AUt 14 



Issued July 16, 1912, 



United States Department of Agriculture, 



BUREAU OF SOILS CIRCULAR NO. 71. 

 MILTON WHITNEY, Chief 



U. S. DEPARTMENT OF AGRICULTURE, 



BUREAU OF SOILS, 

 Washington, D. C., May 28, 1912. 



SIR: I have the honor to transmit herewith the manuscript of an article on 

 the Extraction of Potash from Silicate Rocks, by William H. Ross, Scientist 

 in Physical and Chemical Laboratory Investigations, Bureau of Soils, and to 

 request that it be published as Circular No. 71, of this bureau. 

 Very respectfully, 



MILTON WHITNEY, 



Chief of Bureau. 

 Hon. JAMES WILSON, 



Secretary of Agriculture f OF 



THE EXTRACTION OF POTASH FROM SILICATE ROCKS. 



The potash-bearing minerals of the United States may conven- 

 iently be divided into three classes, as follows: (1) Alunite and simi- 

 lar minerals; (2) the greensand marls; and (3) the igneous rocks. 



Alunite is a hydrated sulphate of aluminum and potassium. It 

 differs from the minerals of the other two groups in that the potas- 

 sium is readily available by simple ignition of the mineral to a dull 

 red heal. 1 When occurring in sufficient quantity and purity alunite 

 is thus a possible economic source of potash and has long served as 

 a source of potassium alum in Italy and other countries. Its occur- 

 rence in this country is limited to comparatively small deposits in 

 Utah, Colorado, and Nevada, the largest so far known, near Marys- 

 vale, Utah, having been recently described. 2 



Greensand, or glauconite, is essentially a hydrated silicate of iron 

 and potassium, but it is extremely variable in composition and never 

 occurs pure. It is formed through the interaction of various altera- 

 tion products, and organic matter is believed to play a part in its 

 formation, 3 which would explain its occurrence in the marl deposits 



1 Waggaman, Circular No. 70, Bureau of Soils, U. S. Dept. Agr. 



2 Butler and Gale. Bui. U. S. Geol. Survey, No. 511. 

 "Clarke, Bui. U. S. Geol. Survey, No. 491, p. 942. 



46621 Cir. 71 12 



