A bio-active glass-ceramic material containing hydroxy apatite was investigated. The crystallization of the material during continuous heating was found to take place in three steps. The kinetics of the crystallization processes as well as their dependence on the particle size of the powder sample was investigated. Changes in the microstructure during the crystallization were observed and the crystallized phases were identified. The local mechanical properties such as microhardness and probability of crack formation as well as their changes with advancing crystallization were determined. The changes in the microstructure were correlated with those of the mechanical properties.