A History Cast in Stone: Geochemical Chert Sourcing Using Portable X-Ray Fluorescence (PXRF) in Southern Ontario

Abstract

To test the validity of portable X-Ray Fluorescence (PXRF) for chert sourcing, 32 chert artifacts from the Waterloo Region Museum in southern Ontario were compared to 56 chert source samples. The use of PXRF in archaeology, due to its lower energy outputs in comparison to lab based XRF devices, has raised questions about the method’s validity. Since chert has such a wide range of internal elemental variation, methods of chemical analysis are difficult. The PXRF used for this study was an Olympus Vanta C Series with a silver anode X-ray tube with the Geochem (3-Beam) mode. The artifacts where geochemically classified using discriminant analysis as well as macroscopically identified. The two modes of sourcing had a match at a rate of 76%. The findings suggest that the PXRF may be helpful in determining chert sources, but it should be used in addition to visual identification. There are many potential pitfalls such as an insufficient number of source samples or statistical error that need to be considered when archaeologists attempt studies of this nature.