Spectroscopic study of phase transitions in dolomite mineral

The process and the formation of new minerals upon heating carbonate rocks containing clay minerals together with dolomite are determined by thermal analysis, X‐ray diffraction (XRD), infrared and Raman spectroscopy. The dolomite–calcite–calcium oxide phase transition sequences were followed up to 947 °C in a naturally occurring dolomite sample. The spectral variations of the internal modes of the carbonate trigonal (ν1, ν2, ν3 and ν4) were used to probe the structural phase transitions. A new Raman mode emerged at 1090 cm−1 in the ν1 mode region, and infrared modes emerged at 713, 874, and 1420 cm−1 in the ν4, ν2 and ν3 regions at 750 °C, indicating the onset of the dolomite phase. The calcium oxide phase, (which on reaction with atmospheric water forms portlandite) with an onset temperature of around 950 °C, was also characterized by the appearance of the infrared mode around 450 cm−1. The minerals, which were formed upon heating the dolomite, were calcite, calcium oxide and diopside.