Tuesday, 17 November 2020

Urban Geology (mostly London, I'm afraid)

 Urban Geology (mostly London, I'm afraid)

Roger Steer has brought THIS WONDERFUL RESOURCE to my notice. It is an excursion guide to the rocks of the built environment, mostly of London, but with a little of Birmingham and Doha, Qatar. It is mainly the work of Ruth Siddall of University College, London, following on from the work of Eric Robinson.

The amount of work which has gone into the many articles is phenomenal. I learned more about Larvikite by reading the London Pub article than I knew before. It is not a syenite but a monzonite with equal amounts of plagioclase and K-feldspar. These are in the form of interlaced laminae forming an antiperthite. These antipethitic feldspars are iridescent and this is known as schillerescence.

But it is not only igneous rocks which are discussed in detail. The fossils of Portland Stone are described and illustrated.

Two sections through once articulated valves of L. gibbosa, now leached away. By chance, the mason has cut through along the long axes of the shells giving the effect of ‘angel wings’. The ribs and costae can be seen on the upper example of the two. Once again, this is from the Roach used on the new wing of BBC Broadcasting House. 

One photograph illustrates that this is indeed Urban Geology - the scale is indicated by a fag end!

I have just started reading this huge archive and it is a cornucopia of geological insights and delights! A pity it is mostly in London. 

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