Gypsum

The word gypsum is derived from the Greek word {{lang|el|γύψος}} ({{transliteration|grc|gypsos}}), "plaster".{{cite web| url= http://www.askoxford.com/concise_oed/gypsum| archive-url= https://archive.today/20120719220246/http://www.askoxford.com/concise_oed/gypsum| url-status= dead| archive-date= 19 July 2012|title=Compact Oxford English Dictionary: gypsum |website=Oxford Dictionaries }} Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris. Upon adding water, after a few dozen minutes, plaster of Paris becomes regular gypsum (dihydrate) again, causing the material to harden or "set" in ways that are useful for casting and construction.{{Cite journal|last1=Szostakowski|first1=B.|last2=Smitham|first2=P.|last3=Khan|first3=W.S.|date=2017-04-17|title=Plaster of Paris–Short History of Casting and Injured Limb Immobilzation|journal=The Open Orthopaedics Journal|volume=11|pages=291–296|doi= 10.2174/1874325001711010291 |doi-access=free|issn=1874-3250|pmc=5420179|pmid=28567158}}

Gypsum was known in Old English as {{lang|ang|spærstān}}, "spear stone", referring to its crystalline projections. Thus, the word spar in mineralogy, by comparison to gypsum, refers to any non-ore mineral or crystal that forms in spearlike projections. In the mid-18th century, the German clergyman and agriculturalist Johann Friderich Mayer investigated and publicized gypsum's use as a fertilizer.See:

• {{cite book|last1=Thaer|first1=Albrecht Daniel|translator-last1=Shaw|translator-first1=William|translator-last2=Johnson|translator-first2=Cuthbert W.|title=The Principles of Agriculture |date=1844 |publisher=Ridgway |location=London, England |volume= 1 |pages=519–520 |url=https://books.google.com/books?id=zAhJAAAAMAAJ&pg=PA519}}
• {{NDB|16|544|545|Mayer, Johann Friedrich|Klaus Herrmann|104138432}} From p. 544: " … er bewirtschaftete nebenbei ein Pfarrgüttchen, … für die Düngung der Felder mit dem in den nahen Waldenburger Bergen gefundenen Gips einsetzte." ( … he also managed a small parson's estate, on which he repeatedly conducted agricultural experiments. In 1768, he first published the fruits of his experiences during this time as "Instruction about Gypsum", in which he espoused the fertilizing of fields with the gypsum that was found in the nearby Waldenburg mountains.)
• {{cite book |last1=Beckmann |first1=Johann |title=Grundsätze der deutschen Landwirthschaft |trans-title=Fundamentals of German Agriculture |date=1775 |publisher=Johann Christian Dieterich |location=Göttingen, (Germany) |page=60 |edition=2nd |url=https://books.google.com/books?id=q8w6AAAAcAAJ&pg=PA60 |language=de}} From p. 60: "Schon seit undenklichen Zeiten … ein Gewinn zu erhalten seyn wird." (Since times immemorial, in our vicinity, in the ministry of Niedeck [a village southeast of Göttingen], one has already made this use of gypsum; but Mr. Mayer has the merit to have made it generally known. In the History of Farming in Kupferzell, he had depicted a crushing mill (p. 74), in order to pulverize gypsum, from which a profit has been obtained, albeit with difficulty.)
• {{cite book |last1=Mayer |first1=Johann Friderich |title=Lehre vom Gyps als vorzueglich guten Dung zu allen Erd-Gewaechsen auf Aeckern und Wiesen, Hopfen- und Weinbergen |trans-title=Instruction in gypsum as an ideal good manure for all things grown in soil on fields and pastures, hops yards and vineyards |date=1768 |publisher=Jacob Christoph Posch |location=Anspach, (Germany) |url=https://books.google.com/books?id=lSlAAAAAcAAJ&pg=PA1 |language=de}} Gypsum may act as a source of sulfur for plant growth, and in the early 19th century, it was regarded as an almost miraculous fertilizer. American farmers were so anxious to acquire it that a lively smuggling trade with Nova Scotia evolved, resulting in the so-called "Plaster War" of 1820.{{cite book|last=Smith|first=Joshua|title=Borderland smuggling: Patriots, loyalists, and illicit trade in the Northeast, 1780–1820|year=2007|publisher=UPF|location=Gainesville, FL|isbn=978-0-8130-2986-3|pages=passim}}

