Tourmaline
Hamburger G E, Buerger M J
American Mineralogist 33 (1948) 532-540
The structure of tourmaline
15.951 15.951 7.24 90 90 120 R3m
atom    x     y    z
Na      0     0 .770
Mg   .133 .0665 .255
B    .117 .2340    0
Al   .050 .3670 .825
Si   .192 .1920 .624
OH1     0     0 .403
O2   .058 .1160    0
OH3  .233 .1165 .032
O4   .142 .0710 .624
O5   .102 .2040 .742
O6   .200 .2000 .403
O7   .279 .2460 .758
O8   .058 .2920    0