Gypsum

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O.[3] It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall. A massive fine-grained white or lightly tinted variety of gypsum, called alabaster, has been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England. Gypsum also crystallizes as translucent crystals of selenite. It also forms as an evaporite mineral and as a hydration product of anhydrite.

The Mohs scale of mineral hardness defines hardness value 2 as gypsum based on scratch hardness comparison.

Gypsum
Gips - Lubin, Poland.
General
CategorySulfate minerals
Formula
(repeating unit)
CaSO4·2H2O
Strunz classification7.CD.40
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
H-M symbol: (2/m)
Space groupMonoclinic
Space group: I2/a
Unit cella = 5.679(5), b = 15.202(14)
c = 6.522(6) [Å]; β = 118.43°; Z = 4
Identification
ColorColorless to white; may be yellow, tan, blue, pink, brown, reddish brown or gray due to impurities
Crystal habitMassive, flat. Elongated and generally prismatic crystals
TwinningVery common on {110}
CleavagePerfect on {010}, distinct on {100}
FractureConchoidal on {100}, splintery parallel to [001]
TenacityFlexible, inelastic
Mohs scale hardness1.5–2 (defining mineral for 2)
LusterVitreous to silky, pearly, or waxy
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.31–2.33
Optical propertiesBiaxial (+)
Refractive indexnα = 1.519–1.521
nβ = 1.522–1.523
nγ = 1.529–1.530
Birefringenceδ = 0.010
PleochroismNone
2V angle58°
Fusibility5
SolubilityHot, dilute HCl
References[1][2][3]
Major varieties
Satin sparPearly, fibrous masses
SeleniteTransparent and bladed crystals
AlabasterFine-grained, slightly colored

Etymology and history

The word gypsum is derived from the Greek word γύψος (gypsos), "plaster".[4] 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 addition of 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.[5] 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.[6] In the 19th century, it was also known as lime sulfate or sulfate of lime.

Physical properties

Gypsum deformed cristal-MCG 7747-P4150901-black
Gypsum crystals are plastic enough to bend under pressure of the hand. Sample on display at Musée cantonal de géologie de Lausanne.

Gypsum is moderately water-soluble (~2.0–2.5 g/l at 25 °C)[7] 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 for anhydrite, its solubility in saline solutions and in brines is also strongly dependent on NaCl (common table salt) concentration.[7]

Gypsum crystals are found to contain anion water and hydrogen bonding.[8]

Crystal varieties

Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. 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". 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 12 m (39 ft) long, in the form of selenite.[9]

Occurrence

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.[10] 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.[11] 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 Monument in the US state of New Mexico have created a 710 km2 (270 sq mi) expanse of white gypsum sand, enough to supply the US construction industry with drywall for 1,000 years.[12] 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. 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,[13] which were later confirmed at ground level by the Mars Exploration Rover (MER) Opportunity.[14]

Cristales cueva de Naica

Crystals in the Cave of the Crystals in Mexico. Note person (lower right) for scale.

GypsumCrystalsLakeLucerno

Crystals that formed as the water evaporated in Lake Lucero, White Sands National Monument.

White Gypsum - geograph.org.uk - 2503198

Veins in the silts/marls of the Tea Green and Grey Marls, Blue Anchor, Somerset, United Kingdom.

Mining

Estimated production of Gypsum in 2015
(thousand metric tons)[15]
Country Production Reserves
China 132,000 N/A
Iran 22,000 1,600
Thailand 12,500 N/A
United States 11,500 700,000
Turkey 10,000 N/A
Spain 6,400 N/A
Mexico 5,300 N/A
Japan 5,000 N/A
Russia 4,500 N/A
Italy 4,100 N/A
India 3,500 39,000
Australia 3,500 N/A
Oman 3,500 N/A
Brazil 3,300 290,000
France 3,300 N/A
Canada 2,700 450,000
Saudi Arabia 2,400 N/A
Algeria 2,200 N/A
Germany 1,800 450,000
Argentina 1,400 N/A
Pakistan 1,300 N/A
United Kingdom 1,200 55,000
Other countries 15,000 N/A
World total 258,000 N/A

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 and Canada[16] 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,[17] 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 aluminum toxicities on soil for agricultural purposes.

