteration 

of rock at Spor Mountain provides keys to understanding 

the chemical reactions that took place. Although gains and 

losses of components can be surmised from the data in 

tables 1 and 2, it is more realistic to recalculate weightpercent data into gram-atoms or gram equivalents per unit 

volume (Hemley and Jones, 1964). Gram equivalents for oxide components were calculated by the formula : 

g equiv 

1,000 cc rock 

wt ~~ce nt X bulk density in gjcc X I ,000 cc 

-----::-::c=:-::::o:-::-:-:::----- X gm""0

1

1

°e.:"a'rx va lence: g molecula r wt ~ 

oxide 

and for elements, by the formula 

g equiv 

I ,000 cc rock 

wt ~~cent X bulk den sity in gf cc X 1,000 cc 

g atomi c wt X va lence. 

This procedure is advantageous in that it reduces gain-andloss data to atomic proportions useful for inferring chemical 

reactions of alteration. Conversion of weight-percent 

analyses into gram equivalents per unit volume presumes 

that alteration proceeded without appreciable change in 

rock volume; this assumption is probably justified for the 

water-laid tuffs and carbonate clasts at Spor Mountain 

because of abundant undeformed relict structures in altered 

rock. Bulk- and powder-density data show that alteration of 

vitric tuff to argillic and feldspathic tuff is accompanied by 

appreciable decrease in porosity (table 1 ); that is, while 

volume remained constant, the mass of 1,000 cc of rock increased by filling of pore space. Thin-section study showed 

that porosity of the carbonate clasts remained low 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A l5 

throughout alteration. Gains and losses during clast alteration were approximated using bulk density computed from 

mineral composition and assuming zero porosity. Gains and 

losses of maj,or components in the clasts were calculated 

from mineralogy because the maximum limit of detection 

FIGU RE 8. - Fluorite-clay-manganese oxide nodules from the Roadside 

and Rainbow beryllium deposits. All samples shown are from the zone of 

feldspathi c alteration. Minera l zones in nodul es are labeled as follows: fl , 

fluorite; T, trioctahedral montmorillonoid clay; D, dioctahedral montmorillonoid clay; td, both clays; ch, chalcophanite . A , Nodules with 

white fluorite cores, trioctahedral montmorillonoid clay zone, and 

manganese oxides (chalcophanite and todorokite(?)) rind . Manganese 

oxides also fill fractures in interior of nodules. Trioctahedral montmorillonoid clay contains 10 percent Mg, 3,000 ppm Li, 5,000 ppm Zn, 

and only 10-30 ppm Be. B, Nodules with purple fluorite core and thin 

rind of both dioctahedral and trioctahedral montmorillonoid clay. Clay 

by spectrographic analysis was often exceeded. The 

resulting data on major chemical gains and losses during 

alteration are summarized in table 3. 

Determination of gains and losses accompanying alteration of vitric tuff to mineralized tuff (argillic or feldspathic) 

is complicated by differing original compositions; the 

mineralized tuff originally contained dolomite clasts not 

present in the unmineralized vitric tuff studied (table l ). The 

Mg + 2 , Ca + l , and C03 - 2 in dolomite clasts should be ignored, and these also cause an apparent dilution of other 

rinds contain as much as 3 percent Mg, 1,500 ppm Li, and 1,000 ppm Zn; 

beryllium can exceed 5,000 ppm in both cores and rinds. C, Nodules with 

fluorite and mixed fluorite-clay cores (dioctahedral montmorillonoid clay) 

and thin chalcophanite rinds. Cores have more than 5,000 ppm Be, 

200-700 ppm Li, and 2,000 ppm Zn. D, Clay-rich nodules with purple 

rinds. Cores contain dioctahedral montmorillonoid clay and lesser fluorite; 

some also contain trioctahedral montmorillonoid clay and abundant 

sericite. Purple rinds contain abundant fluorite, potassium feldspar, and 

clay and minor opal, quartz, and sericite. Rinds contain as much as 2,000 

ppm U but only 50-150 ppm Be. 

components. Small apparent losses may have been due to 

dilution, and any gain registered by other components 

should be considered a minimum value. Chemical aspects of 

more advanced alteration may be evaluated independently 

by comparing the argillic with the feldspathic tuffs because 

these tuffs probably shared a similar original composition. 
AH5 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

