Tourmaline Crystallography

Composition

Na(Mg,Fe,Li,Al,Mn)3Al6(BO3)3Si6O18(OH,F)4

Classification

Six-Member Ring Cyclosilicate

Structural Parameters

a=15.963, b=15.963, c=7.148 Å
alpha=90, beta=90, gamma=120°
Space Group: R3m

atom

x/a

y/b

z/c
Na 0.0000 0.0000 0.2215
Fe 0.1229 0.0615 0.6297
Al 0.2980 0.2613 0.6094
B 0.1101 0.2202 0.4535
Si 0.1918 0.1898 0.0000
O 0.0000 0.0000 0.7771
O 0.0617 0.1233 0.4871
O 0.2666 0.1333 0.5083
O 0.0938 0.1876 0.0694
O 0.1877 0.0939 0.0922
O 0.1971 0.1867 0.7754
O 0.2854 0.2860 0.0783
O 0.2099 0.2706 0.4397
H 0.2680 0.1340 0.3980

Reference

Foit Jr., F.F. 1989. Crystal chemistry of alkali-deficient schorl and tourmaline structural relationships. American Mineralogist 74:422-431.

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Original release: 1 Oct 1998;