Taaffeite

Taaffeite
Magnesiotaaffeite-2N’2S (Mg3Al8BeO16)
General
CategoryOxide minerals
Formula
(repeating unit)		BeMgAl4O8
IMA symbolTf[1]
Strunz classification4.FC.25
Crystal systemHexagonal
Crystal classDihexagonal pyramidal (6mm)
Trigonal dipyramidal (3m)
(magnesiotaaffeite-6N'3S and ferrotaaffeite-6N'3S)
Identification
ColorColorless, greyish violet, violet red, red, greenish, light green, pink violet, mauve
Crystal habitPrismatic, alluvial grains
TwinningBy reflection on (0001)?
CleavageImperfect/fair/absent
FractureConchoidal
Mohs scale hardness8–8.5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity3.60–3.61
Optical propertiesUniaxial
Refractive indexnω = 1.722, nε = 1.777
Birefringenceδ = 0.055
PleochroismWeak
References[2][3]

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]

Since 2002, the International Mineralogical Association-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Cite error: The named reference thom was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference mindat was invoked but never defined (see the help page).
  4. ^ Dept. Mineralogy, British Museum, June 7 1951 Taaffeite, a new beryllium mineral, found as a cut gem-stone. Retrieved February 2015
  5. ^ Cite error: The named reference msa9 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference coll was invoked but never defined (see the help page).