Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Friday, 22 April 2011

Those Fishguard Volcanics

In case anybody wonders what those Fishguard Volcanics (now appearing as important in the debitage or debris at Stonehenge) actually look like, you need look no further than the wall of our house.  We live in Cilgwyn, just beneath the lower slopes of Carningli and on the area of Fishguard Volcanics outcrops.  Some of the rocks are exposed along the stream that crosses our land, but for the most part the land surface is covered in till and sands and gravels dumped during the last glacial episode.

But when we built our house extension in 1978 we obtained our facing stone from a small private quarry at Sychpant, about a mile away, where small tors outcrop at the surface.  In the wall we can see blocks of rhyolite, volcanic ash, quartz, and dolerite.  Some of the stones have got abundant vesicles (gas bubble holes) in them.  Some have foliations or stripes, some are rather crumbly, and some are very hard indeed.  What makes many of these stones attractive as facings for buildings is their tendency to split along very flat cleavage planes, which are also iron-stained -- this gives the foxy red colour.  But when you look at the fresh stone the predominant colours are blues and greens.

A geologist would no doubt give these rocks a whole variety of very complicated names, including welded ash flows, tuffites, ignimbrites etc, but as far as my wife and myself are concerned, they are just very pretty rocks........

Click the photo to enlarge.

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