DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, DIRECTOR

BULLETIN 511

ALUNITE

BY

B. S. BUTLER AND H. S. GALE

WASHINGTON

GOVERNMENT FEINTING OFFICE 

1912

CONTENTS.

Page.

Introduction ____________________________________ 5

Discovery____________________________________ 5

Significance of the deposit as a source of potash____________ 5

Location and railroad facilities______________________ 6

Description of the Marysvale alunite_____________________ 6

Character of the vein____________________________ 6

Physical character of the alunite_____________________ 7

Chemical character of the rock____________.._______ 8

Extent of the Marysvale deposit_______________________ 8

Located claims________________________________ 8

Continuity of the deposit______________ ,_______ 9

Thickness of the main deposit_______________________ 10

Tonnage ________ __ _ __________ 12

Geology and mineralization in the Tushar Range, by B. S. Butler____ 12

Location and general features_______________________ 12

Sedimentary rocks ___ __ __ _ ___ 14

Effusive rocks ___________________ _______..___ 14

Intrusive rocks ________ __ __ 15

Relation of the intrusives to the flow rocks_ ___ _____ 16

Age of the igneous rocks____ __________ ______.. 16

Faulting and fissuring __ _____ _ _____ 16

Mineral veins_________ ____ _____________ 18

Origin of the alunite deposit ________ ___________ 21

Probable extension of the alunite in depth_______________ 37

Known occurrences of alunite in the United States____________ . 38

Alunite deposits of the Rosita Hills, Colo., by Whitman Cross____ 38

Democrat Hill ___ __ _ _ _____ 39

Mount Robinson__ _ _ ______ 40

Rico Mountains, Colo _ 41

Silverton, Colo __________ .______-____________ 43

Cripple Creek, Colo_______ _______ _ ____ 43

Goldfleld, Nev_______________________ ________ 44

Miscellaneous occurrences in Nevada - __ __ ______ 48

Tres Cerritos, Cal______________________________ 49

Cl if ton-Mo reuci district, Ariz__________ ,______ 50

Beaver County, Utah __ _____ _ ______ 50

Foreign occurrences of alunite _ _ 51

Tolfa, Italy____________________________________ 51,

New South Wales___ _____________ ___ 55

Other deposits_________________ 57

Commercial availability of alunite_________ _____ 58

Suggestions as to prospecting for alunite 61

Field, test for alunite___________________ _..___ __ 63

Warning to investors _ ,,_.,_^.^.,.,__ .. . 63

3
ILLUSTRATIONS.

Page.

PLATE I. Prospect crossing the main alunite vein near northwest end center Ouster No. 1 claim______________,__________ G 

II. View of the trench shown in Plate I, looking in the opposite

direction ________________________________ 6

III. Map showing the principal group of claims located on the alunite

deposit near Marysvale, Utah____________________ 8

4
AIUNITE, A NEWLY DISCOVERED DEPOSIT NEAR 

IARTSVAIE, UTAH.

By B. S. BUTLER and HOYT S. GALE.

INTRODUCTION.

If

DISCOVERY.

An important deposit of alunite, whieh has but recently been discovered in Utah, is now being developed with so favorable a showing that it promises to afford one source of the much desired class of 

I materials commonly referred to as " potash." Federal geologists 

visited this locality in March, September, and November, 1911, but 

even at the later visit the prospect pits were not sufficiently complete 

to give satisfactory evidence of either the size or the linear extent of 

the deposit. A reconnaissance study of the geology and ore deposits 

in the vicinity of Marysvale, incidentally including the alunite, was 

made in September by B. S. Butler, and a hurried review of the 

Ouster alunite properties was made on November 2 by Hoyt S. Gale. 

The general review of the geology of the Tushar Range given on 

pages 12-38 is the work of B. S. Butler.

Although a large vein of " pink spar " in the hills southwest of 

. Marysvale had long been known to prospectors and had been repeatedly located for small metalliferous values said to be found in the 

siliceous wall rock of the vein, it was not until 1910 that the true 

nature of the spar was discovered. Specimens sent to the United 

States assay office at Salt Lake in November, 1910, were later forwarded to an eastern chemist, who is said to have recognized the real 

<, value of the material. On January 1, 1911, the claims that had been 

allowed to lapse were relocated for the sake of the newly recognized 

| deposit.

* SIGNIFICANCE OF THE DEPOSIT AS A SOURCE OF POTASH.

Alunite has long been used abroad as a source of potash alum, which, 

it resembles in chemical composition. The alunite contains a relatively larger proportion of alumina than the common potash alum.

5
6 ALUNITE NEAR MARYSVALE, UTAH.

It is insoluble but is readily converted to either the soluble potash 

alum or potassium sulphate by a comparatively simple process of 

heating, or calcination.1 A process that has long been established 

commercially may doubtless be adapted to the American deposits. The 

Marysvale deposit, so far as now known, is not of such magnitude as 

to afford a source of all the potash salts now consumed in the United 

States, but it may prove to be an important factor in providing an 

American supply that will perhaps be especially available to local 

and western markets, particularly in meeting the demand for highergrade salts. Possibly also the greatest importance of the commercial 

development of this deposit will be in the added stimulus it may 

afford to exploration for other similar deposits of this mineral, especially in this general region, and it is on the discovery of such other 

deposits that the provision of a home supply from this source must 

depend.

LOCATION AND RAILROAD FACILITIES.

The newly discovered deposit of alunite is situated near the head 

of Little Cottonwood Canyon, about 7 miles due southwest of Marysvale, Piute County, Utah. It is located in and near sec. 16, T. 28 S., 

R. 4 W., and so far as known is covered by mining-claim locations. 

Marysvale is the present terminus of the San Pete & Sevier branch 

of the Denver & Eio Grande Railroad. The deposit lies high in the 

Tushar Range, outcropping near the top of the ridge separating 

North Fork of Little Cottonwood Creek from the main branches of 

Little Cottonwood Canyon. The vein and siliceous wall rocks form 

the crest of the high ridge leading up to the main divide. The deposit ranges in elevation from approximately 11,000 feet above sea

level to about 9,900 feet at its present recognize^ lower end, which is 

about 4,000 feet above the-railroad at the Marysvale station.

DESCRIPTION OF THE MARYSVALE ALUNITE.

CHARACTER OF THE VEIN.

The alunite of the Marysvale gleposit lies principally in a large 

banded vein, cutting at steep inclination the volcanic rock (dacite 

or andesite) which forms the greater part of the Tushar Range. The 

views given in Plates I and II were taken November 2, 1911, and 

show the character of present development work, and the general 

appearance of the vein at the outcrop. The smooth rock faces shown 

in these views are fractures across the vein.

1 See references to utilization of foreign deposits, pp. 59-61:
U. S. GEOLOGICAL SURVEY BULLETIN 511 PLATE !

PROSPECT CROSSING THE MAIN ALUNITE VEIN NEAR THE NORTHWEST END OF CUSTER NO. 1 

CLAIM, NEAR MARYSVALE, UTAH.

The smooth faces are joints crossing the trend of the vein. Most of the loose material strewn about is alunite, as 

is also the solid face of rock shown in the cut.
U. S. GEOLOGICAL SURVEY BULLETIN 511 PLATE |l

VIEW OF THE TRENCH SHOWN IN PLATE I, LOOKING IN THE OPPOSITE DIRECTION

(SOUTHWEST).

Summit of Tushar Range in the distance.
DESCRIPTION OF THE ALXJNITE. 7

The large vein is evidently a fissure filling and not a replacement 

of the country rock, as the main body of the deposit is remarkably 

pure and has the banded or crusted structure of a typical fissure vein, 

That replacement has not produced' the larger bodies of alunite is 

further attested by the fact that the main vein contains but little 

silica, while in the wall rock where replacement has occurred the 

quartz phenocrysts remain practically unaltered, and silica that has 

been set free from the decomposition of other minerals has not been 

removed.

The real attitude of the vein is not yet very clearly defined. The 

vein banding is assumed to be approximately parallel to the walls 

and if this position is continuous below the part at present exposed, 

the vein is probably nearly vertical in its northern extension and 

has a distinct dip about 60° SW. toward the south end of the recognized deposit.

On each side of the main deposit smaller veins or bands of alunite 

alternate with similar thicknesses of much silicified portions of the 

wall rock, which in place contain iron sulphide in disseminated grains 

or crystals.

A more detailed and technical description of the alunite veins is 

given on pages 20-21.

PHYSICAL CHARACTER OF THE ALUNITE.

The larger bodies of the Marysvale alunite are of unusual size and 

notably free from foreign material. The alunite occurs in massive 

form, being in part a fine-grained compact rock, breaking with conchoidal fracture, and having a porcelain-like appearance, but containing also considerable masses with a distinctly crystalline structure. A considerable part of the vein material at the outcrop, however, is more or less of an amorphous texture and commonly sheared 

to a foliated or schistose structure. The crystalline material is generally clear pink to reddish in color and the finer-grained rock varies 

from a white to a decided pink.

The fine porcelain-like material, of which analysis 19 on page 8 

is representative; is seen under the microscope to be a granular mass 

composed of irregular crystals of alunite. Through this fine-grained 

material are scattered small veinlets of more coarsely crystalline 

alunite.

The coarsely crystalline portion of the deposit, of which analysis 

18 on page 8 is representative, shows the more distinct crusted structure. The crystals are subtransparent, show a distinct cleavage, and 

are of a rather coarse granular or tabular form, yielding a splintery 

fracture in the mass of the rock. The elongation of the crystals, 

though showing a tendency toward radiation in tufts, is, however, 

roughly parallel and is normal to the vein banding and the walls.
8 ALUNITE NEAR MARYSVALE, UTAH.

A considerable portion of the alunite as revealed in the present 

prospects has an amorphous texture and a more or less schistose structure, which may in part be due to weathering but probably is largely 

the result of shearing movements in the mass of the rock.

CHEMICAL CHARACTER OF THE ROCK.

The chemical character of the rock is expressed by the following 

analyses of some of the best and apparently purest material collected at the prospect pits. These analyses, which were made by 

W. T. Schaller, show a very close approximation to the theoretical 

composition of the mineral as quoted from Dana's " Textbook of 

mineralogy " for comparison:

Analyses of alunite from deposit near Harysvale, Utah.

AljOa............. ........................................................

SOs......................................................................

PiOt.................................. ....................................

KtO................................................. .....................

NasO.....................................................................

HsO+....................................................................

HsO.....................................................................

SiOs......................................................................

18

37.18

Trace.

38.34

.58

10.46

.33

12.90

.09

.22

100.10

19

34.40

Trace.

36.54

.50

9.71

.56

13.08

.11

5.28

100. 18

Dana.

37.0

38.6

11.4

13.0

100.0

No. 18 is a selected specimen of the supposedly best material. It 

consists of clear-pink, subtransparent, coarsely granular crystalline 

rock. No. 19 is a selected specimen of a light-pink, very finely 

granular rock, of almost porcelain-like conchoidal fracture and no 

distinct structure.

EXTENT OF THE MARYSVALE DEPOSIT.

LOCATED CLAIMS.

The principal claims located on the Marysvale alunite deposit 

are the duster group, shown on the accompanying plat taken from 

the official surveys (PI. III). This group of claims adjoins patented mineral ground and recorded claims both to the northwest 

and southeast, as is indicated on the map. The Ouster group covers 

the greater part of the alunite deposit as now recognized, the first 

location made expressly for the alunite having been staked January 

1, 1911. Property to the northwest of the Ouster claims is said to 

be covered by mineral locations under the control of the Florence 

Mining & Milling Co., lessee of the Utah Gold Mountain Mining 

Co., including the so-called Log Cabin property and also the patented ground known as the Bradburn property. Southeast of the 

Custer claims is the patented ground of the Clyde property, indicated on the plat.
U. 8. GEOLOGICAL SURVEY BULLETIN 511 PLATE III

MAP SHOWING THE PRINCIPAL GROUP OF CLAIMS LOCATED ON THE ALUNITE DEPOSIT 

NEAR MARYSVALE, UTAH.

Based on plats of mineral survey Nos. 6162, 6163, 6164, 6165, United States Surveyor General's Office, Salt 

Lake City, Utah. The outcrop of the alunite and the contours shown on the map are b'-sed on a hasty 

field sketch and are only approximate. The numbers indicate points at which specimens described in 

the text were collected.
EXTENT OF THE DEPOSIT. 9 

CONTINUITY OF THE DEPOSIT.

As yet only what is understood to represent a single large vein 

deposit of the alunite has been shown by the developments on 

the Marysvale properties. Proof of the actual continuity of this 

deposit beyond the area of most numerous prospects (in claims Nos. 

1 and 2) is not complete. The vein appears to be limited by fairly 

well defined walls and to follow a very regular trend, extending 

nearly due northwest and southeast. As the outcrop and openings 

are all aproximately in the course of this same general trend, it is 

likely that they represent one and the same vein, although it is 

possible that there are more than one possibly related veins. There 

is some evidence indicating that other deposits may exist, but at 

present it is believed that none have been opened by prospects far 

from the main deposit.

The representation of the outcrop of the alunite on Plate III is 

probably only approximately correct, as it is based on a very 

hurried compass traverse made at the time of the visit to the property on November 2. The extension of the alunite deposit along 

the course of the vein to the southeast has not yet been proved 

beyond the outcrop shown on the plat. Float has been found on 

the lower claims of the Custer property and this may indicate the 

existence of some rock in place, but it can not now be said with 

certainty that the vein extends farther southeast than is shown in 

the Custer claim No. 1. The deposit has been recognized northwest 

of the Custer claims, however, where it occurs in massive outcrop, 

apparently very similar in character to that portion of the vein 

that has already been prospected. This, northwestern outcrop is 

situated on the crest of the ridge north of the Log Cabin tunnel and 

about 550 feet above it, near the " Edna Geyser." It is probably 

half a mile or more northwest of the limit of the outcrop represented on Plate III.

The apparent continuity of the vein on the surface and its vertical range of outcrop from an elevation of somewhat more than 

11,000 feet to about 9,900 feet may be assumed as good presumptive 

evidence of a corresponding continuity of the deposit in depth. 

However, some considerations which are more completely reviewed 

in the discussion concerning the probable origin of these deposits (pp. 

21-37) tend to indicate that some alunite deposits are of superficial 

origin and will not be found to be continuous in depth. As will be 

seen, however, by reference to page 36, the evidence in regard to the 

Marysvale deposit is thought to favor a deep-seated rather than a 

superficial origin and the conditions of the deposition of the alunite 

may not have been dependent on a close proximity to the surface 

or on any immediate relation to the topography of the present time.
10 ALUNITE NEAR MARYSVALE, UTAH. 

THICKNESS OF THE MAIN DEPOSIT.

The prospects completed at the time of the last visit to the property had traced only about 3,000 to 3,500 feet of the outcrop, which 

is that portion indicated by the outcrop line of the meander traverse 

in Plate III. Only that portion of the vein that is covered by the 

prospects in claims Nos. 1 and 2 can be said to be known with much 

certainty. Here numerous measurements of the vein as it was exposed in the trenches were made, but most of these were far from 

satisfactory, owing to the incompleteness of the exposures.

The size of the vein and the apparent purity of the material are 

probably its most unusual features. According to a number of measurements made from the present developments, there is in one place 

at least 20 feet of solid alunite in the larger vein and 6 feet more in 

a parallel vein some 25 feet to one side, with considerable quantities 

of alunite rock and alternating purer alunite and siliceous wall rock 

intervening. The lower-grade rock may possibly extend beyond that 

shown in the present pits. Other measurements made reveal less 

thicknesses, but in each case it is doubtful whether the trenches that 

have been dug expose all the alunite that may be present.

With the exception of the outcrop of alunite near the " Edna 

Geyser " already referred to, the northernmost outcrops examined 

were in the prospects indicated on the plat as Nos. 1 and 2 in Custer 

claim No. 15. Alunite was observed in talus, and specimen No. 1 

was collected at an elevation at least 75 feet above and southwest 

of the prospect marked as the discovery on the Custer claim No. 14. 

It is likely, therefore, that more than one vein of the alunite will be 

found near this locality, but at present the prospect only incompletely reveals the one vein, A 10-foot hole and shaft exhibit 6 

feet of apparently good material without showing distinctly that both 

walls have been reached. The alunite is massive, of texture which 

varies from coarsely crystalline to fine porcelain-like, including some 

sheared material.

Specimens 6 and 7 and the block that was afterward analyzed, No. 

19, were collected near the shaft and monument marked " SE. end 

center Custer No. 2 and NW. end center Custer No. 1." Here the 

development consists of a 30-foot trench crossing the crest of the 

ridge, together with a shaft about 20 feet deep. Much alunite has 

been thrown out on the dump. The trench shows 10 feet of apparently very pure alunite and 5 feet at the north end of the cut composed of mixed vein and wall rock. However, a considerable portion of the trench is cut in loose surface material and probably does 

not show the whole thickness of alunite at this place. This is the 

locality illustrated in the views shown in Plates I and II.

Northwest of this point two other prospects were visited, distant 

about 250 and 500 feet from the end center monument described.
EXTENT OF THE DEPOSIT. 11

Specimen No. 18, the anaylsis of which is given on page 8, was collected from the nearer trench. Here a cross section of the alunite 

vein measured 15 feet, with no apparent partings or inclusions of 

other material. The farther trench showed 12 feet of solid alunite, 

but the exposure is probably incomplete, as it runs into slide material at either end. A 15-foot tunnel just below this trench exposed a 

stringer of alunite, apparently an offshoot from the main vein, as it 

differs markedly from the vein in direction and pitch.

About 100 feet southeast of the northwest end center stake of the 

Custer claim No. 1 is an open cut showing a solid face of somewhat 

more than 12 feet of massive alunite, varying in texture from 

coarsely crystalline to fine granular. The west wall of this vein is 

a dense quartz or siliceous rock containing specks of iron sulphide, 

and beyond this at least 6 feet of alternating alunite and siliceous 

rock are exposed. The trench ends in slide rock. About 350 feet 

southeast of the northwest end center stake of the Custer claim 

No. 1 is a trench 30 to 40 feet long, cut transverse to the course of 

the vein, which follows the crest of the ridge at this place. Here 

crustification or banded structure of the vein is quite distinct, and 

from the attitude of this banding the vein is assumed to be dipping 

60° SW. and to have a course N. 50° to 55° W. Some of the ore 

exposed here has a beautifully clear, banded crystalline structure 

and is of pink or reddish color. A detailed tape measurement made, 

allowing for a 60° dip as indicated by the banding, gave a total 

thickness of 17 feet 6 inches of apparently solid alunite, with at 

least 10 feet more of alunite and siliceous wall rock in alternating 

bands exposed in the northeast end of the cut.

About 100 feet southeast of the trench last described is a deep 

trench or open cut and shaft exposing at least 20 feet of solid alunite 

vein rock. The banding here strikes N. 50° W. and dips 60° SW. 

There are some very massive blocks in this exposure, and the whole 

section exposed would afford an excellent opportunity for taking 

an average sample. The extension of the cut to the northeast shows 

admixture with the siliceous wall rock, in part highly stained with 

red material supposedly iron, and 25 feet from the main deposit 

is a second vein containing at least 6 feet of the massive alunite. 

The interval between these veins is made up of alternating bands of 

alunite and wall rock.

The tunnel (marked 13 on the plat) at the lower end of the prospected ground is reported to run in for 100 feet or more and starts 

on a course of N. 4° E. Alunite shows in the slide rock over the 

mouth of the tunnel, but it is said that the main deposit has not been 

struck. Some smaller veins of alunite have been encountered. It 

is possible that the dip of the vein would carry the outcrop south-
12 ALUNITE NEAR MARYSVALE, UTAH.

west of the tunnel mouth, so that this may explain why the tunnel 

apparently misses the main vein entirely, but this can not be stated 

with much certainty from the hasty measurements made in the 

present examination. Below the tunnel to the southeast, in the, 

course of the vein, blocks of massive alunite are found from point 

to point, but it has not yet been shown that the rock in place continues in this direction, and the blocks could readily be accounted for 

as float derived from the present known outcrop.

TONNAGE.

A conservative estimate of the tonnage in this deposit may be had 

by assuming an average width of 10 feet in the principal vein for 

a total length of 3,500 feet and neglecting the rest of the deposit 

as not sufficiently proved to be taken into consideration at present. 

This gives a surface area of substantially proved outcrop of 35,000 

square feet, or about four-fifths of an acre. The specific gravity of 

the Marysvale alunite has been determined in several specimens by 

W. T. Schaller, with results in close accord at about 2.82. Therefore a cubic foot of the ore may be assumed to weigh about 175 

pounds. An acre of ground underlain by this rock to a depth of 

only 1 foot would contain 3,800 short tons of alunite. If the area 

of available alunite is only 35,000 square feet, as stated above, there 

would be approximately 300,000 short tons of the rock for each 100 

feet of depth so long as the deposit maintains its surface dimensions 

and quality. If the recoverable potassa or potash (as K2O) is estimated at 10 per cent of this total, such a deposit would yield 30,000 

tons of potassa for each 100 feet in depth. This is approximately 

one-sixth to one-seventh of the total annual consumption of potash 

in the United States.

GEOLOGY AND MINERALIZATION IN THE TUSHAR

RANGE.

By B. S. BUTLER. 

LOCATION AND GENERAL FEATURES.