Crystals of gypsum up to 11 m (36 ft) 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 58 °C (136 °F), and the cave was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs 55 tonnes (61 short tons) and is around 500,000 years old.[18]

Gypsum-24382

Golden gypsum crystals from Winnipeg

Synthesis

Synthetic gypsum is recovered via 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, 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. 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 (CaSO4·​12H2O).[19] 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.

Occupational safety

People can be exposed to gypsum in the workplace by breathing it in, skin contact, and eye contact.

United States

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 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.[20]

Uses

Gypsum is used in a wide variety of applications:

  • Gypsum board[21] is primarily used as a finish for walls and ceilings, and is known in construction as drywall, wallboard, sheetrock or plasterboard.
  • Gypsum blocks are used like concrete blocks in building construction.
  • Gypsum mortar is an ancient mortar used in building construction.
  • Plaster ingredients are used in surgical splints, casting moulds and modeling.
  • Fertilizer and soil conditioner: 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,[22] such as in the Zuiderzee Works.[23]
  • 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.[24]
  • A tofu (soy bean curd) coagulant, making it ultimately a major source of dietary calcium, especially in Asian cultures which traditionally use few dairy products
  • Adding hardness to water used for brewing[25]
  • Used in baking as a dough conditioner, reducing stickiness, and as a baked-goods source of dietary calcium.[26] The primary component of mineral yeast food.[27]
  • 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 (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[28] or arsenic[29][30] from contaminated waters.

Gallery

Gypsum-71006

Green gypsum crystals from Pernatty Lagoon, Mt Gunson, South Australia - its green color is due to presence of copper ions.

Gypsum-162462

Unusual selenite gypsum from the Red River, Winnipeg, Manitoba, Canada

Gypsum-47190

Classic "ram's horn" gypsum from Santa Eulalia, Chihuahua, Mexico, 7.5×4.3×3.8 cm

Roses des Sables Tunisie

Desert rose, 47 cm long

Gypsum-53691

Gypsum from Pernatty Lagoon, Mt Gunson, Stuart Shelf area, Andamooka Ranges - Lake Torrens area, South Australia, Australia

Copper-Gypsum-203925

Gypsum with crystalline native copper inside

Gypsum J1

Gypsum from Swan Hill, Victoria, Australia. The colouring is due to the copper oxide

Gypsum-21996

Waterclear twined crystal of the form known as "Roman sword". Fuentes de Ebro, Zaragoza (Spain)

Botryogen-Gypsum-199664

Bright, cherry-red gypsum crystals 2.5 cm in height colored by rich inclusions of the rare mineral botryogen

Gypse Naica

Gypsum from Naica, Mun. de Saucillo, Chihuahua, Mexico

Gypsum-251118

Golden color gem, "fishtail"-twinned crystals of gypsum sitting atop a "ball" of gypsum which is composed of several single bladed crystals

