PHYSIOGRAPHY. 271 



White Iron-Pyrites. 



Cleavage, parallel with M rather perfect. Fracture un- 

 even. Surface, c and a deeply streaked parallel to their 

 edges of combination with P. 



Lustre metallic. Color pale bronze-yellow, sometimes 

 inclining to green or grey. Streak greyish-black, or 

 brownish black. 



Brittle. Hardness = 6-0 ... 6-5. Sp. gr. = 4*678, 

 crystals from Schemnitz ; 4-847, crystals from Littmitz. 



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

 position parallel, axis of revolution perpendicular to a face 

 of M. This composition is generally repeated, as in the 

 annexed figure, where a group of five individuals is formed. 



Fig. 473. 



having much the appearance of a five-sided pyramid with 

 truncated apices, each of the five solid angles at the base 

 presenting a re-entering angle. 2. Face of composition 

 parallel, axis of revolution perpendicular to a and c. This 

 composition takes place in varieties already compounded by 

 the first law. They assume a grooved appearance. The 

 re-entering angle formed by the faces P=114 19'. 

 Globular, reniform, stalactitic and other imitative shapes : 

 surface drusy ; composition columnar, individuals straight. 



