Hydroboracite
Hydroboracite | |
---|---|
Hydroboracite, California(?) | |
General | |
Category | Inoborates |
Formula (repeating unit) | CaMgB6O8(OH)6·3H2O |
Strunz classification | 6.CB.15 |
Crystal system | Monoclinic |
Crystal class |
Prismatic (2/m) H-M symbol: (2/m) |
Space group | P2/c |
Unit cell |
a = 11.76, b = 6.68 c = 8.23 [Å]; β = 102.59°; Z = 2 |
Identification | |
Colour | Colourless, white |
Mohs scale hardness | 2 |
Luster | Vitreous, silky |
Diaphaneity | Transparent |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.520 - 1.523 nβ = 1.534 - 1.535 nγ = 1.569 - 1.571 |
Birefringence | δ = 0.049 |
2V angle | Measured: 60° to 66°, calculated: 62° to 66° |
Dispersion | Relatively weak |
Solubility | Very poorly soluble in cold water. Partially dissolved by prolonged submersion in boiling water. |
Hydroboracite is a hydrated borate mineral (hence the name) of calcium and magnesium, whose chemical composition is CaMgB6O8(OH)6·3H2O. It was discovered in 1834 in Atyrau Province, Kazakhstan. Hydroboracite is a minor borate ore mineral.
References
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