CHALCOPYRITE
Chalcopyrite (pronounced /ˌkæl.koʊˈpaɪ.raɪt/:
kal-co-pie-right—"kal" as in "calendar",
"co" as in code) is a copper iron sulfide mineral that
crystallizes in the tetragonal system. It has the chemical composition CuFeS2.
It has a
brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its
streak is diagnostic as green tinged black.
On exposure
to air, chalcopyrite oxidises to a variety of oxides, hydroxides and sulfates.
Associated copper minerals include the sulfides bornite (Cu5FeS4),
chalcocite (Cu2S), covellite (CuS), digenite (Cu9S5);
carbonates such as malachite and azurite, and rarely oxides such as cuprite (Cu2O).
Chalcopyrite is rarely found in association with native copper.
Chalcopyrite
is often confused with pyrite, although the latter has a cubic and not a
tetragonal crystal system. Further, chalcopyrite is often massive, rarely
crystalline, and less brittle. Chalcopyrite is also a darker yellow in color,
with a greenish tinge and diagnostic greasy luster.
Due to its
color and high copper content, chalcopyrite has often been referred to as
"yellow copper".
However, it
is often contaminated by a variety of other trace elements such as Co, Ni, Mn,
Zn and Sn substituting for Cu and Fe. Se, Fe and As substitute for sulfur, and
trace amounts of Ag, Au, Pt, Pd, Pb, V, Cr, In, Al and Sb are reported.
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