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.
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.