Bluestone

The collective name for the stones of Stonehenge's inner settings that came from the Preseli hills of Pembrokeshire rather than from Wiltshire: chiefly the spotted dolerite of Carn Goedog, an igneous rock with white feldspar spots in a dark groundmass, together with the foliated rhyolite of Craig Rhos-y-felin. Both outcrop as natural vertical pillars separated by joints, which is why they could be levered out as ready-made monoliths with wedges and no metal tools. Quarried for monuments rather than for building or aggregate, which makes it unlike any other stone in this archive.