Bismutite

Bismutite
Bismutite from Schneeberg, Germany
General
Category Carbonate mineral
Formula
(repeating unit)		 Bi2(CO3)O2
Strunz classification 5.BE.25
Dana classification 16a.03.05.01
Crystal system Orthorhombic
Crystal class Pyramidal (mm2)
(same H-M symbol)
Space group Immm
Unit cell a = 3.865 Å, b = 3.862 Å,
c = 13.675 Å; Z = 2
Identification
Color Yellow to brown, greenish, green-grey, grey or black
Crystal 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)
Mohs scale hardness 2.5 - 3.5
Luster Vitreous, waxy, may be dull to earthy
Streak Grey
Diaphaneity Opaque to transparent in small grains
Specific gravity 6.7 - 7.4 measured, 8.15 calculated
Optical properties Biaxial (-) (appears uniaxial due to twinning)
Refractive index a=2.12-2.15, b=2.12-2.15, g=2.28
Birefringence 0.1300-0.1600
2V angle 45
References [1][2][3][4]

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.[2] It crystallizes in the orthorhombic system and typically occurs as earthy to fibrous masses.[1]

It was first described in 1841 for an occurrence in Saxony.[1]

The term bismuthite has been used in the past for bismuthinite.[5]

References

  1. 1 2 3 Webmineral
  2. 1 2 Mindat
  3. ↑ Handbook of mineralogy
  4. ↑ Grice, Joel D., A Solution to the Crystal Structures of Bismutite and Beyerite, The Canadian Mineralogist, Vol. 40, pp. 693-698 (2002)
  5. ↑ Wikisource Chisholm, Hugh, ed. (1911). "Bismuthite". Encyclopædia Britannica. 4 (11th ed.). Cambridge University Press. p. 11.


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