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]
Quick Facts General, Category ...
| Bismutite |
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 Bismutite from Schneeberg, Germany |
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| Category | Carbonate mineral |
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| Formula | Bi2(CO3)O2 |
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| IMA symbol | Bit[1] |
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| Strunz classification | 5.BE.25 |
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| Dana classification | 16a.03.05.01 |
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| Crystal system | Orthorhombic |
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| Crystal class | Pyramidal (mm2)
(same H-M symbol) |
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| Space group | Immm |
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| Unit cell | a = 3.865 Å, b = 3.862 Å,
c = 13.675 Å; Z = 2 |
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| Color | Yellow to brown, greenish, green-grey, grey or black |
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| Crystal habit | Very rare as platy crystals; typically radially fibrous to spheroidal, in crusts and earthy to dense massive aggregates |
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| Twinning | pseudo-merohedral twinning simulates tetragonal symmetry |
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| Cleavage | Distinct/Good on {001} (microscopically observable) |
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| Mohs scale hardness | 2.5 – 3.5 |
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| Luster | Vitreous, waxy, may be dull to earthy |
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| Streak | Grey |
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| Diaphaneity | Opaque to transparent in small grains |
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| Specific gravity | 6.7 – 7.4 measured, 8.15 calculated |
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| Optical properties | Biaxial (−) (appears uniaxial due to twinning) |
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| Refractive index | a=2.12–2.15, b=2.12–2.15, g=2.28 |
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| Birefringence | 0.1300–0.1600 |
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| 2V angle | 45 |
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| References | [2][3][4][5] |
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It was first described in 1841 for an occurrence in Saxony.[2]
The term bismuthite has been used in the past for bismuthinite.[6]
_-_Schneeberg,_Erzgebirge.jpg)