The phase equilibria in the “MnO”–Al 2 O 3 –SiO 2 system in equilibrium with metallic alloy have been determined. This paper is the second of two papers presenting research undertaken as part of a broader study on the phase equilibria in the Al 2 O 3 –CaO–Li 2 O–“MnO”–SiO 2 multi-component system, representing the major components of the lithium ion battery recycling slag. The experimental procedures involve equilibration of high purity powder mixtures at high temperatures, rapid quenching, and accurate measurement of phase compositions using electron probe micro-analysis. The liquidus surface is determined at temperatures between 1373 K and 1523 K in the tridymite, rhodonite, tephroite, galaxite, spessartine, corundum and Mn-anorthite primary phase fields resulting in an accurate representation of the phase diagram. The system is found to contain three binary peritectics and four binary eutectics, six ternary peritectics and three ternary eutectics.