Polytechnic Association. 753 



covered accidentally by the chemist II. Rose, in the waste of the salt 

 mine. The matter was at first lightly esteemed, the chloride of potas- 

 sium being even regarded as a nuisance ; but it is now thrice as valu- 

 able as the rock-salt, which was formerly the only product sought. 

 Over 30,000 tons have been extracted and sold in Germany, France 

 and England ; 3,000 tons were brought last year to the United States, 

 to be used in manufacturing saltpeter, by converting the chloride of 

 potassium into the nitrate. 



Pearlashes and potashes were formerly exported from the United 

 States to all foreign countries ; but our forests are getting cleared, and 

 these products are no longer largely prepared. Sweden likewise has 

 failed to supply France and England with vegetable ashes, and the 

 development at this juncture of the great potash mineral deposits of 

 Stassfurt is a striking providence. 



The salt deposits of that locality underlie the new red sandstone 

 of the Triassic period (called the Bunter sandstein), and comprise 

 four distinct levels, having a thickness of nearly 1,000 feet. Begin- 

 ning at the lowest level, we find : 



1. Anhydrite (sample shown). The bed comprises rock-salt and 

 sulphate of lime, which is anhydrous, 350 feet in thickness. 



2. Polyhalite, 100 feet in depth, elsewhere frequently of a brick- 

 red color, but in this locality white. It is composed of sulphate of 

 potash, lime and magnesia; has a weak, bitter taste, and fibrous 

 appearence, and is here likewise imbedded in rock-salt. 



3. Kieserite, a sulphate of magnesia, associated with salt. This 

 bed is seventy-five feet in thickness, and has carnallite also in the 

 gangue. 



4. Carnallite, the potash salt of greatest value. It is properly a 

 double chloride of magnesium and potassium, associated with the rock- 

 salt in the following proportions : Fifty per cent of the potash salt ; 

 twenty-five per cent of the magnesia salt ; twenty-five per cent of the 

 rock-salt. 



5. Tachhydrile, an amphorons salt, composed of chloride of cal- 

 cium and magnesium. 



6. Sylvite, a pure chloride of potassium. 



7. Kainite contains the hydrated chloride of potassium and sul- 

 phate of magnesia. 



8. Boraeite, a borate of magnesia, but in this locality containing 

 more of borate of lime. It is amphorous, and unlike the boraeite 

 crystals found in the gypsum of Luneburg, in Germany. It resembles 

 more the Ilayesine of Peru. This mineral has also been called 



. [Inst.] 48 



