The Mendip Hills, (Mendips) in northern Somerset, are the most southerly Carboniferous Limestone uplands in Britain.
The Mendips comprise three major anticlinal structures, each with a core of older Devonian sandstone and Silurian volcanic rocks. The latter, after crushing, is use in road construction and concrete. Devonian Sandstone is visible around Black Down and Downhead. Carboniferous Limestone, dominates the hills and surround the older rock formations. An outcrop of basalt is also quarried at Moon's Hill.
For centuries the stone of the Mendips, and the Cotswolds to the north, have been used to build the cities of Bristol and Bath, and many Somerset towns. As stone transportation is expensive, the Mendips, and Leicestershire, are important as the nearest sources of hard stone for London and the South East.
The Mendip quarries produce twelve million tonnes of stone a year, employ two thousand people, and have an annual turnover of £150m. Five million tonnes of stone per year is transported by Mendip Rail.