STASSFURT SALTS 1 89 



acid phosphates, liberates some potash. The potash 

 compounds of the soil are in various degrees of com- 

 plexity from forms soluble in dilute acids to insoluble 

 minerals as feldspar. 



232. Commercial Forms of Potash. — Prior to the 

 introduction of the Stassfurt salts, wood ashes were 

 the main source of potash. Since the discovery and 

 development of the Stassfurt mines, the natural prod- 

 ucts as kainit, and muriate and sulphate of potash have 

 been extensively used for fertilizing purposes. A 

 small amount of potash is also obtained from waste 

 products as tobacco stems, cottonseed hulls, and the 

 refuse from beet-sugar factories. 



STASSFURT SALTS 



233. Occurrence. 63 — The Stassfurt mines were first 

 worked with the view of procuring rock salt. The 

 presence of the various compounds of potash, soda, and 

 magnesia, associated with the layers of rock salt, were 

 regarded as troublesome impurities, and attempts were 

 made by sinking new shafts to avoid them, but with 

 the result of finding them in greater abundance. 

 About 1864 their value as potash fertilizers was es- 

 tablished. The mines are now owned and worked by 

 a syndicate. It is supposed that at one time the 

 region about the mines was submerged and filled with 

 sea-water. The tropical climate of that geological period 

 caused rapid evaporation, which resulted in forming 

 mineral deposits, the less soluble material as lime sul- 



