mineral

Bornite

Copper Iron Sulfide (Cu5FeS4)

Hardness: 3 (Mohs). Color: Copper-red to brown on fresh surfaces, tarnishing to iridescent shades of blue, purple, and gold. Luster: Metallic. Crystal Structure: Orthorhombic (pseudo-cubic) at low temperatures. Specific gravity: 5.06-5.09.

Hardness: 3 (Mohs)
Luster: Metallic

Identified July 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, contact metamorphic zones, and as a primary or secondary copper mineral in porphyry deposits. It is often found in association with chalcopyrite and chalcocite.

Uses & applications

Major ore of copper. It is also highly sought after by mineral collectors for its vibrant iridescent tarnish.

Geological facts

Commonly known as 'Peacock Ore' due to the brilliant rainbow-colored tarnish that develops when exposed to air. Most commercial 'Peacock Ore' sold in shops is actually Chalcopyrite treated with acid to enhance colors, but true Bornite occurs naturally with these hues.

Field identification & locations

Identified by its metallic luster and intense blue/purple tarnish. In the field, look for it in copper-rich mining districts such as those in Arizona (USA), Cornwall (UK), or Namibia.