See also

References

  1. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (2003). "Gypsum" (PDF). Handbook of Mineralogy. V (Borates, Carbonates, Sulfates). Chantilly, VA, US: Mineralogical Society of America. ISBN 978-0962209703.
  2. ^ Gypsum. Mindat
  3. ^ a b Klein, Cornelis; Hurlbut, Cornelius S., Jr. (1985), Manual of Mineralogy (20th ed.), John Wiley, pp. 352–353, ISBN 978-0-471-80580-9
  4. ^ "Compact Oxford English Dictionary: gypsum".
  5. ^ See:
    • Thaer, Albrecht Daniel; Shaw, William, trans.; Johnson, Cuthbert W., trans. (1844). The Principles of Agriculture. vol. 1. London, England: Ridgway. pp. 519–520.
    • Klaus Herrmann (1990), "Mayer, Johann Friedrich", Neue Deutsche Biographie (NDB) (in German), 16, Berlin: Duncker & Humblot, pp. 544–545; (full text online) 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.)
    • Beckmann, Johann (1775). Grundsätze der deutschen Landwirthschaft [Fundamentals of German Agriculture] (in German) (2nd ed.). Göttingen, (Germany): Johann Christian Dieterich. p. 60. 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.)
    • Mayer, Johann Friderich (1768). Lehre vom Gyps als vorzueglich guten Dung zu allen Erd-Gewaechsen auf Aeckern und Wiesen, Hopfen- und Weinbergen [Instruction in gypsum as an ideal good manure for all things grown in soil on fields and pastures, hops yards and vineyards] (in German). Anspach, (Germany): Jacob Christoph Posch.
  6. ^ Smith, Joshua (2007). Borderland smuggling: Patriots, loyalists, and illicit trade in the Northeast, 1780–1820. Gainesville, FL: UPF. pp. passim. ISBN 978-0-8130-2986-3.
  7. ^ a b Bock, E. (1961). "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". Canadian Journal of Chemistry. 39 (9): 1746–1751. doi:10.1139/v61-228.
  8. ^ Mandal, Pradip K; Mandal, Tanuj K (2002). "Anion water in gypsum (CaSO4·2H2O) and hemihydrate (CaSO4·1/2H2O)". Cement and Concrete Research. 32 (2): 313. doi:10.1016/S0008-8846(01)00675-5.
  9. ^ García-Ruiz, Juan Manuel; Villasuso, Roberto; Ayora, Carlos; Canals, Angels; Otálora, Fermín (2007). "Formation of natural gypsum megacrystals in Naica, Mexico" (PDF). Geology. 35 (4): 327–330. Bibcode:2007Geo....35..327G. doi:10.1130/G23393A.1. hdl:10261/3439.
  10. ^ Cockell, C. S.; Raven, J. A. (2007). "Ozone and life on the Archaean Earth". Philosophical Transactions of the Royal Society A. 365 (1856): 1889–1901. Bibcode:2007RSPTA.365.1889C. doi:10.1098/rsta.2007.2049. PMID 17513273.
  11. ^ Deer, W.A.; Howie, R.A.; Zussman, J. (1966). An Introduction to the Rock Forming Minerals. London: Longman. p. 469. ISBN 978-0-582-44210-8.
  12. ^ Abarr, James (7 February 1999). "Sea of sand". The Albuquerque Journal. Archived from the original on 30 June 2006. Retrieved 27 January 2007.
  13. ^ High-resolution Mars image gallery. University of Arizona
  14. ^ NASA Mars Rover Finds Mineral Vein Deposited by Water, NASA, 7 December 2011.
  15. ^ "GYPSUM" (PDF). U.S. Geological Survey.
  16. ^ "Mines, mills and concentrators in Canada". Natural Resources Canada. 24 October 2005. Archived from the original on 13 March 2005. Retrieved 27 January 2007.
  17. ^ The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide. Helion. 2018 – via Credo Reference.
  18. ^ Alleyne, Richard (27 October 2008). "World's largest crystal discovered in Mexican cave". The Telegraph. London. Retrieved 6 June 2009.
  19. ^ Van Driessche, A.E.S.; Benning, L. G.; Rodriguez-Blanco, J. D.; Ossorio, M.; Bots, P.; García-Ruiz, J. M. (2012). "The role and implications of bassanite as a stable precursor phase to gypsum precipitation". Science. 336 (6077): 69–72. Bibcode:2012Sci...336...69V. doi:10.1126/science.1215648. PMID 22491851.
  20. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Gypsum". www.cdc.gov. Retrieved 3 November 2015.
  21. ^ *Complimentary list of MasterFormat 2004 Edition numbers and titles (large PDF document)
  22. ^ Oster, J. D.; Frenkel, H. (1980). "The chemistry of the reclamation of sodic soils with gypsum and lime". Soil Science Society of America Journal. 44 (1): 41–45. Bibcode:1980SSASJ..44...41O. doi:10.2136/sssaj1980.03615995004400010010x.
  23. ^ Ley, Willy (October 1961). "The Home-Made Land". For Your Information. Galaxy Science Fiction. pp. 92–106.
  24. ^ Hogan, C. Michael (2007). "Knossos fieldnotes". Modern Antiquarian.
  25. ^ Palmer, John. "Water Chemistry Adjustment for Extract Brewing". HowToBrew.com. Retrieved 15 December 2008.
  26. ^ "Calcium sulphate for the baking industry" (PDF). United States Gypsum Company. Retrieved 1 March 2013.
  27. ^ "Tech sheet for yeast food" (PDF). Lesaffre Yeast Corporation. Archived from the original (PDF) on November 2014. Retrieved 1 March 2013.
  28. ^ Astilleros, J.M.; Godelitsas, A.; Rodríguez-Blanco, J.D.; Fernández-Díaz, L.; Prieto, M.; Lagoyannis, A.; Harissopulos, S. (2010). "Interaction of gypsum with lead in aqueous solutions" (PDF). Applied Geochemistry. 25 (7): 1008. Bibcode:2010ApGC...25.1008A. doi:10.1016/j.apgeochem.2010.04.007.
  29. ^ Rodriguez, J. D.; Jimenez, A.; Prieto, M.; Torre, L.; Garcia-Granda, S. (2008). "Interaction of gypsum with As(V)-bearing aqueous solutions: Surface precipitation of guerinite, sainfeldite, and Ca2NaH(AsO4)2⋅6H2O, a synthetic arsenate". American Mineralogist. 93 (5–6): 928. Bibcode:2008AmMin..93..928R. doi:10.2138/am.2008.2750.
  30. ^ Rodríguez-Blanco, Juan Diego; Jiménez, Amalia; Prieto, Manuel (2007). "Oriented Overgrowth of Pharmacolite (CaHAsO4⋅2H2O) on Gypsum (CaSO4⋅2H2O)". Cryst. Growth Des. 7 (12): 2756–2763. doi:10.1021/cg070222.

