-OBDKR X. HEXAHEDRAL IRON-PYRITES. 459 



are traces of . Fracture conchoidal, uneven. 



Surface, of the hexahedron streaked parallel to 

 the obtuse edges of combination with the penta- 

 gonal dodecahedron ; the faces of this dodeca- 

 hedron are streaked, either parallel to the same 

 edges, or parallel to the edges of combination 



rp 



with -, which are perpendicular upon the for- 

 mer, the faces of that icositetrahedron sometimes 

 are rough, the rest of the faces generally smooth 

 and shining. 



Lustre metallic. Colour, very few shades of a 

 characteristic bronze-yellow. Streak brownish- 

 black. 



Brittle. Hardness =2 5*031, a cleavable variety 

 from Freiberg; =4-981, a crystallised variety 

 from Littmitz in Bohemia. 



Compound Varieties. Twin-crystals : face of 

 composition parallel, axis of revolution perpendicu- 

 lar to a face of the dodecahedron. The individuals 

 continued beyond the face of composition, by which 

 the compound group takes a cruciform appearance 

 (WEiss. Mag. der Berl. Gesellscli. naturf. Fr. VIII. 

 24.). Imbedded and implanted globules : surface 

 drusy ; composition indistinctly columnar. Massive : 

 composition granular, sometimes even impalpable, 

 strongly coherent ; fracture uneven, or on a large 

 scale flat conchoidal. Cellular. 



OBSERVATIONS. 



1. Of the species of Iron-pyrites in the system of WER- 



