Fly ashes from the fluidized bed boiler were used to obtain zeolites by the alkaline fusion process, followed by a hydrothermal procedure. The melting was carried out with 98 % granulated NaOH, mixed with ashes in mass ratios 1.2/1, 1.4/1 and 1.6/1 and using three melting temperatures, 450 °C, 550 °C and 650 °C. For the crystallization of the zeolites, the hydrothermal procedure at 90 °C was used. The crystalline phases of the zeolitic materials were quantified by XRD analysis. The morphology of the crystals was identified by SEM. The FTIR spectra revealed that the transformation of sodalite mineral to zeolite A and zeolite X increased with the NaOH/CVT ratio and the temperature.