Math Is Fun Forum

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 47,696

Chalcopyrite

Chalcopyrite

Gist

Chalcopyrite is the most important and major source of copper metal. It is widely spread copper–iron sulfide mineral with chemical formula (CuFeS2). The color is typically brass to golden-yellow, often tarnished, with greenish-black streak and submetallic luster.

Summary

Chalcopyrite is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. 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 tarnishes 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). It is rarely found in association with native copper. Chalcopyrite is a conductor of electricity.

Copper can be extracted from chalcopyrite ore using various methods. The two predominant methods are pyrometallurgy and hydrometallurgy, the former being the most commercially viable.

Etymology

The name chalcopyrite comes from the Greek words chalkos, which means copper, and pyrites', which means striking fire. It was sometimes historically referred to as "yellow copper".

Identification

Chalcopyrite is often confused with pyrite and gold since all three of these minerals have a yellowish color and a metallic luster. Some important mineral characteristics that help distinguish these minerals are hardness and streak. Chalcopyrite is much softer than pyrite and can be scratched with a knife, whereas pyrite cannot be scratched by a knife. However, chalcopyrite is harder than gold, which, if pure, can be scratched by copper. Chalcopyrite has a distinctive black streak with green flecks in it. Pyrite has a black streak and gold has a yellow streak.

Chemistry

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

Minor amounts of elements such as silver, gold, cadmium, cobalt, nickel, lead, tin, and zinc can be measured (at parts per million levels), likely substituting for copper and iron. Selenium, bismuth, tellurium, and As may substitute for sulfur in minor amounts. Chalcopyrite can be oxidized to form malachite, azurite, and cuprite.

Structure

Chalcopyrite is a member of the tetragonal crystal system. Crystallographically the structure of chalcopyrite is closely related to that of zinc blende ZnS (sphalerite). The unit cell is twice as large, reflecting an alternation of Cu+ and Fe3+ ions replacing Zn2+ ions in adjacent cells. In contrast to the pyrite structure chalcopyrite has single S2− sulfide anions rather than disulfide pairs. Another difference is that the iron cation is not diamagnetic low spin Fe(II) as in pyrite.

In the crystal structure, each metal ion is tetrahedrally coordinated to 4 sulfur anions. Each sulfur anion is bonded to two copper atoms and two iron atoms

Details

Chalcopyrite is a brass-yellow mineral with a chemical composition of CuFeS2. It occurs in most sulfide mineral deposits throughout the world and has been the most important ore of copper for thousands of years.

The surface of chalcopyrite loses its metallic luster and brass-yellow color upon weathering. It tarnishes to a dull, gray-green color, but in the presence of acids the tarnish can develop a red to blue to purple iridescence.

The iridescent colors of weathered chalcopyrite attract attention. Some souvenir shops sell chalcopyrite that has been treated with acid as "peacock ore." But, "peacock ore" is a more appropriate name for the mineral bornite.

Physical Properties of Chalcopyrite

The most obvious physical properties of chalcopyrite are its brassy yellow color, metallic luster, and high specific gravity. These give it a similar appearance to pyrite and gold. Distinguishing these minerals is easy. Gold is soft, has a yellow streak and has a much higher specific gravity. Chalcopyrite is brittle and has a greenish gray streak. Pyrite is hard enough that it cannot be scratched with a nail, but chalcopyrite is easily scratched with a nail.

The name "fool's gold" is most often associated with pyrite because it is more common and more often confused with gold. Chalcopyrite is also confused with gold, so the name "fool's gold" is also applied and appropriate.

Physical Properties of Chalcopyrite

Chemical Classification  :  Sulfide
Color     :  Brass yellow. Tarnishes to gray green, sometimes iridescent.
Streak  :  Greenish black
Luster  :  Metallic
Diaphaneity  :  Opaque
Cleavage  :  Poor
Mohs Hardness  :  3.5 to 4
Specific Gravity  :  4.1 to 4.3
Diagnostic Properties  :  Color, greenish streak, softer than pyrite, brittle.
Chemical Composition  :  Copper iron sulfide, CuFeS2.
Crystal System  :  Tetragonal
Uses  :  The most important ore of copper for thousands of years.

Geologic Occurrence of Chalcopyrite

Chalcopyrite forms under a variety of conditions. Some is primary, crystallizing from melts as accessory minerals in igneous rocks. Some forms by magmatic segregation and is in the stratified rocks of a magma chamber. Some occurs in pegmatite dikes and contact metamorphic rocks. Some is disseminated through schist and gneiss. Many volcanogenic massive sulfide deposits containing chalcopyrite are known.

The most significant chalcopyrite deposits to be mined are hydrothermal in origin. In these, some chalcopyrite occurs in veins and some replaces country rock. Associated ore minerals include pyrite, sphalerite, bornite, galena, and chalcocite.

Chalcopyrite serves as the copper source for many secondary mineral deposits. Copper is removed from chalcopyrite by weathering or solution, transported a short distance, then redeposited as secondary sulfide, oxide, or carbonate minerals. Many malachite, azurite, covellite, chalcocite, and cuprite deposits contain this secondary copper.

Uses of Chalcopyrite

The only important use of chalcopyrite is as an ore of copper, but this single use should not be understated. Chalcopyrite has been the primary ore of copper since smelting began over five thousand years ago.

Some chalcopyrite ores contain significant amounts of zinc substituting for iron. Others contain enough silver or gold that the precious metal content more than pays the costs of mining.

Additional Information

Chalcopyrite, the most common copper mineral, a copper and iron sulfide, and a very important copper ore. It typically occurs in ore veins deposited at medium and high temperatures, as in Río Tinto, Spain; Ani, Japan; Butte, Mont.; and Joplin, Mo. Chalcopyrite (Cu2Fe2S4) is a member of a group of sulfide minerals that crystallize in the tetragonal system; the group also includes stannite. Both minerals have crystalline structures related to sphalerite.

---

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.