A comprehensive investigation of the sandstone megalith’s “geological fingerprint” suggests it did not originate in northeast Scotland, as a surprising study concluded in 2024, sending scientists back into the field to track down the enigmatic slab’s origins
Soumya Sagar | Correspondent
November 6, 2026 4:41 p.m.
At the heart of Stonehenge on Salisbury Plain lies a flat, six-ton slab of sandstone whose origin has long baffled scientists. This mystery was seemingly solved in 2024 when the stone was linked to a potential source in northeast Scotland, at least 465 miles away by land. Now, a rigorous follow-up investigation has overturned that shocking conclusion, revealing that researchers were likely hunting across the wrong terrain.
A new study published this week in the Journal of the Geological Society compared the Altar Stone’s detailed geological signature with field samples gathered across the alleged origin site in Scotland’s Orcadian Basin. The findings determined that the slab’s true origin remains an unresolved puzzle, marking the latest chapter in an evolving scientific detective story about where distinctive 16-foot slab originated.
“This is the most comprehensive geological investigation of the Altar Stone ever undertaken,” Duncan Pirrie, an emeritus geologist at the University of South Wales who led the study, says in a statement.
He adds: “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.”
Combining direct examinations of the Altar Stone with analyses of samples held in museum collections, researchers evaluated its sedimentology, geochemistry and mineralogy. In effect, they created a “geological fingerprint” of the slab, per the statement.
The geologists then travelled across the Orcadian Basin looking for a potential match for this fingerprint. The fieldwork, however, proved formidable, like finding a needle in a haystack, Nick Pearce, an emeritus geochemist at Aberystwyth University and study co-author, tells the Guardian's Steven Morris.
“The problem is, it’s a very big area, thousands of square kilometers. The only way to do it is to get out there and find the samples,” Pearce explains. “We’ve taken about 70 samples, brought them back to laboratories and tested them.”
Laboratory evaluations of those 70 samples failed to produce a match, leading the team to conclude that it is very unlikely the Altar Stone came from northeast Scotland.
Despite the dead end, researchers insist that the negative result brings them closer to the truth. “In a geological detective story such as this, ruling out potential source areas is just as important as identifying new ones,” Pearce says in the statement. “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.”
Constructed in several stages between 3000 B.C.E. and 1520 B.C.E., Stonehenge is composed of massive rock slabs that traveled over immense distances. While the massive sarsens came from nearby Marlborough Downs, the smaller bluestones were transported approximately 140 miles from the Preseli Hills in southwest Wales.
The Preseli Hills were long thought to be the origin of the Altar Stone, which lies flat and partially buried beneath the collapsed upright and lintel of the site’s largest trilithon. The 2024 theory of a Scottish origin dramatically expanded that range to more than 400 miles, igniting questions over whether Neolithic laborers dragged the stone south or sent it by water.
Did you know? Altar Stone
In 1620, landscape architect Inigo Jones suggested that the partially buried stone near the center of Stonehenge might have been used as an altar. It has been known as the Altar Stone ever since.
Earlier this year, glaciologists modeled ancient ice sheets to evaluate whether glaciers could have transported the rock during the last Ice Age. Ice flows could theoretically have pushed Scottish boulders near Dogger Bank, a now-submerged landmass in the North Sea, but humans would have had to rescue the stone thousands of years before construction began at Stonehenge.
With northeast Scotland and southern Britain both ruled out, the search for the Altar Stone’s birthplace now pivots to alternative formations in northern England, other parts of Scotland or even Ireland.
Pinpointing the true quarry remains essential for understanding the builders themselves. As Mike Pitts, an archaeologist who was not involved in the study, tells the Guardian, identifying the source “would greatly help fit the altar stone into the world of the people who moved it. We’d get to see the landscape through their eyes. To know exactly where the journey began.”
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Source: Smithsonian Magazine · Soumya Sagar
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