Silicon nitride powder synthesized from Kimcheon quartzite and commercial reagents, AlN and Y2O3 powders were used to prepare the partially and fully stabilized Y-${alpha}$-Sialon ceramics by the pressureless sintering at 1800$^{circ}C$ for 2 hours in N2 atmosphere. Good mechanical properties of the prepared Y-${alpha}$-Sialon ceramics were found over 0.4∼0.6 of the Yttrium solubility range, X, in the equation Yx(Si12-4.5x, Al4.5x)(O1.5x, N16-1.5x). The properties of these prepared Y-${alpha}$-Sialon ceramics were compared with those prepared in the same way from a commercial Toshiba Si3N4 powder.