The space groups of the alpha - and beta -phases of Ni-Cl- and Ni-Br-boracite were determined to be C/sub 2v//sup 5/ and T/sub d//sup 5/, respectively, in accord with the mineral boracite. The absolute orientations of the alpha - and beta -phase unit cells were determined and correlated to their respective etching behavior. Ferroelectric domains of the beta -phase were studied in detail on Ni-Cl- and Ni-Br-boracite under static conditions. It was found possible to distinguish all six possible domain orientations and to indicate their positive and negative dipole ends by polarization optical means only, provided relevant morphological characteristics are noted before cutting the slabs. Ferroelectric domains of 180 degrees and 90 degrees were observed, the latter occurring in head-head (tail-tail) or head-tail configurations. `Interpenetrating' tetrahedra growth twins of the alpha -phase can be explained by twinning along {100}.