Scanning electron microscope (SEM) and associated energy-dispersive X-Ray (EDX) analysis, along with X-Ray diffraction, are additional tools that we call upon for particularly difficult lithic identification issues (i.e., differentiating between various Onondaga "black cherts" or Pennsylvania/Delaware jaspers). Scanning electron microscopy can provide a useful database of lithic textural characteristics, such as recrystallization fabrics and microfossils, at low and intermediate magnifications (50-500X, 1000-2000X). EDX provides a semi-quantitative, chemical analysis that permits the identification of various radiolarite, volcanogenic, nodular, and bedded cherts.
We also employ X-Ray diffraction to elucidate unique mineral phases in chert and non-chert artifacts when even SEM/EDX cannot provide definitive answers. Our knowledge of geological environments allows us to focus on the minor occurrence of specific elements that may help to characterize those environments.
***Updated Spring, 2012