Spindle-shape goethite (alpha-FeOOH) extremely fine particles were produced by air oxidation of an aqueous suspension consisting of a mixture of FeSO4 and Na2CO3 at 30-40 degrees C, using a standard-type hubble column. The time dependences of the fractional oxidation of total Fe(II) were measured under various combinations of experimental conditions. The shape and size (i.e., major and minor axes) of prepared alpha-FeOOH particles were observed with the aid of transmission electron microscopy. From such measurements and observations, the mechanism of spindle-shape alpha-FeOOH particle formation was deduced; the total number of alpha-FeOOH nuclei is fixed in the early stage of the oxidation reaction, and subsequently, only the particle growth tends to take place until leading to the final size, depending on the reaction condition, i.e., reaction rate.