mineral
Peacock Ore
Bornite (Cu5FeS4) with surface tarnish
Hardness: 3 on the Mohs scale. Color: Iridescent array of blue, purple, green, and gold on tarnished surfaces; fresh surfaces are a bronze-brown. Luster: Metallic. Crystal structure: Orthorhombic. Cleavage: Poor. Specific gravity: 4.9 - 5.3.
- Hardness
- 3 on the Mohs scale
- Luster
- Metallic
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Physical properties
Hardness: 3 on the Mohs scale. Color: Iridescent array of blue, purple, green, and gold on tarnished surfaces; fresh surfaces are a bronze-brown. Luster: Metallic. Crystal structure: Orthorhombic. Cleavage: Poor. Specific gravity: 4.9 - 5.3.
Formation & geological history
Formed in hydrothermal veins, pegmatites, and contact metamorphic zones, often associated with other copper sulfides like chalcopyrite.
Uses & applications
Primarily used as an ore of copper, as a mineral specimen for collectors, and frequently sold tumbled or treated as decorative stones and jewelry.
Geological facts
Natural bornite develops its characteristic vibrant peacock-like colors due to a thin layer of copper oxide or carbonate forming upon exposure to air. Much of the brightly colored peacock ore sold commercially is actually chalcopyrite treated with acid to enhance the tarnish.
Field identification & locations
Easily identified by its distinct iridescent tarnish and relatively soft metallic nature. Found worldwide in major copper-producing regions such as the USA, Mexico, Chile, and Peru.
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