A variety of industrial minerals, such as kaolinite, feldspars, and etc., and industrial solid residues or wastes, such as fly ashes, metallurgical slags , mine wastes, etc., have been used as solid raw materials in the geopolymerization technology. The use of clays as a raw material promises low cost and it is easily available material all over the world. In Latvian clays dominant clay mineral is illite. The aim of this study was to find out the Liepas red and gray clays aptitude for geopolymer production. The raw material in this study was obtained by the use of sedimentation method. Clay fraction and dust fraction, was subjected to the treatment with NaOH solution and afterwards treated at different temperatures. The effect of drying temperatures and aging time, which directly influence final compressive strength values of geopolymer specimens, were investigated and compared. Used methods and instruments in this research include Casagrande method, X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, Brunauer Emmett Teller adsorption method and others. Clay fractions, which are the most delicate particles of clay composition, after thermal activation and treatment with NaOH solution shows significant compressive strength.