Bornite, affectionately known as “peacock ore,” is a stunning mineral admired for its iridescent colors. This copper iron sulfide crystallizes in the orthorhombic system and has a chemical composition of Cu5FeS4. It occurs in igneous, metamorphic, and sedimentary rocks across the world, making it a widespread and common ore of copper.
The fresh surfaces of bornite range from chestnut brown to a coppery red. However, when exposed to air these surfaces quickly tarnish in breathtaking shades of purple, blue, and green. This iridescence is what gives bornite its nickname “peacock ore.” The colors seem to dance and shift dependending on the viewing angle, reminiscent of a peacock’s magnificent feathers. This striking play-of-color makes bornite a favorite among mineral collectors and lapidarists.
Bornite frequently occurs with other sulfide minerals like chalcopyrite, marcasite, and pyrite. Deposits are found globally in locations like Africa, Australia, Canada, and the United States. Two major sources are the Evergreen Mine in Colorado and the Flambeau Mine in Wisconsin. Bornite is also popular in the metaphysical community, believed to help dissolve emotional obstacles and integrate new perspectives. With its stunning colors, global deposits, and mystical associations, bornite has cemented itself as a cherished mineral worldwide.
What is Bornite?
Bornite is a sulfide mineral with a chemical composition of Cu5FeS4. It crystallizes in the orthorhombic crystal system, meaning its crystals have three unequal axes at right angles.
Fresh bornite ranges in color from chestnut brown to copper-red. However, when exposed to air these surfaces quickly tarnish to reveal breathtaking iridescent shades of purple, blue, green, and yellow. This remarkable play-of-color is what inspired bornite’s nickname “peacock ore.” The colors seem to dance and shift depending on the viewing angle, reminiscent of a peacock’s magnificent feathers.
Bornite occurs in igneous, metamorphic, and sedimentary rocks across the world, making it a widespread and common ore of copper. It frequently occurs alongside other sulfide minerals like chalcopyrite, marcasite, and pyrite.
Where Bornite is Found
Significant deposits of bornite have been found across the globe. Some of the most notable locations include:
Africa
- Namibia
- Shaba Province, Democratic Republic of Congo
- Tsumeb, Namibia
- Nkana Mine, Zambia
Australia
- Rum Jungle, Northern Territory
- Mount Isa, Queensland
Asia
- Dzhezkazgan, Kazakhstan
Europe
- Schladming, Austria
- Cornwall, England
- Slovakia
North America
Canada
- Ontario
- Quebec
United States
- Arizona
- Colorado
- Connecticut
- Montana
- New Mexico
- Pennsylvania
- Wisconsin
Major commercial mines include:
- Evergreen Mine – near Apex, Gilpin Co., Colorado. A prolific deposit that has produced beautiful iridescent bornite crystal specimens.
- Flambeau Mine – Ladysmith, Rusk Co., Wisconsin. Known for large volumes of exceptionally bright and colorful bornite.
- White Pine Mine – Ontonagan Co., Michigan
- French Creek Mine – St. Peters, Chester Co., Pennsylvania
- Mangula Mine – Mhangura, Zimbabwe. Known for yielded stunning bornite crystals.
Properties and Characteristics
Bornite has a submetallic to metallic luster. It is opaque and has poor cleavage.
Some key physical properties of bornite include:
- Crystal System: Orthorhombic
- Mohs Hardness: 3
- Specific Gravity: 4.9 – 5.1
- Streak: Grayish black
- Color: Chestnut brown to copper-red when fresh, quickly tarnishes iridescent purplish-blue
- Luminescence: Non-fluorescent
- Magnetism: Slightly magnetic after heating
The low hardness and colorful tarnishing of bornite make it easy to identify. Fresh surfaces will quickly oxidize when exposed to air or moisture, revealing the stunning iridescent colors.
Bornite is easily confused with chalcopyrite and chalcocite. However, chalcopyrite has a brighter brassy yellow color. Chalcocite has a dark gray streak rather than bornite’s black streak.
Comparison of Bornite with Other Rocks and Minerals
| Mineral | Chemical Formula | Crystal System | Hardness | Specific Gravity | Streak | Distinguishing Features |
|---|---|---|---|---|---|---|
| Bornite | Cu5FeS4 | Orthorhombic | 3 | 4.9-5.1 | Grayish black | Tarnishes iridescent purple/blue. Lower hardness than other copper minerals. |
| Chalcopyrite | CuFeS2 | Tetragonal | 3.5-4 | 4.1-4.3 | Greenish black | Brassy yellow color. Does not tarnish like bornite. |
| Chalcocite | Cu2S | Monoclinic | 2.5-3 | 5.5-5.8 | Dark gray | Main copper ore mineral. Does not tarnish. |
| Azurite | Cu3(CO3)2(OH)2 | Monoclinic | 3.5-4 | 3.7-3.9 | Blue | Deep blue color. Effervesces with acid. |
| Malachite | Cu2CO3(OH)2 | Monoclinic | 3.5-4 | 4.0-4.1 | Green | Bright green color. Effervesces with acid. |
| Cuprite | Cu2O | Cubic | 3.5-4 | 5.8-6.2 | Red | Pure copper red color. Much higher specific gravity than bornite. |
| Pyrite | FeS2 | Cubic | 6-6.5 | 4.9-5.2 | Greenish to brownish black | Metallic luster. Higher hardness than bornite. |
Metaphysical Uses of Bornite
In crystal healing, bornite is believed to help dissolve emotional obstacles and negative thought patterns that hold one back. It encourages following one’s true joy and integrating new perspectives into one’s life.
