Molten oxide electrolysis may be used for extracting one or more metals from a mixture of metal oxides. The mixture of metal oxides may be complex and include at least three metal oxides, each present at 0.5 wt % or greater based on a total weight of the metal oxide electrolyte precursor, to produce a metal oxide electrolyte. In some instances, two or more metals may be extracted in a series of molten oxide electrolysis process where metal oxides having higher Gibbs free energy of formation at 1500° C. are preferentially reduced in each respective molten oxide electrolysis unit before metal oxides having lower Gibbs free energy of formation at 1500° C.