Heterogenite , Chrysocolla 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) ( Locality at mindat.org ) Size: 13.3 x 10.0 x 3.3 cm. A really good specimen from this relatively recent find of warty-looking (in an attractive way!) black heterogenite, bubbled up richly upon a crust of bright blue chrysocolla. Ex. Charlie Key Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Heterogenite
Cobalt oxyhydroxide — the most abundant oxidized cobalt mineral of the Katanga Copperbelt in Congo.
Intro adapted from Wikipedia (CC BY-SA).
Heterogenite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Co³⁺O(OH).
It crystallizes in the hexagonal crystal system (space group R-3m).
Key properties: Mohs hardness 3–5; specific gravity 3.07–4.32; Dark brown streak; Dull to vitreous luster.
IMA symbol Htg, IMA status: approved, named in 1872.
A weathering product of smaltite (Schneeberg, Germany); an alteration product of linnaeite, constituting an important ore of cobalt (Shaba Province, Congo); widespread in residual soils above ultramafic rocks (New Caledonia).
It is found associated with Smaltite, pharmacosiderite, calcite (Schneeberg, Germany); linnaeite, sphaerocobaltite, malachite, cuprite (Shaba Province, Congo).
Its name comes from the Greek for of another kind, as differing in composition from similar minerals.