mineral

Peacock Ore

Bornite (Cu5FeS4)

Hardness: 3 on Mohs scale; Color: Copper-red to bronze on fresh surfaces, tarnishing to iridescent blues, purples, and greens; Luster: Metallic; Crystal Structure: Orthorhombic (often massive); Cleavage: Poor; Specific Gravity: 5.06-5.08

Hardness: 3 on Mohs scale
Luster: Metallic

Identified March 9, 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 intrusions. It originates from copper-rich fluids cooling and reacting with sulfur-bearing rocks.

Uses & applications

Used primarily as an important ore of copper. In smaller specimens, it is popular in the lapidary industry for decorative displays, children's mineral collections, and metaphysical jewelry.

Geological facts

The name 'Bornite' honors the Austrian mineralogist Ignaz von Born. While bornite is naturally iridescent, many bright 'peacock ore' specimens sold in shops are actually Chalcopyrite that has been acid-washed (typically with vinegar or silver polish) to enhance the colors.

Field identification & locations

Identify in the field by its distinct iridescent tarnish and the grayish-black streak it leaves on porcelain. It is commonly found in copper mines in Arizona, Montana, Mexico, and Chile. Collectors look for the 'rainbow' effect caused by surface oxidation.