228 



PHYSIOGRAPHY, 



Telluric Silver. 



TELLURIC SILVER. Telluric Polypoione- 



Glanc e. 



Massive. Cleavage, in one direction distinct. 

 Lustre shining. Color between lead grey and steel grey. 

 Hardness- 2-5... 2-75. Sp. gr. = 8412. 



1. Before the blow-pipe, it melts upon charcoal into a black mass, in 

 which dendrites of silver are visible. It is soluble in cold nitric acid, 

 2. Analysis. 



By ROSE. 

 Silver . . . . . . 82-63 



Tellurium 3737 



3. It is found with Iron Pyrites, Blende and Telluric Lead, in the 

 mine of Sawodinski, in Siberia. 



TENNANTITE. 



Primary form. Tetrahedron. 



Secondary forms. 



1. Tetrahedron, with angles truncated. 



3. Fig. 432. 



Cleavage, parallel with d, imperfect. 



Lustre metallic. Color blackish lead-grey. Streak reddish 

 grey. Opake. 



Brittle. Scratches Fahlerz. Sp. gr. =4-375 . . .4-491. 



Compound Varieties. Twin-crystals : axis of revolution per- 

 pendicular, face of composition parallel to a face of the octahe- 

 dron ; the individuals are continued beyond the face of composi- 



