Draft:Okayamalite
| General | |
|---|---|
| Category | Mineral |
| Formula (repeating unit) | Ca2B[BSiO7] |
| Crystal system | Tetragonal |
| Crystal class | P421m |
| Unit cell | a = 7.1248(2) Å, c = 4.8177(2) Å V = 244.56 Å3 Z = 2 |
| Identification | |
| Colour | creamy white |
| Mohs scale hardness | 5½ |
| Luster | earthy |
| Streak | white |
| Diaphaneity | translucent |
| Density | 3.30 |
| Optical properties | Uniaxial (-) |
| Refractive index | nω = 1.700 nε = 1.696 |
| Birefringence | 0.004 |
Okayamalite is a boron-rich sorosilicate mineral from the melilite family with the formula Ca2B(BSiO7). It is the boron analogue of gehlenite.[1]
Originally a synthetic compound, natural okayamalite was first documented at Fuka Mine in Okayama Prefecture, Japan; it is named for the prefecture. It is associated with wollastonite and calcite, and believed to be formed via boron trioxide metasomatism:[1]
- B2O3 + CaSiO3 + CaCO3 → Ca2B(BSiO7) + CO2
References
[edit]- ^ a b Matsubara, Satoshi; Miyawaki, Ritsuro; Kato, Akira; Yokoyama, Kazumi; Okamoto, Akiyoshi (1998). "Okayamalite, Ca2B2SiO7, a new mineral, boron analogue of gehlenite". Mineralogical Magazine. 62 (5): 703–706. Bibcode:1998MinM...62..703M. doi:10.1180/002646198547936.