mineral

Peacock Ore

Bornite (Cu5FeS4)

Hardness: 3 (Mohs scale); Color: Iridescent blue, purple, and green (tarnished), bronze to copper-red (fresh surface); Luster: Metallic; Crystal Structure: Orthorhombic; Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3 (Mohs scale)
Luster: Metallic

Identified March 29, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal veins, contact metamorphic zones, and as a primary mineral in igneous rocks. While found in rocks of various ages, many major deposits are found in Precambrian age formations.

Uses & applications

Bornite is a significant copper ore used in the industrial extraction of copper. Specimens like this are popular in mineral collecting and as decorative stones due to their vibrant colors.

Geological facts

Natural bornite tarnishes to iridescent colors within hours of being exposed to air. However, much of the 'Peacock Ore' sold in shops is actually Chalcopyrite that has been acid-washed to forcefully induce this colorful tarnish.

Field identification & locations

Can be identified by its distinctive 'oil slick' iridescent tarnish and its metallic gray or bronze color when scratched. Common locations include Montana (USA), Mexico, and Cornwall (UK). Collectors should look for vibrant purple hues mixed with blue.