Tschermigite
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| Tschermigite | |
|---|---|
_-_Tschermig%2C_B%C3%B6hmen.jpg) Tschermigite from Tschermig, Bohemia. | |
| General | |
| Category | Sulfate mineral |
| Formula (repeating unit) | NH4AlSO4·12(H2O) |
| Strunz classification | 07.CC.20 |
| Crystal symmetry |
Isometric diploidal H-M symbol: (2/m3) Space group: P a3m3 |
| Unit cell | a = 12.215 Å; Z=4 |
| Identification | |
| Color | Colorless, white; colorless in transmitted light |
| Crystal habit | Octahedral crystals; fibrous columnar; powdery |
| Crystal system | Isometric |
| Cleavage | Perfect on {100} |
| Fracture | Conchoidal |
| Mohs scale hardness | 1½ - 2 |
| Luster | Vitreous, silky |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 1.645 |
| Optical properties | Isotropic |
| Refractive index | 1.458 |
| Birefringence | Anomalously birefringent |
| Solubility | Deliquescent |
| References | [1][2][3] |
Tschermigite is a mineral form of ammonium alum, formula NH4AlSO4·12(H2O). It is found in burning coal seams, bituminous shale and fumaroles. Because of its extreme water solubility it is unlikely to persist except in the dryest of conditions. Discovered in 1852 at Cermiky, also known as Tschermig in Bohemia. It is colorless and named for where it was discovered.
References
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