Bornite

infobox mineral
name = Bornite
category = Sulfide mineral
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formula = Cu₅FeS₄
molweight = 342.681
color = Copper red, bronze brown, purple
habit = Granular, massive, disseminated - Crystals pseudocubic, dodecahedral, octahedral
system = Orthorhombic - Dipyramidal (2/m 2/m 2/m)
twinning = Penetration twins on [111]
cleavage = Imperfect on [111]
fracture = Conchoidal
mohs = 3 - 3.25
luster = Metallic
refractive = Opaque
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streak = grayish black
gravity = 4.9 - 5.3
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other = Magnetic after heating
references = [http://webmineral.com/data/Bornite.shtml Webmineral] [http://rruff.geo.arizona.edu/doclib/hom/bornite.pdf Handbook of Mineralogy]

Bornite is a sulfide mineral with chemical composition Cu₅FeS₄ that crystallizes in the orthorhombic system. It has a brown to copper-red color on fresh surfaces that tarnishes to various iridescent shades of blue to purple in places. Its striking iridescence gives it the nickname "peacock copper" or "peacock ore".

Bornite is an important copper ore mineral and occurs widely in porphyry copper deposits along with the more common chalcopyrite. Chalcopyrite and bornite are both typically replaced by chalcocite and covellite in the supergene enrichment zone of copper deposits. Bornite is also found as disseminations in mafic igneous rocks, in contact metamorphic skarn deposits, in pegmatites and in
sedimentary cupriferous shales. It is important for its copper content of about 63 percent by mass and is found in Arizona, Butte, Montana, and Mexico.

It has been reported since 1725, but in 1845 it was named for Austrian mineralogist Ignaz von Born (1742–1791).

ee also

*Cuprite
*Tennantite
*Tetrahedrite
*List of minerals named after people

References

*Palache, C., H. Berman, and C. Frondel (1944) "Dana’s system of mineralogy", (7th edition), v. I, 195–197.
* [http://www.mindat.org/min-727.html Mindat]