OR/12/032 Industrial applications
|Hobbs, P R N, Entwisle, D C, Northmore, K J, Sumbler, M G, Jones, L D, Kemp, S, Self, S, Barron, M, and Meakin, J L. 2012. Engineering Geology of British rocks and soils - Lias Group. British Geological Survey, Nottingham, UK. (OR/12/032).|
The Lias Group rocks have provided an important industrial resource, from well before the beginning of the industrial revolution in Britain. The juxtaposition of limestones and clays in the interbeds of the Lias Group formations, combined with other locally derived raw materials such as coal, first allowed local industries to flourish, without the need for imported goods. An example of this was the alum industry, which was one of the first chemical industries in Britain. Other examples include the brick and cement industries, both of which were vital in the development of other major industries, such as civil engineering. Less well-known ‘cottage’ industries, such as the production of ‘jet’ ornaments in North Yorkshire, flourished while fashionable in Victorian times. The abundance of fossils, occasionally of a spectacular nature, within the Lias Group, has benefited the study of palaeontology and also the tourist industry in Dorset and Yorkshire, in particular along the ‘Jurassic Coast’.
Alum is a potassium aluminium sulphate used as a fixing agent for dyes. The alum industry thrived from the late 17th to the mid 19th centuries and supplied alum for dyeing to the massive British woollen industry and also the tanning industry. However, it is believed that it was operating on a small scale from as early as the mid-15th century in Guisbrough when Sir T. Chaloner and associates were excommunicated by the Pope for ending Italy’s monopoly of alum production (Fox-Strangways, 1892). As with many early industries, the alum industry in North Yorkshire developed at the same location as the quarrying of the raw materials. This was largely because transport was difficult, while labour was plentiful. Where necessary, ad hoc transport solutions were constructed, in many cases using the sea as a means of both importing some raw material and exporting the finished product. The industry was therefore centred on the cliff tops around Ravenscar, Sandsend, Kettleness, Saltwick, and Lofthouse, following earlier unsuccessful attempts on the Dorset coast (Jecock, 2003). Quarrying on the cliffs has resulted in major alterations to the natural cliff profiles, which are clearly seen today (Figure 4.1) (Osborne & Bowden, 2001). Frequently, multiple industries, sourced solely from the Lias Group formations, were located within the same small area, though not necessarily contemporaneously. A good example of this is found at Kettleness where the important alum industry, along with the smaller cement, iron, and jet industries, lasted from 1727 until 1871, and has been described in detail by Jecock (2003).
The source material was shale from the Alum Shales Member of the Whitby Mudstone Formation. The middle part of the member, the ‘Main Alum Shales’, is particularly low in calcium carbonate and high in sulphate, and hence proved suitable for alum production. The on-site process called ‘calcining’ involved burning shale interlayered with wood in a large pile known as a ‘clamp’. In some cases these were cut into the bedrock in cells separated by ‘baulks’. The calcining process would take months to complete. Oxidised pyrite, and the resulting sulphate, reacted with the aluminium silicates from the shale. The aluminium sulphate produced then reacted with potash from the burning of brushwood or seaweed to produce potash alum. This last reaction was later replaced by producing ammonium alum from the reaction with urine, the bulk of which was shipped in from London (Jecock, 2003; Rayner & Hemingway, 1974). The alum was then concentrated and purified in liquid form by cycles of boiling and cooling in ‘steeping’ pits. These operations were again carried out on site. The pure alum was finally exported in crystalline form. Transport of raw materials and the alum was frequently by flat-bottomed boats beached at low tide. Access from the works to the beach was either by steep roadway using horse and cart, or by inclined tunnel. Evidence of rutways cut into the rock platform can still be found on the foreshore at Kettleness (Jecock, 2003). Over 20 tonnes of shale was required to produce 1 tonne of alum. The industry in North Yorkshire was replaced in the late 19th century by a process based on the treatment of Coal Measures carbonaceous shales by sulphuric acid. The hazards of setting up industries adjacent to sea-cliffs was demonstrated when the operations at Kettleness were disrupted by a major landslide within the sea-cliff in 1829 which destroyed the original alum house.
The preserved remains of the Peak Alum Works can be visited at Ravenscar. Other industrial archaeology remains are at Saltwick, Kettleness, and Boulby. English Heritage and the National Trust are responsible for investigating, archiving and preserving some of these sites.