File:Gypsum deformed cristal-MCG 7747-P4150901-black.jpg

Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C){{Cite journal| last = Bock| first = E.| year = 1961| title = On the solubility of anhydrous calcium sulphate and of gypsum in concentrated solutions of sodium chloride at 25 °C, 30 °C, 40 °C, and 50 °C| journal = Canadian Journal of Chemistry| volume = 39| issue = 9| pages = 1746–1751 | doi = 10.1139/v61-228| df = dmy-all| doi-access = free}} and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures. When gypsum is heated in air it loses water and converts first to calcium sulfate hemihydrate (bassanite, often simply called "plaster") and, if heated further, to anhydrous calcium sulfate (anhydrite). As with anhydrite, the solubility of gypsum in saline solutions and in brines is also strongly dependent on sodium chloride (common table salt) concentration.

The structure of gypsum consists of layers of calcium (Ca²⁺) and sulfate ({{chem2|SO4(2-)}}) ions tightly bound together. These layers are bonded by sheets of anion water molecules via weaker hydrogen bonding, which gives the crystal perfect cleavage along the sheets (in the {010} plane).{{cite journal| doi= 10.1016/S0008-8846(01)00675-5| last1= Mandal| first1= Pradip K|year=2002|pages=313|volume=32|journal=Cement and Concrete Research|last2=Mandal|first2=Tanuj K| title= Anion water in gypsum (CaSO₄·2H₂O) and hemihydrate (CaSO₄·1/2H₂O)|issue=2}}

{{main|Selenite (mineral)}}

Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. In the form of selenite, gypsum forms some of the largest crystals found in nature, up to {{convert|12|m|ft|abbr=on}} long.{{cite journal |first1=Juan Manuel |last1= García-Ruiz |first2= Roberto |last2= Villasuso |first3= Carlos |last3= Ayora |first4= Angels |last4= Canals |first5= Fermín |last5= Otálora |title= Formation of natural gypsum megacrystals in Naica, Mexico |journal= Geology |volume=35 |issue=4 |pages=327–330 |year=2007 |doi= 10.1130/G23393A.1|bibcode = 2007Geo....35..327G |url=https://digital.csic.es/bitstream/10261/3439/1/garciaruiznaica.pdf |archive-url=https://web.archive.org/web/20170816122316/http://digital.csic.es/bitstream/10261/3439/1/garciaruiznaica.pdf |archive-date=2017-08-16 |url-status=live |hdl= 10261/3439 |hdl-access= free }} Selenite contains no significant selenium; rather, both substances were named for the ancient Greek word for the Moon.

Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar".

It may also be granular or quite compact. In hand-sized samples, it can be anywhere from transparent to opaque.

A very fine-grained white or lightly tinted variety of gypsum, called alabaster, is prized for ornamental work of various sorts.

In arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose.

Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon.{{cite journal| last1= Cockell| first1= C. S.|last2= Raven |first2= J. A.|year=2007|title=Ozone and life on the Archaean Earth|journal=Philosophical Transactions of the Royal Society A|volume=365|pages=1889–1901|doi=10.1098/rsta.2007.2049| pmid= 17513273|issue=1856|bibcode = 2007RSPTA.365.1889C | s2cid= 4716}} Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals halite and sulfur. Gypsum is the most common sulfate mineral.{{cite book |title=An Introduction to the Rock Forming Minerals | publisher=Longman |last1=Deer |first1=W.A. |last2=Howie |first2=R.A. |last3=Zussman |first3=J. |year=1966 |location=London |page=469 |isbn=978-0-582-44210-8}} Pure gypsum is white, but other substances found as impurities may give a wide range of colors to local deposits.

Because gypsum dissolves over time in water, gypsum is rarely found in the form of sand. However, the unique conditions of the White Sands National Park in the US state of New Mexico have created a {{convert|710|km2|adj=on|abbr=on}} expanse of white gypsum sand, enough to supply the US construction industry with drywall for 1,000 years.{{cite news |last = Abarr|first = James|title = Sea of sand |newspaper = The Albuquerque Journal|date = 7 February 1999|url = http://www.abqjournal.com/venue/travel/tourism/heritage_whitesands.htm|access-date = 27 January 2007|url-status=dead|archive-url=https://web.archive.org/web/20060630120616/http://www.abqjournal.com:80/venue/travel/tourism/heritage_whitesands.htm|archive-date=30 June 2006}}

Commercial exploitation of the area, strongly opposed by area residents, was permanently prevented in 1933 when President Herbert Hoover declared the gypsum dunes a protected national monument.

