A manufactura do sal é unha das industrias químicas máis antigas.<ref>{{cite web | url=http://www.salt.org.il/arch.html | title=Salt made the world go round | work=Salt.org.il | date=1 de setembro de 1997 | accessdate=7 de xullo de 2011}}</ref> Unha das principais fontes de sal é a [[auga mariña]], que posúe unha [[salinidade]] dun 3,5%. Isto significa que hai uns 35 g de [[sal mariño|sales disoltas]], predominantemente [[ión]]s de [[sodio]] ({{chem|Na||+}}) e [[cloro]] ({{chem|Cl||-}}), por quilogramo de auga.<ref>{{Cite journal | last1 = Millero | first1 = F. J. | last2 = Feistel | first2 = R. | last3 = Wright | first3 = D. G. | last4 = McDougall | first4 = T. J. | title = The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale | doi = 10.1016/j.dsr.2007.10.001 | journal = Deep Sea Research Part I: Oceanographic Research Papers | volume = 55 | pages = 50 | year = 2008 }}</ref> Os [[océano]]s representan unha fonte virtualmente inesgotable de sal, e por mor desta abundancia de subministración non se ten calculado con exactitude o número de reservas dispoñible.<ref name=IHS/> A [[evaporación]] de auga mariña é o método de produción máis habitual nos países costeiros con baixos niveis de [[Precipitación (meteoroloxía)|precipitacións]].<ref>{{cite web | url = http://visibleearth.nasa.gov/view.php?id=2631 | title = Salt Ponds, South San Francisco Bay |work= NASA Visible Earth |publisher=NASA |accessdate=5 May 2015}}</ref>
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Elsewhere, salt is extracted from the vast sedimentary deposits which have been laid down over the millennia from the evaporation of seas and lakes. These are either [[salt mine|mined]] directly, producing rock salt, or are extracted in solution by pumping water into the deposit. In either case, the salt may be purified by mechanical evaporation of brine. Traditionally, this was done in [[Open pan salt making|shallow open pans]] which were heated to increase the rate of evaporation. More recently, the process is performed in pans under [[vacuum]].{{sfn|Kostick|2011}} The raw salt is refined to purify it and improve its storage and handling characteristics. This usually involves recrystallization during which a brine solution is treated with chemicals that precipitate most impurities (largely magnesium and calcium salts). Multiple stages of evaporation are then used to collect pure sodium chloride crystals, which are [[kiln]]-dried.<ref>[http://web.archive.org/web/20090409144219/http://www.saltsense.co.uk/aboutsalt-prod02.htm About salt: Production]. The Salt Manufacturers Association</ref> Some salt is produced using the [[Alberger process]], which involves vacuum pan evaporation combined with the seeding of the solution with cubic crystals, and produces a grainy-type flake.<ref>{{cite web |url=http://www.britannica.com/EBchecked/topic/12642/Alberger-process |title=Alberger process |work=Manufacture of salt: Uses of artificial heat |publisher=Encyclopædia Britannica online |accessdate=9 October 2013}}</ref> The [[Ayoreo people|Ayoreo]], an indigenous group from the Paraguayan [[Gran Chaco people|Chaco]], obtain their salt from the ash produced by burning the timber of the Indian salt tree (''Maytenus vitis-idaea'') and other trees.{{sfn|Schmeda-Hirschmann|1994}}
OneO ofsal theextráese largesttamén [[saltde mining]]depósitos operationssedimentarios informados thedurante worldmiles isde atanos thepola evaporación dos [[Khewramar]]es Salte Mine[[lago]]s. inEstes Pakistan.depósitos Theminanse minedirectamente hasproducindo nineteensal storeysen rocha, elevenou ofextráense whichen areforma underground,de andsolución bombeando auga nos depósitos. Nos dous casos o sal extraído purifícase mediante un proceso de evaporación mecánica.{{convertsfn|400Kostick|km|abbr=on2011}} ofO sal refínase para purificalo e mellorar as súas características de almacenamento e passagesmanexo. TheIsto saltadoita isfacerse dugpor outmedio bydunha therecristalización no que se trata con produtos químicos para precipitar a maioría de impurezas, principalmente sales de [[roommagnesio]] ande pillar[[calcio]].<ref>[http://web.archive.org/web/20090409144219/http://www.saltsense.co.uk/aboutsalt-prod02.htm method,About wheresalt: aboutProduction]. halfThe theSalt materialManufacturers isAssociation</ref> leftParte indo placesal toproducido supportobtense thepor uppermedio levels.do Extraction[[proceso ofAlberger]], que consiste nunha evaporación ó [[Himalayan saltbaleiro]] iscombinada expectedcunha tosementación lastda 350solución yearscon atcristais thecúbicos.<ref>{{cite presentweb rate|url=http://www.britannica.com/EBchecked/topic/12642/Alberger-process |title=Alberger process |work=Manufacture of extractionsalt: Uses of aroundartificial 385heat |publisher=Encyclopædia Britannica online |accessdate=9 October 2013}}</ref> Unha das maiores operacións de extracción de sal do mundo está na [[Mina de sal de Khewra]] en [[Paquistán]]. Esta mina ten 19 plantas,000tons11 delas baixo terra, e uns 400 km perde annumpasaxes.<ref name="The Seattle Times">{{cite news |last=Pennington |first=Matthew |title=Pakistan salt mined old-fashioned way mine|url=http://seattletimes.nwsource.com/html/nationworld/2002159747_saltmine25.html |accessdate=11 October 2013 |newspaper=The Seattle Times |date=25 January 2005}}</ref> -->
