284 



PHYSIOGRAPHY. 



Iron Pyrites. 



gene. H.) 12. The cube, embracing all the previous mod- 

 ifications. 



Cleavage, parallel with the cube and octahedron, in va- 

 rious degrees of perfection ; sometimes highly perfect r, of- 

 ten one of them more distinct, or both lost in conchoidal 

 fracture. Fracture conchoidal, uneven. Surface of the 

 cube streaked parallel to the obtuse edges of combination 

 with the pentagonal dodecahedron : the faces of this dode- 

 cahedron are streaked, either parallel to the same edges, or 

 parallel to edges which are perpendicular to the former. 



Lustre metallic. Color, very few shades of a charac- 

 teristic bronze-yellow. Streak brownish-black. 



Brittle. Hardness = 6-0 ... 6-5. Sp. gr. = 5*031, a 

 cleavable variety, from Freiberg; = 4*981, a crystallized 

 variety, from Littmittz in Bohemia. 



Compound Varieties. Twin-crystals : face of composi- 

 tion parallel, axis of revolution perpendicular to a face of 

 the dodecahedron. The individuals continued beyond the 

 face of composition, by which the compound group takes a 

 cruciform appearance. The composition frequently re- 

 peated. 



Fig. 270. 



Schbharie, (N.Y.) 