External links

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 geologists. The former use is in a wider sense that includes varieties of two different minerals: the fine-grained massive type of gypsum and the fine-grained banded type of calcite. Geologists define alabaster only as the gypsum type. Chemically, gypsum is a hydrous sulfate of calcium, while calcite is a carbonate of calcium.Both types of alabaster have similar properties. They are usually lightly colored, translucent, and soft stones. They have been used throughout history primarily for carving decorative artifacts.The calcite type is also denominated "onyx-marble", "Egyptian alabaster", and "Oriental alabaster" and is geologically described as either a compact banded travertine or "a stalagmitic limestone marked with patterns of swirling bands of cream and brown". "Onyx-marble" is a traditional, but geologically inaccurate, name because both onyx and marble have geological definitions that are distinct from even the broadest definition of "alabaster".

In general, ancient alabaster is calcite in the wider Middle East, including Egypt and Mesopotamia, while it is gypsum in medieval Europe. Modern alabaster is probably calcite but may be either. Both are easy to work and slightly soluble in water. They have been used for making a variety of indoor artwork and carving, and they will not survive long outdoors.

The two kinds are readily distinguished by their different hardnesses: gypsum alabaster is so soft that a fingernail scratches it (Mohs hardness 1.5 to 2), while calcite cannot be scratched in this way (Mohs hardness 3), although it yields to a knife. Moreover, calcite alabaster, being a carbonate, effervesces when treated with hydrochloric acid, while gypsum alabaster remains almost unaffected.

