MgO-rich MgAl2O4 spinel was prepared by adopting solid-state reaction of commercially available sintered seawater magnesia and alpha-alumina. Starting materials were mixed in weight ratio (Al2O3: MgO) of 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, where the developed MgAl2O4 spinel crystal seed in calcined powder varied (5-50%) with respect to addition of MgO content and temperature. Around 70% spinellisation could be noticed in Al2O3: MgO (1:1) batch through double stage sintering. Densification and grain size of the sintered specimen was found to be greatly dependent on initial calcination temperature and content of primary spinel seed. The diametrical compressive strength of sintered specimen was similar to 115 MPa for highest amount of spinel content. The hardness of MgO-rich spinel composite was varied with spinel addition.