Magnesium Oxide Caustic Calcined Magnesite MgO:85% and 90% are the raw material for making Magnesium Sulphate. Please check below specification for your reference. Caustic Calcined Magnesite Item Specification MgO 85%min 90%min CaO 4.0%max 3.0%max SiO2 8.5%max 5.0%max Fe2O3 1.0%max 1.0%max Al2O3 1.0%max 1.0%max LOI 7.0%max 4.0%max Size 200mesh