bismutite

{{infobox mineral | name = Bismutite | category = Carbonate mineral | image = Bismutit (Wismutcarbonat) - Schneeberg, Erzgebirge.jpg | imagesize = 260px | caption = Bismutite from Schneeberg, Germany | formula = Bi2(CO3)O2 | IMAsymbol=Bit | molweight = | strunz = 5.BE.25 | dana = 16a.03.05.01 | system = Orthorhombic | class = Pyramidal (mm2) (same H-M symbol) | symmetry = Immm | unit cell = a = 3.865 Å, b = 3.862 Å, c = 13.675 Å; Z = 2 | color = Yellow to brown, greenish, green-grey, grey or black | colour = | habit = Very rare as platy crystals; typically radially fibrous to spheroidal, in crusts and earthy to dense massive aggregates | twinning = pseudo-merohedral twinning simulates tetragonal symmetry | cleavage = Distinct/Good on {001} (microscopically observable) | fracture = | tenacity = | mohs = 2.5 – 3.5 | luster = Vitreous, waxy, may be dull to earthy | streak = Grey | diaphaneity = Opaque to transparent in small grains | gravity = 6.7 – 7.4 measured, 8.15 calculated | density = | polish = | opticalprop = Biaxial (−) (appears uniaxial due to twinning) | refractive = a=2.12–2.15, b=2.12–2.15, g=2.28 | birefringence = 0.1300–0.1600 | pleochroism = | 2V = 45 | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }} Bismutite or bismuthite is a bismuth carbonate mineral with formula Bi2(CO3)O2 (bismuth subcarbonate). Bismutite occurs as an oxidation product of other bismuth minerals such as bismuthinite and native bismuth in hydrothermal veins and pegmatites. It crystallizes in the orthorhombic system and typically occurs as earthy to fibrous masses.

It was first described in 1841 for an occurrence in Saxony.