Gypsum is also formed as a by-product of sulfide oxidation, amongst others by pyrite oxidation, when the sulfuric acid generated reacts with calcium carbonate. Its presence indicates oxidizing conditions. Under reducing conditions, the sulfates it contains can be reduced back to sulfide by sulfate-reducing bacteria. This can lead to accumulation of elemental sulfur in oil-bearing formations,{{cite journal |last1=Machel |first1=H.G |title=Bacterial and thermochemical sulfate reduction in diagenetic settings — old and new insights |journal=Sedimentary Geology |date=April 2001 |volume=140 |issue=1–2 |pages=143–175 |doi=10.1016/S0037-0738(00)00176-7|bibcode=2001SedG..140..143M |s2cid=4606551 }} such as salt domes,{{cite journal |last1=Sassen |first1=Roger |last2=Chinn |first2=E.W. |last3=McCabe |first3=C. |title=Recent hydrocarbon alteration, sulfate reduction and formation of elemental sulfur and metal sulfides in salt dome cap rock |journal=Chemical Geology |date=December 1988 |volume=74 |issue=1–2 |pages=57–66 |doi=10.1016/0009-2541(88)90146-5|bibcode=1988ChGeo..74...57S }} where it can be mined using the Frasch process{{Ullmann | title = Sulfur | author = Wolfgang Nehb, Karel Vydra | doi = 10.1002/14356007.a25_507.pub2}} Electric power stations burning coal with flue gas desulfurization produce large quantities of gypsum as a byproduct from the scrubbers.

Orbital pictures from the Mars Reconnaissance Orbiter (MRO) have indicated the existence of gypsum dunes in the northern polar region of Mars,[http://hirise.lpl.arizona.edu/nea.php High-resolution Mars image gallery]. University of Arizona which were later confirmed at ground level by the Mars Exploration Rover (MER) Opportunity.[http://www.nasa.gov/mission_pages/mer/news/mer20111207.html NASA Mars Rover Finds Mineral Vein Deposited by Water] {{Webarchive|url=https://web.archive.org/web/20170615235154/https://www.nasa.gov/mission_pages/mer/news/mer20111207.html |date=15 June 2017 }}, NASA, 7 December 2011.

File:Lechuguilla Chandelier Ballroom.jpg|Large gypsum crystals in Lechuguilla Cave's "chandelier ballroom"

File:Cristales cueva de Naica.JPG|Gypsum crystals in the Cave of the Crystals in Mexico (person at lower right for scale)

File:GypsumCrystalsLakeLucerno.jpg|Gypsum crystals formed as the water evaporated in Lake Lucero, White Sands National Park

File:White Gypsum - geograph.org.uk - 2503198.jpg|Gypsum veins in the silts/marls of the Tea Green and Grey Marls, Blue Anchor, Somerset, United Kingdom

File:Gypsum layers Caprock Canyons 1.JPG|Gypsum veins in Caprock Canyons State Park and Trailway, Texas

File:Yardangs in dunes, White Sands National Park, New Mexico, United States.jpg|Dunes made of small crystals of gypsum, White Sands National Park

Commercial quantities of gypsum are found in the cities of Araripina and Grajaú in Brazil; in Pakistan, Jamaica, Iran (world's second largest producer), Thailand, Spain (the main producer in Europe), Germany, Italy, England, Ireland, Canada{{cite web |url=http://mmsd1.mms.nrcan.gc.ca/mmsd/producers/commodityCompany_e.asp?nId=51&mineType=nonMetal |title=Mines, mills and concentrators in Canada |access-date=27 January 2007 |date=24 October 2005 |publisher=Natural Resources Canada |url-status=dead |archive-url=https://web.archive.org/web/20050313183544/http://mmsd1.mms.nrcan.gc.ca/mmsd/producers/commodityCompany_e.asp?nId=51&minetype=nonMetal |archive-date=13 March 2005 |df=dmy-all }} and the United States. Large open pit quarries are located in many places including Fort Dodge, Iowa, which sits on one of the largest deposits of gypsum in the world,{{Cite book|title=The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide|publisher=Helion|year=2018|via=Credo Reference}} and Plaster City, California, United States, and East Kutai, Kalimantan, Indonesia. Several small mines also exist in places such as Kalannie in Western Australia, where gypsum is sold to private buyers for additions of calcium and sulfur as well as reduction of aluminium toxicities on soil for agricultural purposes.{{Cite web |title=Australia - Gypsum industry news from Global Gypsum |url=https://www.globalgypsum.com/news/itemlist/tag/Australia?start=70&utm_source=chatgpt.com |access-date=2025-05-15 |website=www.globalgypsum.com}}{{Cite web |title=Livebearing Aquarium Fish—Habitat, Diet, and Breeding |url=https://www.thesprucepets.com/livebearing-aquarium-fish-1378599?utm_source=chatgpt.com |access-date=2025-05-15 |website=The Spruce Pets |language=en}}

