Efremovite
Efremovite is a rare ammonium sulfate mineral with the chemical formula: (NH4)2Mg2(SO4)3. It is a white to gray cubic mineral.[3] This anhydrous sulfate occurs as constituent in sulfate crusts of burning coal dumps. It is hygroscopic and when exposed to humid air it slowly converts to the hydrate form, boussingaultite.[4][5]
| Efremovite | |
|---|---|
| General | |
| Category | Sulfate minerals |
| Formula (repeating unit) | (NH4)2Mg2(SO4)3 |
| Strunz classification | 7.AC.10 |
| Crystal system | Cubic |
| Crystal class | Tetartoidal (23) H-M symbol: (23) |
| Unit cell | a = 9.99 Å; Z = 2 |
| Identification | |
| Color | White to gray |
| Crystal habit | Equant grains and crusts |
| Cleavage | None |
| Fracture | Uneven |
| Mohs scale hardness | 2 |
| Luster | Vitreous |
| Diaphaneity | Transparent to nearly opaque |
| Specific gravity | 2.52 (calculated) |
| Optical properties | Isotropic |
| Refractive index | n = 1.550 |
| Alters to | Readily hygroscopic |
| References | [1][2][3] |
It was first described in 1989 for an occurrence in the Chelyabinsk coal basin, Southern Urals, Russia. It was named for Russian geologist Ivan Antonovich Yefremov (1907–1972). It has also been reported from several coal mining areas across Europe.[2] It occurs in association with native sulfur, kladnoite, mascagnite, and boussingaultite.[3]
References
- Efremovite, Webmineral.com
- Efremovite, MinDat.org
- Handbook of Mineralogy
- Chesnokov B. V. and Shcherbakova E. P. 1991: Mineralogiya gorelykh otvalov Chelyabinskogo ugolnogo basseina - opyt mineralogii tekhnogenesa. Nauka, Moscow
- Jambor J. L. and Grew E. S. 1991: New mineral names. American Mineralogist, 76, pp. 299-305
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