Up on Carningli today I found several boulders of the rock which I call rhyolite -- it is typically very fine-grained and even glassy in appearance, and has this typical grey-blue colour. The weathered surface of rhyolite boulders is often cream or white. But this one is distinctly spotty, rather like the famous spotted dolerites.
There are some spotted dolerites on Carningli too. There are also quite wide expanses where rhyolites outcrop at the surface-- but I'm note sure where this one has come from. The whole mountain is littered with erratics, many of which have come from within a mile or so of the place where they are now found.
I'm not sure if there are any spotted rhyolites at Stonehenge -- maybe Myris knows.....
No comments:
Post a Comment