The detail microstructures of sintered natural magnesite with addition of titania, zirconia and ilmenite mineralisers were studied using scanning electron microscopy (SEM) with special emphasis on energy dispersive X-ray analyses (EDXA). The study was directed towards the determination of secondary phase composition in sintered magnesite with different mineraliser addition. In order to evaluate the secondary phases with addition of transition metal oxides, keeping titania (TiO2) as a reference mineraliser, a natural analog of titania containing iron i.e., Ilmenite (Fe2O3 . TiO2) and pure Zirconia (ZrO2) were added to magnesite which was then sintered up to 1700 degrees C. The relative behaviour of these pure and mixed oxide mineralisers during the sintering of magnesite has been evaluated with respect to their microstructure and secondary phase composition. The present paper showed that titania addition to natural magnesites resulted in the formation of calcium titanate in the secondary phase upon sintering. Zirconia, on the other hand, did not show any reaction product in the secondary phase. The addition of titania in the form of mixed oxide, ilmenite, also gave rise to calcium titanate formation, providing a similar microstructure, specially with reference to spatial distribution of phases in the secondary phase.