Gregoryite
| Gregoryite | |
|---|---|
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | (Na2,K2,Ca)CO3 |
| Strunz classification | 05.AA.10 |
| Crystal symmetry |
Hexagonal dihexagonal pyramidal H-M symbol: (6mm) Space group: P 63mc |
| Unit cell | a = 5.21 Å, c = 6.58 Å; Z=2 |
| Identification | |
| Color | Brown, milky white |
| Crystal habit | Phenocrysts in carbonatite lava |
| Crystal system | Hexagonal |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.27 (calculated) |
| Optical properties | Uniaxial |
| Solubility | Soluble in water |
| References | [1][2][3] |
Gregoryite is an anhydrous carbonate mineral that is rich in potassium and sodium[4] with formula: [(Na2,K2,Ca)CO3].[1][5][6] It is one of the two main ingredients of natrocarbonatite, found naturally in the lava of Ol Doinyo Lengai volcano, the other being nyerereite.[7]
Because of its anhydrous nature, gregoryite reacts quickly with the environment, causing the dark lava to be converted to white substance within hours.[4]
Gregoryite was first described in 1980 and named after the British geologist and author John Walter Gregory (1864–1932), who studied the East African Rift Valley.[1][2] It occurs associated with nyerereite, alabandite, halite, sylvite, fluorite and calcite.[3]
References
- 1 2 3 Mindat.org
- 1 2 Webmineral.com
- 1 2 Handbook of Mineralogy
- 1 2 "Gregoryite definition". Dictionary of Geology. Retrieved 2011-05-21.
- ↑ Mitchell, Roger H.; Bruce A. Kjarsgaard (2010). "Experimental Studies of the System Na2CO3–CaCO3–MgF2 at 0·1 GPa: Implications for the Differentiation and Low-temperature Crystallization of Natrocarbonatite". Journal of Petrology (Oxford Journals) 52 (7–8): 1265–1280. doi:10.1093/petrology/egq069. Retrieved 2011-05-21.
- ↑ Hay, Richard L (1989). "Holocene carbonatite-nephelinite tephra deposits of Oldoinyo Lengai, Tanzania". Journal of Volcanology and Geothermal Research (Elsevier (Netherlands)) 37 (1): 77–91. Bibcode:1989JVGR...37...77H. doi:10.1016/0377-0273(89)90114-5. Retrieved 2011-05-21.
- ↑ "World's Coolest Lava is in Africa". Volcano Watch. "USGS Hawaiian Volcano Watch". Retrieved 2011-05-21.
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