Crednerite Locality: Somerset , England , UK ( Locality at mindat.org ) Size: small cabinet, 7 x 4 x 4 cm Crednerite This is an extremely rare copper species, CuMnO2; and a very rich specimen featuring a beautiful, bright, metallic spray of flat crednerite crystals to 2 cm. There is also an unidentified microscopic green mineral present at the upper-left (probably a molybdate). — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Crednerite
Crednerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CuMnO₂.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 4; specific gravity 4.98–5.34; Soot-black, with a brownish tint streak; Metallic luster.
IMA symbol Cnr, grandfathered status — known before the IMA’s founding, named in 1849.
A low-temperature secondary mineral, perhaps indicating a reducing chemical environment.
It is found associated with Psilomelane, hausmannite, malachite, volborthite, barite, calcite, “wad” (Friedrichroda, Germany); cerussite, hydrocerussite, malachite, mendipite.
The mineral was named to honor Karl F.H. Credner (1809–1876), German mining geologist and mineralogist.