64 MINERALS OF CHILE. 



Perfectly pure specimens, according to Domeyko, contain 



Arsenic 28 36 



Copper 71.64 



"Which give the formula Cu 3 As. 10 ° 00 



It is found pure, without any admixture of sulphuret, near 

 Illapel, in the same veins which near the surface yield red cop- 

 per 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 copper. 



Besides this species, there is found in the Cordilleras a kind 

 of white native copper, containing from 3 to 5 per cent, of 

 arseniuret of copper, and resembling native silver. 



0LIVEN1TE, 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 



And the formula is Cu 4 (Is, £)+H. 100 - 00 



CHRYSOCOLLA, SILICATE OF COPPER. 



This is very commonly found in all the copper-veins of Chile, 



always massive, sometimes in the form of mamillary coatings 



and concretions. It is of various shades of green and blue, 



and sometimes of a dark and almost black color. Its specific 



gravity is 2.2. It is easily crushed. It is not an easy matter 



to find the chrysocolla perfectly pure. The specimen that 



furnished the material analyzed was a mass of copper pyrites, 



covered with a mamillary coating of the silicate, which was 



detached with much care. It furnished 



Oxide of copper 42.51 



Silica 31.35 



Water 21.62 



Oxide of iron 1.97 



Alumina 2.82 



100.00 



