Gypsum is a common sulfate mineral composed of hydrated calcium sulfate (CaSO_4 \cdot 2H_2O). Gypsum is found in large beds along with other evaporite minerals, especially in Permian and Triassic sedimentary formations. It is also found in salt pans and saline lakes and is a key part of cap rock on salt domes. Gypsum has many uses, including serving as a fluxing agent, fertilizer, filler in paper and textiles, and retarder in portland cement. It is also calcined for use as plaster of paris and as building materials in plaster, board products, Keene’s cement, and tiles and blocks. Gypsum plaster is a white cementing material that hardens when it is recombined with water.

What does gypsum look like and what are its basic properties?

Gypsum is a common and commercially significant sulfate mineral composed of hydrated calcium sulfate ((CaSO_4 \cdot 2H_2O)). It appears in various forms, including selenite (well-developed crystals), satin spar (fibrous, silky, and opalescent), alabaster (fine-grained and massive), and gypsite (earthy and pulverulent). Gypsum has a Mohs hardness of 2, meaning it can be scratched by a fingernail. It is used as a fluxing agent , fertilizer, filler, and retarder in portland cement. When calcined, it becomes plaster of Paris , used in building materials.

Where is gypsum commonly found in nature?

Gypsum, a hydrated calcium sulfate mineral ((CaSO_4 \cdot 2H_2O)), commonly occurs in extensive beds alongside evaporite minerals like anhydrite and halite, especially in Permian and Triassic sedimentary formations. It is often found in saline lakes and salt pans and constitutes a significant part of cap rock on salt domes, such as in Texas and Louisiana. Gypsum also forms from the hydration of anhydrite by surface and groundwaters, leading to the creation of gypsiferous strata that grade into anhydrite rocks. Additionally, it can be found disseminated in limestones, dolomitic limestones, and some shales. Well-developed crystals of gypsum are known as selenite. The fibrous massive variety, called satin spar, is valued for ornaments and jewelry, while the fine-grained massive variety, alabaster, is used for statuary. Leading gypsum producers include Spain, Thailand, the United States, Turkey, and Russia. Crude gypsum serves various purposes, including as a fluxing agent, fertilizer, and retarder in portland cement. Calcined gypsum is used to make plaster of Paris and building materials.

How is gypsum formed in the Earth?

Gypsum, a hydrated calcium sulfate mineral, forms in several ways. It frequently occurs in extensive beds alongside other evaporite minerals like anhydrite and halite within sedimentary formations . Gypsum can be created through ocean brine deposition, followed by anhydrite and halite. It is also found in saline lakes and salt pans. Additionally, gypsum is a key component of cap rock on salt domes . It is also created when surface and ground waters hydrate anhydrite. This replacement leads to a volume increase of 30% to 50%, resulting in intense folding of the remaining anhydrite layers. Sulfate anions, produced by oxidation, may react with calcium carbonate rocks to form gypsum (CaSO_4 \cdot 2H_2O). Groundwater that carries sulfate anions can also react with calcium ions in muds, clays, and limestones to create gypsum beds.

What are some common uses of gypsum in everyday life?

Gypsum , a common sulfate mineral, has many uses in everyday life. Crude gypsum is used as a fertilizer, filler in paper and textiles, a fluxing agent, and a retarder in portland cement. When calcined, gypsum becomes plaster of Paris and is used in building materials like plaster, board products, tiles, and blocks. Gypsum plasters are also used for plastering and in floor-surfacing material. The fine-grained massive variety of gypsum, called alabaster, is carved and polished for ornamental use and statuary.

How does gypsum contribute to building materials such as plaster and drywall?

Gypsum, a hydrated calcium sulfate mineral, is a crucial component in building materials like plaster and drywall . Gypsum plasters are produced by heating natural gypsum and dehydrating it. When mixed with water, gypsum plaster sets and hardens through chemical recombination. Drywall often utilizes gypsum panels, which feature a gypsum rock core between two layers of paper. These panels can also incorporate glass fibers for fire resistance or aluminum backing for insulation. Crude gypsum is also used as a retarder in portland cement.

gypsum

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Selenite gypsum from Naica, Chihuahua, Mex.

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Related Topics:: sulfate mineral; Gypsum plaster; alabaster; satin spar; selenite

On the Web:: ACS Publications - Crystal Growth and Design - Structural Insights into the Dehydration and Rehydration of Gypsum (Nov. 01, 2026)

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gypsum

mineral

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Top Questions

What is gypsum?
Gypsum is a common sulfate mineral composed of hydrated calcium sulfate (CaSO_4 \cdot 2H_2O). Gypsum is found in large beds along with other evaporite minerals, especially in Permian and Triassic sedimentary formations. It is also found in salt pans and saline lakes and is a key part of cap rock on salt domes.

Gypsum has many uses, including serving as a fluxing agent, fertilizer, filler in paper and textiles, and retarder in portland cement. It is also calcined for use as plaster of paris and as building materials in plaster, board products, Keene’s cement, and tiles and blocks. Gypsum plaster is a white cementing material that hardens when it is recombined with water.
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What does gypsum look like and what are its basic properties?
Gypsum is a common and commercially significant sulfate mineral composed of hydrated calcium sulfate ((CaSO_4 \cdot 2H_2O)). It appears in various forms, including selenite (well-developed crystals), satin spar (fibrous, silky, and opalescent), alabaster (fine-grained and massive), and gypsite (earthy and pulverulent).

