Using X-ray fluorescence to examine ancient Maya granite ground stone in Belize

While ubiquitous among ancient Maya sites in Mesoamerica, archaeological analysts frequently overlook the interpretive potential of ground stone tools. The ancient Maya often made these heavy, bulky tools of coarse-grained, heterogeneous materials that are difficult to chemically source, unlike obsidian. This paper describes an application of handheld, energy-dispersive X-ray fluorescence (XRF) to provenance ground stone artifacts (tools and architectural blocks) composed of granite: a nonhomogenous, phaneritic stone. We present a multicomponent methodology that independently tested whole-rock, thin-sectioned, and powdered samples by petrographic microscope, conventional, lab-based XRF, and portable XRF units, which yielded comparable results. After establishing distinct geochemical signatures for the three geographically restricted granite plutons in Belize, we devised a field-based XRF application on a whole rock that could replicate the compositional readings of lab-based XRF on powdered materials with sufficient accuracy and reliability. We applied this multishot XRF technique to granite ground stone items from a range of ancient Maya sites throughout Belize; we discuss two specific case studies herein. Our results underscore the widespread potential of multishot XRF applications for determining the provenance of coarse-grained, heterogeneous rock materials. These results can help push the boundaries from one-dimensional, functional explanations of ground stone items to their social and ideological dimensions, alongside deeper understandings of granite resource management.