Electron Microscopy of Minerals
High-resolution transmission electron microscopy (HRTEM) is an extremely powerful, advanced tool for studying the chemistry and structure of crystalline and sub-crystalline materials. It is now possible to see details within unit cells and even to image atoms (at magnifications up to 20,000,000 times). We can actually observe small irregularities and defects in the crystals and, in the case of minerals, relate these to their geological histories. Chemical reactions, 'frozen' while they were in progress, can be observed and thus mechanisms of reaction understood. Emphasis is being placed on problems of order-disorder, non-stoichiometry, modulated structures, and other deviations from ideality.
We have done research into the structures of carbon and subcrystalline graphite, fullerenes (C60 "buckyballs"), oxides, sulfides, chain and sheet silicates (including clays), and minerals within and formed by bacteria (an aspect of geomicrobiology).
Analytical electron microscopy using X-ray analysis and electron energy-loss analysis enables the determination of chemistry of small regions of mineral. We are using electron energy-loss spectroscopy (EELS) to study Fe2+/Fe3+ ratios in minerals as well as bonding types and light-element analysis (Be and heavier).
Support: NSF and NASA