66 



PHYSIOGRAPHY, 



Black Silver. 



BLACK SILVER. Prismatoidal Polypoione- 

 Gla nee. 



Primary form. Right rhombic prism. MonM'=100 

 O 7 . The dimensions of the primary form, however, can- 

 not be considered as fixed, since LEONHARD and HART- 

 MANN describe crystals of this species, which appear to 

 have a primary form of 107 47'. 



Secondary forms. 



100 0' 



135 15 

 110 



170 10 



160 30 



146 30 



120 12 



145 24 



143 25 



122 15 J 



M on M' 



M or M' on a or a 4 



M on cl 



M on gl 

 M on g2 

 M on g3 

 a on cl 

 a on c2 

 a on c3 

 c3 on c3 



Fig. 62. 



Himmelsfurst mine r Freiberg-. 

 Fig. 63. 



- 72 13' HARTMANN. 

 p, s and o are tangent planes. 



The mutual inclinations of the pyra- 

 midal faces P, which correspond to the 

 lateral edges of the primary form, are 

 130 16 r and 104 19'. It also oc- 

 curs in crystals, destitute of the faces o 

 p and a. 



Przibram, Bohemia. 



Cleavage parallel to M and M 7 easy, and in other direc- 

 tions, of the variety from Freiberg. The variety from 

 Przibram has indistinct cleavages. 



