MINERALS OF CHILE. 65 



Corresponding very nearly to the formula, Cu 3 Si 2 -f- 6 H. Other 

 specimens were found to contain oxide of copper varying from 

 twenty to fifty per cent. 



The name Llanca is given by miners to a silicate of differ- 

 ent shades of green and blue, which very often accompanies 

 the copper minerals, especially the oxysulphurets, forming the 

 envelope of some veins, constituting masses in which native 

 copper, red oxide, carbonate, and at times sulphurets of copper, 

 are found. Most of the copper-veins in Chile abound in these 

 silicates near the surface. The basic silicate found in many of 

 the copper-mines of Coquimbo are always in the upper parts 

 of the veins, forming narrow seams, between red oxide and 

 green and blue Llanca. It is frequently mixed with the black 

 silicate. La Higuera and San Lorenzo furnished the specimens 

 examined. 



AZURITE, BLUE CARBONATE OF COPPER. 



This occurs both crystallized and massive. Among the speci- 

 mens was one, crystallized on copper pyrites, from Andacollo. 

 It possesses all the common characteristics of this mineral as 

 found elsewhere, and is composed of 



Oxide of copper 69.09 



Carbonic acid 25.69 



Water 5.22 



The formula representing it is 2 Cu O-f-Cu H. 

 It is found in many localities associated with the ores of 

 copper. 



MALACHITE, GREEN CARBONATE OF COPPER. 



This mineral exists abundantly in Chile, but is not found in 

 those large compact masses (such as are procured from Siberia 

 and other places) out of which ornaments are made. It has 

 no peculiar properties in which it differs from the malachite 

 of other localities. Crystallized specimens were procured from 

 Tortolas and Tamaya. Other specimens came from Tarienta, 

 San Jose, etc. Its composition is 



Carbonic acid 20.00 



Oxide of copper 71.82 



Water 8.18 



100.00 



Formula is Cu 2 C+H. 



