| 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) (sameH-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 ananhydrouscarbonate mineral that is rich inpotassium andsodium[5] with the chemical formula(Na2,K2,Ca)CO3.[2][6][7] It is one of the two main ingredients ofnatrocarbonatite, found naturally in the lava ofOl Doinyo Lengai volcano ofArusha Region,Tanzania, and the other beingnyerereite.[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 authorJohn Walter Gregory (1864–1932), who studied theEast African Rift Valley.[2][3] It occurs associated with nyerereite,alabandite,halite,sylvite,fluorite andcalcite.[4]