Atomic force microscopy studies of layer silicate minerals

Abstract The surfaces of silicate minerals are important in controlling a number of geochemical phenomena from chemical weathering, to the transport of pollutants in solution. The atomic force microscope (AFM) has proven invaluable for obtaining atomic resolution images of the surface topology and structure of a wide variety of minerals. While the physical basis for the sample—tip interactions responsible for the images remains poorly understood, comparison of AFM images with the calculated bulk mineral structures, provides clear evidence that the AFM is truely capable of resolving structural features on the atomic scale. The phyllosilicate or layered silicate minerals are particularly suited to study by atomic force microscopy because of their perfect {001} cleavage, wide range of structure types and variety of surface properties. Atomic resolution images have been obtained on lizardite, chlorite, apophyllite and muscovite. The AFM resolves the Angstrom-scale surface structure of these minerals and is able to clearly elucidate the different structural layers. These studies have been able to observe surface relaxation effects on the surface of chlorite, as well as the progressive amorphization (through ion beam damage) of the muscovite surface. Further, studies in solution are able to image the equilibrated near surface structure providing fresh insight into the nature of the mineral—water interface.