DIGENITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Trigonal
    Chemistry : Cu9S5
    Rarity : Uncommon

Digenite is a copper sulfide of essentially secondary origin. It comes from the alteration of chalcocite, chalcopyrite and bornite, and systematically accompanies secondary covellite in the oxidation and cemantation zones of copper deposits. Primary digenite is much rarer, known in basic intrusions and pegmatites. Its name comes from the Greek digenês (of two sexes or genders) to translate the supposed presence of two types of ions (copper and cupric), its name would also be an allusion to the error made in the past of believing it to be composed of a mixture of two sulphides (chalcocite and covellite). Digenite is mostly massive, but can sometimes form deformed cubo-octahedrons up to 6 cm, blue-black to black in color. It is a fairly minor copper ore.

Main photo : 6 cm digenite from Leonard Mine, Butte, Montana, USA - Smithsonian Collection © Kelly Nash

Digenite from Leonard Mine, Butte, Montana, USA © Maggie Wilson
Digenite from Leonard Mine, Butte, Montana, USA © Daniel Evanich
Digenite from Leonard Mine, Butte, Montana, USA © Christopher O'Neill
Digenite from Leonard Mine, Butte, Montana, USA © Daniel Evanich

Digenite in the World

Very beautiful digenite crystals come from Tsumeb (Namibia), Jerome and Bisbee (Arizona), and Butte (Montana) and measure up to 6 cm. Good specimens also come from polymetallic veins in Cornwall (Botallack) and Cumbria (Seathwaite Tarn, near Coniston) in England.

Digenite in France

In France, digenite is reported in very numerous occurrences but only massive. We can note Marsanges (Haute-Loire), Chessy (Rhône), Olloix (Puy-de-Dôme), St-Jean-de-Maurienne (Savoie), L’Argentolle (Saône-et-Loire), Sainte-Marie- aux-Mines (Haut-Rhin), Les Farges (Corrèze), Saint-Salvy (Tarn), the Clausis mine (Hautes-Alpes), Cap Garonne (Var), etc...

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 2.5 to 3
Density : 5.54
Fracture : Conchoidal
Streak : Gray-black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid


Magnetism : None
Radioactivity : None

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