Pure and impure clays and their firing products

Mössbauer spectroscopy is highly suited for the study of clays whose industrial uses depend on the iron content. Reactions that take place during clay firing can be readily monitored by Mössbauer spectroscopy. Following dehydroxylation of clay minerals, the quadrupole splitting of octahedrally coordinated iron (III) increases abruptly, but reverts to lower values upon the formation of new, better ordered phases at higher temperatures. It is also shown that iron oxides may account for a considerably higher proportion of the total iron content of many clays than is commonly recognized, and their existence must be taken into consideration for a correct interpretation of the Mössbauer spectra of clays.