Mystery origin of iconic Stonehenge Altar Stone deepens as search narrows

Nation Cymru staff

The hunt for the source of Stonehenge’s mysterious Altar Stone has entered a new phase after scientists rule out several previously proposed locations and move a step closer to identifying its origins.

A new study published in the Journal of the Geological Society provides the most detailed geological analysis to date of the monument’s six-tonne Altar Stone.

For more than a century, archaeologists and geologists believed the distinctive 4.9-metre sandstone slab at the heart of the famous Neolithic monument on Salisbury Plain originated in Wales. That theory was overturned by recent research using modern analytical techniques, which instead pointed to north-east Scotland as a likely source.

In the latest effort to solve one of Stonehenge’s most enduring geological mysteries, an international team of scientists has taken a fresh look at the Altar Stone using a wide range of scientific tests.

Combining new observations of the Stone along with a detailed study of fragments held in museum collections, the researchers examined its structure, minerals, chemical composition and isotopic characteristics to delve deeper into its origins.

So far, the search in the Orcadian Basin in north-east Scotland has not revealed a location with the same characteristics as the Altar Stone.

Professor Duncan Pirrie, Emeritus Professor at the University of South Wales who led the study, said: “This is the most comprehensive geological investigation of the Altar Stone ever undertaken.

“By combining a wide range of analytical techniques, we have built the clearest picture yet of the stone’s composition and tested the leading theories about its origins.

“So far, none of the locations examined have the same set of characteristics as the Altar Stone.

“That tells us the search is not over, but we are now far better equipped to focus on the areas most likely to yield an answer.”

Professor Richard Bevins, Honorary Professor in the Department of Geography and Earth Sciences at Aberystwyth University, said: “For almost a century, the prevailing view was that the Altar Stone came from west Wales. Our previous research overturned that assumption and pointed instead to Scotland as the most likely source.

“This latest study significantly refines the search by identifying the specific geological characteristics we need to look for, allowing future investigations to be targeted more effectively. With each new piece of evidence, we move closer to solving one of Stonehenge’s most enduring mysteries.”

Professor Nick Pearce, Emeritus Professor of Geochemistry in the Department of Geography and Earth Sciences at Aberystwyth University, added: “In a geological detective story such as this, ruling out potential source areas is just as important as identifying new ones.

“Every location eliminated narrows the search and brings us closer to discovering where the Altar Stone originated.

“The stone is unique among those at Stonehenge, and tracing its source would provide valuable new insights into its remarkable journey to Salisbury Plain thousands of years ago.”

Stonehenge was constructed in several phases between around 3000 and 1600 BC. The monument is internationally renowned for the long-distance transport of its stones, with the smaller bluestones having travelled approximately 225 kilometres from west Wales.

The researchers hope that the detailed geological fingerprint established by the study will ultimately help pinpoint the Altar Stone’s source and provide fresh insights into one of prehistory’s most remarkable engineering achievements.

The research brought together geologists and archaeologists from institutions across the UK, Canada, Italy and Sweden, including the University of South Wales, Aberystwyth University, University College London, the University of Aberdeen, the University of Plymouth, the James Hutton Institute, the Swedish University of Agricultural Sciences, the University of Milano-Bicocca and several industry partners.