Identification of Minerals by Electron Diffraction

Abstract

The employment of electron microscopy to monitor the concentration of particles in air and water samples is now an established method in environmental research. A large amount of effort has been expended on improving methods of specimen preparation and particle counting techniques; however, identification procedures using electron diffraction have not been developed to the same extent. Often, identifications are based on visual assessment of what is loosely called "a characteristic diffraction pattern." This may be an acceptable method when the mineral phases to be identified come from a known source (such as a chrysotile asbestos operation) but are not generally useful when minerals in air and water might come from a variety of sources. The methods to be described here have evolved from the normal identification procedures using standard stereograms of minerals (which is perfectly adequate provided not more than 3 or 4 possible structures are to be tested) into a systematic computer search of large numbers of different crystal structures as possible solutions to a given diffraction pattern.