Glass-ceramic materials were developed from fly ash samples obtained from Cayirhan Thermal Power Plant in Turkey. On the basis of DTA analyses, nucleation experiments were carried out at 680 degrees C for 5, 10 and 15 h whereas crystallization experiments were performed at 924 degrees C for 20 min. Crystallized samples were cooled in the furnace. X-ray diffraction analyses revealed the presence of only the diopside [Ca(Mg,Al)(Si,Al)(2)O-6] phase in the produced glass-ceramic samples and scanning electron microscopy (SEM) investigations showed the presence of a homogeneously dispersed phase. The results of the Vickers microhardness tests indicated that the hardness values of the fly ash based glass-ceramic decreased with the increases in holding time at the nucleation temperature. In addition, wear resistance of fly ash-based glass-ceramics decreased with holding time at the nucleation temperature. (C) 2000 Elsevier Science Ltd. All rights reserved.