Bismutite

Bismuth carbonate mineral
(repeating unit)Bi2(CO3)O2IMA symbolBit[1]Strunz classification5.BE.25Dana classification16a.03.05.01Crystal systemOrthorhombicCrystal classPyramidal (mm2)
(same H-M symbol)Space groupImmmUnit cella = 3.865 Å, b = 3.862 Å,
c = 13.675 Å; Z = 2IdentificationColorYellow to brown, greenish, green-grey, grey or blackCrystal habitVery rare as platy crystals; typically radially fibrous to spheroidal, in crusts and earthy to dense massive aggregatesTwinningpseudo-merohedral twinning simulates tetragonal symmetryCleavageDistinct/Good on {001} (microscopically observable)Mohs scale hardness2.5 – 3.5LusterVitreous, waxy, may be dull to earthyStreakGreyDiaphaneityOpaque to transparent in small grainsSpecific gravity6.7 – 7.4 measured, 8.15 calculatedOptical propertiesBiaxial (−) (appears uniaxial due to twinning)Refractive indexa=2.12–2.15, b=2.12–2.15, g=2.28Birefringence0.1300–0.16002V angle45References[2][3][4][5]

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.[3] It crystallizes in the orthorhombic system and typically occurs as earthy to fibrous masses.[2]

It was first described in 1841 for an occurrence in Saxony.[2]

The term bismuthite has been used in the past for bismuthinite.[6]

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Webmineral
  3. ^ a b Mindat
  4. ^ Handbook of mineralogy
  5. ^ Grice, Joel D., A Solution to the Crystal Structures of Bismutite and Beyerite, The Canadian Mineralogist, Vol. 40, pp. 693–698 (2002)
  6. ^ Chisholm, Hugh, ed. (1911). "Bismuthite" . Encyclopædia Britannica. Vol. 4 (11th ed.). Cambridge University Press. p. 11.

See also

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