A new paper in Archaeology in Wales, produced by Dr Rob Ixer of Leicester University and Dr Richard Bevins of Amgueddfa Cymru (National Museum Wales), confirms for the first time the exact origin of some the rhyolite found at Stonehenge, which could lead to important conclusions about how stones were transported from Pembrokeshire to Stonehenge.
     Bevins and Ixer have been carefully collecting and identifying samples from rock outcrops in Pembrokeshire to try and locate the provenance of rocks at one of the world’s most iconic archaeological sites.
     Their discovery confirms that the Stonehenge rhyolite originates from a specific 70 metre long area called Craig Rhos-y-felin near Pont Saeson. Using petrography, Ixer and Bevins found that 99% of these rhyolites could be matched to rocks found in this particular set of outcrops. Rhyolitic rocks at Rhos-y-felin are distinctly different from all others in South Wales, which gives almost all of Stonehenge rhyolites a provenance of just hundreds of square metres.
     What is more, along the crags, the rhyolites are distinctly different on a scale of metres or tens of metres. This has enabled Bevins and Ixer to match some samples even more precisely to the extreme northeastern end of the area - small enough for archaeologists to excavate to try and uncover evidence for associated human activity.
     In addition, the work carried out at Rhos-y-felin confirms that the four remaining above surface rhyolite and dacite menhirs at Stonehenge do not come from Rhos-y-felin and work is in hand to determine if their source can be identified.

Edited from Mike Pitts Blog (17 December 2011), The Independent (18 December 2011), BBC News, Past Horizons (19 December 2011), Yahoo! News (20 December 2011)