A Mössbauer spectroscopic study of some clay minerals of the Eastern Caribbean West Indies. Part I: Spectra from 80 to 300 K

Abstract A Mossbauer spectroscopic investigation of clays from the Eastern Caribbean containing montmorillonite, biotite and kaolinite and mixtures thereof is made over the temperature range 80–300 K to investigate the nature of the iron sites present. In several samples at liquid nitrogen temperature the magnetic component increases considerably at the cost of the paramagnetic component. This behavior is typical of superparamagnetism exhibited by ultrafine magnetic particles. From the values of hyperfine parameters taken from computer fits of the spectra, the particles are identified as α-ferric oxide and goethite.