Beryl

Beryl (/ˈbɛrəl/ BERR-əl) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18.[6] Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, pink, and red (the rarest). It is an ore source of beryllium.[7]

Main beryl producing countries

Beryl
Three varieties of beryl (left to right): morganite, aquamarine and emerald
General
CategoryCyclosilicate
Formula
(repeating unit)
Be
3
Al
2
Si
6
O
18
IMA symbolBrl[1]
Strunz classification9.CJ.05
Crystal systemHexagonal
Crystal classDihexagonal dipyramidal (6/mmm)
H-M symbol: (6/m 2/m 2/m)
Space groupP6/mcc
Unit cella = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Formula mass537.50 g/mol
ColorGreen, blue, yellow, colorless, pink, and others
Crystal habitPrismatic to tabular crystals; radial, columnar; granular to compact massive
TwinningRare
CleavageImperfect on {0001}
FractureConchoidal to irregular
TenacityBrittle
Mohs scale hardness7.5 – 8
LusterVitreous to resinous
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.63 - 2.92
Optical propertiesUniaxial (-)
Refractive indexnω = 1.564–1.595
nε = 1.568–1.602
Birefringenceδ = 0.0040–0.0070
PleochroismWeak to distinct
Ultraviolet fluorescenceNone (some fracture filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not). Morganite has weak violet fluorescence.
References[2][3][4][5]:112

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