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| A detail of the Rough Rock next to the path up the Limb Valley |
The Rough Rock is the most extensive sandstone in the Millstone Grit Group, of which it is the uppermost named sandstone, with many prominent features in the landscapes of the Peak District and Pennines being formed by it.
I have seen the Rough Rock at Beaumont Park in Huddersfield and Roundhay Park in Leeds, and in many buildings in West Yorkshire. The Rough Rock from the Crosland Hill quarry in Huddersfield is uniformly medium/coarse grained and lacks the very coarse pebbly beds that are a feature of Kirkstall Abbey, Leeds Minster and very many of the Victorian historic buildings of Leeds.
In the Sheffield area, it outcrops widely in the area around Brown Edge on the edge of the Peak District National Park, where it was once extensively quarried for stone slates, pavers, flagstone and general building stone; however, it is a part of Sheffield that I have not yet visited and the only places that I had seen it was at Whinfell Quarry Garden and in a quarry at Langsett, while surveying a potential RIGS (Regionally Important Geological Site).
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| Whinfell Quarry Garden |
A few days after my trip to Tickhill, to look at the castle, St. Mary’s church and various historic buildings, I decided to spend an afternoon having another look at the Rough Rock at Whinfell Quarry Garden and around Whirlow, before following Limb Brook down to Ecclesall Woods.
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| The Rough Rock at Whinfell Quarry Garden |
I was interested to note this time that, in one of the quarry faces, there has been some folding and possibly faulting, which is clearly seen in the disruption of the flaggy sandstone, which generally dip a few degrees to the south-east.
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| Disrupted beds in the Rough Rock |
Although I had my Estwing hammer with me, I didn’t see any obvious discrete place where I could obtain a specimen of this rock and, knowing that there were other places on my walk with good rock exposures, I just took a few photographs and continued to another old quarry face adjacent to the path up to Ringinglow.
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| An old quarry face at the bottom of the Limb Valley |
Here there is a succession of alternating beds of flaggy sandstone and mudstone, which have been highlighted by differential weathering to leave substantial overhangs. Shallow angle cross-bedding is seen in the sandstones and in the lower part of the section, there is an excellent example of spheroidal weathering in a bed of iron rich rock.
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| The development of spheroidal weathering in an iron rich bed |
In places, the uniform dip of the strata is interrupted by gentle flexing of the beds, but without the fracturing in the rock that I had seen in Whinfell Quarry Garden a few minutes earlier. Again, I decided not to collect a sample of Rough Rock here and just took a few more photos before continuing with my walk.
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| Gentle flexing in the Rough Rock |
Following the path that runs down the edge of the playing field to the south of Ecclesall Road South, I then diverted into the adjoining woodland to follow the course of Limb Brook, where I had seen many exposures of the Rough Rock in spring 2017.
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| Rough Rock exposed in the streambed of Limb Brook |
This time, at the beginning of the second week in September, I found a few exposures that were clearly visible but quite inaccessible but, after making my way downstream, the undergrowth around the stream banks had grown to such an extent that I was unable to obtain a rock sample.
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| Rough Rock in the streambed of Limb Brook |
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