TABLE 3. - Major chemical gains and losses per 1.000 cc of rock as shown by alteration of water-/aid tuff and carbonate clasts in 

tuffs, Spor Mountain and the Thomas Range, Utah 

[Carbonate clasts in tuff: calculations for Si, Cat 1, C0 , and F - and sum of anions based on mineralogy; forK+, no gain or loss was 

calculable because element abundance was generally below the limit of detection; n.d., no data available; CJ - was presumed to be 

minor when calculating sum of anions] 

Sum of 

alkalis + alkaline Moles H,O co,-2 Sum of Alteration Si AI Ti Fe+3 Mn +2 Mg+2 ca+2 Be +2 Na+ K+ Li + earths (maximum ) Cl - F - anions 

Gram-atoms Gram equi va knts Gram eq uivalents 

Water-laid tuff 

Vitric to argill ic ________ 2.93 1.13 - 0.01 0.30 0 '1.28 '0.67 0.04 0.12 - 0.26 0.05 '1.90 3.85 0.05 0.15 1.03 1.23 Argillic to fddspathic _____ - .43 - .09 0 0 .02 - .54 .25 -.03 -.04 .91 .02 .57 - 2.01 -.33 - .08 .55 .14 

Carbonate clasts in tuff 

Ca kitc to quartz ------- 34.01 0.08 0 - 0.08 - 0.09 - 0.46 -43.3g 

Quartz to opal -9.72 .03 0 .01 0 . 32 6.74 . Opal to nuoritc -------- - 9.02 .II 0 - 01 0 .01 21.20 Calt.:itc to lluorite ------- 15.27 .22 0 - .og - .09 - .13 - 15.44 

'Va lue due mainly to different original composition. 

The first stage of the mineralizing event is believed to 

have been argillization of vitric tuff to form tuff containing 

dioctahedral montmorillonoid clay; this entailed mainly addition of Si, AI, Fe '

3

, Hp, and F - and loss of ~ . (The 

valence of Fe is assumed to be + 3; Fe d may have participated.) Lesser amounts of Be +2, Li +,and Cl- also were 

added. Although meaningful gain-loss calculations are not 

possible for Mg + Z, Ca + 2, and C03 -z, argillization took 

place in an environment rich in these ions. Hydrolysis of 

silicates (or, in this case, rhyolitic glass) to form montmorillonoid clay is favored by an environment with an adequate supply of Mg • 2, Ca • 2, Fe ;z, and Na ' relative to 

H + , high Si relative to AI, and low K " relative to other 

alkali and alkaline earth cations (Keller, 1970, p. 800). 

Inspection of the gain-loss data in table 3 for transformation 

of vitric to argillic tuff shows that nearly all of these conditions were present. A possible reaction is: 

rhyolite glass + V2 Mg+2 + 3 H20 

___.. 2 dioctahedral montmorillonoid clay+9 opal+ K+. (I) 

The equation can be balanced only approximately, but it 

takes into account the actual composition of the rhyolite 

glass as indicated by the vitric tuff. Hydrolysis of glass and 

leaching of K+ were probably important processes. Only a 

slight increase in cristobalite and opal was noted in the 

argillic tuff; some of the silica probably remained in solution 

and was precipitated later in the feldspathic tuff, or it 

replaced nearby carbonate clasts. The proposed reaction 

also requires addition of Mg +2

, perhaps derived from 

alteration of dolomite clasts. Calcium ion and Na+ derived 

from the glass may have been held as exchangeable cations 

in the clay lattice. 

The presence of calcite and lithium-bearing trioctahedral 

montmorillonoid clay correlates with the absence of 

dolomite in the drill samples at the Roadside pit (fig. 6); this 

observation indicates that another argillization reaction 

may also have occurred. The distribution of calcite and 

0.10 - 003 0 - 43.77 n.d. - 43.36 n.d. 0 - 43.36 2.87 . 13 . 01 10.07 n.d . - 4.73 n.d . 11.44 6.7 1 3.05 . 05 0 24.31 n.d. - .47 n.d . 2!,68 21.21 6 02 .16 . 0 1 - 9.3g n.d . - 48.56 n.d. 33. 12 - 15.44 

trioctahedral montmorillonoid clay overlaps into the 

feldspathic zone, indicating that the reaction proceeded also 

during feldspathization. The reactions must have involved 

the leaching of dolomite to form calcite: 

dolomite + H 20___...calcite + Mg + 2 

+ HC03

- + OH - . (2) 

