Bornite

Bornite is a sulfide mineral (Cu₅FeS₄) made of copper, iron and sulfur. A freshly broken surface is copper-red to bronze-brown, but on contact with air it quickly becomes coated with an iridescent layer of blue, purple and red. That is why it is also known as “peacock ore” or “peacock copper”. About 63 per cent of its weight is copper, and it is an important copper ore. Be warned, though: most of the brilliantly coloured stones sold in shops under this name are not bornite but chalcopyrite coloured with acid.

Bornite is an important copper ore; about 63 per cent of its weight is copper. Copper, an excellent conductor of electricity and heat, is used: in electrical and electronic equipment: cables, electric motors and circuit boards, in construction: water pipes and roofing, in alloys: brass (with zinc) and bronze (with tin). In ore processing, bornite is concentrated by froth flotation like the other copper sulfides; according to MTA, a chemical addition (Na₂S) is needed to make bornite cling to the froth. Fine specimens are also sought by collectors.

It has a hardness of 3–3.3 on the Mohs scale. A fingernail cannot scratch it, but a steel knife can. Its specific gravity is 5.06–5.08 g/cm³.

Its best-known localities: Olympic Dam, South Australia; Carn Brea mine, Illogan, Cornwall, England; Butte, Montana, USA; Bristol, Connecticut, USA; Dzhezkazgan (Jezkazgan), Kazakhstan.

Known localities in Türkiye: Çayeli (Madenköy), Rize, Türkiye; Uslu, Sivrice, Elazığ, Türkiye.

A freshly broken surface is copper-red to bronze-brown; the surface soon tarnishes with an iridescent coating of blue, purple and red. Its streak (powder colour) is pale grayish black. It is soft (hardness 3–3.25), scratched by a steel knife; it is brittle and breaks unevenly. Its specific gravity is about 5.1: roughly twice as dense as quartz, it feels heavy for its size. Most of the bright blue, purple, pink and green stones sold as “peacock ore” are not bornite but chalcopyrite whose surface has been artificially coloured with acid. Chalcopyrite is brass-yellow and harder than bornite (3.5–4); on a worn or broken spot the yellow beneath may show.

On the “street to diamond” value ladder it sits on step 4 of nine: Fine dimension stone and ore. Bornite is valued as an ore: the copper content of the ore (bornite itself is about 63 per cent copper), the size of the deposit, by-products such as silver, the cost of mining and processing, and demand for copper are what count. For collectors, well-crystallised, lustrous, undamaged specimens and those from famous localities are sought. For the coloured stones sold as “peacock ore”, the decisive factor is treatment: acid-coloured chalcopyrite must not be treated as equal to natural bornite, and a seller should disclose it.

Crystal-therapy sources claim that “peacock ore” transforms negativity and protects its wearer from negative influences. According to the same sources, bornite activates the third-eye chakra and brings all the chakras into harmony. Some crystal-therapy pages claim that bornite supports health at the cellular level and corrects metabolic imbalances. There is no scientific evidence that bornite transforms negativity, balances chakras or supports cell health. Bornite is a copper-bearing sulfide, and specimens sold as “peacock ore” may have been treated with acid: do not put these stones in water to make “gem water” or an “elixir” and do not put them in the mouth; too much copper causes nausea, vomiting and, in time, liver and kidney damage. For a health problem, see a doctor rather than relying on a stone. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

Bornite contains copper, iron and sulfur. Handling it is generally harmless; washing your hands afterwards is enough. Do not put it in your mouth or lick it, and do not grind or sand it and breathe the dust: copper dust irritates the nose and throat and can cause dizziness and headaches. Do not heat it; irritating sulfur dioxide gas is released. Coloured specimens sold as “peacock ore” may have been treated with acid; keep them out of the mouth and away from children and pets. Do not put bornite in water to make “gem water” or an “elixir”: there is no knowing how much copper will dissolve, and too much copper causes nausea, vomiting, abdominal pain and diarrhoea, and with long exposure liver and kidney damage.