• Chemistry: Cu5FeS4, Copper Iron Sulfide
  • Class: Sulfides
  • Uses: Major ore of copper and as mineral specimens.
  • Specimens

Bornite is an important copper ore mineral. It ranks up there with many of the other copper ores such as chalcocite, chalcopyrite, covellite, digenite, cuprite and tetrahedrite. As a mineral specimen, bornite is usually lacking. Good crystals are rare and thus bornite is commonly known as simply a massive mineral ore.

It does however get used in the mineral trade as a curiosity called "peacock ore". A favorite among children, the bornite chunks sold as peacock ore or alternatively peacock copper have a rich bouquet of colors. The colors are from an iridescent tarnish that forms on bornite upon exposure to air. The tarnish is made of assorted copper oxides or hydroxides that form a mere atoms thin layer over the bornite. The thickness of the layers is close to the wavelength of light. When light waves bounce between the bornite surface and the top of the tarnish layer they will leave with the wavelengths of various colors. This effect is the same as the rainbow effect that occurs with oil on water. In the case of bornite, the tarnish will have a purplish, violet or blue color. Because bornite is often intergrown with chalcopyrite which tarnishes to more greens and yellows, the peacock ore may have many colors ranging from purple to blue to green to yellow.

Bornite's crystals, if found, are usually distorted cubes with curved faces. Even rarer are the distorted octahedrons and dodecahedrons. These are isometric crystals. However, bornite's structure at normal temperatures is not isometric. Bornite is only isometric at temperatures above 228 degrees celsius and it was above this temperature that the crystals formed. As bornite cooled it structurally altered to possibly a tetragonal structure but outwardly it retained the isometric forms.


