MOSSBAUR STUDIES OF IRON IN ILLITE AND MONTMORILLONITE

Three-layer type iron bearing clay minerals, Illite and Montmorillonite, have been analyzed by Mössbauer effect with a view to find the oxidation state, coordination symmetry and site distortion of the iron ion. Furthermore, these samples were treated with concentrated solutions of Fe(NO3)33, pH 0.1 to study the exchange of cations. It is concluded that in the natural samples of Montmorillonite and Illite, Fe3+ ion is in the alumina octahedra in place of Al3+ ion. In the case of Montmorillonite, treated with ferric nitrate solution, the iron ion is taken up in three inequivalent sites of cubic symmetry: into the vacant sites of Si tetrahedra as [FeO4]—, in the basal plane and on the broken edges. In the case of Illite, the main exchange location for Fe 3+3+ is the broken edge and only a small amount goes into the basal plane. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.