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 orthorhombic barium (baryte) and strontium (celestine) sulfates, as might be expected from the chemical formulas. Distinctly developed crystals are somewhat rare, the mineral usually presenting the form of cleavage masses. The Mohs hardness is 3.5, and the specific gravity is 2.9. The color is white, sometimes greyish, bluish, or purple. On the best developed of the three cleavages, the lustre is pearly; on other surfaces it is glassy. When exposed to water, anhydrite readily transforms to the more commonly occurring gypsum, (CaSO4·2H2O) by the absorption of water. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C (400 °F) under normal atmospheric conditions. Anhydrite is commonly associated with calcite, halite, and sulfides such as galena, chalcopyrite, molybdenite, and pyrite in vein deposits.

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 hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. All forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water.

Desert rose (crystal)

Desert rose is the colloquial name given to rose-like formations of crystal clusters of gypsum or baryte which include abundant sand grains. The 'petals' are crystals flattened on the c crystallographic axis, fanning open in radiating flattened crystal clusters.

The rosette crystal habit tends to occur when the crystals form in arid sandy conditions, such as the evaporation of a shallow salt basin. The crystals form a circular array of flat plates, giving the rock a shape similar to a rose blossom. Gypsum roses usually have better defined, sharper edges than baryte roses. Celestine and other bladed evaporite minerals may also form rosette clusters. They can appear either as a single rose-like bloom or as clusters of blooms, with most sizes ranging from pea sized to 4 inches (10 cm) in diameter.

The ambient sand that is incorporated into the crystal structure, or otherwise encrusts the crystals, varies with the local environment. If iron oxides are present, the rosettes take on a rusty tone.

The desert rose may also be known by the names: sand rose, rose rock, selenite rose, gypsum rose and baryte (barite) rose.

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 dihydrate (gypsum), with or without additives, typically extruded between thick sheets of facer and backer paper, used in the construction of interior walls and ceilings. The plaster is mixed with fiber (typically paper, fiberglass, asbestos, or a combination of these materials), plasticizer, foaming agent, and various additives that can reduce mildew, flammability, and water absorption.

In the mid-20th century, drywall construction became prevalent in North America as a time and labor saving alternative to traditional lath and plaster.

Gypcrust

Gypcrete or gypcrust is a hardened layer of soil, consisting of around 95% gypsum (calcium sulfate). Gypcrust is an arid zone duricrust. It can also occur in a semiarid climate in a basin with internal drainage, and is initially developed in a playa as an evaporate. Gypcrete is the arid climate's equivalent to calcrete, which is a duricrust that is unable to generate in very arid climates.

Gypsisol

Gypsisols in the World Reference Base for Soil Resources (WRB) are soils with substantial secondary accumulation of gypsum (CaSO4.2H2O). They are found in the driest parts of the arid climate zone.In the USDA soil taxonomy they are classified as Gypsids (USDA Soil Taxonomy), in the Russian soil classification they are called Desert soils (USSR).

Gypsisols are developed in mostly unconsolidated alluvial, colluvial and aeolian deposits of base-rich weathering material. They are found on level to hilly land in arid regions. The natural vegetation is sparse and dominated by xerophytic shrubs and trees and/or ephemeral grasses

These soils have ABC profiles. Accumulation of calcium sulphate, with or without carbonates, is concentrated in and below the B horizon.

Deep Gypsisols located close to water resources can be planted to a wide range of crops. Yields are severely depressed where a petrogypsic horizon occurs at shallow depth. Nutrient imbalance, stoniness, and uneven subsidence of the land surface upon dissolution of gypsum in percolating (irrigation) water are further limitations. Irrigation canals must be lined to prevent the canal walls from caving in. Large areas of Gypsisols are in use for low volume grazing.

Gypsisols are exclusive to arid regions; their worldwide extent is probably of the order of 100 million hectares. Major occurrences are in and around Mesopotamia in desert areas in the Middle East and adjacent central Asian republics, in the Libyan and Namib deserts, in southeast and central Australia and in the southwestern United States.

