A new study led by the University College London pinpoints the exact locations of two quarries in Wales where the “bluestones” of Stonehenge originated. The research also reveals how the stones were quarried 5,000 years ago.
It was previously established that 42 of Stonehenge’s smaller stones, known as bluestones, came from Pembrokeshire in west Wales. Now, two specific quarries have been identified by a team of archaeologists and geologists.
“What’s really exciting about these discoveries is that they take us a step closer to unlocking Stonehenge’s greatest mystery – why its stones came from so far away,” said Professor Mike Parker Pearson.
“Every other Neolithic monument in Europe was built of megaliths brought from no more than 10 miles away. We’re now looking to find out just what was so special about the Preseli hills 5,000 years ago, and whether there were any important stone circles here, built before the bluestones were moved to Stonehenge.”
The largest quarry was located almost 180 miles away from Stonehenge on the north slope of the Preseli hills in Pembrokeshire.
“This was the dominant source of Stonehenge’s spotted dolerite, so-called because it has white spots in the igneous blue rock. At least five of Stonehenge’s bluestones, and probably more, came from Carn Goedog,” said Dr. Richard Bevins.
The researchers found that the bluestone outcrops were formed of natural pillars with vertical joints. This would have made it easier to access the stones compared to the quarries in ancient Egypt, where obelisks were carved out of the solid rock. In the Welsh quarries, the workers simply inserted wedges into the joints between pillars before removing them.
“The stone wedges are made of imported mudstone, much softer than the hard dolerite pillars. An engineering colleague has suggested that hammering in a hard wedge could have created stress fractures, causing the thin pillars to crack. Using a soft wedge means that, if anything were to break, it would be the wedge and not the pillar,” said Professor Parker Pearson.
The excavations also uncovered the remains of man-made stone and earth platforms at the foot of each outcrop.
“Bluestone pillars could be eased down onto this platform, which acted as a loading bay for lowering them onto wooden sledges before dragging them away,” said Professor Colin Richards.
The team now speculates that Stonehenge was initially a circle of rough, unworked bluestone pillars, and that sandstone blocks were added about 500 years later. The findings also challenge the theory that the bluestones were transported by sea to Stonehenge.
Professor Kate Welham explained, “Some people think that the bluestones were taken southwards to Milford Haven and placed on rafts or slung between boats and then paddled up the Bristol Channel and along the Bristol Avon towards Salisbury Plain. But these quarries are on the north side of the Preseli hills so the megaliths could have simply gone overland all the way to Salisbury Plain.”
The study is published in the journal Antiquity.