Bornite

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Bornite
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General
CategorySulfide mineral
Chemical formulaCu5FeS4
Identification
Molecular Weight342.681
ColorCopper red, bronze brown, purple
Crystal habitGranular, massive, disseminated - Crystals pseudocubic, dodecahedral, octahedral
Crystal systemOrthorhombic - Dipyramidal (2/m 2/m 2/m)
TwinningPenetration twins on [111]
CleavageImperfect on [111]
FractureConchoidal
Mohs Scale hardness3 - 3.25
LusterMetallic
Refractive indexOpaque
Streakgrayish black
Specific gravity4.9 - 5.3
Other CharacteristicsMagnetic after heating
References[1][2]

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 an iridescent purple. Its purple to bronze 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).

See also

References

  • Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7th edition), v. I, 195–197.
  • Mindat

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ca:Bornita cs:Bornit de:Bornit it:Bornite lt:Bornitas nl:Borniet nds:Bornit sk:Bornit sr:Борнит sv:Brokig kopparmalm uk:Борніт


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