Thermal changes of the morphology of fluorophlogopite, tetrasilicic potassium fluor mica, tetrasilicic sodium fluor mica and fluorine bearing phlogopite have been studied by polarized microscope and scanning electron microscope. And the results obtained are as follows:
The forsterite crystals formed from fluorine bearing phlogopites are rounded in outline, whereas the forsterite crystals from fluor micas are idiomorphic. Needle-like crystals of fluormagnesiorichterite are found in heated tetrasilicic sodium fluor mica. The morphological features of the parent crystals are maintained to those of the product crystals through the thermal transformations of fluorine bearing phlogopite, fluorophlogopite and tetrasilicic potassium fluor mica, but there is no evidence showing that the needle-like crystals of fluormagnesiorichterite formed from tetrasilicic sodium fluor mica are the pseudomorphs after the parent crystal. It is, therefore, considered that the fluormagnesiorichterite crystal grows from the vapor phase.
