Spectroscopy Around the Globe, Episode 2: Stonehenge

A ring of massive standing stones on a windswept plain in England does not come out of nowhere. It had to be built by a previous ancient civilization. But who built and why? And if these stones did not come from Wiltshire, where did they come from?

In the second episode of “Spectroscopy Around the Globe,” host Will Wetzel highlights the role of spectroscopy in studying Stonehenge, and how these techniques have helped uncover some of Stonehenge’s secrets.

Stonehenge isn't one type of rock. Towering grey sarsens form its outer ring, smaller bluestones make up an inner circle, and a single Altar Stone lies at its heart.¹ And each of these rocks have a separate, and separately mysterious, origin story.¹

The breakthrough for the sarsens came from portable X-ray fluorescence (pXRF), which reads a stone's elemental "fingerprint" by measuring the X-rays it emits under a beam, all without touching the monument.^2,3 A University of Brighton team scanned all 52 surviving sarsens and found near-identical chemistry across nearly every stone. Laboratory inductively coupled plasma–mass spectrometry (ICP-MS) analysis of a core from Stone 58, a fragment returned decades after a 1958 restoration, confirmed the match: West Woods, roughly 25 kilometers away, published in 2020.^2,3

The Altar Stone proved far stranger. Automated scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) revealed unusually high barium levels, while portable Raman spectroscopy, deployed on-site at night, suggested the stone didn't come from Wales as long assumed.^4–6 The definitive answer arrived through uranium-lead geochronology. In a 2024 Nature study, researchers led by Anthony Clarke at Curtin University dated zircon, apatite, and rutile grains within the stone using laser ablation ICP-MS.⁷ The mineral "age barcode" matched the Old Red Sandstone of Scotland's Orcadian Basin, meaning the Altar Stone traveled at least 700 kilometers, the longest journey known for any Neolithic monument stone on Earth.⁷

Together, these techniques, which include XRF, ICP-MS, SEM-EDS, Raman, and uranium–lead (U-Pb) dating, have rewritten Stonehenge's story, revealing a Neolithic Britain far more interconnected than previously imagined. Spectroscopy has helped unlock the monument's secrets, with each technique contributing something unique.

You can view the first episode of Spectroscopy Around the Globe here: https://www.spectroscopyonline.com/view/spectroscopy-around-the-globe-episode-1-the-giza-pyramids

References

1. Wetzel, W. Decoding the Stones: Spectroscopic Techniques and the Secrets of Stonehenge. Spectroscopy Online, 2026. https://www.spectroscopyonline.com/view/decoding-the-stones-spectroscopic-techniques-and-the-secrets-of-stonehenge (accessed August 11, 2026).
2. Spectroscopy Staff, Using pXRF Analysis and Automated SEM-EDS To Study Stonehenge's Altar Stone. Spectroscopy Online, 2023. https://www.spectroscopyonline.com/view/using-pxrf-analysis-and-automated-sem-eds-to-study-stonehenge-s-altar-stone (accessed July 13, 2026).
3. Spectroscopy Online, Unraveling the Mysteries of Stonehenge: Portable Raman Spectroscopy Sheds Light on Altar Stone's Origins. Spectroscopy Online, 2024. https://www.spectroscopyonline.com/view/unraveling-the-mysteries-of-stonehenge-portable-raman-spectroscopy-sheds-light-on-altar-stone-s-origins (accessed July 13, 2026).
4. Bevins, R. E.; Pearce, N. J. G.; Pirrie, D.; Ixer, R. A.; Hillier, S.; Turner, P.; Power, M. Assessing the Authenticity of a Sample Taken from the Altar Stone at Stonehenge in 1844 Using Portable XRF and Automated SEM-EDS. J. Arch. Sci.: Rep. 2023, 49, 103973. DOI: 10.1016/j.jasrep.2023.103973
5. Pearce, N. J. G.; Bevins, R. E.; Ixer, R. A. Portable XRF investigation of Stonehenge Stone 62 and Potential Source Dolerite Outcrops in the Mynydd Preseli, West Wales. J. Arch. Sci.: Rep. 2022, 44. DOI: 10.1016/j.jasrep.2022.103483
6. Spectroscopy Staff, Using pXRF Analysis and Automated SEM-EDS To Study Stonehenge's Altar Stone. Spectroscopy Online, 2023. https://www.spectroscopyonline.com/view/using-pxrf-analysis-and-automated-sem-eds-to-study-stonehenge-s-altar-stone (accessed August 11, 2026).
7. Clarke, A. J. I.; Kirkland, C. L.; Bevins, R. E.; Pearce, N. J. G.; Glorie, S.; Ixer, R. A. A Scottish Provenance for the Altar Stone of Stonehenge. Nature 2024, 632, 570–575. DOI: 10.1038/s41586-024-07652-1