MINERALS OF CHILE. 63 



MERCURIAL GRAY COPPER. 



This is found in some of the mercurial mines of Chile in 

 small amorphous masses, disseminated in a quarter gangue, 

 accompanied by the blue carbonate of copper and a red earthy 

 substance of deep-red color, apparently an antimoniate of mer- 

 cury. This also has been analyzed by Domeyko, with the 

 following result: 



Antimony 20.7 



Iron 1 5 



Zinc trace. 



Copper 33.6 



Mercury 24.0 



Sulphur 20.2 



100.0 

 ANTIMONIAL GRAY COPPER. 



This is the common form of gray copper, and several speci- 

 mens were brought home by the expedition. It contained but 

 a small amount of silver, as seen by the following analysis : 



Sulphur 26.83 



Antimony 23 21 



Arsenic 3.05 



Copper 36.02 



Iron 2.36 



Zinc 4.52 



Silver 3.41 



99.40 

 The formula of gray copper is represented by — 



(4 Cu 2 , Ag, Fe, Zn) S+(Sb As) S 3 . 



Besides the above species of gray copper, others are found 

 which, whether arsenical or antimonial, contain only a few 

 thousandths of mercury. These varieties are almost invariably 

 destitute of silver. 



DOMEYKITE, ARSENICAL COPPER. 



This mineral is massive, of a tin-white color, with a metallic 



luster, and specific gravity of 4.5. It is about the hardness of 



copper pyrites. The specimen examined was not a pure one; 



it furnished 



Arsenic 22.08 



Copper 72.41 



Iron 3.22 



Sulphur 2.01 



99.72 



