Material name Topaz
Composition Al2SiO4(OH)2
Chemical formula weight 180.06
System Orthorhombic
Temperature (ºC) r.t.
a (Å), b (Å), c (Å) 4.7203(8) 8.9207(15) 8.4189(15) @
α (deg), β (deg), γ (deg) 90 90 90 @
Unit cell volume (Å3) 354.5
Calculated density (g/p3) 3.37
Z 4
Space group Pbnm (No.62)
atom site g x/a y/b z/c B2)
Al 8d 1 0.90499(8) 0.13210(5) 0.07984(6) 0.33(2)
Si 4c 1 0.40189(10) 0.94045(7) 1/4 0.29(2)
O1 4c 1 0.7104(4) 0.0262(2) 1/4 0.38(4)
O2 4c 1 0.4439(3) 0.7561(2) 1/4 0.36(4)
O3 8d 1 0.2141(2) 0.9929(1) 0.0943(1) 0.38(3)
O4 8d 1 0.5906(3) 0.2507(1) 0.0659(1) 0.52(3)
H1 8d 0.5 0.443(11) 0.199(6) 0.088(5) 2.7(12)
H2 8d 0.5 0.607(14) 0.281(8) 0.151(7) 7.1(23)

Reference: P.A. Northrup, K. Leinenweber, and J.B. Parise, American Mineralogist, 79, 401 (1994).