Geopolymers are ceramic-like materials produced by reaction of alumosilicate raw materials in alkaline environments and hydrothermal conditions. Polymerization in sodium silicate solutions comprises a fundamental process in 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 raw material in this study was obtained by the use of sedimentation method. Submicrometer size particle distribution contributes to reactions of geopolymerization process as shows significant compressive strength of final product. The illite clays are suitable for use in geopolymerization showing significant strength after treatment with NaOH solution.