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Gypsum is a soft
sulfate mineral The sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), ...
composed of
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that cove ...

calcium sulfate
dihydrate In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
, with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ...
. It is widely mined and is used as a
fertilizer A fertilizer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

fertilizer
and as the main constituent in many forms of
plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "rend ...
,
blackboard A blackboard (also known as a chalkboard) is a reusable surface on which text or drawings are made with sticks of or , known, when used for this purpose, as . Blackboards were originally made of smooth, thin sheets of or dark grey stone. ...

blackboard
/
sidewalk chalk Sidewalk chalk is typically large and thick sticks of chalk (calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is us ...
, and
drywall Drywall (also known as plasterboard, wallboard, sheet rock, gypsum board, buster board, custard board, or gypsum panel) is a panel made of calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 ...

drywall
. A
massive Massive is an adjective related to mass. Massive may refer to: although the term massive is commonly referred to a large or big object, in this instance it does actually refer to the automotive YouTuber Auto Alex “ kersten “.. Arts, entertain ...

massive
fine-grained white or lightly tinted variety of gypsum, called
alabaster Alabaster is a mineral or rock that is soft, often used for carving, and is processed for plaster powder. Archaeologists and the stone processing industry use the word differently from geologist A geologist is a scientist who studies the soli ...

alabaster
, has been used for
sculpture Sculpture is the branch of the visual arts that operates in three dimensions. It is one of the plastic arts. Durable sculptural processes originally used carving (the removal of material) and modelling (the addition of material, as clay), ...

sculpture
by many cultures including
Ancient Egypt Ancient Egypt was a civilization  A civilization (or civilisation) is a that is characterized by , , a form of government, and systems of communication (such as ). Civilizations are intimately associated with additional char ...

Ancient Egypt
,
Mesopotamia Mesopotamia ( grc, Μεσοποταμία ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in th ...

Mesopotamia
,
Ancient Rome In historiography Historiography is the study of the methods of historian ( 484– 425 BC) was a Greek historian who lived in the 5th century BC and one of the earliest historians whose work survives. A historian is a person who stud ...
, the
Byzantine Empire The Byzantine Empire, also referred to as the Eastern Roman Empire, or Byzantium, was the continuation of the Roman Empire The Roman Empire ( la, Imperium Rōmānum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn ...

Byzantine Empire
, 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 Lon ...
s of
Medieval England England in the Middle Ages concerns the history of England The British Isles became inhabited more than 800,000 years ago, as the discovery of stone tools and footprints at Happisburgh in Norfolk has indicated.; "Earliest footprints outside ...
. Gypsum also crystallizes as translucent crystals of
selenite Selenite may refer to: Substances containing selenium *A selenium-containing anion or ionic compound with the SeO32− anion: **Selenite (ion), anion is a selenium oxoanion with the chemical formula SeO32− ***Selenous acid, the conjugate acid, wi ...
. It forms as an
evaporite An evaporite () is a water-soluble Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depend ...
mineral and as a hydration product of
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
. The
Mohs scale of mineral hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale Ordinal data is a categorical, statistical data type where the variables have natural, ordered categories and the distances between the categories are not known. These data e ...
defines gypsum as hardness value 2 based on scratch
hardness comparisonA variety of hardness Hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation hardness, indentation or abrasion (mechanical), abrasion. In general, different materials differ in their hardn ...
.


Etymology and history

The word ''
gypsum Gypsum is a soft sulfate mineral The sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with ...
'' is derived from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
word γύψος (), "plaster". Because the
quarries A quarry is a type of open-pit mine File:Ende Gelände 2017 CHB 23 (cropped).jpg, The giant bucket-wheel excavators in the German Rhineland coal mines are among the world's biggest land vehicles. Open-pit mining, also known as open-cas ...

quarries
of the
Montmartre Image:StPierreParis.jpg, upSaint-Pierre de Montmartre (originally 1133, much of it destroyed in 1790 and rebuilt in the 19th century) seen from the dome of the Basilica of the Sacré-Cœur Montmartre ( , , ) is a large hill in 18th arrondissem ...

Montmartre
district of
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,175,601 residents , in an area of more than . Since the 17th century, Paris ha ...

