Previous work showed that manganese ore reduction rates are strongly influenced by the extent
of slag phase formation. In this work, the effect of ore composition on slag formation during
manganese oxide reduction was predicted using thermochemical calculations; FactSage 6?4 was
used to calculate the equilibrium phase relations in the oxide system MnO–SiO2–CaO–MgO–
Al2O3. Practically observed differences in ore composition, even within the same orebody, are
predicted to cause significant differences in slag formation during reduction, with large
differences in ore reducibility expected.