“It might be that the Altar Stone arrived later and if so might have been brought from another area than Wales and also possibly by different people,” he continued. “This thinking was something of a game changer and led us to 'uncouple' the Altar Stone from the bluestones from Wales and led to our 'broadening horizons' approach.” Indeed, the tantalizing find has sparked a geological treasure hunt for the true origin of the Altar Stone. Based on its composition, Bevins and his colleagues think that the stone could have come from Old Red Sandstone of the Midland Valley and Orcadian Basins in Scotland, or from deposits that date back some 250 million years to the Permian-Triassic eras in northern England.