Paris
have long furnished burnt gypsum (
calcined Calcination refers to heating a solid to high temperatures in absence of air or oxygen, generally for the purpose of removing impurities or volatile substances. However, calcination is also used to mean a thermal treatment process in the absence o ...
gypsum) used for various purposes, this dehydrated gypsum became known as
plaster of Paris Plaster is a building material Building material is material used for construction Construction is a general term meaning the art and science to form Physical object, objects, systems, or organizations,"Construction" def. 1.a. 1.b. an ...

plaster of Paris
. Upon adding water, after a few tens of 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 ''spærstān'', "spear stone", referring to its crystalline projections. (Thus, the word spar 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. In the 19th century, it was also known as lime sulfate or sulfate of lime.


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 , (bassanite, often simply called "plaster") and, if heated further, to anhydrous
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that cove ...

calcium sulfate
(
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
). As with
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
, the solubility of gypsum in saline solutions and in
brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In different contexts, ''brine'' may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of solutions used for brining food ...

brine
s is also strongly dependent on
NaCl Sodium chloride , commonly known as salt (although sea salt Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking Cooking or cookery is the art, science, and craft of using heat t ...
(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 A hydrogen bond (or H-bond) is a primarily electrostatic Electrostatics is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department ...

hydrogen bond
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 Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformatio ...

crystal
s, and transparent, cleavable masses called
selenite Selenite may refer to: Substances containing selenium *A selenium-containing anion or ionic compound with the SeO32− anion: **Selenite (ion), anion is a selenium oxoanion with the chemical formula SeO32− ***Selenous acid, the conjugate acid, wi ...
. Selenite contains no significant
selenium Selenium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that ...

selenium
; rather, both substances were named for the ancient Greek word for the
Moon The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia (continent), Australia), it is the largest natural satellite in the Solar System relative to the size of its plane ...

Moon
. 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 Alabaster is a mineral or rock that is soft, often used for carving, and is processed for plaster powder. Archaeologists and the stone processing industry use the word differently from geologist A geologist is a scientist who studies the soli ...

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 Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depend ...
beds in association with
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
s. Deposits are known to occur in
strata In geology and related fields, a stratum (plural: strata) is a layer of sedimentary rock or soil, or igneous rock that was formed at the Earth's surface, with internally consistent characteristics that distinguish it from other layers. The "str ...
from as far back as the 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 Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of w ...

hot spring
s, from
volcanic A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet ar ...

volcanic
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 vein, pulmonary and umbilical veins, both of which ca ...
.
Hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC ...
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
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 Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition a ...

halite
and
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
. 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 dun ...

White Sands National Park
in the US state of
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Greater Albuquerque , OfficialLang = None , Languages = English English usually refer ...

New Mexico
have created a expanse of white gypsum sand, enough to supply the US construction industry with
drywall Drywall (also known as plasterboard, wallboard, sheet rock, gypsum board, buster board, custard board, or gypsum panel) is a panel made of calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 ...

drywall
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 and engineer who served as the 31st president of the United States The president of the United States (POTUS) is the head of state and head of gove ...

Herbert Hoover
declared the gypsum dunes a protected
national monument A national monument is a monument is regarded as an enduring symbol of Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the ...
. Gypsum is also formed as a by-product of
sulfide Sulfide (British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and usage a ...

sulfide
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

oxidation
, amongst others by
pyrite The mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. R ...

pyrite
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

oxidation
, when the
sulfuric acid Sulfuric acid (American spelling Despite the various English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography English orthogra ...

sulfuric acid
generated reacts with
calcium carbonate Calcium carbonate is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held togethe ...

calcium carbonate
. Its presence indicates oxidizing conditions. Under reducing conditions, the sulfates it contains can be reduced back to sulfide by
sulfate-reducing bacteria Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate () as termina ...
. This can lead to accumulation of elemental
sulfur Sulfur (in nontechnical British English: sulphur) is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: th ...

sulfur
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 ''Mars Reconnaissance Orbiter'' (MRO) is a spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbi ...

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 The National Aeronautics and Space Administration (NASA; ) is an independent agencies of the United States government, independent agency of the Federal government of the United States, U.S. federal government responsible for the c ...

Mars Exploration Rover
(MER) ''
Opportunity Opportunity may refer to: Places * Opportunity, Montana, an unincorporated community, United States * Opportunity, Nebraska, an unincorporated community, United States * Opportunity, Washington, a former census-designated place, United States * 393 ...
''. File:Cristales cueva de Naica.JPG, Crystals in the
Cave of the Crystals Cave of the Crystals or Giant Crystal Cave () is a cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering Weathering is the breaking down of rocks ...
in
Mexico Mexico, officially the United Mexican States, is a country A country is a distinct territorial body or political entity A polity is an identifiable political entity—any group of people who have a collective identity, who are organi ...