Crystals of gypsum up to {{convert|11|m|abbr=on}} long have been found in the caves of the Naica Mine of Chihuahua, Mexico. The crystals thrived in the cave's extremely rare and stable natural environment. Temperatures stayed at {{cvt|58|C}}, and the cave was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs {{convert|55|t|ST}} and is around 500,000 years old.{{cite news|newspaper = The Telegraph| url = https://www.telegraph.co.uk/news/newstopics/howaboutthat/3269047/Worlds-largest-crystal-discovered-in-Mexican-cave.html| title =World's largest crystal discovered in Mexican cave| access-date=6 June 2009|location=London|first=Richard|last=Alleyne|date=27 October 2008}}

File:Gypsum-24382.jpg|Golden gypsum crystals from Winnipeg

File:WhiteSandsGypsum.jpg|Gypsum sand from White Sands National Park, New Mexico

Synthetic gypsum is produced as a waste product or by-product in a range of industrial processes.

Flue gas desulfurization gypsum (FGDG) is recovered at some coal-fired power plants. The main contaminants are Mg, K, Cl, F, B, Al, Fe, Si, and Se. They come both from the limestone used in desulfurization and from the coal burned. This product is pure enough to replace natural gypsum in a wide variety of fields including drywalls, water treatment, and cement set retarder. Improvements in flue gas desulfurization have greatly reduced the amount of toxic elements present.{{cite journal |last1=Koralegedara |first1=NH |last2=Pinto |first2=PX |last3=Dionysiou |first3=DD |last4=Al-Abed |first4=SR |title=Recent advances in flue gas desulfurization gypsum processes and applications – A review. |journal=Journal of Environmental Management |date=1 December 2019 |volume=251 |pages=109572 |doi=10.1016/j.jenvman.2019.109572 |pmid=31561139 |pmc=7396127}}

Gypsum precipitates onto brackish water membranes, a phenomenon known as mineral salt scaling, such as during brackish water desalination of water with high concentrations of calcium and sulfate. Scaling decreases membrane life and productivity.{{cite journal |last1=Uchymiak |first1=Michal |last2=Lyster |first2=Eric |last3=Glater |first3=Julius |last4=Cohen |first4=Yoram |title=Kinetics of gypsum crystal growth on a reverse osmosis membrane |journal=Journal of Membrane Science |date=April 2008 |volume=314 |issue=1–2 |pages=163–172 |doi=10.1016/j.memsci.2008.01.041}} This is one of the main obstacles in brackish water membrane desalination processes, such as reverse osmosis or nanofiltration. Other forms of scaling, such as calcite scaling, depending on the water source, can also be important considerations in distillation, as well as in heat exchangers, where either the salt solubility or concentration can change rapidly.

A new study has suggested that the formation of gypsum starts as tiny crystals of a mineral called bassanite (2CaSO₄·H₂O).{{Cite journal| last1 = Van Driessche| first1 = A.E.S.| first2 = L. G. | last2= Benning | first3= J. D. | last3= Rodriguez-Blanco| first4= M. | last4= Ossorio| first5= P. | last5= Bots | first6= J. M. | last6= García-Ruiz| year = 2012| title = The role and implications of bassanite as a stable precursor phase to gypsum precipitation| journal = Science| volume = 336| issue = 6077| pages = 69–72 | doi = 10.1126/science.1215648|bibcode = 2012Sci...336...69V| pmid=22491851| s2cid = 9355745}} This process occurs via a three-stage pathway:

1. homogeneous nucleation of nanocrystalline bassanite;
2. self-assembly of bassanite into aggregates, and
3. transformation of bassanite into gypsum.