The Tushar Mountains form part of a long north-south range between the Sevier Eiver valley to the east and a broad desert valley 

to the west. This range attains its highest elevation in Baldy and 

Belknap peaks, northwest of Marysvale. These peaks are nearly 

13,000 feet above the sea and their white tops, rising well above the 

timber line, are prominent landmarks in southwestern Utah. From 

these points the surface slopes in all directions, long spurs separated 

by deep valleys leading down to the lower areas.
GEOLOGY AND MINERALIZATION IN TTJSHAE RANGE. 13

These mountains rising above the general level receive a relatively 

high precipitation. In some seasons the deep snows that collect 

during the winter persist through the entire summer and furnish a 

continuous water supply to the streams, which are of great value 

to this region. Vegetation flourishes, many of the higher valleys 

being clothed with forests. In the matter of water supply and 

timber the district is unusually favored as compared with the surrounding country.

The drainage of the range is to Sevier River. The streams from 

the eastern slope flow directly to that river; those from the western 

slope are tributary to Beaver River, which flows through the Mineral 

Range and in flood times joins the Sevier north of Milford, near its 

entrance into Sevier Lake. In the dry season both Sevier and 

Beaver rivers disappear in the desert sands before their waters reach

Sevier Lake.

The Tushar Range lies between two great physiographic provinces. 

On the east is the plateau province, made up for the most part of 

nearly flat-lying beds; on the west is the Great Basin province, consisting of north-south ranges separated by broad, flat valleys. These 

basin ranges have been produced by the breaking of the region into 

great blocks along north-south faults, and the tilting of these blocks 

has brought parts of them above the general level. The depressed 

areas have been filled with debris from the mountains, forming the 

flat intermountain valleys.

The Tushar Range forms a transition between these two provincial 

types. It is a great block outlined by north-south faults, but the 

tilting of the block has been less pronounced than in the range to the 

west. The outpouring of lavas has built up a great volcanic pile on 

the sedimentary platform, from the summit of which one can overlook the surrounding country for many miles. To the east the range 

is bounded by the remarkable troughlike valley of Sevier River, 

which has been produced by the settling of a great block between two 

parallel faults.

In recent times the streams have cut deep canyons in the mountains, exposed rocks long buried, and revealed something of the 

history of the range.

Geologically the Tushar Range is a complex mountain mass composed of sedimentary, extrusive, and intrusive rocks. The sedimentary rocks, so far as shown by exposures, are of slight extent, being 

confined to a small area west and southwest of Marysvale. The 

extrusive rocks, lavas, and tuffs are by far the most abundant type 

and make up the bulk of the range. Two large masses of intrusive 

rock have been noted, one forming the central part of the Antelope 

Range, northeast of Marysvale, and the other on the west side of the 

range near the head of Indian Creek northeast of Beaver.
14 ALUNITE FEAR MARYSVALE, UTAH. 

SEDIMENTARY BOCKS.

Sedimentary rocks are shown for only a few square miles along 

the front of the range west and southwest of Marysvale, the best 

exposures being in Bullion, Little Cottonwood, and Tenmile canyons. 

The series as seen in Little Cottonwod Canyon consists at the base of 

interbedded quartzites and limestones with an estimated thickness of 

500 to 600 feet. Overlying these rocks is 300 to 400 feet of massive 

quartzite, and this in turn is followed by a series of limestone and 

shaly beds with a thickness probably exceeding 1,000 feet. This 

series is overlain by quartzite, which forms the uppermost member 

and a few hundred feet of which is still preserved. In Tenmile Canyon is exposed a considerable thickness of sandstones and shales that 

show less metamorphism than those exposed in the canyons to the 

north and that may be younger, though the relation was not determined.

The age of the sediments has been determined by earlier workers * 

as Jurassic, on the basis of the presence of the fossil Pentacrinus 

asteriscus.

EFFUSIVE BOCKS.

Eesting on the eroded surface of the sedimentary rocks is an extensive series of effusive rocks. These were evidently thrown out at 

intervals covering a long period of time. During the time between 

eruptions the lavas were eroded and deposits of volcanic sediments 

accumulated. This process has resulted in the building up of a 

rather complex series of flows and breccias, with interbedded volcanic 

sediments derived from the earlier lavas. The lower flows exposed 

in Bullion, Cottonwood, and Tenmile canyons are in large part 

massive, with a pronounced porphyritic texture, though there are

numerous outcrops of a rather coarse breccia that suggests intrusive 

breccia of essentially the same composition as the flows. In mineral 

composition the successive beds show a slight difference, but all are 

of intermediate type. Quartz phenocrysts are present in most of the 

rock, though in some places they are relatively scarce. Plagioclase 

of medium basicity predominates over orthoclase in the phenocrysts. 

In the groundmass the relative abundance of the feldspars can not be 

determined. Both hornblende and biotite were abundant, but have 

usually been partly or entirely altered to secondary minerals. From 

the microscopic study the rocks are classed as dacite, though a 

chemical investigation would doubtless show that some of the flows 

have the composition of quartz latite, and some possibly might be 

classed as andesite.

1 Button, C. E., Geology of the high plateaus of Utah: U. S. Geog. and Geol. Survey 

flocky Mtn. Region, 1880, p. 184,
GEOLOGY AND MINERALIZATION IN TTJSHAB RANGE. 15

Overlying the dacite flows and forming the highest part of the 

range and extending down to the base, especially at the north, is a 

series of light-colored rhyolite flows and tuffs locally known as 

" shale." Whether these rhyolitic rocks ever covered the entire range 

can not be stated positively. Their greater abundance toward the 

north, however, suggests that they were erupted from vents in the 

northern part of the range and that if they ever extended over the 

southern and southeastern portions it was as a relatively thin covering. The latest eruptive rocks in the range are basaltic flows, with 

their principal development southeast of Beaver^ where they cover 

an extensive area.

INTRUSIVE BOCKS.

Intrusive rocks as observed in the range are of relatively slight

areal extent. Two considerable bodies of intrusives were noted and 

numerous dikes are present in various parts of the district. It is 

possible and even probable that sills of porphyry are also present, but 

if so they resemble the flow rocks so closely that a detailed study will 

be necessary to prove their presence. The larger intrusive bodies are 

located in the Antelope Kange north of Marysvale and on the western 

flanks of Baldy and Belknap peaks, several miles north of the town 

of Beaver. Both of these masses are composed of granitic rock, which 

is distinctly porphyritic near the contact with the flows and in places 

so closely resembles the porphyritic lava that distinction between the 

flows and the intrusives is difficult.

Mineralogically the main body of both intrusive masses is composed of rather abundant quartz with orthoclase and plagioclase in 

about equal amounts. The rock contains also considerable augite, 

biotite, and magnetite and in composition corresponds to quartz 

monzonite. Locally the rocks become more acidic and pass into true 

granite. Some phases of the rocks were noted that showed no free 

quartz, and they may be classed as monzonite.

Dikes cut both the volcanic and the sedimentary rocks of the range. 

They are usually rather fine grained, with porphyritic texture, and 

vary in composition from quartz monzonite porphyry to basic types 

containing abundant augite and biotite, with the general composition 

of camptonite. As already stated, the dikes have a porphyritic 

structure and closely resemble the porphj'ritic lavas, so that they are 

not readily distinguished, and without detailed work it is impossible 

to state how abundant they are. Prominent dikes of the more acidic 

type are present near the Sevier Consolidated and Annie Laurie 

mines, and more basic dikes were noted in upper Tenmile Canyon, 

and in the Deertrail mine.
16 ALUNTTE NEAR MARYSVALE, UTAH.

RELATION OF THE INTBUSIVES TO THE FLOW BOCKS.

The relation of the large intrusive masses to the flow rocks is not 

everywhere obvious, but dike rocks extending from the main mass 

into the overlying volcanic rocks were noted, and these, together 

with the change in texture of the intrusive from granitic to distinctly porphyritic near the contact with the flow rocks, show without doubt that the intrusive rocks are later than the flows. Their 

present relation is due to the intrusion of the granitic rocks into the 

flows rather than to the burial of an old erosion surface beneath the 

lavas.

"There has been considerable alteration of the flow rocks near the 

intrusive contact and the outline of the granitic areas in the Antelope Eange can be readily traced from a distance by the highly 

colored rocks produced by the alteration at the contact. A similar 

alteration is present in the Indian Creek area, as is shown at the Ked 

Buttes, north of the Kob Eoy mine.

AGE OF THE IGNEOUS BOCKS.

Within the Tushar Eange only Jurassic sediments and those of 

recent formation are exposed, so that it is impossible to determine 

closely the age of the igneous rocks. The effusive rocks flowed out 

on the eroded surface of the Jurassic sediments and are therefore 

post-Jurassic. From evidence in adjoining areas, however, Button 

has concluded that volcanism began in early Tertiary time and continued through a long period. The latest volcanic activity, the outpouring of basaltic lavas, was of very recent date and may have 

occurred only a few thousand years ago. It seems probable that the 

volcanic activity which built up the main range was active at intervals through middle and possibly into late Tertiary time. The 

granitic rocks are later than the main body of the flows and their 

intrusion may have taken place as recently as late Tertiary.

FAULTING AND FISSUBING.

Faulting has had a prominent part in the production of the present 

Tushar Eange. According to Button a fault extends for miles along 

the eastern front of this range and its extensions. Parallel to this 

fault, a few miles to the east, is the Sevier fault, and the Sevier 

Valley is considered to have been formed by the subsidence of the 

block between these great faults.

The western face of the Tushar Eange is in line with the extension 

of the Hurricane fault, which is prominent farther to the south, and 

this fault is considered by Lee 1 to form the western boundary of the 

range. Within the Tushar Eange there has been considerable fault1 Lee, W. T., Water resources of Beaver Valley, Utah: Water-Supply Paper U. S. Geol. 

Survey No. 217, 1908, p. 13.
GEOLOGY AND MINERALIZATION IN TUSHAE BANGE. 17

ing in a general north-south direction parallel to the great faults that 

outline the range. These minor faults are, as a rule, not readily 

recognized, on account of the similarity of the successive flows and 

the small amount of sedimentary rocks, but in places they are easily 

determined. Such a fault is well exposed near the Crystal mine, 

south of Cottonwood Canyon, where the volcanic rocks are thrown 

down against the quartzites, the fault being marked by a zone of 

fault breccia. The northward extension of this fault marks the 

boundary between the quartzite to the east and the volcanic rocks to 

the west. A similar relation is seen in the workings of the Bully Boy 

mine, in Bullion Canyon, where in places quartzite forms one wall 

of the ore vein and volcanic rocks the other, and strong slickensiding 

testifies to the movement that has taken place. Similar displacements doubtless occur within the volcanic rocks, but, as already 

stated, the similarity of the rocks renders their recognition difficult 

without detailed geologic work.

There has been some faulting in a general east-west direction, but 

this seems to have been less important, both in determining the structure of the range and in connection with the ore deposits, than the 

north-south movements.

In addition to the faulting there may have been some fissuring 

of the rocks which was unaccompanied by important movement but 

which permitted the circulation of mineral-bearing solutions.

The main faulting in the district occurred later than the extrusion 

of the bulk of the flow rocks. The exact geologic time when it 

occurred is not readily fixed and, in fact, the movement doubtless 

continued at intervals over a considerable period. Dutton,1 from a 

study of the faults over a wide area, concluded that the main fault 

movement began in late Tertiary time and continued to a very recent 

period, perhaps even to the present. That movement along some of 

these faults is still in progress has been indicated by severe earthquakes occurring in recent years.

It is likely that faulting has been going on throughout the long 

period of volcanic activity, and, indeed, this has been shown to be the 

case in neighboring regions; but it is equally likely that a very important period of faulting began in late Tertiary time and probably 

extended practically to the present, and that the outlines of the 

Tushar Range as seen to-day are largely resultant from this movement. As already noted, this disturbance took place after the extrusion of practically all the lavas, with the exception of the recent 

basaltic flows, and it seems not improbable that it was closely associated with the intrusion of the granitic masses which marked one of 

the very late events in the volcanic history of the range.

1 Button, C. E., Geology of the high plateaus of Utah: U. S. Geog. and Geol. Survey 

Rocky Mtn. Region, 1880.

21510° Bull. 511 12 2
18 ALUNITE FEAR MARYSVALE, UTAH.

MINERAL VEINS.

The mineral veins of the district are for the most part fissure veins, 

with a general north-south trend corresponding to the faulting and 

fissuring already described. Within the sediments " blanket veins " 

roughly coinciding with the strata are present, as shown in the Deertrail mine, and veins with a general east-west trend also occur. The 

ore and gangue minerals filled open spaces along faults and fissures. 

These veins probably occur in all the rocks except the basalt. They 

are certainly present in the Jurassic sediments, in the earlier porphyritic lavas, in the granitic intrusives, and probably in the rhyolitic 

lavas and tuffs, though they are of little importance in the lastmentioned rocks, probably because the physical character of these 

rocks is not favorable to the formation of open fissures.

The individual veins differ considerably in character, but are of a 

type that is of widespread occurrence in the Tertiary lavas of the 

Great Basin and adjacent regions. These veins may be broadly characterized as quartz-carbonate veins, and many of them contain 

notable amounts of adularia, a nearly pure potash feldspar of characteristic crystallization, together with minor amounts of other minerals, including fluorite and metallic sulphides, sulpharsenides, 

sulphantimonides, selenides, etc. Exceptionally alunite forms an 

important constituent of these veins. Veins of this type have commonly formed as a filling of open fissures and show a more or less 

distinct banded structure. Many of the veins in the Marysvale district are rather typical quartz-carbonate veins, the two minerals 

varying considerably in relative proportion in different veins and in 

different parts of individual veins and the carbonate ranging from 

relatively pure calcium carbonate to one rich in iron and manganese. 

Adularia has been noted in several of them, notably in the Sevier and 

the Wedge, and in material from the Bradburn tunnel, in the Antelope Kange. Fluorite is frequently found, and in the Bradburn 

tunnel magnetite, garnet, epidote, and tourmaline are associated with 

the veins. In the Krotki iron mines, in the Antelope Kange, iron 

minerals are abundant, but are apparently secondary, the present 

developments not having disclosed the original mineralization. In 

the Deertrail mine is a considerable body of ore of which sericite 

(muscovite) forms by far the larger part, an analysis of the ore 

shpwing 8.40 per cent K20. In other parts of the mine quartz is 

abundant and considerable jarosite was noted.

A most unusual exception to the ordinary vein filling is that of the 

vein described in this paper, in which the main vein mineral is alunite.

A study of the vein minerals indicates that they were not all 

formed contemporaneously, and the relative times of deposition of
GEOLOGY AND MINERALIZATION IN TTJSHAE RANGE. 19

the minerals agree in general with those observed in other districts 1 

that is, the earlier vein minerals consisted of abundant carbonate and 

the later solutions were rich in silica, potassium, and aluminum, so that 

the earlier minerals were replaced in varying proportion by quartz 

and adularia, which formed pseudomorphs after the carbonate and 

gave rise to the laminar or hackly structure that is characteristic 

of the ores of this type of vein. In addition to replacing carbonate, fine-grained quartz and adularia form small veinlets transecting the earlier minerals. Many of these veinlets can be detected 

by their slightly yellowish color. As an example of a vein containing abundant carbonate may be mentioned the strong vein which 

outcrops a short distance southwest of the Crystal mine, on the south 

side of Cottonwood Canyon, and which is composed largely of carbonate with quartz and some fluorite. The Sevier and Annie

Laurie and many other veins in the region show abundant pseudomorphs of silicates after carbonates, but other veins show little or no 

evidence of the replacement of carbonates, being composed essentially 

of fine-grained quartz or of quartz and adularia.

The alteration of the rock adjacent to the veins of the district shows 

considerable variation in character. More or less silicification, however, is characteristic and in some of the veins this becomes pronounced. The zone of silicification in some places is many feet wide 

and the outcrops of the vein stand up prominently. These are locally 

known as " geysers." Among them are the Sheep Bock veins, north 

of Beaver, the Krotki iron vein, in the Antelope Range, the veins in 

lower Tenmile Canyon, and the alunite vein in Clyde Basin. To a 

less extent the other veins of the district show a similar alteration of 

the wall rock. The characteristic chemical change of the wall rock 

adjacent to the veins has been a progressive leaching of the more 

soluble oxides, sodium, calcium, and magnesium, the iron, potassium, 

and aluminum usually remaining, at least in part, the iron in the 

form of pyrite and the potassium and aluminum as sericite (muscovite) or alunite. Where there has been extreme alteration practically 

all the oxides have been removed except silica and some iron, the 

resulting rock consisting of finely crystalline quartz. Where alteration has been comparatively slight chlorite, carbonate, and kaolinite 

are important constituents of the altered rock. Sericite, though 

present in the wall rock of many of the veins, in some places in considerable amount, can not be said to be a'characteristic mineral in the 

alteration.

iLindgren, Waldemar, The gold and silver veins of Silver City, De Lamar, and other 

mining districts in Idaho: Twentieth Ann. Kept. U. S. Qeol. Survey, pt. 3, 1900, p. 115. 

Schrader, F. C., Mineral deposits of the Cerbat Range, Black Mountains, and Grand Wash 

Cliffs, Mohave County, Ariz: Bull. U. S. Geol. Survey No. 397, 1909. Observations by 

B. S. Butler in the Gold-Springs and adjacent districts, Utah,
20 ALTJNITE NEAR MARYSVALE, UTAH.

The alteration in connection with the alunite vein has been pronounced and extends for many feet on either side of the fissure. 

Near the vein practically all the sodium, lime, and magnesium of the 

original rock has been removed. Pyrite is usually abundant and 

probably most of the iron of the original rock has combined with 

sulphur to form it. Kaolinite is present in varying amounts. The 

original feldspar crystals have been altered to a felted mass of quartz, 

alunite, and kaolinite crystals. In the absence of a quantitative 

chemical study of the rocks, it is impossible to state positively 

whether there has been a removal of potassium and aluminum, but 

from microscopic study the alunite seems sufficiently abundant to 

account for all the potash present in the fresh rock, it being assumed 

that the alunite in the wall rock, like that in the vein, is practically 

pure potash alunite and does not contain important amounts of soda. 

In some sections of the wall rock examined microscopically small 

apatite crystals are rather abundant. It is noteworthy that in the 

alteration of the wall rock the phenocrysts of quartz have undergone 

almost no change.

A preliminary examination of the wall rock of other veins of the 

district has not disclosed the presence of alunite, though a more 

careful study may do so. It may be noted, however, that metallic 

values are reported from prospects around the " Edna Geyser," 

where alunitization of the rock is pronounced. Unfortunately the 

workings of these prospects were not accessible at the time of visit.

In the alteration of the wall rock the alunite develops as platelike 

crystals in the feldspar, which is finally converted to a felted mass 

of alunite and quartz crystals. The alunite crystals commonly contain rather abundant minute inclusions of a kaolinite-like mineral 

whose character could not be positively determined. Fine secondary

quartz is also abundant.

The alunite deposit is a banded vein between rather definite walls, 

though, as already noted, alunite is an important constituent of the 

wall rock. It is apparent that the main vein is not a replacement of 

the country rock, for where replacement has occurred in the wall rock 

the quartz phenocrysts are practically unaltered and the silica set 

free by the alteration of other minerals is not removed. The vein, 

on the other hand, is almost free from silica. In some portions of 

the vein the material is coarsely crystalline, the crystals having a 

tabular form and in places extending across a layer of the banding. 

Commonly the crystals show a tendency to diverge from a center 

as tufts, this character being more noticeable under the microscope 

than in the hand specimen. The rhombohedral faces of the crystals 

are not usually well developed, but in many places an open cavity 

between two bands shows well-developed rhombohedral faces, which, 

however, have commonly been somewhat etched by later solution.
ORIGIN OF THE ALTJNITE DEPOSIT. 21

What in the hand specimen appear to be crystals are seen under the 

microscope to be composed of numerous smaller crystals diverging 

from a central axis, forming a very striking plumose structure. The 

difference in orientation of these component parts of the " crystal" 

group gives it a wavy extinction between crossed nicols.

The lines marking the separation of the bands forming the vein 

are seen under the microscope to consist of narrow bands of finely 

crystalline material of various orientations. The larger " crystals," 

however, cross these lines without change in orientation and give 

the general impression that the fine material has been deposited in. a 

fissure breaking across the crystals. It is probable that there was a 

slight change in conditions of deposition, after which some of the 

crystals continued their growth while in part crystallization began

from new centers.

As seen under a low power of the microscope the material seems 

to be almost pure, but when studied under the higher power numerous yellow globular masses are seen, most abundantly between the 

crystals or along minute fractures. These masses are probably 

limonite. Some small spaces are filled by a cloudy mineral resembling kaolin. Included in the alunite are numerous irregular microscopic masses of a mineral that appears to be isotropic and has an 

index distinctly below alunite. This mineral has not been determined.

In other parts of the vein the alunite becomes finer grained and 

locally lighter in color. In some places it has a very dense appearance and breaks with a conchoidal fracture; in others, where there 

has been some movement, the alunite has a schistose character and 

shows numerous slickensided faces. Under the microscope the finegrained material is seen to be a granular mass composed of irregular 

crystals of alunite. Associated with these in the section examined is 

a mineral with lower index and having the general characters of 

kaolinite, though it has not been positively determined. The chemical analysis of this material indicates that both kaolinite and some 

quartz are present as impurities in the alunite. Through this finegrained material are scattered small veinlets of more coarsely crystalline alunite. Some such veinlets were noted half an inch or more 

in thickness.

