The crystallization behavior of vitrified industrial waste (fly ash from domiciliary solid waste incineration) was examined by differential thermal analysis, X-ray diffractometry and scanning electron microscopy, It was demonstrated that powder processing route was required to transform the vitrified industrial waste into glass-ceramics products. Time-Temperature-Transformation (TTT) diagrams were drawn for the two main crystalline phases, diopside and wollastonite. The wollastonite existed in both monoclinic and triclinic forms and an iron-rich phase was also observed at the boundaries between glass particles. The morphology of the crystalline phases and the development of microstructure were observed as a function of heat treatment time and temperature. The optimum heat treatment was 900 degreesC for 40-50 minutes.