Dolomite is a mineral material that is formed from limestone which is mostly contains the calcite (CaCO3) and magnesite (MgCO3). This paper aimed to study on thermal decomposition of dolomite under air atmosphere. Calcination of dolomite was carried out by using furnace with heating rate of 10 °C/minute in an air atmosphere. The different temperature of calcination was varied at 400 °C, 600 °C, 800 °C, and 1000 °C within 6 hours. Phase analysis (XRD) and functional group analysis (FTIR) were carried out to analysis the dolomite after calcination. Microstructural (SEM) and Energy Dispersive X-ray (EDX) analysis showed that the main constituents of pure dolomite include CaCO3 (calcite), MgCO3 (magnesite), CaO, and MgO. From the results, XRD showed that the high intensity of CaO and MgO at 800 - 1000 °C was much stronger than that of dolomite at 400 - 600 °C. In addition, FTIR presents strong and intense bands are observed at 3632.23 and 3690.98 cm-1 (800 °C), and also 3694.03 and 3633.60 cm-1 (1000 °C) due to the calcium oxide.