The production of phosphate fertilizers requires breaking down calcium-containing phosphate rock with acid, producing calcium sulfate waste known as phosphogypsum (PG). This form of gypsum is contaminated by impurities found in the rock, namely fluoride, silica, radioactive elements such as radium, and heavy metal elements such as cadmium.{{cite journal|doi=10.1016/j.jenvman.2009.03.007|pmid=19406560|title=Environmental Impact and Management of Phosphogypsum|journal=Journal of Environmental Management|volume=90|pages=2377–2386|year=2009|last1=Tayibi|first1= Hanan|last2=Choura|first2=Mohamed|last3=López|first3=Félix A.|last4=Alguacil|first4=Francisco J.|last5=López-Delgado|first5=Aurora|issue=8|bibcode=2009JEnvM..90.2377T |hdl=10261/45241|hdl-access=free}} Similarly, production of titanium dioxide produces titanium gypsum (TG) due to neutralization of excess acid with lime. The product is contaminated with silica, fluorides, organic matters, and alkalis.{{cite journal |last1=Zhang |first1=Y |last2=Wang |first2=F |last3=Huang |first3=H |last4=Guo |first4=Y |last5=Li |first5=B |last6=Liu |first6=Y |last7=Chu |first7=PK |title=Gypsum blocks produced from TiO2 production by-products. |journal=Environmental Technology |date=2016 |volume=37 |issue=9 |pages=1094–100 |doi=10.1080/09593330.2015.1102329 |url=https://www1.cugb.edu.cn/uploadCms/file/20600/papers_upload/20161008164505966187.pdf |archive-url=https://web.archive.org/web/20220325023932/https://www1.cugb.edu.cn/uploadCms/file/20600/papers_upload/20161008164505966187.pdf |archive-date=2022-03-25 |url-status=live |pmid=26495867|bibcode=2016EnvTe..37.1094Z |s2cid=28458281 }}

Impurities in refinery gypsum waste have, in many cases, prevented them from being used as normal gypsum in fields such as construction. As a result, waste gypsum is stored in stacks indefinitely, with significant risk of leaching their contaminants into water and soil. To reduce the accumulation and ultimately clear out these stacks, research is underway to find more applications for such waste products.

{{NFPA 704 | H= 0 | F= 0 | R= 0 | S= |caption=Gypsum |ref={{cite web |last1=Michigan Gypsum |title=MATERIAL SAFETY DATA SHEET Gypsum (Calcium Sulfate Dihydrate) |url=https://www.ncmissouri.edu/consumerinfo/wp-content/uploads/sites/26/2016/12/Gypsum-Calcium-Sulfate-msds.pdf |archive-url=https://web.archive.org/web/20211121062715/https://www.ncmissouri.edu/consumerinfo/wp-content/uploads/sites/26/2016/12/Gypsum-Calcium-Sulfate-msds.pdf |archive-date=2021-11-21 |url-status=live |website=Consumer Information |publisher=NorthCentral Missouri College |access-date=21 November 2021}}}}

People can be exposed to gypsum in the workplace by breathing it in, skin contact, and eye contact. Calcium sulfate per se is nontoxic and is even approved as a food additive,{{cite web |title=Compound Summary for CID 24497 – Calcium Sulfate |url=https://pubchem.ncbi.nlm.nih.gov/compound/calcium_sulfate#section=Food-Additives-and-Ingredients |publisher=PubChem}} but as powdered gypsum, it can irritate skin and mucous membranes.{{Cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Gypsum|url = https://www.cdc.gov/niosh/npg/npgd0308.html|website = www.cdc.gov|access-date = 2015-11-03}}

The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for gypsum exposure in the workplace as TWA 15 mg/m³ for total exposure and TWA 5 mg/m³ for respiratory exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of TWA 10 mg/m³ for total exposure and TWA 5 mg/m³ for respiratory exposure over an eight-hour workday.

File:2.-Calera. Cal i guix (26561676342).jpg]]

File:Algepsar d'Alfarb. Forn primer, 1 (País Valencià).jpg kiln for making plaster as a construction material]]

File:KirkbyThoreGypsumPlant(SimonLedingham)May2005.jpg]]

File:Geography of Ohio - DPLA - aaba7b3295ff6973b6fd1e23e33cde14 (page 96) (cropped2).jpg

Gypsum is used in a wide variety of applications:

