This paper discusses the systematic analysis of the results of calcination as a function of size fraction performed on a sample of Brazilian silicate-carbonate manganese ore tailing at 800°C. The raw materials and the corresponding calcination products were analysed using several analytical techniques, including determination of density, specific surface area and porosity, chemical analysis and X-ray diffraction. The morphology and chemical composition of the calcination products were analysed by using scanning electronic microscopy equipped with energy-dispersive X-ray spectrometer (SEM/EDS). Results indicate that the manganese ore tailing consists of silicates, namely, spessartine (Mn 3 Al 2 (SiO 4) 3), tephroite (Mn 2 (SiO 4)) and rhodonite ((Mn,Fe,Mg,Ca) 5 (SiO 3) 5) and rhodochrosite (MnCO 3). The loss of CO 2 and OH during the thermal decomposition of the carbonate (rhodochrosite and dolomite) and hydrated minerals (kaolinite, muscovite and antigorite) in air atmosphere at 800°C resulted in: (1) decrease of the specific surface area and porosity, (2) increase in the density and Mn grade from 27.6% to 32.2% and (3) increase in SiO 2 grade from 26.7% to 30.1%. These results indicate that this material is within the chemical specifications of Fe-Si-Mn alloy.