The main component of magnesia is magnesium oxide, with impurities such as CaO, SiO2, and Fe2O3. Magnesium oxide is an alkaline oxide with a melting point of 2800 degrees. After heating at high temperature, it is transformed into stable cubic crystals, commonly known as periclase. Made from magnesium hydroxide calcined at high temperature, it has strong hydration resistance.

The burnt magnesia produced from natural magnesite is called sintered magnesia; Sintered magnesia is divided into 18 grades according to its physical and chemical indicators, as detailed in the national standard GB/T 2273-1998.