Manganite Locality: Ilfeld, Nordhausen, Harz Mts, Thuringia, Germany (Locality at mindat.org) Size: 7.7 x 5.3 x 4.7 cm. A very fine manganite specimen from this — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Manganite
Manganese oxyhydroxide — lustrous striated black prisms, an important manganese ore before weathering destroyed most deposits' crystals.
Intro adapted from Wikipedia (CC BY-SA).
Manganite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Mn³⁺O(OH).
It crystallizes in the monoclinic crystal system (space group B2_1/d). It is a member of the Rutile structural group.
Key properties: Mohs hardness 4; specific gravity 4.29–4.34; typically gray or black; Reddish brown to nearly black streak; Submetallic luster; refractive index 2.18; optically biaxial.
IMA symbol Mnn, grandfathered status — known before the IMA’s founding, named in 1826.
Formed in low-temperature hydrothermal or hot-spring manganese deposits; replacing other manganese minerals in sedimentary deposits; a component in some clay deposits and laterites.
It is found associated with Pyrolusite, braunite, hausmannite, barite, calcite, siderite, goethite.
The name refers to MANGANese in the composition.
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