Institute of Archaeology


First glimpse inside the great sarsen stones at Stonehenge

5 August 2021

New research by an international team of geologists, geomorphologists and archaeologists has provided the first glimpse inside one of the giant sarsen stones at Stonehenge.

Stonehenge (Image copyright and courtesy of Aerial-Cam Ltd.)

Published in the journal PLoS ONE, the study – led by researchers at the University of Brighton and involving expertise from the UCL Institute of Archaeology – has revealed new insights into the geology and chemistry of the stone, showing how it originally formed before being moved into place at the monument during the Neolithic period.

Stonehenge's sarsens, typically weighing 20 tonnes and standing up to 7 metres tall, form the monument's central horseshoe, the uprights and lintels of the outer circle, as well as outlying stones such as the Heel Stone, the Slaughter Stone and the Station Stones. Fifty-two of the original c.80 sarsens remain at the monument. 

The research team were afforded a unique opportunity to analyse a 7cm (3 inch) long sample from a core drilled from Stone 58 at Stonehenge during conservation work in the 1950s which had recently been returned to English Heritage. 

David Nash (University of Brighton) analysing the sarsen core extracted from Stone 58 at Stonehenge (Image credit: Sam Frost, English Heritage)

Analyses of wafer-thin slices of the rock show that the sarsen stone is made up of mainly sand-sized quartz grains that are cemented tightly together by an interlocking mosaic of quartz crystals. This explains the stone's resistance to weathering and why it made an ideal material for monument-building.

Previous chemical analyses of the core had shown that most of the large sarsen stones came from around 15 miles to the north, in West Woods on the edge of the Marlborough Downs, Wiltshire. This new research provides further data that could be used to trace the sources of the remaining stones.

According to Mike Parker Pearson:

This has been an amazing piece of detective work by a team of scientists using all the available techniques of the modern age to explore this ancient mystery. It confirms that Stonehenge was remarkable in being the only stone circle whose stones were deliberately brought from far away."

The research was an interdisciplinary collaboration between the University of Brighton, Bournemouth University, University College London, University of South Wales, Vrije Universiteit Brussel, British Geological Survey, English Heritage, the Natural History Museum (London), Gatan UK and Vidence Inc. (Canada), and was funded by the British Academy and Leverhulme Trust. 

As Rob Ixer (Honorary Research Fellow at the UCL Institute of Archaeology) indicated:

From the lucky rediscovery of the core from sarsen upright 58, the choice of the right researchers and their specialisms, to the final, extensive discussion of the results, Stonehenge has once again provided an opportunity to re-write the text-books. The use of multiple analytical techniques and the integration of their data in order to fully describe the sarsen has given us a gold-standard work that will remain the bench mark for archaeological stone studies for many years to come. Sarsens, the long-time Ugly Sisters to the bluestones, have been dragged into the lime-light. This well-written account is part hard science but part romancing the stone."

In a complementary piece, published recently in the Wiltshire Archaeological & Natural History Magazine (Vol. 114, pp. 18-33), Rob Ixer and colleague Richard Bevins compare aspects of orthostat 58 with other sarsen samples from within the Stonehenge Landscape and show that the stone is part of a ‘broad church’ of lithologies with further investigation being needed. 

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  • Top: Stonehenge (Image credit: Aerial-Cam Ltd.)
  • Right: David Nash (University of Brighton) analysing the sarsen core extracted from Stone 58 at Stonehenge. (Image credit: Sam Frost, English Heritage)