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Gypsum is a soft
sulfate mineral The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal veins and as secondary min ...
composed of calcium sulfate dihydrate, with the
chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
. It is widely mined and is used as a
fertilizer A fertilizer (American English) or fertiliser ( British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
and as the main constituent in many forms of plaster,
blackboard A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of ...
or sidewalk chalk, and
drywall Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate ( gypsum), with or without additives, typically extruded between th ...
. Alabaster, a fine-grained white or lightly tinted variety of gypsum, has been used for
sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...
by many cultures including Ancient Egypt,
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the ...
,
Ancient Rome In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–50 ...
, the
Byzantine Empire The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constanti ...
, and the
Nottingham alabaster Nottingham alabaster is a term used to refer to the English sculpture industry, mostly of relatively small religious carvings, which flourished from the fourteenth century until the early sixteenth century. Alabaster carvers were at work in Lo ...
s of
Medieval England England in the Middle Ages concerns the history of England during the medieval period, from the end of the 5th century through to the start of the Early Modern period in 1485. When England emerged from the collapse of the Roman Empire, the eco ...
. Gypsum also crystallizes as translucent crystals of selenite. It forms as an
evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oc ...
mineral and as a hydration product of
anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
. The
Mohs scale of mineral hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by t ...
defines gypsum as hardness value 2 based on scratch hardness comparison.


Etymology and history

The word '' gypsum'' is derived from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. ** Proto-Greek language, the assumed last common ancestor ...
word (), "plaster". Because the quarries of the
Montmartre Montmartre ( , ) is a large hill in Paris's northern 18th arrondissement. It is high and gives its name to the surrounding district, part of the Right Bank. The historic district established by the City of Paris in 1995 is bordered by Rue C ...
district of
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. ...
have long furnished burnt gypsum (
calcined Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), gener ...
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. Gypsum was known in Old English as , "spear stone", referring to its crystalline projections. (Thus, the word
spar SPAR, originally DESPAR, styled as DE SPAR, is a Dutch multinational that provides branding, supplies and support services for independently owned and operated food retail stores. It was founded in the Netherlands in 1932, by Adriaan van Wel ...
in mineralogy is by way of comparison to gypsum, referring 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. 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.


Physical properties

Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C) 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 Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
). As with
anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
, the solubility of gypsum in saline solutions and in brines is also strongly dependent on NaCl (common table salt) concentration. The structure of gypsum consists of layers of calcium (Ca2+) and sulfate () ions tightly bound together. These layers are bonded by sheets of anion water molecules via weaker
hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing ...
ing, which gives the crystal perfect cleavage along the sheets (in the plane).


Crystal varieties

Gypsum occurs in nature as flattened and often twinned
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s, and transparent, cleavable masses called selenite. Selenite contains no significant
selenium Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium ...
; rather, both substances were named for the ancient Greek word for the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width o ...
. Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar". Finally, 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. It also forms some of the largest crystals found in nature, up to long, in the form of selenite.


Occurrence

Gypsum is a common mineral, with thick and extensive
evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oc ...
beds in association with
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s. Deposits are known to occur in strata from as far back as the Archaean eon. Gypsum is deposited from lake and sea water, as well as in
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by ci ...
s, from
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ar ...
vapors, and sulfate solutions in
veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
.
Hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water ( Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with t ...
anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals
halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...
and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
. Gypsum is the most common sulfate mineral. 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 White Sands National Park is an American national park located in the state of New Mexico and completely surrounded by the White Sands Missile Range. The park covers in the Tularosa Basin, including the southern 41% of a field of white sand du ...
in the US state of
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...
have created a expanse of white gypsum sand, enough to supply the US construction industry with
drywall Drywall (also called plasterboard, dry lining, wallboard, sheet rock, gypsum board, buster board, custard board, and gypsum panel) is a panel made of calcium sulfate dihydrate ( gypsum), with or without additives, typically extruded between th ...
for 1,000 years. Commercial exploitation of the area, strongly opposed by area residents, was permanently prevented in 1933 when President
Herbert Hoover Herbert Clark Hoover (August 10, 1874 – October 20, 1964) was an American politician who served as the 31st president of the United States from 1929 to 1933 and a member of the Republican Party, holding office during the onset of the Gre ...
declared the gypsum
dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...
s a protected national monument. Gypsum is also formed as a by-product of sulfide
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
, amongst others by
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue g ...
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
, when the
sulfuric acid Sulfuric acid ( American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...
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 Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
in oil-bearing formations, such as salt domes, where it can be mined using the Frasch process 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, which were later confirmed at ground level by the
Mars Exploration Rover NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, '' Spirit'' and '' Opportunity'', exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface a ...
(MER) '' Opportunity''. File:Lechuguilla Chandelier Ballroom.jpg, Large gypsum crystals in
Lechuguilla Cave At , Lechuguilla Cave is the eighth-longest explored cave in the world and the second deepest () in the continental United States. It is most famous for its unusual geology, rare formations, and pristine condition. The cave is named for the can ...
'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 ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England , established_date = Ancient , established_by = , preceded_by = , origin = , lord_lieutenant_office =Lord Lieutenant of Somerset , lor ...
, 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


Mining

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 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, and Plaster City, California, United States, and East Kutai,
Kalimantan Kalimantan () is the Indonesian portion of the island of Borneo. It constitutes 73% of the island's area. The non-Indonesian parts of Borneo are Brunei and East Malaysia. In Indonesia, "Kalimantan" refers to the whole island of Borneo. In 2019, ...
, Indonesia. Several small mines also exist in places such as Kalannie in
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...
, where gypsum is sold to private buyers for additions of calcium and sulfur as well as reduction of aluminum toxicities on
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former t ...
for agricultural purposes. Crystals of gypsum up to 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 , and the cave was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs and is around 500,000 years old. File:Gypsum-24382.jpg, Golden gypsum crystals from
Winnipeg Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749, ...
File:WhiteSandsGypsum.jpg, Gypsum
sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of ...
from
White Sands National Park White Sands National Park is an American national park located in the state of New Mexico and completely surrounded by the White Sands Missile Range. The park covers in the Tularosa Basin, including the southern 41% of a field of white sand du ...
,
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...


