... of impurities, resulting in dyed yellow, orange, red, brown and other colors, hardness 7.8, specific gravity 4.6-4.71, 1 ... 01 refractive index, birefringence, absorb light directly; magnetic susceptibility low, non-conductive; the melting point of 2550 °C. Zircon sand normally ... SiO2, and a small amount of Fe2O3, CaO, Al2O3, and other impurities, theoretically pure zircon sand containing 67.23% ZrO2 and ...