| Hydroboracite | |
| Category: | Inoborates |
| Formula: | CaMgB6O8(OH)6·3H2O |
| Imasymbol: | Hbo[1] |
| Strunz: | 6.CB.15 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | P2/c |
| Unit Cell: | a = 11.76, b = 6.68 c = 8.23 [Å]; β = 102.59°; Z = 2 |
| Colour: | Colourless, white |
| Mohs: | 2 |
| Luster: | Vitreous, silky |
| Diaphaneity: | Transparent |
| Opticalprop: | Biaxial (+) |
| Refractive: | nα = 1.520 – 1.523 nβ = 1.534 – 1.535 nγ = 1.569 – 1.571 |
| Birefringence: | δ = 0.049 |
| 2V: | 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. |
| References: | [2] [3] |
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 the Inder lake, Atyrau Province, Kazakhstan. Hydroboracite is a minor borate ore mineral.