Red Sandstone in St. Helen's Church III

 

Samples from St. Helen's church in Burghwallis (21 mm diameter coin)

Unless a programme of repairs is undertaken at St. Helen's church in Burghwallis, which requires the renewal of some of the red sandstone, further investigation of its potential provenance using petrographic analysis or even using a hand held X-ray fluorescence spectrometer is unlikely. 

 

The stone library at Sheffield Hallam University

Although I had to undertake stone identification and matching, when working in the building restoration industry in London, and later produced the Triton Stone Library – now in the Redmires Building at Sheffielld Hallam University as part of a slightly larger collection - and often advised Triton Building Restoration Ltd. and have undertaken various projects as a consultant, I have never had access to this equipment and have relied solely on a simple tool kit of a hand lens, bottle of hydrochloric acid, a stainless steel knife and a Wentworth scale. 

 

My tool kit

 

When starting my investigation of mediaeval churches in February 2016, beginning at St. Helen's church in Treeton, I had hoped to reconnect with an interest in standing buildings archaeology, which had been sparked by work at All Saints church in Pontefract. 

 

St. Helen's church in Treeton

Although this never happened in practice and sometimes it seems quite an academic persuit of knowledge, by visiting nearly 150 mediaeval churches and photograph more than 2700 listed buildings in South Yorkshire and the surrounding counties, it has provided me with the type of experience that cannot be achieved in the laboratory.

 

St. John's church in Hooton Roberts

 

By the time I got to St. John's church in Hooton Roberts, I had already visited churches and the historic buildings in Aston, Todwick, Harthill and Whiston and a couple of old quarries on the Rotherham Red variety of the Mexborough Rock and I had seen considerable colour variation, from a typical dull red/purplish colour to mottled yellow/red varieties.

 

The geology around Hooton Roberts

I had passed through this small village very many times, when driving to work from High Green to Doncaster 30 years earlier and on the bus since living in Rotherham and, although I had never stopped to look around, I never doubted that its vernacular architecture is built with Rotherham Red sandstone or the typical light brown/yellowish coloured Mexborough Rock that I got glimpses of at Hooton Quarry and Denaby New Quarry. 

 

Red sandstone on Holmes Lane and nearby houses

It was only when discovering that the outcrops of rock at the top of Holmes Lane and beneath the churchyard wall are actually stongly reddened and that houses on this road and in the immediately vicinity are built with dark plum coloured stone did I start to think more about the geology here. 

 

Mexborough Rock affected by the Don Monocline

Having looked at the geological memoir and updated maps, and seeing that this is marked as the Pennine Upper Coal Measures Formation (PUCMF), I queried this with the British Geological Survey - based on the apparent dip of the roadside outcrops that is in the opposite direction to the dip of the strata affected by the Don Monocline on the south side of the River Don. 

 

Villages in Rotherham set on PUCMF sandstones

Now realising that the reddening of the soil to the north-east of Thrybergh Country Park is due to the arid and highly oxidising environment that affected the underlying PUCMF Wickersley Rock during the Permian Period – my observations of reddened building stones and soils in the fields in Thurcroft, Brampton-en-le-Morthen, Morthen and Wickersley have made me have some doubts about their provenance. 

 

The stratigraphic column showing PUCMF strata

 

While writing this Language of Stone Blog post, I compared small samples of red sandstone from St. Helen's church in Burghwallis to various specimens of Rotherham Red sandstone that I had collected from St. Helen's church in Treeton, quarries at Canklow Woods and West Bawtry Road in Rotherham and a drill core from my own house. 

 

Specimens of red sandstone in my rock collection

In July 2023, when visiting St. Peter's church in Old Edlington, I had assumed that the red/purple sandstone used in its fabric was a further example of Rotherham Red sandstone and I also included a couple of small specimens that I had obtained during a later visit. 

 

St. Peter's church in Old Edlington

The best colour match, as seen with the naked eye, were the specimens from St. Peter's church, which also contains medium grained sand as measured on my Wentworth scale. Looking at the specimens with my hand lens, the sand grains themselves looked slightly pink stained and constitute the bulk of the specimens, they have an open texture and are poorly cemented, with degraded feldspar or iron containing minerals not being obvious. 

 

Specimens from Burghwallis (L) and Old Edlington (R)

In comparison, the Rotherham Red sandstone samples have a red/lilac colour, are fine grained, well cemented and contain a considerable proportion of feldspar, clay minerals and oxidised iron bearing minerals, which collectively gives them quite a different appearance. 

 

Photomicrographs of Rotherham Red sandstone

 

When undertaking a stone matching exercise at St. Helen's church in Treeton, to find an alternative to the now unavailable Rotherham Red sandstone, a friend in Poland was curious about this and arranged for one of her colleagues to undertake a petrographic analysis for me. 

 

A summary of the petrographic analysis

 

Thin sections were prepared from a sample taken from St. Helen's church, the drill core and from the quarry at Canklow Woods. I have no experience of undertaking petrographic analysis but, to my eye, all three appear to be identical and I would therefore be very interested to see how they compare with the stone from St. Helen's church in Burghwallis. 

 

Specimens of PUCMF sandstone obtained from the farm track

 

Looking more closely at rocks that I had collected from Hooton Roberts back in 2016 and 2023, but I had just stored away, specimens that I obtained from the bank of a farm track to the north-east of the village and from the foundations of a house at the top of Holmes Lane, their colours and textures are much closer to the specimens from St. Helen's church in Burghwallis than those of Rotherham Red sandstone. 

 

Specimens of PUCMF sandstone obtained from Holmes Lane

Although this is by no means proof that the stone at Burghwallis was obtained from a quarry in the local PUCMF sandstone, the dull red/purple sandstone that I found at Hooton Roberts and later in old walls, farm buildings, houses and a few small roadside outcrops in Clifton, which is set on the Magnesian Limestone escarpment, demonstrates that the strata immediately beneath the Carboniferous/Permian unconformity can be uniformly reddened, and not just with a mottled red/yellow colouration as seen at St. James' church in High Melton.

 

Red sandstone in Clifton