Saturday, 14 July 2018

The Building Stones of Sheffield - Part 2

Fluvio-glacial cobbles at Sheffield Cathedral

After Sheffield Central Library, the next stop on the U3A Sheffield Geology Group field trip to Sheffield city centre was at the adjoining Tudor Square, where there are several large Crosland Hill sandstone planters designed by the artist Stephen Broadbent.

A large Crosland Hill sandstone planter in Tudor Square

Three hand-made plaster maquettes produced at 1:10 of the size of the final sculptures were laser scanned in Liverpool and each of the 173 individual stones were then carved at their full size by a robot at Johnsons Wellfield in Huddersfield, before being carefully assembled together.

An extract from the Building Stones of Sheffield - by Peter Kennett

Moving on to Fargate via Chapel Walk, the group then had a quick look at some of the various stones that were used during the remodelling of Sheffield’s main shopping street back in 1998. These include Spanish and Portuguese granite setts - laid by a gang of paviour masons from Naples - Caithness flagstone and Red Lazonby sandstone, with the latter showing considerable signs of wear and physical degradation. 

Grotesques on the gate posts in the forecourt of Sheffield Cathedral

Crossing Church Street from Fargate, we stopped at the gate posts on the corner of the cathedral forecourt - to appreciate the elaborately carved grotesques - before examining the coarse locally quarried Rivelin Grit, which has been used for Sheffield Cathedral and the Employment Tribunals Service building on East Parade. 

The statue of James Montgomery

The plinth to the James Montgomery statue in the old churchyard provides an example of Cornish grey granite, which was formed during the Hercynian period of mountain building - like the granites from the Iberian peninsular used on Fargate - but its colour and well formed feldspar crystals give it a very distinctive character. 

Examining the alabaster tomb at the rear of Sheffield Cathedral

To the rear of the cathedral next to Campo Lane, an alabaster tomb that was formerly sited inside the cathedral was moved to its current location in the 1960’s and, being soluble in rainwater, has subsequently disintegrated at an accelerated rate – with fractures in the stone being extensively weathered and its surfaces deeply furrowed. 

Historic buildings on St. Paul's Parade
The morning session was finished with a brief look at St. Paul’s Parade, where Browns brasserie provides a good example of Triassic Red St Bees sandstone, and a good look at the sandstones, granites and volcanic green slate that have been used in the Goodwin Fountain, which forms the centrepiece of the Peace Gardens.

Various stones used in the Goodwin Fountain

Here, as in Fargate, not all of the stones used have fared well after nearly 20 years of wetting and drying and, in winter, freezing and thawing. The Permian Clashach sandstone, in particular, has deteriorated to the extent that much of it really needs to be replaced – something that I suspected after I observed its very variable mineral content, when reporting on the project for Natural Stone Specialist soon after it was finished.

A detail of the Goodwin Fountain in Sheffield Peace Gardens

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