Gypsum Factory, Isfahan

Gypsum Factory, Isfahan (Persian: مجموعه کوره هاي گچ پزي‎ – Mojmūʿeh Kūreh Hāy-e Gech Pazī) is a village and company town in Sistan Rural District, Kuhpayeh District, Isfahan County, Isfahan Province, Iran. At the 2006 census, its population was 33, in 17 families.

Gypsum Mine, Shiraz

Gypsum Mine, Shiraz (Persian: معدن سنگ گچ‎ – Ma‘dan Sang-e Gech) is a village and company town in Qarah Bagh Rural District, in the Central District of Shiraz County, Fars Province, Iran. At the 2006 census, its population was 23, in 4 families.

Gypsum recycling

Gypsum recycling is the process of turning gypsum waste into recycled gypsum, thereby generating a raw material that can replace virgin gypsum raw materials in the manufacturing of new products.

Karst

Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst features may occur only at subsurface levels and can be totally missing above ground.

The study of karst is considered of prime importance in petroleum geology because as much as 50% of the world's hydrocarbon reserves are hosted in porous karst systems.

Mortar (masonry)

Mortar is a workable paste used to bind building blocks such as stones, bricks, and concrete masonry units, fill and seal the irregular gaps between them, and sometimes add decorative colors or patterns in masonry walls. In its broadest sense mortar includes pitch, asphalt, and soft mud or clay, such as used between mud bricks. Mortar comes from Latin mortarium meaning crushed.

Cement mortar becomes hard when it cures, resulting in a rigid aggregate structure; however, the mortar is intended to be weaker than the building blocks and the sacrificial element in the masonry, because the mortar is easier and less expensive to repair than the building blocks. Mortars are typically made from a mixture of sand, a binder, and water. The most common binder since the early 20th century is Portland cement but the ancient binder lime mortar is still used in some new construction. Lime and gypsum in the form of plaster of Paris are used particularly in the repair and repointing of buildings and structures because it is important the repair materials are similar to the original materials. The type and ratio of the repair mortar is determined by a mortar analysis. There are several types of cement mortars and additives.

Olympia Undae

Olympia Undae is a vast dune field in the north polar region of the planet Mars. It consists of a broad "sand sea" or erg that partly rings the north polar plateau (Planum Boreum) from about 120° to 240°E longitude and 78° to 83°N latitude. Stretching about 1,100 km (680 mi) across and covering an area of 470,000 km2, Olympia Undae is the largest continuous dune field on Mars. It is similar in size to the Rub' Al Khali in the Arabian Peninsula, the largest active erg on Earth.Olympia Undae lies within the informally named Borealis basin (also called the north polar basin), the largest of three topographic basins that occur in the northern lowlands of Mars. The average elevation in Olympia Undae is about 4,250 m below datum (martian "sea" level). The 19-km-diameter crater Jojutla lies near the geographic center of Olympia Undae at 81.63°N latitude and 169.65°E longitude.This crater was named by Andres Eloy Martinez Rojas, Mexican astronomer and science writer.Unda (pl. undae) is a Latin term meaning water, particularly water in motion as waves. The International Astronomical Union (IAU) adopted the term to describe "undulatory," dune-like features on other planets. Olympia Undae contains a variety of dune forms and wind-related (aeolian) depositional features, including sand sheets, transverse dunes, simple barchan dunes, mega-barchans, and complex barchanoid ridges. All of these dune types occur on Earth too.