• Gypsum board*[http://www.csinet.org/s_csi/docs/9400/9361.pdf Complimentary list of MasterFormat 2004 Edition numbers and titles] (large PDF document) is primarily used as a finish for walls and ceilings, and is known in construction as plasterboard, "sheetrock", or drywall. Gypsum provides a degree of fire-resistance to these materials, and glass fibers are added to their composition to accentuate this effect. Gypsum has negligible heat conductivity, giving its plaster some insulative properties.{{Cite book |last=Bonewitz |first=Ronald |title=Rock and Gem: The Definitive Guide to Rocks, Minerals, Gems, and Fossils |publisher=DK |year=2008 |location=United States |pages=47 |language=English}}
• Gypsum blocks are used like concrete blocks in construction.
• Gypsum mortar is an ancient mortar used in construction.
• A component of Portland cement used to prevent flash setting (too rapid hardening) of concrete.
• A wood substitute in the ancient world: For example, when wood became scarce due to deforestation on Bronze Age Crete, gypsum was employed in building construction at locations where wood was previously used.{{cite journal| first= C. Michael |last= Hogan| url= http://www.themodernantiquarian.com/site/10854/knossos.html#fieldnotes |title= Knossos fieldnotes| journal= Modern Antiquarian | year= 2007}}

• Fertilizer: In the late 18th and early 19th centuries, Nova Scotia gypsum, often referred to as plaster, was a highly sought fertilizer for wheat fields in the United States.{{cite journal |jstor=3739630|title=The Gypsum Trade of the Maritime Provinces: Its Relation to American Diplomacy and Agriculture in the Early Nineteenth Century |last1=Graham |first1=Gerald S. |journal=Agricultural History |year=1938 |volume=12 |issue=3 |pages=209–223 }} Gypsum provides two of the secondary plant macronutrients, calcium and sulfur. Unlike limestone, it generally does not affect soil pH.
• Reclamation of saline soils, regardless of pH. When gypsum is added to sodic (saline) and acidic soil, the highly soluble form of boron (sodium metaborate) is converted to the less soluble calcium metaborate. The exchangeable sodium percentage is also reduced by gypsum application.[https://books.google.com/books?id=ANCBDwAAQBAJ&dq=boron+sodium+soil&pg=PA99 Genesis and Management of Sodic (Alkali) Soils.] (2017). (n.p.): Scientific Publishers.{{Cite journal |doi=10.2136/sssaj1980.03615995004400010010x |first1=J. D. |last1=Oster |first2=H. |last2=Frenkel |year=1980 |title=The chemistry of the reclamation of sodic soils with gypsum and lime |journal=Soil Science Society of America Journal |volume=44 |issue=1 |pages=41–45 |bibcode=1980SSASJ..44...41O }} The Zuiderzee Works uses gypsum for the recovered land.{{Cite magazine |last=Ley |first=Willy |date=October 1961 |title=The Home-Made Land |department=For Your Information |url=https://archive.org/stream/Galaxy_v19n06_1961-08#page/n65/mode/1up |magazine=Galaxy Science Fiction |pages=92–106}}
• Other soil conditioner uses: Gypsum reduces aluminium and boron toxicity in acidic soils. It also improves soil structure, water absorption, and aeration.{{cite web |title=Gypsum as an agricultural product {{!}} Soil Science Society of America |url=https://www.soils.org/news/science-news/gypsum-agricultural-product/ |website=www.soils.org}}
• Soil water potential monitoring: a gypsum block can be inserted into the soil, and its electrical resistance can be measured to derive soil moisture.{{cite encyclopedia |last1=Durner |first1=W. |last2=Or |first2=D. |year=2006 |chapter=Soil water potential measurement |title=Encyclopedia of hydrological sciences |editor-last1=Anderson |editor-first1=M.G. |publisher=John Wiley & Sons Ltd. |chapter-url=http://www.soil.tu-bs.de/download/downloads/pubs/2005.hsa077a.Durner-Or.SoilWaterPotentialMeasurement.pdf |archive-url=https://web.archive.org/web/20220616051818/http://www.soil.tu-bs.de/download/downloads/pubs/2005.hsa077a.Durner-Or.SoilWaterPotentialMeasurement.pdf |archive-date=2022-06-16 |url-status=live|access-date=23 May 2022 |isbn=978-0471491033}}

