# Polyhalite > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Polyhalite > Markdown URL: https://mediated.wiki/source/Polyhalite.md > Source: https://en.wikipedia.org/wiki/Polyhalite > Source revision: 1333963741 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Sedimentary mineral}} {{for|polyhalide|Polyhalogen ions}} {{infobox mineral | name = Polyhalite | boxwidth = | boxbgcolor = | image = History museum of Truskavets 081.jpg | imagesize = | alt = | caption = Museum specimen of polyhalite and [anhydrite](/source/anhydrite) | category = [Sulfate mineral](/source/Sulfate_mineral) | formula = {{chem2|K2Ca2Mg(SO4)4*2H2O}} | IMAsymbol = Plhl{{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}} | molweight = | strunz = 7.CC.65 | dana = | system = [Triclinic](/source/Triclinic) | class = Pinacoidal ({{overline|1}})
(same [H-M symbol](/source/H-M_symbol)) | symmetry = ''F''{{overline|1}} | unit cell = a = 6.95 Å, b = 8.88 Å,
c = 6.95 Å; α = 104.06°,
β = 113.94°, γ = 101.15°; Z = 4 | color = Colorless, white, gray; often salmon-pink to brick-red from included iron oxide | colour = | habit = Typically fibrous, foliated, massive; rarely as tabular crystals; pseudo-orthorhombic | twinning = Characteristically polysynthetic on {010}, {100} | cleavage = Perfect on {10{{overline|1}}}; parting on {010} | fracture = Conchoidal | tenacity = Brittle | mohs = 3.5 | luster = Vitreous to resinous | streak = White | diaphaneity = Transparent | gravity = 2.78 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.546 – 1.548 nβ = 1.558 – 1.562 nγ = 1.567 | birefringence = δ = 0.021 | pleochroism = | 2V = Measured: 60° to 62° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = Soluble in water, with precipitation of [gypsum](/source/gypsum) and perhaps [syngenite](/source/syngenite) | impurities = | alteration = | other = | references = [http://www.mindat.org/min-3259.html Polyhalite on Mindat.org][http://webmineral.com/data/Polyhalite.shtml Polyhalite data on Webmin][http://rruff.info/doclib/hom/polyhalite.pdf Handbook of Mineralogy] }} '''Polyhalite''' is an [evaporite](/source/evaporite) mineral, a hydrated [sulfate](/source/sulfate) of [potassium](/source/potassium), [calcium](/source/calcium) and [magnesium](/source/magnesium) with formula: {{chem2|K2Ca2Mg(SO4)4*2H2O}}. Polyhalite crystallizes in the [triclinic](/source/triclinic) system, although crystals are very rare. The normal [habit](/source/crystal_habit) is massive to fibrous. It is typically colorless, white to gray, although it may be brick red due to [iron oxide](/source/iron_oxide) inclusions. It has a [Mohs hardness](/source/Mohs_hardness) of 3.5 and a [specific gravity](/source/specific_gravity) of 2.8. It is used as a valuable fertilizer. Polyhalite was first described in 1818 for specimens from its type locality in [Salzburg](/source/Salzburg), Austria. It occurs in sedimentary marine evaporites and is a major potassium [ore](/source/ore) mineral in the [Carlsbad](/source/Carlsbad%2C_New_Mexico) deposits of [New Mexico](/source/New_Mexico). It is also present as a 2–3% contaminant of [Himalayan salt](/source/Himalayan_salt). The only deposit currently being mined lies under [North Yorkshire](/source/North_Yorkshire), UK, extending under the adjacent North Sea. == Name == The name comes from the German ''Polyhalit'', which comes from the [Ancient Greek](/source/Ancient_Greek) words {{IPA|πολύς}} (''polys'') and ''{{IPA|ἅλς}}'' (''hals''), which mean "many" and "salt", and the German ending ''-it'' (which comes from the Latin ending -ites, which originally also came from Greek), which is used like the English ending ''-ite'' to form the names of certain chemical compounds.{{cite web |url=https://en.oxforddictionaries.com/definition/polyhalite |archive-url=https://web.archive.org/web/20161003065733/https://en.oxforddictionaries.com/definition/polyhalite |url-status=dead |archive-date=October 3, 2016 |title = POLYHALITE {{!}} Meaning & Definition for UK English {{!