Gypsum has a Mohs hardness of 2, meaning it can be scratched by a fingernail. It is used as a fluxing agent, fertilizer, filler, and retarder in portland cement. When calcined, it becomes plaster of Paris, used in building materials.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Where is gypsum commonly found in nature?
Gypsum, a hydrated calcium sulfate mineral ((CaSO_4 \cdot 2H_2O)), commonly occurs in extensive beds alongside evaporite minerals like anhydrite and halite, especially in Permian and Triassic sedimentary formations. It is often found in saline lakes and salt pans and constitutes a significant part of cap rock on salt domes, such as in Texas and Louisiana.

Gypsum also forms from the hydration of anhydrite by surface and groundwaters, leading to the creation of gypsiferous strata that grade into anhydrite rocks. Additionally, it can be found disseminated in limestones, dolomitic limestones, and some shales. Well-developed crystals of gypsum are known as selenite. The fibrous massive variety, called satin spar, is valued for ornaments and jewelry, while the fine-grained massive variety, alabaster, is used for statuary.

Leading gypsum producers include Spain, Thailand, the United States, Turkey, and Russia. Crude gypsum serves various purposes, including as a fluxing agent, fertilizer, and retarder in portland cement. Calcined gypsum is used to make plaster of Paris and building materials.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How is gypsum formed in the Earth?
Gypsum, a hydrated calcium sulfate mineral, forms in several ways. It frequently occurs in extensive beds alongside other evaporite minerals like anhydrite and halite within sedimentary formations.

Gypsum can be created through ocean brine deposition, followed by anhydrite and halite. It is also found in saline lakes and salt pans. Additionally, gypsum is a key component of cap rock on salt domes. It is also created when surface and ground waters hydrate anhydrite. This replacement leads to a volume increase of 30% to 50%, resulting in intense folding of the remaining anhydrite layers.

Sulfate anions, produced by oxidation, may react with calcium carbonate rocks to form gypsum (CaSO_4 \cdot 2H_2O). Groundwater that carries sulfate anions can also react with calcium ions in muds, clays, and limestones to create gypsum beds.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are some common uses of gypsum in everyday life?
Gypsum, a common sulfate mineral, has many uses in everyday life. Crude gypsum is used as a fertilizer, filler in paper and textiles, a fluxing agent, and a retarder in portland cement. When calcined, gypsum becomes plaster of Paris and is used in building materials like plaster, board products, tiles, and blocks. Gypsum plasters are also used for plastering and in floor-surfacing material. The fine-grained massive variety of gypsum, called alabaster, is carved and polished for ornamental use and statuary.
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1. cement: Gypsum plasters
2. gypsum
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does gypsum contribute to building materials such as plaster and drywall?
Gypsum, a hydrated calcium sulfate mineral, is a crucial component in building materials like plaster and drywall. Gypsum plasters are produced by heating natural gypsum and dehydrating it. When mixed with water, gypsum plaster sets and hardens through chemical recombination.

Drywall often utilizes gypsum panels, which feature a gypsum rock core between two layers of paper. These panels can also incorporate glass fibers for fire resistance or aluminum backing for insulation. Crude gypsum is also used as a retarder in portland cement.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

gypsum, common sulfate mineral of great commercial importance, composed of hydrated calcium sulfate (CaSO₄·2H₂O). In well-developed crystals the mineral commonly has been called selenite. The fibrous massive variety has a silky lustre and is called satin spar; it is translucent and opalescent and is valued for ornaments and jewelry. The fine-grained massive variety called alabaster is carved and polished for statuary and ornamental use when pure and translucent. Gypsite is the earthy pulverulent variety.

Gypsum occurs in extensive beds associated with other evaporite minerals (e.g., anhydrite and halite), particularly in Permian and Triassic sedimentary formations; it is deposited from ocean brine, followed by anhydrite and halite. It also occurs in considerable quantity in saline lakes and salt pans and is an important constituent of cap rock, an anhydrite-gypsum rock forming a covering on salt domes, as in Texas and Louisiana. Very commonly it is formed from the hydration of anhydrite by surface waters and groundwaters, and, thus, many gypsiferous strata grade downward into anhydrite rocks. This replacement causes a 30 percent to 50 percent volume increase and results in intense, tight folding of the remaining anhydrite layers. Gypsum also occurs disseminated in limestones, dolomitic limestones, and some shales.

Gypsum deposits occur in many countries, but Spain, Thailand, the United States, Turkey, and Russia are among the leading producers. The largest gypsum crystal was found in the Braden mine in Chile and exceeds 3 metres (about 10 feet) in length and 0.4 metre (about 1.5 feet) in diameter. In the U.S., commercial sedimentary gypsum deposits occur in New York and Michigan; others of economic importance occur in Virginia, Ohio, Iowa, Kansas, Texas, Nevada, and southern California. In Canada, gypsum is produced for export in Nova Scotia and New Brunswick. In France, gypsum is common in the marls and clays of the Paris Basin (hence the name plaster of paris), especially in Montmartre.

Relations between lamellar twinning and cleavage planes in dolomite and calcite. This difference can be discerned best when thin sections of the minerals are viewed under a microscope.

gypsum

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