Stonehenge stone finally analyzed: it is indestructible

A sample from a 1958 restoration opens the door to new discoveries about Stonehenge: dating, composition and origin of the rocks.

The Stonehenge site has always been shrouded in a patina of fascination and mystery, which certainly cannot leave indifferent the scientific community, which for years has wondered why the rocks of Stonehenge are so resistant to wear and physical changes.

The world's most famous and impressive cromlech is located near Amesbury, just a few miles from the town of Salisbury in Wiltshire, and is believed to have remained virtually unchanged since its installation, dating back to the Neolithic period.

The "Phillips" sample, straight from 1958

A new study published in the journal Plos One reveals the composition of Stonehenge's rocks. As David Nash of the University of Brighton, co-author of the research, states, "we now finally have an idea of why that stuff is still there."

It would indeed seem that the composition of the rock that makes up the world's most impressive "stone circle" is particularly resistant to erosion and the effects of time.

But how could the researchers get their hands on the Stonehenge stone, considering that no fragments exist and that it is obviously forbidden to extract new ones? The answer comes from a repair and restoration job that took place back in 1958, by Robert Phillips, a diamond carver who was then called in to repair one of the trilithons of the Neolithic site.

Authorized to core rock 58, and to keep the rock sample for himself as a souvenir, the recently deceased Phillips returned the treasure after nearly sixty years, opening the door to very important unpublished discoveries about Stonehenge.

For example, it was thanks to XRF spectrophotometry performed in 2020 on the sample donated by Phillips that it was finally possible to provide a date for the rocks of Stonehenge, which would date back to 2500 BC.C..

The "Phillip's Core", as the sample of rock 58 is called, is defined by scientists as "a sort of Holy Grail": as Professor Nash says, "it is extremely rare for a scientist to have the opportunity to work on samples of such importance".

The Stonehenge Rock

The Phillips sample has been examined far and wide, and it has even been possible to destroy a good half of it for scientific purposes. Involved are both the Natural History Museum in London and institutions such as English Heritage.

What has emerged from investigations into the composition of rock 58, is that we are dealing with a particularly strong composition of quartz, arranged in an interlocking matrix of crystals that makes the stone virtually indestructible.

As Nash revealed to Science Alert, one would have to wonder "whether the builders of Stonehenge knew the properties of the rocks, rather than having chosen the largest and closest to the site."

On a geochemical level, the composition of rock sample 58 matches 50 of the 52 other rocks that make up the chromlech, so it's safe to believe that the rocks at Stonehenge are of the same type.

Technically, it is silcrete, a crust of soil that is cemented with silica: the rocks of Stonehenge are largely composed of eroded sediments that date back as far as the Paleogene, at the dawn of the Cenozoic, that is, more than 25 million years ago.

The analysis of the Phillips sample has also allowed us to discover the origin of the stones of Stonehenge, which appear to come from the West Woods, among the hills of Marlborough Downs.