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Sunday, 28 February 2010

The Silbury Hill bluestone


This is a pic kindly provided by Pete Glastonbury. The fragment is now on show in the museum at Avebury. Pete says it is very small -- about the size of a thumbnail. Jim says it is hornblende schist:

"However, this one stone fragment is hornblende schist and therefore not of a type normally described as bluestone; it was examined sometime between 1972 and 1983 by the implement petrology committee, and the results were published over 20 years ago (Stone Axe Studies volume 2, ed T Clough & W Cummins, CBA 1988, available to download from ADS). Hopefully myth busted."

....... but it does appear to have some vague spots on it, and on the photo it looks as if it might be spotted dolerite or preselite. Does anybody know anything more?

8 comments:

Anonymous said...

What are the implications if it is a hornblende?

Brian said...

Well, that would be "convenient" from the point of view of people like me, because it would mean that we have yet another rock type from far away -- emphasising yet again that the foreign stones on Salisbury Plain didn't all come from the eastern end of the Preseli Hills. I'm not that bothered really where it came from-- even if it is spotted dolerite that would argue for a "scatter" across the Plain, and would further emphasise the point that the bluestones were not transported in as sacred objects specifically for the Stonehenge project.

Anonymous said...

Brian, you seem to be saying that the geological provenance of a solitary fragment, and it is a tiny fragment at that, of hornblende schist found at Silbury is unimportant?
If it was from Preseli surely it would support the glacial transport theory. Do we find this rock type in Pembroke?
But on the otherhand, the nearest site I am aware of hornblende schist is the Lizard in Cornwall and if this was the origin of the Silbury fragment it would not help your theory. We can't just discount it, I think it's origin is important to the debate.

Brian said...

Thanks, Anon. I'm not saying this fragment is unimportant. It might be, especially if it has come from the Lizard! That would be seriously interesting. I think I'm right in saying that all of the fragments found in the Stonehenge - Cursus area have come from the west. Nothing (except for some packing stones and mauls) appears to be from the N, E or S. That of course does argue for glacial transport -- since if stones were being brought in because of their ritual value, why would they not have been imported from all points of the compass? Yes, it would be great to have that fragment looked at again, and definitively identified. Rob, are you listening?

PeteG said...

something to consider is that the Miners that Drax employed came from Cornwall.
Could this single piece have come from them while they were at work on top in 1776? Maybe from dirt on their tools?
The latest excavations didn't find any more of it.

Brian said...

Interesting thought, Pete! I know that Rob Ixer is very cautious in his interpretations of "strange" stones found around the Cursus etc -- especially those close to roadways -- where there is always a chance of "adventitious" occurrences of very strange and far-travelled stones. The context is all-important. A strange flake on the surface might be suspicious, whereas a strange flake in a "good" archaeological context, maybe in an undisturbed layer a metre below the surface, is more likely to be authentic. I suppose we don't know exactly where Atkinson found this flake?

Anonymous said...

I must say that in the photo the rock does look very like spotted dolerite.
Not every description of the IPG committee was, or is, correct and some are very very wrong.
Hornblende schist suggests to me a poorly informed guess. There is no metamorphic fabric and macroscopical ids are a fool's game.
My, actually your, money is on Preselite. How it got there and when is a far more interesting question.

Anonymous said...

I have studied the stone and it is very clearly a spotted dolerite and very like three other spotted dolerites found at Silbury Hill.

Hornblende schist is an incarnadine herring.

R.A.Ixer