Exact source of Stonehenge rocks pinpointed

London: Scientists have pinpointed the exact source of many of the rocks used to build the prehistoric monument Stonehenge in England.

A new study suggests that the site previously thought to be the starting place of many of Stonehenge's rocks may not have been the source after all.

It looks like the rocks actually came from a different site three kilometres away, instead.

The study focused on the smaller stones at Stonehenge, called bluestones, 'Planet Earth' reported. The chemistry of these rocks varies, but they all originate from the Preseli Hills in Wales and are thought to have been transported to the Stonehenge site over 4000 years ago.

By confirming the source of the rocks, the researchers hope to help answer the long standing question of how around 80 of these bluestones, weighing up to three tonnes each, were transported 250 kilometres from southwest Wales to Wiltshire.

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"The Holy Grail question is how were the stones moved and why," said Dr Richard Bevins of National Museum of Wales who led the research.

"We're trying to discover the source of the stones so archaeologists can excavate sites in order to see if they can find evidence for people working the source stones," Mr Bevins said.

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Researchers took images showing the rocks at Stonehenge and the rocks at Carn Alw. They then asked members of the public with no geological background whether they looked the same.

"We asked people "does A look like B?" and everyone said no," Mr Bevins said.

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Scientists used a new method of identifying the chemical makeup of the rocks, to match the rocks with their origin. They believe that they have now identified Carn Goedog as the source of at least 55 per cent of the spotted dolerite bluestones at Stonehenge.

The study was published in the Journal of Archaeological Science.