For the past several years I have been studying fine grained siltstones and shales using cathodoluminescence and backscattered electrons with the scanning electron microscope.  It has been possible to add information not available to reconstructing ancient environments (Krinsley et al., 1998).  Evidence collected so far suggests that much information is available on diagenesis and somewhat less on depositional and source areas.
In collaboration with others, I have examined shocked quartz in meteoritic impact craters from various parts of the world.  Cathodoluminescence information suggests that much finer features and more detail on shock can be obtained than possible with light microscopic examinations.  Some quartz silt has been found with characteristic shock signals.
I have also been studying desert varnish using the scanning and transmission electron microscopes in order to determine its origin, depositional and diagenetic history.   Clay minerals are sedimented upon rocks, mostly in desert regions, and the Fe and Mn reorganized by bacteria which leave their traces in the varnish.  Nanobacteria have been found encapsulated within layers of varnish. Desert varnish shows some of the thinnest layering ever observed in sedimentary rocks (as thin as 10 nanometers).