Taaffeite
Rare gemstone / From Wikipedia, the free encyclopedia
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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.[4][5] As such, it is the only gemstone to have been initially identified from a faceted stone. 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.[6]
Quick Facts General, Category ...
Taaffeite | |
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General | |
Category | Oxide minerals |
Formula (repeating unit) | BeMgAl4O8 |
IMA symbol | Tf[1] |
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 | [2][3] |
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Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.