ORIGIN OF THE ALUNITE DEPOSIT.

The origin of the alunite deposit is of much interest and of considerable importance as an aid in the search for other deposits. At 

the present time it is not possible to make a positive statement concerning this problem, but certain facts point strongly to the source 

of the material and manner of formation here discussed.
22 ALTJNITE NEAR MARYSVALE, UTAH.

The close relation of this vein to the other veins of the district, as 

shown by the high potassium and aluminum content of the vein 

minerals and further by the reported occurrence of metallic values 

in some of the alunitized rock and the general relation of the veins, 

strongly suggests that they are of a common origin and are results of 

the same general period of mineralization, though the difference in 

character indicates that the veins were formed under somewhat different conditions and possibly at different parts of the same period. 

It will also be remembered that the veins other than the alunite veins 

show considerable difference in mineralogic character^ were probably 

formed under somewhat different physical conditions, and probably 

also represent progressive changes in the composition of the solutions forming them.

In discussing this difference we may recall that the veins are present in the intrusive and flow rocks as well as in the sediments, and 

therefore were later than the main volcanic activity of the district 

(the recent basaltic eruptions excepted).

"Within the intrusive rocks, as indicated by the mineralization of 

the Bradburn tunnel in the intrusive rock of the Antelope Eange, 

occur garnet and magnetite, which point to a relatively high temperature at the time these minerals were formed. In the veins in 

the flow rocks and sediments the minerals are such as are generally 

thought to form under conditions of relatively low temperature and 

pressure.

Moreover, the veins show evidence of a change in the character of 

solutions during the time of formation, namely, the earlier solutions deposited abundant carbonate, which was later partly replaced 

by quartz and adularia, and the latest solutions were apparently rich 

in sulphates.

These facts point to the following order of events: (1) Successive 

beds of lava were poured out, with intervening periods of quiescence 

during which the lavas lost most of their heat. (2) A later event 

in the volcanic history was the intrusion of the monzonitic masses 

with dikes extending into the lavas and more or less fissuring of the 

intruded rock. (3) The outer portions of these intrusive masses 

were crystallized as porphyritic rock, and in the readjustment due 

to cooling and possibly to other forces both the recently intruded 

rock and the overlying flows were further fissured. (4) Along 

these fissures heated solutions rose. Within the intrusive mass they 

were highly heated, probably under considerable pressure, and deposited minerals characteristic of this condition. As they passed into 

the cooler overlying rocks both the temperature and the pressure were 

reduced, and this condition was recorded in the character of the deposits. The solutions seemingly underwent a progressive change in
ORIGIN 63? THE ALUNITE DEPOSIT. 23

composition, first depositing abundant carbonate, later quartz and 

adularia, and finally sulphates.

The origin of these solutions can not be positively determined, 

but the most likely source seems to be the water given off by.the 

crystallization of the magma that formed the intrusive body which 

underlies the lavas.

In this district, as in others where similar deposits have been 

studied, it is apparent that potassium and aluminum minerals were 

more abundantly deposited in the later stages of mineralization 

either the solutions became richer in potassium and aluminum or 

the conditions for deposition of these elements became more favorable. The relative physical conditions under which the quartzadularia veins and the alunite were deposited are not perfectly clear, 

but it seems highly probable that the alunite veins were deposited 

at lower temperature and pressure than the quartz-adularia veins 

and probably represent a later stage when the composition of the 

solutions had undergone a change. This is suggested by the fact 

that the potassium minerals were among the later to be deposited, 

presumably under conditions of less heat and pressure, and these 

potash-rich deposits may well represent the latest stage in the 

deposition of potassium. Moreover, in other districts where the 

occurrence of alunite has been studied the conditions indicate shallow depth and moderate heat and pressure; furthermore, the relative 

rarity of alunite deposits as compared with other veins of the type 

shown in this district may be due to the fact that they form near 

the surface and consequently have only in a few places been preserved. It is evident that when the alunite was formed the solutions were rich in sulphate, and if this deposit is later than the carbonate and quartz-adularia veins, as seems probable, it is to be expected that instances will be found where the sulphate deposits are 

superimposed on the earlier deposits, as the quartz-adularia veins 

are on the earlier carbonate veins.

The source of the potassium and aluminum entering into the deposits has not been positively determined, but certain facts bearing 

on this point may be stated. In general, the potash contained in 

alunite has been thought to have been derived from the alteration 

of the feldspar of the rock in which the deposits occur, and for many 

deposits this is doubtless true. In part, such an origin can be confidently stated for the alunite of the Marysvale deposit, but that it 

holds true for the main vein is not evident.

As already stated, the characteristic alteration of the wall rock 

of veins of this type consists in a progressive leaching of the elements, 

potassium being one of the latest to be removed, but in some places 

potassium also has been leached out. In the wall rock of the alunite
24 ALTJNITE NEAR MABYSVALE, UTAH.

vein near Marysvale, however, alunite appears to be sufficiently abundant to account for all the potassium of the original rock, and it is 

certain that the potassium has not been removed in important amount, 

and therefore the rock immediately adjacent to the vein can not be 

considered as furnishing the potassium for the vein by lateral secretion. In some of the other veins, however, notably that of the Krotki 

iron deposit, in the intrusive rocks of the Antelope Range, practically 

all constituents except silica and iron have been removed and have 

not been deposited near by. This permits the interpretation that a 

part at least of the potassium and aluminum content of the vein may 

have been derived from the wall rock at greater depth where conditions were favorable for solution, the enriched solutions, rising into 

cooler zones, having redeposited these elements. If this is true one 

might expect that if the vein could be traced to the original surface 

the alunite deposit would gradually merge into one carrying other 

salts that were precipitated at still lower temperatures if, indeed, 

alunite did not extend to the surface while more soluble salts were 

carried out on the surface in solution and that on the other hand 

with increasing depth a zone would be reached that was not favorable 

to the deposition of alunite.

That the potassium and aluminum in the veins of this district were 

introduced by the solutions and were not derived directly from the 

wall rock is further indicated by the high potassium and aluminum 

content (as muscovite) of the Deertrail ores; these occur in quartzite 

and limestone, which do not contain notable amounts of potassium 

or aluminum, and consequently both of these elements must have 

been introduced. There seems no reasonable doubt that the mineral 

content of the veins, for the most part at least, was introduced by 

solutions of deep-seated origin.

In this respect the evidence in the Marysvale region agrees with 

that in other districts of the West where Tertiary veins of a similar 

character occur. Lindgren x has already called attention to the similarity of the deposits in the northern part of the district to those 

of the De Lamar deposits of Idaho, and further similarities.are shown 

by the sericitic ores of the Deertrail mine, which seem to resemble 

closely some of the " talcose " ores of the Idaho deposits that carry as 

high as 12.91 per cent 2 of potassa (K2 0). Lindgren concludes 3 

that the main content of the Idaho veins was brought up from depth 

by thermal waters; moreover, he notes that the removal of alumina

1 Lindgren, Waldemar, The Annie Laurie mine, Piute County, Utah: Bull. U. S. Geol. i 

Survey No. 285, 1906, p. 90.

2 Lindgren, Waldemar, The gold and silver veins of Silver City, De Lamar, and other 

mining districts in Idaho: Twentieth Ann. Kept. U. S. Geol. Survey, pt. 3, 1900, p. 171. 

8 Idem, p. 166.
ORIGIN OF THE ALUNITE DEPOSIT. 25

from the wall rock indicates the presence of sulphuric acid in the 

waters, though sulphates do not seem to have been deposited, or if 

they were they have not been preserved. Spurr 1 has concluded that 

the veins in the Tonopah district, Nevada, which contain notable' 

amounts of potassa in the form of adularia and in many respects 

resemble the adularia veins in the Marysvale district, derived their, 

mineral content from heated waters given off by crystallizing 

magmas.

Schrader 2 has described similar deposits in the Black Mountains, 

Mohave County, Ariz., containing notable amounts of potassa in the 

form of adularia, and attributes their origin to hot waters ascending 

through the lavas at the close of igneous activity.

Schrader 3 has also described very similar deposits in the Jarbidge 

district, Elko County, Nev., which contain as high as 11.84 per cent 

of potassa (K,0) in the form of adularia. He concludes that the 

veins were formed by ascending thermal solutions rich in silica, 

aluminum, and potassium.

Similar veins in New Mexico have been attributed by Lindgren, 

Graton, and Gordon 4 to the action of ascending thermal waters, and 

a similar origin has been stated by Umpleby r> for veins carrying some 

adularia in the Eepublic district, Washington. The present writer, 

who has seen the mineral deposits in the Gold Springs and State 

Line districts, Utah, and the adjacent Fay district, Nevada, believes 

that the veins which carry notable amounts of adularia are to be 

attributed to an origin similar to that indicated in the examples cited 

above.

There appears to be a uniformity of opinion, therefore, that the 

veins carrying adularia were deposited by ascending thermal waters 

rich in silica, alumina, and potassa. Nowhere, however, outside of 

the Marysvale district have important alunite deposits associated 

with the adularia veins been recognized.

Of the alunite deposits of which detailed descriptions are available 

the one that shows the closest relation to the type under discussion 

is that at Goldfield, Nev., where alunite occurs as an important primary gangue mineral of gold deposits. As shown in the following 0

1 Spurr, J. E., Geology of the Tonopah mining district, Nevada : Prof. Paper U. S. Geol. 

Survey No. 42, 1905, p. 262.

2 Schrader, P. C., Mineral deposits in the Cerbat Range, Black Mountains, and Grand 

Wash Cliffs. Mohave County, Ariz.: Bull. U. S. Geol. Survey No. 397, 1909, p. 48.

3 Schrader, F. C., A reconnoissance of the Jarbidge, Contact, and Elk Mountain mining 

districts, Elko County, Nev.: Bull. U. S. Geol. Survey No. 497, 1912.

4 Lindgren, Waldemar, Graton, L. C., and Gordon, C. H., The ore deposits of New 

Mexico : Prof. Paper U. S. Geol. Survey No. 68, 1910, p. 71.

6 Umpleby, J. B., Geology and ore deposits of the Republic mining district: Bull. 

Washington Geol. Survey No. 1, 1910, p. 42.
26 ALtTNlTE NEAR MARYSVALE, UTAH.

quotation Eansome x has thoroughly discussed the different methods 

by which the deposit at Goldfield might be formed:

Since the preceding chapters contain an ample presentation of the problem 

now awaiting solution, only a brief recapitulation is needed of some of the 

most significant facts with which an adequate explanation of ore genesis 

must harmonize.

Beyond all question the intimate association of unusually rich gold ores with 

che mineral alunite is the most remarkable feature of the deposits and is the 

one that promises to shed most light on their origin. Alunite is not a common 

mineral, and although it was recognized in small quantity in the oxidized zone 

at Cripple Creek, it is at Goldfield alone, so far as is at present known, that 

it is found with sulphides and tellurides as a characteristic mineral of unoxidized gold ores. The presence of this mineral and the kind of alteration undergone by the rocks containing it prove * * * that the ores were deposited 

from solutions containing sulphuric acid. Whether this acidity was an original 

property of the gold-bearing solutions or whether the solutions, primarily of 

different character, became acidic at the place of precipitation or during their 

journey thither, are questions presently to be considered.

Other chemical and mineralogical features of the ores to be kept in mind 

are the occurrence of telluride and selenide of gold, sulphide of bismuth, and 

compounds of copper, -sulphur, antimony, and arsenic (enargite, famatiuite, 

and golclfieldite), of which the mineral species is not in every case determinable, 

the cryptocrystalline character of the quartz, and the extraordinary concentration of the gold. Due consideration must be given also to the volcanic 

history of the region, the recent age of the deposits, the slight depth at which 

they were formed, and, as a corrollary of these facts, the brief time and the 

short vertical distance available for any secondary concentration that may be 

postulated in connection with erosion.

Attention will first be directed to the question of the source of the sulphuric 

acid, since if it can be satisfactorily answered the other phase of the main 

problem should crystallize clearly about this nucleus.

THE DIRECT VOLCANIC HYPOTHESIS.

That some fumaroles emit sulphur dioxide has long been known. As early 

as 1858 Sainte-Claire Deville and Leblanc 2 found it in gases from Vesuvius 

and other Mediterranean volcanoes. From one fumarole in the crater of 

Vesuvius they collected a gas which proved to contain hydrochloric acid and 

sulphur in the ratio of 86.2 parts of the former to 13.8 parts of the latter, 

together with water vapor and the constituents of ordinary air. They concluded from their investigations that carbon dioxide and sulphur dioxide never 

came simultaneously from the same fumarole. This, however, does not accord 

with the results of some other workers, as is shown by the following table, prepared by F. C. Lincoln,3 which is of theoretic interest from the fact that calcite and alunite occur together at one place in the Goldfield district:

1 Ransome, F. L., The geology and ore deposits of Goldfield, Nev.: Prof. Paper U. S. 

Geol. Survey No. 66, 1909, pp. 189-195.

2 M6moire sur la composition des gaz rejete's par les Events volcaniques de PItalie 

me'ridionale: Annales chim. phys., 3d ser., vol. 52, 1858, p. 45.

3 Econ. Geology, vol. 2, 1907, p. 802.
ORIGIN OF THE ALUNITE, DEPOSIT. 

Piimarole gases containing both GOz and

27

No.

1

?:

3

4

5

fi

7

8

9

in11

1?

Volcano (or locality).

Hekla. ............

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

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

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

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

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

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

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

Spot.

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

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

gios.

and lava stream.

Temperature.

 c.

86

218

360

250

150

115

110

C02 .

93.5

2.44

5.38

4.90

1.42

3.00

3.97

. 23. 40

22.00

59.62

68.5

98.5

S08 .

Trace.

1.54

3.40

2.61

2.25

1.32

Trace.

Trace.

Trace.

12.0

.4

HC1.

0

0

2.14

3.00

1.98

73.80

66.00

27.19

19.4

1.0

Ni.

6.5

81.81

70 1fi

73.48

76.22

73.71

70.88

2.28

9.60

10.99

Oa.

0

14.21

18.46

18.13

17.61

18.04

21.85

.52

2.40

2.20

Authorities: (1) Boussingault, ,T. B., Annales chim. phys., 2d ser., vol. 52, 1833, p. 21. 

(2) Bunsen, R. W., Annales chim. phys., 3d ser., vol. 38, 1853, p. 259. (3) Franco, 

Compt. Rend., vol. 66, 1868, p. 159. (4) Franco, Compt. Rend., vol. 66, 1868, p. 1352. 

(5-7) Franco, Annales chim. phys., 4th ser., vol. 30, 1873, pp. 98-99. (8-10) Fouque". 

P., Compt. Rend., vol. 61, 1865, p. 565. (11-12) Gorceix, H., Compt. Rend., vol. 75, 

1872, p. 270.

Van Hise 1 states that in the gases emitted from fumaroles aud solfataras 

sulphur dioxide is probably next in abundance to steam. This, however, does 

not appear to accord with the testimony of published analyses of volcanic gases. 

F. C. Lincoln,2 on the basis of 50 selected analyses, concludes that, after steam 

and nitrogen (the latter being difficult to rank owing to the possibility of admixture of air), carbon dioxide is the most important gas, followed by hydrogen 

sulphide and sulphur dioxide.

Sulphuric acid or sulphuric anhydride is apparently still less common in 

volcanic emanations than sulphur dioxide. Geikie 8 states that " occasionally, 

also, the production of sulphuric acid is observed at active vents," which probably means merely that the acid is formed superficially by oxidation of sulphur dioxide. In the interesting crater lakes of Taal volcano described by 

R. F. Bacon 4 free sulphuric acid is present in large quantities. It is apparently 

formed, however, by the oxidation of fumarolic sulphur dioxide which bubbles 

up through the boiling water.

On the whole, it appears to be very doubtful whether sulphuric acid or sulphuric anhydride is actually emitted from the deeper part of any volcanic vent. 

There is a strong suggestion, moreover, that the sulphur dioxide which streams 

from some fumaroles is not all of deep-seated origin but may in part be due 

to an admixture of air with the true telluric gases, particularly with hydrogen 

sulphide. Here we are confronted, however, with the difficulty of distinguishing sharply between primary and secondary volcanic products. At what depth, 

for example, must water or oxygen be introduced in order to be classed as a 

primary volcanic product? By magma tic water do we mean only such as has 

been locked in the earth's interior since the planet took its present form, or 

may we mean also water that the magmas have subsequently absorbed in some 

such manner as that advocated by S. Arrhenius? 5

X A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904, p. 491.

2 Magmatic emanations: Econ. Geology, vol. 2, 1907, pp. 261-264.

3 Textbook of geology, vol. 1, 1903, p. 268. 

« Philippine Jour. Sci., vol. 2, 1907, p. 115.

B Zur Physlk des Vulkanismus: Geol. Foreningens Stockholm, Forhandl., vol. 22, 1900, 

pp. 395-419.
28 ALtTNITE NEAR MABYSVALE, UTAH.

May not the water emitted from volcanoes be both niagmatic and meteoric as 

these terms are used by most writers? This is still a vexed question, although 

the available evidence favors the view that meteoric water does not reach the 

source of magmas.1 Granted that the water of volcanic eruptions, however 

introduced or formed, conies mainly from the molten magma, there is no a priori 

difficulty in postulating the emission of oxygen compounds of sulphur, since 

Fouqu6 2 has shown that in some cases the constituent gases of water are dissociated and the liberated oxygen might under some circumstances unite with 

sulphur. As a matter of fact, however, the oxides of sulphur are not nearly so 

common or abundant, and when they do occur are not so clearly of deep derivation as is hydrogen sulphide.

There is evidence also of the deep-seated formation of sulphuric acid in the 

presence of sulphates, such as barite and celestite,3 as primary minerals in 

some veins. Recently, too, Lindgren * has called attention to the occurrence of 

anhydrite as a primary mineral with tourmaline and chalcopyrite at the Cactus 

mine in the Frisco district, Utah. The presence of the minerals hauynite 

[(Na2Ca) a (NaSO-4Al)Al2 (SiO4)3] and noselite [Na^NaSO^AlJAMSiOOs] in 

phonolitic rocks proves that under some circumstances sulphur trioxide may be 

present in molten magmas and consequently may exist in magmatic solutions. 

There are, however, no phonolitic rocks known at Goldfield.

While these occurrences are to be regarded as favoring the view that sulphuric acid can form at volcanic centers, their testimony, as regards importance 

in ore deposition, is opposed by the absence of sulphates from contact metamorphic deposits and of sulphuric acid from most hot springs. Springs carrying sulphuric acid are, it is true, not unknown. The water of a hot-acid spring 

in the so-called geysers of Sonoma County, Gal., according to an analysis by 

Thomas Price, contains 145 grains of free sulphuric acid per gallon.0 Other 

springs at the same locality contain smaller quantities of the same acid. All 

these waters, however, are saturated with hydrogen sulphide, and it is possible 

that the sulphuric acid may have been formed by the oxidation of the sulphydric 

acid within the zone penetrated by surface waters. Hot sulphuric-acid springs 

occur also in the Coso Range, Inyo County, Gal., accompanied by deposits of 

sulphur containing hydrogen sulphide.8 Similar acid springs carrying hydrogen 

sulphide issue from sulphur deposits near Maverick Springs, El Paso County,

Tex. The water from one of these, according to E. M. Skeats,7 contains 136 

parts per 100,000, or 79.08 grains per gallon, of free sulphuric acid. W. T. Lee 

has described a similar occurrence at Sulphurdale, Utah.8 Analyses of 11 other 

springs' waters containing less sulphuric acid than those above mentioned are 

given by F. W. Clarke.9

The chemical activity of free sulphuric acid in spring water would, of course, 

lead to the rapid formation of sulphates during the upward course of the water 

and to consequent neutralization of the free acid. But there is a limit to such

*For a recent discussion of this problem see Chamberlin, R. T., The gases in rocks: 

Pub. Carnegie Inst. Washington No. 106, 1908, p. 69.

2 Santorin et ses Eruptions, Paris, 1879, p. 230.

3 Lindgren, Waldemar, and Ransome, F. L., Geology and gold deposits of the Cripple 

Creek district, Colorado : Prof. Paper U. S. Geol. Survey No. 54, 1906, pp. 220-221.

4 Oral communication before the Geological Society of Washington: Abstract in 

Science, new ser., vol. 28, 1908, p. 933. 

"Andersen, Wlnslow, Mineral springs of California, San Francisco, 1892, p. 150.

6 Idem, p. 254.

7 Bull. Univ. Texas Min. Survey No. 2, 1902, p. 34.

8 Water resources of Beaver Valley, Utah: Water-Supply Paper U. S. Geol. Survey No. 

217, 1908, pp. 19-20. 

0 Data of geochemistry : Bull. U. S. Geol. Survey No. 330, 1908, pp. 155-157.
ORIGIN OF THE ALTJNTTE DEPOSIT. 29

rapid neutralization, and in persistent and copious springs it might be expected 

that some free acid could in most cases be brought to the surface were it commonly generated below. Furthermore, if sulphuric acid were formed in any 

considerable quantity at great depth during volcanic activity we should expect 

to find alunite a more common constituent of rocks which have been uncovered 

by erosion than experience indicates. Moreover, it is questionable whether 

waters rich in sulphuric acid would be efficient carriers of gold, sulphides, and 

tellurides. It is probable that they would precipitate these constituents from 

the alkali sulphide solutions, of which the solvent efficiency has been repeatedly 

shown by experiment 1 and by geologic evidence.