• Plaster for casting moulds and modeling.
• As alabaster, a material for sculpture, it was used especially in the ancient world before steel was developed, when its relative softness made it much easier to carve.{{cite book |last1=Rapp |first1=George |title=Archaeomineralogy |chapter=Soft Stones and Other Carvable Materials |series=Natural Science in Archaeology |date=2009 |pages=121–142 |doi=10.1007/978-3-540-78594-1_6|isbn=978-3-540-78593-4 }} During the Middle Ages and Renaissance, it was preferred even to marble.{{cite journal |last1=Kloppmann |first1=W. |last2=Leroux |first2=L. |last3=Bromblet |first3=P. |last4=Le Pogam |first4=P.-Y. |last5=Cooper |first5=A. H. |last6=Worley |first6=N. |last7=Guerrot |first7=C. |last8=Montech |first8=A. T. |last9=Gallas |first9=A. M. |last10=Aillaud |first10=R. |title=Competing English, Spanish, and French alabaster trade in Europe over five centuries as evidenced by isotope fingerprinting |journal=Proceedings of the National Academy of Sciences |date=7 November 2017 |volume=114 |issue=45 |pages=11856–11860 |doi=10.1073/pnas.1707450114|pmid=29078309 |pmc=5692548 |bibcode=2017PNAS..11411856K |doi-access=free }}
• In the medieval period, scribes and illuminators used it as an ingredient in gesso, which was applied to illuminated letters and gilded with gold in illuminated manuscripts.{{cite book |last1=Brown |first1=Michelle |title=Understanding illuminated manuscripts : a guide to technical terms |date=1995 |location=Los Angeles, California|publisher=Yale University Press |isbn=9780892362172 |pages=58}}

• A tofu (soy bean curd) coagulant, making it ultimately a significant source of dietary calcium.{{cite book |last1=Shurtleff |first1=William |title=Tofu & soymilk production : a craft and technical manual |date=2000 |publisher=Soyfoods Center |location=Lafayette, CA |isbn=9781928914044|page=99}}
• Adding hardness to water used for brewing.{{cite web|url=http://www.howtobrew.com/section1/chapter4-2.html| title= Water Chemistry Adjustment for Extract Brewing|access-date=15 December 2008|first= John |last=Palmer |publisher= HowToBrew.com}}
• Used in baking as a dough conditioner, reducing stickiness, and as a baked goods source of dietary calcium.{{cite web |url=http://www.usg.com/rc/technical-specifications/fillers/food-grade-calcium-sulfate-for-baking-industry-technical-specifications-en-IG130.pdf |work=United States Gypsum Company |title=Calcium sulphate for the baking industry |access-date=1 March 2013 |archive-url=https://web.archive.org/web/20130704125140/http://www.usg.com/rc/technical-specifications/fillers/food-grade-calcium-sulfate-for-baking-industry-technical-specifications-en-IG130.pdf |archive-date=4 July 2013 |url-status=dead }} The primary component of mineral yeast food.{{cite web |url=http://www.lesaffreyeastcorp.com/sites/default/files/products_files/Tech%20Sheet%20-%20RS%20Yeast%20Food.pdf |archive-url=https://web.archive.org/web/20131029185607/http://www.lesaffreyeastcorp.com/sites/default/files/products_files/Tech%20Sheet%20-%20RS%20Yeast%20Food.pdf|work=Lesaffre Yeast Corporation |title=Tech sheet for yeast food |access-date=1 March 2013 |url-status=dead |archive-date=2013-10-29}}
• Used in mushroom cultivation to stop grains from clumping together.

• Plaster for surgical splints.{{cite journal |last1=Austin |first1=R.T. |title=Treatment of broken legs before and after the introduction of gypsum |journal=Injury |date=March 1983 |volume=14 |issue=5 |pages=389–394 |doi=10.1016/0020-1383(83)90089-X|pmid=6347885 }}
• Impression plasters in dentistry.{{cite journal |last1=Drennon |first1=David G. |last2=Johnson |first2=Glen H. |title=The effect of immersion disinfection of elastomeric impressions on the surface detail reproduction of improved gypsum casts |journal=The Journal of Prosthetic Dentistry |date=February 1990 |volume=63 |issue=2 |pages=233–241 |doi=10.1016/0022-3913(90)90111-O|pmid=2106026 }}

