© 2020, The Minerals, Metals & Materials Society and ASM International. The interaction between mineral phases in two commercial iron ores and flux materials (CaO, MgO, SiO2, and Al2O3) was studied under 0.5 kPa O2 partial pressure while heating to different temperatures. CaO was the most effective flux for liquid phase generation during sintering. For a hematite ore with few gangue components (Ore A), the formation of an initial liquid phase commenced at ~ 1275 °C, with the liquid volume increasing dramatically as temperature increased to 1300 °C. For a goethite containing hematite ore (Ore B), the formation of an initial liquid phase through interaction between goethite and CaO was observed when heating to 1225 °C, with the majority of goethite transformed to liquid at 1250 °C. The porous morphology of sintered goethite and finely distributed quartz results in a high reactivity with CaO. The initial liquid phase penetrated into the pores within the hematite matrix, promoting assimilation and by 1300 °C, all hematite in Ore B was dissolved. The hematite/martite phase in Ore B was much easier to assimilate than that in Ore A due to the presence of goethite. MgO diffused into hematite ore grains by solid-state diffusion and formed a solid solution (Fe, Mg)O∙Fe2O3 without the formation of a liquid phase. The reaction layer formed by MgO diffusion was limited to approx. 60 μm at 1300 °C. The porous morphology in goethite facilitated MgO diffusion. However, the cavities and cracks caused by goethite dehydration significantly restricted solid phase diffusion of Mg2+. There was no observed interaction between Al2O3 and SiO2 with Ores A and B when heated to 1300 °C.