manganite

{{Infobox mineral | name = Manganite | category = Oxide mineral | boxwidth = | boxbgcolor = | image = Manganite-180085.jpg | imagesize = | alt = | caption = Manganite, Ilfeld, Thuringia, Germany (size: 5.2×4.1×2.7 cm) | formula = MnO(OH) | IMAsymbol = Mnn | molweight = | strunz = 4.FD.15 | dana = 06.01.03.01 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P21/c | unit cell = a = 5.3 Å, b = 5.278 Å, c = 5.307 Å; β = 114.36°; Z = 4 | color = Dark steel-gray to black, reddish brown in transmitted light, gray-white with brownish tint, with blood-red internal reflections in reflected light | colour = | habit = Slender prismatic crystals, massive to fibrous, pseudo-orthorhombic | twinning = {011} | cleavage = {010} perfect, {110} and {001} good | fracture = Uneven | tenacity = Brittle | mohs = 4 | luster = Sub-metallic | streak = Reddish brown to nearly black | diaphaneity = Opaque, transparent on thin edges | gravity = 4.29–4.34 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 2.250(2) nβ = 2.250(2) nγ = 2.530(2) | birefringence = δ = 0.280, Bireflectance: distinct in grays | pleochroism = Faint | 2V = Small | dispersion = Very strong | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = }}

Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and the luster brilliant and submetallic. The streak is dark reddish brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces. Twinned crystals are not infrequent.