Six-ton stone’s mysterious source eludes scientists searching across Britain for Stonehenge clues
A detailed geological comparison
The study, published in the Journal of the Geological Society, examined the Altar Stone’s mineral composition, chemistry and other geological characteristics. The stone measures 4.9 meters (16 feet) long and weighs about six metric tons (6.6 US tons).
Researchers combined observations of the stone with close examinations of fragments in museum collections. They compared its structure, mineral content, chemical composition and isotopic characteristics to establish features that possible source locations would need to match.
Scotland locations remain unconfirmed
None of the locations examined so far in northeast Scotland’s Orcadian Basin has met all the criteria. The stone’s origin therefore remains unknown, although the comparison gives future fieldwork a clearer target.
The findings build on earlier research that shifted the search away from Wales. Study leader Duncan Pirrie is an emeritus professor at the University of South Wales; Richard Bevins is an honorary professor in Aberystwyth University’s Department of Geography and Earth Sciences.
Ruling out possible sources
Nick Pearce, an emeritus professor of geochemistry in Aberystwyth University’s Department of Geography and Earth Sciences, said eliminating possible source areas is as important as identifying new ones. He described the Altar Stone as unique among Stonehenge’s stones and said tracing its source could reveal more about its journey to Salisbury Plain.
Stonehenge was built in several phases between around 3000 and 1600 BC. Its smaller bluestones traveled approximately 225 kilometers (140 miles) from west Wales, offering context for the challenge of moving stones over long distances.
Key points
- The Altar Stone is about six metric tons and 4.9 meters long.
- The examined Orcadian Basin locations have not matched all the stone’s geological features.
- The study provides criteria to guide future searches for the stone’s origin.
- Stonehenge’s smaller bluestones traveled approximately 225 kilometers from west Wales.