Recent investigations at Stonehenge have been accompanied by new research on the origin of the famous ‘bluestones’, a mixed assemblage of rhyolites and dolerites that stand among the much taller sarsens. Some of the rhyolite debitage has been traced to a quarry site at Craig Rhosyfelin near the Pembrokeshire coast; but fieldwork on the upland outcrops of Carn Menyn has also provided evidence for dolerite extraction in the later third millennium BC, and for the production of pillar-like blocks that resemble the Stonehenge bluestones in shape and size. Quarrying at Carn Menyn began much earlier, however, during the seventh millennium BC, suggesting that Mesolithic communities were the first to exploit the geology of this remote upland location.