From teaching experience. VII. Subordination of symmetry groups and crystallographic criterion of harmony

It is shown by the example of the fences of Saint Petersburg that they combine the borders of all seven symmetry groups in different ways. A criterion is proposed: a lattice is harmonious if the symmetry groups of the borders are subordinate, otherwise it is eclectic. According to the author’s experience, such an approach on the border of crystallography and architecture facilitates the perception of the topic on the subordination of 32 point symmetry groups in the university course of crystallography. The article is dedicated to the memory of the outstanding scientist and popularizer of mineralogy Professor A. G. Bulakh.