EXPERIMENTS ON THE EXTRACTION OF POTASH FROM 

WYOMINGITE. 

By RoGER C. WELLS. 

INTRODUCTION. 

The United States Geological Survey has 

now made a considerable number of explorations in search of a domestic source of potash 

and further explorations are under way. In 

the meantime the Survey has ·studied the 

chemical and physical characteristics of the 

rocks, minerals, and salines so far discovered, 

and it is the object of the present paper to describe laboratory experiments made with the 

rock wyomingite. 

Wyomingite, a lava occurring extensively in 

the Leucite Hills in Sweetwater County, Wyo.,t 

is composed largely of the mineralleucite, a silicate of alumina and potash. Leucite is far 

richer in potash than feldspar, which is commonly regarded as one of the most promising 

prospective sources of potash. Moreover, the 

potash in leucite, although not soluble in water, 

seems to be more easily attackable by reagents than that in feldspar, so that if any 

igneous rock should become a source of potash 

wyomingite would have advantages over a 

feldspar-bearing rock. Data on the properties of wyomingite will therefore be valuable. 

While all the experiments to be described here 

can not be considered as suggestions of commercial possibilities, a record of them may not 

only be suggestive to private investigators, 

but save much repetition of preliminary investigation. 

CHEMICAL COMPOSITION OF WYOMINGITE. 

The wyomingite used in the experiments to 

be described has the following composition: 

I The quantity of leucite-bearing rock present at this locality is estimated at nearly 2,000,000,000 tons, containing an average of 10 per cent 

of potash. See U. S. Geol. Survey Bull. 512, p. 35, 1912. 

Composition of wyomingite. 2 

[W. F. Hillebrand, analyst.] 

Silica (Si02)- •• _ •••••• - - - - - - - - - - • • • • • • • • • • • • • • • 

Titanic acid (Ti02) ••••••••••••••••• - - - -- - - -- -- -

Alumina (Al20 3) •••••• ----------------- • • • • • • • • 

Ferric oxide (Fe20 3) • • ••••• - - - - - - - - - - - • • • • • • • • • 

Ferrous oxide (FeO) .......................... . 

Magnesia (MgO) .............................. . 

Lime (CaO) .................................. . 

Soda (N~O) ................................. . 

Potash (K20) ........ ------------------ · · · · · · · · 

Water (H20) ....... ------ ----------- · · · · · · · · · · 

Phosphoric acid (P20 5) •••••• -----.----- •••• • • • • 

Sulphur trioxide (S03) •••••••••••••••••••• ~ •••• 

. Fluorine (F) ....... . .......... ~ ......... · ...... . 

Other constituents ............................ . 

Specific gravity, 2.627. 

53. 70 

1. 92 

11. 16 

3. 10 

1.21 

6.44 

3.46 

1. 67 

11. 16 

3.41 

1. 75 

. 06 

. 44 

. 92 

~00.40 

This rock was obtained near Fifteen-mile 

Spring, on the northeast side of Zirkel Mesa. 

It is the typical dense reddish-brown wyomingite, such as occurs in many of the mesas and 

hills of this region. 

MINERAL COMPOSITION OF WYOMINGITE. 

According to Cross 3 this wyomingite really 

consists of the following minerals: Uncombined silica, 22.5 per cent; leucite, 35.7 per 

cent; phlogopite, 22.3 per cent; diopside, 10.7 

per cent; and accessory minerals, 8.8 per cent. 

The potash content of wyomingite is distributed 

among leucite, phlogopite, and a glassy base 

which is chiefly uncombined silica. There is 

enough uncombined silica in wyomingite to 

have formed a feldspar, and why leucite was 

formed instead has not yet been explained. 

2 Clarke, F. W., Analyses of rocks and minerals from the laboratory of 

the United States Geological Survey, 188G-1914: U. S. Geol. Survey 

Bull. 591, p. 74, 1915. 

a Cross, Whitman, Igneous rocks of the Leucite Hills and Pilot Butte, 

Wyo.: Am. Jour. Sci., 4th ser., vol. 4, p. 133, 1897. 

