Chalcopyrite

Chalcopyrite

In our earth exists around 4900 species of minerals, and 4660 of these minerals are approved by the International Mineralogical Association (IMA). A mineral is defined as: a naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystalline structure, color, and hardness. In this paper I will talk about one of these minerals. I chose Chalcopyrite because I feel related with Copper. I am from Chile, the country that produces 60% of the copper, followed by USA. This paper is focused to talk about the physical and chemical properties, the occurrence and the uses of chalcopyrite.

Chalcopyrite, named in 1725 by Johann Friedrich Henckel from the Greek words chalkos, "copper" and pyrites, "strike fire" is a copper iron sulfide mineral CuFeS2. The sulfide minerals are inorganic compounds and some of them are economically important as metal ores. This is the case of Chalcopyrite that is the major ore of Copper.

Crystallography

Crystal System: Tetragonal

Class: 4 2m - Scalenohedral

Space Group: I4 2d

Cell Parameters: a = 5.289Å, c = 10.423Å

Ratio: a:c = 1 : 1.971

Unit Cell Volume: V 291.57 ų

Z: 4

Twinning: {112} and {012}

Chalcopyrite is tetragonal at low temperature but isometric above approximately 550°C. The temperature of the transformation is a function of composition.

Chalcopyrite is usually massive, but crystals are also common. The crystals are often large, and the crystal faces are usually uneven with striations. Sphenoidal and disphenoid crystals are usually common in Chalcopyrite. Cristal can also be botryoidal sometimes.

Physical Properties

Chalcopyrite has a poor/indistinct cleavage in only one direction {011}. The Hardness is 3.5-4(Mohs scale) and the specific gravity is approximately 4.2 (average of metallic minerals). It has a metallic luster. The color is brassy yellow, tarnishes to iridescent blues, greens, yellows and purples and the streak color is greenish black. It is opaque in transparency and brittle in tenacity. Chalcopyrite has a density measured of 4.1 - 4.3 g/cm3

Composition

Chalcopyrite is composed by sulfide of copper and iron. This mineral is 34.5% of copper (Cu), 30.5% of iron (Fe), and 35% of Sulfide (S)

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

Insignificant quantities of elements such as Ag, Au, Cd, Co, Ni, Pb, Sn, and Zn can be measured, probable because replacing Cu and Fe. Selenium, Bi, Te, and As may substitute sulfur in trivial amounts.

Structure

Diagnostic features

One of the most important diagnostic features of Chalcopyrite is his relation with Sphalerite. Because the fact that Chalcopyrite structure is so closely related to Sphalerite, sometimes Chalcopyrite

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