• An alternative to iron oxide in some thermite mixes.{{cite journal |last1=Govender |first1=Desania R. |last2=Focke |first2=Walter W. |last3=Tichapondwa |first3=Shepherd M. |last4=Cloete |first4=William E. |title=Burn Rate of Calcium Sulfate Dihydrate–Aluminum Thermites |journal=ACS Applied Materials & Interfaces |date=20 June 2018 |volume=10 |issue=24 |pages=20679–20687 |doi=10.1021/acsami.8b04205|pmid=29842778 |hdl=2263/66006 |s2cid=206483977 |hdl-access=free }}
• Tests have shown that gypsum can be used to remove pollutants such as lead{{cite journal| doi=10.1016/j.apgeochem.2010.04.007| title=Interaction of gypsum with lead in aqueous solutions| journal=Applied Geochemistry| volume=25| issue=7| pages=1008| year=2010| last1=Astilleros| first1=J.M.| last2=Godelitsas| first2=A.| last3=Rodríguez-Blanco| first3=J.D.| last4=Fernández-Díaz| first4=L.| last5=Prieto| first5=M.| last6=Lagoyannis| first6=A.| last7=Harissopulos| first7=S.| bibcode=2010ApGC...25.1008A| url=https://eprints.ucm.es/18174/1/1000958.pdf |archive-url=https://web.archive.org/web/20170809180523/http://eprints.ucm.es/18174/1/1000958.pdf |archive-date=2017-08-09 |url-status=live}} or arsenic{{cite journal| doi=10.2138/am.2008.2750| title=Interaction of gypsum with As(V)-bearing aqueous solutions: Surface precipitation of guerinite, sainfeldite, and Ca₂NaH(AsO₄)₂⋅6H₂O, a synthetic arsenate| journal=American Mineralogist| volume=93| issue=5–6| pages=928| year=2008| last1=Rodriguez| first1=J. D.| last2=Jimenez| first2=A.| last3=Prieto| first3=M.| last4=Torre| first4=L.| last5=Garcia-Granda| first5=S.| bibcode=2008AmMin..93..928R| s2cid=98249784| hdl=10651/5785| hdl-access=free}}{{cite journal| doi=10.1021/cg070222+|title=Oriented Overgrowth of Pharmacolite (CaHAsO₄⋅2H2O) on Gypsum (CaSO₄⋅2H₂O)|author1=Rodríguez-Blanco, Juan Diego |author2=Jiménez, Amalia |author3=Prieto, Manuel |journal=Cryst. Growth Des.|year= 2007|volume= 7 |issue=12|pages=2756–2763}}

from contaminated waters.

File:Gypsum-71006.jpg|Green gypsum crystals from Pernatty Lagoon, Mt Gunson, South Australia - its green color is due to presence of copper ions.

File:Gypsum-162462.jpg|Unusual selenite gypsum from the Red River, Winnipeg, Manitoba, Canada

File:Gypsum-47190.jpg|Classic "ram's horn" gypsum from Santa Eulalia, Chihuahua, Mexico, 7.5×4.3×3.8 cm

File:Roses des Sables Tunisie.jpg|Desert rose, 47 cm long

File:Gypsum-53691.jpg|Gypsum from Pernatty Lagoon, Mt Gunson, Stuart Shelf area, Andamooka Ranges - Lake Torrens area, South Australia, Australia

File:Copper-Gypsum-203925.jpg|Gypsum with crystalline native copper inside

File:Gypsum J1.jpg|Gypsum from Swan Hill, Victoria, Australia. The coloring is due to the copper oxide

File:Gypsum-21996.jpg|Waterclear twined crystal of the form known as "Roman sword". Fuentes de Ebro, Zaragoza (Spain)

File:Botryogen-Gypsum-199664.jpg|Bright, cherry-red gypsum crystals 2.5 cm in height colored by rich inclusions of the rare mineral botryogen

File:Gypse Naica.jpg|Gypsum from Naica, Mun. de Saucillo, Chihuahua, Mexico

File:Gypsum-251118.jpg|Golden color gem, "fishtail"-twinned crystals of gypsum sitting atop a "ball" of gypsum which is composed of several single bladed crystals

• Gypcrust
• Gypsum flora of Nova Scotia
• Gypsum recycling
• Phosphogypsum

{{Reflist|30em}}

{{Commons}}

{{wiktionary}}

• [http://webmineral.com/data/Gypsum.shtml WebMineral data]
• [https://web.archive.org/web/20070814041825/http://mineral.galleries.com/minerals/sulfates/gypsum/gypsum.htm Mineral galleries – gypsum]
• [https://www.cdc.gov/niosh/npg/npgd0308.html CDC – NIOSH Pocket Guide to Chemical Hazards]
• {{Cite EB1911|wstitle=Gypsum|short=x}}
• {{Cite AmCyc|wstitle=Gypsum|short=x}}

{{Mohs}}

{{Authority control}}

Category:Calcium minerals

Category:Sulfate minerals

Category:Sedimentary rocks

Category:Evaporite

Category:Alchemical substances

Category:Monoclinic minerals

Category:Minerals in space group 15

Category:Alabaster

Category:Luminescent minerals

Category:Industrial minerals