The paper presents the results of the researches on improving the physical-mechanical and thermophysical properties (average density, strength and thermal conductivity) of ceramic stone with colloidal silicon dioxide, with and without the mineral thinning additive of silica sand. In the course of the study, the most optimal amount of colloidal silicon dioxide for ceramic stone samples is determined. The dependence of strength, average density and thermal conductivity coefficient on the amount of the modifier and thinner is established. The graphic dependences are constructed by the method of extreme modelling on the basis of Scilab engineering environment. It is ascertained that the application of colloidal silicon dioxide can improve the physical-mechanical and thermophysical properties of ceramic stone. The results of the studies on ceramic stone modified with silica sand and colloidal silicon dioxide were better than without the sand supplement. The optimal amount of colloidal silicon dioxide in the composition of ceramic stone without a sand thinning additive is 0.2%, and 0.3% with this supplement.