Resources


	The main resources and extraction areas of limestone are in the Peak District of Derbyshire, the Mendip Hills, parts of South Wales and North Wales, on the borders of the Lake District, parts of the northern Pennines, in the central valley of Scotland and in Northern Ireland.

Limestones are sedimentary rocks composed mainly of calcium carbonate (CaCO₃). With an increase in magnesium carbonate (MgCO₃) content they grade into dolomite. Most limestones and dolomites are hard and durable and useful for aggregate. They are common rock types and consequently widely extracted for aggregate materials. The major source of limestone aggregate is limestones of Carboniferous age, the main resources and extraction areas of which are in the Peak District of Derbyshire, the Mendip Hills, parts of South Wales and North Wales, on the borders of the Lake District, parts of the northern Pennines, in the central valley of Scotland and in Northern Ireland. The two main producing areas, the Mendips and the Peak District, are distinctly different due to major differences in local geology. The limestones of the Mendips are faulted and folded with many clay-filled fissures contaminating the resource. These limestones are therefore ideal for large-scale quarrying for crushed rock aggregate but are generally unsuitable for high purity industrial uses.

Limestone quarry.

In contrast, the limestones of the Peak District are flat-lying and noted for their chemical uniformity and consistency over wide areas. They were originally largely quarried for industrial use, although they are now increasingly used for aggregate. The Mendips are relatively close to south-east England, the major market for aggregates, and a significant proportion of Mendip limestone output is exported to this region, mostly by train, as the two largest quarries in eastern Mendip are rail-linked.

Other major limestones being worked for aggregates include the Devonian limestones of south Devon, the Permian Magnesian Limestone of north-eastern England and, to a lesser extent, the Silurian limestones of the Welsh Borders. Of these the most important resource is the Permian limestone, which crops out in a narrow belt for some 230 km between Newcastle and Nottingham. Dolomites and calcareous dolomites predominate, but in places there is gradation into limestone. These Permian dolomites and limestones are highly variable and are much softer than typical Carboniferous limestone with higher porosity. Hence, they are frequently too weak and friable to make good quality aggregate and are quarried for low-grade applications, such as sub-base roadstone and fill. However, some beds are sufficiently strong, sound and durable to be used as concreting aggregate and several quarries near Maltby in South Yorkshire and near Durham produce such high-quality aggregate materials. Certain of the harder, less porous Jurassic and Cretaceous (Chalk) limestones are also quarried for less demanding aggregate applications.

Limestone resources map.

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