Kutnohorite
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, but Mg2+ and Fe2+ commonly substitute for Mn2+, with the manganese content varying from 38% to 84%, 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. It was originally spelt "kutnahorite" but "kutnohorite" is the current IMA-approved spelling.
| Kutnohorite | |
|---|---|
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 |
| 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 | |
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