Stonehenge’s altar is not like the other stones.

IFL Science takes a closer look at the massive stones of Stonehenge. Most of them seem to have been transported with great effort from a faraway quarry in Wales. But the monument’s central stone may have come from farther away, in Scotland:

Located on Salisbury Plain in Wiltshire, southwest England, Stonehenge is thought to have been constructed in multiple stages over thousands of years, beginning with the erection of the 56 bluestones around 5,000 years ago. Incredibly, these original building blocks have been traced to the Mynydd Preseli area of Wales, some 225 kilometers (140 miles) west of Stonehenge itself.

However, using a range of techniques including X-ray fluorescence and Raman spectroscopy, the study authors found that the Altar Stone does not match the mineralogy of the Old Red Sandstone (ORS) within the Anglo-Welsh Basin. As a result, they conclude that “the Altar Stone should no longer be included in the “bluestone” grouping of rocks essentially sourced from the Mynydd Preseli.”

Specifically, the researchers detected significantly higher concentrations of baryte – a mineral consisting of barium sulfate – in the Altar Stone than in the Welsh ORS. Seeking alternative sources of sandstone with high baryte content elsewhere in the UK, the authors note that deposits in Cumbria in the north of England and in the Scottish islands of Orkney and Shetland both stand out as candidates for the source of the Altar Stone.

Importantly, both of these regions contain Neolithic monuments, suggesting that the stone in these areas was extracted by local populations and used for ritual purposes. There is also evidence to suggest that long-distance links between Stonehenge and regions as far away as Scotland existed by around 2500 BCE, when the second phase of the monument’s construction occurred.

You can read more about the northern origins of the Altar Stone here, in the Journal of Archaeological Science: Reports.