Magnesite is a general term for minerals with high magnesium content. For example, brucite is a rare high magnesium mineral, also known as magnesium hydroxide. Its chemical composition is Mg (OH) 2, the theoretical content of MgO is 69%, and the metal magnesium content is 41.6%. It is a high-quality magnesium smelting ore. Periclase (mainly MgO) made by roasting brucite is a high-grade refractory material.