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The Mineral Chalcopyrite

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PHYSICAL PROPERTIES:
Chalcopyrite Mineral Specimen
Chemistry: Copper Iron Sulfide
Composition:
CuFeS2
Class: Sulfides
Group: Chalcopyrite
Crystal system: tetragonal
Fracture: conchoidal and brittle
Hardness: 3.5-4
Specific gravity: 4.2
Luster: metallic
Streak: dark green
Cleavage: poor in one direction.
Color: brassy yellow, tarnishes to irredescent
blues, greens, yellows and purples.
Transparency:
opaque
Associated Minerals:
Barite, Calcite, Fluorite, Galena Pyrite, Pyrrhotite, Quartz, Siderite,
Sphalerite and Tetrahedrite are a few of the most common


COMPOSITION:
Sulphide of copper and iron ( 34.5% Cu, 30.5% Fe, 35% S )

DISTINGUISHING CHARACTERISTICS:
Chalcopyrite looks like, and is easily confused with Pyrite and is also one of the minerals referred to as "Fool's Gold" because of its bright golden color. But it is brittle, dissolves in acid and has a dark green streak . It is distinguished from pyrite by ease of scratching, and by copper tests. The color is slightly more yellow than that of pyrite or is often tarnished in brilliant iridescent hues which is also called "peacock copper ore". Like the picture above Pyrite will frequently show striated cubes or pyritohedra, whereas chalcopyrite, if not massive, has the characteristic sphenoidal or disphenoid crystals.
 
ENVIRONMENT:
Chalcopyrite is a common mineral and is found in almost all sulfide deposits and is often Chalcopyrite Crystalsdisseminated through igneous rocks.

CRYSTAL DESCRIPTION:
Chalcopyrite is usually massive, but crystals are also common. Often they are large and the faces usually are somewhat uneven or may have striations on most crystal faces. Chalcopyrite is often tarnished in brilliant iridescent hues.
Sphenoidal crystals are common. Also common are disphenoid crystals which are like two opposing wedges that resemble a tetrahedron. Crystals are sometimes twinned and can also be botryoidal.

TESTS:
On charcoal fuses to magnetic black globule, touched with HC1 tints flame with blue flash. Solution with strong nitric acid is green; ammonia precipitates red iron hydroxide and leaves a blue solution.

LOCALITIES:
Large, well shaped crystals occur in many places such as Cornwall, England, as well as Akita, Ugo, and Tochigi Perfectures, Japan. The northern section of Mexico is well known for chalcopyrite production. Such as the Noche Buena mine, near Mazapil, Zacatecas. Many nice chalcopyrite group specimens were mined near us. In Walace, Idaho and Butte, Montana. Other notable USA localities are the French Creek Mine in Chester Co. Pennsylvania and Large amounts of Chalcopyrite occur with Sphalerite, Galena, and Marcasite in the Joplin district of Missouri, Oklahoma, and Kansas. There are also several notable Colorado localities. I'm sure you have heard of many other foreign and domestic localities so I won't go on.

USES:
Chalcopyrite is a major ore of copper. As a copper ore, the yield of chalcopyrite is rather
low, in terms of copper content. It is only 25%, compared to other copper minerals such as chalcocite, covellite, cuprite, or bornite which may contain 50% to 60% copper. However the great quantities and many localities make chalcopyrite the leading source of copper.


Of course it is also used as a mineral specimen and as a decorative stone because of the
bright colors that are produced with aging or acid treatments.

FACTS & HISTORY:
Chalcopyrite is the primary mineral which by alteration and successive enrichment with copper produces the series starting with chalcopyrite and going through bornite (Cu5FeS4), covellite (CuS), chalcocite (Cu2S), and ending rarely as native copper (Cu).


Its structure is so closely related to that of sphalerite that it forms intergrowths with that mineral, and isolated free-growing crystals perched on crystals of sphalerite are all parallel. The same face on all the chalcopyrites gives simultaneous reflections. (It Sparkles)

From the Greek words chalkos, "copper" and pyrites, "strike fire"