Reaction 2 released Mg + 2 and increased the alkalinity of 

the solutions. Lithium, supplied by solution, and Mg + 2 

may then have displaced AI +J in dioctahedral montmorillonoid clay to produce a lithium-bearing trioctahedral 

montmorillonoid clay similar to hectorite. Disposal of AI +3 

from the latter reaction is an unsolved problem; gibbsite and 

other aluminous minerals were not found, and it is doubtful 

if appreciable quantities of these minerals could have gone 

undetected by X-ray methods. A similar reaction involving 

addition of Mg + 2 to dioctahedral montmorillonite to 

produce saponite and other products was studied in the 

laboratory by Ames and Sand ( 1958). They showed that, 

with optimum substitution in the clay lattice, dioctahedra:l 

montmorillonite is converted to saponite at 480°C, and that 

saponite and hectorite are stable to as much as 750°C. The 

temperature-stability limit of both clays is much lower when 

optimum substitution is not achieved. Probably, therefore, 

conversion of dioctahedral to trioctahedral montmorillonoid clay was driven by an increase in temperature. 

Advanced alteration of argillic to feldspathic tuff was accompanied mainly by addition of K+, Ca +2, and F - and by 

loss of Si, Mg ' 2

, C03 - Z, and appreciable H 20. The following approximate equations suggest the principal reactions 

during feldspathization: 

2 dioctahedral montmorillonoid clay + K+ 

_. K-mica (sericite)+ 5 Si02 + 2 OH - + Mg+z + Na+ 

(exchangeable cations) (3) 

K-mica + 6Si02 + 2K • + 20H -

~3 K-feldspar + 2H20 {4) 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A17 

2 dioctahedral montmorillonoid clay + 3K+ + Si02 

___. K-feldspar + 2H20 + Mg+2 + Na + 

(exchangeable cations) (5) 

Evidence for reaction 3 is clearly visible in figures 4LJ and 

5F, where sericite is seen to have formed on clay-rich clasts. 

This reaction probably began during argillic alteration. 

Reaction 5 is merely the sum of 3 and 4, and reveals that the 

net effect to be expected from feldspathization of argillic 

tuff is the considerable addition of K+ and some Si accompanied by loss of H20, Mg +- 2

, and exchangeable cations 

(Na+, Mg+2, Ca 2) as these become available for removal in 

solutions. Except for the relatively small loss recorded for 

Si, the gain-loss data for argillic to feldspathic tuff correspond remarkably well to the effects of reaction 5. Although 

some of the K involved in feldspathization may have been 

derived from argillic alteration of the original glass, the 

overall gain inK+ suggests that some was added from an external source. Study of reaction 4 by Hemley (1959) showed 

that, at 300°C and above, formation of kaolinite, potassium 

mica, and potassium feldspar is favored by progressively 

higher K+ /H+ ratios as well as by higher temperatures. 

Potassium feldspar is stable at lower (25°C) temperatures 

but only at extremely high K+ /H ... ratios of approximately 

10'-1010 (Garrels and Howard, 1959). Although reactions 3, 

4, and 5 were probably favored by increased temperatures at 

Spar Mountain, rising pH, probably caused by release and 

hydrolysis of co3 -2 as the solutions altered carbonate 

clasts, was probably the mechanism which triggered 

feldspathization. 

Study of the carbonate clasts is particularly informative 

regarding the solubility of calcite, silica, and fluorite in the 

mineralizing solutions. The interpretation of alteration of 

carbonate clasts (table 3) covers only the calcite-silicafluorite stages because those clasts studied did not retain 

any dolomite. No information is now available on the 

minor-element composition of the original dolomite clasts. 