37 
38 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

On the assumption that in any process of ex- 1 placed in 500 cubic centimeters of water. 

traction this silica can be kept from combining Mter shaking one day it was found that 0.0035 

with the potash, the advantage inherent in gram of K20, or 0.31 per cent of the total K20 

the wyomingite can be seen at a glance by com- in the rock, had been extracted by the solution. 

paring the theoretical percentage of potash in A week later the potash in solution was found 

leucite with that in orthoclase feldspar, leucite to be 0.61 per cent of the total K20 originally 

(K20.Al20 3.4Si02) containing 21.5 per cent and in the rock. These facts are also of interest in 

orthoclase (K 0.~t\J .6Si0 ) 16.·9 per cent. relation to agricultural or soil chemistry and 

BEHAVIOR OF CRUSHED WYOMINGITE IN 

WATER. 

As leucite has a specific gravity of 2.45 to 

2.50, while the specific gravities of phlogopite, 

diopside, and silica are 2.7, 3.3, and 2.6, 

respectively, it was hoped that some separation 

of the lighter and more valuable mineral could 

be made by a flotation process. A small 

amount of wyomingite was crushed to pass an 

80-mesh s~reen and separated into two portions, one heavier and one lighter, by panning 

with water. Each of these portions was panned 

similarly. The combined lighter portions 

weighed 0.93 gram and the heavier portions 

0.60 gram.' The lighter portion was analyzed 

with the following results: 

Effect of panning wyommgite. 

Original Lighter k par- roc · tion. 

11.2 

1.7 

12.1 

1.1 

Although the effect was not as great as desired it is evident that the method of concentration used caused some separation of the 

leucite from .the other minerals. According to 

Cross, wyomingite is a very fine grained rock, 

so that it may be too much to expect that a 

mechanical method of concentration will effect 

a complete separation, but if such a method 

could be discovered, it would render an enormous quantity of mineral having a high potash 

content available for chemical treatment: 

Cold water attacks leucite somewhat, but 

the action is so slight that the fact has scarcely 

any significance unless it is in agricultural 

chemistry. When certain other salts are present in the water, however, the action is somewhat more noticeable. This was show-n by 

some experiments carried out with wyomingite 

a:nd gypsum, 10 grams of each, powdered, being 

are probably to be explained as due to a metathetical reaction by which a part of the calcium of the gypsum in the solution exchanges 

itself for the potassium in the leucite. 

In order to see if this exchange could be 

brought about to a greater extent by grinding 

the constituents 10 grams each of wyomingite 

and gypsum were ground with 50 cubic centimeters of water in an agate mortar by a mechanical grinder for two hours. The resulting solution, after filtration, was found to contain 2 per 

cent of all the potash (K20) in soluble form. 

This is, however, only 0.22 per cent of the rock. 

An experiment similar to the last was carried 

out with lime in place of gypsum, resulting in 

the extraction of 2.64 per cent of the potash in 

soluble form, or 0.34 per cent of the rock. 

EFFECT OF HEATING WYOMINGITE. 

Merely heating wyomingite to a dull red 

apparently causes very little change in it. 

Mter it is heated a trace of its potash is found 

to be soluble in water, but this fact can have 

no commercial significance. For effective action some reagent must be added. The following notes describe the effect of heating mixtures 

of the rock and certain reagents: 

EXPERIMENTS WITH GYPSUM. 

In addition to the experiments with gypsum 

already described, the following were made: 

1. A mixture of 1 gram of wyomingite and 

0.2 gram of gypsum was finely ground and ignited until fused. After cooling it was ground 

and extracted with water. The soluble K20 

amounted to 1.8 per cent of the rock, or 16.2 per 

cent of the total K20. 

2. A mixture of 1 gram of wyomingite, 0.22 

gram of gypsum, and 0.10 gram of sodium 

chloride was finely ground, ignited to a dull 

red, and, after cooling, extracted with water. 

The soluble K20 amounted to 2._5 per cent of 

the rock, or 22.4 per cent of the total K20. 

In the light of these results gypsum does not 

appear to be very efficient in decomposing the 
EXPERIMENTS ON THE EXTRACTION OF POTASH FROM WYOMINGITE. 39 

rock, at least when used in the proportions 

tried in these experiments. 

EXPERIMENTS WITH SULPHURIC ACID. 

1. One gram of wyomingite was moistened 

with 1 cubic centimeter of concentrated 

sulphuric acid and heated gently in a large 

platinum crucible for about an hour until 

fumes came off freely. The soluble K20 

extracted amounted to 2.72 per cent of the 

rock, or 24.5 per cent of the total K20. 