Barchans are isolated, crescent-shaped dunes with horns that point downwind. They occur is areas where sand supply is moderate to low. Small simple barchan dunes and large mega-barchans are common at the margins of Olympia Undae and in areas where the sand cover is thin. Barchanoid ridges are broad linear to sinuous sand accumulations. They form through the lateral coalition of individual barchans and indicate increasing sand supply. Where sand is abundant, transverse dunes occur; they are commonly defined as long barchaoid ridges with fairly straight segments that are perpendicular to the wind direction. The majority of dunes in Olympia Undae are transverse dunes. Their spacing ranges from 200 to 800 m apart crest to crest, and comparison to terrestrial dunes with similar spacing indicates that they are 10 to 25 m high.On Earth, dunes are produced by saltating grains of sand. The requirement that dunes are produced by saltation allows scientists to determine the likely grain size for the particles making up the dunes in Olympia Undae and other martian dune fields. On Mars, the particle size most easily moved by wind is about 100 μm in diameter (fine sand). The sand in Olympia Undae is extremely dark in color and probably consists of basaltic rock fragments. The surface of Olympia Undae has a strong TES Type 2 spectral signature, indicating that the surface materials consist of basaltic andesite or weathered basalt and/or basaltic glass.In 2005, the OMEGA instrument on the Mars Express orbiter detected high concentrations of gypsum in the eastern portion of Olympia Undae (centered at 244.5°E, 80.2°N). CRISM data from the Mars Reconnaissance Orbiter (MRO) suggests that the gypsum is more concentrated along the crests of dunes than in the interdune hollows. The source of the gypsum is uncertain. Gypsum is an evaporitic mineral that precipitates from saline water; thus, its presence may indicate conditions different from today’s martian environment. The mineral may have formed through the melting of acidic snow, or the melting and discharge of sulfur-rich water from the base of the polar ice cap. However, the presence of gypsum does not necessarily require large surface water bodies (e.g., playa lakes). The mineral could have formed in volcanically heated groundwater in the shallow subsurface and later been exposed and concentrated by wind erosion and winnowing ("eolian mining").The term Olympia Undae can be the source of some confusion among Mars researchers. The term is used to describe 1) the geographical area described above and the type area for 2) a stratigraphic or geologic map unit (e.g. formation) called the Olympia Undae unit. As a stratigraphic unit, Olympia Undae describes materials that make up the geographic Olympia Undae as well as other sand sheets and dune fields encircling Planum Boreum (e.g., Abalos Undae). The Olympia Undae unit is Amazonian in age. To address some of this confusion, the stratigraphic term Olympia Undae unit has recently been renamed to simply "undae unit," since it encompasses other named dune fields (undae) around Planum Boreum. Another possible source of confusion is the distinction between Olympia Undae and Olympia Planum (formerly, Olympia Planitia). As a geographic area, Olympia Undae refers to the erg that covers a large fraction of Olympia Planum between longitude 120° and 240°E. Olympia Undae and Olympia Planum are not interchangeable terms. Olympia Planum is a broad, plain (and topographic bench) adjacent to Planum Boreum. It is half-domed shaped in profile (cross-section) and slopes southward into the Vastitas Borealis. The Olympia Undae erg covers both the bulk of southern Olympia Planum and part of the northern Vastitas Borealis.

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 "render" commonly refers to external applications. Another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.

The most common types of plaster mainly contain either gypsum, lime, or cement, but all work in a similar way. The plaster is manufactured as a dry powder and is mixed with water to form a stiff but workable paste immediately before it is applied to the surface. The reaction with water liberates heat through crystallization and the hydrated plaster then hardens.

Plaster can be relatively easily worked with metal tools or even sandpaper, and can be moulded, either on site or to make pre-formed sections in advance, which are put in place with adhesive. Plaster is not a strong material; it is suitable for finishing, rather than load-bearing, and when thickly applied for decoration may require a hidden supporting framework, usually in metal.

Forms of plaster have several other uses. In medicine plaster orthopedic casts are still often used for supporting set broken bones. In dentistry plaster is used to make dental impressions. Various types of models and moulds are made with plaster. In art, lime plaster is the traditional matrix for fresco painting; the pigments are applied to a thin wet top layer of plaster and fuse with it so that the painting is actually in coloured plaster. In the ancient world, as well as the sort of ornamental designs in plaster relief that are still used, plaster was also widely used to create large figurative reliefs for walls, though few of these have survived.

