This paper presents the results of comparative studies of the effect of highly dispersed fillers on the mechanical and structural characteristics of pressed composites based on gypsum. As microfillers, powders of metakaolin and the ash were introduced into the composition of the gypsum mixture. The active component in the form of metakaolin affects the structure and properties of pressed stone. The average median grain size of metakaolin predetermines an increase in packing density due to the filling of voids between larger particles of gypsum with a highly dispersed phase. The effect of increasing the density of the modified composite has been established. Studies of water absorption of stone with the addition of metakaolin have established an increase in water resistance and a decrease in water absorption of a modified composite. The results of studies of gypsum with ash additive confirm the effectiveness of the introduction of the ash in terms of strength and density. As in the case of metakaolin. Gypsum with the addition of ash has not only increased density and, as a result, high performance, but also high creep resistance. Based on the results of the microstructural and spectral analysis of pure and modified stone, a comparison was made of the elemental composition of the original stone and the modified composite on the grain surface and in the contact zones of gypsum particles with particles of fillers. They confirm the participation of additives in the formation of crystallites of the composite and the mechanical compaction of its structure.