2. One gram of wyomingite was ground with 

0.22 gram of gypsum, moistened with dilute 

sulphuric acid equivalent to 0.18 gram H2S04 , 

dried, and heated to redness. The soluble 

K20 extracted amounted to 2.75 per cent of 

the rock, or 24.8 per cent of the total K20. 

EXPERIMENT WITH POTASSIUM BISULPHATE. 

On the theory that the action of hot sulphuric acid on wyomingite produces some 

potassium bisulphate, an experiment was 

made with potassium bisulphate itself as a 

reagent. One gram of wyomingite was finely 

ground with 0.5 gram of potassium bisulphate, 

and the mixture was brought up slowly to a 

dull-red heat. The result was disappointing. 

Hardly any more K20 was extracted than had 

been added in the reagent, though nearly all 

the Na20 of the wyomingite had been converted into a soluble form. 

This experiment seems to indicate that the 

rearrangement effected in the sintering is 

governed by the law of mass action, and that 

treatment with a potassium reagent is not 

likely to be efficient, at least for a commercial 

process. 

EXPERIMENTS WITH ALUNITE. 

Notwithstanding the unfavorable result of 

the last experiment it seemed worth while to 

try the effect of heating wyomingite and 

alunite together. Alunite is to be found comparatively near the Leucite Hills, and the idea 

{)f the experiment was that a combination 

of the two rocks might be treated in a single 

process at a lower cost than the combined cost 

of treating each separately. The alunite used 

·came from Marysvale, Utah, and was part of 

that analyzed by W. T. Schaller for Butler 

and Gale,t who described the deposit in 1912. 

I Butler, B. S., and Gale, H. S., Alunite, a newly discovered deposit 

near Marysvale, Utah: U.S. Geol. Survey Bull. 511, 1912. 

Composition of alunite. 

[W. T. Schaller, analyst.] 

Alumina (Al20 3) •••••••••••• • • • • • • • • • • • • • • • • • • • • 

Ferric oxide (Fe20 3) ••••••••••• • • • • • • • • • • • • • • • • • 

Sulphur trioxide (S03) •• • ••••••••••••.. · • • • • • • • • 

Phosphoric anhydride (P20 5) ••••••••••••• • • • • • • • • 

Potash (K20) ........... . ... · · · · · · · · · · · · · · · · · · · · 

Soda (N3.zO) .............. . ................... . 

Water (H20) ...... . ........ · · · · · · · · · · · · · · · · · · · · 

Silica (Si02) •••••••••• • •••••••••••••••••••••••• 

37. 18 

Trace. 

38. 34 

. 58 

10.46 

. 33 

12. 99 

• 22 

100. 10 

1. Wyomingite (0.2 gram) was finely ground 

with 0.2 gram of alunite. After being slowly 

heated to a dull red and then held at a medium red for an hour in a J. Lawrence Smith 

platinum crucible the cooled lump was extracted with water and yielded soluble K20 

equivalent to 6.15 per cent of the mixture. 

As the theoretical yield of K20 would be 5 per 

cent from the alunite and 5.5 per cent from 

the wyomi,ngite, a total of 10.5 per cent, the 

amount actually extracted was 57 per cent of 

the total K20-that is, the K20 extracted 

might be considered all that in the alunite 

alone plus about 20 per cent of that in the 

wyoming~te. As there is a very large quantity of wyomingite available and as the cost 

of mining and crushing would doubtless be 

low, it would appear that when alunite is 

being treated the addition of wyomingite 

might pay. 

2. The next experiments consisted in varying the proportions of alunite and wyomingite. 

By taking 0.2 gram of alunite and 0.4 gram of 

wyomingite, the solubleK20 obtained amounted 

to 7.6 per cent of the mixture. The theoretical yield of K20 would be 3.5 per cent from 

the alunite and 7.4 per cent from the wyomingite, a total of 10.9 per cent; the K20 extracted therefore amounted to 70 per cent of 

the total--'-that is, all the potash in the alunite 

was extracted and 55 per cent of that in the 

wyomingite. 

3. In another experiment with 0.2 gram of 

alunite and 0.6 gram of wyomingite the yield 

in soluble K20 was 3 per cent of the mixture. 