Plaster City, California

Plaster City is an unincorporated community in Imperial County in the U.S. state of California. It is located 17 miles (27 km) west of El Centro, at an elevation of 105 feet (32 m).United States Gypsum operates a large gypsum quarry and plant there and owns the town. The quarry was started in 1920 and was acquired by United States Gypsum in 1945. Plaster City has been noted for its unusual place name. It is the site of the last industrial narrow gauge railroad in the United States. The 3 ft (914 mm) gauge line runs north to a gypsum quarry and brings gypsum from the quarry to the plant.The first post office at Plaster City opened in 1924.The ZIP Code is 92251. The community is inside area code 760.

Red Hills (Kansas)

The Red Hills, also referred to as Gypsum Hills, is the name of a physiographic region located mostly in Clark, Comanche and Barber counties in southern and central Kansas. This undulating terrain of red-tinted sediments, a product of the underlying geology, does not fit the conventional description of the Great Plains landscape of Kansas.The red bed sediments of the Red Hills were deposited in an arid continental closed basin that formed within the Pangaean supercontinent during the Permian Period. Water often flooded this basin forming ephemeral playas of somewhat acidic waters. The shallow playas were intermittently flooded then dried leaving a mixture of lacustrine sediments and gypsum evaporites. The red color derives from the oxidation of iron contained within the deposits.

The region is also known as the Gypsum Hills, because of the large natural deposits of gypsum in this area. The dissolution of underlying gypsum beds has led to the formation of sinkholes which are common features within the Red Hills region. Big Basin and Little Basin are two well-known sinkholes in western Clark County.

The Red Hills have scenic vistas and some small steep canyons. High points include Mount Nebo (2,441 feet (744 m)), Mount Jesus (2,340 feet (710 m)) and Mount Lookout (2,320 feet (710 m)), in Clark County, Kansas.

Selenite (mineral)

Selenite, also known as satin spar, desert rose, or gypsum flower are four crystal structure varieties of the mineral gypsum. These four varieties of gypsum may be grouped together and called selenite.

All varieties of gypsum, including selenite and alabaster, are composed of calcium sulfate dihydrate (meaning that it has two molecules of water), with the chemical formula CaSO4·2H2O. Selenite contains no significant selenium, the similarity of the names of the substances coming from the Ancient Greek word for the Moon.

Some of the largest crystals ever found are of selenite, the largest specimen found in the Naica Mine's Cave of the Crystals being 12 metres long and weighing 55 tons.

USG Corporation

USG Corporation, also known as United States Gypsum Corporation, is an American company which manufactures construction materials, most notably drywall and joint compound. The company is the largest distributor of wallboard in the United States and the largest manufacturer of gypsum products in North America. It is also a major consumer of synthetic gypsum, a byproduct of flue-gas desulfurization. Its corporate offices are located at 550 West Adams Street in Chicago, Illinois.

Together with other construction products, USG's most significant brands are:

Sheetrock Brand Gypsum Panels

Securock Brand Glass-Mat Sheathing

Sheetrock Brand All Purpose Joint CompoundIn December 2013, Warren Buffett's Berkshire Hathaway became the largest shareholder in the company (holding roughly 30%) when it converted USG convertible notes it had acquired in 2008 to common stock.In June 2018, USG entered into an agreement to be purchased by the German building materials company, Knauf. The deal closed in April 2019.

USS Gypsum Queen (SP-430)

USS Gypsum Queen (SP-430) was a tugboat acquired by the United States Navy during World War I. She was assigned to the French coast as a minesweeper, as well as a tugboat to provide assistance to disabled Allied ships. Performing this dangerous work, Gypsum Queen struck a rock near Brest, France, and sunk, sending 15 crew members to their deaths.

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