In view of these considerations, and of others presently to be brought forward, the hypothesis, suggested with some favor in a preliminary paper,2 that 

the ore-depositing solutions may have come from below already charged with 

sulphuric acid, has been abandoned.

HYPOTHESIS OF DERIVATION OF THE SULPHURIC ACID FROM THE OXIDATION OF

PYHITE.

The hypothesis that the alunitization of the rocks at Goldfleld was effected 

by cold sulphate solutions percolating generally downward from masses of 

oxidizing sulphides, principally pyrite, has some facts in its favor. The small 

quantity of impure alunite found at Cripple Creek was undoubtedly formed 

in this manner, and observations indicate that a part of the alunite at Goldfield, namely, some of the soft varieties which fill interstices in the partly 

oxidized ore, may have been, if not originated, at least dissolved and redeposited during oxidation. According to De Launay 8 the alunite at the classic 

locality of Tolfa is the product of such solutions acting upon a particular 

feldspathic trachyte. The formation of alunite by cold percolating solutions 

probably requires these to be more strongly acid than is necessary for the 

production of kaolinite.

The intimate association of the alunite with kaolinite at Goldfield has a 

bearing on the problem. The origin of this mineral has been the subject of 

much recent discussion,* the general trend of which is to emphasize the connection between kaolinization and weathering. Lindgren 0 has recently intimated that although he himself formerly referred to the mineral as characteristic of certain classes of veins, kaolinite should not be considered as a gangue 

mineral of any class of ore deposits except those formed under the influence 

of oxidation. In a subsequent paragraph he somewhat modified this statement 

by the expression of belief that " kaolin is rarely formed by alkaline hot water 

at any considerable depth below the surface." The preponderant weight of 

careful observations made during the last few years is unquestionably on the 

side of the thesis thus moderately stated; and the occurrence of kaolinite at 

Goldfield, where the intimate association of this mineral with the alunite, 

gold, sulphides, tellurides, and sulphautimonites, as determined by microscopical 

work, shows that all were formed at the same time by one general process, 

is an additional point against what has been called the direct volcanic 

hypothesis.

1 As regards tellurides, see Lindgren, Waldemar, and Ransome, F. L., Geology and ore 

deposits of the Cripple Creek district, Colorado: Prof. Paper U. S. Geol. Survey No. 54, 

1906, pp. 223-224.

2 The association of alunite with gold in the Goldfleld district, Nevada: Econ. Geology, 

vol. 2, 1907, p. 688.

3 La me"talloge"nie de 1'Italie: Cong. ge"ol. intern., Mexico, 1906, vol. 1, 1907, p. 681.

4 See especially Zeitschr. prakt. Geologie, 1907 and 1908.

B The relation of ore deposition to physical conditions: Econ. Geology, vol. 2, 1907, 

p. 120.
30 ALUNITE NEAR MARYSVALE, UTAH.

Much kaolin originally described by various authors as formed by the solutions which first brought up the ores associated with it has later been proved 

to have resulted from oxidizing processes, it being one of the most characteristic products of the action of percolating weakly acid solutions upon aluminous 

rocks. The kaolin at Cripple Creek is a good example. Much so-called primary 

or pneumatolytic kaolin, moreover, has been shown to be sericite, and some is 

perhaps alunite.

On the other hand, these facts seem scarcely to warrant the total elimination 

of kaolinite from the list of gangue minerals found in ore deposits, the connection of which with oxidation is at least not obvious, and which are certainly 

not affected by ordinary weathering. The mineral occurs as an original constituent of some of the ores of the San Juan Mountains, Colorado,1 and W. H. 

Weed 3 has described it as a product of the metasomatic action of the waters 

of Boulder Hot Springs, Montana, upon granite. Kaolinization has also been 

noted by Bela von Inkey a in the dacitic country rock of the Nagyag veins, the 

material being afterward investigated by F. Kollbeck,4 whose analysis indicates 

a mixture of kaolinite and sericite.

The principal objections to the view that the alunitization at Goldfield is 

connected with the oxidation of older pyritic ores are based largely on what appears to be the quantitative insufficiency of the proposed explanation. No such 

available primary masses of sulphides are known, and study in the district 

has failed to bring to light any bodies of sulphides that are distinctly older 

than the ores and that are not accompanied by alunite. There is no evidence 

yet found which indicates the superposition of a distinctly younger phase of 

deposition characterized by the formation of alunite upon an older phase not 

associated with that mineral.

The mines of Goldfield are still comparatively shallow, but they have penetrated about 500 feet below the bottom of the weathered ores, and if the alunitization were the result of ordinary weathering it is likely that secondary products would somewhere have been found distinctly imposed upon earlier 

nonalunitic material. It is probable that at a depth greater than that now 

attained alunite will become less abundant, but the change will, it is believed, 

be gradual, and there is nothing to indicate that it will exhibit such a definite 

relation to the general ground-water level as might fairly be expected under 

the hypothesis now under consideration.

The alunitization of the rocks * * * is very extensive, and is by no 

means confined to the immediate vicinity of known ore bodies. Except in 

the zone of superficial oxidation the alunite is crystallized with pyrite and 

consequently has not formed under conditions involving the destruction of 

this sulphide in the zone now accessible. To account for the alunitization 

by the oxidation of pyrite would require the assumption that the material 

stripped from the district by erosion .was much more heavily pyritized than 

the rocks at present visible. The thickness of this vanished overburden, as 

has been shown, can scarcely have exceeded 1,000 feet (305 meters), and 

probably was very much less. Moreover, the period available for alunitization 

was geologically very brief, since the process had already taken place when 

the Pozo formation was laid down. We are thus confronted by the contrast 

of a process remarkable for the extent and intensity of its action with condi1 Ransome, F. L., Economic geology of the Silverton quadrangle, Colorado: Bull. TJ. S. 

Geol. Survey No. 182, 1901, p. 73.

3 Mineral-vein formation at Boulder Hot Springs, Montana: Twenty-first Ann. Rept. 

U. S. Geol. Survey, pt. 2, 1900, p. 253.

3 Nagyag und seine Erzlagerstatten, Budapest, 1885, p. 143.

* Untersuchungen fiber, die Zersetzung des Quarztrachyts neben Goldersgangen von 

Nagyag: Oesterr. Zeitschr. f. Berg- und Huttenwesen, vol. 36, 1888, pp. 25-27.
ORIGIN OF THE ALUNITE DEPOSIT. 31

lions which, if not markedly unfavorable, were at least not such as would 

be expected to produce the observed effects under the present hypothesis. The 

remarkable concentration of the gold and associated minerals in these deposits 

appears to be out of all proportion to any leaching action possible within the 

the time and distance available. This discrepancy will, it is believed, become 

more marked When the character and genesis of the metallic minerals of the 

ores are considered, as they will be in connection with the next hypothesis.

HYPOTHESIS OF SIMULTANEOUS SOLFATABISM AND OXIDATION.

The third hypothesis to be tested postulates that the ore constituents were 

brought up in hot solutions charged with hydrogen sulphide, a little carbon 

dioxide, and probably also with some alkali sulphides; that the hydrogen sulphide was oxidized at and near the surface to sulphuric acid, which percolated 

down through the warm rocks to mingle with the uprising currents carrying 

sulphydric acid; and that the precipitation of the richest ores took place in 

the zone where the two kinds of solutions mingled and as a consequence of such 

mingling. As Van Hise 1 has pointed out, the chemical reactions of weathering

and of solfataric action are not so different as might be supposed, and this 

process differs from that of the second hypothesis chiefly in greater intensity 

of action and in the smaller demands that it makes on time and erosion. The 

hypothesis differs from the first one considered mainly in that the sulphuric 

acid acted as the precipitant rather than as the carrier of the ore constituents 

which came up in sulphide solutions. This latter view has the initial advantage 

of being in much better accord with all that has been learned of the chemistry 

of natural sulphide deposition than is the first supposition. Any explanation 

of the origin of the Goldfield deposits which calls for natural solvents radically 

different from those which carried the carefully studied ores of Tonopah, the 

Comstock, Grass Valley, Cripple Creek, and many other districts in this country 

and abroad is burdened at the outset with presumptive improbability.

In accordance with the third hypothesis the hot ascending waters carried 

abundant hydrogen sulphide, as shown by the extensive change to pyrite of the 

iron originally present in the dacite and other rocks as a constituent of magnetite and silicates. This change was not confined to the rocks now alunitized 

but extended outward to what has been called the propylitic aureole of alteration. The experiments of Becker 2 and Doelter,3 supported by studies of metasomatically altered wall rock in various districts, suggest that the sulphur of the 

original solutions was in part combined with or accompanied by sodium and 

potassium. The changes in the dacite investigated in Chapter XIV, notwithstanding the development of the potassium and sodium bearing mineral alunite, 

do not show any addition of alkalies to the original rock, but such negative 

evidence does not prove that no alkali sulphides were present in the primary 

solutions.

They may have been largely oxidized to sulphates and carried away to 

accumulate in the playa deposits of the region, just as is happening at the 

present day at Alkali Spring. If so, it is to be expected that at greater depth 

than is now reached at Goldfield the feldspars of the rocks are extensively 

sericitized with some addition of alkalies. That the ore-bearing solutions 

contained carbon dioxide is indicated by the alteration of calcium-bearing

*A treatise on metamorphlsm : Mon. U. S. Geol. Survey, vol. 47, 1904, p. 494.

2 Geology of the quicksilver deposits of the Pacific slope : Mon. U. S. Geol. Survey, vol. 

13, 1888, chap. 15.

3 Blnige Versuche uber die Losllchkeit der Minerallen: Tschermak's Min. u. petr. 

Mitth., vol. 11, 1859, p. 319.
32 ALUNITE NEAR MARYSVALE, UTAH.

silicates to calcite in the propylitic zone. It is not to be supposed that calcite 

would form abundantly in rocks soaked with sulphuric acid. It does occur, 

however, with alunite in rhyolite on the east slope of Vindicator Mountain, 

and this association of minerals is probably the result of local conditions 

which retained under pressure and fixed in combination the carbon dioxide 

that otherwise would have escaped in the presence of the acid solutions necessary for the production of alunite. Such local conditions of pressure are more 

readily conceivable in connection with hot uprising waters than under the 

circumstances of ordinary weathering.

In addition to sulphydric and carbonic acids the solutions carried the following, either as compounds or in ionized condition: Gold, silver, copper, zinc, 

lead, bismuth, antimony, arsenic, tellurium, and selenium. They probably 

contained also some iron and silicia, although the study of rock alteration 

recorded in Chapter XIV shows subtraction, not addition, of these constituents 

to the wall rock. On the other hand, the actual ledge matter contains more 

silica and pyrite than was in the original rock. How much of this excess 

was contributed by the uprising solutions directly and how much was merely 

concentrated from the surrounding country rock is not determinable. There 

was probably some direct addition, however, from deep-seated sources in the 

immediate vicinity of the fissures.

It has been shown that the fissuring of the district was very complex and 

irregular, affording innumerable devious channels for the passage of solutions. 

Thus the hot solutions presumably reached the surface at many places, and 

this distribution of the outflow must have been far more favorable to oxidation of the hydrogen sulphide to sulphuric acid and to the subsequent activity 

of the latter than if the uprising waters had flowed from a single vent. There 

is reason to believe that the climate at the time the ores were deposited was 

comparatively arid. It is likely, therefore, that the mineral-bearing solutions 

upon reaching the surface were not only oxidized but were concentrated by 

evaporation as they flowed over the surface or percolated down through the 

rocks. The sulphuric waters as they penetrated downward must have exerted 

a strong leaching action on the superficial rocks similar to that observable 

at Sulphur Bank, Cal., at the present day, where basalt has been altered to 

spongy masses of snowy silica by the removal of its basic constituents. At

moderate depth the acidic descending solutions met uprising solutions charged 

with hydrogen sulphide and ore constituents and mingled with them in a zone 

characterized by the presence of sulphydric, sulphurous, and sulphuric acids 

and by the simultaneous development of alunite and sulphides. The vertical 

range of this zone must have been considerable probably 1,000 feet (305 

meters) or more. The mixing of the solutions may have been effected partly 

by differences in density between the hot ascending currents charged with 

gases and the cooler descending waters, partly by convection, partly by diffusion, and perhaps partly by osmotic action. The sulphuric acid solutions 

would in general have greater power of penetrating the substance of the 

country rock than would the silicia and the in part colloidal bases of the 

uprising solutions.1 It is to be remembered also that the rocks at the time 

of ore deposition were as a whole hard and brittle, had been recently fractured, 

and were much more generally permeable than at present, when much of the 

country rock, softened by alteration, is incompetent to maintain open fissures. 

Evidently, with the process once initiated, the waters reaching the surface 

would no longer represent the original ore-bearing solutions, but would be

1 See Sullivan, E. C., Experiments on the separation of the constituents of a solution 

by filtration through a mineral fiber: Econ. Geology, vol. 3, 1908, pp. 750-756.
OBIGIN OF THE ALUNITE, DEPOSIT. 33

mixtures of these with sulphate waters and would contain various constituents 

abstracted from the rocks during alunitization. * * *

At no time in their history were the depositing solutions, if we may judge 

from their work, strong solvents for silica, and the quantity of this constituent 

transported by them was small. The ledges, it is true, are siliceous, but most 

of the quartz was derived from the rock now altered to ledge matter and from 

the alunitized rock in the vicinity. Some silica doubtless came up with the 

solutions, but had these been very .siliceous it is to be expected that they would 

have filled all interstices with solid crystalline vein quartz of the usual kind. 

On the contrary, the quartz at Goldfield is flinty or cryptocrystalline and 

occurs either as a metasomatic mineral replacing the country roqk or as porous 

vuggy fillings formed by the accumulation of successive thin crusts, the process 

having rarely gone far enough to produce a solid mass of quartz. In this respect the deposits at Goldfield resemble those at Cripple Creek. It is possible 

that the crystallinity of vein quartz does not depend wholly or chiefly .on the 

supply of silica available but is largely a function of pressure and temperature. 

At one end of the series may be the coarsely crystalline quartz of the pegmatite 

dikes or veins; at the other end. the cryptocrystalline quartz of deposits formed 

close to the surface. If so, the character of the quartz at Goldfield is to be 

added to the other evidence in favor of superficial origin of the deposits.

It is believed that the process outlined as the third hypothesis best explains 

the abundant formation of alunite with subordinate diaspore and the intimate 

association of these minerals with the sulphide ores and especially with the 

pyrite in the altered rock which surrounds the ores. This explanation of the 

genesis of the alunite is in accord with the experiments of Sainte-Claire Deville,1 who produced the mineral artificially by subjecting, for several months, 

fragments of volcanic rock, .suspended in water, to a stream of hydrogen sulphide 

mixed with air. By providing an efficient precipitant (sulphuric acid), supplied continuously to a definite zone traversed by the uprising metalliferous 

solutions, the hypothesis appears to account well for the remarkable concentration of the gold and associated constituents in this zone. As already mentioned, 

it is difficult to harmonize the extent and intensity of the alunitization with the 

hypothesis of oxidation of lean deposits during erosion. It is still more difficult to explain, by such secondary enrichment the unusual concentration of the 

gold with so much tellurium and bismuth as are present in the Goldfield ores.

Many of the important minerals of epigenetic deposits, as is well shown in 

the useful tables compiled by W. Lindgren a and W. H. Emmons,8 can be formed 

under different conditions and by solutions of diverse origin. The individual 

minerals that can be accepted with confidence as characteristic of a single 

bathymetric zone and of a single mode of genesis .are certainly very few. Taken 

altogether, the minerals of the Goldfield ores suggest deposition at moderate 

or slight depth. They are not, however, as a group characteristic of what is 

ordinarily understood as secondary enrichment. The tellurides particularly, in 

view of the recent investigation at Cripple Creek,* are mpre indicative of 

deposition from -uprising hot solutions than of enrichment by cold descending 

waters.

1 De I'altSration, par Toie naturelle ,et artificielle, des rocbes sillcatSes, au nioyen de 

1'aclde sulfbyhdrlque et de la vapeur d'eau: Compt. Bend., vol. 35, 1852, pp. 261-264.

2 The relations of ore deposition to physical conditions: Bcon. Geology, vol. 2, 1907, 

p. 125.

3 A. genetic classification of minerals: Econ. Geology, vol. 3, 1908, pp. 618-622.

4 Lindgren, Waldemar, and Eansome, F. L., Geology and gold deposits of the Cripple 

Creek district, Colorado: Prof. Paper U. S. Geol. Survey No. 54, 1906, p. 204, and 

Chapter XI.

21510° Bull, 5U^-12 3
34 ALUNITE NEAR MARYSVALE, UTAH.

In applying these theories of formation to the Marysvale occurrence the theory of formation as the result of oxidation of pyrite 

may be eliminated, it would seem, owing to the fact that oxidation 

has extended but a short distance below the surface, even the shallow pits disclosing rock containing unoxidized pyrite, and this rock 

practically free from oxidation contains abundant alunite. Moreover, it is doubtful if the pyrite present in the rock is sufficient to 

account for the sulphur present in the alunite. Furthermore, if the 

alunite has been produced by the action of surface solutions it is 

logical to expect similar deposits in all the veins in the volcanic 

rocks that contain pyrite; but while pyrite is a characteristic mineral 

in the alteration of the wall rock of the veins in volcanic rocks, 

alunite has not been recognized in them, and although it may be 

present it certainly is not abundant.

The hypothesis that solutions containing hydrogen sulphide rose 

to the surface and were oxidized to sulphuric acid that* descended 

and reacted with the potassium-aluminum silicates of the rocks, 

which Kansome finds to best explain the deposits at Goldfield, does 

not appear to be in accordance with the observed facts of occurrence 

of the Marysvale deposit. In such a mode of origin it would be expected that the solutions in their downward migration would be 

likely to disseminate and there would be little tendency to form 

large and distinct veins of the mineral. Moreover, the potassium 

and aluminum of the deposit would be derived from the altered rock, 

but, as already noted, the contents of the Marysvale vein are believed to have been introduced.

The reasons for rejecting the volcanic theory as accounting for 

the Goldfield deposit do not seem entirely applicable to the occurrence 

at Marysvale. In the first place, both the alumina and the potassa

content of the Goldfield alunite appear to have been derived from the 

alteration of feldspar of the country rock and to have migrated but 

little. At Marysvale this is doubtless true of the alunite occurring 

in the wall rock adjacent to the vein, but apparently not true of the 

vein material, for, as stated elsewhere, there appears to have been 

little leaching of alumina and potassa from the wall rock, and an 

outside source must be sought. Moreover, the alunite veins at Marysvale are not known to carry sulphides or allied minerals, though 

pyrite is present in the wall rock, and sulphides, sulpharsenides, and 

selenides occur in the other veins of the district that are thought to 

be allied to the alunite veins and are possibly closely associated with 

the alunite in the " Edna Geyser " prospects.

That sulphates were present in some of the solutions forming the 

veins of the district is indicated by the fact that barite is rather
OEIGIN OF THE ALUNITE DEPOSIT. 35

abundant in the Lucky Boy deposit and is present to some extent in 

other mines. Moreover, the Horn Silver deposit at Frisco, Beaver 

County, which has been studied by the writer and shows some resemblances to the Marysvale deposits, contains barite in relative abundance as a primary gangue mineral. It may be noted also that at 

Sulphurdale, 20 miles north of Beaver, Lee x has observed a mineral 

spring whose waters contain abundant sulphate and free sulphuric 

acid, but he considers the acid to be the result of the oxidation of 

hydrogen sulphide (H=S).

Hayes 2 has described deposits of alum in Grant County, N. Mex. 

He considers the sulphuric acid that formed the deposits to be of 

volcanic origin.

Spurr 3 has described deposits of potassium alum (kaolinite) near 

Silver Peakj Esmeralda County, Nev., which he considers as being 

formed " by a combination of the steam and the sulphuric acid 

emitted from the solfataras with the potash and aluminum contained in the rhyolite."

The sulphur deposits with which alunite is associated near Humboldt House, Nev., described by Adams,4 are thought to have a similar 

origin.

It may further be noted that deposits of somewhat different character in Shasta County, Cal., contain abundant barite and anhydrite 

(the anhydrite largely altered to gypsum). Graton 5 considers that 

these minerals have been deposited directly from ascending thermal 

solutions of volcanic origin.

Lindgren ° has described the occurrence of abundant sulphate minerals in the primary ores of the Cactus mine, Beaver County, Utah. 

He suggests that " during the later part of the mineralization the 

anhydrite was precipitated by a reaction between ascending solutions 

of sodium sulphate and descending solutions containing calcium carbonate."

From the occurrences cited above, together with those discussed by 

Ransome, it would seem that there are no inherent reasons for considering that the sulphate content of the alunite deposit may not

1 Lee, W. T., Water resources of Beaver Valley, Utah : Water-Supply Paper U. S. Geol. 

Survey No. 217, 1908, p. 19.

3 Hayes, C. W., The Gila River alum deposits, New Mexico : Bull. U. S. Geol. Survey 

No. 315, 1907, p. 215.

3 Spurr, J. E., Alum deposits near Sliver Peak, Esmeralda County, Nev.: Bull. U. S. 

Geol. Survey No. 225, 1904, p. 501.

* Adams, G. I., The Rabbit Hole sulphur mines near Humboldt House, Nev.: Bull. U. S. 

Geol. Survey No. 225, 1904, p. 500.