Synthesis

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


Desulfurization

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.


Desalination

Gypsum precipitates onto brackish water membranes, a phenomenon known as mineral salt scaling, such as during
brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuar ...
water desalination of water with high concentrations of
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
and sulfate. Scaling decreases membrane life and productivity. 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 Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scr ...
scaling, depending on the water source, can also be important considerations in
distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heati ...
, as well as in heat exchangers, where either the salt
solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...
or
concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', ''number concentration'', ...
can change rapidly. A new study has suggested that the formation of gypsum starts as tiny crystals of a mineral called bassanite (). This process occurs via a three-stage pathway: # homogeneous nucleation of nanocrystalline bassanite; # self-assembly of bassanite into aggregates, and # transformation of bassanite into gypsum.


Refinery waste

The production of
phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phos ...
fertilizers requires breaking down calcium-containing
phosphate rock Phosphorite, phosphate rock or rock phosphate is a non- detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pento ...
with acid, producing calcium sulfate waste known as phosphogypsum (PG). This form of gypsum is contaminated by impurities found in the rock, namely
fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...
,
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
, radioactive elements such as
radium Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather ...
, and heavy metal elements such as
cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
. Similarly, production of
titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolubl ...
produces titanium gypsum (TG) due to neutralization of excess acid with
lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...
. The product is contaminated with silica, fluorides, organic matters, and alkalis. 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.


Occupational safety

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, but as powdered gypsum, it can irritate skin and mucous membranes.


United States

The
Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) has set the legal limit (
permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational ...
) for gypsum exposure in the workplace as TWA 15 mg/m3 for total exposure and TWA 5 mg/m3 for respiratory exposure over an 8-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 8-hour workday.


Uses

Gypsum is used in a wide variety of applications:


Construction industry

* Gypsum board 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 little heat conductivity, giving its plaster some insulative properties. * Gypsum blocks are used like concrete blocks in building construction. * Gypsum mortar is an ancient mortar used in building construction. *A component of
Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th ce ...
used to prevent flash setting (too rapid hardening) of
concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
.


Agriculture

*
Fertilizer A fertilizer (American English) or fertiliser ( British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
: 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. 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 Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the ne ...
, the highly
soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solu ...
form of
boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the '' boron group'' it has t ...
(
sodium metaborate Sodium metaborate is a chemical compound of sodium, boron, and oxygen with formula . However, the metaborate ion is trimeric in the anhydrous solid, therefore a more correct formula is or . The formula can be written also as · to highlight the ...
) is converted to the less soluble calcium metaborate. Exchangeable sodium percentage is also reduced by gypsum application. The Zuiderzee Works uses gypsum for the recovered land. *Other
soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...
uses: Gypsum reduces aluminium and boron toxicity in acidic soils. It also improves soil structure, improving water absorption and aeration. *A wood substitute in the ancient world: For example, when wood became scarce due to deforestation on
Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second p ...
Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, an ...
, gypsum was employed in building construction at locations where wood was previously used. *Soil
water potential Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and matr ...
monitoring: a gypsum block can be inserted into soil, its electrical resistance measured to derive soil moisture.


Modeling, sculpture and art

* 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. During the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
and
Renaissance The Renaissance ( , ) , from , with the same meanings. is a period in European history marking the transition from the Middle Ages to modernity and covering the 15th and 16th centuries, characterized by an effort to revive and surpass idea ...
, it was preferred even to
marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...
. *In the medieval period,
scribe A scribe is a person who serves as a professional copyist, especially one who made copies of manuscripts before the invention of automatic printing. The profession of the scribe, previously widespread across cultures, lost most of its promin ...
s and illuminators used it as an ingredient in gesso, which was applied to illuminated letters and gilded with gold in illuminated manuscripts.


Food and drink

*A
tofu Tofu (), also known as bean curd in English, is a food prepared by coagulating soy milk and then pressing the resulting curds into solid white blocks of varying softness; it can be ''silken'', ''soft'', ''firm'', ''extra firm'' or ''super fir ...
(soy bean curd) coagulant, making it ultimately a significant source of dietary
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
. *Adding
hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
to water used for
brewing Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, ...
. *Used in baking as a dough conditioner, reducing stickiness, and as a baked-goods source of dietary calcium. The primary component of mineral yeast food. *Used in mushroom cultivation to stop grains from clumping together.


Medicine and cosmetics

* Plaster for surgical splints. *Impression plasters in dentistry.


Other

*An alternative to iron oxide in some thermite mixes. *Tests have shown that gypsum can be used to remove pollutants such as
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, l ...
or
arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...
from contaminated waters.


Gallery

File:Gypsum-71006.jpg, Green gypsum crystals from Pernatty Lagoon, Mt Gunson,
South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territori ...
- its green color is due to presence of
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish- ...
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 Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native cop ...
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


See also

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


References


External links


WebMineral data
* * {{Authority control Calcium minerals Sulfate minerals Sedimentary rocks Evaporite Alchemical substances Monoclinic minerals Minerals in space group 15 Alabaster Luminescent minerals Industrial minerals