Taaffeite
| Taaffeite | |
|---|---|
Magnesiotaaffeite-2N’2S (Mg3Al8BeO16) | |
| General | |
| Category | Oxide minerals |
| Formula | BeMgAl4O8 |
| IMA symbol | Tf |
| Strunz classification | 4.FC.25 |
| Crystal system | Hexagonal |
| Crystal class | Dihexagonal pyramidal (6mm) Trigonal dipyramidal (3m) (magnesiotaaffeite-6N'3S and ferrotaaffeite-6N'3S) |
| Identification | |
| Color | Colorless, greyish violet, violet red, red, greenish, light green, pink violet, mauve |
| Crystal habit | Prismatic, alluvial grains |
| Twinning | By reflection on (0001)? |
| Cleavage | Imperfect/fair/absent |
| Fracture | Conchoidal |
| Mohs scale hardness | 8–8.5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.60–3.61 |
| Optical properties | Uniaxial |
| Refractive index | nω = 1.722, nε = 1.777 |
| Birefringence | δ = 0.055 |
| Pleochroism | Weak |
| References | |
Taaffeite (/ˈtɑːfaɪt/; BeMgAl4O8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland. As such, it is the only gemstone to have been initially identified from a faceted stone. Taaffeite is a million times rarer than diamonds and comes in shades of purple, pink, red. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel. For many years afterwards, it was known only in a few samples, and it is still one of the rarest gemstone minerals in the world.
Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.