Some critical remarks on the analysis of phengite and paragonite components in muscovite by X-ray diffractometry

In the past lattice parameters b and c of muscovite s.1. from pelitic schists have been used to determine its phengite and paragonite component. A critical review of the literature and of some new data shows, however,

that a convincing statistical correlation between these physical and chemical properties does not exist

that an eventual trend-like correlation cannot be used for a quantitative analysis of phengite and/or paragonite components in muscovite.

Obviously further factors influence the lattice parameters of muscovite s.1., besides octahedral and interlayer chemistry.