Atomic Positional Parameters
Al1 4e  0.1679 0.5295 -0.0023
Al2 4e  0.3344 0.0236 -0.0024
O1  4e  0.1779 0.2183 -0.1115
O2  4e  0.6692 0.6558 -0.1023
O3  4e  0.4984 0.1315 -0.1044

O4  4e -0.0205 0.6293 -0.1068
O5  4e  0.2971 0.7178 -0.1052
O6  4e  0.8194 0.1491 -0.1015
H1  4e  0.1010 0.1520 -0.1240
H2  4e  0.5950 0.5730 -0.0980

H3  4e  0.5030 0.1370 -0.1900
H4  4e -0.0290 0.8010 -0.1070
H5  4e  0.2930 0.7240 -0.1960
H6  4e  0.8150 0.1600 -0.1900

Reference
H Saalfeld and M Wedde (1974)
Zeitschrift fuer Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie, 139, 129

Mineral Chemistry
The structure of gibbsite layers is similar to that of brucite, except that one third of the octahedral sites are vacant. The gibbsite structure type is therefore referred to as dioctahedral - brucite as trioctahedral. In contrast to brucite, the gibbsite layers fit together such that an OH^- group is opposite an OH^- group of the next layer. Gibbsite is a major constituent of bauxites and laterites; bauxites are formed by weathering of aluminium silicate rocks in tropical or subtropical conditions.

The CHIME figure shows aluminiums as grey spheres, oxygens as red spheres, and hydrogens as white spheres. The unit cell is outlined.