Gypsum Rock : Uses, Formation, Composition and Characteristics.

 The gypsum rock is a nonmetallic mineral composed of hydrated calcium sulfate. It can be found in huge quantities. Gypsum is derived from the formation of salt or sedimentary processes. Gypsum is a soft sulfate mineral (chemical formula CaSO4 ∙2H2O). It is commonly known as the "Plaster of Paris" thanks to its near-ubiquitous use in building materials such as plaster or drywall. The abundance of gypsum rocks on land and sea led to its use as a chemical precipitant in some commercial fertilizers. It's found naturally in desert and arid regions. This rock has been used for a variety of industrial uses, and it's also used as a fertilizer. Gypsum is also known as satin spar, selenite, and alabaster.

Gypsum (Willow Creek, Alberta, Canada) 

Formation of Gypsum

Gypsum rocks are formed when magnesium- and calcium-rich water come into contact with sediments. Water that contains dissolved calcium and magnesium comes from hydrothermal circulation, which is very hot and under high pressure. And this water can be found in areas where there is volcanic activity or on the ocean floor. This water slowly moves through the sedimentary layers of the planet's crust and deposits those minerals in rocks like limestone.  Gypsum is a mineral made from the chemical reaction between water and a sulfate rock such as limestone, dolomite, or one of its variants. It forms as a result of these rocks being deposited in an arid environment and it is most commonly found near or on top of these rocks. Gypsum also includes caves, canyons, underwater, underground, and other places where there is little rainfall. The water evaporates leaving behind the mineral gypsum. When the oceans receded these deposits were buried under layers of sediment and subjected to heat and pressure over millions of years which converted them into rock.

 Jewel Cave Gypsum Beard - PICRYL

Characteristics of Gypsum

Gypsum rock is usually white or colorless, but can also have various shades of brown, yellow, red, and pink. These colors are caused by impurities present in the rock such as clay, sand, and organic matter. Rock gypsum is a soft sedimentary rock that formed from the evaporation of water from shallow seas or salt lakes. It forms mostly white, gray, or yellow sedimentary beds. Its color varies depending on the impurities present in it. It has a hardness of 2 on the Mohs scale. Its density varies from 2270 kg/m3 to 2390 kg/m3. The mineral of gypsum crystallizes in the form of masses, fibrous crystals, or tabular crystals. 

Where can Gypsum be found?

Gypsum deposits occur in sedimentary rocks at the Earth's surface. There are also significant sources of gypsum in volcanic areas such as fumaroles and hot springs. Gypsum occurs in evaporite deposits associated with hydrothermal activity, underground water, caves, and seawater desalination plants. It forms in lagoons where ocean waters high in calcium and sulfate content can slowly evaporate and be regularly replenished with new sources of water. The result is the accumulation of extensive beds of sedimentary gypsum. Large deposits of gypsum can be found in Morocco, India, and the U.S., but the largest deposit is at Boraston Quarry in Staffordshire, England. Gypsum often forms along with other minerals such as calcite and dolomite (limestone).

Uses of Gypsum

Gypsum is used for various purposes. In construction, it's used to make plaster, drywall, and wallboard. The most common use for gypsum is plaster, which is used in the walls of homes, commercial buildings, and public structures. Gypsum can also be used as a preservative to stop mold from growing on foods or structural materials that contain water. Gypsum finds its way into many types of industrial products as well. It's used in the manufacture of cement, and it's also used as an additive to increase the hardness of cement, which makes it easier for concrete to set. It's also used as an ingredient in ceramics, plastics, and adhesives. It is used as a flux for creating earthenware and can be used as a fertilizer, it has also been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England.

Plaster of Paris

Classification of Gypsum based on the formation

1. Evaporite gypsum

 Forms when seawater evaporates and leaves behind mineral deposits, often in thick beds. Gypsum that forms this way is often found in massive beds many hundreds of feet thick. It has been mined for centuries as a building material, but it has other uses as well. Evaporite gypsum is used in art and sculpture, to make plaster molds, and even to make blackboards!

2. Hydrothermal gypsum

 Formed when underground water containing minerals like calcium sulfate mix with lava or magma. The chemicals are left behind when the water evaporates during volcanic activity. This type of gypsum forms small crystals that can be seen with the naked eye. It's often associated with other types of minerals such as halite (rock salt) and anhydrite (calcium sulfate).

3. Sedimentary gypsum 

Forms from the evaporation of saline spring waters, or occasionally brackish lake waters. The water first evaporates to form crystalline calcium sulfate (CaSO4), which then recrystallizes. Under these conditions, cooling or boiling of the water results in the precipitation of solid gypsum under high pressure. This occurs especially when evaporation takes place under conditions of aridity or semiaridity.

Conclusion

Gypsum rock is a common, so-called sedimentary rock that forms from the alteration of sulfate minerals. It is commercially mined for industrial uses and also yields archaeological evidence suggesting that humans have been using it for over a thousand years. Gypsum's longevity in the earth, ease of formation, and low weight make it an essential mineral for many uses in industry, agriculture, and construction.