2l6 SOILS AND FERTILIZERS 



STASSFURT SALTS 



248. Occurrence. 64 --The Stassfurt mines were first 

 worked with the view of procuring rock salt. The va- 

 rious compounds of potash, soda, and magnesia, asso- 

 ciated 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 fertilizer was established. It is 

 supposed that at one time the region about the mines 

 was submerged and filled with sea water. The tropi- 

 cal climate of that geological period caused rapid evapo- 

 ration, which resulted in forming mineral deposits, the 

 less soluble material as lime sulphate being first depos- 

 ited, then a layer of rock salt, and finally layers of pot- 

 ash and magnesium salts in the order of their solubility. 



249. Kainit is a mineral composed of potassium 

 sulphate, magnesium sulphate, magnesium chloride, and 

 water of crystallization. As it comes from the mine 

 it is mixed with gypsum, salt, potassium chloride, and 

 other bodies. Kainit contains about 12 per cent potash 

 and is one of the most important of the Stassfurt salts. 

 It is extensively used as a potash fertilizer, and is also 

 mixed with other materials and sold as a complete fer- 

 tilizer. The magnesium chloride causes it to absorb 

 water, and the presence of other compounds results 

 in the formation of hard lumps, whenever kainit is 



