Abstract--Many soils developed from volcanic rocks in southern Brazil exhibit spontaneous magnetization caused by the presence of fine-grained maghemite (3J-Fe203), but few attempts were made to quantify or characterize this important soil component. To that end, clays were separated from freely drained soils derived from acid (>~63% Sit2), intermediate (54-62% SiO~), and basic (--<53% Sit;) igneous rocks produced by the Paranfi flood volcanism. The sample set included soils with a wide range of pedogenic development on different landscape positions. The Fe oxide mineralogy of these samples was examined by using a combination of selective dissolution, magnetic susceptibility, and X-ray diffraction (XRD) techniques. Hematite and maghemite were the primary Fe oxides in mature soils (Oxisols, Ultisols, and Alfisols) developed from basic rocks; whereas goethite was dominant in all other soils, especially those formed from acid-intermediate rocks. The association of maghemite with basic rock materials suggests that it was primarily formed by oxidation of lithogenic magnetite. A strong, positive correlation (R 2 = 0.89) was obtained between mass specific magnetic susceptibility (X) of the clay fractions and maghemite contents estimated by XRD. Either method could be used for quantitative analyses, but X was more sensitive than XRD at low maghemite concentrations (<2 wt. %). The clay-sized maghemites were superparamagnetic with an estimated value for the mass specific magnetic susceptibility (X~f) value of 91,000 • 10 -8 m 3 kg ~ and frequency dependent variations of 10-15%. The maghemites also had low unit cell constants, which, if attributed entirely to replacement of Fe by AI, would correlate with AI substitutions in the range of 5-16 mole %. Selective dissolution of the soil maghemites was achieved by treatment of Fe oxide concentrates with 1.8 M I-I2SO 4 at 75~ for 2 h.