114 PHYSIOGRAPHY. 



Polybasite Polyhallite. 



Secondary form. The primary, having the terminal 

 edges replaced by three or six planes. 



Surface of the crystals streaked upon the terminal planes, 

 parallel to the sides of an equilateral triangle, or parallel 

 to the alternating edges of the six-sided prism. Fracture 

 uneven. 



Lustre splendent. Color, iron-black. 



Sectile. Hardness between Common Salt and Calca- 

 reous Spar. Sp. gr. = 6-214. 



Compound Varieties. Massive. 



2. It occurs partly in super-imposed crystals, partly massive and dis- 

 seminated, in the mine of Guanaxuato, in Mexico ; also at Guansamez 

 in Durango, with yellow Copper Pyrites and Calcareous Spar ; also with 

 Stilbite, at Andreasberg in the Hartz, and probably near Freiberg. 



POLYHALLITE. Stelene Bri thy ne- Salt. 



Massive : composition columnar. Cleavage parallel with 

 a prism of 115. Fracture splintery, uneven. 



Lustre resinous. Color smoke-grey and pearl grey, 

 flesh-red and brick-red. 



Hardness greater than 3-0. Sp. gr. 2-7689. STRO- 



MEYER. 



Taste saline and bitter. 



