(Trapezohedral-hemihedral).
Six dyad axes of two kinds are perpendicular to the hexad axis. The
general form {hikl} is the hexagonal trapezohedron bounded by twelve
trapezoidal faces. The other simple forms are geometrically the same
as in the holosymmetric class. Barium-anti-monyldextro-tartrate +
potassium nitrate (Ba(SbO)2(C4H4O6)2.KNO3) and the corresponding lead
salt crystallize in this class.