92 THE MINERALS OF CHILE. 



Chrysocolla, Silicate of Copper. — This is very commonly found in all the copper veins of 

 Cliile, always massive, sometimes in the form of mamillary coatings and concretions. It is of 

 various shades of green and blue, 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 ------- 2.83 



100.28 



Corresponding very nearly to the formula — 



Cu' '&i' + 6 fi ; 

 other specimens were found to contain oxide of copper varying from 20 to 50 per cent. 



The name Llanca is given by miners to a silicate of different shades of green and blue, which 

 very often accompanies the copper minerals,especially the oxy-sulphurets, forming the envelope 

 of some veins, constituting masses in which native coj^per, 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 Cop^jer.— This occurs both crystallized and massive. Among the 

 specimens was one crystallized on copper pyrites, from AndacoUo. 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 



100.00 



The formula representing it is — 



2 Cu -I- Cu fl. 

 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 some 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, &c. Its composition is — 

 Carbonic acid ------ 20. 



Oxide of copper - - - - - - 71.82 



Water ------- 8.18 



100.00 



Formula is Gu^ C + A- 



