Covellite

Covellite is a rare sulfide mineral (CuS) made of copper and sulfur. It is usually indigo-blue or darker, and often shimmers with iridescent colours running from brass-yellow to deep red. It is very soft and splits into paper-thin, flexible leaves. It mostly forms in the near-surface, air-weathered parts of copper deposits, and is also seen as an iridescent coating on other copper sulfides.

About 64 per cent of covellite’s weight is copper (64.46 in MTA’s table), and it counts as a copper ore; but it is present in small amounts in most deposits, and most copper comes from other minerals such as chalcopyrite. According to MTA, of the copper sulfide minerals, chalcocite and covellite are the best suited to leaching (separating copper from the ore with an acid solution). Covellite also appears in scientific research: copper sulfide is studied for battery electrodes, electrocatalysis, sensor structures and superconductivity. Fine crystals are sought by collectors.

It has a hardness of 1.5–2 on the Mohs scale. It is soft enough to scratch with a fingernail. Its specific gravity is 4.6–4.76 g/cm³.

Its best-known localities: Mount Vesuvius, Campania, Italy; Butte, Montana, USA; Calabona mine, Alghero, Sardinia, Italy; Bor, Serbia; Leogang, Salzburg, Austria.

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

Its colour is indigo-blue or darker, and it often shimmers with iridescent blue, purple, brass-yellow and deep red. It is very soft (hardness 1.5–2): a fingernail scratches it. Its perfect cleavage splits it into leaves, and the thin leaves can be bent (they are flexible). Other copper sulfides such as bornite and chalcopyrite also tarnish to blue-purple iridescent colours, and pieces of acid-coloured “peacock ore” can be mistaken for covellite. Covellite is softer than all of them (hardness 1.5–2), splits into leaves and leaves a shining lead-gray streak.

On the “street to diamond” value ladder it sits on step 4 of nine: Fine dimension stone and ore. Although about two thirds of covellite is copper, it occurs in small amounts in most deposits; as an ore, its worth depends on how much of it a deposit holds and how easily it is concentrated together with the main ore minerals. For collectors, the size and beauty of the crystals, the vividness of the colour, freedom from damage and a famous locality matter; specimens from places such as Butte (Montana) and Calabona (Sardinia) are sought. Because it is soft and brittle, undamaged specimens are scarce.

Crystal-therapy practitioners regard covellite as a “stone of transformation”: they claim it helps to let go of old habits and of feelings of guilt or shame. According to the same sources, covellite is linked to the third-eye chakra and strengthens intuition. Some crystal-therapy pages say that covellite improves circulation and oxygen intake and helps against fatigue. There is no scientific evidence that covellite transforms emotions, strengthens intuition or improves circulation and oxygen intake. Covellite is a copper sulfide: it should not be put in the mouth or in water to make “gem water” or an “elixir”; too much copper causes nausea, vomiting and, in time, liver and kidney damage. Persistent fatigue or circulation problems call for a doctor. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

Covellite is a copper sulfide (about two thirds of its weight is copper). Handling it is generally harmless; wash your hands afterwards. It is very soft and brittle and crumbles easily: do not breathe the dust, because copper dust irritates the nose and throat and can cause dizziness and headaches. Do not put it in your mouth or lick it. Do not heat it; irritating sulfur dioxide gas is released. Do not put it 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. Keep specimens away from children and pets.