Overview
- A multi‑technique paper published in the Journal of the Geological Society presents the most detailed geological analysis yet of Stonehenge’s Altar Stone and says no examined source matches its full signature.
- The Altar Stone shows an unusual combination of features including a scatter of baryte, presence of chrome spinel, the rare clay tosudite, and a mixed‑layer illite/smectite with about 20% expandable layers.
- The authors accept earlier mineral age data that point to a Laurentian signal but argue that age alone is not enough to locate the source because many regions can share similar mineral ages.
- Based on mineralogy, textures and isotopes the study excludes several candidate areas that were sampled, including parts of Orkney and Caithness, the Southern Uplands, the Midland Valley, West Wales, and the wider Anglo‑Welsh Basin.
- Because the in situ Altar Stone cannot be sampled directly the team relied on eight museum fragments and portable X‑ray readings, and they say the new fingerprint will let future fieldwork target likely outcrops and test remaining parts of Britain and Ireland for a match.