280 



PHYSIOGRAPHY. 



Wolfram. 



Secondary form. 



Fig. 483. 



M 



Zinnwald. 



116 34' 

 98 12 



Fracture uneven- 

 P sometimes curv- 



P on a 



u on u over P - 



Cleavage, parallel with a perfect. 

 Surface, M and a streaked vertically, 

 ed. 



Lustre metallic adamantine,, or imperfectly metallic. 

 Color dark greyish or brownish black. Streak dark red- 

 dish-brown. Opake. 



Not very brittle. Hardness = 5-0 . . . 5-5. Sp. gr. = 

 7-155. 



Compound Varieties. Twin-crystals : 1 . Face of com- 

 position parallel, axis of revolution perpendicular to a. 2. 

 Face of composition parallel, axis of revolution perpendic- 

 ular to a face of u. There is often a curious composition 

 in the exterior of crystals parallel to all their faces. Mas- 

 sive : composition irregularly lamellar, easily separated, fa- 

 ces of composition irregularly streaked ; also columnar, the 

 individuals being generally of a considerable size, straight 



