Kutnohorite | |
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![]() Kutnohorite, Wessels Mine, Kalahari manganese fields, Northern Cape Province, South Africa. Size 4.4 x 4.2 x 1.9 cm | |
General | |
Category | Carbonate mineral |
Formula (repeating unit) | CaMn2+(CO3)2 |
IMA symbol | Kut[1] |
Strunz classification | 5.AB.10 |
Dana classification | 14.2.1.3 |
Crystal system | Trigonal |
Crystal class | Rhombohedral (3) H-M symbol: (3) |
Space group | R3 |
Unit cell | 330.60 ų |
Identification | |
Formula mass | 215.0 g/mol (end member) |
Color | White, pale pink or light brown |
Crystal habit | Aggregates of bundled bladed crystals |
Cleavage | Perfect on {1011} |
Fracture | Subconchoidal |
Tenacity | Brittle |
Mohs scale hardness | 3.5–4 |
Luster | Vitreous to dull |
Streak | White to pale pink |
Diaphaneity | Translucent |
Specific gravity | 3.12 |
Density | 3.10–3.12 |
Optical properties | Uniaxial (−) |
Refractive index | no = 1.710–1.727, ne = 1.519–1.535 |
Birefringence | 0.191–0.192 |
Solubility | Soluble in acids |
References | [2][3][4][5] |
Kutnohorite is a rare calcium manganese carbonate mineral with magnesium and iron that is a member of the dolomite group. It forms a series with dolomite, and with ankerite. The end member formula is CaMn2+(CO3)2,[6] but Mg2+ and Fe2+ commonly substitute for Mn2+, with the manganese content varying from 38% to 84%,[2] so the formula Ca(Mn2+,Mg,Fe2+)(CO3)2 better represents the species. It was named by Professor Bukowsky in 1901 after the type locality of Kutná Hora, Bohemia, in the Czech Republic.[7] It was originally spelt "kutnahorite" but "kutnohorite" is the current IMA-approved spelling.
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