chalcopyrite

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(kăl'kə-pī'rīt') pronunciation
n.
A yellow mineral, essentially CuFeS2, that is an important ore of copper. Also called copper pyrites.

[New Latin chalcopyrites : Greek khalkos, copper + PYRITES.]



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.

For more information on chalcopyrite, visit Britannica.com.

A mineral having composition CuFeS2. Crystals are usually small and resemble tetrahedra. Chalcopyrite is usually massive with a metallic luster, brass-yellow color, and sometimes an iridescent tarnish. The Mohs hardness is 3.5–4.0, and the density 4.1–4.3. Chalcopyrite is a so-called fool's gold, but is brittle while gold is sectile. Pyrite, the most widespread fool's gold, is harder than chalcopyrite. See also Pyrite.

Chalcopyrite is the most widespread primary copper ore mineral. It is commonly found in veins (Braden mine, Chile; Cornwall, England; Butte, Montana; Freiberg, Saxony; Tasmania; Rio Tinto, Spain). Chalcopyrite is also found in contact metamorphic deposits in limestone (Bisbee, Arizona) and as sedimentary deposits (Mansfeld, Germany). See also Copper.


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chalcopyrite (kăl'kəpī'rīt, kăl'kōpī'rīt) or copper pyrites (pīrī'tēz, pə-), brass-yellow mineral, sometimes with an iridescent tarnish. It is a sulfide of copper and iron, CuFeS2 . 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.



CuFeS
Tetragonal -- scalenohedral

Environment

Common in multitemperature sulfide veins, and often disseminated through porphyritic igneous rocks.

Crystal description

Though tetragonal, the characteristically sphenoidal crystals of chalcopyrite resemble tetrahedra. Crystals of 2-3 cm are common; often they are even larger, with faces usually somewhat uneven and tarnished from black to brilliant iridescent hues. Usually massive, often making up golden sulfide mixtures of several minerals. Structurally close to sphalerite, it often makes oriented intergrowths, with small crystals studded over sphalerite surfaces.

Physical properties

Golden. Luster metallic, often with iridescent tarnish; hardness 3Ɖ-4; gravity 4.1-4.3; fracture uneven; cleavage 1 poor (and rarely noted). Brittle.

Composition

Sulfide of copper and iron (34.5% Cu, 30.5% Fe, 35% S).

Tests

On charcoal, fuses to magnetic black globule; touched with HCl, tints flame with blue flash. Solution with strong nitric acid is green; ammonia precipitates red iron hydroxide and leaves a blue solution.

Distinguishing characteristics

Confused with gold, but is brittle, crushes to a green-black powder, gives black streak, and dissolves in acid. Distinguished from pyrite by ease of scratching and by copper tests. The color is a richer yellow than pyrite. Also, obviously hard and shiny pyrite will frequently show smooth flat surfaces, striated cubes or pyritohedrons, whereas chalcopyrite, when not massive, is in characteristic sphenoidal crystals.

Occurrence

The basic copper ore. Widely distributed and may be found in all types of primary occurrences. Often associated with other copper minerals: pyrite, sphalerite, galena, and pyrrhotite. The economically important "porphyry coppers" of Bingham, Utah; Ely, Nevada; and Ajo, Arizona; are representative of open-pit-mined, worldwide low-grade (1-3 percent) copper disseminations through igneous rocks. Some of the best crystals are from Cornwall, England; Akita and Tochigi prefectures, Japan; French Creek, Pennsylvania; and several Colorado localities. Often crystallized in the parallel growths on and through crystals of sphalerite in the Joplin District of Missouri, Kansas, and Oklahoma. Giant 6-in. (15 cm) crystals were found in Freirina, n. Chile. Abundant in n. Mexico, another good source of large crystals.

Remarks

Chalcopyrite is the generic copper ore that, by alteration and successive removals of iron, produces a series starting with chalcopyrite and going through bornite (Cu 5 FeS 4 ), covellite (CuS), and chalcocite (Cu 2 S), and ending (rarely) as native copper (Cu). (See discussion of secondary enrichment under chalcocite.)



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Chalcopyrite

Twinned chalcopyrite crystal from the Camp Bird Mine, Ouray County, Colorado. Crystal is about 1 cm x 1 cm.
General
Category Sulfide mineral
Chemical formula CuFeS2
Strunz classification 02.CB.10a
Crystal symmetry Tetragonal 42m – scalenohedral
Unit cell a = 5.289 Å, c = 10.423 Å; Z = 4
Identification
Molar mass 183.54
Color Brass yellow, may have iridescent purplish tarnish.
Crystal habit Predominantly the disphenoid and resembles a tetrahedron, commonly massive, and sometimes botryoidal.
Crystal system Tetragonal Scalenohedral 42m
Twinning Penetration twins
Cleavage Indistinct on {011}
Fracture Irregular to uneven
Tenacity Brittle
Mohs scale hardness 3.5
Luster Metallic
Streak Greenish black
Diaphaneity Opaque
Specific gravity 4.1 – 4.3
Solubility Soluble in HNO3
Other characteristics magnetic on heating
References [1][2][3][4][5]

Chalcopyrite (play /ˌkælkɵˈprt/ KAL-ko-PY-ryt) 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.

Contents

Chemistry

The unit cell of chalcopyrite. Copper is shown in pink, iron in blue and sulfur in yellow.

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, 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 with 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

Fine brassy chalcopyrite crystals below large striated pyrite cubes (size:8.8 x 6.3 x 4.5 cm)

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 associatd with granitic to dioritic intrusives as in the porphyry copper deposits of Broken Hill, the American cordillera and the Andes. The largest deposit of nearly pure chalcopyrite ever discovered in Canada was at the southern end of the Temagami greenstone belt where Copperfields Mine extracted the high-grade copper.[6]

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.

Structure

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.

See also

References

  1. ^ Klein, Cornelis and Cornelius S. Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th ed., 1985, pp. 277 – 278 ISBN 0-471-80580-7
  2. ^ Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7th edition), v. I, 219–224
  3. ^ http://www.mindat.org/min-955.html mindat.org
  4. ^ http://webmineral.com/data/Chalcopyrite.shtml Webmineral.com
  5. ^ Handbook of Mineralogy
  6. ^ Barnes, Michael (2008). More Than Free Gold. Renfrew, Ontario: General Store Publishing House. p. 31. ISBN 978-1-897113-90-5. 

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Covellite (mineralogy and petrology)
Bornite (mineralogy and petrology)
pyrite (mineral – in chemistry)