mineral
Bornite (Peacock Ore)
Bornite (Cu5FeS4)
Hardness: 3-3.25 (Mohs), Color: Copper-red to brown on fresh surfaces, tarnishing to iridescent purple/blue/green, Luster: Metallic, Crystal Structure: Orthorhombic, Cleavage: Poor, 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, tarnishing to iridescent purple/blue/green, Luster: Metallic, Crystal Structure: Orthorhombic, Cleavage: Poor, Specific Gravity: 5.06-5.08
Formation & geological history
Forms in copper ore deposits through hydrothermal processes, occurring in both igneous and metamorphic rocks like pegmatites, contact metamorphic zones, and quartz veins.
Uses & applications
Primary ore of copper, though it is also widely sold as a decorative mineral specimen for collectors and healing crystal gift shops.
Geological facts
The name 'Peacock Ore' is shared with chalcopyrite that has been acid-washed to force tarnish. Real bornite tarnishes naturally upon exposure to air, creating its signature iridescent luster.
Field identification & locations
Identify by its metallic luster and intense purple-blue oily tarnish. It is much denser than non-metallic rocks and will leave a grayish-black streak. Commonly found in Arizona (USA), Montana (USA), Mexico, and Chile.
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