Scanning Electron Microscopy
Scanning electron microscopy provides two major advantages over light microscopy: an extreme depth of focus and a wide range of magnification. The top photo, from the Miocene ‘Hayner Ranch Formation’ of New Mexico (30 μm), illustrates the remarkable depth of focus of the SEM. Clinoptilolite crystals here fill pore space in a sandstone.
The middle photo, from the Permian Rotliegendes Sandstone of the North Sea (7 μm), shows the excellent resolution of extremely small wispy terminations on authigenic illite cements.
The bottom photo, also from the Rotliegendes Sandstone, illustrates a specialized technique—pore casting. The rock was pressure-impregnated with epoxy and the component grains were leached out subsequently with hydrofluoric acid. This leaves a three-dimensional network of epoxy which shows the geometry of the pore system, including small but interconnected pores not normally seen in thin section.
Top photo by C. W. Keighin (courtesy of T. R. Walker); lower photos by E. D. Pittman.