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Chemical Formula | Cu2FeS4 |
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Composition | Copper iron sulfide |
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Color | Copper to yellowish brown on fresh surface. Quickly tarnishes purple, blue, and red. |
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Streak | Dark gray to black |
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Hardness | 3 |
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Crystal Forms and Aggregates |
(Isometric) Crystals are rare, and are cubic or dodecahedral. Octahedral crystals are extremely rare. Bornite occurs mostly massive, as well as in groups of tiny crystals. |
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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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Other Names | Many other names are given to Bornite,
describing its iridescent tarnish, such as: Peacock Ore, Peacock Copper, Variegated Copper, Blushing Copper, Erubescite, and Purple Copper Ore. Additional false names describing Bornite are also known. The name "Peacock Ore" is also used to describe Chalcopyrite with the same iridescent tarnish effect, which is usually artificially enhanced with acid. |
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In Group | Sulfides ; Simple sulfides |
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Uses | Bornite is a common copper bearing mineral,
and is sometimes used as an ore
of copper. "Peacock Ore" which is sold to many amateur mineral collectors and thought to be Bornite is usually Chalcopyrite that is treated with acid to produce a stronger iridescent tarnish. |
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Striking Features | Tarnish, low hardness, and association with copper ores. |
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Popularity (1-4) | 2 |
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Prevalence (1-3) | 1 |
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Demand (1-3) | 2 |
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Distinguishing Similar Minerals |
Pyrrhotite - harder (3½ -
4½), attracted to magnets, no tarnish Nickeline - harder (5 - 5½), heavier (S.G. = 7.8), no tarnish Chalcopyrite - different crystal form, usually lighter in color, less tarnish |
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Commonly Occurs With |
Pyrite, Calcite, Barite, Galena, Chalcopyrite, Chalcocite, Magnetite |
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Noteworthy Localities |
Bornite is common and found in many
locations. The province of Cornwall, England has produced
many specimens, including some crystallized examples.
Large, distinct crystals come from Dzhekazgan Oblast,
Kazakhstan. 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 are known to occur in Butte, Silver Bow Co., Montana, where much massive material is also found. Small crystals were also found at Bristol, Hartford Co., Connecticut. Bountiful material has come from the Evergreen mine near Apex, Gilpin Co., Colorado, and Kenecott in the Copper River District in Alaska. It also has been found in the White Pine mine, Ontonagan Co., Michigan; the French Creek mine, St. Peters, Chester Co., Pennsylvania; and in Luzerne Co., Pennsylvania. In Canada, occurrences are in the Marble Bay mine, Texada Island, British Columbia, and in the Acton mine, Bagot Co., Quebec. |
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