Chemical segregation is fundamental to a host of geologically interesting phenomena. These include exsolution, weathering, dynamic recrystallization, and interface formation. Investigation of these mineralogical processes centers on the relationship between crystal structure and chemistry. While there is an abundance of electron microprobe information available at the micron scale, Energy- Filtered Imaging (EFI) offers the first opportunity to investigate the chemistry of these diverse processes at the nearly atomistic level. In particular, we have been using Energy-Filtered Imaging (EFI) in the TEM to acquire quantitative compositional information at the scale of individual unit cells (<1 nm spatial resolution) in exsolved pyroxenes. Along with the two-orders-of-magnitude improvement in spatial resolution, EFI has greater quantum efficiency and the possibility of lighter element detection than X-ray spectroscopic methods.

The complex, subsolidus phase relations of many minerals are routinely exploited by petrologists investigating the thermal and tectonic evolution of the earth, moon and meteorites.