66 MINERALS OP CHILE. 



BLUE VITRIOL, SULPHATE OF COPPER. 



This 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 consti- 

 tuted of 



Oxide of copper 32.14 



Sulphuric acid 31.72 



Water 36.14 



Its formula is Cu S+5 A. 1000 ° 



VOLBORTHITE, VANADATE OP COPPER AND LEAD. 



This rare mineral was first noticed in Chile by M. Domeyko, 

 in the Mina Grande, about six 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-phos- 

 phate 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 exam- 

 ined by M. Domeyko gave 1 2 



Oxide of lead 54.9 51.97 



Oxide of copper 14.6 16.97 



Vanadicacid 13.5 13.33 



Arsenic acid 4.6 4.68 



Phosphoric acid .6 .68 



Chloride of lead 3 .37 



Silica (?) 1.0 1.33 



Lime..... .5 .58 



Oxide of iron and alumina 3.5 3.42 



Earthy residue 1.0 1.52 



Loss hy heat 2.7 2.70 



97.20 97.55 



Giving for its formula Pb 6 V-j-Cu 6 V. 

 This differs somewhat from the formula furnished by the 

 analysis of the volborthite, as found in the copper - mines 

 between Miash and Katherinenberg, Russia; 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 