The Lias Group mudstones have been used for brick and earthenware manufacture since the Roman times (Woodward, 1893). Currently, there are a small number of brick-making operations within the Lias. One of these is operated by Northcot Bricks Ltd. at Wellacre, near Blockley, in Gloucestershire. Here, the Charmouth Mudstone Formation supplies the raw material for facing bricks (Figure 4.2).
Several former brick clay quarries are being converted to landfill. The liner materials are frequently sourced from the mudstone formations used for brick manufacture, and quarrying operations may be run in parallel with landfill development. An example of landfill embankment emplacement at Sidegate Lane landfill site, Finedon, Northamptonshire, is shown in Figure 4.3.
In the East Midlands, the Charmouth Mudstone Formation (previously referred to as Middle Lias mudstones and siltstones) has provided brick clays (Berridge et al., 1999; Bloodworth et al., 2001).
During the 19th century hydraulic lime was produced from the Blue Lias in Dorset and Somerset, from the Alum Shale Member (formerly referred to as Cement Shales from the Alum Shale Series/Formation) of the Whitby Mudstone Formation in North Yorkshire (Rayner & Hemingway, 1974), and from the Barnstone Member of the Scunthorpe Mudstone Formation in the East Midlands (Carney et al., 2002). The process consisted of calcining in kilns and grinding to a fine powder. The heated calcium carbonate produced calcium oxide (quick-lime) with carbon dioxide given off. This unstable compound reacted with water to produce calcium hydroxide. This could then be mixed with sand to make mortar. Exposed to air, this slowly took on carbon dioxide and reverted to calcium carbonate (carbonation). The industry supplied several watertight Victorian structures at Scarborough (Fox-Strangways, 1892). The industry has recently been revived on a small-scale in the Blue Lias Formation at Tout quarry, Somerset, in order to provide authentic construction materials for restoration and conservation.
Cement has been produced in the Rugby area since 1820, the first operations having been sited at Newbold. Cement was produced under the ‘Portland’ name from 1870. Portland cement is composed principally of anhydrous calcium silicates, and is made by calcining a mixture of clay, silica and limestone to about 1,500°C. Currently, cement is produced from the Blue Lias at two locations in Rugby (Figure 4.4).
Some production of limestone for cement was closely associated with ironstone working, during the 20th c., in the Marlstone Rock Formation in Lincolnshire, Leicestershire, and Rutland.
The once-thriving Teesside iron industry was based on the mining of the Kettleness Member of the Cleveland Ironstone Formation (Howard, 1985; Tuffs, 1999). It contains beds of siderite and berthierine, often somewhat nodular, ooidal ironstone, which occurs at the tops of sedimentary rhythms. There are six, named, ironstone bands which are best developed in the Guisborough-Loftus area near Middlesbrough, and were mined here and elsewhere in East Cleveland (Tuffs, 1999), and also in Rosedale and Eskdale. In these areas they form up to 20 per cent of the thickness of the formation. These were worked during the mid 19th to early 20th centuries. A few mines were situated near the cliff edge as at Huntcliff, Brotton (Chapman, 1997). The raw materials and products were transported by a network of railways, and via a specially constructed harbour, Port Mulgrave, between Staithes and Runswick Bay (Osborne & Bowden, 2001). The Cleveland Ironstone Formation at Kettleness was exploited for a short while during the 1830’s at its outcrop on the foreshore and transferred directly to beached cargo vessels (Jecock, 2003).
A scattered iron industry was operated, beginning in the 1870’s but principally during the 20th c., in the East Midlands, stretching from Corby to Scunthorpe. This used mainly shallow quarries, and in a few cases mines, connected by a complex network of railways and roadways. In the East Midlands, ironstone with a high carbonate content was quarried and mined on a small scale from the Marlstone Rock Formation, for example at Holwell and Wartnaby (Leicestershire) (Carney et al., 2002), and at Harlaxton, Caythorpe, and Fulbeck (Lincolnshire) (Berridge et al., 1999). However, the greater part of the industry, between Corby and Lincoln, and in the Wellingborough area of Northamptonshire, exploited low-carbonate ironstone in the nearby Northampton Sand Formation (Inferior Oolite Group) overlying the Whitby Mudstone Formation (Tonks, 1988). In many cases the two sources were combined to form a self-fluxing ore with optimum composition (Carney et al., 2002). The industry has now ceased, principally due to much greater volumes being readily obtainable from overseas, and the workings and infrastructure largely infilled and abandoned. Some quarries transferred to small-scale limestone extraction for cement, as this constituted the ironstone’s overburden.
