Coal Mining ::
Coal seams are the compressed fossilised remains of tropical forests, which grew 325 million years ago when Europe was part of a larger landmass at equatorial latitudes. The present day Amazon or Niger deltas are comparable environments.
Whilst the coal is the fossilised vegetation, the sandstones and shales separating the coal seams represent the sand banks and muds which supported and buried these forests as a result of oscillations of sea level, and they frequently contain fossilised plant fragments.
The geological succession in North Wales for example contains over 30 coal seams greater than 300mm thick within about 500 metres of Coal Measure strata, with coal seams rarely separated from one another by more than 30 metres.
Not all coal seams are thick enough or of sufficient quality to justify mining.
Those seams that have been mined were given names, which reflected their quality (Brassey Coal, Stone Coal, Crank Coal, etc), their thickness (Five Yard Coal, Main Coal, etc), or locality (Hollin Coal, Nant Coal, etc). In most areas of North Wales the coal seams dip at gradients of between 1 in 3 and 1 in 10, usually to the north-east in Flintshire and the east in Denbighshire.
Other minerals were worked on a small scale, frequently in conjunction with coal. These were iron, especially near Acrefair and Brymbo, fireclay in Rhos and Buckley, and sandstone near Mold. The mining techniques used for the extraction of these minerals were similar to that of coal.
>> Metal Mining for information on coal mining.
>> Investigation for information on research, investigation and remedial work.
>> Mineshafts for information on mineshaft hazards.
Below this depth mining was by pillar and stall techniques, whereby a grid of tunnels were driven in the coal seam, with pillars of unworked coal used to support the workings.
Until the rise of capitalism in the mid 18th century, the majority of mines were shallow and of limited lateral extent, depending on hand labour by a small group of workers with perhaps a horse used to help the women and children haul the coal in baskets.
(far right) This royalty plan of 1832 shows coal being mined by pillar and stall methods at a depth of 90 metres up to the mineral boundary (in this instance a fault) by driving tunnels and leaving coal pillars to support the workings. Upon reaching the fault, the pillars are mined in the retreat to the shafts. The colours are original and represent different royalty payment periods, but also show the sequence of working the coal.
Below this depth mining was by pillar and stall techniques, whereby a grid of tunnels were driven in the coal seam, with pillars of unworked coal used to support the workings.
Until the rise of capitalism in the mid 18th century, the majority of mines were shallow and of limited lateral extent, depending on hand labour by a small group of workers with perhaps a horse used to help the women and children haul the coal in baskets.
(far right) This royalty plan of 1832 shows coal being mined by pillar and stall methods at a depth of 90 metres up to the mineral boundary (in this instance a fault) by driving tunnels and leaving coal pillars to support the workings. Upon reaching the fault, the pillars are mined in the retreat to the shafts. The colours are original and represent different royalty payment periods, but also show the sequence of working the coal.