The Mineral Chalcopyrite
Chemistry: Copper Iron Sulfide
Crystal system: tetragonal
Fracture: conchoidal and brittle
Specific gravity: 4.2
Streak: dark green
Cleavage: poor in one direction.
Color: brassy yellow, tarnishes to irredescent
blues, greens, yellows and purples.
Associated Minerals: Barite, Calcite,
Fluorite, Galena Pyrite, Pyrrhotite, Quartz, Siderite,
Sphalerite and Tetrahedrite are a few of the most common
Sulphide of copper and iron ( 34.5% Cu, 30.5%
Fe, 35% S )
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.
Chalcopyrite is a common mineral and is found in almost all sulfide
deposits and is often disseminated through igneous rocks.
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
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.
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.
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