Jet is a soft or hard, brown, lustrous, high-grade lithified lignite, representing fossilised driftwood of the monkey-puzzle (araucaria) tree, which is capable of being carved and polished to give a black colour. In North Yorkshire, the lowermost part of the Mulgrave Shale Member of the Whitby Mudstone Formation contains a 7 m bed called the Jet Rock. Near the top of the Jet Rock, sporadic bodies of jet were mined for making jewellery and ornaments, principally during the mid-19th century. At the foot of the cliffs at Sandsend, Runswick Bay, and Saltwick, the remains of so-called ‘hob-holes’ can be found which are shallow, adits dug into the cliff at beach level (a process known as ‘dessing’). Some of these have collapsed. Whilst much primitive gathering was done by beachcombing, the in-situ jet was usually excavated as elongate slabs, known as ‘plank jet’, up to 2 m in length (Rayner & Hemingway, 1974; Fox-Strangways, 1892). In addition, jet was mined at Kettleness, on the cliff below the alum workings (Jecock, 2003), and also inland at Bilsdale, Bransdale, and Rosedale (Osborne & Bowden, 2001). The jet industry largely came to be associated with the town of Whitby where it was crafted and sold. The use of jet for ornamental purposes, such as brooches, has been traced back to the Romans and Celts (Fox-Strangways, 1892).
The principal Lias Group rocks that have been used as a source of building stone are limestones and, to a much lesser extent, sandstones. Limestones within the Lias Group have been purposely quarried or mined for building stone, generally for local use (Woodward, 1893), but more often on an ad hoc basis where present as overburden in the pursuit of other minerals, and on the coast where quarrying and transport by sea was easy (Smith, 1974). Examples of limestone building stones exploited in the Lias Group are given in Table 4.1 (Smith, 1999).
|Hornton (f)||Marlstone Rock||Edgehill, Banbury (Oxon.)|
|Wroxton (f)||Marlstone Rock||Hornton Grounds, Wroxton Heath (Oxon.)|
|Blue Lias Marble||Blue Lias.||Tout, Charlton Adam, Charlton Mackerell, Keinton Mandeville (Somerset)|
|Ham Hill (s)||Bridport Sand||Ham Hill, Stoke-sub-Hamdon, (Somerset)|
|Ham Hill (s)||Bridport Sand||Norton, Stoke-sub-Hamdon (Somerset)|
|Marlstone Rock||Grantham (Lincs.)|
The Lias Group limestones are not often used for ‘dressing’ stone, because of poor durability, poor frost-resistance, and thin bedding. They are more usually applied as thin ‘coursed’ stone. The Hornton, Wroxton, Blue Lias Marble, and Ham Hill varieties (Table 4.1) are either still quarried, or have been in the recent past (Hardy, 1999). Formerly, much more widespread use was made of Lias Group limestones for very localised construction. The Blue Lias Formation limestones were traditionally used in central Somerset in the form of large, flat wall, and floor/paving slabs.
The Marlstone Rock Formation, overlying the Dyrham Formation, or the Charmouth Mudstone Formation in the East Midlands Shelf, forms distinct escarpments and outliers, for example on the southeast edge of the Vale of Belvoir in the East Midlands (Carney et al, 2002). Here the formation has been used in the past to supply local building stone, in addition to its more recent use as a source of iron. However, the limestone/ironstone has proved to weather badly and is no longer in use.
In South Wales, limestones from Sutton, near Bridgend (Glamorgan) were of good quality and used for building and walling. Similar stone was quarried at Shepton Mallet and at Street, Somerset (Woodward, 1893).
Currently, building stone is extracted in Somerset (Yeovil, Somerton, Downslade, Tout), Avon (Stowey), Oxfordshire (Balscote), Gloucestershire (Marshfield), Warwickshire (Avon Dassett, Edgehill, Wellesbourne). Other smaller quarries in these counties supply aggregate and ornamental stone (Cameron et al., 2002).
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<ref>tag; name "Woodward 1893" defined multiple times with different content
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