A valuable ore of copper, containing copper, iron, and sulphur; -- also called purple copper ore (or erubescite), in allusion to the colors shown upon the slightly tarnished surface.
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.