Geopolymer materials are obtained by the alkaline activation of alumina-silicate sources, the best of which is metakaolin. The aim of this work is to develop methods for working properties prediction of geopolymer materials based on the starting materials-not only metakaolin. The formation of geopolymers from four types of fly ash samples (FA) from Slovakia derived from various combustion processes was investigated. Chemical bond changes during mechanical activation were examined by X-ray photoelectron spectroscopy (XPS). Formation of new Al-O-Si chemical bonds was detected by the changes in positions of Al and Si atoms during milling. Final mechanical strength achieved by mechanical activation was studied.