B Graton, L. C., The occurrence of copper In Shasta County, Cal.: Bull. U. S. Geol. 

Survey No. 430, 1910, pp. 102, 103.

6 Lindgren, Waldemar, Anhydrite as a gangue mineral: Boon. Geology, vol. 5, 1910, 

p. 522.
36 ALUNITE NEAR MABYSVALE, UTAH.

have been contained in the ascending solutions. On the other hand, 

the alunite deposits are believed to have been formed near the surface and therefore the possibility of the sulphuric acid having been 

produced by the oxidation of hydrogen sulphide or other sulphur 

compounds can not be eliminated.

The evidence in the Marysvale district, however, indicates that 

the materials constituting the veins were deposited by ascending 

solutions and that these solutions brought in the constituents of the 

alunite. At just what stage the sulphuric acid may have been formed 

can not now be positively stated, but it seems most natural to suppose 

that it was a part of the original solutions and that the potassium 

and aluminum were in part original in the solution and in part dissolved from the walls of the fissure at greater depth.

The apparent absence of metallic minerals in the alunite veins and 

their presence in the associated veins are worthy of note and might 

be thought to indicate that the alunite veins of the district constitute 

a separate class of deposits. Such a supposition, however, does not 

appear to be well founded, for the carbonate veins of this and similar 

districts ordinarily carry low, if any, metal values, though there can 

be little doubt that they are most closely allied to the quartz and 

quartz-adularia veins that followed and in many cases partly or 

wholly replaced them. The lack of sulphide and allied metallic 

minerals in these earlier veins is nearly as marked as in the supposedly later sulphate veins, a fact which permits the interpretation 

that the earliest carbonate solutions did not carry important metal 

values. Kansome states that " it is questionable whether waters rich 

in sulphuric acid would be efficient earners of gold, sulphides, and 

tellurides. It is probable that they would precipitate these constituents from the alkali sulphide solutions, of which the solvent 

efficiency has been repeatedly shown by experiment and by geologic 

evidence." The Marysvale deposit seems to support this view and to 

indicate that solutions as rich in sulphates as those depositing the 

alunite did not carry sulphides in solution. In fact, a review of the 

alunite occurrences described gives the impression that the solutions 

which formed or deposited this mineral were not suited to the carrying of metallic values, that the Goldfield deposit is the exception 

rather than the rule, and that ordinarily alunite may be looked upon 

as an unfavorable rather than a favorable indication of metallic 

values. This statement, of course, would not apply to alunite that 

has formed as a secondary mineral, resulting from the oxidation of 

sulphide ores, or to a deposit formed by ascending solutions and superimposed on an earlier metallic deposit, in which case it would have 

had no bearing on the original deposition. It may be noted, however, 

that, so far as the writer has observed^ where alunite has been formed
PROBABLE EXTENSION OF THE ALUNITE IN DEPTH. 37

by descending solutions in considerable bodies showing some migration it is remarkably free from metallic contents.

The deposition of metallic minerals in the Marysvale district seems 

to have occupied a rather sharply defined period between the formation of the earlier carbonate veins on the one hand and the later 

sulphate veins on the other.

PROBABLE EXTENSION OF THE ALTTNITE IN DEPTH.

While definite data making possible a statement as to the probable 

extension in depth of a deposit of this character are highly desirable, 

they are unfortunately not at hand. So far as known to the writer 

no deposit of this type has been worked to a sufficient depth to determine this point in even an individual case, and certainly enough

data to warrant a general conclusion are not available, However,

some facts bearing on this important point may be stated. It is 

assumed as a general rule that a fissure which persists over a long 

distance horizontally will also show persistence in depth. As the 

vein at Marysvale shows a very considerable horizontal extension it 

may reasonably be expected to extend to a depth correspondingly 

great. It may be noted, however, that some veins of the general type 

shown in this district outcrop strongly and yet nearly or quite pinch 

out at no great depth, the downward extension being represented by 

a zone of altered rock with stringers of vein material, while othtrs 

continue downward to very considerable depths with no notable 

change in size.

It is worthy of consideration also that although the vein may persist in depth there may be a change in its mineralogic character. 

The occurrences of alunite indicate that this mineral does not form 

at great depth under conditions of high heat and pressure. It doubtless does form, however, through a vertical range of at least several 

hundred feet, and if the present outcrop of a vein is near the original 

surface it may be expected to have a considerable downward extension without notable change. If, however, many hundred feet have 

been eroded from the original outcrop the downward extension of 

the vein from the present surface will be correspondingly less, and 

in a region where there has been considerable erosion since mineralization occurred veins of this character may have been entirely removed.

The amount of erosion that has taken place in the Marysvale district can not be positively stated, tliough it is believed to have been 

not great. The outcrop of the alunite vein described is among the 

highest of the well-defined outcrops in the district, though nearly 

2,000 feet below the summit of the highest peak. Moreover, it is 

probable that the rhyolitic beds which form the higher areas never
38 ALtTfflTE NEAR MAKYSVALE, UTAH.

extended over this part of the district with the same thickness that 

they show to the northwest. It is therefore reasonable to suppose 

that the erosion of the veins in the district has not been very extensive, and that in consequence the alunite vein is likely to persist downward to some considerable depth.

The observed outcrops of alunite in the district vary in elevation 

from about 9,900 feet to over 11,000 feet, and while it is not safe to 

assume that the veins outcropping at the higher elevation will persist to the depth indicated by the lower, nevertheless the outcrops 

show that the mineral has formed over a very considerable vertical 

range.

KNOWN OCCURRENCES OF ALUNITE IN THE UNITED

STATES.

In papers by members of the United States Geological Survey 

numerous occurrences of alunite have been described, and from these 

the following notes concerning alunite deposits in the United States 

are principally taken.

The first extensive deposit of alunite to be noted in this country 

was that of the Rosita Hills, Colorado, the following description of 

which has been furnished by Dr. Whitman Cross:

* ALUNITE DEPOSITS OF ROSITA HILLS, COLORADO.

By WHITMAN CROSS.

About 25 miles southwest of Canon City, Colo., on the eastern slope 

of the Wet Mountain Valley, is a group of low volcanic hills named 

after the mining town of Rosita, which is situated in a little valley 

on their eastern border. In the Rosita Hills are two localities the 

rocks of which contain notable amounts of the hydrous sulphate of 

alumina and potash called alunite, which is of interest as a possible 

source of potash* salts. The geology of the Rosita Hills was worked 

out more than 20 years ago, and a report with geologic map dealing 

with this area was published in 1896.1 Although no estimate was 

made of the amount of alunite rock present in these occurrences, it 

is known to be considerable, but the material is somewhat impure.

A branch line of the Denver & Rio Grande Railroad reaches Silver 

Cliff. The wagon road from Silver Cliff to Rosita passes near one 

of the localities to be described, and the other is also easily reached. 

The deposits occur in the hills Imown as Democrat Hill and Mount 

Robinson.

1 Cross, Whitman, Geology of Silver Cliff and the Rosita Hills, Colorado: Seventeenth 

Ann. Kept. U. S. Geol. Survey, pt. 2, 1896, pp. 263-403. Bmmons, S. P., the Mines of 

Custer County, Colo.: Idem, pp. 405-472.
ALUNITE IN THE UNITED STATES. 39 

DEMOCRAT HILL.

Democrat Hill is in fact merely the prominent end of Democrat 

Ridge, which lies between Leavenworth and Good Hope gulches. 

The locality is about 5 miles east of Silver Cliff and little more than 

a mile west of Eosita. The wagon road between these places crosses 

Leavenworth Gulch less than half a mile to the south.

The hill rises about 350 feet above the junction of Leavenworth 

and Good Hope gulches at its southern base. The upper part of 

the hill is characterized by rough cliffs and projecting knobs of a 

massive rock resembling granite, as seen at a little distance. This 

is the quartz-alunite rock to be described. Below the cliffs great talus 

heaps obscure the rock in place.

At the south base of the hill are two tunnels, formerly and perhaps still known as the Ben Eaton and the Democrat. These run in

a northerly direction under the summit of the hill, following two. 

parallel trachyte dikes, now greatly altered to kaolin and quartz. A 

raise from one of these tunnels reaches the surface, following the soft 

decomposition product of the dike rock. Several crosscuts from these 

tunnels also assist in revealing the inner constitution of the hill.

The alteration of the rhyolite, producing alunite, was probably 

accomplished by solfataric vapors or by waters containing such 

vapors in solution. The alteration apparently took place before the 

intrusion of the trachyte dikes, for these do not exhibit the alteration to alunite, although trachyte is rich in potash feldspar suitable 

for the production of alunite by the agents that attacked the rhyolite.

The material of the upper part of Democrat Hill is a hard, somewhat porous rock, of light-pinkish or whitish color, weathering in 

roughly rounded masses very much resembling those often seen in 

granite exposures. The rock itself has a strong resemblance to some 

granites, for its most prominent constituent is a mineral looking 

much like orthoclase, with a perfect cleavage and a pearly luster, 

occurring in irregular grains or rude tablets, many of which are 

one-eighth to one-fourth inch in diameter. The angular spaces 

between these tablets are filled by quartz grains, usually smaller 

than the alunite tablets. The quartz grains are also scattered 

through the mass of the alunite and there is a much larger amount 

of quartz in the rock than one would estimate from casual examination.

The cavities common in the rock are lined by rude crystals of 

alunite and quartz and many of them contain some kaolin. Kaolin 

is also found between quartz and alunite in the mass of the rock. 

A part of the rock is fine grained, though apparently as rich in 

alunite as the coarser-grained portion. The microscopic study of 

this rock shows the mineral occurring in tablets to possess the optical and other physical properties of alunite.
40 ALUNITE NEAR MAE.YSVALE, UTAH.

An analysis of the coarse granite-like rock, by L. G. Eakins, gave 

this result:

Analysis of quartz-alivnite rock from Democrat Hill.

SiOj..... .........................................................................

AljOg.................. ...........................................................

KSO..... .........................................................................

Na2O ............................................................................

H20..... ..................................... ......... ........................

S03 -. .............................................................................

Per cent.

65.94

12.95

2.32

1.19

4.47

12.47

.55

99.89

Molecular 

ratio.

127 -3.26

251 , i. 19J-1.13

248 =6.36

156 =4.00

The sulphuric acid, alumina, alkalies, and water are present in 

very nearly the ratio 4:3:1:6 required by the formula of alunite, 

(KNa) 2O.3Al2O3 .4S03 .6H2 0. The analyzed rock therefore consists practically of quartz two-thirds and alunite one-third. But 

of the sulphate nearly one-half is the soda compound corresponding 

to the pure potash of the mineral to which the name alunite is given. 

As a matter of fact the pure potash mineral is rare.

No examination has been made to determine whether the alunite 

of Democrat Hill is throughout so rich in soda as the sample 

analyzed.

As to the amount of the alunite rock in Democrat Hill, nothing 

very definite can be said, without further examination. The upper 

250 feet of the hill, with a diameter of about 800 to 1,000 feet on the 

9,000-foot contour level, is undoubtedly chiefly made up of the aluniterich rock. In the tunnels and crosscuts below no such material was 

seen, but as the workings were driven mainly in the kaolinized 

trachyte they do not give conclusive evidence as to the presence or 

absence of alunite rock in the lower part of the hill. The fact is, 

however, that the partly altered rhyolite noted in a few surface outcrops and in the prospect workings indicates that possibly the alunitization was extensive only in the upper levels of the hill, which 

may have been near the surface at the time of eruption.

MOUNT ROBINSON.

The highest point in the Kosita Hills, known as Mount Robinson, 

is about a mile northwest of Rosita, and reaches an altitude of 9,723 

feet. It is a hill of irregular shape, with a gentle slope to the north 

and a jagged crest line with a cliff or abrupt face to the south. This 

irregular crest is due to a broad dike of rhyolite, which has been 

greatly altered, the principal product being a quartz-alunite rock. 

In some places the mass consists chiefly of quartz and diaspore 

(alumina hydrate); in others kaolin is abundant.
ALUNITE IN THE UNITED STATES. 41

The alunite and diaspore bearing rocks with quartz as the dominant mineral are so resistant to weathering that the portion of the dike 

exhibiting the most thorough alteration stands out above the softer 

neighboring rocks. The dike has a length of about a mile and a 

width in places of 300 feet. It is greatly altered throughout its extent, but the more extreme forms, such as the quartz-alunite and 

quartz-diaspore rocks, are best developed near the summit of the 

mountain. As in the case of Democrat Hill, no definite statements 

can now be given as to the amount of the quartz-alunite rock present.

The quartz-alunite rock of the crest of the mountain near its east 

end has the composition given in column 1 of the table below. The 

quartz-diaspore rock from a prospect pit just west of the summit of 

Mount Eobinson has the composition shown in column 2. Both 

analyses were made by L. G. Eakins.

Analyses of rocks from Mount RoMnson.

Si02 . ...............................................................................

TiOs .................. ..............................................................

AliO........................................................ .........................

CaO........ ........................................................................

KuO..... ...........................................................................

NajO.............. .................................................................

H2O ................................................................................

S08 .. .............................................................................:..

PiO.................................................................................

1

' 69. 67

13.72

.07

2.44

. .34

4.73

9.27

100.24

2

76.22

.11

19.45

Trace.

Trace

3.84

.29

.13

100.02

The analysis of column 1 corresponds to 24 per cent of alunite. a 

very little kaolinite, and the balance quartz. The mass having the 

composition given in column 2 consists almost entirely of quartz and 

diaspore.

As the analysis shows, the alunite of Mount Robinson seems relatively much richer in potash than that of Democrat Hill, but without 

further tests it is unwarrantable to assume that the analyses of 

samples from either locality are representative of the masses.

RICO MOUNTAINS, COLORADO.

Cross 1 later gave a description of an extensive occurrence of alunite 

rock in the Rico Mountains, Colorado, from which the following is 

quoted:

Solfataric action. The alteration of the porphyry of Calico Peak into a 

rock consisting largely of alunite, a hydrous sulphate of alumina and the alkalies, * * * can be explained only as the result of the attack of sulphurous 

agents, and from the circumstances of occurrence there can be no doubt that 

the action is to be attributed to solfataric emanations of the Rico eruptive center 

in the period of waning igneous activity.

1 Cross, Whitman, and Spencer, A. C., Geology of the Rico Mountains, Colorado: 

Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, pp. 92-94.
42 ALUttlTE NEAR MARYSVALE, UTAH.

The cone of Calico Peak is made up of a light-colored rock which is either 

nearly white or stained various shades of red and yellow, often in brilliant 

hues. The rock has either a marked porphyritic structure or is highly 

brecciated. No contacts were seen, owing to the extensive talus slopes which 

conceal it on all sides. * * * The alteration is so extreme that it is not 

certain that all of the rock belongs to a single mass, though it is apparently of 

that character.

The rock of the greater part of the peak was plainly porphyritic and contained many large feldspar crystals, a.nd from this fact it is supposed that the 

rock was originally of the type of monzonite porphyry with large phenocrysts 

of glassy orthoclase, which has been described above and which occurs in fresh 

form only in the vicinity of Calico Peak in long dikes. * * * In its present 

condition the rock of the peak contains no dark silicates; the former feldspar 

phenocrysts are represented either by a mass of white kaolin or by a granular 

mass of an early colorless mineral, ordinarily too fine grained for recognition. 

The groundmass is grayish in tone and may be fine or coarse grained. In some 

places the rock has become largely a porous quartzitic mass. The room of the 

larger feldspar crystals is seldom completely filled by the alteration product, 

which usually appears as an aggregate of rude plates, a definite crystal outline 

being, however, rare. These plates are rough crystals of alunite, the basal 

plane predominating and being bordered by the low hemihedral pyramid commonly developed in this mineral. No good crystals of polished faces were found.

At several places the freshly fractured rock was found to exhibit a very distinct yellow color in the porous areas representing feldspar phenocrysts, the 

color being due to native sulphur in minute round crystalline particles.

The more massive rock found in many places consists of a coarse-grained 

aggregate of irregular rude tablets with kaolin filling the interstices. Small 

veins of uniform fine grain also traverse the rock locally, the character of the 

material being unrecognizable megascopically.

The general character of the Calico Peak rock was recognized by the writer 

from its resemblance to the quartz-alunite rock found by him in the Rosita 

Hills, Custer County, Colo. In the latter case the material was formed by 

solfataric action upon rhyolite in a small volcanic center,1 and the alunite 

made up a much smaller part of the rock than at Calico Peak. But fairly 

good Crystals were found in the Rosita Hills, associated with diaspore.

Microscopial study of the Calico Peak rocks confirms fully the identification 

of the principal substance of the Calico Peak njass as alunite and shows that 

kaolin and quartz are the only other minerals of importance present in the 

specimens examined. Diaspore has not been certainly identified in these rocks, 

and the chemical analyses given below show that there can be but very little 

present.

In the table on the following page are presented quantitative analyses of two 

.of the Calico Peak specimens and one of a rock from the Rosita Hills. I is 

the analysis of a coarse-grained rock almost resembling a pearly-gray marble 

from the west slope of Calico Peak. II is a fine-grained white vein on the 

south ridge of the peak. Ill is an alunite-quartz rock from Mount Robinson, 

in the Rosita Hills, republished from the descriptions cited above. Analyses I 

and II are by George Steiger and III was made by L. G. Eakins, all in the 

laboratory of the Geological Survey. In the column following each analysis 

is given the molecular ratio.

1 Cross, Whitman, Geology of Silver Cliff and the Rosita Hills, Colorado : Seventeenth 

Ann. Kept. U. S. Geol. Survey, pt. 2, 1896, pp. 314-319; On alunite and diaspore from 

the Rosita Hills, Colorado: Am. Jour. Sci., 3d ser., vol. 41, 1891, pp. 466-475.
ALUNITE IN THE UNITED STATES. 

Analyses of alunite rocks.

43

Constituent.

Si03........................... ............

&0a ......................... ..............

AljOs......... ............................

CaO........... ............................

Na2 0.... ..................................

K2O..... ..................................

BsO below 110°. . ..........................

HjO above 110°. . .........................

2

*A.

35.24

a 42. 35

.08

4.02

3.27

.13

11.99

99.62

[

42

440

415

65

35

600

I

1.79

37.92

o37.66

.38

2.12

6.77

.06

13.03

99.73

I

30

474

370

34

72

724

n

69.67

9.27

13.72

.07

.34

2.44

} 4.73

100.24

[I

114

134

O£

263

..........

0 Contains T102 and P20B, if present.

From the molecular ratios of I and II it appears that the substances analyzed consisted mainly of alunite with a little kaolin. The alkalies are a 

little below the required amounts for the sulphuric acid found, but if the losses 

of the analyses be assumed to be soda, and the lime bo supposed to replace 

alkali in alunite, the analyses are very satisfactory. It is notable that the

vein alunite (II) is much richer in KsO than the replaced rock (I).

The alunite-bearing rock of the Rosita Hills contains a great deal of quartz, 

but the Calico Peak mass is, in some parts at least, nearly pure alunite.

SILVER-TON, COLO.

Alunite has been described from the National Belle mine, near 

Silverton, Colo., by Hurlbut x and by Eansome,2 the following quotation being from Eansome's report:

As shown by E. B. Hurlbut, however, not all of the white crystalline powder 

found in the National Belle is kaolin, but alunite also occurs in nearly identical form, clearly associated with enargite. Hurlbut's analysis is here quoted:

Analysis of alunite from National Belle mine. 

S03 __________________________________ 38. 93 

A1,O3 _________________________________ 39.03 

K,O_________________________- _____________ 4. 26

Na 2O_________________________ ______ 4.41 

H,O____________________________________ 13. 35

Insoluble .50

100.48

CRIPPLE CREEK, COLO.

Alunite has also been noted at Cripple Creek by Lindgren and 

Ransome,3 who say:

Alunite was identified from level 5 of the Last Dollar mine. It follows the 

vein fissure as a rather hard and compact, fine-grained white substance, looking 

very much like kaolin. It was also noted from the adjoining Modoc mine and 

probably occurs at many other places. It seems to be confined to the oxidized 

zone.

1 Hurlbut, E. B., On alunite from Red Mountain, Ouray County, Colo.: Am. Jour. Sci., 

3d ser., vol. 48, 1894, pp. 130-131.

2 Ransome, F. L., A report on the economic geology of the Silverton quadrangle, Colo. : 

Bull. U. S. Geol. Survey No. 182, 1901, p. 235.

8 Lindgren, Waldemar, and Ransome, F. L., Geology and gold deposits of the Cripple 

Creek district, Colorado: Prof. Paper U. S. Geol. Survey No. 54, 1906, p. 125.
44 ALtJNITE NEAR MARYSVALE, UTAH.

GOLDFIELD, NEV.

The most extensive deposit of alunite yet discovered in Nevada is 

that at Goldfield, whicKhas been described by Ransome x as follows:

The hexagonal (rhombohedral) hydrous sulphate of potassium (K2O. 

3Al2O3.4SOs.6H2O),2 known as alunite or, in massive form, as alumstone, is 

so abundant in the Goldfield district and so generally associated with the 

intense alteration o'f the rocks in the vicinity of the ore bodies that it must be 

regarded as one of the most characteristic minerals of the gold deposits. It 

is not limited, however, to the immediate vicinity of the ore deposits, but 

* * * occurs in practically all of the Morena rhyolite, in the rhyolite about 

Vindicator Mountain, in the dacite and andesite of Preble Mountain, and elsewhere.

