Definitions

chalcopyrite

chalcopyrite

[kal-kuh-pahy-rahyt]
chalcopyrite or copper pyrites, brass-yellow mineral, sometimes with an iridescent tarnish. It is a sulfide of copper and iron, CuFeS. It crystallizes in the tetragonal system but is usually found in the massive form. Chalcopyrite is of primary origin and occurs in igneous and metamorphic rocks and in metalliferous veins. It is an important ore of copper and is widely distributed throughout the world.

Most common copper mineral, a copper and iron sulfide (CuFeS2), and a very important copper ore. It typically occurs in ore veins deposited at medium and high temperatures, as in parts of Spain, Japan, Montana, and Missouri. Chalcopyrite is a member of a group of sulfide minerals, and it crystallizes in the tetragonal crystal system. Its atomic structure is related to that of sphalerite.

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Chalcopyrite (: 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.

Identification

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".

Chemistry

Natural chalcopyrite has no solid solution series with any other sulfide minerals. There is limited substitution of Zn with Cu despite chalcopyrite having the same crystal structure as sphalerite.

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.

It is likely many of these elements are present in finely intergrown minerals within the chalcopyrite crystal, for instance lamellae of arsenopyrite representing As, molybdenite representing Mo, etc.

Paragenesis

Chalcopyrite is present within many ore bearing environments via a variety of ore forming processes.

Chalcopyrite is present in volcanogenic massive sulfide ore deposits and sedimentary exhalative deposits, formed by deposition of copper during hydrothermal circulation. Chalcopyrite is concentrated in this environment via fluid transport.

Porphyry copper ore deposits are formed by concentration of copper within a granite stock during the ascent and crystallisation of a magma. Chalcopyrite in this environment is produced by concentration within a magma system.

Chalcopyrite is an accessory mineral in Kambalda type komatiitic nickel ore deposits, formed from an immiscible sulfide liquid in sulfur-saturated ultramafic lavas. In this environment chalcopyrite is formed by a sulfide liquid stripping copper from an immiscible silicate liquid.

Occurrence

Chalcopyrite is the most important copper ore. Chalcopyrite ore occurs in a variety of ore types, from huge masses as at Timmins, Ontario, to irregular veins and disseminations associated with granitic to dioritic intrusives as in the porphyry copper deposits of Broken Hill, the American cordillera and the Andes.

Chalcopyrite is present in the supergiant Olympic Dam Cu-Au-U deposit in South Australia.

Chalcopyrite may also be found in coal seams associated with pyrite nodules, and as disseminations in carbonate sedimentary rocks.

Generic term

In Solid State Physics, Chalcopyrite is sometime used as a generic term for any I(A/B)-III-C2 compound, with C a chalcogenide

References

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