Was the Stonehenge Altar Stone from Orkney? Investigating the mineralogy and geochemistry of Orcadian Old Red sandstones and Neolithic circle monuments

A recent study challenges the long-standing hypothesis that the Stonehenge Altar Stone originated from Orkney, despite evidence of Neolithic connections between the two regions. Using advanced mineralogical and geochemical techniques, researchers analyzed the Altar Stone alongside samples from two major Orcadian Neolithic monuments—the Stones of Stenness and the Ring of Brodgar—as well as field samples from Orkney's Old Red Sandstone (ORS) formations. The study found no mineralogical or geochemical match between the Altar Stone and Orkney samples, ruling out Mainland Orkney as its source. Key discriminants included the absence of baryte in Orkney samples (a hallmark of the Altar Stone) and the presence of abundant detrital K-feldspar in Orkney rocks, which is scarce in the Altar Stone. Additionally, the smectite mineral tosudite, unique to the Altar Stone's clay assemblage, was not detected in Orkney samples. The findings suggest that despite Neolithic trade or communication links between Orkney and Stonehenge, the Altar Stone likely originated elsewhere in northern Britain.

Bevins, R. E., Pearce, N. J. G., Hillier, S., Pirrie, D., Ixer, R. A., Andò, S., Barbarano, M., Power, M., & Turner, P. (2024). Was the Stonehenge Altar Stone from Orkney? Investigating the mineralogy and geochemistry of Orcadian Old Red sandstones and Neolithic circle monuments. Journal of Archaeological Science: Reports, 58, 104738. https://doi.org/10.1016/j.jasrep.2024.104738