The SiO2MgO - iron oxide ternary phase diagrams explain why magnesia-based refractory materials perform well in contact with iron oxide - rich slags. Consider the attached 1650C isothermal sections of the MgOFeOSiO2 and MgOMFe3O4SiO2 systems to describe what you would expect would happen if: a) Iron oxide is in contact with a MgO-based material at 1650C. b) A fayalitic slag (Fe2SiO4) at 1650C is contained in a MgO-lined vessel