Salt

Notholt, A.J.G.; Highley, D.E.. 1973 Salt. London, UK, HMSO, 42pp. (Mineral Dossier No. 7)

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Abstract/Summary

Salt or sodium chloride (NaCl) occurs in nature either in the solid form as rock-salt or halite, or in solution as brine. It is a raw material essential to the heavy inorganic chemical industry, being used principally in the production of chlorine, caustic soda and soda ash which, in turn, are used in a wide variety of other processes. Salt is also used extensively in food processing, such as flavouring dairy products and as a preservative, for snow and ice clearance on roads and as a fertilizer. Salt production began in the United Kingdom in at least Roman times, developing into a large scale industry during the 18th century. The Cheshire salt field has been and remains the principal source of supply, at present accounting for over 90 per cent of the total United Kingdom output. Salt is also produced from deposits in Lancashire and Durham and in County Antrim in Northern Ireland. Other deposits which have been of commercial importance in the past are situated in Worcestershire, Staffordshire, the Isle of Man and Somerset. Rock-salt is widely distributed in England and occurs in rocks of either Zechstein (Upper Permian) or Keuper Marl (Upper Triassic) age in beds varying from a few centimetres to hundreds of metres in thickness. Reserves are extremely large, those in the Cheshire - Shropshire Basin alone amounting to perhaps 400,000 million tonnes. Large reserves· also occur in a number of other saltfields and extensions to known deposits are likely to be found. Salt is produced in the United Kingdom by the controlled pumping of artificial brines created by introducing water into beds of rock-salt, by pumping natural brines resulting from the solution of rock-salt by groundwater, by conventional underground mining methods for the production of rock-salt and, on a very small scale, by evaporating sea-water. Most of the brine pumped is used directly in the manufacture of either chlorine and caustic soda (sodium hydroxide) by electrolysis, or soda ash (sodium carbonate) by the Ammonia-Soda or Solvay process. Brine is also used in the production of white salt by evaporation. Rock-salt, accounting for about 18 per cent of the total salt extracted in the United Kingdom, is crushed before use for winter road maintenance. The production of salt by natural brine pumping has in the past caused considerable damage due to subsidence. Subsidence is still a problem but is less extensive than formerly; it is apparently not caused by rock-salt mining and controlled methods of brine pumping. The United Kingdom is one of the world's major producers of salt, ranking fifth in 1970, when output amounted to 9,029,000 tonnes. Of this total 5,698,000 tonnes comprised salt-in-brine, 1,733,000 tonnes was brine salt and 1,598,000 tonnes was rock-salt. Exports amounted to 582,600 tonnes, valued at about £3,989,000, destined chiefly for Sweden, Nigeria, Finland and the USA. Imports were nearly 140,600 tonnes valued at about £717,000, of which nearly 92,800 tonnes was in the form of fishery salt obtained largely from the Federal Republic of Germany. There are three major salt producing companies in the United Kingdom: Imperial Chemical Industries Limited, by far the largest producer which operates in Cheshire, Lancashire and Durham, British Salt Limited and BP Chemicals International Limited, both of which operate in Cheshire. New Cheshire Salt Works Limited and Ingram Thompson and Sons Limited are two independent producers in Cheshire. The American owned Irish Salt Mining and Exploration Company Limited is the sole salt producer in Northern Ireland. Sea salt is produced on a small scale by the Maldon Crystal Salt Company Limited at Maldon in Essex.

Item Type:	Publication - Report
Programmes:	BGS Programmes > Economic Minerals
Funders/Sponsors:	Institute of Geological Sciences
Additional Keywords:	Mineral, Salt
NORA Subject Terms:	Earth Sciences
Date made live:	25 Jul 2025 17:14 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539896

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