MgO is prized as a refractory material,i.e. a solid that is physically and chemically stable at high temperatures. Ithas two useful attributes: high thermal conductivity and low electricalconductivity. "By far the largest consumer of magnesia worldwide is therefractory industry, which consumed about 56 % of the magnesia in the UnitedStates in 2004, the remaining 44 % being used in agricultural, chemical,construction, environmental, and other industrial applications." MgO isused as a basic refractory material for crucibles.

     It is a principal fireproofing ingredientin construction materials. As a construction material, magnesium oxidewallboards have several attractive characteristics: fire resistance, termiteresistance, moisture resistance, mold and mildew resistance, and strength.