Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system (pseudo-cubic).

It is an important copper ore. Bornite has a brown to copper-red color on fresh surfaces that tarnishes to various iridescent shades of blue to purple in places.

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.

[5] Substantial variation in the relative amounts of copper and iron is possible and solid solution extends towards chalcopyrite (CuFeS2) and digenite (Cu9S5).