The formation of ceramic with the prevailing cordierite in the crystalline phase is greatly dependent on the raw materials used. In the present work the cordierite formation processes from compositions of natural raw materials (illite clay, dolomite) with synthetic additives (MgO, Al(OH)3, K2CO3) are studied. XRD – data, obtained from the analysis of crystalline phase formed for different compositions and in dependence on temperature and SEM are presented. The influence of composition and temperature on the crystallisation processand morphology of cordierite phase was discussed It is shown that cordierite starts to form from temperature 1200 0C and remarkably increases at temperature 1300 0C. Increase of content of the illite clay and dolomite in compositions above 20 wt.% prevent the cordierite phase formation. SEM results shown that cordierite forms a well shaped prismatci crystalline forms with weak split