Alunite occurs at Goldfield chiefly in two forms (1) as a soft white or 

slightly pink material, closely resembling kaolinite and like that mineral filling 

cavities in ledge matter or ore, and (2) as an integral constituent of altered 

rocks.

In the earthy, massive form alunite is very abundant in the January and 

Combination mines, where it plays much the same part in the sulphide zone 

that kaolin does in the oxidized zone. It has been found in considerable 

quantity also in the Lone Star mine and in leases on the Commonwealth claims, 

about 2 miles east of Goldfield, and is probably not entirely absent from any 

of the ore bodies in dacite.

In the Combination mine much of the interstitial material between the 

nodules of rich native gold and sulphide ore near the 230-foot level is alunite. 

As a rule, the pure massive alunite can be distinguished from the pure kaolinite 

by a faint pink tint. The crystallinity of alimite, too, is usually greater than 

that of kaolinite, and examination with a hand lens shows tiny crystal faces 

with pearly luster. The texture of kaolinite, on the other hand, is normally 

too fine to show crystal planes, even under the microscope, and with a hand 

lens it appears uniformly dull and earthy. Inasmuch as alunite is a sulphate, 

its distinction from kaolinite or sericite may readily be made by simple chemical 

tests.

While alunite is not entirely absent from the completely oxidized ores, most

of the soft white material found filling crevices in the weathered zone has 

proved to be kaolinite. Kaolinite and limonite often occur together, but the 

association of alunite with an oxide of iron is comparatively rare. Kaolinite 

and alunite occur together, however, in some of the oxidized ore of the Combination mine. The material is pulverulent and slightly yellow, the color being 

perhaps due to the presence of some jarosite, a mineral isomorphous with 

alunite but differing from the latter in containing iron instead of aluminum.8 

The massive aluuite in many places, particularly in the Combination mine, 

contains abundant small, embedded crystals of pyrite.

A somewhat unusual occurrence of massive alunite was observed in 1905 in 

a 95-foot shaft on the Commonwealth No. 3 lease, about 2 miles (3.2 kilometers) east of Goldfield. The country rock is silicified latite. This has been 

irregularly fissured and the fissures and irregular interstices are filled with

1 Ransome, F. L., Geology and ore deposits of Goldfield, Nev.: Prof. Paper U. S. Geol. 

Survey No. 66, 1909, pp.. 129-133.

2 Or, as written by Hillebrand and Penfield in Bull. U. S. Geol. Survey No. 262, 1905, 

p. 38, K2 [A1(OH) 2] 8 [SO4 ]4.

3 See Hillebrand, W. F., and Penfield, S. L., Some additions to the alunite-jarosite 

group of minerals: Bull. U. S. Geol. Survey No. 262, 1905, pp. 32-41.
ALUNITE IF THE UNITED STATES. 45

faintly pink alunite, within which are embedded spherical nodules of-snowy 

kaolinite ranging in size from that of a pea to that of a small marble.

In the Dixie mine, on the west slope of Preble Mountain, massive alunite, 

which in some places is very compact, with almost the texture and hardness 

of some varieties of opal, is. abundant on the 110-foot level, filling fissures and 

irregular crevices in porous silicified dacite.

The most coarsely crystalline form of the mineral found is in an irregular 

veinlet, from a half to 3 inches (1.2 to 7.6 centimeters) in width, in altered 

dacite on the northeast slope of Preble Mountain. This material, as exposed at 

the surface, is a buff-colored aggregate of platy, irregular crystals and resembles some forms of coarse dolomite.

The greatest interest attaches to the alunite as a rock constituent. Attention 

was first directed to its occurrence in this form by the finding of small nests 

or crystalline aggregates, up to 5 millimeters in diameter, of a pale-pink 

mineral in a greatly altered, nearly white rock exposed on the east shoulder 

of Vindicator Mountain, about 2 miles northeast of the town of Goldfield. The 

rock contains quartz phenocrysts and was probably originally a rhyolite. The 

microscope shows that the feldspar phenocrysts, as well as the groundmass, 

have been altered to. an aggregate of quartz and alunite, the optical determination of the latter mineral being checked by chemical tests in the United 

States Geological Survey laboratory by Mr. George Steiger. With the alunite 

is associated a subordinate quantity of diaspore.

Microscopical study of the bleached altered rocks of the district soon showed 

that alunite is present in nearly all of them. The rhyolite forming the summit 

of Columbia Mountain, just north of the towns of Goldfield and Columbia, has 

been altered to a quartz-alunite rock, the alunite with some quartz forming 

pseudoinorphs after the feldspar phenocrysts, which probably were originally 

orthoclase. Alunite is very abundant in the altered andesite and dacite of 

Preble Mountain and vicinity and is present, down to the deepest workings, in 

practically all of the altered dacite which forms the country rock of the 

Mohawk Combination, Florence, January, Bed Top, Jumbo, and other mines 

near Goldfield. * * * It is also abundant directly associated with the 

sulphide ores in these mines, and is in many cases intercrystallized with 

pyrite. * * *

As a constituent of altered rocks in the Goldfield district, the alunite does 

not have complete crystal form. It is usually tabular in habit, the basal pinacoid being well developed and the rhombohedral faces being absent or indistinct. In thin section * * * it shows distinct cleavage parallel to the 

basal pinacoid and parallel extinction with reference to the cleavage. The 

birefringence is apparently rather stronger than the difference 7 a=0.018 

given in the table of Michel Levy and Lacroix,1 the interference colors in 

good thin sections being mostly yellow but rising in places to red or blue 

of the first order. The mineral gives a positive uniaxial interference figure 

in sections showing no cleavage. The index of. refraction is .distinctly higher 

than the balsam of the slide. (1.54), that given for the alunite of Tolfa 

being o>=1.572 and e=1.592.s

In some thin sections alunite might, on superficial examination, be mistaken 

for sericite. The latter mineral, however, has higher double refraction with 

the color mottl.ing characteristic. of the micas, has finer cleavage, and Is op1 Les min^raux des roches, Paris, 1888. Also Iddiags, J. P., Rock minerals, New 

York and London, 1006. - 

* Iddings, J. P., op. cit., p. 476*
46 ALUNITE NEAR MARYSVALE, UTAH.

tically negative. The difference in optical orientation is most quickly detected 

by the use of gypsum plate or quartz wedge. In alunite the higher colors 

appear when the. basal cleavage is parallel to the direction of greatest elasticity 

in the plate or wedge. In sericite the higher colors occur in the transverse 

position.

The minerals most commonly associated with the alunite as constituents of 

the altered rocks are quartz and "pyrite. Some of the andesite on the south 

slope of Preble Mountain has been altered to a nearly white, fine-granular aggregate consisting almost wholly of quartz and alunite. The altered dacite forming the country rock of the Goldfield group of mines consists of quartz, alunite, 

pyrite, and kaolinite in various proportions. In many varieties of the rock 

these minerals are accompanied by small quantities of diaspore.

The gold, famatinite, bismuthinite, and other constituents of the richest ore 

are generally inclosed in quartz, not alunite. The latter mineral, however, 

frequently occurs in the same microscopical section less than a millimeter distant from the metallic minerals. In ore from the Jumbo-Extension mine, near 

Diamondfield, alunite and a telluride of gold are crystallized together, as was 

found by the microscopical study of thin sections.

Calcite and alunite do not ordinarily occur together, but macrocrystalline 

calcite, a little sericite, and probably some kaolinite have been found associated with much larger crystals of alunite in an altered rhyolite from the 

east slope of Vindicator Mountain. The molecular ratio of soda to potash in 

this alunite, as determined by Dr. Hillebrand, is as 40 to 45. It is possible, however, that the result obtained for potash may be high in consequence of some 

decomposition of the sericite by the sulphuric acid used to dissolve the alunite.

The occurrence together of alunite and calcite, apparently developed simultaneously, shows that the alteration took place under conditions which did 

not permit the free escape of carbon dioxide. It is scarcely conceivable, for 

example, that calcite could form in the presence of sulphuric acid percolating 

down from an overlying deposit of oxidizing pyrite.

As shown above, part of the alunite contains considerable sodium, and the 

calculations of the mineralogical compositions of some of the altered rocks 

from their chemical analyses * * * indicate that most of the mineral 

occurring in the Goldfield district is not the pure potash salt but is intermediate 

between alunite proper and natroalunite.1

Alunite differing in habit from most of the mineral thus far found near 

Goldfield occurs in the Hat lease on the Blue Bull Mining Co.'s ground, 1$ 

miles (1.4 kilometers) east of Goldfield. The country rock here is andesite. This 

has been locally brecciated and the fragments are silicified. Between the fragments, and cementing them together, is much bright-red hematite, which in the 

croppings is partly changed to limonite. The workings when visited were only 

about 50 feet (15 meters) deep and the hematite extends at least to that depth. 

. Occurring as irregular bunches and streaks in this hematitic breccia is much 

soft fine-grained material of light-gray color with irregular reddish-gray bands. 

In texture this material resembles a fine sandstone. It is firm but can be 

crumbled between the fingers and gives a reddish streak when struck with a 

pick.

Under the microscope the powdered material proves to be made up of small, 

sharply bounded colorless crystals, the largest being less than 0.03 millimeter 

in diameter. The crystals are apparently octahedral but in reality are probably combinations of a rhombohedron and basal pinacoid. They are doubly 

refracting and can not, therefore, belong to the isometric system.

* H'illtettrand, W. F., and Feftfi'eld', 8. I/., op. dfcv p. 3?8.
ALUNITE IN THE UNITED STATES. 47

Chemical tests by Mr. W. T. Schaller show the presence of alkalies and sulphuric acid, and the mineral is without much doubt alunite, natroalunite, or 

an intermediate variety of this isomorphous group. The crystals are associated 

with microscopic rosettes of hematite, the latter giving the red streak when 

the material is scratched. Such ore as had been sacked for shipment at the 

time of visit consisted mainly of this alunitic material.

The mineral is also abundant, with sulphur in altered rhyolitic pumice, near 

Cuprite, 12 miles south of Goldfleld.

As alunite is still a comparatively rare mineral, as it has not been recognized 

hitherto as an important mineral in ore deposits, and as its presence with the 

rich ores at Goldfield suggests problems of great interest connected with the 

genesis of epigenetic ores, some reference to other occurrences and to opinions 

held as to the origin of the mineral may not be amiss.

Alunite was first noted at Tolfa, near Korne, where it was used as early as 

the fifteenth century for the manufacture of potassium alum (KaO.ALOs. 

4S03.24I-LO).1 This salt, containing 2 parts less of A1208> with 18 parts more 

of water, is obtained from the alunite by roasting and lixiviation. The mineral

is found also on some of the islands of the. Grecian Archipelago, near Muszay 

in Hungary, on Mount Dore in France, and in a few other localities in Europe, 

as well as with the opal of Qu'eretaro, in Mexico. In the United States it has 

been described in the Rosita Hills,2 on Calico Peak, near Rico,3 in the National 

Belle mine near Silverton,4 and at Cripple Creek,5 all in Colorado. It occurs 

also at Tres Cerritos, Mariposa County, Cal.° W. Lindgren 7 found aluuite in 

the Ryerson mine, near Morenci, Ariz., associated with pyrite and kaolin. He 

regarded it as formed by the attack of descending sulphuric acid solutions upon 

sericite away from free oxygen. In Nevada alunite has been described by G. I. 

Adams 8 as associated with sulphur and cinnabar at the Rabbit Hole mines, and 

by S. H. Ball as in. a silicified rhyolite of the Cactus Range, east of Goldfield.0

Until recently geologists and mineralogists have regarded alunite as formed 

exclusively by the attack of sulphurous fumarolic vapors upon feldspathic 

rocks.10 At Cripple Creek, however, the mineral was found only in the oxidized 

ore and, like the kaolinite of that district, is probably secondary with reference 

to the original telluride ores. De Launay,u moreover, has recently maintained

1 For the latest account of this celebrated locality, with a bibliography, see De Lavmay, 

L.i La metalloge'nie de 1'Italie: Tenth Geol. Cong., Mexico, 1906, pp. 125-132. [See also 

pp. 51-55 of the present bulletin.]

2 Cross, Whitman, Geology of Silver Cliff and the Rosita Hills, Colorado: Seventeenth 

Ann. Kept. U. S. Geol. Survey, pt. 2, 1896, pp. 52-56; also Am. Jour. Sci., 3d ser., vol. 41, 

1891, pp. 466-475.

a Cross, Whitman, and Spencer, A. C., The geology of the Rico Mountains, Colorado: 

Twenty-first Ann. Rept. U. S. Geol. Survey, pt. 2, 1900, pp. 92-94.

4 Hurlbut, E. B., On alunite from Red Mountain, Ouray County, Colorado: Am. Jour. 

Sci., 3d ser., vol. 48, 1894, pp. 130-131. Also Ransome, F. L., A report on the economic 

geology of the Silverton quadrangle, Colorado: Bull. U. S. Geol. Survey No. 182, 1901.

5 Lindgren, Waldemar, and Ransome, F. L., Geology and gold deposits of the Cripple 

Creek district, Colorado: Prof. Paper U. S. Geol. Survey No. 54, 1906, p. 125.

B Turner, H. W., Rocks and minerals from California: Am. .Jour. Sol-, 4th ser., vol. 5, 

1898, pp. 424-426.

7 The copper deposits of the Clifton-Morenci district, Arizona: Prof. Paper U. S. Geol. 

Survey No. 43, 1905, pp. 119-120, 169, 193-194.

8 Adams, G. I., The Rabbit Hole sulphur mines near Humboldt House, Nev.: Bull. U. S. 

Geol. Survey No. 225, 1894, p. 500.

0 Ball, S. H., A geologis reconnaissance in southwestern Nevada and eastern California: 

Bull. U. S. Geol. Survey No. 308, 1907, p. 48i

10 Cross, Whitman, Geology of Silver Cliff and the Rosita Hills, Colorado: Seventeenth 

Ann. Rept. U. S. Geol. Survey, pt. 2, 1896, p. 314. Cross, Whitman, and Spencer, A. C., 

Geology of the Rico Mountains, Colorado: Twenty-first Ann. Rept. U. S. Geol. Survey, 

pt. 2, 1900, p. 33. Iddings, J. P., Eock mtoerate, New York, 1906* p. 476. Blllebrand, 

W. F., ana PSntel'd, & D., Op. iSfc, p. 4U pOP.-cut'"
48 ALUNITE NEAR MARYSVALE, UTAH.

with cogency that the alunite of Tolfa is probably not, as commonly supposed, a . 

solfataric product, but is due to the action of percolating surface water, charged 

with sulphuric acid by the oxidation of pyrite, upon a particularly feldspathic 

facies of the trachyte. It is accordingly no longer justifiable to regard the 

occurrence of alunite as proof of former fumarolic activity. The mineral may 

form under very different sets of conditions, and it is necessary in seeking the 

explanation of any occurrence of it to keep alternative hypotheses in mind.

In all four of the Colorado localities the alunite occurs in regions which 

contain ore deposits. In the Rosita Hills and in the Rico and Silverton districts 

it is apparently not a product of superficial oxidation. No close kinship between 

this mineral and the ores, however, has been shown, although it was doubtless 

recognized by all the workers in those districts that there might be some genetic 

relation between the metallic sulphides and the volcanism of which the sporadic 

solfataric metamorphism of feldspathic rocks to quartz-alunite aggregates was 

one manifestation. It is worth noting in this connection that the indexes 

of two of the best and most recent works 1 on ore deposits contain no reference 

to alunite, showing that the mineral has not been commonly recognized as one 

intimately associated with ores. Neither is it mentioned, so far as I am aware, 

in C. R. Van Rise's work on metamorphism.2 J. H. L. Vogt,3 however, in discussing metasomatic vein processes, has remarked: " I would mention also the 

formation of alumstone, quartz-alunite rocks, quartz-diaspore rocks, etc., and 

also the formation of bauxites, etc. But I do not know that these changes 

have been anywhere observed in genetic relation with ore veins."

MISCELLANEOUS OCCURRENCES IN NEVADA.

Ball 4 has noted the occurrence of alunite in silicified rhyolite in 

the Cactus Eange east of Goldfield. Adams 5 has described the 

mineral associated with sulphur deposits near Humboldt House as 

follows:

In the cavities of the rock formations carrying sulphur deposits there is 

found a considerable amount .of white pulverulent material, which on chemical 

examination proves to be alunite. This is hydrous sulphate of aluminum 

and potash, a mineral which is thought to be formed in many cases by the 

reaction of sulphurous vapors on rocks, especially on feldspars that carry 

aluminum and potash. It usually occurs at places where solfataric action 

is known to have taken place, and the fact that alunite is found at the Rabbit 

Hole sulphur mines may be regarded as supplementary proof of the mode of 

origin of the sulphur. Alunite, when it occurs in sufficient quantities, may 

be used as the source of alum, its chemical composition being similar to kaolinite, 

or native alum.

Hill 6 has described alunite as occurring in highly altered rocks 

about 22 miles southeast of Las Vegas, Nev. He considers the min1 Beck, Richard, Lehre von den Erzlagerstatten, Berlin, 1901. Stelzner, A. W., and 

Bergeat, A., Die Erzlagerstatten, Leipzig, 1904-1906.

2 A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904.

3 Problems in the geology of ore deposits: Trans. Am. Inst. Min. Eng., vol. 31, 1902, 

p. 150.

* Ball, S. H., A geologic reconnaissance In southwestern Nevada and eastern California: 

Bull. U. S. Geol. Survey No. 308, 1907, p. 48.

5 Adams, G. I., The Rabbit Hole sulphur mines, near Humboldt House, Nev.: Bull. 

U. S. Geol. Survey No. 225, 1904, p. 500.

6 Hill, E. T., Camp Alunite; a new Nevada gold district: Eng. and Min. Jour., vol. 86, 

1908, PP. 1203i-1208.
ALUNITE IN THE UNITED STATES. 49

eral as the result of the alteration of the rocks by " hot ascending 

acid volcanic mineralized vapors."

TRES CERRITOS, CALIFORNIA.

Turner1 has described an occurrence of alunite at Tres Cerritos, 

Mariposa County, Cal., as follows :

Southwest of Indian Gulch, in Mai'ipofea, County, Cal., are three sharp buttes 

known as the Tres Cerritos. The original material of these buttes appears to 

have been chiefly meta-augite andesite tuffs (augite-porphyrite tuffs) and clay 

slate. The Tres Cerritos lie immediately east of a considerable area of clay 

slates which are pretty certainly of Jurassic age. They are supposed to belong 

to the Mariposa formation. Not fat west of the buttes by the road to Merced 

these slates have been metamorphosed into typical chiastolite schists by a 

granitic rock.

The. rocks of the Tres Cerritos have been subjected to solfataric action and 

their angular outline is due to the hardness of the altered rocks. The larger

portion of these metamorphosed rocks are light brown in color, highly siliceous, 

resembling quartzite megascopically.

The southeast butte, which was examined with the most care, is composed 

chiefly of a greenstone schist which is a dynamometamorphic form of the metaaugite andesite tuff. This contains layers of vein quartz, associated with which 

is pyrophyllite in considerable masses crystallized in beautiful stellate forms. 

The much decomposed and rufety schists in the creek at the west base of the 

butte strike about 60° west of north and dip at an angle of 80°. At one point 

about due west of the butte the schists are covered with an efflorescence. Some 

of this was collected arid examined by Dr. H. N. Stokes in the laboratory of the 

United States Geological Survey, who reported that the efflorescence is composed of hydrated sodium and magnesium s^phates with a little chloride. In 

the interior of this efflorescence are grains of calcium sulphate.

The quartzite-like rock under the microscope is seen to be made up chiefly 

of grains of quartz afad a positive uniaxial mineral of greater relief than the 

quartz, extinguishing parallel to the cleavage and having bright interference 

colors. Dr. Hillebratid made a chemical examination of this rock and came to 

the conclusion that tile unknown mineral might be alunite.

Ch&tnical cwialysis of alwvite No. 870 8. N.

SiO2 2. 64 

.40

Am- ______________ 38. 05 

Fe2O3 ________________ . 23 

FeO _. __________ Not looked for. 

MnO ______ ' ________ None. 

CaO ________________ _ . 55 

BaO ___________ Not looked for. 

MgO _____ __ __ Trace.

K2O ____________ 4.48 

Na2 0 _ ____________ 2. 78 

PoOs __ Trace. 

C02 ___________ None. 

H2 0 100° -___________ None. 

H20100°+ __________ 11.92 

SO3 -________________ 38. 50

99.55

To make this more certain, a quantity of the rock was powdered and the 

alunite-like mineral separated by means of the Thoulet solution. The specific 

gravity of the mineral is 2.78, as determined with the Westphal balance by

1 Turner, H. W., Rocks and minerals from California: Am. Jour. Scl., 4th ser., 

vol. 5, 1898. pp. 424-125.

21510° Bull. 511 12 4
50 ALUNITE NEAR MARYSVALE, UTAH.

grains suspended in Thoulet solution. Some of the material was heavier than 

this, but this greater specific gravity was undoubtedly due to inclusions of a 

brownish-red mineral in minute grains without crystal outlines. These grains 

are too minute for satisfactory determination with the microscope, but a 

quantitative test of some that were separated from the rock, made by Mr. 

William Valentine, shows that the mineral is rich in titanium. The mineral 

does not resemble titanite in color, at least-such titanite as ordinarily is found 

in granitic rocks. It may be brookite, but, as before noted, occurs in somewhat 

rounded forms and not in the small tabular crystals said to be characteristic of 

brookite. Possibly the mineral is rutile.

