The effect of isomorphous substitutions on the intensities of (001) reflections of mica- and chlorite-type structures

A widely used method of quantitative analysis in clay mineralogy . is the comparison of the intensities of X-ray reflections from a socalled standard mineral with the unknown. In the clay minerals where isomorphous substitution is frequent the term 'mineral' generally covers a range of compositions and what is meant by such a term is a group of closely similar minerals. The so-called standard mineral is any member of a group which the particular worker may have in a pure or almost pure condition. If the standard mineral and the mineral in the unknown give different intensities for an equal volume of material the results will be inaccurate.