Gregoryite
Anhydrous carbonate mineral that is rich in potassium and sodium
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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]
| Gregoryite | |
|---|---|
| |
| General | |
| Category | Carbonate mineral |
| Formula | (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] |
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]