mineral
Bornite
Bornite (Cu5FeS4)
Hardness: 3-3.25 (Mohs), Color: Copper-red to brown on fresh surfaces but tarnishes to iridescent blue/purple/pink, Luster: Metallic, Crystal system: Orthorhombic, Cleavage: Poor/indistinct, Specific Gravity: 5.06-5.08
- Hardness
- 3-3
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Physical properties
Hardness: 3-3.25 (Mohs), Color: Copper-red to brown on fresh surfaces but tarnishes to iridescent blue/purple/pink, Luster: Metallic, Crystal system: Orthorhombic, Cleavage: Poor/indistinct, Specific Gravity: 5.06-5.08
Formation & geological history
Formed in copper ore deposits, typically in hydrothermal veins, contact metamorphic zones, and sometimes as a secondary mineral in enriched zones of copper deposits. It can occur in deposits spanning various geological ages from Precambrian to Cenozoic.
Uses & applications
Bornite is a significant ore of copper, containing about 63 percent copper by mass. It is also highly prized by mineral collectors for its vibrant iridescent tarnish.
Geological facts
Commonly nicknamed 'Peacock Ore' because its iridescent tarnish resembles the feathers of a peacock. While natural bornite tarnishes, many samples sold as 'peacock ore' in shops are actually chalcopyrite that has been acid-etched to force the color reaction.
Field identification & locations
Identify in the field by its distinct iridescent tarnish (purple, blue, gold) and its relatively high density. It can be found globally with notable deposits in Mexico, Chile, Montana (USA), and Kazakhstan.
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