An analysis of the alunite has been made by Mr. William Valentine. It is 

probable that the titanic oxide in this analysis was obtained from some of the 

minute grains of the titanium mineral above noted. As the material was 

sensibly pure, the analysis may be regarded as representing its composition 

after deducting the titanic oxide.

Alunite has not been previously found in California so far as known.

CLIFTON-MORENCI DISTRICT, ARIZONA.

The occurrence of alunite in the Clifton-Morenci district, Arizona, 

is described by Lindgren x as follows:

Alunite (K20.3A1203.4SO5.6H2O). This white and inconspicuous sulphate of 

potassium and aluminum was found filling a narrow seam on a contact between 

shale and porphyry in the main adit of the Ryerson mine at Morenci, where 

it forms a white earthy mass not unlike kaolin.

It is also found in some altered porphyries of the same mine associated with 

pyrite and kaolin. It occurs here as microscopic rhombohedral crystals, showing quadratic or hexagonal sections, as grains or irregular ma.sses and as 

fibrous aggregates. The birefringence is of medium strength, the colors at most 

reaching pale yellow. The index of refraction is low.

Developments since the study of these deposits by Lindgren have 

shown alunite to be a more abundant mineral than appeared at that 

time. Alunite has been observed by the writer in the Bisbee district, 

Arizona, where its occurrence seems to be similar to that at Morenci.

Some analyses of the material made for the geologic department 

of the Copper Queen mine show it to be relatively pure alkali aluminum sulphate, though in some of the specimens analyzed sodium 

(Na2 0) was relatively abundant.

BEAVER COUNTY, UTAH.

In Utah, in addition to the occurrence at Marysvale described in 

this paper, alunite has been noted in the Horn Silver mine, Beaver 

County, where it has apparently resulted from the action of sulphuric 

acid, derived from the oxidation of sulphides, on the feldspar of 

the volcanic rocks in which the ores occur. In the upper part of the 

deposit it forms a rather persistent layer on the footwall of the vein, 

varying from a few inches to 18 inches in thickness. It is a white 

kaolin-like material that can be readily powered in the fingers and is 

so fine grained that even between the teeth no grit can be felt in it.

1 Lindgren, Waldemar, The copper deposits of the Clifton-Morenci district, Arizona: 

Prof. Paper U. S. Geol. Survey No. 43, 1905, pp. 119-120.
ALUNITE NEAR MARYSVALE, UTAH. 51

FOREIGN OCCURRENCES OF ALUNITE.

Alunite is reported from a number of foreign localities, among 

which may be mentioned the well-known occurrence at Tolfa, near 

Civita Vecchia, about 35 miles northwest of Eome, and the deposits 

near the village of Bullah Delah, in the county of Gloucester, New 

South Wales; near Smyrna, in Turkey; at La Solfatara, near Naples, 

and at Montioni, Tuscany, in Italy; at Puy de Garcey, Breuil, and on 

Mount Dore, in the Auvergne, France; in Sicily; on the islands of 

Milo, Volcano, and Santorin (Thira), in the Grecian Archipelago; at 

Muszyna and at another locality in Hungary; and near Hadji-Khan, 

Bokhara. Alunite occurs also with the opal and hyalite of Queretaro, in Mexico; and alunite or closely allied minerals are found 

at several localities in Spain, .especially near Benahabux, in the 

province of Almeria.

TOLFA, ITALY.

The Tolfa deposits have been worked for four. centuries and are 

probably the best known. A discussion concerning the origin of 

these deposits is given by De Launay,1 a translation of a part of 

whose paper is appended:

The only deposits worked" in the region of Tolfa are veins of alunite 

deposits, therefore, of a very special type. But I shall endeavor to show that 

these aluuites are in reality a particular case of superficial alteration of 

pyritic veins included in alkaline feldspathic rock. It is therefore desirable 

to assign these deposits of alunite to their proper place in the metallogeny of 

the region of Civita Vecchia, by describing briefly the other complex sulphurbearing veins which are present.

The region of% Tolfa is formed chiefly of Eocene strata, above which have 

been poured out the trachytes of Allumiere, forming a triangular massif of about 

8 or 9 kilometers on the side and overlain, in turn, on the east side, by the 

gypsiferous clays of the upper Miocene. Along the whole south side of the 

trachytic massif, which does not itself appear to have taken part in the phenomena, but at a certain distance from it, the Eocene has undergone an intense 

metamorphism, which shows itself in the limestones by crystalline banks, with 

garnet, wollastonite, epidote, etc., analogous to those which surround the isle 

of Elba, the granitic rocks of Mount Capanne, and in the schists by siliceous 

layers. At the same time, by a connected reaction, veins of pyrite, more or less 

altered, sometimes accompanied by other sulphides (galena at Cava del Piombo, 

etc.), are abundant and their alteration accompanied by substitution has often 

given place in the midst of the limestones to stocks of sesquioxide of iron, 

which extend to the southwest in the direction of Civita Vecchia almost to the 

classic thermal springs, the baths of Trajan.

The most important of these stocks, those of Roccaccia, Plan Ceraso, Edificio 

del Ferro, etc., are, by a phenomenon already seen many times in this study,

1 De Launay, L., La me'talloge'nie de 1'Italie: Compt. Rend. Tenth Internat. Geol. Cong., 

Mexico, pt. 1, 1907, pp. 679-686. De Launay cites the following papers: Gites me'talliferes, t. 2, pp. 607-612." Klitsche de la Grange, Le trachiti della Tolfa e le .formaztonl 

alumlnifere; Sulle miniere di ferro de la Tolfa, Roma, 262 pp., 4°, 1881 et 1882. Lotti 

Brcvl considerazioni sulla trachite de la Tolfa: Tree. verb. Soc. Tosc., V. 1886. Lotti, I 

giacimenti metalllferi della Tolfa: Rassegna mlnerarla, t. 13, Dec. 11, 1900,
52 ALUNITE NEAR MABYSVALE, UTAH.

concentrated at the contact of limestones and the schists altered by superficial 

action. They consist at their outcrop of limonite and hematite visibly substituted for the limestone; going down, pyrite is found. Sometimes a little 

phosphate of iron seems to show the original presence of phosphorus in the 

limestones.1 The lead veins of Cava del Piornbo appear to extend N. 110° E.

When the trachytic mass is penetrated pyritic veins are no longer met, but 

the famous veins of alunite worked for four centuries and a half.2 It appears 

to me unquestionable that these represent another superficial form of deposits 

to add to all the other examples of alteration which I have tried to group in this 

study.

Alunite is, in my opinion, a product of the decomposition of feldspar similar to kaolin, which is worked in the same region, and often from the same 

veins, and, like this kaolin, is bound to disappear in depth. The theory 

which was formerly held is somewhat different. It was thought that the sulphur vapors of solfataric kinds circulated in the fissures of trachyte and 

attacked directly in depth the feldspars of the latter, and a relation was supposed to exist between these different phenomena and the trachyte itself. I believe, on the contrary, that there are two entirely distinct phases in the phenomenon first, a vein deposit clearly delimited, of pyritic trachyte corresponding, perhaps, to the veins of a trachyte particularly feldspathic and at the same 

time pyritic like the granulites of Berezowsk (Oural) ; second, penetration by 

superficial waters of the feldspathic rocks, producing, where pyrite fails, the 

ordinary forms of altered feldspars that is to say, kaolin, but where, on the 

other hand, pyrite furnishes sulphuric acid, crystalline alunite.3

The observations which I have tried to group are well explained by this 

hypothesis.

In the first place the conditions necessary for the production of an intense 

alteration that is, the existence of an abundant water circulation and of a deep 

hydrostatic level are clearly realized. This trachytic massif, which is hardly 

12 kilometers from the port of Civita Vecchia, is 400 to 500 meters above it and 

the absorption of water by the trachytes is so evident that the inhabitants of 

the village of Cave Vecchia, near Tolfa, are obliged to go down 300 meters to 

find drinking water.

l l have noted a fact of the same kind at Boccheggiano. The phosphorus appears

often also in lead outcrops (pyromorphite) and has likewise formed combinations with 

the cinnabar of Idria (coral earth).

2 The alunites of Tolfa have belonged since 1878 to the French Compagnie d'Alun 

Roman, which has, besides the concession of 2,340 hectares granted September 22, 1873, 

a mill at Civita Vecchia and one at Rouen. During four centuries, from 1460 to 1860, 

only large open excavations were made, with a very crude treatment of ores in large 

blocks by simple calcination, leaving the debris, which is worked to-day. About 1873 a 

mill was established at Civita Vecchia and in the following year, by chance, the Provldenza vein was discovered, which has since furnished the entire production. In 1901 

the production was scarcely 4,000 tons.

The present production is about 8,000 tons of raw product, estimated (in 1902 at the 

rate of 7.5 francs per ton, according to actual statistics; in 1904 at the rate of 6 francs), 

or 5,000 tons of commercial product; at Rouen, 4,000 tons composed entirely of sulphate 

fo alumina; at Civita Vecchia 1,000 to 1,200 tons (entirely of alum). The greater part 

of the product is sold in Germany, 700 to 800 tons of " white mineral," with a minimum 

of sulphate of alumina guaranteed. Besides the ancient uses of alum, the manufacture 

of paper consumes large quantities of sulphate of alumina as a substitute for alum, except for certain superior papers. In the manufacture of alum an essential point is the 

elimination of iron which renders the product unsalable.

3 It is known that alunite differs from alum by an excess of alumina which renders it 

Insoluble. While it is formed at the same time as the crystals of alum in all regions of 

volcanic rocks, where, for any reason, waters charged with sulphuric acid circulate, alunite 

is a very rare mineral as its crystallization requires special conditions of temperature and 

pressure, the reactions being otherwise the same.
FOREIGN OCCURRENCES OF ALUNITE. ' 53

On the other hand, note the arrangement of the veins of alunite. The mineral of crystallized alunite and of quartz forms a series of veins in the midst 

of the trachyte, the arrangement of which appears to be lenticular in direction 

as well as in inclination, so that they have been considered contraction fissures 

in the rock filled by a later exudation from sulphurous fumaroles. These veins, 

which individually form well-marked veins, with well-defined walls, may be considered in the aggregate to form a network so complicated 1 by interlacing in 

stockwork that at their outcrops they occupy so much surface that they have 

been able to furnish, for four centuries, immense open excavations, the remains 

of which are seen on all sides. Then, one after another, these networks of 

fissures decrease with depth and the alunite disappears, just as the kaolin 

is always seen to disappear under the same conditions.

Since 1S74 the works have been restricted to one vein, extending northwest 

and southeast, the Providenza vein, besides which some work was done during 

five or six years on the north side on the Rotella vein, now abandoned. This 

Providenza vein, which in places attains a width of 10 meters and ceases to be 

workable when it decreases to less than 0.8 meter, has been worked over 100 

meters in depth; but its limit is clearly seen about the level 390 meters, which 

corresponds very closely to the hydrostatic level, for the termination of the 

pockets of alunite is generally marked by very abundant flows of water.

The impoverishment begins to show itself with the appearance of pyrite at a 

level of 412 meters above the sea; 20 meters farther down the deposit ends. 

* * * * * a *

This pyritic trachyte is, then, certainly the deep form of alunite which disappears where its superficial alteration ceases. This alteration, moreover, follows the usual laws which are seen in reactions of the same kind. For 

example, there are found with the alunite, as with the kaolins, two forms of 

silica first, grains of quartz, constituting the residue of the attack of feldspathic rocks, and, second, quartz retained from the dissolution of the silicates 

dissolved at the same time as the double sulphate of alumina and potassium 

and recrystallized with it. The alunite then appears as a mixture with crystallized quartz, and the entrapping of this silica dissolved in the deep parts 

makes the proportion of quartz in the veins increase with depth. The veins of 

alunite appear thus to become more and more quartzose. The same phenomenon is observed in the kaolins and in the veins of phosphorite of Spain and in 

certain veins of manganese and of baryte which represent other examples of 

similar reactions.

At the same time, the baryte, which is associated with the lime and the alkalies in the feldspars of the rock, is, as always, concentrated in these superficial 

reactions, and secondary crystallizations of barytes are found in certain workings (level 390). In a general way there are found in the alunite all the basicelements of the feldspars, of which the relative proportion is modified only 

according to the laws which I have elsewhere pointed out, by the elimination 

of the soluble elements and accessorily of elements which enter less easily into 

solution; also by increase of potassium with respect to the soda (12 parts in 

100 of sulphate of potash on the average as against 2 parts per 100 of the 

sulphate of soda),2 of baryte with respect to the lime (1 part in 100 altogether), 

and of the manganese with respect to iron, etc.

1 I have given elsewhere (Gltes me"talliferes, t. I, p. 608), according to M. Fuchs, a plan 

of these fissures which appears to be too diagrammatic.

2 There may be as much as 16 parts in the 100 of sulphate of potassium. Pure 

alunite contains 21 parts In the 100, and there are ores containing 90 parts in the 100 

of alunite.
54 ALUNITE NEAB MARYSVALE, UTAH.

The formation of kaolin and that of alunite are two different types of the 

same phenomenon. The passage of the one mode of alteration to the other shows 

itself constantly, and the boundary of the veins of alunite horizontally is often 

formed by the substitution of kaolin for alunite, the primitive vein which 

has furnished the two minerals by alteration having at this point ceased to be 

pyritized. There exist on the outcrops quarries of kaolin in the midst of quarries of alunite, and in the depths pockets of kaolin are frequently encountered.

Finally, in these alteration reactions^ there occur by the oxidation of the 

pyrite the two ordinary forms of peroxidation and of dissolution that are 

found, for example, in calamine deposits of a similar origin. Just as there 

are red calamines, white calamines, and calamine earths, so are there red 

alunites, white alunites (which are sorted out with great care for exportation, 

to avoid the iron in the manufacture of alum), or even yellow earths of alunite, 

sometimes accompanied by kaolin.

The red alunite is found likewise associated with red trachyte under the 

white alunite associated with the white trachyte, not because there are two 

different types of trachyte superposed from which are derived the two types 

of alunite, but because the zone in one case is that of peroxidation, in the 

other that of cementation. So also, when a new opening is made in the pyritic 

trachyte it is seen that with the excess of air alteration begins to show itself 

by spots of oxide of iron among the crystals of sulphate. The encountering 

of the hydrostatic level appears to be accompanied by a deposit of oxide of 

iron corresponding to a very active circulation of superficial waters.

It is also found in approaching a fault, which abruptly limits the workings 

at all levels, that the alunite becomes very white and contains more and more 

quartz. The circulation of waters by this fault has served to carry away 

iron and to bring in silica, etc.

To summarize, the secondary origin of alunite from its relatively superficial character (perhaps localized at the point which was the zone of cementation at the moment of its crystallization) does not appear at all questionable. 

But there remains one obscure point, namely, the exact nature and precise 

origin of these vein zones of pyritic trachyte, which, localized in the midst 

of a trachyte free from pyrite, have been able to produce at certain depths the 

crystallization of alunite.

Sometimes, as I have said, the veins of alunite are clearly inclosed in a very 

hard trachyte, which can then be worked even to a thickness of 0.8 meters. 

It is almost impossible to imagine a partial alteration of such a thin, simple 

vein of pyrite inclosed in the trachyte which can be produced by substitution 

in the inclosing trachyte; we are almost forced to admit that the reactions 

have taken place in a vein already well defined, to which the pyritic impregnation for some cause was limited, and that, for example, a section of dislocated rock comprised between two faults served as channels for ascending 

waters, or that, perhaps, a later vein of some pyritic trachyte, more felidspathic, analogous to those pyritic granulites which form the veins in the 

auriferous field of Berezowsk, played an analogous r61e to that of veins of 

pegmatite in the kaolinization of large granulitic massifs. Besides, it is true 

in the larger number of cases that the alunite, in place of being inclosed in 

hard trachyte, is in contact with decomposed trachyte, but nevertheless the 

contrast still exists; the alteration of the inclosing trachyte is a kaolinization, 

not the formation of alunite that is to say, it did not contain pyrite capable 

of furnishing sulphuric acid to its alkaline and aluminous elements. There 

also the pyrite was limited to the veins which to-day we find in the state of 

alunite. Finally, there should be noted some movements of the ground posterior 

to the crystallization of the alunite, which is cut by faults and shows slicken-
FOREIGN" OCCUREE.NCES OF ALUNITE. ' 55

sides within. I have already noted a large fault which bounds the workings. 

Furthermore, there are frequently found in the alunite hands of ferruginous 

clay which produce slips sometimes.

The minerals resulting from these phenomena are extremely polymorphous. 

Sometimes the alunite is crystallized in lines, sometimes in radial, spherical 

masses; it also has the form of a white petrosiliceous mass which effloresces 

in the air to a yellow earth.

NEW SOUTH WALES.

One of the most important alunite deposits commercially is probably that at the Bullah Delah, in New South Wales, of which a good 

description has been given by Pittman.1 The greater part of this 

description is quoted below:

What is probably one of the most remarkable deposits of alunite in the world 

occurs east of the township of Bullah Delah, in the parish of Bullah Delah, 

County of Gloucester.

It consists of a narrow mountain range about 3 miles long and having a 

maximum altitude of 900 feet, which for a mile or more of its length is composed almost entirely of the mineral alunite of greater or less purity.

In the center of the township of Bullah Delah are seen beds of yellowish-gray, 

calcareous sandstones, containing numerous fossils belonging to the (Upper?) 

Marine series of the Permo-Carboniferous system. These beds dip W. 40° S. 

at 45° and are succeeded conformably on the east by thick-bedded strata, consisting of fine-grained bluish-gray (tuft'aceous?) sandstones, containing a few 

carbonized plant remains and occasional waterworn pebbles of quartz felsite.

Between these beds and the mountain range, a distance of less than a mile, 

the rocks are, for the most part, obscured by soil, etc., but here and there beds 

of this sandstone are seen to outcrop, showing that it forms an important 

feature in the series. The sides of the mountain, for a height of 500 feet, are 

formed of a steeply sloping talus, consisting of fallen alunite rock, which 

effectually obscures the underlying formation. Above this, for a height of 

400 feet, the central escarpment of the mountain range is apparently formed 

of a steep anticline, the beds of alunite on both sides of the summit being inclined in opposite directions at angles of 80°-83° with the horizontal. Although 

the planes of bedding have been almost entirely obliterated, rough traces of 

them can be distinguished in places. A slight cutting has been made, on a 

gap in the range, for a tram line to the alunite quarry, and in this excavation 

the rocks underlying the alunite have been exposed in the form of a distinct 

arch or anticline, and these rocks consist of rhyolites, which show spherulitic 

structure in places. Farther away, to the south of the range, there is a great 

development of these rhyolites, which exhibit remarkable flow structure and in 

places are spherulitic, the spherules being occasionally an inch or more in 

diameter.

Masses or dikes of volcanic glass (obsidian) are also seen at intervals in the 

rhyolites. On the eastern side of the range there is an area of the PermoCarboniferous coal measures, and at least two seams of coal outcrop near the 

northwestern corner of portion 67, parish of Bullah Delah.

It seems evident that the rhyolites are interbedded with the Permo-Carboniferous rocks and that they were deposited as contemporaneous lava sheets.

1 Pittman, B. P., Alunite or alumstone in New South Wales: Kept. Geol. Survey New 

South Wales, 1901, pp. 419-429.
56 ALUNITE NEAR MARYSVALE, UTAH.

The alunite range, which is about Similes long and very narrow, has a singularly symmetrical outline when viewed from the town. A large, almost perpendicular, crown of alunite, 400 feet high, occupies the center, while at 

intervals along the backbone of the ridge, to the north and south of this, are 

other projecting crags of the same material, but of lesser height.. The range 

slopes gradually downward to its northern and southern extremities. Between 

the projecting crags are gaps, or saddles, which are occupied by dikes of 

dolerite, trending across the range. The saddles have, in fact, been formed 

owing to the tendency of the dolerite to decompose more rapidly than the 

alunite rock.

In view of the fact that both sides of the summit of the mountain are formed 

of the same bed, owing to the sharp fold of the anticline, it seems probable 

that the alunite will be found to extend below the talus of fallen rock and 

soil which slopes from the base of the cliff toward the undulating plain.

Although the range may be said to be almost entirely composed of the mineral 

alunite, it must not be supposed that it is all of a quality suitable for commercial purposes. On the contrary, it differs materially in its composition, the 

most impure variety being the most abundant. At the same time, considering 

the comparatively small amount of prospecting work that has been performed, 

there is evidence of the occurrence of large deposits of high-grade mineral.

The impure alunite contains occasional water-worn pebbles of quartz felsite 

similar to those previously mentioned as occurring in the bluish-gray sandstones of the Permo-Carboniferous beds. In some places stalactitic or concretionary forms of alunite are seen, and at intervals the mineral is marbled by 

wavy and more or less concentric markings, such as would be produced by the 

gradual percolation of solutions.

A yellowish waxy-looking mineral, which appears as segregated masses in 

the alunite in places, has the following composition, according to the analyst 

to the department of mines:

Moisture at 100° C_________________________ 1.24 

Combined water _________________________ 13.42 

Silica (SiO2 )_____________________________ 45.84 

Alumina (A120.)_________________1____.__ 39.58 

Magnesia (MgO) ______ _________________ .15

Potash (K,0) . .. ____.. . ___.!

