The huge plates According to chemical analysis, the stone that makes up the most famous buildings in Stonehenge comes from a distance of around 25 kilometers. Since the 16th century, most Stonehenge scholars have assumed that the 6 to 7 meter high, 20-ton Sarsen stones come from nearby Marlborough Downs, and a recent study by archaeologist David Nash and his colleagues from the University of Brighton has now confirmed this.
Recent studies have traced Stonehenge’s bluestones to quarries in the Preseli Hills in west Wales about 300 kilometers away. When another group of archaeologists examined the chemical isotope relationships in the cremated remains of people who were once buried under the bluestones, these researchers found that many of these people between 3100 and 2400 BC. BC came from the same part of Wales. A few centuries after the arrival of the blue stones, old builders built the sarsen stones. Until now, modern scholars could only speculate about where the giant boulders came from.
Sarsen, also called silicone, is a sedimentary rock that mainly consists of quartz sand that is cemented with silica (quartz is only silica in crystal form) and is formed in layers of sandy sediment. Thanks to erosion, blocks of sarsen are now scattered in clumps throughout southern England. Prehistoric Britons built monuments such as Stonehenge and Avebury with sarsen blocks, Roman settlers used sarsen stones to build their villas, and medieval people built sarsen churches and farm buildings. But the biggest Sarsen blocks we know in Britain today are those in Stonehenge.
About 99 percent of the average sarsen block consists of silica, the other 1 percent contains traces of other elements such as aluminum, calcium, iron, potassium, magnesium and others. This additional material differs in different sources of sarsen because it depends on the minerals in the soil in which the rock was formed. Nash and his colleagues used these trace elements as a geochemical fingerprint to assign the Stonehenge Sarsens to their most likely source.
The largest concentration of sarsen in the UK is in Marlborough Downs, an area with rounded grassy hills 25 to 30 kilometers north of Stonehenge. Centuries of archaeologists and antiquarians have assumed that the Stonehenge-Sarsens are from the Marlborough Downs, mainly because the area is nearby and full of the right material. But this idea hadn’t been scientifically tested, and the bluestones show that the Neolithic builders who built Stonehenge had a distant and complex supply network – and their own reasons for doing things that are often unfathomable for modern researchers.
In order to track down the source of the Sarsens, archaeologists first had to solve a new puzzle: what happened to three missing Stonehenge pieces?
One of the trilithons (arched structures of two upright stones that support a horizontal lintel) in the central horseshoe fell in 1797. A century and a half later, in 1958, a restoration project put the massive stones back in position – but one of the posts, called Stone 58, had torn along its length. To hold the cracked stone together so that it could stand and support half of the lintel, restorers drilled three holes in the stone and inserted metal ties. After the project, the three stone cores that they had drilled out seemed to be gone.
In 2018, one of the restorers, Robert Phillips, returned a broken but complete Stone 58 core to the UK. Part of a second core appeared in the Salisbury Museum in 2019, but one and a half of the stone cores are still out there somewhere. Samples from the Phillips core gave Nash and his colleagues the opportunity to compare the chemical composition of Stone 58 with sarsen blocks from locations across the UK.
It turned out that the match was exactly what various researchers had assumed in the past 500 years. The only boulders that matched Stone 58 came from a location in the southeast of Marlborough Downs: West Woods in Wiltshire, about 25 kilometers north of Stonehenge and only 3 kilometers south of the place where most of the studies had searched for Neolithic Sarsen Quarries. West Woods is a 6 square kilometer plateau that is partially wooded and littered with large blocks of sarsen and pits from millennia of the quarry.