Covellite - Encyclopedia

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Hexagonal
    Chemistry : CuS
    Rarity : Common

Primary or secondary sulfide, covellite is common in the majority of hydrothermal copper deposits. It is most often secondary and comes from the alteration of chalcopyrite : it is then found in abundance, in foliated masses, in the cemantation zone in the company of numerous copper minerals (cuprite, digenite, chalcocite, malachitenative copper, etc...), as well as in alteration coatings on most other copper sulphides. More rarely, covellite is a primary mineral of volcanic fumaroles (Vesuvius, Italy), or of epithermal gold deposits. Its name was given to it in honor of the Italian mineralogist Niccolo Covelli who discovered this mineral at Vesuvius. Covellite is lamellar, flexible, of a characteristic deep indigo blue, with brass yellow or purplish red iridescence. Its hardness is low (1.5 to 2). It is systematically associated with pyrite, chalcopyrite or bornite. Its crystals are rare and seem specific to primary covellite. They appear in the form of small hexagonal tablets grouped into hexagonal lamellar aggregates, sometimes assembled into rosettes. This mineral constitutes an interesting related copper ore which has locally formed significant masses. It is occasionally cut into cabochons.

Main photo : Covellite from Leonard Mine, Butte Mining District, Silver Bow County, Montana, USA © Eugene & Sharon Cisneros

Covellite from Calabona, Sardinia, Italy © Simone Citon
Covellite from Leonard Mine, Butte, Montana, USA © Rock Currier
Covellite from Leonard Mine, Butte, Montana, USA © Daniel J. Evanich
31.80 ct covellite cabochon from Butte, Montana, USA

Covellite in the World

The most beautiful crystals come from Butte (Montana), which provided perfect hexagonal specimens measuring 5 cm, and from Calabona (Sardinia, Italy), where decimetric lamellar crystals sometimes grouped in rosettes were extracted. The Serbian deposit of Bor also produced centimeter-sized rosettes of lamellar crystals.

Covellite in France

In France, covellite is known in microcrystals in many deposits, the most remarkable being Cap Garonne (Var), Chessy (Rhône), Échassières (Allier), Steinbach (Haut-Rhin), etc...


No twin known for this mineral species.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 1.5 to 2
Density : 4.6 to 4.7
Fracture : Irregular
Streak : Gray-black

TP : Opaque
RI : 1.450 to 2.620
Birefringence : 1,170
Optical character : Uniaxial +
Pleochroism : Visible
Fluorescence : None

Solubility : -

Magnetism : Diamagnetic
Radioactivity : None


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