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"Peacock Ore", which is sold to many amateur mineral collectors and often labeled as a variety of Bornite, is usually Chalcopyrite that is treated with
acid to produce a stronger iridescent tarnish.
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Chemical Formula |
Cu5FeS4 |
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Composition |
Copper iron sulfide |
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Color |
Copper-red to yellowish brown on fresh surfaces. Quickly tarnishes to a multicolored purple, blue, and red. |
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Streak |
Dark gray to black |
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Hardness |
3 |
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Crystal System |
Orthorhombic |
Crystal Forms
and Aggregates |
Bornite forms as isometric crystals at high temperatures, but when
it cools down to normal temperatures it crystallizes in the
orthorhombic system. However, the crystals retain their original
isometric crystals. Crystals are rare, and are in cubic or dodecahedral form. Octahedral shaped crystals are extremely rare. Bornite occurs mostly massive, as well as in groups of tiny crystals and globular.
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Transparency |
Opaque |
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Specific Gravity |
4.9 - 5.3 |
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Luster |
Metallic |
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Cleavage |
Indiscernible |
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Fracture |
Conchoidal |
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Tenacity |
Brittle |
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Other ID Marks |
Tarnishes to an iridescent purple, blue, and red. |
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In Group |
Sulfides; Simple Sulfides |
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Striking Features |
Tarnish, low hardness, and association with copper ores. |
| Environment |
In copper ore veins, both as a primary and secondary mineral. Mainly in hydrothermal metamorphic rocks, in mesothermal veins, in hydrothermal replacement deposits, and in igneous intrusions and dikes.
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| Rock Type |
Igneous, Metamorphic |
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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1 |
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Demand (1-3) |
2 |
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- Term used to describe Chalcopyrite or Bornite with a colorful iridescent tarnish effect, which is usually artificially enhanced with acid. Most Peacock Ore is sold as a variety of Bornite, when in fact most Peacock Ore is actually Chalcopyrite.
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Bornite is a common copper bearing mineral, and is used as an ore of copper when found in copper deposits.
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Bornite is common and found in many locations. The province of Cornwall, England has produced many specimens, including some crystallized examples (especially in the Carn Brea Mine). Large, distinct crystals also come from Dzhezkazgan, Kazakhstan and Shaba, Congo (Zaire). Nice crystals and mostly massive Bornite comes from Zacatecas, Mexico.
Large quantities of Bornite, mostly in massive form, have been extracted from the Arizona copper mines, particularly the Magma mine in Superior, Pinal Co., and the Copper Queen Mine in Bisbee, Cochise Co. Small crystals also come from Butte, Silver Bow Co., Montana, where much massive material is also found. Small crystals were also once found at the copper mine at Bristol, Hartford Co., Connecticut.
Large amounts of Bornite have come from the Evergreen mine near Apex, Gilpin Co., Colorado, and the Flambeau Mine, Ladysmith, Rusk Co., Wisconsin. It also has been found in the White Pine mine, Ontonagan Co., Michigan; the French Creek mine, St. Peters, Chester Co., Pennsylvania; Luzerne Co., Pennsylvania; and the Chimney Rock Quarry, Bound Brook, New Jersey.
In Canada, occurrences are the Marble Bay mine, Texada Island, British Columbia, and the Acton mine, Bagot Co., Quebec.
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Chalcopyrite - different crystal form, usually lighter in color, less tarnish
Pyrrhotite - harder (3½ - 4½), attracted to magnetic fields, no tarnish
Nickeline - harder (5 - 5½), heavier (S.G. = 7.8), no tarnish
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