1st Grade 2st Grade Al2O3 70-77% 60-70% SiO2 22-29% 25-35% Fe2O3 0.1% max 1.0% max Refractoriness 1850℃ 1800℃ Mullite phase 95% min 90% min Brand Property GRIT(>0.1mm) FINE(≤0.1mm) Chemical Composition Al2O3% 70-77 70-77 SiO2% 22-29 22-29 Fe2O3% ≤0.20 ≤0.30 TiO2% ≤0.10 ≤0.10 CaO% ≤0.30 ≤0.30 Na2O% ≤0.30 ≤0.50 Physical Porperty Apparent Porosity% ≤ 5 Bulk Density% g/cm3≥ 3.00 Refractoriness℃ ≥1850