MAJOR SOURCES.

ALUNITE.

Turning attention now to the more important possible sources of American potash, alunite may be conveniently considered first. This mineral is a basic potassium alumino sulphate, is quite widely distributed in the United States, and is found in notable quantities at several points in Colorado, California, Arizona, Nevada, and Utah. Alunite has long been used in Spain and Italy as a source of alum, obtained by roasting the mineral, lixiviating the roasted mass, and evaporating the solution. Roman alum, produced thus from the mines at Tolfa, has long been known in the trade. Investigation has been made by the Bureau of Soils of the temperature and other conditions best suited to the production of alum or potassium sulphate from alunite and the possibilities of producing potash commercially from the alunite from various localities, of which only one has offered as yet any great promise. Near Marysville, Utah, occurs a large deposit of massive alunite, known for a number of years, but recently investigated by agents of the United States Geological Survey, who state, as a conservative estimate, that the Marysville deposit will yield 300,000 tons of alunite or 30,000 tons of potash for each 100 foot depth. How deep the deposit is can not yet be stated, but it occurs at elevations from 9,000 to 11,000 feet, and there is apparently good evidence that the main vein is a deep-seated one. Most if not all of the workable area is now in the hands of private parties who have substantial resources, and there seems to be good reason to think that potash from alunite may soon be a commercial product on the American market.

FELDSPAR AND POTASH SILICATES.

There are within the United States many and large deposits of rocks and minerals containing potassium. The potash feldspars, orthoclase, and microcline are abundant, frequently massive, and widely distributed through nearly all sections. Another potash silicate, leucite, found in lavas, is important only in the region of the Leucite Hills, Wyoming, but occurs there in very important quantities. The percentage of potassium in these potash-bearing silicates varies considerably, not only with the mineral species, but with each mineral. Probably it would average between 8 and 10 per cent, sometimes running as high as 16 per cent, and it has long been the dream of inventor and chemist to develop a commercially practicable method of extracting the potash from them. To this end a long list of patents has been granted in the United States and other countries. Of the methods so far proposed only a few merit consideration here. A general investigation of the various methods for which

patents have been issued has been made in the laboratories of the. Bureau of Soils. It was found, as has been noted by others, that there is small probability that any "potash from feldspar" proposition which depends on the production of potash salts alone can have a commercial future, but that commercially available by-products must also be produced.

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The temperatures and other conditions necessary for extracting potash from feldspar, by fusion with lime or other reagents, was investigated, and it was shown that by substituting ground feldspar for clay ” or “shale "a satisfactory clinker for cement purposes could be produced and the potash volatilized quantitatively. A somewhat similar process has been devised by Eakel and Spenser where greensand or glauconite was employed instead of feldspar. That the flue dust from cement kilns and other similar industrial operations frequently contains potash or potassium salts has been known for some time past. In the majority of such plants it has been held that the loss of material through the stack is too small to justify the installation of a precipitating or trapping system. One large cement plant in southern California, which has recently been equipped with a highly efficient precipitating device in their flues, and which has been employing a granite containing appreciable proportions of potash feldspars, is now experimenting on the possibilities of recovering potash from the flue dust, with rather promising results so far; and experiments with a small experimental plant are now under way in the Bureau of Soils to test the results of employing a high potashcarrying feldspar.

There is in course of erection at Curtis Bay, near Baltimore, under the auspices of a well-known firm of chemical manufacturers, a small plant for the production of potash salts from feldspar, according to the Firmin-Thompson process. Essentially this consists in heating a mixture of ground spar and niter cake or acid sodium sulphate together with sodium chloride in a rotary or Wedge or other suitable furnace. Hydrochloric acid is given off and trapped in the usual manner. The solid residue is leached with water, and the percolate evaporated, potassium chloride being separated by fractional crystallization. Other products of the operation are a very pure sodium sulphate and a pulverulent soda-lime-alumina silicate, with a probable value for certain types of glazing. No potash from this process is yet on the market, but the promoters expect shortly to produce about 40 tons a day.

In the Cushman-Coggeshall method the ground spar is mixed with calcium chloride, or lime and sodium chloride. By an ingenious "clumping" device the mix is brought into the form of pellets which are then passed through a furnace with definite heat relations. The 73029°-YBK 1912-34

roasted pellets are granular and in a form to be readily pulverized if desired. The product contains about 4.5 per cent of water-soluble potash, although the inventors claim a higher percentage is readily obtainable. It also contains a notable proportion of calcium chloride. It is suggested that this product is to be regarded as a fair substitute for wood ashes and should bring a commensurate price. If, however, the product must be marketed as a low-grade potassium chloride, it can be produced only at a loss. It is understood that this process has been exploited experimentally in the interests of one of the large manufacturers of fertilizers. So far the product has not been marketed.

Another of the large fertilizer manufacturers has been developing a process, the details of which are as yet not public. Essentially the process consists of heating a mixture of ground spar and coal in a stream of nitrogen or ordinary air at certain regulated temperatures and pressures. It is said that a volatile product or mixture of products is obtained which, when treated with steam and then leached yields potash, potassium carbonate, ammonia, carbon monoxide, and iron-free alumina. All of these products are readily salable, and there is left only a small mass of ferruginous material and lime silicate. A factory is now in course of construction, and if the practical results even approximate the laboratory results reported the "potash from feldspar " problem will have been solved.

