Influence of chemical, mechanical and thermal treatment on structure and properties of illite and impact on development of high-temperature ceramics was investigated. The object of this study was illite from Quartenary glacio-limnic clay of state importance deposit Apriki. Treated clay fractions were subjected to X-ray diffraction, SEM and differential thermal analysis. It was found that thermal and chemical treatment is effective. Thermally treated illite with Al(OH)3 additive was used for sintering a new dense ceramic compositions. Ceramics were characterized by bulk density, shrinkage and compressive strength 150−165 N/mm2.