Mexico
. Note person (lower right) for scale. File:GypsumCrystalsLakeLucerno.jpg, Crystals that formed as the water evaporated in
Lake Lucero Lake Lucero is a playa located within that section of the Tularosa Basin The Tularosa Basin is a graben In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Ea ...
,
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 dun ...

White Sands National Park
. File:White Gypsum - geograph.org.uk - 2503198.jpg, Veins in the silts/marls of the Tea Green and Grey Marls,
Blue Anchor Blue Anchor is a seaside village, in the parish of Old Cleeve, close to Carhampton, Somerset, Carhampton in the Somerset West and Taunton district of Somerset, England. The village takes its name from a 17th-century inn; the bay, Blue Anchor Bay, ...

Blue Anchor
,
Somerset ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England South West England is one of nine official regions of England The regions, formerly known as the government office regions, are the ...

Somerset
,
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for the United Kingdom. Some prefer to use Britain as shorth ...

United Kingdom
. File:Gypsum layers Caprock Canyons 1.JPG, Veins in
Caprock Canyons State Park and Trailway Caprock Canyons State Park and Trailway is a Texas state park located along the eastern edge of the Llano Estacado in Briscoe County, Texas, Briscoe County, Texas, United States, approximately southeast of Amarillo, Texas, Amarillo. The state park ...
,
Texas Texas (, ; Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambigu ...

Texas
. File:Yardangs in dunes, White Sands National Park, New Mexico, United States.jpg, Extremely fine crystals of White Sands National Park.


Mining

Commercial quantities of gypsum are found in the cities of and 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 Fort Dodge is a city in, and the county seat of, Webster County, Iowa, Webster County, Iowa, United States, along the Des Moines River. The population was 25,206 in the 2010 United States Census, 2010 census, an increase from 25,136 in 2000 United ...
, which sits on one of the largest deposits of gypsum in the world, and
Plaster City, California Plaster City is an unincorporated community File:Entering Heinola, Minnesota.jpg, Sign at Heinola, Minnesota, Heinola, an unincorporated community in Otter Tail County, Minnesota An unincorporated area is a region not governed by a local municip ...
, United States, and East
Kutai Kutai is a historical region in East Kalimantan East Kalimantan ( Indonesian: ) is a province of Indonesia Provinces of Indonesia are the 34 largest subdivisions of the Indonesia Indonesia ( ), officially the Republic of Indonesia ( ...

Kutai
,
Kalimantan Kalimantan () is the Indonesian portion of the island of Borneo. It comprises 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, the ...

Kalimantan
, Indonesia. Several small mines also exist in places such as Kalannie in
Western Australia Western Australia (abbreviated as WA) is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspape ...

Western Australia
, where gypsum is sold to private buyers for additions of calcium and sulfur as well as reduction of aluminum toxicities on
soil Soil is a mixture In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, comp ...

soil
for agricultural purposes. Crystals of gypsum up to long have been found in the caves of the
Naica Mine The Naica Mine of the Mexican state of Chihuahua (state), Chihuahua, is a lead, zinc and silver Mining, mine. Located in Naica in the municipality of Saucillo (municipality), Saucillo, the Naica Mine is owned by Peñoles, Industrias Peñoles, the ...
of
ChihuahuaChihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Muni ...
, 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 Manitoba ( ) is a at the of the country. It is Canada's , with a population of 1,278,365 as of 2016. The easternmost of the three , Manitoba covers of widely varied ...

Winnipeg
File:WhiteSandsGypsum.jpg, Gypsum
sand Sand is a granular material composed of finely divided rock (geology), rock and 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 ...

sand
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 dun ...

White Sands National Park
,
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Greater Albuquerque , OfficialLang = None , Languages = English English usually refer ...

New Mexico


Synthesis

SyntheticA synthetic is an artificial material produced by organic chemistry, organic chemical synthesis. Synthetic may also refer to: In the sense of both "combination" and "artificial" * Synthetic chemical or synthetic compress, produced by the process ...
gypsum is recovered via
flue-gas desulfurization Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide () from Flue gas, exhaust flue gases of fossil-fuel power plants, and from the emissions of other sulfur oxide emitting processes such as waste incineration. M ...

