Cornetite Locality: L'Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville) , Southern area, Katanga Copper Crescent, Katanga (Shaba) , Democratic Republic of Congo (Zaïre) Size: 7.8 x 6.0 x 2.2 cm. — Photo: Didier Descouens · CC BY-SA 3.0
Cornetite
Cornetite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Cu₃(PO₄)(OH)₃.
It crystallizes in the orthorhombic crystal system (space group Pbca).
Key properties: Mohs hardness 4.5; specific gravity 4.1; Vitreous luster; optically biaxial.
IMA symbol Cne, grandfathered status — known before the IMA’s founding, named in 1912.
A rare secondary mineral found in the oxidized zone of some hydrothermal copper deposits.
It is found associated with Copper, brochantite, pseudomalachite, libethenite, malachite, atacamite, chrysocolla, heterogenite.
The mineral was named to honor Jules Cornet (1865–1929), Belgian geologist.