View source for Halite

{{short description|Mineral form of sodium chloride}}
{{Redirect|Rock salt|edible coarse salt|Kosher salt|the cubic crystal structure known as the "rock-salt" structure|Cubic crystal system#Rock-salt structure}}
{{other uses}}
{{Infobox mineral
| name        = Halite
| category    = [[Halide mineral]]
| boxwidth    =
| boxbgcolor  =#e8e8e8
| image       = Halit (NaCl) - Kopalnia soli Wieliczka, Polska.jpg
| imagesize   = 260px
| caption     = Halite from the [[Wieliczka salt mine]], Małopolskie, Poland
| formula     = NaCl
| IMAsymbol   = Hl<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| molweight   = 58.433{{nbsp}}g/mol
| strunz      = 3.AA.20
| system      = [[Cubic (crystal system)|Cubic]]<ref name=geocomhalite>[https://geology.com/minerals/halite.shtml Geology.com: Halite]</ref>
| class       = Hexoctahedral (m{{overline|3}}m) <br />[[H-M symbol]]: (4/m {{overline|3}} 2/m)
| symmetry    = ''F''m{{overline|3}}m
| unit cell   = {{nowrap|a {{=}} 5.6404(1) Å;}} {{nowrap|Z {{=}} 4}}
| color       = Colorless or white when pure. Impurities produce any color but usually yellow, gray, black, brown, red (Depends on isotopes and purity for various colours)<ref name=geocomhalite />
| habit       = Predominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact
| twinning    =
| cleavage    = Perfect {001}, three directions cubic
| fracture    = Conchoidal
| tenacity    = Brittle
| mohs        = 2.0–2.5
| luster      = Vitreous
| refractive  = {{nowrap|n {{=}} 1.544}}
| opticalprop = Isotropic
| birefringence =
| pleochroism =
| streak      = White
| gravity     = 2.17
| density     =
| melt        = 800.7{{nbsp}}°C
| fusibility  =
| diagnostic  =
| solubility  = Water-soluble
| diaphaneity = Transparent to Translucent 
| other       = Salty flavor, may be fluorescent
| references  = <ref name=Handbook>{{cite web |url=http://rruff.geo.arizona.edu/doclib/hom/halite.pdf |title=Halite |website=Handbook of Mineralogy |access-date=16 April 2018 |url-status=live |archive-url=https://web.archive.org/web/20100628052809/http://rruff.geo.arizona.edu/doclib/hom/halite.pdf |archive-date=June 28, 2010}}</ref><ref name=Mindat>{{cite web |url=http://www.mindat.org/min-1804.html |title=Halite |publisher=[[Mindat.org]] |archive-url=https://web.archive.org/web/20110805033506/http://www.mindat.org/min-1804.html |archive-date=2011-08-05}}</ref><ref name=Webmin>{{cite web |url=http://webmineral.com/data/Halite.shtml |title=Halite |publisher=Webmineral |archive-url=https://web.archive.org/web/20041124083935/http://webmineral.com/data/Halite.shtml |archive-date=2004-11-24}}</ref><ref name=Haynes>{{cite book |editor=Haynes, William M. |year=2011 |title=CRC Handbook of Chemistry and Physics |edition=92nd |publisher=[[CRC Press]] |isbn=978-1439855119 |title-link=CRC Handbook of Chemistry and Physics}}</ref>
}}

