Identification of the Montmorillonite Group of Minerals by X-Rays

Abstract

THIS group of clay minerals (referred to hereafter for brevity simply as "montmorillonite"), which is often found in soil clays, fuller's earth and bentonite, is characterized by the variation of the position of the basal reflexion, on an X-ray powder or aggregate diagram, from about 10 to about 18 A., according to the state of hydration¹. The minerals of the group are notoriously difficult to identify positively from a single X-ray diagram because (a) the line at 14 A., which is given by montmorillonite in a normal state of hydration, is liable to be confused with a basal reflexion from chlorite or vermiculite, both of which might occur in soil clays; and (b) the basal reflexion may be diffuse, due to the simultaneous occurrence, in the crystallites, of two or more different basal spacings.