In discussing the interconnection between the preferred local occurrence of a solid-phase chemical reaction and the geometric-probabilistic description of reaction kinetics, it is shown that the original solid reagent must be represented in this description in the proper manner. A way of doing this for an original single crystal is suggested, through subsequently separating the negative crystal growth and the two-dimensional advance of the front along the surface with the account of its translational symmetry in terms of Wigner-Seitz cells. Symmetry considerations in favor of the proposed essentially two-dimensional approach are discussed.