Monday, 29 November 2021

A Brief Exploration of Jervis Lum

A sample of siltstone from Jervis Lum

Continuing my exploration of Norfolk Heritage Park, I then went to have a look at Jervis Lum, a wooded dell set on the south-western edge of the park, which is ancient woodland and was incorporated into the park by compulsory purchase in 1956.
Approaching its southern end, a large footbridge spans a surprisingly deep valley that is cut into the mudstone and siltstone of the Pennine Lower Coal Measures Formation, which I hoped were clearly exposed in places.
The footbridge over Jervis Lum

Making my way down to the stream that runs through the valley, I soon encountered a very familiar sight of small blocks of sandstone littering the streambed, with a small section of siltstone and mudstone in the stream bank, covered in a mixture of unsorted rock fragments and mud.
A stream bank exposure in Jervis Lum

A little further downstream, the bedding plane of the siltstone/mudstone is exposed in the streambed and, at a slightly higher level in the stream bank, this has been weathered into yellowish clay. Obtaining a fresh sample with my Estwing hammer, it split easily to reveal an orange gelatinous material; however, unlike the rock encountered in Shirtcliff Brook, although quite friable, I couldn’t crumble it into fine mud with my fingers and it survived the journey home, with most of the sample remaining intact.
Fragments of my sample of siltstone from Jervis Lum

The sporadic rock exposures, in both the streambed and stream banks, also include flaggy sandstone that is not easily accessible, but this does also occasionally outcrop in the slopes above the stream.
Flaggy sandstone exposed in the stream bed

The sample that I obtained is a pale grey, fine grained laminated sandstone that is typical of the undifferentiated Pennine Coal Measures Formation strata, as I have seen in many simple boundary walls and as large blocks that form barriers at the Advanced Manufacturing Park in Rotherham.
A sample of grey sandstone

Further downstream still, more massive sandstone can be occasionally seen in the stream banks but, more often than not, its presence is determined by the larger blocks of sandstone that often occupy the streambed.
Blocks of sandstone in the streambed

In one place, a few ochreous patches are seen in the stream bank, which is usually an indication of the break down of pyrite in a coal seam and, looking on the detailed geological map, the Silkstone coal seam is marked here but I didn’t see any exposures of this.
Ochreous deposits in the stream bank

I spent less than an hour in Jervis Lum, half of which time I spent talking to a fellow walker that I met on the way, and the path stretches for less than 500 metres, much of which is away from the stream. Having set off on a day that I had planned mainly for further exploration of urban Sheffield, this green space provided an unexpected surprise and deserves another visit.
A general view of Jervis Lum

A Walk From City Road to Norfolk Park

The former arch to the refreshment pavilion in Norfolk Park

After having a quick look at the Manor Board School, I headed off down St. Aidan’s Road on my way to Norfolk Heritage Park and immediately stopped to look at the masonry in a terrace of houses that had caught my eye the previous week, because the sandstone used in the houses looked similar to the stone used for the dressings in the school.
Terraced houses on St. Aidan's Road

When briefly investigating the area around City Road and Norfolk Road, I encountered sandstone that had sporadic iron staining, which occasionally gave colour to part of the blocks of stone, and I have assumed that they came from a local quarry in the Silkstone Rock or Parkgate Rock; however, except for Gin Stables on Stafford Street, the only place where I have seen this general ‘ginger nut’ hue is in Handsworth – a distance of 3.5 km as the crow flies.
Artificial stone on St.Aidan's Road

Continuing down the hill to the part of St. Aidan’s Road that is lined with interwar semi-detached houses, I was interested to see that, in addition to brick and occasionally stone, many of their front elevations are faced in artificial stone. As seen at St. Aidan’s church on City Road, this material was becoming popular at this time and it is also used for many of the boundary walls.
The Centre in the Park

Arriving at the south-eastern St. Aidan’s entrance to Norfolk Heritage Park, I headed up to the Centre in the Park, which is built in uniformly buff coloured, medium grained gritstone ashlar. On this occasion, I think that this could be Crosland Hill stone from Huddersfield, because this stone was favoured during Phase 1 of the Heart of the City project in Sheffield – as I reported in StonePlus and Stein in Germany, for Tudor Square and Sheaf Square respectively.
Arbourthorne Lodge

Making my way to Arbourthorne Lodge, which doesn’t appear on the 1855 Ordnance Survey map and I assume was built at the same time as the screen wall at the Granville Road entrance to the park, in 1876, I again noticed orange sandstone blocks in the walling, with a massive gritty sandstone from the Millstone Grit used for the gateposts.
A detail of a gate pier at Arbourthorne Lodge

The 1855 map shows various quarries in the immediate vicinity, with Arbourthorne Quarry still being marked as being active on the 1906 map. This is located on the Silkstone Rock which, although described in the Geological Survey of Britain 1957 memoir as an indifferent building stone, is the probable source of the stone for the lodge.
The 1885 Ordnance Survey map of Arbourthorne

