... quality 3,best sevice High purity alumina (aluminum oxide), purity, 99.999% Product discriptions ModelVK-L100GCrystalaappearancewhite loose powderAverage particle size (um)0 ... (g/cm3)0.4-0.6Block density (g/cm3)--------Al2O3content(%)99.999Si (ppm) <2Na (ppm) <1Fe (ppm) <2Ca (ppm) <1Mg (ppm ... gemstones 4, sapphire panel High purity alumina (aluminum oxide), purity, 99.999%