A calculation and experimental analysis of tribotechnical properties of a pair of materials diamond-bearing mineral ceramics – ceramics in a wide range of loads are shown. The molecular-mechanical theory of friction was used for the analysis. It also accepted a linear-elastic nature of microroughness contact after running in in a steady-state mode. A criterion that determines the change in deformation behavior is the load which creates an average elastic pressure on a contact spot equal to material microstrength. Using both theoretical and experimental approaches, we determined the critical nominal pressure and friction coefficient depending on physical and mechanical constants of materials and friction surface profile parameters.