During the preparation of uniform magnetite colloid particles, a series of samples aged for different times ?1 h were obtained by abruptly lowering the temperature The Moessbauer spectra of these samples were measured at liquid N temperature g-FeOOH was the intermediate product in the formation of uniform magnetite colloid particles. The mechanism of formation of magnetite colloid particles is: Fe2+ (OH-) ?Fe(OH)2 (NO3-, O2) ?g-FeOOH ?Fe3-aOr (ultrafine particles) (coagulation) ?Fe3-aO4 (uniform colloid particles) (Fe3+, Fe2+) ?Fe3O4 (uniform colloid particles).

Key words: MAGNESIUM OXIDE, COLLOID, MOSSBAUER SPECTROMETRY, FORMATION MECHANISM