A novel technique has been developed to prepare refractory grade magnesia from sea bittern, which is a heterogeneous precipitation method to precipitate magnesium as double salt by a suitable career reagent. Prepared double salt is converted to magnesium carbonate, which on further calcination gives rise to MgO. The powdered samples of prepared magnesium carbonate and magnesium oxide are characterized by elemental analysis, X-ray powder diffraction, IR, TG/DTA, Particle size analyser and SEM. Commercially available Fluka magnesium carbonate and its calcined product have also been simultaneously characterised for comparison. Prepared boron free magnesia shows high purity of 99.08%, which can be used as basic refractory material.