}} Lexico.com}} Despite the similarity in names between ''polyhalite'' and ''[halite](/source/halite)'' (the naturally occurring form of table salt), their only connection is that both are evaporite minerals. The use of the Greek words for ''many'' and ''salt'' in polyhalite is due to polyhalite consisting of several metals that can form [salts](/source/salt_(chemistry)) in the more general sense of the word salt used in chemistry. == Extraction == The only polyhalite mined in the world comes from a layer of rock over {{convert|1000|m|ft|abbr=on}} below North Yorkshire and extending off the [North Sea](/source/North_Sea) coast in the UK, deposited 260 million years ago. In 2010, the first mining operations of this polyhalite mineral layer commenced at [Boulby Mine](/source/Boulby_Mine), and the mine is in 2023 the only producer of polyhalite, marketed by [ICL Group Ltd.](/source/ICL_Group_Ltd.) as [Polysulphate](/source/Polysulphate). In 2016, [Sirius Minerals](/source/Sirius_Minerals) announced plans for the [Woodsmith Mine](/source/Woodsmith_Mine) in the area.{{cite web|last1=Topf|first1=Andrew|title=Banks backstop Sirius Minerals for $2.9B UK potash mine|url=http://www.mining.com/banks-backstop-sirius-minerals-2-9b-uk-potash-mine/|website=mining.com|date=1 September 2016|accessdate=1 December 2016}} In March 2020, the Woodsmith project was taken over by [Anglo American plc](/source/Anglo_American_plc) and construction of two {{Convert|1500|m|ft|abbr=on}} shafts to reach the {{convert|70|m|ft|abbr=on}} mineral seam was underway in 2015. These will reach a mineable area of around {{convert|25200|ha|acre|abbr=on}} and [Woodsmith Mine](/source/Woodsmith_Mine) will be the deepest in Europe."North York Moors potash mine gets £1.7bn go-ahead". The Guardian. 30 June 2015. Retrieved 3 February 2016. The Woodsmith project was originally slated to begin production in 2027; development has since been slowed, and Anglo American now expects to ramp up construction from 2027, with a new first production date yet to be announced.GeoResources. "Anglo American’s Woodsmith Mine expected to ‘ramp up’ from 2027". 2024. Accessed 14 January 2026. https://www.georesources.net/cms.php/en/news/2502/Anglo-American-s-Woodsmith-Mine-expected-to-ramp-up-from-2027New Ag International. "Anglo American eyeing final investment decision on UK polyhalite project by 2027". 2024. Accessed 14 January 2026. https://www.newaginternational.com/specialty-fertilizer/anglo-american-eyeing-final-investment-decision-on-uk-polyhalite-project-by-2027/The Guardian. "Anglo American takes further £1bn writedown on Yorkshire fertiliser mine". 25 July 2024. Accessed 14 January 2026. https://www.theguardian.com/business/article/2024/jul/25/anglo-american-takes-further-1bn-writedown-on-yorkshire-fertiliser-mine ==Composition and use== Polyhalite is used as a fertilizer since it contains four important nutrients and is low in chloride: *48% {{chem2|SO3}} as sulfate *14% {{chem2|K2O}} as from sulfate of potash *6% MgO as from magnesium sulfate *17% CaO as from calcium sulfate Polyhalite has a variety of other uses, including: Soil amendment: Polyhalite can help to improve the drainage and fertility of soil. It can also help to reduce the acidity of soil. Water treatment additive: Polyhalite can help to remove impurities from water, such as sulfates and chlorides. It can also help to soften water and make it less corrosive. Animal feed additive: Polyhalite can be added to animal feed to improve the nutritional value of the feed. Industrial applications: Polyhale can be used in a variety of industrial applications, such as making glass, soap, and paper. thumb|280px|left|Crystal structure of polyhalite {{clear}} ==References== {{reflist}} Category:Magnesium minerals Category:Calcium minerals Category:Potassium minerals Category:Sulfate minerals Category:Triclinic minerals Category:Evaporite Category:Potash Category:Minerals in space group 2 --- Adapted from the Wikipedia article [Polyhalite](https://en.wikipedia.org/wiki/Polyhalite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Polyhalite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.