'''Halite''' ({{IPAc-en|ˈ|h|æ|l|aɪ|t|,_|ˈ|h|eɪ|l|aɪ|t}} {{respell|HAL|yte|,_|HAY|lyte}}),<ref>{{cite Merriam-Webster|halite}}</ref><ref>{{cite Dictionary.com|halite}}</ref><ref>{{cite web |url=http://dictionary.infoplease.com/halite |title=Halite |website=[[Random House Unabridged Dictionary]] |year=1997 |archive-url=https://web.archive.org/web/20151002235932/http://dictionary.infoplease.com/halite |archive-date=2015-10-02}}</ref> commonly known as '''rock salt''', is a type of [[salt]], the [[mineral]] (natural) form of [[sodium chloride]] ([[sodium|Na]][[chlorine|Cl]]). Halite forms [[Cubic (crystal system)|isometric crystals]].<ref>{{cite book |last=Bonewitz |first=Ronald Louis |title=Rocks and Minerals |date=2012 |publisher=[[DK Publishing]] |isbn=978-0-7566-9042-7 |page=110}}</ref> The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on inclusion of other materials, [[impurities]], and structural or isotopic abnormalities in the crystals.<ref>{{cite journal |last=Sonnenfeld |first=Peter |title=The color of rock salt—A review |journal=Sedimentary Geology |date=January 1995 |volume=94 |issue=3–4 |pages=267–276 |doi=10.1016/0037-0738(94)00093-A |bibcode=1995SedG...94..267S}}</ref> It commonly occurs with  other [[evaporite]] deposit minerals such as several of the [[Sulfate mineral|sulfates]], [[Halide mineral|halides]], and [[Borate mineral|borates]]. The name ''halite'' is derived from the Ancient Greek word for "salt", {{lang|grc|ἅλς}} ({{transliteration|grc|háls}}).<ref name=Handbook />

== Occurrence ==
[[File:Halite-249324.jpg|thumb|upright|left|Halite cubes from the Stassfurt Potash Deposit, [[Saxony-Anhalt]], Germany (size: 6.7 × 1.9 × 1.7 cm)]]
Halite dominantly occurs within sedimentary rocks where it has formed from the evaporation of seawater or salty lake water. Vast beds of [[sedimentary]] evaporite minerals, including halite, can result from the drying up of [[endorheic|enclosed]] lakes and restricted seas. Such salt beds may be hundreds of meters thick and underlie broad areas.<ref>{{Cite web |title=halite {{!}} mineral |url=https://www.britannica.com/science/halite |access-date=2022-04-22 |website=Britannica  |language=en}}</ref> Halite occurs at the surface today in [[Dry lake|playas]] in regions where evaporation exceeds precipitation such as in the salt flats of [[Badwater Basin]] in [[Death Valley National Park]].

In the [[United States]] and [[Canada]], extensive underground beds extend from the [[Appalachian Basin]] of western [[New York (state)|New York]] through parts of [[Ontario]] and under much of the [[Michigan Basin]]. Other deposits are in [[Ohio]], [[Kansas]], [[New Mexico]], [[Nova Scotia]] and [[Saskatchewan]]. Deposits can also be found near [[Dasol]], [[Pangasinan]], [[Philippines]]{{Citation needed|date=December 2024}}. The [[Khewra Salt Mines|Khewra salt mine]] is a massive deposit of halite near [[Islamabad]], Pakistan. 

[[Salt dome]]s are vertical [[diapir]]s or pipe-like masses of salt that have been essentially "squeezed up" from underlying salt beds by mobilization due to the weight of the overlying rock. Salt domes contain [[anhydrite]], [[gypsum]], and native [[sulfur]], in addition to halite and [[sylvite]]. They are common along the [[Gulf of Mexico|Gulf coasts]] of [[Texas]] and [[Louisiana]] and are often associated with [[petroleum]] deposits. [[Germany]], [[Spain]], the [[Netherlands]], [[Denmark]], [[Romania]] and [[Iran]] also have salt domes.<ref>{{Cite web |title=What is a Salt Dome? How do they form? |url=https://geology.com/stories/13/salt-domes/ |access-date=2022-04-22 |website=geology.com}}</ref> [[Salt glacier]]s exist in arid Iran where the salt has broken through the surface at high elevation and flows downhill.  In these cases, halite is said to be behaving like a [[rheid]].

Unusual, purple, fibrous vein-filling halite is found in [[France]] and a few other localities. Halite crystals termed ''hopper crystals'' appear to be "skeletons" of the typical cubes, with the edges present and stairstep depressions on, or rather in, each crystal face. In a rapidly crystallizing environment, the edges of the cubes simply grow faster than the centers. Halite crystals form very quickly in some rapidly evaporating lakes resulting in modern artifacts with a coating or encrustation of halite crystals.<ref name="Halite">{{cite web |url=http://www.galleries.com/Halite |title=HALITE (Sodium Chloride) |publisher=Galleries.com |access-date=2015-12-16 |url-status=live |archive-url=https://web.archive.org/web/20151216011838/http://www.galleries.com/Halite |archive-date=2015-12-16 }}</ref> ''Halite flowers'' are rare [[stalactite]]s of curling fibers of halite that are found in certain arid caves of [[Australia]]'s [[Nullarbor Plain]].<ref>{{Cite book |last=Wales |first=University Of New South |url=https://books.google.com/books?id=CxwDSfpMq2oC&dq=halite+flowers&pg=PA81 |title=Beneath the Surface: A Natural History of Australian Caves |date=2003 |publisher=UNSW Press |isbn=978-0-86840-595-7 |language=en}}</ref> Halite stalactites and encrustations are also reported in the Quincy [[native copper]] mine of [[Hancock, Michigan]].