The gain-loss data show the almost total progressive 

transformation from high CaC03 to Si0 2 to CaF2 as computed from mineralogy. Alteration of [the calcite cores of] 

the clasts to fluorite contributed to the solutions major 

quantities of Ca +2, Mg +2

, and C03 - 2 and minor, but 

significant, quantities of Fe +J and Mn + 2 while extracting 

from solution major amounts of Si, BeT 2

, and F- as well as 

minor amounts of Al, N a+- , Li + , and, of course, the many 

other trace elements listed in table 2. Judged from the 

associated clay mineralogy, solution of calcite was probably 

accomplished by neutral or slightly alkaline solutions which 

became more alkaline as carbonate ions released into ~olution were hydrolyzed to produce bicarbonate and OHAlthough calcite is more readily dissolved under acid conditions, Ames ( 1961) has shown that fluorite can replace 

limestone under alkaline conditions. The alteration sequence in the nodules indicates that Si02 saturation with 

respect to quartz occurred before general saturation with 

respect to CaF 2, and that as alteration progressed, the environment became supersaturated with respect to quartz 

(precipitation of opal). Temperature and pressure, as shown 

by experimental studies, are major influences on silica 

solubility Uilder the pH conditions usually present in 

geological environments (Holland, 1967, p. 388-393). 

Inasmuch as silica replacement was local and sporadic, forming nodules, we can reasonably appeal to decreasing 

temperature as the mechanism for nodule silicification. 

Below 100°C in pure water, and at higher temperatures in 

electrolyte solutions, fluorite can also be precipitated by 

decreasing temperature (Holland, 1967, p. 395). The finegrained intergrowth of fluorite with opal in the nodules indicates that both were precipitated together under the same 

conditions, although the solubility of fluorite was additionally complicated by complexing, as will be discussed 

later. Decreasing temperature of the mineralizing solutions 

may also explain· the pronounced upward decrease of 

cristobalite observed in the drill-hole samples of altered tuff. 

All the preceding reactions are thought to be hypogene 

processes. The role of supergene processes, controlled by 

pas.t or present water tables, is difficult to assess. The 

kaolinite zone observed in the Roadside drill samples does 

not harmonize with the rest of the mineralogy of the altered 

tuff, inasmuch as it indicates a more acid stage of alteration. 

The kaolinite zone is discordant to the bedding and appears 

to have been overprinted on the other alteration zones, all of 

which are concordant. It may be related to the position of 

some past or present water table. 

CHEMICAL TRANSPORT AND PRECIPITATION 

MECHANISMS 

The mechanism for transportation and precipitation of 

Be, Li, U, Mn, and certain other elements at Spar Mountain remains speculative, but the main possibilities can be 

explored. Staatz and Griffitts (1961, p. 949; Staatz, 1963, p. 

M34) suggested that Be, Mn, U, and certain other elements 

were transported in solution as soluble fluoride complex 

ions, and that ,their precipitation occurred when formation 

of fluorite caused a decrease in fluorine concentration sufficient to render the complexes unstable. This mechanism 

could account for the association of Be, U, and other 

elements with fluorite, as demonstrated in the study of the 

calcite-silica-fluorite nodules. We have shown, however, 

that the alteration process has released large quantities of 

carbonate and bicarbonate ions which probably increased 

the alkalinity of the mineralizing solutions (table 3). These 

ions are known to form stable complexes with beryllium 

(Govorov and Stunzhas, 1963), uranium (Miller, 1958; 

Naumov, 1959; Hostetler and Garrels, 1962), and 

manganese (Hem, 1963). These complexes may be 

destroyed by various means, including decrease of a carbonate species (that is, by precipitation of insoluble carbonates, escape of C02 through fractures, and acidification 
Al8 BERYLLIUM-BEARING TUFFS IN WESTERN UTAH 

with resulting production of C02), precipitation as an 

hydroxide if alkalinity increases, or, in the case of uranium, 

by reduction and precipitation of insoluble uranous compounds. 

Beryllium fluoride (fluoroberyllate) complex ions are 

known; and according to Novoselova and Simanov (1955, 

and reported in Beus, 1966, p. 22), these complex ions disintegrate with increasing alkalinity, precipitating Be(OH) 2• 

Phenakite (Be 2Si04) has been produced in the laboratory 

from BeO and Si02 in the presence of beryllium fluoride 

complex ions (Sobolev and N ovoselova, 1959). The 

halogen-bearing carbonatoberyllates studied by Govorov 

and Stunzhas (1963) are stable over a wide range of pH (7-

11) and, when C02 is not allowed to escape, to temperatures 

exceeding 200°C. Beus (1966, p. 22), however, reported that 

the fluoride complex compounds are more stable than corresponding beryllium carbonate complex compounds. Recent work (Mesmer and Baes, 1969) has shown that BeF4 - 2 

and BeF; ions are stable in acid and neutral solutions at 

fluoride concentrations of 10-2 mgjl (milligrams per liter) 

or less, and Bef+ is stable in solution with fluoride concentrations of less than 10- 4 mg/1. The various beryllium 

fluoride complexes are also stable in solution to at least 

60° C. It seems likely, in view of the close beryllium-fluorine 

association at Spor Mountain, that beryllium was 

transported as a beryllium fluoride complex and 

precipitated by removal of fluorine from solution. Alternatively, if beryllium was transported as fluoride complex 

ions, precipitation may have occurred when the solutions 

became markedly alkaline. Experimental verification of this 

possibility is needed. 

