Bandli, B.R., M.E. Gunter, “Mineral Identification Using Electron Backscatter Diffraction from Unpolished Specimens: Applications for Rapid Asbestos Identification”, The Microscope, 61(1) 37-45, January 2013.
Electron backscatter diffraction (EBSD) is a crystallographic technique that, when used in conjunction with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), can allow for the rapid identification of a crystalline phase using both compositional and structural data. SEM/EDS alone is limited as a tool for phase identification by the inability to collect useful crystallographic information from an unknown specimen. Most EBSD work is performed on carefully prepared polished samples. It is possible to use EBSD on powdered specimens, individual crystals (up to several millimeters in size), or by crushing and/or grinding a sample to achieve a particle size in the range of 5 mm – 100 mm. In a matter of minutes a sample can be prepared that is capable of providing high quality electron diffraction patterns and compositional data suitable for phase discrimination. When compared to the effort of polishing a bulk specimen, the methodology presented here provides several advantages. The main advantages of preparing a sample as a particulate is speed and the ability to precisely select phases of interest from a hand sample or thin section. The sample preparation methods described are applied to two case studies for the identification of unknown materials and to demonstrate the potential for the method in the field of asbestos fiber identification.
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