22 



PHYSIOGRAPHY. 



Anhydrite. 



Fig. 27. 



Secondary form. 



Fig. 26. 



M d 



P on M, or T 

 MonT 

 M on d 

 Ton d 



Cleavage parallel with M and T perfect ; less easily ob- 

 tained parallel with P, yet quite distinct. 



Fracture imperfectly conchoidal, uneven. Surfaces M 

 and T smooth ; P rough. 



Lustre vitreous, inclining a little upon the most distinct 

 faces of cleavage to pearly. Color generally white, some- 

 times passing to flesh-red, violet-and smalt-blue or ash-grey. 

 Streak greyish-white. Transparent . . . translucent. 



Brittle. Hardness = 3-0 ... 3-5. Sp. gr.=2'89. 



Compound Varieties. Contorted ; composition colum- r 

 nar in thin fibres, parallel and variously bent. Massive : 

 composition granular, of different sizes, sometimes impalpa- 

 ble, and then the fracture is splintery ; in other massive va- 

 rieties, the composition is columnar, commonly thin and 

 parallel. Faces of composition rough. 



1. This species has been divided into several subspecies in the earlier 

 treatises on mineralogy. Thus the Cubic Muriacite, also called Cube 

 spar, comprehends simple varieties, and easily cleavable compound ones, 

 in which the individuals possess a considerable size. The name Anhy- 

 drite was appropriated to varieties of a smaller granular composition, and 



