mineral

Peacock Ore

Bornite (Cu5FeS4)

Hardness: 3 on Mohs scale; Color: Brownish-bronze (on fresh surface), iridescent purple/blue/green/gold (when tarnished); Luster: Metallic; Crystal Structure: Orthorhombic (pseudocubic); Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3 on Mohs scale
Luster: Metallic

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins, contact metamorphic zones, and as a primary mineral in igneous rocks like pegmatites. It forms at high temperatures and is commonly found in copper-rich deposits throughout geological history.

Uses & applications

Bornite is an important copper ore mined for its high copper content (approx 63%). Showy specimens are popular among collectors and used in decorative lapidary arts and jewelry.

Geological facts

Peacock ore gets its name from the brilliant iridescent tarnish that covers the mineral when it is exposed to air, similar to a peacock's feathers. Frequently, Chalcopyrite is acid-washed in the lab to create a similar effect, so natural Bornite is highly prized.

Field identification & locations

Identify by its 'peacock' iridescence, metallic luster, and its dark gray-black streak on a ceramic plate. It is commonly found in copper mines in locations like Arizona (USA), Cornwall (UK), and Chile. Collectors should look for the vivid blue and purple shifts that appear soon after the mineral is broken.