I then had a quick look at the rear of Arbourthorne Cottages, dated to 1841 when the park opened, and again observed an abundance of orange coloured stone – for general walling and some lintels and other dressings.
The boundary wall to their yards; however, is built in an inferior quality sandstone, with laminated silty beds and blocks that are occasionally purplish in colour. This would seem to suggest that the stone is from one of the quarries that have exploited a sandstone found in the undifferentiated Pennine Lower Coal Measures Formation strata here.
A boundary wall at Arbourthorne Cottages

In one location, the masonry of the yard wall to Arbourthorne Cottages South-West has a very reddened surface but, where the surface has weathered away, a grey interior of the blocks has been revealed. Although I have seen such a colour contrast occur when the iron in blue-hearted Coal Measures sandstone oxidises - as in the buildings of Handsworth and in Bowden Housteads Wood – I think that a fire may be responsible in this instance.
Reddened sandstone at Arbourthorne Cottages

Returning to the main path through the park, I stopped to photograph the front elevations of the estate cottages. Although the park was sited downwind of the principal industrial areas, they have still been blackened by the industrial pollution, which contributed to George Orwell’s opinion that "Sheffield, I suppose, could justly claim to be called the ugliest town in the Old World…", when writing The Road to Wigan Pier in 1936.
Arbourthorne Cottages
Sheffield is a very different place today, with most of the iron and steel works and associated industries, which constantly belched coal smoke, having disappeared and from Norfolk Heritage Park, there are now clear views over the city.
A panaromaic view from Norfolk Heritage Park

I finished this leg of my walk by having a look at the ornate pedimented arch, which was originally the entrance to the refreshment pavilion, built in 1912 to commemorate the 12th Duke of Norfolk giving the park to the City of Sheffield. 
The pedimented arch in Norfolk Park

Sunday, 28 November 2021

Manor and Heeley Bank Board Schools

Manor Board School

Having achieved my primary objective to obtain pieces of crozzle to send to Alessandro Da Mommio in Italy, for petrographic analysis, I had planned to spend the rest of my day photographing various listed buildings in the Park and Arbourthorne Ward of Sheffield, for the British Listed Buildings website.
Manor Board School

Whilst still on Sheffield Road, which is in the Manor Castle Ward, I firstly had a look at the Manor Board School on the corner of Manor Lane, which once comprised three parts: the original Grade II Listed building of 1876 by Innocent and Brown, with later additions by Wightman and Wightman in 1889 (now demolished) and by Charles Hadfield in 1907.
The 1907 addition to Manor Board School

This was the 15th designed by Innocent and Brown, who were responsible for 19 of the Sheffield School Board’s first 21 schools and, although comprising only a single storey with a basement, it shares many of the design details seen at the Walkley Board School, which was built two years earlier – including the Sheffield School Board crest, herringbone masonry and recessed arched windows, with foils, in a Gothic Revival style.
A detail of Manor Board School

The rock-faced walling also looks very similar to that seen in the Walkley Board School and Bolehill School, where Crawshaw Sandstone was obtained from one or more of the quarries that once existed at Bole Hills in Crookes.
Manor Board School

The dressings are made from a massive sandstone, which contrasts strongly with the well bedded sandstone used for the walling, but the frequent brown/orange colouration is very unusual and certainly not a typical characteristic of Stoke Hall stone, which was very often used with Crawshaw Sandstone in the Sheffield Board Schools.
Inscriptions in coarse gritty sandstone

The inscribed stones and the copings to the boundary wall are of quite a different character, being coarse sandstone that is normally associated with the Millstone Grit, however, it could also be very coarse sandstone from the Crawshaw Sandstone or the Loxley Edge Rock – both of which are found in the lower part of the Pennine Lower Coal Measures Formation in north-west Sheffield.
Heeley Bank Board School

With the rest of the school buildings being inaccessible, I continued with my walk around Norfolk Park and Arbourthorne - which I will describe in future posts - before walking up Heeley Bank Road to take a quick a look at the former Heeley Bank Board School, dated 1880.
Heeley Bank Board School

This and the adjoining infants' school was designed by E R Robson, who was architect to the London School Board and employed by the Sheffield School Board to design the School Board Offices, the Central Schools and Firth College on Leopold Street, in Sheffield city centre.
Heeley Bank Infants' School

His Renaissance Revival style, with only the large chimneys and simple Flemish gables forming distinct features, is much more restrained than the work of C J Innocent and this probably reflects a change in policy and a reduction in the level of expenditure by the Board, which had attracted criticism from outside Sheffield.
Heeley Bank Infants' School
The same pattern of building materials appears here, with uniformly buff coloured, well bedded walling stone being used along with massive sandstone for the dressings, which I presume to be Crawshaw sandstone and Stoke Hall stone respectively, together with coarser gritstone for the inscribed gate piers.
An inscribed gate pier

Saturday, 27 November 2021

A Further Investigation of Crozzle

A view of crozzle in plane polarised light by Alessandro Da Mommio

At the end of an afternoon spent in Sheffield, on the last day of March in 2021 - when my main objective was to acquire a sample of Silkstone Rock - I posted a selection of some of my more interesting photographs on Facebook. 