== Mining ==
The world's largest underground salt mine is the [[Sifto Canada|Sifto]] Salt Mine. It produces over 7 million tons of rock salt per year using the [[room and pillar mining]] method. It is located half a kilometre under [[Lake Huron]] in [[Ontario]], Canada.<ref>{{Cite web|url=https://www.worldatlas.com/articles/where-is-the-world-s-largest-underground-salt-mine.html|title=Where is the World's Largest Underground Salt Mine|date=14 November 2018 |access-date=2019-04-10|archive-date=2020-07-08|archive-url=https://web.archive.org/web/20200708232049/https://www.worldatlas.com/articles/where-is-the-world-s-largest-underground-salt-mine.html|url-status=live}}</ref> In the [[United Kingdom]] there are three mines; the largest of these is at [[Winsford]] in [[Cheshire]], producing, on average, one million tonnes of salt per year.

== Uses ==
Salt is used extensively in cooking as a flavor enhancer, and to [[Curing (food preservation)|cure]] a wide variety of foods such as [[bacon]] and [[salted fish|fish]].<ref>{{cite book |title=Salted: A Manifesto on the World's Most Essential Mineral, With Recipes |last=Bitterman |first=Mark |year=2010 |publisher=Ten Speed Press |isbn=978-1-58008-262-4 |pages=267–270}}</ref> It is frequently used in food preservation methods across various cultures. Larger pieces can be ground in a [[Burr mill|salt mill]] or dusted over food from a shaker as finishing salt.

Halite is also often used both residentially and municipally for managing ice. Because [[brine]] (a solution of water and salt) has a lower freezing point than pure water, putting salt or saltwater on ice that is below {{convert|0|°C|°F}} will cause it to melt—this effect is called [[freezing-point depression]]. It is common for homeowners in cold climates to spread salt on their sidewalks and driveways after a [[snow storm]] to melt the ice. It is not necessary to use so much salt that the ice is completely melted; rather, a small amount of salt will weaken the ice so that it can be easily removed by other means. Also, many cities will spread a mixture of sand and salt [[Road salt|on roads]] during and after a snowstorm to improve traction. Using [[salt brine]] is more effective than spreading dry salt because moisture is necessary for the freezing-point depression to work and wet salt sticks to the roads better. Otherwise the salt can be wiped away by traffic.<ref>{{Cite book|url=https://trid.trb.org/view/461997|title=Pre-wetting With Salt Brine|isbn=978-0965231008|date=1996|publisher=Center for Transportation Research and Education |access-date=2019-04-10|archive-date=2020-09-13|archive-url=https://web.archive.org/web/20200913051032/https://trid.trb.org/view/461997|url-status=live}}</ref>

In addition to de-icing, rock salt is occasionally used in agriculture. An example of this would be inducing salt stress to suppress the growth of annual meadow grass in turf production. Other examples involve exposing weeds to salt water to dehydrate and kill them preventing them from affecting other plants. Salt is also used as a household cleaning product. Its coarse nature allows for its use in various cleaning scenarios including grease/oil removal, stain removal, dries out and hardens sticky spills for an easier clean.{{citation needed|date=April 2019}}

