Abstract
A method is described by which clays may be loosely embedded and sections prepared with an ultramicrotome. The embedding medium used consisted of a mixture of butyl methacrylate and methyl methacrylate. For electron-optical work sections of about 300 Å thickness proved suitable.
Investigations on layer silicates, the sections of which were made perpendicular to the ab plane (plane of the layer), enables conclusions to be drawn regarding the thickness and shape of development of the individual particles. The relation of thickness to diameter of the plane of lamination was mostly found to lie between 1:10 and 1:20 in the clay minerals investigated. Electron-diffraction diagrams on single crystals of muscovite-illite and muscovite are reproduced and discussed.
The limits of the method are shown to depend largely on the relative difference between the hardness of the mineral and of the embedding medium. However, they vary also with the sensitivity of the diamond knives amployed. It is apparent that this method of investigation can be applied to very friable rocks and powders containing no minerals of excessive hardness.