Specific features of the mineralogical composition of phyllosilicates and iron oxides in a mountainous chernozem developed from red-earth calcareous deposits in the North Caucasus are analyzed. This soil is characterized by a vividly manifested set of features inherited from the parent rock. An association of clay minerals with the predominance of hydromica is identified in the clay fraction. Mineral forms of iron in the clay fraction are represented by hematite and magnetite diagnosed by the method of Mössbauer spectroscopy and thermomagnetic measurements. A decrease in the intensity of basal reflections from plane (001) and an increase in the intensity of basal reflections from plane (020) in the upper soil horizons are conditioned by the weathering of hydromica accompanied by some disordering of its crystalline lattice. The disordering of the crystalline lattice of hematite also takes place in the clay fraction from upper soil horizons.