Bornite is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the cubic system. It has a brown to copper-red color on fresh surfaces that tarnishes to an iridescent purple surface. Its purple to bronze iridescence gives it the nickname peacock ore. Bornite is an important copper ore mineral and occurs widely in porphyry copper deposits along with more common chalcopyrite. It also is found in pegmatites. It is important for its copper content of about 63 percent by mass and is found in Arizona, Butte, Montana, and Mexico.