![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Combeite.jpg/640px-Combeite.jpg&w=640&q=50)
Combeite
Silicate mineral / From Wikipedia, the free encyclopedia
Combeite is a rare silicate mineral with the formula Na2Ca2Si3O9. It has a trigonal crystal system.
Quick Facts General, Category ...
Combeite | |
---|---|
![]() Pale pink crystal aggregates of the very rare silicate mineral combeite from one of the only 4 localities known worldwide: Mount Oldoinyo Lengai, Arusha Region, Tanzania. | |
General | |
Category | Silicate mineral |
Formula (repeating unit) | Na2Ca2Si3O9 |
IMA symbol | Cbe[1] |
Strunz classification | 9.CJ.15a |
Crystal system | Trigonal |
Crystal class | Trapezohedral (32) (same H-M symbol) |
Space group | P3121 |
Unit cell | a = 10.42 Å, c = 13.14 Å; Z = 6 |
Identification | |
Color | Colorless |
Crystal habit | Stout prisms |
Streak | White |
Diaphaneity | Transparent |
Specific gravity | 2.844 |
Optical properties | Uniaxial (+) |
Refractive index | nω = 1.598 nε = 1.598 |
Birefringence | δ = 0.000 |
References | [2][3][4] |
Close