Uranyl dicarbonate and tricarbonate complex ions have a 

combined pH stability range of 4.5 to 11.5 and are stable at 

temperatures of at least 200°C (Miller, 1958, p. 536; 

Naumov, 1959, p. 17). Although the uranyl carbonate complexes are more stable at 25 °C, the uranyl fluoride complex 

ion becomes the more stable complex ion at higher 

temperatures (Miller, 1958, p. 543). At 215°C the solubility 

of uranyl fluoride is several orders of magnitude larger than 

that of either uranyl carbonate complex. Hence, it seems 

likely, in view of the uranium-fluorine association noted at 

Spor Mountain, and in view of the presumed elevated 

temperatures, that uranium was also transported as the 

uranyl fluoride complex. 

The solubility of manganese at 25°C in aqueous solutions 

is appreciably increased owing to formation of the soluble 

bicarbonate complex cation when the pH is favorable; at 

2,000 ppm HC03

- the bicarbonate complex is stable over a 

pH range of 6.35 to 8.2 (Hem, 1963, p. A38-A43). 

Manganese also forms stable complexes with fluorine 

(SilU~n. 1964, p. 261). As seen from the gain-loss data in 

table 3, manganese is removed from calcite during the early . 

stage of silicification and is not returned during fluoritization. Instead, manganese is precipitated last as nodule 

coatings and fissure fillings. This evidence indicates that 

manganese may not have been transported as a fluoride 

complex; inasmuch as it was leached from the nodules along 

with Ca~+ 2 and C03 - 2

, the bicarbonate complex transport 

mechanism seems most likely. Rising alkalinity would cause 

precipitation of MnC03, which is then commonly oxidized 

to manganese oxides by later supergene processes. 

Stable fluoride complexes with many other elements are 

known or suspected, including Si +4

, Al + \ Ga + \ B + 3, 

Fe + 3, Sn + 2, Zn + 2, and rare earth elements (Sillen, 1964, 

p. 256-267; Mesmer and Baes, 1969, p. 625-626). These 

elements are all demonstrated to have been mobile in the 

Spor Mountain alteration environment (tables 1, 2, and 3). 

In particular, the demonstrated mobility and addition of 

aluminum during alteration of the tuff and of the carbonate 

clasts is striking in view of the widely assumed immobility of 

this element. Beus (1966, p. 276) also noted that aluminum 

is mobilized commonly in the fluorine-rich ·acid environments of greisenization. 

In summary, the foregoing discussion indicates that the 

mineralizing solutions at Spor Mountain were charged with 

abundant silicon, aluminum, alkali and alkaline earth 

metals, and fluorine. The mineralizing solutions were 

probably of low temperature (s200°C) and neutral or 

slightly alkaline when they first entered the tuff; they 

became increasingly alkaline as they reacted with carbonate 

clasts in the tuff. Precipitation and fixation of these 

elements were variously caused by rising pH, declining 

fluorine concentration, and falling temperature. 

ORIGIN OF THE SPOR MOUNTAIN BERYLLIUM DEPOSITS 

The mineralizing solutions at Spor Mountain previously 

were thought to have been derived directly from the magma 

that formed the topaz rhyolite of the Thomas Range 

(Staatz, 1963, p. M33-M34). Indeed, the topaz rhyolite does 

contain anomalous trace quantities of Be, Mn, F, and U and 

undoubtedly is genetically related to the western Utah 

beryllium belt (Staatz, 1963; Shawe, 1966, tables 2 and 3). 

Three other lines of evidence, however, may pertain to the 

problem of the origin of the beryllium deposits: berylbearing granites, beryllium zonation in carbonate rocks, 

and the geologic setting of various types of beryllium 

deposits in western Utah. 

