Bornite (Copper Iron sulfide) is an important Copper ore mineral. Typically found as massive metallic material, it has a copper-red color on fresh exposures which quickly tarnishes to an iridescent purple, blue and red after exposure to air and moisture. This iridescent tarnish is a natural occurrence and has earned this material the name “Peacock Ore”. Note: Popular among some collectors and tourists, and often incorrectly labeled as a variety of Bornite, most “Peacock Ore” is Chalcopyrite treated with acid. This strongly-colored, unnaturally acidified iridescent tarnish is easy to spot.

Its crystal system is orthorhombic. Cubic and dodecahedral crystals are rare. More common forms include globular, granular and massive.

Bornite is found in numerous localities, including Canada, England, Kazakhstan, Mexico, the USA (Arizona, Colorado) and Zimbabwe.