Some believe wearing or carrying bornite can ward off negative energies. It is said to be excellent for overcoming depression, fears, and phobias by allowing one to see the lighter side of life.
Uses of Bornite
The primary commercial use of bornite is as an ore for copper. It has been a major ore of copper across the world.
However, most bornite today is collected by mineral enthusiasts. The stunning iridescent colors make it a highly desirable mineral specimen. Quality bornite has become popular and fast-selling at mineral and gem shows.
Bornite is rarely used for jewelry as it is quite soft. Occasionally it may be found crafted into pendants, but it requires careful handling to prevent scratching.
Museums may display exceptional bornite specimens, like the giant iridescent crystals found at the Mangula Mine in Zimbabwe.
Fun Facts About Bornite
- The play-of-color in bornite is caused by light refracting off a thin oxide layer that forms on the surface. This is why bornite must be exposed to air and moisture to develop its magical iridescence.
- Bornite earned the nicknames “peacock ore” and “purple copper ore” due to its resemblance to the vibrant colors seen on peacocks’ feathers.
- Bornite was first described in 1725 after being discovered in the Ore Mountains on the border region of Germany and the Czech Republic.
- Rare cubic, octahedral, and dodecahedral bornite crystals have occasionally been found. Most bornite occurs in compact granular aggregates.
- Some ancient bronzes derived their copper content from bornite rather than malachite or azurite ores.
- Large bornite crystals up to 2 feet long have been uncovered at the famous Mangula Mine in Zimbabwe.
- Bornite occurs alongside hematite in banded iron formations and is an indicator of hydrothermal activity.
Buying Bornite
Bornite is relatively affordable and available. Small specimens can be purchased online or at rock shops for $5-20. Larger displaying pieces with exceptional iridescence often sell for $50-100. Rare bornite crystals command higher prices depending on size and aesthetics.
When buying bornite, look for vibrant and varied color play rather than a uniform coating. Multicolor iridescence is ideal. Reddish-pink and blue are the most valued colors. Some pieces may even display a rainbow effect.
How to Clean and Care for Bornite
Gentle cleaning is recommended to avoid damaging bornite’s soft, delicate surface. Warm soapy water and a soft toothbrush can remove minor dirt and oils. Avoid harsh chemicals or mechanical polishing that could scratch the iridescence.
Prevent long exposure to air and moisture to slow oxidation. Store specimens in a sealed container with desiccant packs. Never clean in ultrasonic or steam cleaners as moisture can damage surfaces.
Handle carefully as bornite is fragile against bumps and abrasions. Use a soft cloth to polish. Keep away from harsh chemicals and acid rain.
Frequently Asked Questions about Bornite
What causes the iridescent colors in bornite?
The iridescent blues, purples, and greens of bornite are produced when a thin oxide layer forms on the mineral’s surface when exposed to air or moisture. Light refracts off this oxide layer to produce the magical play-of-color.
How did bornite get its nickname “peacock ore”?
Bornite is nicknamed “peacock ore” because the iridescent tarnishing results in colors similar to those seen on a peacock’s feathers. The shifting hues depending on viewing angle resemble a peacock’s display.
Is bornite natural or is it produced artificially?
Bornite is a completely natural mineral and is never produced artificially. However, some sellers may artificially alter chalcopyrite to have iridescent colors and market it as “peacock ore”, which is misleading.
What are some metaphysical properties associated with bornite?
Bornite is believed to dissolve emotional obstacles, encourage joyfulness, integrate new perspectives, and ward off negative energy. It may help overcome depression, fears, and phobias.
What is bornite’s hardness on the Mohs scale?
Bornite has a hardness of 3 on the Mohs scale, making it relatively soft. This limits its use in jewelry compared to quartz or other harder gemstones.
Where are the best places to find bornite specimens?
Notable deposits include Colorado’s Evergreen Mine, Wisconsin’s Flambeau Mine, the Mangula Mine in Zimbabwe, and the Rum Jungle in Australia. These have produced exceptional bornite mineral specimens.
Is bornite expensive or affordable to collect?
Small bornite samples are quite affordable in the $5-$20 range. Larger display pieces with vibrant iridescence can sell for $50-$100. Rare crystal specimens may cost more depending on quality.
How should bornite be cared for and stored?
Bornite should be kept away from harsh chemicals or mechanical abrasion that could damage the soft surface. Store in an airtight container to limit oxidation. Gently clean with mild soap and water only.
Final Thoughts on Bornite
Bornite is a copper ore that reveals nature’s wonders through dazzling iridescent tarnishing. Its chameleon-like colors make each specimen unique. From mineral collections to metaphysical uses, bornite continues to captivate. While copper production relies on more abundant ores today, bornite endures as a favorite mineral specimen for collectors around the world.
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