| Rocks and Minerals for Sale Bornite |
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Item# BOR1207001 Bornite from Mexico $25.00 |
This specimen weighs 0.72 lbs (326g) and measures 2.2 x 2.7 x 2.0 inches (56 x 69 x 51mm)
| Bornite 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 is an important copper ore mineral and occurs widely in porphyry copper deposits along with the more common chalcopyrite. Chalcopyrite and bornite are both typically replaced by chalcocite and covellite in the supergene enrichment zone of copper deposits. Bornite is also found as disseminations in mafic igneous rocks, in contact metamorphic skarn deposits, in pegmatites and in sedimentary cupriferous shales. It is important for its copper content of about 63 percent by mass and is found in Arizona, Butte, Montana, and Mexico. It's existence has been reported since 1725, but in 1845 it was named for Austrian mineralogist Ignaz Edler Von Born (1742–1791). |
Item# BOR1207002 Small Bornite from Mexico $10.00 |
This specimen weighs 1 oz (29.5g) and measures 2 x 1.4 x 0.6 inches (51 x 37 x 15mm)
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