Fused magnesite are manufactured by high purity caustic calcined magnesite through electro-fusing part of SiO2 turns back to SiO and runs out, another part of SiO2, moves to the surface because of the huge difference in the specific gravity with MgO, after this process, the magnesite become pure and the crystal with MgO,after this process, the magnesite become pure and the crystal become strong and big.