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The Mineral chalcopyrite

Curved, tetrahedral Chalcopyrite

Chalcopyrite has a golden yellow color, which often resembles Gold. However, its physical properties such as streak and tenacity are very different from Gold and can easily distinguish it. Chalcopyrite is a beautiful mineral, with good crystals being fairly common. It is also readily available, with quality specimens being surprisingly affordable.

"Peacock Ore" which is sold to many amateur mineral collectors often as a variety of Bornite, is in fact almost always Chalcopyrite treated with acid to produce an iridescent tarnish. Though some Chalcopyrite is naturally iridescent, wild colors such as strong blues and purples are usually formed from acid treatment.

Chemical Formula

CuFeS2

Color

Brass yellow to golden yellow; sometimes dark brown to black. Tarnishes to a multicolored purple, blue, and red.

Crystal System

Tetragonal

Properties

Streak
Black with a slightly green tinge
Hardness
3.5 - 4
Transparency
Opaque
Specific Gravity
4.1 - 4.3
Luster
Metallic
Cleavage
Indiscernible
Fracture
Uneven
Tenacity
Brittle
Other ID Marks
Tarnishes to an iridescent purple, blue, and red.

Crystal Habits

Crystals resemble tetrahedrons and octahedrons, but they are slightly asymmetrical and therefore are categorized in the tetragonal system. Also occurs massive, grainy, reniform, and as groups of small, distorted crystals. Crystals are commonly striated in different directions on different crystal faces.

3D Crystal Atlas

Additional Information

Composition
Copper iron sulfide
In Group
Simple Sulfides
Striking Features
Low hardness, crystal form, iridescent tarnish, and brittleness
Environment
In the sulfide zones of copper deposits, in hypothermal veins and mesothermal veins, hydrothermal replacement deposits, metamorphic schists, and in igneous intrusions and dikes.
Rock Type
Igneous, Sedimentary, Metamorphic

Varieties

 -   Chalcopyrite in a globular or botryoidal rounded form.
 -   Term used to describe Chalcopyrite or Bornite with a colorful iridescent tarnish effect, usually artificially enhanced with acid. Most Peacock Ore is sold as Bornite, when in fact it usually produced from acid-treating Chalcopyrite.

Uses

Chalcopyrite is the main ore of copper. Chalcopyrite is sometimes polished into beads and pendants as cheap jewelry.

Noteworthy Localities

Chalcopyrite is a fairly common mineral, and therefore only the finest of localities will be mentioned. Large, well shaped crystals occur in numerous places in Cornwall, England, especially at the Carn Brea area. Baia Sprie (Felsobanya) and Kapnick both in Maramures Co., are famous Romanian occurrences. Very large crystals come from Krushev Dol, in the Rhodope Mountains of Bulgaria. In the Dreislar Mine, North Rhine-Westphalia, Germany, small Chalcopyrite crystals on white coxcomb Barite occur as an excellent combination with beautiful contrast. In China, large crystals occur at the Yaogangxian Mine, Hunan Province.

Many fine Chalcopyrite crystals occur in Zacatecas Mexico; Concepción del Oro and San Martín are noteworthy. The Huaron Mine in Cerro del Pasco, Peru is also a classic locality.

In the U.S., the Tri-state district of Kansas, Oklahoma, and Missouri has provided the important Chalcopyrite localities of Joplin, Jasper Co., Missouri; Picher, Ottawa Co., Oklahoma; and Treece, Cherokee Co., Kansas. The Sweetwater Mine, Reynolds Co., Missouri produces small sparkling crystals, with some having a natural blue iridescence. Other excellent Chalcopyrite occurrences are the Gilman District, Eagle Co., Colorado; Ouray, Ouray Co., Colorado; and Ellenville, Ulster Co., New York. The Chimney Rock Quarry in Bound Brook, Somerset Co., New Jersey, has produced unique reniform blobs; and the the French Creek Mine in Chester Co., Pennsylvania has produced large distorted and highly tarnished crystals that are highly sought after by collectors.

Common Mineral Associations

Pyrite, Sphalerite, Bornite, Chalcocite, Barite, Dolomite, Fluorite, Quartz, Calcite

Distingushing Similar Minerals

Pyrite and Marcasite - Paler color, harder (6 - 6½).
Gold - Nonbrittle, much heavier (15.5 - 19.3).
Bornite - Usually darker in color, more tarnish.


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