A recent study conducted by researchers from Aberystwyth University has cast doubt on the long-held belief that the Altar Stone at Stonehenge, also known as Stone 80, was sourced from the Old Red Sandstone (ORS) in the Anglo-Welsh Basin, particularly from South Wales. The Altar Stone, one of the most significant stones in the Stonehenge monument, has been shrouded in mystery, but this latest research offers new insights into its possible origin.

Stonehenge’s Altar Stone may not be from Wales. Credit: Professor Nick Pearce, Aberystwyth University

Traditionally, it was believed that the Altar Stone came from the Old Red Sandstone near the Preseli hills in West Wales, approximately 225 kilometers to the west of Stonehenge. This ᴀssumption was based on the unique lithology of the Altar Stone and its proximity to the Preseli area, which is also the source of the majority of Stonehenge’s bluestones. These bluestones, formed through the crystallization of molten rock, are among the earliest stones placed at Stonehenge, estimated to have been erected about 5,000 years ago during the Bronze Age.

However, the recent study, published in the Journal of Archaeological Science, challenges this long-standing theory. The researchers embarked on an extensive analysis of 58 rock samples from various locations in South Wales, the Welsh Borders, the West Midlands, and Somerset. The analysis involved the use of traditional optical petrography, as well as advanced techniques such as portable XRF, automated SEM-EDS, and Raman Spectroscopy.

The key revelation from this analysis was that the Altar Stone’s composition did not match any of the sample locations examined. This crucial finding suggests that the Altar Stone does not originate from the Old Red Sandstone of the Anglo-Welsh Basin in South Wales, as previously believed. The unique geological characteristics of the Altar Stone set it apart from the stones found in these regions.

Recent findings reveal that Stonehenge may have been constructed as a symbol of unity among Britain’s early farming communities. Credit: Jan Židlický

Professor Nick Pearce from Aberystwyth University, one of the authors of the study, commented on the significance of these findings, stating, “The view in terms of the conclusions we’ve drawn from this is that the Altar Stone doesn’t come from Wales. Perhaps we should also now remove the Altar Stone from the broad grouping of bluestones and consider it independently.”

One of the distinctive features of the Altar Stone that drew the researchers’ attention was its notably high barium content, a type of metal. This unusual characteristic could serve as a valuable clue in determining its true source.

As the Altar Stone’s origin is called into question, attention is now shifting to alternative regions for its possible source. The researchers propose broadening the scope of investigation to areas in Northern England and Scotland. The geological characteristics, chemical composition, and evidence of Neolithic activity in these regions may hold the key to pinpointing the true provenance of the Altar Stone.

Stonehenge, a monument constructed around 5,000 years ago, has been a subject of intrigue and speculation for centuries. This latest research offers a promising step toward unraveling one of its long-standing mysteries and reevaluating our understanding of this iconic site’s history. Professor Pearce believes that this research will encourage a fresh perspective on Stonehenge’s development.

More information: Bevins, R. E., et al. (2023). The Stonehenge Altar Stone was probably not sourced from the Old Red Sandstone of the Anglo-Welsh Basin: Time to broaden our geographic and stratigraphic horizons? Journal of Archaeological Science: Reports, 51, 104215. doi:10.1016/j.jasrep.2023.104215