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MnO(OH) A brilliant steel-gray or black polymorphous mineral; crystallizes in the orthorhombic system. Also known as gray manganese ore.



a mineral of the oxide and hydroxide class. It has a chemical composition of MnO(OH) and contains 80.66 percent MnO; admixtures of Fe, Al, Ba, Pb, Cu, and other elements are sometimes present. Manganite crystallizes in the monoclinic system, forming prismatic steel-gray pseudoorthorhombic crystals with a submetallic luster and perfect cleavage. It generally occurs as black or brown (hydromanganite) finely crystalline masses. Concretions and oolitic formations are also widespread. Manganite is brittle. It has a hardness of 3-4 on Mohs’ scale and a density of 4,200-4,330 kg/m3.

Manganite, along with other manganese oxides (pyrolusite, psilomelane), enters into the composition of large sedimentary manganese ore deposits that are formed in the littoral zones of marine basins under conditions of some oxygen deficiency. Manganite also occurs in hydrothermal vein deposits in association with calcite, quartz, barite, and, sometimes, rhodochrosite. It is converted into sooty cryptocrystalline pyrolusite during surface oxidation. Manganite serves as an important source material in the manufacture of ferromanganese and other manganese alloys required for the smelting of special steels.


Mineraly; spravochnik, vol. 2, fasc. 3. Moscow, 1967.