A stone core taken from a sarsen stone of Stonehenge in 1958 has been
returned, and analysis confirms that the sarsens came from a quarry only
25 km from the monument.

<https://www.sciencemag.org/news/2020/07/long-lost-relic-may-reveal-origi ns-stonehenge>

"As Robert Phillips neared his 90th birthday, the former diamond cutter
decided to return a priceless piece of history to the United Kingdom: a 91-centimeter-long cylinder of rock from the heart of Stonehenge. Now, archaeologists working with the so-called Phillips core have all but conclusively shown that the famed monument¹s largest building blocks
came from a forest about 25 kilometers away, confirming a long-standing hypothesis.

It¹s ³a quality piece of work,² says Richard Bevins, a geologist and
Stonehenge researcher at the National Museum Cardiff. Knowing the
stones¹ origin could reveal future excavation sites in the region,
shedding light on the ancient stoneworkers who constructed these
mysterious monuments."
[...]
"In 1958, Phillips was part of a crew contracted to re-erect three
massive blocks that had toppled more than 100 years earlier at
Stonehenge. When the workers lifted one of them, Stone 58, they realized
it was cracked. So they cut a hole through it and pinned it with a metal
bolt to reinforce it. Phillips took the drilled-out core as a souvenir;
it hung in his U.K. office for years before he took it with him when he
retired to Florida.

When the Phillips core re-emerged in 2018, David Nash, an archaeologist
and geographer at the University of Brighton, and colleagues knew they
finally had the missing piece they needed to pinpoint the sarsens¹
origins. Today, destroying intact pieces of Stonehenge is forbidden,
Nash says, but because it has already been removed, the Phillips core
gave them a unique opportunity for analysis.

Nash and University of Brighton geologist Jake Ciborowski used a
portable x-ray spectrometer‹which Nash says ³looks a bit like a ray gun
from an old sci-fi movie²‹to take nondestructive surface readings of all
52 sarsens¹ chemical compositions. Despite being more than 99% silica,
the stones also contained traces of other elements, including aluminum,
carbon, iron, potassium, and magnesium. Critically, 50 of the 52 sarsens‹including the Phillips core¹s parent‹had a practically identical chemical makeup, suggesting the stones all came from a single site.

Nash¹s team then pulverized half of the Phillips core and ran it through
a gantlet of chemical analyses that return a much higher resolution
signature than x-ray spectrometry can provide.

When the researchers compared the core¹s detailed chemical signature to
samples taken from 20 boulder fields from southern and eastern England,
it matched with nearly 100% confidence to boulders from a forest called
West Woods. Located in the southeast of the Marlborough Downs, that¹s
precisely where most experts had long assumed the sarsens originated,
the researchers report today in Science Advances."

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