Many of the elements shown to be mobile at Spor Mountain were also mobilized in the beryl deposits related to 

albitized and greisenized granites in Transbaikalia, Siberia 

(Beus, 1966, p. 255-280). There, alkali and alkaline earth 

metals, alumina, and beryllium were extracted from granite 

country rock by acid, fluorine-rich hydrothermal solutions. 

Decreasing temperature and acidity caused deposition of 

quartz, topaz, mica, and beryl as greisens and as fissure 

fillings. If these or similar solutions were to escape into 

overlying country rocks such as the tuffs at Spor Mountain, 

argillic, sericitic, and feldspathic alteration would be expected to occur. Beryllium and other elements remaining in 

solution could be deposited in the altered zones, as they were 
HYDROTHERMAL ALTERATION, BERYLLIUM DEPOSITS AT SPOR MOUNTAIN, UTAH A19 

at Spar Mountain. If the solutions moved into carbonate 

rocks, fluorite-silica replacement would be expected - for 

example, the fluorite pipes and altered nodules in tuff at 

Spar Mountain. 

A complete sequence of alteration zones around granite 

intrusives in carbonate rocks has been recognized in the tinberyllium deposits of Alaska (Sainsbury, 1969, p. 84-85). 

The sequence consists of six major zones grading outward 

from granite: greisen and skarn (two z<;>nes), transitional tinberyllium -fluorite, beryllium-f1 uorite, f1 uori te-l owtemperature sulfides, and fluorite-chalcedonic silica. 

Fluorite ranges from colorless in the inner zone to purple in 

the outer zone. According to the zonal gangue mineralogy 

and associated fluorite color proposed by Sainsbury, the 

Spar Mountain deposits belong to the outer, fluoritechalcedonic silica zone. This conclusion is also in agreement 

with the incomplete alteration of vitric and zeolitic tuff at 

Spar Mountain to clays, sericite, and potassium feldspar. If 

the Spar Mountain deposit is correctly placed in 

Sainsbury's zonal classification, the distribution of bertrandite and manganese minerals needs to be extended into the 

outer zone. Bertrandite has also been reported as the only 

beryllium mineral in two other beryllium deposits -

Aguachile Mountain, Mexico, and Apache Warm Springs, 

N. Mex. - which probably formed in low-temperature 

hydrothermal environments (Levinson, 1962; Hillard, 

1969). 

The source of the mineralizing solutions may be inferred 

from the surrounding intrusive and extrusive rocks in 

western Utah. The great volume of topaz rhyolite in the 

Thomas Range is evidence for a beryllium-, uranium-, and 

fluorine-rich magmatic source beneath the Spar Mountain 

beryllium and fluorite deposits, as discussed by Staatz 

(1963, p. M33-M34). The beryl-bearing granite of the 

Sheeprock Mountains lies only 40 miles to the northeast . 

and may be a nearby analog to the source of the Spar 

Mountain solutions. The granite of the Sheeprock Mountains contains beryl, and related greisens also contain 

fluorite and topaz (Cohenour, 1959, p. 117-120; 1963b); the 

occurrence may be similar to the beryllium-bearing greisens 

described by Beus (1966). The Sheeprock granite is structurally high and is in contact with Precambrian and 

Paleozoic strata; consequently, it may provide a view of 

moderate to deep-level beryllium deposits in the western 

Utah belt. The Spar Mountain beryllium deposits, however, 

are within a structural low filled with volcanic rock; they 

represent the near-surface environment of beryllium 

deposits in western Utah. 

The foregoing discussions of beryl-bearing granites in 

Siberia, beryllium zonation around granites in Alaska, and 

the possible variation in depth of different beryllium 

deposits in western Utah imply that the deposits at Spar 

Mountain may have been formed in a near-surface environment by solutions derived from intrusives beneath the 

Thomas Range. Leaching of the intrusives by ascending 

fluorine-bearing solutions could bring silica, alumina, 

alkalis, beryllium, and other elements into the near-surface 

environment of porous tuffs and carbonate rocks. Here, rising pH, declining fluorine concentration, and falling 

temperature probably caused argillic and feldspathic alteration in the tuff and fluorite-silica replacement of carbonate 

rock accompanied by emplacement of beryllium deposits. 

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*U.S. GOVERNMENT PRINTING OFFICE: 1973 0-543-576/3