Atomic Positional Parameters
Mg1 1a  0.0000 0.0000 0.0000
O1  2d  0.3333 0.6667 0.2216
H1  2d  0.3333 0.6667 0.4303

Reference
F Zigan and R Rothbauer (1967)
Neues Jahrbuch fuer Mineralogie, 4, 137

Mineral Chemistry
Brucite has a layer structure with hydroxyl (OH^-) groups in hexagonal close packing. Each Mg is octahedrally coordinated to six OH^- groups and these octahedra share edges to form the layers. Because all octahedrally coordinated sites between oxygen layers are occupied by cations, this structure is described as trioctahedral; each OH^- group is surrounded by three occupied octahedral positions.

Brucite forms by alteration of periclase, which is commonly formed in metamorphosed dolomites.

The CHIME figure shows magnesiums as green spheres, oxygens as red spheres, and hydrogens as white spheres.