Zirmond Synthetic Corundum
Synthetic Corundum are including synthetic ruby and synthetic sapphire, they are made from Al2O3 and other chemical such as Cr, their properties are almost the same as natural corundum. The hardness is 9.0 Mohs, heat resistance up to: 1,700 °C / 3,092 °F, dispersion: 0.018, and specific gravity is 4.0.