The lateritization process which causes considerable changes in mineralogical constituent has a great influence on the crystal chemistry of the major mineral constituents (goethite and hematite). Goethite in the laterite shows a wide range of Al substitution as indicated by deviation of peaks location in XRD (Milnes et al., 1987). Aluminum substitution can serve as an indicator of pedogenic environment (Schwertmann and Kampf, 1985). The substitution of Al3+ for Fe3+ in goethite is characterized by lowering the c-parameter corresponding to the reduction in the size of the unit cell (Nahon et al., 1980; Schultz and Schwertmann, 1987). Fitzpatrick and Schwertmann (1982) mentioned that increase of Al substitutes for Fe of goethite in the highly weathered area. The composition of studied goethite ranges from pure FeO(OH) to (Fe0.92Al0.08) O(OH). Most of the studied goethite and hematite shows no substitution, the higher Al content was observed in the pisolites reaching a maximum of 8% moles AlO(OH). The Al substitution of hematite is less than that of the associated goethite.