It is represented by magnesium products. It contains 80% to 85% of magnesia, with periclase as the main phase. The main raw materials for the production of magnesia bricks are magnesite, seawater magnesia and magnesium hydroxide extracted from seawater by high temperature calcination. It has good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800 ° C. Therefore, the refractoriness of magnesia bricks is higher than that of clay bricks and silica bricks.