THE MINERALS OF CHILE. 91 



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) SI 

 Besides the above species of gray copper, others are found, which, whether arsenical or anti- 

 monial, contain only a few thousands of mercury; these varieties are almost invariably destitute 

 of silver. 



Domeylcite, Arsenical Copper. — This mineral is massive, of a tin-white color, with a metallic 

 lustre, 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. T2 



Perfectly pure specimens, according to Domeyko, contain — 



Arsenic - 28.36 



Copper ------- 71.64 



100.00 



Which give the formula Cu' As. 

 It is found pure without any admixture of sulphuret near Illapel, in the same veins which, 

 near the surface, yield red copper with native silver ; it is also found in some of the silver mines 

 of Atacama, particularly in those of San Antonio. 



It is almost always mixed with copper pyrites in varying proportions, and sometimes with 

 the oxide and amorphous green arseniate of copj)er. 



Besides this species, there is found in the Cordilleras a kind of white native copper, contain- 

 ing from 3 to 5 per cent, of arseniuret of copper and resembling native silver. 



Olivenite, Arseniate of Copper. — It always accompanies the arseniurets and is amorphous, 

 with a compact earthy structure, green color^ with varying shades, and is always mixed with 

 carbonate and silicates of copper. This mineral it appears is never found perfectly pure in 

 Chile ; but when pure, as found elsewhere, it contains — 



Arsenic acid - - - - - - 31.78 



Phosphoric acid _ _ _ - _ 6.57 



Oxide of copper ----- 58.34 



Water 3.31 



100.00 



and the formula is — 



Cu" (Is, ^) -I- fi 



