Résumé : A new, simple chemical route was developed for the synthesis of pure nanocalcite crystals by controlling the reaction of an aqueous solution of CaO and CO2 gas. Results revealed formation of well-defined and pure nanocalcite crystals with controlled crystallite and particle size, without additives or organic solvents. The crystallite and particle size can be controlled, and smaller sizes are obtained by decreasing the CaO concentration and increasing the CO2 flow rate. The decrease of crystallite and particle size below a certain threshold provides the nanocalcite crystal signature characteristics that can be clearly observed in XRD patterns, TEM images, FTIR spectra, Raman spectra, XPS spectra, and thermal stability measurements.