New ceramic composites from calcia-magnesia-silica system at a molar ratio of (CaO-MgO)/SiO2 closes to the unity and the addition of different amounts of zirconia (5 wt %, 15 wt % and 25 wt %) have been investigated. These systems powders were formed and fired at 1310 ± 20°C for 2 hr. Phase composition, microstructure, physical and mechanical properties of these composites were determined. The in-vitro bioactivities of these sintered composites were investigated by analysis of their ability for the formation of hydroxyapatite (HA) using SEM-EDS after their soaking in the simulated body fluid (SBF) for 7 days. The findings indicated that beginning of HA formation on the surface of all investigated composites. However, the composite containing 5 wt % ZrO2 gave clear tendency toward the formation-ability of HA typical to cauliflower morphology.