Grandidierite
| Grandidierite | |
|---|---|
|
Grandidierite, 2.43 ct, Madagascar | |
| General | |
| Category | Nesosilicate |
| Formula (repeating unit) | (Mg,Fe2+)Al3(BO3)(SiO4)O2 |
| Strunz classification | 9.AJ.05 |
| Dana classification | 54.01.01.01 |
| Crystal system | Orthorhombic |
| Crystal class |
Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pbnm |
| Identification | |
| Color | Bluish green |
| Twinning | none |
| Cleavage | Perfect |
| Fracture | Brittle |
| Mohs scale hardness | 7.5 |
| Luster | Vitreous, Pearly |
| Streak | White |
| Diaphaneity | Transparent, Translucent |
| Density | 2.976 |
| Optical properties | Biaxial (-) |
| Refractive index | 1.583 - 1.639 |
| Pleochroism | Visible |
| 2V angle | Measured: 24° to 32°, Calculated: 32° |
| Dispersion | strong r < v |
| References | [1][2] |
Grandidierite is an extremely rare mineral and gem that was first discovered in 1902 in southern Madagascar. The mineral was named in honor of French explorer Alfred Grandidier (1836–1912) who studied the natural history of Madagascar.[1]
References
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