While the extraction of potash from silicate carriers has been suggested in many other ways, none of them has acquired sufficient practical promise to justify a mention here.

DESERT BASINS.

Throughout the greater part of the far western States are numerous topographic units known as desert basins. In past geologic times folding and subsequent faulting produced many troughs and depressions, some of which were of stupendous depth. Into these the waters descending from the surrounding heights carried silt and dissolved mineral matter derived from the rims and carrying, of course, more or less potassium. Generally, the resulting topography was such that outlets were either nonexistent, temporary, or, at all events, insufficient, so that lakes were formed, some of vast extent, as the ancient Lahontan, or Bonneville. With the advent of arid periods these lakes evaporated, and their mineral contents concentrated, probably to the points where deposition of previously dissolved content took place. Probably periods of desiccation and of humidity alternated. But throughout all these periods all the troughs were gradually filling up with erosional detrita, until they have reached their present levels.

It is possible that during a period of desiccation salt was deposited from the then existing lakes, and that the deposition proceeded sufficiently far for the potash salts to be laid down in segregated layers. Laboratory investigations, confirmed by observations at Stassfurt and elsewhere, show that the potash salts, if deposited at all, should be expected in the upper layers. If, now, silt deposits covered these salt layers so as to protect them more or less efficiently from subsequent floodings, a "potash mine" may exist potentially in a desert basin if not too far below the surface to make its working commercially feasible.

It is possible, on the other hand, that desiccation never proceeded to the point where potash salts crystallized from the concentrating waters, or that it was not protected by a silt covering, and though indubitably potash, and perhaps much of it gone into the basin, it is disseminated through the silt fill. In such case no potash mine can. be expected.

It is impossible from any known criteria to determine or even intelligently guess a priori whether a segregated layer of potash lies or probably lies below the surface of a desert basin. The only way to find out is to bore. But before doing so it would be wise to consider the drainage area to the basin, the character of the rim rocks, and any other features which might be expected to affect the amount of potash which has been carried into the basin. About 200 basins have been examined in the past 18 months by the Bureau of Soils, and it has been possible to reduce the number in which there is any probability of potash being found to a very limited number, about 20, in which the chance may be regarded as good, and possibly as many more in which it may be considered doubtful. In any event, however, it is only a chance that a segregated layer of potash salts will be found. A boring has been put down by the Geological Survey, near Fallon, Nev., and private enterprise is putting down borings in the Railroad Valley and Dixie Valley, one of which has gone nearly 1,200 feet without "finding potash." An encouraging sign is the fact that the water from these borings has been quite fresh, and since there can be little doubt that much potash has been carried into the basins, the fresh water indicates that it is not disseminated through the fill, but probably segregated. But nothing definite has been indicated regarding the depth at which the segregations may be expected. A potash mine in a desert basin is yet a legitimate hope, but without definite promise of realization.

Sometimes the floor of a desert basin may carry a considerable salt deposit, but more often not. The surrounding mountains are bordered by "aprons" of descending slope merging finally into a flat plain in which there is at the point of greatest depression a “playa ”

or possibly a small lake. Usually the playa is a mud flat, and the place of concentration of the present drainage. One such playa, that of Searles Valley, is known to be of importance as a possible source of potash. The bottom of the Searles depression or Searles Lake is a body of white crystalline salt approximately 12 square miles in area, of varying depth, reaching probably 75 feet. Saline muds and sands, more or less well cemented, underlie the surface salt, the whole being saturated by a brine. The salts are mainly the chloride, carbonate and sulphate of sodium, lesser amounts of borax, and some potassium chloride, the potassium salts being mainly in the brine. This salt body has been until recently in the control of private interests. It is reported that they have satisfactorily worked out methods for separating the commercially desirable constituents, carbonate of soda, borax, and potassium chloride, and that the materials are in preparation for the installation of a large plant to produce and market these products. What is regarded as a very conservative estimate is that this deposit may ultimately yield 4,000,000 tons of potassium chlorid. Probably it will yield more. It has now been withdrawn from entry, at least temporarily, and its exploitation thereby delayed.

If plans now being contemplated for the diversion of the flow from the watershed of Owens Lake are finally consummated, that lake will gradually dry up, and in the final residue a considerable amount of potassium chlorid will be present. The chief value of the products of desiccation, however, will probably be in the borates. Agents of the United States Geological Survey have reported that the muds of Columbus Marsh contain notable quantities of potash salts and suggest that these may be economically recovered from the mother liquors from borings. This marsh is a broad mud plain lying on the line between Esmeralda and Mineral Counties, Nev., near the station of the Coaldale, Tonapah & Goldfield Railroad. The mud is of unknown depth. Wells to a depth of 50 feet have been sunk. On the average, the mud contains about 6 per cent of soluble salts and nearly 2 per cent of potassium chlorid, and it is thought that the mother liquor from the mud, if it can be economically separated from the solid material, will have a sufficiently high potash content to justify working it. Under the recent law, amended August 24, 1912, the President withdrew from entry January 16, 1913, all the lands of Columbus Marsh which are likely to yield workable quantities of potash salts, pending further investigation of their probable economic importance.

The salt mixture in the ocean is chemically neutral, and hence the salt deposits of Stassfurt resulting from the desiccation of sea water are neutral. It does not follow, however, that the solution resulting from the solvent action of meteoric waters on the rock masses of any particular area will be neutral. They may be, and