MGO% SiO2% Fe2O3% Al2O3% CaO% LOI% BD g/cm3
>93  <3.0   <1.2   <0.8  <2.0 <0.5  >3.18
>92  <3.5   <1.4   <1.0  <2.3 <0.5  >3.15
>91  <3.8   <1.5   <1.2  <2.4 <0.5  >3.15
>90  <4.0   <1.6   <1.4  <2.5 <0.5  >3.15
>89  <5.5   <2.0   <1.6  <2.5 <0.7  >3.15
>87  <7.0   <2.0   <1.7  <3.0 <0.7  >3.10

Dead-burned magnesite, also known as refractory magnesia,
is produced from the heating of magnesite or magnesium hydroxide
and is the primary component in refractory materials. 
The refractory industry is the greatest consumer of magnesium compounds, overall.  
Refractory materials are nonmetallic substances which are extremely heat resistant
and are of great industrial value as the linings in furnaces, kilns and reactors. 
The steel industry, for instance, is the largest user of refractory magnesia.