Testing imaging confocal microscopy, laser scanning confocal microscopy, and focus variation microscopy for microscale measurement of edge cross-sections and calculation of edge curvature on stone tools: Preliminary results

Abstract

The application of micro- and nanotechnology, adopted from engineering and materials sciences, is proving valuable in studying stone tool surfaces. Measurement systems for surface characterization have been coupled with parameters that allow for the mathematical characterization of stone tool surfaces. For this project, a Sensofar S neox imaging confocal microscope (ICM)/focus variation microscope (FVM) and an Olympus LEXT OLS4100 laser scanning confocal microscope (LSCM) are used to mathematically document the edge cross-sections on five chipped stone tools made from basalt, chert, obsidian, and quartz. Based on the surface documentation of edge cross-sections, a new algorithm for the calculation of edge curvature at multiple scales is tested. Results indicate the confocal systems experience difficulty documenting edge cross-sections. However, focus variation microscopy can mathematically document edge cross-sections on stone tools made from basalt and chert, thus permitting the calculation of edge curvature over multiple scales of measurement. Microscale documentation of edge cross-sections and calculation of edge curvature will be helpful in understanding the relationships between tool edges, edge sharpness, edge attrition, and microwear. Comparisons between these three measurement systems (ICM, LSCM, FVM) provide information necessary for further method development in edge cross-section measurement and the potential to generate more robust edge analysis protocols.