Will Dunham

(Reuters)-The first comprehensive scientific analysis of the majestic megaliths of Stonehenge revealed some of the characteristics that make them exemplary building materials for famous monuments in southern England, including their strong resistance to weathering.

Researchers on Wednesday described a series of inspections that provided a glimpse of one of Stonehenge’s 52 sandstone boulders, known as sarsens, to gain insight into its geology and chemistry.

They studied a core sample taken from a type of Sasen called Stone 58 during conservation efforts in the 1950s. It has been preserved in the United States for decades before returning to the United Kingdom for research in 2018.

Sarsens is made of a stone called silcrete, which is gradually formed within a few yards (meters) from the surface due to the erosion of groundwater through buried sediments.

The inspection clarified the internal structure of Stone 58. The results show that the siliceous concrete is mainly composed of sand-sized quartz particles, which are tightly bonded together by the interlocking inlay of quartz crystals. Quartz is very durable and will not chip or corrode even when exposed to wind and weather.

“This explains the resistance of stone to weathering and why it is an ideal material for building monuments,” said David Nash, a geomorphologist at the University of Brighton, who led the study, which was published in the journal PLoS ONE.

Around 2500 BC, in the late Neolithic period people achieved an extraordinary engineering achievement, erecting sarsens on the site in Wiltshire, England. Stone 58 is one of the giant upright sarsens in the center of Stonehenge. It is about 7 meters (23 feet) high and 2 meters (7 feet) underground. It is estimated to weigh 24 tons above ground.

The core sample is a rock, about one inch (2.5 cm) in diameter and one yard (meter) long. Its cream color is brighter than the light gray appearance of the boulder, which has been exposed to the elements for thousands of years.

It was given as a souvenir to a man named Robert Phillips, who worked for a company involved in conservation work and was on site during drilling. Phillips got his permission when immigrating to the United States in 1977. Phillips decided to send him back to the UK for research in 2018 and died in 2020.

“Obtaining the core drilled from Stone 58 is the holy grail of our research,” Nash said. “All previous work on Stonehenge sarsens involved samples excavated from the site or knocked out of random stones.”

Researchers use CT scans, X-rays, microanalysis, and various geochemical techniques to study fragments and extremely thin sections of core samples-this type of test is forbidden for boulders in the field.

“This small sample may now be the most analyzed rock besides lunar rocks,” Nash said.

Although researchers have found that some embedded sand grains can be traced back to Mesoproterozoic, between 1 billion and 1.6 billion years ago, the exact time when the rock was formed is not yet known.

The research published by Nash last year https://www.reuters.com/article/us-science-stonehenge/scientists-solve-mystery-of-the-origin-of-stonehenge-megaliths-idUSKCN24U2VG involves the same core sample, showing 52 Fifty of the sarsens share a common origin at a location called West Woods about 15 miles (25 kilometers) from Stonehenge. The builders of Stonehenge may have dragged or moved the boulders on the rollers.

“I think Stonehenge has fascinated archaeologists and other scientists for centuries, partly because we don’t know its exact purpose, and there are many theories about why the site was built,” Nash said. “This is a website that is still full of possibilities for more research.”

(Reporting by Will Dunham in Washington; Editing by Cynthia Osterman)