In this study, homogeneous (unseeded) precipitation of nesquehonite (MgCO3 center dot 3H(2)O)) by the reaction Of MgCl2 with (NH4)(2)CO3 in supersaturated solutions was investigated. Factors that influence the precipitation Of MgCO3 center dot 3H(2)O, such as reaction temperature, initial concentration, stirring speed, titration speed, equilibration time, have been studied. SEM images and particle size distribution show that the temperature, initial concentration and titration speed have significant effect on nesquehonite's crystal morphology and particle size. In addition, stirring speed and equilibration time also have some influence on its properties. X-ray powder diffraction (XRD) results show that the obtained crystals compositions are greatly affected by the reaction temperature. With the morphological transformation, their corresponding composition also change from MgCO3 center dot xH(2)O to Mg-5(CO3)(4)(OH)(2 center dot)4H(2)O in the interval of 288-333K. With the optimization of operating conditions, the crystals can grow up to a length of about 40 mu m and a width of 5 mu m, indicating good filtration properties. High-purity nesquehonite obtained in this study was calcined to produce highly pure MgO at 1073 K as shown by XRD results. (c) 2008 Elsevier B.V. All rights reserved.