bismutite

{{Short description|Bismuth carbonate mineral}}

{{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{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| 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 =

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| references = [http://rruff.geo.arizona.edu/doclib/hom/bismutite.pdf Handbook of mineralogy][http://rruff.info/uploads/CM40_693.pdf Grice, Joel D., A Solution to the Crystal Structures of Bismutite and Beyerite, The Canadian Mineralogist, Vol. 40, pp. 693–698 (2002)]

}}

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.[http://www.mindat.org/min-687.html Mindat] It crystallizes in the orthorhombic system and typically occurs as earthy to fibrous masses.[http://webmineral.com/data/Bismutite.shtml Webmineral]

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

The term bismuthite has been used in the past for bismuthinite.{{Cite EB1911 |wstitle=Bismuthite |volume=4 |page=11}}