mineral
Chalcopyrite (Peacock Ore)
Copper Iron Sulfide (CuFeS2)
Hardness: 3.5 to 4 on the Mohs scale. Color: Brass yellow, often tarnishing to an iridescent purple, blue, green, and golden-red sheen. Luster: Metallic. Crystal structure: Tetragonal. Specific gravity: 4.1 to 4.3.
- Hardness
- 3
- Luster
- Metallic
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Physical properties
Hardness: 3.5 to 4 on the Mohs scale. Color: Brass yellow, often tarnishing to an iridescent purple, blue, green, and golden-red sheen. Luster: Metallic. Crystal structure: Tetragonal. Specific gravity: 4.1 to 4.3.
Formation & geological history
Formed under hydrothermal conditions in medium to high-temperature ore veins, contact metamorphic zones, and magmatic sulfide deposits alongside other sulfide minerals.
Uses & applications
Major ore mineral of copper metal. Also very popular among mineral collectors for its vivid iridescent tarnish (often enhanced artificially by acid washing).
Geological facts
Natural chalcopyrite oxidizes slowly to form colorful coatings, but most highly iridescent commercial 'Peacock Ore' is treated with dilute acid to accelerate and intensify the brilliant rainbow sheen.
Field identification & locations
Identified by its metallic luster, brassy-yellow interior when freshly broken, soft hardness compared to pyrite (it can be scratched with a knife), and rainbow tarnish. Commonly found in major copper mining regions in Chile, Peru, USA, Canada, and South Africa.
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