POTASSIC MAXUEES. 



299 



\Yhich orenerally only occurs with rock salt ; according to certain 

 authors, however, this coloration is due to admixture with blue rock 

 salt. Svlvine as it comes from the mine has the following com- 

 position, according to Mercker : — 



100-00 

 Its potash content is 23-04. 



3. Kainit is met with in large quantities, chiefly in the- 

 Leopoldshall mine and at New Stassfurt. A deposit of more than 

 25 metres (82 feet) has been found at Kalusz of almost pure kainit. 

 It is colourless, or yellow to reddish or even a very dark brown. 

 It is very hard in comparison ^\'ith the other minerals mentioned 

 in this chapter. Its density is 2-131. Its fracture has a crystalline 

 lustre ; it rarely gives true crystals. It contains, according ta 

 Eeichardt : — 



TABLE XCYIIL— SHO^YING ANALYSIS OF KAINIT. (EEICHARDT.) 



or 



Sulphate of potash 32-12 | 



,, magnesia 22-87 ) 



Magnesium chloride 



Water 17-37 



A -^ -i.- ( Common salt 9*90 



As impurities - x i ui a oo 



^ ' Insoluble 0-22 



54-9^ 

 16-95 



100-00 



Pure kainit responds to the formula — 



KoSO, + MgSO, + MgCl, + H.O. 



Kainit is, therefore, a double sulphate of potassium and magnesium 

 combined with magnesium chloride. It forms, therefore, a peculiar 

 compound, which no one as yet has succeeded in reproducing- 

 artificially like svlvine and carnallite. Its mode of formation is thus 

 uncertain ; it is supposed, however, that it results from the action of 

 water on a mixture of carnallite and kieserite found in the salt 



