9.19: Twinning by reticular merohedry
In the presence of a sublattice whose oriented point group D( L T ) differs from that of the crystal (individual) lattice D( L ind ), a symmetry element belonging to D( L T ) but not to D( L ind ) can act as twin element.
If lattice and sublattice have the same point group but (some of) their symmetry elements are differently oriented, twinning by reticular polyholohedry can occur.