Crozzle used for decorative purposes on a boundary wall

One of these was a photo of crozzle, the black lava like slag that was produced during the now obsolete process of making steel in a cementation furnace and, when Alessandro Da Mommio said he would love to see it under the microscope, I decided to take another trip to Sheffield and obtain a couple of pieces for him.

Samples of crozzle

When researching definitions of minerals for my Language of Stone Blog, I had often made a link to his Alex Streckeisen website, which I think provide very clear definitions of various rocks and minerals, accompanied by his excellent photomicrographs.

The cementation furnace in Sheffield

The cementation process essentially involved alternate layers of wrought iron and ground charcoal being packed into a stone chest, sealed from the air with wheelswarf and then a fire lit to gradually bring it to red heat - with the load then left at that temperature for 7 to 10 days.

An information panel at the cementation furnace in Sheffield

Having obtained a couple more samples of crozzle from City Road, I selected both black and grey samples and, having carefully packaged them to minimise postage costs and jumped through hoops because of BREXIT,
I sent them off to Alessandro in Italy.
Samples of crozzle

The black crozzle is black and very dense, often with glassy surfaces, but there are no obvious inclusions of material of a different character. The grey crozzle that I collected, however, is much less dense and contains irregularly shaped inclusions of a soft white material that scratches very easily with a fingernail.
A view of crozzle in plane polarized light by Alessandro Da Mommio

I know very little about any of the processes for making steel, or the chemistry of slag, but having made a thin section of the black crozzle and examined it with a petrological microscope, Alex informed me that “it is a bit boring in the sense that it only contains silica, glass and bubbles".

A view of crozzle with crossed polars by Alessandro Da Mommio

Having myself been very interested in examining a wide variety of rocks under a microscope, as a geology undergraduate, and more recently when producing my own Glowing Edges Designs – based on the kaleidoscope of colours very often seen when using crossed polars – I fully appreciate his comments.
A view of olivines with crossed polars by Glowing Edges Designs

As seen in nature as quartz, silica appears as a very dull mineral with very little aesthetic merit – viewed with both plane polarised light and crossed polars – and glassy material, for example in volcanic obsidian, virtually disappears from view.

A view of crozzle in plane polarized light by Alessandro Da Mommio

Not having access to a petrological microscope myself and with Alex being very pleased to add such an unusual building material to his collection of thin sections, I consider this to be a great example of post-BREXIT Anglo-Italian collaboration - which will be continued with a piece of coal from Charlton Brook in Sheffield.

A view of crozzle with crossed polars by Alessandro Da Mommio

Friday, 26 November 2021

The Silkstone Rock in Sheffield

Silkstone Rock along the northern approach to Sheffield station

Having obtained a decent sample of Silkstone Rock from the remaining exposure of the quarry face at the old Clay Wood Quarry, at the edge of the Cholera Monument Grounds, I thought that it would now be a good moment to describe my previous efforts to see the best example of this rock formation in Sheffield.
The line of the railway cutting from the Parkway to Sheffield station

When approaching Sheffield railway station from the north, starting at the Sheffield Parkway, the train enters a vertical sided cutting that is perhaps 10 metres deep and approximately 650 metres long, which is lined partly with sandstone masonry retaining walls, but also has extensive exposures of Silkstone Rock along its length.
In places, the cutting is interrupted by short lengths of tunnel but, in several places along its length, it is crossed by various bridges; however, for safety reasons, these exposed sections are surrounded by high brick walls, which need a ladder to be able to see over.
A view along the Sheffield railway station cutting

Nevertheless, being curious, on a couple of occasions when passing time before journeys on the train to Leeds, I discovered a couple of places where I could step up onto some kind of ledge or rail and take a few ‘blind’ photographs, without using the viewfinder on my camera.
Silkstone Rock in the Sheffield railway station cutting

If I captured an area of the cutting, where the rock was exposed, it was more by luck than judgement, as I really didn't have much idea of what I was photographing and, sometimes, although I encountered a good exposure of sandstone, the part of the cutting was in deep shadow.
A view along the Sheffield railway station cutting

Although the restricted number of points of access, with their limited views, prevented me form obtaining a good comprehensive record of the Silkstone Rock here, I was able to determine that is was a yellow/brown flaggy sandstone with cross-bedding.
Silkstone Rock in the Sheffield railway station cutting

Having determined, by trial and error, the places where I could get a view of the bedrock and the best time of the day for them to be illuminated, I made a mental note to return at another time in the not too distant future, when I was in the area.
A view of the Sheffield railway station cutting

With the arrival of the COVID-19 Pandemic in March 2020, just as the weather was improving, my subsquent visits to Sheffield were few and far between for essential shopping only. When finally returning to the site, after the best part of two years, I was very surprised to discover that parts of the best exposures were now substantially overgrown with vegetation.
Vegetation growth along the Sheffield railway station cutting