Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.
Related to gypsum: gypsum board


(jĭp`səm), mineral composed of calcium sulfate (calcium, sulfur, and oxygen) with two molecules of water, CaSO4·2H2O. It is the most common sulfate mineral, occurring in many places in a variety of forms. A transparent crystalline variety is selenite. A massive gypsum of delicate color and texture, readily worked into ornamental vases, boxes, and the like, is called alabaster. A lustrous gypsum with fibrous structure, called satin spar, is used in jewelry and for other ornaments, but it is soft and easily marred. Plaster of Paris, a fine white powder, is produced by heating gypsum to expel the water. If this powder is moistened and then allowed to dry, it becomes hard, or sets. Its major use is in the manufacture of gypsum lath and wall board, and for casts and molds. It is widely used for staff, the material of which temporary exposition buildings are made. Uncalcined gypsum is added to Portland cement as a retarder.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a mineral, hydrous calcium sulfate CaSO4 · 2H2O; when pure it contains 32.56 percent CaO, 46.51 percent SO3, and 20.93 percent H2O.

Gypsum crystallizes in the monoclinic system. The crystal lattice structure of gypsum is of the layer type. Double layers consist of tetrahedra (SO4) joined through calcium. Crystals are tabular, acicular (single or twinned, so-called swallow-tailed), needle-shaped, and fibrous. Gypsum is found mainly as continuous granular (alabaster) and fibrous (selenite) masses and as various crystal groups (such as gypsum rosettes). Pure gypsum is colorless and transparent; if impurities are present, it can be gray, yellowish, pinkish, brown, or other colors. The mineralogical-scale hardness is 1.5, density 2,300 kg/m3, and solubility 2.05 g per liter at 20° C (maximum between 32° and 41° C). It is precipitated from aqueous solutions rich in sulfates (in the drying up of marine lagoons and salt lakes). Gypsum is precipitated at relatively low salinity; when the salinity is raised, anhydrous calcium sulfate, or anhydrite, starts developing instead, followed by salts. Because of this effect, gypsum is often found with anhydrite, more rarely with halite and other salts. Many deposits were formed through hydration of anhydrite. The main gypsum formations are of the sedimentary type and are widely distributed in deposits of varying age. In the USSR the largest deposits occur in the Donbas and in Moscow, Kuibyshev, and Perm oblasts, as well as in the Caucasus and Middle Asia. Gypsum is widely used to make cementing materials, gypsum concrete, and articles made from gypsum and gypsum concrete; as sundry-purpose stone (selenite) and lining or facing stone; in making paints, enamels, and glazes; for gypsuming of the soil; and in medicine and optics.

Gypsum is used as the starting material in solutions for making hollow molds from a sculptured original, these molds serving for casting copies from bronze, porcelain, or other materials or from gypsum (details of modeled architectural decoration). Gypsum enters into the composition of ganch (a gypsum-clay mixture) and stucco, and stands up well to assembling and coloring.


Budnikov, P. P. Gips, ego issledovanie i primenenie, 3rd ed. Moscow-Leningrad, 1943.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


CaSO4·2H2O A mineral, the commonest sulfate mineral; crystals are monoclinic, clear, white to gray, yellowish, or brownish in color, with well-developed cleavages; luster is subvitreous to pearly, hardness is 2 on Mohs scale, and specific gravity is 2.3; it is calcined at 190-200°C to produce plaster of paris.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A soft mineral consisting of a hydrated calcium sulfate from which gypsum plaster is made (by heating); colorless when pure; used as a retarder in portland cement.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


in egg shaped form, brings good fortune. [Gem Symbolism: Kunz, 80]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.


a colourless or white mineral sometimes tinted by impurities, found in beds as an evaporite. It is used in the manufacture of plaster of Paris, cement, paint, school chalk, glass, and fertilizer. Composition: hydrated calcium sulphate. Formula: CaSO4.2H2O. Crystal structure: monoclinic
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Gypsum plaster is prepared by partial or complete dehydration of the mineral gypsum.
British Gypsum's mine manager Dale Whittaker said: "It's not every day that we get to showcase our gypsum extraction work on film.
"To be awarded Bronze status by British Gypsum recognises the work that we are doing here at the college and the opportunities it opens up to our students."
They emphasised the need for common machinery pool for the gypsum cluster.
The stakeholders expressed that the as the low-priced gypsum products require the industry to be established within closest proximity to mine areas, therefore the government should ensure separate electric grid station, and gas connections especially to the plaster producers.
They identified major issues including poor access roads, mineral act related issues, unavailability of loans and heavy machinery to mine owners, absence of facilities to mine workers, limited markets for gypsum products, and gas and electricity problems.
Grain yield of wheat was increased by 28.3, 20.7 and 11.9 percent over control with application of 2.5 t/ha of gypsum districts of Chakwal, Attock and Jhelum/Rawalpindi respectively.
It can be seen that the morphology of R-P is totally different from that of POP, depending on their origin of gypsum. The morphology of plaster, made of needle-shaped gypsum crystals, changes with the properties of gypsum.
Keval Patel, a managing director at H.I.G, said, "We are pleased to support ACG Materials in its acquisition of Diamond Gypsum and continue our successful track record of acquiring leading mining and processing operations in attractive, high-growth markets."
Located in Watonga, Oklahoma, Diamond Gypsum is a miner of gypsum products sold into various oil & gas, infrastructure and agricultural applications.
Diamond Gypsum helps expand its presence in the STACK shale basin.
The framer ([dagger]) installs a membrane strip, sealing the subfloor to the gypsum fire wall (Figure 2).