“We quickly ruled these out and so worked away from those sites, across south Wales, the Welsh Borderlands, Somerset, and the West Midlands,” he added. “Failing to find any matches led us to reappraise our thinking.” Bevins and co-author Rob Ixer, an archaeologist at University College London, first started investigating the provenance of the Altar Stone in 2009 by examining samples held by the Salisbury Museum. This work snowballed into a comprehensive effort to constrain the mineralogy, petrology, and geochemistry of the Stonehenge bluestones using sophisticated analytical techniques, such as automated scanning electron microscopy (SEM-EDS), U-Pb zircon age determination, and preliminary portable X-ray fluorescence (pXRF) analysis.