With and without magnetization, the growth rates of aragonite seeds were measured in a stirred-tank crystallizer in the presence of Fe2+ or Sr2+ acting as an impurity at two temperature levels, using the constant-composition technique. The concentration range of the impurity investigated was between 0 and 2 ppm, and the temperature settings were either 25 or 35 degrees C. The individual factors each had a distinct effect on the growth rate of aragonite, and the combined effects became complicated, especially in the presence of Sr2+, which changed the surface structure of the aragonite seed dramatically.