  • Color is brown to black with a typical purplish-bluish tarnish, a reddish bronze color on freshly broken surfaces.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System is isometric; 4/m bar 3 2/m above 228 degrees celsius but below this temperature its structure becomes less symmetrical possibly tetragonal; bar 4 2/m.
  • Crystal Habits include rare distorted cubes and even more rarely dodecahedrons and octahedrons. Most common habit is massive or disseminated grains.
  • Cleavage is very poor, octahedral.
  • Fracture is conchoidal.
  • Hardness is 3
  • Specific Gravity is approximately 4.9 - 5.3 (average for metallic minerals)
  • Streak is a gray black.
  • Other Characteristics: The tarnish that occurs on fresh surfaces can form in only hours and will become black over time.
  • Associated Minerals are magnetite, chalcocite, chalcopyrite, covellite, pyrrhotite, pyrite and other sulfides.
  • Notable Occurances include Bristol, Connecticut, Butte, Montana, Plumas Co., Colorado and Superior, Arizona, USA; Cornwall, England; Rhineland, Germany; Tsumeb, Namibia; South Africa; Morocco; Bolivia; Chile; Peru and Mexico.
  • Best Field Indicators are lack of good crystals, tarnish, streak, color of fresh surfaces and associations.
BORNITE specimens:
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BORNITE specimen brn-1
$ 26.00
Dims: 3.5 x 2.6 x 1.6" (8.9 x 6.6 x 4.1 cm)
Wt: 10.7 oz. (303.0 g)
Junction Mine, Bisbee, Cochise County, Arizona, U.S.A.
This small hand specimen consists of a chunk of massive Bornite that is intermixed with at least 2 other metallic sulfides. The Bornite that is visble has been well oxidized so that its deep blue-violet iridescent color is its most significant aspect. It has the obligatory metallic luster and is accompanied by a significant amount of chalcopyrite and some pyrite. The Bornite makes up the bulk of the specimen's mass, however.
no photo
brn-1 ($ 26.00)
Junction Mine, Bisbee, Cochise County, Arizona, U.S.A.
BORNITE specimen brn-2
$ 45.00
Dims: 4.3 x 3.2 x 2.5" (10.9 x 8.1 x 6.4 cm)
Wt: 12.3 oz. (350 g)
Sern Martin
This hand specimen consists of a chunk of massive and semicrystalline Bornite, off of which grow what appear to be several parallel intergrown barite blades. The Bornite base appears to be made up of hundreds of intergrown crystals that do not exceed 0.3" (8 mm) along any axis, and are generally in good condition. Only a small portion of their orthorhombic prismatic form is present, but many portions of clean faces and several well-defined edges are visible. The Bornite has a color that varies from dark gray to an almost steel blue, and shows a very dull matte to a submetallic luster. Many very tiny pyrite crystals are interspersed in the Bornite matrix, and the barite blades that extend from it are in very good condition and have good orthorhombic bladed form. They have a milky-white c
no photo
brn-2 ($ 45.00)
Sern Martin
BORNITE specimen brn-3
$ 60.00
Dims: 3.2 x 2.1 x 1.6" (8.2 x 5.2 x 4.1 cm)
Wt: 13.1 oz. (372 g)
Mountain Consolidated Mine, Butte, Montana, U.S.A.
A thick layer of semicrystalline Bornite rests on the pyrite/chalcopyrite base of this small cabinet specimen. The crust is generally in very good condition, showing no fresh damage, and exhibits some warped form, but I cannot define it. Its iridescent, deep-blue color is quite obvious, and its luster is nearly matte. The accompanying pyrite and chalcopyrite is much more crystalline in nature, and several crystals of one or the other are visible.
no photo
brn-3 ($ 60.00)
Mountain Consolidated Mine, Butte, Montana, U.S.A.
BORNITE specimen brn-5
$ 84.00
Dims: 1.1 x 0.7 x 0.7" (2.7 x 1.8 x 1.7 cm)
Wt: 6 g
Dzhezkazgan, Kazakhstan
A single Bornite crystal rests on the quartz-and-calcite base of this thumbnail piece. The crystal is in excellent condition and measures 0.4 - 0.5" (1.0 - 1.3 cm) along each axis. It has an uncommon octahedral form that is slightly warped and a very dark blue-gray color and dull metallic luster. The base on which it rests is made up of many small, intergrown quartz and a few calcite crystals that are in good condition and have excellent form.
no photo
brn-5 ($ 84.00)
Dzhezkazgan, Kazakhstan
BORNITE specimen brn-4
$ 75.00
Dims: 1.5 x 1,3 x 0.4" (3.9 x 3.3 x 1.1 cm)
Wt: 9 g
Dzhezkazgan, Kazakhstan
At least 12 small Bornite orbs rest on the gray quartz base of this small hand specimen. These orbs are in excellent condition and reach diameters of 0.4" (9 mm) - each seems to be made up of 2 or more intergrown crystals that have moderately good, cubic form that is possibly octahedral. All have a dark gray coloration with a bluish iridescence and a dull metallic luster. The orbs are accompanied by several rust-red calcite "dogteeth" that are in good condition. The quartz crust also contains scores of tiny quartz prisms.
no photo
brn-4 ($ 75.00)
Dzhezkazgan, Kazakhstan
BORNITE specimen brn-6
$ 96.00
Dims: 4.43x3.67x0.72" (11.25x9.32x1.83cm)
Wt: 4.67oz (132.2g)
Mine 57, 180 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
This slab of quartz crystals displays a dozen larger bornite crystals on one side, and at least a hundred tiny ones on the reverse. The bornite is in rounded, distorted dodecahedrons, and it has a dark blue-black metallic appearance. Of course, much of the bornite is irridescent in hues of blue and purple. Many of the crystals have a coating of bronze chalcopyrite crystals, and some of these also show an irridescent tarnish in shades of red and purple.
no photo
brn-6 ($ 96.00)
Mine 57, 180 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
BORNITE specimen brn-7
$ 48.00
Dims: 2.19x0.84x0.56" (5.56x2.14x1.43cm)
Wt: 0.39oz (11.0g)
Mine 57, 60 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
This specimen displays at least 4 minerals. The two largest crystals are bornite, a blue irridescent cluster that is over 12mm across, and a purple irridescent crystal that is 5mm in diameter. The matrix is mostly tiny quartz crystals, but there is also numerous tiny white frosted crystals that are mostly rounded, but a few clearly orthorhombic (it could be calcite, of course). There is a red patch that looks like cuprite, with tiny reddish crystals sporting a purple irridescence. There is also an unidentified black mineral coating many of the quartz crystals.
no photo
brn-7 ($ 48.00)
Mine 57, 60 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
BORNITE specimen brn-8
$ 38.00
Dims: 1.15x1.46x1.07" (2.92x3.71x2.71cm)
Wt: 0.92oz (26.0g)
Mine 57, 60 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
This specimen has two clusters of bornite. The largest may be a single distorted octahedral crystal and is irridescent in shades of blue and violet. The smaller is a cluster based on a very nice elongated (but incomplete) octahedron with several smaller clusters attached. This crystal is irridescent in blues but mostly purples, but also displays some reds, yellows, and greens (at least under a loupe). These crystals rest on a druze of colorless quartz crystals, which in turn cover a complex rock containing at least 4 minerals.
no photo
brn-8 ($ 38.00)
Mine 57, 60 m level, Dzeskazgan, Karaganda oblast, Kazakhstan
BORNITE specimen brn-9
$ 30.00
Dims: 2.18x1.27x0.64" (5.53x3.24x1.62cm)
Wt: 1.50oz (42.4g)
San Martin, Zacatecas, Mexico
This is mostly bornite, with a sheet of silver attached to one end. THe bornite shows poor crystal form except under a loupe which reveals many good although small crystals. One surface of the silver is completely covered with bornite as well. All of the bornite is irridescent in shades of blue, with a few small areas of orange and even smaller spots of purple.
no photo
brn-9 ($ 30.00)
San Martin, Zacatecas, Mexico


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