Material name Emerald
Composition Be3Al2Si6O18· 0.48H2O
Chemical formula weight 546.15
System Hexagonal
Temperature (ºC) 22(1)
a (Å), b (Å), c (Å) 9.218(2) 9.218(2) 9.197(2) @
α (deg), β (deg), γ (deg) 90 90 120 @
Unit cell volume (Å3) 677
Calculated density (g/p3) 2.68
Z 2
Space group P6/mcc (No.192)
atom site g x/a y/b z/c B2)
Be 6f 1 1/2 0 1/4 0.45(2)
Al 4c 1 2/3 1/3 1/4 0.21(2)
Si 12l 1 0.38735(4) 0.11563(4) 0 0.24(2)
O1 12l 1 0.3099(1) 0.2365(1) 0 0.80(3)
O2 24m 1 0.4986(1) 0.1454(1) 0.1452(1) 0.47(2)
O3 2a 0.48(4) 0 0 1/4 8.5(6)

Reference: G. Artioli, R. Rinaldi, K. Ståhl, and P.F. Zanazzi, American Mineralogist, 78, 762 (1993).