William sent in a link to an MSN story. A couple of months ago geologists claimed the blue stones at Stonehenge mainly came from Wales – but a few of them had origins elsewhere. One of these was the Altar Stone. They said it came from somewhere up north – and thought it worthwhile to look at rock formations in Scotland. Why they said Scotland rather than shall we say, northern England, must have had something to do with their suspicions. It now turns out the Altar Stone does indeed come from Scotland – with an origin in the NE. About as high as you can get – 400 miles or so from Stonehenge.
The problem here is the manner of its transportation. Was it a glacial erratic moved by the snout of a glacier at some indeterminant point during the Ice Ages. Mind you, archaeologists will be gazing at maps to see if it is possible that humans transported the stone to Salisbury Plain.
No doubt more will be revealed in due course.
See for example https://www.ucl.ac.uk/news/2024/aug/stonehenge-altar-stone-came-scotland-not-wales …