Magnesium oxide-based minerals (serpentine, olivine) may be used for long-term storage of CO2, from combustion of fossil fuels or industrial processes in the form of magnesium carbonate. Large resources of suitable minerals appear to exist in Finland and at many other locations worldwide. The efficiency of mineral carbonation processing can be evaluated using exergy analysis, which will allow for comparing different mineral types characterised by different composition and quality. Other important factors are temperature and pressure and the degree of magnesium carbonation conversion. Important for the analysis is the calculation of the standard chemical exergy of the chemical species involved.