Chemistry of smectitic and illitic phases in interstratified soil smectite

The objective of this investigation was to determine the elemental composition and mineralogy in interstratified smectite-illite from a typical upper Midwestern agricultural soil. A sample of soil clay (<2 μm fraction) from the Ap horizon of a Webster (fine-loamy, mixed, mesic Type Haplaquoll) pedon was fractionated by centrifugation to prepare various fine-clay samples. X-ray diffraction analyes indicated that interstratified smectite-illite was the only mineral present in significant quantities in the fine-clay samples. The elemental analyses revealed significant linear correlations for K vs. Si, Al, Fe, Ca, Ti, Mn, Zn and Mg. The smectitic phase was a high-charge, Fe-rich montmorillonite. The illitic phase consisted of dioctahedral, tetrahedrally charged elementary illite particles; it comprised at least 36% of the interstratified smectite-illite. -from Authors