Bentonite/iron oxide system is prepared by isothermal calcination of powder composed of bentonite clay and precursor containing ferric acetate. This preparation technique enables one to get the composite material directly, that is, iron oxide particles embedded in a bentonite matrix. Calcination temperatureTcalcis varied from 320°C to 700°C. The resulting series of samples is characterized by local methods based on hyperfine interactions:⁵⁷Fe nuclear magnetic resonance (NMR) and the Mössbauer spectroscopy. The results show that the phase composition changes significantly in dependence on calcination temperature. The amount of maghemite phase rapidly increases up toTcalc=420°C and decreases abruptly forTcalchigher than 460°C.