From their pXRF data, Professor David Nash's team discovered that 50 of the 52 sarsen stones at Stonehenge share a consistent chemistry, pointing strongly to a common source. More excitingly still, they were able to use their ICP-MS data to identify the most likely source of the sarsen stones as West Woods, on the edge of the Marlborough Downs, around 15 miles north of the famous stone circle.
Susan Greaney, Senior Properties Historian for English Heritage, the charity that cares for Stonehenge, said: “This research provides a fantastic leap forward in our knowledge about Stonehenge, as we can finally answer the question of where the iconic sarsen stones were brought from. We’re so pleased that the core from Stone 58, which the Phillips family returned to Stonehenge, has enabled the team to undertake a small amount of destructive sampling, adding a crucial piece of evidence to the jigsaw.”
The ‘Philips Core’ she refers to was drilled from Stone 58 during conservation work at Stonehenge in 1958. The location of the core remained a mystery until Robert Phillips, a representative of the company who did the drilling work, returned it to the UK from his home in Florida. Stone 58 was one of several stones at the site that had toppled over in the distant past. During conservation work in the 1950s, a longitudinal crack was discovered running through the stone. To conserve the stone, three cores around 2.5cm in diameter were drilled through its full thickness (around 1m) to insert metal rods.
Two of the cores then disappeared, though part of one was rediscovered at Salisbury Museum in 2019. The third core was given to Robert Phillips, who worked for the drilling company, and went with him to the USA when he retired. Phillips returned the core to English Heritage in 2018 to provide material for research, before he passed away in 2020.
Further to the pioneering research using the ‘Phillip’s Core’ and other samples to show where Stonehenge's large sarsen stones were likely to originate, in a paper published in the journal PLoS ONE, an international team led by David Nash were able to reveal that the geological structure of the stone made the sarsen ideal for building a monument made to last. Analysing a small section of the 1950s core, David Nash's team found that the sarsen's structure of sand-sized quartz grains cemented tightly together by an interlocking mosaic of quartz crystals was what made the stone so impervious to crumbling or erosion.