Permanent magnets of different intensities were used to investigate the effect of a magnetic field on the crystal growth of calcite suspended in a fluidized bed. The magnets were fixed on the suspended bed where the crystal grew. The growth rates of calcite were measured at various levels of supersaturation (sigma), pH, and ionic strength (I) using the constant-composition technique. The calcite growth rates in the presence of the magnetic field were lower than those in the absence of the magnetic field, and higher magnetic intensity yielded a lower growth rate. The effect of a magnetic field on CaCO3 polymorphism was also studied. The percentage of polymorphs was dependent on the magnetization time. Aragonite was the predominant polymorphic form in the precipitate mixture, which was induced spontaneously by changing the solution pH after the supersaturated solution had been magnetized for 48 h. (C) 2008 Elsevier Ltd. All rights reserved.