Stonehenge mystery solved: where do the large stones come from?

A two-year investigation led by Professor David Nash, the university’s professor of physical geography, has revealed that most of the sarsen stones came from West Woods on the edge of the Marlborough Downs in Wiltshire, around 15 miles north of Stonehenge.

Commenting on the research, Professor David Nash said: “Archaeologists and geologists have been debating where the sarsen stones used to build Stonehenge came from for more than four centuries.

“This significant new data will help explain more of how the monument was constructed and, perhaps, offer insights into the routes by which the 20 to 30 tonne stones were transported.”

How did they make the discovery?

In 1958, conservation work at Stonehenge resulted in a core of rock being extracted from Stone 58.

The location of this core was a mystery until last year, when engineer Robert Phillips – a representative of the company that conducted the drilling work – returned it to the UK from his home in Florida.

Following this development, English Heritage granted permission for the University of Brighton to conduct research into the origins of the sarsens and in 2018 scientists began chemical analysis of the stones.

Using non-invasive techniques such as x-ray, the Brighton research team proved that 50 out of 52 of the sarsen stones share a consistent chemistry and therefore come from a common source area.

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This data was then compared closely to the core extracted from Stone 58 – which could be examined more invasively – which allowed them to identify the location of West Woods.

Susan Greaney, senior properties historian for English Heritage, the charity that cares for Stonehenge, said: “We’re so pleased that the core from Stone 58, which the Phillips family returned to Stonehenge last year, has enabled the team to undertake a small amount of destructive sampling, adding a crucial piece of evidence to the jigsaw.”

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But there are still a few mysteries left to solve, as Professor Nash explains:

“We still don’t know where two of the 52 remaining sarsens at the monument came from. These are upright Stone 26 at the northernmost point of the outer sarsen circle, and lintel Stone 160 from the inner trilithon horseshoe. It is possible that these stones were once more local to Stonehenge, but at this stage we do not know.

“We also don’t know the exact areas of West Woods where the sarsens were extracted. Further geochemical testing of sarsens and archaeological investigations to discover extraction pits are needed to answer these questions.”

Find out more about how to visit Stonehenge from English Heritage

Interview with Mike Pitts: “This really is just the beginning”

All this week we have been counting down the top five of our History’s Greatest Mysteries poll. In second place was the mystery of Stonehenge, nominated by archaeologist Mike Pitts.

We caught up with Mike to get his thoughts on the recent discovery...

How significant is the discovery that the sarsen stones come from Marlborough Downs?

It’s a really significant breakthrough. With Stonehenge archaeology, the focus so far has been largely on bluestones, which are the small stones that come from Wales. We’ve known which part of Wales these come from, more or less, since the 1920s.

All this time, we had no idea – in terms of actual evidence – where the sarsens come from. For centuries, people have said that they probably came from the Marlborough Downs – because that's where you can still find a lot of sarsens today.

In the past decade, there has been a contrary feeling growing among some archaeologists that the stones might come from a site closer to Stonehenge: Salisbury plain. Personally, I never bought into that theory, because the scale of the stones at Stonehenge is just so enormous.

Today, we can't find any sarsens anywhere near as big as at Stonehenge anywhere in England, but it seemed that the most likely source was somewhere up on the Marlborough Downs. In the 1980s, an archaeologist called Hilary Howard attempted to characterise the sarsens and establish if there was a way that we could prove that this is where they came from. But the resources and technology weren't available to do it then.

• Listen | Mike Pitts considers how and why the monument was created, more than 4,000 years ago

Why weren’t we able to identify where the stones came from before?

We didn’t have the technology to do so.

The Welsh blue stones are a mixture of different types of igneous rock from different locations. They look, visually, very different. The sarsens, on the other hand, look absolutely identical – even if you look at themunder the microscope. They are made of a very pure sandstone, which is, geologically speaking, very difficult to source (because there is nothing really in the stones except silica). Theoretically, these stones could have come from anywhere.

With the new study, they were able to record in considerable detail elements that are present in the sarsens in really small quantities. Let’s say, for argument’s sake, that 99 per cent of the sarsens is just pure silica. There are other elements still there in small quantities – in that one per cent. Recent technology developments allowed researchers to measure these trace elements and pinpoint a source site: in this case, West Woods in Wiltshire.

In the traditional narratives of Stonehenge, West Woods was never suggested as a location

In the traditional narratives of Stonehenge, West Woods was never suggested as a location. It’s a very popular location for walkers and it’s full of sarsens, but archaeologists were oblivious (I think because it’s in woodland). Locals know about it, but archaeologists were looking for sarsens mostly out on the open downs.

What’s next for Stonehenge? Are there any mysteries left to solve?

One might ask ‘Why does all of this matter’? If we can say precisely where the sarsens came from – if the location of ‘West Woods’ is narrowed down further to a manageable size – it should be possible to identify the hole in the ground where the really big sarsens were first removed. If we can identify this site and excavate it, we can literally prove where the Stonehenge sarsens came from. This is where it gets really exciting.

If, as is quite likely, some of the dressing took place at the quarry (in other words, the really rough shaping to get rid of the huge irregular lumps on these boulders. Logically, you would think that the people who built Stonehenge would have done this before moving these huge stones many miles to their final resting point). So we can learn about how they were dressed, whereas at the moment we are completely guessing.

It could transform our entire understanding of Stonehenge

If we can excavate those pits, we can date the excavation of the stones. If we can do that, it would transform our entire understanding of Stonehenge itself. One of the main problems for Stonehenge archaeologists is dating the monument itself, literally dating the erection of the megaliths themselves. If we can do that, we can learn much more about the people, landscape and societies involved in the building of Stonehenge.

So this is really just the beginning of a new episode. The next step is to refine the locations further and to take more samples. Current analysis also indicates that two of the stones don’t come from Stonehenge – so where do they come from? And why do they come from a different place? So there is still a mystery there.

Mike Pitts is an English journalist and archaeologist who specialises in the study of British prehistory. He was speaking to Rachel Dinning, digital editorial assistant at HistoryExtra