Peacock Ore

Hardness of 3 on the Mohs scale. Metallic luster with iridescent tarnish displaying vibrant blues, purples, greens, and golds. Crystal structure is tetragonal, though it is commonly found massive or compact. Blackish lead-gray streak. Specific gravity is about 4.9 to 5.3.

Forms primarily in hydrothermal veins, pegmatites, and contact metamorphic zones, as well as a secondary enrichment mineral in copper ore deposits. It is created through the precipitation of copper and iron sulfides from hot mineralizing fluids.

Used as a minor copper ore, carved into decorative ornamental items, and highly valued as a specimen for mineral collections.

Natural fresh-mined bornite is a dull copper-red or brown color. The striking peacock iridescence is caused by a thin surface film of alteration (oxidation/tarnishing) that forms when exposed to air and light, though some commercial specimens are artificially treated with acid to enhance the colors (indicated by the German sign in the image reading 'Buntkupfer nicht coloriert!', meaning 'Peacock copper not colored!').

Easily identified by its colorful metallic iridescence and copper-bearing association. Found worldwide including in the USA, Mexico, Chile, and various European localities. Collectors look for specimens with stable, vibrant tarnish.