Salt mining extracts naturalsalt deposits from underground. The mined salt is usually in the form ofhalite (commonly known as rock salt), and extracted fromevaporiteformations.[1]
Before the advent of the moderninternal combustion engine and earth-moving equipment, mining salt was one of the most expensive and dangerous of operations because of rapid dehydration caused by constant contact with the salt (both in the mine passages and scattered in the air as salt dust) and of other problems caused by accidental excessive sodium intake. Salt is now plentiful, but until theIndustrial Revolution, it was difficult to come by, and salt was often mined by slaves or prisoners. Life expectancy for the miners was low.
The earliest found salt mine was inHallstatt, Austria where salt was mined, starting in 5000BC.[2]
As salt is a necessity of life, pre-industrial governments were usually keen to exercise stringent control over its production, often through direct ownership of the mines. Whereas the collection of mosttaxes generally required at least the grudging cooperation of the upper classes, ownership of salt mines could provide monarchs with a lucrative source of income for which they did not need to rely on the goodwill of other strata of society such as thenobility to remit to the monarch. For example,Polish kingCasimir the Great relied on salt mines for over a third of his revenue in the14th century.
Ancient China was among the earliest civilizations in the world withcultivation and trade in mined salt.[3] They first discovered natural gas when they excavated rock salt. The Chinese writer, poet, and politicianZhang Hua of theJin dynasty wrote in his bookBowuzhi how people inZigong,Sichuan, excavated natural gas and used it to boil a rock salt solution.[4] The ancient Chinese gradually mastered and advanced the techniques of producing salt. Salt mining was an arduous task for them, as they faced geographical and technological constraints. Salt was extracted mainly from the sea, and salt works in the coastal areas in late imperial China equated to more than 80 percent of national production.[5] The Chinese made use ofnatural crystallization of salt lakes and constructed someartificial evaporation basins close to shore.[3] In 1041, during theSong dynasty, a well with a diameter about the size of a bowl and several dozen feet deep was drilled forsalt production.[4] In Southwestern China, natural salt deposits were mined withbores that could reach to a depth of more than 1,000 m (3,300 ft), but the yields of salt were relatively low.[5] Salt mining played a pivotal role as one of the most important sources of the Imperial Chinese government's revenue and state development.[5]
Most modern salt mines are privately operated or operated by large multinational companies such asK+S,AkzoNobel,Cargill, andCompass Minerals.
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Some notable salt mines include:
| Country | Site(s) |
|---|---|
| Austria | Hallstatt andSalzkammergut. |
| Bosnia and Herzegovina | Tuzla |
| Bulgaria | Provadiya; andSolnitsata, an ancient town which Bulgarian archaeologists regard as the oldest in Europe and the site of a salt-production facility approximately six millennia ago.[6] |
| Canada | Sifto Salt Mine[7] in Goderich, Ontario, which, at 1.5miles (2.4 km) wide and 2 miles (3.2 km) long, is one of the largest salt mines in the world extending 7 km2 (2.7 sq mi).[8][9][need quotation to verify] |
| Colombia | Zipaquirá |
| England | The "-wich towns" ofCheshire andWorcestershire. |
| Ethiopia,Eritrea,Djibouti | Danakil Desert, where manual labor is used.[10] |
| Germany | Rheinberg,Berchtesgaden,Heilbronn |
| Republic of Ireland | Mountcharles |
| Italy | Racalmuto,Realmonte andPetralia Soprana[11] within the production sites managed byItalkali. |
| Morocco | Société de Sel de Mohammedia (Mohammedia Rock Salt company) nearCasablanca |
| Northern Ireland | Kilroot, nearCarrickfergus, more than a century old and containing passages whose combined length exceeds 25 km. |
| Pakistan | Khewra Salt Mines, the world's second largest salt-mining operation, spanning over 300 km. It was first discovered by a horse of Alexander the Great. The mine is still operation till today. |
| Poland | Wieliczka andBochnia, both established in the mid-13th century and still operating, mostly as museums.Kłodawa Salt Mine. |
| Romania | Slănic (withSalina Veche, Europe's largest salt mine),Cacica,Ocnele Mari,Salina Turda,Târgu Ocna,Ocna Sibiului,Praid andSalina Ocna Dej. |
| Russia |
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| Ukraine | Soledar Salt Mine in Soledar, Donetsk oblast. |
| United States |
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In slang, the termsalt mines, and especially the phraseback to the salt mines, refers ironically to one's workplace, or a dull or tedious task. This phrase originates fromc. 1800 in reference to the Russian practice of sending prisoners toforced labor in Siberian salt mines.[17][18]
Sifto Canada Inc. [...] (Goderich Mine)
