The effects of alumina and chromite impurities on the liquidus temperatures in the cristobalite/tridymite (SiO₂) primary phase fields in the MgO-“FeO”-SiO₂ system in equilibrium with metallic iron have been investigated experimentally. Using high temperature equilibration and quenching followed by electron probe X-ray microanalysis (EPMA), liquidus isotherms have been determined in the temperatures range 1673 to 1898 K. The results are presented in the form of pseudo-ternary sections of the MgO-“FeO”-SiO₂ system at 2, 3 and 5 wt% Al₂O₃, 2 wt% Cr₂O₃, and 2 wt% Cr₂O₃+2 wt% Al₂O₃. The study enables the liquidus to be described for a range of SiO₂/MgO and MgO/FeO ratios. It was found that liquidus temperatures in the cristobalite and tridymite primary phase fields, decrease significantly with the addition of Al₂O₃ and Cr₂O₃.