In 1958, Robert Phillips, a representative of the drilling company helping to restore Stonehenge, took the cylindrical core after it was drilled from one of Stonehenge’s pillars — Stone 58. Later, when he emigrated to the United States, Phillips took the core with him. Because of Stonehenge’s protected status, it’s no longer possible to extract samples from the stones. But with the core’s return in 2018, researchers had the opportunity to perform unprecedented geochemical analyses of a Stonehenge pillar, which they described in a new study.
They found that Stonehenge’s towering standing stones, or sarsens, were made of rock containing sediments that formed when dinosaurs walked the Earth. Other grains in the rock date as far back as 1.6 billion years.
“We have CT-scanned the rock, zapped it with X-rays, looked at it under various microscopes and analyzed its sedimentology and chemistry,” said study lead author David Nash, a professor of physical geography at the University of Brighton in England.
“With the exception of thin-section analyses and a couple of the chemical methods, all of the techniques we used in the study were new both to Stonehenge and the study of sarsen stones in the U.K.,” Nash told Live Science in an email.
Stonehenge’s central circle of pillars was erected during the Neolithic period, about 4,500 years ago, according to English Heritage, a nonprofit organization that manages historic monuments in England.
“Sarsens were erected in two concentric arrangements — an inner horseshoe and an outer circle — and the bluestones [smaller monument stones] were set up between them in a double arc,” English Heritage said on its website.
When the scientists peered through a microscope at thin slices of sarsen rock from Stone 58, they were surprised to discover that the stone was 99.7% quartz. A quartz “cement” held fine-to-medium quartz grains and formed “an interlocking mosaic of crystals,” Nash said. That made the rock more durable, and it may have been why the builders chose that type of rock for their massive monument thousands of years ago.
“These cements are incredibly strong. I’ve wondered if the builders of Stonehenge could tell something about the stone properties, and not only chose the closest, biggest boulders, but also the ones that were most likely to stand the test of time,” Nash said.