Magadiite
| Magadiite | |
|---|---|
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | NaSi7O13(OH)3·4(H2O) |
| Strunz classification | 09.EA.20 |
| Crystal system | Monoclinic |
| Unit cell | a = 7.25 Å, b = 7.25 Å, c = 15.69 Å; β = 96.8°; Z=2 |
| Identification | |
| Color | White |
| Crystal habit | Minute platy crystals; spherulitic aggregates; powdery |
| Tenacity | Puttylike |
| Mohs scale hardness | 2 |
| Luster | Vitreous - dull |
| Streak | White |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 2.25 calculated |
| Optical properties | Biaxial |
| Refractive index | nα = 1.470 |
| Ultraviolet fluorescence | Yellow-white under both long and short wave |
| References | [1][2][3] |
Magadiite is a hydrous sodium silicate mineral (NaSi7O13(OH)3·4(H2O)) which precipitates from alkali brines as an evaporite phase. It forms as soft (Mohs hardness of 2) white powdery monoclinic crystal masses.[1][2] The mineral is unstable and decomposes during diagenesis leaving a distinctive variety of chert (Magadi-type chert).[4]
The mineral was first described by Hans P. Eugster in 1967 for an occurrence in Lake Magadi, Olduvai Gorge, Kenya.[2][4] It is also reported from alkalic intrusive syenites as in Mont Saint-Hilaire, Canada.[1]
References
- 1 2 3 Mineral Handbook
- 1 2 3 Webmineral
- ↑ Mindat.org
- 1 2 Encyclopedia of Sediments & Sedimentary Rocks, Springer, 2003, p. 417, ISBN 1-4020-0872-4
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