OEDEJJ. XI. PlilSMATIC COPPER-GLANCE. 9 



particularly Pr -f oo, are streaked parallel to their 



common intersections, often deeply furrowed. 

 Lustre metallic. Colour blackish lead-grey. Streak 



unchanged, sometimes shining. 

 Very sectile. Hardness = 2-5 ... 3-0. Sp. Gr. = 



5-695, the compact variety from the Bannat. 



Compound Varieties. Twin-crystals : 1. Axis of 

 revolution perpendicular to one or to both faces of 

 Pr ; face of composition parallel to it ; Sim. Fig, 

 38., only that the re-entering angles between / and 

 I are filled up ; 2. Axis of revolution perpendicu- 

 lar, face of composition parallel to a face of (Pr) 5 , 

 the individuals are continued beyond the face of 

 composition, Fig. 41. The inclination of s on ' is 

 equal to that of the acute terminal edge of (Pr) 5 = 

 88 9 / on one side, and 91 51' on the other ; the 

 respective inclinations of a on a' are = 153 37' and 

 =z: 157 19 7 . Massive : composition granular, of 

 various sizes of individuals, generally small, and 

 often impalpable ; in the last case, the fracture be- 

 comes uneven, even or flat conchoidal. Plates. 



OBSERVATIONS. 



1. The division of Vitreous Copper in the Wernerian 

 system, into foliated and compact Vitreous Copper, depends 

 upon the state of mechanical composition and the perfec- 

 tion of cleavage. But few varieties only are comprehended 

 in the first subspecies, namely, such as possess a granular 

 composition and distinct traces of cleavage. Far the greater 

 part is compact Vitreous Copper, which embraces not only 

 the compact varieties, consisting of impalpable individuals, 