As the theoretical yield would be 2.6 per cent 

from the alunite and 8.2 per cent from the 

wyomingite, or 10.8 per cent in all, the result 

represents only 28 per cent of the total K20. 

In this experiment the wyomingite was only 

slightly attacked. 
40 SHORTER. CONTRIBUTIONS TO GENERAL GEOLOGY, 1916. 

EXPERIMENT WITH CALCIUM CARBONATE. 

The well-known method devised by J. Lawrence Smith for determining the alkalies in silicate rocks, involving the use of calcium carbonate and ammonium chloride, probably owes 

its success to the action of calcium chloride 

formed during the reaction. However that 

may be, the proportions of the reagents used 

in this method are too great to be practicable 

for commercial process, and accordingly it 

seemed desirable to make a few experiments 

to see if the proportions of the reagents could be 

reduced. One experiment was tried out with 

calcium carbonate alone, 0.3 gram of ca1cium 

carbonate to 1 gram of wyomingite being used. 

At the temperature employed, a dull-red heat, 

scarcely more than a trace of potash was rendered soluble. This result seemed to show that 

the chief attack in the Smith method is due to 

the calcium chloride, and accordingly the next 

experiments were made with calcium chloride 

alone. 

EXPERIMENTS WITH CALCIUM CHLORIDE. 

It was found that with moderate proportions 

of calcium chloride too high a heat, say 1,000° 

C., causes the mixture to vitrify so that extraction of the potash by water is impracticable. The temperature used was therefore limited to a dull-red heat. The calcium chloride 

was added in solution to finely ground wyomingite in a platinum crucible, and the mixture was 

slowly stirred during evaporation until the 

mass was dry. 

The results of the experiments are summarized below: 

Potash rendered soluble when wyomingite is heated to a dull 

red with calcium chloride. 

K20 rendered 

soluble. 

Wyoming- CaCl2 • ite. Percent- Percentage of 

age of total rock. KzO. 

Gram. Gram. 

1 0.2 3.03 27.3 

1 .4 6.44 58.0 

1 .6 8. 10 73.0 

EXPERIMENT WITH MAGNESIUM CHLORIDE. 

One gram of powdered wyomingite was moistened with a saturated solution of magnesium 

chloride, dried, and heated slowly to dull redness in an open ·crucible. On extraction the 

soluble K20 amounted to 3.22 per cent of the 

rock, or 29 per cent of the total K20 in the rock. 

EXPERIMENT WITH A BITTERN. 

When it was found that a part of the alkalies 

in wyomingite is rendered soluble by heating 

with ·magnesium chloride, an experiment was 

made with a bittern, such as is obtained in the 

manufacture of salt at Great Salt Lake, having 

the composition shown below: 

Composition of bittern used. 

Grams per Per cent 

liter. of salts. 

Magnesium (Mg) .................. 24.9 7. 76 

Potassium (K) .................... 15.9 4. 94 

Sodium (Na) ..................... 69.3 21. 60 

Sulphate (804) •••••••••••••• - •• -- 65.0 20.27 

Chloride (Cl) ...................... 145.9 45.43 

321.0 100.00 

One gram of wyomingite was drenched with 

2 cubic centimeters of the bittern, dried, and 

heated to dull redness, with the following results: Soluble K20, 5.32 per cent of the dry 

mixture; theoretical yield of K20, 2.3 per cent 

from the bittern and 6.8 per cent from the wyomingite, or 9.1 per cent in all; K20 extracted, 58 

per cent of total K20. The K20 extracted may 

be considered to be all that of the bittern used 

and 44 per cent of that in the wyomingite. 

EXPERIMENT WITH AMMONIUM SULPHATE. 

Ammonium chloride in excess and under 

pressure is known to react with leucite at 350° 

in such a way as to set potassium chloride free.t. . 

It seemed worth while to try ammonium sulphate also. In a single experiment 1 gram of 

wyomingite was heated over night in a closed 

glass tube at 310° with 0.2 gram of ammonium 

sulphate. The potash rendered soluble by this 

treatment amounted to 0.0352 gram, or 31.8 

per cent of the total potash in the rock. 

1 Clarke, F. W., and Steiger, George, The action of ammonium chloride upon silicates: U.S. Geol. Survey Bull. 207, p. 16, 1902.