The effect of precipitation of ?.qss. and gahnite phases during heat treatment of glass frits in the ZnO-Al2O3-SiO2 system on the mechanical property of resulting glass-ceramic specimens were investigated. It was shown that gahnite glass-ceramics had higher bend strength and toughness values than ?.qss. ones. The results are attributed to the higher modulus of elasticity as well as higher therm...