PHYSIOGRAPHY. 



Proustite. 



121 



4. Fig. 344. 



5. Fig. 343, with the edges between d and d truncated. 



Cleavage, parallel with P rarely distinct. Fracture con- 

 choidal . . . uneven. Surface, d streaked parallel to its up- 

 per edges ; , vertically. 



Lustre adamantine. Color cochineal-red. Streak the 

 same as color. Semi-transparent to translucent on the 

 edges. 



Hardness =2-0. . .2-5. Sp. gr. =5-524, a cleavable 

 variety from Annaberg ; 5-422, a dark red variety, from 

 the Churprinz mine near Freiberg. 



Compound Varieties. Twin-crystals, and massive, com- 

 position granular, of various sizes of individuals. 



1. When heated before the blow-pipe, it decrepitates at first ; it then 

 melts with a bluish flame, emitting sulphurous acid, and in a more pow- 

 erful heat, the odor of arsenic ; and finally yields a metallic globule, 

 which is reducible to pure silver. Its solution in nitric acid, gives a 

 citron-yellow precipitate of sulphate of arsenic. 



2. Analysis. 



By ROSE. By PROUST. 



from Joachirnsthal. 



Sulphur . . 19-51 : Sulphuret of arsenic . 25-00 



Antimony . . 0-69 : Sulphuret of silver . 7435 



Arsenic . . 15-09 : Oxide of iron . 0-65 



Silver . . 64 67 : 



VOL. II. 



11 



