Transmission Electron Microscopy Applied to the Studies of Sheet Silicates and Related Minerals.

Recent high resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM) permit us to observe structural imperfection and chemical composition of minerals even at atomic scale. The performance of high resolution electron microscope is now surpassing 0.2 nm point-to-point resolution. Since the early seventies, when HRTEM was established in mineralogical studies, the real structures of minerals, such as crystal defects, intergrowths of different structure types, twinning, and exsolution lamella, have been investigated to obtain information about geological events and to understand crystal structures and crystal chemistry by this method. In this article crystal structure and crystal chemistry of sheet silicates and related minerals are reviewed. Some recent results of the studies on fine texture and fine structure of serpentine and mica minerals using HRTEM and AEM are briefly shown. Examples of atomic resolution images of sericite and antigorite, calculated HRTEM and conventional TEM images of muscovite, technological developments of HRTEM and utilization of TEM in mineral sciences for two decades are presented. Practical analytical method and analytical conditions in microanalysis by AEM and application to sheet silicate mineralogy are also demonstrated.