| Gregoryite | |
|---|---|
 | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | (Na2,K2,Ca)CO3 |
| IMA symbol | Ggy[1] |
| Strunz classification | 5.AA.10 |
| Crystal system | Hexagonal |
| Crystal class | Dihexagonal pyramidal (6mm) (same H-M symbol) |
| Space group | P63mc |
| Unit cell | a = 5.21 c = 6.58 [Å]; Z = 2 |
| Identification | |
| Color | Brown, milky white |
| Crystal habit | Phenocrysts in carbonatite lava |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.27 (calculated) |
| Optical properties | Uniaxial |
| Solubility | Soluble in water |
| References | [2][3][4] |
Gregoryite is an anhydrous carbonate mineral that is rich in potassium and sodium[5] with the chemical formula (Na2,K2,Ca)CO3.[2][6][7] It is one of the two main ingredients of natrocarbonatite, found naturally in the lava of Ol Doinyo Lengai volcano of Arusha Region, Tanzania, and the other being nyerereite.[8]
Because of its anhydrous nature, gregoryite reacts quickly with the environment, causing the dark lava to be converted to white substance within hours.[5]
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.[2][3] It occurs associated with nyerereite, alabandite, halite, sylvite, fluorite and calcite.[4]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b c Mindat.org
- ^ a b Webmineral.com
- ^ a b "Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2019-05-08. Retrieved 2011-06-03.
- ^ a b "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. 52 (7–8). Oxford Journals: 1265–1280. doi:10.1093/petrology/egq069.
- ^ Hay, Richard L (1989). "Holocene carbonatite-nephelinite tephra deposits of Oldoinyo Lengai, Tanzania". Journal of Volcanology and Geothermal Research. 37 (1). Elsevier (Netherlands): 77–91. Bibcode:1989JVGR...37...77H. doi:10.1016/0377-0273(89)90114-5.[dead link]
- ^ "World's Coolest Lava is in Africa". Volcano Watch. USGS Hawaiian Volcano Watch. Retrieved 2011-05-21.