Chemical dynamics provides quite a number of examples of interesting and useful discrete models. But it catches one's eye that the majority of them are from the field of homogeneous chemistry. Whereas the chemical individuality of solid substances is represented in discrete terms of crystal lattices, the conventional description of solid state reaction dynamics is essentially continual. The recent progress in the theory of random mosaics and theory of planigons opens the way for developing an alternative discrete description in terms of Dirichlet tessellations. In the present paper the two approaches are compared from the angle of meaningful simulation. It seems that this may be of interest not only for chemists but also in the broad context of developing and employing discrete dynamical models.