Beryl

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Beryl
Beryl09.jpg
Three varieties o beryl: morganite, aquamarine an heliodor
General
Category Cyclosilicate
Formula
(repeating unit)
Be3Al2(SiO3)6
Strunz classification 09.CJ.05
Crystal symmetry Hexagonal dihexagonal dipyramidal
H-M symbol (6/m 2/m 2/m)
Space group: P 6/mmc
Unit cell a = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Formula mass 537.50
Color Green, blue, yellae, colourless, pink an ithers
Crystal habit Prismatic tae tabular cystals; radial, columnar; granular tae compact massive
Crystal seestem Hexagonal
Twinnin Rare
Cleavage Imperfect on {0001}
Fractur Conchoidal to irregular
Tenacity Brittle
Mohs scale hairdness 7.5–8
Luster Vitreous tae resinous
Streak White
Diaphaneity Transparent tae translucent
Specific gravity Average 2.76
Optical properties Uniaxial (-)
Refractive index nω = 1.564–1.595
nε = 1.568–1.602
Birefringence δ = 0.0040–0.0070
Pleochroism Weak tae distinct
Ultraviolet fluorescence None (some fractur fillin materials uised tae improve emerald's clarity dae fluoresce, but the stane itself daes nae)
References [1][2][3]

In geology, beryl is a mineral componed o beryllium aluminium cyclosilicate wi the chemical formula Be3Al2(SiO3)6. The hexagonal crystals of beryl mey be very smaa or range tae several meters in size. Terminated crystals are relatively rare. Pure beryl is colourless, but it is frequently tintit bi impurities; possible colors are green, blue, yellae, reid, an white.

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