The quest to find the origins of Stonehenge’s iconic Altar Stone continues – just weeks after experts thought they had finally cracked it.
Scientists revealed last month that the massive slab came from Orkney in Scotland and not Wales, where the monument’s bluestones have been traced to.
The archipelago is home to other famous Neolithic sites, including the Ring of Brodgar and Stones of Stenness.
But while its geology was right for a possible match to the Altar Stone, chemical and mineralogical analysis have revealed striking differences – meaning the hunt goes on.
Previous geological research suggested that the six-tonne slab probably originated from the Brecon Beacons in south east Wales.
But last month scientists concluded the monumental Altar Stone actually hails over 460 miles from Salisbury Plain in north east Scotland.
The Australian team used state-of-the-art equipment, including specialist mass spectrometers, to examine the composition of the Altar Stone.
Their findings, published in the journal Nature, also point to the existence of ‘unexpectedly advanced’ transport methods and organisation at the time of the stone’s arrival in Wiltshire around 5,000 years ago.
Researchers from Curtin University in Perth, Western Australia, studied the age and chemistry of mineral grains within fragments of the Altar Stone, which is a nearly 20 inch thick sandstone block measuring 16x3ft, sitting at the centre of Stonehenge’s iconic stone circle.
Study lead author Anthony Clarke explained that analysis of the age and chemical composition of minerals within fragments of the Altar Stone matched it with rocks from Scotland, while also clearly differentiating them from Welsh bedrock.
Mr Clarke said: ‘Our analysis found specific mineral grains in the Altar Stone are mostly between 1,000 to 2,000 million-years-old, while other minerals are around 450 million years old.
‘This provides a distinct chemical fingerprint suggesting the stone came from rocks in the Orcadian Basin, Scotland, at least 750 kilometres away from Stonehenge.
‘Given its Scottish origins, the findings raise fascinating questions, considering the technological constraints of the Neolithic era, as to how such a massive stone was transported over vast distances around 2600 BC.’
Mr Clarke, a PhD student within Curtin’s School of Earth and Planetary Sciences, said the discovery holds ‘signifance’ for him as he grew up in the Mynydd Preseli, Wales, where some of Stonehenge’s stones came from.
He added: ‘I first visited Stonehenge when I was one year old and now at 25, I returned from Australia to help make this scientific discovery – you could say I’ve come full circle at the stone circle.’
Study co-author Professor Chris Kirkland, also from the Timescales of Mineral Systems Group at Curtin, said the findings had “significant” implications for understanding ancient communities, their connections, and their transport methods.
Prof Kirkland said: ‘Our discovery of the Altar Stone’s origins highlights a significant level of societal coordination during the Neolithic period and helps paint a fascinating picture of prehistoric Britain.
‘Transporting such massive cargo overland from Scotland to southern England would have been extremely challenging, indicating a likely marine shipping route along the coast of Britain.
‘This implies long-distance trade networks and a higher level of societal organisation than is widely understood to have existed during the Neolithic period in Britain.’
But with Orkney now ruled out researchers are left searching elsewhere.
Writing in the Journal of Archaeological Science, Professor Richard Bevins from Aberystwyth University, the lead author of the study, said: ‘This research is radically changing our thinking about the origins of the Altar Stone.
‘It’s thrilling to know that our chemical analysis and dating work is slowly unlocking this great mystery.’
Prof Bevins and his colleagues will now continue to try and ‘pin down’ the stone’s exact origin.
He told MailOnline: ‘I am optimistic that the source of the Altar Stone will be found. However, the Orcadian Basin covers a large area in north-east Scotland so it might take some time to locate the source.
‘But we have some clues in terms of the mineralogy and geochemistry of the Altar Stone so we are not going in blind.’
It is unclear when the Altar Stone came to Stonehenge, but construction started around 5,000 years ago with changes over 2,000 years.
This article was first published on August 14.
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