Material name Lepidolite
Composition K(Li1.56Al1.3)(Al0.51Si3.49O10)F2
Chemical formula weight 394.77
System Monoclinic
Temperature (ºC) r.t.
a (Å), b (Å), c (Å) 5.209(2) 9.011(5) 10.149(5) @
α (deg), β (deg), γ (deg) 90 100.77(4) 90 @
Unit cell volume (Å3) 468.0
Calculated density (g/p3) 2.80
Z 2
Space group C2/m (No.12)
atom site g x/a y/b z/c B2)
K 2b 1 0 1/2 0 1.99(2)
Li1 2c 1 0 0 1/2 1.8(1)
Al1 4h 0.650 0 0.3289(1) 1/2 0.73(2)
Li2 4h 0.280 0 0.3289(1) 1/2 0.73(2)
Si 8j 0.873 0.08100(8) 0.16860(5) 0.23203(4) 0.73(1)
Al2 8j 0.127 0.08100(8) 0.16860(5) 0.23203(4) 0.73(1)
O1 4i 1 0.0218(4) 0 0.1750(2) 1.42(4)
O2 8j 1 0.3252(2) 0.2319(2) 0.1680(1) 1.46(3)
O3 8j 1 0.1418(3) 0.1768(1) 0.3945(1) 1.26(3)
F 8j 0.5 0.1076(3) 1/2 0.4017(2) 2.11(5)

Reference: S. Guggenheim, American Mineralogist, 66, 1221 (1981).