Bornite

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).