468 PHYSIOGRAPHY. CLASS II. 



Cleavage, traces in the direction of the octahedron, 

 Fracture small conchoidal, uneven. Surface ge- 

 nerally rough, particularly the hexahedron, and 

 often curved, much subject to tarnish. 



Lustre metallic. Colour intermediate between 

 copper-red and pinchbeck-brown. Streak pale 

 greyish-black, a little shining. 



Rather sectile. Hardness = 3-0. Sp. Gr. = 5*003, 

 from the Bannat. 



Compound Varieties. Twin-crystals: axis of 

 revolution perpendicular, face of composition paral- 

 lel to a face of the octahedron, the individuals be- 

 ing continued beyond the face of composition. Fig. 

 128. Massive : composition granular, strongly con- 

 nected, fracture conchoidal and uneven. 



OBSERVATIONS. 



1. The tessular form of the present species has been first 

 recognised by Mr W. PHILLIPS in very distinct crystals, 

 resembling Fig. 3. (Vol. I.). Generally, however, parti, 

 cularly the larger crystals, are less regularly formed, and 

 grouped in twins resembling those of octahedral Fluor-ha- 

 loide and rhombohedral Kouphone-spar. 



2. According to Mr It. PHILLIPS, it consists of 



Copper 6 1-07. 



Sulphur 23-75. 



Iron 14-00. 



Silica 0-50. 



The formula Fe S 2 + 4 Cu S agrees very nearly with this 

 analysis, giving the proportions of copper, iron, and sul- 

 phur, = 62-67 : 13-44 : 23-89. Before the blowpipe it 

 comports itself very much like pyramidal Copper-pyrites. 



3. It occurs in beds and veins, the crystallised varieties 