Soda (Na20)_______.__..._____________ _____________.} '

Phosphoric oxide (P2O3 )______________________ .04

100. 46

It is evident, therefore, that the mineral is halloysite.

Four varietes of alunite are recognized by the manager of the mines, viz, 

(1) "light pink," containing 1.7 per cent of silica; (2) " chalk white," containing 16.4 per cent of silica; (3) "purple," containing 19.5 per cent of silica; 

(4) "granular," containing 39.5 per cent of silica. The light-pink variety is 

much the best as regards percentage of alumina, but some of it carries badly, 

being very brittle, and consequently making much " smalls " in transit. It is 

an exceedingly pretty waxy-looking mineral of a bright pink color. It occurs 

in patches, sometimes showing as thin veins and splashes, at others being 

massive and many feet in width. Only the pink ore is at present worked, and 

shipments are kept below 10 per cent of silica contents.

In .the main quarry a face of 60 feet in width is being taken out, and the 

stone is subjected to rough hand picking before being loaded into trucks, the 

" purple" and " chalk-white" ore being discarded. It is carried by a horse 

tram to the base of the central escarpment, and is then sent down an incline,
FOREIGN OCCURRENCES OF ALUNITE. 57

worked on the main and trail-rope system, on the slope of the talus. From 

the.bottom of the incline it is conveyed in carts to the wharf on Myall River, 

half a mile distant, whence it is shipped to England for the manufacture of 

alum. The works are situated at Runcorn, on the Manchester Canal, and the 

mines are owned by the Australian Alum Co. (Limited).

Typical samples of the four varieties of mineral were selected at the mine 

and were analyzed in the laboratory of the department of mines with the 

following results:

Moisture at 100° C. .............................................

Combined water. ..............................................

Silica (SiO') ...................................................

Ferric oxide (Fe2 08) ...........................................

Alumina (A IjOs) ...............................................

Lime (CaO). ...................................................

Magnesia (MeO) ...............................................

Potash (EaO)..................................................

Soda (Na2O) . ..................................................

Chlorine (Cl) ...................................................

Light 

pink.

0.06

13.19

1.92

.26

37.52

Nil.

Nil.

9.51

1.12

36.76

Trace.

Trace.

100.34

Chalk 

white.

0.46

13.86

19.34

.27

37.37

Nil.

Nil.

5.68

1.08

22.09

Trace.

Trace.

100. 15

Purple.

0.16

9.65

32.40

.07

25.91

.07

Trace.

6.53

.82

24.47

.02

Trace.

100. 10

Granular.

0.22

10.26

23.45

.04

30.17

.01

Trace.

8.00

.63

26.88

.07

Trace.

99.73

Origin of the deposit. It has already been mentioned that deposits of 

alunite in other parts of the world, where their mode of occurrence has been 

studied, are believed to have been formed by the action of sulphurous vapors 

upon trachytic and other allied igneous rocks.

At Bullah Delah everything points to the rhyolites as the origin of the 

ahmite. They occur interbedded with the Permo-Carboniferous rocks in the 

form of contemporaneous lava sheets, and it is possible that the whole series 

of sandstones and lava sheets was folded into the form of an anticline by 

earth movements. Subsequently, during the Tertiary period, these rocks were 

intersected in an east and west direction by a number of dolerite dikes. These 

later volcanic intrusions were probably attended or followed by evolutions of 

steam and sulphurous acid vapors, and it is reasonable to suppose that it was 

by the action of these that the rhyolites were decomposed, with the production 

of beds of alunite. Finally, in post-Tertiary times, the softer sandstones were 

removed by denudation, leaving the anticlinal arch of the harder alunite rock 

to form the summit of the Bullah Delah Mountain.

OTHER DEPOSITS.

Other data concerning the occurrence or utilization of the foreign 

alunite deposits are not at present at hand. Alum is reported to have 

been manufactured from the rock at Smyrna, but whether the raw 

material was obtained near by or from a more distant source, is not 

clear. Eecent interest in the development of similar minerals in 

Spain seems to warrant a brief quotation of recent date concerning 

these deposits. The Spanish occurrences are noted as containing a 

new mineral galafatite, an aluminum-potassium sulphate, similar 

in composition to alunite. From the following description 1 it ap1 Preus, Nordal, A new mineral and a new source of potassium sulphate: Eng. and 

Mln. Jour., Feb. 4, 1911, p. 261.
58 ALUNITE NEAR MARYSVALE, -UTAH.

pears that the occurrence and treatment of the ore is similar to that 

of alunite.

The most important deposit was that found near Benahabux railway station, 

only 10 kilometers from the port of Almeria.

The ore is especially interesting on account of its composition, which is as 

follows: 80s, 77 per cent; A1203 , 37.98 per cent; K2 0, 9.64 per cent; H20, 17.61 

per cent. The compact ore has a specific gravity of 2.75 and a hardness of 

3.5. It is an aluminum-potassium sulphate and, as it is a new mineral, has been 

given the name galafatite, after its discoverer, Galafat. The ore when pure is 

perfectly white, has a conchoidal fracture, and when recently taken from the 

lode is very compact. In its natural state it does not dissolve in water and 

resists the action of acids. Heated, it will partially dissolve in hydrochloric 

acid and somewhat better in dilute sulphuric acid. It is easily dissolved after 

being fused with a sufficient quantity of sodium bicarbonate and attacked with 

hydrochloric acid.

Alumina, potassium sulphate, and alum may be produced from this ore. The 

ore is transformed into marketable condition through calcination and washing 

in water. By the calcination process water and the part of the sulphuric 

anhydride which is combined with the alumina are eliminated, leaving a residue 

of a mixture of alumina and potassium sulphate. By washing, the potassium 

sulphate is dissolved in water, leaving the alumina almost pure, only retaining 

small quantities of hygroscopic water.

The average contents of the calcined mineral are as follows: Alumina, 65 

to 70 per cent; potassium sulphate, 25 to 30 per cent.

The situation of the mine is favorable, being, as stated above, only 10 kilometers from the port of Almeria, the climate of which is especially effective 

for the necessary evaporation. The mining concessions cover 1,000 hectares, 

or 10,000,000 square meters. Several parallel veins have been found, with a 

width of 5 to 6 meters. The working of these lodes is easy, and the extraction 

of the crude ore should be done cheaply. Considerable quantities will be put 

on the. market in 1911.

COMMERCIAL AVAILABILITY OF ALUNITE.

Alunite has not until recently been widely recognized in the United 

States, and hitherto no attempt has been made in this country to save 

or utilize this mineral. From the results of simple experiments with 

the Marysvale alunite in the laboratory of the Geological Survey 

W. T. Schaller has made the following observations:

Laboratory experiments showed that on igniting the powdered alunite all of 

the water and three-quarters of the sulphuric acid are volatilized. On leaching the residue with water the potassium sulphate is dissolved, leaving the 

insoluble aluminum oxide behind.

The average amount of potassium sulphate leached from the ignited mineral 

powder is 17.9 per cent of the original material used. As the coarsely crystallized alunite was found to contain 19.4 per cent of potassium sulphate, 92 

per cent of the total potash present was obtained by simple ignition and subsequent leaching.

It is worth noting that, according to the laboratory experiments, 32.7 per 

cent of the ignited alunite consists of available potassium sulphate, which can 

be extracted by simple water leaching and evaporation. The remaining 67.3 

per cent consists of nearly pure aluminum oxide.
COMMEKCIAL AVAILABILITY OF ALUNTTE. 59

Several of the foreign deposits have, however, been successfully 

worked, and the commercial availability of the mineral in this country 

may be inferred by a consideration of the processes that have been 

developed. The foreign alunite has been utilized chiefly in the manufacture of alum, as indicated in the following description: 1

A considerable amount of alum is prepared from alunite. Alunite contains 

the elements of potassium alum, basic aluminum sulphate, and free alumina. 

In Sicily it is made into heaps and calcined in the open air. At Tolfa, where 

the manufacture is carried out on a larger scale, the roasting is conducted in 

furnaces like limekilns, lined with refractory materials. The mineral is heated 

in large pieces by the flame without direct contact with the fuel until sulphur 

dioxide begins to escape. The calcination requires about six hours, the mass 

losing about 35 per cent of water. During the ignition the excess of alumina 

beyond that necessary to produce alum is rendered insoluble and no longer has 

the property of precipitating basic sulphates from the solution. The calcined 

mass is exposed to the air upon a clay floor for some weeks, during which time 

it is occasionally moistened. The mud-like product is agitated in boilers with 

water at 70° C., and the clear decanted liquid, of density 10°-12° B., is evaporated to 32° B. and crystallized in small wooden tubs. The crystals are cubic, 

opaque, and reddish from the presence of ferric oxide. This iron is, however, 

quite insoluble, and may be separated by recrystallization; the soluble iron is 

said to be less than 0.005 per cent. In this way " Roman alum " -was formerly 

largely produced. On account of their great purity the red crystals were much 

sought after.

Alunite is now largely converted into alum by treatment with sulphuric acid 

and addition of potassium sulphate. Guyot 2 has examined this process and 

recommends the following method:

On ignition of alunite the free alumina is first rendered anhydrous and 

soluble in sulphuric acid; at a higher temperature the basic sulphates become 

soluble, but if the temperature be allowed to rise too high the alumina becomes 

vitrified and is insoluble. Guyot recommends ignition at 800° C. for three hours 

as the best means of rendering the maximum of both these substances soluble. 

The composition of the calcined mass is determined, and acid is used in proportion to the amount of soluble sulphate contained. For a product of the following 

composition, K2SO<, 14 per cent; Al2O8 .3SOs (present as alum), 26.55; Al2Os.3SO8 

(free), 6.56; A1208 (free), 18.58; OHi, 11.90; FeaOs, 0.80; siliceous residue, 

21.61 per cent, the proportions given below would be most satisfactory. Into a 

clay oven is poured 12.5 tons of sulphuric acid of 52° B. diluted to 30° B. and 

heated to 80° or 90° C. Eight tons of the calcined mineral is then added in 

portions and well stirred. After the whole has been added, the liquid is left 

for two hours, then evaporated to 38° B. and treated with 2.7 tons potassium 

sulphate. The process up to this point occupies 10 hours; after a further 

period of 13 hours, the clear liquid is decanted off; its density should not exceed 

42° B. The muddy liquid remaining is reduced to 24° B. by the addition of 

mother liquor from a previous crystallization, stirred, allowed to settle, drawn 

off clear, mixed with the first decantate, and crystallized in a vat. After one 

day the crystals are removed, redissolved, and recrystallized. The muddy 

residue is crystallized out for a further crop of alum. The total yield of alum 

is about 2.3 times the original weight of ore. The insoluble matter contains 

3 per cent alumina and 2.01 per cent potassium sulphate, in addition to silica, etc.

1 Thorpe, T. E., Dictionary of applied chemistry, London, 1890, p. 78.

2 Guyot, M. P., Sur la rlchesse industrielle de 1'alunite crue, en. poudre: Compt. Rend. 

Acad. Sci. Paris, vol. 95, pp. 693, 694; Experiences sur la calcination de 1'alunite en 

poudre, destined 4 la fabrication de 1'alum et du sulfate I'alumine: Idem, pp. 1001-1003.
60 ALUNITE NEAR MARYSVALE, UTAH.

According to C. Schwartz,1 the best temperature for the roasting is 500° C., 

and the acid used should have a density between 1.297 and 1.530.

The summary concerning the utilization of the Australian deposit 

at Bullah Delah is contained in the following paragraph from the 

description of this deposit already quoted: 2

The following is a process by which alum is manufactured from alunite: 

The mineral is ground and then calcined in reverberatory furnaces, to dehydrate it and drive off part of the 80s. It is next treated with a weak solution 

of sulphuric acid in lead-lined tanks, heated to boiling point by steam jets. 

The liquor is allowed to settle in the same vats, and the clear solution is run 

off into crystallizing tanks, which are kept in constant agitation while cooling, 

the alum crystallizing out and sulphate of alumina remaining in solution. The 

residue in the vat is boiled again with water, and the solution run off again 

in the same way. The liquor containing sulphate of alumina is then returned 

to the vats and sufficient of the calcined mineral added to completely neutralize any free acid. It is then heated to boiling point and ebullition continued until partial reversion takes place, the reversion being accompanied 

by a precipitation of the hydrated ferric oxide.

The alum, after collection, is washed and then refined in vats, similar to 

but deeper than those originally employed, and the concentrated solution is 

run into roaching tuns, in which it is crystallized; it is then broken up and 

packed ready for the market.

The sulphate of alumina solution, after all the alum has been crystallized 

from it, is concentrated in small vats heated with steam coils, and the lower 

qualities of sulphate of alumina are formed by running the liquor onto lead 

tables and breaking the solidified material into blocks, the higher qualities 

(containing over 17 per cent of soluble alumina) being cast on copper trays. 

These higher qualities, which vary in color from yellow to green in the slabs, 

are then ground in a disintegrator, and the material assumes a snow-white 

appearance.

It is, of course, feasible, by the addition of K2SO4, to convert the whole of 

the alumina contained in the stone into alum if desired, but the more profitable 

method of treatment, when the better classes of sulphate of alumina can be 

sold at standard prices, is to make only so much alum as there is sulphate of 

potash present in the stone to produce, and convert the rest of the alumina 

into soluble sulphates of alumina (of commerce).

Sulphur may be obtained by distilling the mineral in the presence of any 

reducing gas like coal gas. Sulphuric acid may also be distilled from the 

mineral. Heating with carbonate of baryta produces aluminate of potash.

Pittman also gives the following statistics of production: 

Production of alunite at Bullah Delah, Australia.

Year.

1890.......................

1891.......................

1892. ......................

1893.......................

1804. ......................

1895.......................

Quantity.

Tons. 

220

704

821

1,284

OHO

832

Value.

£3,000

1,888

3,284

5,136

3,448

3,328

Year.

1896......................

1897......................

1898......................

1899. .....................

Quantity.

Tons. 

1,372.0

724.5

2,941.0

921.0

10,681.5

Value.

£4,116

2,172

8,823

2,763

37,958

1 Ueber die Auschliessung des romischen Alunits: Ber. Deutsch. chem. Gesell., vol. 17, 

p. 2887.

2 Pittman, B. P., Alunite or alumstone in New South Wales: Kept. Geol. Survey New 

South Wales, 1901, pp. 419-429.
SUGGESTIONS AS TO PROSPECTING. 61

One subject that does not appear to have received direct consideration in the processes applied to the foreign alunites is suggested in 

Schaller's experiments and relates to the feasibility of utilizing the 

potassium in the form of the simple sulphate instead of as an alum. 

For agricultural purposes the sulphate is probably the most desired 

form in which to use the potash; at least it is so quoted in regard to 

the German salts.

It is also evident that the oxide of aluminum in a rather pure state 

would result as a by-product in the reduction suggested by Schaller's 

experiments. At present it is not known that this alumina is directly 

available for the manufacture of metallic aluminum, but its use as a 

possible substitute for the mineral bauxite is a natural suggestion. 

Bauxite, a natural hydrous oxide of aluminum and now the principal 

source of the metal, is rapidly becoming scarcer, as the deposits are of

a type that may become exhausted unless some satisfactory substitute 

can be found. This suggestion is further borne out in the following 

note: l

The expiration of the aluminum-process patents and the great increase in 

output of metallic aluminum, have given rise to many scientific researches and 

commercial inquiries regarding new methods of producing metallic aluminum. 

These inquiries are appropriate in view of the fact that bauxite is found in 

comparatively few places, must be transported long distances, and contains so 

much silica as to require costly chemical operations to purify it in the manufacture of metallic aluminum. Aluminum silicates, on the other hand, are found 

almost everywhere, and the separation of the silica' from them may, at some 

future time, not cost more than to counterbalance the scarcity, inaccessibility, 

and impurities of the bauxite deposits.

SUGGESTIONS AS TO PROSPECTING FOR ALUNITE.

Until recently there has been no incentive to search for alunite and 

most of the known occurrences in this country have been noted by 

geologists who were making studies of the areas where it occurs. 

There is little doubt that if prospectors had searched for alunite with 

the same diligence that they have shown in their search for the 

metallic ores a far greater number of occurrences would be known. 

Since it was shown by Ransome that alunite is associated with the 

rich gold ores of Goldfield, Nev., it has attracted more attention, and 

if the mineral itself proves to be of commercial value the search for 

it will be still further stimulated.

In the case of a mineral whose occurrence has been studied in so 

few places it is impossible to give a definite and positive statement 

of the conditions under which it may be expected to be found; or if 

such a statement were made it would probably be modified by future 

discoveries. The study of the occurrences thus far described, how1 Mineral Resources U. S. for 1910, chapter on production of bauxite and aluminum, 

U. S. Geol. Survey, 1911,
62 ALUNITE NEAR MARYSVALE, UTAH.

ever, does point rather definitely to certain conditions under which 

the mineral may form and the conclusions derived from this study 

may therefore aid in a further search for it.

As has been shown in the foregoing pages, there are at least two 

distinct conditions under which the mineral is deposited:

1. It may form by the action of descending acid solutions, derived 

from the oxidation of sulphides, on potassium-aluminum silicates 

(feldspars or micas). Several occurrences have been noted where 

the mineral is thus associated with oxidized ores, usually in or close 

to feldspathic rocks, and a more careful examination of material that 

has been called kaolin and talc will doubtless show some of it to be 

alunite. As yet no body of this type that promises to be of commercial importance has been discovered, but it is by no means impossible that such bodies exist and large bodies now described as kaolin 

and talc, but not definitely known to be such, may well be tested to 

determine whether they are not alunite. It may be stated in this 

connection also that the closely allied mineral jarosite has been noted 

in the oxidized zone of several ore bodies, and this mineral, too, may 

in some places occur in considerable abundance.

2. The deposits that at present give the greatest promise of commercial importance have resulted either from the action of hot waters 

carrying sulphuric acid on rocks containing potassium-aluminum 

silicates or from the deposition in veins from ascending thermal solutions. In the former type the resulting alunite is largely disseminated through the altered rock, though small veins of nearly pure 

material are not uncommon;'in the latter type, as shown in the 

Marysvale deposit, it has been carried in the solutions and deposited 

as a large vein. The deposits of these types thus far discovered have 

been in or closely associated with the extensive bodies of Tertiary

igneous rocks that are abundant in the Great Basin and Rocky Mountain region.

In connection with the alteration that has produced the alunite 

there has been a silicification of the rock which has rendered it resistant to weathering and the outcrops are usually rugged, standing 

above the surrounding rocks. Pyrite is also commonly formed in the 

wall rock during the alteration, and in places the oxidation of this 

mineral at the surface imparts an iron stain to the outcrop. As has 

already been pointed out, it is believed that the Marysvale deposit 

is closely associated with metallic veins of a type widely distributed 

through the Western States. It is certain that in some of the districts where such veins occur alunite is not present, at least not in 

important amounts, but it is by no means improbable that it may 

be found in other districts, and an examination of supposed " spar,"
WARNING TO INVESTORS. 63

" talc," or " kaolin " veins may show the presence of the mineral. 

Although it may be expected to occur in districts with metal veins 

and is believed to be closely related to them in origin, the alunite 

deposits themselves may not contain important metal values, as is 

indicated by the Marysvale deposit and the two Colorado deposits 

mentioned above. On the other hand,-as at Goldfield, it may be 

closely associated with the metallic deposits.

In the Tushar and neighboring ranges there are reported to be 

numerous silicified vein outcrops described as " geysers," which on 

examination may prove to carry alunite or other salts of commercial 

importance.

FIELD TEST FOR ALUNITE.

The following simple field test for the mineral alunite has been 

suggested by W. T. Schaller: Boil the powdered sample with water

or with hydrochloric acid for several minutes; after allowing the 

powder to settle pour off the liquid and repeat the operation to insure 

the removal of all soluble sulphates. Dry the powder and heat to a 

dull red. Again boil in water and, after settling, pour off some of the 

clear liquid. To this add a.small fragment or a solution of barium 

chloride. If the mineral is alunite a heavy white precipitate will 

form. To be sure that the water used in this test does not contain 

sulphates in solution it should be tested with barium chloride, and 

if it gives a marked precipitate it can not be used. For this test all 

that is required that is not included in a miner's or prospector's outfit is a little barium chloride, which can be carried in a small bottle 

or cartridge.

WARNING TO INVESTORS.

Deposits may exist on ground adjoining the claims already located 

and partly developed, but it should be borne in mind that the 

present developments have not yet proved the continuity either in 

depth or even with certainty for a very great distance on the surface. 

Prospective investors should understand that until the true character 

and commercial availability of a deposit of this type have been demonstrated, they are taking chances in investing in the stock of any 

company professing to be about to develop such a deposit. The 

Geological Survey has been assured on reliable authority that the 

property covering the best-known part of the alunite deposit, which 

is described in the foregoing pages, is not for sale, and its owners 

are not in need of assistance, financial, technical, or otherwise, for 

the development of the property to its best advantage. It should be 

unnecessary to say to anyone who is familiar with the usual procedure in such an enterprise that if responsible persons have secured
64 ALTJNITE NEAR MAEYSVALE, UTAH.

control of a deposit which offers large and unusual promise but whose 

actual commercial value is not wholly proved, it will not be necessary 

for them to advertise widely for contributions or express a willingness to distribute large quantities of stock, if they actually intend to 

develop the property on a commercial basis. Such a procedure 

should of itself be a warning to any who may be contemplating an 

investment of this character.

o