Taaffeite information

Taaffeite
Taaffeite
	Magnesiotaaffeite-2N’2S (Mg3Al8BeO16)
General
Category	Oxide minerals
Formula; (repeating unit)	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.^[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.

^ 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.
^ Cite error: The named reference thom was invoked but never defined (see the help page).
^ Cite error: The named reference mindat was invoked but never defined (see the help page).
^ Dept. Mineralogy, British Museum, June 7 1951 Taaffeite, a new beryllium mineral, found as a cut gem-stone. Retrieved February 2015
^ Cite error: The named reference msa9 was invoked but never defined (see the help page).
^ Cite error: The named reference coll was invoked but never defined (see the help page).

[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.

[thom-2] Cite error: The named reference thom was invoked but never defined (see the help page).

[mindat-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

[msa9-5] Cite error: The named reference msa9 was invoked but never defined (see the help page).

[coll-6] Cite error: The named reference coll was invoked but never defined (see the help page).

Taaffeite information

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Taaffeite
Magnesiotaaffeite-2N’2S (Mg₃Al₈BeO₁₆)
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	n_ω = 1.722, n_ε = 1.777
Birefringence	δ = 0.055
Pleochroism	Weak
References	^[2]^[3]