CHAPTER VI 
ORES OF COPPER 
CoppEr—QuaLITIES, Uses, AND PricE—Copper (Cu, named 
after Cyprus; at. wt., 63:5; sp. gr, 89; melting-point, 
1950° F.), the red metal, was one of the metals most used by 
prehistoric man, for native copper is widely distributed, 
easily wrought, and bronze, its alloy with tin, makes excellent 
tools, Copper being soft, malleable, ductile, and tough, 
can be hammered into sheets, drawn into strong thin wire, 
and beaten into cooking pots and water vessels: it is used 
for electric cables as it is the best conductor of electricity, 
and is the main constituent of bronze and brass. It does not 
readily rust, but the surface slowly alters into green carbonate, 
which gives a pleasing colour to copper sheathing on roofs. 
Copper is found in many altered basic igneous rocks, and 
silicate of copper is possibly a primary constituent of some 
ferro-magnesian minerals. The primary ores are chiefly 
sulphides, usually combined with iron, as in chalcopyrite 
(CuFeS,, 34-5 per cent. copper) and bornite (CuyFeS, with 
55-5 per cent. copper) ; the secondary ores include chalcocite 
(Cu,S, 29-8 per cent. copper) and cuprite (CuO, 88-8 per cent. 
copper). Most copper ores are easily dissolved and their 
constituents separately deposited; chalcocite is often thus 
formed in secondary enrichments, though it is sometimes 
primary, as at Butte, Montana, Mt. Lyell in Tasmania, 
and in Connecticut (Bateman, Econ. Geol., xviii, 1923, 
. 122). 
P =. mines, mainly in Cornwall and Devon, from 1821 
to 1830 yielded 45 per cent, of the world’s copper supply 
(N. Brown and Turnbull, Century of Copper, 1906, p. 6). 
The British output fell to 30 per cent. after 1840, but was 
important until 1871. In the last decade it was only ‘15 
So