Some cultures, especially in Africa and Brazil, prefer a wide variety of different rock salts for different dishes. Pure salt is avoided as particular colors of salt indicates the presence of different impurities. Many recipes call for particular kinds of rock salt, and imported pure salt often has impurities added to adapt to local tastes.<ref>{{cite book |title=Salt: A World History|url=https://archive.org/details/saltworldhistory00kurl|url-access=registration|last=Kurlansky |first=Mark |year=2003|publisher=Thorndike Press |isbn=9780786243891 }}</ref> [[History of salt|Historically]], salt was used as a form of currency in barter systems and was exclusively controlled by authorities and their appointees. In some ancient civilizations the practice of [[salting the earth]] was done to make conquered land of an enemy infertile and inhospitable as an act of domination or spite. One biblical reference to this practice is in [[Judge (Bible)|Judges 9:45]]: "he killed the people in it, pulled the wall down and sowed the site with salt."<ref>{{Cite web|url=https://biblehub.com/judges/9-45.htm|title=Bible: Judges 9:45|website=Bible Hub|url-status=live|archive-url=https://web.archive.org/web/20181030021559/https://biblehub.com/judges/9-45.htm|archive-date=October 30, 2018|access-date=November 26, 2019}}</ref>

[[Polyhalite]], a mineral fertilizer, is not an NaCl-polymer, but hydrated sulfate of potassium, calcium and magnesium (K<sub>2</sub>Ca<sub>2</sub>Mg-[[sulfate]]).

[[Shotgun shell]]s containing rock salt (instead of metal pellets) are a ''less lethal'' deterrent.<ref>{{cite web | url=https://www.ammoman.com/blog/rock-salt-shotgun-shells/ | title=Less Lethal Loadout: Rock Salt Shotgun Shells | date=15 September 2020 }}</ref>

== Gallery ==
<gallery widths="133px" heights="130px">
File:Halite-Egypt.jpg|Unusual halite crystals from [[Faiyum]], [[Egypt]]
File:SaltCrystalCasts.JPG|Hopper crystal cast of halite in a [[Jurassic]] rock, [[Carmel Formation]], [[Utah]]
File:Halite-233134.jpg|Sharp halite crystals that have this green color from inclusions of copper minerals (atacamite?)
File:HALIT X NaCl Natriumchlorid WÜRFEL KUBUS 50P.jpg|Large natural crystal of halite, showing cubic crystal form
File:Halite-Nahcolite-60710.jpg|Pink color halite on a matrix covered with minute [[nahcolite]]
File:Halite-57430.jpg|Halite from [[Potash Corporation of Saskatchewan]] Mine in [[Rocanville, Saskatchewan]], Canada
File:Halite Dead Sea Beach Pebbles.JPG|Pebbles made of halite from the western [[Dead Sea]] coast, Israel
</gallery>

==See also==
* [[Coarse salt]] (edible)
* [[Salt tectonics]]
* [[Grozon coal and saltworks]]

==References==
{{reflist}}
{{Commons category|Halite}}

== External links ==
{{refbegin}}
* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York {{ISBN|0-471-80580-7}}
* Anthony, John W; Bideaux, R.A.; Bladh, K.W.; Nicois, M.C. (1997). ''Handbook of Mineralogy: Halides, Hydroxides, Oxides'', Mineral Data Publishing, Tucson {{ISBN|0-9622097-2-4}}
* [http://www.minerals.net/mineral/halides/halite/halite.htm Minerals.net] {{Webarchive|url=https://web.archive.org/web/20081221201301/http://www.minerals.net/mineral/halides/halite/halite.htm |date=2008-12-21 }}
* [http://www.onlinerocksalt.co.uk/resources/MSDS-Rock-Salt.pdf Material Safety Data Sheet] {{Webarchive|url=https://web.archive.org/web/20120425234840/http://www.onlinerocksalt.co.uk/resources/MSDS-Rock-Salt.pdf |date=2012-04-25 }}
* [http://www.desertusa.com/mag99/jan/papr/geo_halite.html Desert USA] {{Webarchive|url=https://web.archive.org/web/20071214234626/http://www.desertusa.com/mag99/jan/papr/geo_halite.html |date=2007-12-14 }}
* [http://www.minsocam.org/MSA/collectors_corner/arc/mihalite.htm Halite stalactites] {{Webarchive|url=https://web.archive.org/web/20071222204331/http://www.minsocam.org/MSA/collectors_corner/arc/mihalite.htm |date=2007-12-22 }}
{{refend}}

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[[Category:Sodium minerals]]
[[Category:Chloride minerals]]
[[Category:Cubic minerals]]
[[Category:Minerals in space group 225]]
[[Category:Edible salt]]
[[Category:Evaporite]]
[[Category:Luminescent minerals]]
[[Category:Industrial minerals]]
[[Category:Rocksalt group]]