Biotite Crystallography

Composition

K(Mg,Fe2+)3(Al,Fe3+)Si3O10(OH,F)2

Classification

2:1 Phyllosilicate, Mica Group

Structural Parameters

a=5.337, b=9.242, c=10.211Å
alpha=90, beta=100.15, gamma=90°
Space Group: C2/m

atom

x/a

y/b

z/c
Fe1 0 0 0.5
Mg2 0 0.3350 0.5
K 0 0.5 0
Al 0.0746 0.1666 0.2255
Si 0.0746 0.1666 0.2255
O1 .0239 0 0.1698
O2 .3207 0.2340 0.1681
O3 .1303 0.1676 0.3909
O4 0.1305 0.5 0.3952
H 0.09 0.5 0.315

Reference

Brigatti, M. F., and P. Davoli. 1990. Crystal-structure refinement of 1M plutonic biotites sample M62 from a rock transitional between granitic and monzonitic in the Valle del Cervo pluton. American Mineralogist. 75:305-313

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Original release: 1 Oct 1998;