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] It occurs globally in copper ores with notable crystal localities in Butte, Montana and at Bristol, Connecticut in the U.S.