Cu 2 FeS 4 Composition Copper iron sulfide Color Copper to yellowish brown on fresh surface. Quickly tarnishes purple, blue, and red.
Octahedral crystals are extremely rare.
Bornite occurs mostly massive , as well as in groups of tiny crystals. Purple Copper Ore. Additional false names describing Bornite are also known. Striking Features Tarnish, low hardness, and association with copper ores . Commonly Occurs With Pyrite , Calcite , Barite , Galena , Chalcopyrite , Chalcocite, Magnetite Noteworthy Localities Bornite is common and found in many locations. The province of Cornwall, England has produced many specimens, including some crystallized examples.