57Fe Mössbauer spectra of the Na+- and Ca2+-saturated forms of four ferruginous smectites,displaying a range of compositions, have been fitted with Voigtian profiles to represent (principally) two correlated distributions of isomer shifts and quadrupole splittings for the Fe3+ sites. Correlating the areas and hyperfine parameters of these distributions with simulations of the octahedral array of cations based on chemical analyses and infrared spectroscopy has enabled identification of the Fe3+ ions that contribute to the outer quadrupole doublet. The octahedral Fe3+ sites are characterized as having at least one Mg2+ nearest-cation neighbour and probably a cisconfiguration with respect to the OH– ions.
