Although we may speak of coalfields in terms of counties – social, administrative, or political distinctions – nature knows its own bounds. The Yorkshire coalfield is only one part of the continuous coal measures that spread across Yorkshire, Derbyshire and Nottinghamshire. The coal measures themselves consist of a variety of individual coal seams occurring between sandstones, clay bands, shales and other strata, each of which vary in thickness and extent over the area and may include local geological disruptions or faults. They extend as far north as Leeds and far south as Nottingham.
The city of Sheffield marks a central point on the western edge of this area of coal-bearing strata, bounded by the peat-topped Pennine range of older millstone grit and limestone rocks. From here the coal measures dip away gently the further east one goes. The coal measures mostly belong to the Carboniferous period, that is from 350 to 300 million years ago.
Up to the mid-nineteenth century the earliest (and easiest) coal working occurred at the western outcrop, nearest to the surface. As these seams were exhausted, collieries were forced to go deeper, either by deepening existing pits, or more likely following familiar seams as they dipped into the ‘concealed coalfield’ out beyond Doncaster, under the newer rocks of the Permian and Triassic periods. ‘Newer’ is relative in geological time being some 300 to 200 million years ago.
A seam by any other name…
Over time the naming of individual coal seams has tended to reflect the locality in which they were first found or first worked commercially, or the physical properties and uses of the coal. This means different places may call the same seam of coal by different names. With such a profusion of names for the same thing it is not surprising that coal merchants would call similar coals by similar names – and coal masters would seek to match their own minerals to the most salable seams; a sort of brand name if you will.
Coal is coal, right?
Not quite, the different structural and chemical composition of different coal seams made them more or less appropriate for a variety of domestic and industrial uses, whether sorted by size from nuts up to large coal, or washed to improve the product.
- Steam – steam-raising coal that burns very hot with a low ash content – to fire water boilers and raise steam whether for stationary or locomotive engines, whether on land or sea.
- Gas – Coal for the burgeoning gas producers. Before electric light gas lamps and power was often generated and stored in local gasworks.
- House – Domestic fire coal; usually bright and smudgy
- Coke – Baked coal suitable for ironworking and other industrial uses
It was only in the late nineteenth and early twentieth centuries that extensive geological survey work and comparison of coal sections and boring records enabled a greater understanding of the continuity of seams and endeavoured to standardise the terminology.
So, let’s dive down through the strata, in a representative section of the seams in the South Yorkshire coalfield in late Victorian Britain. The precise seams and depths vary from place to place, but the sequence here is illustrative:
In 1910 Matthew Henry Habergham Habershon (1855-1913) colliery manager and mining engineer, and Francis William Hardwick (1861-1934) the first Professor of Mining at the University of Sheffield authored an article on the mining industry surrounding Sheffield and elaborated on the local characters of the seams (names in bold) in the coalfield.
“In the portion of the coalfield adjacent to Sheffield the principal seams are the “Barnsley” of South Yorkshire, know as the Top Hard Seam of Derbyshire and Nottinghamshire; the Silkstone of South Yorkshire, or Blackshale of Derbyshire; and the Parkgate seam which corresponds with the Deep Hard of Derbyshire.The Barnsley seam in the district between Rotherham and Barnsley has been found 9 to 10 feet in thickness, but to the south and east the thickness of the seam is not so great. The Top Hard in Derbyshire and Nottinghamshire has been found to average 4 feet 6 inches to 5 feet 6 inches over a considerable area. The Hard Coal of this seam is semi-anthracitic in character and of special value for steam-raising purposes.
The Silkstone or Black Shale is a house and gas coal of very high quality, and is probably the best known of all the seam of the district. The thickness along the outcrop has been from 4 feet 6 inches to 5 feet, but is variable at greater depths.
The Parkgate of South Yorkshire (Deep Hard of Derbyshire) which lies between the two above-named seams is a seam of very variable thickness, and is worked at various places as a house, gas and steam coal.
In South Yorkshire only one seam is worked between the Silkstone an the Parkgate – the Thorncliffe Thin, a good house, gas and coking coal; in Derbyshire on the same horizon the Tupton is largely worked, and the Piper is worked in some places.
The Swallow Wood seam, which is also known as the Haigh Moor in West Yorkshire, is also worked in the district; this seam lies between the Barnsley and the Parkgate. The Lidget, the Flockton and the Fenton are seams in this horizon and are also worked locally.
Above the Barnsley seam the Kents Thick or High Hazels Coal is worked in the neighbourhood of Sheffield, and the Shafton Coal some 400 to 500 yards above the Barnsley Bed is being worked at collieries further to the North.”
Habershon, M.H.H. & Hardwick, F.W., ‘The mining industries of the district’, pp.350-351, from Porter, W.S. and Watson, A.T. (eds) British Association, Sheffield, 1910. Handbook & Guide to Sheffield: British Association, 1910, pp.342-362
Some years before, in 1892, Horace Broughton Nash (1858-1938) delivered a paper to the Barnsley Naturalist and Scientific Society.
It is he raised the need to look to the lesser-known seams to keep mining in Barnsley alive if and when the Barnsley seam should fail
“As you are well aware, the main seam in the district is the one which takes its name from the town, the well-known Barnsley Bed, valuable alike for its excellent steam and house-fire qualities, the unworked areas of which in the district under notice is now becoming very rapidly exhausted, and in ten years’ time from now very little but postings will be available within a radius of four miles from the town itself. Such then, being the fact, it behoves us to look around and take active measures to ascertain the commercial value, area, thickness, and possibility of those seams still remaining undeveloped in the district, being worked profitably, and to see if by some means they cannot be made in some measure to take its place.
Several of the seams lying above the Barnsley Bed have been opened out during the past two years, but owing to the difference in thickness and inferior quality, and consequently increased cost of working, they have not been able to compete successfully with the thicker and more valuable bed, and their development has therefore been comparatively slow; but still sufficient has been done to show that a very valuable field remains to be opened out and developed as time and circumstances warrant the same, and I purpose to-night giving you a short resumé of the seams of coal likely to be found under Barnsley, showing on the sketch the probable depth to and thickness of each in descending order, and will attempt to describe their quality and thickness as proved in the nearest sinkings and workings to Barnsley.”
Nash, H.B. ‘The unworked coal seams of Barnsley and District’, a paper read before the Barnsley Naturalist and Scientific Society, 15th February 1892, Barnsley: George Shaw, 1892, pp.3-4
Nash’s highlights included:
- Woodmoor, Wath Wood or Summer Bed – averaging 3ft 6inches thick;
- Abdy or Winter Seam – 3 to 3 1/2 feet
- Beamshaw – varying in thickness
- Kents Thin – 1-2 feet
- Whinmoor – 2ft 9 inches
As Richard Sutcliffe would prophesy a few years later:
“At present all thin seams above the Barnsley bed are much neglected, but no doubt a time will come when they will all be turned to good account, and the shafts sunk through them to the thick coal will greatly contribute to their extraction when required. […] It only requires the price of coal to go up a few shillings per ton to enable the thinnest to be worked.”
Sutcliffe, Richard [1849-1930] ‘Notes on the Yorkshire Coalfield’, p.253, in: Transactions of the Manchester Geological Society, Vol. XXV(Part VIII), 1896-97, pp.246-255, Manchester: Manchester Geological Society