(Holohedral; Ditetragonal bipyramidal).
Crystals of this class are symmetrical with respect to five planes,
which are of three kinds; one is perpendicular to the principal axis,
and the other four intersect in it; of the latter, two are
perpendicular to the equal crystallographic axes, while the two others
bisect the angles between them. There are five axes of symmetry, one
tetrad and two pairs of dyad, each perpendicular to a plane of
symmetry. Finally, there is a centre of symmetry.