178 THE MINERALS OF TASMANIA. 



100° C. Discarding the solubles and traces of antimony 

 and lime, it would appear that this mineral, 'per se, has 

 the following composition : — 



This separation is on the assumption that the pyritic 

 mineral which is visible in the mass with the ordinary 

 glass is chiefly iron pyrites. The appearance of it, how- 

 ever, would lead one to think that it was at least cuprifer- 

 ous, if not straight chalcopyrite. However, right through 

 the larger specimen there is a flat vein J-inch thick of 

 solid iron pyrites, associated with a very little chalco- 

 pyrite. Abiding by the assumption that the main foreign 

 material is iron pyrites as above, the composition, 2^^'^ ^^> 

 of the pure mineral would be: — 



Per cent. 



Copper = 46 • 86 



Arsenic = 18-55 



Sulphur = 27-80 



Zinc = 7-29 



100-00 



Now, taking the original analysis, and dividing by the 



atomic weights to get the number of atoms present, we 



find the following : — Atoms 



Copper 3= 12 



Iron = 1 



Arsenic- = 4 



Sulphur = 16 



Zinc = 2 



This corresponds to a percentage composition as follows : — 



Per cent. 

 Copper = 43 - 34 

 Iron = 3-19 



Arsenic = 17-07 



Sulphur = 29-12 

 Zinc = 7-28 



100-10 



and a formula as follows : — 



Fe Sa (6CU2 S -f- Zn S2 As^ S3 

 Fe Sg [4 (Cu^ Zn) S As^ S3] 