flue-gas desulfurization
at some coal-fired power plants. It can be used interchangeably with natural gypsum in some applications. Gypsum also precipitates onto brackish water
membranes Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membr ...
, a phenomenon known as mineral salt
scaling Scaling may refer to: Science and technology Mathematics and physics * Scaling (geometry), a linear transformation that enlarges or diminishes objects * Scale invariance, a feature of objects or laws that do not change if scales of length, energy ...
, such as during
brackish Brackish water, also sometimes termed brack water, is water occurring in a natural environment having more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) with fresh water together, as in est ...
water
desalination Desalination is a process that takes away mineral components from saline water Saline water (more commonly known as salt water) is water that contains a high concentration of solvation, dissolved salts (mainly sodium chloride). The salt conce ...
of water with high concentrations of
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
and
sulfate The sulfate or sulphate ion is a polyatomic anion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having ...

sulfate
. Scaling decreases membrane life and productivity. This is one of the main obstacles in brackish water membrane desalination processes, such as
reverse osmosis Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic press ...

reverse osmosis
or
nanofiltration Nanofiltration is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening and removal of disinfection by-product precursors suc ...
. Other forms of scaling, such as
calcite Calcite is a carbonate mineral Carbonate minerals are those mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid E ...

calcite
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 In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically com ...

distillation
, as well as in
heat exchanger A heat exchanger is a system used to transfer heat between two or more fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (m ...

heat exchanger
s, where either the salt
solubility In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence i ...

solubility
or
concentration In chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in t ...

concentration
can change rapidly. A new study has suggested that the formation of gypsum starts as tiny crystals of a mineral called
bassanite Bassanite is a calcium sulfate mineral with formula calcium sulfate, CaSO4·water of crystallization, H2O or 2CaSO4·H2O. In other words it has half a water per CaSO4 unit hence its synonym ''calcium sulfate hemihydrate''. Bassanite was first des ...
(). 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.


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 The United States Department of Labor (DOL) is a cabinet-level department of the U.S. federal government, re ...
(OSHA) has set the legal limit (
permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal Law is a system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and ...
) 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 The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury Injury, also known as physical ...
(NIOSH) has set a
recommended exposure limit A recommended exposure limit (REL) is an occupational exposure limit An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. It i ...
(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: *
Gypsum board Drywall (also known as plasterboard, wallboard, sheet rock, gypsum board, buster board, custard board, or gypsum panel) is a panel made of calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and ...

Gypsum board
is primarily used as a finish for walls and ceilings, and is known in construction as plasterboard, sheet rock, or drywall. *
Gypsum blockGypsum block is a massive lightweight building material composed of solid gypsum, for building and erecting lightweight, Fireproofing, fire-resistant, non-load bearing interior walls, partition walls, cavity walls, skin walls, and pillar casing indoo ...
s are used like concrete blocks in building construction. *
Gypsum mortar Mortar is a workable paste which hardens to bind building blocks such as rock (geology), stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorati ...
is an ancient mortar used in building construction. *
Plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "rend ...
ingredients are used in surgical splints, casting moulds and modeling. *
Fertilizer A fertilizer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

Fertilizer
and
soil conditioner A soil conditioner is a product which is added to soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive maps ...
: 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. It is also used in ameliorating high-sodium soils, such as in the
Zuiderzee Works The Zuiderzee Works ( nl, Zuiderzeewerken) is a man-made system of dams and Levee, dikes, land reclamation and water drainage work, in total the largest hydraulic engineering project undertaken by the Netherlands during the twentieth century. The ...
. *Used for reclamation of
saline soils 249x249px, Saline incrustation in a PVC irrigation pipe from Brazil Soil salinity is the salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; sal ...
: when gypsum is added to sodic and acidic soil the highly soluble form of boron (sodium metaborate) is converted to the less soluble calcium metaborate and exchangeable sodium percentage is also reduced by gypsum application. *A binder in fast-dry tennis court clay. *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. *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. *A tofu (soy bean curd) coagulant, making it ultimately a major source of dietary
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
, especially in Asian cultures, which traditionally use few dairy products. *Adding hard water, hardness to water used for brewing. *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. *A component of Portland cement used to prevent flash setting of concrete. *Soil/water potential monitoring (soil moisture). *A common ingredient in making mead. *In the medieval period, scribes and illuminators mixed it with lead carbonate, lead carbonate (powdered white lead) to make gesso, which was applied to illuminated letters and gilded with gold in illuminated manuscripts. *In foot creams, shampoos and many other hair products. *A medicinal agent in traditional Chinese medicine called ''shi gao''. *Impression plasters in dentistry. *Used in mushroom cultivation to stop grains from clumping together. *Tests have shown that gypsum can be used to remove pollutants such as lead or arsenic from contaminated waters.


Gallery

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 of the North, 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 (crystal), 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 colouring 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