Scientists have conducted a comprehensive scientific investigation of Stonehenge's enormous megaliths for the first time, revealing some of the features of its sturdy structure and weathering resistance.
Researchers described a series of tests that allowed them to peer into one of Stonehenge's 52 sandstone megaliths, known as sarsens, to learn more about their chemistry and geology.
The findings were published Aug. 4 in the journal PLOS One.
Robert Phillips, a representative of the drilling business assisting in the restoration of Stonehenge, took the cylindrical core after it was drilled from one of Stonehenge's pillars - Stone 58 - in 1958. Phillips later brought the core with him when he moved to the U.S., according to the study.
Because of Stonehenge's protected status, extracting samples from the stones is no longer possible. However, with the recovery of the core in 2018, researchers were able to conduct unparalleled geochemical tests of a Stonehenge pillar, which they revealed in a new study.
To study pieces and wafer-thin slices of the core sample, the researchers used CT scans, X-rays, microscopic analyses and numerous geochemical techniques - such testing is prohibited for megaliths at the site.
They discovered that Stonehenge's gigantic standing stones, known as sarsens, were made of rock that had dinosaur-era sediments. The rock also had grains from approximately 1.6 billion years ago.
Sarsens are built of silcrete, a type of stone that formed gradually within a few yards (meters) of the ground surface as a result of groundwater washing through buried sediment.
The study revealed the interior structure of Stone 58. It revealed that silcrete is mostly made up of sand-sized quartz grains that are held together firmly by an interlocking mosaic of quartz crystals.
Even when subjected to centuries of wind and weather, quartz is incredibly resilient and does not easily shatter or erode.
While this investigation provided answers to some Stonehenge mysteries, others remain unanswered, including the location of two other cores dug from Stone 58 during the 1958 repair and which also disappeared from the record.
The team mentioned in the report a discovered fragment of one of those cores in their collection in 2019 by Salisbury Museum workers.
Where the third core (as well as the rest of the core discovered at the Salisbury Museum) is "similarly unknown," according to the scientists.