Mineral - Beryl
Beryl
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Al₂Be₃[Si₆O₁₈]
Unit Cell
a=9.20 c=9.25 Z=2
Physical Properties
Hardness
7.5 - 8
Streak
white
Density
Normal (2-3,5)
Cleavage
Imperfect after {0001}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
whiteredyellowgreenbluepinkcolorless
Birefringence
0.007
Luster
Vitreous,
Greasy
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
hexagonal
Point Group
dihexagonal-dipyramidal - 6/m 2/m 2/m
Space Group
P6/mcc (192)
Habit
prismatic, tabular
Formation
(1) Magmatic, through crystallization from the residual melt of granitic magmas
(2) In the magmatic-pneumatolytic to hydrothermal stage, through the impregnation of solutions into the surrounding rocks (Greisen)
(3) Through the regional metamorphism of beryllium-bearing sediments under high pressure and high temperatures (blackwalls)
Paragenesis
Twinning
Rarity
Common
Synonyms
Beryl, Beryll, Berylite, Alkali-Beryl, Caesium-Beryl, Rosterite, Vorobyevite, Aquamarine, Davidsonite, Emerald, Goshenite, Heliodor, Morganite, Red Beryl
Composition
Elements
Mass
SiO₂
63.29
Al₂O₃
17.76
BeO
10.79
Li₂O
1.30
Na₂O
1.23
Cs₂O
3.79
Rb₂O
0.05
Afghanistan (Deer et al. 1986)
Groups and Members
Beryl-Group