An X-ray study on the crystal-structure of gümbelite

Dana classifies gümbelite in the kaolin division under pyrophyllite, and expresses the view that it may be an impure pyrophyllite. The present study, however, has shown that the unit cell of gümbelite is very similar to that of muscovite. Also the chemical analysis reveals a Closer similarity to muscovite, particularly to a variety called hydromuscovite.