Stonehenge offers mysteries aplenty. Just when we think we’ve solved one, we have to re-solve questions we thought were already answered. Such is the case with the origin story of the Altar Stone—one of the roughly 80-plus stones still on site in southern England.
The stones of Stonehenge feature a variety of compositions and originate from a number of potential source locations. Scholars previously believed that they knew most of what there was to be known about the Altar Stone—the largest of the non-sarsen stones on site, which is now partially buried beneath two fallen stones. But researchers led by a team from Curtin University may have upended that history, writing that a stone long believed to originate from Wales actually hails from Scotland.
By studying the age and chemistry of mineral grains within fragments of the six-ton Alter Stone—a thick sandstone block measuring 16 feet by 3 feet in the center of the iconic Wiltshire circle—the team crafted a chemical fingerprint of the stone. That chemical composition matched that of rocks from northeast Scotland, and clearly differentiated it from Welsh bedrock.
“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,” Anthony Clarke, lead author and Ph.D. student from the Timescales of Mineral Systems Group at Curtin’s School of Earth and Planetary Sciences, said in a statement. “This provides a distinct chemical fingerprint suggesting the stone came from rocks in the Orcadian Basin, Scotland, at least 750 kilometers [466 miles] away from Stonehenge.”
According to English Heritage, the Altar Stone is a large slab of greenish Old Red Sandstone. Recent geological research had pinpointed the source of the stone to the Brecon Beacons area of southeast Wales. But the study, which was published in the journal Nature, discounts that reigning theory.
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