%0 Journal Article %A Santiago Buey, Cristina de %A Súarez Barrios, Mercedes %A García Romero, Emilia %A Domínguez Díaz, M.C. %A Doval, Mercedes %T Electron microscopic study of the illite–smectite transformation in the bentonitesfrom Cerro del Aguila (Toledo, Spain) %D 1998 %@ 0009-8558 %U https://hdl.handle.net/20.500.14352/58536 %X A mineralogical and microstructural study of bentonites from ‘Cerro del Aguila’located in the Tagus Basin (Toledo, Spain) was carried out using XRD, SEM and TEM observationsand chemical data obtained by TEM-EDX. The bentonites are mainly composed of trioctahedralsmectite with a unit-cell formula (Si3.76Al0.24)(Al0.44Fe3+0.26Mg1.81)Ca0.05K0.19O10(OH)2 and smallamounts of illite. The relationships between illite and smectite particles observed by SEM and TEMallowed the study of the weathering process of illite to form smectite through possible intermediatestages. The transformation begins as an exfoliation normal to the stacking direction and develops byopening of the interlayer spacing, the replacement of K+ by hydrated interlayer cations and slightreorganization of the 2:1 layer structure. The so-called solid-state transformation process thenproceeds by further dissolution and the formation of a colloidal phase acting as raw material in thegrowth of new phyllosilicates such as smectite. %~