THE MINERALS OP CHILE. 93 



Blue Vitriol, Sulphate of Copper .—IhiB salt is found associated with the sulphate of iron 

 and alumina, at Tierra Amarilla, in the valley of Copiapo. It arises from the decomposition 

 of copper pyrites. It is constituted of — 



Oxide of copper ----__ 32.14 



Sulphuric acid ------ 31.72 



Water - - 36.14 



100.00 

 Its formula is Cu 5 -|- 5 S. 



Volhortliite, Vanadate of Copper and Lead. — This rare mineral was first noticed in Chile by 

 M. Domeyko, in the Mina Grande, about 6 miles from the silver mines of Arqueros. It is an 

 amorphous substance, porous, heavy, and of a dark brown color. It lines the cavities of an 

 arsenio-phosphate of lead. At first view, it would be confounded with the hydrated oxide of 

 iron, from which it differs, however, by its great fusibility and ready solubility in nitric acid. 



There were no specimens sufficiently pure for analysis. Those examined by M. Domeyko gave 



1. a. 



Oxide of lead - - - 



Oxide of co]Dper - - - 



Vanadic acid - _ - 



Arsenic acid - - - - 



Phosphoric acid - - - 



Chloride of lead - - - 



Silica (?) 



Lime - - - - - 



Oxide of iron and alumina 



Earthy residue - - - 



Loss by heat - - - - 



Giving for its formula Pb« V + Cu"* V. 



This differs somewhat from the formula furnished by the analysis of the volborthite, as found 

 in the copper mines between Miash and Katherinenberg, Eussia; but, as the Chile variety 

 has not yet been found crystallized, the differences may be due to impurities. 



Remarks on the Copper Minerals. — The minerals of copper have been described after gold 

 from the fact that the great mass of them occur in Chile in the same geological formation as the 

 gold. It is the granite that is most commonly traversed by copper veins, sometimes of a 

 considerable size. Along the coast it is found in the form of copper pyrites alone, or associated 

 with two varieties of iron pyrites, and also as peacock or purj)le copper. Galena and blende 

 are rarely found with them, and scarcely ever gray copper. Native copper, red oxide, oxy- 

 chloride, oxy-sulphuret, green carbonate, and hydrous and an-hydrous silicates of copper, of a 

 great variety of colors, are also abundant, especially at the upper jDart of the veins. The 

 silicates sometimes line the walls of the veins, and penetrate to some distance in the enclosing 

 rock, which becomes unequally colored blue or green. The numerous veins of copper are dis- 

 seminated very irregularly in the granite, and their value is equally variable ; sometimes the 

 veins have a breadth of from 6 to 9 feet, as at Tamaya, near Coquimbo, where, at the depth 

 of 600 feet, there is a daily yield of from 8 to 10 tons of an ore yielding seldom less than 50? 

 and oftentimes as much as To, per cent, of copper. 



54.9 



51.97 



14.6 



16.97 



13.5 



13.33 



4.6 



4.68 



.6 



.68 



.3 



.37 



1.0 



1.33 



.5 



.58 



3.5 



3.42 



1.0 



1.52 



2.7 



2.70 



97.20 



97.55 



