mineral

Bornite (peacock ore), likely with chalcopyrite

Bornite, Cu5FeS4; associated copper sulfides may include chalcopyrite, CuFeS2

AI-generated identification · may be incorrect

Metallic to submetallic luster; iridescent blue, purple, pink, bronze, and yellow tarnish over a dark gray-black sulfide surface. Bornite is typically Mohs 3–3.25, brittle, with indistinct cleavage, and has a cubic crystal structure; specific gravity is about 4.9–5.3.

Identified August 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms in hydrothermal copper-ore deposits, commonly replacing other sulfides in veins and disseminated ores. It is usually Paleozoic to younger, though age depends on the deposit; the photograph may show naturally weathered or polished specimens.

Uses & applications

An important copper ore historically, though chalcopyrite is more abundant; colorful pieces are sold as “peacock ore” for mineral collections and decorative objects. It has limited jewelry use because it is soft and tarnishes readily.

Geological facts

The vivid colors are usually a thin iridescent oxidation or tarnish film, not bornite’s fresh color. Bright brassy-yellow patches likely indicate chalcopyrite or related copper sulfides.

Field identification & locations

Look for high density, metallic appearance, dark sulfide interiors, and blue-purple-bronze tarnish; a streak test, hardness test, and copper-sulfide analysis distinguish it from similarly colored slag or treated material. Common localities include Montana, Arizona, Peru, Mexico, and Cornwall.